JP2006251167A - Apparatus and method of forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high quality image by preventing the positional deviation of a latent image in a subscanning direction which intersect substantially perpendicularly to a main scanning direction in an image forming apparatus which has a controller for outputting an image signal corresponding to a received image command and an engine part for forming a latent image on a latent image carrier by scanning a light beam modulated corresponding to the image signal from the controller in a main scanning direction with a resonant oscillation mirror. <P>SOLUTION: A horizontal synchronous signal Hsync is inputted into a driving signal control part 10Y as a driving periodic signal related to the driving cycle of a deflection mirror face. Further, a driving signal Sd is so controlled that the phase of a reference signal Sr and the phase of the horizontal synchronous signal Hsync have a predetermined relative relation with the driving signal control part 10Y, and a deflector 65 is operated synchronized with the reference signal Sr. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  According to the present invention, a light beam from a light source is modulated in accordance with an image signal from a controller, and the light beam is scanned in a main scanning direction by a vibrating mirror that resonates and oscillates to form a latent image on a latent image carrier. The present invention relates to an image forming apparatus and an image forming method.

  In an electrophotographic image forming apparatus such as a printer, a copying machine, and a facsimile machine, an image forming command is given to a controller from an external device such as a host computer in response to an image forming request from a user. Then, the controller converts the image formation command into data in a format suitable for the operation instruction of the engine unit. Based on these data, the engine unit is controlled to form an image corresponding to the image formation command on a sheet (recording material) such as copy paper, transfer paper, paper, and an OHP transparent sheet. In other words, the light source of the exposure unit of the engine unit is ON / OFF controlled based on the image data included in the image formation command, and a light beam modulated according to the image data is emitted. This light beam is scanned in the main scanning direction by the deflector of the exposure unit, and a latent image corresponding to the image data is formed on a latent image carrier such as a photoconductor. These latent images are then developed with toner to form a toner image.

  By the way, in order to reduce the size and speed of the deflector, it has been conventionally proposed to use a resonance-type oscillating mirror as the deflector (see, for example, Patent Document 1). That is, in this device, the frequency of the driving signal applied to the vibrating mirror (hereinafter referred to as “driving frequency”) and the natural resonant frequency of the vibrating mirror are made to coincide with each other, so that the vibrating mirror is resonated and a relatively large amplitude is obtained. ing. Then, the light beam from the light source is irradiated to the vibrating mirror that is oscillating at resonance to scan the light beam.

JP-A-1-302317 (second page, FIGS. 2-4)

  By the way, the resonant frequency of the oscillating mirror may vary depending on the processing method when manufacturing the oscillating mirror, the ambient temperature of the oscillating mirror, and the like. When such variations occur, the scanning speed of the light beam on the latent image carrier changes, and the latent image formed on the latent image carrier expands and contracts in the main scanning direction, leading to a reduction in image quality. Therefore, in the apparatus described in Patent Document 1, control means for driving the vibrating mirror while controlling the amplitude of the drive signal is provided in the engine unit, and the scanning speed of the light beam on the latent image carrier is constant. As described above, the amplitude of the drive signal is adjusted.

  As described above, in the conventional apparatus, the vibration mirror is driven and controlled in the engine unit provided with the exposure unit, that is, in the closed system. That is, the controller and the control means are not synchronized, and the control means operates asynchronously with the controller. For this reason, it is asynchronous in the sub-scanning direction substantially orthogonal to the main scanning direction, and a shift of the latent image formation position (line latent image shift) occurs in the sub-scanning direction. It was one.

  The present invention has been made in view of the above problems, and performs main scanning by a controller that outputs an image signal corresponding to a received image command and a vibrating mirror that resonates and vibrates a light beam modulated in accordance with the image signal from the controller. In an image forming apparatus having an engine section that scans in the direction and forms a latent image on a latent image carrier, it prevents the displacement of the latent image forming position in the sub-scanning direction substantially orthogonal to the main scanning direction and has good quality The purpose is to form an image.

  The present invention carries a latent image by scanning in the main scanning direction by a controller that outputs an image signal corresponding to a received image formation command and a vibrating mirror that resonates and vibrates a light beam modulated according to the image signal from the controller. In order to achieve the above object, the controller generates a reference signal and outputs the reference signal to the engine unit. The engine unit drives the vibration mirror. Detecting means for outputting a driving period signal related to the driving period, a driving signal control means for outputting a driving signal for controlling the driving of the vibrating mirror, and a driving signal output from the driving signal control means Mirror drive means for driving the vibrating mirror based on the reference signal, the drive signal control means receives the reference signal and the drive cycle signal, and receives the reference signal phase and drive cycle signal. And the phase is characterized by controlling the way, driving signals having a predetermined relative relationship.

  In the invention thus configured, the mirror control means drives the vibrating mirror based on the drive signal output from the drive signal control means. As a result, the light beam is scanned in the main scanning direction by the vibrating mirror to form a line latent image on the latent image carrier. On the other hand, the detection means outputs a drive cycle signal related to the drive cycle of the vibrating mirror driven by the mirror control means. This drive cycle signal is received by the drive signal control means receiving the reference signal from the controller. The drive signal control means controls the drive signal so that the phase of the reference signal and the phase of the drive cycle signal have a predetermined relative relationship, and the oscillating mirror operates in synchronization with the reference signal. Accordingly, the latent image formation position in the sub-scanning direction substantially orthogonal to the light beam scanning direction (main scanning direction) is adjusted by adjusting the phase of the reference signal and the drive cycle signal, and the line latent image shift in the sub-scanning direction is adjusted. Can be suppressed. As a result, the image quality can be improved.

