Overrunning Coupling Latching Mechanism for Low-Temperature Clutch Stability
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Solution Overview
Problem
One-way clutches in automatic transmissions can inadvertently change from their overrun position to locked position due to highly viscous hydraulic fluid at low ambient temperatures, leading to potential clutch failure.
Innovation Solution
An overrunning coupling and control assembly with a latching mechanism that includes a piston, actuator arm, and biasing members, where a control pressure signal changes the latching mechanism's condition from locked to unlocked, allowing the actuator arm to shift the control element between overrun and locked modes, preventing unintended mode changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a one-way clutch is used in automatic transmission, then the clutch can free-wheel in overrun mode, but the clutch may inadvertently change to locked mode at low temperatures due to highly viscous hydraulic fluid
Solution Approach 1:
A latching mechanism acts as an intermediary between the control element and the clutch members. The latching mechanism includes a latch member that can engage with a ratchet member to prevent inadvertent mode changes. The control element controls the latching mechanism, which in turn controls the engagement between clutch members, providing an intermediate control stage that prevents direct unwanted engagement caused by viscous fluid effects.
Solution Approach 2:
The latching mechanism is designed to preemptively prevent the harmful effect of viscous hydraulic fluid by mechanically blocking the transition to locked mode before it can occur inadvertently. The latch member engages with the ratchet member to create a mechanical barrier that counteracts the force transmitted through the viscous fluid, ensuring the clutch remains in the intended overrun mode until deliberately switched.
2Reliability
If a latching mechanism is added to prevent inadvertent mode changes, then the clutch mode stability is improved, but the device complexity increases
Solution Approach 1:
The latching mechanism is merged with the existing control element structure. The control element is designed to simultaneously control the clutch members and the latching mechanism, combining multiple functions into a single integrated component. This reduces the number of separate parts and simplifies the overall assembly while maintaining the reliability benefits of the latching mechanism.
Solution Approach 2:
The control element is designed with multi-functionality, serving both to control the engagement between clutch members and to operate the latching mechanism. This universal component approach reduces device complexity by eliminating the need for separate control mechanisms for each function, while still providing the desired clutch mode stability through the latching feature.
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
Prevents inadvertent mode changes of the one-way clutch, ensuring reliable operation even at low temperatures by maintaining the clutch in its intended mode until a control pressure is applied, thus preventing failure.
Implementation Method 1
The control pressure signal causes the piston to slide within the bore against the biasing force of the at least one biasing member
Implementation Method 2
at least one biasing member disposed within the bore of the housing to exert a biasing force on the piston
Implementation Method 3
The unlocked actuator arm moves along the first direction within the slot and the control element moves along the shift direction to the second position
Data Source
AI summary
Overrunning coupling and control assemblies, each of which includes control apparatus having a latching mechanism are provided. Each latching mechanism prevents an actuator arm of an overrunning coupling assembly from moving in a first direction substantially parallel to a shift direction of a control plate of the coupling assembly within a housing slot in a locked condition of the mechanism in a first position of the control plate. A control pressure signal within a bore of the housing changes the condition of the latching mechanism from locked to unlocked to unlock the actuator arm and causes the unlocked actuator arm to move along the first direction within the slot and the control element to move along the shift direction to a second position. The control pressure signal also causes a piston which has a groove formed in its outer surface to receive and retain a free end portion of the actuator arm to slide within the bore in the housing against the biasing force of the at least one biasing member. In the absence of a control pressure signal, the at least one biasing member moves the piston and thereby the unlocked actuator arm in a second direction opposite the first direction within the slot and the control element along the shift direction from the second position back to the first position and changes the condition of the latching mechanism from unlocked to locked to lock the actuator arm.