EP3802397A1

EP3802397A1 - Hydraulic system, hydraulic unit, vehicle, method and use

Info

Publication number: EP3802397A1
Application number: EP19728003.5A
Authority: EP
Inventors: Wolfgang Bauer; Nicolas GROO; Sebastian FELLHAUER
Original assignee: Argo Hytos Group AG
Current assignee: Argo Hytos Group AG
Priority date: 2018-05-29
Filing date: 2019-05-28
Publication date: 2021-04-14
Also published as: US11312202B2; CN210033996U; CN110541861A; WO2019229068A1; DE102018112835A1; US20210197639A1

Abstract

The invention relates to a hydraulic system for the open- or closed-loop control of a hydraulic cylinder (19a, 19b), having at least one hydraulic cylinder (19a, 19b), at least one hydraulic unit (10, 11) by means of which the hydraulic cylinder (19a, 19b) can selectively be connected to a pressure source and a tank (15), and at least one open- or closed-loop control device (31) for the open- or closed-loop control of the supply of hydraulic liquid to the hydraulic cylinder (19a, 19b), the open- or closed-loop control device (31) forming a first assembly and the hydraulic unit (10, 11) forming a second assembly, which assemblies are structurally separate from one another and are fluidically connected, wherein the supply of hydraulic liquid to the hydraulic cylinder (19a, 19b) is predominantly controllable, in open- or closed-loop fashion, from outside the hydraulic unit (10, 11) by means of the open- or closed-loop control device (31), and wherein the hydraulic unit (10, 11) is rigidly connected to the hydraulic cylinder (19a, 19b).

Description

Hydraulic system, hydraulic unit, vehicle, procedures and use

DESCRIPTION

The invention relates to a hydraulic system for controlling or regulating a hydraulic cylinder having the features of the preamble of claim 1. Such a hydraulic system is known, for example, from EP 1 067 296 A1. The invention further relates to a hydraulic unit, a vehicle, a method and a use of the hydraulic unit.

The known hydraulic system is used in self-propelled industrial trucks, which are to be operated energy-saving. This will be a

load-related pressure potential of the hydraulic fluid used. The known hydraulic system is concerned with the problem that a second

Supply pump for operating a consumer for a secondary function is provided. To control the secondary functions, the well-known

Hydraulic system on a complex hydraulic control circuit, which too

Throttle losses leads.

The invention is based on the object to provide a hydraulic system for controlling or regulating a hydraulic cylinder, which is simple, compact and safe. In addition, the hydraulic system should be suitable for vehicles with electric drive. The invention is further based on the objects to provide a hydraulic unit, a vehicle, a method and the use of the hydraulic unit.

According to the invention the object is achieved with regard to the hydraulic system by the subject of claim 1. With regard to the hydraulic unit, the object is achieved according to the invention by the subject matter of claim 20, with a view to the use of the hydraulic unit by the subject of claim 21, with a view of the vehicle by the subject of claim 22 and with regard to the method by the article of claim 23 solved.

Specifically, the object is achieved by a hydraulic system for controlling or regulating a hydraulic cylinder, the at least one hydraulic cylinder and has at least one hydraulic unit. The hydraulic cylinder can be connected by the hydraulic unit optionally with a pressure source and a tank.

The hydraulic system has at least one control or regulating device for controlling or regulating the supply of hydraulic fluid to

Hydraulic cylinder on. The control or regulating device forms a first

Assembly. The hydraulic unit forms a second module. The first and second assemblies are structurally separated and fluidly connected. The supply of hydrau likflüssig speed to the hydraulic cylinder is mainly controlled or regulated by the control or regulating device from outside the hydraulic unit. The hydraulic unit is rigidly attached to the hydraulic cylinder.

The invention has the advantage that the hydraulic device is simple, compact and constructed safe against hose breakage. Due to the simple structure and the division in hydraulic unit and control or regulating device

Throttle losses avoided during the lifting process, which are caused in the prior art by the usually integrated into the hydraulic unit control elements. These control elements are not or less required in the invention. For this purpose, the invention provides that the two modules, which are formed by the control or regulating device and the hydraulic unit, are structurally separated from each other. The structural separation can be achieved for example by a spatial separation and mechanical delimitation of the modules. For this purpose, the two modules, for example, in different, separate from each other, in particular from each other

be housed spaced apart housings. The assemblies form mechanically separate and independently manageable, in particular independently mountable units.

The hydraulic system according to the invention saves space and allows flexible use of the available space, because a simple control and regulating device can be centrally located, which is connected to one or more decentralized attached to the hydraulic cylinders small, simple hydraulic units. This avoids that a larger space must be provided at a single point of the vehicle. The hydraulic units can each be equipped with pressure accumulators for suspension.

For the control function, the two modules are fluidly connected to each other. This is done, for example, by wires which are the two connect structurally separate modules together. In other words, the two assemblies are on the one hand mechanically separated from each other and on the other hand fluidly connected to each other. In this case, the hydraulic unit is primarily for the control of the outflow of the hydraulic fluid from the hydraulic cylinder and the control and regulating devices primarily for the control of the inflow of the hydraulic fluid to the

Hydraulic cylinder responsible. According to the invention, it is therefore provided that the supply of hydraulic fluid to the hydraulic cylinder can be controlled or regulated predominantly from outside the hydraulic unit by the control or regulating device.

