JP2010210874A - Drive transmission device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive transmission device that has a marking detectable a reference position with a sensor, capable of minimizing eccentricity of a tooth face, which may occur on an injection mold, and is free from displacement of the axis, and to provide an image forming apparatus that has this drive transmission device. <P>SOLUTION: The drive transmission device includes: a drum drive gear 33 coupled to the photoreceptor drum 1 of a printer A; a drive motor 31 for rotating and driving the photoreceptor drum 1 via the drum drive gear 33; a detection mark 35 disposed on the drum drive gear 33; and a position detecting sensor 34 for detecting the detection mark 35 and detecting the rotated position of the driven member. The detection mark 35 is provided as the area where the surface of the drum drive gear 33 is roughened. The detection mark 35 may be provided more than one on the circumference of a side of the drum drive gear 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drive transmission device and an image forming apparatus, and in particular, a drive transmission unit coupled to a driven member, a drive unit that rotationally drives the driven member via the drive transmission unit, and a drive transmission unit. The present invention relates to a position detection unit, a drive transmission device including a position detection unit that detects the rotational position of the driven member by detecting the position detection unit, and an image forming apparatus including the drive transmission device.

  In general, in a multi-color image forming apparatus having a plurality of photoconductive drums as image carriers, a problem that the deviation of the speed variation of each photoconductive drum becomes a color shift of each color and appears in the formed image. There is. That is, a drive transmission member is integrally coupled to the photosensitive drum by engagement or the like, and a driving force is transmitted to the drive transmission member to drive the photosensitive drum to a predetermined level. The deviation of fluctuation is often caused by the accuracy error of the drive transmission member, the eccentricity of the attachment of the drive transmission member to the photosensitive drum, and it is difficult to deal with these. For this reason, the speed variation period of each photosensitive drum axis, that is, each photosensitive drum is made to coincide with a certain period so as to minimize the relative color misregistration amount and improve the image quality. It was.

  As a method of matching the speed fluctuation periods, that is, a method of adjusting the phase of each speed fluctuation period to a predetermined value, a color misregistration correction pattern drawn on an intermediate carrier such as an intermediate transfer belt is read by a pattern detection device, The speed fluctuation period and period deviation amount of the body drum axis are calculated, the phase difference between the respective photosensitive drums is obtained so that the color deviation amount is minimized, and the information of the phase difference is rewritten as a profile in a nonvolatile memory or the like. There is known a method of storing and copying the phase relationship of each photosensitive drum axis to a profile before image formation (see Patent Document 1 and Patent Document 2).

  Therefore, conventionally, each photoconductive drum has a phase relationship that follows the profile. Therefore, a position (hereinafter referred to as a marking) serving as a reference for detecting the rotational position is set in each drive gear or dedicated member of each photoconductive drum. In addition to setting a single location, a marking detection sensor for detecting markings is fixedly arranged on the apparatus main body side, and by these marking detection sensors, the detection timing difference of each photosensitive drum at a predetermined rotational position is measured. On the basis of this, there has been a configuration in which each photosensitive drum drive motor is controlled so that the speed fluctuation periods of the respective photosensitive drums coincide with each other. That is, in this configuration, when each marking passes through the detection range of each marking detection sensor with the rotation of each photosensitive drum, a detection signal indicating the passage of this marking is transmitted from the marking detection sensor, The current phase relationship is detected from the difference between the timings at which these detection signals are transmitted, and then each photoconductor drum drive motor is controlled to a predetermined phase so that the rotational state of each photoconductor drum is made to follow the profile. ing.

  However, the marking on the drive gear has a problem that the speed variation of the rotation cycle of the drive gear occurs. This was thought to be due to the eccentricity caused by the center of gravity shifting from the center due to the weight of the marking. For this reason, the device described in Patent Document 3 has a configuration in which the mass rotation moment is constant in the circumferential direction by balancing so as to eliminate the vertical center-of-gravity shift of the shaft due to the weight of the marking. Thereby, it is made uniform and the gravity center balance is stabilized. That is, even when the balance of the center of gravity is not balanced by the marking, the center of gravity of the drum drive gear shaft in the vertical direction can be made to coincide with the photosensitive drum axis.

  However, the thing of patent document 3 will produce the speed fluctuation | variation of one rotation period by the speed fluctuation | variation resulting from a large eccentricity and gear accumulated pitch error in a gear tooth surface shape. FIG. 17 is a perspective view showing a drum drive gear according to a conventional example. The drum drive gear 61 is a molded product, and a marking (hereinafter referred to as a filler 62) is also integrated. In this case, the presence of the filler causes partial shrinkage on the tooth surface due to non-uniformity in internal pressure and temperature during injection molding, resulting in eccentricity of the tooth surface shape. Specifically, in the vicinity of the filler 62, an extra material is required for the volume of the filler 62, so that it is difficult to reach the tooth surface at the tip, and the surface area is widened by the amount of the filler, so the distribution is partially low. . As a result, the tooth surface in the vicinity of the filler 62 is likely to be attracted, resulting in eccentricity due to temperature and pressure deviations. FIG. 18 is a graph obtained by measuring gear teeth of a gear according to a conventional example. The thin line is the reference circle and the thick line is the measured tooth trace, and the thick line enlarges the error from the reference circle 1000 times for visualization. As can be seen from the figure, it can be confirmed that a large shrinkage occurs in the upper portion where the filler is present. As described above, although the center of gravity balance can be corrected with the one described in Patent Document 3, there remains a problem that the eccentricity of the gear tooth surface shape and the accumulated pitch error are likely to occur. It turns out that it cannot be minimized.

