JP2003241611A - Image forming device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the reduction of through-put in forming an image when an image forming device is provided with a low-speed mode as a transfer paper carrier speed. <P>SOLUTION: A CPU 111 drives an intermediate transfer belt at a first speed in a normal mode, and reduces the first speed to a second speed in the low-speed mode when forming a toner image is ended. In the intermediate transfer belt, N toner image transfer areas from the first area to the N-th area corresponding to predetermined transfer paper sizes are juxtaposed in a rotary driving direction from a downstream side to an upstream side. The CPU 111 controls image forming to allow the toner image to be transferred by first-order onto the transfer areas other than at least the first one of the N toner image transfer areas, in the case of an image forming condition that the M (an integer being 1≤M<N) toner images are transferred by the predetermined transfer paper size and also in the low-speed mode. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming technique for printers, copiers, facsimile machines and the like.

[0002]

2. Description of the Related Art Conventionally, a developing means attaches toner to an electrostatic latent image formed on a photoconductor by an exposing means to form a toner image, the toner image is transferred to a transfer paper, and the transferred toner is transferred. There is known an electrophotographic image forming apparatus in which an image is fixed on a transfer sheet by a fixing unit while the transfer sheet is being conveyed. In particular, as an apparatus capable of forming a color image, it is formed on a photoreceptor. An image forming apparatus is known in which the toner image is primarily transferred to an intermediate transfer medium and the toner image transferred to the intermediate transfer medium is secondarily transferred to a transfer paper.

In this image forming apparatus, when forming a color image, toner images of a plurality of colors are sequentially formed on a photosensitive member,
Each time a toner image of each color is formed, primary transfer to the intermediate transfer medium is performed to form a color toner image on which the toner images of a plurality of colors are superposed, and the color toner image is secondarily transferred to a transfer paper. I try to get a color image. In the image forming apparatus thus configured, it is possible to perform a single color printing using a specific color among a plurality of colors, and in many cases, black toner.

On the other hand, conventionally, as a transfer paper, in addition to plain paper, an image forming apparatus capable of using thick paper such as high-quality paper, postcards, envelopes, glossy paper, and high-definition paper that is thicker than plain paper has been put into practical use. ing. However, when the above thick paper is conveyed at the same speed as the plain paper and the fixing unit is operated, sufficient fixing performance cannot be obtained and the image quality is deteriorated. Such a situation can be prevented by improving the fixing performance, for example, by increasing the heat capacity of the fixing unit, but as a result, the size of the apparatus is increased, and conversely, excessive heat is applied during fixing of plain paper to improve the image quality. In such an image forming apparatus, when thick paper is used as the transfer paper, it is sufficient to reduce the paper conveyance speed and increase the fixing time as compared with plain paper. Secures fixing performance.

In this case, an apparatus in which the process speed such as image formation on the photoconductor or primary transfer to the intermediate transfer medium is set to a low speed together with the paper transfer speed, and the process speed is usually set to a low speed. It is possible that the device remains at the speed. In the former device, since the image forming process is performed at two kinds of speeds, it takes twice as much time to find a good process set value for the developing condition and the transfer condition as compared with the case of one kind, and the device design and Although there is a problem that it takes time to confirm the operation, the latter device does not have the above problem because the image forming process has only one speed.

[0006]

However, when adopting the latter device, it is necessary to sufficiently consider the switching timing from the normal speed to the low speed. If this switching timing is synchronized with, for example, the time when the development of the photoconductor is completed,
Since it is possible to prevent the control program from becoming complicated because an increase in the number of control parameters can be avoided, the throughput of image formation may be reduced depending on the timing of completion of development of the photoconductor. For example, in the case of an apparatus that performs image forming control based on one round of the intermediate transfer medium, if the switching timing from the normal speed to the low speed is too early, the operation time at the low speed becomes long, and thus the throughput of image formation is increased. Will be reduced. Particularly, in the case where N toner image transfer areas corresponding to a preset transfer paper size are arranged in parallel in the rotational drive direction from the 1st to the Nth (N is an integer of 2 or more) as the intermediate transfer medium, When there is only one toner image to be transferred, when the one toner image is formed in the first transfer area and decelerated in synchronization with the stop of the developing unit, the remaining (N-1) transfer images are transferred. Since it takes time to pass through the area, the throughput of image formation is reduced.

The present invention has been made in view of the above problems, and provides an image forming apparatus and method capable of suppressing a decrease in the throughput of image formation in the case where a low speed mode is provided as a transfer paper conveying speed. To aim.

[0008]

In order to achieve the above object, the invention according to claim 1 is a developing means for forming a toner image by adhering toner to an electrostatic latent image formed on a photoreceptor. An intermediate transfer medium to which the toner image is primarily transferred while rotating, a secondary transfer unit to secondarily transfer the toner image primarily transferred to the intermediate transfer medium onto a transfer sheet, and the transfer sheet is conveyed. Meanwhile, in an image forming apparatus including a fixing unit that fixes the toner image onto the transfer sheet, the normal mode in which the transfer sheet is conveyed at a first speed, and the transfer sheet from at least the secondary transfer position to the fixing end position. A transport control unit having a low speed mode for transporting at a second speed lower than one speed, the intermediate transfer medium is driven at the first speed in the normal mode, and the intermediate transfer medium is driven in the low speed mode. At least the development The driving is performed at the first speed until the toner image formation by the step is completed, and the driving speed of the intermediate transfer medium is decreased from the first speed to the second speed after the toner image formation is completed, and at least until the secondary transfer is completed. An intermediate transfer medium control unit that maintains the second speed and an image formation control unit that controls the image formation on the photoconductor to change the primary transfer start position on the intermediate transfer medium according to the transfer paper size. The intermediate transfer medium has a toner image transfer area corresponding to a preset transfer paper size from the first to the Nth (N is an integer of 2 or more) from the downstream side to the upstream side in the rotational driving direction. The image forming control means transfers M toner images (M is an integer of 1 or more and less than N) of the set transfer paper size in the low speed mode. Image formation In the case of the matter is,
The image forming control is performed so that the toner image is primarily transferred to a transfer area other than at least the first transfer area of the N toner image transfer areas.

According to this structure, the normal mode for conveying the transfer sheet at the first speed and the low speed mode for conveying the transfer sheet from the secondary transfer position to the fixing end position at the second speed lower than the first speed are provided. In the normal mode, the intermediate transfer medium is driven at the first speed, and in the low speed mode, the intermediate transfer medium is driven at the first speed at least until the toner image formation by the developing unit is completed, and the toner image formation is performed. After the end, the driving speed of the intermediate transfer medium decreases from the first speed to the second speed, and is maintained at the second speed at least until the end of the secondary transfer. The intermediate transfer medium is one in which N toner image transfer areas corresponding to a preset transfer paper size are arranged in parallel from the downstream side to the upstream side in the rotational driving direction from the first to the Nth.

Then, in the case of the low speed mode and under the image forming condition for transferring the M toner images of the set transfer paper size, the image forming control means
Image formation control is performed so that the toner image is primarily transferred to a transfer area other than at least the first transfer area of the N toner image transfer areas. Here, since the driving speed of the intermediate transfer medium decreases from the first speed to the second speed after the toner image formation is completed, when the toner image is primarily transferred to the first toner image transfer area of the intermediate transfer medium, On the other hand, since the period for which the first speed is maintained becomes longer, the reduction in the throughput of image formation is suppressed.

