Ferromagnetic Sleeve Protects Powder Metal Stator Core
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Solution Overview
Problem
Solenoid actuators with powder metal stator cores face issues of erosion and fragmentation due to weak particle bonds, leading to performance degradation and potential injector failure from liberated debris, and existing protective measures occupy valuable space that could carry magnetic flux.
Innovation Solution
A solenoid stator assembly with a ferromagnetic protective sleeve covering the powder metal stator core and flux ring, which is electrically isolated from the housing, prevents erosion and fragmentation while maintaining magnetic flux functionality, and a method of assembling this configuration to ensure the stator core is encapsulated and protected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a powder metal stator core is used to improve magnetic permeability, then magnetic performance is improved, but the weak bonds between particles lead to erosion and fragmentation
Solution Approach 1:
The patent uses a composite structure combining powder metal stator core with a ferromagnetic protective sleeve. The powder metal core provides superior magnetic permeability while the ferromagnetic sleeve provides structural strength and erosion resistance. This composite approach allows both materials to contribute their advantageous properties to the overall stator assembly.
Solution Approach 2:
The ferromagnetic protective sleeve acts as an intermediary layer between the powder metal core and the erosive fuel environment. This intermediate protective layer shields the fragile powder metal particles from direct exposure to high-velocity fuel flow, preventing erosion and particle liberation while maintaining the magnetic functionality of the core.
2Object-affected harmful factors
If a non-ferromagnetic plating is applied to protect the powder metal core, then erosion resistance is improved, but valuable space for magnetic flux is occupied
Solution Approach 1:
The patent changes the material parameter of the protective layer from non-ferromagnetic to ferromagnetic. This allows the protective sleeve to maintain ferromagnetic properties that enable magnetic flux penetration, thereby preventing the space occupation problem associated with non-ferromagnetic platings while still providing erosion protection.
Solution Approach 2:
The combination of powder metal core and ferromagnetic protective sleeve creates a composite structure where both layers are ferromagnetic. This ensures continuity of magnetic flux paths through the entire stator assembly, eliminating the magnetic flux obstruction that would occur with non-ferromagnetic protective coatings.
3Ease of manufacture
If the powder metal stator core is exposed in the air gap region, then assembly is simplified, but fuel erosion and particle liberation occur
Solution Approach 1:
The stator is segmented into two distinct components: the powder metal core and the ferromagnetic protective sleeve. This segmentation allows each component to be optimized for its specific function - the core for magnetic performance and the sleeve for erosion protection - while being assembled together to form the complete stator assembly.
Solution Approach 2:
The ferromagnetic protective sleeve serves as an intermediary barrier between the fuel environment and the powder metal core. It intercepts the erosive effects of high-velocity fuel flow before the fuel can directly impact and erode the powder metal particles, thereby preventing particle liberation and maintaining reliability.
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 effectively prevents fragmentation and erosion of the powder metal stator core, maintaining performance and preventing debris from entering critical areas, while allowing the ferromagnetic sleeve to contribute to magnetic flux without occupying valuable space.
Implementation Method 1
A ferromagnetic protective sleeve has a surface in contact with the inner end face and cylindrical wall of the stator core
Implementation Method 2
The solenoid coil is wound on a bobbin and positioned in the housing and surrounded by the stator core. A magnetic flux line around the coil passes through the stator core, the ferromagnetic protective sleeve and the flux ring
Data Source
AI summary
A solenoid actuator includes a stator assembly with a stator core of formed powder metal received in a stator housing. A ferromagnetic protective sleeve is in contact with and covers a majority of an inner end face and a cylindrical wall of the stator core, while a flux ring is in contact with and covers an outer end face of the stator core. An armature assembly includes an armature attached to a stem that is movable in an air gap relative to the ferromagnetic protective sleeve. A spring is operably positioned in the ferromagnetic protective sleeve but electrically isolated from the stator housing. The stator core is encapsulated to protect against erosion and fragmentation. A magnetic flux line around a solenoid coil passes through the stator core, the ferromagnetic protective sleeve, the armature, the flux ring and back to the stator core.