Electromagnetic Injector Drive With Sensorless Armature Position Sensing
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Solution Overview
Problem
Current injection devices, both manual and auto-injectors, face challenges such as user discomfort due to injection force and button extension, potential for incomplete doses, and the need for improved drive units in drug delivery devices.
Innovation Solution
A drive unit comprising a stator with consecutively arranged coils and an axially movable armature with magnets and pole shoes, which functions as a linear actuator, allowing for precise determination of the armature's position using inductance differences, eliminating the need for additional sensors and enabling efficient drug delivery and dosage tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a spring or electric motor is used as a drive unit, then the injection can be automated, but the device complexity increases
Solution Approach 1:
The patent combines the drive function and position sensing function into a single integrated system. The coils serve dual purposes: generating electromagnetic force for driving the armature and sensing position through inductance variations. This eliminates the need for separate sensors and reduces overall device complexity while maintaining automation.
Solution Approach 2:
The electromagnetic drive unit performs multiple functions simultaneously: it provides the driving force for injection and acts as a position sensor through inductance measurement. This multi-functionality reduces the number of components needed and simplifies the overall device architecture.
2Measurement precision
If additional sensors are added for position determination, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The coils are designed to serve dual purposes: electromagnetic actuation and position sensing. By measuring inductance variations as the armature moves, the system achieves precise position determination without requiring separate sensors, thus maintaining measurement precision while reducing device complexity.
Solution Approach 2:
The drive unit itself provides the sensing function through its electromagnetic coils. The inductance of the coils naturally varies with armature position, allowing the system to sense position without external sensors. The system essentially senses its own state through the electrical characteristics of its drive components.
3Device complexity
If manual button pressing is used, then the device complexity is reduced, but the reliability of complete dose delivery decreases
Solution Approach 1:
The system continuously monitors armature position through inductance measurements and uses this feedback to control the injection process. The control unit can determine when the injection is complete based on position feedback, ensuring reliable dose delivery without requiring complex manual operation mechanisms.
Solution Approach 2:
The patent replaces manual mechanical button pressing with an electromagnetic drive system. This substitution eliminates the need for continuous user effort while providing automated control and monitoring of the injection process, thereby improving reliability without significantly increasing operational 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 drive unit provides a precise and efficient mechanism for drug delivery, reducing user discomfort and ensuring accurate dosing without the need for further sensors, enhancing the usability and reliability of drug delivery devices.
Implementation Method 1
a stator comprising a plurality of coils consecutively arranged in an axial direction, an armature axially movable within the stator, the armature comprising a number of magnets and pole shoes consecutively arranged in the axial direction
Implementation Method 2
a control unit is connected to the individual coils for determining their inductance, wherein the control unit is adapted to determine an axial position of the armature within the stator from the determined inductances
Data Source
AI summary
The disclosure relates to a drug delivery device having a drive unit includes a stator comprising a plurality of coils consecutively arranged in an axial direction, and an armature axially movable within the stator, the armature including a number of magnets and pole shoes consecutively arranged in the axial direction. A respective pole shoe is arranged between respectively neighbouring magnets. At least one axial end of the armature comprises a terminal pole shoe.