JP2006293229A - Optical write-in apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a photoreceptor from being exposed prior to a synchronized detection when the synchronized detection is initially detected. <P>SOLUTION: This optical write-in apparatus includes a laser light source, a rotating polygon mirror, a driving motor, and a synchronization detection sensor which receives laser light which exists out of the main scanning region of the image forming region of a photoreceptor in a main scanning region, and deflected with the rotating polygon mirror. Control means 24b to 24d are provided in which the count of clock is started synchronized with the switching of mirror faces which deflect laser light, the emission of the laser light is started at a deflection timing Ws toward the out of the main scanning region of the photoreceptor and immediately before the synchronization detection sensor, the emission of laser light is stopped just after the synchronization sensor detects the laser light, and a counted value Wd when the synchronization detection sensor detects the laser light is stored, then the count of a clock pulse is started synchronized with the switching of the mirror faces and the emission of the laser light is started at the timing Wd corresponding to the stored count value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical writing device that scans and projects a laser beam modulated with image data onto a charged photoconductor to form an electrostatic latent image of an image represented by the image data on the photoconductor, and an image forming apparatus using the same. . The optical writing apparatus of the present invention can be used in printers, copying machines, and facsimile machines.

Japanese Patent Laid-Open No. 10-73780 Japanese Patent No. 3179813.

  In Patent Document 1, an electric motor that rotationally drives a rotary polygon mirror is equipped with a Hall element that detects the N and S poles of the rotor to generate a rotation synchronization pulse, and the phase of the rotation synchronization pulse matches the rotation reference pulse. Thus, PLL (Phase Locked Loop) control is described in which the electric motor is accelerated and decelerated to rotate the electric motor at a constant speed corresponding to the frequency of the rotation reference pulse. Patent Document 2 describes a laser light source driving circuit that detects synchronization by causing a laser light source to emit light with a minimum light output outside an image writing range of a photoconductor.

  The optical writing device aligns the optical writing start position in the main scanning direction of the laser beam reflected from the mirror surface of the rotary polygon mirror (polygon mirror) toward the photosensitive member, so that it is outside the scanning range of the photosensitive member in the main scanning direction. Laser light detection is performed by the arranged synchronous detection sensor (photoelectric conversion element). This is called synchronization detection. In addition to the state where the printer is not activated, the rotation of the rotary polygon mirror is stopped and the laser emission is stopped when the printing operation is not performed for a certain period of time such as a so-called low power consumption state. Therefore, when the printer is started up or returned from the low power consumption state, it is necessary to perform synchronization detection again for each surface of the rotary polygon mirror.

  At this time, as shown in FIG. 13, since the initial synchronization detection has conventionally been started at an arbitrary asynchronous timing, the photosensitive member as a recording medium is exposed to light, and a phenomenon occurs in which a horizontal line is latent. In addition, the deterioration of the photosensitive member has been accelerated.

  An object of the present invention is to solve the problem of deterioration of horizontal lines and a recording medium by preventing exposure to a photosensitive member when synchronization detection is first detected from a state where synchronization detection is not possible.

(1) A laser light source (31m), a rotating polygon mirror (34p) for deflecting the laser light emitted from the laser light source to main-scan the image forming area of the photosensitive member (56), and an electric drive for rotating the rotating polygon mirror Optical writing comprising: a motor (34d); and a synchronization detection sensor (38mc) that receives the deflected laser light that is outside the main scanning range of the image forming region of the photoconductor in the main scanning direction. In the device
Clock pulse counting is started in synchronization with switching of the mirror surface of the rotating polygon mirror (34p) that deflects the laser beam emitted by the laser light source (31m), and the main body of the photoconductor is based on the count value. The laser beam is emitted at a deflection timing (Ws) immediately outside the scanning range and immediately before the synchronization detection sensor, and the laser beam is emitted immediately after the synchronization detection sensor (38mc) detects the laser beam. And the count value (Wd) when the synchronous detection sensor detects the laser beam is stored, and thereafter, the clock pulse count starts in synchronization with the mirror surface switching, and the stored count An optical writing apparatus comprising: synchronization signal generation control means (24b-24d) for starting emission of the laser beam at a timing (Wd) corresponding to a value.

  In addition, in order to make an understanding easy, the code | symbol of the corresponding element or the corresponding matter of the Example which is shown in drawing and mentions later in a parenthesis was added as an example for reference. The same applies to the following.

  According to this, the motor control signal of the rotary polygon mirror drive motor synchronized with the switching of the reflection mirror surface of the conventional rotary polygon mirror (34p) for the initial synchronization detection for searching the laser beam emission timing for synchronization detection Can be realized without unnecessary exposure to the photoreceptor.

(2) A laser light source (31m), a rotating polygon mirror (34p) for deflecting the laser light emitted from the laser light source to main-scan the image forming area of the photosensitive member (56), and an electric drive for rotating the rotating polygon mirror Optical writing comprising: a motor (34d); and a synchronization detection sensor (38mc) that receives the deflected laser light that is outside the main scanning range of the image forming region of the photoconductor in the main scanning direction. In the device
A shutter (90m) interposed in a laser light path from the laser light source (31m) to the rotary polygon mirror (34p); and
The counting of clock pulses is started in synchronization with the switching of the mirror surface of the rotating polygon mirror that deflects the laser light emitted from the laser light source, and based on the count value, outside the main scanning range of the photoconductor and the The shutter is opened at the deflection timing (Ws) immediately before the synchronization detection sensor, the laser light emission starts before the shutter is opened, and immediately after the synchronization detection sensor (38mc) detects the laser light. The emission of the laser beam is stopped, and the count value (Wd) when the synchronization detection sensor detects the laser beam is stored. Thereafter, the clock pulse is counted in synchronization with the switching of the mirror surface. An optical writing device comprising: synchronization signal generation control means (24b-24d) that starts and starts emitting the laser beam at a timing (Wd) corresponding to the stored count value.

