JP5931016B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

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

  For example, an image forming apparatus such as a laser printer or a multifunction peripheral has a fixing device that fixes a toner image transferred to a sheet to the sheet.

  The fixing device described in Patent Document 1 includes a heating roller, a fixing roller, a tension roller, and a pressure roller. A metal belt that is dielectrically heated by a heating mechanism is wound around the heating roller, the fixing roller, and the tension roller. The pressure roller is disposed so as to be in pressure contact with the fixing roller via the belt. Then, the toner image is fixed to the sheet by passing the sheet through a nip portion formed between the belt on the fixing roller and the pressure roller.

  Japanese Patent Application Laid-Open No. H10-228688 describes that the bushing is attached to both ends of the heating roller, thereby restricting belt movement in the axial direction of the heating roller and suppressing the meandering of the belt.

JP 2012-8487 A JP 2012-155350 A

  In order to attach the bush to the end of the heating roller, a slit-shaped notch extending in the axial direction is formed at the end of the heating roller, while a key portion inserted into the notch is formed at the bush. It is possible. Thereby, the bush can be rotated together with the heating roller.

  However, in this configuration, since the notch is formed at the end of the heating roller, it is difficult to form the end of the heating roller in a perfect circle. In addition, since the mechanical strength of the end portion of the heating roller is lowered, the end portion of the heating roller may be deformed during the manufacturing process or transportation of the heating roller. As a result, a load is easily applied to the belt side portion, so that there is a problem that a crack occurs in the belt side portion and the life of the belt is reduced.

  Furthermore, since the key portion is movable in the axial direction of the heating roller at the cutout portion, there is a problem that the bushing moves outward in the axial direction of the heating roller and the belt meandering cannot be prevented appropriately.

  The present invention has been made in view of the above points, and an object of the present invention is not only to suppress belt meandering but also to prevent deformation of the roller end of a fixing device having a roller around which the belt is wound. It is to increase the life of the belt.

  The fixing device according to the present invention includes a cylindrical roller around which a belt is wound, and a roller shaft of the belt which is attached to an end of the roller and abuts on the belt wound around the roller. And a bush that restricts movement in the direction, and a protrusion projecting radially inward of the roller is formed at the end of the roller, and the bush is attached to the end of the roller. An engaging portion that engages with the protruding portion in the state is formed.

  According to this configuration, the bush is attached to the end portion of the roller by engaging the engaging portion formed on the bush with the protruding portion protruding inward in the radial direction of the roller. The belt rotates as the roller rotates. At that time, the movement of the belt in the roller axial direction is restricted by abutting against a bush fixed to the roller. As a result, the meandering of the belt is appropriately suppressed.

  Furthermore, since the engaging portion of the bush is engaged with the protruding portion of the roller, a slit-like notch is formed at the end of the roller for the purpose of mounting the bush on the end of the roller as in the prior art. There is no need. Therefore, since the mechanical strength of the roller end portion is not significantly reduced and the shape of the roller end portion can be maintained in a perfect circle shape, it is possible to reduce the load on the belt and increase the life of the belt. .

  The engaging portion is formed with a locking claw that protrudes to one side in the circumferential direction of the roller and that locks an end surface of the protruding portion on the inner side in the axial direction of the roller. It is preferable to have a support surface that supports the side surface on one side in the circumferential direction of the roller in the section.

  According to this configuration, since the locking claw in the engaging portion of the bush is configured to lock the end surface on the axially inner side of the roller in the protruding portion of the roller, the movement of the bush to the axially outer side of the roller is restricted. be able to. Therefore, it becomes possible to suitably fix the bush to the roller.

  Furthermore, since the engaging portion of the bush can be supported by the support surface of the protrusion of the roller when the roller is rotating, the bush can be rotated integrally with the roller.

  It is preferable that the two sets of the projecting portions and the engaging portions that are engaged with each other are arranged symmetrically with respect to a plane that passes through the axis of the roller.

  According to this configuration, the movement of the bush to one side in the circumferential direction of the roller can be restricted by the one set of protrusions and engaging portions, while the other circumferential direction of the roller can be regulated by the other set of protrusions and engaging portions. The movement of the bush to the side can be restricted. That is, it becomes possible to restrict the rotational movement of the bush relative to the roller in any circumferential direction of the roller.

