JP2005227509A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus of high image quality without any color slippage, etc., by suppressing load variation portion of an intermediate transfer belt occurring owing to a load member brought into contact with or separated from an intermediate transfer belt. <P>SOLUTION: The image forming apparatus is provided with one or two or more image carriers 1, an image forming means 2, an endless intermediate transfer belt 4 stretched on two or more stretching members 3 and made to be circulated and conveyed, and one or more load members 5 brought into contact with and separated from the intermediate transfer belt 4. The apparatus is provided with: a main driving means 7 applying main driving force 6 to the intermediate transfer belt 4 by making the intermediate transfer belt 4 follow and rotate in a position of contact with the image carrier 1 and the intermediate transfer belt 4 by rotating and driving the image carrier 1; and an auxiliary driving means 9 applying to the intermediate transfer belt 4 auxiliary driving force 8 which is more than the load variation portion of the intermediate transfer belt 4 due to contact and separation of the load member 5 to the intermediate transfer belt 4 and is smaller than the main driving force 6, by rotating and driving the intermediate transfer belt 4 in a portion other than the image carrier 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to an improvement of an image forming apparatus using an endless belt-shaped intermediate transfer member.

Conventionally, as an image forming apparatus of this type, for example, an intermediate transfer type image forming apparatus adopting an electrophotographic method is taken as an example. Each color component (for example, Y (yellow), M (magenta)) is provided on an image carrier such as a photoconductor. , C (cyan), K (black)) toner image is formed, and this is temporarily transferred (primary transfer) at the same location on the intermediate transfer member, and then this multiple toner image is applied to a sheet as a sheet. There is a type that performs batch transfer (secondary transfer).
In an embodiment using this type of intermediate transfer member, the toner images of the respective colors sequentially formed on the intermediate transfer member are configured to be superimposed. Therefore, it is necessary to superimpose the color toner images on the intermediate transfer member with high accuracy.
Further, as this type of intermediate transfer member, a belt-like one is frequently used because of the high degree of freedom of layout in the apparatus and the small occupied area.

The intermediate transfer belt is stretched around a plurality of stretching rolls, and circulates and conveys a multiple transfer toner image. The intermediate transfer belt, which varies in angular velocity of the photosensitive member due to eccentricity of various gears, the photosensitive member and the tensioning belt. Variations in the surface speed of the photosensitive member and the intermediate transfer belt occur due to the swing of the roll. The speed fluctuation between the photosensitive member and the intermediate transfer belt causes a surface slip between the two and further expansion and contraction of the intermediate transfer belt itself, resulting in a color shift of the multiple transfer toner image.
In particular, in the case of a multi-pass (4-cycle) image forming method in which multiple transfer is performed on an intermediate transfer belt, the secondary transfer member and the cleaning member are usually brought into contact with or separated from the intermediate transfer belt during image formation. For this reason, load fluctuations on the intermediate transfer belt occur, and color misregistration due to this occurs.

  In order to solve such problems, the photosensitive member and the intermediate transfer belt are driven by the same drive source, the surface speed of the intermediate transfer belt is detected, and a latent image is not formed on the photosensitive member or transfer is performed. There have been proposed methods such as increasing / decreasing the speed of the intermediate transfer belt or correcting the operation timing of the exposure apparatus when not being noticed (see, for example, Patent Document 1).

JP 2000-298389 A (column of embodiment of the invention, FIG. 2)

However, in such a technique, there is no problem with respect to load fluctuations on the intermediate transfer belt due to contact / separation of a load member such as a secondary transfer member or a cleaning member that is a load on the intermediate transfer belt during image formation. However, when the load member comes into contact with or separates from the intermediate transfer belt, the speed fluctuation of the intermediate transfer belt occurs. Therefore, in the above-mentioned Patent Document 1 and the like, the color misregistration due to these load fluctuations is not solved. Further, when the intermediate transfer belt is made of an elastic material, expansion and contraction of the intermediate transfer belt due to the above-described load fluctuation also promotes color misregistration.
The present invention is for solving the above-described technical problems, and suppresses a load fluctuation of the intermediate transfer belt caused by a load member that comes in contact with and separates from the intermediate transfer belt. A forming apparatus is provided.

