Hydraulic drive device for traveling work machine

Abstract

Provided is a hydraulic drive device capable of a suitable hydraulic fluid supply when a traveling body of a work machine slips. The hydraulic drive device comprises a specific work actuator (27) that causes a work arm to perform a travel assist action during a slip; first and second travel motors (25R, 25L); first and second hydraulic pumps (31, 32); a travel switch valve (39) capable of switching between a neutral position (PN) and a travel straight position (PS); a communication throttle (39b) provided to a communication path through which a travel oil path and a work oil path in the travel straight position communicate; and a switch control unit (50) that switches the travel switch valve (39) to the neutral position (PN) when an independent operative action is carried out, and switches the travel switch valve (39) to the travel straight position (PS) when a specific combined operative action is carried out in which a forward travel operation and a specific work operation are performed simultaneously. The switch control unit (50) adjusts the opening degree of the communication throttle (39b) so as to commensurately reduce the flow rate in a communication path (39c) as the difference between a first pump pressure and a second pump pressure increases.

Description

technical field [0001] The present invention relates to a hydraulic drive device installed in a walking construction machine such as a hydraulic excavator. Background technique [0002] Conventionally, a device described in Patent Document 1 is known as a hydraulic drive device installed in a walking construction machine such as a hydraulic excavator. [0003] The hydraulic drive device includes: a left travel motor and a right travel motor that receive a supply of hydraulic oil to move the lower travel body; It includes a boom cylinder, an arm cylinder, and a bucket cylinder; a first hydraulic pump and a second hydraulic pump that respectively discharge working oil; and a travel control valve. The travel control valve has a neutral position, a travel independent position and a travel straight position. The travel control valve is switched to the neutral position when only travel operation is performed, that is, when the travel operation is performed alone, and is used to ...

AI Technical Summary

Problems solved by technology

[0005] When the walking body slips relative to the walking surface under different walking conditions, the walking body will idle and may not be able to walk

Under the situation of this walking body idling, for example, when the far end of the bucket of the working device is inserted into the ground and the arm of the working device is moved in the retracting direction, although the driving force of the working device can be used to assist the walking of the walking body , but the idling of the walking body causes the driving load of the left and right traveling motors to drop significantly. Therefore, the working oil that should be supplied to the working device will flow into the side of the left and right traveling motors through the communication path in the middle position, which may cause the working device to Can't move

[0006] In the above-mentioned patent document 1, it is disclosed that when the pump pressure difference between the first and second hydraulic pumps reaches a certain value or more during the composite operation, the The communication between the first and second hydraulic pumps is locked or cut off, but such control is difficult to realize the supply of working oil corresponding to the degree of slippage of the walking body

In particular, the communication is not jammed or cut off when the pump pressure difference is small, so even a small amount of slippage will cause a large fluctuation in the operating oil supplied to the travel motor. Deviation, which may cause the operation device to not move smoothly

Conversely, when the communication is blocked or cut off, the supply of the operating oil ejected from the second hydraulic pump to the traveling motor is cut off or suppressed collectively, so even if the degree of slippage is very slight, the traveling body can walk , and cannot supply enough working oil to the travel motor

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