WO2015178316A1 - Shovel and control method therefor - Google Patents

Shovel and control method therefor Download PDF

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Publication number
WO2015178316A1
WO2015178316A1 PCT/JP2015/064091 JP2015064091W WO2015178316A1 WO 2015178316 A1 WO2015178316 A1 WO 2015178316A1 JP 2015064091 W JP2015064091 W JP 2015064091W WO 2015178316 A1 WO2015178316 A1 WO 2015178316A1
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WO
WIPO (PCT)
Prior art keywords
flow rate
discharge flow
oil
boom
command value
Prior art date
Application number
PCT/JP2015/064091
Other languages
French (fr)
Japanese (ja)
Inventor
宏治 川島
Original Assignee
住友重機械工業株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 住友重機械工業株式会社 filed Critical 住友重機械工業株式会社
Priority to JP2016521079A priority Critical patent/JP6629189B2/en
Priority to CN201580025526.8A priority patent/CN106460888B/en
Publication of WO2015178316A1 publication Critical patent/WO2015178316A1/en

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/024—Systems essentially incorporating special features for controlling the speed or actuating force of an output member by means of differential connection of the servomotor lines, e.g. regenerative circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/028—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/14—Energy-recuperation means

Definitions

  • the present invention relates to an excavator provided with a regenerative oil passage that allows hydraulic oil flowing out from a contraction side oil chamber of a boom cylinder to flow into an extension side oil chamber during a boom lowering operation, and a control method thereof.
  • a construction machine control device in which a boom cylinder and a bucket cylinder are simultaneously driven by hydraulic oil discharged from one hydraulic pump to simultaneously move a boom and a bucket as an operating body (see Patent Document 1). ).
  • This control device includes a regenerative oil passage that allows hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder to flow into the rod side oil chamber of the boom cylinder when the boom lowering operation is performed.
  • the discharge flow rate of the hydraulic pump is reduced and the discharge pressure of the hydraulic pump does not increase excessively compared to the case where the boom lowering operation and the bucket opening operation are performed simultaneously.
  • the above-described control device does not change the discharge flow rate of the hydraulic pump according to the operation amount of the boom operation lever even when only the boom lowering operation is performed. Therefore, even when the magnitude of the external force (for example, the force due to the weight of the attachment including the weight of earth and sand) that causes the boom cylinder to contract is different, if the operation amount of the boom operation lever is the same, the hydraulic pump The discharge flow rate is also the same. As a result, the smaller the external force, the lower the regeneration efficiency (the ratio of the amount of regenerated oil to the amount of hydraulic oil flowing into the rod side oil chamber of the boom cylinder).
  • the external force for example, the force due to the weight of the attachment including the weight of earth and sand
  • a shovel includes a boom cylinder that receives at least a part of hydraulic oil discharged from a hydraulic pump as pump supply oil, and a part of the hydraulic oil that flows out from a contraction-side oil chamber of the boom cylinder.
  • a regenerative oil passage that flows into the extension side oil chamber, and a control device that controls the discharge flow rate of the hydraulic oil discharged from the hydraulic pump to adjust the supply flow rate of the pump supply oil, and the control device includes: When a boom lowering operation is performed, the discharge flow rate is determined according to the thrust acting on the boom cylinder, and the regeneration flow rate of the regenerated oil is maximized while keeping the pressure in the extension side oil chamber at or above a predetermined pressure.
  • the above-mentioned means provides an excavator that can improve the regeneration efficiency during the boom lowering operation.
  • FIG. 1 is a side view showing a configuration example of a work machine according to an embodiment of the present invention.
  • an excavator (excavator) 1 as a work machine has an upper swing body 3 mounted on a crawler-type lower traveling body 2 via a swing mechanism so as to be rotatable around the X axis.
  • the upper swing body 3 is provided with a drilling attachment at the front center.
  • the excavation attachment includes a boom 4, an arm 5, and a bucket 6, and includes a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 as hydraulic actuators.
  • FIG. 2 is a diagram showing a configuration example of a hydraulic circuit mounted on the excavator of FIG.
  • the broken line of FIG. 2 shows a control pressure line
  • the dotted line of FIG. 2 shows an electric signal line.
  • Hydraulic pumps 10L and 10R are variable displacement pumps driven by a drive source such as an engine or an electric motor.
  • the hydraulic pump 10L circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass oil passage 30L that communicates each of the control valves 11L to 15L.
  • the hydraulic pump 10L can supply hydraulic oil to each of the control valves 11L to 15L through a parallel oil passage 31L extending in parallel to the center bypass oil passage 30L.
  • the hydraulic pump 10R circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass oil passage 30R that communicates each of the control valves 11R to 15R.
  • the hydraulic pump 10R can supply hydraulic oil to each of the control valves 12R to 15R through a parallel oil passage 31R extending in parallel with the center bypass oil passage 30R.
  • the hydraulic pump 10L and the hydraulic pump 10R may be collectively referred to as the “hydraulic pump 10”. The same applies to the other components configured by a pair of left and right.
  • the control valve 11L operates to supply hydraulic oil discharged from the hydraulic pump 10L to the left traveling hydraulic motor 42L as a hydraulic actuator when a left traveling lever (not shown) as an operation device is operated. It is a spool valve that switches the flow of oil.
  • the control valve 11R is a spool valve as a traveling straight valve.
  • the straight travel valve 11R is a 4-port 2-position spool valve, and has a first valve position and a second valve position.
  • the first valve position has a flow path that connects the hydraulic pump 10L and the parallel oil path 31L, and a flow path that connects the hydraulic pump 10R and the control valve 12R.
  • the second valve position has a flow path that connects the hydraulic pump 10R and the parallel oil path 31L, and a flow path that connects the hydraulic pump 10L and the control valve 12R.
  • the control valve 12L is a spool valve that switches the flow of hydraulic oil to supply hydraulic oil discharged from the hydraulic pump 10 to an optional hydraulic actuator (not shown).
  • the control valve 12R operates to supply hydraulic oil discharged from the hydraulic pump 10 to the right traveling hydraulic motor 42R as a hydraulic actuator when a right traveling lever (not shown) as an operating device is operated. It is a spool valve that switches the flow of oil.
  • the control valve 13L is hydraulic oil for supplying hydraulic oil discharged from the hydraulic pump 10 to the hydraulic hydraulic motor 44 for rotation as a hydraulic actuator when a swing operation lever (not shown) as an operation device is operated. It is a spool valve that switches the flow of the.
  • the control valve 13R is a spool valve that switches the flow of hydraulic oil to supply hydraulic oil discharged from the hydraulic pump 10 to the bucket cylinder 9 when a bucket operating lever (not shown) as an operating device is operated. It is.
  • the control valves 14 ⁇ / b> L and 14 ⁇ / b> R switch the flow of hydraulic oil to supply the hydraulic oil discharged from the hydraulic pump 10 to the boom cylinder 7 when a boom operation lever (not shown) as an operation device is operated. It is a spool valve.
  • the control valve 14L additionally supplies hydraulic oil to the boom cylinder 7 when the boom operation lever is operated in the boom raising direction with a predetermined lever operation amount or more.
  • the control valves 15L and 15R switch the flow of hydraulic oil so as to supply hydraulic oil discharged from the hydraulic pump 10 to the arm cylinder 8 when an arm operation lever (not shown) as an operation device is operated. It is a spool valve.
  • the control valve 15R additionally supplies hydraulic oil to the arm cylinder 8 when the arm operation lever is operated at a predetermined lever operation amount or more.
  • the center bypass oil passages 30L and 30R are respectively provided with negative control throttles 20L and 20R between the control valves 15L and 15R located on the most downstream side and the hydraulic oil tank 22.
  • the negative control is abbreviated as “negative control”.
  • the negative control throttles 20L and 20R generate a negative control pressure upstream of the negative control throttles 20L and 20R by limiting the flow of hydraulic oil discharged from the hydraulic pumps 10L and 10R.
  • the pressure sensors S1 and S2 detect the negative control pressure generated upstream of the negative control throttles 20L and 20R, and output the detected value to the controller 54 as an electrical negative control pressure signal.
  • Pressure sensors S3 and S4 detect the discharge pressures of the hydraulic pumps 10L and 10R, and output the detected values to the controller 54 as electrical discharge pressure signals.
  • the pressure sensor S5 detects the pressure of the hydraulic oil in the rod side oil chamber of the boom cylinder 7, and outputs the detected value to the controller 54 as an electric boom rod pressure signal.
  • the pressure sensor S6 detects the pressure of the hydraulic oil in the bottom side oil chamber of the boom cylinder 7, and outputs the detected value to the controller 54 as an electric boom bottom pressure signal.
  • an operation content detection unit is attached to operation devices such as a left travel lever, a right travel lever, an arm operation lever, a turning operation lever, a boom operation lever, and a bucket operation lever.
  • the operation content detection unit is, for example, a pressure sensor (not shown) that detects a pilot pressure generated by each operation device. These pressure sensors output the detected value to the controller 54 as an electrical pilot pressure signal.
  • the controller 54 is a functional element that controls the hydraulic circuit, and is, for example, a computer including a CPU, RAM, ROM, NVRAM, and the like.
  • the controller 54 electrically operates the operation contents (for example, presence / absence of lever operation, lever operation direction, lever operation amount, etc.) of various operation devices based on the output of the operation content detection unit such as a pressure sensor.
  • the operation content detection unit may be configured by a sensor other than the pressure sensor, such as an inclination sensor that detects the inclination of various operation levers.
  • the controller 54 causes the CPU to execute programs corresponding to various functional elements that operate the pump regulators 40L, 40R and the like according to the operation contents of the various operation devices.
  • the pump regulators 40L and 40R are mechanisms for controlling the discharge flow rates of the hydraulic pumps 10L and 10R.
  • the pump regulators 40L and 40R control the discharge flow rates of the hydraulic pumps 10L and 10R by adjusting the swash plate tilt angles of the hydraulic pumps 10L and 10R according to the commands generated by the controller 54.
  • the pump regulators 40L and 40R reduce the discharge flow rates of the hydraulic pumps 10L and 10R according to a command generated by the controller 54 based on the negative control pressure signal. As a result, pressure loss (pumping loss) when hydraulic oil discharged from the hydraulic pumps 10L and 10R passes through the center bypass oil passages 30L and 30R is suppressed.
  • the pump regulators 40L and 40R increase the discharge flow rates of the hydraulic pumps 10L and 10R, circulate sufficient hydraulic oil to each hydraulic actuator, and ensure the driving of each actuator.
  • the pump regulators 40L and 40R cause the hydraulic pump 10L to respond to a command generated by the controller 54 based on the discharge pressure signal.
  • the discharge flow rate of 10R is reduced. This is to prevent the absorption horsepower of the hydraulic pumps 10L and 10R from exceeding the output horsepower of the engine as the drive source.
  • the pump regulators 40L and 40R use the negative control pressure upstream of the negative control throttles 20L and 20R, the discharge pressure of the hydraulic pump 10L, and the discharge pressure of the hydraulic pump 10R to hydraulically control the discharge flow rates of the hydraulic pumps 10L and 10R. You may control to.
  • FIG. 3 is a diagram illustrating a state of the hydraulic circuit when the boom lowering operation is performed independently, and corresponds to FIG.
  • the boom lowering operation means an operation for lowering the boom 4 when the excavation attachment is moved in the air.
  • 3 represents the flow of hydraulic oil toward the boom cylinder 7
  • the thick dotted line in FIG. 3 represents the flow of hydraulic oil toward the hydraulic oil tank 22.
  • the boom lowering operation is performed by a full lever operation.
  • “Full lever operation” means a lever operation performed with a predetermined operation amount or more, and the predetermined operation amount is, for example, an operation amount of 80% or more.
  • the operation amount 100% corresponds to the operation amount when the operation lever is tilted to the maximum
  • the operation amount 0% corresponds to the operation amount when the operation lever is neutral (when the operation lever is not operated). To do.
  • control valve 14R receives the pilot pressure at the pilot port on the right side of the figure and moves to the left side of the figure.
  • FIG. 4 is a diagram showing the relationship of hydraulic oil flowing into and out of the boom cylinder 7.
  • the pressure receiving area on the rod side of the piston sliding in the boom cylinder 7 is Ar, the pressure receiving area on the bottom side is Ab, the pressure in the rod side oil chamber is the boom rod pressure Pr, and the pressure in the bottom side oil chamber is the boom bottom.
  • the thrust F acting on the boom cylinder 7 is expressed by the following equation (1).
  • the regeneration flow rate Qg of the regeneration oil passage 33 is expressed by the following equation (3).
  • the pressure downstream of the return oil passage 34 is Pt
  • the hydraulic oil density is ⁇
  • the return oil passage 34 If the flow area (throttle section) is Ac and the hydraulic oil outflow coefficient is C, the return flow rate Qc of the return oil path 34 is expressed by the following equation (6).
  • the flow passage area Ag of the regenerative oil passage 33 and the flow passage area Ac of the return oil passage 34 correspond to a lever operation amount in the direction in which the boom operation lever is lowered (hereinafter referred to as a “boom lowering operation amount”). This value is uniquely determined.
  • FIG. 5 shows an example of a correspondence relationship between the boom lowering operation amount and each of the flow path area Ag and the flow path area Ac. Specifically, both the flow path area Ag and the flow path area Ac increase as the boom lowering operation amount increases. For example, when the boom lowering operation amount is 100% (maximum lever operation amount), the flow path area Ag is the maximum value Agmax, and the flow path area Ac is the maximum value Acmax.
  • the correspondence relationship between the first diaphragm coefficient Cg and the second diaphragm coefficient Cc and the boom lowering operation amount is derived in advance based on the equations (4) and (7), and is stored in the ROM of the controller 54 or the like. Pre-stored in the form of a correspondence table. Therefore, the controller 54 can uniquely determine each of the first aperture coefficient Cg and the second aperture coefficient Cc when the boom lowering operation amount is determined.
  • the discharge flow rate Qe Is represented by the following formula (9).
  • FIG. 6 is a graph showing the relationship between the discharge flow rate Qp, the boom cylinder inflow rate Qs, the regeneration flow rate Qg, and the boom rod pressure Pr when the boom control lever is fully operated in the lowering direction.
  • FIG. 6A is a graph showing the relationship between the discharge flow rate Qp and the boom cylinder inflow rate Qs.
