JP5866929B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device that thermally fixes a developer image transferred to a recording sheet.

  Conventionally, as a fixing device used in an electrophotographic image forming apparatus, a cylindrical fixing belt, a heating unit having a heater and a nip plate disposed inside the fixing belt, and a fixing belt between the heating unit are used. There are known ones that include a backup roller to be sandwiched (see, for example, Patent Document 1). In this fixing device, the fixing belt is heated by the heating unit, and the recording sheet is conveyed between the heated fixing belt and the backup roller, whereby the developer image transferred to the recording sheet is thermally fixed. ing.

JP 2011-137933 A

  By the way, in the above-described fixing device, when recording sheets of a small size are continuously conveyed, the temperature of the heating unit outside the conveyance area of the recording sheet gradually increases and becomes high. And when it became high temperature in this way, there existed a possibility that a heating unit might deteriorate.

  Accordingly, the present invention provides a fixing device capable of preventing an excessive increase in the temperature of the heating unit outside the recording sheet conveyance area when printing is performed on a recording sheet having a small size. With the goal.

In order to achieve the above-described object, the fixing device of the present invention is a fixing device that thermally fixes a developer image on a recording sheet, and is disposed inside a flexible cylindrical member and the cylindrical member, and generates heat. A heating unit having a body, a backup member that forms a nip portion by sandwiching a cylindrical member between the heating unit, a deformable member that can change its shape by a temperature change, and a heat removal member are provided.
The deformable member is provided in the heating unit on the outer side in the recording sheet width direction than the minimum recording sheet conveyance region.
The heat removal member is provided apart from the heating unit.
The deforming member is separated from the heat removal member at a temperature lower than a predetermined temperature, and is deformed to contact the heat removal member at a predetermined temperature or higher.

  According to the fixing device configured in this way, when the portion outside the recording sheet width direction of the heating unit in the recording sheet width direction exceeds a predetermined temperature, the deformation member deforms and the heat removal member Since the heating unit is connected by the deformable member, the heat is removed from the heating unit by the heat removal member. Accordingly, when printing is performed on the smallest recording sheet, it is possible to prevent the temperature of the portion on the outer side in the recording sheet width direction from excessively rising from the conveyance region of the smallest recording sheet of the heating unit. Further, when the portion outside the recording sheet width direction of the heating unit in the recording sheet width direction is lower than a predetermined temperature, the heating unit and the heat removal member are not connected by the deformable member. Does not interfere with heating of the heating unit by a heating element.

In the fixing device described above, the heating unit may further include a nip member that is heated by the heating element and forms a nip portion by sandwiching the cylindrical member with the backup member.
In this case, it is desirable that the deformation member is provided on the nip member.

  According to the fixing device configured as described above, it is possible to reliably prevent the nip member that directly heats the cylindrical member from becoming high temperature.

In the fixing device having the nip member, the heating element may be a member that emits radiant heat, and the heating unit may have a shielding member that covers the heating element.
In this case, it is desirable that the deformable member is disposed outside the shielding member.

  According to the fixing device configured as described above, since the deformable member does not directly receive the radiant heat from the heating element, it is possible to prevent the deformable member from being deformed before the nip member reaches a predetermined temperature or higher. Can do.

  And the above-mentioned deformable member may be comprised from the bimetal, and may be comprised from the shape memory alloy.

  In the fixing device described above, it is desirable that at least a part of the heat removal member is disposed outside the cylindrical member.

  According to the fixing device configured as described above, the heat removal member can easily remove heat from the heating unit by bringing the heat removal member into contact with outside air that is cooler than the inside of the cylindrical member.

  According to the present invention, when the outside of the conveyance area of the minimum recording sheet of the heating unit reaches a predetermined temperature or more, the heat can be removed by the heat removal member via the deformable member. During printing, it is possible to prevent the portion outside the recording sheet conveyance area in the heating unit from becoming excessively hot.

1 is a side sectional view showing a laser printer including a fixing device according to an embodiment of the present invention. FIG. 4 is a cross-sectional view taken along a plane orthogonal to the left-right direction of the fixing device. It is a perspective view of a halogen lamp, a nip plate, a reflector, a stay, a cover, a deformable member, and a heat removal member. FIG. 3 is a partial cross-sectional view showing the inside of a fixing belt of the fixing device. FIG. 7 is a cross-sectional view taken along a direction orthogonal to the left-right direction of the fixing device when the deformable member is deformed. FIG. 9 is a partial cross-sectional view showing the inside of a fixing belt of a fixing device according to a modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, a schematic configuration of the laser printer 1 including the fixing device 100 of the present invention will be described, and then a detailed configuration of the fixing device 100 will be described.

