JP4361284B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a digital copying machine, a laser printer, or a laser facsimile machine. More specifically, when the same image continues in the same position, the main scanning writing start position in laser beam writing is changed. The present invention relates to an image forming apparatus that avoids toner concentration on a fixing device and reduces the occurrence of contamination on recording paper.
[0002]
[Prior art]
With the recent spread of IT, when recording digital information on recording paper in an environment that handles image information and drawing information such as offices and design fields, as an image forming method with high density, high speed, and versatility, Image forming apparatuses such as laser printers and digital copying machines using laser light irradiation are often used. In particular, the recording density has been increased, and it is frequently used in fields such as CAD (computer aided design) and DTP (desktop publishing).
[0003]
Such an image forming apparatus scans a photosensitive member with laser light deflected by an optical deflector (polygon scanner) based on an electrophotographic process to form an electrostatic latent image, and develops the electrostatic latent image. The toner image is visualized with toner by the apparatus, the visualized toner image is transferred to a recording paper, the recording paper to which the toner image is transferred is heated and fixed by a fixing device, and discharged (for example, (See Patent Document 1).
[0004]
The laser optical system for writing the laser beam includes a light source (LD) that irradiates the laser beam in one direction and a polygon mirror that deflects and scans the laser beam emitted from the light source to the photosensitive member for each line. The light source and the polygon scanner are controlled based on the input image information to form an image on the photoconductor.
[0005]
The laser optical system is provided with a photodiode (synchronization sensor) that is provided on the scanning line and synchronizes the irradiation timing of the laser light when the photosensitive member is scanned with laser light for each line. When light is incident, a synchronization signal is output, and the irradiation timing of laser light for each line is controlled according to the synchronization signal.
[0006]
[Patent Document 1]
JP 2002-36624 A
[Problems to be solved by the invention]
However, in the conventional image forming apparatus as described above, when there is an environment for drawing output such as CAD, there is a line drawing at a predetermined position such as a drawing frame, so that a continuous straight line in the sub-scanning direction is formed. If the image of the same portion is output continuously, the toner is always input to the same portion of the fixing portion, so that it exceeds the cleaning ability to collect the toner adhering to the surface of the fixing roller. Fixing offset occurs due to accumulation of unrecoverable toner on the fixing roller. As a result, abnormal images such as black streaks and periodic stains are transferred onto the recording paper, resulting in degradation of image quality. there were.
[0008]
The present invention has been made in view of the above, and by avoiding concentration of input to one portion of the toner with respect to the fixing device, image smear that occurs on the recording paper is prevented and image quality is improved. For the purpose.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in the image forming apparatus according to claim 1, a copy function for performing a copy operation of a document image and a printer function for converting data sent from the outside into image information and printing it out The electrostatic latent image is formed on the photosensitive member by a light beam, and the toner image formed by the electrostatic latent image and the heat-soluble toner is transferred onto a recording paper, and the transferred toner image In the image forming apparatus for fixing the light beam on the recording paper by a thermal fixing device that contacts the recording paper, a mode for changing the light beam writing start position in the main scanning direction on the photosensitive member to a predetermined position by the printer function. A mode selection means that is effective only when operating, and a write start position change commanding the change of the write start position in accordance with the mode selection from the mode selection means. A voltage generation means for generating a voltage for adjusting the write start position in accordance with an instruction from the write start position changing means, and a synchronization signal that is the write start position in accordance with the voltage from the voltage generation means. Synchronization signal output means for outputting.
[0010]
According to the present invention, by changing the laser beam writing start position on the photosensitive member only when operating with the printer function, it is possible to avoid the concentration of toner at one place and to operate with the copy function. The horizontal registration accuracy at the time can be maintained .
[0011]
In the image forming apparatus according to claim 2, when the mode selection unit performs image formation with the same image information multiple times in succession, the writing start position is set for each sheet or a predetermined value. It includes a mode that changes for each number.
[0012]
According to the present invention, in the first aspect, when the image formation is performed a plurality of times with the same image information, the mode in which the light beam writing start position in the main scanning direction is changed for each sheet or for each predetermined number of sheets. By selecting, the user can intentionally instruct the change of the main scanning writing start position, so that it is possible to avoid the continuous toner input to the fixing device at the same position in the sub-scanning direction.
