JP2001209264A - Fixation heater, fixing device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation heater capable of preventing the temperature unevenness at the time of power supply, a fixing device and an image forming device. SOLUTION: A strip-shaped heating resistor 3 and electrode conductors 4a and 4b are formed parallel to the longitudinal direction of an insulating base plate 2 formed of insulating material in an oblong shape. The center part of the heating resistor 3 and the electrode conductor 4b are connected by a connecting conductor 9 formed on the electrode conductor 4b. Moreover, the heating resistor 3 on a surface of the insulating base plate 2 and electrode conductors 4a and 4b are respectively coated with a glass coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing heater for fixing toner on a recording medium, a fixing device, and an image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus for forming an image by electrophotography transfers toner in the form of an image to a recording medium such as copying paper, presses the toner with a fixing device, and heats the toner on the recording medium. Fix it. As such a fixing device, for example, there is a fixing device in which a rotatable pressure roller is pressed against a fixed fixing heater provided in a flat shape.

FIG. 5 is an explanatory view of such a fixing heater 1. FIG. 5 (a) is a plan view, and FIG. 5 (b) is FIG. 5 (a).
5 (c) is a cross-sectional view taken along line AA ′ of FIG. 5 (b).

In FIG. 5A, a fixing heater 1 is formed by screen-printing a heating resistor 3 and an electrode conductor 4 on a surface of an insulating substrate 2 having electrical insulation. 4 is a glass coat layer 5 of high softening glass
Covered. Although not shown, a thermistor as a temperature detecting element is mounted on the back surface.

The insulating substrate 2 is formed in an elongated shape, and a pair of power supply terminals 6a and 6b are formed at one end of the surface, and a pair of detection terminals 7a and 7b are formed at the other end. I have. The pair of power supply terminals 6a and 6b are terminals for supplying current to the heating resistor 3, and the pair of detection terminals 7a and 7b are terminals for extracting the temperature detected by the thermistor.

[0006] Both ends of the heating resistor 3 are connected by an electrode conductor 4a and connected to a power supply terminal 6a. The center of the heating resistor 3 is connected to a power supply terminal 6b via an electrode conductor 4b. Therefore, the heating resistor 3 forms a parallel circuit that is electrically branched at the center.

[0007] At the center of the heating resistor 3, FIG.
As shown in FIG. 5B, a projection 8 is formed for connection with the electrode conductor 4b, and as shown in FIG. Connected.

[0008]

However, in such a fixing heater, the connection between the heating resistor 3 and the electrode conductor 4a is made by providing a projection 8 at the center of the heating resistor 3, and the projection 8
Since the electrode conductors 4a are overlapped and connected to each other, the heat generated at the central portion of the heating resistor 3 increases.

Further, when the glass coat layer 5 is formed on the heating resistor 3 and the electrode conductor 4 by firing, the glass melts into the heating resistor 3, so that the resistance value of the heating resistor 3 is further increased. However, there is a problem that the resistance temperature characteristic (TCR) of the fixing heater greatly changes depending on the presence or absence of the glass coat layer 5.

[0010] When the temperature of the fixing heater becomes uneven, the amount of heat generated also becomes uneven, and the deterioration of the insulating substrate 2 progresses to cause cracks and peeling.

An object of the present invention is to provide a fixing heater, a fixing device, and an image forming apparatus capable of suppressing temperature unevenness during energization.

[0012]

According to a first aspect of the present invention, there is provided a fixing heater comprising: an insulating substrate formed in an elongated shape from an insulating material; and a heating resistor formed in a strip shape in a longitudinal direction of a surface of the insulating substrate. An electrode conductor provided in parallel with the heating resistor for supplying a current between a central portion of the heating resistor and both ends of the heating resistor; and an electrode conductor provided at a central portion of the heating resistor. A connection conductor for connecting the electrode conductor,
And a glass coat layer formed so as to cover the heating resistor and the electrode conductor on the surface of the insulating substrate.

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

The insulating substrate is a ceramic substrate, a glass substrate, or a metal substrate coated with an insulating layer having electrical insulation. The heating resistor is a resistor that generates heat when energized, and includes a thin film and a thick film.

