JP2012008250A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of suppressing color shift when performing image forming processing using all of optical scanning devices after performing image forming processing without using at least one optical scanning device among a plurality thereof.SOLUTION: A control section 200 determines whether it is a first image forming mode or a second image forming mode from the image data. If image data is the second image forming mode (YES for S2) in which an image is formed using all of the optical scanning devices 4a and 4b, all of rotation polygon mirrors 49 are rotated (S3). If an energy saving mode is ON (YES for S9) in the first image forming mode (NO for S2) in which an image is formed using another optical scanning device, only the rotation polygon of the optical scanning device used is rotated (S10), and if the energy saving mode is OFF, all of the polygon mirrors are rotated (S3).

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile.

  Patent Documents 1 and 2 describe an image forming apparatus in which a plurality of optical scanning devices for forming an electrostatic latent image on a photosensitive member as a latent image carrier by deflecting and scanning light by rotation of a rotary polygon mirror are arranged. ing.

  In the image forming apparatuses described in Patent Documents 1 and 2, four photoconductors corresponding to yellow (Y), magenta (M), cyan (C), and black (K) are arranged side by side along the moving direction of the transfer body. This is a so-called tandem image forming apparatus. Four optical scanning devices corresponding to Y, M, C, and K are provided.

  When forming a monochrome image, only the rotary polygon mirror of the K-color optical scanning device is rotated to form a latent image on the K-color photoconductor. On the other hand, in the case of forming a full-color image, the rotary polygon mirror of the all-color optical scanning device is rotated to form a latent image on each color photoconductor.

  In general, the optical scanning device includes the rotary polygon mirror and optical system components such as an imaging lens for imaging light on the surface of the photoreceptor. These components are housed in a housing, and the housing is covered and sealed with a cover member or the like so that dust and dust do not adhere to optical system components such as an imaging lens.

  In such an image forming apparatus, when a full-color image is formed after forming a monochrome image, the K-color image forming position is greatly shifted from the image forming positions of other colors, resulting in color shift. There was a problem.

  As a result of intensive studies on the above problems, the present applicants have found the following. That is, during image formation, the rotary polygon mirror rotates at a high speed, so that the bearing portion of the rotary polygon mirror generates heat. Due to this heat generation, the housing is deformed due to thermal expansion, and the posture of an optical system component such as an imaging lens attached to the housing changes under the influence of the thermal expansion. As described above, when the posture of the optical system component is changed, the scanning position on the photoconductor is different before and after the housing is thermally expanded. In the monochrome mode as the first image forming mode, only the rotary polygon mirror of the K-color optical scanning device is rotated to form a latent image on the K-color photoconductor. For this reason, when a full-color image is formed after the monochrome image is formed, the scanning position of the K-color optical scanning device is shifted from the scanning position before the thermal expansion due to the thermal expansion of the housing. Since the scanning position of the apparatus is not affected by the thermal expansion of the housing, there is almost no displacement. As a result, when a full-color image is formed after the monochrome image is formed, the K-color image formation position is greatly shifted from the image formation positions of other colors.

  As described above, when image forming processing is performed using all of the optical scanning devices after performing image forming processing without using at least one of the plurality of optical scanning devices, it is used in the previous image forming processing. A positional shift occurs between an image formed using the optical scanning device that has not been used and an image formed using the optical scanning device used in the previous image forming process, resulting in a color shift.

  The present invention has been made in view of the above-described problems, and its object is to use all optical scanning devices after performing image forming processing without using at least one of the plurality of optical scanning devices. An image forming apparatus capable of suppressing color misregistration when image forming processing is performed.

In order to achieve the above object, the invention of claim 1 comprises a rotating polygon mirror, and by rotating the rotating polygon mirror, light is deflected and scanned in the main scanning direction with respect to the surface of the latent image carrier. A first image forming mode in which a plurality of optical scanning devices for forming an electrostatic latent image on the body are provided and an image is formed without using at least one of the plurality of optical scanning devices, and all optical scanning Control means for controlling the rotary polygon mirror of the optical scanning device not used in the first image forming mode to rotate for a predetermined time in an image forming apparatus having a second image forming mode for forming an image using the apparatus; It is characterized by having.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, each optical scanning device has the same configuration.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, selection means for selecting whether or not to rotate the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode. It is characterized by having.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control means rotates the optical scanning device that is not used in the first image forming mode at a timing at which color misregistration occurs. Control is performed to start rotation of the polygon mirror.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, each optical scanning device is provided with temperature detecting means for detecting the temperature in the vicinity of the rotary polygon mirror, and the control means is provided in the first image forming mode. When the difference between the temperature in the vicinity of the rotating polygon mirror of the optical scanning device used in the above and the temperature in the vicinity of the rotating polygon mirror of the optical scanning device not used in the first image forming mode exceeds a threshold value, in the first image forming mode. The rotating polygon mirror of the optical scanning device that is not used is controlled to rotate.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the rotation time of the rotary polygon mirror of the optical scanning device used in the first image forming mode exceeds the threshold value, the control means The rotary polygon mirror of the optical scanning device that is not used in one image forming mode is controlled to rotate.
The invention according to claim 7 is the image forming apparatus according to claim 4, wherein when the number of continuous images formed in the first image forming mode exceeds a threshold value, the control means does not use light in the first image forming mode. The rotating polygon mirror of the scanning device is controlled to rotate.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the control means sets the temperature in the vicinity of the rotary polygon mirror of the optical scanning device not used in the first image forming mode to a predetermined value. If it reaches, control is performed so as to stop the rotation of the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode.
The invention according to claim 9 is the image forming apparatus according to claim 8, wherein the control means is configured such that when the rotation time of the rotary polygon mirror of the optical scanning device not used in the first image forming mode exceeds a threshold value, The rotation of the rotary polygon mirror of the optical scanning device that is not used in the one image forming mode is stopped.
According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the control means includes a first image forming mode after the rotation of the rotary polygon mirror of the optical scanning device not used in the first image forming mode. When the number of continuous images formed by the above exceeds a threshold value, the rotation polygon mirror of the optical scanning device that is not used in the first image forming mode is controlled to stop rotating.

