JP4333402B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a technique for preventing rotation unevenness of an image carrier in an image forming apparatus or a color toner image formed on a plurality of image carriers in a color image forming apparatus to a transfer medium such as an intermediate transfer body. The present invention relates to a technique for preventing color misregistration during transfer.

  The color image forming apparatus has an image carrier for each primary color of yellow (Y), magenta (M), cyan (C), and black (K), and forms a toner image of each color with each image carrier. This is superimposed on an intermediate transfer member, and a toner image with four colors superimposed is transferred onto transfer paper to form a color image.

  Each image carrier constitutes an image forming unit having a charging device, a developing device, a transfer device, a cleaning device, etc., and the image forming unit for each color and the intermediate transfer member are integrated into a process. The cartridge is configured. This process cartridge can be pulled out from the main body of the image forming apparatus, and each image carrier unit and developing device can be attached to and detached from the process cartridge while the process cartridge is pulled out.

  The toner images of the respective colors formed by the image forming portions of the respective colors are sequentially transferred onto a rotating intermediate transfer body by a transfer device, and a combined color image is formed. In order to create a color image without color misregistration, it is necessary to superimpose the next toner image on the previous toner image.

  For this purpose, the linear velocities of the transfer medium such as the image carrier and the intermediate transfer member when transferring the toner image need to match with high accuracy. This is because a difference in linear velocity between the two causes a color shift or an image shift.

  Each image carrier is driven by a driving device provided for each image carrier. The driving device transmits the rotation reduced from the main motor through the plurality of gears to the rotating shaft. The rotating shaft penetrates through the cylindrical image carrier so as to be freely inserted and removed, and is supported by a bearing on the opposite side to rotate the image carrier.

  Since the image carrier receives the rotation from the main motor through the gear train composed of a plurality of gears as described above, all the accuracy of each gear is required, and from the influence of the accumulated tolerance of each gear, Although it is slight, uneven rotation occurs. On the other hand, since the intermediate transfer member is also driven by the same driving means, there is rotation unevenness. Therefore, even if the linear speeds of the image carrier and the intermediate transfer body are matched, if uneven rotation occurs, the image at that time is blurred.

  On the other hand, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-112194), transmission of rotation from the rotation shaft to the image carrier is directly connected to one large gear connected via a fitting member. The large gear bearing has a coupling shape in which the fitting portion of the fitting member is fitted. With such a configuration, the main motor to the image carrier are decelerated by one large gear, and the influence of cumulative tolerance can be reduced by reducing the number of gears, thereby improving rotation unevenness.

However, although the rotation unevenness can be improved, it does not become zero. In the color image forming apparatus, since the intermediate transfer member also has rotation unevenness, the above-described configuration cannot prevent rotation unevenness that occurs during transfer to the intermediate transfer member.
JP, 2000-112194, A, Claim 0003, Paragraph 0010, FIG.

  The present invention has been conceived from the above facts. In an image forming apparatus having an image carrier, the rotational unevenness of the image carrier is reduced, or the linear velocity is almost the same as that of a transfer medium such as an intermediate transfer member. An object of the present invention is to provide an image forming apparatus that can hold the image forming apparatus.

In order to achieve the above object, an image forming apparatus according to a first invention of the present application is an image forming apparatus for transferring rotation of a driving unit to an image carrier to transfer a toner image onto a transfer medium. image and carrier are connected by couplings, have a play in the connection portion of the coupling, said coupling image carrier-side coupling is constituted by a drive means side coupling, at least one of the coupling A hollow cylindrical portion having a rotary shaft loosely fitted in the hollow cylindrical portion, and a coupling in which the rotary shaft loosely engages with the rotary shaft in a state where there is no play in the rotational direction; A plurality of convex portions extending in the axial direction of the rotation shaft are formed, a plurality of concave portions are formed in the other coupling, and the convex portions are loosely fitted into the concave portions so as to have the play, and from the one coupling The other When transmitting the rotation to the pulling, is characterized in that said a plurality of projections and recesses is into contact simultaneously with two or more positions in the rotational direction of the rotary shaft.