Further, under the image forming condition, the image forming control means transfers from the N-th toner image transfer area to the M transfer areas from the N-th toner image transfer area toward the downstream side in the rotational driving direction. The image formation control may be performed so that the toner image is primarily transferred (claim 2).

According to this structure, under the above-mentioned image forming conditions, the image forming control means causes M from the Nth toner image transfer area toward the downstream side in the rotational driving direction from the Nth toner image transfer area.
Since the image formation control is performed so that the toner image is primarily transferred to each transfer area, compared with the case where the toner image is primarily transferred to the first to Mth toner image transfer areas of the intermediate transfer medium. , The period maintained at the first speed is lengthened by (N−M), so that the decrease in the throughput of image formation is suppressed accordingly.

Further, in the image forming control means, the rear end of the Mth toner image coincides with the upstream end of the Nth toner image transfer area in the rotational drive direction under the image forming condition. As described above, the image forming control may be performed (claim 3).

According to this structure, under the above-mentioned image forming conditions, the rear end of the Mth toner image is located at the upstream end of the Nth toner image transfer area in the rotational driving direction by the image forming control means. Since the image formation control is performed so that they match,
Since the period maintained at the first speed is set to the upper limit value, the decrease in the throughput of image formation is most suppressed.

According to a fourth aspect of the present invention, there is provided an abutting member that is switched between the abutting position and the separating position with respect to the intermediate transfer medium, and the abutting operation of the abutting member with respect to the intermediate transfer medium. It is further characterized by further comprising contact member control means for performing the separating operation after a preset time from the time when the toner image formation on the photoconductor is completed.

According to this structure, the contacting operation and the separating operation of the contacting member, which is arranged to be switched to the contacting position and the separating position with respect to the intermediate transfer medium, with respect to the intermediate transfer medium are performed.
The contact member control means performs the setting after a preset time from the time when the toner image is formed on the photoconductor, so that the M-th toner image primarily transferred to the intermediate transfer medium in the low speed mode. Since the image forming control is performed so that the trailing edge of the trailing edge coincides with the upstream edge of the Nth toner image transfer area in the rotational driving direction, the trailing edge of the toner image is always located at the same position. The contacting operation and the separating operation are always performed at the same timing. Therefore,
For example, at the time of primary transfer of toner images of different colors to form a color image on the intermediate transfer medium, the image formation start timing should be eliminated in order to eliminate the registration shift caused by the contact and separation operations of the contact member with respect to the intermediate transfer medium. When performing the registration control for correcting the above, the image formation start timing correction amount for the registration control becomes a constant value, so that the control configuration is simplified, and thereby the control design is easily performed.

The contact member may be, for example, a cleaning member that contacts the intermediate transfer medium to remove the residual toner on the surface, or, for example, a toner image that contacts the intermediate transfer medium and is primarily transferred to the intermediate transfer medium. A secondary transfer unit including a secondary transfer roller that secondarily transfers the image onto the transfer paper can be applied.

Further, the contact member control means contacts the intermediate transfer medium by the contact member when the primary transfer of the toner image from the photoconductor to the intermediate transfer medium is not performed. And a separating operation may be performed (Claim 5).

According to this structure, when the contact member control means does not perform the primary transfer of the toner image from the photosensitive member to the intermediate transfer medium, the contact operation of the contact member with respect to the intermediate transfer medium and Since the separating operation is performed, when the toner images of different colors are primarily transferred to the intermediate transfer medium to form a color image, for example, the contact displacement and the separating operation of the contact member with respect to the intermediate transfer medium cause registration deviation. Therefore, the deterioration of the image quality can be prevented in advance.

Here, when the abutting member is a cleaning member for removing the toner remaining on the intermediate transfer medium at the abutting position on the intermediate transfer medium (claim 6), the low speed mode is used. At this time, since the trailing edge of the toner image primarily transferred to the intermediate transfer medium is always at the same position, the contacting operation and the separating operation of the contacting member are always performed at the same timing. The contact and separation positions with respect to the medium can always be set to substantially the same position, and thus the contact and separation positions can be easily set to regions other than the N toner image transfer regions.

According to a seventh aspect of the invention, the toner image obtained by adhering toner to the electrostatic latent image formed on the photosensitive member is primarily transferred to the intermediate transfer medium, and the primary transfer is performed. In an image forming method in which a toner image is secondarily transferred to a transfer sheet and the toner image is fixed on the transfer sheet while the transfer sheet is being conveyed, a normal mode in which the transfer sheet is conveyed at a first speed, and a transfer sheet And a low speed mode in which the intermediate transfer medium is conveyed from at least a secondary transfer position to a fixing end position at a second speed lower than the first speed. In the normal mode, the intermediate transfer medium is driven at the first speed, In the low speed mode, the driving is performed at the first speed at least until the toner image formation by the developing unit is completed, and the driving speed of the intermediate transfer medium is changed from the first speed to the second speed after the toner image formation is completed.
The speed is reduced to the second speed until at least the secondary transfer is completed.
An intermediate transfer medium control step of maintaining the speed, and an image formation control step of performing image formation control on the photoconductor to change the primary transfer start position on the intermediate transfer medium according to the transfer paper size, In the intermediate transfer medium, N toner image transfer areas corresponding to a preset transfer paper size are arranged from the first to the Nth (N is an integer of 2 or more) from the downstream side to the upstream side in the rotational driving direction. In the case where the image forming control step is in the low speed mode, the set transfer paper size is M (M is an integer of 1 or more and less than N).
In the case of the image forming condition for transferring the individual toner images, the image is transferred so that the toner image is primarily transferred to a transfer area other than at least the first transfer area of the N toner image transfer areas. It is characterized by performing formation control.

According to this structure, the normal mode for transporting the transfer paper at the first speed and the low speed mode for transporting the transfer paper from at least the secondary transfer position to the fixing end position at the second speed lower than the first speed. In the normal mode, the intermediate transfer medium is driven at the first speed, and in the low speed mode, the intermediate transfer medium is driven at the first speed at least until the toner image formation by the developing unit is completed, and the toner image formation is performed. After the end, the driving speed of the intermediate transfer medium decreases from the first speed to the second speed, and is maintained at the second speed at least until the end of the secondary transfer. The intermediate transfer medium is one in which N toner image transfer areas corresponding to a preset transfer paper size are arranged in parallel from the downstream side to the upstream side in the rotational driving direction from the first to the Nth.

In the case of the low speed mode and the image forming condition for transferring the M toner images of the set transfer paper size, at least one of the N toner image transfer areas is formed. The image forming control is performed so that the toner image is primarily transferred to the transfer area excluding the transfer area. Here, since the driving speed of the intermediate transfer medium decreases from the first speed to the second speed after the toner image formation is completed, when the toner image is primarily transferred to the first toner image transfer area of the intermediate transfer medium, On the other hand, since the period for which the first speed is maintained becomes longer, the reduction in the throughput of image formation is suppressed.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a printer which is an embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an internal configuration of the printer, FIG. 2 is a block diagram showing an electrical configuration of the printer, and FIG. 3 is a development view of an intermediate transfer belt.