  That is, as shown in FIG. 1, the present invention includes one or a plurality of image carriers 1 on which an image is maintained, an image forming means 2 for producing an image on the image carrier 1, and an image carrier 1 An image provided with an endless intermediate transfer belt 4 that is arranged opposite to each other and is circulated and conveyed by a plurality of stretching members 3, and one or a plurality of load members 5 that are in contact with and away from the intermediate transfer belt 4. In the forming apparatus, by rotating the image carrier 1, the intermediate transfer belt 4 is driven at the contact portion between the image carrier 1 and the intermediate transfer belt 4, and a main driving force 6 is applied to the intermediate transfer belt 4. The intermediate transfer belt 4 is driven to rotate at a portion other than the main driving means 7 and the image carrier 1 to be equal to or more than the load fluctuation of the intermediate transfer belt 4 due to the contact and separation of the load member 5 with respect to the intermediate transfer belt 4. And less than the main driving force 6 It is characterized in that an auxiliary driving means 9 for applying a driving force 8 to the intermediate transfer belt 4.

In such technical means, the present invention includes a multi-pass method (4 cycles), a tandem method, and a dual tandem method, and prevents color misregistration against load fluctuations and belt speed fluctuations on the intermediate transfer belt 4. The present invention relates to an improvement of an image forming apparatus which can be made.
The image carrier 1 may be either a drum shape or a belt shape as long as the intermediate transfer belt 4 is driven by the image carrier 1. In this case, it does not matter whether or not the intermediate transfer belt 4 overlaps with the image carrier 1, but in order to efficiently perform the driven system, an overlapping mode is preferable.
Further, the intermediate transfer belt 4 may be an elastic belt or a rigid belt, but from the viewpoint of efficiently transferring the toner image on the image carrier 1 onto the intermediate transfer belt 4, the Young's modulus is used. Is preferably an elastic belt provided with an elastic layer of 30 MPa or less, and from the viewpoint of ensuring cleanliness against dirt on the surface of the intermediate transfer belt 4, a multilayer structure in which a release layer is laminated on the surface of this elastic layer It is preferable that

  Examples of the load member 5 include a secondary transfer member, a cleaning member, and the like. Further, the load member 5 may be rotated like a roll or a brush. Even if it is a mode which does not rotate like this, it does not interfere. Then, the aspect in which the load member 5 rotates may be an aspect in which the load member 5 itself rotates or an aspect in which the load member 5 is rotated by the intermediate transfer belt 4.

Here, the following requirements are required as the auxiliary driving force 8 in the present invention.
a. Must be less than main driving force 6.
b. It must be greater than or equal to the load fluctuation accompanying the contact and separation of the load member 5.
The requirement a indicates that the main driving force 6 is dominant in moving the intermediate transfer belt 4. In this state, when an auxiliary driving force 8 smaller than the main driving force 6 is applied to the intermediate transfer belt 4, the auxiliary driving force 8 does not substantially act in a no-load state where the load by the load member 5 does not act. Therefore, the driving force of the intermediate transfer belt 4 does not increase to the main driving force 6 or more. Further, when a load due to the contact of the load member 5 is applied, the auxiliary driving force 8 acts on the intermediate transfer belt 4 by an amount corresponding to the load, so that the intermediate driving belt 6 has a main driving force 6 applied thereto. The corresponding driving force always works.
On the other hand, the requirement b requires an auxiliary driving force 8 that is equal to or greater than the load fluctuation in order to cancel the load fluctuation due to the contact / separation of the load member 5, and if the auxiliary driving force 8 is less than the load fluctuation, the load This is based on the fact that the fluctuation cannot be canceled and the difference leads to the speed fluctuation error of the intermediate transfer belt 4.

The main driving force 6 provided by the main driving means 7 on the image carrier 1 side in the present invention includes a plurality of image carriers 1 in the tandem system, for example, so the main driving force 6 is added up. Therefore, the auxiliary driving force 8 only needs to be smaller than the total value in this case.
When the load member 5 rotates in the same direction at the portion facing the intermediate transfer belt 4 and the surface speed is higher than the moving speed of the intermediate transfer belt 4, the load member 5 contacts the intermediate transfer belt 4. As a result, the moving speed of the intermediate transfer belt 4 may increase. Even in this case, the auxiliary driving force 8 acts in the negative direction so as to cancel the acceleration (acts as a braking force).

