Hydraulic Control Device Fail-Safe for Automatic Transmission
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Solution Overview
Problem
Existing hydraulic control devices for automatic transmissions, such as shift-by-wire-type automatic transmissions, often fail to output forward range pressure when one or both solenoid valves fail, leading to disabled forward traveling.
Innovation Solution
A hydraulic control device with a shift controller, first and second solenoid valves, and corresponding switching valves that can switch between positions to ensure forward range pressure output even in the event of solenoid valve failure, using a fail-safe mechanism to maintain forward traveling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional hydraulic control device uses two switching valves controlled by solenoid valves to switch travel ranges, then the device can achieve range switching functionality, but forward traveling becomes disabled when one or both solenoid valves fail
Solution Approach 1:
The patent applies beforehand cushioning by providing a fail-safe valve that can be activated in advance to supply lockup pressure as forward range pressure when solenoid valve failure is detected. This preparatory measure ensures that forward traveling capability is maintained even after failure, as the fail-safe mechanism is already in place to compensate for the lost function.
Solution Approach 2:
The patent uses an intermediary approach by introducing a fail-safe valve as a mediator between the solenoid valve failure and the forward range pressure output. This fail-safe valve acts as an intermediate component that can take over the function of supplying forward range pressure when the primary solenoid valves fail, thus maintaining system functionality.
2Reliability
If the first switching valve is configured to be self-held with output range pressure to maintain traveling state, then the traveling state can be maintained during off failure of the solenoid valve, but the first switching valve remains blocked after engine restart, disabling forward traveling
Solution Approach 1:
The patent applies taking out by extracting the self-holding function from the first switching valve and transferring it to the fail-safe valve. The fail-safe valve independently supplies forward range pressure using lockup pressure, removing the problematic self-holding mechanism that caused the blocking issue after engine restart.
Solution Approach 2:
The patent segments the pressure supply function by separating the normal operation path (through the first switching valve) from the fail-safe path (through the fail-safe valve). This segmentation allows the fail-safe valve to independently manage forward range pressure supply without being affected by the state of the first switching valve.
Data Source
AI summary
A hydraulic control device that includes a second switching valve that is switchable between a third position in which the forward range pressure input from the first switching valve is output to the shift controller and the reverse range pressure is blocked when the second signal pressure is off and a fourth position in which the reverse range pressure input from the first switching valve is output to the shift controller and the forward range pressure is blocked when the second signal pressure is on.