Directional Shift Control in Powershift Transmissions
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Solution Overview
Problem
High-speed directional shifts in vehicles with powershift transmissions can cause premature clutch failure due to excessive energy transmission, leading to heat generation and material durability issues, as existing control strategies either warn of potential damage or inhibit shifts, which may degrade vehicle control or require inconvenient stopping mechanisms.
Innovation Solution
A method and control system that determine if the current transmission output speed is below a predetermined threshold, allowing direction shifts to proceed, and inhibit shifts if above the threshold, executing sequential downshifts or engine speed reductions to slow the vehicle to a safe speed before allowing direction changes, thereby preventing transmission damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If high-speed directional shifts are allowed in powershift transmissions, then operator control and vehicle maneuverability are improved, but clutch durability and transmission reliability deteriorate due to excessive energy transmission and heat generation
Solution Approach 1:
The control system performs preliminary speed reduction actions before allowing the directional shift to occur. When a directional shift is requested at high speed, the system automatically executes sequential downshifts or engine speed reductions to slow the vehicle to a safe threshold speed before the clutch engagement, preventing excessive energy transmission and heat generation that would damage the clutch components
Solution Approach 2:
The control system continuously monitors vehicle speed and provides feedback to the shift control logic. When the vehicle speed exceeds the predetermined threshold during a directional shift request, the system uses this feedback information to inhibit the shift and instead execute speed reduction maneuvers, creating a closed-loop control that adapts to real-time operating conditions to protect the transmission system
2Reliability
If directional shifts are inhibited at high speeds to prevent transmission damage, then clutch durability is improved, but vehicle control and operator expectations deteriorate
Solution Approach 1:
The system converts the potentially harmful high-speed condition into a beneficial speed reduction opportunity. By detecting high-speed shift requests, the system automatically executes sequential downshifts that serve dual purposes: reducing vehicle speed to protect the transmission while also preparing the vehicle for the upcoming directional shift, thereby maintaining operational smoothness and control
Solution Approach 2:
The control system acts as an intermediary between the operator's shift request and the transmission's mechanical response. When a high-speed directional shift is requested, the system introduces intermediate speed reduction steps (through sequential downshifts or engine braking) that mediate between the operator's intent and the transmission's protective requirements, maintaining control while preventing damage
3Reliability
If sequential downshifts are executed to reduce vehicle speed before directional shifts, then transmission reliability is improved by preventing clutch damage, but shift time and operational efficiency worsen
Solution Approach 1:
The control system dynamically adjusts the speed reduction strategy based on real-time vehicle conditions. The system selects from multiple approaches (sequential downshifts, engine speed reduction, or brake application) and determines the optimal sequence and timing based on current speed, load, and operator inputs, allowing flexible adaptation that minimizes time loss while ensuring transmission protection
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 approach effectively prevents transmission damage during high-speed directional shifts by ensuring the vehicle slows to a safe speed before shifting, maintaining control and reducing the risk of clutch failure, while allowing smooth operation as per operator expectations.
Implementation Method 1
a large amount of energy may be transmitted to the clutch plates, being converted from kinetic energy to heat energy due to friction
Data Source
AI summary
The present disclosure relates to a method of controlling gear selection in a transmission of a vehicle in response to a directional shift requested by an operator and to a control system for controlling gear selection to manage directional shifts in vehicles, from a first direct to a second direction (e.g. forward to reverse). The method compares the current transmission output speed with a predetermined direction shift threshold transmission output speed. If the current transmission output speed is less than or equal to the predetermined direction shift threshold transmission output speed, the transmission is caused to execute a direction shift from the initial first direction gear to the same second direction gear, or a next highest second direction gear if there is no second direction gear which corresponds to the initial first direction gear. If the current transmission output speed is greater than the predetermined direction shift threshold transmission output speed, the direction shift is inhibited until the current transmission output speed slows to less than or equal to the predetermined direction shift threshold transmission output speed.