JPH0744036A - Heater and fixing device - Google Patents

Abstract

PURPOSE:To provide a heater which lessens the generation of the heat from a high-temp. exothermic part on the surface in the other parts of a substrate and the fixing device for copying paper capable of well fixing toners. CONSTITUTION:This heater H is formed with a band-shaped resistance heating element 2 in the longitudinal direction on the substrate 1 consisting of an electrical insulating material. A rugged surface or stepped part 11 is formed on the surface of the substrate 1 of the heater H exclusive of its band-shaped resistance heating element 2 part. This fixing device is constituted by using this heater. Only the part of the resistance heating element 2 turns to a high temp. and the parts exclusive of the heating element does not come into contact with other objects exclusive of the very slight part and, therefore, undesirable thermal influence is less exerted on the object and worked articles mounted with the heater H. The fixing device mounted with the heater H is not heated to the extent that the copying paper is affected. Rounding near the end of the copying paper is thus prevented and the paper is orderly arrayed and discharged even in the case of continuous copying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater used for toner fixing of office automation equipment such as copying machines, facsimiles and computers, and a fixing device using the heater.

[0002]

2. Description of the Related Art In the light, thin, short, and small flows of electronic equipment, in order to increase the density of circuit boards, miniaturization and multifunctionalization of constituent boards and parts are actively underway.

For example, in an electronic copying machine, a copy sheet on which a toner image is formed is passed while being pinched between a heater and a pressure roller, and the heat of the heater heats the copy sheet to melt and fix the toner. I am trying to do it.

As a conventional fixing device, a heat roller in which a tubular infrared light bulb or a rod-shaped heater is arranged in the center of a hollow roller is used, and at least one of a pair of upper and lower rollers is pressed as this heat roller. There is a heat roller fixing method in which a toner image is melted and fixed by passing an unfixed copy paper between the roller and the roller.

This heat roller fixing method involves heating a copy sheet indirectly through a roller from a heater, and it has a problem that it takes a long time to start, preheating is required, and a large amount of power is consumed.

Therefore, instead of the heat roller fixing method, a fixing method of a flat heater is being developed and put into practical use. The heater used for the fixing method of the flat-plate heater is composed of an alumina / ceramics surface having a flat surface, a curved surface, or an inclined surface on a long heat-resistant / electrically insulating substrate, and a silver / palladium alloy (Ag / Pd alloy). ) A paste containing a mixture of powder, water glass (inorganic binder), and water-soluble organic binder is applied by printing and firing to form a strip-shaped resistance heating element, and both ends of this resistance heating element are widened. A film made of a good conductor such as silver (Ag) is formed on this portion to form a terminal portion, and the surface of this resistance heating element is covered with a vitreous overcoat layer.

The pressure roller is a roller having a rotating shaft parallel to the heater, the surface of which is made of a heat resistant elastic material, and is adapted to rotate while lightly contacting the overcoat layer of the heater. Then, when the copy sheet is supplied between the heater and the pressure roller, the copy sheet is conveyed while sliding on the surface of the overcoat layer of the heater by the rotation of the pressure roller, and the heat of the heater causes the copy sheet to move on the copy sheet. The toner is heated and melted and fixed.

[0008]

In the fixing method of such a flat heater, the surface of the heating resistor on the substrate having a flat surface, a curved surface, or an inclined surface has a vitreous overcoat layer. Since it is covered with, the copy paper has good smoothness and the flow of the copy paper is good, but if the copy paper is in contact with the resistance heating element that is at a high temperature for a long time (less than a few seconds), the copy paper is not heated. Therefore, the phenomenon of curling up is not preferable.

Further, this is because when the leading end side or the trailing end side of the copy sheet hangs down from the position of the resistance heating element, the hanging portion is heated by conduction heat or radiant heat from the resistance heating element. The adjacent copy of the body also comes into contact with the adjacent parts of the body by dragging, which further heats the copy paper on which the toner has been burned. As described above, the copy paper is curled to obtain a substantially flat copy paper. However, if there is a curled sheet in the middle of continuous copying, the finished sheets are not arranged and ejected in order, and there is a problem in that the curled sheet must be flattened and collated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heater in which heat from a high temperature heat generating portion does not appear on the surface of the other portion of the substrate and a fixing device for copying paper which can perform good toner fixing.

