GB2222664A - Hydraulic transmission with braking - Google Patents

Hydraulic transmission with braking Download PDF

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Publication number
GB2222664A
GB2222664A GB8916794A GB8916794A GB2222664A GB 2222664 A GB2222664 A GB 2222664A GB 8916794 A GB8916794 A GB 8916794A GB 8916794 A GB8916794 A GB 8916794A GB 2222664 A GB2222664 A GB 2222664A
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United Kingdom
Prior art keywords
line
hydraulic
valve
pressure
pressure line
Prior art date
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Granted
Application number
GB8916794A
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GB2222664B (en
GB8916794D0 (en
Inventor
Franz Fleckenstein
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Linde GmbH
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Linde GmbH
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Publication of GB8916794D0 publication Critical patent/GB8916794D0/en
Publication of GB2222664A publication Critical patent/GB2222664A/en
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Publication of GB2222664B publication Critical patent/GB2222664B/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/4157—Control of braking, e.g. preventing pump over-speeding when motor acts as a pump
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T1/00—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles
    • B60T1/02—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels
    • B60T1/08—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels using fluid or powdered medium
    • 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
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/165—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for adjusting the pump output or bypass in response to demand
    • 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
    • F15B2211/20507—Type of prime mover
    • F15B2211/20523—Internal combustion engine
    • 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
    • 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
    • F15B2211/26—Power control functions
    • 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
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/30535—In combination with a pressure compensating valve the pressure compensating valve is arranged between pressure source and 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
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3105—Neutral or centre positions
    • F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • 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
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3144—Directional control characterised by the positions of the valve element the positions being continuously variable, e.g. as realised by proportional 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
    • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/3157—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
    • F15B2211/31576—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line having a single pressure source and a single 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
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/321—Directional control characterised by the type of actuation mechanically
    • F15B2211/324—Directional control characterised by the type of actuation mechanically manually, e.g. by using a lever or pedal
    • 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
    • F15B2211/35—Directional control combined with flow control
    • F15B2211/351—Flow control by regulating means in feed line, i.e. meter-in 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
    • F15B2211/30—Directional control
    • F15B2211/35—Directional control combined with flow control
    • F15B2211/353—Flow control by regulating means in return line, i.e. meter-out 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
    • F15B2211/50—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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6054—Load sensing circuits having valve means between output member and the load sensing circuit using shuttle 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6055—Load sensing circuits having valve means between output member and the load sensing circuit 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
    • F15B2211/70—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
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058—Rotary 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
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7135—Combinations of output members of different types, e.g. single-acting cylinders with rotary motors

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Transportation (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Control Of Fluid Gearings (AREA)
  • Control Of Transmission Device (AREA)

