JP2009015241A - Image forming apparatus and its color shift correcting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and its color shift correcting method for carrying out color shift correcting operation at suitable timing without worsening a color shift according to a print mode. <P>SOLUTION: Temperature in the image forming apparatus is measured by a temperature sensor 304, and each amount of temperature rise in the print mode is computed. Each computed amount of temperature rise is converted into a color shift amount by conversion data for every print mode, and when the total of the converted color shift amounts exceeds a predetermined value, the color shift correcting operation is carried out. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image using an electrophotographic process, and more particularly to an image forming apparatus capable of printing a color image and a color misregistration correction method thereof.

  2. Description of the Related Art Conventionally, some image forming apparatuses such as copying machines and printers that print color images (multicolor images) using an electrophotographic process are equipped with a scanning optical device 7 shown in FIG. In such an image forming apparatus, the temperature inside the apparatus is raised by heat generated during operation, and color misregistration occurs due to thermal expansion and deformation of each part. The main factors that cause color misregistration due to temperature rise include the following.

  1. The thermal expansion of the optical box 34 shown in FIG. 3 and the change in the refractive index of the lens disposed in the scanning optical device 7 occur, and yellow (Y), magenta (M), cyan (C), and black (Bk). The irradiation position of the beam for exposing each color varies.

  2. The relative position between the photosensitive drum and the beam fluctuates due to thermal expansion of the member that supports the photosensitive drum.

  3. When the driving gears and the like are thermally expanded, the feed speed of the photosensitive drum and the transfer unit is fluctuated, and the exposure timing of each color of Y, M, C, and Bk is shifted.

  FIGS. 7A and 7B show the state of the scanning line when color misregistration occurs due to temperature rise and when color misregistration is corrected. In FIGS. 7A and 7B, for easy understanding, the change in the scanning line due to the inclination or bending of each part is not taken into account, and the fluctuation amount in the figure is also expressed greatly. ing.

  As shown in FIG. 7A, the Y, M, C, and Bk scanning lines on the same line move to different positions as the temperature rises in the image forming apparatus, so that color images are properly formed. It becomes impossible to do. Therefore, in the conventional image forming apparatus, as shown in FIG. 7B, a color misregistration correction operation for correcting a scanning line in which color misregistration has occurred is performed at a predetermined timing, and the misaligned scanning lines are overlapped again. Adjustments have been made to match.

  In such a color misregistration correction operation, an image (for example, a registration pattern) for measuring the amount of color misregistration is formed on the transfer body before or during the start of the job, and the registration pattern is arranged downstream of the photosensitive drum. Reading is performed by a detecting means such as a CCD. Then, the color misregistration amount of each color is measured, and a correction value for the scanning line of each color is calculated based on the result.

  As other examples of the color misregistration correction method, a method of correcting the exposure timing of laser light and a method of performing readjustment by driving a mirror or a lens with a motor or the like are generally used. With respect to the timing of performing the color misregistration correction operation and its operation, a method has been proposed in which the temperature in the light beam scanning device is detected and color misregistration correction is performed based on the output of the detecting means (for example, Patent Document 1). reference).

  In order to correct color misregistration, a method is known in which a temperature sensor is arranged at a predetermined position and the timing of color misregistration correction is determined using the output of the temperature sensor.

On the other hand, in recent image forming apparatuses, in order to improve the productivity at the time of monochromatic image formation, measures such as increasing the process speed and shortening the interval between sheets when taking a monochromatic image compared with the case of forming a multicolor image are taken. It has been.
JP-A-8-272936

  However, not only the temperature increase amount of the image forming apparatus is different between the monochrome image formation and the multicolor image formation, but also the temperature increase rate and the temperature increase characteristics of each part in the apparatus change. For example, if the process speed is different between monochromatic image formation and multicolor image formation, the number of revolutions of the motor arranged in the drive system of the main body or the polygon motor in the scanning optical apparatus is increased during monochromatic image formation. Thereby, not only the temperature rise amount but also the rising speed of the temperature rise changes in each part as compared with the time of forming the multicolor image.

  Further, as described above, the color misregistration due to the temperature rise occurs due to a combination of a plurality of factors. Therefore, when the temperature rise characteristic of each part changes relatively, the color misregistration amount also changes. On the other hand, in the image forming apparatus, for example, the timing for color misregistration correction is determined from the output result of a temperature sensor installed in the apparatus. For this reason, when a change in the temperature rise characteristic occurs due to the print mode, a deviation occurs between the temperature change in the vicinity of the temperature sensor and the actual color misregistration amount. In that case, the color misregistration correction operation cannot be performed at an appropriate timing, and the color misregistration amount exceeds the allowable value before judging that the color misregistration correction operation is necessary based on the output result of the temperature sensor, resulting in poor quality. An image will be output.

