JP2001043956A - Heating device, heat fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably execute the heating process over the whole image area to form an image of high quality free from the unnevenness of the image by partially overlapping end parts of heating elements in the conveying direction, and partially lowering a value of resistance value of the overlapped part to allow a synthetized heating value of the overlapped part to agree with a heating value of the other area. SOLUTION: End parts of heating elements at boundary parts of the heating elements are overlapped longitudinally with respect to the lateral (width) direction of a base, and heating element overlapped end parts 8e for large size formed by expanding a width of the end part of each heating element twice to partially reduce the resistance in half, and common heating element overlapped end parts 8f are provided. For example when an overlap width of the overlapped part is 1 mm, a gap is not generated on the overlapped part when a temperature of a heater is raised to a target temperature even though the central common heating element is displaced to right by 0.5 mm in the manufacturing of the heater. The lowering of a printing speed can be prevented by driving the central common heating element in the fixing of the paper of a small size, and the generation of the unevenness in fixing on the boundary part of the heating elements can be prevented in the fixing of the paper of a large size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a pressing member forming a pressure contact portion with the surface of a rotating body, and a heating element including a resistance heating element capable of being electrically heated and brought into contact with the inner surface of the rotating body.
A heating device for nipping and conveying the material to be heated in the press contact portion to heat, a heating and fixing device for fixing unfixed toner on the recording material to the recording material using the heating device as a heat source, and an electronic device to which the heating and fixing device is applied The present invention relates to an image forming apparatus such as a photographic printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile, etc., which uses an electrophotographic method, a fixing method for adhering an unfixed toner image formed on a recording material onto the recording material has been known as thermal efficiency and safety. 2. Description of the Related Art A contact heating type fixing device having good operability is widely known. In particular, in recent years, from the viewpoint of promoting energy saving, a film heating type fixing method of heating through a film having a small heat capacity has attracted attention as a method having a high heat transfer efficiency and a quick start-up of the apparatus. JP, JP-A-2-1
57878, JP-A-4-44075 to JP-A-4-44083, JP-A-4-204980 to JP-A-4-204984, and the like.

[0003] The film heating and fixing apparatus includes a method of transporting the film between the pressure roller while applying tension using a transport roller and a driven roller dedicated to transport the film, and a method of adding a cylindrical film. There is a method in which the film is driven by the conveying force of the pressure roller. The former has an advantage that the film transportability can be enhanced, and the latter has an advantage that the configuration can be simplified and a low-cost fixing device can be realized.

FIG. 11 shows a cross-sectional structure of a film fixing device driven by a pressure roller as a specific example. In FIG. 1, an image formed by a toner 2 formed on a recording material 1 is pressed to a total pressure of about 4 to 15 kgf between a pressure roller 3 made of heat-resistant rubber and the pressure roller, and is applied by a frictional force. Conveyed to the nip portion with the cylindrical fixing film 4 which is rotated and conveyed along the heater holder 10 also serving as a film guide member with the rotation of the pressure roller,
Heating and pressurization is performed by the heater 5 via the fixing film, and fixing is performed.

At this time, the fixing film has a thickness of 1 to reduce the heat capacity and improve the quick start property.
PTFE, PF having heat resistance, releasing property and durability of 00 μm or less, more preferably 40 μm or less and 20 μm or more
A, PPS monolayer film or polyimide, polyamide imide, PEEK, PES, etc.
It is composed of a composite layer film coated with E, PFA and FEP as a release layer.

On the other hand, a heater 5 as a heat source has a pattern of a heating element 8 formed on a heater substrate 6 made of a heat-resistant insulating material such as ceramics, the surface of which is protected by heat-resistant glass 9, and the back surface of the substrate has A temperature detecting element 7 is provided, and the temperature of the fixing device is controlled by detecting the temperature of the back surface of the substrate.

FIG. 12 is a front view of a heating element forming surface of the heater from which the protective glass is omitted. The heating element 8 has a belt-like pattern, and the material of the heating element 8 is silver palladium (Ag).
/ Pd), an electric heating element such as Ru02, Ta2N, etc., which generates heat when energized from an energizing electrode 11 made of silver platinum (Ag / Pt) formed on the substrate surface via a wiring pattern 11 '.

As described above, various image forming apparatuses such as printers using the above-described fixing device are capable of eliminating the need for preheating during standby due to high heating efficiency and the speed of rising, and eliminating waiting time. It has many advantages, especially since the method of driving a cylindrical film with the conveying force of a pressure roller can be realized at low cost. It is as expected.