This printer superimposes four color toners of yellow (Y), magenta (M), cyan (C), and black (K) to form a full-color image, for example, only black (K) toner. Is used to form a monochrome image. In this printer, when a print command signal including an image signal is given to the main control unit 100 from an external device such as a host computer, the engine control unit 110 causes each unit of the engine unit 1 to respond to the control signal from the main control unit 100. Is controlled to print out an image corresponding to the image signal on the transfer paper 4 conveyed from the paper feed cassette 3 arranged below the apparatus main body 2.

As the transfer paper 4, in addition to plain paper, fine paper, postcards, envelopes, glossy paper, high-definition paper (for example, white PET)
A thick paper thicker than plain paper such as a sheet) or a transparent sheet for OHP can be used. And with this printer,
In the case of plain paper or a transparent sheet for OHP, it is conveyed at a normal first speed, and as described later, in the case of thick paper, it is conveyed at a second speed lower than the first speed.

The engine unit 1 includes the photoconductor unit 1
0, a rotary developing unit 20, an intermediate transfer unit 30, a fixing unit 40, and an exposure unit 50. The photoconductor unit 10 includes a photoconductor 11, a charging unit 12, and a cleaning unit 13, and the rotary developing unit 20 includes
Yellow developing unit 2 containing yellow toner
Y, magenta developing unit 2M containing magenta toner, cyan developing unit 2 containing cyan toner
C, a black developing unit 2K containing black toner, and the like. The intermediate transfer unit 30 includes an intermediate transfer belt 31, a vertical synchronization sensor 32, a belt cleaner 33,
A gate roller pair 34, a secondary transfer roller 35, a photoconductor driving motor 36, and the like are provided. Above 7 units 1
Each of 0, 2Y, 2M, 2C, 2K, 30, and 40 is configured to be detachable from the apparatus body 2.

The photoconductor 11 of the photoconductor unit 10 includes the seven units 10, 2Y, 2M, 2C, 2K, 30,
In the state in which 40 is attached to the apparatus main body 2, it is rotated in the direction of arrow 5 by the photoconductor driving motor 36. Around the photoconductor 11 along the rotation direction 5, the charging unit 1
2. A rotary developing unit 20 and a cleaning unit 13 are arranged.

The charging section 12 is provided with a wire electrode to which a high voltage of a predetermined level is applied, and uniformly charges the outer peripheral surface of the photoconductor 11 by, for example, corona discharge. The cleaning unit 13 is disposed on the upstream side of the charging unit 12 in the rotation direction 5 of the photoconductor 11 and remains on the outer peripheral surface of the photoconductor 11 after the primary transfer of the toner image from the photoconductor 11 to the intermediate transfer belt 31. The surface of the photoconductor 11 is cleaned by scraping off the existing toner.

The exposure unit 50 includes a laser light source 51 formed of, for example, a semiconductor laser, a polygon mirror 52 that reflects the laser light from the laser light source 51, a scanner motor 53 that drives the polygon mirror 52 to rotate at high speed, and a polygon mirror 52. A lens unit 54 for focusing the reflected laser light, a plurality of reflection mirrors 55, a horizontal synchronization sensor 5
6 and so on. The laser beam 57 reflected by the polygon mirror 52 and emitted through the lens unit 54 and the reflection mirror 55 scans the surface of the photoconductor 11 in the main scanning direction (direction perpendicular to the paper surface of FIG. 1). ,
An electrostatic latent image corresponding to the image signal is formed on the surface of the photoconductor 11. At this time, the horizontal synchronization sensor 56 obtains a synchronization signal in the main scanning direction, that is, a horizontal synchronization signal. The exposure unit 50 functions as an exposure unit.

The rotary developing section 20 adheres the toner of each color to the electrostatic latent image and develops it. The yellow developing unit 2Y, the magenta developing unit 2M, the cyan developing unit 2C, and the black developing unit 2K of the rotary developing unit 20 are rotatably provided around the axis, and these developing units 2Y, 2M, 2C and 2K are predetermined. It is movably arranged at the plurality of positions, and is selectively arranged at the contact position and the separated position with respect to the photoconductor 11. Then, a developing bias in which a direct current component or a direct current component and an alternating current component are superimposed is applied, and the toner of the color is attached to the surface of the photoconductor 11 from the developing unit in the contact position with respect to the photoconductor 11. This rotary development unit 2
0 functions as a developing unit.

Intermediate transfer belt 3 of intermediate transfer unit 30
Reference numeral 1 denotes a photoconductor driving motor 3 which is wound around a plurality of rollers and abuts on the photoconductor 11 at the primary transfer portion 14.
6 rotates together with the photoconductor 11. As shown in FIG. 3, the intermediate transfer belt 31 is an endless belt formed by joining substantially rectangular sheet bodies at a joint 71. In FIG. 3, an arrow 72 indicates a rotation driving direction, and an arrow 73 indicates a rotation axis direction. This intermediate transfer belt 31 has one end side in the rotation axis direction 73 (see FIG.
A protrusion 74 is provided on the upper side).

Further, the intermediate transfer belt 31 has a transfer inhibition area 75 and a transfer permission area 76. The transfer inhibition area 75 is set in a range of predetermined dimensions on both sides of the seam 71 from one end to the other end in the rotation axis direction 73.
The transfer permission area 76 is an area other than the transfer prohibition area 75, and is set to a rectangular area excluding one end and the other end in the rotation axis direction 73. The transfer permission area 76 has a size larger than the A3 size in the long side direction in the rotation driving direction 72. Then, as shown in FIG. 3A, an A3-size image 77, which is the long side direction in the rotational driving direction 72, can be transferred. Further, as shown in FIG. 3B, the transfer permission area 76 is divided into two sub areas 76A and 76B.
When the intermediate transfer belt 31 is rotated once, the A4 size image 78, which is the short side direction in the rotation driving direction 72, is divided into two.
It is possible to transfer sheets.

The vertical synchronizing sensor 32 is composed of, for example, a photo interrupter having a light emitting portion and a light receiving portion which are arranged to face each other, is arranged on one end side in the rotating shaft direction 73 of the rotating intermediate transfer belt 31, and passes through the protruding portion 74. Is detected, and this detection signal is used as a vertical synchronization signal that serves as a reference for image formation control by the engine control unit 110. The belt cleaner 33 is the cleaner connecting / disconnecting clutch 3.
The contact state (solid line in FIG. 1) and the separated state (broken line in FIG. 1) of the intermediate transfer belt 31 are switchably arranged by means of 7, and remain on the intermediate transfer belt 31 in the contact state. Scrape off the toner. The gate roller pair 34 is rotationally driven by the driving force of the transport system driving motor 60 being transmitted when the gate clutch is turned on.

The secondary transfer roller 35 is switched between the contact state (solid line in FIG. 1) and the separated state (broken line in FIG. 1) with respect to the intermediate transfer belt 31 by the secondary transfer roller separation / contact clutch 38. The secondary transfer roller 35 is applied with a predetermined secondary transfer bias while being in contact with the intermediate transfer belt 31, and conveys the transfer paper 4 while the intermediate transfer belt 31 is being conveyed.
The upper toner image is secondarily transferred to the transfer paper 4, and the contact position is set in the secondary transfer portion 39.

