Automatic Transmission Hydraulic Control Failure Site Identification

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Solution Overview

Problem

Current hydraulic control apparatuses for vehicular automatic transmissions fail to identify the site of failure when a failure occurs, leading to degraded controllability and increased repair times.

Innovation Solution

Incorporation of an engagement oil pressure state determination portion, a speed change stage non-establishment determination portion, and an identification portion that identifies the hydraulic friction engagement device with a bad engagement based on oil pressure states and rotation speed differences between input and output shafts, allowing for the identification of failure sites and adaptive shift control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If automatic transmission switches to a fixed low speed gear upon failure detection, then vehicle can be taken off again, but the site of failure cannot be identified

Engineering Contradiction:

Improvevehicle operability after failureVSAvoidfailure site identification

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent implements feedback mechanisms by detecting engagement oil pressure states of friction engagement devices and comparing actual speed change ratios with target values. This feedback enables identification of which specific friction engagement device has failed, rather than just detecting that a failure occurred. The system continuously monitors oil pressure in engagement circuits and uses this information to pinpoint the faulty component.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent segments the failure detection process into multiple independent detection circuits, each monitoring a specific friction engagement device. By dividing the transmission system into separate detectable units (each with its own oil pressure sensor and control logic), the system can identify which specific segment (friction engagement device) has failed, enabling precise localization of the problem.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If no failure identification system is implemented, then device complexity is low, but repair time increases due to undetermined failure site

Engineering Contradiction:

Improvecontrol system structureVSAvoidrepair time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The system performs self-diagnosis by automatically detecting and identifying failed friction engagement devices through oil pressure sensors and control unit analysis. This self-service capability eliminates the need for manual inspection and testing during repair, allowing mechanics to immediately know which component to replace, thereby significantly reducing repair time.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces manual failure detection methods with electronic sensing and computational analysis. Oil pressure sensors, speed sensors, and a microprocessor-based control unit automatically detect and diagnose failures, substituting mechanical inspection processes with electronic measurement and data analysis systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If engagement oil pressure is monitored for each friction engagement device, then failure site can be identified, but device complexity increases

Engineering Contradiction:

Improvefailure detection accuracyVSAvoidsensor and control system

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The control unit serves multiple functions: it controls normal shift operations, monitors engagement oil pressures, detects failures, and identifies specific failed components. By making the control unit multi-functional, the system avoids adding separate dedicated hardware for each function, thereby reducing overall device complexity while maintaining high measurement precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the oil pressure sensing function, speed detection function, and control logic into an integrated system. The control unit combines multiple sensing inputs (oil pressure, speed, position) and processes them together to achieve both normal operation and failure diagnosis, reducing the number of separate components needed.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7481734B2Hydraulic control apparatus and hydraulic control method of vehicular automatic transmission

Publication Date: 2009.01.27 TOYOTA JIDOSHA KK

AI summary

A hydraulic control apparatus of a vehicular automatic transmission has a plurality of hydraulic friction engagement devices that are selectively engaged and released to establish a plurality of forward speed change stages of different speed change ratios. The forward speed change stages are achieved through engagement of predetermined friction engagement devices, of the plurality of friction engagement devices. If it is determined that a predetermined speed change stage corresponding to a predetermined shift output is not established, the hydraulic control apparatus identifies a hydraulic friction engagement device having a bad engagement that is a cause of the non-establishment of the predetermined speed change stage, on the basis of the state of engagement oil pressure of the predetermined friction engagement device.