  Accordingly, the present invention can suppress the eccentricity of the tooth surface generated during injection molding while providing a marking capable of detecting the reference position by a sensor, and a drive transmission device in which the axial center does not deviate, and image formation provided with this drive transmission device An object is to provide an apparatus.

  The invention according to claim 1 is a drive transmission unit coupled to the driven member, a drive unit that rotationally drives the driven member via the drive transmission unit, and a position detection unit disposed in the drive transmission unit. And a position detecting means for detecting the rotational position of the driven member by detecting the position detecting portion, and forming a region where the surface state of the drive transmitting member is rough as the detecting portion. It is a drive transmission device.

  According to a second aspect of the present invention, in the drive transmission device according to the first aspect, a plurality of the detection units are provided on the circuit.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the drive transmission device according to the first or second aspect is provided.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the driven member is an image carrier.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the phase difference between the plurality of image carriers is adjusted based on the plurality of detection results detected by the position detection unit by the driving device. Further, it is characterized in that a control means for controlling each of the driving means is provided.

  According to the present invention, in the component in which the detection unit is integrally formed with the drive transmission unit, the detection unit is a region where the surface shape of the drive transmission member is roughened, and the detection unit has a volume of substantially zero. The presence of the presence detector does not affect the volume, and the pressure distribution and temperature distribution at the time of molding become uniform. One rotation period fluctuation component can be reduced.

1A and 1B show a basic structure of an image forming apparatus, in which FIG. 1A is a sectional configuration diagram of the image forming apparatus, and FIG. 2B is a schematic configuration diagram showing a process cartridge for generating a yellow toner image. FIG. 2 is a schematic diagram of a printer when each photosensitive drum is viewed from the axial direction. FIG. 3 is a perspective view illustrating a drum driving gear in the image forming apparatus according to the embodiment. It is a schematic diagram which shows the detection state of a position detection sensor. It is a graph which shows the output of a position detection sensor when a drum drive gear is rotated once. It is a graph which shows the output of a position detection sensor when a drum drive gear is rotated once. It is the graph which measured the tooth trace of the gear which concerns on an Example. It is a perspective view which shows the drum drive gear which concerns on a 2nd Example. It is a graph which shows the output of a position detection sensor when the drum drive gear which concerns on a 2nd Example is rotated once. 1 is a block diagram illustrating a part of an electric circuit of an image forming apparatus according to an embodiment. It is a schematic diagram showing a reference pattern image group for each of Y, C, M, and K for detecting displacement. It is a graph which shows the output of the position detection sensor of each color. It is a graph which shows the shift | offset | difference from a reference position. 5 is a graph showing a rotational speed variation of a K-color photosensitive drum and a rotational speed variation of an M-color photosensitive drum obtained by calculation. It is a flowchart which shows the procedure of phase difference adjustment. It is a timing chart which shows the ON / OFF state of the drive motor and each clutch at the time of phase difference adjustment according to the flowchart shown in FIG. It is a perspective view which shows the drum drive gear which concerns on a prior art example. It is the graph which measured the tooth trace of the gear which concerns on a prior art example.

  In an electrophotographic image forming apparatus, a photosensitive drum as a driven member is driven by a drum driving gear as a drive transmission unit. A position detection sensor, which is a reflection type photosensor for position detection, is disposed close to the drum drive gear, and detects the position of the photosensitive drum and controls the print position of each color. As a detection mark, a region having a rougher surface than the other regions is formed on the side surface of the drum drive gear, and this is detected by a position detection sensor. A plurality of detection marks are formed on the circumference.

  With such a configuration, the formation of the detection mark roughens the surface roughness, so the increase or decrease in volume is substantially zero, and when the drum drive gear is formed by forming the detection mark, The pressure distribution and temperature distribution become uniform, and tooth surface shrinkage can be minimized, and the rotation cycle fluctuation component during drive transmission can be reduced. In addition, since a plurality of detection marks are provided on the circuit, a plurality of reference positions can be detected while the drum drive gear rotates once, so that initial detection can be accelerated. Since the image forming apparatus can reduce the rotation variation of the photosensitive drum, the color shift in the rotation rotation cycle of the photosensitive drum can be reduced.

  An image forming apparatus according to an embodiment of the present invention will be described below. 1A and 1B show a basic structure of an image forming apparatus. FIG. 1A is a sectional configuration diagram of the image forming apparatus, FIG. 1B is a schematic configuration diagram showing a process cartridge for generating a yellow toner image, and FIG. FIG. 2 is a schematic diagram of a printer when each photosensitive drum is viewed from the axial direction. As shown in FIGS. 1A, 1 </ b> B, and 2, the printer A has a toner image for transfer onto a sheet P as a transfer material that is a final image fixing target in the apparatus main body 3. Intermediate transfer belt 8 as an intermediate image carrier on which the image is temporarily transferred and carried, and photosensitive drums 1Y, 1M, 1C, and 1K, which are a plurality of image carriers in contact with the intermediate transfer belt 8, respectively. Drive motors, which are a plurality of drive means for rotating the photosensitive drums 1Y to 1K by engaging photosensitive drum drive transmission gears (hereinafter referred to as drum drive gears) 33Y, 33M, 33C, 33K as drive transmission members. 31Y, 31M, 31C, 31K, position detection sensors 34Y, 34M, 43C, 34K which are position detection means for detecting the rotational position of each of the photosensitive drums 1Y-1K, and the plurality of photosensitive drums 1 -1K are rotated, and the rotational drive of the photosensitive drums 1Y-1K is controlled in a predetermined manner based on the phase difference information between the drums detected by the position detection sensors 34Y-34K, that is, the rotational speed is changed or rotated. Control means for controlling the phases of the plurality of photosensitive drums 1Y to 1K by changing the start time and the rotation stop time for each of the photosensitive drums 1Y to 1K is housed.

