Patent Application
20170097584
This application is based upon, and claims the benefit of priority from, corresponding Japanese Patent Application No. 2015-197367 filed in the Japan Patent Office on Oct. 5, 2015, the entire contents of which are incorporated herein by reference.
Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
As a typical image forming apparatus employing an electrophotographic method such as a printer and a copier, there has been known an image forming apparatus that includes a photoreceptor drum, a charging apparatus, an exposure apparatus, a developing device, and a transfer apparatus. The charging apparatus uniformly charges a circumference surface of the photoreceptor drum. The exposure apparatus irradiates the photoreceptor drum with exposure light according to image information to form an electrostatic latent image. The developing device supplies the photoreceptor drum with toner to develop the electrostatic latent image into a toner image. The transfer apparatus transfers the toner image from the photoreceptor drum to a sheet.
To obtain good images, it is necessary for a surface potential of the photoreceptor drum in the image forming apparatus to be set to a desired electric potential. Especially, when the charging apparatus includes a charging roller that rotates while contacting a surface of the photoreceptor drum, even if a voltage applied to the charging roller is identical, the surface potential of the photoreceptor drum is likely to vary depending on an environmental variation or a similar factor. With the charging roller to which an ion conducting agent is combined, since a resistance value of the roller is likely to vary depending on the environment or a similar factor, a variation in displacement of the photoreceptor drum is likely to be especially remarkable.
There has been disclosed a typical image forming apparatus that includes a surface electrometer opposed to a circumference surface of a photoreceptor drum. Feeding back a measurement result of an electric potential by the surface electrometer to a voltage applied to a charging apparatus sets a surface potential of the photoreceptor drum to be a desired electric potential.
An image forming apparatus according to one aspect of the disclosure includes an apparatus main body, a photoreceptor drum, a charging apparatus, a developing device, a transfer apparatus, a charging bias applying unit, a developing bias applying unit, a bias adjusting unit, and a print density measurement unit. The photoreceptor drum has a circumference surface on which an electrostatic latent image including a background portion and an image portion is formed. The photoreceptor drum is rotationally driven in a predetermined rotation direction. The charging apparatus is arranged in contact with or close to the circumference surface of the photoreceptor drum. The charging apparatus charges the circumference surface at a predetermined electric potential. The developing device includes a developing roller disposed opposed to the photoreceptor drum. The developing device supplies the photoreceptor drum with toner to develop the electrostatic latent image into a toner image. The transfer apparatus transfers the toner image from the photoreceptor drum to a sheet or an intermediate transfer belt. The charging bias applying unit applies a predetermined charging bias to the charging apparatus. The developing bias applying unit applies a predetermined developing bias to the developing roller. The bias adjusting unit performs a charging bias adjusting operation. The charging bias adjusting operation adjusts an electric potential at the background portion in the electrostatic latent image on the photoreceptor drum to a predetermined target electric potential. The print density measurement unit measures a print density of the toner image. In the charging bias adjusting operation, the bias adjusting unit controls the charging bias applying unit to form a plurality of electric potential areas of electric potentials with different magnitudes. The electric potential areas are formed on the circumference surface of the photoreceptor drum along the rotation direction. The bias adjusting unit controls the developing bias applying unit to apply the predetermined developing bias corresponding to the target electric potential to the developing roller, so as to form a plurality of toner images by electric potential differences between the developing bias and the plurality of electric potential areas. The bias adjusting unit decides a value of the charging bias corresponding to the target electric potential from measurement results of the print densities of the plurality of toner images measured by the print density measurement unit.
These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description with reference where appropriate to the accompanying drawings. Further, it should be understood that the description provided in this summary section and elsewhere in this document is intended to illustrate the claimed subject matter by way of example and not by way of limitation.
Example apparatuses are described herein. Other example embodiments or features may further be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. In the following detailed description, reference is made to the accompanying drawings, which form a part thereof.
The example embodiments described herein are not meant to be limiting. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the drawings, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.
The following describes an image forming apparatus 10 according to embodiments of the disclosure in detail with reference to the accompanying drawings. This embodiment exemplifies a tandem type color printer as an exemplary image forming apparatus. The image forming apparatus may be devices such as a copier, a facsimile device, and a multi-functional peripheral of these devices.