<Schematic configuration of laser printer>
As shown in FIG. 1, the laser printer 1 includes a main body housing 2 in which a paper sheet 3 as an example of a recording sheet is fed, an exposure device 4, and a toner image (developer) on the paper P. And the fixing device 100 for thermally fixing the toner image on the paper P.

  In the following description, the direction will be described with reference to the user who uses the laser printer 1. That is, the right side in FIG. 1 is “front”, the left side is “rear”, the front side is “left”, and the back side is “right”. Also, the vertical direction in FIG.

  The paper feed unit 3 is provided in the lower part of the main body housing 2, and includes a paper feed tray 31 that accommodates the paper P, a paper pressing plate 32 that lifts the front side of the paper P, a paper feed roller 33, and a paper feed pad 34. And paper dust removing rollers 35 and 36 and a registration roller 37 are mainly provided. The paper P in the paper feed tray 31 is brought close to the paper feed roller 33 by the paper pressing plate 32 and separated one by one by the paper feed roller 33 and the paper feed pad 34, and the paper dust removing rollers 35, 36 and the registration roller 37. Then, it is conveyed toward the process cartridge 5.

  The exposure apparatus 4 is arranged at the upper part in the main body housing 2 and mainly includes a laser light emitting unit (not shown), a polygon mirror 41 that is rotationally driven, lenses 42 and 43, and reflecting mirrors 44, 45, and 46. In preparation. In the exposure apparatus 4, the laser light (see the chain line) based on the image data emitted from the laser light emitting part is reflected or passed through the polygon mirror 41, the lens 42, the reflecting mirrors 44 and 45, the lens 43 and the reflecting mirror 46 in this order. The surface of the photosensitive drum 61 is scanned at high speed.

  The process cartridge 5 is disposed below the exposure apparatus 4 and is detachably mounted on the main body housing 2 through an opening formed when the front cover 21 provided on the main body housing 2 is opened. Yes. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be detachably attached to the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner that contains toner (developer). The housing part 74 is mainly provided.

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 4, whereby image data is transferred onto the photosensitive drum 61. An electrostatic latent image based on is formed. Further, the toner in the toner container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer of a certain thickness on the developing roller 71. It is carried on.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the paper P is conveyed between the photosensitive drum 61 and the transfer roller 63, whereby the toner image on the photosensitive drum 61 is transferred onto the paper P.

  The fixing device 100 is provided behind the process cartridge 5. The toner image (toner) transferred onto the paper P is thermally fixed onto the paper P by passing through the fixing device 100. The paper P on which the toner image is thermally fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

<Detailed configuration of fixing device>
2, the fixing device 100 includes a fixing belt 110 as an example of a cylindrical member, a heating unit 200, a backup roller 120 as an example of a backup member, a cover member 130, and a guide member 140 (see FIG. 2). 4), a heat removal member 150, and a deformation member 160.

  The fixing belt 110 is an endless (cylindrical) belt having heat resistance and flexibility, and both ends of the fixing belt 110 are guided by a guide member 140 (see FIG. 4).

  The heating unit 200 is a unit disposed inside the fixing belt 110, and includes a halogen lamp 210 as an example of a heating element, a nip plate 220 as an example of a nip member, and a reflection member 230 as an example of a shielding member. , And stay 240.

  The halogen lamp 210 is a known heating element that heats the toner on the paper P by generating radiant heat to heat the nip plate 220 and the fixing belt 110. The halogen lamp 210 is a predetermined distance from the inner surfaces of the fixing belt 110 and the nip plate 220. It is arranged with a gap.

  The nip plate 220 is a plate-like member that is heated by receiving radiant heat from the halogen lamp 210, and is disposed so as to be in sliding contact with the inner surface of the cylindrical fixing belt 110. The nip plate 220 is made of, for example, an aluminum plate having a higher thermal conductivity than a steel stay 240 described later.

  As shown in FIG. 3, the nip plate 220 mainly has a base portion 221 and a protruding portion 222.

