JP6935676B2 - Image forming device and image forming program - Google Patents

Description

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

Conventionally, a toner image is held in an image holder, a transfer voltage is applied to the transfer unit while conveying a recording medium such as paper, and the held toner image is transferred to the recording medium, and then the toner image is transferred. There is known an image forming apparatus that fixes and forms an image on a recording medium. In this image forming apparatus, when the recording medium is separated from the transfer unit after the process of transferring the retained toner image to the recording medium is completed, the behavior of the rear end of the recording medium becomes unstable, and the image holder becomes an image holder. The retained toner may adhere to the rear end of the recording medium, for example, the back surface and the cut surface of the paper, and stain the rear end of the recording medium.

An image forming apparatus for increasing the transport speed of a recording medium after the rear end of the recording medium is separated from the transfer unit is disclosed in order to suppress stains due to adhesion of toner to the rear end of the recording medium (for example, Patent Document). 1). Further, when forming an image on paper in the borderless mode, an image forming apparatus that suppresses stains due to adhesion of toner to the edges of the recording medium by changing the transport speed when the tip of the recording medium enters the transfer portion. Is also disclosed (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2012-226039 Japanese Unexamined Patent Publication No. 2009-163227

By the way, in the transfer unit that transfers while sandwiching the recording medium, resistance fluctuation occurs at the time when the recording medium is detached from the transfer to the recording medium, and a steep fluctuation of the transfer voltage occurs after the recording medium. Toner may adhere to the edges.
In the present invention, as compared with the case where the transport speed of the recording medium is controlled after the rear end of the recording medium is separated from the transfer portion or the transport speed when the front end of the recording medium enters the transfer portion is controlled, the rear end of the recording medium is controlled. It is an object of the present invention to provide an image forming apparatus and an image forming program capable of suppressing stains due to adhesion of toner to edges.

In order to achieve the above object, the image forming apparatus according to the first aspect has a transfer unit that transfers an image held in an image holder to the recording medium by applying pressure while sandwiching and transporting the recording medium, and a transfer unit. A processing unit that processes the recording medium on which the image is transferred while transporting the image is provided, and a transfer processing unit that forms a slack portion in the recording medium between the transfer unit and the processing unit, and after the recording medium. When the front end of the margin region on the end side, the rear end of the image-forming region on the rear end side of the recording medium, or the rear end of the toner image-forming region formed on the recording medium reaches the nip portion in the transfer portion. When the sagging suppression process is started and the rear end of the recording medium passes through the transfer portion, the degree of sagging of the sagging portion is the degree of sagging of the sagging portion before the rear end of the recording medium passes through the transfer portion. It is provided with a control unit that controls so as to be suppressed from the degree of slack.

In the second aspect, in the image forming apparatus according to the first aspect, the control unit suppresses the degree of slack in the slack portion of the recording medium by controlling the transfer speed of at least one of the transfer unit and the processing unit. do.

A third aspect is the image forming apparatus according to the first aspect or the second aspect , wherein the control unit increases the transfer speed of the processing unit or slows down the transfer speed of the transfer unit. Suppress the degree of slack in the slack part of the medium.

A fourth aspect is the image forming apparatus according to any one of the first to third aspects , wherein the control unit determines the degree of slack in the slack portion when the rear end of the recording medium passes through the transfer unit. Suppresses the degree of slack in the slack portion of the recording medium so that is the degree of slack in the state where the recording medium is stretched between the transfer unit and the processing unit.

The image forming program according to the fifth aspect is a transfer unit that transfers an image held in an image holder to the recording medium by applying pressure while sandwiching the recording medium , and a recording medium on which the image is transferred. In an image forming apparatus provided with a processing unit for processing while transporting, a process of forming a slack portion in the recording medium is performed between the transfer unit and the processing unit, and a margin on the rear end side of the recording medium is performed. The sagging suppression process is performed when the front end of the region, the rear end of the image-forming region on the rear end side of the recording medium, or the rear end of the toner image-forming region formed on the recording medium reaches the nip portion in the transfer portion. The degree of slack in the slack portion when the rear end of the recording medium passes through the transfer portion is suppressed from the degree of slack in the slack portion before the rear end of the recording medium passes through the transfer portion. Have the computer perform processing, including controlling it to be.

According to the present disclosure , recording is performed as compared with the case where the transport speed of the recording medium is controlled or the transport speed when the front end of the recording medium enters the transfer section is controlled after the rear end of the recording medium is separated from the transfer section. It has the effect of suppressing stains due to adhesion of toner to the rear end of the medium.

It is a schematic side view which shows an example of the main part structure of an image forming apparatus. It is a schematic diagram provided for the explanation of the main part structure of a transfer apparatus. It is a block diagram which shows an example of the main part structure of the electric system of an image forming apparatus. It is a block diagram which shows an example of the main part structure of the electric system of a transfer apparatus. It is an image figure which shows an example of the state which conveys a paper while forming a slack part between a secondary transfer apparatus and a fixing device. It is an image diagram which shows an example of the time characteristic of the transfer voltage when the toner image on the intermediate transfer belt is transferred to the paper by a secondary transfer apparatus. It is an image figure which shows an example of the relationship between the time that the rear end of a paper stays in the vicinity of the downstream of the nip part of a secondary transfer apparatus, and toner stain. This is an image showing an example of a state in which paper is conveyed with a slack between the secondary transfer device and the fixing device. This is an image showing an example of a state in which paper is conveyed with a slack between the secondary transfer device and the fixing device. It is an image figure which shows an example of the position in the paper of the processing start. It is a flowchart which shows an example of the processing flow in the transfer control part of a secondary transfer apparatus. It is a conceptual diagram which shows an example of the structure which reduces the degree of slack of a slack part by a physical action.

Hereinafter, an example of the image forming apparatus according to the embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that components and processes having the same function and function may be given the same code throughout the drawings, and duplicate explanations may be omitted as appropriate.

