JP5084240B2 - Belt device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a belt device installed therein, and in particular, an intermediate transfer belt, a transfer fixing belt, etc. The present invention relates to a belt device including the belt member and an image forming apparatus.

Conventionally, in an image forming apparatus such as a copying machine or a printer, a tandem type color image forming apparatus provided with an intermediate transfer belt (belt device) is known (for example, see Patent Document 1).
Specifically, four photosensitive drums (image carriers) are arranged side by side so as to face the intermediate transfer belt. On these four photosensitive drums, black, yellow, magenta, and cyan toner images are formed, respectively. Then, the toner images of the respective colors formed on the respective photosensitive drums are transferred (primary transfer) while being superimposed on the intermediate transfer belt. Further, the toner images of a plurality of colors carried on the intermediate transfer belt are transferred (secondary transfer) onto the recording medium as a color image.

  In Patent Document 1, etc., an intermediate transfer belt as a belt member is stretched by a plurality of roller members. One of the plurality of roller members is a tension roller that applies tension to the intermediate transfer belt. Further, a position sensor for detecting the displacement of the tension roller is installed, and the execution timing of the color misregistration correction process is controlled based on the displacement amount of the tension roller.

  Japanese Patent Application Laid-Open No. 2004-228561 is an image forming apparatus using a conveyance belt (transfer conveyance belt) as a belt member, and an object of the present invention is to prevent the conveyance belt from sagging when a recording medium enters the conveyance belt. As a technique, a tension roller that is urged by a spring and applies tension to the conveyor belt is installed on the upstream side of the driven roller.

  Further, Patent Document 3 discloses an image forming apparatus using a photosensitive belt as a belt member, and alleviates the influence on the photosensitive belt due to disturbance generated when the recording medium is fed into the transfer nip. As an object, a technique is disclosed in which a position change of a tension roller that applies tension to the photosensitive belt is detected and feedback control is performed so as to correct the position change.

JP 2006-194996 A JP-A-6-115752 Japanese Patent No. 3294342

  The conventional image forming apparatus described above cannot sufficiently absorb the tension variation of the belt member due to the load variation when a sudden load variation occurs in the belt device in which the belt member is driven.

Details are as follows.
When a recording medium is fed into or sent out from the transfer nip of the belt device, sudden and sudden load fluctuations occur in the belt device. Such load fluctuations are high-frequency, which causes high-frequency tension fluctuations in the belt member. This high-frequency tension fluctuation cannot be sufficiently absorbed by a tension roller that applies a tension to the belt member by being displaced by being biased by a spring or the like. That is, since the tension roller has a certain amount of mass, it cannot quickly respond and follow the high-frequency tension fluctuation and cannot be displaced (optimizing the belt member tension).

In a device in which two transfer processes (primary transfer and secondary transfer) are performed on a belt member, such as a belt device using an intermediate transfer belt or a transfer fixing belt as a belt member, a secondary is used. When high-frequency tension fluctuations occur in the belt member due to feeding / sending of the recording medium to / from the transfer nip, shock jitter (image distortion) occurs on the image.
Also in a belt device using a transfer conveyance belt as a belt member and a belt device using a photosensitive belt as a belt member, when a high-frequency tension fluctuation of the belt member suddenly occurs, a shock jitter is displayed on the image. (Image distortion) may occur.
On the other hand, in order to solve such a problem, it is conceivable to install a high-output drive source and a high-transmission-rigidity reduction mechanism. However, in that case, the apparatus is increased in cost, weight, and size.

  The present invention has been made to solve the above-described problems, and has a relatively simple configuration that causes rapid load fluctuations in the apparatus without increasing the cost, weight, and size of the apparatus. Another object of the present invention is to provide a belt device and an image forming apparatus in which no shock jitter is generated on an image.

According to a first aspect of the present invention, a belt device includes a belt member stretched around a plurality of roller members, and an abutting member that abuts against an inner peripheral surface of the belt member and applies tension to the belt member. The contact member is a non-rotating member comprising a sliding contact portion that is in sliding contact with the belt member and a support portion that supports the sliding contact portion, and the sliding contact portion is a transfer nip of the apparatus. The belt member is formed so as to be elastically deformable in accordance with fluctuations in the tension of the belt member caused by feeding or / and feeding of the recording medium, and toner images carried on a plurality of image carriers are transferred onto the belt member in a superimposed manner. This is an intermediate transfer belt .

