Variable Compression Ratio Actuator Fail-Safe Control
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Solution Overview
Problem
In variable compression ratio mechanisms for internal combustion engines, abrupt changes in torque occur when the electric actuator fails, leading to unintended changes in compression ratio.
Innovation Solution
A control device and method that prohibit changing the compression ratio to a higher ratio and stop current supply to the electric actuator if the drive current does not reduce by a predetermined value, ensuring fail-safe operation and preventing abrupt torque changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric actuator is stopped to protect it upon failure, then the electric actuator is protected, but the compression ratio changes to a minimum against the driver's will, resulting in abrupt torque changes
Solution Approach 1:
The control device changes the compression ratio parameter to a predetermined value (not necessarily minimum) when actuator failure is detected, rather than simply stopping the actuator. This parameter change is controlled to prevent abrupt torque changes while still protecting the actuator from further damage
Solution Approach 2:
The control device continuously monitors the drive current of the electric actuator and detects failures based on current characteristics. When a failure is detected, the control device provides feedback by prohibiting further compression ratio increases and stopping current supply, preventing additional harm while maintaining engine stability
2Object-generated harmful factors
If control of changing compression ratio to higher ratio is prohibited upon failure, then abrupt torque changes are prevented, but the electric actuator may still be damaged if current supply is not stopped
Solution Approach 1:
The control device is pre-programmed with failure detection logic that monitors drive current characteristics. When failure conditions are detected, the control device immediately prohibits compression ratio increases and stops current supply to the actuator, preventing both abrupt torque changes and further actuator damage through preliminary protective actions
Data Source
AI summary
A control device for an internal combustion engine including a variable compression ratio mechanism for changing a compression ratio by using an electric actuator prohibits control of changing the compression ratio to a higher compression ratio when a failure occurs in the variable compression ratio mechanism. Thereby, upon failure occurrence, the compression ratio of the variable compression ratio mechanism at the time of the failure occurrence is maintained or reduced to less than this compression ratio so as to protect the electric actuator and prevent abrupt changes in torque.