DE102021200166B3 - Hydraulic system, especially for a chassis - Google Patents

Abstract

Hydraulic system for controlling at least one hydraulic chassis component, comprising a pump, the suction side of which is connected to a hydraulic accumulator which has a minimum accumulator pressure that is greater than atmospheric pressure, one pressure side of the pump having a connection for the chassis component, the pump having two Has conveying directions to also convey pressure medium from the pressure-side connection into the hydraulic accumulator, the hydraulic system having a second accumulator, the maximum pressure level of which is higher than the maximum pressure level of the first accumulator, the two accumulators being hydraulically connected in parallel to the suction side of the pump

Description

The invention relates to a hydraulic system, in particular for a chassis, according to the preamble of patent claim 1.

From the DE 10 2014 207 055 A1 a hydraulic system is known which has a hydraulic pump which is hydraulically connected on its suction side to a pressure-preloaded accumulator. The advantage of such an accumulator compared to an accumulator with atmospheric pressure is that the pump has to overcome a smaller pressure gradient to a hydraulic actuator. Ultimately, this can improve the pump's energy balance. In practice, however, it has been shown that there are limits to this design. Furthermore, only a limited power consumption is available for the pump in a vehicle. It is also not possible to enlarge the memory as desired, since the installation space is very limited anyway.

In the DE 10 2011 084 089 A1 a very similar hydraulic system is disclosed. A pump with two delivery directions is used for this. Furthermore, the reservoir from which the pump delivers in the direction of the hydraulic chassis component, in this case a vibration damper, has a spring constant that is at least equal to or higher than the spring constant of a suspension spring that is mechanically connected in parallel with the vibration damper. Another advantage of this design is the improved energy balance of the pump.

The object of the present invention is to optimize the power input of a pump for operating the hydraulic system.

The object is achieved in a generic hydraulic system in that the hydraulic system has a second accumulator, the maximum pressure level of which is higher than the maximum pressure level of the first accumulator, the two accumulators being hydraulically connected in parallel to the suction side of the pump.

With the use of two accumulators, the use of the pump can be further reduced compared to the prior art. With the pressure filling, the two storage tanks cover two working areas. Depending on the requirements of the hydraulic system, the two accumulators can be adapted more precisely with regard to the accumulator volume compared to a system with only one accumulator.

In a further advantageous embodiment, a switching valve is functionally arranged between the two accumulators and the pump, which alternately activates one of the two accumulators with the pump. In this way, a targeted supportive use of the memory is achieved. The reservoirs can also be refilled from the hydraulic chassis components according to a desired prioritization.

With a view to the simplest possible and thus cost-effective structure, the switching valve is designed as a 3/2-way valve. The two memories are connected to parallel connections A; B connected, whereby a connection A of the switching valve is in a first switching position a in a through position and the connection B for the second memory is in a blocking position and in a second switching position b the connection A is in a blocking position and the connection B is in a through position.

A sensor that provides a switching signal could be used to control the switching valve. However, it is simpler if the switching valve is connected to a control line which is acted upon by the pressure corresponding to the pressure-side connection of the pump.

In order to be able to use a switching valve that does not require any external energy, a switching force that corresponds to the minimum pressure of the second accumulator acts on the switching valve against the control force based on the pressure of the control line. The desired switching position is set solely on the basis of the mutual forces on the switching valve.

The chassis component is intended to exert an actuating force in its application. For this, the chassis component has a pressurized filling. So that the undercarriage component can be filled with a limited expenditure of energy, the minimum pressure of the first accumulator corresponds to a nominal pressure within the hydraulic undercarriage component at a defined load. The defined load can, for. B. correspond to a certain load in connection with a certain height of a vehicle body to a chassis. Another application can be the level control of a vehicle cabin.

According to an advantageous dependent claim, the minimum pressure of the second reservoir is at least as high as the maximum pressure of the first reservoir. This design promotes the needs-based use of the pump.

With regard to an optimized leakage function of the hydraulic system, a check valve is functionally arranged between the accumulators and the pump. The shut-off valve is preferably designed separately from the switching valve in order to be able to use simple valves as a whole.

Optionally, a shut-off valve can also be functionally arranged between the pump and the chassis component in order to relieve the pump of the system pressure of the chassis component.

It is possible that the two shut-off valves are operated via a common actuator.

The invention is to be explained in more detail on the basis of the following description of the figures.