  According to the present invention, since the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode is rotated for a certain time, the housing of the optical scanning device that is not used in the first image forming mode is also used. Like the scanning device, the thermal expansion is caused by the heat generated in the bearing portion of the rotary polygon mirror. Therefore, even if the second image forming mode is executed after the first image forming mode is executed, the scanning position of the optical scanning device not used in the first image forming mode is the same as that of the optical scanning device used in the first image forming mode. Deviation occurs with respect to the scanning position before thermal expansion. If the configurations of the optical scanning devices are the same, the shift of the scanning position due to the thermal expansion of the housing of the optical scanning device used in the first image forming mode and the heat of the housing of the optical scanning device not used are used. The scanning position shift due to expansion has the same tendency. As a result, after the first image forming mode, even if the second image forming mode for forming an image using all the optical scanning devices is executed, the image formed using the optical scanning device used in the first image forming mode The positional deviation from the image formed by using the optical scanning device not used in the first image forming mode is suppressed, and the color deviation can be suppressed.

1 is a side view schematically showing an image forming apparatus according to the present invention. 1 is a schematic cross-sectional view showing a configuration of an optical scanning device according to the present invention. FIG. 2 is a schematic top view showing a configuration of the optical scanning device. The block diagram which shows the principal part of the control system of the image forming apparatus The schematic of an operation display part. The graph which measured the temperature inside an optical scanning device. FIG. 6 is a control flow diagram of each optical scanning device. (A) is a figure which shows rotation of the rotary polygon mirror of each optical scanning device in the case of image data being a K-color single-color image and in an energy saving mode. FIG. 6B is a diagram illustrating rotation of the rotary polygon mirror of each optical scanning device when the image data is a K-color single color image and the energy saving mode is not set. FIG. 6C is a diagram illustrating rotation of the rotary polygon mirror of each optical scanning device in the case of a full-color image. FIG. 9 is a control flow diagram of each optical scanning device in a modified image forming apparatus. 1 is a schematic configuration diagram of a direct-rotation type color image forming apparatus including four optical scanning devices.

An example of a color image forming apparatus to which the present invention is applied will be described with reference to FIG.
FIG. 1 shows an example of a full-color image forming apparatus in which a plurality of four drum-shaped photoconductors 10Y, 10C, 10M, and 10K as latent image carriers are arranged in tandem. It is configured as a part of the image devices 7Y, 7C, 7M, and 7K. These image forming devices 7Y, 7C, 7M, and 7K sequentially correspond to the respective colors of yellow, cyan, magenta, and black, and create images of these colors.

  In the type of the image forming apparatus of FIG. 1, there is an intermediate transfer belt 14 as a surface moving member that is supported by three support rollers 15a, 15b, 15c and rotates, and a tension line below the intermediate transfer belt 14 is provided. The image forming devices 7Y, 7C, 7M, and 7K are arranged at intervals from the upstream side in the order of movement of the intermediate transfer belt 14 indicated by arrows.

  When forming a full-color image, toner images of respective colors are formed on the photoreceptors 10Y, 10C, 10M, and 10K provided in the image forming devices 7Y, 7C, 7M, and 7K, as described later. Next, the toner images of different colors are transferred to the intermediate transfer belt 14 as the intermediate transfer belt 14 is moved by the function of the primary transfer roller 16 as a transfer unit disposed opposite to each photoconductor with the intermediate transfer belt 14 therebetween. The images are sequentially transferred onto the transfer belt 14. Specifically, the portion of the intermediate transfer belt 14 in contact with the primary transfer roller 16 is called a transfer position, and transfer is performed at this transfer position.

The four superimposed transfer toner images are collectively transferred to the recording material as the final recording medium at the nip portion between the support roller 15a and the secondary transfer roller 9, and after passing between the fixing pair rollers of the fixing device 6, the conveyance roller After that, the paper is discharged onto a paper discharge tray 19 from a pair of paper discharge rollers. Thus, a full color image is obtained on the recording material.
The intermediate transfer belt 14 is configured such that the photoconductor 10K is always brought into contact with the primary transfer roller 16 in order to conform to the monochrome image forming mode which is the first image forming mode. The intermediate transfer belt 14 is brought into contact with and separated from each other by the function of the roller. A cleaning device 17 for removing residual toner on the intermediate transfer belt 14 is provided in the roller 15b portion.

  In FIG. 1, the image forming devices 7Y, 7C, 7M, and 7K differ only in the color of the toner to be handled, and the mechanical configuration and the image forming process are the same. Therefore, the constituent members other than the photoreceptor are the same. A configuration and an image forming process will be described with respect to an arbitrary image forming device, for example, the image forming device 7Y.

  Around the photoconductor 10Y of the image forming device 7Y, in the order of the clockwise rotation in the drawing, a charging roller 11 as a charging unit for charging the photoconductor 10Y, an irradiation position of the writing light L, and development as a developing unit. A device 12, a primary transfer roller 16, a cleaning device 13, and the like are arranged.

  Two optical scanning devices 4a and 4b are arranged below the image forming devices 7Y, 7C, 7M, and 7K. The writing light L to the photoconductors 10Y and 10C is emitted from the second optical scanning device 4b, and the writing light L to the photoconductors 10M and 10K is emitted from the first optical scanning device 4a. Each of the optical scanning devices 4a and 4b emits writing light L for each color toward the photoconductor to form an electrostatic latent image. Details will be described later.

  The developing device 12 of the image forming device 7Y contains a yellow developer and visualizes the latent image with a yellow image. The other image forming apparatuses also store the developer of each color, and visualize the latent image with the color of the stored developer.

