JP2005274970A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, enabling cost reduction by changing drive of a plurality of rollers with few one-way clutches in image formation of full color and image formation of monochrome and simplifying the constitution. <P>SOLUTION: The image forming apparatus is provided with a plurality of image forming parts, mutually forming color-different images. The plurality of the image forming parts are provided with image carriers and developing rollers for developing electrostatic latent images formed on the image carriers, respectively. The image carrier and the developing roller of each image forming part is driven by different drive motors provided on the image-forming apparatus body side. The rotating directions of the drive motors for driving a plurality of the developing rollers are changed by switching to normal rotation and to reverse rotation to switch to driving of all the developing rollers in full color image formation, so as to switch to driving of the monochrome developing rollers in monochrome image formation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus capable of forming a color image, such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions, to which an electrophotographic system is applied, and more particularly, a plurality of images that form images having different colors. The present invention relates to a driving mechanism of a so-called tandem type image forming apparatus in which forming units are arranged in parallel.

JP 2002-6579 A JP 2002-341621 A

  Conventionally, as an image forming apparatus capable of forming a color image such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions to which this type of electrophotographic method is applied, there are mutually used yellow, magenta, cyan, black, etc. A so-called tandem type in which a plurality of image forming portions that form images of different colors are arranged in parallel is widely used.

  In such a tandem image forming apparatus, the photosensitive drum provided in each color image forming unit such as yellow, magenta, cyan, black, and the developing roll of the developing device are driven to rotate. Thus, by providing independent drive motors or switching the driving force of the drive motors by turning on / off the electromagnetic clutch, a development roll used for full-color image formation and a development roll used for monochrome image formation are used. Configured to communicate.

  However, in the tandem image forming apparatus, if a drive motor or an electromagnetic clutch is frequently used, the cost increases, the configuration of the drive circuit becomes complicated, and there is a disadvantage in terms of power consumption. Yes.

  Therefore, as a technique that can solve such a problem, for example, those disclosed in Japanese Patent Application Laid-Open Nos. 2002-6579 and 2002-341621 have already been proposed.

  In the tandem full-color image forming apparatus according to Japanese Patent Application Laid-Open No. 2002-6579, a monochrome image forming area for forming a monochrome image and at least one color image forming area for forming a color image convey transfer paper. A tandem type that is arranged side by side on a transfer belt and includes a developing unit and a photosensitive drum each having a developing roller that supplies toner of a predetermined color onto the developing area for each image forming area. In a full-color image forming apparatus, when forming a full-color image, both the photosensitive drum and the developing roller in the developing device are driven and rotated in both the monochrome image forming area and the color image forming area, thereby forming a monochrome image. Sometimes, in the monochrome image forming area, both the photosensitive drum and the developing roller in the developing device are driven and rotated, and In over the image forming area, although the photosensitive drum is driven to rotate, the developing roller in the developing device, which is constituted so as to rotated at a low speed as compared with the time of driving the rotation by not or full-color image formation.

  The image forming apparatus according to Japanese Patent Application Laid-Open No. 2002-341621 includes a driving unit for driving a plurality of the photoconductors in an image forming apparatus including a plurality of photoconductors for each color, and the driving unit. The plurality of photoconductors are selectively driven by switching between forward driving and reverse driving.

  However, the conventional technique has the following problems. That is, in the case of the tandem type full-color image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2002-6579, the driving gear is moved during monochrome image formation, so that the driving of the color developing device is released. However, there is a problem that the configuration for moving the drive gear is complicated and the cost is increased.

  In the case of the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2002-341621, a worm gear is used as a driving means for driving a plurality of photosensitive members, and the photosensitive member is provided by a one-way clutch built in the worm gear. However, when the worm gear is used, there is a problem that the transmission efficiency of the gear is very poor and the load of the drive motor becomes large.

  Further, in the case of the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2002-341621, as many as five one-way clutches are used to switch the driving of a plurality of photosensitive members, the configuration becomes complicated and the cost is high. Had the problem of becoming. In the case of the image forming apparatus according to Japanese Patent Laid-Open No. 2002-341621, a method of switching the driving of a plurality of photoconductors is employed, and the driving is transmitted from the photoconductor gear to the developing roll. However, in such a configuration, the influence of the developing roll drive tends to appear as rotation unevenness of the photoconductor, which is a disadvantageous configuration for obtaining a good quality image. It was.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to drive a plurality of developing rolls during full-color image formation and monochrome image formation. Can be switched with a small number of one-way clutches, the structure can be simplified and the cost can be reduced, and a plurality of developing rolls can be driven separately from the image carrier to obtain good image quality. An object of the present invention is to provide an image forming apparatus that can be used.

In order to solve the above problems, the invention described in claim 1 includes a plurality of image forming units that form images of different colors, and the plurality of image forming units include an image carrier and the image. A developing roller for developing the electrostatic latent image formed on the carrier is provided, and the image carrier and the developing roller of each image forming unit are driven by different drive motors provided on the image forming apparatus main body side. In the image forming apparatus configured as described above,
By switching the rotation direction of the drive motor for driving the plurality of developing rolls between forward rotation and reverse rotation, driving of all the developing rolls at the time of full-color image formation and of the single-color development roll at the time of monochrome image formation are performed. An image forming apparatus configured to switch to driving.

