The present invention relates to an image forming apparatus, such as a copying machine, a facsimile machine or a printer of an electrophotographic type or an electrostatic recording type.
Conventionally, for example, in the image forming apparatus of the electrophotographic type, there is a tandem type in which toner images formed with different color toners on a plurality of photosensitive members as image bearing members are successively transferred superposedly onto an intermediary transfer member or a recording material carried on a recording material carrying member. The image forming apparatus of the tandem type has an advantage such that speed-up of the image forming apparatus is easy.
The image forming apparatus of the tandem type using the intermediary transfer member will be further described as an example. In the image forming apparatus of this type, the intermediary transfer member contacts the photosensitive members at primary transfer portions where the toner images are transferred from the photosensitive members onto the intermediary transfer member. For that reason, depending on friction and contact pressures, the photosensitive members and the intermediary transfer member are gradually abraded or are changed in surface characteristic in some instances. For that reason, for example, in an image forming apparatus capable of carrying out image formation by an operation in a full-color mode and an operation in a black (single color) mode, the intermediary transfer member is spaced, during the operation in the black mode, from the photosensitive member which is not in the image formation. As a result, a deterioration of the photosensitive members and the intermediary transfer member is suppressed, so that lifetimes of these members can be extended.
On the other hand, in the image forming apparatus of this type, there is a wide variety of print data to be processed, and there arises a problem such that a density of a character image and a line image (particularly a thin line image) is ensured while forming a high-quality color image. In order to solve this problem, Japanese Laid-Open Patent Application 2009-105827 has proposed an image forming apparatus including a thin line command detecting means for detecting a thin line command by a drawing instruction, a thin line color acquiring means for acquiring a color of a thin line, and a thin line width changing means for thickening a thickness (width) of the thin line.
However, in a constitution in which a process for thickening the thin line on the basis of object data or command data of the image, it becomes difficult to discriminate the character image itself and the line image itself, and therefore the density of the character image and the line image (particularly thin line image) cannot be sufficiently ensured in some cases.
For example, depending on a kind of documents, even when the image is the character image or the line image, in some instances, an attribute of the image is treated as an attribute, of decreasing image data, such as a graphic or image attribute, not a character or line attribute. In this case, when the image (data) is discriminated as the object image (data), this image is not discriminated as the character image or the line image, so that the thickening process as described above cannot be carried out.
A principal object of the present invention is to provide an image forming apparatus capable of acquiring a density of a character image or a line image of a black (monochromatic) image.
According to an aspect of the present invention, there is provided an image forming apparatus comprising: a black image forming portion including an image bearing member and a black developing device including a black toner; a color image forming portion configured to form an image with a yellow toner, a magenta toner and a cyan toner; an intermediary transfer member capable of carrying a toner image formed at the black image forming portion and a toner image formed at the color image forming portion; a transfer portion configured to transfer the toner image from the intermediary transfer member onto a recording material; and an executing portion capable of executing an operation in a color mode in which a color image is formed on the recording material by using the color image forming portion and the black image forming portion and an operation in a monochromatic mode in which a monochromatic image is formed on the recording material by using only the black image forming portion, wherein the executing portion is capable of forming the monochromatic image in the operation in the monochromatic mode under application of a voltage to the black developing device, the voltage being applied under a voltage condition such that a line width is broader than a line width under a voltage condition inputted to the black developing device when the operation in the color mode is executed.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
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An image forming apparatus according to the present invention will be described with reference to the drawings.
1. General Constitution and Operation of Image Forming Apparatus
The image forming apparatus 100 in this embodiment is a tandem-type (in-line type) color image forming apparatus employing an intermediary transfer type. The image forming apparatus 100 includes, as a plurality of image forming portions (stations), first to fourth image forming portions Pa, Pb, Pc and Pd for forming toner images of yellow (Y), magenta (M), cyan (C) and black (Bk), respectively. As regards elements having the same or corresponding function and constitutions in the respective image forming portions Pa, Pb, Pc and Pd, suffixes a, b, c and d representing the elements for associated colors are omitted, and the elements will be collectively described in some instances.
