JP2004361974A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that an image forming apparatus gets larger, that the number of prints per unit time is a few, and that many image formation processing devices are required. <P>SOLUTION: In the image forming apparatus provided with an intermediate transfer belt to which a toner image on a photoreceptor drum is transferred, a color image on the intermediate transfer belt is transferred to transfer paper by a transfer means. The apparatus has 1st and 2nd image forming units (I and II) arranged along the intermediate transfer belt (10) by leaving space in between, and the 1st image forming unit is equipped with one photoreceptor drum and a developing means for developing an electrostatic latent image on the photoreceptor drum with toner of color A and a developing means for developing it with toner of color B, and the 2nd image forming unit is equipped with one photoreceptor drum and a developing means for developing the electrostatic latent image on the photoreceptor drum with toner of color C and a developing means for developing it with black toner. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming method for temporarily transferring a toner image formed on an image carrier such as a photosensitive drum to an intermediate transfer belt, and transferring the transferred color image on the intermediate transfer belt to transfer paper, and an image forming method therefor. Equipment related.

Examples of the color image forming method include a color image forming method in which a color image formed on a photosensitive drum is directly transferred to a transfer paper supported on a peripheral surface of a transfer drum (Japanese Patent Laid-Open No. 2-127323), A color image forming method using a transferred endless intermediate transfer belt (Japanese Patent Application Laid-Open No. H8-160697) or a color image forming method in which four photosensitive drums are arranged side by side on one transfer belt are known. .
In the color image forming method using the transfer drum, the first and second photosensitive drums are arranged around the transfer drum, and the electrostatic latent images on each photosensitive drum are developed by two developing units. Is done. The developing devices for the first photosensitive drum are a yellow toner developing device and a cyan toner developing device, and the developing devices for the second photosensitive drum are a magenta toner developing device and a black toner developing device. The color images on the respective photosensitive drums obtained by these developing devices are transferred onto transfer paper supported on the transfer drum.

On the other hand, in the color image forming method using the intermediate transfer belt, a black toner developing device, a yellow toner developing device, a magenta toner developing device, and a cyan toner developing device are arranged in this order around one photosensitive drum, The color image on the photosensitive drum obtained by these developing units is transferred to an intermediate transfer belt partially contacting the photosensitive drum, and the color image on the intermediate transfer belt is transferred to transfer paper. .
In the color image forming method in which four photosensitive drums are provided for one transfer belt, one developing unit is provided for each photosensitive drum, and the transfer belt obtained by four photosensitive drums is provided. The upper color image is transferred to transfer paper.

Japanese Unexamined Patent Publication No. Hei. Japanese Patent Application Laid-Open No. 8-160597

In a color image forming method in which a color image formed on a photoconductor drum is directly transferred to a transfer paper supported on a transfer drum, the first and second photoconductor drums are arranged at intervals around the transfer drum. Therefore, when the photosensitive drums are arranged on the transfer drum in the same posture, the contact positions (image transfer units) of the first photosensitive drum and the second photosensitive drum with respect to the transfer drum are different from each other. Therefore, there is no compatibility between the first photosensitive drum unit provided with the charging means and the developing means and the second photosensitive drum unit, and therefore, there is a problem that each photosensitive drum unit must be prepared separately.
The color image forming method described in JP-A-8-160697 using the intermediate transfer belt has a problem that the number of copies and the number of prints per unit time are small.
In a color image forming method in which four photosensitive drums are provided for one transfer belt, the copying speed is relatively high, but the image forming process including four photosensitive drums and a charger for each photosensitive drum is performed. There is a problem that requires each device.

According to the first aspect of the present invention, a toner image formed of at least three primary colors of A, B, and C on an image carrier is transferred to an intermediate transfer belt, and the color image on the intermediate transfer belt is transferred by a transfer unit. In the image forming method for transferring to paper, the first and second image forming means arranged at a fixed interval along the same moving surface of the intermediate transfer belt, on the intermediate transfer belt in the following order. An image forming method comprising the steps (1), (2) and (3) of transferring a toner image, wherein the color image obtained on the intermediate transfer belt is transferred to transfer paper.
(1) a step of transferring the A-color toner image onto the intermediate transfer belt by the first image forming means;
(2) a step of superimposing and transferring the B color toner image on the A color toner image on the intermediate transfer belt by the second image forming means;
(3) A step of superimposing and transferring the C color toner image on the A and B color toner images on the intermediate transfer belt by the first image forming means.

According to a second aspect of the invention, a toner image formed of at least three primary colors of A, B, and C on an image carrier is transferred to an intermediate transfer belt, and the color image on the intermediate transfer belt is transferred by a transfer unit. In the image forming method for transferring to paper, the first and second image forming means arranged at a fixed interval along the same moving surface of the intermediate transfer belt, on the intermediate transfer belt in the following order. An image forming method comprising the steps (1), (2) and (3) of transferring a toner image, wherein the color image obtained on the intermediate transfer belt is transferred to transfer paper.
(1) a step of transferring the A-color toner image onto the intermediate transfer belt by the first image forming means;
(2) While transferring the subsequent A-color toner image to the intermediate transfer belt by the first image forming means, the B-color toner image is transferred to the A-color toner image on the preceding intermediate transfer belt by the second image forming means. Superimposing transfer process,
(3) A step of superimposing and transferring the C color toner image on the A and B color toner images on the intermediate transfer belt by the first image forming means.

