JP5017880B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming apparatus and an image forming method using electrophotography such as a copying machine and a printer that perform image stabilization control at a predetermined timing.

  In general, in an image forming apparatus based on electrophotography, the optimum image forming process conditions are greatly influenced by environmental conditions (temperature / humidity) at the time of image formation along with the aging of each image forming element such as a photoreceptor and a developing device. .

  Therefore, at a predetermined timing such as immediately after turning on the power to the apparatus or after printing a predetermined number of sheets, each imaging element is set to a predetermined parameter, and a test pattern for each color is tested on the photosensitive drum or intermediate transfer body. The current image formation status is detected by detecting the pattern density, and the image forming process conditions that affect the image density, for example, the charging voltage, the developing bias voltage, etc. are corrected, thereby stabilizing the image forming process. The image quality is maintained.

  However, in order to execute the image stabilization control accompanied with the formation of the test pattern, a corresponding processing time is required. For example, when image stabilization control is executed for each predetermined number of prints, if image stabilization control is executed in the middle of a series of print jobs in which a large amount of a single document is printed, for the user. Becomes dead time.

  In view of this, Japanese Patent Application Laid-Open No. H10-228707 discloses that when the timing for executing image stabilization control is reached during a reserved print job, the image stabilization control is executed prior to the print job. Further, in Patent Document 2, when a specific print mode is set, image stabilization control in a print job is performed by executing image stabilization control before or after the print job depending on conditions. Is disclosed.

However, if image stabilization control is executed in the middle of a print job, the user will feel uncomfortable due to the occurrence of dead time. Even if the image stabilization control is executed prior to the print job, the time required for the end of the print job does not change, so the time waiting for the user is the same. Further, when the image stabilization control is executed after the print job, it is not possible to avoid a reduction in image quality.
JP 2004-142250 A JP 2000-227684 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus and an image forming method capable of avoiding the generation of dead time due to image stabilization control as much as possible and avoiding degradation of image quality as much as possible.

To achieve the above object, according to a first aspect of the present invention, there is provided image formation for executing image stabilization control for correcting an image forming process condition in an image forming unit for forming an image on a sheet by electrophotography at a predetermined timing. In the device
An actual image stabilization control mode that forms a test pattern on a trial basis and corrects an image forming process condition based on the test pattern formation result;
A predictive image stabilization control mode that corrects the imaging process conditions based on the previous imaging process conditions and environmental conditions without forming a test pattern;
The image forming section, the predicted image stabilization control mode is running during a print job executed if that led to the timing to perform the image stabilization control during the execution of the print job, image stabilization in not printing job execution control means for Ru to execute the actual image stabilization control mode when reaching the timing of executing the reduction control,
Equipped with a,
When the control means corrects the image forming process condition in the predicted image stabilization control mode and determines that the image forming process condition to be corrected is changed beyond a predetermined value, the image forming process condition Is gradually changed within a range not exceeding the predetermined value,
It is characterized by.

A second invention is an image forming method for executing image stabilization control for correcting an image forming process condition in an image forming unit that forms an image on a sheet by electrophotography at a predetermined timing.
An actual image stabilization control mode that forms a test pattern on a trial basis and corrects an image forming process condition based on the test pattern formation result;
A predictive image stabilization control mode that corrects the imaging process conditions based on the previous imaging process conditions and environmental conditions without forming a test pattern, and
The image forming section, the predicted image stabilization control mode is running during a print job executed if that led to the timing to perform the image stabilization control during the execution of the print job, image stabilization in not printing job execution When it is time to execute the control, the measured image stabilization control mode is executed,
When the imaging process condition is corrected by the predicted image stabilization control mode, if it is determined that the corrected imaging process condition is changed beyond a predetermined value, the imaging process condition exceeds the predetermined value. Gradually change within a range,
It is characterized by.

In the first and second aspects of the present invention, when having reached the timing for performing image stabilization control during the execution of the print job, while the print job execution, found the image stabilization relatively time-consuming with formation of the test pattern Instead of the control mode, the predicted image stabilization control mode is executed. The predictive image stabilization control mode is a short time-series correction that corrects the imaging process conditions based on the previous imaging process conditions and environmental conditions without forming a test pattern. Dead time is shortened. In addition, compared with a case where no image stabilization control is performed, a reduction in image quality is avoided.

In the first and second inventions, the measured image stabilization control mode may be executed when the image forming unit ends the print job after the image forming process conditions are corrected by the predicted image stabilization control mode. Image quality can be stabilized earlier.

