JP3973818B2 - Image forming apparatus, toner adhesion amount detection means - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a toner adhesion amount detecting means for detecting the toner adhesion amount on an image carrier, and an image forming apparatus such as various printers, copying machines, facsimiles and the like equipped with the toner adhesion amount detection means.
[0002]
[Prior art]
In general, in a color image forming apparatus, toner images of different colors are formed on the surface of an image carrier, the toner images are superimposed and transferred to the same position on the intermediate transfer member, and the toner image on the intermediate transfer member is transferred. It is transferred to paper.
[0003]
In order to keep the image density on the transfer paper always constant and good, it is necessary to stabilize the toner adhesion amount on the surface of the image carrier. For this reason, the toner adhesion amount on the surface of the image carrier is detected by a reflective toner density sensor. It is known to control the toner adhesion amount based on the detection result.
[0004]
Recently, in order to more accurately detect the amount of color toner adhered, a method for measuring the amount of diffusely reflected light has been proposed in, for example, Japanese Patent Application Laid-Open No. 5-249787. When infrared light is applied to the color toner, diffuse reflected light is generated. Diffuse reflected light quantity is to show the characteristics you increase depending on the toner adhesion amount can be measured with high sensitivity from a low coating weight to high adhesion amount.
[0005]
Among the full-color image forming apparatuses as described above, there has been proposed an apparatus that detects the toner adhesion amount on an intermediate transfer member as an image carrier, not on a photosensitive member as an image carrier.
[0006]
In general, in the case of a reflection type toner adhesion amount sensor, it has been considered that the relationship between the toner adhesion amount of the same toner and the sensor output is always the same if the output change due to variations in the sensor or temperature and humidity is calibrated.
[0007]
However, in actuality, the relationship between the toner adhesion amount and the sensor output gradually changes due to the deterioration of the toner over time, for example, the change of the characteristic value, mainly the change of the particle shape, the fine powder content, the circularity, etc. As a result, an accurate toner adhesion amount cannot be detected over time, and the toner adhesion amount control is shifted, resulting in an abnormal image with an imbalanced density balance. In particular, this tendency is remarkable in a color image forming apparatus in which a subtle hue affects the image quality.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a toner adhesion amount detection means and an image forming apparatus capable of detecting an accurate toner adhesion amount over time.
[0009]
[Means for Solving the Problems]
In order to achieve the object, the present invention has the following configuration.
(1). In an image forming apparatus that forms a toner image on an image carrier through at least charging, exposure, and development processes by means of charging, exposure, and development.
A toner-end sensor for detecting that has decreased from a certain amount is a remaining amount of toner in the developing device that constitutes the means of the development,
Control means for detecting the toner adhesion amount on the image bearing member from the output of the light receiving means receiving means Toko emitting means emitting means Toko for irradiating light on the surface of the image bearing member for receiving reflected light of the light emitted And a toner adhesion amount detection means comprising
And said toner-end detection sensor to correct the toner adhesion amount in accordance with the deterioration state of the toner with determining the deteriorated state of the litho toner by the said control means based on the sensor output number to display the toner end (Claim 1).
(2). (1) In the image forming apparatus described in
Based on the auxiliary Tadashisa the the toner adhesion amount, it was decided to change the control value relating to the image density (claim 2).
(3). (2) In the image forming apparatus according to (2), the control value related to the image density is at least one control value among a charging potential of the photosensitive member by the charging unit, an exposure light amount by the exposing unit, and a developing bias by the developing unit. (Claim 3) .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A color image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a photosensitive belt-like photoconductor as an image carrier. The photosensitive member 1 is stretched between the supporting rollers 2 and 3, and is rotated and conveyed in the direction of arrow A (clockwise direction) in the drawing by the rotational driving of the roller 2. Reference numeral 4 denotes a charging charger as charging means for uniformly charging the surface of the photoreceptor 1. A charging roller may be provided in place of the charging charger.
[0011]
Reference numeral 5 denotes an optical scanning device using a laser as an exposure means for forming an electrostatic latent image, and reference numeral 6 denotes a developing means for supplying a developer (toner) of yellow, magenta, cyan, and black, which will be described later, to the photoreceptor 1. A color developing apparatus as shown in FIG. This color developing device 6 is a so-called revolver type of rotation type, a developing device 6Y for developing with yellow toner, a developing device 6C for developing with cyan toner, a developing device 6Y for developing with yellow toner, and a developing device for developing with black toner. 6K is provided around the central axis.
