JP2006171334A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing the color smear of an image by controlling rotational speeds of a plurality of image carriers. <P>SOLUTION: The image forming apparatus includes: the plurality of image carriers (1); a moving body (5) on which images formed on the image carriers (1) are transferred in order; a displacement quantitatively detecting means for detecting quantities of displacement between the plurality of images formed on the moving body (5) by the plurality of image carriers (1); and a control means for exerting control based on the detected amounts of displacement such that the rotating speed of the image carrier (1B) on the downstream side of the moving body (5) is higher than the rotating speeds of the other image carriers (1C, 1M, and 1Y). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a PPC, MFP, or FAX, and more particularly to an image forming apparatus applicable to an intermediate transfer method or a direct transfer method and a control method thereof.

  Conventionally, in a color image forming apparatus, when colors are superimposed, the overlapping position of the colors may deviate from the target position, and defects such as color unevenness may occur in the finally formed image. . For this reason, the registration of the image is corrected by changing the registration position of the image formation for forming the electrostatic latent image on the photosensitive member in units of one dot and shifting the transfer position at the transfer unit. However, when the four colors are overlaid due to the looseness of the intermediate transfer belt during image formation or the vibration of the intermediate transfer belt, the optimum overlay position may be shifted.

  Therefore, as a technical document filed prior to the present invention, in a color image forming apparatus having a function of correcting color misregistration due to uneven rotation of a plurality of cylindrical image carriers, a specific cylindrical image carrier Means for detecting a difference between the rotation time of the specific cylindrical image carrier and the rotation time of the other cylindrical image carrier with respect to the body, and another cylindrical image based on the detected difference in rotation time. 2. Description of the Related Art There is a color image forming apparatus that corrects color misregistration caused by uneven rotation of a rotating drum, and includes a unit that corrects an image writing position on a carrier (see, for example, Patent Document 1).

  In addition, a plurality of image carriers on which toner images of different colors are respectively formed, and each image carrier can be brought into contact with each transfer unit, and a transfer material is carried and conveyed to each transfer unit. In the image forming apparatus including a transfer material carrier and a transfer unit that sequentially superimposes and transfers the transfer material on the transfer member at each of the transfer units, the transfer material carrier has a speed higher than that of each image carrier. The moving speed is controlled so as to be faster, and the peripheral speed of the image carrier positioned on the upstream side of each of the image carriers with respect to the moving direction of the transfer material carrier in the transfer portions is set. There is an image forming apparatus that forms a multi-colored visible image that can be controlled so as to be faster and can obtain a good image with no void or color shift (see, for example, Patent Document 2).

  Also, an image is formed on the image carrier and transferred to a transfer conveyance belt or a transfer material conveyed by the conveyance belt to form an image. A control unit that forms an image on the transfer conveyance belt, and a special toner replacement operation time after color misregistration correction and image density correction by forming the non-detection toner image while detecting the toner image and acquiring information There is an image forming apparatus that can output a good image without using the image forming apparatus (for example, see Patent Document 3).

In addition, n photoconductors that individually carry two or more n different color toner images and rotate respectively, and each photoconductor for writing an image of a color corresponding to each photoconductor. Image writing means for irradiating light at respective light emission timings according to the distance between them, and intermediate transfer that rotates so that the toner images of the respective colors formed on the respective photoreceptors are sequentially transferred in an overlapping state In the intermediate transfer apparatus, the intermediate transfer device is provided with a moving speed control means for controlling the speed of the intermediate transfer member so that the n toner images are superposed on each other. A pattern forming means for forming a color misregistration detection pattern consisting of a combination over the entire circumference, and the transfer of the intermediate transfer member of the color toner image forming the pattern from the pattern formed by the means. A displacement detection means for detecting a relative displacement in the direction, and a movement speed for correcting the movement speed of the intermediate transfer member so as to correct the displacement based on the displacement information detected by the displacement detection means. Some correction means are provided to perform speed correction so as not to cause color misregistration (see, for example, Patent Document 4).
JP 2004-243742 A JP 2003-29489 A JP 2004-271912 A JP 2004-280016 A

  As disclosed in Patent Documents 1 to 4, various methods have been proposed in order to eliminate color misregistration of images.

  However, Patent Documents 1 to 4 do not take into consideration any attempt to eliminate color misregistration of an image by controlling the rotation speed of the image carrier.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus that controls the rotational speed of a plurality of image carriers and reduces image color misregistration, and a control method therefor. It is.