  (3) The electric motor (34d) is adjusted so that the phase of one rotation synchronizing pulse (11 detection signals) per rotation of the electric motor (34d) at a predetermined angle matches the phase of the rotation reference pulse (rotation reference signal). ) Is increased and decelerated to rotate the electric motor at a constant speed corresponding to the frequency of the rotation reference pulse. The optical writing according to (1) or (2), further including a PLL control rotation drive means (24a); apparatus.

  (4) The synchronization signal generation control means (24b-24d) generates a PLL lock signal indicating that the rotation drive means (24a) is in the constant speed control state, and then based on the rotation synchronization pulse. The switching of the mirror surface is detected, and when the switching is detected, counting of the clock pulse is started; the optical writing device according to (3) above.

  (5) The synchronization signal generation control means (24b-24d) generates an initial synchronization detection instruction signal when receiving an initial synchronization detection start instruction, and detects the initial synchronization detection when the synchronization detection sensor (38mc) detects a laser beam. Initial synchronization detection start means (24b) for stopping the instruction signal; when the initial synchronization detection instruction signal, the PLL lock signal and the mirror surface are switched, the clock pulse starts to be counted, and the count value is the main value of the photoconductor. When the value corresponding to the deflection timing (Ws) immediately outside the scanning range and immediately before the synchronization detection sensor is reached, an initial synchronization detection signal instructing the emission of the laser beam is generated, and the laser beam detection signal of the synchronization detection sensor (38mc) In response to the initial synchronization detection means (24c) that holds the count value (Wd) at that time in the data holding means (79); and the initial synchronization detection start means (24b) stops the initial synchronization detection instruction signal After When the surface is switched, the clock pulse starts to be counted. When the count value reaches the count value (Wd) held by the data holding means (79), the synchronization detection signal (synchronization signal) that instructs the emission of the laser beam The optical writing apparatus according to (4), further comprising: synchronous detection laser emission timing means (24d) for generating a detection laser emission ON / OFF signal).

(6) The optical writing device (30, 16c) according to any one of (1) to (5) above;
The photoconductor (56) that is exposed to light that the optical writing device performs main scanning to form an electrostatic latent image, and a charging means that precharges the photoconductor;
Means for developing an electrostatic latent image formed on the photoreceptor (55); and
An image forming apparatus (14) including means (57) for transferring a visible image developed by development onto a sheet. According to this, it is possible to suppress the deterioration of the photoreceptor due to the initial synchronization detection.

(7) A document scanner (10) that reads an image of a document and generates image data;
The image forming apparatus (14) according to the above (6); and
A copying apparatus (FIGS. 1 and 3) including image data processing means (ACP) for converting image data generated by the document scanner (10) into image data suitable for image formation of the image forming apparatus (14); .

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows a multi-function full-color digital copying machine equipped with a first embodiment of the present invention. This full-color copying machine is roughly constituted by units of an automatic document feeder (ADF) 13, an operation board 20, a color scanner 10, a color printer 14 and a finisher 100. The operation board 20, the color scanner 10 with the ADF 13, and the finisher 100 are units that can be separated from the printer 14. The color scanner 10 includes a control board having a power device driver, a sensor input, and a controller. 14 communicates directly or indirectly with the image data processing device ACP (FIG. 3) of the control board 14 in the machine to read the document image under timing control.

  A LAN (Local Area Network) connected to a personal computer PC is connected to the image data processing apparatus ACP (FIG. 3), and a telephone line PN (facsimile communication line) is connected to the facsimile control unit FCU (FIG. 3). The exchange PBX is connected. The printed paper of the color printer 14 is discharged to the finisher 100.

  FIG. 2 shows the mechanism of the color printer 14. The color printer 14 of this embodiment is a laser printer. An assembly (image forming unit) of a photoconductor 56 and a developing device 55 and a charger, a cleaning device, and a transfer device (illustration unit) (not shown) that forms a one-color toner image is M (magenta), C (cyan), Y ( There are 4 sets in total, one set for each image formation of yellow) and Bk (black), arranged in tandem along the conveying belt 57 in order, and each color toner image formed by them is sequentially Are transferred onto a single transfer sheet.

  The transfer sheets stacked on the first tray 48, the second tray 49, and the third tray 50 are fed by the first paper feeding device 51, the second paper feeding device 52, and the third paper feeding device 53, respectively, and are conveyed vertically. The unit 54 is transported to a position where it abuts against the photoreceptor 56.

  The image data read by the scanner 10 is corrected by the image data processor IPP (FIG. 3), once written in the memory MEM (FIG. 3), read, and using the read image data in FIG. By the laser exposure from the writing unit 30, it is written on the uniformly charged photoreceptor 56 by a charger (not shown), thereby forming an electrostatic latent image. As the electrostatic latent image passes through the developing unit 55, a toner image appears on the photoreceptor 56. The toner image on the photoconductor 56 is transferred while the transfer paper is conveyed by the conveyance belt 57 at the same speed as the rotation of the photoconductor 56. Thereafter, the image is fixed by the fixing unit 58 and discharged by the paper discharge unit 59 to the finisher 100 of the post-processing apparatus.

  The finisher 100 of the post-processing apparatus shown in FIG. 2 can guide the transfer paper conveyed by the paper discharge unit 59 of the main body in the normal paper discharge roller 103 direction and the staple processing unit direction. By switching the switching plate 101 upward, the sheet can be discharged to the normal discharge tray 104 side via the transport roller 103. Further, by switching the switching plate 101 downward, the switching plate 101 can be conveyed to the staple table 108 via the conveying rollers 105 and 107. The transfer paper loaded on the staple table 108 is aligned by the paper jogger 109 every time one sheet is discharged, and is bound by the stapler 106 upon completion of partial copying. The group of transfer sheets bound by the stapler 106 is stored in the staple completion discharge tray 110 by its own weight.

  On the other hand, the normal paper discharge tray 104 is a paper discharge tray that can move back and forth (in a direction perpendicular to the paper surface of FIG. 2). The paper discharge tray section 104 that can be moved back and forth moves forward and back for each original or each copy section sorted by the image memory, and simply sorts the discharged copy paper.