At an appropriate position on the top surface of the apparatus main body 11, an operation panel (not illustrated) for an input operation of an output condition or a similar operation to the sheet P is located. This operation panel includes a power key, a touch panel to input the output condition, and various operation keys. Additionally, the apparatus main body 11 internally includes a sheet conveyance path 111, which extends in a vertical direction, at a position right side of the image forming unit 13. The sheet conveyance path 111 includes a conveyance roller pair 112 to feed the sheet at an appropriate position. A registration roller pair 113 is arranged upstream with respect to a secondary transfer nip portion, which will be described later, in the sheet conveyance path 111. The registration roller pair 113 performs skew correction on the sheet and sends out the sheet to the nip portion at a predetermined timing. The sheet conveyance path 111 is a conveyance path that feeds the sheet P from the paper sheet feeder 12 to the paper sheet discharge unit 17 via the image forming unit 13 (the secondary transfer nip portion) and the fixing unit 16.
The paper sheet feeder 12 includes a sheet feed tray 121, a pickup roller 122, and a feed roller pair 123. The sheet feed tray 121 is insertably/removably mounted to a lower position of the apparatus main body 11 to accumulate a sheet bundle P1, which is the plurality of stacked sheets P. The pickup roller 122 feeds out the sheet P on the uppermost surface of the sheet bundle P1 accumulated at the sheet feed tray 121 one by one. The feed roller pair 123 sends out the sheet P fed out by the pickup roller 122 to the sheet conveyance path 111. The paper sheet feeder 12 includes a manual paper feed tray, which is mounted to a left side surface of the apparatus main body 11 illustrated in
The image forming unit 13 forms a toner image to be transferred to the sheet P. The image forming unit 13 includes a plurality of image forming units, which form toner images of different colors. As this image forming unit, this embodiment includes a magenta unit 13M, which uses a magenta (M) color developer, a cyan unit 13C, which uses a cyan (C) color developer, a yellow unit 13Y, which uses a yellow (Y) color developer, and a black unit 13Bk, which uses a black (Bk) color developer, sequentially from upstream to downstream in a rotation direction of an intermediate transfer belt 141 (from the left side to the right side shown in
The photoreceptor drum 20 is rotatably driven in a direction of the arrow in
The charging apparatus 21 uniformly charges the circumference surface of the photoreceptor drum 20 at a predetermined electric potential. As the charging apparatus 21, a charging apparatus with a contact electrification method can be employed. The charging apparatus 21 includes a charging roller 21A, which contacts the circumference surface of the photoreceptor drum 20 and is arranged and rotationally driven, and a charging cleaning brush 21B to remove toner attached to the charging roller 21A. In another embodiment, the charging roller 21A may be arranged close to the circumference surface of the photoreceptor drum 20. The exposure apparatus 22 includes various optical system devices such as a light source, a polygon mirror, a reflection mirror, and a deflecting mirror. The exposure apparatus 22 irradiates the uniformly charged circumference surface of the photoreceptor drum 20 with light modulated based on image data to form the above-described electrostatic latent image. The cleaning apparatus 25 cleans the circumference surface of the photoreceptor drum 20 after toner image transfer.
The developing device 23 supplies the circumference surface of the photoreceptor drum 20 with toner to develop the electrostatic latent image formed on the photoreceptor drum 20. The developing device 23 is for two-component developer constituted of toner and a carrier. The developing device 23 supplies the toner to the circumference surface of the photoreceptor drum 20 to develop the electrostatic latent image. The developing device 23 includes a developing roller 23C opposed to the photoreceptor drum 20, a magnetic roller 23B, and a pair of screws 23A. As the developing device 23, another constitution including the developing roller 23C may be applied. In this embodiment, the toner has a property that charges to a positive polarity.
The intermediate transfer unit 14 is located at the space between the image forming unit 13 and the toner replenishment unit 15. The intermediate transfer unit 14 includes the intermediate transfer belt 141, a drive roller 142, a driven roller 143, a plurality of primary transfer rollers 24 (transfer rollers), and a belt cleaning apparatus 144.
The intermediate transfer belt 141 is an endless belt-shaped rotator and is suspended across the drive roller 142 and the driven roller 143 such that its circumference surface side is brought into abutment with the circumference surfaces of the respective photoreceptor drums 20. The intermediate transfer belt 141 is circularly driven in one direction along a second direction and carries the toner image transferred from the plurality of photoreceptor drums 20 on its surface. The intermediate transfer belt 141 is a conductive soft belt with a laminated structure formed of a base layer, an elastic layer, and a coat layer.
