EP0027743B1 - Control system for a hydraulic circuit including a plurality of parallel variable-delivery pumps - Google Patents

Control system for a hydraulic circuit including a plurality of parallel variable-delivery pumps Download PDF

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Publication number
EP0027743B1
EP0027743B1 EP19800303741 EP80303741A EP0027743B1 EP 0027743 B1 EP0027743 B1 EP 0027743B1 EP 19800303741 EP19800303741 EP 19800303741 EP 80303741 A EP80303741 A EP 80303741A EP 0027743 B1 EP0027743 B1 EP 0027743B1
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EP
European Patent Office
Prior art keywords
pumps
delivery
pump
control system
maximum
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
EP19800303741
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German (de)
French (fr)
Other versions
EP0027743A1 (en
Inventor
Kiyoshi Gotoda
Masayuki Eguma
Akira Asari
Masaru Takeda
Yasuhiro Nakashima
Tatsuhiko Noyori
Munenori Soejima
Masanobu Aoki
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Kobe Steel Ltd
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Kobe Steel Ltd
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Publication date
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Publication of EP0027743A1 publication Critical patent/EP0027743A1/en
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Expired legal-status Critical Current

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    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F15B2211/20553—Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/30575—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve in a Wheatstone Bridge arrangement (also half bridges)
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50518—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief valves
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50536—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using unloading valves controlling the supply pressure by diverting fluid to the return line
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5151—Pressure control characterised by the connections of the pressure control means in the circuit being connected to a pressure source and a directional control valve
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5153—Pressure control characterised by the connections of the pressure control means in the circuit being connected to an output member and a directional control valve
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/55—Pressure control for limiting a pressure up to a maximum pressure, e.g. by using a pressure relief valve
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/615—Filtering means
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/635—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements
    • F15B2211/6355—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements having valve means
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6651—Control of the prime mover, e.g. control of the output torque or rotational speed
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6653—Pressure control
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7052—Single-acting output members
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7107—Multiple output members, e.g. multiple hydraulic motors or cylinders the output members being mechanically linked
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7114—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators
    • F15B2211/7128—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators the chambers being connected in parallel
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/88—Control measures for saving energy