At the time of image formation, the photoconductor 10Y rotates and is uniformly charged by the charging roller 11, and an electrostatic latent image is formed by irradiation of the writing light L including yellow image information at the writing position. The latent image is visualized with yellow toner while passing through the developing device.
The yellow toner image on the photoreceptor 10 </ b> Y is transferred to the intermediate transfer belt 14 by the primary transfer roller 16. This yellow toner image on the intermediate transfer belt 14 is sequentially superimposed and transferred with a cyan toner image by the image forming device 7C, a magenta toner image by the image forming device 7M, and a black toner image by the image forming device 7B. Thereby, a full-color toner image is formed.

  In order to reach the secondary transfer roller 9 at the same timing as the overlapped toner image reaches the secondary transfer roller 9, the recording material is sent out at the timing from the paper feeding unit 5 and the registration roller. Batch transfer is performed at the nip portion between the support roller 15 a and the secondary transfer roller 9.

On the other hand, after the transferred toner is removed by the cleaning device 13, the photosensitive member is discharged by a discharging lamp to prepare for the next image formation. Similarly, residual toner and the like are also removed from the intermediate transfer belt 14 by the cleaning device 17.
In the image forming apparatus of this example, the toner image on each photoconductor is temporarily transferred onto the intermediate transfer belt 14, and this overlapped toner image is collectively transferred onto a sheet-like medium. Instead, a recording paper conveying belt as a surface moving member is provided, and the recording material is carried by the recording paper conveying belt, and a color toner image is sequentially transferred from each photosensitive member onto the recording material in the course of the conveying. Thus, a color image forming apparatus that synthesizes a full-color image is also known. The present invention can be applied to any of these types of image forming apparatuses.

Next, the optical scanning devices 4a and 4b will be described. Since the optical scanning devices have the same structure, the first optical scanning device 4a will be described.
FIG. 2 is a schematic cross-sectional view showing the configuration of the first optical scanning device 4a, and FIG. 3 is a schematic view of the first optical scanning device 4a as viewed from above.
The first optical scanning device 4a includes optical elements such as a rotating deflector 50, various reflection mirrors, and various lenses. An optical system for K is disposed on the right side of the rotary deflector 50 in the drawing. An optical system for M is disposed on the left side of the rotary deflector 50 in the drawing. In the rotary deflector 50, the rotary polygon mirror 49 is fixed to the rotary shaft 151. The rotating shaft 151 is rotatably fixed to the optical housing 100 via a bearing 50a (see FIG. 2). The rotary shaft 151 is rotationally driven by a polygon motor (not shown), and the rotary polygon mirror 49 rotates.

  Further, as shown in FIG. 3, light source units 41K and 41M which are light beam emitting means for emitting light beams Lk and Lm respectively corresponding to the photoconductors 10K and 10M are provided. The light source units 41K and 41M are composed of semiconductor lasers 46K and 46M, collimating lenses 47K and 47M, and holders 48K and 48M that support them, and are fixed to the optical housing 100.

  The apertures 52K and 52M and the imaging lenses (cylinder lenses) 53K and 53M are disposed on the optical path of the light beam from the light source units 41K and 41M to the rotary deflector 50. Further, the scanning lenses (fθ lenses) 25a and 25b, the first folding mirrors 45aK and 45aM, and the second folding mirrors 45bK and 45bM, which are optical elements, are on the optical path from the rotary deflector 50 to the photosensitive body 10 that is the irradiated body. Is arranged. Although not shown, long lenses corresponding to the respective colors may be disposed on the optical path from the rotary deflector 50 to the photosensitive member 10 that is an object to be irradiated. In this embodiment, two folding mirrors 45 are arranged from the scanning lens (fθ lens) 25 to the photosensitive member. The number of folding mirrors 45 is used to adjust the optical path length. Is appropriately selected.

  A tip beam detection unit 44K as a beam detection sensor for detecting the tip of the K-color light beam Lk is provided at the lower right in FIG. Further, a rear end beam detection unit 54K as a beam detection sensor for detecting the rear end of the K-color light beam Lk is provided on the upper right side in the drawing. Further, an M tip beam detection unit 44M is provided at a position (upper left in the drawing) that is point-symmetric with the K tip beam detection unit 44K around the rotation shaft 151 of the rotary deflector 50. Similarly, an M rear end beam detection unit 54M is provided at a position (pointed to the lower left in the drawing) that is point-symmetric with the K rear end beam detection unit 54K around the rotation shaft 151 of the rotary deflector 50. .

  The light beam emitted from the K light source unit 41K passes through the aperture 52K to form a light beam Lk having a predetermined shape. The light beam Lk that has passed through the aperture 52K enters the imaging lens 53K (cylinder lens) and is condensed in the sub-scanning direction (direction corresponding to the direction of movement of the photosensitive member surface on the photosensitive member surface). The light beam Lk that has passed through the imaging lens 53K is incident on the side surface of the rotating polygon mirror 49 that is rotating. When the light beam Lk is incident on the side surface of the rotary polygon mirror 49, the light beam is deflected and scanned in the main scanning line direction. The light beam Lk deflected and scanned by the rotary polygon mirror 49 passes through the soundproof glass 51 (see FIG. 2) and is deflected in the main scanning direction by the scanning lens 25a (fθ lens) at a constant angular velocity. Convert travel speed to constant speed. The K-color light beam Lk that has passed through the scanning lens 25a is reflected by the folding mirror 44aK prior to scanning onto the photoconductor 10K, and after the beam diameter is reduced by the synchronization lens 44bK, it enters the synchronization detection sensor 44cK. The tip beam detection unit 44K detects the light beam Lk. When the tip beam detection unit 44K detects the light beam Lk, a synchronization signal is output, and the output timing of the light source signal converted based on the image data is adjusted according to the synchronization signal.

