JP2007030250A - Print head and image forming apparatus using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a print head capable of performing an exposure for an image with good accuracy without resulting a remarkable increase in cost even for a long LED array and for a machine type with a high process speed, and an image forming apparatus using this. <P>SOLUTION: In the print head equipped with an LED array arranging a plurality of LED elements ON/OFF driven in accordance with image data, the print head is equipped with a temperature controlling means for correcting a dot position of image exposure by controlling the temperature of the print head, and as the temperature controlling means, a circuit substrate for controlling the temperature in which a functional element similar to the LED array is mounted is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an LED array that performs image exposure on an image carrier such as a photosensitive drum in an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions, which employs an electrophotographic system. And an image forming apparatus using the print head.

JP 2002-370400 A JP 2003-182141 A

  Conventionally, image forming apparatuses such as printers and copiers that employ this type of electrophotographic system are compatible with each color such as cyan (C), magenta (M), yellow (Y), and black (K). The image forming units are sequentially arranged, and the toner images formed by the cyan (C), magenta (M), yellow (Y), and black (K) image forming units are directly transferred onto a recording medium. Various so-called tandem color image forming apparatuses that form full-color images by transferring images onto a recording medium via an intermediate transfer belt have been proposed and have been commercialized.

  In the image forming apparatus, as an image exposure unit that performs image exposure on the photosensitive drum of each image forming unit, a print head including an LED array or a ROS (Raster Output Scanner) that irradiates a laser beam according to image information. However, when the size of an image to be formed increases, a print head provided with an LED array is mainly used because of the layout of the apparatus.

  By the way, in such a color image forming apparatus, there is a positional shift between toner images formed by cyan (C), magenta (M), yellow (Y), and black (K) image forming units. Then, since color misregistration and image misregistration occur, it is necessary to control the image forming position by each image forming unit.

  Therefore, in the color image forming apparatus, the dot positions between the print heads in the cyan (C), magenta (M), yellow (Y), and black (K) image forming units are aligned, and color misregistration and image It is necessary to form a good image without deviation.

  Further, not only a color image forming apparatus but also a monochrome image forming apparatus, such as a plotter, is controlled so that the dot position of the print head is constant in an apparatus that requires a high printing accuracy. Therefore, it is necessary to form a good image without image displacement.

  Most of the commercially available image forming apparatuses that are produced are compatible with A4 size and A3 size, and have a large production volume and short length, so only standard products are used. However, in the long class of 20 inches, 26 inches, and 36 inches, the limit is ± 100 μm, and if higher accuracy is desired, A correction method is required.

  Therefore, as a technique capable of controlling the dot position of the print head in the color image forming apparatus or the monochrome image forming apparatus, for example, techniques disclosed in Japanese Patent Laid-Open Nos. 2002-370400 and 2003-182141. Has already been proposed.

  As shown in FIG. 6, the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2002-370400 includes: (a) a base 100; and (b) a recording on which a plurality of recording elements 101 are formed. An element array 102; (c) a drive unit 103 which is arranged on the base 100 and selectively drives each recording element 101; and (d) heat generated by driving the recording element 101. The preheating unit 104 is configured to include a preheating unit 104 that generates heat at a predetermined location in advance. For example, a heating unit disposed along the base 100 is used as the preheating unit 104. In FIG. 6, reference numeral 105 denotes an imaging lens.

  Further, the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2003-182141 forms an image by scanning a light beam on an image carrier according to image data with an image recording head having a self-scanning LED chip. A transfer signal generating means for generating a transfer signal for transferring image data to the self-scanning LED chip, and transmitting the transfer signal to the self-scanning LED chip for a predetermined time, Setting means for setting the operation time of the transfer signal generating means so that the temperature of the image recording head falls within a predetermined range.

