JPH10301410A - Heat fixing device and image forming device - Google Patents

Abstract

(57) [Problem] To provide an apparatus in which a material to be heated is pressed by a pressing member to a horizontally long rod-shaped heating body and the heating body heats the material to be heated via a heat-resistant film, the area where the material to be heated does not pass. To prevent overheating of the heating element and damage to the heating element. SOLUTION: A recording material carrying an unfixed image is passed through a nip portion between a heating member 3 and a pressing member pressed against the heating member, thereby applying heat energy of the heating member to the recording material to thereby generate heat. In the heat fixing device for fixing, a heat conduction pattern 201 is formed on the back surface of the heating element, and heat is conducted from the pattern formation region to the non-formation region, thereby preventing an excessive temperature rise in the formation region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element for heating an object to be heated, and more particularly to a heat fixing device for permanently fixing a toner image in electrophotography to the object to be heated, and an image forming apparatus having the heating apparatus. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile or the like using an appropriate image forming process such as electrophotography, electrostatic recording, or magnetic recording, a transfer method or a direct method is applied to a recording material. As a fixing device (image heating device) for fixing the formed and carried toner image on the recording material surface, a heating device of a heat roller type has been used.

[0003] The heating device of the heat roller type basically comprises a metal roller provided with a heater therein and an elastic pressure roller which presses against the metal roller, and has a fixing nip portion (press-contact nip) formed by the pair of rollers. A recording material or a transfer material as a member to be heated is introduced into the unit, and the toner image is heated, pressed, and fixed by being nipped, conveyed, and passed.

However, in such a heating apparatus of the heat roller type, it takes a very long time to raise the roller surface to the fixing temperature because the heat capacity of the roller is large. Therefore, in order to quickly execute the image output operation, it is necessary to control the temperature of the roller surface to a certain temperature even when the apparatus is not used.

[0005] Therefore, as a heating system and a device devised to satisfy these needs, for example, Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No.
There is a film heating method and apparatus disclosed in, for example, JP-A-1577878.

A conventional film heating type heating apparatus will be briefly described with reference to FIG. 8 according to the present invention. Generally, a thin heat-resistant film 1 and a fixed heat-resistant film are arranged on one side of the film. It has a heating element (heater) 3 and a pressing member 4 disposed on the other surface of the heating element to face the heater with the film 1 in close contact with the heater. The heating element 3 has an elongated rod shape extending in a direction perpendicular to a conveying direction of a recording material as a member to be heated.

A member to be heated and, in the case of an image heating apparatus, a toner image are formed and carried between a film and a pressure member in a pressure nip portion formed by pressing the heater and the pressure member with the film interposed therebetween. When the recording material P is introduced and passed, the surface of the visible image carrier of the recording material is heated by the heater via the film, and thermal energy is applied to the unfixed image, and the toner is softened and melted to heat the image. Fixation is made.

Next, a conventional example of a heating element will be described with reference to FIG. FIG. 9A is a partially cutaway front view of the heating body, and FIG. 9B is a rear view.

Reference numeral 20a denotes a first electrode pattern provided on a surface portion on the left end side in the longitudinal direction of the ceramic substrate 8,
The left end of the resistance heating element 6 is electrically connected and conductive.
Reference numeral 15 denotes a conductive pattern provided on the surface side of the ceramic substrate 8 substantially in parallel with the resistance heating element 6, and the right end thereof is connected to and connected to the right end of the resistance heating element 6. The left end is connected to and connected to a second electrode pattern 20b provided on the left surface of the ceramic substrate 8 in the longitudinal direction.

Therefore, the first and second electrode patterns 2
When power is supplied from the primary circuit system AC between 0a and 20b, the resistance heating element 6 generates heat over the entire length.

The surface side of the heating element is covered with a withstand voltage coat 7 such as heat-resistant glass by covering the resistance heating element 6 and the conductive pattern 15 except for the first and second electrode patterns 20a and 20b for surface protection. Coated.

Reference numerals 21a and 21b denote third and fourth electrode patterns provided on the back surface on the left end side of the ceramic substrate 3 in the longitudinal direction, and these two electrode patterns 21a and 21b are respectively provided via conductive patterns 22a and 22b. It is electrically connected to the thermistor 5. The heating element temperature information of the thermistor 5 is fed back to the power supply control circuit by the secondary circuit system DC from the third and fourth electrode patterns 21a and 21b.

