JPH1092553A - Heating element, heater for fixing, fixing apparatus, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control temperature without installing a thermistor and an electric power controlling circuit besides a heat radiating body attributed to a self-temperature controlling function by using a resistor having positive temperature coefficient of resistance and a desiring resistance. SOLUTION: A first and a second electrodes 2, 4 are formed in a the film formation method using a silver-based conductor. Without being overlapped on the electrode 2, the electrode 4 is formed in a position on the opposite to and near the electrode 2 while sandwiching a resistor body 3 having a positive temperature coefficient of resistance and formed by a thick film forming method using barium titanate. Consequently, high withstand voltage is provided, the distance between the electrode 2 and the electrode 4a can be narrowed, and a desiring resistance value can be obtained. Moreover, the resistance value can be adjusted by slightly changing the mutually parted distance of the electrodes 2, 4 to outside in the width direction of the substrate 1. In this case, since the resistor 3 with a positive temperature coefficient of resistance has a self-temperature controlling function, temperature control is carried out without requiring a thermistor and an electric power controlling circuit and furthermore the resistance value is easily set to be within a desiring range and the resistance value adjustment is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heating element, a fixing heater, a fixing device, and an image forming apparatus.

[0002]

2. Description of the Related Art As a fixing heater used for fixing an image forming apparatus, a thick film of a silver-palladium-based resistor is formed on a thin and long insulated substrate, and a current is generated between both ends of the resistor to generate heat. Things are known. Since this fixing heater has a very small heat capacity unlike a conventional roller-type fixing heater, it can be immediately heated to a predetermined temperature. Therefore, it is only necessary to energize only when fixing, and it is not necessary to always energize. Therefore, by using this fixing heater, remarkable power saving can be achieved. Further, since the fixing heater is extremely thin, it is possible to reduce the size of the fixing device and thus the image forming apparatus.

However, it is necessary to control the power consumption of the heater by using a thermistor and a power control circuit in order to maintain the temperature at a predetermined value, and it is unavoidable that the cost increases due to the increase in circuit components.

On the other hand, there is a resistor having a positive temperature coefficient of resistance, which is known to have a self-temperature control action. By using a resistor having a positive resistance temperature coefficient, a heating element capable of controlling temperature without using a thermistor and a power control circuit can be obtained.

FIG. 7 is a plan view showing an example of such a conventional heating element.

FIG. 8 is an enlarged sectional view taken along line 8-8 in FIG.

In the figure, 31 is an insulating substrate, and 32 is a first substrate.
, 33 is a resistor having a positive resistance temperature coefficient, 34 is a second electrode, and 35 is a power receiving terminal.

The insulating substrate 31 is made of ceramics and is formed to be thin and elongated.

[0009] The first electrode 32 is formed on the insulating substrate 31 so as to extend along the longitudinal direction of the insulating substrate 31.

A resistor 33 having a positive resistance temperature coefficient is formed on the insulating substrate 31 while surrounding the first electrode 32 from above.

The second electrode 34 is formed on the resistor 33 so as to face the first electrode 32 and extend along the longitudinal direction of the insulating substrate 31.

The power receiving terminals 35 are led out of the electrodes 32 and 34 and are disposed near the opposite ends of the insulating substrate 31 in the opposite directions.

Further, a vitreous protective layer 36 is formed on the insulating substrate 31 so as to surround the resistor 33 having the positive temperature coefficient and the second electrode 34 to constitute a heating element.

In this manner, electricity is supplied between the two electrodes 32 and 34 with the resistor 33 having a positive resistance temperature coefficient interposed therebetween to generate heat.

FIG. 9 is a plan view showing another example of this type of conventional heating element.

FIG. 10 is an enlarged cross-sectional view taken along line 10-10 of FIG.

In the figure, the same parts as those in FIGS. 7 and 8 are denoted by the same reference numerals, and description thereof will be omitted. This example is an insulating substrate 3
First, a resistor 33 having a temperature coefficient of positive resistance is formed on
The first electrode 32 ′ and the second electrode 3
4 'are formed apart from each other. And each electrode 3
2 ', 34' are each comb-shaped and are staggered.

[0018]

A resistor having a positive temperature coefficient of resistance generally has a considerably higher specific resistance than a silver-palladium-based resistor. For this reason, when a relatively long heating element is to be obtained, it is necessary to shorten the conduction distance of the resistor by conducting electricity in a direction perpendicular to the longitudinal direction of the heating element.

