JP5063178B2 - Image forming apparatus - Google Patents

Description

The present invention is a copying machine, a printer, it relates to an image forming equipment of a facsimile apparatus or the like. In particular, it relates to an image forming equipment which employs an electrostatic recording method or an electrophotographic recording method or the like.

  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 toner of each color, and each image forming unit forms a visible image of each color on a photosensitive drum as an image carrier in 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.

  One of the main causes of this 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 the 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 speed fluctuation 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 conveying 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 sensor detects the conveyance speed of the intermediate transfer belt from the time interval at which the two sensors detect the mark, and the intermediate conveyance belt is kept constant. This is to control the driving speed of the transfer belt.

Further, the conveyance speed of the intermediate transfer belt is detected from the time interval at which the two sensors detect the marks, the speed after color misregistration correction is stored, and the subsequent conveyance speed of the intermediate transfer belt matches the stored speed. A correction is proposed (for example, see Patent Document 2).
Japanese Patent No. 3344614 JP 2005-156877 A

  Since the conventional example detects the conveyance speed of the intermediate transfer belt from the time interval at which the two sensors detect the mark, the conveyance speed of the intermediate transfer belt is detected without being affected by the thermal expansion of the intermediate transfer belt. Can do.

  However, even in the conventional example, when the support member supporting the two sensors expands under the influence of heat, there is a problem that an error occurs in the detection speed due to the influence of the thermal expansion.

  The amount of color misregistration due to thermal expansion of the support member is an amount that cannot be ignored in response to the recent demand for higher image quality. Hereinafter, the color shift due to the thermal expansion of the support member will be described.

When two sensors are supported at a predetermined interval by a support member having a linear expansion coefficient α, and the temperature variation of the support member is ΔT, the sensor interval r is
r ′ = (1 + α * ΔT) * r (1)
It becomes. Therefore, if the detection time interval of the two sensors is tb, the speed V of the intermediate transfer belt is
V = (1 + α * ΔT) * r / tb (2)
It is represented by

On the other hand, when the intermediate transfer belt speed is measured without considering the linear expansion of the support member as in the conventional example, the measured belt speed Ve is
Ve = r / tb (3)
It becomes.

  Therefore, the difference ΔV between the measured belt speed Ve and the true speed V of the intermediate transfer belt is an error due to linear expansion of the support member.

ΔV = V−Ve = α * ΔT * r / tb (4)
The color shift amount ΔX of the intermediate transfer belt due to the speed error ΔV is as follows.

That is, let L be the interval between two image forming units that are the farthest apart from each other among the plurality of image forming units. The image forming apparatus then superimposes and transfers the images in the image forming units separated by the distance L at the time when the image of the first image forming unit is transferred by the distance L after being transferred to the intermediate transfer belt. Correct the device. Here, the target time ta to match the timing is the time that the intermediate transfer belt advances by L at the measured belt speed Ve.
ta = L / Ve (5)
It is. During this time ta, the amount of positional deviation caused by the speed error ΔV is ΔX.

Therefore,
ΔX = ΔV * ta (6)
It becomes. Therefore, the color misregistration amount ΔX is calculated by substituting the equations (3), (4), and (5) into the equation (6). ΔX = L * α * ΔT (7)
It becomes.

Here, for example, it is assumed that the support members of the two sensors are iron having a linear expansion coefficient of 11.7 × 10 ⁻⁶ , and an image forming apparatus in which an interval between four image forming units is 100 [mm]. Then, it is assumed that a temperature variation of 5 [° C.] occurs in the support member. In this case, the amount of color misregistration occurring between the both-end image forming units is that the distance L between both-end image forming units is 300 [mm].
ΔX = 300 × 11.7 × 10 ⁻⁶ × 5 = 0.01755 [mm]
Thus, a color shift of about 18 μm occurs.

  This is a non-negligible amount for the current image target value.

The present invention has been made under such circumstances, and an object thereof is to provide an image forming equipment which can be used to calculate the conveying speed of the intermediate transfer member with high accuracy regardless of the temperature variations in the apparatus .

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

(1) A plurality of image carriers on which developer images are formed, an intermediate transfer member on which marks are provided , and developer images formed on the plurality of image carriers are superimposed and transferred, and the marks A first mark detection means and a second mark detection means for detecting; a period counting means for counting a time interval at which the first mark detection means and the second mark detection means detect the mark twice; and Storage means for storing a correspondence relationship between the count value of the period count means and the arrangement interval value indicating the arrangement interval from the first mark detection means to the second mark detection means; and the count value of the period count means Selection means for selecting the corresponding arrangement interval value based on the correspondence stored in the storage means; and the second mark after the first mark detection means detects the mark. Time detecting means until detecting the mark, and characterized in that the said arrangement interval value selected by said selecting means, comprising a a transport speed calculation means for calculating the transport speed of the intermediate transfer body Image forming apparatus.

