JP2005173483A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce start-up time in an image forming apparatus. <P>SOLUTION: The apparatus has a means for acquiring an environmental variation history during power-OFF, and a state of image forming operation is enabled without performing image adjustment control, if the range of the acquired environmental variation is within a predetermined range when powered ON. Also, the apparatus has a learning function for associating the environmental variation history during power-OFF with the results of the image adjustment when powered ON and storing it. When there is the same environmental variation as the environmental variation history during power-OFF, a state of image forming operation is enabled by referring to image adjustment results at that point of time without performing the image adjustment control. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to image adjustment control of an image forming apparatus that forms a grayscale image by forming an electrostatic latent image on a photoreceptor and developing it with toner.

  As a conventional color image forming apparatus, an image forming apparatus employing an electrophotographic system is known. As a configuration of such a color image forming apparatus, a rotary developing device including a developing cartridge of four colors of black (Bk), magenta (M), cyan (C), and yellow (Y) is provided. The structure of the intermediate transfer system is frequently used.

  This intermediate transfer system includes a photoconductor as an image carrier, charges the photoconductor and exposes it with a light beam to form an electrostatic latent image on the photoconductor, and develops the electrostatic latent image. The toner image is visualized as a toner image, and the first color toner image is once transferred onto an insulating or medium resistance intermediate transfer member to complete the first color transfer process. Similarly, the remaining three color toner images are also intermediate. The image is transferred onto a transfer member, and the four color toner images are superimposed on the intermediate transfer member, and then transferred onto the transfer material at once.

  FIG. 7 shows a cross-sectional view of a color image forming apparatus using an intermediate transfer system as a conventional image forming apparatus. In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier. Around the photosensitive drum 1, an exposure device 3, a charging roller 2, a cleaning blade 4, a rotatable developing rotary 5, and an intermediate transfer belt 6 are provided.

  The development rotary 5 includes a black (Bk) color development cartridge 5Bk, a magenta (M) color development cartridge 5M, a cyan (C) color development cartridge 5C, and a yellow (Y) color development cartridge 5Y.

  In FIG. 7, the photosensitive drum 1 is rotated in the direction of arrow R <b> 1 by a driving unit (not shown), and the surface of the photosensitive drum 1 is charged by the charging roller 2.

  Then, an electrostatic latent image of the first color is formed on the surface of the photosensitive drum 1 by the exposure device 3. A black (Bk) color developing cartridge 5Bk, a magenta (M) color developing cartridge 5M, a cyan (C) color developing cartridge 5C, or a yellow (Y) color developing cartridge 5Y is in contact with the photosensitive drum 1 in the developing rotary 5. The electrostatic latent image on the photosensitive drum 1 is developed by the abutting developing cartridge, and a toner image is formed and visualized. The obtained toner image is primarily transferred onto the intermediate transfer belt 6.

  The formation of the electrostatic latent image, the formation of the toner image, and the primary transfer of the toner image onto the intermediate transfer belt 6 are sequentially performed with respect to the four color toners. A toner image is formed.

  Next, the toner images on the intermediate transfer belt 6 are secondarily transferred collectively onto a transfer material conveyed by the secondary transfer roller 7 and the intermediate transfer belt 6.

  The transfer material on which the toner images of a plurality of colors are formed is conveyed to the fixing device 8, where the toner is fixed to the transfer material, and the transfer material on which the color image is formed is discharged out of the image forming apparatus. .

  Further, the primary transfer residual toner on the photosensitive drum 1 is cleaned by the cleaning blade 4, and the secondary transfer residual toner on the intermediate transfer belt 6 is charged to a reverse polarity by the second charging roller 10 on the intermediate transfer belt 6. The toner is transferred from the intermediate transfer belt 6 to the photosensitive drum 1 by primary transfer, and is collected by the cleaning blade 4 in the same manner as the primary transfer residual toner on the photosensitive drum 1 described above.

