JP2008065195A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of energy or the like when forming an image by using a part of developing devices in an image forming apparatus equipped with a plurality of developing devices. <P>SOLUTION: A multifunction machine 100 is equipped with: a reception part 10 equipped with a scanner or the like and receiving image information; a master control part 11 capable of obtaining image data including image signals of four kinds of color components YMCK from one image; an image forming part 14 forming an electrostatic latent image corresponding to the relevant color component and developing it with toner; and an engine control part 13 controlling the image forming part 14 so as not to perform formation and development of the electrostatic latent image for the color component whose image signal level is under a threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copier.

  Various techniques have been proposed so far to improve the energy or time efficiency of processing operations in image forming apparatuses. As an example, Patent Documents 1 and 2 describe inventions relating to image forming apparatuses that print out color images on paper, such as color copiers and color printers.

  Patent Document 1 discloses a revolver-type developing unit including three developing units each having one photosensitive drum and yellow (Y), magenta (M), and cyan (C) toners around the same rotation axis. And a developing unit having a black (K) toner provided separately from the revolver type developing unit (rotary type). The revolver-type developing unit develops a color electrostatic latent image in the order of yellow, magenta, and cyan with the developing roller of each developing unit sequentially facing the photoconductor. In the revolver type developing unit, the developing roller interval between yellow-magenta and magenta-cyan is the same first distance, and the cyan-yellow interval is a second distance longer than the first distance. ing. The image forming apparatus performs development by a black developing unit during switching from cyan to yellow.

In Patent Document 2, a rotary-type image forming apparatus provided with a plurality of developing units so as to be rotatable around the same rotation axis with respect to one photosensitive drum, and a plurality of photosensitive drums, An image forming apparatus having a two-color mode and a three-color mode in which an image is formed in two or three colors in a tandem type image forming apparatus provided with developing units of respective colors is described. For example, in the two-color mode when four colors (C, M, Y, K) are used, the image forming apparatus automatically selects two colors from among the colors having the highest image signal level in CMYK, or is selected by the user. These two colors are used.
JP 2003-233239 A (released on August 22, 2003) JP 2004-325597 A (published on November 18, 2004)

  Depending on the image or the user's request, it may be possible to form an image using only two or three of the four colors of toner. However, the technique such as Patent Document 1 only considers forming an image using toners of all colors. On the other hand, with the technique of Patent Document 2, it is possible to reduce the color itself constituting the toner image. However, there is room for further improvement in improving the efficiency of image formation when an image is formed using only some colors.

  An object of the present invention is to improve the efficiency of energy or the like when an image is formed using a part of the developing device in an image forming apparatus including a plurality of developing devices.

  The image forming apparatus according to claim 1, an image processing unit capable of obtaining image data including image signals of two or more color components from one image, an image carrier that carries an electrostatic latent image, and the above An electrostatic latent image forming unit capable of forming an electrostatic latent image corresponding to a color component on the image carrier, and a developer for conveying a developer corresponding to each color component onto the image carrier. A rotary developing device capable of developing each electrostatic latent image by providing a plurality of the image bearing members on the same rotation axis and sequentially facing the developing device to the image bearing member, and an image signal For the color component whose level is less than the threshold value, the electrostatic latent image forming unit and the control unit capable of controlling the developing device are provided so as not to form the electrostatic latent image and transport the developer. .

  Even if an image signal of two or more color components is obtained, the image forming apparatus does not form an electrostatic latent image or transport a developer for a color component whose image signal level is less than a threshold value. Therefore, the energy efficiency for image formation can be improved.

  The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the developing device conveys the developer corresponding to each color component onto the image carrier. On the same rotation axis with respect to one image carrier, and a rotary developing device capable of developing each electrostatic latent image by sequentially facing the developing device to the image carrier. And the control unit sets the time when the developing unit corresponding to the color component whose image signal level is less than the threshold value and the image carrier to be opposed to the color component whose image signal level is equal to or more than the threshold value. The time required for the corresponding developing device and the image carrier to face each other can be shortened.

  The image forming apparatus can shorten the time required for development of a color component whose image signal level is less than a threshold value. Therefore, the time required for image formation can be shortened.

  The image forming apparatus of the present invention does not form an electrostatic latent image nor transport a developer for a color component having an image signal level less than a threshold even if an image signal of two or more color components is obtained. Therefore, the energy efficiency for image formation can be improved.