  Here, a reference drive signal generator for generating a reference drive signal having a predetermined drive frequency is provided in the drive signal control means so that the vibration mirror is driven based on the reference drive signal at the start of driving the vibration mirror. You may comprise. As a result, the vibrating mirror can be reliably and oscillated at an early stage. Then, after the oscillating mirror is caused to resonate in this manner, the oscillating mirror may be driven at the driving frequency by controlling the driving signal based on the driving cycle signal of the oscillating mirror and the reference signal given from the controller. In this way, before the drive signal is controlled based on the drive cycle signal and the reference signal, the vibrating mirror is driven by the reference drive signal to cause the vibrating mirror to resonate and vibrate at an early stage and stably in synchronization with the controller. Can do.

  In addition, the resonance frequency of the oscillating mirror varies, and a desired deflection characteristic cannot be obtained due to a deviation from the drive frequency, which may cause a reduction in image quality. Therefore, in order to solve this problem, the following configuration may be adopted.

  A resonance frequency adjusting unit that adjusts the resonance frequency of the vibrating mirror; and a frequency control unit that controls the resonance frequency adjusting unit so that the resonance frequency of the vibrating mirror substantially matches the driving frequency based on the driving cycle signal output from the detecting unit; May be further provided in the engine unit. Further, it is desirable to adjust the resonance frequency (resonance adjustment) of the oscillating mirror before controlling the drive signal based on the drive cycle signal and the reference signal.

  Further, the mirror control unit may be configured to adjust the amplitude of the vibrating mirror based on the drive cycle signal output from the detection unit. The amplitude adjustment of the oscillating mirror is desirably performed before the control of the drive signal based on the drive cycle signal and the reference signal, similarly to the resonance adjustment described above.

  Furthermore, the present invention provides a controller that outputs an image signal corresponding to a received image formation command, and a light beam modulated in accordance with the image signal from the controller by a vibrating mirror that resonates and vibrates based on a drive signal. In an image forming method for forming an image using an image forming apparatus having an engine unit that forms a latent image on a latent image carrier by scanning the image, a reference drive provided in the engine unit to achieve the above object From the controller, starting the driving of the vibrating mirror using the reference driving signal output from the signal generator as driving vibration, detecting the driving cycle of the vibrating mirror and outputting a driving cycle signal related to the driving cycle, The drive signal is controlled so that the phase of the reference signal given to the engine unit and the phase of the drive cycle signal have a predetermined relative relationship, and the vibration mirror It is characterized by comprising a step of synchronizing the oscillation operation with respective units.

  In the invention configured as described above, driving of the vibrating mirror is started based on the reference driving signal, and a driving cycle signal related to the driving cycle of the vibrating mirror is output. Then, the drive signal is controlled so that the phase of the reference signal provided from the controller to the engine unit and the phase of the drive cycle signal have a predetermined relative relationship, and the vibrating mirror operates in synchronization with the reference signal. Accordingly, the latent image formation position in the sub-scanning direction substantially orthogonal to the light beam scanning direction (main scanning direction) is adjusted by adjusting the phase of the reference signal and the drive cycle signal, and the line latent image shift in the sub-scanning direction is adjusted. Can be suppressed. As a result, the image quality can be improved.

<First Embodiment>
FIG. 1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This image forming apparatus is a so-called tandem type color printer, and yellow (Y), magenta (M), cyan (C), and black (K) photoconductors 2Y, 2M, and 2C as latent image carriers. , 2K are arranged in the apparatus main body 5 side by side. The apparatus forms a full color image by superimposing the toner images on the photoreceptors 2Y, 2M, 2C, and 2K, or forms a monochrome image using only the black (K) toner image. That is, in this image forming apparatus, when an image forming command is given to the main controller MC from an external device such as a host computer in response to an image forming request from the user, the image signal, the reference signal, and various kinds of signals from the main controller MC. In response to the control signal, the engine unit EG operates to form an image corresponding to the image formation command on a sheet S such as copy paper, transfer paper, paper, and an OHP transparent sheet. Thus, in this embodiment, the main controller MC corresponds to the “controller” of the present invention.

  In the engine unit EG, a charging unit, a developing unit, an exposure unit, and a cleaning unit are provided corresponding to each of the four photosensitive members 2Y, 2M, 2C, and 2K. As described above, for each toner color, an image forming unit that includes a photoreceptor, a charging unit, a developing unit, an exposure unit, and a cleaning unit and forms a toner image of the toner color is provided. Then, the engine controller 1 provided in the engine unit EG controls each unit of the image forming unit in accordance with a signal from the main controller MC to execute image formation. The configuration of these image forming means (photosensitive member, charging unit, developing unit, exposure unit, and cleaning unit) is the same for all color components. Therefore, the configuration relating to yellow will be described here, and the other color components will be described. Are denoted by corresponding reference numerals, and description thereof is omitted.

