JPH01221778A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent unfavorable influences such as an excessive temperature rise caused by fluctuation of temperature difference, turning off of a heat source at the time of energizing by providing a temperature detecting member and abnormality detecting member on almost one and the same circumference in the direction intersecting orthogonally with the rotating direction of a rotary heating body. CONSTITUTION:A thermo-switch 7 which detects the abnormal temperature rise of a heat roller and a thermistor 8 which is a surface temperature detecting means are provided on the surface of a heat roller 2 and they are respectively held by elastic members 9 and 10 of leaf springs, etc., in such a state that they can be brought into contact with the surface of the roller 2 with light pressures. When such temperature detecting means 8 and abnormal temperature rise detecting member 7 are provided on almost one and the same circumference in the direction intersecting orthogonally with the rotating direction of the rotary heating body 2, the temperature difference between the temperature detecting section and abnormal temperature rise detecting section becomes almost or completely zero. Therefore, the temperature of the member 7 can be set to an appropriate temperature against the control temperature of the heating rotary body 2. Thus the unfavorable influences caused by the fluctuation of the temperature difference between the temperature detecting section and abnormal temperature rise detecting section can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application of the Invention) The present invention relates to a fixing device for fixing an unfixed image used in an electrophotographic device or the like. In particular, the present invention relates to a fixing device that fixes an unfixed image using heat.

(Prior Art) In recent years, in order to improve fixing performance and downsize devices, it has become common practice to convey an image support material between a pair of rotating bodies and to fix the image by applying heat and pressure between them.

In this device that applies heat and pressure to an unfixed image using a pair of rotating bodies, it is necessary to keep the surface temperature of the heating rotating bodies constant.

Therefore, the surface temperature is detected using a thermistor or the like, and the amount of heat generated by the heat source for heating the heating rotor is controlled based on the detection result.

In addition, in order to prevent the heating rotor from becoming abnormally heated due to a malfunction of the temperature sensing element or heat source control circuit, causing damage to the heat source or melting of the rotor, a thermoswitch or the like is installed on the heating rotor. When the surface temperature of a device abnormally rises above a set temperature, the abnormal temperature rise is detected and the heat source is turned off.

Conventionally, thermistors and thermoswitches have been arranged in parallel in the axial direction of a rotating body.

This conventional configuration is shown in FIG.

Reference numeral 2 denotes a heating roller on the side that contacts the unfixed image and has a heater 11 built therein.

Reference numeral 3 denotes a pressure roller that faces the heating roller 2, and the recording material supporting the unfixed image is fixed by applying heat and pressure when it is conveyed between the heating roller 2 and the pressure roller 3. .

(Problems solved by the invention) However, the conventional example has the following problems.

Since the thermistor and thermo switch are arranged parallel to the @ line of the heat roller, the surface temperature of the heat roller detected by the thermistor and the thermo A temperature difference occurs between the surface temperature of the heat roller and the temperature detected by the switch. Therefore, the set temperature for the abnormal temperature rise detected by the thermoswitch must be set to a temperature that takes into account variations in the heater, and there is a risk that the operation may become unstable. That is, when the heat roller is abnormally heated (when there is an abnormality in the thermistor or temperature control), the fixing device is heated until the thermoswitch detects the set temperature. In other words, if the set temperature of the thermoswitch is high, it will take a long time to detect an abnormality, which may lead to a risk of fire, etc., and if an abnormal temperature rise occurs, damage will increase due to the temperature rise of parts related to the fixing device. However, repairs require time and cost.

Furthermore, in order to minimize the damage, the heat resistance of the related parts must be increased, which leads to deterioration of productivity due to heat-resistant materials and the use of expensive parts.

On the other hand, if the set temperature of the thermoswitch is low, even a slight overshoot of the heater will turn off the heater, which may interfere with normal fusing operation.

(Means for Solving the Problems) The present invention, which solves the above problems, is a fixing device that fixes an unfixed image by passing an image support material between a pair of rotating bodies, wherein at least one of the rotating bodies One of the fixing devices is a heating rotor that is heated by a heat source, and one is a temperature detection member that detects the temperature of the heating rotor in order to control the temperature of the heating rotor, and the other is a temperature detection member that detects the temperature of the heating rotor when the temperature of the heating rotor increases abnormally. an abnormality detection member for stopping the heating rotary body, and the temperature detection member and the abnormality detection member are provided on substantially the same circumference in a direction orthogonal to the rotational direction of the heating rotating body. It is.

(Example of actual invention) Embodiments of the present invention will be described below based on the drawings.

Note that the same numbers are given to members that perform the same function.