According to a second aspect of the present invention, there is provided a belt device comprising: a belt member stretched around a plurality of roller members; an abutting member that abuts against an inner peripheral surface of the belt member and applies tension to the belt member; The contact member is a non-rotating member that includes a sliding contact portion that is in sliding contact with the belt member and a support portion that supports the sliding contact portion, and the sliding contact portion corresponds to a transfer nip of the apparatus. The belt member is formed to be elastically deformable in accordance with fluctuations in the tension of the belt member caused by feeding or / and feeding of the recording medium, and the toner images carried on a plurality of image carriers are transferred onto the belt member in a superimposed manner. The transfer fixing belt is heated and melted by a heating unit.

According to a third aspect of the present invention, in the belt device according to the first or second aspect, the support portion is formed so as to be deformable in accordance with a change in tension of the belt member. is there.

A belt device according to a fourth aspect of the present invention is the belt device according to any one of the third to third aspects, wherein the sliding contact portion is formed of a material having a low friction coefficient.

A belt device according to a fifth aspect of the present invention is the belt device according to any one of the first to fourth aspects, further comprising detection means for detecting a deformation amount of the contact member. The driving speed is varied based on the detection result of the detection means.

According to a sixth aspect of the present invention, in the belt device according to the fifth aspect, the belt member is attached to one of the plurality of roller members based on a detection result of the detection means. The drive speed of the opposing member which opposes via is variable.

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 one of the plurality of roller members is interposed via the belt member. The abutting member is disposed on the upstream side in the driving direction and the downstream side in the driving direction of the roller member facing the opposing member.

The belt device according to an eighth aspect of the present invention is the belt device according to any one of the first to seventh aspects, further comprising detection means for detecting a deformation amount of the contact member, and the plurality of rollers. One roller member among the members is opposed to the opposing member via the belt member, and the detection result of the detecting means when the belt member is driven such that a speed difference is generated with respect to the driving speed of the opposing member. Accordingly, the speed difference amount and forward / reverse are controlled in accordance with the timing at which the tension of the belt member fluctuates.

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

  In the present invention, the abutting member that abuts on the belt member and applies tension is fixed so that the relative position in the apparatus is not displaced, and is formed to be deformable so that the tension of the belt member does not fluctuate. ing. As a result, the belt device and the image have a relatively simple configuration and do not cause shock jitter on the image even if the device undergoes sudden load fluctuations without increasing the cost, weight, and size of the device. A forming apparatus can be provided.

  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.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIGS.
FIG. 1 is a block diagram showing a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing an image forming unit thereof.
As shown in FIG. 1, four toner bottles 32Y, 32M, 32C, and 32K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably attached to the bottle housing portion 31 above the image forming apparatus main body 100. Is installed.
An intermediate transfer device 15 as a belt device is disposed below the bottle housing portion 31. Image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 (belt member) of the intermediate transfer device 15.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y as an image carrier, a charging unit 4Y disposed around the photosensitive drum 21, a developing unit 5Y, and a cleaning unit 2Y. , And a static elimination unit (not shown). Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y.

  The other three image forming units 6M, 6C, and 6K have substantially the same configuration as that of the image forming unit 6Y corresponding to yellow except that the color of the toner used is different. A corresponding image is formed. Hereinafter, description of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be described.

Referring to FIG. 2, the photosensitive drum 1Y is driven to rotate clockwise in FIG. 2 by a drive motor (not shown). Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (a charging process).
Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure unit 7, and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (in the exposure process). is there.).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing portion 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 (belt member) and the transfer roller 9Y, and the toner image on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 8 at this position. (This is a primary transfer process.) At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

Thereafter, the surface of the photoreceptor 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photoreceptor drum 1Y is collected at this position (cleaning process).
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, the laser beam L based on the image information is emitted from the exposure unit 7 disposed below the image forming unit onto the photosensitive drums of the image forming units 6M, 6C, and 6K. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, the intermediate transfer device 15 (belt device) includes an intermediate transfer belt 8, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12, driven rollers 13 and 16, an elastic roller 14 as a contact member, and an intermediate roller. The transfer cleaning unit 10 is configured. The intermediate transfer belt 8 is stretched and supported by the three roller members 12, 13, 16 and the elastic roller 14, and is endlessly moved in the direction of the arrow in FIG.