Description

HYDRAULIC SWITCHING ARRANGEMENT FOR A VEHICLE HAVING A HYDROSTATIC
TRANSMISSION 1 The invention relates to a hydraulic switching arrangement for a vehicle having a hydrostatic transmission formed by at least one hydraulic pump, preferably a displacement pump, and at least one hydraulic motor, which delivers driving effort and takes up drag effort. where a drive engine is coupled to a hydraulic operating pump which has a constant volumetric displacement and which is connected to at least one consumer of hydraulic energy via a directional control valve in a feed pressure line, where a pressure balance Is arranged upstream of the directional control valve. which pressure balance occupies a first switching position which connects the feed pressure line to an outlet line when the directional control valve is not actuated, and occupies a second switching position which obstructs the delivered flow when the directional control valve Is actuated, and which has a first control surface which is acted upon by spring force and is connected to a load pressure line and a second control surface which is acted upon by feed pressure.
A switching arrangement of this type has been disclosed in German Patent application P 38 21 348.6 and can be used, for example, In fork-lift trucks. The drive engine, normally an internal combustion engine, drives both the displacement pump of a hydrostatic transmission for the locomotive drive and an additional operating pump for the power hydraulics. The operating pump is generally In the form of a positive displacement pump, whose output is thus dependent upon the rotation speed of the drive engine. When the directional control valves of the power hydraulics are not actuated. an Input pressure balance in the directional control valve block ensures that the delivered flow of the positive displacement pump passes directly into an outlet line leading to the tank.
As Is known. when vehicles with a hydrostatic transmission are braked by reducing the gear ratio of the transmission, the hydraulic machine connected to the drive wheels of the vehicle operates as a pump and the hydraulic machine connected to the drive engine operates as a motor. In this way the drive engine Is driven by the driving wheels and braking energy is fed Into the drive engine. The braking energy Is taken up by the drive engine which Is 2222664 2 driven at a higher speed than the speed governed by the position of the speed control device. In this way the drive engine takes up from its drive shaft a moment which also referred to as so-called drag effort.
Under certain circumstances, for example when the vehicle is braked on a steep incline, the drag effort available from the drive engine is Insufficient to terminate the braking process, I.e. the braking energy cannot be completely taken up by the drive engine without an Increase In the speed of the drive engine and thus also of the hydraulic engines in excess of the permissible degree. This would lead to destruction in the drive line.
From DE-OS 32 47 335 it is known in this case to use the additional pump, which is normally responsible only for the power hydraulics, to consume braking energy. This takes place in that when a specific, predetermined limit speed has been exceeded, a throttle is switched into the speeddependent delivered flow of the additional pump so that the additional pump can thus take up drag effort.
The aim of the present invention is, using simple means and largely employing existing switching elements, to provide a hydraulic switching arrangement which facilitates the braking of a vehicle with a hydrostatic drive by additionally exploiting the available drag effort of the operating pump.
According to the present invention, a hydraulic switching arrangement for a vehicle having a hydrostatic transmission formed by at least one hydrostatic pump, preferably a displacement pump, and at least one hydraulic motor which delivers driving effort and takes up drag effort. wherein a drive engine is coupled to a hydraulic operating pump which has a constant volumetric displacement and to which at least one consumer of hydraulic energy is connected via a directional control valve in a feed pressure line, and wherein a pressure balance is arranged upstream of the directional control valve, which pressure balance occupies a first switching position connecting the feed pressure line to an outlet line when the directional control valve is not actuated, and occupies a second position obstructing the delivered flow when the directional control 3 valve is actuated, and which has a first control surface which is acted upon by biasing force and is in communication with a load pressure line, and a second control surface which is acted upon by feed pressure is characterised in that in the feed pressure line between the operating pump and the pressure balance there is arranged a delivered flow measuring valve which has a switching position which is governed by the delivered flow and in which the feed pressure line is connected to the first control surface of the pressure balance. The delivered flow measuring valve indirectly measures the speed of the operating pump and thus of the drive engine which drive the operating pump. If a specific, still permissible speed is exceeded during the braking process, the delivered flow measuring valve switches the output pressure of the operating pump to the first control surface of the pressure balance. As the output pressure of the operating pump also acts upon the second control surface of the pressure balance, their counteracting control forces cancel one another so that the spring biasing force acting upon the first control surface brings the pressure balance into the blocked position and thus obstructs the pump flow. In this way an additional braking effect Is produced.