  The printer A includes four process cartridges that generate toner images as visible images of yellow, magenta, cyan, and black (hereinafter referred to as “Y”, “M”, “C”, and “K”, respectively) colors. 6Y, 6M, 6C, 6K. That is, these four process cartridges 6Y to 6K are capable of rotating the photosensitive drums 1Y to 1K around a horizontal rotation axis, and a part of the drum surface is arranged outside the process cartridges 6Y to 6K. Each of the process cartridges 6Y to 6K is mounted in the apparatus main body 3 in a state in which the process cartridges 6Y to 6K are in contact with the intermediate transfer belt 8, and in this state, A toner image of any one of colors Y to K in charge is generated. These process cartridges 6Y to 6K are basically configured in the same manner, and Y toner, M toner, C toner, and K toner of different colors are supplied to each as an image forming agent. Each of the process cartridges 6Y to 6K is configured to be easily detachable from the apparatus main body 3, and can be replaced as a consumable item. The process cartridge 6Y for generating a Y toner image will be described below, but the process cartridges 6M to 6K for other color toner images basically have the same members and are configured identically.

  As shown in FIG. 1 (b), the process cartridge 6Y has at least a photosensitive drum 1Y as an image carrier that is rotationally driven around a horizontal axis while being mounted on the apparatus body 3. Around this photosensitive drum 1Y, from the upstream side to the downstream side in the clockwise rotation direction in the drawing, the drum cleaning device 2Y, the neutralizing device (not shown), the charging device 4Y, and the developing device to which the agent is supplied It is set as the structure which provided any one or more, such as 5Y. The charging device 4Y has a charging roller that is driven and rotated by the photoreceptor drum 1Y when a predetermined voltage is applied, and uniformly charges the surface of the photoreceptor drum 1Y that is rotated clockwise. The uniformly charged surface of the photosensitive drum 1Y is exposed and scanned by the laser beam L, and an electrostatic latent image for Y is generated.

The developing device 5Y includes a developing roller that rotates at a predetermined minute interval on the surface of the photosensitive drum 1Y and is driven to follow the photosensitive drum 1Y. A toner brush for Y toner is formed on the developing roller. The brush-like Y toner that is configured and formed can move to the drum surface. Accordingly, the Y electrostatic latent image generated on the surface of the photosensitive drum 1Y is visualized as a Y toner image by the developing device 5Y using Y toner, and this Y toner image is transferred onto the intermediate transfer belt 8 as an intermediate transfer. Is done. The drum cleaning device 2Y has a cleaning blade in which the blade edge at the tip thereof is in contact with the surface of the photosensitive drum 1Y after the intermediate transfer process at a predetermined pressure and a predetermined contact angle, and remains on the surface. Toner carried along with drum rotation is removed. The static eliminator neutralizes residual charges on the photosensitive drum 1Y after cleaning. By this charge removal, the surface of the photosensitive drum 1Y is initialized and used for the next image formation. The other process cartridges 6M, 6C, and 6K operate in the same manner to form M toner images, C toner images, and K toner images on the photosensitive drums 1M, 1C, and 1K, respectively. The toner image is superimposed on the intermediate transfer belt 8 and intermediate transferred.
As shown in FIG. 1A, an exposure device 7 is disposed below the process cartridges 6Y to 6K in the drawing. That is, the exposure device 7 serving as a latent image forming unit irradiates each of the photosensitive drums 1Y, 1M, 1C, and 1K in the process cartridges 6Y to 6K with a laser beam L emitted based on the image information to perform exposure. By this exposure, a Y electrostatic latent image, an M electrostatic latent image, a C electrostatic latent image, and a K electrostatic latent image are formed on each of the photosensitive drums 1Y to 1K. The exposure device 7 irradiates the photosensitive drum with a laser beam L emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor. The exposure device 7 constitutes visible image forming means for forming toner images, which are visible images, on the photosensitive drums 1Y to 1K together with the process cartridges 6Y to 6K.

  Further, as shown in FIG. 1A, a sheet feeding means is disposed on the lower side of the exposure apparatus 7 in the drawing, and the sheet feeding means is a sheet storage cassette 26 and a sheet feeding roller incorporated therein. 27, a registration roller pair 28, and the like. A plurality of sheets P as recording materials are stacked and stored in the sheet storage cassette 26, and a sheet feeding roller 27 is in contact with the uppermost sheet P. Accordingly, when the paper feeding roller 27 is rotated counterclockwise in the figure by a driving means such as a motor (not shown), only the uppermost paper P is sent to the conveyance path between the rollers of the registration roller pair 28. Be paid. The registration roller pair 28 is rotationally driven so that the paper P is sandwiched. As soon as the paper is sandwiched, the registration roller pair 28 temporarily stops its rotation and sandwiches the paper P. Then, the registration roller pair 28 sends out the paper P toward the secondary transfer nip at an appropriate timing for transferring the toner image on the intermediate transfer belt 8 onto the paper P.

