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In a hydraulic control device, when a solenoid pressure from a linear solenoid valve is not supplied to a brake, which is normally not engaged at the same time as a brake, not to engage the brake, a switching valve is supplied with a line pressure as a signal pressure for establishing a blocked/disc

In a hydraulic control device, when a solenoid pressure from a linear solenoid valve is not supplied to a brake, which is normally not engaged at the same time as a brake, not to engage the brake, a switching valve is supplied with a line pressure as a signal pressure for establishing a blocked/discharge state in which supply of the solenoid pressure to the brake is blocked and a hydraulic pressure can be discharged from the brake. When the solenoid pressure is supplied to the brake to engage the brake, the switching valve is supplied with a modulator pressure, which is lower than the line pressure, as a signal pressure for establishing a communicated state in which the solenoid pressure can be supplied to the brake.

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1. A hydraulic control device for a speed change device capable of transferring power applied to an input member to an output member at a speed change ratio that is changeable in a plurality of stages by engaging and disengaging a plurality of hydraulic friction engagement elements, the hydraulic co

1. A hydraulic control device for a speed change device capable of transferring power applied to an input member to an output member at a speed change ratio that is changeable in a plurality of stages by engaging and disengaging a plurality of hydraulic friction engagement elements, the hydraulic control device comprising: a first pressure regulation valve that regulates a hydraulic pressure to be supplied to a first hydraulic friction engagement element;a second pressure regulation valve that regulates a hydraulic pressure to be supplied to a second hydraulic friction engagement element that is normally not engaged at the same time as the first hydraulic friction engagement element; anda switching valve that can establish a blocked/discharge state, in which supply of the hydraulic pressure from the second pressure regulation valve to the second hydraulic friction engagement element is blocked and a hydraulic pressure can be discharged from the second hydraulic friction engagement element, and a communicated state, in which the hydraulic pressure from the second pressure regulation valve can be supplied to the second hydraulic friction engagement element, and that can receive a signal pressure for establishing the blocked/discharge state and the communicated state and the hydraulic pressure from the first pressure regulation valve, whereinthe switching valve is supplied with a first signal pressure as the signal pressure when the blocked/discharge state is established and supplied with a second signal pressure, which is lower than the first signal pressure, as the signal pressure when the communicated state is established, and the switching valve establishes the blocked/discharge state when the hydraulic pressure from the first pressure regulation valve is input in the communicated state. 2. The hydraulic control device according to claim 1, further comprising: a second switching valve that can establish a first state, in which the hydraulic pressure from the second pressure regulation valve can be supplied to a third hydraulic friction engagement element that is not engaged at the same time as the second hydraulic friction engagement element, and a second state, in which the hydraulic pressure from the second pressure regulation valve can be supplied to the second hydraulic friction engagement element and a hydraulic pressure can be discharged from the third hydraulic friction engagement element, whereinthe second switching valve can receive the first signal pressure and the second signal pressure, and supplies the first signal pressure to the switching valve as the signal pressure when the first state is established and supplies the second signal pressure to the switching valve as the signal pressure when the second state is established. 3. The hydraulic control device according to claim 2, wherein the first signal pressure is a line pressure, and the second signal pressure is a hydraulic pressure obtained by reducing the line pressure. 4. The hydraulic control device according to claim 2, wherein the switching valve includes a plunger disposed so as to be axially movable, a spool disposed coaxially with the plunger so as to be movable and capable of establishing the blocked/discharge state and the communicated state, and a spring that urges the spool against the plunger, andthe spool includes a first pressure receiving surface that receives the hydraulic pressure from the first pressure regulation valve and a second pressure receiving surface formed on the opposite side from the first pressure receiving surface to receive an urging force of the spring, and the plunger includes a pressure receiving surface that faces the first pressure receiving surface of the spool to receive the hydraulic pressure from the first pressure regulation valve and a signal pressure receiving surface formed on the opposite side from the pressure receiving surface to receive the signal pressure. 5. The hydraulic control device according to claim 4, wherein the switching valve is supplied with a hydraulic pressure from an additional pressure regulation valve that is different from the first and second pressure regulation valves so that the hydraulic pressure from the additional pressure regulation valve acts on the second pressure receiving surface of the spool when the communicated state is established, and the switching valve is not supplied with the hydraulic pressure from the additional pressure regulation valve when the blocked/discharge state is established. 6. The hydraulic control device according to claim 5, further comprising: a lock-up solenoid valve that generates a lock-up control pressure used to set a lock-up pressure to be supplied to a lock-up clutch, whereinthe additional pressure regulation valve is the lock-up solenoid valve. 