EP2171286B1 - Method and hydraulic control arrangement for supplying a pressure medium to at least one hydraulic consumer - Google Patents

Description

The invention relates to a method for controlling a hydraulic consumer according to the preamble of claim 1 and a hydraulic control arrangement for supplying pressure medium to the consumer according to the independent claim 7.

In the US 513 883 A a hydraulic control arrangement is disclosed in which a consumer, for example a differential cylinder via a valve device with two continuously adjustable directional valves with pressure medium is supplied, which is provided by a pump. In the flow to and in the return from the consumer, each a continuously adjustable directional control valve is arranged. The directional control valves are biased in their neutral position into a blocking position and can be adjusted via pressure reducing valves in each case in one direction, in which the pump with the associated pressure chamber and in another direction, in each of which the associated pressure chamber is connected to the tank. In this known control arrangement can be operated by a suitable control of the two-way valves, the consumer with a so-called regeneration circuit. In this case, for example, during the extension of a cylinder, the decreasing annular space is connected via the associated directional control valve to the pressure medium inlet to the enlarging pressure chamber, so that the cylinder is extended in rapid traverse. A disadvantage of the regeneration / differential circuit, however, is that due to the clamping of the load (effective effective area corresponds approximately to the piston rod surface) of the consumer can not be operated with the maximum power.

If such a control arrangement is used, for example, in a mobile implement, such as a backhoe loader, a mini and compact excavator or a telehandler, the retrievable tomb performance in the regeneration mode is too low due to the clamping of the consumer. The regeneration mode is accordingly preferably used when lowering the equipment of the mobile implement. To operate the consumer with high performance, such as when digging or lifting a load is then switched to the normal function in which the increasing pressure chamber with the pump and the decreasing pressure chamber is connected to the tank.

In order to avoid the formation of cavitations in the pressure medium flow at pulling load, a lowering brake valve can be provided in the return from the consumer, as for example from the DE 196 08 801 C2 or from the data sheet VPSO-SEC-42; 04.52.12-X-99-Z of the company Oil Control, a subsidiary of the applicant is known.

The adjustment of the directional control valves via a controlled by a joystick pilot control device with pressure reducing valves, the operator decides himself when switched from regeneration to normal operation. It is often difficult to determine the correct switching time, so that the consumer is too long time in the regeneration mode with reduced power or already prematurely switched to the normal mode, although a method of the consumer would be advantageous at high speed.

In contrast, the invention has for its object to optimize the switching from regeneration to normal operation in terms of the energy savings associated with the regeneration and the load available at the consumer.

This object is achieved by a method with the feature combination of claim 1 and a hydraulic control arrangement with the feature combination of the independent claim 7.

According to the invention, a supply-side and a discharge-side pressure chamber of a hydraulic consumer are connected to a pump or a tank via a valve device which can be activated by means of a control unit in order to actuate the consumer. For a quick process of the consumer, the valve device is moved into a regeneration mode in which the pressure medium flowing from the return-side pressure chamber is summed to the flow rate of the pump, so that it can be adjusted to a lower flow or the consumer extends at a higher speed. The adjustment of the pressure medium requirement by means of an actuator, such as a joystick. According to the adjustment of the pump takes place after a pressure control. It is automatically switched to normal operation when the pump flow is reduced with unchanged set pressure medium requirement (adjustment of the actuator) via the pump control, so that the consumer slows down or stops. In other words, the pressure of the variable displacement pump is monitored. If this reaches its maximum pressure in the regeneration mode, since the consumer counteracting resistance increases, the pivot angle of the Reset pump according to the characteristics of the pump control, so that the pumped by the pump pressure fluid flow no longer corresponds to the predetermined pressure for the actuator pressure medium requirement. According to the invention, a decision is made from a comparison of the pump delivery flow with the pressure medium requirement set via the actuator when switching to normal operation. The optimal switching time is therefore no longer dependent on the subjective assessment of the operator, so that the consumer can be operated with higher reliability and improved efficiency.