The four transfer rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. Then, a transfer voltage (transfer bias) opposite to the polarity of the toner is applied to the transfer rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19. At this position, the drive roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning unit 10. At this position, the untransferred toner on the intermediate transfer belt 8 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed. The configuration and operation of the intermediate transfer device 15 as a belt device will be described in detail later with reference to FIG.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from a paper feeding unit 26 disposed below the apparatus main body 100 via a paper feeding roller 27, a registration roller pair 28, and the like. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged to the outside of the apparatus through the rollers of the discharge roller pair 29. The transferred P discharged from the apparatus by the discharge roller pair 29 is sequentially stacked on the stack unit 30 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration and operation of the developing unit in the image forming unit will be described in more detail with reference to FIG.
The developing unit 5Y includes a developing roller 51Y that faces the photosensitive drum 1Y, a doctor blade 52Y that faces the developing roller 51Y, two transport screws 55Y disposed in the developer containing portions 53Y and 54Y, and a developer. The toner supply unit 58Y communicates with the storage unit 54Y through the opening, the density detection sensor 56Y that detects the toner density in the developer, and the like. The developing roller 51Y includes a magnet fixed inside, a sleeve rotating around the magnet, and the like. In the developer accommodating portions 53Y and 54Y, a two-component developer composed of a carrier and a toner is accommodated.

The developing unit 5Y configured as described above operates as follows.
The sleeve of the developing roller 51Y rotates in the direction of the arrow in FIG. The developer carried on the developing roller 51Y by the magnetic field formed by the magnet moves on the developing roller 51Y as the sleeve rotates.

  Here, the developer in the developing device 5Y is adjusted so that the toner ratio (toner concentration) in the developer is within a predetermined range. Specifically, according to toner consumption in the developing device 5Y, the toner contained in the toner bottle 32Y is replenished into the developer accommodating portion 54Y via the toner conveying pipe 43Y of the toner conveying portion 40Y and the toner replenishing portion 58Y. Is done.

  Thereafter, the toner replenished in the developer accommodating portion 54Y is circulated through the two developer accommodating portions 53Y and 54Y while being mixed and stirred together with the developer by the two conveying screws 55Y (in the direction perpendicular to the plane of FIG. 2). Move.). The toner in the developer is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller 51Y together with the carrier by the magnetic force formed on the developing roller 51Y.

  The developer carried on the developing roller 51Y is conveyed in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52Y. The developer on the developing roller 51Y is conveyed to a position facing the photosensitive drum 1Y (development area) after the developer amount is made appropriate at this position. The toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field formed in the development area. Thereafter, the developer remaining on the developing roller 51Y reaches above the developer containing portion 53Y as the sleeve rotates, and is detached from the developing roller 51Y at this position.

Next, the intermediate transfer device 15 (belt device) characteristic of the image forming apparatus according to the first embodiment will be described in detail with reference to FIG.
As shown in FIG. 3, the intermediate transfer device 15 as a belt device includes an intermediate transfer belt 8 as a belt member, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12, driven rollers 13 and 16, and an abutment. An elastic roller 14 (sponge roller) as a member, an intermediate transfer cleaning unit 10, a distance sensor 60 as a detection means, and the like.

The intermediate transfer belt 8 as a belt member is disposed so as to face the photosensitive drums 1Y, 1M, 1C, and 1K as four image carriers that respectively carry toner images of respective colors. The intermediate transfer belt 8 is stretched and supported mainly by four roller members (the driving roller 12, the driven rollers 13, 16 and the elastic roller 14).
The transfer rollers 9Y, 9M, 9C, and 9K are opposed to the corresponding photosensitive drums 1Y, 1M, 1C, and 1K through the intermediate transfer belt 8, respectively. More specifically, the yellow transfer roller 9Y faces the yellow photosensitive drum 1Y via the intermediate transfer belt 8, and the magenta transfer roller 9M contacts the magenta photosensitive drum 1M via the intermediate transfer belt 8. The cyan transfer roller 9C faces the cyan photosensitive drum 1C via the intermediate transfer belt 8, and the black transfer roller 9K faces the black photosensitive drum 1K via the intermediate transfer belt 8. Opposite.

