JP4575307B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention uses an optical scanning device in which a predetermined number of laser beams are synchronized and deflected in a predetermined direction at a constant speed, and an image forming point of each laser beam scans the surface of a photosensitive member, and the same. The present invention relates to an image forming apparatus such as a printer or a copying machine.

Conventionally, as an image forming apparatus of this type, a laser beam in the form of a beam modulated by an image density signal is reflected through a deflecting device having a polygon mirror, so that the imaging point of the laser beam is set on the surface of the photoreceptor. There has been proposed an optical scanning device that scans above to form an electrostatic latent image. In the image forming apparatus, the photosensitive member is moved at a predetermined speed in the sub-scanning direction orthogonal to the scanning direction, whereby an electrostatic latent image is formed on the surface of the photosensitive member, and then a toner image is formed by the developing device. After being formed, it is transferred to recording paper. In such an optical scanning device and an image forming apparatus, it is necessary to narrow the pitch of the laser beam in the sub-scanning direction because of a request for increasing the definition of the output image, and electrostatic latent potential is required due to a request for a higher processing speed. It is necessary to increase the image formation speed. Patent Documents 1 to 3 propose a multi-beam method in which a plurality of light sources are provided in one laser array (light emitting unit) and light beams from the respective light sources are emitted simultaneously in order to meet the above requirements.
Japanese Patent Publication No. 1-445065 Japanese Patent Publication No. 6-48846 JP-A-11-202230

  In the multi-beam method, although it is necessary to manufacture a plurality of light sources as close as possible on one laser array (light emitting unit), in particular, when a laser element in the red wavelength region is employed, the light beam is turned on. In addition, the thermal and electrical influences in the are large, and it is technically very difficult to manufacture a plurality of light sources as close as possible.

  In the multi-beam method, a method of narrowing the interval between image forming points formed by a plurality of laser beams by interlaced scanning with laser beams from a plurality of light sources can be adopted. Therefore, there is a limit to narrowing the interval between the imaging points, that is, the pitch in the sub-scanning direction. On the other hand, in order to increase the processing speed, it is conceivable to rotate a polygon mirror that reflects a plurality of laser beams at a high speed and scan the laser beam at a high speed. There is a limit to the high speed rotation, and in addition, there is a disadvantage that abnormal noise such as wind noise is generated at high speed rotation.

  The present invention has been made in view of the above circumstances, and it is possible to narrow the pitch in the sub-scanning direction and increase the processing speed while securing a certain distance between the plurality of light sources on the light emitting unit. An object of the present invention is to provide an optical scanning device and an image forming apparatus.

The invention according to claim 1 is an optical scanning device in which a predetermined number of laser beams are synchronized and deflected in a predetermined direction at a constant speed, and an image forming point of each laser beam scans the surface of the photosensitive member. Each of which has two laser emission sources, and the laser light from each of the laser emission sources has an imaging point at a predetermined sub-scanning pitch in a sub-scanning direction orthogonal to the scanning direction of the photosensitive member. 1 to 3, and the first and third light emitting units are configured such that each laser beam has two sub-scanning pitches equal to each other to obtain an imaging point , and the first One image forming point of the light emitting unit and one image forming point of the third light emitting unit are configured to be shifted by three sub scanning pitches in the sub scanning direction, and the second light emitting unit includes two during one image formation point of the laser beam of the laser emission source is a two imaging point of the laser beam of the first light emitting portion, Imaging point of square of the laser beam is characterized in that it has been configured to position between the two imaging point of the laser light of the third light emitting portion.

According to this configuration, each of the first to third light emitting units has two laser light sources, and the laser light from each laser light source is predetermined in the sub-scanning direction orthogonal to the scanning direction of the photosensitive member. It has an imaging point at a sub-scanning pitch. The first and third light emitting units are configured such that each laser beam has two sub-scanning pitches equal to each other to obtain an image forming point , and one image forming point of the first light emitting unit. And the image forming point of one of the third light emitting units are shifted from each other by 3 sub-scanning pitches in the sub-scanning direction, and the second light emitting unit is one of the two laser light sources. The imaging point of light is between the imaging points of the two laser beams of the first light emitting unit, and the imaging point of the other laser beam is between the imaging points of the two laser beams of the third light emitting unit. Since the structure is located between them, the pitch in the sub-scanning direction can be narrowed and the processing speed can be increased (increase in the number of prints) while simplifying manufacturing by securing a certain distance between the light sources. It becomes possible. The six laser beams are synchronized and deflected at a constant speed in a predetermined direction, and the image formation point of each laser beam is scanned on the surface of the photosensitive member.

