Range Switching Device Solving Valve Sticking with Single Solenoid
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Solution Overview
Problem
Conventional range switching devices using a shift-by-wire method face challenges in switching the parking device from a parking release state to a parking state when a valve sticks, and they are structurally difficult to downsize due to the use of two solenoid valves.
Innovation Solution
A range switching device with a solenoid valve that pressure-regulates the source pressure and a parking switching valve with a first spool and a second spool, where the second spool moves to the fourth position when the control pressure is stopped, preventing hydraulic pressure from being supplied to the parking device, allowing the device to be switched into a parking state even if the first spool sticks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two solenoid valves are used to operate the range switching device, then the parking device can be switched from parking release state to parking state even if a valve sticks, but the device becomes structurally complex and difficult to downsize
Solution Approach 1:
The patent combines two separate solenoid valves into a single integrated solenoid valve that controls both the first and second switching valves. This merging reduces the total number of components while maintaining the functional capability to switch the parking device reliably even when a valve sticks, thereby resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The single solenoid valve is designed to perform multiple functions by controlling both the first switching valve (which controls the first hydraulic circuit) and the second switching valve (which controls the second hydraulic circuit). This multi-functionality allows one component to replace two, reducing overall device complexity while maintaining switching reliability.
2Reliability
If a valve sticks in the position where parking release state is achieved, then the parking device cannot be switched to parking state in conventional designs, but the device structure becomes more complex to handle this failure mode
Solution Approach 1:
The patent implements a preliminary anti-action mechanism where the second switching valve is designed to override the first switching valve when a sticking occurs. The second switching valve can force the hydraulic circuit to drain even if the first switching valve remains stuck in the open position, preventing the parking device from remaining in the release state. This built-in fail-safe mechanism handles valve sticking without requiring additional complex components.
Solution Approach 2:
The second switching valve acts as an intermediary or backup mechanism that mediates between the solenoid valve control and the first switching valve. When the first switching valve sticks, the second switching valve serves as a mediator to force the hydraulic pressure to drain, ensuring the parking device can still be switched to the parking state without requiring complex additional failure detection and correction systems.
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
Enables the parking device to be switched into a parking state effectively even if the first spool sticks, while downsizing the device by using a single solenoid valve to stop the control pressure, thus addressing the sticking issue and reducing the device's size.
Implementation Method 1
a solenoid valve that pressure-regulates the source pressure to output a control pressure
Implementation Method 2
a biasing member that is disposed on one end side of the first spool and biases the first spool to the first position
Implementation Method 3
in a case in which the control pressure is input to the control port and is applied to the other end side of the first spool and the one end side of the second spool, the first spool is moved to reach the second position against biasing force of the biasing member
Implementation Method 4
the second spool is moved to reach the third position, so that the source pressure is supplied to the parking device through the second output port
Data Source
AI summary
A range switching device for switching supply and non-supply of a source pressure based on a hydraulic pressure from a hydraulic pressure generating source to a parking device, the parking device being switched into a parking release state while the source pressure is supplied thereto and being switched into a parking state while the source pressure is not supplied thereto.