JP5123552B2 - Belt device, fixing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a belt device that travels an endless belt member that is stretched around a plurality of roller members, and a fixing device and an image forming apparatus that include the belt device.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a facsimile, or a complex machine thereof, a technique for preventing a belt member such as a fixing belt and a transfer belt from greatly moving in the width direction (belt shift) is known. (For example, refer to Patent Document 1 and Patent Document 2.)

  In a belt device (belt driving device) in Patent Document 1 or the like, protrusions (rib-like protrusions) are provided at both ends of a belt member (belt), and a journal portion (shaft member) of a roller member on which the belt member is stretched ) Is rotatably installed. Then, when the belt member is largely displaced from the belt, the belt member protruding portion comes into contact with the rotary member that is rotatably installed, so that the belt member can be surely removed without destabilizing the belt member. To be prevented.

  On the other hand, in Patent Document 2 and the like, protrusions (meandering prevention members) are provided at both ends of a belt member (fixing belt), and at the journal portion of a hollow roller member (heating roller) on which the belt member is stretched. A technique for providing a groove-like locking portion by forming a protruding portion is disclosed. Then, when the belt member is largely shifted from the belt, the protruding portion of the belt member comes into contact with the engaging portion of the roller member, thereby preventing the belt member from meandering.

JP 2002-328772 A JP 2005-31080 A

The technique disclosed in Patent Document 1 described above has three problems.
The first problem is that it is difficult to secure a space for installing the rotating member with respect to the roller member having a small outer diameter difference between the roller main portion (the position where the belt member directly contacts) and the journal portion. That's what it means. Such a problem is caused when the inner diameters of the roller main portion and the journal portion are increased when it is necessary to insert and install a plurality of heaters (for example, three or more heaters) inside the hollow roller member. It must be set, and the difference between the outer diameters of the roller main portion and the journal portion becomes small, which cannot be ignored.
The second problem is that it is necessary to install a retaining ring to prevent the rotating member from falling off the journal part, which increases the number of parts and costs, and complicates the assembly work. is there.
The third problem is that since the rotating member is formed in a donut shape, when the rotating member is formed of a resin material, a weld line is formed by injection molding, and the component strength is reduced. In order to solve this, if the rotating member is formed by compression molding, the cost of the parts becomes high.

  On the other hand, since the technology disclosed in Patent Document 2 described above forms a bulging portion that protrudes inside the journal portion of the roller member, the inner diameter of the journal portion is reduced and a heater is inserted into the roller member. There was a problem that it was difficult to do. Further, when the belt is deviated, the protrusion of the belt member is directly brought into contact with the roller member, so that the belt member or the roller member is worn out or the protrusion is on the outer peripheral surface of the roller member. There was a problem that the running speed of the belt member becomes unstable.

  The present invention has been made to solve the above-described problems. Even when the belt member is stretched around a roller member having a small outer diameter difference between the roller main portion and the journal portion, the belt member Therefore, it is possible to provide a belt device, a fixing device, and an image forming apparatus that are relatively inexpensive and have good assembling properties without reliably suppressing the meandering and unstable running.

Such belt device to a first aspect of the present invention of this invention is a belt system for running a plurality of roller members in stretched the endless belt member, the belt member is configured to protrude on the inner peripheral side Protruding portions having inclined surfaces inclined with respect to the protruding direction are formed at both ends in the width direction, and at least one roller member of the plurality of roller members is formed on the belt member. A hollow roller member having a journal portion having an outer diameter smaller than the outer diameter of the roller main portion with which the inner peripheral surface abuts at both ends in the width direction, the journal portion having a circumferential groove. with engaged rotatably to the groove of the journal portion, provided abutting the ring member to the protruding portion when the belt member has a predetermined amount displaced in the width direction, the ring member may have an outer diameter A C-shaped ring member provided with the notch in a part of the circumferential direction while being formed so as to be equal to the outer diameter of the serial roller main portion, the journal portion of the roller member is elastically deformed by an external force An inclined surface that is inclined at an angle substantially equal to the inclination angle of the inclined surface so as to come into surface contact with the inclined surface when coming into contact with the protrusion is formed toward the end in the width direction. It has been done .

The belt device according to a second aspect of the present invention is the belt device according to the first aspect, wherein the ring member has a gap formed on the inner diameter side for reducing a contact area with the journal portion. It is.

  A belt device according to a third aspect of the present invention is the belt device according to the second aspect, wherein the ring member is formed so that a notch width of the notch is 1 mm or less.

