JP3484436B2 - Fixing heater, fixing device, and image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing heater, a fixing device, and an image forming apparatus suitable for fixing the toner image-formed on a sheet.

[0002]

2. Description of the Related Art As one of image forming methods used in image forming apparatuses such as copying machines and printers, a toner image is fused to a sheet by heating the sheet while moving the sheet relative to a heater. Those that allow the image to be fixed are commonly used in practice. Further, as the above-mentioned heater, one obtained by screen-printing a silver / palladium-based resistance heating element on a ceramic substrate is known, for example, from Japanese Patent Application Laid-Open No. 2-65086.

FIG. 10 is a cross-sectional view showing the main part of another prior art in this type of heater, showing a cross-section in the longitudinal direction of the substrate. In the figure, reference numeral 100 denotes a ceramic substrate, and a flat surface 101 parallel to the back surface and a flat surface 1 on the front surface side.
01, and an inclined surface 102 extending along the longitudinal direction of the substrate 100. Reference numeral 103 denotes a resistance heating element formed on one surface of the substrate 100 by screen printing. In addition, the substrate 100 has an inclined surface 10 at one end along the longitudinal direction.
2 is formed. A protective layer 104 is formed continuously by a screen printing method over the surface of the resistance heating element and the surface of the substrate including a part of the inclined surface.

FIG. 3 is a sectional view showing a fixing device having this fixing heater. The fixing device 30 includes a fixing heater 3
The pressure roller 32 is arranged so as to face the surface of the resistance heating element 31 of No. 0, and a film-shaped fixing film 33 is movably provided between the fixing heater 30 and the pressure roller 32. Then, the sheet 35 having the toner 36 attached to the predetermined image is fixed to the fixing heater 3 through the fixing film 33.
The toner 36 is conveyed while being pressed against 0 and the pressure roller 32, and the toner 36 is melted and fixed by the heating of the fixing heater 30. Here, the inclined surface of the fixing heater 30 is located on the discharge side of the conveyed sheet. The pressure roller 32 is in pressure contact with a part of the inclined surface including the surface of the resistance heating element 31 of the fixing heater 30. FIG. 4 is a sectional view showing an image forming apparatus provided with this fixing device. This image forming apparatus is a copying machine. The copying machine includes an image forming unit 40 that attaches toner to an electrostatic latent image formed on a photosensitive drum and transfers the toner to a sheet to form a predetermined image.
The above-mentioned fixing device 41 for fixing the toner on which this image is formed is provided.

In the above fixing device, since the fixing heater 30 has the inclined surface 37, the sheet has the inclined surface 37 and the flat surface on which the resistance heating element 31 is formed in the process of discharging the sheet. The pressure roller 32 is squeezed by the ridgeline 38 at the boundary of the sheet 35, so that the sheet 35 can be guided and discharged in a certain direction to prevent the sheet 35 from curling.

[0006]

By the way, up to the present day, along with the speeding up of image formation, there is a demand for thinner fixing heaters. In other words, in order to speed up the image formation, it is necessary to make the volume of the substrate as small as possible in order to increase the heating rising speed of the fixing heater. For this purpose, it is effective to make the fixing heater thin.

However, since the fixing heater shown in the above-mentioned conventional example needs a portion for heating the paper and a portion for squeezing the paper, the width of the fixing heater in the paper conveying direction becomes large, and as a result, the substrate becomes large. The heat was absorbed by the substrate, which impeded the agility of the rise of heating. Therefore, the fixing device and the image forming apparatus equipped with this fixing heater also impede the speeding up of image formation.

Therefore, it is an object of the present invention to provide a fixing heater, a fixing device and an image forming apparatus which solve the above-mentioned conventional drawbacks by improving the structure of the resistance heating element.

[0009]

A fixing heater according to claim 1 is formed of an electrically insulating material including a flat surface having one surface substantially parallel to the other surface and an inclined surface adjacent to the flat surface and extending in the longitudinal direction. And an elongated resistance heating element that is formed along the longitudinal direction of the substrate across the flat surface and the inclined surface of the substrate.