Definitions

  • This invention relates to a control system for use in a hydraulic circuit supplying pressurized oil or fluid from a plurality of parallel connected variable delivery pumps to a hydraulic appliance.
  • variable delivery pumps are used then it is conventional, when the amount of oil or fluid is less than the maximum which can be pumped by all of the pumps, to run all the pumps together but at the same fraction of their maximum output. Thus if, for example, only half of the maximum oil or fluid which can be pumped by all of the pumps is required, then each of the pumps will operate at half of its maximum output.
  • the control for such a system is simple since all of the variable pumps can be controlled together.
  • the present invention provides a control system for use in a hydraulic circuit including a plurality of parallel pumps; said control system comprising means for bringing a variable number of pumps into a loaded state dependent on the required volume of pressure fluid, characterised in that the pumps are variable delivery pumps and the control system controls the plurality of pumps so that when the required volume of pressure fluid does not exceed the maximum ⁇ oIume ⁇ deliverabIe from one pump, one only of said pumps is in a loaded state for delivering the required volume of pressure fluid and the other pumps are in an unloaded state, and when the required volume of pressure fluid exceeds the maximum volume deliverable from one or more pumps, one or more of said pumps are in their substantially maximum delivery state, one only of the other pumps is in an intermediate delivery state and the remaining pumps are in an unloaded state.
  • the quantity of fluid delivered from each of the pumps is controlled by the control system dynamically and according to the demanded quantity required by the appliance which may be an extrusion press.
  • the system ensures the pumps operate in an optimum manner to reduce energy losses and power consumption.
  • Figure 1 shows a hydraulic circuit of an extrusion press, which comprises variable-delivery (11, 12, 13 and 14), pump driving motors (21, 22, 23 and 24), delivery regulators (31,32,33 and 34) one for each of the pumps, loading control valves (41, 42, 43 and 44) for loading and unloading the respective pumps, relief valves (45, 46, 47 and 48), direction switching solenoid valves (51,52,53,54, 55 and 56), a pilot controlled check valve (57), relief valves (58 and 59) an extrusion press (60) having a main cylinder (61), side cylinders (62 and 63) and a stem ⁇ (64), and pilot pumps (71 and 72). These hydraulic component parts are interconnected as shown in Figure 1.
  • variable-delivery pumps 11, 12, 13 and 14
  • the volume of pressure fluid e.g. oil
  • the volume of pressure fluid e.g. oil
  • programmed electric signals are fed from a control panel not shown to actuate one or more of the solenoid valves (51, 52, 53, 54, 55 and 56), thus establishing flow paths between the cylinders (61, 62 and 63) and the pumps or an oil reservoir and actuating the cylinders (61, 62 and 63) according to the control program.
  • the operation speed of the stem (64), that is, the volume of oil supplied to each of the cylinders (61, 62 and 63) is controlled by switching on and off the loading control valves (41, 42, 43 and 44) which in turn govern the delivery of each of the respective pumps (11, 12, 13 and 14).
  • the operation speed of the stem (64) (this is referred to as "extrusion speed” hereinafter) is monitored with a sensor (81) operatively associated with a stem speed setting (80) installed on the extrusion press (60).
  • the function of the sensor is to detect the demanded extrusion speed in terms of percentage wherein rated maximum speed is denoted as 100%.
  • the output of the sensor (81) is converted into an AC or DC signal and supplied to a controller (82) which in turn provides individual signals (C1, C2, C3 and C4) for the delivery regulators (31, 32, 33 and 34) and individual signals (C1', C2', C3' and C4') for the loading control solenoid valves (41, 42, 43 and 44 in response to a previously programmed extrusion start signal.
  • a controller which in turn provides individual signals (C1, C2, C3 and C4) for the delivery regulators (31, 32, 33 and 34) and individual signals (C1', C2', C3' and C4') for the loading control solenoid valves (41, 42, 43 and 44 in response to a previously programmed extrusion start signal.
  • the delivery regulators (31, 32, 33 and 34) are supplied with a given pilot pressure (Pa) from the pilot pump (71).
  • the respective solenoid valves (41, 42, 43 and 44) are switched on and off to load and unload the respective pumps (11, 12, 13 and 14) according to the extrusion speed or the required volume of oil for each of the cylinders (61, 62 and 63) as seen from Figure 3.
  • Figure 3 shows four vertical columns, the first vertical column between the lines 0 and 25 relating to the situation when the extrusion speed is between 0 and 25% of the rated specified maximum speed.
