JP5205736B2 - Exposure equipment - Google Patents

Description

  The present invention relates to an exposure apparatus mounted on an image forming apparatus capable of forming a large-size image such as A0 (841 mm × 1189 mm) or A1 (594 mm × 841 mm). In particular, the present invention relates to an exposure apparatus that performs wide exposure by connecting a plurality of LED (Light Emitting Diode) print heads (hereinafter simply referred to as LED heads).

Conventionally, in order to form an electrostatic latent image for wide originals such A0 and A1 on the photosensitive member, an image forming apparatus that performs wide exposure by arranging a plurality of LED heads in the axial direction of the photosensitive drum is known ing. Monochrome copiers and printers that support a wide width (for example, A0 size width) realize a wide LED head at low cost by connecting a plurality of small size (for example, A3 size width) LED heads. .

FIG. 1 shows an example of the arrangement of LED heads that perform wide exposure. In the arrangement example shown in FIG. 1, the three LED heads of the first LED head 7a, the second LED head 7b, and the third LED head 7c are arranged in a staggered manner to perform exposure of a large size such as A0 width.
In addition, as shown in FIG. 2, the end portions of the LED heads arranged in a staggered manner are overlapped with each other so that a gap is not formed in an image to be formed.
Furthermore, in the overlap part of the LED head, a joint position where the LED heads are joined together is set as shown in FIG. 2, and the end side of the joint position is set as an unused dot.

  However, since the LED head generates heat and expands as the image is exposed, there is a problem that the position of the joint of the joined LED heads is shifted, and density unevenness such as white stripes and black stripes occurs in the image. .

  Therefore, in Patent Document 1, a plurality of LEDs are detected based on the detection means for detecting at least one positional shift of the position of the LED head in the axial direction and the rotational direction of the LED head and the focal position, and the detection result of the detection means. Correction means for correcting the exposure state of the head is provided.

JP 2002-052757 A

  In a copying machine or printer that forms an image using an electrophotographic method, there are a method in which an image portion is exposed when an image is exposed on a photoreceptor, and a method in which a background portion is exposed. When the above-described misalignment between the LED heads deviates in the direction in which the joints are separated, if the image exposure method exposes the image portion, white streaks are generated between the images at the joints of the LED heads. However, in the background exposure method, if the joints are displaced in the direction away from each other, an image streak is drawn in the vertical direction from the top to the bottom of the paper, which is a serious problem. This is because, in the case of the background exposure method, a portion where the LED head is turned on becomes a background image, and an image is drawn on the portion where the LED head is turned off. The appearance of image streaks is shown in FIG. FIG. 3 shows an example in which the entire surface of the paper is output in white (not drawn) by the LED head shifted by half a dot in the “separating direction of the joint”.

  The technology disclosed in Patent Document 1 also assumes an exposure method that exposes an image portion, and cannot completely eliminate image streaks that occur in background exposure.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exposure apparatus capable of forming a good image without image streaks.

The exposure apparatus of the present invention in order to achieve the above object, an exposure head having a plurality of exposure devices, and a plurality arranged along the axial direction of the image carrier, and between the adjacent exposure head of the image bearing member An exposure apparatus that is fixed in a state shifted in the rotation direction, and is a joint position where images formed by the exposure head and the exposure head adjacent to the exposure head among the exposure elements included in each exposure head are joined together. First control means for controlling lighting of an exposure element on the inner side, second control means for controlling lighting of an unused exposure element that is located outside the joint position and is not used for image exposure, and the exposure head Calculating means for calculating a positional deviation amount from the joint position, and when the second control means determines that a positional deviation has occurred in the exposure head, An exposure element that is adjacent to the exposure head and that is exposed to the outside of a position obtained by adding the amount of displacement to the joint position from the exposure element that is adjacent to the exposure element that is controlled by the first control unit. Lighting control is performed up to the exposure element to be performed.
According to the present invention, even if a positional shift occurs at the joint between the connected exposure heads, the unused exposure elements that are not used for exposure are also controlled to be lighted, thereby preventing image streaks due to the positional shift and improving the image quality. Deterioration can be prevented.
In addition, the power consumption can be reduced by obtaining the amount of displacement and turning on only the exposure elements necessary to prevent image streaks.

