JP2008012694A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a rotating speed of a polygon mirror without controlling separation to a photoconductor drum of a developing instrument at a time of continuous printing when the rotating speed of the polygon mirror is changed. <P>SOLUTION: An image forming apparatus equipped is with: a laser beam generating means; an image carrying body; and a rotational polygon body for polarizing and scanning the laser beam, and has at least binary values image forming modes of the rotating speed of the rotational polygon body. The apparatus also has a constitution equipped with: an image forming mode discriminating means for discriminating the image forming mode; and a horizontal synchronizing signal estimating means for estimating outputting timing of a horizontal synchronizing signal detected next. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to rotational speed control of a rotating polyhedron that uses a plurality of rotational speeds for image formation.

  In recent years, the use of laser printers has expanded, and the demand for printing on various media has increased, and printers equipped with many print modes have been commercialized. Up to now, print modes corresponding to various media have been realized by arbitrarily changing a development bias voltage contributing to developability, a fixing temperature contributing to fixability, a fixing speed, and the like. In particular, changing the fixing speed is indispensable for printing on a medium with high heat capacity and high gloss printing, and is performed in conjunction with the conveyance speed of the medium (hereinafter referred to as process speed). Changing the process speed also changes the image forming speed in the image forming processing unit. However, with conventional printers, image thinning (images for each light scanning) This is realized while controlling the image forming speed to be 1 / N by performing (control to form an image only one scan at N times) without forming.

  However, due to recent demands for further increases in printer speed and multifunction, in addition to controlling the process speed by thinning out images, the process speed has been changed by changing the scanning speed of the scanner.

  In a printer having scanning speeds of a plurality of scanners, for example, when image formation is performed continuously at different scanning speeds of the scanner, the scanning speed of the scanner is from the completion of the transfer process of the previous image to the start of the latent image processing of the next image. Need to change.

  Here, FIG. 13 shows a timing chart showing scanner speed at the time of image formation and laser on / off control. The signal in the figure is the main scanning synchronization signal obtained from the laser detection sensor, A is the printer specific value (0 <A <1), P is the period of the scanning synchronization signal, AP is forcing the laser from the main scanning synchronization signal It shows the time to turn on. Also, in the figure, there are a section in which the photosensitive drum is irradiated with a laser at the time of an image latent image and a section in which the laser is forcibly turned on to detect a main scanning synchronization signal (here, APC emission is used). It is written together. A is determined so that the AP is between the time when the photosensitive member irradiation section ends and the time when the next main scanning synchronization signal arrives. As shown in the figure, the forced lighting timing of the laser is determined by the period of the immediately preceding main scanning synchronization signal. For this reason, when the scanner rotates at a stable speed, the forced lighting timing of the laser can be accurately set between the time when the photosensitive member irradiation section ends and the time when the next main scanning synchronization signal arrives. it can. By performing laser lighting at the above timing (hereinafter referred to as unblanking lighting), it is possible to perform laser lighting corresponding to image data in the photosensitive member irradiation section while reliably detecting the main scanning synchronization signal. However, when the scanning speed of the scanner fluctuates greatly, the AP is not always between the time when the photosensitive member irradiation section ends and the time when the next main scanning synchronization signal arrives. In some cases, forced lighting of the laser occurs in the photosensitive member irradiation section when the scanner is decelerated, and there is a possibility that the forced lighting of the laser is after the time when the main scanning synchronization signal can be detected when the scanner is accelerated.

  Therefore, conventionally, the scanning speed of the scanner is controlled by constantly turning on the laser beam and detecting the main scanning synchronization signal for the purpose of stable scanning speed transition.

For example, Patent Document 1 and Patent Document 2 can be cited as conventional examples.
Japanese Patent Laid-Open No. 10-133136 JP 11-34393 A

  However, in this speed control, since the laser beam is always turned on, unnecessary laser irradiation is performed on the photosensitive drum. Therefore, in order to prevent unnecessary image development by laser irradiation and image transfer to a medium or belt, it is necessary to perform a process of separating the developing device from the photosensitive drum when the scanning speed of the scanner is changed.