According to a second aspect of the present invention, there is provided a first driving force transmission path for transmitting the rotational driving force of the driving motor to a plurality of developing rolls other than black, and the rotational driving force of the driving motor. A second driving force transmission path for transmitting to the black developing roll,
At least one one-way clutch built-in gear with a built-in one-way clutch is disposed in the first driving force transmission path before the drive is branched to the plurality of developing rollers other than the black color. While transmitting driving force during full color image formation,
The second driving force transmission path has two driving force transmission paths, and one-way clutch built-in gears each including a one-way clutch are arranged in the two driving force transmission paths,
When a full-color image is formed, the one one-way clutch built-in gear transmits a driving force, and the other one-way clutch built-in gear rotates idle. When a monochrome image is formed, one one-way clutch built-in gear rotates idle and the other one-way clutch built-in. The image forming apparatus according to claim 1, wherein the built-in gear is configured to transmit a driving force.

  Furthermore, in the invention described in claim 3, one of the two driving force transmission paths in the second driving force transmission path is such that one of the driving force transmission paths is a gear with respect to the other driving force transmission path. The image forming apparatus according to claim 2, wherein the number is different by one.

  According to a fourth aspect of the present invention, a one-way clutch built-in gear incorporating the one-way clutch is disposed at a branch position between the first driving force transmission path and the second driving force transmission path, and the one-way clutch As an output gear provided on the developing roll side other than the black color of the clutch built-in gear, the input gear of the one-way clutch built-in gear is used as it is, and the output gear provided on the black developing roll side of the one-way clutch built-in gear. The image forming apparatus according to claim 2, wherein an output gear of the one-way clutch built-in gear is used.

  Furthermore, the invention described in claim 5 is arranged such that a one-way clutch built-in gear incorporating the one-way clutch is arranged at a branch position between the first driving force transmission path and the second driving force transmission path. A one-way clutch built-in gear with another one-way clutch is arranged on the black developing roll side of the one-way clutch built-in gear, and the input gear of the other one-way clutch built-in gear is directly driven by the drive motor. 3. The image forming apparatus according to claim 2, wherein the other one-way clutch built-in gear transmits driving force during monochrome image formation and idles during full-color image formation.

  According to a sixth aspect of the present invention, the black with respect to the rotational speed of the drive motor is transmitted through any one of the two driving force transmission paths in the second driving force transmission path. The image forming apparatus according to claim 2, wherein the rotation speed ratios of the color developing rolls are set to be the same.

  Further, the invention described in claim 7 is that among the two driving force transmission paths in the second driving force transmission path, a driving force transmission path used during full-color image formation and a driving force transmission path used during monochrome image formation. The image forming apparatus according to claim 2, wherein the rotation speed ratio of the black color developing roll is set to be different from the rotation speed of the drive motor.

  In the invention described in claim 8, the rotation speed of the drive motor is set to be the same for forward rotation and reverse rotation, and the rotation speeds of all developing rolls used for full-color image formation, 8. The rotation speed of a black developing roll used for image formation is set so that the rotation speed of the black developing roll is different from the rotation speed of the drive motor. An image forming apparatus.

  According to the present invention, the driving of a plurality of developing rolls can be switched by a small number of one-way clutches during full color image formation and monochrome image formation, and the configuration can be simplified and the cost can be reduced. In addition, it is possible to provide an image forming apparatus capable of obtaining good image quality by driving a plurality of developing rolls separately from the image carrier.

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

Embodiment 1
2 and 3 show a tandem full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. In addition, the arrow in FIG. 3 has shown the rotation direction of each rotation member.

  As shown in FIGS. 2 and 3, the full-color printer 01 includes photosensitive drums (image carriers) 11, 12, 11 for yellow (Y), magenta (M), cyan (C), and black (K). Image forming units 1, 2, 3, 4 having 13, 14, and charging rolls (contact type charging devices) 21, 22, 23, 24 for primary charging contacting these photosensitive drums 11, 12, 13, 14 And a laser optical unit 03 (exposure apparatus) shown in FIG. 2 that irradiates laser beams 31, 32, 33, and 34 of each color of yellow (Y), magenta (M), cyan (C), and black (K), The first primary intermediate transfer drum (intermediate transfer member) that contacts the developing devices 41, 42, 43, 44 and the two photosensitive drums 11, 12, among the four photosensitive drums 11, 12, 13, 14. 51 and a second primary intermediate transfer drum (intermediate transfer body) 52 in contact with the other two photosensitive drums 13 and 14, and the first and second primary intermediate transfer drums. The secondary intermediate transfer drum (intermediate transfer member) 53 in contact with the arm 51, 52, between the transfer roller (transfer member) 60 in contact with the secondary intermediate transfer drum 53, a main part is configured.

  As shown in FIG. 3, the photoconductor drums 11, 12, 13, and 14 are arranged at regular intervals so as to have a common tangential plane M.sub.2. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 are surfaces whose respective rotation axes are parallel to the photosensitive drums 11, 12, 13, and 14 and have predetermined target surfaces as boundaries. They are arranged in a symmetrical relationship. Further, the secondary intermediate transfer drum 53 is arranged so that the rotation axis thereof is parallel to the photosensitive drums 11, 12, 13, and 14.

  Signals corresponding to the image information for each color are rasterized by an image processing unit (not shown) and input to the laser optical unit 03 shown in FIG. In this laser optical unit 03, the laser beams 31, 32, 33, 34 of yellow (Y), magenta (M), cyan (C), and black (K) are modulated, and the corresponding photosensitive drum 11 is obtained. , 12, 13 and 14.

  Around each of the photosensitive drums 11, 12, 13, and 14, an image forming process for each color is performed by a known electrophotographic method. First, as the photosensitive drums 11, 12, 13, and 14, for example, photosensitive drums (image carriers) using an OPC photosensitive member having a diameter of 20 mm are used, and these photosensitive drums 11, 12, 13, and 14 are used. For example, 14 is rotationally driven at a rotational speed of 95 mm / sec. As shown in FIG. 3, the surfaces of the photosensitive drums 11, 12, 13, and 14 are applied with a DC voltage of about -840V to charging rolls 21, 22, 23, and 24 as contact-type charging devices. For example, it is charged to about -300V. The contact-type charging device includes a roll type, a film type, a brush type, and the like, but any type may be used. In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. Further, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, in this embodiment, a charging method in which only DC is applied is used, but a charging method in which AC + DC is applied may be used.

