| 主权项 |
1. A liquid pressure motor comprising:
a first inlet/outlet port and a second inlet/outlet port both connected to a direction switching valve; a first inlet/outlet passage which connects the first inlet/outlet port with a liquid pressure motor mechanism; a second inlet/outlet passage which connects the second inlet/outlet port with the liquid pressure motor mechanism; a counter balance valve which is connected to the first inlet/outlet passage and the second inlet/outlet passage; a bypass passage which connects the first inlet/outlet passage between the counter balance valve and the liquid pressure motor mechanism with the second inlet/outlet passage between the counter balance valve and the liquid pressure motor mechanism; a connection valve which is provided in the bypass passage and is opened when a fluid pressure in the first inlet/outlet passage or the second inlet/outlet passage becomes not lower than a working pressure; and a pilot passage which is connected to the counter balance valve and through which a fluid pressure flows, the fluid pressure being introduced into a back pressure chamber of the connection valve by which chamber the working pressure of the connection valve is controlled, a switching valve connected to the pilot passage being provided to have a first changeover position where the back pressure chamber is connected to the tank and a second changeover position where the pilot passage is connected to the back pressure chamber, and by the switching valve the liquid pressure supplied to the liquid pressure motor mechanism being introduced into the back pressure chamber via the pilot passage when the liquid pressure motor mechanism is in operation, whereas, when the liquid pressure motor mechanism is being braked, the back pressure chamber being connected to the tank when the fluid pressure in the pilot passage becomes equal to or lower than a predetermined pressure, wherein, a neutral spring is provided at one or each end portion of the counter balance valve, a liquid pressure is introduced from the first inlet/outlet passage to one chamber of the counter balance valve, and a liquid pressure is introduced from the second inlet/outlet passage to the other chamber of the counter balance valve, a return spring is provided at one end portion of the switching valve, whereas a pilot pressure is introduced from the pilot passage to the other end portion of the switching valve, and a spring force of the return spring by which the switching valve returns to the first changeover position is arranged to be larger than a spring force of the neutral spring by which the counter balance valve returns to a neutral position. |
