JP2011099927A - Image-forming device, transfer pressure-controlling method, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust a transfer pressure in accordance with a recording medium and a printing image, while reducing a frictional load on a transfer means, to gain a good result in printing. <P>SOLUTION: A CPU part 35 stores, in a RAM part 37, image information to be used to adjust a transfer pressure, transmits the image information to an image-forming mechanism part to make it form a toner image on an image carrier, makes a transfer roller transfer the toner image on a recording medium, and makes a fixing device fix the image. After that, the CPU part 35 makes an image density detecting part detect the density of the toner image posterior to the fixation to the recording medium, stores the result of the image-density detection in the RAM part 37, compares the image information in the RAM part 37 with the result of the image-density detection (detected image density) to find difference information (comparison information) which indicates the difference between their densities, and alters a step angle of a stepping motor 33 in accordance with the difference information, that is, the step angle which conforms to the difference information is found, and then the stepping motor 33 is rotated, by the step angle, to control the transfer pressure of the transfer roller. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention controls an image forming apparatus such as a digital copying machine, a facsimile apparatus, a digital multifunction peripheral (multifunction printer: MFP) using an electrophotographic system, a transfer pressure control method in the image forming apparatus, and the image forming apparatus. The present invention relates to a program for realizing a function necessary for a computer (function related to the present invention) and a computer-readable recording medium on which the program is recorded, and more particularly to a technique for reducing a friction load on a transfer unit.

  In the image forming apparatus as described above, optical writing is performed by an optical writer on the image carrier that is rotated in the sub-scanning direction (uniformly charged in advance by a charger) according to image information such as a document. After forming an electrostatic latent image, a toner is attached to the electrostatic latent image by a developing device to form a toner image, and the toner image is transferred onto a recording medium by a transfer device using a transfer roller. The toner image on the recording medium is subjected to a series of image forming processes in which the toner image is fixed by thermocompression using a fixing device using a heating roller with a built-in heater.

  As such an image forming apparatus, for example, as disclosed in Patent Document 1, transfer to a recording medium according to the type of recording medium (standard paper, thick paper 1, thick paper 2, etc.) explicitly selected by the user in advance is performed. A configuration for changing a transfer pressure of a roller (hereinafter also simply referred to as “transfer pressure”) is disclosed. According to this image forming apparatus, when the thickness of the recording medium to be used is known, the transfer pressure can be adjusted according to the recording medium.

  However, there are other factors that determine the optimum transfer pressure for the recording medium, such as the smoothness and stiffness of the recording medium. For example, even when the thickness is the same, if the smoothness is low or the rigidity is high, the transfer pressure is insufficient, and the occurrence of blurring or white spots cannot be avoided. On the other hand, as the transfer pressure increases, the wear load of the transfer roller increases. For example, when using a transfer pressure with a large setting such as thick paper, the transfer roller has a higher load than when using a transfer pressure with a low setting such as standard paper. There was a problem that the wear was large.

That is, it is difficult to reduce the wear load of the transfer roller while avoiding blurring and white spots caused by characteristics of the recording medium such as thickness, smoothness, and rigidity and an image to be printed.
The present invention has been made in view of the above points, and while adjusting the transfer pressure in accordance with the recording medium and the print image while reducing the wear load of the transfer means such as the transfer roller, it is possible to obtain a good print result. It aims to be able to obtain.

  In order to achieve the above object, the present invention provides an image forming apparatus, a transfer pressure control method in the image forming apparatus, a program executed by a computer that controls the image forming apparatus, and a computer reading that records the program A possible recording medium is provided.

  An image forming apparatus according to the present invention includes a transfer unit that transfers an image formed on an image carrier in accordance with image information to a moving path of a recording medium, and the recording unit that records the recording medium. An image forming apparatus comprising: a fixing unit configured to heat and fuse an image transferred onto a medium; and an image density detecting unit configured to detect an image density on the recording medium after being fixed by the fixing unit; The image density detection unit detects the image density on the recording medium after the fixing, and the transfer unit performs the above-described transfer information based on comparison information between the image information and the image density detected by the image density detection unit. And a transfer pressure control means for controlling the transfer pressure with respect to the recording medium.

Note that the transfer pressure control means has a plurality of positions (for example, a front end portion, a central portion, a rear end portion) on the recording medium along the traveling direction of the recording medium after the fixing by the image density detection means. It is desirable to control the transfer pressure based on the maximum value of the comparison information between the image information and each image density detected by the image density detecting means.
In addition, it is preferable to provide storage means for storing image information used when the transfer pressure control means controls the transfer pressure.