  The present invention has been made in view of the above problems, and an image forming apparatus capable of performing a color misregistration correction operation at an appropriate timing without deteriorating the color misregistration in accordance with a print mode, and the color misregistration correction. It aims to provide a method.

  In order to achieve the above object, the image forming apparatus according to claim 1 includes an image forming unit that performs image formation in a first print mode that performs monochromatic image formation or a second print mode that performs multicolor image formation; In an image forming apparatus including a color misregistration correction unit that corrects color misregistration during image formation, a measurement unit that measures a temperature in the image forming apparatus, and a calculation that calculates a temperature increase amount in each print mode And a conversion unit that converts each calculated temperature increase amount into a color misregistration amount based on conversion data for each printing mode, and the color misregistration correction unit has a predetermined sum of the converted color misregistration amounts. The color misregistration correction is executed when the value is exceeded.

  In order to achieve the above object, an image forming apparatus according to claim 3, image forming means for forming an image in a first print mode for performing monochromatic image formation or a second print mode for performing multicolor image formation; In an image forming apparatus including a color misregistration correction unit that corrects color misregistration during image formation, a calculation unit that calculates the number of prints in each print mode, and the calculated number of prints for each print mode. Conversion means for converting the amount of color misregistration into the amount of color misregistration, and the color misregistration correction means performs the color misregistration correction when the total of the converted color misregistration amounts exceeds a predetermined value. And

  In order to achieve the above object, an image forming apparatus according to claim 4, image forming means for performing image formation in a first print mode for performing monochromatic image formation or a second print mode for performing multicolor image formation; In an image forming apparatus including a color misregistration correction unit that corrects color misregistration during image formation, a calculation unit that calculates an operation time in each print mode, and the calculated operation time for each print mode. Conversion means for converting the amount of color misregistration into the amount of color misregistration, and the color misregistration correction means performs the color misregistration correction when the total of the converted color misregistration amounts exceeds a predetermined value. And

  In order to achieve the above object, a color misregistration correction method for an image forming apparatus according to claim 9 performs image formation in a first print mode for forming a single color image or a second print mode for forming a multicolor image. In a color misregistration correction method for an image forming apparatus, comprising: an image forming unit; and a color misregistration correcting unit that corrects the color misregistration at the time of image formation; a measuring step of measuring a temperature in the image forming apparatus; and each printing mode A calculation step for calculating a temperature rise amount at each time, a conversion step for converting each calculated temperature rise amount into a color misregistration amount based on conversion data for each printing mode, and a total of the converted color misregistration amounts. And a color misregistration correction step of executing color misregistration correction by the color misregistration correction means when a predetermined value is exceeded.

  In order to achieve the above object, the color misregistration correction method of the image forming apparatus according to claim 11 is an image in which image formation is performed in a first print mode for performing monochromatic image formation or a second print mode for performing multicolor image formation. In a color misregistration correction method for an image forming apparatus comprising a forming unit and a color misregistration correction unit for correcting color misregistration at the time of image formation, a calculation step of calculating the number of prints in each of the print modes, and the calculation A conversion step of converting each print number into a color shift amount by using conversion data for each print mode, and color shift correction by the color shift correction means when the total of the converted color shift amounts exceeds a predetermined value. And a color misregistration correction step to be executed.

  In order to achieve the above object, the color misregistration correction method of the image forming apparatus according to claim 12 is an image in which image formation is performed in a first print mode for performing monochromatic image formation or a second print mode for performing multicolor image formation. In a color misregistration correction method for an image forming apparatus comprising a forming unit and a color misregistration correction unit for correcting color misregistration during image formation, a calculation step of calculating an operation time in each printing mode, and the calculation A conversion step of converting each operation time into a color misregistration amount using conversion data for each print mode, and color misregistration correction by the color misregistration correction means when the total of the converted color misregistration amounts exceeds a predetermined value. And a color misregistration correction step to be executed.

  In order to achieve the above object, an image forming apparatus according to claim 17, an image forming unit that forms an image in a first print mode that performs monochromatic image formation or a second print mode that performs multicolor image formation; In an image forming apparatus comprising color misregistration correction means for correcting color misregistration at the time of image formation, calculation means for calculating a temperature increase amount or the number of prints in each print mode or an operation time of the image forming apparatus, Conversion means for converting the calculated result into a color misregistration amount based on the conversion data for each print mode, and the color misregistration correction means performs color misregistration correction every time the amount of change in the color misregistration amount changes by a certain amount. It is characterized by performing.

