JP5196299B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

  Conventionally, a so-called tandem type color image forming apparatus that forms images of different colors (visible images) on a plurality of latent image carriers and overlays these images to form a color image is known. Yes.

  In this tandem type image forming apparatus, each toner image on a plurality of latent image carriers is sequentially overlapped to form a color image. Therefore, when the toner images overlap, so-called color shift occurs. This color misregistration is mainly caused by speed fluctuations caused by the mounting eccentricity of the drive gear provided on the latent image carrier, the gear molding accuracy, the engaging portion that engages the drive gear and the latent image carrier, and the like. Responsible. For example, when the eccentricity occurs in the drive gear of the latent image carrier, the surface moving speed of the latent image carrier fluctuates periodically, and the toner image transferred onto the surface of the transfer material due to this fluctuation It expands and contracts periodically. Therefore, when the phase of the expansion / contraction period of the toner image by each latent image carrier does not match, color misregistration occurs.

  Patent Document 1 describes an image forming apparatus that can suppress color misregistration caused by periodic fluctuations in the surface moving speed of a latent image carrier. The image forming apparatus described in Patent Document 1 performs feedback control so that a drive motor that rotates and drives a latent image carrier provided for each latent image carrier is rotated at a constant speed, and a plurality of latent image carriers are used. A pattern image is formed on the transfer material. The pattern image is read, and periodic fluctuations in the surface moving speed of each latent image carrier are detected. Then, based on the detection result, the speed control of each latent image carrier is performed so that the periodic fluctuation of the surface moving speed of each latent image carrier is offset. As a result, periodic fluctuations in the surface movement speed of each image carrier are suppressed, the expansion and contraction of the toner image transferred onto the surface of the transfer material is suppressed, and color misregistration is suppressed.

JP 2002-72816 A

  However, there is an error between the detected surface movement speed fluctuation of the latent image carrier and the actual surface movement speed fluctuation of the latent image carrier due to the detection accuracy of the pattern image, the dimensional accuracy of the constituent machine elements, the calculation accuracy, etc. Arise. As a result, even if the speed control is performed based on the detected surface movement speed fluctuation of the latent image carrier, the periodic fluctuation of the surface movement speed of each latent image carrier is not completely eliminated, and color misregistration occurs. It will remain. Therefore, by increasing the detection accuracy of the pattern image, the dimensional accuracy of the constituent machine elements, the calculation accuracy, etc., between the detected surface movement speed fluctuation of the latent image carrier and the actual surface movement speed fluctuation of the latent image carrier. It is also conceivable to reduce the error and bring the periodic fluctuation of the surface moving speed of each latent image carrier close to zero when speed control is performed. However, in this case, it is necessary to provide a sensor with high detection accuracy in order to increase the detection accuracy of the pattern image, or to provide a calculation device (CPU) with high information processing capability in order to increase the calculation accuracy. There was a problem that led to up.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an image forming apparatus that can suppress an increase in cost of the apparatus and can suppress color misregistration when speed control is performed by a speed control unit. Is to provide.

In order to achieve the above object, a first aspect of the present invention provides a plurality of latent image carriers that carry a latent image on a surface that moves endlessly, and a plurality of drive sources that individually drive each latent image carrier. A latent image writing means for writing a latent image on each latent image carrier based on image information, and a plurality of latent images written on each latent image carrier to individually develop a visible image. An endless moving body that moves the surface endlessly so as to sequentially pass through the opposing positions of the developing means and each latent image carrier, and a visible image formed on the surface of each latent image carrier. A toner image on the endless moving body , wherein the toner image is transferred to a recording body held on the surface of the body or transferred to the recording body after being transferred to the surface of the endless moving body. The image detecting means to detect and the surface of each latent image carrier are predetermined. Forming a plurality of toner images for speed variation detection, transferring the speed variation detection image formed on the surface of each latent image carrier to the endless moving body, and detecting the speed variation by the image detecting means. A speed fluctuation detecting means for detecting a movement speed fluctuation of each latent image carrier based on a detection time interval of each toner image in the image, and a surface of each image carrier detected by the speed fluctuation detecting means Based on the movement speed fluctuation, each drive source is controlled to control the speed of each latent image carrier, and the surface movement speed fluctuation of each image carrier detected by the speed fluctuation detection means. On the basis of the phase control means for adjusting the phase of the surface movement speed fluctuation of each latent image carrier when the speed control is executed by the speed control means, and by controlling the drive of each drive source, Rotated at a constant speed Then, after the first speed change detecting means detects each first latent image carrier surface movement speed change, the speed control means determines the first time movement of each latent image carrier surface movement speed. By controlling each drive source, the speed fluctuation detecting means detects each second latent image carrier surface movement speed fluctuation, and based on these detected second latent image carrier surface movement speed fluctuations, And a control unit that controls the phase adjustment unit to adjust the phase of the surface movement speed fluctuation of each latent image carrier .
The invention according to claim 2 is based on a plurality of latent image carriers that carry a latent image on a surface that moves endlessly, a plurality of drive sources for individually driving each latent image carrier, and image information. A latent image writing means for writing a latent image on each latent image carrier, a plurality of developing means for individually developing the latent image written on each latent image carrier to obtain a visible image, and An endless moving body that moves the surface endlessly so as to sequentially pass a position facing the latent image carrier, and a visible image formed on the surface of each latent image carrier are held on the surface of the endless moving body. An image detecting device for detecting a toner image on the endless moving body, and an image forming apparatus comprising: a transfer means for transferring to the recording body after transferring to the surface of the endless moving body; A plurality of predetermined toner images on the surface of each latent image carrier Each of the toner images in the image for detecting speed fluctuations by the image detecting means is formed by transferring the speed fluctuation detecting image formed on the surface of each latent image carrier to the endless moving body. Speed fluctuation detecting means for detecting fluctuations in the surface movement speed of each latent image carrier based on the detection time interval, and based on the fluctuations in the surface movement speed of each image carrier detected by the speed fluctuation detecting means. A speed control means for controlling each drive source to control the speed of each latent image carrier, and each drive based on the surface movement speed fluctuation of each image carrier detected by the speed fluctuation detection means. By controlling the driving of the source, the phase adjusting means for adjusting the phase of the surface movement speed fluctuation of each latent image carrier when the speed control is executed by the speed control means, and each driving source is rotated at a constant speed. Speed fluctuation detection And detecting the phase movement speed fluctuation of each latent image carrier based on the detected fluctuation of the surface movement speed of each latent image carrier. Each of the latent image carriers is adjusted by the speed control means on the basis of the variation in the moving speed of the surface of each latent image carrier that has been adjusted to an amplitude smaller than the detected amplitude of the moving speed of the surface of each latent image carrier. And a control means for performing control so as to perform speed control .
According to a third aspect of the present invention , in the image forming apparatus according to the first or second aspect , the phase adjusting means controls a stop timing of driving of each driving source based on a surface moving speed variation of each latent image carrier. It is characterized by doing.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the speed control means is in phase opposite to the surface movement speed fluctuation of the latent image carrier detected by the speed fluctuation detection means. The drive control is performed so that the drive source is rotationally driven with the speed fluctuation.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a manual instructing unit is provided that allows a user to instruct the execution of the speed fluctuation detecting unit. It is.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect , the speed fluctuation detecting means allows a user to detect only surface movement speed fluctuation data for the speed control means to control each drive source. The manual instructing means is configured so that it can be instructed.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, each latent image carrier is a one-stage reduction mechanism using a drive transmission member having the same rotation center as that of the latent image carrier. It is characterized by being driven by.
According to an eighth aspect of the present invention, in the image forming apparatus of the seventh aspect , the drive transmission member and the engagement member that engages with the engaged portion provided on the rotation shaft of the latent image carrier are the same. It is characterized in that it is formed as a single piece made of a material.
The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8 , further comprising replacement detection means for detecting that the latent image carrier has been replaced. When the replacement detection means detects the replacement of the latent image carrier, the speed fluctuation of each latent image carrier is detected.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the image carrier and at least one of a charging device, a developing device, and a cleaning device are integrally attached to and detached from the main body. A process cartridge configured to be capable of being provided is provided.

  According to the present invention, each latent image carrier based on the surface movement speed fluctuation at the time of speed control execution is controlled so that the color shift due to the speed fluctuation of each latent image carrier at the time of speed control execution is suppressed. It is possible to adjust the phase of the surface movement speed fluctuation of each latent image carrier during the speed control of the image carrier. Therefore, even if there is a speed fluctuation of each latent image carrier when speed control is performed and the toner image transferred to the endless moving body or the recording material on the endless moving body is periodically expanded and contracted, When the toner on the image carrier is transferred onto the endless moving body or the recording material on the endless moving body, the phases of the expansion / contraction periods of the color toner images can be matched. This is because the expansion and contraction of each color toner image is caused by the fluctuation in the surface movement speed of the latent image carrier. Therefore, if the phase of the fluctuation in the surface movement speed of each latent image carrier is adjusted, the phase of the expansion and contraction cycle of the toner image is changed. It can be matched. As a result, the stretched portion of the toner image of each color is transferred to the endless moving body or the portion where the toner image of the recording material on the endless moving body is stretched. The toner image shrinkage portion is transferred. As a result, color misregistration is suppressed.

According to the onset bright, dimensional accuracy of the structure mechanical element, such as to increase the calculation accuracy, without increasing the color misregistration suppression effect by suppressing the surface moving speed fluctuation of the latent image bearing member by the speed control, a color shift It is possible to suppress the color deviation by suppressing the cost increase of the apparatus.

