JP2007210137A - Exposure device and method for adjusting exposure width - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device which precisely performs adjustment of exposure width of an LED array and reduces wasting of power consumption. <P>SOLUTION: The exposure device has a plurality of the LED arrays 30; a heating element 50 for exposure width adjustment which is attached to each LED array 30; and a power supply controlling part 60 which controls an electric power supplied to each heating element 51 or a power supply time from a count value by counting the number of data to make each LED array 30 emit light within a unit time from printing data. The adjustment of the exposure width of the LED arrays can be carried out precisely. Moreover, the power consumption can be reduced by making temperature ripples of the LED arrays small. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image using an electrophotographic system. More particularly, the present invention relates to an exposure apparatus equipped with an LED print head for exposing a photosensitive member.

  In recent years, various xerographic image forming apparatuses using an LED print head as a recording head have been proposed for image forming apparatuses such as printers, copiers, and facsimiles.

  A general LED print head used for forming an electrostatic latent image has a plurality of LED arrays arranged in the axial direction of a photoreceptor. In such an LED print head, processing for adjusting the exposure position by adjusting the exposure width of each LED array is required in order to obtain a high-quality image.

  In the case of a tandem color printing apparatus using a plurality of LED arrays, as shown in FIG. 1, the printing position is adjusted by matching the writing position on the left side of the LED array of each color printing unit, but the length of each LED array is different. There is a problem that color misregistration occurs and the color of the printed result is different.

  Therefore, a heater is provided in each color LED array to heat the LED array, thereby adjusting the exposure width in the main scanning direction of each color LED head by thermal expansion of the LED array.

  However, the temperature of the LED array also rises by performing exposure using the LED array during printing. In a color image, since the printing rate for each color is different, the temperature rise of the LED array is different for each color, and the length of the LED array is also different.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for constantly keeping the temperature of the LED array constant by controlling the sum of the power for driving the LED array and the power applied to the heater to be constant.

Japanese Patent No. 2797255

  However, Patent Document 1 described above performs control so that the sum of the electric power applied to the heater is constant after detecting the current flowing through the LED array. For this reason, it corrects after the temperature of the LED array deviates from the target temperature, and wasteful power consumption occurs.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exposure apparatus and an exposure width adjustment method that accurately adjust the exposure width of an LED array and reduce waste of power consumption.

In order to achieve such an object, the exposure apparatus of the present invention counts the number of data for causing each LED array to emit light from a plurality of LED arrays, a heating element for adjusting the exposure width attached to each LED array, and print data. And a control means for controlling the electric power supplied to each heating element or the electric power supply time from the count value.
Therefore, the exposure width of the LED array can be adjusted with high accuracy. Further, the temperature ripple of the LED array can be reduced to reduce power consumption.

  The exposure apparatus includes a temperature detection unit that detects a temperature of each LED array, and the control unit controls power supplied to each heating element from the temperature detected by the temperature detection unit and the count value. Good.

  In the above exposure apparatus, the control means is a temperature that is increased by light emission of the LED array that is obtained from the count value from power or a power supply time that is supplied to bring the LED array from the detected temperature to a target temperature. The power corresponding to the minute or the power supply time may be subtracted.

  In the above exposure apparatus, the heating element may be provided for each block including a plurality of LEDs, and the control means may control power supplied to the heating elements of each block or power supply time.

  In the exposure width adjusting method of the present invention, the step of counting the number of times of light emission for causing the plurality of LED arrays to emit light is counted for each LED array, and the power or power supply time to be supplied to the heating element attached to each LED array. , Calculating based on the count value, and supplying power and adjusting the exposure width of each LED array.

  The present invention can accurately adjust the exposure width of the LED array. Further, the temperature ripple of the LED array can be reduced to reduce power consumption.

