Control of drive train noises during a shift operation of an automatic,

Abstract

A system for controlling the hydraulic pressure of a hydraulic control circuit associated with an automatic, variable speed transmission is provided. The hydraulic control circuit comprises a plurality of hydraulic pressure control valves, a plurality of flow path switching means and a plurality of solenoid valves, and operates to control the engagement and disengagement of the clutches and brakes disposed within the transmission. The energization of the solenoid valves of the hydraulic control circuit is controlled by an electronic system, which comprises a large scale integrated semiconductor logic unit, a semiconductor read-only memory, a semiconductor read-write memory and as required, input/output ports. A plurality of signals are applied to the electronic system, including a signal indicative of shift lever position supplied by shift lever detecting means, a signal indicative of the current vehicle speed supplied by vehicle speed signal generating means and a signal indicative of the throttle opening supplied by throttle opening detecting means. In response to these signals and in accordance with the program data and constants data, the electronic system determines a new gear ratio to be established. If the shift mode, defined by a combination of the current gear ratio and the new gear ratio to be established, has a likelihood to produce drive train noises, the shift controlling sub-program data is utilized to delay the timing at which the shift controlling solenoid valves are deenergized and energized, thus avoiding or reducing the occurrence of drive train noises during the shift operation.