Hereinafter, an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as an image forming apparatus to which the present invention is applied.
First, a basic configuration of the printer according to the embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. The printer shown in the figure includes four process units 1Y, 1C, 1M, and 1K for yellow, magenta, cyan, and black (hereinafter referred to as Y, C, M, and K) as process units as toner image forming means. ing. These use Y, C, M, and K toners of different colors as image forming substances for forming an image, but the other configurations are the same. Taking a process unit 1Y for generating a Y toner image as an example, this has a photoconductor unit 2Y and a developing unit 7Y as shown in FIG. As shown in FIG. 3, the photosensitive unit 2Y and the developing unit 7Y are integrally attached to and detached from the printer body as a process unit 1Y. However, in a state where it is detached from the printer main body, the developing unit 7Y can be attached to and detached from a photosensitive unit (not shown) as shown in FIG.

  In FIG. 2 described above, the photoconductor unit 2Y includes a drum-shaped photoconductor 3Y, a drum cleaning device 4Y, a static eliminator (not shown), a charging device 5Y, and the like.

  The charging device 5Y uniformly charges the surface of the photoreceptor 3Y that is driven to rotate in the clockwise direction in the drawing by a driving unit (not shown). In the figure, the charging roller 6Y that is driven to rotate counterclockwise in the drawing while a charging bias is applied by a power source (not shown) is brought close to the photosensitive member 3Y, thereby charging the photosensitive member 3Y uniformly. Device 5Y is shown. Instead of the charging roller 6Y, a roller that contacts a charging brush may be used. Further, a charger that uniformly charges the photoreceptor 3Y by a charger method, such as a scorotron charger, may be used. The surface of the photoreceptor 3Y uniformly charged by the charging device 5Y is exposed and scanned by a laser beam emitted from an optical writing unit to be described later, and carries a Y electrostatic latent image.

  The developing unit 7Y as developing means has a first agent accommodating portion 9Y in which a first conveying screw 8Y is disposed. Further, it also has a second agent storage portion 14Y in which a toner concentration sensor (hereinafter referred to as a toner concentration sensor) 10Y composed of a magnetic permeability sensor, a second conveying screw 11Y, a developing roll 12Y, a doctor blade 13Y, and the like are disposed. . In these two agent storage portions, a Y developer (not shown) composed of a magnetic carrier and a negatively chargeable Y toner is included. The first transport screw 8Y is driven to rotate by a driving unit (not shown), thereby transporting the Y developer in the first agent storage unit 9Y from the near side to the far side in the direction perpendicular to the drawing sheet. And it penetrates into the 2nd agent accommodating part 14Y through the communication port which is not shown in the partition wall between the 1st agent accommodating part 9Y and the 2nd agent accommodating part 14Y.

  The second transport screw 11Y in the second agent storage portion 14Y is driven to rotate by a driving means (not shown), thereby transporting the Y developer from the back side to the front side in the drawing. The toner concentration of the Y developer being conveyed is detected by the toner concentration sensor 10Y fixed to the bottom of the first agent storage portion 14Y. In this manner, the developing roll 11Y is arranged in a posture parallel to the second transport screw 11Y above the second transport screw 11Y that transports the Y developer. The developing roller 11Y includes a magnet roller 16Y in a developing sleeve 15Y made of a non-magnetic pipe that is driven to rotate counterclockwise in the drawing. A part of the Y developer conveyed by the second conveying screw 11Y is pumped up to the surface of the developing sleeve 15Y by the magnetic force generated by the magnet roller 16Y. Then, after the layer thickness is regulated by the doctor blade 13Y disposed so as to maintain a predetermined gap from the developing sleeve 15Y as a developing member, the layer thickness is regulated and conveyed to the developing area facing the photosensitive member 3Y. Y toner is adhered to the Y electrostatic latent image. This adhesion forms a Y toner image on the photoreceptor 3Y. The Y developer that has consumed the Y toner by the development is returned to the second conveying screw 11Y as the developing sleeve 15Y of the developing roll 12Y rotates. And if it conveys to the near end in a figure, it will return in the 1st agent accommodating part 9Y via the communication port which is not shown in figure.

  The result of detecting the magnetic permeability of the Y developer by the toner concentration sensor 10Y is sent as a voltage signal to a control unit described later. Since the magnetic permeability of the Y developer shows a correlation with the Y toner density of the Y developer, the toner density sensor 10Y outputs a voltage having a value corresponding to the Y toner density. The control unit includes a RAM, in which a V Vref for Y which is a target value of the output voltage from the toner density sensor 10Y and a toner density sensor for C, M, and K mounted in another developing unit. The data of C Vtref, M Vtref, and K Vtref, which are target values of the output voltage, are stored. For the Y developing unit 7Y, the value of the output voltage from the toner density sensor 10Y is compared with the Y Vtref, and the Y toner supply device (not shown) is driven for a time corresponding to the comparison result. By this driving, an appropriate amount of Y toner is supplied to the Y developer whose Y toner density has been reduced by consumption of Y toner accompanying development in the first agent storage portion 9Y. For this reason, the Y toner concentration of the Y developer in the second agent container 14Y is maintained within a predetermined range. Similar toner supply control is performed for the developers in the process units (1C, M, K) for other colors.

  The Y toner image formed on the photoreceptor 3Y which is an image carrier and a latent image carrier is intermediately transferred to an intermediate transfer belt described later. The drum cleaning device 4Y of the photoreceptor unit 2Y removes the toner remaining on the surface of the photoreceptor 3Y after the intermediate transfer process. As a result, the surface of the photoreceptor 3Y that has been subjected to the cleaning process is neutralized by a neutralizing device (not shown). By this charge removal, the surface of the photoreceptor 3Y is initialized and prepared for the next image formation. In FIG. 1 described above, in the process units 1C, M, and K for other colors, C, M, and K toner images are formed on the photoreceptors 3C, M, and K in the same manner as an endless moving body. Intermediate transfer is performed on the intermediate transfer belt.

  An optical writing unit 20 is arranged below the process units 1Y, 1C, 1M, and 1K in the drawing. The optical writing unit 20 serving as a latent image forming unit irradiates the photoreceptors 3Y, C, M, and K of the process units 1Y, C, M, and K with the laser light L emitted based on the image information. Thereby, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 3Y, 3C, 3M, and 3K. The optical writing unit 20 deflects the laser light L emitted from the light source by the polygon mirror 21 that is rotationally driven by a motor, and passes through the photosensitive members 3Y, 3C, 3M, and 3K via a plurality of optical lenses and mirrors. Is irradiated. In place of such a configuration, an optical scanning device using an LDE array may be employed.

  A first paper feed cassette 31 and a second paper feed cassette 32 are disposed below the optical writing unit 20 so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of recording papers P as recording members are accommodated in a stack of recording papers. The uppermost recording paper P includes a first paper feed roller 31a, The second paper feed rollers 32a are in contact with each other. When the first paper feed roller 31a is driven to rotate counterclockwise in the figure by a driving means (not shown), the uppermost recording paper P in the first paper feed cassette 31 is vertically oriented on the right side of the cassette in the figure. The paper is discharged toward the paper feed path 33 arranged so as to extend. Further, when the second paper feed roller 32 a is driven to rotate counterclockwise in the figure by a driving means (not shown), the uppermost recording paper P in the second paper feed cassette 32 is directed toward the paper feed path 33. Discharged. A plurality of transport roller pairs 34 are arranged in the paper feed path 33, and the recording paper P fed into the paper feed path 33 is sandwiched between the rollers of the transport roller pair 34 while being fed between the paper feed paths 33. 33 is conveyed from the lower side to the upper side in the figure.

  A registration roller pair 35 is disposed at the end of the paper feed path 33. The registration roller pair 35 temporarily stops the rotation of both rollers as soon as the recording paper P fed from the conveyance roller pair 34 is sandwiched between the rollers. Then, the recording paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above each of the process units 1Y, 1C, 1M, and 1K, a transfer unit 40 that is endlessly moved counterclockwise in the drawing while an intermediate transfer belt 41 that is an endless moving body is stretched is disposed. The transfer unit 40 serving as transfer means includes an intermediate transfer belt 41, a belt cleaning unit 42, a first bracket 43, a second bracket 44, and the like. Further, four primary transfer rollers 45Y, 45C, 45M, 45K, a secondary transfer backup roller 46, a drive roller 47, an auxiliary roller 48, a tension roller 49, and the like are also provided. The intermediate transfer belt 41 is endlessly moved counterclockwise in the figure by the rotational driving of the driving roller 47 while being stretched by these eight rollers. The four primary transfer rollers 45Y, 45C, 45M, 45K each sandwich the intermediate transfer belt 41 moved endlessly in this manner from the photoreceptors 3Y, 3C, 3M, and 3K to form primary transfer nips. ing. Then, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 41. The intermediate transfer belt 41 sequentially passes through the primary transfer nips for Y, C, M, and K along with its endless movement, and on the photoreceptor 3Y, C, M, and K on the front surface. The Y, C, M, and K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 41.

  The secondary transfer backup roller 46 sandwiches the intermediate transfer belt 41 with the secondary transfer roller 50 disposed outside the loop of the intermediate transfer belt 41 to form a secondary transfer nip. The registration roller pair 35 described above feeds the recording paper P sandwiched between the rollers toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 41. The four-color toner image on the intermediate transfer belt 41 is affected by the secondary transfer electric field formed between the secondary transfer roller 50 to which the secondary transfer bias is applied and the secondary transfer backup roller 46, and the influence of the nip pressure. The secondary transfer is batch-transferred onto the recording paper P in the secondary transfer nip. Then, combined with the white color of the recording paper P, a full color toner image is obtained.

  Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 41 after passing through the secondary transfer nip. This is cleaned by the belt cleaning unit 42. In the belt cleaning unit 42, the cleaning blade 42a is brought into contact with the front surface of the intermediate transfer belt 41, whereby the transfer residual toner on the belt is scraped off and removed.