It is sufficient if the supply of hydraulic fluid to

Hydraulic cylinder is controlled or regulated mainly from outside the hydraulic unit. A maximum reduction in throttle losses is achieved when the supply of hydraulic fluid, i. the lifting operation is completely controlled from outside the hydraulic unit, wherein

Security organs, eg. A check valve can be integrated into the hydraulic unit. In extreme cases, the entire supply control or regulation is done externally. This means that in the extreme case, at least one lifting branch of

Hydraulic unit, so the intended for the supply of the hydraulic fluid area of the hydraulic unit, free of switching elements, control elements and

Regulatory organs is.

Other areas of the hydraulic unit, for example, a Senkzweig the hydraulic unit, which is used for the outflow of the hydraulic fluid, have switching elements,

Control organs and control devices for the hydraulic fluid on.

Predominantly means that insignificant control activities in the lifting branch of the hydraulic unit, ie in the supply of hydraulic fluid to

Hydraulic cylinders are allowed. For example. For example, up to 25%, in particular up to 20%, in particular up to 10%, in particular up to 5%, of the delivery rate for the cylinder stroke within the hydraulic unit can be controlled. At least 75% of the delivery rate is controlled from outside the hydraulic unit by the controller.

The rigid attachment of the hydraulic unit on the hydraulic cylinder has the advantage that a uniformly manageable unit of hydraulic unit and

Hydraulic cylinder is created that is robust, simple and, above all, safe is constructed, because between the hydraulic cylinder and the hydraulic unit can be dispensed with flexible hose connections. This achieves a hose rupture protection. In a preferred embodiment, the rigid attachment of the hydraulic unit to the hydraulic cylinder is achieved in that the hydraulic unit is arranged directly on the hydraulic cylinder and fluidly connected thereto. As a result, a hose break is safely excluded at this point. It is also possible that the hydraulic unit of the

Hydraulic cylinder is spaced by a gap and the fluid connection is made by solid pieces of pipe that bridge the gap.

The assembly of hydraulic unit and hydraulic cylinder is assembled together and removed or replaced together for maintenance purposes. The structurally separate control or regulating device is provided at a different, spatial location of the hydraulic system.

The invention has the further advantage that the structurally separate control or regulating device can be coupled and operated with an electric drive of the vehicle.

Preferred embodiments of the invention are specified in the subclaims.

Thus, the pressure source preferably comprises at least one switchable or controllable or controllable fluid source. The fluid source is for forming a

Displacement control or regulation of the hydraulic cylinder Part of the control or regulating device. For energy reasons, the hydraulic power is preferably displacement-controlled, ie without the use of throttle devices for flow control.

In the displacement control or the displacement control, the hydraulic power is controlled or regulated by the connection or adjustment of the fluid source. The hydraulic power is variable by the fluid source, in particular continuously variable or switchable, i. switched on and off. For the connection of the hydraulic power can a

Constant pump, so a non-adjustable pump, are used, which is switched on or off or. Due to the demand-oriented provision of hydraulic power, a high degree of efficiency is achieved. The at the Resistance control caused by valves throttle losses are avoided.

The use of a constant-displacement pump as a fluid source is particularly preferred in order to obtain a simple system in which the lifting operation with low

Throttle losses occurs, and a high degree of safety against hose breakage is achieved.

In a further preferred embodiment, the fluid source is on the one hand drive-connected with an electric motor and on the other hand with the

Hydraulic cylinder by the hydraulic unit for controlling or regulating the supply of hydrau likflüssig speed fluidly connected to the hydraulic cylinder. This embodiment is particularly suitable for higher-level systems that have an electric power source as the main power source for the driving and working functions, such as electric-powered vehicles. There are various possibilities conceivable. The electric motor can

battery powered and / or connected to a generator which is operated by an internal combustion engine.

Preferably, a backflow of hydraulic fluid at the hydraulic cylinder to the fluid source is prevented by a valve which is integrated in the hydraulic unit. The valve, such as a check valve, has the advantage that when a line break between the control or regulating device and the

Hydraulic unit hydraulic fluid can escape from the hydraulic unit or the outlet is limited. The valve is therefore a safety device.

Preferably, the electric motor for power limitation is adjustable so that the maximum positive displacement pressure can be limited. This avoids damage to the system caused by overpressures.

For the displacement control, the electric motor can be a frequency-controlled

Be a variable speed electric motor.

The control or regulating device may comprise means for power sharing, for example a flow divider, and / or a valve control or regulation with at least one control or regulating valve. Variable hydraulic resistances (valves) are used to control or distribute the hydraulic power. In a particularly preferred embodiment, the hydraulic system comprises a hydropneumatic suspension system for leveling a vehicle with at least one accumulator connected to the hydraulic cylinder

fluidly connected. This embodiment is particularly suitable for the suspension of vehicles having an electric power source as the main power source for the driving and working functions.