In particular, in the present invention, the drive transfer member 10 that transmits the auxiliary drive force 8 in contact with the intermediate transfer belt 4 includes the drive force member 8 from the auxiliary drive unit 9 easily. It is preferable from a viewpoint of transmitting to. At this time, the drive transmission member 10 is preferably a roll-like member from the viewpoint of driving the intermediate transfer belt 4, but is not limited thereto, and may be a belt-like member, for example.
Further, the drive transmission member 10 is an opposing member that is disposed opposite to the load member 5 with the intermediate transfer belt 4 interposed therebetween, so that the auxiliary driving force 8 to the intermediate transfer belt 4 can be more stably applied. become. Furthermore, it is preferable that the drive transmission member 10 is the tension member 3 that stretches the intermediate transfer belt 4 from the viewpoint of reliably transmitting the auxiliary driving force 8 to the intermediate transfer belt 4. A typical embodiment of the tension member 3 includes a tension roll.

In the present invention, the number of drive transmission members 10 is not limited to one, and a plurality of drive transmission members 10 may be provided. For example, by arranging the drive transmission members 10 corresponding to all of the load members 5 contacting and separating from the intermediate transfer belt 4, The most effective mode can be constructed with respect to the load fluctuation due to the contact and separation of the member 5 with respect to the intermediate transfer belt 4.
Further, the auxiliary drive means 9 in the present invention includes an auxiliary drive source 11 for driving the drive transmission member 10, a detection means 12 for detecting the moving speed of the intermediate transfer belt 4, and auxiliary drive based on information from the detection means 12. It is preferable to provide auxiliary drive control means 13 for controlling the source 11. As a result, it is possible to control the speed of the intermediate transfer belt 4 so as to reduce the influence according to the load fluctuation of the intermediate transfer belt 4. For example, the auxiliary drive control unit 13 may control the main drive unit 7 together.
A typical example of the auxiliary drive source 11 in the present invention is a motor.
A typical embodiment of the detecting means 12 is composed of a mark provided on the back surface of the intermediate transfer belt 4 and a sensor for detecting this mark. At this time, the sensor may be installed at any location, but in particular, disposing the image carrier 1 upstream from the position where the image carrier 1 is in contact with the intermediate transfer belt 4 has an influence on the image formation with respect to the axial variation of the stretching member 3. It is preferable from a viewpoint of making it smaller. Furthermore, the mark only needs to be detected by a sensor, and the number of marks may be one or plural.
Then, for example, a profile similar to that at the time of image formation is performed in advance, and changes in the moving speed of the intermediate transfer belt 4 are collected from information from the detection means 12, and the auxiliary drive control means 13 is controlled based on this information at the time of image formation. For example, the auxiliary drive source 11 may be controlled via, for example, a plurality of marks may be provided to collect more detailed information from the detection means 12 and be controlled in real time.
Furthermore, the auxiliary drive means 9 may be provided with a torque limiter between the auxiliary drive source 11 and the drive transmission member 10. For example, when the speed of the intermediate transfer belt 4 decreases, an auxiliary drive force 8 by the auxiliary drive means 9 is provided. Can be easily actuated, and a reduction in the speed of the intermediate transfer belt 4 can be suppressed. The torque limiter may be disposed on the drive transmission member 10 side to restrict the driving force of the auxiliary drive source 11, or may be mounted on the auxiliary drive source 11 side and regulated. Alternatively, the drive transmission member 10 may be driven.

