Classifications

• • 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
  • F15B11/163—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
• • 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
  • F15B11/003—Systems with load-holding 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
  • F15B2211/50545—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using braking valves to maintain a back pressure

Definitions

• the invention relates to a hydraulic control arrangement for a mobile work machine with at least two hydraulic consumers, one of which is provided for a lifting function.
• a forklift usually has a mast along which a fork is movable to raise or lower a load.
• the mast can also be tilted and moved laterally, these functions are each operated by hydraulic cylinders.
• proportional valves are provided in the known solution, via which the pressure medium volume flow to the respective hydraulic cylinder can be adjusted.
• the pressure medium supply usually takes place via an LS variable displacement pump or a fixed displacement pump with bypass pressure compensator. Depending on the highest load pressure of all consumers, the variable displacement pump or the bypass pressure compensator can be controlled such that the pump pressure is above the highest load pressure by a predetermined ⁇ p.
• a problem may occur when, for example, raised the empty, unloaded fork and at the same time the mast tilt is to be changed.
• the load pressure at the tilting cylinder in this case is greater than the load pressure of the lifting cylinder, so that the latter is preferably supplied with pressure medium and the fork is raised relatively quickly, while the tilting movement is very slow or even stopped. This problem occurs in virtually all conventional forklifts.
• the object of the invention is to provide a hydraulic control arrangement for a mobile work machine in which several consumers can be controlled simultaneously.
• the at least two consumers of the mobile working machine are supplied with pressure medium via a pump as a function of the highest load pressure.
• the pressure medium volume flow to an effective in the direction of lifting the consumer and the pressure medium flow to another consumer are each controlled by a LUDV valve with a Zulaufmessblende and a downstream pressure compensator in the closing direction of a pressure corresponding to about the highest load pressure of the consumer and in the opening direction downstream of the inlet orifice is acted upon.
• LUDV controls load pressure-independent flow distribution
• LUDV pressure compensators throttle the pressure medium flow rate so strong that the pressure after all Zumessblenden same, preferably equal to the highest load pressure or slightly above this. When undersatured, the pressure downstream of the metering orifice does not change.
• the pump pressure is applied in the same way, so that the pressure difference at all metering orifices changes in the same way if the pump pressure becomes lower during undersaturation - thus ensuring a proportional flow distribution of the delivery rate to the consumers, so that, for example, an unloaded fork lifted a fork lift and at the same time a mast of the forklift can be tilted.
• a LUDV valve with a metering orifice and a LUDV pressure compensator two consumers are assigned, which are provided, for example, for tilting and moving a mast of a forklift.
• the pressure medium flow direction to and from the consumer is then controlled via a respective directional control valve.
• a respective directional control valve D. h.,
• the metering orifices of the LUDV valves are very simple, designed to be continuously adjustable in one direction, so that the circuit can be implemented very inexpensively.
• the pressure compensator of the common LUDV valve can be assigned a pressure reducing valve.
• the hydraulic actuation of a steering of the mobile work machine is preferably carried out via an LS valve with an inlet orifice and a steering pressure compensator.
• the steering pressure compensator in the closing direction is acted upon by the pressure in front of the associated inlet orifice and in the opening direction by a spring and the pressure in a control line.
• This control line is connected to a line section leading the load pressure of the steering.
• a line section located downstream of the steering pressure scale prefferably to be connected via a control channel and a check valve closing in the direction of the steering to a LS line leading to the highest load pressure of the loads.
• control line (118) leads from a pressure medium flow path upstream of the steering pressure balance (112) to a line section carrying the load pressure of the steering, wherein two nozzles (120, 122) are arranged in the control line (118) and in the area between the two two nozzles (120, 122) branches off to an effective in the opening direction of the steering pressure balance (112) control chamber control channel (124) which is connected via a check valve (126) with a highest load pressure leading LS line (60).
• the control arrangement can be implemented particularly easily if the pump for supplying pressure medium is a constant-displacement pump to which a bypass pressure compensator is assigned, which is acted upon in the opening direction by the pump pressure and in the closing direction by the highest load pressure of the consumers.
• the LS line can be connected to a pressure relief valve via a relief valve with a tank.
• This relief valve is designed as a flow control valve.
• the control arrangement according to the invention is preferably used for controlling a forklift, wherein a LUDV valve for controlling the lifting function and a LUDV valve for controlling the tilting and the lateral displacement of a mast of the fork-lift truck are provided.