According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the first to third light emitting units are arranged in series, and the second light emitting unit is located in the center. It is a feature. According to this configuration, since the light emitting units are arranged in the same manner as the relationship between the image formation point positions, adjustment based on the difference in arrangement is unnecessary, and the entire configuration is simplified correspondingly.

  According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the first to third light emitting units are laser beams in a red wavelength region. According to this configuration, there is an advantage that the pitch in the sub-scanning direction can be narrowed even in an apparatus in which the arrangement pitch of the light sources is a problem.

According to a fourth aspect of the present invention, there is provided the optical scanning device according to any one of the first to third aspects, a moving unit that moves the photosensitive member at a predetermined speed in a sub-scanning direction, and the second light emitting unit. Control means for controlling on / off of the lighting operation of the image forming apparatus, wherein the control means instructs the moving means to switch the predetermined speed in accordance with the on / off operation. Device. According to this configuration, the moving speed of the photosensitive member in the sub-scanning direction is changed and switched in accordance with turning on and off of the lighting operation of the second light emitting unit. Therefore, when the lighting operation of the second light emitting unit is on. Therefore, the processing speed is improved, and when the lighting operation of the second light emitting unit is turned on, the processing speed can be increased accordingly.

According to a fifth aspect of the present invention, at least one of the optical scanning device according to any one of the first to third aspects and the photoconductor is provided and forms at least one electrostatic latent image corresponding to a different color. an image forming section, wherein the first of the optical scanning apparatus according to any one of claim 1 to 3, the third optical scanning device and including at least said photosensitive member consisting of only the light emitting unit, different colors At least one image forming unit that forms an electrostatic latent image corresponding to the above, a moving unit that moves the photosensitive member of each image forming unit at a predetermined speed in the sub-scanning direction, and all the image forming units said first, third least comprising at least one image formed by the optical scanning device and the photosensitive member according to the first mode any one of claims 1 to 3 in which only the light emitting unit is operated A mode for selectively setting the second mode in which only the forming section is operated. An image forming apparatus, wherein the mode setting means instructs the moving means to switch the predetermined speed in accordance with the operation of the first and second modes. . According to this configuration, since the optical scanning device excluding the second light emitting unit is used for a part of the image forming units, the corresponding configuration is simplified, and the first mode and the second mode are changed. An image forming apparatus that can be selectively switched is realized.

According to a sixth aspect of the present invention, an image forming unit configured to include at least the optical scanning device according to any one of the first to third aspects and the photosensitive member forms a black electrostatic latent image. are those, first, third least provided with configured image an optical scanning device composed of only the light-emitting portion and said photosensitive member of the light scanning apparatus according to any one of the claims 1-3 The forming unit forms an electrostatic latent image corresponding to colors corresponding to cyan, magenta, and yellow. According to this configuration, the configuration of the image forming unit that forms an electrostatic latent image of a color corresponding to cyan, magenta, and yellow is simplified by removing the second light emitting unit.

  According to the first aspect of the invention, the pitch in the sub-scanning direction can be reduced to a required width or narrow while securing a certain distance between the two light sources of each of the first to third light emitting units. In addition, an optical scanning device that can increase the processing speed can be provided.

  According to the second aspect of the present invention, since the light emitting units are arranged in the same manner as the relationship of the imaging point positions, adjustment based on the difference in arrangement is unnecessary, and the entire configuration can be simplified correspondingly.

  According to the third aspect of the present invention, there is an advantage that the pitch in the sub-scanning direction can be narrowed even in an apparatus in which the arrangement pitch of the light source is a problem, such as laser light in the red wavelength region.

