CN104698795A - Heater and image forming device - Google Patents

Abstract

The invention provides a heater whose resistance heater has NTC character, and an image forming device. The heater (1A) comprises a substrate (2), a conductor (3), a resistance heater (4), and an outer sheath layer (7). The conductor (3) is formed on the substrate (2). The resistance heater (4) is electrically connected with the conductor (3), and is formed on the substrate (2). The outer sheath layer (7) covers the conductor (3) and the resistance heater (4) on the substrate (2). The resistance heater (4) contains ruthenium oxide, glass, silver, and mixture containing titanium oxide, manganese oxide, and ferric oxide. The content of silver is more than 1% by weight and lower than 8% by weight.

Description

Heater and image forming device

technical field

Embodiments of the present invention relate to a heater and an image forming apparatus.

Background technique

Heaters are installed on electronic equipment such as OA equipment, home appliances, and precision manufacturing equipment. The heater is used, for example, as a fixing device for fixing toner to paper in an image forming apparatus such as a copying machine or a facsimile machine. And, in the case of a visible card reader/writer, it is used to clear printed characters, etc. The heater is constituted by forming an electrode for power supply, a conductor, and a resistance heating element on a substrate, receives power from the electrode for power supply, and generates heat from the resistance heating element.

A heater used in a fixing device usually uses a resistance heating element with PTC (Positive Temperature Coefficient) characteristics, which mainly consists of silver and palladium, or ruthenium oxide and glass, and has a temperature coefficient of resistance [ppm/°C] of zero or positive temperature coefficient.

The length of the heater is set to an effective length corresponding to the maximum size of the medium that can be heated by the fixing device (the length of the medium parallel to the long side direction of the heater), that is, set to the same length as the maximum size, or set to longer. Therefore, when a medium smaller than the medium of the largest size is heated, the temperature of the heater in the area where the paper does not pass among the PTC characteristic heaters increases. Therefore, in order to suppress the temperature rise in the area where the paper does not pass, it is also considered to use a resistance heating element with NTC (Negative Temperature Coefficient) characteristics whose temperature coefficient of resistance [ppm/°C] becomes a negative temperature coefficient.

Patent Document 1: Japanese Patent Application Laid-Open No. 2-65086

Patent Document 2: Japanese Patent Application Laid-Open No. 7-94260

Patent Document 3: Japanese Patent Laid-Open No. 2009-244867

Contents of the invention

An object of the present invention is to provide a heater and an image forming apparatus in which a resistance heating element has NTC characteristics.

A heater according to an embodiment of the present invention includes a substrate, a conductor, a resistance heating element, and an outer sheath. The conductor is formed on the substrate. The resistance heating element is electrically connected to the conductor and formed on the substrate. The outer sheath covers the conductor and the resistance heating element on the substrate. The resistance heating element contains: ruthenium oxide; glass; a mixture containing titanium oxide, manganese oxide and iron oxide; silver. The silver content is not less than 1% by weight and not more than 8% by weight.

According to the present invention, it is possible to provide a heater and an image forming apparatus in which a resistance heating element has NTC characteristics.

Description of drawings

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

FIG. 2 is an explanatory diagram showing the relationship between silver and the temperature coefficient of resistance.

Fig. 3 is a plan view showing a modified example of the heater according to the embodiment of the present invention.

4 is an explanatory view showing a fixing device as an example of use of a heater.

5 is an explanatory view showing an image forming apparatus as an example of use of a heater.

Among the figure: 1, 1A, 1B-heater, 2-substrate, 3, 8-conductor, 4, 9-resistance heating element, 5, 6-electrode for power supply, 7-outer sheath, 100-copier (image forming device), 120-control device, 200-fixing device.

Detailed ways

Heaters 1A and 1B according to the embodiments of the present invention described below include: a substrate 2 ; conductors 3 and 8 ; resistance heating elements 4 and 9 ; and an outer sheath 7 . Conductors 3 , 8 are formed on substrate 2 . The resistance heating elements 4 and 9 are electrically connected to the conductors 3 and 8 and formed on the substrate 2 . The outer sheath 7 covers the resistance heating elements 4, 9 and the conductors 3, 8 on the substrate 2. The resistance heating elements 4 and 9 contain: ruthenium oxide; glass; a mixture including titanium oxide, manganese oxide and iron oxide; silver. The silver content is not less than 1% by weight and not more than 8% by weight.

Furthermore, in the heaters 1A and 1B according to the embodiments described below, the conductor 3 contains silver as a main component.

