JP2009258203A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a user-friendly fixing device which prevents an excessive temperature rise in a paper non-passage area without increasing the size of the fixing device while securing satisfactory energy-saving performance, and to provide an image forming apparatus. <P>SOLUTION: The fixing device includes: a heater lamp 52 having a reflecting plate 53 over a first width perpendicular to a heating belt 39 in the sheet passing direction, the reflecting plate 53 being configured to emit light only within a second width in the sheet passing direction; a light shield plate 54 having an opening through which light from the heater lamp 52 passes while preventing the light from passing through the other part; and a motor 57 for rotating the light shield plate 54. The opening is formed such that the opening width in a direction perpendicular to the sheet passing direction is within the first width and different according to the position in the sheet passing direction. The motor 57 moves the light shield plate 54 so that one area of the opening coincides with the position where light is emitted to the heating belt 39 from the heater lamp 52. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer, and a fixing device used therefor. More specifically, the present invention relates to an image forming apparatus capable of printing on a plurality of types of paper having different paper widths and a fixing device used therefor.

  Conventional fixing devices through which various sizes of paper are passed have the following problems. In other words, in the width direction (the direction perpendicular to the paper passing direction), the part where the paper is actually passed takes heat away from the paper and the temperature drops, but the part where the paper is not passed is deprived of heat. There is no so much temperature drop. For this reason, when relatively small-sized sheets are continuously passed, a temperature difference occurs between the sheet passing area and the non-sheet passing area. If the heating of the entire fixing range is continued in order to raise the temperature of the paper passing area to an appropriate temperature from that state, the temperature of the non-paper passing area may be overheated.

  If the fixing operation is performed at a location where the temperature is excessively high, a state called a high temperature offset due to excessive melting of the toner results in a deterioration in image quality. In addition, if the overheated state continues for a long time, the heat may cause damage to peripheral members. In order to solve the above problems, for example, a fixing device that moves a cylindrical reflecting mirror covering the end of the halogen heater in the longitudinal direction of the fixing roller has been proposed (<Example 2 of Patent Document 1). >, <Example 3>). According to the technique of this document, when a small-sized recording material is continuously conveyed, the non-sheet passing regions at both ends of the halogen heater are covered with a reflecting mirror. As a result, heat is not applied to the portion of the fixing roller corresponding to the range covered with the reflecting mirror, and it is said that excessive temperature rise in the non-sheet passing region is prevented.

In recent years, in order to improve energy saving even in high-speed printers, it is desired to reduce the energy consumption by lowering the fixing unit temperature during standby. In order not to increase the user's waiting time even if the temperature during standby is lowered, it is necessary to reduce the heat capacity of the fixing device. As one of the methods, there has been proposed a fixing device in which a fixing nip is constituted by a fixing film having a low heat capacity, and a light beam emitted from a halogen lamp is irradiated to the fixing film in the fixing nip portion (see, for example, Patent Document 2). ).
Japanese Patent Laid-Open No. 5-341685 (paragraphs [0130] to [0137]) JP-A-8-146996

  However, in the apparatus described in Patent Document 1, since the reflecting mirror is moved in the longitudinal direction of the fixing roller, the end portion thereof may be protruded outside the roller length. Therefore, a certain amount of space is required further outside in the longitudinal direction of the fixing roller. Therefore, there is a problem that the fixing device is increased in size.

  Further, in the apparatus described in Patent Document 2 described above, if high-speed printing of small-size paper is continuously performed, there is a risk that the temperature will rise particularly rapidly because of the low heat capacity in the non-sheet passing area. Therefore, it is necessary to frequently control the temperature in order to prevent the low heat capacity member such as the fixing film from being damaged. This contributes to an increase in the waiting time of the user, and thus there is a possibility that the usability is deteriorated.

  The present invention has been made to solve the problems of the conventional fixing device described above. That is, an object of the present invention is to provide a fixing device and an image forming apparatus that can prevent an excessive temperature rise in the non-sheet-passing area without causing an increase in the size of the fixing device, and that are easy to use while ensuring good energy saving. It is in.

