JP2006137087A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has an extension in life of a light source by suppressing a deterioration in power of a laser beam, prevents erroneous operation by suppressing a deterioration in a synchronous signal detection sensor, and has an extension in the life of the synchronous signal detection sensor. <P>SOLUTION: This image forming apparatus 1 comprises a synchronous sensor 244 for reading synchronous timings of laser beams La1, Lb-Ld, laser control units 42a-42d for controlling the laser beams La1, Lb-Ld, laser beam scanner units 227a-227d for forming latent images on photosensitive drums 222a-222d according to image information, and image forming stations Pa-Pd for forming developer images, and then transfers the developer images formed on the photosensitive drums 222a-222d to a recording paper. The synchronous timings of the laser beams Lb, Lc, Ld are controlled from the synchronous timing of the laser beam La1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that performs a printing process of image information by forming an electrostatic image latent image with laser irradiation light.

  In recent years, colorization is becoming common in image forming apparatuses, and color image forming apparatuses are increasingly employed as color image forming apparatuses develop.

  In an image forming apparatus, conventionally, as an image writing technique, a method of writing image information on a photosensitive drum with a single light beam emitted from a light source at a predetermined timing is used. The synchronization of writing timing in the main scanning direction with respect to the photosensitive drum by the light beam is performed after the light beam is detected by a synchronization signal detection sensor (usually referred to as a BD sensor), and image information is written by the light beam after a predetermined time has elapsed. The method that started is used.

  In recent years, as the development of color image forming apparatuses is progressing, the printing process speed equivalent to that of a printing press is desired from the market. Therefore, the development of a higher printing process speed in the color image forming apparatus is desired.

However, there are a plurality of problems in increasing the printing processing speed.
In particular,
First, sensitivity characteristics of an electrostatic latent image carrier (photosensitive drum) for forming an image,
Secondly, image writing technology to the electrostatic latent image carrier,
Third, the followability of the developer that visualizes the electrostatic latent image,
Fourth, transport technology that transports paper with high speed and accuracy,
Fifth, high-speed fixing technology that fixes unfixed developer on paper to paper,
Etc.

  Therefore, in order to increase the image writing processing speed, a number of so-called multi-beam writing techniques have been developed in which high-speed processing is performed using a plurality of different light beams for each line, instead of speeding up with one light beam. ing.

  For example, in a color image forming apparatus, a plurality of recording light sources that are independently modulated and driven according to image information signals are provided obliquely with respect to the main scanning direction, and a plurality of beams emitted from these recording light sources. Has been proposed that performs scanning by deflecting scanning in the main scanning direction with a common rotating polygonal mirror, and focusing and imaging as a minute spot on a recording medium by an imaging optical system (Patent) See reference 1.)

As another example, in a color image forming apparatus, a light source unit that synthesizes and emits two laser beams that are modulated by writing information of different colors and have different deflection directions, and 2 emitted from the light source unit. Deflection means for deflecting the two laser beams in the main scanning direction, separation deflection means for separating the two laser beams deflected by the deflection means, and each laser beam separated by the deflection separation means as one photosensitive Use of a multi-beam scanning device comprising an imaging means for imaging at different positions on the body and a drive control means for controlling the laser beam from the light source unit improves the maintainability of the multi-beam scanning device. At the same time, an improvement in the color overlay accuracy has been proposed (see Patent Document 2).
Japanese Patent Laid-Open No. 06-233074 JP 09-127444 A

  However, in the conventional method described above, when writing is performed using a plurality of laser beams, the respective laser beams are detected by a synchronization signal detection sensor to synchronize the writing timing in the main scanning direction with respect to the photosensitive drum. I need to take it. For this reason, in order to increase the printing processing speed, a synchronization signal detection sensor with good light receiving sensitivity is required.

  Actually, since the light receiving sensitivity of the synchronization signal detection sensor is related to the time for which the laser beam is attenuated after the detection, the higher the speed, the higher the sensitivity and the higher the sensitivity, and the higher the cost.

  Further, as the printing processing speed is increased, the usage of the synchronization signal detection sensor is increased, so that the deterioration is easily caused.

  Furthermore, the multi-beam method has a problem that the printing process control becomes complicated because the timing of writing by a plurality of laser beams is synchronized.

  The present invention has been made in view of the above-described conventional problems, and suppresses power deterioration of the light beam to extend the life of the light source, and suppresses deterioration of the synchronization signal detection sensor to prevent malfunction. At the same time, an object of the present invention is to provide an image forming apparatus in which the life of the synchronization detection sensor is extended.

  Each configuration of the image forming apparatus according to the present invention for solving the above-described problems is as follows.

  The image forming apparatus according to claim 1 includes a synchronization signal detection sensor that reads a synchronization timing when the image carrier is irradiated with a light beam emitted from a light source, and a light beam based on the synchronization signal from the synchronization signal detection sensor. A control means for controlling the image, an exposure means for generating image information as an electrostatic latent image on the image carrier by a plurality of light beams, and an image carrier by a developer that matches each hue according to the color-separated image information In the image forming apparatus comprising: an image forming unit that forms a developer image based on the electrostatic latent image generated on the body, wherein the developer image formed on the image carrier is transferred; The means is controlled so as to take the synchronization timing of the light beams from the other light sources based on the synchronization timing of the light beams from the light sources selected from among the plurality of light sources. It is intended.

