Hydraulic arrangement and commercial vehicle

Abstract

The invention relates to a hydraulic arrangement (42) for a commercial vehicle (10) with a hydraulic variable displacement pump (46) which is connected via a pump outlet (54) to a supply port (48) as a hydraulic interface for supplying hydraulic consumers (58) of the commercial vehicle (10). Furthermore, the hydraulic arrangement (42) includes an auxiliary hydraulic pump (70) and an auxiliary supply port (52) as a hydraulic interface for the auxiliary supply of at least some of the consumers (60, 62). An adjustment control (64) for the variable displacement pump (46), which is dependent on an output pressure (p_v) of the auxiliary pump (70), has an adjustment cylinder (96) with a hydraulic working port (98). The working port (98) is hydraulically connected to an outlet (72, 90) of the auxiliary pump (70). The invention further relates to a commercial vehicle (10) with such a hydraulic arrangement (42).

Description

[0001] The invention relates to a hydraulic arrangement for a commercial vehicle with a hydraulic variable displacement pump for supplying hydraulic consumers of the commercial vehicle. Furthermore, the invention relates to a commercial vehicle with such a hydraulic arrangement.

[0002] In tractors, it is common practice to use variable displacement pumps to supply internal or external hydraulic consumers (e.g., on attachments). The variable displacement pump is driven, preferably via a gearbox, by the drive engine of the commercial vehicle or tractor. When the drive engine is started, the control system of the variable displacement pump is often set to a maximum delivery position, i.e., to deliver a maximum hydraulic flow. This requires a correspondingly high drive power from the drive engine. A cold start of the commercial vehicle can further increase the power consumption of the variable displacement pump due to the increased viscosity of the hydraulic fluid.

[0003] The present invention is based on the object of proposing a hydraulic arrangement and a commercial vehicle which reduces the power required for the variable displacement pump when starting the commercial vehicle.

[0004] This object is achieved by a hydraulic arrangement having the features of patent claim 1 and by a commercial vehicle having the features of patent claim 10.

[0005] Further advantageous embodiments of the hydraulic arrangement according to the invention and of the commercial vehicle according to the invention emerge from the subclaims.

[0006] According to claim 1, a hydraulic arrangement for a commercial vehicle is proposed which contains a hydraulic variable displacement pump. It is connected via a pump outlet to a supply connection as a hydraulic interface for supplying hydraulic consumers of the commercial vehicle. Furthermore, the hydraulic arrangement contains an auxiliary pump and an auxiliary supply connection as a hydraulic interface for the auxiliary supply of at least some of the hydraulic consumers (e.g. a steering system and / or braking system), in particular in an emergency in which the variable displacement pump fails. The variable displacement pump has an adjustment control with an adjustment cylinder. A hydraulic working connection of the adjustment cylinder is hydraulically connected to an output of the auxiliary pump. This effects an adjustment control for adjusting the variable displacement pump that is dependent on an output pressure of the auxiliary pump.

[0007] The pump outlet or variable displacement pump outlet can be a hydraulic outlet directly on the variable displacement pump itself or a hydraulic outlet of a pump unit containing the variable displacement pump. Similarly, the auxiliary pump outlet can be a hydraulic outlet directly on the auxiliary pump itself or a hydraulic outlet of an auxiliary pump unit containing the auxiliary pump.

[0008] With variable displacement pumps, the delivery rate or volume flow of the pumped hydraulic medium (e.g., oil) can be adjusted not only by varying the drive speed, but also at a constant drive speed of the variable displacement pump. Various parameters can be used as control variables, such as the current hydraulic pressure. The respective control variable(s) can influence a suitable control system, which adjusts the delivery rate of the variable displacement pump, particularly continuously.

[0009] The adjustment control can be adjusted between a maximum flow rate position and a minimum flow rate position. The aforementioned hydraulic adjustment cylinder is used for this purpose.