  In order to achieve the above object, the color misregistration correction method for an image forming apparatus according to claim 18 forms an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image. In a color misregistration correction method for an image forming apparatus comprising an image forming unit and a color misregistration correcting unit for correcting color misregistration at the time of image formation, the temperature rise amount or the number of prints in each of the print modes, or the image forming apparatus A calculation step for calculating an operation time; a conversion means for converting the calculated result into a color shift amount based on conversion data for each print mode; and the color shift every time the amount of change in the color shift amount changes by a certain amount. And a color misregistration correction step of performing color misregistration correction by a correcting means.

  According to the present invention, it is possible to perform the color misregistration correction operation at an appropriate timing without deteriorating the color misregistration according to the print mode.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, an image forming apparatus 1 includes an image forming unit using an electrophotographic process and a tandem intermediate transfer belt (intermediate transfer member), and forms a predetermined toner image on the intermediate transfer belt to form an image. Do.

  The image forming apparatus 1 includes an image forming unit 1Y that forms a yellow (Y) image, an image forming unit 1M that forms a magenta (M) image, and an image forming unit 1C that forms a cyan (C) image. The image forming unit 1Bk for forming a black (Bk) image is provided. These image forming units 1Y, 1M, 1C, and 1Bk are arranged in a line at regular intervals.

  The paper feed cassette 17 stores a plurality of recording media (transfer materials) P. The manual feed tray 20 is used when the recording medium P is manually printed. The pickup roller 30 feeds the recording medium P from the paper feed cassette 17 or the manual feed tray 20 one by one.

  The paper feed guide 18 is for guiding the recording medium P sent out from each pickup roller 30 to the registration roller 19. The registration roller 19 feeds the recording medium P to the secondary transfer area in accordance with the image formation timing of each image forming unit. The secondary transfer area includes a secondary transfer counter roller 10 and a secondary transfer roller 12.

  In each of the image forming units 1Y, 1M, 1C, and 1Bk, drum-type electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) 2a, 2b, 2c, and 2d are installed as image carriers. Around the photosensitive drums 2a to 2d, primary chargers 3a, 3b, 3c, and 3d as primary charging units, developing devices 4a, 4b, 4c, and 4d, and transfer rollers 5a, 5b, and 5c as primary transfer units, respectively. , 5d, drum cleaner devices 6a, 6b, 6c, 6d are disposed. A laser exposure device (scanning optical device) 7 is installed below the primary chargers 3a to 3d and the developing devices 4a to 4d.

  Each of the photosensitive drums 2a to 2d is composed of a negatively charged OPC photosensitive member in which a photoconductive layer is laminated on an aluminum drum base, and is driven in an arrow direction (clockwise direction) by a driving device (not shown). It is rotationally driven at a predetermined process speed. The primary chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown).

  The scanning optical device 7 exposes each of the photosensitive drums 2a to 2d, so that each surface of the photosensitive drums 2a to 2d charged by the primary chargers 3a to 3d forms an electrostatic latent image of each color according to the image information. Form. A temperature sensor 304 is installed on the scanning optical device 7, and the temperature in the image forming apparatus can be measured by the temperature sensor 304.

  The developing device 4a stores yellow (Y) toner, the developing device 4b stores cyan (C) toner, the developing device 4c stores magenta (M) toner, and the developing device 4d stores black (Bk) toner. ing. Each of the developing devices 4a to 4d attaches toner of each color to each electrostatic latent image formed on each of the photosensitive drums 2a to 2d, and develops (visualizes) the toner image.

  The transfer rollers 5a to 5d are disposed so as to be in contact with the photosensitive drums 2a to 2d via the intermediate transfer belt 8 at primary transfer portions 32a, 32b, 32c, and 32d, respectively. Each of the transfer rollers 5a to 5d sequentially transfers the toner images on the photosensitive drums 2a to 2d onto the intermediate transfer belt 8 and superimposes them.

  The drum cleaners 6a to 6d are constituted by cleaning blades or the like, and scrape off the residual transfer toner remaining on the photosensitive drums 2a to 2d during the primary transfer from the photosensitive drums 2a to 2d, thereby removing the surface of each photosensitive drum. to clean up.

  The intermediate transfer belt 8 is disposed on the upper surface side of each of the photosensitive drums 2 a to 2 d and is stretched between the secondary transfer counter roller 10 and the tension roller 11. The intermediate transfer belt 8 is made of dielectric resin such as polycarbonate, polyethylene terephthalate resin film, and polyvinylidene fluoride resin film.

  The secondary transfer counter roller 10 is disposed so as to be in contact with the secondary transfer roller 12 via the intermediate transfer belt 8.

