JP5077401B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a color printer.

  Conventionally, a so-called tandem type image forming apparatus is known in which photosensitive drums corresponding to yellow, magenta, cyan, and black are arranged in parallel. In this tandem type image forming apparatus, toner images are formed almost simultaneously on the respective photosensitive drums. In the case of using the direct transfer method, the conveyance belt is provided so as to come into contact with each photosensitive drum, and the toner image on each photosensitive drum is superimposed and transferred onto a sheet conveyed by the conveyance belt. . As a result, a color image is formed on the paper.

  Toner is transferred and adhered from the photosensitive drum to the transport belt. Therefore, a cleaning unit for removing toner (waste toner) from the transport belt is provided. The cleaning unit includes, for example, a primary cleaning roller that comes into contact with the conveyance belt and a secondary cleaning roller that comes into contact with the primary cleaning roller. A predetermined cleaning bias is applied to each of the primary cleaning roller and the secondary cleaning roller, and a potential difference between the conveying belt and the primary cleaning roller and a potential difference between the primary cleaning roller and the secondary cleaning roller are applied. As a result, the toner on the transport belt is transferred in the order of the primary cleaning roller and the secondary cleaning roller. As a result, the toner is removed from the transport belt.

JP 2009-3377 A

  In addition to the toner, paper dust generated from the paper adheres to the transport belt. Since the adhesion of paper dust to the transport belt occurs during transport of the paper, an operation for forming an image (image forming operation) is necessary to eliminate the influence of paper dust on the quality of the image formed on the paper. Among them, it is necessary to apply a cleaning bias to the primary cleaning roller and the secondary cleaning roller.

  However, continuing to apply the cleaning bias to the primary cleaning roller and the secondary cleaning roller not only in the cleaning mode after the image formation on the paper is completed but also during the image forming operation may cause power consumption. It is not preferable from the aspect.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing the power consumption while eliminating the influence of deposits on the conveying belt on the image quality.

  In order to achieve the above object, according to the present invention, in an image forming apparatus for forming an image composed of a developer image on paper, an image carrier that carries a developer image, and a position where the paper faces the image carrier. A conveying belt for conveying via, a belt cleaner for removing deposits adhering to the conveying belt, a driving means for driving the image carrier and the conveying belt, and a cleaning bias for the belt cleaner. And a bias applying means for applying the cleaning bias to the belt cleaner when the image carrier is driven at a first speed and the conveying belt is driven at a speed corresponding to the first speed. And when the image carrier is driven at a second speed that is lower than the first speed, and the transport belt is driven at a speed corresponding to the second speed. As the cleaning bias to the belt cleaner is not applied, it is characterized in that a control means for controlling said drive means and said bias applying means.

  According to the present invention, the paper is transported by the transport belt via the position facing the image carrier. For this reason, the developer is transferred from the image carrier and attached to the transport belt, or paper dust generated from the paper is attached. A belt cleaner is provided to remove deposits such as developer and paper dust adhering to the conveyor belt.

  And a control means is provided. The control means controls the drive means for driving the image carrier and the transport belt and the bias applying means for applying a cleaning bias to the belt cleaner, the image carrier is driven at the first speed, and the transport belt is the first. When driven at a speed corresponding to the speed, a cleaning bias is applied to the belt cleaner. On the other hand, when the image carrier is driven at the second speed, which is lower than the first speed, and the conveying belt is driven at a speed corresponding to the second speed, no cleaning bias is applied to the belt cleaner.

  When the image carrier is driven at a relatively high first speed and the conveying belt is driven at a speed corresponding to the first speed so that the sheet is conveyed at high speed in the apparatus, paper dust generated from the sheet is generated. The amount of paper dust attached to the conveyor belt is also large. At this time, since a cleaning bias is applied to the belt cleaner, the adhered paper dust can be removed satisfactorily.

  On the other hand, when the image carrier is driven at a relatively low second speed and the conveyance belt is driven at a speed corresponding to the second speed, and the paper is conveyed through the apparatus at a low speed, the image is generated from the paper. The amount of paper dust is small, and the amount of paper dust attached to the conveyor belt is also small. At this time, power consumption can be reduced by stopping the application of the cleaning bias to the belt cleaner.

  Therefore, it is possible to reduce the power consumption while eliminating the influence of the deposits on the conveying belt on the image quality.

FIG. 1 is a schematic cross-sectional view of a color printer according to an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of the color printer shown in FIG. FIG. 3 is a flowchart showing the contents of the cleaning bias control (cleaning bias determination process) executed by the control unit shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1. Overall Configuration of Color Printer As shown in FIG. 1, a color printer 1 as an example of an image forming apparatus is a tandem type color laser printer.