  When images are formed on both sides of the transfer paper, the transfer paper fed from each of the paper feed trays 48 to 50 is not guided to the paper discharge tray 104 side, and the branching claw 60 for switching the path is used. By turning it downward, it is once guided to the reversing unit 112 and then stocked in the duplex feeding unit 111.

  Thereafter, the transfer paper stocked on the double-sided paper feed unit 111 is again fed from the double-sided paper feed unit 111 to transfer the toner image formed on the photosensitive member 56, and the branching claw for switching the path. 60 is returned to the illustrated horizontal position and guided to the paper discharge tray 104. In this way, when creating images on both sides of the transfer paper, the reversing unit 112 and the duplex feeding unit 111 are used.

  The photoconductor 56, the conveyance belt 57, the fixing unit 58, the paper discharge unit 59, and the development unit 55 are driven by a main motor (not shown), and each of the paper feeding devices 51 to 53 is also not shown. It is driven by being transmitted by each sheet feeding clutch. The vertical conveyance unit 54 is driven by transmitting the drive of the main motor by an intermediate clutch (not shown).

  FIG. 3 shows a system configuration of the image processing system of the copying machine shown in FIG. In this system, a color document scanner 10 including a reading unit 11 and an image data output I / F (Interface) 12 is connected to an image data interface control CDIC (hereinafter simply referred to as CDIC) of an image data processing apparatus ACP. Yes. A color printer 14 is also connected to the image data processing apparatus ACP. The color printer 14 receives the recorded image data from the image data processor IPP (Image Processing Processor; hereinafter simply referred to as IPP) of the image data processing apparatus ACP to the writing I / F 15 and prints it out by the image forming unit 16. . The image forming unit 16 is shown in FIG.

  The image data processing device ACP (hereinafter simply referred to as ACP) includes a parallel bus Pb, an image memory access control IMAC (hereinafter simply referred to as IMAC), a memory module MEM (hereinafter simply referred to as MEM) as an image memory, a program And a hard disk device HDD (hereinafter simply referred to as HDD) for storing and storing document information, a system controller 1, RAM 4, nonvolatile memory 5, font ROM 6, CDIC, IPP, and the like. A facsimile control unit FCU (hereinafter simply referred to as FCU) is connected to the parallel bus Pb. The operation board 20 is connected to the system controller 1.

  The reading unit 11 for optically reading the original of the color original scanner 10 photoelectrically converts the reflected light of the lamp irradiation on the original with a CCD on a sensor board unit SBU (hereinafter simply referred to as SBU). , B image signals are generated, converted to RGB image data by an A / D converter, shading corrected, and sent to the CDIC via the output I / F 12.

  The CDIC performs data transfer between the document scanner 10 (output I / F 12), the parallel bus Pb, and the IPP, and communication between the process controller 17 and the system controller 1 that controls the entire ACP. The RAM 18 is used as a work area for the process controller 17, and the nonvolatile memory 19 stores an operation program for the process controller 17.

  An image memory access control IMAC (hereinafter simply referred to as IMAC) controls writing / reading of image data to / from the MEM or HDD. The system controller 1 controls the reading and writing of data other than document information such as programs and control data with respect to the HDD, and controls the operation of each component connected to the parallel bus Pb. The RAM 4 is used as a work area for the system controller 1, and the nonvolatile memory 5 stores an operation program for the system controller 1.

  The operation board 20 instructs processing to be performed by the ACP. For example, the type of processing (copying, facsimile transmission, image reading, printing, etc.), the number of processings, etc. are input. Thereby, the image data control information can be input.

  The image data read from the reading unit 11 of the scanner 10 is subjected to shading correction 210 by the SBU of the scanner 10 and then subjected to image processing for correcting reading distortion such as scanner gamma correction and filter processing by IPP. Accumulate in MEM or HDD. When printing out MEM or HDD image data, IPP performs color conversion of RGB signals to YMCK signals, printer gamma conversion, gradation conversion, and image quality processing such as gradation processing such as dither processing or error diffusion processing. Do it. The image data after the image quality processing is transferred from the IPP to the writing I / F 15. The writing I / F 15 performs laser control on the gradation-processed signal by pulse width and power modulation. Thereafter, the image data is sent to the image forming unit 16, and the image forming unit 16 forms a reproduced image on the transfer paper.

  Based on the control of the system controller 1, the IMAC controls the access of image data to the MEM and HDD, develops print data of a personal computer PC (not shown) connected to the LAN (hereinafter simply referred to as PC), Compress / decompress image data for effective use.

  The image data sent to the IMAC is stored in the MEM and HDD after data compression, and the stored image data is read out as necessary. The read image data is decompressed, returned to the original image data, and returned from the IMAC to the CDIC via the parallel bus Pb. After the transfer from the CDIC to the IPP, the image quality processing is performed and output to the writing I / F 15, and a reproduced image is formed on the transfer paper in the image forming unit 16.

  In the flow of image data, the functions of the digital multi-function peripheral are realized by the bus control by the parallel bus Pb and the CDIC. Facsimile transmission is performed by performing image processing on the read image data by IPP and transferring it to the FCU via the CDIC and the parallel bus Pb. The FCU performs data conversion to the communication network and transmits it as facsimile data to the public line PN. Facsimile reception is performed by converting line data from the public line PN into image data by the FCU and transferring it to the IPP via the parallel bus Pb and CDIC. In this case, no special image quality processing is performed, and the image is output from the writing I / F 15 and a reproduced image is formed on the transfer paper in the image forming unit 16.

  In a situation where a plurality of jobs, for example, a copy function, a facsimile transmission / reception function, and a printer output function operate in parallel, the usage rights of the reading unit 11, the image forming unit 16, and the parallel bus Pb are assigned to the system controller 1 and the process. Control is performed by the controller 17. The process controller 17 controls the flow of image data, and the system controller 1 controls the entire system and manages the activation of each resource. The function selection of the digital multi-function peripheral is performed on the operation board 20, and processing contents such as a copy function and a facsimile function are set by a selection input of the operation board 20.