The heating element 3 is heated by being supplied with power to the resistance heating element 6, the temperature of the heating element is detected by the thermistor 5, and the temperature of the heating element 3 is controlled by a power supply control circuit (not shown) based on the detected information. Is maintained at a predetermined fixing temperature, the power supply to the resistance heating element 6 is controlled, and the temperature of the heating element 3 is adjusted. For power control, for example, phase control of AC voltage is used.

Reference numeral 17 denotes a thermal fuse as a safety device, which is connected in series to the power supply line of the resistance heating element 6 and is disposed in contact with or close to the back surface of the ceramic substrate 8.

FIG. 10 is a partially cutaway front view and a rear view of another conventional heating element. In this heating element, the folded pattern 15 of the heating element is electrically connected to the back surface through the through hole 18, and an AC electrode is formed on the back surface.

[0016]

In these systems, low heat capacity is required for each part in order to quickly control the temperature to a target temperature, and a material having a low heat capacity such as ceramic is used for a heater substrate. In addition, it is necessary to rapidly raise the temperature. Further, higher speed is required, and the startup power consumption itself tends to be large. In the normal operating environment, there is no particular harm caused by designing in consideration of these quick start, low heat capacity, high heat conduction, but for example, several small thick papers and envelopes overlapped When the paper is passed in the state, the temperature is controlled at the normal temperature control temperature in the so-called paper passing area where the paper exists, but in the so-called non-paper passing area where there is no paper, the heater unit is There is a problem that heat is not absorbed by the pressure roller due to floating from the pressure roller, and the surface of the heater is abnormally heated. It is conceivable that a heater crack may occur due to the thermal stress caused by the abnormal temperature rise of the non-sheet passing portion.

An object of the present invention is to provide a heating and fixing device which prevents the above-mentioned abnormal temperature rise due to non-sheet passing of a recording material.

[0018]

In order to achieve the above object, a heating and fixing apparatus according to a first aspect of the present invention comprises an elongated rod-shaped heating element extending perpendicularly to a recording material conveying direction, and In a heat fixing device that applies heat energy of a heating body to a recording material and heat-fixes the recording material by passing the recording material carrying an unfixed image through a nip portion between the pressure member and a pressing member that presses against the body, A heat conductive pattern is formed on the back surface of the body.

In the second invention according to the present application, the heat conduction pattern may be formed on the back surface of the recording material non-sheet passing area of the heating element.

In a third aspect of the present invention, the heat conduction pattern may be formed by an electrode for a heating element temperature detecting means.

In a fourth aspect of the present invention, the heat conduction pattern on the back surface of the heating element may be formed of an Ag-based material.

In the fifth invention according to the present application, a heat-resistant polymer layer may be formed on a heat conductive pattern formed on a back surface of the heating element.

In a sixth aspect of the present invention, the heat-resistant polymer layer may be a polyimide film.

An image forming apparatus according to a seventh aspect of the present invention is an image forming section for forming an image on a recording material, and a heat fixing apparatus according to any one of the first to sixth aspects for heating and fixing an image on a recording material. It is characterized by having.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] FIG. 8 shows a schematic cross section of an example of a tensionless type film heating and fixing apparatus according to the present invention. In the figure, 1 is an endless heat-resistant film,
It is externally fitted to a heater support 2 which is also a guide member for a film including a heater. The inner peripheral length of this endless heat-resistant film and the outer peripheral length of the heating element support 2 including the heating element are larger than that of the film 1 by, for example, about 3 mm. It is loosely fitted outside.

The film 1 has a film thickness of 100 to reduce the heat capacity and improve the quick start property.
μm or less, preferably 50 μm or less 20 μm or more heat-resistant single layer of PTFE, PFA, FEP, or polyimide, polyamideimide, PEEK, PES, PP
A composite layer film in which the outer peripheral surface of S or the like is coated with PTFE, PFA, FEP, or the like can be used. In this embodiment, a polyimide film whose outer peripheral surface is coated with PTFE is used.

The heating element (heater) 3 is, as described later,
The basic structure consists of a horizontally long thin plate-shaped ceramic substrate and a resistance heating element formed on the surface of the substrate along the length of the substrate. The temperature is controlled to a predetermined fixing temperature. The heater 3 is fitted and held in a groove formed along the length of the lower surface of the holder with respect to the heater holder.

