Hydraulic Control Device for Automatic Transmission Engagement
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Solution Overview
Problem
Conventional hydraulic control devices for automatic transmissions do not account for changes in engine speed during the engagement of the vehicle start-up engagement element, leading to excessive hydraulic pressure supply and engagement shocks due to the mismatch between the required torque and hydraulic pressure.
Innovation Solution
A hydraulic control device that calculates a target hydraulic pressure for the vehicle start-up engagement element based on the input torque of the automatic transmission and periodically corrects this target value according to changing transmission input torque, ensuring the hydraulic pressure reaches the corrected target value at engagement completion, thereby preventing engagement shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the hydraulic pressure increase rate is set based on engine speed at D range selection, then the engagement control is simplified, but engagement shock occurs when engine speed decreases during engagement
Solution Approach 1:
The patent applies dynamics by making the hydraulic pressure control adaptive rather than fixed. The control device continuously adjusts the hydraulic pressure increase rate based on real-time engine speed changes during engagement. This dynamic adjustment ensures that the pressure supply matches the actual engagement requirements, preventing engagement shock while maintaining smooth operation across varying engine speed conditions.
Solution Approach 2:
The patent implements feedback control by monitoring engine speed throughout the engagement process and using this information to adjust the hydraulic pressure supply. The control device compares the actual engine speed with the expected speed profile and modifies the pressure increase rate accordingly. This feedback mechanism eliminates engagement shock by ensuring the hydraulic pressure remains synchronized with the actual engagement state, even when engine speed deviates from initial predictions.
2Force
If engine idle speed is set lower in D range to prevent excessive creep force, then creep force control is improved, but engagement shock increases due to excessive hydraulic pressure supply
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the hydraulic pressure increase rate to match the reduced engine idle speed in D range. The control device detects the lower engine speed condition and automatically reduces the pressure supply rate accordingly. This dynamic adaptation maintains proper creep force control while preventing the excessive hydraulic pressure that would otherwise cause engagement shock under low-speed conditions.
Solution Approach 2:
The patent applies parameter changes by modifying the hydraulic pressure increase rate based on engine speed conditions. When engine idle speed is set lower in D range, the control device changes the pressure supply parameter (increase rate) to match the reduced speed. This parameter adjustment ensures that the hydraulic pressure remains appropriate for the current operating conditions, preventing engagement shock while maintaining the desired creep force characteristics.
3Temperature
If engine idle speed is set higher in N range under cold conditions to promote engine warm-up, then engine warm-up is improved, but engagement shock occurs due to greater engine speed decrease during shift
Solution Approach 1:
The patent applies dynamics by continuously monitoring engine speed during the engagement process and adjusting the hydraulic pressure supply in real-time. Under cold conditions with higher N range idle speed, the control device detects the larger speed decrease when shifting to D range and dynamically reduces the pressure increase rate. This dynamic adjustment prevents engagement shock caused by the greater speed differential, while allowing the engine to maintain higher idle speed for effective warm-up.
Solution Approach 2:
The patent implements feedback control that specifically addresses cold condition operations. The control device monitors engine speed throughout engagement and uses this feedback to adjust pressure supply. When cold conditions cause larger engine speed decreases, the feedback mechanism detects this and modifies the hydraulic pressure profile accordingly, preventing engagement shock while maintaining the beneficial high idle speed for engine warm-up during the engagement process.
Data Source
AI summary
There is provided a hydraulic control device for controlling a hydraulic pressure supplied to a vehicle start-up engagement element in an automatic transmission when a shift lever is moved from a non-drive range position to a drive range position. The hydraulic control device has a target pressure setting section that sets, based on an input torque of the automatic transmission, a target value of hydraulic pressure supplied to the vehicle start-up engagement element at the completion of engagement of the vehicle start-up engagement element and corrects the target value periodically based on the transmission input torque until the completion of engagement of the vehicle start-up engagement element and a hydraulic pressure control section that controls the hydraulic pressure in such a manner that the hydraulic pressure supplied to the vehicle start-up engagement element reaches the corrected target value at the completion of engagement of the vehicle start-up engagement element.