In order to realize this high speed, first, naturally, the motor is powered up to increase the rotation speed of the pressure roller and the fixing film, and at the same time, sufficient heat energy is supplied to the paper having a short passage time. To supply, set the fixing temperature even higher, increase the nip width so as to widen the heating area by increasing the pressing force of the pressure roller, and change the material of the heater substrate and fixing film to a material with high thermal conductivity. It is necessary to improve such as.

[0010] On the other hand, as the speed is increased, the amount of heat that is not deprived of the paper in the non-paper passing portion where the paper does not exist is accumulated when continuous feeding of small-sized paper having a narrow width is performed.
The temperature of this part rises abnormally, and the temperature of the peripheral members rises above the heat resistance temperature, and non-paper passing portions that cause problems such as paper deformation, image defects due to high temperature offset of toner, and toner contamination of the pressure roller. A phenomenon called temperature rise is a major problem.

FIG. 13 is a conceptual diagram showing a case where the small-size paper is passed through an on-demand heater at a position based on the center paper passing. FIG. 14 shows a corresponding temperature distribution in the longitudinal direction of the heater substrate surface. The central part of the heater through which the paper is passed is temperature-controlled by temperature detection by a thermistor 7 provided near the center, so that the target fixing temperature t1 is maintained. The amount of heat not taken away is accumulated, and the temperature rises to t2, which exceeds the fixing temperature.

In particular, in such an on-demand fixing device, a material having a low heat capacity is used for a heater, a fixing film and the like in order to enhance responsiveness. = When setting the 200 ° C setting, 16 sheets of A4 size paper can be continuously fixed in one minute and the envelope with the paper width less than half is continuously passed, t2 = 300 ° C can be easily reached just by passing several sheets, The heat-resistant temperature of the heat-resistant resin used for the heater holder is quickly exceeded. For this reason, when passing the envelope, it is necessary to extend the paper passing interval to provide a temperature relaxation time, and the number of envelopes that can be passed per minute has to be reduced to less than half that of the normal size paper.

Several measures have been proposed to cope with such a problem. However, as a method which can be dealt with only by changing the configuration of the heater, a plurality of heating elements as shown in FIGS. A method of switching the heating area according to the width of the paper to be passed by using the method has been considered.

In FIG. 15, a heating element 8a for large size paper is formed over the entire area of the paper passing area exclusively for fixing large size paper, and a heating element 8b for small size is provided at the center of the central sheet passing reference paper passing area. This is a paper size heating element switching method in which the heaters used completely for large size paper and small size paper are switched and fixed, and in FIG. 16, the large size dedicated end heating element 8c and the common heating for all sizes are used. The heating elements are arranged in close proximity so that the bodies 8d are arranged in substantially the same straight line, and all the heating elements are driven and fixed when fixing large-size paper, and fixed only by the common heating element when fixing small-size paper. It is a driving method.

In these systems, it is necessary to separately provide and control the temperature detecting means in both the non-sheet passing portion and the sheet passing portion when the small-size sheet is passed. Area and a paper passing section).

In this case, in the former method of switching the heating elements by paper size, the heating elements are arranged in parallel at a distance in a paper passing area common to both large and small sizes. In order to use a thermistor, make sure that the detected temperatures when both heating elements are driven separately are almost equal, and that the detected temperature difference does not increase even when the measurement point is shifted within the accuracy of the thermistor mounting position. Since it is necessary to measure in a stable temperature distribution area of each heating element, it is necessary to devise a method of attaching the temperature detecting means. In addition, since the two heating elements are basically used separately, with increasing speed, A new device is required to suppress flicker at the time of wave number control and noise due to harmonic distortion at the time of phase control, which are problems when the resistance of the heating element is reduced in order to increase the heat generation amount of the heating element.

On the other hand, in the latter heating-element-division driving method for each heating area, since there is only one heating element in one sheet passing area,
The setting of the thermistor is easy, and the power of each heating element can be allocated and controlled independently, so that flicker and harmonic distortion can be suppressed.

However, in the above-mentioned heating element division driving method for each heating area, a problem occurs depending on how to process a boundary portion generated between the heating elements. That is, if even a small gap is provided at the boundary between the heat generating elements, a heat source disappears in the gap, so that an area having a low temperature is locally formed. Is formed in a position where the fixing property is deteriorated continuously in the transport direction at a position corresponding to.