Embodiment
Hereinafter, an MFP 100 will be described as an example of an image reading apparatus according to the present invention with reference to the drawings. The multifunction device 100 has functions as a copier, a facsimile machine, and a printer. However, the present invention is not limited to this, and can be implemented as a known image forming apparatus.

<1. Overview of MFP 100>
First, the configuration of the entire multifunction peripheral 100 will be described with reference to FIG. FIG. 1 is a block diagram illustrating a schematic configuration of the multifunction peripheral 100.

  The multi-function device 100 includes a receiving unit 10 that receives input of various images from the outside, a main control unit 10 that generates image data based on image information from the receiving unit 10, and an image storage unit that stores the image data. 12. An image forming unit 14 that executes image formation, and an engine control unit 13 that controls the image forming unit 14 based on image data.

  The accepting unit 10 can accept jobs such as image forming jobs. Specifically, a modem connected to a line, an interface (I / F) connected to a computer, a hard key, a soft key on a display screen, and the like An operation panel that accepts input from the user via a scanner, a scanner that reads a document on the mounting table, and the like.

  The main control unit 11 sends and receives data signals and control signals to and from each unit of the multifunction peripheral 100 to control the copying operation and the printing operation in general, and performs facsimile transmission control including a circulation transfer function. It is something to do.

  Specifically, the main control unit 11 can be configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU can digitize image information from the scanner to generate image data and perform various calculations. The ROM stores a program related to control performed by the CPU, a program related to the operation of each unit in the multifunction peripheral 100, and the like. In addition to functioning as a work area for the CPU, the RAM also holds an area for holding contents received by the receiving unit 10 such as user input received via the operation panel, an area for holding image data received from a computer, etc. have.

  Image information from the receiving unit 10 is decomposed for each of the Y, M, C, and K color components by image processing in the main control unit 11 and accumulated in the image storage unit 12. That is, the main control unit 11 functions as an image processing unit. Based on the image data stored in the image storage unit 12, the main control unit 11 transmits color information necessary for image formation to the engine control unit 13 before starting transmission of each page data. Based on this information, the engine control unit 13 performs main control when preparation for image formation in the image forming unit 14 (adjustment of the temperature of a fixing device 8 described later to a predetermined range, confirmation of toner amount of the developing device 41, etc.) is completed. The image forming unit 14 is requested of the image data, and the image forming unit 14 is controlled to form an image based on the image data.

<2. Configuration of image forming unit>
The multifunction peripheral 100 further includes a housing 101 illustrated in FIG. 2 and an image forming unit 14 provided in the housing 101. FIG. 2 is a front view illustrating a main configuration of the image forming unit 102.

  The housing 101 has an inside of the above <1. Each member described in the> column and the image forming unit 14 can be held at least.

  As shown in FIG. 1, the image forming unit 14 includes a photosensitive drum (image carrier) 1 that can rotate in a direction indicated by an arrow, and a photosensitive member around the photosensitive drum 1 along the rotation direction. A charging unit 2 that charges the drum 1, an exposure unit 3 that forms an electrostatic latent image by irradiating light onto the photosensitive drum 1, a developing device 4 that develops the electrostatic latent image as a toner image, and the photosensitive drum 1 An intermediate transfer device 5 for primary transfer of the upper toner image and a cleaning device 6 for removing residual toner on the photosensitive drum 1 after the primary transfer are provided. The multifunction device 100 includes a secondary transfer device 7 that secondarily transfers the toner image after the primary transfer onto the paper, a fixing device 8 that fixes the toner image onto the paper after the secondary transfer, and the paper storage unit 91. A transport belt 9 and the like that pass through the secondary transfer device 7 and the fixing device 8 and are discharged to the outside of the multifunction peripheral 100 are provided.

  The image forming unit 14 includes a photosensitive drum motor, and the photosensitive drum 1 is rotationally driven by the photosensitive drum motor in an arrow direction shown in the drawing. The photoreceptor drum 1 is only required to be able to carry an electrostatic latent image, and a photoreceptor that has been used in a conventional electrophotographic image forming apparatus can be preferably used.