  The first bracket 43 of the transfer unit 40 swings at a predetermined rotation angle about the rotation axis of the auxiliary roller 48 as the solenoid (not shown) is turned on / off. When forming a monochrome image, the printer of the present image forming system rotates the first bracket 43 a little counterclockwise in the drawing by driving the solenoid described above. This rotation causes the Y, C, M primary transfer rollers 45Y, C, M to revolve counterclockwise in the drawing around the rotation axis of the auxiliary roller 48, thereby causing the intermediate transfer belt 41 to move in the Y, C direction. , M is separated from the photoconductors 3Y, 3C, 3M. Of the four process units 1Y, 1C, 1M, and 1K, only the K process unit 1K is driven to form a monochrome image. As a result, it is possible to avoid exhaustion of the process units due to wastefully driving the process units for Y, C, and M during monochrome image formation.

  A fixing unit 60 is disposed above the secondary transfer nip in the drawing. The fixing unit 60 includes a pressure heating roller 61 that includes a heat source such as a halogen lamp, and a fixing belt unit 62. The fixing belt unit 62 includes a fixing belt 64 as a fixing member, a heating roller 63 containing a heat source such as a halogen lamp, a tension roller 65, a driving roller 66, a temperature sensor (not shown), and the like. Then, the endless fixing belt 64 is endlessly moved in the counterclockwise direction in the drawing while being stretched by the heating roller 63, the tension roller 65, and the driving roller 66. In the process of endless movement, the fixing belt 64 is heated from the back side by the heating roller 63. A pressure heating roller 61 that is rotationally driven in the clockwise direction in the drawing is in contact with the surface of the fixing belt 64 that is heated in this manner from the front side. Thereby, a fixing nip where the pressure heating roller 61 and the fixing belt 64 abut is formed.

  Outside the loop of the fixing belt 64, a temperature sensor (not shown) is disposed so as to face the front surface of the fixing belt 64 with a predetermined gap, and the fixing belt 64 just before entering the fixing nip. Detect surface temperature. This detection result is sent to a fixing power supply circuit (not shown). The fixing power supply circuit performs on / off control of power supply to the heat generation source included in the heating roller 63 and the heat generation source included in the pressure heating roller 61 based on the detection result of the temperature sensor. As a result, the surface temperature of the fixing belt 64 is maintained at about 140 [°].

  In FIG. 1 described above, the recording paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 41 and then sent into the fixing unit 60. Then, in the process of being conveyed from the lower side to the upper side in the figure while being sandwiched between the fixing nips in the fixing unit 60, the full-color toner image is fixed by being heated or pressed by the fixing belt 64.

  The recording paper P subjected to the fixing process in this manner is discharged outside the apparatus after passing between the rollers of the paper discharge roller pair 67. A stack unit 68 is formed on the upper surface of the housing of the printer main body, and the recording paper P discharged to the outside by the discharge roller pair 67 is sequentially stacked on the stack unit 68.

  Above the transfer unit 40, four toner cartridges 100 Y, C, M, and K that store Y, C, M, and K toners are disposed. The Y, C, M, and K toners in the toner cartridges 100Y, 100C, M, and K are appropriately supplied to the developing units 7Y, C, M, and K of the process units 1Y, C, M, and K. These toner cartridges 100Y, 100C, 100M, and 100K are detachable from the printer main body independently of the process units 1Y, 1C, 1M, and 1K.

  FIG. 5 is a perspective view showing a main body side drive transmission unit which is a drive transmission system fixed in the printer housing. FIG. 6 is a plan view showing the main body side drive transmission portion from above. A support plate is erected in the printer housing, and four process drive motors 120Y, 120C, 120M, 120K, and 120K are fixed thereto. Driving gears 121Y, C, M, and K are connected to the rotation shafts of process drive motors 120Y, 120C, 120M, and 120K serving as drive sources so as to rotate on the same axis as the rotation shaft.

  Below the rotation shafts of the process drive motors 120Y, 120C, 120M, 120K, development gears 122Y, 122C, 122M, 122K, which are slidably rotatable while engaging with a fixed shaft (not shown) projecting from the support plate. Is arranged. The developing gears 122Y, 122C, 122M, 122C, 122C, 122C, and 122K include first gear portions 123Y, 123C, 123M, and 122K that rotate on the same rotation axis. The second gear portions 124Y, C, M, K are located closer to the front end side of the rotation shafts of the process drive motors 120Y, C, M, K than the first gear portions 123Y, 123C, 123M, 123K. The developing gears 122Y, 122M, 122C, 122K, and 122K are engaged with the first gear portions 123Y, 123M, 123C, and 123K in mesh with the driving gears 121Y, 121C, 121M, 121K of the process drive motors 120Y, 120C, 120M, 120K, By the rotation of the drive motors 120Y, 120C, 120M, and 120K, sliding rotation is performed on the fixed shaft.

  The process drive motors 120Y, 120C, 120M, 120K, which are drive sources, include a DC servo motor, which is a kind of DC brushless motor, a stepping motor, and the like. The reduction ratio between the driving gears 121Y, 121C, 121M, and 121K and the photoconductor gears 133Y, 133C, 133M, and K serving as drive transmission members is, for example, 1:20. The reason why the number of speed reduction stages from the driving gear to the photosensitive gear is set to one is to reduce the number of parts and reduce the cost, as well as to reduce the cause of transmission errors due to meshing errors and eccentricity by using two gears. It is from the aim to do. By reducing the speed by one step, the photosensitive member gear has a larger diameter than the photosensitive member at a relatively large reduction ratio of 1:20. By using such a large-diameter photoconductor gear, it is possible to reduce the pitch error on the photoconductor surface corresponding to one gear meshing and to reduce the influence of print density unevenness (banding) in the sub-scanning direction. There is also an aim. The reduction ratio is determined based on the speed region where high efficiency and high rotation accuracy can be obtained from the relationship between the target speed of the photoreceptor and the motor characteristics.

  On the left side of the developing gears 122Y, 122C, 122M, and 122K, first relay gears 125Y, 125C, 125M, and 125K that slide and rotate while engaging with a fixed shaft (not shown) are disposed. These mesh with the second gear portions 124Y, C, M, and K of the developing gears 122Y, 122C, 122K, and receive rotational driving force from the developing gears 122Y, 122C, 122M, and 122K, on the fixed shaft. Slide and rotate. The first relay gears 125Y, C, M, and K are engaged with the second gear portions 124Y, C, M, and K on the upstream side in the drive transmission direction, and the clutch input gears 126Y, C on the downstream side in the drive transmission direction. , M, K are engaged. These clutch input gears 126Y, C, M, and K are supported by the developing clutches 127Y, 127C, 127M, and 127K. The development clutches 127Y, 127C, 127M, 127K, and the like are connected to the clutch shaft with the rotational driving force of the clutch input gears 126Y, 126C, 126M, 126K, as the power supply is turned on / off by a control unit (not shown). The input gear 126Y, C, M, K is idled. Clutch output gears 128Y, 128C, 128M, and 128K are fixed to the front ends of the clutch shafts of the developing clutches 127Y, 127C, 127M, and 127K. When power is supplied to the developing clutches 127Y, 127C, 127C, 127M, 127K, the rotational driving force of the clutch input gears 126Y, 126C, 126M is connected to the clutch shaft, and the clutch output gears 128Y, 128C, 128M, 128K Rotate. On the other hand, when the power supply to the development clutches 127Y, 127C, 127M, 127K is cut off, the clutch input gears 126Y, 126C, 126M, 126K, 126Y, 126C, 126M, 126K, 126Y, 126C, 126M Rotates idly on the clutch shaft, the rotation of the clutch output gears 128Y, 128C, 128M, 128K stops.

  On the left side of the clutch output gears 128Y, C, M, and K, second relay gears 129Y, 129Y, C, M, and K that are slidably rotated while being engaged with a fixed shaft (not shown) are disposed. It rotates while meshing with the clutch output gear 128Y, C, M, K.

  FIG. 7 is a partial perspective view showing one end of the Y process unit 1Y. The developing sleeve 15Y in the casing of the developing unit 7Y has a shaft member penetrating the side surface of the casing and protruding outside. The sleeve upstream gear 131Y is fixed to the protruding shaft member portion. A fixed shaft 132Y projects from the side of the casing, and the third relay gear 130Y engages with the sleeve upstream gear 131Y while being slidably rotated.

  In a state where the Y process unit 1Y is set in the printer main body, the second relay gear 129Y previously shown in FIGS. 5 and 6 is engaged with the third relay gear 130Y in addition to the sleeve upstream gear 131Y. Then, the rotational driving force of the second relay gear 129Y is sequentially transmitted to the third relay gear 130Y and the sleeve upstream gear 131Y, and the developing sleeve 15Y is rotationally driven.

  Although only the process unit 1Y for Y has been described with reference to the drawings, the rotational driving force is similarly transmitted to the developing sleeve also in the process units for other colors.

  Further, in FIG. 7, only one end portion of the Y process unit 1Y is shown, but the shaft member on the other end side of the developing sleeve 15Y penetrates the side surface on the other end side of the casing and protrudes to the outside. A sleeve downstream gear (not shown) is fixed to the protruding portion. Further, the first conveying screw 7Y and the second conveying screw 10Y previously shown in FIG. 2 also have their shaft members penetrating through the side surface on the other end side of the casing, and the protruding portion includes a first screw gear (not shown), The second screw gear is fixed. When the developing sleeve 15Y is rotated by drive transmission by the sleeve upstream gear 131Y, the sleeve downstream gear is rotated on the other end side. Then, the second conveying screw 11Y receiving the driving force by the second screw gear meshed with the sleeve downstream gear rotates and the first conveying screw 8Y receiving the driving force by the first screw gear meshed with the second screw gear. Rotates. The process units for other colors have the same configuration.