  By the way, in an electrophotographic color image forming apparatus, there are fluctuations in characteristics due to endurance of the developing cartridge and photosensitive drum, variation in sensitivity during manufacture of the photosensitive drum, and frictional charging characteristics during manufacture of the toner. Variations in the density characteristics of the printed image occur due to variations and the like, and the original correct color tone cannot be obtained. Therefore, many color image forming apparatuses have image density control means.

  Here, the image density control will be described. The image density control includes maximum density control (hereinafter also referred to as Dmax control) which is density control in a narrow sense and halftone control which is gradation control.

  First, Dmax control will be described. First, an electrostatic latent image of, for example, a maximum exposure detection image (hereinafter also referred to as a patch) corresponding to the maximum density Dmax is created on the photosensitive drum 1, and the latent image is developed in the developing rotary 5. Development with a cartridge forms a patch for Dmax control on the photosensitive drum 1.

  At this time, a plurality of patch latent images are formed on the photosensitive drum 1 and developed while changing the developing bias. The patches created in this way are primarily transferred to the intermediate transfer belt 6, and the density of the patches on the intermediate transfer belt 6 is detected by a density sensor 9 adjacent to the intermediate transfer belt 6.

  In this example, from the detected density value of the patch, an appropriate development bias that makes the density of the output image constant is calculated and determined, and density control is performed by using this optimized development bias.

  After the density detection, the patch toner is charged to the reverse polarity by the second charging roller 10 on the intermediate transfer belt 6, transferred again from the intermediate transfer belt 6 onto the photosensitive drum 1, and cleaned by the cleaning blade 4. Then, the process proceeds to Dmax control for the next color.

  The development bias optimization described above is performed for all four colors, and the Dmax control ends.

  Next, halftone control will be described. In the halftone control, as in the Dmax control, a density detection patch is formed on the photosensitive drum 1, but unlike the Dmax control, a plurality of halftone patches used in the halftone control are provided for each patch. Each latent image potential is changed.

  For example, when five patches are formed on the photosensitive drum 1, the image signal (input signal) is an 8-bit signal obtained by linearly changing an exposure signal (for example, a signal for changing an exposure amount such as a signal to a laser driver). Among 256 gradations from 00h to FFh (Dmax), an electrostatic latent image of five halftone patches corresponding to exposure signals such as 10h, 40h, 80h, A0h, F0h, etc. is created as representative values.

  The latent image of the patch created on the photosensitive drum 1 is developed with the developing bias optimized by the above-described Dmax control, and is primarily transferred to the intermediate transfer belt 6, and the density of the obtained patch is changed to the intermediate transfer belt. 6 is detected by a density sensor 9 adjacent to 6.

  From this detection result, the difference between the density of the developed patch and the image signal of the input patch is determined, and the corresponding relationship is gamma-corrected so that the image signal and the exposure signal have a linear relationship. Thereafter, the image density control is completed by performing the process for all four colors as in the case of the Dmax control.

  By performing the image density control as described above at the time of turning on the power or every time a predetermined number of prints are made, it is possible to compensate for the effects of various kinds as described above and obtain an image with good image quality.

  By the way, when such image control is performed, particularly in the case of halftone control, it is necessary to form a large number of gradation patches for each color. There is a problem that it takes a lot of time to form a large number of patches for each color and read them. Depending on the patch used, there are cases where it takes about 30 seconds per color, in which case it takes 2 minutes to perform 4 colors.

  As one solution to this problem, for example, as described in Japanese Patent Application Laid-Open No. 11-143164, many patches are formed and measurement is performed in order to perform detailed measurement only for the first color. A proposal has been made to reduce the time required for image adjustment by forming a simple patch with reference to FIG.

  According to the above conventional example, it is possible to shorten the time required for image adjustment. In particular, in a case where the adjustment is performed regularly for every predetermined number of prints, for example, when no one is using it, the time can be shortened. Since the adjustment is completed and the toner consumption can be reduced, it can be said to be a very effective means. However, although the time that the user waits for the first copy after the power is turned on to make a copy becomes short, it may still wait for about 1 minute, which is very much when actually waiting It feels like a long time.