Reference numeral 4 denotes a pressure roller as a rotating body for driving the film by forming a nip N between the heating body 3 and the film 1 and releasing the core metal 4-a from the silicone rubber or the like. And is driven from the end of the metal core 4-a by means (not shown).

The output of the thermistor 5 provided on the heating element 3 is A / D converted, taken into the CPU 10, and based on the information, the AC voltage applied to the heating element by the triac 11 is subjected to pulse width modulation such as phase and waveform control. And controlling the power supplied to the heating element. Although the above example is of a tensionless type, the present invention can also be applied to a driving roller, a tension roller, or a tension-type heating device that winds a film around a heating body.

Next, the heating element or heater will be described. Reference numeral 3 denotes a heating element, which is a substrate 8 made of alumina or the like.
Is coated with an electric resistance material 6 such as Ag / Pd (silver palladium) to a thickness of about 10 μm and a width of 1 to 3 mm by screen printing or the like, and a glass or fluorine resin or the like is coated thereon as a protective layer 7. I have. Further, a thermistor 5 is attached to the back surface to detect the temperature of the heating element 3 and control the temperature of the heating element.

Next, an example of an image forming apparatus having the above-described heating device will be described with reference to FIG. 7. Reference numeral 101 denotes a laser unit, and laser light emitted from the unit is reflected by a mirror 102, The photosensitive drum 103 such as a body is irradiated and exposed to form an electrostatic latent image on the photosensitive drum. The surface of the photosensitive drum 103 is the primary charger 10
4 is uniformly charged in advance. The toner 106 that is the developer contained in the container 105 is
07, the latent image on the photosensitive drum is developed and turned into a toner image. A recording material 109 such as plain paper loaded on a cassette 108 serving as a recording material loading unit is conveyed to a transfer unit by a feed roller 110, and the toner image on the photosensitive drum is transferred to the recording material 109 by a transfer unit 111. The transferred recording material 109 is conveyed to fixing means 112, where the toner image is heated and fixed on the recording material.

FIG. 1 is a partially cutaway front view and a rear view of a heating element used in the first embodiment of the present invention. Where 20
Reference numeral 1 denotes a pattern made of a good heat conductive paste. 1, the same reference numerals as those in FIG. 9 indicate the same parts. The difference from the heating element described with reference to FIG. 9 is that a heat conduction pattern 201 having good heat conduction is provided in a non-sheet passing area of a small size paper such as an envelope on the back surface of the ceramic substrate 8. .
The heat conductive pattern is formed of a metal paste having a high thermal conductivity. In the present embodiment, an Ag paste is printed and formed on the back surface of the substrate 8. In the example of FIG. 1, the paper passing reference is an end reference, and the heat conduction pattern 201 is
The central end of the pattern 201 is near the paper passing area of the small-size recording material, and the side end of the pattern 201 is formed on the back surface of the substrate 8. One end near the edge, and the center end of the pattern may or may not partially overlap the sheet passing area of the recording material.

In the above embodiment, an experiment was performed using an image forming apparatus having a process speed of 50 mm / sec.

Next, the results of the heater split test in the severe mode of the ceramic heater used in this embodiment and the conventional ceramic heater, and the measurement results of the heater surface temperature are shown.

The heater split test in the severe mode is L / L
In an environment (15 ° C., 10%), 10 sheets of 315 g paper were continuously passed, and cooling with a fan was defined as one cycle for 10 minutes. The paper size used in this embodiment is B5 size and irregular size (B5 size−15 mm in this embodiment).
Size).

[0036]

[Table 1]

Table 1 shows the results of the severe mode heater split test described above.

In the case of using the heater of the conventional configuration, the severe test failed in about 3 to 5 cycles, whereas the use of the heater of the present embodiment performed the test for 10 or more cycles. No cracking of the heater occurred. As is clear from these results, it has been found that the adoption of the heater configuration of the present embodiment with respect to the conventional heater is very effective against heater cracking.