The actual pump delivery flow can be determined, for example, from the swivel angle of the pump designed as a variable displacement pump and the pump speed at a given pump pressure.

The variable displacement pump is preferably designed with an electro-proportional swivel angle control, wherein preferably a control signal of a pressure control loop is then proportional to the swivel angle of the pump.

For this purpose, the actual pump pressure can be detected and compared with a predetermined pump pressure via the actuator. The pressure difference is then fed as input to a controller, such as a PI or a PID controller whose output is a measure of the swing angle and forms the input signal of the pump controller.

The control of the consumer is further optimized if the regeneration mode is preset in certain directions of movement of the consumer, for example when lowering an excavator equipment as a starting situation. That as soon as the actuator (joystick) is moved in the direction of lowering, the regeneration mode is automatically set. This is maintained until the operator moves the joystick back to the zero position or moves beyond this zero position. The switch to normal operation then runs in the manner described above.

The switching between the regeneration mode and the normal operation is preferably carried out via a ramp, wherein the pressure medium connection between the variable displacement pump and the increasing pressure chamber remains open and the pressure medium connection of the decreasing pressure chamber is opened in accordance with the course of the ramp.

The swivel angle control of the variable displacement pump, with a suitable design, also allows power control.

The device complexity of the control arrangement can be reduced if a continuously adjustable directional control valve with two switching positions and a lowering brake valve are arranged in the flow and in the return of each consumer, so that flow and return are independently controlled.

The electrically or electro-hydraulically adjustable directional control valves are preferably open in their neutral position towards the tank.

The reliability of the control arrangement is improved when the lowering brake valves are designed with a secondary pressure limiting function.

Other advantageous developments of the invention are the subject of further subclaims.

• Figur 1 ein Schaltschema einer erfindungsgemäßen Steueranordnung zur Ansteuerung zweier Verbraucher;
• Figur 2 eine vergrößerte Darstellung einer Verstellpumpe der Steueranordnung aus Figur 1;
• Figur 3 eine Teildarstellung einer Wegeventilsektion der Steueranordnung aus Figur 1;
• die Figuren 4 bis 6 unterschiedliche Lastfälle im Regenerationsmodus oder im Normalbetrieb der Steueranordnung und
• Figur 7 eine vereinfachte Ausführung der Wegeventilsektion aus Fig. 3.

In the following, a preferred embodiment of the invention is explained in more detail with reference to schematic drawings. Show it:

• FIG. 1 a circuit diagram of a control arrangement according to the invention for controlling two consumers;
• FIG. 2 an enlarged view of a variable displacement of the control arrangement FIG. 1 ;
• FIG. 3 a partial view of a directional control valve section of the control arrangement FIG. 1 ;
• the FIGS. 4 to 6 different load cases in regeneration mode or in normal operation of the control arrangement and
• FIG. 7 a simplified version of the directional control valve section Fig. 3 ,

FIG. 1 shows a hydraulic control arrangement 1 for pressure medium supply to two consumers 2, 4 of a mobile implement, such as an excavator, a backhoe loader, a mini and compact excavator or a telehandler. It This is a so-called EFM system (electronic flow management), in which the control of the pressure medium volume flow and the pressure fluid flow direction determining valve elements is carried out electrically or electro-hydraulically depending on, stored in a control unit 6, characteristic fields. The input of the setpoints is carried out via a joystick 8, which is actuated by the operator to control the equipment (for example, boom, bucket) of the implement in terms of speed and position.

In the illustrated embodiment, the two consumers 2, 4 are each designed as a differential cylinder with a bottom-side pressure chamber 10 and 12 and a piston rod side annular space 14 and 16 respectively. These pressure chambers 10, 14; 12, 16 can each be connected via a directional control valve section 18, 20 with a variable displacement pump 22 or a tank 24 to the cylinder on or extend. The variable displacement pump 22 is pressure-controlled via a pump regulator 26, via which, after reaching the predetermined pressure, the delivery flow of the pump is adjusted so that the pressure in the system remains constant independently of the delivery flow. With a pressure medium volume flow change virtually no pressure change should be connected.