The drive roller 142 stretches the intermediate transfer belt 141 at a right end side of the intermediate transfer unit 14 and causes the intermediate transfer belt 141 to circularly drive. The drive roller 142 is constituted of a metal roller. The driven roller 143 passively rotates at a left end side of the intermediate transfer unit 14. The driven roller 143 stretches the intermediate transfer belt 141. The driven roller 143 provides the intermediate transfer belt 141 with a tensile force. The belt cleaning apparatus 144 (see
The primary transfer roller 24 is located across the intermediate transfer belt 141 and opposed to the photoreceptor drum 20. This forms primary transfer nip portions between the primary transfer rollers 24 and the photoreceptor drums 20 to primarily transfer the toner images, which are on the photoreceptor drums 20, on the intermediate transfer belt 141. As illustrated in
The secondary transfer roller 145 is opposed to the drive roller 142 across the intermediate transfer belt 141. The secondary transfer roller 145 is pressed and contacts with the circumference surface of the intermediate transfer belt 141 to form the secondary transfer nip portion. The toner image primarily transferred on the intermediate transfer belt 141 is secondarily transferred on the sheet P supplied from the paper sheet feeder 12 at the secondary transfer nip portion. In this embodiment, the intermediate transfer unit 14 and the secondary transfer roller 145 constitute a transfer apparatus. The transfer apparatus transfers the toner image from the photoreceptor drum 20 to the sheet P.
The toner replenishment unit 15 retains toner used for an image formation. The toner replenishment unit 15 according to the embodiment includes a magenta toner container 15M, a cyan toner container 15C, a yellow toner container 15Y, and a black toner container 15Bk. These toner containers 15M, 15C, 15Y, and 15Bk retain each replenishment toner for the respective colors M, C, Y, and Bk. The toner replenishment unit 15 replenishes the toners for the respective colors to the developing devices 23 for the image forming units 13M, 13C, 13Y, and 13Bk, which correspond to the respective colors M, C, Y, and Bk, from toner discharge ports 15H, which are formed on the bottom surfaces of the containers, via a toner conveying unit (not illustrated).
The fixing unit 16 includes a heating roller 161, which internally includes a heat source, a fixing roller 162, which is located opposed to the heating roller 161, a fixing belt 163, which is stretched between the fixing roller 162 and heating roller 161, and a pressure roller 164, which is opposed to the fixing roller 162 via the fixing belt 163 and forms a fixing nip portion. The sheet P supplied to the fixing unit 16 passes through the fixing nip portion to be heated and pressurized. This fixes the toner image, which has been transferred to the sheet P at the secondary transfer nip portion, to the sheet P.
The paper sheet discharge unit 17 is formed by depressing the top of the apparatus main body 11. The bottom portion of this concave portion forms a sheet discharge tray 171 that receives the discharged sheet P. The sheet P on which the fixing process has been performed is discharged to a sheet discharge tray 171 via the sheet conveyance path 111 running from the upper portion of the fixing unit 16.
The driving unit 61 is formed of a gear mechanism that transmits a motor and a torque of the motor. The driving unit 61 rotates the respective members such as the image forming unit 13 and the secondary transfer roller 145 according to a control signal from a drive control unit 51, which will be described later.
The charging bias applying unit 62 is constituted of a DC power supply. Based on a control signal from a bias control unit 52, which will be described later, the charging bias applying unit 62 applies a predetermined charging bias to the charging roller 21A of the charging apparatus 21.
The developing bias applying unit 63 is constituted of a DC power supply and an AC power supply. Based on the control signal from the bias control unit 52, the developing bias applying unit 63 applies a predetermined developing bias to the developing roller 23C and the magnetic roller 23B of the developing device 23.
The environmental sensor 64 (see
The print density sensor 65 (see
An execution of the control program stored in the ROM by the CPU causes the control unit 50 to function as the drive control unit 51, the bias control unit 52, the image condition adjusting unit 53, a storage unit 54, and a count unit 55.
The drive control unit 51 controls the driving unit 61 according to an image forming operation by the image forming apparatus 10 and the charging bias adjusting operation and the calibration operation, which will be described later. The drive control unit 51 controls a driving mechanism (not illustrated) as well as the driving unit 61 to drive other driving members in the image forming apparatus 10.
