JPH1115297A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily form an image having a single color and an image having two or more colors and to simplify the control of primary transfer. SOLUTION: In an image non-formation area in the longitudinal direction of an intermediate transfer belt 21 on which toner images equivalent to images on two sheets of A4-size, normal size, can be transferred at the same time, two reference marks 27a and 27b for the determination of a temporary transfer position are provided with a fixed amount of space left between them. Also, in the case an image to be formed has a single color, a toner image formed on a photoreceptor 11 is primarily transferred to the intermediate transfer belt 21 based on the detection of the reference marks 27a and 27b, likewise in the case of an image having two or more colors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of forming images on two surfaces simultaneously with a digital color copying machine, a printer, or the like, and more particularly to an improvement in image forming efficiency.

[0002]

2. Description of the Related Art As shown in FIG. 7, an image forming apparatus for forming an image of a document read by a document reading device or image information sent from a host device includes an image forming unit 1, primary transfer units 2 and 2 as shown in FIG. Next transfer unit 3 and fixing unit 4
Having. The image forming unit 1 includes a charging charger 2 disposed around a photoconductor 11, an image writing unit 13, and a rotary or fixed type including black (K), cyan (C), magenta (M), and yellow (Y). And an electrostatic latent image is formed on the photoreceptor 11 by the laser beam from the image writing unit 13, and the formed electrostatic latent image is formed by the color developing unit 14. Visualize to form a toner image. The primary transfer unit 2 includes an intermediate transfer belt 21, a primary transfer unit 22, and a plurality of tension rollers 2.
It has a reference position sensor 25 for reading a reference mark 27 of the intermediate transfer belt 21, a secondary transfer roller 24, and a cleaning unit 26, and primarily transfers a toner image formed on the photoconductor 11 to the intermediate transfer belt 21. Intermediate transfer belt 21
Has a length equal to or more than twice as large as the reference image size, for example, A4 size, and can simultaneously transfer toner images of two surfaces. As shown in FIG. It has a mark 27. The intermediate transfer belt 21 is separated from the surface of the photoconductor 11 by a contact / separation mechanism (not shown) except when the toner image on the photoconductor 11 is primarily transferred, and is pressed against the surface of the photoconductor 11 only when the toner is primarily transferred. The secondary transfer unit 3 secondarily transfers the toner image transferred to the intermediate transfer belt 21 to the transfer paper 5.

When a document read by the image forming apparatus configured as described above or image information sent from the host device is sent and an image forming cycle is started, image data for forming an image is one or more colors. Is determined by a command.
If the image to be formed is of one color, it is not necessary to detect the reference mark 27 of the intermediate transfer belt 21 of the primary transfer unit 2, so that the toner image formed on the photoconductor 11 of the image forming unit 1 The primary transfer is performed on the intermediate transfer belt 21 regardless of the position. The secondary transfer unit 3 secondary-transfers the toner image to the transfer paper 5 fed according to the leading end of the toner image transferred to the intermediate transfer belt 21, and the fixing unit 4 transfers the toner image to the transfer paper 5. Is heated and pressed to fix. The toner remaining on the intermediate transfer belt 21 is collected by the cleaning unit 28.

When an image to be formed has two or more colors, the toner image formed on the photoreceptor 11 is
The reference mark 27 on the intermediate transfer belt 21 is used to superimpose each color image so that there is no color shift at the time of next transfer.
Is detected by the reference position sensor 25, and the toner image formed on the photoconductor 11 is primarily transferred to the intermediate transfer belt 21 based on the mark detection signal. This primary transfer is repeated for each color. That is, when forming a two-color image, the intermediate transfer belt 21 is rotated twice, and when a full-color image is formed, the intermediate transfer belt 21 is rotated four times. The primary transfer of the toner image formed on the photoreceptor 11 to the intermediate transfer belt 21 is performed, and the images of the respective colors are superimposed without displacement. When the toner image of a predetermined color is transferred to the intermediate transfer belt 21, the intermediate transfer belt 2
The toner image is secondarily transferred onto transfer paper 5 fed in accordance with the leading end of the toner image transferred onto the transfer paper 1, and the fixing unit 4 fixes the toner image transferred onto the transfer paper 5 by heating and pressing.