  In order to achieve this object, the present invention has the following features.

  An image forming apparatus according to the present invention includes a plurality of image carriers, a moving body to which images formed on the image carrier are sequentially transferred, and a plurality of images formed on the moving body by the plurality of image carriers. Based on the positional deviation amount detecting means for detecting the positional deviation amount and the detected positional deviation amount, the rotational speed of the image carrier on the downstream side of the moving body is set to be faster than the rotational speeds of the other image carriers. And a control means for controlling.

  In the image forming apparatus according to the present invention, the moving body is an intermediate transfer belt capable of directly transferring an image on the image carrier.

  In the image forming apparatus according to the present invention, the moving body is a conveyance belt that conveys a recording medium to which an image on the image carrier is transferred.

  An image forming apparatus according to the present invention independently rotates a plurality of image carriers, an exposure unit that exposes the image carrier, a resist control unit that controls an exposure sub-scanning resist position, and an image carrier. An image carrier drive motor, a motor control unit that controls the rotation speed of the image carrier drive motor, a control unit that controls the motor control unit with a difference in rotation speed between the image carrier drive motor, and an image carrier An intermediate transfer unit that transfers an image formed on the body, a secondary transfer unit that transfers the image transferred to the intermediate transfer unit to paper, and a detection unit that detects the amount of positional deviation of the image transferred to the intermediate transfer unit; The control unit adjusts the exposure sub-scanning resist position based on the amount of misregistration detected by the detecting means, and controls the image carrier that forms the last image. Control the rotation speed of the motor, other image carrier Is characterized in that the controls to faster than the rotational speed of the carrier driving motor.

  An image forming apparatus according to the present invention independently rotates a plurality of image carriers, an exposure unit that exposes the image carrier, a resist control unit that controls an exposure sub-scanning resist position, and an image carrier. An image carrier drive motor, a motor control unit that controls the rotation speed of the image carrier drive motor, a control unit that controls the motor control unit with a difference in rotation speed between the image carrier drive motor, and an image carrier An image forming apparatus comprising: a medium transfer transport body that transfers an image formed on a body to a recording medium; and a detection unit that detects a positional deviation amount of the image transferred to the medium transfer transport body. Based on the amount of misregistration detected by the detecting means, the exposure sub-scanning resist position is adjusted, and the rotation speed of the image carrier driving motor that controls the image carrier that forms the last image is controlled, and the other image carriers are controlled. Compared to the rotational speed of the image carrier drive motor It is controlled to be faster Te is characterized in.

  Further, a control method of an image forming apparatus according to the present invention is a control method in an image forming apparatus having a plurality of image carriers and a moving body to which images formed on the image carriers are sequentially transferred, A positional deviation amount detecting step for detecting a positional deviation amount of a plurality of images formed on the moving body by a plurality of image carriers, and an image carrier on the downstream side of the moving body based on the detected positional deviation amounts. The image forming apparatus performs a control process for controlling the rotation speed to be higher than the rotation speed of the other image carrier and the image forming apparatus.

  In the control method of the image forming apparatus according to the present invention, the moving body is an intermediate transfer belt capable of directly transferring an image on the image carrier.

  In the control method of the image forming apparatus according to the present invention, the moving body is a conveyance belt that conveys a recording medium to which an image on the image carrier is transferred.

  The image forming apparatus control method according to the present invention includes a plurality of image carriers, an exposure unit that exposes the image carrier, a resist control unit that controls an exposure sub-scanning resist position, and an image carrier. An image carrier driving motor for rotational driving, a motor control unit for controlling the rotational speed of the image carrier driving motor, a control unit for controlling the motor control unit with a speed difference in the rotational speed of the image carrier driving motor, , An intermediate transfer unit that transfers an image formed on the image carrier, a secondary transfer unit that transfers the image transferred to the intermediate transfer unit to paper, and a displacement amount of the image transferred to the intermediate transfer unit And a control unit that adjusts the exposure sub-scanning resist position based on the amount of misalignment detected by the detection unit, and determines an image carrier to be imaged last. Rotational speed of image carrier drive motor to be controlled , It is characterized in that the controls to faster than the rotational speed of the image carrier driving motor for controlling the other of the image bearing member.