The adjustment of the variable displacement pump 22 by means of a pump controller 25, the structure of the enlarged representation in FIG FIG. 2 is explained. The pump controller 25 allows via an electro-proportional swivel angle control directly controlled via a pivoting cradle of the variable displacement continuous and reproducible adjustment of the displacement of the pump. Such pump regulators are known, for example, from the data sheet RE 92 708 - see here in particular the variants EP and EK, so that only the features of the pump controller 25 required for understanding the invention are explained here.

Such a pump regulator 25 has a pump control valve 26, which is designed with three connections and which is biased via a control spring 27 in the direction of a neutral position in which the three connections of the pump control valve 26 are shut off. The control spring 27 is supported on the actuating piston 28 of an actuating cylinder 29, over which the pivoting cradle of the variable displacement pump 22 is pivotable. The adjusting piston 28 is biased by a spring in a basic position in which the pivot angle of the variable displacement pump 22 is maximum. The actuation of the valve spool of the pump control valve 26 via a proportional solenoid 30 which is energized via a connected to the control unit 6 signal line 51. About this proportional solenoid 30, the control force on the control piston of the Pump control valve 26 applied, wherein the adjustment is proportional to the current. An input connection of the pump control valve 26 is connected via a control line 31 to a pump line 38 connected to the pressure connection of the variable displacement pump 22. An output port of the pump control valve 26 is connected via a channel 32 with a control surface of the control piston effective in the direction of the neutral position. This control surface limits a spring chamber of the control spring 27. The pressure in the channel 32 also acts on an effective in the adjustment of the pump control valve 26 control surface, so that the control piston is acted upon on both sides by the pressure at the outlet of the pump control valve.

The channel 32 is connected via a nozzle 33 with a connecting channel 34, in which two pressure-limiting valves 35, 36 connected in series are arranged. The output of in FIG. 2 downstream pressure relief valve 36 is connected via a tank control channel 37 to the tank 24.

The two pressure limiting valves 35, 36 are biased in the direction of their illustrated basic position in which the pressure medium connection to the tank control channel 37 is opened.

In reversing direction acts on the two pressure relief valves 35, 36, the pressure in the control line 31, which is tapped via a pressure limiting line 39. This also leads to the respective third connection of the two pressure limiting valves 35, 36. The region of the connecting channel 34 located in the region between the pressure limiting valve 35 and the nozzle 33 is connected to the spring chamber of the control spring 27 via a branch line 40 and a check valve opening in the direction of the pressure limiting valve 35 connected. In the pressure medium flow path between the nozzle 33 and the pressure relief valve 35 further branches off a connecting line, which is connected via two further nozzles 41, 42 with the tank control channel 37. Between the two nozzles 41, 42 branches off an angle channel 43, which opens into the pressure medium flow path between the two pressure compensators 35, 36. In the direction of the spring-biased basic position of the pressure relief valves 35, 36 effective control surfaces are also still connected via pilot lines 44, 45 with the tank control channel 37.

The two pressure relief valves 35, 36 are set to different pressures. Upon reaching the respective pressure, the relevant pressure relief valve 35, 36 adjusted from its illustrated home position, so that a Control oil flow path from the pump line 38 via the control line 31, the pressure limiting line 39, the relevant pressure relief valve 35, 36, the connecting channel 34 and the branch line 40 is opened to the spring chamber of the control spring, so that in this spring chamber as the pump pressure is effective. Accordingly, then the actuator piston 28 against the force of the return spring in the illustration according to FIG. 2 moved to the left and the swing angle is reset to zero, so that the delivery volume is correspondingly minimal or equal to zero.

In normal operation of the variable displacement pump, the two pressure relief valves 35, 36 are biased in their basic position shown. To adjust the pivot angle of the pump, a predetermined stand-by pressure of, for example, 20 bar is required, only then can the force of the return spring be overcome.