In the exposure apparatus of the present invention, a plurality of exposure heads having a plurality of exposure elements are arranged along the axial direction of the image carrier, and adjacent exposure heads are shifted in the rotation direction of the image carrier. The exposure apparatus is a fixed exposure apparatus, and the exposure element provided inside each exposure head includes an exposure element inside the joint position where the images formed by the exposure head and the exposure head adjacent to the exposure head are joined together. First control means for controlling lighting, and second control means for controlling lighting of an unused exposure element that is located outside the exposure element positioned at the joint position and is not used for image exposure, The control means controls the lighting of all the unused exposure elements during the lighting control of the first control means.
  According to the present invention, even if a positional shift occurs at the joint between the connected exposure heads, the unused exposure elements that are not used for exposure are also controlled to be lighted, thereby preventing image streaks due to the positional shift and improving the image quality. Deterioration can be prevented.

  According to the present invention, it is possible to form a good image without image stripes.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the configuration of the present embodiment will be described with reference to FIG. The image forming apparatus 1 mainly includes an image forming unit 2, a paper feeding unit 3, and a storage unit 4 that stores a control device, a spare paper feeding roll, and the like.

In the image forming unit 2, the charging roll 6, the exposure device 7, the developing device 8, the transfer roll 12, and the static eliminator 13 are arranged in this order along the peripheral surface of the photosensitive drum 5.
Photosensitive drum 5 is rotated at a predetermined rotational speed in the arrow direction about the axis of its own by driving means (not shown).
The charging roll 6 uniformly charges the surface of the photosensitive drum 5 to a predetermined potential. The means for charging the surface of the photosensitive drum 5 is not limited to the charging roll 6, and a charger such as a scorotron may be used.
The exposure device 7 is provided with a plurality of exposure bodies. FIG. 4 shows three exposure bodies: a first LED head 7a, a second LED head 7b, and a third LED head 7c. The first to third LED heads 7a, 7b, 7c expose an image on the surface of the photosensitive drum 5, and form an electrostatic latent image according to the image information. Details of these will be described later.
The developing device 8 develops the electrostatic latent image formed on the surface of the photosensitive drum 5 to form a toner image. As a developing method of the developing device 8, there are a one-component developing method and a two-component developing method composed of a toner and a carrier.
The transfer roll 12 transfers the toner image formed on the surface of the photosensitive drum 5 onto the roll paper 11 supplied from the paper feeding unit 3. The static eliminator 13 separates the toner image from the surface of the photosensitive drum 5 by a static elimination action.
The conveyance belt 14 feeds the roll paper 11 from the upstream photosensitive drum 5 to the downstream fixing device 15. The fixing device 15 applies heat and pressure to the roll paper 11 to perform fixing processing of the toner image. The roll paper 11 on which the toner image is fixed is cut into a predetermined size such as A0 size as required, and then discharged onto a paper discharge tray (not shown) disposed outside the image forming apparatus main body 1.

Next, the configuration of the image processing system of the image forming apparatus 1 will be described with reference to FIG.
The communication interface (I / F) unit 20 is connected to a network such as a LAN (Local Area Network) and receives a PDL command created by the personal computer 50 or the workstation 51. The received PDL command is sent to the image processing unit 24 in the controller unit 22.

  The image processing unit 24 interprets a PDL command sent via the network and executes a drawing process to create image data for each page. The created image data is temporarily stored in the page memory 25 in association with the ID of each page. The image data stored in the page memory 25 is sent to the exposure device 7 under the control of the control unit 23. The control unit 23 functions as first control means and second control means of the present invention.

  The data read by the scanner 21 is subjected to image processing such as color correction, color space conversion, and screen processing by the image processing unit 24, and the image data after the image processing is temporarily stored in the page memory 25. The image data recorded in the page memory 25 is sent to the exposure device 7 under the control of the control unit 23.

  The configuration of the exposure unit 7 will be described. The exposure unit 7 is mainly composed of first to third LED heads 7a to 7c and a drive control unit 30 that drives and controls these LED heads 7a to 7c. According to the image data received from the image processing unit 24, the drive control unit 30 includes an LED head control circuit 31 that performs drive control of the first to third LED heads 7a to 7c, and a control of the LED head control circuit 31. It has an LED drive circuit 34 that controls lighting of each LED of the first to third LED heads 7a to 7c, a RAM 32, and a ROM 33. The RAM 32 temporarily stores image data sent from the image processing unit 24, and the ROM 33 stores LED head light amount correction data and the like.

