JPH08153571A - Heat emitting body, fixing device, and image forming device - Google Patents

Abstract

PURPOSE: To suppress abnormal heating of a heat emitting body at the end of the heat emission part. CONSTITUTION: The arrangement according to the present invention comprises an electric insulative base board 3 which is thin and long, a plurality of electric resistance type heat emitting bodies 1, 2 which are formed on the surface of the base board straight in the longitudinal direction, a low resistance connecting piece 4 which is formed so as to connect electrically one-side ends of adjoining heat emitting bodies 1, 2 and whereby series connection of the heat emitting bodies 1, 2 is generated, and a pair of terminal layers 5 which are formed at the ends of the heat emitting bodies 1, 2 in series connection. Because low resistance conductor layer 4 to make electric connection of the heat emitting body layers 1, 2 remains without emitting heat, it is possible to suppress local heat emission of the heating body and prevent cracking of the base board 3 and uneven fixation of toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element, a fixing device and an image forming apparatus which prevent local heat generation of a linear electric resistance heating element layer.

[0002]

As disclosed in Japanese Patent Application Laid-Open No. 2-65086, a heating element having a linear electric resistance heating element layer formed by thick film printing on an electrically insulating elongated substrate as a heat source,
A fixing device and an image forming apparatus using this heating element have been put into practical use.

FIG. 15 is a front view showing an example of a conventional heating body of this type. This heating element has a U-shaped linear electric resistance heating element layer formed on one surface of the substrate 151 by screen printing, for example. Since this heating element generates a large amount of heat as compared with a linear heating element, the speed can be increased when it is used for fixing. Note that 153, 1
Reference numeral 53 is a terminal portion provided on one end side of the linear electric resistance heating element layer 152. 154 is a protective coating layer deposited on the substrate 151 so as to cover the linear electric resistance heating element layer 152.

[0004]

However, since this heating element has a large amount of heat generation per unit area in the vicinity of the folded portion on the other end side of the linear electric resistance heating element layer 152,
There has been a problem that the temperature in the vicinity of the folded-back portion locally excessively rises, stress concentrates on the folded-back portion, and the substrate is easily damaged.

According to the present invention, a plurality of linear electric resistance heating elements are formed along the longitudinal direction of a substrate, and when these are connected in series, a heating element in which a local excessive temperature rise at a connecting portion, that is, a folded portion is less likely to occur. It is an object of the present invention to provide a fixing device and an image forming apparatus.

[0006]

A heating element according to claim 1, wherein an electrically insulating elongated substrate, and a plurality of linear electric resistance heating elements formed along a longitudinal direction on a plate surface of the substrate,
A low-resistance connector formed so that one end of a pair of adjacent linear electric resistance heating elements is electrically connected, and as a result, each linear electric resistance heating element is connected in series, and a linear electrical resistance connected in series It is characterized by comprising a pair of terminals formed at both ends of the heating element.

The low resistance connecting body may have a relatively lower resistance than the heat generating body, and a substance having a small specific resistance may be used. However, if necessary, the same substance as the heat generating body may be used. It may be formed by forming the width wider or thicker than that.

Further, in the heating element described in each claim,
When the number of linear electric resistance heating elements is 2, the folded portion is bent into a U-shape of 1 by the low resistance connection body and the resistor, and when it is 3, the folded portion is bent into a deformed S shape of 2. However, if the number of resistors increases thereafter, a bent shape having a folded-back portion of a number obtained by subtracting 1 from that number is exhibited.

Further, the plurality of linear electric resistance heating elements are not necessarily formed in parallel with each other, and the intervals between them may be partially different.

Further, the linear electric resistance heating element may be partially different in width and thickness in the longitudinal direction.

Alumina ceramics and the like are suitable as the material of the substrate, but other insulating materials may be used.

The linear electric resistance heating element is made of a resistance material such as a silver / palladium alloy-based material or a ruthenium oxide-based material.
For example, it is generally formed by deposition using a screen printing method, but it may be provided by using another method using another material.

Further, the one end of the linear electric resistance heating element provided with the low resistance connecting member is not limited to the end portion of the linear electric resistance heating element, but the central portion of the linear electric resistance heating element is fixed. It means the part excluding the area through which the body passes.

