JPS6391546U - - Google Patents

Description

[Brief explanation of the drawing]

1 and 2 are hydraulic circuit diagrams of the present invention, and FIG. 3 is a hydraulic circuit diagram of the prior art. 1L, 1R... Left and right travel motor, 5... Arm cylinder, 6... First pump, 8... Second pump, 11L, 11R... Left and right travel valve, 15... Arm valve, 16... Straight travel valve , 18...Opening/closing valve, 2
5... Remote control valve, 44L, 44R... Boost type relief valve.

Claims (1)

[Scope of utility model registration request] The various hydraulic actuators installed in the hydraulic excavator are divided into two groups A and B, the left and right traveling valves are provided in the front row of each group, and all other actuator switching valves are arranged in parallel with this,
In addition, a foot relief valve and a throttle part are connected in parallel to the outlet sides of the center bypass oil passages passing through the switching valves in groups A and B, respectively, and the upstream side thereof is connected to the outlet side of the center bypass oil passage.
, each of the second pumps is connected to the regulator, and its downstream side is communicated with the oil tank, and a straight-travel valve is provided in the oil passage on the discharge side of the first and second pumps, while,
An on-off valve is provided in parallel with the left-hand drive motor in the oil path that communicates the left-hand drive motor and the left-hand drive valve, and the on-off valve is used to shut off the pilot oil path from the remote control valve when the left-right drive motor is stopped, and to shut off the pilot oil path from the remote control valve when the left-right drive motor is activated. By opening the oil passage, the pilot pressure for the remote control from the pilot pump can be applied to the pilot pressure receiving part of the straight travel valve, and the left and right travel valves are both neutral or only the right and left travel valves are in the first position where they are simultaneously operated. In this case, the oil passage from the first pump is shut off, and the oil passage from the second pump is opened. In this case, in a hydraulic circuit in which the oil passages from the first and second pumps can be switched to the parallel open oil passage position, the pressure oil supply oil passages of the switching valves for work attachments in groups A and B and the first and second oil passages are connected to each other. A step-up relief valve is interposed between each regulator for two pumps, and a pilot of one or more remote control valves that controls and operates various actuator switching valves other than travel valves. 1. A hydraulic circuit for a hydraulic excavator, characterized in that a pressure outlet side oil passage is configured to communicate with a boost pilot pressure receiving portion of each of the boost type relief valves.