On the other hand, if the heating elements are shifted back and forth in the transport direction, and if the ends of the heating elements are arranged so as to overlap in the transport direction at the boundary between the heating elements, the above-mentioned gap is eliminated, and the fixing property is reduced. Eliminates the risk of forming a partially degraded area, but conversely, in the overlapped portion, the calorific values of both heating elements are combined and a high-temperature area is formed locally,
There is a risk that an image defect such as gloss unevenness or density unevenness may occur in the image after fixing, or the toner may be partially heated excessively, causing so-called high-temperature offset. In addition, when a ceramic having relatively low thermal conductivity is used for the heating substrate, local concentration of stress occurs due to local temperature rise, which may cause cracks in the portion and damage the heater.

It is possible that such a problem can be alleviated to some extent by forming a heating element pattern so as to minimize the amount of overlap at these boundary portions. When the positional deviation due to the tolerance of the printing accuracy of the heating element formed in the printing process becomes large, and the central heating element is printed shifted to the right as shown in FIG. 17, the temperature distribution of the heater in the substrate longitudinal direction is obtained. As shown in FIG. 18, a region where the calorific value becomes zero occurs on the left side where a gap is generated as shown in FIG. 18, and the temperature locally decreases, and conversely, an excessively overlapping region occurs on the right side and a local abnormal temperature rise occurs. These temperature variation widths can easily cause temperature unevenness of ± 10 ° C. or more, and such temperature unevenness of 10 ° C. or more has a risk of causing fixing property unevenness.

[0021]

In a conventional heating apparatus using a heating substrate and a heat-resistant film, the heating area is adjusted according to the paper size in order to secure high-speed and stable fixing regardless of the paper size used. The heating elements are divided into a plurality of parts in the longitudinal direction of the heating area so that each heating element can be independently driven. There has been a problem that there is a danger of causing a partial image defect or damage to the contamination of the apparatus due to a local temperature decrease or temperature increase due to a gap or an overlapping portion formed at the boundary portion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and a stable heat treatment can be performed over the entire image irrespective of the paper size without lowering the throughput even when fixing small-sized paper. Heating device capable of performing a stable toner image heating device using the heating device as a heat source, and image forming enabling high quality image formation without image unevenness by applying the heat fixing device The aim is to obtain a device.

[0023]

According to the present invention, there is provided a fixing device and an image forming apparatus having the following constitution.

(1) A pressing member for forming a pressure contact portion with the surface of the rotating body, and a heating element including a resistance heating element capable of being electrically heated and brought into contact with the inner surface of the rotating body. In a heating device for heating by holding and transporting a heating material, the heating element is divided into a plurality of portions in a direction perpendicular to a transport direction of the heating material so that a heating area can be selected according to a width of the heating material. Are arranged so that each heating element can be driven independently,
At the boundary between the heating elements, at least the ends of the heating elements are shifted back and forth with respect to the transport direction to provide a portion that overlaps in the transport direction. A heating device characterized in that the resistance value of the overlapping portion of each heating element is locally reduced so as to match the amount.

(2) The heating device according to claim 1, wherein a cross-sectional area of the overlapping portion is locally increased so as to locally reduce a resistance value of the overlapping portion of each heating element. .

(3) The heat generating element according to (2), wherein, as the shape in which the cross-sectional area of the overlapping portion locally increases, the width of the heating element is increased only in the area of the overlapping portion at the end of the rectangular heating element. Heating equipment.

(4) The cross-sectional area of the overlapping portion is locally increased so that the width of the heating element continuously increases from the inside of the overlapping portion to the end of the rectangular heating element. The heating device according to (2), wherein:

(5) The heating device according to (1), wherein the material of the overlapping portion of each heating element is locally made of a low-resistance material, and the resistance value of the overlapping portion is locally reduced.

(6) All the resistance heating elements are arranged so as to be aligned on the same straight line in the longitudinal direction of the heating substrate, and the boundary between the heating elements is connected to the wiring connection portion at the other end of the heating element. In the area where the width of the heating element overlaps in the direction, the area where the resistance in the direction of conduction is maintained by reducing the material resistance while reducing the material resistance, and the end of each heating element where the ends of the heating elements overlap each other in the same shape with the same shape (1) The heating device according to (1), wherein the heating device is configured by a region in which the material resistance is adjusted so as to maintain the same resistivity as the heating element in the other region by matching and combining the resistances.

(7) The position of the overlapped portion in the longitudinal direction of the heating substrate is provided at least outside the position where the small size paper passes through the end of the image forming area.
The heating device according to any one of (6).

(8) The heating apparatus according to any one of (1) to (7), wherein aluminum nitride is used as a material of the heating substrate.

(9) The member to be heated is a recording material carrying an unfixed image, and any one of (1) to (8) may be used as a heat source for heating and fixing the unfixed image on the recording material.
A heating fixing device comprising the heating device according to any one of the preceding claims.