  The color printer 1 includes a main body casing 2.

  In the main casing 2, photosensitive drums 3 as an example of four image carriers are provided for each color of black (K), yellow (Y), magenta (M), and cyan (C). The four photosensitive drums 3 are arranged in parallel at equal intervals in the transport direction in the order of black, yellow, magenta, and cyan from the upstream side in the transport direction of the paper P by the transport belt 9, which will be described later, in the central portion of the main casing 2. Has been placed.

  A developing device 4 is provided in association with each photosensitive drum 3. The developing device 4 includes a housing 5 and a developing roller 6 held at the lower end of the housing 5. The housing 5 contains toner. The developing roller 6 is provided to be rotatable around a rotation axis parallel to the rotation axis of the photosensitive drum 3. A part of the surface of the developing roller 6 is exposed from the lower end of the housing 5 and is in contact with the surface of the photosensitive drum 3.

  An exposure unit 7 that emits laser beams toward the four photosensitive drums 3 is disposed at the top of the main casing 2.

  As the photosensitive drum 3 rotates, the surface of the photosensitive drum 3 is uniformly charged by discharge from a charger (not shown) and then selectively exposed by a laser beam from the exposure unit 7. By this exposure, electric charges are selectively removed from the surface of the photosensitive drum 3, and an electrostatic latent image is formed on the surface of the photosensitive drum 3. When the electrostatic latent image faces the developing roller 6, toner is supplied from the developing roller 6 to the electrostatic latent image. As a result, a toner image is carried on the surface of the photosensitive drum 3.

  Instead of the exposure device 7, four LED arrays may be provided corresponding to each photosensitive drum 3.

  A paper feed cassette 8 that accommodates the paper P is disposed at the bottom of the main casing 2.

  A transport belt 9 is disposed above the paper feed cassette 8. The conveyor belt 9 is stretched between the driving roller 10 and the driven roller 11. The driving roller 10 and the driven roller 11 are arranged at intervals in the direction in which the photosensitive drums 3 are arranged, and are provided so as to be rotatable around a rotational axis parallel to the rotational axis of the photosensitive drum 3. A portion (hereinafter referred to as “upper portion”) extending between the upper ends of the driving roller 10 and the driven roller 11 in the conveying belt 9 is in contact with the surfaces of the four photosensitive drums 3 from below.

  The paper P stored in the paper feed cassette 8 is transported onto the transport belt 9 by various rollers. The conveyor belt 9 is disposed facing the four photosensitive drums 3 from below. A transfer roller 12 is disposed at each position facing the photosensitive drum 3 across the upper portion of the transport belt 9. The transfer roller 12 is provided to be rotatable about a rotation axis parallel to the rotation axis of the photosensitive drum 3. The paper P transported on the transport belt 9 sequentially passes between the transport belt 9 and each photosensitive drum 3 as the transport belt 9 travels. The toner image on the surface of the photosensitive drum 3 is transferred to the paper P when it faces the paper P between the photosensitive drum 3 and the transfer roller 12.

  A fixing device 13 is provided on the downstream side in the conveyance direction of the paper P with respect to the conveyance belt 9. The sheet P on which the toner image is transferred is conveyed to the fixing device 13. In the fixing device 13, the toner image is fixed on the paper P by heating and pressing. The paper P on which the toner image is fixed is discharged to a paper discharge tray 14 on the upper surface of the main body casing 2 by various rollers.

  A belt cleaner unit 15 is disposed between the paper feed cassette 8 and the conveyor belt 9. The belt cleaner unit 15 includes a unit case 16 and a cleaning roller 17 as an example of a belt cleaner held by the unit case 16.

  The cleaning roller 17 has a rotation axis that is parallel to the rotation axis of the photosensitive drum 3, and is below a portion (hereinafter referred to as a “lower portion”) that extends between the lower ends of the driving roller 10 and the driven roller 11 in the conveyance belt 9. It is arranged so that it touches.

  A backup roller 18 is disposed at a position facing the cleaning roller 17 with the lower portion of the conveyor belt 9 interposed therebetween. The backup roller 18 is provided so as to be rotatable about a rotation axis parallel to the rotation axis of the photosensitive drum 3, and is in contact with the lower portion of the transport belt 9 from above (inside).

