DE102010020132A1 - Drive system with at least one hydraulic actuator - Google Patents

Abstract

The invention relates to a drive system with at least one hydraulic actuator (2) which is supplied with pressure medium (4) by means of at least one pressure medium pump (3). The fact that the pressure medium pump (3) is a speed-controlled pressure medium pump which is driven by a motor (5) with variable speed and controlled torque, a drive system is created that only when required and adaptively to the desired actuating movement pressure medium from a pressure medium container to the respective hydraulic actuator promotes and vice versa.

Description

The invention relates to a drive system with at least one hydraulic actuator, which is supplied by means of at least one pressure medium pump with pressure medium.

Hydraulic drive systems with one or more actuators that can also sequentially perform various work motions are often supplied with hydraulic energy by means of a control valve circuit driven by one or more constant speed pressure medium pumps. The technical disadvantage of such drive systems is a poor efficiency, since the control valves inherently implement hydraulic energy into heat energy.

Such drive systems are also known in chassis for motor vehicles. That's how it describes DE 199 30 444 C2 an active stabilizer for a motor vehicle, which couples two wheels of a vehicle axle and which is formed from a first stabilizer part associated with the one wheel and from a second stabilizer part assigned to the other wheel and from an actuator coupling the stabilizer parts. The actuator controls the lateral inclination of the motor vehicle by bracing the stabilizer parts against each other. Each stabilizer part extends from a port associated with the actuator to a port associated with the wheel. In the meantime, there are also active suspension systems that have been developed into more complex combination systems and that, in addition to active roll stabilization, also enable level control of a vehicle body. Under level control is to be understood as the active change in the distance between the vehicle body and a vehicle axle.

In a two-axle passenger car usually both a level control on the front and on the rear axle is possible, the level control on the vehicle axles can be made independently.

The DE 10 2004 039 973 A1 describes an active suspension system with level control, which has good spring properties and reduces the tendency of the vehicle to tip over. At the same time a lifting and lowering of the vehicle superstructure over the vehicle wheels is possible. This is done by the simultaneous possible actuation of a directional control valve for pressure change in a piston-side cylinder chamber of the active suspension system in conjunction with an adjustable throttle valve and an adjustment enabling, between a piston rod side cylinder chamber of the suspension system and a pressure medium pump carriage part.

Based on this prior art, the present invention seeks to provide a hydraulic drive system that is structurally simple, has good control characteristics and thereby avoiding principle throttling losses of control valves, so that in this respect a very good efficiency is achieved.

This object is achieved with a drive system with the features of claim 1 in its entirety.

Characterized in that the pressure medium pump, which supplies the hydraulic actuator with pressure medium, preferably as bi-directional speed-controlled pump, preferably without control valve and thus extremely low loss, is operated in two- or four-quadrant operation, and is driven by a motor with variable speed and controlled torque , a drive system is provided which promotes pressure medium from a pressure medium container to the respective hydraulic actuator only when needed and adaptively to the desired adjusting movement and vice versa.

If the hydraulic actuator is, for example, a double-acting cylinder, then both ports of the pressure medium pump are connected to a respective working space of the cylinder, so that in a direction of rotation or conveying direction of the pressure medium pump in one direction, for example, filled the rod space and the piston bottom side working space is emptied and vice versa. This results in a function of the direction of rotation and rotational speed of the pressure medium pump exact control and traversing movement of the actuating element of the hydraulic actuator. The motor driving the pressure medium pump, preferably an electric motor, is torque-controlled and controlled as a function of sensor signals of a control and / or regulating device which determines the demand requirement of the hydraulic actuator. The motor can be so far, for example, a pulse width modulated electric motor.

In order to compensate for leakage losses in the hydraulic circuit between the hydraulic actuator and the pressure medium pump, it is advantageous to remove the leakage fluid escaping from the pressure medium pump by means of a fluid-conducting connection to the pressure medium flow generated by it via a check valve. By using a check valve, on the one hand, the leakage fluid flow can be controlled and the leakage oil in the total pressure medium flow can be kept in circulation with the other fluid quantity.