Furthermore, the image forming apparatus according to the embodiment described below includes the heater 1 that heats the passing medium and the pressure roller 203 that pressurizes the medium when the medium is heated. The pressure roller 203 pressurizes the medium, thereby fixing the toner image adhering to the medium.

[implementation mode]

This embodiment will be described with reference to FIGS. 1 and 2 . FIG. 1 is a plan view showing a heater according to the embodiment. FIG. 2 is an explanatory diagram showing the relationship between silver and the temperature coefficient of resistance. The silver ratio [% by weight] in FIG. 2 is the silver ratio when the resistance heating element is 100% by weight.

The heater 1A of this embodiment is mounted on electronic devices, and mainly heats media such as paper passing through. As shown in FIG. 1 , a heater 1A is configured to include a substrate 2 , a conductor 3 , a resistance heating element 4 , a pair of power supply electrodes 5 and 6 , and an outer sheath 7 .

The substrate 2 has heat resistance and insulation properties, and is formed in a rectangular shape in this embodiment. The substrate 2 is, for example, a flat plate made of ceramics such as alumina, heat-resistant composite materials, and the like. The substrate 2 has a thickness corresponding to a space where the heater 1A can be mounted, for example, about 0.5 mm to 1.0 mm. In addition, the shape of the substrate 2 is not limited as long as it has a short side direction and a long side direction intersecting with the short side direction, and recesses, protrusions, and cutouts may be formed on the outer periphery.

The conductor 3 is used to supply electric power to the resistance heating element 4 and is formed on the substrate 2 . The conductor 3 in this embodiment is electrically connected to the resistance heating element 4 in the longitudinal direction of the heater 1A (substrate 2 ) (hereinafter, simply referred to as “longitudinal direction”). The conductor 31 , the conductor 32 , and the conductor 33 included in the conductor 3 are formed separately in the longitudinal direction, and the resistance heating elements 41 and 42 are respectively arranged therebetween. The conductor 31 is formed along the longitudinal direction of the resistance heating element 41 , and one end thereof is electrically connected to the power supply electrode 5 , and the other end thereof is electrically connected to one end of the resistance heating element 41 . The conductor 32 is formed along the longitudinal direction of the resistance heating element 42 , and one end thereof is electrically connected to the power supply electrode 6 , and the other end thereof is electrically connected to one end of the resistance heating element 42 . The conductors 33 are electrically connected to the other end portions of the resistance heating elements 41 , 42 , respectively. That is, the conductor 3 is electrically connected along the longitudinal direction of the resistance heating element 4 .

The conductor 3 in this embodiment contains silver (Ag) as a main component. Here, the term "main component" refers to a substance accounting for the main weight % of the substances constituting the conductor 3 . Therefore, in the conductor 3, the total of silver and additives becomes almost 100% by weight. Since the conductor 3 contains an additive, the diffusion of silver to the resistance heating element 4 can be suppressed.

The conductor 3 is formed by applying a conductive paste containing the above substances and having a resistance value sufficiently lower than that of the resistance heating element 4 on the substrate 2 and firing it. Here, the term "coating" can be used in any manner as long as the conductive paste can be coated on the substrate 2, including screen printing.

The resistance heating element 4 is electrically connected to the conductor 3 , generates heat by passing electricity, and is formed on the substrate 2 . In this embodiment, the resistance heating element 4 is formed along the longitudinal direction. The resistance heating element 41 and the resistance heating element 42 included in the resistance heating element 4 are separately formed in the short side direction. The resistance heating elements 41 and 42 are each formed in a strip shape along the longitudinal direction, and have a constant length in the short direction of the heater 1A (hereinafter simply referred to as "short direction").

_The resistance heating _element 4 _of this embodiment contains: _ruthenium oxide _{( RuO 4} ); glass; Mixture; Silver (Ag). The resistance heating element 4 is formed by coating the resistance heating element slurry containing the above substances on the substrate 2 . In the resistance heating element 4, ruthenium oxide, glass, a mixture, and silver account for almost 100% by weight. The resistance heating element 4 contains glass with a high softening point (for example, 600°C to 800°C). As shown in FIG. 2, in the resistance heating element 4, when the whole is 100% by weight, silver accounts for 1% to 8% by weight or less, glass accounts for about 2 times of the mixture, and ruthenium oxide accounts for about 2.5 times of glass. Here, the reason why silver accounts for 1% by weight to 8% by weight or less is to make the temperature coefficient of resistance less than -800ppm/°C, preferably in the range of -800ppm/°C to -1050ppm/°C. If the temperature coefficient of resistance exceeds -800 ppm/°C, the effect of suppressing the temperature rise in the paper non-passing area described later will be reduced. Therefore, by making silver occupy 1% by weight to 8% by weight or less, the effect of suppressing the temperature rise in the paper non-passing area can be enhanced.