(First Embodiment)
FIG. 1 shows a schematic side view showing a main configuration of an image forming apparatus 20 using the electrophotographic method according to the present embodiment. The image forming apparatus 20 is equipped with an image forming function that receives various data via a communication line (not shown) and performs color image forming processing based on the received data.

The case where the image forming apparatus 20 according to the present embodiment performs the color image forming process using four colors of yellow, magenta, cyan, and black will be described, but the colors used for the color image forming process are limited to four colors. It's not a thing. For example, the three colors of yellow, magenta, and cyan may be used, or a plurality of colors in which one or more different colors are added to the three colors of yellow, magenta, and cyan may be used.

Further, regarding the colors, each of yellow, magenta, cyan, and black will be described by notating them with alphabetic characters (color codes) of Y, M, C, and K. Further, when distinguishing each color of yellow, magenta, cyan, and black in the constituent elements of the image forming apparatus 20, the letters Y, M, C, and K (color codes) are added after the numbers. When it is not necessary to distinguish each color, the letters Y, M, C, and K (color code) after the number are omitted.

The image forming apparatus 20 includes a photoconductor 1, a charger 2, a laser output unit 3, a developer 4, and a primary transfer device 5. Each of the photoconductor 1, the charger 2, the laser output unit 3, the developing roll 34, the developing device 4, and the primary transfer device 5 is provided for each of the colors Y, M, C, and K.

The photoconductor 1 includes photoconductors 1Y, 1M, 1C, and 1K that rotate in the direction of arrow A in the drawing, and the charger 2 charges the surface of each photoconductor by applying a charging bias. It has 2M, 2C and 2K. The laser output unit 3 exposes the surface of the charged photoconductor 1 with exposure light modulated based on the image information of each color, and forms an electrostatic latent image on the photoconductor 1. Laser output units 3Y, 3M, 3C It has 3K. The developer 4 includes a developing roll 34, which is a developer holder that holds a developer (toner) of each color. The developer 4 includes developers 4Y, 4M, 4C, and 4K, and by applying a development bias to the development rolls 34Y, 34M, 34C, and 34K with a development bias power supply (not shown), the electrostatic latency on the photoconductor 1 is obtained. The image is developed with toner of each color to form a toner image on the photoconductor 1. The primary transfer device 5 includes primary transfer devices 5Y, 5M, 5C, and 5K that transfer each color toner image on the photoconductor 1 to the intermediate transfer belt 6.

Further, the image forming apparatus 20 includes a paper accommodating unit T for storing the paper P as a recording medium, a secondary transfer device 7 as a transfer unit for transferring the toner image on the intermediate transfer belt 6 to the paper P, and the paper P. A fixing device 9 as a processing unit for fixing the toner image transferred to the paper P, and a belt cleaner 8 for cleaning the toner remaining on the surface of the intermediate transfer belt 6 after transferring the toner image to the paper P are provided. Further, the image forming apparatus 20 includes a cleaner (not shown) for cleaning the surface of each photoconductor 1 and a static eliminator (not shown) for removing the residual charge on the surface of each photoconductor 1.

Further, the image forming apparatus 20 includes a thermometer 58 for measuring the temperature in the image forming operating environment and a hygrometer 60 for measuring the humidity in the image forming operating environment.

Furthermore, the image forming apparatus 20 includes an image forming control unit 40 that controls image formation and a transfer control unit 70 that controls transfer among the controls related to image formation as control units.

Next, the image forming operation in the image forming apparatus 20 shown in FIG. 1 will be described.

First, the original image information of the image forming target is output to the image forming apparatus 20 from a terminal device such as a personal computer (not shown) via a communication line (not shown). When the original image information is input to the image forming apparatus 20, the image forming apparatus 20 applies a charging bias to the charging device 2 to charge the surface of the photoconductor 1 to the negative electrode.

On the other hand, the original image information is input to the image formation control unit 40. The image formation control unit 40 decomposes the original image information into image data of each color of YMCK, and then outputs a modulation signal based on the image data of each color to the laser output unit 3 of the corresponding color. The laser output unit 3 outputs the laser beam 11 modulated according to the input modulation signal.

The modulated laser beam 11 irradiates the surface of the photoconductor 1. The surface of the photoconductor 1 is in a state of being charged to the negative electrode by the charger 2, and when the surface of the photoconductor 1 is irradiated with the laser beam 11, the charge of the portion irradiated with the laser beam 11 disappears and the photoconductor 1 is subjected to the photoconductor 1. An electrostatic latent image corresponding to the image data (each color of YMCK) included in the original image information is formed on the 1.

Further, the developing devices 4Y, 4M, 4C, and 4K of each color include toners colored in Y, M, C, and K and charged on the negative electrode, and a developing roll 34 for adhering each toner to the surface of the photoconductor 1.

When the electrostatic latent image formed on the photoconductor 1 reaches the developing device 4, a developing bias is applied to the developing roll 34 in the developing device 4 by a developing bias power supply (not shown). Then, the toners of each color held on the peripheral surfaces of the developing rolls 34Y, 34M, 34C, and 34K adhere to the electrostatic latent images of the photoconductors 1Y, 1M, 1C, and 1K, respectively, and the photoconductors 1Y, 1M, 1C, A toner image corresponding to the image data of each color of the original image information is formed in 1K.

Further, the rollers 12A, 12D, 12E, and the backup roll 7A of the secondary transfer device 7 are rotated by a motor (not shown), and the intermediate transfer belt 6 is conveyed to the gap formed by the primary transfer device 5 and the photoconductor 1. Then, the intermediate transfer belt 6 is pressed against the photoconductor 1. At this time, when the primary transfer bias is applied by the primary transfer device 5, the toner image of the image data of each color formed on the photoconductor 1 is transferred to the intermediate transfer belt 6. Therefore, by controlling the rotation of the rollers 12A, 7A, 12D, and 12E so that the transfer start positions of the toner images of each color to the intermediate transfer belt 6 are matched, the toner images of each color are superposed and the original image information is supported. The toner image is formed on the intermediate transfer belt 6.