According to a second aspect of the present invention, there is provided an image forming apparatus in which rotation of a driving unit is transmitted to an image carrier to transfer a toner image onto a transfer medium. The driving unit and the image carrier are coupled by a coupling. The coupling has a play, and the coupling comprises an image carrier side coupling and a driving means side coupling, and at least one coupling has a hollow cylindrical portion, A rotary shaft is loosely fitted in the hollow cylindrical portion, and a plurality of convex portions extending in the axial direction of the rotary shaft are formed in the coupling in which the rotary shaft is loosely fitted, and a plurality of concave portions are formed in the other coupling, and the play When the convex part loosely fits in the concave part and transmits rotation from one coupling to the other coupling, the plurality of convex parts and the concave part are two or more places in the rotational direction of the rotating shaft. Same Contact, is characterized to include the central axis of the coupling to the extension plane of the abutment surface of the abutting points on.

An image forming apparatus according to a third invention of the present application is characterized in that there are a plurality of the image carriers, and the respective toner images are transferred to a transfer medium and superimposed .

The image forming apparatus according to a fourth invention of this application, [phi] D the diameter of the hollow cylindrical portion of the coupling of the one, the outer diameter of the rotary shaft when the .phi.d, contact portions of the plurality of the protrusions recess It is characterized in that (φD−φd) is set to be larger than the accumulated amount of component tolerances.

An image forming apparatus according to a fifth invention of the present application is characterized in that the convex portion is a nail and the concave portion is a space between the nail and the nail .

An image forming apparatus according to a sixth invention of the present application is characterized in that both the couplings have hollow cylindrical portions, and a rotation shaft common to both hollow cylindrical portions penetrates .

[Action]
When the rotation of the motor or the like is transmitted to the image carrier through a gear train or the like, a driving unit such as a motor and the image carrier are connected by a coupling. According to the first invention of the present application, since there is play in this coupling, even if an error such as eccentricity occurs between the drive shaft and the driven member, it is not necessary to deteriorate the rotation unevenness.

  In the case of a color image forming apparatus, a plurality of image carriers are provided, and a toner image of each image carrier is transferred to a transfer medium such as an intermediate transfer member. At the time of transfer, both of them are rotating in close contact with each other. However, uneven rotation may occur in the driving means of the image carrier, or uneven rotation may occur on the intermediate transfer member side. Even in such a case, in the second invention of the present application, since the rotation unevenness of the image carrier can be suppressed to be small by the play of the coupling, the image carrier can follow the transfer medium. The image is rotated at the same linear speed without shifting from the transfer medium, and no image shift occurs.

  When the locking portion and the locked portion are loosely fitted, when the rotation is transmitted from one coupling to the other coupling, the plurality of locking portions and the locked portion are at least at one place. Although it is possible to make contact, it is difficult to make contact at two locations because of the manufacturing accuracy and position accuracy of the parts. On the other hand, the rotation center of the image carrier is different from the rotation axis and the center of the coupling due to the cleaning blade and its own weight. Therefore, if the contact is made only at one place, the center position of the rotation changes and the rotation unevenness is increased. On the other hand, in the third invention of the present application, in addition to the loose fitting of the locking portion and the locked portion, the rotating shaft and the coupling are loosely fitted. It is possible to make contact at two or more locations at the same time, the rotation center position does not change, and rotation unevenness can be absorbed.

  In the fourth invention of the present application, the difference (φD−φd) between the hollow cylindrical portion inner diameter φD and the rotation shaft outer diameter φd is made larger than the amount of accumulated component tolerances of the plurality of locking portions and the locked portions. Thus, the locking portion and the locked portion can be simultaneously brought into contact with each other at two or more locations, the rotation center position does not change, and rotation unevenness can be absorbed.

