Automatic Transmission Control for Judder Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional automatic transmission control methods reduce engine driving force to prevent judder in frictional engagement elements, leading to driver discomfort and undesired reduction in driving force, especially during accelerator pedal increases.
Innovation Solution
A control apparatus and method that coordinate shifts between a continuously variable transmission mechanism and a stepped transmission mechanism, adjusting the shift speed of the continuously variable transmission to suppress through speed ratio variations and predictively reduce judder by modifying the inertia phase periods of both mechanisms during upshifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If engine driving force is reduced to prevent judder in frictional engagement elements, then judder prevention is improved, but driver comfort deteriorates due to undesired reduction in driving force
Solution Approach 1:
The control unit predicts judder occurrence based on accelerator opening increase before the shift is completed, and prepares to reduce shift speed of the continuously variable transmission mechanism in advance. This preliminary action allows the system to prevent judder while maintaining driving force, as the reduction in shift speed is executed only when necessary based on the prediction, rather than continuously reducing engine driving force.
Solution Approach 2:
The invention changes the parameter being controlled from engine driving force to shift speed of the continuously variable transmission mechanism. By adjusting the shift speed parameter instead of reducing engine torque, the system can suppress judder occurrence while maintaining the driving force that the driver requests through accelerator pedal operation.
2Reliability
If shift speed of continuously variable transmission mechanism is reduced to prevent judder, then judder prevention is improved, but through speed ratio variation increases
Solution Approach 1:
The control unit executes the shift speed reduction in advance, during the prediction period before judder actually occurs. By performing the speed reduction preliminarily based on accelerator opening increase detection, the system suppresses judder while completing the shift before the through speed ratio becomes unstable.
Solution Approach 2:
The invention dynamically adjusts the shift speed of the continuously variable transmission mechanism based on real-time accelerator opening conditions. The shift speed is reduced only when accelerator opening increases indicating potential judder, and maintained at normal levels otherwise, allowing the system to adapt to changing operating conditions and maintain through speed ratio stability when needed.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In a control apparatus for an automatic transmission including a continuously variable transmission mechanism continuously modifying speed ratio and a stepped transmission mechanism that is disposed on a downstream side of the continuously variable transmission mechanism and being switched between a plurality of gear positions by engaging and disengaging a plurality of frictional engagement elements, the control apparatus comprises a control unit that performs a coordinated shift by shifting the stepped transmission mechanism and simultaneously shifting the continuously variable transmission mechanism in an opposite direction to a shift direction of the stepped transmission mechanism in order to suppress variation in a through speed ratio, which is an overall speed ratio of the automatic transmission, when the stepped transmission mechanism is upshifted and the control unit predicts, on the basis of an increase in an accelerator opening, that judder will occur in the frictional engagement element during the upshift, the control unit reduces a shift speed of the continuously variable transmission mechanism while shudder is predicted to occur in the frictional engagement element in comparison with a shift speed of the continuously variable transmission mechanism during the coordinated shift, the coordinated shift being executed at an accelerator opening corresponding to the increased accelerator opening.