Patent ID: 6045483
Filing Date: 2000-04-04
Classification: F16H,Y10T

Abstract:
A control apparatus of a hydraulically operated vehicular transmission having at least two speed gears including a low speed gear and a high speed gear, comprising:a first hydraulic signal output means for outputting a first hydraulic signal according to an engine load;a second hydraulic signal output means for outputting a second hydraulic signal according to a vehicle speed;a shift valve being switched between a low speed position at which a low speed stage is established and a high speed position at which a high speed stage is established, the shift valve being pushed onto the low speed position side by the first hydraulic signal and an energizing means, the shift valve being pushed onto the high speed position side by the second hydraulic signal; anda down-shift means for changing over the shift valve to the low speed position by stopping the input of the second hydraulic signal into the shift vale when an operator conducts a down-shift operation,the down-shift means including a control valve arranged in a hydraulic oil path for inputting the second hydraulic signal into the shift valve, the control valve having:an input port communicated with an upper stream section of the hydraulic oil path;an output port communicated with a downstream section of the hydraulic oil path;a drain port; anda spool being changeable over between an opening position for connecting the input port with the output port and a closing position for cutting the connection and connecting the output port with the drain port,the down-shift means further including a third hydraulic signal output means for outputting a third hydraulic signal in the down-shift operation,wherein the control valve is provided with a first pressure chamber for pushing the spool onto the closing position side and a second pressure chamber for pushing the spool onto the opening position side, and the third hydraulic signal is inputted into the first pressure chamber and the second hydraulic signal is inputted into the second pressure chamber.