  • the second column is indicated between 25 and 50 and similarly indicates the situation when the extrusion speed is rated between 25 and 50% of the specified maximum speed and similarly for the third and fourth columns between the 50 and 75 line and the 75 and 100 line.
  • the state of load of each pump 11, 12,13 and 14 which is listed to the left of the first column is indicated by a hatched area.
  • the hatched area indicates whether, in respect of pump 11, the electromagnetic valve 41 is on and with respect to pump 12 the electromagnetic valve 42 is on and with respect to pumps 13 and 14 whether the electromagnetic valves 43, 44 respectively are on.
  • the solenoid valve 41 is energised (indicated by hatching in the first vertical column of Figure 3) to load only one pump (11) of which the inclination is varied by the delivery regulator (31) (as indicated by Figures 0% to 100% in first vertical column of Figure 4) in accordance with control signals C1 (as indicated in Figure 4) to control its delivery output within the range of 0 to 100%.
  • the solenoid valves (41 and 42) are energised (indicated by hatching in the second vertical column of Figure 3) to load the two pumps (11 and 12).
  • the delivery regulator (31) increases the inclination of one of the two pumps (11) to its maximum (100%) and the delivery of that pump (11) to its maximum (100%).
  • the delivery regulator (32) controls the inclination of the other pump (12) and regulates its delivery within the range of 0-100% (as indicated in the second column of Figure 4 alongside pump (12)).
  • the 100% delivery pump (11) combined with the other pump (12) which supplies the deficiency of oil, provides exactly the required volume of oil for actuation of the stem (64).
  • the solenoid valves (43 and 44) are disenergised to unload the remaining pumps (13 and 14) and place the same into no-load state (indicated by no hatching in the second vertical column of Figure 3).
  • the pumps (11, 12, 13 and 14) are loaded in the numerical order in this manner (the reverse of order with a decrease in oil requirement).
  • One or more 100% delivery pumps and one supplemental pump under half-load state satisfy exactly the oil requirement, while the remaining pump or pumps are maintained under no-load state with no delivery.
  • This control method ensures up to 40% power saving as compared with the conventional method wherein all of the pumps are loaded at one time.
  • a particular pump is adapted to start inclining after 100% inclination of the preceding pump.
  • the particular pump may start inclining subsequent to 95% inclination.ofthe preceding pump, for example, in order to provide smooth and continuous operation as a whole.
  • the relationship between the extrusion speed and the inclination speed is controlled to be one half of that with only one pump.
  • variable-delivery pump the volume efficiency and the overall efficiency vary in dependence on the inclination (a) or the delivery volume of oil delivered as shown in Figure 5 and 6.
  • the characteristic of the variable-delivery pump is that its volume efficiency amount to maximum values when it operates with its rated maximum delivery (maximum inclination).
  • the operation speed of the stem within the extrusion press is varied frequently and within a wide range so that the volume of oil supplied and the delivery of the pump are varied frequently and within a wide range.
  • the respective pumps operate less frequently with its rated maximum speed (the required volume of oil is equal to the total of the maximum deliveries of the overall pumps).
  • the present invention only a minimum number of the pumps are loaded depending upon oil requirement and the remaining pumps are unloaded, thus reducing power consumption. Moreover, only one of the loaded pumps is held in half-load state while all of the remaining pumps operate with full or 100% delivery. This leads to a substantial increase in the total efficiency of the pumps and remarkable energy-saving characteristics.
  • the motor (24) is disenergized when the pump (11) is in 100% delivery state and the pump (12) is in half-load state.
  • the motor (23) is disenergized when the delivery control signal (C3) for the pump (12) is less than 70% and energized when the same exceeds 70%.
  • the pump (13) is maintained in no-load state.
  • the line (a) depicts power saving when the extrusion speed is 25% of the rated value, while the line (b) power saving when the extrusion speed is 50% of the rated speed. It is clear from Figure 7, that the present invention ensures 20-40% power saving in the case of the line (a) and 8-18% power saving in the case of the line (b). The lower the extrusion pressure (remarkable especially with less than 50 kg/cm 2 ) and the extrusion speed, the greater the power saving effect.
  • the present invention provides effective and power-saving actuation of the pumps.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Control Of Presses (AREA)
  • Press Drives And Press Lines (AREA)

