JPH0895403A - Fixing heater and fixing device and image forming device - Google Patents

Abstract

PURPOSE: To prevent crack generation accompanying the warpage of an insulating board. CONSTITUTION: This fixing heater is provided with the long, narrow insulating board 11 having a flat surface 11b and slopes 11a constituted in such a manner that both top end surfaces are inclined along the longitudinal direction, a heating element 12 formed in the longitudinal direction of the insulating board 11 on the flat surface 11b of the board 11 and an insulator layer 13 formed so as to cover the heating element 12 on the board 11 and the insulator layer 13 is formed only on two flat surfaces 11b.

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 toner in, for example, a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, in an OA device such as a copying machine or a printer, a copy paper on which a toner image is formed is passed while being in contact with the surface of a heater to fuse and fix the toner image on the paper surface. There is.

As a fixing heater of this type, a fixing heater shown in FIG.
Those shown in are known. Reference numeral 51 in the figure is a long and narrow insulating substrate made of alumina, for example. This insulating substrate 51
An inclined surface (notch) 51a is formed at the upper end of the paper discharge side (one end side along the longitudinal direction of the substrate). On the flat surface of the insulating substrate 51, an elongated heating element 52 made of an Ag-based material is formed by screen printing. A glass layer 53 is formed on the flat surface of the substrate including the heating element 52.

As described above, in the conventional fixing heater, since the notch 51a is formed at the upper end of the insulating substrate 51 on the paper discharge side, the copy sheet is quickly separated from the fixing heater after the toner is heated by the fixing heater. Therefore, there is an advantage that the paper can be cooled rapidly and the bleeding and show-through of the toner image can be prevented.

[0005]

However, according to the conventional fixing heater, since the notch 51a is formed at the upper end of the insulating substrate 51 on the paper discharge side as shown in FIG. 5, the fixing heater has an asymmetric cross section. Therefore, when the fixing operation starts, a large electric power is applied to the fixing heater for the first few seconds, so that a large temperature distribution occurs in the fixing heater. That is, as shown in FIG. 6, the temperature of the cutout portion 51a of the insulating substrate 51 becomes higher than that of the opposite surface of the insulating substrate 51. Therefore, the thermal expansion in the cutout 51a causes the insulating substrate
Since it is larger than the surface opposite to 51, the internal stress of the cutout 51a increases during the fixing operation (during temperature control).

FIG. 7 is an explanatory view of the warp of the fixing heater viewed from above in FIG. In the case of this fixing heater, the warp occurs when the temperature of the cutout portion 51a of the insulating substrate 51 changes depending on the temperature of the insulating substrate 51.
This is because the temperature is higher than the opposite surface and the material expands more thermally than the opposite surface. Here, the warp timing is cycled with the temperature control timing. The amount of warpage is larger when the heater is attached to the stay than when the heater is attached alone, because the temperature difference between the front, back, center, and end of the substrate is large (because heat escapes to the stay). Since several places are fixed to the stay with an adhesive such as Si, it becomes large.

When the insulating substrate is deformed as described above, in the fixing device, the pressure roller is used in a state of being pressed against the insulating substrate, so that the force for suppressing the warp is further applied to the fixing heater. Therefore, the stress in the insulating substrate is further increased, and finally the insulating substrate 51 is cracked 55.

The present invention has been made in consideration of such circumstances, and an elongated insulating substrate is provided with inclined surfaces having both upper end surfaces inclined along the longitudinal direction of the substrate, and heat is generated on the flat surface of the substrate. By providing a body and covering this heating element with an insulating layer, the temperature distribution on the substrate is made symmetrical so that the stress in the substrate acts uniformly on the inclined surface, and thus the fixing heater that can avoid cracking of the substrate , And a fixing device using the same,
An object is to provide an image forming apparatus.

[0009]

According to a first aspect of the present invention, an elongated insulating substrate having a flat surface and an inclined surface having both upper end surfaces inclined along a longitudinal direction, and a flat surface of the insulating substrate are provided. A heating element formed along the longitudinal direction of the substrate; and an insulating layer formed on the insulating substrate so as to cover the heating element, the insulating layer having two inclinations of the substrate. The fixing heater is formed so as to extend up to the surface.

A second aspect of the present invention is an elongated insulating substrate having a flat surface and an inclined surface having both upper end surfaces inclined along the longitudinal direction, and a flat surface of the insulating substrate in the longitudinal direction of the substrate. A heating element formed on the insulating substrate, and an insulating layer formed on the insulating substrate to cover the heating element, the insulating layer being formed only on two flat surfaces of the substrate. Is a fixing heater.

