JP2022093046A - Image forming device and image forming method - Google Patents

Abstract

To provide an image forming apparatus and an image forming method that, despite its simple control structure, maintain the accuracy of superposition of toner images, and reduce the consumption of toner and processing time for printing when the timing to convey a sheet to a secondary transfer unit is delayed.SOLUTION: When a sheet does not reach a predetermined sheet delay determination position on a sheet conveyance path at a predetermined sheet delay determination timing, and an image forming apparatus starts exposure by the predetermined sheet delay determination timing even with one of the rays of light used for colors obtained by color separation, the image forming apparatus cancels an image forming operation, and on the other hand, when the sheet does not reach the predetermined sheet delay determination position on the sheet conveyance path at the predetermined sheet delay determination timing, and the image forming apparatus starts exposure after the predetermined sheet delay determination timing with all the rays of light used for the colors obtained by color separation, the image forming apparatus does not cancel the image forming operation and continues to perform the image forming operation.SELECTED DRAWING: Figure 5

Description

The present invention relates to an image forming apparatus and an image forming method.

As an image forming apparatus, image data is color-separated into a plurality of colors, and light corresponding to the plurality of colors is exposed to a plurality of charged image carriers at predetermined exposure timings to obtain a plurality of toner images of a plurality of colors. Toner images of multiple colors formed on a plurality of image carriers are sequentially superposed and primary transferred to an intermediate transfer body, and the toner image primary transferred to the intermediate transfer body is transferred from the sheet accommodating portion. A so-called tandem image forming apparatus is known, in which a sheet transferred to a secondary transfer unit along a sheet transfer path is secondarily transferred at a predetermined secondary transfer timing.

The sheet is conveyed to the secondary transfer section at the timing of the secondary transfer, but it is transferred to the secondary transfer section due to slippage of the paper feed roller that feeds the sheet or the transfer roller that transfers the sheet. The sheet transfer timing may be delayed. Conventionally, when the sheet does not reach the predetermined sheet delay determination position on the sheet transfer path at the predetermined sheet delay determination timing, it is determined that the sheet transfer timing to the secondary transfer unit is not in time for the secondary transfer timing. At the same time, since the toner image once formed was uniformly discarded, waste of toner and an increase in printing time occurred (see the flowchart showing an example of control of the conventional image forming operation in FIG. 4). ..

Therefore, when a sheet transfer delay occurs, an image forming apparatus that delays the toner image formation speed and the image data transmission speed in order to make the sheet transfer timing to the secondary transfer unit in time for the secondary transfer timing is provided. It was considered (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-7949

However, if the toner image formation speed and the image data transmission speed are slowed down as in Patent Document 1, there is a problem that the control becomes complicated. Further, in the tandem image forming apparatus, there is a problem that it is extremely difficult to accurately superimpose the toner images while delaying the forming speed of the toner images.

The present invention has been made to solve the above-mentioned conventional problems, and while maintaining the accuracy of overlaying toner images while having a simple control configuration, the timing of transferring the sheet to the secondary transfer unit is set. It is an object of the present invention to provide an image forming apparatus and an image forming method for suppressing toner consumption and printing processing time in the case of delay.

In order to achieve the above object, the image forming apparatus of the present invention color-separates image data into a plurality of colors, and emits light corresponding to the plurality of colors to a plurality of charged image carriers at predetermined exposure timings. After exposure, the plurality of color toner images are sequentially formed on the plurality of image carriers, and the plurality of color toner images formed on the plurality of image carriers are sequentially superposed and primaryly transferred to the intermediate transfer body. In an image forming apparatus that secondarily transfers a toner image primaryly transferred to the intermediate transfer body from a sheet accommodating portion to a sheet conveyed to a secondary transfer portion along a sheet transport path at a predetermined secondary transfer timing, the sheet. The transfer timing of the sheet to the secondary transfer unit is based on whether or not the predetermined sheet delay determination position on the sheet transfer path is reached at the predetermined sheet delay determination timing with respect to the secondary transfer timing. The sheet delay determining means for determining whether or not the color is delayed, and the light used for the color-separated color when the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing. When even one of them starts exposure by the sheet delay determination timing, the image formation canceling means for canceling the image formation operation and the transfer timing of the sheet to the secondary transfer unit are set to the secondary transfer timing. On the other hand, when the exposure is started after the sheet delay determination timing with all of the light used for the color-separated color, the image forming operation is performed without canceling the image forming operation. It is characterized by having a means for continuing image formation to be continued.

Further, in the image forming apparatus, when the image forming continuation means starts exposure after the sheet delay determination timing of the sheet with all of the light used for the color-separated color, the color-separated color is obtained. You may wait for the start of exposure of the light used for.

Further, in the image forming apparatus, the image forming continuing means may start the exposure at the timing of transporting the sheet to the secondary transfer unit, which is delayed with respect to the secondary transfer timing.

Further, in the image forming apparatus, the sheet delay determination timing is after the exposure timing of the first light of the light corresponding to the plurality of colors and the exposure timing of the last light of the light corresponding to the plurality of colors. It may be in front of.

Further, in the image forming apparatus, the sheet delay determination timing may be before the exposure timing of the second light among the lights corresponding to the plurality of colors.

Further, in the image forming apparatus, the sheet accommodating portion includes a plurality of cassettes.
The sheet delay determination position may be provided at a position for detecting whether or not the sheet has been supplied from the plurality of cassettes.

Further, in the image forming apparatus, the sheet delay determination timing may be set according to the exposure timing of the light used for the color-separated color.

