Fluid pressure circuit, energy recovery device, and fluid pressure recovery circuit for working machine

Abstract

A fluid pressure circuit where energy possessed by return fluid from a fluid pressure actuator can be smoothly absorbed by an energy recovery motor and where stable operation of the fluid pressure actuator can be obtained. A return fluid path (55) to which return fluid discharged from a boom cylinder (8bmc) is branched is provided on the tank path side of a solenoid valve (49) of a boom control circuit (45). In one return path (56) and the other return path (57) of the return path (55) are provided proportional flow control valves (58, 59) for controlling flow ratios branched to the return paths (56, 57). The proportional flow control valves (58, 59) are composed of one solenoid valve (58) for flow control provided in the one return path (56) having the energy recovery motor (26) and of the other solenoid valve (59) for flow control provided in the other return path (57) branched off on the upstream side of the one solenoid valve (58).

Description

technical field [0001] The invention relates to a fluid pressure circuit with an energy regeneration motor, an energy regeneration device, a fluid pressure circuit of a working machine with a boom auxiliary pump. Background technique [0002] A driving device of a work machine such as a hydraulic excavator includes a generator driven by an engine, and a battery storing electric power generated by the generator. The pump or the pump / motor is driven by an electric motor or an electric / generator operated by electric power supplied from at least one of these generators and accumulators. For example, the drive circuit of the boom cylinder is equipped with a bidirectional output pump / motor that has both the pump function of providing working fluid and the function of a fluid pressure motor that receives the supply of working fluid in a closed circuit, and also has a motor / generator. It has both a motor function for driving a pump / motor driven by electric power supplied from a gen...

AI Technical Summary

Problems solved by technology

[0005] The driving device of the above-mentioned work machine is provided with a pump / motor in the closed circuit of the boom cylinder, so when the pump / motor functions as a fluid pressure motor, it starts up rapidly due to the return fluid from the boom cylinder, and due to The disappearance of the return fluid causes a sudden stop, which causes a shock, and the pump / motor becomes a load on the boom cylinder, and the load fluctuates depending on whether the pump / motor is in a stopped state or an operating state, so the operation of the boom cylinder is unstable.

[0006] Also, devices combining the pump / motor and motor / generator described are limited to closed circuits and cannot be adapted for open circuits where return fluid exhausted from a fluid pressure actuator is returned to the tank

[0007] In addition, the support circuit supplements the working fluid between the plurality of fluid pressure actuators, but there are cases where the supplementary amount of the working fluid is insufficient.

For example, in the boom raising operation in which the boom cylinder of a hydraulic excavator is extended and the boom is raised, the working fluid supply flow rate required by the boom cylinder with a large diameter may not be obtained, and the working speed may decrease.

[0008] On the other hand, the conventional operating system uses the electric motor to drive the crawler through the reduction gear, so it is not possible to provide a backup circuit for mutually supplementing the working fluid with respect to this operating system.

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