초록 ▼

The fail-safe gear step switching valve (120) can be switched to the first position to establish the low-speed side fail-safe gear step (third speed-change gear step) or the second position to establish the high-speed side fail-safe gear step (fifth speed-change gear step). Upon the failure state of

The fail-safe gear step switching valve (120) can be switched to the first position to establish the low-speed side fail-safe gear step (third speed-change gear step) or the second position to establish the high-speed side fail-safe gear step (fifth speed-change gear step). Upon the failure state of the solenoid valve device (SLC1, SLC2), the fail-safe gear step switching valve is held at the second position by the line hydraulic pressure (PL1). Two kinds of the fail-safe gear steps i.e., the third speed-change gear step and the fifth speed-change gear step can be established depending on the vehicle state just before the failure occurrence of the fail-safe gear step switching valve. Even if the D→N operation of the shift lever (72) is performed during the vehicle running in the fifth speed-change gear step, the fail-safe gear step switching valve remains at the second position to establish the fifth speed-change gear step even upon the shifting operation of the shift lever to the "D" position again.

대표청구항 ▼

What is claimed is: 1. A hydraulic controlling apparatus for an automatic transmission for vehicle, comprising: a hydraulic pump that outputs an operation oil pressure; a manual valve that generates a hydraulic pressure for forward running based on the operation oil pressure, when a valve position

What is claimed is: 1. A hydraulic controlling apparatus for an automatic transmission for vehicle, comprising: a hydraulic pump that outputs an operation oil pressure; a manual valve that generates a hydraulic pressure for forward running based on the operation oil pressure, when a valve position of the manual valve is switched in accordance with a shifting operation to a forward running position; a first solenoid valve device, that, when the first solenoid valve is in a normal state selectively supplies an output hydraulic pressure to plural hydraulic type frictionally engaging devices to establish plural speed-change steps of the automatic transmission; and a fail-safe gear step switching valve that (i) upon a failure state of the first solenoid valve, switches to a first position to establish a low-speed side fail-safe gear step or to a second position to establish a high-speed side fail-fail gear step, of plural speed-change steps of the automatic transmission, both the first position and the second position being set in advance based on the output hydraulic pressure from the solenoid valve device just before failure thereof occurs, so that the low-speed side fail-safe gear step or the high-speed side fail-safe gear step is selected in an alternative way, and (ii) is held at the second position based on a base pressure which is based on the operation oil pressure from the hydraulic pump, wherein the base pressure is supplied independent of the valve position of the manual valve. 2. A hydraulic controlling apparatus according to claim 1, wherein the fail-safe gear step switching valve is held at the first position based on a decreased base pressure and biasing force of a bias member. 3. A hydraulic controlling apparatus for an automatic transmission for vehicle, comprising: a hydraulic pump that outputs an operation oil pressure; a manual valve that generates a hydraulic pressure for forward running based on the operation oil pressure, when a valve position of the manual valve is switched in accordance with a shifting operation to a forward running position; a solenoid valve device, that, when the first solenoid valve is in a normal state, selectively supplies an output hydraulic pressure to plural hydraulic type frictionally engaging devices to establish plural speed-change steps of the automatic transmission; and a fail-safe gear step switching valve that (i) upon a failure state of the solenoid valve, switches to a first position to establish a low-speed side fail-safe gear step or to a second position to establish a high-speed side fail-fail gear step, of plural speed-change steps of the automatic transmission, both the first position and the second position being set in advance based on the output hydraulic pressure from the solenoid valve device just before failure thereof occurs, so that the low-speed side fail-safe gear step or the high-speed side fail-safe gear step is selected in an alternative way, and (ii) is held at the second position based on a base pressure which is based on the operation oil pressure from the hydraulic pump and which does not fluctuate regardless of the valve position of the manual valve, wherein the fail-safe gear step switching valve is held at the first position based on a decreased base pressure and biasing force of a bias member, the solenoid valve device includes a first solenoid pressure regulation valve that supplies the output hydraulic pressure to a first hydraulic type frictionally engaging device for establishing the low-speed side gear step including a lowest-speed gear step and the fail-safe gear step switching valve, and a second solenoid pressure regulation valve that supplies the output hydraulic pressure to a second hydraulic type frictionally engaging device for establishing the high-speed side gear step including a highest-speed gear step and the fail-safe gear step switching valve, and the fail-safe gear step switching valve is switched to the first position based on the output hydraulic pressure from the first solenoid pressure regulation valve, and switched to the second position based on the output hydraulic pressure from the second solenoid pressure regulation valve. 4. A hydraulic controlling apparatus according to claim 3, wherein the fail-safe gear step switching valve in the first position thereof outputs the hydraulic pressure for forward running to the first hydraulic type frictionally engaging device, and in the second position thereof outputs the hydraulic pressure for forward running to the second hydraulic type frictionally engaging device. 5. A hydraulic controlling apparatus according to claim 4, wherein the solenoid valve device further includes a third solenoid pressure regulation valve that supplies the output hydraulic pressure to a third hydraulic type frictionally engaging device establishing the low-speed side fail-safe gear step and the high-speed side fail-safe gear step together with the first hydraulic type frictionally engaging device and the second hydraulic type frictionally engaging device. 6. A hydraulic controlling apparatus according to claim 5, further including a normal/failure switching valve to be switched to a normal side position upon normal state of the solenoid valve device for allowing the output hydraulic pressure from the solenoid valve device to be supplied to the hydraulic type frictionally engaging device, or a failure side position upon failure state of the solenoid valve device for allowing the hydraulic pressure for forward running or the base pressure to be supplied to the hydraulic type frictionally engaging device. 7. A hydraulic controlling apparatus according to claim 6, wherein the normal failure switching valve in the normal side position thereof allows the output hydraulic pressure from the first solenoid pressure regulation valve to be supplied to the first hydraulic type frictionally engaging device, from the second solenoid pressure regulation valve to be supplied to the second hydraulic type frictionally engaging device, and from the third solenoid pressure regulation valve to be supplied to the third hydraulic type frictionally engaging device, and in the failure side position thereof allows the hydraulic pressure for forward running from the fail-safe gear step switching valve to be supplied to the first hydraulic type frictionally engaging device or second hydraulic type frictionally engaging device, and the base pressure or the hydraulic pressure for forward running to be supplied to the third hydraulic type frictionally engaging device. 8. A hydraulic controlling apparatus according to claim 7, wherein the first solenoid pressure regulation valve, second solenoid pressure regulation valve and third solenoid pressure regulation valve are normally-closed type pressure regulation solenoid valves. 9. A hydraulic controlling apparatus according to claim 8, wherein the base pressure is a pressure-regulated value regulated by the pressure regulated valve. 10. A hydraulic controlling apparatus according to claim 1, further comprising a second solenoid valve device, that, when the second solenoid valve is in a normal state, supplies a predetermined control pressure to a normal/failure switching valve. 11. A hydraulic controlling apparatus according to claim 10, wherein the second solenoid valve device is independently controlled by an electronic controlling apparatus. 12. A hydraulic controlling apparatus according to claim 10, wherein the predetermined control pressure is less than a modulate hydraulic pressure. 13. A hydraulic controlling apparatus according to claim 12, wherein the predetermined control pressure is in a range from 0 to 80% of the modulate hydraulic pressure upon the normal state.