Here, the elastic roller 14 as an abutting member is formed by forming an elastic layer of fluoro rubber, silicone rubber, foamable silicone rubber or the like on a core metal, and abuts against the intermediate transfer belt 8 to perform intermediate transfer. Tension is applied to the belt 8. The elastic roller 14 is fixed so that the relative position in the intermediate transfer device 15 is not displaced. Specifically, both ends of the elastic roller 14 are fixed to the case of the intermediate transfer device 15 via a bearing.
The elastic roller 14 is formed to be deformable so that the tension of the intermediate transfer belt 8 does not fluctuate. That is, when the tension of the intermediate transfer belt 8 increases, the elastic layer of the elastic roller 14 is deformed (crushed), and the intermediate transfer belt 8 is displaced as shown by the broken line in FIG. (Tension fluctuation is reduced.) On the other hand, when the tension of the intermediate transfer belt 8 is reduced, the elastic layer of the elastic roller 14 is deformed (restored) in the direction of swelling, and the tension of the intermediate transfer belt 8 is restored. As described above, the elastic roller 14 is not displaced according to the fluctuation of the tension of the intermediate transfer belt 8 but is deformed, so that a highly responsive tension adjustment can be performed. The material (characteristic values such as hardness and elastic coefficient) of the elastic layer of the elastic roller 14 is preferably selected in accordance with the tension of the intermediate transfer belt 8 and the like.

Specifically, when the recording medium P is sent (or sent) to the secondary transfer nip (between the intermediate transfer belt 8 and the secondary transfer roller 19), a sudden and sudden load is applied to the belt device. Variations occur. Such load fluctuations are high-frequency, and thereby high-frequency tension fluctuations occur in the intermediate transfer belt 8. When the tension variation of the intermediate transfer belt 8 occurs in this way, shock jitter (image distortion) occurs on the image transferred onto the intermediate transfer belt 8 in the primary transfer nip.
This high-frequency tension fluctuation cannot be sufficiently absorbed by a tension roller that applies a tension to the belt member by being displaced by being biased by a spring or the like. That is, since the tension roller has a certain amount of mass, inertia occurs and it cannot be displaced by quickly responding to and following high-frequency tension fluctuations.
On the other hand, in the first embodiment, the elastic roller 14 (contact member) is deformed by quickly responding and following the high-frequency tension fluctuation of the intermediate transfer belt 8 with almost no inertia, and the tension fluctuation. Therefore, the occurrence of the above-mentioned shock jitter (image distortion) can be suppressed.

In the first embodiment, a distance sensor 60 (detection means for detecting deformation (displacement of the intermediate transfer belt 8) of the elastic roller 14 at a position facing the elastic roller 14 with the intermediate transfer belt 8 interposed therebetween. Displacement sensor) is installed. As the distance sensor 60, a laser displacement meter or the like can be used.
Based on the detection result of the distance sensor 60 (the amount of deformation of the elastic roller 14), the driving speed (traveling speed) of the intermediate transfer belt 8 is varied. Specifically, a drive motor (not shown) that rotates the drive roller 12 is feedback-controlled based on the detection result of the distance sensor 60. Specifically, as indicated by the broken line in FIG. 3, when the elastic roller 14 is deformed (smaller in diameter) than normal, the distance sensor 60 detects the state and the recording medium P is placed in the secondary transfer nip. As a result, the load on the drive motor that drives the drive roller 12 suddenly increases and the drive speed decreases, and control is performed to increase the drive speed of the drive motor.
By performing such control, the tension fluctuation of the intermediate transfer belt 8 is further reduced, and the occurrence of shock jitter can be reliably suppressed.

Further, in addition to the variable control of the driving speed of the intermediate transfer belt 8 based on the detection result of the distance sensor 60, the driving speed of the secondary transfer roller 19 as the opposing member based on the detection result of the distance sensor 60 ( The number of revolutions) can also be variably controlled. Specifically, when the driving speed of the intermediate transfer belt 8 is varied based on the detection result of the distance sensor 60, a linear speed difference between the intermediate transfer belt 8 and the secondary transfer roller 19 does not occur in the secondary transfer nip. In addition, the drive speed of the secondary transfer roller 19 is also variably controlled.
As a result, it is possible to suppress a problem that a transfer failure such as a transfer shift occurs on the recording medium P in the secondary transfer process.

  As described above, in the first embodiment, the elastic roller 14 (contact member) that abuts against the intermediate transfer belt 8 (belt member) and applies tension is displaced in the relative position in the intermediate transfer device 15. The intermediate transfer belt 8 is configured to be deformable so that the tension of the intermediate transfer belt 8 does not fluctuate. As a result, shock jitter is generated on the image even if a sudden load fluctuation occurs in the intermediate transfer device 15 without increasing the cost, weight, and size of the intermediate transfer device 15 with a relatively simple configuration. Can be deterred.