  14 and 15 show a part of the conventional image forming system. FIG. 14 shows a state where the developing device is in contact with the photosensitive drum, and FIG. 15 shows a state where the developing device is separated from the photosensitive drum. In the figure, 101 is a photosensitive drum that forms a toner image, 108 is a charging roller that uniformly charges the surface of the photosensitive drum 101, 111 is a developing device that holds development toner, and 103 is a latent image on the photosensitive drum 101. A developing roller for supplying toner, 106 a conveyance belt for conveying a medium for printing a toner image, and 107 a transfer roller for transferring the toner image to the medium. In the drawing, an arrow directed to the photosensitive drum indicates a laser beam emitted from the laser scanner. As shown in FIG. 15, when changing the scanning speed of the scanner, the developing roller is separated from the photosensitive drum to prevent development of the latent image by forced laser lighting.

  FIGS. 16 and 17 are diagrams showing the contact and separation of the developing devices, with a part of the drive system added. In the figure, reference numeral 118 denotes a cam that mechanically drives the developing device, and 109 denotes an axis that is a base point of the swinging motion of the developing device by the cam 118. The position of the cam 118 is always controlled by a drive source (not shown) and position control means such as an encoder. During image formation, the developing roller is brought into contact with the photosensitive drum by controlling the cam 118 to the position shown in FIG. On the other hand, when changing the scanning speed of the scanner, the cam 118 is controlled to the position shown in FIG. 17, and the developing roller is separated from the photosensitive drum.

  Next, FIG. 18 shows a sequence diagram when changing the scanning speed of the scanner in the conventional control. The printer determines whether the rotation speed of the scanner is changed in the next image formation during the image formation process (S11 in FIG. 18). If there is no change in the scanner rotation speed, the next printing process is started immediately (S18 in FIG. 18). When there is a change in the scanning speed of the scanner, after the image formation is completed, the developing device is separated (FIG. 18 S12), and then the laser is forcibly turned on (FIG. 18 S13). Next, the scanning speed of the scanner is changed so that it becomes the next print mode (S14 in FIG. 18). After the scanning speed of the scanner reaches the target speed (Fig. 18 S15), the laser control is changed to unblank lighting control (Fig. 18 S16), and the developer is brought into contact (Fig. 18 S17). The image forming process is started (S18 in FIG. 18).

  FIG. 19 shows the transition of the scanner scanning speed of the printer. In the figure, (1) is the scanner activation section, (2) is the image forming section at the first scanner scanning speed V1, and (3) is the execution / release of the separation / contact operation of the developing roller 103 and the forced laser lighting control. A speed change section from the first scanner scanning speed V1 to the second scanner scanning speed V2 including (4) is an image forming section at the second scanner scanning speed V2, and (5) is the separation / applying of the developing roller 103. A speed change section from the second scanner scanning speed V2 to the first scanner scanning speed V1 including the contact operation and the implementation / cancellation of the laser always-on control is shown. As shown in the figure, in the conventional scanner scanning speed control, it is necessary to perform the separation / contact process of the developing roller 103 before and after actually changing the scanning speed of the scanner, so it takes time until the next printing process can be started. It was over. In addition, the system control is complicated, and the control capability of the CPU is temporarily reduced greatly. Furthermore, there is a possibility that the drum life may be reduced due to unnecessary laser irradiation on the photosensitive drum 101.

  In view of the above, the present invention corrects the scanning speed of the scanner without performing contact / separation control with respect to the photosensitive drum of the developing device during continuous printing in which the scanning speed of the scanner is changed. It is an object of the present invention to provide an image forming apparatus that simplifies mechanical control at the time, suppresses unnecessary exposure and development control, and causes little device deterioration.

