JP2008276064A - Image forming apparatus and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for correcting an operating state of the image forming apparatus more accurately and to provide a control method for the apparatus. <P>SOLUTION: The image forming apparatus includes: an intermediate transfer belt 31 which has marks 126 and 127 and on which toner images formed on photoreceptor drums 11a to 11d are transferred thereon; mark detection sensors 122 and 123 for detecting marks 126 and 127; a speed calculation circuit 128 which detects the mark 126 or 127 by means of the mark detection sensors 122 and 123, thereby calculating the conveyance speed of the intermediate transfer belt 31, also detects the marks 126 and 127 by means of the mark detection sensor 122 or 123, thereby calculating the conveyance speed of the intermediate transfer belt 31, and further calculates a difference between the conveyance speeds; and a conveyance speed control section 200 which corrects the conveyance speed of the intermediate transfer belt 31 on the basis of the detection information of the mark detection sensors 122 and 123 and on the basis of the speed difference calculated by the speed calculating circuit 128. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and a control method thereof. In particular, the present invention relates to an image forming apparatus employing an electrostatic recording method, an electrophotographic recording method, and the like, and a control method thereof.

  Conventionally, various types of color image forming apparatuses have been proposed. One of them is an intermediate transfer type color image forming apparatus. In this color image forming apparatus, an image forming unit is provided for each color developer, and a visible image of each color is formed on a photosensitive drum as an image carrier in each image forming unit by a known image forming process. Then, these visible images are sequentially transferred (primary transfer) onto a conveyance body (intermediate transfer body) that performs endless circulation motion (circular drive), so-called intermediate transfer belt, and batch transfer (secondary transfer) to the supplied recording paper. After fixing, a color image is obtained.

  In such an intermediate transfer type image forming apparatus, a visible image of each color on the photosensitive drum is superimposed on the intermediate transfer belt to obtain one color image. For this reason, some image forming apparatuses include a correction unit that forms a registration correction pattern image of each color on an intermediate transfer belt and detects the amount of deviation to correct the color deviation.

  Incidentally, one of the main causes of color misregistration is due to the speed fluctuation of the intermediate transfer belt. Therefore, a technique for correcting the operation state of the image forming apparatus by detecting the speed of the intermediate transfer belt has been proposed. For example, two marks are provided on the intermediate transfer belt with an interval in the belt conveyance direction, the time for which this mark passes the mark detection sensor is detected, and the conveyance speed of the intermediate transfer belt is determined from the two mark passage times. There is something to calculate.

  In this case, when the temperature rise in the image forming apparatus, which is a factor of fluctuation in the speed of the intermediate transfer belt, occurs, the intermediate transfer belt also expands and the distance between the two marks also changes. For this reason, accurate belt speed fluctuations could not be detected.

On the other hand, the following belt conveyance apparatus is proposed (for example, refer patent document 1). That is, two sensors are arranged at intervals in the conveyance direction of the intermediate transfer belt, the intermediate transfer belt is detected from the time interval at which the two sensors detect the mark, and the intermediate transfer belt is kept constant. This is to control the driving speed of the transfer belt.
Japanese Patent No. 3344614

  However, when two sensors are used as in the conventional example, the mounting interval between the two sensors varies due to an assembly error due to the positional accuracy of the assembly and a mechanical dimensional error of the sensor mounting member. There is a risk that. Therefore, there is a problem that an error occurs in the detection speed of the intermediate conveyance belt when the conveyance speed of the intermediate transfer belt is detected from the time interval at which the two sensors detect the marks.

  The present invention has been made under such circumstances, and an object thereof is to provide an image forming apparatus capable of correcting the operation state of the image forming apparatus with higher accuracy and a control method thereof.

  The present invention has been made to solve the above-described problems, and includes the following configuration.