  In the fifth invention of the present application, the pin is attached to the rotating shaft so that both ends thereof protrude, and both ends of the pin are inserted through the elongated holes of the coupling. The diameter of the pin is smaller than the width of the long hole, so that a gap is formed between the pin and the long hole. When relative rotation is applied between the coupling and the rotating shaft, both ends of the pin move in opposite directions in the slot. At this time, since there is a gap between the rotation shaft and the hollow cylindrical portion in addition to the gap between the pin and the long hole, both end portions of the pin can simultaneously contact the side surface of the long hole, and the rotation center does not move. Therefore, rotation unevenness can be reduced.

  In the sixth invention of the present application, when the inner diameter of the hollow cylindrical portion of the one coupling is φD and the outer diameter of the rotating shaft is φd, the component tolerance of the contact portion between the two pins and the rotating shaft is determined. By setting (φD−φd) to be larger than the accumulated amount, the pin and the contact portion of the rotating shaft can be in contact with each other at two or more locations at the same time. Can be absorbed.

  In the seventh invention of the present application, there is no play in the rotating direction between the rotating shaft and the coupling in which the rotating shaft is loosely fitted. The plurality of convex portions formed on one coupling are loosely fitted into the plurality of concave portions formed on the other coupling to couple the coupling. Due to the gap between the convex portion and the concave portion and the gap between the hollow cylindrical portion and the rotation shaft, the convex portion and the concave portion can be simultaneously contacted at two or more places, and the rotation center is not moved. Therefore, rotation unevenness can be reduced.

  In the eighth invention of the present application, when the convex portion loosely fits in the concave portion and transmits rotation from one coupling to the other coupling, the plurality of convex portions and the concave portion are simultaneously in contact at two or more locations, Since the center axis of the coupling is included in the extended surface of the contact surface at the contact point, the force in the rotational direction can be stably and efficiently transmitted between the couplings, and rotation unevenness is further reduced. Can be reduced.

  In the ninth invention of the present application, when the inner diameter of the hollow cylindrical portion of the one coupling is φD and the outer diameter of the rotating shaft is φd, the component tolerance of the contact portions of the plurality of convex portions and the concave portions is reduced. By setting (φD-φd) to be larger than the accumulated amount, the convex part and the concave part can be in contact with each other at two or more locations at the same time, the rotation center position does not change, and rotational irregularities are absorbed. can do.

  According to the tenth invention of the present application, since the convex portion and the concave portion can be formed by forming the claw having the same shape in both couplings, the configuration is simplified.

  In the eleventh aspect of the present invention, since the image carrier side coupling and the driving means side coupling are coupled by a single rotating shaft, coupling coupling is stable.

  According to the present invention, in the image forming apparatus that transmits the rotation of the driving unit to the image carrier, the driving unit and the image carrier are connected by a coupling, and play is provided at a connection portion of the coupling. Since the rotation irregularity of the body is reduced, the color image forming apparatus can obtain an image having no color misregistration. Further, in the case of a monochrome image forming apparatus, the rotation unevenness of the image carrier is reduced, so that an image with little distortion can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a color image forming apparatus according to an embodiment of the present invention. The color image forming apparatus shown in FIG. 1 is called a tandem type color image forming apparatus, and includes an automatic document feeder 30, an image reading device 60, image writing devices 3Y, 3M, 3C, 3K, an image carrier 1Y, 1M, 1C, 1K, charging devices 2Y, 2M, 2C, 2K, developing devices 4Y, 4M, 4C, 4K, fixing device 24, belt-like intermediate transfer body 6, paper feeding means 21A, 21B, 21C, transport system 22 Etc.

  The automatic document conveying means 30 is means for automatically conveying a double-sided or single-sided original d. The image reading device 60 is a device in which image information is read by a movable optical system, and the contents of a large number of documents d fed from the document table are reflected by three movable mirrors 60C, and a condensing lens. With 60B, an image is formed on an image sensor 60A made of a CCD and read.