  In order to achieve the above object, a first invention according to the present application includes a laser beam generating means for generating a laser beam, an image carrier, a rotating polyhedron for causing the image carrier to scan the laser beam with polarization, and Development means for developing a developer on a latent image on the image carrier scanned by a laser beam, and a laser that generates a horizontal synchronization signal that serves as a reference for image writing timing on the image carrier when the laser beam is input A beam detection means; a rotation speed calculation means for calculating the rotation speed of the first rotating polyhedron from the laser beam detection means; and a laser beam control means for controlling turning on and off of the laser beam at a predetermined timing synchronized with the horizontal synchronization signal. An image forming apparatus having an image forming mode at a rotational speed of the rotating polyhedron of at least two or more. An image forming mode discriminating unit for discriminating the image, and a horizontal synchronizing signal predicting unit for predicting an output timing of a horizontal synchronizing signal detected next from the detected horizontal synchronizing signal, and images of different image modes from the result of the discriminating unit. When it is determined that the image forming body is to be formed, the image carrier is not irradiated with the laser beam from the laser beam control means and the horizontal synchronization signal prediction means when correcting the speed of the rotating polyhedron during the image forming process. The rotational speed of the rotating polyhedron is changed. With the above configuration, continuous printing in image formation with different scanning speeds can be performed without performing the separating operation of the developing device, and the mechanical operation is simplified and the CPU is controlled when the rotational speed of the rotating polyhedron is changed. Resources can be reduced.

  A second invention according to the present application is provided with a contact / separation function for performing contact and separation operations between the image carrier and the developing unit, and bringing the image carrier and the development unit into contact at the time of speed correction in the previous period. Further, the rotational speed of the rotating polyhedron is changed. With the above configuration, the time required for changing the scanning speed of the scanner can be shortened.

  According to a third aspect of the present application, the horizontal synchronization signal predicting means calculates a current rotational speed from the immediately preceding rotational speed obtained from the rotational speed calculating means and at least one previous rotational speed, It is a means for predicting the output timing of the next detected horizontal synchronizing signal. With the above-described configuration, it is possible to suppress unnecessary laser irradiation to the image carrier, and deterioration of the image carrier can be reduced.

  According to a fourth aspect of the present application, the horizontal synchronization signal predicting means includes a rotation speed immediately before obtained from the rotation speed calculation means, at least one previous rotation speed, and a current rotation speed from the temperature detection means. Is a means for predicting the output timing of the horizontal synchronization signal detected next. With the above-described configuration, it is possible to eliminate unnecessary laser irradiation on the image carrier corresponding to the change in the speed profile depending on the use environment of the printer.

  A fifth invention according to the present application has a rotational speed fluctuation amount control means, and controls the speed of the rotary polyhedron with a speed fluctuation amount different from that of image formation when correcting the speed of the rotary polyhedron during the image forming process. It is characterized by performing. With the above configuration, unnecessary laser irradiation can be deleted, and the change of the rotation speed of the rotating polyhedron can be completed at an early stage.

  The sixth invention according to the present application is characterized in that the rotational speed fluctuation amount control means controls a gain of an acceleration / deceleration signal supplied to a drive source for driving the rotary polyhedron.

  As described above, according to the present invention, in the continuous image forming process in which the scanning speed of the scanner is changed, the scanning speed of the scanner is changed without performing contact / separation control with respect to the photosensitive drum of the developing device. As a result, mechanical control when changing the scanning speed of the scanner can be simplified, and device deterioration due to unnecessary exposure and development control can be reduced.

  Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

  In the present embodiment, the first scanning speed V1 and the second scanning speed V2 are used as the scanning speed of the scanner, and the two scanning speed information detected immediately before the control for changing the scanning speed of the scanner at the time of continuous printing between sheets. The case where it carries out from will be described.

  First, FIG. 2 shows the configuration of an image forming apparatus according to an embodiment of the present invention.

  In the figure, 101 is a photosensitive drum for forming an electrostatic latent image (Y, M, C, and K are yellow, magenta, cyan, and black), 104 is a motor that drives each photosensitive drum, and 110 is in accordance with an image signal. A laser scanner for exposing the photosensitive drum 101 to form an electrostatic latent image; 111, a developing device for storing toner; 103, a developing roller for discharging the toner discharged from the developing device 111 onto the photosensitive drum 101; Is a developing / separating motor that contacts and separates the developing roller 103 from the photosensitive drum 101, 106 is an endless conveying belt that sequentially conveys the paper to the image forming unit of each color, and 115 is a driving unit that includes a motor and a gear. A driving roller connected to drive the conveying belt 106, a motor 116 driving the driving roller 115, and a toner 117 melting and fixing the toner transferred onto the paper. That the fixing device, 112 pickup roller for transporting the paper from the paper cassette, 113 and 114 is a conveyance roller for guiding the sheet to the conveying belt 106.