  At the contact portion between the conveyance belt 9 and the cleaning roller 17, the cleaning roller 17 is in the same direction as the circumferential direction of the conveyance belt 9 so that the surface of the conveyance belt 9 and the surface of the cleaning roller 17 move in opposite directions. It is rotated (Against rotation). In addition, a predetermined cleaning bias (for example, −1400 V) is applied to the cleaning roller 17. On the other hand, the backup roller 18 is grounded. As a result, a potential difference is generated between the cleaning roller 17 and the backup roller 18. Due to this potential difference, deposits such as toner and paper dust on the conveyor belt 9 are transferred to the cleaning roller 17, and removal of deposits from the conveyor belt 9 is achieved.

In the unit case 16, for example, a secondary cleaning roller in contact with the cleaning roller 17 and a blade in contact with the secondary cleaning roller are provided. The adhering matter transferred to the cleaning roller 17 is transferred from the cleaning roller 17 to the secondary cleaning roller due to a potential difference between the cleaning roller 17 and the secondary cleaning roller. The deposits transferred to the secondary cleaning roller are scraped off by the blade, fall off the secondary cleaning roller, and are stored in the unit case 16.
2. Electrical Configuration of Color Printer As shown in FIG. 2, the color printer 1 includes a control unit 21 as an example of a control unit for controlling each unit of the color printer 1. The control unit 21 is composed of a microcomputer including a CPU, RAM, ROM, and the like.

  A first motor M1, a second motor M2, and a third motor M3 are connected to the control unit 21 via a first motor driver 22, a second motor driver 23, and a third motor driver 24, respectively, as control targets. .

  A first motor M <b> 1 as an example of a driving unit is a driving source for the photosensitive drum 3 and the driving roller 10. The drive of the first motor M1 is indirectly controlled by the control unit 21 via the first motor driver 22. That is, on / off of a drive element (for example, FET: Field Effect Transistor) included in the first motor driver 22 is controlled, and drive power corresponding to the on / off ratio is supplied from the first motor driver 22 to the first motor. By being supplied to M1, the drive of the first motor M1 is controlled.

  The second motor M2 is a driving source for the yellow, magenta, and cyan developing devices 4 and the fixing device 13. The drive of the second motor M2 is indirectly controlled by the control unit 21 via the second motor driver 23. That is, on / off of the driving element included in the second motor driver 23 is controlled, and driving power corresponding to the on / off ratio is supplied from the second motor driver 23 to the second motor M2, thereby 2 Driving of the motor M2 is controlled.

  The third motor M 3 is a driving source for the black developing device 4 and the cleaning roller 17. The driving of the third motor M3 is indirectly controlled by the control unit 21 via the third motor driver 24. That is, on / off of the drive element included in the third motor driver 24 is controlled, and drive power corresponding to the on / off ratio is supplied from the third motor driver 24 to the third motor M3, so that the first The driving of the three motor M3 is controlled.

  Further, a bias application circuit 25 as an example of a bias application unit for applying a cleaning bias to the cleaning roller 17 is connected to the control unit 21 as a control target. The control unit 21 controls the bias application circuit 25 so that the cleaning bias is applied from the bias application circuit 25 to the cleaning roller 17.

The control unit 21 is connected to, for example, a LAN (Local Area Network), and can receive setting information, image data, and the like from a personal computer connected to the LAN. When the control unit 21 receives the setting information and the image data, the control unit 21 controls each unit of the color printer 1 based on the setting information and the image data, and an image (color image or monochrome image) corresponding to the image data is applied to the paper P. It is formed.
3. Cleaning Bias Control The color printer 1 has, as operation modes, a full speed mode as an example of a first image forming mode, a half speed mode as an example of a second image forming mode, and a cleaning mode.

  In the full speed mode, the photosensitive drum 3 is rotated at a predetermined first speed (for example, 105 rpm). Further, the developing device 4 (developing roller 6), the driving roller 10, the fixing device 13, the cleaning roller 17 and the like are each driven at a speed corresponding to the first speed. When the driving roller 10 is driven at a speed corresponding to the first speed, the conveying belt 9 has a speed corresponding to the first speed, that is, the moving speed of the contact portion of the conveying belt 9 with the photosensitive drum 3 is the photosensitive drum 3. Circulates (runs) at a speed that matches the circumferential speed. Then, the paper P is conveyed in the main body casing 2 at a speed corresponding to the first speed, and an image is formed on the paper P at a predetermined first process speed (for example, 28 sheets / min).