  The image forming unit 10Y that forms a yellow image includes a charging device 2Y, an image writing device 3Y, a developing device 4Y, and a cleaning device 8Y disposed around an image carrier 1Y as an image forming body. The image forming unit 10M that forms a magenta image includes an image carrier 1M as an image forming body, a charging device 2M, an image writing device 3M, a developing device 4M, and a cleaning device 8M. The image forming unit 10C that forms a cyan image includes an image carrier 1C as an image forming body, a charging device 2C, an image writing device 3C, a developing device 4C, and a cleaning device 8C. The image forming unit 10K that forms a black image includes an image carrier 1K as an image forming body, a charging device 2K, an image writing device 3K, a developing device 4K, and a cleaning device 8K. The charging device 2Y and the image writing device 3Y, the charging device 2M and the image writing device 3M, the charging device 2C and the image writing device 3C, and the charging device 2K and the image writing device 3K constitute a latent image forming unit.

  The intermediate transfer member 6 is an endless belt, is stretched by a plurality of rollers, and is rotatably supported.

  A signal of image information formed on the image sensor 60A is sent to an image processing unit (not shown). The image processing unit performs analog processing, A / D conversion, shading correction, image compression processing, and the like, and then sends a signal for each color to the image writing devices 3Y, 3M, 3C, and 3K.

  In the image writing apparatuses 3Y, 3M, 3C, and 3K, a semiconductor laser is used as a laser light source, and a light beam emitted from the semiconductor laser is formed into a scanning light beam by an optical element such as a polygon mirror to form an image as a scanned object. It enters the carriers 1Y, 1M, 1C, 1K and forms an electrostatic latent image of each color.

  The respective color images formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating intermediate transfer body 6 by transfer devices 7Y, 7M, 7C, and 7K as primary transfer devices (1). Next transfer), a synthesized color image is formed. The recording paper P stored in the paper feed cassettes 20A, 20B, and 20C is fed by the paper feed means 21A, 21B, and 21C, passes through the transport system 22, and is timed by the registration roller 23 as a secondary transfer device. Is transferred to the transfer device 7A, and a color image is transferred onto the recording paper P (secondary transfer). The recording paper P onto which the color image has been transferred is fixed by the fixing device 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer device 7A, the intermediate transfer body 6 from which the recording paper P has been separated is cleaned by the cleaning device 8A.

  5Y, 5M, 5C, and 5K are toner replenishing units that replenish new toner to the developing devices 4Y, 4M, 4C, and 4K, respectively.

  FIG. 2 is a perspective view showing from the driving means of the image carrier 1 (showing any one of 1Y, 1M, 1C, 1K) to the driving means side coupling. FIG. 3 is an exploded perspective view of the periphery of the driving means side coupling in FIG. 2 as seen from a slightly different angle. The drive unit 100 contains a gear train and the like, and transmits the reduced speed rotation to the rotary shaft 110 by a main motor (not shown).

  A driving means side coupling 120 is attached to the rotating shaft 110. The driving means side coupling 120 is formed on one end side of the hollow cylindrical portion 121 so that the two claws 122 and 122 face each other as convex portions, and the two concave portions 123 and 123 between the claws 122 and the claws 122 are formed. Is formed. The main body 121 is formed with a long hole 124 extending in the axial direction. A through hole 111 is formed in the rotating shaft 110 so as to overlap the elongated hole 124. The drive means side coupling 120 is inserted from the tip of the rotating shaft 110, and the long hole 124 and the through hole 111 are overlapped. Next, when the pin 125 is inserted into the through hole 111, both ends of the pin 125 protrude to both sides of the driving means side coupling 120. When the E-rings 126 and 126 are fitted in the grooves 125a and 125a so that the grooves 125a and 125a at both ends of the pin 125 are substantially the same height as the outer peripheral surface of the main body 121, the drive means side coupling 120 is shown in FIG. As shown in FIG.

  Before the drive means side coupling 120 is inserted into the rotating shaft 110, a coil spring 112 is inserted, and when the drive means side coupling 120 is fitted to the image carrier side coupling 130, the couplings of both couplings are combined. Energize to hold.

  FIG. 4 is a perspective view illustrating a state before the coupling 150 including the driving unit side coupling 120 and the image carrier side coupling 130 is fitted. The rotation axis 110 is represented by an imaginary line so that the configuration of the image carrier side coupling 130 can be easily understood.