  FIG. 3 is a plan view of a laser scanner unit having a laser light source using a semiconductor laser with a part of an operation system added. 40 is a semiconductor laser, 11 is a polygon mirror for deflecting laser light (LD) oscillated from the semiconductor laser 40, 50 is a BD sensor for detecting the irradiation of the deflected laser light, and 14 and 15 are lasers deflected by a polygon mirror. An fθ lens for correcting the scanning speed of light to a constant speed, 16 a reflection mirror for reflecting the laser light whose speed has been corrected to the image carrier, 30 a laser driver for controlling light emission of the semiconductor laser, and 20 for speed control of the polygon mirror A scanner motor driver 10 performs a control related to instruction image formation, such as a scanner activation instruction, a paper conveyance start instruction, and a fixing device temperature control start. The print controller 10 controls the scanner motor driver 20 to rotate the polygon mirror 11 at a desired speed. Further, the print control unit 10 controls the laser driver 30 to cause the semiconductor laser having a laser light source to oscillate at a desired light source and timing. The oscillated laser light is changed by the polygon mirror 11 and applied to the BD sensor 50 disposed in the scanner unit. The BD sensor 50 outputs a main scanning synchronization signal to the print control unit when a prescribed amount of light is irradiated. The print control unit 10 adjusts the image writing timing in the main scanning direction and monitors the rotational speed of the polygon mirror based on the output value of the main scanning synchronization signal.

  When data to be printed is sent from an external device (not shown) such as a PC to the printer and image formation according to the printer engine system is completed and printing is possible, paper is supplied from the paper cassette and reaches the conveyor belt 106. Then, the paper is sequentially conveyed to the image forming units of the respective colors by the conveying belt 106. The image signal of each color is sent to each laser scanner 110 in synchronization with the conveyance of the paper by the conveyance belt 106, and an electrostatic latent image is formed on the photosensitive drum 101. The developing separation motor 105 contacts the photosensitive drum 101. The electrostatic latent image is developed with toner by the developed developing device 111 and the developing roller 103, and is transferred onto a sheet by a transfer unit (not shown). In the figure, images are sequentially formed in the order of K, C, M, and Y. Thereafter, the sheet is separated from the conveyance belt, and the toner image is fixed on the sheet by heat by the fixing device 117 and discharged to the outside. Through the above steps, the image information instructed from the external device is printed on the paper.

  Next, the scanning speed control of the scanner at the time of continuous printing in which the scanning speed of the scanner according to the present embodiment is changed will be described with reference to FIGS. 1, 4, 5, and 6.

  FIG. 1 is a block diagram relating to scanner scanning speed control of this embodiment. In the figure, reference numeral 60 is a scanner control circuit for transmitting an acceleration / deceleration signal to the scanner driver, and further a laser emission control signal is transmitted to the laser driver. Reference numeral 80 is a scanner scanning speed based on the main scanning synchronization signal transmitted from the BD sensor 50. 83 is a main scanning synchronization signal arrival prediction circuit for predicting the arrival time of the main scanning synchronization signal detected next time from the data obtained by the scanning speed detection circuit 80, and 70 is an external device (not shown). The video controller converts print data sent from the printer into image data that can be printed by a printer engine. In this embodiment, the scanning speed and acceleration of the scanner are detected from the main scanning synchronization signal data detected by the BD sensor 50, and the scanner control circuit 60 controls the scanning speed of the scanner and the output timing of the laser.

  FIG. 4 is a sequence diagram related to the scanner control unit when a continuous print is requested in this embodiment.