  The image forming apparatus control method according to the present invention includes a plurality of image carriers, an exposure unit that exposes the image carrier, a resist control unit that controls an exposure sub-scanning resist position, and an image carrier. An image carrier driving motor for rotational driving, a motor control unit for controlling the rotational speed of the image carrier driving motor, a control unit for controlling the motor control unit with a speed difference in the rotational speed of the image carrier driving motor, A control method in an image forming apparatus, comprising: a medium transfer conveyance body that transfers an image formed on an image carrier to a recording medium; and a detection unit that detects a displacement amount of the image transferred to the medium transfer conveyance body. The control unit adjusts the exposure sub-scanning registration position based on the amount of positional deviation detected by the detecting means, and sets the rotation speed of the image carrier driving motor that controls the image carrier to be imaged last. Image carrier to control the image carrier Is characterized in that the controls to faster than the rotational speed of the drive motor.

  According to the image forming apparatus and the control method of the image forming apparatus of the present invention, it is possible to control the rotational speed of the plurality of image carriers and reduce the color misregistration of the image.

  First, an image forming apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the first image forming apparatus according to the present embodiment includes an exposure device (9) that exposes four colors to the photoconductor (1) independently, and a control unit that adjusts the exposure sub-scanning resist position. A photoconductor drive motor (14) that can rotate the photoconductor (1) independently, a motor control unit that can change the rotation speed of the photoconductor drive motor (14), and each photoconductor drive motor ( 14) having a speed difference in the rotational speed and controlling the photosensitive member drive motor (14), an intermediate transfer unit (5), and the intermediate transfer unit (5) and a secondary transfer unit for transferring paper. And a means for detecting the amount of color misregistration, the exposure sub-scanning registration position is adjusted, and the rotational speed of the photosensitive member drive motor (14B) of the photosensitive member (1B) to be imaged last is adjusted. Photoconductors (1M, 1C, 1Y) that create images in the other three colors The photosensitive body driving motor (14M, 14C, 14Y) which is an image forming apparatus and controls to faster than.

  Further, as shown in FIG. 2, the second image forming apparatus according to the present embodiment adjusts the exposure sub-scanning resist position and the exposure apparatus (9) that independently exposes the four colors onto the photoreceptor (1). A control unit, a photoconductor drive motor (14) that can rotate the photoconductor (1) independently, a motor control unit that can change the rotation speed of the photoconductor drive motor (14), and each photoconductor drive A controller for controlling the photosensitive member driving motor (14) having a speed difference in the rotational speed of the motor (14), and a paper transfer carrier (for transferring the toner image generated on the photosensitive member (1)). 30) and a means for detecting the amount of color misregistration, the image forming apparatus having the other three colors at the rotational speed of the photoconductor drive motor (14Y) of the photoconductor (1Y) to be imaged last is formed. Photoconductor drive motor (1C, 1M, 1B) 4C, an image forming apparatus and controls to faster than 14M, the 14B).

  As described above, in the image forming apparatus according to the present embodiment, the rotation speed of each photoconductor drive motor (14) is changed, the most downstream photoconductor drive motor (14) is replaced with another photoconductor drive motor (14). ) To drive and control the photosensitive member (1) at a faster rotational speed than the above, eliminating the slackness of the transfer belt (5, 30) and changing the exposure timing of the exposure device (9), thereby eliminating image misalignment. It becomes possible to do. Hereinafter, an image forming apparatus according to this embodiment will be described with reference to the accompanying drawings.

  First, the configuration of the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram illustrating a control system related to image formation of an image forming apparatus which is an example of the present embodiment.

  As shown in FIG. 1, the image forming apparatus in this embodiment includes a photoreceptor (1Y, 1C, 1M, 1B “hereinafter referred to simply as photoreceptor 1 if not specified”) and a developing device (2Y, 2C). , 2M, 2B “hereinafter simply referred to as developing device 2 if not specified”) and transfer device (3Y, 3C, 3M, 3B “hereinafter referred to simply as transfer device 3 if not specified”), A single color toner image is formed on each photoreceptor (1), and the formed single color toner image is brought into contact with the intermediate transfer belt (5) to form a toner image on the intermediate transfer belt (5). A combined color image is formed by sequential transfer, and the formed combined color image is transferred onto a sheet-like transfer paper (P) conveyed by a conveying belt at a time so that a full color image is formed on the transfer paper (P). Tandem type that will form an image An image forming apparatus.

