Patent ID: 9086140
Filing Date: 2015-07-21
Classification: F16H

Abstract:
1. A power transmission device that is mounted on a vehicle equipped with a motor and transmits power from the motor to a driving wheel side via a hydraulically driven friction engagement element, the power transmission device comprising: a mechanical pump that is driven by the power from the motor to produce a hydraulic pressure; a pressure regulating valve that regulates the hydraulic pressure from the mechanical pump; an electric pump that is driven by supplied electric power to produce a hydraulic pressure; a switching mechanism that is formed of one or more switching valves operated by a signal pressure produced based on the hydraulic pressure from the mechanical pump and that establishes a first state in which an output pressure of the pressure regulating valve can be supplied to a hydraulic servo of the friction engagement element when the signal pressure is a preset pressure or more, and establishes a second state in which the hydraulic pressure from the electric pump can be supplied to the hydraulic servo when the signal pressure is below the preset pressure; an electric pump oil passage configured to supply hydraulic pressure from the electric pump to the switching mechanism; a bypass oil passage that is connected to a downstream side of the mechanical pump, and is configured to supply hydraulic pressure output from the mechanical pump to the electric pump oil passage via the switching mechanism; and a check valve that is arranged in the bypass oil passage, and allows supply of the hydraulic pressure from the mechanical pump to the hydraulic servo and prohibits supply of the hydraulic pressure from the electric pump to the mechanical pump, wherein the switching mechanism is further structured so as to shut off communication through the bypass oil passage to the electric pump oil passage in the first state and allow communication through the bypass oil passage to the electric pump oil passage in the second state.