The photosensitive drum 1 which is a drum-shaped photosensitive member (electrophotographic photosensitive member) as an image bearing member is rotationally driven in an indicated arrow R1 direction (clockwise direction) in
The surface of the charged photosensitive drum 1 is subjected to scanning exposure to light by the exposure device (laser scanner) 3 as an exposure means, so that an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. In this embodiment, an electrostatic latent image forming means for forming the electrostatic latent image on each of the plurality of image bearing members is constituted by the charging rollers 2a-2d and the exposure devices 3a-3d. The electrostatic image formed on the photosensitive drum 1 is developed by supplying the toner as a developer by the developing device 4 as a developing means, so that the toner image is formed on the photosensitive drum 1. The developing device 4 includes a developing roller 41 feeding the toner to an opposing portion (developing portion) to the photosensitive drum 1 while carrying the toner and includes a developing container 42 for accommodating the toner. The developing rollers 41a-41d are provided correspondingly to the plurality of image bearing members, respectively, and are an example of a plurality of developing members (developer carrying members) for developing the electrostatic latent images on the image bearing members with toners under application of a developing voltage. During development, to each of the developing rollers 41, the developing voltage (developing bias), which is an oscillating voltage in the form of an AC voltage biased with a DC voltage, is applied from a developing voltage source (high voltage source circuit) E2. A DC component of the developing voltage is set at a predetermined negative potential between a charge potential and an exposed portion potential of the photosensitive drum 1. In this embodiment, the toner negatively charged to the same polarity (negative in this embodiment) as the charge polarity of the photosensitive drum 1 is deposited on an exposed portion of the photosensitive drum 1 which is lowered in absolute value of the potential by the exposure to light after the photosensitive drum 1 is charged uniformly. That is, in this embodiment, the charge polarity (normal charge polarity) of the toner during the development is the negative polarity. In this embodiment, as shown in (a) of
An endless belt-shaped intermediary transfer belt 7 as an intermediary transfer member is provided opposed to the respective photosensitive drums 1 of the image forming portions Pa-Pd. The intermediary transfer belt 7 is an example of a conveying member for carrying and conveying the toner images transferred from the plurality of the image bearing members. The intermediary transfer belt 7 is extended around a driving roller 13, a tension roller 12 and an idler roller 11 which are used as a plurality of stretching rollers (supporting rollers), and is stretched with a predetermined tension. In this embodiment, the intermediary transfer belt 7 is formed with an endless film formed of polyimide, which is an example of a dielectric resin material. The driving roller 13 is rotationally driven by a belt driving motor M2 (
The toner image formed on the rotating photosensitive drum 1 is transferred (primary-transferred) electrostatically onto the intermediary transfer belt 7. During a primary transfer step, to the primary transfer roller 5, a primary transfer voltage (primary transfer bias) which is a DC voltage of an opposite polarity to the normal charge polarity of the toner is applied from a primary transfer voltage source (high voltage source circuit) E3. For example, during full-color image formation, the respective color toner images of yellow, magenta, cyan and black formed on the respective photosensitive drums 1a-1d are successively transferred superposedly onto the intermediary transfer belt 7.
The toner (residual toner) remaining on the surface of the photosensitive drum 1 without being transferred onto the intermediary transfer belt 7 during the primary transfer is removed and collected from the surface of the photosensitive drum 1 by the drum cleaning device 6 as a photosensitive member cleaning means. The drum cleaning device 6 scrapes off the residual toner from the surface of the rotating photosensitive drum 1 by a cleaning blade 61 as a cleaning member, so that the residual toner is accommodated in a cleaning container 62. The toner accommodated in the cleaning container 62 is fed to a collecting toner container (not shown) by a feeding screw 63.
At a position opposing the driving roller 13 also functioning as a secondary transfer opposite roller on an outer peripheral surface side of the intermediary transfer belt 7, a secondary transfer roller 14 which is a roller-type secondary transfer member as a secondary transfer means is provided. The secondary transfer roller 14 is pressed (urged) against the intermediary transfer belt 7 toward the driving roller 13 and forms a secondary transfer portion (secondary transfer nip) N2 where the intermediary transfer belt 7 and the secondary transfer roller 14 are in contact with each other.