According to the present invention, it is possible to provide an image forming equipment which can be used to calculate the conveying speed of the intermediate transfer member with high accuracy regardless of the temperature variations in the apparatus.

  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, the image forming apparatus according to the present embodiment adopts an electrophotographic system, and is a four-drum color image forming apparatus using an intermediate transfer belt as an intermediate transfer body, which is provided with a plurality of image forming units. .

  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 delivered from each of the pickup rollers 22a, 22b, and 26 is conveyed through the paper feed guide 24 by the paper feed roller pair 23. 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. 5 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. 6 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. 7, 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. If the distances between the centers of gravity of the respective Lo output 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.

To prevent this, in the present embodiment detects the conveying speed of the intermediate transfer belt 31, provided with a speed detection portion 120 for correcting (speed detection means) and the conveying speed control section 300 (speed control means) Yes. As shown in FIG. 4, the speed detection unit 120 includes a support member 121, and a mark detection sensor 122 (second mark detection unit) and a mark detection sensor 123 (first mark detection unit) are held on the support member 121. Yes. The speed detector 120 is disposed to face the inner surface of the intermediate transfer belt 31. Further, a line 129 (mark) previously formed with immortal ink is provided on the inner surface of the intermediate transfer belt 31, and the mark detection sensors 122 and 123 are configured to change the output signal when the line 129 passes. Has been.

  Further, the conveyance speed control unit 300 includes a speed calculation circuit 126, a comparison circuit 127, and a control circuit 128.

  Next, operations of the speed detection unit 120 and the conveyance speed control unit 300 will be described.

  As shown in FIG. 4, when the intermediate transfer belt 31 is conveyed, the line 129 passes through the position opposite to the mark detection sensors 122 and 123. At this time, the line detection timing information whose timing is shifted by the distance between the sensors is output from the mark detection sensors 122 and 123 and input to the speed calculation circuit 126. In the speed calculation circuit 126, the belt conveyance speed V1 [mm / sec] = R from the difference Δt [sec] in the line passing timing of the mark detection sensors 122 and 123 and the design distance R [mm] between the mark detection sensors 122 and 123. / Δt is derived.

  The comparison circuit 127 compares the belt conveyance speed V1 calculated by the speed calculation circuit 126 with the conveyance speed V0 [mm / sec] when the registration of the intermediate transfer belt 31 is corrected. Then, an acceleration / deceleration signal for maintaining the conveyance speed V0 at the time of registration correction is transmitted from the comparison circuit 127 to the control circuit 128. The control circuit 128 transmits a control pulse to the motor 202 that transmits the rotational driving force to the driving roller 32 in order to correct the driving speed of the driving roller 32.

  Next, a configuration and operation for indirectly detecting a temperature variation in the apparatus and selecting a correction value R ′ of the design distance R between the mark detection sensors 122 and 123 from the table will be described. FIG. 8 is a flowchart of intermediate conveyance belt conveyance speed control.

  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.

  In FIG. 8, the drive motors of the photosensitive drums 11a to 11d and the intermediate transfer belt 31 are turned on (step S1), and the intermediate transfer belt 31 starts to be driven. Next, it is determined whether or not the mark detection sensor 123 has detected the line 129 (step S2). When the mark detection sensor 123 detects the line 129, it is determined whether or not the mark detection sensor 122 has detected the line 129 (step S3). When the mark detection sensor 122 detects the line 129, the speed calculation circuit 126 stores the movement time between the sensors on the line 129 (step S4).

  Thereafter, it is determined again whether or not the mark detection sensor 122 has detected the line 129 (step S5). Thereafter, the interval counter 200 (period counting means) shown in FIG. 4 counts the time interval when the mark detection sensor 122 detects the line 129 twice, and outputs it as a count value of the period of the intermediate transfer belt 31. In this embodiment, the mark detection sensor 122 is used to detect the cycle of the intermediate transfer belt 31, but the mark detection sensor 123 may be used. When the temperature in the apparatus rises, the driving roller 32 expands to increase its diameter, and the intermediate transfer belt 31 is conveyed at a higher speed. Therefore, as shown in FIG. 2, when the count value output by the interval counter 200 is ITVL_1 at a predetermined constant temperature, ITVL_2 when the temperature rises becomes shorter than ITVL_1.

201, corresponding to the count value of the interval counter 200, a correction table that arrangement interval value of the mark detection sensor 122 and 123 is stored. That is, a correspondence relationship between the count value of the interval counter 200 at a predetermined temperature and the arrangement interval values of the mark detection sensors 122 and 123 is obtained in advance by experiments. Then, as shown in FIG. 3, when the count value of the interval counter 200 is within a predetermined range, the correspondence between the belt period and the sensor interval is stored in the correction table 201 so that the corresponding mark detection sensor interval information is selected. Has been.