  FIG. 8 is a perspective view showing the Y photoconductor gear 133Y and its peripheral configuration. In the figure, the driving gear 121Y fixed to the motor shaft of the process drive motor 120Y meshes with the first gear portion 123Y of the developing gear 122Y and the photosensitive gear 133Y as a driven gear. The photoconductor gear 133Y includes a disc-shaped gear portion 133aY and a cylindrical gear-side coupling portion 133b that is an engaging portion. The gear portion 133aY and the gear-side coupling portion 133b are respectively made of the same material (for example, Resin material). In this way, since the gear portion and the gear side coupling portion are an integral photosensitive gear, no rattling occurs between the gear portion and the gear side coupling portion. As a result, it is possible to eliminate fluctuations in the speed of the photosensitive member due to backlash between the gear portion and the gear side coupling portion. The photoconductor gear 133Y is rotatably supported by the main body side drive transmission unit. The diameter of the photoconductor gear 133Y is larger than the diameter of the photoconductor. Further, as shown in FIG. 9, an internal gear 133cY having a plurality of teeth is formed on the inner peripheral surface of the cylindrical recess of the gear side coupling portion 133bY. The rotating shaft of the photoconductor 3Y is provided with a photoconductor side coupling that is a not-shown engaged portion having a gear that meshes with the internal gear 133cY of the gear side coupling portion 133bY. Then, the photoconductor side coupling as the engaged portion is inserted into the cylindrical concave portion of the gear side coupling portion 133cY as the engaging portion, and the gear of the photoconductor side coupling and the gear of the gear side coupling portion 133cY are engaged. Thus, the photoconductor side coupling and the gear side coupling portion 133cY are engaged, and the rotational driving force of the process drive motor 120Y is transmitted to the photoconductor 3Y. The photoconductor side coupling attached to the rotating shaft of each photoconductor may be a cylindrical coupling, and the gear side coupling integral with the gear portion of the photoconductor gear 133Y may be inserted into the photoconductor side coupling. . The process units for other colors have the same configuration.

  In the printer configured as described above, when the photosensitive member gear 133Y is rotationally driven by the process drive motor 120Y, the Y photosensitive member makes one rotation of the photosensitive member due to the eccentricity of the photosensitive member gear 133Y or the eccentricity of the photosensitive member. Causes speed fluctuations to be one cycle.

  In FIG. 1 described above, when speed fluctuations occur in the photoreceptors 3Y, 3C, 3M, and 3K, latent images formed on the photoreceptors 3Y, 3C, 3M, and 3K at the light irradiation position by the optical writing unit 20 are displayed. The time required to move to the primary transfer nip immediately after formation changes. This causes subtle misalignment of each color dot in the primary transfer nip. Specifically, focusing on the two colors of K and M, as shown in FIG. 10A, the amplitude and phase of the speed fluctuation component of the K-color photoconductor 3K and the M-color photoconductor 3M Assume that the amplitude and phase of the velocity fluctuation component are different. At this time, if the M color speed fluctuation component is subtracted from the K color speed component, an amplitude residual is generated between the K color and the M color, as shown in FIG. This amplitude difference A causes a relative positional shift between the two colors, resulting in a color shift.

  FIG. 11 is a perspective view showing the Y photoconductor gear 133Y and its peripheral configuration from the process drive motor side. In the drawing, a marking blade member 134Y is projected from a predetermined position in the rotation direction of the gear portion of the photoconductor gear 133Y. A position sensor 135Y is disposed on the side of the photoconductor gear 133Y. The position sensor 135Y is configured such that the signal is HIGH when the blade member 134Y is within the reading range, and the signal is LOW when the blade member 134Y is not within the reading range. By detecting that this signal switches from HIGH to LOW or from LOW to HIGH, it is detected that the photosensitive member has reached a predetermined rotation angle.

  FIG. 12 is a side view showing the four photoconductors 3Y, 3C, 3M, and 3K, the transfer unit 40, and the optical writing unit 20. The blade members 134Y, C, M, K provided on the photoconductor gears 133Y, 133C, M, K rotating on the same axis as the photoconductors 3Y, C, M, K are photoconductor gears 133Y, 133C, M, K, respectively. Each time K rotates once, it is detected by position sensors 135Y, 135C, 135M, and 135K including photo sensors.

  The transfer unit 40 includes an optical sensor unit 136 composed of two reflection type photosensors (not shown) arranged at a predetermined interval in the width direction of the intermediate transfer belt 41 via a stretched surface of the intermediate transfer belt 41 and a predetermined gap. It arrange | positions so that it may oppose.

  Each process drive motor 120Y, 120C, 120M, 120M, and 120K is controlled by the control unit 140 serving as a speed control unit, and the rotation speed, rotation start timing, and stop timing are controlled. The control unit 140 performs process control of the entire printer, and includes a CPU, a ROM, a RAM, and the like. The control unit 140 receives detection signals output from the position sensors 135Y, 135C, M, and K provided to detect the rotational positions of the photoreceptors 3Y, 3C, 3M, and 3K. Based on this detection signal, the control unit 140 controls the process drive motors 120Y, 120C, 120M, 120K, and performs speed control of the respective photoreceptors 3Y, 3C, 3M, and 3K.

  The control unit 140, which is a speed fluctuation detecting unit of the printer, detects a fluctuation pattern for detecting a speed fluctuation pattern per one rotation of the photosensitive member due to the eccentricity of the photosensitive member gear or the eccentricity of the photosensitive member. Control is performed at a predetermined timing. Examples of the predetermined timing include when an operation for changing a speed fluctuation pattern such as when a process unit is replaced, or when a print command is issued in a state where the high-quality print mode is selected.

  In the fluctuation pattern detection control, the drive motors 120Y, 120C, 120M, 120K, and 120K are rotated at a constant speed to form speed change detection images on the photoreceptors 3Y, 3C, 3M, and K, respectively, and intermediate transfer is performed. Transfer is performed without overlapping on the belt 41. As shown in FIG. 13, the speed fluctuation detection image is an example of a speed fluctuation detection image for K. As shown in FIG. 13, a plurality of K toner images tk01, tk02, tk03, tk04, tk05, tk06,. The image is transferred onto the belt so as to be arranged at a predetermined pitch along the moving direction (sub-scanning direction). However, although theoretically arranged at a predetermined pitch, the actual arrangement pitch of these K toner images has an error corresponding to the speed fluctuation due to the speed fluctuation of the K photoconductor (3K). come.

  In FIG. 1 described above, each toner image in the speed variation detection image formed on the intermediate transfer belt 41 is being conveyed to a position facing the optical sensor unit 136 as the belt moves endlessly. Passes the position facing the secondary transfer roller 50. Prior to this passage, a roller contact / separation mechanism (not shown) is driven to separate the secondary transfer roller 50 from the intermediate transfer belt 50. This avoids transfer of the speed variation detection image to the secondary transfer roller 50.

  Each of the toner images in the speed variation detection image that has been prevented from being transferred to the secondary transfer roller 50 in this way passes immediately below the optical sensor unit 136 as the belt moves, so that the optical sensor unit 136 is moved. Respectively. Thereby, the detection time pitch error of each toner image in the speed fluctuation detection image of each color is detected.

  Further, in this printer, for the purpose of shortening the execution time of the fluctuation pattern detection control, as shown in FIG. 14, a speed fluctuation detection image PVk for K, a speed fluctuation detection image PVm for M, Are formed side by side in the belt width direction with respect to the intermediate transfer belt 41. Then, the speed change detection image PVk for K formed at one end in the belt width direction is detected by the first optical sensor 137 of the optical sensor unit 136, and for M formed at the other end in the belt width direction. Are detected by the second optical sensor 138 of the optical sensor unit 136. Thus, the detection time pitch error of each K toner image in the K speed fluctuation detection image PVk and the detection time pitch error of each M toner image in the M speed fluctuation detection image PVm are detected simultaneously, The execution time of the fluctuation pattern detection control can be shortened. Similarly, for Y and C, the respective detection time pitch errors are simultaneously detected.

  This detection time pitch error corresponds to the speed variation caused by the eccentricity of each color photoconductor and the photoconductor, but this detection time pitch error is different from the actual speed variation of the photoconductor. . This will be described with reference to more detailed drawings. In FIG. 15, the Y electrostatic latent image is formed on the Y photoconductor 3 </ b> Y by the irradiation of the writing light from the optical writing unit 20. On the rotation orbit of the photoreceptor 3Y, the latent image writing position by the writing light from the optical writing unit 20 is a position denoted by a symbol Sa in the drawing. Further, the transfer position of the Y toner image onto the intermediate transfer belt 41 is a position denoted by a symbol Sb in the drawing.

  Since each Y toner image in the Y speed fluctuation detection image needs to be formed at equal intervals in the circumferential direction with respect to the photoreceptor 3Y, each Y latent image that is a precursor of each Y toner image. The writing light for forming each is emitted at equal intervals. However, at this time, if the speed of the photosensitive member 3Y changes, the interval (distance) of the Y latent images changes according to the speed change. Specifically, when the photoreceptor 3Y is moving faster than the standard speed at the latent image writing position Sa, the interval between the Y latent images becomes larger than the original. On the other hand, when the photoreceptor 3Y moves on the surface slower than the standard speed, the interval between the Y latent images becomes smaller than the original. For this reason, if the surface of the photoreceptor 3Y undergoes a speed fluctuation with a fluctuation characteristic as shown in FIG. 16 at the latent image writing position Sa, the Y latent image formation interval has a characteristic as shown in FIG. fluctuate. It can be seen that the phases of both characteristics are perfectly matched.