  (1) An intermediate transfer member provided with a plurality of image carriers, a first mark and a second mark, and onto which a developer image formed on each of the plurality of image carriers is superimposed and transferred, and the intermediate transfer An image forming apparatus for forming an image by transferring a developer image superimposed and transferred onto the intermediate transfer body to a recording medium, the first mark and the second mark being First mark detection means and second mark detection means to detect, and either the first mark or the second mark is detected by the first mark detection means and the second mark detection means to convey the intermediate transfer member The speed is calculated, the first mark and the second mark are detected by either the first mark detection means or the second mark detection means, and the transfer speed of the intermediate transfer member is calculated. Calculate speed difference The transport speed of the intermediate transfer member is corrected based on speed difference calculation means, detection information by the first mark detection means and second mark detection means, and transport speed difference information calculated by the speed difference calculation means. An image forming apparatus comprising: a conveyance speed correction unit.

  (2) An intermediate transfer member provided with a plurality of image carriers, a first mark, and a second mark, onto which a developer image formed on each of the plurality of image carriers is superimposed and transferred, and the first An image forming apparatus comprising: a first mark detecting unit that detects a mark and a second mark; and a second mark detecting unit that transfers a developer image superimposed on the intermediate transfer member to a recording medium to form an image. In the control method, either the first mark or the second mark is detected by the first mark detection means and the second mark detection means to calculate the conveyance speed of the intermediate transfer member, and the first mark And the second mark is detected by either the first mark detection means or the second mark detection means to calculate the conveyance speed of the intermediate transfer member, and the speed difference between the two calculated conveyance speeds is calculated. Calculation step and the first tool And a conveyance speed correction step of correcting the conveyance speed of the intermediate transfer body based on the detection information by the mark detection means and the second mark detection means and the conveyance speed difference information calculated in the speed difference calculation step. And a control method for the image forming apparatus.

  According to the present invention, it is possible to provide an image forming apparatus capable of correcting the operation state of the image forming apparatus with higher accuracy and a control method therefor.

  The best mode for carrying out the present invention will be described based on the following examples.

  However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

  The image forming apparatus according to the present embodiment will be described below with reference to the drawings. As an example of the image forming apparatus according to the present embodiment, a four-drum type color image forming apparatus that employs an electrophotographic method and includes a plurality of image forming units and uses an intermediate transfer belt as an intermediate transfer member; did.

  FIG. 1 is a schematic cross-sectional view of the image forming apparatus of this embodiment.

  The image forming apparatus 1 is provided with an image output unit 1P. The image output unit 1P is roughly divided into an image forming unit 10 (four image forming units (stations) a, b, c, and d having the same configuration are arranged in parallel), a paper feeding unit 20, an intermediate transfer unit 30, a fixing unit. It comprises a unit 40 and a control unit (not shown).

  Here, each part and unit will be described.

  Photosensitive drums 11a, 11b, 11c, and 11d (image bearing members) that are rotationally driven in the direction of arrow C in the drawing are pivotally supported at the center of the image forming unit 10. Each of the photoconductive drums 11a to 11d is opposed to the outer peripheral surface thereof, and in order of rotation, primary chargers 12a, 12b, 12c, and 12d, exposure units 13a, 13b, 13c, and 13d (optical system), a developing device. 14a, 14b, 14c, 14d are arranged.

  The photoreceptor drums 11a to 11d are given a uniform charge amount of charge on their surfaces by the primary chargers 12a to 12d. Next, light beams such as laser beams modulated according to the recording image signal are exposed on the photosensitive drums 11a to 11d by the exposure units 13a to 13d, and electrostatic latent images are formed on the photosensitive drums 11a to 11d. Is done. Each electrostatic latent image is visualized as a toner image (developer image) by developing devices 14a to 14d that respectively store toners (developer) of four colors of yellow, cyan, magenta, and black.

  The photosensitive drums 11 a to 11 d and the intermediate transfer belt 31 abut on the downstream side of the developing devices 14 a to 14 d in the rotation direction of the photosensitive drum, and the toner images formed on the photosensitive drums 11 a to 11 d are transferred to the intermediate transfer belt 31. Primary transfer portions Ta, Tb, Tc, and Td to be transferred are formed. On the downstream side of the photosensitive drum rotation direction of the primary transfer portions Ta to Td, the toner remaining on the photosensitive drums 11a to 11d is scraped off by the cleaning devices 15a, 15b, 15c, and 15d, and the photosensitive drums 11a to 11d. The surface of is cleaned.

  Through the processes described above, image formation with each toner is sequentially performed.