The pair of terminals formed at both ends of the linear electric resistance heating element connected in series does not need to be provided at the end of the linear electric resistance heating element in terms of shape, and is electrically connected in series. It suffices that it is provided at the end of the formed linear electric resistance heating element. Therefore, another conductor may be provided between the linear electric resistance heating element and the terminal, and the terminal can be arranged at various portions on the heating element. Further, when the terminal and the linear electric resistance heating element are directly connected to each other, any electrical connection may be made between them.

According to a second aspect of the present invention, there is provided an electrically insulating elongated substrate, a plurality of linear electric resistance heating elements formed along a longitudinal direction on a plate surface of the substrate, and a pair of adjacent straight lines. One end of the linear electric resistance heating element is made of the same material as the linear electric resistance heating element and is electrically connected to the linear electric resistance heating element with a portion wider than the linear electric resistance heating element in the energizing direction. Are connected in series, and a pair of terminals formed at both ends of the linear electric resistance heating element connected in series.

The shape in which the low resistance connection body is wider than the linear electric resistance heating element in the energization direction means that the width of the one surface of the substrate in the direction perpendicular to the energization direction in plan view is large. ing.

A heating element according to a third aspect is the heating element according to the first aspect, wherein the low-resistance connecting body is made of a material in which a part of a current path is made of a material having an electric resistance lower than that of the linear electric resistance heating element. It is characterized by having a resistance conductor.

The part of the energization path means a part of the energization path divided in series.

Further, the low resistance connecting body need not be provided on the surface of the substrate on which the linear electric resistance heating element is formed, and the form thereof is not limited.

According to a fourth aspect of the present invention, there is provided an electrically insulating elongated substrate, a plurality of linear electric resistance heating elements formed along a longitudinal direction on a plate surface of the substrate, and a linear electric resistance heating element. A high resistance conductor which is made of the same material as the body and is integrally formed at its end, and a low resistance conductor which is configured to electrically short-circuit the high resistance conductor with a material having a lower electric resistance than the linear electric resistance heating element. Is formed so as to electrically connect one end of a pair of adjacent linear electric resistance heating elements to each other, and as a result, each linear electric resistance heating element is connected in series with a low resistance connection body and a linear shape connected in series. The electric resistance heating element is provided with a pair of terminals formed at both ends thereof.

As a method of making the resistance value different between the high resistance conductor and the low resistance conductor depending on the material, for example, the above-mentioned silver / palladium alloy-based material is used, and the low resistance conductor is the high resistance conductor material. There is a method of reducing the content ratio of palladium than that.

Further, in the heating element according to claim 3 or 4, the form or shape of the low resistance conductor is not particularly limited.
When the low resistance conductor is formed into a film, the electrical connection portion with the linear electric resistance heating element layer may be provided on the upper layer or the lower layer.

According to a fifth aspect of the present invention, there is provided a fixing device in which the heating body according to any one of the first to fourth aspects, a conveying sheet that can travel in a direction intersecting the longitudinal direction of the heating body, and the conveying sheet are interposed. And a heating member which is arranged so as to be in pressure contact with the heating member so that the heat from the heating member acts on the toner forming the image on the fixing member via the conveying sheet, and the fixing member conveys the fixing member. And a roller.

In the image forming apparatus according to the sixth aspect of the present invention, toner is attached to the electrostatic latent image formed on the medium to form a reverse image, and the reverse image is transferred to the fixing member to form a predetermined image. And a fixing device according to a fifth aspect of the present invention.

[0025]

When a voltage is applied to the terminals of the fixing heating element of the present invention, a current flows through the linear electric resistance heating element layer, and a heating state is instantaneously generated.

At this time, in the heating element according to the first aspect, since the resistance connecting element has a lower resistance than the linear electric resistance heating element layer, heat generation at the folded portion is suppressed and local temperature rise is reduced. it can. Therefore, stress is not concentrated on the folded-back portion.

Since a plurality of linear electric resistance heating elements are electrically connected in series, the amount of heat generated can be increased.