  The photoreceptor 2Y is rotatably provided in the arrow direction (sub-scanning direction) in FIG. More specifically, a drive motor (not shown) is mechanically connected to one end of the photoreceptor 2 </ b> Y, and is driven and controlled based on a rotation drive command from the engine controller 1. As a result, the photoreceptor 2Y rotates. In addition, a charging unit 3Y, a developing unit 4Y, and a cleaning unit (not shown) are arranged around the photosensitive member 2Y driven in this way along the rotation direction thereof. The charging unit 3Y is composed of, for example, a scorotron charger, and uniformly charges the outer peripheral surface of the photoreceptor 2Y to a predetermined surface potential by applying a charging bias from the engine controller 1. Then, a scanning light beam Ly is emitted from the exposure unit 6Y toward the outer peripheral surface of the photoreceptor 2Y charged by the charging unit 3Y. As a result, an electrostatic latent image corresponding to yellow image data included in the image formation command is formed on the photoreceptor 2Y. The configuration and operation of the exposure unit 6 (6Y, 6M, 6C, 6K) and the control unit (drive signal control unit 10 and mirror control unit 11) for controlling the exposure unit will be described in detail later.

  The electrostatic latent image formed in this way is developed with toner by the developing unit 4Y. The developing unit 4Y contains yellow toner. When a developing bias is applied from the engine controller 1 to the developing roller 41Y, the toner carried on the developing roller 41Y partially adheres to each surface portion of the photoreceptor 2Y according to the surface potential. As a result, the electrostatic latent image on the photoreceptor 2Y is visualized as a yellow toner image. As the developing bias applied to the developing roller 41Y, a DC voltage or a voltage obtained by superimposing an AC voltage on the DC voltage can be used. In particular, the photosensitive member 2Y and the developing roller 41Y are spaced apart from each other. In a non-contact development type image forming apparatus that develops toner by flying toner with a voltage waveform in which an alternating voltage such as a sine wave, a triangular wave, or a rectangular wave is superimposed on a direct current voltage in order to efficiently fly the toner It is preferable that

  The yellow toner image developed by the developing unit 4Y is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TRy1. The color components other than yellow are also configured in exactly the same way as yellow, and a magenta toner image, a cyan toner image, and a black toner image are formed on the photoreceptors 2M, 2C, and 2K, respectively, and a primary transfer region. Primary transfer is performed on the intermediate transfer belt 71 by TRm1, TRc1, and TRk1, respectively.

  The transfer unit 7 includes an intermediate transfer belt 71 stretched between two rollers 72 and 73, and a belt driving unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction R2 by driving the roller 72 to rotate. ). Further, a secondary transfer roller 74 is provided at a position facing the roller 73 with the intermediate transfer belt 71 interposed therebetween, and is configured to be able to contact and separate with respect to the surface of the belt 71 by an electromagnetic clutch (not shown). Yes. When transferring a color image to the sheet S, the primary transfer timing is controlled to superimpose the toner images to form a color image on the intermediate transfer belt 71, and the color image is taken out from the cassette 8 and transferred to the intermediate transfer belt 71. The color image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2 between the belt 71 and the secondary transfer roller 74. On the other hand, when a monochrome image is transferred to the sheet S, only the black toner image is formed on the photoreceptor 2K, and the monochrome image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2. Further, the sheet S that has received the secondary transfer of the image in this way is conveyed toward the discharge tray portion provided on the upper surface portion of the apparatus main body via the fixing unit 9.

  The surface potential of each of the photoreceptors 2Y, 2M, 2C, and 2K after the toner image is primarily transferred to the intermediate transfer belt 71 is reset by a neutralizing unit (not shown), and the toner remaining on the surface is cleaned. After being removed by the charging unit, the charging unit 3Y, 3M, 3C, 3K receives the next charging.

  In the vicinity of the roller 72, the transfer belt cleaner 75 can be moved close to and away from the roller 72 by an electromagnetic clutch (not shown). Then, the blade of the cleaner 75 abuts on the surface of the intermediate transfer belt 71 that is stretched over the roller 72 while moving to the roller 72 side, and the toner that remains on the outer peripheral surface of the intermediate transfer belt 71 after the secondary transfer. Remove.

  3 is a main scanning sectional view showing the configuration of the exposure unit provided in the image forming apparatus of FIG. 1, and FIG. 4 is a control unit (drive signal control) for controlling the exposure unit and the exposure unit of the image forming apparatus of FIG. FIG. 3 is a diagram illustrating a configuration of a unit and a mirror control unit. Hereinafter, the configurations and operations of the exposure unit 6, the drive signal control unit 10, and the mirror control unit 11 will be described in detail with reference to these drawings. The configuration of the exposure unit 6, the drive signal control unit 10, and the mirror control unit 11 is the same for all color components. Therefore, here, the configuration related to yellow will be described, and the other color components will be denoted by corresponding reference numerals. The description is omitted.