[0011]

A heater according to claim 1 of the present invention is a heater in which a strip-shaped resistance heating element is formed in the longitudinal direction on a substrate made of an electrically insulating material, and the strip surface is formed on the substrate surface. It is characterized in that an uneven surface is formed except for the resistance heating element part.

A heater according to a second aspect of the present invention is a heater in which a strip-shaped resistance heating element is formed in a longitudinal direction on a substrate made of an electrically insulating material, and a strip-shaped resistance heating element portion is provided on the substrate surface. Except for this, a step is formed in which the edge side of the substrate is lowered.

In the heater according to claim 3 of the present invention, a vitreous overcoat layer is formed on the substrate surface and the resistance heating element of the heater according to claim 1 or 2. Is characterized by.

A fixing device according to a fourth aspect of the present invention is characterized in that the pressure roller and the heater according to the first to third aspects are arranged opposite to each other.

[0015]

The curling of the copy paper is prevented by reducing the contact of the copy paper that has passed through the resistance heating element with the heater substrate in a high temperature state to lower the temperature of the paper.

[0016]

Embodiments of the heater of the present invention will be described below with reference to the drawings. 1 is a plan view of the heater H, and FIG. 2 is an enlarged cross-sectional side view taken along the line XX in FIG. In the figure, 1 is an elongated substrate made of a heat-resistant and electrically insulating material such as alumina ceramics and having a length of about 300 mm, a width of about 10 mm and a thickness of about 1 mm. 2 is a length of about 230 mm and a width of about 2 mm formed on the surface of the substrate 1 along the longitudinal direction,
A resistance heating element mainly made of a silver-palladium alloy having a thickness of about 10 μm, and 21 is a wide electrode having a length of about 25 mm and a width of about 7 mm made of the same material as the heating element 2 continuously formed at both ends of the resistance heating element 2. It is a forming part. Further, 22 is the electrode forming portion 21.
The electrode layers 3 formed above are glassy overcoat layers that cover and protect the entire surface of the resistance heating element 2 and a part of the electrode forming portion 21.

The substrate 1 becomes lower along the longitudinal direction on the surface of about half of the upper side (the thickness of the substrate 1 becomes thinner) as it goes to the edge, and four step portions 11, 12, 13, 14 and these. Corners (steps) between steps 11, 12, 13 and 14
11a, 12a, 13a, 14a are formed.

To form the resistance heating element 2 and the electrode forming portion 21, first, a silver-palladium alloy (Ag
/ Pd) or a metal with ruthenium oxide added (Ag /
A conductive paste paint is prepared by kneading powder of Pd + RuO ₂ ) with water glass (inorganic binder), water-soluble organic binder and the like with water. Then, the paste-like paint is applied by printing on the elongated substrate 1, dried and then baked at about 850 ° C. for about 10 minutes. By this firing, the residual water contained in the paint is scattered, then the organic binder is decomposed and gasified and scattered, and finally the water glass is dehydrated and becomes vitreous, and as a result, the silver / baladium powder Becomes a thin film and becomes vitreous on the substrate 1 and is firmly bound to form the resistance heating element 2.

Then, on the surfaces of both ends of the resistance heating element 2, a material having a smaller contact electric resistance than the resistance heating element 2, for example, silver (Ag), silver-platinum alloy (Ag / Pt), gold (Au), platinum. A metal paste such as (Pt) is applied in a thick film form, dried and baked to form the electrode layer 22.

After that, the strip-shaped resistance heating element 2 portion,
A glassy overcoat layer 3 is formed on the surface of the electrode forming portion 21 and the substrate 1 which are connected to the strip-shaped portion. This overcoat layer 3 is formed by using PbO (55 to 85 Wt%)-B ₂ O ₃ (5 to 5) containing lead oxide (PbO) as a main component.
15 wt%)-SiO ₂ (10 to 30 Wt%) type glass powder is kneaded with an organic solvent together with nitrocellulose (organic binder) to apply a glass paste manufactured by Tanaka Kikinzoku International Co., Ltd. Form a continuous coating film. Then, after drying, it is baked at about 700 ° C. for about 8 minutes to form a glass layer having a thickness of 15 μm to 30 μm.