A fixing heater according to a second aspect is the fixing heater according to the first aspect, wherein a protective layer is continuously applied to the flat surface and the inclined surface so as to cover the resistance heating element, and the resistance heating element extends. The total thickness of the resistance heating element and the protective layer on the boundary between the flat surface and the inclined surface in the direction perpendicular to the direction is smaller than the film thickness at the edge of the resistance heating element on the flat surface and the inclined surface. And

According to a third aspect of the present invention, there is provided a fixing heater including a flat surface having one surface substantially parallel to the other surface and a stepped portion adjacent to the flat surface and extending in the longitudinal direction and made of an electrically insulating material. It is characterized by comprising an elongated resistance heating element formed along the longitudinal direction of the substrate across the flat surface of the substrate and the step portion.

A fixing heater according to a fourth aspect is the fixing heater according to the third aspect, wherein a protective layer is continuously applied to the flat surface and the step portion so as to cover the resistance heating element, and the resistance heating element extends. The combined thickness of the resistance heating element and the protective layer on the boundary between the flat surface and the step portion in the direction perpendicular to the direction is smaller than the film thickness at the edge portion of the resistance heating element on the flat surface.

According to a fifth aspect of the present invention, in the fixing device, the pressure roller, the resistance heating element facing the pressure roller, and the inclined surface or the stepped portion are disposed on the paper discharge side. The fixing heater according to any one of claims 1 to 4 and a fixing film movably provided between the fixing heater and the pressure roller.

A fixing device according to a sixth aspect of the present invention is the fixing device according to the fifth aspect, wherein the rotary shaft of the pressure roller is located substantially near the boundary between the flat surface and the inclined surface of the fixing heater or corresponding to a step portion. It is characterized by

A fixing device according to a seventh aspect is the fixing device according to the fifth aspect, wherein the rotating shaft of the pressure roller is closer to the sheet discharging side than the boundary between the flat surface and the inclined surface of the fixing heater or the step portion. It is characterized by being located.

According to another aspect of the present invention, there is provided an image forming apparatus in which a toner is attached to an electrostatic latent image formed on a medium and the toner is transferred to a sheet to form a predetermined image, and a sheet on which the image is formed. The fixing device according to any one of claims 5 to 7, characterized in that the toner is fixed by passing the toner through a fixing film while being pressed against a fixing heater by a pressure roller.

[0017]

In the fixing heater according to the first aspect of the invention, the resistance heating element is formed in a slender shape along the longitudinal direction of the substrate across the flat surface and the inclined surface of the substrate. It is possible to reduce the width in the carrying direction. The resistance heating element generates heat by applying a voltage to both ends of the resistance heating element. However, since the resistance heating element is provided on the inclined surface, the width of the resistance heating element is narrow, so that the volume of the substrate is reduced and the heat capacity is reduced. Becomes smaller. Therefore, the rising speed of the heat generated by the fixing heater can be increased.

Further, the fixing heater having the inclined surface is
The transported paper is squeezed by the pressure roller along the ridgeline at the boundary between the flat surface and the inclined surface of the substrate, and the curl of the paper can be reduced by applying a force to discharge the heated paper in a certain direction. However, in the present invention, since the resistance heating element is formed on the ridge line, it is possible to squeeze the paper while heating it, and it is possible to further reduce the curl of the paper.

The fixing heater according to the second aspect has the same operation as the fixing heater according to the first aspect.

Further, in the fixing heater according to claim 1, a protective layer is continuously formed on the flat surface and the inclined surface so as to cover the resistance heating element, and the resistance heating element and the protection are provided on the boundary between the flat surface and the inclined surface. Since the combined thickness of the layers is made smaller than that of the edge of the resistance heating element on the flat surface and the inclined surface, the surface of the protective layer on the boundary between the flat surface and the inclined surface is rounded. With such a structure of the resistance heating element and the protective layer, it is very easy to form, and for example, the screen printing method is also easy to form.

If the surface of the protective layer is slightly curved, it is possible to prevent the fixing film and paper from being damaged.

