JP2005091913A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent image misalignment (color slurring) caused by a difference between sheet conveyance speed and image carrier speed in an area where transfer takes place on a sheet. <P>SOLUTION: The image forming apparatus has: an image carrier 1 on which an image is held; an image forming means 2 for forming the image on the image carrier 1; and a transfer means 3 for transferring the image on the image carrier to a sheet 4. The image forming apparatus is characterized by including: an image carrier drive means 6 for driving the image carrier 1; a sheet conveyance drive means 7 for driving a sheet conveyance member 5; a speed difference determination means 8 which determines a difference between the sheet conveyance speed v<SB>1</SB>and the moving speed v<SB>2</SB>of the image carrier 1 passing through the transfer means 3; and a drive control means 9 which, based on the result of the determination by the speed difference determination means, controls the drive of the sheet conveyance drive means 7 and image carrier drive means 6 so that the speed difference between them becomes smaller. <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 in an image forming apparatus in which a plurality of color component images are superimposed on an image carrier and then transferred to a sheet.

As an example of a conventional image forming apparatus, for example, an intermediate transfer type image forming apparatus, an image forming unit that forms each color component image of yellow, magenta, cyan, and black, and an image transfer portion of the image forming unit And an intermediate transfer belt that primarily transfers and holds each color component image formed by the image forming unit, and a secondary transfer device (batch transfer device) that secondarily transfers each color component image on the intermediate transfer belt to a sheet. ), And each color component image formed by each image forming unit is sequentially transferred onto an intermediate transfer belt and then transferred to a sheet by a batch transfer device.
In this type of image forming apparatus, as the batch transfer apparatus, for example, a tension roll of the intermediate transfer belt is used as a backup roll, and a transfer roll that is driven and rotated in contact with the intermediate transfer belt is used. Thus, the sheet is conveyed in the nip.
As the sheet conveyance system, a registration roll for registration (hereinafter referred to as a resist roll) is disposed on the upstream side of the batch transfer device in the sheet conveyance path. The rush timing of the seat is adjusted.

Japanese Unexamined Patent Publication No. 2000-199988 (Embodiment of the Invention, FIG. 3) JP-A-10-194530 (Embodiment of the Invention, FIG. 2)

In this type of image forming apparatus, the sheet conveyance speed at the batch transfer portion corresponds to the sheet conveyance speed fed out by the registration roll, but there is a speed difference between the sheet conveyance speed and the intermediate transfer belt speed. If it is large, the sheet is attracted or pressed between the batch transfer site and the resist roll, and this causes the speed fluctuation of the intermediate transfer belt, and the primary transfer site and the secondary transfer site (collective transfer site). This is likely to cause image displacement (typically, color displacement). In particular, the effect becomes significant in a sheet of thick paper or the like that is stiff.
Here, when the factors of the speed difference between the sheet conveyance speed and the intermediate transfer belt speed are examined, the following factors can be considered.
(1) Whereas the resist roll is made of an elastic roll such as rubber, the driving roll for driving the intermediate transfer belt is made of an aluminum metal roll, for example, and the surface speed difference between the rolls due to temperature changes and wear. Becomes larger. For this reason, the sheet conveyance speed is likely to change, and accordingly, the difference in speed between the sheet conveyance speed and the intermediate transfer belt speed is increased, which is likely to cause an image displacement.
(2) When a stiff sheet is used, the greater the speed difference between the sheet conveyance speed and the intermediate transfer belt speed, the greater the speed fluctuation of the intermediate transfer belt when the sheet enters the batch transfer site. It tends to lead to image misalignment.
Such a technical problem is not limited to an intermediate transfer type image forming apparatus, but also occurs in a direct transfer type image forming apparatus that directly transfers an image on a photoreceptor or a dielectric to a sheet. Is.

