JP2003065853A - Temperature detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent service life decline caused by adhesion of dirt such as toner or oil in a noncontact thermistor of a heat absorbing film type, and to constitute it recyclably. SOLUTION: A protective film and the heat absorbing film are allowed to adhere to each other detachably. The adhesion face of the protective film is formed in a projecting shape to thereby prevent formation of an air layer. Adhesion is executed by applying a pressure sensitive adhesive onto the protective film or by pressing the protective film. The protective film has a hat shape, and a cylindrical part is used as a guide at the insertion time, and a collar part is used as a pinching part at the dismantling time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detector used in an electrophotographic apparatus, an electrostatic recording apparatus and the like, and more particularly to a temperature detector arranged in a non-contact manner with a heating roll used in a fixing device.

[0002]

2. Description of the Related Art A fixing device using a heat roller heated by a heater is widely used in image forming apparatuses such as copying machines and laser printers.

In such a fixing device, the temperature of a thermistor for maintaining the surface temperature of the heat roller at a predetermined temperature, a temperature fuse for shutting off the energizing path to the heater when the temperature of the heat roller abnormally rises, a temperature of a thermoswitch, etc. The detection element is brought into contact with the surface of the heat roller.

As a result, contact flaws may occur on the fixing roller, causing problems such as white lines, black lines, and defective fixing.

Therefore, it is conceivable to bring the temperature detecting member into contact with the fixing roller outside the image area which is the passage area of the recording material, but it is impossible to detect the temperature in the image area and the fixing device becomes large. Therefore, recently, a method has been considered in which the temperature detecting means is brought into contact with the fixing roller in the image area in a non-contact manner.

The non-contact temperature detecting means has a casing having a transparent window for transmitting infrared rays, an infrared absorbing film made of a polymer material which is installed in the casing and absorbs infrared rays transmitted through the transparent window, and A thermistor element for film temperature detection, which is arranged so as to be in close contact with the infrared absorption film, and a thermistor element for temperature compensation, which detects the ambient temperature, are provided in the vicinity of the thermistor element for infrared detection.

In this non-contact temperature detecting means, the infrared ray that has passed through the transparent window of the casing is absorbed by the infrared ray absorbing film disposed immediately below the transparent window, so that the temperature of the infrared ray absorbing film rises and the infrared ray absorbing film. The thermistor element, which is disposed so as to be in close contact with, detects the temperature change. Then, by detecting the temperature difference with the thermistor element for temperature compensation as a potential difference by the bridge circuit, the absolute amount of infrared rays transmitted through the transmission window is detected, and the temperature of the measured object is measured in a non-contact manner.

[0008]

However, since the non-contact temperature detecting means described in the above-mentioned conventional example detects the temperature change of the infrared absorbing film, if the infrared absorbing film is contaminated by toner scattering or paper dust. There is a problem that the temperature change of the infrared absorbing film cannot follow the temperature change of the heating roller, and the temperature of the heating roller cannot be accurately detected. Therefore, the film of the non-contact temperature detection sensor must be cleaned before the infrared absorption film becomes dirty and the detection temperature shifts. However, at present, since the casing has a cylindrical transparent window to limit the measurement area of the temperature detection target, it is difficult to clean the infrared absorbing film from the outside of the cylindrical transparent window. In addition, the temperature detection accuracy cannot be guaranteed because cleaning irregularities may remain even after cleaning, so the non-contact temperature detection sensor is replaced before the heat absorbing film surface becomes dirty. Further, in recent years, there is a strong demand for recycling and using products, and it is desired that the non-contact sensor can be reused and used in the same manner.

[0009]

The present invention has solved the above problems by having the following configuration.

(1) A heat absorbing film facing the heating element, a film temperature detecting means for detecting the temperature of the heat absorbing film, and a case having a cylindrical opening in a portion of the film temperature detecting means facing the heating element. A temperature detector having a thin film sheet that is in close contact with and attached to the heating element side of the heat absorbing film.

(2) The temperature detector according to (1), wherein the surface of the thin film sheet facing the heat absorbing film has a convex shape on the heat absorbing film side.