Further, when correcting the image forming process conditions by the predictive image stabilization control mode, when the corrected result has been image forming process condition is determined to be changed beyond a predetermined value, a predetermined value the image forming process conditions Since the change is gradually made within a range not exceeding , a sudden image change can be avoided.

  Hereinafter, embodiments of an image forming apparatus and an image forming method according to the present invention will be described with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows an electrophotographic digital copying machine 10 which is an embodiment of an image forming apparatus according to the present invention. The digital copying machine 10 generally includes an automatic document feeder 20, an image reading device 30 (scanner), and a printer unit 40.

  The automatic document feeder 20 feeds documents placed on the document tray 21 one by one along the outer peripheral surface of the drum 22 onto the contact glass 31 and discharges them onto the tray 23. In addition, a document reversing unit 24 for reversing and reading the front and back of a double-sided document is provided.

  The image reading device 30 (scanner) is a well-known device including an illumination lamp 33, mirrors 34a, 34b, and 34c, an imaging lens 35, and a line sensor 36. The image reading device 30 is a lamp that reads an image of a document placed on the platen glass 32. 33 etc. are read as digital data while scanning in the direction of arrow A. Further, the image of the document conveyed on the contact glass 31 is read as digital data at the stationary position B. The configurations and operations of the automatic document feeder 20 and the image reading device 30 are well known, and detailed description thereof is omitted.

  The printer unit 40 has a charging device 42, a laser scanning optical device 43, a developing device 44, a transfer device 45, a paper separation device 46, and a residual charge and residual toner cleaning device 47 around the photosensitive drum 41. Further, an automatic paper feed unit 50 including paper feed cassettes 51, 52, and 53, a toner heat fixing device 55, a paper reversing device 56 for double-sided printing, and the like are further provided.

  The image forming process based on the electrophotographic method by the printer unit 40 is conventionally well-known, and an outline thereof will be described. First, a uniform charge is applied by the charging device 42 to the outer peripheral surface of the photosensitive drum 41 that is driven to rotate in the clockwise direction in FIG. 1, and laser scanning is performed by the image data transferred from the image reading device 30. The optical device 43 is driven to form an electrostatic latent image. This electrostatic latent image is visualized by toner supplied from the developing device 44.

  On the other hand, the sheets are fed one by one from one of the sheet feeding cassettes 51, 52, 53, transported to the lower part of the photosensitive drum 41 along the transport path indicated by the broken line, and an electric field applied from the transfer device 45. The toner image is transferred onto the paper. Thereafter, the sheet is neutralized by the electric field applied from the separation device 46 and peeled off from the photosensitive drum 41, and the toner is fixed by the fixing device 55 and discharged onto a tray (not shown). The photosensitive drum 41 continues to rotate thereafter, and the residual charge and residual toner are removed by the cleaning device 47 to prepare for the next printing operation.

  Further, the printer unit 40 includes a reflection type density sensor 61 for optically detecting the density of the toner image formed on the photosensitive drum 41, and an internal environment condition (temperature / humidity). A temperature / humidity sensor 62 is installed.

(Image stabilization control)
The printer unit 40 is basically configured to perform image formation over a long period of time without maintenance other than toner replenishment. However, each image forming element is deteriorated with time according to changes in environmental conditions (temperature / humidity), usage frequency of the user, and the like, and the image is deteriorated. In view of this, image stabilization control for automatically correcting the image forming process conditions is performed in order to maintain a constant image quality.

The measured image stabilization control includes output values of the respective image forming elements, that is, output values of the charging device 42 and the laser scanning optical device 43, development bias values of the developing device 44, output values of the transfer device 45 and the paper separating device 46, and the like. Is set to a predetermined condition to form a test pattern on the photosensitive drum 41, the density sensor 61 optically reads the test pattern, and forms an image with good reproducibility based on the read information. The charging output value, the developing bias output value, the exposure output value, the transfer output value, etc. of each image forming element are corrected.

  In the digital copying machine 10, the image stabilization control includes an actual image stabilization control mode in which a test pattern is formed on the photosensitive drum 41 as a test and all the output values are corrected, and a test pattern. For example, the output value of the developing bias of the charging device 42 or the developing device 44 is determined based on the previous image forming process condition, the elapsed time from the execution of the previous image stabilization control, and the environmental condition (temperature / humidity). A predicted image stabilization control mode to be corrected is prepared. The execution procedure of these image stabilization controls will be described later.

