JP2018087844A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device with a simple configuration that can prevent an excessive increase in temperature of a non-paper feed area of a fixing member and reduce the size of the device.SOLUTION: A fixing device comprises: a rotatable fixing member 22; a heat source 24 that heats the fixing member; an opposing member 23 that is in contact with an outer peripheral surface of the fixing member to form a fixing nip N; and shield members 31 and 32 that are arranged between the fixing member and heat source and shield the fixing member from heat from the heat source. The shield members are formed of a plurality of shield members; at least one of the shield members has a plurality of shield patterns regulating a shield width in the longitudinal direction of the fixing member; the plurality of shield members can be moved in a laminated state; the shield members have different movable areas.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fixing device and an image forming apparatus.

  2. Description of the Related Art Image forming apparatuses such as copiers, printers, facsimiles, and multifunction peripherals thereof are provided with a fixing device that fixes a toner image carried on a recording medium such as paper.

  Generally, a fixing device includes a fixing member heated from a heat source such as a heater, and an opposing member that forms a fixing nip in contact with the fixing member. When an image forming operation is started in the image forming apparatus and a toner image is transferred onto a recording medium (for example, paper), the recording medium is heated between a fixing member and a counter member heated to a predetermined temperature. By passing through the fixing nip, the toner carried on the recording medium is heated and melted to fix the image.

  In the fixing device configured as described above, there is a problem that an excessive temperature rise occurs in a non-sheet passing region of the fixing member.

  On the other hand, a configuration is known in which a shielding member that shields heat from the heat source is provided between the heat source and the fixing member so as to be movable in the circumferential direction of the fixing member (see, for example, Patent Documents 1 and 2). ).

  The apparatus described in Patent Document 1 allows a shielding member having a small shielding part and a large shielding part to be moved between a retracted position and a shielding position, and prevents an excessive temperature rise in a non-sheet passing region of the fixing member.

  However, the apparatus described in Patent Document 1 has a problem that the size of the shielding member in the moving direction is large and a large retreat space for the shielding member is required, and the apparatus cannot be reduced in size. In addition, there is a problem that it takes time to move the shielding member.

  The apparatus described in Patent Document 2 has two shielding members, each of which can be moved independently, and prevents an excessive temperature rise in the non-sheet passing region of the fixing member.

  However, the apparatus described in Patent Document 2 requires a retreat space for two shielding members, and there is a problem that the apparatus cannot be reduced in size. In addition, there is a problem that the configuration for driving the shielding member is complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device having a simple configuration that can prevent overheating of a non-sheet passing region of a fixing member and can reduce the size of the device.

In order to solve the above-described problem, a fixing device according to a first aspect of the present invention includes:
A rotatable fixing member;
A heat source for heating the fixing member;
An opposing member that forms a fixing nip in contact with the outer peripheral surface of the fixing member;
A fixing device that is disposed between the fixing member and the heat source and shields heat from the heat source;
The shielding member is composed of a plurality of shielding members,
At least one shielding member has a plurality of shielding patterns defining a shielding width in the longitudinal direction of the fixing member;
The plurality of shielding members are movable in a stacked state,
The movable region of each shielding member is different.

  According to the present invention, it is possible to provide a fixing device having a simple configuration that can prevent overheating of a non-sheet passing region of a fixing member and can reduce the size of the device.

1 is a configuration diagram schematically illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating a partial cross-sectional view of a configuration of a fixing device according to an exemplary embodiment of the present invention. 1 is a cross-sectional view illustrating a configuration of a fixing device according to an embodiment of the present invention. It is explanatory drawing explaining operation | movement of the 1st shielding member 31 and the 2nd shielding member 32, (a) shows a retracted position, (b) shows a 1st shielding position, (c) is 2nd Indicates the shielding position. It is explanatory drawing explaining operation | movement of the 1st shielding member 31 and the 2nd shielding member 32, (a) shows a retracted position, (b) shows a 1st shielding position, (c) is 2nd Indicates the shielding position. FIG. 3 is a block diagram illustrating a fixing device control system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the overall configuration of the image forming apparatus will be described. FIG. 1 is a block diagram schematically showing the configuration of an image forming apparatus according to an embodiment of the present invention.

