JP2008080615A - Line head, image forming apparatus using the same, and control method of line head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a line head which can suitably carry out control of a quantity of light, and to provide an image forming apparatus using the same, and a control method of the line head. <P>SOLUTION: A quantity of light compensation data forming part 53 is prepared at a control part 51 of the line head. The quantity of light of each light emitting element is measured and compared with a reference quantity of light, whereby quantity of light compensation data are formed. The quantity of light compensation data are stored in a table of a memory 56. Moreover, a table of a normal quantity of light compensation data and quantity of light compensation data for correction which corrects the normal quantity of light compensation data is prepared in a memory 56. The quantity of light compensation data different for every line in a main scan direction is stored in the table when an image carrier moves in a sub scan direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a line head capable of appropriately performing light amount control, an image forming apparatus using the same, and a method for controlling the line head.

  In general, an electrophotographic toner image forming unit includes a photosensitive member as an image bearing member having a photosensitive layer on an outer peripheral surface, a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and a uniform charging unit using the charging unit. An exposure unit that selectively exposes the outer peripheral surface charged to form an electrostatic latent image, and a toner as a developer is applied to the electrostatic latent image formed by the exposure unit to form a visible image ( Developing means for forming a toner image).

  As an electrophotographic image forming apparatus, a tandem image forming apparatus having an intermediate transfer belt and a rotary image forming apparatus are known. These image forming apparatuses may use a light emitting element as an exposure light source. In such a color image forming apparatus, a gradation control unit for adjusting the density of an image and a light amount control unit for correcting variations in the light amount of the light emitting elements are provided. For example, Patent Document 1 describes an example in which a light emitting element is used as an exposure light source in the tandem type image forming apparatus provided with the intermediate transfer belt. In addition, it is described that image formation is performed by providing a gradation control unit and a light amount control unit. Japanese Patent Application Laid-Open No. H10-228561 describes that an LED light amount correction is performed in an image forming apparatus using LEDs as light emitting elements.

JP 2003-131469 A JP 11-138899 A

  In the image forming apparatuses described in Patent Document 1 and Patent Document 2, when the light amount is controlled, the same light amount correction data for each line in the main scanning direction of the image formed on the image carrier. Is used. For this reason, depending on the set light amount correction value, a portion where light amount correction cannot be performed also appears. For example, when the light amount difference between adjacent light emitting elements is within an allowable range but is a large value, sufficient light amount correction may not be performed, and there is a problem that print lines appear on the recording medium.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a line head capable of appropriately performing light amount control, an image forming apparatus using the same, and a method for controlling the line head. There is.

The line head of the present invention forms a light emitting element line by arranging a plurality of light emitting elements in the main scanning direction, supplies image data to each of the light emitting elements, and forms one line image in the main scanning direction of the image carrier. A line head to be formed,
First storage means for storing first light amount correction data for correcting the light amount of each light emitting element, and second for correcting the first light amount correction data for each line in the main scanning direction of the image carrier. Means for generating the light quantity correction data, a second storage means for storing the second light quantity correction data, the first light quantity correction data and the second light quantity correction data are read out, together with the image data, Control means for supplying each light emitting element is provided.

  In the line head according to the present invention, the second light quantity correction data is a table of the second storage means in which correction values for the first light quantity correction data are set in steps of +1, 0, −1. Are randomly arranged in the main scanning direction.

  In the line head of the present invention, the control means supplies gradation correction data to each light emitting element together.

  The line head of the present invention is characterized in that the gradation correction data is formed by an external control means.

  In the line head of the invention, the light emitting element is an organic EL light emitting element.

  The image forming apparatus according to the present invention includes at least an image forming station in which each of the image forming units including the charging unit, the line head described in any of the above, the developing unit, and the transfer unit is arranged around the image carrier. Two or more are provided, and an image is formed by a tandem method by passing a transfer medium through each station.

  The image forming apparatus of the present invention includes an image carrier configured to carry an electrostatic latent image, a rotary developing unit, and the line head described in any one of the above, and the rotary developing unit includes: The toner contained in a plurality of toner cartridges is carried on the surface thereof, and the toners of different colors are sequentially conveyed to a position facing the image carrier by rotating in a predetermined rotation direction. A developing bias is applied between the rotary developing unit and the toner is moved from the rotary developing unit to the image carrier, whereby the electrostatic latent image is visualized to form a toner image. And

  In addition, the image forming apparatus of the present invention includes an intermediate transfer member.

