Vehicle hydraulic device

Abstract

A vehicle hydraulic device is provided with an electric motor-driven oil pump and a shuttle valve, so that a vane pump operates smoothly, even at the start, with a backpressure applied from the electric motor-driven oil pump to the vanes. Even when the oil pressure of a working fluid discharged from the vane pump exceeds the backpressure inside vane housing grooves, the working fluid flows from a vane pump discharge oil passage to a backpressure oil passage, so that the vanes are not pushed into the housing grooves. Thus, it is possible to reduce the fluctuations in discharge amount of the vane pump due to fluctuations in oil pressure of the vane pump discharge oil passage during operation of the vane pump.

What is claimed is: 
     
         1 . A vehicle hydraulic device comprising:
 a vane pump that is driven to rotate by an engine, and the vane pump including a pump housing, a plurality of vanes, and a rotor,
 the pump housing having an inner peripheral cam surface with an elliptical sectional shape, 
 the plurality of vanes being provided inside the pump housing, 
 the rotor providing vane housing grooves that house the plurality of vanes so as to be movable in a radial direction of the rotor; 
   an oil pressure control circuit including a first discharge oil passage, a second discharge oil passage, and a backpressure oil passage,
 the first discharge oil passage being configured to introduce a working fluid discharged from the vane pump to a device other than the vehicle hydraulic device, 
 the backpressure oil passage being configured to supply a backpressure to the plurality of vanes inside the vane housing grooves; 
   an electric motor-driven oil pump configured to discharge the working fluid through the second discharge oil passage to the backpressure oil passage; and   a shuttle valve provided at a junction of the first discharge oil passage, the second discharge oil passage, and the backpressure oil passage,
 the shuttle valve being configured to: (i) allow the working fluid to flow from the first discharge oil passage to the backpressure oil passage when the oil pressure of the working fluid in the first discharge oil passage discharged from the vane pump is higher than the oil pressure of the working fluid in the second discharge oil passage discharged from the electric motor-driven oil pump, and (ii) allow the working fluid to flow from the electric motor-driven oil pump to the backpressure oil passage when the oil pressure of the working fluid in the first discharge oil passage discharged from the vane pump is equal to or lower than the oil pressure of the working fluid in the second discharge oil passage discharged from the electric motor-driven oil pump. 
   
     
     
         2 . The vehicle hydraulic device according to  claim 1 , wherein the electric motor-driven oil pump is configured to actuate, only at a start of the engine and when a temperature of the working fluid is equal to or lower than a predetermined temperature. 
     
     
         3 . The vehicle hydraulic device according to  claim 1 , wherein the oil pressure of the working fluid discharged from the electric motor-driven oil pump decreases as a temperature of the working fluid rises. 
     
     
         4 . The vehicle hydraulic device according to  claim 1 , wherein the electric motor-driven oil pump does not start when the time taken for the engine to restart after stopping of the engine is within a predetermined time.