JP2006039455A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent irregularities in an image in image formation due to variation in torque caused by pressurized contact/separation of a secondary transfer roller and a cleaning device with/from an intermediate transfer body. <P>SOLUTION: In formation of a superposed toner image, primary transfer is completed for a toner image formed by light for exposure corresponding to the last color (Y) among the lights for exposure with which a photoreceptor drum 7 is sequentially irradiated; in formation of the next superposed toner image, the secondary transfer roller 18 and a cleaning roller 11 are brought into a pressurized contact with the intermediate transfer belt 4 at approximately the same timing before the light for exposure corresponding to the first color (K) among the lights for exposure with which the photoreceptor drum 7 is sequentially irradiated; in formation of next superposed toner image, the primary transfer is completed for the toner image formed by the light for exposure corresponding to the first color (K) among the lights for exposure with which the photoreceptor drum 7 is irradiated; and before the photoreceptor drum 7 is irradiated with the light for exposure corresponding to the next color (C), the secondary transfer roller 18 and the cleaning roller 11 are separated from the intermediate transfer belt 4 at approximately the same time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more specifically, a secondary transfer unit that secondary-transfers a toner image on an intermediate transfer member, and a toner remaining on the intermediate transfer member after the secondary transfer. The present invention relates to an image forming apparatus including a cleaning unit that cleans an image.

  2. Description of the Related Art Conventionally, many technologies capable of forming color images, such as color copying machines and color printers, have been proposed in image forming apparatuses such as copying machines, printers, and facsimiles. In general, color image forming apparatuses of a single drum type and a multi-drum type are known. For example, a one-drum type is provided with a plurality of color developing devices around one photosensitive drum, and a toner image of each color is formed by these multi-color developing devices, and is in contact with the intermediate transfer belt. The toner images are sequentially primary transferred onto the intermediate transfer belt to form a superimposed toner image, and the superimposed toner images on the intermediate transfer belt are collectively transferred onto the sheet material at the secondary transfer position. A technique for obtaining a color image by this method is known.

  The multi-drum type has a plurality of photosensitive drums each provided with a single color developing device, and forms a single color toner image on each photosensitive drum, and these single color toner images are placed on a sheet material. In this way, a color image is obtained by sequentially transferring the image.

  The one-drum type has only one photosensitive drum, so the apparatus can be downsized and the cost can be reduced. However, full color can be achieved by forming an image on a single photosensitive drum a plurality of times (for example, four times). Since an image is formed, it is considered difficult to speed up image formation. On the other hand, the multi-drum type has the advantage that it is easy to increase the speed although it is large (see Patent Document 1).

JP 2003-57915 A (page 6, FIG. 4)

  By the way, for example, in a one-drum type color image forming apparatus, if a secondary transfer roller or a belt cleaning device is pressed against or separated from an intermediate transfer belt while an image is being formed, the image is disturbed by torque fluctuation or impact. There was a problem that occurred. Conventionally, the timing at which the secondary transfer roller and the belt cleaning device are pressed against and separated from the intermediate transfer belt is shifted, so that torque fluctuations and impacts occur twice.

  However, because the total length of the intermediate transfer belt has been long, the problem of image distortion due to absorbing torque fluctuations and shocks has not surfaced. However, due to the recent demand for downsizing of the device, the total length of the intermediate transfer belt has been reduced. The above problem has surfaced because of the need to shorten it. Further, it has been proposed to provide a mechanism for reducing the impact of each individual. However, the impact is not actually reduced, and it has been difficult to eliminate the disturbance of the image.

  That is, when forming the electrostatic latent image on the photosensitive drum, if the secondary transfer roller or the belt cleaning device is pressed against or separated from the intermediate transfer belt, image disturbance such as image blurring occurs.

  Accordingly, the present invention provides an image forming apparatus that is free from image distortion during image formation due to torque fluctuation, intermediate transfer body speed change, or impact due to pressure contact / separation of the secondary transfer unit and cleaning unit to the intermediate transfer body. The purpose is to do.

