JP2000150113A - Heater, fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater, a fixing device and an image forming device capable of reducing uneven heating of an body to be fixed, by forming a thermister on the heating surface side of the body to be fixed and uniformalizing the temperature on the heating surface. SOLUTION: This heater has a slender electrical insulating board 2, a slender resistance heater 3 formed on one surface of the board 2 along its longitudinal direction, a thermister 5 formed on another surface of the board 2 to detect heat from the heater 3, and an electrical insulating layer 6 formed in a heating area including the thermister 5 on the board surface to be formed with the thermister 5 and the peripheral part of the thermister, while having thermal conductivity almost equivalent to that of the thermister 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element for fixing toner adhered to an object to be fixed, a fixing device, and an image forming apparatus.

[0002]

[Prior art]

A heating element of this type which reduces or prevents uneven heating of a member to be fixed is disclosed in, for example, JP-A-5-8994.
No. 9 (prior art). As shown in FIG. 6, this prior art heating element 21 has a wear-resistant ceramic 23 having a large heat capacity and a wear-resistant heater 23 made of a thick film or a thin film formed on the lower surface of a ceramic substrate 22 made of alumina or the like. I have. The ceramic substrate 22 is provided with a glass coating 24 as an electrical insulating coating almost entirely on one surface thereof to cover the entire exposed surface of the heater 23, and the other surface is formed as a smooth surface, and is fixed. Body paper 2
5 and the like are formed on a sliding surface 22a for sliding. The paper 25 or the like is provided with a sliding surface 22a through a heat-resistant film in which a Teflon resin is coated on the surface of a polyimide film.
Is fed in a predetermined direction by the feed roller 26 above the sheet.
Further, a temperature sensor 27 is provided in contact with the lower surface of the glass coating 24, and based on a temperature detection value detected by the temperature sensor 27, power supply to the heater 23 is controlled by a temperature control system (not shown) based on a temperature detection value. Then, the heat generation is appropriately controlled.

The sliding surface 22 on the upper surface of the ceramic substrate 22
a, the paper 25 is slid by a feed roller 26 via a heat-resistant film, and is sequentially sent out.
Heat is applied through the second sliding surface 22a. Thereby, the paper 25 is heated, and the toner image formed on the paper 25 is heated and melted, and is fixed on the paper 25.

The heating element 21 slides the paper 25 on the sliding surface 22a of the abrasion-resistant ceramic substrate 22 via a heat-resistant film, and the sliding surface 22a has good flatness. The wear of the sliding surface 22a is small, and the life can be extended. In addition, since the paper 25 is heated via the ceramic substrate 22 having a large heat capacity, even if the heater 23 has uneven heating, the heating is substantially equalized by the ceramic substrate 22.
Can reduce or prevent uneven heating.

[0006]

[Problems to be solved by the invention]

The heating element 21 of the prior art has a sliding surface 22a for heating the paper 25 when the temperature of the heater 23 is adjusted.
The temperature on the glass coating 24 is detected by the temperature sensor 27 instead of the temperature of the paper 25.
There is a disadvantage that the temperature above cannot be detected accurately. In this case, a thermistor is formed on the sliding surface 22a to form the sliding surface 2a.
Although the temperature of the paper 25 can be detected by detecting the temperature of 2a, there is a problem in that the thermal resistance is interposed in the thermistor portion, so that the sliding surface 22a (heating surface) has uneven temperature.

The present invention has been made in view of the above problems, and has a thermistor formed on a heating surface side of a fixing member and a heating member capable of reducing the uneven heating of the fixing member by making the temperature of the heating surface uniform. It is an object to provide a fixing device and an image forming apparatus.

[0009]

According to a first aspect of the present invention, there is provided a heating element comprising: an electrically insulating elongated substrate; and an elongated resistance heating element formed on one surface of the substrate along a longitudinal direction thereof. A thermistor formed on one surface of the substrate in proximity to the resistance heating element and detecting heat of the resistance heating element; An electrical insulating layer formed with a thermal conductivity of

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

The heating element has an electric insulating layer formed on the side of the heating surface of the fixing member.