The electrode conductor is a metal having conductivity and includes a thin film and a thick film. The connection conductor is a conductor that connects the central portion of the heating resistor and the electrode conductor, and is formed of a conductive metal and includes a thin film and a thick film. The glass coat layer is a layer exhibiting excellent properties such as abrasion resistance and electrical insulation, and includes a vitreous thin film and a thick film.

In the present invention, since the central portion of the heating resistor and the electrode conductor are electrically connected by the connecting conductor instead of the convex portion of the heating resistor, a rise in the temperature of the center portion of the heating resistor is suppressed. it can. This can prevent the fixing heater from cracking or peeling.

According to a second aspect of the present invention, there is provided a fixing heater comprising: an insulating substrate formed of an insulating material in an elongated shape; and a heating resistor formed in a band shape in the longitudinal direction of the surface of the insulating substrate and divided into two parts at a central portion. An electrode conductor provided in parallel with the heating resistor for supplying a current between a center portion of the heating resistor and both end portions of the heating resistor; A connection conductor for connecting the resistor and the electrode conductor, and a glass coat layer formed on the surface of the insulating substrate so as to cover the heating resistor and the electrode conductor are provided.

The insulating substrate, the heating resistor, the electrode conductor, the connection conductor, and the glass coat layer are the same as those described above.

According to the present invention, the heating resistor is divided into two parts on the surface of the insulating substrate, and the heating resistor and the electrode conductor divided into two parts at the center are connected to each other, so that the temperature of the central part at the time of energization is increased. The rise can be suppressed, and the thickness of the central portion can also be suppressed.

A fixing heater according to a third aspect of the present invention is the fixing heater according to any one of the first and second aspects, wherein a low softening point glass is used for the glass coat layer.

The low softening point glass is a glass which can be sintered at a relatively low temperature. By forming a low softening point glass coating layer on the heating resistor and the electrode conductor, the heating resistance is high when the sheet resistance is high. The reaction between the body and the glass coat layer is suppressed. Therefore, the resistance temperature characteristic does not significantly change depending on the presence or absence of the glass coat layer.

According to a fourth aspect of the present invention, there is provided a fixing device according to any one of the first or second aspects, and a pressure roller for pressing a recording medium into contact with the fixing heater and conveying the recording medium in a predetermined direction. A fixing device comprising:

The fixing heater of the present invention is preferably used as a fixing heater in a fixing device. In this case, the recording medium onto which the toner has been transferred is sent to a fixing device, and the recording medium is sequentially pressed against a fixing heater that generates heat by a pressure roller. The toner is fixed on the recording medium by the pressing and heating.

According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising:
An image forming mechanism for transferring toner to the recording medium in the form of an image, and a fixing device according to claim 4 for fixing the toner transferred to the recording medium by the image forming mechanism.

The fixing device of the present invention is preferably used as a fixing device in an image forming apparatus. In this case, the toner is transferred in the shape of an image onto the recording medium by the image forming mechanism, and the toner transferred by the fixing device is fixed on the recording medium.

[0026]

Embodiments of the present invention will be described below. FIG. 1 is an explanatory view of a fixing heater 1 according to a first embodiment of the present invention. FIG.
FIG. 1B is an enlarged view of a portion X in FIG. 1A, and FIG.
It is sectional drawing of the BB 'line of (b). The first embodiment is different from the conventional example shown in FIG. 5 in that the central portion of the heating resistor 3 and the electrode conductor 4a are electrically connected by the connecting conductor 9 instead of the projection 8 of the heating resistor 3. It is intended to be connected. As a result, a rise in the temperature of the central portion of the heating resistor 3 is suppressed, and cracks and peeling of the fixing heater 1 are prevented from occurring.

