Hydrostatic CVT Swash Plate Control for Work Vehicle Torque
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Solution Overview
Problem
Existing speed change systems for work vehicles with continuously variable transmission devices face challenges in maintaining stable vehicle speed and power transmission efficiency, especially during low-speed operations and when handling large loads, leading to difficulties in smooth travel and accurate work performance.
Innovation Solution
A speed change system that includes a pump swash plate operation mechanism for the variable capacity pump and a motor swash plate operation mechanism for the variable capacity motor, with a swash plate angle control unit that adjusts both swash plate angles based on an operation position detector, allowing for non-stepwise adjustment of the pump swash plate angle and stepwise adjustment of the motor swash plate angle, thereby compensating for changes in the transmission gear ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the variable capacity motor is kept in a high-speed state, then the system is simple to operate, but the work vehicle cannot smoothly travel in large load situations such as hill-climbing and working states with connected devices
Solution Approach 1:
The system dynamically switches the variable capacity motor between high-speed and low-speed states based on detected work conditions. When a working device is detected as connected, the motor switches to low-speed state to provide high torque for smooth travel under load. When no working device is connected, the motor operates in high-speed state for normal traveling, thus adapting the system behavior to actual operational needs.
2Speed
If the speed change operation tool is operated to the low-speed side position, then the change gear ratio is increased for low-speed traveling, but the swash plate angle of the variable capacity pump operates at low hydraulic pressure transmission efficiency angles more frequently
Solution Approach 1:
The system changes the operating parameters of both the variable capacity pump and variable capacity motor in a coordinated manner. When the speed change operation tool is positioned at the low-speed side, the system not only increases the change gear ratio but also adjusts the swash plate angles of both pump and motor to optimize hydraulic pressure transmission efficiency, thereby reducing energy loss while maintaining low-speed traveling capability.
3Adaptability or versatility
If a special operation tool is provided for manual switching of the variable capacity motor, then the motor can be switched between high-speed and low-speed states, but the number of operation tools increases and speed change operation becomes more complex
Solution Approach 1:
The system makes the existing speed change operation tool serve multiple functions. By detecting the position of this single tool, the system can determine both the desired vehicle speed and the appropriate motor speed state, eliminating the need for a separate special operation tool. The control unit integrates multiple control functions into one operational interface, reducing device complexity while maintaining adaptability.
4Productivity
If the change gear ratio is set to a small value (high-speed side) to enhance work efficiency, then work efficiency is improved, but engine stall due to overload is likely to occur during vehicle start
Solution Approach 1:
The system performs preliminary detection of working device connection status before vehicle start. When a working device is detected as connected, the system proactively switches the variable capacity motor to low-speed state in advance, ensuring high torque availability during engine start. This preliminary action prevents engine stall due to overload while maintaining the high work efficiency enabled by the small change gear ratio setting.
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 configuration enables smooth travel even under large loads by providing high torque and stabilizing vehicle speed during low-speed operations, reduces the need for additional operation tools, and maintains constant gear ratio stability, enhancing work accuracy and operability.
Implementation Method 1
a hydrostatic continuously variable transmission device, the variable capacity pump and the variable capacity motor
Data Source
AI summary
A speed change system for work vehicle having a continuously variable transmission device selects a first change gear ratio which is set larger than a smallest change gear ratio, when an engine rotational speed is a first set rotational speed which is set equal or close to an idling rotational speed of an engine; retains the change gear ratio of the continuously variable transmission device at the smallest change gear ratio, when the engine rotational speed is equal to or above a second set rotational speed set on a high-speed side relative to the first set rotational speed; and makes the change gear ratio of the continuously variable transmission device larger between the first change gear ratio and the smallest change gear ratio, as the engine rotational speed at that moment becomes lower, when the engine rotational speed is between the first and second set rotational speeds.