JP2012159707A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which right-side and left-side conveyance speeds of a recording material from a registration unit to a transfer unit (secondary transfer unit) can be adjusted and the recording material can be stably conveyed.SOLUTION: The image forming apparatus includes: a registration roller 4 that timely conveys a recording material P one by one toward an image carrier 6 as a transfer member carrying a toner image; and a transfer device 5 transferring the image on the image carrier 6 onto the recording material P. The image forming apparatus also includes speed adjusting means 15a, 15b between the registration roller 4 and the transfer device, the means for adjusting right-side and left-side speeds of the recording material P with respect to the conveyance direction of the recording material P. The speed adjusting means is set based on a parallel degree of an image formed on the recording material P.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine that forms an image on a recording material by an electrophotographic method.

  In recent years, so-called full-color tandem machines have been proposed in image forming apparatuses such as printers, copiers, and facsimile machines for the purpose of forming color images at high speed and high image quality.

  A typical example of the tandem machine is one in which four image forming units of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in parallel to each other.

  In this, the toner images of each color of yellow, magenta, cyan, and black, which are sequentially formed in each of these image forming units, are once subjected to multiple transfer (primary transfer) to an intermediate transfer belt as a transfer member that is an intermediate transfer member, The intermediate transfer belt is collectively transferred (secondary transfer) onto a transfer sheet as a recording material, and a toner image formed on the transfer sheet is fixed to form a full-color or monochrome (monochrome) image. Yes.

  This type of full-color tandem machine regulates left and right manufacturing errors, pressure deviations, mounting position errors, and further movement of the transfer paper, such as rollers, in the transfer section that forms the image or the registration section in front of the transfer section. Differences in the left and right movements of the transfer paper easily occur due to the position deviation of the guide plate and the like. These differences result in an influence on the transfer portion that forms the image, and disturb the parallelism of the image.

As a method for correcting this parallelism, means for adjusting the speed of a transfer member that rotates relative to a carrier on which a toner image is carried has been proposed (see Patent Document 1).
In addition, means for making a difference in the amount of biting at both ends in the axial direction of the transfer roller of the transfer portion has been proposed (see Patent Document 2).

However, since the technique disclosed in Patent Document 1 adjusts the speed difference between the carrier and the transfer member, it is particularly difficult to ensure transferability of fine lines.
In the technique disclosed in Patent Document 2, the amount of biting at both ends in the axial direction of the transfer roller is differentiated, that is, the difference in transfer pressure is imparted, so that transfer properties such as peelability and density unevenness are ensured. Is difficult.

Further, by changing the transfer pressure, there is no possibility of paper escape in the transfer paper between the transfer and fixing, which may cause paper wrinkles and the like.
The present invention has been made in view of the above-described problems, and an object thereof is an image forming apparatus capable of forming an image with parallelism while ensuring transferability to a transfer member and a recording material. Is to provide.

  The image forming apparatus according to claim 1, a registration roller that conveys a recording material toward an image carrier as a transfer member on which a toner image is carried while timing each sheet, and an image on the image carrier. In the image forming apparatus having the transfer device for transferring the recording material to the recording material, a speed adjustment for adjusting a right and left speed of the recording material in a conveyance direction of the recording material in a portion between the registration roller and the transfer device And the speed adjusting means is set based on the parallelism of the image formed on the recording material.

It is desirable that the speed adjusting means is composed of at least one roller pair provided in a portion between the registration roller and the transfer device.
Further, it is desirable that the speed adjusting means adjusts the rotational speed of the roller pair based on the parallelism of images formed on a plurality of recording materials.
Furthermore, it is desirable to adjust the rotation speed of the roller pair by the combination of the paper feed cassette, the size of the recording material, and one side and both sides.

  According to the image forming apparatus of the present invention, it is possible to adjust the left and right conveyance speed of the recording material from the resist unit to the transfer unit (secondary transfer unit), and the image forming apparatus capable of stably conveying the recording material. Can be provided.