  The transfer pressure control method according to the present invention includes a transfer unit that transfers an image formed on an image carrier in accordance with image information to a moving path of a recording medium, and the transfer unit that transfers the image to the recording medium. Transfer pressure in an image forming apparatus comprising: a fixing unit that heats and fixes an image transferred on a recording medium; and an image density detection unit that detects an image density on the recording medium after fixing by the fixing unit. Comparing information between the image information and the image density detected by the image density detecting unit by causing the image density detecting unit to detect the image density on the recording medium after being fixed by the fixing unit. Based on the above, the transfer pressure to the recording medium by the transfer unit is controlled.

The image density detecting means detects each image density at a plurality of locations (for example, a front end portion, a central portion, and a rear end portion) on the recording medium along the traveling direction of the recording medium after the fixing. It is desirable to control the transfer pressure based on the maximum value of the comparison information between the image information and each image density detected by the image density detecting means.
The program according to the present invention is a program that causes a computer that controls the image forming apparatus to execute the transfer pressure control method.
A recording medium according to the present invention is a computer-readable recording medium on which the above program is recorded.

  According to the present invention, the image forming apparatus (or the computer that controls the image forming apparatus) causes the image density detection unit to detect the image density on the recording medium after being fixed by the fixing unit, and detects the image information and the image density detection unit. Based on the comparison information with the image density, the transfer pressure on the recording medium by the transfer unit is controlled.

  According to the present invention, it is possible to adjust the transfer pressure in accordance with the recording medium and the print image while reducing the wear load on the transfer means, and obtain a good print result.

1 is a diagram illustrating an example of an overall configuration of an image forming apparatus using an electrophotographic system according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a main configuration example of a control unit of the image forming apparatus illustrated in FIG. 1. It is a flowchart which shows an example of the control in connection with this invention by the control part shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 1 is a diagram showing an example of the overall configuration of an image forming apparatus using an electrophotographic system according to an embodiment of the present invention.

This image forming apparatus is an MFP (digital multi-function peripheral), and a secondary transfer device 301 serving as a transfer unit, a fixing unit 60 serving as a fixing unit, and an image serving as an image density detecting unit are provided on a moving path of a recording medium. A density detector 701.
In addition, image forming mechanisms 501 to 504 which are image forming units for a plurality of colors for forming a full color image are provided.

  The image forming mechanism 501 includes an image carrier (photosensitive drum) 54 that rotates in the direction of the arrow, a charger 56 that charges the surface (outer peripheral surface) of the image carrier 54, and a semiconductor laser or LED array. An optical writer 55 for forming on the image carrier 54 an electrostatic latent image corresponding to image information for printing to be recorded by light beam scanning as a light source, and an image formed by attaching toner to the electrostatic latent image. A developing unit 53 that forms an image (toner image) with toner on the carrier 54 and a bias having a polarity opposite to that of the toner image on the image carrier 54 are applied to the toner image on the image carrier 54, The image forming apparatus includes a primary transfer device (transfer roller) 58 that transfers a toner image on the carrier 54 onto an intermediate transfer member (intermediate transfer belt) 20 and a cleaning device 57 that cleans the surface of the image carrier 54 after transfer. ing.

Image forming mechanisms 502, 503, and 504 having the same configuration as that of the image forming mechanism 501 and different toner colors are arranged along the traveling (rotating) direction of the intermediate transfer body 20. .
The full-color toner images superimposed on the intermediate transfer member 20 in the order of the image forming mechanism portions 501, 502, 503, and 504 are rotated by the secondary transfer device by the rotation of the plurality of rollers 21, 22, 23 including the drive roller 23 301 is reached.

  If the image information for printing is monochromatic image information, only the monochromatic toner image is transferred onto the intermediate transfer member 20 by operating only the image forming mechanism corresponding to the color. If the image information for printing is image information of two colors or three colors, an image forming mechanism corresponding to each color is operated, so that a toner image of two colors or three colors is formed on the intermediate transfer body 20. It is superimposed and transferred.