  First, the print controller 10 determines whether the next print request matches the current scanning speed (S81 in FIG. 4). If the scanning speeds match, the process immediately shifts to the next printing process (S88 in FIG. 4). When the scanning speeds are different, the printer needs to change the scanning speed for the next print, so the print control unit 10 controls the scanner to change the target scanning speed of the scanner to a scanning speed corresponding to the next printing process. The circuit 60 is instructed (S82 in FIG. 4). While the scanner control unit 60 changes to the scanning speed of the next print, the scanning speed calculation circuit 80 calculates the scanning speed of the scanner (FIG. 4 S83), and the main scanning synchronization signal arrival prediction circuit 83 further scans the scanner. Based on this, the predicted arrival time of the next main scanning synchronization signal, that is, the next main scanning speed (cycle) is calculated (S84 in FIG. 4). The scanner control unit 60 calculates the lighting timing of the laser that is turned on to capture the next main scanning synchronization signal from the predicted main scanning speed (FIG. 4 S85), and turns on the laser at a predetermined timing (FIG. 4 S86). ). The above control is performed until the scanning speed of the scanner reaches the target speed (FIG. 4 S87), and when the target speed is reached, the print control unit instructs to perform the next print process (S88 in FIG. 4).

Next, a method for predicting the arrival time of the main scanning synchronization signal will be described with reference to the timing chart of FIG. Although the figure shows a case where the scanning speed of the scanner is increased, the prediction method is the same when the scanning speed is decreased. The signal in the figure is the main scanning synchronization signal obtained from the laser detection sensor, A is the printer specific value (0 <A <1), P is the period of the scanning synchronization signal, N is the serial number for the period of the main scanning synchronization signal, A (2P _N -P _N-1 ) indicates the time from the main scanning synchronization signal to forcibly turning on the laser. Also, in the figure, there are a section in which the photosensitive drum is irradiated with a laser at the time of an image latent image and a section in which the laser is forcibly turned on to detect a main scanning synchronization signal (here, APC emission is used). It is written together. A is determined so that when P is stable, AP is between the time when the photosensitive member irradiation section ends and the time when the next main scanning synchronization signal arrives. As shown, to calculate the amount of variation in the period from the period P _N-2 of the periodic P _N-1 and before the previous detection scanning synchronizing signal before detection scanning synchronizing signal, for predicting the cycle P _N of the scanning synchronization signal.

  Next, the transition of the scanning speed of the scanner in this embodiment is shown in FIG. In the figure, (1) is the scanner start-up section, (2) is the image forming section at the scanner rotation speed V1, (3) is the section for changing the speed from the scanner rotation speed V1 to V2, and (4) is at the scanner rotation speed V2. An image forming section (5) is a speed changing section from the scanner rotation speed V2 to V1. By changing the scanning speed in the scanning speed changing section ((3) and (5)) of the scanner excluding the start time without changing the developer separation and contact processing, the scanning speed changing section can be shortened. .

  As described above, by performing this execution control, the scanning speed of the scanner can be changed without irradiating the photosensitive drum with laser. As a result, the separation control between the developing device and the photosensitive drum between prints during continuous printing can be omitted, so that the next print can be immediately executed. Further, drum deterioration due to unnecessary laser irradiation can be suppressed.

  In the present embodiment, an example in which a print mode with two rotational speeds is provided is shown, but the present invention can also be implemented in a system having a print mode with two or more scanning speeds. In addition, although the control example is shown with the number of laser light sources being one, it is needless to say that a multi-beam light source may be used. Furthermore, it goes without saying that the number of polygon mirrors is any number. Further, in this embodiment, the predicted arrival time of the main scanning synchronization signal is calculated from the period of the previous main scanning synchronization signal and the period of the main scanning synchronization signal, but is calculated using the previous period. (A timing chart in the case where a period of 3 points is used is shown in FIG. 7). Of course, you may estimate from the period beyond it.

  A second embodiment of the present invention will be described.

  Since the configuration of the image forming apparatus according to the embodiment of the present invention and the method for predicting the arrival time of the main scanning synchronization signal are the same as those in the first embodiment, description thereof will be omitted.

  This embodiment is different from the first embodiment in that a control gain circuit for controlling the scanning speed of the scanner is added, and the control gain is increased compared to the normal control when the scanning speed of the scanner is changed.

  Next, the scanning speed control of the scanner during continuous printing in which the scanning speed of the scanner according to the present embodiment is changed will be described with reference to FIGS. 8, 9, and 10. FIG.