According to the present invention, in addition to the main drive means for driving the intermediate transfer belt at the contact portion between the image carrier and the intermediate transfer belt and applying the main driving force to the intermediate transfer belt, Since there is provided auxiliary drive means that applies to the intermediate transfer belt an auxiliary drive force that is equal to or greater than the load fluctuation of the intermediate transfer belt due to contact and separation of the members and is smaller than the main drive force, load on the secondary transfer member, cleaning member, etc. It is possible to correct the speed fluctuation and expansion / contraction of the intermediate transfer belt caused by the contact and separation of the member with the intermediate transfer belt, and to prevent color misregistration of each color.
The same effect can be obtained also when the intermediate transfer belt is a soft elastic belt.
Therefore, it is possible to provide an image forming apparatus that suppresses color misregistration over a long period of time.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the present invention is applied.
In the figure, an image forming apparatus includes a photosensitive drum 20 and an intermediate transfer belt 30 disposed opposite to the photosensitive drum 20 for transferring a toner image from the photosensitive drum 20 in an apparatus main body 50. And a so-called four-cycle intermediate transfer type image forming apparatus that performs four times of multiple transfers on the intermediate transfer belt 30 in order to obtain four color images.
In this embodiment, the photosensitive drum 20 is provided with a photosensitive layer whose resistance value is reduced by light irradiation, and a toner image is formed on the photosensitive drum 20 around the photosensitive drum 20. Various devices are arranged as image forming means. That is, a charging device 21 that charges the photosensitive drum 20 and each color component (in this example, yellow (Y), magenta (M), cyan (C), and black (K)) on the charged photosensitive drum 20. An exposure device 22 that writes an electrostatic latent image, a rotary developing device 23 that visualizes each color component latent image formed on the photosensitive drum 20 with each color component toner, and residual toner on the photosensitive drum 20 And a cleaning device 24 for cleaning.

Here, as the charging device 21, for example, a charging roll is used, but a charging device such as a corotron may be used.
The exposure device 22 may be any device that can write an image on the photosensitive drum 20 with light. In this example, for example, a print head using an LED is used, but the present invention is not limited to this, and a print head using an EL. However, a scanner that scans a laser beam with a polygon mirror may be selected as appropriate.
Further, the rotary type developing device 23 is rotatably mounted with developing units 23a to 23d containing respective color component toners. For example, the respective color component toners are attached to a portion where the potential is lowered by exposure on the photosensitive drum 20. The toner to be used is not particularly limited in shape and particle size, and any toner may be used as long as it is accurately placed on the electrostatic latent image on the photosensitive drum 20. In this example, the rotary developing device 23 is used, but four developing devices may be used.
Furthermore, the cleaning device 24 may be selected as appropriate so long as the toner remaining on the photosensitive drum 20 is cleaned, such as a blade cleaning method. However, there may be a mode in which the cleaning device 24 is not used when toner having a high transfer rate is used.

Further, the intermediate transfer belt 30 is stretched around three stretching rolls 31 to 33, and is driven by the rotation of the photosensitive drum 20 so as to circulate.
Here, the intermediate transfer belt 30 may be appropriately selected from resin materials such as polyimide and polycarbonate resin. However, in order to effectively suppress image quality defects such as holocharacter, the contact surface pressure with the photosensitive drum 20 is lowered. In view of the viewpoint of walkless and tensionerless, it is preferable to use a rubber belt material having an elastic rubber as a base (an elastic layer having a Young's modulus of 30 MPa or less).
Therefore, as the intermediate transfer belt 30 in the present embodiment, silicone rubber, NBR, H-NBR, CR, EPDM are used as the main base material of the conductive elastic layer having a volume resistivity of 10 ⁶ to 10 ¹⁴ Ω · cm. Urethane rubber or the like is used, and a structure in which a release layer is laminated on the elastic layer is used. The material of the release layer is not particularly limited as long as it can achieve the objectives of reducing frictional resistance, stability of electrical characteristics to the environment, and improvement of residual toner cleaning performance by reducing surface roughness. Fluororesin polymers such as fluoroethylene (PTFE), copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA), PVdF, alcohol-soluble nylon, silicone resin, silane coupler, urethane resin emulsions and organic A paint dissolved and dispersed in a solvent can be used. The release layer can be provided with the above-mentioned paint by dip coating, spray coating, electrostatic coating, roll coating or the like. Further, by subjecting the release layer to surface treatment or polishing, it is possible to further improve release properties, conductivity, wear resistance, surface cleaning properties, and the like.