In the photoconductor 1 on which the toner image is transferred to the intermediate transfer belt 6, deposits such as residual toner adhering to the surface of the photoconductor 1 are removed by a cleaner (not shown), and residual charges are removed by a static eliminator (not shown).

On the other hand, the secondary transfer device 7 includes a backup roll 7A for stretching the intermediate transfer belt 6 and a secondary transfer roll 7B, and the secondary transfer roll 7B comes into contact with the intermediate transfer belt 6 to contact the intermediate transfer belt 6 and the intermediate transfer belt 6 It rotates following the transport of.

Further, when the paper transport roller 13 is rotated by a motor (not shown), the paper P in the paper accommodating portion T is transferred to the backup roll 7A of the secondary transfer device 7 via the transport path 7J including the transport roller (not shown). It is conveyed to the gap between the roll 7B (hereinafter referred to as a roll pair).

When the paper P is pressed against the intermediate transfer belt 6 by the roll pair while facing the surface of the intermediate transfer belt 6 on which the toner image is formed, a secondary transfer bias is applied to the roll pair and the intermediate transfer belt is applied. The toner image corresponding to the original image information formed in No. 6 is transferred to the paper P. The toner image transferred onto the paper P is heated and melted by the fixing device 9 and fixed on the paper P.

Further, the intermediate transfer belt 6 on which the toner image is transferred to the paper P is removed by the belt cleaner 8 from deposits such as residual toner adhering to the surface.

As described above, the image corresponding to the original image information is formed on the paper P, and the image forming operation is completed.

FIG. 2 shows an example of the configuration of the secondary transfer device 7 of the image forming device 20 according to the present embodiment. The transfer operation to the paper P when the image is formed on the paper P by the secondary transfer device 7 shown in FIG. 2 will be described.

The secondary transfer device 7 is provided at a position facing the backup roll 7A with the intermediate transfer belt 6 sandwiched between the backup roll 7A which is conveyed while the intermediate transfer belt 6 is stretched together with the rollers 12A, 12D, and 12E by the drive motor 7M. The secondary transfer roll 7B is composed of a secondary transfer power source 7G for applying a voltage to the roll pair, and a transfer current detection unit 7H including an ammeter for detecting the current flowing through the roll pair. Further, the intermediate transfer belt 6 is conveyed by the rotational drive of the drive motor 7M.

The present embodiment includes a transfer speed detection unit 7V that detects the transfer speed of the intermediate transfer belt 6 by detecting the rotation speed of the drive motor 7M. The transfer speed detection unit 7V may directly detect the transfer speed of the intermediate transfer belt 6.

The voltage applied to the roll pair by the secondary transfer power source 7G can be adjusted by the transfer control unit 70 described later. The positive electrode of the secondary transfer power source 7G is connected to the ground potential (for example, 0V) which is the reference potential (not shown), and the negative electrode is connected to the metal shaft 7D of the backup roll 7A. A transfer current detection unit 7H is also connected to the metal shaft 7D of the backup roll 7A.

The backup roll 7A is, for example, a rotatable roller having a diameter of 18 mm in which a solid rubber 7C is formed around a metal shaft 7D having a diameter of 14 mm. In solid rubber 7C, an ionic conductive agent is mixed with acrylonitrile butadiene rubber (NBR), which has excellent oil resistance, abrasion resistance, and aging resistance, to reduce the resistance value to 1 × 10 ⁶ Ω or more and 1 × 10 ⁷ Ω or less. A conditioned conductive material is used.

As an example of the solid rubber 7C, a conductive material in which NBR and epichlorohydrin rubber (ECO) are blended can also be used. Further, as another example, a conductive material made of urethane rubber in which an ionic conductive agent is mixed with rubber obtained by reacting a polyether polyol with isodianate can be used. Furthermore, as another example, a conductive material made of ethylene propylene diene rubber (EPDM) can be used.

On the other hand, the secondary transfer roll 7B is, for example, a rotatable roller having a diameter of 18 mm in which foam rubber 7E is formed around a metal shaft 7F having a diameter of 12 mm. A conductive material is mixed to adjust the resistance value of the foam rubber 7E to 1 × 10 ⁷ Ω or more and 1 × 10 ⁸ Ω or less. The metal shaft 7F is connected to the ground potential.

The transfer control unit 70 (details will be described later) of the secondary transfer device 7 applies a negative electrode voltage from the secondary transfer power source 7G to the roll pair at the timing when the paper P is conveyed to the gap formed by the roll pair.

In this way, in addition to the pressing force that presses the paper P and the intermediate transfer belt 6 while the roll pair rotates, the electric field of the negative electrode generated in the gap between the roll pairs causes the toner image charged on the negative electrode to be transferred to the intermediate transfer belt. A force for peeling from 6 is generated, and the toner image formed on the intermediate transfer belt 6 is transferred to the paper P.

FIG. 3 shows an example of the configuration of the image forming control unit 40 that performs the image forming operation by the image forming apparatus 20. FIG. 3 shows an example of a computer 40X in which the image formation control unit 40 is composed of a computer. The computer 40X has a CPU (Central Processing Unit) 40A, a ROM (Read Only Memory) 40B, a RAM (Random Access Memory) 40C, a non-volatile memory 40D, and an input / output interface (I / O) 40E via a bus 40F. The I / O 40E is connected to an image forming unit 50, an operation display unit 52, a paper supply unit 54, a paper ejection unit 56, a thermometer 58, a humidity meter 60, and a communication I / F 62. ..

The image formation control program 40P to be executed by the computer 40X is stored in the ROM 40B. The CPU 40A expands the image formation control program 40P from the ROM 40B into the reading RAM 40C, and executes processing by the image formation control program 40P. When the CPU 40A executes the process by the image formation control program 40P, the computer 40X operates as the image formation control unit 40. The image formation control program 40P may be provided by a recording medium such as a CD-ROM.

