JP5011741B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus such as a copying machine or a printer that performs an image forming condition adjusting operation at a predetermined time.

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

  Conventionally, an image forming condition adjusting operation accompanied by an actual image forming operation with each image forming element set to a predetermined parameter is mainly automatically executed mainly in accordance with a time-dependent condition of the apparatus (image forming number, etc.). It was done. In this case, medium- and long-term changes in the image forming element over time can be accommodated, but there are cases where it is not possible to cope with short-term changes in environmental conditions (temperature and humidity).

  Therefore, in the medium-to-long-term change of the image forming element over time, the image forming condition adjustment operation with the actual image forming operation is executed mainly according to the time-dependent condition of the apparatus, and the short-term environmental conditions (temperature and humidity) ) Is dealt with by correcting the image forming condition with respect to a predetermined environmental condition at the time of actual image formation.

  Further, in Patent Document 1, predicted image correction is executed during fixing warm-up, and the image forming conditions obtained in the previous image condition adjusting operation are the elapsed time from the previous image forming operation and environmental conditions (relative humidity). It is described that the correction is made based on the above. Patent Document 2 describes that the execution timing of the image forming condition adjustment operation is determined based on the usage state of the apparatus and environmental conditions, for example, the history of the number of key inputs over time.

  By the way, the image forming condition adjusting operation is performed based on the actual image forming operation result with respect to the history of the apparatus at that time and the environmental condition, so that at that time, a highly accurate adjustment result can be obtained. Can be expected.

  Therefore, if the image forming condition adjusting operation is frequently performed, a more stable image can be formed. However, since the image forming condition adjustment operation is normally automatically executed according to the time-dependent conditions of the apparatus, setting a high frequency adversely affects the productivity of the user's print job. In addition, the life of each imaging element may be adversely affected. Therefore, it has been desired that the image forming condition adjusting operation be performed with as little frequency and high accuracy as possible.

Therefore, an image forming condition adjustment operation is executed for the deterioration of the image forming element over time, i.e., medium- and long-term image forming elements, and the environmental condition of the apparatus during image formation for short-term environmental condition changes. Is measured, and the image forming condition is corrected based on a correction table for a predetermined image forming condition (see Patent Document 1). However, in this countermeasure, since a fixed correction table is used for correcting the image forming condition based on the environmental condition measurement result at the time of image formation, the time history of each apparatus is not reflected in the actual image forming operation. Has the problem.
JP 2004-347666 A Japanese Patent Laid-Open No. 10-2222023

  Accordingly, an object of the present invention is to improve the correction accuracy by the image forming condition adjustment operation, to enable stable image formation with respect to the history of each apparatus and the environmental conditions at the time of image formation, and to adjust the image forming condition. An object of the present invention is to provide an image forming apparatus capable of reducing the execution frequency of operations.

In order to achieve the above object, the first invention performs part or all of the image forming process to thereby obtain the output value of the charging device, the output value of the exposure device, the development bias value, or the output value of the transfer device. An image forming condition adjusting operation for adjusting at least one of the image forming conditions is executed at a predetermined timing, and the image forming condition obtained by the image forming condition adjusting operation is corrected based on the environmental condition measurement result of the apparatus during image formation. In the image forming apparatus,
Stores and accumulates the imaging conditions obtained at the time of executing the imaging condition adjustment operation and the environmental conditions at that time, and the relationship between the imaging condition correction to the change in the environmental conditions at the time of image formation indicates the environment during the imaging condition adjustment operation. The image forming condition is corrected based on the calculation from the accumulated information of the condition and the image forming condition, and the image forming condition is set based on the environmental condition of the apparatus and the corrected image forming condition correction relationship at the time of image formation.

A second invention is an image forming apparatus using electrophotography,
A means of measuring environmental conditions;
An image forming condition adjusting operation for adjusting at least one of the output value of the charging device, the output value of the exposure device, the developing bias value, or the output value of the transfer device by executing part or all of the image forming process. Means for executing at a predetermined elapsed time;
Means for correcting the image forming condition obtained by the image forming condition adjusting operation based on the environmental condition measurement result of the apparatus during image formation;
Means for storing and storing the imaging conditions obtained at the time of executing the imaging condition adjustment operation and the environmental conditions at that time;
Means for correcting the imaging condition correction relationship with respect to changes in environmental conditions during image formation based on the calculation from the environmental conditions during the imaging condition adjustment operation and the accumulated information of the imaging conditions;
Means for setting image forming conditions based on the environmental condition of the apparatus and the corrected image forming condition correction relationship at the time of image formation;
It is provided with.

