TWI743753B

The present invention relates to a hydraulic drive system, which includes a vacuum actuator which expands and contracts to be able to pressurize an object in a chamber of a vacuum atmosphere, a hydraulic drive unit, and a drive unit. The vacuum actuator includes an extension rod which can extend toward an object, and a biasing member which biases the extension rod in a direction of separating from the object. The vacuum actuator generates a driving force greater than the biasing force of the biasing member by hydraulic pressure supplied from the hydraulic drive unit to drive the elastic rod. The drive unit is provided with a hydraulic pressure suppression unit which suppresses an increase in hydraulic pressure in response to the reversal of a motor when the extension rod moves in a direction of being close to the object by the biasing force of the hydraulic biasing member. Accordingly, it is possible to prevent damage to components at the end of springback.