  The base portion 221 is a portion whose bottom surface is in sliding contact with the inner peripheral surface of the fixing belt 110, and transmits radiant heat received from the halogen lamp 210 to the toner on the paper P via the fixing belt 110. .

  The protruding portion 222 extends from the rear end of the base portion 221 in the paper transport direction along the paper transport direction and is formed in a substantially flat plate shape. The projecting portions 222 are formed at two locations on the left and right sides of the rear end of the base portion 221. More specifically, the protrusion 222 is formed on the outer side in the paper width direction with respect to the conveyance area W of the minimum size paper P that can be printed by the laser printer 1. Further, as shown in FIG. 2, the protruding portion 222 extends rearward from a flange portion 232 of the reflecting member 230 described later.

  The reflection member 230 is a member that reflects the radiant heat (radiant heat radiated mainly in the front-rear direction and the upward direction) from the halogen lamp 210 toward the nip plate 220 (the upper surface of the nip plate 220). Is arranged at a predetermined interval from the halogen lamp 210 so as to cover.

  By collecting the radiant heat from the halogen lamp 210 to the nip plate 220 by such a reflecting member 230, the radiant heat from the halogen lamp 210 can be used efficiently, and the nip plate 220 and the fixing belt 110 can be heated quickly. Can do.

  The reflecting member 230 has a high reflectance of infrared rays and far infrared rays, and is formed by, for example, bending an aluminum plate or the like into a substantially U shape in sectional view. More specifically, as shown in FIG. 3, the reflecting member 230 mainly includes a reflecting portion 231 having a curved shape (substantially U shape in cross section), and a flange portion 232 extending outward in the front-rear direction from both ends of the reflecting portion 231. Have.

  As shown in FIG. 2, the stay 240 is a member that ensures the rigidity of the nip plate 220 by supporting both end portions of the nip plate 220 in the front-rear direction via the flange portion 232 of the reflecting member 230. The stay 240 has a shape (substantially U shape in sectional view) along the outer surface shape of the reflecting member 230 (reflecting portion 231) and is disposed so as to cover the reflecting member 230. Such a stay 240 has relatively high rigidity, for example, is formed by bending a steel plate or the like into a substantially U shape in cross section.

  The backup roller 120 is an elastically deformable member and is disposed below the nip plate 220. The backup roller 120 is elastically deformed and sandwiches the fixing belt 110 with the nip plate 220 to form a nip portion N with the fixing belt 110.

  The backup roller 120 is configured to rotate by being driven by a driving force that is applied from a motor (not shown) provided in the main body housing 2, and is connected to the fixing belt 110 (or the paper P) by being rotated. The fixing belt 110 is driven to rotate by frictional force. As a result, the sheet P on which the toner image is transferred is conveyed between the backup roller 120 and the heated fixing belt 110 (nip portion N) so that the toner image (toner) is thermally fixed. Yes.

  The cover member 130 is a member that supports a heat removal member 150 described later, and is disposed so as to cover the heating unit 200 inside the fixing belt 110. The cover member 130 is formed in a substantially U shape in sectional view, and has a support portion 131 that extends rearward from the lower end of the rear wall along the paper transport direction. The support portion 131 is formed at a position away from the protrusion 222 so as not to contact the protrusion 222 of the nip plate 220.

  As shown in FIG. 3, the support portion 131 has two places on the left and right sides, more specifically, as shown in FIG. A through-hole 132 is formed. The hole 132 is a portion that exposes the lower surface of the heat removal member 150 disposed on the support portion 131, and is formed in a size smaller than the heat removal member 150 so that the heat removal member 150 is stably supported. Has been.

  The guide members 140 are provided at both ends of the fixing belt 110 and support the fixing belt 110, the heating unit 200, and the cover member 130.

  The heat removal member 150 is a member with high heat dissipation, for example, a heat sink. The heat removal member 150 is supported by the support portion 131 of the cover member 130 inside the fixing belt 110 and is disposed on each hole 132. Thus, since the heat removal member 150 is disposed outside the cover member 130 that covers the heating unit 200, the heat removal member 150 is provided apart from the heating unit 200.