(10) An image forming apparatus having image forming means for forming and carrying an unfixed toner image on a recording material, and fixing means for heating and fixing the unfixed toner image formed and carried on the recording material to the recording material. The image forming apparatus according to claim 1, further comprising a heat fixing device according to (9) as the fixing unit.

[0034]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a front view of a heater of a heating device according to Embodiment 1 of the present invention, and FIG. 2 is a diagram showing a case where the heater is heated to a target temperature in order to fix large-size paper with the heater. FIG. 7 is a diagram showing a temperature distribution in a substrate longitudinal direction on a heater surface when the heating is performed.

In FIG. 1, the same parts as those in FIG. 17 are denoted by the same reference numerals, and redundant description will be omitted. In the first embodiment, two large-size dedicated end heating elements 8 connected in series
Since the longitudinal length of the single heater c and the longitudinal length of the large and small common heater 8d are the same, the resistance of the common heater 8d is set so that the power consumption of each heater connected in parallel for the same power supply voltage of 100 V is equal to 400W. The rate is twice as large as that of the large-size dedicated end heating element 8c.

Further, in the first embodiment, a region where the end of the heating element at the boundary between the heating elements is overlapped in the front-back direction with respect to the short (width) direction of the substrate is provided, and the width of the end of each heating element is set. Are enlarged twice to provide a large-sized dedicated heating element overlapping end 8e and a common heating element overlapping end 8f in which each resistance is locally reduced by half.

By using such a configuration, for example, if the overlapping width of these overlapping portions is 1 mm, the common heating element at the center is shifted by 0.5 mm to the right in the pressure film printing step in the manufacture of the heater. Even if the heater is heated to the target temperature, no gap is formed in the overlapped portion, so that the temperature is locally lowered by 10 ° C. or more as shown in FIG. The calorific value doubles, and a large temperature rise that locally increases by 10 ° C. or more does not occur. As shown in FIG. 1B, the calorific value is only 0.5 mm wide, and the combined calorific value is on the left side. In accordance with the change in the calorific value of the two places halved at the end of each heating element and the two places rising 1.5 times on the right side, only slight temperature unevenness within ± 5 ° C. occurs, and the heat of the heater substrate is reduced. More than ordinary alumina, depending on conduction properties If thermal conductivity, the heat value difference between the degree, the paper to form a toner image, did not lead to fixing poor image in question as was fixed by using the heating evening.

The length of the central common heating element is set to be longer than the width of the small-sized paper used in this apparatus, and the length of the resistance value at least at the left and right ends is reduced by half. The length of the small paper is secured so that the whole of the small paper can be accommodated inside, and the small paper is conveyed on the basis of the center in this device. No problem occurred.

As described above, according to the first embodiment, when fixing small-sized paper, the power supply voltage is applied only to the central common heating element to drive the same, so that the conventional non-paper-passing portion is raised. Since no heat is generated, high-speed printing of small-size paper can be continuously performed without lowering the printing speed. There was no fixing unevenness at a position corresponding to the boundary between the heat generating elements, and good fixing properties could be maintained.

Embodiment 2 FIG. 3 is a front view of a heater of a heating device according to Embodiment 2 of the present invention, and FIG. 4 is a diagram in which the heater is heated to a target temperature in order to fix large-size paper with the heater. FIG. 4 is a diagram showing a temperature distribution in a substrate longitudinal direction on a heater surface in a case.

In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. In the second embodiment, the width of the heating element gradually increases from the start point of the overlapping portion of the heating elements at the boundary between the heating elements toward the end, and the width at the extreme end is twice the width of the normal heating element. In this case, a trapezoidal large-sized heating element overlapping end portion 8g and a trapezoidal common heating element overlapping end portion 8h are provided.

By using such a configuration, the resistance of the end of the heating element at the boundary of each heating element gradually decreases, and accordingly, the amount of heat generated in this portion also gradually decreases. If the overlapping width of these overlapping portions is 1 mm as in the first embodiment, even if the central common heating element is formed to be shifted to the right by 0.5 mm to the right in the thick film printing process during the production of the heater, this heater When the temperature was raised to the target temperature, the temperature non-uniformity of each overlapped portion was further reduced, and FIG.
As described above, very slight temperature unevenness occurs only in a 0.5 mm width at two locations on the left and right sides, and even if the paper on which the toner image is formed is fixed using this heater, there is a problem with poor fixability. Did not reach.