  On the other hand, the paper feed unit 20 includes cassettes 21a and 21b and a manual feed tray 27 for storing the recording material P (recording medium). The cassettes 21a, 21b, and the manual feed tray 27 are provided with pickup rollers 22a, 22b, 26 for feeding the stored recording materials P one by one. The recording material P sent out from each of the pickup rollers 22 a, 22 b, 26 is conveyed by the paper feed roller pair 23 through the paper feed guide 24. Then, the recording material P is conveyed to registration rollers 25 a and 25 b for sending the recording material P to the secondary transfer unit Te in accordance with the image forming timing in the image forming unit 10. The number of cassettes and manual feed trays installed is not particularly limited to this.

  The intermediate transfer unit 30 has an intermediate transfer belt 31 (intermediate transfer member). Further, the intermediate transfer unit 30 includes a driving roller 32 (driving means) that transmits a driving force to the intermediate transfer belt 31 to drive and transport, and a backup roller 62 provided to face the registration mark detection sensors 60 and 61. Further, a tension roller 33 that applies an appropriate tension to the intermediate transfer belt 31 by an urging force of a pressure mechanism such as a spring (not shown), and a position facing a secondary transfer device 36 described later with the intermediate transfer belt 31 interposed therebetween. And a secondary transfer inner roller 34. The intermediate transfer belt 31 is wound around a driving roller 32, a backup roller 62, a tension roller 33, and a secondary transfer inner roller 34. As the material of the intermediate transfer belt 31, for example, PI [polyimide] or PVdF [polyvinylidene fluoride] is selected.

  A primary transfer plane A is formed between the drive roller 32 and the backup roller 62. The driving roller 32 is formed by coating the surface of a metal roller with rubber (urethane or chloroprene) having a thickness of several millimeters, thereby preventing slippage with the intermediate transfer belt 31. The drive roller 32 is rotationally driven by a pulse motor (not shown). The alignment of the tension roller 33 urged by a pressure mechanism (not shown) can be adjusted, and the meandering of the intermediate transfer belt 31 can be corrected.

  In the primary transfer portions Ta to Td where the photosensitive drums 11a to 11d and the intermediate transfer belt 31 face each other, the primary transfer devices 35a, 35b, and 35c are arranged at positions facing the photosensitive drums 11a to 11d with the intermediate transfer belt 31 interposed therebetween. , 35d are arranged. Further, a secondary transfer device 36 is disposed at a position facing the secondary transfer inner roller 34 with the intermediate transfer belt 31 in between, and a secondary transfer portion Te is formed.

  A cleaning device 50 for cleaning the toner image carrying surface of the intermediate transfer belt 31 is disposed downstream of the secondary transfer portion Te in the conveyance direction of the intermediate transfer belt 31 (in the direction of arrow B in the figure). The cleaning device 50 includes a cleaner blade 51 and a waste toner box 52 that stores waste toner. As the material of the cleaner blade 51, polyurethane rubber or the like is used.

  The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater inside, and a pressure roller 41b in pressure contact with the fixing roller 41a. The pressure roller 41b may also be provided with a heat source. Further, the fixing unit 40 guides the recording material P discharged from the fixing roller 41a and the pressure roller 41b to the outside of the apparatus, the conveyance guide 43 for guiding the recording material P to the nip portion between the fixing roller 41a and the pressure roller 41b. An inner discharge roller 44, an outer discharge roller 45, and the like.

  The control unit is composed of a control board 90 for controlling the operation of each part and the mechanism in the unit, a motor drive board (not shown), and the like.

  Next, the operation of the image forming apparatus will be described.

  When the image forming operation start signal is issued, first, for example, the recording material P is sent out one by one from the cassette 21a by the pickup roller 22a. The recording material P is guided between the paper feed guides 24 by the paper feed roller pair 23 and conveyed to the registration rollers 25a and 25b. At this time, the registration rollers 25a and 25b are stopped, and the leading edge of the recording material P abuts against a nip portion formed by the registration rollers 25a and 25b.