In the heating element according to claim 2, one end of a pair of adjacent linear electric resistance heating elements is made of the same material as that of the linear electric resistance heating element and has a portion wider than the linear electric resistance heating element in the energizing direction. Since they are electrically connected in series by the low resistance connection body, the same operation as the heating body according to claim 1 is provided. Further, this low resistance connection body can be formed integrally with the linear electric resistance heating element layer, and these can be formed at the same time.

The heating element according to claim 3 has the same action as the heating element according to claim 1.

The heating element according to claim 4 has the same action as the heating element according to claim 1.

Further, when the low-resistance conductor is formed in a film shape, no step is formed on the high-resistance conductor, so that even if there is a difference in thermal expansion between the low-resistance conductor and the high-resistance conductor, the difference is small. The resistance conductor layer does not weaken mechanical strength against strain,
It is possible to prevent disconnection of the low resistance conductor layer.

According to a fifth aspect of the present invention, the fixing device, to which the toner is adhered, is conveyed while being in pressure contact with the heating element and the fixing roller of the first aspect through the conveying sheet, and the toner is heated by heating the heating element. Is melted and fixed. Since this fixing device includes the heating element according to any one of claims 1 to 4, it exhibits the same function as the heating element according to any one of claims 1 to 4.

An image forming apparatus according to a sixth aspect of the present invention includes the fixing device according to the fifth aspect, and therefore exhibits the action of the fixing device.

[0034]

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

FIG. 1 is a partially cutaway plan view of the heating element according to the first embodiment, FIG. 2 is a vertical sectional view taken along the line − in FIG. 1, FIG. 3 is a lateral sectional view taken along the line −, and FIG. 4 is the same. -It is a cross-sectional view taken along the line. 2 to 4, the scale of the substrate in the thickness direction is enlarged, and the characteristic portions of the invention are exaggerated. Therefore, the shapes are not faithfully represented.

In the figure, 1 and 2 are each about 300 m long
m, a width of about 1.5 mm, and a thickness of about 10 μm, which is an elongated linear electric resistance heating element layer, for example, a length of about 350 mm and a width of about 10 mm made of alumina ceramics,
It is deposited on an elongated insulating substrate 3 having a thickness of about 1 mm. The linear electric resistance heating element layers 1 and 2 are formed by screen-printing a silver / palladium-based conductive paste on one surface of the insulating substrate 3 and then firing the paste. Other than this, the conductive paste may be a ruthenium oxide-based paste or the like. And two linear electric resistance heating element layers 1,
2 are formed in parallel with each other.

The respective ends of the linear electric resistance heating element layers 1 and 2 are electrically connected to each other by a low resistance connecting member 4 to form a folded portion. The low resistance connection body 4 includes a resistance resistance conductor 4a formed by a material whose electric path has a lower electric resistance than the linear electric resistance heating elements 1 and 2, for example, a silver material to which a small amount of palladium is added. Have The resistance conductor 4a is formed by laminating a part of silver-based conductive paste on one end of the extended linear electric resistance heating element layers 1, 2 by screen printing, and then firing. ing. Since the conductive paste contains a small amount of palladium, it does not substantially generate heat. The resistance conductor 4a has a thickness of about 20 μm. In addition, the resistance metal conductor 4a may be made of a metal having a small electric resistance such as silver / platinum alloy, silver / platinum alloy, platinum or gold.

At the other ends of the linear electric resistance heating layers 1 and 2, terminal layers 5 and 5 each having a thickness of about 10 μm and formed of a good silver-based conductor made of the same material as the resistance conductor 4a are partially formed. They are stacked on top of each other. The terminal layers 5 and 5 are formed to have a sufficiently large area in order to obtain electrical contact with the outside, and are not laminated on the linear electric resistance heating element layers 1 and 2 but on the insulating substrate 3. The area of the directly formed portion is larger than the area of the portion laminated on the linear electric resistance heating element layers 1 and 2. Further, in order to reduce the contact resistance between the terminal layers 5 and 5 and the linear electric resistance heating element layers 1 and 2, the bonding area between the two is sufficiently large by lamination. The broken lines 1a and 2a indicate the boundaries between the ends of the linear electric resistance heating element layers 1 and 2 formed below the terminal layers 5 and 5, respectively. Further, the terminal layers 5 and 5 are formed in the same manner as the resistance conductor 4a, and at the same time, they are applied by the screen printing method and then baked.

