Hydraulic pressure producing system for automatic transmission and control method thereof

Abstract

A hydraulic pressure producing system for an automatic transmission, and a control method thereof may include a first hydraulic pump adapted to generate hydraulic pressure for shifting, a second hydraulic pump adapted to additionally generate hydraulic pressure when hydraulic pressure supplied from the first hydraulic pump is insufficient, an accumulator adapted to store hydraulic pressure excessively generated from the first hydraulic pump, and a control unit controlling the second hydraulic pump. The method may include operating the first hydraulic pump in a state of idle stop, predicting a finish point of the idle stop state, starting operation of the second hydraulic pump prior to a predetermined time from the predicted finish point, operating the second hydraulic pump with a predetermined maximum rotation speed, and operating the second hydraulic pump with a target rotation speed.

What is claimed is: 
     
         1 . A control method of a hydraulic pressure producing system for an automatic transmission, the hydraulic pressure producing system having a first hydraulic pump adapted to generate a first hydraulic pressure for shifting, a second hydraulic pump adapted to additionally generate a second hydraulic pressure when the first hydraulic pressure supplied from the first hydraulic pump is insufficient fir shifting, an accumulator adapted to store hydraulic pressure excessively generated from the first hydraulic pump, and a control unit controlling the second hydraulic pump, the method comprising:
 operating the first hydraulic pump in a state of idle stop;   predicting a finish point of the state of the idle stop;   starting operation of the second hydraulic pump prior to a predetermined time from the predicted finish point;   operating the second hydraulic pump with a predetermined maximum rotation speed; and   operating the second hydraulic pump with a target rotation speed after the second hydraulic pump is operated with the predetermined maximum rotation speed.   
     
     
         2 . The method of  claim 1 , wherein a generated hydraulic pressure of the second hydraulic pump is increased to more than a target hydraulic pressure when the second hydraulic pump is operated with the predetermined maximum rotation speed. 
     
     
         3 . The method of  claim 2 , wherein hydraulic pressure stored in the accumulator is used to shorten a time in which the generated hydraulic pressure is increased. 
     
     
         4 . A hydraulic pressure producing system for an automatic transmission, comprising:
 a first hydraulic pump adapted to generate a first hydraulic pressure for shifting;   a second hydraulic pump adapted to additionally generate a second hydraulic pressure when the first hydraulic pressure generated by the first hydraulic pump is insufficient for shifting;   a control unit controlling the second hydraulic pump; and   an oil tank fluid-connected to the first and second hydraulic pumps and supplying oil to the first hydraulic pump and the second hydraulic pump,   wherein the control unit predicts a finish point of an idle stop state and operates the second hydraulic pump prior to a predetermined time from the predicted finish point when the first hydraulic pump is operated in the idle stop state.   
     
     
         5 . The system of  claim 4 , wherein the first hydraulic pump is a mechanical hydraulic pump. 
     
     
         6 . The system of  claim 4 , wherein the second hydraulic pump is an electric hydraulic pump having a motor. 
     
     
         7 . The system of  claim 6 , wherein the control unit controls operation of the motor so as to control rotation speed of the second hydraulic pump. 
     
     
         8 . A hydraulic pressure producing system for an automatic transmission, comprising:
 a first hydraulic pump supplying a first hydraulic pressure for shifting to the transmission;   a second hydraulic pump selectively supplying a second hydraulic pressure to the transmission;   an accumulator fluid-connected to the first hydraulic pump and the second hydraulic pump and storing hydraulic pressure excessively generated by the first hydraulic pump and selectively transmitting the stored hydraulic pressure to the transmission;   a control unit controlling operation of the second hydraulic pump; and   an oil tank fluid-connected to the first hydraulic pump and the second hydraulic pump and supplying oil to the first and second hydraulic pumps,   wherein the control unit determines a starting point for operating the second hydraulic pump, and   wherein hydraulic pressure of the accumulator and the second hydraulic pressure of the second hydraulic pump are transmitted to the transmission when the second hydraulic pump is operated.   
     
     
         9 . The system of  claim 8 , wherein the second hydraulic pump is an electric hydraulic pump having a motor. 
     
     
         10 . The system of  claim 9 , wherein the control unit controls operation of the motor so as to control rotation speed of the second hydraulic pump. 
     
     
         11 . The system of  claim 9 , wherein the control unit predicts a finish point of an idle stop state and operates the second hydraulic pump prior to a predetermined time from the predicted finish point when the first hydraulic pump is operated in the idle stop state.