[0005]

When an image of one color is formed as described above, the toner image formed on the photoreceptor 11 is primarily transferred to the intermediate transfer belt 21 irrespective of the reference mark, and two or more colors are formed. Since the toner image formed on the photoconductor 11 is primary-transferred to the intermediate transfer belt 21 with reference to the reference mark 27 when the image is formed, the control during the primary transfer is complicated.

When switching from one-color image formation to two-color or more image formation, two-sided toner images of a reference image size can be simultaneously transferred to the intermediate transfer belt 21 by two surfaces. It is necessary to switch after waiting for the detection, and the image of one color and the image of two or more colors cannot be transferred to the intermediate transfer belt 21 at the same time, and it takes time to form the image of two or more colors.

In order to prevent these problems, when forming an image of one color, the toner image formed on the photoreceptor 11 is applied to the intermediate transfer belt 21 with one reference mark 27 as a reference.
If the next transfer is performed, a waiting time until the reference mark 27 is detected is required, and it takes a long time to form an image.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages and to provide an image forming apparatus capable of rapidly forming an image of one color and an image of two or more colors.

[0009]

An image forming apparatus according to the present invention has an intermediate transfer belt capable of simultaneously transferring toner images of a reference image size formed on a photosensitive member for a plurality of surfaces. Transfer the transferred toner image to the transfer material 2
Next, a plurality of reference marks are provided as reference positions when a toner image is transferred to the intermediate transfer belt. The reference marks are formed on the photoconductor based on detection signals of the respective reference marks detected by the reference position sensor. The toner image is primarily transferred onto an intermediate transfer belt.

The image transferred to the first surface determined by the first detected reference mark of the intermediate transfer belt is a one-color image, and the image transferred to the second surface determined by the next detected reference mark is two or more colors. When the one color toner image is transferred to the first surface of the intermediate transfer belt, the one color transferred to the first surface without waiting for the completion of the transfer of the two or more color toner images on the second surface The toner image is preferably secondarily transferred to a transfer material and discharged immediately.

The image transferred to the first surface determined by the first reference mark detected on the intermediate transfer belt is an image of two or more colors, and the image transferred to the second surface determined by the next detected reference mark is one image. When a color image is transferred, the first color toner image is transferred to the second surface of the intermediate transfer belt.
It is preferable that the one-color toner image transferred to the second surface is immediately secondarily transferred to a transfer material and discharged without waiting for the completion of the transfer of the toner images of two or more colors on the surface.

Further, when the image to be transferred to the first surface determined by the first detected reference mark of the intermediate transfer belt is an image of one color of the reference size, an arbitrary image is transferred to the second surface determined by the next detected reference mark. When the image of the size is transferred, and the one-color toner image is transferred to the first surface of the intermediate transfer belt, the one-color toner image transferred to the first surface is transferred without waiting for the completion of the transfer of the toner image on the second surface. It is preferable to immediately perform secondary transfer to the transfer material and discharge the transfer material.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention has an image forming unit, a primary transfer unit, a secondary transfer unit, and a fixing unit. The image forming unit forms an electrostatic latent image on a photoreceptor by a laser beam from an image writing unit, and visualizes the formed electrostatic latent image by a color developing unit to form a toner image. The primary transfer unit includes an intermediate transfer belt wound around a plurality of tension rollers, a primary transfer unit, a secondary transfer roller, a reference position sensor, and a cleaning unit, and transfers a toner image formed on a photoconductor to the intermediate transfer belt. 1 in
Next transfer. The intermediate transfer belt has a length equal to or more than twice as large as an A4 size, which is one round, and is capable of simultaneously transferring toner images for two surfaces. The image portion has two fiducial marks at regular intervals. The secondary transfer unit secondarily transfers the toner image transferred to the intermediate transfer belt to transfer paper.

A control unit of the image forming apparatus is connected to a document reading unit and a host interface, and processes image information of the read document and image information sent from the host apparatus to manage the operation of the entire apparatus. And a transfer control unit for controlling the operations of the image forming unit, the primary transfer unit and the secondary transfer unit, and a mark detection signal from a reference position sensor, and a reference position signal including a mark determination signal to the transfer control unit. It has a position mark discriminator for outputting.