As described above, according to the second embodiment, the power supply voltage is applied only to the central common heating element when the small-sized paper is fixed, and the paper is driven in the same manner as the conventional non-paper-passing portion. Since no heat is generated, high-speed printing of small-size paper can be continuously performed without lowering the printing speed. Since the fixing unevenness does not occur at the position corresponding to the boundary portion of each heating element, and the occurrence level of the temperature unevenness is further suppressed as compared with the first embodiment, it is used in a high-speed machine for fixing at a higher temperature. Therefore, it is possible to cope with a printing deviation of a larger heating element.

Embodiment 3 FIG. 5 is a front view of a heater of a heating device according to Embodiment 3 of the present invention, and FIG. 6 is a diagram in which the heater is heated to a target temperature in order to fix large-size paper with the heater. FIG. 7 is a diagram showing a temperature distribution in the substrate longitudinal direction on the heater surface when the heater is turned on.

In FIG. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals, and a duplicate description will be omitted. In the third embodiment, the heating elements are limited to these overlapping portions so that the heating values at the ends of the heating elements at the boundaries between the heating elements are equal and the combined heating value is equal to the heating value of the heating elements at the non-overlapping portions. A low-resistance large-size dedicated heating element overlapping end portion 8i and a low-resistance common heating element overlapping end portion 8j in which the resistance value of the heating element is partially halved by adjusting the material of the heating element material are provided.

By using such a configuration, it is not necessary to partially change the shape of the heating element pattern as in the first and second embodiments, so that it is possible to reduce the width of the entire substrate. This can contribute to downsizing of the apparatus and cost reduction.

Using this configuration, as in the first and second embodiments, for example, if the overlapping width of these overlapping portions is 1 mm, the common heat generation in the center should be performed in the pressure film printing step when the heater is manufactured. Even if the body is shifted to the right by 0.5 mm, when this heater is heated to the target temperature, no gap is formed in each overlapped portion, so that it is locally 10 ° C. or more as shown in FIG. There is no longer a large temperature drop that decreases and the heat generation doubles in the overlap area on the right side, and a large temperature increase that rises more than 10 ° C. locally occurs. In accordance with the change in the calorific value in two places where the amount is halved at the end of each heating element and in the two places where it rises 1.5 times on the right side, only slight temperature unevenness within ± 5 ° C. occurs, and the heater substrate Although it depends on the thermal conductivity of If there is a thermally conductive, the heat generation amount difference of the degree, the paper to form a toner image, did not lead to fixing poor image in question as was fixed using a heater.

As described above, according to the third embodiment, even if the heating element is formed with a heater having a narrow substrate width and a heating element width of the lower limit of the accuracy of the printing process, the center of the heating element is not fixed when small-size paper is fixed. By driving by applying a power supply voltage only to the common heating element, the non-paper-passing portion temperature rise unlike the conventional one is eliminated, so that high-speed printing of small-size paper can be continuously performed without lowering the printing speed. In addition to this, even when fixing large-size paper, there is no fixing unevenness at the position corresponding to the boundary of each heating element in the paper width direction (longitudinal direction of the heating substrate), and good fixing performance is maintained. We were able to.

Fourth Embodiment FIG. 7 is a front view of a heater of a heating device according to a fourth embodiment of the present invention, and FIG. 8 is a diagram in which the heater is heated to a target temperature in order to fix large-size paper with the heater. FIG. 4 is a diagram showing a temperature distribution in a substrate longitudinal direction on a heater surface in a case.

In FIG. 7, the same parts as those in FIG. In the fourth embodiment, the heat generating element 12 is arranged such that the heat generating element center and the front and rear ends of the heat generating elements in the short direction of the heating substrate and the front and rear ends thereof are completely aligned in a straight line. And the short direction matching common heating element 13 is arranged. Even when the overlapping sections of the two heating elements are arranged side by side, the total width is not In order to make the shape equal to the width of the heating element in the overlapped part, the shape is reduced in size, and the heating value is equal to each other, so that the combined heating value is equal to the heating value of the heating element in the non-overlapping part. In addition, a short-side position matching type large-sized dedicated heating element overlapping end portion 12 ″ and a short-direction position matching type common heating element overlapping end portion 13 ″ whose resistance value is changed by adjusting the material of the heating element material are provided.

Further, in order to secure an area necessary for routing the wiring pattern from the end of the overlapping portion, the width of the heating element is partially avoided by avoiding the wiring pattern routing area at the end of the heating element at the boundary between the heating elements. And a large-sized dedicated heating element overlapping end connection portion 12 'and a common heating element overlapping end connection portion 13' for connecting the overlapping portion and the non-overlapping portion are provided.