  The system controller 1 and the process controller 17 communicate with each other via parallel buses Pb, CDIC, and serial bus Sb. Specifically, communication between the system controller 1 and the process controller 17 is performed by performing data format conversion for data and interface between the parallel bus Pb and the serial bus Sb in the CDIC.

  Various bus interfaces, such as a parallel bus I / F 7, a serial bus I / F 9, a local bus I / F 3, and a network I / F 8, are connected to the IMAC. The controller unit 1 is connected to related units via a plurality of types of buses in order to maintain independence in the entire ACP.

  The system controller 1 controls other functional units via the parallel bus Pb. The parallel bus Pb is used for transferring image data. The system controller 1 issues an operation control command for storing image data in the MEM to the IMAC. This operation control command is sent via IMAC, parallel bus I / F 7, and parallel bus Pb.

  In response to this operation control command, the image data is sent from the CDIC to the IMAC via the parallel bus Pb and the parallel bus I / F 7. Then, the image data is stored in the MEM under the control of the IMAC.

  On the other hand, the ACP system controller 1 functions as a printer controller, network control, and serial bus control in the case of a call from the PC as a printer function. In the case of via the network, the IMAC receives print output request data via the network I / F 8.

  In the case of a general-purpose serial bus connection, the IMAC receives print output request data via the serial bus I / F 9. The general-purpose serial bus I / F 9 corresponds to a plurality of types of standards, and corresponds to an interface of a standard such as USB (Universal Serial Bus), 1284 or 1394, for example.

  Print output request data from the PC is developed into image data by the system controller 1. The development destination is an area in MEM. Font data necessary for expansion is obtained by referring to the font ROM 6 via the local bus I / F 3 and the local bus Rb. The local bus Rb connects the controller 1 to the nonvolatile memory 5 and the RAM 4.

  Regarding the serial bus Sb, in addition to the external serial port 2 for connection with the PC, there is also an interface for transfer with the operation board 20 which is an operation unit of the ACP. This is not print development data, but communicates with the system controller 1 via the IMAC, accepts processing procedures, displays the system status, and the like.

  Data transmission / reception between the system controller 1 and the MEM, HDD, and various buses is performed via the IMAC. Jobs that use MEM and HDD are centrally managed in the entire ACP.

  4 is a plan view of the optical unit constituting the writing unit (writing optical system) 30 in FIG. 2 as viewed from above. In the figure, light beams from a semiconductor laser 31bk and a semiconductor laser 31m including a laser diode and a laser driver that modulates the laser light pass through cylinder lenses 32bk and 32m, and are reflected from the polygon mirror 34 by the reflecting mirror 33bk and the reflecting mirror 33m. The light enters the lower surface and the polygon mirror 34 rotates to deflect the light beam, pass through the fθ lens 35ybk and the fθ lens 35mc, and is folded back by the first mirror 36bk and the first mirror 36m.

  On the other hand, the light beams from the semiconductor laser 31y and the semiconductor laser 31c pass through the cylinder lenses 32y and 32c, enter the upper surface of the polygon mirror 34, and the polygon mirror 34 rotates to deflect the light beam, and the fθ lens. The light passes through 35ybk and the fθ lens 35mc and is folded by the first mirror 36y and the first mirror 36c.

  Cylinder mirrors 37ybk and 37mc and sensors 38ybk and 38mc are provided on the upstream side from the writing position in the main scanning direction. It is configured to be incident on the sensors 38ybk and 38mc. These sensors 38ybk and 38mc are synchronization detection sensors for synchronizing in the main scanning direction.

  In the detection of the light beams from the semiconductor lasers 31bk and 31y, a common sensor 38ybk is used on the writing side. Similarly, for the detection of the light beams from the semiconductor lasers 31m and 31c, a common sensor 38mc is used on the writing side. Since two color imaging light beams are incident on the same sensor, the timing at which each light beam is incident on each sensor can be set by making the incident angles of the polygon mirrors 34 different from each other. Instead, it is output as a pulse train in time series. As can be seen from the figure, K (bk) and Y (y) and M (m) and C (c) are scanned in the opposite directions.

  Each signal obtained by detecting each light beam of the semiconductor lasers 31m and 31c included in the photoelectric conversion signal of the sensor 38mc of the writing unit 30 is separated by the separation circuit 65 (FIG. 5), and is shaped into a predetermined pulse shape, respectively. As line synchronizations M and C, they are output to the writing I / F 15, IPP and image forming unit 16 of FIG. Similarly, each signal obtained by detecting each light beam of the semiconductor lasers 31y and 31bk included in the photoelectric conversion signal of the sensor 38ybk of the writing unit 30 is separated by the separation circuit 66 (FIG. 5), and is shaped into a predetermined pulse shape. Then, the line synchronization Y and K are output to the writing I / F 15, IPP and image forming unit 16.

  The writing I / F 15 shown in FIG. 3 includes M, C, Y, and K writing I / Fs 15m, 15c, 15y, and 15k having substantially the same function, and each of the image data M, C, Y, and K are converted into image signals M, C, Y, and K, which are pulse signals (modulation pulses) that modulate the light emission of the semiconductor lasers 31m, 31c, 31y, and 31k, and the image in the image forming unit 16 is converted. The data is output to the print image controllers 25m, 25c, 25y, and 25k (FIG. 5) of the writing controller 16c.

