JPS6135554B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a temperature detection device for detecting the surface temperature of a moving heated member in a copying machine or the like. In particular, the present invention relates to a detection device that detects the surface temperature of a heat fixing roller. Conventionally, as shown in FIG. 1, a thermistor 1 was embedded in silicone rubber 2, and the holding frame 2a was brought into contact with the surface of the fixing roller to detect the temperature of the surface. This causes the holding frame 2a to come into contact with the surface of the fixing roller, which may damage the offset prevention layer made of Teflon or silicone rubber, etc.
Furthermore, since the silicone rubber 2 has a large heat capacity, it took a considerable amount of time for the temperature detection device 3 made up of the thermistor 1 and the silicone rubber 2 to reach the ambient temperature. Therefore, when detecting the surface temperature of the roller, this time delay accompanies it, which increases the temperature control range, causing the fixing roller to be heated more than necessary and thermally deteriorating the offset prevention layer on the surface.
Since the temperature range is large, the offset phenomenon tends to occur easily. In order to prevent such defects, there is also a method in which only the tip of the thermistor 1 is partially exposed from the silicone rubber 2 and the thermistor is brought into contact with the roller surface to detect the temperature of the surface, as shown in Figure 2. It was considered, but no sufficient effect could be obtained. Since the thermistor comes into point contact with the offset prevention layer of the fixing roller, the thermistor damages the offset prevention layer, and toner enters there, causing an offset phenomenon or uneven fixing. However, it was not possible to accurately detect the roller surface temperature. There is also a method that does not cover the thermistor with silicone rubber, etc., but it has the drawbacks mentioned above.
However, it has the disadvantage that it is susceptible to the influence of the surrounding atmospheric temperature and cannot accurately detect temperature. SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks and provides a temperature detection device for a copying machine or the like that detects the surface temperature of a heated member with excellent responsiveness and reduces the temperature control range. The present invention is a temperature sensing device for a copying machine or the like, which is provided in contact with or in close proximity to a moving surface, and in which a temperature sensing element is coated with a heat-resistant resin mixed with a substance having good thermal conductivity. Embodiments of the present invention will be described below with reference to the drawings. 3 and 4 show a temperature sensing device according to an embodiment of the present invention. FIG. 3 is a front view of the temperature sensing device 4, and FIG. 4 is a sectional view. The temperature detection device 4 includes a heat-resistant resin 5, a holding frame 6 holding the resin, and the resin 5.
It consists of a sensing element 7 buried inside. A hole 6a is bored in the holding frame 6 at a location where the detection element 7 is provided. The hole 6a is formed when the holding frame 6 is placed facing a heated moving surface.
Since the radiant heat from the moving surface is directly guided to the sensing element 7, responsiveness to temperature changes is improved. As the above-mentioned heat-resistant resin, silicone rubber such as product names KE-119, KE-1093, KE-1205 manufactured by Shin-Etsu Chemical Co., Ltd. is used.
Contains μ metal powder. Metal powders include aluminum, magnesium, copper, etc., which have good thermal conductivity.
Duralumin, sirumin, brass, etc. are used and mixed in the resin at a ratio of 5 to 80%. Note that polyester, epoxy resin, phenol resin, fluororesin, etc. can also be used as the heat-resistant resin. The following table shows the results of a comparative experiment between the temperature sensing device shown in FIG. 1 and the temperature sensing device of the present invention. The one shown in FIG. 1 is a heat-resistant resin in which a temperature sensing element is coated with KE-119 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. without mixing metal powder, and the heat-resistant resin according to the present invention is , particle size 500μ in the above KE-119
40% aluminum powder mixed in is used, and this is brought into contact with the heated surface to heat the surface.
The temperature was controlled at 165°C.