By the way, as a prior art for preventing such image misregistration (color misregistration), for example, image exposure is performed by detecting a change in the thickness of a transfer belt (corresponding to an intermediate transfer belt) or wear of a driving roll of the transfer belt. A technique for correcting timing (for example, see Patent Document 1), and a technique for controlling the conveying force of a registration roll for a stiff sheet so that the sheet is driven at the transfer belt speed (for example, see Patent Document 2). Has been proposed.
However, in Patent Document 1, there is no mention of an image misregistration (color misregistration) caused by a speed difference between the sheet conveyance speed and the transfer belt speed.
In Patent Document 2, the conveyance force of the resist roll is influenced not only by the roll pressure and roll frictional resistance but also by the type of sheet, change with time, dirt, etc. It is difficult to control stably.

  The present invention has been made in order to solve the above technical problem, and is an image misregistration (typically caused by a speed difference between a sheet conveyance speed and an image carrier speed at a transfer portion to a sheet. Is an image forming apparatus that can effectively avoid color misregistration.

That is, as shown in FIG. 1, the present invention provides an image carrier 1 on which an image is carried, an image forming means 2 for forming an image on the image carrier 1, and an image on the image carrier 1 as a sheet. In the image forming apparatus including the transfer unit 3 for transferring to the image transfer unit 3, the image carrier drive unit 6 that drives the image carrier 1, the sheet conveyance drive unit 7 that drives the sheet conveyance member 5, and the sheet conveyance member 5. A speed difference discriminating means 8 for discriminating a speed difference between the sheet conveying speed v ₁ and a moving speed v ₂ of the image carrier 1 passing through the transfer means 3, and a speed difference between the two based on the discrimination result by the speed difference discriminating means 8. The sheet transport driving means 7 and the drive control means 9 for driving and controlling the image carrier driving means 6 are provided.

  In such technical means, as long as the image carrier 1 carries an image, not only an image forming carrier such as a photoconductor and a dielectric, but also a combination of this image forming carrier and an intermediate transfer member. Embodiments are also included. Further, as the image forming means 2, an electrophotographic system or an electrostatic recording system is mainly used, but is not limited thereto. Further, the transfer means 3 may be any means as long as it transfers the image on the image carrier 1 to the sheet 4, and includes a means for conveying the sheet 4 to and from the image carrier 1.

Further, as the speed difference discriminating means 8, if it can discriminate the difference between the sheet conveying speed v ₁ by the sheet conveying member 5 and the moving speed v ₂ of the image carrier 1 at the transfer site, it is indirectly or directly. Widely included regardless of purpose.
Here, as a typical aspect of the speed difference discriminating means 8, for example, there is one that discriminates the speed difference based on the environmental temperature change. This is because expansion or contraction occurs in the sheet conveying member 5 due to a change in the environmental temperature, and thereby a speed difference can be determined.
Further, as another representative aspect, there is one that discriminates the speed difference based on the number of image forming sheets. This is because the sheet conveying member 5 is worn depending on the number of image forming sheets, and the speed difference can be determined on the assumption of this.

Furthermore, as another aspect, it is provided with a misregistration detecting means capable of detecting the misregistration of the image on the image carrier 1, and the position of the image is detected by the misregistration detecting means in a state where the sheet 4 to be used is conveyed in advance. Examples include detecting a deviation and discriminating a speed difference based on the deviation. This is because it is possible to determine the speed difference by detecting the positional deviation of the image when passing through the sheet 4.
In particular, in this aspect, it is preferable to detect the misalignment detection pattern formed outside the image forming area of the image carrier 1 by the misalignment detection means. If a positional deviation detection pattern is created outside the image forming area and an image positional deviation is detected, the speed difference can be determined while suppressing the influence on the image forming area.

