Automatic Transmission Jump-Down Shift Pre-Engagement Control
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Solution Overview
Problem
In automatic transmissions, jump-down shifting operations often result in significant rotation speed changes of the input shaft, leading to shifting shocks due to large differences in rotation speeds between engaged elements, which can prolong shifting times and require complex control of multiple engaging elements.
Innovation Solution
A control device for automatic transmissions that executes a pre-engaging process to reduce rotation speed differences between engaging elements before establishing an intermediate gear position during jump-down shifting, allowing for earlier initiation of the intermediate gear position while minimizing shifting shocks and reducing the number of elements to be controlled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the engaging elements are gradually engaged to reduce rotation speed difference, then shifting shock is suppressed, but the shifting time required for establishing the intermediate gear position becomes long
Solution Approach 1:
The control device executes a pre-engaging process that generates torque capacity in the speed difference reducing element before the intermediate gear position is established. This preliminary action reduces the rotation speed difference between rotating bodies in advance, allowing the engaging elements to be engaged more quickly without causing excessive shifting shock.
Solution Approach 2:
The control device applies counter-action in advance by generating torque capacity in the speed difference reducing element before the engaging elements are fully engaged. This preliminary anti-action offsets the potential harmful effect of rotation speed difference, enabling faster engagement while suppressing shifting shock.
2Reliability
If multiple engaging elements are controlled to establish the intermediate gear position, then the gear position can be established accurately, but the control complexity increases
Solution Approach 1:
The control device identifies and extracts the speed difference reducing element from the set of engaging elements. By focusing control on this specific element that can reduce rotation speed difference, the control complexity is reduced while maintaining reliable gear position establishment.
Solution Approach 2:
The control device applies different control strategies to different engaging elements. The speed difference reducing element is given special attention with a pre-engaging process, while other engaging elements follow standard engagement procedures. This localized quality approach simplifies overall control while ensuring accurate gear position establishment.
Data Source
AI summary
A control device executes, when a jump-down shifting is executed, shifting control in which, after engaging elements establishing a pre-shifting gear position are released, an intermediate gear position that is a gear position between the pre-shifting gear position and a post-shifting gear position is established, and after the intermediate gear position is established, the post-shifting gear position is established. When an engaging element able to reduce a rotation speed difference between two rotating bodies connected by engaging elements establishing the intermediate gear position is regarded as a speed difference reducing element, the control device executes a pre-engaging process for generating a torque capacity in the speed difference reducing element while the shifting control is being executed and before establishing the intermediate gear position.