HST Transmission Control for Responsive Low-High Gear Switching
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Solution Overview
Problem
Conventional transmission structures experience deteriorated vehicle speed responsiveness during gear switching due to the cancellation of HST load control when a traveling load is applied, leading to a mismatch between intended and actual vehicle speed.
Innovation Solution
A transmission structure that includes a control device which calculates an excess vehicle speed gear ratio by adding a correction value to the actual vehicle speed ratio, maintaining the HST actuator's control target value during an idling state to ensure smooth gear switching, and uses load correction values based on traveling load to improve responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If HST load control is canceled during gear switching, then gear switching can be executed, but vehicle speed responsiveness deteriorates and speed mismatch occurs
Solution Approach 1:
The control device maintains the HST load control during gear switching by using the load correction value calculated before switching as the basis for control after switching. This preliminary action ensures that the vehicle speed responsiveness is not deteriorated during the transition period, as the load correction value is continuously applied rather than canceled.
2Reliability
If HST load control is maintained during gear switching, then vehicle speed responsiveness is improved, but control complexity increases
Solution Approach 1:
The control device uses feedback from the vehicle speed sensor and HST sensor to continuously monitor the actual vehicle speed and HST output rotation speed. Based on this feedback, the control device calculates the load correction value and maintains the HST load control during gear switching, ensuring that the vehicle speed accuracy is maintained while the control complexity is managed through automated feedback loops.
3Productivity
If gear switching is executed under traveling load, then operational continuity is maintained, but speed mismatch between intended and actual vehicle speed occurs
Solution Approach 1:
The control device changes the control parameter by applying the load correction value to the reference HST gear ratio to obtain the target HST gear ratio. This parameter change allows the HST to adjust its output rotation speed in response to traveling load variations during gear switching, ensuring that the actual vehicle speed matches the intended vehicle speed while maintaining operational continuity.
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
Enhances vehicle speed responsiveness by ensuring accurate and rapid adjustment of gear ratios during switching, minimizing speed discrepancies and improving operational smoothness.
Implementation Method 1
a Hydro Static Transmission (HST) that operates in a cooperative manner with the low gear and high gear clutch mechanisms and is capable of continuously-variable gear shift of the rotational power
Data Source
AI summary
The problem is in providing a transmission structure which includes low gear and high gear transmission mechanisms and an HST and can improve the vehicle speed responsiveness at the time of switching between a low gear transmission state and a high gear transmission state. Solution: At the time of switching between low gear and high gear transmission states, the present invention creates an idling state in which the power transmission state from a drive source to a drive wheel is cut off, and calculates an excess vehicle speed HST gear ratio by adding an excess correction value, which is for changing the vehicle speed at the switching completion point in time in excess of the actual vehicle speed by a predetermined speed, to an actual vehicle speed ratio, which represents an HST gear ratio that causes the vehicle speed at the switching completion point in time to match the actual vehicle speed attained immediately before the completion of the switching, so as to operate an HST actuator using the excess vehicle speed HST gear ratio as a control target value during the idling state.