  According to a fourth aspect of the present invention, in the belt device according to the second or third aspect of the invention, the ring member has a part or all of the ridgeline of the notch chamfered. .

  A belt device according to a fifth aspect of the present invention is the belt device according to any one of the second to fourth aspects, wherein the ring member is formed by injection molding.

  A belt device according to a sixth aspect of the present invention is the belt device according to any one of the first to fifth aspects, wherein the hollow roller member is provided between the roller main portion and the journal portion. The diameter difference is 5 mm or less.

  A belt device according to a seventh aspect of the present invention is the belt device according to any one of the first to sixth aspects, wherein the belt member travels at 200 mm / second or more.

Further, the belt device according to the invention of claim 8 is the invention according to any of the claims 1 to 7, wherein the ring member, and is formed of polyimide.

According to a ninth aspect of the present invention, there is provided a fixing device for fixing a toner image on a recording medium, comprising the belt device according to any one of the first to eighth aspects. .

According to a tenth aspect of the present invention, there is provided a fixing device according to the ninth aspect, wherein the fixing auxiliary roller, a heating roller provided with a heater, and a fixing belt stretched between the fixing auxiliary roller and the fixing roller. A pressure member that forms a nip portion for conveying the recording medium by being pressed against the fixing auxiliary roller via a belt, and the belt member is the fixing belt, and the hollow structure roller member The heating roller is used.

According to an eleventh aspect of the present invention, in the fixing device according to the tenth aspect, the heating roller has three or more heaters.

Further, the fixing device according to the invention of claim 12, wherein, in the invention according to claim 10 or claim 11, wherein the auxiliary fixing roller is one having an elastic layer made of foamed material.

An image forming apparatus according to a thirteenth aspect of the present invention includes the belt device according to any one of the first to eighth aspects.
An image forming apparatus according to a fourteenth aspect of the present invention includes the fixing device according to any one of the ninth to twelfth aspects.

  The present invention forms a groove portion in the journal portion of the roller member, and rotatably installs a ring member in the groove portion, and when the belt shift occurs, the protruding portion of the belt member abuts on the ring member, The ring member is elastically deformed so that it can be attached to and detached from the groove portion of the journal portion. As a result, even when the belt member is stretched around a roller member having a small outer diameter difference between the roller main portion and the journal portion, meandering and unstable running of the belt member are reliably suppressed, and the component strength Therefore, it is possible to provide a belt device, a fixing device, and an image forming apparatus that are relatively inexpensive and have good assembling properties without lowering.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, and 11C. , 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is each photosensitive drum. A developing unit that develops electrostatic latent images formed on 11Y, 11M, 11C, and 11BK, and a toner image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK Transfer bias roller for transferring superimposed on the recording medium P (1 transfer bias roller), 15 denotes the photosensitive drums 11Y, 11M, 11C, cleaning unit for collecting the untransferred toner on 11BK, a.

  Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P is a fixing device for fixing the toner image (unfixed image) on the recording medium P.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the transfer bias roller 14 (in the primary transfer process). is there.).

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. Then, a color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

Here, the recording medium P transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is transported from the paper supply unit 7 via the registration roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, the color image (toner) is fixed on the recording medium P at the nip between the fixing belt and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
FIG. 2 is a schematic cross-sectional view showing the fixing device 20. FIG. 3 is a front view showing the fixing device 20, and mainly shows the configuration of the pressure mechanism. FIG. 4 is a partially enlarged cross-sectional view showing the heating roller 23 on which the fixing belt 21 is stretched. 5 is a perspective view showing the ring member 24 that is detachably installed on the heating roller 23, and FIG. 6 is a partially enlarged view showing the vicinity of the notch 24a of the ring member 24. As shown in FIG.
As shown in FIG. 2, the fixing device 20 includes belt devices 21 to 25, a pressure roller 31 as a pressure member, a temperature sensor 40, a guide plate 35, and the like. The belt device includes a fixing belt 21 as a belt member, a fixing auxiliary roller 22 (roller member), a heating roller 23 (roller member), and the like.

Here, the fixing belt 21 as a belt member is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a base layer made of a resin material. The elastic layer of the fixing belt 21 is formed of an elastic material such as fluorine rubber, silicone rubber, or foamable silicone rubber. The release layer of the fixing belt 21 is formed of PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. By providing the release layer on the surface layer of the fixing belt 21, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by two roller members (a fixing auxiliary roller 22 and a heating roller 23), and travels in the direction of the arrow in FIG.
By using the fixing belt 21 having a low heat capacity as the fixing member, the temperature rise characteristic of the apparatus is improved.
Referring to FIG. 3, protrusions 21 a (detent members) that protrude toward the inner periphery are formed at both ends in the width direction of the fixing belt 21. This will be described in detail later.