  On the other hand, when the Y toner image obtained by developing the Y latent image is primarily transferred to the intermediate transfer belt 41, if the speed of the photosensitive member 3Y changes, even if a plurality of Y toner images are formed on the photosensitive member 3Y, etc. Even if they are arranged at intervals, they are transferred to the intermediate transfer belt 41 at non-uniform intervals. At this time, when the photoreceptor 3Y is moving faster than the standard speed at the transfer position Sb, the interval between the Y toner images on the belt becomes smaller than the original. On the other hand, when the photoreceptor 3Y moves on the surface slower than the standard speed, the interval between the Y toner images on the belt becomes larger than the original. Therefore, at the transfer position Sb, if the surface of the photoreceptor 3Y is fluctuating in speed with the fluctuation characteristics shown in FIG. 18, for example, the interval between the Y toner images on the belt fluctuates with the characteristics shown in FIG. To do. It can be seen that the phases of both characteristics are completely reversed.

  As a result, the Y toner image interval in the Y speed fluctuation detection image on the intermediate transfer belt 41 is changed due to the fluctuation of the photosensitive member surface speed at the latent image writing position Sa and the photosensitive member at the transfer position Sb. The fluctuation due to the surface speed fluctuation is superimposed. More specifically, in FIG. 15 shown above, it is assumed that the angle formed between the latent image writing position Sa and the transfer position Sb is α [°]. Then, as shown in FIG. 20, the characteristics of the photoreceptor surface speed fluctuation at the latent image writing position Sa and the characteristics of the photoreceptor surface speed fluctuation at the transfer position Sb are shifted from each other by α [°]. Become a relationship. However, the relationship between the speed of the photosensitive member and the relationship between the sizes of the image intervals are reversed between the latent image writing time and the transfer time. As shown in FIG. 21, it can be considered that α + 180 [°] is shifted.

  Therefore, the pitch error of each toner image detected based on the detection time pitch error of each toner image in the speed variation detection image is the interval between the latent images generated at the latent image writing position Sa as shown in FIG. The variation characteristic and the interval variation characteristic of the toner image generated at the transfer position are superimposed (a composite wave of two characteristic waves). By using a well-known analysis method, it is possible to detect the speed fluctuation pattern of the photoconductor based on the detection time pitch error from the relationship between the phase and amplitude of the composite wave and α + 180 [°] described above. For example, when the angle α [°] formed by the latent image writing position Sa and the transfer position Sb is 180 °, the pitch error of each toner image is multiplied by (1/2), so that the speed fluctuation of the photosensitive member is obtained. A pattern can be detected. If the process drive motor is driven with a drive speed pattern that has an opposite phase relationship to the detected speed change pattern of the photoconductor, the speed change of the photoconductor can be almost eliminated.

  However, in the control based on the drive speed pattern, the rotation position of the photoconductor gear (at the beginning of the formation of a latent image corresponding to the leading edge of the speed change detection image) of the photoconductor speed fluctuation waveform ( It is necessary to grasp whether it is the timing when the rotation angle is reached. Therefore, the control unit 140 of this printer sets the latent image formation start timing of the speed variation detection image of each color at the timing at which the position sensor 135 detects the blade member 134 of the corresponding color photoconductor gear 133 (hereinafter, referred to as the following). It is determined based on a predetermined gear angle timing).

  The method for determining the latent image formation start timing will be described in more detail. The control unit 140 is a timing (latent image formation start timing) in which the latent image of the speed variation detection image of each color is shifted from the gear predetermined angle timing by a predetermined time t1. Start forming with. This latent image formation start timing is a time point when a predetermined time t1 is added to the gear predetermined angle timing. That is, the time when the predetermined time t1 has elapsed from the moment when the position sensor 135 detects the blade member 134 of the photoconductor gear 133 is the waveform of the latent image interval variation characteristic at the latent image writing position Sa (the actual photoconductor gear 133 actual condition). This is the beginning of the speed fluctuation pattern. If the process drive motor is driven with a drive speed pattern having a phase opposite to that of the waveform of the photoreceptor speed fluctuation, as shown in FIG. Further, the speed fluctuation of the photoconductor in one rotation period due to the eccentricity of the photoconductor gear can be canceled by the fluctuation of the driving speed, so that the speed fluctuation of the photoconductor can be almost eliminated (see FIG. 23B). .

However, for example, if there is an error in the angle α [°] between the latent image writing position Sa and the transfer position Sb, the detected speed variation pattern of the photoconductor differs from the actual photoconductor speed variation, and the driving speed An error occurs in the pattern. For example, as shown in FIG. 24A, if there is an error between the amplitude of the driving speed pattern and the amplitude of the actual photosensitive member speed fluctuation, even after the process driving motor is driven with the driving speed pattern, FIG. As shown in (), speed fluctuation occurs in the photoconductor.
Further, as shown in FIG. 25A, even when there is an error in the amplitude and phase of the drive speed pattern, speed fluctuations occur in the photosensitive member as shown in FIG. Such an error in the driving speed pattern is calculated when detecting the dimensional accuracy of the machine element, such as the error in the angle α [°] between the latent image writing position Sa and the transfer position Sb, or the speed fluctuation pattern. It depends on accuracy. Therefore, as shown in FIG. 23B, in order to substantially eliminate the speed fluctuation of the photoconductors of the respective colors, it is necessary to increase the dimensional accuracy of the machine elements and the calculation accuracy. If the calculation accuracy is increased, the cost of the apparatus is inevitably increased.

  Therefore, the control unit 140 serving as a control unit of the printer does not increase the dimensional accuracy or calculation accuracy of the machine elements, and suppresses the color misregistration caused by the drive control of the process drive motor 120 in the drive speed pattern. Such control is executed. That is, the speed fluctuation pattern of each photoconductor when the driving of each process drive motor 120 is controlled by the driving speed pattern of each color, and the phase of the speed fluctuation of each photoconductor is adjusted based on the detection result. It is.

FIG. 26 is a control flow of color misregistration adjustment in this embodiment.
First, the control unit 140 drives the process drive motor 120 at a constant speed, executes fluctuation pattern detection control, and obtains a drive speed pattern (S1 to S3). That is, the process drive motor 120 is driven at a constant speed, and a speed variation detection image for each color is formed based on the timing when each color position sensor 135 detects the blade member 134. Next, the control unit 140 detects the toner image detection time pitch error in the speed change detection image of each color by the optical sensor unit 136, and detects the speed change pattern of each photoconductor based on the detection result. . Then, a driving speed pattern for each color for controlling the process driving motor for each color is calculated from the detected speed variation pattern for each photoconductor (S3).

  Next, the control unit 140 drives (speed control) the process driving motor 120 with the driving speed pattern obtained in step S3 (S4), executes the variation pattern detection control again, and drives the process with the driving speed pattern. A speed variation pattern of each photoconductor when the motor 120 is driven is detected (S5). Then, a driving speed pattern of each photoconductor is calculated from the detected speed fluctuation pattern of each photoconductor (S6). Next, the control unit 140, which is a phase adjustment unit, performs phase adjustment based on the speed variation pattern detected in step S5 (S7). By this phase adjustment, when the toner images of the respective colors are superimposed on the intermediate transfer belt, the phases of the expansion / contraction cycles due to the fluctuations in the photoreceptor speed are matched. In this printer, since the arrangement pitch of each photoconductor is one time the circumference of the photoconductor, in order to do this, the phases of the speed fluctuation patterns of each photoconductor should be synchronized with each other. Specifically, the control unit 140, which is a phase adjusting unit, determines the phase difference between KM and the level between K-C from the speed variation pattern when the process driving motor is driven with the driving speed pattern of each photoconductor. The phase difference and the phase difference between KY are calculated, and the target stop time of the C, M, and Y color photoconductors for matching the phase of the speed fluctuation pattern of each color is calculated from these phase differences. Then, the controller 140 controls the K-color process drive motor 120K so that the K-color position sensor 135K stops at the timing at which the blade member 134 is detected when each photoconductor is stopped. For the C, M, and Y colors, the C, M, and Y colors are stopped so that the target stop time calculated based on the phase difference elapses after the K-color position sensor 135K detects the blade member 134. The process drive motors 120C, 120M, and 120Y are controlled. When driving each photoconductor, such as during image formation, the controller 140 controls the process drive motors so that the photoconductors rotate at the same time, thereby matching the phases of the speed variation patterns. Each photoconductor can be driven to rotate in the state. Thereby, when the toner images of the respective colors are superimposed on the intermediate transfer belt, the phases of the expansion and contraction cycles due to the fluctuations in the photoreceptor speed can be matched.

  At the time of image formation, the photosensitive members are driven to rotate at the same time, and the speed control is started at a timing when a predetermined time t1 has elapsed since the position sensor was detected. When the speed control of each photoconductor is executed, an image forming operation is started. At this time, since the photoreceptor speed control is executed, the speed fluctuation of the photoreceptor is suppressed, and the periodic expansion and contraction of the toner images of the respective colors on the intermediate transfer belt is suppressed. Further, since the phases of the speed fluctuations of the respective photoconductors coincide with each other, it is possible to superimpose the toner images of the respective colors by matching the phases of the expansion and contraction periods of the toner images due to the photoconductor speed fluctuations. Thereby, color shift is suppressed. After the image formation is completed, the K color photoconductor is stopped at the timing when the K color position sensor 135K detects the blade member 134. For the C, M, and Y color photoconductors, the K color position sensor 135K After the blade member 134 is detected, the blade member 134 is stopped at the timing when the target stop time has elapsed.