  Also, the position of the transfer plate that forms the image of the full-color tandem machine, the right and left manufacturing errors, pressure deviations, mounting position errors, etc. of the rollers in the resist section in front of the transfer member, as well as the position of the guide plate that regulates the movement of the recording material It is possible to alleviate the difference in the left and right movements of the paper due to the deviation, and it is possible to reduce the component tolerance and reduce the cost.

FIG. 1 is a configuration diagram showing an outline of an image forming apparatus according to the present invention. FIG. 2 is a perspective view showing a configuration between the pair of registration rollers and the secondary transfer roller shown in FIG. FIG. 3 is a flowchart showing a procedure for adjusting the parallelism of the image. FIG. 4 is an explanatory diagram showing an example of measurement of parallelism of an image. FIG. 5 is a graph showing the relationship between the rotational speed deviation and parallelism of the roller pair shown in FIG.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an outline of an image forming apparatus according to the present invention. In FIG. 1, reference numeral G denotes an intermediate transfer type tandem color image forming apparatus.

  The color image forming apparatus G includes, for example, a sheet feeding unit, four image forming units that form toner images of the respective color components (in this embodiment, yellow, magenta, cyan, and black) by electrophotography. A primary transfer portion having an intermediate transfer belt as an image carrier for sequentially transferring (primary transfer) each color component toner image formed by each image forming unit, and a toner image of each color transferred onto the intermediate transfer belt in a multiple manner Are collectively provided with a batch transfer device for batch transfer (secondary transfer) to a recording material, and a fixing device.

(Schematic configuration and operation of paper feed unit)
The paper feed unit is roughly constituted by a paper feed cassette 10, a paper feed roller 1, and a transport roller 1 ′, and the recording material P is fed by the paper feed roller 1 and fed to a pair of registration rollers 4. .

  When the leading edge of the recording material P reaches the pair of registration rollers 4, the leading edge is detected by a sensor (not shown). The recording material P is conveyed to a nip portion between a secondary transfer roller and an intermediate transfer belt, which will be described later, by a pair of registration rollers 4 while taking a timing according to a detection signal of the sensor.

(Schematic configuration and operation of the imaging unit)
The image forming unit includes an exposure device 7 and a photosensitive drum device. The exposure apparatus 7 includes irradiation optical systems 7Y, 7M, 7C, and 7K that irradiate laser light.

  The photosensitive drum device includes photosensitive drums 1Y, 1M, 1C, and 1K as image carriers, charging devices 2Y, 2M, 2C, and 2K, developing devices 3Y, 3C, 3M, and 3K, cleaning devices 13Y, 13M, and 13C, It is roughly composed of 13K.

  The photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged beforehand by the charging devices 2Y, 2M, 2C, and 2K, and the irradiation optical systems 7Y, 7M, 7C, and 7K of the exposure device 7 are used. The charged portion is exposed and scanned by the laser beam of each of the yellow (Y), magenta (M), cyan (C), and black (K) portions where the images of the photosensitive drums 1Y, 1M, 1C, and 1K are to be formed. An electrostatic latent image is created.

  Each electrostatic latent image is developed by each color developing device 3Y, 3C, 3M, and 3K, and yellow, magenta, cyan, and black toner images are formed on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. .

(Schematic configuration and operation of the primary transfer unit)
The primary transfer portion is roughly composed of an intermediate transfer belt 6 as an image carrier and primary transfer rollers 8Y, 8M, 8C and 8K. The intermediate transfer belt 6 is driven to rotate by frictional forces of the rotating photosensitive drums 1Y, 1M, 1C, and 1K.

  A voltage is applied to the primary transfer rollers 8Y, 8M, 8C, and 8K. The toners on the photosensitive drums 1Y, 1M, 1C, and 1K are sequentially transferred onto the intermediate transfer belt 6 by applying voltages to the primary transfer rollers 8Y, 8M, 8C, and 8K.