Description

  • This invention relates to a control system for use in a hydraulic circuit supplying pressurized oil or fluid from a plurality of parallel connected variable delivery pumps to a hydraulic appliance.
  • In a hydraulic circuit in which pressurized oil or fluid is to be supplied in a variable amount, the maximum amount being provided by a plurality of pumps, it is known to vary the amount of pressurized oil supply by switching some of the pumps off when less than the maximum amount of oil or fluid is required. Such an arrangement is described, for example, in US patent 2 947 317. However it seems in that US patent that the pumps which are operating, operate at maximum output and so the total supply of hydraulic fluid provided in discontinuous steps depending upon the number of pumps which are connected.
  • If variable delivery pumps are used then it is conventional, when the amount of oil or fluid is less than the maximum which can be pumped by all of the pumps, to run all the pumps together but at the same fraction of their maximum output. Thus if, for example, only half of the maximum oil or fluid which can be pumped by all of the pumps is required, then each of the pumps will operate at half of its maximum output. The control for such a system is simple since all of the variable pumps can be controlled together.
  • The present invention provides a control system for use in a hydraulic circuit including a plurality of parallel pumps; said control system comprising means for bringing a variable number of pumps into a loaded state dependent on the required volume of pressure fluid, characterised in that the pumps are variable delivery pumps and the control system controls the plurality of pumps so that when the required volume of pressure fluid does not exceed the maximum νoIume·deliverabIe from one pump, one only of said pumps is in a loaded state for delivering the required volume of pressure fluid and the other pumps are in an unloaded state, and when the required volume of pressure fluid exceeds the maximum volume deliverable from one or more pumps, one or more of said pumps are in their substantially maximum delivery state, one only of the other pumps is in an intermediate delivery state and the remaining pumps are in an unloaded state.
  • In general the quantity of fluid delivered from each of the pumps is controlled by the control system dynamically and according to the demanded quantity required by the appliance which may be an extrusion press. The system ensures the pumps operate in an optimum manner to reduce energy losses and power consumption.
  • The invention may be understood more readily, and various other features of the invention may become apparent from consideration of the following description.
  • A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:
    • Figure 1 is a schematic circuit diagram of a hydraulic circuit for an extrusion press control system constructed in accordance with the present invention;
    • Figure 2 is a schematic electric circuit diagram showing an example of means for developing control signals:
    • Figure 3 is a table for explaing the relationship between press extrusion speed and the loaded state of the pumps;
    • Figure 4 is a table for explaining the relationship between press extrusion speed and the inclinations of the pumps;
    • Figure 5 is a characteristic graph showing the volume efficiency of one of the variable-delivery pumps;
    • Figure 6 is a characteristic graph showing the overall efficiency of one of the variable-delivery pumps; and
    • Figure 7 is a graph representing the energy-saving effect of the present invention.
  • Figure 1 shows a hydraulic circuit of an extrusion press, which comprises variable-delivery (11, 12, 13 and 14), pump driving motors (21, 22, 23 and 24), delivery regulators (31,32,33 and 34) one for each of the pumps, loading control valves (41, 42, 43 and 44) for loading and unloading the respective pumps, relief valves (45, 46, 47 and 48), direction switching solenoid valves (51,52,53,54, 55 and 56), a pilot controlled check valve (57), relief valves (58 and 59) an extrusion press (60) having a main cylinder (61), side cylinders (62 and 63) and a stem·(64), and pilot pumps (71 and 72). These hydraulic component parts are interconnected as shown in Figure 1.
  • In the illustrative embodiment, only the four variable-delivery pumps (11, 12, 13 and 14) are connected in parallel and the volume of pressure fluid, e.g. oil, delivered from the pumps is supplied to cylinders (61, 62 and 63) of the extrusion press (6) to actuate the stem (64). When this occurs, programmed electric signals are fed from a control panel not shown to actuate one or more of the solenoid valves (51, 52, 53, 54, 55 and 56), thus establishing flow paths between the cylinders (61, 62 and 63) and the pumps or an oil reservoir and actuating the cylinders (61, 62 and 63) according to the control program.
  • The operation speed of the stem (64), that is, the volume of oil supplied to each of the cylinders (61, 62 and 63) is controlled by switching on and off the loading control valves (41, 42, 43 and 44) which in turn govern the delivery of each of the respective pumps (11, 12, 13 and 14). As best shown in Figure 2, the operation speed of the stem (64) (this is referred to as "extrusion speed" hereinafter) is monitored with a sensor (81) operatively associated with a stem speed setting (80) installed on the extrusion press (60). The function of the sensor is to detect the demanded extrusion speed in terms of percentage wherein rated maximum speed is denoted as 100%. The output of the sensor (81) is converted into an AC or DC signal and supplied to a controller (82) which in turn provides individual signals (C1, C2, C3 and C4) for the delivery regulators (31, 32, 33 and 34) and individual signals (C1', C2', C3' and C4') for the loading control solenoid valves (41, 42, 43 and 44 in response to a previously programmed extrusion start signal. It is noted that the delivery regulators (31, 32, 33 and 34) are supplied with a given pilot pressure (Pa) from the pilot pump (71).
  • In order that the inclinations of the respective pumps (11, 12, 13 and 14) may control its delivery as depicted in Figure 4, the respective solenoid valves (41, 42, 43 and 44) are switched on and off to load and unload the respective pumps (11, 12, 13 and 14) according to the extrusion speed or the required volume of oil for each of the cylinders (61, 62 and 63) as seen from Figure 3.
  • Figure 3 shows four vertical columns, the first vertical column between the lines 0 and 25 relating to the situation when the extrusion speed is between 0 and 25% of the rated specified maximum speed. The second column is indicated between 25 and 50 and similarly indicates the situation when the extrusion speed is rated between 25 and 50% of the specified maximum speed and similarly for the third and fourth columns between the 50 and 75 line and the 75 and 100 line. The state of load of each pump 11, 12,13 and 14 which is listed to the left of the first column is indicated by a hatched area. Similarly the hatched area indicates whether, in respect of pump 11, the electromagnetic valve 41 is on and with respect to pump 12 the electromagnetic valve 42 is on and with respect to pumps 13 and 14 whether the electromagnetic valves 43, 44 respectively are on.
  • In respect of Figure 4 the vertical columns are arranged as in Figure 3 but in this case in place of the hatched areas there is indicated the percentage inclination of each pump and in place of the electromagnetic valve state the corresponding inclination control signal is indicated.