  In addition to the configuration described in claim 1, the image forming apparatus described in claim 2 is configured such that the synchronization timing of the light beam from the other light source is synchronized with the synchronization timing of the light beam from the selected light source and the image carrier. It is characterized in that it is positioned in between the write timing of.

  The image forming apparatus described in claim 3 is configured such that, in addition to the configuration described in claim 1 or 2, the selected light source can be switched to another light source according to the operating conditions of the image forming apparatus. It is a feature.

  The operating conditions of the image forming apparatus include operating conditions of the apparatus, printing conditions, image writing conditions, and the like.

  Specifically, in the case of operating conditions of the apparatus, for example, the light source is switched according to the ON / OFF state of the apparatus power supply, the operation (energization) time of the apparatus, the number of operation days, and the like.

  Also, depending on the printing conditions, for example, the printing time, the number of print jobs, the number of print processes performed, the number of rotations of the photosensitive drum, the odd color (first color, third color) and even color (2) The light source is switched according to the color, the third color), the developer replenishment timing, and the like.

  Further, when the image information writing condition is used, the light source is switched in accordance with, for example, the number of detections of the synchronization signal detection sensor, the rotation speed of the polygon mirror, the irradiation time of the light beam, and the like.

  According to the first to third aspects of the present invention, in the image forming apparatus, the synchronization signal detection sensor for reading the synchronization timing when the light beam emitted from the light source is irradiated on the image carrier, and the synchronization signal detection sensor A control means for controlling the light beam based on the synchronization signal, an exposure means for generating image information as an electrostatic latent image on the image carrier by a plurality of light beams, and for each hue according to the color-separated image information. Image forming means for forming a developer image based on the electrostatic latent image generated on the image carrier by the matched developer, and transferring the developer image formed on the image carrier. In the image forming apparatus, the control unit is controlled to obtain the synchronization timing of the light beams from the other light sources based on the synchronization timing of the light beams from the light sources selected from the plurality of light sources. By doing so, the number of times of detection of the light beam by the synchronization signal detection sensor can be reduced, so that the power degradation of the light beam is suppressed to extend the life of the light source, and the malfunction of the synchronization signal detection sensor is suppressed. In addition to preventing this, it is possible to extend the life of the synchronous detection sensor.

  In addition to the common effects obtained by the inventions according to claims 1 to 3, the following effects can be obtained according to the inventions described in the claims.

  Specifically, according to the second aspect of the invention, the synchronization timing of the light beam from the other light source is positioned between the synchronization timing of the light beam from the selected light source and the writing timing to the image carrier. By doing so, the synchronization timing of the light beams from other light sources can be measured reliably.

  According to the invention described in claim 3, the selected light source can be switched to another light source according to the operating conditions of the image forming apparatus, so that the light source for synchronizing timing is limited and used. Without using the light source, the life of the light source can be extended by selectively using a plurality of light sources.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1 to 4 are examples of embodiments for carrying out the invention. FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an image constituting the image forming apparatus. FIG. 3 is an explanatory diagram showing a schematic configuration of a processing unit, FIG. 3 is an explanatory diagram showing an example of image writing processing by a laser beam scanner unit and a photosensitive drum that form a black component image constituting the image forming apparatus, and FIG. It is explanatory drawing which shows the structure of the image writing process in a forming apparatus.

First, an outline of the image forming apparatus of the present embodiment will be described.
The image forming apparatus 1 according to the present embodiment performs so-called copying in which an image of a document is read and the same image is recorded on a recording sheet. As shown in FIG. A document table 111 is provided, and an operation panel (not shown) is provided near the document table 111.

An image reading unit 110 and an image forming unit 210 are provided inside the apparatus main body 1a.
On the document table 111, a double-sided automatic document feeder (RADF) 112 supported so as to be openable and closable with respect to the document table 111 is provided.

The double-sided automatic document feeder 112 conveys the document to a predetermined position on the document table 111 so that the document is opposed to the image reading unit 110, and after the image reading unit 110 finishes reading an image on one side of the document, Then, the document is conveyed again to a predetermined position on the document table 111 so that the image reading unit 110 can read an image on the other side of the document.
Then, when the image reading on both sides of the document is completed, the duplex automatic document feeder 112 discharges the document, and transports and inverts the next other document.

  Such document conveyance and reversal operations are controlled in relation to the overall operation of the image forming apparatus 1. Of course, it is also possible to discharge the original document only by reading an image on one side of the document and not reading the other side.

The image reading unit 110 reads an image of a document conveyed on the document table 111 by the double-sided automatic document feeder 112.
The image reading unit 110 includes first and second document scanning bodies 113 and 114 that reciprocate in parallel along the lower surface of the document table 111, an optical lens 115, and a CCD line sensor 116 that is a photoelectric conversion element. .

  The first document scanning body 113 reciprocates in parallel at a predetermined scanning speed while maintaining a certain distance with respect to the lower surface of the document table 111, and an exposure lamp that exposes the document surface and reflected light from the document. Has a first mirror for deflecting in a predetermined direction.

  The second document scanning body 114 reciprocates in parallel with the first document scanning body 113 while maintaining a constant speed relationship, and the reflected light from the document passes through the first mirror of the first document scanning body 113. The second and third mirrors are further provided for deflecting the reflected light in a predetermined direction.

  The optical lens 115 receives the reflected light of the original deflected by the second and third mirrors of the second original scanning body 113, collects the reflected light, and projects the optical image on the CCD line sensor 116. is there.