Naturally, in order to equalize the heat generation amount of the heating element in all the regions, these large-sized dedicated heating element overlapping end connecting portions 12 'and the common heating element overlapping end connecting portion 1 are connected.
The material of the heating element 3 'is changed so that the resistance value is equal to that of the other heating elements even though the width is small. Conventionally, the temperature distribution in the short direction of the heating substrate tends to have a temperature peak on the downstream side because heat is carried by the paper or the fixing film heated in the upstream part of the heater holder and accumulated on the downstream side. There is.

Further, when a heat source exists near the downstream side,
There is the danger that the temperature will rise excessively and the toner will be melted too much and reattached to the film side, which is called a high-temperature offset, or that the heating will exceed the heat resistance of the heater holder and accelerate the deterioration of the members. For this reason, it is not preferable to bring the divided heating elements closer to the downstream end of the substrate. However, by eliminating the necessity of displacing each heating element by using the configuration of the fourth embodiment, such an adverse effect is obtained. Excessive temperature rise of a certain downstream heater holder can be avoided.

Using this configuration, as in the first and second embodiments, for example, if the overlapping width of these overlapping portions is 1 mm, the common heat generation at the center in the pressure film printing step should be performed during the manufacture of the heater. Even if the body is formed to be shifted to the right by 0.5 mm, when this heater is heated to the target temperature, no gap is formed in the nest portion, so that the heater is locally lowered by 10 ° C. or more as shown in FIG. A large temperature drop and a large temperature increase of 10 ° C. or more locally due to a doubling of the calorific value at the right overlap portion are eliminated, and as shown in FIG. There is only slight temperature unevenness within ± 5 ° C according to the change of the calorific value of the two places on the left where the combined calorific value is reduced by half at the end of each heating element and the two places where the combined calorific value rises 1.5 times on the right. And depending on the heat conduction characteristics of the heater substrate, If alumina or the thermal conductivity of the normal, the paper forms a toner image by heating value difference of the degree, it did not lead to fixing poor image in question as was fixed using a heater.

As described above, according to the fourth embodiment, even if a heating element is formed with a heater having a narrow substrate width and a heating element width that is the lower limit of the accuracy of the printing process, the center of the heating element is not fixed when small-size paper is fixed. By applying the power supply voltage to only the common heating element and driving it, the non-paper-passing part temperature rise unlike the conventional one is eliminated, so that high-speed printing of small-size paper continuously without lowering the printing speed is achieved. In addition to this, even when fixing large-size paper, there is no fixing unevenness at the position corresponding to the boundary of each heating element in the paper width direction (longitudinal direction of the heating substrate), and good fixing performance is maintained. We were able to.

In each of the above embodiments, satisfactory results were obtained even when an alumina ceramic substrate was used as the material for the heating substrate. However, when the substrate material was changed to aluminum nitride, the thermal conductivity of the substrate was reduced to 10%. Since the temperature is improved about twice, the above-mentioned temperature unevenness is further reduced. In addition, for such a configuration in which the calorific value is easily shifted, the effect of preventing the substrate from being damaged by thermal shock can be obtained by using aluminum nitride having excellent thermal stress characteristics.

Embodiment 5 FIG. FIG. 9 is a schematic sectional view of a heat fixing device according to a fifth embodiment of the present invention using any one of the heating devices of the first to fourth embodiments as a heat source. As shown in FIG.
Includes a heater 21, a heater holder 22 that supports the heater 21 and guides a cylindrical film 23,
A pressure roller 24 made of heat-resistant rubber, a pressing member 25 for pressing the heater holder 22 toward the pressure roller 24, and the like are provided. The film 23 receives a frictional force by the rotation of the pressure roller 24 and is rotated and conveyed along the heater holder 22. Then, the sheet P on which the unfixed toner image t is formed on the surface is
When the nip N formed by the heater 21 and the pressure roller 24 is conveyed while being heated while being pressed to a total pressure of about 4 to 15 kgf, the toner image t is fixed on the sheet P. You. Usually, this film 23 has a film thickness of 100 μm or less, such as a polyimide or other film having a thickness of 100 μm or less, made of PTFE, P
It is composed of a composite film coated with FA and FEP as a release layer.

On the other hand, the heater 21 is made of aluminum nitride (A
The heating element 21b is formed on one surface of a heater substrate 21a having LN) as a base material, and a temperature detecting element 21c is arranged on the opposite surface, and the temperature of the fixing device is controlled by this temperature detection. ing. Also, the heater 21
Is made of a thermoplastic resin having good moldability, for example, a liquid crystal polymer.

