Patent ID: 8088039
Filing Date: 2012-01-03
Classification: F16H,Y10T

Abstract:
1. A hydraulic control apparatus for a vehicle automatic transmission that includes a first engagement element and a second engagement element that are released or engaged through hydraulic control in order to switch speed change steps, comprising: an engagement pressure regulating valve whose input port is supplied with engagement basic pressure for engaging the first engagement element, and which continuously changes oil pressure of an output port of the engagement pressure regulating valve; a first oil passageway switching valve that is selectively switched between a first position in which the first oil passageway switching valve connects the output port of the engagement pressure regulating valve and the first engagement element to each other, and disconnects the second engagement element and an oil pressure supply passageway to the second engagement element from each other, and a second position in which the first oil passageway switching valve disconnects the output port of the engagement pressure regulating valve and the first engagement element from each other, and interconnects the second engagement element and the oil pressure supply passageway; and a check valve that is provided parallel to the first oil passageway switching valve, between the output port of the engagement pressure regulating valve and the first engagement element, and that permits pressure oil to flow in a direction from a side of the first engagement element to a side of the output port, and prevents the pressure oil from flowing in a direction opposite to the direction from the side of the first engagement element to the side of the output port, wherein the first oil passageway switching valve is switched to the first position when the first engagement element is engaged and the second engagement element is released.