  As described above, the light beam Lk emitted based on the input image data passes through the imaging lens 53K and the like, is scanned by the rotary polygon mirror 49, and enters the scanning lens 25a. As shown in FIG. 2, the light beam Lk incident on the scanning lens 25a is applied to the photoconductor 10K through the first and second folding mirrors 45aK and 45bK and the dustproof glass 55K.

  Then, after optical scanning on the photoconductor 10K, the light beam Lk is reflected by the folding mirror 54aK, and after the beam diameter is reduced by the lens 54bK, the light beam Lk enters the rear end detection sensor 54cK and the rear end beam detection unit 54K performs light. The beam Lk is detected. When the rear end beam detection unit 54K detects the light beam Lk, a synchronization signal is output, and the output of the next light beam is adjusted or the magnification is adjusted according to the synchronization signal.

  The light beam Lm emitted from the M light source unit 41M passes through the aperture 52M, the imaging lens 53M, and the like, and is scanned by the rotary polygon mirror 49. The M light beam Lm scanned by the rotary polygon mirror 49 is incident on the scanning lens 25b, is incident on the tip beam detection unit 44M prior to scanning on the photosensitive member 10M, and outputs a synchronization signal. The light beam Lm based on the image data emitted in synchronization passes through the imaging lens 53M, the rotary polygon mirror 49, the scanning lens 25b, the first folding mirror 45aM, the second folding mirror 45bM, and the dustproof glass 55M. Then, the photoconductor 10M is irradiated.

  In this embodiment, a sensor (front end beam detection unit) that synchronizes writing for each light beam and a sensor (rear end beam detection unit) that synchronizes writing end are provided, but only the front end beam detection unit is provided. It is also possible to provide only synchronization of writing. Further, the writing position of the light beams of a plurality of colors may be controlled with only one synchronization sensor. Further, the optical scanning device 4 of the present embodiment is a tandem writing optical system and employs a scanning lens system, but can be applied to either a scanning lens system or a scanning mirror system.

  FIG. 4 is a block diagram illustrating a main part of a control system of the image forming apparatus. In the figure, a control unit 200 as a control means is composed of, for example, a microcomputer, a CPU (Central Processing Unit) as an arithmetic processing means, a non-volatile memory RAM (Random Access Memory) and a ROM (Read Only) as storage means. Memory) and the like. The controller 200 is electrically connected to the image forming devices 7Y, 7M, 7C, and 7K, the optical scanning devices 4a and 4b, the operation display unit 201, and the like. And the control part 200 controls these various apparatuses based on the control program memorize | stored in RAM.

FIG. 5 is a schematic diagram of the operation display unit 201.
The operation display unit 201 has an input device using a touch panel. As shown in the figure, the operation display unit 201 displays GUI (Graphical User Interface) parts as operation parts such as buttons. . The operation display unit 201 displays a predetermined GUI component based on a control signal from the control unit 200, and transmits operation information received by the input device to the control unit 200.

  In the optical scanning devices 4a and 4b, since the rotary polygon mirror 49 rotates at a high speed during image formation, the bearing portion 50a generates heat. FIG. 6 is a graph obtained by measuring the temperature inside the optical scanning device. As shown in the drawing, it is well understood that the heat generated in the bearing portion 50a is transmitted to the housing 100, and the temperature gradually rises from a portion of the housing 100 close to the bearing portion 50a.

  As described above, the heat of the bearing portion 50a is transmitted to the housing 100, so that the vicinity of the rotary polygon mirror and the vicinity of the scanning lens 25 of the housing 100 are expanded and deformed by the heat (hereinafter, this deformation is referred to as thermal deformation). In particular, when the housing 100 is resin-molded, the thermal deformation is prominent. When the vicinity of the rotating polygon mirror or the scanning lens in the housing 100 is thermally deformed, the rotating polygon mirror 49 or the scanning lenses 25a and 25b fixed to the vicinity of the rotating polygon mirror are inclined. As described above, when the rotary polygon mirror 49, the scanning lenses 25a and 25b, and the like are inclined, the irradiation position of the light beam on the photosensitive member is shifted in the sub-scanning direction (photosensitive member surface moving direction). When the housing 100 is deformed by (1/100) mm and the scanning lenses 25a and 25b and the rotary polygon mirror 49 are slightly inclined, the scanning position is shifted in the sub-scanning direction so that it can be visually confirmed when reaching the photosensitive member 10. End up.

  In the case of a monochrome image, when only the first optical scanning device 4a is driven, the temperature rises only in the first optical scanning device, and a temperature difference is generated between the first optical scanning device 4a and the second optical scanning device 4b. In particular, when a user who prints many monochrome images occasionally prints a full color image, the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b increases. As a result, the scanning position scanned by the first optical scanning device 4a is shifted in the sub-scanning direction from the scanning position before the thermal deformation due to the influence of the thermal deformation of the housing 100. On the other hand, since the second optical scanning device 4b is not used when printing a monochrome image, the inside of the device is at substantially room temperature, and the housing 100 is not thermally deformed. For this reason, there is no deviation in the scanning position. As a result, there is a color between the image (M color and K color) formed using the first optical scanning device 4a and the image (Y color and C color) formed using the second optical scanning device 4b. There was a problem that a shift occurred. In addition, although the example in the case of a monochrome image was demonstrated above, it is not restricted to this. For example, even if a full-color image is formed after an M-color single-color image is formed, the same color shift as described above occurs.

  Therefore, in this embodiment, based on the image data, the first image forming mode in which an image is formed without using any one of the first and second optical scanning devices 4a and 4b, or all It is determined whether the second image forming mode in which an image is formed by using the optical scanning device, and the rotary polygon mirror of the optical scanning device that is not used is rotated for a predetermined time even in the first image forming mode.