In FIG. 1A, a fixing heater 1 has main components on the surface of an insulating substrate 2. The insulating substrate 2 is formed in an elongated shape, and a film-like heating resistor 3 is formed on the surface of the insulating substrate 2 together with the electrode conductors 4a and 4b by screen printing. The heating resistor 3 and the electrode conductors 4a and 4b are covered with a glass coat layer 5 of low softening point glass. Therefore, the heating resistor 3 and the electrode conductors 4a, 4a
When the glass coat layer 5 is formed by firing on the upper layer of b,
Glass can be prevented from melting into the heating resistor 3, and the resistance value of the heating resistor 3 can be prevented from further increasing. Although not shown, a thermistor as a temperature detecting element is mounted on the back surface of the insulating substrate 2.

A pair of power supply terminals 6a and 6b are formed at one end of the surface of the insulating substrate 2, and a pair of detection terminals 7a and 7b are formed at the other end. The pair of power supply terminals 6a and 6b are terminals for supplying current to the heating resistor 3, and the pair of detection terminals 7a and 7b are terminals for extracting the temperature detected by the thermistor.

Both ends of the heating resistor 3 are connected to the electrode conductors 4a.
And is connected to the power supply terminal 6a. On the other hand, the center of the heating resistor 3 is connected to the electrode conductor 4b via the connection conductor 9 and to the power supply terminal 6b, as shown in FIG. Therefore, the heating resistor 3 forms a parallel circuit that is electrically branched at the center.

That is, a connection conductor 9 for connection to the heating resistor 3 is formed on the electrode conductor 4b located at the center of the heating resistor 3, and as shown in FIG.
The connection conductor 9 and the heating resistor 3 are overlapped and brought into contact to be electrically connected.

Here, the insulating substrate 2 has, for example, a thickness of 0.1 mm.
It is formed using long aluminum nitride, alumina, or the like having a length of 635 mm. In addition, the heating resistor 3 is formed by screen printing in a belt shape using, for example, a material mainly containing silver, palladium, manganese, nickel, cobalt, iron, or copper. The electrode conductors 4a and 4b, the power supply terminal 6a,
6b, the detection terminal portions 7a and 7b, and the connection conductor 9 are formed by screen printing in a belt shape using, for example, silver, silver / platinum-based, silver / palladium-based, gold, or platinum-based materials. In this case, the central portion of the heating resistor 3 and the connection conductor 9 are formed so as to overlap.

The glass coat layer 5 has, for example, a softening point of 500
The heating resistor 3 and the electrode conductor 4 are made of lead borosilicate glass having a temperature of about 100 ° C., a lead-free low-softening point glass paste, or the like.
a, 4b and the connection conductor 9 are formed on the upper layer by screen printing.

According to the first embodiment, the connecting portion between the central portion of the heating resistor 3 and the electrode conductor 4b is connected by the connecting conductor 9 as a conductor instead of the convex portion 8 of the resistor. Therefore, the temperature of the portion does not become extremely high and the fixing heater is not cracked and cracked.

Further, since a glass coating layer having a low softening point is formed on this upper layer, the reaction between the heating resistor having a high area resistivity and the glass coating layer is suppressed, and the resistance temperature characteristic is greatly increased depending on the presence or absence of the glass coating layer. It doesn't change.

Next, a second embodiment of the present invention will be described. FIG. 2 is an explanatory view of a fixing heater 1 according to a second embodiment of the present invention. FIG. 2A is a plan view, and FIG.
2 (b) is an enlarged view of a portion X in FIG. 1 (a), and FIG.
2B is a cross-sectional view taken along the line CC ′, and FIG.
13 is a sectional view taken along line DD ′ of FIG.

The second embodiment is similar to the first embodiment shown in FIG.
In the third embodiment, the heating resistor 3 is divided into two parts at the center, and the heating resistor 3 and the electrode conductor 4b which are divided into two are connected by the connection conductor 9. This suppresses a rise in temperature at the center of the heating resistor 3 during energization, and also suppresses the thickness of the center. Other configurations are the same as those of the first embodiment shown in FIG. 1, and therefore, the same components are denoted by the same reference symbols, and overlapping description will be omitted.