  At this time, the voltage application timings of the primary transfer rollers 8Y, 8M, 8C, and 8K are shifted from the upstream side to the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 6. Transcription is performed.

(Schematic configuration and operation of batch transfer device)
The batch transfer device has a secondary transfer roller 5 and a secondary transfer portion intermediate belt transfer portion roller 16 which is paired with the secondary transfer roller 5. The toner image formed on the intermediate transfer belt 6 is conveyed to the position of the secondary transfer roller 5. A voltage is applied to the secondary transfer roller 5, and the toner image on the intermediate transfer belt 6 is secondarily transferred to the recording material P by the voltage applied to the secondary transfer roller 5.

(Schematic configuration and operation of the fixing device)
The fixing device 9 includes a pressure roller 9b and a fixing roller 9a. The recording material P onto which the toner images of the respective colors are collectively transferred is conveyed toward the fixing device, and the toner images of the respective colors transferred onto the recording material P are formed between the pressure roller 9b and the fixing roller 9a. In the fixing region, the image is fixed on the recording material P by being melted by heat and pressure. Thereafter, the recording material P is discharged by the paper discharge roller 12. Thereby, one image forming job is completed.

  The residual toner on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K is cleaned by the cleaning devices 13Y, 13M, 13C, and 13K, and then the charging device 2Y in which the bias of the AC component is superimposed and applied to the direct current. 2M, 2C, 2K are charged simultaneously with static elimination. This prepares for the next image forming job.

The residual toner on the intermediate transfer belt 6 is cleaned by the elastic intermediate transfer belt cleaning device 14 and is prepared for the next image forming job.
The above is the outline of the operation of the image forming apparatus.
Details of the image forming apparatus according to the present invention will be described below.

(Detailed configuration between the pair of registration rollers 4 and the secondary transfer roller 5 and arrangement of conventional problems)
FIG. 2 is an image forming apparatus according to an embodiment of the present invention, and shows a configuration between a pair of registration rollers 4 and a secondary transfer roller 5.

  As described above, the recording material P is conveyed toward the secondary transfer roller 5 by the pair of registration rollers 4, and an image is formed on the recording material P by the secondary transfer roller 5.

  However, the transfer paper as the recording material P is disturbed by the influence of the secondary transfer roller 5 or the air current in the image forming apparatus, and is skewed, for example, skewed, or the secondary transfer roller 5 and the intermediate transfer belt. In some cases, the recording material P is jammed without being conveyed to the transfer nip portion between the recording material P6 and the recording material P6.

  This disturbance in the movement of the recording material P causes disturbance in image formation at the transfer nip portion of the secondary transfer roller 5, resulting in a slight change in the transfer time of the image onto the recording material P and disturbing the image parallelism. Become.

  Further, in an image forming apparatus that transports a paper path from a paper feeding unit that supplies paper as a recording material P to a portion where an image is formed, in the vertical direction, which is the vertical direction, the secondary transfer nip unit and the fixing unit A guide plate is provided between the apparatuses, and the non-uniformity around the guide plate becomes a transport load of the recording material P, and the transfer time of the image onto the recording material P becomes a slight change, thereby reducing the image parallelism. Will be disturbed.

  In addition, regarding the formation of an image on the recording material P, the size of the outer diameters of the pair of registration rollers 4, the secondary transfer roller 5, the fixing roller 9a of the fixing device 9, and the pressure roller 9b are greatly related.

  For example, when the size of the outer diameter of the secondary transfer roller 5 is different between the left end portion and the right end portion of the recording material P, the paper feed speed becomes slower on the thin outer diameter side, and the intermediate transfer belt 6 is formed. When the transferred image is transferred to the recording material P, the image is stretched.

  Similarly, when the fixing roller 9a and the pressure roller 9b of the fixing device 9 have different roller diameters at the left end and the right end, the image is affected.