Further, in the present embodiment, a primary transfer roll 34 as a primary transfer member from the back surface side of the intermediate transfer belt 30 is connected to the photosensitive drum 20 and the intermediate transfer belt at a portion facing the photosensitive drum 20 of the intermediate transfer belt 30. It is disposed on the downstream side in the nip range with the belt 30. For this reason, it is possible to reduce the influence of discharge or the like due to the primary transfer bias, and to obtain an image quality without a holocharacter.
Furthermore, a secondary transfer roll 35 as a secondary transfer member is disposed opposite to the tension roll 32 of the intermediate transfer belt 30 with the tension roll 32 as a backup roll, for example, secondary transfer. A predetermined secondary transfer bias is applied to the roll 35, and the stretching roll 32 that also serves as a backup roll is grounded. In addition, a cleaning roll 36 is detachably disposed at a portion facing the stretching roll 33 via the intermediate transfer belt 30, and is in contact with the intermediate transfer belt 30 at the time of cleaning and what is the moving direction of the intermediate transfer belt 30? Rotating in the reverse direction cleans residual toner on the intermediate transfer belt 30. Therefore, in the present embodiment, the tension roll 33 is a drive transmission member, and the secondary transfer roll 35 and the cleaning roll 36 are load members for the intermediate transfer belt 30.

  Further, in the present embodiment, the sheet 40 as a recording material is accommodated in a supply tray (not shown), and is supplied by a feed roll 41 and then guided to a secondary transfer site through a resist roll 42. Then, the toner is conveyed to the fixing device 45 via the conveying belt 43, and then accommodated in a discharge tray 48 formed on the upper portion of the apparatus main body 50 via a conveying roll 46 and a discharge roll 47.

Here, the main drive device 80 provided on the photosensitive drum 20 side and the auxiliary drive device 90 provided on the intermediate transfer belt 30 side, which are characteristic points of the present case, are configured as shown in FIG.
The main drive device 80 includes a drum gear 81 provided at the end of the photosensitive drum 20, an intermediate gear 82 that meshes with the drum gear 81, and a drive motor 83 as a main drive source that includes a motor gear 84 that meshes with the intermediate gear 82. It is configured. For this reason, the photosensitive drum 20 is rotated by the rotation of the driving motor 83, and the rotation of the photosensitive drum 20 acts as a main driving force for driving the intermediate transfer belt 30.
On the other hand, the auxiliary drive device 90 is provided on the back surface of the intermediate transfer belt 30 with an auxiliary drive motor 91 as an auxiliary drive source for driving the tension roll 33, the auxiliary roll 33, and the intermediate transfer belt 30. A mark 92 having a surface, a mark sensor 93 that detects the mark 92, and a control device 100 that controls the auxiliary drive motor 91 based on information from the mark sensor 93. The mark sensor 93 is disposed between the stretching roll 31 and the primary transfer roll 34. Therefore, by controlling the auxiliary drive motor 91 by the control device 100, the tension roll 33 is driven and controlled, and an auxiliary drive force is applied to the intermediate transfer belt 30. In particular, in the present embodiment, the auxiliary driving force is set to be smaller than the main driving force.

Further, the control device 100 according to the present embodiment controls the auxiliary drive motor 91 according to a control flow as shown in FIG.
First, the belt position of the intermediate transfer belt 30 is detected based on information from the mark sensor 93 that detects the mark 92 on the back surface of the intermediate transfer belt 30 (step S1).
Next, based on this information, the speed of the intermediate transfer belt 30 is calculated by the calculation unit (step S2). At this time, the load member (corresponding to the secondary transfer roll 35 and the cleaning roll 36 in the present embodiment) is compared with the average speed of the intermediate transfer belt 30 when it is separated from the intermediate transfer belt 30, A correct correction amount is calculated.
Then, the auxiliary drive motor 91 of the auxiliary drive source is controlled based on the calculated correction amount (step S3).
In the present embodiment, the control flow described above is operated, for example, at the initial time of the image forming apparatus, and the state where the load member is not in contact with the state when the load member is in contact is compared. The appropriate auxiliary driving force is determined in advance. In subsequent image formation, for example, the auxiliary drive motor 91 is controlled based on the timing at which the load member contacts and separates from the intermediate transfer belt 30.