Further, in the image forming method of the present invention, the image data is color-separated into a plurality of colors, and the light corresponding to the plurality of colors is exposed to the plurality of charged image carriers at predetermined exposure timings. Color toner images are sequentially formed on the plurality of image carriers, the plurality of color toner images formed on the plurality of image carriers are superimposed and primary transferred to the intermediate transfer body, and the primary transfer is performed on the intermediate transfer body. In an image forming method in which a transferred toner image is secondarily transferred from a sheet accommodating portion to a sheet supplied from a sheet accommodating portion along a sheet transport path to a sheet supplied at a predetermined secondary transfer timing at a predetermined secondary transfer timing, the sheet is determined to have a predetermined sheet delay. Based on whether or not a predetermined sheet delay determination position on the sheet transfer path is reached at the timing, it is determined whether or not the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing. One of the lights used for the color-separated color when the sheet delay determination means is executed and the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing. However, when the exposure is started by the sheet delay determination timing, the image formation canceling means for canceling the image formation operation is executed, and the transfer timing of the sheet to the secondary transfer unit is relative to the secondary transfer timing. When the exposure is delayed and when the exposure is started after the sheet delay determination timing with all of the light used for the color-separated color, the image forming operation is continued without canceling the image forming operation. It is characterized by executing an image formation continuation means.

According to the present invention, there is an image forming apparatus and an image forming method capable of avoiding waste of toner and an increase in printing time when a delay in sheet transfer occurs while maintaining the accuracy of superimposing toner images. , Can be realized with a simple control configuration.

It is a schematic sectional drawing which shows the structure of the image forming apparatus in Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view showing an image forming unit according to the first embodiment. It is a schematic block diagram which shows the control composition in Embodiment 1. FIG. It is a flowchart which shows an example of the control of the conventional image formation operation. It is a flowchart which shows an example of the control of the image formation operation in Embodiment 1. FIG. It is a schematic sectional drawing which shows the sheet delay determination position in Embodiment 2. FIG. 6 is a timing chart showing an image forming operation when yellow (Y) is the color used. 6 is a timing chart showing an image forming operation when yellow (Y) is an unused color and magenta (M) is a used color. It is a timing chart which shows the correction of the exposure timing of the light corresponding to magenta (M) in FIG. 7A. 6 is a timing chart showing an image forming operation when both yellow (Y) and magenta (M) are unused colors and cyan (C) is a used color. It is a timing chart which shows the correction of the exposure timing of the light corresponding to cyan (C) in FIG. 8A. 6 is a timing chart showing an image forming operation when all of yellow (Y), magenta (M), and cyan (C) are unused colors. It is a timing chart which shows the correction of the exposure timing of the light corresponding to black (K) in FIG. 9A. It is a flowchart which shows an example of the control of the image formation operation in Embodiment 3.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same parts and the like are designated by the same reference numerals, and the names and functions of the parts and the like are also the same. Therefore, detailed description of those parts and the like is omitted.

(Embodiment 1)
-Structure of image forming apparatus-
FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus A in the first embodiment. FIG. 2 is a schematic cross-sectional view showing the image forming unit U in the first embodiment. In the figure, reference numeral X indicates a width direction (depth direction), the −X direction (minus X direction) is the front direction, and the + X direction (plus X direction) is the rear direction. The symbol Y indicates the left-right direction Y orthogonal to the width direction X, and the −Y direction (minus Y direction) is the left direction and the + Y direction (plus Y direction) is the right direction. The reference numeral Z indicates a vertical direction, in which the −Z direction (minus Z direction) is the downward direction and the + Z direction (plus Z direction) is the upward direction.

First, the configuration of the image forming apparatus A will be described with reference to FIGS. 1 and 2. The image forming apparatus A includes an image reading unit 1, an image forming unit 2, an intermediate transfer body 3, a secondary transfer unit 4, a sheet accommodating unit 5, a sheet detection unit 6, and a sheet roller 7. (See Fig. 1). The image forming apparatus A is provided with a sheet transport path S through which the sheet P is transported (see FIG. 1). For printing by the image forming apparatus A in the present embodiment, toners of each color of yellow (Y), magenta (M), cyan (C), and black (K) are used.

<Image reader>
The image reading unit 1 reads an image from a document and is provided on the upper part of the image forming apparatus A. The image reading unit 1 includes a document reading device 10, a document placing table 11, and an automatic document processing device 12 (see FIG. 1).

The document reading device 10 irradiates the document with light and reads an image from the document based on the reflected light. The document reading device 10 includes, for example, a light source that irradiates the document with light, a lens and an image sensor, and a mirror that guides the reflected light of the document to the lens. Image data D is generated by photoelectric conversion of the reflected light of the document incident on the image sensor through the lens by the image sensor.

The document placing table 11 is a portion on which a document is placed by a user, and is provided on the upper side of the document reading device 10 (see FIG. 1). The document mounting table 11 is made of transparent glass. The automatic document processing device 12 automatically and continuously conveys the document inserted by the user to the document reading device 10, and is provided on the upper side of the document placing table 11 (see FIG. 1). The image of the original is read by the original reading device 10 while being placed on the original placing table 11 or being conveyed to the original reading device 10 by the automatic original processing apparatus 12.

<Image forming part>
The image forming unit 2 forms a toner image based on the image data D, and includes an exposure device 20, a developing device 21 (21a to 21d), an image carrier 22 (22a to 22d), and a charger 23. It has (23a to 23d) and a cleaning unit 24 (24a to 24d) (see FIG. 2).

The exposure apparatus 20 exposes the surface of the charged image carrier 22 (22a to 22d) at predetermined exposure timings tE1 to tE4 according to each color, thereby producing an electrostatic latent image corresponding to each color. It is formed on the surface of 22 (22a to 22d). The exposure device 20 includes a light source 200, a polygon mirror 201 that scans a laser beam emitted from the light source 200, and an optical element 202 (for example, an optical element 202) for guiding the laser light reflected by the polygon mirror 201 to the image carrier 22. Lenses, mirrors, etc.) and are built-in.