(Control unit, see FIG. 2)
FIG. 2 shows the control unit 100 of the digital copying machine 10. The control unit 100 includes a read processing unit 101, a DRAM control unit 102, an image compression / decompression unit 103, an image memory 104, a write processing unit 105, a program memory 106, a system memory 107, and a nonvolatile memory. 108, an input / output interface 109, and a CPU 110.

  The image data read by the line sensor 36 of the image reading device 30 is transferred to the reading processing unit 101 and subjected to necessary image processing, then sent to the DRAM control unit 102 and stored in the image memory 104. This image data is sent to the writing processing unit 105 and becomes a drive signal for the light source (laser diode LD) of the laser scanning optical device 43.

  The CPU 110 appropriately transmits a signal to the printer control unit 230 to control operations of various image forming elements and the paper transport mechanism of the printer unit 40, and performs a print operation and a warm-up operation immediately after power-on, and an ADF control unit. Signals are appropriately transmitted to 200 and the scanner control unit 210 to control operations of the automatic document feeder 20 and the image reading device 30. The CPU 110 also communicates with the control unit 223 of the operation display unit 220 of the copying machine 10. The operation display unit 220 includes a display unit 221 formed of a liquid crystal display and an operation unit 222 formed of a touch panel and other switches.

  The CPU 110 incorporates an execution program for the measured image stabilization control mode and the predicted image stabilization control mode, and performs image stabilization control at a predetermined timing described below, and the measured stabilization control mode and predicted image stabilization control. Run selectively for each mode.

  In addition, detection signals from the sensors 61 and 62 are input to the nonvolatile memory 108 via the interface 109 and stored. Further, a clock signal from the clock unit 63 that clocks the date and time is input to the CPU 110 via the interface unit 109.

(Image stabilization control, see FIGS. 3 and 4)
The image stabilization control is executed when a preset execution condition is reached. The execution conditions are (1) when the power is turned on, (2) when the number of prints from the previous execution of image stabilization control exceeds a predetermined number, (3) the elapsed time since the previous execution of image stabilization control. When the predetermined time is exceeded, (4) the environmental condition (temperature / humidity) is changed by a predetermined amount from the previous execution of the image stabilization control. Basically, the image stabilization control is executed under the conditions (1) and (2), but the image stabilization control may be executed under the conditions (3) and (4) and other conditions. Good.

  When the power is turned on as in the condition (1) and when the print job is not executed even in the condition (2), the measured image stabilization control mode is executed. On the other hand, when the condition (2) is reached during execution of the print job (step S1 in FIG. 3) (YES in step S2 in FIG. 3, for example, the number of prints exceeds 200), the predicted image The stabilization control mode is executed, and new image forming process conditions are set (step S3 in FIG. 3). Thereafter, the print job is continued and terminated (step S4 in FIG. 3).

  Further, when the print job is not executed (NO in step S11 in FIG. 4), if the image forming process condition is set in the predicted image stabilization control mode (YES in step S12 in FIG. 4), the actual measurement is performed. The image stabilization process mode is executed to set image forming process conditions (step S13 in FIG. 4).

  In other words, in this embodiment, when it is time to execute image stabilization control during print job execution, instead of the measured image stabilization control mode that requires a relatively long time with test pattern formation, predictive image stabilization is performed. Execute control mode. The predictive image stabilization control mode is a short time-series correction that corrects the imaging process conditions based on the previous imaging process conditions and environmental conditions without forming a test pattern. Dead time is shortened. In addition, compared with a case where no image stabilization control is performed, a reduction in image quality is avoided.

  Incidentally, the measured image stabilization control mode may be executed after the image forming process conditions are set by the predicted image stabilization control mode and the print job is completed (step S5 in FIG. 3). As a result, the image quality can be stabilized earlier.

  Further, when correcting the imaging process condition by the predicted image stabilization control mode, if the corrected imaging process condition is changed beyond a predetermined value, the imaging process condition is set within a range not exceeding the predetermined value. You may change gradually. Here, the predetermined value differs depending on the image forming element.

  For example, when the changeable value of the surface potential of the photosensitive drum 41 is 50V, even if it is determined that the predicted image stabilization control mode changes 70V, the change is set to 50V and a new surface potential is set. . The remaining change may be changed after printing a predetermined number of sheets (for example, 50 sheets), or may be corrected as it is to be corrected when the next image stabilization control is executed. By such control, it is possible to prevent an abrupt change in the image caused by the image forming process condition being significantly changed by the predicted image stabilization control mode.