[0012]
Each of the developing devices 6Y, 6M, 6C, and 6K is provided with a toner end detection sensor that electrically (magnetically) detects the toner shortage. In the case of a two-component developer, The toner ratio can be detected by a magnetic permeability sensor as a toner end detection sensor.
[0013]
The developing devices 6Y, 6M, 6C, and 6K can be replenished with toner from a toner bottle that replenishes the corresponding color toner. When the toner end sensor detects a shortage of toner, a warning is issued, and in accordance with this warning, the toner is replenished by replacing the toner bottle.
[0014]
In addition, a bias voltage (development bias) can be applied between the developing rollers of the developing devices 6Y, 6M, 6C, and 6K and the photosensitive member 1 by a biasing unit (not shown). This bias voltage is variable.
[0015]
Reference numeral 10 denotes an intermediate transfer belt as an image carrier configured as an intermediate transfer member. The intermediate transfer belt 10 is stretched between the support rollers 11 and 12, and is rotated and conveyed in the direction of arrow B (counterclockwise direction) by the rotation of the rotating roller 11.
[0016]
The photosensitive member 1 and the intermediate transfer belt 10 are in contact with each other at a portion of the roller 3 that supports the photosensitive member 1. On the intermediate transfer belt 10 side of the contact portion, a conductive bias roller 13 is in contact with the back surface of the intermediate transfer belt 10 under predetermined conditions.
[0017]
An image forming operation of this color image forming apparatus will be described.
In FIG. 1, the photosensitive member 1 is uniformly charged by a charging charger 4 and then subjected to scanning exposure based on image information by an optical scanning device 5 to form an electrostatic latent image on the surface. Here, the image information to be exposed is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information, and a laser generated by a semiconductor laser (not shown) based on this image information. The beam Lb is scanned and optical path adjusted by an optical device (not shown), and the photosensitive member 1 is scanned to carry an electrostatic latent image.
[0018]
The electrostatic latent image formed here is monochromaticly developed with predetermined yellow, cyan, magenta, and black toners by the color developing device 6, and images of the respective colors are sequentially formed on the photoreceptor 1.
[0019]
Each single-color image formed on the photosensitive member 1 rotating in the direction of arrow A in the drawing is yellow, cyan, magenta, and magenta on the intermediate transfer belt 10 rotating in the direction of arrow B in the drawing in synchronization with the photosensitive member 1. For each black single color, the images are sequentially superimposed and transferred by a predetermined transfer bias applied to the bias roller 13.
[0020]
The yellow, cyan, magenta, and black images superimposed on the intermediate transfer belt 10 are fed from a sheet feeding table 17 including a sheet feeding cassette to a sheet feeding roller 18, a conveyance roller pair 19a, 19b, and a registration roller pair 20a, 20b. Then, the transfer roller 14 is transferred onto the transfer paper 17a at a transfer portion where the transfer roller 14 is disposed.
[0021]
After the transfer is completed, the transfer paper 17a is fixed by the fixing device 80, and a full-color image is completed, and is discharged to the paper discharge stack portion 82 through the paper discharge roller pair 81a and 81b.
[0022]
Reference numeral 15 denotes a cleaning device that includes a cleaning blade that always contacts the photoreceptor 1 and cleans the toner on the photoreceptor 1, and reference numeral 15c denotes a waste toner collection container.
[0023]
Reference numeral 16 denotes a cleaning device for the intermediate transfer belt 10. The cleaning blade 16a of the cleaning device 16 is held at a position separated from the surface of the intermediate transfer belt 10 during the image forming operation, and after the formed image is transferred onto the transfer paper 17a, the surface of the intermediate transfer belt 10 is contacted. Touched.
[0024]
The waste toner scraped off from the intermediate transfer belt 10 by the cleaning blade 16a is conveyed toward the front of the drawing by the auger 16b provided in the cleaning device 16, and further provided on the front side of the process cartridge 31. The toner is transported to the waste toner collecting device 15c by the omitted transport unit. By replacing the waste toner collecting device 15c with the process cartridge 31 when a predetermined amount or more of waste toner is stored in the waste toner collecting device 15c, the life of the process cartridge 31 can be extended.