Furthermore, as another aspect, there is provided a speed detection unit that can detect the sheet conveyance speed v ₁ by the sheet conveyance member 5 and discriminates a speed difference based on speed information from the speed detection unit. . This is because the sheet conveying speed v ₁ by the sheet conveying member 5 can be directly monitored, and the speed difference can be determined based on this speed change.
As another aspect, a speed detection unit capable of detecting the sheet conveyance speed v ₁ by the sheet conveyance member 5 and the sheet conveyance speed v ₂ after passing through the transfer unit 3 (corresponding to the moving speed v ₂ of the image carrier 1). Are provided, and the speed difference is discriminated based on the speed information from both speed detecting means. This is because if the sheet conveying speed v ₁ by the sheet conveying member 5 and the sheet conveying speed v ₂ after passing through the transfer means 3 are directly monitored, the difference between the two can be directly discriminated. By being possible.

Furthermore, the drive control means 9 may change and control the speed of at least one of the drive means 6 and 7 so as to reduce the speed difference based on the determination result of the speed difference determination means 8.
However, from the viewpoint of simplifying the control method, there is an aspect in which the sheet conveyance drive unit 7 is driven and controlled based on the determination result by the speed difference determination unit 8 and the sheet conveyance speed v ₁ by the sheet conveyance member 5 is changed. preferable. According to this aspect, it is possible to control the image carrier 1 without changing the speed, and in this way, the speed difference control can be performed without changing the image forming process by the image forming means 2. Can be realized easily.

In the present invention, since the speed control is performed so as to reduce the speed difference between the sheet conveyance speed and the image carrier speed at the transfer portion to the sheet, the sheet is pressed between the transfer portion and the sheet conveyance member, The attraction force is reduced, and accordingly, the speed fluctuation of the image carrier can be suppressed, and the deterioration of the image position shift (typically color shift) can be effectively prevented.
In particular, when using a stiff sheet, image misalignment is likely to occur. However, the present invention is extremely effective because the speed difference that causes image misregistration can be kept small. is there.

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, the image forming apparatus is an intermediate transfer type, and four image forming units 20 (specifically, 20Y, 20M, 20C, and 20K) for forming each color component image of yellow, magenta, cyan, and black are arranged. An intermediate transfer belt 30 that circulates in opposition to the image transfer portions of the four image forming units 20 is disposed on the upper side, and one side of the intermediate transfer belt 30 is used for image transfer onto the sheet 100. The batch transfer device 40 (secondary transfer device) is arranged to sequentially transfer the respective color component images formed by the image forming unit 20 to the intermediate transfer belt 30 in order, and the batch transfer device 40 uses the intermediate transfer belt. The primary transfer image multiple-transferred onto the sheet 30 is collectively transferred to the sheet 100.

Here, each of the image forming units 20 (20Y to 20K) adopts an electrophotographic system, and a charging device, an exposure device, and the like that are not shown around the photosensitive drum 21 (specifically 21Y to 21K), A developing device and a cleaning device are disposed, and a primary transfer device (a charger such as a corotron or a transfer roll) (not shown) is disposed on the back side of the intermediate transfer belt 30 facing the photosensitive drum 21. is there.
Further, the intermediate transfer belt 30 is stretched around a plurality of stretching rolls 31 to 34. For example, the stretching roll 31 is configured as a driving roll by a metal roll made of aluminum, for example, and the driving roll 31 is configured as a driving motor 71. It is adapted to circulate rotational movement by driving in (figure displayed in M _B).
Further, the batch transfer device 40 is constituted by, for example, a transfer roll that is disposed opposite to the stretch roll 34 with the stretch roll 34 of the intermediate transfer belt 30 as a backup roll with the intermediate transfer belt 30 interposed therebetween. The transfer roll 40 is disposed in contact with the intermediate transfer belt 30 and is driven to rotate by the intermediate transfer belt 30.

In this embodiment, the sheet conveying system guides the sheet 100 sent from a sheet tray (not shown) to a sheet conveying path extending in a substantially vertical direction, and a batch transfer portion (secondary transfer portion) in the sheet conveying path. ) And a fixing device 60 are provided downstream of the batch transfer portion, and the sheet 100 that has passed through the resist roll 50, the batch transfer portion, and the fixing device 60 is not shown. It is discharged to the discharge tray.
Here, for example, as shown in FIG. 3, the resist roll 50 has a resist driving roll 51 and a resist driven roll 52 arranged to face each other, at least one of which is an elastic layer such as rubber around a metal core 53. 54 is composed of an elastic roll covering 54.
The registration drive roll 51 is driven by a drive motor 72 (indicated by _MR in the figure).