  • FIG. 6B is a graph showing the relationship between the discharge flow rate Qp and the regeneration flow rate Qg, and FIG.
  • 6C is a graph showing the relationship between the discharge flow rate Qp and the boom rod pressure Pr.
  • the horizontal axis corresponding to the discharge flow rate Qp is common.
  • the transition indicated by the solid line represents the transition when the external force for contracting the boom cylinder 7 is large.
  • a transition indicated by a broken line represents a transition when the external force is medium, and a transition indicated by a one-dot chain line represents a transition when the external force is small.
  • the external force for contracting the boom cylinder 7 varies depending on the amount of earth and sand in the bucket 6, the position of the shovel 1 (whether it is on an inclined land or a flat ground), the position of the excavation attachment, and the like.
  • the boom cylinder inflow flow rate Qs is substantially constant regardless of the magnitude of the discharge flow rate Qp. That is, even if the discharge flow rate Qp is increased, the boom cylinder inflow rate Qs does not increase, and the boom lowering speed does not increase. As shown in FIG. 6B, the regeneration flow rate Qg decreases as the discharge flow rate Qp increases regardless of the magnitude of the external force.
  • the regeneration flow rate Qg can be increased without decreasing the boom cylinder inflow rate Qs.
  • the boom rod pressure Pr has a tendency to decrease as the discharge flow rate Qp decreases regardless of the magnitude of the external force. Therefore, if the discharge flow rate Qp is excessively decreased, the boom rod pressure Pr is excessively decreased, and cavitation may occur.
  • the boom rod pressure Pr becomes lower as the external force becomes larger if the discharge flow rate Qp is constant. That is, if the external force is large, the boom rod pressure Pr may be lowered to a level that causes cavitation even when the discharge flow rate Qp is relatively large.
  • the reduction of the discharge flow rate Qp can realize the increase of the regeneration flow rate Qg, and is effective in achieving energy saving.
  • the discharge flow rate Qp necessary for maximizing the regeneration flow rate Qg without generating cavitation varies depending on the magnitude of the external force, the discharge flow rate Qp cannot be reduced indefinitely.
  • the controller 54 determines the discharge flow rate Qp so that the boom rod pressure Pr becomes the predetermined target pressure Ptg, and makes the regeneration flow rate Qg as large as possible unless cavitation is generated.
  • the predetermined target pressure Ptg is a pressure at a level that does not cause cavitation, and is 4 [MPa], for example.
  • the controller 54 sets the discharge flow rate Qp when the external force is small to QpL in order to set the boom rod pressure Pr to the target pressure Ptg. Further, the controller 54 sets the discharge flow rate Qp when the external force is medium to QpM (> QpL), and sets the discharge flow rate Qp when the external force is large to QpH (> QpM).
  • the regeneration flow rate Qg when the external force is small becomes QgL
  • the discharge flow rate Qp when the external force is medium is determined to be QpM
  • the regeneration flow rate Qg when the external force is medium becomes QgM (> QgL)
  • the increase in the regeneration flow rate Qg is larger as the external force is smaller than when the common discharge flow rate QpR is discharged regardless of the magnitude of the external force.
  • the increase in the regeneration flow rate Qg is DH when the external force is large, DM (> DH) when the external force is medium, and DL (> DM) when the external force is small.
  • the boom rod pressure Pr decreases as the external force increases.
  • the discharge flow rate Qp is reduced from QpR to QpL, QpM, or QpH, if the external force is the same, it can be seen that there is almost no change in the boom cylinder inflow rate Qs.
  • FIG. 7 is a flowchart showing an exemplary flow of the discharge flow rate optimization process, and the controller 54 repeatedly executes the discharge flow rate optimization process at a predetermined control cycle.
  • “optimization of the discharge flow rate Qp” means that the discharge flow rate that maximizes the regeneration flow rate Qg is realized as long as cavitation is not generated.
  • the controller 54 determines whether a boom lowering operation is being performed (step ST1). In this embodiment, the controller 54 determines whether a boom lowering operation is being performed from the operation content of the boom operation lever based on the output of the operation content detection unit such as a pressure sensor. Further, in the present embodiment, the controller 54 determines that the boom lowering operation is being performed when it is detected that the boom operating lever has been operated alone in the lowering direction. In this embodiment, the controller 54 determines that the boom lowering operation is being performed when it is determined that the excavation attachment is not pressed against the excavation target, that is, when the excavation attachment is determined to be moving in the air. . The controller 54 determines whether or not the excavation attachment is pressed against the excavation target based on at least one of the boom rod pressure signal output from the pressure sensor S5 and the boom bottom pressure signal output from the pressure sensor S6.
  • step ST1 If it is determined that the boom lowering operation is not being performed (NO in step ST1), the controller 54 ends the current discharge flow rate optimization process.
  • the controller 54 derives a first command value that is a command to the pump regulator 40R (step ST2).
  • the controller 54 derives the first command value according to the negative control pressure signal.
  • the first command value is a discharge flow rate command value that is uniquely determined according to the negative control pressure signal, and increases as the boom lowering operation amount increases. Specifically, the greater the boom lowering operation amount, the greater the movement amount of the control valve 14R, and the smaller the channel area of the center bypass oil passage 30R. When the flow path area of the center bypass oil path 30R is reduced, the negative control pressure is reduced and the discharge flow rate command value is increased. When the discharge flow rate command value increases, the discharge flow rate Qp of the hydraulic pump 10R increases.
  • the controller 54 may derive the first command value according to the boom lowering operation amount.
  • the controller 54 outputs the first command value to the pump regulator 40R, and controls the swash plate tilt angle so that the discharge flow rate Qp of the hydraulic pump 10R becomes a flow rate corresponding to the first command value (step). ST3).
  • the controller 54 determines whether the fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value (step ST4). This is because the thrust F acting on the boom cylinder 7 cannot be accurately estimated if the fluctuation range is large.
  • the controller 54 derives the difference between the previous value and the current value of the boom rod pressure signal output from the pressure sensor S5 as the fluctuation range of the boom bottom pressure Pb. The same applies to the fluctuation range of the boom rod pressure Pr.
  • step ST4 When it is determined that at least one fluctuation range of the boom bottom pressure Pb and the boom rod pressure Pr is equal to or greater than a predetermined value (NO in step ST4), the controller 54 repeats the determination in step ST4.
  • the controller 54 derives a second command value that is a command to the pump regulator 40R. (Step ST5).
  • the second command value is This is a discharge flow rate command value that changes in accordance with the thrust F acting on the boom cylinder 7, and is larger as the thrust F is larger.
  • the controller 54 thrusts acting on the boom cylinder 7 based on the boom rod pressure signal output from the pressure sensor S5, the boom bottom pressure signal output from the pressure sensor S6, and the above equation (1). Derive F.
  • the controller 54 reads out a predetermined target pressure Ptg related to the boom rod pressure Pr from the ROM or the like, and the boom bottom when the boom rod pressure Pr is set to the target pressure Ptg based on the thrust F and the above equation (2).
  • the pressure Pb is derived.
  • the controller 54 refers to a correspondence table that stores in advance the correspondence relationship between the first aperture coefficient Cg and the second aperture coefficient Cc and the boom lowering operation amount, and the first aperture coefficient Cg corresponding to the current boom lowering operation amount. And the second aperture coefficient Cc.
  • the correspondence table is stored in advance in a ROM or the like.
  • the controller 54 derives the regeneration flow rate Qg of the regeneration oil passage 33 based on the acquired first throttle coefficient Cg and the equation (5). Further, the controller 54 derives the return flow rate Qc of the return oil passage 34 based on the acquired second throttle coefficient Cc and the equation (8).
  • the controller 54 derives a discharge flow rate corresponding to the second command value based on the regeneration flow rate Qg, the return flow rate Qc, and the equation (10).
  • the controller 54 does not necessarily have to derive the boom bottom pressure Pb, the regeneration flow rate Qg, the return flow rate Qc, and the like each time when the boom rod pressure Pr is set to the target pressure Ptg in order to derive the second command value.
  • the controller 54 may refer to a correspondence table in which a correspondence relationship between a combination of a pilot pressure signal, a boom bottom pressure signal, and a boom rod pressure signal related to the boom operation lever and the second command value is stored in advance.
  • the controller 54 refers to the correspondence table stored in advance in the ROM or the like, and directly determines the second command value corresponding to the combination of the current boom lowering operation amount, the boom rod pressure Pr, and the boom bottom pressure Pb. To derive.
  • the controller 54 outputs a second command value to the pump regulator 40R, and controls the discharge flow rate Qp of the hydraulic pump 10R to be a discharge flow rate corresponding to the second command value (step ST6).
  • the controller 54 optimizes the discharge flow rate Qp of the hydraulic pump 10R so as to maximize the regeneration flow rate Qg unless cavitation is generated.
  • FIG. 8 is a graph which shows the time transition of various parameters when boom lowering operation is performed independently.
  • FIG. 8A shows temporal transition of the boom rod pressure Pr and the boom bottom pressure Pb.
  • FIG. 8B shows a temporal transition of the discharge flow rate command value
  • FIG. 8C shows a temporal transition of the boom lowering speed. Note that in FIGS. 8A to 8C, the horizontal axis as a time axis is common.
  • the boom bottom pressure Pb and the boom rod pressure Pr change with a small fluctuation range as shown in FIG.
  • the fluctuation range of boom bottom pressure Pb and boom rod pressure Pr will become large.
  • the boom bottom pressure Pb temporarily decreases when hydraulic oil flows out from the bottom side oil chamber, and the boom rod pressure Pr increases temporarily when hydraulic fluid flows into the rod side oil chamber.
  • each of the boom bottom pressure Pb and the boom rod pressure Pr is stabilized, and the fluctuation width thereof is less than a predetermined value at time t2.
  • the controller 54 uses the first command value d1 as the discharge flow rate command value until it is determined that the respective fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value. For this reason, the discharge flow rate command value remains the first command value d1.
  • the controller 54 determines that the fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value at time t2, the controller 54 sets the second command value d2 corresponding to the thrust F acting on the boom cylinder 7. derive. At this time, the controller 54 determines the discharge flow rate command value so that the actual discharge flow rate Qp of the hydraulic pump 10R becomes the discharge flow rate corresponding to the second command value after the elapse of the predetermined time T1. This is to avoid a sudden change in the discharge flow rate Qp.
  • the controller 54 linearly interpolates between the first command value d1 as the current discharge flow rate command value and the second command value d2 as the discharge flow rate command value after a predetermined time T1 has elapsed.
  • the command value is derived.
  • the pump regulator 40R is controlled so that the actual discharge flow rate Qp matches the discharge flow rate corresponding to the intermediate command value. Therefore, as shown in FIG. 8B, the discharge flow rate command value decreases relatively slowly from the first command value d1 at time t2, and reaches the second command value d2 at time t3 after the elapse of the predetermined time T1. .
  • the boom lowering speed gradually increases after the boom lowering operation is performed at time t1, and reaches a speed Vt corresponding to the boom lowering operation amount at time t2. Then, the reduction of the discharge flow rate command value is started at time t2, and the speed Vt is maintained even after the actual reduction of the discharge flow rate Qp is started. Further, the discharge flow rate command value becomes the second command value d2 at time t3, and the speed Vt is maintained even after the actual discharge flow rate Qp becomes the discharge flow rate corresponding to the second command value d2. This is because the regeneration flow rate Qg increases by the amount that the discharge flow rate Qp decreases.
  • the controller 54 determines the discharge flow rate Qp according to the thrust F acting on the boom cylinder 7 and regenerates the boom rod pressure Pr at a predetermined target pressure Ptg or more. Maximize the flow rate Qg. Therefore, it is possible to improve the regeneration efficiency during the boom lowering operation while preventing the occurrence of cavitation. Further, since the discharge flow rate Qp is reduced to the minimum necessary, energy saving can be achieved.
  • the controller 54 determines the first command value d1 according to the negative control pressure or the boom lowering operation amount. Then, the pump regulator 40R is controlled so that the actual discharge flow rate Qp of the hydraulic pump 10R matches the discharge flow rate corresponding to the first command value d1. Further, after the pressure of the hydraulic oil in the boom cylinder 7 is stabilized, the thrust F acting on the boom cylinder 7, the flow passage area Ag of the regenerated oil passage 33, and the flow passage area Ac of the return oil passage 34 are determined. To determine the second command value d2. Then, the pump regulator 40R is controlled so that the actual discharge flow rate Qp of the hydraulic pump 10R matches the discharge flow rate corresponding to the second command value d2.
  • the controller 54 determines the second command value when the fluctuation range of the hydraulic oil pressure in the boom cylinder 7 becomes less than a predetermined value. Therefore, the controller 54 derives the second command value d2 corresponding to the discharge flow rate Qp that can maximize the regeneration flow rate Qg while making the boom rod pressure Pr equal to or higher than the predetermined target pressure Ptg after deriving the thrust F with high accuracy. be able to.
  • the thrust F acting on the boom cylinder 7 is derived based on the boom bottom pressure Pb and the pressure receiving area Ab, the boom rod pressure Pr and the pressure receiving area Ar. Therefore, the controller 54 can derive the thrust F with high accuracy with a simple configuration.
  • the flow passage area Ag of the regenerated oil passage 33 and the flow passage area Ac of the return oil passage 34 are derived based on the boom lowering operation amount. Therefore, the controller 54 can realize the boom lowering speed according to the boom lowering operation amount while preventing the occurrence of cavitation and improving the regeneration efficiency at the time of the boom lowering operation.
  • the controller 54 derives an intermediate command value by interpolating between the first command value d1 and the second command value d2. Then, the actual discharge flow rate Qp is matched with the discharge flow rate corresponding to the intermediate command value so that the actual discharge flow rate Qp of the hydraulic pump 10R becomes the discharge flow rate corresponding to the second command value d2 after a predetermined time has elapsed.
  • the pump regulator 40R is controlled. Therefore, the controller 54 prevents a sudden change in the discharge flow rate Qp, a sudden change in the regeneration flow rate Qg, and a sudden change in the boom cylinder inflow rate Qs (boom lowering speed), and prevents the occurrence of cavitation while performing the boom lowering operation. Can improve the reproduction efficiency.
  • the controller 54 determines that the boom lowering operation is being performed when it is detected that the boom operating lever has been operated alone in the lowering direction.