  • Thus, when the extrusion speed is within the range from 0 to 25% of the rated maximum speed (see first vertical column of Figures 3 and 4 between 0 and 25) or when the volume of oil necessary for the cylinder is within the range from 0% to 25% of the total of the maximum delivery volumes of the pumps (11, 12, 13 and 14) (i.e. the rated maximum flow rate) the solenoid valve 41 is energised (indicated by hatching in the first vertical column of Figure 3) to load only one pump (11) of which the inclination is varied by the delivery regulator (31) (as indicated by Figures 0% to 100% in first vertical column of Figure 4) in accordance with control signals C1 (as indicated in Figure 4) to control its delivery output within the range of 0 to 100%. As a result the only pump which supplies the required volume of oil and actuates the stem (64) is the pump (11). Under these circumstances the remaining solenoid valves (42, 43 and 44) are disenergised to place the corresponding pumps (12, 13 and 14) into no load state (indicated by no hatching in the first vertical column of Figure 3).
  • With the extrusion speed within the range of 25 to 50% of the rated maximum speed (see second vertical column of Figures 3 and 4 between 25 and 50) or the required volume of oil within the range of 25 to 50% of the total of the rated maximum delivery volumes, the solenoid valves (41 and 42) are energised (indicated by hatching in the second vertical column of Figure 3) to load the two pumps (11 and 12). The delivery regulator (31) increases the inclination of one of the two pumps (11) to its maximum (100%) and the delivery of that pump (11) to its maximum (100%). The delivery regulator (32), on the other hand, controls the inclination of the other pump (12) and regulates its delivery within the range of 0-100% (as indicated in the second column of Figure 4 alongside pump (12)). Accordingly, the 100% delivery pump (11) combined with the other pump (12) which supplies the deficiency of oil, provides exactly the required volume of oil for actuation of the stem (64). In this instance, the solenoid valves (43 and 44) are disenergised to unload the remaining pumps (13 and 14) and place the same into no-load state (indicated by no hatching in the second vertical column of Figure 3).
  • Similarly, with the extrusion speed within the range of 50-75% of the rated maximum speed, two of the pumps (11 and 12) are loaded with 100% delivery and one of the remaining pumps (13) is placed into half-load state with its delivery within the range of G-1 00% so as to compensate for the deficiency of oil, thus exactly the required volume of oil. The remaining one pump (14) is unloaded under these circumstances. When the extrusion speed is within the range of 75-100% of the rated maximum speed, there are three of the pumps (11, 12 and 13) loaded with 100% delivery and the remaining one of the pumps (14) whose delivery is controlled within the range of 0-100% under half-load state so as to compensate for deficient oil.
  • With an increase in the required volume of oil the pumps (11, 12, 13 and 14) are loaded in the numerical order in this manner (the reverse of order with a decrease in oil requirement). One or more 100% delivery pumps and one supplemental pump under half-load state satisfy exactly the oil requirement, while the remaining pump or pumps are maintained under no-load state with no delivery. This control method ensures up to 40% power saving as compared with the conventional method wherein all of the pumps are loaded at one time.
  • In Figure 4, a particular pump is adapted to start inclining after 100% inclination of the preceding pump. However, in the case where speed should vary during one operation stroke, the particular pump may start inclining subsequent to 95% inclination.ofthe preceding pump, for example, in order to provide smooth and continuous operation as a whole. In this case, the relationship between the extrusion speed and the inclination speed is controlled to be one half of that with only one pump.
  • For the variable-delivery pump the volume efficiency and the overall efficiency vary in dependence on the inclination (a) or the delivery volume of oil delivered as shown in Figure 5 and 6. The characteristic of the variable-delivery pump is that its volume efficiency amount to maximum values when it operates with its rated maximum delivery (maximum inclination).
  • As discussed with regard to the illustrative embodiment, the operation speed of the stem within the extrusion press is varied frequently and within a wide range so that the volume of oil supplied and the delivery of the pump are varied frequently and within a wide range. As a result, the respective pumps operate less frequently with its rated maximum speed (the required volume of oil is equal to the total of the maximum deliveries of the overall pumps).
  • According to the present invention, only a minimum number of the pumps are loaded depending upon oil requirement and the remaining pumps are unloaded, thus reducing power consumption. Moreover, only one of the loaded pumps is held in half-load state while all of the remaining pumps operate with full or 100% delivery. This leads to a substantial increase in the total efficiency of the pumps and remarkable energy-saving characteristics.
  • Further energy-saving effected is ensured if the hydraulic circuit is unloaded in conjunction with the unloaded pumps and the drive motors (21, 22, 23 and 24) are disenergized. Under the circumstance it is easy to incorporate an automatic sequence as follows: For example, the motor (24) is disenergized when the pump (11) is in 100% delivery state and the pump (12) is in half-load state. The motor (23) is disenergized when the delivery control signal (C3) for the pump (12) is less than 70% and energized when the same exceeds 70%. The pump (13) is maintained in no-load state.
  • Assume now that the four main pumps are used and the extrusion speed is selected at 25% . and 50% of the rated speed. Power-saving effects can be evaluated and compared as follows. In the conventional pump uniform control method all of the pumps are loaded with 25% delivery and 50% delivery, respectively, whereas according to the present invention only one of the pumps is energized with 100% delivery and the remaining three pumps are unloaded when the extrusion speed is desired to be 25% of the rated speed. Moreover, when the extrusion is 50% of the rated speed, two of the pumps are loaded under 100% delivery state and the remaining two pumps are unloaded. Under these circumstances the present invention exhibits outstanding energy-effects as depicted in Figure 7. Figure 7 shows estimated ratios of percentages of power saving by the present invention wherein power saving by the conventional method is 100%. The line (a) depicts power saving when the extrusion speed is 25% of the rated value, while the line (b) power saving when the extrusion speed is 50% of the rated speed. It is clear from Figure 7, that the present invention ensures 20-40% power saving in the case of the line (a) and 8-18% power saving in the case of the line (b). The lower the extrusion pressure (remarkable especially with less than 50 kg/cm2) and the extrusion speed, the greater the power saving effect.
  • As noted earlier, the present invention provides effective and power-saving actuation of the pumps.
  • Whereas in the above illustrated embodiment of the present invention the power-saving effect is ensured in the extrusion press wherein the extrusion speed (the required volume of oil) is varied frequently and within a wide range, it is obvious that the concept of the present invention is equally applicable to any hydraulic actuators including an extrusion press.