[0039]

[Table 2]

Table 2 shows a comparison of the heater surface temperature between the case where the conventional heater is used and the non-sheet passing area where the heater of the present embodiment is used. In the present embodiment, two points were measured on the heating element in the heater width direction and on the ceramic substrate on the upstream side. Here, T1 is the surface temperature on the heating element, and T2 is a portion without the heating element (in the present embodiment, an intermediate point between the substrate end and the center of the heating element).
Surface temperature. Here, the measurement was performed by fixing a thermocouple at a place where the heater floats. As can be seen from this result, in the case where the conventional heater is used and the case where the configuration of the present embodiment is adopted, the maximum temperature of the heater can be lowered by dispersing the maximum temperature of the heater by increasing the heat conduction, and It can be seen that it is possible to reduce the temperature difference ΔT between the surface temperature T1 on the heating element and the surface temperature T2 of the part without the heating element. Regarding thermal stress, reducing this temperature difference ΔT is very effective in preventing cracking of the heater. As can be seen from these results, by employing the heater of the present embodiment, it is possible to provide a very large margin for cracking of the heater.

In the conventional configuration, when several small-sized thick papers or envelopes are passed while being overlapped, an abnormal rise in the non-paper passing area due to the heater unit floating from the pressure roller. Although there was a possibility that a heater crack might occur due to the temperature, according to the present embodiment, a material having good thermal conductivity is formed in a place where the temperature rises abnormally by floating from the pressure roller. Heat cracks can be suppressed by diffusing heat in both the direction and the width direction to reduce thermal stress.

In this embodiment, as shown in FIG. 1, the heat conducting pattern 201 is a single rectangular shape. However, the heat conducting pattern may be composed of a plurality of patterns. It may be shaped.

[Second Embodiment] FIG. 2 is a rear view of a second embodiment according to the present invention. In this embodiment, one AC electrode is formed on the back surface through a through hole. In such a configuration, A
Since the configuration is such that a connector (not shown) is inserted into the C electrode to establish electrical continuity, there is inevitably formed a gap where the heater stay (support) does not contact near the connector contact on the back surface of the heater. These gaps cause the heat insulating effect of the heater, and the difference in the heat conduction of the heater between the portion having the gap and the portion not having the gap may cause a further temperature difference. Therefore, with this configuration, when multiple small-sized thick papers are fed, the temperature rises to a very high temperature at the location where the heater unit and the pressure roller in the non-sheet passing portion float.

In the present embodiment, the AC electrode formed on the back surface of the heater having the above configuration is different from the conventional one in which the heat conductivity on the back surface is not taken into account. As shown in FIG. 2, the electrode pattern 202 formed on the back surface is formed so as to cover a portion of the non-sheet passing area where the temperature rises sharply. Thereby, in particular, without forming a pattern using a good heat conductive paste separately,
By employing such an AC electrode pattern and good heat conduction pattern, the heat of the overheated portion of the heater can be dispersed.

As a result, the heater crack in the severe test mode described in the first embodiment does not occur even after 10 cycles or more, similar to the heater described in the first embodiment.
As compared with the conventional heater, a margin for the heater crack could be secured.

[Embodiment 3] FIG. 3 is a rear view of the third embodiment. In this embodiment, a system in which the paper passing reference is the center is used. In the fixing device configuration of the present embodiment,
When small-sized thick paper is passed through the center, both ends may float, and abnormal temperature rise occurs in the non-sheet passing areas at both ends. However, since a thermistor electrode is formed on at least one of the back surfaces, it is not possible to form a heat conduction pattern on the thermistor electrode pattern side. Therefore, it is preferable to adopt a configuration utilizing this thermistor electrode pattern.

In this embodiment, the same heat conduction pattern 201 as that of the first embodiment is formed on the AC electrode side, and the DC electrode pattern 203 is formed on the DC electrode side of the thermistor.
Is formed wider than the conventional heater. In particular, when the small-size sheet is passed, the edge of the sheet is applied, and the heater unit and the pressure roller are formed to be wide in a floating range. The heater cracking in the severe test mode described in the first and second embodiments using the heater of the present embodiment is similar to that of the heater described in the first embodiment.
No heater cracking occurred even at 0 cycles or more, and a margin for the heater cracking could be secured as compared with the conventional heater.

[Embodiment 4] FIGS. 4, 5 and 6 are rear views of the heater used in this embodiment. In this embodiment, a good heat conductive paste is printed on the back surface of the heater,
Further, a heat-resistant polymer layer, for example, a polyimide film was attached to the back surface of the heater with an adhesive.

In this embodiment, FIGS. 4, 5, and 6
The polyimide film 301 is adhered on the heat conductive pattern 201, 202 or 203 as shown in FIG.

