Hydraulic power steering system for motor vehicles

Abstract

A vane cell pump is provided for a hydraulic steering system for motor vehicles for pressure supply, a flow valve whose opening cross section is at least substantially closed during cold start operation being arranged downstream of said vane cell pump on the delivery side.

1 . A hydraulic power steering system for motor vehicles having a steering mechanism, a steering valve and a fixed displacement high pressure pump which has a connection to the steering valve in which a flow valve is situated whose opening cross section can be adjusted via an electromagnetic actuator with parameters which influence the steering behavior being taken into consideration, the high pressure pump being configured as a vane cell pump followed on the delivery side by the flow valve with a pressure relief valve connected in between, and the opening cross section of the flow valve is at least substantially closed during cold start opening of the vane cell pump.  
   
   
       2 . The hydraulic power steering system as claimed in  claim 1 , wherein the flow valve is configured as a throttling valve.  
   
   
       3 . The hydraulic power steering system as claimed in  claim 2 , wherein the closing direction of the throttling valve corresponds to the direction of throughflow.  
   
   
       4 . The hydraulic power steering system as claimed in  claim 2 , wherein the throttling valve is spring-loaded in the closing direction.  
   
   
       5 . The hydraulic power steering system as claimed in  claim 2 , wherein the throttling valve is configured to be relieved of pressure.  
   
   
       6 . The hydraulic power steering system as claimed in  claim 1 , wherein it is possible to actuate the electromagnetic actuator with parameters which limit cold start conditions of the vane cell pump being taken into consideration.  
   
   
       7 . The hydraulic power steering system as claimed in  claim 6 , wherein the engine temperature of the vehicle engine, the outside temperature, the rotational speed of the vehicle engine, the standstill time of the vehicle engine starting are provided as cold start parameters.