  Also, depending on the magnitude of the pressure of the pair of registration rollers 4, the secondary transfer roller 5 and the fixing device 9, that is, the balance of the force transported to the recording material P and the slip factor of the recording material P, or the secondary Depending on which one of the pair of the transfer roller 5 and the intermediate transfer belt roller (stretching roller) 16 of the secondary transfer portion that forms a pair with the transfer roller 5 and the fixing roller 9a and the pressure roller 9b has a force for conveying the recording material P. However, there is no difference in the influence of the outer diameter on the image parallelism.

  In order to solve these problems, in the image forming apparatus according to the embodiment of the present invention, driving speed adjustment means is provided between the pair of registration rollers 4, the secondary transfer roller 5, and the intermediate transfer belt portion roller 16. The roller pair 15a, 15b is provided.

  The roller pairs 15a and 15b are provided with a gap in the paper width direction perpendicular to the transport direction, which sandwiches the recording paper P from the thickness direction. These roller pairs 15a and 15b are driven by motors Ma and Mb, respectively.

  The roller pair 15a, for example, sandwiches the left side portion Pl of the recording paper P, and the roller pair 15b, for example, sandwiches the right side portion Pr of the recording paper P. Based on the parallelism of the recording material P, the left side portion Pl and the right side It is possible to make a deviation in the speed with respect to the part Pr. Thereby, the conveyance parallelism of the recording paper P is maintained, and the image parallelism is maintained.

The velocity deviation between the left side portion Pl and the right side portion Pr of the recording paper P is determined by measuring the parallelism of the image from the toner image transferred to the recording material P, and depending on whether or not the parallelism of the toner image is within an intersection. Make adjustments.
Further, the speed deviation adjustment of the motors Ma and Mb is started after the recording material P enters the secondary transfer nip portion.

(Explanation of speed deviation adjustment)
The speed deviation adjustment will be described below with reference to the flowchart of FIG. 3 showing the speed adjustment procedure, the image parallelism explanatory diagram shown in FIG. 4, and the graph shown in FIG.

In FIG. 3, ΔV is a rotational speed deviation between the rotational speed Va of the driving roller pair 15a and the rotational speed Vb of the driving roller pair 15b, and the rotational speed deviation ΔV is expressed by the following equation. .
ΔV = {(Va−Vb) / Vc} * 100 (%) (1)
Here, Vc is the rotational speed of the intermediate transfer belt section roller (stretching roller) 16.

As shown in FIG. 4, the parallelism ΔL of the image is the front side of the recording material P (the front side with respect to the normal standing position of the user using the image forming apparatus (the left side with respect to the conveyance direction)) and the rear. When an image having the same length is formed on the side (the back side of the image forming apparatus (the right side with respect to the conveyance direction)), the length L1 (mm) on the front side of the recording material P and the recording material P This is the difference from the length L2 (mm) on the rear side, and the parallelism ΔL is expressed by the following equation.
ΔL = L1-L2 (2)

  Therefore, an image symmetrical to the conveying direction of the recording material P is output as data to the image forming unit, an intermediate transfer image of this image is formed on the intermediate transfer belt 6, and this intermediate transfer image is transferred to the recording material P. An image is formed on the recording material P by the next transfer, and a relationship diagram between the rotational speed deviation ΔV and the parallelism ΔL shown in FIG. 5 is created (see S.1 in FIG. 3).

That is, the rotation speed of the roller pair 15a is set to Va, the rotation speed of the roller pair 15b is set to Vb, and the rotation speed of the intermediate transfer belt section roller 16 is set to Vc, and the length L1 from the image formed on the recording material P is set. , L2 is calculated to obtain the parallelism ΔL from the above equation (2), and the rotational speed difference (Va−) between the rotational speed Va of the roller pair 15a and the rotational speed Vb of the roller pair 15b at this time. Vb), the rotational speed deviation ΔV is obtained from the above equation (1) based on the rotational speed Vc of the stretching roller 16, and the relationship shown in FIG. 5 is obtained from the relationship between the obtained rotational speed deviation ΔV and the parallelism ΔL of the image. Create a diagram.