  The deformable member 160 is a member having a high thermal conductivity and capable of changing its shape depending on a temperature change. As shown in FIG. 2, the deformable member 160 is provided outside the reflecting member 230 in the heating unit 200. Specifically, the deformable member 160 is provided on each protrusion 222 of the nip plate 220.

  The deformable member 160 is made of a plate-shaped bimetal, and the rear end is fixed to the nip plate 220. When the temperature of the nip plate 220 is sufficiently low, the deformable member 160 has a flat plate shape as shown in FIG. 2 and is not in contact with the heat removal member 150. Then, when the temperature of the nip plate 220 rises by using the fixing device 100, the deformable member 160 is warped by moving the front end upward, and the nip plate 220 becomes equal to or higher than a predetermined temperature. At this time, as shown in FIG. 5, the front end comes into contact with the lower surface of the heat removal member 150.

  Note that the bimetal used in the present embodiment is preferably one in which the relationship between the temperature and the amount of deformation is proportional in the temperature range including when the fixing device 100 is stopped and when it is operating. The bimetal having such a proportional temperature range is, for example, the electrical bimetal TM4 defined by the JIS standard. In this way, by using a bimetal having a proportional relationship between the temperature and the deformation amount as the deformation member 160 in a temperature range including when the fixing device 100 is stopped and operating, variation in the deformation amount of the deformation member 160 is suppressed. The deformable member 160 is deformed so as not to contact the heat removal member 150 when the nip plate 220 is lower than a predetermined temperature, and to contact the heat removal member 150 when the nip plate 220 reaches a predetermined temperature or higher. Can be made.

  In the present embodiment, the “predetermined temperature” is a temperature higher than the fixing temperature for fixing the toner on the paper P.

Next, operations and effects of the fixing device 100 of the present invention configured as described above will be described.
When the nip plate 220 is below a predetermined temperature, such as when the fixing device 100 is not used or when printing is performed on a large size paper P, the deformable member 160 is as shown in FIG. The heat removal member 150 is separated.

  When continuous printing is performed with the minimum size paper P, the temperature of the portion of the nip plate 220 outside the paper P conveyance area W in the paper width direction gradually increases. As a result, the deformable member 160 is deformed so that the front end gradually moves upward as the temperature of the nip plate 220 rises. When the portion of the nip plate 220 on the outer side in the paper width direction with respect to the conveyance area W of the paper P reaches a predetermined temperature or more, the front end of the deformation member 160 is the lower surface of the heat removal member 150 as shown in FIG. To touch.

  As a result, the portion of the nip plate 220 outside the sheet P conveyance area W in the sheet width direction is removed by the heat removal member 150 via the deformable member 160, so that printing is performed on the small size sheet P. In some cases, it is possible to prevent the portion of the nip plate 220 on the outer side in the paper width direction from the conveyance region W of the paper P from becoming excessively high in temperature.

  Then, when the portion of the nip plate 220 outside the conveyance region W of the sheet P in the sheet width direction becomes less than a predetermined temperature, the front end of the deformation member 160 is deformed so as to move downward, and FIG. As shown, the heat removal member 150 is separated from the lower surface.

  As a result, when the portion of the nip plate 220 outside the conveyance region W of the paper P in the paper width direction is lower than the predetermined temperature, the heat removal member 150 does not disturb the heating of the heating unit 200.

  Since the deformable member 160 is provided on the nip plate 220, the nip plate 220 that directly heats the fixing belt 110 can be reliably prevented from becoming high temperature.

  In addition, since the deformable member 160 is disposed outside the reflecting member 230, the deformable member 160 does not receive radiant heat directly from the halogen lamp 210, so that the deformable member 160 is not heated before the nip plate 220 reaches a predetermined temperature or higher. Can be prevented from being deformed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the said embodiment, although the deformation member was comprised from the bimetal, this invention is not limited to this. For example, the deformable member may be made of a bidirectional shape memory alloy.

  In the above embodiment, the heat removal member 150 is disposed inside the fixing belt 110 as shown in FIG. 4, but the present invention is not limited to this, and at least a part of the heat removal member is a fixing belt. It may be arranged outside 110.

  Specifically, an example of such a form will be described. As shown in FIG. 6, the heat removal member 150 ′ is a member that is long in the paper width direction, and the outer end in the left-right direction penetrates the guide member 140. , And protrudes outward from the end of the fixing belt 110.