  The CCD line sensor 116 sequentially photoelectrically converts the light image, thereby reading a black and white image or a color image, and outputting an image signal indicating the image. The CCD line sensor 116 is a three-line color CCD that outputs line data color-separated into R (red), G (green), and B (blue) color components as an image signal.

  Here, when scanning by the first and second document scanning bodies 113 and 114 is sub-scanning, and scanning by the CCD line sensor 116 is main scanning, a plurality of main scannings are repeated during one sub-scanning, As a result, the image on the original is read. During this reading, the CCD line sensor 116 repeatedly outputs line data corresponding to each pixel on the main scanning line, and these line data (image signals) are continuously obtained. This image signal is transferred to an image processing unit described later and processed.

On the other hand, below the image forming unit 210, a paper feeding mechanism 211 that separates recording sheets (recording media) P one by one and supplies them to the image forming unit 210 is provided.
The recording paper P is cut sheet-like paper, is stacked and accommodated in a paper tray, separated one by one by the paper feeding mechanism 211, and supplied to the image forming unit 210.

  The recording paper P is guided to a pair of registration rollers 212 arranged in front of the image forming unit 210, and when the leading edge of the recording paper P is detected by a sensor (not shown), in response to a detection signal of the sensor. The recording paper P is temporarily stopped by each registration roller 212, and then the recording paper P is conveyed to the image forming unit 210 while the conveyance timing is controlled by each registration roller 212. The image forming unit 210 records an image on one side of the recording paper P.

  Thereafter, the recording paper P is turned upside down and guided again to the registration rollers 212, the image is recorded on the other surface of the recording paper P by the image forming unit 210, and the recording paper P is discharged. Of course, it is also possible to record the recording paper P only by recording an image on one side of the recording paper P and without recording an image on the other side.

A transfer conveyance belt mechanism 213 is arranged below the image forming unit 210.
The transfer / conveying belt mechanism 213 includes a driving roller 214, a driven roller 215, and a transfer / conveying belt 216 stretched between the rollers 214 and 215, and electrostatically adsorbs the recording paper P onto the transfer / conveying belt 216. While conveying in the direction of arrow Z.
During the conveyance by the transfer conveyance belt mechanism 213, a toner image is transferred and formed on the recording paper P as described later.

  A sheet adsorbing (brush) charger 228 is disposed immediately after each registration roller 212, and charges the transfer conveyance belt 216 so that the recording sheet P is reliably adsorbed onto the transfer conveyance belt 216. Transport in 210.

  A static eliminator 229 is provided between the image forming unit 210 and the fixing device 217. The static eliminator 229 is applied with an alternating current for peeling the recording paper P electrostatically attracted to the transfer conveyance belt 216 from the transfer conveyance belt 216.

The fixing device 217 includes a pair of fixing rollers, receives the recording paper P from the transfer conveyance belt mechanism 213, passes the recording paper P through the nip portion between these fixing rollers, and thereby on the recording paper P. The transferred toner image is fixed.
Thereafter, the recording paper P is discharged to a paper discharge tray 220 attached to the outer wall of the apparatus main body 1 a by a discharge roller 219 through a conveyance switching gate 218.

  The switching gate 218 selectively switches a path for discharging the fixed recording paper P to the paper discharge tray 220 and a path for supplying the fixed recording paper P to the image forming unit 210 again. When the recording paper P is supplied again to the image forming unit 210 by the switching gate 218, the recording paper P is turned upside down via the switchback conveyance path 221 and then guided to the image forming unit 210.

  The first image forming station Pa, the second image forming station Pb, the third image forming station Pc, and the fourth image forming unit are located near the upper side of the transfer conveying belt 216 in the image forming unit 210 and from the upstream side of the conveying path of the recording paper P. Stations Pd are juxtaposed.

As described above, the recording paper P on the transfer conveyance belt 216 is conveyed in the arrow Z direction.
As a result, the recording paper P passes through the first, second, third and fourth image forming stations Pa, Pb, Pc, Pd in the order described.

  The first to fourth image forming stations Pa to Pd have substantially the same configuration, and include respective photosensitive drums 222a, 222b, 222c, and 222d that are rotationally driven in the direction of arrow F.

  In the vicinity of the photosensitive drums 222a to 222d, the chargers 223a, 223b, 223c, and 223d for uniformly charging the photosensitive drums 222a to 222d, and the electrostatic latent images on the photosensitive drums 222a to 222d, respectively. Developing units 224a, 224b, 224c, 224d, developing each electrostatic latent image on each photosensitive drum 222a-222d to form each toner image Each of the transfer dischargers 225a, 225b, 225c, 225d for transferring the toner images on the photosensitive drums 222a to 222d onto the recording paper P, and the toners remaining on the photosensitive drums 222a to 222d are removed. Each cleaning device 226a, 226b, 226c, 226d is disposed.

  Each of the laser scanner units 227a to 227d deflects a semiconductor laser element (not shown) as a light source that emits a laser beam (light beam) modulated according to an image signal, and a laser beam from the semiconductor laser element in the main scanning direction. Polygon mirror (deflecting device) 240, an fθ lens 241 for focusing the laser beam deflected by the polygon mirror 240 on each of the photosensitive drums 222a to 222d, and mirrors 242, 243, and the like. Yes.

  The laser beam scanner unit 227a receives an image signal corresponding to the black component image of the color image, modulates the laser beam according to the image signal, and irradiates the photosensitive drum 222a with the laser beam corresponding to the black component image. .

