Electromagnetic Valve Switching Near Neutral for HST Gear Ratio Stability
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Solution Overview
Problem
The existing electromagnetic valve control systems for hydrostatic continuously variable transmissions in work vehicles face challenges in accurately and timely switching the valves, leading to inappropriate gear ratio control near the neutral position due to varying electric current values influenced by load, temperature, and engine revolutions, resulting in delayed swash plate tilt and unstable transmission operation.
Innovation Solution
An electromagnetic valve control device that includes a switching controller programmed to switch the first and second electromagnetic valves based on the current electric current value and gear ratio difference, using threshold values to determine timely and accurate valve switching, even if the electric current value has not reached the rising value, to ensure appropriate gear ratio adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If electromagnetic valves are switched based on a fixed rising electric current value, then the control system is simple, but the gear ratio control becomes inappropriate near the neutral position due to varying current values influenced by load, temperature, and engine revolutions
Solution Approach 1:
The control device predicts the rising electric current value before the electromagnetic valve is actually switched by adding a predetermined time lag to the current switching timing. This preliminary prediction compensates for the delay between switching the valve and the actual swash plate tilt, ensuring accurate gear ratio control near the neutral position without increasing overall system complexity.
Solution Approach 2:
The control device uses feedback from the actual gear ratio and swash plate position to adjust the predicted rising electric current value. By continuously monitoring the system state and comparing it with expected values, the control system refines its prediction of when the valve should switch, improving gear ratio control accuracy while maintaining a relatively simple control architecture.
2Ease of operation
If electromagnetic valve switching is delayed until the electric current reaches the rising value, then the control timing is simplified, but the swash plate tilt is delayed causing unstable transmission operation
Solution Approach 1:
The control device performs preliminary switching of the electromagnetic valve before the actual rising electric current value is reached. By calculating the predicted rising current value with a predetermined time lag added to the current switching timing, the system advances the valve switching action, eliminating the delay between valve switching and swash plate tilt while keeping the control logic relatively simple.
Solution Approach 2:
The control device dynamically adjusts the switching timing based on real-time system conditions including load, temperature, and engine revolutions. Instead of using a fixed switching point, the system continuously updates the predicted rising electric current value, allowing the valve switching timing to adapt to changing operating conditions and maintain stable transmission operation.
3Adaptability or versatility
If the electric current value varies due to load, temperature, and engine revolutions, then the system adapts to different operating conditions, but the gear ratio control becomes inaccurate near the neutral position
Solution Approach 1:
The control device uses feedback mechanisms to monitor actual system performance and adjust the predicted rising electric current value accordingly. By comparing the actual gear ratio and swash plate position with expected values, the system refines its predictions and compensates for variations caused by load, temperature, and engine revolutions, maintaining accurate gear ratio control while adapting to different operating conditions.
Solution Approach 2:
The control device changes the parameter of predicted rising electric current value based on operating conditions. Instead of using a fixed current threshold, the system adjusts this critical parameter dynamically according to load, temperature, and engine revolutions, allowing accurate gear ratio control to be maintained across varying operating conditions near the neutral position.
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 allows for precise and timely electromagnetic valve switching, improving the stability and accuracy of gear ratio control, reducing delays and instability in the continuously variable transmission, and ensuring appropriate input of control signals for stable vehicle operation.
Implementation Method 1
a first electromagnetic valve to control a pump swash plate on a normal rotation side of a neutral position and a second electromagnetic valve to control the pump swash plate on a reverse rotation side of the neutral position
Data Source
AI summary
An electromagnetic valve control device includes a current gear ratio obtainer to obtain a current gear ratio as a ratio of an output revolutions number of a driver and an output revolutions number of a transmission, a current electric current value obtainer to obtain a current electric current value as a value of an electric current to be inputted to a first electromagnetic valve or a second electromagnetic valve, and a switching controller to, based on the current electric current value and a gear ratio difference as a difference between a target gear ratio and the current gear ratio, perform electromagnetic valve switching control to switch between use of the first electromagnetic valve to control a pump swash plate and use of the second electromagnetic valve to control the pump swash plate.