Automatic Transmission Sensor Fault Detection via Oil Pressure Comparison
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Solution Overview
Problem
Existing control apparatuses for automatic transmissions fail to accurately determine the operation state of hydraulic oil temperature sensors when a fault occurs, especially when the engine is steadily rotating at a predetermined speed, leading to potential undetected characteristic abnormalities.
Innovation Solution
A control apparatus that determines the operation state of the hydraulic oil temperature sensor by comparing the difference between hydraulic oil temperature and cooling water temperature, and further uses the operation state of the oil pressure sensor and engine rotation speed to assess the hydraulic oil temperature sensor's state, thereby avoiding faults without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only cooling water temperature and hydraulic oil temperature difference is used to determine sensor operation state, then the determination method is simple, but sensor faults cannot be detected when engine rotates at predetermined speed
Solution Approach 1:
The patent introduces oil pressure as an intermediary parameter to mediate between the temperature sensor readings and the actual hydraulic system state. By comparing oil pressure readings with expected values calculated from temperature and engine speed, the system can detect temperature sensor faults that would otherwise be undetectable when the engine operates at steady predetermined speeds.
Solution Approach 2:
The patent changes the determination parameters from solely temperature-based (hydraulic oil temperature and cooling water temperature difference) to a multi-parameter approach including oil pressure, engine rotation speed, and temperature. This parameter expansion enables reliable fault detection across all operating conditions, particularly when the engine rotates at predetermined speeds where temperature differential methods fail.
2Reliability
If additional sensors are added to detect sensor faults, then fault detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The system uses existing sensors (oil pressure sensor, temperature sensor, rotation speed sensor) to perform self-diagnosis of the temperature sensor's operational state. The control unit calculates expected oil pressure based on temperature and rotation speed, then compares this with actual oil pressure readings to detect temperature sensor faults, eliminating the need for dedicated fault detection sensors.
Solution Approach 2:
The existing oil pressure sensor serves dual functions: monitoring actual oil pressure for transmission control and detecting temperature sensor faults through comparative analysis. This multi-functionality approach allows the same sensor to contribute to both operational control and diagnostic capabilities without adding hardware.
3Productivity
If temperature difference method is used alone, then determination process is quick, but determination accuracy decreases under steady-state conditions
Solution Approach 1:
The patent applies a two-stage determination process: first using the quick temperature difference method for initial assessment, then applying the more comprehensive multi-parameter oil pressure-based determination when needed. This partial application of the more accurate (but slower) method maintains overall determination speed while improving accuracy in critical steady-state conditions.
Data Source
AI summary
A control apparatus of an automatic transmission connected to an internal combustion engine of a vehicle includes a determination unit configured to determine an operation state of a hydraulic oil temperature sensor based on comparison between a threshold and a difference between a hydraulic oil temperature of the automatic transmission and a cooling water temperature of the internal combustion engine. When the operation state of the hydraulic oil temperature sensor is determined as normal by the comparison with the threshold, the determination unit further determines the operation state of the hydraulic oil temperature sensor based on an operation state of an oil pressure sensor determined using the hydraulic oil temperature, an oil pressure of hydraulic oil, and a rotation speed.