Sub-CPU Alternative Control for Transmission Fail-Safe Stability
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Solution Overview
Problem
Conventional electronic control devices for vehicular automatic transmissions fail to maintain smooth operation when the main CPU encounters an abnormality, leading to sudden braking, deceleration, or acceleration, and gear shift shocks due to the transition to a fail-safe mode, as the sub-CPU lacks sufficient arithmetic capability to perform alternative control effectively.
Innovation Solution
An electronic control device configuration where the sub-CPU, with lower arithmetic capability, performs alternative control by maintaining or shifting gear positions using pre-stored actuator control information, allowing the vehicle to continue operating smoothly until the main CPU recovers, by managing gear shift operations and hydraulic pressure to prevent sudden changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sub-CPU performs alternative control when detecting main CPU abnormality, then the vehicle can maintain stable operation, but the sub-CPU's lower arithmetic capability limits the complexity of control that can be performed
Solution Approach 1:
The patent applies preliminary action by having the sub-CPU pre-acquire actuator control information (including drive signals and timing data) before the main CPU abnormality occurs. When the abnormality is detected, the sub-CPU can immediately execute the pre-acquired control information without needing to perform complex real-time calculations, thus maintaining vehicle operation stability despite its limited arithmetic capability.
2Reliability
If the gear is fixed at a specific position in fail-safe mode, then the transmission can operate reliably, but sudden gear shifts cause mechanical load and driver discomfort
Solution Approach 1:
The patent applies beforehand cushioning by having the sub-CPU execute pre-acquired actuator control information that includes smooth transition commands. Instead of forcing an immediate gear shift to the fail-safe position, the control information guides the transmission through gradual hydraulic pressure changes and timing-controlled solenoid activation, cushioning the transition to prevent sudden mechanical loads and driver discomfort.
3Productivity
If the sub-CPU resets the main CPU quickly upon detecting abnormality, then the system can recover, but the transition to fail-safe mode causes sudden gear shift shock
Solution Approach 1:
The patent applies continuity of useful action by having the sub-CPU continuously execute actuator control information acquired before the main CPU abnormality. This continuous control execution maintains smooth gear shift operations throughout the transition period, preventing gear shift shock even as the system prepares for and executes the fail-safe mode transition, while still enabling quick main CPU recovery through timely reset signals.
Data Source
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AI summary
The present invention addresses the problem of obtaining an electronic control device for a vehicular automatic transmission that suppresses sudden acceleration, sudden deceleration, and gear shift shock that occur when the transmission moves into a fail-safe mode due to the electronic control device stopping during a main CPU abnormality. An electronic control device 100 for a vehicular automatic transmission has: a main CPU 3 that performs gear shift control for the vehicular automatic transmission; and a sub-CPU 4 that detects abnormalities in the main CPU 3. When the sub-CPU 4 detects an abnormality in the main CPU 3 while the vehicle is traveling, the sub-CPU 4 stops the gear shift control executed by the main CPU 3. Next, when the control status of the vehicular automatic transmission is in a state of maintaining the gear position, the sub-PCU 4 continues the maintaining of the gear position; when the control status is in a state of changing the gear position, the sub-PCU 4 continues a gear shift operation for the gear position, and, instead of the main CPU 3, performs alternative control for maintaining the gear position after the gear position is changed. Subsequently, as a result of a stop in the traveling of the vehicle, the sub-PCU 4 finishes the alternative control and abnormally stops the electronic control of the automatic transmission.