JP2003202774A - Process cartridge and image forming apparatus provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent developer left after transfer from adhering to an electrifying means in an image forming apparatus, and to reduce density irregularity caused immediately after the process cartridge is installed in the image forming apparatus. <P>SOLUTION: This image forming apparatus is provided with a photoreceptor drum 1, an electrifying roller 2, an exposure device 3 and a developing device 4 for making an electrostatic latent image on the drum 1 visualizable by supplying toner to the electrostatic latent image. Transfer material P fed to a transfer part (d) is held and carried between the rotating drum 1 and a rotating transfer roller 5, a toner image on the surface side of the drum 1 is successively electrostatically transferred to the surface of the material P, and the material P is successively separated from the surface of the rotating drum 1 and carried to a fixing device 6, then the material P is outputted as an image formed matter after the toner image is fixed. Then, the image forming apparatus is provided with a toner-left-after-transfer uniformizing means 8 and a toner electrified amount control means 7 for making the electrifying polarity of the toner left after transfer a negative polarity being a normal polarity at a position on a more downstream side in the rotating direction of the drum 1 than the means 8 and on a more upstream side in the rotating direction of the drum 1 than an electrifying part (a). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleanerless image forming apparatus and a process cartridge detachably attached to the image forming apparatus. More specifically, the developer (toner) remaining on the image carrier after the transfer step is removed and collected from the image carrier by cleaning at the same time in the developing device by cleaning at the same time, and is reused to remove the cleaning device. System image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a transfer type image forming apparatus such as a copying machine, a printer or a facsimile using an electrophotographic system has a photosensitive member which is a rotary drum type image carrier, and the photosensitive member has a predetermined size. A charging device (charging step) for uniformly charging to polarity / potential, an exposure device (exposure step) as an information writing means for forming an electrostatic latent image on the charged photoreceptor, and a charging device formed on the photoreceptor. A developing device (developing process) that visualizes an electrostatic latent image with toner that is a developer, a transfer device (transfer process) that transfers the toner image from a photoconductor surface to a transfer material such as paper, and a photoconductor after the transfer process. It consists of a cleaning device (cleaning process) that removes a little residual toner on the top to clean the surface of the photoconductor, and a fixing device (fixing process) that fixes the toner image on the transfer material. Electrophotographic process (charging, exposure, development, transfer and cleaning) is applied is subjected to image formation.

The toner remaining on the photoconductor after the transfer process is removed from the photoconductor surface by the cleaning device and collected in the cleaning device to become waste toner, but such a toner is used in view of environmental protection and effective use of resources. It is desirable not to produce waste toner.

Therefore, there is an image forming apparatus in which the transfer residual toner, so-called waste toner, collected by the cleaning device is returned to the developing device for reuse.

Further, the cleaning device is abolished, and the transfer residual toner on the photoconductor after the transfer process is removed / collected from the photoconductor by "simultaneous development cleaning" in the developing device to reuse the image. There is a forming device.

Simultaneous development cleaning is performed by cleaning the transfer residual toner on the photoconductor after transfer during the subsequent developing process, that is, by continuously charging and exposing the photoconductor to form an electrostatic latent image. During the process of affirming the development of the image, the fog removal bias (fog removal potential difference Vback which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor) causes the toner to be developed on the surface of the photoconductor which should not be developed with toner (non-image area). The transfer residual toner present in (1) is collected in the developing device.
According to this method, the residual toner after transfer is collected by the developing device and reused for the development of the electrostatic latent image in the subsequent steps, so that the waste toner is eliminated and the troublesomeness during maintenance is reduced. You can Further, the cleanerless structure is advantageous for downsizing the image forming apparatus.

[0007]

A) As described above,
In a cleanerless-type image forming apparatus that removes and collects residual toner remaining on the photoconductor after the transfer process in a developing device through cleaning and cleaning at the same time, the charging device of the photoconductor contacts the photoconductor to clean the surface of the photoconductor. In the case of the contact charging device that performs the charging process, when the transfer residual toner on the photoconductor passes through the charging part, which is the contact nip part between the photoconductor and the contact charging device, the charge polarity of the transfer residual toner becomes normal. The toner having the opposite polarity adheres to the contact charging device and contaminates the contact charging device with more than allowable amount of toner, resulting in poor charging.

That is, although the toner as a developer is small in quantity, there is a mixture of toners whose charge polarity is originally reversed to the opposite polarity from the normal polarity. Further, there are some toners whose charge polarity is regular polarity and whose charge polarity is reversed due to the influence of transfer bias or peeling discharge, and those whose charge amount is reduced by reducing the charge amount.

