JP2021131466A - Fixing device and image forming apparatus - Google Patents

Abstract

To improve the winding resistance of a fixing device.SOLUTION: A fixing device has: a film; a nip part forming unit that has a heater (22) and a holding member (21); and a pressure member (30). The heater has a metal substrate, an insulating layer that is formed on the substrate, and heating elements that are arranged on the insulating layer and generate heat upon energization. When the heater is seen in a longitudinal direction of the fixing device, a surface of the pressure member side of the heater is held by the holding member while being bent in a concave shape.SELECTED DRAWING: Figure 12

Description

The present invention relates to a fixing device for fixing an image on a recording material and an image forming device for forming an image on the recording material.

As a heat fixing type fixing device mounted on an electrophotographic printer or a copying machine, a heater having a heat generating resistor on a substrate made of ceramics or the like, a fixing film that moves while contacting the heater, and a fixing film are used. Some have a pressurizing roller facing the heater. The recording material carrying the unfixed toner image is heated while being sandwiched and conveyed by the nip portion (fixing nip portion) between the fixing film and the pressure roller, whereby the toner image on the recording material is heated and fixed to the recording material. NS.

In the fixing device, when the recording material on which the toner image is placed is separated from the film, if the amount of toner supported on the tip of the recording material is large, the transfer material may be wrapped around the film and not discharged normally. .. Especially in a high temperature and high humidity environment, the amount of water in the recording material increases and the rigidity of the recording material (so-called “paper stiffness”) decreases, so that the risk of wrapping increases. As the speed of printers and copiers increases and the usage rate of thin paper increases, it is necessary to improve the wrapping resistance of the fixing device. According to Patent Document 1, when a full-scale image is output, the transfer material is passed through a fixing device (pre-fixing) before image formation to reduce the amount of water, increase the rigidity of the transfer material, and further separate the transfer material. It is described that image formation and fixing processing are performed after curling in a direction advantageous to the above.

Japanese Unexamined Patent Publication No. 2006-195347

However, since the productivity of the image forming apparatus is lowered by the method of the above document, it has been required to improve the wrapping resistance performance by a method having less influence on the productivity.

Therefore, an object of the present invention is to provide a fixing device and an image forming device capable of improving the wrapping resistance performance of the fixing device.

One aspect of the present invention is a tubular film, a nip portion forming unit having a heater and a holding member for holding the heater and in sliding contact with the inner surface of the film, and facing the nip portion forming unit with the film interposed therebetween. A fixing device that has a pressurizing member that forms a nip portion between the film and the film, and heats the toner image on the recording material and fixes it to the recording material while sandwiching and transporting the recording material between the nip portions. The heater includes a metal substrate, an insulating layer formed on the substrate, and a heating element arranged on the insulating layer and generating heat when energized. The fixing device is characterized in that the surface of the heater on the pressurizing member side is held by the holding member in a concavely curved state when viewed in the longitudinal direction of the fixing device.

According to the present invention, the wrapping resistance performance of the fixing device can be improved.

The schematic block diagram of the image forming apparatus which concerns on Example 1. FIG. The cross-sectional view which shows the fixing apparatus which concerns on Example 1. FIG. Exploded view of the film assembly used for the fixing device according to the first embodiment. The front view which shows a part of the fixing apparatus which concerns on Example 1. FIG. Sectional drawing of the heater which concerns on Example 1. FIG. The perspective view of the heater holder which concerns on Example 1. FIG. The schematic block diagram of the heater which concerns on Example 1. FIG. The perspective view of the heater holder which concerns on Example 1. FIG. Schematic configuration diagram (a) and schematic diagram (b) of the heater holder and the heater according to the first embodiment. FIG. 5 is a cross-sectional view of the heater holder according to the first embodiment. The schematic diagram which shows the deformation in the pressurized state of the heater which concerns on Example 1. FIG. The schematic diagram which shows the discharge state of the recording material in the fixing device which concerns on Example 1. FIG. FIG. 6 is a schematic configuration diagram of a fixing device according to Comparative Example 1. FIG. 6 is a schematic configuration diagram of a fixing device according to Comparative Example 2. FIG. 6 is a schematic configuration diagram of a fixing device according to Comparative Example 3. FIG. 6 is a schematic view showing a pressure distribution in a fixing nip portion according to Comparative Example 1. The schematic diagram which shows the pressure distribution in the fixing nip part which concerns on Example 1. FIG. The schematic diagram which shows the deformation in the pressurized state of the heater which concerns on Example 2. FIG. The schematic diagram which shows the deformation in the pressurized state of the heater which concerns on Example 3. FIG. The perspective view of the heater holder which concerns on Example 4. FIG. FIG. 5 is a cross-sectional view of a part of the heater holder according to the fourth embodiment. FIG. 5 is a cross-sectional view of another part of the heater holder according to the fourth embodiment. The schematic diagram of the heater holder which concerns on the modification of Example 4.

Hereinafter, exemplary embodiments for carrying out the present invention will be described with reference to the drawings.

(1) Image Forming Device FIG. 1 is a cross-sectional view of a laser beam printer (hereinafter, simply referred to as a printer 100) using electrophotographic technology as the image forming device according to the first embodiment. Hereinafter, the configuration and operation of the printer 100 will be briefly described.

When the printer 100 receives a print instruction, the scanner unit 3 emits a laser beam L corresponding to the image information to the photoconductor 1 as an image carrier. The photoconductor 1 charged to a predetermined polarity by the charging roller 2 is scanned by the laser beam L, whereby an electrostatic latent image corresponding to the image information is formed on the surface of the photoconductor 1. After that, the developer 4 supplies toner to the photoconductor 1, and forms a toner image on the photoconductor 1 according to the image information. The toner image that reaches the transfer portion (transfer nip portion) formed between the photoconductor 1 and the transfer roller 5 as the transfer means by the rotation of the photoconductor 1 in the direction of the arrow R1 is obtained from the cassette 6 to the pickup roller 7. It is transferred to the recording material P supplied by. The surface of the photoconductor 1 that has passed through the transfer nip portion is cleaned with the cleaner 8. The recording material P to which the toner image t (FIG. 2) is transferred is subjected to heat and pressure by a heat fixing type fixing device 9 to be fixed.