A part of the linear electric resistance heating element layers 1, 2, the low resistance conductor 4, and the terminal layers 5, 5 are covered with a vitreous protective coating layer 6. A part of the terminal layers 5 and 5 means the tips 5a and 5a of the terminal resistance layers 5 and 5 on the low resistance connection body 4 side in the laminated region of the linear electric resistance heating element layers 1 and 2 and the terminal layers 5 and 5, respectively.
This is a region including at least the neighborhood, and this neighborhood becomes the boundary between the heat generation region and the non-heat generation region, and the linear electric resistance heating layers 1 and 2 are disconnected due to the difference in thermal expansion due to a steep temperature-temperature gradient in this region. This is to prevent it from happening. Here, as shown in the cross-sections of the heating element in FIGS. 3 and 4, in the protective coating layer 6, the portions 6b and 6c corresponding to the linear electric resistance heating element layers 1 and 2 protrude most. The portion 6d corresponding to the gap between the linear electric resistance heating element layers 1 and 2 is slightly lower than the portions 6b and 6c corresponding to the linear electric resistance heating element layers 1 and 2, respectively. In this way, the shape in which the portion 6d corresponding to the gap between the linear electric resistance heating element layers 1 and 2 is lowered is to make the thickness of the protective coating layer 6 relatively small, specifically, about 40 μm or less. Can be formed. In the above embodiment, it is about 20 μm.

FIG. 5 is a graph showing the temperature distribution in the longitudinal direction of the heating element of the present invention. The horizontal axis represents the longitudinal position on the heating element, and the vertical axis represents the temperature (° C). The temperature was measured with an infrared radiation thermometer. As can be seen from this figure, no local temperature rise is observed in the longitudinal direction of the linear electric resistance heating element layer.

FIG. 6 is a sectional view showing the first embodiment of the fixing device of the present invention. This fixing device incorporates the heating element 60 shown in the first embodiment for fixing toner.
In this fixing device, a fixing roller 61 is arranged so as to face the surface of the heating body 60 on the side of the linear electric resistance heating layers 1 and 2, and between the heating body 60 and the fixing roller 61 with respect to the longitudinal direction of the heating body. It has a structure in which a film-shaped transport sheet 62 that can travel in a crossing direction is provided. And toner 63
An object to be fixed, such as a sheet of paper 64 to which is attached, is conveyed while being pressed against the heating body 60 and the fixing roller 61 via the conveying sheet 62, and the toner 65 is melted and fixed by heating the heating body 60. .

FIG. 7 is an enlarged sectional view of the main part of the fixing device. In the figure, the heating element and the like are drawn in an enlarged manner in the thickness direction. As shown in this figure, the curved surface of the fixing roller 61 and the curved surface of the surface of the protective coating layer 61 can easily correspond to each other, and the pressing force of the sheet 64 is applied relatively uniformly in the vicinity of the linear electric resistance heating layers 1 and 2.

FIG. 8 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. In this copying machine, toner is attached to an electrostatic latent image formed on a photosensitive drum to form a reverse image, and the toner is transferred to a sheet 80 to form a predetermined image on an image forming unit 81.
And the fixing device 82 for fixing the toner on which the image is formed.

FIG. 9 is a partially cutaway front view showing a second embodiment of the heating element of the present invention. Since this heating element has basically the same structure as the heating element of the first embodiment, only the differences will be described.

This heating element is a linear electric resistance heating element layer 9
Reference numerals 1 and 92 are formed in parallel with each other along the longitudinal direction of the substrate. Then, one ends of the linear electric resistance heating element layers 91 and 92 are electrically connected by a low resistance connection body 94. The low resistance connection body 94 includes a high resistance conductor 94a integrally formed of the same material as the linear electric resistance heating elements 91 and 92, and the linear electric resistance heating elements 91 and 9.
The low resistance conductor 94b is configured to electrically short-circuit the high resistance conductor with a material having an electric resistance lower than that of the low resistance conductor 2.