In the illustrated basic position - as already mentioned - the pivot angle of the variable displacement pump 22 is set to its maximum value. When current is supplied to the proportional solenoid 30, the control piston of the pump control valve 26 in the illustration in accordance FIG. 2 shifted to the left, so that the control line 31 is connected to the channel 32 and a pressure corresponding to the pump pressure in the spring chamber of the control spring 27 is effective. By this pressure, the return piston 28 is then adjusted against the force of its return spring in the direction of minimizing the pivot angle, so that the pump delivery flow goes to zero. Upon further adjustment of the pump control valve 26 to the left, the pressure medium connection between the control line 31 and the channel 32 is controlled and the spring chamber of the control spring 27 via the branch line 40 to the connecting channel 34 and thus connected to the tank control channel 37, so that the control oil from the spring chamber to Can flow out tank 24 and is adjusted according to the actuating piston 28 by the force of the return spring in the direction of increasing the pivot angle. Accordingly, the pump delivery flow increases proportional to the current at the proportional solenoid 30. In the event of a cable break or a loss of control signal, the variable-displacement pump 22 shown returns to its basic position, in which the maximum pivoting angle is set.

For further details of the construction of the pump controller 26 reference is made to the above-mentioned data sheet RD 92 708.

As further shown in the illustration FIG. 1 can be removed, the pressure in the pump line 38 is detected by a pressure sensor 48 and reported via a signal line 46 to the control unit 6. This corresponding to the actual pump pressure Pressure signal is compared with the target pressure set by means of the joystick 8 and the output signal is applied to an electronic PI or PID controller 47. Its output signal is then taken into account via the control unit 6 by software in the control of the directional control valve sections 18, 20. The output signal is further applied via a signal amplifier 49 and a signal line 51 to the proportional solenoid 30 to adjust the control piston of the pump control valve 26, wherein in the control position of the control piston equilibrium between the force applied by the proportional magnet 30 and the force over the control spring 27th and adjusts the actuator piston 28 in the opposite direction applied force to the control piston.

The suction connection of the variable displacement pump 22 is connected to the tank 24 via a suction line 50 and a filter. The pressure medium conveyed by the variable displacement pump 22 flows via the pump line 38 and the two directional control valve sections 18, 20, the structure of which is described below FIG. 2 is explained to the consumers 2, 4. The pressure medium flows from the back of the consumers 2, 4 via the associated directional control valve sections 18, 20 and a tank line 52 to the tank 24, wherein in the end portion of the tank line 52, a further filter is provided over a pressure relief valve is bypassed and that opens when the filter clogging and thus the increase in pressure drop across the filter.

The temperature of the pressure medium received in the tank 24 is detected by a temperature sensor 54 and reported to the control unit 6 via a signal line. In order to prevent overheating of the pressure medium, a purge valve 57 is provided between the tank line 52 and the pump line 38. This purge valve 57 also has a pressure limiting function, so that the pressure in the pump line 38 can be limited to a maximum pressure. When the purge valve 57 is open, the pressure medium used to actuate the consumers, in particular in the regeneration circuit, can be exchanged for "fresh" pressure medium from the tank 24. The control of the flushing valve 57 is also carried out electrically in response to a signal of the control unit 6.

FIG. 3 shows the basic structure of the two-way valve sections 18, 20, wherein for example the directional control valve segment 18 is shown and the variable displacement pump 22 and the tank 24 are shown in simplified form.

According to FIG. 3 the directional valve section 18 has two pressure ports P, which are each connected via a feed line 56, 58 to the pump line 38. Two tank connections T of the directional valve section 18 are connected to the tank line 52 via discharge lines 60, 62. Each connection pair P, T of the directional control valve section 18 is associated with a working port A and B, which is connected via a flow line 64 and a return line 66 to the pressure chamber 10 and the annular space 14 of the consumer 2. In the pressure medium flow path between the terminals P, T and the associated working ports A, B, a continuously adjustable 3-way valve 68, 70 with two switching positions and three terminals and a lowering brake valve 72 and 74 are respectively arranged. Each directional control valve 68,70 is biased via a control spring in its neutral position shown, in which the drain line 60, 62 is in fluid communication with a connecting channel 76, 78, which extends in each case to the adjacent lowering brake valve 72, 74.