  Thereafter, the surfaces of the photosensitive drums 11, 12, 13, and 14 correspond to yellow (Y), magenta (M), cyan (C), and black (K) colors by a laser optical unit 03 as an exposure apparatus. The laser beams 31, 32, 33, and 34 are irradiated, and an electrostatic latent image corresponding to input image information for each color is formed. When the electrostatic latent image is written by the laser optical unit, the photosensitive drums 11, 12, 13, and 14 are discharged to a surface potential of the image exposure portion of about −60 V or less.

  Further, the electrostatic latent images corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 are compatible. Are developed by the developing devices 41, 42, 43, and 44, and yellow (Y), magenta (M), cyan (C), and black (K) are provided on the photosensitive drums 11, 12, 13, and 14, respectively. Visualized as a toner image.

  In this embodiment, as the developing devices 41, 42, 43, 44, a magnetic brush contact type two-component developing method is adopted, but the scope of application of the present invention is not limited to this developing method, Of course, the present invention can be sufficiently applied to other development systems such as a one-component development system and a non-contact development system.

The developing devices 41, 42, 43, 44 are filled with yellow (Y), magenta (M), cyan (C), and black (K) toners of different colors and a developer consisting of a carrier. Yes. When the toner is replenished from the toner cartridges 04Y, 04M, 04C, and 04K shown in FIG. 2, these replenishing devices 41, 42, 43, and 44 are sufficiently agitated with the carrier by the auger 404. Frictionally charged. Inside the developing roll 401, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is fixed. By the paddle 403 that conveys the developer to the developing roll 401, the amount of the developer conveyed to the vicinity of the surface of the developing roll 401 is regulated by the developer amount regulating member 402. In this embodiment, the amount of the developer is 30 to 50 g / m ² , and the charge amount of the toner existing on the developing roll 401 at this time is approximately about −20 to 35 μC / g.

The toner used in the developing devices 41, 42, 43, 44 has a shape factor MLS2 defined by the following equation of 100 to 140, for example, MLS2 = 130, and an average particle size of 3 μm to 10 μm. So-called “spherical toner” is used.
MLS2 = {(absolute maximum length of toner particles) × 2)}
/ {(Projection area of toner particles) × π × 1/4 × 100}

  The toner supplied onto the developing roll 401 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 11, 12, 13, and 14. ing. A developing bias voltage of AC + DC is applied to the developing roll 401 to develop the toner on the developing roll 401 into an electrostatic latent image formed on the photosensitive drums 11, 12, 13, and 14. It is formed. In this embodiment, the developing bias voltage is about 4 kHz for AC, 1.5 kVpp, and about −230 V for DC.

  Next, the yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the photosensitive drums 11, 12, 13, and 14 are first primary images. The secondary transfer is electrostatically performed on the intermediate transfer drum 51 and the second primary intermediate transfer drum 52. The yellow (Y) and magenta (M) color toner images formed on the photoconductive drums 11 and 12 are formed on the first primary intermediate transfer drum 51 and cyan (on the photoconductive drums 13 and 14). The toner images of C) and black (K) are transferred onto the second primary intermediate transfer drum 52, respectively. Therefore, on the first primary intermediate transfer drum 51, the single color image transferred from either the photosensitive drum 11 or 12 and the two color toner images transferred from both the photosensitive drums 11 and 12 are superimposed. A double color image is formed. In addition, similar single-color images and double-color images are also formed on the second primary intermediate transfer drum 52 from the photosensitive drums 13 and 14.

  The surface potential necessary for electrostatically transferring the toner image from the photosensitive drums 11, 12, 13, 14 onto the first and second primary intermediate transfer drums 51, 52 is about +250 to 500V. It is. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. The ambient temperature and humidity can be easily known by detecting the resistance value of a member having a characteristic that the resistance value varies depending on the ambient temperature and humidity. As described above, when the charge amount of the toner is in the range of −20 to 35 μC / g and is in a normal temperature and humidity environment, the surface potential of the first and second primary intermediate transfer drums 51 and 52 is + 380V is desirable.

The first and second primary intermediate transfer drums 51 and 52 used in this embodiment have an outer diameter of 42 mm, for example, and a resistance value of about 10 ⁸ Ω. The first and second primary intermediate transfer drums 51 and 52 are cylindrical rotating bodies having a single layer or a plurality of layers whose surfaces are flexible or elastic, and are generally made of Fe, Al, or the like. A low resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) typified by conductive silicone rubber or the like is provided on a metal pipe as a metal core as described above to a thickness of about 0.1 to 10 mm. Further, the outermost surfaces of the first and second intermediate transfer drums 51 and 52 are typically made of a high release layer (R = 10 ⁵ to 3) having a thickness of 3 to 100 μm of fluororubber in which fluororesin fine particles are dispersed. 10 ⁹ Ω) and bonded with a silane coupling agent-based adhesive (primer). What is important here is the resistance value and the releasability of the surface, and the resistance value of the high release layer is about R = 10 ⁵ to 10 ⁹ Ω. It is not limited.

  The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 in this way are electrostatically secondary-transferred onto the secondary intermediate transfer drum 53. Accordingly, a final toner image from a single color image to a quadruple color image of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the secondary intermediate transfer drum 53. Will be.