The developing apparatus 21 (21a to 21d) visualizes (visualizes) an electrostatic latent image formed on the surface of each image carrier 22 with toner of each color (Y, M, C, K). .. When the developing device 21 flies the toner to the image carrier 22, the toner is supplied to the electrostatic latent image formed on the surface of the image carrier 22.

An electrostatic latent image is formed on the surface of the image carrier 22 (22a to 22d), and the image carrier 22 (22a to 22d) is rotationally driven in a predetermined direction by being driven by the main motor 910. By the rotational drive of the image carrier 22, the toner image visualized on the image carrier 22 is conveyed to the intermediate transfer body 3.

The chargers 23 (23a to 23d) uniformly charge the surface of the image carrier 22 to a predetermined potential. As the charger 23, for example, a contact type charger (for example, a roller type or a brush type) or a charger type charger is used.

The cleaning units 24 (24a to 24d) remove and recover the toner remaining on the surface of the image carrier 22 after development and image transfer.

<Intermediate transcript>
The intermediate transfer body 3 is arranged above the image carrier 22, and the toner image of each color formed on the surface of the image carrier 22 is once transferred. The intermediate transfer body 3 has an intermediate transfer belt 30, a drive roller 31, a driven roller 32, and a primary transfer roller 33.

The intermediate transfer belt 30 is an endless belt that is rotated in a predetermined direction, and is suspended from a drive roller 31 and a driven roller 32. The outer surface of the intermediate transfer belt 30 is in contact with the image carrier 22. The toner images of each color visualized on the image carriers 22 (22a to 22d) are sequentially superimposed and transferred onto the intermediate transfer belt 30. The toner image transferred onto the intermediate transfer belt 30 is conveyed to the secondary transfer unit 4 by the rotation of the intermediate transfer belt 30. The intermediate transfer belt 30 is made of, for example, a film having a thickness of about 100 μm to 150 μm.

The drive roller 31 is a roller that is rotationally driven in a predetermined direction by driving the belt motor 911, and is provided on the right end side of the intermediate transfer body 3 (see FIG. 2). The intermediate transfer belt 30 is rotated by the rotational drive of the drive roller 31.

The driven roller 32 is a roller rotatably provided along the intermediate transfer belt 30 (see FIG. 2). The driven roller 32 is rotated according to the rotation of the intermediate transfer belt 30.

The primary transfer rollers 33 (33a to 33d) are respectively arranged in a row so as to correspond to the image carrier 22 (22a to 22d) via the intermediate transfer belt 30 (see FIG. 2). By applying the transfer bias to the primary transfer roller 33, the toner image of the image carrier 22 is transferred to the intermediate transfer belt 30. This transfer bias is a high voltage transfer bias having a polarity opposite to the charging polarity (for example, the negative electrode) of the toner (for example, the positive electrode).

A conductive elastic material (for example, one made of a material such as EPDM or urethane foam) is provided on the outer peripheral surface of the primary transfer roller 33. By providing this conductive elastic material, it is possible to uniformly apply a high voltage to the intermediate transfer belt 30. Hereinafter, the transfer of the toner images of each color formed on the image carrier 22 onto the intermediate transfer belt 30 is referred to as "primary transfer".

The developing apparatus 21 (21a to 21d), the image carrier 22 (22a to 22d), the charger 23 (23a to 23d), the cleaning unit 24 (24a to 24d), and the primary transfer roller 33 (64a to 64d) are respectively. Image forming units U (U1 to U4) are configured according to the colors of yellow (Y), magenta (M), cyan (C), and black (K) (see FIG. 2). Specifically, the image forming unit (Y) U1 for forming a yellow (Y) image is provided with a developing device 21a, an image carrier 22a, a charging device 23a, and a cleaning unit 24a. .. The image forming unit (M) U2 for forming an image of magenta (M) is provided with a developing device 21b, an image carrier 22b, a charger 23b, and a cleaning unit 24b. The image forming unit (C) U3 for forming an image of cyan (C) is provided with a developing device 21c, an image carrier 22c, a charger 23c, and a cleaning unit 24c. The image forming unit (K) U4 for forming a black (K) image is provided with a developing device 21d, an image carrier 22d, a charger 23d, and a cleaning unit 24d. In the image forming unit (Y) U1, the image forming unit (M) U2, the image forming unit (C) U3, and the image forming unit (K) U4, the images of the respective colors are sequentially and sequentially transferred to the intermediate transfer body 3. , Arranged along the intermediate transfer body 3 (see FIG. 2).

<Secondary transfer unit>
The secondary transfer unit 4 transfers the toner images of each color primary transferred onto the intermediate transfer belt 30 onto the sheet P at the secondary transfer timing tP. The secondary transfer timing tP is the timing at which the toner image on the intermediate transfer belt 30 reaches the secondary transfer unit 4. The secondary transfer unit 4 has a secondary transfer roller 40 provided at a transfer site where the sheet P and the intermediate transfer belt 30 face each other. The voltage for transferring the toner image of each color on the intermediate transfer belt 30 to the sheet P on the secondary transfer roller 40, that is, the voltage having the opposite polarity (for example, positive electrode) to the charging polarity (for example, negative electrode) of the toner. Is applied. Hereinafter, the transfer of the toner image of each color transferred on the intermediate transfer belt 30 to the sheet P is referred to as "secondary transfer".

<Seat storage>
The sheet accommodating portion 5 is arranged in the lower part of the image forming apparatus A, and has a cassette 50 accommodating the sheet P used for image forming. The sheet accommodating portion 5 may have a plurality of cassettes 50. Further, the plurality of cassettes 50 may each contain sheets of any material and size.

<Sheet detector>
The seat detection unit 6 detects whether or not the seat P has reached the seat delay determination position α. The sheet delay determination position α is provided on the downstream side of the sheet accommodating portion 5 and on the upstream side of the secondary transfer portion 4 in the sheet transport path S (see FIG. 1). The sheet detection unit 6 is, for example, an optical sensor, which is a sensor that changes the level of the output signal depending on the presence or absence of the sheet P at the sheet delay determination position α.