Next, the configuration of the LED head portion of the exposure device 7 will be described.
The first to third LED heads 7a to 7c are obtained by arranging a plurality of LED elements in an array, and are fixed in a state where the LED elements are directed to the photosensitive drum 5 side. First to 3LED head 7a~7c the longitudinal direction of each as shown in FIG. 1 becomes substantially parallel to the axis of the photosensitive drum 5, and each is separated by the same distance and the peripheral surface of the photosensitive drum 5 Are arranged as follows. Therefore, the first to third LED heads 7 a to 7 c are parallel to each other in a state along the peripheral surface of the photosensitive drum 5. The first LED head 7a and the second LED head 7b, the second LED head 7b and the third LED head 7c are fixed in a state of being shifted in the rotational direction of the photosensitive drum 5, and further, the first LED head 7a and the third LED head 7c Are arranged on the same straight line in the longitudinal direction. That is, the arrangement of the first to third LED heads 7a to 7c is staggered, and when viewed from the downstream side in the rotation direction of the photosensitive drum 5, both ends of the second LED head 7b are respectively connected to the first LED head 7a and the first LED head 7a. The first to third LED heads 7a to 7c are arranged so as to overlap one end side of the 3LED head 7c. The number of LED heads is not limited to three, and may be two or four or more.

Thus, a plurality of first through 3LED head 7a~7c that arranged without gaps occurs across the entire image width of the axial direction of the photosensitive drum 5, the axial direction of the image area of the photosensitive drum 5 It is divided. And the 1st-3rd LED head 7a-7c exposes each area | region, and the whole image width of the photosensitive drum 5 is image-exposed. As described above, the second LED head 7b is located downstream of the first LED head 7a and the third LED head 7c. Therefore, by delaying the exposure start time of the second LED head 7b from the exposure start times of the first LED head 7a and the third LED head 7c in accordance with the rotational speed of the photoconductor drum 5, the axis of the peripheral surface of the photoconductor drum 5 is used. The same line in the core direction is exposed. Further, the first LED head 7a and the third LED head 7c do not necessarily have to be on the same straight line. By making the exposure start delay time appropriate, the same line can be exposed by the first to third LED heads 7a to 7c.

A region where the first LED head 7a and the second LED head 7b, and the second LED head 7b and the third LED head 7c overlap (hereinafter referred to as an overlap region) is provided. Usually, a joint position is determined in the overlap region as shown in FIG. 2, and the joint element position is set as a boundary line, and LED elements (hereinafter referred to as dots) on the end side of the line are not used. It was. These dots are hereinafter referred to as unused dots.
In this embodiment, as shown in FIG. 6, the dot on the end side which has not been used is also turned on during exposure. Even if the joint position is changed in the direction away from the joint, it is possible to expose the unused dot to light as a background portion, thereby preventing image streaking. In the following description, the overlap area between the first LED head 7a and the second LED head 7b will be described. And

  In the embodiment shown in FIG. 6, the unused dots of both the first LED head 7a and the second LED head 7b are lit, but the unused dots of either one of the LED heads may be lit. In the example shown in FIG. 7, only the unused dots of the first LED head 7a are lit during exposure.

  Furthermore, in the embodiment shown in FIG. 6, all the unused dots of the first LED head 7a and the second LED head 7b are lit, but if the maximum shift amount of the joint position is known in advance, this maximum shift amount is set. Based on this, only the unused dots of the required number of dots need be lit. FIG. 8 shows an example in which each dot of the first LED head 7a and the second LED head 7b is turned on because the shift amount of the joint position is less than one dot.

As an example of a calculation formula for obtaining the shift amount of the joint position, the shift amount at the time of temperature change shown below can be given.
Deviation amount = A × (T−25) + B (1)
Here, A is the amount of seam deviation per unit temperature change, T is the temperature, and B is the amount of deviation from the reference position at the reference temperature measured when the LED head is fixed to the photosensitive drum 5. . Here, A may be calculated from the linear expansion coefficient of the material used and the distance from the fixed position of the LED head to the joint position, or may be obtained by collecting measured data with a sample machine in advance.