The recording medium 4 such as standard paper or thick paper is fed out by the pickup roller 9 and conveyed toward the secondary transfer device 301 by the conveyance roller pairs 10 to 12. A secondary transfer bias having a reverse polarity to the toner image on the body 20 is applied, and the toner image on the intermediate transfer body 20 is transferred onto the recording medium 4.
The secondary transfer device 301 is connected to a transfer roller 31 with a power supply unit (not shown), and is used to apply a secondary transfer bias between the intermediate transfer member 20 and the transfer roller 30 facing the recording medium 4. The circuit is configured. The transfer roller 30 is mechanically connected to the eccentric cam 32 by the rotation angle of the eccentric cam 32, so that the transfer pressure to the transfer roller 31, that is, the transfer pressure to the recording medium 4 passing between the transfer roller 31 and the transfer roller 30 is mechanically connected. The stepping motor 33 can be adjusted. Instead of the stepping motor 33, another motor such as a servo motor can be used.

The recording medium 4 to which the toner image has been transferred is transported toward the fixing device 60 by the transport belt 8.
The fixing device 60 includes a fixing belt 61, a driving roller 62, a heating roller 63, and a backup roller 64.
The heating roller 63 is heated to a predetermined fixing temperature by a built-in heater (not shown), and the toner image on the recording medium 4 is heated and melted to be fixed.

The recording medium 4 after the toner image is fixed is detected by the image density detection unit 701 having a configuration of a reflection type optical sensor including a light emitting unit 70 and a light receiving unit 71. And then discharged from the image forming apparatus.
In this image forming apparatus, in order to obtain an output image with a predetermined density, density adjustment processing called process control is performed using an image density detection unit 701. In this embodiment, the density adjustment process is performed by adjusting the transfer pressure described later.

FIG. 2 is a block diagram illustrating a main configuration example of the control unit of the image forming apparatus illustrated in FIG.
With reference to this figure, the mechanism of image density detection by the image density detection unit 701 of FIG.
The image forming apparatus includes a control unit using a microcomputer including a CPU (Central Processing Unit) unit 35, a ROM (Read Only Memory) unit 36, and a RAM (Random Access Memory) unit 37.

The CPU unit 35 is a central processing unit that comprehensively controls the entire apparatus.
The ROM section 36 is a read-only memory (storage means) that stores programs executed by the CPU section 35 and fixed data including information related to the present invention described later.
The RAM unit 37 is a readable / writable memory that stores various data such as image information and image density detection results described later.
Note that a nonvolatile memory (nonvolatile storage means) such as a flash ROM may be provided, and data in the ROM unit 36 may be stored therein.

The transfer pressure in the initial state is defined according to the thickness category of the recording medium 4, and information on the step angle of the stepping motor 33 for realizing the corresponding rotation angle of the eccentric cam 32 is stored in the ROM section. 36 is stored in advance.
Here, the CPU unit 35 executes a program stored in the ROM unit 36 (which may be another storage unit) and controls the apparatus including the stepping motor 33, thereby serving as a transfer pressure control unit according to the present invention. Fulfills the functions of

FIG. 3 is a flowchart showing an example of control according to the present invention by the control unit shown in FIG.
The CPU unit 35 in FIG. 2 starts the control shown in FIG. 3 when an operation unit (not shown) is operated by the user, for example, when there is a request for adjusting the transfer pressure from the outside. Forming) action. For example, image information used for transfer pressure adjustment (that is, when detecting image density) read from an original by an image reading device (image reading means) such as a scanner (not shown) is stored in the RAM unit 37, or a personal computer (not shown) is used. Image data (single color or multiple color image information) stored in the RAM unit 37 after storing print data (character code or the like) used for adjusting the transfer pressure from the external device as image information for printing in the RAM unit 37 Is sent to the optical writer 55 in the corresponding image forming mechanism in FIG. 1 to execute a series of printing operations as described above.

In step S 2, the image density detector 701 detects the density of the toner image after being fixed on the recording medium 4 by the fixing device 60. As a result, the output result (image density detection result) from the image density detection unit 701 is sent via a communication mechanism (not shown), and the image density detection result is stored in the RAM unit 37.
Thereafter, the process proceeds to step S3, where the image information used for the transfer pressure adjustment stored in the RAM unit 37 is compared with the detected image density as the image density detection result, and difference information (comparison) indicating the density difference between the two. Information).

  And it progresses to step S4 and changes the step angle of the stepping motor 33 connected via the communication mechanism which is not illustrated according to the calculated | required difference information. That is, a step angle corresponding to the difference information is obtained, and step angle information indicating the step angle is transmitted to the stepping motor 33 to be driven to rotate by the step angle. As a result, the rotation angle of the eccentric cam 32 changes, and the transfer pressure is adjusted based on the density detection result of the toner image after fixing by the image density detection unit 701.