  The image transferred to the intermediate transfer belt 8 is transferred onto the recording medium P conveyed from the paper feed cassette 17. A belt cleaning device (not shown) that removes and collects transfer residual toner remaining on the surface of the intermediate transfer belt 8 is installed outside the intermediate transfer belt 8 and in the vicinity of the tension roller 11.

  The fixing device 16 includes a fixing film 16a having a heat source such as a ceramic heater substrate therein, and a pressure roller 16b (which may be provided with a heat source in some cases) pressed with the film sandwiched between the film. Become.

  The conveyance guide 34 guides the recording medium P discharged from the secondary transfer area to the nip portion 31 of the fixing device 16. The outer paper discharge roller 21 is for guiding the recording medium P discharged from the fixing device 16 to the paper discharge tray 22.

  The controller unit (not shown) includes a control board and a motor driver board (not shown) for controlling the operation of the mechanism in the scanning optical device.

  Next, an image forming operation in the image forming apparatus 1 of FIG. 1 will be described.

  When the image forming apparatus 1 receives an image forming operation start signal from a personal computer (hereinafter referred to as “PC”) or an operation unit (not shown) connected to the image forming apparatus 1, the selected paper cassette 17 Alternatively, the paper feeding operation is started from the manual feed tray 20. For example, a case where paper is fed from the paper feed cassette 17 will be described. First, the recording medium P is sent out one by one from the paper feed cassette 17 by the pickup roller 30.

  Then, the recording medium P is conveyed to the registration roller 19 via the paper feed guide 18. At that time, the registration roller 19 is stopped, and the leading end of the recording medium P hits the nip. Thereafter, the registration roller 19 starts rotating based on a timing signal at which the image forming units 1Y, 1M, 1C, and 1Bk start image formation. The timing of the rotation is set so that the toner image primarily transferred onto the intermediate transfer belt 8 by the image forming units 1Y, 1M, 1C, and 1Bk and the recording medium P exactly coincide with each other in the secondary transfer region. ing.

  On the other hand, when the image forming units 1Y, 1M, 1C, and 1Bk receive the image forming operation start signal, they form electrostatic latent images of the respective colors on the photosensitive drums 2a to 2d.

  The image forming timing of each photosensitive drum in the sub-scanning direction is the distance between the image forming units in order from the photosensitive drum 2a that is the most upstream in the driving direction of the intermediate transfer belt 8 (image forming unit 1Y in this embodiment). Are determined and controlled accordingly.

  Further, the writing timing in the main scanning direction of each photosensitive drum is determined by using a single BD sensor signal (arranged in the image forming unit 1Bk in the present embodiment) by a circuit (not shown) and using a pseudo BD sensor signal. Generate and control.

  The formed electrostatic latent image is developed by the process described above. Then, in the primary transfer area, the toner image formed on the photosensitive drum 2 a located at the most upstream is primarily transferred to the intermediate transfer belt 8 by the transfer roller 5 a to which a high voltage is applied.

  The primarily transferred toner image is conveyed to the position of the transfer roller 5b. In response to the timing signal generated there, image formation is performed with a delay by the time during which the toner image is conveyed between the image forming units. As a result, the next toner image is transferred by aligning the resist on the previous image. Thereafter, the processing is repeated in the same manner, and eventually, four color toner images are primarily transferred onto the intermediate transfer belt 8.

  Thereafter, when the recording medium P is conveyed to the secondary transfer area and contacts the intermediate transfer belt 8, a high voltage is applied to the secondary transfer roller 12 in accordance with the passage timing of the recording medium P. Then, the four color toner images transferred onto the intermediate transfer belt 8 by the above-described process are transferred onto the surface of the recording medium P.

  After the toner image is transferred, the recording medium P is guided to the fixing roller nip portion by the conveyance guide 34. The toner image is fixed on the surface of the recording medium by the heat of the fixing film 16a and the pressure roller 16b and the pressure of the nip. Thereafter, the recording medium P is discharged out of the apparatus by the external paper discharge roller 21, and a series of image forming operations is completed.

  In this embodiment, the image forming units are arranged in the order of Y, M, C, and Bk from the upstream side. However, this is determined by the characteristics of the apparatus, and is not limited to this. Absent.

  FIG. 2 is a block diagram showing an internal configuration of the controller unit in the image forming apparatus 1 of FIG.

  In FIG. 2, the controller unit 150 can be directly connected to an external personal computer (or via a network (not shown)).

  The controller unit 150 includes a CPU 2201, a bus driver circuit / address decoder circuit 2202, a ROM 2203, a RAM 2204, an I / O interface 206, and a laser drive signal generation unit (PWM: PulseWidthModulation) 2215.