As long as the shape of the substrate is elongated and as thin as possible, other shapes are free.

The heating region includes not only the region where the resistance heating element is formed on the substrate, but also the front and back surfaces of the substrate that are as hot as the region.

The electric insulating layer may be an organic heat-resistant electric insulating layer such as a glass layer or a Teflon layer, and may be formed at least in a heat generating area which is a heating surface of the member to be fixed. Since the electrical insulating layer has substantially the same thermal conductivity as that of the thermistor, the temperature of the resistance heating element is substantially equal to the temperature of the thermistor when the resistance heating element generates heat. In order to adjust the thermal conductivity of the electric insulating layer, for example, a method of adjusting the content of the filler using a glass paste containing a ceramic filler such as alumina or silica may be used.
Further, the substantially same thermal conductivity means that when the resistance heating element is heated to a temperature required for fixing the toner, the heat generation area on the surface of the resistance heating element has a uniform temperature distribution at least not obstructive to fixing. Means something that can be done.

In the present invention, the resistance heating element and the thermistor may be close to each other in any of the upper, lower, left and right directions.
And when it overlaps up and down, an intermediate such as a heat-resistant electrical insulating layer is interposed.

When the resistance heating element is energized, the resistance heating element generates heat. The heat of the resistance heating element is detected by a thermistor to control the amount of heat generated. At this time, in the portion where the thermistor is formed, heat conduction is hindered by the presence of the thermistor, so that heat is not easily transmitted to the fixing member. Therefore, the electric insulating layer formed so as to include the thermistor or the periphery of the thermistor is made to have a temperature substantially equal to that of the thermistor by appropriately selecting the thermal conductivity.

The electric insulating layer has a thermal conductivity substantially equal to that of the thermistor, and the heat insulating flow rate of the electric insulating layer is substantially equal to that of the thermistor, so that the area where the electric insulating layer is formed has a substantially uniform temperature distribution. Further, since the thermistor is formed on the surface of the resistance heating element on the heating surface side of the fixing object, it is possible to provide a heating element capable of accurately controlling the temperature for heating the fixing object.

A heating element according to a second aspect of the present invention provides an electrically insulating elongated substrate; an elongated resistance heating element formed on one surface of the substrate along a longitudinal direction thereof; A thermistor that is formed on the surface and detects the heat of the resistance heating element; and is formed in a heating area including the thermistor or the periphery of the thermistor on the substrate surface on which the thermistor is formed, with a heat conductivity substantially equal to that of the thermistor. An electrical insulating layer;
Is provided.

In the present invention, the thermistor detects the temperature due to the heat generated by the resistance heating element on the other side of the substrate on which the resistance heating element is formed, and controls the amount of heat generated by the resistance heating element according to the detection result. You. In the portion where the thermistor is formed, heat conduction is hindered by the presence of the thermistor, so that heat is not easily transmitted to the fixing member. Therefore, by optimizing the thermal conductivity of the thermistor or the electrical insulating layer formed around the thermistor peripheral portion, the temperature of the electrical insulating layer is made substantially equal to that of the thermistor.

The electric insulation layer has a thermal conductivity substantially equal to that of the thermistor, the temperature of the electric insulation layer is set to be substantially equal to that of the thermistor, and the region where the electric insulation layer is formed has a substantially uniform temperature. Since the thermistor is formed on the electrical insulating layer on the heating surface side of the fixing member, it is possible to provide a heating element capable of accurately controlling the temperature for heating the fixing member.

According to a third aspect of the present invention, there is provided a fixing device comprising: a heating element according to the first or second aspect; and a pressure roller disposed in pressure contact with the heating element.

A conveyance sheet made of a plastic sheet such as a thin polyimide resin may be interposed between the heating element and the fixing object to facilitate conveyance of the fixing object. Further, the transport sheet can be made endless.