  Here, when the detected image density, which is the image density detection result after fixing, is lower than the image information used for adjusting the transfer pressure (hereinafter also simply referred to as “image information”), in the secondary transfer unit 301. The transfer pressure is adjusted so as to increase the transfer pressure. As a result, the transfer efficiency of the secondary transfer device 301 is increased, the density difference between the image information and the detected image density is reduced, and a good image can be obtained.

  On the other hand, when the detected image density is higher than the image information, the transfer pressure is not changed. Since the secondary transfer device 301 cannot theoretically transfer the toner image to the recording medium 4 beyond the amount of the toner image on the intermediate transfer member 20, the detected image density is determined based on the image information. Is not a phenomenon caused by the secondary transfer device 301, for example, an excessive amount of toner adhered to the image carrier 54. At this time, if the control for lowering the transfer pressure is performed in the secondary transfer device 301, the adhesion between the transfer roller 30 or 31 and the recording medium 4 is lowered, discharge due to a minute gap occurs, and abnormal images such as white spots are generated. There are concerns to trigger.

  Image density detection after fixing by the image density detection unit 701 is preferably executed a plurality of times for one recording medium 4. For example, the blur due to the unstable behavior of the recording medium 4 at the front and rear ends, which occurs when the recording medium 4 has a high rigidity, occurs on the recording medium 4 along the traveling direction of the recording medium 4. By detecting the image density at the leading edge, center, and rear edge of the image (may be the image density at other multiple locations), the degree of blur is the worst, that is, the image information and the detected image density By adjusting the transfer pressure based on the maximum value of the density difference, it is possible to obtain a good image over the entire area of the recording medium 4.

  Further, since the transfer pressure adjustment is performed according to the image information to be used, even when the same recording medium 4 is used, image information such as characters and line drawings that are less likely to be blurred or missing, For example, it is possible to adjust the transfer pressure to a different value with image information that is likely to be blurred or missing. For this reason, it is not necessary to increase the transfer pressure more than necessary. Therefore, the wear load on the transfer rollers 30 and 31 can be reduced.

  Note that image information used for adjusting the transfer pressure may be determined in advance, and the image information may be stored in the ROM unit 36 (or nonvolatile memory). This eliminates the need to store the image information used for the transfer pressure adjustment in the RAM unit 37, thereby reducing the time required for the transfer pressure adjustment. Predetermined image information is not likely to cause blurring or omissions such as text or line drawings, and image information that does not require high transfer pressure, or color overlays are likely to cause blurring or omissions, etc. It is desirable to prepare a plurality of pieces of image information such as image information that requires a transfer pressure.

  Further, the adjustment of the transfer pressure based on the image density detection result after fixing by the image density detection unit 701 may be the above-described feedforward control, or a plurality of printing (image formation), image density detection, and adjustment of the transfer pressure. Any feedback control to be executed may be used.

  In this way, the image density on the recording medium after fixing is detected, and the recording pressure is controlled by controlling the transfer pressure of the transfer portion (transfer roller) based on the comparison information between the image information and the detected image density. The transfer pressure is adjusted according to the medium and the print image, and a good print result can be obtained. In addition, since the adjustment of the transfer pressure is performed according to the image information used for the transfer pressure adjustment, even when using the same recording medium, an image that is less likely to cause blurring or omission, such as characters and line drawings, It is possible to adjust the transfer pressure to a different value in an image that tends to cause blurring or missing, such as a color overlay. For this reason, it is not necessary to increase the transfer pressure more than necessary. Therefore, it is possible to reduce the wear load on the transfer portion.

  Further, the image density on the recording medium after fixing is detected at a plurality of locations on the recording medium, and the transfer portion is transferred based on the maximum value of a plurality of comparison information between the image information and the detected image density. If the pressure is controlled, a better printing result can be obtained, and the wear load on the transfer portion can be further reduced.

  Further, the image density on the recording medium after fixing is detected at the front end, the center, and the rear end on the recording medium along the traveling direction of the recording medium. If the transfer pressure of the transfer part is controlled based on the maximum value of a plurality of comparison information with the image density, the behavior of the recording medium at the leading and trailing edges that occurs particularly in the case of a recording medium with high rigidity. It can detect blurring due to instability and adjust the transfer pressure based on the maximum density difference between the image information used for printing and the detected image density. By doing so, a good image can be obtained over the entire area of the recording medium, and the wear load on the transfer portion can be further reduced.

