JPH06149099A - Heater and fixing method and device - Google Patents

Abstract

PURPOSE:To obtain a heater not having the occurrence of the unevenness of fixing, etc., by providing plural belt-like resistance heating elements whose lengths are different, in parallel with a substrate. CONSTITUTION:The heater is composed of the substrate 1 made of a heat- resistant insulating material, for instance, alumina ceramics, plural resistance heating elements, for instance, five resistance heating elements 21-25 formed so as to make their lengths different, in parallel with a longitudinal direction on the surface of the substrate 1 and composed of a silver and palladium alloy, etc., and electrodes 31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b, 35a and 35b successively formed on both ends of the resistance heating elements 21-25 and composed of a silver paste, etc. Then, plural resistance heating elements not having a branch, etc., on an intermediate part corresponding to the length of a body to be heated can execute the irradiation of an almost uniform temperature distribution with heat along the axes of the heating elements, respectively. Thus, an unexpected danger caused by overheating can be evaded and a fixing function can be improved.

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 copiers, facsimiles and printers, a fixing method using the heater, and a fixing device.

[0002]

2. Description of the Related Art For example, in an electronic copying machine, a toner image formed on the surface of a photosensitive drum is transferred onto a copy sheet, and then the copy sheet is passed while being pinched between a heater and a pressure roller. The copy paper is heated by the heat of the heater to fuse and fix the toner.

However, copy papers of various sizes are used, and the portion of the heating element constituting the heater that is in contact with the copy paper is deprived of heat and kept at an appropriate temperature.
The portion not in contact with the copy paper is not taken away from the heat, so that it may be overheated and the device may be damaged.

As a countermeasure against this, the applicants of the present invention have filed Japanese Patent Application No. 1-
No. 253645 and Japanese Patent Application No. 2-3218 propose a heater that can change the effective length of a heating element according to the size of a heated object such as copy paper. However, these proposals have the advantage that the effective length of the heating element can be changed by branching the branch heating element in the middle of one main heating element and taking out the intermediate electrode. During this time, the heat generated by this amount is useless and is merely a loss of electric power (Fig. 7 (a),
(B)) Further, at the branch point, the amount of heat generation is reduced due to a decrease in resistance value (FIG. 7 (c)). There is a problem that uneven fixing occurs due to insufficient fusion.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heater in which even if the heating element is changed according to the size of the object to be heated, the temperature distribution does not have unevenness, and thus the fixing unevenness does not occur. To aim.

[0006]

A heater according to claim 1 of the present invention is characterized in that a plurality of strip-shaped resistance heating elements having different lengths are provided in parallel on a substrate.

A heater according to a second aspect of the present invention is characterized in that the resistance heating element is a printed resistor formed on an insulating substrate.

A heater according to a third aspect of the present invention is characterized in that the resistance heating element is a printed resistor formed on an insulating plate body, and the plate body is provided on the substrate.

The heater according to claim 4 of the present invention is characterized in that the central portions of the plurality of resistance heating elements are on the same line.

The heater according to claim 5 of the present invention is characterized in that one end of each of the plurality of resistance heating elements is on the same line.

The heater according to claim 6 of the present invention is characterized in that one end of each of the plurality of resistance heating elements is connected to a common electrode.

According to a seventh aspect of the present invention, in the fixing method, the copying paper on which the toner is placed is passed between the opposing pressure roller and the heater according to the first to sixth aspects, and the copying is performed. It is characterized in that the resistance heating element corresponding to the width of the paper is heated to fuse the toner.

In the fixing method according to the eighth aspect of the present invention, the heater is juxtaposed so as to be horizontally movable in opposition to the pressure roller, and the copy paper passing between the pressure roller and the heater at the time of copying. It is characterized in that the resistance heating element corresponding to the width length is moved directly below the rotation axis of the pressure roller to generate heat.

According to a ninth aspect of the present invention, a fixing device is characterized in that the pressure roller and the heater according to the first to sixth aspects are arranged to face each other.

A fixing device according to a tenth aspect of the present invention is
It is characterized in that the heaters are arranged side by side so as to be movable in the horizontal direction so as to face the rotation axis of the pressure roller.

[0016]

In the heater of the present invention, a plurality of resistance heating elements having no branch in the middle portion corresponding to the length of the object to be heated irradiate heat with a substantially uniform temperature distribution along the heating element axis. be able to.