  The surface potential necessary for electrostatically transferring the toner image from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200V. This surface potential is the same as when the toner is transferred from the photosensitive drums 11, 12, 13, 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Will be set to the optimum value. Further, since what is necessary for the transfer is a potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 52 have different potentials. It is necessary to set the value according to the surface potential. As described above, the charge amount of the toner is in the range of −20 to 35 μC / g, and the surface potential of the first and second primary intermediate transfer drums 51 and 52 is +380 V in a normal temperature and humidity environment. The surface potential of the secondary intermediate transfer drum 53 is about +880 V, that is, the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is + It is desirable to set it to about 500V.

The secondary intermediate transfer drum 53 used in this embodiment is formed to have the same outer diameter as that of the first and second primary intermediate transfer drums 51 and 52, for example, 42 mm, and the resistance value is set to about 10 ¹¹ Ω. . Similarly to the first and second primary intermediate transfer drums 51 and 52, the secondary intermediate transfer drum 53 is a cylindrical rotating body having a single layer or a plurality of layers whose surface is flexible or elastic. In general, a low resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) typified by conductive silicone rubber or the like is formed on a metal pipe as a metal core made of Fe or Al. It is provided at about 0.1-10mm. Further, the outermost surface of the secondary intermediate transfer drum 53 is typically formed by forming fluororubber in which fine particles of fluororesin are dispersed as a high release layer having a thickness of 3 to 100 μm, and a silane coupling agent-based adhesive (Primer). Here, the resistance value of the secondary intermediate transfer drum 53 needs to be set higher than that of the first and second primary intermediate transfer drums 51 and 52. Otherwise, the secondary intermediate transfer drum 53 will charge the first and second primary intermediate transfer drums 51, 52, making it difficult to control the surface potential of the first and second primary intermediate transfer drums 51, 52. Become. The material is not particularly limited as long as the material satisfies such conditions.

  Next, the final toner image from the single color image to the quadruple color image formed on the secondary intermediate transfer drum 53 is tertiary transferred onto the transfer paper 101 passing through the paper conveyance path by the final transfer roll 60. Is done. The transfer paper 101 passes through the registration roller 90 through a paper feeding process as shown in FIG. 3, and is fed into the nip portion between the secondary intermediate transfer drum 53 and the transfer roll 60. After this final transfer step, the final toner image formed on the transfer paper 101 is fixed by heat and pressure by the fixing device 70, and a series of image forming processes is completed.

  By the way, this embodiment includes a plurality of image forming units that form images of different colors, and the plurality of image forming units include an image carrier and an electrostatic latent image formed on the image carrier. A tandem type image forming system that is provided with a developing roll for developing an image, and that drives the image carrier and the developing roll of each of the image forming units by different drive motors provided on the image forming apparatus main body side. In the apparatus, by switching the rotation direction of the drive motor for driving the plurality of developing rolls between forward rotation and reverse rotation, driving of all the developing rolls at the time of full-color image formation and monochromatic at the time of monochrome image formation are performed. It is configured to switch to driving of the developing roll.

  Further, in this embodiment, the first driving force transmission path for transmitting the rotational driving force of the driving motor to a plurality of developing rolls other than the black color, and the rotational driving force of the driving motor for developing the black color A one-way clutch having a built-in one-way clutch before the drive is branched to the plurality of developing rolls other than the black color. At least one built-in gear is arranged, and the one-way clutch built-in gear transmits driving force during full-color image formation, while the second driving force transmission path has two driving force transmission paths, A one-way clutch built-in gear with a built-in one-way clutch is arranged in each of the two driving force transmission paths. The built-in gear transmits the driving force, and the other one-way clutch built-in gear rotates idle, and when forming a monochrome image, the one-way clutch built-in gear rotates idle and the other one-way clutch built-in gear transmits the driving force. It is configured.

  Further, in this embodiment, of the two driving force transmission paths in the second driving force transmission path, one driving force transmission path has one gear with respect to the other driving force transmission path. Configured differently.

  Further, in this embodiment, a one-way clutch built-in gear incorporating the one-way clutch is arranged at a branch position between the first driving force transmission path and the second driving force transmission path, and the one-way clutch built-in gear As the output gear provided on the side of the plurality of developing rolls other than the black color, the input gear of the one-way clutch built-in gear is used as it is, and as the output gear provided on the black developing roll side of the one-way clutch built-in gear, The output gear of the one-way clutch built-in gear is used.

  Furthermore, in this embodiment, a one-way clutch built-in gear incorporating the one-way clutch is arranged at a branch position between the first driving force transmission path and the second driving force transmission path, and the one-way clutch built-in gear is arranged. The one-way clutch built-in gear that incorporates another one-way clutch is arranged on the black color developing roll side, and the input gear of the other one-way clutch built-in gear receives the rotational driving force directly from the drive motor, The other one-way clutch built-in gear is configured to transmit a driving force when forming a monochrome image and to idle when forming a full-color image.

  Further, in this embodiment, the black developing roll with respect to the number of rotations of the drive motor, regardless of which of the two driving force transmission paths in the second driving force transmission path is passed. The rotation speed ratio is set to be the same.

  That is, in the full-color printer 01 according to the first embodiment, as shown in FIG. 4, in order to improve the maintainability and the like, the four photosensitive drums 11, 12, 13, 14 and the first and second primary The intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 are integrally provided to form an image forming unit 101. The image forming unit 101 is connected to the apparatus main body 102 of the full-color printer 01. It is removable.