(3) The temperature detector according to (2), wherein the thin film sheet and the heat absorbing film are adhered to each other with an adhesive material.

(4) The temperature detector according to (2), wherein the thin film sheet and the heat absorbing film are in close contact with each other by a pressing force.

(5) The temperature detector according to the above (2), wherein the thin film sheet has a hat shape.

(6) The temperature detector according to (3), wherein the adhesive material is applied to the heat-absorbing film facing surface side of the thin film sheet.

(7) The temperature detector according to (5), wherein the hat shape of the thin film sheet is larger on the outside of the flange of the hat than on the outside of the cylinder of the cylindrical opening of the case.

(8) A heat absorbing film facing the heating element, a film temperature detecting means for detecting the temperature of the heat absorbing film, and a case having a cylindrical opening in a portion of the film temperature detecting means facing the heating element. In the temperature detector having, the heat absorption film is removable from the temperature detector.

(9) The temperature detector according to the above (8), wherein the surface of the heat absorbing film facing the film temperature detecting means is convex toward the film temperature detecting means.

(10) The temperature detector according to (9), wherein the heat absorbing film and the film temperature detecting means are in close contact with each other with an adhesive material.

(11) The temperature detector according to (9), wherein the heat absorbing film and the film temperature detecting means are in close contact with each other by a pressing force.

(12) The temperature detector according to (9), wherein the heat absorbing film has a hat shape.

(13) The temperature detector according to the above (10), wherein the adhesive material is applied to a surface of the heat absorbing film facing the film temperature detecting means.

(14) The temperature detector according to the above (12), wherein the hat shape of the heat absorbing film is larger on the outside of the flange portion of the hat than on the outside of the cylinder of the cylindrical opening of the case.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

An image recording device for fixing an unfixed image on a recording paper is provided inside the image recording device, although not shown, but an image carrier for forming an electrostatic latent image on the surface thereof, and electric charges on the surface of the image carrier. Pre-exposure means for removing static electricity, primary charging means for charging the surface of the image carrier to a desired potential, exposure means for exposing the charged image carrier to form an electrostatic latent image, and static charge on the image carrier. A developing device that develops the latent image with a developer to make it visible, a transfer device that transfers the toner image on the image carrier developed by the developing device to a recording material, and the like are provided. Further, a fixing device 1 which is a roller fixing device for melting and fixing a toner image transferred onto a recording material by a fixing roller which is heated and pressed is arranged at a predetermined position of the image recording device, and each member forms each image forming process. A desired image can be obtained by performing the above. As the recording material, recording paper or OHP paper is used.

Next, the structure of the fixing device 1 will be described. In FIG. 1, reference numeral 2 denotes a heating roller, which is a roller in which a layer of a heat resistant elastic material such as silicone rubber or fluororubber is formed on a pipe material such as aluminum or iron and a release layer such as PFA or PTFE is coated on the surface. Similarly to the heating roller, the pressure roller 3 arranged in pressure contact with the heating roller 2 is also a roller in which a layer of a heat resistant elastic material such as silicone rubber or fluororubber is formed on a core metal. The transfer material S is passed through the heating roller (heating member) 2 and the pressure roller (backup member) 3,
The toner T on the transfer material S is heated and pressed between the heating roller and the pressure roller to be fixed. The heating roller 2
A heater 4 is disposed inside the heating roller 2 and heats the heating roller 2 from the inside. Further, in order to detect the surface temperature of the heating roller 2, a temperature detecting element 5 serving as a temperature detecting means is arranged so as to face the heating roller in a non-contact manner.
Detects the temperature of. Based on the data from the temperature detection element 5, the surface temperature of the heating roller 3 is set to a predetermined set temperature (printing temperature) or a standby temperature during non-fixing (standby temperature).
It is designed to keep