According to a third aspect of the present invention, in the image forming method according to the first or second aspect, after the C color toner image is transferred by being superimposed on the A and B color toner images by the first image forming means, A, B, C The black toner image is transferred onto the color toner image by the second image forming means.
According to a third aspect of the present invention, in the image forming method of the first, second or third aspect, the color A is set to magenta or cyan, the color B is set to cyan or magenta, and the color C is set to yellow.

  According to a fifth aspect of the present invention, in the image forming apparatus, the intermediate transfer belt on which the toner image on the image carrier is transferred, and the image forming apparatus for transferring the toner image on the intermediate transfer belt to transfer paper are provided. The image forming apparatus includes first and second image forming units that are arranged at regular intervals along the same moving surface of the transfer belt, wherein the first image forming unit includes one image carrier and the image carrier. Developing means for developing the electrostatic latent image with at least two colors of developer, wherein the second image forming unit has one image carrier and a color different from the developer of the first image forming unit. Developing means for developing with a developer.

  According to a sixth aspect of the present invention, in the image forming apparatus, an intermediate transfer belt on which a toner image formed by at least three primary colors of A, B, and C on an image carrier is transferred, and an intermediate transfer belt on the intermediate transfer belt An image forming apparatus for transferring a color image to transfer paper by a transfer unit, comprising: a first and a second image forming unit arranged at a predetermined interval along the same moving plane of the intermediate transfer belt; One image forming unit includes one image carrier, a developing unit for developing the electrostatic latent image on the image carrier with the A color toner, and a developing unit for developing the electrostatic latent image with the C color toner. The image forming unit includes one image carrier and developing means for developing the electrostatic latent image on the image carrier with a developing means for developing with a B color toner.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the image carrier is a drum-shaped or belt-shaped photoconductor, and the second image forming unit includes one photoconductor and the photoconductor. Developing means for developing the above electrostatic latent image with black toner is provided.

According to an eighth aspect of the present invention, in the image forming apparatus according to the fifth, sixth or seventh aspect, the intermediate transfer belt is at least twice as long as a length of a transfer sheet of a minimum size for a full-color image in a feeding direction. Has a length of
According to a ninth aspect of the present invention, in the image forming apparatus according to the fifth, sixth, seventh or eighth aspect, the first and second image forming units are detachable from the apparatus main body.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the fifth to ninth aspects, the first image forming unit and the second image forming unit have the same configuration.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the fifth to tenth aspects, the first image forming unit and the second image forming unit have the same intermediate transfer position as each other. The belts are arranged along the moving direction of the same moving plane.

According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the fifth to eleventh aspects, the first image forming unit is provided along a moving direction of the intermediate transfer belt on the same moving plane. The second image forming unit and the transfer unit are arranged in this order, and the developing unit for the toner of the most frequently used color is provided in the second image forming unit.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the fifth to twelfth aspects, a first image forming unit is provided along a moving direction of the intermediate transfer belt on the same moving plane. The second image forming unit and the transfer unit are arranged in this order, and the developing unit for the toner of the color having the least visibility is provided in the second image forming unit.

According to a fourteenth aspect of the present invention, in the image forming apparatus according to any one of the fifth to twelfth aspects, the first image forming unit includes a first image forming unit along a moving direction of the intermediate transfer belt on the same moving plane. The second image forming unit and the transfer unit are arranged in this order, and the developing unit for the toner of the color most frequently used and the developing unit for the toner of the color with the least visibility are arranged in the second image forming unit. It is provided in.
According to a fifteenth aspect of the present invention, in the image forming apparatus according to the twelfth aspect, the most frequently used color toner is black.
According to a sixteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the toner having a color having the least visual sensitivity is yellow.
According to a seventeenth aspect of the present invention, in the image forming apparatus according to the fourteenth aspect, the toner of the most frequently used color is black, and the toner of the least perceptible color is yellow.

  According to an eighteenth aspect of the present invention, in the image forming apparatus, the toner image formed by at least the three primary colors of A, B, and C is stretched between the rollers such that the image holding surface to which the toner image is transferred substantially faces downward. A transferred intermediate transfer belt, a first photosensitive drum and a second photosensitive drum that are sequentially arranged along a moving direction of the image holding surface of the intermediate transfer belt and form an electrostatic latent image; Developing means for developing the electrostatic latent image on the first photosensitive drum with the A color toner and developing means for developing the electrostatic latent image on the second photosensitive drum; Developing means for developing with toner; transfer means disposed near the downstream side of the second photosensitive drum in the moving direction of the intermediate transfer belt, for transferring a color image on the intermediate transfer belt to transfer paper; Transfer the transfer paper from paper means to the transfer Includes a transfer-sheet conveying path for feeding upward, and heat fixing device of an image disposed above the intermediate transfer belt, a directed to.