  The image carrier side coupling 130 is made of metal, is fitted into both ends of the cylindrical image carrier 1 and is integrated, and has a shape complementary to the drive means side coupling 120. That is, the image carrier side coupling 130 has two claws 132 and 132 as convex portions and two concave portions 133 and 133 formed therebetween. The claws 132, 132 are fitted into the recesses 123, 123 of the drive means side coupling 120, and the claws 122, 122 of the drive means side coupling 120 are fitted into the recesses 133, 133.

  5A and 5B show a state in which the coupling 150 is fitted, in which FIG. 5A is a cross-sectional view at the positions of the claws 122 and 132 of both couplings, and FIG. 5B is a cross-sectional view at the position of the pin 125. In order to fit the coupling 150, the rotating shaft 110 is inserted through the central hole of the image carrier side coupling 130. The rotating shaft 110 penetrates the cylindrical image carrier 1. Next, either the rotating shaft 110 or the image carrier 1 is rotated, and the claw 122 of the driving means side coupling 120 and the claw 132 of the image carrier side coupling 130 are aligned and pushed. When the coupling 150 is fitted, the tip of the rotating shaft 110 protruding from the opposite side of the image carrier 1 is fitted to and supported by a bearing (not shown) provided on the frame. Due to the urging force of the coil spring 112, the drive means side coupling 120 advances and retreats in the axial direction along the long hole 124, and the coupling 150 can maintain the fitted state.

  In the conventional coupling, when both couplings are fitted, the fitting portions of the claws 122 and 132 and the recesses 123 and 133, the fitting portion of the long hole 124 and the pin 125, the rotating shaft 110 and both the couplings 120, All 130 fitting parts are fitted with no gaps.

  On the other hand, the present invention is characterized in that there is play in the fitting of the coupling 150. That is, the fitting between the long hole 124 and the pin 125 and the fitting between the driving means side coupling 120 and the rotating shaft 110 are loose fitting. This loose fitting will be described in detail below.

  As shown in FIG. 5A, the claw 122 of the driving means side coupling 120 and the claw 132 of the image carrier side coupling 130 are fitted with no gap. This is the same as a normal coupling fitting state.

  In contrast, as shown in FIGS. 5A and 5B, there is a relationship of D = d + 2γ between the hole diameter D of the drive means side coupling 120 and the diameter d of the rotating shaft, and the radius (one side) ) A gap γ is provided. Further, as shown in FIG. 5B, a gap on one side δ is provided between the pin 125 and the long hole 124. The present invention is characterized in that the coupling 150 is thus provided with the gaps γ and δ so as to be loosely fitted.

  Due to the gaps γ and δ, even when rotation unevenness occurs due to various causes such as a gear pitch error in the rotation transmitted from the driving unit 100 to the rotating shaft 110, the rotation unevenness can be absorbed. This will be described in more detail below.

  FIG. 6A shows the case where γ≈0. Although the clearance between the rotating shaft 110 and the drive means side coupling 120 is substantially zero, it is assumed that they can rotate with each other. In FIG. 6A, when the rotation shaft 110 is rotated by a slight angle in the counterclockwise direction with respect to the drive means side coupling 120, the position of the pin 125 and the long hole 124 and the processing accuracy vary. The upper end of the pin 125 that is the locking portion is in contact with the side surface of the long hole 124 as the locked portion on the left side A in the figure, but the lower end of the pin 125 that is the other locking portion is the long hole 124 on both the left and right sides. It is in a state separated from both sides. Here, an error of the engaging portion caused by accumulation of component tolerances such as variations in position and machining accuracy is assumed to be δ1. In this way, if the locking portion and the locked portion are in contact with only one place, the rotation center is shifted and rotation unevenness is increased. When the backlash of the coupling is small, such one point is likely to occur.