In the fixing heater according to the third aspect, the resistance heating element is formed in a slender shape along the longitudinal direction of the substrate across the flat surface of the substrate and the step portion. Therefore, the sheet having the step portion is provided. It is possible to reduce the width in the carrying direction. The resistance heating element generates heat by applying a voltage to both ends of the resistance heating element. However, since the resistance heating element is provided on the stepped portion, the width is narrow, so that the volume of the substrate is reduced. The heat capacity is reduced. Therefore, the rising speed of the heat generated by the fixing heater can be increased.

Further, since the resistance heating element is formed across the flat surface and the step portion, it is possible to squeeze the paper with the pressure roller while heating the paper, and it is possible to reduce the curl of the paper.

The fixing heater according to claim 4 has the same operation as the fixing heater according to claim 3.

Further, in the fixing heater according to the third aspect, a protective layer is continuously applied to the flat surface and the step portion so as to cover the resistance heating element, and the resistance heating element and the protection are provided on the boundary between the flat surface and the step portion. Since the combined thickness of the layers is made smaller than that of the edge portion of the resistance heating element on the flat surface, the surface of the protective layer on the boundary between the flat surface and the step portion is rounded. With such a structure of the resistance heating element and the protective layer, it is very easy to form, and for example, the screen printing method is also easy to form.

If the surface of the protective layer is slightly curved, it is possible to prevent the fixing film or paper from being damaged.

According to a fifth aspect of the fixing device, the fixing heater according to any one of the first to fourth aspects is arranged so that the inclined surface or the step portion is on the sheet discharge side. Due to the above-described operation of the fixing heater according to the first aspect to the fourth aspect, the rising speed of the start-up is fast and the high-speed image formation can be dealt with. Further, the curl of the paper is also reduced.

According to a sixth aspect of the present invention, there is provided the fixing device according to the fifth aspect, wherein the rotation shaft of the pressure roller is located substantially near the boundary between the flat surface and the inclined surface of the fixing heater or corresponding to a step portion. Therefore, the conveyed sheet can be reliably and squeezed, curling of the sheet can be reduced, and the sheet can be prevented from being caught in the pressure roller or the like.

A fixing device according to a seventh aspect is the fixing device according to the fifth aspect, wherein the rotation shaft of the pressure roller is closer to the paper discharge side than the boundary between the flat surface and the inclined surface of the fixing heater or the step portion. Since the sheet is positioned, the sheet can be securely and squeezed similarly to the fixing device according to the sixth aspect, curling of the sheet can be reduced, and the sheet can be prevented from being caught in the pressure roller or the like.

An image forming apparatus according to claim 8 adheres toner to an electrostatic latent image formed on a medium such as a photosensitive drum and transfers the toner onto a sheet, and then the image forming apparatus according to claim 5 or claim 7. The image is fixed by conveying the paper on which the image is transferred by the fixing device through the fixing film while being pressed against the fixing heater by the pressure roller.

Therefore, in this image forming apparatus, the above-described operation of the fixing device according to the fifth to seventh aspects makes it possible to speed up the image formation and reduce the curl of the paper.

[0032]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a front view of the fixing heater of the first embodiment. In the figure, 1 is about 300 mm in length and about 2.2 m in width
m is a slender resistance heating element, and is formed on one surface of a slender substrate 2 made of alumina ceramics, for example, by a screen printing method using a silver-palladium-based conductive paste. The size of this substrate is about 3
The width is 50 mm, the width is about 6 mm, and the thickness is about 1 mm. Also,
Reference numerals 3 and 3 denote a pair of terminals provided at both ends of the resistance heating element 1 for applying a voltage thereto. These terminals 3 and 3 are also silver
It is formed by screen printing with a palladium-based conductive paste.
Since it is lower than that, it does not generate heat. The resistance heating element 1 is covered with a protective layer 4 made of glass. By applying a predetermined voltage between the pair of terminals 3 and 3, the resistance heating element 1 generates heat and functions as a heater.

FIG. 2 is a longitudinal cross-sectional view (cross section XX ') of the fixing heater of the first embodiment. The substrate 2 has a flat surface 5 whose one surface is substantially parallel to the other surface and an inclined surface 6 adjacent to the flat surface 5. The inclined surface 5 is formed longer than the resistance heating element 1 and has a surface dimension of about 280 mm.
× 2.5 mm.