From the pressure medium pump of various types of hydraulic actuators can be driven, such as a double-acting actuator cylinder or a hydraulic motor, which can also be used to actuate stabilizers of a roll stabilization system of a vehicle.

It is also advantageous to pressurize a pressure accumulator with pressure medium, which can serve to equalize the volume of the pressure medium on the consumer side or on the suction side of the pressure medium pump. The accumulator can also be used for direct loading of a working space of a hydraulic actuator. If the suction side of the pressure medium pump is acted upon by the pressure accumulator, the system bias cavitation in the drive system is avoided by this measure.

The pressure medium pump has a constant displacement volume, wherein in combination with the torque-controlled, variable-speed drive of the pressure medium pump variable flow rates are possible. Thus, it requires no valves to control the flow rate and conveying direction of the pressure medium pump. For the operation of the drive system check valves, which act on the Leckagefluidabfluß sufficient. Nevertheless, it may be advantageous to switch fast-switching directional control valves between the pressure medium pump and the hydraulic actuator or between a plurality of hydraulic actuators.

It is also advantageous to discharge the leakage fluid to a low pressure port of the pressure medium pump or to supply the low pressure side of the pertinent pressure medium flow of the pressure medium pump. It is also advantageous to supply the leakage fluid flow to a high pressure port of the pressure medium pump, wherein the check valve or the two check valves, which bias the leakage fluid flow depending on the conveying direction of the pressure medium pump, prevent pressure medium under high pressure in the corresponding housing interior the pressure medium pump can get. In that regard, it is provided that the non-return valves have mutually mutual opening directions. Each of the leakage fluid dissipating fluid-carrying connections is connected to a high-pressure port of the pressure medium pump, so that a total of parallel connection of the fluid-carrying connection lines is given to the high-pressure fluid lines to the powered by the pressure medium pump consumers or hydraulic actuators. The leakage return is so far on the respective low pressure fluid line formed in the form of high pressure fluid line, just not needed for the high pressure guide.

In order to superimpose a level control function on the functions of the roll stabilization, it is advantageous to associate with each hydraulic actuator associated with the drive system a valve with the aid of which a working space of the relevant hydraulic actuator can be emptied or filled so that, for example, the absolute position of a piston of an actuating cylinder is displaced can be.

Thus, for example, the absolute position of wheels of a motor vehicle relative to a chassis change in height and lower or raise a car superstructure of a motor vehicle.

Hydraulic actuators such as in the form of actuating cylinders can also be coupled to effect a sequence control or an opposite coupling. For example, it is possible to lift a wheel of a vehicle on the inside of a curve and to lower a wheel on the outside of the vehicle.

Further advantages, features and details of the invention will become apparent from the dependent claims and the following description in which several embodiments are described with reference to the drawings. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination.

1 shows a schematic circuit diagram of a drive system with a double-acting actuator cylinder and a pressure accumulator as a consumer;

2 shows a schematic circuit diagram of a drive system with a double-acting actuator cylinder and a pressure accumulator, which acts on a working space of the actuating cylinder;

3 shows a drive system whose consumer is a swivel motor for a roll stabilization system, with a pressure accumulator for leakage fluid compensation and for biasing the suction-side pressure medium;

4 shows a drive system, as in 3 , but without accumulator;

5 shows a drive system whose consumers are two actuating cylinder with kreuzverschaltetem working space, and having a pressure accumulator for leakage fluid compensation and biasing the suction-side pressure medium;

6 shows one to the 5 corresponding drive system, but without accumulator; and

7 shows a schematic circuit diagram of a drive system with two actuating cylinders as consumers as shown in the 6 , Wherein the pressure medium supply to the adjusting cylinders of each a 2/2-way valve for the removal of pressure medium from each one working space of each actuating cylinder is overridden.