  Furthermore, it is preferable that the support surface of the protrusion is inclined toward the engagement portion from the outer side in the axial direction of the roller toward the inner side in the axial direction.

  According to this configuration, as the bush is moved inward in the axial direction of the roller, the pressing force that the locking claw receives from the support surface of the protrusion gradually increases. And when the locking claw moves inward in the axial direction of the roller from the protrusion and the pressing force received by the locking claw from the support surface disappears, the engaging part comes into pressure contact with the protruding part. The engaging portion and the protruding portion are firmly engaged with each other.

  An image forming apparatus according to the present invention includes the fixing device. According to this configuration, in the fixing device, the belt meandering is appropriately suppressed when the belt contacts the bush. Furthermore, since the shape of the roller end portion can be maintained in a perfect circle shape, it is possible to reduce the load on the belt and increase the life of the belt.

  According to the present invention, in a fixing device having a roller on which a belt is wound, not only the belt meandering can be suppressed, but also deformation of the roller end portion can be suppressed to increase the life of the belt.

FIG. 1 is a cross-sectional view illustrating a schematic structure of an image forming apparatus according to the present embodiment. FIG. 2 is a side view illustrating a schematic configuration of the fixing device. FIG. 3 is a front view showing the appearance of the heating roller to which the bush is attached. FIG. 4 is an enlarged perspective view showing a heating roller to which a bush is attached. FIG. 5 is an enlarged perspective view showing a heating roller not equipped with a bush. FIG. 6 is a perspective view showing the appearance of the bush. FIG. 7 is a perspective view showing the appearance of the bush. FIG. 8 is a cross-sectional view showing the bush mounted on the heating roller. FIG. 9 is a plan view showing the engaging portion of the bush mounted on the heating roller. 10 is a cross-sectional view taken along line XX in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.
<Image forming apparatus>

  FIG. 1 is a cross-sectional view illustrating a schematic structure of the image forming apparatus 1. The image forming apparatus 1 is, for example, a tandem color printer. As shown in FIG. 1, the intermediate transfer belt 7, the primary transfer unit 8 and the secondary transfer unit 9, a fixing device 11, and an optical scanning device 15. And a plurality of image forming units 16.

  A paper feed cassette 3 is disposed below the inside of the main body 2 of the image forming apparatus 1. The paper feed cassette 3 stores and accommodates sheets (not shown) such as paper before printing. A first paper transport unit 21 is provided on the side of the paper feed cassette 3. The first paper transport unit 21 receives the paper fed from the paper feed cassette 3 and transports the paper to the upper secondary transfer unit 9.

  A manual paper feed unit 5 is provided on the right side of the paper feed cassette 3. A second paper transport unit 22 is provided on the left side of the manual paper feed unit 5. The second paper transport unit 22 receives the paper sent from the manual paper feed unit 5 and transports it to the first paper transport unit 21.

  The optical scanning device 15 is disposed above the second paper transport unit 22 and irradiates the image forming unit 16 with laser light based on the image data received by the image forming device 1. For example, four image forming units 16 are provided above the optical scanning device 15. An endless intermediate transfer belt 7 is provided above each image forming unit 16. The intermediate transfer belt 7 is wound around a plurality of rollers and is rotationally driven by a driving device (not shown).

  As shown in FIG. 1, the four image forming units 16 are arranged in a line along the intermediate transfer belt 7, and respectively form yellow, magenta, cyan, or black toner images. That is, in each image forming unit 16, an electrostatic latent image of a document image is formed by the laser light emitted by the optical scanning device 15, and each color toner image is formed by developing the electrostatic latent image. .

  The primary transfer unit 8 is disposed above each image forming unit 16. The primary transfer unit 8 includes a transfer roller that primarily transfers the toner image formed by the image forming unit 16 to the surface of the intermediate transfer belt 7.

  Then, the intermediate transfer belt 7 is driven to rotate, and the toner image of each image forming unit 16 is transferred to the intermediate transfer belt 7 at a predetermined timing, so that the surface of the intermediate transfer belt 7 has yellow, magenta, A color toner image in which toner images of four colors of cyan and black are superimposed on each other is formed.