  In order to solve this problem, a fixing device according to the present invention has a pair of fixing members, at least one of which rotates, and a toner image carrying sheet is passed between the nips of the pair of fixing members. A fixing device for fixing the toner image on the sheet, wherein the fixing device is within a second width range in the sheet passing direction over a first width in a direction orthogonal to the sheet passing direction with respect to one of the pair of fixing members. As long as a light irradiating member that irradiates light and an opening that allows light from the light irradiating member to pass through are formed, the light shielding member that does not allow light to pass through the portion other than the opening, and the light shielding member to move in the sheet passing direction The opening portion has an opening width in a direction perpendicular to the sheet passing direction within the first width range and varies depending on the position in the sheet passing direction. Member, one portion of the opening, so as to match the position where light is irradiated from the light irradiation member in one of the pair of fixing members, and moves the light shielding member.

  According to the fixing device of the present invention, one of the pair of fixing members is within the range of the first width in the direction orthogonal to the sheet passing direction and the second width in the sheet passing direction by the light irradiation member. , Irradiated with light. Furthermore, since the light from the light irradiation member is blocked by a portion other than the opening of the light blocking member, one of the pair of fixing members is heated within a range corresponding to the opening. The opening width of the opening of the light shielding member varies depending on the position in the sheet passing direction within the range of the first width, and the light shielding member is moved by the moving member. As a result, one position of the opening coincides with the position where light is irradiated from the light irradiation member to one of the pair of fixing members, and thus the light having the opening width at that position is irradiated. Since this moving direction is the sheet passing direction, there is no risk of increasing the size of the apparatus, and overheating can be easily prevented. As a result, an excessive temperature rise in the non-sheet passing region can be prevented without causing an increase in the size of the fixing device, and the fixing device is easy to use while ensuring good energy saving.

  Here, the movement by the moving member may be rotational movement or linear movement. When this movement is a rotational movement, the direction of movement of the opening due to the rotation is the sheet passing direction, and is not moved in a direction intersecting the sheet passing direction. In the case where only one of the pair of fixing members is rotated, it is preferable that the member irradiated with light by the light irradiation member is the one rotated.

Further, in the present invention, the opening is formed with a step having a different opening width in a direction orthogonal to the sheet passing direction, and the width of the step in the sheet passing direction is not less than the second width. desirable.
If this is the case, if the light blocking member is stopped so that the light irradiation range from the light irradiation member is located within the range of the step, the range of light irradiated to one of the pair of fixing members is: The opening width of the step in the direction orthogonal to the sheet passing direction is within the range of the second width in the sheet passing direction. That is, the light irradiation range in the direction orthogonal to the sheet passing direction can be adjusted by the opening width of the step.

Furthermore, in the present invention, it is desirable that the light shielding member has a cylindrical shape with an inner surface having a mirror surface, and has tapered surfaces that gradually increase in diameter from the outside toward the inside at both ends in the first width direction.
If it is such, a light shielding member will reflect the light received in the both ends of the 1st width direction toward inner side. Since the opening is provided on the inner side, it is possible to irradiate one of the pair of fixing members with the reflected light. Therefore, the light by the light irradiation member can be used without waste.

Further, in the present invention, it is desirable that the position where light is irradiated by the light irradiation member is the back side of one nip of the pair of fixing members.
If it is such, the position near the nip of the fixing member can be heated. Therefore, an efficient fixing device can be obtained.

Furthermore, the present invention has a control unit that controls the movement of the light shielding member by the moving member, and the control unit has a position having an opening width corresponding to the width of the passing sheet in one of the pair of fixing members. It is desirable that the light shielding member is moved so as to coincide with the position where the light is irradiated.
In such a case, the range in which light is applied to one of the pair of fixing members can be set as the range of the opening width corresponding to the width of the passing sheet. That is, one of the pair of fixing members is heated with the width of the passing sheet. Therefore, it is possible to prevent light from being applied to the non-sheet passing area, and it is easy to prevent overheating.