  • the present invention is not limited to this configuration.
  • the controller 54 may determine that the boom lowering operation is being performed when it is detected that the boom operating lever has been operated halfway in the lowering direction alone.
  • the “half lever operation” means a lever operation performed with a smaller operation amount than a full lever operation.
  • the regenerated oil passage 33 is formed inside the control valve 14R, but may be formed outside the control valve 14R.

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Abstract

A shovel (1) is provided with: a boom cylinder (7) that receives at least one part of hydraulic oil that is discharged by a hydraulic pump (10R) as pump supply oil; a regenerated oil path (33) that causes at least one part of the hydraulic oil that flows out from a bottom-side oil chamber of the boom cylinder (7) to flow into a rod-side oil chamber as regenerated oil; and a controller (54) that controls the discharge flow rate (Qp) of the hydraulic oil that is discharged by the hydraulic pump (10R) and adjusts the boom cylinder inflow rate (Qs). The controller (54) determines the discharge flow rate (Qp) in accordance with the thrust force (F) that acts on the boom cylinder (7) when a boom lowering operation is performed and maximizes a regeneration flow rate (Qg) while setting the pressure of the rod-side oil chamber to be equal to or greater than a predetermined target pressure (Ptg).

Description

ショベル及びその制御方法Excavator and control method thereof
　本発明は、ブーム下げ操作時にブームシリンダの収縮側油室から流出する作動油を伸張側油室に流入させる再生油路を備えたショベル及びその制御方法に関する。 The present invention relates to an excavator provided with a regenerative oil passage that allows hydraulic oil flowing out from a contraction side oil chamber of a boom cylinder to flow into an extension side oil chamber during a boom lowering operation, and a control method thereof.
　１台の油圧ポンプが吐出する作動油によってブームシリンダ及びバケットシリンダを同時に駆動して操作体としてのブーム及びバケットを同時に動かすようにする建設機械の制御装置が知られている（特許文献１参照。）。 A construction machine control device is known in which a boom cylinder and a bucket cylinder are simultaneously driven by hydraulic oil discharged from one hydraulic pump to simultaneously move a boom and a bucket as an operating body (see Patent Document 1). ).
　この制御装置は、ブーム下げ操作が行われた場合にブームシリンダのボトム側油室から流出する作動油をブームシリンダのロッド側油室に流入させる再生油路を含む。また、ブーム下げ操作のみが行われた場合には、ブーム下げ操作とバケット開き操作とが同時に行われた場合に比べ、油圧ポンプの吐出流量を減少させ、油圧ポンプの吐出圧が過度に上昇しないようにする。 This control device includes a regenerative oil passage that allows hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder to flow into the rod side oil chamber of the boom cylinder when the boom lowering operation is performed. In addition, when only the boom lowering operation is performed, the discharge flow rate of the hydraulic pump is reduced and the discharge pressure of the hydraulic pump does not increase excessively compared to the case where the boom lowering operation and the bucket opening operation are performed simultaneously. Like that.
特開２０００－３０９９４９号公報JP 2000-309949 A
　しかしながら、上述の制御装置は、ブーム下げ操作のみが行われる場合であってもブーム操作レバーの操作量に応じて油圧ポンプの吐出流量を決定することに変わりはない。そのため、ブームシリンダを収縮させようとする外力（例えば、土砂の重量を含むアタッチメントの重量による力）の大きさが異なる場合であっても、ブーム操作レバーの操作量が同じであれば油圧ポンプの吐出流量も同じとなる。その結果、外力が小さいほど再生効率（ブームシリンダのロッド側油室に流入する作動油量に占める再生油量の割合）が低くなる。 However, the above-described control device does not change the discharge flow rate of the hydraulic pump according to the operation amount of the boom operation lever even when only the boom lowering operation is performed. Therefore, even when the magnitude of the external force (for example, the force due to the weight of the attachment including the weight of earth and sand) that causes the boom cylinder to contract is different, if the operation amount of the boom operation lever is the same, the hydraulic pump The discharge flow rate is also the same. As a result, the smaller the external force, the lower the regeneration efficiency (the ratio of the amount of regenerated oil to the amount of hydraulic oil flowing into the rod side oil chamber of the boom cylinder).
　上述に鑑み、ブーム下げ操作の際の再生効率を向上できるショベルを提供することが望ましい。 In view of the above, it is desirable to provide an excavator that can improve the regeneration efficiency during the boom lowering operation.
　本発明の実施例に係るショベルは、油圧ポンプが吐出する作動油の少なくとも一部をポンプ供給油として受け入れるブームシリンダと、前記ブームシリンダの収縮側油室から流出する作動油の一部を再生油として伸張側油室に流入させる再生油路と、前記油圧ポンプが吐出する作動油の吐出流量を制御して前記ポンプ供給油の供給流量を調整する制御装置と、を備え、前記制御装置は、ブーム下げ操作が行われた場合、前記ブームシリンダに作用する推力に応じて前記吐出流量を決定し、前記伸張側油室の圧力を所定圧以上としながら前記再生油の再生流量を最大化する。 A shovel according to an embodiment of the present invention includes a boom cylinder that receives at least a part of hydraulic oil discharged from a hydraulic pump as pump supply oil, and a part of the hydraulic oil that flows out from a contraction-side oil chamber of the boom cylinder. A regenerative oil passage that flows into the extension side oil chamber, and a control device that controls the discharge flow rate of the hydraulic oil discharged from the hydraulic pump to adjust the supply flow rate of the pump supply oil, and the control device includes: When a boom lowering operation is performed, the discharge flow rate is determined according to the thrust acting on the boom cylinder, and the regeneration flow rate of the regenerated oil is maximized while keeping the pressure in the extension side oil chamber at or above a predetermined pressure.
　上述の手段により、ブーム下げ操作の際の再生効率を向上できるショベルが提供される。 The above-mentioned means provides an excavator that can improve the regeneration efficiency during the boom lowering operation.
本発明の実施例に係るショベルの構成例を示す側面図である。It is a side view which shows the structural example of the shovel which concerns on the Example of this invention. 図１のショベルに搭載される油圧回路の構成例を示す図である。It is a figure which shows the structural example of the hydraulic circuit mounted in the shovel of FIG. ブーム下げ操作が単独で行われたときの油圧回路の状態を示す図である。It is a figure which shows the state of the hydraulic circuit when boom lowering operation is performed independently. ブームシリンダに流出入する作動油の関係を示す図である。It is a figure which shows the relationship of the hydraulic fluid which flows in and flows in into a boom cylinder. ブーム下げ操作量と再生油路及び戻り油路のそれぞれの流路面積との対応関係の一例を示す図である。It is a figure which shows an example of the correspondence of the boom lowering operation amount and each flow path area of a regeneration oil path and a return oil path. 吐出流量とブームシリンダ流入流量、再生流量、及びブームロッド圧のそれぞれとの関係を示すグラフである。It is a graph which shows the relationship with each of discharge flow volume, boom cylinder inflow flow, regeneration flow, and boom rod pressure. 吐出流量最適化処理の一例の流れを示すフローチャートである。It is a flowchart which shows the flow of an example of a discharge flow volume optimization process. ブーム下げ操作が単独で行われるときの各種パラメータの時間的推移を示すグラフである。It is a graph which shows the time transition of various parameters when boom lowering operation is performed independently.
　図１は、本発明の実施例に係る作業機械の構成例を示す側面図である。図１において、作業機械としてのショベル（掘削機）１は、クローラ式の下部走行体２の上に、旋回機構を介して、上部旋回体３をＸ軸周りに旋回自在に搭載している。 FIG. 1 is a side view showing a configuration example of a work machine according to an embodiment of the present invention. In FIG. 1, an excavator (excavator) 1 as a work machine has an upper swing body 3 mounted on a crawler-type lower traveling body 2 via a swing mechanism so as to be rotatable around the X axis.
　また、上部旋回体３は、前方中央部に掘削アタッチメントを備える。掘削アタッチメントは、ブーム４、アーム５、及び、バケット６を含み、且つ、油圧アクチュエータとしてのブームシリンダ７、アームシリンダ８、及び、バケットシリンダ９を含む。 Also, the upper swing body 3 is provided with a drilling attachment at the front center. The excavation attachment includes a boom 4, an arm 5, and a bucket 6, and includes a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 as hydraulic actuators.
　図２は、図１のショベルに搭載される油圧回路の構成例を示す図である。なお、図２の破線は制御圧ラインを示し、図２の点線は電気信号ラインを示す。 FIG. 2 is a diagram showing a configuration example of a hydraulic circuit mounted on the excavator of FIG. In addition, the broken line of FIG. 2 shows a control pressure line, and the dotted line of FIG. 2 shows an electric signal line.
　油圧ポンプ１０Ｌ、１０Ｒは、エンジン、電動モータ等の駆動源によって駆動される可変容量型ポンプである。本実施例では、油圧ポンプ１０Ｌは、制御弁１１Ｌ～１５Ｌのそれぞれを連通するセンターバイパス油路３０Ｌを通じて作動油タンク２２まで作動油を循環させる。また、油圧ポンプ１０Ｌは、センターバイパス油路３０Ｌに平行に伸びるパラレル油路３１Ｌを通じて制御弁１１Ｌ～１５Ｌのそれぞれに作動油を供給可能である。同様に、油圧ポンプ１０Ｒは、制御弁１１Ｒ～１５Ｒのそれぞれを連通するセンターバイパス油路３０Ｒを通じて作動油タンク２２まで作動油を循環させる。また、油圧ポンプ１０Ｒは、センターバイパス油路３０Ｒに平行して伸びるパラレル油路３１Ｒを通じて制御弁１２Ｒ～１５Ｒのそれぞれに作動油を供給可能である。なお、以下では、油圧ポンプ１０Ｌ及び油圧ポンプ１０Ｒは、集合的に「油圧ポンプ１０」として参照される場合もある。左右一対で構成される他の構成要素についても同様である。 Hydraulic pumps 10L and 10R are variable displacement pumps driven by a drive source such as an engine or an electric motor. In this embodiment, the hydraulic pump 10L circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass oil passage 30L that communicates each of the control valves 11L to 15L. The hydraulic pump 10L can supply hydraulic oil to each of the control valves 11L to 15L through a parallel oil passage 31L extending in parallel to the center bypass oil passage 30L. Similarly, the hydraulic pump 10R circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass oil passage 30R that communicates each of the control valves 11R to 15R. The hydraulic pump 10R can supply hydraulic oil to each of the control valves 12R to 15R through a parallel oil passage 31R extending in parallel with the center bypass oil passage 30R. Hereinafter, the hydraulic pump 10L and the hydraulic pump 10R may be collectively referred to as the “hydraulic pump 10”. The same applies to the other components configured by a pair of left and right.
　制御弁１１Ｌは、操作装置としての左側走行レバー（図示せず。）が操作された場合に、油圧ポンプ１０Ｌが吐出する作動油を油圧アクチュエータとしての左側走行用油圧モータ４２Ｌに供給するために作動油の流れを切り替えるスプール弁である。 The control valve 11L operates to supply hydraulic oil discharged from the hydraulic pump 10L to the left traveling hydraulic motor 42L as a hydraulic actuator when a left traveling lever (not shown) as an operation device is operated. It is a spool valve that switches the flow of oil.
　制御弁１１Ｒは、走行直進弁としてのスプール弁である。本実施例では、走行直進弁１１Ｒは、４ポート２位置のスプール弁であり、第１弁位置及び第２弁位置を有する。具体的には、第１弁位置は、油圧ポンプ１０Ｌとパラレル油路３１Ｌとを連通する流路と、油圧ポンプ１０Ｒと制御弁１２Ｒとを連通する流路と有する。また、第２弁位置は、油圧ポンプ１０Ｒとパラレル油路３１Ｌとを連通する流路と、油圧ポンプ１０Ｌと制御弁１２Ｒとを連通する流路とを有する。 The control valve 11R is a spool valve as a traveling straight valve. In the present embodiment, the straight travel valve 11R is a 4-port 2-position spool valve, and has a first valve position and a second valve position. Specifically, the first valve position has a flow path that connects the hydraulic pump 10L and the parallel oil path 31L, and a flow path that connects the hydraulic pump 10R and the control valve 12R. Further, the second valve position has a flow path that connects the hydraulic pump 10R and the parallel oil path 31L, and a flow path that connects the hydraulic pump 10L and the control valve 12R.
　制御弁１２Ｌは、油圧ポンプ１０が吐出する作動油をオプションの油圧アクチュエータ（図示せず。）に供給するために作動油の流れを切り替えるスプール弁である。 The control valve 12L is a spool valve that switches the flow of hydraulic oil to supply hydraulic oil discharged from the hydraulic pump 10 to an optional hydraulic actuator (not shown).
　制御弁１２Ｒは、操作装置としての右側走行レバー（図示せず。）が操作された場合に、油圧ポンプ１０が吐出する作動油を油圧アクチュエータとしての右側走行用油圧モータ４２Ｒに供給するために作動油の流れを切り替えるスプール弁である。 The control valve 12R operates to supply hydraulic oil discharged from the hydraulic pump 10 to the right traveling hydraulic motor 42R as a hydraulic actuator when a right traveling lever (not shown) as an operating device is operated. It is a spool valve that switches the flow of oil.
　制御弁１３Ｌは、操作装置としての旋回操作レバー（図示せず。）が操作された場合に、油圧ポンプ１０が吐出する作動油を油圧アクチュエータとしての旋回用油圧モータ４４に供給するために作動油の流れを切り替えるスプール弁である。 The control valve 13L is hydraulic oil for supplying hydraulic oil discharged from the hydraulic pump 10 to the hydraulic hydraulic motor 44 for rotation as a hydraulic actuator when a swing operation lever (not shown) as an operation device is operated. It is a spool valve that switches the flow of the.
　制御弁１３Ｒは、操作装置としてのバケット操作レバー（図示せず。）が操作された場合に、油圧ポンプ１０が吐出する作動油をバケットシリンダ９へ供給するために作動油の流れを切り替えるスプール弁である。 The control valve 13R is a spool valve that switches the flow of hydraulic oil to supply hydraulic oil discharged from the hydraulic pump 10 to the bucket cylinder 9 when a bucket operating lever (not shown) as an operating device is operated. It is.