  According to the fourth aspect of the present invention, since the moving speed of the photoconductor in the sub-scanning direction is changed and switched in accordance with turning on and off of the lighting operation of the second light emitting unit, the lighting operation of the second light emitting unit is performed. The processing speed can be improved when is turned on, and the processing speed can be increased accordingly.

  According to the fifth aspect of the present invention, by using the optical scanning device excluding the second light emitting unit for a part of the image forming units, the configuration can be simplified, and the first mode is also provided. And an image forming apparatus capable of selectively switching between the second mode and the second mode.

  According to the sixth aspect of the present invention, the configuration of the image forming unit that forms an electrostatic latent image of a color corresponding to cyan, magenta, and yellow is simplified as the second light emitting unit is removed. The

  FIG. 1 is a schematic configuration diagram of a tandem type color printer showing an embodiment of an image forming apparatus according to the present invention. In FIG. 1, a color printer 1 has a housing having a predetermined shape, for example, a rectangular parallelepiped shape, and a toner image is formed on the recording paper 11 by an electrophotographic process in a paper feeding unit 10 that accommodates the recording paper 11 therein. A predetermined number of four image forming units 30C, 30M, 30Y, and 30K for each color, a fixing unit 40 that fixes the toner image on the recording paper 11, and the paper supply unit 10 to the image forming unit 30C. , 30M, 30Y, and 30K, a paper transport unit 20 that transports the recording paper 11, a discharge unit 50 that discharges the recording paper 11 after image formation, and a reading unit that reads characters and the like of the original 81 that are employed as necessary. 70, an external media I / F (interface) unit 90, and an operation display panel 120.

  The paper feeding unit 10 includes a feed roller 21 that feeds the recording paper 11 stacked and loaded in the paper feeding cassette 13 one by one to the outlet side of the paper feeding cassette 13 (right side in FIG. 1). Paper is fed to the paper transport unit 20. The paper transport unit 20 includes a required number of transport roller pairs and transport guides, and transports the fed recording paper toward the image forming units 30C, 30M, 30Y, and 30K.

  The tray 80 is for placing the document 81 to be read, and the transport roller pair 82 is for transporting the placed document 81 toward the reading unit 70 in the printer by rotational driving. The paper sensor 24 is arranged on the upstream side of the reading unit 70 and detects the presence or absence of a document 81 to be carried in. The reading unit 70 is configured by a line sensor or the like that is an optical reading element. When the document 81 is detected by the paper sensor 24, the reading unit 70 continuously synchronizes the image on the paper surface of the document 81 with conveyance. The image data of the read original and the read original is stored in an internal storage unit. The document 81 after being read passes through the image forming units 30C, 30M, 30Y, and 30K that are in an inoperative state and is discharged to the discharge unit 50.

  Four image forming units 30C, 30M, 30Y, and 30K are provided corresponding to toners of cyan, magenta, yellow, and black, respectively, and the image forming unit 30C having cyan toner from the upstream side along the transport direction. The image forming unit 30M having magenta toner, the image forming unit 30Y having yellow toner, and the image forming unit 30K having black toner are arranged in series. The image forming units 30C, 30M, 30Y, and 30K have cylindrical (drum) -shaped photoreceptors 31C, 31M, 31Y, and 31K, respectively, and around the rotation direction, the chargers 32C, 32M, 32Y, and the like in order from the upstream side. 32K, optical scanning devices 33C, 33M, 33Y, and 33K, developing units 34C, 34M, 34Y, and 34K, transfer rollers 35C, 35M, 35Y, and 35K, and cleaners 36C, 36M, 36Y, and 36K are provided. Yes.

  The sheet conveying belt 38 is stretched between a belt driving roller 602 and a belt driven roller 601, and a belt traveling path is provided between the photoreceptors 31C, 31M, 31Y, and 31K and the transfer rollers 35C, 35M, 35Y, and 35K. It is installed. The conveyance motor 603 drives the belt driving roller 602. The sheet conveying belt 38 travels when the belt driving roller 602 is rotationally driven, and the recording sheet 11 (or the document 81) conveyed to the upstream end of the sheet conveying belt 38 is imaged downstream from the image forming unit 30C. It is transported toward the forming unit 30K. The toner tanks 39C, 39M, 39Y, and 39K are accommodated in the corresponding developing devices 34C, 34M, 34Y, and 34K so that the respective toners can be supplied.