  FIG. 5 shows an example of the relationship diagram, which is a graph created with the horizontal axis as the rotational speed deviation ΔV and the vertical axis as the image parallelism ΔL. From this graph, the relationship between the parallelism ΔL and the rotational speed deviation ΔV is obtained.

  In FIG. 5, the rotational speed deviation ΔV when the parallelism ΔL = 0 is determined, and the rotational speed Va of the roller pair 15a, the rotational speed Vb of the roller pair 15b, and the tension are set so as to be this rotational speed deviation ΔV. If the rotation speed Vc of the gantry roller 16 is set, the parallelism of the image can be obtained.

  The rotational speeds Va and Vb of the roller pair 15a and the roller pair 15b depend on conditions such as the paper feed cassette 10, the size and single-sided printing of the recording material P, the combination of double-sided printing, the conveyance speed of the recording paper P, and the enlargement / reduction. Mode) (S.2).

Next, when the image length is shorter than the target image length (L1, L2), the rotational speeds Va, Vb of the roller pairs 15a, 15b are increased to the target image length (L1, L2). On the other hand, when the image length is long, the rotation speeds Va and Vb of the roller pair 15a and 15b are slowed down to adjust the target image length (L1 and L2) for each mode (S. 3).
The adjustment to the target length of the image is performed by adjusting the rotation speeds Va and Vb with ΔV being constant (in a state where ΔV is fixed).

  In detail, the adjustment of the parallelism of the images is performed by forming a symmetric image on a plurality (10 or more) of recording materials P, and adjusting the parallelism of each image formed on the plurality of recording materials P. The measurement is performed by obtaining an average value of the parallelism measurement and finally determining the speed deviation of the motor Ma and the motor Mb.

This speed adjustment is performed manually using a controller from outside the machine of the image forming apparatus based on the relationship diagram shown in FIG. That is, for each mode, the set values of the rotation speeds Va and Vb are read into the storage unit (not shown) of the image forming apparatus (S.4).
Then, the motors Ma and Mb are driven so that the roller pair 15a rotates at the rotation speed Va and the roller pair 15b rotates at the rotation speed Vb (S.5).

  As a result, the parallelism of the image is maintained while ensuring transferability to the recording paper P for each mode. Since the sensitivity of the change in parallelism with respect to the rotational speed deviation is different for each machine of the image forming apparatus, it is necessary to adjust for each machine.

  Further, due to the rotational speeds Va and Vb, the recording material P is bent between the registration roller pair 4 and the roller pair 15a and 15b, and between the roller pair 15a and 15b and the secondary transfer nip, thereby causing a paper jam and an image defect. Since this may occur, the rotational speeds Va and Vb are preferably set to ± 3% with respect to the rotational speed Vc.

4 ... Registration roller 5 ... Transfer device (secondary transfer device)
6. Image carrier (intermediate transfer belt)
15a, 15b ... Speed adjusting means (a pair of rollers)
P ... Recording material

JP 2004-246074 A JP 2006-276294 A

Claims (4)

A registration roller that conveys a recording material to an image carrier as a transfer member on which a toner image is carried one by one at a time, and a transfer device that transfers an image on the image carrier to the recording material In an image forming apparatus having
A speed adjusting unit that adjusts the left and right speeds of the recording material with respect to the conveyance direction of the recording material is provided at a portion between the registration roller and the transfer device, and the speed adjusting unit is an image formed on the recording material. The image forming apparatus is set based on the parallelism of the image.   The image forming apparatus according to claim 1, wherein the speed adjusting unit includes at least one roller pair provided in a portion between the registration roller and the transfer device. Image forming apparatus.   3. The image forming apparatus according to claim 1, wherein the speed adjusting unit adjusts the rotational speed of the roller pair based on the parallelism of images formed on a plurality of recording materials. apparatus.   4. The image forming apparatus according to claim 3, wherein the rotation speed of the roller pair is adjusted by a combination of a paper feed cassette, the size of the recording material, and one side and both sides.