  However, the conventional technique has the following problems. In other words, the image forming apparatus according to Japanese Patent Application Laid-Open No. 2002-370400 includes preheating means for generating heat in a predetermined portion in advance in correspondence with heat generated by driving the recording element. As shown in FIG. 6, it is necessary to provide a heating means 104 composed of a planar heater or the like disposed along the base 100 as a preheating means. Since it is necessary to manufacture a special one corresponding to the recording element array 102, there is a problem in that the cost is significantly increased accordingly.

  In addition, when a heating means or the like disposed along the base is provided as a preheating means as described above, it is necessary to install a thermostat separately as a safety measure. Had a point.

  Further, in the case of the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2003-182141, the operation time of the transfer signal generating means is set by the setting means so that the temperature of the image recording head falls within a predetermined range. Therefore, it is impossible to take into account the temperature rise when the LED chip is not emitting light, and it takes time to suppress variations, and it is not possible to cope with models with high process speed. Had.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to provide a long LED array and a high process speed without causing a significant cost increase. An object of the present invention is to provide a print head capable of performing image exposure with high accuracy and an image forming apparatus using the same.

That is, the invention described in claim 1 is a print head including an LED array in which a plurality of LED elements that are ON / OFF driven according to image data are linearly arranged.
The print head includes temperature control means for correcting a dot position of image exposure by controlling the temperature of the print head, and the temperature control means is a temperature at which a functional element similar to the LED array is mounted. A print head using a control circuit board.

  According to a second aspect of the present invention, in the print head according to the first aspect, the circuit board for temperature control comprises an inexpensive LED array in which a plurality of LED elements are linearly arranged. It is.

  Furthermore, the invention described in claim 3 is characterized in that the temperature control circuit board is configured by connecting a plurality of temperature control circuit boards to the LED array of the print head. The print head according to claim 1 or 2.

  Further, the invention described in claim 4 is characterized in that the circuit board for temperature control is arranged on an insulating sheet having a good thermal conductivity laid under the LED array of the print head. The print head according to claim 1.

  Furthermore, an invention described in claim 5 is an image forming apparatus including the print head according to any one of claims 1 to 4.

  According to the present invention, a print head capable of performing image exposure with high accuracy even in a long LED array or a model having a high process speed without causing a significant cost increase, and an image forming apparatus using the print head Can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 2 is a schematic configuration diagram showing a tandem type color image forming apparatus to which the print head is applied to Embodiment 1 of the present invention.

  As shown in FIG. 2, the color image forming apparatus 1 is roughly divided into a drive unit 3 for feeding continuous paper 2 as a recording medium, a first print unit 4 for forming a cyan image, and a magenta color. A second print unit 5 that forms a blue image, a third print unit 6 that forms a yellow image, a fourth print unit 7 that forms a black image, cyan (C), magenta (M), and yellow (Y). The toner image is composed of a fixing unit 8 for fixing the toner image on the continuous paper 2 on which the toner images of each color of black (K) are transferred in multiple, and a controller 10 having a controller 9 and the like.

  The drive unit 3 includes a driving roller 11 and a driven roller 12 that convey the continuous paper 2 fed from a paper supply unit (not shown) while being sandwiched between a pair of rollers, and the continuous paper 3 Guide rollers 13 and 14 for guiding the above are disposed. Here, the continuous paper is a series of continuous long sheets, and is a recording medium that is separated by creases (perforations) for each page.

  The first to fourth print units 4 to 7 of cyan (C), magenta (M), yellow (Y), and black (K) differ only in the color of the image to be formed, and the others are the same. Here, the first print unit 4 will be described as an example.

  The first print unit 4 includes a photosensitive drum 15 as an image carrier, and the photosensitive drum 15 is rotationally driven at a predetermined speed in the direction of the arrow by a driving unit (not shown). ing. The color image forming apparatus 1 is configured to be able to form a full-color image on the continuous paper 2 at high speed, and the rotational speed of the photosensitive drum 15 is set to a high speed of several hundred mm / sec. Further, the color image forming apparatus 1 can form a full color image even on a continuous paper 2 having a large size, and the photosensitive drum 15 has a size of 20 inches, 26 inches, 36 inches, or the like. It is set to be long corresponding to a long (wide) image.