According to the line head control method of the present invention, a plurality of light emitting elements are arranged in the main scanning direction to form a light emitting element line, and image data is supplied to each of the light emitting elements to provide one line in the main scanning direction of the image carrier. A line head for forming an image of
A step of storing first light amount correction data for correcting the light amount of each light emitting element in a first storage means, and correcting the first light amount correction data for each line in the main scanning direction of the image carrier. Creating second light quantity correction data; storing the second light quantity correction data in second storage means; and
Reading the first light quantity correction data and the second light quantity correction data as the image carrier moves in the sub-scanning direction, and supplying the first light quantity correction data and the second light quantity correction data together with the image data to the light emitting elements. To do.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 3 is a longitudinal side view showing an example of a tandem type image forming apparatus to which the present invention is applied. The image forming apparatus 1 according to the present embodiment includes a housing body 2, a first opening / closing member 3 that is openably / closably attached to the front surface of the housing body 2, and a second openable / closably attached to the upper surface of the housing body 2. And an opening / closing member (also serving as a paper discharge tray) 4.

  The first opening / closing member 3 includes an opening / closing lid 3 ′ attached to the front surface of the housing body 2 so as to be freely opened and closed. In the housing body 2, an electrical component box 5 containing a power circuit board and a control circuit board, an image forming unit 6, a blower fan 7, a transfer belt unit 9, and a paper feeding unit 10 are disposed. In the first opening / closing member 3, a secondary transfer unit 11, a fixing unit 12, and a recording medium conveying unit 13 are provided.

  The transfer belt unit 9 is disposed below the housing body 2 and is driven to rotate by a drive source (not shown), a driven roller 15 disposed obliquely above the drive roller 14, An intermediate stretched between two rollers 14 and 15 and circulated and driven by the drive roller 14 and the driven roller 15 in the direction of the arrow (the contact surface of the primary transfer member 21 is downward in the illustrated example). A transfer belt 16. The cleaning unit 17 is separated and brought into contact with the surface of the intermediate transfer belt 16.

  The image forming unit 6 includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of (four in this embodiment) different color images. I have. Each of the image forming stations Y, M, C, and K includes a photosensitive member 20 including a photosensitive drum, a charging unit 22 disposed around the photosensitive member 20, a line head 23 that is an image writing unit, and Developing means 24 is provided. A primary transfer member 21 made of a leaf spring electrode is brought into contact with the photoreceptor 20 of the image forming stations Y, M, C, and K corresponding to each color by its elastic force, and the primary transfer member 21 has a transfer bias. Applied. A test pattern sensor 18 is installed at a position close to the drive roller 14.

  The photoconductor 20 is driven to rotate in the direction of the arrow (clockwise direction). The charging means 22 is composed of a conductive brush roller connected to a high voltage generation source, and the outer periphery of the brush is in the reverse direction (counterclockwise direction) with respect to the photoconductor 20 and is 2 to 3 times the photoconductor 20. The surface of the photoconductor 20 is uniformly charged by abutting and rotating on the photoconductor 20 at a peripheral speed of. The line head 23 uses an organic EL light emitting element line in which a plurality of organic EL light emitting elements are arranged in a plurality of rows, for example, two rows in the axial direction (main scanning direction) of the photoconductor 20. The line head 23 using the organic EL light emitting element line has a shorter optical path length than the laser scanning optical system, is compact, and can be disposed close to the photoconductor 20, so that the entire apparatus can be downsized. Has the advantage. Further, since the number of parts is not large as in the laser scanning optical system, the configuration is simplified. In this embodiment, the photoconductor 20, the charging unit 22, and the line head 23 of each image forming station Y, M, C, and K are unitized as one photoconductor unit 25.

  Next, details of the developing unit 24 will be described using the image forming station K as an example. The developing unit 24 includes a toner storage container 26 that stores toner (hatched portion in the drawing), a toner storage part 27 formed in the toner storage container 26, and a toner stirring member disposed in the toner storage part 27. 29, and a partition member 30 that is partitioned and formed on the upper portion of the toner storage portion 27. Further, the toner supply roller 31 disposed above the partition member 30, the blade 32 provided on the partition member 30 and in contact with the toner supply roller 31, and the toner supply roller 31 and the image carrier 20 are in contact with each other. And a regulating blade 34 that is in contact with the developing roller 33.

