Transmission Downshift Delay in Following Mode for Smoother Deceleration
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Solution Overview
Problem
In vehicles, significant changes in deceleration acceleration (deceleration G) due to transmission downshift during following mode can deteriorate drivability, especially when overtaking is restricted and the accelerator and brake are off.
Innovation Solution
Implementing a downshift delay process that adjusts the timing of transmission downshift to a lower vehicle speed side when overtaking is restricted and the accelerator and brake are off, and compensating for torque output by increasing engine torque when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission downshifts during deceleration in following mode, then the vehicle speed is reduced appropriately, but the rotational speed of the drive source changes significantly causing deterioration in drivability
Solution Approach 1:
The control device determines in advance whether the vehicle is in following mode with overtaking restriction before executing downshift. By preliminarily identifying the operational context, the system can adjust downshift timing to avoid large rotational speed changes of the drive source, thereby maintaining drivability while still achieving speed reduction.
Solution Approach 2:
The downshift timing is made dynamic based on real-time detection of vehicle operating conditions. The control device continuously monitors whether the vehicle is in following mode with overtaking restriction and adjusts the downshift execution timing accordingly, making the transmission control adaptive rather than fixed.
2Speed
If the transmission downshifts during deceleration, then the power transmission ratio is adjusted for lower speed, but the deceleration acceleration changes significantly affecting driver comfort
Solution Approach 1:
The control device preliminarily determines the downshift execution timing based on detected vehicle operating conditions before actually executing the downshift. This preliminary determination allows the system to avoid downshifting at moments when it would cause excessive deceleration acceleration changes, thereby reducing the harmful impact on driver comfort.
Solution Approach 2:
The system converts the potential harmful effect of downshift-induced deceleration changes into a beneficial outcome by using the downshift timing adjustment to smooth out deceleration profiles. By strategically delaying or advancing downshift execution, the system transforms what would be a disruptive event into a controlled deceleration process that maintains driver comfort.
3Ease of operation
If the downshift timing is delayed to suppress rotational speed changes, then drivability is improved, but the time to reach lower vehicle speed is extended
Solution Approach 1:
The downshift execution timing is dynamically adjusted based on real-time vehicle operating conditions rather than following a fixed schedule. The control device continuously evaluates whether the vehicle is in following mode with overtaking restriction and adapts the downshift timing accordingly, optimizing the balance between drivability and speed reduction efficiency.
Solution Approach 2:
The system changes the downshift execution timing parameter based on detected operating conditions. By adjusting this critical parameter, the system achieves suppression of rotational speed changes and improvement in drivability while accepting the necessary trade-off in time to reach lower vehicle speed.
Data Source
AI summary
The vehicle includes a drive source, a transmission that shifts power from the drive source and transmits the power to the drive wheels, and a control device that controls the drive source and the transmission. The control device executes a downshift delay process of changing the timing of the downshift of the transmission to the low vehicle speed side as compared with the case where the predetermined condition is not satisfied when the predetermined condition is not satisfied, when the subject vehicle is in the following mode that follows the forward vehicle, the overtaking with respect to the forward vehicle is restricted, and the predetermined condition of the accelerator off and the brake off is satisfied.