  In the first embodiment, the elastic roller 14 as the contact member is disposed in the vicinity of the driving roller 12 and upstream of the driving roller 12 in the belt driving direction (traveling direction). On the other hand, the elastic roller 14 can be disposed downstream of the driving roller 12 in the belt driving direction. Even in this case, the same effect as in the first embodiment can be obtained.

Embodiment 2. FIG.
The second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 4 is a configuration diagram illustrating the belt device 15 according to the second embodiment, and corresponds to FIG. 3 according to the first embodiment. The belt device according to the second embodiment is different from that of the first embodiment in that a non-rotating member is used as the contact member 65.

As shown in FIG. 4, the intermediate transfer device 15 (belt device) in the second embodiment is also similar to that in the first embodiment, the intermediate transfer belt 8 (belt member), and the four transfer rollers 9Y and 9M. , 9C, 9K, driving roller 12, driven rollers 13, 16, contact member 65, intermediate transfer cleaning unit 10, distance sensor 60 (detecting means), and the like.
Here, the contact member 65 according to the second embodiment is a non-rotating member including a sliding contact portion 65a that is in sliding contact with the intermediate transfer belt 8 and a support portion 65b that supports the sliding contact portion 65a. Specifically, a sliding contact portion 65a made of a resin material having a low friction coefficient is installed at one end of a support member 65b formed of sheet metal or the like, and the other end of the support member 65b is fixed to a case of the intermediate transfer device 15. Yes. The contact member 65 is in contact with the intermediate transfer belt 8 and applies tension to the intermediate transfer belt 8. At this time, since the sliding contact portion 65a is formed of a material having a low friction coefficient, wear of the intermediate transfer belt 8 can be reduced.

The sliding portion 65a of the contact member 65 is made of an elastic material and is formed so as to be deformable so that the tension of the intermediate transfer belt 8 does not fluctuate. That is, when the tension of the intermediate transfer belt 8 is increased, the sliding portion 65a is deformed (crushed), and the intermediate transfer belt 8 is displaced and the tension is reduced (variation in tension is reduced). . As described above, the contact member 65 (sliding portion 65a) itself is deformed in accordance with the fluctuation of the tension of the intermediate transfer belt 8, so that a highly responsive tension adjustment can be performed.
Thus, even if a high-frequency tension fluctuation occurs in the intermediate transfer belt 8 due to a sudden load fluctuation, the contact member 65 is deformed and absorbs the tension fluctuation, so that the occurrence of shock jitter on the image can be suppressed. it can.

  In the second embodiment, the sliding portion 65a of the contact member 65 is formed to be deformed in accordance with the tension fluctuation of the intermediate transfer belt 8. However, the support portion 65b of the contact member 65 is made of a leaf spring member or the like. It is also possible to form the support portion 65b so as to be deformed as the tension of the intermediate transfer belt 8 changes. Furthermore, the sliding part 65a and the support part 65b can be integrally formed of the same material.

  As described above, also in the second embodiment, as in the first embodiment, the abutting member 65 that abuts on the intermediate transfer belt 8 (belt member) and applies tension is a relative force in the intermediate transfer device 15. In addition to being fixed so as not to displace, the intermediate transfer belt 8 is formed to be deformable so that the tension of the intermediate transfer belt 8 does not fluctuate. As a result, shock jitter is generated on the image even if a sudden load fluctuation occurs in the intermediate transfer device 15 without increasing the cost, weight, and size of the intermediate transfer device 15 with a relatively simple configuration. Can be deterred.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a configuration diagram illustrating the belt device 15 according to the third embodiment. The belt device according to the third embodiment is different from that of the first embodiment which is an intermediate transfer device in that it is a transfer fixing device. Further, the belt device in the third embodiment is different from that in the first embodiment in the control method by the detecting means 60A and 60B.

In the image forming apparatus according to the third embodiment, as shown in FIG. 5, a transfer fixing device 70 as a belt device is installed between the intermediate transfer device 15 and the secondary transfer roller 19.
The transfer fixing device 70 as a belt device includes a transfer fixing belt 71 as a belt member, a driving roller 73, a driven roller 72, two elastic rollers 14A and 14B as contact members, a heater 75 as a heating means, and a detection means. Distance sensors 60A, 60B, etc.