  According to the image forming apparatus of the present invention, the image forming condition correction relationship with respect to changes in the environmental conditions during image formation is corrected based on the calculation from the environmental conditions during the image forming condition adjustment operation and the history information of the image forming conditions. As a result, the accuracy of correction is improved, and stable image formation is possible with respect to the history of individual devices and environmental conditions during image formation. As a result of improving the accuracy of the image forming condition correction, it is possible to reduce the frequency of the image forming condition adjusting operation at the normal timing, and the number of times that execution of the image forming condition adjusting operation hinders the user's print job. Will be reduced.

  In the image forming apparatus according to the present invention, it may be determined whether or not the image forming condition adjustment operation is executed based on a change in the environmental conditions of the apparatus. Whether or not to execute at the second predetermined time timing may be determined based on a change in the environmental conditions of the apparatus.

  Further, when correcting the imaging condition correction relationship with respect to changes in environmental conditions during image formation, it is preferable to exclude from the calculation or change the weighting for the calculation based on the time-dependent condition during execution of the imaging condition adjustment operation. . Thereby, the correction accuracy of the image forming condition by the image forming condition adjusting operation is further improved.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows an electrophotographic color printer 10 which is an embodiment of an image forming apparatus according to the present invention. The color printer 10 is configured to synthesize four-color images in a so-called tandem system. The photosensitive drum 21, the charging device 22, the image exposure device 23, the developing device 24, and a residual toner and residual charge cleaning device. Print heads 20Y, 20M, 20C, and 20K that form YMCK (yellow, magenta, cyan, and black) images including 25 and the like are juxtaposed directly below the intermediate transfer belt 11.

  The image data is transmitted to the image memory of the control unit 40 from an image reading device (scanner) (not shown) or a computer (see FIG. 3). The controller 40 drives the various image forming devices, forms an electrostatic latent image on each photosensitive drum 21 based on the transmitted image data, and develops the latent image to form a toner image. Such an electrophotographic process is well known and will not be described.

  The intermediate transfer belt 11 is stretched endlessly on the drive roller 12 and the support rollers 13 and 14 and is rotationally driven in the direction of arrow A, and a portion facing the intermediate transfer belt 11 where the drive roller 12 is installed (secondary). A transfer roller 16 is arranged in the transfer section 15).

  In the lower part of the color printer 10, an automatic paper feeding unit 30 for feeding the stacked transfer materials one by one is installed. A toner fixing device 50 is installed immediately above the secondary transfer unit 15. Further, a toner container (not shown) is disposed above each developing device 24, and toner is replenished in a timely manner to supplement the consumed amount.

  The toner images formed on the respective photosensitive drums 21 are sequentially primary-transferred onto the intermediate transfer belt 11 that is rotationally driven in the direction of arrow A by an electric field applied from the primary transfer roller 26, and four-color images are formed. Synthesized. On the other hand, the transfer materials are fed one by one from the automatic paper feeding unit 30 one by one, and the composite image is secondarily transferred from the intermediate transfer belt 11 by the electric field applied from the transfer roller 16 by the secondary transfer unit 15. Thereafter, the transfer material is conveyed to the fixing device 50 where the toner is heated and fixed, and is discharged from the paper discharge roller 38 onto the tray 39.

  The color printer 10 is basically configured to perform image formation over a long period of time without maintenance other than toner replenishment. However, the image may be deteriorated due to a change in environmental conditions (temperature / humidity) or a user's usage frequency. Therefore, a program for executing an image forming condition adjusting operation in order to keep the image quality constant is stored in the control unit 40.

  In the image forming condition adjusting operation, the output value of each image forming element, that is, the output value of the charging device 22 or the image exposure device 23, the developing bias value of the developing device 24, the output value of the transfer roller 26, and the like are set to predetermined conditions. Then, the test image is transferred onto the intermediate transfer belt 11, the test image is optically read by the sensor 45, the color image is subjected to resist adjustment based on the read information, and charging in each print head 20 is performed. Adjust (correct) output values, development bias output values, exposure output values, transfer output values, and the like. A sensor 46 for detecting environmental conditions (temperature / humidity) is installed inside the color printer 10.

(Refer to Control Example 1 and FIG. 2)
FIG. 2 shows an outline of the control example 1 regarding the image forming condition adjusting operation. The printer 10 constantly monitors the environmental conditions (temperature / humidity) in the machine using the sensor 46 (steps S1 and S2), and stores the measurement results (step S3). Further, in response to a print job request from the user (YES in step S61), image forming conditions for the printing operation are set based on the environmental conditions at that time and a correction table described below, that is, each image forming The output value of the element is set (step S62), and the printing operation is executed (step S63).