The adjustment of the directional control valve 68, 70 in each case via a pilot valve 81, 83 with a proportional solenoid 80, 82 which can be supplied with current via signal lines from the central control unit 6, by adjusting the pilot valves 81, 83, for example of pressure reducing valves, the directional control valves 68, 70 independently in the direction of their in FIG. 3 to shift shown position in which the pressure medium connection of the supply lines 56, 58 are opened to the connection channels 78 and 76, respectively. Accordingly, the two-way valves 68, 70 with their open to the tank 24 neutral position an extremely simple structure, wherein the adjustment - in contrast to the prior art described above - only a pilot valve and a proportional solenoid 80, 82 is required, while in the known Solutions with closed center position each two expensive proportional magnets must be used. In principle, the directional control valves 68, 70 can also be controlled directly via proportional solenoids.

The two Senkbremsventile 72, 74 have a known structure, such as, for example, from the aforementioned DE 196 08 801 C2 or the publication of the company Oil Control is known. Such lowering brake valves allow the controlled lowering of a load and simultaneously act as a secondary pressure relief valve. For this purpose, the lowering brake valves are biased by an adjustable biasing spring 84, 86 in a locking position. As in FIG. 2 indicated, the spring chambers of the two bias springs 84, 86 are vented to the atmosphere. In the opening direction of the respective pressure acts on the associated working port A, B, which is tapped in each case via a pressure limiting control line 88, 90. In the opening direction, furthermore, the pressure in the respective other connection channel 76, 78 acts, which is tapped, as it were, "crosswise" by means of control lines 92, 94. Beyond the two lowering brake valves 72, 74 may also be the consumer 2 attacking load are supported leak-free. The pressure medium supply from the directional control valve 68, 70 to the respective pressure chamber of the consumer 2 is in each case via a bypass channel 96, 98 which connects the connecting channel 76, 78 with the respective flow line 64, 66, wherein in each bypass channel 96, 98 in the direction of the consumer 2 opening check valve 100, 102 is arranged.

In the in the FIGS. 1 and 3 illustrated neutral positions of the two-way valves 68, 70, the two pressure chambers of each consumer 2, 4 are connected to the tank 24. The load F acting on the load 2 is supported leak-free by the lowering brake valve 72, 74 designed as a seat valve. In this case, the load F can be designed as a pulling or pushing load. About the pressure limiting function of the two lowering brake valves 72, 74 ensures that a maximum pressure in the lines 64, 66 can not be exceeded.

For a better understanding of the invention, some load cases are explained.

It is first assumed that acts on the cylinder 2, a pulling load F and that this as shown in FIG FIG. 4 to be extended (movement to the right). This extension should be at maximum speed (rapid traverse). For this purpose, the two-way valves 68, 70 in the direction of in FIG. 4 shown position in which a regeneration takes place. That is, the consumer 2 is driven via a differential circuit, in which both the annular space 14 and the bottom-side pressure chamber 10 are connected to the pump 22. For this purpose, the directional control valves via the two proportional magnets 80, 82 from the neutral position ( Fig. 3 ) are shifted to the left, so that both pressure ports P of the directional valve section 18 with the connecting channels 76, 78 are connected. The pressure medium is pumped by the pump 22 via the pressure port P, the directional control valve 68, the connecting line 76, the bypass channel 96, the check valve 100 and the supply line 64 in the increasing bottom pressure chamber 10. The pressure medium displaced from the annular space 14 flows via the return line 66 and the counterbalancing valve 74, which is completely opened by the pressure in the connecting channel 76 in the pressure limiting function, the connecting channel 78 and the directional control valve 70 to the inlet line 56 and from there into the pump line 38, so that the pressure from the Consumables running pressure fluid flow is summed to the funded by the pump 22 pressure fluid flow.