  As described above, a part of the heat removal member 150 ′ is disposed outside the fixing belt 110, so that a part of the heat removal member 150 ′ is in contact with the outside air that is cooler than the inside of the fixing belt 110. Therefore, the heat removal member 150 ′ can efficiently dissipate heat, and heat can be easily taken from the nip plate 220.

  In the embodiment, the deformable member 160 is provided on the nip plate 220. However, the present invention is not limited to this, and may be provided on a member other than the halogen lamp 210 constituting the heating unit 200. . For example, the flange portion 232 of the reflecting member 230 may be extended to the outside of the stay 240, and the deformable member 160 may be provided on the flange portion 232.

  In the embodiment, the deformable member 160 is disposed at two positions outside the conveyance area W of the minimum size paper P of the heating unit 200 in the paper width direction, that is, at both ends of the heating unit 200. The invention is not limited to this. For example, in the fixing device in which the paper P is transported while being moved toward one end in the left-right direction, the deformation member 160 may be provided only at the other end in the left-right direction of the heating unit 200.

  Moreover, in the said embodiment, although the heat removal member 150 was a heat sink with high heat dissipation, this invention is not limited to this, The heat removal member may be comprised from the raw material with a large heat capacity.

  In the embodiment, the reflective member 230 is exemplified as an example of the shielding member. However, the present invention is not limited to this, and the stay 240 may be a shielding member that covers the halogen lamp 210.

  In the embodiment, the nip member and the heating element are separate parts, but the present invention is not limited to this. For example, a plate-shaped ceramic heater may be employed as a member that serves as both a nip member and a heating element.

  In the embodiment, the backup roller 120 is exemplified as the backup member. However, the present invention is not limited to this, and may be, for example, a belt-like backup member.

  In the embodiment, the paper P such as plain paper or postcard is exemplified as the recording sheet. However, the present invention is not limited to this, and may be, for example, an OHP sheet.

DESCRIPTION OF SYMBOLS 100 Fixing device 110 Fixing belt 120 Backup roller 130 Cover member 140 Guide member 150 Heat removal member 160 Deformation member 200 Heating unit 210 Halogen lamp 220 Nip plate 230 Reflection member 240 Stay N Nip part P Paper W Transport area

Claims (7)

A flexible tubular member;
A heating unit disposed inside the cylindrical member and having a heating element;
A backup member that forms a nip portion by sandwiching the cylindrical member with the heating unit, and a fixing device that thermally fixes a developer image on a recording sheet,
A deformation member that is provided in the heating unit on the outer side in the recording sheet width direction than the smallest recording sheet conveyance region, and capable of changing its shape by a temperature change;
A heat removal member provided apart from the heating unit,
The deforming member is separated from the heat removal member at a temperature lower than a predetermined temperature, and is deformed to contact the heat removal member at the predetermined temperature or higher .
The heating unit includes a nip member that is heated by the heating element and forms the nip portion by sandwiching the cylindrical member with the backup member,
The fixing device , wherein the deformable member is provided in the nip member . The heating element is a member that emits radiant heat,
The heating unit has a shielding member that covers the heating element,
The fixing device according to claim 1, wherein the deformable member is disposed outside the shielding member.   A flexible tubular member;
  A heating unit disposed inside the cylindrical member and having a heating element;
  A backup member that forms a nip portion by sandwiching the cylindrical member with the heating unit, and a fixing device that thermally fixes a developer image on a recording sheet,
  A deformation member that is provided in the heating unit on the outer side in the recording sheet width direction than the smallest recording sheet conveyance region, and capable of changing its shape by a temperature change;
  A heat removal member provided apart from the heating unit,
  The deforming member is separated from the heat removal member at a temperature lower than a predetermined temperature, and is deformed to contact the heat removal member at the predetermined temperature or higher.
  The heating element is a member that emits radiant heat,
  The heating unit has a shielding member that covers the heating element,
  The fixing device, wherein the deformable member is disposed outside the shielding member.   The fixing device according to claim 3, wherein the shielding member is separated from the heating element. The deformable member is a fixing device according to any one of claims 1 to 4, characterized in that the bimetal. The deformable member is a fixing device according to any one of claims 1 to 4, characterized in that a shape memory alloy. At least in part, a fixing device according to any one of claims 1 to 6, characterized in that it is disposed outside the said tubular member of said heat removal member.

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