• Figure 1 is a circuit diagram of a control arrangement of a forklift truck with a lift, a tilt and a shift function
• Figure 2 is a detail of the control arrangement of Figure 1;
• Figure 3 shows the control arrangement of Figure 1 with integrated LS steering and
• FIG. 4 shows a variant of the circuit according to FIG. 3.
• FIG. 1 shows a circuit diagram of a hydraulic control arrangement of a fork-lift truck.
• This control arrangement is formed for example by a mobile control block 1, which consists essentially of a LUDV section 2, two-way valve sections 4, 6 and an end plate 8.
• the mobile control block 1 has a pressure port P, a tank port T and a working port A at the LUDV section 2 and each working ports A, B at the two-way valve sections 4, 6.
• the illustrated mobile control block 1 is for driving a mast and the fork of the forklift provided, via a lifting cylinder 10, the fork can be raised or lowered.
• a tilting cylinder 12 is provided for tilting the fork leading the fork and a displacement cylinder 14 for laterally displacing the mast.
• the lifting cylinder 10 is a differential cylinder, wherein a bottom-side cylinder chamber 16 is connected via a working line 18 to the working port A of the LUDV section 2.
• the tilting cylinder 12 is designed as a double cylinder with two parallel-connected differential cylinders, wherein the bottom-side cylinder chambers are connected via a consumer line 20 and the two piston rod-side annular spaces via a further consumer line 22 to the working ports B and A of the directional valve section 4.
• a lowering brake valve 24 is arranged, which allows a pressure medium supply from the working port A to the two annular spaces unhindered and throttles the return of the two annular spaces to the working port A, so that a controlled tilting of the mast is made possible.
• Such lowering brake valves or counter-balance valves are known from the prior art, so that further explanations are unnecessary.
• the displacement cylinder 14 is designed as a synchronous cylinder, wherein the two annular spaces are connected via a working line 26 and a further working line 28 to the working ports A, B of the directional valve section 6.
• a 4/3-way switching valve 34 and 32 is respectively provided, which are biased in the blocking position shown and over - as will be explained in more detail - the pressure fluid flow direction to and from the cylinders 12, 14 adjustable is.
• the LUDV section 2 has a LUDV valve 34 which is assigned to the two cylinders 12, 14 and which consists of a metering orifice 36 and a LUDV pressure compensator 38 connected downstream thereof.
• the LUDV pressure compensator 38 is acted upon in the direction of its closed position by the highest load pressure or a pressure approximately corresponding thereto and in the opening direction by the pressure downstream of the respective upstream metering orifice 36.
• the metering orifice 36 is designed by a continuously adjustable 2/2-way valve, which is biased in its closed position shown.
• the metering orifice can be opened by energizing a proportional magnet 40 for adjusting the pressure medium volume flow to the consumers 12, 14.
• the pressure medium volume flow to the lifting cylinder 10 is also set via a LUDV valve, which is referred to below as lifting LUDV valve 42.
• lifting LUDV valve 42 Its basic structure corresponds to that of the LUDV valve 34 - it thus essentially consists of a lifting metering orifice 44 and one of these downstream lifting LUDV pressure compensator 46.
• the lifting metering orifice 44 is also designed by a continuously adjustable 2/2-way valve, whose opening cross-section is in turn adjustable via a proportional magnet 48.
• the lifting of a load by supplying pressure medium in the bottom-side cylinder chamber 16 of the lifting cylinder 10.
• a LS-valve 50 Such a LS-valve consists essentially of a continuously adjustable LS metering orifice 52, which is associated with a LS-pressure compensator 54. This is in the illustrated embodiment, the LS metering orifice 52 upstream and applied in the direction of its closed position by the force of a spring and the pressure after the LS metering orifice and in the opening direction of the pressure upstream of the LS metering orifice 52.
• the LS metering orifice 52 is designed as a 2/2-way seat valve, which allows a leak-free shut-off of the working line 18 in its illustrated blocking position.
• the LS metering orifice 52 can be adjusted by means of a proportional solenoid 56 or by hand. Further details of the described LS / LUDV valves are explained with reference to FIG.
• the pressure port P of the mobile control block 1 is designed to the output port of a LS pump, which may be formed for example as a fixed displacement pump.
• the flow of this constant pump, not shown, is then adjusted via a bypass pressure compensator 58, which is acted upon in the opening direction by the pump pressure and in the closing direction of the highest load pressure of all consumers and by the force of a pressure compensator spring.
• the pump pressure is always adjusted by a force corresponding to the spring corresponding pump ⁇ above the highest load pressure, which is tapped in an LS line 60.
• this is connected via a designed as a flow control valve relief valve 62 connected to the tank port T of the mobile control block 1 drain line 64.
• a LS pressure relief valve 66 is provided to protect the pressure in the LS line 60. Further details of the LUDV section 2 will be explained with reference to the enlarged view in FIG.
• the pressure medium flows from the pressure port P via an inlet channel 68 to the input port of the lifting metering orifice 44 and the LUDV metering orifice 36.