  FIG. 8 is a control block diagram of a portion related to optical image formation of the printer in this embodiment. In the figure, reference numeral 60 is a scanner control circuit for transmitting an acceleration / deceleration signal to the scanner driver, and further a laser emission control signal is transmitted to the laser driver. Reference numeral 80 is a scanner scanning speed based on the main scanning synchronization signal transmitted from the BD sensor 50. 81 is a speed gain control block for controlling a speed gain related to the speed control of the polygon mirror in the scanner control circuit, and 83 is a main scan detected next time from the data obtained by the scanning speed detection circuit 80. A main scanning synchronization signal arrival prediction circuit 70 for predicting the arrival time of the synchronization signal is a video controller that converts print data sent from an external device (not shown) into image data that can be printed by the printer engine.

  FIG. 9 is a sequence diagram related to the scanner control unit at the time of continuous print request in this embodiment.

  First, the print controller 10 determines whether the next print request matches the current scanning speed (S61 in FIG. 9). If the scanning speeds match, the process immediately proceeds to the next print process (S70 in FIG. 9). When the scanning speeds are different, the printer control unit 10 first increases the scanning gain for controlling the change intensity of the scanner scanning speed (S62 in FIG. 9). Next, the print control unit 10 instructs the scanner control circuit 60 to change the target scanning speed of the scanner to a scanning speed corresponding to the next printing process (S63 in FIG. 9). While the scanner controller 60 changes to the scanning speed of the next print, the scanning speed calculation circuit 80 calculates the scanning speed of the scanner (S64 in FIG. 9), and the main scanning synchronization signal arrival prediction circuit 83 further scans the scanner. Based on this, the predicted arrival time of the next main scanning synchronization signal, that is, the next main scanning speed (cycle) is calculated (S65 in FIG. 9). The scanner control unit 60 calculates the lighting timing of the laser that is turned on to capture the next main scanning synchronization signal from the predicted main scanning speed (FIG. 9 S66), and turns on the laser at a predetermined timing (FIG. 9 S67). ). The above control is performed until the scanning speed of the scanner reaches the target speed (FIG. 9 S68), and the print control unit 10 returns the scanning gain to the original value (FIG. 9 S69), and then performs the next print processing. Instruction is given (FIG. 9, S70).

  Next, the transition of the scanning speed of the scanner in this embodiment is shown in FIG. In the figure, (1) is the scanner start-up section, (2) is the image forming section at the scanner rotation speed V1, (3) is the section for changing the speed from the scanner rotation speed V1 to V2, and (4) is at the scanner rotation speed V2. An image forming section (5) is a speed changing section from the scanner rotation speed V2 to V1. In the scanning speed changing section ((3) and (5)) excluding the start-up time, the separation and contact processing of the developing device is not performed, and the scanning speed is changed while the speed control gain is increased more than usual. Compared with the normal speed control, the scanning speed change section can be shortened.

  As described above, by performing this execution control, the scanning speed of the scanner can be changed without irradiating the photosensitive drum with laser. As a result, the separation control between the developing device and the photosensitive drum between prints during continuous printing can be omitted, so that the next print can be immediately executed. Further, drum deterioration due to unnecessary laser irradiation can be suppressed.

  In the present embodiment, an example in which a print mode with two rotational speeds is provided is shown, but the present invention can also be implemented in a system having a print mode with two or more scanning speeds. In addition, although the control example is shown with the number of laser light sources being one, it is needless to say that a multi-beam light source may be used. Furthermore, it goes without saying that the number of polygon mirrors is any number. Further, in this embodiment, the predicted arrival time of the main scanning synchronization signal is calculated from the period of the previous main scanning synchronization signal and the period of the main scanning synchronization signal, but is calculated using the previous period. May be. Of course, you may estimate from the period beyond it. In this embodiment, the speed control gain is switched at the start and end of the speed change. However, the gain may be switched at a plurality of points.

  A third embodiment of the present invention will be described.

  Since the configuration of the image forming apparatus according to the embodiment of the present invention is the same as that of the first embodiment, description thereof is omitted.