  The laser beam scanner unit 227b receives an image signal corresponding to the cyan component image of the color image, modulates the laser beam according to the image signal, and applies the laser beam corresponding to the cyan component image to the photosensitive drum 222b. Irradiate.

  The laser beam scanner unit 227c receives an image signal corresponding to the magenta color component image of the color image, modulates the laser beam in accordance with the image signal, and applies the laser beam corresponding to the magenta color component image to the photosensitive drum 222c. Irradiate.

  The laser beam scanner unit 227d receives an image signal corresponding to the yellow color component image of the color image, modulates the laser beam according to the image signal, and applies the laser beam corresponding to the yellow color component image to the photosensitive drum 222d. Irradiate.

  In this way, the photosensitive drum is exposed by the laser beam, so that the electrostatic latent image of the black component image, the electrostatic latent image of the cyan component image, and the magenta color component are formed on each of the photosensitive drums 222a to 222d. An electrostatic latent image of an image and an electrostatic latent image of a yellow color component image are formed.

  The developing device 224a contains black toner, and the black toner adheres to the electrostatic latent image of the black component image on the photosensitive drum 222a, thereby developing the black toner image.

  The developing device 224b contains cyan toner, and the cyan toner adheres to the electrostatic latent image of the cyan component image on the photosensitive drum 222b, thereby developing the cyan toner image. The

  The developing device 224c contains magenta toner, and the magenta toner adheres to the electrostatic latent image of the magenta component image, thereby developing the magenta toner image.

  The developing device 224d contains yellow toner, and this yellow toner adheres to the electrostatic latent image of the yellow color component image, thereby developing the yellow toner image.

  As the photosensitive drums 222a to 222d rotate, the photosensitive drums 222a to 222d are sequentially pressed against the recording paper P on the transfer conveyance belt 216, and the toner images on the photosensitive drums 222a to 222d are recorded on the recording paper P. The images are sequentially superimposed and transferred on top.

  Thereafter, the recording paper P is conveyed to the discharger 229 for discharging, the static electricity is discharged by the discharger 229 for discharging, and peeled off from the transfer transfer belt 216 and guided to the fixing device 217. The fixing device 217 fixes the toner image transferred and formed on the recording paper P onto the recording paper P.

  The recording paper P is discharged to the paper discharge tray 220 by the discharge roller 219 via the transfer switching gate 218 or turned upside down from the switching gate 218 via the switchback transfer path 221 and then to the image forming unit 210. Guided again.

  Here, the laser scanner units 227a to 227d write images on the photosensitive drums 222a to 222d, but instead of the laser scanner units 227a to 227d, they are connected to a light emitting diode array serving as a light source. A writing optical system (LED head) composed of an image lens array may be used.

  This LED head is smaller in size than the laser scanner unit, has no moving parts, and has no operating sound. For this reason, an LED head is suitable for an image forming apparatus such as a tandem digital color copying machine that requires a plurality of writing units.

Next, the configuration and function of the image processing unit in the image forming apparatus 1 of the present embodiment will be described with reference to the drawings.
In FIG. 2, the same reference numerals are given to portions that perform the same function as in FIG. 1, and description thereof is omitted.

  The image processing unit includes an image data input unit 40, an arithmetic processing unit 41, an image memory 43 including a hard disk device or a RAM (random access memory), an image data output unit 42, a CPU (central processing unit) 44, an image An editing unit 45 and external interfaces 46 and 47 are provided.

  The image data input unit 40 reads a black and white image or a color image on a document and outputs line data that is color-separated into R, G, and B (red component, green component, blue component) as an image signal. The shading correction circuit 40b for correcting the level of the image signal output from the CCD 116, the line matching unit 40c including a line buffer for correcting the shift of the line data of each color read by the three-line CCD 116, the line data for each color A sensor color correction unit 40d that performs color correction on the image, an MTF correction unit 40e that corrects the line data of each color in order to give a change to each pixel, and a gamma correction that corrects the brightness of the image and corrects the visibility. It consists of a correction unit 40f and the like.

  The arithmetic processing unit 41 generates monochrome data generation units 41a, R, and R that generate image signals indicating monochrome images (monochrome images) from the line data (R, G, and B image signals) of the respective colors from the image data input unit 40. G, B image signals of C, M, Y (cyan color component, magenta color component, yellow color component) corresponding to the second, third and fourth image forming stations Pb, Pc, Pd of the image forming unit 210 are displayed. An input processing unit 41b that converts to each image signal and performs clock conversion, a region separation unit 41c that separates the image indicated by the image signal into a character region, a halftone dot photo region, and a photographic paper photo region, and an input processing unit 41a A black generation unit 41d that performs undercolor removal processing based on the C, M, and Y image signals to generate a K (black component) image signal, and converts the C, M, and Y image signals based on the color conversion tables. Each color correction circuit 41e for correcting each color, each zoom processing circuit 41f for processing an image signal so that the image is enlarged / reduced according to a designated magnification, each spatial filter 41g, each print data input unit 41i And halftone processing units 41h for expressing gradation such as multilevel error diffusion and multilevel dither.

  The C, M, Y, and K image signals processed by each halftone processing unit 41 h of the arithmetic processing unit 41 are temporarily stored in the image memory 43. Each image signal of C, M, Y, and K is 8 bits (32 bits in 4 colors of C, M, Y, and K) that are serially output for each pixel. The Y and K image signals are stored in the hard disks 43a, 43b, 43c and 43d as image data of the respective colors.