In the 1 is a schematic diagram of a hydraulic drive system 1 with a double acting actuator cylinder 19 trained hydraulic actuator 2 shown. The hydraulic actuator 2 is in known per se with a piston 20 which is axially displaceable in a cylinder housing 21 is guided, provided and forms in the cylinder housing 21 two workrooms 13 . 13 ' out. A pressure medium pump equipped with a constant displacement 3 serves the pressure medium supply of the actuator 2 , The pressure medium pump 3 is made by a motor formed as a torque-controlled, variable-speed electric motor 5 over a merely indicated wave 22 driven. Instead of an electric motor 5 but can also be a conventional internal combustion engine, for example in the form of a diesel engine, occur. It is also possible to use an axial piston machine (not shown), as they subject of DE 10 2007 058 859 A1 is, in which the electric motor and the hydraulic pump are combined in a common housing as a unit.

In the embodiment of the 1 are the two workrooms 13 . 13 ' of the adjusting cylinder 19 fluid leading to the high pressure port 15 the pressure medium pump 3 connected and in the embodiment of the 2 is every working space 13 . 13 ' of the adjusting cylinder 19 to a high pressure connection 15 respectively. 15 ' the pressure medium pump 3 connected. Depending on the direction of rotation of the motor 5 and the rotational speed is so far from the pressure medium pump 3 lever 4 in a closed hydraulic circuit without interposition of switching or directional valves in one or the other working space 13 . 13 ' of the adjusting cylinder 19 promoted. This results in a movement or possibly blocking the position of the piston 20 of the respective adjusting cylinder 19 , It is a four-quadrant engine of the engine 5 or a four-quadrant operation of the pressure medium pump 3 provided, whereby in particular a use of the drive system 1 in a motor vehicle (not shown) is shown as an active stabilization system.

An accumulator 10 serves for fluid compensation concerning the difference volume between the two chamber sides of the adjusting cylinder 19 or the pressure medium pump 3 and for biasing the pressure medium 4 on the high pressure side of the pressure medium pump 3 , In the in 1 shown drive system 1 become the two workrooms 13 . 13 ' equally with the pressure of the pressure accumulator 10 whereas in the 2 shown embodiment of a drive system 1 the piston rod side working space 13 ' of the adjusting cylinder 19 with the pressure of the pressure accumulator 10 directly, without interposition of the pressure medium pump 3 is charged. The pressure medium pump 3 has a low pressure connection in both possible directions 14 on, which is always effective when the other, opposite high-pressure port 15 . 15 ' provides the respectively required high pressure for the hydraulic circuit. The respective low pressure connection 14 provides a connection for a fluid-carrying connection 8th ago, the leakage fluid 7 from a repressive space 6 the pressure medium pump 3 again leads back, via the low-pressure connection to the respective high-pressure side and so far to the high-pressure connections 15 . 15 ' , This constitutes a design measure for a hydraulically closed drive system as a whole 1 without pressure medium container.

The fluid-carrying connection 8th leads over the respective low-pressure connection 14 to every high-pressure connection 15 . 15 ' , wherein in each terminal branch of the compound 8th a check valve 9 . 16 is turned on. Each check valve 9 . 16 is so in the fluid-carrying connection 8th built-in that there is a pressure fluid return from the main circuit in the displacement chamber 6 or the other interior of the pressure medium pump 3 prevents and at a slight pressure increase leakage fluid 7 into the main flow of the drive system 1 feeds.

The 3 and 4 show schematic diagrams of a hydraulic drive system 1 with a swing motor 23 formed hydraulic actuator 2 , Swivel motors, in particular so-called single-wing pivot motors, are known. They are used for example in conjunction with stabilizers for roll stabilization of a motor vehicle. Such a swing motor has, inter alia, a housing and a rotor, which comprises a shaft and at least one wing. The wing is used to divide a space enclosed by the housing working space in at least two pressure chambers. The two pressure chambers are, as shown, in each case to the one high pressure port 15 . 15 ' the pressure medium pump 3 connected. To effect a rotation of the wing relative to the housing, a chamber with more or less pressure medium 4 acted upon, so that there is a certain relative position between the housing and a rotor rotatably connected to the wing.