  The center of rotation of the image carrier 1 is different from that of the rotating shaft 110 and the coupling 150 due to a cleaning blade and its own weight. If the backlash is small, only one of the two transmission points is used, so that the rotation center moves from the rotation center of the image carrier 1, and the rotation unevenness is worsened.

  On the other hand, in FIG. 6B, since there is a difference in diameter 2γ satisfying the condition of 2δ <2γ between the rotating shaft 110 and the driving means side coupling 120, the rotating shaft 110 is in the driving means side coupling 120. The upper end of the pin 125 as a locking portion abuts on the left side B of the long hole 124 as a locked portion, and the lower end of the pin 125 as another locking portion is the right side of the long hole 124 It can abut on B ′. As described above, the two locking portions are simultaneously brought into contact with the locked portion, so that the rotation center can be prevented from being moved and the rotation unevenness can be suppressed to be small. Δ shown here is set corresponding to δ1 in FIG. 6A, and δ1 ≦ δ.

  FIG. 7 is a cross-sectional view at the position of the claw in a state where the coupling is fitted in another embodiment. The claw 122 of the drive means side coupling 120 and the claw 132 of the image carrier side coupling 130 are loosely fitted with a gap 2γ. Although not shown, the gap between the pin 125 and the long hole 124 shown in FIG. Therefore, all the rotations of the rotating shaft 110 are transmitted to the drive means side coupling 120.

  FIG. 7A shows the case where γ = 0. In FIG. 7A, when the drive means side coupling 120 is rotated by a slight angle counterclockwise with respect to the image carrier side coupling 130, the positions of the claws 122 and the claws 132 and the processing accuracy vary. The upper side of the nail 122 which is one locking part abuts on the nail 132 as the locked part in FIG. B, but the lower side of the nail 122 which is the other locking part is separated from the nail 132. It has become. Here, an error of the engaging portion that has occurred due to variations in position and processing accuracy is represented by δ2.

  In this way, if the locking portion and the locked portion are in contact with only one place, the rotation center is shifted and rotation unevenness is increased.

  FIG. 7B shows a state in which the rotating shaft 110 is slightly rotated counterclockwise with respect to the driving means side coupling 120. Since the gap between the pin 125 and the long hole 124 is zero, the rotation of the rotating shaft 110 is directly transmitted to the driving means side coupling 120. Then, the claws 122 and 122 come into contact with the claws 132 and 132. In this embodiment, since there is a gap 2γ that satisfies the condition of δ2 <2γ between the rotating shaft 110 and the hollow cylindrical portion 121 of the driving means side coupling 120, the claw 122 as the locking portion and the locked portion The claw 132 can be press-contacted at two points C and C ′. Further, a gap of δ3 is provided between the claw 122 and the claw 132. This δ3 is set corresponding to δ2 in FIG. 7A, and δ2 ≦ δ3.

  In this embodiment, when the rotation is transmitted from the claw 122 to the claw 132, as shown in FIG. 7B, the contact surfaces C and C ′ extended by the contact between the claw 122 and the claw 132 are obtained. It is desirable to design so that the central axis O of the coupling 150 of the rotating shaft 110 is included therein. As shown in FIG. 7B, if there are two claws at an interval of 180 ° and there are two contact surfaces C and C ′, the contact surfaces C and C ′ and the central axis O of the coupling are the same. It is included in the plane m. When there are three or more claws, it is designed to abut at least two of the claws and to include the central axis O of the coupling within the extended surface of each abutment surface. In general, when two contact surfaces are not included in one plane, the coupling center axis O may be included in the extended surface of each contact surface. By doing in this way, the force of the rotation direction of the rotating shaft 110 can be efficiently transmitted in a stable state from the claw 122 to the claw 132, and rotation unevenness can be further reduced.

  When the image carrier 1 is in close contact with a transfer medium such as the intermediate transfer member 6 to transfer the toner image, there is no play in the conventional coupling, and therefore rotation unevenness is likely to occur in the image carrier. The image carrier 1 during transfer and the intermediate transfer member 6 are misaligned, causing image defects.

  In the case of a monochrome image forming apparatus, when there is no play in the coupling, the image carrier 1 is unevenly rotated, causing image defects.