  The charging unit 2 includes a charging bias applying unit and a charging roller. The charging roller uniformly charges the surface of the photosensitive drum 1 by applying a voltage from the charging bias application unit. Instead of the charging roller, a conventionally known charging member that can charge the surface of the photosensitive drum 1 can be appropriately used.

  The exposure unit 3 includes a laser unit including a laser light source and a movable mirror, an exposure driving unit that drives the laser unit, and the like. The exposure unit 3 forms an electrostatic latent image for each color component by discharging the surface of the photosensitive drum 1 charged by the charging unit 2 with light from a laser light source. The exposure unit 3 functions as an electrostatic latent image forming unit together with the charging unit 2. Since the multifunction peripheral 100 can form a full-color image with four color toners as will be described later, the charging unit 2 and the exposure unit 3 form four electrostatic latent images corresponding to these four color components for one image. can do.

  The developing device 4 is a so-called rotary type developing device, and includes a rotating shaft 43 parallel to the rotating shaft of the photosensitive drum 1, and around the rotating shaft, four developing devices 41 (41 Y, 41 Y, 41M, 41C, 41K) are provided in this order. The developing device 4 further includes a developing bias applying unit, a developing motor, and a rotary motor (not shown).

  The developing devices 41 (41Y, 41M, 41C, and 41K) have four color toners (Y (yellow), M (magenta), C (cyan), and K (black)), respectively. In the present embodiment, the developer is a two-component developer, but of course, the developing device 41 can be replaced with a developing device using a one-component developer. Each of the developing devices 41 includes a toner tank 42 that stores toner of each color, and a developing roller 44 for conveying the toner to the photosensitive drum 1. The developing roller 44 is capable of attracting toner by electrostatic attraction by being applied with a developing bias by the developing bias applying unit, and is rotationally driven by the developing motor so that the attracted toner is placed on the photosensitive drum 1. Transport. By transporting the toner in this way, the electrostatic latent image of each color component on the photosensitive drum 1 can be developed with the toner.

  At the time of development, the developing device 4 is rotated by the rotary motor about the rotation shaft 43 in the rotation direction indicated by the arrow in the drawing, and the four developing devices 41 are sequentially arranged at the developing position. The developing position is a position where the developing roller 44 of the developing device 41 is held so as to face the photosensitive drum 1, and the developing roller 44 has a color component corresponding to the electrostatic latent image on the photosensitive drum 1. This is a position where toner can be conveyed.

  The intermediate transfer device 5 includes an intermediate transfer belt (intermediate transfer member) 51 movable in the direction of an arrow, an intermediate transfer roller 52 provided so as to sandwich the intermediate transfer belt 51 between the photosensitive drum 1, and an intermediate transfer belt 51. The cleaning member 53 is provided downstream of the secondary transfer unit 7 in the moving direction.

  During the primary transfer, the toner image is transferred from the photosensitive drum 1 to the intermediate transfer belt 51. Development by the developing device 4 and primary transfer by the intermediate transfer roller 52 are sequentially executed for the four color toners, so that the four color toner images are superimposed on the intermediate transfer belt 51. The toner image thus formed is secondarily transferred onto the paper by the secondary transfer device 7.

  The cleaning device 6 removes toner remaining on the photosensitive drum 1 after the primary transfer. About the cleaning apparatus 6, the form can be changed suitably, such as a blade shape and a roll brush shape.

  The fixing device 8 is provided downstream of the secondary transfer device 7 in the moving direction of the conveyance belt 9 and fixes the toner image on the paper by thermocompression bonding.

<3. Development operation>
(3-1) Four-color development operation When image formation is performed using all four-color toners, each unit of the multifunction peripheral 100 is controlled as shown in the timing chart of FIG.

  That is, first, rotation of the photosensitive drum 1 by the photosensitive drum motor is started (photosensitive drum motor ON). At the same time, charging of the photosensitive drum 1 by the charging bias application unit via the charging unit 2 is started (not shown). Then, the exposure unit 3 draws an electrostatic latent image corresponding to the image data of the first color on the charged area of the photosensitive drum 1 (not shown).

  The rotary motor rotates the developing device 4 (rotary motor ON), and the developing roller 44 of the developing device 41Y for the first color (here, Y) is placed on the area where the electrostatic latent image is drawn on the photosensitive drum 1. Make them face each other. When the developing device 41Y reaches the developing position, the rotation of the developing device 4 stops (rotary motor OFF).