  The fixing unit 40 is disposed on the downstream side of the image forming unit 30K, and heats and pressurizes the recording paper 11 onto which the toner image has been transferred in the image forming units 30C, 30M, 30Y, and 30K, thereby forming a toner image on the surface of the recording paper 11. Weld. The recording paper 11 that has passed through the fixing unit 40 is discharged to the discharge unit 50 via the paper conveyance path 15. Although not shown in FIG. 1, the tandem color printer 1 is provided with a control unit (see FIG. 2) described later, and the operation of each unit is controlled by commands from the control unit. .

  The operation display panel 120 includes an input unit 121 such as a touch panel and buttons for inputting an instruction from a user, and a display such as a liquid crystal display panel for confirming input contents and displaying the operation status of the color printer 1. ing. The external media I / F unit 90 is a slot for reading predetermined data. The external media I / F unit 90 receives image data to be printed from an external memory through a network or the like, and stores it in an internal storage unit.

  FIG. 2 is a perspective view showing an internal configuration of the optical scanning device 33K. Note that the optical scanning devices 33C, 33M, and 33Y have the same configuration as the optical scanning device 33K, and thus description thereof is omitted. The optical scanning device 33K includes a case 33K0 for shielding light, and includes therein a deflection unit including a polygon mirror 2 and a polygon motor 3, an fθ lens 4, a collimator lens 5, a laser beam generation unit 6, a folding mirror 7, and A mirror 8 and a photosensor 9 for detecting scanning timing are provided.

  The laser light generating unit 6 includes three light emitting units 61, 62, and 63, each of which is composed of the same laser diode that emits laser light in the wavelength region that the photoconductor 31K is sensitive to, in this case, the red wavelength region. A beam-shaped laser beam whose intensity is modulated with density data, which is data, is emitted toward the collimator lens 5. The collimator lens 5 is disposed in the vicinity of the emission of the laser beam, and adjusts the beam diameter so that the emitted laser beam becomes a required imaging point on the surface of the photosensitive member 31K. The polygon mirror 2 has a rotation center attached to the rotation shaft of the polygon motor 3 and rotates at a constant speed in the direction of the arrow shown in FIG. 2 so that the laser beam that has passed through the collimator lens 5 is reflected by the mirror surface in the circumferential direction. Turn, that is, deflect. The fθ lens 4 is installed in parallel to the deflection surface at the deflection destination of the laser beam, and the deflected laser beam passes through the fθ lens 4 so that it is in the axial direction (main scanning direction) on the surface of the photosensitive member 31K. The traveling speed of the image point, that is, the scanning speed is corrected so as to be as constant as possible regardless of the deflection direction. The folding mirror 7 directs the optical axis of the laser beam that has passed through the fθ lens 4 to the surface of the photoreceptor 31K through a slit (not shown). The photo sensor 9 receives laser light during deflection scanning via a mirror 8 provided on the upstream side in the scanning direction of the laser light, and controls the output start timing of image data using the light reception timing. It is.

  FIG. 3 is a diagram illustrating the configuration of the laser light generator 6 and is a view of the emission surface. The three light emitting units 61, 62, and 63 that constitute the laser light generating unit 6 each include two light sources that emit laser light. The light emitting unit 61 has light sources 611 and 612 arranged with an interval Ha1, the central light emitting unit 62 has light sources 621 and 622 arranged with a space Ha2, and the light emitting unit 63 has a space Ha3 and has a light source 631. , 632 are arranged. In the present embodiment, the light emitting units 61, 62, and 63 are arranged in the vertical direction in FIG. 3 so that the light sources 611 to 632 are arranged in a line. The series direction in which the light sources 611 to 632 are arranged corresponds to the direction orthogonal to the axial direction on the surface of the photoreceptor 31K, that is, the sub-scanning direction.