• 1 Ersatzschaubild des Hydrauliksystems mit einer Fahrwerkskomponente
• 2 Energieschaubild des Hydrauliksystems bei der Befüllung der Fahrwerkskomponente
• 3 Energieschaubild des Hydrauliksystem beim Entleeren der Fahrwerkskomponente

It shows:

• 1 Replacement diagram of the hydraulic system with a chassis component
• 2 Energy diagram of the hydraulic system when filling the chassis components
• 3 Energy diagram of the hydraulic system when emptying the chassis components

the 1 shows a hydraulic system for operating a hydraulic chassis component. The chassis component can, for example, be formed by a hydraulic vibration damper of any type, but also by a swivel motor for an adjustable stabilizer, whereby this list should be viewed without any claim to completeness. Combination with a hydraulic steering device is also conceivable.

In this 1 is as a chassis component 3 a known vibration damper shown, which has a piston rod 5 and a printing cylinder 7th comprises, wherein a piston 9 on the piston rod 5 the printing cylinder 7th into a working space on the piston rod side and one remote from the piston rod 11 ; 13th divided. An outer container 15th envelops the printing cylinder 7th and delimits a compensation space that is at least partially filled with a pressure medium 17th one that is used to compensate for the from the piston rod 5 displaced print medium volume is used. The compensation room 17th is often via a bottom valve 19th with the working area remote from the piston rod 13th hydraulically connected. In the compensation room 17th there is a preload pressure on the piston rod 5 exerts an extension force. The preload pressure is well above atmospheric pressure, e.g. B. at 40bar based on an extended position of the piston rod 5 in connection with a defined load. When using the vibration damper in a car, the extension position of the piston rod 5 z. B. exist the load corresponding to two vehicle occupants in combination with a defined level of a vehicle body.

The hydraulic system 1 includes a pump 21 with a pump drive 23 , e.g. B. an electric motor. The exact structural design of the pump 21 is irrelevant to the invention. The pump 21 has two funding directions. One suction side 25th the pump is hydraulic with a first and a second accumulator 27 ; 29 tied together. Here, too, the exact construction of the memory plays a role 27 ; 29 not matter. Both stores 27 ; 29 had a compressive preload, which, however, is different.

The attainable minimum pressure Sp1 _{min of} the first storage tank 27 corresponds to a nominal pressure p _n within the hydraulic chassis component3 at a defined load. At an exemplary pressure of 40bar in the chassis component 3 In relation to a defined load and level, the first storage 27 a minimum pressure Sp1 _min of approx. 40 bar. The maximum pressure Sp1 _{max of} the first storage tank 27 is significantly higher. In an exemplary design of the hydraulic system 1 and the vibration damper 3 from a maximum pressure of 180 bar, the maximum pressure Sp1 _{max of} the first accumulator 27z. B. be at 110bar. This is used for reaching the maximum extended position of the piston rod 5 In connection with the maximum load, the necessary operating pressure of 180 bar, for example, is used as the basis and of this the filling pressure of the vibration damper 3 subtracted from 40bar. The differential pressure of 140 bar is set to 70 bar per storage tank 27 ; 29 set. Consequently, the first memory could 27 have a maximum pressure Sp1 _max of 110 bar.

The minimum pressure level Sp2 _{min of} the second storage tank 29 At 110bar, it is at least as high as the maximum pressure level Sp1 _{max of} the first reservoir 27 and at 180 bar is well above the maximum pressure level Sp1 _{max of} the first reservoir 27 . The pressure distribution between the two accumulators 27 ; 29 is only to be understood as an example and is by no means mandatory. Both stores 27 ; 29 are hydraulically parallel on the suction side 25th the pump 21 connected.

Functionally between the two stores 27 ; 29 and the suction side 25th the pump 21 is a switching valve 31 is arranged, which alternately one of the two memory 27 ; 29 with the pump 21 unlocks.

The switching valve is preferred 31 designed as a 3/2-way valve. The two memories are connected to parallel connections A; B of the switching valve connected, with a connection A of the switching valve in a first switching position a in a through position and the connection B for the second memory in a blocking position. In a second switching position b, port A is in a blocking position and port B is in a through position. With the alternating blocked and open position, the preset remains The differential pressure is permanently set when the two storage tanks are filled to the minimum or maximum. The switching valve 31 is with a control line 33 connected by the pressure corresponding to a pressure-side connection 35 the pump 21 is applied. The control line 33 can be mechanically connected directly to the pressure-side connection 35 , a supply line 37 between the pump 21 and the chassis component 3 or separately with the chassis component 3 be connected. The pressure level in the control line 33 corresponds to the pressure at the pressure-side connection in all embodiments 35 .