  As shown in FIG. 5, the image forming unit 101 has four photosensitive drums 11, 12, 13, 14 and first and second primary intermediate transfer drums 51, 52, Frames 103 and 104 for rotatably supporting the next intermediate transfer drum 53 are provided. Further, in the image forming unit 101, a rotating shaft 105 as a shaft-like member for rotatably supporting the secondary intermediate transfer drum 53 protrudes outward from the right and left frames 103, 104 by a predetermined amount. It is attached to do. The rotating shaft 105 of the secondary intermediate transfer drum 53 is positioned and fixed at a predetermined position when the image forming unit 101 is mounted on the main body 102 of the full-color printer 01, as shown in FIG. It serves as a fixing member for the purpose. The rotating shaft 105 for rotatably supporting the secondary intermediate transfer drum 53 may be any one that supports the secondary intermediate transfer drum 53 rotatably. The rotating shaft 105 itself is provided rotatably. It may be provided in a state fixed to the image forming unit 101. In this embodiment, the rotating shaft 105 is attached to the image forming unit 101 in a fixed state.

  In this embodiment, the image forming unit 101 includes four photosensitive drums 11, 12, 13, 14 and first and second primary intermediate transfer drums 51, 52 as shown in FIG. In addition to the secondary intermediate transfer drum 53, charging rolls 21, 22, 23, 24, and a refresher roll (not shown) are attached as necessary.

  As shown in FIG. 6, the image forming unit 101 includes a front unit 106 that covers the side of the apparatus main body 102 and a cover member 107 that covers the upper part of the apparatus main body 102 with respect to the apparatus main body 102 of the full-color printer 01. When the image forming unit 101 is lifted upward in the open state, the image forming unit 101 can be removed from the apparatus main body 102 as shown in FIG. The vertical direction along the direction.

  A drive mechanism for rotationally driving the developing roll 401 of the developing devices 41, 42, 43, 44 is attached to the frame 108 of the main body 102 of the full-color printer 01 as shown in FIGS. .

  FIG. 1 is a perspective view showing a drive mechanism for rotationally driving the developing rolls 401 Y, 401 M, 401 C, and 401 K of the developing devices 41, 42, 43, and 44 for yellow, magenta, cyan, and black colors. is there.

  In FIG. 1, reference numeral 70 denotes a driving mechanism that rotationally drives the developing rolls 401Y, 401M, 401C, and 401K of the developing devices 41, 42, 43, and 44 of yellow, magenta, cyan, and black. This drive mechanism 70 includes a drive mechanism case 71 formed of sheet metal or the like. A drive motor 72 as a drive source is fixedly attached to a case 71 of the drive mechanism, and a drive gear 74 is integrally formed on a rotating shaft 73 of the drive motor 72. The rotation direction of the drive motor 72 can be switched between forward rotation and reverse rotation. In this embodiment, the rotational speed of the drive motor 72 is set to be the same between forward rotation and reverse rotation.

  As shown in FIG. 10, the driving mechanism 70 includes a first driving force transmission path 91 that transmits the rotational driving force of the driving motor 72 to a plurality of developing rolls 401 Y, 401 M, 401 C other than black. And a second driving force transmission path 92 for transmitting the rotational driving force of the driving motor 72 to the black color developing roll 401K. The first driving force transmission path 91 includes a plurality of non-black colors. A second one-way clutch built-in gear 78 having a built-in one-way clutch is disposed before the drive is branched to the developing rolls 401 Y, 401 M, and 401 C.

  In the driving mechanism 70, the second driving force transmission path 92 includes two driving force transmission paths 92a and 92b, and the first driving force transmission path 91 and the second driving force transmission path 92 are provided. The first one-way clutch built-in gear 77 with a built-in one-way clutch is arranged at the branch position with the other, and another one-way clutch is built into the black developing roll side of the first one-way clutch built-in gear 77. The third one-way clutch built-in gear 87 is arranged. The input gear 87a of the third one-way clutch built-in gear 87 receives a rotational driving force directly from the drive motor 72 via the first gear 75, and the third one-way clutch built-in gear 87 is a monochrome image. A driving force is transmitted at the time of formation, and is configured to idle when a full-color image is formed.

  Further, the configuration of the drive mechanism 70 will be described in detail. The drive gear 74 of the drive motor 72 is engaged with a first gear 75 as shown in FIG. As shown in FIG. 11, the second gear 76 is coaxially attached. The second gear 76 is attached to the first gear 75 so as to be idled over 215 °. The first gear 75 is formed with a fan-shaped groove 75a on the inner periphery thereof, and the convex portion 76a of the second gear 76 is slidable along the circumferential direction in the fan-shaped groove 75a. It is comprised so that it may be fitted to. Even when the first gear 75 rotates, the rotational driving force is transmitted to the second gear 76 after the first gear 75 has idled 215 °.

  The second gear 76 meshes with the input gear 77a of the first one-way clutch built-in gear 77. The first one-way clutch built-in gear 77 transmits a rotational force when the input gear 77a rotates in the clockwise direction, the output gear 77b rotates in the clockwise direction, and the input gear 77a rotates in the counterclockwise direction. In this case, the output gear 77b is idled without transmitting a rotational force. As shown in FIG. 12, the input gear 78a of the second one-way clutch built-in gear 78 having the same one-way clutch is meshed with the input gear 77a of the first one-way clutch built-in gear 77. Two double gears 79 and 80 having large diameters 79a and 80a are meshed with the output gear 78b of the two one-way clutch built-in gear 78. The second one-way clutch built-in gear 78 transmits a rotational force when the input gear 78a rotates counterclockwise, the output gear 78b rotates counterclockwise, and the input gear 78a rotates clockwise. When rotating in the direction, the rotational force is not transmitted and the output gear 78b is not rotated. Further, a gear 81b having a small diameter of the double gear 81 for reduction is meshed with the gear 79b having a small diameter of the one double gear 79, and the diameter of the double gear 81 for reduction is small. A gear 82 provided at the end of the yellow developing roll 401Y is meshed with the gear 81b.