  Next, members provided in the conveyance path of the recording medium PP will be described. The paper feed unit 10 includes a paper feed unit including a paper feed cassette 35 in which the recording media PP are stacked and held, and a pickup roller 36 that feeds the recording media PP one by one from the paper feed cassette 35. In the first opening / closing member 3, a registration roller pair 37 that defines the timing of feeding the recording medium PP to the secondary transfer portion, and a secondary transfer unit that is pressed against the drive roller 14 and the intermediate transfer belt 16. A secondary transfer unit 11, a fixing unit 12, a recording medium conveyance path 13, a discharge roller pair 39, and a duplex printing conveyance path 40 are provided. When performing double-sided printing on a recording medium, the recording medium on which image data has been transferred and fixed on one side is reversely fed from the position of the paper discharge roller pair 39 and conveyed through the double-sided printing conveyance path 40, and again from the registration roller pair 37. It is conveyed by the recording medium conveyance path 13.

  The fixing unit 12 includes a heating roller 45 that includes a heating element such as a halogen heater and is rotatable, a pressure roller 46 that presses and biases the heating roller 45, and is swingable on the pressure roller 46. A belt tension member 47 and a heat-resistant belt 49 stretched between the pressure roller 45 and the belt tension member 47. The color image secondarily transferred to the recording medium is fixed to the recording medium at a predetermined temperature at a nip formed by the heating roller 45 and the heat-resistant belt 49.

  FIG. 1 is a block diagram showing a control unit of the line head of the present invention. In FIG. 1, 51 is a control unit of the line head, 52 is a control circuit, 53 is a light quantity correction data creation unit, 54 is a drive circuit comprising TFTs, and 55 is a light emitting element line in which a plurality of light emitting elements La are arranged in one line. , 56 are memories, and 57 is a main body controller. The light amount correction data creating unit 53 measures the light amount of each light emitting element and creates light amount correction data by comparing with the reference light amount. This light quantity correction data is stored in a table in the memory 56. Here, the light amount correction data includes normal light amount correction data (first light amount correction data) and corrected light amount correction data (second light amount correction data) described later.

  The main body controller 57 sets the gradation correction value and transmits it to the control unit 51 of the line head together with the print data. The memory 56 stores image data corresponding to each color light emitting element line. The memory 56 stores the gradation correction data from the main body controller 57 in a table. As described above, since the gradation control data is created by the main body controller 57 (external control means), it is possible to cope with a small processing capacity of the control unit 51 of the line head, and the cost can be reduced.

  Conventionally, correction data obtained by combining the light amount correction data and the gradation correction data is supplied together with the image data to the light emitting element lines arranged in the main scanning direction of the line head. Therefore, the same value is supplied to the light amount correction data supplied to the light emitting element line even if the image carrier moves in the sub-scanning direction. For this reason, the image formed on each line in the main scanning direction on the image carrier after the image carrier has moved in the sub-scanning direction is based on the same light amount correction data. Therefore, when there is a large light amount difference between adjacent light emitting elements, or there are cases where the light amount correction is not sufficiently performed at a specific location such as a position between chips where light emitting elements are arranged. Occurs and the image quality deteriorates.

  Therefore, in the embodiment of the present invention, the light amount correction data supplied to the light emitting element line is separated from the gradation correction data, and the light amount correction data is moved in the main scanning direction along with the movement of the image carrier in the sub-scanning direction. A different value can be selected for each line. That is, the memory 56 of FIG. 1 has a table (first storage unit) for storing normal light amount correction data and a table of correction light amount correction data for correcting normal light amount correction data (second storage unit). In this table (second storage means), different light amount correction data is stored for each line in the main scanning direction. The control circuit 52 selects appropriate data for each line in the main scanning direction from the table storing correction light quantity correction data as the image carrier moves in the sub-scanning direction. Therefore, when the image carrier moves in the sub-scanning direction, each light emitting element is supplied with the same value of gradation correction data and different values of light amount correction data before and after the movement.

  FIG. 2 is an explanatory diagram showing an example of a table 58 of correction light quantity correction data stored in the memory 56. In FIG. 2, the corrected light quantity correction data A, B, C,... Of the light emitting element lines are randomly changed in steps (widths) of +1, 0, −1 with respect to the normal light quantity correction data. ing. Each time the image carrier moves in the sub-scanning direction, the corrected light amount correction data A, B, C,... Are appropriately selected, superimposed on the normal light amount correction data, and supplied to the light emitting element line. For this reason, in the image formed on the image carrier, the light amount correction value is set randomly in the same row in the sub-scanning direction, so that the generation of printing streaks can be suppressed and the deterioration of the image quality can be prevented.