  The surface of the photosensitive drum 15 is uniformly charged to a predetermined potential by a primary charger 16 composed of a scorotron, a charging roll or the like, and then subjected to image exposure according to image data by a print head 17 as image exposure means. And an electrostatic latent image is formed. The print head 17 is also configured to be able to expose a long image such as 20 inches, 26 inches, and 36 inches corresponding to the long photosensitive drum 15. The electrostatic latent image formed on the photosensitive drum 15 is developed by the developing roll 18 of the corresponding color developing device to become a toner image, and is transferred onto the continuous paper 2 as a recording medium by the transfer roll 19. Transcribed. The continuous paper 2 conveyed to the transfer portion of the photosensitive drum 15 is configured such that the front and rear thereof are guided by guide rollers 20 and 21. Further, residual toner and the like are removed from the surface of the photosensitive drum 15 after the toner image transfer process is finished by a cleaning device (not shown), and the next image forming process is performed.

  As described above, the continuous paper 2 on which the toner images of each color are transferred in multiple by the first to fourth print units 4 to 7 of cyan (C), magenta (M), yellow (Y), and black (K) The registration mark formed on the continuous paper 2 at a predetermined timing is detected by the registration mark detection means 22, and the image forming position is controlled as will be described later.

  Further, the continuous paper 2 on which the toner images of the respective colors are transferred in a multiple manner by the first to fourth print units 4 to 7 of cyan (C), magenta (M), yellow (Y), and black (K), After being transported to the fixing unit 8 and subjected to a fixing process by the flash fixing device 23 disposed in the fixing unit 8, it is discharged to a paper discharge unit (not shown).

  The fixing unit 8 includes a sub driving roller 24 and a driven roller 25 that convey the continuous paper 2 on which the toner image is fixed by the flash fixing device 23 while being sandwiched by a pair of rollers. A plurality of guide rollers 26 to 30 for guiding the book 2 are provided.

  Further, the control unit 10 includes a controller 9, and the main print control unit 31 is controlled by exchanging commands and status by the controller 9. The main print control unit 31 is a sub print control unit 32 provided in the first to fourth print units 4 to 7 for cyan (C), magenta (M), yellow (Y), and black (K). Are configured to control the image data of corresponding colors from the controller 9 to the sub print control units 32 to 35.

  By the way, in this embodiment, in a print head including an LED array in which a plurality of LED elements that are ON / OFF driven in accordance with image data are linearly arranged, the print head controls the temperature of the print head. Thus, a temperature control means for correcting the dot position of image exposure is provided, and the temperature control means is configured to use a temperature control circuit board mounted with a functional element similar to the LED array. Yes.

  In this embodiment, the temperature control circuit board is constituted by an inexpensive LED array in which a plurality of LED elements are linearly arranged.

  That is, as shown in FIG. 1, the print head 17 includes a frame 40 formed of a metal such as aluminum or stainless steel. The frame 40 is 20 inches according to the print size of the print head 17. It is formed in a long length such as 26 inches or 36 inches. An upper portion of the frame 40 is formed with a storage space 41 for placing the LED array having a rectangular cross section in a stored state. The storage space 41 illustrates the upper portion of the frame 40. The upper part can be opened by allowing the separating part to be separated vertically.

  An insulating sheet 42 with good thermal conductivity is laid on the bottom of the storage space 41 of the print head 17, and an LED array 43 is disposed on the insulating sheet 42 along the longitudinal direction. ing. As shown in FIGS. 1 and 3, the LED array 43 includes a printed wiring board 44. On the printed board 44, LED chips 45 as LED elements have a predetermined recording density (for example, 1200 dpi or the like). 2400 dpi, etc.), they are linearly arranged over a long length of 20 inches, 26 inches, 36 inches, or the like. On both sides of the LED chip 45, driver ICs 46 for driving the LED chips 45 on / off with a predetermined light amount according to image data are arranged in a state of being divided corresponding to a predetermined number of LED chips 45. Yes. The LED chip 45 and the driver IC 46 are connected to each other by a bonding wire 47.