  The image forming apparatus shown in FIG. 1 has a drum shape, which is a plurality of image carriers on which toner images of different colors are formed and the formed toner images can be independently transferred onto the intermediate transfer belt (5). Each of the photosensitive members (1), the intermediate transfer belt (5) to which each image formed on the plurality of photosensitive members (1) is transferred at a transfer position corresponding to each of the photosensitive members (1), Each image on the photoconductor (1) is configured to have a contact / separation mechanism (4) that moves the transfer device (3) up and down as needed at each transfer position on the intermediate transfer belt (5). Is done.

  The transfer device (3) moves up and down by moving the contact / separation mechanism (4), and contacts and separates from the intermediate transfer belt (5). A charging device (6), a cleaning device (7), a charge removal device (8), and the like are provided around each photoconductor (1). Each photoconductor (1) is based on an image signal. The laser beam corresponding to the image of each color is scanned from the exposure device (9), and an electrostatic latent image is formed on the photoreceptor (1).

  The transfer belt (5) is stretched between the driving roller (21) and the driven roller (22), and moves in the belt rotation direction shown in FIG. The drive roller (21) is driven and controlled by the drive motor (25).

  Further, the transfer belt (5) has a secondary transfer roller (23) and a secondary transfer counter roller (24), and the toner image formed on the intermediate transfer belt (5) is printed on paper. This is a secondary transfer mechanism for transferring.

  The primary transfer process system is such that a negative polarity toner image and a positive polarity bias opposite to the positive polarity are applied to the transfer device (3), whereby the toner image formed on the photoreceptor (1) is transferred to the intermediate transfer belt. In this method, the toner image is drawn from the inside of (5) and the toner image is transferred onto the intermediate belt (5).

  The process method of the secondary transfer mechanism is an extrusion bias method using a secondary transfer roller (23), a secondary transfer counter roller (24), and an intermediate transfer belt (5). By applying a negative polarity toner image transferred onto the intermediate transfer belt (5) to the secondary transfer roller (23) with the same polarity as the toner, the inner side of the intermediate transfer belt (5) is obtained. The toner image is extruded from the toner image and transferred onto a transfer sheet on the conveying belt.

  Next, the configuration of the second image forming apparatus in the present embodiment will be described with reference to FIG. FIG. 2 shows a direct transfer type image forming apparatus that directly transfers an image on a photoreceptor onto a recording sheet.

  The image forming apparatus shown in FIG. 2 includes a photoreceptor (1), which is a plurality of image carriers that are formed with images of different colors and can be rotated independently, and the plurality of photoreceptors (1). A transfer device (3) for transferring each image on the photoconductor (1) directly onto a transfer paper (P) as a recording paper at a transfer position where each formed image corresponds to each of the plurality of photoconductors (1); And a contact / separation mechanism (4) for moving the transfer device (3) up and down as needed at each transfer position on the transfer conveyance belt (30).

  The transfer device (3) moves up and down by moving the contact / separation mechanism (4), and contacts and separates from the transfer conveyance belt (30). A developing device (2), a charging device (6), a cleaning device (7), a charge eliminating device (8), and the like are provided around each photoconductor (1). The laser beam corresponding to the image of each color based on the image signal is scanned from the exposure device (9), and an electrostatic latent image is formed on the photoreceptor (1).

  The transfer conveying belt (30) is stretched between the driving roller (32) and the driven roller (33), and moves in the direction of the arrow shown in FIG. The drive roller (32) is driven and controlled by the drive motor (31).

  Next, the control operation in the image forming apparatus shown in FIGS. 1 and 2 will be described with reference to FIG. FIG. 3 is a block diagram of motor drive control in the image forming apparatus.

  As shown in FIG. 3, the image forming apparatus control unit includes an exposure apparatus (9 shown in FIGS. 1 and 2) and a motor control unit (a control unit that controls the photoconductor drive motor 14 shown in FIGS. 1 and 2). And a transfer motor control section (control section for controlling the drive motor 25 shown in FIG. 1 and the drive motor 31 shown in FIG. 2). Note that the image forming apparatus control unit controls the entire image forming apparatus.

  The image forming apparatus control unit and the motor control unit are connected to at least a motor ON / OFF signal, a speed signal (clock frequency, etc.), a rotation direction signal, a power source, and a ground. For this reason, it becomes possible to set the rotational speed of the motor individually and drive the motor at different speeds.