In the first and second aspects of the invention, when the heating element is located in the center of the insulating substrate in the width direction and the dimensions of both inclined surfaces are the same, or the heating element is located at one end side from the center of the insulating substrate. It is conceivable that the size of the inclined surface located closer to the heating element may be smaller than the other. This is for equalizing the heat capacities on both sides of the substrate.

According to a third aspect of the present invention, the fixing heater, a pressure roller arranged on the surface side of the heating element of the fixing heater so as to face the fixing heater, and between the fixing heater and the pressure roller are provided. A fixing device comprising a fixing film movably provided.

According to a fourth aspect of the present invention, there is provided a first means for forming an electrostatic latent image of an image on a printing sheet, a second means for adhering toner to the electrostatic latent image to form an image on the printing sheet, and an image. An image forming apparatus comprising: the fixing device for fixing an image by passing the printing paper on which the image has been formed through a fixing film while pressingly contacting a fixing heater with a pressure roller.

[0014]

According to the present invention, since the inclined surfaces (notches) are formed on both upper end surfaces along the longitudinal direction of the insulating substrate, the cross section of the fixing heater is symmetrical, and the fixing operation starts and the fixing heater is formed. Even if high power is applied for the first few seconds, the temperature distribution on the substrate becomes symmetrical on the substrate as shown in FIG. Therefore, since there is no thermal deformation in the longitudinal direction of the insulating substrate,
As shown in FIG. 3, the insulating substrate is not warped, and the insulating substrate can be prevented from cracking.

Further, as shown in FIG. 8, if the fixing heater is used by being incorporated in a fixing device for fixing the toner, a copying paper having toner adhered to a predetermined image on the surface of the paper is mediated by the fixing film. Then, the toner is conveyed while being pressed against the fixing heater and the pressure roller, and the toner is melted by the heating of the fixing heater, so that good fixing can be performed.

Further, the fixing device having the structure shown in FIG. 8 is incorporated in an image forming apparatus such as a copying machine shown in FIG. According to this apparatus, it is possible to reduce the occurrence of show-through due to insufficient fixing of toner due to the temperature of the fixing heater being too low and the temperature being too high. Further, when the fixing device is used by being incorporated in an OA device such as a copying machine, a laser printer or a facsimile, the standby power consumption is low, the fixing operation start-up time is short, the adjustment power is low, and it is very clear. It is possible to obtain various printed images.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Reference numeral 11 in the figure is an elongated insulating substrate made of, for example, alumina. Inclined surfaces (notches) 11a, 11a are formed on both upper end surfaces of the insulating substrate 11 along the longitudinal direction, and the remaining flat surfaces 11b are formed. Here, the thickness T ₁ from the back surface of the insulating substrate 11 to the flat surface is 1.0.
mm, thickness T ₂ from the back surface of the substrate to the lowest point of the cutout 11a
Is 0.5 mm, the distance L ₁ from the end face of the substrate to the uppermost point of the notch 11a is 2.0 mm, the substrate length L ₂ is 360 mm, and the substrate width W is 8.0 mm.

Ag is formed on the flat surface 11b of the insulating substrate 11.
An elongated heating element 12 made of a Pd-based material is formed by screen printing. The substrate 11 including the heating element 12
A glass layer (insulator layer) 13 is formed on the flat surface 11b.

As described above, the fixing heater according to the above-described embodiment has inclined surfaces (notches) 11a on both upper end surfaces along the longitudinal direction.
An elongated insulating substrate 11 made of alumina and having 11a formed thereon;
It is composed of an elongated heating element 12 made of AgPd-based material formed on the flat surface 11b of the substrate 11, and an insulating layer 13 formed on the flat surface 11b of the substrate 11 including the heating element 12. There is.

Therefore, as shown in FIG. 1, since the cutout portions 11a, 11a are formed on both upper end surfaces along the longitudinal direction of the insulating substrate 11, the fixing heater cross section is symmetrical, and the fixing operation starts and the fixing heater starts. Even if a high power is applied to the substrate for the first few seconds, the temperature distribution on the substrate becomes symmetrical on the substrate as shown in FIG. Therefore, since the insulating substrate 11 is not thermally deformed in the longitudinal direction, the insulating substrate 11 is not warped as shown in FIG. 3, and the generation of cracks in the insulating substrate 11 can be avoided.