[0010] The hydraulic arrangement according to the invention makes it possible to achieve the technical objective of ensuring that the adjustment control is in a delivery position with a minimum delivery rate during the starting phase of the commercial vehicle's drive engine or is set to this delivery position. This results in the lowest possible, in particular a minimum, delivery rate of the variable displacement pump during the starting phase of the drive engine. This minimizes the power consumption or power consumption of the variable displacement pump, thus relieving the load on the commercial vehicle's drive engine and the starter motor that drives it during the starting phase.

[0011] According to the invention, this desired physical state of the variable displacement pump during the start-up phase of the commercial vehicle is supported by the auxiliary pump. The activated auxiliary pump can supply an adjusting pressure to the working port of the adjusting cylinder through its output pressure, allowing the adjusting cylinder to adjust the delivery position with a minimum delivery rate.

[0012] The required adjustment pressure for setting the minimum delivery rate preferably depends solely on the characteristics of the variable displacement pump, in particular its adjustment cylinder, and is preferably less than 10 bar. Thus, the variable displacement pump and consequently the drive motor and starter motor of the commercial vehicle can be supported during the starting phase of the commercial vehicle with low energy consumption and low energy losses.

[0013] Hydraulic interfaces, such as the supply connection and the auxiliary supply connection, support a modular design of the hydraulic system for technically simple integration into the commercial vehicle. The hydraulic system can have additional hydraulic interfaces, e.g., a return connection for the return of hydraulic fluid to a reservoir or hydraulic tank. For example, hydraulic fluid can flow back from the adjustment cylinder to the hydraulic tank via this return connection. Furthermore, a feedback connection can be provided on the hydraulic system, which acts as an interface for pressure feedback from consumers.

[0014] Preferably, the adjustment cylinder is designed as a single-acting cylinder with a single hydraulic working connection, whereby the technical-hydraulic structure of the adjustment control is kept technically simple.

[0015] In a preferred embodiment, a hydraulic check valve is installed upstream of the working port in the flow path between the output of the auxiliary pump and the working port of the adjusting cylinder. The flow direction of the check valve is oriented toward the adjusting cylinder. This makes it technically simple to maintain the output pressure or adjustment pressure for the adjustment control, which is built up by the activated or driven auxiliary pump at the working port.

[0016] Further preferably, a holding valve unit with at least two different switching positions is hydraulically interposed in the hydraulic flow path between the working port of the adjusting cylinder on the one hand and a return port and the pump outlet of the variable displacement pump on the other. The return port serves for the return of hydraulic fluid to a reservoir or hydraulic tank. For example, hydraulic fluid can flow back from the adjusting cylinder to the hydraulic tank via this return port.

[0017] Depending on its activated switching position, the holding valve unit acts either as a hydraulic interruption or as a hydraulic connection in the flow path. For example, the interruption effect of the holding valve unit can be a simple technical measure that helps prevent potential leaks. The adjustment pressure built up at the working port of the adjustment cylinder can be reliably maintained before the commercial vehicle starts and, if necessary, even during the start-up process.

[0018] The holding valve unit has, for example, an electromagnet for electrical actuation. This actuation is carried out in particular by means of a suitable control unit. Preferably, the switching position acting as a hydraulic connection corresponds to a rest position of the holding valve unit.

[0019] To support the hydraulic functionality of the adjustment control, the holding valve unit is preferably designed such that it has a hydraulic valve connection in the flow path on its connection side facing away from the working connection of the adjustment cylinder, which can be connected to the pump outlet depending on the output pressure of the variable displacement pump. This can be advantageously achieved by integrating at least one suitable directional control valve or proportional valve into the adjustment control.

[0020] Further preferably, the holding valve unit contains a control pressure input that acts in the switching direction and is hydraulically connected to the aforementioned valve connection. In particular, the control pressure input can be used to automatically activate the switching position of the holding valve unit, which acts as a hydraulic connection in the flow path, when the output pressure of the variable displacement pump increases at the valve connection. This allows the adjusting cylinder to be supplied with increasing pressure and automatically adjust the delivery position with the minimum delivery rate. This automatic mechanism supports the hydraulic arrangement in the event of a fault in the auxiliary pump, so that even if the auxiliary pump fails, the adjustment cylinder can still set a minimum adjustment or a minimum delivery rate.