Hydropneumatic suspensions are commonly used on machines

applied, on which already a hydraulic supply is already available.

For machines that have no hydraulics and instead one

Pneumatic supply is present (eg for a brake system), the

Suspension usually pneumatic, so designed with air bellows. This is z. B. the case of trucks and buses. In some vehicles bump

pneumatic suspensions to their limits, z. B. due to increasing axle loads, roll stability, possible control speed or even when

Power consumption. Among other things by the electrification of

Vehicle drives increase the requirements regarding loads (mass of batteries) and energy consumption. As a result, hydropneumatic suspensions, especially in heavy electric vehicles, are coming to the fore, all the above.

Properties can be fulfilled very well here.

Due to the structural and functional separation of the hydraulic unit and the control or regulating device, this embodiment can be particularly well coupled with the electric motor to provide the required for the level control of the vehicle hydraulic power. In this embodiment, it is about a long-term height control by the hydraulic cylinder to compensate for load changes. So it does not depend on a particular dynamic and a good response of the scheme. Rather, a hydropneumatic suspension and attitude control is created, which is inexpensive, energy efficient and safe and can be accommodated in the vehicle to save space. In the future, as part of the electrification of vehicles and functions with the (partial) omission of the hydraulic from these

To count vehicles. This embodiment contributes to this development

Bill and then still allows hydropneumatic suspension.

In a further particularly preferred embodiment, at least two position control circuits are provided, each having a hydraulic unit, each having a hydraulic cylinder and optionally each a pressure accumulator. Both Position control circuits are coupled to a common drive unit. The drive unit has an electric motor provided with a single fluid source, for example a single pump, or with a multiple fluid source for the two position control circuits, for example with a plurality of pumps with one

common drive shaft is connected. This embodiment is particularly suitable for the suspension of a vehicle axle with 2 wheel suspensions, wherein the suspension is effected by a hydropneumatic suspension system, in particular by the suspension system according to the preceding embodiment. The suspension of a vehicle axle with 2 suspensions can also be done with a single pump, for example. A fixed displacement pump for both suspensions. For the power distribution to the suspension of the pump downstream flow divider may be provided. The power distribution can also be done in other ways. It is also possible to provide several, in particular two electric motors, which are each drive-connected with their own fluid source and the position control circuits separately with

Supply hydraulic fluid.

In a further embodiment, the hydraulic unit comprises the following

components:

at least one first connection for a fluid source;

at least one second connection for a tank;

optionally at least a third port for a pressure accumulator;

at least a fourth connection for a hydraulic cylinder;

The hydraulic unit comprises a lifting branch between the first port and the fourth port for supplying hydraulic fluid to the

Hydraulic cylinder. The hydraulic unit further comprises a lowering branch between the second port and the fourth port for discharging

Hydraulic fluid from the hydraulic cylinder.

The Senkzweig preferably branches off from the lifting branch or is fluidly connected to this. The area between the branch and the fourth port or generally between the branch and the hydraulic cylinder temporarily connects the lifting branch to the hydraulic cylinder and temporarily the lowering branch to the hydraulic cylinder, specifically to the fourth connection, depending on whether the lifting operation or the lowering operation takes place. This area, too

Called connection branch, is flowed through in different directions by hydraulic oil. This embodiment forms a possibility which has been explained above

To realize suspension system. Other versions are possible.

Preferably, the fourth port includes a double port for a piston side and a rod side of a double-acting hydraulic cylinder with a piston. The hydraulic unit is thus particularly compact.

If a flow-influencing element, in particular a diaphragm or a throttle between the third port and the fourth port is arranged, the flow between these two ports is hindered and thereby loses flow energy, whereby the spring movement is attenuated.

The Senkzweig may have switching elements and / or control elements for changing the discharge of hydraulic fluid from the hydraulic cylinder. This affects the lowering speed of the hydraulic cylinder. For clarification, it should be noted that the structural and functional separation between hydraulic unit and control and regulating device, the lifting function of the

Hydraulic cylinder concerns. This does not exclude that the hydraulic unit has switching elements or control elements that the lowering function of the

Concern hydraulic cylinder.

The lowering branch may have at least one switching valve, in particular a proportional seat valve, in particular a corresponding valve as a 2/2-way valve. The lowering branch may have at least one flow-influencing element, in particular a throttle and / or at least one pressure-limiting valve and / or at least one proportional seat valve and / or at least one current regulator.

Preferably, the hydraulic cylinder is mechanically rigidly connected to a wall of the hydraulic unit. In this case, the hydraulic cylinder can rest directly on the wall of the hydraulic unit. Alternatively, a gap may be formed between the wall of the hydraulic unit and the hydraulic cylinder.

If the hydraulic cylinder rests directly against the wall of the hydraulic unit, the fourth connection, in particular the double connection, can be fluid-connected directly via this wall to the hydraulic cylinder. This embodiment is particularly advantageous because flexible hose connections and thus the risk be reliably avoided by hose break between the hydraulic cylinder and the hydraulic unit. If a gap is formed between the hydraulic cylinder and the wall of the hydraulic unit, this gap can be bridged by a rigid pipe section.