It Is advantageous for the connection between the feed pressure line and the first control surface of the pressure balance to be formed by a connection line connected to the load pressure line. The directional control valve to the Individual consumers, the input pressure balance and the load pressure line consisting of a two-way valve chain are normally combined to form a valve block. Therefore it is sufficient to provide a connecting line to the load pressure line in order to be able to influence the first control surface of the pressure balance without additional outlay and without redesigning the valve block. Expediently the relief pressure valve usually present in the load pressure line of the valve block can be used to prevent the pressure which has built up in the feed pressure line during braking from becoming too high.
4 In an advantageous further development of the invention it is provided that in the switching position governed by the delivered flow. a connection is established between the outlet line and a line leading to an additional brake. When the vehicle is operating in the travelling mode the additional brake, which consists of a springloaded brake, is acted upon by a control pressure which holds the brake off, against the spring force.
In the described braking process in which, as a result of excessively high braking energy, the predetermined speed of the drive engine is exceeded and therefore the operating pump is used to consume the braking energy, it is possible to also use the additional pump if the control pressure line of the additional pump is connected to the delivered flow measuring valve and, in the previously described switching position, a connection is established to the outlet line so that the additional brake closes.
The aim of the invention is also fulfilled in that in the feed pressure line between the operating pump and the pressure balance there is arranged a delivered flow measuring valve which has a switching position which is governed by the delivered flow and in which an outlet line is connected to the second control surface of the pressure balance. This switching permits a reduction in the feed pressure acting upon the second control surface so that, as a result of the spring force acting upon the first control surface, the pressure balance assumes the blocked position and thus obstructs the pump flow, leading to an additional braking effect.
It is favourable for the delivered flow measuring valve to comprise a valve piston which is subject to spring force, is longitudinally displaceable in a housing and is provided with a concentric through-bore in which an orifice gauge Is located. Such a valve is simple and economical to produce and in normal operation obstructs the delivered flow only slightly. The construction of such a valve is further simplified if the valve piston is provided with control edges which are formed by annular grooves and which, in specific switching positions, are actively connected to bores in the valve housing connected to hydraulic lines.
The embodiments of the invention will now be explained in detail, with reference to following Figures, in which:
Figure 1 is a diagram of a first switching arrangement corresponding to the invention; Figure 2 is a diagram of a second embodiment.. a variant of Figure 1; Figure 3 is a diagram of a third variant of Figure 1.
Referring to the Figures, In which like elements are given like reference numerals there is seen a drive engine 1, for example a diesel motor, which comprises a speed control device 2 consisting of a control cylinder 3 and a piston 5 which is longitudinally displaceable therein against the force of a spring 4. The speed control device 2 Is connected by linkage 6 to the speed controller (not shown) of the drive engine 1, for example a fuel injection pump or a mechanical governor. The drive engine 1 drives at least one hydraulic displacement pump which is connected to at least one hydraulic motor with which it forms a hydrostatic transmission for a travelling mechanism. The hydrostatic transmission is not illustrated in the Figures. The drive engine 1 Is connected to a hydraulic operating pump 7 by which fluid is drawn from a tank 8 and fed via a feed pressure line 9 for example to the power hydraulics of a fork-lift truck. The feed pressure line 9 leads to a spring-biased delivered flow measuring valve 10 which fundamentally consists of a housing 10a, a valve piston 10b provided with a concentric through-bore 10c, and an orifice gauge 10d, and from here on to a directional control valve block 11 In which are arranged the arbitrarily operable directional control valves 12, 131 14 of consumers 15a, 15b, 161 17 of hydraulic energy. The directional control valve block 11 comprises sub- elements lla, llb, llc. lld and is extendable by further sub-elements to enable further consumers of hydraulic energy to be connected. The directional control valves 12. 13, 14 can consist of 5 port/3 position directional control valves. The single-acting consumers 15a, 15b which represent the two lifting cylinders of a fork-lift truck lifting frame. are connected via a supply line 18 to the associated directional control valve 12. The 6 double-acting consumers 16, 17 are connected via supply lines 19a. 19b and 20a, 20b to the associated directional control valves 13, 14. The feed line 9 is connected via branch lines containing non-return valves to the directional control valves 12, 13, 14, each of which is in turn connected to an outlet line 21 which leads into the tank 8. From the directional control valves 12, 13, 14 the lines which signal the respective load pressure when the directional control valve is actuated lead to two-way valves 23, 24, 25 which are connected to one another and which are connected via a throttle 26 and a pressure limiting valve 27 to the outlet line 21 and thus form a chain of two-way valves.
Between the feed pressure line 9 and the outlet line 21 in the subelement lla of the directional control valve block 11 a pressure balance 28 which has a first control surface 28a and second control surface 28b is arranged in a bypass line 29. The first control surface 28a is springloaded and is approached by a connecting line 30 which branches from the two-way valve chain between the throttle 26 and the pressure limting valve 27. The second control surface 28b is connected to the feed pressure line 9. In the basic position, i.e. when no directional control valve is actuated, the pressure balance 28 is displaced against the spring force by the feed pressure present in the feed pressure line 9 and thus on the control surface 28b into a position which connects the feed pressure line 9 to the outlet line 21.