  A printer 1 as an image forming apparatus includes a box-shaped printer main body 2, and a paper feed cassette 3 for storing paper as a recording medium is accommodated in a lower portion of the printer main body 2. Is provided with a paper discharge tray 4. Here, the recording medium includes, in addition to plain paper, thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is stored below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the discharge tray 4 above the printer main body 2, and an image forming unit 8 is provided below the exposure unit 7. Yes. The image forming unit 8 is rotatably provided with a photosensitive drum 10 as an image carrier. Around the photosensitive drum 10, a charger 11, a developing device 12, a transfer roller 13, and a cleaning device are provided. The apparatus 14 is disposed along the rotation direction of the photosensitive drum 10 (see arrow X in FIG. 1).

  A paper transport path 15 is provided inside the printer main body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 constituted by the photosensitive drum 10 and the transfer roller 13 is provided at a midstream part of the conveyance path 15. A fixing device 18 is provided at the section, and a paper discharge section 19 is provided at the downstream end of the transport path 15. A reverse path 20 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initialization processing such as temperature setting of the fixing device 18 is executed. When image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 10 is charged by the charger 11, the exposure corresponding to the image data is performed on the photosensitive drum 10 by laser light from the exposure device 7 (see the two-dot chain line P in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the developing device 12 develops the electrostatic latent image into a toner image with toner.

  On the other hand, the sheet taken out from the sheet cassette 3 by the sheet feeding unit 16 is conveyed to the transfer unit 17 in synchronization with the above-described image forming operation, and the toner image on the photosensitive drum 10 is transferred to the sheet by the transfer unit 17. Is transferred to. The sheet onto which the toner image has been transferred is conveyed downstream in the conveyance path 15 and enters the fixing device 18 where the toner image is fixed on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 19 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning device 14.

  Next, the configuration of the fixing device will be described. FIG. 2 is a block diagram showing a partial cross-sectional view of the configuration of the fixing device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view showing the configuration of the fixing device according to the embodiment of the present invention. Hereinafter, for convenience of description, the front side of the sheet in FIG. An arrow Y attached to FIG. 2 indicates the sheet conveyance direction.

  As shown in FIGS. 2 and 3, the fixing device 18 includes an upper fixing frame 35, a lower fixing frame 36, a fixing belt 22 as a fixing member housed in upper portions of the fixing upper and lower frames 35, 36, In the pressure roller 23 as a facing member housed in the lower parts of the fixing upper and lower frames 35, 36, the heater 24 as a heat source disposed in the inner diameter side space of the fixing belt 22, and the inner diameter side space of the fixing belt 22 The reflecting member 25 disposed below the heater 24, the pressing member 26 disposed at the lower end of the inner diameter side space of the fixing belt 22, and the reflecting member 25 and the pressing member 26 in the inner diameter side space of the fixing belt 22. And a support member 27 disposed between the two. Further, the fixing device 18 includes a drive mechanism 28 disposed on the rear side of the fixing upper and lower frames 35 and 36. The fixing device 18 includes a first shielding member 31 as a shielding member, a second shielding member 32 as a shielding member, PI sensors 30a, 30b, and 30c, a first shielding member 31, and a second shielding member 32. And a bracket 37 that holds a support shaft 65 that supports the bracket.

  The fixing upper and lower frames 35 and 36 are fixed to the rear side plate 43 and the front side plate with screws or the like. The rear side plate 43 and the front side plate constitute a structure of the fixing device 18. A bracket 37 is fixed to the rear side plate 43 and the front side plate with screws or the like. A fixing belt holding member 38 that rotatably holds the fixing belt 22 is fixed to the bracket 37 with screws or the like via the rear side plate 43 and the front side plate. A circular insertion hole 40 is provided in the rear side plate 43 and the front side plate.

  As shown in FIGS. 2 and 3, the fixing belt 22 has a cylindrical shape that is long in the front-rear direction. The fixing belt 22 has flexibility and is endless in the circumferential direction. The fixing belt 22 includes, for example, a base material layer, an elastic layer provided around the base material layer, and a release layer that covers the elastic layer. The base material layer of the fixing belt 22 is formed of a metal such as SUS, for example. The base material layer of the fixing belt 22 may be formed of a resin such as PI (polyimide). The elastic layer of the fixing belt 22 is made of, for example, silicone rubber. The release layer of the fixing belt 22 is formed of, for example, a PFA tube. In each figure, each layer (base material layer, elastic layer, release layer) of the fixing belt 22 is displayed without being particularly distinguished.

