Hydraulic Travel Drive Flow Balancing During Machine Slip
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Solution Overview
Problem
Conventional hydraulic drive apparatuses for traveling type working machines, such as hydraulic excavators, face challenges in supplying hydraulic fluid effectively during slip conditions, leading to idling and reduced load on traveling motors, which hinders both traveling and working device operations.
Innovation Solution
A hydraulic drive apparatus with a traveling selector valve and communication throttle portion that adjusts the flow rate of hydraulic fluid between traveling and working fluid passages based on the pump pressure difference, allowing suitable hydraulic fluid distribution to both the traveling and working actuators, even during slip conditions, by varying the communication opening area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic fluid is freely communicated between traveling and working passages during slip conditions, then hydraulic fluid can be supplied to traveling motors, but hydraulic fluid overflows to lightly loaded traveling motors and cannot be supplied to working actuators
Solution Approach 1:
A communication throttle portion is introduced as an intermediary element between the traveling fluid passage and working fluid passage. This throttle portion mediates the hydraulic fluid flow during slip conditions, allowing controlled communication that prevents complete overflow to traveling motors while still enabling some traveling assistance, thereby maintaining working device operation reliability
Solution Approach 2:
The communication throttle portion dynamically adjusts the flow parameters (flow rate, pressure) of hydraulic fluid between passages based on operating conditions. During slip conditions, the throttle restricts flow parameters to prevent hydraulic fluid from completely diverting to traveling motors, ensuring sufficient pressure and flow are maintained for working actuators
2Reliability
If communication between first and second hydraulic pumps is restricted during combined operations, then pressure interference is prevented, but hydraulic fluid cannot be supplied to traveling motors when slip occurs
Solution Approach 1:
The communication throttle portion provides dynamic control of hydraulic fluid communication between pumps. During normal combined operations, communication is restricted to prevent pressure interference. During slip conditions, the system dynamically opens the communication path through the throttle, allowing hydraulic fluid to flow to traveling motors for slip recovery, thus adapting to changing operational requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient hydraulic fluid supply to both traveling and working actuators, ensuring effective operation during slips by optimizing fluid distribution and reducing torque shocks, thus maintaining operational efficiency and preventing hydraulic fluid overload on lightly loaded motors.
Implementation Method 1
a communication throttle portion provided in a communication passage providing communication between the working fluid passage and the traveling fluid passage so as to allow hydraulic fluid to flow from the working fluid passage to the traveling fluid passage
Data Source
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AI summary
Provided is a hydraulic drive apparatus capable of suitably supplying hydraulic fluid upon slip of a traveling body of a working machine. The hydraulic drive apparatus includes a specific working actuator (27) making a working arm perform a traveling assist motion upon the slip, first and second traveling motors (25R, 25L), first and second hydraulic pumps (31, 32), a traveling selector valve (39) switchable to a neutral position (PN) and a straight traveling position (PS), a communication throttle portion (39b) provided in a communication passage providing communication between a working fluid passage and a traveling fluid passage in the straight traveling position, and a switching control part (50) switching the traveling selector valve (39) to the neutral position (PN) when a single operation action is performed and switches the traveling selector valve (39) to the straight traveling position (PS) when a specific combined operation action of simultaneously making a forward traveling operation and the specific working operation is performed. The switching control section (50) adjusts the opening degree of the communication throttle section (39b) to decrease the flow rate in the communication passage (39c) with an increase in the difference between the first pump pressure and the second pump pressure.