Door Drive Unit Regulating Closing Speed via Motor Back-EMF
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Solution Overview
Problem
Conventional door closers often set the end stop too strongly to ensure reliable latch engagement, leading to loud noises and potential failure in closing the door due to external influences like friction and temperature changes, causing the door to hit the frame with either too much or too little speed.
Innovation Solution
A control module is introduced to regulate the electric motor's counter-EMF, intermittently short-circuiting or adjusting the motor's back EMF via pulse-width modulation to maintain a target closing speed, ensuring the door leaf hits the frame at a consistent, low final impact speed for reliable latch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the end stop is set too strongly to ensure reliable latch engagement, then the latch engagement reliability is improved, but the noise level increases and the door may bounce off the frame
Solution Approach 1:
The control module continuously monitors the actual closing speed of the door leaf and compares it to the target closing speed. Based on this feedback, the control module dynamically adjusts the damping force of the electric motor to maintain the target speed, ensuring reliable latch engagement without excessive force that would cause noise or bouncing.
Solution Approach 2:
The system transitions from a static, fixed damping setting to a dynamic, continuously adjustable damping force. The electric motor's counter-EMF is dynamically controlled based on real-time speed measurements, allowing the damping force to adapt to changing conditions and maintain optimal closing speed throughout the closing process.
2Device complexity
If conventional door closers use fixed damping settings, then the device complexity is reduced, but the closing speed becomes unstable under external influences like friction and temperature changes
Solution Approach 1:
The control module uses feedback from speed sensors to continuously monitor the actual closing speed and adjusts the electric motor's damping force accordingly. This closed-loop control compensates for external influences such as friction variations and temperature changes, maintaining consistent closing speed without requiring complex mechanical adjustments.
Solution Approach 2:
The patent replaces traditional mechanical damping mechanisms (such as hydraulic pistons or regenerative damping with switches) with an electrically controlled system. The electric motor's counter-EMF provides electronic damping control that is more responsive and adjustable than mechanical alternatives, achieving better speed consistency with comparable or reduced complexity.
3Reliability
If the door closing speed is increased to ensure latch engagement, then the latch engagement reliability is improved, but the impact force on the frame increases causing noise and potential damage
Solution Approach 1:
The control module monitors the actual closing speed and dynamically adjusts the damping force to maintain the target closing speed. This ensures the door closes fast enough for reliable latch engagement while preventing excessive impact force on the frame that would cause noise or damage.
Solution Approach 2:
The system dynamically changes the damping parameter (counter-EMF of the electric motor) throughout the closing process. By adjusting the electrical resistance or voltage applied to the motor, the damping force is optimized at different stages: higher damping during most of the closing to control speed, and reduced damping near the end to ensure positive latch engagement without excessive impact.
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 control module ensures the door leaf consistently meets the frame at a predetermined speed, reducing noise and ensuring reliable latch engagement despite external influences, by dynamically adjusting the damping effect to match the target closing speed.
Implementation Method 1
a short-circuited DC motor can be used here, the so-called counter-electromotive force (counter-EMF for short) of which counteracts the closing force of the closing spring in order to ensure the desired damping
Implementation Method 2
adjusting the motor's back EMF via pulse-width modulation to maintain a target closing speed
Data Source
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Figure 5
AI summary
The present invention relates to a drive unit and a method for closing a door or window sash, comprising an energy storage device for storing potential energy to provide a force for closing the sash and a damping device counteracting the closing force, with a generator-driven electric motor. The drive unit includes a control module for the electric motor, which is configured to control the electric motor based on the actual closing speed of the sash, such that the sash moves towards its closed position at a target closing speed.