  Referring to the M write I / F 15m, line synchronization M is provided to the frame delay and memory controller in the M write I / F 15m. In this embodiment, the line synchronization M of the laser beam for image exposure of the photosensitive drum M that starts image formation first in color image recording is used as a reference line synchronization signal, and the image forming unit 16 can perform image formation. After the process controller 17 sets the image forming mode and transmission / reception of image data in the writing I / F 15 and IPP, when the IPP is ready to transmit image data, an Enable signal is sent in synchronization with the line synchronization M. It is assumed that H (image forming instruction signal) for instructing image forming. As for the frame delay, when the line synchronization M of the set number STD-M is counted up after the Enable signal is generated, the FGATE-M that defines the M image forming period of one page (one frame) is enabled. In the other write I / Fs 15c, 15y, and 15k, the count value (set number) STD-C of the line synchronization M from when the Enable signal is generated until FGATE-C, FGATE-Y, and FGATE-K are enabled. , STD-Y, STD-K are the set number STD- of the writing I / F 15m corresponding to the number of times of line synchronization M during the transfer belt moves from the photosensitive drum M to the photosensitive drums C, Y, K. A value larger than M. Data representing these set values is set in the memory controllers of the respective write I / Fs 15m, 15c, 15y, and 15k, and is given to the frame delay from the memory controller. When FGATE-M is enabled, control signals are exchanged between the memory controller and the IPP, and the timing is synchronized with the line synchronization M, C, Y, K and the pixel clock CLK. Write to buffer memory. In parallel with this, the memory controller sends the image data in the buffer memory from the image data buffer memory to the image signal generation circuit in synchronization with the line synchronization M and the pixel clock CLK. The image signal generation circuit converts the image data into a pulse signal (image signal) for laser light modulation of the semiconductor laser 31m and outputs it to the image writing control unit 16c (FIG. 5) of the image forming unit 16.

  FIG. 5 shows a configuration of the image writing control unit 16 c in the image forming unit 16 of the color printer 14. The print image control units 25m, 25c, 25y and 25k addressed to the magenta M, cyan C, yellow Y and black K color image signals control the entire write control unit 16c by the command of the CPU of the process controller 17, and write The image signals M, C, Y and K output from the image signal generators 64 of the color writing I / Fs 15m, 15c, 15y and 15k of the built-in I / F 15 are transferred to the laser drive circuits 23m, 23c, 23y and 23k. .

  In the following, in order to simplify the description, the component component codes m, c, y, and k are omitted and the element codes are shown.

  The write clock generation circuit 21 sends a pixel synchronization clock CLK, which is a clock signal having a period in units of main scanning pixels, to the phase synchronization circuit 22. The phase synchronization circuit 22 corrects the phase of the pixel synchronization clock CLK sent from the write clock generation circuit 21 with the line synchronization signal (line synchronization pulse) sent from the separators 65 and 66 (FIG. 5), and transfers it to the laser drive circuit 23. To do.

  The print image control unit 25 holds the control data given by the process controller 17 and outputs it to each unit of the image writing control unit 16c, and sets a trim area in the image data frame (paper surface), Image processing such as overlaying an arbitrary frame line on the surface) is performed according to the contents designated by the CPU in the process controller 17. That is, based on the paper size, trim area data, and border line writing presence / absence given by the process controller 17, the print position of the incoming image signal on the paper is determined by the main scanning count (pixel synchronization pulse count) and the sub-scanning count (line The output of the image signal assigned to the trim area is stopped or converted to a non-record signal, and if there is boundary writing, several pixels inside the edge of the trim area The image signal is converted into a line writing signal (writing of a trim boundary line).

  The laser drive circuit 23 modulates a pixel drive signal having a period of the CLK signal (pixel synchronization pulse) coming from the phase synchronization circuit 22 with the image signals M, C, Y, and K sent from the print image control unit 25 to perform laser drive. A signal is generated and applied to the semiconductor laser 31. The semiconductor laser 31 emits a beam having a light amount corresponding to the level of the laser drive signal sent from the laser drive circuit 23. The laser drive circuit 23 also emits a laser beam at a synchronization detection level in response to the ON signal of the synchronization detection laser emission ON / OFF signal (FIGS. 6 and 8) provided by the polygon motor control circuit 24. The polygon motor control circuit 24 performs PLL (Phase Locked Loop) control of the polygon motor at a predetermined rotational speed in accordance with a control signal from the print image control unit 25, and generates a laser emission ON / OFF signal for synchronization detection. And output to the laser drive circuits 23m to 23k.

  FIG. 6 shows a configuration of an electric circuit portion of the polygon motor control circuit 24 that generates a laser emission ON / OFF signal mainly for synchronization detection. A polygon motor 34d (FIG. 4) that rotationally drives the polygon mirror 34p includes a hall element 34h that detects the rotation of the N and S poles of the rotor of the motor 34d. As shown in FIG. 7, the magnetic pole detection signal generated by the Hall element 34h pulsates to a high level H during N pole detection and to a low level L during S pole detection. The motor drive circuit 24a shown in FIG. 6 starts (starts) the rotational drive of the polygon motor 34d when the ON / OFF signal reaches the ON instruction level, and converts the detection signal generated by the Hall element 34h into a motor rotational speed signal. When the motor rotation speed signal reaches the target speed, PLL control is started, and the phase of the detection signal generated by the Hall element 34h matches the phase of the rotation reference signal (speed instruction pulse) given by the writing I / F 15. In this manner, the polygon motor 34d is accelerated and decelerated, and when the phases match, a PLL lock signal (high level H) indicating this is output to the initial synchronization detection 24c.

  In the initial synchronization detection 24c, when the PLL lock signal (H) is given, the AND gate 72 outputs the detection signal of the hall element 34h as a mirror surface switching synchronization signal. This mirror surface switching synchronization signal is output to the writing I / F 15 and the AND gates 73 and 82.

  In this embodiment, the rotor of the polygon motor 34d is polarized in six pairs in one rotation, and each mirror surface of the six mirror surfaces of the polygon mirror 34p has a pair of N and S poles as shown in FIG. Correspondingly, one cycle of the detection signal of the Hall element 34h is aligned with one mirror surface. Before the PLL lock in which the phase of the detection signal generated by the Hall element 34h does not match the phase of the rotation reference signal given by the writing I / F 15, as shown in FIG. 7A, the mirror surface is switched with respect to the rotation reference signal. The synchronization signal (the detection signal of the Hall element 34) is not matched (synchronized). However, while the PLL lock signal (H) is generated, the rotation reference signal is displayed as shown in FIG. On the other hand, the mirror surface switching synchronization signal (the detection signal of the Hall element 34) is matched (synchronized). A mirror surface switching synchronization signal (a detection signal of the Hall element 34) synchronized with the rotation reference signal is output from the AND gate 72 to the writing I / F 15 and the AND gates 73 and 82. The write I / F 15 outputs an initial synchronization detection start signal (start pulse) to the flip-flop 70 at the initial synchronization detection start 24b of the polygon motor control circuit 24 when the mirror surface switching synchronization signal has arrived. .