The transfer control unit forms the image on the photosensitive member based on the reference position signal including the mark discrimination signal output from the position mark discrimination unit in the same manner as when the image to be formed is one color or two or more colors. The transferred toner image is primarily transferred to the intermediate transfer belt, and the control at the time of the primary transfer is simplified.

Further, when a standard size image is formed, the toner image formed on the photoreceptor is transferred to the intermediate transfer belt based on detection of two reference marks provided on the intermediate transfer belt.
The reference mark waiting time when the next transfer is performed and a standard size image is continuously formed is greatly reduced, and a plurality of images are quickly formed.

Further, when an image of two or more colors is formed subsequent to an image of one color of the standard size, a toner image of one color is transferred to the first surface of the intermediate transfer belt, which is determined by the first detected reference mark. At this point, the one-color toner image transferred on the first surface is immediately secondary-transferred to the transfer material without waiting for the completion of the transfer of the toner image of two or more colors on the second surface determined by the reference mark detected next to the intermediate transfer belt. To form a one-color image quickly.

As described above, when one or two or more color images are sent following the standard size one color image, the first one color image formed on the first surface of the intermediate transfer belt is immediately Since the toner is secondarily transferred to the transfer material and the remaining toner is removed by the cleaning unit, the image primarily transferred to the second surface of the intermediate transfer belt on the basis of the reference mark to be detected next is larger than the standard A4 size. Images can be continuously formed even if the size is large.

Further, when an image of one color is formed on the second surface while an image of two or more colors is primarily transferred on the first surface of the intermediate transfer belt, the formed one-color image is immediately transferred to the second surface. The next transfer is performed to quickly obtain a one-color image. In addition, when an image of two or more colors is primary-transferred to the first surface of the intermediate transfer belt, an image of one color can be sequentially formed on the second surface and secondary-transferred, thereby improving image forming efficiency. be able to.

[0020]

FIG. 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention. As shown in the figure, the image forming apparatus has an image forming unit 1, a primary transfer unit 2, a secondary transfer unit 3, and a fixing unit 4. The image forming unit 1 includes a charging charger 2 disposed around a photoconductor 11, an image writing unit 13, and a rotary or fixed type including black (K), cyan (C), magenta (M), and yellow (Y). A color developing section 14 and a drum cleaning section 15,
An electrostatic latent image is formed on the photoconductor 11 by the laser beam from the image writing unit 13, and the formed electrostatic latent image is visualized by the color developing unit 14 to form a toner image. The primary transfer unit 2 includes an intermediate transfer belt 21, a primary transfer unit 22, a plurality of tension rollers 23, a secondary transfer roller 24, a reference position sensor 25, and a cleaning unit 26, and a toner image formed on the photoreceptor 11. Is primarily transferred to the intermediate transfer belt 21. As shown in the development explanatory diagram of FIG. 2, the intermediate transfer belt 21 has a length L for one rotation twice or more as large as the standard A4 size, and at the same time, toner images 6a and 6a for two surfaces. 6b can be transferred, and two reference marks 27a, 27b are provided at regular intervals in a non-image portion along the length direction.
Having. The intermediate transfer belt 21 is separated from the surface of the photoconductor 11 by a contact / separation mechanism (not shown) except when the toner image on the photoconductor 11 is primarily transferred, and is pressed against the surface of the photoconductor 11 only when the toner is primarily transferred. The secondary transfer unit 3 secondarily transfers the toner image transferred to the intermediate transfer belt 21 to the transfer paper 5.

As shown in the block diagram of FIG. 3, a controller 7 of the image forming apparatus is connected to a document reading unit 8 and a host interface 9 to read image information of the read document and an image transmitted from the host device. A central control unit 10 that processes information to manage the operation of the entire apparatus, a transfer control unit 11 that controls the operations of the image forming unit 1, the primary transfer unit 2 and the secondary transfer unit 3, and a reference position sensor 25. It has a position mark discrimination unit 12 that inputs a mark detection signal and outputs a reference position signal including a mark discrimination signal to the transfer control unit 11.