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

FIG. 2 shows a schematic configuration of a tandem color printer 1 as an image forming apparatus.
Inside the color printer main body, as image forming units, black (K), yellow (Y), magenta (M), and cyan (C) image forming units 13K, 13Y, 13M, and 13C are arranged in the horizontal direction. Are arranged at regular intervals along the line. Further, below the four image forming units 13K, 13Y, 13M, and 13C, an intermediate transfer member serving as an intermediate transfer body that transfers toner images of respective colors sequentially formed by these image forming units in a state of being superimposed on each other. The transfer belt 20 is disposed so as to be rotatable along the arrow direction. The respective color toner images transferred onto the intermediate transfer belt 20 are transferred onto a recording sheet 21 as a recording medium fed from a sheet feeding tray 22 and the like, and then the fixing unit 23. Is fixed on the recording paper 21 and discharged to the outside.

  The four image forming units 13K, 13Y, 13M, and 13C are all configured in the same manner except that the colors of the images to be formed are different. Broadly speaking, the image carrier rotates at a predetermined rotational speed in the direction of the arrow. As photosensitive drums 12K, 12Y, 12M, and 12C, a charger that uniformly charges the surfaces of the photosensitive drums 12K, 12Y, 12M, and 12C, and the surfaces of the photosensitive drums 12K, 12Y, 12M, and 12C The exposure apparatuses 11Y, 11M, 11C, and 11K that expose the images corresponding to the respective colors to form electrostatic latent images and the electrostatic latent images formed on the photosensitive drums 12K, 12Y, 12M, and 12C are developed. It comprises a developing device and a cleaning device 14.

  Next, the LED printer head of the exposure apparatus 11 will be described in detail with reference to FIG. As shown in FIG. 3, the LED printer head 40 adjusts and fixes the LED array 42, the housing 43, and the LED array 32, and a printed circuit board on which circuits for supplying various signals for controlling the driving of the LED array 32 are formed. 40 and a SELFOC lens array (SLA: registered trademark) 34 for forming an image of the light emitted from the LED array 32 on the photosensitive drum 12.

  The LED array 32 and the printed circuit board 40 are mounted in the housing 36. The printed circuit board 40 has the mounting surface of the LED array 32 opposed to the photosensitive drum 12.

  The LED array 30 includes a plurality of LED chips 31 arranged in series along the axial direction (main scanning direction) of the photosensitive drum 12, and a plurality of LED chips 31 arranged in series. A light beam can be irradiated with a predetermined resolution in the axial direction of the body drum (see FIG. 4).

  The LED array 30 is integrally formed with a heating element 50 as shown in FIG. The heating element 50 is a resistor that generates heat when an electric current flows. The heating element 50 controls the amount of heat of the heating element by controlling the voltage applied to the heating element 50 or the pulse width of a signal flowing through the heating element 50.

FIG. 5 shows a configuration of a power supply control unit 60 (corresponding to the control means of the present invention) 60 that controls power supply to the heating element 50. The power supply control unit 60 adjusts the length of the LED array provided for each color plate and makes the exposure width constant so that the power supply amount or power supply time to the heating elements provided in each LED array is set. Control. At this time, a control signal for controlling the electric power supplied to the heating element 50 to obtain a target temperature is set to V1. Further, when the LED array emits light to draw an exposure image, the temperature rises due to its own light emission and deviates from the target temperature. Therefore, the power supply control unit 60 counts the number of times the LED array emits light from the print data for each color. A temperature rise caused by light emission of the LED array is calculated from the number of counts, and a heating element power corresponding to the temperature rise is obtained. This correction signal is set to V2. And electric power V2 for the temperature rise by light emission is subtracted from electric power V1 supplied in order to set it as target temperature.
As shown in FIG. 5, the power supply control unit 60 includes a temperature sensor 51, a control unit 52, a printing rate calculation unit 53, a correction data generation unit 54, a subtraction unit 55, and a power supply unit 56. Yes. The functional units other than the control unit 52 are provided for each LED array of each color, and the control unit 52 is input for each color by inputting the sensor signal of the temperature sensor 51 provided for each color. The control signal V1 is output to the subtracting unit 56.