  In the half speed mode, the photosensitive drum 3 is rotated at a second speed that is half the first speed. Further, the developing device 4 (developing roller 6), the driving roller 10, the fixing device 13 and the cleaning roller 17 are each driven at a speed corresponding to the second speed. When the driving roller 10 is driven at a speed corresponding to the second speed, the conveyor belt 9 circulates (runs) at a speed corresponding to the second speed, that is, half the speed of the conveyor belt 9 in the full speed mode. . Then, the paper P is conveyed in the main body casing 2 at a speed corresponding to the second speed, and an image is formed (output) on the paper P at a second process speed that is half of the first process speed.

  In the cleaning mode, the photosensitive drum 3 is rotated at the first speed, the driving roller 10 is driven at a speed corresponding to the first speed, and the conveyor belt 9 circulates (runs) at a speed corresponding to the first speed.

  The rotational speed of the photosensitive drum 3 is switched between the first speed and the second speed by changing the on / off ratio of the driving element included in the first motor driver 22. Along with this, the rotation speed of the driving roller 10 is switched between a speed corresponding to the first speed and a speed corresponding to the second speed. The driving speeds of the yellow, magenta and cyan developing devices 4 and the fixing device 13 are changed according to the first speed by changing the on / off ratio of the driving elements included in the second motor driver 23. And a speed corresponding to the second speed. Furthermore, the driving speeds of the black developing device 4 and the cleaning roller 17 are changed according to the first speed and the second speed by changing the on / off ratio of the driving elements included in the third motor driver 24. The speed can be switched according to the speed.

  In the color printer 1, as shown in FIG. 3, the application of the cleaning bias to the cleaning roller 17 is controlled according to the operation mode.

  A command instructing the start of printing is transmitted from the personal computer in advance of the setting information and image data, and the control unit 21 receives this command as a trigger to form an image on the paper P in the color printer 1 ( The operation shown in FIG. 3 starts.

  When the control unit 21 receives setting information and image data following the command, it is first determined whether or not the operation mode is the full speed mode based on the setting information (S1). Further, the image data is expanded in a bitmap memory (not shown).

  In the color printer 1, for example, in the setting box displayed on the screen (display) of the personal computer in which the printer driver for the color printer 1 is installed, the image is output on the paper P, the type of the paper P on which the image is output. The resolution (quality) of the image to be set can be set. When the user sets the type of paper P, the resolution of the image, and the like, the set contents are transmitted from the personal computer to the color printer 1 as setting information.

  For example, when plain paper (copy paper) is set as the type of paper P and normal (for example, 600 dpi) is set as the image resolution, when the setting information is received by the control unit 21, the control unit 21 The operation mode is determined to be the full speed mode. Further, when thick paper is set as the type of the paper P, or when fine (for example, 1200 dpi) is set as the resolution of the image, when the setting information is received by the control unit 21, the control unit 21 It is determined that the operation mode is the half speed mode.

  When it is determined that the operation mode is the full speed mode (S1: YES), a cleaning bias is applied from the bias application circuit 25 to the cleaning roller 17 (S2). Then, an image is formed on the paper P at the first process speed in the full speed mode.

  On the other hand, when it is determined that the operation mode is not the full speed mode, that is, when it is determined that the operation mode is the half speed mode (S1: NO), the cleaning bias is not applied to the cleaning roller 17 from the bias application circuit 25. Then, an image is formed on the paper P at the second process speed in the half-speed mode with no cleaning bias applied to the cleaning roller 17.

  When a series of image forming operations (printing) in the full speed mode or the half speed mode is completed (S4: YES), the operation mode shifts to the cleaning mode. In the cleaning mode, a cleaning bias is applied from the bias application circuit 25 to the cleaning roller 17 (S5). As a result, a potential difference is generated between the cleaning roller 17 and the backup roller 18, and deposits such as toner and paper dust on the transport belt 9 are transferred to the cleaning roller 17 and removed.

When the operation in the cleaning mode is continued for a predetermined time, it is determined that the cleaning of the conveying belt 9 is finished (S6: YES), and the application of the cleaning bias from the bias applying circuit 25 to the cleaning roller 17 is stopped. (S7), the process shown in FIG. 3 ends.
4). Function and Effect (1) Function and Effect 1
As described above, in the color printer 1, the paper P is transported by the transport belt 9 via the position facing the photosensitive drum 3. Therefore, toner is transferred from the photosensitive drum 3 and attached to the conveyor belt 9, or paper dust generated from the paper P is attached. A cleaning roller 17 is provided to remove deposits such as toner and paper dust deposited on the transport belt 9.