[0013]
In the image forming apparatus according to claim 3, the mode in the mode selection unit is configured to set the writing start position for each sheet or for a predetermined number when image formation is performed multiple times continuously with the same image size. It includes a mode that changes for each number.
[0014]
According to the present invention, in the first aspect, in the case where the image formation is performed a plurality of times with the same image size, the write start position of the light beam in the main scanning direction is changed for every one sheet or every predetermined number of sheets. By selecting, the user can intentionally instruct the change of the main scanning writing start position, so that it is possible to avoid the continuous toner input to the fixing device at the same position in the sub-scanning direction.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of an image forming apparatus according to the invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to this embodiment.
[0018]
In the present invention, an electrostatic latent image is formed by irradiating a photosensitive member with a light beam in accordance with digital image information, and a heat-soluble toner is developed on the electrostatic latent image to form a toner image and recorded. In an image forming apparatus equipped with a thermal fixing device that transfers images onto paper, fixes unfixed toner on the recording paper by a thermal fixing device, and discharges the paper according to a so-called electrophotographic process. By providing a function to change the optical writing start position in the main scanning direction (correction of the writing position) according to the instruction, it is accumulated (input) in the fixing roller portion when images are continuously formed at the same writing start position. This reduces the amount of toner generated and reduces the occurrence of abnormal images such as black streaks. This will be specifically described below.
[0019]
The image forming apparatus according to the present invention is applied to a printing apparatus such as a laser printer that forms an electrostatic latent image on a photosensitive member by laser light and prints input image information, or a multi-function machine having a copy / printer / facsimile function. Applied.
[0020]
FIG. 1 is a block diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a configuration of an optical writing system in FIG. In these drawings, the image forming apparatus 100 mainly forms an electrostatic latent image on the photosensitive member 12 by controlling a laser diode (hereinafter referred to as LD) 10 and a polygon mirror 11 in accordance with input image information. A plotter unit 110 to be operated, an operation unit 120 having a function of mode selection means for instructing the plotter unit 110 to perform an operation, and a control unit having a function of a writing reference position changing unit for controlling the plotter unit 110 in accordance with an instruction from the operation unit 120 130.
[0021]
As shown in FIG. 2, the plotter unit 110 includes an LD 10 that is a light source, a polygon mirror 11, and a photoconductor 12. The plotter unit 110 is emitted from the LD 10 and is exposed by a cylinder lens 15 through a collimator lens 13 and an aperture 14. The laser beam condensed so as to have a predetermined beam diameter on the body 12 is scanned (optical writing) in the main scanning direction (long axis direction of the photoreceptor 12) x by the polygon mirror 11 rotated at high speed by the polygon motor 16. ) Is configured to. The laser light is condensed in the sub-scanning direction (rotating direction of the photoconductor 12) y by the cylinder lens 18 while changing the angle by the mirror 17. Further, the pair of fθ lenses 19 correct the curvature of field on the photoconductor 12 by optically correcting the equiangular scanning of the laser light scanned by the polygon mirror 11 to the constant speed scanning.
[0022]
Further, the plotter unit 110 includes a photodiode (hereinafter referred to as PD) 20 and is configured to detect laser light reflected by the polygon mirror 11 via the mirror 21 and the cylinder lens 22. A synchronization detection signal DEPT in the main scanning direction is acquired according to the detected laser beam, and the emission start timing of the image writing laser beam is controlled for each scan.
[0023]
As shown in FIG. 1, the plotter unit 110 configured as described above includes a pixel clock generation unit 31 that generates a pixel clock signal from the reference high-frequency clock SLCK by varying a frequency division ratio for each pixel density, and a pixel clock signal. A plotter timing control unit 32 that generates a predetermined timing signal using WCLK as a reference clock, a memory 33 that reads and stores data necessary for the operation of the plotter timing control unit 32, and a personal computer (hereinafter referred to as a PC) 34. The printer controller 35 which converts the data output from the image data into image information (hereinafter referred to as printer image data) and outputs it in accordance with the timing signal output from the plotter timing control unit 32, and the printer image output from the printer controller 35 Attaching predetermined data to data PRDAT A plot data control unit 36 which then outputs, based on the data LDDAT outputted from the plot data control unit 36, and a LD drive unit 37 for emitting control LD 10, a. In this way, each unit such as the LD 10 and the photoconductor 12 is controlled to write printer image data to the photoconductor 12.