  The present invention also includes an image forming unit that forms a toner image on a sheet, and a pair of fixing members that rotate at least one, and the sheet that carries the toner image formed by the image forming unit is inserted into a nip between the pair of fixing members. An image forming apparatus having a fixing device that fixes a toner image on a sheet by passing between the fixing member and the fixing device in a direction perpendicular to the sheet passing direction with respect to one of the pair of fixing members. A light irradiating member that irradiates light only within a second width range in the sheet passing direction and an opening that allows light from the light irradiating member to pass through are formed over a width of 1, and a portion other than the opening Has a light blocking member that does not allow light to pass through and a moving member that moves the light blocking member in the sheet passing direction, and the opening has an opening width in a direction perpendicular to the sheet passing direction within the range of the first width. In The moving member has a light shielding member so that one position of the opening coincides with the position where light is irradiated from the light irradiation member to one of the pair of fixing members. It extends to an image forming apparatus that moves the image.

  According to the fixing device and the image forming apparatus of the present invention, it is possible to prevent an excessive temperature rise in the non-sheet passing area without causing an increase in size of the fixing device, and it is easy to use while ensuring good energy saving. .

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a copying machine, a printer, a facsimile machine, or an electrophotographic color printer having a combination of these functions.

  The color printer 1 of this embodiment is a so-called tandem color printer, as shown in FIG. The color printer 1 of this embodiment has an endless intermediate transfer belt 11 in the middle of FIG. The intermediate transfer belt 11 is wound around two rollers 11A and 11B provided at the left and right ends in FIG. The roller 11B on the right side in the figure is driven to rotate counterclockwise in the figure during image formation. As a result, the intermediate transfer belt 11 and the left roller 11A in the drawing are driven to rotate. The intermediate transfer belt 11 of this embodiment is formed using a conductive material.

  Further, four color image forming portions 10Y, 10M, 10C, and 10K are provided along the intermediate transfer belt 11. The image forming units 10Y, 10M, 10C, and 10K for the respective colors are provided with a charging unit 22, a developing unit 24, a primary transfer unit 25, and a photoconductor cleaner 26 in the clockwise order in FIG. It has been. Among these, the primary transfer portion 25 is provided on the inner peripheral side of the intermediate transfer belt 11. An exposure unit 23 is provided below the image forming units 10Y, 10M, 10C, and 10K for the respective colors. A belt cleaner 27 is provided in contact with the left end of the intermediate transfer belt 11 in the figure.

  Although FIG. 1 shows a roller-shaped charging unit 22, the present invention is not limited to this, and a corona discharge charging charger, a blade-shaped charging member, a brush-shaped charging member, etc. It may be used. In FIG. 1, the photoconductor cleaner 26 is a plate and has one end in contact with the outer peripheral surface of the photoconductor 21. However, the present invention is not limited to this. For example, a fixed brush, a rotating brush, a roller, or a combination of a plurality of members can be used. Further, if a so-called cleaner-less system that collects the untransferred toner on the photosensitive member 21 to the developing unit 24 is employed, the photosensitive member cleaner 26 may be omitted.

  Further, toner accommodating portions 12Y, 12M, 12C, and 12K that accommodate the toners of the respective colors are provided above the intermediate transfer belt 11 in FIG. The toners stored in the toner storage units 12Y, 12M, 12C, and 12K are appropriately supplied into the developing units 24 for the respective colors. A detachable paper feed cassette 13 is mounted on the lower portion of the color printer 1 in FIG. Further, on the right side in the figure, a sheet conveyance path 14 is provided in the vertical direction in the figure. A paper feed roller 15, a secondary transfer unit 16, a fixing unit 17, and a paper discharge roller 18 are provided from the bottom along the paper conveyance path 14. A discharge tray 19 is provided on the upper surface of the color printer 1. Further, a registration roller 28 is provided in the paper transport path 14 for adjusting the paper transport timing.

  The color printer 1 according to this embodiment can switch between a monochrome mode in which a monochrome image is formed using one color toner (for example, black) and a color mode in which a color image is formed using four color toners. is there. An example of image forming operation in the color mode will be briefly described below.