The toner images formed on the intermediary transfer belt 7 as described above are transferred (secondary-transferred) electrostatically onto the recording material S, such as paper, nipped and fed at the secondary transfer portion N2 by the intermediary transfer belt 7 and the secondary transfer roller 14. During a secondary transfer step, to the secondary transfer roller 14, a secondary transfer voltage (secondary transfer bias) which is a DC voltage of an opposite polarity to the normal charge polarity of the toner during primary transfer is applied from a secondary transfer voltage source (high voltage source circuit) E4. The recording material S is accommodated in a recording material accommodating cassette (not shown) and is fed to a registration roller pair 15 by a feeding and conveying device (not shown) including a feeding roller, a conveying roller and a conveying guide and the like.
The toner (residual toner) remaining on the surface of the intermediary transfer belt without being transferred onto the recording material S during the secondary transfer is removed and collected from the surface of the intermediary transfer belt 7 by a belt cleaning device 9 as an intermediary transfer member cleaning means. The belt cleaning device 9 scrapes off the residual toner from the surface of the rotating intermediary transfer belt 7 by a cleaning blade 91 as a cleaning member, and accommodates the residual toner in a belt cleaning container 92. The toner accommodated in the belt cleaning container 92 is fed to a cleaning toner container (not shown) by a feeding member (not shown). The belt cleaning device 9 is disposed at a position opposing the tension roller 12 via the intermediary transfer belt 7.
The recording material S on which the toner image is transferred is fed to a fixing device 16 as a fixing means. The recording material S is, after the toner image is fixed (melt-fixed) on the surface thereof by being heated and pressed by the fixing device 16, discharged (outputted) to an outside of the apparatus main assembly 110 of the image forming apparatus 100.
In this embodiment, in each of the image forming portions P, the photosensitive drum 1, the charging roller 2, the developing device 4 and the drum cleaning device 6 are integrally assembled with a cartridge container 8 into a unit, and constitute a process cartridge 10 detachably mountable to the apparatus main assembly 110.
In this embodiment, the intermediary transfer belt 7, the stretching rollers 11, 12 and 13, the primary transfer rollers 5a-5d and the like are supported by a unit frame 71 (
2. Contact and Spacing Mechanism
In this embodiment, the image forming apparatus 100 is capable of executing the image formation by operations in two image forming modes consisting of a full-color mode (first mode) and a black (monochromatic) mode (second mode). In the operation in the full-color mode, the toner images are formed by the first to fourth image forming portions Pa-Pd, so that a full-color image can be formed. In the operation in the black mode, the toner image is formed only by the fourth image forming portion Pd of the first to fourth image forming portions Pa-Pd, so that a black (monochromatic) image can be formed. In this embodiment, the image forming apparatus 100 includes a contact and spacing mechanism 20 (
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In this embodiment, the contact and spacing mechanism 20 is constituted so as to move also the idler roller 11 in synchronism with movement of the primary transfer roller 5d of the fourth image forming portion Pd. As a result, the intermediary transfer belt 7 is spaced from the photosensitive drums 1a-1d of all of the image forming portions Pa-Pd with reliability.
An operation of the contact and spacing mechanism 20 will be described also with reference to
As shown in
In this embodiment, the cams 27 provided at the end portions of the rotation shaft 26 with respect to the rotational axis direction have a line-symmetrical constitution with respect to a substantially center line of a widthwise direction (substantially perpendicular to a movement direction) of the intermediary transfer belt 7. Further, the sliders 29 and 30, holders 21 and 25 and the like, which are described later, are provided correspondingly to each of the cams 27 so as to have a line-symmetrical constitution with respect to the substantially center line of the widthwise direction of the intermediary transfer belt 7. Further, the cams 27 act on the corresponding sliders 29 and 30 and holders 21 and 25 and the like so as to move these members in the same direction in synchronism with each other. Accordingly, in the following, description will be made by paying attention to one of the cams 27 and its associated elements.
As shown in
Further, as shown in
The contact and spacing mechanism 20 switches the contact and spacing state between the intermediary transfer belt 7 and the photosensitive drums 1a-1d to three states consisting of the above-described “all contact state”, “black contact state” and “all spaced state” depending on a rotation stop position of the cam 27. In
In this embodiment, the contact and spacing mechanism 20 is constituted by the contact and spacing motor M3, the rotation shaft 26, the cam 27, the sliders 29 and 30, the holders 21 and 25, and the like.