FIG. 7 is a control flowchart of each optical scanning device of the present embodiment.
When image data (image signal) sent from a connected personal computer or read by a scanner is input to the control unit 200 (S1), the control unit 200 determines from the image data whether the first image forming mode is set. It is determined whether the second image forming mode. In the present embodiment, when the image data is a single color image, a two-color image of K and M colors, or a two-color image of Y and C colors, any one optical scanning device is not used. It is determined that the image forming mode is the one image forming mode. Otherwise, since all the optical scanning devices are used, the image forming mode is determined as the second image forming mode. In the second image formation mode (YES in S2) in which image formation processing is performed using all the optical scanning scans 4a and 4b, such as when the image data is a full-color image, all the rotary polygon mirrors 49 are rotated ( S3). Then, the light source unit of the corresponding color is turned on by the light source signal generated based on the image data, and writing of the latent image on the corresponding photoconductor is started (S4). When the writing of the latent image on the photosensitive member is completed, the corresponding light source unit is turned off (S5). It is confirmed whether or not there is next image data. If not (NO in S6), all rotary polygon mirrors 49 are stopped (S7), and a standby mode is entered (S8).

  On the other hand, in the first image forming mode (NO in S2) in which the image forming process is performed using one optical scanning device, it is confirmed whether the energy saving mode is set (S9). As illustrated in FIG. 5, the operation display unit 201 is provided with an energy saving button. When the energy saving button is pressed, the control unit 200 determines that the energy saving mode is set. That is, the operation display unit 201 functions as a selection unit. Further, the energy saving mode may be set from the printer application software of the personal computer. When the energy saving mode is set (YES in S9), energy saving is prioritized over image quality, and color misregistration is accepted. Therefore, only the rotating polygon mirror of one of the optical scanning devices is used. Rotate (S10). On the other hand, when the energy saving mode is Off, the image quality is prioritized, so all the rotating polygon mirrors are rotated (S3). Then, the light source unit of any one of the optical scanning devices is turned on to start writing. When the energy saving mode is set to ON, when writing is completed, as described above, it is confirmed whether or not there is the next image data. If not (NO in S6), all the rotary polygon mirrors 49 are stopped. (S7), the standby mode is entered (S8).

  For example, when the image data is a K color single color image, the first image forming mode is set. When the energy saving mode is set, as shown in FIG. 8A, only the rotary polygon mirror of the first optical scanning device 4a rotates, and a latent image is written on the K-color photoconductor 10K. It is. In this case, since the rotary polygon mirror of the second optical scanning device 4b does not rotate, power consumption can be suppressed. On the other hand, when the energy saving mode is not set, as shown in FIG. 8B, the rotary polygon mirrors of the first and second optical scanning devices 4a and 4b are rotated so that the K-color photoconductor 10K is moved. A latent image is written in Thus, after the first image forming mode in which the image is processed without using either the first or second optical scanning device, the image is processed using all the optical scanning devices 4a and 4b. Even if the second image forming mode is executed, an image of a color formed using an optical scanning device that was not used in the first image forming mode, and an image of a color formed using an optical scanning device that was used And a high-quality color image can be obtained. Further, for example, when the image data is a full-color image, the second image forming mode is set, and as shown in FIG. 8C, the rotary polygon mirrors of all the optical scanning devices 4a and 4b are rotated so that each color is changed. Latent images are written on the photoreceptors 10Y, 10M, 10C, and 10K.

  Next, a modification of this embodiment will be described.

[Modification]
For example, when the second image forming mode is executed after the first image forming mode is executed once, the temperature of the optical scanning device used in the first image forming mode has not increased so much, and the housing 100 thermal deformation hardly occurs. Therefore, in such a case, a high-quality image in which color misregistration is suppressed can be obtained without rotating the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode. . For this reason, in Modification 1, based on the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b, the rotating polygon mirror that is not used in the first image forming mode. Whether or not to rotate is determined.

  A thermistor 70 as temperature detecting means is provided in the first optical scanning device 4a and the second optical scanning device 4b in the vicinity of the rotary polygon mirror 49, such as between the rotary polygon mirror 49 and the scanning lens 25. By disposing the thermistor 70 in the vicinity of the rotary polygon mirror 49, the difference between the temperature in the optical scanning device used in the first image forming mode and the temperature in the optical scanning device not in use is increased, thereby increasing the sensitivity. Can do. Therefore, it is possible to improve the accuracy of determining whether to rotate the rotary polygon mirror of the optical scanning device that is not used.

FIG. 9 is a control flowchart of each optical scanning device in the image forming apparatus according to the modification.
As shown in FIG. 9, when it is determined as the first image forming mode (NO in S12) and the energy saving mode is OFF (NO in S19), it is determined whether or not to rotate the rotary polygon mirror that is not used ( S20). When the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b is equal to or less than the threshold value, the rotation-on condition for rotating the rotary polygon mirror of the unused optical scanning device is not reached (in S20). NO), only the rotary polygon mirror of the optical scanning device to be used is rotated (S21). On the other hand, when the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b exceeds the threshold value, the rotation on condition for rotating the rotating polygon mirror that is not used is reached (YES in S20). Therefore, all the rotary polygon mirrors are rotated (S13). The threshold value is a temperature difference at a level at which color misregistration is recognized, and is a value obtained in advance by experiments.