  According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum; an exposure apparatus that irradiates the photosensitive drum with light for exposure to form an electrostatic latent image according to image information; and the exposure apparatus. In order to develop the formed electrostatic latent image as a toner image, a developing device disposed around the photosensitive drum, and a toner image formed on the photosensitive drum by the developing device are transferred to an intermediate transfer member. Primary transfer means for primary transfer onto the intermediate transfer body at the contact position to form a toner image; and secondary transfer means for secondary transfer of the toner image on the intermediate transfer body onto the sheet material at the secondary transfer position; A cleaning unit that cleans a toner image remaining on the intermediate transfer member after the secondary transfer; and a contact / separation unit that contacts and separates the secondary transfer unit and the cleaning unit from the intermediate transfer member. Yes.

  In this image forming apparatus, when the toner image is continuously formed on the sheet material, the primary image of the toner image formed by the exposure light irradiated on the photosensitive drum in the first toner image formation. When the transfer is completed and the next toner image is formed and before the photosensitive drum is irradiated with exposure light, the contact / separation unit causes the secondary transfer unit and the cleaning unit to substantially simultaneously move the intermediate unit. It is characterized by being pressed against the transfer body.

  According to a second aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum; an exposure apparatus that irradiates the photosensitive drum with light for exposure to form an electrostatic latent image according to image information; and the exposure apparatus. In order to develop the formed electrostatic latent image as a toner image, a plurality of color developing devices arranged around the photosensitive drum, and a plurality of color toner images formed on the photosensitive drum by the developing device A primary transfer unit that sequentially performs primary transfer on the intermediate transfer member at a contact position with the intermediate transfer member to form a superimposed toner image; and a sheet material that transfers the superimposed toner image on the intermediate transfer member at a secondary transfer position. A secondary transfer unit that performs secondary transfer in a batch, a cleaning unit that cleans a toner image remaining on the intermediate transfer body after the secondary transfer, and the secondary transfer unit and the cleaning unit that are connected to the intermediate transfer unit. Get in and out of the body A moving means, a has.

In this image forming apparatus, when the toner image is continuously formed on the sheet material, the last of the plurality of colors of exposure light sequentially irradiated on the photosensitive drum when the superimposed toner image is formed. When the primary transfer of the toner image formed with the exposure light corresponding to the color is completed and the next superimposed toner image is formed, the first of the multiple colors of exposure light sequentially irradiated onto the photosensitive drum The secondary transfer unit and the cleaning unit are pressed against the intermediate transfer member substantially simultaneously by the contact / separation unit until the exposure light corresponding to the color of the light is irradiated.
In addition, when the next superimposed toner image is formed, primary transfer of the toner image formed with the exposure light corresponding to the first color among the plurality of colors of exposure light irradiated on the photosensitive drum is completed. In addition, the secondary transfer unit and the cleaning unit are separated from the intermediate transfer member substantially simultaneously by the contact / separation unit until the exposure light corresponding to the next color is irradiated. And

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the contact / separation unit is connected / disconnected via a clutch to a drive shaft that rotationally drives the intermediate transfer member at a secondary transfer position. An eccentric cam attached freely,
Secondary transfer is supported so as to be swingable integrally with the secondary transfer unit so as to be able to contact the eccentric cam, and the secondary transfer unit is brought into contact with and separated from the intermediate transfer body according to the rotation of the eccentric cam. A side abutting part;
A cleaning-side contact portion that is swingably supported integrally with the cleaning means so as to be able to contact the eccentric cam, and that contacts and separates the cleaning means with respect to the intermediate transfer body according to rotation of the eccentric cam; It is characterized by having.

  According to the first aspect of the present invention, when the toner image is continuously formed on the sheet material, the primary transfer of the first toner image is completed, and exposure light is irradiated when the next toner image is formed. In the meantime, since the secondary transfer unit and the cleaning unit are pressed against the intermediate transfer member almost simultaneously, torque fluctuations due to pressure contact / separation to the intermediate transfer member, speed change of the intermediate transfer member, or impact It is possible to prevent image disturbance during image formation.

  According to the second aspect of the present invention, when the toner images are continuously formed on the sheet material, the primary transfer of the last color toner image among the plurality of colors of exposure light is performed when the superimposed toner images are formed. Is completed, and the secondary transfer unit and the cleaning unit are substantially simultaneously operated during the next superposed toner image formation until the first color exposure light among the multiple color exposure lights is irradiated. When the next superimposed toner image is formed in pressure contact with the intermediate transfer member, the primary transfer of the first color toner image among the multiple colors of exposure light is completed, and the exposure light corresponding to the next color is emitted. Before the irradiation, the secondary transfer unit and the cleaning unit are separated from the intermediate transfer member at substantially the same time, so that torque fluctuations due to pressure contact / separation to the intermediate transfer member, speed change of the intermediate transfer member, or Image distortion during image formation due to impact It is possible to stop.