  The fixing belt 22 is rotatably supported by the fixing belt holding member 38. As shown in FIG. 3, the fixing belt 22 is provided to be rotatable around a rotation center A of the fixing belt 22. That is, in the present embodiment, the rotation axis direction of the fixing belt 22 is the front-rear direction.

  As shown in FIG. 5, the fixing belt 22 includes a central region 45 (first region) and end regions 46 (second regions) provided outside the central region 45 (on both sides of the central region 45). ing. The central area 45 is an area through which a first size sheet (for example, A4 size sheet) passes. A first thermistor 47 (see FIG. 6) is disposed in the central region 45. The first thermistor 47 is, for example, a non-contact type temperature sensor. The edge area 46 is an area through which a second size sheet (for example, A3 size sheet) having a width larger than that of the first size sheet does not pass through the first size sheet. A second thermistor 48 (see FIGS. 2 and 6) is disposed in the end region 46. The second thermistor 48 is, for example, a contact type temperature sensor.

  As shown in FIG. 2, the pressure roller 23 has a long cylindrical shape in the front-rear direction. A third thermistor 49 (see FIG. 6) is disposed on the pressure roller 23. The third thermistor is, for example, a contact type temperature sensor.

  The pressure roller 23 includes, for example, a cylindrical core member 50, an elastic layer 51 provided around the core member 50, and a release layer that covers the elastic layer 51. The core material 50 of the pressure roller 23 is made of metal such as iron, for example. The elastic layer 51 of the pressure roller 23 is made of, for example, silicone rubber. The release layer of the pressure roller 23 is formed by, for example, a PFA tube.

  The pressure roller 23 is disposed on the lower side (outer diameter side) of the fixing belt 22. The pressure roller 23 is in pressure contact with the fixing belt 22, and a fixing nip N is formed between the fixing belt 22 and the pressure roller 23. The pressure roller 23 is rotatably supported by the lower fixing frame 36. The pressure roller 23 is connected to a driving unit 52 (see FIG. 6) disposed on the rear side of the fixing upper and lower frames 35 and 36. The drive unit 52 is configured by, for example, a motor.

  The heater 24 is composed of, for example, a halogen heater. The heater 24 is attached to the bracket 37 as shown in FIGS. The center B of the heater 24 is disposed slightly above the rotation center A of the fixing belt 22 (on the side away from the pressure roller 23). Therefore, the central region upper end portion 45 a (see FIG. 3) of the central region 45 of the fixing belt 22 is closest to the heater 24 in the central region 45 of the fixing belt 22. Similarly, the end region upper end portion 46 a (see FIG. 3) of the end region 46 of the fixing belt 22 is closest to the heater 24 in the end region 46 of the fixing belt 22. The central region upper end 45a of the central region 45 of the fixing belt 22 and the end region upper end 46a of the end region 46 are located on the opposite side of the fixing nip N across the rotation center A of the fixing belt 22, and are fixed. Opposite the nip N.

  The reflection member 25 has a long shape in the front-rear direction, as shown in FIGS. The reflecting member 25 is made of a metal such as bright aluminum, for example. The reflection member 25 is disposed between the heater 24 and the support member 27 and covers the upper side of the support member 27. The reflecting member 25 includes a reflecting plate portion 53 that forms a groove toward the lower side (the pressure roller 23 side), and a pair of bent portions that are bent outward in the left-right direction from the left and right upper corners of the reflecting plate portion 53. A plate portion 54. The reflecting plate portion 53 has a function of reflecting the radiant heat radiated from the heater 24 toward the inner peripheral surface of the fixing belt 22.

  As shown in FIGS. 2 and 3, the pressing member 26 has a long shape in the front-rear direction. The pressing member 26 is formed of, for example, a heat resistant resin such as LCP (liquid crystal polymer). The lower surface of the pressing member 26 presses the fixing belt 22 downward (pressure roller 23 side). A fitting protrusion 55 is provided on the upper surface of the pressing member 26.

  As shown in FIGS. 2 and 3, the support member 27 has a long shape in the front-rear direction. The support member 27 is formed of sheet metal such as SECC (galvanized steel sheet).