  The color printer 1 includes a control unit 21. The controller 21 controls the first motor M1 that drives the photosensitive drum 3 and the conveying belt 9 and the bias application circuit 25 that applies a cleaning bias to the cleaning roller 17, and the photosensitive drum 3 is driven at the first speed. When the conveyor belt 9 is driven at a speed corresponding to the first speed, a cleaning bias is applied to the cleaning roller 17. On the other hand, when the photosensitive drum 3 is driven at a second speed that is lower than the first speed and the transport belt 9 is driven at a speed corresponding to the second speed, no cleaning bias is applied to the cleaning roller 17.

  When the photosensitive drum 3 is driven at a relatively high first speed and the conveying belt 9 is driven at a speed corresponding to the first speed, and the sheet P is conveyed at high speed in the apparatus, the sheet P The amount of paper dust that is generated is large, and the amount of paper dust that adheres to the conveyor belt 9 is also large. At this time, since the cleaning bias is applied to the cleaning roller 17, the adhered paper dust can be removed satisfactorily.

  On the other hand, when the photosensitive drum 3 is driven at a relatively low second speed and the transport belt 9 is driven at a speed corresponding to the second speed, and the paper P is transported through the apparatus at a low speed, The amount of paper dust generated from P is small, and the amount of paper dust attached to the conveyor belt 9 is also small. At this time, the application of the cleaning bias to the cleaning roller 17 is stopped, so that the power consumption can be reduced.

Therefore, it is possible to reduce the power consumption while eliminating the influence of the deposits on the conveyor belt 9 on the image quality.
(2) Action effect 2
The color printer 1 has a full speed mode, a half speed mode, and a cleaning mode as operation modes. In the full speed mode, the photosensitive drum 3 is driven at the first speed, and the conveying belt 9 is driven at a speed corresponding to the first speed, so that an image is formed on the paper P at the first process speed. A cleaning bias is applied to the cleaning roller 17. In the half speed mode, the photosensitive drum 3 is driven at the second speed, and the conveying belt 9 is driven at a speed corresponding to the second speed, so that an image is formed on the paper P at the second process speed. In the cleaning mode, a cleaning bias is applied to the cleaning roller 17 to remove the deposits on the conveyor belt 9.

The cleaning mode is performed after completion of the full speed mode and the half speed mode. Thereby, by the time the next full speed mode or the half speed mode is started, the deposits are removed from the transport belt 9, and the transport belt 9 can be in a clean state.
(3) Effect 3
In the cleaning mode, the photosensitive drum 3 is driven at the first speed, and the transport belt 9 is driven at a speed corresponding to the first speed. Thereby, it is possible to shorten the time required to make the conveyor belt 9 make one round, and it is possible to reduce the time required to remove the deposits from the entire circumference of the conveyor belt 9.
5. Modifications One embodiment of the present invention has been described above, but various design changes can be made to the embodiment within the scope of the matters described in the claims.

  Further, the present invention is not limited to the tandem type color printer 1 and may be applied to a monochrome printer.

DESCRIPTION OF SYMBOLS 1 Color printer 3 Photosensitive drum 9 Conveyance belt 17 Cleaning roller 21 Control part 25 Bias application circuit M1 1st motor

Claims (3)

An image forming apparatus for forming an image composed of a developer image on paper,
An image carrier for carrying a developer image;
A transport belt for transporting paper via a position facing the image carrier;
A belt cleaner for removing deposits adhering to the conveyor belt;
Drive means for driving the image carrier and the conveyor belt;
Bias applying means for applying a cleaning bias to the belt cleaner;
When the image carrier is driven at a first speed and the conveyor belt is driven at a speed corresponding to the first speed, the cleaning bias is applied to the belt cleaner, and the image carrier is The driving is performed so that the cleaning bias is not applied to the belt cleaner when the belt is driven at a second speed that is lower than the first speed and the conveyor belt is driven at a speed corresponding to the second speed. And a control means for controlling the bias applying means. A first image forming mode in which the image carrier is driven at the first speed and an image is formed on a sheet at a first process speed; and the image carrier is driven at the second speed to perform a second process. A second image forming mode in which an image is formed on a sheet at a speed, and a cleaning mode for removing deposits adhering to the conveying belt after the first image forming mode and the second image forming mode are completed. Have
The control means is configured so that the cleaning bias is applied to the belt cleaner during the first image forming mode and the cleaning mode, and the cleaning bias is not applied to the belt cleaner during the second image forming mode. The image forming apparatus according to claim 1, wherein the bias applying unit is controlled.   The control means controls the driving means so that the image carrier is driven at the first speed and the conveying belt is driven at a speed corresponding to the first speed in the cleaning mode. The image forming apparatus according to claim 2.

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