Next, the operation of the image forming apparatus according to the present embodiment will be described.
In the present embodiment, the respective color component toner images are sequentially formed on the photosensitive drum 20, transferred to the intermediate transfer belt 30 through the contact area (primary transfer area), and then the sheet 40 at the secondary transfer position. It is batch-transferred on the top.
In the present embodiment, the intermediate transfer belt 30 receives the main driving force from the driving motor 83, and the auxiliary driving force from the auxiliary driving motor 91 is smaller than the main driving force. When the load member such as 35 or the cleaning roll 36 is not in contact, the intermediate transfer belt 30 slips between the tension roll 33 and the intermediate transfer belt 30 that apply an auxiliary driving force to the intermediate transfer belt 30, and the moving speed of the intermediate transfer belt 30 is as follows. It is done by the main driving force.
In such an image forming process, when a load member such as the secondary transfer roll 35 or the cleaning roll 36 comes into contact with the intermediate transfer belt 30, a force is generated on the surface of the intermediate transfer belt 30 to prevent the belt from moving. At this time, the intermediate transfer belt 30 receives the auxiliary driving force by the driving force from the auxiliary driving motor 91 connected to the stretching roll 33 so that the intermediate transfer belt 30 is always conveyed constantly. Therefore, the amount obtained by subtracting the auxiliary driving force from the load applied by the secondary transfer roll 35 or the cleaning roll 36 corresponds to the speed fluctuation that affects the speed fluctuation of the intermediate transfer belt 30.
In general, these load members are often roll-shaped or brush-shaped rotating bodies, and the load due to these is sufficiently smaller than the auxiliary drive force. In this case, the influence of the load member on and away from the intermediate transfer belt 30 can be greatly reduced.

Further, if the load member itself is provided with a driving force (or a rotational force when the load member is a roll), and the surface speed of the load member is higher than the surface speed of the intermediate transfer belt 30, the load member is subjected to intermediate transfer. By contacting the belt 30, the surface speed of the intermediate transfer belt 30 becomes higher. However, even in this case, if the driving force of the load member is smaller than the auxiliary driving force, the influence of the load can be reduced as in the case described above.
Further, the control on the intermediate transfer belt 30 can be further reduced by controlling the auxiliary drive force to be slightly slower.

Further, the surface speed of the intermediate transfer belt 30 affected by the auxiliary driving force is periodically changed due to eccentricity of a gear or the like that transmits the auxiliary driving force from the auxiliary driving motor 91 or eccentricity of the stretching rolls 31 to 33 or the like. Speed fluctuation occurs.
Here, assuming that the intermediate transfer belt 30 is driven with an auxiliary driving force equal to that of the main driving force, the intermediate transfer belt 30 is subjected to expansion / contraction or push / pull force, and as a result. Periodic slip occurs in the nip region between the photosensitive drum 20 and the intermediate transfer belt 30 which is the transmission region of the main driving force. This corresponds to slipping between the photosensitive drum 20 and the intermediate transfer belt 30, and image disturbance on the intermediate transfer belt 30 occurs. Therefore, in order to prevent such image defects, it is necessary to make the auxiliary driving force smaller than the main driving force.
As a method of reducing the auxiliary driving force, the winding angle between the tension roll 33 and the intermediate transfer belt 30 that transmits the auxiliary driving force is reduced, or the surface friction coefficient of the tension roll 33 is set to the photosensitive drum. There are, for example, smaller than 20 surfaces.
In this embodiment, since the auxiliary driving force is smaller than the main driving force, such image defects can be suppressed.

  On the other hand, if the surface speed of the intermediate transfer belt 30 due to the auxiliary driving force is substantially equal to the surface speed of the intermediate transfer belt 30 due to the main driving force, the speed fluctuation of the intermediate transfer belt 30 due to the contact and separation of the load member. Can be almost eliminated. In this case, the average surface speed of the intermediate transfer belt 30 per round with only the main driving force is obtained, and the auxiliary driving motor 91 is controlled to match the average surface speed of the intermediate transfer belt 30 when the auxiliary driving force is applied. That's fine.

Further, as another method for reducing the auxiliary driving force, it can be easily realized by using a torque suppressing means (for example, a torque limiter) between the auxiliary driving motor 91 and the tension roll 33. FIG. 5 shows a configuration in which a torque limiter 94 is disposed on the tension roll 33 side. In this case, the torque limiter 94 is connected to the rotary shaft 95 of the auxiliary drive motor 91 and is regulated by the torque limiter 94. What is necessary is just to give the drive force which it had to the tension roll 33. FIG. For example, the torque limiter 94 may be provided inside the tension roll 33 or may be provided on the auxiliary drive motor 91 side.
At this time, for example, the driving force from the auxiliary driving motor 91 is absorbed by always sliding the torque limiter 94, and the tension roll 33 is driven to rotate only by the main driving force. For example, when the cleaning roll 36 comes into contact with the intermediate transfer belt 30, a force greater than the threshold value of the torque limiter 94 acts on the torque limiter 94, and the torque limiter 94 stops sliding. Therefore, the driving force from the auxiliary drive motor 91 is directly applied to the intermediate transfer belt 30, and the load fluctuation due to the cleaning roll 36 can be canceled.