  Further, the sequence diagram related to the scanner control unit at the time of continuous print request according to the embodiment of the present invention is the same as that of the second embodiment, and the description thereof will be omitted.

  In this embodiment, a control gain circuit for controlling the scanning speed of the scanner is added, and the points that the control gain is increased from the normal control when the scanning speed of the scanner is changed and the timing of turning on the laser from the value of the temperature sensor are adjusted. Different from one embodiment.

  Next, the scanning speed control of the scanner at the time of continuous printing in which the scanning speed of the scanner according to the present embodiment is changed will be described with reference to FIGS.

  FIG. 11 is a control block diagram of a portion related to optical image formation of the printer in this embodiment. In the figure, reference numeral 60 is a scanner control circuit for transmitting an acceleration / deceleration signal to the scanner driver, and further a laser emission control signal is transmitted to the laser driver. Reference numeral 80 is a scanner scanning speed based on the main scanning synchronization signal transmitted from the BD sensor 50. 81 is a speed gain control block that controls a speed gain related to speed control of the polygon mirror in the scanner control circuit, 82 is a temperature sensor that detects the temperature in the vicinity of the scanner unit in the printer, and 83 is a scan. A main scanning synchronization signal arrival prediction circuit for predicting the arrival time of the next main scanning synchronization signal detected from the data obtained by the speed detection circuit 80, 70 can print print data sent from an external device (not shown) by a printer engine It is a video controller that converts image data.

Next, a method for predicting the arrival time of the main scanning synchronization signal will be described with reference to the timing chart of FIG. The signal in the figure is the main scanning synchronization signal obtained from the laser detection sensor, A is the printer specific value (0 <A <1), and E is the coefficient for correcting the temperature characteristics related to the scanning speed of the scanner (0 <E <1). , P is the period of the scanning synchronization signal, N is the serial number for the period of the main scanning synchronization signal, and A (2P _N -P _N-1 ) is the time from the main scanning synchronization signal to forcibly turning on the laser. Yes. Also, in the figure, there are a section in which the photosensitive drum is irradiated with a laser at the time of an image latent image and a section in which the laser is forcibly turned on to detect a main scanning synchronization signal (here, APC emission is used). It is written together. A is determined so that AP is between the time when the photosensitive member irradiation section ends and the time when the next main scanning synchronization signal arrives when P is stable at room temperature. As shown in the figure, the timing for turning on the laser for detecting the main scanning synchronization signal, the coefficient value E determined by A and the value of the temperature sensor, the period P _N-1 of the previous detection scanning synchronization signal, and the previous detection scanning synchronization signal. It is determined using a scanning synchronization signal obtained from the cycle P _N-2 from the period of the periodic P _N.

  As described above, by performing this execution control, the scanning speed of the scanner can be changed without irradiating the photosensitive drum with laser. As a result, the separation control between the developing device and the photosensitive drum between prints during continuous printing can be omitted, so that the next print can be immediately executed. Further, drum deterioration due to unnecessary laser irradiation can be suppressed.

  In the present embodiment, an example in which a print mode with two rotational speeds is provided is shown, but the present invention can also be implemented in a system having a print mode with two or more scanning speeds. In addition, although the control example is shown with the number of laser light sources being one, it is needless to say that a multi-beam light source may be used. Furthermore, it goes without saying that the number of polygon mirrors is any number. Further, in this embodiment, the predicted arrival time of the main scanning synchronization signal is calculated from the period of the previous main scanning synchronization signal and the period of the main scanning synchronization signal, but is calculated using the previous period. May be. Of course, you may estimate from the period beyond it. In this embodiment, the speed control gain is switched at the start and end of the speed change. However, the gain may be switched at a plurality of points.