  The fixing auxiliary roller 22 is a roller member in which an elastic layer 22b made of a foam material such as foamable silicone rubber is formed on a core metal 22a such as SUS304, and the fixing belt 22 is attached to a pressure roller 31 as a pressure member. 21 to contact and form a nip portion. By forming the elastic layer 22b from a foamed material, the nip width (nip amount) at the nip portion can be set relatively large, and the heat of the fixing belt 21 is difficult to transfer to the auxiliary fixing roller 22. The fixing auxiliary roller 22 rotates in the clockwise direction in FIG.

The heating roller 23 is a hollow roller member (cylindrical body) made of a metal material such as aluminum or stainless steel, and three heaters 25 (heat sources) are fixed inside the cylindrical body.
The heater 25 of the heating roller 23 is a halogen heater, and both ends thereof are fixed to a side plate (not shown) of the fixing device 20. Then, the heating roller 23 is heated by the radiant heat from the heater 25 whose output is controlled by the power supply unit (AC power supply) of the apparatus main body 1, and further on the recording medium P from the surface of the fixing belt 21 heated by the heating roller 23. Heat is applied to the toner image T. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature sensor 40 (thermopile) that faces the surface of the fixing belt 21 in a non-contact manner. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the temperature sensor 40. By such output control of the heater 25, the temperature (fixing temperature) of the fixing belt 21 can be adjusted and controlled to a desired temperature (target control temperature).
Here, the heater 25 is temporarily detached from the fixing device 20 when the fixing auxiliary roller 22, the fixing belt 21, the heating roller 23, and the like are replaced. In particular, since the fixing auxiliary roller 22 has a shorter life than other components, the heater 25 is attached and detached in a predetermined cycle. The heater 25 is attached / detached by inserting / removing the heater 25 through / from the opening of the journal portion 23b of the heating roller 23 with reference to FIG. By installing three heaters 25, the temperature raising efficiency of the fixing device 20 is improved.

The pressure roller 31 as a pressure member mainly includes a cored bar 32 and an elastic layer 33 formed on the outer peripheral surface of the cored bar 32 via an adhesive layer. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, fluorine rubber, or silicone rubber. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is pressed against the auxiliary fixing roller 22 via the fixing belt 21 by the pressure mechanisms 50 to 52 shown in FIG. In this way, a desired nip portion is formed between the pressure roller 31 and the fixing belt 21.

Further, the above-described pressurizing mechanism is configured to be capable of releasing pressure (or reducing pressure). Specifically, as shown in FIG. 3, the pressure mechanism acts on the lever 50 that engages the shaft portion of the pressure roller 31 and the lever 50 to urge the pressure roller 31 toward the fixing auxiliary roller 22. A spring 51, a cam 51 for engaging and releasing the pressure roller 31 by engaging with the lever 50, a drive motor (not shown) for driving the cam 51, and the like. When the fixing process is performed, the cam 51 is rotationally driven so as to be in the posture shown in FIG. 3, and the pressure roller 31 is pressed against the fixing belt 21 (fixing auxiliary roller 22) (in the state shown in FIG. 3). is there.). On the other hand, when the fixing process is not performed, the cam 51 is rotationally driven from the posture of FIG. 3 by a half turn to release the pressure of the pressure roller 31 against the fixing belt 21 (fixing auxiliary roller 22) (or the pressure reduction). )
In the present embodiment, heating means such as a heater that directly heats the pressure roller 31 may be provided. Thereby, the temperature rise characteristic of the fixing device 20 is further improved.

Referring to FIG. 2, guide plates 35 for guiding the conveyance of the recording medium P are respectively provided at the entrance side and the exit side of the contact portion (nip portion) between the fixing belt 21 and the pressure roller 31. It is arranged. The guide plate 35 is fixed to the side plate of the fixing device 20.
Although not shown, a separation plate is disposed at a position facing the outer peripheral surface of the fixing belt 21 and in the vicinity of the exit side of the nip portion. The separation plate prevents a problem that the recording medium P after the fixing process is wound around the fixing belt 21 along the travel of the fixing belt 21.