  The exposure unit 6Y (6M, 6C, 6K) has an exposure housing 61. A single laser light source 62 is fixed to the exposure housing 61, and a light beam can be emitted from the laser light source 62. As shown in FIG. 4, the laser light source 62 receives an image signal Sv output from the main controller MC. This image signal Sv is a signal corresponding to the yellow image data included in the image formation command, and the laser light source 62 is ON / OFF controlled in accordance with the image signal Sv and modulated from the laser light source 62 in accordance with the yellow image data. The emitted light beam Ly is emitted.

  Further, in the exposure housing 61, a collimator lens 631, a cylindrical lens 632, a deflector 65, a scanning lens are used to scan and expose the light beam from the laser light source 62 onto the surface (not shown) of the photoreceptor 2Y. 66 is provided. That is, the light beam from the laser light source 62 is shaped into collimated light of an appropriate size by the collimator lens 631 and then incident on the cylindrical lens 632 having power only in the sub-scanning direction Y. Then, by adjusting the cylindrical lens 632, the collimated light is imaged in the vicinity of the deflection mirror surface 651 of the deflector 65 in the sub-scanning direction Y. Thus, in this embodiment, the collimator lens 631 and the cylindrical lens 632 function as the beam shaping system 63 that shapes the light beam from the laser light source 62.

  The deflector 65 is formed by using a micromachining technique in which a micromachine is integrally formed on a semiconductor substrate by applying a semiconductor manufacturing technique, and includes a vibrating mirror that resonates and oscillates. That is, in the deflector 65, the light beam can be deflected in the main scanning direction X by the deflecting mirror surface 651 that resonates and vibrates. More specifically, the deflection mirror surface 651 is pivotally supported around a swing shaft (torsion spring) that is substantially orthogonal to the main scanning direction X, and swings in accordance with an external force applied from the operating portion 652. Swing around the axis. The actuating unit 652 controls the deflection mirror surface 651 by applying an electrostatic, electromagnetic or mechanical external force to the deflection mirror surface 651 based on the mirror drive signal from the mirror drive unit 111 of the mirror control unit 11Y. It is vibrated at the frequency of the drive signal Sd given from the unit 10Y. Note that any driving method such as electrostatic attraction, electromagnetic force, or mechanical force may be employed as the driving method by the operating unit 652, and since these driving methods are well known, description thereof is omitted here.

  The deflector 65 driven in this way is provided with a resonance frequency adjusting unit 653 as described in, for example, Japanese Patent Laid-Open No. 9-197334, and the resonance frequency of the deflector 65 can be changed. It has become. That is, in the resonance frequency adjusting unit 653, an electric resistance element is formed on a torsion spring (not shown) of the deflector 65, and the electric resistance element is electrically connected to the frequency control unit 112 of the mirror control unit 11Y. Yes. Then, the temperature of the torsion spring changes due to energization control of the electric resistance element by the frequency control unit 112. Thereby, the spring constant of the torsion spring is changed, and the resonance frequency of the deflector 65 can be changed. Therefore, in this embodiment, as will be described later, when the resonance frequency does not match the frequency of the mirror drive signal (drive signal Sd), that is, the drive frequency, the resonance frequency of the deflector 65 is changed by the resonance frequency adjustment unit 653. Thus, the drive frequency is substantially matched. Note that the specific configuration for changing the resonance frequency of the deflector 65 is not limited to this, and a conventionally known configuration can be adopted.

  Further, the mirror driving unit 111 is configured to be able to change and set driving conditions such as the frequency and voltage of the mirror driving signal. Therefore, the frequency of the mirror drive signal can be changed and set as necessary. In addition, the amplitude value can be adjusted by changing the voltage of the mirror drive signal.

  Then, the light beam deflected by the deflecting mirror surface 651 of the deflector 65 is deflected toward the scanning lens 66. In this embodiment, the scanning lens 66 is configured so that the F values are substantially the same over the entire effective scanning area on the surface of the photoreceptor 2. Therefore, the light beam deflected toward the scanning lens 66 is focused on the effective scanning area on the surface of the photoreceptor 2Y through the scanning lens 66 with substantially the same spot diameter. As a result, a light beam is scanned in parallel with the main scanning direction X, and a line-like latent image extending in the main scanning direction X is formed on the surface of the photoreceptor 2.

  In this embodiment, as shown in FIG. 3, the start or end of the scanning path of the scanning light beam is guided to the horizontal synchronization sensors 60A and 60B by the folding mirrors 69a and 69b. The folding mirrors 69a and 69b and the horizontal synchronization sensors 60A and 60B are disposed outside the sweep surface formed by sweeping the light beam when scanning the effective scanning area. The folding mirrors 69a and 69b are disposed substantially symmetrically with respect to the optical axis when the light beam scans the substantial center of the effective scanning region. Therefore, it can be considered that the horizontal synchronization sensors 60A and 60B are arranged substantially symmetrically with respect to the optical axis.

  Scanning light beam detection signals Hsync from the horizontal synchronization sensors 60A and 60B are transmitted to the measurement unit 113 of the mirror control unit 11Y, and the measurement unit 113 relates to the scanning time, the driving cycle, and the like for scanning the effective scanning region. Driving information to be calculated is calculated. The actual measurement information calculated by the measurement unit 113 is transmitted to the frequency control unit 112, and the frequency control unit 112 adjusts the resonance frequency of the deflector 65.

