WO2008019863A1

WO2008019863A1 - Hydraulic valve and hydraulic circuit having a hydraulic valve of said type

Info

Publication number: WO2008019863A1
Application number: PCT/EP2007/007259
Authority: WO
Inventors: Dirk Nissing; Stephan Walentowski
Original assignee: Trw Automative Gmbh
Priority date: 2006-08-17
Filing date: 2007-08-16
Publication date: 2008-02-21
Also published as: DE102006038472A1

Abstract

The invention relates to a hydraulic valve (18) having a valve housing, having a valve seat and having a valve element which is movable in the valve housing and in which a duct (30) is formed from a first end side of the valve element to an opposite, second end side of the valve element, wherein the first end side is acted on with a system pressure in the direction of the valve seat and the second end side is acted on by a spring (36) in the opposite direction, away from the valve seat. The invention also relates to a hydraulic circuit for an active chassis stabilization system, having a hydraulic valve (18) of said type and having a hydraulic control unit (12), wherein the hydraulic valve (18) is connected parallel to the hydraulic control unit (12) between a pump (8) and an unpressurized reservoir (16).

Description

Hydraulic valve and Hvdraulikkreislauf with such Hvdraulikventil

The invention relates to a hydraulic valve and a hydraulic circuit for an active chassis stabilization system with such a hydraulic valve.

Active chassis stabilization systems generally have a hydraulic circuit with a hydraulic control unit, wherein the hydraulic circuit is supplied by a pump with hydraulic fluid, which in turn can be delivered to a reservoir.

Currently, the hydraulic control unit and the pump used are coordinated so that, with active stabilization of the chassis, ie at a working pressure of about 100 to 200 bar fluid flow adjusts the connected cylinder-piston units moves at a required speed. With inactive suspension stabilization, this flow supplies the chassis stabilization system with a minimum back pressure, which is usually in a range below 10 bar. On the one hand, this minimum back pressure should be as low as possible in order to prevent unsteady vehicle behavior during roll stabilization, ie when compensating movements of the vehicle about its longitudinal axis. On the other hand, the minimum back pressure must be large enough to switch pressure-controlled, passive valves in the hydraulic control unit. To meet the above conditions, the hydraulic control unit is currently designed for a specific pump or an associated pump capacity. The hydraulic circuit of the active chassis stabilization system is characterized very inflexible and must be adapted to changed conditions with great effort. For example, when using larger cylinder-piston units, a larger, higher-capacity pump is required to continue to move the larger cylinder-piston units at the required speed. With otherwise unchanged chassis stabilization system, however, this would also result in an undesirable increase in the minimum back pressure. To avoid this, were So far adjustments to the complex hydraulic control unit necessary, which represents a considerable effort.

The object of the invention is to keep the minimum back pressure of a hydraulic circuit at variable flow with little effort to a desired, predetermined value.

To achieve this object, the invention provides a hydraulic valve with a valve housing, a valve seat and a valve housing movable valve element, in which a channel is formed from a first end side of the valve element to an opposite second end side of the valve element, wherein the first end face with a system pressure in Direction to the valve seat and the second end face is acted upon by a spring in the opposite direction, away from the valve seat. The hydraulic valve is thus acted upon by the spring in an open valve position, in which the hydraulic valve establishes a flow connection between a pressure line and a reservoir of a hydraulic circuit. Consequently, the spring ensures a pressure relief in the hydraulic circuit at low system pressure. As a result, the system pressure falls, for example, from an existing minimum back pressure (which depends on the pump used in each case) to the predetermined, desired minimum back pressure. At higher system pressure in the range of the working pressure, the valve is closed by the valve element moves against the spring force in the direction of the valve seat. Thus, a pressure relief of the hydraulic circuit is prevented under working pressure, since there is no flow connection to the reservoir via the hydraulic valve. The entire capacity of the pump is available for the movement of the connected cylinder-piston unit (s). Overall, can be reduced by the hydraulic valve according to the invention at low system pressure, a flow and prevent high system pressure Durchflußverringerung.