  Here, when the printer 10 has achieved condition 1 of a predetermined time-lapse timing from the execution of the previous image formation condition adjustment operation (YES in step S5), for example, the number of prints from the previous image formation condition adjustment operation is a fixed number. The image forming process is determined to require correction, such as when the elapsed time from the previous image forming condition adjustment operation reaches a certain time, or when the printer is turned on. The image forming conditions are adjusted and stored so that a high-quality image can be obtained by executing part or all of (Step S51), and the correction table is modified as described below (Step S52). Thus, new image forming conditions corresponding to the environmental conditions at that time are set during the subsequent printing operation (step S62).

  In the imaging condition adjustment operation, the latest environmental conditions and adjustment results are added to the stored information of the environmental conditions and adjustment results at the time of the previous imaging condition adjustment operation. The correction relationship (correction table) is corrected and stored. That is, the correction table for the environmental condition is updated every time the image forming condition adjustment operation is executed.

  Here, Tables 1, 2, 3 and FIG. 3 show an example of the update of the correction table of the image forming conditions performed by the control unit 40. In the initial state (at the time of shipment) of the printer 10, a standard initial correction table shown in Table 1 is set. In the correction table, “control value correction (%)” indicates what percentage of the reference value the output value of a certain image forming element is set to. Note that Table 1 shows control correction values relating only to humidity, but actually, a correction table corresponding to environmental conditions including correction items such as temperature is prepared.

  In the initial state, image forming conditions are set based on the correction table shown in Table 1 and the environmental conditions measured during printing. Whenever the condition 1 is satisfied (YES in step S5), the image forming condition adjustment operation is automatically executed, and the environmental condition and the adjusted image forming condition data at that time are added as the adjustment history each time. Are stored in the control unit 40. The image forming condition adjustment history information accumulated here is shown in Table 2, and the current correction table is shown in Table 3. FIG. 3 shows the correction table as a chart.

  Table 2 shows a case where 20 image forming condition adjustment operations are executed for each of the two printers 10A and 10B. At this stage, a new imaging condition correction table is set from the linear regression equation obtained by the linear regression analysis using the least square method based on the data of the environmental conditions and the adjusted imaging conditions for 20 times. . Note that the calculation method is not limited to the one using the linear regression equation. For example, history data before a certain time-dependent condition from the present time may be excluded from the calculation of the correction value. Alternatively, it is possible to obtain a correction value with higher accuracy by weighting the history data based on the aging condition from the present time. Further, instead of the correction table, a relational expression may be used to establish an image forming condition correction relationship.

  The weighting is a time condition such as the cumulative number of prints. In other words, the number of data up to 500 sheets before the current is multiplied by 5 in the primary regression analysis, the data from 500 to 1000 sheets is tripled in the primary regression analysis, and 1000 to 2000 sheets before. The number of data is multiplied by 1 in the linear regression analysis, and the previous data is not used.

  By the way, the characteristic change with respect to the environmental condition of each image forming element in the printer 10 is not irrelevant to the time history, and when more accurate environmental correction is performed for each printer, correction by the time history of each printer is corrected. It is necessary to add to. A specific example of the reason will be described below.

  For example, in the case of a printer using a two-component developer composed of toner and a carrier, the charging characteristics of the carrier change due to the history over time, which causes image instability. It is known that this is mainly due to the contamination (spent) of the carrier surface by the additive of the toner, and the charging characteristics with respect to the environmental conditions of the carrier also change depending on the state of the spent.

  Here, even though the state of the spent is deteriorated due to the same number of prints, it greatly varies depending on the use conditions of each printer, for example, the type of print image (whether the main character is a photograph or the main photograph). In other words, the deterioration state of the carrier changes depending on the time history, and the characteristics of the carrier with respect to the environmental conditions also change. In this case, it is necessary to apply a different correction table to each printer even if the number of prints is the same.

  In this control example 1, the image forming condition correction relationship (correction table) with respect to changes in the environmental conditions during the printing operation is corrected based on calculations from the environmental conditions during the image forming condition adjusting operation and the history information of the image forming conditions. As a result, the accuracy of correction is improved, and stable image formation is possible with respect to the history of individual printers and environmental conditions during printing operations. As a result of improving the accuracy of the image forming condition correction, it is possible to reduce the frequency of the image forming condition adjusting operation at the normal timing with time. Therefore, the number of times that the execution of the image forming condition adjustment operation hinders the user's print job is reduced.

(Refer to Control Example 2 and FIG. 4)
FIG. 4 shows an outline of the control example 2 regarding the image forming condition adjusting operation. In the control example 2, in addition to the determination of the condition 1 for executing the image forming condition adjustment operation shown in the control example 1, the in-machine environmental condition of the printer 10 greatly changes from the previous image forming condition adjustment operation by a certain amount or more. (YES in step S4), the image forming condition adjustment operation is forcibly executed, the environmental conditions and adjustment data at that time are stored (step S51), and the correction table is corrected based on the historical data. (Step S52).