  As shown in FIG. 1, the secondary transfer unit 9 has a transfer roller 18 disposed on the left side of the intermediate transfer belt 7. The secondary transfer unit 9 applies a transfer bias voltage having a polarity opposite to that of the toner to the sheet sent from the first sheet transport unit 21 so as to transfer the toner image from the intermediate transfer belt 7 to the sheet. It has become.

  The fixing device 11 is provided above the secondary transfer unit 9. Between the secondary transfer unit 9 and the fixing device 11, a third paper transport unit 23 that transports the paper on which the toner image has been secondarily transferred to the fixing device 11 is formed. The fixing device 11 heats and pressurizes the sheet conveyed from the third sheet conveying unit 23 to fix the toner image on the sheet.

A branch portion 27 is provided above the fixing device 11. The sheet discharged from the fixing device 11 is discharged from the branching unit 27 to the sheet discharging unit 28 formed on the upper portion of the image forming apparatus 1 when double-sided printing is not performed. When performing duplex printing, the paper is conveyed again from the branching unit 27 to the secondary transfer unit 9 via the fourth paper conveying unit 24.
<Fixing device>

  FIG. 2 shows a schematic configuration of the fixing device 11. The fixing device 11 includes a pressure roller 31, a fixing roller 32, a heating roller 33, and a tension roller 34. Each roller 31-34 is arrange | positioned so that the axial direction may become mutually parallel.

  An endless belt 35 is wound around the fixing roller 32, the heating roller 33, and the tension roller 34. The belt 35 has a sheet-like metal substrate such as a nickel electroformed substrate. Although illustration is omitted, it is possible to laminate a silicon rubber layer on the nickel electroformed base material constituting the belt 35 and further laminate a release layer on the silicon rubber layer. The release layer is a layer provided so that the paper can be easily peeled from the belt 35, and is formed of a fluororesin such as PFA, for example.

  The belt 35 is sandwiched between the pressure roller 31 and the fixing roller 32. A nip is formed between the fixing roller 32 and the belt 35.

  The fixing device 11 includes an IH coil unit 36 as a heating mechanism for heating the belt 35. The IH coil unit 36 is disposed to face the heating roller 33. The IH coil unit 36 includes a coil (not shown) that generates a magnetic field, and is configured to electromagnetically heat the belt 35 wound around the heating roller 33.

  The fixing roller 32 is formed in a cylindrical shape, for example. Although not shown, the fixing roller 32 has a cored bar roller made of stainless steel and a sponge layer made of silicon rubber that covers the outer peripheral surface of the cored bar roller.

  The pressure roller 31 is formed in a columnar shape, for example. Although not shown, the pressure roller 31 includes a cored bar roller made of stainless steel, and a sponge layer and a release layer (for example, a PFA layer) made of silicon rubber covering the outer peripheral surface of the cored bar roller. Yes.

  The tension roller 34 is disposed so as to contact the inner surface of the belt 35 from the heating roller 33 toward the fixing roller 32. The tension roller 34 is a cylindrical roller made of, for example, aluminum, and suppresses the bending of the running belt 35 and causes the belt 35 to run stably. Since aluminum has a relatively high thermal conductivity, fluctuations in temperature distribution in the belt 35 can be reduced.

  FIG. 3 shows the appearance of the heating roller 33. As shown in FIG. 3, the heating roller 33 includes a cylindrical roller body 38 and bushes 39 attached to both ends of the roller body 38.

  FIG. 4 shows an enlarged end portion of the heating roller 33. FIG. 5 shows an enlarged end portion of the roller body 38. 6 and 7 show the appearance of the bush 39. FIG. 8 shows a cross section of the bush 39 attached to the roller body 38.

  The roller main body 38 has, for example, a cylindrical iron base and a release layer such as a PFA layer formed on the outer peripheral surface of the iron base. When the bush 39 is attached to the roller body 38, the bush 39 abuts on the side end of the belt 35 wound around the heating roller 33, thereby restricting the movement of the belt 35 in the roller axis direction. ing.