FIG. 10 is a partially cutaway plan view showing a third embodiment of the heating element of the present invention. This drawing is drawn by enlarging the thickness of the linear electric resistance heating element layer and its interval, and does not show the actual shape.

In the figure, reference numerals 100, 101 and 102 denote elongated linear electric resistance heating element layers which are adhered on an insulating substrate 103 such as alumina ceramics. The linear electric resistance heating element layers 100 ... Are formed by screen-printing a silver / palladium-based conductive paste on one surface of the insulating substrate 103 and then firing the paste. The three linear electric resistance heating element layers 100 ...
They are formed in parallel with each other.

One ends of the linear electric resistance heating element layers 100 ... Are electrically connected by the low resistance connecting members 104 and 105. The low resistance connection layers 104 and 105 are
For example, it has the low resistance conductors 104a and 105b made of a silver material to which a trace amount of palladium is added. The low resistance conductors 104a and 105b are linear electric resistance heating element layers 10
It is formed by stacking and coating by screen printing on one end portion of which 0 is extended and then firing. Linear electric resistance heating element layer 10 located on the edge side of the insulating substrate 103
0 and 102 are low resistance conductors 104a and 10 at the ends on the side where the low resistance connectors 104 and 105 are not provided.
5b, a thickness of about 10 made of a good silver-based conductor
The terminal layers 106 and 107 of μm are stacked. Linear electric resistance heating element layer 100 ..., Low resistance connection element layer 10
4, 105 and part of the terminal layers 106, 107 are covered with a vitreous protective coating layer 108. The protective coating layer is not essential to the constitution of the present invention.

FIG. 11 is a partially cutaway front view of a heating element according to the fourth embodiment of the present invention. It should be noted that this drawing is drawn by enlarging the thickness of the linear electric resistance heating element layer and its interval, and does not show the actual shape. As shown in this figure, the linear electrical resistance heating element layers 111 and 112 may be electrically connected to each other by using, for example, a thermal fuse 113, or instead of the thermal fuse 113, a wire may be welded to the linear electrical resistance heating element layer. May be connected. Further, instead of the terminal layer, the leads 114 may be soldered to the ends of the linear electric resistance heating element layers 111 and 112 to form terminals.

FIG. 12 is a partially cutaway front view of the heating element according to the fifth embodiment of the present invention, and FIG. 13 is a partially cutaway rear view of the same. It should be noted that this drawing is drawn by enlarging the thickness of the linear electric resistance heating element layer and its interval, and does not show the actual shape. As shown in these drawings, the low resistance connection body layer 123 connecting the linear electric resistance heating body layers 121 and 122 may be provided on the other surface side of the substrate 124. in this case,
The linear electric resistance heating layers 121, 122 and the low resistance connection layer 123 may be electrically connected to each other by using, for example, through holes 125, and the linear electric resistance heating layers 121, 1 may be formed.
If a plurality of through holes 125 are provided for each 22, a large current can flow through the linear electric resistance heating element layers 121 and 122.

FIG. 14 is a partially cutaway plan view showing a sixth embodiment of the heating element of the present invention. This heating element is basically the first
The structure is similar to that of the heating element of the embodiment, but the low resistance connecting element 1 is used.
The linear resistance heating elements 141, 142 are integrally formed of the same material as each other, and are formed wider than the main body portion in the energization direction to form a low resistance connection body.

[0052]

According to the invention described in claim 1, since the linear electric resistance heating element layers are connected by the resistance resistance connecting body.
Since the folded-back portion does not locally overheat, stress is not concentrated and it is possible to provide a heating body with reduced damage to the substrate.

According to the second aspect of the invention, in addition to the effect of the heating element according to the first aspect, the resistance connecting body can be integrated with the linear electric resistance heating element layer and can be simultaneously formed. A heating element that can simplify the process can be provided.

According to the invention described in claim 3, it is possible to provide a heating body having the same effect as that of the heating body according to claim 1.

According to the invention described in claim 4, in addition to the same effect as the heating body according to claim 1, it is possible to provide a heating body capable of preventing disconnection of the low resistance conductor layer.