FIG. 3 is a control block diagram of a portion related to optical image formation of the printer according to the first embodiment of the present invention. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a scanner unit and a system configuration that controls the scanner unit according to an embodiment of the present invention. FIG. It is a sequence diagram explaining rotation control of the scanner motor between print processing concerning the 1st example of the present invention. FIG. 6 is a first diagram illustrating a timing chart for explaining a method for calculating a predicted arrival time of a main scanning synchronization signal according to the first embodiment of the present invention. It is a figure which shows the rotational speed of the scanner motor which concerns on the 1st Example of this invention. It is a 2nd figure which shows the timing chart explaining the calculation method of the arrival prediction time of the main scanning synchronizing signal which concerns on 1st Example of this invention. FIG. 6 is a control block diagram of a portion related to optical image formation of a printer according to a second embodiment of the present invention. It is a sequence diagram explaining rotation control of the scanner motor between the printing processes which concern on the 2nd Example of this invention. It is a figure which shows the rotational speed of the scanner motor which concerns on the 2nd Example of this invention. FIG. 10 is a control block diagram of a portion related to optical image formation of a printer according to a third embodiment of the present invention. It is a figure which shows the timing chart explaining the calculation method of the arrival prediction time of the main scanning synchronizing signal which concerns on 3rd Example of this invention. It is a figure which shows the timing chart explaining the calculation method of the arrival arrival time of the main scanning synchronizing signal which concerns on the prior art example of this invention. FIG. 3 is a first view of a portion related to optical image formation of the printer according to the present invention. It is a 2nd figure of the part in connection with the optical image formation of the printer which concerns on this invention. FIG. 6 is a first diagram illustrating a contact / separation operation of the developing device according to the present invention. FIG. 10 is a second diagram illustrating the contact / separation operation of the developing device according to the present invention. It is a sequence diagram explaining rotation control of the scanner motor between print processing concerning the conventional example of the present invention. It is a figure which shows the rotational speed of the scanner motor based on the prior art example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Print control part 40 Semiconductor laser 50 BD sensor 30 Laser driver 20 Scanner driver 80 Speed detection circuit 81 Speed gain control block 82 Temperature sensor 83 Main scanning synchronous signal arrival prediction circuit

Claims (6)

  Laser beam generating means for generating a laser beam, an image carrier, a rotating polyhedron for causing the laser beam to be polarized and scanned on the image carrier, and a developer for developing a latent image on the image carrier scanned by the laser beam. A developing means for developing the laser, a laser beam detecting means for generating a horizontal synchronization signal that becomes a reference of an image writing timing on the image carrier when a laser beam is inputted, and a rotational speed of the rotating polyhedron in the previous period from the laser beam detecting means And a laser beam control unit for controlling the turning on and off of the laser beam at a predetermined timing synchronized with the horizontal synchronizing signal, and forming an image of the rotational speed of the rotating polyhedron of at least two values or more In an image forming apparatus having a mode, image forming mode determining means for determining the image forming mode, and the rotation speed Horizontal synchronization signal prediction means for predicting the output timing of the horizontal synchronization signal detected next from the value of the calculation means, and when it is determined from the result of the determination means to perform image formation in a different image mode, the image The rotational speed of the rotating polyhedron is changed without irradiating the image carrier with a laser beam from the laser beam control unit and the horizontal synchronization signal prediction unit when correcting the speed of the rotating polyhedron during the forming process. Image forming apparatus.   A contact / separation function for abutting and separating the image carrier and the developing means is provided, and the rotational speed of the rotating polyhedron is adjusted while the image carrier and the developing means are kept in contact with each other at the time of speed correction. The image forming apparatus according to claim 1, wherein the image forming apparatus is changed.   The horizontal synchronization signal prediction means calculates a current rotation speed from the immediately preceding rotation speed obtained from the rotation speed calculation means and at least one previous rotation speed, and outputs a horizontal synchronization signal detected next. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is means for predicting timing.   The horizontal synchronization signal predicting means calculates the current rotational speed from the immediately preceding rotational speed obtained from the rotational speed calculating means, at least one previous rotational speed, and the temperature detecting means, and then detects the horizontal speed detected next. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is means for predicting an output timing of the synchronization signal.   The rotational polyhedron control means is provided, and when the speed of the rotating polyhedron is corrected during the image forming process, speed control of the rotating polyhedron is performed with a speed fluctuation amount different from that of image formation. The image forming apparatus according to claim 4.   6. The image forming apparatus according to claim 5, wherein the rotational speed variation control means is means for controlling a gain of an acceleration / deceleration signal supplied to a driving source for driving the rotating polyhedron.

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