  Thereafter, the registration rollers 25a and 25b start rotating in accordance with the timing at which the image forming unit 10 starts image formation. The rotation start timing of the registration rollers 25a and 25b is set so that the recording material P and the toner image primarily transferred from the image forming unit 10 to the intermediate transfer belt 31 coincide with each other in the secondary transfer unit Te.

  On the other hand, when an image forming operation start signal is issued, the image forming unit 10 forms a toner image on the photosensitive drum 11d on the most upstream side in the rotation direction of the intermediate transfer belt 31 through the process described above. The formed toner image is primarily transferred to the intermediate transfer belt 31 at the primary transfer portion Td by the primary transfer device 35d to which a high voltage is applied. Then, the toner image primarily transferred to the intermediate transfer belt 31 is conveyed to the next primary transfer portion Tc. On the next photosensitive drum 11c on the downstream side in the transport direction of the intermediate transfer belt 31, image formation is performed with a delay by a time during which the toner image is transported between the stations. The toner image formed on the photosensitive drum 11c is transferred with the resist aligned on the image transferred from the photosensitive drum 11d to the intermediate transfer belt 31. The same process is repeated, and finally the four color toner images are superimposed on the intermediate transfer belt 31 and primarily transferred. The superimposed color toner image is conveyed to the secondary transfer portion Te.

  Thereafter, when the recording material P enters the secondary transfer portion Te and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer device 36 in accordance with the passing timing of the recording material P. Then, the four color toner images formed on the intermediate transfer belt 31 by the process described above are transferred to the recording material P. The recording material P to which the toner image has been transferred is guided to the nip portion between the fixing roller 41 a of the fixing unit 40 and the pressure roller 41 b by the conveyance guide 43. The toner image is fixed on the recording material P by the heat of the fixing roller 41 a and the pressure roller 41 b and the pressure of the nip, and the recording material P on which the toner image is fixed is conveyed by the inner discharge roller 44 and the outer discharge roller 45. Discharged outside the machine.

  Next, the registration correction mechanism will be described.

  FIG. 6 is a schematic diagram for explaining the registration correction mechanism.

  The registration mark detection sensors 60 and 61 include an LED as a light source and a light receiving element that detects reflected light, and are arranged at intervals in the main scanning direction (a direction perpendicular to the recording material conveyance direction). The electrical signals obtained from the registration mark detection sensors 60 and 61 are sent to the CPU 80, and the color misregistration amount is calculated by the image position detection circuit 81 of the CPU 80.

  The registration marks 70 and 71 will be described with reference to FIGS.

  Registration marks 70 and 71 are formed between the image transferred to the kth recording material P and the image transferred to the (k + 1) th recording material P. The arrows in FIG. 7 indicate the image conveyance direction. The registration marks 70 and 71 are formed on the intermediate transfer belt 31 at positions corresponding to the thrust positions of the registration mark detection sensors 60 and 61, respectively. When the registration marks 70 and 71 pass directly below the registration mark detection sensors 60 and 61, a predetermined electrical signal is obtained.

  For example, as shown in FIG. 8, the registration marks 70 and 71 are between the diagonal line Ca of the correction target color formed between the diagonal lines Ka and Kb of any reference color and the diagonal lines Kc and Kd of the reference color. And an oblique line Cb of the color to be corrected formed. Here, when a color shift of ΔV occurs in the main scanning direction (perpendicular to the recording material conveyance direction) and ΔH occurs in the sub-scanning direction (a direction parallel to the recording material conveyance direction), the oblique lines Ca and Cb are the ideal positions. Are formed at positions shifted by ΔV and ΔH from the diagonal lines CaS and CbS, respectively.

  At this time, as the outputs of the registration mark detection sensors 60 and 61, Hi is output in a portion where there is no image (a base portion of the intermediate transfer belt 31), and a portion where there is an image (diagonal lines Ka, Ca, Kb, Kc, Cb). , Kd), Lo output is obtained. When the distances between the centers of gravity of the outputs of the respective Lo portions are A1, A2, B1, and B2, the color shift amount ΔV in the main scanning direction and the color shift amount ΔH in the sub scanning direction are calculated based on the following equations.

