| 摘要 |
An object of this invention is to prevent a diaphragm of an actuator from being damaged by a high temperature, and improve a heat resistance property of the actuator. A valve actuator 30 includes a communication hole 76 that allows communication between a high pressure chamber 64 and a low pressure chamber 66 that are separated by a diaphragm 62, and a normally closed reed valve 78 that opens and closes the communication hole 76. When a temperature t of the valve actuator 30 is less than a pressure release temperature T1, an ECU 50 changes a differential pressure between the high pressure chamber 64 and low pressure chamber 66 by means of a pressure regulating valve 86, to control the valve actuator 30. This control is executed within a range of differential pressures at which the reed valve 78 does not open. If the temperature t exceeds the pressure release temperature T1, a differential pressure at which the reed valve 78 opens is realized by the pressure regulating valve 86. Thus, pressure is released from the high pressure chamber 64 to the low pressure chamber 66 at a high temperature, and the diaphragm 62 can be protected.
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