[0021] In a preferred embodiment, at least one valve unit with multiple switching positions is provided in the flow path between the working port or the holding valve unit on the one hand and a return port and the pump outlet on the other. This valve unit has two hydraulic control inputs opposite each other in the switching direction. The return port serves for the return of hydraulic fluid to a reservoir or hydraulic tank. For example, hydraulic fluid can flow back from the adjusting cylinder into the hydraulic tank via this return port.

[0022] While one control input of the holding valve unit is hydraulically connected to the output of the variable displacement pump, the other control input is either hydraulically connected to the return connection or hydraulically connected to a feedback connection that acts as an interface for pressure feedback from consumers. This provides reliable technical support for the variable displacement control.

[0023] In an advantageous development of the invention, the output pressure or adjustment pressure at the output of the auxiliary pump can be compared with a predetermined target pressure. This target pressure preferably corresponds to the pressure at the working port of the adjustment cylinder at which the delivery position with the minimum delivery rate is established. Depending on the comparison result, the operation of the auxiliary pump can then be efficiently controlled, for example. The value of the target pressure is usually dependent on the physical characteristics of the variable-displacement pump, in particular its adjustment cylinder.

[0024] Further preferably, the hydraulic arrangement has at least one of the following states or at least one of the following features when the output pressure or adjustment pressure at the output of the auxiliary pump has increased after reaching or exceeding the predetermined target pressure: The holding valve unit is in its switching position, which acts as a hydraulic connection in the flow path. The drive of the auxiliary pump is reduced or deactivated. This takes into account that the adjustment control of the variable displacement pump assumes the delivery position with a minimum delivery rate once the predetermined target pressure has been reached or exceeded. Support from the auxiliary pump is then no longer required or only required to a reduced extent. The variable displacement pump is driven. Since the predetermined target pressure on the adjustment cylinder has been reached or exceeded and the delivery position with the minimum delivery rate has thus been set, the variable displacement pump is driven with reduced or minimal pump adjustment and consequently with low power consumption. The variable displacement pump is driven in particular by the starting drive motor.

[0025] In a preferred embodiment, a pressure sensor is hydraulically connected to the output of the auxiliary pump, which generates sensor signals. This allows the current output pressure or adjustment pressure of the auxiliary pump to be continuously compared with the predetermined target pressure. As soon as the target pressure is reached or exceeded, the auxiliary pump can be deactivated or its pumping activity reduced. The reaching or exceeding of the predetermined target pressure at the output of the auxiliary pump can be detected simply and reliably using the pressure sensor.

[0026] The pressure sensor is connected, for example, to a control unit, which processes the pressure sensor signals and compares them, among other things, with the predetermined target pressure. Advantageously, the control unit can then control a drive or auxiliary pump motor (e.g., electric motor) of the auxiliary pump depending on the sensor signals. The control unit can also control other components within the hydraulic arrangement, such as hydraulic valves, in particular the holding valve unit. The control can be dependent on the pressure sensor signals and / or other signals or data (e.g., speed of the drive motor, bus signals of a control and / or data bus of the commercial vehicle).

[0027] The invention further relates to a commercial vehicle, preferably an agricultural or forestry towing vehicle (e.g. a tractor or tractor) or a construction machine, with a drive motor and with a hydraulic arrangement according to one of claims 1 to 9.

[0028] The commercial vehicle according to the invention has the above-described advantages of the hydraulic arrangement according to the invention. The hydraulic arrangement enables efficient technical operation of the variable displacement pump before, during, and after a starting process of the drive engine of a commercial vehicle. Conventional impairments during the starting phase of the drive engine can be avoided, particularly during a cold start. The hydraulic arrangement allows the variable displacement pump and the drive motor to be relieved of load, particularly during a cold start with a high viscosity of the hydraulic medium. The starting process of the commercial vehicle can be carried out with significantly lower power requirements, which also supports the technical process of a successful cold start.

