| 摘要 |
A communication passageway is formed to extend from the end surface of a cover member opposed to the axial end surface of the shoulder portion of a main shaft and through the main shaft so that in only one of the two particular phase conditions obtained per revolution of an oil cylinder, it establishes the communication between high and low pressure chambers to thereby equalize their pressures. The communication passageway establishes the communication between high and low pressure chambers in only one of the two particular phase conditions obtained per revolution of the oil cylinder and makes it possible to produce percussion torque in the other particular phase condition. |