  As shown in FIGS. 6 and 7, the bush 39 has a cylindrical small-diameter portion 39a inserted into the roller body 38 and a large-diameter portion 39b formed at one end of the small-diameter portion 39a. That is, the large diameter portion 39b is formed in a flange shape. As shown in FIG. 8, the outer diameter of the small diameter portion 39 a is slightly smaller than the inner diameter of the roller body 38. The small-diameter portion 39a is arranged inside the roller main body 38 so that the outer peripheral surface of the small-diameter portion 39a is along the inner peripheral surface of the roller main body 38 in a state where the bush 39 is mounted on the roller main body 38. The end of the roller main body 38 is in contact with the side surface of the portion 39b.

  In addition, although illustration is abbreviate | omitted, the gearwheel is formed in the outer periphery of the large diameter part 39b. And the sensor which detects the rotation state of the heating roller 33 based on the rotation output of a gear is provided.

  The bush 39 is configured to engage with the roller body 38 in a state of being mounted on the roller body 38. Here, FIGS. 9 and 10 show an engaged state between the bush 39 and the roller body 38.

  That is, as shown in FIGS. 5 and 10, a protrusion 41 that protrudes radially inward of the roller body 38 is formed at the end of the roller body 38. An opening 42 is formed at the end of the roller body 38 at a position away from the edge of the roller body 38. The opening 42 is formed in a long hole shape extending in the axial direction of the roller body 38.

  The protrusion 41 is formed by bending a part of the roller body 38 inside the opening 42 inward in the radial direction of the roller body 38.

  On the other hand, the bush 39 is formed with an engaging portion 43 that engages with the protruding portion 41 while being attached to the end of the roller body 38. As shown in FIG. 9, the engaging portion 43 protrudes to one side A in the circumferential direction of the roller main body 38, and the engaging claw that locks the end surface 41 a on the inner side B of the roller main body 38 in the protruding portion 41. 45 is formed.

  The engaging portion 43 is inserted inside the roller body 38 along the inner wall surface of the roller body 38 when the bush 39 is attached to the end of the roller body 38. Therefore, the engaging portion 43 is disposed on the inner side in the radial direction of the roller body 38 than the opening 42.

  The protrusion 41 has a support surface 41 b that supports a side surface on one side A in the circumferential direction of the roller body 38 in the engaging portion 43. The support surface 41b of the protrusion 41 is inclined toward the engaging portion 43 side (that is, the left side in FIG. 9) from the outer side in the axial direction of the roller body 38 toward the inner side B in the axial direction.

  As shown in FIG. 8, the two sets of protrusions 41 and engaging portions 43 that engage with each other are arranged symmetrically with respect to a plane H that passes through the axis of the roller body 38. It is preferable that the two sets of protrusions 41 and engaging portions 43 are opposed to each other in the diameter direction of the roller body 38.

  Therefore, according to the present embodiment, the engaging portion 43 formed on the bush 39 engages with the protrusion 41 projecting radially inward of the roller body 38, so that the bush 39 is placed at the end of the roller body 38. Can be installed. The belt 35 rotates as the roller body 38 of the heating roller 33 rotates. At this time, the belt 35 is restricted from moving in the axial direction of the roller body 38 by contacting the large diameter portion 39b of the bush 39 fixed to the roller body 38. As a result, the meandering of the belt 35 can be appropriately suppressed.

  Further, since the engaging portion 43 of the bush 39 is engaged with the protrusion 41 of the roller body 38, the end of the roller body 38 is attached for the purpose of attaching the bush 39 to the end of the roller body 38 as in the prior art. There is no need to form a slit-like cutout in the part. Therefore, the end of the roller body 38 can be maintained in a perfect circle shape without significantly reducing the mechanical strength. Therefore, the load applied to the belt 35 traveling from the roller body 38 can be reduced, and the life of the belt 35 can be increased.

  Furthermore, since the locking claw 45 in the engaging portion 43 of the bush 39 locks the end surface on the axially inner side B of the roller body 38 in the protruding portion 41, the bushing toward the axially outer side of the roller body 38. 39 movement can be restricted. Therefore, the bush 39 can be suitably fixed to the roller body 38.

  Further, when the roller main body 38 is rotating, the engaging portion 43 of the bush 39 can be supported by the support surface 41b of the protrusion 41 of the roller main body 38, so that the bush 39 can be rotated integrally with the roller main body 38. it can.