  According to the third aspect of the invention, the contacting / separating means contacts the eccentric cam, which is attached to the drive shaft that rotationally drives the intermediate transfer member at the secondary transfer position via the clutch. A secondary transfer side abutting portion that is swingably supported integrally with the secondary transfer means so as to be able to come into contact with the intermediate transfer body according to the rotation of the eccentric cam, and an eccentric cam. A cleaning-side contact portion that is supported so as to be swingable integrally with the cleaning means so as to be able to come into contact, and that contacts and separates the cleaning means from the intermediate transfer body in accordance with the rotation of the eccentric cam. Thus, the secondary transfer unit and the cleaning unit can be pressed against or separated from the intermediate transfer member substantially simultaneously.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
[Configuration of Image Forming Apparatus]
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to the present embodiment.

  The image forming apparatus main body 2 has an image forming unit 16, and the image forming unit 16 applies a charge to the photoconductive drum 7 around the photoconductive drum 7 and the photoconductive drum 7. Development of four colors of black (K), cyan (C), magenta (M) and yellow (Y) in order to form a toner image on the outer peripheral surface of the photosensitive drum 7 and the charging device 15 for charging the body drum 7 The image forming apparatus includes a developing device 13 having portions arranged side by side on the circumference, a primary transfer roller 8 as a primary transfer unit, and a cleaning device 14 that removes residual toner on the photosensitive drum 7. An exposure device 17 is provided above the image forming unit 16.

  The charging device 15 has a charging roller (not shown) disposed in contact with the surface of the photosensitive drum 7, and a charging bias is applied to the charging roller so that the surface of the photosensitive drum 7 has a uniform polarity and potential. And a charging bias application power source (not shown) for charging the battery.

  The developing device 13 is fixed to a rotary rack 31 that can rotate around a rotating shaft 30, and the above-described four color developers (toners) of black (K), cyan (C), magenta (M), and yellow (Y). ), And developing rollers 36 to 39 that carry the toner of each color in the developing containers 32 to 35 on the surface and transport them to the developing unit (photosensitive drum surface), respectively. And a developing bias applying power source (not shown) for applying a developing bias to each of the developing rollers 36 to 39 to attach each color toner to the electrostatic latent image formed on the photosensitive drum 7 and developing the toner image. Z).

  The cleaning device 14 has a cleaning blade (not shown) for removing toner (residual toner) remaining on the surface of the photosensitive drum 7 without being transferred to an intermediate transfer belt 4 described later during primary transfer.

  The exposure device 17 exposes the surface of the photosensitive drum 7 after charging in accordance with image information, and removes the charge in the exposed portion to form an electrostatic latent image. The exposure device 17 includes a laser scanner, polygon mirror, It has a lens, a reflection mirror, and the like.

  An intermediate transfer belt 4 as an intermediate transfer member is sandwiched between the primary transfer roller 8 and the photosensitive drum 7 described above below the photosensitive drum 7. The intermediate transfer belt 4 is formed in an endless shape made of a fluorine-based resin material, and is wound around three rollers of a driving roller 5, a tension roller 6, and a guide roller 10. The intermediate transfer belt 4 can be conveyed in the clockwise direction in the figure while being sandwiched between the primary transfer roller 8 and the photosensitive drum 7 with a predetermined pressing force.

  The intermediate transfer belt 4 is provided with a reference hole (not shown) at a predetermined position. This reference hole is detected by a detection sensor 28 provided on the upstream side in the belt conveyance direction with respect to the drive roller 5. The reference position of the intermediate transfer belt 4 is detected. The detection of the reference position is the reference for all image forming operations.

  The primary transfer roller 8 is disposed so as to face the photosensitive drum 7, and forms a primary transfer nip portion between the primary transfer roller 8 and the photosensitive drum 7. The toner image on the photosensitive drum 7 is electrostatically transferred to the intermediate transfer belt 4 by applying a primary transfer bias to the primary transfer roller 8 from the primary transfer bias application power source to the intermediate transfer belt 4. It has become so.