  The support member 27 includes a bottom plate portion 56 and a pair of side plate portions 57 bent toward the upper side (side away from the pressure roller 23) from the left and right end portions of the bottom plate portion 56. The bottom plate portion 56 is provided with a fitting hole 58, and the fitting protrusion 55 of the pressing member 26 is fitted into the fitting hole 58. The lower surface of the bottom plate portion 56 is in contact with the upper surface of the pressing member 26, whereby the support member 27 supports the pressing member 26 from the upper side.

  As shown in FIG. 2, the drive mechanism 28 includes a drive motor 60 and a drive gear train disposed on the right side of the drive motor 60.

  The drive motor 60 is a motor that can rotate forward and reverse, and includes a drive shaft 62. A drive gear 63 is fixed to the drive shaft 62.

  The drive gear train includes a driven gear 64 that meshes with the drive gear 63 of the drive motor 60.

  As shown in FIG. 2, the support shaft 65 is rotatably held by the bracket 37. A driven gear 64 that receives a rotational force from a drive gear 63 that is fixed to the rotation shaft of the drive motor 60 is fixed to the support shaft 65 in order to rotate the support shaft 65. Further, the support shaft 65 is provided with a first shielding member 31 and a second shielding member 32. The first shielding member 31 is rotatably held with respect to the support shaft 65. The 2nd shielding member 32 is fixed to the spindle 65, and the rotational force of the spindle 65 is transmitted directly. The first shielding member 31 and the second shielding member 32 are connected by a spring 66 that is an elastic member. Therefore, the rotational force of the support shaft 65 is directly transmitted to the second shielding member 32 and then transmitted to the first shielding member 31 via the spring 66. That is, the first shielding member 31 operates in conjunction with the second shielding member 32.

  Each of the PI sensors 30a, 30b, and 30c includes a light emitting unit that emits light and a light receiving unit that receives the light emitted from the light emitting unit. The PI sensor 30a is provided on the bracket 37 and detects the presence or absence of the second shielding member 32 at a second shielding position described later. The PI sensor 30b is provided on the bracket 37 and detects the presence or absence of the first shielding member 31 at a first shielding position described later. The PI sensor 30c is provided on the bracket 37 and detects the presence / absence of the first shielding member 31 at a later-described retraction position.

  As shown in FIG. 2, the first shielding member 31 has a shape that is long in the front-rear direction. The first shielding member 31 is curved in an arc shape along the inner peripheral surface of the fixing belt 22.

  As shown in FIG. 5A, the first shielding member 31 includes a main body 81 and a recess 83 as an opening. The main body 81 is provided with an interval from the inner peripheral surface of the fixing belt 22. The concave portion 83 is provided in a shape that is cut out in a rectangular shape at the central portion in the front-rear direction of the main body portion 81 (the central portion in the longitudinal direction of the fixing belt 22). That is, the first shielding member 31 has two shielding patterns in the longitudinal direction of the fixing belt 22. The position in the front-rear direction of the recess 83 overlaps with the position in the front-rear direction of the central region 45 of the fixing belt 22.

  The 2nd shielding member 32 has comprised the shape long in the front-back direction, as shown in FIG. The second shielding member 32 is curved in an arc shape along the inner peripheral surface of the fixing belt 22. The second shielding member 32 is provided on the inner peripheral surface side of the first shielding member 31. The width of the second shielding member 32 in the circumferential direction of the fixing belt 22 is formed larger than the width of the recess 83.

  The first shielding member 31 may be configured by a resin material having heat resistance and low friction, or a member obtained by coating a metal plate with a resin having heat resistance and low friction. Thereby, even if it contacts with the fixing belt 22, it is also possible to reduce a friction coefficient with the fixing belt 22 and to reduce damage.

  Next, a control system for the fixing device 18 will be described. FIG. 6 is a block diagram illustrating a control system of the fixing device.

  As shown in FIG. 6, the fixing device 18 is provided with a control unit 91. The control unit 91 is connected to the storage unit 92. The storage unit 92 stores a reference temperature T of the end region 46 of the fixing belt 22.