  In order to solve this problem, it is possible to further simplify the image adjustment operation using the patch as described in the conventional example, or not to perform the image adjustment operation at all. There is a problem in that a desired image quality cannot be obtained in the above image.

  As another method, a method of determining an image correction parameter from an environmental condition such as an air temperature when the power is turned on is also conceivable. However, the image forming unit may be greatly affected by environmental fluctuations before the power is turned on. As a specific example, an example of temperature change during power OFF for two days (A day and B day) shown in FIG. 8 is shown. The temperature when the power is turned on is the same on both days, but the temperature fluctuations during the off time are greatly different. That is, there is no significant temperature fluctuation on day A, but there is a significant fluctuation on day B. In particular, the temperature rises immediately before the power is turned on, and in this case, it is conceivable that condensation is formed on the image forming unit such as the photosensitive drum. In other words, it is effective to determine the correction parameters of the image from the environmental conditions when the power is turned on on the A day, but on the B day, the physical characteristics of the image forming unit are greatly different from the A day. Without such image adjustment, an image with good image quality cannot be formed.

  According to a first aspect of the present invention, there is provided means for forming an electrostatic latent image on a photoreceptor based on an image signal, and means for forming a toner image by adhering toner to the photoreceptor on which the latent image has been formed. An image adjustment control means for forming a toner image on a photosensitive drum, measuring its density, and determining a parameter for correcting the image based on the result, and the periphery of the image forming apparatus, or An environment measurement unit for measuring an internal environment; and an environment history storage unit for storing a history of a temporal change in a measurement result by the environment measurement unit, and the environment while the image forming apparatus is turned off. Based on the environmental change stored in the history storage means, it is determined whether image adjustment by the image adjustment control means is necessary. If it is determined that image adjustment control is unnecessary, the image adjustment operation is omitted. An image forming apparatus is provided.

  The second invention according to the present invention has means for holding "previous image adjustment data" before the power is turned off last time, and when the environmental fluctuation range during power-off is smaller than a predetermined range, It is determined that the image adjustment operation is unnecessary, and an image forming apparatus is provided that performs image correction based on the “previous image adjustment data”.

  According to a third aspect of the present invention, when the environmental fluctuation range during power OFF is larger than a predetermined range, it is determined that the image adjustment operation is necessary, and the image forming operation can be performed after performing the image adjustment operation. The present invention provides an image forming apparatus.

  According to a fourth aspect of the present invention, there is provided learning means for storing an environmental change history during power-off and an image adjustment result after power-on in correspondence with each other, and the environment when the power is turned on. Comparing the environmental fluctuation history during power OFF stored in the history storage means with the environmental fluctuation history remaining in the learning means, if there is something similar, use the image adjustment data at that time An image forming apparatus characterized by performing image correction is provided.

  The fifth invention according to the present invention determines that the image adjustment operation is necessary when the environment change history during power OFF is not similar to any of the past environment change histories stored in the learning means. It is another object of the present invention to provide an image forming apparatus characterized in that an image forming operation can be performed after image adjustment.

  According to a sixth aspect of the present invention, an image adjustment operation is determined to be unnecessary if the environmental variation during power-off is within a predetermined range, and even if the environmental variation exceeds the predetermined range, the learning means When there is something similar to the past environmental change history stored, it is determined that the image adjustment operation is unnecessary, and an image forming apparatus is provided.

  A seventh invention according to the present invention is characterized in that if the power-off time is within a predetermined range, it is determined that the image adjustment operation is unnecessary, and the image correction based on the “previous image adjustment data” is performed. An image forming apparatus is provided.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the first aspect, if the power-off time exceeds a predetermined range, an image adjustment operation is required without referring to the past history. It is an object of the present invention to provide an image forming apparatus characterized in that it is possible to form an image after judging and performing an image adjustment operation.

  According to a ninth aspect of the present invention, there is provided an image forming apparatus characterized in that, among environmental change history data stored in a learning means, data that has passed a predetermined period is deleted.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus characterized in that the environmental change history data stored in the learning means is deleted when a predetermined number of prints are subsequently performed. It is to provide.