  Further, in the present embodiment, the drive control system has a control device 70 constituted by a microcomputer system comprising a CPU, a ROM, a RAM, and an I / O port, as shown in FIG. Stores a speed control program in advance, fetches temperature information from the temperature sensor 73 capable of detecting the ambient temperature, executes the speed control program by the CPU, and sends control signals to the drive motors 71 and 72, respectively. It is supposed to do.

Next, the operation of the image forming apparatus according to the present embodiment will be described.
In the present embodiment, when attention is paid to the resist driving roll 51 among the resist rolls 50, the elastic layer 54 of the resist driving roll 51 expands or contracts according to a change in the ambient temperature, and as shown in FIG. The thickness m of the elastic layer 54 changes, and the outer diameter of the resist driving roll 51 changes with the ambient temperature. In this case, the surface speed of the resist driving roll 51 is changed, which causes a change in the conveying speed of the sheet 100 by the resist roll 50.

Therefore, in the present embodiment, the control device 70 recognizes a change in the outer diameter of the resist driving roll 51 according to the temperature information from the temperature sensor 73, and based on this, the surface speed of the resist driving roll 51, that is, Then, the conveyance speed v ₁ of the sheet 100 by the registration roll 50 is determined.
Then, the control device 70 compares the conveyance speed v ₁ of the sheet 100 by the determined registration roll 50 and the moving speed v ₂ of the intermediate transfer belt 30 (preliminarily set to a predetermined process speed), and the speed difference Δv between the two. = | V ₁ −v ₂ | exceeds the predetermined permissible range, for example, the speed control signal for the drive motor 72 is controlled so that the speed difference Δv falls within the permissible range, and the registration roll 50 to change the conveying speed _{v 1} of the sheet 100 by.
In this state, the conveying speed v ₁ of the sheet 100 by the registration roll 50 and the moving speed v ₂ of the intermediate transfer belt 30 are kept substantially coincident with each other, so that the sheet 100 becomes a batch transfer site (secondary transfer site). Even if it enters, no attracting or pushing force acts on the sheet 100 between the batch transfer site and the resist roll 50 site. For this reason, even if the sheet 100 enters the batch transfer portion, the intermediate transfer belt 30 does not fluctuate in speed, and image displacement (mainly color displacement) occurs in the primary transfer portion and the secondary transfer portion. There is no.

Embodiment 2
FIG. 4 shows Embodiment 2 of an image forming apparatus to which the present invention is applied.
In the drawing, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment. However, unlike the first embodiment, a count counter 75 for detecting the number of image forming sheets is used instead of the temperature sensor 73. the a, captures the image formation sheet number information from the count counter 75 to the controller 70, and changing control of the conveying speed v ₁ of the sheet 100 by the registration roll 50 by the controller 70. Components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here. The same applies to the following third and subsequent embodiments.

In the present embodiment, when attention is paid to the resist driving roll 51 among the resist rolls 50, the elastic layer 54 of the resist driving roll 51 is worn as the number of image forming sheets increases, and as a result, as shown in FIG. The thickness m of the elastic layer 54 changes, and the outer diameter of the resist driving roll 51 changes according to the number of image forming sheets. In this case, the surface speed of the resist driving roll 51 is changed, which causes a change in the conveying speed of the sheet 100 by the resist roll 50.
Therefore, in the present embodiment, in this embodiment, the control device 70 recognizes a change in the outer diameter of the registration driving roll 51 according to the count information from the counting counter 75, and based on this, the registration driving roll 51 surface speed of 51, i.e., determine the conveying speed _{v 1} of the sheet 100 by the registration roll 50. As a method for determining this, for example, there is a method in which a correlation between the count information and the sheet conveyance speed v ₁ is previously provided as a memory table and the memory table is searched according to the count information.