The intermediate transfer belt 31 corresponds to an intermediate transfer medium, and the belt cleaner 33 and the secondary transfer roller 35 correspond to a contact member. The secondary transfer roller 35 constitutes a secondary transfer means.

The fixing unit 40 is provided with a heating roller 41 and a pressure roller 42, and conveys the transfer paper 4 by a heat roller fixing method while transferring the toner image on the transfer paper 4 to the transfer paper 4.
It functions as a fixing means.

A half-moon-shaped pickup roller 61 is provided upward from the front end of the paper feed cassette 3 (the right end in FIG. 1).
The feed roller pair 62 is disposed, and the gate roller pair 3
4, the secondary transfer roller 35 and the fixing unit 40 are sandwiched, and a conveyance roller pair 63 and a discharge roller pair 64 are further provided, and a conveyance path for the transfer paper 4 (a chain line in FIG. 1) is formed by these. ing.

The pickup roller 61 is driven by a pickup solenoid. The feed roller pair 62, the gate roller pair 34, the secondary transfer roller 35, the heating roller 41 of the fixing unit 40, the conveyance roller pair 63, and the discharge roller pair 64 are the same conveyance system drive motor via the drive force transmission mechanism. It is connected to 60. When the feed clutch is turned on, the feed roller pair 62 is rotationally driven by transmitting the driving force of the transport system driving motor 60. The rotation speed of the transport system drive motor 60 is the same as that of the transfer paper 4
The normal first speed S for transporting plain paper as the transport speed of
1 and a second speed S2 (<S1) for transporting thick paper can be switched.

Feed roller pair 62, gate roller pair 3
4, the conveyance roller pair 63, and the discharge roller pair 64 are the transfer paper 4
Constituting the transport means.

In FIG. 2, the main controller 100 is a CPU
101, an interface 102 for exchanging control signals with an external device such as a host computer, and an image memory 103 for storing an image signal given via the interface 102. CP
Upon receiving a print command signal including an image signal from an external device via the interface 102, the U 101 converts the job data into a job data in a format suitable for an operation instruction of the engine unit 1 and sends the job data to the engine control unit 110.

The engine control unit 110 includes a CPU 111,
The ROM 112 and the RAM 113 are provided. ROM
Reference numeral 112 stores a control program of the CPU 111, and the RAM 113 temporarily stores control data of the engine unit 1, a calculation result by the CPU 111, and the like.

The CPU 111 receives the vertical synchronization signal Vsy from the vertical synchronization sensor 32 as an input signal from the engine unit 1.
nc is received and the horizontal sync signal H is sent from the horizontal sync sensor 56.
Receive sync etc. Then, the CPU 111 controls the operation of each unit of the engine unit 1 based on these input signals and the control program.

That is, the CPU 111 sends a control signal to the motor drive circuit 114 for driving the photoconductor driving motor 36 to synchronously rotate the photoconductor 11 and the intermediate transfer belt 31. Further, a control signal is sent to the motor drive circuit 115 that drives the transport system drive motor 60 to control the transport of the transfer paper 4 from the paper feed cassette 3.

At this time, the transfer paper 4 is plain paper or OHP.
If it is a transparent sheet, the transfer paper 4 is set to the first preset
While being conveyed at the speed S1, the peripheral speeds of the photoconductor 11 and the intermediate transfer belt 31 are controlled so as to match the first speed S1. On the other hand, when the transfer paper 4 is the thick paper, the thick paper (transfer paper) 4 is transported at the preset second speed S2 (<S1). Further, the photoconductor 11 and the intermediate transfer belt 31
Is controlled so that the peripheral speed thereof matches the first speed S1 until the end of the development of the photoconductor 11 (the end of the development of the fourth color in the case of a color image), and is synchronized with the end of the development. Then, deceleration is started, and the peripheral speed is controlled so as to match the second speed S2. This increases the passage time of the transfer paper 4 in the fixing unit 40, thereby compensating for the lack of the fixing capacity that occurs when the transfer paper 4 is thick paper.

Further, the CPU 111 sends a control signal to the separation clutch driving circuit 116 which drives the cleaner separation clutch 37 to control the separation and contact of the belt cleaner 33 with respect to the intermediate transfer belt 31. Also, CPU
Reference numeral 111 sends a control signal to a separation / engagement clutch drive circuit 117 that drives the separation / connection clutch 38 for the secondary transfer roller, and controls separation and contact of the secondary transfer roller 35 with respect to the intermediate transfer belt 31.

Further, the CPU 111 sends a control signal to the transfer bias generation circuit 118 which generates a transfer bias to apply the primary transfer bias to the intermediate transfer belt 31 and the secondary transfer bias to the secondary transfer roller 35. Control.

Further, the CPU 111 is, for example, the apparatus main body 2
It receives the operation content of the operation keys of the operation display panel 8 arranged on the surface of the display panel and controls the display content of the display section.

Further, when the CPU 111 forms only one image of a size capable of taking two sheets, and the transfer paper 4 is the thick paper (for example, the rotation driving direction 72).
In the case of forming only one A4 size image in the short side direction on thick paper), the toner image is transferred to the sub-region 76B of the transfer permission region 76 on the upstream side in the rotational driving direction 72. , Controls the formation of an electrostatic latent image on the photoconductor 11. The operation by this control will be described later.

The CPU 111 constitutes a conveyance control means, an intermediate transfer medium control means, an image formation control means, and a contact member control means.

Next, with reference to FIG. 4 and FIG. 5, the operation in the case of forming two images of a size capable of taking two sheets and when the transfer paper 4 is the thick paper will be described. 4 and 5 are timing charts for explaining the operation of each unit of the engine unit 1.

When a print command signal including an image signal is given to the main control unit 100 from an external device such as a host computer, the engine control unit 110 causes each unit of the engine unit 1 to respond to the control signal from the main control unit 100. Start operation. At this time, if the size of the transfer paper 4 loaded in the paper feed cassette 3 does not match the size instructed by the print command signal, a message prompting the replacement of the paper feed cassette is displayed on the operation display panel 8. To do. In addition, in FIG.
Although the printer is provided with one sheet feeding cassette 3, the present invention is not limited to this and may be a printer having a plurality of sheet feeding cassettes.

Transfer paper 4 loaded in paper feed cassette 3
When the size of the laser beam is equal to the size instructed by the print command signal, the laser light 5 from the exposure unit 50 is applied to the surface of the photoconductor 11 uniformly charged by the charging unit 12.
7 forms an electrostatic latent image according to the image signal, and the electrostatic latent image is developed by the rotary developing unit 20 to form a toner image. The toner image is formed in the primary transfer unit 14 by the intermediate transfer belt 31. Primary transfer is performed on top.

That is, in FIG. 4, the photoconductor driving motor 36 is driven at the first speed S1 to drive the intermediate transfer belt 3
1 rotates, and the vertical synchronization signal Vsync is output at times t1, t2, t3, and t4, respectively. Vertical sync signal Vsync
The image request signal Vreq for the first sheet is output after a predetermined time T1 from the trailing edge of, and an electrostatic latent image corresponding to the image signal for the first sheet is formed in synchronization with the trailing edge of the image request signal Vreq. When it is started, the developing bias is turned on.
Further, the image request signal Vreq for the second sheet is output after a predetermined time T2 (> T1) from the falling point of each vertical synchronization signal Vsync, and the second image request signal Vreq is output in synchronization with the falling edge of the image request signal Vreq.
Formation of an electrostatic latent image corresponding to the image signal of the first sheet is started.