  According to the present invention, since the history of environmental fluctuations during the power-off period is referred to and the image correction parameters are set using the previous image adjustment results, the image adjustment takes time when the power is turned on. It is possible to form an image with good image quality without performing the above.

  In addition, by providing a learning function that stores the history of environmental changes during power-off and the image adjustment results after power-on at that time and stores them in a database, similar environmental fluctuations during power-off have occurred in the past. In such a case, the optimum image correction parameter can be set by referring to the image adjustment result at that time.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, an image forming operation in this embodiment will be described with reference to FIG. FIG. 2 is obtained by adding an environmental sensor 100 to the cross-sectional view of FIG. 7 described in the conventional example. This environmental sensor 100 is the same as the environmental sensor 100 in FIG. 1, and is disposed in the vicinity of the photosensitive drum 1 in this embodiment. This is to accurately measure environmental fluctuations in the vicinity of the components of the image forming unit that are most susceptible to environmental fluctuations.

  The developing rotary 5 is rotated in the direction of the arrow R5 by driving means (not shown), and the yellow (Y) color developing cartridge 5Y moves to a position facing the photosensitive drum 1. The photosensitive drum 1 is rotated in the direction of arrow R1 by a driving unit (not shown), and the surface of the photosensitive drum 1 is charged by the charging roller 2 that rotates according to the rotation of the photosensitive drum 1. Next, a first yellow electrostatic latent image is formed on the surface of the photosensitive drum 1 by the exposure device 3. Then, the electrostatic latent image on the photosensitive drum 1 is developed by a yellow (Y) color cartridge 5Y in contact with the photosensitive drum 1 to form a toner image. The toner image obtained here is primarily transferred onto the intermediate transfer belt 6, and a yellow toner image is obtained on the intermediate transfer belt 6. Further, the primary transfer residual toner on the photosensitive drum 1 that has not been primarily transferred is cleaned by the cleaning blade 4. Then, the developing rotary 5 rotates in the direction of the arrow R5, and the process proceeds to the second magenta toner image forming process.

  By sequentially performing the above operation for four color toners, a four color toner image is formed on the intermediate transfer belt 6. The toner image transferred onto the intermediate transfer belt moves in the direction of arrow R6 and is secondarily transferred onto the transfer material (paper) of the secondary transfer roller 7. The transfer material to which the toner image has been transferred moves on the conveyance path indicated by P in FIG. 2, and the toner image is fixed on the transfer material by the fixing device 8, and then is discharged from the device to complete printing.

  Next, FIG. 1 shows a block diagram of a circuit for acquiring a history of temperature fluctuation during power OFF in the embodiment of the present invention. Reference numeral 106 denotes a CPU that controls the image forming apparatus according to the present exemplary embodiment based on a program stored in the ROM 107. The CPU 106 uses the RAM 108 as a work when performing control. The RAM 108 is connected to a battery (not shown) and can back up necessary data even when the apparatus is turned off. Reference numeral 100 denotes an environmental sensor that can detect the ambient temperature. Reference numeral 101 denotes an A / D converter that converts an analog signal that changes according to the temperature detected by the environmental sensor 100 into a digital signal. A history acquisition control circuit 102 acquires digital data indicating the temperature converted by the A / D converter at predetermined intervals. In this embodiment, it is acquired every 30 minutes. A memory control circuit 103 is a circuit for writing the temperature change history data acquired in 102 to the nonvolatile memory 104. The memory control circuit is connected to the CPU 106 via the CPU bus 108, and the CPU 106 can read the contents of the memory 104. In addition, a battery (not shown) is connected to a circuit in a range surrounded by a broken line 105 so that the circuit can operate even when the apparatus is turned off.

  FIG. 3 shows a temperature fluctuation history during power OFF of a certain day. In FIG. 3, if the temperature fluctuation during power OFF is within the area between the two broken lines (TrefH, TrefL) in the graph, the image adjustment operation immediately after power ON is not performed. Judge that it is also good. That is, in this embodiment, it can be determined that the temperature fluctuation during the power-off of day A is within a predetermined range, but on day B, it exceeds the predetermined range.