[0029] The commercial vehicle may have a drive motor for driving the variable displacement pump included in the hydraulic arrangement.

[0030] Preferably, the auxiliary supply connection is hydraulically connected to a braking system and / or a steering system of the commercial vehicle. Thus, the technical prerequisites for a technically simple emergency operation of the braking and / or steering system are created by the hydraulic arrangement according to the invention being able to be integrated into the commercial vehicle in a modular manner, and the hydraulic interfaces of the arrangement, such as the supply connection, the auxiliary supply connection, the return connection, and the feedback connection, are hydraulically connected to the vehicle's mating connections.

[0031] The invention is explained in more detail below with reference to the accompanying drawings. Components that are identical or comparable in terms of their function are designated by the same reference numerals. They show: Fig. 1 is a schematic representation of a commercial vehicle according to the invention, Fig. 2 is a hydraulic circuit diagram with the hydraulic arrangement according to the invention in one embodiment, Fig. 3a is a hydraulic circuit diagram of detail III within the hydraulic arrangement according to Fig. 2 in a first embodiment, Fig. 3b hydraulic circuit diagram of the detail III within the hydraulic arrangement according to Fig. 2 in a further embodiment, and Fig. 3c a hydraulic circuit diagram of the detail III within the hydraulic arrangement according to Fig. 2 in another embodiment.

[0032] Fig. 1 shows a schematic representation of an agricultural utility vehicle 10 according to the invention, in particular in the form of a tractor, with a drive train 20. The utility vehicle 10 further comprises a cab 12, a front vehicle axle 14, and a rear vehicle axle 26. The utility vehicle 10 can have one or more ground engagement means in the form of wheels 28. The drive train 20 comprises a drive motor 22, which can be embodied as an internal combustion engine, and a transmission structure 30, which can be composed of various individual transmission components.

[0033] The commercial vehicle 10 has a hydraulic arrangement 42 with a pump unit 40. According to Fig. 2 The drive motor 22 can drive the transmission structure 30, which drives a variable-displacement pump 46 of the pump unit 40 via a transmission component and a pump drive shaft 44. The hydraulic arrangement 42 can be integrated into the commercial vehicle 10 in a modular manner. A modular installation of the hydraulic arrangement 42 into the commercial vehicle 10 can be supported by various hydraulic interfaces. Such interfaces can include a supply connection 48, a feedback connection 50, an auxiliary supply connection 52, and a return connection 92.

[0034] According to Fig. 2 A pump outlet 54 of the pump unit 40 is connected to the supply connection 48 for supplying hydraulic consumers 58 of the commercial vehicle 10. The consumers 58 include, among others, a steering system 60 and a braking system 62. An adjustment control 64 for adjusting the variable displacement pump 46 depends on an output pressure of an auxiliary pump unit 66. This output pressure can be referred to as an adjustment pressure p_v for influencing the adjustment control 64.

[0035] The auxiliary pump unit 66, which functions as a component of the hydraulic arrangement 42, contains an auxiliary pump 70 driven by an auxiliary pump motor 68 (e.g., an electric motor). Its auxiliary pump outlet 72 is hydraulically connected to the auxiliary supply connection 52. In the event of a failure of the pump unit 40, the auxiliary pump unit 66 can be used to supply hydraulic consumers required for driving, in particular the steering system 60 and the braking system 62, in an emergency mode.

[0036] On the input side, the variable displacement pump 46 and the auxiliary pump 70 are each connected to a reservoir or hydraulic tank 76. The hydraulic medium delivered to the consumers 58 flows back to the hydraulic tank 76 via return lines.

[0037] The aforementioned hydraulic interfaces - supply connection 48, feedback connection 50, auxiliary supply connection 52, return connection 92 - of the hydraulic arrangement 42 can, for example, be arranged directly on or in the pump unit 40 or auxiliary pump unit 66 or can be arranged at a distance from the pump unit 40 or auxiliary pump unit 66 by means of a line-like extension.