In the present embodiment, the auxiliary drive motor 91 as the auxiliary drive source is provided only in the tension roll 33 that faces the cleaning roll 36. However, the auxiliary drive motor 91 is provided corresponding to each load member. It is better to prepare. In this case, it is possible to cope more closely with the contact and separation of the load member with respect to the intermediate transfer belt 30, and the speed fluctuation of the intermediate transfer belt 30 is further reduced.
Furthermore, as shown in FIG. 6, the auxiliary transfer motor 91 (specifically 91a, 91b) is provided on the stretching rolls 32, 33 facing both the secondary transfer roll 35 and the cleaning roll 36, thereby enabling intermediate transfer. It is possible to further reduce the influence of load members that contact and separate from the belt 30 (corresponding to the secondary transfer roll 35 and the cleaning roll 36 in the present embodiment).
In this case, the two auxiliary drive motors 91a and 91b may be controlled by the same control device 100.

Embodiment 2
FIG. 7 shows a main part of the second embodiment of the image forming apparatus to which the present invention is applied.
The basic configuration of the image forming apparatus according to the present embodiment is substantially the same as that of the first embodiment, but is different from the first embodiment in that the intermediate transfer belt 30 does not overlap the photosensitive drum 20. Components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted here.
Also in this embodiment, since the intermediate transfer belt 30 is driven by the photosensitive drum 20 as in the first embodiment, the speed fluctuation of the intermediate transfer belt 30 due to the auxiliary driving force is suppressed. Color shift can be suppressed.

Embodiment 3
FIG. 8 shows Embodiment 3 of the image forming apparatus to which the present invention is applied.
The image forming apparatus in the present embodiment is a tandem type color image forming apparatus, and each color component toner of four colors (in this embodiment, Y (yellow), M (magenta), C (cyan), K (black)). Four image forming units 51 (specifically 51 a to 51 d) for forming an image are arranged in parallel, and each color component toner image formed by the image forming unit 51 is placed on the intermediate transfer belt 60 on the primary transfer roll 53. (Specifically, 53a to 53d) sequentially perform primary transfer, and secondary transfer of each color component toner image on the intermediate transfer belt 60 onto a recording sheet at a secondary transfer site (specifically, secondary transfer roll 65). The recording sheet is guided to a fixing device (not shown).

Each image forming unit 51 has a photosensitive drum 52 (specifically, 52a to 52d), and a charging roll (not shown) that charges the photosensitive drum 52 around the photosensitive drum 52. A laser exposure device (not shown) for writing an electrostatic latent image on the photosensitive drum 52; and a developing device (not shown) that stores each color component toner and visualizes the electrostatic latent image on the photosensitive drum 52. 1), a primary transfer roll 53 for transferring each color component toner image on the photosensitive drum 52 onto the intermediate transfer belt 60, a cleaner (not shown) for removing residual toner and the like on the photosensitive drum 52, and the like. ing.
The intermediate transfer belt 60 is stretched around a plurality of stretching rolls 61 to 64, is driven by the rotation of the photosensitive drum 52, and is circulated and conveyed.

In this embodiment, a portion of the intermediate transfer belt 60 that faces the stretch roll 63 is set as a secondary transfer portion, and a secondary transfer roll is provided on the surface of the secondary transfer portion of the intermediate transfer belt 60. 65 is arranged, and a transfer bias is applied between the secondary transfer roll 65 and a tension roll 63 as a backup roll facing the secondary transfer roll 65.
Further, a cleaning roll 66 for cleaning residual toner on the intermediate transfer belt 60 is provided at a position facing the stretching roll 64 so as to be able to contact and separate from the intermediate transfer belt 60.
Further, in the present embodiment, the mark sensor 72 for detecting the mark 71 disposed on the back surface of the intermediate transfer belt 60 includes the primary transfer roll 53a disposed on the most upstream side and the tension adjacent to the upstream side thereof. It is disposed between the rack roll 61.