  FIG. 5 shows an operation after the first image forming operation (1stJOB) is completed. When 1stJOB ends, image adjustment is performed in S1. Thereafter, the result is written in the RAM 108 in S2. Thereafter, the image formation is continuously performed in the apparatus, but image adjustment is performed every time a predetermined number of prints are performed in order to maintain a good image quality (S3, S4). Each time image adjustment is performed, the result is updated in the RAM 108.

  FIG. 6 is a flowchart for explaining the image adjustment operation in S5 of FIG. 4 and S1 and S4 of FIG. First, in S1, yellow Dmax control is performed. (Details of Dmax control are the same as in the conventional example described above.) Thereafter, Dmax control is similarly performed for magenta, cyan, and black colors in S2, S3, and S4. Next, in step S5, yellow halftone control is performed. (Details of halftone control are the same as in the conventional example described above.) Thereafter, halftone control is similarly performed for magenta, cyan, and black colors in S6, S7, and S8.

  FIG. 4 is a flowchart for explaining the operation after the power is turned on in this embodiment. When the power is turned on, a reserved copy is waited for a predetermined time in S1 and S2. If there is a reserved copy, it is determined in S3 whether the temperature fluctuation during power OFF is within a predetermined range. Here, in the case of the A day, it is determined that it is within the predetermined range, so the image correction parameters are set by referring to the image adjustment result of the previous day in S4. (The image adjustment result on the previous day refers to the image adjustment data described in the description of FIG. 5 described above.) Thereafter, a transition is made to a standby state where image formation is possible. On the other hand, in the case of the B day, it is determined that the temperature fluctuation during power-off in S3 exceeds the predetermined range, so that the image adjustment operation is performed in S5 and then the standby state is entered.

  As described above, in this embodiment, there is provided means for recording the temperature fluctuation history during power OFF. Then, when the power is turned on, if the temperature fluctuation range when the power is turned off is within the predetermined range, the image correction parameters are determined by referring to the image adjustment result of the previous day instead of performing the image adjustment operation. Therefore, it is possible to shorten the time from when the user turns on the power to when the user can perform the first printing operation, and to output an image with good image quality from the initial image formation. Even if the temperature when the power is on is within the specified range, normal image adjustment operation is performed if the temperature fluctuation during power off is large. It is possible to perform image formation.

  In the present embodiment, only the temperature is taken as the environmental data for taking a history. However, more accurate environmental conditions can be grasped by taking the humidity data. Further, when the power OFF time is sufficiently short when the power is turned on, there is almost no environmental change, so it is possible to omit the image adjustment unconditionally and use the image adjustment result of the previous day.

  Next, a second embodiment will be described. In the first embodiment, if the temperature fluctuation during power-off is within a predetermined range, the time from the power-on to the start of the printing operation could be shortened, but the temperature fluctuation during power-off is predetermined. If it exceeds this range, it is necessary to perform image adjustment as before, and therefore the startup time after turning on the power cannot be shortened. In this embodiment, a learning function is provided for storing the temperature fluctuation history during power OFF and the subsequent image adjustment results in correspondence with each other, and image adjustment can be performed even when the temperature fluctuation during power OFF is large. An example will be described in which image correction parameters can be set so that an image can be formed with good image quality without performing. Since the block diagram of FIG. 1 and the cross-sectional view of FIG. 2 are the same as those of the first embodiment, detailed description thereof is omitted.

  FIG. 9 is a flowchart showing the learning function operation in this embodiment. First, in S1, the first image adjustment after turning on the power is performed. As described in the first embodiment, the image adjustment is performed when there is no reserved copy after 1st JOB or after a predetermined time elapses after the power is turned on. If the next job occurs in a short time after the end of 1st job, it may be after that. Next, in S2, the temperature fluctuation history data during the previous power OFF is acquired. This history data is stored in the non-volatile memory 104 in FIG. 1 and is read into the CPU 106 via the memory control circuit 103. Next, in S3, it is investigated whether there has been a similar temperature fluctuation history in the past. Here, past data is stored in the RAM 108.