In one embodiment of the hydraulic valve, the valve element in the valve housing defines a valve chamber into which hydraulic fluid can flow via the channel and from which hydraulic fluid can flow out via a valve housing opening. Through the channel cross section and the cross section of the valve housing opening can be easily adjusted in this embodiment, a pressure relief flow. In addition, can be through the Ratio of the channel and the valve housing opening produce a hydraulic valve chamber pressure that supports the spring.

Preferably, the valve seat is formed in the valve chamber. The valve seat thus adjoins the first end face of the valve element and thus can close the channel well. In a particularly cost-effective variant, the valve seat is integrally formed on the valve housing.

The spring may also be arranged in the valve chamber. Thus, the spring is protected against external influences and damage inside the valve housing.

In a further embodiment of the hydraulic valve is the

Channel cross section smaller than the cross section of the valve housing opening. This offers the advantage that the size of the pressure relief or the flow rate can be controlled for pressure relief alone on the channel cross-section. In addition, a pressure build-up in the valve chamber is prevented, so that the force with which the valve element is acted upon by the valve seat away, depends solely on the well-adjustable spring force.

Preferably, the spring is a helical spring, which is supported with a first spring end at a bottom of the valve housing and with a second spring end on the valve element. Coil springs are simple and inexpensive springs whose spring force can be adjusted precisely. In addition, can be realized by the use of the coil spring a very simple and reliable valve design.

Particularly preferably, the valve seat is formed as a projection on the bottom of the valve housing and extends into the interior of the coil spring. On the one hand, the valve seat thus fixes the helical spring in the region of its first spring end transversely to the helical spring longitudinal axis; on the other hand, the valve seat forms a guide in the direction of the helical spring longitudinal axis in the region of the first spring end.

Another embodiment of the valve is characterized in that the valve element in a closed valve position on the valve seat tightly rests, so that the channel is closed, and in an open valve position - A -

is spaced from the valve seat, so that hydraulic fluid can flow through the channel in the direction from the first end side to the second end face.

Moreover, the invention relates to a hydraulic circuit for an active chassis stabilization system with a hydraulic valve described above and a hydraulic control unit, wherein the hydraulic valve is connected in parallel to the hydraulic control unit between a pump and a non-pressurized reservoir. In a hydraulic circuit connected in this way, the hydraulic valve adapted to the delivery rate of the pump ensures a desired minimum dynamic pressure with an identical hydraulic control unit.

Preferably, a valve chamber of the hydraulic valve via a

Valve housing opening and a non-pressurized return line connected to the reservoir. The pressure-free return of the hydraulic fluid from the valve chamber, a pressure build-up in the valve chamber and thus influencing the valve position of the hydraulic valve is prevented.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. In these show:

- Figure 1 is a diagram of a hydraulic circuit according to the invention with a hydraulic valve according to the invention;

- Figure 2 shows a section through the hydraulic valve according to the invention

Figure 1 in an open valve position; and

- Figure 3 shows a section through the hydraulic valve according to the invention according to Figure 1 in a blocking position of the valve.

The circuit diagram of a hydraulic circuit for an active chassis stabilization system illustrated in FIG. 1 shows a pump 8 which supplies via a supply line 10 a hydraulic control unit 12 with hydraulic fluid which is under system pressure. The hydraulic control unit 12 is connected via a return line 14 with a non-pressurized reservoir 16. The hydraulic circuit further comprises a hydraulic valve 18 which is connected in parallel to the hydraulic control unit 12 between the pump 8 and the non-pressurized reservoir 16. The

Hydraulic valve 18 in this case has a pressure connection 20 (Figures 2 and 3), the is coupled to the supply line 10, and a terminal 22 (Figures 2 and 3) which is coupled to the return line 14.