Here, the transfer fixing belt 71 as a belt member is stretched and supported mainly by four roller members (the driving roller 12, the driven roller 13, and the elastic rollers 14A and 14B). The transfer and fixing belt 71 is an endless belt in which an elastic layer and a release layer are sequentially formed on a base material, and forms a fixing nip (secondary transfer nip) by contacting a secondary transfer roller 19 as an opposing member. To do.
As in the first embodiment, the elastic rollers 14A and 14B as the contact members are formed by forming an elastic layer on the core metal, and contact the transfer fixing belt 71 to transfer the fixing belt 71. The tension is given to. The elastic rollers 14A and 14B are fixed so that the relative positions in the transfer and fixing device 70 are not displaced. The elastic rollers 14A and 14B are formed to be deformable so that the tension of the transfer and fixing belt 71 does not fluctuate. As described above, the elastic rollers 14A and 14B themselves are deformed according to the fluctuation of the tension of the transfer and fixing belt 71, so that a highly responsive tension adjustment can be performed.
As a result, even if a high-frequency tension fluctuation occurs in the transfer and fixing belt 71 due to a sudden load fluctuation, the elastic rollers 14A and 14B are deformed to absorb the tension fluctuation, thereby preventing the occurrence of shock jitter on the image. Can do.

  The heater 75 as a heating means is a halogen heater, and both ends thereof are fixed to a case of the transfer fixing device. The transfer fixing belt 71 is heated by the heater 75 whose output is controlled by the power supply unit (AC power supply) of the apparatus main body, and the toner image (the toner image transferred from the intermediate transfer belt 8) on the transfer fixing belt 71 is heated from the surface. Is heated. The output control of the heater 75 is performed based on the detection result of the belt surface temperature by a temperature sensor (not shown) that contacts the surface of the transfer fixing belt 71. By such output control of the heater 75, the temperature (fixing temperature) of the transfer fixing belt 71 can be adjusted and controlled to a desired temperature (target control temperature).

The transfer fixing device 70 configured as described above operates as follows.
The surface of the intermediate transfer belt 8 onto which the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are superimposed and transferred through the same image forming process as in the first embodiment travels in the direction of the arrow in the figure. Then, it reaches the position facing the transfer fixing belt 71. Then, the full color image on the intermediate transfer belt 8 is transferred onto the transfer fixing belt 71.

  The surface of the transfer and fixing belt 71 carrying the toner image transferred from the intermediate transfer belt 8 travels in the direction of the arrow in FIG. 5 and reaches a contact position (a fixing nip) with the secondary transfer roller 19. Here, the transfer and fixing belt 71 is heated by the opposed heater 75, and the toner image carried on the transfer and fixing belt 71 is heated and melted. Then, at the fixing nip between the transfer fixing belt 71 and the secondary transfer roller 19, the toner image (full color image) carried on the transfer fixing belt 71 is transferred to the recording medium P and fixed (transfer and fixing). At the same time).

Here, the recording medium P at the position of the transfer and fixing device 70 is conveyed from the paper supply unit 26 via the registration roller pair 28 and the like.
Specifically, the transfer paper P fed from the paper feeding unit 26 that stores the recording medium P is guided to the registration roller pair 28 after passing through the transport path. The recording medium P that has reached the registration roller pair 28 is conveyed toward the fixing nip in synchronization with the toner image on the transfer and fixing belt 71.
Thereafter, the recording medium P on which the full-color image is transferred and fixed is discharged as an output image outside the apparatus main body 100 by the discharge roller pair 29, and a series of image forming processes is completed.

Here, in the third embodiment, the elastic rollers 14A and 14B as the contact members are respectively provided on the upstream side in the driving direction and the downstream side in the driving direction of the driving roller 73 facing the secondary transfer roller 19 as the opposing member. It is arranged. That is, the first elastic roller 14 </ b> A is disposed on the upstream side in the driving direction of the driving roller 73, and the second elastic roller 14 </ b> B is disposed on the downstream side in the driving direction of the driving roller 73. Further, the two elastic rollers 14A and 14B are disposed in the vicinity of the fixing nip that is a source of load fluctuation.
As a result, the tension of the transfer / fixing belt 71 is fluctuated due to a sudden load change that occurs when the recording medium P is sent to / from the fixing nip (between the transfer / fixing belt 71 and the secondary transfer roller 19). Can be absorbed with higher responsiveness.