  FIG. 4 is a diagram showing the positional relationship between the image forming points of the laser light on the surface of the photoconductor 31K. The horizontal direction in the figure corresponds to the scanning direction, and the vertical direction corresponds to the sub-scanning direction. In FIG. 4, the laser beams from the light sources 611 and 612 and the light sources 631 and 632 of the light emitting units 61 and 63 are equally spaced from each other in the sub-scanning direction, here two pitches in the sub-scanning direction (two sub-scanning portions = 2p). The imaging points La11 and La12 and the imaging points La31 and La32 are obtained. Further, the image formation points La11 and La12 and the image formation points La31 and La32 are formed so as to be shifted by 3 pitches in the sub-scanning direction. That is, when the laser beam imaging point La11 from the light source 611 of the light emitting unit 61 is the first line in the sub-scanning direction, the laser beam imaging point La12 from the light source 612 is the third line. The laser beam imaging point La31 from the light source 631 is the fourth line, and the laser beam imaging point La32 from the light source 632 is the sixth line. In this way, the light-emitting unit 61 (also the light-emitting unit 63) can be easily manufactured by setting the imaging point of the light sources 611 and 612 (also the light sources 631 and 632) to exceed one pitch.

  The laser beams from the light sources 621 and 622 of the light emitting unit 62 are arranged so as to obtain the imaging points La21 and La22 with an interval of 3 pitches in the sub-scanning direction, and the imaging point La21 is the imaging point La11. The image forming point La22 is positioned at an intermediate position between the image forming point La31 and the image forming point La32. That is, the laser beam imaging point La21 from the light source 621 of the light emitting unit 62 is the second line, and the laser beam imaging point La22 from the light source 622 is the fifth line. This facilitates the manufacture of the light emitting unit 62 as described above. As a result, when all the light emitting units 61 to 63 operate, line scanning for 6 pitches continuous in the sub-scanning direction is possible. As will be described later, in this case, the moving speed of the photosensitive member 31K in the sub-scanning direction is set to a moving speed corresponding to line scanning every 6 pitches.

  FIG. 5 is a block diagram of a portion of the color printer to which the present invention is related. The control unit 100 is composed of a microcomputer or the like, and controls the operation of the entire color printer 1. The ROM 110 stores a control program, various setting data, and the like. The RAM 111 temporarily stores data being processed, and also functions as a storage unit for the above-described image data fetched from the reading unit 70 or the external media I / F (interface) unit 90. The image data is a two-dimensional structure in which a plurality of pixel data for one line has a plurality of lines in the line direction. The conveyance motor drive unit 111 outputs a rotation drive signal to the conveyance motor 603. The photosensitive member rotation driving unit 112 outputs a rotation driving signal to the photosensitive member motor 310 that rotates the photosensitive members 31C to 31K via a driving force transmission mechanism (not shown). The image forming units 30C, 30M, and 30Y are connected to a driving force transmission mechanism via a clutch (not shown). As will be described later, all the image forming units are driven when the clutch is turned on. When off, only the image forming unit 30K is driven.

  The line buffer unit 140 inputs image data for one line in the main scanning direction and outputs it to the corresponding light source, and is composed of six line buffers corresponding to the six light sources 611 to 632. ing. Note that the image data for one line in the main scanning direction is a set of a predetermined number of pixel data, and each line buffer includes, for example, a shift register having a memory unit corresponding to the number of pixel data for one line. . In addition, the line buffer unit 140 is actually provided corresponding to each of the four image forming units 30C to 30K (the remainder is indicated by broken lines in FIG. 5).

  The control unit 100 transfers and inputs (for example, collectively in parallel) image data for one line in the sub-scanning direction to each line buffer, and at a predetermined read clock speed from the clock generation unit (CLK) 114, The pixel data is sequentially output in series toward the corresponding light source.

  The control unit 100 includes a mode determination unit 101, a light source control unit 102, an image formation control unit 103, and an image data output control unit 104. According to the mode selection from the input unit 121, the mode determination unit 101 is designated as either a color mode (first mode) for printing in color or a monochrome mode (second mode) for printing in monochrome. It is a judgment. The monochrome mode is a process of forming an image using only one of the image forming units 30C to 30K, for example, the image forming unit 30K. The color mode uses all of the image forming units 30C to 30K and emits light. In this process, image formation is performed in a state where the driving of the unit 62 is turned off (that is, the light is turned off).