3. Control Mode
The apparatus main assembly 110 of the image forming apparatus 100 is provided with an operation display portion (operation panel) 17. The operation display portion 17 has a function of an operating portion for inputting various pieces of information on operation setting of image formation to the controller 50 and a function of a display portion for displaying information for an operator such as a user or a service person. In this embodiment, the operation display portion 17 is in the form of a touch panel which can be touch-operable by the operator.
In this embodiment, particularly, the controller 50 not only causes the contact and spacing mechanism 20 to operate depending on the image forming mode but also effects control of changing setting of the developing voltage applied to the developing roller 41d for black depending on the image forming mode as described later.
4. Operation Sequence of Print Job
With reference to
When the controller 50 receives the print job, the controller 50 starts the print job (S1), and starts drive of the photosensitive drum 1d for black and the intermediary transfer belt 7 (S2). Then, the controller 50 discriminates whether the print job should be performed by the operation in the black mode or the operation in the full-color mode (S3).
In S3, in the case where the controller 50 discriminated that the print job should be performed by the operation in the full-color mode, the controller 50 starts drive of the photosensitive drums 1a-1c for color (S4). Then, the controller 50 causes the contact and spacing mechanism 20 to move the primary transfer rollers 5a-5c for color, so that the intermediary transfer belt 7 is contacted to the photosensitive drums 1a-1c for color (S5). Then, the controller 50 checks whether or not the respective primary transfer rollers 5a-5d are disposed at predetermined positions (i.e., are in the “all contact state”), by a position detecting mechanism (not shown) (S6). In S6, in the case where the controller 50 discriminated that the primary transfer rollers 5a-5d are disposed at the predetermined positions, the color slider 50 starts full-color image formation (S7) and ends the image formation when the images are formed on a designated number of sheets (recording materials) (S8). Thereafter, the controller 50 causes the contact and spacing mechanism 20 to space the primary transfer rollers 5a-5c for color from the photosensitive drums 1a-1c for color (S9). Then, the controller 50 checks whether or not the respective primary transfer rollers 5a-5d are disposed at predetermined positions (i.e., in the “black contact state”), by the position detecting mechanism (S10). In S10, in the case where the controller 50 discriminated that the primary transfer rollers 5a-5d are disposed at the predetermined positions, the controller 50 stops drive of the photosensitive drum 1d for black, the photosensitive drums 1a-1c for color and the intermediary transfer belt 7 (S11), and then ends the print job (S15).
On the other hand, in S3, in the case where the controller 50 discriminated that the print job should be performed in the operation in the black mode, the color slider 50 starts black image formation (S12) and ends the image formation when the images are formed on a designated number of sheets (recording materials) (S13). Thereafter, the controller 50 stops drive of the photosensitive drum 1d for black color and the intermediary transfer belt 7 (S14), and then ends the print job (S15).
In this embodiment, as regards the contact and spacing state between the intermediary transfer belt 7 and the photosensitive drums 1a-1d, the position of the “belt contact state” is a home position during standby of the print job (stand-by state). However, the present invention is not limited thereto. For example, the position of the “all spaced state” may also be the home position. Or, the position of the “all contact state” may also be the home position.
When the intermediary transfer unit 70 is demounted from the apparatus main assembly 110, for example, through the operation display portion 17, it is possible to notify the controller 50 of a message to the effect that the intermediary transfer unit 70 should be demounted (in such a manner that an exchanging button, of the intermediary transfer unit 70, displayed on the operation display portion 17 is pressed). The controller 50 responds to this notification, so that the controller 50 can cause the contact and spacing mechanism 20 to switch the contact and spacing state between the intermediary transfer belt 7 and the photosensitive drums 1a-1d to the “all spaced state”.
5. Change of Setting of Developing Voltage
As described above, for example, in the color image forming apparatus as in this embodiment, there arises a problem such that a density of a character image and a line image (particularly thin line image) is ensured while forming a high-quality color image.