  According to a nineteenth aspect of the present invention, in the image forming apparatus, between the rollers such that an image holding surface to which a toner image formed by at least three primary colors of A, B, and C is transferred is substantially directed sideways. A stretched intermediate transfer belt, a first photosensitive belt and a second photosensitive belt which are sequentially arranged along a moving direction of the image holding surface of the intermediate transfer belt and form an electrostatic latent image; Developing means for developing the electrostatic latent image on the first photoreceptor belt with toner of color A and developing means for developing the electrostatic latent image on the photoreceptor belt with toner of color C; Developing means for developing with the toner of the type described above, and transfer means arranged near the downstream side of the second photoreceptor belt in the moving direction of the intermediate transfer belt and transferring a color image on the intermediate transfer belt to transfer paper. Have.

  According to a twentieth aspect, in the image forming apparatus according to any one of the fifth to twelfth aspects, the color A is magenta or cyan, the color B is cyan or magenta, and the color C is yellow.

  According to the present invention, the problem of increasing the size of the image forming apparatus, the problem of a small number of copies and the number of prints per unit time, and the problem of requiring many image forming process devices are solved. Since the same configuration can be used for the two image forming units, there is an effect that the manufacture, assembly, and maintenance of the image forming apparatus are extremely easy.

A toner image formed of at least three primary colors of A, B, and C on an image carrier such as a photosensitive drum or a photosensitive belt is transferred to an intermediate transfer belt, and the color image on the intermediate transfer belt is transferred by a transfer unit. In the image forming method for transferring to a transfer sheet, as shown in FIG. 1, a photoconductor drum, a charging unit and a photoconductor drum are arranged at regular intervals along the same moving surface of the intermediate transfer belt 10 running in the direction of arrow a. The toner image is transferred onto the intermediate transfer belt 10 in the order shown in FIG. 2 or 3 by the first image forming unit I and the second image forming unit II each having a developing unit. Is transferred to the transfer paper P by the transfer means 11.
Here, assuming that the total length of the intermediate transfer belt 10 is L and the length corresponding to the length of the transfer paper in the moving direction at the time of transfer is l, FIG. 2 illustrates a color image forming process when L = l + α. FIG. 3 shows a color image forming process when L = 2 (l + α). However, in FIGS. 2 and 3, α is the length of the non-image area on the intermediate transfer belt in the direction of movement of the intermediate transfer belt, and in FIGS. 2 and 3, it is assumed that α <1. Note that the length of α changes depending on the length of the image area on the intermediate transfer belt or the length of the transfer paper used. Therefore, depending on the length of the transfer sheet, there may be cases where α> l.

In FIG.
(1) The A-color toner image is transferred to the intermediate transfer belt 10 by the first image forming unit I having the A-color developing unit.
(2) The A- and B-color toner images are obtained by superimposing and transferring the B-color toner image on the A-color toner image by the second image forming means II. The color toner images are superimposed and transferred to obtain A, B, and C color toner images. At this point, the intermediate transfer belt 10 makes one rotation.
(3) A D-color toner (black toner) image is transferred onto the A, B, and C color toner images obtained in the step (2) by a second image forming hand, and the obtained full-color image is transferred onto a transfer paper. The image is transferred to P1 by the transfer means 11. The transfer to the transfer paper P1 is performed during the second rotation of the intermediate transfer belt.
(4) When a plurality of color prints are to be taken, the A-color toner image is formed by the first image forming means I at the same time as the D-color toner image is overlaid and transferred by the second image forming unit in the step (3). The image is transferred and the B color toner image is overlaid and transferred by the second image forming means II to obtain the A and B color toner images.
(5) A first color toner image is superimposed on the A and B color toner images obtained in the step (4) by the first image forming means I, and then a D color toner image is superimposed by the second image forming means II. The image is transferred and transferred to a second transfer sheet P2. The transfer to the transfer paper P2 is performed during the fourth rotation of the intermediate transfer belt.
(6) The third and subsequent prints are obtained at the sixth rotation of the intermediate transfer belt by repeating the steps from step (3).

In FIG. 3, (L / 2 = 1 + α)
(1) The A-color toner image is transferred to the intermediate transfer belt 10 by the first image forming unit I having the A-color developing unit.
(2) Further, while the subsequent A-color toner image is transferred to the intermediate transfer belt 10 by the first image forming means I, the B-color toner image is superimposed on the preceding A-color toner image by the second image forming means II. Transfer is performed to obtain A and B color toner images. At this point, the intermediate transfer belt 10 makes one rotation.
(3) The C-color toner image is superimposed on the A- and B-color toner images on the intermediate transfer belt obtained in the step (2) by the first image forming means I, and the A-, B-, and C-color toner images are transferred. Then, a D color toner (black toner) image is superimposed and transferred on the A, B, and C color toner images by the second image forming means II, and the obtained full-color image is transferred onto the transfer paper P1 by the transfer means 11. . The transfer to the transfer paper P1 is started from approximately 1.5 rotations of the intermediate transfer belt.
(4) In the case of making a plurality of color copies, the first image forming means I obtains the A, B, and C color toner images in the step (3), and the first image forming means I forms the A color toner images. While transferring, the D color toner image is superimposed and transferred on the A, B, and C color toner images by the second image forming means II, and the obtained full color image is transferred onto the second transfer paper P2. The transfer to the transfer paper P2 is started from approximately 2.5 rotations of the intermediate transfer belt.
(5) The B image is superimposed and transferred by the second image forming means II on the A toner image transferred by the first image forming means I in the step (4).
(6) While the subsequent A-color toner image is transferred to the intermediate transfer belt 10 by the first image forming means I, the B-color image is obtained by the second image forming means II on the A-color toner image obtained in the step (4). The toner images are superimposed and transferred to obtain A and B color toner images.
(7) The C-color toner image is superimposed on the A- and B-color toner images obtained in the step (6) by the first image forming means I and transferred to obtain A, B, and C-color toner images. , B and C toner images are superimposed and transferred by the second image forming means II, and the obtained color image is transferred to a third transfer sheet P3. The transfer to the transfer paper P3 is started from approximately 3.5 rotations of the intermediate transfer belt.
(8) While transferring the A color toner image by the first image forming means I, the D color toner image is formed by the second image forming means II on the A, B, and C color toner images obtained in the step (7). The transfer is performed in a superimposed manner, and the obtained color image is transferred to a fourth transfer sheet P4. The transfer to the transfer paper P4 is started from about 4.5 rotations of the intermediate transfer belt.

