Crawler Hydraulic Drive Flow Balancing for Straight Travel
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Solution Overview
Problem
In hydraulic drive systems for crawler-type track devices, such as hydraulic mini-excavators, differences in speed between left and right track motors can occur due to manufacturing or machining errors, leading to skewing and inability to travel in a straight line, requiring costly and labor-intensive replacement of large components.
Innovation Solution
The system incorporates a flow rate correction device with a target compensating differential pressure adjusting mechanism, allowing for adjustment of the biasing force of pressure compensating valves to equalize flow rates between track motors without replacing track motors or modifying the main circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If track motors are replaced to correct speed differences, then straight line traveling stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent adjusts the target compensating differential pressure parameter of the pressure compensating valve to correct speed differences between track motors. By changing this pressure parameter, the flow rate to each track motor can be adjusted without replacing any components, thereby maintaining straight line traveling stability while avoiding increased device complexity
Solution Approach 2:
The patent uses a simple pressure adjusting mechanism that copies the function of complex track motor replacement. Instead of replacing the entire track motor assembly when speed differences occur, a simpler pressure adjusting device is used to achieve the same corrective effect, reducing both device complexity and cost
2Reliability
If track motors are replaced to correct speed differences, then straight line traveling stability is improved, but loss of time and productivity decrease
Solution Approach 1:
The patent incorporates a preliminary adjustable pressure compensating valve that can be tuned during initial setup or maintenance. This allows speed balancing to be performed in advance during routine inspections rather than waiting for skew traveling problems to develop, significantly reducing downtime and maintaining productivity
Solution Approach 2:
The pressure compensating valve is designed to be easily adjustable by operators during routine maintenance without requiring specialized service or track motor replacement. This self-service capability allows quick adjustments during inspections, minimizing downtime and maintaining operational productivity
3Reliability
If manufacturing precision is increased to eliminate speed differences, then straight line traveling stability is improved, but ease of manufacture decreases
Solution Approach 1:
Rather than requiring extremely precise manufacturing of track motors to eliminate speed differences, the patent uses adjustable pressure parameters in the compensating valve to correct variations. This approach maintains straight line traveling stability while allowing standard manufacturing tolerances, significantly improving ease of manufacture
Solution Approach 2:
The patent transforms a static manufacturing precision problem into a dynamic adjustment problem. Instead of relying on fixed manufacturing precision, the system provides dynamic adjustability through the pressure compensating valve, allowing speed balancing to be tuned after assembly. This maintains reliability while greatly improving ease of manufacture
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
This solution enables easy correction of skew traveling for straight-line travel without replacing track motors or modifying the main circuit, improving operational efficiency and reducing costs by allowing for prompt adjustments during inspections or operations.
Implementation Method 1
a pressure compensating valve (27b) for the left track which has a valve opening-side pressure receiving portion (28b) into which a output pressure of the differential pressure reducing valve (24) is introduced
Implementation Method 2
each have a valve opening-side pressure receiving portion (28b) to which an output pressure of the differential pressure reducing valve is introduced and each control a respective differential pressure across each of the flow control valves
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A hydraulic drive system for a working machine including a track device of crawler type is provided. The track device of crawler type travels with hydraulic fluid supplied from at least one hydraulic pump to right and left track motors. The hydraulic drive system is capable of easily correcting skew traveling for straight line traveling without having to replace a track motor or other large-size device and without having to specially modify a main circuit. A traveling test is conducted upon shipment from a factory. If skew is noted during the test, a plug 65b disposed on the side of a valve opening-side pressure receiving portion 28b (or 28d) of a pressure compensating valve 27b (or 27d) for track whichever is lower in speed is removed and, instead, an adjusting mechanism-mounted plug 37 is mounted. An adjusting pin 37b of the adjusting mechanism-mounted plug 37 is operated so as to strengthen a biasing force of a target compensating differential pressure adjusting spring 36b. An opening in the pressure compensating valve 27b (or 27d) is thereby corrected in an opening direction and a flow rate to a left track motor 6 (or 8) is thereby adjusted to be equal to that of a right track motor 8 (or 6).