The second embodiment of the present invention will be described in detail with reference to the accompanying drawings.
In the first embodiment described above, the control is based on the premise that there is no image in the overlap portion between the LED head 7a and the LED head 7b. That is, when all the unused dots are lit as shown in FIG. 6, there is a problem that an image is not drawn because a portion where an image is desired to be drawn is also affected as shown in FIG.
Therefore, in this embodiment, as shown in FIG. 10, the unused dots are not merely turned on, but the exposed image is not erased by the unused dots by turning off the dots at the positions where the image is drawn. To.
In Figure 10, among the unused side dots lit of the 1LED head 7a, it is off only dots 71 of the portion to draw the image. Similarly, only the dot 72 of the part which draws an image is light-extinguished among the unused dots which the 2nd LED head 7b turned on.

In order for the lighting / extinguishing control shown in FIG. 10 to be effective, it is a condition that there is almost no gap between the LED heads. When the seam shift occurs, an image of a necessary part is erased or the width of the image is reduced.
FIG. 11 shows a case where a positional deviation of 1 dot occurs between the first LED head 7a and the second LED head 7b. In this case, a control is performed to turn off the dot 73 of the portion of the second LED head 7b that is an image and turn off the dot 74 of the unused dot of the first LED head 7a that overlaps the image. However, since the position of one dot is shifted between the first LED head 7a and the second LED head 7b, the image has disappeared by one dot.

  Such an inconvenience can prevent the writing of the LED head used for image writing from being erased by turning off the unused dot side of the LED head extra. In other words, the problem of the disappearance of the image and the narrowing of the line width can be solved by extinguishing the dots overlapping the image among the unused dots and several dots in the vicinity thereof. In the example shown in FIG. 12, among the unused dots of the first LED head 7a, the dot 75 overlapping the image portion and the two dots 76 adjacent to the dot 75 are turned off. Similarly, among the unused dots of the second LED head 7b, the dot 77 overlapping the image portion and the 2 dots 78 adjacent to the dot 77 are turned off. If the maximum deviation amount of the joint of the LED head is obtained by the above-described equation (1), the number of dots in the vicinity to be turned off can be obtained according to the maximum deviation amount.

  Note that the joint position of the LED head may be shifted not only in the main scanning direction but also in the sub-scanning direction. For example, if one dot is displaced in the sub-scanning direction, the one-dot horizontal line image disappears by the width of the overlapping lighting. In order to prevent this, the dot extinction range may be expanded according to the amount of deviation. In addition to obtaining the effect of temperature by applying Equation (1) in the sub-scanning direction as well, the maximum amount of deviation is obtained in advance by measuring the deviation due to vibration and uneven drum rotation speed using actual measurement data and component specifications of the sample machine. It is good to add.

When a halftone image is drawn at the overlap portion of the LED head, if there is a misalignment at the joint, the dot arrangement of lighting and extinguishing is disturbed, resulting in an image streak. This is a problem common to both image exposure and background exposure, and it cannot be solved even if the overlap portion is turned on or off.
Conversely, if the overlap exposure range for turning on / off unused dots is too wide, the range of dot arrangement is disturbed, so it is desirable to set the minimum number of dots to be turned on / off.
Therefore, in this embodiment, as shown in FIG. 13, among the unused dots, the dots that overlap the image are turned off, and several dots in the vicinity thereof are turned on darkly. Such lighting control can minimize image streaks that occur at the joints of halftone images. In the example shown in FIG. 13, among the unused dots of the first LED head 7a, the dots 79 that overlap the image portion are turned off, and the left and right adjacent dots (dot 80 shown in FIG. 13) are darkened. Lights up. Similarly, of the unused dots of the second LED head 7b, the dots 81 that overlap the image portion are turned off, and the left and right dots adjacent to the dots 81 (dots 82 shown in FIG. 13) are lit darkly. Note that FIG. 13 illustrates a case where the first LED head 7a and the second LED head 7b are displaced by 1 dot, so the dot 79 of the first LED head 7a that should overlap the image is 1 dot. Minutes are out of the image area, and the second LED head 81 is out of the image area.