[0050]

[Table 3]

Table 3 shows the experimental results of the heater described in the first embodiment and the severe heater cracking test of the fourth embodiment.
In the heater cracking test, the temperature control temperature was further increased by 20 ° C. in comparison with the severe heater cracking test performed in Embodiment 1, and a comparative experiment was performed under more severe conditions.

As is clear from Table 3, the strength is remarkably increased as compared with the heater of the first embodiment.

[0053]

[Table 4]

Further, Table 4 shows the measured surface temperature of the heater in the excessively high temperature portion in the non-sheet passing area when the heater of this embodiment is used. As is apparent from this result, by adopting the configuration of the present embodiment, T1 and Δ
Both T can be kept low, which is more advantageous against heater cracking. In the present embodiment, first, a good heat conduction pattern is formed on the back surface of the heater substrate, so that even when the heater unit and the pressure roller float, heat is dispersed on the ceramic substrate, resulting in local excessive temperature rise. Can be prevented,
Further, since the heat conduction is good, the temperature gradient on the substrate can be reduced by diffusing in the longitudinal direction and the width direction of the substrate, and the heater can be prevented from cracking by reducing the thermal stress of the heater. From the overheated portion to the vicinity thereof, a heat-resistant polymer layer, by providing a polyimide film layer in the present embodiment, increases the heat capacity of the heater, and at the same time, promotes heat transfer from the heater to the heater stay, It has been found that the temperature of the overheated portion of the heater can be further reduced, and at the same time, the temperature difference between the heating element and the other substrate portion can be reduced.

[0055]

As described above, according to the present invention,
By forming a heat conductive pattern on the back side of the non-sheet passing area of the recording material of the heating element, the heating element is generated when multiple small-size feeds or small-size thick paper are passed. Abnormal overheating in the non-sheet passing area due to the gap of the pressure member is reduced, and the temperature gradient at the location of abnormal heating is distributed by a good heat conduction pattern, and the thermal stress of the heating element caused by the temperature gradient Can be suppressed. This can prevent the occurrence of heater cracks. Further, in addition to alleviating the thermal stress by the good heat conduction pattern, by forming the heat resistant polymer layer, it is possible to provide a configuration having more margin for the heater crack, and to prevent the heater crack. Was.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front and rear view of a heating element according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway front and rear view of a heating body according to a second embodiment of the present invention.

FIG. 3 is a partially cutaway front and rear view of a heating element according to a third embodiment of the present invention.

FIG. 4 is a partially cutaway front and rear view of a heating element according to a fourth embodiment of the present invention.

FIG. 5 is a partially cutaway front and rear view of a heating body according to a fourth embodiment of the present invention.

FIG. 6 is a partially cutaway front and rear view of a heating body according to a fourth embodiment of the present invention.

FIG. 7 is a schematic diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 8 is a view showing one embodiment of a film heat fixing device according to the present invention.

FIG. 9 is a partially cutaway front and rear view showing an example of a conventional heating element.

FIG. 10 is a partially cutaway front and rear view showing another example of a conventional heating element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Film 2 ... Heating body support 3 ... Heating body 4 ... Pressure roller 6 ... Thermistor 8 ... Ceramic substrate 201 ... Good heat conduction pattern 202 ... Good heat conduction pattern 203 ... AC electrode and good heat conduction pattern 301 ... Heat resistant polymer the film

Claims (7)

[Claims] An unfixed image-passing recording material is passed through a nip portion between an elongated rod-shaped heating element extending perpendicularly to a recording material conveyance direction and a pressing member pressed against the heating element. A heat fixing device for applying heat energy of a heating element to a recording material to thereby thermally fix the recording material, wherein a heat conduction pattern is formed on a back surface of the heating element. 2. The heat fixing device according to claim 1, wherein the heat conduction pattern is formed on a back surface of a recording material non-sheet passing area of the heating member. 3. The heat fixing device according to claim 1, wherein the heat conduction pattern is formed by an electrode for a heating element temperature detecting unit. 4. The heat fixing device according to claim 1, wherein the heat conduction pattern on the back surface of the heating body is formed of an Ag-based material. 5. The heat fixing device according to claim 4, wherein a heat resistant polymer layer is formed on a heat conductive pattern formed on a back surface of the heating element. 6. The heat fixing device according to claim 5, wherein the heat-resistant polymer layer is a polyimide film. 7. An image forming unit for forming an image on a recording material,
An image forming apparatus comprising the heat fixing device according to claim 1, which heats and fixes an image on a recording material.