Here, the silver component of the conductor easily diffuses into the resistance heating element 4 containing ruthenium oxide. If silver is mixed into the resistance heating element 4 that does not contain silver, a deviation in heater resistance value or temperature coefficient of resistance occurs between the silver-diffused area and the non-diffused area. Therefore, by preliminarily containing more silver than the amount of silver (less than 0.5% by weight) mixed into the resistance heating element 4 by diffusion in the resistance heating element 4, variations in heater resistance or temperature coefficient of resistance can be suppressed. Thereby, the resistance heating element 4 having a desired heater resistance value or temperature coefficient of resistance can be formed on the substrate 2 .

The pair of power supply electrodes 5 and 6 are electrically connected to the conductor 3 and formed on the substrate 2 . As shown in FIG. 1 , a pair of power supply electrodes 5 and 6 are formed at the ends of the substrate 2 in the longitudinal direction. The pair of power supply electrodes 5 and 6 are electrically connected to conductors 31 and 32 , respectively, and conduct electricity through conductors 31 and 32 . In addition, in FIG. 1 , a pair of power supply electrodes 5 and 6 are formed at one end of the substrate 2 , but they may be formed at both ends, respectively, or may be formed at the other end. Furthermore, the pair of power supply electrodes 5 and 6 are usually formed integrally with the conductors 31 and 32 on the substrate 2 , but the pair of power supply electrodes 5 and 6 may be formed separately from the conductors 31 and 32 . Furthermore, the pair of power feeding electrodes 5 and 6 are formed on the surface of the substrate 2 on which the conductors 31 and 32 are formed, but may also be formed on the surface opposite to the surface on which the conductors 31 and 32 are formed. At this time, the pair of power supply electrodes 5 and 6 are electrically connected to the conductors 31 and 32 through the through holes formed in the substrate 2 .

The outer sheath 7 is a protective layer for covering the conductor 3 and the resistance heating element 4 formed on the substrate 2, and is formed in a belt shape in this embodiment. Because the outer sheath 7 covers the conductor 3 and the resistance heating element 4, it prevents the conductor 3 and the resistance heating element 4 from being directly exposed to the atmosphere, and suppresses the conductor 3 and the resistance heating element 4 from being interfered with from the outside (for example, mechanically, chemically). , electrical interference) and damage, breakage. The outer sheath 7 is formed as a glass layer having a thermal conductivity higher than that of the substrate 2, for example, 25 to 35% by weight of an inorganic oxide filler having excellent thermal conductivity such as alumina at 2 [W/(m·k)] or more.

Next, the operation of the heater 1A will be described. The heater 1A receives power from the outside through a pair of electrodes 5 and 6 for power supply. When the heater 1A is supplied with electricity, the conductor 3 is energized, and the resistance heating element 41 between the conductors 31 and 33 and the resistance heating element 42 between the conductors 32 and 33 are respectively energized in the longitudinal direction. As a result, the resistance heating elements 41 and 42 generate heat, respectively, and the heater 1A generates heat in substantially the entire area in the longitudinal direction.

As described above, in the heater 1A according to the present embodiment, the resistance heating element 4 containing ruthenium oxide has NTC characteristics. As a resistance heating element having NTC characteristics, there is a heating element containing graphite. For the glass contained in the graphite-containing resistance heating element and the glass constituting the outer sheath, glass having a relatively low softening point is used. Furthermore, graphite has high reactivity to softened glass, and generates carbon dioxide (CO ₂ ) through the reaction. That is, for example, carbon dioxide is generated when the coated resistance heating element is fired, and the graphite is burnt from the substrate. Therefore, it is not preferable to use a graphite-containing material as a resistance heating element for a heater. Ruthenium oxide, on the other hand, is less reactive towards softened glass at high temperatures. Glass having a higher softening point (for example, about 600° C. to 800° C.) can be used for the resistance heating element 4 containing ruthenium oxide than for the resistance heating element containing graphite. Therefore, in the heater 1A, ruthenium oxide having low reactivity to glass and glass having a high softening point can be used. That is, for example, carbon dioxide will not be generated when the coated resistance heating element is fired, and the resistance heating element will not be burned from the substrate like when graphite is used as the resistance heating element. Therefore, ruthenium oxide is preferably used as the resistance heating element of the heater.