The resistance heating element 1 is formed along the longitudinal direction of the substrate across the flat surface and the inclined surface.
The resistance heating element 1 has a width of about 1.5 mm, and the inclined surface 6 has a width of about 7 mm. The ratio of the width of the resistance heating element 1 formed on the flat surface 5 and the inclined surface 6 is not limited to the above value.

The protective layer 4 is widely formed on the surface of the substrate 2 including the surface of the resistance heating element 1. The thickness of the protective layer 4 that covers the flat surface is about 10 μm, and the thickness of the protective layer 4 that covers the inclined surface 6 is slightly thicker than that of the flat surface 5 and about 17 μm at the thickest part of the central portion of the inclined surface 6. Has become.
Next, the manufacturing process of the fixing heater of the first embodiment will be described. The substrate 2 is made of alumina ceramics, and a substrate formed by multiple chamfering is divided into individual pieces by a scribe method. Then, one end edge of the substrate 2 is mechanically polished to form an inclined surface 5. At this time, the regions at both ends of the substrate 2 are not polished and the flat portions are left.

Next, the resistance heating element 1 is printed on the substrate 2. At this time, as shown in FIG. 3, the main surface of the screen printing is the flat surface 5 of the substrate 2. That is, the resistance heating element 1 is printed by moving the printing squeegee 7 in parallel with the flat surface of the substrate 2. Therefore, since the pressing force by the printing squeegee 7 is lower on the inclined surface 6 than on the flat surface 5, the amount of crushing the screen is small, and the film thickness of the resistance heating element 1 on the inclined surface 6 is smaller than that on the flat surface 5. Is also formed slightly larger.

The conductive paste forming the resistance heating element 1 is a mixture of silver-palladium alloy powder and glass frit (inorganic binder) kneaded with a water-soluble organic solvent. After printing, the conductive paste is dried to about 850
The substrate 2 is baked by baking at 10 ° C. for about 10 minutes. In addition, the conductive paste may be a silver / ruthenium oxide alloy or the like.

Next, terminals 3 are formed on the flat surfaces of the two ends of the substrate by partially overlapping the both ends of the resistance heating element 1. First, the terminals 3 and 3 are printed by a screen printing method using a silver / palladium-based conductive paste having a palladium content lower than that of the conductive paste of the resistance heating element 1. This conductive paste differs from the conductive paste of the resistance heating element 1 in that the content of the metal component is low and the melting point of the glass frit is low as described above. The conductive paste is dried and then baked at about 700 ° C. for about 10 minutes to be baked on the substrate 2. In addition to the above, the conductive paste may be a silver-platinum alloy, platinum, gold or the like having a small electric resistance.

Finally, a protective layer 4 is printed on the surface of the substrate 2 including the surface of the resistance heating element 1 by a screen printing method,
It is fired in the same manner as the conductive paste.

FIG. 3 is a sectional view showing the first embodiment of the fixing device of the present invention. This fixing device incorporates the fixing heater 30 shown in the first embodiment for fixing toner. This fixing device includes a resistance heating element 31 of a fixing heater 30.
The pressure roller 32 is arranged so as to face the side surface, and a film-shaped fixing film 33 is movably provided between the fixing heater 30 and the pressure roller 32. The inclined surface 34 of the fixing heater 30 is provided on the side of the fixing film 33 in the carrying-out direction,
That is, the sheet 35 is positioned in the discharge direction. And
The paper 35 to which the toner 36 is attached is attached to the fixing film 33.
The fixing heater 30 and the pressure roller 32 are conveyed while being in pressure contact with each other, and the toner of the toner 36 is heated by the fixing heater 30.
Is melted and fixed.

FIG. 4 is a sectional view showing an embodiment of the image forming apparatus of the present invention. The image forming apparatus shown in the figure is a copying machine. This copying machine fixes an electrostatic latent image formed on a photosensitive drum with toner and transfers the toner onto a sheet to form a predetermined image, and an image forming section 40 for fixing the toner on which the image is formed. The fixing device 41 is provided.

Next, the operation of the first embodiment of the fixing heater, the fixing device and the embodiment of the image forming apparatus will be described.