The image forming unit 50 is a device necessary for the image forming apparatus 20 to perform an image forming operation, for example, a photoconductor 1, a charger 2, a laser output unit 3, a developing device 4, an intermediate transfer belt 6, and a secondary. It includes a transfer device 7, a fixing device 9, and the like.

The operation display unit 52 includes a display button for receiving operation instructions, a touch panel type display (not shown) for displaying various information, and hardware keys (not shown) such as a numeric keypad and a start button. ..

The paper supply unit 54 includes, for example, a paper storage unit T in which the paper P is stored, a supply mechanism for supplying the paper P from the paper storage unit T to the image forming unit 50, and the like.

The paper ejection unit 56 includes, for example, an ejection unit from which the paper P is ejected, an ejection mechanism for ejecting the paper P on which the image is formed by the image forming unit 50 onto the ejection unit, and the like.

The thermometer 58 measures the temperature of the image forming apparatus 20 in the image forming operating environment. The thermometer 58 is not limited to measuring the internal temperature of the image forming apparatus 20, and may, for example, measure the temperature of the place where the image forming apparatus 20 is installed, for example, the external temperature of the image forming apparatus 20. ..

The hygrometer 60 measures the humidity in the image forming operating environment of the image forming apparatus 20. Like the thermometer 58, the hygrometer 60 is not limited to measuring the internal humidity of the image forming apparatus 20, for example, measuring the humidity of the place where the image forming apparatus 20 is installed, for example, the external humidity of the image forming apparatus 20. You may try to measure.

The communication I / F 62 is an interface for mutual data communication with a terminal device such as a personal computer (not shown).

FIG. 4 shows an example of the configuration of the transfer control unit 70 of the secondary transfer device 7 according to the present embodiment.
FIG. 4 shows an example of a computer 70X in which the transfer control unit 70 is composed of a computer. The computer 70X has a configuration in which a CPU 70A, a ROM 70B, a RAM 70C, and an I / O 70E are connected via a bus 70F, and the backup roll 7A, a secondary transfer roll 7B, a secondary transfer power supply 7G, and a transfer are connected to the I / O 70E. The current detection unit 7H, the non-volatile memory 82, and the communication I / F 84 are connected. The CPU 70A can be connected to the formation control unit 40 (I / O 40E of the computer 40X) of the image forming apparatus 20 via the communication I / F 84. Further, the I / O 70E is connected to a drive motor 7M for rotating the backup roll 7A and the like to convey the intermediate transfer belt 6, and a transfer speed detection unit 7V for detecting the transfer speed of the paper P. Further, a slack detecting unit 7T for detecting the size of the slack portion Pt (see FIG. 5) formed on the paper P on the downstream side of the secondary transfer device 7 is also connected to the I / O 70E.

The slack portion Pt, for example, stabilizes the behavior of the rear end of the paper P when the paper P is separated from the secondary transfer device 7, the processing speed of the secondary transfer device 7, and the downstream side of the secondary transfer device 7. It is provided to absorb the difference from the processing speed of the fuser 9 (details will be described later).

The ROM 70B stores a transfer control program 70P to be executed by the computer 70X. The CPU 70A expands the transfer control program 70P from the ROM 70B into the reading RAM 70C, and executes processing by the transfer control program 70P. When the CPU 70A executes the process by the transfer control program 70P, the computer 70X operates as the transfer control unit 70. The transfer control program 70P may be provided in a state of being stored in a computer-readable recording medium such as a CD-ROM, or may be distributed via a wired or wireless communication means. ..

In the secondary transfer power supply 7G, the voltage value applied to the roll pair is set by the transfer control unit 70, and the voltage from the secondary transfer power supply 7G can be adjusted. Further, the transfer current detection unit 7H detects the current of the roll pair when a voltage is applied to the roll pair.

The non-volatile memory 82 stores various values used in the secondary transfer device 7 (details will be described later). The non-volatile memory 82 is not essential to the secondary transfer device 7, and may be replaced by, for example, the non-volatile memory 40D included in the computer 40X of the image forming device 20.

By the way, in the secondary transfer device 7 that transfers while sandwiching the paper P, a sudden resistance fluctuation occurs at the time when the paper P is separated from the transfer to the paper P, and a steep minute fluctuation of the transfer voltage occurs. It may occur momentarily. In this way, if a steep minute fluctuation in the transfer voltage occurs momentarily at the time when the paper P is detached, toner may adhere to the rear end of the paper P even though the paper P is detached. ..

FIG. 5 shows an example of a state in which the paper P is sandwiched and conveyed while forming a slack portion Pt between the secondary transfer device 7 and the fixing device 9. FIG. 5A shows a state in which the paper P is sandwiched between the secondary transfer device 7 and the fixing device 9, a slack portion Pt is formed, and the paper P is sandwiched and conveyed. FIG. 5B shows a state in which the rear end Pe of the paper P is detached from the secondary transfer device 7.

As shown in FIG. 5 (A), the degree of slack is Lmax from the position (the position indicated by the alternate long and short dash line) in the state where the paper P is stretched by the secondary transfer device 7 and the fixing device 9. , The slack portion Pt is formed. This degree of slack can be detected by the slack detecting unit 7T. Then, as shown in FIG. 5 (B), when the rear end Pe of the paper P separates from the nip portion 6P of the secondary transfer device 7, the rear end Pe of the paper P becomes the nip portion 6P while the slack portion Pt is maintained. It stays near the downstream.

The distance Lmax of the degree of slack of the slack portion Pt is the stability of the behavior of the rear end of the paper P when the paper P is separated from the secondary transfer device 7, and the processing speeds of the secondary transfer device 7 and the fixing device 9. Predetermined for difference absorption.

On the other hand, when the rear end Pe of the paper P is separated, resistance fluctuation occurs, and a steep minute fluctuation of the transfer voltage occurs.