In addition to the hydraulic system is within the scope of the invention a

Hydraulic unit for a hydropneumatic suspension system for

Level control of a vehicle claimed. Thus, the unit as such, that is independent of the hydraulic cylinder and more

Components of the suspension system or general hydraulic system disclosed and claimed. The hydraulic unit has the same connections as the aforementioned embodiment of the hydraulic system. In addition, the hydraulic unit is characterized in that the lifting branch,

in particular, the lifting branch and a connecting branch between the lifting branch and the fourth connection, substantially free of switching and control elements for changing the supply of hydraulic fluid to the hydraulic cylinder.

The hydraulic unit according to the invention has the advantage that it is simple and compact, wherein in the lifting branch, i. in connection with the lifting function of the hydraulic cylinder little or no throttle losses occur. The control or regulation of the cylinder stroke is done externally by a separate control and regulating device.

Other areas of the hydraulic unit, for example, the Senkzweig may have switching and control elements.

The hydraulic unit according to the invention is disclosed and claimed as such and in connection with the hydraulic system. It should be noted that the hydraulic unit according to claim 20 in connection with the hydraulic system according to the invention represents a preferred embodiment, to which the hydraulic system is not limited. Other

Hydraulic units can be used with the hydraulic system according to the invention.

The inventive method for leveling a vehicle uses the hydraulic system according to claim 1. In the method, the vehicle is raised by a control of the fluid source, in which the electric motor is driven, wherein when lifting substantially the same Pressure at the fluid source and the hydraulic cylinder is applied. This has the advantage that virtually no throttle losses occur during the stroke of the hydraulic cylinder.

Preferably, in the case of a plurality of fluid sources, a fluid source is made ineffective by opening a diverting branch and thereby an oil circulation. As a result, individual consumers or hydraulic cylinders can be controlled separately.

The invention will be explained in more detail with reference to an embodiment with reference to the accompanying schematic drawing with further details.

In this, the single figure shows a circuit diagram of a hydraulic system according to an embodiment of the invention.

The illustrated in the single figure embodiment of a hydraulic system according to the invention can be used as a suspension system in mobile machines specifically for the position control of a vehicle axle, the left and right wheels of the axle can be controlled separately. The hydraulic system is suitable for the suspension of vehicles of all kinds, especially if there is no hydraulic supply (more) or in which an air suspension is not suitable. The invention is not limited to the position control shown in the single figure. Specifically, the illustrated hydraulic system can be used as axle suspension or Einzelradfederung. Other suspensions that require level control, for example to adjust loading conditions or to adjust ground clearance, are possible.

Specifically, the hydraulic system comprised two position control circuits 29, 30, which are constructed accordingly. The position control circuits 29, 30 can

be structured differently. The invention is not limited to a two-circuit system, but may have a single position control loop or more than two position control circuits, for example, three, four or more

Position control circuits. The following explanations in connection with the first position control circuit 29 apply analogously to the second

Position control loop 30 or all other position control loops. With regard to the reference numerals of corresponding components of the position control circuits, reference is made to the list of reference numerals. The position control circuit 29 or generally the hydraulic system 10 has a hydraulic cylinder 19a. On the hydraulic cylinder 19a, a hydraulic unit 10 is rigidly fixed, for example screwed or welded. The

Hydraulic unit 10 is flanged directly on the hydraulic cylinder 19a. The rigidly connected to the hydraulic cylinder 19 a hydraulic unit 10 and the

Hydraulic cylinders 19a form a fixed unit.

The hydraulic unit 10 has the function of selectively connecting the hydraulic cylinder 19a to a pressure source and a tank 15. The rigid attachment of the hydraulic unit 10 to the hydraulic cylinder 19a increases the safety of the system because closed by the directly flanged hydraulic unit 10 of the suspension circuit and thus a hose or pipe break has no effect on the suspension properties.

The position control circuit 29 or generally the hydraulic system 10 has a control or regulating device 31, which serves the supply of

Hydra ul ikflüssigkeit to control the hydraulic cylinder 19a or regulate. In the following, for the sake of simplicity, the term control is also included.

The control or regulating device 31 forms a first module and is characterized by a dashed system boundary. The hydraulic unit 10 is also characterized by a dashed system boundary which delimits a second assembly from the first assembly. The system limit means that the control or regulating device 31 is not only functionally separate from the hydraulic unit 10, but also that the two assemblies are structurally separated from each other. The control or regulating device 31 is arranged at a different spatial location of the hydraulic system or the position control circuits 29 and mechanically independent of the hydraulic unit 10th

As can be seen in the single figure, the two assemblies, i. the

Hydraulic unit 10 and the control or regulating device 31 fluidly connected by a line, in particular pipe, or by a hose connection. Through this fluid connection, the supply of hydraulic ikflüssigkeit to

Hydraulic cylinder 19 a regulated. The supply control takes place predominantly from outside the hydraulic unit 10 by the control or regulating device 31. In other words, the required for the stroke of the hydraulic cylinder 19a, pressure-loaded delivery volume by the control or regulating device 31st provided. The hydraulic system is constructed according to the displacement principle, wherein the control or regulating device 31 promotes hoch Hochregeln the position, ie for lifting the hydraulic cylinder 19 a Hydraulic ikflüssigkeit in the hydraulic cylinder 19 a. Thus, essentially all the energy used is converted into mechanical energy, so that the hydraulic system very

energy efficient works. As can be seen in the single figure, the hydraulic system completely dispenses with high control valves. Instead, the controller 31 is used to control.