  Further, the phase of the speed fluctuation pattern of the photosensitive member may be adjusted by controlling as follows. That is, each photoconductor is stopped at the timing when each position sensor detects the blade member. When each photoconductor is driven, when the K-color photoconductor is driven and the target drive start time corresponding to each of the Y, M, and C colors calculated from the phase difference is reached, the Y, M, and C colors are obtained. Each photoconductor is driven. By controlling each process drive motor and controlling the driving of each photoconductor in this way, each photoconductor can be driven to rotate in a state where the phases of the respective speed variation patterns are matched.

FIG. 27 is a diagram showing the speed variation of K color, the M color, and the speed variation at each step when color misregistration adjustment is performed in the present embodiment. FIG. 27A is a diagram showing the K color speed fluctuation, the M color, and the speed fluctuation when the process drive motor is driven at a constant speed. FIG. 27B is a diagram showing the K color speed fluctuation, the M color, and the speed fluctuation when the process driving motor is driven with the calculated driving speed pattern. FIG. 27C is a diagram showing the speed variation of the K color, the M color, and the speed variation after the phase control.
As shown in FIGS. 27A and 27B, the amplitude of the speed fluctuation is reduced by driving the process drive motor with the drive speed pattern. Thereby, the periodic expansion and contraction of the toner image transferred onto the intermediate transfer belt is improved, and a good image can be obtained. However, as shown in FIG. 27B, even when the process drive motor is driven with the drive speed pattern, it can be seen that the color deviation occurs because the speed fluctuation is not completely eliminated. For example, when focusing on the speed variation of the K color, the phase is shifted by about a half cycle in FIGS. 27 (a) and 27 (b). This is because the amplitude of the calculated drive pattern is larger than the actual amplitude due to the dimensional accuracy and calculation accuracy of the machine elements. Thus, due to the dimensional accuracy and calculation accuracy of the machine elements, even if the process drive motor is driven with the drive speed pattern, the speed fluctuation is not completely eliminated. Therefore, as shown in FIG. 27C, by controlling the phase based on the speed variation of the K color, the M color, and the speed variation when the process driving motor is driven with the calculated driving speed pattern, The speed fluctuation, the M color, and the speed fluctuation almost overlap each other, and the color shift is suppressed.

Note that the color misregistration adjustment shown in FIG. 26 is an example, and various modifications are possible.
FIG. 31 is a control flow showing an example of modification of color misregistration adjustment.
First, the control unit 140 drives the process drive motor 120 at a constant speed, executes fluctuation pattern detection control, and obtains a drive speed pattern (S31 to S33). That is, the process drive motor 120 is driven at a constant speed, and a speed variation detection image for each color is formed based on the timing when each color position sensor 135 detects the blade member 134. Next, the control unit 140 detects the toner image detection time pitch error in the speed change detection image of each color by the optical sensor unit 136, and detects the speed change pattern of each photoconductor based on the detection result. . Then, a driving speed pattern for each color for controlling the process driving motor for each color is calculated from the detected speed fluctuation pattern for each photoconductor (S33). Then, the photosensitive member speed control is performed based on the calculated driving speed pattern (S34). Moreover, the control part 140 which is a phase adjustment means implements phase adjustment based on the speed fluctuation pattern detected at step S32 (S35).

In the color misregistration adjustment shown in FIG. 31, since the color misregistration can be adjusted by a single speed variation pattern detection and calculation process, the color misregistration adjustment time is shortened compared to the color misregistration adjustment shown in FIG. Can be made. However, in the color misregistration adjustment shown in FIG. 31, when the calculated drive speed pattern amplitude is larger than the actual amplitude, the speed fluctuation pattern when the process drive motor is driven with the calculated drive speed pattern is detected. The phase is opposite to the phase of the speed variation pattern. As a result, when phase adjustment is performed, color misregistration is worsened. For this reason, the amplitude amount of the driving speed pattern is set to a value smaller than the amplitude amount of the detected speed fluctuation pattern, and the speed fluctuation pattern when the process drive motor is driven with the calculated driving speed pattern is the detected speed fluctuation pattern. The phase is not reversed.
On the other hand, in the color misregistration adjustment shown in FIG. 26, the speed fluctuation pattern detection control is performed to calculate the driving speed pattern, and then the speed fluctuation pattern detection control is performed again by controlling the process driving motor with the calculated driving speed pattern. Because the phase is adjusted based on the speed fluctuation pattern when the process drive motor is controlled with the drive speed pattern, the phase adjustment can be performed regardless of whether the calculated drive speed pattern amplitude is larger or smaller than the actual amplitude. Thus, color misregistration can be suppressed. Therefore, the amplitude of the speed fluctuation pattern when the process drive motor is driven with the drive speed pattern can be reduced as compared with the color misregistration adjustment shown in FIG. 31, and the image expansion and contraction and color can be reduced compared with the color misregistration adjustment shown in FIG. Deviation can be suppressed. In addition, the color misregistration adjustment shown in FIG. 26 actually controls the process drive motor with the drive speed pattern, detects the speed fluctuation pattern, and adjusts the phase based on the detected speed fluctuation pattern. Compared with the color misregistration adjustment shown in FIG. 31, it is possible to eliminate the influence of the control error when the process drive motor is controlled by the calculation error of the drive speed pattern and the drive speed pattern.

  Further, for example, phase control is performed based on a speed fluctuation pattern obtained by driving a process drive motor at a constant speed, and a driving speed pattern is calculated based on speed fluctuation data after phase control. Then, the speed fluctuation pattern of each color when the process drive motor is driven with the calculated drive speed pattern is detected, and phase control is performed based on the speed fluctuation pattern of each color when the process drive motor is driven with the detected drive speed pattern. May be performed. The speed fluctuation pattern to obtain the drive speed pattern is the phase variation control based on the speed fluctuation pattern when the process drive motor is rotated at a constant speed, and then the fluctuation pattern detection control is performed again by rotating the process drive motor at a constant speed. It may be obtained by executing. Also, after phase control based on the speed fluctuation pattern when the process drive motor is rotated at a constant speed, the speed when the process drive motor before the phase adjustment is rotated at a constant speed without executing the fluctuation pattern detection control. By calculating based on the fluctuation pattern, a speed fluctuation pattern for obtaining a driving speed pattern (speed fluctuation pattern when the phase-adjusted process driving motor is rotated at a constant speed) may be obtained.

  The color misregistration adjustment described above is (1) when any of the K, Y, C and M process units is replaced with a new one. (2) There is a color matching instruction from the operation display unit or personal computer as manual instruction means. Sometimes color misalignment adjustment is performed.

FIG. 28 is a diagram for explaining a detection mechanism that is a replacement detection unit that detects that a process unit has been mounted and has been replaced with a new one. Here, since each of the process units 1Y, 1M, 1C, and 1K has the same detection mechanism, the Y, M, C, and K symbols are omitted.
As shown in FIG. 28, the face plate 81 of the apparatus main body has a large-diameter hole into which a normally closed microswitch 169 for detecting the presence or absence of the process unit 1 is fitted. The microswitch 169 is supported by the printed circuit board 82. The inner surface of the face plate 81 is covered with an inner cover 84, and the outer surface on the printed circuit board 82 side is covered with an outer surface cover 83.

  The charging roller 6 has a threaded pin 164 that protrudes from the unit cover 167 and that is used to operate the micro switch 169.

  A charging roller 6 for uniformly charging the photoconductor 3 contacts the photoconductor 3 and rotates at substantially the same peripheral speed as the photoconductor 3. The rotating shaft 6a of the charging roller 6 is rotatably supported by a support plate 168 of the process unit 1Y via a bearing. A connecting sleeve 165 is fixed to the tip of the rotating shaft 6a and rotates integrally with the rotating shaft 6a. At the center of the connecting sleeve 165, there is a hole having a square cross section, into which a roughly square prismatic leg 164b of a threaded bottle 164 is fitted. The castle having a length of about 2/3 on the male screw 164s side of the leg 164b is a square prism that engages with the square hole of the connecting sleeve 165, but the remaining length of about 1/3 on the tip side of the leg 164b. The castle is in the shape of a round bar that can idle with respect to the connecting sleeve 165.

  As shown in FIG. 28A, there is a large-diameter male screw 164s between the leading pin 164p of the threaded pin 164 and the leg 164b. In the new (unused) process unit 1, the return spring 166 is compressed by being screwed into the female screw hole of the unit cover 167. In this state, the protruding length of the pin 164 from the front surface of the unit is short. However, when the charging roller 6 is rotationally driven in this state, the threaded pin 164 is rotated thereby to be coupled to the female screw hole. Due to the screw connection, it moves in a direction approaching the face plate 81 and hits the switching operator of the micro switch 169. Immediately before the male screw 164s of the threaded pin 164 penetrates the female screw hole due to this movement, the normally closed micro switch 169 is switched from closed to open.

  As shown in FIG. 28 (b), when the male screw 164 s penetrates the female screw hole, the pin 164 is projected by the return spring 166. As a result, the prism portion of the leg 164b of the pin 164 comes out of the square hole of the sleeve 165, and the pin 164 does not rotate even if the charging roller 6 rotates.

  Accordingly, when a process unit (for example, 1Y) that has already been used is mounted on the printer as it is, the microswitch (169Y) is always open (off). Even if a new (unused) process unit (IY) is mounted, that is, the unit is replaced, the microswitch (169Y) is closed (on) until the charging roller (6Y) is driven to rotate. It is. If the microswitch (169Y) is closed (on) when the printer power is turned on and is switched to open (off) when driving of the image forming mechanism is started, it is understood that the power was turned on for the first time after the unit replacement. That is, it can be seen that the unit has been replaced immediately before the power is turned on. The installation detection of other process units (1M, 1C, 1K) and the detection of the replacement with a new one are similarly performed.

FIG. 29 is a diagram showing the main part of the control flow of the printer.
When the power is turned on and the operating voltage is applied, the control unit 140 sets the signal level of the input / output port to the standby state, and also sets the internal registers, timers, and the like to the standby state (S11).