  A secondary transfer roller 18 as a secondary transfer unit is provided on the opposite side of the intermediate transfer belt 4 from the drive roller 5. The secondary transfer roller 18 is pressed against the driving roller 5 via the intermediate transfer belt 4 to form a secondary transfer nip, so that the toner image on the intermediate transfer belt 4 is secondarily transferred to the sheet material P. Further, a cleaning roller 11 as a cleaning unit is disposed in the vicinity of the driving roller 5 on the downstream side of the driving roller 5 in the belt conveyance direction. The cleaning roller 11 is pressed against the driving roller 5 via the intermediate transfer belt 4, so that a toner image (overlapping toner) remaining on the intermediate transfer belt 4 after the secondary transfer onto the sheet material P by the secondary transfer roller 18 is performed. Image) residual toner is removed.

  The sheet material conveyance unit 23 includes a sheet feeding cassette 24, a sheet feeding roller 25, a registration switch 26, a registration roller pair 27, and the like in order from the upstream side in the conveyance direction of the sheet material P. The paper feed cassette 24 stores a large number of sheet materials P on which toner images are formed, and the paper feed roller 25 feeds the sheet materials P in the paper feed cassette 24 one by one. The registration switch 26 is a switch that detects the sheet material P, and the registration roller pair 27 temporarily stops the conveyed sheet material P, corrects the skew of the sheet material P, and performs the intermediate transfer belt 4. The toner image is supplied to the secondary transfer nip portion in synchronization with the upper superimposed toner image (using a signal from the registration switch 26).

A fixing device 20 that fixes an image transferred to the sheet material P is provided downstream of the secondary transfer roller 18 in the conveyance direction of the sheet material P. The fixing device 20 includes a fixing roller 21 and a pressure roller 22 that is pressed by the fixing roller 21 to form a fixing nip portion. Here, the sheet material P having the toner image transferred on the surface is heated and pressurized while being nipped and conveyed by the fixing nip portion, and the toner image is fixedly fixed on the surface by welding. The sheet material P on which the toner image is fixed is carried out of the apparatus by the discharge roller pair 29.
[Description of full-color image forming operation]
FIG. 2 shows a flowchart when a full-color image is formed.

  As shown in the figure, when the main switch of the apparatus main body is turned on, the content (image information) of the document is read by the scanner (S1). In accordance with the image read at this time, an electrostatic latent image is formed on the surface of the photosensitive drum 7 by the exposure device 17 (S2). In this case, taking the case where the read image information is a full-color image as an example, first, a black (K) electrostatic latent image is formed on the surface of the photosensitive drum 7, and then the electrostatic latent image is Black (K) toner is adhered by the developing device 13 (S3). Further, the black (K) toner is primarily transferred to the intermediate transfer belt 4 at the primary transfer position (S4).

  Next, in S5, it is determined whether or not the primary transfer of all the color toner images of black (K), cyan (C), magenta (M), and yellow (Y) has been completed. The intermediate transfer belt 4 is rotated once and the process returns to S2. Similarly, when the superimposed toner images of all colors are primarily transferred to the intermediate transfer belt 4 in S5 (Yes), the process proceeds to S7, and the secondary transfer roller 18 and the cleaning roller 11 are transferred to the intermediate transfer belt 4. Weld together. Thereafter, the sheet material P enters the secondary transfer nip at a timing, and the secondary toner image is superimposed on the sheet material P. Next, after a predetermined time has elapsed, the secondary transfer roller 18 and the cleaning roller 11 are simultaneously separated from the intermediate transfer belt 4. The timing at which the secondary transfer roller 18 and the cleaning roller 11 are simultaneously pressed and separated from the intermediate transfer belt 4 will be described later.

On the other hand, the sheet material P onto which the full-color toner image has been transferred is fixed on the toner image by the fixing device 20, and then discharged to the discharge tray side by the discharge roller pair 29, thus completing the image forming operation.
[Structure of contact / separation means]
FIG. 3 shows a configuration of contact / separation means 53 that presses and separates the secondary transfer roller 18 and the cleaning roller 11 from the intermediate transfer belt 4.

  The secondary transfer roller 18 is supported by a support frame 44 that can swing about a shaft 43, and the support frame 44 is formed with a contact portion 44 </ b> A as a secondary transfer side contact portion. . The secondary transfer roller 18 is constantly urged toward the drive roller 5 by an urging member 45 such as a spring. On the other hand, the cleaning roller 11 is supported by a support frame 47 that can swing around a shaft 46, and the support frame 47 is formed with a contact portion 47 </ b> A as a cleaning side contact portion. The cleaning roller 11 is constantly urged toward the drive roller 5 by an urging member 48 such as a spring.