[0024]
The pixel clock generation unit 31 is configured to generate a pixel clock signal WCLK by dividing the reference high-frequency clock SCLK according to the pixel density, and to match the pixel clock signal WCLK with the phase of the synchronization detection signal. It has become.
[0025]
The plotter timing control unit 32 uses the pixel clock signal WCLK as a reference clock, PRCK which is a printer image data transfer clock, PRSYNC which is a synchronization detection signal at the start of one line, PRLGAT which indicates the effective width of one line, and one page writing effective period A timing signal such as PRFGAT is generated and output to the printer controller 35.
[0026]
The printer controller 35 is configured to convert (decompress) the character data sent from the PC 34 into bitmap data and develop it in an internal page memory (not shown), and the above-mentioned output from the plotter timing control unit 32. The print image data PRDAT is output to the plot data control unit 36 in accordance with the timing signal.
[0027]
The plot data control unit 36 adds information to be emitted to detect the synchronization detection signal to the print image data PRDAT output from the printer controller 35, and outputs it to the LD drive unit 37 as serial image data (laser diode data) LDDAT. Is configured to do. The LD drive unit 37 causes the LD 10 to emit light according to the input serial image data (laser diode data) LDDAT.
[0028]
The page memory 43 stores scanner data obtained by optically reading an original image by the scanner 41 and converted into an electrical signal, and data received from the communication control 42, and stores parallel image data to the plot data control unit 36. To be transferred.
[0029]
The plotter unit 110 includes a PD 20 that detects a laser beam scanned in the main scanning direction, and has a synchronization detection unit 38 that functions as a synchronization signal output unit that outputs a synchronization detection signal according to the detected laser beam. Based on the synchronization detection signal DETP in the main scanning direction in the synchronization detection unit 38 and the synchronization detection counter 40 that detects the pulse width of the synchronization detection signal output from the synchronization detection unit 38, the image forming laser light is scanned for each scan. The light emission start timing is controlled.
[0030]
The synchronization detection unit 38 includes a PD 20 provided on a laser light scanning line. The PD 20 outputs a pulse signal (synchronization detection signal) during a period in which the laser light is scanned. The circuit shown in FIG. 3 is a typical circuit example of the synchronization detection unit 38. Further, the pulse width of the synchronization detection signal depends on the synchronization detection reference voltage (reference voltage of the comparator 25), the time that the LD 10 scans the PD 20, and the power of the LD 10 that the PD 20 receives.
[0031]
The synchronization detection counter 40 is configured to receive the synchronization detection signal output from the synchronization detection unit 38 and the reference high frequency clock SLCK, and to detect the pulse width of the synchronization detection signal, and to detect the detected pulse width via the control unit 130. To the synchronization detection voltage generator 39.
[0032]
The synchronization detection voltage generation unit 39 is constituted by a digital / analog (D / A) converter, generates a synchronization detection reference voltage when generating a synchronization detection signal, and outputs the synchronization detection reference voltage to the synchronization detection unit 38. It is configured. Further, in the synchronization detection counter 40, the voltage level of the synchronization detection reference voltage is controlled by the control unit 130 to which the pulse width of the detected synchronization detection signal is input.
[0033]
By adopting a configuration in which the level of the synchronization detection reference voltage can be controlled in this way, the laser light that operates based on the transferred image information controls the writing start position in the main scanning direction on the photoconductor 12 to a predetermined position. can do. That is, by controlling the level of the synchronization detection reference voltage, the writing start position in the main scanning direction can be moved (corrected). That is, the image position can be corrected within a predetermined range.
[0034]
In FIG. 1, the operation unit 120 sends a mode selection signal to the control unit 130 when the write position change mode is selected, and the control unit 130 sends a write position control signal to the synchronization detection reference voltage generation unit 39 based on the mode selection signal. Send. The synchronization detection reference voltage generation unit 39 generates a synchronization reference voltage (write position correction voltage) according to the write position control signal and sends it to the synchronization detection unit 38. The synchronization detection unit 38 outputs a synchronization detection signal based on the synchronization reference voltage (write position correction voltage). As a result, the image writing position can be corrected within a predetermined range.