  Also, in the drawing, an intermediate transfer unit 15 having a configuration in which an intermediate transfer belt 8 as an intermediate transfer member is moved endlessly while being stretched is disposed above the process cartridges 6Y, 6M, 6C, and 6K. ing. The intermediate transfer unit 15 includes a belt cleaning device 10 in addition to the intermediate transfer belt 8. Further, it also has four primary transfer bias rollers 9Y, 9M, 9C, 9K, a secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14, and the like. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the drawing by at least one of the rollers being rotationally driven while being stretched by these seven rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K facing each other, and a primary transfer nip is formed at each location. Forming. In these primary transfer nips, a transfer bias having a polarity opposite to that of the toner (for example, plus polarity) is applied to the back surface (belt loop inner peripheral surface) of the intermediate transfer belt 8. All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and the Y toner image on each of the photosensitive drums 1Y, 1M, 1C, and 1K. , The M toner image, the C toner image, and the K toner image are superimposed and primarily transferred, and a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

  Further, the intermediate transfer unit 15 is shown in order to bring the intermediate transfer belt 8 into contact with and away from the photosensitive drums 1Y, 1M, and 1C from the state in which the intermediate transfer belt 8 is in contact with the photosensitive drum 1K. A contact / separation mechanism is also provided.

  The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the paper P at the secondary transfer nip. Then, combined with the white color of the paper P, a full color toner image is obtained. The surface of the intermediate transfer belt 8 after passing through the secondary transfer nip may have a transfer residual toner that has not been transferred to the paper P attached thereto. I am trying to clean.

  In the secondary transfer nip, the paper P is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 that move in the forward direction to each other, and conveyed in the opposite direction to the registration roller pair 28 side. . When the paper P sent out from the secondary transfer nip passes between the rollers of the fixing device 20, it is affected by heat and pressure, and the color toner image is fixed on the surface thereof. Then, the paper P is discharged out of the apparatus through the rollers of the paper discharge roller pair 29. A stack portion 50a is formed on the upper surface of the housing of the printer main body, and the sheets P discharged to the outside by the discharge roller pair 29 are sequentially stacked on the stack portion 50a.

  A bottle storage unit 51 is disposed between the intermediate transfer unit 15 and the stack unit 50a located above the intermediate transfer unit 15. In the bottle storage portion 51, toner bottles 52Y, 52M, 52C, and 52K are set as agent containers for storing the respective color toners. Each color toner in each of the toner bottles 52Y to 52K is appropriately supplied to the developing devices of the process cartridges 6Y, 6M, 6C, and 6K by a toner supply device (not shown). Each of the toner bottles 52Y to 52K is configured to be detachable from the apparatus main body 3 of the printer A independently of the process cartridges 6Y to 6K and individually. Accordingly, toner is replenished to the process cartridges 6Y to 6K, and any of the empty toner bottles 52Y to 52K is replaced with new toner bottles 52Y to 52K filled with new toner.

Next, a description will be given of a configuration in which the photosensitive drums 1Y to 1K are rotationally driven in a predetermined manner independently of each other and the rotational driving is controlled in a predetermined manner. That is, with respect to the photosensitive drums 1Y to 1K to which the drum driving gears 33Y to 33K are coupled, the rotational driving force is transmitted to the drum driving gears 33Y to 33K from the driving sources for the photosensitive drums individually provided on the apparatus body 3 side. A configuration for individually rotating the respective photosensitive drums 1Y to 1K in a predetermined manner and a control unit for controlling the rotational driving in a predetermined manner will be described.
As shown in FIG. 2, drum driving gears 33Y, 33M, 33C, and 33K are provided at one end in the axial direction of each of the photosensitive drums 1Y to 1K (the end on the far side in the drawing). The drum drive gears 33Y to 33K are coupled to the photosensitive drum shaft 11 of the photosensitive drums 1Y to 1K by a joint member so that the shafts are integrated with the ends of the photosensitive drums 1Y to 1K. It is provided and rotates integrally with the photosensitive drums 1Y to 1K.

That is, for example, a gear shaft (not shown) of the drum driving gears 33Y to 33K and a photosensitive drum shaft 11 of each of the photosensitive drums 1Y to 1K are formed by a pair of engaging members fixed to the respective shaft end portions. Through the member, it is coaxially and detachably coupled so as to be able to transmit the rotational driving force. That is, a first coupling (not shown), which is a first engaging member as a joint member that rotates integrally with the photosensitive drum shaft 11, is fixed to the end of the photosensitive drum shaft 11, A second coupling (not shown), which is a second engaging member serving as a joint member that rotates integrally with the gear shaft, is fixed to the end of the drum drive gear shaft. Accordingly, when the process cartridges 6Y to 6K are mounted at predetermined positions of the apparatus main body 3, the first coupling on the driven side that is the first engaging member is the driving side that is the second engaging member. The coupling is engaged and meshed with each other so that the rotational driving force can be transmitted. Thus, since the shaft ends are connected coaxially via the joint member, the shaft connection and the release of the connection are facilitated. In this example, photosensitive member clutches 37Y, 37M, 37, 37C, and 37K (not shown, see FIG. 10) are disposed in the drive path, and the drive motors 31Y, 31M, 31C, and 31K Rotation can be connected and disconnected.