For this purpose, the control or regulating device 31 has a switchable or controllable or controllable fluid source 13a.

The fluid source 13a is on the one hand drive-connected to an electric motor 23. On the other hand, the fluid source 13a is fluidly connected to the hydraulic unit 10, so that by controlling (on / off or variable) of the electric motor 23, the hydraulic power can be regulated, with which the hydraulic cylinder 19a is supplied via the hydraulic unit 10 with hydraulic fluid.

The switchable fluid source 13a may, for example, be a constant-displacement pump, that is to say a pump with a constant displacement volume per revolution. The switchability of the fluid source 13a is usually realized by the drive member which is connected to the fluid source 13a, for example by the electric motor 23. In this case, the electric motor 23 connected to the fixed displacement pump is used for the

Lifting on and off. Alternatively, the constant displacement pump may be coupled by a clutch to the electric motor 23 as needed. Other possibilities are conceivable.

The electric motor 23 may be implemented as a variable-speed variable-frequency electric motor, so that the stroke speed of the hydraulic cylinder 19a is adjustable. The electric motor 23 has a power / torque limit to limit the maximum positive displacement pressure. The pump is adapted to the electric motor 23 accordingly.

Instead of the displacement control described above, the hydraulic power can be provided by a resistance control, the

having corresponding control valves. Again, it is true that the constructed according to the principle of resistance control control or regulating device (not shown) is structurally separated from the hydraulic unit 10. The hydraulic unit 10 is constructed as follows:

The hydraulic unit 10 forms a hydraulic block with a first port 12, which is connected to the fluid source 13 a, specifically connected to the electric motor driven pump or connectable. The hydraulic unit 10 has a second port 14 which fluidly connected to a tank 15 or

is fluid-connectable. The tank 15 belongs to the first assembly of the controller 31. Alternatively, a common tank could be used with other systems. A third port 16 of the

Hydraulic unit 10 is connected to a pressure accumulator 17a, for example a

Diaphragm memory connected or connectable. Such accumulators are known per se.

A fourth port 18 is connected to the hydraulic cylinder 19a. As can be seen in the single figure, the fourth port 18 is directly connected to the

Hydraulic cylinder, i. connected without intermediate hose connections. For this purpose, the hydraulic unit 10 with a wall of the

Hydraulic cylinder 19 directly or generally rigidly connected, wherein the fourth port 18 takes place directly over the wall. This is illustrated in the single figure in that the system boundary (dashed line) of the hydraulic unit 10 coincides with the wall of the hydraulic cylinder 19.

The fourth port 18 is designed as a double port, which is connected on the one hand to the piston side and on the other hand to the rod side of the hydraulic cylinder 19a. The rod side or piston side results from the arrangement of the piston 24 in the hydraulic cylinder 19a. The piston 24 may be part of a double-acting hydraulic cylinder. Other pistons or cylinders are possible, for example a plunger cylinder. In the double-acting

Hydraulic cylinder can prevail in the annulus, for example, due to a hydraulically biased suspension, a different pressure.

The hydraulic unit 10 includes a lifting branch 20 and a Senkzweig 21 and optionally other branches with other functions, such as a suspension branch 33, a connecting branch 34 and a

Pressure limiting branch 35.

The lifting branch 20 includes those lines or channels of the hydraulic unit 10, through which the hydraulic oil flows exclusively to the hydraulic cylinder 19a. The direction of flow is in a single direction towards the hydraulic cylinder 19a. By the lifting branch 20 of the hydraulic cylinder 19 a with

Hydra ul ikflüssigkeit supplied and pressurized so that it can perform the desired lifting function for the position control.

Concretely, the lifting branch 20 comprises the line from the first connection 12, which is connected or connectable to the fluid source 13 a, to the first junction Kl, at which the lowering branch 21 is fluidically connected to the lifting branch 20 or branches off from the lifting branch 20. As can be seen in the single figure, only the check valve 22 is arranged in the lifting branch 20, which prevents

Hydraulic fluid exits from the hydraulic unit 10, when the line or hose connection between the hydraulic unit 10 and the spaced therefrom arranged control or regulating device 31 breaks or is leaking. Incidentally, the lifting branch 20 is free or at least substantially free of switching devices, control elements or control devices for regulating the

Supply power.

The connecting branch 34 is the lifting branch 20 in the flow direction

downstream.