This glass has a melting point of about 600 ° C., which is lower than the firing temperature of the paste-like paint which constitutes the resistance heating element 2, and the glass paste is used for the strip-shaped portion and the step portions 11, 12, 13 of the resistance heating element 2. , 14 are coated on a portion of the substrate 1 to be coated in the longitudinal direction, dried, and then baked. In this firing, the molten glass paste is formed on the substrate 1 and the step portion 11 formed by the step portions 11, 12, 13, and 14.
a, 12a, 13a, 14a also flows, and when these surfaces reach a flat and even state, heating is stopped. When such a heater H is energized from the electrode layers 22 at both ends, the resistance heating element 2 in the narrow strip portion excluding the electrode forming portion 21 generates heat. The temperature is highest in the portion directly above the resistance heating element 2 (the maximum outer surface temperature of the heater H is the portion of the overcoat layer 3 directly above the resistance heating element 2), and becomes lower toward the outer peripheral edge of the substrate 1. Has become. Further, in the heater H, palladium contained in the metal alloy serves as an electric resistance element, and the resistance value of the heating element 2 is adjusted by the ratio. In this embodiment, the resistance value is about 32 Ω [Ω], and a current of about 2.2 A flows when a voltage of 70 V is applied.
The heating value is about 155W.

Further, FIG. 3 shows an example of a fixing device such as a copying machine or a facsimile in which the heater H is incorporated. In the figure, the heater H portion is the same as that in FIG. The description is omitted. R is a pressure roller, which is a cylindrical roller body 5 having a rotary shaft 51 protruding from both end surfaces.
2 has a heat-resistant elastic material such as silicone rubber 53 on its surface.
Is fitted. The rotary shaft 5 of the pressure roller R
1, a fixing heater H is juxtaposed, and the silicone rubber 53 is in light contact with the surface of the overcoat layer 3 directly above the resistance heating element 2 of the heater H. Reference numeral 6 denotes a connector made of phosphor bronze plate or the like, which is provided with elasticity, and contacts the electrode layer 22 of the heater H to supply power to the heater H.

The copying machine is used, for example, at a commercial voltage of 100 V, and the heater H is energized with its current controlled by a current controller in the copying machine. The heater H is energized through the electrode layer 22 in the same manner as above, and the rated temperature is about 200 ° C.
The copy paper P is pinched between the surface of the overcoat layer 3 of the resistance heating element 2 and the silicone rubber 53 which have generated heat, and the copy paper P is conveyed in the direction of the arrow by the rotation of the pressure roller R and becomes the copy paper P. The adhered toner is heated and melted and fixed. (See FIG. 2 and FIG. 3.) Then, in the above, the copy sheet P is conveyed in a substantially horizontal state by the rotation of the pressure roller R, and is in contact only with the surface of the overcoat layer 3 directly above the resistance heating element 2. In the case where the front end side or the rear end side of the copy paper P hangs down, the hanging portion does not form the resistance heating element 2, but due to conduction heat or radiant heat from the resistance heating element 2. The resistance heating element 2 which is heated is also brought into contact with the portion adjacent to the resistance heating element 2 while sliding.

However, according to the structure of the present invention, the copy paper P is formed into the stepped portions 11, 12, 13, in the portion without the resistance heating element 2.
Corner portion (step portion) 11 formed by 14 and having a small contact area
a, 12a, 13a, 14a are only contacted in a point-contact manner, and after passing through the resistance heating element 2 parts, the copy paper P is not heated so as to be thermally affected and passes through the resistance heating element 2 part. It is possible to prevent the temperature of the post-copying paper P from rapidly lowering and curling the end portion thereof into a curl shape.

Further, the means for forming the stepped step portion on the substrate as in the present invention can be formed accurately and easily because the polishing can be repeated in parallel with the longitudinal direction of the substrate.