  For example, when the transfer position of each color is shifted due to the assembly variation of the photoconductor (1) or when the distance from the exposure position by the laser of each color to the transfer position varies, the photoconductor drive motor (14) By changing the rotation speed, it is possible to control the time from the exposure position to the transfer position, and it is possible to correct the positional deviation of each color.

  Next, referring to FIG. 4, a description will be given of a processing operation when detecting a positional deviation that occurs in the image forming apparatus of the present embodiment. FIG. 4 is a diagram illustrating a processing operation when detecting the amount of misregistration of each color in the present embodiment.

  In the present embodiment, when the amount of misregistration of each color is detected, a station for each color, yellow (Y), cyan (C), magenta (M), and black (B) is used for color (position) misalignment detection. The pattern is transferred onto the moving body (the intermediate transfer belt 5 shown in FIG. 1 and the transfer conveyance belt 30 shown in FIG. 2). In addition, (a) has shown the case where a moving body is seen from the upper surface, (b) has shown the case where the moving body is seen from the side.

  For example, in the case of the detection pattern 1 shown in FIG. 4, a pattern in which yellow, cyan, and magenta are overlapped with a black color as a reference and the overlapping amount is gradually changed is formed on the moving body a plurality of times. Become. Then, the pattern 1 that has been imaged a plurality of times is irradiated with light from an LED or LD, the reflected light is detected by a photosensor, and the amount of displacement from the target position of each color is calculated using the detected amount. become.

  For example, the exposure timing for forming yellow for measuring misregistration is shifted, and the overlapping amount of reference black formed on the moving body and yellow for measuring misregistration is changed little by little. A plurality of patterns are formed on the moving body. Then, the amount of positional deviation on the moving body is calculated based on the amount of change in the detection amount obtained by detecting the reflected light of the plurality of patterns formed on the moving body. That is, the pattern when black and yellow overlap exactly has a large amount of detection, and the pattern when black and yellow do not overlap at all has a small amount of detection and is based on the amount of change. In addition, the amount of positional deviation from the target position of each color is calculated. This calculation is similarly performed for cyan and magenta.

  Further, in the case of the pattern 2 shown in FIG. 4, lines of a certain color (pattern 2) in the main scanning direction are transferred onto the moving body. Then, each color line (pattern 2) transferred onto the moving body is irradiated with light from an LED or LD, the reflected light is detected by a photosensor, and the amount of deviation from the target position of the line (pattern 2) is detected. Will be calculated.

  For example, the distance between the lines of each color formed on the moving body at a predetermined exposure timing is measured, and the amount of positional deviation from the target position of each color is calculated based on the measured distance between the lines of each color. Become.

  There is also a method of detecting a color (position) shift of each color from the RGB output result using a color CCD as a color (position) shift detection method. The method for detecting the amount of misregistration of each color in the present embodiment is not particularly limited, and any detection method can be applied as long as the amount of misregistration of each color transferred from the photoconductor can be detected. It is. Note that the above-described calculation of the amount of misregistration is executed when the image forming apparatus is turned on or after a predetermined number of sheets have been printed. Further, when there is a temperature sensor such as a thermistor in the image forming apparatus, the image forming apparatus can be configured to execute when a temperature difference from the previous adjustment exceeds a predetermined threshold. It can also be performed when the photosensitive member (1) or the developing device (2) is replaced. It can also be executed manually using an operation panel or the like.

  In the initial state during image formation, the moving body is in contact with only the black photoconductor (1B). During color printing, the moving body is raised by the contact / separation mechanism (4), and the color photoconductor (1M 1C, 1B). When color printing is performed after monochrome printing, the monochrome paper passes through the transfer device (3), and then the contact / separation mechanism (4) is turned on to lift the moving body, so that the color photoconductor (1M 1C, 1B) (adjusting the paper feed timing to make the interval between the papers longer). At this time, by performing control so as to execute the misregistration correction process, the misregistration correction process can be executed even when performing color printing.

  Next, a method for controlling the photosensitive member drive motor (14) in the image forming apparatus according to the present embodiment will be described with reference to FIGS.

  FIG. 5 is a diagram showing a positional shift amount at the transfer positions of magenta (M), cyan (C), and yellow (Y) with black (B) as the most downstream and black (B) as a reference.