In addition, in the above-described embodiment, the conductor 3 is electrically connected to the resistance heating element 4 in the longitudinal direction, but the present invention is not limited thereto. Fig. 3 is a plan view showing a modified example of the heater of the embodiment. As shown in FIG. 3 , in the heater 1B, the electrical connection direction between the conductor 8 and the resistance heating element 9 is not in the longitudinal direction. The conductor 8 and the resistance heating element 9 of the heater 1B are different from the conductor 3 and the resistance heating element 4 of the heater 1A only in shape, but their constituent materials, weight %, etc. are the same.

The conductor 8 is arranged at a portion facing the resistance heating element 9 in the short-side direction, and is electrically connected to the resistance heating element 9 . The conductors 84 , 86 , 88 and the conductors 82 , 85 , 87 included in the conductor 8 are formed separately in the short-side direction, and the resistance heating elements 91 to 95 are respectively disposed therebetween. Conductor 81 is formed along the longitudinal direction of resistance heating element 9 , and one end thereof is electrically connected to power supply electrode 5 , and the other end thereof is electrically connected to conductor 84 via conductor 83 . One end of the conductor 82 is electrically connected to the power supply electrode 6 , and the other end is electrically connected to one end of the resistance heating element 95 . The conductor 84 is electrically connected to the conductor 83 and one end of the resistance heating element 91 . The conductor 85 is electrically connected to the other end of the resistance heating element 91 and one end of the resistance heating element 92 . The conductor 86 is electrically connected to the other end of the resistance heating element 92 and one end of the resistance heating element 93 . The conductor 87 is electrically connected to the other end of the resistance heating element 93 and one end of the resistance heating element 94 . The conductor 88 is electrically connected to the other end of the resistance heating element 94 and the other end of the resistance heating element 95 . In addition, the conductors 81, 83, and 84 are usually integrally formed on the substrate 2, but the conductors 81, 83, and 84 may be separately formed.

The resistance heating element 9 is formed along the longitudinal direction as a whole. The resistance heating elements 91 to 95 included in the resistance heating element 9 are formed separately in the longitudinal direction, that is, arranged along the longitudinal direction. The resistance heating elements 91 to 95 are each formed in a rectangular shape that is long in the long side direction, and has a constant length in the short side direction.

Next, the operation of the heater 1B will be described. The heater 1B receives power from the outside through a pair of electrodes 5 and 6 for power supply. If the heater 1B is powered, the conductor 8 is energized, the resistance heating element 91 between the conductors 84,85, the resistance heating element 92 between the conductors 85,86, the resistance heating element 93 between the conductors 86,87, the conductor The resistance heating element 94 between 87 and 88 and the resistance heating element 95 between conductors 88 and 82 are respectively energized in the short-side direction. Accordingly, each of the resistance heating elements 91 to 95 generates heat, and the heater 1B generates heat in almost the entire area in the longitudinal direction.

Next, an embodiment of a fixing device including a heater will be described. 4 is an explanatory view showing a fixing device as an example of use of a heater. As shown in FIG. 4 , the fixing device 200 can use any of the heaters 1A and 1B (hereinafter, simply referred to as “heater 1 ”) according to the above-described embodiment and its modifications. In the fixing device 200 , the heater 1 is provided at the bottom of a cylindrical fixing belt 201 wound around a support 202 . The fixing belt 201 is formed of, for example, a heat-resistant resin material such as polyimide. A pressure roller 203 is disposed at a position facing the heater 1 and the fixing belt 201 . The pressure roller 203 has a heat-resistant elastic material such as silicone resin on its surface, and rotates in the direction of the arrow A around the rotation shaft 205 while the fixing belt 201 is pressed against it.

In the toner fixing step, the toner image T1 adhering to the copy paper P as a medium is heated and melted by the heater 1 at the contact surface between the fixing belt 201 and the silicone resin layer 204 via the fixing belt 201 . As a result, at least the surface portion of the toner image T1 is softened and melted beyond the melting point. Thereafter, on the paper discharge side of the pressure roller 203, the copy paper P is separated from the heater 1 and at the same time from the fixing belt 201, and the toner image T2 is naturally dissipated and solidified again, whereby the toner image T2 is fixed to the copy paper P. superior.