Then, the developing units of the rotary developing section 20 are switched at times t1, t2, t3, and t4, and toner images of respective colors are formed on the photoconductor 11 and sequentially primary-transferred onto the intermediate transfer belt 31. It During this time, the secondary transfer roller 35 is separated from the intermediate transfer belt 31, so that the toner images of the respective colors are superposed on the intermediate transfer belt 31. The developing bias is at time t1, t2, t
It is turned off after a predetermined time T3, which is predetermined by the transfer paper size, from the trailing edge of each vertical synchronization signal Vsync of 3 and t4.

As a result, the toner images Y1, C1, M
The color image in which 1 and K1 are superimposed is primarily transferred to the sub-region 76A of the transfer permission region 76 of the intermediate transfer belt 31 which is the downstream side in the rotational driving direction 72, and the toner image Y
The color image in which 2, C2, M2 and K2 are superimposed is
The primary transfer is performed to the sub-region 76B on the upstream side in the rotational driving direction 72 of the transfer permission region 76 of the intermediate transfer belt 31.

Subsequently, in FIG. 5, when the last electrostatic latent image is developed (toner image K2 is formed), a predetermined time corresponding to the transfer paper size is started from time t4 (falling point of the vertical synchronizing signal Vsync). In synchronization with the developing bias being turned off at time t5, which is after T3, the deceleration of the photoconductor driving motor 36 is started, and the photoconductor driving motor 36 is driven at the peripheral speed of the second speed S2.

On the other hand, the uppermost transfer paper 4 of the transfer paper stack loaded in the paper feed cassette 3 is taken out by the pickup roller 61, conveyed by the feed roller pair 62 at the second speed S2, and transferred to the gate roller pair 34. Be nipped.
Then, the gate clutch is turned on in synchronization with the toner image on the intermediate transfer belt 31, and the transfer paper 4 is conveyed from the gate roller pair 34 toward the secondary transfer portion 39 at the second speed S2.

Then, at time t which is a predetermined time after time t6.
7, the secondary transfer roller separation / contact clutch 38 is turned on, and the secondary transfer roller 35 contacts the intermediate transfer belt 31. Next, at a time t8, which is a predetermined time after the time t6, the transfer bias generation circuit 118 transfers the secondary transfer roller 35 to the secondary transfer roller 35.
The application of the next transfer bias is turned on.

As a result, the toner images Y1 and C that have been primarily transferred to the sub-region 76A of the transfer permission region 76 of the intermediate transfer belt 31 which is the downstream side in the rotational driving direction 72.
A color image in which 1, M1 and K1 are superimposed is transferred to the first transfer paper 4.

The gate clutch is temporarily turned off after the first transfer sheet 4 is carried out, and the secondary transfer bias application time T4
Is preset according to the size of the transfer paper 4. At this time, the next transfer paper 4 is taken out by the pickup roller 61, and is fed by the feed roller pair 62 at the second speed S2.
And is nipped by the gate roller pair 34.

After the application of the gate clutch and the secondary transfer bias is turned off, the gate clutch is turned on in synchronization with the timing of the next toner image and the next transfer sheet 4 is conveyed. At time t9, which is a predetermined time after time t6. The application of the secondary transfer bias is turned on. Then, when the set application time T4 of the secondary transfer bias elapses, the application of the secondary transfer bias is turned off and the separation clutch 38 for the secondary transfer roller is turned on so that the secondary transfer is performed. The roller 35 separates from the intermediate transfer belt 31.

As a result, the toner images Y2 and C that have been primarily transferred to the sub-region 76B on the upstream side in the rotational driving direction 72 of the transfer permission region 76 of the intermediate transfer belt 31.
The color image in which 2, M2 and K2 are superimposed is transferred to the second transfer paper 4.

Then, in the fixing unit 40, the toner image is fixed on the transfer paper 4 while the transfer paper 4 is being conveyed. At this time, the transfer paper 4 moves to the second speed lower than the first speed S1.
Since the sheet is conveyed at the speed S2, a sufficient fixing time can be secured. The transfer paper 4 further includes a pair of transport rollers 6.
The sheet is conveyed by the sheet discharging unit 3 and is discharged by the pair of discharging rollers 64 to the sheet discharging unit 7 provided on the upper portion of the apparatus main body 2.

On the other hand, the contact position of the belt cleaner 33 is
The sub-region 7 of the transfer permission region 76 to which the color image in which the toner images Y2, C2, M2 and K2 are superimposed is transferred.
Immediately after the passage of 6B, the cleaner separation clutch 37 is turned on at a time t10 which is set a predetermined time after the time t6 and is set in advance so that the transfer prohibiting area 75 is passing. The cleaning of the residual toner on the intermediate transfer belt 31 is started. Then, at time t12, which is a predetermined time after the time t11 at which the vertical synchronizing signal Vsync falls next, at time t12, the cleaner engagement / disengagement clutch 37 is turned on again, and the belt cleaner 33 causes the intermediate transfer belt 31 to move.
Away from.

In the present embodiment, the next print command signal is input from the external device via the main control unit 100 by time t11, and the photoconductor drive motor 36 is driven by the photoconductor drive motor 36 at time t13, which is a predetermined time after time t11. Since the vehicle is accelerated and returned from the second speed S2 to the first speed S1, the belt cleaner 33
Considering this speed change, the separation timing of is set in advance so as to coincide with the timing at which the transfer-prohibited area 75 after one round passes the contact position of the belt cleaner 33. Then, the next image forming control is performed with reference to the time t14 which is the falling time of the next vertical synchronizing signal Vsync.

As described above, according to the operation described in FIGS. 4 and 5, the transfer paper 4 is moved to the second speed S2 lower than the first speed S1.
Since the sheet is conveyed by, it is possible to secure a sufficient fixing time, and thereby, the fixing to the transfer sheet 4, which is a thick sheet, can be performed well.

Further, since the deceleration to the second speed S2 is started in synchronization with the stop of application of the developing bias, it is not necessary to newly set the control parameter for starting the deceleration, and the control program design becomes complicated. Can be prevented in advance.

When the primary transfer is not performed, 2
Since the contacting operation and the separating operation of the next transfer roller 35 with respect to the intermediate transfer belt 31 are performed, it is possible to prevent the registration deviation due to the contacting and the separation when the color image is primarily transferred. . Further, since the contacting operation and the separating operation of the belt cleaner 33 with respect to the intermediate transfer belt 31 are performed when the primary transfer is not performed, the contacting and separating operations are performed when the color image is primarily transferred. It is possible to prevent the occurrence of the resist deviation due to.

Next, referring to FIGS. 6 to 8, the case where only one image is formed in a size capable of taking two sheets (here, the same size as in FIGS. 4 and 5), and The operation when the transfer paper 4 is the thick paper will be described. 6 and 7 are timing charts for explaining the operation of each part of the engine unit 1, and FIG. 8 is a view for explaining the image transfer position with respect to the intermediate transfer belt 31. 6 and 7, the same timings as those in FIGS. 4 and 5 are designated by the same reference numerals.