  As described above, when the intermediate transfer belt 10 has a length that is twice or more the length of the transfer paper P to be used, the first print is performed twice, the second print is performed three times, and the third print is performed three times. The fourth sheet is obtained by four rotations, and the fourth sheet is obtained by five rotations. That is, each print starts at the number of rotations of the intermediate transfer belt obtained by adding about 0.5 to the number of prints, and the number of prints to be obtained is obtained by adding the number of prints to one.

In FIG. 4 showing the first embodiment, the intermediate transfer belt 10 is stretched between a driving roller 13 and a driven roller 12, and is driven by the driving roller 13 to travel in the direction of arrow a. The intermediate transfer belt 10 is given an optimal tension by a tension roller 60. A first image forming unit I and a second image forming unit II are arranged on the lower traveling surface of the intermediate transfer belt 10 at regular intervals along the traveling direction of the intermediate transfer belt 10. . The intermediate transfer belt 10 is longer by the non-image area than the length of the maximum size transfer paper used in the image forming apparatus of this embodiment in the moving direction.
The first image forming unit I includes a charger 17 composed of a roller for uniformly charging the surface of a photosensitive drum 16 as an image carrier, and a charged surface of the photosensitive drum 16 modulated by an image signal based on a document. It mainly comprises a writing unit 18 for writing with a beam, an A-color developing unit 100, a C-color developing unit 200, and a cleaning unit 20.

  The A-color developing device 100 includes a developing roller 101, a paddle roller 102, a screw conveyor 103, and a developer supply port 104. The paddle roller 102 has screw-shaped fins 102 a, agitates while rotating in one direction while transporting the developer in the A-color developing device 100 in the axial direction, and supplies the developer to the developing roller 101. The screw conveyor 103 conveys the developer in the A-color developing device 100 in a direction opposite to the direction in which the paddle roller 102 conveys the developer. The developer in the A-color developing device 100 is supplied to the developing roller 101 while being sufficiently stirred by the paddle roller 102 and the screw conveyor 103.

A toner supply container (not shown) is detachably attached to the developer supply port 104, and the A-color toner is supplied to one end of the screw conveyor 103 at an appropriate time, and the developer in the A-color developing device 100 is supplied. The concentration is kept at a predetermined value.
The C-color developing device 200 also includes a developing roller 203, a paddle roller 202, a screw conveyor 203, and a developer supply port 204 having the same configuration and functions as those of the A-color developing device 100.
As shown in FIG. 5, a paddle roller 102 and a screw conveyor 103 in the A-color developing device 100 have a gear 102G fixed to their respective shafts 102S and 103S outside one end plate of the A-color developing device 100. , 103G via an intermediate idle gear 10G.

Similarly, the paddle roller 102 and the developing roller 101 are connected to each other via intermediate idle gears by gears 102G, 101G fixed to their respective shafts 102S, 101S.
As shown in FIG. 5, the paddle roller 202 and the screw conveyor 203 in the C-color developing device 200 are connected to each other via gears 202G, 203G fixed to their shafts 202S, 203S via an intermediate idle gear 20G. I have.
Similarly, the paddle roller 202 and the developing roller 201 are connected to each other via intermediate idle gears by gears 202G, 201G fixed to their respective shafts 202S, 201S.

Each of the developing rollers 101 and 201 rotates in the direction of the arrow as the gears 103G and 203G of each screw conveyor are driven by a driving source. In FIG. 5, a drive gear 500G is fixed to a drive shaft 500S connected to a motor (not shown) as a drive source provided on the apparatus main body side. The gears 501G and 502G are always engaged. The switching gears 501G and 502G are pivotally supported by a switching plate 600 that is swingably provided on the drive shaft 500S. When either one of the gears meshes with the gear 103G or the gear 203G, the developing roller 101 or 201 rotates. In FIG. 5, the switching gear 501G meshes with the gear 103G, so that the developing roller 101 rotates in the direction of the arrow.
A partial worm gear 800 meshing with a worm 700 provided on a shaft of the motor 900 is formed in a part of the switching plate 600, and the switching plate 600 is rocked by the forward / reverse rotation of the worm 700 by the motor 900. Move.