[0038] A pressure sensor 78 with a pressure input 80 is connected to the auxiliary pump output 72. A signal output 82 of the pressure sensor 78 is connected to an electrical control unit 84, which, among other things, processes the output signals or sensor signals S of the pressure sensor 78. In this way, the control unit 84 can detect the current pressure present at the auxiliary pump output 72 or the current adjustment pressure p_v. Depending on this pressure detection, the control unit 84 can, among other things, control the auxiliary pump motor 68.

[0039] To support the operation of the hydraulic arrangement 42, a hydraulic check valve 86 is interposed between the auxiliary pump outlet 72 and an outlet 90 of the auxiliary pump unit 66. Furthermore, the auxiliary pump 70 is combined with a hydraulic pressure relief valve 88.

[0040] Fig. 3a, Fig. 3b and Fig. 3c show the pump unit 40 with different embodiments of the adjustment control 64. As can also be seen from Fig. 2 As can be seen, in all embodiments the auxiliary pump outlet 72 or the outlet 90 of the auxiliary pump unit 66 is hydraulically connected to a pressure connection 94 of the pump unit 40.

[0041] The adjustment control 64 has a single-acting adjustment cylinder 96. A working port 98 of the adjustment cylinder 96 is hydraulically connected to the output 90 or the auxiliary pump output 72 via the pressure port 94. A check valve 100 is connected upstream of the working port 98 in the flow path between the output 90 and the working port 98. The flow direction of the check valve 100 is directed toward the working port 98.

[0042] In the pump unit 40 according to Fig. 3a Two valve units 102, 104, each with two different switching positions 102-0, 102-a and 104-0, 104-a, are hydraulically interposed in the flow path between the working port 98 on the one hand and the return port 92 and the pump outlet 54 on the other. In the switching position 102-0, which forms the rest position, the working port 98 can be connected to the return port 92, whereby this connection depends on the activated rest position 104-0 of the valve unit 104. In a second switching position 102-a of the valve unit 102, the working port 98 is hydraulically connected to the pump outlet 54.

[0043] The two valve units 102, 104 can each be designed as a directional control valve or proportional valve with intermediate positions and the two aforementioned switching positions 102-0, 102-a and 104-0, 104-a as end positions.

[0044] The valve units 102, 104 each have two hydraulic control inputs located opposite one another in the switching direction. A first control input 106 or 110 is hydraulically connected to the pump outlet 54 of the variable displacement pump 46, while a second control input 108 of the valve unit 102 is hydraulically connected to the return connection 92, and a second control input 112 of the valve unit 104 is hydraulically connected to the feedback connection 50.

[0045] The embodiment according to Fig. 3b differs from the variant according to Fig. 3a essentially in that a holding valve unit 114 with two different switching positions 114-0, 114-a is hydraulically interposed in the hydraulic flow path between the working connection 98 on the one hand and the return connection 92 and the pump outlet 54 on the other. The holding valve unit 114 is arranged in the flow path between the two valve units 102, 104. Depending on its activated switching position 114-0 or 114-a, the holding valve unit 114 acts either as a hydraulic connection (with the activated rest position or switching position 114-0) or as a hydraulic interruption (with the activated switching position 114-a) in the flow path. The holding valve unit 114 can be electrically actuated by means of the control unit 84 in order to activate or deactivate its different switching positions 114-0, 114-a.

[0046] The embodiment according to Fig. 3c differs from the variant according to Fig. 3b essentially by a different arrangement of the holding valve unit 114 in the flow path and a different structure of the holding valve unit 114. In Fig. 3c The holding valve unit 114 has a hydraulic valve connection 116 in the flow path on its connection side facing away from the working connection 98 of the adjusting cylinder 96, which can be connected to the pump outlet 54 by means of the valve unit 102 depending on an output pressure p_a of the variable displacement pump 46. A control pressure inlet 118 of the holding valve unit 114, which is effective in the switching direction, is hydraulically connected to the valve connection 116.

[0047] By means of the described hydraulic logic, the starting phase of the drive motor 22 can be supported with particularly low energy consumption and low energy losses, which means technical advantages, especially during a cold start.