  At the time of image formation, the intermediate transfer belt 11 and the photosensitive members 21 of the respective colors are rotated at predetermined peripheral speeds in the directions indicated by arrows in FIG. First, the outer peripheral surface of the photoreceptor 21 is charged almost uniformly by the charging unit 22. Next, the outer peripheral surface of the charged photoconductor 21 is irradiated with light based on the image data by the exposure unit 23 to form an electrostatic latent image. Next, toner is supplied to the electrostatic latent image by the developing unit 24, and a toner image is formed on the photoreceptor 21. The toner images of the respective colors are transferred onto the intermediate transfer belt 11 by the primary transfer unit 25 and superimposed. The toner remaining on the photoconductor 21 after passing the primary transfer portion 25 is scraped off by the photoconductor cleaner 26.

  The superimposed toner images are carried on the intermediate transfer belt 11 to a place facing the secondary transfer unit 16. On the other hand, the sheets stored in the sheet feeding cassette 13 are pulled out one by one from the uppermost one by the sheet feeding roller 15. Then, the drawn paper is transported along the paper transporting path 14 and transported so as to reach the secondary transfer unit 16 in synchronization with the toner image placed on the intermediate transfer belt 11. In the secondary transfer unit 16, the superimposed toner images are transferred to a sheet.

  The sheet on which the toner image is transferred is further conveyed upward in FIG. 1 and reaches the fixing unit 17. In the fixing unit 17, the toner is fixed to the sheet by being heated and pressurized. As a result, the paper on which the image has been formed is discharged to the paper discharge tray 19 by the paper discharge roller 18. Note that the toner remaining on the intermediate transfer belt 11 even after passing through the secondary transfer region is scraped off by the belt cleaner 27.

  Next, the fixing unit 17 of this embodiment will be described. As shown in FIG. 2, the fixing unit 17 of this embodiment includes a pressure belt unit 31 and a heating belt unit 32. The pressure belt unit 31 includes a pressure side inlet roller 34, a pressure side outlet roller 35, and a pressure belt 36 spanned between them. Further, the heating belt unit 32 includes a heating side inlet roller 37, a heating side outlet roller 38, and a heating belt 39 spanning them.

  The pressure side inlet roller 34 and the heating side inlet roller 37 are in pressure contact with each other, and an inlet roller nip 41 is formed between them. Further, the pressure side outlet roller 35 and the heating side outlet roller 38 are in pressure contact with each other, and an outlet roller nip 42 is formed between them. Further, a free nip portion 43 is formed between the inlet roller nip 41 and the outlet roller nip 42 by contacting the pressure belt 36 and the heating belt 39 with each other. The free nip portion 43 is a nip portion having a smaller pressing force than the entrance roller nip 41 and the exit roller nip 42. The entire entrance roller nip 41, free nip portion 43, and exit roller nip 42 constitute a fixing nip.

  The pressure belt 36 has a heat-resistant layer on the inner peripheral side and a release layer on the outer peripheral side. For example, a polyimide resin having a thickness of 80 μm is suitable as the heat-resistant layer. As the release layer, for example, a fluororesin having a thickness of 30 μm is suitable. Another layer may be provided between the heat-resistant layer and the release layer, and the structure may be three or more.

  The heating belt 39 is an endless belt made of SUS, Ni or the like as a base material. An elastic layer is formed on the outer peripheral side of the substrate, and a release layer is further formed on the outer peripheral side thereof. For example, a silicone rubber having a thickness of 200 μm is suitable as the elastic layer. As the release layer, for example, a 30 μm thick PFA (tetrafluoroethylene / perfluoroalkoxyethylene copolymer) tube or PFA coat is suitable. As the thickness of the substrate, for example, about 35 μm is suitable.

  When the pressure belt 36 and the heating belt 39 are made of such materials, the heating belt 39 having a metal base has higher rigidity. Accordingly, the heating belt 39 presses the pressure belt 36 at the free nip portion 43 between them. Then, flapping during conveyance of the sheet passing through the free nip portion 43 can be suppressed, and occurrence of toner bleeding, sheet wrinkling, and the like can be prevented.