In the prior art shown in FIGS. 7 and 8, current is applied across the surface of the resistor 13, so that the resistance can be set to a desired range.

However, there are problems that it is difficult to adjust the resistance value and that the withstand voltage characteristics are deteriorated when the resistor has a local defect.

On the other hand, in the prior art shown in FIGS. 9 and 10, although the resistance value can be reduced to some extent by the comb-shaped electrode, there is a problem that the resistance value is still too large and it is difficult to adjust the resistance value.

According to the present invention, a heating element using a resistor having a positive resistance temperature coefficient that can easily set a desired value by reducing a resistance value, and a resistance value is easily adjusted, a fixing heater and a fixing device using the same. And an image forming apparatus.

[0023]

According to a first aspect of the present invention, there is provided a heating element comprising: a resistor having a positive resistance temperature coefficient formed in a planar shape; and a first electrode disposed on a first surface of the resistor. And a second electrode disposed at least partially on the second surface of the resistor so as not to face the first electrode.

In the present invention and each of the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.

The resistor having a positive temperature coefficient of resistance is made of a material having a positive temperature coefficient of resistance, such as barium titanate BaTiO _3, and can be formed as a molded body or a thick film body.

The first and second electrodes are formed of an appropriate conductor, and may be, for example, a film-shaped conductor containing silver, copper, aluminum or the like as a main component. In the case of a film-shaped conductor, it can be formed by a thick film, vapor deposition, or another manufacturing method.

The first and second electrodes are arranged so that they do not overlap each other with the resistor interposed therebetween, or only partially overlap.

Thus, in the present invention, the resistance value between the electrodes can be arbitrarily adjusted by shifting the position of the second electrode relative to the first electrode. That is, the resistance value decreases when the second electrode approaches or overlaps the first electrode in the overlapping direction, and increases when the second electrode is separated from the first electrode. For example, when the electrodes are arranged so as to partially overlap as compared with the comb-shaped arrangement in the same plane shown in FIGS. 9 and 10, the resistance value is reduced to about 1/100. If the two electrodes are arranged so as not to overlap, the resistance value is reduced to about 1/50. Therefore, the adjustment range between the latter two, that is, about twice in the present invention, can be obtained. Also, even if both electrodes are partially overlapped with each other, the amount is small relative to the whole, so that the problem of withstand voltage is very small.

As is clear from the above, according to the present invention,
Since a resistor having a desired resistance value and a problem of withstand voltage is small and a resistor having a positive resistance temperature coefficient is used,
By the self-temperature control action, a heating element capable of performing temperature control without using a thermistor and a power control circuit separately from the heating element can be obtained.

A heating element according to a second aspect of the present invention is a heating element having a positive temperature coefficient of resistance formed in a planar shape; a first electrode disposed on a first surface of the resistor; and a first electrode. And a second element disposed on the second surface of the resistor so as to be close to but not facing
And an electrode;

In the present invention, since the first and second electrodes do not face each other with the resistor interposed therebetween, the withstand voltage does not decrease even if the resistor has a defect.
The resistance value is relatively small because both electrodes are close to each other,
It can be set in a desired value range. Further, the adjustment of the resistance value can be performed by slightly shifting the positions of the two electrodes in the separating direction.

A heating element according to a third aspect of the present invention is a heating element having a positive resistance temperature coefficient formed in a planar shape; a first electrode provided on a first surface of the resistance element; And a second electrode disposed on the second surface of the resistor facing a part thereof.

In the present invention, both electrodes are partially opposed to each other with the resistor interposed therebetween, but the resistance value can be adjusted by changing the degree of overlap of the electrodes by relatively shifting the electrodes. Further, the resistance value can be further reduced as compared with the second aspect.

A heating element according to a fourth aspect of the present invention is the heating element according to any one of the first to third aspects, wherein the resistor is elongated and the first and second electrodes are elongated in the longitudinal direction of the resistor. Extending along the direction; .

According to a fifth aspect of the present invention, in the heating element according to any one of the first to fourth aspects, the first electrode and the resistor are adhered to an insulating substrate. And

When the resistor and both electrodes are formed by a thick film or vapor deposition, the insulating substrate is preferably made of a material having high heat resistance such as ceramics.