  The image forming apparatus according to the present exemplary embodiment transfers yellow (Y), cyan (C), magenta (M), and black (B) onto the moving body in this order. The misregistration correction in this embodiment is based on the rotational speed of the black (B) photoconductor (1), and the rotational speed of each photoconductor (1) is changed from the difference in positional deviation from each color. The transfer position of each color is matched. The rotational speed of the photoconductor drive motor (14) that rotates the photoconductor (1) is controlled by a motor control unit that controls the photoconductor drive motor (14) based on the frequency of the clock. Become.

<When magenta (M) is shifted from black (B) in an early direction>
First, with reference to FIG. 5, a case where the transfer position of magenta (M) is shifted in the early direction from black (B) will be described.

A time t ₀ from exposure of black (B) as a reference to transfer is obtained by the following equation (1).
Formula (1): t ₀ = θ ₀ / ω ₀
Note that θ ₀ represents an angle from exposure of black (B) to transfer, and ω ₀ represents each speed of the photoreceptor (1) of black (B).

  Further, the positional deviation amount a of magenta (M) is obtained by the following equation (2).

Formula (2): a = r × Δθ _m
Here, r represents the radius of the photoconductor (1), and Δθ _m represents an angle with respect to the positional deviation amount: a.

Note that the time t _m from exposure of magenta (M) to transfer is obtained by the following equation (3).

Formula (3): t _m = (θ ₀ −Δθm) / ω ₀

Here, θ ₀ / ω ₀ = (θ ₀ −Δθm) / ωm... To change each speed ω _m of the magenta (M) photoconductor (1) to t ₀ = t _m. Equation (4) is obtained.

From equation (2), Δθm = a / r, and when this is substituted into equation (4), ω _m = (1−a / r · θ ₀ ) × ω ₀ .

The frequency f is, since the obtained by f = 2Paiomega, the clock frequency f _m of the speed signal of the photosensitive body driving motor (14) of magenta (M) will be determined by the following equation (5).

Formula (5): f _m = (1−a / r · θ ₀ ) × f ₀
Note that f ₀ represents the clock frequency of the speed signal of the black (B) photoconductor drive motor (14).

Further, similarly to the magenta as described above (M), cyan (C), yellow (Y) of the clock frequency f _c of the speed signal of the photosensitive body driving motor (14), f _y, the following equation (6), wherein (7).

Formula (6): f _c = (1−b / r · θ ₀ ) × f ₀
Expression (7): f _y = (1−c / r · θ ₀ ) × f ₀

<When magenta (M) is shifted in a slow direction from black (B)>
Next, a case where the transfer position is shifted in the slow direction from black (B) in magenta (M) will be described with reference to FIG.

By making the exposure sub-scanning resist position (exposure timing) of the exposure device (9) that exposes the photosensitive member (1) with LD (or LED) faster, magenta (M) is always black (B) at the transfer position. It is possible to shift in a fast direction from When the exposure sub-scanning direction is adjusted at a pitch of tx seconds, a time t ₀ from exposure of black (B) as a reference to transfer is obtained by the following equation (8).

Formula (8): t ₀ = θ ₀ / ω ₀

  Further, the positional deviation amount a of magenta (M) is obtained by the following equation (9).

Formula (9): a = r × Δθ _m

The adjustment angle Δθx when the exposure timing is changed by tx from the reference time at the rotational speed of each speed ω ₀ of the black (B) photoconductor (1) is obtained by the following equation (10). .

Formula (10): Δθ _x = x / r
Note that x represents the transfer movement amount when the exposure timing of tx seconds during the reference rotation of the black (B) photoconductor (1) is changed.

  Further, the adjustment shift amount xa at that time is obtained by the following equation (11).

Expression (11): x−a = r × Δθ _x −r × Δθ _m = r × (Δθ _x −Δθ _m )

Further, the time t _m from the exposure of magenta (M) to the transfer is obtained by the following equation (12).

Expression (12): t _m = (θ ₀ + Δθ _m −Δθ _x ) / ω ₀

Here, θ ₀ / ω ₀ = (θ ₀ + Δθ _m −Δθ _x ) / ω to change t ₀ = t _m by changing each speed ω _m of the photoconductor (1) of magenta (M). _m: Expression (13).

Note that, by substituting Δθ _m = a / r in equation (9) and Δθ _x = x / r in equation (10) into equation (13), ω _m = {(1− (x−a ) / R · θ ₀ )} × ω ₀ .