Since the temperature of the heating surface of the heating element is substantially uniform, it is possible to provide a fixing device capable of fixing the toner on the fixing object by heating the fixing object without uneven heating.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising:
An image forming means for adhering toner so as to form a required image on the fixing member; and a fixing device according to claim 3 for fixing the toner adhering to the fixing member.

The image forming apparatus includes all devices having a function of forming an image using toner. The image means a character, a figure, a code, a video, and the like. For example,
There are image devices such as copying machines, printers, and facsimile machines.

According to a third aspect of the present invention, there is provided an image forming apparatus including a fixing device having the functions and effects described above.

[0027]

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

FIGS. 1A and 1B are schematic views of a heating element according to a first embodiment of the present invention, wherein FIG. 1A is a sectional view and FIG. 1B is a bottom view. In the drawing, 1 is a heating element, 2 is a substrate, 3 is a resistance heating element, 4 is a protective film, 5 is a thermistor, 6 is an electric insulating layer, 7
Is an overcoat glass layer.

The substrate 2 is a thin, electrically insulating thin plate made of alumina ceramics.

The resistance heating element 3 is formed on one surface (back surface) of the substrate 2 over a predetermined width, and one end of the substrate 2 is provided with electrodes 3a, 3b made of silver or a silver-palladium alloy or a silver-platinum alloy. And is formed to be elongated along the longitudinal direction of the substrate 2 and to be folded back. Resistance heating element 3
Is a pressure film formed by screen-printing a conductive paste mainly containing a silver-palladium alloy containing 55% by weight of palladium on the back surface of the substrate 2, drying and firing. When power is supplied between the electrodes 3a and 3b, the resistance heating element 3 generates heat.

The protective film 4 is formed by covering one surface (back surface) of the resistance heating element 3 and the substrate 2 with, for example, low-melting glass or the like, and electrically connecting the resistance heating element 3 and the thermistor 5 to each other. This is to ensure insulation.

The thermistor 5 has electrodes 5 a and 5 b at the other end of the back surface of the substrate 2 and is formed by printing on the protective film 4. That is, the thermistor 5 is formed close to the resistance heating element 3 on one surface (back surface) of the substrate 2, and the electrodes 5 a,
The heat of the resistance heating element 3 is detected via 5b. The thermistor 5 may have either NTC characteristics or PTC characteristics.

The electric insulating layer 6 is a glass layer made of crystallized glass or amorphous glass, and includes a thermistor 5 and is disposed in a heat generating region on the substrate surface (back surface) on which the resistance heating element 3 is formed. 5 has a thermal conductivity substantially equal to that of No. 5 and is formed by printing with a thick film. Note that the electrical insulating layer does not need to cover the thermistor 5 and only needs to cover the periphery of the thermistor.

A thick overcoat glass layer 7 made of, for example, lead silicate glass is formed so as to cover the electric insulating layer 6. The heating element 1 uses the surface of the overcoat glass layer 7 as a heating surface.

Next, the operation of the above embodiment will be described.

When the resistance heating element 3 is energized through the electrodes 3a and 3b, the resistance heating element 3 generates heat. The heat of the resistance heating element 3 is transferred to the electric insulating layer 6 via the protective film 4 and detected by the thermistor 5. The electric insulating layer 6 conducts heat and has a temperature substantially equal to that of the thermistor 5. The temperature of the electrical insulating layer 6 is substantially uniform in the formed region, and is transferred to the surface of the overcoat glass layer 7. The surface of the overcoat glass layer 7 generates heat as a heating surface and heats the member to be fixed. The temperature of the heating surface is
As shown in FIG. 2A, the temperature is substantially constant in the heat generation region. The thermistor 5 adjusts the amount of heat generated from the resistance heating element 3 by varying the state of energization to the resistance heating element 3 according to the detected temperature. If the electric insulating layer 6 is not formed, heat conduction is hindered in the portion where the thermistor 5 is formed, so that heat is difficult to be transmitted. As shown in FIG. 2B, the portion where the thermistor 5 is formed is formed. , The temperature of the heating surface corresponding to the temperature decreases, and the temperature of the entire heating surface becomes non-uniform. As a result, uneven heating occurs on the fixing member.