[0035]
As described above, when the electrostatic latent image is formed on the photoconductor 12 by the laser beam corresponding to the image information, the electrostatic latent image is subsequently applied to the toner by a developing device (not shown). The toner image is attached and visualized. Further, the recording paper is fed out from the paper feeding device (not shown) to the photoconductor 12 at a predetermined timing, the toner image is transferred onto the recording paper P, and the recording paper P is pressurized and heated by the fixing device 150 in the same manner. In this way, the toner image is fixed on the recording paper while being melted, and discharged outside the apparatus.
[0036]
The fixing device 150 includes a fixing roller 151 having an inner cylinder and a surface excellent in releasability. The fixing device 150 is provided facing the fixing roller 151 and is urged against the fixing roller 151 with a predetermined pressure. And a fixing cleaning blade 153 that is in contact with the fixing roller 151 and removes toner, paper dust, and the like adhering to the fixing roller 151, and is unfixed transferred onto the recording paper P. The toner image is discharged as a fixed image by the action of nip pressure and fixing heat. In the fixing device 150, a fixing heater, a thermistor for detecting a fixing temperature, a thermal fuse, a driving unit, and the like are omitted.
[0037]
By the way, the writing start position is usually a fixed reference position, but the image continuously concentrates at a certain position in the sub-scanning direction, and is sent to the fixing device 150 (see FIG. 2) or the photoreceptor cleaning device (not shown). When it is desired to reduce the load (cleaning ability), the toner is prevented from being concentrated at one place by slightly shifting the reference position. That is, when the write start position is changed (corrected), the distance corresponding to the position interval and the level and value of the synchronization detection voltage are set, and the write start position is changed based on this value.
[0038]
Next, the writing position change which is a feature of the present invention will be described. FIG. 4 is an explanatory diagram showing a writing position setting screen in the operation unit of the image forming apparatus according to the embodiment of the present invention. This figure shows a writing position change screen 122 on a touch panel 121 formed by an LCD provided in the operation unit 120, which is displayed by inputting a writing position change mode (setting screen for various modes).
[0039]
In FIG. 4, when the user wants to set an operation only at the time of printing, the user presses the “only at the time of printing” button 124, and otherwise presses the “normal” button 123 to instruct whether to change the writing position. In the selection of the write position change mode, if the “normal” button 123 is selected and the normal button 125 is displayed, the write position is not changed. When “same image repeat” button 126 or “same size repeat” button 127 is pressed, the writing position is changed in accordance with a preset repeat condition. These setting operations are performed by a “return” button 128 used for re-setting and a “setting” button 129 for pressing when the setting state is good. When the setting for changing the writing position is performed, a writing position changing condition setting screen 140 shown in FIG. 5 is displayed.
[0040]
That is, in setting the write position change condition, the change of the write position is repeatedly executed during repeat printing according to the number of sheets to be changed, the position interval to be changed, and the change position range. For example, as shown in FIG. 5, when the number of sheets to be changed is 5, the position interval to be changed is 1 mm, and the change position range is −1 mm to 1 mm, the first 1 to 5 sheets have a write correction value of 0 mm. 6 to 10 sheets are corrected by a write correction value +1 mm, and 11 to 15 sheets are corrected by -1 mm. If the number of repeats is 4 or less, no correction is made. In addition, when the number of changed sheets is 1, the writing position is corrected for each sheet.
[0041]
Similarly, when the “same size repeat” button 126 is pressed by the user, the write position is corrected with reference to the previous write position correction value when the write position change condition is met. Normally, when the power is turned OFF / ON or the size is changed, the previous writing position correction value is cleared, but the previous writing position correction value and the total number of sheets are stored in a nonvolatile RAM (not shown), You may correct | amend by the total number of sheets.
[0042]
Considering that there is a variation in the main scanning direction when setting the original during copying, the variation in horizontal registration (position accuracy in the sub-scanning direction) is changed by enabling the change of the writing start position only during the printer operation. Since it can be limited only during the operation, the lateral registration accuracy (position accuracy between the recording paper edge and the image in the main scanning direction) at the time of copying can be maintained at the current level.