The connection branch 34 comprises those lines or channels of the

Hydraulic unit 10, which is functional to both the lifting branch 20 and the

Senkzweig 21 belong. The connecting branch 34 is therefore characterized in that the hydraulic fluid flows through the lines or channels of the connecting branch 34 in both directions, namely in the direction of

Hydraulic cylinder 19a during the lifting operation and in a direction away from the hydraulic cylinder 19a during the lowering process. The connecting branch 34 comprises those lines which on the one hand during the lifting operation in the feed direction, i. flowed through to the hydraulic cylinder 19 a, and on the other hand are flowed through in the opposite direction in the lowering operation, i. are flowed through by the guided from the hydraulic cylinder 19a from hydraulic oil.

The connecting branch 34 connects both the lifting branch 20 and the lowering branch 21 with the hydraulic cylinder 19 a.

Due to the at least temporary, functional affiliation of the

Connecting branch 34 to the lifting branch 20, the connecting branch 34 can be seen as part of the lifting branch 20. The comments on lifting branch 20 apply also for the connection branch 34. The connection branch 34 is constructed corresponding to the lifting branch 20. The connecting branch 34 is free, in particular substantially free of switching elements or control elements, at least free of switching elements or control elements that significantly influence the hydraulic fluid when it flows to the hydraulic cylinder 19 a.

Concretely, the connection branch 34 extends from the first one

Node Kl up to and including the fourth terminals 18, the

Hydraulic cylinder 19 a fluidly connect to the hydraulic unit 10.

The suspension branch 33 is fluidly connected to the hydraulic cylinder 19a. There are various possibilities for this. For example, the suspension branch 33, as shown in the single figure, with the second node K2

be fluidly connected. The second node K2 is located in

Connecting branch 34. The second node K2 forms the branch of the lines to the fourth terminals 18 and generally to the hydraulic cylinder 19a. It is also possible, the suspension branch 33 directly to the

To connect hydraulic cylinder 19a and the corresponding working space.

The suspension branch 33 comprises a first throttle 25 which is the second

Node K2 is downstream. In addition, the suspension branch 33 has a pressure accumulator 17a, for example in the form of a diaphragm pressure accumulator. Other accumulators are possible.

The Senkzweig 21 includes those lines or channels, which are flowed through only during the lowering of hydraulic oil, which from the

Hydraulic cylinder 19a is discharged. The lines of the Senkzweig 21 are flowed through in a single flow direction and indeed in a direction toward the tank 15. The lowering branch 21 has a function of lowering the hydraulic fluid contained in the hydraulic cylinder 19a upon lowering, i.e., lowering. When the hydraulic cylinder 19a is downwardly controlled to discharge or partially remove. to

Change in the lowering speed of the hydraulic cylinder 19a 21 switching members or control elements are provided in Senkzweig. Since the sinking process, the system no electrical energy is supplied, the occurring

Throttling losses less relevant.

Specifically, the Senkzweig 21 comprises a line starting from the first

Junction Kl up to and including the second port 14, with the tank 15 is connected or is connectable. The lowering branch 21 has a switching valve 26. The switching valve 26 is a proportional seat valve, which regulates the volume flow from the hydraulic cylinder 19 a to the tank 15. Other valves are possible.

The switching valve 26 is preceded by a second throttle 27 in the flow direction.

The combination of the switching valve 26 and the second throttle 27 or a diaphragm can be replaced by a correspondingly sized proportional seat valve. Instead of the second throttle 27, a flow regulator can also be used, whereby the discharged volume flow is independent of the pressure in the hydraulic cylinder 19a. This has the advantage that then the volume flow through the current regulator z. B. can be tuned exactly to the flow rate of the pump, so that the lowering as fast as the lifting is done. In addition, this has the advantage that when lifting only one side of the dual-circuit system shown in the single figure, the other side (with activated switching valve 26) regardless of the pressure in the two hydraulic cylinders 19a, 19b does not change their position.

The pressure limiting branch 35 comprises a bypass line 32, which in the

Connecting branch 34 and the Senkzweig 21, bypassing the switching valve 26 connects. Specifically, the pressure limiting branch 35 connects the

Connecting branch 34 between the two nodes Kl, K2 with a point Senkzweiges 21, which is downstream of the switching valve 26. Of the

Pressure limiting branch 35 has a pressure limiting valve 28 which opens at excessive pressures in the connecting branch 34 in order to protect the hydraulic cylinder 19 a from damage. Excessive pressures can occur, for example, by impacts that occur when driving over bumps on the

Hydraulic cylinder 19a act from the outside. For pressure protection of the supply, a pressure limiting valve in the control or regulating device 31 may be provided behind the fluid sources 13a, 13b. Other

Safety precautions for the protection of the hydraulic cylinder 19a are possibly

possible, for example, a waiver of the pressure relief valve 28 when the maximum pump delivery pressure is limited by a reduction of the electric motor 23 and z. B. external forces are limited to the hydraulic cylinder 19a. The embodiment shown in the single figure is not exhaustive. Other interconnections are possible. For example. For example, the fluid sources 13a, 13b may consist of only a single pump with a pressure-compensated flow divider.