In this embodiment, in order to acquire a stable density of the character image and the line image (particularly the thin line image) irrespective of information on an attribute of the image such as object data, the image forming apparatus 100 roughly has the following constitution. That is, particularly, during the operation in the black mode, operation setting other than normal operation setting of the image formation (image forming condition) is selectable, so that the density (or width) of a black character image or line image is adjustable depending on a demand of the user or the like. The normal operation setting is a standard operation setting in the case where the operation setting is not changed in accordance with this embodiment. Specifically, particularly, during the operation in the black mode, it can be assumed that a ratio of the character image or the line image is large. For that reason, in this embodiment, a developing property can be adjusted by changing setting of the developing voltage in operation setting particularly during the operation in the black mode relative to that in the normal operation setting. As a result, typically, a necessary constant of the character image or the line image is ensured, so that it is possible to ensure the density of the black character image or the black line image. Further, by employing such a constitution, the density of the character image or the line image can be adjusted depending on the demand of the user or the like while suppressing a fluctuation in uniform image density over an entirety of the image.
With reference to
When the controller 50 receives the print job, the controller 50 starts the print job (S1), and starts drive of the photosensitive drum 1d for black and the intermediary transfer belt 7 (S2). Then, the controller 50 discriminates whether the print job should be performed by the operation in the black mode or the operation in the full-color mode (S3).
In S3, in the case where the controller 50 discriminated that the print job should be performed by the operation in the full-color mode, the controller 50 executes the processes of S4 to S11 similarly as in those described with reference to
On the other hand, in S3, in the case where the controller 50 discriminated that the print job should be performed by the operation in the black mode, the controller 50 changes the setting of the black developing voltage to that during the operation in the black mode, designated as described later (S21).
Thereafter, the controller 50 starts black image formation (S12) and ends the image formation when the images are formed on a designated number of sheets (recording materials) (S13). Thereafter, the controller 50 stops drive of the photosensitive drum 1d for black color and the intermediary transfer belt 7 (S14), and then ends the print job (S15). In the case where the change of the setting of the black developing voltage during the operation in the black mode relative to the normal operation setting is not designated, the image formation by the operation in the black mode is executed at the normal operation setting.
In this embodiment, the setting of the black developing voltage during the operation in the black mode can be controlled by the operator such as the user or the service person. In this embodiment, the character image and the line image (particularly the thin line image) can be reproduced in a thick state (high density state) and in a thin state (low density state).
In this embodiment, as described above, the developing voltage is the oscillating voltage in the form of the DC voltage (DC component) biased with the AC voltage (AC component). In this embodiment, as regards the setting of the black developing voltage during the operation in the black mode, a peak-to-peak voltage (Vpp) of the AC component can be changed. In general, a developing property (developing power) changes depending on the AC component of the developing voltage. When the Vpp of the AC component of the developing voltage is increased, a potential difference at a light portion increases and therefore the developing property is improved, so that the image with a high density (thickened thin line) can be obtained. On the other hand, when the Vpp of the AC component of the developing voltage is decreased, the image with a low density (thinned thin line) is obtained. For example, as shown in (a) of
The setting of the black developing voltage during the operation in the black mode can be made by changing a frequency of the AC component in place of or in addition to the change of the Vpp. In general, when the frequency is decreased, toner imparting power increases and therefore the developing property is improved, so that the image with a high density (thickened thin line) can be obtained. On the other hand, when the frequency is increased, the image with a low density (thinned thin line) is obtained. For example, as shown in (b) of
Incidentally, as regards the setting of the black developing voltage during the operation in the black mode, in place of or in addition to at least one of the Vpp of the AC component and the frequency, the DC component can be changed. In general, when an absolute value of the DC component of the developing voltage having the normal polarity of the toner is increased, the image with a high density (thickened thin line) can be obtained. On the other hand, when the absolute value of the DC component of the developing voltage having the normal polarity of the toner is decreased, the image with a low density (thinned thin line) is obtained. A relationship between the absolute value of the DC component of the developing voltage and the image density can be acquired in advance by an experiment or the like. In this case, with reference to this normal operation setting, the absolute value of the DC component of the developing voltage of the same polarity as the normal charge polarity of the toner can be increased and decreased in a predetermined range on a predetermined changing rate basis. In the case where the density of the character image or the line image is intended to be increased (i.e., in the case where the thin line is intended to be thickened), setting is made so as to increase the absolute value of the DC component. On the other hand, in the case where the density of the character image or the line image is intended to be decreased (i.e., in the case where the thin line is intended to be thinned), setting is made so as to decrease the absolute value of the DC component. In the case where both of the absolute value of the DC component and at least one of the Vpp and the frequency of the AC component are made changeable, by changing these parameters in interrelation with each other, setting can be made in advance so that the density of the character image or the line image can be set at a desired density in a predetermined range. The absolute value of the DC component and at least one of the Vpp and the frequency of the AC component can be made independently changeable.