The electric insulating layer 6 has a thermal conductivity substantially equal to that of the thermistor 5 and a temperature substantially equal to that of the thermistor 5, and a temperature of the electric insulating layer 6 substantially uniform. Since the thermistor is formed on the surface of the resistance heating element on the surface side, it is possible to provide the heating element 1 that can accurately control the temperature for heating the fixing target.

FIGS. 3A and 3B are schematic views of a heating element according to a second embodiment of the present invention, wherein FIG. 3A is a sectional view, FIG. 3B is a top view, and FIG. 3C is a bottom view. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The heating element 8 shown in FIG. 3 is the same as the heating element 1 shown in FIG.
Is formed by printing a thermistor 5 on the other surface (front surface). Then, an electric insulating layer 6 having substantially the same thermal conductivity as that of the thermistor 5 is printed and formed on the heat generating area on the surface of the substrate 2 including the thermistor 5.
To form a thick overcoat glass layer 7. The resistance heating element 3 is formed on one surface (back surface) of the substrate 2 over a predetermined width, and its electrodes 3a and 3b are formed on both ends of the substrate 2, respectively.
Note that the electrical insulating layer does not need to cover the thermistor 5 and only needs to cover the periphery of the thermistor.

When the resistance heating element 3 is energized through the electrodes 3a and 3b, the resistance heating element 3 generates heat. The heat of the resistance heating element 3 is transmitted to the electric insulating layer 6 via the substrate 2 and
Detected by the thermistor 5. The electric insulating layer 6 conducts heat and has a temperature substantially equal to that of the thermistor 5. The temperature of the electric insulating layer 6 becomes substantially uniform in the formed region, and heat is transferred through the overcoat glass layer 7. The surface of the overcoat glass layer 7 generates heat as a heating surface and heats the member to be fixed. Fig. 2
As in (a), the temperature is almost constant in the heat generation region. The thermistor 5 adjusts the amount of heat generated from the resistance heating element 3 by varying the state of energization to the resistance heating element 3 according to the detected temperature.

Since the electric insulating layer 6 has a heat conductivity substantially equal to that of the thermistor 5 and a temperature substantially equal to that of the thermistor 5, the heat generation region on the substrate surface on which the electric insulating layer 6 is formed has a substantially uniform temperature. In addition, since the thermistor 5 is formed so as to be included in the electric insulating layer 6 on the heating surface side of the fixing member, the heat generating member 8 capable of accurately controlling the temperature for heating the fixing member is formed. Can be provided.

FIG. 4 is a sectional view of a fixing device according to a third embodiment of the present invention.

In the fixing device 10 shown in FIG. 4, a heating element 11 has a structure shown in FIG. 1 or FIG. 12
Is a pressure roller, which has a pressure contact with the heating element 11,
By transporting the fixing member 13 while clamping the same, the toner 13 a attached to the fixing member 13 is melted by the heat of the heating element 11 and fixing is performed. Note that a conveyance sheet 14a made of a polyimide resin or the like is interposed between the fixing member 13 and the pressure roller 12. Reference numeral 14 denotes a support for the heating element 11. Reference numeral 15 denotes a fixing device main body, which accommodates each of the above components.

In both the heating element 1 shown in FIG. 1 and the heating element 8 shown in FIG. 3, the overcoat glass layer 7 serves as a heating surface.
The toner 13a is fixed by contacting the fixing member 13.
The thermistor 5 is included in the electrical insulation layer 6 and the thermistor 5
And the electric insulating layer 6 have substantially the same temperature, and since the electric insulating layer 6 has a substantially uniform temperature in the region where the electric insulating layer 6 is formed, it is possible to accurately control the heating temperature of the fixing member 13 and eliminate uneven heating. can do.

Since the temperature of the heating surface of the heating element 11 is substantially uniform, the fixing device 1 capable of fixing the toner 13a to the fixing member 13 by heating the fixing member 13 evenly and uniformly.
0 can be provided.

