Built-In Oven Door Zero Position Detection with Hall Sensor Feedback
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Solution Overview
Problem
High-level built-in cooking appliances face issues with unreliable zero point determination due to high switching point tolerances in existing limit switches, leading to improper operation, such as heating with the base door still slightly open.
Innovation Solution
The cooking appliance incorporates a control device that processes actuation signals from switches to determine the zero or closed position of the door, using a combination of switch actuation and travel path measurement within a tolerance range, along with additional conditions like motor standstill, to ensure accurate zero point determination, and employs a Hall sensor unit to count sensor pulses for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a limit switch is used to detect the closed position of the door, then the door position can be detected, but the switching point tolerance is high leading to unreliable zero point determination
Solution Approach 1:
The patent combines multiple detection methods (switch actuation signals, travel path measurement, motor standstill detection) into a unified zero point determination system. The control device evaluates multiple conditions simultaneously to confirm the closed position, where the switch signal provides the primary detection and travel path measurement provides verification within a tolerance range, thereby compensating for the high switching point tolerance of individual switches and improving overall reliability
Solution Approach 2:
The system implements feedback by continuously monitoring the door position through travel path measurement and comparing it against the expected zero position. The control device receives feedback from the switch actuation signals and adjusts the zero point determination based on the measured travel path, ensuring accurate positioning despite switch tolerance variations. The system also provides feedback by detecting motor standstill to confirm the door has reached its final position
2Reliability
If the drive device continues moving the door after switch actuation, then the switch tolerance is compensated, but the door may overshoot the closed position
Solution Approach 1:
The system performs preliminary action by continuing to move the door slightly past the switch actuation point to compensate for switch tolerance. The control device is programmed to move the door beyond the initial switch trigger position, ensuring that the true closed position is reached despite the switch's inherent tolerance. This preliminary overshoot is controlled and bounded by the travel path measurement tolerance range
Solution Approach 2:
Feedback control prevents overshooting by continuously monitoring the travel path and comparing it against the expected zero position. When the measured travel path indicates that the door has reached the closed position within the defined tolerance range, the control device stops further movement. The feedback mechanism uses the difference between the measured travel path and the expected zero position to determine when to halt the door movement, preventing excessive overshoot
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 approach enhances the reliability of zero point determination, reducing switching tolerance errors and ensuring proper operation by accurately setting and maintaining the door's closed position, thereby preventing heating issues when the door is not fully closed.
Implementation Method 1
at least one sensor unit, in particular a Hall sensor unit, is present for measuring the number of revolutions of a motor shaft or a fraction thereof
Data Source
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AI summary
The invention relates to a cooking appliance, especially a built-in wall cooking appliance, which comprises at least one muffle (5), delimiting a cooking compartment (3) and having a muffle opening (6), a door (7) for closing said muffle opening (6) and a drive device (48), controlled by a control device (13), for displacing the door (7) and at least one switch (24) which transmits actuation signals for determining a zero position (P0) of the door (7) to the control device (13) when the door (7) touches the muffle (5). The control device (13) is also configured in such a manner that the presence of the actuation signals of the at least one switch (24) is required but not sufficient to determine the zero position (P0).