JPH0254907U - - Google Patents

Description

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of one embodiment of the present invention, FIG. 2 is a schematic diagram of a pump discharge amount control device, and FIG. 3 is a hydraulic circuit diagram showing another embodiment of the present invention. 1... Pump, 2, 3, 4, 5... Directional switching valve, 6... Bypass oil passage, 7... Tank passage, 8...
...Pressure generating valve, 9... Parent and child piston, 10... Child cylinder, 11... Main cylinder, 14... Main pilot valve, 15... Auxiliary pilot valve, 15a...
...Pilot operating section, 16...Oil cooler, 17,
18... Valve device, 19... Pilot oil path, 20
...Switching valve, 33... Temperature detector, 34... Solenoid operated switching valve, 35... Temperature detector controller, 36... Controller control switch.

Claims (1)

[Claims for Utility Model Registration] 1. A bypass oil passage that is controlled to open and close in conjunction with directional control valves 2, 3, 4, and 5 that are supplied with pressure oil from a variable discharge pump 1 so as to be conductive at a neutral position. 6 and a tank passage 7 through which return oil from the tank port of the directional control valve passes, a pressure generating valve 8 is connected which generates pilot operation pressure on the primary side when the bypass oil passage is conducted. Construction with a pump discharge amount control device that is controlled by the pressure on the primary side of the pressure generating valve so that the pump discharge amount is reduced when pressure is generated and the pump discharge amount is increased when the pilot operating pressure is not generated. In a hydraulic circuit of a machine, etc., a second passage 7b for bypass is connected in parallel to a first passage 7a passing through an oil cooler 16 downstream of a tank passage 7, and the first passage is opened to open the second passage. Valve devices 17 and 18 are attached to the first and second passages, and the valve devices 17 and 18 are always energized to close the first passage and open the second passage when the first passage is closed by the pilot operating pressure. In the middle of the pilot oil passage 19 between the pump and the pilot operation part 15a of the pump discharge amount control device, there is a position where the pilot oil passage is conducted and the pilot operation part 17a of the valve device is connected to the tank, and a pump discharge amount. A switching valve 20 having a position where the pilot operating section 15a of the control device is connected to the tank and the pilot operating section 17a of the valve device is connected to the primary side of the pressure generating valve.
, 34 is inserted. 2. A switch-controlled temperature sensor 33 that issues a signal when the oil temperature in the tank T falls below a predetermined temperature is attached to the tank, and the primary side of the pressure generating valve 8 is connected to the pilot operating section 15a of the pump discharge amount control device. At the same time, the pilot operating parts 17a of the valve devices 17 and 18 are connected to the tank in the normal position, and the pilot operating part 15a of the pump discharge amount control device is connected to the tank, and the pilot operating part 17a of the valve devices is connected to the pressure generating valve. 2. The warm-up operation device for a hydraulic circuit according to claim 1, wherein a solenoid-operated switching valve (34) having a switching position connected to the primary side is configured to be switched to the switching position in response to the signal generated by a temperature sensor.