FIG. 5 is a conceptual diagram of an image forming apparatus showing a fourth embodiment of the present invention. The same parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

An image forming apparatus 16 shown in FIG. 5 is a copying machine, in which 17 is a reading device, 18 is image forming means,
19 is a fixing device, and 20 is an image forming apparatus main body.

The reading device 17 optically reads the base paper to form an image signal. The image forming means 18 forms an electrostatic latent image on the photosensitive drum 18a based on the image signal, forms a reverse image by attaching toner 13a to the electrostatic latent image, 13 to form an image. The fixing device 19 has a structure shown in FIG. 4, and heats and fuses the toner 13a attached to the body 13 to be fixed. The image forming apparatus main body 20 houses the above-described reading device 17, image forming means 18, and fixing device 19, and includes a transport device, a power supply device, a control device, and the like.

The temperature of the heating surface of the heating element 11 is substantially uniform.
The image forming apparatus 16 provided with the fixing device 19 capable of fixing the toner 13a to the image forming apparatus can be provided.

[0050]

According to the first aspect of the present invention, the electrical insulating layer has a thermal conductivity substantially equal to that of the thermistor, a temperature substantially equal to that of the thermistor, and a uniform temperature. Since the thermistor is formed on the surface of a certain resistance heating element, it is possible to provide a heating element capable of accurately controlling the temperature for heating the fixing target.

According to the second aspect of the present invention, the electric insulating layer has a thermal conductivity substantially equal to that of the thermistor and a temperature substantially equal to that of the thermistor. Temperature can be made substantially uniform, and since the thermistor is formed so as to be included in the electric insulating layer on the heating surface side of the fixing member, the heat generation for accurately controlling the temperature for heating the fixing member can be performed. Can provide body.

According to the third aspect of the present invention, since the temperature of the heating surface of the heating element is substantially equal, a fixing device capable of fixing the toner on the fixing object by heating the fixing object evenly is provided. Can be provided.

According to the fourth aspect of the present invention, there is provided a fixing device in which the temperature of the heating surface of the heating element is substantially uniform, and the fixing member can be heated evenly to fix the toner on the fixing member. Image forming apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a heating element according to a first embodiment of the present invention, in which (a) is a cross-sectional view and (b) is a bottom view.

FIG. 2 is also a temperature distribution of a heating surface of a heating element.

FIGS. 3A and 3B are schematic views of a heating element according to a second embodiment of the present invention, wherein FIG. 3A is a cross-sectional view, FIG. 3B is a top view, and FIG.

FIG. 4 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 5 is a conceptual diagram of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a schematic view of a conventional fixing device.

[Explanation of symbols]

 1, 8, 11: Heating element 2: Substrate 3: Resistance heating element 5: Thermistor 6: Electric insulating layer 10, 19: Fixing device 12: Pressurizing roller 16: Image forming device 18: Image forming means

Claims (4)

[Claims] 1. An elongated substrate having electrical insulation; an elongated resistance heating element formed on one surface of the substrate along a longitudinal direction; and a resistance heating element formed on one surface of the substrate in proximity to the resistance heating element. A thermistor for detecting the heat of the resistance heating element; and an electrical insulating layer formed at least in a heating area on the resistance heating element including the thermistor or the periphery of the thermistor and having substantially the same thermal conductivity as the thermistor; A heating element, comprising: 2. An elongated substrate having electrical insulation; an elongated resistance heating element formed on one surface of the substrate along a longitudinal direction thereof; and a heat generated by the resistance heating element formed on the other surface of the substrate. And an electric insulating layer formed in a heat generating area including the thermistor or the periphery of the thermistor on the substrate surface on which the thermistor is formed, and having a thermal conductivity substantially equal to that of the thermistor. A heating element characterized in that: 3. A fixing device comprising: the heating element according to claim 1; and a pressure roller disposed in pressure contact with the heating element. 4. An image forming means for adhering toner so as to form a required image on an object to be fixed; and the fixing device according to claim 3, which fixes the toner adhering to the object to be fixed. An image forming apparatus comprising: