JP2004021134A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease the exchange frequencies of cartridges of less frequently used colors and to reduce a cost by avoiding the useless exchange of the cartridges even when the cartridge of a single color is used. <P>SOLUTION: The image forming section of the image forming apparatus is constituted by providing the device with the plurality of process cartridges having photoreceptor drums 21 for forming toner images, cleaning devices 26 for removing residual toners and waste toner containers 27 for storing the waste toners. The capacity of the the waste toner container 17a of the process cartridge Pa having the toners of the first color forming the images first to an intermediate transfer member 28 for primarily transferring the toner images and the capacity of the waste toner container 27a of the process cartridge Pd having the toners of the Bk color having the highest frequency of use are made greater than the capacity of the other waste toner containers 27b and 27c. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and is particularly suitable for application to an in-line type image forming apparatus for forming a monochrome image and / or a color image on a recording material.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine or a laser beam printer, an image forming apparatus having a configuration using an intermediate transfer member is known. This image forming apparatus forms a color image (multicolor image) on a transfer material by a primary transfer step and a secondary transfer step.
[0003]
That is, first, as a primary transfer step, a toner image as a transferable image formed on the surface of a photosensitive drum as a first image carrier is transferred to an intermediate transfer body.
[0004]
Thereafter, the primary transfer step is repeatedly performed for the toner images of a plurality of colors, thereby forming a toner image of a plurality of colors on the surface of the intermediate transfer body.
[0005]
Subsequently, as a secondary transfer step, a plurality of color toner images formed on the surface of the intermediate transfer member are collectively transferred onto a transfer material surface such as paper.
[0006]
An image forming apparatus using such an intermediate transfer member has an advantage that a color image can be formed in which superposition misalignment of toner images of respective colors, that is, a so-called color shift is suppressed.
[0007]
However, after the secondary transfer from the intermediate transfer member to the transfer material, there is a problem that the secondary transfer residual toner, that is, the transfer residual toner, remains on the surface of the intermediate transfer member.
[0008]
Therefore, in order to remove transfer residual toner remaining on the surface of the intermediate transfer member, the following image forming apparatus described in Japanese Patent Application Laid-Open No. 9-50167 (first document) has been proposed. .
[0009]
That is, the basic structure of the image forming apparatus described in the first document forms the primary transfer nip by bringing the surface of the movable second image carrier into contact with the surface of the movable first image carrier. In addition, a secondary transfer position is provided on the surface of the second image bearing member by disposing a secondary transfer member facing the secondary image transfer member.
[0010]
Further, the image forming apparatus sequentially primary-transfers the toner images sequentially formed on the surface of the first image carrier to the surface of the second image carrier via the primary transfer nip, and The secondary transfer member collectively and secondarily transfers a plurality of toner images primarily transferred to the third image carrier at a secondary transfer position.
[0011]
In such an image forming apparatus, a charge applying means for applying an electric charge to the toner image before the secondary transfer is provided, on the downstream side of the secondary transfer position in the moving direction of the surface of the second image carrier, and on the primary side. A charging unit disposed on the upstream side of the transfer nip, and the charging unit removes the secondary transfer residual toner remaining on the surface of the second image carrier without being transferred to the third image carrier at the secondary transfer position. The surface of the first image carrier is charged to a polarity opposite to the surface potential of the first image carrier, and the secondary transfer residual toner of the opposite polarity on the second image carrier is simultaneously transferred to the surface of the first image carrier via the primary transfer nip. It is configured to be returned to.
[0012]
Specifically, as shown in FIG. 4, in the image forming apparatus, first, from the process cartridge Pa for transferring the magenta (M) color, the process cartridge Pb for transferring the cyan (C) color, and the yellow (Y) color. An image is sequentially formed on the intermediate transfer body 28 in the order of the process cartridge Pc for transferring and the process cartridge Pd for transferring black (Bk) color, and the image is transferred to the transfer material 8 by the secondary transfer member 29.
[0013]
The untransferred toner remaining on the intermediate transfer body 28 is charged to the opposite polarity by the charging roller (ICL roller 31), and at the transfer position P of the process cartridge Pa, which is the first station, at the same time as the next image formation, The image is reversely transferred to the surface of the drum 21a and collected by a cleaning device 26a provided inside the process cartridge Pa.
[0014]
[Problems to be solved by the invention]
However, the present inventor has conducted various studies on the above-described conventional image forming apparatus, and has found that the following problems occur in practical use and in use level.
[0015]
That is, in the above-described image forming apparatus, a monochrome image may be formed using a process cartridge in which a photosensitive drum, a charger, a developing device, a cleaner, and a waste toner container are integrated. At this time, even when a black single-color image is formed, when the process unit of another color is operated, the secondary transfer residual toner is collected by the process cartridge which is the first station and performs the transfer of magenta color. Pa.
[0016]
Specifically, when a single black color is frequently used, it is necessary to replace a cartridge for waste toner in a magenta (M) cartridge that is used less frequently than a black (Bk) color. .
[0017]
That is, the present inventor has paid attention to the point that the balance between the color used for forming an image and the color for executing toner collection is lost. Then, the balance between the use frequency of the specific color and the replacement of the specific cartridge is broken, and the problem that is extremely uneconomical has been found.
[0018]
Further, the inventor has further studied diligently based on the use pattern in the image forming apparatus described above. That is, a case where a monochrome image is formed by alternately outputting monochrome and full-color originals was studied.
[0019]
According to this study, if the operation of the process units for other colors is performed only for the rotation of the drum and the charging, development and transfer are not performed in order to extend the life of the drum, the collection of the waste toner of the intermediate transfer body 28 is performed in the first station. The process cartridge Pa of magenta (M) color and the process cartridge Pd of black (Bk) color are collected.
[0020]
As a result, the magenta (M) color process cartridge Pa of the first station and the black (Bk) color process cartridge Pd need to be replaced because of waste toner. The equilibrium is lost between the cartridges of the color that contributes frequently and the cartridges that are frequently exchanged, leading to a new problem that is extremely uneconomical.
[0021]
Therefore, an object of the present invention is to suppress the frequency of replacing cartridges for colors that are not frequently used, to eliminate unnecessary cartridge replacement, and to reduce unnecessary cartridge replacement even when only black is used. It is an object of the present invention to provide an image forming apparatus capable of suppressing the cartridge and performing the cartridge replacement economically.
[0022]
[Means for Solving the Problems]
In order to solve the above problems, a first invention of the present invention is:
A first image carrier on which a toner image is formed, a cleaning unit for removing residual toner on the surface of the first image carrier, and a waste toner for storing residual toner removed from the surface of the first image carrier An in-line type image forming unit provided with a plurality of process cartridges having a container,
Having a second image carrier on which the toner image is primarily transferred,
The toner image primarily transferred to the second image carrier is secondarily transferred to the third image carrier,
The capacity of the waste toner container in the process cartridge for performing the secondary transfer of the first color toner on which an image is first formed on the second image carrier, and the secondary transfer of the most frequently used second color toner The capacity of the waste toner container in the process cartridge that performs the second transfer is larger than the capacity of any one of the waste toner containers in the process cartridge that performs the secondary transfer of the toner of another color.
It is characterized by the following.
[0023]
The present invention is extremely effective when used when a process cartridge including a waste toner container for storing waste toner removed by a cleaner is used. Further, the present invention can be applied to an in-line system having a plurality of replaceable image forming units (process cartridges).
[0024]
In the first invention, typically, the color most frequently used, that is, the second color is black (black (Bk)).
[0025]
In the first invention, typically, a primary transfer means for transferring the toner image on the surface of the first image carrier to the second image carrier, and a secondary transfer means on the surface of the second image carrier. A secondary transfer position is set, and a charging unit is disposed downstream of the secondary transfer position along the moving direction of the surface of the second image carrier and upstream of the primary transfer unit. A plurality of toner images sequentially formed on the surface of the one image carrier are sequentially primary-transferred to the surface of the second image carrier via the primary transfer means, and are primarily transferred to the surface of the second image carrier. Is secondary-collectively transferred to the third image carrier by the secondary transfer unit at the secondary transfer position, and the secondary unit remaining on the surface of the second image carrier without being transferred at the secondary transfer position is charged. The transfer residual toner is charged to a polarity opposite to that of the toner of the first image carrier, and the second image carrier is charged. The secondary transfer residual toner having the opposite polarity of the surface has the configuration back to through the primary transfer unit together with the first transfer first image bearing member surface.
[0026]
In the first invention, preferably, the capacity of the waste toner container in the process cartridge for performing the secondary transfer of the first color toner and the waste toner in the process cartridge for performing the secondary transfer of the second color toner The capacity of the container is larger than the capacity of any of the waste toner containers in the process cartridge that performs the secondary transfer of the toner of another color.
[0027]
Further, the second invention of the present invention
A plurality of process cartridges having a first image carrier on which a toner image is formed, cleaning means for removing residual toner on the surface of the first image carrier, and a waste toner container for storing the cleaned toner are provided. An in-line type image forming unit,
A second image carrier on which the toner image is transferred,
The toner image primarily transferred to the second image carrier is secondarily transferred to the third image carrier,
The capacity of the waste toner container of the process cartridge of the color for which an image is first formed on the second image carrier is larger than the capacity of any one of the other colors.
It is characterized by the following.
[0028]
In the second invention, typically, a primary transfer unit for transferring a toner image from the first image carrier to the second image carrier, and a secondary transfer unit arranged on the surface of the second image carrier, The next transfer position is set, and the toner images sequentially formed on the surface of the first image carrier are sequentially primary-transferred onto the surface of the second image carrier via the primary transfer unit, and the second image carrier is sequentially transferred by the secondary transfer unit. A plurality of toner images primary-transferred to the surface are secondarily transferred collectively to the third image carrier at the secondary transfer position, and the downstream side of the secondary transfer position along the moving direction of the second image carrier surface and A charging unit disposed upstream of the primary transfer unit, wherein the charging unit is a secondary transfer residual toner remaining on the surface of the second image carrier without being transferred to the third image carrier at the secondary transfer position. Is charged to the opposite polarity to the toner of the first image carrier, and the opposite polarity on the second image carrier is charged. The following transfer residual toner has a configuration back to the first image bearing member surface via simultaneously primary transfer means and the primary transfer.
[0029]
In the second invention, typically, the color for first forming an image on the second carrier is black, and preferably, the capacity of the black waste toner container is any of the other colors. Larger than the capacity of.
[0030]
According to the image forming apparatus of the present invention configured as described above, the capacity of the waste toner container in the process cartridge that performs the secondary transfer of the first color toner on which the image is first formed on the second image carrier. And the capacity of the waste toner container in the process cartridge that performs the secondary transfer of the second color toner that is most frequently used is the capacity of the waste toner container in the process cartridge that performs the secondary transfer of the other color toner. The capacity of the waste toner container of the process cartridge of the color in which the image is first formed on the second image carrier may be larger than the capacity of any one waste toner container, or the capacity of the waste toner container of any one of the other colors. By increasing the size of the cartridge, it is possible to reduce the possibility that the waste toner container is filled even though the frequency of image formation is low. It is possible to reduce the deviation of the frequency of replacement of each color.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.
[0032]
(1st Embodiment)
First, an image forming apparatus according to a first embodiment of the present invention will be described. FIG. 1 shows a schematic configuration of one of the plurality of process cartridges constituting an image forming unit of the image forming apparatus according to the first embodiment.
[0033]
As shown in FIG. 1, the process cartridge according to the first embodiment has a photosensitive drum 21 rotating in the direction of arrow R as an image carrier.
[0034]
The surface of the photosensitive drum 21 is uniformly charged by a charging roller 22 serving as a charging unit, and then is provided with, for example, a light emitting diode (LED) or a laser (LD) provided inside or outside the cartridge. The exposure is performed by the device 23 based on the image information. By this exposure, an electrostatic latent image is formed on the surface of the photosensitive drum 21.
[0035]
Toner is attached to this electrostatic latent image by the developing sleeve 24r of the developing device 24 that rotates in the direction of arrow R '. The toner attached by the developing sleeve 24r is developed as a toner image. This toner image is carried on the intermediate transfer member 28 and is electrostatically transferred by the primary transfer portion 25 onto the intermediate transfer member 28 conveyed in the arrow X direction.
[0036]
On the other hand, the toner (primary transfer residual toner) remaining on the surface of the photosensitive drum 21 without being transferred to the intermediate transfer body 28 during the transfer of the toner image is removed by the cleaning blade of the cleaning device 26 and stored in the waste toner container 27. Is done.
[0037]
The photosensitive drum 21 whose surface has been cleaned as described above is ready for the next image formation. The process cartridge according to the first embodiment includes at least the photosensitive drum 21, the cleaning device 26, and the waste toner container 27.
[0038]
Next, an image forming apparatus will be described in which a plurality of process cartridges configured as described above are arranged, and a plurality of color toner images are sequentially superimposed and formed on the same transfer material. FIG. 2 shows an image forming apparatus according to the first embodiment.
[0039]
As shown in FIG. 2, process stations are arranged in the main body of the image forming apparatus according to the first embodiment. In the main body, an intermediate transfer member 28 as an endless second image carrier that runs in the direction of arrow X is provided.
[0040]
Then, the transfer material 8 carried out from a paper feed cassette (not shown) is supplied to a secondary transfer portion of the intermediate transfer body 28 via a registration roller 32. At this position, a secondary transfer member 29 as a secondary transfer unit is provided, and a secondary transfer position is set.
[0041]
Above the intermediate transfer member 28, four process cartridges Pa, Pb, Pc, and Pd that form an image forming unit are arranged in series, and an in-line type image forming unit is formed. Here, the configuration will be described using the process cartridge Pa as an example.
[0042]
That is, the process cartridge Pa includes the photosensitive drum 21a as a first image carrier rotatably arranged. Process devices such as a charging roller 22a as a charging unit, a developing device 24a, and a cleaning device 26a as a cleaning unit are arranged around the photosensitive drum 21a. The other process cartridges Pb, Pc, and Pd have the same configuration. The developing devices 24a, 24b, 24c, and 24d of the process cartridges Pa, Pb, Pc, and Pd contain magenta toner, cyan toner, yellow toner, and black toner, respectively.
[0043]
Further, as shown in FIG. 2, the image forming apparatus according to the first embodiment has a configuration in which a black (Bk) process cartridge Pd is used as the last station. As described above, since the black (Bk) color image forming section is the last station, the first printout speed can be increased when a monochrome image of only the black (Bk) color is printed. This is particularly effective when a so-called full-color copying machine is employed as the image forming apparatus according to the first embodiment.
[0044]
The photosensitive drum 21a is irradiated with a laser beam based on an image signal of the magenta component color of the document via a polygon mirror (not shown) or the like. The irradiation of the laser beam forms an electrostatic latent image on the photosensitive drum 21a. Thereafter, magenta toner is supplied to the electrostatic latent image from the developing device 24a to perform development. Thereby, the electrostatic latent image is visualized as a magenta toner image.
[0045]
Subsequently, with the rotation of the photosensitive drum 21a, this toner image arrives at a primary transfer portion where the photosensitive drum 21a and the intermediate transfer body 28 are in contact. At this time, the magenta toner image on the photosensitive drum 21a is transferred to the intermediate transfer member 28 by the primary transfer bias applied to the primary transfer section 25a as the primary transfer means. Thus, primary transfer is performed.
[0046]
Next, when the portion carrying the magenta toner image of the intermediate transfer member 28 moves to the process cartridge Pb, a cyan toner image is formed on the photosensitive drum 21b by this point in the same manner as in the process cartridge Pb. You. Thereafter, the cyan toner image is transferred from the magenta toner image to the intermediate transfer member 28.
[0047]
Similarly, as the intermediate transfer member 28 moves, the yellow toner image and the black toner image are respectively superposed on the magenta toner image and the cyan toner image at the respective primary transfer portions of the process cartridges Pc and Pd. Is superimposed and transferred.
[0048]
By this time, the transfer material 8 from the paper feed cassette reaches the secondary transfer member 29 at the secondary transfer position via the registration roller 32. Then, with the secondary transfer bias applied to the secondary transfer member 29, the four color toner images on the intermediate transfer member 28 are collectively transferred onto the transfer material 8 as the third image carrier. Thus, the secondary transfer is performed.
[0049]
As described above, the transfer material 8 onto which the four color toner images have been transferred is separated from the intermediate transfer body 28 and then conveyed to the fixing device 30 by the conveyance belt 33. In the fixing device 30, the transfer material 8 is heated by a pair of rollers and pressure is applied to fix the toner image to the transfer material 8.
[0050]
At this stage, a method using a toner collecting means for forcibly charging the secondary transfer residual toner after the secondary transfer and collecting the toner on the photosensitive drum 21 has been proposed.
[0051]
According to this method, a charging roller of a contact charging member is used as a toner collecting unit. Then, the charging roller is brought into contact with the intermediate transfer member 28, and a current flows from a charging bias power supply (not shown). As a result, the secondary transfer residual toner is charged simultaneously with the charging of the intermediate transfer body 28. Hereinafter, the charging roller for removing the secondary transfer residual toner is referred to as an ICL roller 31 in order to distinguish it from the charging roller 22 that is in contact with the photosensitive drum 21.
[0052]
The charging of the toner layer by the ICL roller 31 is performed by discharging. This is because the toner used in the first embodiment is an insulating toner. This insulating toner receives little charge from the intermediate transfer body 28 and the ICL roller 31 having a medium resistance, and is charged only by discharging from the surface of the ICL roller 31.
[0053]
However, when only the DC voltage is applied to the ICL roller 31 and the toner layer is charged, only the outermost layer of the toner layer receives the charge.
[0054]
That is, the surface layer of the toner layer becomes a plus toner holding a high tribo, and a relatively low tribo toner not charged remains in the inner layer. If an attempt is made to clean the toner layer in such a state, a problem of poor cleaning and a problem of negative ghost occur.
[0055]
First, regarding the problem of poor cleaning, if the inner layer of the toner that has passed through the ICL roller 31 and is charged remains at a low tribo, a poor cleaning occurs in the next image.
[0056]
That is, in the cleaning process in this case, the secondary transfer residual toner is collected by using the positively charged secondary transfer residual toner as an electric field between the electrolysis on the photosensitive drum 21 and the electrolysis on the intermediate transfer body 28. You. Therefore, toner having a weak plus or minus tribo will not be collected.
[0057]
Then, the uncollected toner appears as a positive ghost of poor cleaning in a solid white portion of the next image, resulting in a large image defect.
[0058]
Therefore, in order to prevent this, it is necessary to flow a large current to the ICL roller 31 so that even the toner tribo of the inner layer becomes positive. However, in this case, the tribo of the surface layer of the toner layer has a higher tribo.
[0059]
Next, regarding the problem of negative ghost, the outermost layer of the toner layer after passing through the ICL roller 31 is strongly charged. Specifically, the tribo reaches up to +50 μC / g or more. Such a toner adversely affects an image to be formed next when the cleaning process is performed by the primary transfer nip. Note that the toner tribo of the next image on which the primary transfer is performed simultaneously with the cleaning process is only about −20 μC / g.
[0060]
Therefore, such toner is electrostatically attracted to the toner having a strong positive tribo to be cleaned, and is returned to the photosensitive drum without being primarily transferred to the intermediate transfer body 28.
[0061]
Since the toner in the portion corresponding to the previous image has returned to the photosensitive drum, a specific density difference occurs even when an attempt is made to form a “solid” black image, and this is observed as a negative ghost.
[0062]
In order to prevent the above-described phenomenon, it is effective to reduce the current flowing to the ICL roller 31 and reduce the tribo of the surface layer which is strongly positively charged with the secondary transfer residual toner. However, if such a measure is adopted, the toner in the inner layer will not be charged. For this reason, cleaning failure becomes more severe.
[0063]
As described above, the suppression of the occurrence of the cleaning failure and the suppression of the occurrence of the negative ghost are in a trade-off relationship. That is, when the current flowing through the ICL roller 31 is increased, the negative ghost increases, and when the current is decreased, the cleaning failure increases. Therefore, it has been extremely difficult to find a region that satisfies both.
[0064]
Therefore, as a result of various studies by the present inventors, it has been found that it is necessary to equalize the toner tribo after passing through the ICL roller 31 in order to solve these two problems. Was.
[0065]
That is, the present inventor pays attention to the fact that the positive toner having a strong surface layer causes a negative ghost, and the toner having a weak tribo of the inner layer causes cleaning failure, and it is possible to uniformly charge all the toner layers positively. It has been recalled that, if possible, the above two problems can be solved.
[0066]
In order to realize this, it is desirable to superimpose an AC voltage on a DC voltage as a charging bias applied to the ICL roller 31 from a charging bias power supply. Therefore, in the first embodiment, control is performed so that an AC voltage is applied.
[0067]
As a result, not only the discharge from the ICL roller 31 but also the reverse discharge from the intermediate transfer member 28 can be excited. Therefore, an electric field can be applied to the inside of the toner layer.
[0068]
In addition, the inventor conducted an experiment from the viewpoint described above, and applied a higher AC voltage. At this time, a phenomenon that the toner starts to fly between the intermediate transfer body 28 and the ICL roller 31 occurred, and the toner was replaced in the toner layer. Then, they came to find that the toner layer can be charged more uniformly.
[0069]
That is, as the ICL roller 31 used in the first embodiment, for example, a single-layer solid roller having a diameter of 20 mm is employed. In the ICL roller 31, a conductive rubber layer is provided on a core metal having a diameter of 6 mm. This conductive rubber layer has a volume resistivity of 10 when carbon (C) is dispersed in EPDM rubber. ⁷ It consists of medium resistance rubber adjusted to Ωcm.
[0070]
The resistance value of the ICL roller 31 is determined by pressing the ICL roller 31 against a metal drum of the intermediate transfer member 28 to form a contact nip having a width of 3 mm, and applying a DC voltage of 100 V between the contact nip and the roller core. The resistance value measured by applying voltage is 10 ⁶ Ω.
[0071]
Further, a bias in which an AC constant current is superimposed on a DC constant current is applied to the ICL roller 31 as an ICL current. The reason why these biases are controlled to a constant current is to provide a constant charge to the toner even when the resistance values of the intermediate transfer member 28 and the ICL roller 31 change.
[0072]
Specifically, the DC component is a DC constant current of +60 μA, and the AC component is an AC constant current composed of a sine wave of 2000 μA and a frequency of 1000 Hz.
[0073]
When these currents were passed through the ICL roller 31, a peak-to-peak voltage of 4000 V was generated in a high-temperature and high-humidity environment (hereinafter, H / H) at a temperature of 30 ° C. and a humidity of 80%.
[0074]
In addition, when the above constant current was applied to the ICL roller 31, a peak-to-peak voltage of 8000 V was generated in a low-temperature and low-humidity environment with a temperature of 15 ° C. and a humidity of 10% (hereinafter, L / L).
[0075]
When the above-described constant current was applied to the ICL roller 31, an AC voltage having a peak-to-peak voltage of 6000 V was generated under a normal environment.
[0076]
As described above, the secondary transfer residual toner is discharged from both the ICL roller 31 and the intermediate transfer member 28 by the generated voltage, and is uniformly charged. Further, since jumping occurs between the two, the toner layer is disturbed, and further uniform charging becomes possible.
[0077]
In addition, when an AC voltage is superimposed on a DC voltage and applied, discharge is likely to occur in a DC component as well. Therefore, the DC voltage required to flow a current of +60 μA was 500 V in any environment (normal environment, high-temperature high-humidity environment, low-temperature low-humidity environment).
[0078]
The frequency of the AC voltage superimposed on the DC voltage is determined from the process speed of the image forming apparatus. In the first embodiment, since the process speed is 100 mm / sec, the period of the AC component on the intermediate transfer member 28 is determined to be sufficiently short. Then, a frequency of 1000 Hz (s ^-1 ), The pitch corresponding to the AC cycle mark when charging the photosensitive drum 21 is 100 μm. In general, the period is desirably 1 mm or less.
[0079]
Further, the AC voltage needs a peak-to-peak voltage Vpp such that reverse discharge starts to occur from the intermediate transfer member 28 to the ICL roller 31. For this purpose, it is desirable that the intermediate transfer member 28 and the ICL roller 31 have a peak-to-peak voltage that is at least twice the discharge start voltage. Furthermore, when flying (jumping) of toner occurs, it is necessary to apply a higher voltage.
[0080]
Regarding the AC (alternating current) waveform, a sine wave that does not include harmonics is desirable in order to reduce damage to the intermediate transfer body 28. Further, in the AC waveform, a rectangular wave capable of maintaining the peak-to-peak voltage Vpp for a long time is desirable in order to cause efficient charging and toner flying at a low peak-to-peak voltage Vpp.
[0081]
Further, regarding the DC voltage (current) on which the AC voltage (current) is superimposed, the toner voltage after passing through the ICL roller 31 can be controlled by changing the DC voltage (current). That is, by increasing the applied DC voltage, the toner tribo after passing through the ICL roller 31 can be set to a high value.
[0082]
Also, by superimposing the AC component on the DC component, the convergence of the toner tribo can be expected. Even if the toner tribo is not stable before passing through the ICL roller 31, the tribo after passing can be set to a stable predetermined value. Yes, reverse transcription became possible.
[0083]
The toner reversely charged by the ICL roller 31 is conveyed as it is, and in the primary transfer portion 25a of the process cartridge Pa, the image on the photosensitive drum 21a is transferred to the intermediate transfer body 28, and at the same time, the toner is reversed to the photosensitive drum 21a. Will be copied.
[0084]
Therefore, most of the residual toner on the intermediate belt is collected in the cleaner container of the first station (Pa), and even if an image having the same toner consumption rate is taken, the magenta (M) waste toner container is first. Will be full.
[0085]
Further, when forming a mixed image of a monochrome image and a color image, when the color process unit is not operated, the secondary transfer residual toner is collected in the first station of Pa (magenta (M in FIG. 4). )) Or black (Bk) station.
[0086]
For this reason, the magenta (M) process cartridge and the black (Bk) process cartridge are uneconomical in that the cartridge needs to be replaced because of waste toner. In particular, magenta (M) process cartridges need to be replaced frequently, despite their relatively infrequent use.
[0087]
Therefore, the waste toner container 27a of the first station (Pa) and the waste toner container 27d of black (Bk) are made larger than the other waste toner containers 27b and 27c. As a result, the above-described problem can be solved, wasteful cartridge replacement can be avoided, and a longer life of the process cartridge can be achieved.
[0088]
(Second embodiment)
Next, an image forming apparatus according to a second embodiment of the present invention will be described. FIG. 3 shows an image forming apparatus according to the second embodiment.
[0089]
That is, as shown in FIG. 3, in the image forming apparatus according to the second embodiment, magenta (M) is used for the first station in the first embodiment, and the magenta (M) is eliminated from the process cartridge Pa. Unlike the case where the toner container 27a is enlarged, the first station is a black (Bk) process cartridge Pa, and the waste toner container 27a of the black (Bk) process cartridge is replaced with other waste toner containers 27b, 27c, and 27c. Make it larger than 27d.
[0090]
That is, unlike the first embodiment, the process cartridges are arranged in the order of magenta (M), cyan (C), yellow (Y), and black (Bk). In the second embodiment, The process cartridges are arranged in the order of black (Bk), magenta (M), cyan (C), and yellow (Y).
[0091]
Then, as described in the first embodiment, when a color image is taken, most of the secondary transfer residual toner remaining on the intermediate transfer body 28 is collected in the first station Pa. Therefore, it is possible to cope by increasing the size of the waste toner container 27a in the first station Pa.
[0092]
However, the secondary transfer residual toner is collected in the first station Pa (magenta in the case of FIG. 2) even when a monochrome image is formed, when the color process unit is operated, and when a black monochrome image is formed. (M)).
[0093]
Therefore, when a large amount of image formation is performed with a single black color, the magenta (M) waste toner container becomes full. As a result, even if the waste toner capacity of the cartridge is increased, it is extremely uneconomical that the cartridge needs to be replaced for the waste toner, even though image formation using magenta (M) is hardly performed. Things happen.
[0094]
This is the same as in the case where the black monochrome image and the full-color image are alternately formed, unless the process cartridge and the intermediate transfer member 28 are detached.
[0095]
Therefore, in the second embodiment, the black (Bk), which is used most frequently in characters and the like and consumes a large amount, is placed in the first station (Pa), and the waste toner capacity of black is increased, thereby achieving the above-described operation. It is possible to solve the problem, avoid wasteful cartridge replacement, and achieve a longer life of the cartridge.
[0096]
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications based on the technical idea of the present invention are possible.
[0097]
For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as needed.
[0098]
For example, in the above-described first and second embodiments, a full-color copying machine is cited as an example of the configuration of the image forming apparatus. However, the present invention is not limited to this, and the present invention is not limited to a printer or a facsimile. The present invention can be applied to an image forming apparatus having the above process cartridge.
[0099]
【The invention's effect】
As described above, according to the present invention, in a system having a process cartridge of each color including a waste toner container and reversely charging the residual toner of the intermediate to the photoreceptor, the first color of the image formed on the intermediate is By making the capacity of the waste toner container of the process cartridge larger than the capacity of any of the waste toner containers, it is possible to eliminate unnecessary cartridge replacement.
[0100]
Further, by setting the capacity of the waste toner container for the color to be secondarily transferred to the second carrier to the most frequently used color, it is possible to obtain an image forming apparatus capable of handling even a single color. it can.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a process unit according to a first embodiment of the present invention.
FIG. 2 is a sectional view showing the image forming apparatus according to the first embodiment of the present invention.
FIG. 3 is a sectional view showing an image forming apparatus according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating an image forming apparatus according to the related art.