  In contrast, in the present invention, since the rotation of the image carrier 1 can be suppressed by the action of the gap γ, the image carrier 1 is kept in close contact with the intermediate transfer member 6 at the same linear velocity. Now you can rotate. In the case of monochrome, the image carrier 1 can be rotated while maintaining a constant linear velocity. Therefore, it was possible to reduce monochrome image defects and color shifts in color images.

  Further, when the connection with play as described above is used, the coupling 150 can be easily assembled. Further, the configuration of the driving means side coupling 120 and the image carrier side coupling 130 shown in the above-described embodiment is simple, the manufacturing cost is low, and the assembly is easy.

  In the above configuration, the intermediate transfer member 6 is illustrated as the transfer medium, but transfer paper may be used. Further, the configuration in which the pin 125 is inserted into the through-hole 111 of the rotating shaft 110 and fitted into the pin 125 and the long hole 124 and the engagement of the claw 122 and the claw 132 are illustrated, but the present invention is not limited to these forms. .

  For example, a locking portion that replaces the through-hole 111 and the pin 125 is provided on the rotating shaft 110, and a locked portion that replaces the long hole 124 is provided on the drive means side coupling 120 so that both are loosely fitted. .

  The locking portion and the locked portion may be a protrusion formed on one of the rotating shaft 110 and the driving means side coupling 120 and a recess formed on the other. Further, the rotation shaft 110 may be provided in either one of the driving means side coupling 120 and the image carrier side coupling 130, and does not need to penetrate both.

  In the present invention, it is important that the connecting portion of the coupling 150 is free to play and can be contacted at two locations. Therefore, in the said Example, it is set as the structure which loosely fits both fitting with the long hole 124 and the pin 125, and fitting with the drive means side coupling 120 and the rotating shaft 110. FIG. However, either one of them may be used. Moreover, you may use combining the loose fitting structure of the pin 125 and the long hole 124 which are shown in FIG.6 (b), and the loose fitting structure of the nail | claw 122 and the nail | claw 132 which are shown in FIG.

  Moreover, although it is a value of 2γ, it is preferably within a range of 0.03 to 0.5 mm, and more preferably within a range of 0.05 to 0.4 mm. This is because if it is less than 0.03 mm, absorption of rotation unevenness may be insufficient, and if it exceeds 0.5 mm, it becomes impossible to follow the driving of the rotating shaft 110.

  8 uses two types of couplings shown in FIGS. 5A and 7 for the image carrier of three colors Y, M, and C among four colors Y, M, C, and K. It is a diagram which shows a position shift when using the conventional coupling without backlash only. The gaps δ and δ3 were both 50 μm. The three colors of Y, M, and C using a loose coupling change almost coincident and there is almost no deviation between the colors. That is, the image carriers 1Y, 1M, and 1C can follow the rotation of the intermediate transfer member 6 within a slight error. On the other hand, 1K was not able to follow the rotation of the intermediate transfer member 6 and was greatly displaced.

  FIG. 9 shows a case where a coupling having a large backlash is attached to the coupling of the K image carrier 1K as well as other colors. It can be seen that the four colors Y, M, C, and K coincide and follow the rotation of the intermediate transfer member 6.

  FIG. 10A is a diagram showing the relationship between the change in the value of 2γ and the maximum color misregistration amount when δ = 50 μm, and FIG. 10B is a diagram when δ3 = 50 μm. In any case, when 2γ is less than 50 μm, the color shift increases abruptly, but when it is 50 μm or more, the color shift is almost zero up to 320 μm.

  In the above-described embodiment, the play function of the coupling 150 is provided to the driving means side coupling 120. However, a recess corresponding to the long hole 124 may be formed in the image carrier side coupling 130. However, since processing becomes difficult, it can be said that it is preferable to form the driving means side coupling 120 as in the embodiment.

