Neutral control device of automatic transmission

Abstract

A neutral control device of an automatic transmission is provided which includes a forward-drive engaging element that is engaged when a hydraulic pressure is supplied from a shift valve, so as to place the transmission in at least a 1st-speed gear position of a forward-drive range, and in which the pressure to the forward-drive engaging element is controlled so as to establish a neutral condition by slipping and engaging the forward-drive engaging element, while an accelerator pedal is being released just before the start or stopping of the vehicle. The neutral control device includes a neutral control switch valve located in a hydraulic circuit that connects the forward-drive engaging element and the shift valve, for allowing a selected one of a pressure from the shift valve and an accumulator back pressure to be supplied to the forward-drive engaging element, a first actuator that operates to produce an oil pressure in response to a control command from a controller; accumulator back pressure control device for controlling the accumulator back pressure, using a forward-drive range pressure as an original pressure, and the oil pressure produced by the first actuator as a signal pressure, and a second actuator that operates in response to an ON/OFF command from the controller, so as to perform switching of the neutral control switch valve.