[Table] This data measures the temperature of the heater as a heating source from on to off. As described above, by mixing metal powder into the heat-resistant resin, the temperature control range has been significantly narrowed. FIG. 5 shows an embodiment in which the temperature detection device of the present invention is used in a heat fixing roller of a copying machine. In the figure, the upper fixing roller 8 and the lower heating roller 9 are pressed against each other and rotated in the direction indicated by the arrow. A recording paper 10 on which a toner powder image has been formed is passed between both rollers 8 and 9, and the toner image is melted and fixed thereon. The upper fixing roller 8 has a heating lamp 11 inside and is coated with silicone rubber 12 to prevent offset as an outer layer. The lower heating roller 9 has a heating lamp 13 inside and is coated with Teflon 14 (trade name) as an outer layer as a relatively thin offset prevention layer. On the surface of the upper fixing roller 8, a cleaning device 15, an anti-offset liquid coating device 16, and a temperature detecting device 4 are arranged in this order in the rotational direction of the fixing roller 8. The cleaning device 15 includes a roller 17 made of metal, Teflon-coated metal, resin, etc., a blade 18 that is in pressure contact with the roller 17 and prevents toner from adhering to its surface, and a blade 18 that removes toner and offset prevention liquid from the blade 18. The roller 17 continuously removes the toner adhered to the fixing roller 8 from the roller surface before the offset prevention liquid is supplied. The offset prevention liquid application device 16 uniformly applies a liquid such as silicone oil to the surface of the fixing roller 8 using a known method. Next, the temperature sensing device 4 is configured so that the shape of the holding frame 6 has the same curvature as the curvature of the fixing roller 8, and a spring (Fig. (not shown) or other suitable means. Therefore, since the contact area with the fixing roller 8 increases, the pressure is reduced and wear of the silicone rubber 12 can be prevented. On the other hand, the surface of the lower heating roller 9 also has a fixing roller.
A cleaning device 20 similar to that provided in the air cleaner 8 is attached, and its function is the same, so a description thereof will be omitted. The surface temperature of the fixing roller 8 is detected by the temperature detection device 4, and the heaters 11 and 13 are controlled on and off by a control circuit (not shown) to maintain the surface temperature of the fixing roller 8 and the heating roller 9 constant. . Note that the temperature detection device 4 may be provided on the lower heating roller. Furthermore, it can be used not only for the fixing roller device but also for detecting the temperature of other heated surfaces. It is also convenient to make the heat-resistant resin as thin as possible in order to reduce its heat capacity. As described above, according to the present invention, the temperature detection device is not greatly influenced by the ambient temperature around it and has good responsiveness to temperature changes, so that the temperature control width can be narrowed. In particular, when used in a temperature detection device for a fixing roller or heating roller having an offset prevention layer on its surface, it has the advantage of not damaging the roller surface and preventing the occurrence of offset phenomenon.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional temperature sensing device, FIG. 3 is a front view of a temperature sensing device showing an embodiment of the present invention, and FIG. 4 is a cross-sectional view of a temperature sensing device of the present invention. FIG. 5 is a sectional view of a heat fixing roller device showing an embodiment of the present invention. 1, 7... Temperature detection element, 2, 5... Heat resistant resin, 3, 4... Temperature detection device, 6... Holding frame, 6
a... Small hole, 8... Fixing roller, 11, 13...
...heater. 〓〓〓〓〓

Claims (1)

[Scope of Claims] 1. A temperature sensing element is embedded in a heat resistant resin mixed with a substance having good thermal conductivity, and the heat resistant resin is surrounded by a holding frame having small holes on the surface facing the temperature sensing element. . A temperature sensing device for a copying machine, etc., in which the small hole portion of the holding frame is brought into contact with or close to a heated moving surface of the copying machine, etc. 2. A temperature detection device for a copying machine or the like according to claim 1, wherein the heated member is a fixing roller. 3. The temperature detecting device for a copying machine or the like according to claim 2, wherein a portion of the temperature detecting device that contacts the fixing roller has the same curvature as a circumferential surface of the fixing roller.