On the switching valve 31 acts against the control force based on the pressure in the control line 33 a switching force that corresponds to the minimum pressure Sp2 _{min of} the second accumulator 29 is equivalent to. The control force can come from an actuator, but also from a very simple spring force of a mechanical spring 39 are generated so that the switching valve 31 Depending on the operation, indirectly from the pump 21 is switched.

There is a possibility that functionally between stores 27 ; 29 and the pump 21 a check valve 41 is arranged. This enables the connection between the vibration damper 3 and the memories 27 ; 29 blocked, leaving an inactive pump 21 Even if there is an internal leak, it has no effect on the level of the vibration damper 3 would have.

In addition, it can also functionally between the pump 21 and the chassis component 3 a check valve 43 be arranged. In the present example, the check valve is 43 arranged in such a way that the control line is also in the block position 33 from the chassis component 3 is separated. When the shut-off valve is in a locked position 43 can pressure fluctuations within the chassis component 3 no influence on the pressure level in the control line 33 exercise. The shut-off valves 41 ; 43 are preferably designed as 2/2-way valves. The shut-off valves 41 ; 43 Both sides of the pump could be combined or via a common actuator 45 be operated.

the 2 shows the energy diagram of the hydraulic system 1 when filling the chassis component 3 to z. B. to maintain a predefined level of a vehicle body in the event of an increased load or generally to raise the vehicle body. To do this, the two shut-off valves 41 ; 43 brought into the open position. In the starting position of the hydraulic system 1 is the switching valve 31 in the switch position "a" shown, ie the first store 27 with the lower pressure level is with the suction side 25th the pump 21 tied together. This acts on the piston rod 5 in addition, the excess pressure of the first storage tank 27 , e.g. B. the said 70bar. With the extension movement of the piston rod 5 arises caused by a load on the vibration damper 3 between the first memory 27 and the compensation room 17th in the vibration damper 3 a pressure equilibrium, as indicated by the point of intersection p _{G1 of} a pressure characteristic 47 of the vibration damper 3 and a pressure characteristic 48 of the first store 27 is described. During this phase of the pressure charging of the vibration damper 3 is the pump 21 a passive element. No pump power has to be brought in. From the operating point of pressure equilibrium p _G1 between the first reservoir 27 and the vibration damper 3 resets the pump 21 and conveys pressure medium from the first reservoir 27 into the vibration damper 3 like a pump curve 49 made clear. This also increases the pressure in the control line. From the pressure in the control line 33 corresponding to the minimum pressure Sp2 _{min of} the second storage tank 29 switches the switching valve 31 from switch position "a" shown to switch position "b" and connects the second storage tank 29 with the pump 21 .

Then the pump can 21 again as a passive element, ie without an active pump drive 23 operated and the excess pressure from the second memory 29 used to fill the vibration damper 3 continue as the second store 29 has an exemplary excess pressure of 70 bar. This excess pressure will increase as the vibration damper is filled 3 reduce until a second pressure equalization point is reached, which is through the intersection point p _{G2 of} the pressure characteristic 51 of the second store 29 with the pressure characteristic 47 of the vibration damper 3 is defined. From this operating point, the pump starts 21 with a delivery rate until the desired extended position of the piston rod 5 is reached, z. B. at a pressure level of 180 bar in the vibration damper 3 .

With the 3 should the interaction of the pump 21 and the memory 27 ; 29 for backfilling the pressure medium from the vibration damper 3 into the memory 27 ; 29 to be discribed. As an example, it is assumed that the vibration damper 3 is maximally pressure biased, for example with 180bar. The two shut-off valves 41 ; 43 are switched to open position. The second store 29 has a residual pressure or minimum pressure Sp2 _min of said 110 bar, the first memory 27 still contains a minimum pressure of 40 bar. Due to the pressure level in the supply line 37 are at the pressure-side connection 35 the pump 21 and in the control line also 180bar, so that the switching valve 31 adopts or maintains switching position "b". The overpressure in the vibration damper 3 leads to a pressure medium filling of the second memory 29 without active use of the pump 21 . Only when the second store 29 and the vibration damper 3 have reached the same pressure level, recognizable at the intersection point p _{G2 of} the pressure characteristic 47 of the vibration damper 3 and the rising pressure characteristic 51 of the second store 27 , sets the pumping activity of the pump 21 one to get pressure medium from the vibration damper 3 in the second memory 29 to promote. The pressure level in the vibration damper falls 3 further down. The pump 21 pumps up to the maximum pressure of the second accumulator 29 . Then is in the vibration damper 3 an instantaneous pressure of 110 bar corresponding to the maximum pressure Sp1 _{max of} the first accumulator 27 achieved.