Then, the control device 70 compares the conveyance speed v ₁ of the sheet 100 by the determined registration roll 50 and the moving speed v ₂ of the intermediate transfer belt 30 (preliminarily set to a predetermined process speed), and the speed difference Δv between the two. = | V ₁ −v ₂ | exceeds the predetermined permissible range, for example, the speed control signal for the drive motor 72 is controlled so that the speed difference Δv falls within the permissible range, and the registration roll 50 to change the conveying speed _{v 1} of the sheet 100 by.
In this state, the conveying speed v ₁ of the sheet 100 by the registration roll 50 and the moving speed v ₂ of the intermediate transfer belt 30 are kept substantially coincident with each other, so that the sheet 100 becomes a batch transfer site (secondary transfer site). Even if it enters, the drawing or pressing force does not act on the sheet 100 between the batch transfer site and the resist roll 50 site, and the image misalignment (mainly color misregistration) at the primary transfer site or the secondary transfer site. ) Will not occur.

Embodiment 3
FIG. 5 shows Embodiment 3 of an image forming apparatus to which the present invention is applied.
In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment. However, unlike the first embodiment, a misregistration detection sensor 80 is provided on the outer side corresponding to one side in the width direction of the intermediate transfer belt 30. disposed captures the positional displacement information from the displacement detection sensor 80 to the controller 70, and changing control of the conveying speed v ₁ of the sheet 100 by the registration roll 50 by the controller 70.
The misregistration detection sensor 80 is disposed so as to face the outside of the intermediate transfer belt 30 located on the downstream side of the most downstream image forming unit 20K, and the misregistration formed on the intermediate transfer belt 30. The state of the detection pattern M (see FIG. 6A) is detected.

In the present embodiment, as shown in FIG. 6A, for example, the misregistration detection pattern M is an area other than the image forming area R of the intermediate transfer belt 30 (for example, the widthwise side of the image forming area R). Region or an interimage between image forming regions R), for example, cyan and black ladder charts M _C and M _K , as shown in FIG. it is obtained so as to form alternately every gap d _0.
Then, positional deviation detecting sensor 80, the cyan ladder chart to detect the gap between the M _C and black ladder chart M _K, positional deviation that indicates the gap therebetween is deviated degree relative to the reference gap d ₀ (Variation direction, variation amount) can be discriminated.
In particular, in the present embodiment, a misregistration detection cycle is provided in addition to the normal image forming cycle, and the control device 70 passes the sheet 100 to be used during the misregistration detection cycle. The positional deviation of the positional deviation detection pattern M is determined, and the above-described speed control is performed. Here, the misregistration detection cycle may be arbitrarily set, for example, at the same time when the communication report is automatically printed out, but can be executed in advance in a situation where misalignment of the image is likely to occur. It is preferable to do so.
In this example, the misregistration detection cycle is provided separately from the imaging cycle, but it may be performed simultaneously with the imaging cycle.

Next, the operation of the image forming apparatus according to the present embodiment will be described.
Assuming that the misregistration detection cycle is executed, the control device 70 passes the sheet 100 to be used, and the misregistration detection pattern M is used by the cyan and black image forming units 20 (20C, 20K). (Specifically, M _C , M _K ) are formed, and after primary transfer onto the intermediate transfer belt 30, the positional deviation detection sensor 80 detects the positional deviation detection pattern M.
Here, for example, if it is assumed that a sheet 100 such as a thick cardboard sheet having entered the collective transfer portion, the sheet 100 is attracted and pressed between the collective transfer portion and the resist roll 50 portion, and the intermediate transfer belt 30 is pulled. Speed fluctuation occurs. If the misregistration detection cycle is performed in this state, misregistration detection patterns M (specifically, M _C and M _K ) formed on the intermediate transfer belt 30 are shown in FIG. 6C, for example. shown as the become cyan ladder chart M _C and black ladder chart M value greater than the gap, for example, reference gap d ₀ between the _K d _{1 (or} smaller), the gap difference between the two (change direction, Fluctuation amount) is determined as an image positional deviation (registration deviation).
Specifically, when the sheet 100 is attracted or pressed between the batch transfer site and the resist roll 50 site, image misalignment (registration misalignment) occurs as shown in part A of FIG.