Specifically, when the recording medium P is fed into the fixing nip (particularly when thick paper is fed), a large load fluctuation occurs and the rotational speed of the drive roller 73 is momentarily decreased. At this time, since the belt tension on the downstream side in the driving direction of the driving roller 73 is increased, the fluctuation of the belt tension is instantaneously absorbed by the deformation of the second elastic roller 14B disposed in the vicinity thereof. At this time, the detection result of the distance sensor 60B that detects the deformation of the second elastic roller 14B is sent to the control unit 80, and the drive unit 81 is configured so that the rotational speed of the drive roller 73 is increased based on the detection result. Since the feedback control is performed, fluctuations in the belt tension of the transfer fixing belt 71 are further reduced.
On the other hand, when the recording medium P is sent out from the fixing nip, a large load fluctuation occurs, and the rotation speed of the driving roller 73 increases momentarily. At this time, since the belt tension on the upstream side in the driving direction of the driving roller 73 becomes high, the fluctuation of the belt tension is instantaneously absorbed by the deformation of the first elastic roller 14A disposed in the vicinity thereof. At this time, feedback control is performed so that the rotational speed of the drive roller 73 becomes slow based on the detection result of the distance sensor 60A that detects the deformation of the first elastic roller 14A, and therefore fluctuations in belt tension are further reduced. It will be.

In the third embodiment, the operation timing of the registration roller pair 28 is detected, the control unit 80 obtains the timing when the recording medium P is sent to and sent from the fixing nip, and the driving roller 73 is based on the timing. The timing of feedback control is defined. Thereby, the effect mentioned above becomes further certainty.
The same control can be performed by separately providing a sensor for detecting the timing at which the recording medium P is fed into and sent out from the fixing nip.

Also in the transfer fixing device 70 according to the third embodiment, when the tension fluctuation of the transfer fixing belt 71 occurs, the shock image (when the toner image carried on the intermediate transfer belt 8 is transferred onto the transfer fixing belt 71) Image distortion) will occur.
In contrast, in the third embodiment, the elastic rollers 14A and 14B are deformed on both sides of the load fluctuation reduction and absorb the tension fluctuation by quickly responding and following the high-frequency tension fluctuation of the transfer fixing belt 71. Therefore, the occurrence of the above-mentioned shock jitter (image distortion) can be reliably suppressed.

  Further, in the third embodiment, the transfer fixing belt 71 has a speed difference with respect to the driving speed of the driving roller 12 (a driving roller of the intermediate transfer device 15) as a facing member facing the driven roller 72. , And the speed difference amount and forward / reverse are controlled in accordance with the timing at which the tension of the transfer fixing belt 71 fluctuates based on the detection results of the distance sensors 60A and 60B at that time.

Specifically, a speed difference is provided between the driving speed of the intermediate transfer device 15 and the driving speed of the transfer fixing device 70 so that the transfer fixing belt 71 is loosened downstream of the load fluctuation generation source in the transfer fixing device 70. Then, the timing at which the recording paper medium P enters the fixing nip is detected, and the speed difference is controlled so that the slack side of the transfer fixing belt 71 is reversed. As a result, when the recording medium P is fed into and sent out to the fixing nip, a part of the belt slack amount on the downstream side of the load fluctuation generation source (fixing nip) shifts to the upstream side, and very little tension ( Alternatively, the recording medium P passes through the fixing nip in a state where almost no tension is applied. Therefore, the fluctuation in tension of the transfer fixing belt 71 is not transmitted to the transfer nip (between the intermediate transfer device 15 and the transfer fixing device 70), and the occurrence of shock jitter can be reduced.
In performing such control, it is preferable that the circumferential length of the transfer and fixing belt 71 is set equal to or slightly longer than the geometric circumferential length determined by the position of each roller member and the roller diameter. As a result, the effect of blocking the tension fluctuation due to the slack of the belt described above is ensured.

  In general, when the tension of the belt member is low, surface undulation, belt deviation, and the like are likely to occur when the belt member travels. Therefore, in the third embodiment, when performing the above-described control, a certain amount of tension is applied to the transfer fixing belt 71 during normal operation to perform stable running, and the tension that fluctuates in accordance with the timing at which load fluctuation occurs is absorbed. This controls the tension and slack of the belt. As a result, the running stability of the transfer and fixing belt 71 is improved, and the tension fluctuation of the transfer and fixing belt 71 due to load fluctuations can be reduced, and an image with less shock jitter can be provided.