If the current pressure falls below 110bar in the vibration damper 3 this pressure level is also due to the connection on the pressure side 35 the pump 21 and in the control line 33 to the switching valve. This becomes the switching valve 31 switched from the spring force to switch position "a". As a result, there is then a clear excess pressure between the vibration damper 3 and the minimum pressure Sp1 _min in the first memory 27 . This will be the first memory 27 without pumping power of the pump 21 filled until there is again a pressure equalization between the vibration damper and the first reservoir 27. This operating state is determined by the point of intersection p _{G1 of} the pressure characteristic 47 of the vibration damper 3 and the pressure curve 48 of the first memory. Only then does the pump power begin to generate the first storage tank 27 for the next filling process of the vibration damper 3 to fill again to the maximum pressure of 110bar.

List of reference symbols

1

Hydraulic system

3

Chassis component

5

Piston rod

7th

Printing cylinder

9

Pistons

11

Working space on the piston rod side

13th

Working area remote from the piston rod

15th

container

17th

Compensation space

19th

Bottom valve

21

pump

23

Pump drive

25th

Suction side

27

first store

29

second memory

31

Switching valve

33

Control line

35

connection on the pressure side

37

supply line

39

feather

41

Check valve

43

Check valve

45

Actuator

47

Pressure curve

48

Pressure curve

49

Pump curve

51

Pressure curve

Claims (10)

Hydraulic system (1) for controlling at least one hydraulic chassis component (3), comprising a pump (21) whose suction side (25) is connected to a hydraulic accumulator (27) which has a minimum accumulator pressure (Sp1 _min ) which is greater than the atmospheric pressure, one pressure side of the pump (21) having a connection (35) for the chassis component (3), the pump (21) having two conveying directions in order to also transfer pressure medium from the pressure-side connection (35) into the hydraulic accumulator (27 ), characterized in that the hydraulic system (1) has a second accumulator (29), the maximum pressure level (Sp2 _max ) of which is higher than the maximum pressure level (Sp1 _max ) of the first accumulator (27), the two accumulators (27 ; 29) are hydraulically connected in parallel to the suction side (25) of the pump (21) Hydraulic system according to Claim 1 , characterized in that a switching valve (31) is functionally arranged between the two accumulators (27; 29) and the pump (21), which alternately activates one of the two accumulators (27; 29) with the pump (21). Hydraulic system according to Claim 2 , characterized in that the switching valve (31) is designed as a 3/2-way valve and the two accumulators (27; 29) are connected to parallel ports A; B are connected, whereby a port A of the switching valve is in a first switching position a in a through position and port B for the second accumulator (29) is in a blocking position and in a second switching position b port A is in a blocking position and port B is in a through position. Hydraulic system according to at least one of the Claims 2 and 3 , characterized in that the switching valve (31) is connected to a control line (33) which is acted upon by the pressure corresponding to the pressure-side connection (35) of the pump (21). Hydraulic system according to Claim 4 , characterized _{in that a switching force, which corresponds to the minimum pressure (Sp2 min} ) of the second accumulator (29), acts on the switching valve (31) against the control force based on the pressure of the control line (33). Hydraulic system according to at least one of the Claims 1 until 5 , characterized in that the minimum pressure (Sp1 _min ) of the first accumulator (27) _{corresponds to a nominal pressure (p n} ) within the hydraulic chassis component (3) at a defined load. Hydraulic system according to at least one of the Claims 1 until 6th , characterized in that the minimum pressure (Sp2 _min ) of the second reservoir (29) is at least as high as the maximum pressure (Sp1 _max ) of the first reservoir (29). Hydraulic system according to at least one of the Claims 1 until 7th , characterized in that a shut-off valve (41) is functionally arranged between the stores (27; 29) and the pump (21). Hydraulic system according to at least one of the Claims 1 until 8th , characterized in that a shut-off valve (43) is functionally arranged between the pump (21) and the chassis component (3) Hydraulic system according to the Claims 8 and 9 , characterized in that the two shut-off valves (41; 43) are actuated via a common actuator (45).

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