The operation of the image forming cycle of the document read by the document reading unit 8 and the image information sent from the host device in the image forming apparatus will be described with reference to the flowchart of FIG.

When the image information is sent, the central control unit 10 judges whether the image is a standard size or not, that is, an image of two or more colors or an image of one color, based on the sent command. 11 to start an image forming operation (step S1). When the image forming operation starts and the image to be formed is one color and the standard A4 size, the two reference marks 27 on the intermediate transfer belt 21 of the primary transfer unit 2
For example, the reference mark 27a first detected by the reference position sensor 25 out of the reference position sensor 25
When the mark detection signal is sent to the mark discrimination unit 12 and the mark detection signal is sent, the mark discrimination unit 12 counts the sent mark detection signal, for example, and transfers the reference position signal including the first mark discrimination signal from the count value. Send to control unit 11 (step S
2). The transfer control unit 11 transfers the toner image of the first image formed on the photoconductor 11 of the image forming unit 1 to the first image on the intermediate transfer belt 21 with reference to the reference position signal including the sent first mark determination signal. First transfer to the surface (step S
3). The secondary transfer unit 3 secondary-transfers the toner image onto the transfer paper 5 fed according to the leading end of the toner image transferred onto the intermediate transfer belt 21 (Step S4). In this state, when the next reference mark 27b is detected by the reference position sensor 25 and a mark detection signal is sent to the mark discrimination unit 12, the mark discrimination unit 12 counts the sent mark detection signal, and based on the counted value, The reference position signal including the mark determination signal of No. 2 is sent to the transfer control unit 11 (step S5). Transfer control unit 1
Reference numeral 1 designates a toner image of the next image formed on the photoreceptor 11 of the image forming unit 1 on the second surface of the intermediate transfer belt 21 with reference to a reference position signal including the transmitted second mark determination signal. Transfer is performed (step S6). The secondary transfer unit 3 secondary-transfers the toner image onto the transfer paper 5 fed according to the leading end of the toner image transferred onto the intermediate transfer belt 21 (Step S7). This process is repeated until all the sent images are transferred to the transfer paper 5 (step S8).

When the image to be formed has two or more colors, the standard A
For example, in the case of A3 size larger than four sizes (steps S1 and S9), the first reference mark 27a of the two reference marks 27a and 27b of the intermediate transfer belt 21 of the primary transfer unit 2 is detected by the reference position sensor 25. When the mark detection signal is sent to the mark discrimination unit 12 and the mark detection unit 12 detects the mark detection signal, the mark discrimination unit 12 counts the sent mark detection signal and, based on the counted value, converts the reference position signal including the first mark discrimination signal into the transfer control unit. 11 (step S10). Transfer control unit 1
1 primarily transfers the toner image formed on the photoconductor 11 of the image forming unit 1 to the intermediate transfer belt 21 based on the reference position signal including the sent first mark determination signal (step S11). During this primary transfer, the reference position sensor 25
When the next reference mark 27b is detected and a mark detection signal is sent to the mark discrimination unit 12, the mark discrimination unit 12 counts the sent mark detection signal, and judges the second mark discrimination signal from the count value. I do. At this time, the mark discriminating unit 12 does not output the reference position signal including the second mark discriminating signal because, for example, an A3 size larger than the standard A4 size is transferred. When the primary transfer of the image of the first color is completed, the primary transfer process of the next color is started. Similarly to the first color, the image forming unit 1 uses the reference position signal including the first mark determination signal as a reference. The toner image formed on the photoconductor 11 is primarily transferred to the intermediate transfer belt 21 (steps S14, S10 to S13). This primary transfer is repeated for a predetermined color, and when images of all colors are primarily transferred to the intermediate transfer belt 21 (step S14), the intermediate transfer belt 2
The toner image is secondarily transferred to the transfer paper 5 fed in accordance with the leading end of the toner image transferred to the printer 1 (step S15).
This process is repeated until all the transmitted images are transferred to the transfer paper 5 (step S16).