1 is a diagram illustrating a color image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view showing the drive from the image carrier driving means to the driving means side coupling. It is the disassembled perspective view which looked at the drive means side coupling peripheral part of FIG. FIG. 4 is a perspective view showing a state before coupling of a coupling composed of a driving means side coupling and an image carrier side coupling. It is a figure of the state which the coupling fitted, (a) is sectional drawing in the position of the nail | claw of both couplings, (b) is sectional drawing in the position of a pin. (A) is a cross-sectional view at the position of the pin, and when the gap γ≈0, (b) is when the gap γ is present. (A) is sectional drawing in the position of the nail | claw in the state in which the coupling was fitted in another Example, (b) is sectional drawing of the state in which the rotating shaft rotated a little counterclockwise. FIG. 7 is a diagram showing a positional deviation when the coupling of the present invention is used for the image carrier of three colors Y, M, and C and a conventional coupling without backlash is used only for K. It is a diagram which shows position shift when using the coupling of this invention for all four colors. (A) is a diagram showing the relationship between the change in the value of 2γ and the maximum color misregistration amount when δ = 50 μm, and (b) is a diagram when δ3 = 50 μm.

Explanation of symbols

1 Image carrier 6 Intermediate transfer member (transfer medium)
DESCRIPTION OF SYMBOLS 100 Drive means 110 Rotating shaft 111 Through-hole 120 Drive means side coupling 121 Hollow cylindrical part 122 Claw (convex part)
123 Recess 124 Long hole (locked part)
125 pin (locking part)
130 Image carrier side coupling 132 Claw (convex part)
133 Recess 150 Coupling

Claims (6)

In the image forming apparatus for transferring the rotation of the driving means to the image carrier and transferring the toner image to the transfer medium,
The drive means and the image bearing member is connected by a coupling, we have a play in the connection portion of the coupling,
The coupling comprises an image carrier side coupling and a drive means side coupling;
At least one of the couplings has a hollow cylindrical portion, and the rotary shaft is loosely fitted in the hollow cylindrical portion,
The coupling in which the rotary shaft is loosely engaged is engaged with the rotary shaft in a state where there is no play in the rotational direction,
A plurality of convex portions extending in the axial direction of the rotation shaft are formed on one coupling,
A plurality of recesses are formed in the other coupling,
When the convex part loosely fits in the concave part so as to have the play and the rotation is transmitted from one coupling to the other coupling, the plurality of convex parts and the concave part are 2 in the rotational direction of the rotating shaft. An image forming apparatus characterized by being in contact at the same time at more than one location . In the image forming apparatus for transferring the rotation of the driving means to the image carrier and transferring the toner image to the transfer medium,
The driving means and the image carrier are connected by a coupling, and there is play in a connection portion of the coupling;
The coupling comprises an image carrier side coupling and a drive means side coupling;
At least one of the couplings has a hollow cylindrical portion, and the rotary shaft is loosely fitted in the hollow cylindrical portion,
A plurality of protrusions extending in the axial direction of the rotating shaft are formed in the coupling in which the rotating shaft is loosely fitted,
A plurality of recesses are formed in the other coupling,
When the convex part loosely fits in the concave part so as to have the play and the rotation is transmitted from one coupling to the other coupling, the plurality of convex parts and the concave part are 2 in the rotational direction of the rotating shaft. An image forming apparatus, wherein a central axis of a coupling is included in an extended surface of an abutting surface of the abutted portion at the same time at a portion or more . 3. The image forming apparatus according to claim 1, wherein there are a plurality of the image carriers, and the respective toner images are transferred to a transfer medium and superimposed. ΦD a pore size of hollow cylindrical portion of the coupling of the one, the outer diameter when the φd of the rotary shaft, than the amount piled component tolerances of the contact portion of the plurality of the convex portion recess (Faidi- The image forming apparatus according to claim 1, wherein φd) is set to be large. The image forming apparatus according to claim 1 , wherein the convex portion is a nail and the concave portion is a space between the nail. 6. The image forming apparatus according to claim 1, wherein both of the couplings have hollow cylindrical portions, and a rotation shaft common to both of the hollow cylindrical portions penetrates.

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