After that, the recording material P is discharged to the tray 11 by the discharge roller 10. The size and material of the recording material P include paper such as plain paper and cardboard, sheet material with surface treatment such as plastic film, cloth, and coated paper, and sheet material having a special shape such as envelope and index paper. A variety of different sheets can be used. Further, although the method of directly transferring the toner image from the photoconductor 1 to the recording material P is mentioned here, the method of transferring the toner image formed on the photoconductor to the recording material via an intermediate transfer body such as an intermediate transfer belt is used. The technique described below may be applied to the image forming apparatus.

(2) Fixing device The fixing device 9 will be described. The fixing device 9 is a tensionless type film heating system. That is, the fixing device 9 uses a flexible endless belt-shaped (or cylindrical) fixing film as a heat-resistant film, and keeps at least a part of the peripheral length of the fixing film in a state where tension is not always applied to the fixing film. Is configured to rotate by the rotational driving force of the pressurizing member.

Hereinafter, the film heating type fixing device 9 according to the present embodiment will be described in detail. FIG. 2 is a cross-sectional view of the fixing device 9. FIG. 3 is an exploded perspective view of the film assembly 20 used in the fixing device 9. FIG. 4 is a front view showing a part of the fixing device 9. Hereinafter, regarding the positional relationship of the components of the fixing device 9, the pressing direction of the pressurizing roller 30 against the fixing film 23 is the Z'-Z direction, the conveying direction of the recording material is the YY direction, and the length of the fixing device 9. The direction (axial direction of the pressurizing roller 30) is the X'-X direction.

As shown in FIGS. 2 to 4, the fixing device 9 of the present embodiment has a tubular fixing film 23, a heater 22 which is a heating body in contact with the inner surface of the fixing film 23, and a heater 22 via the fixing film 23. It has a pressurizing roller 30 as a pressurizing member that is pressed toward. A fixing nip portion Nf is formed as a nip portion (pressure contact portion) between the fixing film 23 and the pressure roller 30 at a portion where the heater 22 overlaps the region in contact with the fixing film 23. The heater 22 is held by the heater holder 21, which is a holding member for the heat-resistant resin. The heater 22 and the heater holder 21 function as a nip portion forming unit of the present embodiment for forming the fixing nip portion Nf. The heater holder 21 also has a function of a guide for guiding the rotation of the fixing film 23. The pressurizing roller 30 receives power from the motor and rotates in the direction of arrow b. As the pressure roller 30 rotates, the fixing film 23 is driven and rotates in the direction of arrow a.

The heater holder 21 is, for example, a molded product of a heat-resistant resin such as PPS (polyphenylene sulfide) or a liquid crystal polymer. The heater 22 includes at least an elongated plate-shaped substrate (metal substrate) mainly made of metal or alloy, a resistance heating element (heating element) that generates heat when energized, an insulating layer that insulates the resistance heating element and the substrate, and heat generation. It has a glass coat layer that protects the body. Details of the heater 22 will be described later.

The thermistor 25, which is a temperature detecting element, is in contact with the side of the heater 22 opposite to the contact surface with the fixing film 23 (upper side in the drawing). By controlling the energization of the heating element according to the detection temperature of the thermistor 25, the temperature of the fixing nip portion Nf is maintained at a set temperature suitable for fixing the image.

The thickness of the fixing film 23 is preferably about 20 μm or more and 100 μm or less in order to ensure good thermal conductivity. As the fixing film 23, a single-layer film made of a material such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), or PPS is suitable. The fixing film 23 includes PTFE, PFA, and FEP (tetra) on the surface of a base layer made of a material such as PI (polyimide), PAI (polyetherimide), PEEK (polyetheretherketone), and PES (polyethersulfone). A composite layer film coated with fluoroethylene-perfluoroalkyl vinyl ether) or the like as a release layer (surface layer) is also suitable. Further, it is also preferable that a pure metal such as SUS, Al, Ni, Cu, Zn or the like having high thermal conductivity, an alloy or the like is used as a base layer, and the release layer is coated with the above-mentioned coating treatment and a fluororesin tube. ..

In this embodiment, the base layer of the fixing film 23 is a PI having a thickness of 60 μm, and the release layer is coated with PFA having a thickness of 12 μm in consideration of both wear of the release layer due to passing paper and thermal conductivity. Using.

The pressurizing roller 30 as a pressurizing member (pressurizing rotating body) includes a core metal 30a made of a material such as iron or aluminum, an elastic layer 30b made of a material such as silicone rubber, and a mold release layer 30c made of a material such as PFA. , (Fig. 2). The elastic layer 30b is formed on the outer periphery of the core metal 30a, and the release layer 30c is formed on the outer periphery of the elastic layer 30b to form the outermost layer of the pressure roller 30. A drive gear 33 (FIG. 3) is attached to one end of the core metal 30a of the pressure roller 30 in the axial direction, and receives rotational driving force from a drive means (not shown) via the drive gear 33. The pressure roller 30 rotates.

The configuration of the fixing device will be described with reference to the cross-sectional view of FIG. The reinforcing member 24 is made of a metal such as iron, and is a member that maintains the strength so as not to be significantly deformed even by the pressure of pressing the heater holder 21 toward the pressurizing roller 30. The heater 22 is pressed toward the pressurizing roller 30 side via the heater holder 21 and the reinforcing member 24 by the pressing means described later. The region (pressure contact region) in which the pressure roller 30 and the fixing film 23 are in close contact with each other due to this pressing force is the fixing nip portion Nf in this embodiment. The pressurizing position of the pressurizing roller 30 (the position of the pressing force of the heater 22 with respect to the pressurizing roller 30) and the position of the central portion of the heater 22 in the transport direction of the recording material are substantially the same.

Next, it will be described with reference to the perspective view of FIG. The heater holder 21 has a substantially gutter-shaped (U-shaped) shape in cross section, and the reinforcing member 24 is fitted inside the tub shape. A heater receiving groove is provided on the side of the heater holder 21 facing the pressure roller 30, and the heater 22 is positioned in a desired position by fitting into the heater receiving groove. The detailed shape of the heater holder 21 will be described later. The fixing film 23 is externally fitted to the outside of the heater holder 21 to which the above-mentioned parts are assembled with a margin in peripheral length. The axial direction of the cylindrical shape of the fixing film 23 (the direction of the arrow in which the fixing film 23 is inserted in the drawing) is referred to as the "longitudinal direction" of the fixing device 9. In this embodiment, the pressure roller 30, the heater 22, and the heater holder 21 are all elongated members extending in the longitudinal direction.

Both ends of the reinforcing member 24 in the longitudinal direction are overhanging portions protruding from both ends of the fixing film 23, and flange members 26 and 26 are fitted, respectively. The fixing film 23, the heater 22, the heater holder 21, the reinforcing member 24, and the flange members 26, 26 are assembled as a film assembly 20 as a whole.

The power supply terminal of the heater 22 also protrudes to one side in the longitudinal direction with respect to the fixing film 23, and the power supply connector 27 is fitted to the power supply terminal. The power supply connector 27 contacts the electrode portion of the heater 22 with contact pressure, and constitutes a power supply path for supplying the electric power supplied from the commercial power source to the heater 22.

A heater clip 28 is attached to the other side of the heater 22 in the longitudinal direction (the side opposite to the power feeding terminal). The heater clip 28 is a metal plate bent into a U-shape (U-shape), and the end portion of the heater 22 is held against the heater holder 21 due to its springiness.

Next, it will be described with reference to the front view of FIG. Each flange member 26 regulates the movement of the rotating fixing film 23 in the longitudinal direction, and regulates the position of the fixing film 23 while the fixing device is in operation. The distance between the flange members 26, 26 on both sides in the longitudinal direction (the portion in sliding contact with the end of the fixing film) is set to be longer than the length in the longitudinal direction of the fixing film 23. This is because the edge of the fixing film is not damaged during normal use.

Further, the length of the pressure roller 30 in the longitudinal direction is shorter than that of the fixing film 23 by about 10 mm. This is to prevent the grease protruding from the end of the fixing film 23 from adhering to the pressure roller 30 and causing the pressure roller 30 to lose its grip on the recording material and cause slippage.

The film assembly 20 is provided so as to face the pressure roller 30, and is restricted from moving in the longitudinal direction (horizontal direction in the drawing) and can be moved in the vertical direction. It is supported by the body 41. A pressure spring 45 is attached to the top plate side housing 41 in a compressed state. The pressing force of the pressurizing spring 45 is received by the overhanging portion of the reinforcing member 24, and the reinforcing member 24 is pressed toward the pressurizing roller 30, so that the entire film assembly 20 is pressed against the pressurizing roller 30.

A bearing member 31 is provided so as to pivotally support the core metal of the pressure roller 30 (see also FIG. 3). The bearing member 31 receives the pressing force from the film assembly 20 via the pressurizing roller 30. In order to rotatably support the core metal of the pressure roller 30 which becomes relatively high temperature, a material having heat resistance and excellent slidability is used as the material of the bearing. The bearing member 31 is attached to the bottom housing 43 of the fixing device.

The bottom side housing 43 and the top plate side housing 41 form a housing (frame body) of the fixing device 9 together with the frame side plates 42 and 42 provided on both sides in the longitudinal direction with respect to the film assembly 20 and extending vertically. ing.

(3) Heater Next, the materials, manufacturing methods, and the like constituting the heater 22 of this embodiment will be described with reference to FIGS. 5 to 7.

FIG. 5 is a cross-sectional view of the heater 22. The heater 22 protects a metal substrate 22a, a heating element 22c as a heating resistance layer that generates heat when energized, an insulating layer 22b that insulates the heating element 22c and the substrate 22a, and a glass coat layer that protects the heating element. It has a layer 22d and. The substrate 22a has an elongated plate shape mainly made of metal or alloy. Further, in order to reduce the warp of the substrate 22a during manufacturing, an insulating layer is also formed on a surface (second surface) opposite to the surface (first surface) on which the heating element 22c is provided in the thickness direction of the substrate 22a. It has 22e (a second insulating layer when the insulating layer 22b is used as the first insulating layer).

As the material used for the substrate 22a, any one of stainless steel, nickel, copper and aluminum, or an alloy containing them as a main material is preferably used. Of these, stainless steel is most preferable from the viewpoint of strength, heat resistance, and corrosion. The type of stainless steel is not particularly limited, and can be appropriately selected in consideration of the required mechanical strength, the coefficient of linear expansion according to the formation of the insulating layer and the heating element described in the next section, and the availability of plate materials in the market. good.

As an example, martensitic and ferritic chrome stainless steels (400 series) have a relatively low coefficient of linear expansion among stainless steels, and are preferably used because they can easily form an insulating layer and a heating element.

The materials of the insulating layers 22b and 22e are not particularly limited, but it is necessary to select a heat-resistant material in consideration of the actual operating temperature. As the material of the insulating layers 22b and 22e, glass or PI (polyimide) is preferable from the viewpoint of heat resistance, and the specific powder material in the case of glass may be appropriately selected as long as the characteristics of the embodiment are not impaired. .. If necessary, a heat conductive filler having an insulating property may be mixed. There is no problem whether the insulating layers 22b and 22e are made of the same material or different materials. Similarly, the thickness may be the same for the insulating layers 22b and 22e, or may be changed as necessary.

Generally, the heater 22 used in the image forming apparatus preferably has an insulation withstand voltage of about 1.5 KV. Therefore, the film thickness of the insulating layer 22b may be secured according to the material in order to obtain the dielectric strength performance of 1.5 KV between the heating element 22c and the substrate 22a.

The method for molding the insulating layers 22b and 22e is not particularly limited, but as an example, the insulating layers 22b and 22e can be smoothly molded by a screen printing method or the like. When forming an insulating layer of glass or PI (polyimide) on the substrate 22a, the linear expansion coefficient of the substrate and the insulating layer material is set so that the insulating layer does not crack or peel due to the difference in linear expansion coefficient between the materials. It is necessary to adjust accordingly.

The heating element 22c is obtained by printing a heating element paste, which is a mixture of (A) a conductive component, (B) a glass component, and (C) an organic binding component, on the insulating layer 22b and then firing it. When the heating resistor paste is fired, the organic binding component (C) is burnt out and the components (A) and (B) remain, so that a heating element 22c containing a conductive component and a glass component is formed.

Here, as the conductive component of (A), silver / palladium (Ag / Pd), ruthenium oxide (RuO ₂ ), etc. are used alone or in combination, and 0.1 [Ω / □] to 100 [KΩ / It is preferable to use the sheet resistance value of [□]. In addition to the above (A) to (C), other materials may be contained as long as the trace amount does not impair the characteristics of the embodiment.

Examples of the power feeding electrode 22f and the conductive pattern 22g shown in FIG. 6 are silver (Ag), platinum (Pt), gold (Au), silver / platinum (Ag / Pt) alloy, and silver / palladium (Ag / Pd) alloy. Mainly the conductive component. The power feeding electrode 22f and the conductive pattern 22g are formed by printing a paste obtained by mixing (A) a conductive component, (B) a glass component, and (C) an organic binding component on the insulating layer 22b in the same manner as the heat generating resistor paste. It is baked. The feeding electrode 22f and the conductive pattern 22g are conductive portions provided for the purpose of feeding the heating element 22c, and the resistance is sufficiently lower than that of the heating element 22c.

Here, for the heat-generating resistor paste, the feeding electrode, and the conductive pattern paste described above, a material that softens and melts at a temperature lower than the melting point of the substrate 22a is selected, and a heat-resistant material is selected in consideration of the actual temperature. There is a need to.

As shown in FIG. 5, a protective layer 22d that covers the heating element 22c and the conductive pattern 22g is provided on the insulating layer 22b (on the insulating layer) of the heater 22. When the heating element 22c is arranged on the side of the substrate 22a that comes into contact with the fixing film 23 (lower side in FIG. 2), the protective layer 22d secures the electrical insulation between the heating element 22c and the fixing film 23 and generates heat. It has a protective function that ensures the slidability between the body 22c and the fixing film 23. As the material, glass or PI (polyimide) is preferable from the viewpoint of heat resistance, and if necessary, a heat conductive filler having insulating properties may be mixed.

In this embodiment, since the heater 22 is deformed by utilizing the flexibility of the metal substrate, it is desirable that the thickness of the substrate 22a is not too thick. For example, the thickness of the substrate 22a is preferably less than 0.6 mm. As another factor, the thickness of the substrate 22a may be determined in consideration of strength, heat capacity, and heat dissipation performance. Since the thin substrate 22a has a small heat capacity, it is advantageous for quick startability (short time from the start of energization of the heater 22 to the arrival at the target temperature), but if it is too thin, problems such as distortion occur during heat molding of the heat generating resistor. It will be easier. On the contrary, the thick substrate 22a is advantageous in terms of distortion during heat molding of the heat generating resistor, but if it is too thick, the heat capacity is large, which is disadvantageous for quick start. The lower limit of the preferable thickness of the substrate 22a is, for example, 0.2 mm.

In this embodiment, a ferrite-based stainless steel substrate (SUS430: 18Cr stainless steel) having a width of 20 mm, a length of 376 mm, and a thickness of 0.3 mm was prepared as the substrate 22a.

Next, the insulating layer glass paste was applied to the above-mentioned stainless steel substrate by screen printing, and then dried at 180 ° C. and fired at 850 ° C. to form insulating layers 22b and 22e. The thickness of the insulating layers 22b and 22e after firing was 25 μm on both sides of the stainless steel substrate.

After that, a heat-generating resistor paste in which silver / palladium (Ag / Pd) is used as a conductive component and other glass components and organic binding components are mixed, and silver is used as a conductive component and other glass components and organic binding components are mixed to supply power. A paste for the electrode and the conductive pattern was prepared. Each paste was applied to a stainless steel substrate by screen printing, and then dried at 180 ° C. and fired at 850 ° C. to form a heating element 22c, a feeding electrode 22f, and a conductive pattern 22g. The thickness of the heating element 22c after firing was 15 μm, the length was 312 mm, and the width was 2.0 mm.

Next, a protective layer glass paste is prepared, the protective layer glass paste is applied on the heating element 22c and the conductive pattern 22 g by screen printing, and then dried at 180 ° C. and fired at 850 ° C. to form the protective layer 22d. bottom. The thickness of the protective layer 22d after firing was 30 μm.

In this embodiment, since the heater is deformed by utilizing the flexibility of the heater, the insulating layers 22b and 22e and the protective layer 22d should not be too thick from the viewpoint of preventing cracks and peeling. Specifically, 100 μm should be used. It is desirable that it does not exceed.

(4) Heater Holder and Heater Holding Method The heater holder 21 functions as a support member (holding member) for supporting the heater 22, and is also a guide for guiding the rotational running of the cylindrical fixing film 23. For the heater holder 21, a highly heat-resistant resin such as polyimide, polyamide-imide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, or the like can be preferably used.

Among them, the liquid crystal polymer can be particularly preferably used because of the following advantages. First, since the heat resistant temperature is high, the degree of freedom of the set temperature of the heater 22 can be increased. Moreover, since it can be molded, it has good productivity and can be mass-produced. Furthermore, since it is excellent in dimensional stability, the pressing force on the pressurizing member can be made uniform, and the paper transport performance can be stabilized. In this example, a composite material in which glass fiber is mixed with a liquid crystal polymer was used.

FIG. 7 is a schematic view of the heater holder 21 viewed in the Z'-Z direction. In this embodiment, the fixing nip portion Nf is pressurized while the heater 22 is held by the holding portion W1 indicated by the diagonal line, and the pressing force acts on the heater 22. Hereinafter, a method of holding the heater 22 will be described with reference to FIGS. 8, 9 and 10.

FIG. 8 is a perspective view of the heater holder 21 as viewed from the pressure roller 30 side. The holding portion W1 is a portion where the heater holder 21 holds the heater 22 pressurized from the pressurizing roller 30 as in FIG. 7. Further, FIG. 9A is a schematic view (viewed in the Z'-Z direction) seen from the pressure roller 30 side in a state where the heater 22 is arranged in the heater holder 21, and FIG. 9B is a schematic view thereof. It is a figure.

As shown in FIGS. 9A and 9B, the heater 22 positions the pressure roller 30 in the axial direction (X'-X direction) with the heater holder 21 at the half-moon-shaped convex portion (dotted line portion C) of the heater holder 21. It is positioned. With such positioning, the heater 22 can be appropriately held even if the heater 22 expands and contracts due to heating. Further, the heater 22 positions the recording material in the transport direction (Y'-Y direction) at the abutting portions (dotted lines) formed on the wall portions on both sides in the axial direction (X'-X direction) of the pressure roller 30. In part B), it is positioned on the heater holder 21. With such positioning, the heater 22 can be appropriately held even when the fixing film 23 slides with respect to the heater 22 when the pressure roller 30 is rotationally driven.

FIG. 10 is a view of the cross section of the heater holder 21 in the dotted line portions AA of FIGS. 8 and 9 as viewed in the axial direction (X'-X direction) of the pressure roller 30. The notch portion of the heater holder 21 indicated by the arrows a and d is a portion that accommodates the heater 22 (is held in the heater holder 21). The dimension of a is 20.3 mm, which is slightly larger than the width dimension (20 mm) of the heater 22. The dimension of d is 0.3 mm, which is substantially the same as the thickness dimension (0.3 mm) of the heater 22.

The stepped portion of the heater holder 21 indicated by the arrows b and c is the holding portion W1 shown by the diagonal lines in FIGS. 7 and 8, and indicates a place where the heater 22 is held against the pressing force from the pressurizing roller 30. ing. Both the dimension of b and the dimension of c are 1.0 mm, and the distance f between the step portions (b, c) is smaller than the width dimension (20 mm) of the heater 22 (18 mm). Further, the step portions (b, c) are steps generated by the notch portion (concave shape) indicated by the arrow e. The dimension of e is 0.2 mm. With such a configuration, the heater 22 receives the pressing force from the pressurizing roller 30 while both ends in the width direction within the width dimension (20 mm) of the heater 22 are held by the heater holder 21.

The notch between the holding portion W1 and the holding portion W1 is provided over the entire length of the heater 22 in the longitudinal direction. When one step portion (b) in the width direction of the heater 22 is used as the first holding portion of this embodiment, the other step portion (c) is the second holding portion of this embodiment.

FIG. 11 shows a schematic view of deformation of the heater 22 and the heater holder 21 in the fixing device 9 in this embodiment in a pressurized state. Since the heater 22 is made of a metal which is superior to ceramics in terms of strength against thermal stress, even if the thickness thereof is sufficiently reduced, sufficient strength during use can be obtained as compared with the conventional heater. On the other hand, it is more flexible than conventional heaters because it is mechanically made thinner and the base material is softer than ceramics. The heater 22 of the metal substrate is configured to be held at both ends in the width direction, and can be bent (deformed) by applying a pressing force of the pressurizing roller 30.

FIG. 12 shows a schematic view of the discharge state of the recording material of the fixing device 9 in this embodiment. By deforming the heater 22 described above, the shape of the pressure contact portion (fixing nip portion Nf) between the pressure roller 30 and the fixing film 23 can be made concave on the pressure roller side (concave on the pressure member side). "Concave on the pressure roller side (convex on the fixing film side)" means that both ends of the target portion are added compared to the central portion of the target portion in the transport direction of the recording material (Y'-Y direction). It means that the pressure roller 30 is on the pressure roller 30 side with respect to the pressure direction (Z'-Z direction).

It is also possible to configure the pressure roller 30 and the film assembly 20 to be relatively movable so that the pressure of the pressure contact portion (fixing nip portion Nf) can be released. In that case, in the pressurized state, the heater 22 is in a deformed state as described above, and in the pressure released state in which the pressurization is released, the heater 22 is in a linearly extended state when viewed in the longitudinal direction.

(5) Action and effect The action and effect of this example will be described in comparison with a comparative example. First, as Comparative Example 1, a configuration using a heater 122 having a heat generating resistor on a ceramic substrate and a heater holder 121 that does not allow deformation of the heater, as shown in a schematic diagram in FIG. 13, will be mentioned. Further, as Comparative Example 2, a configuration using a metal substrate heater 22 used in this embodiment and a heater holder 121 that does not allow deformation of the heater, as shown in a schematic diagram in FIG. 14, will be mentioned. Further, as Comparative Example 3, as shown in the schematic diagram in FIG. 15, a configuration using a heater 122 having a heat generating resistor on a ceramic substrate and a heater holder 21 of the heater holding method used in this embodiment will be mentioned. .. As shown in FIG. 16, the heater holder 121 in Comparative Examples 1 and 2 supports the heaters 22 and 122 on the flat support surface 121a, so that the heaters 22 and 122 are not deformed even when the pressure of the pressurizing roller 30 is applied. ..

The following experiments were conducted to verify the effects of this example. The experimental method and results are described below.

1) Experimental method 1 (wrapping test)
As the recording material, CS-060F (Canon Marketing Japan, product name) A4 paper (horizontal feed) was used. Then, a full-scale monochrome image having a density of 100% was sampled for continuous 10-sheet printing from a state in which the fixing device was sufficiently cooled by using a thin paper mode as a printing mode with a margin of 5 mm. In the image forming apparatus used in the experiment, the process speed at this time was 190 mm / sec, and the throughput was 46 images per minute. The case where the recording material was wrapped around the fixing device during printing was marked with x, and the case where it was not wrapped was marked with ○. The atmospheric environment in which the experiment was conducted has a temperature of 32.5 ° C. and a humidity of 80%.

2) Experimental method 2 (fixable power)
As the recording material, A4 paper (horizontal feed) of Office70 (Canon Marketing Japan, product name) was used. Then, a blank of 5 mm was set for a full-scale monochrome image having a density of 100%, and a plain paper mode was used as the printing mode, and sampling was performed for continuous printing of 50 sheets from a state in which the fixing device was sufficiently cooled. In the image forming apparatus used in the experiment, the process speed at this time was 190 mm / sec, and the throughput was 46 images per minute. Printing is performed experimentally while changing the fixing set temperature in 1 ° C increments, and the power consumed by the fixing device during printing is sampled. (Set as fixable power) was requested.

Specifically, the digital power meter WT300E (Yokogawa Test & Measurement Corporation, trade name) is used to measure the integrated electric energy (Wh) by energizing the heater of the fixing device when printing 50 sheets continuously, and the power consumption is measured from there. I asked for (W). For example, when the fixing set temperature is 200 ° C., the power consumption is 800 W and the entire solid image is fixed, and when the fixing set temperature is 199 ° C., the power consumption is 795 W and the entire solid image is not fixed. Suppose. At this time, the fixable power was set to 800 W as the minimum power consumption for fixing the solid image on the entire surface. The atmospheric environment in which the experiment was conducted has a temperature of 23 ° C. and a humidity of 50%.

3) Experimental method 3 (fixation life)
Use Office70 (Canon Marketing Japan, trade name) A4 paper (horizontal feed) as the recording material, set a margin of 5 mm for a full-face halftone image with a density of 10%, and use plain paper mode as the printing mode for continuous printing. Repeated sampling of two-sheet printing was performed. In the image forming apparatus used in the experiment, the process speed at this time was 190 mm / sec, and the throughput was 46 images per minute. Image sampling and stick-slip noise (abnormal noise due to deterioration of the sliding property of the heater and the fixing film) were checked at the start of the durability test and every 20,000 sheets thereafter. Printing was completed when the stick-slip sound was confirmed, and the number of prints confirmed to have not occurred 20,000 sheets before that was taken as the life of the fixing device. The atmospheric environment in which the experiment was conducted has a temperature of 23 ° C. and a humidity of 50%.

Table 1 shows the results of experimental methods 1, 2 and 3 in this example and comparative example.

First, using the results of Experimental Method 1, the effects brought about by the configuration of this example will be described. explain. As shown in Table 1, wrapping did not occur in the fixing device of the present embodiment, but wrapping occurred in the fixing devices of Comparative Examples 1, 2, and 3. In this embodiment, as described above with reference to FIGS. 11 and 12, the heater 22 of the metal substrate is configured to be held at both ends in the width direction (transportation direction of the recording material) from the pressure roller 30. It is configured to be deformed concavely toward the pressurizing roller side by the pressing force of. As a result, the shape of the pressure contact portion between the pressure roller 30 and the fixing film 23 can be made concave in the pressure roller direction. Due to this action, the paper ejection direction can be set to the pressure roller direction, and the margin for wrapping can be improved.

Next, using the results of Experimental Method 2, other effects brought about by the configuration of this example will be described. The fixable power of the fixing device in this embodiment was slightly lower than that of the fixing devices of Comparative Examples 1, 2 and 3, and the power consumption could be reduced. FIG. 16 shows a schematic view of the fixing device of Comparative Example 1 and a pressure distribution between the heater and the fixing film in the fixing device (the pressure distribution between the fixing film and the recording material is also substantially the same). The pressure distribution is shown by the dotted line. A mountain shape in which the pressure is high at the pressure center of the pressure roller 30 in the Y'-Y direction and gradually decreases at the end of the pressure contact due to the deformation caused by the crushing of the pressure roller and its reaction force. It becomes the pressure distribution of. The shape of the pressure distribution is the same for Comparative Examples 2 and 3.

FIG. 17 shows a schematic view of the fixing device of this embodiment and the pressure distribution of the pressure distribution between the heater and the fixing film in the fixing device. The pressure distribution of this example is shown by a solid line, and the pressure distribution of Comparative Example 1 is shown by a dotted line so that the difference from the comparative example can be easily understood. In this embodiment, unlike Comparative Example 1, the heater 22 on the metal substrate is deformed by being pressed by the pressure roller 30. As a result, the pressure peak at the pressure center portion of the pressure roller 30 in the Y'-Y direction is lower than that of Comparative Examples 1, 2 and 3, and the vicinity of the end portion of the pressure contact portion is lower than that of Comparative Examples 1, 2 and 3. The pressure distribution is mountain-shaped so that the pressure becomes high.

The effect of reducing the fixable power of the fixing device of this embodiment is due to the difference in the pressure distribution shape. In the fixing device, the toner image on the recording material is melt-deformed by heating and pressurizing to obtain a fixed image. As the recording material advances in the Y'-Y direction, the recording material and the toner image are heated in the fixing device. Since the deformation of the toner image becomes easier as the temperature rises, the deformation efficiency of the toner image becomes better when a higher pressure is applied downstream in the transport direction (a portion advanced in the Y direction). Due to this action, the fixing device of this embodiment has high deformation efficiency of the toner image and can be fixed with lower power consumption.

Furthermore, using the results of Experimental Method 3, other effects brought about by the configuration of this example will be described. The fixing life of the fixing device in this example was 20,000 sheets longer than that of the fixing devices of Comparative Examples 1, 2 and 3.

The effect of extending the fixing life of the fixing device of this embodiment is also due to the difference in the pressure distribution shape described above. The stick-slip sound is generated by the deterioration of the slidability due to the deterioration of the durability of the heat-resistant grease. In the fixing device of this embodiment, since the height of the pressure peak is low, the sliding deterioration of grease can be suppressed. This action makes it possible to extend the life of the fixing device.

As described above, in the present embodiment, the heater 22 of the metal substrate is configured to be held at both ends in the width direction, and is deformed by applying a pressing force of the pressurizing roller 30 to form a recording material. It has become possible to improve the wrapping resistance of.

The fixing device and the image forming device according to the second embodiment will be described. In this embodiment, since the holding shape of the heater 22 in the heater holder 21 is different from that in the first embodiment, the holding shape of the heater holder 21 will be described. The other elements having the same reference numerals as those of the first embodiment shall have the same configuration and operation as those of the first embodiment.

FIG. 18 shows a schematic view of the shape of the heater holder 21 and the holding state of the heater 22 in the second embodiment. In the second embodiment, unlike the first embodiment in which both ends in the width direction of the heater 22 are held, two holding portions W2 separated in the width direction of the heater 22 (conveying direction of recording material, Y'-Y direction). Holds the inner part of the heater 22 from both ends. When one holding portion W2 is used as the first holding portion of this embodiment, the other holding portion W2 is the second holding portion of this embodiment. It is preferable that the two holding portions W2 are separated by 3 mm or more (and less than the width dimension of the heater 22) in the width direction in order to allow the heater 22 to be deformed.

Even with the heater holder 21 of this embodiment, the heater 22 is deformed by the pressure applied from the pressure roller 30, so that the pressure contact portion (fixing nip portion) of the fixing film 23 and the pressure roller 30 is deformed in a concave shape. Therefore, the wrapping resistance performance of the recording material is improved. Further, as in the first embodiment, the pressure distribution in the pressure contact portion (fixing nip portion) is dispersed, so that the power consumption can be reduced and the life of the fixing device can be extended.

The fixing device and the image forming device according to the third embodiment will be described. In this embodiment, since the holding shape of the heater 22 in the heater holder 21 is different from that of both the first and second embodiments, the holding shape of the heater holder 21 will be described. The other elements having the same reference numerals as those of Examples 1 and 2 shall have the same configuration and operation as those of Examples 1 and 2.

FIG. 19 shows a schematic view of the cross-sectional shape of the heater holder 21 and the holding state of the heater 22 in the third embodiment. In this embodiment, the holding portion W3 in which the heater holder 21 holds the heater 22 (the portion where the heater holder 21 holds the surface of the heater 22 opposite to the surface facing the pressure roller 30) is concave on the pressure roller side. It is composed of curved surfaces.

Even with the heater holder 21 of this embodiment, the heater 22 is deformed concavely toward the pressure roller side along the curvature of the holding portion W3 due to the pressure applied from the pressure roller 30, so that the fixing film 23 and the pressure roller 30 are pressure-welded. The portion (fixing nip portion) is deformed in a concave shape. Further, as in the first embodiment, the pressure distribution in the pressure contact portion (fixing nip portion) is dispersed, so that the power consumption can be reduced and the life of the fixing device can be extended.

The fixing device and the image forming device according to the fourth embodiment will be described. In this embodiment, since the holding shape of the heater 22 in the heater holder 21 is different from that of any of the first to third embodiments, the holding shape of the heater holder 21 will be described. The other elements having the same reference numerals as those of Examples 1 and 2 shall have the same configuration and operation as those of Examples 1 to 3.

FIG. 20 is a perspective view of the heater holder 21 in the fourth embodiment as viewed from the pressure roller 30 side. The holding portion W4 shown as a shaded portion is a portion where the heater holder 21 holds the heater 22 pressurized by the pressurizing roller, similarly to the holding portion W1 of the first embodiment shown in FIG. In this embodiment, the concave shape of the heater holder 21 that enables the heater 22 to be deformed is a part of the range in which the heater 22 is provided in the longitudinal direction, with respect to the central position of the fixing nip portion in the longitudinal direction. It is provided symmetrically.

FIG. 21 shows a cross section of the heater holder 21 of the dotted line portion A (center position of the heater 22 and the fixing nip portion Nf in the longitudinal direction) in FIG. 20. At this position, the holding portion W4 is divided into two positions separated from each other in the width direction of the heater 22, and the heater holder 21 has a shape that allows the heater 22 to be concavely deformed toward the pressurizing roller side.

On the other hand, FIG. 22 shows a cross section of the heater holder 21 of the dotted line portions D and E (positions near the ends of the heater 22 in the longitudinal direction) in FIG. 20. At this position, the holding portion W4 is flat, and the heater holder 21 regulates that the heater 22 is concavely deformed toward the pressure roller side.

In this way, the heater 22 is provided in the longitudinal direction of the portion where the heater holder 21 holds the heater 22 while allowing the deformation of the heater 22 in the axial direction (X'-X direction, longitudinal direction of the fixing device) of the pressurizing roller 30. It may be a part of the range. In the configuration examples shown in FIGS. 20 to 22, the heater 22 is allowed to be deformed at the central portion in the longitudinal direction, and the heater 22 is not allowed to be deformed at other portions (both ends in the longitudinal direction).

The winding of the recording material may have a predetermined starting point in the axial direction (X'-X direction) of the pressure roller 30. This configuration is effective when the central portion in the longitudinal direction is the starting point of winding. Since the heater 22 on the metal substrate used in this embodiment is more flexible than the heater on a general ceramic substrate, it is possible to obtain an effect even in such a holding method of deforming into three dimensions.

When the starting point for winding the recording material is the end portion in the longitudinal direction, the configuration shown in FIG. 23 is also possible. In the case of this modification, the cross section of the heater holder 21 of the dotted line portion A (the center position of the heater 22 and the fixing nip portion Nf in the longitudinal direction) is the same as that in FIG. 22, and has a shape that regulates the deformation of the heater 22. On the other hand, the cross sections of the heater holders 21 of the dotted line portions D and E (positions near the ends of the heater 22 in the longitudinal direction) are the same as those in FIG. It has become. This modification also makes it possible to improve the wrapping resistance performance of the recording material of the recording material.

(Other Examples)
Each of the above-described examples has been described using a monochrome image forming apparatus. However, this technology is also applied to tandem type color image forming devices using recording material transport belts, 4-cycle type intermediate transfer type color image forming devices, and tandem type intermediate transfer type color image forming devices. can. The present technology can also be applied to a fixing device used in a similar configuration, such as a color image forming device using a recording material transport belt in an intermediate transfer method, and an image forming device using four or more toners.

Further, in each of the above-described examples, three shape examples have been described as the holding shapes of the heater holder 21. However, the same effect can be obtained with other sizes and other shapes as long as the heater 22 on the metal substrate can be held in a concave shape, and the present technology can be applied.

In Example 4, as the holding shape of the heater holder 21, a shape example in which the pressure roller 30 is divided into three in the axial direction has been described. However, the heater 22 on the metal substrate can be held in a concave shape even in a configuration in which the heater 22 is divided into two or more, or in a configuration in which the heater 22 is continuously connected from a deformable shape to a non-deformable shape. If the same effect is obtained, this technology can be applied.

Further, for example, by adhering the heater 22 to the concave heater holder 21, the heater 22 is always held in the heater holder 21 in a state of being concave toward the pressurizing roller side regardless of the presence or absence of pressurization by the pressurizing roller 30. It may be configured as such.

Further, in the fixing device of each of the above-described embodiments, the heater 22 is in direct contact with the inner surface of the film, but a sheet-like member having high thermal conductivity (for example, the material is ferroalloy) is used between the heater and the inner surface of the film. (Aluminum sheet-like member) may be arranged. That is, a nip portion forming unit having a structure in which the heater heats the film via the sheet-shaped member may be used.

9 ... Fixing device / 21 ... Nip part forming unit, holding member (heater holder) / 22 ... Nip part forming unit, heater / 22a ... Substrate / 22b ... Insulating layer / 22c ... Heating element / 23 ... Film (fixing film) / 30 ... Pressurizing member (pressurizing roller) / 100 ... Image forming device (printer) / Nf ... Nip part (fixing nip part)

Claims (8)

Between a tubular film, a nip portion forming unit having a heater and a holding member for holding the heater and in sliding contact with the inner surface of the film, and the film facing the nip portion forming unit with the film sandwiched between them. In a fixing device having a pressurizing member forming a nip portion, the toner image on the recording material is heated and fixed to the recording material while the recording material is sandwiched and conveyed by the nip portion.
The heater has a metal substrate, an insulating layer formed on the substrate, and a heating element arranged on the insulating layer and generating heat when energized.
The heater is held by the holding member in a state where the surface of the heater on the pressure member side is concavely curved when viewed in the longitudinal direction of the fixing device.
A fixing device characterized in that. The holding member is provided with a concave shape that allows the heater to bend.
The heater is linear when viewed in the longitudinal direction when not pressed by the pressurizing member via the film, and has a concave shape when pressed by the pressurizing member via the film. Bend towards
The fixing device according to claim 1. The holding member is a first holding portion and a second holding portion provided on both sides of the concave shape with respect to the transport direction of the recording material, and is a surface of the heater opposite to the surface of the heater facing the pressure member. Has a first holding part and a second holding part for holding the
The fixing device according to claim 2, wherein the fixing device is characterized by the above. The distance between the first holding portion and the second holding portion in the transport direction is 3 mm or more.
The fixing device according to claim 3, wherein the fixing device is characterized by the above. The concave shape is provided over the entire length of the range in which the heater is provided in the longitudinal direction.
The fixing device according to any one of claims 2 to 4, wherein the fixing device is characterized by the above. The concave shape is a part of the range in which the heater is provided in the longitudinal direction, and is provided symmetrically with respect to the central position of the nip portion in the longitudinal direction.
The fixing device according to any one of claims 2 to 4, wherein the fixing device is characterized by the above. The thickness of the substrate is less than 0.6 mm.
The fixing device according to any one of claims 1 to 6, characterized in that. With a rotating image carrier,
A transfer means for transferring a toner image supported on the surface of the image carrier to a recording material, and
The fixing device according to any one of claims 1 to 7, wherein the toner image transferred to the recording material by the transfer means is fixed to the recording material.
An image forming apparatus comprising.

Images