The present invention is not limited to the above embodiment,
For example, the means for preventing the copying paper on the substrate surface portion other than the resistance heating element from continuously contacting is not limited to the stepped portion, and may be an uneven surface such as a flutter or a groove. In the case of a stepped portion having a lower edge side, the number of steps is not limited to four but may be two or more steps or may be formed with a fine pitch, and the extending direction is not parallel to the heating element and is oblique. You may go. Further, the portion other than the resistance heating element forming portion on the surface of the substrate may be an inclined surface having a low edge side instead of the horizontal surface. Further, uneven surfaces or stepped portions may be formed on both sides in the longitudinal direction of the resistance heating element. Further, the material of the substrate is not limited to alumina ceramics, but may be other ceramics, glass, a synthetic resin member having high heat resistance and electrical insulation such as polyimide resin, or the like in order to enhance its mechanical strength. The lower surface side of the substrate may be made higher as it goes to the edge so that the whole has the same thickness.

Further, in the above embodiment, the vitreous overcoat layer is formed on the resistance heating element and the substrate, but the overcoat layer is not essential, and when it is formed, the material is the same as that of the embodiment. Not exclusively.

The materials for forming the resistance heating element and the electrode layer are not limited to those of the examples, and it goes without saying that they can be appropriately selected according to the heating temperature and the condition of the heater used. The number of band-shaped resistance heating elements is not limited to one, and a plurality of band-shaped resistance heating elements may be formed. Further, in the above-mentioned embodiment, the power supply to the resistance heating element is performed by the elastic connector,
The present invention is not limited to this, and a lead wire may be directly connected to the electrode layer.

Furthermore, in the above embodiment, the copy paper was brought into direct contact with the surface of the overcoat layer, but it may be indirect contact with a plastic sheet interposed for protection of the fixing heater and paper feeding. The heater of the present invention is OA
The present invention can be put to various practical uses not only for fixing devices but also in other fields.

[0030]

The heater of the present invention having the above structure is
Only the strip-shaped resistance heating element has a high temperature, and the parts other than the resistance heating element do not come into contact with other objects except for a very small portion (corner or flat surface), so the heater is installed. Undesirable thermal influence on the object or processed product is reduced. Further, in a toner fixing device such as a copying machine equipped with this heater, the copy sheet is not heated to such an extent that it is affected, and the temperature of the copy sheet rapidly decreases after passing through the resistance heating element portion. It is possible to prevent the vicinity of the end from curling, and to obtain a substantially flat copy sheet. Even when continuous copying is performed, the sheets of paper after the copying are ejected in order.

[Brief description of drawings]

FIG. 1 is a plan view of a heater showing an embodiment of the present invention.

FIG. 2 is a cross-sectional side view taken along the line XX of FIG.

FIG. 3 is a partial cross-sectional front view of a fixing device showing an embodiment of the present invention.

[Explanation of symbols]

 H: Heater R: Pressure roller P: Copying paper 1: Substrate 2: Resistance heating element 3: Overcoat layer 11, 12, 13, 14: Step portion 11a, 12a, 13a, 14a: Corner portion (step portion)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takaaki Kanabe 3-3-9 Shimbashi, Minato-ku, Tokyo Toshiba Abu E. Co., Ltd.

Claims (4)

[Claims] 1. A heater having a strip-shaped resistance heating element formed in a longitudinal direction on a substrate made of an electrically insulating material, wherein a concavo-convex surface is formed on a surface of the substrate except a strip-shaped resistance heating element portion. Characteristic heater. 2. A heater in which a strip-shaped resistance heating element is formed in a longitudinal direction on a substrate made of an electrically insulating material, and a step portion in which the end edge side of the substrate is lowered except for the strip-shaped resistance heating element portion on the surface of the substrate. A heater characterized by being formed. 3. A heater having a vitreous overcoat layer formed on the substrate surface and the resistance heating element of the heater according to claim 1 or 2. 4. A fixing device in which a pressure roller and the heater according to any one of claims 1 to 3 are arranged to face each other.