Cooling Fan Speed Detection via Current Voltage Correlation
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Solution Overview
Problem
Existing methods for detecting a reduction in the rotational speed of a cooling fan, such as those using encoders, are costly and prone to failure due to contamination, and current monitoring techniques struggle to distinguish between rotational speed reduction and power source voltage fluctuations when using a commercial power source.
Innovation Solution
A machine tool system that includes a current measuring unit, a voltage measuring unit, and a storage unit to determine if the measured current exceeds a threshold associated with the voltage, or estimates the rotational speed reduction rate based on measured current and voltage values, allowing for accurate detection of rotational speed reduction even under fluctuating power source conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an encoder is attached to the fan to detect rotational speed, then detection precision is improved, but device cost increases and reliability deteriorates due to contamination exposure
Solution Approach 1:
The patent introduces a current measuring unit as an intermediary device to detect fan rotational speed indirectly through motor current consumption rather than directly measuring the fan's mechanical rotation. This mediator approach allows detection without exposing sensitive components to the contaminated fan environment, resolving the contradiction between detection precision and reliability.
2Reliability
If current monitoring is used to detect rotational speed reduction, then device cost is reduced and reliability is improved, but measurement precision deteriorates due to inability to distinguish voltage fluctuations from actual speed reduction
Solution Approach 1:
The system continuously monitors both voltage and current parameters, using voltage information as feedback to compensate for power source fluctuations. By comparing current consumption against voltage-corrected thresholds stored in memory, the system achieves precise detection of actual rotational speed reduction while filtering out false signals caused by voltage variations.
Solution Approach 2:
The patent dynamically adjusts the current threshold parameter based on measured voltage values. When voltage fluctuates, the corresponding current threshold is retrieved from memory to maintain accurate detection. This parameter adaptation allows the system to distinguish between current changes caused by voltage fluctuations versus those caused by actual fan speed reduction.
3Ease of operation
If direct connection to commercial power source is used, then ease of operation is improved, but measurement precision deteriorates due to voltage fluctuations
Solution Approach 1:
The voltage measuring unit provides continuous feedback about power source conditions, enabling the system to adapt its detection thresholds accordingly. This feedback mechanism allows the fan to operate directly from commercial power sources with voltage fluctuations while maintaining precise detection capability through dynamic threshold 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
Enables reliable detection of cooling fan rotational speed reduction, preventing fan stoppages and distinguishing between voltage fluctuations and actual rotational speed issues, thus reducing downtime and maintenance needs.
Implementation Method 1
a current measuring unit (15) that measures an input current to the cooling fan (14)
Implementation Method 2
a voltage measuring unit (16) that measures an input power source voltage to the machine tool (1)
Data Source
AI summary
A machine tool including a cooling fan measures an input power source voltage to the machine tool and an input current to the cooling fan. If the measured current value is outside a predetermined current value range corresponding to the measured voltage value, the machine determines that the rotational speed of the cooling fan has decreased.