Premixing Apparatus Throttle Valve Hysteresis Control
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Solution Overview
Problem
Existing premixing apparatuses face challenges in efficiently regulating the variable throttle valve due to changes in hysteresis amount, leading to prolonged regulation times and potential poor combustion.
Innovation Solution
The apparatus includes a control device that implements specific control strategies to quickly adjust the stepping motor's rotation direction and positions to maintain optimal excess air ratio, thereby minimizing the impact of hysteresis changes on throttle valve regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the stepping motor is quickly caused to rotate by the hysteresis amount in the reversal direction to reduce regulation time, then the regulation time is reduced, but the opening degree of the variable throttle valve changes excessively due to variation in hysteresis amount
Solution Approach 1:
The control device causes the stepping motor to rotate in the normal rotation direction by a predetermined angle before causing it to rotate in the reversal direction. This preliminary action positions the throttle valve mechanism in advance, ensuring that when the motor rotates in the reversal direction, the opening degree changes smoothly without excessive variation, even when hysteresis amount varies.
Solution Approach 2:
The control device repeatedly determines whether the opening degree has reached the target value during the rotation process. This feedback mechanism allows the system to monitor the actual position and make adjustments, preventing excessive changes in opening degree while maintaining efficient regulation time.
2Reliability
If the opening degree of the variable throttle valve is regulated frequently to maintain constant excess air ratio, then combustion quality is improved, but the regulation process takes excessive time due to hysteresis changes
Solution Approach 1:
By rotating the stepping motor in the normal direction before the reversal direction, the system prepares the mechanism in advance, reducing the time required for subsequent regulation operations while maintaining accurate control of the opening degree for reliable combustion.
Solution Approach 2:
The control device efficiently moves through the regulation process by using the preliminary rotation to overcome hysteresis effects, allowing the system to quickly reach the target opening degree without unnecessary delays, thus maintaining combustion quality while reducing regulation time.
3Ease of operation
If the stepping motor rotates in the reversal direction to adjust opening degree, then the opening degree changes, but the change characteristic line deviates due to backlash causing regulation inaccuracy
Solution Approach 1:
The control device rotates the stepping motor in the normal rotation direction by a predetermined angle before rotating in the reversal direction. This preliminary action eliminates the effects of backlash by pre-positioning the mechanism, ensuring that subsequent reversal rotation produces accurate and predictable opening degree changes.
Solution Approach 2:
Instead of directly rotating in the reversal direction, the system first rotates in the opposite (normal) direction to overcome backlash, then proceeds with the intended reversal rotation. This inverted approach ensures accurate positioning by eliminating mechanical play before the actual adjustment.
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 allows for rapid and precise regulation of the variable throttle valve, reducing the time required to achieve the desired excess air ratio and preventing prolonged regulation due to hysteresis changes.
Implementation Method 1
a variable throttle valve (74) that is interposed in a portion, on a downstream side of the zero governor (73), of the gas supply passage (7) and is driven by a stepping motor (74a)
Implementation Method 2
an air supply passage (6) on an upstream side of the fan (5); a gas supply passage (7) of which a downstream end is connected to a gas suction part (61) that is arranged in the air supply passage (6)
Data Source
AI summary
In a premixing apparatus that mixes a fuel gas with air, supplies an air-fuel mixture to a burner through a fan, and carries out a control that regulates an opening degree of a variable throttle valve, which is interposed in a gas supply passage, so that an excess air ratio of an air-fuel mixture becomes an appropriate value, in a case where a detected excess air ratio deviates to one side, e.g., a large side, from an acceptable range, a motor is repeatedly caused to rotate by a unit-angle in an opening-degree increasing direction until the detected excess air ratio becomes an appropriate value. In a case where the detected air ratio deviates to the other side, e.g., a small side, from the acceptable range, the motor is caused to rotate, at a high speed in an opening-degree decreasing direction, till a first position that is anticipated that the excess air ratio will become a value that deviates by a fixed quantity from the acceptable range to a large side, thereafter, the motor is caused to rotate, at the high speed in an opening-degree increasing direction, till a second position that is a short of a target position, and subsequently, the motor is caused to rotate by the unit-angle in the opening-increasing direction.