Next, details of the structure of the temperature detecting element 5 will be described with reference to FIG. FIG. 2 shows the temperature detecting element 5, (a) is a vertical sectional view, (b) is a horizontal sectional view, and (c) is a plan view. Reference numeral 6 denotes a case made of a material having high thermal conductivity such as aluminum, and a heat-resistant film 8 for absorbing infrared light emitted from a heating roller is provided in an opening 7 provided on one surface of the case.
Are provided so as to be closed. The heat-resistant film is a sheet material made of heat-resistant resin such as polyimide and having a thickness of about 0.2 mm. On the inner surface of the case of the heat-resistant film 8,
The infrared detecting thermistor element 9 is fixed by being brought into close contact with an adhesive or the like. In the vicinity of the infrared detection thermistor element 9,
A temperature compensating thermistor element 10 for measuring the ambient temperature in the case is provided. Lead wire 11 of thermistor element 9 for infrared detection and thermistor element 10 for temperature compensation
Are connected to sockets (not shown) provided in the case 6 so as to be taken out to the outside.

The temperature compensating thermistor element 10 and the infrared detecting thermistor element 9 have resistors R2 and R2 as shown in FIG.
It is used by constructing a bridge circuit with R3, and the output thereof is output as a potential difference generated between terminals A and B to detect the absolute amount of infrared rays.

Next, the operation of the temperature detecting element 5 will be briefly described. First, when infrared rays from the heating roller enter the resin film 8 attached to the opening 7 of the case 6,
Infrared rays are absorbed by the film 8 and the temperature of the film 8 rises according to the amount of infrared rays. Then, the temperature of the resin film 8 is conducted to the infrared detecting thermistor element 9 which is closely fixed to the back surface of the film, and is detected as a resistance change of the thermistor element. The resistance of the infrared detection thermistor element 9 is affected by room temperature, and the temperature compensation thermistor element 10 is used to detect a temperature corresponding to room temperature and eliminate the effect. The casing is made of a material having a high thermal conductivity such as aluminum in order to improve the followability of the temperature compensating thermistor element 10 with respect to changes in ambient temperature.

Next, the protective sheet 14 will be described.
The protective sheet 14 is made of a heat-resistant resin thin film, and is made of a heat-resistant resin such as polyimide, similar to the infrared absorbing film, and has a thickness of about 0.2 mm. The shape is a hat that is slightly smaller than the case opening.
The case 6 can be attached from the outside of the opening 7. When the protective sheet 14 is attached to the temperature detector 5, the hat tubular portion 14b of the protective sheet serves as a guide and is easily attached to a desired position of the temperature detector even when the tubular opening of the case is deep. There is. Further, the surface 14a facing the infrared absorbing film 8 has a convex shape on the infrared absorbing film side, and the protective sheet 1
When the surface 14a facing the infrared absorbing film 8 of 4 and the infrared absorbing film 8 are brought into close contact with each other, no air layer is generated on the contact surface. If an air layer is formed between the infrared absorbing film and the protective sheet during contact, the air layer becomes a heat insulating layer, and heat change of the fixing roller is hard to be transmitted to the heat absorbing film, resulting in poor heat response. A method for bringing the surface 14a of the protective sheet 14 facing the infrared absorbing film 8 into close contact with the infrared absorbing film 8 will be described below.

The first method is the infrared absorbing film 8
This is a method of applying an adhesive material to the surface 14a facing the.
When the protective sheet is attached to the temperature detector 5, the protective sheet 14 and the infrared absorbing film 8 are in close contact with each other by an adhesive material. The adhesive property of the adhesive material is light so that the protective sheet can be removed from the case. Further, since the protective sheet 14 and the infrared absorbing film 8 are in close contact with each other, the hat-shaped depth B of the protective sheet is larger than the depth A of the cylindrical opening of the case (A
<B). Here, the reason why the protective sheet is coated with the adhesive is that the protective sheet is a replacement part. This is because it always stabilizes.