In FIG. 1, the fixing heater of the first embodiment is
Since the resistance heating element 1 is formed in a slender shape along the longitudinal direction of the substrate 2 while straddling the flat surface 5 and the inclined surface 6 of the substrate 2, the width in the sheet conveying direction can be increased even though the inclined surface 6 is provided. It can be reduced. The resistance heating element 1 generates heat by applying a voltage to both ends of the resistance heating element 1, that is, the terminals 3 and 3, but the width is narrow as much as the resistance heating element 1 is provided on the inclined surface 6. The substrate 2
Has a small volume and a small heat capacity. Therefore, the rising speed of the heat generated by the fixing heater can be increased.

Further, in the fixing device of the first embodiment in which the fixing heater 30 of the first embodiment is incorporated in FIG. 3, the boundary between the flat surface of the substrate 2 and the inclined surface 34 for squeezing the conveyed paper 35. Since the resistance heating element 31 is formed on the ridge line 37 formed in the above, it is possible to squeeze the paper 35 while heating it, and it is possible to further reduce the curl of the paper 35.

Further, in the image forming apparatus of the first embodiment, the action of the fixing heater and the fixing device makes it possible to speed up the image formation and reduce the curl of the paper.

FIG. 5 is a longitudinal cross sectional view showing a second embodiment of the fixing heater of the present invention. This fixing heater has the same structure as that of the fixing heater of the first embodiment except the shape of the protective layer, and therefore only the differences will be described.

The substrate 50 of this fixing heater has a flat surface 51 whose one surface is substantially parallel to the other surface and a step portion 52 adjacent to the flat surface 51. The resistance heating element 53 is formed so as to cover the flat surface 51 and the step portion 52 of the substrate 50 along the longitudinal direction of the substrate 50. Further, a vitreous protective layer 54 is formed so as to cover the flat surface 51 including the resistance heating element 53 and the step portion 52.

Next, the operation of the fixing heater of the second embodiment will be described. In this fixing heater, the resistance heating element 53 is formed in a slender shape along the longitudinal direction of the substrate so as to straddle the flat surface 51 of the substrate 50 and the step portion 52. Therefore, the sheet is conveyed while the step portion 52 is provided. It is possible to reduce the width in the direction. Since the width of the substrate 50 is narrow, the volume of the substrate 50 can be reduced and its heat capacity can be reduced. Therefore, the rising speed of the heat generated by the fixing heater can be increased.

Further, since the resistance heating element 53 is formed so as to extend over the flat surface 51 and the step portion 52, the sheet is heated when used by being incorporated in the fixing device as in the fixing device of the first embodiment. On the other hand, it is possible to squeeze with the pressure roller, and curl of the paper can be reduced.

FIG. 6 is an enlarged cross-sectional view of the essential parts showing the second embodiment of the fixing device. The basic structure of this fixing device is
Since it is similar to the fixing device of the embodiment, only the differences will be described.

In this fixing device, the rotating shaft of the pressure roller 60 is positioned so as to correspond to substantially the boundary between the flat surface 62 and the inclined surface 63 of the fixing heater 61.

According to this structure, the conveyed sheet 64 can be securely squeezed with a strong force, the curl of the sheet 64 can be further reduced, and the sheet 64 can be prevented from being caught in the pressure roller or the like. Then, as shown in FIG. 7, substantially the same effect can be obtained even if the rotation shaft of the pressure roller 70 is located closer to the discharge side of the paper 73 than the boundary between the flat surface 71 and the inclined surface 72 of the fixing heater. it can.

Further, in the fixing heater in which the resistance heating element is formed on the stepped portion of the substrate, when the rotating shaft of the pressure roller is arranged at a position corresponding to the stepped portion, or on the paper discharge side of the stepped portion. Even when the rotary shaft of the pressure roller is arranged, the same effect as that of the fixing device of the second embodiment can be obtained.