　制御弁１４Ｌ、１４Ｒは、操作装置としてのブーム操作レバー（図示せず。）が操作された場合に、油圧ポンプ１０が吐出する作動油をブームシリンダ７へ供給するために作動油の流れを切り替えるスプール弁である。なお、制御弁１４Ｌは、ブーム操作レバーが所定のレバー操作量以上でブーム上げ方向に操作された場合に、作動油を追加的にブームシリンダ７に供給する。 The control valves 14 </ b> L and 14 </ b> R switch the flow of hydraulic oil to supply the hydraulic oil discharged from the hydraulic pump 10 to the boom cylinder 7 when a boom operation lever (not shown) as an operation device is operated. It is a spool valve. The control valve 14L additionally supplies hydraulic oil to the boom cylinder 7 when the boom operation lever is operated in the boom raising direction with a predetermined lever operation amount or more.
　制御弁１５Ｌ、１５Ｒは、操作装置としてのアーム操作レバー（図示せず。）が操作された場合に、油圧ポンプ１０が吐出する作動油をアームシリンダ８へ供給するために作動油の流れを切り替えるスプール弁である。なお、制御弁１５Ｒは、アーム操作レバーが所定のレバー操作量以上で操作された場合に、作動油を追加的にアームシリンダ８に供給する。 The control valves 15L and 15R switch the flow of hydraulic oil so as to supply hydraulic oil discharged from the hydraulic pump 10 to the arm cylinder 8 when an arm operation lever (not shown) as an operation device is operated. It is a spool valve. The control valve 15R additionally supplies hydraulic oil to the arm cylinder 8 when the arm operation lever is operated at a predetermined lever operation amount or more.
　センターバイパス油路３０Ｌ、３０Ｒはそれぞれ、最も下流にある制御弁１５Ｌ、１５Ｒと作動油タンク２２との間にネガティブコントロール絞り２０Ｌ、２０Ｒを備える。なお、以下では、ネガティブコントロールを「ネガコン」と略称する。ネガコン絞り２０Ｌ、２０Ｒは、油圧ポンプ１０Ｌ、１０Ｒが吐出する作動油の流れを制限してネガコン絞り２０Ｌ、２０Ｒの上流でネガコン圧を発生させる。 The center bypass oil passages 30L and 30R are respectively provided with negative control throttles 20L and 20R between the control valves 15L and 15R located on the most downstream side and the hydraulic oil tank 22. Hereinafter, the negative control is abbreviated as “negative control”. The negative control throttles 20L and 20R generate a negative control pressure upstream of the negative control throttles 20L and 20R by limiting the flow of hydraulic oil discharged from the hydraulic pumps 10L and 10R.
　圧力センサＳ１、Ｓ２は、ネガコン絞り２０Ｌ、２０Ｒの上流で発生したネガコン圧を検出し、検出した値を電気的なネガコン圧信号としてコントローラ５４に対して出力する。 The pressure sensors S1 and S2 detect the negative control pressure generated upstream of the negative control throttles 20L and 20R, and output the detected value to the controller 54 as an electrical negative control pressure signal.
　圧力センサＳ３、Ｓ４は、油圧ポンプ１０Ｌ、１０Ｒの吐出圧を検出し、検出した値を電気的な吐出圧信号としてコントローラ５４に対して出力する。 Pressure sensors S3 and S4 detect the discharge pressures of the hydraulic pumps 10L and 10R, and output the detected values to the controller 54 as electrical discharge pressure signals.
　圧力センサＳ５は、ブームシリンダ７のロッド側油室における作動油の圧力を検出し、検出した値を電気的なブームロッド圧信号としてコントローラ５４に対して出力する。また、圧力センサＳ６は、ブームシリンダ７のボトム側油室における作動油の圧力を検出し、検出した値を電気的なブームボトム圧信号としてコントローラ５４に対して出力する。 The pressure sensor S5 detects the pressure of the hydraulic oil in the rod side oil chamber of the boom cylinder 7, and outputs the detected value to the controller 54 as an electric boom rod pressure signal. The pressure sensor S6 detects the pressure of the hydraulic oil in the bottom side oil chamber of the boom cylinder 7, and outputs the detected value to the controller 54 as an electric boom bottom pressure signal.
　なお、左側走行レバー、右側走行レバー、アーム操作レバー、旋回操作レバー、ブーム操作レバー、バケット操作レバー等の操作装置には操作内容検出部が取り付けられる。操作内容検出部は、例えば、各操作装置が生成するパイロット圧を検出する圧力センサ（図示せず。）である。これら圧力センサは、検出した値を電気的なパイロット圧信号としてコントローラ５４に対して出力する。 Note that an operation content detection unit is attached to operation devices such as a left travel lever, a right travel lever, an arm operation lever, a turning operation lever, a boom operation lever, and a bucket operation lever. The operation content detection unit is, for example, a pressure sensor (not shown) that detects a pilot pressure generated by each operation device. These pressure sensors output the detected value to the controller 54 as an electrical pilot pressure signal.
　コントローラ５４は、油圧回路を制御する機能要素であり、例えば、ＣＰＵ、ＲＡＭ、ＲＯＭ、ＮＶＲＡＭ等を備えたコンピュータである。本実施例では、コントローラ５４は、圧力センサ等の操作内容検出部の出力に基づいて各種操作装置の操作内容（例えば、レバー操作の有無、レバー操作方向、レバー操作量等である。）を電気的に検出する。なお、操作内容検出部は、各種操作レバーの傾きを検出する傾きセンサ等、圧力センサ以外のセンサで構成されてもよい。 The controller 54 is a functional element that controls the hydraulic circuit, and is, for example, a computer including a CPU, RAM, ROM, NVRAM, and the like. In this embodiment, the controller 54 electrically operates the operation contents (for example, presence / absence of lever operation, lever operation direction, lever operation amount, etc.) of various operation devices based on the output of the operation content detection unit such as a pressure sensor. Detect. Note that the operation content detection unit may be configured by a sensor other than the pressure sensor, such as an inclination sensor that detects the inclination of various operation levers.
　そして、コントローラ５４は、各種操作装置の操作内容に応じてポンプレギュレータ４０Ｌ、４０Ｒ等を動作させる各種機能要素に対応するプログラムをＣＰＵに実行させる。 Then, the controller 54 causes the CPU to execute programs corresponding to various functional elements that operate the pump regulators 40L, 40R and the like according to the operation contents of the various operation devices.
　ポンプレギュレータ４０Ｌ、４０Ｒは、油圧ポンプ１０Ｌ、１０Ｒの吐出流量を制御する機構である。本実施例では、ポンプレギュレータ４０Ｌ、４０Ｒは、コントローラ５４が生成する指令に応じて油圧ポンプ１０Ｌ、１０Ｒの斜板傾転角を調整して油圧ポンプ１０Ｌ、１０Ｒの吐出流量を制御する。 The pump regulators 40L and 40R are mechanisms for controlling the discharge flow rates of the hydraulic pumps 10L and 10R. In the present embodiment, the pump regulators 40L and 40R control the discharge flow rates of the hydraulic pumps 10L and 10R by adjusting the swash plate tilt angles of the hydraulic pumps 10L and 10R according to the commands generated by the controller 54.
　例えば、ショベル１における油圧アクチュエータが何れも操作されていない状態では、油圧ポンプ１０Ｌ、１０Ｒが吐出する作動油は、センターバイパス油路３０Ｌ、３０Ｒを通ってネガコン絞り２０Ｌ、２０Ｒに至り、ネガコン絞り２０Ｌ、２０Ｒの上流で発生するネガコン圧を増大させる。この場合、ポンプレギュレータ４０Ｌ、４０Ｒは、ネガコン圧信号に基づいてコントローラ５４が生成する指令に応じて油圧ポンプ１０Ｌ、１０Ｒの吐出流量を低減させる。その結果、油圧ポンプ１０Ｌ、１０Ｒが吐出する作動油がセンターバイパス油路３０Ｌ、３０Ｒを通過する際の圧力損失（ポンピングロス）が抑制される。 For example, when none of the hydraulic actuators in the excavator 1 is operated, the hydraulic oil discharged from the hydraulic pumps 10L and 10R passes through the center bypass oil passages 30L and 30R to the negative control throttles 20L and 20R, and the negative control throttle 20L. , Increase negative control pressure generated upstream of 20R. In this case, the pump regulators 40L and 40R reduce the discharge flow rates of the hydraulic pumps 10L and 10R according to a command generated by the controller 54 based on the negative control pressure signal. As a result, pressure loss (pumping loss) when hydraulic oil discharged from the hydraulic pumps 10L and 10R passes through the center bypass oil passages 30L and 30R is suppressed.
　一方、何れかの油圧アクチュエータが操作された場合、油圧ポンプ１０Ｌ、１０Ｒが吐出する作動油は、その油圧アクチュエータに対応する制御弁を介してその油圧アクチュエータに流れ込む。そのため、ネガコン絞り２０Ｌ、２０Ｒに至る量は減少或いは消滅し、ネガコン絞り２０Ｌ、２０Ｒの上流で発生するネガコン圧は低下する。この場合、ポンプレギュレータ４０Ｌ、４０Ｒは、油圧ポンプ１０Ｌ、１０Ｒの吐出流量を増大させ、各油圧アクチュエータに十分な作動油を循環させ、各アクチュエータの駆動を確かなものとする。 On the other hand, when one of the hydraulic actuators is operated, the hydraulic oil discharged from the hydraulic pumps 10L and 10R flows into the hydraulic actuator via a control valve corresponding to the hydraulic actuator. Therefore, the amount reaching the negative control throttles 20L and 20R decreases or disappears, and the negative control pressure generated upstream of the negative control throttles 20L and 20R decreases. In this case, the pump regulators 40L and 40R increase the discharge flow rates of the hydraulic pumps 10L and 10R, circulate sufficient hydraulic oil to each hydraulic actuator, and ensure the driving of each actuator.
　また、油圧ポンプ１０Ｌ、１０Ｒの吐出圧が、吐出流量に応じて決まる所定値を上回った場合、ポンプレギュレータ４０Ｌ、４０Ｒは、吐出圧信号に基づいてコントローラ５４が生成する指令に応じて油圧ポンプ１０Ｌ、１０Ｒの吐出流量を低減させる。油圧ポンプ１０Ｌ、１０Ｒの吸収馬力が駆動源としてのエンジンの出力馬力を上回るのを防止するためである。 Further, when the discharge pressures of the hydraulic pumps 10L and 10R exceed a predetermined value determined according to the discharge flow rate, the pump regulators 40L and 40R cause the hydraulic pump 10L to respond to a command generated by the controller 54 based on the discharge pressure signal. The discharge flow rate of 10R is reduced. This is to prevent the absorption horsepower of the hydraulic pumps 10L and 10R from exceeding the output horsepower of the engine as the drive source.
　なお、ポンプレギュレータ４０Ｌ、４０Ｒは、ネガコン絞り２０Ｌ、２０Ｒの上流のネガコン圧、油圧ポンプ１０Ｌの吐出圧、及び油圧ポンプ１０Ｒの吐出圧を利用して、油圧ポンプ１０Ｌ、１０Ｒの吐出流量を油圧的に制御してもよい。 The pump regulators 40L and 40R use the negative control pressure upstream of the negative control throttles 20L and 20R, the discharge pressure of the hydraulic pump 10L, and the discharge pressure of the hydraulic pump 10R to hydraulically control the discharge flow rates of the hydraulic pumps 10L and 10R. You may control to.
　次に、図３を参照してブーム下げ操作が単独で行われた場合の油圧回路の状態について説明する。なお、図３は、ブーム下げ操作が単独で行われた場合の油圧回路の状態を示す図であり、図２に対応する。また、本実施例では、ブーム下げ操作は、掘削アタッチメントを空中で動かす際にブーム４を下降させるための操作を意味する。また、図３の太実線はブームシリンダ７に向かう作動油の流れを表し、図３の太点線は作動油タンク２２に向かう作動油の流れを表す。また、本実施例では、ブーム下げ操作はフルレバー操作で行われる。「フルレバー操作」は、所定の操作量以上で行われるレバー操作を意味し、所定の操作量は例えば８０％以上の操作量である。なお、操作量１００％は操作レバーを最大限傾斜させたときの操作量に対応し、操作量０％は操作レバーを中立にしたとき（操作レバーを操作していないとき）の操作量に対応する。 Next, the state of the hydraulic circuit when the boom lowering operation is performed alone will be described with reference to FIG. FIG. 3 is a diagram illustrating a state of the hydraulic circuit when the boom lowering operation is performed independently, and corresponds to FIG. In the present embodiment, the boom lowering operation means an operation for lowering the boom 4 when the excavation attachment is moved in the air. 3 represents the flow of hydraulic oil toward the boom cylinder 7, and the thick dotted line in FIG. 3 represents the flow of hydraulic oil toward the hydraulic oil tank 22. In the present embodiment, the boom lowering operation is performed by a full lever operation. “Full lever operation” means a lever operation performed with a predetermined operation amount or more, and the predetermined operation amount is, for example, an operation amount of 80% or more. The operation amount 100% corresponds to the operation amount when the operation lever is tilted to the maximum, and the operation amount 0% corresponds to the operation amount when the operation lever is neutral (when the operation lever is not operated). To do.
　具体的には、ブーム操作レバーが下げ方向に操作されると、制御弁１４Ｒは、図の右側のパイロットポートでパイロット圧を受けて図の左側に移動する。 Specifically, when the boom operation lever is operated in the downward direction, the control valve 14R receives the pilot pressure at the pilot port on the right side of the figure and moves to the left side of the figure.
　制御弁１４Ｒが左に移動するとセンターバイパス油路３０Ｒが遮断されるため、油圧ポンプ１０Ｒが吐出する作動油はパラレル油路３１Ｒを通って制御弁１４Ｒに向かう。そして、パラレル油路３１Ｒの作動油は、制御弁１４Ｒを通じてブームシリンダ７のロッド側油室に流入する。また、ブームシリンダ７のボトム側油室から流出する作動油の一部は、制御弁１４Ｒ内に形成された再生油路３３を通じてパラレル油路３１Ｒからの作動油と合流してブームシリンダ７のロッド側油室に流入する。また、ブームシリンダ７のボトム側油室から流出する作動油の残りの部分は、制御弁１４Ｒ内に形成された戻り油路３４を通じて作動油タンク２２に排出される。 When the control valve 14R moves to the left, the center bypass oil passage 30R is cut off, so that the hydraulic oil discharged by the hydraulic pump 10R passes through the parallel oil passage 31R toward the control valve 14R. Then, the hydraulic oil in the parallel oil passage 31R flows into the rod side oil chamber of the boom cylinder 7 through the control valve 14R. Further, a part of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 merges with the hydraulic oil from the parallel oil passage 31R through the regeneration oil passage 33 formed in the control valve 14R, and the rod of the boom cylinder 7 It flows into the side oil chamber. Further, the remaining portion of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is discharged to the hydraulic oil tank 22 through a return oil passage 34 formed in the control valve 14R.