  FIG. 4 corresponds to a scanning state in the sub-scanning direction in the monochrome mode. In this case, the photoconductor 31K is rotated at a predetermined high speed, and scanning is performed every six lines in the sub-scanning direction. This is because in the case of a monochrome toner image, the fixing performance of the fixing unit 40 can be exhibited even at a certain high speed, so that a higher-speed processing is realized.

  On the other hand, FIG. 6 shows the scanning position in the sub-scanning direction when the driving of the light emitting units 61 and 63 is turned on, that is, the driving of the light emitting unit 62 is turned off. The fourth, sixth and sixth lines are scanned. In this case, the rotational speeds of the photoconductors 31C, 31M, 31Y, and 31K are predetermined speeds that can be originally set from the viewpoint of fixing performance in the fixing unit 40, and as a result, the predetermined speeds in the monochrome mode are set. The image is rotated at a speed set to be lower than the high speed, and scanning (interlace) is performed every four lines in the sub-scanning direction as will be described later.

  The transfer roller 35, the paper transport belt 38, and the rollers of the fixing unit 40 are driven and controlled at a speed (process speed set in each mode) equal to the peripheral speed in each mode of the photoreceptors 31C, 31M, 31Y, and 31K. Smooth conveyance of the recording paper 11 can be achieved in each mode. Note that the paper conveyance belt 38 and the rollers of the fixing unit 40 may be drivably connected to the photoreceptors 31C to 31K via a driving force transmission mechanism.

  The light source control unit 102 drives only the image forming unit 30K when the monochrome mode is designated, and lights all the light emitting units 61 to 63. On the other hand, when the color mode is designated, the image forming unit. While driving 30C-30K, only those light emission parts 61 and 63 are lighted.

  The image formation control unit 103 is driven in response to a print instruction. When the monochrome mode is designated, the rotation speed of the photoconductor 31K of the image formation unit 30K is set to the predetermined high speed, and the color mode is set. When specified, the rotational speed of the photoconductors 31C to 31K of the image forming units 30C to 30K is set to the predetermined speed. Here, the predetermined high speed in the monochrome mode can be 6/4 times the predetermined speed in the color mode. By setting the speed in this manner, the image data read speed (clock speed from the clock generator (CLK) 114) can be kept constant regardless of the mode, and the processing speed in the monochrome mode can be increased. It is possible to increase compared to the color mode.

  The image data output control unit 104 transfers the image data for one line in the scanning direction to each line buffer of the line buffer unit 140, and serially reads out the corresponding light sources 611 to 632 at a predetermined timing and a predetermined clock speed. It leads to sequentially. When the monochrome mode is designated, the image data output control unit 104 outputs the image data to all the line buffers of the line buffer unit 140, and shifts by 6 lines in the sub-scanning direction every reading cycle. In addition, the image data of the 6 lines are sequentially output in synchronization with each other, that is, in accordance with the rotation angle of the photoconductor 31. Further, when the color mode is designated, the image data output control unit 104 has four lines corresponding to the light sources 611 and 622 of the light emitting unit 61 and the light sources 631 and 632 of the light emitting unit 63 in the line buffer unit 140. The image data of the first, third, fourth, and sixth lines in the sub-scanning direction is output only to the buffer, and the image data of the lines shifted by four lines in the sub-scanning direction (so-called interlaced scanning) is read at every reading cycle. Output in synchronization.

  FIG. 7 is a diagram showing a scanning state on the photosensitive member in the monochrome mode, and FIG. 8 is a diagram showing a scanning state on the photosensitive member in the color mode (interlaced scanning). The horizontal axis indicates the number of scans.

  In the monochrome mode, all of the 1st to 6th lines are scanned in the first scan, and in the second scan, the photosensitive member 31 is moved in the sub-scanning direction by 6 pitches. The twelfth to thirteenth lines are scanned, and in the third scan, since the photosensitive member 31 is further moved in the sub-scanning direction by six pitches, the thirteenth to eighteenth lines are scanned, and the photosensitive member 31 is scanned. The movement and scanning are repeated. As a result, all the lines are scanned, and an electrostatic image without line omission is formed on the photoreceptor 31. In the color mode, the first, third, fourth, and sixth lines are scanned in the first scan, and in the second scan, the photosensitive member 31 moves in the sub-scanning direction by four pitches. The fifth, seventh, eighth, and tenth lines are scanned by interlaced scanning, and in the third scanning, the photosensitive member 31 is further moved in the sub-scanning direction by four pitches. , Twelfth and fourteenth lines are scanned, and the movement and scanning of the photoreceptor 31 are repeated. As a result, except for the first second line (and the previous line from the last), all the lines after the third line are scanned, and there is no missing line on the photosensitive member 31. An electrostatic image is formed.