7. The hydraulic control device according to claim 6, further comprising: a signal pressure output valve that can output a signal pressure for switching the second switching valve from the first state into the second state; anda lock-up relay valve that can establish a lock-up pressure supply state in which the lock-up pressure can be supplied to the lock-up clutch and a lock-up pressure block state in which supply of the lock-up pressure to the lock-up clutch is blocked, whereinthe lock-up relay valve is configured to receive the signal pressure from the signal pressure output valve, and to establish the lock-up pressure block state when the signal pressure from the signal pressure output valve is input. 8. The hydraulic control device according to claim 3, wherein the switching valve includes a plunger disposed so as to be axially movable, a spool disposed coaxially with the plunger so as to be movable and capable of establishing the blocked/discharge state and the communicated state, and a spring that urges the spool against the plunger, andthe spool includes a first pressure receiving surface that receives the hydraulic pressure from the first pressure regulation valve and a second pressure receiving surface formed on the opposite side from the first pressure receiving surface to receive an urging force of the spring, and the plunger includes a pressure receiving surface that faces the first pressure receiving surface of the spool to receive the hydraulic pressure from the first pressure regulation valve and a signal pressure receiving surface formed on the opposite side from the pressure receiving surface to receive the signal pressure. 9. The hydraulic control device according to claim 8, wherein the switching valve is supplied with a hydraulic pressure from an additional pressure regulation valve that is different from the first and second pressure regulation valves so that the hydraulic pressure from the additional pressure regulation valve acts on the second pressure receiving surface of the spool when the communicated state is established, and the switching valve is not supplied with the hydraulic pressure from the additional pressure regulation valve when the blocked/discharge state is established. 10. The hydraulic control device according to claim 9, further comprising: a lock-up solenoid valve that generates a lock-up control pressure used to set a lock-up pressure to be supplied to a lock-up clutch, whereinthe additional pressure regulation valve is the lock-up solenoid valve. 11. The hydraulic control device according to claim 10, further comprising: a signal pressure output valve that can output a signal pressure for switching the second switching valve from the first state into the second state; anda lock-up relay valve that can establish a lock-up pressure supply state in which the lock-up pressure can be supplied to the lock-up clutch and a lock-up pressure block state in which supply of the lock-up pressure to the lock-up clutch is blocked, whereinthe lock-up relay valve is configured to receive the signal pressure from the signal pressure output valve, and to establish the lock-up pressure block state when the signal pressure from the signal pressure output valve is input. 12. A hydraulic control device for a speed change device capable of transferring power applied to an input member to an output member at a speed change ratio that is changeable in a plurality of stages by engaging and disengaging a plurality of hydraulic friction engagement elements, the hydraulic control device comprising: a first pressure regulation valve that regulates a hydraulic pressure to be supplied to a first hydraulic friction engagement element;a second pressure regulation valve that regulates a hydraulic pressure to be supplied to a second hydraulic friction engagement element that is normally not engaged at the same time as the first hydraulic friction engagement element; anda switching valve that can establish a blocked/discharge state, in which supply of the hydraulic pressure from the second pressure regulation valve to the second hydraulic friction engagement element is blocked and a hydraulic pressure can be discharged from the second hydraulic friction engagement element, and a communicated state, in which the hydraulic pressure from the second pressure regulation valve can be supplied to the second hydraulic friction engagement element, and that can receive a holding pressure for holding the communicated state and the hydraulic pressure from the first pressure regulation valve, whereinthe switching valve is supplied with the holding pressure and not supplied with the hydraulic pressure from the second hydraulic friction engagement element when the second hydraulic friction engagement element is not engaged, the switching valve is supplied with the hydraulic pressure from the second hydraulic friction engagement element and not supplied with the holding pressure when the second hydraulic friction engagement element is engaged, and the switching valve can establish the communicated state irrespective of presence or absence of the holding pressure and establishes the blocked/discharge state when the hydraulic pressure from the first pressure regulation valve is input with the holding pressure not supplied. 13. The hydraulic control device according to claim 12, wherein the switching valve includes a spool disposed so as to be movable and capable of establishing the blocked/discharge state and the communicated state, and a spring that urges the spool, andthe spool includes a first pressure receiving surface that receives the hydraulic pressure from the first pressure regulation valve and a second pressure receiving surface formed on the opposite side from the first pressure receiving surface to receive the holding pressure and an urging force of the spring. 14. The hydraulic control device according to claim 13, further comprising: a second switching valve that can establish a first state, in which the hydraulic pressure from the second pressure regulation valve can be supplied to a third hydraulic friction engagement element that is not engaged at the same time as the second hydraulic friction engagement element, and a second state, in which the hydraulic pressure from the second pressure regulation valve can be supplied to the second hydraulic friction engagement element and a hydraulic pressure can be discharged from the third hydraulic friction engagement element, and that can receive the holding pressure, whereinthe second switching valve supplies the holding pressure to the switching valve when the first state is established, and blocks supply of the holding pressure to the switching valve and can discharge a hydraulic pressure from a spring chamber in which the spring of the switching valve is disposed when the second state is established.