Control system for limiting engine speed down on automatic transmission shifting at low engine temperature

Claim 1

In a motor vehicle having an internal combustion engine, a thermal reactor for burning harmful substances in the exhaust gas before emission into the atmosphere and an automatic transmission of the type having a shifter valve for governing friction units, a governor valve for supplying a vehicle speed-sensitive governor pressure to the shifter valve, a throttle valve for supplying a throttle pressure responsive to vacuum developed in an intake manifold of the engine to the shifter valve and means to provide a regulated fluid pressure to the above three valves, the throttle valve having a flexible diaphragm, a face thereof being exposed to a chamber normally communicating with the intake manifold through a pipe, and means to modulate the regulated fluid pressure to a less magnitude of throttle pressure as the vacuum exerted on the diaphragm multiplies, an engine speed at which a shifting in the transmission occurs lowering as the vacuum multiplies, the improvement comprising a selector valve having a port communicating with the atmosphere and being mounted on said pipe such that said chamber normally communicates exclusively with said intake manifold, a temperature-sensitive switch attached to the engine and means to operate said selector valve at a position of said switch such that said chamber is caused to communicate exclusively with the atmosphere through said port, said switch being held at said position hereof when the temperature of the engine is below a predetermined temperature, thereby to raise the engine speed at which the shifting occurs and elevate the temperature of the exhaust gas.