In FIG. 4, the second image forming unit II has the same configuration as the first image forming unit I, and includes a photosensitive drum 26, a charging device 27, a writing unit 28, a B color developing device 300, The image forming apparatus includes a developing unit 400 and a cleaning unit 31 and is mounted on the apparatus main body in the same posture as the first image forming unit I.
The second image forming unit II also has the same mechanism as the rotation transmitting mechanism shown in FIG. 5, which is applied to the first image forming unit I.
Each of the image forming units I and II is provided detachably with respect to the apparatus main body. The rotation of each of the photoconductor drums 16 and 26 is synchronized with the running of the intermediate transfer belt 10, and the peripheral speed thereof is determined to exactly match the running speed of the intermediate transfer belt 10. Instead of the chargers 17 and 27, charging means using a corona discharger or a brush can be employed.

The A color developing device 100 of the first image forming unit I contains magenta toner, and the C color developing device 200 contains cyan toner. In the second image forming unit II, that is, in the image forming unit closer to the transfer unit 45, the B color developing device 300 stores yellow toner, and the D color developing device 400 stores black toner.
Since the black toner is used not only for the color copy but also for the black and white copy, in order to increase the copying speed when making the black and white copy, the D color developing device 400 Advantageously, it is provided.
Further, the yellow toner, which has a low contrast with the white color of the transfer paper, that is, has low visibility, consumes more toner than the other color toners except the black toner. On the other hand, black toner is frequently used for black-and-white copying, and toner consumption increases. Accordingly, assuming that toner replenishing containers having substantially the same volume are used, the replenishment timings of the yellow toner and the black toner are substantially the same, so that the developing units of both toners are connected to one image forming unit, that is, the second image. If provided in the forming unit II, both toners can be simultaneously replaced with the image forming unit of each developing unit, which is convenient.
The electrostatic latent images formed on the photosensitive drums 16 and 26 by the well-known method by the charger 17 and the writing unit 18 are developed by the respective developing rollers 101, 201, 301 and 401. The four developing devices 100, 200, 300, and 400 have the same configuration as each other, and for example, a known color developing device described in Japanese Patent Application Laid-Open No. H8-160697 can be employed.

A first transfer roller 41 and a second transfer roller 42, to which a bias voltage for transfer is applied, can be respectively connected to and separated from the photosensitive drums 16 and 26 with the intermediate transfer belt 10 therebetween. The roller 13 is provided with a transfer roller 11 to which a bias voltage for transfer is applied so as to be able to freely contact and separate via an intermediate transfer belt 10.
Each of the photosensitive drums 16 and 26 is slightly separated from the intermediate transfer belt 10 downward, and the first transfer roller 41 and the second transfer roller 42 are separated upward from the intermediate transfer belt 10. In the step of transferring the toner images on the respective photosensitive drums 16 and 26 to the intermediate transfer belt 10, the first transfer roller 41 and / or the second transfer roller 42 transfer the intermediate transfer belt 10 to the photosensitive drums 16 and / or 26. Or 26.
The drive roller 13 and the transfer roller 11 constitute a transfer section 45 for a color image. Instead of the first transfer roller 41 and the second transfer roller 42, a transfer unit using a corona discharger or a brush charger can be employed.
The driven roller 12 is provided with a cleaning device 61 for removing toner remaining on the surface of the intermediate transfer belt 10 so as to be able to freely contact and separate.

Below the first and second image forming units I and II, a paper feeder (not shown) that feeds the stacked transfer papers one by one rightward in FIG. 4 is arranged. One transfer sheet P sent from the sheet feeding device is fed to a transfer section 45 by a feed roller pair 44 and a registration roller 44.
A fixing device 50 composed of a heating roller 47 that is driven to rotate in the direction of arrow b and a pressure roller 48 that rotates in pressure contact with the heating roller 47 is disposed diagonally above the transfer unit 45. A roller 51 for applying an anti-offset liquid to the surface of the heating roller 47 contacts the heating roller 47 as necessary.

  On the downstream side of the fixing device 50, a sheet discharge roller pair 54 for sending the transfer sheet sent from the fixing device 50 onto a sheet discharge tray 53 is arranged. An exhaust fan 55 for exhausting heat is provided at the upper left of FIG. 4 to prevent the electrical components housed below the sheet ejection tray 53 from being heated by the heat of the fixing device 50. .

