Automatic Transmission Control for Downhill Shift Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional automatic transmission control systems often experience delays or unintended downshifts on downhill roads, leading to poor drivability due to the reliance on shift maps and inadequate detection of road slope and driver intent.
Innovation Solution
A control apparatus that includes operational condition detection, slope detection, acceleration/deceleration calculation, and brake detection to dynamically adjust gear positions based on deceleration characteristics, allowing for smooth shifts according to the driver's intention by using a deceleration shift characteristic and limiting excessive deceleration, thereby reducing unexpected shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a downshift vehicle speed is changed by changing the shift map to a shift map for a downhill road, then the transmission can adapt to downhill conditions, but downshift occurs with delay from brake operation or multiple steps of downshift occur against driver's intention
Solution Approach 1:
The control apparatus preliminarily determines that the vehicle is running on a downhill road by comparing expected acceleration (from engine output) with actual acceleration before the brake operation occurs. This preliminary determination allows the system to prepare the appropriate shift map in advance, so when brake operation is detected, the correct downshift can be executed immediately without delay or multiple unintended steps.
2Adaptability or versatility
If multiple shift maps are prepared for different road conditions, then the transmission can provide various shift characteristics, but the device complexity increases
Solution Approach 1:
Instead of preparing completely separate shift maps for all possible conditions, the invention applies local quality by using a base shift map and making localized adjustments specifically for downhill conditions. The control apparatus determines downhill running by comparing accelerations and then applies specific modifications to the shift characteristics only when needed, rather than maintaining entirely separate shift maps for every scenario.
3Adaptability or versatility
If downshift vehicle speed is adjusted for downhill roads, then downhill driving can be improved, but unexpected downshift and upshift frequency increases
Solution Approach 1:
The control apparatus continuously monitors brake operation status and vehicle acceleration to determine when the vehicle is running on a downhill road. This feedback mechanism ensures that the modified shift characteristics are applied only when actually needed (during downhill brake operations) and not during normal driving conditions, thereby preventing unexpected downshifts and upshifts while maintaining reliable shift stability.
Data Source
AI summary
A control apparatus for an automatic transmission includes an operational condition detecting unit for detecting a vehicle operational condition, a slope detecting unit for detecting a road surface slope, and a shift characteristic selecting unit for selecting one of a plurality of shift maps preliminarily set according to the road surface slope. The control apparatus further includes an acceleration/deceleration calculating unit for calculating an acceleration or deceleration from the degree of increase or decrease in vehicle speed per unit time, a deceleration shift characteristic for deciding a gear position according to the deceleration and the vehicle speed, and a brake detecting unit for detecting a brake operation. When the road surface slope is determined to be a downhill slope and the brake operation is detected, the selected shift map is changed to the deceleration shift characteristic and the gear position is decided according to the deceleration shift characteristic.