　次に、図４を参照し、ブーム下げ操作が単独で行われた場合におけるブームシリンダ７に作用する推力Ｆ、油圧ポンプ１０Ｒの吐出流量Ｑｐ、再生油路３３の再生流量Ｑｇ、及び戻り油路３４の戻り流量Ｑｃの関係について説明する。なお、図４は、ブームシリンダ７に流出入する作動油の関係を示す図である。 Next, referring to FIG. 4, the thrust F acting on the boom cylinder 7 when the boom lowering operation is performed alone, the discharge flow rate Qp of the hydraulic pump 10R, the regeneration flow rate Qg of the regeneration oil passage 33, and the return oil passage The relationship of the return flow rate Qc of 34 will be described. FIG. 4 is a diagram showing the relationship of hydraulic oil flowing into and out of the boom cylinder 7.
　ブームシリンダ７内を摺動するピストンのロッド側の受圧面積をＡｒとし、ボトム側の受圧面積をＡｂとし、ロッド側油室の圧力をブームロッド圧Ｐｒとし、ボトム側油室の圧力をブームボトム圧Ｐｂとすると、ブームシリンダ７に作用する推力Ｆは、以下の式（１）で表される。 The pressure receiving area on the rod side of the piston sliding in the boom cylinder 7 is Ar, the pressure receiving area on the bottom side is Ab, the pressure in the rod side oil chamber is the boom rod pressure Pr, and the pressure in the bottom side oil chamber is the boom bottom. When the pressure is Pb, the thrust F acting on the boom cylinder 7 is expressed by the following equation (1).
Figure JPOXMLDOC01-appb-M000001
 　
また、式（１）は以下の式（２）で書き換えられる。
Figure JPOXMLDOC01-appb-M000001
Further, the formula (1) can be rewritten by the following formula (2).
Figure JPOXMLDOC01-appb-M000002
 　また、再生油路３３が構成する絞りの前後の差圧をΔＰ（＝Ｐｂ－Ｐｒ）とし、作動油の密度をρとし、再生油路３３の流路面積（絞り断面）をＡｇとし、作動油の流出係数をＣとすると、再生油路３３の再生流量Ｑｇは、以下の式（３）で表される。
Figure JPOXMLDOC01-appb-M000002
 Further, the differential pressure before and after the throttle formed by the regenerated oil passage 33 is ΔP (= Pb−Pr), the density of the hydraulic oil is ρ, and the flow passage area (throttle section) of the regenerated oil passage 33 is Ag. When the oil outflow coefficient is C, the regeneration flow rate Qg of the regeneration oil passage 33 is expressed by the following equation (3).
Figure JPOXMLDOC01-appb-M000003
 　ここで、式（４）で示す第１絞り係数Ｃｇを用いると、式（３）は以下の式（５）で書き換えられる。
Figure JPOXMLDOC01-appb-M000003
 Here, when the first aperture coefficient Cg shown by the equation (4) is used, the equation (3) can be rewritten by the following equation (5).
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000005
 　同様に、戻り油路３４の下流の圧力をＰｔとし、戻り油路３４を構成する絞りの前後の差圧をΔＰ（＝Ｐｂ－Ｐｔ）とし、作動油の密度をρとし、戻り油路３４の流路面積（絞り断面）をＡｃとし、作動油の流出係数をＣとすると、戻り油路３４の戻り流量Ｑｃは、以下の式（６）で表される。
Figure JPOXMLDOC01-appb-M000005
 Similarly, the pressure downstream of the return oil passage 34 is Pt, the differential pressure before and after the throttle constituting the return oil passage 34 is ΔP (= Pb−Pt), the hydraulic oil density is ρ, and the return oil passage 34 If the flow area (throttle section) is Ac and the hydraulic oil outflow coefficient is C, the return flow rate Qc of the return oil path 34 is expressed by the following equation (6).
Figure JPOXMLDOC01-appb-M000006
 　ここで、式（７）で示す第２絞り係数Ｃｃを用いると、式（６）は以下の式（８）で書き換えられる。
Figure JPOXMLDOC01-appb-M000006
 Here, when the second aperture coefficient Cc shown by the equation (7) is used, the equation (6) can be rewritten by the following equation (8).
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000008
 　なお、再生油路３３の流路面積Ａｇと戻り油路３４の流路面積Ａｃは、ブーム操作レバーの下げ方向へのレバー操作量（以下、「ブーム下げ操作量」とする。）に応じて一意に決まる値である。図５は、ブーム下げ操作量と流路面積Ａｇ及び流路面積Ａｃのそれぞれとの対応関係の一例を示す。具体的には、流路面積Ａｇ及び流路面積Ａｃは何れもブーム下げ操作量が大きいほど大きくなる。例えば、ブーム下げ操作量が１００％（最大レバー操作量）の場合、流路面積Ａｇは最大値Ａｇｍａｘとなり、流路面積Ａｃは最大値Ａｃｍａｘとなる。
Figure JPOXMLDOC01-appb-M000008
 The flow passage area Ag of the regenerative oil passage 33 and the flow passage area Ac of the return oil passage 34 correspond to a lever operation amount in the direction in which the boom operation lever is lowered (hereinafter referred to as a “boom lowering operation amount”). This value is uniquely determined. FIG. 5 shows an example of a correspondence relationship between the boom lowering operation amount and each of the flow path area Ag and the flow path area Ac. Specifically, both the flow path area Ag and the flow path area Ac increase as the boom lowering operation amount increases. For example, when the boom lowering operation amount is 100% (maximum lever operation amount), the flow path area Ag is the maximum value Agmax, and the flow path area Ac is the maximum value Acmax.
　そのため、本実施例では、第１絞り係数Ｃｇ及び第２絞り係数Ｃｃとブーム下げ操作量との対応関係は式（４）及び式（７）に基づいて予め導き出され、コントローラ５４のＲＯＭ等に対応テーブルの形で予め記憶される。したがって、コントローラ５４は、ブーム下げ操作量が決まれば第１絞り係数Ｃｇ及び第２絞り係数Ｃｃのそれぞれを一意に決定できる。 Therefore, in this embodiment, the correspondence relationship between the first diaphragm coefficient Cg and the second diaphragm coefficient Cc and the boom lowering operation amount is derived in advance based on the equations (4) and (7), and is stored in the ROM of the controller 54 or the like. Pre-stored in the form of a correspondence table. Therefore, the controller 54 can uniquely determine each of the first aperture coefficient Cg and the second aperture coefficient Cc when the boom lowering operation amount is determined.
　また、ブームシリンダ７のロッド側油室に流入する作動油の流量をブームシリンダ流入流量Ｑｓとし、ブームシリンダ７のボトム側油室から流出する作動油の流量を排出流量Ｑｅとすると、排出流量Ｑｅは、以下の式（９）で表される。 Further, assuming that the flow rate of the hydraulic oil flowing into the rod side oil chamber of the boom cylinder 7 is the boom cylinder inflow rate Qs and the flow rate of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is the discharge flow rate Qe, the discharge flow rate Qe Is represented by the following formula (9).
Figure JPOXMLDOC01-appb-M000009
 　そして、ブームシリンダ流入流量Ｑｓは再生流量Ｑｇと油圧ポンプ１０Ｒの吐出流量Ｑｐの和であり、排出流量Ｑｅは再生流量Ｑｇと戻り流量Ｑｃの和であるとすると、式（９）は以下の式（１０）で書き換えられる。
Figure JPOXMLDOC01-appb-M000009
 When the boom cylinder inflow flow rate Qs is the sum of the regeneration flow rate Qg and the discharge flow rate Qp of the hydraulic pump 10R, and the discharge flow rate Qe is the sum of the regeneration flow rate Qg and the return flow rate Qc, the equation (9) is It is rewritten by (10).
Figure JPOXMLDOC01-appb-M000010
 　次に、図６を参照し、ブーム操作レバーを下げ方向にフルレバー操作した場合における吐出流量Ｑｐと、ブームシリンダ流入流量Ｑｓ、再生流量Ｑｇ、及びブームロッド圧Ｐｒのそれぞれとの関係について説明する。図６は、ブーム操作レバーを下げ方向にフルレバー操作した場合における吐出流量Ｑｐと、ブームシリンダ流入流量Ｑｓ、再生流量Ｑｇ、及びブームロッド圧Ｐｒのそれぞれとの関係を示すグラフである。具体的には、図６（Ａ）は、吐出流量Ｑｐとブームシリンダ流入流量Ｑｓとの関係を示すグラフである。また、図６（Ｂ）は吐出流量Ｑｐと再生流量Ｑｇとの関係を示すグラフであり、図６（Ｃ）は吐出流量Ｑｐとブームロッド圧Ｐｒとの関係を示すグラフである。なお、図６（Ａ）～図６（Ｃ）では吐出流量Ｑｐに対応する横軸は共通である。また、図６（Ａ）～図６（Ｃ）において、実線で示す推移は、ブームシリンダ７を収縮させようとする外力が大きい場合の推移を表す。また、破線で示す推移は外力が中程度の場合の推移を表し、一点鎖線で示す推移は外力が小さい場合の推移を表す。なお、ブームシリンダ７を収縮させようとする外力は、バケット６内の土砂の量、ショベル１の姿勢（傾斜地にあるか平坦地にあるか）、掘削アタッチメントの姿勢等によって変化する。
Figure JPOXMLDOC01-appb-M000010
 Next, the relationship between the discharge flow rate Qp and the boom cylinder inflow rate Qs, the regeneration flow rate Qg, and the boom rod pressure Pr when the boom control lever is fully operated in the lowering direction will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the discharge flow rate Qp, the boom cylinder inflow rate Qs, the regeneration flow rate Qg, and the boom rod pressure Pr when the boom operation lever is fully operated in the downward direction. Specifically, FIG. 6A is a graph showing the relationship between the discharge flow rate Qp and the boom cylinder inflow rate Qs. FIG. 6B is a graph showing the relationship between the discharge flow rate Qp and the regeneration flow rate Qg, and FIG. 6C is a graph showing the relationship between the discharge flow rate Qp and the boom rod pressure Pr. In FIGS. 6A to 6C, the horizontal axis corresponding to the discharge flow rate Qp is common. 6A to 6C, the transition indicated by the solid line represents the transition when the external force for contracting the boom cylinder 7 is large. A transition indicated by a broken line represents a transition when the external force is medium, and a transition indicated by a one-dot chain line represents a transition when the external force is small. The external force for contracting the boom cylinder 7 varies depending on the amount of earth and sand in the bucket 6, the position of the shovel 1 (whether it is on an inclined land or a flat ground), the position of the excavation attachment, and the like.
　具体的には、図６（Ａ）に示すように、ブーム操作レバーを下げ方向にフルレバー操作した場合、すなわち、戻り油路３４の流路面積Ａｃを最大値Ａｃｍａｘとした場合、ブームシリンダ流入流量Ｑｓは、吐出流量Ｑｐの大きさにかかわらず、外力が大きいほど大きくなる。 Specifically, as shown in FIG. 6A, when the boom operating lever is fully operated in the downward direction, that is, when the flow passage area Ac of the return oil passage 34 is set to the maximum value Acmax, the boom cylinder inflow rate Regardless of the magnitude of the discharge flow rate Qp, Qs increases as the external force increases.
　一方で、ブームシリンダ流入流量Ｑｓは、外力が一定であれば、吐出流量Ｑｐの大きさにかかわらずほぼ一定となる。すなわち、吐出流量Ｑｐを増大させたとしても、ブームシリンダ流入流量Ｑｓは増大せず、ブーム下げ速度も増大しない。図６（Ｂ）に示すように、再生流量Ｑｇは、外力の大きさにかかわらず、吐出流量Ｑｐが増大するにつれて減少するためである。 On the other hand, if the external force is constant, the boom cylinder inflow flow rate Qs is substantially constant regardless of the magnitude of the discharge flow rate Qp. That is, even if the discharge flow rate Qp is increased, the boom cylinder inflow rate Qs does not increase, and the boom lowering speed does not increase. As shown in FIG. 6B, the regeneration flow rate Qg decreases as the discharge flow rate Qp increases regardless of the magnitude of the external force.
　そのため、吐出流量Ｑｐを減少させれば、ブームシリンダ流入流量Ｑｓを減少させることなく、再生流量Ｑｇを増大させることができる。 Therefore, if the discharge flow rate Qp is decreased, the regeneration flow rate Qg can be increased without decreasing the boom cylinder inflow rate Qs.
　しかしながら、図６（Ｃ）に示すように、ブームロッド圧Ｐｒは、外力の大きさにかかわらず、吐出流量Ｑｐが減少するにつれて低下する傾向を有する。そのため、吐出流量Ｑｐを過度に減少させると、ブームロッド圧Ｐｒを過度に低下させてしまい、キャビテーションを発生させてしまうおそれがある。 However, as shown in FIG. 6C, the boom rod pressure Pr has a tendency to decrease as the discharge flow rate Qp decreases regardless of the magnitude of the external force. Therefore, if the discharge flow rate Qp is excessively decreased, the boom rod pressure Pr is excessively decreased, and cavitation may occur.
　また、図６（Ｃ）に示すように、ブームロッド圧Ｐｒは、吐出流量Ｑｐが一定であれば、外力が大きいほど低くなる。すなわち、ブームロッド圧Ｐｒは、外力が大きければ、吐出流量Ｑｐが比較的大きい場合であっても、キャビテーションを発生させるレベルまで低下してしまうおそれがある。 Further, as shown in FIG. 6C, the boom rod pressure Pr becomes lower as the external force becomes larger if the discharge flow rate Qp is constant. That is, if the external force is large, the boom rod pressure Pr may be lowered to a level that causes cavitation even when the discharge flow rate Qp is relatively large.