[0017]

Embodiments 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 a heater H of FIG.
FIG. 3 is a partially cutaway vertical cross-sectional view showing a state in which the printer is assembled in a toner fixing device such as a copying machine or a facsimile, and FIG. In the figure, 1 is a substrate made of a heat-resistant / electrically insulating material such as alumina ceramics, 21, 22, 23, 24, 25.
Are resistance heating elements 31a, 31b, 32a, 32 made of a plurality of, for example, five silver-palladium alloys, which are formed in parallel on the surface of the substrate 1 in the longitudinal direction and have different lengths.
b, 33a, 33b, 34a, 34b, 35a, 35b
Is an electrode made of silver paste, which is continuously formed at both ends of the resistance heating elements 21, ..., 25. Also, 41a, 41
b, 42a, 42b, 43a, 43b, 44a, 44
b, 45a, 45b are respective electrodes 31a, 31b,
32a, 32b, 33a, 33b, 34a, 34b, 3
It is a lead wire connected to 5a and 35b. Reference numeral 5 is a vitreous overcoat layer that covers and protects substantially all of the electrodes 31a, ..., 35b and a part of the resistance heating elements 21 ,.

Further, R is a pressure roller, and a heat resistant elastic material such as a silicone rubber roller 63 is fitted on the surface of a cylindrical roller body 62 having rotary shafts 61 protruding from both end surfaces. Note that P indicates a copy sheet.

To form the resistance heating elements 21, ..., 25 and the electrodes 31a, .., 35b, first, a silver-palladium alloy (Ag / Pd) or ruthenium oxide (Ru) is formed.
A conductive paste paint is prepared by kneading a metal (Ag / Pd + RuO ₂ ) powder to which O ₂ is added, water glass (inorganic binder), a water-soluble organic binder and the like with water. Then, the paste-like coating material is sequentially applied by printing on the substrate 1 in the same width and at different lengths and thicknesses, dried, and then baked at about 850 ° C. for about 10 minutes to form the resistance heating element 2.
1, ..., 25 are formed.

Although the resistance heating elements 21, ..., 25 have different lengths, they are formed by changing the film thickness or changing the material even if they have the same width in order to obtain the same heating temperature. There is.

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 to become vitreous, resulting in silver. -Varadium powder becomes a thin film and is strongly bound to the substrate 1 in a vitreous form. Then, this resistance heating element 2
The resistance heating elements 21, ..., 2 are provided on the upper surfaces of both ends of 1 ,.
A material having a contact electric resistance smaller than that of 5, for example, silver (A
g), silver-platinum alloy (Ag / Pt), gold (Au),
A metal paste such as platinum (Pt) is applied in the form of a thick film, dried and then baked to form the electrodes 31a, ..., 35b.

Next, the strip-shaped portions of the resistance heating elements 21, ..., 25, and the electrodes 31a, ..., 3 connected to the strip-shaped portions.
A glassy overcoat layer 5 is formed on the surface of 5b and the substrate 1 adjacent thereto. The overcoat layer 5 is formed by using PbO- containing lead oxide (PbO) as a main component.
A powder of B ₂ O ₃ —SiO ₂ glass is kneaded together with nitrocellulose (organic binder) in an organic solvent to form a glass paste, and the glass paste is applied to form a continuous coating film without gaps. And after drying, about 700
Baking at about 10 minutes for about 10 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. and is lower than the firing temperature of the paste-like coating material that constitutes the resistance heating elements 21, ..., 25, and the glass paste is a substrate including the strip-shaped portions of the resistance heating elements 21 ,. When the glass paste melted has good fluidity when applied to a portion to be coated in the longitudinal direction of 1 and dried and then fired, the glass paste flows uniformly without gaps, and not only the surface is not uneven,
The tip of the glass is gradually thinned so as to bleed on the electrodes 31a, ..., 35b. Further, when the baking temperature of the glass may be low, decomposed gas or the like is not generated from the heating element layers 21, ..., 25, and the heating element layer 2 is not separated from the substrate 1.

Further, the resistance heating elements 21, ..., 25 and the electrodes 31a, ..
35b also has a peripheral surface that bleeds onto the substrate 1 due to the heating during the formation of the overcoat layer 5 to improve the adhesion with the substrate 1, and the surface thereof can be made extremely smooth without unevenness.

The lead wires 41a, ..., 45b may be connected to the electrodes 31a, .., 35b before or after the overcoat layer 5 is formed.

The heater H thus formed has a resistance heating element 2 when, for example, the longest heating portion is desired.
Lead wire 41 connected to electrodes 31a and 31b at both ends
When electricity is supplied to a and 41b, the resistance heating element 21 generates heat. On the contrary, when it is desired to obtain the shortest heat generating portion, by energizing the lead wires 45a and 45b connected to the electrodes 35a and 35b at both ends of the resistance heating element 25, the resistance heating element 25 is heated.
Heats up.