FIG. 2 shows a section through the hydraulic valve 18, which is a

Valve housing 24, a valve seat 26 and a valve housing 24 movable in the valve element 28 has. In the valve element 28 is a channel 30 of a first

End face 32 of the valve element 28 to an opposite second

End face 34 of the valve element 28 is formed. Furthermore, the first end face 32 faces the pressure port 20 and is subjected to a system pressure in the direction of the valve seat 26. The second end face 34 is acted upon by a spring 36 in the opposite direction, away from the valve seat 26.

The valve element 28 defines in the valve housing 24 a valve chamber 38 into which hydraulic fluid can flow via the channel 30 and from which hydraulic fluid can flow out via the port 22 designed as a valve housing opening 40. The valve seat 26 is integrally formed in the valve chamber 38 as a projection on a bottom 42 of the valve housing 24. The spring 36 is a helical spring and is also located in the valve chamber 38. It is supported by a first spring end 44 on the bottom 42 of the valve housing 24 and with a second spring end 46 on the valve element 28. The valve seat 26 extends into the interior of the coil spring and forms a guide in the longitudinal direction of the coil spring in the region of the first spring end 44.

In the figure 2, the hydraulic valve 18 is analogous to Figure 1 in an open valve position to see. In this open valve position, the system pressure is too low to move the valve element 28 against the spring force in the direction of the valve seat 26. The counteracting forces are shown in FIG. 2 as arrows, wherein F _c symbolizes the spring force and F _P a force resulting from the system pressure on the first end face 32 of the valve element 28. In the open valve position shown so a flow from the pressure port 20 via the channel 30 into the valve chamber 38 and from there via the valve housing opening 40 and the return line 14 to the reservoir 16 is possible.

As indicated in Figure 2, the cross section of the channel 30 is preferably smaller than the cross section of the valve housing opening 40. Thus, the pressure drop in the supply line 10 and the flow branched off from the supply line 10 solely determined by the cross section of the channel 30. In addition, no pressure builds up in the valve chamber 38 at substantially unpressurized return line 14, which act on the valve member 28 away from the valve seat 26 and thus would support the spring 36. From such a valve chamber pressure would result in addition to the counteracting forces F _c and F _P nor a resulting spring support force, which would affect the valve position. The switching of the hydraulic valve would be correspondingly more complicated and inaccurate. Nevertheless, embodiments of the hydraulic valve 18 are conceivable in which the cross section of the channel 30 is greater than the cross section of the valve housing opening 40 and the resulting valve chamber pressure affects the valve position of the hydraulic valve 18.

When the suspension stabilization system is not activated, the system pressure applied to the pressure connection 20 is low, but is above the desired minimum back pressure. Due to the low pressure, the resultant force F _P on the valve element is less than the oppositely acting spring force F _c (Figure 2). Accordingly, the hydraulic valve 18 branches off via the channel 30 hydraulic fluid from the supply line 10 into the reservoir 16, so that the fluid flow in the supply line 10 is reduced. Due to this reduced flow in the supply line 10, the pressure in the hydraulic control unit 12 is also reduced. The cross section of the duct 30 is chosen exactly so that the reduced pressure in the supply line 10 corresponds to the desired minimum back pressure.

When activating the chassis stabilization system, the pressure in the supply line rises very rapidly to a working pressure, which is generally above 100 bar. As a result of this pressure increase in the supply line 10 and the resulting force F _{P increases} to the valve element 28 at. The force F _P finally exceeds the spring force F _c and moves the valve element 28 in the direction of the valve seat 26. Ultimately, the hydraulic valve 18 assumes a blocking position shown in Figure 3, in which the valve element 28, more precisely, the second end face 34 of the valve element 28 sealingly Valve seat 26 is applied, so that the channel 30 is closed by the valve seat 26. Since the sliding connection between the valve element 28 and the valve housing 24 is largely tight, no hydraulic fluid is diverted from the supply line 10 via the hydraulic valve 18. Accordingly, the maximum capacity of the pump 8 is in the supply line 10th to disposal. This is also desirable with the chassis stabilization system activated to provide the maximum flow and working pressure for movement of at least one connected cylinder-piston unit (not shown).