  Since the first, second, third, and fourth image forming stations Pa, Pb, Pc, and Pd of the image forming unit 210 are spaced apart from each other, the respective image forming timings by these image forming stations. Is different. For this reason, the image data of each color in each hard disk 43a, 43b, 43c, 43d is temporarily stored in each delay buffer memory 43e, and each image formation is performed as an image signal of each color after given each delay time. Sent to the station. As a result, the respective images are superimposed on the same recording paper P at each image forming station without shifting.

  The image data output unit 42 includes the laser scanner units 227a to 227d and the laser control units 42a to 42d that modulate the drive signals of the laser scanner units 227a to 227d in accordance with the image signals of the respective colors from the image memory 43. 42d. Each of the laser scanner units 227a to 227d receives respective pulse width modulated drive signals, and controls the output level of the laser beam in accordance with these drive signals.

  The CPU 44 comprehensively controls the image processing unit, and includes an image data input unit 40, an arithmetic processing unit 41, an image memory 43, an image data output unit 42, an image editing unit 45, and external interfaces 46, 47 is controlled based on a predetermined sequence.

  The image editing unit 45 is for performing predetermined image editing processing on the image data in the image memory 43, and performs this editing processing in the image memory 43. The image data in the image memory 43 is input from the image data input unit 40 or the external interface 46 (or 47) and processed by the arithmetic processing unit 41.

  The external interface 46 is a communication interface for receiving image data from an external terminal (communication portable terminal, digital camera, digital video camera, etc.). The image data input from the external interface 46 is converted into data that can be handled by the image forming unit 210 by being once input to the arithmetic processing unit 41 of the image processing unit and subjected to color space correction or the like. Stored in the memory 43.

  The external interface 47 is for inputting image data created by a personal computer or image data by FAX reception, and can input either monochrome or color image data. The image data input through the external interface 47 is already an image signal of C, M, Y, K, and is stored and managed in the image memory 43 after being processed by the halftone processing unit 41h.

In the image forming apparatus 1 of the present embodiment, a laser beam scanner unit 227a is configured as shown in FIG.
The laser beam scanner unit 227a includes two semiconductor laser elements 11 and 12, which are laser light sources, a beam splitter 13, a polygon mirror 240, an fθ lens 241, a synchronization sensor (synchronization signal detection sensor) 244, and mirrors (not shown). Etc.). Each of the semiconductor laser elements 11 and 12 includes a pair of laser beam light emitting units (light sources) 11a, 11b, 12a, and 12b, and therefore, a total of four laser beam light emitting units are provided.

  The laser beams La1, La2, La3, La4 emitted from the laser beam emitting units 11a, 11b, 12a, and 12b are deflected by the beam splitter 13, reflected by the polygon mirror 240 that rotates at high speed, and the photosensitive drum. The light is incident on 222a and scans on the photosensitive drum 222a.

  The synchronization sensor 244 detects a laser beam emitted from a laser beam emission unit selected from the laser beam emission units 11a, 11b, 12a, and 12b and outputs a synchronization signal. In the present embodiment, the laser beam emission unit 11a is specified as a light source for irradiating the synchronization sensor 244 with a laser beam, and the laser beam La1 emitted from the laser beam emission unit 11a is detected.

  The image writing process to the photosensitive drum 222a by the laser beams La1, La2, La3, La4 emitted from the laser beam emitting units 11a, 11b, 12a, 12b is synchronized with the laser beam La1 detected by the synchronization sensor 244. Based on the signal (input signal), the CPU 44 controls the laser beam La1, L2, L3, L4 to synchronize the writing timing in the main scanning direction on the photosensitive drum.

  The other laser beam scanner units 227b, 227c, and 227d include a semiconductor laser element serving as a light source that emits only one laser beam, a polygon mirror, an fθ lens, and each mirror.

  In addition, image writing processing on the photosensitive drums 222b, 222c, and 222d in the other laser beam scanner units 227b, 227c, and 227d is also performed on the photosensitive drums 222b, 222c, and 222d based on the synchronization signal of the laser beam La1. Control is performed so as to synchronize writing timing in the scanning direction.

  Here, when the recording of the color image is instructed by the input operation of the operation panel (not shown), the CPU 44 sets the first image forming mode, and is instructed to record the monochrome image by the input operation of the operation panel. Then, the second image forming mode is set. Alternatively, the image data input through the external interfaces 46 and 47 includes data indicating whether the image is a color image or a monochrome image.

  When the image data is input through the external interfaces 46 and 47, the CPU 44 determines whether the image is a color image or a monochrome image based on the image data. If the image is a color image, the CPU 44 sets the first image formation mode. If the image is black and white, the second image forming mode is set.

  When the first image forming mode is set when forming a color image, the CPU 44 switches the selector 14 to connect the laser control units 42b to 42d to the respective laser beam scanner units 227b to 227d as shown in FIG. To do. In this state, the semiconductor laser elements of the laser beam scanner units 227b to 227d are controlled to blink by the laser control units 42b to 42d, and the respective laser beams are emitted from the laser beam scanner units 227b to 227d. By the beam, an electrostatic latent image of a cyan color component image, an electrostatic latent image of a magenta color component image, and an electrostatic latent image of a yellow color component image are formed on each of the photosensitive drums 222b to 222d.