  By the way, in a series of print jobs in which a large number of originals are printed at a time, the development characteristics change due to factors such as changes in internal temperature and humidity and an increase in the developer charge amount in the developing device 44. The reason why the image stabilization control is executed when the number of prints from the previous execution of the image stabilization control exceeds a predetermined number is to follow the change in development characteristics. In the predicted image stabilization control mode, a necessary correction value such as a developing bias voltage is predicted in response to a change in development characteristics corresponding to a change in environmental conditions. Also, in a print job that prints a small amount of a document at a time, changes in the internal temperature and humidity are small in the job, so there are few factors that change development characteristics, and a necessary correction amount such as a development bias voltage is small.

  Table 1 shown below is an example of a correction table for correcting the correction amount of the developing bias voltage value according to the amount of change in absolute humidity with respect to the value set in the previous image stabilization control in the predicted image stabilization control mode. Is shown.

(Other examples)
The image forming apparatus and the image forming method according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  For example, the present invention can be applied to various image forming apparatuses such as a color printer and a facsimile without being limited to the monochrome digital copying machine shown in the above embodiment.

1 is a schematic configuration diagram showing a digital copying machine as an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating a control unit of the digital copying machine. It is a flowchart figure which shows the control example 1 of image stabilization control. It is a flowchart figure which shows the control example 2 of image stabilization control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital copying machine 41 ... Photoconductor drum 42 ... Charging device 43 ... Laser scanning optical device 44 ... Developing device 45 ... Transfer device 61 ... Density sensor 62 ... Temperature / humidity sensor 100 ... Control part 110 ... CPU

Claims (6)

In an image forming apparatus that executes image stabilization control for correcting an image forming process condition in an image forming unit that forms an image on a sheet by electrophotography at a predetermined timing,
An actual image stabilization control mode that forms a test pattern on a trial basis and corrects an image forming process condition based on the test pattern formation result;
A predictive image stabilization control mode that corrects the imaging process conditions based on the previous imaging process conditions and environmental conditions without forming a test pattern;
The image forming section, the predicted image stabilization control mode is running during a print job executed if that led to the timing to perform the image stabilization control during the execution of the print job, image stabilization in not printing job execution control means for Ru to execute the actual image stabilization control mode when reaching the timing of executing the reduction control,
Equipped with a,
When the control means corrects the image forming process condition in the predicted image stabilization control mode and determines that the image forming process condition to be corrected is changed beyond a predetermined value, the image forming process condition Is gradually changed within a range not exceeding the predetermined value,
An image forming apparatus.   The control unit is configured to execute the measured image stabilization control mode when the image forming unit finishes the print job after the image forming process condition is corrected by the predicted image stabilization control mode. Item 2. The image forming apparatus according to Item 1. When it is determined that the image forming process condition to be corrected is changed beyond a predetermined value, the control means calculates the difference between the determined change amount and the actually changed change amount for the next predicted image stabilization The image forming apparatus according to claim 1, wherein the image forming apparatus is changed when the control mode is executed . In an image forming method for executing image stabilization control for correcting an image forming process condition in an image forming unit that forms an image on a sheet by electrophotography at a predetermined timing,
An actual image stabilization control mode that forms a test pattern on a trial basis and corrects an image forming process condition based on the test pattern formation result;
A predictive image stabilization control mode that corrects the imaging process conditions based on the previous imaging process conditions and environmental conditions without forming a test pattern, and
The image forming section, the predicted image stabilization control mode is running during a print job executed if that led to the timing to perform the image stabilization control during the execution of the print job, image stabilization in not printing job execution When it is time to execute the control, the measured image stabilization control mode is executed,
When the imaging process condition is corrected by the predicted image stabilization control mode, if it is determined that the corrected imaging process condition is changed beyond a predetermined value, the imaging process condition exceeds the predetermined value. Gradually change within a range,
An image forming method.   5. The measured image stabilization control mode is executed when the image forming unit finishes a print job after the image forming process condition is corrected by the predicted image stabilization control mode. Image forming method. When it is determined that the image forming process condition to be corrected is changed beyond a predetermined value, the difference between the determined change amount and the actually changed change amount is calculated at the next execution of the predicted image stabilization control mode. the image forming method according to claim 4 or claim 5, characterized in that to change.

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