Furthermore, if image information used for adjusting the transfer pressure is stored in advance in a ROM or a non-volatile memory, the time required for adjusting the transfer pressure can be shortened.
As described above, the embodiment in which the present invention is applied to a digital multifunction peripheral capable of forming a color image has been described. However, the present invention is not limited to this. The present invention can also be applied to other image forming apparatuses such as a digital copying machine, a facsimile machine, or a laser printer capable of only monochrome image formation.

[Program related to this invention]
This program is a program for causing a CPU, which is a computer that controls the image forming apparatus, to realize a function as a transfer pressure control unit according to the present invention. It is possible to obtain such operational effects.

Such a program may be stored in a ROM provided in the image forming apparatus from the beginning, a non-volatile memory (flash ROM, EEPROM, etc.), or a storage means such as an HDD, or a CD-ROM which is a recording medium Or a non-volatile recording medium (memory) such as a memory card, flexible disk, MO, CD-R, CD-RW, DVD + R, DVD + RW, DVD-R, DVD-RW, or DVD-RAM. You can also. The programs recorded on those recording media can be installed in the image forming apparatus and executed by the CPU, or each program described above can be executed by causing the CPU to read out and execute this program from those recording media. .
Furthermore, it is also possible to download and execute an external device that is connected to a network and includes a recording medium that records the program, or an external device that stores the program in the storage unit.

  As is apparent from the above description, according to the present invention, it is possible to adjust the transfer pressure according to the recording medium and the print image and obtain a good print result while reducing the wear load of the transfer means. . Therefore, an image forming apparatus capable of printing a high quality image can be provided.

4: Recording medium 20: Intermediate transfer member 30, 31: Transfer roller 32: Eccentric cam 33: Stepping motor 35: CPU unit 36: ROM unit 37: RAM unit 53: Developer 53: Image carrier 55: Optical writing Embedded device 56: Charging device 57: Cleaning device 58: Primary transfer device 60: Fixing device 70: Light emitting portion 71: Light receiving portion 301: Secondary transfer device 501 to 504: Image forming mechanism portion 701: Image density detecting portion

JP 2004-109493 A

Claims (9)

Transfer means for transferring an image formed on an image carrier in accordance with image information onto the recording medium in a moving path of the recording medium, and an image transferred onto the recording medium by the transfer means An image forming apparatus having fixing means for fixing by heating and melting,
Image density detecting means for detecting the image density on the recording medium after being fixed by the fixing means;
The image density detecting unit detects the image density on the recording medium after the fixing, and the transfer unit performs the image density based on comparison information between the image information and the image density detected by the image density detecting unit. An image forming apparatus comprising: a transfer pressure control unit that controls a transfer pressure with respect to a recording medium.   The transfer pressure control unit causes the image density detection unit to detect each image density at a plurality of locations on the recording medium along the traveling direction of the recording medium after the fixing. The image forming apparatus according to claim 1, wherein the transfer pressure is controlled based on a maximum value of comparison information with each image density detected by an image density detecting unit.   The transfer pressure control means detects the image density at the front end, the center, and the rear end on the recording medium along the traveling direction of the recording medium after the fixing by the image density detection means. The image forming apparatus according to claim 2, wherein: The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus comprising storage means for storing image information used when the transfer pressure control means controls the transfer pressure. Transfer means for transferring an image formed on an image carrier in accordance with image information onto the recording medium in a moving path of the recording medium, and an image transferred onto the recording medium by the transfer means A transfer pressure control method in an image forming apparatus, comprising: a fixing unit for fixing by heating and melting; and an image density detecting unit for detecting an image density on the recording medium after being fixed by the fixing unit.
The image density detecting unit detects the image density on the recording medium after being fixed by the fixing unit, and based on the comparison information between the image information and the image density detected by the image density detecting unit, the transfer A transfer pressure control method, comprising: controlling a transfer pressure applied to the recording medium by a section. In the transfer pressure control method according to claim 5,
The image density detection means detects each image density at a plurality of locations on the recording medium along the traveling direction of the recording medium after the fixing, and is detected by the image information and the image density detection means. A transfer pressure control method, wherein the transfer pressure is controlled based on a maximum value of comparison information with each image density. The transfer pressure control method according to claim 6, wherein
The image density detecting means detects the image density of each of the front end portion, the central portion, and the rear end portion on the recording medium along the traveling direction of the recording medium after the fixing. Pressure control method.   A program that causes a computer that controls the image forming apparatus to execute the transfer pressure control method according to any one of claims 5 to 7.   A computer-readable recording medium on which the program according to claim 8 is recorded.

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