The fixing device 20 configured as described above operates as follows.
When the power switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) from the AC power source to the heater 25, and the fixing belt 21 (fixing auxiliary roller 22, heating roller 23) and pressure roller 31 are shown in FIG. The rotational drive in the direction of the arrow in the middle is started.
Thereafter, the recording medium P is fed from the paper supply unit 7 and the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are carried on the recording medium P as unfixed images. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portion between the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. The toner image T is fixed on the surface of the recording medium P by the heating by the fixing belt 21 and the pressing force of the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31. Thereafter, the recording medium P sent out from the nip portion by the rotating fixing belt 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

Hereinafter, the characteristic configuration and operation of the fixing device 20 of the present embodiment will be described in detail with reference to FIGS.
As shown in FIG. 4, the heating roller 23 as a hollow roller member has a roller main portion 23a with which the inner peripheral surface of the fixing belt 21 abuts and an outer diameter smaller than the outer diameter of the roller main portion 23a. A journal unit 23b. The journal portions 23b are provided at both ends in the axial direction, and the journal portions 23b are rotatably supported on the side plate of the device 20 via bearings (not shown). The heating roller 23 rotates in a predetermined direction following the travel of the fixing belt 21 due to the frictional resistance with the fixing belt 21 in contact therewith.
Although not shown in the figure, the other end in the width direction of the heating roller 23 and the fixing belt 21 is also configured in the same manner as in FIG.

In the present embodiment, the roller main portion 23a is set to have an outer diameter of 35 mm and an inner diameter of 33.8 mm, and the journal portion 23b is set to have an outer diameter of 30 mm and an inner diameter of 28 mm.
As described above, the difference between the outer diameters of the roller main portion 23a and the journal portion 23b is reduced, and the inner diameters of the roller main portion 23a and the journal portion 23b are set to be large. A plurality of heaters 25 (for example, three or more heaters) can be inserted and installed in the interior of the heater 23, so that the fixing device 20 can be downsized and the temperature rise characteristics of the fixing device 20 can be improved. be able to.

The journal portion 23b is formed with a groove portion 23b1 in a circumferential shape. A ring member 24 (rotating member) is rotatably engaged with the groove 23b1. Specifically, the ring member 24 is formed so that its inner diameter is slightly larger than the outer diameter of the groove 23b1. This ring member 24 is for abutting against the protruding portion 21a when the fixing belt 21 is displaced by a predetermined amount in the width direction (the left-right direction in FIG. 4), thereby suppressing a large belt deviation.
In the present embodiment, the height of the protruding portion 21a (the distance protruding inward from the inner peripheral surface of the fixing belt 21) is set to 2 mm. Therefore, the gap between the protruding portion 21a and the journal portion 23b is about 0.5 mm.

Specifically, the inner circumferential surface of the fixing belt 21 is provided with protrusions 21a that stand inward at both ends in the width direction. The protrusion 21 a is made of a rubber material and can be formed integrally with the fixing belt 21.
When the fixing belt 21 moves by a predetermined amount in the width direction (closer to the belt), the protruding portion 21a of the fixing belt 21 comes into contact with the ring member 24 installed in the groove portion 23b1 of the heating roller 23. As a result, even if the fixing belt 21 is likely to be displaced (moved to the right side in FIG. 4) toward one end in the width direction, the other end in the width direction (the end in the width direction shown in FIG. 4). The protrusion 21a provided in the contact with the ring member 24 functioning as a stopper restricts the movement of the fixing belt 21 in the width direction.

  Here, since the ring member 24 is rotatably held by the heating roller 23, when the protrusion 21a tries to ride on the outer peripheral surface of the roller main portion 23a, the movement energy is rotated by the rotation of the ring member 24. Converted into energy. That is, by providing the ring member 24, the protrusion of the protrusion 21a onto the heating roller 23 is suppressed.

Moreover, in this Embodiment, the ring member 24 is formed so that the outer diameter may become equal to the outer diameter of the heating roller 23 (roller main part 23a). As a result, the ring member 24 prevents the protrusion 21a from climbing without damaging the inner peripheral surface of the fixing belt 21.
Further, the protruding portion 21a is formed with an inclined surface that is inclined with respect to the protruding direction. The ring member 24 is formed so as to be in surface contact with the inclined surface of the protruding portion 21a. That is, the ring member 24 has an inclined surface that is inclined at an angle substantially equal to the inclination angle of the inclined surface of the protruding portion 21a. As a result, the contact area between the protruding portion 21a and the ring member 24 is increased, and it becomes easier to convert the movement energy that the protruding portion 21a tries to ride on the outer peripheral surface of the heating roller 23 into the rotational energy of the ring member 24. The protrusion 21a can be prevented from climbing up.

