JPH03225235A - Noncontact temperature detector - Google Patents

Abstract

PURPOSE:To prevent the generation of fluctuation in temperature and to attain stable temperature detection by covering a temperature detecting element with a cover. CONSTITUTION:The temperature detecting element 2 is stuck to the lead pattern of a base 3 by high temperature soldering or conductive past. A cover member 4 for preventing the generation a turbulent flow is arranged so as to surround the element 2 with a fixed distance with the element 2 and its one end is fixed on the base 3. The cover 4 is constituted of a metal plate or heat resisting resin. Since the cover 4 is arranged so as to cover the element 2, an air flow to be dispersed to the periphery of the roller 1 is interrupted and a laminar flow is generated along the cover 4. Thereby the air flow around the element 2 is stabilized, and even if the distance between the roller 1 and the element 2 is slightly large, temperature detection can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact temperature detection device that is used in a fixing device and the like and detects the surface temperature of a rotating body in a non-contact manner.

[Prior Art] Conventionally, in order to control the temperature of the heat roller of a heat roller fixing device used in an electrostatic photographic image recording device, a contact type temperature sensor is used in which a thermistor for temperature detection is pressed onto the surface of the heat roller with a sponge. A sensing element was used.

However, in the conventional example described above, since the thermistor is in contact with the heat roller, when the roller rotates, both the thermistor and the roller are scraped, which shortens the life of the roller. There was also a drawback that the withstand voltage between the thermistor and the roller was reduced due to the abrasion.

In order to eliminate such drawbacks, temperature sensing elements that do not come into contact with the roller have been considered.

[Problems to be solved by the invention] However, in this case, if the distance between the roller and the sensing element is very close, it is possible to stably detect the temperature, but it is difficult to place it very close to the roller surface due to accuracy;
If the distance is about m, there is a phenomenon in which the detected temperature changes irregularly.

This phenomenon occurs when a heat roller heated to about 200°C rotates, as shown in Figure 3, an air flow that flows parallel to the roller surface, that is, a laminar flow, is generated near the roller surface, but turbulence occurs slightly away from the surface. It is thought that temperature fluctuations occur because of the flow.

[Means for Solving the Problems] The present invention that solves the above problems includes: a rotating body heated by a heating source; a temperature sensing element disposed in a non-contact manner on the rotating body to detect the surface temperature of the rotating body; The non-contact temperature sensing device has a feature that a cover is provided to cover the temperature sensing element.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1(a) is a cross-sectional view of an embodiment of the present invention, in which 1 is a fixing roller which is a rotating body having a heater H inside, 2 is a temperature sensing element, and 3 is a 50 to 100 μm roller that holds the temperature sensing element. The thin substrate 4 is a turbulence prevention member. FIG. 1(b) is a top view of the temperature sensing element of the embodiment shown in FIG. 1(a). 2 is a temperature sensing element such as a thermistor, a thin film resistance sensor, or a thermocouple; the smaller the size, the smaller the heat capacity, the smaller the thermal time constant, and the better the response of the sensor.

The temperature sensing element 2 is attached to the substrate 3.

This substrate 3 is made of a heat-resistant insulating material such as polyimide or ceramic, and has lead wires electrically connected to the temperature sensing element 2 printed thereon. The substrate 3 has a large thermal resistance so as to prevent heat from escaping from the temperature sensing element 2 portion. Therefore, make it as thin as possible. Furthermore, the width a of the portion where the sensing element 2 is attached is made as narrow as possible, as shown in the top view of FIG. 1(b), and the heat capacity is further reduced.

The sensing element 2 is attached to the substrate 3 using high-temperature solder or conductive paste.
is glued to the lead pattern. A cover member 4 for preventing turbulent flow is arranged so as to surround the temperature sensing element 2 at a distance III from the temperature sensing element 2, and one end thereof is fixed to the substrate 3.

The cover 4 that prevents turbulence is made of a metal plate, heat-resistant resin, or the like.

By arranging the cover 4 to cover the temperature sensing element 2 in this way, the airflow that tends to diffuse around the roller 1 is blocked and a laminar flow is generated along the cover 4. Therefore, sensing element 2
The airflow around the roller is stabilized, and even if the distance between the roller and the temperature sensing element is slightly large, temperature sensing can be performed stably.

FIG. 2 shows a mechanism for holding the holding member 3 at a constant distance from the roller 1.

By providing a holder 5 having contact portions that contact both ends of the roller 1 and attaching the substrate 3 to the holder 5, the substrate 3 can always be kept at a constant distance from the roller 1.

Furthermore, the cover 4 of this embodiment also has the function of reflecting infrared rays emitted from the roller 1. For this purpose, the inner surface of the cover 4 on the temperature detection element side is plated with chrome or the like to easily reflect infrared rays to enhance the reflection effect.

[Example 2] FIG. 4 is a sectional view showing another embodiment of the present invention.

In this embodiment, the holding table 5 that holds the substrate 3 also serves as a cover to prevent turbulence.

Providing a recess in the holding base 5 has an effect of preventing turbulent flow, makes it easy to secure a distance from the temperature sensing element 2, and is advantageous in terms of cost. A circular shape of the depression as shown in FIG. 4 is more effective in concentrating the radiated infrared rays on the detection element.

[Embodiment 3] FIG. 5 shows yet another embodiment of the present invention, in which the holding stand 5 is made into a flat plate shape, and when the holding stand 5 is made of sheet metal, it has a simple shape and is easy to implement.

Although the present invention has been described in detail above, the rotating body is not limited to a roller shape, but can also be used in a belt shape.

[Effects of the Invention] As described above, according to the present invention, temperature fluctuation can be prevented and stable temperature detection can be performed, and the distance between the surface of the rotating body and the temperature sensing element can be set to 0.2 mm or more. can.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of an embodiment of the present invention, FIG. 1(b)
is a top view of the embodiment shown in FIG. 1(a), FIG. 2 is a perspective view of the entire device, FIG. 3 is a diagram showing airflow around the heat roller, and FIGS. FIG. 3 is a cross-sectional view of another embodiment of the invention. 1 is the heat generating roller 2 is the temperature sensing element 3 is the substrate 4 is the cover Figure 1

Claims (2)

[Claims] (1) A non-contact temperature sensing device comprising a rotating body heated by a heat source and a temperature sensing element disposed in a non-contact manner on the rotating body to detect the surface temperature of the rotating body, wherein the temperature sensing element is A non-contact temperature detection device characterized by having a cover. (2) The non-contact temperature sensing device according to claim 1, wherein the inner surface of the cover reflects infrared rays from the rotating body.