[0025]
The photosensitive member, the charging charger 4, the intermediate transfer belt 10, and the cleaning devices 15 and 16 are integrally formed with the process cartridge 31, and the waste toner collecting device 15c is incorporated in the process cartridge 31 in an exchangeable manner. . The case exterior portion on the registration roller 20b side of the process cartridge 31 also has a function as a paper transport guide.
[0026]
Reference numeral 100 denotes a toner adhesion amount sensor for detecting the toner adhesion amount on the intermediate transfer belt 10. As shown in FIG. 2, the toner adhesion amount sensor 100 of this example includes an infrared light emitting diode 100A as light emitting means for irradiating light on the surface of the intermediate transfer belt 10, and diffusion of light irradiated by the infrared light emitting diode 100A. It comprises a photodiode 100B as light receiving means for receiving reflected light.
[0027]
As shown in FIG. 3, the toner adhesion amount detection patch formed on the photoreceptor 1 is transferred onto the intermediate transfer belt at a position where the photoreceptor 1 and the intermediate transfer belt 10 are in contact with each other. As a result, the toner patch 18 is formed on the intermediate transfer belt 10. The toner patch 18 is detected by a toner adhesion amount sensor 100 attached so as to face the intermediate transfer belt 10.
[0028]
In FIG. 2, the photodiode 100B is configured to output a voltage corresponding to the amount of light received, and the photodiode 100B receives the diffusely reflected light of the toner patch 18 irradiated by the infrared light emitting diode 100A and is photoelectrically converted. An output signal is input to the control means 101.
[0029]
The control means 101 with built-in CPU that receives the output of the photodiode 100B detects the toner adhesion amount on the intermediate transfer belt 10 by calculation, and if the toner adhesion amount deviates from the target amount, the image in the image forming apparatus is displayed. The control value related to the density is changed so that the amount of deviation is controlled.
[0030]
Examples of the control value related to the image density include the charging voltage of the photosensitive member 1 by the charging charger 4, the exposure light amount by the optical scanning device 5, and the developing bias in the developing units 6Y, 6M, 6C, and 6K. The image density can be adjusted by changing at least one control value.
The toner adhesion amount detection sensor 100 and the control means 101 constitute a toner adhesion amount detection means 102.
[0031]
The area of the patch 18 is determined by the exposure area by the optical scanning device 5 and is a known value having a certain size. Therefore, the toner adhesion amount M / A per unit area can be measured from the toner adhesion amount per patch 18, and the output voltage Vs of the toner adhesion amount sensor 100 at the adhesion amount can also be measured.
[0032]
FIG. 4 shows the relationship between the adhesion amount M / A per unit area and the toner adhesion amount sensor output voltage Vs. In the figure, the broken line is the output voltage value of the initial toner, and the solid line is the output voltage value of the same toner that has deteriorated with time.
[0033]
When the adhesion amount M / A per unit area is made equal and the output voltages Vs of the toner deteriorated with time and the initial toner are compared, the output voltage Vs of the toner deteriorated with time tends to be lower than that of the initial toner. .
[0034]
This is because the toner shape changes over time (generally rounds off corners) while the toner circulates in the developing units 6Y, 6C, 6M, and 6K, and fine powder, coarse content, etc. This is probably because the amount of diffusely reflected light decreases as the amount of light increases.
[0035]
As described above, the control relating to the image density is performed only by the relationship between the adhesion amount M / A per unit area of the initial toner and the output voltage Vs, despite the difference in the amount of diffuse reflected light between the initial toner and the deteriorated toner. When the value is to be changed, it is determined that the output voltage Vs is smaller than the target control value for the deteriorated toner. Therefore, the density of the image is controlled so as to increase with time, and a deviation from the actual value is detected. It will occur.
[0036]
With respect to the output voltage Vs, the deviation amount of the output voltage Vs depending on the degree of deterioration of the new toner can be grasped. Therefore, by determining the degree of toner deterioration, it is possible to perform correction to change the control value related to the image density.
[0037]
The following are indicators for judging the degree of toner deterioration.