  Further, a motor 41 is connected via a clutch 40 to the drive shaft 5A of the drive roller 5 that rotationally drives the intermediate transfer belt 4, and the clutch 40 is controlled to be turned on and off by a control unit 42. . An eccentric cam 50 that contacts the contact portion 44A of the support frame 44 on the secondary transfer roller 18 side and an eccentric cam 51 that contacts the contact portion 47A of the support frame 47 on the cleaning roller 11 side are integrated with the drive shaft 5A. Attached.

  The eccentric cams 50 and 51, the abutting portion 44A, the abutting portion 47A, the clutch 40, and the like constitute the contacting / separating means 53 that presses and separates from the intermediate transfer belt 4.

  As described above, for example, as shown in FIG. 3, the secondary transfer roller 18 and the cleaning roller 11 are driven in a state in which the portions where the eccentric cams 50 and 51 have a low head and the contact portions 44A and 47A are in contact with each other. The secondary transfer roller 18 and the cleaning roller 11 are brought into pressure contact with the intermediate transfer belt 4 in contact with the roller 5 side to form a secondary transfer nip portion. Further, in a state where the lifted portions of the eccentric cams 50 and 51 and the contact portions 44A and 47A are in contact with each other, the secondary transfer roller 18 and the cleaning roller 11 are separated from the drive roller 5 side, and the two The next transfer roller 18 and the cleaning roller 28 are separated from the intermediate transfer belt 4.

For this reason, by controlling the clutch 40 at an appropriate timing, power can be transmitted to or disconnected from the drive shaft 5A of the drive roller 5. Therefore, if the clutch 40 is controlled, the secondary transfer roller 18 and the cleaning roller 11 can be pressed against or separated from the intermediate transfer belt 4 at an appropriate timing.
[Operation of image forming apparatus]
FIG. 4 shows a time chart of the image forming operation in the case of two or more monochrome continuous prints.

  In the figure, when the detection sensor 28 detects the reference hole of the intermediate transfer belt 4 by the first rotation of the intermediate transfer belt 4, the rotation shaft 30 (see FIG. 1) of the developing device 13 rotates 2260 ms after the detection. The black (K) developing roller rotates from the standby position and moves to a predetermined position (approximately 230 ms). At approximately the same time, the developing bias signal is turned on. When the reference hole is detected by one rotation of the next intermediate transfer belt 4 for printing the first sheet, the exposure signal is turned ON and exposure light is emitted from the exposure device 17 to the photosensitive drum 7. Then, an electrostatic latent image is formed on the photosensitive drum 7. When the electrostatic latent image reaches the developing nip, which is in the vicinity of the photosensitive drum 7 and the black (K) developing roller, as the photosensitive drum 7 rotates, black (K) toner is added to the electrostatic latent image. Is attached to form a toner image. Next, when the photosensitive drum 7 rotates and the toner image reaches the primary transfer position, the toner image is primarily transferred to the intermediate transfer belt 4 here.

  Further, 2282 ms after the detection of the reference hole accompanying the rotation of the intermediate transfer belt 4, that is, after the completion of the primary transfer to the first intermediate transfer belt 4 and before the start of exposure for forming the second image. In the meantime, the secondary transfer roller 18 and the cleaning roller 11 are pressed against the intermediate transfer belt 4. At substantially the same time as the press contact, the secondary transfer bias signal is turned ON, and the toner image is secondarily transferred to the sheet material P that has entered the secondary transfer nip portion with timing. Further, after the secondary transfer, the toner image remaining on the intermediate transfer belt 4 without being transferred is removed by the cleaning roller 11. The above operation is repeated up to the final page, and when the primary transfer bias signal is turned OFF after the printing of the final page is completed, the secondary transfer roller 18 and the cleaning roller 11 are separated from the intermediate transfer belt 4 substantially simultaneously. Is done.

  The separation timing of the secondary transfer roller 18 and the cleaning roller 11 from the intermediate transfer belt 4 corresponds to 4781 ms after the detection of the reference hole accompanying the rotation of the intermediate transfer belt 4 for printing the final page.

  FIG. 5 shows a time chart of the image forming operation in the case of two or more full-color continuous printing.