<Seat roller>
The seat rollers 7 (7a to 7d) include a pickup roller 7a, a transport roller 7b to 7d, and a resist roller 7e.

The pickup roller 7a draws out the recording paper (sheet P) on the uppermost layer of the paper bundle of the sheet accommodating portion 5 and conveys it to the sheet transfer path S. The pickup roller 7a is rotationally driven by the drive of the pickup motor 912.

The transfer rollers 7b to 7d convey the sheet P along the sheet transfer path S. The transfer rollers 7b to 7d are rotationally driven by the drive of the transfer motor 913.

The resist roller 7e temporarily stops the sheet P conveyed from the sheet accommodating portion 5 to align the tips of the sheets P. The resist roller 7e is rotationally driven by the drive of the transfer motor 913. The transmission of the driving force to the resist roller 7e by the transfer motor 913 is turned ON / OFF by the clutch 914.

<Other configurations>
In addition to the above, the image forming apparatus A is provided with a fixing device 70 and a discharging unit 71 (see FIG. 1).

The fixing device 70 fixes the toner image on the sheet P by heating and melting the toner image transferred on the sheet P and fixing it on the sheet P, and is a secondary transfer unit in the sheet transport path S. It is provided on the upstream side of 4.

The discharge unit 71 is provided on the upper part of the image forming apparatus A, and mounts the printed sheet P face-down.

It is printed on the sheet P as follows by the image forming apparatus A described above. First, the seat P is pulled out from the seat accommodating portion 5 by the pickup roller 7a. The sheet P is conveyed to the resist roller 7e by the conveying roller 11a. Next, the sheet P is conveyed to the secondary transfer unit 4 by the resist roller 7e at a predetermined transfer timing tC. In the secondary transfer unit 4, the toner image primaryly transferred onto the intermediate transfer belt 30 is secondarily transferred to the sheet P at the secondary transfer timing tP. After that, the toner image is fixed to the sheet P by the fixing device 70. After that, the sheet P is discharged onto the discharge unit 71 via the transport roller 11b, so that printing on the sheet P is completed.
-Control of image formation-
FIG. 3 is a schematic block diagram showing a control configuration according to the first embodiment. The image forming apparatus A has a control unit 8 in addition to the above configuration. Hereinafter, the control unit 8 will be described.

<Control unit>
The control unit 8 includes a processing unit 80 including a computer such as a CPU (Central Processing Unit), a non-volatile memory such as a ROM (Read Only Memory), and a storage unit 81 including a volatile memory such as a RAM (Random Access Memory). , An I / F unit 82 that transmits / receives data to / from an external device such as a PC (personal computer) (see FIG. 3).

The image reading unit 1 and the sheet detection unit 6 are electrically connected to the input system of the control unit 8 (see FIG. 3). The image forming unit 2, the bias control circuit 90, and the controller 91 are electrically connected to the output system of the control unit 8 (see FIG. 3). The bias control circuit 90 is electrically connected to a bias power supply 900 that applies a transfer bias to the primary transfer roller 33 and a DC power supply 901 that applies a voltage to the secondary transfer roller 40. A main motor 910, a belt motor 911, a pickup motor 912, a transfer motor 913, and a clutch 914 are electrically connected to the controller 91. The main motor 910, the belt motor 911, the pickup motor 912, the transfer motor 913, and the clutch 914 are controlled by the controller 91.

The control unit 8 has a role of controlling the operation of various components (exposure / development operation of the image forming unit 2, primary transfer operation of the intermediate transfer body 3, secondary transfer operation of the secondary transfer unit 4, etc.). When the control program stored in advance in the ROM of the storage unit 81 is called by the processing unit 80 and loaded on the RAM of the storage unit 81, the operation control of the various components is executed.

<Control of operation of various components>
Hereinafter, control of operation of various components by the control unit 8 will be described.

First, the control of the exposure / development operation of the image forming unit 2 will be described. The processing unit 80 of the control unit 8 color-separates the image data D into yellow (Y), magenta (M), cyan (C), and black (K) colors. The image data D is input by the image reading unit 1 or is input from an external device such as a PC via the I / F unit 82. The image data D is a color image or a monochrome image, but even in the case of a monochrome image, the image data D may be color-separated into each color for processing for improving print quality (for example, antialiasing processing).

The processing unit 80 causes the exposure device 20 of the image forming unit 2 to start the exposure operation based on the color in which the image data D is color-separated. The exposure operation is executed for a color (hereinafter, referred to as "used color") included in the color in which the image data D is color-separated. The light exposed according to the color used is referred to as "light used for the color-separated color". For colors whose image data D is not included in the color-separated colors (hereinafter referred to as "unused colors"), the exposure operation is not executed because the toner of the unused colors does not need to be printed.

In the present embodiment, the toner images are sequentially stacked on the intermediate transfer belt 30 from the image carrier 22 (22a to 22d) in the order of yellow (Y), magenta (M), cyan (C), and black (K). Since the light is transferred, the processing unit 80 color-separates the exposure device 20 at the exposure timings tE1 to tE4 corresponding to each of yellow (Y), magenta (M), cyan (C), and black (K). The exposure operation of the light used for the color is sequentially started.

The processing unit 80 causes the developing device 21 (21a to 21d) to perform a developing operation in accordance with the exposure operation of the exposure device 20, and drives the image carrier 22 to rotate by driving the main motor 910 via the controller 91. Let me.

Next, the primary transfer operation of the intermediate transfer body 3 will be described. The processing unit 80 drives the drive roller 31 of the intermediate transfer body 3 to rotate by driving the belt motor 911 via the controller 91. The intermediate transfer belt 30 is rotated by the rotational drive of the drive roller 31.