  The CPU 2201 controls the apparatus main body, and sequentially reads out and executes the program from the ROM 2203 storing the control procedure (control program) of the apparatus main body. The address bus and data bus of the CPU 2201 are connected to each load via a bus driver circuit / address decoder circuit 202. A RAM 2204 is a random access memory (RAM) that is a main storage device used as a storage area for input data, a working storage area, or the like.

  The I / O interface 206 is an image forming apparatus such as an operation panel 151, a motor 207 that drives the paper feed system, a transport system, and an optical system, a clutch 208, a solenoid 209, and a detection sensor 210 such as a temperature sensor 304. 1 connected to each load.

  The toner residual detection sensor 211 is disposed in each of the developing devices 4 a to 4 d described above, detects the amount of toner in the developing device, and inputs the output signal to the I / O interface 206. The switches 212 detect the home position of each load, the open / closed state of the door, and the like, and input the output signals to the I / O interface 206. The high voltage unit 213 applies high voltage to the primary chargers 3a to 3d, the developing devices 4a to 4d, the pre-transfer charger (not shown), the transfer charger (not shown), and the separation charger (not shown) according to the instruction of the CPU 2201. Output.

  The image processing unit 300 performs image processing on the image signal input from the personal computer 106 or the like, and outputs a laser drive signal to the scanning optical device 7 via the PWM 2215. The laser light output from the scanning optical device 7 is exposed by irradiating the photosensitive drums 2a to 2d, the light emission state is detected by the beam detection sensor 214 as a light receiving sensor, and the output signal thereof is the I / O interface 206. Is output.

  FIG. 3 is a longitudinal sectional view showing a schematic configuration of the scanning optical device 7 in FIG.

  The scanning optical device 7 includes a rotary polygon mirror (hereinafter referred to as “polygon mirror”) 30 that deflects and scans laser light emitted based on image information, constant-speed scanning of laser light and spot imaging on a drum. Fθ lenses 31a and 31b to be provided. Further, the apparatus includes a plurality of folding mirrors 32 that reflect laser light in a predetermined direction, an optical box 34 that stores each component, and an upper lid 35 to which dustproof glasses 33a to 33d are fixed.

  Next, temperature rise characteristics in the apparatus when image formation is performed in a print mode (monochrome mode) for forming a monochromatic image (monochrome image) and a print mode (color mode) for forming a multicolor image (color image) explain.

  The image forming apparatus 1 has a productivity of 20 ppm at the time of forming a multicolor image and a process speed of 100 mm / s, whereas a productivity at the time of forming a monochromatic image is 30 ppm and the process speed is 150 mm / s. When the productivity is different between single-color image formation and multi-color image formation, the temperature rise rate of each heat source such as a motor or heater differs depending on the print mode.

  As described above, the color misregistration due to the temperature rise occurs due to the thermal expansion of each part or the refractive index change of the optical system. Therefore, when the temperature rise rate of each part changes relatively, the behavior of color misregistration changes. As a result, a change occurs in the correlation between the output of the temperature sensor installed at a predetermined location and the amount of color misregistration generated.

  Therefore, in the present embodiment, conversion data for each print mode for converting the amount of temperature rise in the print mode, the number of printed sheets, or the operation time of the image forming apparatus into the color misregistration amount is prepared in advance. The amount of color misregistration for each job is calculated from the contents of each job. Then, the calculated color misregistration amount is cumulatively added, and when the cumulative color misregistration amount exceeds a predetermined value, the color misregistration correction operation is executed. This will be specifically described below.

  4A to 4C are diagrams showing the temperature rise characteristics in the image forming apparatus in the single color mode and in the color mode. FIG. 4A shows the inside of the scanning optical apparatus 7, and FIG. The periphery of the photosensitive drum, (c) is the vicinity of the fixing device. As shown in the figure, each part in the apparatus has different characteristic values such as a temperature rise and a time constant because the heat sources for raising the temperature are different.

  In the image forming apparatus 1, a polygon motor (not shown) that drives the polygon mirror 30, a motor (not shown) that drives the paper conveyance unit and the image forming unit, and a motor and heater disposed in the fixing device 16 during image formation. Heat is generated from (not shown). Further, the heat of the recording medium P that has passed through the fixing device 16 also remains in the apparatus via the conveyance path. These heats are accumulated over time, and generally the temperature in the apparatus rises in a predetermined temperature rising curve according to a first-order lag function.

  As described above, since image formation is performed at a lower process speed in the color mode (second print mode) than in the single color mode (first print mode), the amount of heat generated by each heat source compared to the single color mode. The temperature rise rate and the maximum temperature rise amount are small. Further, the difference between the temperature increase rate and the maximum temperature increase amount between the color output and the black monochrome output differs depending on each part.