In the bottom-side pressure chamber 10 while a pressure is applied, depending on the slider setting between the maximum pump pressure (for example 250th bar) and 0 bar (slide in neutral position) is. Assuming that the pressure in the annular space 14 is about 250 bar (slide of the directional control valve 70 completely, pump set to 250 bar) and that the pulling load corresponds to a pressure of 50 bar, then a pressure should be set in the bottom pressure chamber 10 , which is the difference of the pressure in the annular space 14 minus the load divided by the area ratio of the differential cylinder (for example 2), so that at 250 bar in the annular space 14 and a load of 50 bar, a pressure of about 100 bar results in the pressure chamber 10 ,

When the load is pressing the function is corresponding, wherein the pressure in the flow-side supply line 64 is limited by the pressure limiting function of the lowering brake valve 72.

During regeneration, the consumer is moved at maximum speed, but the force applied by the consumer is comparatively low, since the effective effective area of the consumer corresponds to the piston rod area. In order to retrieve the maximum power of the load 2, the control arrangement of regeneration on the in FIG. 5 shown normal operation by the directional control valve 70 is moved in the direction of its neutral position, so that the pressure fluid from the annular space 14 via the return line 66, the aufgesteuerte Senkbremsventil 74, the connecting channel 78 and via the directional control valve 70 and the drain line 60 to the tank 24 flows out , With pulling load ( FIG. 5 Cavitations in the region of the supply line 64 are reliably prevented by the lowering brake valve 74, since this prevents an uncontrolled, too fast extension of the consumer 2 due to the pulling load by the clamping of the load 2. The maximum pressure in the return line 66 is limited by the secondary pressure limiting function of the lowering brake valve 74. The pressure in the pressure medium flow is in turn determined by the opening cross section set by the slide of the directional control valve 68 and is thus between 0 bar and the maximum pump pressure (for example 250 bar).

With pushing load and with extending cylinder 2 ( Fig. 5 ) is a function of the slide position of the directional control valve 68 and the control of the variable displacement pump 22, a pressure in the bottom pressure chamber 10, which is between the load pressure and the maximum pump pressure (consumer to stop). The counter-sunk lowering valve 74 is completely opened by the pressure in the inlet (tapped via the pilot line 94), so that the pressure medium can flow out of the annular space 14 to the tank 24. In this load case, no regeneration operation is provided and cavitations are not to be feared.

When the cylinder and pulling or pushing load, the directional control valve section 18 is in the in FIG. 6 shown switched position in which the directional control valve 68 controls the pressure medium connection to the tank 24 and via the directional control valve 70 pressure medium from the pump 22 is conveyed into the annular space 14. The pressure in the inlet to the annular space 14 then depends on the load, the opening cross section of the directional control valve 70 and the set pump pressure. The pressure medium is conveyed via the bypass channel 98 and the opening check valve 102 and the return line 66 into the annular space 14 and flows from the decreasing pressure chamber 10 via the feed line 64 and the pressure in the inlet (connecting channel 78) open lowering brake valve 72 and the in the direction of its neutral position adjusted directional valve 68 and the drain line 62 to the tank 24 from. The pressure level in the process is limited by the lowering brake valve 72. Depending on the direction of the load, the pressure level in the inlet is between the maximum pump pressure and 0 bar (pushing load, minimum retraction speed).

According to the invention, it is preferred if the regeneration mode is activated as the default for a specific direction of movement of the consumers 2, 4. This may for example be the case when the equipment of an excavator, such as the boom is lowered with a shovel. Now, if the resistance to the movement of the working equipment increases, the pump pressure of the variable displacement pump 22 increases accordingly and limited by the pump controller to a maximum value. Upon reaching this maximum value is - as described above - the swivel angle and thus also the control signal for the swivel angle of the variable 22, so that the pressure fluid flow provided by this no longer corresponds to the pre-set via the joystick 8 pressure medium requirement. According to the invention, the relevant way valve section 18, 20 is then switched to the above-described normal operation without the action of the operator, so that, for example, the maximum digging power can be called up. To determine the pivot angle, the variable displacement pump 22 may be designed with a swivel angle sensor.