  The controller 91 is connected to the first thermistor 47, and the temperature of the central region 45 of the fixing belt 22 detected by the first thermistor 47 is output to the controller 91. The control unit 91 is connected to the second thermistor 48, and the temperature of the end region 46 of the fixing belt 22 detected by the second thermistor 48 is output to the control unit 91. The controller 91 is connected to the third thermistor 49, and the temperature of the pressure roller 23 detected by the third thermistor 49 is output to the controller 91.

  The control unit 91 is connected to the PI sensors 30a, 30b, and 30c, and the detection results of the PI sensors 30a, 30b, and 30c are output to the control unit 91.

  The control unit 91 is connected to the drive motor 60, and the drive motor 60 rotates based on a signal from the control unit 91 to rotate the second shielding member 32 via the drive mechanism 28. . The control unit 91 is connected to the drive unit 52, and the drive unit 52 rotates the pressure roller 23 based on a signal from the control unit 91.

  The control unit 91 is connected to the heater 24, and the heater 24 is energized and generates heat based on a signal from the control unit 91, and radiates heat.

  Next, the operation of the fixing device will be described. In the fixing device 18 configured as described above, when the toner image is fixed on the paper, the driving roller 52 rotates the pressure roller 23. When the pressure roller 23 rotates, the fixing belt 22 in pressure contact with the pressure roller 23 is driven to rotate in the direction opposite to the pressure roller 23. When the fixing belt 22 rotates, the fixing belt 22 slides with respect to the pressing member 26.

  Further, when fixing the toner image on the paper, the heater 24 is operated. When the heater 24 is operated, the heater 24 radiates radiant heat toward the inner peripheral surface of the fixing belt 22, and the fixing belt 22 is heated by the radiant heat. When the sheet passes through the fixing nip N while the fixing belt 22 is heated, the sheet and the toner image are heated and pressurized to fix the toner image on the sheet.

  Next, operations of the first shielding member 31 and the second shielding member 32 will be described. 4A and 4B are explanatory diagrams for explaining the operation of the first shielding member 31 and the second shielding member 32, where FIG. 4A shows the retracted position, FIG. 4B shows the first shielding position, and FIG. Indicates a second shielding position. FIG. 5 is an explanatory diagram for explaining the operation of the first shielding member 31 and the second shielding member 32, where (a) shows the retracted position, (b) shows the first shielding position, and (c). Indicates a second shielding position.

  When the temperature of the end region 46 of the fixing belt 22 does not reach the reference temperature T, as shown in FIGS. 4A and 5A, the first shielding member 31 and the second shielding member 32 are On the right side of the support member 27, the support member 27 is retracted to a retracted position where it is retracted. At the retracted position, the lower end portion of the main body portion 81 of the first shielding member 31 is in a state detected by the PI sensor 30 c provided on the bracket 37.

  When the temperature of the end region 46 of the fixing belt 22 reaches the reference temperature T, a signal is sent to the drive motor 60 and the drive motor 60 starts to rotate. The rotational force of the drive motor 60 is transmitted to the support shaft 65 via the drive gear 63 and the driven gear 64, and the support shaft 65 rotates counterclockwise in FIG. Thereby, the 2nd shielding member 32 and the 1st shielding member 31 connected with the 2nd shielding member 32 and the spring 66 move. When the arm portion of the first shielding member 31 reaches the PI sensor 30b, the drive motor 60 stops, and the first shielding member 31 and the second shielding member 32 are shown in FIGS. 4B and 5B. Thus, it stops at the first shielding position. That is, the first shielding member 31 and the second shielding member 32 move from the retracted position to the first shielding position in a stacked state. The first shielding member 31 is held by the PI sensor 30b so as not to move beyond the first shielding position. In addition, you may provide the stop member which stops the movement of the 1st shielding member 31 separately from PI sensor 30b. At the first shielding position, the second shielding member 32 is stacked (overlapped) at a position other than the recess 83 of the first shielding member 31 and is in a state of being within the shape of the first shielding member 31.