The processing unit 80 operates the bias power supply 900 via the bias control circuit 90 in order to sequentially apply the transfer bias to the primary transfer rollers 33 (33a to 33d) in accordance with the rotation of the intermediate transfer belt 30. By applying the transfer bias to the primary transfer roller 33, the toner image is sequentially superimposed and transferred from the image carrier 22 (22a to 22d) onto the intermediate transfer belt 30. The toner images sequentially stacked and transferred on the intermediate transfer belt 30 are conveyed to the secondary transfer unit 4 by the rotation of the intermediate transfer belt 30.

Further, the control of the secondary transfer operation of the secondary transfer unit 4 will be described. In order to convey the sheet P to the secondary transfer unit 4 in accordance with the secondary transfer timing tP, the processing unit 80 turns on the clutch 914 via the controller 91 and drives the transfer motor 913 to drive the resist roller. The 7e is driven to rotate.

The processing unit 80 operates the DC power supply 901 via the bias control circuit 90 in order to apply a voltage to the secondary transfer roller 40 in accordance with the secondary transfer timing. When a voltage is applied to the secondary transfer roller, the toner image is secondarily transferred to the sheet P.

In addition to controlling the operation of the various components described above, the processing unit 80 includes a sheet delay determining means 801, an image forming canceling means 802, and an image forming continuing means 803 (see FIG. 3).

<Sheet delay determination means>
FIG. 5 is a flowchart showing an example of control of the image forming operation in the present embodiment.

The processing unit 80 executes the sheet delay determination means 801 for determining whether or not the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP. The transfer timing tC of the sheet P to the secondary transfer unit 4 may be delayed with respect to the secondary transfer timing tP due to the slip of the sheet P in the pickup rollers 7a and the transfer rollers 7b to 7d.

Specifically, the sheet delay determining means 801 transfers the sheet P to the secondary transfer unit 4 based on whether or not the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP. It is a means for determining whether or not the transfer timing tC of the above is delayed with respect to the secondary transfer timing tP, and is executed as follows.

The processing unit 80 acquires information on whether or not the sheet P has reached the sheet delay determination position α from the sheet detection unit 6 at a predetermined sheet delay determination timing tJ. The sheet delay determination timing tJ is a timing set in advance in the storage unit 81 as a timing for the processing unit 80 to acquire information from the sheet detection unit 6. The sheet delay determination timing tJ is such that at least the transfer timing tC of the sheet P to the secondary transfer unit 4 when the sheet P reaches the sheet delay determination position α at the sheet delay determination timing tJ is in time for the secondary transfer timing tP. It is set to the timing. That is, when the sheet P reaches the sheet delay determination position α by the sheet delay determination timing tJ, the processing unit 80 determines that the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP. do. On the other hand, when the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ, the processing unit 80 delays the transfer timing tC of the sheet P to the secondary transfer unit 4 with respect to the secondary transfer timing tP. Is determined.

<Means for canceling image formation>
In the processing unit 80, when the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, and even one of the lights used for the color-separated color is delayed in the sheet. When the exposure is started by the determination timing tJ, the image formation canceling means 802 is executed. The image formation canceling means 802 is a means for canceling a series of image forming operations from exposure to secondary transfer.

Cancellation of the image forming operation means that the image forming apparatus A is in a state where the image forming operation can be executed again by removing the electric charge and the toner on the image carrier 22 and removing the toner of the intermediate transfer belt 30. Refers to restoring. Cancellation of the image forming operation increases the printing processing time. Further, if the toner has already been used on the image carrier 22 or the intermediate transfer belt 30 at the time of canceling the image forming operation, the toner is wasted. Even if the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, the toner consumption and the printing processing time can be reduced by continuing the image forming operation as much as possible. It is desirable to suppress it as much as possible. Therefore, the processing unit 80 executes the following image formation continuation means 803 when the transfer timing tC of the sheet P to the secondary transfer unit 4 below is delayed with respect to the secondary transfer timing tP.

<Means for continuing image formation>
In the processing unit 80, when the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, and the sheet P of the sheet P is used for all the light used for the color-separated color. When the exposure is started after the delay determination timing tJ, the image forming continuation means 803 is executed. The image forming continuation means 803 is a means for continuing the image forming operation without canceling the image forming operation.

Even if the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, the sheet delay determination timing of the sheet P is determined by all of the light used for the color-separated colors. When the exposure is started after tJ, all of the lights used at the time of the sheet delay determination timing tJ are unexposed. Therefore, the image forming operation is canceled by waiting the exposure timing of these lights. It becomes possible to continue performing the image forming operation without any problem. As a result, when the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, the image formation operation is uniformly canceled as compared with the conventional case where the image formation operation is canceled. There is an effect that waste of toner and increase in printing time due to cancellation of the above can be suppressed. Further, since the above control does not interrupt a series of image forming operations from exposure to secondary transfer and does not affect the speed of image formation, the accuracy of superimposing the toner image on the intermediate transfer belt 30 is correct. Has the effect of being maintained.

In the present embodiment, the image forming continuation means 803 by the processing unit 80 changes to the color-separated color when the exposure is started after the sheet delay determination timing tJ of the sheet P in all of the light used for the color-separated color. Wait for the start of exposure of the light used. The processing unit 80 waits for the start of the exposure operation of the exposure apparatus 20 for a predetermined exposure standby time from the sheet delay determination timing tJ. The exposure standby time is set in advance in the storage unit 81 according to each color. Since the secondary transfer timing tP is delayed as the exposure operation starts, a grace period is given to the transfer timing tC of the sheet P to the secondary transfer unit 4 with respect to the secondary transfer timing tP. This has the effect of reducing the rate of cancellation of the image forming operation when the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP.