  The print head 17 can perform image exposure at a predetermined recording density (for example, 1200 dpi, 2400 dpi, etc.) according to image data by driving the LED chip 45 with a predetermined light amount by the driver IC 46. A self-scanning LED array 43 is formed.

  Further, the ceiling 48 of the frame 40 of the print head 17 is emitted from each LED chip 45 of the LED array 43 at a position corresponding to the upper portion of the LED array 43 as shown in FIGS. 1 and 4. An imaging lens 49 made up of a SELFOC lens array (trade name) or the like for exposing light onto the photosensitive drum 15 at the same magnification is disposed. The imaging lens 49 is integrally attached to the ceiling portion 48 of the frame 40, but may be attached as a separate body. In FIG. 4, reference numeral 55 denotes a storage element that stores parameters for temperature control of the print head 17.

  Further, in the storage space 41 of the frame 40 of the print head 17, a printed wiring board 50 for temperature control as temperature control means is disposed in parallel with the LED array 43. As the printed wiring board 50 for temperature control, for example, an inexpensive LED array corresponding to A4 size or A3 size is used, and there is an LED chip with poor lighting. Therefore, it is possible to use what is discarded.

  As shown in FIG. 1, the printed wiring board 50 for temperature control is provided inside a storage space 41 of a frame 40 partitioned by a partition plate 51, and heat laid inside the frame 40. It arrange | positions at the upper part of the insulating sheet 42 with sufficient conductivity. The LED array 50 for temperature control includes a printed wiring board 51, and LED chips 52 are linearly arranged on the printed board 51 in accordance with a predetermined recording density (for example, 600 dpi). . On one side of the LED chip 52, a driver IC 53 for driving the LED chip 52 to be turned on / off is arranged in a state of being divided corresponding to the plurality of LED chips 52. The LED chip 52 and the driver IC 53 are connected to each other by a bonding wire 54.

  The LED array 50 for temperature control is an LED array for low brightness corresponding to A4 size or A3 size, whereas the LED array 43 displays images over a long length of 20 inches, 26 inches, and 36 inches. The LED array 50 for temperature control is arranged over the entire length of the LED array 43 by connecting the plurality of LED arrays 50 to each other because the LED array 50 for temperature control is configured to be exposed. At that time, there is no problem even if there is a gap between the printed wiring boards 51 between the LED arrays 50 for temperature control as shown in FIG.

  Further, in this embodiment, a plurality of temperature release fins 56 project from the back side of the frame 40 of the print head 17, and in the vicinity of the base end portion of the temperature release fins 56, A thermistor 57 is attached as temperature detecting means for detecting the temperature of the frame 40 of the print head 17. The thermistor 57 may be disposed on the inner surface of the frame 40 in the storage space 41 of the print head 17.

  FIG. 5 is a block diagram showing a control circuit of a color image forming apparatus to which the print head according to this embodiment is applied.

  As shown in FIG. 5, the cyan (C), magenta (M), yellow (Y), and black (K) first to fourth print units 4 to 7 correspond to the print heads 17, respectively. A storage means 55 and a thermistor 57 as temperature detection means are provided. The correction data from the storage means 55 and the thermistor 57 are input to the main print control unit 31, and the main print control unit 31 sends image data and prints to the sub print control units 32-35. A synchronization signal or correction data is sent. The sub print control units 32 to 35 control energization to the temperature control printed wiring boards 50 arranged in the print heads 17 of the first to fourth print units 4 to 7 based on the correction data. Is configured to do.