If the image to be formed is of two or more colors and has the standard A4 size (steps S1 and S9),
Of the two reference marks 27a, 27b of the intermediate transfer belt 21 of the next transfer unit 2, for example, the first reference mark 2
7a is detected by the reference position sensor 25 and the mark discriminating section 12 is detected.
When the mark detection signal is sent to the transfer control unit 11, the mark discrimination unit 12 counts the transmitted mark detection signal, and sends a reference position signal including the first mark discrimination signal to the transfer control unit 11 based on the counted value (step S17). . The transfer control unit 11 transfers the toner image of the first image formed on the photoconductor 11 of the image forming unit 1 to the first image on the intermediate transfer belt 21 with reference to the reference position signal including the sent first mark determination signal. The primary transfer is performed on the surface (step S18). In this state, the reference position sensor 2
5, the next reference mark 27b is detected and the mark discrimination unit 12
When the mark detection signal is sent to the transfer control unit 11, the mark discrimination unit 12 counts the transmitted mark detection signal, and sends a reference position signal including a second mark discrimination signal to the transfer control unit 11 based on the counted value (step S19). . The transfer control unit 11 applies the toner image of the next image formed on the photoconductor 11 of the image forming unit 1 to the second surface of the intermediate transfer belt 21 based on the sent reference position signal including the second mark determination signal. (Step S20). When the primary transfer of the toner image of the first color is completed, the primary transfer process of the next color is started, and the reference position signal including the first mark determination signal and the second mark determination signal is transmitted similarly to the first color. The toner image formed on the photoconductor 11 of the image forming unit 1 is primarily transferred to the intermediate transfer belt 21 on the basis of each reference (steps S21, S17 to S17).
20). This primary transfer is repeated for a predetermined color, and when images of all colors are primary-transferred to the intermediate transfer belt 21 (step S21), paper is fed in accordance with the leading end of the toner image transferred to the intermediate transfer belt 21. The toner image is secondarily transferred onto the transfer paper 5 (step S22). This process is repeated until all the sent images are transferred to the transfer paper 5 (step S23).

In the case where a one-color image is formed in this way, two
The reference mark 27 is formed in the same manner as when forming an image of more than
Since the primary transfer of the toner image formed on the photoconductor 11 to the intermediate transfer belt 21 is performed based on the detections a and 27b, the control at the time of the primary transfer can be simplified. Further, since the two reference marks 27a and 27b are provided on the intermediate transfer belt 21, the reference mark waiting time when forming images continuously can be greatly reduced, and a plurality of images can be formed quickly. Can be.

Next, the operation when an image of one color or two or more colors is transmitted following an image of one color of standard size will be described with reference to FIG.
This will be described with reference to the flowchart of FIG.

When the image forming operation is started and the image to be formed is of one color, the intermediate transfer belt 21 of the primary transfer unit 2
Of the first reference mark 27a by the mark detection signal
The toner image formed on the photoconductor 11 of the image forming unit 1 is primarily transferred to the first surface of the intermediate transfer belt 21 with reference to the reference position signal including the mark discrimination signal. Transfer the toner image of the first image to the transfer paper 5
(Steps S31 to S33). In this state, when the central control unit 10 sends that the next image is one color (step S34), the reference position sensor 25 includes the second mark discrimination signal based on the mark detection signal of the next reference mark 27b. The toner image of the next image formed on the photoconductor 11 of the image forming unit 1 is primarily transferred to the second surface of the intermediate transfer belt 21 with reference to the reference position signal, and the toner image transferred to the intermediate transfer belt 21 Is secondarily transferred to the transfer paper 5 (steps S35 to S37). If the central control unit 10 sends the next image of two or more colors (step S34), the reference position sensor 25 includes a second mark discrimination signal based on the mark detection signal of the next reference mark 27b. Image forming unit 1 based on reference position signal
Is primarily transferred to the second surface of the intermediate transfer belt 21 (step S3).
8, S39). When the primary transfer of the image of the first color to the second surface of the intermediate transfer belt 21 is completed, a primary transfer process for the next color is started (step S40). Then, after detecting the first reference mark 27a (step S41), the reference position sensor 25 sets the image forming unit 1 based on the reference position signal including the second mark discrimination signal based on the mark detection signal of the next reference mark 27b. The next color toner image formed on the photoconductor 11 is primarily transferred to the second surface of the intermediate transfer belt 21 (steps S38 and S39). This primary transfer is repeated for a predetermined color, and when images of all colors are primary-transferred to the intermediate transfer belt 21 (step S40), paper is fed according to the leading end of the toner image transferred to the intermediate transfer belt 21. The toner image is secondarily transferred onto the transfer paper 5 (Step S4)
2).

