Vehicle Shift Control Device Torque Shock Suppression
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Solution Overview
Problem
Existing vehicle control devices experience torque shock due to the deviation in engagement pressure timing of the engagement-side engagement device during downshift control, especially when transitioning to a higher speed ratio, leading to variations in torque transmission to the wheels.
Innovation Solution
A control device that includes a shift control section which, when a target shift speed with a higher speed ratio is determined, transitions the release-side engagement device from a direct-coupled to a non-direct-coupled state and increases the rotation speed of the input member beyond the synchronized rotation speed before engaging the engagement-side device, thereby preventing torque shock by maintaining the input member's rotation speed higher than the synchronized speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engagement pressure of the engagement-side engagement device is increased quickly to transition to direct-coupled state, then the shifting speed is improved, but torque shock occurs due to timing deviation
Solution Approach 1:
The release-side engagement device is transitioned to non-direct-coupled state before the engagement-side engagement device is engaged. This preliminary action prepares the system by reducing the engagement pressure of the release-side device, allowing the input member rotation speed to increase smoothly before the engagement-side device takes over, thereby preventing torque shock during the shift transition.
Solution Approach 2:
The engagement pressure of the engagement-side engagement device is controlled dynamically based on the rotation speed difference between the input member and the synchronized rotation speed. When the rotation speed exceeds the synchronized rotation speed by a predetermined value, the engagement pressure is increased to transition to direct-coupled state, otherwise it is kept in non-direct-coupled state. This dynamic control prevents torque shock while maintaining shifting speed.
2Object-affected harmful factors
If the rotation speed of the input member is increased to synchronized rotation speed before engagement, then torque shock is reduced, but the control complexity increases
Solution Approach 1:
The shift control section continuously monitors the rotation speed of the input member and compares it with the synchronized rotation speed. Based on this feedback, the control section adjusts the engagement pressure of the engagement-side engagement device accordingly. When the rotation speed exceeds the synchronized rotation speed by a predetermined value, the engagement pressure is increased; otherwise, it is maintained in non-direct-coupled state. This feedback mechanism simplifies the control logic while effectively preventing torque shock.
3Speed
If the engagement-side engagement device is engaged immediately after downshift control starts, then the shifting speed is improved, but torque variations occur due to timing deviation
Solution Approach 1:
The release-side engagement device is transitioned to non-direct-coupled state before the engagement-side engagement device is engaged. This preliminary action allows the input member rotation speed to increase smoothly without the constraint of the release-side device, ensuring that when the engagement-side device is engaged, the rotation speed is already above the synchronized rotation speed, thereby maintaining torque stability.
Solution Approach 2:
The engagement pressure of the engagement-side engagement device is changed based on the rotation speed condition. When the rotation speed of the input member exceeds the synchronized rotation speed by a predetermined value, the engagement pressure is increased to transition to direct-coupled state; otherwise, it is kept in non-direct-coupled state. This parameter change ensures smooth torque transmission while maintaining shifting speed.
Data Source
AI summary
A control device configured to control a vehicle. When the required driving force is equal to or less than a control judgment value, the shift control section judges that an implementing condition of engagement limited downshift control is met, starts transition control to cause the release-side engagement device to transition to a non-direct-coupled engagement state and, after the release-side engagement device transitions to a non-direct-coupled engagement state, starts increasing rotation speed control to control rotation speed of the input member to be higher than synchronized rotation speed, starts differential rotation speed control to control the rotation speed to be higher than the synchronized rotation speed, and prohibits engagement of the engagement-side engagement device until it becomes higher than the synchronized rotation speed.