| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic two speed switching mechanism for a hydraulic motor having a high pressure selection mechanism built in. SOLUTION: The hydraulic motor 1 revolving in a regular and reverse direction by motor pressure M1, M2 selectively supplied from a first and a second supply and discharge passage is provided with a hollow structure speed change switching spool 21 switching revolution speed of the hydraulic motor 1, a first and a second pin 31, 32 put inside of the speed change switching spool 21 in series and slidably installed. One end of the first pin 31 projects from the speed change switching spool 21 and is supported by a housing 7, and a first pressure chamber 41 formed between end parts of the first and the second pin 31, 32 opposing each other and a second pressure chamber 42 formed between one end of the second pin 32 and the speed change switching spool 21 are provided. The speed change switching spool 21 is automatically switched from a second speed position to a first speed position according to the motor pressure M1, M2 led from the first and the second supply and discharge passage 8, 9 to the first and the second pressure chamber 41, 42. COPYRIGHT: (C)2004,JPO
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