　このように、吐出流量Ｑｐの低減は再生流量Ｑｇの増大を実現でき、省エネルギ化を図る上で有効である。しかしながら、キャビテーションを発生させることなく再生流量Ｑｇを最大化させるために必要な吐出流量Ｑｐは外力の大きさによって異なるため、吐出流量Ｑｐを無制限に低減させることはできない。 Thus, the reduction of the discharge flow rate Qp can realize the increase of the regeneration flow rate Qg, and is effective in achieving energy saving. However, since the discharge flow rate Qp necessary for maximizing the regeneration flow rate Qg without generating cavitation varies depending on the magnitude of the external force, the discharge flow rate Qp cannot be reduced indefinitely.
　そこで、コントローラ５４は、ブームロッド圧Ｐｒが所定の目標圧Ｐｔｇとなるように吐出流量Ｑｐを決定し、キャビテーションを発生させない限りにおいて、再生流量Ｑｇができるだけ大きくなるようにする。なお、所定の目標圧Ｐｔｇは、キャビテーションを発生させるおそれのないレベルの圧力であり、例えば４［ＭＰａ］である。 Therefore, the controller 54 determines the discharge flow rate Qp so that the boom rod pressure Pr becomes the predetermined target pressure Ptg, and makes the regeneration flow rate Qg as large as possible unless cavitation is generated. The predetermined target pressure Ptg is a pressure at a level that does not cause cavitation, and is 4 [MPa], for example.
　図６（Ｃ）の例では、コントローラ５４は、ブームロッド圧Ｐｒを目標圧Ｐｔｇとするために、外力が小さいときの吐出流量ＱｐをＱｐＬとする。また、コントローラ５４は、外力が中程度のときの吐出流量ＱｐをＱｐＭ（＞ＱｐＬ）とし、外力が大きいときの吐出流量ＱｐをＱｐＨ（＞ＱｐＭ）とする。 6C, the controller 54 sets the discharge flow rate Qp when the external force is small to QpL in order to set the boom rod pressure Pr to the target pressure Ptg. Further, the controller 54 sets the discharge flow rate Qp when the external force is medium to QpM (> QpL), and sets the discharge flow rate Qp when the external force is large to QpH (> QpM).
　そして、外力が小さいときの吐出流量ＱｐがＱｐＬに決定されると、外力が小さいときの再生流量ＱｇはＱｇＬとなり、ブームシリンダ流入流量ＱｓはＱｓＬ（＝ＱｇＬ＋ＱｐＬ）となる。また、外力が中程度のときの吐出流量ＱｐがＱｐＭに決定されると、外力が中程度のときの再生流量ＱｇはＱｇＭ（＞ＱｇＬ）となり、ブームシリンダ流入流量ＱｓはＱｓＭ（＝ＱｇＭ＋ＱｐＭ＞ＱｓＬ）となる。また、外力が大きいときの吐出流量ＱｐがＱｐＨに決定されると、外力が大きいときの再生流量ＱｇはＱｇＨ（＞ＱｇＭ）となり、ブームシリンダ流入流量ＱｓはＱｓＨ（＝ＱｇＨ＋ＱｐＨ＞ＱｓＭ）となる。 When the discharge flow rate Qp when the external force is small is determined to be QpL, the regeneration flow rate Qg when the external force is small becomes QgL, and the boom cylinder inflow flow rate Qs becomes QsL (= QgL + QpL). When the discharge flow rate Qp when the external force is medium is determined to be QpM, the regeneration flow rate Qg when the external force is medium becomes QgM (> QgL), and the boom cylinder inflow flow rate Qs is QsM (= QgM + QpM> QsL). ) When the discharge flow rate Qp when the external force is large is determined to be QpH, the regeneration flow rate Qg when the external force is large is QgH (> QgM), and the boom cylinder inflow flow rate Qs is QsH (= QgH + QpH> QsM).
　また、ブーム操作レバーが下げ方向にフルレバー操作された場合に外力の大きさに関係なく共通の吐出流量ＱｐＲを吐出していたときと比較すると、再生流量Ｑｇの増分は、外力が小さいときほど大きくなることが分かる。具体的には、再生流量Ｑｇの増分は、外力が大きいときにＤＨとなり、外力が中程度のときにＤＭ（＞ＤＨ）となり、外力が小さいときにＤＬ（＞ＤＭ）となる。また、共通の吐出流量ＱｐＲを吐出していたときには、外力が大きいほどブームロッド圧Ｐｒが小さくなることが分かる。一方で、吐出流量ＱｐをＱｐＲからＱｐＬ、ＱｐＭ、又はＱｐＨに低減させた場合であっても、外力が同じであれば、ブームシリンダ流入流量Ｑｓにはほとんど変化が見られないことが分かる。 Further, when the boom operating lever is fully operated in the lowering direction, the increase in the regeneration flow rate Qg is larger as the external force is smaller than when the common discharge flow rate QpR is discharged regardless of the magnitude of the external force. I understand that Specifically, the increase in the regeneration flow rate Qg is DH when the external force is large, DM (> DH) when the external force is medium, and DL (> DM) when the external force is small. It can also be seen that when the common discharge flow rate QpR is discharged, the boom rod pressure Pr decreases as the external force increases. On the other hand, even when the discharge flow rate Qp is reduced from QpR to QpL, QpM, or QpH, if the external force is the same, it can be seen that there is almost no change in the boom cylinder inflow rate Qs.
　次に、図７を参照し、コントローラ５４が油圧ポンプ１０Ｒの吐出流量Ｑｐを最適化する処理（以下、「吐出流量最適化処理」とする。）について説明する。なお、図７は、吐出流量最適化処理の一例の流れを示すフローチャートであり、コントローラ５４は、所定の制御周期でこの吐出流量最適化処理を繰り返し実行する。また、本実施例では、「吐出流量Ｑｐの最適化」は、キャビテーションを発生させない限りにおいて、再生流量Ｑｇを最大化させる吐出流量を実現することを意味する。 Next, a process in which the controller 54 optimizes the discharge flow rate Qp of the hydraulic pump 10R (hereinafter referred to as “discharge flow optimization process”) will be described with reference to FIG. FIG. 7 is a flowchart showing an exemplary flow of the discharge flow rate optimization process, and the controller 54 repeatedly executes the discharge flow rate optimization process at a predetermined control cycle. In the present embodiment, “optimization of the discharge flow rate Qp” means that the discharge flow rate that maximizes the regeneration flow rate Qg is realized as long as cavitation is not generated.
　最初に、コントローラ５４は、ブーム下げ操作中であるかを判定する（ステップＳＴ１）。本実施例では、コントローラ５４は、圧力センサ等の操作内容検出部の出力に基づいてブーム操作レバーの操作内容からブーム下げ操作中であるかを判定する。また、本実施例では、コントローラ５４は、ブーム操作レバーが単独で下げ方向にフルレバー操作されたことを検知した場合にブーム下げ操作中であると判定する。また、本実施例では、コントローラ５４は、掘削アタッチメントを掘削対象に押し付けていないと判断した場合、すなわち、掘削アタッチメントを空中で動かしていると判断した場合に、ブーム下げ操作中であると判定する。なお、コントローラ５４は、圧力センサＳ５が出力するブームロッド圧信号、及び、圧力センサＳ６が出力するブームボトム圧信号の少なくとも一方に基づいて掘削アタッチメントを掘削対象に押し付けているかを判断する。 First, the controller 54 determines whether a boom lowering operation is being performed (step ST1). In this embodiment, the controller 54 determines whether a boom lowering operation is being performed from the operation content of the boom operation lever based on the output of the operation content detection unit such as a pressure sensor. Further, in the present embodiment, the controller 54 determines that the boom lowering operation is being performed when it is detected that the boom operating lever has been operated alone in the lowering direction. In this embodiment, the controller 54 determines that the boom lowering operation is being performed when it is determined that the excavation attachment is not pressed against the excavation target, that is, when the excavation attachment is determined to be moving in the air. . The controller 54 determines whether or not the excavation attachment is pressed against the excavation target based on at least one of the boom rod pressure signal output from the pressure sensor S5 and the boom bottom pressure signal output from the pressure sensor S6.
　ブーム下げ操作中でないと判定した場合（ステップＳＴ１のＮＯ）、コントローラ５４は、今回の吐出流量最適化処理を終了させる。 If it is determined that the boom lowering operation is not being performed (NO in step ST1), the controller 54 ends the current discharge flow rate optimization process.
　ブーム下げ操作中であると判定した場合（ステップＳＴ１のＹＥＳ）、コントローラ５４は、ポンプレギュレータ４０Ｒに対する指令である第１指令値を導き出す（ステップＳＴ２）。本実施例では、コントローラ５４は、ネガコン圧信号に応じて第１指令値を導き出す。第１指令値は、ネガコン圧信号に応じて一意に決まる吐出流量指令値であり、ブーム下げ操作量が大きいほど大きい。具体的には、ブーム下げ操作量が大きいほど、制御弁１４Ｒの移動量が大きくなり、センターバイパス油路３０Ｒの流路面積が小さくなる。そして、センターバイパス油路３０Ｒの流路面積が小さくなると、ネガコン圧が低くなり、吐出流量指令値は大きくなる。そして、吐出流量指令値が大きくなると、油圧ポンプ１０Ｒの吐出流量Ｑｐは大きくなる。なお、コントローラ５４は、ブーム下げ操作量に応じて第１指令値を導き出してもよい。 If it is determined that the boom lowering operation is being performed (YES in step ST1), the controller 54 derives a first command value that is a command to the pump regulator 40R (step ST2). In the present embodiment, the controller 54 derives the first command value according to the negative control pressure signal. The first command value is a discharge flow rate command value that is uniquely determined according to the negative control pressure signal, and increases as the boom lowering operation amount increases. Specifically, the greater the boom lowering operation amount, the greater the movement amount of the control valve 14R, and the smaller the channel area of the center bypass oil passage 30R. When the flow path area of the center bypass oil path 30R is reduced, the negative control pressure is reduced and the discharge flow rate command value is increased. When the discharge flow rate command value increases, the discharge flow rate Qp of the hydraulic pump 10R increases. The controller 54 may derive the first command value according to the boom lowering operation amount.
　その後、コントローラ５４は、第１指令値をポンプレギュレータ４０Ｒに対して出力し、油圧ポンプ１０Ｒの吐出流量Ｑｐが第１指令値に対応する流量となるように斜板傾転角を制御する（ステップＳＴ３）。 Thereafter, the controller 54 outputs the first command value to the pump regulator 40R, and controls the swash plate tilt angle so that the discharge flow rate Qp of the hydraulic pump 10R becomes a flow rate corresponding to the first command value (step). ST3).
　その後、コントローラ５４は、ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒのそれぞれの変動幅が所定値未満となったかを判定する（ステップＳＴ４）。変動幅が大きいとブームシリンダ７に作用する推力Ｆを正確に推定することができないためである。なお、本実施例では、コントローラ５４は、圧力センサＳ５が出力するブームロッド圧信号の前回値と今回値の差をブームボトム圧Ｐｂの変動幅として導き出す。ブームロッド圧Ｐｒの変動幅についても同様である。 Thereafter, the controller 54 determines whether the fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value (step ST4). This is because the thrust F acting on the boom cylinder 7 cannot be accurately estimated if the fluctuation range is large. In this embodiment, the controller 54 derives the difference between the previous value and the current value of the boom rod pressure signal output from the pressure sensor S5 as the fluctuation range of the boom bottom pressure Pb. The same applies to the fluctuation range of the boom rod pressure Pr.
　ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒの少なくとも１つの変動幅が所定値以上であると判定した場合（ステップＳＴ４のＮＯ）、コントローラ５４は、ステップＳＴ４の判定を繰り返す。 When it is determined that at least one fluctuation range of the boom bottom pressure Pb and the boom rod pressure Pr is equal to or greater than a predetermined value (NO in step ST4), the controller 54 repeats the determination in step ST4.
　その後、ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒのそれぞれの変動幅が所定値未満になったと判定した場合（ステップＳＴ４のＹＥＳ）、コントローラ５４は、ポンプレギュレータ４０Ｒに対する指令である第２指令値を導き出す（ステップＳＴ５）。第２指令値は、
ブームシリンダ７に作用する推力Ｆに応じて変化する吐出流量指令値であり、推力Ｆが大きいほど大きい。 Thereafter, when it is determined that the respective fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value (YES in step ST4), the controller 54 derives a second command value that is a command to the pump regulator 40R. (Step ST5). The second command value is
This is a discharge flow rate command value that changes in accordance with the thrust F acting on the boom cylinder 7, and is larger as the thrust F is larger.
　具体的には、コントローラ５４は、圧力センサＳ５が出力するブームロッド圧信号と、圧力センサＳ６が出力するブームボトム圧信号と、上述の式（１）とに基づいてブームシリンダ７に作用する推力Ｆを導き出す。 Specifically, the controller 54 thrusts acting on the boom cylinder 7 based on the boom rod pressure signal output from the pressure sensor S5, the boom bottom pressure signal output from the pressure sensor S6, and the above equation (1). Derive F.
　また、コントローラ５４は、ブームロッド圧Ｐｒに関する所定の目標圧ＰｔｇをＲＯＭ等から読み出し、推力Ｆと上述の式（２）とに基づいて、ブームロッド圧Ｐｒを目標圧Ｐｔｇとした場合のブームボトム圧Ｐｂを導き出す。 Further, the controller 54 reads out a predetermined target pressure Ptg related to the boom rod pressure Pr from the ROM or the like, and the boom bottom when the boom rod pressure Pr is set to the target pressure Ptg based on the thrust F and the above equation (2). The pressure Pb is derived.
　また、コントローラ５４は、第１絞り係数Ｃｇ及び第２絞り係数Ｃｃとブーム下げ操作量との対応関係を予め記憶した対応テーブルを参照し、現在のブーム下げ操作量に対応する第１絞り係数Ｃｇ及び第２絞り係数Ｃｃを取得する。なお、対応テーブルはＲＯＭ等に予め記憶される。 In addition, the controller 54 refers to a correspondence table that stores in advance the correspondence relationship between the first aperture coefficient Cg and the second aperture coefficient Cc and the boom lowering operation amount, and the first aperture coefficient Cg corresponding to the current boom lowering operation amount. And the second aperture coefficient Cc. The correspondence table is stored in advance in a ROM or the like.