At a rest position of the pressure medium pump is thus also the position of the wing and the rotational position fixed to the rotor. The rotor may be fixedly connected to stabilizer bars of a chassis of a motor vehicle and thus raise or lower the position of a wheel relative to a vehicle superstructure.

To corresponding actuating tasks loss with a drive system 1 , which largely manages without valves to realize, is preferably a pulse width modulated electric motor 5 for driving the pressure medium pump 3 , The control of such an electric motor expediently takes over a control and / or regulating device (not shown), which processes sensor signals in the form of measured and vehicle-specific measured values and forwards accordingly. In addition, an adaptive control can be realized in that the torque is measured at an output shaft of the electric motor or the swing motor and in the driving of the motor 5 with flows. Instead of said electric motor and an internal combustion engine of conventional design, such as a diesel engine, occur.

The electric motor can also be commutated electronically, resulting in an improvement in the efficiency together with an increase in reliability and reliability. In addition, such electronically commutated motors build constructively less expensive. See also the disclosure of the DE 10 2007 058 859 A1 ,

According to the embodiments of the 3 and 4 is each a drive system 1 shown whose fluid-carrying connection 8th for the removal of leakage oil 7 from the displacement or low pressure chamber of the pressure medium pump in the same manner as in the 1 and 2 shown, namely via check valves 9 . 16 connected to the high pressure connections 15 . 15 ' are connected. In the 3 is the drive system 1 with an additional accumulator 10 provided, depending on the operating direction of the pressure medium pump 3 to the respective low pressure connection 14 is connected and total for an absolute pressure medium loss compensation of the entire drive system 1 provides. The accumulator 10 ensures a low fluid pressure at the point of return of the leakage fluid and at the same time becomes the drive system 1 Hydraulic biased so far that no negative pressure and associated cavitation in the drive system 1 can occur. In the in the 4 shown embodiment of the drive system 1 This preload function takes over the elasticity of the fluid-carrying connection between the individual components of the drive system 1 even.

In the in the 5 and 6 shown embodiments of a drive system 1 are as consumers or regulatory bodies 11 two opposing working cylinders 17 shown as a positioning cylinder 19 can serve for an active chassis of a motor vehicle, not shown. The pistons 20 the cylinder 17 can due to the cross-linked connection of their work spaces 13 . 13 ' together in an inactive phase of operation of the drive system 1 in which the position of the displacement elements of the pressure medium pump 3 is not fixed, move and allow unhindered movement of the wheels of a motor vehicle in the vertical direction.

In the embodiment of the 5 is again an accumulator 10 in the same way and to represent the same function as in the 3 shown embodiment shown.

In the in 7 shown embodiment of a hydraulic drive system 1 are to the high pressure connections 15 . 15 ' the pressure medium pump 3 each designed as a 2/2-way valve valve 18 connected. The valves 18 are each in a fluid-carrying connection 24 between the high pressure connections 15 . 15 ' and a pressure medium container arranged in the form of a hydraulic tank. In every fluid-carrying connection 24 a check valve R is connected, which is in the direction of the high pressure connections 15 . 15 ' can be overflowed and locks in the opposite direction. This circuit allows a tight clamping of a piston 20 a working cylinder 17 at one end stop and at the same time controlled movement of the other piston 20 the further working cylinder 17 , This can be a working space of the cylinder in question 17 with pressure medium 4 be supplied from the pressure fluid tank (tank). This constructional measure is necessary because the required pressure medium volume is not from a working space 13 . 13 ' of the so far fixed piston 20 can be obtained.

The valves 18 can be controlled by the control and / or regulating device. The control takes place when at one or the other cylinder 17 a rolling moment is required. A signal for a pending actuation of the valve 18 can be measured by measuring a rolling moment on the respective piston 20 or by a pressure signal on a valve 18 or further from a torque signal of the motor 5 be obtained.