  When the temperature of the central region 45 of the fixing belt 22 reaches the reference temperature T, a signal is sent to the drive motor 60 and the drive motor 60 starts to rotate. The rotational force of the drive motor 60 is transmitted to the support shaft 65 via the drive gear 63 and the driven gear 64, and the support shaft 65 rotates counterclockwise in FIG. Thereby, the 2nd shielding member 32 moves. When the arm portion of the second shielding member 32 reaches the PI sensor 30a, the drive motor 60 stops, and the second shielding member 32 is second shielded as shown in FIGS. 4 (c) and 5 (c). Stop at position. That is, the second shielding member 32 moves from the first shielding position to the second shielding position in a state of being stacked with the first shielding member 31. The second shielding member 32 is held by the PI sensor 30a so as not to move beyond the second shielding position. That is, the movable region is different between the first shielding member 31 and the second shielding member 32. In addition, you may provide the stop member which stops the movement of the 2nd shielding member 32 separately from PI sensor 30a. At the second shielding position, the second shielding member 32 is stacked (overlapped) at the position of the recess 83 of the first shielding member 31.

  In the state where the first shielding member 31 and the second shielding member 32 are in the retracted position, the radiant heat from the heater 24 toward the central region upper end 45a of the central region 45 of the fixing belt 22 is as shown in FIG. It reaches the central region upper end 45a of the central region 45 of the fixing belt 22 without being blocked by the first shielding member 31 and the second shielding member 32. Further, radiant heat from the heater 24 toward the end region upper end 46a of the end region 46 of the fixing belt 22 is also blocked by the first shielding member 31 and the second shielding member 32 as shown in FIG. Without reaching the end region upper end 46 a of the end region 46 of the fixing belt 22.

  Thereby, it is possible to have a shielding pattern for heating the central region 45 and the end region 46 of the fixing belt 22 at the same time.

  When the first shielding member 31 and the second shielding member 32 move from the retracted position to the first shielding position, the radiant heat from the heater 24 toward the central region upper end 45a of the central region 45 of the fixing belt 22 is shown in FIG. As shown by an arrow, the central region upper end 45a of the central region 45 of the fixing belt 22 passes through the recess 83 of the first shielding member 31 and is not blocked by the first shielding member 31 and the second shielding member 32. To reach. On the other hand, the radiant heat from the heater 24 toward the end region upper end 46a of the end region 46 of the fixing belt 22 is blocked by the main body 81 of the first shielding member 31 as shown in FIG. It does not reach the end region upper end 46 a of the end region 46 of the fixing belt 22.

  As a result, it is possible to have a shielding pattern that heats the central region 45 of the fixing belt 22 while preventing the end region 46 of the fixing belt 22 from overheating.

  When the first shielding member 31 and the second shielding member 32 move from the first shielding position to the second shielding position, the radiant heat from the heater 24 toward the central region upper end 45a of the central region 45 of the fixing belt 22 is as shown in FIG. As indicated by an arrow in c), since it is blocked by the second shielding member 32, it does not reach the central region upper end 45 a of the central region 45 of the fixing belt 22. In addition, the radiant heat from the heater 24 toward the end region upper end 46a of the end region 46 of the fixing belt 22 is also shown in FIG. 5C, and the main body 81 and the second shielding member 32 of the first shielding member 31. Therefore, it does not reach the upper end portion of the end region 46 of the fixing belt 22.

  Accordingly, it is possible to have a shielding pattern that simultaneously shields the central region 45 and the end region 46 of the fixing belt 22, and it is possible to suppress overshooting of the fixing belt 22.

  When the thermistors 47, 48, 49 detect that the temperature abnormality has been resolved, the drive motor 60 is driven to rotate in the opposite direction, and the presence of the arm portion of the first shielding member 31 is detected by the PI sensor 30c. The drive motor 60 is stopped, and the first shielding member 31 and the second shielding member 32 are returned to the retracted position.

  Since the first shielding member 31 and the second shielding member 32 are stacked and retracted to the retracted position, the retracting space is small, and the apparatus can be made compact.

  Since the first shielding member 31 and the second shielding member 32 operate in conjunction with each other and a plurality of shielding patterns can be realized by a simple rotation operation, the driving member can be simplified and the cost can be reduced.

  By connecting the first shielding member 31 and the second shielding member 32 with a spring, a plurality of shielding patterns can be realized only by a rotational operation.

  Since the first shielding member 31 has heat resistance and low friction, the coefficient of friction with the fixing belt 22 can be reduced, the first shielding member 31 and the heater 24 can be as close to the fixing belt as possible, and heating efficiency can be improved. Can be improved. Note that the second shielding member may also be configured to have heat resistance and low friction.

  In this embodiment, the case where two shielding members 31 and 32 are used has been described. However, in other different embodiments, three or more shielding members may be used.