As described above, according to the fifth embodiment, by having the heating device shown in the first embodiment as a heat source, there is no trouble caused by the heater spot.
Stable heat fixing can be performed.

Embodiment 6 FIG. 10 is a schematic diagram showing an example of an image forming apparatus provided with a heat fixing device according to Embodiment 3 of the present invention. This image forming apparatus is a laser beam printer using an electrophotographic process. Reference numeral 51 denotes a housing; and 52, an electrophotographic photosensitive drum as an image carrier. The photosensitive drum 52 is driven to rotate in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed). Then, the photosensitive drum 52 is rotated by the charging roller 53
Is primary-charged uniformly to a predetermined polarity and potential, and modulated on the charged surface in accordance with a time-series electric digital pixel signal of target image information output by a laser scanning exposure device (laser beam scanner) 54. Laser light L
, An electrostatic latent image corresponding to the target image information is formed on the peripheral surface of the drum. The latent image is stored in the developing device 5
5, the toner image is developed, and the toner image reaches a transfer nip portion N between the photosensitive drum 52 and the transfer roller 56.

On the other hand, the recording material P in the paper feed cassette 58 is conveyed one by one by the paper feed roller 57 and
Through the transfer nip N at a predetermined timing, and an electric field having a polarity opposite to that of the toner is applied from the back surface of the recording material P by the transfer roller 56, so that the toner image of the photosensitive drum 52 is applied to the surface of the recording material P. Transcribed.

The transfer nip N
Is separated from the surface of the photosensitive drum 52, guided to the conveyance guide 60, enters the heat fixing device 100 of the present invention shown in FIG. 3, and passes through the fixing nip portion N as described above. The toner image is heated and fixed, and is discharged out of the apparatus through the sheet path 62. The surface of the photosensitive drum 52 after the transfer of the toner image onto the recording material P is cleaned by the cleaning device 63 and is repeatedly provided for image formation.

As described above, according to the fifth embodiment, a stable fixing operation can be performed, and a high-quality image can be formed.

[0065]

As described above, according to the present invention, an apparatus for holding, transporting, and heating a material to be heated via a rotating film between a heating substrate and a pressing member that generates heat by energizing a resistance heating element. In, when trying to speed up the heating device,
In order to ensure high-speed and stable fixing regardless of the paper size used, the heating element is divided into a plurality of parts in the longitudinal direction of the heating area so that the heating area can be selected according to the paper size. In a heater using a heating element divided driving method for each heating area in which the heating elements can be driven independently, the heating element ends are displaced from each other in the paper conveyance direction so that no gap is generated at a boundary portion between the heating elements. At the same time as overlapping, the resistance value of this overlapping part was combined and the end resistance of each heating element was adjusted so as to generate the same heating value as the other heating element parts, so excessive temperature drop at the boundary between each heating element Almost uniform temperature distribution can be formed in the longitudinal direction of the heating substrate without causing temperature rise or temperature rise, and there is an effect that a heating device that does not reduce the throughput of small-sized paper even at high speed can be obtained. .

Further, since this heating device is used as a heat source, it is possible to obtain a heating and fixing device capable of performing stable heating and fixing, and to apply this heating and fixing device to form a high quality image. And the like.

[Brief description of the drawings]

FIG. 1 is a front view of a heater substrate according to a first embodiment of the present invention.

FIG. 2 is a longitudinal temperature distribution diagram of a heater surface substrate according to the first embodiment of the present invention.

FIG. 3 is a front view of a heater substrate according to a second embodiment of the present invention.

FIG. 4 is a longitudinal temperature distribution diagram of a heater surface substrate according to a second embodiment of the present invention.

FIG. 5 is a front view of a heater substrate according to a third embodiment of the present invention.

FIG. 6 is a longitudinal temperature distribution diagram of a heater surface substrate according to a third embodiment of the present invention.

FIG. 7 is a front view of a heater substrate according to a fourth embodiment of the present invention.

FIG. 8 is a longitudinal temperature distribution diagram of a heater surface substrate according to a fourth embodiment of the present invention.

FIG. 9 is a schematic sectional view of a heat fixing device according to a fifth embodiment using the heating device of the present invention as a heat source.

FIG. 10 is a schematic sectional view of an image forming apparatus according to a fifth embodiment provided with the heat fixing device of the present invention.

FIG. 11 is a cross-sectional view of a configuration of a conventional pressure roller drive type film fixing device.

FIG. 12 is a front view of a conventional heater substrate.