As described above, when one or two or more color images are sent following the standard size one color image, the first one color image formed on the first surface of the intermediate transfer belt 21 is Immediately after the secondary transfer to the transfer paper 5 and the remaining toner is removed by the cleaning unit 26, the reference mark 27
The image primarily transferred to the second surface of the intermediate transfer belt 21 on the basis of the reference position signal including the second mark discrimination signal based on the mark detection signal b is continuous even if the image is A3 size larger than the standard A4 size. To form an image.

Next, the operation when a standard size image of two or more colors is transmitted following a standard size image of two or more colors will be described with reference to the flowchart of FIG.

When an image to be formed has two or more colors, a standard A
In the case of four sizes, the photosensitive member 11 of the image forming unit 1 is mounted on the basis of a reference position signal including a first mark discrimination signal based on a mark detection signal of the first reference mark 27a of the intermediate transfer belt 21 of the primary transfer unit 2. The formed toner image is primarily transferred to the first surface of the intermediate transfer belt 21 (Steps S51 and S52). If the image of the first color is primary-transferred to the first surface of the intermediate transfer belt 21 and the central control unit 10 sends a message indicating that the next image has two or more colors (steps S53 and S54). The reference position sensor 25 forms a toner image of the second image formed on the photoconductor 11 of the image forming unit 1 with reference to a reference position signal including a second mark discrimination signal based on a mark detection signal of the next reference mark 27b. The primary transfer is performed on the second surface of the intermediate transfer belt 21 (Steps S55 and S56). After the primary transfer of the toner image of the first color of the second image to the second surface of the intermediate transfer belt 21 is completed, the primary transfer process of the next color is started (step S5).
7). This primary transfer is repeated for a predetermined color. When the images of all colors are primarily transferred to the intermediate transfer belt 21 (step S57), the first image and the second image transferred to the intermediate transfer belt 21 are respectively The secondary transfer is performed on the transfer paper 5 (step S58). In the case where the image of the first color is primary-transferred to the first surface of the intermediate transfer belt 21 and the central control unit 10 sends that the next image is one color (steps S53 and S54). A toner image of a second image formed on the photoconductor 11 of the image forming unit 1 with reference to a reference position signal including a second mark discrimination signal based on a mark detection signal of the next reference mark 27b by the reference position sensor 25. Is firstly transferred to the second surface of the intermediate transfer belt 21 and then immediately transferred to the transfer paper 5 (steps S59 and S6).
0, S61). After all the toner images of the predetermined color are primarily transferred to the first surface of the intermediate transfer belt 21, the toner images of two or more colors formed on the first surface are secondarily transferred to transfer paper (steps S62 and S63).

The first transfer of the intermediate transfer belt 21 is thus performed.
When an image of one color is formed on the second surface while an image of two or more colors is primarily transferred on the surface, the formed one-color image is immediately secondary-transferred. Can be obtained. Also, the second surface of the intermediate transfer belt 21 is
When an image of more than one color is primary-transferred, an image of one color can be sequentially formed on the second surface and secondary-transferred, so that image forming efficiency can be improved.

[0033]

As described above, according to the present invention, the photosensitive member is formed on the non-image portion along the length direction of the intermediate transfer belt capable of simultaneously transferring the toner images for a plurality of surfaces of the standard size image. A plurality of reference marks for determining the position where the toner image is primarily transferred are provided at regular intervals, and the
In the case of the color, similarly to the case of two or more colors, the toner image formed on the photosensitive member is primarily transferred to the intermediate transfer belt based on the detection of each reference mark. Can be simplified.

Further, when a standard size image is formed, the toner image formed on the photoreceptor is transferred to the intermediate transfer belt based on the detection of a plurality of reference marks provided on the intermediate transfer belt.
Since the next transfer is performed, a plurality of images can be quickly formed by greatly shortening the reference mark waiting time when continuously forming images of the standard size.