  Further, since the two pairs of the protrusions 41 and the engagement portions 43 that are engaged with each other are arranged symmetrically with respect to the plane H passing through the axis of the roller body 38, as shown in FIG. The movement of the bush 39 with respect to the roller main body 38 toward the circumferential side one side A of the roller main body 38 can be regulated by the portion 41A and the engaging portion 43A. Moreover, the movement of the bush 39 with respect to the roller main body 38 to the circumferential direction other side C of the roller main body 38 can be regulated by the protrusion 41B and the engaging portion 43B of the other set.

  Therefore, by providing the two sets of the projecting portions 41 and the engaging portions 43, the rotational movement of the bush 39 with respect to the roller body 38 can be restricted on either side in the circumferential direction A or C of the roller body 38.

  In addition, in this embodiment, as shown in FIG. 9, the support surface 41 b of the protrusion 41 is inclined toward the engagement portion 43 from the outer side in the axial direction of the roller body 38 toward the inner side B in the axial direction. I made it. Therefore, when the bush 39 is mounted on the roller body 38, the pressing force that the tip of the locking claw 45 receives from the support surface 41b of the protrusion 41 as the bush 39 is moved to the inner side B in the axial direction of the roller body 38. Gradually increases and the tip of the locking claw 45 is compressed.

  When the locking claw 45 moves to the inner side B of the roller body 38 from the end surface 41a of the protruding portion 41, and the pressing force received by the locking claw 45 from the support surface 41b disappears, the engaging portion 43 Comes into pressure contact with the support surface 41b of the protrusion 41, so that the engagement portion 43 and the protrusion 41 can be firmly engaged with each other.

  In the above-described embodiment, the example in which the bush 39 is provided on the roller body 38 of the heating roller 33 has been described. However, the invention is not limited thereto, and the bush 39 is provided on another roller around which the belt 35 is wound in the fixing device 11. You may do it.

  Moreover, although the said embodiment demonstrated the example which formed the opening part 42 in the roller main body 38, the opening part 42 does not necessarily need to form. That is, the protrusion 41 may be formed on the inner peripheral surface of the cylindrical roller body 38 without the opening 42. However, the configuration in which the opening 42 is provided is preferable in that the protrusion 41 can be easily formed when the opening 42 is processed.

  In the above-described embodiment, the color printer is described as an example of the image forming apparatus. However, the present invention is not limited to this. For example, the image forming apparatus may be another image forming apparatus such as a multifunction peripheral or a monochrome printer having a fixing device that fixes a toner image. Also good.

  As described above, the present invention is useful for a fixing device and an image forming apparatus including the fixing device.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Fixing apparatus 31 Pressure roller 32 Fixing roller 33 Heating roller 34 Tension roller 35 Belt 38 Roller main body 39 Bush 41 Protrusion part 41a End surface 41b Support surface 43 Engagement part 45 Locking claw A One circumferential direction of a roller main body Side B Inner side of the roller body in the axial direction H

Claims (5)

A cylindrical roller around which a belt is wound;
A bush that is attached to the end of the roller and that regulates the movement of the belt in the roller axial direction by contacting the belt wound around the roller;
At the end of the roller, a protrusion protruding inward in the radial direction of the roller is formed,
The fixing device, wherein the bush is formed with an engaging portion that engages with the protruding portion while being attached to an end portion of the roller. The fixing device according to claim 1,
The engaging portion is formed with a locking claw that protrudes to one side in the circumferential direction of the roller and that locks the end surface on the inner side in the axial direction of the roller in the protruding portion,
The fixing device, wherein the protrusion has a support surface that supports a side surface of the engagement portion on one side in the circumferential direction of the roller. The fixing device according to claim 1 or 2,
The fixing device, wherein two sets of the protrusions and the engagement portions that are engaged with each other are arranged symmetrically with respect to a plane that passes through the axis of the roller. The fixing device according to claim 3.
The fixing device, wherein a support surface of the protruding portion is inclined toward the engaging portion side from the outer side in the axial direction of the roller toward the inner side in the axial direction. An image forming apparatus comprising the fixing device according to claim 1.

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