In FIG. 6, as in the case of FIG. 4, the photoconductor driving motor 36 is driven at the first speed S1 to rotate the intermediate transfer belt 31, and the vertical synchronization is performed at times t1, t2, t3, and t4. The signal Vsync is output. In this operation, the image request signal Vreq is output after a predetermined time T2 from the falling edge of each vertical synchronization signal Vsync, and the electrostatic latent image corresponding to the image signal is synchronized with the falling edge of the image request signal Vreq. When the image formation is started, the developing bias is turned on. Then, at times t1, t2, t3,
The developing unit of the rotary developing unit 20 is switched every t4, and toner images Y2, C2, M2, and K2 of each color are formed on the photoconductor 11, and the toner images Y1, C2, M2, and K2 are sequentially transferred to the intermediate transfer belt 31.
Next is transcribed. During this time, the secondary transfer roller 35 is separated from the intermediate transfer belt 31, so that the toner images of the respective colors are superposed on the intermediate transfer belt 31. The developing bias starts from the falling edge of each vertical synchronization signal Vsync,
A predetermined time T3 that is predetermined according to the transfer paper size
Later turned off.

As a result, the toner images Y2, C2, M
The color image in which 2, K2 are superposed is primarily transferred to the sub-region 76B of the transfer permission region 76 of the intermediate transfer belt 31, which is on the upstream side in the rotational driving direction 72.

Then, in FIG. 7, as in the case of FIG. 5, when the last electrostatic latent image development (formation of the toner image K2) is performed, from time t4 (falling point of the vertical synchronizing signal Vsync). The developing bias is turned off at a time t5 after a predetermined time T3 corresponding to the transfer sheet size, the deceleration of the photoconductor driving motor 36 is started in synchronization with the turning off of the developing bias, and the peripheral speed of the second speed S2 is reached. Driven by.

On the other hand, the transfer paper 4 is conveyed from the paper feed cassette 3 at the same timing as in the case of the second sheet in FIG. 5, and the gate clutch is turned on in synchronization with the toner image on the intermediate transfer belt 31. Then, the transfer paper 4 moves from the gate roller pair 34 toward the secondary transfer portion 39 at the second speed S.
It is transported by 2.

Then, at time t which is a predetermined time after time t6.
The secondary transfer roller separation / contact clutch 38 is turned on to turn the secondary transfer roller 35 into contact with the intermediate transfer belt 31. Next, at a time t9, which is a predetermined time after the time t6, the transfer bias generation circuit 118 transfers the secondary voltage to the secondary transfer roller 35.
The application of the next transfer bias is turned on. At the time when the set application time T4 of the secondary transfer bias has elapsed, the application of the secondary transfer bias is turned off, the separation clutch 38 for the secondary transfer roller is turned on, and the secondary transfer roller 35 is turned on. Separate from the intermediate transfer belt 31.

As a result, as shown in FIG. 8, in the transfer permission area 76 of the intermediate transfer belt 31, the rotational drive direction 7 is set.
The color image 78B in which the toner images Y2, C2, M2, and K2 are primarily transferred, which is primarily transferred to the sub-region 76B on the upstream side of 2, is transferred to the transfer paper 4.

On the other hand, as in the case of FIG. 5, time t10
Then, the cleaner connecting / disconnecting clutch 37 is turned on to start cleaning the residual toner on the intermediate transfer belt 31, and at time t12, the cleaner connecting / disconnecting clutch 37 is turned on again so that the belt cleaner 33 is set to the intermediate position. It is separated from the transfer belt 31. Then, the next image forming control is performed with reference to the time t14 which is the falling time of the next vertical synchronizing signal Vsync.

As described above, according to the operations of FIGS. 6 and 7,
As in the case of FIG. 4 and FIG. 5, since deceleration to the second speed S2 is started in synchronization with the stop of application of the developing bias, it is not necessary to newly set a control parameter for starting deceleration. It is possible to prevent the control program design from becoming complicated.

In this case, when the toner image is transferred to the sub-region 76A on the downstream side in the rotational driving direction 72 of the transfer permission region 76 of the intermediate transfer belt 31 and the deceleration is synchronized with the stop of the application of the developing bias. Is the sub-region 76B
The driving time at the second speed S2 is lengthened by the dimension of, and the throughput is reduced.
Of the transfer permission area 76,
Since the toner image is transferred to the sub-region 76B on the upstream side of, the decrease in throughput can be prevented.

Further, according to the operation shown in FIGS. 6 and 7, when the primary transfer of the toner image from the photoconductor 11 to the intermediate transfer belt 31 is not performed, the belt cleaner 33 and the secondary transfer roller 35 are operated. Since the contacting operation and the separating operation with respect to the intermediate transfer belt 31 are performed, the registration deviation is not caused by the contacting operation and the separating operation during the color image formation.

Next, different operations of the printer will be described with reference to FIGS. 9 and 10. FIG. 9 is a diagram illustrating an image transfer position with respect to the intermediate transfer belt 31, FIG.
Reference numeral 0 is a flowchart showing the operation procedure.

Here, in the operation of FIGS. 6 to 8, the rear end (upstream end) of the toner image on the intermediate transfer belt 31 in the rotational driving direction 72 is the upstream end of the transfer permission area 76. For each transfer paper size,
The toner image transfer start position on the downstream side is set. For example, as shown in FIG. 9, the toner image transfer start position 80 is set so that the rear end of the A4 size toner image 79 coincides with the upstream end of the transfer permission area 76.

Therefore, for each transfer paper size, the elapsed time from the output of the vertical synchronizing signal Vsync to the image request signal Vreq is obtained in advance. That is, for example, in order to start the transfer of the toner image at the toner image transfer start position 80, the vertical synchronization signal Vsync is changed to the image request signal V
The elapsed time until the output of req is obtained in advance.
These elapsed times are stored in the ROM 11 as a control program.
It is stored in 2.

Then, the CPU 111 causes the transfer permission area 7
The electrostatic latent image formation on the photoconductor 11 is controlled so that the rear end of the toner image coincides with the upstream end of the rotational drive direction 72 of 6.

When a print command signal is received from an external device such as a host computer, the routine shown in FIG. 10 is started. First, the transfer paper size included in the job data sent from the main controller 100 to the engine controller 110 is extracted. The corresponding elapsed time T0 is selected, and the driving of the engine unit 1 is started (step S1).

Next, when the vertical synchronization signal Vsync is detected from the vertical synchronization sensor 32 (step S2), the elapsed time is counted from the falling time point, and this count value reaches the elapsed time T0 selected in step S1. Then, the image request signal Vreq is output (step S3).

Then, based on the image request signal Vreq, the image formation control on the photoconductor 11 is performed (step S
4) It is determined whether the development is completed (step S5).

Here, for example, when the image based on the print command signal is a color image and yellow is developed on the photoconductor 11 (NO in step S5), the process returns to step S2, and the above steps are repeated to repeat cyan. , Magenta, and black toner images are sequentially formed, and are primary-transferred onto the intermediate transfer belt 31 and superposed on each other to form a color image.

When the development is completed, that is, the development of black is performed for a color image and the development of the single color is completed for a monochrome image (YES in step S5), the developing bias is turned off and the rotary developing unit 20 is turned on. The stop control is started, and in synchronization therewith, the deceleration of the photoconductor drive motor 36 to the second speed S2 is started (step S6).