Note that FIG. 5 shows, as an example, a case where the tarmi portion Pt is formed on the paper P on the downstream side of the secondary transfer device 7. That is, in FIG. 5, the tarmi portion Pt is formed between the secondary transfer device 7 and the fixing device 9. However, the configuration for forming the tarmi portion Pt is not limited to the configuration shown in FIG. For example, a transport unit for transporting the paper P may be provided between the secondary transfer device 7 and the fixing device 9, and the paper P from the secondary transfer device 7 may be transported to the fixing device 9. When a transport unit is provided between the secondary transfer device 7 and the fixing device 9, the transport unit functions as a processing unit of the disclosed technology.

Further, the secondary transfer device 7 and the fixing device 9 of the example shown in FIG. 5 function as a transfer processing unit of the disclosed technology. Further, when a transfer unit is provided between the secondary transfer device 7 and the fixing device 9, the secondary transfer device 7 and the transfer unit function as a transfer processing unit of the disclosed technology.

FIG. 6 shows an example of the time characteristics of the transfer voltage when the toner image on the intermediate transfer belt 6 is transferred to the paper P by the secondary transfer device 7. In the example shown in FIG. 6, a case where a negative electrode bias voltage is applied is shown.

As shown in FIG. 6, resistance fluctuations occur at the time when the tip of the paper P enters the nip portion 6P of the secondary transfer device 7 and at the time when the rear end Pe of the paper P separates, resulting in a steep minute transfer voltage. Fluctuations occur. In the example shown in FIG. 6, the time Tp indicates the transport time of the paper P. Here, a steep minute fluctuation of the transfer voltage generated at the time when the rear end Pe of the paper P is separated, that is, a slight minute fluctuation in which the transfer voltage momentarily drops occurs. In this way, the toner adhering to the secondary transfer roll 7B, for example, is moved to the paper P side by the steep minute fluctuation of the transfer voltage momentarily generated at the time when the rear end Pe of the paper P is released, and the paper is used. Toner stains occur on the rear end Pe of P. The toner stain generated on the rear end Pe of the paper P varies depending on the time that the rear end Pe of the paper P stays in the vicinity of the downstream side of the nip portion 6P.

FIG. 7 shows an example of the relationship between the time that the rear end Pe of the paper P stays in the vicinity of the downstream side of the nip portion 6P of the secondary transfer device 7 and the toner stain.

As shown in FIG. 7, as the time for the rear end Pe of the paper P to stay in the vicinity of the downstream side of the nip portion 6P becomes longer, the toner stain increases, that is, the toner stain amount varies from the minimum toner stain amount Gmin to the maximum toner stain amount Gmax. do. Further, FIG. 7 shows the allowable toner stain amount Gth as the toner stain amount G generated at the rear end Pe of the paper P, which was derived in advance by an experiment. Therefore, if the time before the toner stain amount Gth is reached, that is, the time during which the rear end Pe of the paper P stays in the vicinity of the downstream side of the nip portion 6P is set to be shorter than the time Tth, the rear end Pe of the paper P can be reached. It is acceptable as the amount of toner stain G generated.

Therefore, the degree of slack in the slack detection unit 7T may be reduced. That is, the slack portion Pt has a slack of a distance Lmin that is close to the position (the position indicated by the alternate long and short dash line) when the paper P is stretched between the secondary transfer device 7 and the fixing device 9. The paper P may be conveyed so that In this case, for example, it can be realized by adjusting the process speeds of the secondary transfer device 7 and the fuser 9 to be substantially the same.

The distance Lmin of the degree of slack is set to the distance Lmin of the degree of slack that is close to the position (the position indicated by the alternate long and short dash line) in the state where the paper P is stretched between the secondary transfer device 7 and the fixing device 9. Not limited. For example, the distance Lmin of the degree of slack is the estimated residence time for toner stain generation, that is, the rear end Pe of the paper P is separated from the nip portion 6P and then stays in the vicinity of the downstream side of the nip portion 6P to generate toner stain. It suffices to set a distance less than the degree of slack corresponding to the predicted time.

FIG. 8 shows an example of a state in which the paper P is sandwiched and conveyed while forming the slack portion Pt at a slack degree having a slack of a distance of Lmin between the secondary transfer device 7 and the fixing device 9. FIG. 8A shows a state in which the paper P is conveyed while sandwiching the paper P between the secondary transfer device 7 and the fixing device 9. FIG. 8B shows a state in which the rear end Pe of the paper P is detached from the secondary transfer device 7.

As shown in FIG. 8B, when the rear end Pe of the paper P is separated from the nip portion 6P by reducing the degree of slack of the slack portion Pt, the rear end Pe of the paper P is downstream of the nip portion 6P. The time to stay in the vicinity can be shortened.

However, for example, when it is difficult to adjust the process speeds of the secondary transfer device 7 and the fuser 9 to be substantially the same, it is difficult to keep the degree of slack of the slack detection unit 7T always small. be. Therefore, in the present embodiment, the degree of slack of the slack detecting unit 7T is reduced before the rear end Pe of the paper P reaches the nip portion 6P, so that the rear end Pe of the paper P is downstream of the nip portion 6P. The time to stay in the vicinity is controlled to be shorter than the time Tth.

FIG. 9 shows an example of a state in which the paper P is sandwiched and conveyed between the secondary transfer device 7 and the fixing device 9 by shifting from the degree of slack at the distance Lmax to the degree of slack at the distance Lmin. FIG. 9A shows a state in which the paper P is conveyed while sandwiching the paper P with a degree of slack at a distance Lmax. FIG. 9B shows a state in which the rear end Pe of the paper P shifts to a slack degree of the distance Lmin before reaching the nip portion 6P of the secondary transfer device 7, and the paper P is sandwiched and conveyed. ing.

