Vehicle Door Checker Using Motor Cogging Torque for Stable Hold
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Solution Overview
Problem
Conventional mechanical door checkers add weight to vehicles and wear over time, while DC electric motors used for door opening and closing suffer from cogging effects that reduce efficiency and stability, leading to insufficient resistance to maintain door positions under external forces.
Innovation Solution
Enhancing the cogging effect of a DC permanent magnet motor by adding pairs of oppositely magnetized permanent magnets coaxially with the motor shaft, which increases the cogging torque and is multiplied by the gear train ratio, providing stable door check positions without significant size or weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DC electric motor is used for door opening and closing, then the door can be powered to open and close, but the cogging effect reduces efficiency and stability, leading to insufficient resistance to maintain door positions under external forces
Solution Approach 1:
The patent converts the harmful cogging effect into a beneficial force by adding permanent magnets to the rotor that create controlled magnetic resistance. This cogging torque is used intentionally to hold the door at discrete positions, transforming the previously problematic periodic slowing effect into a useful positioning mechanism that provides stability without additional mechanical components
Solution Approach 2:
The patent merges the door checking function with the motor itself by integrating permanent magnets directly into the rotor. This combines the motor's driving function with the position-holding function, eliminating the need for separate mechanical door checker components and reducing overall system complexity while improving reliability
2Reliability
If a larger motor with more mass is used to provide sufficient resistance to maintain door positions, then the door checking ability is improved, but the cost and weight increase significantly
Solution Approach 1:
Instead of using a larger motor to provide resistance, the patent utilizes the cogging effect created by permanent magnets on the rotor. This converts a previously harmful effect into a useful positioning force that provides sufficient resistance to maintain door positions without increasing motor size or weight
Solution Approach 2:
The patent changes the magnetic field parameters by adding permanent magnets with specific polarity arrangements to the rotor. This modifies the motor's torque characteristics to include controlled cogging torque that provides position-holding capability, achieving the desired reliability without changing the motor's physical size or weight
3Reliability
If mechanical door checkers are used to hold door positions, then discrete check positions are achieved, but weight is added to the vehicle and the components wear over time
Solution Approach 1:
The patent merges the door checking function with the motor by integrating permanent magnets directly into the rotor. This combination eliminates the need for separate mechanical door checker components, reducing weight while maintaining the ability to hold discrete door positions through controlled cogging torque
Solution Approach 2:
The patent replaces the mechanical friction-based door checking system with a magnetic field-based system. Instead of using mechanical components that engage through friction and wear, the patent uses the motor's own magnetic field and permanent magnets to create cogging torque that holds door positions, eliminating mechanical wear and reducing weight
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 enhanced cogging torque effectively maintains door positions with minimal additional weight or cost, allowing for virtually infinite door check positions within the desired range of motion, improving efficiency and reducing wear.
Implementation Method 1
DC electric motors used for door opening and closing suffer from cogging effects that reduce efficiency and stability
Implementation Method 2
the cogging torque is increased by the gear train ratio and efficiency. This produces a sufficient resistance to maintain the position of the door
Data Source
AI summary
A vehicle door checker integrated with a power drive unit for an automobile door includes a direct current permanent magnet electric motor subject to cogging torque. The electric motor includes a central shaft. The vehicle door checker also includes a cogging torque increase device that is mounted to the central shaft externally of the motor. The cogging torque increase device includes pairs of oppositely magnetized permanent magnets that are mounted coaxially in a stator and rotor respectively about the motor shaft. The stator magnets and the rotor magnets shift into and out of alignment with each other as the shaft is rotated such that the motor is held in multiple discrete stable positions that correspond to check positions of an automobile door.