　そして、コントローラ５４は、取得した第１絞り係数Ｃｇと式（５）とに基づいて再生油路３３の再生流量Ｑｇを導き出す。また、コントローラ５４は、取得した第２絞り係数Ｃｃと式（８）とに基づいて戻り油路３４の戻り流量Ｑｃを導き出す。 Then, the controller 54 derives the regeneration flow rate Qg of the regeneration oil passage 33 based on the acquired first throttle coefficient Cg and the equation (5). Further, the controller 54 derives the return flow rate Qc of the return oil passage 34 based on the acquired second throttle coefficient Cc and the equation (8).
　そして、コントローラ５４は、再生流量Ｑｇと、戻り流量Ｑｃと、式（１０）とに基づいて第２指令値に対応する吐出流量を導き出す。 Then, the controller 54 derives a discharge flow rate corresponding to the second command value based on the regeneration flow rate Qg, the return flow rate Qc, and the equation (10).
　なお、コントローラ５４は、第２指令値を導き出すために、必ずしも、ブームロッド圧Ｐｒを目標圧Ｐｔｇとした場合のブームボトム圧Ｐｂ、再生流量Ｑｇ、戻り流量Ｑｃ等をその都度導き出す必要はない。例えば、コントローラ５４は、ブーム操作レバーに関するパイロット圧信号、ブームボトム圧信号、及びブームロッド圧信号の組み合わせと、第２指令値との対応関係を予め記憶した対応テーブルを参照してもよい。この場合、コントローラ５４は、ＲＯＭ等に予め記憶されたその対応テーブルを参照し、現在のブーム下げ操作量、ブームロッド圧Ｐｒ、及びブームボトム圧Ｐｂの組み合わせに対応する第２指令値を直接的に導き出す。 The controller 54 does not necessarily have to derive the boom bottom pressure Pb, the regeneration flow rate Qg, the return flow rate Qc, and the like each time when the boom rod pressure Pr is set to the target pressure Ptg in order to derive the second command value. For example, the controller 54 may refer to a correspondence table in which a correspondence relationship between a combination of a pilot pressure signal, a boom bottom pressure signal, and a boom rod pressure signal related to the boom operation lever and the second command value is stored in advance. In this case, the controller 54 refers to the correspondence table stored in advance in the ROM or the like, and directly determines the second command value corresponding to the combination of the current boom lowering operation amount, the boom rod pressure Pr, and the boom bottom pressure Pb. To derive.
　その後、コントローラ５４は、第２指令値をポンプレギュレータ４０Ｒに対して出力し、油圧ポンプ１０Ｒの吐出流量Ｑｐが第２指令値に対応する吐出流量となるように制御する（ステップＳＴ６）。 Thereafter, the controller 54 outputs a second command value to the pump regulator 40R, and controls the discharge flow rate Qp of the hydraulic pump 10R to be a discharge flow rate corresponding to the second command value (step ST6).
　このようにして、コントローラ５４は、キャビテーションを発生させない限りにおいて、再生流量Ｑｇを最大化させるべく、油圧ポンプ１０Ｒの吐出流量Ｑｐを最適化する。 Thus, the controller 54 optimizes the discharge flow rate Qp of the hydraulic pump 10R so as to maximize the regeneration flow rate Qg unless cavitation is generated.
　次に、図８を参照し、コントローラ５４が吐出流量最適化処理を実行する場合における各種パラメータの時間的推移について説明する。なお、図８は、ブーム下げ操作が単独で行われるときの各種パラメータの時間的推移を示すグラフである。具体的には、図８（Ａ）は、ブームロッド圧Ｐｒ及びブームボトム圧Ｐｂの時間的推移を表す。また、図８（Ｂ）は吐出流量指令値の時間的推移を表し、図８（Ｃ）はブーム下げ速度の時間的推移を表す。なお、図８（Ａ）～図８（Ｃ）では時間軸としての横軸は共通である。 Next, with reference to FIG. 8, the time transition of various parameters when the controller 54 executes the discharge flow rate optimization process will be described. In addition, FIG. 8 is a graph which shows the time transition of various parameters when boom lowering operation is performed independently. Specifically, FIG. 8A shows temporal transition of the boom rod pressure Pr and the boom bottom pressure Pb. FIG. 8B shows a temporal transition of the discharge flow rate command value, and FIG. 8C shows a temporal transition of the boom lowering speed. Note that in FIGS. 8A to 8C, the horizontal axis as a time axis is common.
　具体的には、時刻ｔ１においてブーム下げ操作が単独で行われるまでは、ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒは、図８（Ａ）に示すように、変動幅が小さい状態で推移する。そして、時刻ｔ１においてブーム下げ操作が単独で行われると、ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒの変動幅は大きくなる。例えば、ブームボトム圧Ｐｂはボトム側油室から作動油が流出することによって一時的に低下し、ブームロッド圧Ｐｒはロッド側油室に作動油が流入することによって一時的に増大する。その後、ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒのそれぞれは安定に向かい、時刻ｔ２においてそれぞれの変動幅は所定値未満となる。 Specifically, until the boom lowering operation is performed independently at time t1, the boom bottom pressure Pb and the boom rod pressure Pr change with a small fluctuation range as shown in FIG. And if boom lowering operation is performed independently at the time t1, the fluctuation range of boom bottom pressure Pb and boom rod pressure Pr will become large. For example, the boom bottom pressure Pb temporarily decreases when hydraulic oil flows out from the bottom side oil chamber, and the boom rod pressure Pr increases temporarily when hydraulic fluid flows into the rod side oil chamber. Thereafter, each of the boom bottom pressure Pb and the boom rod pressure Pr is stabilized, and the fluctuation width thereof is less than a predetermined value at time t2.
　吐出流量指令値に関しては、時刻ｔ１においてブーム下げ操作が単独で行われると、コントローラ５４は、ネガコン圧に応じた第１指令値ｄ１を導き出し、吐出流量指令値として第１指令値ｄ１を設定する。そのため、吐出流量指令値は、図８（Ｂ）に示すように、時刻ｔ１において第１指令値ｄ１まで増加する。その後、コントローラ５４は、ブームボトム圧Ｐｂ及びブームロッド圧Ｐｒのそれぞれの変動幅が所定値未満になったと判定するまでは吐出流量指令値として第１指令値ｄ１を使用する。そのため、吐出流量指令値は第１指令値ｄ１のまま推移する。その後、コントローラ５４は、時刻ｔ２においてブームボトム圧Ｐｂ及びブームロッド圧Ｐｒのそれぞれの変動幅が所定値未満になったと判定すると、ブームシリンダ７に作用する推力Ｆに応じた第２指令値ｄ２を導き出す。このとき、コントローラ５４は、所定時間Ｔ１の経過後に油圧ポンプ１０Ｒの実際の吐出流量Ｑｐが第２指令値に対応する吐出流量となるように吐出流量指令値を決定する。吐出流量Ｑｐの急変を避けるためである。具体的には、コントローラ５４は、現在の吐出流量指令値としての第１指令値ｄ１と、所定時間Ｔ１経過後の吐出流量指令値としての第２指令値ｄ２との間を線形補間して中間の指令値を導き出す。そして、実際の吐出流量Ｑｐを中間の指令値に対応する吐出流量に合致させるようにポンプレギュレータ４０Ｒを制御する。そのため、吐出流量指令値は、図８（Ｂ）に示すように、時刻ｔ２における第１指令値ｄ１から比較的緩やかに低下し、所定時間Ｔ１経過後の時刻ｔ３において第２指令値ｄ２に至る。 As for the discharge flow rate command value, when the boom lowering operation is performed alone at time t1, the controller 54 derives the first command value d1 corresponding to the negative control pressure, and sets the first command value d1 as the discharge flow rate command value. . Therefore, the discharge flow rate command value increases to the first command value d1 at time t1, as shown in FIG. 8B. Thereafter, the controller 54 uses the first command value d1 as the discharge flow rate command value until it is determined that the respective fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value. For this reason, the discharge flow rate command value remains the first command value d1. Thereafter, when the controller 54 determines that the fluctuation ranges of the boom bottom pressure Pb and the boom rod pressure Pr are less than a predetermined value at time t2, the controller 54 sets the second command value d2 corresponding to the thrust F acting on the boom cylinder 7. derive. At this time, the controller 54 determines the discharge flow rate command value so that the actual discharge flow rate Qp of the hydraulic pump 10R becomes the discharge flow rate corresponding to the second command value after the elapse of the predetermined time T1. This is to avoid a sudden change in the discharge flow rate Qp. Specifically, the controller 54 linearly interpolates between the first command value d1 as the current discharge flow rate command value and the second command value d2 as the discharge flow rate command value after a predetermined time T1 has elapsed. The command value is derived. Then, the pump regulator 40R is controlled so that the actual discharge flow rate Qp matches the discharge flow rate corresponding to the intermediate command value. Therefore, as shown in FIG. 8B, the discharge flow rate command value decreases relatively slowly from the first command value d1 at time t2, and reaches the second command value d2 at time t3 after the elapse of the predetermined time T1. .
　ブーム下げ速度は、図８（Ｃ）に示すように、時刻ｔ１においてブーム下げ操作が行われた後で徐々に増加し、時刻ｔ２において、ブーム下げ操作量に応じた速度Ｖｔに至る。そして、時刻ｔ２において吐出流量指令値の低減が開始され、実際の吐出流量Ｑｐの低減が開始された後もその速度Ｖｔが維持される。さらに、時刻ｔ３において吐出流量指令値が第２指令値ｄ２となり、実際の吐出流量Ｑｐが第２指令値ｄ２に対応する吐出流量となった後もその速度Ｖｔが維持される。吐出流量Ｑｐが減少した分だけ再生流量Ｑｇが増大するためである。 As shown in FIG. 8C, the boom lowering speed gradually increases after the boom lowering operation is performed at time t1, and reaches a speed Vt corresponding to the boom lowering operation amount at time t2. Then, the reduction of the discharge flow rate command value is started at time t2, and the speed Vt is maintained even after the actual reduction of the discharge flow rate Qp is started. Further, the discharge flow rate command value becomes the second command value d2 at time t3, and the speed Vt is maintained even after the actual discharge flow rate Qp becomes the discharge flow rate corresponding to the second command value d2. This is because the regeneration flow rate Qg increases by the amount that the discharge flow rate Qp decreases.
　以上の構成により、コントローラ５４は、ブーム下げ操作が行われた場合、ブームシリンダ７に作用する推力Ｆに応じて吐出流量Ｑｐを決定し、ブームロッド圧Ｐｒを所定の目標圧Ｐｔｇ以上としながら再生流量Ｑｇを最大化する。そのため、キャビテーションの発生を防止しながら、ブーム下げ操作の際の再生効率を向上できる。また、吐出流量Ｑｐを必要最小限に低減させるため、省エネルギ化を図ることができる。 With the above configuration, when the boom lowering operation is performed, the controller 54 determines the discharge flow rate Qp according to the thrust F acting on the boom cylinder 7 and regenerates the boom rod pressure Pr at a predetermined target pressure Ptg or more. Maximize the flow rate Qg. Therefore, it is possible to improve the regeneration efficiency during the boom lowering operation while preventing the occurrence of cavitation. Further, since the discharge flow rate Qp is reduced to the minimum necessary, energy saving can be achieved.
　また、コントローラ５４は、ブーム下げ操作が行われた直後では、ネガコン圧又はブーム下げ操作量に応じて第１指令値ｄ１を決定する。そして、油圧ポンプ１０Ｒの実際の吐出流量Ｑｐを第１指令値ｄ１に対応する吐出流量に合致させるようにポンプレギュレータ４０Ｒを制御する。また、ブームシリンダ７内の作動油の圧力が安定化した後で、ブームシリンダ７に作用する推力Ｆ、再生油路３３の流路面積Ａｇ、及び、戻り油路３４の流路面積Ａｃに応じて第２指令値ｄ２を決定する。そして、油圧ポンプ１０Ｒの実際の吐出流量Ｑｐを第２指令値ｄ２に対応する吐出流量に合致させるようにポンプレギュレータ４０Ｒを制御する。具体的には、コントローラ５４は、ブームシリンダ７における作動油の圧力の変動幅が所定値未満となった場合に第２指令値を決定する。そのため、コントローラ５４は、推力Ｆを高精度に導き出した上で、ブームロッド圧Ｐｒを所定の目標圧Ｐｔｇ以上としながら再生流量Ｑｇを最大化できる吐出流量Ｑｐに対応する第２指令値ｄ２を導き出すことができる。 Further, immediately after the boom lowering operation is performed, the controller 54 determines the first command value d1 according to the negative control pressure or the boom lowering operation amount. Then, the pump regulator 40R is controlled so that the actual discharge flow rate Qp of the hydraulic pump 10R matches the discharge flow rate corresponding to the first command value d1. Further, after the pressure of the hydraulic oil in the boom cylinder 7 is stabilized, the thrust F acting on the boom cylinder 7, the flow passage area Ag of the regenerated oil passage 33, and the flow passage area Ac of the return oil passage 34 are determined. To determine the second command value d2. Then, the pump regulator 40R is controlled so that the actual discharge flow rate Qp of the hydraulic pump 10R matches the discharge flow rate corresponding to the second command value d2. Specifically, the controller 54 determines the second command value when the fluctuation range of the hydraulic oil pressure in the boom cylinder 7 becomes less than a predetermined value. Therefore, the controller 54 derives the second command value d2 corresponding to the discharge flow rate Qp that can maximize the regeneration flow rate Qg while making the boom rod pressure Pr equal to or higher than the predetermined target pressure Ptg after deriving the thrust F with high accuracy. be able to.
　なお、ブームシリンダ７に作用する推力Ｆは、ブームボトム圧Ｐｂ及び受圧面積Ａｂとブームロッド圧Ｐｒ及び受圧面積Ａｒとに基づいて導き出される。そのため、コントローラ５４は、簡易な構成で高精度に推力Ｆを導き出すことができる。 The thrust F acting on the boom cylinder 7 is derived based on the boom bottom pressure Pb and the pressure receiving area Ab, the boom rod pressure Pr and the pressure receiving area Ar. Therefore, the controller 54 can derive the thrust F with high accuracy with a simple configuration.