Thereafter, as in the case of FIG. 7, the operation of the secondary transfer roller 35, the conveyance of the transfer paper 4, the belt cleaner 33, etc. are performed based on the vertical synchronizing signal Vsync (step S7). If there is no next print command signal, the process ends.

As described above, according to the operation shown in FIGS. 9 and 10, the rear end (upstream end) of the toner image in the rotational driving direction 72 is aligned with the upstream end of the transfer permission area 76. Since the intermediate transfer belt 31 starts decelerating in synchronism with the development bias being turned off, the secondary transfer roller 35 is brought into contact with and separated from the belt cleaner 33, and the belt cleaner 33 is brought into contact with and separated from it. Since the timing is always the same, it is possible to prevent control parameter settings from becoming complicated and prevent the control program from becoming difficult to design.

Further, in general, the secondary transfer roller 3 for the intermediate transfer belt 31 which is performed until the primary transfer is completed.
5, a contact member such as the belt cleaner 33 and the belt cleaner 33 moves the load on the intermediate transfer belt 31 and the intermediate transfer belt 31 expands and contracts to cause registration deviation. Registration control that corrects the start timing may be performed.
When this registration control is performed, according to the operation described with reference to FIGS. 9 and 10, the timing of contact and separation of the contact member is always the same, so the timing correction amount for registration control becomes a constant value. Therefore, complicated resist control can be prevented.

The present invention is not limited to the above embodiment, and various changes can be made to the above without departing from the spirit of the present invention.

For example, in the above embodiment, the intermediate transfer belt 31 which is an endless belt spliced at the seam 71.
However, the intermediate transfer medium of the present invention is not limited to this, and for example, an intermediate transfer belt composed of a seamless seamless endless belt or a cylindrical intermediate transfer drum may be used.

Further, in the above embodiment, the intermediate transfer belt 31 has the two sub-areas 76A and 76B of the transfer permission area 76 as the toner image transfer area arranged in parallel from the downstream side to the upstream side in the rotational driving direction 72. The sub-regions 76A and 76B each have a size capable of transferring an image of A4 size or smaller, but the size of the intermediate transfer belt 31 is not limited to this. N sub-areas as toner image transfer areas corresponding to a preset transfer paper size such as 1 to N (N is an integer of 2 or more) from the downstream side to the upstream side in the rotational drive direction 72. They may be arranged side by side. That is,
In the above embodiment, the sub area 76A corresponds to the first toner image transfer area, and the sub area 76B corresponds to the N = second toner image transfer area.

Further, in the above-mentioned embodiment, the case where only one image having a size capable of taking two sheets is formed is described with reference to FIGS. 6 to 8, but the present invention is not limited to this. For example, a sub-region as a toner image transfer region corresponding to a preset transfer paper size is the first to N from the downstream side to the upstream side in the rotational driving direction 72 (here, N is an integer of 3 or more). In the case where N sheets are arranged side by side up to the Nth sheet, N sheets are transferred under the image forming conditions for transferring M (M is an integer of 1 or more and less than N) toner images of the transfer paper size set above. Of the electrostatic latent image on the photoconductor 11 so that the toner image is primarily transferred to a transfer area other than at least the first transfer area (corresponding to the sub area 76A in the above embodiment) of the toner image transfer area. You may make it control.
In particular, if the toner image is primarily transferred from the Nth toner image transfer area to the downstream side in the rotational drive direction 72 from the Nth toner image transfer area, the decrease in throughput is most suppressed. You can

Further, under the above-mentioned image forming conditions, the photoconductor 11 is so arranged that the rear end of the Mth toner image coincides with the upstream end of the Nth toner image transfer area in the rotational driving direction 72.
If the electrostatic latent image formation control is performed, the operation control after the primary transfer can always be performed at the same timing regardless of the transfer paper size.

Further, in the above embodiment, when the toner image is not primarily transferred from the photoconductor 11 to the intermediate transfer belt 31, the belt cleaner 33 and the secondary transfer roller 35 contact the intermediate transfer belt 31. Although the contacting operation and the separating operation are performed, the present invention is not limited to this. For example, the contacting operation and the separating operation may be performed after a preset time from the time when the toner image is formed (developed) on the photoconductor 11.

Further, in the above-described embodiment, the printer which prints the image given from the external device such as the host computer is printed on the transfer paper. However, the present invention is not limited to this, and a general printer including a copying machine and a facsimile device is provided. It can be applied to an electrophotographic image forming apparatus.

[0100]

As described above, according to the first and seventh aspects of the invention, the toner image transfer area corresponding to the preset transfer paper size is 1 from the downstream side to the upstream side in the rotational driving direction. In the case of the low speed mode and the image forming condition for transferring M toner images of the set transfer paper size, the number of N intermediate transfer media from the Nth to the Nth is provided. At least one of the toner image transfer areas
Since the image formation control is performed so that the toner image is primarily transferred to the transfer area excluding the th transfer area, the driving speed of the intermediate transfer medium decreases from the first speed to the second speed after the toner image formation is completed. Therefore, compared with the case where the toner image is primarily transferred to the first toner image transfer area of the intermediate transfer medium,
Since the period maintained at the first speed becomes long, it is possible to suppress the decrease in the throughput of image formation.

According to the second aspect of the invention, in the case of the image forming conditions, N of the N toner image transfer areas are used.
Since the image forming control is performed so that the toner image is primarily transferred to the M transfer areas from the second to the downstream side in the rotational driving direction, the first to Mth toner image transfer areas of the intermediate transfer medium are transferred. As compared with the case where the toner image is primary-transferred, the period maintained at the first speed is longer by (N−M), so that the decrease in the throughput of image formation can be suppressed by that much. .

According to the third aspect of the invention, in the case of the image forming condition, the rear end of the Mth toner image coincides with the upstream end of the Nth toner image transfer area in the rotational driving direction. Since the image forming control is performed so that the period for which the first speed is maintained is set to the upper limit value, it is possible to suppress the decrease in the throughput of the image forming most.

According to the fourth aspect of the invention, the contacting operation and the separating operation with respect to the intermediate transfer medium of the contacting member arranged by switching between the contacting position and the separating position with respect to the intermediate transfer medium are respectively exposed. Since it is performed after a preset time from the time when the toner image is formed on the body, in the low speed mode, the trailing edge of the Mth toner image primarily transferred to the intermediate transfer medium is the Nth toner image. Since the image forming control is performed so as to coincide with the upstream end of the toner image transfer area in the rotational drive direction, the trailing edge of the toner image is always at the same position, so that the contacting operation and the separating operation of the contact member are performed. It can always be performed at the same timing. Therefore, when the toner images of different colors are primarily transferred to the intermediate transfer medium to form a color image, for example, image formation is performed to eliminate the registration deviation caused by the contacting operation and the separating operation of the contacting member with respect to the intermediate transfer medium. When the registration control for correcting the start timing is performed, the image formation start timing correction amount for the registration control becomes a constant value, so that the control configuration can be simplified, which facilitates the control design. You can

Further, according to the invention of claim 5, when the primary transfer of the toner image from the photoconductor to the intermediate transfer medium is not performed, the contacting operation and the separating operation of the contacting member with respect to the intermediate transfer medium are performed. Therefore, when the toner images of different colors are primarily transferred to the intermediate transfer medium to form a color image, for example, the contact deviation and the separation operation of the contact member with respect to the intermediate transfer medium cause misregistration. Does not occur, and this makes it possible to prevent deterioration of image quality.