Only the non-return valves used are sufficient for the function. In practice, these should be check valves with a so-called. Minimum ΔP. Alternatively, one could provide directional valves with a very fast control. Also are combinations of a directional control valve and a check valve (see 7 ) possible and represent a good solution. For the control signal this has to correspond to the direction of the rolling moment, the size of the rolling moment is meaningless. Overall, it should be noted that the solution presented a very energy-efficient circuit for hydraulic roll stabilization is created. In that regard, only as much energy is provided as is actually needed for roll stabilization. In the previous systems, as explained, the pump is mounted on the drive train, which means that it is always a Volumenstsrom is to promote, which requires a corresponding amount of energy. If no roll stabilization is required, the flow is pumped at low pressure in the circuit, which represents a loss. If roll stabilization is required, in the known solutions the volumetric flow is promoted with the pressure corresponding to the rolling moment, although actually only the leakage should be compensated after reaching the pressure for the rolling moment. With the solution according to the invention, such energy losses are effectively counteracted.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19930444 C2 [0003]
• DE 102004039973 A1 [0005]
• DE 102007058859 A1 [0026, 0033]

Claims (13)

Drive system with at least one hydraulic actuator ( 2 ), by means of at least one pressure medium pump ( 3 ) with pressure medium ( 4 ), characterized in that the pressure medium pump ( 3 ) is a speed-controlled pressure medium pump, which by a motor ( 5 ) is driven with variable speed and controlled torque. Drive system according to claim 1, characterized in that the pressure medium pump ( 3 ) is bi-directional in two-tandem operation or speed-controlled in four-quadrant operation. Drive system according to claim 1 or 2, characterized in that from a displacement space ( 6 ) of the pressure medium pump ( 3 ) escaping leakage fluid ( 7 ) via a fluid-conducting connection ( 8th ) with at least one check valve ( 9 . 16 ) is dissipated. Drive system according to one of claims 1 to 3, characterized in that the pressure medium pump ( 3 ) an accumulator ( 10 ) with pressure medium ( 4 ), which also controls the hydraulic actuator ( 2 ) with pressure medium ( 4 ). Drive system according to one of claims 1 to 4, characterized in that the hydraulic actuator ( 2 ) an adjusting device ( 11 ) is for a hydraulic system for roll stabilization of a vehicle. Drive system according to claim 4 or 5, characterized in that the pressure accumulator ( 10 ) the pressure medium ( 4 ) on the suction side ( 12 ) of the pressure medium pump ( 3 ). Drive system according to one of claims 4 to 6, characterized in that the pressure accumulator ( 10 ) the pressure medium ( 4 ) in a workroom ( 13 . 13 ' ) of the hydraulic actuator ( 2 ). Drive system according to one of claims 4 to 7, characterized in that the hydraulic actuator ( 2 ) and the pressure medium container are driven by a directional control valve, that a Nachsaugvorgang is realized. Drive system according to one of claims 1 to 8, characterized in that the leakage fluid ( 7 ) to a low pressure port ( 14 ) of the pressure medium pump ( 3 ) is dissipated. Drive system according to one of claims 1 to 9, characterized in that the pressure medium pump ( 3 ) is an axial piston machine, wherein in the fluid-conducting connection ( 8th ) two oppositely opening non-return valves ( 9 . 16 ) are switched on and the fluid-carrying connection ( 8th ) is parallel to a respective high-pressure connection ( 15 . 15 ' ) of the axial piston machine switched. Drive system according to one of claims 1 to 10, characterized in that the pressure medium pump ( 3 ) for the pressure medium supply of two counter-rotating hydrostatic power cylinder ( 17 ) is used. Drive system according to claim 11, characterized in that the counter-rotating working cylinders ( 17 ) each with a valve ( 18 ) for emptying pressure medium ( 4 ) from one of their workspaces ( 13 . 13 ' ) are connected. Drive system according to claim 12, characterized in that parallel to the valve ( 18 ) each have a check valve (R) in a valve ( 18 ) bridging pressure medium line is arranged and that at least one check valve (R) an overflow of pressure medium ( 4 ) from the pressure medium container to the respective hydraulic actuators ( 2 ).

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