The operation according to the above-described configuration will be described by taking the case of L = 1 + α as an example.
(1) An electrostatic latent image corresponding to the A-color developing unit 19 is formed on the photosensitive drum 16 of the first image forming unit I by the charger 17 and the writing unit 18, and the electrostatic latent image is The image is visualized by the developing device 19 to obtain a magenta toner image (hereinafter, referred to as an M image). This M image is transferred to the intermediate transfer belt 10 by the first transfer roller 41.
(2) On the other hand, as the M image approaches the second image forming unit II as the intermediate transfer belt 10 travels in the direction of the arrow a, the photosensitive drum 26 is charged by the charger 27 and the writing means 28 with the B color development. An electrostatic latent image corresponding to the developing unit 29 is formed, and the electrostatic latent image is visualized by the B color developing unit 29 to obtain a yellow toner image (hereinafter, referred to as a Y image). The Y image is superimposed and transferred by the second transfer roller 42 onto the M image obtained by the first image forming unit 14 on the intermediate transfer belt 10.
(3) While the superimposed image of the M and Y images approaches the first image forming unit I as the intermediate transfer belt 10 travels, the photosensitive drum 16 is subjected to C color development by the charger 17 and the writing means 18. An electrostatic latent image corresponding to the developing device 20 is formed, and this electrostatic latent image is visualized by the C developing device 20 to obtain a cyan toner image (hereinafter, referred to as a C image). The C image is superimposed and transferred by the first transfer roller 41 on the M and Y images obtained by the second image forming unit II on the intermediate transfer belt 10.
(4) While the superimposed image of the M, Y, and C images approaches the second image forming unit II as the intermediate transfer belt 10 travels, the D-color is applied to the photosensitive drum 26 by the charger 27 and the writing unit 28. An electrostatic latent image corresponding to the developing device 35 is formed, and the electrostatic latent image is visualized by the D color developing device 35 to obtain a black toner image (hereinafter, referred to as a BK image). The BK image is transferred onto the intermediate transfer belt 10 by the second transfer roller 42 on the M, Y, and C images obtained by the first image forming unit I.

When a color image is finally formed on the intermediate transfer belt 10 by the second transfer roller 42, the transfer paper sent from the paper feeding device is sent to the transfer unit 45 by the pair of registration rollers 44, where the transfer paper is transferred. The color image is transferred to paper. The transferred color image is fixed on the transfer paper by the fixing device 50, and is sent to the paper output tray 53 by the paper output roller 54. After the transfer of the color image, the intermediate transfer belt 10 is cleaned by a cleaning device 61 to remove residual toner.
When a plurality of prints are to be obtained, when the superimposed image of the M and Y images is transferred to the intermediate transfer belt 10 in the second image forming unit II, the M image is successively transferred to the first image forming unit I. The image is transferred onto the transfer belt 10, and the above steps (1) to (4) are repeated.

When one of the four developing rollers 101, 201, 301, and 401 rotates and works to develop the electrostatic latent image on the photosensitive drum, the other developing rollers are stopped. As the developing roller, a known developing roller including a non-magnetic sleeve that rotates during a developing operation and a magnet disposed in the non-magnetic sleeve can be used.
When one developing roller is in operation, the magnets in the three non-operating developing rollers are stopped to prevent color mixing due to the transfer of the developer on the other developing roller to the photosensitive drum. By slightly rotating and shifting the position of the magnetic pole with respect to the photosensitive drum, the developer on the developing roller is prevented from contacting the photosensitive drum. As a means for preventing color mixture, a developing roller retracting mechanism that moves the non-operating developing roller away from the peripheral surface of the photosensitive drum to such an extent that the developer on these rollers does not contact the photosensitive drum can be adopted.

FIG. 6 shows a second embodiment of the present invention. In the figure, the intermediate transfer belt 110 is stretched between a driving roller 113 and a driven roller 112 disposed vertically, and is driven by the driving roller 113 so as to travel in a direction of an arrow a. The intermediate transfer belt 110 is given an optimal tension by a tension roller 160. A first image forming unit 114 and a second image forming unit 124 are arranged at a fixed interval on the surface running above the intermediate transfer belt 110 along the running direction of the intermediate transfer belt 110. . In the figure, a cleaning device 161 that removes toner remaining on the surface of the intermediate transfer belt 110 is provided at the upper left of the intermediate transfer belt 110.
The first image forming unit 114 includes a charger 117 composed of a corona discharger that uniformly charges the surface of the photoreceptor belt 116 as an image carrier, and an image signal based on a document on the charged surface of the photoreceptor belt 116. It mainly includes a writing unit 118 for writing with a modulated beam, an M developing unit 119, a C developing unit 120, and a cleaning unit 121. The photoreceptor belt 116 is stretched between a driving roller 116a and a driven roller 116b disposed substantially horizontally, and is driven by the driving roller 116a to travel in the direction of the arrow.
The second image forming unit 124 has the same configuration as the first image forming unit 114, and includes a photoreceptor belt 126, a charger 127, a writing unit 128, a Y developing unit 129, a BK developing unit 130, and a cleaning unit. 131, and is attached to the apparatus main body in the same posture as the first image forming unit 114. The photoreceptor belt 126 is stretched between a driving roller 126a and a driven roller 126b, and is driven by the driving roller 126a to travel in the direction of the arrow.
Each of the image forming units 114 and 124 is detachably provided to the apparatus main body. The rotation of each of the photoreceptor belts 116 and 126 is synchronized with the travel of the intermediate transfer belt 110, and the peripheral speed thereof is determined to exactly match the travel speed of the intermediate transfer belt 110.

