Automatic Transmission Shift Control Engine Speed Feedback
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Solution Overview
Problem
Conventional shift control systems for automatic vehicle transmissions experience significant drops in driving force and shocks during clutch-to-clutch upshifting due to variations in engine torque and torque transmitting capacity, as they rely on constant torque compensating rates determined by experimentation, which fail to accurately reflect current conditions and do not effectively reduce drive force fluctuations.
Innovation Solution
A shift control system that includes a controller managing the first and second frictional engagement devices and engine torque, reducing the torque transmitting capacity of the first device while increasing the second's, setting a target engine speed, and executing feedback control to maintain engine speed, using equations of motion to calculate and correct engine torque and torque transmitting capacities to prevent drive torque drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant torque compensating rate determined by experimentation is used, then the control system is simple to implement, but the torque cannot be controlled accurately taking account of variations in engine torque and clutch torque transmitting capacity
Solution Approach 1:
The patent applies dynamics by making the torque compensating rate variable rather than constant. The control device dynamically adjusts the torque compensating rate based on real-time operating conditions including engine torque variations and clutch torque transmitting capacity changes. This is achieved through continuous monitoring of engine speed, clutch slip speed, and torque values, then modifying the compensating rate accordingly to maintain accurate torque control throughout the shifting process.
Solution Approach 2:
The patent implements feedback control by continuously measuring actual engine speed and clutch slip speed during the shifting operation, comparing these values against target values, and using the deviations to adjust the torque compensating rate. The control device receives feedback signals from sensors monitoring engine parameters and clutch engagement state, then modifies the torque compensation in real-time to achieve accurate torque control despite variations in engine and clutch characteristics.
2Adaptability or versatility
If the torque compensating rate is reduced before learning the timing of torque compensation sufficiently, then the learning control can progress, but the torque may not be controlled accurately and drop in drive force and shocks may not be reduced sufficiently
Solution Approach 1:
The patent applies preliminary action by performing torque compensation from the very beginning of the clutch-to-clutch shifting operation, rather than waiting for learning to be complete. The control device initiates torque compensation immediately when shifting starts, using initial parameter values, and simultaneously progresses the learning control in parallel. This allows torque control to be effective throughout the entire shifting process while still accumulating learning data.
Solution Approach 2:
The patent maintains continuous torque compensation throughout the shifting operation and learning process. The torque compensating rate is continuously adjusted based on real-time conditions rather than being reduced or interrupted during learning. This ensures uninterrupted torque control and prevents drive force drops and shocks while the learning control continuously refines the torque compensation parameters based on accumulated data.
3Measurement precision
If feedback control of engine speed is executed to maintain engine speed to synchronous engine speed, then engine speed control is achieved, but drive torque drops and shocks during upshifting cannot be prevented
Solution Approach 1:
The patent applies preliminary action by increasing engine torque before the actual clutch engagement in the torque phase. The control device detects the commencement of the torque phase (when clutch slip speed becomes small) and immediately increases engine torque above the value required for synchronous speed maintenance. This preliminary torque increase prepares the engine to compensate for the upcoming drive torque drop when the clutch engages, preventing shocks while maintaining engine speed control.
Solution Approach 2:
The patent implements preliminary anti-action by counteracting the anticipated drive torque drop before it occurs. The control device predicts the torque drop that will happen during clutch engagement and applies compensatory torque increase in advance. By increasing engine torque above the synchronous speed requirement just before clutch engagement, the system creates a reserve torque that offsets the harmful torque drop, preventing shocks to the drivetrain.
Data Source
AI summary
A shift control system that reduces drop in driving force and shocks during execution of clutch-to-clutch upshifting is provided. The control system is configured to reduce a torque transmitting capacity of a first clutch at a predetermined rate while increasing a torque transmitting capacity of a second clutch with a reduction in the torque transmitting capacity of the first clutch during execution of the upshifting, to set a target speed of the engine to a level determined by adding a predetermined speed to a synchronous engine speed corresponding to a low speed stage, during a torque phase in which the torque transmitting capacity of the first clutch is being reduced and the torque transmitting capacity of the second clutch is being increased, and to execute a feedback control of an engine torque in such a manner as to maintain the engine speed to the target speed based on a difference between the target speed and an actual engine speed.