Apparatus for preventing faulty operation in transmission of motorcars

Abstract

Apparatus for preventing faulty operation in automatic transmissions of motorcars, the transmission having a speed-change sensor and a shift valve therein, for controlling the operation of the latter, the apparatus comprising oil-pressure operated high-speed and low-speed clutches interposed in respective high-speed and low-speed systems of the transmission, the system being selectively connectable through the shift valve to a main line pressure circuit connected to an oil-pressure source, wherein the shift valve is operable by the oil pressure and has at one end an oil-pressure chamber connectable to the main circuit through a pilot valve that can be opened by operation of the sensor. The oil-pressure chamber is connected to the low-speed clutch through a by-pass, and a flow passage is connected between the chamber and the main circuit, provided with a restrictor therein, while the low-speed clutch is provided with a leak valve that is opened for discharging the oil pressure when the low-speed clutch is operated at a speed higher than a predetermined value. Preferably the apparatus comprises a manually operable valve for appropriate selective operation in one of a plurality of operational modes of the transmission. One or more check valves may be associated with the manually operable valve.