Automatic Transmission Control Device for Shock Reduction
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Solution Overview
Problem
Automatic transmissions experience shocks during range switching due to abrupt changes in fluid pressure when the hydraulic circuit is switched back to the D range before the fluid pressure on the friction engagement element has fully decreased.
Innovation Solution
A control device with a manual valve and fluid-pressure control valve, including a controller that determines if the fluid pressure has fully decreased and delays the hydraulic circuit switching if not, preventing abrupt pressure rises by ensuring the fluid pressure is fully decreased before switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hydraulic circuit is switched back to the D range immediately after switching to the N range, then the range switching response is fast, but the fluid pressure on the friction engagement element has not fully decreased causing a shock in the automatic transmission
Solution Approach 1:
The control device determines whether the fluid pressure has fully decreased before switching the hydraulic circuit back to the D range. This preliminary check ensures that the friction engagement element is fully released before re-engagement, preventing shock while maintaining efficient range switching response.
2Speed
If the fluid pressure control is started before the fluid pressure fully decreases, then the control response is fast, but the fluid pressure rises steeply and abruptly causing a shock
Solution Approach 1:
The control device uses feedback from the decreased fluid-pressure determiner to monitor the actual fluid pressure state on the friction engagement element. Based on this feedback, the controller decides whether to delay the hydraulic circuit switching, ensuring that fluid pressure control starts only when appropriate, thus preventing abrupt pressure rises while maintaining responsive control.
Data Source
AI summary
A control device for controlling an automatic transmission determines whether a fluid pressure of the operation fluid acting on a friction engagement element that is switched from a released-state to an engaged-state is in a fully-decreased state. If determined that the fluid pressure is not in a fully-decreased state, control of a manual valve is delayed. In such manner, the hydraulic circuit is switched by the manual valve after the full decrease of the fluid pressure of the operation fluid acting on the just-engaged friction engagement element. As a result, an abrupt rise of the fluid pressure is prevented and a shock in the automatic transmission is reduced.