FIG. 8 is a longitudinal cross-sectional view showing a third embodiment of the fixing heater of the present invention. This fixing heater has the same structure as that of the fixing heater of the first embodiment except the shape of the protective layer, and therefore only the differences will be described. The protective layer 80 is a resistance heating element 81.
Of the resistance heating element 81 and the protective layer 80 on the boundary between the flat surface 82 and the inclined surface 83 in the direction perpendicular to the extending direction of the flat surface 82 and the inclined surface 83. The resistance heating element 81 and the protective layer 8 at the edge of the resistance heating element 81
It is formed to be smaller than the combined film thickness of 0 and 0 (A and C in the figure). As a result, the surface of the protective layer on the boundary between the flat surface and the inclined surface is necessarily rounded.

According to this fixing heater, it is possible to squeeze the paper while heating it, like the fixing heater of the first embodiment, and it is possible to reduce the curl of the paper. Further, it can be formed more easily than by making the surface of the protective layer on the boundary between the flat surface and the inclined surface square, and can be formed by, for example, a screen printing method. Further, if the surface of the protective layer is slightly curved, it is possible to prevent the fixing film and the paper from being damaged.

FIG. 9 is a longitudinal cross-sectional view showing a fourth embodiment of the fixing heater of the present invention. This fixing heater is a fixing heater in which a resistance heating element 92 is formed on a stepped portion 91 of a substrate 90, and a flat surface 93 covers the resistance heating element 92.
A protective layer 95 is continuously applied to the step portion 94, and the resistance heating element 92 and the protective layer 95 on the boundary between the flat surface 93 and the step portion 91 in the direction perpendicular to the extending direction of the resistance heating element 92. The combined film thickness (B in the drawing) is formed smaller than the film thickness (A in the drawing) of the edge of the resistance heating element 92 on the flat surface 93. According to this fixing heater, similarly to the fixing heater of the third embodiment, the resistance heating element 92 and the protective layer 95 can be easily formed, and the fixing film and the paper are not easily damaged.

By the way, the substrate surface may be processed to have a flat surface, an inclined surface, or a stepped portion. Further, the inclined surface may be curved to some extent as long as the ridgeline is formed at the boundary with the flat surface. Further, the lower surface of the step portion does not need to be parallel to the flat surface.

[0059]

According to the first aspect of the present invention, since the width of the substrate is narrowed by the amount of the resistance heating element provided on the inclined surface, the volume of the substrate is reduced and the heat capacity is reduced. Therefore, it is possible to provide a fixing heater having a high rate of heat generation.

Further, since the resistance heating element is formed on the ridge, it becomes possible to squeeze the paper while heating it.
The curl of the paper can be further reduced.

According to the second aspect of the present invention, the combined thickness of the resistance heating element and the protective layer on the boundary between the flat surface and the inclined surface is made smaller than that of the edge portion of the resistance heating element on the flat surface and the inclined surface. Since it is made small, the surface of the protective layer on the boundary between the flat surface and the inclined surface is rounded and can be formed very easily by, for example, the screen printing method. Further, if the surface of the protective layer is slightly curved, it is possible to prevent the fixing film and the paper from being damaged.

According to the third aspect of the present invention, since the width of the substrate is narrowed by the amount of the resistance heating element provided on the step portion, the volume of the substrate is reduced and the heat capacity is reduced. Therefore, it is possible to provide a fixing heater having a high rate of heat generation.

Further, since the resistance heating element is formed across the flat surface and the step portion, it is possible to squeeze the paper with the pressure roller while heating the paper, and curl of the paper can be reduced.

According to the invention of claim 4, it has the same operation as the fixing heater of claim 3. Since the combined thickness of the resistance heating element and the protective layer on the boundary between the flat surface and the step portion is smaller than that at the edge of the resistance heating element on the flat surface,
The surface of the protective layer on the boundary between the flat surface and the step is rounded,
For example, it can be formed very easily by a screen printing method. Further, if the surface of the protective layer is slightly curved, it is possible to prevent the fixing film and the paper from being damaged.

According to the fifth aspect of the invention, by the action of the fixing heater of the first or the fourth aspect, the rising speed of the heat generation start is fast and the high speed image formation can be dealt with, and the curling of the paper is also reduced. A device can be provided.

According to the sixth aspect of the invention, it is possible to provide a fixing device in which the conveyed sheet can be reliably and squeezed and curling of the sheet is reduced.