In the present embodiment, the photosensitive drum 52 (specifically 52a to 52d) is provided with a drive motor (not shown) as a main driving source, and the photosensitive drum 52 (specifically 52a to 52d) is provided. The intermediate transfer belt 60 is moved by the nip between the intermediate transfer belt 60 and the intermediate transfer belt 60. The tension roll 64 facing the cleaning roll 66 is provided with an auxiliary drive motor (not shown) as an auxiliary drive source. In this case, the auxiliary driving force by the auxiliary driving motor is smaller than the main driving force obtained by adding the driving forces of the four photosensitive drums 52a to 52d.
Therefore, also in the present embodiment, even if a load member such as the secondary transfer roll 65 or the cleaning roll 66 abuts against the intermediate transfer belt 60, fluctuations in the speed of the intermediate transfer belt 60 are suppressed by an auxiliary driving force (not shown). Color misregistration can be prevented.

1 is an explanatory diagram showing an outline of an image forming apparatus according to the present invention. 1 is an explanatory diagram showing Embodiment 1 of an image forming apparatus to which the present invention is applied. FIG. 3 is an explanatory diagram showing a main part of the first embodiment. 3 is an explanatory diagram illustrating a control flow according to Embodiment 1. FIG. FIG. 6 is an explanatory diagram showing an example provided with a torque limiter as a modification of the first embodiment. FIG. 6 is an explanatory diagram showing an example in which auxiliary drive sources are provided at two locations as a modification of the first embodiment. FIG. 6 is an explanatory diagram illustrating a main part of an image forming apparatus according to a second embodiment. FIG. 10 is an explanatory diagram illustrating a main part of an image forming apparatus according to a third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Image forming means, 3 ... Stretch member, 4 ... Intermediate transfer belt, 5 ... Load member, 6 ... Main drive force, 7 ... Main drive means, 8 ... Auxiliary drive force, 9 ... Auxiliary Drive means, 10 ... drive transmission member, 11 ... auxiliary drive source, 12 ... detection means, 13 ... auxiliary drive control means

Claims (8)

One or a plurality of image carriers that maintain the image, image forming means for producing an image on the image carrier, and the circular conveyance that is arranged opposite to the image carrier and stretched by a plurality of stretching members In an image forming apparatus comprising an endless intermediate transfer belt to be fastened and one or a plurality of load members contacting and separating from the intermediate transfer belt,
A main drive means for driving the intermediate transfer belt at a contact portion between the image carrier and the intermediate transfer belt by rotationally driving the image carrier and applying a main driving force to the intermediate transfer belt;
By rotating and driving the intermediate transfer belt at a portion other than the image carrier, an auxiliary driving force that is greater than the load fluctuation of the intermediate transfer belt due to the contact and separation of the load member with respect to the intermediate transfer belt and smaller than the main driving force. An image forming apparatus comprising: an auxiliary driving unit that applies to the intermediate transfer belt. The image forming apparatus according to claim 1.
An image forming apparatus comprising: a drive transmission member that contacts an intermediate transfer belt and transmits an auxiliary drive force. The image forming apparatus according to claim 2.
The image forming apparatus, wherein the drive transmission member is a facing member disposed to face the load member with the intermediate transfer belt interposed therebetween. The image forming apparatus according to claim 3.
The image forming apparatus, wherein the drive transmission member is a stretching member that stretches the intermediate transfer belt. The image forming apparatus according to claim 2.
The auxiliary drive means includes an auxiliary drive source for driving the drive transmission member,
Detecting means for detecting the moving speed of the intermediate transfer belt;
An image forming apparatus comprising: an auxiliary drive control unit that controls an auxiliary drive source based on information from the detection unit. The image forming apparatus according to claim 2.
The image forming apparatus, wherein the auxiliary drive means includes a torque limiter between the auxiliary drive source and the drive transmission member. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the intermediate transfer belt has a laminated structure of at least an elastic layer and a release layer. The image forming apparatus according to claim 7.
An image forming apparatus, wherein the elastic layer of the intermediate transfer belt has a Young's modulus of 30 MPa or less.

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