  The horizontal synchronization signal Hsync from the horizontal synchronization sensors 60A and 60B is also directly input to the main controller MC, and functions as a synchronization signal when the light beam scans the effective scanning region in the main scanning direction X. That is, these sensors 60A and 60B function as horizontal synchronization reading sensors for obtaining the horizontal synchronization signal Hsync.

  Further, in this embodiment, the sensors 60A and 60B function as the “detection means” of the present invention, and the detection signal Hsync is input to the drive signal control unit 10Y of the engine controller 1 as the “drive period signal” of the present invention. ing. The drive signal control unit 10Y includes a PLL processing unit 101, and a detection signal Hsync output from the horizontal synchronization sensors 60A and 60B is input to the PLL processing unit 101. The PLL processing unit 101 is electrically connected to the main controller MC and can receive the reference signal Sr from the main controller MC. Then, based on the reference signal Sr from the main controller MC and the detection signal Hsync, the drive signal is controlled by performing PLL processing so that the phase of the reference signal and the phase of the drive cycle signal have a predetermined relative relationship. In this embodiment, a reference drive signal generator 102 is provided in addition to the PLL processor 101 in order to control the drive signal Sd. The reference drive signal generation unit 102 generates a reference drive signal having a preset drive frequency, and can be configured by a memory that stores the reference drive signal, an oscillation circuit that generates the reference drive signal, or the like. . Then, the switching unit 103 selectively switches a signal output from each of the PLL processing unit 101 and the reference drive signal generation unit 102, and a signal from either one is given to the mirror control unit 11Y as the drive signal Sd. The switching timing and drive signal selection mode are as follows.

  By the way, in the apparatus configured as described above, when an image formation command is given in a state where the deflector 65 is in a vibration stopped state, the activation process is executed before the image formation is started and the light beam is synchronized with the main controller MC. However, adjustment is made so that the deflector 65 scans well. More specifically, drive processing, resonance control processing, and PLL processing are executed as startup processing.

  FIG. 5 is a flowchart showing processing executed by the image forming apparatus shown in FIG. FIG. 6 is a diagram schematically showing a resonance control process of the deflector performed before color image formation. Here, a case where a color image formation command is given as an image formation command will be described. However, when a monochrome image formation command is given, the following operation is executed only for the black color.

  When the color image formation command is given, the activation process of the deflector 65 is executed for the yellow color. First, in step S1, the switching unit 103 is switched to the reference drive signal generation unit 102 side of the drive signal control unit 10Y, and the reference drive signal output from the reference drive signal generation unit 102 is used as the drive signal Sd in the mirror of the mirror control unit 11Y. It is given to the drive unit 111. Then, the mirror drive unit 111 creates a mirror drive signal based on the drive signal Sd, and operates the operation unit 652 at the drive frequency Fd. As a result, the deflection mirror surface 651 of the deflector 65 starts to vibrate at the drive frequency Fd (step S2). As described above, since the deflector 65 is driven based on the reference drive signal generated by the reference drive signal generator 102 at the driving start stage of the deflector 65, the deflecting mirror surface 651 of the deflector 65 is surely moved. Resonance vibration can be performed at an early stage.

  Here, for example, as shown in FIG. 6A, the deflecting mirror surface 651 vibrates at the frequency Fd, but when the resonance frequency Fry of the deflector 65 deviates from the driving frequency Fd, the deflecting mirror surface 651 The maximum amplitude value θ (y) is greatly reduced from the maximum amplitude at the time of resonance vibration. Therefore, after a predetermined time has elapsed (step S3), the resonance control process is executed for the yellow deflector 65.

  In this resonance control process, the image signal Sv is output from the main controller MC to the laser light source 62, and the laser light source 62 is turned on (step S4). Here, an image signal suitable for the resonance control process may be given from the engine controller 1 to the laser light source 62, and the resonance control process may be performed as described below. When the laser light source 62 is turned on in this way, the deflector 65 has already resonated and vibrated, so that the light beam scans the surface of the photoconductor 2Y, and the light beam is partially applied to the photoconductor 2Y. Intensive irradiation can be prevented. Simultaneously with the scanning of the light beam, a horizontal synchronization signal Hsync is output from the horizontal synchronization sensors 60A and 60B. In the next step S5, the temperature of the torsion spring of the deflector 65 is changed by energization control of the electric resistance element by the frequency control unit 112 based on the sensor output, and the deflector 65 is moved as shown in FIG. The resonance characteristic is shifted from the broken line (before adjustment) to the drive frequency side. As a result, the resonance frequency Fry of the deflector 65 substantially coincides with the drive frequency Fd, and the amplitude value θ (y) shows the maximum amplitude.

  When the resonance control process is thus completed, the switching unit 103 is switched to the PLL processing unit 101 side of the drive signal control unit 10Y (step S6). Then, based on the reference signal Sr from the main controller MC and the detection signal Hsync, the drive signal Sd is controlled by performing PLL processing so that the phase of the reference signal and the phase of the drive cycle signal have a predetermined relative relationship. (Step S7). The drive signal Sd is given to the mirror drive unit 111 of the mirror control unit 11Y via the switching unit 103. As a result, the mirror driving unit 111 resonates and vibrates the deflecting mirror surface 651 of the deflector 65 at the driving frequency Fd while maintaining the above relative relationship. Accordingly, the scanning light beam Ly can be stably scanned while being synchronized with the reference signal of the main controller MC. When the stabilization of the scanning speed is completed, the laser light source 62 is turned off and a control signal such as a Ready signal is output to the main controller MC to complete the start-up process for the yellow exposure unit 6Y. For the toner colors other than yellow, the drive process, the resonance control process, and the PLL process (steps S1 to S7) are executed in the same manner as described above.