At this time, in the present embodiment, the control device 70 stores in advance the image positional deviation (registration deviation) based on the positional deviation detection pattern M as data, and based on the detection information from the positional deviation detection sensor 80. in a direction to eliminate the positional deviation of the image, to change the conveying speed v ₁ of the sheet 100 by the registration roll 50.
In this state, the conveying speed v ₁ of the sheet 100 by the registration roll 50 and the moving speed v ₂ of the intermediate transfer belt 30 are kept substantially coincident with each other, so that the sheet 100 becomes a batch transfer site (secondary transfer site). Even if it enters, the drawing or pressing force does not act on the sheet 100 between the batch transfer site and the resist roll 50 site, and the image misalignment (mainly color misregistration) at the primary transfer site or the secondary transfer site. ) Will not occur.

Embodiment 4
FIG. 8 shows Embodiment 4 of an image forming apparatus to which the present invention is applied.
In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, a speed sensor 91 is disposed immediately downstream of the registration roll 50 in the sheet conveyance path. captures the speed information from the speed sensor 91 to the controller 70, and changing control of the conveying speed v ₁ of the sheet 100 by the registration roll 50 by the controller 70.

In the present embodiment, the control device 70 stores, for example, the normal temperature and the conveying speed v ₁ of the sheet 100 by the registration roll 50 at the initial time in the RAM, and based on the speed information from the speed sensor 91. Then, after grasping the conveyance speed v ₁ of the sheet 100 by the registration roll 50, this is compared with the initial speed data, and under the condition that the difference between the two exceeds a predetermined allowable range, the speed difference For example, a speed control signal for the drive motor 72 is controlled so that the conveyance speed v ₁ of the sheet 100 by the registration roll 50 is changed.
In this state, the velocity data of the initial stage, because that corresponds approximately normal to the moving velocity v ₂ of the intermediate transfer belt 30, the movement of the conveying speed v ₁ and the intermediate transfer belt 30 of the sheet 100 by the registration roll 50 has been changed It kept approximately identical to the state of the speed v _2. For this reason, even if the sheet 100 enters the batch transfer site (secondary transfer site), the attracting or pressing force does not act on the sheet 100 between the batch transfer site and the resist roll 50 site, and the primary transfer. There is no image displacement (mainly color misregistration) at the site or secondary transfer site.

Embodiment 5
FIG. 9 shows Embodiment 5 of an image forming apparatus to which the present invention is applied.
In the drawing, the basic configuration of the image forming apparatus is substantially the same as that of the fourth embodiment, but unlike the fourth embodiment, the first speed sensor 91 is provided immediately downstream of the registration roll 50 in the sheet conveyance path. The second speed sensor 92 is disposed immediately after the batch transfer portion, and the speed information from each of the speed sensors 91 and 92 is taken into the control device 70, and the control device 70 uses the registration roll 50 for the sheet 100. It controls the conveying speed v ₁ of the change.

In the present embodiment, the control device 70 grasps the conveyance speed v ₁ of the sheet 100 by the registration roll 50 based on the speed information of the first speed sensor 91 and uses the speed information from the second speed sensor 92. after indexing the conveying speed by grasping the (corresponding to the moving velocity v ₂ of the intermediate transfer belt 30), both the speed difference Δv at these velocity information of the sheet 100 in the collective transfer sites based, the speed difference is previously Under a condition that exceeds the predetermined allowable range, for example, a speed control signal for the drive motor 72 is controlled so that the speed difference falls within the allowable range, and the conveyance speed v ₁ of the sheet 100 by the registration roll 50 is changed. .
In this state, the conveying speed v ₁ of the sheet 100 by the registration roll 50 and the moving speed v ₂ of the intermediate transfer belt 30 are kept substantially coincident with each other, so that the sheet 100 becomes a batch transfer site (secondary transfer site). Even if it enters, the drawing or pressing force does not act on the sheet 100 between the batch transfer site and the resist roll 50 site, and the image misalignment (mainly color misregistration) at the primary transfer site or the secondary transfer site. ) Will not occur.