  At this developing position, toner conveyance by the developing roller 44 is started (developing motor ON), and simultaneously, voltage application to the developing roller 44 by the developing bias applying unit is started (developing bias ON). As a result, the first color toner is conveyed onto the electrostatic latent image on the photosensitive drum 1, and the image is developed. When all the electrostatic latent images corresponding to the image data of the first color are developed, the development operation is finished (development motor and development bias OFF), and the development of the first color image is completed.

  The rotation of the photosensitive drum 1, the charging of the photosensitive drum 1, and the drawing by the exposure unit 3 are continued during the development of the first color image, and the second to fourth colors are spaced on the photosensitive drum 1 with an appropriate interval. An electrostatic latent image corresponding to the image data is formed. When the formation of the electrostatic latent image is completed for all the color components, the electrostatic latent image formation by the exposure unit 3 and the charging unit 2 and the rotation of the photosensitive drum 1 are also completed.

  After the development of the first color image is completed, the developing device 41 is switched. That is, the developing device 4 is rotated 90 degrees by the rotary motor, and the next developing device 41M is arranged at the developing position. After that, the second color image is developed as described for the first color.

  By repeating the same operation, the third color image and the fourth color image are also developed, and when the development for all the color components is completed, the rotation of the photosensitive drum 1 is also stopped (photosensitive drum motor OFF), Complete the development operation. The process of outputting an image on paper after development is described in <2. As described in the> column.

(3-2) Three-color development operation When the image signal level of each color component obtained by the main control unit 11 is less than the threshold value, the engine control unit 13 causes the image forming unit 14 to form an electrostatic latent image. It can be controlled not to perform development. The image formation using only a part of the color toners as described above will be described by taking as an example an operation in the case where development is performed with the first, third, and fourth color (Y, C, and K) toners. .

  In this case, for the development of the three color images of the first, third, and fourth colors (Y, C, and K), the same operation as described in (3-1) is performed, and the second color (M) is charged. Both the formation of the electrostatic latent image by the unit 2 and the exposure unit 3 and the conveyance of the developer by the developing roller 44 are not performed.

  Specifically, the operation of each part of the image forming unit 14 is as shown in the timing chart of FIG. In this example, after the development of the first color image is completed, the developing device is switched twice by the rotary motor while the developing motor and the developing bias are kept OFF. As a result, the developing device 41C for the third color can be arranged at the developing position without developing the second color, and the development of the image for the third color can be started.

  The photosensitive drum 1 rotates at a constant speed from the completion of the first color development to the start of the development of the third color (photosensitive drum motor ON). In the region where the developing roller 44 of the developing device 41M passes (opposites) on the surface of the photosensitive drum 1, the charging bias and the exposure driving are turned off so that neither charging by the charging unit 2 nor drawing by the exposure unit 3 is performed. Kept. By doing so, it is possible to reduce the power required for forming and developing the electrostatic latent image for unnecessary colors.

  In addition, since the blank electrostatic latent image is not formed in this way, the engine control unit 13 determines that the developing roller 44 of the developing device 41M for the second color faces the photosensitive drum 1 during normal development. It can be made shorter than the same time. That is, the time from the completion of the switching of the developing device 41 from the first color to the second color (41Y → 41M) to the start of the switching to the third color (41M → 41C), which is the next color, from the completion of the switching to the third color to the next The time until the start of switching to the fourth color (41C → 41K) can be made shorter.

  As described with reference to FIG. 4, the multi-function device 100 can execute development using any three of the four colors. Further, the multi-function device 100 can execute not only three-color development but also one-color or two-color development in the same manner. In particular, in the case of an image forming apparatus in which an unused color developing device passes over a photosensitive drum during development, an effect of high time reduction can be obtained.

<4. Determination of color to use>
<3. The “threshold value” of> can be set as appropriate and is not particularly limited. For example, in the image data obtained by the main control unit 11, the multi-function device 100 does not include YMCK at all, or color components that do not affect the image quality even if they are not developed are described in the above < 3. As described in the section>, image formation can be performed without development.