The outlet line 21 is connected to an outlet line 22 which commences from a bore 31 in the housing 10a of the delivered flow measuring valve 10 and likewise leads into the tank 8. In the basic position, i.e. when the operating pump rotates at a low speed and therefore delivers only a small delivered flow, the bore 31 is connected to an annular groove 10e of the valve piston 10b. A further bore 32 in the housing 10a of the delivered flow measuring valve 10 is connected to a connecting line 33 which leads to the twowaY valve 23 of the two-way valve chain-and the load pressure line, and in the basic position is likewise connected to the annular groove 10e.
7 Downstream of the bypass line 294. a line 34 leads from the feed pressure line 9 to a pressure reducing valve 35 which determines the control pressure in a control pressure line 36 which leads to the speed control device 2 of the drive engine 1. The pressure control valve 35 Is coupled to the outlet line 21 so that excess fluid can be fed Into the tank 8. The control pressure line 36 contains a two-way valve 37 which Is connected to a line 38. The line 38 can represent, for example, a signal line which supplies a control signal to increase the speed of the drive engine when travelling motion of the fork-lift truck is required.
The mode of operation of the hydraulic switching arrangement is as follows: In the basic position the drive engine 1 operates at Idling speed and none of the directional control valves 12, 131 14 is actuated. The pump 7 conveys fluid at a low pressure through the feed pressure line 9 to the pressure balance 28 where, when the second control surface 28b is acted upon, the fluid is fed via the open pressure balance 28 Into the outlet line 21 and thus into the tank 8. Via the line 34 fluid flows to the pressure control valve 35 and from here via the two-way valve 37 to the speed control device 2. However the pressure is insufficient to result in an Increase in speed.
As soon as one of the directional control valves 12, 13, 14 is actuated, a connection is established between the activated consumer and the two- way valve chain and from here via the connecting line 30 to the first control surface 28a of the pressure balance 28. Then the pressure balance 28 Is brought by spring force Into a position which Interrupts the connection from the feed pressure line 9 to the outlet line 21. The fluid delivered by the pump 7 flows through the line 34 to the pressure control valve 35 and thus to the speed control device 2. The occurring pressure is sufficient to displace the control piston 5 in the control cylinder 3 against the force of the spring 4 and thus to result In an increase In speed of the drive engine 1.
8 When the vehicle is not in direct operative use the speed control device 2 is supplied with the speed signal from a control pressure line 38 connected to the accelerator pedal. On braking, thus when the accelerator pedal is released and the speed signal approaches zero.. the speed of the drive engine 1 falls more or less rapidly to the idling speed depending upon the drag effort which is to be taken up. The operating pump 7 continues to operate during this process and its output is conveyed virtually without pressure into the tank 8 via the open pressure balance 28 and the outlet line 21. If, on braking, a specific speed of the drive engine 1 and thus a specific output of the operating pump 7 is exceeded because too much braking energy is to be consumed, as a result of the congestion in the orifice gauge 10d the valve piston 10b of the delivered flow measuring valve 10 Is displaced against the spring force and connects the feed pressure line 9 to the connection line 33 either before or after the delivered flow measuring valve 10 considered in the direction of flow. The pressure in the connecting line 33 is propagated via the two-way valve chain to the first control surface 28a of the pressure balance 28. The pressures acting upon the two control surfaces 28a and 28b cancel one another out so that the pressure balance 28, which is subject to spring force. assumes the blocked position and a pressure builds up in the feed pressure line 9. As a result an additional braking moment arises in the operating pump 7. If the accumulated pressure In the feed pressure line 9 becomes too great, the pressure limiting valve 27 is activated and conducts fluid into the outlet line 21.
Figure 2 differs from Figure 1 in that when the valve piston 10b is displaced, in addition to the connection of the feed pressure line 9 to the load pressure line via the connecting line 33, the bore 31 in the housing 10a is connected via the annular groove 10c to a further bore 39 from which a line 40 leads to the control pressure line 41 of two springloaded brakes 42 and 43 which act upon the drive - and driven shafts of two hydraulic motors in the hydrostatic transmission. In this way the pressure prevailing in the control pressure line 41 can be propagated into the outlet line 22 where the 9 pressure is reduced by expelling the fluid into the tank 8. The spring- loaded brakes 42 and 43 thus close and reinforce the braking effect emanating from the hydrostatic transmission or drive engine 1 and the operating pump 7.
In contrast to Figure 1, Figure 3 does not illustrate the connecting line 33 and the bore 32 in the housing 10a of the delivered flow measuring valve 10. The bore 31 is connected via a line 44 to the second control surface 28b of the pressure balance 28. Above the limit speed of the drive engine 7 the valve piston 10b Is displaced to such an extent that the annular groove 10e connects the bore 31 to the bore 39 which Is In turn connected to the tank 8 via the outlet line 22. The obstructing and thus braking effect in the feed pressure line 9 results from a throttle 45 in the feed pressure line 9 preceding the second control surface 28b of the pressure balance 28 considered in the flow direction, and from the control edges in the delivered flow measuring valve 10. When an excessive increase occurs in the pressure In the feed pressure line 9, the pressure balance 28 re-assumes the open position.