Further, in the case where the black developing voltage during the operation in the black mode is changed, in interrelation with this change, a fog-removing voltage (Vback) and laser power (exposure light quantity: light quantity per unit time of light radiation per unit area) of the exposure device 3 may also be changed. For example, in the case where the Vpp of the AC component is changed, the charge potential of the photosensitive drum 1d for black by the charging roller 2d for black can be changed so as to approach the Vback (dark-portion potential difference) before the change of the Vpp. With the change of the charge potential, in order to ensure a desired light-portion potential difference, the laser power of the exposure device 3d for black can be changed correspondingly.
In
The image forming mode may also be selected by the operator by touching a mode selecting button 127 displayed on an initial screen or the like at the operation display portion 17 as shown in (c) of
Further, the selection of the density setting during the operation in the black mode and the selection of the image forming mode may also be carried out, through a driver software of the image forming apparatus 100, in the external device 200 such as a personal computer communicatably connected with the controller 50.
Thus, the image forming apparatus 100 of this embodiment includes the controller 50 capable of causing the image forming apparatus 100 to carry out the image formation by the operation in a first mode as the image forming mode and by the operation in a second mode as the image forming mode. The first mode (full-color mode) is the image forming mode in which the toner images are formed on, of the plurality of the image bearing members 1, a predetermined image bearing member 1d and other image bearing member 1a-1c different from the predetermined image bearing member 1d. The second mode (black (monochromatic) mode) is the image forming mode in which the toner image is formed on the predetermined image bearing member 1d but is not formed on other image bearing member 1a-1c. The image forming apparatus 100 further includes the following designating portion. The designating portion causes the controller 50 to change setting of the developing voltage applied to a predetermined developing member 41d which is a developing member corresponding to the predetermined image bearing member 1d in the operation in the second mode, relative to setting of the developing voltage applied to the predetermined developing member 41d in the operation in the first mode. In this embodiment, the designating means is constituted by the operation display portion 17, the communication I/F portion 80 through which the designation from the external device 200 is inputted to the controller 50, and the like. In the case where the designation by the designating means is made, when the image formation is carried out by the operation in the second mode, the setting of the developing voltage applied to the predetermined developing member 41d is changed by the controller 50 relative to the setting of the developing voltage applied to the predetermined developing member 41d in the operation in the first mode. Further, in this embodiment, the designating means is capable of variably designating a difference of the setting of the developing voltage applied to the predetermined developing member 41d in the operation in the second mode relative to the setting of the developing voltage applied to the predetermined developing member 41d in the operation in the first mode. Further, in this embodiment, the image formation by the operation in the second mode is carried out in a state in which the conveying member 7 contacts the predetermined image bearing member 1d and is spaced from other image bearing members 1a-1c.
As described above, in this embodiment, during the operation in the black mode in which it is assumed that an image ratio of particularly the character image or the line image is large, the operation setting different from the normal operation setting is selectable. Further, when the image formation is carried out by the operation in the black mode, the image is formed automatically in the selected operation setting. Accordingly, during the operation in the black mode, irrespective of the information on the attribute of the image such as object data, the density (or the width) of the character image or the line image (particularly the thin line) corresponding to the selection of the operator can be obtained.
In this embodiment, as shown in (a) of
That is, in this embodiment, the image forming apparatus 100 may also include another designating means as described below. Another designating means causes the controller 50 to change the setting of the developing voltage applied to the developing member 41d in the operation in the first mode relative to the setting of the developing voltage applied to other developing members 41a-41c corresponding to other image bearing members 1a-1c in the operation in the first mode. In this embodiment, similarly as in the designating means, another designating means is constituted by the operation display portion 17, the communication I/F portion 80 through which the designation from the external device 200 is inputted to the controller 50, and the like. In the case where the designation by another designating means is made, when the image is formed by the operation in the first mode, the controller 50 changes the setting of the developing voltage applied to the predetermined developing member 41d relative to the setting of the developing voltage applied to other developing members 41a-41c.