  When the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b is equal to or smaller than the threshold value, even if the second image forming mode is executed after the first image forming mode, there is almost no color misregistration. By rotating only the rotating polygon mirror of the optical scanning device to be used, useless rotation of the rotating polygon mirror can be prevented and the life of the apparatus can be extended. On the other hand, if the temperature difference exceeds the threshold value, color misregistration occurs when the second image forming mode is executed after the first image forming mode. Therefore, all the rotary polygon mirrors are rotated to eliminate the temperature difference. As shown in FIG. 6, when the rotary polygon mirror is rotated for a predetermined time, the temperature in the vicinity of the rotary polygon mirror in the housing and the temperature in the vicinity of the scanning lens settle to predetermined values. Therefore, when all the rotary polygon mirrors are rotated after the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b exceeds the threshold, the temperature in the optical scanning device to be used becomes a predetermined value. Only the temperature in the optical scanning device that is calm and unused is rapidly increased. Therefore, even if all the rotary polygon mirrors are rotated after the temperature difference between the first optical scanning device 4a and the second optical scanning device 4b exceeds the threshold value, the first optical scanning device 4a and the second optical scanning device 4b. The temperature difference between and immediately becomes smaller. Thereby, after the first image forming mode, color misregistration in the second image forming mode can be suppressed. As described above, the optical scanning device according to the modification can stop the rotation of the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode when there is no influence on the color misregistration. Therefore, it is possible to extend the life of the rotary polygon mirror 49 and suppress power consumption while suppressing color misregistration.

  In the case of this modification, when determining whether to rotate the rotary polygon mirror of the optical scanning device that is not used, even if the temperature difference is equal to or less than the threshold value, the temperature difference becomes the threshold value after the end of the first image forming mode. It may be over. If the next print is in the second image forming mode, the difference between the temperature in the first optical scanning device 4a and the temperature in the second optical scanning device 4b exceeds the threshold value. May be executed. Therefore, in the second image forming mode, the temperature in the first optical scanning device 4a and the temperature in the second optical scanning device 4b are detected and the temperature difference is examined. If the temperature difference exceeds the threshold value, the rotary polygon mirror 49 of the optical scanning device having the lower temperature is rotated for a predetermined period (time D shown in FIG. 6), and then the higher temperature is applied. Writing may be started by rotating the rotary polygon mirror of the optical scanning device. As a result, color misregistration during execution of the second image forming mode can be reliably suppressed.

  Further, the rotation-on condition may be that the bearing temperature of the optical scanning device that is not used is equal to or lower than the temperature in the vicinity of the graph A shown in FIG. In this case, the bearing temperature of the unused optical scanning device is detected, and when the temperature of the bearing portion of the unused optical scanning device is equal to or lower than the temperature near the graph A shown in FIG. All the rotating polygonal mirrors are rotated (S13). On the other hand, if the bearing temperature of the unused optical scanning device exceeds the temperature in the vicinity of A, the rotation-on condition is not satisfied (NO in S20 in FIG. 9), so the rotating polygon mirror of the used optical scanning device is not used. Control is performed so as to rotate only (S21). By controlling in this way, when there is no risk of color misregistration, rotation of the rotary polygon mirror 49 of the optical scanning device that is not used is stopped, so that the life of the rotary polygon mirror 49 can be extended while suppressing color misregistration. And power consumption can be reduced.

  Further, the rotation-on condition may be that the rotation time of the optical scanning device used in the first image forming mode exceeds a threshold value. In this case, the control unit 200 provides means for measuring the rotation time of the rotary polygon mirror of each optical scanning device, and measures the rotation time of the optical scanning device to be used. When the measurement time exceeds the threshold value, the rotation-on condition is satisfied (YES in S20), so all the rotary polygon mirrors are rotated (S13). This threshold value is a value obtained by examining the correlation between the color shift and the rotation time in advance through experiments or the like. If the rotation on condition that the rotation time of the optical scanning device used in the first image formation mode has exceeded the threshold value does not affect the color shift, it is used in the first image formation mode. Since the rotation of the rotary polygon mirror 49 of the optical scanning device that has not been operated can be stopped, the life of the rotary polygon mirror 49 can be extended while suppressing color misregistration, and the power consumption can also be reduced.

  Further, the rotation-on condition may be that the rotation time of the optical scanning device not used in the first image forming mode is equal to or less than a threshold value. This threshold is the time D shown in FIG. In this case, at the time of the first printing, the rotation time of the optical scanning device that is not used in the first image forming mode is naturally equal to or less than the threshold value, and therefore satisfies the rotation on condition (YES in S20). The rotating polygon mirror is rotated (S13). There is a next image, printing continues (YES in S16), and the rotation time of the optical scanning device that is not used in the first image forming mode when determining whether or not the second and subsequent rotation on conditions are satisfied is a threshold value (NO in S20), the rotation of the rotary polygon mirror of the unused optical scanning device is stopped, and only the rotary polygon mirror of the optical scanning device to be used is rotated (S21).

  Further, when the rotation on condition is that the rotation time of the optical scanning device not used in the first image forming mode is equal to or less than the threshold value, once the rotation on condition is not satisfied and the rotation stops, In this image forming operation, all rotary polygon mirrors satisfy the rotation on condition and the temperature difference between the unused optical scanning device and the used optical scanning device is sufficiently small. There is a problem of rotating. Therefore, when the rotation on condition that the rotation time of the optical scanning device not used in the first image forming mode is equal to or less than the threshold value is controlled as follows, the above problem can be dealt with. Good. In other words, when the rotation of the rotary polygon mirror of the optical scanning device that is not being used is stopped, the rotation time is not reset, and control is performed so as to be reset when the device standby mode is entered. Thus, after the rotating polygon mirror of the unused optical scanning device rotates for the time D shown in FIG. 6, the rotation on condition is satisfied even when the rotating polygon mirror of the unused optical scanning device is stopped. It will not be satisfied, and all the rotating polygon mirrors will not rotate. By controlling in this way, the rotation of the rotating polygon mirror 49 which is not used can be suppressed, the life of the rotating polygon mirror can be extended, and the power consumption can also be suppressed.