  Moreover, the ring member 24 and the journal part 23b (groove part 23b1) are formed so that only a part of mutual opposing surface may become a contact surface. That is, the ring member 24 and the groove portion 23b1 are set so that not all of the mutually facing surfaces become contact surfaces, but the area of the contact surfaces becomes as small as possible. Specifically, a gap 24 a (step) is formed on the inner diameter side of the ring member 24. Thereby, the frictional resistance of the ring member 24 with respect to the groove part 23b1 is reduced, and the ring member 24 becomes easy to rotate. Therefore, the conversion to the rotational energy of the ring member 24 is performed smoothly, and the protrusion 21a is prevented from riding up. As a material for the ring member 24 (particularly, a material for a contact surface with the groove 23b1), a polyimide having a low frictional resistance and a high heat resistance is suitable.

Here, in the present embodiment, the ring member 24 is configured to be elastically deformed by an external force so as to be detachable from the journal portion 23b (groove portion 23b1). Specifically, referring to FIG. 5, the ring member 24 is a C-shaped ring member provided with a notch 24a in a part in the circumferential direction.
Specifically, when the ring member 24 is attached to the groove 23b1, the ring member 24 is elastically stretched in the circumferential direction by an external force (manpower) so that the inner diameter of the ring member 24 is pushed and expanded (so that the notch 24a is expanded). In the deformed state, the outer diameter part of the journal part 23b is slid. Then, by removing the external force when the ring member 24 reaches the position of the groove 23b1, the ring member 24 returns to its original shape and fits into the groove 23b1. Further, when the ring member 24 is taken out from the groove 23b1, a process reverse to the process at the time of mounting described above is performed.

Thus, in the present embodiment, when the difference in outer diameter between the roller main portion 23a and the journal portion 23b is small (when the outer diameter difference from the roller main portion 23a is so small that a retaining ring cannot be installed in the journal portion 23b). Even so, since the groove 23b1 is provided in the journal 23b to secure a space for installing the ring member 24, meandering and unstable running of the fixing belt 21 can be reliably suppressed.
Further, since the ring member 24 is elastically deformed and detached from the journal portion 23b (groove portion 23b1), it is not necessary to install a retaining ring to prevent the ring member 24 from falling off the journal portion 23b. Therefore, the number of parts is reduced and the cost is reduced as compared with the conventional apparatus, and the assembling work is also simplified.
Further, since the ring member 24 has an end shape with a notch 24a formed, it can be formed by injection molding using a resin material as compared with a conventional endless shape (doughnut shape). Weld lines are less likely to occur. Therefore, the ring member 24 can be formed with a wide range of material options and a relatively low cost without reducing the component strength.

Moreover, in this Embodiment, with reference to FIG. 6, it forms so that the notch width A of the notch 24a of the ring member 24 may be 1 mm or less. As a result, the ring member 24 has a shape approximate to a donut shape in which the inner peripheral surface is continuously formed, and smoothly rotates with respect to the journal portion 23b (groove portion 23b1).
Furthermore, in the present embodiment, part or all of the ridgeline of the notch 24a of the ring member 24 is chamfered. Specifically, referring to FIG. 6, a chamfered portion 24 b of about C0.5 mm is formed on the ridge line of the notch 24 a that contacts the outer peripheral surface of the ring member 24. As a result, it is possible to prevent the fixing belt 21 and the protruding portion 21a from being caught in the notch 24a of the ring member 24.

In addition, the effect by providing the ring member 24 having the groove portion 23b and the notch 24a described above is that a roller member (a plurality of roller members formed so that an outer diameter difference between the roller main portion 23a and the journal portion 23b is 5 mm or less. This is particularly remarkable for a belt device using a relatively small-diameter roller member in which the heater 25 is provided. In other words, in the present embodiment, the height of the protruding portion 21a is set to about 2 mm, and the gap between the protruding portion 21a and the journal portion 23b is about 0.5 mm. If a ring is installed, the retaining ring and the protruding portion interfere with each other. However, in the present embodiment, the groove portion 23b is provided in the journal portion 23b, and the notch 24a is formed in the ring member 24. Therefore, the ring member 24 is provided in a limited space without installing a retaining ring. Can be installed.
Further, in the high-speed fixing device 20 (belt device) in which the fixing belt 21 (belt member) travels at 200 mm / second or more, the fixing belt 21 is likely to meander or unstablely travel, and the temperature of the fixing device 20 is increased. Since there are many cases where three or more heaters 25 are installed in order to improve the characteristics, the configuration in the present embodiment is useful.