  When the initialization (S11) is completed, the control unit 140 reads the state of each mechanism of the printer and the state of the electric circuit to check whether there is an abnormality that is hindering image formation (S12, S13). If there is an abnormality (NO in S3), the open / close state of the micro switches 169Y to 169K is checked (S14). When any of the micro switches 169Y to 169K is closed (ON) (YES in S14), there is no process unit corresponding to the closed micro switch, or immediately after the process unit is replaced with a new unit. The power is on.

  When any one of the micro switches 169Y to 169K is closed (ON) (YES in S14), the control unit 140 temporarily drives the image forming system (S15). Specifically, the intermediate transfer belt 41 is driven, and the photoreceptors 3Y to 3K, the charging rollers 6Y to 6K that are in contact therewith, and the developing rollers of the developing units 7Y to 7K are rotated. If the process unit is just after being replaced with a new unit, the closed micro switch is switched to open (with unit mounted) by driving the image forming system. On the other hand, when the process unit is not mounted on the apparatus, the micro switch remains closed.

  When any of the closed micro switches 169Y to 169K is switched to open as a result of driving the image forming system (NO in S16), for example, the control unit 140 attaches / detaches the K (black) color process unit 1K. When the micro switch 169K that detects the change is switched from closed to open, it indicates that the unit has been replaced in the register FPC (one area on the nonvolatile memory) corresponding to the K (black) latent image carrying unit 60d. 1 "is written (S17).

  On the other hand, when the micro switch is not switched to the open position (YES in S16), it is assumed that no unit is mounted, and the control unit 140 notifies the operation display unit (operation panel) of an abnormality (S18). Then, the flow of status reading, abnormality check, and abnormality notification (S12 to S18) is repeated until there is no abnormality.

  When it is determined that there is no abnormality (YES in S13), the control unit 140 starts energizing the fixing unit 60, and information indicating unit replacement is generated in the above-described step S7 (FPC = 1). It is checked whether or not (S19). When information indicating unit replacement has been generated (FPC = 1) (YES in S19), the operation display unit displays that color misregistration adjustment is being performed (S20). Next, the control unit 140 executes the above-described color misregistration adjustment (S21), and when that is finished, clears the register FPC (S23).

  When the process units 1Y to 1K have not been replaced (NO in S29), when the fixing temperature of the fixing unit 60 reaches the fixable temperature, a printable display is performed on an operation display unit (not shown) (S24). Next, the control unit 140 waits for a user input via the operation display unit and a command from the personal computer PC connected to the printer, and reads the command (S25). When a “color misregistration adjustment” instruction is given from the user via the operation display unit or the personal computer PC (YES in S26), the control unit 140 performs color misregistration adjustment (S20 to S23).

  When the fixing temperature of the fixing unit 60 is the fixable temperature and each part is ready, if there is a copy start instruction (print instruction) from the operation display section or a print start instruction from the personal computer PC (YES in 27), The control unit 140 forms a specified number of images (S28).

  According to the control flow shown in FIG. 28, when the control unit 140 (1) replaces any of the K, Y, C, and M process units with a new one, (2) an operation display unit serving as a manual instruction means or When color matching is instructed from the computer, color misregistration adjustment is executed. The execution of (1) is called automatic execution, and the execution of (2) is called manual execution.

  Further, it may be configured such that it is possible to instruct the operation display unit or the personal computer to execute the color misregistration adjustment for obtaining only the driving speed pattern. In addition, it is possible to instruct the operation display unit or personal computer to execute color misregistration adjustment that obtains only the speed fluctuation for controlling the phase (speed fluctuation of each color when the process drive motor is driven with the driving speed pattern). It may be configured. Specifically, in addition to the normal “color misregistration adjustment mode”, the “shortened color misregistration adjustment mode” is displayed on the operation display unit or the personal computer, and the drive is performed when the user selects “shortened color misregistration adjustment mode”. Color misregistration adjustment is performed to obtain only the speed fluctuation (speed fluctuation of each color when the process drive motor is driven with the driving speed pattern) for performing color misregistration adjustment or phase control to obtain only the speed pattern. By providing such a “shortened color misregistration adjustment mode”, the color misregistration adjustment time can be shortened.

  Further, as shown in FIG. 30, a direct transfer system for transferring each monochrome image formed on the surface of each photoconductor 3Y, 3M, 3C, 3K so as to sequentially overlap a recording material on a conveyance belt as an endless moving body. The present invention can also be applied to a tandem type image forming apparatus employing the above.

  As described above, according to the image forming apparatus of the present embodiment, the control unit 140 serving as the speed control unit, the speed variation detection unit, the phase adjustment unit, and the control unit is provided for each of the photosensitive members serving as the latent image carriers. Based on the speed fluctuation pattern, which is the surface movement speed fluctuation of the photoconductor when the speed is controlled, the phase of the surface movement speed fluctuation of each photoconductor when the speed control of each photoconductor is executed is adjusted. By carrying out such control, it is possible to suppress color misregistration at the time of executing speed control without increasing the dimensional accuracy and calculation accuracy of the machine elements and enhancing the color misregistration suppressing effect by speed control. Thereby, it is possible to suppress an increase in cost due to an increase in the dimensional accuracy and calculation accuracy of the machine element, and to suppress color misregistration during execution of speed control.

  In addition, after detecting the speed fluctuation pattern of the photoconductor for controlling the process drive motor as each drive source, the control unit 140 controls each process drive motor based on the detected speed fluctuation pattern. Thus, a speed fluctuation pattern of the photoconductor for performing the phase adjustment control is detected. Then, the control unit 140 performs phase adjustment based on the detected speed variation pattern of the photoreceptor for performing phase adjustment control. As described above, when the speed fluctuation pattern of the photosensitive member for controlling the process drive motor as each drive source is detected, the color adjustment during the speed control is surely suppressed by performing the phase adjustment control. Can do.

  In addition, prior to detection of the speed variation pattern of the photoconductor for controlling the process drive motor as each drive source, the phase of the photoconductor is determined based on the speed variation pattern of the photoconductor when each drive source is rotated at a constant speed. Adjustments may be made.

  In addition, after adjusting the phase based on the speed variation pattern of the photoconductor when each drive source is rotated at a constant speed prior to detection of the speed variation pattern of the photoconductor for controlling each process drive motor, You may make it detect the speed fluctuation pattern of each photoconductor for rotating each drive source at a fixed speed and controlling each process drive motor.

  In addition, after each drive source is rotated at a constant speed and the speed fluctuation pattern of each photoconductor is detected, speed control and speed control are performed based on the detected speed change pattern of each photoconductor. You may make it perform the phase adjustment of the speed fluctuation pattern of each photoconductor. Thereby, the time for color misregistration adjustment can be shortened.

  Further, the control unit 140 controls the driving of the process drive motor with a driving speed pattern opposite in phase to the speed fluctuation pattern of the photoconductor, whereby the amplitude of the speed fluctuation of the photoconductor can be brought close to zero, and the toner image Expansion and contraction can be suppressed.

  In addition, the control unit 140 forms a speed fluctuation detection image including a plurality of predetermined toner images on the photoconductor, and transfers the speed fluctuation detection image formed on the surface of the photoconductor to the intermediate transfer belt 41. Then, the speed fluctuation pattern is detected based on the detection time interval of each toner image in the speed fluctuation detection image by the optical sensors 137 and 138 as toner image detection means. Thereby, it is possible to detect the speed fluctuation of each photoconductor without providing an encoder or the like for each photoconductor. Thereby, an apparatus can be made cheap.

  In addition, since the fluctuation pattern detection control can be performed from the operation display unit or the personal computer as the manual instruction means, the fluctuation pattern detection control is performed at an arbitrary timing, such as when the color misregistration of the image deteriorates, and the speed control is performed. It is possible to obtain a speed fluctuation pattern for performing a speed change and a speed fluctuation pattern when executing speed control for performing phase adjustment.

  In addition, it is possible to instruct to detect only the speed fluctuation pattern for speed control from the operation display unit or the personal computer, so the speed fluctuation pattern for speed control and the speed control for phase adjustment are executed. As compared with the case of detecting both of the speed fluctuation patterns in FIG. 1, the time for fluctuation pattern detection control can be shortened.

  Further, since the one-stage reduction mechanism using the photoconductor gear as the drive transmission member having the same rotation center as that of the photoconductor, the number of parts can be reduced and the cost can be reduced. Further, by using two gears, the cause of meshing errors and transmission errors due to eccentricity can be reduced, and the speed fluctuation cycle of the photoconductor can be almost limited to one rotation cycle of the photoconductor.

  Further, since the photoconductor gear and the gear side coupling that is the engaging portion that engages with the photoconductor coupling that is the engaged portion of the photoconductor are integrated, there is no backlash between the photoconductor gear and the gear side coupling. It does not occur. As a result, the speed fluctuation of the photoconductor due to the backlash between the photoconductor gear and the gear side coupling does not occur, and the cause of the speed fluctuation of the photoconductor can be further limited.

  In addition, when it is detected that each photoconductor has been replaced, a speed fluctuation pattern is detected and a speed fluctuation pattern for speed control or a speed fluctuation pattern at the time of speed control execution for phase adjustment Is detected. Thereby, the color shift after the photoconductor is replaced can be made inconspicuous.

  In addition, the photosensitive member can be easily replaced by integrally forming the photosensitive member and at least one of the charging device, the developing device, and the cleaning device so as to be detachable from the apparatus main body.