  Further, the control unit 200 includes means for measuring the time during which the rotating polygon mirror is stopped, the rotation time of the optical scanning device not used in the first image forming mode is equal to or less than a threshold value, and A case where the stop time exceeds the threshold may be set as the rotation-on condition. Even in this way, after the rotating polygon mirror of the unused optical scanning device is rotated for the time D shown in FIG. 6, the rotating polygon mirror of the unused optical scanning device is stopped, The rotation-on condition is not satisfied, and all the rotary polygon mirrors do not rotate.

  Further, the rotation-on condition may be that the number of continuous prints in the first image forming mode exceeds a threshold value. In this case, the control unit 200 is provided with means for counting the number of printed sheets. When printing is continued and in the first image forming mode, the count value of the number of printed sheets is incremented. On the other hand, when printing is continued and in the second image forming mode, or when printing is finished and the standby mode is set, the count value of the number of printed sheets is reset. If the count value of the number of printed sheets exceeds the threshold value, the rotation-on condition is satisfied (YES in S20), so that all the rotary polygon mirrors are rotated (S13). The threshold value is a value set based on a correlation obtained in advance by experimenting with a correlation between the number of printed sheets in the first image forming mode and the subsequent color misregistration in the second image forming mode. On the other hand, if it is equal to or less than the threshold value, the rotation-on condition is not satisfied (NO in S20), so only the rotary polygon mirror of the optical scanning device to be used is rotated. As described above, when the continuous printing number in the first image forming mode exceeds the threshold value, even if the rotation-on condition is satisfied, the continuous printing number in the first image forming mode is equal to or less than the threshold value and the color misregistration is not affected. Stops the rotation of the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode, so that the life of the rotary polygon mirror 49 can be extended while suppressing color misregistration, and the power consumption is reduced. Can also be suppressed.

  Further, the rotation-on condition may be that the number of continuous prints in the first image forming mode is less than a threshold value. In this case, at the time of the first printing, the number of continuous prints in the first image forming mode is naturally less than the threshold value and satisfies the rotation on condition (YES in S20), so all the rotating polygon mirrors are rotated. (S13). If the number of continuous prints in the first image forming mode is equal to or greater than the threshold value, the rotation-on condition is not satisfied (NO in S20). Only the polygon mirror is rotated (S21). In this way, by setting the rotation-on condition that the number of continuous prints in the first image forming mode is less than the threshold value, the temperature difference between the first optical scanning device and the second optical scanning device is almost eliminated and the color shift is affected. If there is no more, the rotation of the rotary polygon mirror of the optical scanning device that is not used can be stopped. Therefore, the lifetime of the rotary polygon mirror 49 can be extended while suppressing color misregistration, and power consumption can also be suppressed.

  In the above description, the image forming apparatus includes the first optical scanning device 4a that forms a latent image of K and M colors and the second optical scanning device 4b that forms a latent image of Y and C colors. Although an example to which the invention is applied has been described, as shown in FIG. 10, the present invention is also applied to an image forming apparatus provided with optical scanning devices 4Y, 4M, 4C, and 4K corresponding to Y, M, C, and K, respectively. can do. In this case, the second image forming mode is a case where a full color image using four colors Y, M, C, and K is formed, and other images (single color image, two color image, three color image) are formed. This is the first image forming mode. Further, by applying the present invention to the image forming apparatus shown in FIG. 10, for example, color misregistration in the case of forming a two-color image of C color and K color after forming a single color image of K color can be suppressed. .

  In FIG. 10, a recording paper conveyance belt 140 as a surface moving member is provided instead of the intermediate transfer belt 14, and a recording material is loaded and conveyed by the recording paper conveyance belt 140. This is a linear image forming apparatus that synthesizes a full-color image by sequentially transferring a color toner image onto a recording material.

As described above, according to the image forming apparatus of this embodiment, the rotary polygon mirror 49 is provided, and the rotation of the rotary polygon mirror 49 causes light to be deflected and scanned in the main scanning direction with respect to the surface of the photoreceptor 10 as a latent image carrier. A plurality of optical scanning devices 4 a and 4 b for forming an electrostatic latent image on the photoreceptor 10 are provided. Also, a first image forming mode in which an image is formed without using one of the plurality of optical scanning devices 4a and 4b, and a second image forming mode in which an image is formed using all the optical scanning devices. And a control unit 200 that is a control unit that controls the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode to rotate for a predetermined time.
By having such a configuration, the housing of the optical scanning device that is not used in the first image forming mode is also thermally expanded in the same manner as the housing of the optical scanning device that is used, and similarly, the scanning position is shifted. . Thereby, color misregistration when the second image forming mode is executed after the first image forming mode can be suppressed.

  In particular, by making the optical scanning devices 4a and 4b have the same configuration, the tendency of deformation (thermal deformation) due to the thermal expansion of the housing and the change in the posture of the scanning lenses 25a and 25b due to the thermal deformation are substantially reduced. Be the same. As a result, the positional shift due to the thermal expansion of the housing tends to be the same, so that the color shift when the second image forming mode is executed after the first image forming mode can be suppressed.

  In addition, in the first image forming mode, the operation display unit 201 is provided as a selection unit for selecting whether or not to rotate the rotary polygon mirror of the optical scanning device that is not used, so that it is not used in the first image forming mode. The user can select whether or not to rotate the rotary polygon mirror 49 of the optical scanning device. Accordingly, if the user having a high degree of tolerance of image quality selects not to rotate the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode, the consumption in the first image forming mode is performed. Power can be reduced. In addition, if it is selected not to rotate the rotating polygon mirror 49 of the optical scanning device that is not used in the first image forming mode, the life of the rotating polygon mirror 49 can be extended.

  In addition, the control unit 200 controls to start rotation of the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode at the timing when the color misregistration occurs. Thereby, when there is no influence on the color misregistration, the rotation of the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode can be stopped, and the same timing as that of the optical scanning device to be used. Thus, the life of the rotating polygon mirror 49 can be extended as compared with the case where the rotating polygon mirror 49 is rotated. In addition, power consumption can be suppressed.

