Moving Coil Electronic Locking Differential Actuation
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Solution Overview
Problem
Existing differential mechanisms for locking and unlocking side gears in differential assemblies rely on complex mechanisms like ball-and-ramp or cam-and-ramp systems, which are unreliable and require rotating coils that complicate power connection, limiting their operation in various vehicle configurations.
Innovation Solution
A moving coil electronic locking differential that uses an electromagnetic coil assembly to alternately engage and disengage the side gear relative to the differential case, utilizing a spring mechanism for reliable operation without brushes or slip rings, and beveled surfaces to manage air gaps and forces for efficient engagement and disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ball-and-ramp or cam-and-ramp mechanisms are used to actuate the locking member, then the differential can achieve locking and unlocking functionality, but the mechanism becomes unreliable and complex
Solution Approach 1:
The patent replaces the mechanical ball-and-ramp or cam-and-ramp actuation system with an electromagnetic coil assembly. The coil generates magnetic force to move the locking member axially, eliminating the need for complex mechanical ramps and balls. This substitution of electromagnetic actuation for mechanical actuation directly resolves the contradiction by improving reliability while reducing mechanism complexity.
2Device complexity
If the electromagnetic coil is made stationary to simplify power connection, then conventional electric connectors can be used, but the coil must be positioned outside the rotating differential case
Solution Approach 1:
The patent segments the electromagnetic actuation system into two parts: a stationary coil assembly fixed to the housing and a movable locking member attached to the rotating differential case. The coil remains stationary while the locking member rotates with the case, allowing conventional electric connectors to be used for the stationary coil while still achieving the locking function on the rotating component.
3Reliability
If the locking member is engaged to prevent side gear rotation, then wheel slip is prevented, but the mechanism must reliably disengage to allow normal differential operation
Solution Approach 1:
The patent uses periodic electromagnetic actuation to control the locking member. The coil is energized and de-energized in response to detected wheel slip conditions, creating periodic engagement and disengagement cycles. This periodic action allows the system to reliably lock when needed while easily disengaging to restore normal differential operation, resolving the contradiction between locking reliability and ease of operation control.
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 provides a reliable and uncomplicated mechanism for locking and unlocking side gears in differential assemblies, ensuring reliable operation across normal temperatures in various vehicle applications, including 4×4 and AWD vehicles, by using conventional electric connectors and minimizing the risk of inadvertent locking.
Implementation Method 1
An electromagnetic coil assembly is located adjacent the locking member and is operable to move the locking member into engagement with the side gear in response to an electrical input signal
Implementation Method 2
disengagement occurs upon deenergizing the coil by a spring
Data Source
AI summary
A differential mechanism for transmitting power from an input to an output includes a case containing a side gear, a locking member rotatably secured to the case and axially displaceable relative to the case. The locking member alternately engages the side gear to limit rotation of the side gear relative to the case, and disengages the side gear to permit rotation of the side gear relative to the case. An electromagnetic coil assembly is supported on the case for movement toward and away from the locking member. A first actuator including an electromagnetic coil is supported on the case for moving the locking member toward engagement with the side gear in response to energizing the coil. A second actuator urges the locking member away from engagement with the side gear.