In FIG. 7 is a simplified embodiment of the control arrangement 1 according to FIG. 2 shown. The only difference from the above-described embodiment according to FIG. 2 is that in the designated there with return line 66, connected to the consumer 2 line no Senkbremsventil and associated with this directional control valve with two so-called "switching positions" but a single continuously variable directional control valve 104 is biased via a Zentrierfederanordnung 105 in a basic position (0) and by operating two pilot valves 108, 83 in the direction of FIG. 7 shown positions (a) and (b) is adjustable. The two pilot valves 83, 108 are - as in the above-described embodiment - designed as pressure reducing valves, which are each controlled by a proportional solenoid 82, 106. The structure of the formed in the flow line 64 valves, with the lowering brake valve 72, the check valve 100 and the biased in an open position directional control valve 68 which is adjustable only in one direction via a single pilot valve 81 and the pressure medium supply correspond to the above-described embodiment, so that respect Explanations are dispensable. For the sake of simplicity, the corresponding hydraulic components are provided with the same reference numerals as in the embodiment described above and referred to the relevant description.

In the illustrated basic position (0) of the continuously variable directional control valve 104, the pressure medium connection between the drain line 60, the supply line 56 and the return line 66 is shut off. By energizing the proportional magnet 106, a control pressure can be adjusted via the pressure reducing valve 108, so that the valve spool of the directional control valve 104 is adjusted to the right in the direction of (a) marked positions in which the connection between the return line 66 and the drain line 60 is turned on , The pressure medium connection to the supply line 56 remains blocked. When the pilot valve 83 is actuated, the valve slide of the directional valve 104 is adjusted in the direction (b), so that the pressure medium connection between the supply line 56 and the return line 66 acting as a supply line is correspondingly opened, and the pressure medium connection between the return line 66 and the discharge line 60 is controlled.

The actuation of the arranged in the flow line 64 lowering brake valve 72 is carried out - as in the embodiment described above - on the pressure in the return line 66th

Of course, the directional control valve 104 can also be integrated into the supply line 64, so that then the lowering brake valve 74 and the directional control valve 70 from FIG. 3 are arranged in the return line 66.

For retracting the hydraulic cylinder (consumer 2), the directional control valve 104 is adjusted in the direction of its position (b), so that pressure medium of variable displacement pump 22 via the pump line 38, the supply line 56, the directional control valve 104 and then acting as a supply line return line 66 for Annular space 14 of the consumer is promoted. About the directional control valve 104 is then set according to the pressure medium flow rate and the effective pressure in the annular space 14. Due to the pressure in the return line 66, the lowering brake valve 72 is adjusted to its open position, so that, for example cavitations are prevented at a pressing load, since then the consumer 2 remains clamped. In the case of a pulling load, the lowering brake valve 72 is completely or almost completely opened by the preselected pressure via the control line 92, so that the pressure medium can flow to the tank 24 via the lowering brake valve 72 and the corresponding directional control valve 68.

When extending the load (hydraulic cylinder 2), the control arrangement can also be operated again in the regeneration mode, in which case the directional control valve 68 is switched over the pilot valve 81 and the directional valve 104 is adjusted via the pilot valve 83 in the direction of its position (b), so that Pressure fluid from the annular space 14 via the directional control valve 104 in the supply line 58 and from there via the directional control valve 68 and the check valve 100, the bypass channel 96 and the flow line 64 to the pressure chamber 10 flows, so that the consumer 2 is extended at great speed. To apply a large force, the directional control valve 104 is adjusted in the direction of its positions (a), so that the pressure medium flows from the annular space 14 to the tank 24. With regard to further details of the different operating modes, reference is made to the above statements.