  In this embodiment, a case has been described in which a paper that is not the maximum size paper (for example, A4 size paper) is the first size paper. However, in other different embodiments, the maximum size paper is used. A first size paper may be used. In this case, the end region 46 of the fixing belt 22 is a region through which no size paper passes.

  In the present embodiment, the heater 24 is disposed on the inner diameter side of the fixing belt 22, and the first shielding member 31 and the second shielding member 32 rotate along the inner peripheral surface of the fixing belt 22. However, it is not limited to this aspect. In another different embodiment, the heat source such as the heater 24 is disposed on the outer diameter side of the fixing belt 22, and the first shielding member 31 and the second shielding member 32 rotate along the outer peripheral surface of the fixing belt 22. May be.

  Moreover, although the case where the 1st shielding member 31 and the 2nd shielding member 32 rotate was demonstrated in this Embodiment, in another different embodiment, either one of the 1st shielding member 31 and the 2nd shielding member 32 or Both may move linearly.

  In the present embodiment, the case where a halogen heater is used as the heater 24 has been described. However, in another different embodiment, a ceramic heater or the like may be used as the heater 24.

  In this embodiment, the case where the configuration of the present invention is applied to the fixing device 18 that presses the fixing belt 22 downward (on the pressure roller 23 side) with the pressing member 26 has been described. In the different embodiments, the configuration of the present invention may be applied to the fixing device 18 that rotates the fixing belt 22 together with one or a plurality of rollers disposed on the inner diameter side of the fixing belt 22.

  Further, in the present embodiment, the case where the first shielding member 31 and the second shielding member 32 move counterclockwise from the retracted position of the support member 27 on the right side in FIG. 2 has been described. In this embodiment, the first shielding member 31 and the second shielding member 32 may move clockwise from the retracted position on the left side in FIG.

  In the present embodiment, the case where the first shielding member 31 operates in conjunction with the second shielding member 32 has been described. However, in another different embodiment, the second shielding member 32 is the first shielding member. It may operate in conjunction with the member 31.

  In the present embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile, and a multifunction peripheral. It is also possible to apply.

18 Fixing device 22 Fixing belt (an example of a fixing member)
23 Pressure roller (example of counter member)
24 Heater (Example of heat source)
31 1st shielding member (an example of shielding member)
32 2nd shielding member (an example of shielding member)
83 Concavity (an example of an opening)
N fixing nip

Japanese Patent No. 5907358 JP 2006-48332 A

Claims (6)

A rotatable fixing member;
A heat source for heating the fixing member;
An opposing member that forms a fixing nip in contact with the outer peripheral surface of the fixing member;
A fixing device that is disposed between the fixing member and the heat source and shields heat from the heat source;
The shielding member is composed of a plurality of shielding members,
At least one shielding member has a plurality of shielding patterns defining a shielding width in the longitudinal direction of the fixing member;
The plurality of shielding members are movable in a stacked state,
A fixing device in which movable regions of the respective shielding members are different. A rotatable fixing member;
A heat source for heating the fixing member;
An opposing member that forms a fixing nip in contact with the outer peripheral surface of the fixing member;
A fixing device that is disposed between the fixing member and the heat source and shields heat from the heat source;
The shielding member is composed of a first shielding member and a second shielding member as a plurality of shielding members,
The first shielding member has at least one opening in the longitudinal direction of the fixing member,
The second shielding member has a width greater than or equal to the opening in the circumferential direction of the fixing member,
The first shielding member and the second shielding member are stacked,
A retreat position that does not shield the heat from the heat source;
A first shielding position that partially shields heat from the heat source;
It is possible to move between the second shielding position that shields all the heat from the heat source,
In the first shielding position, the first shielding member and the second shielding member are laminated at a position other than the opening,
In the second shielding position, the first shielding member and the second shielding member are stacked at the position of the opening.   3. The fixing device according to claim 1, wherein the plurality of shielding members operate in conjunction with one shielding member, and the other shielding members operate.   The fixing device according to claim 1, wherein the plurality of shielding members are connected to each other by an elastic member.   The fixing device according to claim 1, wherein a shielding member closer to the fixing member among the plurality of shielding members has heat resistance and low friction properties.   An image forming apparatus comprising the fixing device according to claim 1.

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