  The gear 80b having the smaller diameter of the other double gear 80 is engaged with the gears 83a and 84a having the larger diameters of the two speed reducing double gears 83 and 84, and the speed reducing double gear 83a is engaged. The gears 83 and 84 having small diameters of the gears 83 and 84 are engaged with gears 85 and 86 provided at the ends of the magenta developing roll 401M and the cyan developing roll 401C.

  Further, as shown in FIGS. 1 and 12, the first gear 75 is meshed with the input gear 87a of the third one-way clutch built-in gear 87 and the third one-way clutch built-in gear 87. An output gear 77b of the first one-way clutch built-in gear 77 is meshed with the output gear 87b. The third one-way clutch built-in gear 87 transmits a rotational force when the input gear 87a rotates counterclockwise, the output gear 87b rotates counterclockwise, and the input gear 87a rotates clockwise. When rotating in the direction, the rotational force is not transmitted to the output gear 87b side. Further, a gear 88a having a large diameter of the double gear 88 is meshed with the output gear 87b of the third one-way clutch built-in gear 87. Further, the gear 88b having the small diameter of the double gear 88 is engaged with the gear 89a having the large diameter of the double gear 89 for reduction, and the gear 89b having the small diameter of the double gear 89 for reduction. Is engaged with a gear 90 provided at the end of the black color developing roll 40K.

  In the above configuration, in the tandem full-color printer as the image forming apparatus according to this embodiment, the number of one-way clutches used is reduced to switch the driving of a plurality of developing rolls as follows. In addition, it is possible to reduce the cost and to obtain a good image quality.

  That is, in the tandem-type full-color printer according to this embodiment, as shown in FIGS. 2 and 3, the photosensitive drums 11, 12, 13, and 14 of yellow, magenta, cyan, and black are rotated and driven. Electrostatic latent images are formed on the photosensitive drums 11, 12, 13, and 14 for the respective colors. The electrostatic latent images formed on the photosensitive drums 11, 12, 13 and 14 of the respective colors are processed by the yellow, magenta, cyan, and black developing devices 41, 42, 43, and 44 when full-color images are formed. Developed. At this time, the developing rolls 401 Y, 401 M, 401 C, and 401 K of the yellow, magenta, cyan, and black developing devices 41, 42, 43, and 44 have a driving mechanism 70 as shown in FIGS. 1 and 12. It is rotationally driven by.

  In the drive mechanism 70, as shown in FIG. 13, when the drive motor 72 is rotated forward in the clockwise direction, the first drive gear 74 formed integrally with the rotation shaft 73 of the drive motor 72 causes the first The gear 75 is driven to rotate. Since the second gear 76 is coaxially attached to the first gear 75, the second gear 76 is rotationally driven along the counterclockwise direction, and the second gear 76 is Thus, the input gear 77a of the first one-way clutch built-in gear 77 is rotationally driven along the clockwise direction. The input gear 77a of the second one-way clutch gear 78 is meshed with the input gear 77a of the first one-way clutch gear 77, and the input gear 78a of the second one-way clutch gear 78 is counterclockwise. It is rotationally driven in the surrounding direction. Since the second one-way clutch built-in gear 78 is configured to transmit the rotational force in the counterclockwise direction, the output gear 78b of the second one-way clutch built-in gear 78 also extends in the counterclockwise direction. Is rotated. Double gears 79 and 80 are meshed with the output gear 78b of the second one-way clutch built-in gear 78, and the reduction double gears 81, 83 and 84 meshed with the double gears 79 and 80, respectively. The yellow, magenta, and cyan developing rolls 401Y, 401M, and 401C are driven to rotate.

  Further, since the first one-way clutch built-in gear 77 is configured to transmit a rotational force in the clockwise direction, the output gear 77b of the first one-way clutch built-in gear 77 also rotates in the clockwise direction. Driven. Then, the input gear 87a of the third one-way clutch built-in gear 87 is meshed with the output gear 77b of the first one-way clutch built-in gear 77. Since the third one-way clutch built-in gear 87 is configured to transmit a rotational force in the counterclockwise direction, the input gear 87a of the third one-way clutch built-in gear 87 is arranged along the clockwise direction. It is supposed to run idle.

  Further, since the output gear 87b of the first one-way clutch built-in gear 77 is meshed with the output gear 87b of the third one-way clutch built-in gear 87, the output gear 87b of the third one-way clutch built-in gear 87 is engaged. Is driven to rotate in the counterclockwise direction by the output gear 77b of the first one-way clutch built-in gear 77. Further, a double gear 88 is meshed with the output gear 87b of the third one-way clutch built-in gear 87, and the black color is transmitted through the double gear 89 for speed reduction meshed with the double gear 88. The developing roller 401K for use is rotated.

  In this way, in the drive mechanism 70, as shown in FIG. 10, the development rolls 401Y, 401M for yellow, magenta, cyan, and black are rotated by rotating the drive motor 72 in the clockwise direction. , 401C, 401K are driven to rotate at a predetermined speed.