Further, when an image of two or more colors is formed subsequent to an image of one color of the standard size, a one-color toner image is transferred to the first surface determined by the first reference mark detected on the intermediate transfer belt. At this point, the one-color toner image transferred on the first surface is immediately secondary-transferred to the transfer material without waiting for the completion of the transfer of the toner image of two or more colors on the second surface determined by the reference mark detected next to the intermediate transfer belt. Therefore, a one-color image can be formed quickly.

As described above, when one or two or more colors of images are sent following the one-color image of the standard size, the first one-color image formed on the first surface of the intermediate transfer belt is immediately Since the toner is secondarily transferred to the transfer material and the remaining toner is removed by the cleaning unit, the image primarily transferred to the second surface of the intermediate transfer belt on the basis of the reference mark to be detected next is larger than the standard size. However, an image can be continuously formed. Image forming efficiency can be increased.

When an image of one or more colors is formed on the second surface while an image of two or more colors is primarily transferred on the first surface of the intermediate transfer belt, the formed one-color image is immediately transferred to the second surface. Since the next transfer is performed, 1 is sent following the image of two or more colors.
A color image can be obtained quickly. In addition, when an image of two or more colors is primary-transferred to the first surface of the intermediate transfer belt, an image of one color can be sequentially formed on the second surface and secondary-transferred, thereby improving image forming efficiency. be able to.

[Brief description of the drawings]

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

FIG. 2 is a development explanatory view showing reference marks provided on an intermediate transfer belt.

FIG. 3 is a block diagram illustrating a configuration of a control unit according to the embodiment.

FIG. 4 is a flowchart showing the operation of the embodiment.

FIG. 5 is a flowchart showing a second operation of the embodiment.

FIG. 6 is a flowchart showing a third operation of the embodiment.

FIG. 7 is a configuration diagram of a conventional image forming apparatus.

FIG. 8 is a perspective view showing a reference mark and a reference position sensor of the intermediate transfer belt.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Primary transfer unit 3 Secondary transfer unit 11 Photoconductor 21 Intermediate transfer belt 22 Primary transfer part 25 Reference position sensor 27a, 27b Reference mark

Claims (4)

[Claims] An intermediate transfer belt capable of simultaneously transferring toner images of a reference image size formed on a photoreceptor for a plurality of surfaces is provided, and the toner image transferred to the intermediate transfer belt is secondarily transferred to a transfer material. In an image forming apparatus, a plurality of reference marks serving as reference positions when a toner image is transferred to an intermediate transfer belt are provided, and a toner image formed on a photoconductor based on a detection signal of each reference mark detected by a reference position sensor. An image forming apparatus for performing primary transfer of an image on an intermediate transfer belt. 2. An image to be transferred to the first surface determined by the first detected reference mark of the intermediate transfer belt is a one-color image, and an image to be transferred to the second surface determined by the next detected reference mark is two. When the toner image of one color is transferred to the first surface of the intermediate transfer belt,
2. The image forming apparatus according to claim 1, wherein the one-color toner image transferred to the first surface is immediately secondarily transferred to a transfer material and discharged without waiting for the completion of the transfer of the two or more color toner images on the surface. 3. An image to be transferred to the first surface determined by the first detected reference mark of the intermediate transfer belt is an image of two or more colors, and an image to be transferred to the second surface determined by the next detected reference mark is When a one-color image is transferred to the second surface of the intermediate transfer belt when the image is a one-color image,
2. The image forming apparatus according to claim 1, wherein the one-color toner image transferred on the second surface is immediately secondarily transferred to a transfer material and discharged without waiting for the transfer of the toner images of two or more colors on the surface. 4. When the image transferred to the first surface determined by the first detected reference mark of the intermediate transfer belt is an image of one color of the reference size, the image is transferred to the second surface determined by the next detected reference mark. When an image of an arbitrary size is transferred and a one-color toner image is transferred to the first surface of the intermediate transfer belt, the one-color toner transferred to the first surface without waiting for the completion of the transfer of the toner image on the second surface 2. The image forming apparatus according to claim 1, wherein the image is immediately secondarily transferred to a transfer material and discharged.