Similarly, the bias control unit 52 controls the charging bias applying unit 62 and the developing bias applying unit 63 according to the image forming operation by the image forming apparatus 10, the charging bias adjusting operation, and the calibration operation. The bias control unit 52 controls a bias applying unit (not illustrated) as well as the charging bias applying unit 62 and the developing bias applying unit 63 to apply a predetermined bias to other members inside the image forming apparatus 10. As one example, the bias control unit 52 applies a primary transfer bias and a secondary transfer bias to the primary transfer roller 24 and the secondary transfer roller 145, respectively.
The image condition adjusting unit 53 performs various image condition adjusting operations in the image forming apparatus 10. This image condition adjusting operation includes the charging bias adjusting operation and the calibration operation. In the charging bias adjusting operation, the image condition adjusting unit 53 adjusts an electric potential at the background portion in the electrostatic latent image on the photoreceptor drum 20 to a predetermined target electric potential.
The storage unit 54 stores various pieces of reference information referred to by the drive control unit 51, the bias control unit 52, and the image condition adjusting unit 53. As one example, the storage unit 54 stores electric potential information referred to in the charging bias adjusting operation.
The count unit 55 counts various pieces of accumulated information in the image forming operation by the image forming apparatus 10 and the image condition adjusting operation. As one example, the count unit 55 counts the number of printed sheets to which the toner images are transferred, a printing interval period of the sheets (a period during which the image forming apparatus 10 is left), the number of accumulated rotations of the photoreceptor drum 20, and an accumulated application period of the charging bias by the charging apparatus 21.
The following describes the charging bias adjusting operation according to a first embodiment of the disclosure.
With reference to
The execution of the charging bias adjusting operation forms the band image in
At Step S1, the image condition adjusting unit 53 refers to a charging bias Vref preliminary stored in the storage unit 54 (see
This embodiment sets b=50 (V) and t1=30 msec, and sets t2=60 msec. The storage unit 54 (see
At Step S2, the image condition adjusting unit 53 sets a developing bias Vdc applied to the developing roller 23C to the value of the above-described target electric potential V0 and then develops the latent images formed at Step S1. In other words, in
At Step S3, the print densities of the toner images formed at Step S2 is measured. The toner image on the photoreceptor drum 20 is transferred to the intermediate transfer belt 141 at a predetermined primary transfer bias applied to the primary transfer roller 24. The toner image carried on the intermediate transfer belt 141 passes through immediately above the print density sensor 65 in
At Step S4, the charging bias according to the target electric potential V0 is decided. The image condition adjusting unit 53 decides the charging bias according to the target electric potential V0 from the plurality of charging biases applied by the charging bias applying unit 62 when the plurality of latent images are formed at Step S1 and the measurement results (ID) of the print densities of the plurality of toner images measured at Step S3. With reference to
The derivation of the charging bias at Step S4 is not limited to the above-described one. Among the plurality of pieces of data in the graph of
As described above, in this embodiment, the image condition adjusting unit 53 controls the charging bias applying unit 62 and forms the plurality of electric potential areas with different electric potential magnitudes on the circumference surface of the photoreceptor drum 20 along the rotation direction in the charging bias adjusting operation. Further, the image condition adjusting unit 53 controls the developing bias applying unit 63 to apply the predetermined developing bias corresponding to the target electric potential of the photoreceptor drum 20 to the developing roller 23C. Consequently, the electric potential difference between the developing bias and the plurality of electric potential areas on the photoreceptor drums 20 forms the plurality of toner images. From the measurement results of the print densities of the plurality of toner images measured by the print density sensor 65, the value of charging bias corresponding to the target electric potential is decided. This ensures setting the surface potential of the photoreceptor drum 20 to the target electric potential with a simple configuration without providing a surface electrometer opposed to the photoreceptor drum 20.