1 is a schematic configuration diagram illustrating a printer according to a first embodiment. FIG. 3 is an enlarged configuration diagram illustrating a process unit for Y of the printer. The perspective view which shows the process unit. The perspective view which shows the image development unit of the process unit. The perspective view which shows the main body side drive transmission part which is a drive transmission system fixed in the housing of the printer. The top view which shows the same main body side drive transmission part from upper direction. The fragmentary perspective view which shows the one end part of the process unit for Y. FIG. 2 is a perspective view showing a Y photoconductor gear and its peripheral configuration in the printer. The perspective view of a photoconductor gear. (A) is a figure which shows the speed fluctuation | variation of the photoreceptor of K color, and the speed fluctuation | variation of M color. FIG. 7B is a diagram illustrating an amplitude residual after subtracting the M color speed fluctuation component from the K color speed fluctuation component. FIG. 3 is a perspective view showing the photoconductor gear and its peripheral configuration from the process drive motor side. FIG. 2 is a schematic diagram of a printer when each photoconductor is viewed from the axial direction. FIG. 3 is a schematic plan view showing a speed variation detection image for K formed by the printer. The perspective view which shows a transfer unit and an optical sensor unit. FIG. 5 is a schematic diagram for explaining a relationship between a latent image writing position and a transfer position. 6 is a graph showing the speed fluctuation characteristics of the photoreceptor at the latent image writing position. The graph which shows the latent image formation space | interval fluctuation | variation characteristic in a latent image writing position. 6 is a graph showing speed fluctuation characteristics of a photoconductor at a transfer position. The graph which shows the latent image formation space | interval fluctuation | variation characteristic in a transfer position. 6 is a graph showing the relationship between the speed fluctuation characteristics of the photoconductor at the latent image writing position and the speed fluctuation characteristics of the photoconductor at the transfer position. The graph which shows the relationship between the latent image formation space | interval fluctuation | variation characteristic in a latent image writing position, and the latent image formation space | interval fluctuation | variation characteristic in a transfer position. 7 is a graph showing the relationship between the speed fluctuation characteristics of the photoconductor detected based on the detection time pitch error and the speed fluctuation characteristics of the photoconductor at the latent image writing position. (A) is a figure which shows a drive speed pattern and a photoreceptor speed fluctuation | variation, (b) is a figure which shows the photoreceptor speed fluctuation | variation after speed control. (A) is a figure which shows a drive speed pattern and a photoreceptor speed fluctuation | variation in case there exists an error in the amplitude of a drive speed pattern, and the amplitude of a photoreceptor speed fluctuation | variation. FIG. 5B is a diagram illustrating the photoreceptor speed fluctuation after speed control when there is an error between the amplitude of the driving speed pattern and the amplitude of the photoreceptor speed fluctuation. (A) is a figure which shows a drive speed pattern and a photoreceptor speed fluctuation | variation in case there exists an error in the amplitude and phase of a drive speed pattern, and the amplitude and phase of a photoreceptor speed fluctuation | variation. FIG. 6B is a diagram showing the photoreceptor speed fluctuation after speed control when there is an error between the amplitude and phase of the driving speed pattern and the amplitude and phase of the photoreceptor speed fluctuation. FIG. 5 is a control flow diagram for color misregistration adjustment. (A) is a figure which shows the speed fluctuation of K color before speed control, and the speed fluctuation of M color. (B) is a figure which shows the speed fluctuation | variation of K color after speed control, and the speed fluctuation | variation of M color. FIG. 6C is a diagram illustrating a K-color speed fluctuation and a M-color speed fluctuation after the phase adjustment control based on a speed fluctuation pattern after the speed control. (A) shows a state immediately after the process unit is new and is mounted on the copying machine, and (b) shows a state after the charging roller is rotationally driven after mounting. FIG. 3 is a diagram illustrating a part of a control flow of the printer. 1 is a diagram illustrating a direct transfer type image forming apparatus. FIG. The control flow figure which shows an example of the deformation | transformation of color misregistration adjustment.

Explanation of symbols

1Y, C, M, K: Process unit 3Y, C, M, K: Photoconductor 40: Transfer unit 41: Intermediate transfer belt 20: Optical writing unit 120Y, C, M, K: Process drive motor 133Y, C, M, K: photoconductor gear 135Y, C, M, K: position sensor 136: optical sensor unit

Claims (10)

A plurality of latent image carriers that carry a latent image on an endlessly moving surface;
A plurality of drive sources for individually driving each latent image carrier;
Latent image writing means for writing a latent image to each latent image carrier based on image information;
A plurality of developing means for individually developing the latent image written on each latent image carrier to obtain a visible image;
An endless moving body that moves the surface endlessly so as to sequentially pass a position facing each latent image carrier;
The visible image formed on the surface of each latent image carrier is transferred to the recording medium held on the surface of the endless moving body, or transferred to the recording body after being transferred to the surface of the endless moving body. In an image forming apparatus provided with a transfer unit,
Image detecting means for detecting a toner image on the endless moving body;
A speed fluctuation detection image comprising a plurality of predetermined toner images is formed on the surface of each latent image carrier, and the speed fluctuation detection image formed on the surface of each latent image carrier is transferred to the endless moving body. A speed fluctuation detecting means for detecting a movement speed fluctuation of each latent image carrier based on a detection time interval of each toner image in the speed fluctuation detecting image by the image detecting means;
Based on the surface moving speed variation of the Re respectively'll detected by the speed fluctuation detection means image carrier, and a speed control means for controlling each driving source, the speed control of the respective latent image carriers,
By controlling the driving of each drive source based on the surface movement speed fluctuation of each image carrier detected by the speed fluctuation detecting means, each latent image when the speed control is executed by the speed control means. Phase adjusting means for adjusting the phase of the surface movement speed fluctuation of the carrier;
Each of the driving sources is rotated at a constant speed, and the first variation of the surface movement speed of each latent image carrier is detected by the speed variation detecting means. Each drive source is controlled by the speed control means based on the fluctuation, and the second fluctuation of the surface movement speed of each latent image carrier is detected by the speed fluctuation detection means. An image forming apparatus comprising: control means for controlling the phase adjustment means to adjust the phase of the surface movement speed fluctuation of each latent image carrier based on the body surface movement speed fluctuation . A plurality of latent image carriers that carry a latent image on an endlessly moving surface;
A plurality of drive sources for individually driving each latent image carrier;
Latent image writing means for writing a latent image to each latent image carrier based on image information;
A plurality of developing means for individually developing the latent image written on each latent image carrier to obtain a visible image;
An endless moving body that moves the surface endlessly so as to sequentially pass a position facing each latent image carrier;
The visible image formed on the surface of each latent image carrier is transferred to the recording medium held on the surface of the endless moving body, or transferred to the recording body after being transferred to the surface of the endless moving body. In an image forming apparatus provided with a transfer unit,
Image detecting means for detecting a toner image on the endless moving body;
A speed fluctuation detection image comprising a plurality of predetermined toner images is formed on the surface of each latent image carrier, and the speed fluctuation detection image formed on the surface of each latent image carrier is transferred to the endless moving body. A speed fluctuation detecting means for detecting a movement speed fluctuation of each latent image carrier based on a detection time interval of each toner image in the speed fluctuation detecting image by the image detecting means;
Speed control means for controlling each drive source based on the surface movement speed fluctuation of each image carrier detected by the speed fluctuation detection means, and for controlling the speed of each latent image carrier;
By controlling the driving of each drive source based on the surface movement speed fluctuation of each image carrier detected by the speed fluctuation detecting means, each latent image when the speed control is executed by the speed control means. Phase adjusting means for adjusting the phase of the surface movement speed fluctuation of the carrier;
Each drive source is rotated at a constant speed, and the speed fluctuation detecting means detects each latent image carrier surface movement speed fluctuation. Based on the detected latent image carrier surface movement speed fluctuation, each latent image carrier is detected. The phase of the surface movement speed fluctuation of the body is adjusted by the phase adjusting means, and each of the latent image carrier surface movement speed fluctuations is set to an amplitude smaller than the amplitude of each detected latent image carrier surface movement speed fluctuation. An image forming apparatus comprising: a control unit that controls the speed control unit to control the speed of each latent image carrier based on the above . The image forming apparatus according to claim 1 or 2 ,
The phase adjusting means controls the drive stop timing of each drive source based on the surface movement speed fluctuation of each latent image carrier. The image forming apparatus according to any one of claims 1 to 3 ,
The speed control means performs drive control so that the drive source is rotationally driven by a speed fluctuation in a phase opposite to the surface movement speed fluctuation of the latent image carrier detected by the speed fluctuation detection means. Image forming apparatus. In any one of the image forming apparatus according to claim 1 to 4,
An image forming apparatus, comprising: a manual instruction unit that allows a user to instruct execution of the speed fluctuation detection unit. The image forming apparatus according to claim 5 .
The manual instruction means is configured so that a user can instruct the speed fluctuation detection means to detect only surface movement speed fluctuation data for the speed control means to control each drive source. Image forming apparatus. In any one of the image forming apparatus according to claim 1 to 6,
A drive device characterized in that each latent image carrier is driven by a one-stage reduction mechanism using a drive transmission member having the same rotation center as that of the latent image carrier. The image forming apparatus according to claim 7 .
An image forming apparatus, wherein the drive transmission member and an engaging member that engages with an engaged portion provided on a rotation shaft of the latent image carrier are formed as a single body. The image forming apparatus according to any one of claims 1 to 8 ,
The latent image carrier includes an exchange detection means for detecting that the latent image carrier has been exchanged,
The image forming apparatus according to claim 1, wherein the speed fluctuation detecting unit detects the speed fluctuation of each latent image carrier when the replacement detection unit detects the replacement of the latent image carrier. In any one of the image forming apparatus according to claim 1 to 9,
An image forming apparatus comprising a process cartridge in which the image carrier and at least one of a charging device, a developing device, and a cleaning device are integrally detachable from the apparatus main body.

Images