  FIG. 9 is a flowchart showing a printing operation procedure. When a print instruction is issued from the input unit 121 (step ST1), it is determined whether or not a monochrome mode is selected by the input unit 121 (step ST3). The selection of the monochrome mode and the color mode may be performed by inputting each of them. However, the monochrome mode is set as a default, and the input operation may be performed only in the color mode.

When it is determined that the monochrome mode is selected, an instruction for forming a monochrome image is sent to each unit (step ST5), only the image forming unit 30K is driven, and all the light sources 611 to 632 are turned on. The image forming process is executed in a state where the photosensitive member 31K and the belt driving motor 603 are driven at a predetermined high speed by being driven (step ST7), whereby a monochrome image is printed on the recording paper 11 at a high speed. . On the other hand, if it is determined that the color mode has been selected, an instruction for forming a color image is sent to each unit (step ST9), all the image forming units 30C to 30K are driven, and the light emitting unit. 61 and the light emitting unit 63 are driven, and the image forming process is executed in a state where the photosensitive members 31C to 31K and the belt driving motor 603 are driven at a synchronized speed (step ST11), whereby a color image is formed on the recording paper. The toner is transferred at a predetermined speed, and the toner of each color is suitably fixed by the fixing unit 40.

  In the above embodiment, all the light emitting units 61 to 63 are driven by the image forming unit 30K that forms a black toner image in the monochrome mode, and the color toner image forming units 30C, 30M, and 30Y in the color mode. In the above description, the light emitting unit 62 is not driven. However, the monochrome mode may be configured to allow printing with a specific color other than black toner.

  In the present embodiment, the light emitting units 61, 62, and 63 are arranged in this order, and the light emitting units 62 having different imaging point intervals are formed at the center of the light emitting units 61 and 63. However, the present invention is not limited to this. The light emitting unit 62 may be formed in the upper part or the lower part. In this case, for example, the position of the laser light is set so that the imaging point of the laser light from each light emitting part has the positional relationship shown in FIG. The injection direction may be adjusted.

  In the present embodiment, the light sources 611 to 632 are arranged in a line. However, the present invention is not limited to this, and each light source is formed so as to have an imaging point position having a predetermined pitch p in the sub-scanning direction. Is possible. In this case, each imaging point position with respect to the main scanning direction can be made to coincide, for example, by adjusting the emission direction of the laser beam, or the deviation of the imaging point position in the main scanning direction can be The read timing of the image data from the corresponding line buffer of the line buffer unit 140 may be adjusted by the deviation.

  FIG. 10 is a view as seen from the exit surface showing another embodiment of the laser beam generator. The laser beam generator 6 ′ shown in FIG. 10 is employed for the image forming units 30C, 30M, and 30Y. Compared to the configuration of the laser beam generator 6 shown in FIG. The light emitting units 61 'and 63' are excluded. The laser beam generator 6 in FIG. 3 has the advantage that it can be used without any distinction in any of the image forming units 30C, 30M, 30Y, 30K. On the other hand, since the image forming units 30C, 30M, and 30Y in the laser light generating unit 6 ′ in FIG. 10 do not operate in the monochrome mode, the light emitting unit 62 is not required, and the configuration can be simplified accordingly. There is.

  In the above embodiment, the light sources are arranged at the same position in the main scanning direction and arranged in a line in the sub scanning direction. However, the positions may be shifted in the main scanning direction.