Example 1: Example of judging toner degradation status based on the number of image forming counts (reference example)
Case 1: In the toner adhesion amount detection means, the deterioration state of the toner is determined from the number of image formations on the image carrier. In the example of the image forming apparatus shown in FIG. 1, the state of toner deterioration can be determined using the number of developments by the color developing device 6 for the intermediate transfer belt 10 as an image carrier as the number of image formations. Here, the deterioration state means the degree of deterioration that affects the detection result by the toner adhesion amount detection means 102.
[0038]
The number of times of use in each of the developing devices 6Y, 6M, 6C, and 6K is counted, and the accumulated value of each of these counters is used as the image forming number count value, and the toner deterioration is calculated from the image forming number count value. Judge the degree of. In this case, since the degree of toner deterioration is determined, each developer bottle 6Y, 6M, 6C, 6K clears each counter value when each toner bottle is replenished, and the cumulative count from this clearing point. The state of toner deterioration is determined according to the number.
[0039]
At the time of process control, if the image forming number counter value so far is n, the calculation formula of the calculation in the control means 101 shown in FIG. 2 is changed according to the value of n, so that it depends on the deterioration according to the output voltage Vs. The toner adhesion amount without error can be obtained, and from this toner adhesion amount data, the optimum toner adhesion amount with good color balance in color image formation and the optimum charge potential of the photosensitive member, the optimum exposure light amount, It is possible to control the optimum developing bias.
[0040]
For example, an arithmetic expression is prepared in advance to check the deterioration state (degree) according to the image forming number count value, and to calculate the toner adhesion amount in which the error due to deterioration is corrected according to the image forming number count value. Keep it. Based on this, the calculation formula for determining the toner adhesion amount according to the image formation count value is used separately to determine the toner adhesion amount with the error due to deterioration corrected. Based on this toner adhesion amount, a control value related to the image density is obtained. change.
[0041]
An example of control by the control means 101 will be described with reference to FIG.
The control means 101 is inputted with the current image forming number count value n. Further, in advance, when the image forming number count value n is A <n ≦ B, the adhesion amount calculating formula 1, when the image forming number count value n is B <n ≦ C, the adhesion amount calculating formula 2, and the image forming number count value n. The error due to deterioration is corrected in accordance with the degree of deterioration, so that the adhesion amount calculation formula 3 is used when C <n ≦ D, and the adhesion amount calculation formula 4 is used when the image forming number count value n is n> D. An adhesion amount calculation formula for determining the adhered toner adhesion amount is determined.
[0042]
Under such a premise, when the process control relating to the toner adhesion amount starts, for example, for the yellow toner, the toner patch 18 described in FIG. In Step P2, the toner patch 18 is detected by the toner adhesion amount sensor 100, and this output Vs is input to the control means 101 in FIG.
[0043]
In Step P3, it is determined whether or not the current image forming number count value n is A <n ≦ B. If “Yes”, the process proceeds to Step P4, where the toner error whose error due to deterioration has been corrected using the attached amount arithmetic expression 1 is used. Find the amount of adhesion. If “NO”, the process proceeds to Step P5.
[0044]
In Step P5, it is determined whether or not the current image forming number count value n is B <n ≦ C. If “Yes”, the process proceeds to Step P6, and the error of the toner whose error due to deterioration has been corrected using the attached amount arithmetic expression 2 is determined. Find the amount of adhesion. If “NO”, the process proceeds to Step P7.
[0045]
In Step P7, it is determined whether or not the current image forming number count value n is C <n ≦ D. If “yes”, the process proceeds to Step P8 and the error of the toner whose error due to deterioration has been corrected using the attached amount arithmetic expression 3 is determined. Find the amount of adhesion. If “NO”, the process proceeds to Step P9. In Step P9, the current image forming number count value n is n <D, and the adhesion amount of the toner in which the error due to deterioration is corrected is obtained using the adhesion amount calculation formula 4.
[0046]
As described above, by changing the arithmetic expression according to the value of the image forming number count value n, it is possible to obtain the toner adhesion amount that does not include an error due to toner deterioration. From the toner adhesion amount data, in step P10, Control values related to image density, for example, charging potential of the photosensitive member by the charging means (charging voltage for the charging roller, grid bias for charging by the charging charger), exposure light amount by the exposure means (light amount of the laser diode LD as the light source) By changing at least one control value of the developing bias by the developing means, it is possible to control the yellow toner to an optimum toner adhesion amount that is in color balance with other colors.