  As described above, according to this embodiment, the horizontal synchronization signal Hsync is input to the drive signal control unit 10 (10Y, 10M, 10C, 10K) as a drive cycle signal related to the drive cycle of the deflecting mirror surface 651. . Then, the drive signal controller 10 controls the drive signal Sd so that the phase of the reference signal Sr and the phase of the horizontal period signal Hsync have a predetermined relative relationship, and the deflector 65 is synchronized with the reference signal Sr. It is operating. Therefore, the latent image formation position in the sub-scanning direction Y is adjusted by adjusting the phase of the reference signal Sr and the horizontal period signal Hsync, and the line latent image shift in the sub-scanning direction Y can be suppressed. As a result, an image can be formed with good quality.

  In this embodiment, a color image is formed by a so-called tandem method. If the latent image forming positions in the exposure units 6 (6Y, 6M, 6C, and 6K) are shifted from each other, a color shift occurs and the image is shifted. It will degrade the quality. However, the reference signal Sr from the main controller MC is input to the drive signal control unit 10 (10Y, 10M, 10C, 10K) for each toner color, and the PLL processing is performed simultaneously. Therefore, in any toner color, the deflecting mirror surface 651 resonates and oscillates at the predetermined drive frequency Fd with the single reference signal Sr as a reference, and scanning of the light beam is performed. Therefore, it is possible to prevent the shift of the latent image forming position between the toner colors in the sub-scanning direction Y, and a good color image can be formed.

  Further, the resonance frequency adjustment unit 653 is controlled by the frequency control unit 112 to adjust the resonance frequency of the deflector 65 so as to substantially match the drive frequency Fd (resonance control processing). Therefore, even if the resonance frequency of the deflector 65 deviates from the drive frequency Fd at the start of driving, the deflector 65 resonates and vibrates at the predetermined drive frequency Fd and with the maximum amplitude by the resonance control processing, thereby forming an image. Can be carried out satisfactorily and stably.

  Further, when a color image is formed, the drive process, resonance control process, and PLL process (steps S1 to S7) are performed for each toner color as described above. However, when a monochrome image is formed, a black image is formed. Running only for colors. Therefore, the startup process can be performed efficiently.

Second Embodiment
FIG. 7 is a diagram showing a configuration of an exposure unit and a control unit (drive signal control unit and mirror control unit) for controlling the exposure unit in the second embodiment of the present invention. The second embodiment is greatly different from the first embodiment in that the resonance control process is not performed, while the amplitude control process is performed based on the horizontal synchronization signal Hsync, and the other configurations are basically the same. It is. Hereinafter, the configuration and operation will be described focusing on the differences.

  In the second embodiment, the detection signal Hsync of the scanning light beam by the horizontal synchronization sensors 60A and 60B is transmitted to the measuring unit 113 of the mirror control unit 11 (11Y, 11M, 11C, 11K), and the effective scanning region is measured in the measuring unit. The driving information related to the scanning time and the driving period during which the light beam scans is calculated. Then, the drive information calculated by the measurement unit 113 is transmitted to the mirror drive unit 111, and the mirror drive unit 111 changes the drive condition of the mirror drive signal for driving the deflection mirror surface 651 in accordance with the transmitted drive information. It can be set.

  FIG. 8 is a flowchart illustrating processing executed by the image forming apparatus according to the second embodiment. FIG. 9 is a diagram schematically showing the deflection control process of the deflector performed before the color image formation. Here, a case where a color image formation command is given as an image formation command will be described. However, when a monochrome image formation command is given, the following operation is executed only for the black color.

  When the color image formation command is given, the activation process of the deflector 65 is executed for the yellow color. First, as in the first embodiment, the switching unit 103 is switched to the reference drive signal generation unit 102 side of the drive signal control unit 10Y, and the reference drive signal output from the reference drive signal generation unit 102 is mirrored as the drive signal Sd. This is given to the mirror drive unit 111 of the control unit 11Y (step S1). As a result, the actuator 652 is operated at the drive frequency Fd to start the vibration of the deflecting mirror surface 651 at the drive frequency Fd (step S2). Here, the deflection mirror surface 651 vibrates at the frequency Fd. As shown in FIG. 9A, for example, the waveform indicating the amplitude phase of the deflection mirror surface 651 is different from the desired vibration waveform (one-dot chain line). The maximum amplitude θ (y) may be lower than the desired value θr. Conversely, the maximum amplitude θ (y) may be higher than the desired value θr. When the maximum amplitude θ (y) is different from the desired value θr in this way, the scanning speed of the light beam on the photoreceptor 2Y changes and the line latent image formed on the photoreceptor 2Y becomes the main scanning direction X. The image quality is reduced due to expansion and contraction. Therefore, after a predetermined time has elapsed (step S3), the amplitude control process is executed for the yellow deflector 65.

