Hydraulic Travel Control for Stable Engine Speed in Working Machines
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Solution Overview
Problem
Existing working machines, such as skid steer loaders and compact track loaders, experience reduced work efficiency and operator dissatisfaction due to excessive engine-speed dropping, which leads to a perceived reduction in traveling force, especially when the engine speed is in the middle or high speed ranges.
Innovation Solution
A working machine equipped with a controller that adjusts the setting of a control signal to an actuation valve based on differential pressure or derivative values, using a solenoid proportional valve to manage primary pressure, thereby preventing excessive engine-speed dropping and maintaining optimal traveling force perception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the output of the pressure control valve is lowered to secure climbing speed in the middle speed range, then engine speed dropping is suppressed and appropriate engine speed is maintained, but work efficiency is reduced due to excessive engine-speed dropping when response is poor
Solution Approach 1:
The patent applies dynamics by making the pressure control valve output dynamically adjustable based on engine speed range. The controller changes the output characteristics of the pressure control valve according to whether the engine speed is in the middle speed range or high speed range, optimizing performance for each operating condition rather than using a fixed control characteristic
Solution Approach 2:
The patent changes the control parameter (pressure control valve output) based on the engine speed condition. When engine speed is in the middle range, the output is lowered to maintain speed; when in the high range, the output is increased to prevent high speed remaining, thus adapting the system behavior to different operating parameters
2Speed
If the output of the pressure control valve is increased to prevent high engine speed remaining in the high speed range, then high engine speed is prevented, but traveling power is reduced
Solution Approach 1:
The controller adjusts the pressure control valve output parameter based on engine speed range. In the high speed range, the output is set high to prevent high engine speed remaining, while in the middle speed range, the output is lowered to preserve traveling power for climbing, thus optimizing the parameter setting for each operating condition
3Speed
If the difference between the output of the pressure control valve at middle speed range and high speed range is made extremely large, then climbing speed is prioritized and high engine speed remaining is prevented, but hunting in the engine speed occurs
Solution Approach 1:
The system dynamically adjusts the pressure control valve output based on the actual engine speed range, allowing the control characteristic to change smoothly between operating conditions. This dynamic adaptation prevents the abrupt transitions that would cause hunting while still achieving the goals of maintaining climbing speed and preventing high speed remaining
4Speed
If the pressure control valve output is optimized for middle speed range to prioritize hill climbing speed, then climbing performance is improved, but traveling power in the high speed range is reduced
Solution Approach 1:
The controller changes the pressure control valve output parameter according to engine speed range. When the engine operates in the middle speed range, the output is optimized for hill climbing by lowering it to maintain speed. When in the high speed range, the output is increased to prevent high speed remaining, thus adapting the power delivery to match the operational requirements of each speed range
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
The solution effectively prevents work efficiency deterioration and operator dissatisfaction by stabilizing engine speed and traveling force, ensuring the machine feels productive even during engine-speed fluctuations.
Implementation Method 1
an actuation valve configured to be activated according to a control signal so as to change a primary pressure that is the pilot pressure of the pilot fluid to be supplied to the operation valve
Data Source
AI summary
A working machine includes a prime mover, a traveling pump driven by power of the prime mover to deliver hydraulic fluid, a traveling motor rotated by the hydraulic fluid delivered from the traveling pump, an operation valve configured to change a pilot pressure of pilot fluid output therefrom to the traveling pump according to operation of an operation member, an actuation valve to be activated according to a control signal so as to change a primary pressure supplied to the operation valve, a controller to perform setting of the control signal to be output to the actuation valve, and a pressure detection device to detect a secondary pressure output from the operation valve. The controller includes a setting change unit to change, based on the primary pressure and the secondary pressure, the setting of the control signal to be output to the actuation valve.