Linear Motor Rotor Positioning via Electromagnetic Locking
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Solution Overview
Problem
Hand-held power tools with air spring percussion mechanisms driven by linear motors face challenges in maintaining stable operation across various load ranges and transitioning between percussion and idle states, due to issues with rotor guidance and reversal point consistency, leading to unreliable performance under different operating conditions.
Innovation Solution
A hand-held power tool with a rotor movable along a percussion axis, driven by an air spring and connected to sensors and computing means via power electronics, where the rotor is electromagnetically pressed against a contact element to ensure consistent reversal points, and a mechanical lock-in mechanism is used to secure the rotor position, along with a ventilation system to control air spring pressure and idle stroke operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the rotor is constructed as a light structural component to be accelerated back and forth with little energy, then energy consumption is reduced, but the pressure peak substantially influences the movement of the driving piston and stable regulation becomes difficult
Solution Approach 1:
The patent replaces mechanical guidance mechanisms with an electromagnetic field-based solution. A holding coil generates a magnetic field that magnetically locks the rotor at the reversal point, eliminating the need for complex mechanical positive guidance while maintaining stable regulation despite the light construction of the driving piston.
Solution Approach 2:
The patent changes the operational parameters by using electromagnetic fields (magnetic holding force) instead of mechanical constraints. The holding coil creates a magnetic field that dynamically holds the rotor position, allowing the system to maintain stability while consuming less energy to accelerate the lightweight piston.
2Stability of the object's composition
If mechanical positive guidance of the driving piston is implemented, then stable regulation of rotor movement is achieved, but device complexity increases
Solution Approach 1:
The patent substitutes mechanical guidance with an electromagnetic holding system. The holding coil positioned at the reversal point creates a magnetic field that locks the rotor in place during the reversal phase, eliminating the need for mechanical guidance structures while maintaining stable and repeatable rotor movement.
Solution Approach 2:
The patent introduces an electromagnetic field as an intermediary between the rotor and the housing. The holding coil acts as a mediator that provides the necessary positional control and stability without requiring direct mechanical contact or guidance mechanisms, thereby simplifying the overall device structure.
3Reliability
If the rotor is held magnetically by a holding coil at a reference position, then the rotor position is stabilized, but additional holding coil components and control complexity are required
Solution Approach 1:
The patent merges the holding coil function with the existing stator structure of the linear motor. The holding coil is integrated into the stator assembly, sharing the same magnetic circuit and structural support, which reduces the number of separate components and simplifies the overall device complexity while maintaining reliable rotor position stabilization.
Solution Approach 2:
The holding coil serves multiple functions: it acts as both a positioning element for the rotor and an integral part of the motor's magnetic circuit. This multi-functionality reduces the need for separate components and simplifies the control system, as the holding coil can be activated in conjunction with the existing motor control infrastructure.
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
This solution provides a robust and reliable operation by ensuring consistent rotor positioning and controlled movement, maintaining stable percussion and efficiently transitioning between states, thereby enhancing the tool's performance under real-life conditions.
Implementation Method 1
an air spring (4) which is formed in such a way that the rotor (3) and the striking piston (5) are guided coaxially with low friction in a temporarily air-tight guide tube (28)
Implementation Method 2
a linear motor (2) with at least one field coil (10) and whose rotor (3), which is movable in a limited manner axially between two reversal points (W), drives a striking piston (5) via an air spring (4)
Implementation Method 3
Sensors (8) designed for determining the actual movement state l(x(t), v(t), a(t)) of the rotor (3) and of the striking piston (5)
Data Source
AI summary
A hand-held power tool (1) includes a linear motor (2) having a rotor (3) which is movable along a percussion axis (A) in an axially limited manner between two reversal points (W) and which can be driven by the striking piston (5) of the power tool with the intermediary of an air spring (4), sensors designed for determining the actual state of the rotor (3) and connected to a computer (9) connected via power electronics (33) to at least one field coil (10) of the linear motor (2), with the rotor (3) being displaced against a contact element (11a, 11b) at least at one reversal point (W) and being pressed against the contact element electromagnetically; and a control process for the hand-held power tool.