  At substantially the same time, the CPU 44 instructs the laser control unit 42a to control only one laser beam light emitting section of one semiconductor laser element 11 of the laser beam scanner unit 227a. In response to this, the laser control unit 42a controls blinking of only one laser beam emission part of one semiconductor laser element 11, and emits one laser beam La from this laser beam emission part. The laser beam La enters the photosensitive drum 222a via the beam splitter 13, the polygon mirror 240, and the like, scans the photosensitive drum 222a, and forms an electrostatic latent image of a black component image on the photosensitive drum 222a. To do.

  Therefore, in the laser beam scanner unit 227a, only one laser beam light emitting portion of one semiconductor laser element 11 is used when forming a color image. One laser beam emitting section 11a of the semiconductor laser element 11 is controlled to blink by the laser control unit 42a, emits one laser beam La1 to the photosensitive drum 222a, and forms a black component image on the photosensitive drum 222a. An electrostatic latent image is formed.

  Further, when the second image forming mode is set when forming the monochrome image, the CPU 44 switches the selector 14 to connect the laser control units 42b to 42d to the laser beam scanner unit 227a as shown in FIG.

  As a result, a pair of laser beam emitting units of each semiconductor laser element 11 and 12 of the laser beam scanner unit 227a, that is, a total of four laser beam emitting units 11a, 11b, 12a and 12b are controlled by the four laser control units 42a to 42d. It becomes possible to do.

  That is, the laser control unit 42 a controls blinking of one laser beam light emitting unit 11 a of the semiconductor laser element 11. Each of the other laser control units 42 b to 42 d controls blinking of the other laser beam emitting unit 11 b of the semiconductor laser element 11 and the pair of laser beam emitting units 12 a and 12 b of the semiconductor laser element 12. However, at this time, the other laser beam scanner units 227b to 227d are not used.

  Each of the laser control units 42a to 42d receives the image data of the black component image in the buffer memory 43e of the image memory 43 by mutually allocating in units of scanning lines, and according to the data of each scanning line, the laser beam scanner unit 227a. The four laser beam light emitting units 11a, 11b, 12a, and 12b are controlled to blink.

  For example, the 1 + 4nth scan line data is allocated to the laser control unit 42a, the 2 + 4nth scan line data is allocated to the laser control unit 42a, the 3 + 4nth scan line data is allocated to the laser control unit 42a, and the 4 + 4nth scan line data is allocated. Scan line data is allocated to the laser control unit 42a. However, n = 0, 1, 2,.

As a result, as shown in FIG. 3, the respective laser beams La1, La2, La3, and La4 are incident on the photosensitive drum 222a, and four scanning lines are simultaneously scanned on the photosensitive drum 222a. An electrostatic latent image of a black component image is formed on the drum 222a.

  When forming a color image, each scanning line is sequentially scanned on the photosensitive drum 222a by one laser beam La1, whereas when forming a monochrome image, four laser beams La1, Four scanning lines are sequentially scanned on the photosensitive drum 222a by La2, La3, and La4. For this reason, the rotation speed of the photosensitive drum 222a is quadrupled for black and white images. As a result, the monochrome image formation time is shortened to ¼ of the color image formation time.

  As described above, in the present embodiment, the laser beam scanner unit 227a for forming the black component image is provided with four laser beam light emitting units, and when the black and white image is formed, the four laser control units 42a to 42d provide four laser beam emission units. The laser beam emitters 11a, 11b, 12a, and 12b are controlled to blink, and four laser beams La1, La2, La3, and La4 are incident on the photosensitive drum 222a, and each scanning line is sequentially scanned four by four. Therefore, the monochrome image formation time can be shortened to ¼ of the color image formation time.

Next, the image writing process on the photosensitive drum by the laser beam in this embodiment will be described by taking the image writing process in the laser beam scanner unit 227a as an example.
FIG. 5 illustrates an example of the relationship between the synchronization timing of a plurality of laser beams and the image writing timing in a K (black) laser beam scanner unit when a black component image is formed by the image forming apparatus according to the present embodiment. FIG.

  When the image forming apparatus 1 forms a black and white image, the photosensitive drum is formed by the laser beams La1, La2, La3, and La4 from the laser beam light emitting units 11a, 11b, 12a, and 12b provided in the black laser beam scanner unit 227a. The image writing process to 222a is controlled by the CPU 44 and the laser control units 42a to 42d.

  The CPU 44 uses the laser beams La2, La3, and La4 emitted from the laser beam emitting units 11b, 12a, and 12b, respectively, based on the synchronization signal Sa1 that is output from the synchronization sensor 244 and emitted from the laser beam emitting unit 11a. It has a function of controlling so as to synchronize the writing timing in the main scanning direction to the photosensitive drums 222b, 222c, and 222d.

  In the laser beam scanner unit 227a, as shown in FIG. 5, the writing timing of the laser beams L2, L3, and L4 emitted from the laser beam emitting units 11b, 12a, and 12b by the CPU 44 based on the synchronization signal Sa1 of the laser beam La1. It is made to measure.

  The laser control units 42a to 42d control the laser beam emitting units 11a, 11b, 12a, and 12b, and image information is written on the photosensitive drum 222a.

In the figure, reference numeral T1 is a synchronization signal detection position of the laser beam La1, T2 is a writing start position, T3 is a synchronization signal detection position of the laser beam La3, and a is image writing after detecting the synchronization signal of the laser beam La1. The time to start, b denotes the time from the detection of the synchronization signal of the laser beam La3 to the start of image writing.
Symbols Sa2, Sa3, and Sa4 are synchronization signals of the laser beams La2, La3, and La4 output from the synchronization sensor 244.