  The method of determining similarity is not described in detail in this embodiment, but for example, temperature measurement data every 30 minutes is compared with reference to temperature fluctuation history data for about 8 hours before turning on the power. Similarity is judged by whether or not is within a predetermined range.

  If there has been a similar temperature change in the past, the data is overwritten in the RAM 108 in S4, and the apparatus is put into a standby state. On the other hand, if it is determined in S3 that there was no similar temperature fluctuation in the past, it is added to the RAM 108 as new data in S5. In this way, the RAM 108 is updated with a recorded database in which temperature fluctuations during power OFF and image adjustment control results when the power is turned ON are associated with each other.

  Next, the operation when the power is turned on will be described with reference to FIG. In S1 and S2, it is determined whether there is a reserved copy within a predetermined time after the power is turned on. If there is a reserved copy, it is determined whether or not the temperature fluctuation during power OFF is within a predetermined range in S3, and if it is within the predetermined range, image correction parameters are set using the image adjustment result of the previous day in S4. In S3, if the temperature fluctuation range exceeds the specified range, investigate whether there was a similar fluctuation in the past in S5, and if there was a similar temperature fluctuation, use the image adjustment result at that time. Set image correction parameters. If it is determined in S5 that there is no similar temperature variation in the past, an image adjustment operation is performed in S7.

  As described above, in this embodiment, there is provided a learning function for storing the history of temperature fluctuation during power OFF and the image adjustment result after power ON in association with each other. Using this learning function, even if the temperature fluctuation during power-off exceeds the specified range, if there is a similar fluctuation in the past, the image adjustment result at that time can be used to obtain the optimum Image correction parameters can be set.

  Although not described in the present embodiment, the characteristics of the image forming unit such as the photosensitive drum are the physical characteristics such that the surface of the photosensitive drum is worn after a long time has elapsed or a predetermined number of images have been formed. Has changed. Therefore, the data acquired by the learning function before the predetermined period cannot provide the optimum image correction data. That is, when image correction is performed with such data, good image quality cannot be obtained. Therefore, it is necessary to invalidate the data when a predetermined period after the acquisition or when a predetermined number of images are formed.

  Next, a third embodiment will be described. In this embodiment, an example in which the power OFF time is long will be described.

  When the power is turned off for a long period of time, such as on weekends or the year-end and New Year holidays, the physical characteristics of the image forming unit such as the photosensitive drum are likely to have changed significantly. Good image quality cannot be obtained. In addition, since there is a limit to the amount of history of temperature fluctuation, it is necessary to perform normal image adjustment when the power is turned off for a predetermined period. An embodiment considering this will be described with reference to the flowchart of FIG.

  First, in S1, it is determined whether the power OFF period is longer than a predetermined period. If the power has been turned off for a longer period than the predetermined period, the image adjustment operation is performed in S6, and then a standby state in which an image can be formed is set. On the other hand, if it is determined in S1 that the power-off period is shorter than the predetermined period, S2 and S3 wait for a reserved copy for a predetermined time. If there is no reserved copy, the image adjustment of S6 is performed, but if a reserved copy occurs, it is judged in S4 whether the temperature fluctuation during the power OFF period is within the predetermined range, and if it is within the predetermined range In S5, the image correction parameters are set using the image adjustment result of the previous day.

  As explained above, when the power is turned on after being turned off for a long period of time, it may not be possible to perform sufficient correction only with the previous image adjustment result. When it is OFF, image adjustment is performed so that image formation can be performed with good image quality.