When the suspension stabilization system is deactivated, the pressure in the supply line and thus also the force F _P drop to a value F _P '. The spring force F _c is set via a spring stiffness so that it is greater than the pressure force F _P ', so that the valve element 28 is removed again from the valve seat 26 after deactivation of the chassis stabilization system and the hydraulic valve 18 assumes its open valve position according to FIG , The pending in the supply line 10 pressure, or the resulting pressure force F _P 'continues to decrease after release of the channel 30 until the desired minimum back pressure is reached.

The advantage of this invention is that the desired minimum back pressure of a given hydraulic control unit 12 is kept constant for different pumps 8 without having to make structural changes to the hydraulic control unit 12. In this case, the hydraulic control unit 12 is preferably set to the pump with the lowest flow rate so that the desired minimum back pressure is achieved without the hydraulic valve 18. For each pump having a higher capacity, the hydraulic valve 18 is to be connected in parallel to the hydraulic control unit 12 between the pump 8 and the non-pressurized reservoir 16 (Figure 1). In this case, different hydraulic valves 18 are to be used for different delivery rates of the pumps 8. The respective hydraulic valves 18 differ in the rule, however, only by the cross section of the channel 30, which is to be selected depending on the capacity of the pump 8 so that in the open valve position of the hydraulic valve 18, the desired flow or the desired minimum Dynamic pressure in the supply line 10 of the hydraulic control unit 12 sets.

Claims

claims

Hydraulic valve having a valve housing (24), a valve seat (26) and a valve housing (24) movable valve element (28) in which a channel

(30) from a first end face (32) of the valve element (28) to an opposite second end face (34) of the valve element (28) is formed, wherein the first end face (32) with a system pressure in the direction of the valve seat (26) and the second end face (34) by a spring (36) in the opposite direction, from the valve seat (26) is acted upon away.

2. Hydraulic valve according to claim 1, characterized in that the

Valve element (28) in the valve housing (24) defines a valve chamber (38) into which hydraulic fluid can flow via the channel (30) and from which hydraulic fluid can flow out via a valve housing opening (40).

3. Hydraulic valve according to claim 2, characterized in that the valve seat (26) in the valve chamber (38) is formed.

4. Hydraulic valve according to claim 2 or 3, characterized in that the spring (36) in the valve chamber (38) is arranged.

5. Hydraulic valve according to one of claims 2 to 4, characterized in that the cross section of the channel (30) is smaller than the cross section of the valve housing opening (40).

6. Hydraulic valve according to one of the preceding claims, characterized in that the spring (36) is a helical spring which extends with a first spring end (44) on a bottom (42) of the valve housing (24) and with a second spring end (46). on the valve element (28) is supported.

7. Hydraulic valve according to claim 6, characterized in that the

Valve seat (26) is formed as a projection on the bottom (42) of the valve housing (24) and extends into the interior of the coil spring.

8. Hydraulic valve according to one of the preceding claims, characterized in that the valve element (28) in a closed valve position on the valve seat (26) tightly rests, so that the channel (30) closed is, and in an open valve position from the valve seat (26) is spaced so that hydraulic fluid through the channel (30) in the direction of the first end face (32) to the second end face (34) can flow.

9. hydraulic circuit for an active chassis stabilization system, comprising a hydraulic valve (18) according to one of the preceding claims and a hydraulic control unit (12), characterized in that the hydraulic valve (18) parallel to the hydraulic control unit (12) between a pump (8) and an unpressurized reservoir (16) is connected.

10. A hydraulic circuit according to claim 9, characterized in that a valve chamber (38) of the hydraulic valve (18) via a valve housing opening (40) and a non-pressurized return line (14) to the reservoir (16) is connected.