  According to the present embodiment, since the same photosensitive drum 222a is written with a plurality of lines by a plurality of laser beams, the position at which image writing in the scanning direction is started is the same, and thus, for example, a plurality of laser beams are supported. Even when the synchronizing sensors are provided at positions where the distances to the positions where writing by each laser beam is started are different, image writing by another laser beam based on the synchronizing signal Sa1 of one laser beam La1. Timing can be controlled.

  In this embodiment, the laser beam light emitting unit 11a is selected as the light source of the laser beam La1 for outputting the synchronization signal Sa1, but the light source of the laser beam for outputting the synchronization signal is limited to this. Instead of this, any one of the laser beam emitters 11b, 12a, 12b may be used.

  For example, as a modification of the present embodiment, as shown in FIG. 6, based on the synchronization signal Sa3 of the laser beam La3, the CPU 44 performs image writing of the laser beams L1, L2, and L4 by the laser beam emitting units 11a, 11b, and 12b. The timing may be measured.

  Further, the laser beam emitting units 11a, 11b, 12a, and 12b may be switched and used sequentially according to the operating conditions of the image forming apparatus 1.

  Specifically, any one of the laser beam light emitting units 11a, 11b, 12a, and 12b is used as the light source of the laser beam emitted to the synchronization sensor 244 every time the power source of the image forming apparatus 1 is turned on / off. May be selected sequentially.

  Further, the switching of the laser beam light source may be performed sequentially every operation (energization) time of the apparatus or every operation days.

Next, image writing processing when a color image is formed by the image forming apparatus according to the present embodiment will be described.
FIG. 7 is an explanatory diagram showing an example of the relationship between laser beam synchronization timing and image writing timing in a plurality of laser beam scanner units forming a color image constituting the image forming apparatus according to the present embodiment.

  When a color image is formed in the image forming apparatus 1, laser beam scanner units 227a to 227d for K, C, M, and Y are used.

  Image writing processing to the photosensitive drums 222a to 222d by the laser beams La1, Lb, Lc, and Ld from laser beam light emitting units (not shown) provided in the laser beam scanner units 227a to 227d is performed by the CPU 44 and the laser control. It is controlled by the units 42a to 42d.

  The CPU 44 performs photosensitivity by the laser beams La1, Lb, Lc, and Ld emitted from the respective laser beam light emitting units based on the synchronization signal Sa1 by the laser beam La1 from the laser beam light emitting unit 11a output from the synchronization sensor 244. The main drums 222a, 222b, 222c, and 222d have a function of controlling to synchronize the writing timing in the main scanning direction.

  In the laser beam scanner units 227a to 227d, as shown in FIG. 7, the CPU 44 provides the laser beam scanner units 227b to 227d with the synchronization signal Sa1 of the laser beam La1 provided to the laser beam scanner unit 227a, respectively. The writing timing of the laser beams Lb, Lc, and Ld emitted from the laser beam emitting unit is measured.

Then, image information is written onto the photosensitive drums 222a to 222d by the laser beams La, Lb, Lc, and Ld from the respective laser beam emitting units controlled by the laser control units 42a to 42d.
In the figure, reference numeral Ta1 denotes a synchronization signal detection position of the laser beam La1, Ta2 denotes a writing start position, and a1 denotes a time from when the synchronization signal of the laser beam La is detected until image writing is started. .

  According to this embodiment, the synchronization signal detection positions Tb1, Tc1, and Td1 of the laser beams Lb, Lc, and Ld from the laser beam emitting units of the laser beam scanner units 227b to 227d are converted into the laser beam emitting unit of the laser beam scanner unit 227a. 11a is positioned between the synchronization signal detection position Ta1 of the laser beam La1 and the writing start position Ta2 to the photosensitive drum 222a, so that the image writing timing by another laser beam is set based on the synchronization signal of one laser beam. Can be controlled. That is, the timing of image writing by each of the laser beams La to Ld can be measured based on any synchronization timing of the laser beams La to Ld.

  Therefore, in this embodiment, the laser beam light emitting unit 11a of the laser beam scanner unit 227a is selected as the laser beam light source for detecting the synchronization signal. However, the laser beam light source for detecting the synchronization signal is: However, the present invention is not limited to this, and any one of the laser beam emitting units of the laser beam scanner units 227a to 227d may be used.

  Further, the laser beam light sources of the laser beam scanner units 227a to 227d may be switched and used sequentially according to the operating conditions of the image forming apparatus 1.

  Specifically, any one of the laser beam light emitting units of the laser beam scanner units 227a to 227d is used as a light source of a laser beam emitted to the synchronization sensor 244 every time the power supply of the image forming apparatus 1 is switched ON / OFF. One of them may be selected sequentially.

  Further, the switching of the laser beam light source may be performed sequentially every operation (energization) time of the apparatus or every operation days.

  Further, when switching the light source of the laser beam depending on the printing conditions, for example, the printing time, the number of printing jobs, the number of printing processes performed, the number of rotations of the photosensitive drum, a plurality of laser beam scanner units arranged in parallel The light source may be switched according to the odd-numbered color (first color, third color) and even-numbered color (second color, third color), the developer replenishment timing, and the like.

