REGULATOR OF FLUID PRESSURE MOTOR FOR DRILLING

To provide a regulator of a fluid pressure motor for drilling capable of reducing an excessive rotation of the fluid pressure motor caused by releasing a twist of a drilling shaft.SOLUTION: A regulator 2 comprises a servo piston 4, a first switching valve 5 and a second switching valve 7. The servo piston 4 includes a small diameter part 41 and a large diameter part 42. An annular surface of the large diameter part 42 faces a first pressure receiving chamber 4a and an end surface of the large diameter part 42 faces a second pressure receiving chamber 4b. An input passage 3 to which an inlet pressure of a fluid pressure motor 9 is supplied and a tank passage 5a are connected to the first switching valve 5, which is connected to the second pressure receiving chamber 4b by a pressure adjustment passage 6. The second switching valve 7 is interposed between a first flow passage 61 and a second flow passage 62 of the pressure adjustment passage 6 and a bypass 75 branching from the input passage 3 is connected to the second switching valve 7. The second switching valve 7 makes the first flow passage 61 in communication with the second flow passage 62 or makes the bypass 75 in communication with the second flow passage 62.SELECTED DRAWING: Figure 1 【課題】掘削軸の捩れの解放によって生じる液圧モータの過回転を低減することができる掘削用液圧モータのレギュレータを提供する。【解決手段】レギュレータ２は、サーボピストン４、第１切換弁５および第２切換弁７を含む。サーボピストン４は小径部４１および大径部４２を含み、大径部４２の環状面が第１受圧室４ａに面し、大径部４２の端面が第２受圧室４ｂに面する。第１切換弁５には、液圧モータ９の入口圧が供給される入力路３およびタンク路４ａが接続されるとともに、調圧路６により第２受圧室４ｂと接続されている。第２切換弁７は、調圧路６の第１流路６１と第２流路６２との間に介在し、第２切換弁７には、入力路３から分岐する迂回路７５が接続されている。第２切換弁７は、第１流路６１を第２流路６２と連通させたり、迂回路７５を第２流路６２と連通させたりする。【選択図】図１