  The drum driving gears 33Y to 33K receive driving force from the driving motors 31Y, 31M, 31C, and 31K, and rotate the photosensitive drums 1Y to 1K in a predetermined manner. That is, each of the drum drive gears 33Y to 33K is an external gear having teeth engraved on the outer peripheral surface thereof, and is an external gear having a smaller diameter than the gear diameter of the drum drive gears 33Y to 33K. The drive transmission gears 32Y, 32M, 32C, and 32K are engaged with each other so as to be able to transmit the driving force, or the outer peripheral surfaces of both are formed on a flat surface with a predetermined coefficient of friction, and the friction is maintained. Each of them is in contact with a predetermined contact pressure so as to be able to transmit the driving force due to the contact. Therefore, in the configuration in which the driving force is transmitted by frictional contact, the noise and collision noise that are generated when the teeth in the gear configuration come into contact with each other can be eliminated, so that it is possible to achieve quietness during the image generation operation.

  These drive transmission gears 32Y to 32K are fixed to the output shafts of drive motors 31Y, 31M, 31C, 31K as drive means provided on the apparatus main body 3 side, and from the drive motors 31Y, 31M, 31C, 31K. Are driven to rotate independently of each other by the rotational driving force. As described above, since the drive motors 31Y, 31M, 31C, and 31K as the drive sources are individually provided for the respective photosensitive drums 1Y, 1M, 1C, and 1K, the respective photosensitive drums are independent of each other. Thus, each rotation can be controlled individually. On the other hand, the rotational driving force is transmitted to the drum driving gears 33Y to 33K configured to rotate and drive the photosensitive drums 1Y to 1K in a single speed reduction manner, that is, the drum driving gears 33Y to 33K that rotate integrally with the photosensitive drums 1Y to 1K. Since no other gear is interposed, the transmission efficiency can be improved and the rotation control of each of the photosensitive drums 1Y to 1K can be performed accurately and precisely.

  Each of the drive motors 31Y, 31M, 31C, 31K is controlled by the control unit 150 serving as control means for the rotation speed of the output shaft, the timing for starting rotation, and the timing for stopping. The photosensitive member clutches 37Y, 37M, 37, 37C, and 37K are also connected and disconnected by the control unit 150. The control unit 150 performs process control of the entire printer, and includes an IO port, a CPU, a ROM, a RAM, and the like. That is, a drive circuit (not shown) that supplies power to each of the drive motors 31Y to 31K is wired to the control unit 150, and in accordance with a command signal from the control unit 150, at a predetermined power supply timing, a predetermined voltage or a predetermined current, The electric power set or adjusted to a predetermined frequency is supplied, or the supply is stopped at a predetermined timing, and various rotation operations such as the above speed and timing are controlled.

  The control unit 150 is wired to position detection sensors 34Y to 34K serving as position detection means provided for detecting the rotational positions of the photosensitive drums 1Y, 1M, 1C, and 1K, and the position detection sensors 34Y. The detection signals output from .about.34K are input so that the rotational positions of the photosensitive drums 1Y.about.1K can be recognized. In other words, the control unit 150 controls each of the drive motors 31Y to 31K based on this detection signal, so that the amount of deviation of each color toner image transferred onto the intermediate transfer belt 8 is minimized. Drive control of 1Y to 1K is performed. Reference numeral 36 denotes an image reading sensor installed in the intermediate transfer belt 8 with its imaging direction directed, and the image reading sensor 36 is connected to the control unit 150 by wiring. Accordingly, the toner image on the intermediate transfer belt 8 is read by the image reading sensor 36, and the read toner image can be output to the control unit 150.

  Next, an outline of a series of processing processes from phase difference detection to phase difference control of each photosensitive drum will be described. In a quadruple tandem multi-function machine, the relative position of the rotational positions between the photosensitive drums that minimizes the amount of shift between the color toner images that overlap each other on the intermediate transfer belt is the printer manufactured through the same manufacturing process. Even there are individual differences. Such individual differences that cause color misregistration are produced by the mounting eccentricity of the drum drive gear provided on the photosensitive drum, the gear molding accuracy, the speed fluctuation caused by the joint portion that couples the drive gear and the image carrier, and the like. It arises from the slight differences between printers. For this reason, color misregistration occurs when the surface movement speed of the photosensitive drum fluctuates due to these eccentricities, and the color toner images on the intermediate transfer belt extend or contract in the surface movement direction. The amount of color misregistration is maximized on the intermediate transfer belt so that a portion where a toner image of a certain color is extended and a portion where a toner image of any other color is shrunk overlap each other. Is the time. Therefore, in this embodiment, the relative relationship of the rotational positions between the photosensitive drums is measured as follows so that the amount of deviation between the color toner images overlapping each other on the intermediate transfer belt is minimized. It has data storage means configured to store relative relationship data based on the results in the ROM. More specifically, the control unit functioning as a data storage unit first forms test toner images for detecting the color misregistration amounts on the surfaces of the photosensitive drums 1Y to 1K, and these are formed on the intermediate transfer belt. Transcript to. In this embodiment, the relative angle of the rotational position of the other photosensitive drums 1Y to 1K with respect to the rotational position of the black photosensitive drum 1K is shifted by 45 °, and the test toner image is intermediately transferred eight times for each photosensitive drum. Transfer onto the belt. Then, each test toner image on the intermediate transfer belt transferred in this way is read by the image reading sensor 36 and outputted as data to the control unit. Based on the data read for each test toner image, the control unit 150 has the least amount of color misregistration between the non-black photosensitive drums 1Y, 1M, and 1C and the test toner image of the black photosensitive drum 1K. Specify the relative angle. Position detecting sensors 34Y to 34K of position detecting means provided for detecting the rotational positions of the photosensitive drums 1Y to 1K are wired to the control unit 150 and output from the position detecting sensors 34Y to 34K. The detection signal is input, and the rotation reference position of each of the photosensitive drums 1Y to 1K can be recognized. That is, the control unit controls each of the drive motors 31Y to 31K based on this detection signal, so that the shift amount of each color toner image transferred onto the intermediate transfer belt 8 is minimized. Drive control of ˜1K is performed.

  Further, the rotation reference position detecting means for the drum drive gear will be described. FIG. 3 is a perspective view illustrating a drum driving gear in the image forming apparatus according to the embodiment. In the illustrated drum drive gear 33, the photosensitive drum is located on the back side in the drawing. A detection mark 35 is formed on the front face of the drum drive gear 33 as a position detection unit. In the drum drive gear 33, the flat portions other than the detection mark 35 have a center average roughness of Ra32 or less and a sufficiently flat surface as in the conventional gear, whereas only the region of the detection mark 35 is the center. The average roughness is Ra128 or more, and the surface irregularities are large. For example, the surface is lightly rubbed with a rough file and the surface is roughened. When the drum drive gear 33 is rotated by the driving force from the drive motor, the detection mark 35 draws a circumferential path around the rotation axis, and the position detection sensor 34, for example, a reflection type photosensor installed on the apparatus main body 3 side. Is focused on the circumferential orbit of the detection mark 35 and receives the reflected light from this surface to detect the detection mark 35.

  FIG. 4 is a schematic diagram showing a detection state of the position detection sensor. The position detection sensor 34 applies the light from the light emitting element 41 to the detection object, and receives and detects the regularly reflected light by the light receiving element 42. A High signal (hereinafter referred to as H) is returned when the amount of light is a certain amount or more, and a Low signal (hereinafter referred to as L) is returned when the amount of light is less than a certain amount.

  FIG. 5 is a graph showing the output of the position detection sensor when the drum drive gear is rotated once, and FIG. 6 is a schematic diagram showing the light state of the position detection sensor at the detection mark. In the figure, H indicates a state where the amount of light is large, and L indicates a state where the amount of light is small. FIG. 5 shows L when the detection mark 35 passes through the detection position of the reflective photosensor. In a region where the surface has many irregularities, such as the detection mark 35, that is, a region where the surface is rough, the amount of received light is reduced by irregular reflection as shown in FIG. On the other hand, when there is a plane other than the detection mark 35 at the detection position of the reflection type photosensor, as shown in FIG. By paying attention to the change of the position detection sensor 34 from the H signal to the L signal, it is possible to detect the position of the detection mark 35 when the drum drive gear 33 rotates.

  In the prior art, since the filler 12 is necessary for detecting the reference position of the drum driving gear 61 as shown in FIG. 17, the volume of the drum driving gear 61 becomes non-uniform in the circumferential direction, and the drum driving gear 61 provided with the filler 12. In the injection molding, the material needs to flow in excess by the volume of the filler 12, so that the tooth surface region near the portion tends to be closed. That is, since the tooth trace error of the gear tooth surface is partially pulled as shown in FIG. 18, the frequency component of one rotation of the drive gear is transmitted to the surface of the photosensitive member due to the effect of increasing the eccentricity of the drum drive gear.

  On the other hand, the drum drive gear 33 according to the present embodiment includes a detection mark. Since the volume of the detection mark 35 is substantially 0, the volume of the drum drive gear 33 is uniform in the circumferential direction, and the tooth surface is kept from being pulled down to the minimum during injection molding. FIG. 7 is a graph obtained by measuring gear teeth of the gear according to the example. It can be seen that the tooth trace error of the drum drive gear 33 according to this example is close to a perfect circle. According to this example, the eccentricity of the gear can be suppressed to be small, so that the rotational component of the driving gear that is placed on the surface of the photosensitive member at the time of driving transmission is very small, and the color shift of the rotational cycle of the drum is suppressed to be small. be able to.

FIG. 8 is a perspective view showing a drum drive gear according to the second embodiment. In this example, one drum drive gear 33 has detection marks formed at three concentric circles. FIG. 9 is a graph showing the output of the position detection sensor when the drum driving gear according to the second embodiment is rotated once.
According to the present embodiment, the output of the position detection sensor 34 causes the L signal to appear about three times per rotation. That is, since the reference position can be detected within 1/3 rotation of the reference position, the initial detection is faster than the configuration of one detection mark.

  Next, specific rotation reference position detection means in this example will be described. First, the time when the first L signal is detected is stored as a reference position. Next, since the reference position comes after one revolution of the gear, it is determined as the reference position when the L signal is detected for the fourth time. Further, when the L signal is detected for the seventh time, the reference position is determined. When the gear rotates n times in this way, it can be determined that the gear is in the reference position when the L signal is detected for the (1 + 3 × n) (n = 1, 2, 3,...) Times. The above-described example is the case where there are three detection marks, and the same applies when there are more detection marks. When there are k detection marks, it can be determined that the gear is at the reference position when the L signal is detected for the 1 + k × n (n = 1, 2, 3...) Times.