[0043]
FIG. 6 is a flowchart showing an operation procedure for changing the writing position described above. This operation is performed by the control unit 130 in accordance with an instruction from the operation unit 120. In FIG. 6, first, the writing position is initialized to the reference position (step S11), and it is determined whether or not the setting is only for the printer (step S12). That is, it is determined whether or not the “printer only” button 124 is pressed. Here, when it is determined that the setting is not only for the printer, it is further determined whether or not it matches a preset write position change condition (step S13). On the other hand, if it is determined in step S12 that the setting is only for the printer, it is further determined whether the output is a printer output (step S14). If it is determined that the output is a printer, the process proceeds to step S13. If it is determined in step S13 that the write position change condition is met, the write position is executed (step S15).
[0044]
That is, as described above, the synchronization detection reference voltage generation unit 39 is controlled by an instruction from the control unit 130, and the write detection position is changed by changing the synchronization detection reference value in the synchronization detection unit 38 to a predetermined value.
[0045]
For the user, it is desirable that all the images to be output have the same printing result on the recording paper, but it is better that the image is slightly misaligned than when the recording paper is output dirty. As described above, by selectively shifting the writing position and correcting, it is possible to prevent the toner from being input to the same position in the sub-scanning direction of the fixing device 150. As a result, the input load when the surface of the fixing roller 151 is cleaned by the fixing cleaning blade 153 is reduced, and stable image output without toner contamination is realized.
[0046]
In this embodiment, the change of only the writing position in the main scanning direction has been described. However, the paper feed tray can be moved and changed to the writing position corresponding to the moving position, so that the horizontal direction for each recording sheet can be changed. Variations in registration can be suppressed, and the occurrence of contamination of the recording paper due to partial scratches on the surface of the photoreceptor can be avoided. Further, by changing the writing position as in this embodiment, in addition to avoiding the concentration of toner input to the fixing roller 151, the blade portion of the cleaning device that cleans the toner remaining after the transfer of the photoconductor 12 is used. This is also effective for cleaning performance.
[0047]
【The invention's effect】
As described above, according to the image forming equipment according to the present invention, only by changing the write start position of the laser beam to the photoconductor when operating the printer function, to avoid one part toner concentration And the lateral registration accuracy when operating with the copy function can be maintained.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating a configuration of a writing system and a fixing state of the image forming apparatus in FIG. 1;
FIG. 3 is an explanatory diagram showing a writing-system synchronization detection circuit of the image forming apparatus according to the embodiment of the present invention;
FIG. 4 is an explanatory diagram showing a writing position setting screen in the operation unit of the image forming apparatus according to the embodiment of the present invention;
FIG. 5 is an explanatory diagram illustrating a setting screen for setting a write position change condition in the operation unit of the image forming apparatus according to the embodiment of the present invention;
FIG. 6 is a flowchart showing an operation procedure for changing a writing position of the image forming apparatus according to the embodiment of the present invention;
[Explanation of symbols]
10 LD
DESCRIPTION OF SYMBOLS 12 Photoconductor 38 Synchronization detection part 39 Synchronization detection reference voltage generation part 100 Image forming apparatus 110 Plotter part 120 Operation part 121 Touch panel 122 Write position change setting screen 130 Control part 140 Write position change condition setting screen 150 Fixing device

Claims (3)

A copy function for performing a copy operation of a document image; and a printer function for converting data sent from the outside into image information and printing it out. In an image forming apparatus for transferring a toner image formed of a latent image and a heat-soluble toner to a recording paper, and fixing the transferred toner image on the recording paper by a heat fixing device in contact with the recording paper.
A mode selection unit that makes the mode for changing the writing start position of the light beam in the main scanning direction on the photosensitive member a predetermined position, which is effective only when operating with the printer function;
Write start position changing means for instructing change of the write start position in accordance with mode selection from the mode selection means;
Voltage generating means for generating a voltage for adjusting the write start position in accordance with an instruction from the write start position changing means;
Synchronization signal output means for outputting a synchronization signal to be the write start position according to the voltage from the voltage generation means;
An image forming apparatus comprising:   The mode in the mode selection means includes a mode for changing the writing start position for each sheet or for each predetermined number of sheets when the same image information is formed continuously for a plurality of times. 2. The image forming apparatus according to 1.   The mode in the mode selection means includes a mode in which the writing start position is changed for every one sheet or every predetermined number of sheets when the same image size is formed continuously for a plurality of times. 2. The image forming apparatus according to 1.

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