As shown in FIG. 2A, the heating resistor 3 is divided into two parts at the center, and as shown in FIG. 2B, the electrode conductor located at the center of the heating resistor 3 The divided heating resistor 3 and the electrode conductor 4b are connected by the connection conductor 9 formed in 4b. That is, as shown in FIGS. 2C and 2D, the connection conductor 9 is located between the divided heating resistors 3, and as shown in FIG. The connection conductor 9 connecting between the generated heating resistors 3 is connected to the electrode conductor 4b.

Thus, the heating resistor 3 when energized is
And the thickness of the central portion can be suppressed.

Further, a third embodiment of the present invention will be described. FIG. 3 is a longitudinal sectional view of a fixing device 10 according to a third embodiment of the present invention. The fixing device 10 includes the fixing heater 1 according to the first embodiment and the second embodiment. .

The fixing heater 1 has a fixing film 1 on its outer peripheral surface.
2 is fixed to the lower surface of the cylindrical support member 11 on which is disposed. The fixing film 12 is supported endlessly and freely. A pressure roller 13 is rotatably supported on a bearing below the support member 11, and the pressure roller 54 is pressed against the fixing heater 1 via the fixing film 12. Then, the recording medium 15 onto which the toner 14 has been transferred passes between the fixing film 12 and the pressure roller 54.

The fixing device 10 is used as one of the components constituting the image forming apparatus as described later. When the pressure roller 13 is driven, the fixing film 12 mounted on the outer periphery of the support member 11 circulates. When the recording medium 15 onto which the toner 14 has been transferred is sent to the fixing device 10 while the fixing heater 1 is generating heat at a certain temperature, the recording medium 15
Are sequentially pressed against the fixing heater 1 which generates heat by a pressure roller 13 via a fixing film 12. This allows
The toner 14 is fixed on the recording medium 15.

Since the fixing heater 1 can suppress temperature unevenness at the time of energization, cracks and peeling are less likely to occur, and the life of the fixing device 10 can be extended.

Further, a fourth embodiment of the present invention will be described. FIG. 4 is a configuration diagram of an image forming apparatus 16 according to a fourth embodiment of the present invention.
The fixing device 10 according to the embodiment is provided.

The main body housing 17 of the image forming apparatus 16
Has a paper feed cassette 18 at one end and a paper discharge tray 19 at the other end. A transport path 20 for the recording medium 15 is formed from the paper feed cassette 18 to the discharge tray 19, and an image forming mechanism 21 and a fixing device 10 are sequentially provided in the path of the transport path 20.

The image forming mechanism 21 includes the rotating photosensitive drum 2
2, a uniform charging process is performed by the charger 23, and an electrostatic latent image corresponding to the original image formed and exposed on the photosensitive drum 22 by the photoconductor 24 is formed. This electrostatic latent image is visualized sequentially with toner by the developing device 25, and is transferred to the transfer device 26 as a toner image.

Then, the recording medium 15 is transferred to the sheet feeding cassette 18.
In the process of transporting the toner from the printer to the paper output tray 19, the transfer device 26 of the image forming mechanism 21 transfers the toner onto the recording medium 15 in the shape of an image. After the toner is transferred to the recording medium 15, the photosensitive drum 22 undergoes a process of removing extraneous matter such as toner by the toner cleaner 27, so that an electrostatic latent image of the original image is formed again. On the other hand, the toner transferred to the recording medium 15 is
Is established.

[0047]

As described above, according to the first aspect of the present invention, a strip-shaped heating resistor is formed on the surface of the insulating substrate, and the strip-shaped heating resistor and the electrode conductor are connected via the connection conductor. Therefore, it is possible to suppress a temperature rise in a portion where the electrode conductor overlaps the central portion of the heating resistor. Therefore, it is possible to prevent the fixing heater from being damaged by heat.

According to the second aspect of the present invention, since the heating resistor and the electrode conductor divided into two parts are connected by the connection conductor, the temperature rise at the center of the heating resistor during energization can be suppressed and the thickness of the center can be reduced. Can be suppressed.

According to the third aspect of the present invention, since the glass coating layer having a low softening point is formed on the heating resistor and the electrode conductor, the reaction between the heating resistor having a high area resistivity and the glass coating layer is suppressed. Therefore, the resistance temperature characteristic does not significantly change depending on the presence or absence of the glass coat layer.