  On the other hand, in the drive mechanism 70, as shown in FIG. 14, when the drive motor 72 is rotated in the counterclockwise direction, the drive gear 74 formed integrally with the rotation shaft 73 of the drive motor 72 is used. The first gear 75 is rotationally driven along the clockwise direction. When the first gear 75 is rotationally driven, the second gear 76 that is coaxially attached to the first gear 75 is also rotationally driven along the clockwise direction, via the second gear 76. Thus, the input gear 77a of the first one-way clutch built-in gear 77 is rotationally driven. Since the input gear 78a of the second one-way clutch built-in gear 78 is meshed with the input gear 77a of the first one-way clutch built-in gear 77, the input gear 78a of the second one-way clutch built-in gear 78 is connected to the timepiece. It is rotationally driven along the circumferential direction. However, since the second one-way clutch built-in gear 78 is configured to transmit a counterclockwise rotational force, the output gear 78b of the second one-way clutch built-in gear 78 has a driving force. It is not transmitted and is in a stopped state. As a result, the yellow, magenta, and cyan developing rolls 401Y, 401M, and 401C connected to the output gear 78b of the second one-way clutch built-in gear 78 are stopped.

  Further, when the first gear 75 is rotationally driven along the counterclockwise direction, the input gear 87a of the third one-way clutch built-in gear 87 is rotationally driven by the first gear 75 in the counterclockwise direction. The Since the third one-way clutch built-in gear 87 is configured to transmit the rotational force in the counterclockwise direction, the output gear 87b of the third one-way clutch built-in gear 87 also extends in the counterclockwise direction. Is rotated. A double gear 88 is meshed with the output gear 87 b of the third one-way clutch built-in gear 87, and the black color is transmitted through the double gear 89 for speed reduction meshed with the double gear 88. The developing roll 401K is rotationally driven.

  Thus, in the drive mechanism 70, as shown in FIG. 10, the yellow, magenta, and cyan developing rolls 401Y, 401M, and 401C are rotated by rotating the drive motor 72 in the counterclockwise direction. Is stopped, and only the black developing roll 401K is driven to rotate at a predetermined speed.

  Therefore, in the above embodiment, in order to switch the driving of the plurality of developing rolls 401 Y, 401 M, 401 C, and 401 K, the number of gears incorporating a one-way clutch can be reduced to three, and the configuration is simplified. The development rolls 401 Y, 401 M, 401 C, and 401 K are driven separately from the photosensitive drum, and thus the development rolls 401 Y, 401 M, 401 C, and 401 K are reduced in cost. Therefore, it is possible to form a good image quality.

Embodiment 2
15 to 18 show a second embodiment of the present invention. The same reference numerals are given to the same parts as those of the first embodiment. In the second embodiment, the second embodiment is shown in FIG. Of the two driving force transmission paths in the driving force transmission path, the driving force transmission path used during full-color image formation and the driving force transmission path used during monochrome image formation include the black developing rolls corresponding to the rotational speed of the driving motor. The rotation speed ratio is set to be different.

  In the second embodiment, the rotation speed of the drive motor is set to be the same for forward rotation and reverse rotation, and the rotation speeds of all developing rolls used for full-color image formation and monochrome image formation are used. In the black developing roll, the rotation speed of the black developing roll is set to be different from the rotational speed of the drive motor.

  That is, in the second embodiment, as shown in FIGS. 15 to 18, one driving force transmission path 92b of the second driving force transmission paths 92 is driven by the black developing roll 401K. The input gear 87a of the third one-way clutch built-in gear 87 that transmits force is set to have a smaller diameter and a smaller number of teeth than the output gear 87b.

  Therefore, in the second driving force transmission path 92, the black color of the developing roller 401K of black color is rotated via the driving force transmission path 92a as compared with the case where the black developing roller 401K is rotationally driven. When the developing roll 401K is rotationally driven, the reduction ratio is set to be small, and even when the driving motor 72 is rotationally driven at the same speed, the black developing roll 401K is rotated during monochrome image formation. The number is set to be large.

  As a result, it is possible to set a large number of rotations of the black developing roll 401K when forming a monochrome image, and it is possible to increase the development efficiency and to improve the quality of the monochrome image.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

Embodiment 3
19 and 20 show a third embodiment of the present invention. The same parts as those in the first embodiment will be described with the same reference numerals. The transmission path of the driving force is changed to cope with an increase in the size of the developing device.

  That is, in the third embodiment, as shown in FIGS. 19 and 20, the input gear 78a of the second one-way clutch built-in gear 78 is directly connected to the drive gear of the drive motor 72 via the third gear 93. The input gear 77 a of the first one-way clutch built-in gear 77 is meshed with the third gear 93 via the fourth gear 94. Further, the third gear 93 is configured to directly mesh with the input gear 87a of the third one-way clutch built-in gear 87. The output gear 77b of the first one-way clutch built-in gear 77 and the output gear 87b of the third one-way clutch built-in gear 87 are both meshed with a gear 88a having a large diameter of the reduction gear 88.

  Even in such a configuration, only the rotation direction of the drive motor 72 is switched between forward rotation and reverse rotation, and all the developing rolls 401 Y, 401 M, 401 C, and 401 K are rotated and driven only in black. It is possible to switch the rotational drive of the developing roll 401K.

  Also in this embodiment, the black color at the time of full-color image formation is changed by changing the number of teeth of the fourth gear 94 and the number of teeth of the input gear 87a and the output gear 87b of the third one-way clutch built-in gear 87. It is possible to make the rotational speed of the developing roller 401K different from the rotational speed of the black developing roller 401K when forming a monochrome image.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

Embodiment 4
21 and 22 show the fourth embodiment of the present invention. The same reference numerals are given to the same parts as those of the first embodiment, and in the fourth embodiment, the embodiment will be described. As in the case of No. 3, the transmission path of the driving force from the driving motor is changed so that the development device can be increased in size.

  That is, in the fourth embodiment, as shown in FIG. 21 and FIG. 22, the configuration is basically the same as in the third embodiment. However, unlike the third embodiment, the fourth gear 94 directly The input gear of the third one-way clutch built-in gear 87 is not transmitted to the input gear 87a of the third one-way clutch built-in gear 87 but via the fifth gear 95 and the sixth gear 96 in the middle. The driving force is transmitted to 87a.