[0048] Before starting the commercial vehicle 10, the adjustment control 64, in particular its adjustment cylinder 96, is usually set to a delivery position for a maximum delivery rate due to the pressure conditions at the pump outlet 54, the feedback connection 50, and the return connection 92. However, the goal is to keep the power consumption of the variable displacement pump 46 as low as possible during the start-up phase of the commercial vehicle 10 and consequently to set the adjustment control 64 to a delivery position for a minimum delivery rate. This goal is achieved with the hydraulic arrangements 42 according to Fig. 3a, Fig. 3b and Fig. 3c reached.

[0049] In the hydraulic arrangement 42 according to Fig. 3a Starting from the rest positions or first switching positions 102-0, 104-0 of the valve units 102, 104, an intended start of the drive motor 22 is detected by the control unit 84 (e.g. via received bus signals from a vehicle bus, such as ISO, CAN), which then activates the auxiliary pump motor 68 so that the auxiliary pump 70 is driven while the variable displacement pump 46 is stationary. As soon as the adjusting pressure p_v rising at the working connection 98 has reached or exceeded a predetermined target pressure p_soll - preferably below 10 bar depending on the system of the adjusting control 64 - the adjusting control 64 is in its minimum delivery position so that the variable displacement pump 46 (if it is operating) has no or only a low power consumption.As a result, the power consumption of the variable displacement pump 46 can be significantly reduced during the starting phase of the commercial vehicle 10, whereby the drive motor 22 and its starter motor are relieved during the starting phase.

[0050] Since the adjusting pressure p_v is continuously detected by the pressure sensor 78, the control unit 84 can control the hydraulic arrangement 42 in the desired manner after the predetermined target pressure p_soll is reached or exceeded. In particular, after the predetermined target pressure p_soll is reached or exceeded, the drive motor 22 is started and the variable displacement pump 46 is driven at low or minimal power consumption. The auxiliary pump motor 68 can be reduced in terms of its drive power or switched off again. The valve unit 102 can cause the adjusting cylinder 96 to automatically set the delivery position with the minimum delivery rate when a maximum output pressure p_a is reached at the driven variable displacement pump 46.

[0051] The hydraulic arrangement 42 according to Fig. 3b works in contrast to the embodiment according to Fig. 3a additionally with the holding valve unit 114. In case of an intended start of the drive motor 22, the hydraulic arrangement 42 is actuated according to Fig. 3b , in particular the auxiliary pump motor 68, is controlled in the same way as in the variant according to Fig. 3a . In addition, the control unit 84 activates the switching position 114-a of the holding valve unit 114, which acts as an interruption. This prevents pressure losses at the working connection 98 due to possible leaks when the adjusting pressure p_v increases. During or after the start of the drive motor 22, the holding valve unit 114 can be moved back to its rest position or switching position 114-0, which acts as a hydraulic connection. If the control unit 84 delays the moving of the holding valve unit 114 into the rest position or switching position 114-0, which acts as a hydraulic connection, the output pressure p_a continues to rise or increases noticeably. To take this circumstance into account, when the maximum output pressure p_a is reached at the driven variable displacement pump 46, the valve unit 102 automatically resets the delivery position with a reduced delivery rate on the variable displacement pump 46.

[0052] The holding valve unit 114 used to protect against possible leaks according to Fig. 3c In contrast to the variant according to Fig. 3b equipped with the control pressure input 118. In the event that the holding valve unit 114 is moved by the control unit 84 with a delay into the rest position or switching position 114-0, which acts as a hydraulic connection, the output pressure p_a also increases further or noticeably. The control pressure input 118 ensures that when the maximum output pressure p_a is reached at the driven variable displacement pump 46, the holding valve unit 114 is transferred into the rest position or switching position 114-0, which acts as a hydraulic connection. This allows the delivery position with a reduced delivery rate to be automatically set via the adjustment cylinder 96.