  In this amplitude control process, the image signal Sv is output from the main controller MC to the laser light source 62, and the laser light source 62 is turned on (step S4). Here, an image signal suitable for the amplitude control process may be given from the engine controller 1 to the laser light source 62 and the amplitude control process may be performed as described below. When the laser light source 62 is turned on in this way, the deflector 65 has already resonated and vibrated, so that the light beam scans the surface of the photoconductor 2Y, and the light beam is partially applied to the photoconductor 2Y. Intensive irradiation can be prevented. Simultaneously with the scanning of the light beam, a horizontal synchronization signal Hsync is output from the horizontal synchronization sensors 60A and 60B. Then, in the next step S8, the drive voltage of the mirror drive signal given from the mirror drive unit 111 to the deflector 65Y is controlled based on the sensor output, and the maximum amplitude value θ of the deflector 65Y as shown in FIG. 9B. The amplitude is controlled so that (y) substantially matches the desired value θr (amplitude control processing). Thereby, the scanning light beam Ly can be stably scanned by adjusting the speed of the scanning light beam Ly.

  When the amplitude control process is thus completed, the switching unit 103 is switched to the PLL processing unit 101 side of the drive signal control unit 10Y as in the first embodiment (step S6). As a result, the drive signal Sd subjected to PLL processing based on the reference signal Sr and the detection signal Hsync from the main controller MC is given to the mirror drive unit 111 of the mirror control unit 11Y via the switching unit 103 (step S7). As a result, the mirror driving unit 111 resonates and vibrates the deflecting mirror surface 651 of the deflector 65 at the driving frequency Fd while maintaining the above relative relationship. Accordingly, the scanning light beam Ly can be stably scanned while being synchronized with the reference signal of the main controller MC. When the stabilization of the scanning speed is completed, the laser light source 62 is turned off and a control signal such as a Ready signal is output to the main controller MC to complete the start-up process for the yellow exposure unit 6Y. For the toner colors other than yellow, the drive process, the amplitude control process, and the PLL process (steps S1 to S4, S8, S6, and S7) are executed in the same manner as described above.

  As described above, also in the second embodiment, the drive signal control unit 10 causes the drive signal Sd so that the phase of the reference signal Sr and the phase of the horizontal cycle signal (drive cycle signal) Hsync have a predetermined relative relationship. Since the deflector 65 is operated in synchronization with the reference signal Sr, the line latent image shift in the sub-scanning direction Y can be suppressed. In any toner color, the deflecting mirror surface 651 is resonantly oscillated at a predetermined driving frequency Fd with the single reference signal Sr as a reference, and scanning of the light beam is performed. Therefore, it is possible to prevent the shift of the latent image forming position between the toner colors in the sub-scanning direction Y, and a good color image can be formed.

  In this embodiment, even if the maximum amplitude values θ (y), θ (m), θ (c), and θ (k) of the deflection mirror surface 651 are deviated from the desired value θr at the start of driving, the amplitude Each maximum amplitude value θ (y), θ (m), θ (c), θ (k) is aligned with the desired value θr by the control process, so that the speed of the light beam between the toner colors matches and the image Formation can be performed satisfactorily and stably. Here, the amplitude control process is performed so that the maximum amplitude value coincides with the desired value θr. However, the maximum amplitude value of one of the toner colors is used as a reference, and the maximum amplitude value of the other toner color is set as the reference amplitude value. Amplitude control processing may be performed so as to match.

  Further, when forming a color image, the drive process, the amplitude control process, and the PLL process (steps S1 to S4, S8, S6, and S7) are performed for each toner color as described above, but a monochrome image is formed. If so, it is only running for black. Therefore, the startup process can be performed efficiently.

<Others>
The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the PLL process, the resonance control process, and the amplitude control process are performed using the horizontal synchronization signal Hsync from the horizontal synchronization sensors 60A and 60B as the “drive period signal” of the present invention. That is, the horizontal synchronization sensors 60A and 60B are used as “detection means” of the present invention. However, information that can be used for adjusting the phase of the drive signal, adjusting the resonance frequency, and the drive voltage is not limited to the horizontal synchronization signal Hsync, but may be information related to the drive cycle of the deflector 65. Is optional. For example, a displacement detection sensor as described in JP-A-7-218857 is provided in the deflector 65 to detect the amount of displacement of the deflection mirror surface 651, and based on the detected value, PLL processing, resonance control processing and amplitude control are performed. Processing may be performed. In this case, the displacement detection sensor corresponds to the “detection means” of the present invention.

  In the above-described embodiment, the resonance frequency adjustment unit 653 using a change in spring constant based on a temperature change is employed. However, the configuration of the resonance frequency adjustment unit 653 is not limited to this, and is conventionally known. The resonance frequency can be adjusted by this method.

  Moreover, in the said embodiment, although the resonance control process and the amplitude control process are performed, these control processes are not essential processes, and can be performed in arbitrary combinations. For example, the resonance control process can be omitted in the first embodiment, and the amplitude control process can be omitted in the second embodiment.

  In the above-described embodiment, the present invention is applied to a color image forming apparatus. However, the application target of the present invention is not limited to this, and it is also applicable to a monochrome image forming apparatus that forms a so-called monochromatic image. The present invention can be applied.

