Non-contact Temperature Sensor with Segmented Lead Frames
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Solution Overview
Problem
Conventional non-contact temperature sensors for heat rollers in copying machines and printers face issues with reduced precision due to heat escape and mechanical instability, especially during paper jams, which affect detection accuracy and sensor positioning.
Innovation Solution
A non-contact temperature sensor design featuring a thin film thermistor with comb-shaped electrodes, pad electrodes, pattern wiring, and lead frames that surround the thermistor region, providing mechanical protection and reducing heat conductance, while the sensor's elasticity allows it to maintain original position after paper jams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the flexible printed circuit board or film is fixed to the casing or base at its peripheral edge, then the sensor can be mechanically supported, but heat escapes through the film to the surrounding casing or base causing deterioration of temperature detection precision
Solution Approach 1:
The sensor structure is divided into distinct functional regions: a heat-sensitive detection region with the thermistor and comb electrodes that remains unfixed and isolated from heat-conducting structures, and a support region with lead frames that provide mechanical support. This segmentation allows the detection region to remain thermally isolated while the support region handles mechanical loads, resolving the contradiction between mechanical support and heat isolation.
Solution Approach 2:
The lead frames serve as an intermediary element that provides mechanical support to the sensor structure without directly contacting the heat-sensitive thermistor region. The lead frames are positioned to surround and support the peripheral edge of the insulating film while maintaining a gap from the thermistor, thus mediating between the need for mechanical support and the requirement for thermal isolation.
2Reliability
If the temperature-sensitive element has large heat capacity and wiring makes heat conductance high, then the structure is mechanically stable, but the responsivity is decreased
Solution Approach 1:
The patent employs a thin-film thermistor and thin insulating film structure that provides sufficient mechanical flexibility and stability while minimizing heat capacity. The thin-film construction reduces the thermal mass of the heat-sensitive elements, enabling faster response to temperature changes while maintaining adequate mechanical stability through the overall sensor structure and lead frame support.
3Reliability
If the sensor is arranged separated from the roller by a distance to prevent machine failure during paper jams, then mechanical reliability is improved, but detection precision deteriorates
Solution Approach 1:
The sensor structure incorporates flexible lead frames that can dynamically adjust their position. During normal operation, the lead frames maintain the sensor at an optimal detection distance from the roller for high precision. During paper jams, the flexible lead frames can deform to accommodate the mechanical stress, preventing machine failure. After the jam is cleared, the lead frames elastically return to their original position, restoring the optimal detection distance.
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 design enhances detection precision and responsivity by minimizing heat loss and mechanical stress, enabling accurate temperature measurement with improved reliability and reduced size.
Implementation Method 1
a thin film thermistor portion made of a thermistor material that is patterned on a front-surface of the insulating film
Implementation Method 2
the heat caused by infrared radiation can escape through the film
Implementation Method 3
the sensor can be restored to its original position due to the spring property (elasticity) of the lead frames
Implementation Method 4
heat does not easily escape to the lead frames, thereby resulting in a high responsivity and detection precision
Data Source
AI summary
A non-contact temperature sensor is provided, the sensor including: an insulating film, a thin film thermistor portion formed on a front-surface of the insulating film, a pair of comb shaped electrodes formed on the thin film thermistor portion, a pair of pad electrodes formed on the front-surface of the insulating film, a pair of pattern wiring portions, and a pair of lead frames that is adhered to the pair of pad electrodes on the front-surface side of the insulating film, wherein the thin film thermistor portion is formed in a thermistor forming region arranged on the front-end side of the insulating film, the pad electrodes are formed in an electrode forming region arranged on the base-end side of the insulating film, the front-end side of the pair of lead frames is arranged to surround the circumference of the thermistor forming region in a non-contact manner.