Four-Pole Commutator Motor for Sensorless Position Detection
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Solution Overview
Problem
Two-pole commutator motors used in ripple counter methods have an unfavorable weight-to-power ratio and struggle with reliable position detection due to less pronounced current ripples, making them inefficient for sensorless operation.
Innovation Solution
A four-pole commutator motor design with brushes angled at 90° and an offset, featuring a contact surface radius matching or exceeding the commutator's radius, and brush guides without play, enhances current ripple amplitude and frequency, enabling precise sensorless position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two-pole commutator motors are used for sensorless operation, then the device complexity is reduced, but the measurement precision of position detection deteriorates due to less pronounced current ripples
Solution Approach 1:
The patent changes the number of poles from two to four, and adjusts the brush angle from the conventional 180° to approximately 90°, thereby changing the electrical parameters to generate more pronounced current ripples with better shape and time interval characteristics for reliable position detection
Solution Approach 2:
The patent uses an asymmetric brush angle of approximately 90° instead of the symmetric 180° arrangement, creating an optimized commutation pattern that enhances current ripple characteristics for better sensorless position detection
2Device complexity
If two-pole commutator motors are used, then the device complexity is reduced, but the power-to-weight ratio worsens
Solution Approach 1:
The patent transitions from a two-pole to a four-pole motor configuration, which fundamentally changes the motor's power density characteristics, enabling higher power output for the same weight or reduced weight for the same power level
3Ease of manufacture
If brushes are arranged at 180° angle in two-pole motors, then the ease of manufacture is improved, but the measurement precision deteriorates due to insufficient current ripple amplitude
Solution Approach 1:
The patent changes the brush angle parameter from 180° to approximately 90°, which fundamentally alters the commutation characteristics and current ripple generation, enabling reliable sensorless position detection while maintaining manufacturing feasibility
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 design achieves high performance with low weight, allowing for accurate and reliable sensorless position detection and speed regulation, suitable for vehicle component adjustments like seat and window regulators.
Implementation Method 1
The laminations are isolated from one another on the circumference of the commutator and are energized in succession via the brushes when the rotor rotates. In this way, each brush from one slat subsequently arrives at the insulated intermediate area or groove between two slats, contacting and short-circuiting the two adjacent slats at the same time, resulting in a change in the current signal read out by the controller.
Implementation Method 2
The construction of the commutator motor according to the invention as a four-pole motor enables high performance with low weight. Because the two brushes are designed in such a way that they short-circuit two adjacent lamellae at the same time, the characteristic of the current ripple, in particular the 'amplitude' of the current ripple, is improved.
Data Source
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AI summary
The invention relates to a DC commutator motor, in particular for an adjustment of a vehicle seat, wherein the commutator motor (1) comprises the following: anchor windings (5), a commutator (6) with laminates (7) distributed in a peripheral direction, two brushes (8) resting against the laminates (7) for supplying current to the anchor windings (5) and for receiving the ripple current signals (Ir) generated in the anchor windings (5), a motor shaft (4) and a set of magnets (3) for forming a four-pole magnetic field, wherein the anchor windings (5) and the commutator (6) are disposed on the motor shaft (4) as a rotatable rotor. According to the invention, both brushes (8) are always short-circuiting two adjacent laminates (7) simultaneously. Furthermore, a suitable brush arrangement can be selected.