3 is a block diagram of a temperature fluctuation history acquisition circuit during power OFF in the image forming apparatus to which the present invention is applied. FIG. 1 is a cross-sectional view around an image forming unit of an image forming apparatus to which the present invention is applied. The graph which recorded the temperature change in the Example of this invention during the power-OFF period. 3 is a flowchart showing an operation when the power is turned on in the first embodiment of the present invention. 6 is a flowchart showing an operation after the first job is completed in the first embodiment of the present invention. 5 is a flowchart showing an image adjustment operation in the embodiment of the present invention. FIG. 10 is a cross-sectional view of an image forming apparatus showing a conventional example. The graph which shows the temperature fluctuation around an apparatus. 12 is a flowchart for creating a learning function database according to the second embodiment of the present invention. 9 is a flowchart showing an operation at power-on in the second embodiment of the present invention. 10 is a flowchart showing an operation at power-on in the third embodiment of the present invention.

Explanation of symbols

1 Photosensitive drum
2 Charging roller
3 Exposure equipment
4 Cleaning blade
5 Development rotary
6 Intermediate transfer belt
7 Secondary transfer roller
8 Fixing device
9 Concentration sensor
10 Second charging roller
11 Paper cassette
100 environmental sensors
101 A / D converter
102 History acquisition control circuit
103 Memory control circuit
104 Nonvolatile memory
106 CPU
107 ROM

Claims (10)

In an image forming apparatus comprising: means for forming an electrostatic latent image on a photoreceptor based on an image signal; and means for forming a toner image by attaching toner to the photoreceptor on which the latent image is formed.
An image adjustment control means for forming a toner image on a photosensitive drum, measuring its density, and determining a parameter for correcting the image based on the result;
Environment measuring means for measuring the environment around or inside the image forming apparatus;
Environmental history storage means for storing a history of changes in time of measurement results by the environmental measurement means,
Based on the environmental change stored in the environmental history storage unit while the image forming apparatus is powered off, it is determined whether image adjustment by the image adjustment control unit is necessary, and image adjustment control is unnecessary. An image forming apparatus characterized in that an image adjustment operation is omitted when it is determined that   The image forming apparatus according to claim 1, further comprising a unit that retains “previous image adjustment data” before the power is turned off last time, and the environmental variation range during power-off is smaller than a predetermined range. An image forming apparatus that determines that an image adjustment operation is unnecessary and performs image correction based on the “previous image adjustment data”.   3. The image forming apparatus according to claim 2, wherein when the environmental fluctuation range during power OFF is larger than a predetermined range, it is determined that the image adjustment operation is necessary, and the image formation operation is enabled after the image adjustment operation is performed. An image forming apparatus.   2. The image forming apparatus according to claim 1, further comprising learning means for storing an environmental change history when the power is turned off and an image adjustment result after the power is turned on, and storing the environmental history when the power is turned on. Comparing the environmental change history during power OFF stored in the storage means and the environmental change history remaining in the learning means, if there is something similar, the image by the image adjustment data at that time An image forming apparatus that performs correction.   In the image forming apparatus according to claim 4, when the environmental change history during power OFF is not similar to any of the past environmental change history stored in the learning means, it is determined that the image adjustment operation is necessary, An image forming apparatus capable of performing an image forming operation after image adjustment.   6. The image forming apparatus according to claim 1, wherein if the environmental fluctuation during power OFF is within a predetermined range, it is determined that an image adjustment operation is unnecessary, and the learning unit even when the environmental fluctuation exceeds a predetermined range. The image forming apparatus determines that the image adjustment operation is unnecessary when there is something similar to the past environmental change history stored in   2. The image forming apparatus according to claim 1, wherein if the power-off time is within a predetermined range, it is determined that an image adjustment operation is unnecessary, and image correction is performed using the “previous image adjustment data”. Image forming apparatus.   2. The image forming apparatus according to claim 1, wherein if the power-off time exceeds a predetermined range, it is determined that the image adjustment operation is necessary without referring to the past history, and the image adjustment operation is performed. An image forming apparatus capable of forming an image.   5. The image forming apparatus according to claim 4, wherein the environmental change history data stored in the learning unit is deleted after a predetermined period.   5. The image forming apparatus according to claim 4, wherein the environmental change history data stored in the learning means is deleted when a predetermined number of prints are subsequently performed.

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