  Further, when the laser beam emitting unit is switched according to the image information writing condition, for example, the laser beam emitting unit may be switched according to the number of detections of the synchronization sensor 244, the rotation number of the polygon mirror 240, the irradiation time of the laser beam, and the like.

  In this embodiment, the synchronization timing of the laser beams Lb, Lc, and Ld from the laser beam emitting units of the laser beam scanner units 227b to 227d is synchronized with the laser beam La1 from the laser beam emitting unit 11a of the laser beam scanner unit 227a. Although it is located between the signal detection position Ta1 and the writing start position Ta2 to the photosensitive drum 222a, the present invention is not limited to this, and the synchronization timing by all the laser beams depends on the apparatus layout and the like. It does not have to be located between the synchronization signal detection position of one laser beam and the writing start position on the photosensitive drum.

  For example, as a modification of the present embodiment, as shown in FIG. 8, the synchronization signal detection positions Tb11 and Tb11 of the laser beams Lb and Lc are positioned between the synchronization signal detection position Ta11 of the laser beam La1 and the write start position Ta12. However, the synchronization signal detection position Td11 of the laser beam Ld is off, and the synchronization signal detection position Td11 of the laser beam Ld is positioned between the synchronization signal detection position Tc11 of the laser beam Lc and the writing start position Tc12. If there is, the synchronization timing of the laser beams Lb and Ld may be measured by the synchronization timing of the laser beams La1 and Lc, respectively.

In the figure, symbol a1 indicates the time from when the synchronization signal of the laser beam La1 is detected until image writing is started, and a2 indicates the time after the detection of the synchronization signal of the laser beam Lc until image writing is started. It is shown.
Symbols Sa1, Sb, Sc, and Sd are synchronization signals of the laser beams La1, Lb, Lc, and Ld output from the synchronization sensor 244.

  In this case, since one synchronization signal detection sensor is used for two laser beams, two synchronization signal detection sensors are required. Compared to the case where a synchronization signal is detected for each laser beam, the laser beam This makes it possible to extend the life of the light source and the sync signal detection sensor and to simplify the control of the image writing timing.

  In addition, the laser beam light source used for obtaining the synchronization timing is used sequentially by switching the light source of each laser beam according to the operating conditions of the image forming apparatus, as in the above-described embodiment. It may be a thing.

  Note that the image device of the present invention is not limited to the above-described embodiments and modifications, and can be variously modified. For example, the number of laser beam emission units or the number of laser beams in the laser beam scanner unit 227a may be changed. For example, a two-beam type scanner unit provided with two single emission laser emission units or a two-beam type scanner unit provided with one twin emission laser emission unit may be used.

  In addition, the image forming apparatus of the present invention can be variously modified without departing from the gist of the present invention.

1 is an explanatory diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating a schematic configuration of an image processing unit configuring the image forming apparatus. FIG. 4 is an explanatory diagram illustrating an example of an image writing process by a laser beam scanner unit that forms a black component image and a photosensitive drum constituting the image forming apparatus. FIG. 4 is an explanatory diagram illustrating a configuration of image writing processing in the image forming apparatus. FIG. 5 is an explanatory diagram illustrating an example of a relationship between a synchronization timing of a plurality of laser beams and an image writing timing in a K (black) laser beam scanner unit when a black component image is formed by the image forming apparatus. It is explanatory drawing which shows the other example of the relationship between the synchronous timing of several laser beams in the said laser beam scanner unit, and image writing timing. FIG. 4 is an explanatory diagram illustrating an example of a relationship between laser beam synchronization timing and image writing timing in a plurality of laser beam scanner units forming a color image constituting the image forming apparatus. It is explanatory drawing which shows the other example of the relationship between the synchronous timing of a laser beam and image writing timing in the said several laser beam scanner unit.

Explanation of symbols

1 Image forming apparatus 11, 12 Semiconductor laser element (light source)
11a, 11b, 12a, 12b Laser beam emitter (light source)
42a, 42b, 42c, 42d Laser control unit (control means)
44 CPU (control means)
222a, 222b, 222c, 222d Photosensitive drum (image carrier)
227a, 227b, 227c, 227d Laser beam scanner unit (exposure means)
244 Synchronous sensor (Synchronous signal detection sensor)
Pa First image forming station (image forming means)
Pb Second image forming station (image forming means)
Pc Third image forming station (image forming means)
Pd Fourth image forming station (image forming means)
La1, La2, La3, La4, Lb, Lc, Ld Laser beam (light beam)

Claims (3)

A synchronization signal detection sensor that reads a synchronization timing when the image carrier is irradiated with a light beam emitted from a light source; a control unit that controls the light beam based on a synchronization signal from the synchronization signal detection sensor; and a plurality of light beams An electrostatic latent image generated on the image carrier by an exposure unit that generates image information as an electrostatic latent image on the image carrier, and a developer that matches each hue according to the color-separated image information. An image forming unit that forms a developer image based on the image forming apparatus, and transfers the developer image formed on the image carrier.
The image forming apparatus according to claim 1, wherein the control unit performs control so as to obtain synchronization timing of light beams from other light sources based on synchronization timing of light beams from a light source selected from among a plurality of light sources.   2. The image formation according to claim 1, wherein the synchronization timing of the light beam from the other light source is located between the synchronization timing of the light beam from the selected light source and the writing timing to the image carrier. apparatus. The image forming apparatus according to claim 1, wherein the selected light source is switched to another light source according to an operating condition of the image forming apparatus.

Images