As shown in FIG. 9A, when the paper P is conveyed while maintaining the degree of slack at the distance Lmax, the transfer speed Va of the secondary transfer device 7 is set to the speed V1, and the transfer speed Vb of the fuser 9 is set. The speed is set to V2, which is almost the same as the speed V1. Further, as shown in FIG. 9B, when the degree of slack of the slack portion Pt is reduced, the transfer speed Va of the secondary transfer device 7 is maintained at the speed V1, and the transfer speed Vb of the fuser 9 is higher than the speed V2. It is set to a high speed V3. When the transport speed Vb of the fuser 9 is set to a speed V3 higher than the speed V2, the speed is gradually increased from the speed V2 to the speed V3 so that the speed increases as the paper P approaches the rear end Pe. Is preferable. Here, the case where the transfer speed Vb of the fixing device 9 is increased has been described as an example, but by adjusting either the transfer speed Va of the secondary transfer device 7 or the transfer speed Vb of the fixer 9. It is sufficient that the transfer speed Vb of the fixing device 9 can be set higher than the transfer speed Va of the secondary transfer device 7. That is, the transfer speed Vb of the fixing device 9 may be relatively higher than the transfer speed Va of the secondary transfer device 7.

By doing so, as shown in FIG. 9A, the paper P is conveyed while maintaining the degree of slack at the distance Lmax, and the effect obtained by having the slack portion Pt can be maximized. Further, as shown in FIG. 9B, by reducing the degree of slack of the slack portion Pt to the degree of slack of the distance Lmin, when the rear end Pe of the paper P is separated from the nip portion 6P, the paper P The time for the rear end Pe to stay in the vicinity of the downstream side of the nip portion 6P can be shortened, and toner contamination can be suppressed.

When reducing the degree of slack in the slack portion Pt, the toner formed on the paper P is before the rear end Pe of the paper P, which shifts to the degree of slack at the distance Lmin, reaches the nip portion 6P of the secondary transfer device 7. The time after image transfer is preferred.

FIG. 10 shows an example of the position on the paper P corresponding to the time when the distance shifts to the degree of slack of the Lmin.
As shown in FIG. 10, for example, the time when the front end of the margin area on the rear end Pe side of the paper P reaches (t5) is preferable, and the time when the rear end of the image formable region on the rear end Pe side of the paper P reaches. (T5) is more preferable. Further, the time (t4) at which the rear end of the toner image forming region formed on the paper P reaches is more preferable. In the example shown in FIG. 10, a case is shown in which the time when the front end of the margin region reaches and the time when the rear end of the image formable region on the rear end Pe side of the paper P arrives are the same time. However, they may be at different times.

Next, the image forming operation in the image forming apparatus 20 according to the present embodiment will be described in detail.

The position on the paper P corresponding to the time when the distance Lmin shifts to the degree of slack used in the following description is such that a predetermined position according to the size of the paper P is stored in the non-volatile memory 82 in advance. And.

FIG. 11 shows the processing flow of the transfer control program 70P executed by the CPU 70A of the computer 70X operating as the transfer control unit 70 of the secondary transfer device 7.

The transfer control program 70P is executed by the CPU 70A when a transfer start instruction is received from the CPU 40A of the image forming apparatus 20 via the I / O 40E.

Here, assuming that the transfer process of transferring the toner image to the paper P is separately executed (not shown), the transfer control process of one sheet P in the transfer control will be described. In the transfer process, the drive motor 7M starts driving the roll pair (backup roll 7A and the secondary transfer roll 7B), and the roll pair is controlled to apply a voltage to the roll pair by the secondary transfer power supply 7G. In this case, the current flowing through the roll pair is detected, the transfer voltage applied to the roll pair from the secondary transfer power source 7G is set, and the toner image is transferred to the paper P. For example, the toner image is transferred to the paper P for an image-generating region including at least the toner image-forming region shown in FIG. In this case, the process speed of the secondary transfer device 7 is predetermined, and the paper P is transferred at the process speed, that is, the transfer speed Va of the secondary transfer device 7.

First, in step S100, the paper information including the size of the paper P to be conveyed is acquired in response to the reception of the transfer start instruction from the CPU 40A of the image forming apparatus 20. The paper information acquired in step S100 is acquired from the CPU 40A of the image forming apparatus 20 via the I / O 40E. In this step S100, a predetermined position on the paper P corresponding to the time when the distance shifts to the degree of slack of the distance Lmin corresponding to the size of the paper P to be conveyed is set. Here, a case where the front end (position corresponding to the arrival time t5) of the margin area on the rear end Pe side of the paper P shown in FIG. 10 is set to a predetermined position will be described as an example.

Next, in step S102, position information indicating the position of the paper P on the nip portion 6P is acquired. The position information acquired in step S102 can be derived from the elapsed time from the timing when the tip of the paper P rushes into the nip portion 6P and the transfer speed detected by the transfer speed detection 7V. The timing at which the tip of the paper P rushes into the nip portion 6P can be derived as the elapsed time from the distance from the removal of the paper P to the rush of the tip of the paper P into the nip portion 6P and the transport speed. .. Further, at this timing, the tip position of the paper P can be detected in real time by the fluctuation of the transfer voltage and the paper tip position sensor (not shown).

In the next step S104, the predetermined position on the paper P set in step S100, that is, the predetermined position on the paper P corresponding to the time for reducing the slack of the slack portion Pt (shifting to the degree of slack of the distance Lmin) is reached. Whether or not it is judged. Specifically, by the elapsed time from the timing when the leading end of the paper P is rushed into nip 6P it is determined that the elapsed time t5, the tip of the rear end Pe side margin area of the sheet P is nip It is determined whether or not the player has entered 6P.

If a positive judgment is made in step S104, the process is transferred to step S104, the slack suppression process is executed as the high quality mode, and the process is transferred to step S112 after the process. On the other hand, in the case of a negative determination in step S104, the process is shifted to step S108, the normal process is executed as the normal mode, and then the process is shifted to step S112.