Apart from the above safety elements of the lifting branch 20 is free of switching or controllable or controllable actuators. The stroke control thus takes place exclusively by the external control or regulating device 31, i. according to the principle of positive displacement control. It is possible that unessential controls are arranged in the lifting branch 20, as long as the control of the hydraulic supply to the hydraulic cylinder 19a predominantly by the external

Control or regulating device 31 takes place.

Cost-effective, the hydraulic system according to the single figure is also characterized by the fact that valves for Hochregeln, i. is completely dispensed with for the extension of the hydraulic cylinder 19 a and instead only the control of the

Pump drive (electric motor) is used for this. It can be for the

Control of two position control circuits a single drive motor or

Electric motor can be provided which drives a single pump, two pumps or a double pump or generally more pumps, whereby a further electrical circuit is saved.

The two position control circuits 29, 30 are supplied by a single, common control or regulating device 31 with hydraulic fluid. The

illustrated principle can be used for a single position control loop or multiple position control circuits, for example, for three, four or more position control circuits, with a corresponding number of pumps or a corresponding number of divided volume flows is provided. In the present example, two pumps are provided, the two

Position control circuits 29, 30 are assigned accordingly. Both pumps are driven together by the electric motor 23. Other

Constellations are possible.

Hydraulic circuits for synchronizing the hydraulic cylinders 19a, 19b, for example, by series connection or coupled hydraulic motors or flow dividers are known. These circuits can work with the

Position control circuits 29, 30 and the displacement control are combined. Space saving, the system is characterized in that a very simple hydraulic unit is centrally located and with decentralized to the hydraulic cylinders 19a, 19b mounted small, simple hydraulic units 10, 11 each with

Pressure accumulator is connected to the suspension. This avoids that a larger space must be provided at one point of the vehicle.

The hydraulic system shown in the single figure functions as follows:

To raise the vehicle axle, the electric motor 23 is turned on.

Hydraulic fluid is conveyed into the hydraulic units 10, 11, in each case through the first connection 12 into the respective lifting branch 20 and connecting branch 34 of the two hydraulic units 10, 11. The fourth connection 18 causes the hydraulic fluid to flow out of the respective lifting branch 20 via the connecting branch 34 promoted in the hydraulic cylinders 19a, 19b. The pistons 24 are extended for lifting the vehicle or the vehicle axle.

To lower the vehicle axle, the two switching valves 26 are energized and opened according to the desired switching position. Depending on the switching position of the two switching valves 26 is a corresponding

Volumetric flow via the connecting branch 34 through the Senkzweig 21 via the second port 14 into the tank 15 returned. The pistons 24 are retracted and lowered the vehicle axle.

If only the right wheel to be raised, the electric motor 23 is turned on and the left switching valve 26 is energized. If only the left wheel is to be raised, the electric motor 23 is turned on and, conversely, the right switching valve 26 is energized. In general, in order to lift only a first wheel or only a first side, the respective lifting function of the other, second wheel or the other, second side is rendered ineffective by opening the lowering branch 21 of the hydraulic unit 10, 11 of the second wheel or the second side.

If only the left wheel or only the left side to be lowered, only the left switching valve 26 is energized or vice versa when lowering only the right wheel or only the right side of the right switching valve 26th LIST OF REFERENCE NUMBERS

10, 11 Hydraulic unit

12 first connection

13a, 13b fluid source

14 second connection

15 tank

16 third connection

17a, 17b pressure accumulator

18 fourth connection

19a, 19b hydraulic cylinder

20 lifting branch

21 Senkzweig

22 valve

23 electric motor

24 pistons

25 second throttle

26 switching valve

27 first throttle

28 pressure relief valve

29, 30 position control circle

31 control or regulating device

32 bypass line

33 suspension branch

34 connection branch

35 Pressure limiting branch

Kl first node

K2 second node

Claims

1. Hydraulic system for controlling or regulating a hydraulic cylinder (19a, 19b) with

at least one hydraulic cylinder (19a, 19b),

at least one hydraulic unit (10, 11) through which the hydraulic cylinder (19a, 19b) is selectively connectable to a pressure source and a tank (15), and

at least one control device (31) for controlling or regulating the supply of hydraulic fluid to the

Hydraulic cylinder (19a, 19b),

That's why that is

the control or regulating device (31) a first assembly and the hydraulic unit (10, 11) form a second assembly, which are structurally separated from each other and fluidly connected, wherein the supply of hydrau likflüssig speed to the hydraulic cylinder (19 a, 19 b) predominantly from outside the Hydraulic unit (10, 11) by the control or

Control device (31) is controllable or regulated, and wherein the

Hydraulic unit (10, 11) is rigidly attached to the hydraulic cylinder (19a, 19b).

2. Hydraulic system according to claim 1

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the pressure source comprises at least one switchable or controllable or controllable fluid source (13a, 13b) which is part of the control or regulating device (31) for forming a displacement control of the hydraulic cylinder (19a, 19b).