  Specifically, the control unit 200 calculates the temperature near the rotating polygon mirror of the optical scanning device used in the first image forming mode and the temperature near the rotating polygon mirror of the optical scanning device not used in the first image forming mode. When the difference exceeds a threshold value, control is performed to rotate the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode. It is possible to start rotation of the rotary polygon mirror of the optical scanning device that does not.

  Further, when the rotation time of the rotary polygon mirror 49 of the optical scanning device used in the first image forming mode exceeds a threshold value, control is performed to rotate the rotary polygon mirror 49 of the optical scanning device not used in the first image forming mode. Even when the color misregistration occurs, the rotation of the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode can be started.

  Further, when the number of continuous image formations in the first image formation mode exceeds a threshold value, the timing at which color misregistration occurs even if the rotary polygon mirror 49 of the optical scanning device not used in the first image formation mode is controlled to rotate. Thus, the rotation of the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode can be started.

  As shown in FIG. 6, when the rotary polygon mirror 49 is rotated for a certain period, the temperature becomes substantially constant. Accordingly, when the temperature in the vicinity of the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode rises to some extent, even if the rotation of the rotary polygon mirror 49 that is not used is stopped, a temperature difference at a level at which color misregistration can be ignored. Can be maintained. Therefore, when the temperature in the vicinity of the rotary polygon mirror of the optical scanning device not used in the first image forming mode reaches a predetermined value, the rotation of the rotary polygon mirror 49 of the optical scanning device not used in the first image forming mode is stopped. By controlling, the lifetime of the rotary polygon mirror 49 can be extended, and color misregistration can be suppressed. Furthermore, power consumption can be suppressed.

  Specifically, when the rotation time of the rotary polygon mirror 49 of the optical scanning device that is not used in the first image forming mode exceeds a threshold value, the rotation of the rotary polygon mirror 49 of the optical scanning device that is not used in the first image formation mode. Is stopped, the rotary polygon mirror 49 can be stopped when the temperature in the vicinity of the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode reaches a predetermined value.

  Further, when the number of continuous image formations in the first image forming mode after the rotation of the rotary polygon mirror 49 of the optical scanning device not used in the first image forming mode exceeds a threshold value, the optical scanning device is not used in the first image forming mode. Even if control is performed to stop the rotation of the rotary polygon mirror 49 of the optical scanning device, the rotary polygon mirror is turned on when the temperature in the vicinity of the rotary polygon mirror of the optical scanning device that is not used in the first image forming mode reaches a predetermined value. Can be stopped.

4a, 4b: optical scanning device 10: photoconductor 25a, 25b: scanning lens 41: light source unit 49: rotary polygon mirror 50: rotary deflector 50a: bearing 70: thermistor 100: optical housing 200: control unit 201: operation display unit

Japanese Patent No. 4058975 Japanese Patent No. 4350270

Claims (10)

A plurality of optical scanning devices each including a rotating polygon mirror and forming an electrostatic latent image on the latent image carrier by deflecting and scanning light in the main scanning direction with respect to the surface of the latent image carrier by rotation of the rotating polygon mirror. Prepared,
An image having a first image forming mode in which an image is formed without using at least one of the plurality of optical scanning devices, and a second image forming mode in which an image is formed using all the optical scanning devices. In the forming device,
An image forming apparatus comprising: control means for controlling to rotate a rotary polygon mirror of an optical scanning apparatus not used in the first image forming mode for a predetermined time. 2. The image forming apparatus according to claim 1, wherein each of the optical scanning devices has the same configuration. The image forming apparatus according to claim 1 or 2,
An image forming apparatus comprising: selection means for selecting whether or not to rotate a rotary polygon mirror of an optical scanning apparatus that is not used in the first image forming mode. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the control means controls to start rotation of a rotary polygon mirror of an optical scanning device that is not used in the first image forming mode at a timing when color misregistration occurs. The image forming apparatus according to claim 4.
Each optical scanning device is provided with temperature detecting means for detecting the temperature in the vicinity of the rotary polygon mirror,
The control means determines that the difference between the temperature near the rotating polygon mirror of the optical scanning device used in the first image forming mode and the temperature near the rotating polygon mirror of the optical scanning device not used in the first image forming mode sets a threshold value. An image forming apparatus that controls to rotate a rotating polygon mirror of an optical scanning device that is not used in the first image forming mode when exceeding. The image forming apparatus according to claim 4.
The control means rotates the rotary polygon mirror of the optical scanning device not used in the first image formation mode when the rotation time of the rotary polygon mirror of the optical scanning device used in the first image formation mode exceeds a threshold value. An image forming apparatus that controls the image forming apparatus. The image forming apparatus according to claim 4.
The control means controls the rotating polygon mirror of the optical scanning device not used in the first image forming mode to rotate when the number of continuous images formed in the first image forming mode exceeds a threshold value. Forming equipment. The image forming apparatus according to claim 1,
The control means stops the rotation of the rotating polygon mirror of the optical scanning device not used in the first image forming mode when the temperature in the vicinity of the rotating polygon mirror of the optical scanning device not used in the first image forming mode reaches a predetermined value. An image forming apparatus that is controlled to perform. The image forming apparatus according to claim 8.
The control means stops rotation of the rotating polygon mirror of the optical scanning device not used in the first image forming mode when the rotation time of the rotating polygon mirror of the optical scanning device not used in the first image forming mode exceeds a threshold value. An image forming apparatus. The image forming apparatus according to claim 8.
The control means is used in the first image forming mode when the number of continuous image formations in the first image forming mode after the rotation of the rotary polygon mirror of the optical scanning device not used in the first image forming mode exceeds a threshold value. An image forming apparatus that controls to stop the rotation of the rotary polygon mirror of the optical scanning device that does not perform the operation.

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