The M developing device 119 contains magenta toner, the C developing device 120 contains cyan toner, the Y developing device 129 contains yellow toner, and the BK developing device 130 contains black toner. The electrostatic latent images formed on the respective photoreceptor belts 116 and 126 formed by a known method are developed by respective developing rollers 132, 133, 134 and 135. Each of the four developing devices 119, 120, 129, and 130 has a similar configuration including a developer stirring device, a toner replenishing device, and the like, and a well-known color developing device can be employed. ,
A first transfer charger 141 and a second transfer charger 142 to which a bias voltage for transfer is applied are disposed on each of the photosensitive belts 116 and 126 with the intermediate transfer belt 110 interposed therebetween. The transfer roller 111 to which a bias voltage for transfer is applied is provided so as to be able to freely contact and separate via an intermediate transfer belt 110. The drive roller 113 and the transfer roller 111 constitute a color image transfer unit 145.
One transfer sheet P sent from a sheet feeding device (not shown) is fed to a transfer unit 145 by a registration roller 144. A fixing device 150 is disposed diagonally above the transfer unit 145.
In the configuration of the second embodiment, the process of forming a color image when L = l + α is the same as that of the first embodiment, and a description thereof will be omitted.

As understood from the first and second embodiments, the first and second image forming units having the image carrier and the developing device have the same configuration, and are arranged along one plane of the intermediate transfer belt. They are arranged at regular intervals and in the same posture. Therefore, if a pair of image forming units having the same configuration are arranged in the same posture, the direction of one plane of the intermediate transfer belt is not limited to the horizontal or vertical shown in the first and second embodiments, but may be inclined. You can do it.
Although not shown in each embodiment, when the present invention is applied to an electrophotographic copying machine, a reading means for a document to be copied is also used.
As the toner used in the first and second image forming units, for example, gold, silver, flesh color, fluorescent color, or the like can be used in addition to the three primary colors and black toner. For example, when the first image forming unit has three colors of yellow toner, cyan toner, and skin color toner, and the second image forming unit has three colors of magenta toner, black toner, and gold toner, the first and second image forming units may be used. Each of the two image forming units has three developing units, and obtains a color image by selecting a yellow toner and a flesh color toner of the first image forming unit and a black toner of the second image forming unit. Can be.

1 is a schematic diagram illustrating the present invention. FIG. 4 is an explanatory diagram illustrating an operation of a first example of a color image forming process according to the present invention. FIG. 11 is an explanatory diagram illustrating an operation of a second example of the color image forming process according to the present invention. FIG. 2 is a side view of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 4 is a side view illustrating a rotation transmission mechanism that drives a developing roller. FIG. 6 is a side view of an image forming apparatus according to a second embodiment of the present invention.

Explanation of reference numerals

10, 110 Intermediate transfer belt 11, 111 Transfer roller 14, 114 First image forming unit 16 First photosensitive drum 17, 117 Charger 18, 118 Writing means 19 A developing device 20 C developing device 24, 124 Second Image forming unit 26 second photosensitive drum 27, 127 charging device 28, 128 writing means 29, 129 B developing device 30, 130 D developing device 41 first transfer roller 42 second transfer roller 141 first transfer Charger 142 Second transfer charger 44, 144 Registration roller 45, 145 Transfer unit 50, 150 Fixing device 116 First photoreceptor belt 126 Second photoreceptor belt 141 First transfer charger 142 Second transfer charger

Claims (20)