In the present embodiment, in the normal process, for example, the transfer speed Va of the secondary transfer device 7 is controlled to be the speed V1 so that the paper P is conveyed while maintaining the degree of slack at the distance Lmax, and the fuser The transport speed Vb of 9 is controlled to a speed V2 which is substantially the same as the speed V1 (see FIG. 9A). That is, the CPU 70A controls the drive motor 7M so that the transfer speed Va of the secondary transfer device 7 becomes the speed V1. Further, the CPU 70A outputs information indicating the speed V2 to the CPU 40A of the image forming apparatus 20 so that the transport speed Vb of the fixing device 9 becomes a speed V2 substantially the same as the speed V1.

In the next step S112, it is determined whether or not the transfer of the paper P is completed, and in the case of an affirmative determination, the processing of the transfer control program 70P is terminated. In the case of a negative determination, the process returns to step S104 and the process is repeated until the paper P passes through the nip portion 6P. That is, the CPU 70A determines whether or not the rear end Pe of the paper P, which is the processing end position, has passed through the nip portion 6P. This determination is made by determining whether or not the elapsed time from the timing at which the tip of the paper P enters the nip portion 6P has elapsed the time (for example, time t6) for the paper P to pass through the nip portion 6P. can.

In the sagging suppression process in the high quality mode in step S106 of the transfer control program 70P, the transfer speed Va of the secondary transfer device 7 is controlled so as to maintain the speed V1, and the transfer speed Vb of the fuser 9 is faster than the speed V2. The speed is controlled to V3 (see FIG. 9B). That is, the CPU 70A controls the drive motor 7M so that the transfer speed Va of the secondary transfer device 7 maintains the speed V1. Further, the CPU 70A outputs information indicating the speed V3 to the CPU 40A of the image forming apparatus 20 so that the transport speed Vb of the fixing device 9 gradually becomes the speed V3. Thereby, the degree of slack can be gradually reduced.

When the sagging suppression process is executed in step S106, when the affirmative determination is made in step S112, the secondary transfer device 7 is as if it was executed in the normal process for the next processing of the paper P. The transfer speed Va may be controlled, and information indicating the transfer speed Vb of the fixing device 9 may be output.

As described above, according to the present embodiment, normally, the paper P is conveyed while maintaining the degree of slack at the distance Lmax, and the effect obtained by the slack portion Pt can be maximized. Further, by reducing the degree of slack of the slack portion Pt, when the rear end Pe of the paper P is separated from the nip portion 6P, the time for the rear end Pe of the paper P to stay in the vicinity of the downstream side of the nip portion 6P is shortened. It is possible to suppress toner stains.

(Second Embodiment)
Next, the second embodiment will be described. Since the second embodiment has substantially the same configuration as the first embodiment, the same parts are designated by the same reference numerals and detailed description thereof will be omitted.

In the first embodiment, the transfer speed Vb of the fixing device 9 is set to be relatively higher than the transfer speed Va of the secondary transfer device 7, so that the degree of slack of the slack portion Pt is reduced and the rear end of the paper P is reduced. The time for Pe to stay in the vicinity of the downstream side of the nip portion 6P was shortened, and toner contamination was suppressed. In the second embodiment, the degree of slack of the slack portion Pt is physically reduced by a movable member.

That is, the image forming apparatus according to the second embodiment is installed immediately after the secondary transfer apparatus 7, the paper stays for a predetermined time without entering the transport path of the paper P, and the paper P enters the transport path. The transfer control unit 70 controls the approaching member to enter at a specific time, including a rotating body as an approaching member whose residence time of the paper is shorter than the predetermined time when approaching.

FIG. 12 shows an example of a configuration in which the degree of slack of the slack portion Pt is reduced by a physical action in the secondary transfer device 7 according to the present embodiment. FIG. 12A shows a state in which the paper P is conveyed while sandwiching the paper P with a degree of slack at a distance Lmax. FIG. 12B shows a state in which the rear end Pe of the paper P shifts to a degree of slack of a distance Lmin before reaching the nip portion 6P of the secondary transfer device 7, and the paper P is sandwiched and conveyed. ing.

As shown in FIG. 12, in the present embodiment, in order to physically reduce the slack portion Pt of the paper P, the slack portion Pt of the paper P is physically placed between the secondary transfer device 7 and the fixing device 9. A rotating body 7W that can move in the direction of making the paper smaller (the direction indicated by the arrow U) is provided.

The rotating body 7W is rotationally driven in the rotation direction in which the paper P is conveyed, that is, in the same direction as the rotation direction of the secondary transfer roll 7B that comes into contact with the intermediate transfer belt 6 and rotates following the transfer of the intermediate transfer belt 6. Is preferable. In this case, it is preferable that the rotating body 7W is rotationally driven so that the paper P is conveyed at a speed at least equal to or higher than the transfer speed of the paper P conveyed by the rotation of the secondary transfer roll 7B. ..

As shown in FIG. 12A, when the paper P is conveyed while maintaining the degree of slack at the distance Lmax, the rotating body 7W is set at a position separated from the paper P. Further, as shown in FIG. 12B, when the degree of slack of the slack portion Pt is reduced, the rotating body 7W is set at a position where the slack portion Pt of the paper P is pressed so that the degree of slack becomes the distance Lmin. NS. As a result, when the rear end Pe of the paper P is separated from the nip portion 6P, the time for the rear end Pe of the paper P to stay in the vicinity of the downstream side of the nip portion 6P can be shortened, and toner stains can be suppressed. can.

Next, the operation of the computer functioning as the control unit 70 according to the second embodiment will be described.

In the second embodiment, in the sagging suppression process of the high quality mode executed in step S106 shown in FIG. 11, the control of pressing the rotating body 7W against the sagging portion Pt of the paper P is controlled so that the sagging degree becomes the distance Lmin. Will be executed. In step S106 of the present embodiment, it is preferable to control the movement of the rotating body 7W so that the slack portion Pt is gradually pressed so that the degree of slack gradually decreases from the distance Lmax to the distance Lmin. In the present embodiment, since the degree of slack in the slack portion Pt is reduced by the movement of the rotating body 7W, it is required to control the transfer speed Va of the secondary transfer device 7 and the transfer speed Vb of the fuser 9. do not.