Since the heating element of the present invention is mounted on the substrate, the substrate can be used for supporting the heating element and the film formation is facilitated.

A heating element according to a sixth aspect of the present invention comprises an elongated insulating substrate; an elongated first electrode extending along the longitudinal direction of the substrate; and an elongated first electrode extending along the longitudinal direction of the substrate. There
And a resistor having a temperature coefficient of positive resistance disposed on the substrate so as to surround the first electrode; and at least a part of the resistor is disposed on the resistor along the longitudinal direction of the substrate so as not to face the first electrode. And a second electrode extending and provided.

In the present invention, an elongated heating element can be obtained. Since the current flowing through the resistor is in a direction orthogonal to the length direction of the substrate, the length of the heating element can be arbitrarily set according to the application. Further, the use of the heating element is not limited.

A heating element according to a seventh aspect of the present invention is the heating element according to the sixth aspect, further comprising a pair of power receiving terminals respectively derived from the first and second electrodes and disposed near one end of the substrate. It is characterized by.

In the present invention, since the power receiving terminal is disposed near one end of the substrate, wiring for supplying current is facilitated.

According to an eighth aspect of the present invention, there is provided a heating element according to any one of the first to seventh aspects, wherein the heating element is covered with a vitreous protective layer.

Since the protective layer is covered with the vitreous protective layer, the electrical insulation is improved, and the mechanical strength against friction can be improved.

According to a ninth aspect of the present invention, there is provided a fixing heater comprising the heating element according to the sixth or seventh aspect.

According to the present invention, it is not necessary to mount a thermistor on a substrate, and the temperature can be controlled without using a power control circuit. Therefore, an excellent fixing heater can be provided. As a fixing heater for an image forming apparatus, for example, a length of 270 to 350 mm, a width of 5 to 10 mm, and a thickness of about 1 m
m substrates can be used.

According to a tenth aspect of the present invention, there is provided a fixing heater according to the ninth aspect, and a pressure roller disposed in pressure contact with the fixing heater.

The fixing device of the present invention is suitable for an image forming apparatus, but is not limited to this. Further, the fixing heater and the pressure roller do not need to be in direct contact with each other, and for example, a conveyance sheet may be interposed. Further, the transport sheet can be formed in an endless belt shape.

An image forming apparatus according to an eleventh aspect of the present invention is an image forming means for obtaining a fixed member on which an image is formed by attaching toner to the formed reversible electrostatic latent image; and heating and melting the toner on the fixed member. And a fixing device according to claim 10 for fixing the image.

[0049]

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

FIG. 1 is a plan view showing a first embodiment of the heating element of the present invention.

FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG.

In the figure, 1 is a substrate, 2 is a first electrode,
Reference numeral 3 denotes a resistor having a positive resistance temperature coefficient, 4 denotes a second electrode, 5 denotes a power receiving terminal, and 6 denotes a protective layer.

The substrate 1 is made of alumina ceramics.

The first and second electrodes 2 and 4 are each formed of a thick silver-based conductor.

The resistor 3 having a positive temperature coefficient of resistance is made of barium titanate and is obtained by forming a thick film.

The second electrode 4 is formed so as not to be directly opposed to the first electrode 2 with the resistor 3 interposed therebetween, that is, not to overlap but to be close to the first electrode 2.

The power receiving terminal 5 is made of a silver-based conductor like the electrodes 2 and 4 and is formed at the same time as the electrodes, and is formed so as to be thicker than the electrodes so as to withstand sliding contact with the power supply terminals by recoating.

The protective layer 5 is made of glass and is attached to the substrate 1 so as to surround the resistor 3 and the second electrode 4.

Thus, in the present embodiment, the first and second electrodes 2 and 4 are adjacent to each other with the resistor 3 interposed therebetween.
Since the positions do not overlap, the withstand voltage is good, and the distance between the electrodes 2 and 4 can be reduced, so that a desired resistance value can be obtained. Further, the resistance value can be adjusted by slightly shifting the distance between the electrodes 2 and 4 outward in the width direction of the substrate 1 in the figure.

FIG. 3 is an enlarged sectional view showing a second embodiment of the present invention.

In the figure, the same parts as those in FIG.