  The temperature sensor 51 is attached to the heating element 50, measures the temperature of the heating element 50, or the temperature around the LED array when power is not supplied to the heating element 50, and transmits it to the control unit 52 as a sensor signal. To do.

  The controller 52 inputs a sensor signal from the temperature sensor 51 at the start of heating of the LED array, and grasps the temperature around each LED array. Further, as shown in FIG. 6, the control unit 52 stores a table in which the relationship between the change in length of each LED array and the temperature is recorded, and the table is supplied to the LED array of each color with reference to this table. Calculate power and power supply time. First, the control unit 52 obtains the length of the LED array from the ambient temperature at the start of heating the LED array. Next, a target length is set to align the lengths of the LED arrays of the respective colors, and power or power supply time to be supplied to the LED array is determined for each LED array in order to match the target length. The calculated power or power supply time is output to the subtractor 55 provided for each color as a control signal V1 for turning on and off the heating element.

  FIG. 7 shows a detailed configuration of the control unit 52. The control unit 52 includes an A / D converter (hereinafter abbreviated as ADC) 61, a microprocessor unit (hereinafter abbreviated as MPU) 62, and a D / A converter 63. The ADC 61 converts the temperature information of the LED array measured by the temperature sensor 51 into a digital signal. The MPU 62 calculates the power or power supply time necessary for setting the target temperature (target length) from the current temperature of the LED array, and outputs it to the DAC 63 as the control signal V1. The control signal V 1 is converted into an analog signal by the DAC 63 and output to the subtracting unit 55.

  FIG. 8 shows detailed configurations of the LED control unit 70 and the printing rate calculation unit 53. As shown in FIG. 8, the LED control unit 70 is provided with a buffer memory 71 and a drive control unit 72. The print data is once stored in the buffer memory 71. The drive control unit 72 reads print data from the buffer memory 71, performs drive control of the LED array according to the read print data, and forms an exposure image on the photoconductor 12. The print data input to the LED control unit 70 is also output to the print rate calculation unit 53.

  Further, the printing rate calculation unit 53 is provided with a light emission data detection unit 75, an adder 76, and a latch circuit 77 as shown in FIG. For example, the light emission data detection unit 75 detects data for causing the LED array to emit light from the print data. The LED array emits light to detect data for drawing an image on the photoreceptor. When data is detected, a detection signal is output to the adder 76. The adder 76 increments the count value by 1 each time a detection signal is input from the light emission data detection unit 75. For example, when the print data for one page is counted, the obtained count value is output to the latch circuit 77. The count value is once latched by the latch circuit 77 and output to the DAC 78 of the correction data generation unit 55. The DAC 78 outputs the count value to the subtractor 55 as a control signal V2 converted into analog data.

FIG. 9 shows the configuration of the subtraction unit 55 and the power supply unit 56. As shown in FIG. 9, the subtracting unit 55 includes a subtracter 85 including a resistor R and an operational amplifier 81, an inverting amplifier 86 including a resistor R and an operational amplifier 82, and a comparator 83.
In order to bring the LED array to the target temperature, the control unit 52 outputs a control signal V1 for controlling the switching transistor Tr87 that connects the heating element 50 and the power source Vdd in analog form. That is, the control signal V1 corresponding to the voltage applied to the heating element 50 is output in analog.
The subtracter 85 subtracts the count value voltage V2 from the control signal voltage V1. The subtraction result is amplified by the inverting amplifier 86 and compared with the output of the power supply unit 56 by the comparator 83. The comparator 83 compares the voltage supplied to the heating element 50 with the output voltage of the inverting amplifier 86, and supplies a signal corresponding to the comparison result to the switching transistor Tr87 of the power supply unit 56.