Especially, the image condition adjusting unit 53 controls the developing bias applying unit 63 to apply the developing bias Vdc (=V0=Vdc (0)+a), which is the value identical to the target electric potential V0 for the photoreceptor drum 20, to the developing roller 23C. The image condition adjusting unit 53 derives the value of the charging bias where the print density of the toner image becomes zero from the relationship between the print density measurement results of the plurality of toner images and the plurality of charging biases corresponding to the plurality of electric potential areas. The image condition adjusting unit 53 decides the derived charging bias as the charging bias corresponding to the target electric potential. That is, using the developing bias Vdc, which eases grasping the actual output voltage, as the reference, this embodiment utilizes that the print density of the toner image becomes zero when this developing bias Vdc matches the surface potential V0(I) of the photoreceptor drum 20. Accordingly, the surface potential setting with small error range is achievable with simple configuration.
Further, the image condition adjusting unit 53 causes the charging bias applying unit 62 to apply the charging bias Vref preset corresponding to the target electric potential of the photoreceptor drum 20. The application of the plurality of charging biases such that the absolute values decrease in order from the charging bias Vref forms the plurality of latent images (the electric potential regions) (see
At Step S1, a latent image pattern formed on the circumference surface of the photoreceptor drum 20 is not limited to the form illustrated in
Meanwhile, in
In
The following describes the charging bias adjusting operation according to a second embodiment of the disclosure.
With reference to
Further, at Step S2 (see
Meanwhile, with the large electric potential difference between the developing bias Vdc and the surface potential V0(I) on the photoreceptor drum 20 by the charging bias Vref, the use of the two-component developer to the developing device 23 is likely to move the carrier to the photoreceptor drum 20 side during the charging bias adjusting operation. This possibly causes an image defect in the image formation after the adjustment operation. In view of this, it is preferable that the reference charging bias Vref is also set low according to the value of the developing bias Vdc. In this embodiment, as described above, the bias lower than the charging bias Vref of the first embodiment by a (V) is set as Vref.
Compared with the first embodiment, this embodiment describes the aspect where the differential electrical potential b (V) when the charging bias Vref is reduced (the second differential electrical potential) (V0(I)′−V0(I)) is set to be the value identical to the differential electrical potential a (V) when the developing bias Vdc is reduced from the target surface potential V0 for the photoreceptor drum 20 (the first differential electrical potential) (b=a). However, in other embodiments, both constant values may be different values. Like this embodiment, when both constant values are set to be identical, the relationship between the developing bias Vdc and the surface potential V0 for the photoreceptor drum 20 in the charging bias adjusting operation has a relative relationship identical to one in the usual development (in the image formation). Accordingly, this is preferable also in terms of carrier development, toner fogging, and further tone reproducibility.
After performing Step S3 similar to the first embodiment, the image condition adjusting unit 53 decides the charging bias at Step S4 (see
As described above, in this embodiment, the image condition adjusting unit 53 controls the developing bias applying unit 63 to apply the developing bias Vdc (V0−a), which has the value smaller than the target electric potential V0 for the photoreceptor drum 20 by a (V), the preset value (the first differential electrical potential), to the developing roller 23C. Further, the image condition adjusting unit 53 derives the value of the charging bias where the print density of the toner image becomes zero from the relationship between the print density measurement results of the plurality of toner images and the plurality of charging biases corresponding to the plurality of electric potential areas. Then, the image condition adjusting unit 53 decides the value found by adding a (V) to this derived charging bias as the charging bias corresponding to the target electric potential for the photoreceptor drum 20.
The following describes the execution timing of the charging bias adjusting operation according to the above-described first and second embodiments (hereinafter referred to as the embodiments). In the image forming apparatus 10, when the surface potential of the photoreceptor drum 20 varies, an image defect such as a print density variation occurs. Accordingly, it is preferable to perform the charging bias adjusting operation under conditions where the surface potential of the photoreceptor drum 20 is likely to vary from the target electric potential V0. The following describes the preferable conditions.
First, it is preferable that the charging bias adjusting operation is performed when the image forming apparatus 10 is left for a long time after a termination of the previous image forming operation. In this case, temperature and humidity environments inside and outside the image forming apparatus 10 or a similar factor may vary or the property of the charging roller 21A of the charging apparatus 21 may change. In the embodiments, the image forming apparatus 10 includes the count unit 55 (see
Secondary, if the temperature and humidity inside and outside the machine of the image forming apparatus 10 largely change, the charging bias adjusting operation is preferably performed. In this case, due to the variation of the temperature and humidity environments, the property of the charging roller 21A of the charging apparatus 21 may change. In the embodiments, the image forming apparatus 10 includes the environmental sensor 64 (see
Thirdly, if the number of printed sheets printed within a predetermined period exceeds the preset threshold stored in the storage unit 54, the image condition adjusting unit 53 may perform the charging bias adjusting operation. Continuous executions of the image forming operation over a long time are likely to vary the surface potential of the photoreceptor drum 20 due to a temperature rise of the photoreceptor drum 20, the property change of the charging roller 21A, or a similar cause. Accordingly, with the large number of printed sheets within the predetermined time, accurately adjusting the surface potential V0 of the photoreceptor drum 20 prevents the image defect.