• the output port of the LUDV metering orifice 36 is connected via a pressure compensator channel 70 to the input port of the LUDV pressure compensator 38, so that these in Opening direction of the pressure downstream of the LUDV metering orifice 36 is acted upon.
• this opening cross section is set via the proportional magnet 40.
• a rear control chamber 72 of the LUDV pressure compensator 38 is connected to the LS line 60, so that acts on the back of the pressure compensator piston, the pressure in the LS line 60 in the closing direction. Since the highest load pressure of all consumers or at least a corresponding pressure is present in this, the highest load pressure also arises at the entrance of the LUDV pressure compensator 38 in the control position. This highest load pressure is throttled over the LUDV pressure compensator 38 to the actual load pressure of the associated consumer and guided via the connected to the output terminal of the LUDV pressure compensator 38 feed line 74 to the associated consumer. In the flow line 74 a in the direction of the two cylinders 12, 14 opening check valve 76 is arranged, so that a pressure medium backflow to the LUDV valve 34 is prevented. The displaced from the cylinders 12, 14 pressure fluid flows through the drain passage 64 and the tank port T to the tank down.
• the lift-LUDV valve 42 has in principle the same structure as the LUDV valve 34.
• the input of the lifting metering orifice 44 is connected to the inlet channel 68 and the output via a further pressure compensator channel 74 to the input of the lifting LUDV pressure compensator 46 connected.
• Their rear control chamber 76 is also connected to the LS line 60, so that the pressure compensator piston of the lifting LUDV pressure compensator 46 is acted upon in the closing direction by the highest load pressure and in the opening direction by the pressure downstream of the lifting metering orifice 44. The adjustment of this lifting metering orifice 44 takes place via the proportional magnet 48.
• the output connection of the lifting LUDV pressure compensator 46 is connected to the working connection A via a feed channel 82 and a check valve 84 which opens in the direction of the working connection A.
• a feed channel 82 In the area between the Working port A and the check valve 84 branches from the feed channel 82 from a return channel 86, in which the effective in the lowering direction LS-valve 50 is arranged.
• the input of the LS inlet orifice 52 is connected to the return channel 86.
• the output is connected via a pressure compensator channel 88 to the input of the LS-pressure compensator 54.
• Their pressure compensator piston is acted upon in the closing direction by the force of a spring 90 and the pressure at the outlet of the LS inlet orifice 52.
• This control pressure is tapped via a control channel 92 in the pressure compensator channel 88. In the opening direction, the pressure acts upstream of the LS Zulaufmessblende 52.
• This pressure is tapped via a control channel 94, wherein a part of the control oil flow path, indicated in Figure 2 with 94a, is integrated into the LS metering orifice 52.
• the adjustment of the opening cross section of the LS metering orifice 52 takes place via the proportional magnet 56 or manually via a handle 96.
• the LS-valve 50 running off the lifting cylinder 10 pressure medium flow rate is held constant load pressure independent.
• the LS metering orifice 52 is designed as a seat valve, so that in the illustrated closed position a leakage-free support of the lifting cylinder 10 takes place.
• the LS Zumeßblende 52 is opened, the lowering speed can be kept constant load pressure, as in the control position of the LS pressure compensator 54 a constant, the force of the spring 90 corresponding pressure difference across the LS Zulaufmessblende 52 is adjusted.
• the bypass pressure compensator 58 is, as already mentioned, acted upon by the force of a pressure compensator spring 98 and the pressure in the LS line in the closing direction and in the opening direction by the pressure in the inlet channel 68, which is tapped off via a channel 100.
• the relief valve 62 and the LS pressure relief valve 66 each extend between the LS line 60 and the drain channel 64.
• the two cylinders 12, 14 are connected in parallel, it being provided that only one of the two consumers is switched on.
• the two cylinders 12, 14 upstream directional control valves 30, 32 are each designed as 4/3-way valves and biased by a centering spring assembly in its illustrated basic position.
• the adjustment in the switching positions a, b via switching magnets.
• switching the Wegevntils 30 in the switching position a of the flow channel 74 is connected to the working port A and the drain line 64 to the working port B.
• the two tilting cylinders 12 are extended and the mast tilt is correspondingly reduced.
• switching the directional control valve 32 in the switching position a is then moved according to the displacement cylinder 14 as shown in Figure 1 to the right.
• the two working ports A, B of the cylinder 12 are connected to the flow channel 64 and the feed channel 74 so that, for example, the mast is tilted over the tilting cylinder 12, wherein the tilting speed over that in the return located lowering brake valve 24 is determined.
• FIG. 3 shows an exemplary embodiment in which a steering system 102 is integrated into the circuit according to FIGS. 1 and 2.
• a steering system 102 is integrated into the circuit according to FIGS. 1 and 2.
• Such steering usually has a steering cylinder 104 which is supplied for steering via a steering unit 106 with pressure medium.
• Such steering units 106 also called Orbitrol, are described for example in the data sheet RD 14 365 Bosch Rexroth AG.