Claims (2)

1. A control system for use in a hydraulic circuit including a plurality of parallel pumps (11 to 14); said control system (37 to 34; 41 to 44; 80 to 82) comprising means (41 to 44) for bringing a variable number of pumps into a loaded state dependent on the required volume of pressure fluid, characterised in that the pumps are variable-delivery pumps (11 to 14) and the control system controls the plurality of pumps (11 to 14) so that when the required volume of pressure fluid does not exceed the maximum volume deliverable from one pump, one only of said pumps (11) is in a loaded state for delivering the required volume of pressure fluid and the other pumps (12 to 14) are in an unloaded state, and when the required volume of pressure fluid exceeds the maximum volume deliverable from one or more pumps, one or more of said pumps (11 to 14) are in their substantially maximum delivery state, one only of the other pumps is in an intermediate delivery state and the remaining pumps are in an unloaded state.
2. A control system as claimed in claim 1 characterised in that the control system includes a delivery regulator (31 to 34) and a loading control valve (41 to 44) for each pump (11 to 14), said delivery regulators and loading control valves being responsive to control signals (Ci to C4; C↑' to C4') provided by controller means (82) in response to a demanded quantity of pressure fluid.
EP19800303741 1979-10-22 1980-10-22 Control system for a hydraulic circuit including a plurality of parallel variable-delivery pumps Expired EP0027743B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP13661879A JPS5659005A (en) 1979-10-22 1979-10-22 Controller for hydraulic circuit including plural variable-capacity pumps in parallel
JP136618/79 1979-10-22

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EP0027743A1 EP0027743A1 (en) 1981-04-29
EP0027743B1 true EP0027743B1 (en) 1985-05-15

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EP0027743A1 (en) 1981-04-29
JPS5659005A (en) 1981-05-22
DE3070650D1 (en) 1985-06-20

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