  As described above, the temperature rise characteristics of each heat source differ depending on the print mode such as the color mode or the single color mode, and therefore the speed and behavior of the color misregistration generated in the image forming apparatus 1 change. As a result, in the method of estimating the color misregistration amount from the measurement result by the temperature sensor 304 provided in the image forming apparatus 1, the color misregistration amount recognized by the apparatus is different from the actual color misregistration amount. Therefore, the image forming apparatus 1 controls the color misregistration correction timing by executing the processing shown in FIG.

  FIG. 5 is a flowchart showing a control process of the color misregistration correction operation executed in the image forming apparatus 1.

  In FIG. 5, in step S201, it is determined whether or not the print mode of the given job is the color mode. If the print mode is the color mode, the process proceeds to step S201, and if not the color mode, that is, the single color mode, the process proceeds to step S209. . In this embodiment, since the amount of color misregistration varies depending on the print mode, when a job is given, the processing path is changed according to the print mode of the job.

  Steps S202 to S204 and S209 to S211 all indicate processing when control is performed using the output of the temperature sensor 304 serving as a change amount measuring unit. For example, when a color mode job is given to the image forming apparatus 1 (YES in step S201), first, the temperature (h1) in the apparatus before starting the job is measured by the temperature sensor 304, and the temperature information is stored in the memory. (Step S202). Next, the temperature (h2) in the apparatus at the end of the job is measured (step S203), and the temperature rise due to the job is calculated (h2-h1) (step S203).

  Next, the color misregistration amount is calculated using the conversion data in the color mode stored in advance in the image forming apparatus 1 with respect to the temperature increase amount calculated in step S203 (step S205). Next, the calculated color misregistration amount is cumulatively added to the color misregistration amount calculated by the previous job (step S206).

  If the accumulated color misregistration amount exceeds a predetermined value (YES in step S207), the color misregistration correction operation of the image forming apparatus 1 is executed (step S208). On the other hand, if the predetermined value is not exceeded (NO in step S207), the color misregistration correction operation is not performed, the process returns to step S201, and the image forming apparatus 1 enters a standby state.

  In steps S209 to S211, processing similar to that in steps S202 to 204 is performed. In step S212, the amount of color misregistration is calculated using conversion data other than in the color mode, and the process proceeds to step S206.

  The change amount measurement unit described above exemplifies the temperature sensor 304 that is a measurement unit for measuring the temperature rise amount. However, the change amount measurement unit may be a measurement unit that counts the number of printed sheets in the job, and the operation of the image forming apparatus 1. It may be a measuring means for counting time. In these cases, the same effect can be obtained by converting the calculated number of printed sheets and the operation time of the image forming apparatus 1 into the amount of color misregistration using the conversion data for each printing mode.

  Next, the process of calculating the color misregistration amount due to the temperature rise will be described with reference to FIGS. 6 (a) and 6 (b).

  FIG. 6 is a diagram showing an example of conversion data for converting the temperature rise amount into the color misregistration amount, and FIG. 6A shows the correlation between the job and the temperature in the apparatus (output value of the temperature sensor 304). (B) is a diagram showing the correlation between the temperature rise amount and the color misregistration amount.

  In FIG. 6A, it can be seen that the temperature increase amount and the temperature increase rate in the apparatus are larger in the monochromatic mode than in the color mode. Here, the cumulative addition of color misregistration amounts when job 1 and job 2 are given will be described. Job 1 is a job when the print mode is the color mode, and job 2 is a job when the print mode is the single color mode.

  When the color mode job 1 is given, the image forming apparatus 1 rises in temperature by T1 (for example, 7 ° C.). The color misregistration amount at that time is converted to X1 = 20 [μm] based on the conversion data in the color mode of the graph shown in FIG.

  Next, when the monochrome mode job 2 is given, the image forming apparatus 1 raises the temperature based on the temperature rise characteristic in the monochrome mode, not the temperature rise characteristic in the color mode. Following the path of the arrow, the temperature changes. The amount of temperature rise at that time is T2 (4 ° C.) from the graph. Then, the color misregistration amount due to the temperature rise of T2 becomes the converted value X2 = 15 [μm] based on the conversion data in the single color mode of the graph shown in FIG. From these results, the color misregistration amount generated by the two jobs 1 and 2 can be calculated by the following equation. The color misregistration correction operation is executed when the total value of the color misregistration amounts exceeds a predetermined value. The color misregistration correction operation may be performed every time the total value of the color misregistration amounts after executing the previous color misregistration correction exceeds a predetermined value.

Total color shift amount generated by jobs 1 and 2 = X1 + X2 = 20 + 15 = 35 [μm]
In this embodiment, the color misregistration correction operation when the image forming apparatus 1 continuously executes the job 1 in the color mode and the job 2 in the single color mode has been described. However, when the job in the color mode is continuously executed The color misregistration correction operation is executed in the same manner as described above. Further, the number of jobs to be executed is not limited to the above embodiment.

  If the color misregistration correction operation is performed for each predetermined amount of change in color misregistration, uniform performance can be obtained, but the interval for executing the color misregistration correction operation does not necessarily have to be the same. The color misregistration correction operation may be executed every time the amount of color misregistration change changes by a certain amount. For example, when the color misregistration amount is Y1 [μm] when job 1 is executed and the color misregistration amount is Y2 [μm] when job 2 is executed, the change amount of the color misregistration amount is (Y2−Y1) ≧ 10 [μm. ], The color misregistration correction operation may be performed.

  About the conversion data from the temperature rise amount in the apparatus to the color misregistration amount, instead of the graph format illustrated in FIGS. 6A and 6B, a conversion table, a conversion formula, or a conversion table may be used. Any shape can be used as long as the color shift amount can be converted from the output of the temperature sensor 304. Further, even when the number of printed sheets or the operation time of the image forming apparatus 1 is converted into the color misregistration amount, it may be in the illustrated graph format, a conversion table, a conversion formula, or a conversion table.

  When the scanning optical device is arranged for each of the plurality of photosensitive drums, the temperature increase amount may be lower in the single color mode than in the color mode depending on conditions. Even in this case, the change speed and behavior of the color misregistration differ depending on the print mode. If conversion data is prepared for each print mode, the same effect can be obtained by the method described above.

  If the color misregistration correction operation is performed at the time of color image formation, a desired purpose can be achieved. Therefore, when the color misregistration amount exceeds a predetermined value at the time of monochromatic image formation, it is not necessary to perform the color misregistration correction operation. Furthermore, in order to eliminate machine downtime during image formation, if the amount of color misregistration exceeds a predetermined value during a job, the color misregistration correction operation is waited until the end of the job, and the color at the end of the job or job starts. A shift correction operation may be performed. The job start time is, for example, immediately before the next color image formation.

  The method described in the above embodiment is not applied only to a scanning optical device that exposes a plurality of photosensitive drums with a single polygon mirror, regardless of the optical arrangement and number of scanning optical devices. The same effect can be obtained.

  According to the above embodiment, the temperature in the image forming apparatus is measured by the temperature sensor 304, and the temperature increase amount in the print mode is calculated. Then, each calculated temperature rise amount is converted into a color misregistration amount using conversion data for each printing mode, and a color misregistration correction operation is executed when the total of the converted color misregistration amounts exceeds a predetermined value. Thereby, the color misregistration correction operation can be performed at an appropriate timing without deteriorating the color misregistration according to the print mode.

  In the above embodiment, the temperature sensor 304 is disposed on the scanning optical device 7, but the present invention is not limited to this. ~ 3. It may be arranged in a portion where color misregistration occurs due to thermal expansion. In the above embodiment, the color misregistration amount is converted based on the temperature rise amount, but it may be a temperature rise rate.

  The object of the present invention is achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, a case where the functions of the above-described embodiment are realized by the following processing is also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an internal configuration of a controller unit in the image forming apparatus of FIG. 1. It is a longitudinal cross-sectional view which shows schematic structure of the scanning optical apparatus in FIG. 3A and 3B are diagrams illustrating temperature rise characteristics in the image forming apparatus in a single color mode and a color mode, in which FIG. 5A shows the inside of the scanning optical device 7, FIG. . 4 is a flowchart showing a control process of a color misregistration correction operation executed in the image forming apparatus 1. It is a figure which shows an example of the conversion data for converting temperature rising amount into color misregistration amount, (a) is a figure which shows the correlation with a job and apparatus internal temperature (output value of the temperature sensor 304), b) is a diagram showing a correlation between the temperature rise amount and the color misregistration amount. It is a figure which shows the state of the scanning line at the time of the color shift generation | occurrence | production and color shift correction | amendment by a temperature rise, (a) shows the scanning line before and behind operation | movement start, (b) shows the scanning line before and behind correction | amendment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1Y, 1M, 1C, 1Bk Image forming part 2a, 2b, 2c, 2d Photosensitive drum 7 Scanning optical apparatus 8 Intermediate transfer belt 304 Temperature sensor

Claims (18)