Further, by rotationally driving the rotating body 7W at at least the same speed as the transport speed of the paper P conveyed by the rotation of the secondary transfer roll 7B, the slack formed by the slack portion Pt is suppressed, and the secondary transfer roll The paper P is conveyed at a speed at least the same as the transfer speed of the paper P conveyed by the rotation of 7B. As a result, the degree of slack in the slack portion Pt is the distance Lmax, and the rear end Pe of the paper P can be separated from the vicinity of the nip portion 6P in a shorter time than when the slack is formed, and stays in the vicinity of the downstream of the nip portion 6P. You can save time. Further, by rotationally driving the rotating body 7W so that the paper P is conveyed at a speed equal to or higher than the conveying speed of the paper P conveyed by the rotation of the secondary transfer roll 7B, the rear end Pe of the paper P is further increased. The time of staying in the vicinity of the downstream side of the nip portion 6P can be shortened.

As described above, according to the second embodiment, the rotating body 7W provided between the secondary transfer device 7 and the fixing device 9 is in the direction in which the slack portion Pt of the paper P is physically reduced (direction indicated by the arrow U). ), The degree of slack in the slack portion Pt is reduced. As a result, as in the first embodiment, the time for the rear end Pe of the paper P to stay in the vicinity of the downstream side of the nip portion 6P can be shortened, and toner stains can be suppressed.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be made to the above embodiments without departing from the gist of the invention, and the modified or improved forms are also included in the technical scope of the present invention.

Further, in the above embodiment, the case where the transfer control process is realized by the software configuration by the process using the flowchart shown in FIG. 11 has been described, but the present invention is not limited to this, and for example, the transfer control process is hardware. It may be a form realized by a wear configuration.

As a form example in this case, for example, there is a form in which a functional device that executes the same processing as the transfer control unit 70 of the secondary transfer device 7 is created and used. In this case, the processing speed is expected to be higher than that of the above embodiment.

Although the image forming apparatus 20 according to the present embodiment is intended to form a color image, it goes without saying that the image forming apparatus 20 may be an image forming apparatus 20 that forms a monochrome image. Further, the secondary transfer roll 7B of the transfer device 7 according to the present embodiment is not limited to a form composed of a single roller, for example, a secondary transfer roll 7B, another roller (not shown), and a secondary transfer roll. It may be composed of a plurality of rollers and belts, including a belt stretched around 7B and another roller (not shown).

Further, in the secondary transfer device 7 according to the present embodiment, the transfer voltage of the negative electrode is applied to the roll pair from the secondary transfer power source 7G, because the toner image charged on the negative electrode is peeled off from the intermediate transfer belt 6. If the toner image is charged on the positive electrode, the transfer voltage of the positive electrode may be applied to the roll pair.

Further, the transfer control process according to the present embodiment is not limited to the transfer device of the image forming apparatus 20, and is a transferred object such as a plastic sheet represented by paper, an OHP (OverHead Projector) sheet, metal, rubber, or the like. It may be used in a transfer device that transfers a toner image charged in plastic.

1 Photoreceptor 2 Charger 3 Laser output unit 4 Developer 5 Primary transfer device 6 Intermediate transfer belt 7 Transfer device 7A Backup roll 7B Secondary transfer roll 7C Solid rubber 7D Metal shaft 7E Foam rubber 7F Metal shaft 7M Drive motor 7S Drive current Detection unit 8 Belt cleaner 9 Fixer 13 Paper transfer roller 20 Image forming device 34 Development roll 40 Formation control unit 40X Computer 70 Transfer control unit 70X Computer

Claims (5)

It is provided with a transfer unit that transfers an image held in an image holder to the recording medium by pressurizing while conveying the image while sandwiching the recording medium, and a processing unit that processes the image while transporting the recording medium on which the image is transferred. A transfer processing unit that forms a slack portion in the recording medium between the transfer unit and the processing unit,
The tip of the margin region on the rear end side of the recording medium, the rear end of the image-forming region on the rear end side of the recording medium, or the rear end of the toner image-forming region formed on the recording medium is a nip in the transfer portion. The slack suppressing process is started when the portion reaches the portion, and the degree of slack of the slack portion when the rear end of the recording medium passes through the transfer portion is before the rear end of the recording medium passes through the transfer portion. A control unit that controls so as to be suppressed by the degree of slack of the slack portion of the above.
An image forming apparatus equipped with. The image forming apparatus according to claim 1, wherein the control unit controls the transfer speed of at least one of the transfer unit and the processing unit to suppress the degree of slack in the slack portion of the recording medium. The first or second aspect of the present invention, wherein the control unit suppresses the degree of sagging of the sagging portion of the recording medium by increasing the transport speed of the processing unit or slowing down the transport speed of the transfer unit. Image forming device. In the control unit, the degree of slack of the slack portion when the rear end of the recording medium passes through the transfer unit is the degree of slack in a state where the recording medium is stretched between the transfer unit and the processing unit. The image forming apparatus according to any one of claims 1 to 3, wherein the degree of sagging of the sagging portion of the recording medium is suppressed so as to be. It is provided with a transfer unit that transfers an image held in an image holder to the recording medium by pressurizing while conveying the image while sandwiching the recording medium , and a processing unit that processes the image while transporting the recording medium on which the image is transferred. In the image forming apparatus, a process of forming a slack portion in the recording medium is performed between the transfer portion and the processing portion.
The tip of the margin region on the rear end side of the recording medium, the rear end of the image-forming region on the rear end side of the recording medium, or the rear end of the toner image-forming region formed on the recording medium is a nip in the transfer portion. The slack suppressing process is started when the portion reaches the portion, and the degree of slack of the slack portion when the rear end of the recording medium passes through the transfer portion is before the rear end of the recording medium passes through the transfer portion. An image forming program that causes a computer to execute a process including controlling the slack portion so as to be suppressed by the degree of slack.

Images