Frequency f, since the determined by f = 2Paiomega, the clock frequency f _m of the photoreceptor speed signal of the drive motor (14) of magenta (M) will be determined by the following equation (14).

Formula (14): f _m = {(1- (x−a) / r · θ ₀ )} × f ₀
Note that f ₀ represents the clock frequency of the speed signal of the black (B) photoconductor drive motor (14).

Similarly to the magenta (M) described above, the clock frequencies f _c and f _y of the speed signals of the cyan (C) and yellow (Y) photoconductor drive motors (14) are expressed by the following equations (15) and (15). (16).

Formula (15): f _c = {(1− (x−b) / r · θ ₀ )} × f ₀
Expression (16): f _y = {(1− (x−c) / r · θ ₀ )} × f ₀

  As described above, the image forming apparatus according to the present exemplary embodiment adjusts the reference black station and the transfer timing of each station by changing the clock frequency f (motor rotation speed), so that the black photosensitive member driving motor ( 14) can be rotated faster than other colors to suppress color misregistration.

For example, when r = 0.03 [m], θ ₀ = 2.827433 [rad], f ₀ = 1000 [Hz], and x = 30 [μ], the amount of deviation from black (B) is faster. Assuming 10 [μm], the drum rotation speed signal of the shifted station may be set to 999.882 [Hz]. Further, when it is assumed that the deviation amount is 10 [μm] in the slow direction, the rotational speed may be set to 999.764 [Hz].

  Similarly, when the downstream photoconductor drive motor (14) is speeded up, the frequency f may be determined so that the upstream photoconductor drive motor (14) is slowed by changing the exposure timing.

  As described above, the tandem type image forming apparatus according to the present embodiment drives the photoreceptor driving motor (14) of the color to be imaged last among the photoreceptor driving motors (14) of the respective colors. By rotating faster than the motor (14), the transfer belt (5 shown in FIG. 1 and 30 shown in FIG. 2) can be pulled to suppress looseness and vibration of the transfer belt, thereby reducing color misregistration. It becomes possible.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible. For example, the image forming order of the image forming apparatus in the above-described embodiment is yellow (Y), cyan (C), magenta (M), and black (B), but the order of each color can be arbitrarily changed. is there.

  The image forming apparatus and the control method thereof according to the present invention can be applied to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine.

1 is a diagram illustrating a first configuration example of an image forming apparatus according to an exemplary embodiment and is a diagram illustrating an intermediate transfer type image forming apparatus. FIG. It is a figure which shows the 2nd structural example of the image forming apparatus in this embodiment, and is a figure which shows the image forming apparatus of a direct transfer system. FIG. 4 is a block diagram illustrating motor drive control in the image forming apparatus according to the present exemplary embodiment. It is a figure which shows the processing operation at the time of detecting the positional offset amount of each color in this embodiment. FIG. 6 is a diagram illustrating control of a photosensitive member drive motor (14) of the image forming apparatus according to the present exemplary embodiment, and is a diagram for explaining a case where a transfer position is shifted in a direction in which magenta (M) is earlier than black (B). is there. FIG. 6 is a diagram illustrating control of a photosensitive member drive motor (14) of the image forming apparatus according to the present exemplary embodiment, and is a diagram for explaining a case where a transfer position is shifted in a slow direction from magenta (M) to black (B). is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing device 3 Transfer device 4 Contacting / separating mechanism 5 Intermediate transfer belt 6 Charging device 7 Cleaning device 8 Static eliminating device 9 Exposure device 14 Photoconductor drive motor 21, 32 Drive roller 22, 33 Driven roller 23 Secondary transfer roller 24 Secondary transfer counter roller 25 Drive motor 30 Transfer conveyor belt 31 Drive motor P Transfer paper

Claims (10)