Further, in the present embodiment, the image forming continuation means 803 by the processing unit 80 starts the exposure in accordance with the transfer timing tC of the sheet P to the secondary transfer unit 4 which is delayed with respect to the secondary transfer timing tP. The processing unit 80 starts the exposure operation of the exposure apparatus 20 in accordance with the transfer timing tC of the sheet P to the secondary transfer unit 4 which is delayed with respect to the secondary transfer timing tP. In other words, the exposure timings tE1 to tE4 corresponding to each color are modified exposure timings based on the modified secondary transfer timing tP'modified according to the transfer timing tC in which the sheet P is conveyed to the secondary transfer unit 4. It is modified to tR1 to tR4. As a result, even when the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, the effect that the toner image is accurately secondarily transferred to the sheet P is produced. ..

A specific procedure of control by the processing unit 80 will be described with reference to FIG.

First, in step S1, the sheet delay determination means 801 is executed. Specifically, in step S1, it is determined whether or not the sheet P has reached the sheet delay determination position α by the sheet delay determination timing tJ. When the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ, that is, when the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, step S2. Proceed to. When the sheet P reaches the sheet delay determination position α by the sheet delay determination timing tJ, that is, when the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP, the process proceeds to step S16. move on.

If yellow (Y) is the color used in step S2, the process proceeds to step S5. If the exposure of the light corresponding to yellow (Y) has been started in step S5, the process proceeds to step S8, and the image formation canceling means 802 is executed. In step S5, if the exposure of the light corresponding to yellow (Y) is before the start, the process proceeds to step S11, the image formation continuing means 803 is executed, and the exposure of the light corresponding to yellow (Y) is performed. Wait for the start.

In step S3 [that is, when yellow (Y) is an unused color], and when magenta (M) is a used color, the process proceeds to step S6. If the exposure of the light corresponding to the magenta (M) has been started in step S6, the process proceeds to step S9, and the image formation canceling means 802 is executed. In step S6, if the exposure of the light corresponding to the magenta (M) is before the start, the process proceeds to step S12, the image formation continuation means 803 is executed, and the exposure of the light corresponding to the magenta (M) is performed. Wait for the start.

In step S4 [that is, when both yellow (Y) and magenta (M) are unused colors], and when cyan (C) is a used color, the process proceeds to step S7. If the exposure of the light corresponding to cyan (C) has been started in step S7, the process proceeds to step S10, and the image formation canceling means 802 is executed. In step S7, if the exposure of the light corresponding to cyan (C) is before the start, the process proceeds to step S13, the image formation continuing means 803 is executed, and the exposure of the light corresponding to cyan (C) is performed. Wait for the start.

When all of the above steps S2 to S4 are NO [that is, when all of yellow (Y), magenta (M), and cyan (C) are unused colors], black (K) is used. Only the color used. In this embodiment, in this case, since the exposure of the light corresponding to the black (K) is not started in step S4, the process proceeds to step S14, the image formation continuing means 803 is executed, and the black (K) is obtained. Wait for the start of exposure of the corresponding light.

After waiting for exposure in steps S11 to S14, the sheet P reaches the sheet delay determination position α in step 15. In the next step 16, the transfer of the sheet P to the secondary transfer unit 4 is started. Further, in the next step 17, the exposure of the light used for the color-separated color is started. The image forming operation is completed when the secondary transfer is executed on the sheet P conveyed to the secondary transfer unit 4 in step 18.

(Embodiment 2)
FIG. 6 is a schematic cross-sectional view showing the seat delay determination position α in the second embodiment.

Hereinafter, the seat delay determination position α and the seat delay determination timing tJ in the second embodiment will be described.

<Sheet delay judgment position>
In the second embodiment, the seat accommodating portion 5 has a plurality of cassettes 50 (50a to 50c). The sheet P is drawn out from the plurality of cassettes 50 (50a to 50c) into the sheet supply paths S1 to S3, and then joins the sheet transfer path S (see FIG. 6).

The seat delay determination positions α (α1 to α3) are provided in the seat supply paths S1 to S3, respectively. In other words, the sheet delay determination positions α (α1 to α3) are provided at positions for detecting whether or not the sheet P has been supplied from the plurality of cassettes 50. For example, when the sheet P is supplied from the cassette 50a, the sheet to the secondary transfer unit 4 is based on the information of whether or not the sheet P has reached the sheet delay determination position α1 at the sheet delay determination timing tJ. It is determined whether or not the transport timing tC of P is in time for the secondary transfer timing tP. This has the effect of reliably determining whether or not the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP according to the plurality of cassettes 50 (50a to 50c). ..

<Sheet delay judgment timing>
Similar to the first embodiment, the exposure apparatus 20 makes the surface of the charged image carrier 22 (22a to 22d) into each color of yellow (Y), magenta (M), cyan (C), and black (K). The exposure is performed at predetermined exposure timings tE1 to tE4 accordingly.

Here, the sheet delay determination timing tJ in the second embodiment corresponds to the black (K) corresponding to the last light after the exposure timing tE1 of the light corresponding to the yellow (Y) corresponding to the first light. It is set before the light exposure timing tE4. This has the effect that the exposure operation is started earlier and the efficiency of the image formation operation is improved as compared with the case where the sheet delay determination timing tJ is set before the exposure timing tE1. Further, when the sheet delay determination timing tJ is set before the exposure timing tE4, the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, and the image is uniformly formed. There is an effect that the situation where the operation is canceled is avoided and the consumption of toner is suppressed.

Further, the sheet delay determination timing tJ in the second embodiment is set before the exposure timing tE2 of the light corresponding to the magenta (M) corresponding to the second light. This has the effect of improving the efficiency of the image forming operation and reducing the waste of toner due to the cancellation of the image forming operation in an appropriate balance.

The seat delay determination timing tJ in the second embodiment will be further described with reference to FIGS. 7 to 10B.