  In the example of FIG. 1, an organic EL light emitting element is used as the light emitting element La. Since the organic EL light emitting element can be arranged corresponding to the dot of the pixel formed on the image carrier, the deterioration of the image quality can be suppressed with high accuracy by correcting the variation of the light amount in dot units. it can. Note that the light-emitting element is not limited to the organic EL light-emitting element, and other light-emitting elements such as LEDs can also be used.

  Next, another embodiment of the image forming apparatus according to the present invention will be described. FIG. 4 is a longitudinal side view of the image forming apparatus. In FIG. 4, the image forming apparatus 160 includes, as main constituent members, a rotary developing device 161, a photosensitive drum 165 that functions as an image carrier, and an image writing unit (line head) 167 provided with an organic EL array. In addition, an intermediate transfer belt 169, a paper conveyance path 174, a fixing roller heating roller 172, and a paper feed tray 178 are provided.

  In the developing device 161, the developing rotary 161a rotates in the arrow A direction about the shaft 161b. The inside of the development rotary 161a is divided into four, and image forming units for four colors of yellow (Y), cyan (C), magenta (M), and black (K) are provided. Reference numerals 162a to 162d are arranged in the image forming units for the four colors. The developing rollers rotate in the arrow B direction, and the toner supply rollers 163a to 163d rotate in the arrow C direction. Reference numerals 164a to 164d are regulating blades that regulate the toner to a predetermined thickness.

  As described above, reference numeral 165 denotes a photosensitive drum that functions as an image carrier, 166 denotes a primary transfer member, 168 denotes a charger, and 167 denotes an image writing unit, which is provided with an organic EL array. The photosensitive drum 165 is driven in the direction of arrow D opposite to the developing roller 162a by a drive motor (not shown), for example, a step motor.

  The intermediate transfer belt 169 is stretched between the driven roller 170b and the drive roller 170a, and the drive roller 170a is connected to the drive motor of the photosensitive drum 165 to transmit power to the intermediate transfer belt. By driving the drive motor, the drive roller 170 a of the intermediate transfer belt 169 is rotated in the arrow E direction opposite to the photosensitive drum 165.

  The paper conveyance path 174 is provided with a plurality of conveyance rollers, a pair of paper discharge rollers 176, and the like, and conveys the paper. An image (toner image) on one side carried on the intermediate transfer belt 169 is transferred to one side of the paper at the position of the secondary transfer roller 171. The secondary transfer roller 171 is separated from and brought into contact with the intermediate transfer belt 169 by a clutch, and is brought into contact with the intermediate transfer belt 169 when the clutch is turned on, so that an image is transferred onto the sheet.

  The sheet on which the image has been transferred as described above is then subjected to a fixing process by a fixing device having a fixing heater. The fixing device is provided with a heating roller 172 and a pressure roller 173. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the arrow F direction. When the paper discharge roller pair 176 rotates in the opposite direction from this state, the paper reverses its direction and advances in the double-sided printing conveyance path 175 in the arrow G direction. 177 is an electrical component box, 178 is a paper feed tray for storing paper, and 179 is a pickup roller provided at the outlet of the paper feed tray 178. The number of recording sheets to be printed is counted by a sensor provided at an appropriate position in the paper feed path such as in the vicinity of the paper feed tray. For example, a low-speed brushless motor is used as a drive motor for driving the transport roller in the paper transport path. The intermediate transfer belt 169 uses a step motor because it requires color misregistration correction. Each of these motors is controlled by a signal from a control means (not shown).

  In the state shown in the drawing, a yellow (Y) electrostatic latent image is formed on the photosensitive drum 165, and a high voltage is applied to the developing roller 62a, whereby a yellow image is formed on the photosensitive drum 165. When all of the yellow back side and front side images are carried on the intermediate transfer belt 169, the development rotary 161a rotates 90 degrees in the direction of arrow A. The intermediate transfer belt 169 rotates once and returns to the position of the photosensitive drum 165. Next, two images of cyan (C) are formed on the photosensitive drum 165, and this image is carried on the yellow image carried on the intermediate transfer belt 169. Thereafter, the 90-degree rotation of the development rotary 161 and the one-rotation process after the image is carried on the intermediate transfer belt 169 are repeated in the same manner.