[Explanation of symbols]
8 Transfer material
21, 21a, 21b, 21c, 21d Photoconductor drum
22, 22a, 22b, 22c, 22d Charging roller
23 Exposure equipment
24, 24a, 24b, 24c, 24d Developing device
24r developing sleeve
25, 25a, 25b, 25c, 25d Primary transfer unit
26, 26a, 26b, 26c, 26d Cleaning device
27, 27a, 27b, 27c, 27d Waste toner container
28 Intermediate transfer member
29 Secondary transfer member
30 Fixing device
31 ICL roller
32 registration roller
33 Conveyor belt

Claims (9)

A first image carrier on which a toner image is formed on the surface, a cleaning unit for removing residual toner on the surface of the first image carrier, and the residual toner removed from the surface of the first image carrier. A plurality of image forming units having a waste toner container to store,
A second image carrier on which the toner image is primarily transferred,
The toner image primarily transferred to the second image carrier is secondarily transferred to the third image carrier,
The capacity of the waste toner container of the image forming unit having the first color toner on which an image is first formed on the second image carrier is determined by the capacity of the image forming unit having the most frequently used second color toner. An image forming apparatus, wherein the capacity of the waste toner container is larger than the capacity of any one of the waste toner containers of the image forming section having the toner of another color. The image forming apparatus according to claim 1, wherein the second color is black. Primary transfer means for transferring the toner image on the surface of the first image carrier to the second image carrier,
A secondary transfer unit is disposed on the surface of the second image carrier, a secondary transfer position is set, and the primary transfer is performed downstream of the secondary transfer position along the moving direction of the surface of the second image carrier. Charging means disposed upstream of the means,
The toner images sequentially formed on the surface of the first image carrier are sequentially primary-transferred to the surface of the second image carrier via the primary transfer unit,
The plurality of toner images primarily transferred to the surface of the second image carrier are collectively secondarily transferred to the third image carrier by the secondary transfer means at the secondary transfer position,
The charging unit charges the secondary transfer residual toner remaining on the surface of the second image carrier without being transferred at the secondary transfer position to a polarity opposite to that of the toner of the first image carrier, and 2. The structure according to claim 1, wherein the secondary transfer residual toner having the opposite polarity on the surface of the second image carrier is returned to the surface of the first image carrier via the primary transfer means together with the primary transfer. Image forming device. The capacity of the waste toner container of the image forming unit having the toner of the first color and the capacity of the waste toner container of the image forming unit having the toner of the second color are different from each other. 2. The image forming apparatus according to claim 1, wherein the capacity of each of the waste toner containers is larger than the capacity of any of the waste toner containers. A plurality of image forming units each including: a first image carrier on which a toner image is formed, a cleaning unit that removes residual toner on the surface of the first image carrier, and a waste toner container that stores the cleaned toner. When,
A second image carrier on which the toner image is transferred,
The toner image primarily transferred to the second image carrier is secondarily transferred to the third image carrier,
The capacity of the waste toner container of the image forming unit for the color in which the image is first formed on the second image carrier is larger than the capacity of any one of the waste toner containers of the image forming units for the other colors. Image forming device. A primary transfer unit for transferring the toner image from the first image carrier to the second image carrier, and a secondary transfer unit disposed on the surface of the second image carrier to set a secondary transfer position; Toner images sequentially formed on the surface of the first image carrier,
Primary transfer sequentially to the surface of the second image carrier through the primary transfer means,
A plurality of toner images primary-transferred onto the surface of the second image carrier by the secondary transfer unit are secondarily transferred collectively to a third image carrier at the secondary transfer position, and the second image carrier Charging means disposed downstream of the secondary transfer position and upstream of the primary transfer means along the surface movement direction, the charging means being provided at the secondary transfer position with the second image carrier The secondary transfer residual toner remaining on the surface is charged to a polarity opposite to that of the toner of the first image carrier, and the secondary transfer residual toner of the opposite polarity on the second image carrier is simultaneously transferred to the primary transfer. 6. The image forming apparatus according to claim 5, wherein the image forming apparatus is configured to return to a surface of the first image carrier via a primary transfer unit. 6. The image forming apparatus according to claim 5, wherein a color for forming an image on the second image carrier first is black. 6. The image forming apparatus according to claim 5, wherein the first image forming color on the second image carrier is black, and the capacity of the black waste toner container is larger than the capacity of any of the other color waste toner containers. Image forming apparatus. The image forming apparatus according to claim 1, wherein the plurality of image forming units are configured to be detachable from an image forming apparatus main body.

Images