ΔV = {(B2-B1) / 2- (A2-A1) / 2} / 2
ΔH = {(B2−B1) / 2 + (A2−A1) / 2} / 2

  When the color misregistration amount is calculated by the image position detection circuit 81, a correction amount necessary for correcting the color misregistration amounts ΔV and ΔH is then calculated by the correction amount calculation circuit 82. Further, the control circuit 83 adjusts a lens or a mirror (not shown) in the exposure units 13a to 13d according to the correction amount calculated by the correction amount calculation circuit 82, thereby correcting the color misregistration.

  If this color misregistration correction is performed with all colors other than an arbitrary reference color as target colors, correction can be performed so that all colors match the reference color.

  As described above, registration correction performed by forming registration marks 70 and 71 on the intermediate transfer belt 31 and detecting them can correct color misregistration with high accuracy. However, the registration correction performed by forming the registration mark leads to consumption of the toner because the registration mark is actually formed with toner. Further, downtime of the image forming apparatus occurs due to registration mark formation, cleaning, and the like. Therefore, the registration correction is performed according to a predetermined interval and a temperature fluctuation state in the apparatus.

  Here, since there is a temperature variation in the image forming apparatus during the period from the above-described registration correction to the next registration correction, a problem arises that color misregistration occurs during that time. One of the factors that most affect color misregistration due to variations between registration corrections is a change in diameter due to temperature variations of the driving roller 32 of the intermediate transfer belt 31. When the outer diameter of the drive roller 32 changes due to temperature rise, it appears as a change in the conveyance speed of the intermediate transfer belt 31. For this reason, the image forming position in each image forming unit combined by the registration correction and the position of the image of the other color conveyed by the intermediate transfer belt 31 do not match, and a color misregistration image is generated.

  In order to prevent this, in this embodiment, a speed detection unit 120 (speed detection unit) and a conveyance speed control unit 200 (conveyance speed correction unit) for detecting and correcting the conveyance speed of the intermediate transfer belt 31 are provided. Yes. As shown in FIG. 2, the speed detection unit 120 includes a support member 121. The first mark detection sensor 122 (first mark detection unit) and the second mark detection sensor 123 (second mark detection unit) are provided on the support member 121. Is held. The speed detection unit 120 is disposed to face the inner surface of the intermediate transfer belt 31 as shown in FIG. A first mark 126 and a second mark 127 made of immortal ink are provided on the inner surface of the intermediate transfer belt 31. The first mark detection sensor 122 and the second mark detection sensor 123 are configured to change the output signal when the first mark 126 and the second mark 127 pass. The number of mark detection sensors and marks installed is not particularly limited to this.

  Further, as shown in FIG. 3, the circumferential length of the driving roller 32 is X mm. The pitch (distance) between the first mark 126 and the second mark 127 applied on the intermediate transfer belt 31 is set to an integral multiple of the circumferential length of the driving roller 32. If the pitch is Ymm, Y = n × X. In this embodiment, the relationship of n = 1 is established. Further, the pitch of the first mark detection sensor 122 and the second mark detection sensor 123 is similarly set to an integral multiple of the drive roller 32, and y = n × X where Ymm is the pitch. In this embodiment, the relationship of n = 1 is established.

  The conveyance speed control unit 200 includes a speed calculation circuit 128 (speed difference calculation means), a correction amount calculation circuit 129, and a control circuit 130. The speed calculation circuit 128 calculates the speed of the intermediate transfer belt 31 based on timing information (detection information) from the first mark detection sensor 122 and the second mark detection sensor 123. The correction amount calculation circuit 129 calculates the speed correction amount of the intermediate transfer belt 31 based on the information from the speed calculation circuit 128, and the control circuit 130 determines the driving roller based on the correction amount calculated by the correction amount calculation circuit 129. 32 drive speed correction is performed. The conveyance speed control unit 200 is provided in a control unit, for example.

  Next, operations of the speed detection unit 120 and the conveyance speed control unit 200 will be described.

  As shown in FIG. 3, when the intermediate transfer belt 31 is conveyed, the first mark 126 passes through a position where the first mark detection sensor 122 and the second mark detection sensor 123 are opposed to each other. At this time, the line passing timing information t1 with the timing difference between the sensors from the first mark detection sensor 122 and the second mark detection sensor 123 is output and input to the speed calculation circuit 128. The conveyance speed V1 of the intermediate transfer belt 31 at this time is calculated as V1 = Y / t1 as shown in FIG.