According to the sixth aspect of the invention, the contact member is a cleaning member for removing the toner remaining on the intermediate transfer medium at the position of contact with the intermediate transfer medium. At this time, since the trailing edge of the toner image primarily transferred to the intermediate transfer medium is always at the same position, the contacting operation and the separating operation of the contacting member are always performed at the same timing. The contact and separation positions with respect to the medium can always be set to substantially the same position, and thus the contact and separation positions can be easily set to regions other than the N toner image transfer regions.

[Brief description of drawings]

FIG. 1 is a diagram showing an internal configuration of a printer which is an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the printer.

3A and 3B are development views of an intermediate transfer belt.

FIG. 4 is a timing chart illustrating an operation of each unit of the engine unit.

FIG. 5 is a timing chart for explaining the operation of each part of the engine part, showing the continuation of FIG.

FIG. 6 is a timing chart illustrating the operation of each unit of the engine unit.

FIG. 7 is a timing chart for explaining the operation of each part of the engine part, showing the continuation of FIG.

FIG. 8 is a diagram illustrating an image transfer position with respect to an intermediate transfer belt.

FIG. 9 is a diagram illustrating an image transfer position on the intermediate transfer belt in different operations.

FIG. 10 is a flowchart showing an operation procedure.

[Explanation of symbols]

4 Transfer Paper 11 Photoreceptor 20 Rotary Developing Unit (Developing Means) 31 Intermediate Transfer Belt (Intermediate Transfer Medium) 33 Belt Cleaner (Abutting Member, Cleaning Member) 35 Secondary Transfer Roller (Secondary Transfer Means, Abutting Member) 40 Fixing unit (fixing means) 76 Transfer permission areas 76A, 76B Sub area (toner image transfer area) 110 Engine control section 111 CPU (conveyance control means, intermediate transfer medium control means, image formation control means, contact member control means) S1 First speed S2 Second speed

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/10 G03G 21/00 310 F term (reference) 2H027 DA33 DA34 DA40 DC02 DC04 DC10 DC19 ED02 ED06 ED08 ED16 ED24 ED28 EE03 EE07 EF06 2H030 AD05 AD08 AD17 BB24 BB42 BB56 2H134 GA06 GB02 HD08 HD18 KA33 KA40 KB07 KC03 KG04 KH02 KJ02 2H200 FA20 GA02 GA04 GA23 GA34 GA47 GA50 GB25 HA03 HB12 HB22 JA02 JA29 JA30 JC04 JC12 JC19 LB02 LB09 LB13 LB39 PA10 PA11 PA26 PB13

Claims (7)

[Claims] 1. A developing unit that adheres toner to an electrostatic latent image formed on a photoconductor to form a toner image, an intermediate transfer medium on which the toner image is primarily transferred while rotating, and the intermediate transfer. An image forming apparatus comprising: a secondary transfer unit that secondarily transfers a toner image that is primarily transferred to a medium onto a transfer sheet; and a fixing unit that fixes the toner image onto the transfer sheet while conveying the transfer sheet. A transport control unit having a normal mode for transporting the transfer paper at a first speed and a low speed mode for transporting the transfer paper from at least the secondary transfer position to the fixing end position at a second speed lower than the first speed; In the normal mode, the intermediate transfer medium is driven at the first speed, and in the low speed mode, the intermediate transfer medium is driven at the first speed at least until the toner image formation by the developing unit is completed. An intermediate transfer medium control unit that reduces the driving speed of the intermediate transfer medium from the first speed to the second speed after completion of the toner image formation and maintains the second speed at least until the end of the secondary transfer; Image forming control means for performing image formation control on the photoconductor to change the primary transfer start position on the intermediate transfer medium, the intermediate transfer medium corresponding to a preset transfer paper size. The toner image transfer areas are arranged in parallel from the first to the Nth (N is an integer of 2 or more) from the downstream side to the upstream side in the rotational drive direction. In the case of the mode, and under the image forming condition of transferring M (M is an integer of 1 or more and less than N) toner images of the set transfer paper size, the N toner image transfer regions At least of the above Toner image 1 to a transfer region excluding the second transfer region
An image forming apparatus, wherein the image forming control is performed so that the image is transferred next. 2. The image forming control means sets N out of the N toner image transfer areas under the image forming condition.
2. The image forming control according to claim 1, wherein the image forming control is performed so that a toner image is primarily transferred to M transfer areas from the second to the downstream side in the rotational driving direction. Forming equipment. 3. The image forming control means, in the case of the image forming condition, a rear end of the Mth toner image coincides with an upstream end of the Nth toner image transfer area in the rotational driving direction. The image forming apparatus according to claim 2, wherein the image forming control is performed as described above. 4. An abutting member that is switched between a contacting position and a separating position with respect to the intermediate transfer medium, and a contacting operation and a separating operation of the contacting member with respect to the intermediate transfer medium, respectively. The image forming apparatus according to claim 3, further comprising an abutting member control unit that is configured to perform a preset time after the completion of toner image formation on the sheet. 5. The abutting member control means causes the abutting member to abut on the intermediate transfer medium when primary transfer of the toner image from the photoconductor to the intermediate transfer medium is not performed. The image forming apparatus according to claim 4, wherein the image forming apparatus performs a separating operation. 6. The cleaning member according to claim 4, wherein the contact member is a cleaning member that removes toner remaining on the intermediate transfer medium at a position where the contact member contacts the intermediate transfer medium. Image forming device. 7. A toner image obtained by adhering toner to an electrostatic latent image formed on a photoconductor is primarily transferred to an intermediate transfer medium, and the toner image that is primarily transferred is secondarily transferred to a transfer paper. Then, in the image forming method in which the toner image is fixed on the transfer sheet while conveying the transfer sheet, the normal mode in which the transfer sheet is conveyed at the first speed and the fixing of the transfer sheet from at least the secondary transfer position are completed. A low speed mode in which the intermediate transfer medium is conveyed to a position at a second speed lower than the first speed, the intermediate transfer medium is driven at the first speed in the normal mode, and at least the developing unit in the low speed mode. Is driven at the first speed until the toner image formation is completed, and the driving speed of the intermediate transfer medium is decreased from the first speed to the second speed after the toner image formation is completed, and at least before the secondary transfer is completed. An intermediate transfer medium control step of maintaining the second speed, and an image formation control step of performing image formation control on the photoconductor to change the primary transfer start position on the intermediate transfer medium according to the transfer paper size. The intermediate transfer medium has a toner image transfer area corresponding to a preset transfer paper size from the first to the Nth (N is an integer of 2 or more) from the downstream side to the upstream side in the rotational driving direction. In the image forming control step, M toner images of the set transfer paper size (M is an integer of 1 or more and less than N) are transferred in the image forming control step. If the image forming condition is such that the toner image is 1 in the transfer area excluding at least the first transfer area among the N toner image transfer areas.
An image forming method, wherein the image forming control is performed so that the image is transferred next.