[0047]
The same applies to other cyan, magenta, yellow, and black.
Case 2:
As in Case 1, instead of using an adhesion amount calculation formula depending on the value of the image formation count value n, the image formation count value n is directly applied to the adhesion amount calculation formula to correct an error in toner adhesion due to deterioration. It is also possible to determine the amount of adhered toner. In this case, as compared with the case of Example 1, the arithmetic expression becomes complicated and the calculation is complicated, but a more detailed result can be obtained.
[0048]
An example of the control will be described with reference to FIG. 6, assuming that this control is also performed by the control means 101 in FIG. The control means 101 is inputted with the current image forming number count value n. The control unit 101 is programmed in advance with an adhesion amount calculation formula using the image forming number count value n. Here, an arithmetic expression of the toner adhesion amount M at the image forming number count value n is represented by M = f (Vs) × f (n). However, f (Vs) is a function equation of the output voltage Vs, which is a basic equation for directly obtaining the toner adhesion amount from the output voltage Vs, and f (n) is a function equation of the image formation count value n, and the state of toner deterioration. In other words, the correction formula is corrected in accordance with the above.
[0049]
In FIG. 6, when the process control relating to the toner adhesion amount starts, for example, for the yellow toner, the toner patch 18 as described in FIG. In step PP2, the toner patch 18 is detected by the toner adhesion amount sensor 100, and this output Vs is input to the control means 101 in FIG.
[0050]
In step PP3, the current image formation number count value n and the current output voltage Vs are put into the equation M = f (Vs) × f (n), and the toner adhesion amount M is calculated. Thus, the toner adhesion amount in which the error due to deterioration is corrected is obtained.
[0051]
In this way, it is possible to determine the toner adhesion amount that does not include an error due to toner degradation according to the value of the image formation count value n. From the toner adhesion amount data, in step PP4, a control value related to the image density. For example, the charging potential of the photosensitive member by the charging unit (charging voltage for the charging roller, grid bias for charging by the charging charger), the exposure light amount by the exposure unit (the light amount of the laser diode LD as the light source), the developing bias by the developing unit Among them, it is possible to change the at least one control value to control the yellow toner to an optimum toner adhesion amount that is in a color balance with other colors. The same applies to other cyan, magenta, yellow, and black.
[0052]
In the case of Example 1, since the toner deterioration state is determined from indirect data such as the number of times of image formation on the image carrier, it cannot be said that it is precise. There is an advantage that it can be implemented relatively easily.
Example 2: Example of determining the deterioration state of toner from the cumulative value of the number of pixels of image data formed on the image carrier (reference example)
Toner deterioration occurs when the shape of the toner changes over time as the toner circulates in the developing devices 6Y, 6C, 6M, and 6K other than the above-described image forming number counter value n. The toner circulation in the developing device is related to the operation amount of the developing device. The operation amount of the developing device is related to the cumulative value of the number of pixels of the imaged data.
[0053]
The remaining amount of toner in the developing device can be ascertained from the cumulative value of the number of pixels of the imaged data, and a small amount of toner means that the operation amount of the developing device is large. Therefore, the toner deterioration state can be predicted more reliably from the cumulative value of the number of pixels of the imaged data.
[0054]
Here, for example, in the case of 600 × 600 dots / inch, the number of pixels is the number of pixels of about 34.8 Mdots in A4 size. At this time, if the amount of toner per pixel is 10 ng, 17.4 g of toner is consumed when 1000 sheets of A4, 5% chart are output. As a result, the state of toner deterioration corresponding to the toner consumption is grasped using the accumulated value of the number of pixels of the imaged data instead of the image forming number counter value n, and based on this, the image density is determined. It is also possible to change the control value related to.
[0055]
As a specific method, in the contents described in FIG. 5 and FIG. 6 in Example 1, an accumulated value of the number of pixels of imaged data may be used instead of the image forming number counter value n. The accumulated value of the number of pixels of the imaged data can be easily obtained by an image forming apparatus that performs digital writing, and this data can be used in the control according to FIGS.