  At the same time, timing information t <b> 2 when the first mark 126 and the second mark 127 pass the position opposite the first mark detection sensor 122 is output and input to the speed calculation circuit 128. The conveyance speed V2 of the intermediate transfer belt 31 at this time is calculated as V2 = Y / t2 as shown in FIG.

  As described above, since the pitch between the first mark 126 and the second mark 127 and the pitch between the first mark detection sensor 122 and the second mark detection sensor 123 coincide with each other, originally t1 = t2. Should be. However, in practice, the pitch between the first mark detection sensor 122 and the second mark detection sensor 123 may not match due to sensor mounting error, mechanical tolerance of the support member 121, sensitivity variation between the two sensors, and the like. .

  On the other hand, between the first mark 126 and the second mark 127, the first mark 126 and the second mark 127 are formed or processed integrally with the intermediate transfer belt 31 so that there is almost no error. can do. Further, regarding the influence of expansion / contraction of the intermediate transfer belt 31 due to temperature fluctuations, the speed of the intermediate transfer belt 31 is detected before the operation of the image forming apparatus on that day, or the temperature is detected by an environmental sensor (not shown) and a predetermined temperature range. It can be avoided by doing in the inside.

  Therefore, the speed difference ΔV (= V1−V2) between the two conveyance speeds calculated by this control is generated due to an error between the first mark detection sensor 122 and the second mark detection sensor 123. The speed difference ΔV calculated at this time is stored in the speed calculation circuit 128 as conveyance speed difference information.

  As a result, the speed calculation circuit 128 calculates the conveyance speed fluctuation amount ΔV0 [mm / sec] from the conveyance speed V0 [mm / sec] at the time of registration correction of the intermediate transfer belt 31 from the following relational expression.

ΔV0 = (V1−ΔV) −V0 [mm / sec]
Here, V1 is a speed obtained by detecting the passage of the first mark 126 by the first mark detection sensor 122 and the second mark detection sensor 123. V2 is a speed obtained by detecting the passage of the first mark 126 and the second mark 127 by the first mark detection sensor 122, and ΔV = V1−V2.

  The control circuit 130 corrects the driving speed of the driving roller 32 so as to correct ΔV0 calculated in this way and maintain the conveyance speed V0 at the time of registration correction.

  In this embodiment, the speed detection of V1 is calculated from the time that the first mark 126 passes through the first mark detection sensor 122 and the second mark detection sensor 123. However, the present invention is not particularly limited thereto, and may be calculated from the time that the second mark 127 passes through the first mark detection sensor 122 and the second mark detection sensor 123. In this embodiment, the speed detection of V2 is calculated from the time during which the first mark 126 and the second mark 127 pass through the first mark detection sensor 122. However, the present invention is not particularly limited thereto, and may be calculated from the time during which the first mark 126 and the second mark 127 pass through the second mark detection sensor 123.

  Next, speed correction control in the present embodiment will be described with reference to the flowchart of FIG.

  This processing is executed by a CPU (not shown) of the image forming apparatus using a RAM (not shown) as a work area while controlling each part based on a control program stored in a ROM (not shown). is there.

  First, it is determined whether the image forming apparatus 1 is powered on (step S501). If the power is on, it is determined whether the environmental temperature is within a predetermined temperature range (step S502). If the environmental temperature is within a predetermined range, the speed correction of the intermediate transfer belt 31 is started (step S503), and the first speed detection operation is performed (step S504). Specifically, the time required for the first mark 126 to pass through the opposing positions of the first mark detection sensor 122 and the second mark detection sensor 123 is measured, and the conveyance speed V1 of the intermediate transfer belt 31 is calculated. Next, a second speed detection operation is executed (step S505). Specifically, the time required for the first mark 126 and the second mark 127 to pass the position facing the first mark detection sensor 122 is measured, and the conveyance speed V2 of the intermediate transfer belt 31 is calculated.