  A plurality of image carriers, a moving body to which images formed on the image carrier are sequentially transferred, and a positional deviation amount of the plurality of images formed on the moving body by the plurality of image carriers are detected. A control for controlling the rotational speed of the image carrier on the downstream side of the movable body to be higher than the rotational speed of the other image carriers based on the positional deviation amount detecting means and the detected positional deviation amount. And an image forming apparatus.   The image forming apparatus according to claim 1, wherein the moving body is an intermediate transfer belt capable of directly transferring an image on the image carrier.   The image forming apparatus according to claim 1, wherein the moving body is a conveyance belt that conveys a recording medium to which an image of the image carrier is transferred.   A plurality of image carriers, an exposure unit that exposes the image carrier, a registration control unit that controls an exposure sub-scanning resist position, an image carrier drive motor that independently rotates the image carrier, and the image A motor control unit for controlling the rotation speed of the carrier driving motor, a control unit for controlling the motor control unit having a speed difference in the rotation speed of the image carrier driving motor, and the image carrier. An intermediate transfer unit that transfers the image, a secondary transfer unit that transfers the image transferred to the intermediate transfer unit to paper, and a detection unit that detects the amount of positional deviation of the image transferred to the intermediate transfer unit. In the image forming apparatus, the control unit adjusts the exposure sub-scanning registration position based on the amount of misalignment detected by the detection unit, and controls the image carrier that forms an image last. Rotation speed of drive motor, other image bearing Image forming apparatus and controls to faster than the rotational speed of the image bearing member driving motor for controlling.   A plurality of image carriers, an exposure unit that exposes the image carrier, a registration control unit that controls an exposure sub-scanning resist position, an image carrier drive motor that independently rotates the image carrier, and the image A motor control unit for controlling the rotation speed of the carrier driving motor, a control unit for controlling the motor control unit having a speed difference in the rotation speed of the image carrier driving motor, and the image carrier. An image forming apparatus comprising: a medium transfer transport body that transfers an image to a recording medium; and a detection unit that detects a positional deviation amount of the image transferred to the medium transfer transport body, wherein the control unit is configured to detect the detection The exposure sub-scanning registration position is adjusted based on the amount of misalignment detected by the means, and the rotational speed of the image carrier driving motor that controls the image carrier that forms the last image is controlled, and the other image carriers are controlled. Of the image carrier driving motor Image forming apparatus and controls to faster than the rolling speed. A control method in an image forming apparatus having a plurality of image carriers and a moving body to which images formed on the image carriers are sequentially transferred,
A misregistration amount detection step of detecting misregistration amounts of a plurality of images formed on the movable body by the plurality of image carriers;
A control step for controlling the rotational speed of the image carrier on the downstream side of the movable body based on the detected displacement amount to be higher than the rotational speed of the other image carriers;
A control method performed by the image forming apparatus.   The control method according to claim 6, wherein the moving body is an intermediate transfer belt capable of directly transferring an image of the image carrier.   The control method according to claim 6, wherein the moving body is a conveyance belt that conveys a recording medium to which an image of the image carrier is transferred. A plurality of image carriers, an exposure unit that exposes the image carrier, a registration control unit that controls an exposure sub-scanning resist position, an image carrier drive motor that independently rotates the image carrier, and the image A motor control unit for controlling the rotation speed of the carrier driving motor, a control unit for controlling the motor control unit having a speed difference in the rotation speed of the image carrier driving motor, and the image carrier. An intermediate transfer unit that transfers the image, a secondary transfer unit that transfers the image transferred to the intermediate transfer unit to paper, and a detection unit that detects the amount of positional deviation of the image transferred to the intermediate transfer unit. A control method in an image forming apparatus,
The control unit adjusts the exposure sub-scanning registration position based on the amount of positional deviation detected by the detection means, and controls the rotation speed of the image carrier drive motor that controls the image carrier to be imaged last. A control method, characterized in that control is performed so as to be faster than a rotation speed of the image carrier drive motor for controlling another image carrier. A plurality of image carriers, an exposure unit that exposes the image carrier, a registration control unit that controls an exposure sub-scanning resist position, an image carrier drive motor that independently rotates the image carrier, and the image A motor control unit for controlling the rotation speed of the carrier driving motor, a control unit for controlling the motor control unit having a speed difference in the rotation speed of the image carrier driving motor, and the image carrier. A control method in an image forming apparatus, comprising: a medium transfer transport body that transfers an image to a recording medium; and a detection unit that detects a positional deviation amount of the image transferred to the medium transfer transport body,
The control unit adjusts the exposure sub-scanning registration position based on the amount of positional deviation detected by the detection means, and controls the rotation speed of the image carrier drive motor that controls the image carrier to be imaged last. A control method, characterized in that control is performed so as to be faster than a rotation speed of the image carrier drive motor for controlling another image carrier.

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