FIG. 7 is a timing chart showing an image forming operation when yellow (Y) is the color used. FIG. 8A is a timing chart showing an image forming operation when yellow (Y) is an unused color and magenta (M) is a used color. FIG. 8B is a timing chart showing the correction of the exposure timing of the light corresponding to the magenta (M) in FIG. 8A. FIG. 9A is a timing chart showing an image forming operation when both yellow (Y) and magenta (M) are unused colors and cyan (C) is a used color. FIG. 9B is a timing chart showing the correction of the exposure timing of the light corresponding to cyan (C) in FIG. 9A. FIG. 10A is a timing chart showing an image forming operation when all of yellow (Y), magenta (M), and cyan (C) are unused colors. FIG. 10B is a timing chart showing the correction of the exposure timing of the light corresponding to the black (K) in FIG. 10A. In FIGS. 7 to 10B, the two-point chain line represents the electrostatic latent image and the toner image corresponding to yellow (Y), and the one-point chain line represents the electrostatic latent image and the toner image corresponding to magenta (M). The broken line represents the electrostatic latent image and the toner image corresponding to cyan (C), and the solid line represents the electrostatic latent image and the toner image corresponding to black (K).

As shown in FIG. 7, since the sheet delay determination timing tJ in the second embodiment is set after the exposure timing tE1 of the light corresponding to the yellow (Y) corresponding to the first light, the yellow (Y) is set. In the case of the color to be used, the exposure of the light corresponding to yellow (Y) has already started at the sheet delay determination timing tJ. When yellow (Y) is the color to be used and the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ, it is unavoidable to cancel the image forming operation.

However, as shown in FIG. 8A, since the sheet delay determination timing tJ in the second embodiment is set before the exposure timing tE2 of the light corresponding to the magenta (M) corresponding to the second light, it is yellow. When (Y) is an unused color, cancellation of the image forming operation is avoided even when the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ.

In the second embodiment, as shown in FIG. 8A, when yellow (Y) is an unused color and magenta (M) is a used color, the transfer timing of the sheet P to the secondary transfer unit 4 is performed. When tC is in time for the secondary transfer timing tP, the exposure of light corresponding to magenta (M) is started at the exposure timing tE2. On the other hand, as shown in FIG. 8B, when yellow (Y) is an unused color and magenta (M) is a used color, the transfer timing tC of the sheet P to the secondary transfer unit 4 is two. When the secondary transfer timing tP is delayed, the magenta (M) is supported by the modified exposure timing tR2 modified according to the transfer timing tC of the sheet P to the secondary transfer unit 4 delayed with respect to the secondary transfer timing tP. Start the exposure of the light.

Further, in the second embodiment, as shown in FIG. 9A, when both yellow (Y) and magenta (M) are unused colors and cyan (C) is the used color, the secondary color is used. When the transfer timing tC of the sheet P to the transfer unit 4 is in time for the secondary transfer timing tP, the exposure timing tE3 starts the exposure of the light corresponding to cyan (C). On the other hand, as shown in FIG. 9B, when both yellow (Y) and magenta (M) are unused colors and cyan (C) is the used color, the color is transferred to the secondary transfer unit 4. When the transfer timing tC of the sheet P is delayed with respect to the secondary transfer timing tP, the corrected exposure timing is corrected according to the transfer timing tC of the sheet P to the secondary transfer unit 4 delayed with respect to the secondary transfer timing tP. The exposure of the light corresponding to cyan (C) is started at tR3.

Further, in the second embodiment, as shown in FIG. 10A, when all of yellow (Y), magenta (M) and cyan (C) are unused colors, the sheet P to the secondary transfer unit 4 When the transfer timing tC is in time for the secondary transfer timing tP, the exposure timing tE4 starts the exposure of the light corresponding to black (K). On the other hand, as shown in FIG. 10B, when all of yellow (Y), magenta (M) and cyan (C) are unused colors, the transfer timing tC of the sheet P to the secondary transfer unit 4 is two. When it is delayed with respect to the secondary transfer timing tP, it corresponds to black (K) with the modified exposure timing tR4 modified according to the transfer timing tC of the sheet P to the secondary transfer unit 4 delayed with respect to the secondary transfer timing tP. Start the exposure of light.

(Embodiment 3)
FIG. 11 is a flowchart showing an example of control of the image forming operation in the third embodiment.

In the third embodiment, the sheet delay determination timing tJ (tJ1 to tJ4) is set according to the exposure timing tE (tE1 to tE4) of the light used for the color-separated color. The sheet delay determination timing tJ (tJ1 to tJ4) is set in the storage unit 81 in advance. Thereby, it is determined whether or not the transfer timing tC of the sheet P to the secondary transfer unit 4 is delayed with respect to the secondary transfer timing tP, respectively, according to the exposure timing of the light used for the color-separated color. Therefore, there is an effect that the efficiency of the image forming operation is improved.

Hereinafter, the procedure for controlling the image forming operation in the third embodiment will be described with reference to FIG. Steps S8 to S21 in the third embodiment are the same as steps S5 to S18 in the first embodiment, respectively.

In the third embodiment, if yellow (Y) is the color used in step S1, the process proceeds to step S4. In step S4, the sheet delay determination means 801 is executed. When the sheet P reaches the sheet delay determination position α by the sheet delay determination timing tJ1 corresponding to the exposure timing tE1, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP. At that time, the process proceeds to step S19. On the other hand, in step S4, when the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ1, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is relative to the secondary transfer timing tP. If it is late, the process proceeds to step S8.

In step S2 [that is, when yellow (Y) is an unused color], and when magenta (M) is a used color, the process proceeds to step S5. In step S5, the sheet delay determination means 801 is executed. When the sheet P reaches the sheet delay determination position α by the sheet delay determination timing tJ2 corresponding to the exposure timing tE2, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP. At that time, the process proceeds to step S19. On the other hand, in step S5, when the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ2, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is relative to the secondary transfer timing tP. If it is late, the process proceeds to step S9.