  Furthermore, in the above-described embodiment, the deflector 65 formed by using micromachining technology is employed as the vibration mirror. However, the light beam is deflected by using the vibration mirror that resonates and oscillates on the latent image carrier. The present invention can be applied to any image forming apparatus that scans a beam.

1 is a diagram illustrating a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. FIG. 2 is a main scanning sectional view showing a configuration of an exposure unit of the image forming apparatus of FIG. 1. FIG. 2 is a diagram showing a configuration of an exposure unit and a control unit for controlling the exposure unit of the image forming apparatus of FIG. 1. 3 is a flowchart showing start-up processing executed by the image forming apparatus in FIG. 1. FIG. 3 is a diagram schematically illustrating an amplitude control process before color image formation in the first embodiment. The figure which shows the structure of the control part for controlling the exposure unit and exposure unit in 2nd Embodiment of the image forming apparatus concerning this invention. 9 is a flowchart illustrating processing executed by the image forming apparatus according to the second embodiment. The figure which shows typically the amplitude control process before the color image formation in 2nd Embodiment.

Explanation of symbols

  2Y, 2M, 2C, 2K ... photosensitive member (latent image carrier) 10, 10Y, 10M, 10C, 10K ... drive signal control unit 11, 11Y, 11M, 11C, 11K ... mirror control unit, 60A, 60B ... Horizontal synchronization sensor (detection means), 65 ... deflector (vibrating mirror), 101 ... PLL processing unit, 102 ... reference drive signal generation unit, 112 ... frequency control unit, 651 ... deflection mirror surface, 653 ... resonance frequency adjustment unit, EG: engine unit, Fd: drive frequency, Fry, Frm, Frc, Frk: resonance frequency, Hsync: horizontal synchronization signal (drive synchronization signal), Ly, Lm, Lc, Lk (scanning) light beam, MC: main controller Sd: drive signal, Sr: reference signal, Sv: image signal, X: main scanning direction

Claims (8)

A controller that outputs an image signal corresponding to the received image formation command, and a light beam modulated according to the image signal from the controller is scanned in the main scanning direction by a vibrating mirror that resonates and vibrates on the latent image carrier. In an image forming apparatus having an engine unit for forming a latent image,
The controller generates a reference signal and outputs it to the engine unit,
The engine unit detects a driving cycle of the vibrating mirror and outputs a driving cycle signal related to the driving cycle, and a driving signal control unit outputs a driving signal for controlling the driving of the vibrating mirror. And mirror control means for driving the vibrating mirror based on the drive signal output from the drive signal control means,
The drive signal control means receives the reference signal and the drive cycle signal, and controls the drive signal so that a phase of the reference signal and a phase of the drive cycle signal have a predetermined relative relationship. A featured image forming apparatus.   The drive signal control unit includes a reference drive signal generation unit that generates a reference drive signal having a predetermined drive frequency, and drives the vibrating mirror based on the reference drive signal at a driving start stage of the vibrating mirror. 2. The image forming apparatus according to claim 1, wherein the vibration mirror is driven at the drive frequency by controlling a drive signal based on the drive cycle signal output from the detection unit and the reference signal provided from the controller. . The engine part is
Resonance frequency adjusting means for adjusting the resonance frequency of the vibrating mirror;
The frequency control unit according to claim 2, further comprising: a frequency control unit that controls the resonance frequency adjusting unit so that a resonance frequency of the vibrating mirror substantially matches the driving frequency based on the driving cycle signal output from the detection unit. Image forming apparatus.   The drive signal control means adjusts the resonance frequency of the oscillating mirror so that it substantially coincides with the drive frequency by the frequency control unit while the oscillating mirror is driven based on the reference drive signal. The image forming apparatus according to claim 3, wherein the vibration mirror is driven by controlling a drive signal based on the reference signal and the reference signal.   The image forming apparatus according to claim 2, wherein the mirror control unit adjusts an amplitude of the vibrating mirror based on the drive period signal output from the detection unit.   The drive signal control means adjusts the amplitude of the oscillating mirror by the mirror control means while driving the oscillating mirror based on the reference drive signal, and then outputs a drive signal based on the drive cycle signal and the reference signal. The image forming apparatus according to claim 5, wherein the image forming apparatus is controlled to drive the vibrating mirror.   The image forming apparatus according to claim 1, wherein the drive signal is controlled by the drive signal control unit by PLL control. A controller that outputs an image signal corresponding to the received image formation command, and a light beam modulated according to the image signal from the controller is scanned in the main scanning direction by a vibrating mirror that resonates and oscillates based on the drive signal. In an image forming method for forming an image using an image forming apparatus having an engine unit for forming a latent image on an image carrier,
Starting driving the vibrating mirror using the reference drive signal output from a reference drive signal generator provided in the engine as the drive vibration;
Detecting a driving cycle of the vibrating mirror and outputting a driving cycle signal related to the driving cycle;
The drive signal is controlled so that the resonance operation of the vibrating mirror is synchronized with each part of the apparatus so that the phase of the reference signal given from the controller to the engine unit and the phase of the drive cycle signal have a predetermined relative relationship. And an image forming method.

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