  Next, a drive control method using the above-described position detection sensor will be described. FIG. 10 is a block diagram illustrating a part of an electric circuit of the image forming apparatus according to the embodiment. In the figure, a control unit 150 includes photosensitive drums 1Y, 1M, 1C, and 1K that are electrically connected to each other, an exposure device 7, a paper storage cassette 26, a registration roller pair 28, an intermediate transfer unit 15, a reflective photosensor 69a, 69b, position detection sensors 34Y to 34K, and photoconductor clutches 35Y, 35M, 35, 35C, 35K, and the like. The control unit 150 includes a CPU 150a that performs arithmetic processing, a RAM 150b that stores data, and a DSP (Digital Signal Processor) 150c. The RAM 150b is provided with a phase adjustment program for adjusting the phase of the speed fluctuation of the photosensitive drum based on the detection result of the reflection type photosensor. This program is executed by the CPU 150a or the like, and the control unit 150 performs the phase difference adjustment. It functions as a means.

  FIG. 11 is a schematic diagram showing Y, C, M, and K reference pattern image groups for detecting misalignment. The control unit 150 of the printer A according to the present embodiment corrects a phase difference caused by a periodic rotation speed fluctuation of each photosensitive drum, and performs color misregistration correction. In this color misregistration correction, a reference image, which is a reference visible image, is developed near both ends of each of the photosensitive drums 1Y to 1K, and sequentially transferred to the vicinity of the end of the intermediate transfer belt 8. As a result of this transfer, Y, C, M, and K reference pattern image groups SK, SM, SC, and SY for detecting misregistration are formed at both ends of the intermediate transfer belt 8 as shown in FIG. . Among the reference pattern images, the K reference pattern images (SK1 to SKn) and the C reference pattern images (SC1 to SCn) are reflected on the upper side in the drawing as pattern image detection means as the intermediate transfer belt 8 moves endlessly. Detected by the mold photo sensor 69b. On the other hand, the M reference pattern images (SM1 to SMn) and the Y reference pattern images (SY1 to SYn) are detected by the reflection type photosensor 69a on the lower side in the drawing as the intermediate transfer belt 8 moves endlessly. .

  FIG. 12 is a graph showing the output of the position detection sensor for each color, and FIG. 13 is a graph showing the deviation from the reference position. When forming the reference pattern image group of each color, as shown in FIG. 12, the detection signals of the position detection sensors 34 are aligned, and the reference positions of the photosensitive drums 1Y to 1K of the respective colors are matched. Here, as shown in FIG. 13, the upper reference pattern image SU in the drawing of the intermediate transfer belt 8 is formed by an ideal photosensitive drum having no periodic fluctuation, and the lower reference pattern image in the drawing. SD is assumed to be formed by a photosensitive drum having a rotational speed variation. Since the upper reference pattern image SU in the drawing is created by a photoconductive drum having no rotational speed fluctuation, the reference pattern images SU are formed at equal intervals p. As a result, the detection times ta1, ta2, ta3,... Of the reflective photosensor 69b are equally spaced. On the other hand, each reference pattern image (SD) on the lower side in the figure formed by the photosensitive drum having fluctuations in the rotational speed is displaced in the sub-scanning direction, and the intervals between the reference pattern images SD are not equal.

  As a result, as shown in FIG. 13, the lower reference pattern images (SD2, SD3, SD4) on the lower side of the intermediate transfer belt 8 from the formation position of the ideal reference pattern image (SU) formed on the upper side of the intermediate transfer belt 8. ) Are formed at positions separated by d1, d2, d3, and d4, respectively. As a result, the detection times tb1, tb2, tb3, tb4... Of the reflective photosensor 69a are also different. Therefore, the control unit 150 calculates a deviation amount (d1, d2, d3...) From the reference position of the reference pattern image based on the detection time between the reference pattern images and the moving speed of the intermediate transfer belt 8. By doing so, fluctuations in the rotational speed of the photosensitive drums 1Y to 1K are obtained.

  More specifically, as shown in FIG. 11, the detection time between the reference pattern images of the K color reference pattern image group (SK) formed on the upper side of the intermediate transfer belt 8 is stored in the storage unit in the control unit. . In parallel with this, the detection time between the reference pattern images of the M color reference pattern image group (SM) formed on the lower side of the intermediate transfer belt is stored in the storage unit in the control unit. Based on the detection time of the K color reference pattern image and the moving speed of the intermediate transfer belt 8, the deviation amount (d1, d2, d3...) From the ideal position for the K color reference pattern image is calculated. It is. As a result, the rotational speed fluctuation of the K-color photosensitive drum 1K can be obtained. Further, based on the detection time of the M color reference pattern image and the moving speed of the intermediate transfer belt 8, the registration deviation amount (d1, d2, d3...) From the ideal position for the M color reference pattern image is calculated. Then, the rotational speed fluctuation of the M photoconductor drum 1M is obtained.

  The C reference pattern image group SC formed on the downstream side in the moving direction of the intermediate transfer belt 8 of the K reference pattern image group SK also performs the same processing as described above, thereby performing the C color photosensitive drum 1C. Obtain the rotation speed fluctuation. Further, the Y-color reference image group SY formed on the downstream side in the moving direction of the intermediate transfer belt 8 of the M-color reference pattern image group SM is also subjected to the same processing as described above, so that the Y-color photoconductor drum. The rotational speed fluctuation of 1Y is obtained.