The present embodiment differs from FIG. 2 in that a part of the second electrode 4 ′ is directly opposed to the first electrode 2 with the resistor 3 interposed therebetween.

In the present embodiment, by changing the degree of overlap between the first electrode 2 and the second electrode 4 ',
Further, the resistance value can be adjusted. Further, the resistance value can be made smaller than in the first embodiment.

FIG. 4 is a sectional view showing an embodiment of the fixing device of the present invention.

In the drawing, 7 is a fixing heater, 8 is a heater support, 9 is a pressure roller, 10 is a conveying sheet, 11 is a case, 12 is a guide roller, and 13 is a fixing member.

The fixing heater 7 is supported by a heater support 8.

The heater support 8 supports the fixing heater 7 and also serves as a guide for the transport sheet 10.

The pressure roller 9 is in pressure contact with the fixing heater 7.

The transport sheet 10 is positioned in front of the fixing heater 7 and rotates around the heater support 8 with the rotation of the pressure roller 9.

The case 11 houses each of the above-described components and supports the guide roller 12.

The image of the fixed member 13 is, for example, an image such as a character, a figure, or a video drawn on a plain paper with toner.

The fixing member 13 is fed between the pressure roller 9 and the conveying sheet 10 by the guide roller 12 from the previous process. At this time, the fixing heater 7 is energized and generates heat, and heats the portion of the fixing member 13 facing the fixing heater 7 via the conveyance sheet 10. Melts and settles on plain paper. Therefore, the image of the fixing target 13 that has passed through the fixing heater 7 and exited from the fixing device has been completely fixed.

FIG. 5 is a conceptual sectional view of a laser beam printer showing the first embodiment of the image forming apparatus of the present invention.

In the figure, 14 is a scanner device, 15 is an image forming device, 16 is a fixing device, 17a, 17b and 17c are guide rollers, 18 is a paper feed tray, and 19 is a case.

The scanner device 14 scans a laser beam of serial image data with the polygon mirror of the scanner motor 14a and makes the laser beam incident on the image forming device 15 via the reflection plate 14b.

The image forming apparatus 15 applies the laser beam scanned from the scanner 14 to the photosensitive drum 15a.
, An inverted electrostatic latent image is sequentially scanned and drawn on the outer peripheral surface of the photosensitive drum 15a.

The fixing device 16 has the same configuration as that shown in FIG.

The reversal electrostatic latent image drawn on the image forming device 15 by the scanner device 14 is
When the plain paper sent from the paper feed tray 18 passes through the photosensitive drum 15a while being in contact with the photosensitive drum 15a, the electrostatic latent image is transferred to become a normal rotation latent image, and toner is further transferred to the normal rotation electrostatic latent image. The image is drawn by being attracted and attached to the charge,
It becomes an object to be fixed. The image to be fixed is fixed to the image to be fixed next when the image passes through the body attaching device 16 as described with reference to FIG. The fixed plain paper is guided by guide rollers 17b and 17
c and is taken out of the case 19.

FIG. 6 is a conceptual sectional view of a copying machine showing an image forming apparatus according to a second embodiment of the present invention.

In the figure, 20 is a photosensitive drum, 21 is an image forming apparatus, 22 is a fixing device, 23 is a paper feed tray, 24
Is the case.

In the copying machine according to the present embodiment, an image on a base paper is optically read by an optical reading device (not shown) to form an image signal. Image forming apparatus 21 by image signal
Of the photosensitive drum 20 is formed. The inverted electrostatic latent image is transferred to plain paper taken out from the paper feed tray 23 to become a normal rotation electrostatic latent image, and further a toner is attached to the electrostatic latent image to form a fixing member on which an image is formed. Next, the fixing member is sent to a fixing device 22 having the same configuration as that shown in FIG. 4, and the toner is heated and melted by the above-described operation to fix the image. After the fixing, the image of the fixed object copied by a guide roller (not shown) is taken out of the case 24.

[0082]

According to the first and eighth aspects of the present invention, there is provided a heating element using a resistor having a positive resistance temperature coefficient, which can easily set a resistance value in a desired range and can easily adjust the resistance value. be able to.

According to the second aspect of the present invention, in addition, the first and second electrodes are close to each other across the resistor having a positive resistance temperature coefficient, but do not face each other. In addition, it is possible to provide a heating element whose resistance value can be made relatively small.