  Even in this configuration, although the number of gears to be used increases, all the developing rolls 401 Y, 401 M, 401 C, and 401 K can be simply switched by switching the rotation direction of the drive motor 72 between forward rotation and reverse rotation. It is possible to switch between the rotational driving of the developing roller 401K and the rotational driving of only the black color developing roll 401K.

  Also in this embodiment, a full color image can be obtained by changing the number of teeth of the fourth to sixth gears 94 to 96 and the number of teeth of the input gear 87a and the output gear 87b of the third one-way clutch built-in gear 87. It is possible to make the rotational speed of the black developing roll 401K during formation different from the rotational speed of the black developing roll 401K during monochrome image formation.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

FIG. 1 is a perspective view showing a main part of a driving mechanism of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a block diagram showing the image forming unit of the full-color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 4 is a block diagram showing an image forming unit of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 5 is a block diagram showing an image forming unit of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 6 is a block diagram showing a state in which the cover of the full-color printer as the image forming apparatus according to Embodiment 1 of the present invention is opened. FIG. 7 is a perspective configuration diagram showing a frame of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 8 is a perspective configuration diagram showing a frame of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 9 is a perspective configuration diagram showing a frame of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 10 is a block diagram showing the drive mechanism of the full-color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 11 is a block diagram showing gears. FIG. 12 is a perspective configuration diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 13 is a perspective configuration diagram showing the operation of the drive mechanism of the full-color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 14 is a perspective configuration diagram showing the operation of the drive mechanism of the full-color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 15 is a perspective configuration diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 2 of the present invention. FIG. 16 is a block diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 2 of the present invention. FIG. 17 is a perspective configuration diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 2 of the present invention. FIG. 18 is a block diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 2 of the present invention. FIG. 19 is a perspective configuration diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 3 of the present invention. FIG. 20 is a block diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 3 of the present invention. FIG. 21 is a perspective configuration diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 4 of the present invention. FIG. 22 is a block diagram showing a drive mechanism of a full-color printer as an image forming apparatus according to Embodiment 4 of the present invention.

Explanation of symbols

  70: drive mechanism, 72: drive motor, 91: first drive force transmission path, 92: second drive force transmission path, 401 Y, 401 M, 401 C, 401 K: developing roll.

Claims (8)

A plurality of image forming units that form images of different colors, and the plurality of image forming units each include an image carrier and a developing roll that develops an electrostatic latent image formed on the image carrier; In each of the image forming apparatuses configured to drive the image carrier and the developing roll of each image forming unit by different drive motors provided on the image forming apparatus main body side,
By switching the rotation direction of the drive motor for driving the plurality of developing rolls between forward rotation and reverse rotation, driving of all the developing rolls at the time of full-color image formation and of the single-color development roll at the time of monochrome image formation are performed. An image forming apparatus configured to switch to driving. A first driving force transmission path for transmitting the rotational driving force of the driving motor to a plurality of developing rolls other than black; and a second driving for transmitting the rotational driving force of the driving motor to the black developing roll. Power transmission path,
At least one one-way clutch built-in gear with a built-in one-way clutch is disposed in the first driving force transmission path before the drive is branched to the plurality of developing rollers other than the black color. While transmitting driving force during full color image formation,
The second driving force transmission path has two driving force transmission paths, and one-way clutch built-in gears each including a one-way clutch are arranged in the two driving force transmission paths,
When a full-color image is formed, the one one-way clutch built-in gear transmits a driving force, and the other one-way clutch built-in gear rotates idle. When a monochrome image is formed, one one-way clutch built-in gear rotates idle and the other one-way clutch built-in. The image forming apparatus according to claim 1, wherein the built-in gear is configured to transmit a driving force. The driving force transmission path of one of the two driving force transmission paths in the second driving force transmission path is different in number of gears from the other driving force transmission path. The image forming apparatus according to 2. A one-way clutch built-in gear having the one-way clutch is disposed at a branch position between the first driving force transmitting path and the second driving force transmitting path, and a plurality of developing rolls other than the black color of the one-way clutch built-in gear As the output gear provided on the side, the input gear of the one-way clutch built-in gear is used as it is, and as the output gear provided on the black developing roll side of the one-way clutch built-in gear, the output gear of the one-way clutch built-in gear is used. The image forming apparatus according to claim 2, wherein the image forming apparatus is used. A one-way clutch built-in gear having the one-way clutch is disposed at a branch position between the first driving force transmission path and the second driving force transmission path, and the black-color developing roll side of the one-way clutch built-in gear is disposed. The other one-way clutch built-in gear is arranged, the input gear of the other one-way clutch built-in gear receives the rotational driving force directly from the drive motor, and the other one-way clutch built-in gear The image forming apparatus according to claim 2, wherein a driving force is transmitted when a monochrome image is formed and idles when a full-color image is formed. The rotation speed ratio of the black developing roller to the rotation speed of the drive motor is set to be the same regardless of which of the two driving force transmission paths in the second driving force transmission path. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. Of the two driving force transmission paths in the second driving force transmission path, the driving force transmission path used for full-color image formation and the driving force transmission path used for monochrome image formation have a black color corresponding to the rotational speed of the drive motor. The image forming apparatus according to claim 2, wherein the rotation speed ratio of the developing rolls is set to be different. The rotational speed of the drive motor is set to be the same for forward rotation and reverse rotation, and the rotational speeds of all the developing rolls used for full-color image formation and the black color development rolls used for monochrome image formation. The image forming apparatus according to claim 7, wherein the rotation speed of the black developing roller is set to be different from the rotation speed of the drive motor.

Images