Next, an embodiment of an image forming apparatus including a heater will be described. 5 is an explanatory view showing an image forming apparatus as an example of use of a heater. Components including the fixing device 200 are accommodated in a casing 101 of the copier 100 . On the upper part of the housing 101, a document placement table formed of a transparent member such as glass is provided, and the document P1 to be read for image information is reciprocated in the arrow Y direction for scanning. Furthermore, the control device 120 performs control of each device constituting the copier 100 .

An illuminating device 102 composed of a light irradiation lamp and a reflector is provided on the upper part of the frame body 101. The light irradiated from the illuminating device 102 is reflected on the surface of the original P1, and passes through the short-focus small-diameter imaging element array 103 on the photosensitive drum 104. Upper slit exposure. In addition, the photosensitive drum 104 is provided so as to be rotatable in the arrow Z direction. The photosensitive drum 104 is wrapped with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, for example.

Further, a charger 105 is provided near the photosensitive drum 104 arranged in the housing 101 , and the photosensitive drum 104 is substantially uniformly charged by the charger 105 . On the charged photosensitive drum 104 is formed an electrostatic image subjected to image exposure by the short-focus small-diameter imaging element array 103 . This electrostatic image is developed using toner made of resin or the like that is softened and melted by heating by the developing device 106 to become a toner image.

The copy paper P accommodated in the paper feed cassette 107 is fed onto the photosensitive drum 104 by a pair of feed rollers 109 that are pressed against each other in the vertical direction and rotate synchronously with the paper feed roller 108 and the toner image on the photosensitive drum 104 . Then, the toner image formed on the photosensitive drum 104 is transferred onto the copy paper P by the transfer discharger 110 .

Thereafter, the copy paper P conveyed downstream from the photosensitive drum 104 is guided to the fixing device 200 by the conveyance guide 111 , subjected to a heat fixing process (the toner fixing process described above), and discharged to the tray 112 . In addition, after the toner image is transferred, the residual toner on the photosensitive drum 104 is removed using the cleaner 113 .

Fixing device 200 is installed in a state where heater 1 including resistance heating elements 4 and 9 is pressed by silicone resin layer 204 attached to the outer periphery of pressure roller 203 in a direction perpendicular to the moving direction of copy paper P. Here, the length in the longitudinal direction of the heater 1 is set to an effective length corresponding to the maximum size (the length of the medium parallel to the longitudinal direction of the heater 1 ) that the copier 100 can copy, that is, set to be the same as the maximum size. length, or set to longer.

Moreover, the unfixed toner image on the copy paper P sent between the heater 1 and the pressure roller 203 is melted by the heat generated by the resistance heating elements 4 and 9, so that letters, alphanumerics, symbols, figures, etc. A copy image is displayed on the copy paper P surface.

In addition, as an image forming apparatus such as the copier 100 using the heater 1 , the frequently used medium size is often not the maximum size. At this time, if the medium with high frequency of use passes continuously, the temperature of the paper non-passing area in the heater 1 will rise. 9, so it is possible to suppress the temperature rise in the area where the paper does not pass. Thereby, it is possible to suppress the temperature of the heater 1 from becoming higher than the shutdown temperature, and it is possible to reduce the frequency of stopping the operation of the image forming apparatus.

In addition, an example in which the heater 1 is used for the fixing purpose of an image forming apparatus such as a copying machine 100 has been described here, but it is not limited thereto, and may be installed in home appliances, precision equipment for business use or experiments, or for chemical reactions. Equipment, etc. used as a heat source for heating or heat preservation.

Although some embodiments of the present invention have been described above, these embodiments are merely examples and are not intended to limit the scope of the present invention. These embodiments can be implemented in other various forms, and various omissions, substitutions, and changes can be made without departing from the gist of the present invention. These embodiments and modifications thereof are included in the scope and gist of the present invention, and are also included in the inventions described in the claims and their equivalents.

Claims (3)

1. a well heater, is characterized in that, possesses:

Substrate;

Conductor, is formed on described substrate;

Resistance heater, is electrically connected with described conductor, and is formed on described substrate;

Outer jacket, covers described conductor and described resistance heater on the substrate,

Described resistance heater contains: ruthenium-oxide, glass, comprises the potpourri of titanium dioxide, manganese oxide and iron oxide, silver;

Described silver content is less than more than 1 % by weight 8 % by weight.

2. well heater according to claim 1, is characterized in that:

Described conductor is using silver as major component.

3. an image processing system, is characterized in that, possesses:

Well heater described in claim 1 or 2, heats the medium passed through;

Backer roll, pressurizes when heating described medium,

By described well heater described medium heated and by described backer roll, described pressurization carried out to described medium, making the toner image set being attached to described medium thus.