An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the forming device,
Measuring means for measuring the temperature in the image forming apparatus;
A calculating means for calculating a temperature increase amount in each printing mode;
Conversion means for converting each calculated temperature increase amount into a color misregistration amount by conversion data for each printing mode;
The color misregistration correction unit performs the color misregistration correction when the total of the converted color misregistration amounts exceeds a predetermined value.   The image forming apparatus according to claim 1, wherein the measurement unit is disposed in a portion where color misregistration occurs due to thermal expansion, and measures temperatures before and after the start of a job. An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the forming device,
Calculating means for calculating the number of printed sheets in each of the print modes;
Conversion means for converting the calculated number of printed sheets into a color misregistration amount by conversion data for each printing mode;
The color misregistration correction unit performs the color misregistration correction when the total of the converted color misregistration amounts exceeds a predetermined value. An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the forming device,
Calculating means for calculating the operation time in each of the print modes;
Conversion means for converting each calculated operation time into a color misregistration amount by conversion data for each printing mode;
The color misregistration correction unit performs the color misregistration correction when the total of the converted color misregistration amounts exceeds a predetermined value.   5. The color misregistration correction unit performs the color misregistration correction every time a total value of the color misregistration amounts after the color misregistration correction is performed exceeds the predetermined value. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the color misregistration correction unit performs the color misregistration correction at the end or before the start of the job.   The image forming apparatus according to claim 1, wherein the conversion data includes a conversion table and a conversion formula.   The image forming apparatus according to claim 1, wherein productivity in the first printing mode is higher than that in the second printing mode. An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the color misregistration correction method of the forming apparatus,
A measuring step of measuring the temperature in the image forming apparatus;
A calculation step for calculating a temperature increase amount in each of the print modes,
A conversion step of converting each calculated temperature increase amount into a color misregistration amount by conversion data for each printing mode;
A color misregistration correction method for an image forming apparatus, comprising: a color misregistration correction step of performing color misregistration correction by the color misregistration correction means when the total of the converted color misregistration amounts exceeds a predetermined value.   10. The color misregistration of an image forming apparatus according to claim 9, wherein in the measurement step, the temperature before and after the start of the job is measured by a measuring unit arranged in a portion where the color misregistration occurs due to thermal expansion. Correction method. Image forming means for forming an image in a first printing mode for forming a single color image or a second printing mode for forming a multicolor image, and a color shift correcting means for correcting a color shift at the time of forming the multicolor image. In the color misregistration correction method of the image forming apparatus provided,
A calculation step of calculating the number of printed sheets in each of the print modes,
A conversion step of converting each calculated number of printed sheets into a color misregistration amount by conversion data for each print mode;
A color misregistration correction method for an image forming apparatus, comprising: a color misregistration correction step of performing color misregistration correction by the color misregistration correction means when the total of the converted color misregistration amounts exceeds a predetermined value. An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the color misregistration correction method of the forming apparatus,
A calculation step of calculating the operation time in each of the print modes,
A conversion step of converting each calculated operation time into a color misregistration amount by conversion data for each printing mode;
A color misregistration correction method for an image forming apparatus, comprising: a color misregistration correction step of performing color misregistration correction by the color misregistration correction means when the total of the converted color misregistration amounts exceeds a predetermined value.   The color misregistration correction step performs the color misregistration correction every time a total value of the color misregistration amounts after the color misregistration correction is performed exceeds the predetermined value. A method for correcting color misregistration of an image forming apparatus according to claim 1.   The color misregistration correction method for an image forming apparatus according to claim 9, wherein the color misregistration correction step performs the color misregistration correction at the end of the job or before the start of the job.   The color shift correction method for an image forming apparatus according to claim 9, wherein the conversion data includes a conversion table and a conversion formula.   16. The color misregistration correction method for an image forming apparatus according to claim 9, wherein productivity in the first print mode is higher than that in the second print mode. An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the forming device,
A calculating means for calculating a temperature rise amount or the number of printed sheets or an operation time of the image forming apparatus in each printing mode;
Conversion means for converting the calculated result into a color misregistration amount by conversion data for each printing mode;
The image forming apparatus according to claim 1, wherein the color misregistration correction unit performs color misregistration correction each time the amount of change in the color misregistration amount changes by a certain amount. An image comprising image forming means for forming an image in a first print mode for forming a monochromatic image or a second print mode for forming a multicolor image, and a color misregistration correcting means for correcting color misregistration during the image formation. In the color misregistration correction method of the forming apparatus,
A calculation step of calculating a temperature increase amount or the number of printed sheets or an operation time of the image forming apparatus in each printing mode;
Conversion means for converting the calculated result into a color misregistration amount by conversion data for each printing mode;
A color misregistration correction method for an image forming apparatus, comprising: a color misregistration correction step of performing color misregistration correction by the color misregistration correction means each time the amount of change in the color misregistration amount changes by a certain amount.

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