• the steering unit 106 consists essentially of a metering pump and a hand-operated servo valve in rotary valve construction. The size of the metering pump is chosen so that with three to five steering wheel turns from the stop to the stop of the steering can be steered. About the servo valve while a metering orifice is set.
• the pressure medium supply of the steering unit 106 via a branched off from the inlet channel 68 steering line 108 which is connected via a steering port C and a working line 110 to the steering unit 106.
• a steering pressure compensator 112 is arranged, which forms an LS valve together with the integrated into the steering unit 106 metering orifice, via which the pressure medium flow rate for adjusting the steering cylinder 104 can be kept constant independent of load.
• the steering pressure gauge 112 is in the closing direction from the upstream pressure, i. acted upon by the pressure in the region of the terminal C.
• This control pressure is tapped via a steering control line 114.
• an adjustable pressure compensator spring 116 and a steering control pressure, which is tapped on a control line 118.
• This extends from the steering unit 106 to an upstream of the steering pressure balance 112 located portion of the steering line 108.
• the load pressure of the steering can be tapped.
• two nozzles 120, 122 are arranged in the control line 118, which together form a pressure divider.
• control channel 124 In the area between the two nozzles 120, 122 branches off a control channel 124 which is also connected to a spring-side control chamber of the steering pressure balance 112, so that the pressure in the control channel 124 acts in the opening direction on the piston of the steering pressure balance 112.
• control channel 124 is connected via a further check valve 126 to the LS line 60.
• a predetermined pressure can then be set in the area between the nozzles 120, 122, which is a certain pressure difference above the steering load pressure.
• the steering 102 is supplied with pressure medium, wherein above the two orifices 36 and 44 of the LUDV consumers 10, 12, 14 no ⁇ is present, since with a suitable choice of the nozzle 120 at the entrance of associated LUDV pressure compensator 38, 46, the same pressure as in the control channel 124 is adjusted and this pressure with a suitable nozzle selection (nozzle 120) corresponds to the pump pressure, so that no Pressure medium or only a small volume flow to the other LUDV consumers flows, but the steering remains fully functional.
• a pressure reducing valve 128 is provided, via which in the directional control valve sections 4, 6, a lower working pressure than in the LUDV section 2 can be set.
• the pressure reducing valve 128 is preferably arranged in the region between the LUDV pressure compensator 38 and the check valve 76.
• FIG. 4 shows a further possibility of integrating the steering system 102 into the circuit according to FIG. 1, wherein the differences between the exemplary embodiments in FIGS. 3 and 4 lie merely in the tapping of the load pressure acting on the steering pressure compensator 112.
• the load pressure of the steering unit 106 is tapped via a channel 130, which has no connection to the steering line 108 in contrast to the control line 118 from the above-described embodiment.
• the control channel 124 connects in this embodiment, the LS line 60 to the working line 110, so that the pressure downstream of the steering pressure gauge 112 is reported via the check valve 126 in the LS line 60.
• This pressure is higher than the load pressure of the steering.
• the pressure balance spring 116 and the pressure in the channel 130 act on the steering pressure balance 112 in the opening direction. This pressure corresponds approximately to the load pressure of the steering (pressure downstream of the steering metering orifice).
• the pressure in the inlet channel 68 decreases and the respective load pressure of the LUDV consumers is applied to the outlet metering orifice via the LUDV pressure compensators, so that the pressure difference correspondingly exceeds the LUDV orifices fall and less pressure fluid flows to the LUDV consumers or these are no longer supplied with pressure medium.
• the steering unit 106 is supplied with pressure medium fully open steering pressure balance 112, so that the steering can still be operated.
• Such integration of a steering in a LUDV control arrangement is known per se from DE 101 19 276 A1, so that further embodiments are unnecessary. In principle, the above-described control arrangements can also be applied to other mobile machines, such as wheel loaders, mini excavators, etc.
• a hydraulic control arrangement for a mobile work machine in particular for a forklift, with at least two hydraulic consumers, one of which has a lifting function.
• the two consumers are each controlled via a LUDV valve with inlet orifice plate and downstream LUDV pressure compensator.
• Control channel further check valve

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Forklifts And Lifting Vehicles (AREA)
• Fluid-Pressure Circuits (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=39719645

Family Applications (1)

Country Status (5)

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• 2007
  • 2007-06-22 DE DE102007028864A patent/DE102007028864A1/de not_active Withdrawn
• 2008
  • 2008-03-20 WO PCT/DE2008/000491 patent/WO2008116451A1/fr not_active Ceased
  • 2008-03-20 AT AT08734422T patent/ATE544954T1/de active
  • 2008-03-20 US US12/532,973 patent/US8915075B2/en not_active Expired - Fee Related
  • 2008-03-20 EP EP08734422A patent/EP2142808B1/fr not_active Not-in-force

Non-Patent Citations (1)

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