  See also FIG. 8 and FIG. The flip-flop 70 at the initial synchronization detection start 24b is set by the initial synchronization detection start signal and inverts the Q output from the low level L to the high level H. This H is an initial synchronization detection enable valid signal (FIGS. 8 and 9). When the mirror surface switching synchronization signal (the detection signal of the Hall element 34h) rises to H after the generation of the initial synchronization detection enable valid signal (H), the flip-flop 74 is set and its Q output is L (counter). In response to this, the counter 75 starts counting up the reference clock (clock pulse) provided by the write I / F 15. Timing when the count data of the counter 75 is set in the Ws code generator 77 and the laser scanning is out of the laser exposure scanning region of the photosensitive member 56 and becomes the region of the synchronization detection sensor 38mc (and the mirror 37mc that reflects the laser beam). When the value (reference clock count value) Ws (set value) is represented, the comparator 76 switches its output from L to H, and the flip-flop 78 is set by the rise to H, and its Q output becomes The first initial synchronization detection enable signal (H) is output to the phase synchronization circuits 22m to 22k. When the count data of the counter 75 represents the timing value We set in the We code generator 81 and passed through the synchronization detection sensor 38mc, the comparator 80 switches its output from L to H, The flip-flops 78 and 74 are reset by the rise, the Q output becomes L, the first initial synchronization detection enable signal (H) disappears, and the Q output becomes L by the reset of the flip-flop 74. The counter 75 is cleared and the counting operation is stopped.

  In response to the first initial synchronization detection enable signal (H), the phase synchronization circuits 22m to 22k generate laser emission command signals (H; FIG. 8) to the AND gate 88 of the synchronization detection laser emission timing 24d. give. Thereafter, when the mirror surface switching synchronization signal (the detection signal of the Hall element 34h) rises to H, the flip-flop 74 is set again and its Q output rises from L to H. In response, the counter 75 The reference clock provided by the write I / F 15 starts counting up. When the count data of the counter 75 represents the timing value Ws set in the Ws code generator 77 and the laser scanning is the region of the synchronous detection sensor 38mc, the output of the comparator 76 is switched to H. The flip-flop 78 is set at the rising edge, and its Q output is output to the phase synchronization circuits 22m to 22k as the second initial synchronization detection enable signal (H). Further, it is also given to the AND gate 88 through the OR gate 87 at the laser light emission timing 24d for synchronization detection. At this time, since the laser emission command is H as shown in FIG. 8, the output signal of the AND gate 88 becomes H instructing laser emission (ON), which is given to the laser drive circuits 23m-23k, and the laser drive circuit 23 m to 23 k turn on the laser light sources 31 m to 31 bk (laser output energization), the laser light scans the synchronization detection sensors 38 mc and 38 ybk, and the separations 65 and 66 are line synchronization signals M, C, Y and K are generated. Since these line synchronization signals M, C, Y, K reset the flip-flop 70 through the OR gate 71 at the initial synchronization detection start 24b, the Q output is inverted to L. That is, the initial synchronization detection enable valid signal (H) disappears. At the same time, the line synchronization signals M, C, Y, and K are given to the update instruction input terminal of the latch 79 through the AND gate 89, and the latch 79 responds to the rising of H of the line synchronization signals M, C, Y, and K. The count data Wd of the counter 75 at that time (line synchronization signal generation timing) is latched. That is, it is memorized or retained.

  The line synchronization signals M, C, Y, K (H) are also applied to the phase synchronization circuits 22m-22k as shown in FIG. 5, and the phase synchronization circuits 22m-22k are connected to the line synchronization signals M, C, Y, When K (H) arrives, the timing is set to the next laser emission command output timing, and the output of the laser emission command (H) is continued while the line synchronization signals M, C, Y, K (H) are present. When the laser light passes through the synchronization detection sensors 38mc, 38ybk and the line synchronization signals M, C, Y, K (H) disappear (becomes L), the output of the laser emission command (H) is stopped (L ). As a result, the output of the AND gate 88 (synchronous detection laser emission ON / OFF signal) becomes L instructing to turn off the laser, and the laser drive circuits 23m to 23k stop turning on the laser light sources 31m to 31bk (laser output energization). To do. The above is the initial synchronization detection sequence.

  After that, since the Q output of the flip-flop 70 is L, that is, the initial synchronization detection enable valid signal (H) has disappeared, the AND gate 73 is disabled, and the initial synchronization detection 24c is the initial synchronization. No detection enable signal (H) is generated. However, since the Q output of the flip-flop 70 is L, the AND gate 82 is turned on, and the flip-flop 83 is set when the mirror surface switching synchronization signal (detection signal of the Hall element 34h) rises to H. The Q output rises from L (counter clear instruction) to H (count instruction), and in response, the counter 84 starts counting up the reference clock provided by the write I / F 15. When the count data of the counter 84 represents the data Wd held by the latch 79, the comparator 85 switches its output from L to H, and the flip-flop 86 is set by this rising to H, and its Q output However, the laser emission ON signal (H) is output to the laser drive circuits 23m to 23k through the OR gate 87 and the OR gate 88 only during a period overlapping with the laser emission command (H) given by the phase synchronization circuits 22m to 22k. This is a steady synchronization detection sequence. Thereafter, each time the mirror surface switching synchronization signal has a level change (rising to H) indicating mirror surface switching, the steady synchronization detection sequence is executed, and the line synchronization signals M, C, Y and K are generated.