1 is a schematic configuration diagram of a tandem color printer showing an embodiment of an image forming apparatus according to the present invention. It is a perspective view which shows the internal structure of an optical scanning device. It is the figure seen from the emission side for demonstrating the structure of a laser generation part. It is a figure which shows the positional relationship of the image formation point of the laser beam on the surface of a photoreceptor, and the horizontal direction of a figure corresponds to a scanning direction and the vertical direction corresponds to a sub-scanning direction. It is a block diagram of the part to which this invention relates among color printers. It shows the scanning position in the sub-scanning direction when driving of the light emitting unit 62 is turned off. It is a figure which shows the scanning state on the photoconductor in a monochrome mode. FIG. 5 is a diagram illustrating a scanning state on a photoconductor in a color mode (interlaced scanning), where a broken line on the vertical axis indicates a sub-scanning line, and a horizontal axis indicates the number of scans. 6 is a flowchart illustrating a printing operation procedure. It is the figure seen from the emission surface which shows other embodiment of a laser generation part.

Explanation of symbols

1 Color printers 30C, 30M, 30Y, 30K Image forming units 31C, 31M, 31Y, 31K Photoconductors 33C, 33M, 33Y, 33K Optical scanning device 6 Laser beam generating units 61, 62, 63 Light emitting units (first to third light emitting units) (Light emitting part)
611-632 Light source (laser emission source)
La11 to La32 Imaging point 100 Control unit 101 Mode determination unit 102 Light source control unit 103 Image formation control unit (control means)
104 Image data output control unit 112 Conveyance motor drive unit 113 Photoconductor rotation drive unit (moving means)

Claims (6)

In an optical scanning device in which a predetermined number of laser beams are synchronized and deflected in a predetermined direction at a constant speed, and an imaging point of each laser beam scans the surface of the photosensitive member,
Each of the two laser emission sources has a first sub-scanning pitch in the sub-scanning direction perpendicular to the scanning direction of the photosensitive member. To a third light emitting unit, and the first and third light emitting units are configured such that each laser beam has two sub-scanning pitches equal to each other to obtain an image point , and the first light emitting unit One imaging point of the first part and one imaging point of the third light emitting part are configured to be shifted by 3 sub-scanning pitches in the sub-scanning direction, and the second light emitting part has two lasers. Among the light emission sources, one laser beam imaging point is between the two laser beam imaging points of the first light emitting unit, and the other laser beam imaging point is the two laser beam imaging points of the third light emitting unit. An optical scanning device characterized in that the optical scanning device is positioned between the imaging points of laser light. The first to third light emitting part, are arranged in series, and an optical scanning apparatus according to claim 1, wherein the second light emitting portion and being located in the center. The optical scanning device according to claim 1, wherein the first to third light emitting units are laser beams in a red wavelength region. An optical scanning apparatus according to claim 1, wherein a moving means for moving the photoreceptor in a sub-scanning direction at a predetermined speed, the second on the lighting operation of the light emitting portion, controls the off An image forming apparatus, wherein the control unit instructs the moving unit to switch the predetermined speed in response to the on / off operation. Comprising at least an optical scanning apparatus according to any one of claims 1 to 3 and the photosensitive member, and at least one image forming unit to form a different electrostatic latent image on the color corresponding respectively, claim 1 The optical scanning device according to any one of 1 to 3 includes at least an optical scanning device including only the first and third light emitting units and the photoconductor, and forms electrostatic latent images corresponding to different colors, respectively. At least one image forming unit, a moving means for moving the photosensitive member of each image forming unit at a predetermined speed in the sub-scanning direction, and the first and third light emitting units with respect to all the image forming units. only the first operating mode and billing of claim 1 to 3 any one optical scanning device and includes at least the photoreceptor second operating only at least one of the image forming portion configured according to Mode setting means for selectively setting the mode, and Mode setting means, the image forming apparatus characterized by instructing the switching to the predetermined speed relative to said moving means in response to operation of said first, second mode. Wherein the image forming unit which is configured with at least an optical scanning device and the photosensitive member according to any one of claims 1 to 3 is intended to form an electrostatic latent image of black, claim 1 The image forming unit configured to include at least the optical scanning device including only the first and third light emitting units and the photoconductor among the optical scanning devices according to any one of 3 is provided in cyan, magenta, and yellow. The image forming apparatus according to claim 5, wherein the image forming apparatus forms an electrostatic latent image corresponding to a corresponding color.

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