The second method is to bring the protective sheet 14 and the infrared absorbing film 8 into close contact with each other by pressing force. As shown in FIG. 6, a protrusion 14d is provided on the protective sheet, and a hook 6a is provided on the case side. If the distance between the protrusion 14d of the protective sheet and the surface 14a facing the infrared absorbing film 8 is D, and the relationship between the hooking portion 6a of the case and the infrared absorbing film surface 8 is C, then the relationship of C> D Is configured to be. With the above configuration, when attaching the protective sheet, an air layer cannot be formed between the infrared absorbing film and the protective sheet,
The protrusion 14 of the protective sheet is generated due to the reaction force when they are brought into close contact with each other.
The d and the hooking portion 6a of the case are securely hooked to fix the protective sheet. Since the protective sheet is made of a thin film resin, when it is attached to the case, the protrusion bends into the case opening and is caught by the hooked portion of the case.

With the above-mentioned structure, only the protective sheet is not contaminated by the toner scattering and the oil scattering generated when the transfer sheet S is fixed by the fixing device 1, and the heat absorbing film is not contaminated. Replacing only the seat eliminates the need to replace the temperature sensor. Further, even when the fixing device is replaced, the temperature detector itself can still be used, so that it can be recycled and used. Needless to say, the temperature detector is made of a case, a heat absorbing film, and a thermistor element, and thus can be used antipermanently.

Further, details of the hat shape of the protective sheet 14 will be described. As shown in FIG. 5, the brim portion 14 c of the hat is larger than the outer side of the cylindrical opening 7 of the case 6. With the above configuration, when the protective sheet is removed from the temperature detector, the protective sheet 14 can be easily removed by pinching the hat collar portion 14c. Needless to say, the hat collar portion 14c forms a knob portion when the protective sheet is removed.
It suffices that a part of the hat brim portion 14c protrudes from the outer circumference of the cylindrical opening 7.

(Other Embodiments) In recent years, in order to shorten the first copy time and the wait time of the copying machine, the core of the fixing roller is improved so as to improve the followability of the roller surface temperature to the lighting of the heater. There is a tendency to reduce the thickness of the gold part. As a result, the temperature detector 5 is also required to have thermal responsiveness to the surface temperature of the fixing roller.

On the other hand, when the protective film 14 as shown in this embodiment is brought into close contact with the heat absorbing film 8, the infrared amount of the fixing roller must be detected by the combined thickness of the protective film and the heat absorbing film. As the heat capacity increases, the heat response becomes worse. In order to solve the above problem, the heat absorption film and the protective film may be thinned to reduce the heat capacity, but another method will be described in another embodiment.

4A and 4B are views showing another embodiment of the temperature detecting element 5a. FIG. 4A is a vertical sectional view, FIG. 4B is a horizontal sectional view,
(C) is a plan view. is there. 6 is a case made of a material having high thermal conductivity such as aluminum. On the inner surface of the case, the infrared detection thermistor element 9 is fixed to a thin film 16 made of resin with an adhesive or the like, and the thin film is fixed to the case so that the infrared detection thermistor element 9 does not touch the case. The thin film 16 is formed to have the minimum size necessary for fixing the infrared detection thermistor 9, and is configured to minimize the heat capacity of the thin film. In the vicinity of the infrared detecting thermistor element 9, a temperature compensating thermistor element 10 for measuring the ambient temperature in the case is arranged as in the embodiment. The infrared absorption film 15 is made of a heat-resistant resin thin film and has a hat shape. The case 6 can be attached from the outside of the opening 7.

An adhesive material is attached to the surface facing the infrared detecting thermistor element, and when the infrared absorbing film 15 is attached to the temperature detector 5, the infrared absorbing film 15 and the infrared detecting film are detected by the adhesive material. The thermistor element for use is closely attached. The adhesiveness of the adhesive material is light so that the infrared absorbing film 15 can be removed from the case.

Further, since the infrared absorbing film 15 and the infrared detecting thermistor element 9 are in close contact with each other, the depth of the hat shape of the infrared absorbing film is larger than the depth of the cylindrical opening of the case as in the embodiment.

As for the detachability of the heat absorbing film 15, as in the case of the embodiment, since the knob portion is formed, it is sufficient that a part of the hat-shaped flange portion projects from the outer periphery of the cylindrical opening 7.

