Honda Giken Kogyo Kabushiki Kaisha

Shyoji Arai

Tetsuya Mochizuki

Kazuma Hatakeyama

Shoji Asatsuke

An oil ejection control valve is interposed in a first hydraulic engagement element of an automatic transmission system from which oil is ejected when a certain speed stage shifting operation is to be carried out. The oil ejection control valve is provided with a valve member which is normally biased to a closed position by a spring. The valve member is provided with a first pressure receiving surface to which the ejection pressure from the first hydraulic engagement element is applied and a second pressure receiving surface to which the supply pressure to a second hydraulic engagement element is applied during the afore-mentioned shifting operation, the second hydraulic engagement element being the one to which pressure is supplied so as to engage the same during the speed stage shifting operation. Since the ejection pressure can favorably contribute to the reduction in the engagement pressure of the first hydraulic engagement element that is about to be disengaged without waiting for the engagement pressure for the second hydraulic engagement element to be engaged to build up, a smooth shifting operation is made possible either in an upshift operation or a downshift operation, and a transmission shock can be avoided at all time.

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Saitama, Japan

Shyoji Arai