The lengths of the resistance heating elements 21, ..., 25 of the fixing heater H incorporated in a toner fixing device such as a copying machine or a facsimile shown in FIGS.
3 size (21), A4 size (23), B4 size (22), B5
Different sizes are formed so as to irradiate the size corresponding to the short side of the copy paper P of size 24 (24) and size B6 (25). Further, the fixing heater H is juxtaposed so as to be movable in the horizontal direction so as to face the rotating shaft 61 of the pressure roller R of the fixing device, and the silicone rubber roller 63 is formed in the central portion of the heater H so that the resistance heating element 23 is formed. Is slightly elastically contacted with the surface of the overcoat layer 5 directly above.

When copying a document of A4 size, for example, a sensor (not shown) detects that a copy sheet P of A4 size is flowing, and a heater H moving device (not shown) is used. Immediately below the pressure roller R, a resistance heating element 23, which is the third longest of the fixing heater H, is arranged to face the pressure roller R. When this is detected and power is supplied to the lead wires 43a and 43b, the resistance heating element 23 is energized via the electrodes 33a and 33b, and the resistance heating element 23 generates heat. Then, the sent A4 size copy paper P is pinched between the surface of the overcoat layer 5 of the resistance heating element 23 and the silicone rubber roller 63, and conveyed by the rotation of the pressure roller R in the direction of the arrow. Is fixed.

When copying a B6 size document, for example, a sensor (not shown) detects that a B6 size copy sheet P is flowing and activates a moving device (not shown) of the heater H, Immediately below the pressure roller R, a resistance heating element 25 corresponding to the width length of the fixing heater H of B6 size is arranged oppositely. When this is detected and power is supplied to the lead wires 45a and 45b, the resistance heating element 25 is energized via the electrodes 35a and 35b, and the resistance heating element 25 generates heat. Then, the sent B6 size copy paper P is pinched between the surface of the overcoat layer 5 of the resistance heating element 25 and the silicone rubber roller 63, and conveyed by the rotation of the pressure roller R in the direction of the arrow. Is fixed.

As described above, according to the present invention, the heating element can be switched according to the width of the heated object such as copy paper, so that a substantially uniform heat irradiation distribution can be obtained along the axis of the heating element and an undesired portion can be obtained. There is no irradiation of heat and no wasted power is consumed. Further, when it is used as a fixing heater for a copying machine or the like, a resistance heating element corresponding to the width of the contact portion of the copy paper is formed as shown in FIGS. 6 (a) (A4 size) and (b) (B6 size). Since the heat is generated, the resistance heating element is heated to an appropriate temperature over the entire length thereof, the toner can be well fixed without causing partial fixing failure, and the unexpected danger due to overheating as in the conventional case can be avoided.

FIGS. 4A and 4B show another embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In the above-described embodiment, the centers of the resistance heating elements 21 to 25 are on the same center line and the centers of the copy sheets of each size in a copying machine are on the same line, whereas the heater H of FIG. This is effective when one end of each of the bodies 21 to 25 is on the same line and the side edge of each copy sheet is designed to be on the same line in a copying machine or the like. Further, in the case where the resistance heating elements 21 to 25 are arranged at random as shown in (b), the heating elements that are used infrequently are placed outside with the heating elements that are used frequently as the center, and the heater H of This is due to the small range of movement.

The ones shown in FIGS. 5A to 5C are as follows.
One electrode of the end portions of the plurality of resistance heating elements 21 to 25 is used as the common electrode 30, and lead wires are respectively provided to the narrower electrodes as compared with the case where electrodes are individually formed on the resistance heating elements 21 to 25. Since no external terminals are connected, the connection structure can be simplified both structurally and electrically. 4A shows a structure in which the left electrodes 31a to 35a shown in FIG. 4A or 4B are combined to form a common electrode 30.
(B) shows the left side electrodes 31a to 35a shown in FIG. 1 combined into a common electrode 30, and (c) shows the right side electrodes 31b to 35b shown in FIG. 4 (b) combined into a common electrode 30. Is.

In the fixing device having the above structure, only the resistance heating element having a width corresponding to the size of the copy paper conveyed horizontally by the rotation of the pressure roller generates heat and heats the copy paper. Unlike the conventional case, a part of the resistance heating element outside the copy paper frame does not overheat, and the transparent film made of synthetic resin for protecting copy paper provided in the fixing device is not melted. Further, there is no branching in the middle portion of the resistance heating element, the temperature distribution can be made uniform over the entire length of the resistance heating element, and the fixing function can be greatly improved as compared with the prior art without causing defects such as uneven fixing.

