Locking Differential Armature Position Sensing by Inductance
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Solution Overview
Problem
Existing electronically actuated locking differentials face challenges in accurately sensing the locked state due to rotating armatures, which can increase costs and durability concerns from non-contacting sensors, and wear issues.
Innovation Solution
A position detection device is integrated with a locking differential, utilizing a secondary coil to determine the armature's position relative to a stator by measuring changes in inductance, with the secondary coil disposed radially within the primary coil's boundary, allowing for precise detection of locked and unlocked states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is attached to a rotating armature to sense the locked state, then the ability to electronically sense the differential state is improved, but the cost increases and wear and durability concerns arise
Solution Approach 1:
Instead of attaching the sensor to the rotating armature, the patent inverts the arrangement by placing the sensor on the stationary stator and using the rotating armature itself as the sensing element. The armature's magnetic properties change with position, providing sensor output without requiring a physical sensor on the rotating component, thereby eliminating wear and durability issues.
Solution Approach 2:
The armature serves a dual function: it acts as both the actuating component and the sensing element. As the armature rotates and its magnetic properties change with position, it automatically provides the sensing signal to the stationary sensor, eliminating the need for separate sensing mechanisms on rotating parts and reducing system complexity.
2Measurement precision
If a sensor is attached to a rotating armature to sense the locked state, then the ability to electronically sense the differential state is improved, but the cost increases due to non-contacting sensor requirements
Solution Approach 1:
The patent reverses the conventional sensor placement by positioning the sensor on the stationary stator rather than on the rotating armature. This inversion allows the use of simpler, less expensive sensors that do not need to withstand rotation, vibration, and centrifugal forces, thereby reducing manufacturing costs while maintaining sensing accuracy.
Solution Approach 2:
The patent extracts the sensing function from the rotating armature and places it on the stationary stator. This separation allows the sensor to be a simpler, more cost-effective component that does not need to be designed for rotating applications, reducing overall system cost while maintaining the ability to sense the differential state.
3Volume of moving object
If the secondary coil is disposed within the primary coil boundary, then the design compactness is improved, but the coil arrangement complexity increases
Solution Approach 1:
The patent implements a nested coil configuration where the secondary coil is positioned within the boundary of the primary coil. This nesting arrangement maximizes space utilization and creates a compact coil assembly. The concentric or radially offset arrangement of the coils within the same cylindrical space reduces the overall volume while maintaining electromagnetic functionality.
Solution Approach 2:
The patent resolves the complexity issue by transitioning from a planar to a radial dimension in coil arrangement. The secondary coil is positioned radially within the primary coil's outer diameter, with parallel but offset central axes. This three-dimensional spatial arrangement optimizes magnetic coupling and inductance detection while maintaining a compact footprint, effectively using vertical and radial spacing to reduce horizontal complexity.
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 accurate detection of the differential's locked state, reduces wear and maintenance costs, and minimizes parasitic losses by eliminating friction, providing real-time status updates to the driver.
Implementation Method 1
The secondary coil is configured to determine a change in inductance based on movement of the armature. The change in inductance is indicative of a change in position of the armature relative to the stator.
Data Source
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AI summary
A position detection device configured for use with a locking differential (10) is configured to determine a position of an armature (46) in relation to a stator (38). The stator has a primary coil (40). The armature moves relative to the stator between engaged and disengaged positions corresponding to the locking differential being in a locked and unlocked state. The position detection device includes a secondary coil (60) or a sensor (360) disposed proximate to the primary coil. The secondary coil or sensor is configured to determine a change in inductance based on movement of the armature. The change in inductance is indicative of a change in position of the armature relative to the stator.