The above-described execution timing of the charging bias adjusting operation may be almost identical to a timing of the calibration operation (adjustments of developability, an amount of exposure, and color-shift correction) performed by the image forming apparatus 10. In view of this, the image condition adjusting unit 53 may perform the charging bias adjusting operation simultaneous with the execution of the calibration operation.
Thus, in this embodiment, the image condition adjusting unit 53 performs the charging bias adjusting operation (Step S12), and then the calibration operation (Step S13), which adjusts the print density tone of the toner image, is performed. Accordingly, the print density tone of the toner image is adjusted with the surface potential V0 of the photoreceptor drum 20 stably held. This ensures obtaining a stable image quality in the subsequent image forming operation.
The following describes a third embodiment of the disclosure. Compared with the above-described first and second embodiments, this embodiment differs in predictive control of the charging bias Vref performed beforehand prior to the formation of the band latent image in
Table 1 shows an amount of correction of the charging bias Vref corrected by the image condition adjusting unit 53 when the temperature and the humidity detected by the environmental sensor 64 change. The storage unit 54 preliminary stores this amount of correction. As one example, with the detected temperature and humidity at 18 degrees and 30% RH, a value found by adding 76 V to a predetermined reference value is set as the charging bias Vref, and the charging bias adjusting operation is started. With this correction, even if the properties of the photoreceptor drum 20 and the charging apparatus 21 change according to the temperature and humidity, the adjusting operation is performed in the electric potential area close to the actual target electric potential V0. Therefore, the charging bias adjusting operation is quickly and accurately achieved.
Table 2 shows an amount of correction of the charging bias Vref corrected by the image condition adjusting unit 53 according to a driving period of the photoreceptor drum 20 detected by the count unit 55. The storage unit 54 preliminary stores this amount of correction. As one example, with the detected driving period of the photoreceptor drum 20 of 50 hours, a value found by adding 50 V to a predetermined reference value is set as the charging bias Vref and the charging bias adjusting operation is started. In this case, even if the charging characteristic of the photoreceptor drum 20 changes according to the driving period of the photoreceptor drum 20, the charging bias adjusting operation is quickly and accurately achieved. In another modified embodiment, the count unit 55 may count an accumulated application period of the charging bias by the charging apparatus 21. It is only necessary that the storage unit 54 preliminary stores correction values shown in Table 2 according to the accumulated application period of the charging bias. In this case as well, even if the charging characteristic of the charging roller 21A changes according to the accumulated application period of the charging bias, the charging bias adjusting operation is quickly and accurately achieved. With the above-described respective amounts of correction in combination with one another, the charging bias Vref may be adjusted by the temperature and humidity inside and outside the machine of the image forming apparatus 10, the driving period of the photoreceptor drum 20, and a similar factor. The charging bias Vref may be adjusted according to other correction conditions. The above-described respective correction values may be stored not as a table but as a predetermined correction formula.
After the above-described charging bias Vref is corrected, the charging bias adjusting operation similar to the above-described first or second embodiment is performed. In this respect, at Step S3 in
The image forming apparatus 10 according to the embodiments of the disclosure is described above in detail; however, the disclosure is not limited to this. The disclosure can employ, for example, the following modified embodiments.
(1) The above-described respective embodiments describe the aspect that the toner is charged to a positive polarity; however, the disclosure is not limited to this. When the toner is charged to a negative polarity, the similar charging bias adjusting control is executable with polarities of the above-described respective biases inverted.
(2) The above-described embodiments describe the aspect that the image forming apparatus 10 is the full-color image forming apparatus; however, the disclosure is not limited to this. The image forming apparatus 10 may be a monochrome printer or a similar printer that forms a single color image.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-197367 | Oct 2015 | JP | national |