The present invention is not limited to the above embodiment,
For example, 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 such as a polyimide resin, or a metal whose surface is subjected to an insulation treatment such as glass coating.

Although the present invention has been described with respect to the substrate in which five narrow resistance heating elements are formed, the number of resistance heating element layers is not limited to five, and two or more resistance heating elements may be used according to the specifications. Alternatively, one heater may be formed by providing a substrate with a plurality of plates such as 1 to a plurality of resistance heating element layers.

Further, the materials for forming the resistance heating element, the electrode and the overcoat layer are not limited to those of the embodiment, and it goes without saying that they can be appropriately selected according to the heating temperature and the materials used. Furthermore, the resistance heating element layer may have the same width and film thickness other than the length, and the voltage applied to each heating element may be adjusted using a transformer or the like.

Further, in the above-mentioned embodiment, the copy paper directly contacts 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.

Furthermore, in the above-mentioned embodiment, the position of the heater (resistance heating element) is moved according to the copy paper size. However, the heater (resistance heating element) remains fixed, or the axis of the pressure roller is fixed. There is no restriction on the position of the heater (resistance heating element) and whether the heater is a fixed type or a movable type as long as the toner applied to the copy paper can be fixed even if it is not directly below.

[0038]

According to the present invention having the above-mentioned structure, since the heating elements can be switched according to the width and length of the object to be heated such as several kinds of copying paper, a substantially uniform heat irradiation distribution can be obtained and an undesired portion can be obtained. There is no heat irradiation and no wasted power is consumed. If used as a fixing heater for a copying machine,
Since the resistance heating element corresponding to the width of the contacting part such as copy paper generates heat, the resistance heating element is not heated to an appropriate temperature over the entire length and a part of the resistance heating element does not overheat. The toner can be satisfactorily fixed without causing any trouble, the unexpected danger due to overheating as in the past can be avoided, and the fixing function can be greatly improved.

[Brief description of drawings]

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

FIG. 2 is a partially cutaway vertical sectional view showing a state in which the heater of FIG. 1 is assembled to a toner fixing device.

3 is a cross-sectional view of FIG.

4A and 4B are plan views of a heater according to another embodiment of the present invention.

5 (a), (b) and (c) are plan views of a main part of a heater according to another embodiment of the present invention.

6A and 6B are temperature distribution diagrams in the longitudinal direction of the heater when the heater of FIG. 1 is assembled in the toner fixing device and the size of the copy paper is different.

7A, 7B, and 7C are temperature distribution diagrams in a heater longitudinal direction in a conventional toner fixing device.

[Explanation of symbols]

 H: Heater R: Pressure roller P: Copy paper 1: Substrate 21-25: Resistance heating element layer 31a-35a 31b-35b: Electrode 5: Overcoat layer

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

Claims (10)

[Claims] 1. A heater comprising a plurality of strip-shaped resistance heating elements having different lengths provided in parallel on a substrate. 2. The heater according to claim 1, wherein the resistance heating element is a printed resistor formed on an insulating substrate. 3. The heater according to claim 1, wherein the resistance heating element is a printed resistor formed on an insulating plate, and the plate is provided on a substrate. 4. The heater according to claim 1, wherein each of the plurality of resistance heating elements has a central portion of each heating portion on the same line. 5. The heater according to claim 1, wherein one end of each heating portion of the plurality of resistance heating elements is on the same line. 6. The heater according to claim 1, wherein one end of each heating portion of the plurality of resistance heating elements is connected to a common electrode. 7. A copying paper sheet on which toner is placed is passed between opposing pressure rollers and the heater according to any one of claims 1 to 6, and a resistance heating element corresponding to the width of the copying paper sheet is provided. A fixing method characterized in that heat is applied to fuse the toner. 8. A heater is juxtaposed so as to be horizontally movable relative to a pressure roller, and a resistance heating element corresponding to a width of a copy sheet passing between the pressure roller and the heater is pressed during copying. 8. The fixing method according to claim 7, wherein the roller is moved right below the rotation axis of the roller to generate heat. 9. A fixing device in which a pressure roller and the heater according to any one of claims 1 to 6 are arranged so as to face each other. 10. The fixing device according to claim 9, wherein the heaters are arranged side by side so as to be movable in the horizontal direction so as to face the rotary shaft of the pressure roller.