  FIG. 14 is a graph showing fluctuations in the rotational speed of the K-color photosensitive drum and fluctuations in the rotational speed of the M-color photosensitive drum obtained by the calculation. The horizontal axis in FIG. 14 represents the elapsed time since the first reference image of the reference image group was detected by the reflective photosensor, and the vertical axis represents the amount of deviation from the reference position at each elapsed time. As shown in FIG. 14, there is a phase difference B between the rotational speed fluctuation of the K photosensitive drum 1K and the rotational speed fluctuation of the M photosensitive drum 1M. As a result, at a certain elapsed time, the M and K colors Will cause a large color shift. Therefore, the control unit 150 calculates and obtains information on the phase difference B between the M and K colors based on the periodic fluctuations of the K and M photosensitive drums 1K and 1M obtained by the above calculation. Phase adjustment is performed based on the phase difference information.

  FIG. 15 is a flowchart showing the procedure of phase difference adjustment. In this example, as shown in FIG. 15A, when phase difference information is acquired in step 1 and it is determined that phase adjustment is necessary, for example, ± 10 degrees or less is set as a threshold and the range of ± 10 degrees is exceeded. In the case (YES in Step 2), the phase adjustment flow shown in FIG. Here, the phase adjustment is performed by the photoconductor clutches 35Y, 35M, 35, 35C, and 35K provided in the drum drive gear 33 with reference to the phase of the speed fluctuation of the black photoconductor drum 1K. First, when the phase difference between KM is determined in Step 3, the M photoconductor clutch 37M is turned off (= drive is disconnected) (Step 4), and the drive motor 31 is rotated for a time corresponding to the phase difference (Step 5). ), The drive motor 31 is stopped. Next, if it is determined after phase difference between K and C in step 4 (YES in step 6), the C photoconductor clutch 37C is turned off (step 7), and the drive motor 31 is rotated by the time corresponding to the phase difference (step). 8) The drive motor 31 is stopped.

  Finally, if it is determined after the phase difference between KY (YES in Step 9), the Y photoconductor clutch 35Y is turned off (Step 10), and the drive motor 31 is rotated by the time corresponding to the phase difference (Step 11). The drive motor 31 is stopped.

  Here, the process may be terminated, but in the example shown in FIG. 15, the phase difference information is acquired again (step 1), and it is confirmed whether or not the phase adjustment is successful.

  FIG. 16 is a timing chart showing the ON / OFF states of the drive motor and each clutch during phase difference adjustment according to the flowchart shown in FIG. The photoconductor clutch is connected when ON, and disconnected when turned OFF. However, a brake connected when turned OFF and connected may be used instead of the clutch for photoconductor.

  As described above, according to the present embodiment, since the area where the surface shape of the drum drive gear which is the drive transmission member is rough is used as the detection mark, there is no increase / decrease in volume due to the formation of the detection mark. Since the presence of the mark does not affect the gear volume, the pressure distribution and temperature distribution during gear molding become uniform, minimizing gear tooth surface shrinkage, and one rotation during drive transmission Periodic fluctuation components can be reduced.

  Further, since a plurality of detection marks are formed on the circumference of the drum drive gear, a plurality of reference positions can be detected during one rotation of the drum drive gear, so that the initial detection can be accelerated. Further, according to the image forming apparatus according to the present embodiment, since the one-rotation variation can be small in the photosensitive drum driving device, it is possible to reduce the color misregistration of one rotation variation period of the photosensitive drum. It is possible to form a good image without any defects.

1Y, 1M, 1C, 1K: photosensitive drum 2Y: drum cleaning device 3: device main body 4Y: charging device 5Y: developing devices 6Y, 6M, 6C, 6K: process cartridge 7: exposure device 8: intermediate transfer belts 9Y, 9M , 9C, 9K: primary transfer bias roller 10: belt cleaning device 11: photosensitive drum shaft 12: secondary transfer backup roller 13: cleaning backup roller 14: tension roller 15: intermediate transfer unit 19: secondary transfer roller 20: Fixing device 26: Paper storage cassette 27: Paper feed roller 28: Registration roller pair 29: Paper discharge roller pair 31: Drive motors 31Y, 31M, 31C, 31K: Drive motor 33: Drum drive gears 33Y, 33M, 33C, 33K: Photosensitive drum drive transmission gear 34: position detection sensors 34Y, 34M, 4 C, 34K: Position detection sensor 35: Detection mark 36: Image reading sensor 37Y, 37M, 37, 37C, 37K Photosensitive member clutch 41: Light emitting element 42: Light receiving element 50a: Stack part 51: Bottle storage part 52Y, 52M , 52C, 52K: Toner bottle 69a: Reflective photo sensor 69b: Reflective photo sensor 150: Control unit 150a: CPU
150b: RAM
150c: DSP
A: Printer B: Phase difference C: C Photosensitive drum clutch L: Laser light P: Paper SK, SM, SC, SY: Reference pattern image group

JP-A-9-146329 JP 2001-305820 A JP 2006-208916 A

Claims (5)

A drive transmission unit coupled to the driven member, a driving means for rotationally driving the driven member via the drive transmission unit, a position detection unit disposed in the drive transmission unit, and detecting the position detection unit And a position detecting means for detecting the rotational position of the driven member,
A drive transmission device characterized in that a region where the surface state of the drive transmission member is roughened is formed as the detection unit.   The drive transmission device according to claim 1, wherein there are a plurality of the detection units on the circuit.   An image forming apparatus comprising the drive transmission device according to claim 1.   4. The image forming apparatus according to claim 3, wherein the driven member is an image carrier.   Control means for controlling each of the driving means is provided so as to adjust a phase difference between the plurality of image carriers based on a plurality of detection results detected by the position detecting means by the driving device. The image forming apparatus according to claim 4.