  As shown in FIG. 2, a heating unit 51 is provided on the inner peripheral side of the heating belt 39. The heating unit 51 includes a heater lamp 52, a reflection plate 53, and a light shielding plate 54. The heater lamp 52 is a bar-shaped light irradiation member elongated in the depth direction in the drawing. The heater lamp 52 heats the irradiated object by irradiating light such as infrared rays. In this embodiment, the heater lamp 52 irradiates light in the entire circumferential direction.

  As shown in FIG. 3, the reflection plate 53 is a substantially cylindrical plate member opened at one place, and is disposed coaxially around the heater lamp 52. The openings of the reflecting plate 53 are formed to have the same width over the entire range in the longitudinal direction. The heater lamp 52 is covered and fixed at a portion other than the opening. Note that the color printer 1 of the present embodiment is a central paper passing type. In other words, regardless of the size of the sheet, the sheet is conveyed so that the center in the width direction (direction perpendicular to the sheet passing direction) is positioned at the center in the width direction of the fixing unit 17. For this reason, the members such as the heater lamp 52 and the reflector 53 are all symmetrical in the width direction (longitudinal direction), and are representatively shown by about half of them in FIGS.

  The reflecting plate 53 is made of, for example, an aluminum plate, and reflects the light from the heater lamp 52 well by increasing the smoothness of the inner peripheral surface thereof. Thereby, outside the reflector 53, the light emitted from the heater lamp 52 is irradiated only in the opening direction of the reflector 53. As shown in FIG. 2, since the opening of the reflector 53 is directed toward the free nip portion 43, a large part of the light emitted from the heater lamp 52 is guided toward the free nip portion 43. .

  The combination of the heater lamp 52 and the reflection plate 53 corresponds to a light irradiation member. Further, the longitudinal lengths of the heater lamp 52 and the reflecting plate 53 correspond to the first width, and the size in the circumferential direction of the opening of the reflecting plate 53 corresponds to the second width.

  As shown in FIG. 4 and FIG. 5, the light shielding plate 54 is a substantially cylindrical plate member that is partially opened, and is provided coaxially on the outer peripheral side of the reflection plate 53. However, the opening of the light shielding plate 54 does not have the same width over the entire range in the axial direction. The light shielding plate 54 is formed of, for example, an aluminum plate, and shields light at portions other than the opening.

  Further, as shown in FIG. 6, a motor 57 is connected to the light shielding plate 54 via gears 55 and 56. The motor 57 is provided independently of the rotation driving system of the pressure belt unit 31 and the heating belt unit 32. Furthermore, this embodiment has a control unit 58 that controls rotation / stop of the motor 57. Thereby, the light shielding plate 54 is rotated or stopped along the outer periphery of the reflecting plate 53 under the control of the control unit 58. FIGS. 4 and 5 show a state where the stop position of the light shielding plate 54 is different.

  Next, FIG. 7 shows a shape in which the light shielding plate 54 is opened in the circumferential direction to be planar. The horizontal direction in the figure is arranged in parallel to the longitudinal direction of the heater lamp 52. “All around” in the figure is the circumferential length of the light shielding plate 54 when the light shielding plate 54 is extended to cover the entire circumference. That is, the light shielding plate 54 is formed with an opening having a size of the gap A at least in the circumferential direction over the entire width in the left-right direction in the drawing.

  The size of the gap A in the circumferential direction is greater than or equal to the size of the opening of the reflector 53 in the circumferential direction. Therefore, when the direction of the opening of the reflecting plate 53 is adjusted within the range of the gap A, an opening having an opening width equivalent to the entire length of the heater lamp 52 is obtained as shown in FIG. The opening width at this time can be considered to be equal to that shown in FIG. 7 as “large size”. This is because the outer side is not relevant in this embodiment. In this state, the light from the heater lamp 52 is applied to the heating belt 39 of the free nip portion 43 over the entire length thereof. Therefore, in the free nip portion 43, the heating belt 39 is heated over the entire width direction.