  The rotation reference signal that is the control signal of the polygon motor that rotates the polygon mirror 34p that is a rotating polygon mirror and the magnetic pole detection signal of the Hall element 34h maintain a predetermined phase relationship with the switching of each surface of the polygon mirror. The relative relationship between the main scanning width period of the photosensitive member with respect to the scanning period per one surface of the polygon mirror and the synchronization detection period a (FIG. 8) is also determined. As before, even if the laser emission command becomes valid (H) at asynchronous timing, synchronous detection can be performed from any position where the photoconductor is not exposed with reference to the switching timing of the polygon motor control signal without causing laser emission. By controlling the laser emission with the initial synchronization detection enable signal (H) that enables the laser emission up to any arbitrary position, it has become possible to prevent exposure to the photoconductor that occurred at the time of initial synchronization detection.

  In addition, by preparing an initial synchronization detection enable valid signal (H) for controlling whether to enable the laser emission control by the initial synchronization detection enable (H) (FIGS. 8 and 9), the initial synchronization detection enable is enabled. Regardless of the state, it is possible to satisfy the laser emission control after the initial synchronization detection as in the prior art.

  Referring to FIG. 9, each output signal is actually output in synchronization with the reference clock, and the reference clock cycle is sufficiently small with respect to the period from the rear end of the photoconductor to the synchronization detection sensor in one scanning period. It is. There are counters 75 and 84 that perform a counting operation in synchronization with the reference clock with reference to the switching of the mirror surface of the polygon mirror 34p with respect to the incident laser light, and the counter laser beam is converted from the mirror surface switching to the synchronous detection sensor. By comparing with the reaching timing value Ws, a laser emission ON signal for synchronization detection is generated. The initial synchronization detection enable signal is generated by comparing the initial synchronization detection enable start / end position setting value (Ws / We) with the counter value. The initial synchronization detection enable valid signal becomes H level at startup or in a low power consumption state to enable the initial synchronization detection enable signal, and is set to L level by the first synchronization detection signal obtained by initial synchronization detection. Thus, the initial synchronization detection enable signal is invalidated so as not to affect the second and subsequent synchronization detection operations.

  FIG. 10 shows the configuration of the writing unit 30 of the second embodiment, and FIG. 11 shows the configuration of an electric circuit portion of the polygon motor control circuit 24 that mainly generates a laser emission ON / OFF signal for synchronization detection. Show. As shown in FIG. 10, shutters 90 m to 90 bk are provided near the laser emission ports of the laser light sources 31 m to 31 bk, and the laser light is physically emitted by opening (ON) / closing (OFF) the shutters 90 m to 90 bk. Exit / shut off. The shutter may be arranged anywhere from the laser emission port to the deflection position by the polygon mirror 34p.

  As shown in FIG. 11, the OR gate 91 added to the initial synchronization detection 24c gives a shutter ON / OFF signal to the shutter drivers 90c to 90y that turn ON / OFF the shutters 90m to 90bk. See also the time chart shown in FIG. The OR gate 91 is supplied with an initial synchronization detection enable signal and an initial synchronization detection enable invalid signal (H: Q bar signal of the flip-flop 70) of the initial synchronization detection start 24b. The laser emission command (H) is the same as that in the first embodiment, but is supplied as it is to the laser drive circuits 23m to 23k through the OR gate 87 of the synchronization detection laser emission timing 24d. Although the first and second initial synchronization detection enable signals (H) are given through the OR gate 91, the first initial synchronization detection enable signal (H) has no laser emission command (H). Laser light is not generated. When the second initial synchronization detection enable signal (H) is given, there is a laser emission command (H), so that the laser light sources 31m to 31bk emit laser light and the shutters 90m to 90bk are opened, so that the laser light is synchronized. The detection sensors 38mc and 38ybk are scanned to generate line synchronization signals M, C, Y, and K. As a result, the flip-flop 70 is reset and the initial synchronization detection enable valid signal (H) disappears, and the initial detection enable (H ) Will no longer occur. Accordingly, in order to avoid the shutters 90m to 90bk being closed (OFF) thereafter, the initial synchronization detection enable valid signal (H) disappears and the initial synchronization detection enable invalid signal (H: Q bar signal of the flip-flop 70). ) Is provided to the shutter drivers 92c to 92y via the OR gate 91.

  Therefore, when the initial synchronization detection is completed, that is, when the initial synchronization detection enable valid signal (H) disappears, the shutters 90m to 90bk are continuously opened (ON). This is because it is necessary to emit laser light modulated by an image signal (laser light scanning of the photosensitive member). After completing the initial synchronization detection, the phase synchronization circuits 22m to 22k hold the generation timing of the line synchronization signals M, C, Y, and K and generate the laser emission command (H) for synchronization detection only at the timing. Therefore, even when the shutters 90m to 90bk are continuously opened (ON), the laser emission command (H) for synchronization detection is substantially generated only during the scanning period of the synchronization detection sensors 38mc and 38ybk. The laser emission command (H) is not different from the conventional one, and the laser light during the period in which the photosensitive member has been exposed at the time of the initial synchronization detection is blocked by the shutters 90m to 90bk. Other structures and functions of the second embodiment are the same as those of the first embodiment.