[0056]
In the case of this example, since the number of pixels of the imaged data is used, it can be easily used in the digital image forming apparatus.
Example 3: Example of determining toner deterioration state based on output of toner end detection sensor Toner deterioration is caused by the change in toner shape over time due to toner circulating in developing units 6Y, 6C, 6M, and 6K. Arise. The toner circulation in the developing device is related to the operating amount of the developing device, and a small amount of toner means that the operating amount of the developing device is large, and therefore the deterioration state of the toner is also progressing. It can be said.
[0057]
Therefore, if the developing unit is provided with a toner end detection sensor that detects that the remaining amount of toner is less than a certain amount, the toner deterioration state can be grasped from the output of the toner end detection sensor.
[0058]
The toner end detection sensor constantly monitors the ratio of the toner to the carrier, for example, by checking the change in magnetic permeability, and displays the toner end when it is determined that the ratio of the toner to the carrier is equal to or less than a certain value. The toner end detection sensor outputs the sensor output hundreds of times before displaying the toner end. Therefore, the toner deterioration state can be determined from the number of times of detection.
[0059]
As a specific method, in the content described in FIGS. 5 and 6 in Example 1, the number of sensor outputs until the toner end detection sensor performs toner end display may be used instead of the image forming number counter value n. The accumulated value of the number of pixels of the imaged data can be easily obtained by an image forming apparatus that performs digital writing, and this data can be used in the control according to FIGS.
[0060]
In the case of this example, since it is based on data relating to actual toner consumption in the developing device, accurate correction control can be performed.
[0061]
When the correction control in each example described above is applied to the color image forming apparatus described in FIG. 1, an image having a color balance can be obtained. In the black and white image forming apparatus, an image having an appropriate density can be obtained.
[0062]
In addition to the above examples, even when the light receiving method of the toner adhesion amount sensor is a regular reflection type or when the toner is a polymerized toner, the toner characteristics basically change due to deterioration over time. Since the relationship between the toner adhesion amount and the sensor output changes, correction is required, and correction can be performed according to the above-described example.
[0063]
【The invention's effect】
In the first aspect of the present invention, since it is to based on the data relating to the actual toner consumption, that enables accurate correction control.
According to the second aspect of the present invention, it is possible to obtain a color balanced image in the color image forming apparatus. In the black and white image forming apparatus, an image having an appropriate density can be obtained.
According to the third aspect of the invention, a sufficient correction effect can be obtained by selecting at least one of the control values related to the image density that is easy to use.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a color image forming apparatus.
FIG. 2 is a perspective view around an intermediate transfer belt, explaining a toner patch formation state.
FIG. 3 is a schematic configuration diagram of toner adhesion amount detection means.
FIG. 4 is a characteristic diagram comparing the relationship between the sensor output and the toner adhesion amount between the initial toner and the deteriorated toner.
FIG. 5 is a diagram illustrating a control process of the present invention.
FIG. 6 is a diagram illustrating a control process of the present invention.
[Explanation of symbols]
10 Intermediate transfer belt 100 Toner adhesion amount sensor 102 Toner adhesion amount detection means

Claims (3)

In an image forming apparatus for forming a toner image on an image carrier through at least charging, exposure and development processes by means of charging, exposure and development,
A toner-end sensor for detecting that has decreased from a certain amount is a remaining amount of toner in the developing device that constitutes the means of the development,
Control means for detecting the toner adhesion amount on the image bearing member from the output of the light receiving means receiving means Toko emitting means emitting means Toko for irradiating light on the surface of the image bearing member for receiving reflected light of the light emitted And a toner adhesion amount detection means comprising
Said toner end detection sensor to correct the toner adhesion amount in accordance with the deterioration state of the toner with determining the deteriorated state of the litho toner by the said control means based on the sensor output number to display the toner end An image forming apparatus. The image forming apparatus according to claim 1 .
Based on the auxiliary Tadashisa the the toner adhesion amount, an image forming apparatus characterized by changing a control value relating to the image density. The image forming apparatus according to claim 2.
The image forming apparatus according to claim 1, wherein the control value related to the image density is at least one of a charging potential of the photosensitive member by the charging unit, an exposure light amount by the exposure unit, and a developing bias by the developing unit.

Images