Claims (8)

Claims
1. A hydraulic switching arrangement for a vehicle having a hydrostatic transmission formed by at least one hydrostatic pump. preferably a displacement pump, and at least one hydraulic motor which delivers driving effort and takes up drag effort. wherein a drive engine is coupled to a hydraulic operating pump which has a constant volumetric displacement and to which at least one consumer of hydraulic energy is connected via a directional control valve In a feed pressure line, and wherein a pressure balance is arranged upstream of the directional control valve, which pressure balance occupies a first switching position connecting the feed pressure line to an outlet line when the directional control valve is not actuated. and occupies a second position obstructing the delivered flow when the directional control valve is actuated, and which has a first control surface which is acted upon by biasing force and is in communication with a load pressure line, and a second control surface which is acted upon by feed pressure. characterised in that in the feed pressure line between the operating pump and the pressure balance there is arranged a delivered flow measuring valve which has a switching position whichis governed by the delivered flow and in which the feed pressure line is connected to the first control surface of the pressure balance.
2. A hydraulic switching arrangement as claimed In Claim 1. characterised in that the connection between the feed pressure line and the first control surface of the pressure balance is formed by a connection line connected to the load pressure line.
3. A hydraulic switching arrangement as claimed in Claim 2. characterised In that a pressure relief valve is arranged in the load pressure line.
11
4. A hydraulic switching arrangement as claimed in one of the preceding Claims, characterised in that a connection between the outlet line and a line leading to an auxiliary brake is established when the delivered flow measuring valve is in its switching position governed by the delivered flow.
5. A hydraulic switching arrangement for a vehicle having a ransmission formed by a least one hydraulic pump, hydrostatic 1. preferably a displacement pump, and at least one hydraulic motor which delivers driving effort and takes up drag effort, wherein a drive engine is coupled to a hydraulic operating pump which has a constant volumetric displacement and which is connected to at least one consumer of hydraulic energy via a directional control valve in a feed pressure line, where a pressure balance is arranged upstream of the directional control valve, which pressure balance occupies a first switching position which connects the feed pressure line to an outlet line when the directional control valve is not actuated, and occupies a second switching position obstructing the delivered flow when the directional control valve is actuated, and which has a first control surface which is acted upon by biasing force and is In communication with a load pressure line, and a second control surface which is acted upon by feed pressure, characterised in that in the feed pressure line between the operating pump and the pressure balance there is arranged a delivered flow measuring valve which has a switching position which is governed by the delivered flow and In which an outlet line is connected to the second control surface of the pressure balance.
6. A hydraulic switching arrangement as claimed in one of the preceding Claims, characterised In that the delivered flow measuring valve comprises a spring-biased valve piston which is longitudinally displaceable In a housing and is provided with a concentric through-bore In which an orifice gauge Is arranged.
12
7. A hydraulic switching arrangement as claimed Claim 6, characterised in that the valve piston has control edges which are formed by annular grooves and which In specified switch4ng positions are in communication with bores In the valve housing connected to hydraulic lines.
8. A hydraulic switching arrangement substantially as herein descibed, with reference to Figure 1. Figure 2. or Figure 3, of the accompanying drawings.
Published 1990 atThe Patent Office. State House e43.7 t F4h Holburn. London WClR 4TP. Further Copies Maybe obtained from The Patent Omce. 53aes Branch. St Uary Cray. OrpLnitca. K2n.'aBZ 3RD. Printed by Uuluplex techruques ltd, St Uary Cray, Kent, Com 1.87
GB8916794A 1988-07-28 1989-07-21 Hydraulic switching arrangement for a vehicle having a hydrostatic transmission Expired - Fee Related GB2222664B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19883825726 DE3825726C2 (en) 1988-07-28 1988-07-28 Hydraulic shift arrangement for a vehicle with a hydrostatic transmission