  Also in this embodiment, if the maximum deviation amount of the joint of the LED heads is obtained by the above-described equation (1), the number of neighboring dots to be turned off can be obtained according to the maximum deviation amount.

  In the above-described embodiment, special lighting control for background exposure is required. Further, in order to overlap adjacent LED heads, an extra space is required around the photosensitive drum 5. Therefore, in a multicolor image forming apparatus in which an LED head that exposes an image portion and an LED head that exposes a background portion are mixed, a single LED head that is wide only for the LED head that exposes the background portion is used. It may be. FIG. 14 shows a configuration in which the LED heads 7a, 7b, and 7c that expose the image portion and the LED head 9 that exposes the background portion are separately provided.

  In the above-described embodiment, an example in which both unused dots of the overlapped LED heads are turned on and off is controlled. However, only one of the LED heads is controlled to be turned on and off. Also good.

  The above-described embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

It is a figure which shows the structure of the LED head part of an exposure device. It is a figure which shows a mode that two LED heads were provided and provided with the overlap area | region. It is a figure which shows a mode that an image stripe generate | occur | produces by a joint gap. 1 is a diagram illustrating a configuration of an image forming apparatus. 1 is a diagram illustrating a configuration of an image processing system of an image forming apparatus. It is a figure which shows the state which lighted all the unused dots of the LED head. It is a figure which shows the state which lighted the unused side dot of any one LED head. It is a figure which shows the state which lighted only the required unused dot based on the shift | offset | difference amount of a joint position. It is a figure which shows a problem in case an image image exists in the overlap part of an LED head. It is a figure which shows the state which turned off the unused side dot of the position drawn according to an image position. It is a figure which shows a problem when there exists an image image in the overlap part of an LED head, and also the position shift has arisen in the LED head. It is a figure which shows the state which turned off the dot which overlaps with an image among the unused dots, and several dots in the vicinity. It is a figure which shows the state which turned off the dot which overlaps an image among unused side dots, and also turned on several dots of the vicinity darkly. It is a figure which shows the structure which provided the exposure device for image exposure and background exposure separately.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Paper feeding part 4 Storage part 5 Photosensitive drum 6 Charging roll 7 Exposure device 7a 1st LED head 7b 2nd LED head 7c 3rd LED head 8 Developing device 11 Roll paper 12 Transfer roll 13 Static remover 14 Conveying belt 15 Fixing device 20 Communication interface unit 21 Scanner 22 Controller unit 23 Control unit 24 Image processing unit 25 Page memory 30 Drive control unit 31 LED head control circuit 34 LED drive circuit 32 RAM
33 ROM

Claims (2)

A exposure head having a plurality of exposure devices, a plurality arranged with and secured in a state between the adjacent exposure head is shifted in the rotation direction of the image bearing member exposure apparatus along the axial direction of the image carrier And
Of the exposure elements provided in each exposure head, a first control means for controlling lighting of the exposure elements inside the joint position where the images formed by the exposure head and the exposure head adjacent to the exposure head are joined together;
Second control means for controlling lighting of an unused exposure element that is located outside the joint position and is not used for image exposure;
Calculating means for calculating a positional deviation amount from the joint position of the exposure head,
When the second control means determines that the exposure head is misaligned, it is an exposure element between the exposure head and an exposure head adjacent to the exposure head, and the exposure is controlled to turn on the first control means. An exposure apparatus characterized in that lighting control is performed from an exposure element adjacent to an element to an exposure element that exposes an outside of a position obtained by adding the positional deviation amount to the joint position . A exposure head having a plurality of exposure devices, a plurality arranged with and secured in a state between the adjacent exposure head is shifted in the rotation direction of the image bearing member exposure apparatus along the axial direction of the image carrier And
Of the exposure elements provided in each exposure head, a first control means for controlling lighting of the exposure elements inside the joint position where the images formed by the exposure head and the exposure head adjacent to the exposure head are joined together ;
Second control means for controlling lighting of an unused exposure element that is located outside the joint position and is not used for image exposure ;
The exposure apparatus according to claim 2, wherein the second control means controls the lighting of all the unused exposure elements during the lighting control of the first control means .

Images