  The multi-function device 100 may allow the user to select a monochrome mode for performing monochrome development and a color mode for performing color development via the display screen of the reception unit 10 or the like. In the conventional image forming apparatus, when the color mode is selected, the electrostatic latent image is always formed and developed for the four color components regardless of the color components included in the image data obtained by the image processing. (See [Comparative Example] below). On the other hand, in the MFP 100 according to the present embodiment, even when the color mode is selected and the main control unit 11 performs an operation for acquiring the four types of color components, these unnecessary color components are detected. Since this operation can be omitted, the time required for image formation can be shortened.

  The multi-function device 100 can also execute the image quality priority mode or the speed priority mode as the color mode. In the speed priority mode, the “threshold value” is set higher than in the image quality priority mode. In the speed priority mode, it is also possible to select 1 to 3 color components that are included most in YMCK, that is, 1 to 3 colors having the highest image signal level.

  In the above embodiment, the type of toner and the number of developing units are four, and the angles formed by the adjacent developing units with respect to the rotation axis are all 90 degrees. However, the present invention is not limited to this. The number of developing units may be three or more, and may be appropriately set according to the type of toner to be used, such as 5, 6 and the like. Further, all the angles may be the same or may be different for each developing device. In other words, the distances between the developing devices do not have to be the same.

  In this embodiment, the order of development is YMCK. However, the order is not limited to this, and the developing devices 41 may be arranged in other orders.

[Comparative example]
Unlike the embodiment described in (3-2) of the above embodiment, the MFP of this comparative example develops a blank image for development using two or three color toners. It is supposed to be. Other than that, it has substantially the same structure as the multifunction machine 100 in the above-described embodiment. Therefore, members having substantially the same functions as those of the multifunction machine 100 will be described below with the same reference numerals.

  The operation of the MFP of this comparative example will be described by taking three-color development without using the second color toner as an example as in (3-2) above. The timing chart of this operation is the same as that in FIG. 3, and the multi-function device 100 performs the same operation as in the above (3-1) except that the second color image is blank. In this comparative example, an electrostatic latent image of the first color is formed on the photosensitive drum 1, and then a blank electrostatic latent image is formed on the photosensitive drum 1 by the charging unit 2 and the exposure unit 3. After the development of the first color is completed, the developing device 4 is rotated 90 degrees by the rotary motor, and the developing device 41M for the second color is arranged at the development position. The developing device 41M performs a normal developing operation. That is, the developing roller 44 is applied with a normal developing bias and rotates in the same manner as in normal developing. After development of this blank paper image, the third and fourth color images are developed in the same manner as in (3-1) above. As a result of these series of operations, the same time and power as the normal development operation are consumed for the blank image of the second color.

FIG. 2 is a front view illustrating a configuration of a main part of an image forming unit of a multifunction machine that is an embodiment of the present invention. The block diagram which shows the principal part structure of the control system of the said multifunctional device. 4 is a timing chart of a four-color developing operation in the multifunction machine. 3 is a timing chart of a three-color developing operation in the multifunction machine.

Explanation of symbols

100 MFP (image forming device)
2 Charging part (electrostatic latent image forming part)
3 Exposure section (electrostatic latent image forming section)
4 Developing device 41 (41Y, 41M, 41C, 41K)
Developing device 42 Toner tank 43 Rotating shaft 44 Developing roller 11 Main control unit (image processing unit)
13 Engine control unit (control unit)

Claims (2)

An image processing unit capable of obtaining image data including image signals of two or more color components from one image;
An image carrier for carrying an electrostatic latent image;
An electrostatic latent image forming unit capable of forming an electrostatic latent image corresponding to the color component on the image carrier,
A developing device for developing the electrostatic latent image with a developer corresponding to each color component;
A control unit capable of controlling the electrostatic latent image forming unit and the developing device so as not to form an electrostatic latent image and transport a developer for a color component having an image signal level less than a threshold;
An image forming apparatus comprising: The developing device includes a plurality of developing devices for conveying the developer corresponding to each color component on the image carrier on the same rotation axis as the one image carrier, and the developer is provided on the same rotation axis. A rotary developing device capable of developing each electrostatic latent image by sequentially facing the image carrier,
The control unit determines the time during which the developing device corresponding to the color component whose image signal level is less than the threshold value and the image carrier face each other, and the development corresponding to the color component whose image signal level is equal to or more than the threshold value. The image forming apparatus according to claim 1, wherein the image forming apparatus can be made shorter than a time in which the container and the image carrier face each other.

Images