Non-Rotating Armature Locking Differential
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electronically actuated locking differentials face challenges in sensing the locked state due to rotating armatures, leading to increased costs and wear, and they are not capable of independently locking right-hand and left-hand axles independent of driveline rotation or vehicle direction.
Innovation Solution
An electronically actuated locking differential with a non-rotating stator and armature, where the armature is mechanically coupled to a lock plate, allowing for axial movement and using an electromagnetic coil to generate a locking force through a return spring, enabling easy lock detection and reducing parasitic losses and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a sensor is attached to a rotating armature to sense the locked state, then lock detection capability is improved, but cost increases due to non-contacting sensor requirements and wear and durability concerns arise
Solution Approach 1:
The patent replaces the mechanical sensing approach (attaching sensors to rotating armatures) with a magnetic field-based sensing system. The stator contains magnets that generate a magnetic field, and a sensor on the stationary housing detects changes in this field as the armature moves between locked and unlocked positions. This substitution eliminates the need for physical contact between sensing components, thereby improving reliability while maintaining lock detection capability.
2Productivity
If the armature is allowed to rotate with the differential, then the differential can function properly, but parasitic losses occur due to friction between the armature and stator
Solution Approach 1:
The patent inverts the traditional arrangement by making the stator rotate with the differential instead of the armature. The stator is mechanically coupled to the differential case, while the armature remains stationary and coupled to the locking mechanism. This inversion eliminates friction between rotating and stationary components, reducing parasitic losses while maintaining proper differential function.
3Productivity
If the armature rotates with the differential, then the differential operates correctly, but heat is generated due to friction between rotating components
Solution Approach 1:
The patent reverses the conventional design by having the stator rotate with the differential case while the armature remains stationary. This inversion minimizes friction between moving and stationary parts, thereby reducing heat generation. The magnetic coupling between the rotating stator magnets and stationary armature maintains operational effectiveness without the thermal penalties of traditional rotating armature designs.
4Difficulty of detecting and measuring
If a mechanical or electronic slip ring arrangement is used for contact sensors on a rotating armature, then sensing is possible, but runout and gap changes during rotation create reliability issues
Solution Approach 1:
The patent replaces mechanical slip ring arrangements with a magnetic field-based sensing system. The stator contains magnets that generate a magnetic field detectable by a sensor on the stationary housing. As the stator rotates with the differential, the magnetic field patterns change in a predictable manner that the sensor can detect, providing reliable lock state sensing without the runout and gap issues inherent in mechanical contact-based 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
The solution allows for independent locking of axles without driveline rotation, simplifies lock detection, reduces friction and heat, and eliminates concerns related to sensor attachment on rotating parts, enhancing durability and cost-effectiveness.
Implementation Method 1
When direct current (DC) power is supplied to the electromagnetic coil, magnetic energy is generated within the stator creating an attractive force between the armature and the stator
Implementation Method 2
a return spring disposed within the gear case and cooperating with the lock plate to bias the lock plate axially away from the one of the side gears
Data Source
Figure 1
Figure 2
AI summary
An electronically actuated locking differential for an automotive vehicle includes a gear case, a pair of side gears disposed within the gear case and operatively adapted for rotation with a corresponding pair of axle half shafts, and a lock plate disposed within the gear case and operably associated with one of the side gears and being movable axially relative to the one of the side gears. The electronically actuated locking differential also includes a return spring disposed within the gear case and cooperating with the lock plate to bias the lock plate axially away from one of the side gears and an electronic actuator cooperating with the lock plate, the electronic actuator having a non-rotating stator disposed about a portion of the gear case, an electromagnetic coil associated with the stator, and a non-rotating armature coupled to the lock plate and being axially movable relative to the stator.