  As described above, in this embodiment, the groove portion 23b1 is formed in the journal portion 23b of the heating roller 23 (roller member), and the ring member 24 is rotatably installed in the groove portion 23b1, thereby causing a belt shift. At this time, the protruding portion 21a of the fixing belt 21 (belt member) is brought into contact with the ring member 24, and the ring member 24 is elastically deformed so as to be detachable from the groove portion 23b1 of the journal portion 23b. Accordingly, even when the fixing belt 21 is stretched around the heating roller 23 having a small outer diameter difference between the roller main portion 23a and the journal portion 23b, the meandering and unstable running of the fixing belt 21 are surely suppressed. Thus, the assembling property can be improved at a relatively low cost without reducing the component strength.

In this embodiment, the pressure roller 31 is used as the pressure member, but a pressure belt or a pressure pad may be used as the pressure member. Even in that case, the same effect as the present embodiment can be obtained.
In the present embodiment, the present invention is applied to the belt device installed in the fixing device 20, but other belt devices installed in the image forming apparatus (for example, a photosensitive belt, a transfer belt, an intermediate transfer). Naturally, the present invention can also be applied to a belt device using a belt as a belt member) or a belt device used other than the image forming apparatus. Even in that case, the same effect as the present embodiment can be obtained.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a fixing device installed in the image forming apparatus of FIG. 1. It is a front view showing a fixing device. It is a partial expanded sectional view which shows the heating roller by which the fixing belt was stretched. It is a perspective view which shows a ring member. It is the elements on larger scale which show the vicinity of the notch of a ring member.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt (belt member),
21a protrusion,
22 fixing auxiliary roller (roller member),
22b elastic layer,
23 Heating roller (hollow structure roller member),
23a Roller main part,
23b Journal part, 23b1 Groove part,
24 ring member,
24a notch, 24b chamfer,
25 heater,
31 Pressure roller (pressure member).

Claims (14)

A belt device that travels an endless belt member stretched around a plurality of roller members,
The belt member includes protrusions at both ends in the width direction , the protrusions protruding toward the inner peripheral side and inclined surfaces that are inclined with respect to the protruding direction are formed toward the center portion in the width direction.
At least one of the plurality of roller members has a hollow structure roller having journal portions at both ends in the width direction having an outer diameter smaller than the outer diameter of the main roller portion with which the inner peripheral surface of the belt member abuts. A member,
The journal portion has a circumferential groove portion,
A ring member that rotatably engages with the groove portion of the journal portion and abuts against the protrusion when the belt member is displaced by a predetermined amount in the width direction;
The ring member is a C-shaped ring member that is formed so that its outer diameter is equal to the outer diameter of the roller main portion and has a notch in a part of the circumferential direction, and is elastically deformed by an external force. And an inclined surface that is configured to be detachable from the journal portion of the roller member, and is inclined at an angle substantially equal to the inclined angle of the inclined surface so as to come into surface contact with the inclined surface when contacting the protruding portion. A belt device characterized by being formed toward the end in the width direction . The belt device according to claim 1, wherein the ring member has a gap formed on an inner diameter side for reducing a contact area with the journal portion.   The belt device according to claim 2, wherein the ring member is formed so that a notch width of the notch is 1 mm or less.   4. The belt device according to claim 2, wherein a part or all of the ridge line of the notch is chamfered on the ring member. 5.   The belt device according to claim 2, wherein the ring member is formed by injection molding.   The belt according to any one of claims 1 to 5, wherein the hollow roller member is formed such that a difference in outer diameter between the roller main portion and the journal portion is 5 mm or less. apparatus.   The belt device according to claim 1, wherein the belt member travels at 200 mm / second or more. The belt device according to claim 1, wherein the ring member is made of polyimide. A fixing device for fixing a toner image on a recording medium,
A fixing device comprising the belt device according to claim 1. A fixing auxiliary roller, a heating roller in which a heater is installed, a fixing belt stretched around,
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the fixing auxiliary roller via the fixing belt;
With
The belt member is the fixing belt,
The fixing device according to claim 9, wherein the hollow roller member is the heating roller. The fixing device according to claim 10, wherein the heating roller includes three or more heaters. The fixing device according to claim 10, wherein the auxiliary fixing roller includes an elastic layer made of a foam material. An image forming apparatus comprising the belt device according to claim 1. An image forming apparatus comprising the fixing device according to claim 9.

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