According to the fourth aspect of the present invention, since the fixing heater which suppresses temperature unevenness at the time of energization and does not easily cause thermal damage is used, the life of the fixing device can be extended.

According to the fifth aspect of the present invention, since a fixing device having a long life is provided, a highly reliable image forming apparatus can be provided.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory views of a fixing heater according to a first embodiment of the present invention, wherein FIG. 1A is a plan view, FIG. 1B is an enlarged view of a portion X in FIG. FIG. 1 (c) is a view B of FIG. 1 (b).
Sectional drawing of the line -B '.

2A and 2B are explanatory views of a fixing heater according to a second embodiment of the present invention, wherein FIG. 2A is a plan view, FIG. 2B is an enlarged view of an X part in FIG. 1A, FIG. 2 (c) shows C in FIG. 2 (b).
FIG. 2D is a cross-sectional view taken along line C-D ′, and FIG.
Sectional view of the line.

FIG. 3 shows a fixing device 1 according to a third embodiment of the present invention.
0 is a longitudinal sectional view.

FIG. 4 is a configuration diagram of an image forming apparatus 16 according to a fourth embodiment of the present invention.

FIG. 5 is an explanatory view of a conventional fixing heater, and FIG.
5B is a plan view, FIG. 5B is an enlarged view of a portion X in FIG. 5A, and FIG. 5C is a cross-sectional view taken along line AA ′ in FIG. 5B.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing heater, 2 ... Insulating substrate, 3 ... Heating resistor, 4 ...
Electrode conductor, 5: glass coat layer, 6: power supply terminal, 7 ...
Detecting terminal portion, 8: convex portion, 9: connecting conductor, 10: fixing device, 11: supporting member, 12: fixing film, 13: pressure roller, 14: toner, 15: recording medium, 16: image forming device, 17 ... body housing, 18 ... paper cassette,
19: paper ejection tray, 20: conveyance path, 21: image forming mechanism, 22: photosensitive drum, 23: charger, 24: photoconductor,
25: developing unit, 26: transfer unit, 27: toner cleaner

Continued on the front page F-term (reference) 2H033 AA03 AA23 BA25 BE03 3K034 AA20 AA34 BA05 BA17 BB05 BB06 BB14 CA02 CA03 CA14 CA17 CA22 CA32 DA05 HA01 HA10 3K058 AA12 AA45 AA86 BA18 CE02 CE13 CE19 DA04 GA06 3K05B Q18 RF18 Q03 RFQ RF17 RF22 UA06 UA17 VV22 VV25 VV28 VV31 VV34

Claims (5)

[Claims] An insulating substrate formed in an elongated shape with an insulating material; a heating resistor formed in a strip shape in a longitudinal direction of a surface of the insulating substrate; and a heating resistor provided in parallel with the heating resistor. An electrode conductor for supplying a current between the center of the body and both ends of the heating resistor; a connection conductor for connecting the electrode conductor to the center of the heating resistor;
A glass coat layer formed so as to cover the heating resistor and the electrode conductor on the surface of the insulating substrate. 2. An insulating substrate formed in an elongated shape with an insulating material; a heating resistor formed in a strip shape in a longitudinal direction of a surface of the insulating substrate and divided into two at a center; An electrode conductor for supplying a current between a central portion of the heating resistor and both ends of the heating resistor; connecting the heating resistor and the electrode conductor divided into two portions at the center portion And a glass coat layer formed so as to cover the heating resistor and the electrode conductor on the surface of the insulating substrate. 3. The fixing heater according to claim 1, wherein a low softening point glass is used for the glass coat layer. 4. A fixing heater according to claim 1, further comprising: a pressure roller that presses a recording medium against the fixing heater and conveys the recording medium in a predetermined direction. Fixing device. 5. An image forming mechanism for transferring toner in a shape of an image to the recording medium; and a fixing device according to claim 4, for fixing the toner transferred to the recording medium by the image forming mechanism. An image forming apparatus comprising: