JP2020067464A - Heat fixing device and image forming apparatus - Google Patents

Abstract

To solve the problem in which: in a fixing device using a halogen heater as heating means of a fixing member, radiation from the halogen heater is transmitted to a member other than a fixing film, and thereby heating efficiency is reduced.SOLUTION: A reflecting plate holding part is provided in a non-paper feed area of an intermediate member to provide an air space between a reflecting plate and a pressure member in a paper feed area.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electrophotographic heat fixing device capable of forming an image on a recording material such as a multifunction peripheral, a copying machine, a printer, a fax machine, and an image forming apparatus.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, a fixing member is slidably contacted with an inner peripheral surface of an endless belt member, and the fixing member is pressed against a rotating body via the belt member to form a belt member. A fixing device is widely used in which a nip portion is formed between a rotating body and a recording medium is conveyed to the nip portion to fix a toner image on the recording medium (see Patent Documents 1 to 3).

  Patent Documents 1 and 2 disclose an on-demand type fixing device having a short warm-up time. The on-demand type fixing device includes a fixing film (endless film) as a belt member, a pressure roller as a rotating body, a heater as a fixing member, and the like. The heater is installed inside the fixing film, presses against the pressure roller via the fixing film to form a nip portion, and heats the fixing film at the position of the nip portion. Then, the toner image on the recording medium conveyed toward the nip portion receives heat and pressure at the nip portion and is fixed on the recording medium.

  Patent Document 3 discloses a fixing device that uses a fixing film (endless belt) in which a heating unit (halogen heater) is provided as a fixing member and uses a pressure roller. Specifically, a pressure member (pressure pad) as a fixing member is fixed so as to be in sliding contact with the inner peripheral surface of the fixing film while being urged toward the nip portion side by a spring. As a result, the pressure member is pressed against the pressure roller via the pressure belt to form the nip portion. Then, the toner image on the recording medium conveyed toward the nip portion receives heat and pressure at the nip portion and is fixed on the recording medium.

  An advantage of the film-type fixing device is that the warm-up time is shortened by reducing the heat capacity of the fixing member. However, in the fixing device using the halogen heater as the heating source as described in Patent Document 3, the amount of heat from the heating source flows into the pressure member other than the fixing film, so that the fixing film is heated. The efficiency will decrease. Therefore, Patent Document 4 proposes a technique of suppressing the heat inflow to the pressure member by providing a metal reflection plate between the halogen heater and the pressure member.

JP-A-63-313182 JP-A-2-157878 JP, 2010-032973, A U.S. Patent Application Publication No. 2015/0030362

  However, during continuous paper feeding, the temperature of the metal reflection plate of Patent Document 4 gradually rises, and the heat thereof flows into the pressing member. At present, several% of the electric power required to heat the fixing film during continuous paper feeding is used for other than the fixing film such as the pressing member.

  An object of the present invention is to solve the above problems, and in a fixing device using a halogen heater as a heat source, suppress the heat inflow to members other than the fixing film during warm-up and during continuous paper feeding. By doing so, it is possible to improve the heating efficiency during warm-up and during continuous paper feeding.

In order to achieve the above object, the fixing device according to the present invention,
Heat source,
A fixing film arranged so that it can be heated from a heat source,
A reflector that reflects the heat from the heat source to the fixing film,
A pressure roller that applies pressure from the outside of the fixing film,
A pressure member for forming a fixing nip between the fixing film and the pressure roller,
A sliding member that slides on the inner surface of the fixing film,
An intermediate member arranged between the reflector and the sliding member and the pressure member,
A holding portion installed on the intermediate member to hold the reflector,
In the fixing device having
The holding portion is installed at both ends in the longitudinal direction outside the paper passing area,
The reflection plate is joined to the intermediate member outside the paper passing area by the holding portion.

  According to the fixing device of the present invention, by improving the heating efficiency from the halogen heater that transmits to the fixing film with a simple structure, the warm-up time of the fixing device is shortened and the power consumption during continuous paper feeding is reduced. can do.

FIG. 3 is a schematic diagram of an image forming apparatus in this embodiment. FIG. 3 is a schematic diagram of a fixing device in this embodiment. FIG. 4 is a longitudinal plan view of the fixing device in this embodiment. It is the figure which showed the shape of the intermediate member in a present Example. FIG. 3 is a schematic diagram of a sheet passing area of the fixing device in this embodiment. It is explanatory drawing of the effect in a present Example.

  Next, specific examples (examples) of the embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.

(Fixing device)
FIG. 1 is a cross-sectional view of a color electrophotographic printer, which is an example of the image forming apparatus according to the present exemplary embodiment, and is a cross-sectional view taken along a sheet conveying direction. In this embodiment, the color electrophotographic printer is simply referred to as "printer".

  The printer shown in FIG. 1 includes an image forming unit 10 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum 11 is precharged by the charger 12. After that, a latent image is formed on the photosensitive drum 11 by the laser scanner 13. The latent image becomes a toner image by the developing device 14. The toner image on the photosensitive drum 11 is sequentially transferred by the primary transfer blade 17 onto an intermediate transfer belt 31, which is an image carrier. After the transfer, the toner remaining on the photosensitive drum 11 is removed by the cleaner 15. As a result, the surface of the photosensitive drum 11 is cleaned and prepared for the next image formation.

  On the other hand, the sheets P are sent out one by one from the paper feed cassette 20 or the multi-paper feed tray 25 and sent to the registration roller pair 23. The pair of registration rollers 23 temporarily receives the sheet P, and if the sheet is skewed, straightens it. Then, the registration roller pair 23 sends the sheet between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The color toner image on the intermediate transfer belt is transferred to the sheet P by a transfer member such as a secondary transfer roller 35. After that, the toner image on the sheet is fixed on the sheet by being heated and pressed by the fixing device 40.

  Next, the fixing device used in this embodiment will be described. FIG. 2 uses a belt heating type heating device (tensionless type) as shown in the schematic configuration diagram of the fixing device 40. Reference numeral 43 denotes a halogen heater (hereinafter referred to as a heater) as a heating body, and both ends thereof are fixed to the side plates of the fixing device 40. The radiant heat of the heater 43, the output of which is controlled by the power supply unit of the apparatus body, is reflected by the reflection plate 42 to reach the fixing film 41, and the fixing film 41 is heated.

  Reference numeral 41 denotes a cylindrical (endless) heat-resistant fixing film as a heating member for transmitting heat, which is loosely fitted onto the supporting member including the heater 43. The fixing film 41 in this embodiment is a fixing film having a four-layer composite structure including a surface layer, an elastic layer, a base layer, and an inner coat layer.

  The release layer may be made of a fluororesin material having a thickness of 100 μm or less, preferably 20 to 70 μm. For example, as the fluororesin layer, for example, PTFE, FEP, PFA, etc. may be mentioned. In this example, a PFA tube having a thickness of 30 μm was used. For the elastic layer, a rubber material having a thickness of 1000 μm or less, preferably 500 μm or less can be used in order to reduce the heat capacity and improve the quick start property. Examples thereof include silicone rubber and fluororubber. A silicone rubber having a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m · K and a thickness of 300 μm was used. Similarly to the elastic layer, the base metal layer may be made of a heat-resistant material having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more in order to improve the quick start property. For example, a metal film such as SUS or nickel can be used. In this example, a cylindrical nickel metal film having a thickness of 30 μm and a diameter of 25 mm was used. Since the inner coat layer is in contact with the pressure member, a heat resistant resin layer, ceramics, metal or the like can be used. For example, polyimide, polyimide amide, PEEK, polytetrafluoroethylene resin (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin ( Engineering plastics such as PFA) and diamond-like carbon (DLC) are listed, and the inner surface of the inner surface coating layer is coated with a black paint or a coating that promotes heat absorption.

  Reference numeral 44 denotes a heat resistant elastic pressure roller as a pressure member, which is made of a metal core made of a metal material (for example, aluminum or SUS), a heat resistant rubber such as silicone rubber or fluororubber, or a foam of silicone rubber. The core layer is composed of an elastic layer, and both ends of the cored bar are rotatably supported by bearings. The fixing film 41 and the heater 43 are arranged above the pressure roller 44 in parallel to the pressure roller 44 with respect to the heater 43 side, and are pressed by a pressing member (not shown). The lower surface of the heater 43 and the upper surface of the pressure roller 44 are pressed against each other against the elasticity of the roller elastic layer to form a fixing nip N having a predetermined width as a heating portion.

  The pressure roller 44 is rotationally driven in the counterclockwise direction indicated by an arrow at a predetermined rotational peripheral speed by a driving unit (not shown). Due to the pressure contact frictional force between the pressure roller 44 and the fixing film 41 in the fixing nip N due to the rotational driving of the pressure roller 44, the rotating force acts on the cylindrical fixing film 41, and the fixing film 41 presses the fixing member 46. While being in close contact with the downward surface of the and sliding, it is driven and rotated in the clockwise direction of the arrow. The support member is also a rotation guide member for the cylindrical fixing film 41. Reference numeral 46 denotes a pressure member, which is in contact with the pressure roller to form a nip portion.

  The pressure roller 44 is rotatably driven, the cylindrical fixing film 41 is driven to rotate accordingly, and the heater 43 is energized to raise the temperature of the fixing film 41 to a predetermined temperature and the temperature is controlled. At the fixing nip N, the recording material P carrying the unfixed toner image T is introduced between the fixing film 41 in the fixing nip N and the pressure roller 44, and the toner image carrying side surface of the recording material P is fixed in the fixing nip portion N. The fixing nip N is sandwiched and conveyed together with the fixing film 41 in close contact with the outer surface of the fixing film 41. In the sandwiching and conveying process, the recording material P is heated by the heat of the fixing film 41 heated by the heater 43, and the unfixed toner image T on the recording material P is heated and pressed on the recording material P to be fused and fixed. . The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 41 by curvature and is discharged and conveyed.

  Here, the pressing member 46 is fixed so as to be in sliding contact with the inner peripheral surface of the fixing film 41. Then, the pressure member 46 is pressed against the pressure roller 44 via the fixing film 41 to form the nip N in which the recording medium P is conveyed. With reference to FIG. 3, the pressure member 46 is fixedly supported by the side plates 43 of the fixing device 20 at both widthwise ends thereof. The reflection plate 42 is provided on the pressure members 45a and 45b, and its longitudinal length is 330 mm, which is the same as that of the pressure roller 44. The reflection plate 42 is fixedly supported by a flange 49, and a constant pressurizing force is applied to the flange 49 by a structure (not shown) so that pressure is applied to the entire length of the fixing film 41. In this embodiment, each flange 49 is provided with 160N.

  The relationship between the lengths of the respective members in the fixing device 40 in the longitudinal direction is as shown in FIG. 3, and in the fixing device of the present embodiment, the length of the fixing film 41 in the longitudinal direction is 340 mm, and the reflecting plate 42 and the pressure member are applied. The roller 44 has a longitudinal length of 330 mm. The pressure roller 44 has both ends of a metal shaft rotatably supported by bearings fixed to the frame of the fixing device 40. The length of the metal member 47, the pressing member 46, and the pressing member 45 in the longitudinal direction is 360 mm.

(Pressure member)
First, the details of the pressing member 46 in the configuration of this embodiment will be described.

  The pressurizing members are provided on the upper part of the pressurizing members 45 (45a, 45b) for applying the pressurizing force applied to the flange 49 to the entire length of the fixing film by a constitution (not shown). A reflecting plate 42, an intermediate member 47 provided under the pressure member, and a heat transfer member 48 provided under the intermediate member and connected to the outer peripheral portion of the reflecting plate 42. There is.

  The heat transfer member 48 is a metal material having a high thermal conductivity (for example, aluminum, copper, or an alloy thereof), and slides on the inner peripheral surface of the fixing film 41 to transfer the heat from the reflection plate 42 to the fixing nip N. It plays a role of assisting heating of the fixing film 41.

  The intermediate member 47 is arranged between the heat transfer member 48 and the pressure member 45, and prevents heat transfer from the heat transfer member 48 to the pressure member 45. Therefore, the intermediate member 47 is made of a material having low thermal conductivity and heat resistance, for example, a material containing heat resistant resin or ceramic, PEEK, liquid crystal polymer.

  The reflection plate 42 is provided on the surface of the heat transfer member 48 so as to face the heater 43, and is made of a material having a high reflectance such as silver. At this time, the radiation from the heater 43 is reflected to the inner surface of the fixing film 41 by the reflecting plate.

  Here, it is preferable that the reflection plate 42 is not in contact with the pressing member 45.

  The pressure member 45 is composed of a first pressure member 45a and a second pressure member 45b. The first and second pressure members have a U-shape, and the openings of the first pressure member and the second pressure member are connected in a manner intersecting each other. The pressing member 45 is a metal material having high strength, and is made of, for example, SUS or carbon steel, and is bent and deformed when the pressing force applied to the flange 49 is applied to the entire length of the fixing film. A structure (for example, I shape, H shape) having a high second moment of area that does not occur may be provided.

  As shown in FIG. 4, the holding portion 471 is provided between the outside of the sheet passing area L in the longitudinal direction of 297 mm and the longitudinal length of the reflecting plate 42 in the longitudinal direction of 330 mm so as to have a U-shape from the intermediate member 47. There is. The positions of the reflection plate 42, the intermediate member 47, and the pressing member 45 are determined by the holding portion 471 contacting between the reflection plate 42 and the pressing member 45 outside the paper passing area L. The reason why the holding portion 471 is provided outside the paper passing area L is that when there are areas where the following effects are exhibited and areas where the following effects are not exhibited in the paper passing area longitudinal direction, the fixing nip and the fixing film are provided in the longitudinal direction. This is because temperature unevenness may occur, which may cause image defects. In the fixing device of this embodiment, the length of the holding member 471 in the longitudinal direction is 10 mm and the thickness is 1 mm.

  FIG. 5 shows a cross section of the paper passing area L in this embodiment. As shown in FIG. 5, in the paper passing area L, an air layer 472 is formed between the reflection plate 42 and the pressing member 45. The thermal conductivity of the air layer 472 is 0.03 W / m · K, which is more adiabatic than the thermal conductivity of 0.4 W / m · K of the liquid crystal polymer, which is an example of the material of the intermediate member 47.

  Next, the effect obtained by the configuration of this embodiment will be described.

  Since the reflection plate 42 used in the fixing device of this embodiment has a reflectance of about 90%, the radiant heat from the heater 43 is gradually transmitted to the reflection plate 42 so that the surface temperature of the fixing film 41 is 170 ° C. During continuous paper feeding, the temperature rises to about 160 ° C. and the heat is transmitted to the pressing member 45. Since the pressure member 45 is a high heat capacity material, when heat flows into the pressure member 45, the electric power supplied to the heater 43 to heat the fixing film 41 is used to raise the temperature of the pressure member 45. Will be done. Therefore, as in the present embodiment, an air layer 472 having a smaller thermal conductivity than the intermediate member 47 in the paper passing area is provided between the pressure member and the reflection plate, so that the pressure member 45 is heated when the reflection plate 42 is heated. It is possible to suppress heat inflow to the. As a result, the heating efficiency of the fixing film 41 by the heater 43 is improved, so that the warm-up time can be shortened and the power consumption during continuous sheet feeding can be reduced.

[Effects of this embodiment]
(Warm-up experiment)
The effect of shortening the warm-up time in this embodiment is shown below. In this experiment, the time from the start of warm-up of the fixing device until the surface temperature of the fixing film reaches 170 ° C. at which paper can pass is measured. The experimental conditions were an input power of 1000 W, a sheet passing speed of 246 mm / sec, and an environment of 23 ° C.-50%. As a verification experiment, the warm-up time was compared using a fixing device having an air layer 472 provided between the pressure member 45 and the reflection plate 42 and a conventional fixing device. The result is shown in FIG.

  FIG. 6 shows the relationship between the surface temperature of the fixing film and the temperature of the reflecting plate with respect to the elapsed time from the start of warm-up in this embodiment and the conventional example.

  As shown in FIG. 6, the warm-up completion time was 14.8 seconds in the conventional example, and the warm-up completion time was 14.0 seconds in this embodiment. Therefore, the warm-up time could be shortened by 0.8 seconds by the present example under the condition that the input powers are the same.

  This suppresses the temperature drop of the reflection plate 42 by suppressing the amount of heat transferred from the reflection plate 42 to the intermediate member 47 and the pressing member 45 according to the present embodiment, and the electric power supplied to the heater 43 raises the fixing film 41. It was shown that it was used efficiently at high temperature, and the effect of this example could be verified.

(Continuous paper feed experiment)
The power reduction effect during continuous paper feeding in this embodiment is shown below. In this experiment, the fixing device was rotated at a paper feeding speed of 246 mm / sec so that the electric power control for maintaining the surface temperature of the fixing film at 170 ° C. was operated, and 10 sheets of plain paper having a basis weight of 105 g were continuously fed at 60 ppm. The power required when doing was measured. As a verification experiment, the required power was compared using a fixing device having an air layer 472 provided between the pressure member 45 and the reflection plate 42 and a conventional fixing device. The results are shown in Table 1.

  Table 1 shows the results of measuring the required power when continuous paper is passed for the conventional example and the present example.

In the conventional example, the required power was 916 W, and in the present example, the required power was 864 W. Therefore, according to the present embodiment, the power required during continuous paper feeding could be reduced by 52W.

  This suppresses the temperature drop of the reflection plate 42 by suppressing the amount of heat transferred from the reflection plate 42 to the intermediate member 47 and the pressing member 45 according to the present embodiment, and the electric power supplied to the heater 43 causes the temperature of the fixing film 41 to rise. Thus, the effect of this example could be verified.

10 image forming unit, 11 photosensitive drum, 12 charger, 13 laser scanner,
14 developing device, 15 cleaner, 17 primary transfer blade, 20 paper feed cassette,
25 multi paper feed tray, 23 registration roller pair, 31 intermediate transfer belt,
35 secondary transfer roller, 40 fixing device, 41 fixing film, 42 reflecting plate,
43 heating body, 44 pressure roller, 45 pressure member, 47 intermediate member,
471 holding part, 472 air layer, 48 heat transfer member, 49 flange,
P sheet, T toner, L paper passing area

Claims (1)

Heat source,
A fixing film arranged so that it can be heated from a heat source,
A reflector that reflects the heat from the heat source to the fixing film,
A pressure roller that applies pressure from the outside of the fixing film,
A pressure member for forming a fixing nip between the fixing film and the pressure roller,
A heat transfer member that slides on the inner surface of the fixing film;
An intermediate member arranged between the reflector and the heat transfer member and the pressure member,
A holding portion installed on the intermediate member to hold the reflector,
In the fixing device having
The holding portion is installed outside the maximum paper passing width,
The fixing device is characterized in that the reflecting plate is joined to the intermediate member outside the maximum sheet passing width by the holding portion.