Publications (3)

Publication Number Publication Date
GB8916794D0 GB8916794D0 (en) 1989-09-06
GB2222664A true GB2222664A (en) 1990-03-14
GB2222664B GB2222664B (en) 1992-02-05

Family

ID=6359800

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8916794A Expired - Fee Related GB2222664B (en) 1988-07-28 1989-07-21 Hydraulic switching arrangement for a vehicle having a hydrostatic transmission

Country Status (3)

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DE (1) DE3825726C2 (en)
FR (1) FR2636893B1 (en)
GB (1) GB2222664B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2418473A (en) * 2004-09-24 2006-03-29 Linde Ag Hydrostatic braking system using working hydraulic pump of fork lift

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4020561A1 (en) * 1990-06-28 1992-01-09 Man Nutzfahrzeuge Ag COMPRESSED AIR SYSTEM IN A COMMERCIAL VEHICLE
DE19852039A1 (en) * 1998-11-11 2000-05-25 Sauer Sundstrand Gmbh & Co Vehicle with hydrostatic drive has retarder valve for hydraulically acquiring braking energy with connected pressure-limiting valve for choking output vol. flow of variable delivery pump
DE10224730B4 (en) * 2001-06-29 2012-09-27 Linde Material Handling Gmbh Hydraulic control device
DE102004062388B4 (en) 2004-12-23 2006-10-19 Brueninghaus Hydromatik Gmbh Hydrostatic drive with speed limitation
DE102017114704B4 (en) * 2017-06-30 2019-10-10 Vemcon Gmbh Modular hydraulic unit, vehicle and control system for a working machine
CN109139598A (en) * 2018-08-23 2019-01-04 江苏理工学院 A kind of double valve-regulated load port separate control valves based on the compensation of machine hydraulic pressure difference

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Publication number Priority date Publication date Assignee Title
DE3247335A1 (en) * 1981-12-21 1983-09-01 Linde Ag, 6200 Wiesbaden Drive assembly with a primary energy source and with a device for braking
DE3821348C2 (en) * 1988-06-24 1997-09-11 Linde Ag Hydraulic system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2418473A (en) * 2004-09-24 2006-03-29 Linde Ag Hydrostatic braking system using working hydraulic pump of fork lift
US7559401B2 (en) 2004-09-24 2009-07-14 Linde Material Handling Gmbh Hydrostatic drive system
GB2418473B (en) * 2004-09-24 2009-12-09 Linde Ag Hydrostatic drive system

Also Published As

Publication number Publication date
FR2636893A1 (en) 1990-03-30
DE3825726C2 (en) 1997-07-10
DE3825726A1 (en) 1990-02-01
GB2222664B (en) 1992-02-05
GB8916794D0 (en) 1989-09-06
FR2636893B1 (en) 1994-04-15

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