  In this control example 2, when the environmental condition has greatly changed since the previous image forming condition adjustment operation, a more accurate image forming condition can be set, and the environmental condition and adjustment data when the environmental condition has changed greatly are additionally stored. By doing so, more accurate correction data can be obtained.

(Refer to Control Example 3, FIG. 5)
FIG. 5 shows an outline of the control example 3 regarding the image forming condition adjusting operation. In this control example 3, when the printer 10 reaches a certain time condition 1 (step S7), the image forming condition adjustment operation is forcibly executed (steps S51 and S52). Even if the time condition 1 has not been reached, it is further determined whether or not a certain time condition 2 has been reached (step S8), and if not, the image forming condition adjustment operation is not executed. Even when the aging condition 2 is reached, the image forming condition adjustment operation is executed only when the environmental conditions have greatly changed since the previous execution of the image forming condition adjustment operation (YES in step S9) (step S51, S52).

  In this control example 3, by adding changes in the time-dependent conditions 1 and 2 and the environmental conditions to the execution requirements of the image-forming condition adjustment operation, it is possible to set the correct image-forming conditions at that time, and to make more accurate correction tables more efficient Can get well. For example, the aging condition 1 is power on / off, and the aging condition 2 is the cumulative number of prints.

(Other examples)
Note that the image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  For example, the present invention can be applied not only to the tandem type color printer shown in the above embodiment but also to various image forming apparatuses such as a monochrome printer, a color / monochrome copying machine, and a facsimile.

1 is a schematic configuration diagram illustrating a color printer which is an example of an image forming apparatus according to the present invention. It is a flowchart figure which shows the example 1 of control. It is a chart figure which shows a correction table. It is a flowchart figure which shows the example 2 of control. It is a flowchart figure which shows the example 3 of control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Color printer 11 ... Intermediate transfer belt 16 ... Transfer roller 21 ... Photoconductor drum 22 ... Charging device 23 ... Image exposure device 24 ... Development device 26 ... Transfer roller 40 ... Control part 45 ... Toner density detection sensor 46 ... Environmental condition detection Sensor

Claims (5)

An image forming condition adjusting operation for adjusting at least one of the output value of the charging device, the output value of the exposure device, the developing bias value, or the output value of the transfer device by executing part or all of the image forming process. In the image forming apparatus that executes at predetermined timing, and corrects the image forming condition obtained by the image forming condition adjusting operation based on the environmental condition measurement result of the apparatus at the time of image formation.
Stores and accumulates the imaging conditions obtained at the time of executing the imaging condition adjustment operation and the environmental conditions at that time, and the relationship between the imaging condition correction to the change in the environmental conditions at the time of image formation indicates the environment during the imaging condition adjustment operation. Correction based on the calculation from the accumulated information of the condition and image forming condition, and setting the image forming condition based on the environmental condition of the apparatus and the corrected image forming condition correction relationship at the time of image formation,
An image forming apparatus.   The image forming apparatus according to claim 1, wherein it is determined whether or not the image forming condition adjustment operation is executed based on a change in an environmental condition of the apparatus.   The image forming condition adjustment operation is executed at a first predetermined time timing, and it is determined whether or not the image forming condition adjustment operation is executed based on a change in an environmental condition of the apparatus at a second predetermined time timing. Item 2. The image forming apparatus according to Item 1.   When correcting the imaging condition correction relationship with respect to changes in environmental conditions during image formation, it is excluded from the calculation based on the time-dependent condition during the execution of the imaging condition adjustment operation, or the weighting for the calculation is changed The image forming apparatus according to claim 1. In an image forming apparatus using electrophotography,
A means of measuring environmental conditions;
An image forming condition adjusting operation for adjusting at least one of the output value of the charging device, the output value of the exposure device, the developing bias value, or the output value of the transfer device by executing part or all of the image forming process. Means for executing at a predetermined elapsed time;
Means for correcting the image forming condition obtained by the image forming condition adjusting operation based on the environmental condition measurement result of the apparatus during image formation;
Means for storing and storing the imaging conditions obtained at the time of executing the imaging condition adjustment operation and the environmental conditions at that time;
Means for correcting the imaging condition correction relationship with respect to changes in environmental conditions during image formation based on the calculation from the environmental conditions during the imaging condition adjustment operation and the accumulated information of the imaging conditions;
Means for setting image forming conditions based on the environmental condition of the apparatus and the corrected image forming condition correction relationship at the time of image formation;
An image forming apparatus comprising:

Images