1 is an explanatory diagram showing an outline of an image forming apparatus according to the present invention. 2 is an explanatory diagram illustrating details of the image forming apparatus according to Embodiment 1. FIG. It is explanatory drawing which shows the structure of a batch transfer site | part periphery. 6 is an explanatory diagram illustrating details of an image forming apparatus according to Embodiment 2. FIG. 10 is an explanatory diagram illustrating details of an image forming apparatus according to Embodiment 3. FIG. (A) is explanatory drawing which shows the example of preparation of the color misregistration detection pattern used in Embodiment 3, (b) is explanatory drawing which shows the state without color misregistration of the color misregistration detection pattern, (c) is color misregistration. It is explanatory drawing which shows the state with the color shift of the pattern for a detection. FIG. 10 is an explanatory diagram illustrating a state in which image displacement (registration displacement) according to Embodiment 3 has occurred. FIG. 10 is an explanatory diagram illustrating details of an image forming apparatus according to a fourth embodiment. FIG. 10 is an explanatory diagram illustrating details of an image forming apparatus according to a fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Image formation means, 3 ... Transfer means, 4 ... Sheet, 5 ... Sheet conveyance member, 6 ... Image carrier drive means, 7 ... Sheet conveyance drive means, 8 ... Speed difference discrimination means, 9 ... Drive control means, v ₁ ... Sheet conveyance speed, v ₂ ... Movement speed of the image carrier

Claims (8)

In an image forming apparatus comprising: an image carrier on which an image is carried; an image forming unit that forms an image on the image carrier; and a transfer unit that transfers an image on the image carrier to a sheet.
An image carrier driving means for driving the image carrier;
Sheet conveyance drive means for driving the sheet conveyance member;
A speed difference discriminating means for discriminating a speed difference between the sheet conveying speed by the sheet conveying member and the moving speed of the image carrier at the transfer means passing portion;
An image forming apparatus comprising: a drive control unit that controls driving of the sheet conveyance driving unit and the image carrier driving unit so that the speed difference between the two decreases based on a determination result by the speed difference determination unit. The image forming apparatus according to claim 1.
An image forming apparatus characterized in that the drive control means drives and controls the sheet conveyance driving means based on the determination result by the speed difference determination means, and changes the sheet conveyance speed by the sheet conveyance member. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the speed difference determining means determines a speed difference based on a change in environmental temperature. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the speed difference determining means determines a speed difference based on the number of image forming sheets. The image forming apparatus according to claim 1.
The speed difference discriminating means includes a misregistration detecting means capable of detecting the misregistration of the image on the image carrier, and detects the misregistration of the image by the misregistration detecting means in a state where the sheet to be used is conveyed in advance. An image forming apparatus characterized in that, based on this, a speed difference is discriminated. The image forming apparatus according to claim 5.
An image forming apparatus, wherein the speed difference determination means detects a position deviation detection pattern formed outside the image forming area of the image carrier by the position deviation detection means. The image forming apparatus according to claim 1.
The speed difference determining means includes a speed detecting means capable of detecting the sheet conveying speed by the sheet conveying member, and determines a speed difference based on speed information from the speed detecting means. apparatus. The image forming apparatus according to claim 1.
The speed difference determination means includes speed detection means capable of detecting the sheet conveyance speed by the sheet conveyance member and the sheet conveyance speed after passing through the transfer means, and determines the speed difference based on the speed information from both speed detection means. What is claimed is: 1. An image forming apparatus comprising:

Images