Hydraulic Control Device for Automatic Transmission Fail-Safe Shift
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Solution Overview
Problem
Existing hydraulic control devices for automatic transmissions face challenges in compactness and cost reduction while maintaining functionality during a solenoid-all-off state, which can occur due to electrical failures, leading to inefficient shift control and increased complexity.
Innovation Solution
A hydraulic control device with a simplified structure using two main valves - a preliminary shift speed switching valve and a hydraulic pressure supply switching valve - that allows for switching between low and high speed settings based on the engaged state of friction engagement elements, ensuring continuous operation even without electrical pressure regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three valves (fail-safe shift valve, high shift speed storage shift valve, high shift speed cancel shift valve) and complicated oil passage structure are used to achieve limp-home function, then reliability is improved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
The patent combines the functions of multiple valves into a single fail-safe shift valve. This single valve integrates the capabilities previously requiring separate storage, cancellation, and shifting valves, thereby reducing the total number of components while maintaining the limp-home function reliability.
Solution Approach 2:
The fail-safe shift valve is designed to perform multiple functions: it can store high shift speed states, cancel stored states, and execute shift operations. This multi-functional design eliminates the need for dedicated separate valves for each function, reducing device complexity while preserving reliability.
2Reliability
If three valves and complicated oil passage structure are used to achieve limp-home function, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
By merging multiple valve functions into a single fail-safe shift valve, the patent reduces the number of parts that need to be manufactured, assembled, and quality-checked. This consolidation directly lowers manufacturing costs while maintaining the required reliability for limp-home operation.
Solution Approach 2:
The patent extracts and eliminates unnecessary valves and complex oil passage structures from the system, keeping only the essential fail-safe shift valve that performs all required functions. This simplification reduces manufacturing complexity and cost.
3Reliability
If multiple valves are used for fail-safe operation, then reliability during solenoid-all-off state is improved, but compactness deteriorates
Solution Approach 1:
The patent merges multiple valve functions into a single compact fail-safe shift valve, significantly reducing the volume occupied by the hydraulic control device while maintaining fail-safe operation reliability during solenoid-all-off states.
4Reliability
If three valves are used to achieve shift speed switching, then reliability during electrical failure is improved, but device complexity increases
Solution Approach 1:
The patent combines the shift control functions that previously required three separate valves into a single integrated fail-safe shift valve, reducing device complexity while maintaining reliable shift control during electrical failures.
Solution Approach 2:
The fail-safe shift valve is designed as a universal component that can handle all shift speed switching operations and store/cancel high shift speed states, eliminating the need for multiple specialized valves and simplifying the overall valve structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables compactness and cost reduction by achieving low or high speed shifts based on pre-failure settings, ensuring continuous vehicle operation and limp-home functionality during solenoid-all-off failures with a reduced number of valves and complex components.
Implementation Method 1
a third solenoid valve (SLC3) capable of supplying a third operating hydraulic pressure (P SLC3 ) to a hydraulic servo (43) of a third friction engagement element (C-3)
Implementation Method 2
a preliminary shift speed switching valve (21, 121) capable of switching to a low speed side position (right half position of FIG. 4 and FIG. 5) to output a first preliminary hydraulic pressure (P DC1 ) for the hydraulic servo (41) of the first friction engagement element (C-1) and a high speed side position (left half position of FIG. 4 and FIG. 5) to output a second preliminary hydraulic pressure (P DC2 ) for the hydraulic servo (42) of the second friction engagement element (C-2)
Implementation Method 3
a hydraulic pressure supply switching valve (22, 122) capable of switching to a normal position (left half position of FIG. 4 and FIG. 5) capable of supplying the first and second operating hydraulic pressures (P SLC1 , P SLC2 ) to the hydraulic servos (41, 42) of the first and second friction engagement elements (C-1, C-2), respectively, and a failure position (right half position of FIG. 4 and FIG. 5) capable of supplying the first and second preliminary hydraulic pressures (P DC1 , P DC2 ) to the hydraulic servos (41, 42) of the first and second friction engagement elements (C-1, C-2), respectively
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A linear solenoid valve SLC3 is formed by a normal open type, and even when non-energizing occurs, the engaging pressure of a clutch C-3 is output. A first clutch apply relay valve 121 outputs a first preliminary hydraulic pressure in forward first to third speeds based on the engaging pressure of a clutch C-2, and outputs a second preliminary hydraulic pressure in forward fourth to sixth speeds. Then, during normal operation, a second clutch apply relay valve 122 supplies controlled pressure of linear solenoid valves SLC1, SLC2 to hydraulic servos 41, 42, respectively, while it supplies a first preliminary pressure PDC1 or second preliminary hydraulic pressure PDC2 to the hydraulic servos 41, 42 at all-off failure, thereby engaging a clutch C-1 or the clutch C-2 and achieving the forward third speed or forward fifth speed. In other words, while a low speed or high speed can be provided at all-off failure, compactness and cost reduction can be achieved.