  The power supply unit 56 is provided with a switching transistor Tr87 and a low-pass filter 88 including a coil L and a capacitor C as shown in FIG. When the control signal from the subtractor 55 is applied to the gate of the switching transistor Tr87, a current corresponding to the voltage of the control signal is cut by the low-pass filter 88 and flows into the heating element 50.

  Thus, this embodiment can adjust the exposure width of the color LED array provided for each color plate with high accuracy. Further, since the temperature rise due to the light emission of the LED array is subtracted before supplying power to the LED array, the temperature ripple can be kept small and the power consumption can be reduced.

  The control procedure of the power supply control unit 60 will be described with reference to the flowchart shown in FIG. When the sensor information is input from the temperature sensor 51 (step S1), the control unit 52 obtains power or power supply time necessary for setting the LED array to the target temperature from the measured temperature, and subtracts the control signal V1. (Step S2). The printing rate calculation unit 53 counts the number of data for turning on the LED array from the print data, and outputs the count result to the correction data generation unit 54. The correction data generation unit 54 that has input the count value (Step S3) obtains the temperature rise due to the self-light emission of the LED array from the count value, and obtains the power or power supply time of the heating element 51 corresponding to this temperature rise ( Step S4). The obtained power or power supply time V2 is output to the subtracting unit 55. The subtracting unit 55 subtracts the correction signal V2 output from the correction data generating unit 54 from the control signal V1 output from the control unit 52, and supplies electric power to the heating element 51 using the obtained signal V1-V2 (step). S5).

The embodiment described above is 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.
For example, as shown in FIG. 11, the LED array can be divided into blocks, a heating element is provided for each block, and the power supplied to the heating element can be controlled.

It is a figure which shows the exposure width | variety of the LED array provided for every color plate. 1 is a diagram illustrating a configuration of an image forming apparatus. It is a figure which shows the structure of an LED printer head. It is a figure which shows the structure of an LED array. It is a block diagram which shows the structure of an electric power supply control part. It is a figure which shows the relationship between the temperature rise of an LED array, and the change of exposure width. It is a figure which shows the structure of a control part. It is a figure which shows the structure of a LED control part and a printing rate calculation part. It is a figure which shows the structure of a subtraction part and an electric power supply part. It is a flowchart which shows the process sequence of an electric power supply control part. It is a figure which shows the structure of a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Exposure apparatus 12 Photosensitive drum 13 Image forming unit 14 Cleaning apparatus 20 Intermediate transfer belt 21 Recording paper 22 Paper feed tray 23 Fixing device 30 LED array 50 Heating element 51 Temperature sensor 52 Control part 53 Print rate calculation part 54 Correction data generation unit 55 Subtraction unit 56 Power supply unit 60 Power supply control unit 70 LED control unit

Claims (5)

A plurality of LED arrays;
A heating element for adjusting the exposure width attached to each LED array;
An exposure apparatus comprising: a control unit that counts the number of data for causing each LED array to emit light from print data, and controls the power supplied to each heating element or the power supply time from the count value. Temperature detecting means for detecting the temperature of each LED array;
2. The exposure apparatus according to claim 1, wherein the control unit controls electric power supplied to each heating element from the temperature detected by the temperature detection unit and the count value.   The control means is a power corresponding to a temperature increased by light emission of the LED array obtained from the count value from a power or a power supply time for supplying the LED array from the detected temperature to a target temperature. The exposure apparatus according to claim 2, wherein the power supply time is subtracted. The heating element is provided for each block composed of a plurality of LEDs,
4. The exposure apparatus according to claim 1, wherein the control unit controls power supplied to a heating element of each block or a power supply time. 5. A step of counting the number of times of light emission for causing the plurality of LED arrays to emit light, for each LED array;
Calculating power or power supply time supplied to the heating element attached to each LED array based on the count value;
Supplying power and adjusting the exposure width of each LED array;
An exposure width adjustment method comprising:

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