  In the above configuration, in the tandem type color image forming apparatus to which the print head according to the first embodiment is applied, a long LED array and a process speed can be achieved without causing a significant cost increase as follows. It is possible to perform image exposure with high accuracy even in a fast model.

  That is, in the tandem color image forming apparatus to which the print head according to the first embodiment of the present invention is applied, first, cyan (C), magenta (M) ), Yellow (Y), black (K) first to fourth printing units 4 to 7 are formed with registration marks (not shown) for controlling the image forming positions, and the registration marks are registered as shown in FIG. It is detected by the mark detection means 22.

  In the registration mark detection means 22, image forming positions in the main scanning direction (LED eye alignment direction) and the sub-scanning direction (direction orthogonal to the LED eye alignment direction) in each of the first to fourth print units 4 to 7. Are detected in units of several tens of μm or in units of several μm.

  The storage means 55 provided in each print head 17 of the first to fourth print units 4 to 7 stores dot position data and temperature characteristics in the initial state of each print head 17. The print controller 31 reads the dot position data and temperature characteristics stored in the storage means 55 provided in each print head 17 and calculates the relative temperature value based on the temperature detection value of the thermistor 57. Thus, the control temperature by the printed wiring board 50 for temperature control is determined.

  At this time, the control characteristics of the temperature control printed wiring board 50 are known in advance, and it is already known how much the temperature of the temperature control printed wiring board 50 becomes when it is energized. .

  The sub print control units 32 to 35 control energization to the temperature control printed wiring board 50 provided in each print head 17 based on the correction data from the main print control unit 31, and The print head 17 is controlled to have a temperature equal to the target predetermined temperature.

  Thereafter, the main print control unit 31 performs the same control as described above after printing a certain number of sheets or when the temperature inside the apparatus changes by a predetermined temperature or more.

  As described above, in the above embodiment, the temperature control printed wiring board 50 mounted with the same functional elements as the LED array is used as the temperature control means. Therefore, the temperature control circuit board includes a plurality of temperature control circuit boards. An inexpensive LED array in which LED elements are arranged in a straight line can be used, and image exposure can be performed with high accuracy even in a long LED array or a model with a high process speed without causing a significant increase in cost. It is possible.

  Further, since the printed wiring board 50 for temperature control constitutes a circuit board on which functional elements similar to those of the LED array 43 are mounted, the heat generation characteristics of the printed wiring board 50 for temperature control are also the LED array 43. The temperature control can be performed in an extremely short time, and from this point, it is possible to perform image exposure with high accuracy even in a model having a high process speed.

FIG. 1 is a sectional view showing a print head according to Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram showing a color image forming apparatus to which the print head according to Embodiment 1 of the present invention is applied. FIG. 3 is a plan view showing the print head according to Embodiment 1 of the present invention. FIG. 4 is a perspective view showing the exposure state of the print head according to Embodiment 1 of the present invention. FIG. 5 is a block diagram showing a control circuit of the color image forming apparatus to which the print head according to Embodiment 1 of the present invention is applied. FIG. 6 is a sectional view showing a conventional print head.

Explanation of symbols

  17: Print head, 43: LED array, 50: Printed wiring board for temperature control.

Claims (5)

In a print head including an LED array in which a plurality of LED elements that are driven ON / OFF according to image data are arranged,
The print head includes temperature control means for correcting a dot position of image exposure by controlling the temperature of the print head, and the temperature control means is a temperature at which a functional element similar to the LED array is mounted. A print head using a circuit board for control. The print head according to claim 1, wherein the temperature control circuit board includes an inexpensive LED array in which a plurality of LED elements are arranged. 3. The print head according to claim 1, wherein the temperature control circuit board is configured by connecting a plurality of temperature control circuit boards to an LED array of the print head. . 4. The print according to claim 1, wherein the circuit board for temperature control is disposed on an insulating sheet having a high thermal conductivity that is laid under the LED array of the print head. 5. head. An image forming apparatus comprising the print head according to claim 1.

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