3. Hydraulic system according to claim 2

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the fluid source (13a, 13b) is drivingly connected on the one hand to an electric motor (23) and, on the other hand, fluidically connected to the hydraulic cylinder (19a, 19b) by the hydraulic unit (10, 11) for controlling or regulating the supply of the hydraulic fluid to the hydraulic cylinder (19a, 19b) ,

4. Hydraulic system according to claim 3

dad u rch nets that net a backflow of hydraulic fluid from the hydraulic cylinder (19a, 19b) to the fluid source (13a, 13b) is prevented by a valve (22) integrated in the hydraulic unit (10, 11).

5. Hydraulic system according to claim 3 or 4

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the electric motor (23) can be regulated to limit the power so that the maximum positive displacement pressure can be limited.

6. Hydraulic system according to one of claims 3 to 5

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the electric motor (23) is a variable speed variable frequency electric motor.

7. Hydraulic system according to one of claims 1 to 6

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the control means (31) comprises valve control having at least one controlling valve.

8. Hydraulic system according to one of claims 1 to 7

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the hydraulic system is a hydropneumatic suspension system for

Level control of a vehicle having at least one pressure accumulator (17a, 17b) which is connected to the hydraulic cylinder (19a, 19b)

fluidly connected.

9. Hydraulic system according to one of the preceding claims

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at least two position control circuits (29, 30) each having a hydraulic unit (10, 11), each having a hydraulic cylinder (19a, 19b) and optionally each have a pressure accumulator (17a, 17b), both

Position control circuits (29, 30) are coupled to a common drive unit (31) having the electric motor (23) provided with a single fluid source or with a multiple fluid source or with at least two separate fluid sources (13a, 13b) for the two

Position control circuits (29, 30) is connected.

10. Hydraulic system according to one of the preceding claims

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the hydraulic unit (10, 11) comprises

at least one first connection (12) for a fluid source (13a, 13b),

at least one second connection (14) for a tank (15), optionally at least one third connection (16) for a pressure accumulator (17a, 17b),

at least one fourth connection (18) for a hydraulic cylinder (19a, 19b)

a lift branch (20) between the first port (12) and the fourth port (18) for supplying hydraulic fluid to the hydraulic cylinder (19a, 19b) and

a lowering branch (21) between the second port (14) and the fourth port (18) for discharging hydraulic fluid from the hydraulic cylinder (19a, 19b),

11. Hydraulic system according to claim 10

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the fourth port (18) comprises a double port for a piston side and a rod side of a double-acting hydraulic cylinder (19a, 19b) with a piston (24).

12. Hydraulic system according to claim 10 or 11

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at least one flow-influencing element, in particular a diaphragm or a throttle (25) between the third port (16) and the fourth port (18) is arranged.

13. Hydraulic system according to one of claims 10 to 12

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the lowering branch (21) has switching elements and / or regulating elements for changing the removal of hydraulic fluid from the hydraulic cylinder (19a, 19b).

14. Hydraulic system according to one of claims 10 to 13

dad u rch nets that net the lowering branch (21) has at least one switching valve (26), in particular a proportional seat valve.

15. Hydraulic system according to one of claims 10 to 14

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the lowering branch (21) has at least one flow-influencing element, in particular a throttle (27).

16. Hydraulic system according to one of claims 10 to 15

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at least one pressure limiting valve (28) is arranged parallel to the lowering branch (21).

17. Hydraulic system according to one of claims 10 to 16

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the lowering branch (21) has at least one current regulator.

18. Hydraulic system according to one of claims 10 to 17

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the hydraulic cylinder (19a, 19b) is mechanically rigidly connected to a wall of the hydraulic unit (10).

19. Hydraulic system according to claim 18

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the fourth connection (18), in particular the double connection, is directly fluid-connected to the hydraulic cylinder (19a, 19b) via the wall of the hydraulic unit (10).

20. Hydraulic unit for a hydropneumatic suspension system for

Level control of a vehicle with

at least one first connection (12) for a fluid source (13a, 13b),

at least one fourth connection (18) for a hydraulic cylinder (19a, 19b) a lifting branch (20) between the first port (12) and the fourth port (18) for supplying hy likflüssigkeit to the hydraulic cylinder (19 a, 19 b) and

a lowering branch (21) between the second port (16) and the fourth port (18) for removing hydraulic fluid from the hydraulic cylinder (19a, 19b),

That's why that is

the lifting branch (20), in particular the lifting branch (20) and a

Connecting branch (34) between the lifting branch (20) and the fourth port (18), substantially free of switching and control elements for changing the supply of hydraulic fluid to the hydraulic cylinder (19a, 19b).

21. Use of a hydraulic unit according to claim 20 for

Level control of a vehicle with a hydropneumatic

Suspension system.

22. Vehicle with a hydraulic system according to claim 1 and / or a hydraulic unit according to claim 20.

23. A method for leveling a vehicle with a

Hydraulic system according to claim 1, in which the vehicle is raised by regulation of the fluid source (13a, 13b), wherein substantially the same pressure is applied to the fluid source (13a, 13b) and the hydraulic cylinder (19a, 19b) during lifting.

24. The method according to claim 23

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in the case of a plurality of fluid sources (13a, 13b), a fluid source (13a, 13b) is made ineffective by opening the lowering branch (21) and thereby an oil circulation.