An image forming method in which a toner image formed of at least three primary colors of A, B, and C on an image carrier is transferred to an intermediate transfer belt, and the color image on the intermediate transfer belt is transferred to transfer paper by a transfer unit. ,
Transferring a toner image onto the intermediate transfer belt in the following order by first and second image forming means arranged at a constant interval along the same moving surface of the intermediate transfer belt, An image forming method for transferring the color image obtained on the intermediate transfer belt to transfer paper.
Transferring the A color toner image onto the intermediate transfer belt by the first image forming unit;
A step of superimposing and transferring the B color toner image on the A color toner image on the intermediate transfer belt by the second image forming means;
A step of superimposing and transferring the C color toner image on the A and B color toner images on the intermediate transfer belt by the first image forming means; An image forming method in which a toner image formed of at least three primary colors of A, B, and C on an image carrier is transferred to an intermediate transfer belt, and the color image on the intermediate transfer belt is transferred to transfer paper by a transfer unit. ,
Transferring a toner image onto the intermediate transfer belt in the following order by first and second image forming means arranged at a constant interval along the same moving surface of the intermediate transfer belt, An image forming method for transferring the color image obtained on the intermediate transfer belt to transfer paper.
Transferring the A color toner image onto the intermediate transfer belt by the first image forming unit;
While transferring the subsequent A-color toner image to the intermediate transfer belt by the first image forming unit, the B-color toner image is transferred by the second image forming unit to the A-color toner image on the preceding intermediate transfer belt. Process,
A step of superimposing and transferring the C color toner image on the A and B color toner images on the intermediate transfer belt by the first image forming means;   3. The image forming method according to claim 1, wherein the first image forming unit superimposes the C color toner image on the A and B color toner images and transfers the second image to the A, B and C color toner images. An image forming method in which a black toner image is overlaid and transferred by a forming unit.   4. The image forming method according to claim 1, wherein the color A is magenta or cyan, the color B is cyan or magenta, and the color C is yellow. An intermediate transfer belt on which a toner image on an image carrier is transferred, and an image forming apparatus for transferring the toner image on the intermediate transfer belt to transfer paper,
First and second image forming units arranged at regular intervals along the same moving surface of the intermediate transfer belt,
A first image forming unit including one image carrier, and developing means for developing the electrostatic latent image on the image carrier with at least two colors of developer;
An image forming apparatus, wherein the second image forming unit includes one image carrier and developing means for developing with a developer of a different color from the developer of the first image forming unit. An intermediate transfer belt on which a toner image formed of at least three primary colors A, B, and C on the image carrier is transferred, and image formation for transferring the color image on the intermediate transfer belt to transfer paper by a transfer unit In the device,
First and second image forming units arranged at regular intervals along the same moving plane of the intermediate transfer belt,
A first image forming unit including one image carrier, a developing unit for developing the electrostatic latent image on the image carrier with the A color toner, and a developing unit for developing the electrostatic latent image with the C color toner;
An image characterized in that the second image forming unit comprises one image carrier and a developing means for developing the electrostatic latent image on the image carrier with a developing means for developing with a B color toner. Forming equipment. The image forming apparatus according to claim 6,
The image carrier is a drum-shaped or belt-shaped photoconductor,
An image forming apparatus, wherein the second image forming unit includes one photoreceptor and developing means for developing the electrostatic latent image on the photoreceptor with black toner. The image forming apparatus according to claim 5, 6, or 7,
The image forming apparatus according to claim 1, wherein the intermediate transfer belt has a length at least twice as long as a length of a transfer sheet of a minimum size for a full-color image in a feeding direction. The image forming apparatus according to any one of claims 5 to 8,
An image forming apparatus, wherein the first and second image forming units are detachable from the apparatus main body. The image forming apparatus according to any one of claims 5 to 9,
An image forming apparatus, wherein the first image forming unit and the second image forming unit have the same configuration. The image forming apparatus according to any one of claims 5 to 10,
An image forming apparatus, wherein the first image forming unit and the second image forming unit are arranged in the same posture and along the moving direction of the intermediate transfer belt on the same moving plane. The image forming apparatus according to any one of claims 5 to 11,
A first image forming unit, a second image forming unit, and the transfer unit are arranged in this order along a moving direction of the intermediate transfer belt on the same moving plane, and a developing unit for toner of a color most frequently used is provided. Provided in the second image forming unit. The image forming apparatus according to any one of claims 5 to 12,
A first image forming unit, a second image forming unit, and the transfer unit are arranged in this order along a moving direction of the intermediate transfer belt on the same moving plane, and a developing unit for toner of a color having the lowest visibility is provided. Provided in the second image forming unit. The image forming apparatus according to any one of claims 5 to 12,
A first image forming unit, a second image forming unit, and the transfer unit are arranged in this order along a moving direction of the intermediate transfer belt on the same moving plane, and a developing unit for toner of a color most frequently used is provided. An image forming apparatus comprising: a developing unit for a toner of a color having the least visual sensitivity; The image forming apparatus according to claim 12,
An image forming apparatus in which the most frequently used color toner is black. The image forming apparatus according to claim 13,
An image forming apparatus in which the toner of the color with the lowest visibility is yellow. The image forming apparatus according to claim 14,
An image forming apparatus in which the most frequently used color toner is black and the least visually perceptible color toner is yellow. An intermediate transfer belt stretched between rollers such that an image holding surface to which a toner image formed of at least three primary colors of A, B, and C is substantially directed downward;
A first photosensitive drum and a second photosensitive drum that are sequentially arranged along a moving direction of the image holding surface of the intermediate transfer belt and form an electrostatic latent image;
Developing means for developing the electrostatic latent image on the first photosensitive drum with the A color toner and developing means for developing with the C color toner;
Developing means for developing the electrostatic latent image on the second photosensitive drum with B-color toner;
A transfer unit that is disposed near the downstream side of the second photosensitive drum in the moving direction of the intermediate transfer belt and transfers a color image on the intermediate transfer belt to transfer paper;
A transfer paper transport path for feeding the transfer paper from the paper feeding means upward toward the transfer means,
A heating and fixing device for an image disposed above the intermediate transfer belt;
An image forming apparatus comprising: An intermediate transfer belt stretched between rollers such that an image holding surface to which a toner image formed by at least three primary colors of A, B, and C is substantially directed sideways;
A first photoreceptor belt and a second photoreceptor belt sequentially arranged along a moving direction of the image holding surface of the intermediate transfer belt and forming an electrostatic latent image;
Developing means for developing the electrostatic latent image on the first photoreceptor belt with the A color toner, and developing means for developing with the C color toner;
Developing means for developing the electrostatic latent image on the second photosensitive belt with B-color toner;
A transfer unit that is disposed near the downstream side of the second photosensitive belt in the moving direction of the intermediate transfer belt and transfers a color image on the intermediate transfer belt to transfer paper;
An image forming apparatus comprising: The image forming apparatus according to any one of claims 5 to 12,
An image forming apparatus in which A is magenta or cyan, B is cyan or magenta, and C is yellow.

Images