By making the heat-absorbing film removable as described above, the temperature detector can be used semi-permanently and can be recycled only by exchanging the heat-absorbing film. Further, even if the heat absorbing film can be replaced, the heat capacity of the heat absorbing film is almost the same as that of the conventional one, so that the thermal response of the temperature detector is not deteriorated.

[0042]

As described above, the temperature detector is provided with a protective sheet detachably, or the heat absorption film of the temperature detector is detachable, so that toner scattering and oil during fixing can be prevented. Even if the heat-absorbing film becomes dirty due to scattering, the temperature detector can be used semi-permanently by replacing only the protective sheet or the heat-absorbing film, and the temperature detector can be recycled. In addition, the shape of the protective sheet or heat-absorbing film is made into a hat shape, and a part of the hat-shaped collar portion is projected from the outer periphery of the cylindrical opening of the case, so that the exchangeability of the protective sheet or heat-absorbing film is significantly improved. Improve to.

[Brief description of drawings]

FIG. 1 is a sectional view showing a fixing device according to an embodiment.

FIG. 2 is a sectional view showing a temperature detector according to an embodiment.

FIG. 3 is a circuit diagram of a temperature detector according to an embodiment.

FIG. 4 is a sectional view showing a temperature detector of another embodiment.

FIG. 5 is a cross-sectional view showing a process of attaching a protective sheet to the temperature detector.

FIG. 6 is a cross-sectional view showing a process of attaching another protective sheet to the temperature detector.

[Explanation of symbols]

1 fixing device 2 heating roller 3 pressure roller 4 heater 5 Temperature sensing element 6 cases 8 Heat-resistant film 7 openings 9 Thermistor element for infrared detection 10 Thermistor element for temperature compensation 11 lead wire 14 Protective sheet 14a side 14b hat cylinder 14c hat brim 14d protrusion 15 Infrared absorbing film 16 thin film S transfer material

Claims (14)

[Claims] 1. A heat absorbing film facing a heating element,
In a temperature detector having a film temperature detecting means for detecting the heat absorbing film temperature and a case having a cylindrical opening in a portion facing the heating element of the film temperature detecting means, on the heating element side of the heat absorbing film. A temperature detector characterized by having a thin film sheet that is in close contact with and removable from the temperature sensor. 2. The temperature detector according to claim 1, wherein a surface of the thin film sheet facing the heat absorbing film is convex toward the heat absorbing film. 3. The thin film sheet and the heat absorbing film are adhered to each other with an adhesive material.
The temperature detector described. 4. The temperature detector according to claim 2, wherein the thin film sheet and the heat absorption film are in close contact with each other by a pressing force. 5. The temperature detector according to claim 2, wherein the thin film sheet has a hat shape. 6. The temperature detector according to claim 3, wherein the adhesive material is applied to the heat-absorbing film facing surface side of the thin film sheet. 7. The temperature detector according to claim 5, wherein the hat shape of the thin film sheet is larger on the outside of the brim portion of the hat than on the outside of the cylinder of the cylindrical opening of the case. 8. A heat absorbing film facing the heating element,
In a temperature detector having a film temperature detecting means for detecting the temperature of the heat absorbing film and a case having a cylindrical opening in a portion facing the heating element of the film temperature detecting means, the heat absorbing film is the temperature detector. A temperature detector characterized by being removable. 9. The temperature detector according to claim 8, wherein a surface of the heat absorbing film facing the film temperature detecting means is convex toward the film temperature detecting means. 10. The temperature detector according to claim 9, wherein the heat absorbing film and the film temperature detecting means are in close contact with each other with an adhesive material. 11. The temperature detector according to claim 9, wherein the heat absorbing film and the film temperature detecting means are in close contact with each other by a pressing force. 12. The temperature detector according to claim 9, wherein the heat absorption film has a hat shape. 13. The temperature detector according to claim 10, wherein the adhesive material is applied to a surface of the heat absorbing film facing the film temperature detecting means. 14. The hat shape of the heat absorbing film is
13. The temperature detector according to claim 12, wherein the outside of the collar of the hat is larger than the outside of the cylinder of the cylindrical opening of the case.