　また、再生油路３３の流路面積Ａｇ及び戻り油路３４の流路面積Ａｃは、ブーム下げ操作量に基づいて導き出される。そのため、コントローラ５４は、キャビテーションの発生を防止し、ブーム下げ操作の際の再生効率を向上させながらも、ブーム下げ操作量に応じたブーム下げ速度を実現できる。 Also, the flow passage area Ag of the regenerated oil passage 33 and the flow passage area Ac of the return oil passage 34 are derived based on the boom lowering operation amount. Therefore, the controller 54 can realize the boom lowering speed according to the boom lowering operation amount while preventing the occurrence of cavitation and improving the regeneration efficiency at the time of the boom lowering operation.
　また、コントローラ５４は、第１指令値ｄ１と第２指令値ｄ２との間を補間して中間指令値を導き出す。そして、所定時間経過後に油圧ポンプ１０Ｒの実際の吐出流量Ｑｐが第２指令値ｄ２に対応する吐出流量となるように、実際の吐出流量Ｑｐをその中間指令値に対応する吐出流量に合致させるようにポンプレギュレータ４０Ｒを制御する。そのため、コントローラ５４は、吐出流量Ｑｐの急変、再生流量Ｑｇの急変、及びブームシリンダ流入流量Ｑｓ（ブーム下げ速度）の急変を防止し、且つ、キャビテーションの発生を防止しながら、ブーム下げ操作の際の再生効率を向上できる。 Also, the controller 54 derives an intermediate command value by interpolating between the first command value d1 and the second command value d2. Then, the actual discharge flow rate Qp is matched with the discharge flow rate corresponding to the intermediate command value so that the actual discharge flow rate Qp of the hydraulic pump 10R becomes the discharge flow rate corresponding to the second command value d2 after a predetermined time has elapsed. The pump regulator 40R is controlled. Therefore, the controller 54 prevents a sudden change in the discharge flow rate Qp, a sudden change in the regeneration flow rate Qg, and a sudden change in the boom cylinder inflow rate Qs (boom lowering speed), and prevents the occurrence of cavitation while performing the boom lowering operation. Can improve the reproduction efficiency.
　以上、本発明の実施例について詳述したが、本発明は特定の実施例に限定されるものではなく、特許請求の範囲に記載された本発明の要旨の範囲内において、種々の変形及び変更が可能である。 Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.
　例えば、上述の実施例では、コントローラ５４は、ブーム操作レバーが単独で下げ方向にフルレバー操作されたことを検知した場合にブーム下げ操作中であると判定する。しかしながら、本発明はこの構成に限定されるものではない。例えば、コントローラ５４は、ブーム操作レバーが単独で下げ方向にハーフレバー操作されたことを検知した場合にブーム下げ操作中であると判定してもよい。なお、「ハーフレバー操作」は、フルレバー操作よりも小さい操作量で行われるレバー操作を意味する。 For example, in the above-described embodiment, the controller 54 determines that the boom lowering operation is being performed when it is detected that the boom operating lever has been operated alone in the lowering direction. However, the present invention is not limited to this configuration. For example, the controller 54 may determine that the boom lowering operation is being performed when it is detected that the boom operating lever has been operated halfway in the lowering direction alone. The “half lever operation” means a lever operation performed with a smaller operation amount than a full lever operation.
　また、上述の実施例では、再生油路３３は制御弁１４Ｒの内部に形成されるが、制御弁１４Ｒの外部に形成されてもよい。 In the above-described embodiment, the regenerated oil passage 33 is formed inside the control valve 14R, but may be formed outside the control valve 14R.
　また、本願は、２０１４年５月１９日に出願した日本国特許出願２０１４－１０３７１０号に基づく優先権を主張するものであり、これらの日本国特許出願の全内容を本願に参照により援用する。 In addition, this application claims priority based on Japanese Patent Application No. 2014-103710 filed on May 19, 2014, and the entire contents of these Japanese Patent Applications are incorporated herein by reference.
　１・・・ショベル　２・・・下部走行体　３・・・上部旋回体　４・・・ブーム　５・・・アーム　６・・・バケット　７・・・ブームシリンダ　８・・・アームシリンダ　９・・・バケットシリンダ　１０Ｌ、１０Ｒ・・・油圧ポンプ　１１Ｌ、１１Ｒ、１２Ｌ、１２Ｒ、１３Ｌ、１３Ｒ、１４Ｌ、１４Ｒ、１５Ｌ、１５Ｒ・・・制御弁　２０Ｌ、２０Ｒ・・・ネガコン絞り　２２・・・作動油タンク　３０Ｌ、３０Ｒ・・・センターバイパス油路　３１Ｌ、３１Ｒ・・・パラレル油路　３３・・・再生油路　３４・・・戻り油路　４０Ｌ、４０Ｒ・・・ポンプレギュレータ　４２Ｌ、４２Ｒ・・・走行用油圧モータ　４４・・・旋回用油圧モータ　５４・・・コントローラ　Ｓ１～Ｓ６・・・圧力センサ DESCRIPTION OF SYMBOLS 1 ... Excavator 2 ... Lower traveling body 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10L, 10R ... Hydraulic pump 11L, 11R, 12L, 12R, 13L, 13R, 14L, 14R, 15L, 15R ... Control valve 20L, 20R ... Negative control throttle 22 ... Hydraulic oil tank 30L , 30R ... Center bypass oil passage 31L, 31R ... Parallel oil passage 33 ... Regeneration oil passage 34 ... Return oil passage 40L, 40R ... Pump regulator 42L, 42R ... Travel hydraulic motor 44 ... Hydraulic hydraulic motor 54 ... Controller S1-S6 ... Pressure sensor

Claims (10)

  1. 　油圧ポンプが吐出する作動油の少なくとも一部をポンプ供給油として受け入れるブームシリンダと、
    　前記ブームシリンダの収縮側油室から流出する作動油の一部を再生油として伸張側油室に流入させる再生油路と、
    　前記油圧ポンプが吐出する作動油の吐出流量を制御して前記ポンプ供給油の供給流量を調整する制御装置と、を備え、
    　前記制御装置は、ブーム下げ操作が行われた場合、前記ブームシリンダに作用する推力に応じて前記吐出流量を決定し、前記伸張側油室の圧力を所定圧以上としながら前記再生油の再生流量を最大化する、
    　ショベル。     A boom cylinder that receives at least part of the hydraulic oil discharged from the hydraulic pump as pump supply oil;
    A regeneration oil passage for allowing a part of the hydraulic oil flowing out from the contraction side oil chamber of the boom cylinder to flow into the extension side oil chamber as regeneration oil;
    A control device for adjusting the supply flow rate of the pump supply oil by controlling the discharge flow rate of the hydraulic oil discharged by the hydraulic pump;
    When the boom lowering operation is performed, the control device determines the discharge flow rate according to a thrust acting on the boom cylinder, and makes the expansion oil chamber pressure equal to or higher than a predetermined pressure while regenerating the regenerated flow rate of the regenerated oil. To maximize the
    Excavator.
  2. 　前記制御装置は、
    　　ブーム下げ操作量に応じて前記吐出流量の第１指令値を決定して前記油圧ポンプの実際の吐出流量を該第１指令値に対応する吐出流量に合致させるように前記吐出流量を制御し、
    　　その後に、前記ブームシリンダに作用する推力、前記再生油路の流路面積、及び、前記ブームシリンダと作動油タンクとを連通する戻り油路の流路面積に応じて前記吐出流量の第２指令値を決定して前記油圧ポンプの実際の吐出流量を該第２指令値に対応する吐出流量に合致させるように前記吐出流量を制御する、
    　請求項１に記載のショベル。     The controller is
    A first command value for the discharge flow rate is determined according to a boom lowering operation amount, and the discharge flow rate is controlled so that an actual discharge flow rate of the hydraulic pump matches a discharge flow rate corresponding to the first command value;
    Thereafter, the second command for the discharge flow rate is determined according to the thrust acting on the boom cylinder, the flow passage area of the regenerated oil passage, and the flow passage area of the return oil passage communicating the boom cylinder and the hydraulic oil tank. Determining the value and controlling the discharge flow rate so that the actual discharge flow rate of the hydraulic pump matches the discharge flow rate corresponding to the second command value;
    The excavator according to claim 1.
  3. 　前記制御装置は、前記ブームシリンダにおける作動油の圧力の変動幅が所定値未満となった場合に前記第２指令値を決定する、
    　請求項２に記載のショベル。     The control device determines the second command value when a fluctuation range of the pressure of hydraulic oil in the boom cylinder becomes less than a predetermined value.
    The shovel according to claim 2.
  4. 　前記制御装置は、前記第１指令値と前記第２指令値との間を補間して中間指令値を導き出し、所定時間経過後に前記油圧ポンプの実際の吐出流量が前記第２指令値に対応する吐出流量となるように、前記油圧ポンプの実際の吐出流量を該中間指令値に対応する吐出流量に合致させるように前記吐出流量を制御する、
    　請求項２又は３に記載のショベル。     The control device interpolates between the first command value and the second command value to derive an intermediate command value, and an actual discharge flow rate of the hydraulic pump corresponds to the second command value after a predetermined time has elapsed. Controlling the discharge flow rate so that the actual discharge flow rate of the hydraulic pump matches the discharge flow rate corresponding to the intermediate command value so as to be the discharge flow rate;
    The shovel according to claim 2 or 3.
  5. 　前記制御装置は、前記収縮側油室の圧力及び受圧面積と前記伸張側油室の圧力及び受圧面積とに基づいて前記ブームシリンダに作用する推力を導き出す、
    　請求項２又は３に記載のショベル。     The control device derives thrust acting on the boom cylinder based on the pressure and pressure receiving area of the contraction side oil chamber and the pressure and pressure receiving area of the extension side oil chamber.
    The shovel according to claim 2 or 3.
  6. 　前記制御装置は、前記再生油路の流路面積及び前記戻り油路の流路面積のそれぞれとブーム下げ操作量との対応関係を予め記憶した対応テーブルを参照し、現在のブーム下げ操作量に対応する前記再生油路の流路面積及び前記戻り油路の流路面積を導き出す、
    　請求項２又は３に記載のショベル。     The control device refers to a correspondence table that stores in advance the correspondence relationship between the flow passage area of the regenerated oil passage and the flow passage area of the return oil passage and the boom lowering operation amount, and sets the current boom lowering operation amount. Deriving the corresponding flow passage area of the reclaimed oil passage and the flow passage area of the return oil passage;
    The shovel according to claim 2 or 3.
  7. 　油圧ポンプが吐出する作動油の少なくとも一部をポンプ供給油として受け入れるブームシリンダと、前記ブームシリンダの収縮側油室から流出する作動油の一部を再生油として伸張側油室に流入させる再生油路と、前記油圧ポンプが吐出する作動油の吐出流量を制御して前記ポンプ供給油の供給流量を調整する制御装置と、を備えるショベルの制御方法であって、
    　ブーム下げ操作が行われた場合、前記ブームシリンダに作用する推力に応じて前記制御装置が前記吐出流量を決定し、前記伸張側油室の圧力を所定圧以上としながら前記制御装置が前記再生油の再生流量を最大化する、
    　制御方法。     A boom cylinder that receives at least part of the hydraulic oil discharged from the hydraulic pump as pump supply oil, and a regenerated oil that causes a part of the hydraulic oil flowing out from the contraction side oil chamber of the boom cylinder to flow into the expansion side oil chamber as regenerated oil A control method of an excavator comprising a passage and a control device for adjusting a supply flow rate of the pump supply oil by controlling a discharge flow rate of the hydraulic oil discharged from the hydraulic pump,
    When a boom lowering operation is performed, the control device determines the discharge flow rate according to a thrust acting on the boom cylinder, and the control device sets the pressure of the extension side oil chamber to a predetermined pressure or more, and the control device To maximize the regeneration flow of
    Control method.
  8. 　ブーム下げ操作量に応じて前記吐出流量の第１指令値を決定して前記油圧ポンプの実際の吐出流量を該第１指令値に対応する吐出流量に合致させるように前記制御装置が前記吐出流量を制御し、その後に、前記ブームシリンダに作用する推力、前記再生油路の流路面積、及び、前記ブームシリンダと作動油タンクとを連通する戻り油路の流路面積に応じて前記吐出流量の第２指令値を決定して前記油圧ポンプの実際の吐出流量を該第２指令値に対応する吐出流量に合致させるように前記制御装置が前記吐出流量を制御する、
    　請求項７に記載の制御方法。     The control device determines the first command value of the discharge flow rate in accordance with the boom lowering operation amount, and the control device causes the actual discharge flow rate of the hydraulic pump to match the discharge flow rate corresponding to the first command value. And then the discharge flow rate according to the thrust acting on the boom cylinder, the flow passage area of the regeneration oil passage, and the flow passage area of the return oil passage communicating the boom cylinder and the hydraulic oil tank. The control device controls the discharge flow rate so as to match the actual discharge flow rate of the hydraulic pump with the discharge flow rate corresponding to the second command value.
    The control method according to claim 7.
  9. 　前記ブームシリンダにおける作動油の圧力の変動幅が所定値未満となった場合に前記制御装置が前記第２指令値を決定する、
    　請求項８に記載の制御方法。     The control device determines the second command value when the fluctuation range of the hydraulic oil pressure in the boom cylinder becomes less than a predetermined value;
    The control method according to claim 8.
  10. 　前記第１指令値と前記第２指令値との間を補間して中間指令値を導き出し、所定時間経過後に前記油圧ポンプの実際の吐出流量が前記第２指令値に対応する吐出流量となるように、前記油圧ポンプの実際の吐出流量を該中間指令値に対応する吐出流量に合致させるように前記制御装置が前記吐出流量を制御する、
    　請求項８又は９に記載の制御方法。     An intermediate command value is derived by interpolating between the first command value and the second command value so that the actual discharge flow rate of the hydraulic pump becomes a discharge flow rate corresponding to the second command value after a predetermined time has elapsed. In addition, the control device controls the discharge flow rate so that the actual discharge flow rate of the hydraulic pump matches the discharge flow rate corresponding to the intermediate command value.
    The control method according to claim 8 or 9.
PCT/JP2015/064091 2014-05-19 2015-05-15 Shovel and control method therefor WO2015178316A1 (en)

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