According to the third aspect of the present invention, since the first and second electrodes are partially opposed to each other, the resistance value can be further reduced and the resistance value can be easily adjusted. In addition, it is possible to provide a heating element having relatively good withstand voltage.

According to the fourth aspect of the present invention, in addition, the resistor is elongated, and the first and second electrodes are extended along the longitudinal direction of the resistor, so that a desired length of heat is generated. Body can be provided.

According to the fifth aspect of the present invention, since the first electrode and the resistor are attached to the insulating substrate, the substrate can be used for supporting the heating element, and the film can be formed. An easy heating element can be provided.

According to the sixth aspect of the present invention, it is possible to provide a heating element having a desired length according to the intended use.

According to the seventh aspect of the present invention, in addition, since the power receiving terminal is disposed near one end of the substrate, it is possible to provide a heating element in which wiring for supplying current is easy.

According to the eighth aspect of the present invention, it is possible to provide a heating element having improved electrical insulation and body friction due to the vitreous protective layer.

According to the ninth aspect of the present invention, it is possible to provide a fixing heater having the effect of the sixth or seventh aspect.

According to the tenth aspect, a fixing device having the effect of the ninth aspect can be provided.

According to the eleventh aspect, an image forming apparatus having the effect of the tenth aspect can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment of a heating element of the present invention.

FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is an enlarged cross-sectional view showing a second embodiment of the heating element of the present invention.

FIG. 4 is a sectional view showing an embodiment of the fixing device of the present invention.

FIG. 5 is a conceptual sectional view of a laser beam printer showing a first embodiment of the image forming apparatus of the present invention.

FIG. 6 is a conceptual cross-sectional view of a copying machine showing a second embodiment of the image forming apparatus of the present invention.

FIG. 7 is a plan view showing an example of this type of conventional heating element.

8 is an enlarged sectional view taken along line 8-8 in FIG. 7;

FIG. 9 is a plan view showing another example of this type of conventional heating element.

FIG. 10 is an enlarged sectional view taken along line 10-10 of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st electrode 3 ... Resistor of positive temperature coefficient of resistance 4 ... 2nd electrode 5 ... Protective layer

[Procedure amendment]

[Submission date] November 28, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Added

[Correction contents]

Title of the Invention Heating Element, Fixing Heater, Fixing Device, and Image Forming Apparatus

Claims (11)

[Claims] A resistor having a temperature coefficient of positive resistance formed in a plane; a first electrode provided on a first surface of the resistor; at least a part not facing the first electrode And a second electrode disposed on the second surface of the resistor. 2. A resistor having a temperature coefficient of positive resistance formed in a planar shape; a first electrode disposed on a first surface of the resistor;
A second electrode disposed on the second surface of the resistor so as to be close to, but not directly opposite, the first electrode. 3. A resistor having a temperature coefficient of positive resistance formed in a planar shape; a first electrode disposed on a first surface of the resistor;
A second electrode disposed on the second surface of the resistor with a part facing the second electrode. 4. The first and second resistors extend elongately.
The heating element according to any one of claims 1 to 3, wherein the electrode extends in a longitudinal direction of the resistor. 5. The heating element according to claim 1, wherein the first electrode and the resistor are attached to an insulating substrate. 6. An elongated insulating substrate; an elongated first electrode extending along a longitudinal direction of the substrate; and a first electrode extending along a longitudinal direction of the substrate. A resistor having a temperature coefficient of positive resistance disposed on the substrate so as to surround the resistor; at least a portion extending over the resistor along the longitudinal direction of the substrate so as not to face the first electrode. A second electrode provided;
A heating element, comprising: 7. The heating element according to claim 6, further comprising a pair of power receiving terminals respectively derived from the first and second electrodes and disposed near one end of the substrate. 8. The heating element according to claim 1, wherein the heating element is covered with a vitreous protective layer. 9. A fixing heater comprising the heating element according to claim 6. 10. A fixing heater according to claim 9, and a pressing roller disposed in pressure contact with the fixing heater;
A fixing device comprising: 11. An image forming means for transferring a formed reversal electrostatic latent image and adhering toner to obtain a fixed body on which an image is formed; and heating and melting the toner on the fixed body to fix the image. An image forming apparatus comprising: the fixing device according to claim 10.