1 is a front view of a full-color composite function copying machine equipped with a first embodiment of the present invention. FIG. FIG. 2 is an enlarged longitudinal sectional view showing an outline of an image forming mechanism of the full color printer 14 shown in FIG. 1. It is a block diagram which shows the outline | summary of the image processing system of the copying machine shown in FIG. FIG. 3 is an enlarged plan view of the writing unit 30 shown in FIG. 2. It is a block diagram which shows the function structure of the image writing control part 16c in the image formation unit 16 shown in FIG. FIG. 6 is a block diagram showing a configuration of an electric circuit part that generates a laser emission ON / OFF signal mainly for synchronization detection in the polygon motor control circuit 24 shown in FIG. 5. 4 is a time chart showing a time-series change in the rotation reference signal given to the PLL control circuit for driving the polygon motor 34d shown in FIGS. 4 and 6 and the detection signal of the Hall element 34h corresponding to the magnetic pole distribution of the rotor of the polygon motor 34d. (A) shows before PLL lock, and (b) shows after PLL lock. It is a time chart which shows the change of the input-output electric signal of the polygon motor control circuit 24 shown in FIG. 7 is a time chart showing a relative relationship between changes in input / output electric signals of the polygon motor control circuit 24 shown in FIG. 6 and count values Ws, Wd, We of a counter 75; It is an enlarged plan view of the writing unit 30 of the second embodiment. It is a block diagram which shows the structure of the electric circuit part which generate | occur | produces the laser emission ON / OFF signal mainly for a synchronous detection of the polygon motor control circuit 24 of 2nd Example. It is a time chart which shows the change of the input-output electric signal of the polygon motor control circuit 24 shown in FIG. It is a time chart which shows the change of the laser emission instruction | indication signal for a synchronous detection in the conventional initial synchronous detection.

Explanation of symbols

30: Write unit 31y, 31m, 31c, 31bk: Semiconductor laser 32y, 32m, 32c, 32bk: Cylinder lens 33bk, 33m: Reflection mirror 34p: Polygon mirror 34d: Polygon motor 34h: Hall element 35ybk, 35mc: fθ lens 36y , 36m, 36c, 36bk: first mirror 37ybk, 37mc: cylinder mirror 38ybk, 38mc: synchronization detection sensor 48: first tray 49: second tray 50: third tray 51: first paper feeder 52: second feed Paper device 53: Third paper feeding device 54: Vertical conveyance unit 56: Photoconductor 57: Conveyance belt 58: Fixing unit 59: Paper discharge unit 60: Branch claw 26: Conveyance motor 55: Developer
90c to 90y: Shutter 100: Finisher 101: Switching plate 103: Paper discharge roller 104: Paper discharge tray 105: Carriage roller 106: Stapler 107: Carriage roller 108: Staple table 109: Jogger 110: Paper discharge tray 111: Double-sided paper feed Unit 112: Inversion unit

Claims (6)

A laser light source, a rotating polygon mirror that deflects the laser light emitted from the laser light source to main scan the image forming area of the photosensitive member, an electric motor that rotationally drives the rotating polygon mirror, and the photosensitive sensor in the main scanning direction. In an optical writing device comprising a synchronization detection sensor that is outside the main scanning range of the image forming region of the body and receives the deflected laser light,
The counting of clock pulses is started in synchronization with the switching of the mirror surface of the rotating polygon mirror that deflects the laser light emitted from the laser light source, and based on the count value, outside the main scanning range of the photoconductor and the The laser beam emission is started at the timing of deflection immediately before the synchronization detection sensor, the laser beam emission is stopped immediately after the synchronization detection sensor detects the laser beam, and the synchronization detection sensor detects the laser beam. The count value when the light is detected is stored, and then the clock pulse count is started in synchronization with the switching of the mirror surface, and the emission of the laser beam is started at the timing corresponding to the stored count value. An optical writing device comprising: a signal generation control unit. A laser light source, a rotating polygon mirror that deflects the laser light emitted from the laser light source to perform main scanning on the photosensitive member, an electric motor that rotationally drives the rotating polygon mirror, and a scanning range of the photosensitive member in the main scanning direction In an optical writing device comprising a synchronization detection sensor that receives the deflected laser light,
A shutter interposed in a laser light path from the laser light source to the rotating polygon mirror; and
The counting of clock pulses is started in synchronization with the switching of the mirror surface of the rotating polygon mirror that deflects the laser light emitted from the laser light source, and based on the count value, outside the main scanning range of the photoconductor and the The shutter is opened at the timing of deflection immediately before the synchronization detection sensor, and the laser beam is emitted before the shutter is opened. The laser beam is emitted immediately after the synchronization detection sensor detects the laser beam. Stop and store the count value when the synchronization detection sensor detects the laser beam, and then start counting clock pulses in synchronization with the switching of the mirror surface, corresponding to the stored count value An optical writing device comprising: synchronization signal generation control means for starting emission of the laser beam at timing.   The electric motor is accelerated and decelerated so that the phase of one rotation synchronization pulse matches the phase of the rotation reference pulse per rotation of the electric motor at a predetermined angle, and the electric motor is driven at a constant speed corresponding to the frequency of the rotation reference pulse. The optical writing device according to claim 1, further comprising: a PLL-controlled rotational driving unit that rotationally drives.   The synchronization signal generation control means detects a mirror surface change based on the rotation synchronization pulse after generating a PLL lock signal indicating that the rotation drive means is in the controlled state at the constant speed. 4. The optical writing device according to claim 3, wherein counting of the clock pulse is started upon detecting a signal.   The synchronization signal generation control means generates an initial synchronization detection instruction signal upon receiving an initial synchronization detection start instruction, and stops the initial synchronization detection instruction signal when the synchronization detection sensor detects a laser beam; When the initial synchronization detection instruction signal, the PLL lock signal, and the mirror surface are switched, the clock pulse starts counting, and the count value is deflected to the outside of the main scanning range of the photoconductor and immediately before the synchronization detection sensor. Initial synchronization detection means for generating an initial synchronization detection signal for instructing the emission of the laser beam when the timing equivalent value is reached, and holding the count value at that time in the data holding means in response to the laser beam detection signal of the synchronization detection sensor And when the mirror surface is switched after the initial synchronization detection start means stops the initial synchronization detection instruction signal, 5. Synchronous detection laser emission timing means for generating a synchronous detection signal for instructing the emission of the laser beam when the count value reaches the count value held by the data holding means. The optical writing device described. An optical writing device according to any one of claims 1 to 5;
The photosensitive member that is exposed to light scanned by the optical writing device to form an electrostatic latent image, and a charging unit that precharges the photosensitive member;
Means for developing an electrostatic latent image formed on the photoreceptor; and
An image forming apparatus including: means for transferring a visible image developed by development onto a sheet;

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