According to the invention described in claim 5, it is possible to provide a fixing device having the effect of the heating element described in claims 1 to 4.

According to the invention of claim 6, it is possible to provide an image forming apparatus having the effect of the fixing device of claim 5.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing a first embodiment of a heating element of the present invention.

FIG. 2 is a vertical cross-sectional view taken along the line − of the heating element of FIG.

FIG. 3 is a transverse cross-sectional view taken along the line -similarly.

FIG. 4 is a transverse cross-sectional view taken along line-similarly.

FIG. 5 is a graph showing a heat generation temperature distribution in the longitudinal direction of the heating body of the first embodiment.

FIG. 6 is a sectional view showing the first embodiment of the fixing device of the present invention.

FIG. 7 is an enlarged cross-sectional view of the same main part.

FIG. 8 is a sectional view showing a first embodiment of the image forming apparatus of the invention.

FIG. 9 is a partially cutaway front view showing a second embodiment of the heating element of the present invention.

FIG. 10 is a partially cutaway front view showing a third embodiment of the heating element of the present invention.

FIG. 11 is a partially cutaway front view showing a fourth embodiment of the heating element of the present invention.

FIG. 12 is a partially cutaway front view showing a fifth embodiment of the heating element of the present invention.

FIG. 13 is a partially cutaway rear view showing a fifth embodiment of the heating body of the present invention.

FIG. 14 is a partially cutaway front view showing a sixth embodiment of the heating element of the present invention.

FIG. 15 is a partially cutaway plan view of a conventional heating body.

[Explanation of symbols]

1, 2, 91, 92, 101, 102, 111, 11
2, 121, 122, 141, 142 ... Linear electric resistance heating element, 3 ... Substrate, 4, 94, 104, 105, 14
0 ... Low-resistance connector, 5 ... Terminal layer, 6 ... Protective coating layer,
4a, 94b, 104a, 105a ... Low resistance conductor

Claims (6)

[Claims] 1. An electrically insulating elongated substrate; a plurality of linear electric resistance heating elements formed along a longitudinal direction on a plate surface of the substrate; one end of a pair of adjacent linear electric resistance heating elements. A low resistance connecting body formed so as to electrically connect the linear electric resistance heating elements to each other in series, and a pair of terminals formed at both ends of the linear electric resistance heating elements connected in series. And a heating element. 2. An electrically insulating elongated substrate; a plurality of linear electric resistance heating elements formed on a plate surface of the substrate in a longitudinal direction; one ends of a pair of adjacent linear electric resistance heating elements. Are electrically connected to each other with a material wider than that of the linear electric resistance heating element in the energizing direction by the same material as the linear electric resistance heating element, so that each linear electric resistance heating element is connected in series. A heating body, comprising: a resistance connecting body; and a pair of terminals formed at both ends of a linear electric resistance heating body connected in series. 3. The heating element according to claim 1, wherein the low-resistance connecting body has a low-resistance conductor in which a part of an electric conduction path is made of a material having an electric resistance lower than that of a linear electric resistance heating element. . 4. An electrically insulating elongated substrate; a plurality of linear electric resistance heating elements formed along a longitudinal direction on a plate surface of the substrate; the same material as the linear electric resistance heating element and an end thereof. A high-resistance conductor integrally formed in the portion and a low-resistance conductor configured to electrically short-circuit the high-resistance conductor with a material having a lower electric resistance than the linear electric resistance heating element, A low resistance connector formed so as to electrically connect one end of the linear electric resistance heating element, and as a result, each linear electric resistance heating element is connected in series; A heating body, comprising: a pair of terminals formed at both ends. 5. The heating element according to claim 1, a conveying sheet that can travel in a direction intersecting the longitudinal direction of the heating element, and a heating sheet that faces the heating element via the conveying sheet. A fixing roller which is arranged so as to press the heating body and which causes heat from the heating body to act on the toner forming the image of the fixing body via the conveying sheet and conveys the fixing body. The fixing device is characterized in that 6. A means for adhering toner to an electrostatic latent image formed on a medium to form a reverse image, and transferring the reverse image to a fixing member to form a predetermined image; An image forming apparatus comprising: a fixing device;