  As described above, in the third embodiment, the elastic rollers 14A and 14B (contact members) that contact and apply tension to the transfer fixing belt 71 (belt member) are positioned relative to each other in the transfer fixing device 70. Are fixed so as not to displace, and are formed so as to be deformable so that the tension of the transfer and fixing belt 71 does not fluctuate. As a result, shock jitter is generated on the image even if a sudden load fluctuation occurs in the transfer fixing device 70 without increasing the cost, weight, and size of the transfer fixing device 70 with a relatively simple configuration. Can be deterred.

In each of the above embodiments, the present invention is applied to the belt device using the intermediate transfer belt or the transfer fixing belt as a belt member. However, the present invention is applied to the belt device using the photosensitive belt or the transfer conveyance belt as a belt member. The present invention can be applied. Even in such a case, it is possible to suppress a problem when a high-frequency tension fluctuation of the belt member suddenly occurs.

  Further, the present invention is not limited to each of the above-described embodiments, and within the scope of the technical idea of the present invention, each of the above-described embodiments can be modified as appropriate other than suggested in each of the above-described embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus of FIG. 1. FIG. 2 is a configuration diagram illustrating a belt device installed in the image forming apparatus of FIG. 1. It is a block diagram which shows the belt apparatus in Embodiment 2 of this invention. It is a block diagram which shows the belt apparatus in Embodiment 3 of this invention.

Explanation of symbols

1Y, 1M, 1C, 1K photosensitive drum (image carrier),
8 Intermediate transfer belt (belt member),
9Y, 9M, 9C, 9K transfer roller,
14, 14A, 14B Elastic roller (contact member),
15 Intermediate transfer device (belt device),
19 Secondary transfer roller (opposing member),
60, 60A, 60B Distance sensor (detection means),
65 Contact member (non-rotating member),
65a sliding contact portion, 65b support portion,
70 Transfer fixing device (belt device),
71 transfer fixing belt (belt member),
75 heater (heating means),
100 Image forming apparatus body (apparatus body), P recording medium.

Claims (9)

A belt member stretched around a plurality of roller members;
An abutting member that abuts on the inner peripheral surface of the belt member and applies tension to the belt member;
With
The contact member is a non-rotating member composed of a sliding contact portion that is in sliding contact with the belt member and a support portion that supports the sliding contact portion,
The sliding contact portion is formed to be elastically deformable in accordance with fluctuations in the tension of the belt member caused by feeding or / and feeding the recording medium to the transfer nip of the apparatus ,
The belt device, wherein the belt member is an intermediate transfer belt onto which toner images carried on a plurality of image carriers are transferred in an overlapping manner . A belt member stretched around a plurality of roller members;
An abutting member that abuts on the inner peripheral surface of the belt member and applies tension to the belt member;
With
The contact member is a non-rotating member composed of a sliding contact portion that is in sliding contact with the belt member and a support portion that supports the sliding contact portion,
The sliding contact portion is formed to be elastically deformable in accordance with fluctuations in the tension of the belt member caused by feeding or / and feeding the recording medium to the transfer nip of the apparatus,
The belt device, wherein the belt member is a transfer fixing belt on which toner images carried on a plurality of image carriers are transferred in a superimposed manner and heated and melted by a heating unit. The belt device according to claim 1, wherein the support portion is formed to be deformable in accordance with a change in tension of the belt member. The belt device according to any one of claims 1 to 3, wherein the sliding contact portion is formed of a material having a low friction coefficient. A detecting means for detecting a deformation amount of the contact member;
The belt device according to any one of claims 1 to 4, wherein a driving speed of the belt member is variable based on a detection result of the detection means. 6. The driving speed of an opposing member that faces one of the plurality of roller members via the belt member is varied based on a detection result of the detecting means. Belt device. One roller member of the plurality of roller members is opposed to the opposing member via the belt member,
The said contact member is each arrange | positioned by the drive direction upstream and the drive direction downstream of the said roller member which opposes the said opposing member, The Claim 1 characterized by the above-mentioned. Belt device. A detecting means for detecting a deformation amount of the contact member;
One roller member of the plurality of roller members is opposed to the opposing member via the belt member,
Based on the detection result of the detection means when the belt member is driven such that a speed difference is generated with respect to the driving speed of the facing member, the amount of the speed difference is adjusted in accordance with the timing at which the tension of the belt member varies. The belt device according to any one of claims 1 to 7, wherein forward and reverse are controlled. An image forming apparatus comprising the belt device according to claim 1.

Images