In step S3 [that is, when both yellow (Y) and magenta (M) are unused colors], and when cyan (C) is a used color, the process proceeds to step S6. In step S6, the sheet delay determination means 801 is executed. When the sheet P reaches the sheet delay determination position α by the sheet delay determination timing tJ3 corresponding to the exposure timing tE3, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP. At that time, the process proceeds to step S19. On the other hand, in step S6, when the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ3, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is relative to the secondary transfer timing tP. If it is late, the process proceeds to step S10.

If only black (K) is the color to be used, the process proceeds to step S7. In step S7, the sheet delay determination means 801 is executed. When the sheet P reaches the sheet delay determination position α by the sheet delay determination timing tJ4 corresponding to the exposure timing tE4, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is in time for the secondary transfer timing tP. When, the process proceeds to step S19, while the sheet P does not reach the sheet delay determination position α at the sheet delay determination timing tJ4, that is, the transfer timing tC of the sheet P to the secondary transfer unit 4 is the secondary transfer. When it is delayed with respect to the timing tP, the process proceeds to step S17.

The above embodiments and examples are exemplary in all respects and are not grounds for limited interpretation. Therefore, the technical scope of the present invention is not construed solely by the above-described embodiments and examples, but is defined based on the description of the scope of claims. It also includes all changes within the meaning and scope of the claims.

A Image forming device 1 Image reading unit 2 Image forming unit 3 Intermediate transfer unit 4 Secondary transfer unit 5 Sheet storage unit 6 Sheet detection unit 7 Sheet roller 8 Control unit 80 Processing unit 81 Storage unit 82 I / F unit 90 Bias control circuit 91 Controller tP Secondary transfer timing tC Transfer timing tE Exposure timing tJ Sheet delay judgment timing α Sheet delay judgment position

Claims (8)

The image data is color-separated into a plurality of colors, and the light corresponding to the plurality of colors is exposed to the plurality of charged image carriers at predetermined exposure timings, and the toner images of the plurality of colors are each exposed to the plurality of images. The toner images of the plurality of colors formed on the plurality of image carriers are sequentially superposed on the carrier and primaryly transferred to the intermediate transfer body, and the toner image primaryly transferred to the intermediate transfer body is transferred to the sheet accommodating portion. In an image forming apparatus for secondary transfer at a predetermined secondary transfer timing to a sheet transferred from the sheet to the secondary transfer unit along the sheet transfer path.
Based on whether or not the sheet reaches a predetermined sheet delay determination position on the sheet transfer path at a predetermined sheet delay determination timing, the transfer timing of the sheet to the secondary transfer unit becomes the secondary transfer timing. On the other hand, a sheet delay determining means for determining whether or not a delay is made,
When the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing, and even one of the lights used for the color-separated color is exposed by the sheet delay determination timing. Image formation canceling means for canceling the image formation operation when starting
Exposure is started when the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing, and after the sheet delay determination timing with all of the light used for the color-separated color. An image forming apparatus comprising: an image forming continuation means for continuing the image forming operation without canceling the image forming operation. The image forming apparatus according to claim 1.
When the image forming continuation means starts the exposure after the sheet delay determination timing of the sheet with all of the light used for the color-separated color, the exposure of the light used for the color-separated color An image forming apparatus characterized by waiting for a start. The image forming apparatus according to claim 2.
The image forming continuation means is an image forming apparatus, characterized in that the exposure is started at the timing of conveying the sheet to the secondary transfer unit, which is delayed with respect to the secondary transfer timing. The image forming apparatus according to any one of claims 1 to 3.
The sheet delay determination timing is characterized by being after the exposure timing of the first light of the light corresponding to the plurality of colors and before the exposure timing of the last light of the light corresponding to the plurality of colors. Image forming device. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the sheet delay determination timing is before the exposure timing of the second light among the lights corresponding to the plurality of colors. The image forming apparatus according to any one of claims 1 to 5.
The sheet accommodating portion includes a plurality of cassettes.
The image forming apparatus is characterized in that the sheet delay determination position is provided at a position for detecting whether or not the sheet is supplied from the plurality of cassettes. The image forming apparatus according to any one of claims 1 to 6.
The image forming apparatus, wherein the sheet delay determination timing is set according to the exposure timing of the light used for the color-separated color. The image data is color-separated into a plurality of colors, and the light corresponding to the plurality of colors is exposed to the plurality of charged image carriers at predetermined exposure timings, and the toner images of the plurality of colors are each exposed to the plurality of images. The toner images of the plurality of colors formed on the plurality of image carriers are sequentially formed on the carrier, and the toner images of the plurality of colors are superimposed and primary transferred to the intermediate transfer body, and the toner image primary transferred to the intermediate transfer body is transferred from the sheet accommodating portion. In an image forming method in which secondary transfer is performed at a predetermined secondary transfer timing on a sheet supplied to a secondary transfer unit along a sheet transfer path.
Based on whether or not the sheet reaches a predetermined sheet delay determination position on the sheet transfer path at a predetermined sheet delay determination timing, the transfer timing of the sheet to the secondary transfer unit becomes the secondary transfer timing. On the other hand, the sheet delay determination means for determining whether or not the delay is executed is executed, and the sheet delay determination means is executed.
When the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing, and even one of the lights used for the color-separated color is exposed by the sheet delay determination timing. When the image formation canceling means for canceling the image formation operation is executed,
When the transfer timing of the sheet to the secondary transfer unit is delayed with respect to the secondary transfer timing, and the exposure is started after the sheet delay determination timing with all of the light used for the color-separated color. An image forming method, characterized in that, when the image forming operation is performed, the image forming continuing means for continuing the image forming operation is executed without canceling the image forming operation.

Images