Automatic Transmission Downshift Control for Cornering
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Solution Overview
Problem
Conventional automatic transmission downshift control during cornering is inefficient, requiring multiple manual operations and often failing to match the driver's intention for engine braking, especially in multi-staged transmissions where the ratio difference between speed stages is small, leading to time-consuming downshifts and insufficient control.
Innovation Solution
A transmission control device that automatically performs downshift control by detecting corners and predicting rolling amounts, determining necessary engine braking based on road data, and calculating required speed change stages considering both corner characteristics and inter-vehicle distance, allowing for seamless engine braking and maintaining a safe distance from the vehicle ahead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual downshift operation is performed through shift lever or paddle switch, then driver can control speed change stage, but multiple operations are required and it takes time especially from high speed stage
Solution Approach 1:
The system performs preliminary detection of corner ahead and pre-calculates the target speed change stage based on corner characteristics (rolling amount, necessary engine braking) before the driver completes manual operation. This allows the transmission to be ready to execute the optimal downshift without waiting for multiple manual inputs.
Solution Approach 2:
The system continuously monitors driver's manual operation status and feedbacks by comparing current speed change stage with target stage determined from corner detection. When driver operates shift lever or paddle switch, the system adjusts target stage selection to match driver's intention while still optimizing for corner conditions.
2Extent of automation
If corner detection and downshift control is performed according to conventional technology, then automatic downshift is achieved, but downshift control according to corner characteristics is insufficient and does not coincide with driver's intention
Solution Approach 1:
The system calculates two different target speed change stages: one based on corner characteristics (rolling amount, engine braking requirements) and another based on driver's manual operation intention. It then selects the appropriate target stage from these multiple options, ensuring both corner safety and driver intention are satisfied.
Solution Approach 2:
The transmission control device integrates multiple functions: corner detection, rolling amount prediction, engine braking calculation, driver operation detection, and target speed change stage determination. This multi-functional system handles both automatic corner-based downshift and manual driver-based downshift within a unified control framework.
3Productivity
If multi-staged transmission with small ratio difference between speed change stages is used, then transmission efficiency is improved, but downshift operation becomes more time consuming
Solution Approach 1:
The system pre-determines the target speed change stage based on corner detection and characteristics calculation before the actual downshift is needed. This eliminates the need for multiple sequential manual operations, as the transmission control is already prepared with the optimal target stage for the upcoming corner.
Solution Approach 2:
The system enables direct downshift to the target speed change stage determined from corner characteristics, skipping intermediate stages that would otherwise require multiple manual operations. This is achieved by calculating the optimal target stage in advance and executing a single controlled downshift rather than sequential stage changes.
Data Source
AI summary
A transmission controller includes: a corner detector that detects a corner; a predictor to predict a rolling amount based upon road data when the corner is detected and an accelerator opening degree is fully closed; a device to determine a first necessary engine braking amount in accordance with the rolling amount; a device to determine a first required speed change stage corresponding to the first necessary engine braking amount; a calculator to calculate a second necessary engine braking amount when the corner is detected and the accelerator opening degree is fully closed based upon a minimum required inter-vehicle distance with the vehicle ahead; a device to determine a second required speed change stage corresponding to the second engine braking amount; and a transmission controller to select, as a target speed change stage, either smaller one of the first or second required speed change stage, and then perform downshift control.