  A speed difference ΔV between the two transport speeds V1 and V2 thus obtained is calculated (step S506), and the speed difference ΔV is stored (step S507). When an output request is made (step S508), drive speed correction control of the intermediate transfer belt 31 is performed so as to maintain the conveyance speed V0 at the time of registration correction (step S509). When the output is completed (step S510), the driving of the intermediate transfer belt 31 is stopped and the operation is ended (step S511).

  As described above, in the image forming apparatus according to the present exemplary embodiment, two marks are provided on the intermediate transfer belt at an interval that is an integral multiple of the driving roller, and this is detected by the two sensors, thereby controlling the conveyance speed of the intermediate transfer belt. Two types are calculated. Further, the difference between the two types is obtained and fed back to the motor that drives the drive roller of the intermediate transfer belt. As a result, the conveyance speed of the intermediate transfer belt can be controlled in real time without being affected by the attachment error of the mark detection sensor, and color misregistration can be prevented with high accuracy.

  In addition, the operation state correction of the image forming apparatus can be performed with high accuracy and efficiency while maintaining high productivity regardless of temperature fluctuations in the apparatus.

Schematic sectional view of the image forming apparatus of Example 1 Schematic configuration diagram of speed detector Explanation of operation of speed detector The figure which shows the mark detection timing of the mark detection sensor Flowchart explaining conveyance speed correction control Schematic diagram for explaining the registration correction mechanism Schematic for explaining the registration mark Schematic for explaining the registration mark

Explanation of symbols

P Recording material (compatible with recording media)
11a, 11b, 11c, 11d Photosensitive drum (corresponding to image carrier)
31 Intermediate transfer belt (compatible with intermediate transfer members)
32 Drive roller (corresponding to drive means)
122 First mark detection sensor (corresponding to first mark detection means)
123 Second mark detection sensor (corresponding to second mark detection means)
126 First mark 127 Second mark 128 Speed calculation circuit (corresponding to speed difference calculation means)
200 Conveying speed control unit (corresponding to conveying speed correcting means)

Claims (4)

A plurality of image carriers, a first mark, and a second mark are provided, and an intermediate transfer member on which a developer image formed on each of the plurality of image carriers is superimposed and transferred, and the intermediate transfer member is conveyed An image forming apparatus for forming an image by transferring the developer image superimposed and transferred to the intermediate transfer member to a recording medium,
First mark detection means and second mark detection means for detecting the first mark and the second mark;
Either the first mark or the second mark is detected by the first mark detection means and the second mark detection means to calculate the conveyance speed of the intermediate transfer member, and the first mark and the second mark are A speed difference calculating means for calculating a transport speed of the intermediate transfer body by detecting by either the first mark detecting means or the second mark detecting means, and calculating a speed difference between the two calculated transport speeds;
A conveyance speed correction unit that corrects a conveyance speed of the intermediate transfer body based on detection information by the first mark detection unit and the second mark detection unit and conveyance speed difference information calculated by the speed difference calculation unit; An image forming apparatus comprising: The image forming apparatus according to claim 1,
The drive means is a drive roller;
The distance between the first mark detection means and the second mark detection means is an integral multiple of the circumference of the drive roller. The image forming apparatus according to claim 1, wherein
The drive means is a drive roller;
The distance between the first mark and the second mark is an integral multiple of the circumference of the drive roller. A plurality of image carriers, a first mark and a second mark, and an intermediate transfer member onto which a developer image formed on each of the plurality of image carriers is superimposed and transferred; A control method for an image forming apparatus, comprising: a first mark detecting unit that detects two marks; and a second mark detecting unit that transfers a developer image superimposed on the intermediate transfer member to a recording medium to form an image. There,
Either the first mark or the second mark is detected by the first mark detection means and the second mark detection means to calculate the conveyance speed of the intermediate transfer member, and the first mark and the second mark are A speed difference calculating step of calculating a transport speed of the intermediate transfer body by detecting by either the first mark detecting means or the second mark detecting means, and calculating a speed difference between the two calculated transport speeds;
A conveyance speed correction step of correcting the conveyance speed of the intermediate transfer body based on the detection information by the first mark detection unit and the second mark detection unit and the conveyance speed difference information calculated in the speed difference calculation step; A control method for an image forming apparatus.

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