  In this figure, when the detection sensor 28 detects the reference hole of the intermediate transfer belt 4 in one rotation of the first intermediate transfer belt 4, the rotation shaft 30 (see FIG. 1) of the developing device 13 rotates after 2260 ms from the detection. Then, the black (K) developing roller rotates from the standby position and moves to a predetermined position (approximately 230 ms). At approximately the same time, the developing bias signal is turned on. When the reference hole is detected by one rotation of the next intermediate transfer belt 4 in order to form the first black (K) toner image, the black (K) exposure signal is turned ON and the exposure device 17 is turned on. Then, exposure light is applied to the photosensitive drum 7, and a black (K) electrostatic latent image is formed on the photosensitive drum 7. When the electrostatic latent image reaches the developing nip, which is in the vicinity of the photosensitive drum 7 and the black (K) developing roller, as the photosensitive drum 7 rotates, black (K) toner is added to the electrostatic latent image. Is attached to form a toner image. Next, when the photosensitive drum 7 rotates and the toner image reaches the primary transfer position, the black (K) toner image is primarily transferred to the intermediate transfer belt 4.

  On the other hand, 2282 ms after the detection of the reference hole of the intermediate transfer belt 4, the rotating shaft 30 (see FIG. 1) of the developing device 13 rotates and the cyan (C) developing roller moves to a predetermined position. At approximately the same time, the developing bias signal is turned on. When the reference hole is detected by one rotation of the next intermediate transfer belt 4 in order to print the first sheet of cyan (C), the cyan (C) exposure signal is turned on and the exposure device 17 performs exposure. Is irradiated onto the photosensitive drum 7, and an electrostatic latent image of cyan (C) is formed on the photosensitive drum 7. When the electrostatic latent image reaches the developing nip in the vicinity of the photosensitive drum 7 and the cyan (C) developing roller as the photosensitive drum 7 rotates, cyan (C) toner is added to the electrostatic latent image. Is attached to form a toner image. Next, when the photosensitive drum 7 rotates and the toner image comes to the primary transfer position, the cyan (C) toner image is superimposed on the intermediate transfer belt 4 and the black (K) toner image described above to be the primary image. Transcribed.

  Thereafter, in the same manner, magenta (M) and yellow (Y) toner images are sequentially primary-transferred onto the intermediate transfer belt 4 and a superimposed toner image is formed on the intermediate transfer belt 4.

  Furthermore, 2282 ms after the detection of the reference hole accompanying one rotation of the intermediate transfer belt 4 in order to form a yellow (Y) toner image, that is, yellow which is a color to be primarily transferred to the intermediate transfer belt 4 at the end of the first sheet. (Y) After completion of the primary transfer, and before the start of exposure for image formation of black (K), which is the color to be transferred first on the second sheet, the secondary transfer roller 18 and the cleaning roller 11 Substantially simultaneously, the intermediate transfer belt 4 is brought into pressure contact. At substantially the same time as the press contact, the secondary transfer bias signal is turned ON, and the superimposed toner image is secondarily transferred onto the sheet material P that has entered the secondary transfer nip portion with timing. Further, after this secondary transfer, the superimposed toner image remaining without being transferred onto the intermediate transfer belt 4 is removed by the cleaning roller 28.

  Next, when the reference hole is detected by one rotation of the intermediate transfer belt 4 in order to form the second black (K) toner image, the black (K) exposure signal is turned ON and the exposure device 17 performs exposure. Is irradiated to the photosensitive drum 7, and a black (K) electrostatic latent image is formed on the photosensitive drum 7. A black (K) toner is attached to the electrostatic latent image to form a toner image. Next, when the photosensitive drum 7 rotates and the toner image reaches the primary transfer position, the black (K) toner image is primarily transferred onto the intermediate transfer belt 4. Until the primary transfer of the black (K) toner image is completed and the photosensitive drum 7 is irradiated with cyan (C) exposure light, the secondary transfer roller 18 and the cleaning roller 11 are substantially omitted. At the same time, it is separated from the intermediate transfer belt 4. Thereafter, in the same manner, magenta (M) and yellow (Y) toner images are sequentially primary-transferred onto the intermediate transfer belt 4 and a superimposed toner image is formed on the intermediate transfer belt 4.