Claims

1. Hydraulic arrangement (42) for a commercial vehicle (10), - with a hydraulic variable displacement pump (46) which is connected via a pump outlet (54) to a supply connection (48) as a hydraulic interface for supplying hydraulic consumers (58) of the commercial vehicle (10), - with a hydraulic auxiliary pump (70) and an auxiliary supply connection (52) as a hydraulic interface for the auxiliary supply of at least some of the consumers (60, 62), and - with an adjustment control (64) which is dependent on an output pressure (p_v) of the auxiliary pump (70) for adjusting the variable displacement pump (46) in such a way that a hydraulic working connection (98) of an adjustment cylinder (96) of the adjustment control (64) is hydraulically connected to an outlet (72, 90) of the auxiliary pump (70).

2. Hydraulic arrangement according to claim 1, characterized by a single-acting adjusting cylinder (96).

3. Hydraulic arrangement according to claim 1 or 2, characterized in thatin the flow path between the outlet (72, 90) of the auxiliary pump (70) and the working connection (98) of the adjusting cylinder (96), a check valve (100) is hydraulically connected upstream of the working connection (98), wherein the flow direction of the check valve (100) is directed in the direction of the working connection (98).

4. Hydraulic arrangement according to one of the preceding claims, characterized in that in the hydraulic flow path between the working connection (98) of the adjusting cylinder (96) on the one hand and the pump outlet (54) and a return connection (92) on the other hand, a holding valve unit (114) is hydraulically interposed, which has two different switching positions (114-0, 114-a) such that the holding valve unit (114) acts either as a hydraulic interruption or as a hydraulic connection in the flow path depending on its activated switching position (114-0, 114-a).

5. Hydraulic arrangement according to claim 4, characterized in that the holding valve unit (114) has a hydraulic valve connection (116) in the flow path on its connection side facing away from the working connection (98) of the adjusting cylinder (96), which can be connected to the pump outlet (54) depending on an output pressure (p_a) of the variable displacement pump (46).

6. Hydraulic arrangement according to claim 5, characterized in that the holding valve unit (114) has a control pressure inlet (118) which is effective in the switching direction and which is hydraulically connected to the valve connection (116).

7. Hydraulic arrangement according to one of the preceding claims, characterized in thatin the flow path between the working connection (98) or the holding valve unit (114) on the one hand and the pump outlet (54) and a return connection (92) on the other hand, at least one valve unit (102, 104) having a plurality of switching positions (102-0, 102-a; 104-0, 104-a) is arranged, which has two hydraulic control inputs (106, 108; 110, 112) opposite one another in the switching direction, - one control input (106, 110) of which is hydraulically connected to the pump outlet (54), and - the other control input (108, 112) of which is hydraulically connected either to the return connection (92) or to a feedback connection (50) acting as an interface for pressure feedback from consumers (58).

8. Hydraulic arrangement according to one of the preceding claims, characterized in thatwhen the output pressure (p_v) at the output (72, 90) of the auxiliary pump (70) has increased after reaching or exceeding a predetermined target pressure (p_soll) at the output (72, 90) of the auxiliary pump (70), it has at least one of the following features: - the holding valve unit (114) is in the switching position (114-0) acting as a hydraulic connection in the flow path; - a drive (68) of the auxiliary pump (70) is reduced or deactivated; - the variable displacement pump (46) is driven.

9. Hydraulic arrangement according to one of the preceding claims, characterized in that a pressure sensor (78) generating sensor signals (S) is hydraulically connected to the output (72, 90) of the auxiliary pump (70), wherein, depending on the sensor signals (S), - a drive (68) of the auxiliary pump (70) can be controlled, and / or - the holding valve unit (114) can be controlled to change its switching position (114-0, 114-a).

10. Commercial vehicle (10) with a drive motor (22) and with a hydraulic arrangement (42) according to one of claims 1 to 9.

11. Commercial vehicle according to claim 10, characterized in that the drive motor (22) is drive-connected to the variable displacement pump (46).

12. Commercial vehicle according to claim 10 or 11, characterized in that the auxiliary supply connection (52) is hydraulically connected to a braking system (62) and / or to a steering system (60) of the commercial vehicle (10).

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