Hydraulic control system for high flow applications in motor vehicles

A hydraulic control system for high flow applications in motor vehicles, in particular for active wheel suspensions and active steering arrangements, includes at least one passive high flow valve which is controlled hydraulically by at least one low flow valve.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a national stage of International Application No. PCT/EP2005/009524 filed Sep. 5, 2005, the disclosures of which are incorporated herein by reference, and which claimed priority to German Patent Application No. DE 20 2004 013 836.0 filed Sep. 6, 2004, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a hydraulic control system for high flow applications in motor vehicles.

For the hydraulic actuation of actuators which are used in motor vehicles with active wheel suspension (active chassis) and/or active steering, special high flow valves are used because of the high oil flow requirements. On the other hand, in control systems for brake regulation applications such as ABS (anti-blocking system), ESP (electronic stability program) or EHB (electro-hydraulic brake system), valves are used which, owing to the broad distribution of the said applications (partially already standard equipment in many vehicles) are able to be produced in large numbers and hence at a favourable price. Such brake regulation valves are, however, not designed for high oil flows and are therefore not suitable for high flow applications.

It is an object of the invention to provide a possibility for designing hydraulic control systems for high flow applications in motor vehicles at a more favourable cost.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a hydraulic control system for high flow applications in motor vehicles, in particular for active wheel suspensions and active steering arrangements, includes at least one passive high flow valve which is controlled hydraulically by at least one low flow valve. Through the use of low flow valves, in accordance with the invention, as pilot valves with which passive high flow valves are controlled, the costs for a control system for high flow applications, in particular for active chassis, can be distinctly reduced. The invention makes use of the fact that low flow valves are offered at a favourable cost as a “package” with integrated control apparatus (e.g. for brake regulation applications). The low flow valves are coupled magnetically and/or electrically to the control apparatus. Such a package can be extended according to the invention in a simple manner by the passive high flow valves, in that the latter are coupled hydraulically to the low flow valves. On the basis of such a structure in accordance with the invention, various tasks of a hydraulic control arrangement can be realized.

DETAILED DESCRIPTION OF THE INVENTION

The structure illustrated inFIG. 1shows the structure of a hydraulic control system10according to the invention. A control apparatus12and low flow valves14coupled thereto represent a package16for brake regulating applications. This package16with two levels is extended by a third level, namely the passive high flow valves18. The passive high flow valves18are coupled hydraulically to the low flow valves14, so that the passive high flow valves18can be controlled hydraulically by the low flow valves14. The low flow valves14therefore serve as pilot valves for the passive high flow valves18. The extended package16in accordance with the invention is therefore basically able to be used for active high flow applications.

FIG. 2shows how, for example, an oil flow can be controlled with the control system10according to the invention. The oil flow is adjusted by means of a passive high flow valve in the form of a slide valve20. The passive slide valve20is controlled by means of two low flow valves. The low flow valves are two 2/2-way valves22,24, which are otherwise used as ABS valves. The first valve is a “normally closed” valve, which is arranged in a pressure line in which a system pressure pPprevails. The second valve24is a “normally open” valve, which is arranged in a return line to a tank in which a tank pressure pTprevails. By means of a control apparatus (not illustrated here) the two 2/2-way valves22,24can be set simultaneously into the respectively other switching state. Through this pre-control, the control surface of the passive slide valve20can therefore be acted upon by means of the two 2/2-way valves either with the system pressure pPor with the tank pressure pT. This control can be applied to any n/2-way slide valves. Through an extending to four 2/2-way valves, in addition n/3-way slider functions can be realized.

A control system10according to the invention can also be used for regulating a pressure. Thus, for example, a proportionally acting brake regulating valve (proportional brake regulating valve), as is known from EHB- or ESP applications, can control a passive proportional pressure control valve or a proportional pressure reducing valve. In this case, the pressure control valve or the pressure reducing valve is in equilibrium with the brake regulating valve. For regulating a pressure circuit, an active proportional brake regulating valve with a passive proportional pressure control valve is necessary. For the regulating of n pressure circuits, an active proportional brake regulating valve with a passive proportional pressure limiting valve and n active proportional brake regulating valves with n passive proportional pressure reducing valves are necessary.

Through combination of the functions achievable with a control system10according to the invention, in particular the pressure regulation and the controlling of passive high flow valves, also complex device controls can be realized. InFIG. 3, as a further example application, a hydraulic pressure regulating device26is illustrated, with which front and rear actuators28and30, respectively, of a vehicle chassis can be actuated. The pressure regulating device26comprises a motor-driven pump32which conveys hydraulic oil from a tank34, and a hydraulic control system10according to the invention with respectively two connections A1, A2and B1, B2for each actuator28,30and also a return line to the tank34. A control apparatus36of the control system10controls a proportional pressure control valve38and a proportional pressure reducing valve40and also two 2/2-way valves42,44. The two 2/2-way valves42,44serve as pre-control valves for a direction control valve arrangement46, with which the direction of the actuator movement is established, and for a blocking valve arrangement48, with which the front actuator28can be blocked. Both the proportional valves38,40and also the 2/2-way valves42,44are active low flow valves, whereas the direction control valve arrangement46and the blocking valve arrangement48, which can also be replaced by a similar valve arrangement, are formed from passive high flow valves.