  For carrying four color images, the intermediate transfer belt 169 rotates four times, and then the rotation position is further controlled to transfer the image onto the sheet at the position of the secondary transfer roller 171. The sheet fed from the sheet feed tray 178 is conveyed by the conveyance path 174, and the color image is transferred to one side of the sheet at the position of the secondary transfer roller 171. The sheet on which the image is transferred on one side is reversed by the discharge roller pair 176 as described above, and stands by on the conveyance path. Thereafter, the sheet is conveyed to the position of the secondary transfer roller 171 at an appropriate timing, and the color image is transferred to the other side. The housing 180 is provided with an exhaust fan 181.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment.

It is a block diagram which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. 1 is a longitudinal side view showing an image forming apparatus according to the present invention. It is a vertical side view which shows the other image forming apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Housing main body, 3 ... 1st opening / closing member, 6 ... Image forming unit, 10 ... Paper feed unit, 11 ... Secondary transfer unit, DESCRIPTION OF SYMBOLS 12 ... Fixing unit, 13 ... Recording medium conveyance path, 16 ... Intermediate transfer belt, 20 ... Photoconductor (image carrier), 21 ... Primary transfer member, 22 ... Charging means , 23 ... line head, 24 ... developing means, 25 ... photoconductor unit, 33 ... developing roller, 51 ... control unit, 52 ... control circuit, 53 ... light quantity correction. Data creation unit 54 ... Drive circuit 55 ... Light emitting element line 56 ... Memory 57 ... Main body controller 161 ... Developing device 165 ... Photosensitive drum 167 .Exposure head (line head), 169... Intermediate transfer belt 171 ... secondary transfer roller, La ... organic EL light emitting element,

Claims (9)

A line head that forms a light emitting element line by arranging a plurality of light emitting elements in a main scanning direction, supplies image data to each light emitting element, and forms an image of one line in the main scanning direction of the image carrier. ,
First storage means for storing first light amount correction data for correcting the light amount of each light emitting element, and second for correcting the first light amount correction data for each line in the main scanning direction of the image carrier. Reading out the light quantity correction data, the second storage means for storing the second light quantity correction data, the first light quantity correction data, and the second light quantity correction data are read out together with the image data. A line head comprising a control means for supplying each light emitting element. The second light quantity correction data is randomly arranged in the main scanning direction of the table of the second storage means by setting correction values for the first light quantity correction data in steps of +1, 0, −1. The line head according to claim 1, wherein the line head is provided. The line head according to claim 1, wherein the control unit supplies gradation correction data to each of the light emitting elements together. The line head according to claim 1, wherein the gradation correction data is formed by an external control unit. The line head according to claim 1, wherein the light emitting element is an organic EL light emitting element. At least two image forming stations each having image forming units each including a charging unit, a line head according to any one of claims 1 to 5, a developing unit, and a transfer unit are disposed around the image carrier. One or more image forming apparatuses are provided, and an image forming apparatus performs image formation by a tandem method by passing a transfer medium through each station. An image carrier configured to carry an electrostatic latent image, a rotary development unit, and the line head according to claim 1, wherein the rotary development unit includes a plurality of toners. The toner stored in the cartridge is carried on the surface thereof, and the toners of different colors are sequentially conveyed to a position facing the image carrier by rotating in a predetermined rotation direction, and the image carrier and the rotary developing unit A developing bias is applied between the rotary developing unit and the image bearing member to move the toner to the image bearing member to visualize the electrostatic latent image to form a toner image. Forming equipment. The image forming apparatus according to claim 6, further comprising an intermediate transfer member. A line head that forms a light emitting element line by arranging a plurality of light emitting elements in a main scanning direction, supplies image data to each light emitting element, and forms an image of one line in the main scanning direction of the image carrier. ,
A step of storing first light amount correction data for correcting the light amount of each light emitting element in a first storage means, and correcting the first light amount correction data for each line in the main scanning direction of the image carrier. Creating second light quantity correction data; storing the second light quantity correction data in second storage means; and
Reading the first light quantity correction data and the second light quantity correction data as the image carrier moves in the sub-scanning direction, and supplying the first light quantity correction data and the second light quantity correction data together with the image data to the light emitting elements. To control the line head.

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