  For example, if the count value ITVL_1 at the constant temperature is in the range of the belt period t4 to t5, R'4 is selected as the interval value of the mark detection sensor. Then, if the count value ITVL_2 at the time of the temperature rise is shorter than ITVL_1 and is in the range of the belt period t3 to t4, R'3 longer than R'4 is selected as the interval value of the mark detection sensor (step) S6).

  The selected sensor interval value R ′ is replaced with the design distance R between the mark detection sensors 122 and 123 in the speed calculation circuit 126, and the conveyance speed of the intermediate transfer belt 31 is calculated from the inter-sensor movement time stored in step S4. (Step S7). Thereafter, the comparison circuit 127 compares the conveyance speed V0 (target speed) during registration correction. The comparison result is transmitted to the control circuit 128, and increase / decrease control of the motor speed is performed (step S8).

  Thereafter, it is determined whether or not the drive motor is turned off (step S9). If the drive motor is turned on, the above control is started again, and if it is turned off, the control is terminated (step S10).

  As described above, in this embodiment, the cycle of the intermediate transfer belt is obtained by counting the interval at which one mark detection sensor detects a mark twice. Then, from the information, an arrangement interval value of mark detection sensors whose correlation is grasped in advance by an experiment is obtained and applied to the calculation of the conveyance speed of the intermediate transfer belt. Accordingly, it is possible to detect the degree of expansion of the support member of the mark detection sensor of the intermediate transfer belt without using a temperature sensor. Even when the support member of the mark detection sensor expands due to the influence of the environmental temperature, the speed fluctuation of the intermediate transfer belt can be grasped, and this is fed back to the rotation speed control of the drive roller, thereby stabilizing the speed of the intermediate transfer belt. Control can be carried out.

  Further, as one method for reducing the influence of the conveyance speed error of the intermediate transfer belt due to the thermal expansion of the support member, a method of frequently performing registration correction can be considered. However, as described above, since registration correction requires time for forming a registration pattern, there is a problem in that downtime occurs and productivity of the image forming apparatus decreases. In addition, since the registration pattern is formed using toner, there is a problem that toner consumption is increased. On the other hand, according to the present invention, while maintaining high productivity of the image forming apparatus and avoiding an increase in toner consumption, the correction of the operation state of the image forming apparatus can be further improved regardless of temperature fluctuations in the apparatus. The accuracy can be controlled.

Schematic sectional view of the image forming apparatus of Example 1 Schematic diagram showing the peripheral speed fluctuation of the intermediate transfer belt The figure which shows the correction table which stored the correspondence of the belt period and the sensor interval Schematic diagram of speed detector and transport speed controller Schematic diagram for explaining the registration correction mechanism Schematic for explaining the registration mark Schematic for explaining the registration mark Flow chart of intermediate conveyance belt conveyance speed control

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)
122 Mark detection sensor (corresponding to the second mark detection means)
123 Mark detection sensor (corresponding to the first mark detection means)
129 lines (corresponding to the mark)
200 interval counter (corresponding to period counting means)
201 correction tables 300 conveying speed control section (corresponding to the speed control means)

Claims (3)

A plurality of image carriers on which developer images are formed ;
An intermediate transfer member provided with a mark, onto which a developer image formed on each of the plurality of image carriers is superimposed and transferred ,
First mark detection means and second mark detection means for detecting the mark;
A period counting unit that counts a time interval at which the first mark detection unit and the second mark detection unit detect the mark twice, and
Storage means for storing a correspondence relationship between a count value of the cycle count means and an arrangement interval value indicating an arrangement interval from the first mark detection means to the second mark detection means;
Selecting means for selecting the arrangement interval value corresponding to the count value of the period counting means based on the correspondence stored in the storage means;
From the time from when the first mark detection means detects the mark until the second mark detection means detects the mark, and the arrangement interval value selected by the selection means, the intermediate transfer member An image forming apparatus comprising: a conveyance speed calculating unit that calculates a conveyance speed . The image forming apparatus according to claim 1.
Drive means for driving the intermediate transfer member ;
Speed control means for comparing the transport speed calculated by the transport speed calculation means with a predetermined target speed and controlling the drive speed of the drive means based on the comparison result ;
An image forming apparatus comprising: The image forming apparatus according to claim 2.
The predetermined target speed corrects the positions of the developer images formed on the plurality of image carriers by forming a predetermined developer image on the intermediate transfer member and detecting the formation positions of the developer images. An image forming apparatus having a conveyance speed of the intermediate transfer member in registration correction.

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