In a power transmission apparatus for a vehicle, in event of detection of an anomaly with a possibility of an ON failure of a lockup hydraulic control valve, a fail safe mode is established by placing a first switching valve and a third switching valve in respective predetermined connection states, and placing a failure switching valve in a predetermined connection state based on an output of the lockup hydraulic control valve, whereby a lockup clutch is held in its released state, and a forward-driving engagement device is engaged by a control pressure of a second hydraulic control valve, for thereby enabling a forward driving of the vehicle. Upon selection of a neutral range in the event of the detection of the anomaly, an output of the lockup hydraulic control valve and an output of the second hydraulic control valve are stopped.

A transmission includes an accumulator to hold one of more shift elements in an engaged state while an engine is off. The transmission also includes a hydraulic park system that disengages park in response to engagement of two shift elements. In some circumstance, draining the accumulator in an uncontrolled manner in the presence of a failed valve may lead to unintentionally disengaging park. To avoid this, the accumulator is discharged in a controlled manner. Fluid is first transferred from the accumulator to a shift element apply chamber. Then, the fluid is vented from the shift element apply chamber.

An automatic transmission where the control portion controls the adjustment solenoid valve so that the circulation hydraulic pressure equals to a second circulation hydraulic pressure higher than the first circulation hydraulic pressure when the rotational speed difference between the output rotational speed of the fluid transmission device and the rotational speed of the driving source is more than the predetermined rotational speed.

A hydraulic system for an automatic transmission a valve slide longitudinally adjustable in a valve housing between a first axial position and a second axial position such that a plurality of valve seat pockets are selectively brought into operative connection with each other. A control surface of the valve slide, first and second additional control surface of the valve slide and a spring of a parking brake valve are matched to one another such that the total actuating force applied to the slide valve displaces the slide valve to the first axial position when an actuating pressure of the parking brake unit, a pressure signal at the control surface of the valve slide and an additional pressure signal at the second additional control surface of the valve slide are applied.

A hydraulic control device for an automatic transmission where the spool is locked at the first position and the switching pressure can regulate the belt holding force of the primary pulley or the secondary pulley without switching a position of the spool when the engagement pressure is supplied to the second working oil chamber, and the spool is not locked at the first position and the switching pressure can switch the spool to the second position against the urging member when the engagement pressure is not supplied to the second working oil chamber.

A control apparatus for a vehicular continuously variable transmission is provided. The control apparatus includes a pair of pulley pressure adjusting valves, a pair of electromagnetic valves, a source pressure adjusting valve and an electronic control unit. The electronic control unit is configured to control the source pressure adjusting valve in such a manner as to lower the source pressure at a time of a fail mode below the source pressure at a time of a non-fail mode, at the time of the fail mode, and control command signals to the pair of the electromagnetic valves such that the command signals temporarily decrease below command signals at the time of the non-fail mode, before cancelling the lowering of the source pressure in making a changeover from the fail mode to the non-fail mode.

In a non-forward range, the same gear position as a forward first gear position is established in a stepped transmission. A hydraulic controller includes a second linear solenoid valve and third linear solenoid valve that respectively supply hydraulic pressure to a second clutch and first brake, and a selector valve that is provided in an oil passage upstream of the second and third linear solenoid valves and that switches between a state where hydraulic pressure is supplied to the oil passage and a state where supply of hydraulic pressure is cut off. When the non-forward range is set or when a vehicle is moving backward, the selector valve cuts off supply of hydraulic pressure to the oil passage. Thus, when there is a failure in the second or third linear solenoid valve, it is possible to suitably establish a gear position wherein the vehicle is not allowed to move backward.

A vehicle power transmission device comprises: a continuously variable transmission configured to include a primary pulley, a secondary pulley, and a transmission belt wound between the primary pulley and the secondary pulley; a belt running clutch of hydraulic type for transmitting power to the continuously variable transmission; and a hydraulic control circuit controlling the continuously variable transmission and the belt running clutch, the hydraulic control circuit comprising a fail-safe valve switching a communication destination of an oil supply passage for supplying a hydraulic fluid to the belt running clutch to one of a first oil passage supplied with a control hydraulic pressure and a second oil passage supplied with a hydraulic pressure higher than the control hydraulic pressure, the fail-safe valve connecting the oil supply passage with the second oil passage when the fail-safe valve is switched to a failure position. The second oil passage is provided with an orifice.

A fluid pressure control circuit for a transmission, includes plural electromagnetic valves each switching one of engagement elements between an engaged state and a disengaged state, plural passages configured to connect the engagement elements to a fluid pressure source, a first electromagnetic valve corresponding to one of the electromagnetic valves and switching one of the engagement elements between the engaged and disengaged states, a second electromagnetic valve corresponding to another of the electromagnetic valves and switching another of the engagement elements between the engaged and disengaged states, and a shut-off valve, when the first electromagnetic valve and the second electromagnetic valve are open, closing the passages among the first electromagnetic valve, the engagement elements switched by the first electromagnetic valve and the fluid pressure source with the use of the fluid pressure to establish a closed state, and maintaining the closed state with the use of the fluid pressure.

A hydraulic pressure control device of a vehicle driving device, the hydraulic pressure control device includes a range switcher having a first signal solenoid valve capable of supplying a first signal pressure and a spool switchable between a first position reached via the first signal pressure and a second position reached via a biasing force of a biasing member.