According to the invention described in claim 7, it is possible to provide a fixing device in which the curl of the paper is reduced as in the fixing device according to claim 6.

According to the eighth aspect of the invention, the image forming apparatus capable of speeding up the image formation and reducing the curl of the paper can be obtained by the above-described operation of the fixing device according to the fifth aspect. Can be provided.

[Brief description of drawings]

FIG. 1 is a front view showing one surface of a fixing heater according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of an essential part showing a first embodiment of a fixing heater in the present invention.

FIG. 3 is a sectional view showing a first embodiment of the fixing device according to the present invention.

FIG. 4 is a sectional view showing a first embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a cross-sectional view of essential parts showing a second embodiment of the fixing heater in the present invention.

FIG. 6 is a sectional view showing a second embodiment of the fixing device according to the present invention.

FIG. 7 is a cross-sectional view showing a third embodiment of the fixing device in the present invention.

FIG. 8 is a cross-sectional view of essential parts showing a third embodiment of the fixing heater in the present invention.

FIG. 9 is a cross-sectional view of essential parts showing a fourth embodiment of the fixing heater in the present invention.

FIG. 10 is a sectional view of a main part of a conventional fixing heater.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Resistance heating element, 2 ... Substrate, 5 ... Flat surface, 6 ... Inclined surface 52 ... Step portion

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuya Sato 4-3-1, Higashi-Shinagawa, Shinagawa-ku, Tokyo Inside Toshiba Lighting & Technology Co., Ltd. (56) Reference JP-A-7-219362 (JP, A) JP Hei 6-230624 (JP, A) JP-A-4-242774 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (8)

(57) [Claims] 1. An elongated substrate of a longitudinally extending electrically insulating material comprising a flat surface substantially parallel to the other surface and an inclined surface adjacent to the flat surface; and at least a portion of the flat surface of the substrate. And a slender resistance heating element formed along the longitudinal direction of the substrate across the surface and the inclined portion. 2. A protective layer is continuously applied to the flat surface and the inclined surface so as to cover the resistance heating element; on a boundary between the flat surface and the inclined surface in a direction perpendicular to the extending direction of the resistance heating element. The fixing heater according to claim 1, wherein the combined thickness of the resistance heating element and the protective layer is smaller than the film thickness of the edge portion of the resistance heating element on the flat surface and the inclined surface. 3. An elongated substrate made of an electrically insulative material extending in a longitudinal direction and including a flat surface having one surface substantially parallel to the other surface and a step portion adjacent to the flat surface; and at least a part of the flat surface of the substrate. A long and narrow resistance heating element formed along the longitudinal direction of the substrate across the surface and the step portion; and a fixing heater. 4. A protective layer is continuously applied to the flat surface and the step portion so as to cover the resistance heating element; on a boundary between the flat surface and the step portion in a direction perpendicular to the extending direction of the resistance heating element. The fixing heater according to claim 3, wherein the combined thickness of the resistance heating element and the protective layer is smaller than the thickness of the edge portion of the resistance heating element on the flat surface. 5. A pressure roller; and a resistance heating element that faces the pressure roller, and is arranged such that a portion of the substrate whose thickness is smaller than that of the inclined surface or the stepped portion is on the paper discharge side. An image forming apparatus comprising: the fixing heater according to any one of claims 1 to 4; and a fixing film movably provided between the fixing heater and the pressure roller. 6. The fixing device according to claim 5, wherein the rotating shaft of the pressure roller is positioned substantially near the boundary between the flat surface and the inclined surface of the fixing heater or corresponding to a step portion. 7. The fixing device according to claim 5, wherein the rotary shaft of the pressure roller is located closer to the paper discharge side than the boundary between the flat surface and the inclined surface of the fixing heater or the stepped portion. . 8. A means for adhering toner to an electrostatic latent image formed on a medium and transferring the toner to a sheet to form a predetermined image; a sheet on which the image is formed is pressed through a fixing film. An image forming apparatus comprising: the fixing device according to any one of claims 5 to 7, wherein the fixing device fixes the toner by passing the toner while pressing it against the fixing heater.