By employing such a constitution, also the density (or the width) of the black character image and the black line image during the operation in the full-color mode can be adjusted depending on the demand of the user or the like. Accordingly, also during the operation in the full-color mode, irrespective of the information on the image attribute such as the object data, it is possible to obtain the density (or the width) of a stable character image or a stable line image (particularly the thin line) corresponding to the selection of the operator. In order to realize such a constitution, the developing voltage source E2d for black may only be required to be provided independently of the voltage sources for other colors used during the operation in the full-color mode. Accordingly, for example, as shown in (b) of
Then, another embodiment of the present invention will be described. A basic constitution and an operation of an image forming apparatus in this embodiment are the same as those in Embodiment 1. Accordingly, in the image forming apparatus in this embodiment, elements having the same or corresponding functions and constitutions as those in Embodiment 1 are represented by the same reference numerals or symbols and will be omitted from description.
In this embodiment, as shown in (c) of
However, during the operation in the full-color mode, only the setting of the black developing voltage cannot be arbitrarily changed to setting other than the normal operation setting. This is because the developing voltage source for black and the developing voltage sources for other colors used in the operation in the full-color mode (in this embodiment, the developing voltage sources for all of the colors) are used in common, and therefore the setting of the black developing voltage has an influence on other colors.
Accordingly, in this embodiment, the setting of the black developing voltage applied from the common developing voltage source E2 to the developing roller 41d for black can be changed to the setting other than the normal operation setting only during the operation in the black mode. Further, during the operation in the full-color mode, the common developing voltage source E2 is constituted so as to output the developing voltage in setting (normal operation setting) before the change. Typically, during the operation in the full-color mode, in this normal operation setting, the image is formed using all of the image forming portions Pa-Pd.
Here, the following constitution can be employed in order to enable ensuring of the density of particularly the character image or the line image (particularly the thin line) by selecting the operation setting different from the normal operation setting also during the operation in the full-color mode. That is, during the operation in the full-color mode, the black image is formed using the toners of the plurality of colors (in this embodiment, yellow, magenta and cyan) in place of the black toner. In this case, even when the normal setting developing voltage is outputted from the common developing voltage source E2, the density (or the width) of the black image during the operation in the full-color mode is easily ensured. This is because a toner amount per unit area can be increased by forming the black image with the toners of the plurality of colors. In this case, for example, in a setting screen similar to that shown in (a) of
That is, in this embodiment, the image forming apparatus 100 may also include another designating means as described below. In the operation in the second mode, another designating means causes the controller 50 to cause the image forming apparatus to form the image of the color (black) of the toner image formed on the predetermined image bearing member 1d in the operation in the first mode by superposing the toner images formed on other image bearing members 1a-1c. In this embodiment, similarly as in Embodiment 1, another designating means is constituted by the operation display portion 17, the communication I/F portion 80 through which the designation from the external device 200 is inputted to the controller 50, and the like. In the case where the designation by another designating means is made, during the operation in the second mode, the controller 50 effects control so that the image of the color (black) of the toner image formed on the predetermined image bearing member 1d in the operation in the first mode is formed by superposing the toner images formed on the plurality of other image bearing members 1a-1c.
By employing such a constitution, during the operation in the black mode and during the operation in the full-color mode, irrespective of the information on the image attribute such as the object data, it is possible to obtain the density (or the width) of a stable character image or a stable line image (particularly the thin line) corresponding to the selection of the operator.
The present invention was described based on the specific embodiments mentioned above, but is not limited to the above-mentioned embodiments.
In the above-described embodiments, the present invention was applied to the image forming apparatus of the intermediary transfer type, but is also applicable to an image forming apparatus of a direct transfer type.
In the above-described embodiments, the operator such as the user arbitrarily designated that the operation setting for black is operation setting different from the normal operation setting. However, the present invention is not limited thereto. Irrespective of the designation by the operator such as the user, the operation setting for black may also be made in advance so as to be different from the normal operation setting. In this case, the designating means and another designating means are constituted by a program or the like constituted to change the setting in advance.
In the above-described embodiments, the black image was able to be reproduced so as to be not only thick (high density) but also thin (low density). However, the present invention is not limited thereto. Typically, the black image may also be adjustable only in a direction of reproducing the black image as the thick image (with the high density).
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2016-143421 filed on Jul. 21, 2016, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2016-143421 | Jul 2016 | JP | national |
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