FIG. 1 shows a cross-sectional view of a fixing device according to the present invention, in which a recording material P onto which an unfixed toner image has been transferred is transported in the direction of the arrow from a transport section (not shown), and rotated for heating by an entrance guide 1. The unfixed toner image is guided to the nip formed by the heat roller 2, which is a body, and the pressure roller 3, which is a rotary pressure body, and the unfixed toner image is transferred to the paper by the heat of the heat roller 2 and the pressure of the pressure roller 3. It will be established. The heat roller 2 is a hollow cylindrical roller that is heated by an internal heat source such as a halogen lamp 4, and its surface is coated with a fluororesin having good mold releasability. Further, the pressure roller 3 is a soft roller whose surface is coated with silicone rubber.

The recording material P fixed by the pair of rollers described above is guided by a guide 5 to a pair of paper ejection rollers 6, and is ejected to the outside.

The surface of the heat roller 2 is provided with a thermoswitch 7 for detecting abnormal temperature rise of the heat roller and a thermistor 8 as a surface temperature detection means, each of which is configured to contact the surface of the heat roller 2 with light pressure. It is held by bony members 9.10, such as leaf springs. Normally, the heat generation of the heater 4 is controlled based on the detection result of the thermistor 8, and when the thermoswitch 8 detects an abnormal temperature rise, the heater 4 is turned off.

FIG. 2 shows a thermistor that is an embodiment of the present invention.

This is a perspective view showing the arrangement of thermoswitches, which are arranged on the dotted line in the figure (on the same circumference of the heat roller).

In this way, by arranging the temperature detection member and the abnormal temperature rise detection member on substantially the same circumference in the direction orthogonal to the rotation direction of the heating rotor, the temperature at the temperature detection part and the abnormal temperature rise detection part can be adjusted. Since the difference is almost completely eliminated, the set temperature of the abnormal temperature rise detection member can be set to an appropriate value with respect to the control temperature of the heating rotating body.

Therefore, it is possible to prevent the adverse effects caused by variations in the temperature difference between the temperature detecting section and the abnormal temperature rise detecting section, which has been a problem in the prior art.

In the arrangement of the thermistor and thermoswitch according to the present invention, the most effective arrangement is to arrange them on the same circumference outside the recording material passage area in the longitudinal direction of the heat roller. In this case, the contact range of the heat roller due to the thermistor and thermoswitch becomes smaller, and at the same time it is outside the paper passing area.
The image will not be adversely affected by scratches. Furthermore, it is also preferable that the thermoswitch be disposed on the upstream side of the circumference of the heat roller with which the thermistor contacts.

That is, since the thermoswitch reduces dirt on the heat roller, dirt on the contact portion of the thermistor with the heat roller can be reduced, the temperature detection accuracy of the thermistor can be improved, and stable temperature control can be achieved.

Further, the heat resistance distribution of the heater 4 is such that the portion where the thermistor and the thermoswitch are arranged is higher than at least the recording material passing portion, and particularly has a peak.

Therefore, safety and thermal responsiveness are further improved.

Furthermore, although the present invention is applicable not only to heat rolls but also to all rotating bodies that move endlessly, it is preferable that at least the distance between the surface of the rotating body and the heat source is approximately equal between the surface temperature detection section and the abnormal temperature rise detection section. .

(Effects of the Invention) As explained above, according to the present invention, the temperature difference between the temperature detection part and the abnormal temperature rise detection part is almost eliminated, so that there is no problem such as excessive temperature rise due to variations in this temperature difference or turning off of the heat source during normal times. can prevent the negative effects of

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view showing features of the invention more clearly, and FIG. 3 is a perspective view showing the prior art.

Claims (5)

[Claims] (1) In a fixing device that fixes an unfixed image by passing an image support material between a pair of rotating bodies, at least one of the rotating bodies is a heating rotating body heated by a heat source. , a temperature detection member for detecting the temperature of the heating rotor in order to control the temperature of the heating rotor, and an abnormality detection member for stopping the heat source when the temperature of the heating rotor increases abnormally; A fixing device characterized in that the detection member and the abnormality detection member are provided on substantially the same circumference in a direction perpendicular to the rotational direction of the heating rotor. (2) The fixing device according to claim 1, wherein the heating rotor has a heat source inside and is heated by the heat source. (3) The fixing according to claim 1 or 2, wherein the image support material does not pass on substantially the same circumference where the temperature detection member and the abnormality detection member are provided. Device. (4) The fixing device according to claim 1 or 2, wherein the temperature detection member and the abnormality detection member are provided in contact with the heating rotating body. (5) The fixing device according to any one of claims 1 to 4, wherein the abnormality detection member is provided upstream of the temperature detection member in the rotational direction of the rotating body.