Disclosed are a hydraulic control arrangement and a method for controlling a hydraulic consumer, which has a flow-side and a return-side pressure chamber, which can be connected via a valve device with a pump or a tank. The control of the valve device by means of a control unit, via which the valve device is adjustable in a regeneration mode, in which both pressure chambers are connected to the pump. According to the invention, the pump is pressure-controlled, wherein in the regeneration mode automatically switching to normal operation, in which the inlet-side pressure chamber with the pump and the return-side pressure chamber is connected to the tank, then takes place when the pump flow drops below the pressure medium requirement.

Claims (16)

1. Method for activating a hydraulic consumer (2, 4) which has an outgoing-side and a return-side pressure space (10, 12) which can be connected to a pump (22) or a tank (24) via a valve device (18, 20), the activation of the valve device (18, 20) taking place by means of a control unit (6), via which the valve device (18, 20) can be adjusted into a regeneration mode in which both pressure spaces (10, 12) are connected to the variable-displacement pump (22), characterized by the steps:

   - adjustment of the valve device (18, 20) into the regeneration mode;

   - setting of a pressure-medium demand at an actuator, for example a joystick;

   - regulation of the pump pressure as a function of the pressure-medium demand;

   - automatic changeover of the valve device (18, 20) to normal operation, in which the inflow-side pressure space is connected to the pump (22) and the outflow-side pressure space is connected to the tank (24) when the pump delivery flow falls in the presence of an unchanged pressure-medium demand.
2. Method according to Patent Claim 1, the pump delivery flow being determined from the pivot angle and the pump rotational speed at a given pump pressure.
3. Method according to Patent Claim 1 or 2, the actual pump pressure being detected and compared with a stipulated desired pump pressure, and the pressure difference being fed as an input signal to a controller (47), the output signal of which is a measure of the pivot angle.
4. Method according to one of the preceding patent claims, the variable-displacement pump (22) being assigned electroproportional pivot-angle regulation.
5. Method according to one of the preceding patent claims, the regeneration mode being preset as an initial situation in the case of a specific direction of movement for the consumers (2, 4).
6. Method according to one of the preceding patent claims, the changeover from the regeneration mode to normal operation taking place in ramp form.
7. Hydraulic control arrangement for supplying a pressure medium to at least one consumer (2, 4), with an electrically or electrohydraulically continuously adjustable valve device (18, 20), via which an outgoing-side pressure space of the consumer (2, 4) can be connected to a pump (22) and a return-side pressure space of the consumer (2, 4) can be connected to a tank (24), and with a control unit (6), via which the valve device (18, 20) can be activated in such a way that both pressure spaces are connected to the pump, and via which, when a maximum pump pressure is reached or when the pressure-medium volume flow in the inflow falls in the presence of an essentially unchanged pressure-medium demand, there can be an automatic changeover to normal operation in which the outgoing side is connected to the pump (22) and the return side is connected to the tank (24).
8. Control arrangement according to Patent Claim 7, the pump being a variable-displacement pump (22) with electroproportional pivot-angle regulation.
9. Control arrangement according to Patent Claim 7 or 8, with a pressure sensor (48) for detecting the actual pump pressure.
10. Control arrangement according to Patent Claim 9, with a controller (47) for generating an input signal for a pump controller (25) as the function of comparison between the actual pump pressure and a desired pump pressure.
11. Control arrangement according to Patent Claim 10, the controller (47) being a PI or PID controller.
12. Control arrangement according to one of Patent Claims 7 to 11, with a pivot-angle sensor for detecting a pivot angle of a variable-displacement pump (22).
13. Control arrangement according to one of Patent Claims 7 to 12, the pivot-angle regulation allowing power regulation.
14. Control arrangement according to one of Patent Claims 7 to 13, an electrically or electrohydraulically continuously adjustable directional valve (68, 70) with two switching positions and with an open neutral position and a lowering brake valve (72, 74) being arranged in the outgoing side and in the return side of each consumer (2, 4).
15. Control arrangement according to Patent Claim 14, the lowering brake valve (72, 74) having a pressure-limiting function.
16. Control arrangement according to Patent Claim 14 or 15, the directional valves (68, 70) being open towards the tank (24) in the neutral position.

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