  Furthermore, as shown in FIG. 7, the light shielding plate 54 is formed with a step shape (B, C, D). The height in the vertical direction of each step shape in the figure is formed to be equal to or greater than the circumferential size of the opening of the reflecting plate 53. Therefore, when the light shielding plate 54 is rotated from the state shown in FIG. 4 so that the position of the opening of the reflecting plate 53 is set within the range of the step B, the result is as shown in FIG. In this state, only the range indicated by the opening width in the drawing in the longitudinal direction of the heater lamp 52 is not shielded from light.

  That is, only the light from the heater lamp 52 corresponding to the opening width is applied to the heating belt 39. The opening width in this state is equal to that shown in FIG. 7 as “small size 3”. In this state, only the range of the opening width of the heating belt 39 is heated, so that the heating distribution as shown by the solid line in the lower part of FIG. 7 is obtained.

  Further, when the position of the opening of the reflecting plate 53 is adjusted within the range of the step C by rotating the light shielding plate 54, the opening width is equal to that shown as “small size 2” in FIG. . Further, when the position of the opening of the reflecting plate 53 is set within the range of the step D, the opening width is equal to that indicated as “small size 1” in FIG. In this way, only different ranges can be heated, as indicated by the broken lines in the lower part of FIG.

  Alternatively, the light shielding plate may have an opening whose width is continuously changed instead of the opening whose size is changed in stages. If it is such, the location of arbitrary opening widths can be selected with the rotation angle of a light-shielding plate. Alternatively, a plurality of openings having different opening widths may be arranged in the circumferential direction.

  Moreover, as shown in FIG. 8, it is good also as the light-shielding plate 61 inclined at both ends. That is, the light shielding plate 61 is formed in a tapered shape having a smaller radius toward both ends in a range facing the heater lamp 52 through the opening of the reflecting plate 53. The angle θ with respect to the tapered heater lamp 52 is preferably about 1 to 2 degrees. In this way, the light in the range blocked by the light shielding plate 61 is reflected toward the center as shown by the dashed arrows in the figure. The heating belt 39 is irradiated from the central opening. Therefore, the light in the range blocked by the light shielding plate 61 can also contribute to heating effectively. In the light shielding plate 61 of this shape, it is desirable to use a member having good reflectivity, for example, an aluminum material having high surface smoothness, at least in the range facing the heater lamp 52 on the inner peripheral surface. .

  As described above in detail, according to the color printer of this embodiment, the light emitted from the heater lamp 52 is reflected and collected by the reflecting plate 53 and irradiated to the free nip portion 43. Further, since the light shielding plate 54 is provided, the light irradiated to the non-sheet passing region can be blocked. In addition, since there is no member moved in the longitudinal direction of the heater lamp 52, the apparatus is not increased in size. Therefore, it is possible to prevent an excessive temperature rise in the non-sheet passing region without causing an increase in the size of the fixing device, and the fixing device is easy to use while ensuring good energy saving.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the material of the reflecting plate 53 and the light shielding plate 54 is not limited to this, and any material having appropriate reflectivity, light shielding properties, and heat resistance may be used. Further, the light shielding plate 54 can be the inner peripheral side, and the reflection plate 53 can be disposed on the outer peripheral side. In this case, it is desirable that the inner peripheral surface of the light shielding plate 54 has good reflectivity. Alternatively, in the above embodiment, the light shielding plate 54 is a substantially cylindrical rotating member. For example, the light shielding plate 54 is disposed between the heater lamp 52 and the heating belt 39 as a flat plate member having a plurality of openings having different opening widths. May be. The opening width can be changed by moving in the sheet passing direction along the free nip portion 43 of the heating belt 39.

  Further, in the present embodiment, the heating belt 39 is an oval belt that is stretched between two rollers, but is not limited thereto, and may have three or more rollers. Moreover, the circular thing rotated by one cylindrical roller may be sufficient. The heating unit 51 is not limited to the free nip 43 and may heat the heating belt 39 at other locations. Further, it may be arranged on the outer peripheral side of the heating belt 39. Furthermore, you may have the other heating member which heats the full width other than the heating part 51. FIG. In this case, the light shielding plate can be closed without a gap A.