FIG. 13 is a conceptual diagram in a case where small-sized paper is passed using a heater of a conventional example.

FIG. 14 is a longitudinal temperature distribution diagram of a heater surface substrate when small-size paper is passed using a conventional heater.

FIG. 15 is a front view of a conventional heating substrate switching system for each paper size.

FIG. 16 is a front view of a heater substrate divided driving system for each heating area according to a conventional example.

FIG. 17 is a front view of a substrate in a case where a heating element forming position is shifted by a heating element division driving method by heating area according to a conventional example.

FIG. 18 is a longitudinal temperature distribution diagram of a heater surface substrate of a heating-element-division-drive heater for each heating region in which a heating element formation position has shifted in a conventional example.

[Explanation of symbols]

Reference Signs List 1 recording material, 2 toner, 3 pressure roller, 4 fixing film, 4 "metal film 5 heater, 6 heater base, 7 temperature detecting element, 8 heating element, 8a heating element for large size paper, 8b heating element for small size , 8c Large size dedicated heating element, 8d Common heating element two, 8e Large size dedicated heating element overlapping end, 8f Common heating element overlapping end, 8g
Trap-type large-sized heating element overlapping end, 8h Trapezoid-shaped common heating element overlapping end, 8i Low-resistance large-size dedicated heating element overlapping end, 8j Low-resistance common heating element overlapping end, 9 Heat resistant glass, 10 heater Holder, 11 electrodes, 11 'Wiring pattern, 12 Short-side position matching type large-size dedicated end heating element, 12' Large-size dedicated end heating element overlapping end connection part, 12 "Short-direction position matching large Heating element stacking end for exclusive use of size, 13
3 'Connection portion 13 "for short-side direction coincidence type common heating element overlapping end portion.

Claims (10)

[Claims] A pressurizing member for forming a pressure contact portion with the surface of the rotating body; and a heating element including a resistance heating element capable of being electrically heated and brought into contact with the inner surface of the rotating body. In the heating device for heating by holding and conveying the material, the heating element is divided into a plurality of portions in a direction perpendicular to the conveying direction of the material to be heated so that a heating area can be selected according to the width of the material to be heated. Each of the heating elements can be independently driven, and at least at the boundary between the heating elements, at least the ends of the heating elements are shifted back and forth with respect to the transport direction to provide a portion overlapping with the transport direction. A heating device characterized in that the heating value of a portion is combined and the resistance value of the overlapping portion of each heating element is locally reduced so as to match the heating value of another region. 2. The heating device according to claim 1, wherein the cross-sectional area of the overlapping portion is locally increased so as to locally reduce the resistance value of the overlapping portion of each heating element. 3. The heating device according to claim 2, wherein the shape of the cross-sectional area of the overlapping portion locally increases, and the width of the heating element is increased only in the region of the overlapping portion at the end of the rectangular heating element. apparatus. 4. The shape in which the cross-sectional area of the overlapping portion locally increases is such that the width of the heating element continuously increases from the inside of the overlapping portion to the end of the rectangular heating element end. The heating device according to claim 2, characterized in that: 5. The heating apparatus according to claim 1, wherein the material of the overlapping portion of each heating element is locally made of a low-resistance material, and the resistance value of the overlapping portion is locally reduced. 6. The resistance heating elements are all arranged on the same straight line in the longitudinal direction of the heating substrate, and the boundary between the heating elements is connected to the wiring connection portion at the other end of the heating element and the conveying direction. The area where the heating element width is reduced and the material resistance is reduced to maintain the resistivity in the energizing direction, and the heating element end resistance of the overlapping part in the conveyance direction with the end of each heating element having the same shape 3. A region whose material resistance is adjusted so that the same resistance is maintained and the same resistivity as that of the heating element in the other region is obtained by combining.
A heating device as described. 7. The image forming apparatus according to claim 1, wherein the position of the overlapping portion in the longitudinal direction of the heating substrate is provided at least outside the position where the small size paper passes through the end of the image forming area. The heating device according to claim 1. 8. The heating apparatus according to claim 1, wherein aluminum nitride is used as a material of the heating substrate. 9. The recording medium according to claim 1, wherein the member to be heated is a recording material carrying an unfixed image, and a heat source for heating and fixing the unfixed image on the recording material. A heating fixing device comprising the heating device of (1). 10. An image forming apparatus comprising: an image forming unit for forming and supporting an unfixed toner image on a recording material; and a fixing unit for heating and fixing the unfixed toner image formed and supported on the recording material to the recording material. An image forming apparatus comprising the heat fixing device according to claim 4 as the fixing unit.