  The present invention can be used in the field of image forming apparatuses such as copying machines, facsimile machines, printers, or multifunction machines having both functions.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is a figure which shows the flowchart when forming a full-color image. FIG. 4 is a diagram illustrating a configuration of a contact / separation unit that presses and separates a secondary transfer roller and a cleaning roller from an intermediate transfer belt. It is a figure which shows the time chart of the image formation operation | movement of monochrome continuous printing. It is a figure which shows the time chart of the image formation operation | movement of full-color continuous printing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Image forming apparatus main body, 4 ... Intermediate transfer belt (intermediate transfer body), 5 ... Drive roller, 7 ... Photosensitive drum, 8 ... Primary transfer roller (Primary transfer means) ), 11... Cleaning roller (cleaning means), 13... Developing device, 17... Exposure device, 18... Secondary transfer roller (secondary transfer means), 40. Secondary transfer side abutting part), 47A... Abutting part (cleaning side abutting part), 50... Eccentric cam, 51.

Claims (3)

A photosensitive drum, an exposure device that irradiates the photosensitive drum with light for exposure to form an electrostatic latent image according to image information, and develops the electrostatic latent image formed by the exposure device as a toner image In order to achieve this, a developing device disposed around the photosensitive drum and a toner image formed on the photosensitive drum by the developing device are primarily transferred onto the intermediate transfer member at a contact position with the intermediate transfer member. A primary transfer means for forming a toner image; a secondary transfer means for secondary transfer of the toner image on the intermediate transfer body onto a sheet material at a secondary transfer position; and on the intermediate transfer body after the secondary transfer. In an image forming apparatus comprising: a cleaning unit that cleans a residual toner image; and a contact / separation unit that contacts and separates the secondary transfer unit and the cleaning unit from the intermediate transfer member.
When the toner image is continuously formed on the sheet material, the primary transfer of the toner image formed by the exposure light irradiated on the photosensitive drum is completed and the next toner image is formed when the first toner image is formed. When the toner image is formed, the secondary transfer unit and the cleaning unit are brought into pressure contact with the intermediate transfer member substantially simultaneously by the contact / separation unit until the photosensitive drum is irradiated with exposure light.
An image forming apparatus. A photosensitive drum, an exposure device that irradiates the photosensitive drum with light for exposure to form an electrostatic latent image according to image information, and develops the electrostatic latent image formed by the exposure device as a toner image A plurality of color developing devices arranged around the photosensitive drum, and a plurality of color toner images formed on the photosensitive drum by the developing device at the contact position with the intermediate transfer member. A primary transfer unit that sequentially transfers primary images onto a body to form a superimposed toner image; and secondary transfer that collectively transfers the superimposed toner images on the intermediate transfer body onto a sheet material at a secondary transfer position. Means, cleaning means for cleaning a toner image remaining on the intermediate transfer body after secondary transfer, and contact / separation means for contacting and separating the secondary transfer means and the cleaning means to and from the intermediate transfer body. In the image forming apparatus
In the case where toner images are continuously formed on a sheet material, exposure light corresponding to the last color among a plurality of colors of exposure light sequentially irradiated onto the photosensitive drum in forming a superimposed toner image. When the primary transfer of the toner image formed in step 1 is completed and the next superimposed toner image is formed, the exposure light corresponding to the first color among the plurality of colors of exposure light sequentially irradiated onto the photosensitive drum is used. Until the light is irradiated, the secondary transfer unit and the cleaning unit are pressed against the intermediate transfer member substantially simultaneously by the contact / separation unit,
When the next superimposed toner image is formed, primary transfer of the toner image formed with the exposure light corresponding to the first color among the plurality of colors of exposure light irradiated on the photosensitive drum is completed, The secondary transfer unit and the cleaning unit are separated from the intermediate transfer body substantially simultaneously by the contact / separation unit until the exposure light corresponding to the next color is irradiated.
An image forming apparatus. The contact / separation means includes an eccentric cam attached to a drive shaft that rotationally drives the intermediate transfer member at a secondary transfer position via a clutch.
Secondary transfer is supported so as to be swingable integrally with the secondary transfer unit so as to be able to contact the eccentric cam, and the secondary transfer unit is brought into contact with and separated from the intermediate transfer body according to the rotation of the eccentric cam. A side abutting part;
A cleaning-side contact portion that is swingably supported integrally with the cleaning means so as to be able to contact the eccentric cam, and that contacts and separates the cleaning means with respect to the intermediate transfer body according to rotation of the eccentric cam; Having
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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