As shown in FIG. 8, the fixing heater is used by being incorporated in a fixing device for fixing toner. In this fixing device, a pressure roller 82 is arranged so as to face the surface of the fixing heater 81 opposite to the heating element, and a film-shaped fixing film 83 is movably provided between the fixing heater 81 and the pressure roller 82. It has a different structure. Then, the copy paper having the toner 84 attached to the predetermined image on the paper surface is conveyed while being pressed against the fixing heater 81 and the pressure roller 82 through the fixing film 82, and the toner 84 is heated by the fixing heater 81. It is melted and fixed.

The fixing device 85 having the structure shown in FIG. 8 is incorporated in an image forming apparatus such as a copying machine shown in FIG. According to this apparatus, it is possible to reduce the occurrence of show-through due to insufficient fixing of the toner due to the temperature of the fixing heater being too low and the temperature being too high, and to prevent defects due to copying of the substrate during use. Further, when the fixing device is used by being incorporated in an OA device such as a copying machine, a laser printer or a facsimile, a very clear printed image can be obtained.

In the above embodiment, the case where the insulating layer is formed only on the flat surface of the substrate including the heating element has been described, but the present invention is not limited to this, and as shown in FIG.
May extend on the inclined surface 11b of the insulating substrate 11. With such a configuration, the flatness and the coefficient of friction of the insulating substrate 11 are further increased, and the thermal resistances on both sides of the substrate located in the paper transport direction are equalized. Here, it is ideal that the insulating layer 13 extends to the inclined surface 11b of the insulating substrate 11 at the same distance, but even if the distance is not necessarily equal as shown in FIG. It would be effective.

[0024]

As described above in detail, according to the present invention,
By providing an elongated insulating substrate with an inclined surface having both upper end surfaces inclined along the longitudinal direction of the substrate, providing a heating element on the flat surface of the substrate, and covering the heating element with an insulating layer, A fixing heater that reduces the coefficient of friction on the substrate and makes the temperature distribution on the substrate symmetrical so that the stress in the substrate acts uniformly on the inclined surface, thereby avoiding cracking of the substrate, and a fixing device using the same. An image forming apparatus can be provided.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a fixing heater according to an embodiment of the present invention.

FIG. 2 is a temperature distribution characteristic diagram of the fixing heater of FIG.

FIG. 3 is a schematic plan view of the fixing heater of FIG.

FIG. 4 is a schematic perspective view of a fixing heater according to another embodiment of the present invention.

FIG. 5 is a schematic perspective view of a conventional fixing heater.

FIG. 6 is a temperature distribution characteristic diagram of the fixing heater of FIG.

FIG. 7 is an explanatory view of cracks when the fixing heater of FIG. 5 is used.

8 is an explanatory view of a fixing device using the fixing heater of FIG.

9 is an explanatory diagram of an image forming apparatus using the fixing device of FIG.

[Explanation of symbols]

11 ... Insulating substrate, 11a ... Inclined surface (notch),
11b ... Flat surface, 12 ... Heating element, 13 ... Glass layer (insulator layer), 81 ... Fixing heater, 82 ... Pressure roller,
83… Fixing film, 84… Toner, 85
… Fixing device.

Claims (6)

[Claims] 1. An elongated insulating substrate having a flat surface and an inclined surface having both upper end surfaces inclined along the longitudinal direction, and a flat surface of the insulating substrate formed along the longitudinal direction of the substrate. A heating element and an insulating layer formed on the insulating substrate so as to cover the heating element, wherein the insulating layer is formed to extend onto the two inclined surfaces of the substrate. A fixing heater characterized in that 2. An elongated insulating substrate having a flat surface and an inclined surface having both upper end surfaces inclined along the longitudinal direction, and formed on the flat surface of the insulating substrate along the longitudinal direction of the substrate. A heating element and an insulating layer formed on the insulating substrate so as to cover the heating element, wherein the insulating layer is formed only on two flat surfaces of the substrate. Fixing heater. 3. The fixing heater according to claim 1, wherein the heating element is located at the center of the insulating substrate in the width direction, and the dimensions of both inclined surfaces are equal. 4. The heating element according to claim 1 or 2, wherein the heating element is biased toward the one end side from the center of the insulating substrate, and the size of the inclined surface closer to the heating element is smaller than the other. Fixing heater. 5. The fixing heater according to claim 1, a pressure roller arranged on the surface side of the heating element of the fixing heater so as to face the fixing heater, and the fixing heater. A fixing device comprising a fixing film movably provided between pressure rollers. 6. A first means for forming an electrostatic latent image of an image on a print sheet, a second means for forming a toner image on the electrostatic latent image to form an image on the print sheet, and a print sheet on which the image is formed. An image forming apparatus comprising the fixing device according to claim 5, wherein the fixing device fixes the image by passing the toner through a fixing film while being pressed against a fixing heater by a pressure roller.