  Further, the pressure belt unit 31 is not limited to the shape shown in FIG. For example, a belt may be wound around one roller having a larger diameter than the entrance roller and the exit roller. Alternatively, a fixed pad that is pressed against the heating belt 39 in the range of the free nip portion can be substituted.

  The present invention is not limited to the color printer of the above-described form, and can be applied to various image forming apparatuses. For example, the present invention can be applied to a so-called four-cycle type color printer in which four developing devices are arranged around a rotating shaft and these are sequentially opposed to an electrostatic latent image carrier to form a color image. . The present invention can also be applied to a monochrome image forming apparatus having only one developing device.

1 is a schematic configuration diagram illustrating a color printer according to an embodiment. It is a schematic block diagram which shows the fixing | fixed part of this form. It is a perspective view which shows a heater lamp and a reflecting plate. It is a perspective view which shows a heater lamp, a reflecting plate, and a light-shielding plate. It is a perspective view which shows a heater lamp, a reflecting plate, and a light-shielding plate. It is explanatory drawing which shows the structure which rotationally drives a light-shielding plate. It is explanatory drawing which shows the relationship between the shape of a light-shielding plate, and temperature distribution. It is explanatory drawing which shows the light shielding plate of another shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color printer 17 Fixing part 31 Pressure belt unit 32 Heating belt unit 39 Heating belt 52 Heater lamp 53 Reflecting plate 54 Light shielding plate 57 Motor 58 Control part

Claims (6)

In a fixing device that has a pair of fixing members rotating at least one and passing a sheet carrying a toner image between the nips of the pair of fixing members to fix the toner image on the sheet,
A light irradiating member that irradiates light to one of the pair of fixing members over a first width in a direction orthogonal to the sheet passing direction and within a second width in the sheet passing direction;
An opening that allows light from the light irradiating member to pass therethrough, and a light shielding member that does not allow light to pass through a portion other than the opening;
A moving member that moves the light shielding member in the sheet passing direction;
The opening has an opening width in a direction orthogonal to the sheet passing direction within the range of the first width, and varies depending on the position in the sheet passing direction,
The moving member moves the light shielding member so that one position of the opening coincides with a position where light is irradiated from the light irradiation member to one of the pair of fixing members. A fixing device. The fixing device according to claim 1,
The opening is formed with a step having a different opening width in a direction orthogonal to the sheet passing direction,
The fixing device according to claim 1, wherein a width of the step in the sheet passing direction is equal to or greater than the second width. The fixing device according to claim 1 or 2,
The shading member is
The inner surface is a cylindrical shape with a mirror surface.
A fixing device having tapered surfaces having gradually increasing diameters from outside to inside at both ends in the first width direction. In the fixing device according to any one of claims 1 to 3,
The fixing device characterized in that a position irradiated with light by the light irradiation member is a back side of the nip of one of a pair of fixing members. In the fixing device according to any one of claims 1 to 4,
A control unit that controls movement of the light shielding member by the moving member;
The control unit moves the light shielding member so that a position of the opening width corresponding to the width of the sheet passing therethrough coincides with a position where light is irradiated to one of the pair of fixing members. A fixing device characterized by that. An image forming unit that forms a toner image on a sheet and a pair of fixing members that rotate at least one of the sheets, and a sheet carrying the toner image formed by the image forming unit is passed between the nips of the pair of fixing members In an image forming apparatus having a fixing device for fixing a toner image on a sheet,
The fixing device includes:
A light irradiating member that irradiates light to one of the pair of fixing members over a first width in a direction orthogonal to the sheet passing direction and within a second width in the sheet passing direction;
An opening that allows light from the light irradiating member to pass therethrough, and a light shielding member that does not allow light to pass through a portion other than the opening;
A moving member that moves the light shielding member in the sheet passing direction;
The opening has an opening width in a direction orthogonal to the sheet passing direction within the range of the first width, and varies depending on the position in the sheet passing direction,
The moving member moves the light shielding member so that one position of the opening coincides with a position where light is irradiated from the light irradiation member to one of the pair of fixing members. An image forming apparatus.

Images