Therefore, the transfer residual toner is a mixture of toner having a normal charge polarity, reverse toner having a reverse polarity, and a toner having a small charge amount, and the reverse toner and the toner having a small charge amount are used as the photoconductor. It easily adheres to the contact charging device when passing through the charging part which is the contact nip part of the contact charging device.

B) Further, in order to remove and collect the transfer residual toner on the photosensitive member by cleaning the developing device at the same time as the developing device, the transfer residual toner on the photosensitive member is carried to the developing unit through the charging unit. It is necessary that the charging polarity is normal polarity and that the charging amount is the charging amount of the toner capable of developing the electrostatic latent image on the photoconductor by the developing device. Reversed toner and toner having an unsuitable charge amount cannot be removed / collected from the photoconductor by the developing device, resulting in defective images.

C) The toner adhered to the contact charging device of the above a) is mixed in that it is carried from the transfer section to the charging section and has a regular charge polarity, a reverse polarity, and a small charge amount. The transfer residual toner on the photoconductor is charged to the normal polarity by the toner charge amount control means so that the charge polarity is aligned to the normal polarity and the charge amount is made uniform, which can be prevented.

However, the transfer residual toner charged by the toner charge amount control means in order to prevent the toner from adhering to the contact charging device is larger than the charge amount of the toner capable of developing the electrostatic latent image on the photoconductor. Therefore, it is difficult for the developing device to be removed / collected by simultaneous cleaning with development. In such a case, the toner remaining on the photoconductor overlaps with the next image, resulting in a defective image.

In order to prevent such image defects, a transfer residual toner equalizing means is installed upstream of the photosensitive member of the toner charge amount control means, and the charge amount of the transfer residual toner is controlled to collect the toner in the developing device. Was efficiently performed, and image stains due to poor collection were eliminated.

[Transfer residual toner uniformizing means] as described above
It is desirable that the "toner charge amount control means" always keep the grounding position with the photoconductor constant in order to perform uniform toner control, and as the number of image forming sheets increases, the transfer residual toner becomes uniform. Since the toner charge amount control unit and the toner charge amount control unit are gradually contaminated by the toner and fine powder externally added to the toner, the transfer residual toner equalizing unit and the toner charge amount control unit are integrated with the photoconductor. A desirable process cartridge is desirable.

However, when the process cartridge is left outside the main body of the image forming apparatus for a long period of time, the "transfer residual toner equalizing means" and the "toner charge amount control means" are members for contacting with the photoconductor, and the transfer residual toner is uniformized. Since the means and the toner charge amount control means are in contact with the same part of the photoconductor for a long time, for example, in the environment where moisture is likely to adhere to the photoconductor, the part which is not in contact and the part which is not in contact There will be a difference in resistance. When such a process cartridge is installed in the main body of the image forming apparatus to perform paper passing durability, uneven density on the image occurs due to the resistance difference of the photoconductor up to about 100 sheets at the initial stage.

Therefore, the present invention relates to a cleanerless type image forming apparatus which removes and collects the transfer residual developer on the image bearing member after the transfer step by cleaning at the same time as development and reuses the same. A process cartridge is provided which prevents the transfer residual developer from adhering to the charging device and also allows the transfer residual developer to be efficiently collected by the developing device. Further, another object of the present invention is to make the process cartridge detachable from the main body of the image forming apparatus and to reduce density unevenness that occurs immediately after installing the process cartridge in the image forming apparatus.

[0017]

According to a first aspect of the present invention, an image bearing member, charging means for charging the surface of the image bearing member, and an electrostatic latent image are formed on the image bearing member subjected to the charging treatment. An image forming apparatus including an information writing unit, a developing unit that supplies a developer to an electrostatic latent image to visualize the electrostatic latent image, a transfer unit that transfers the visualized image to a transfer material, and a fixing unit. Developer charge amount control means that is detachable from the main body, is located upstream of the charging means and downstream of the transfer means, and charges the developer on the developer surface on the image carrier surface. A residual developer image uniform, which is located upstream of the developer charge amount control means and downstream of the transfer means, and which makes the residual developer image remaining on the surface of the image carrier after transferring the developer onto the transfer material uniform. In a process cartridge having a converting means, The filtrate Seth cartridge only when installed in the image forming apparatus main body, a process cartridge wherein the developer charge amount controlling means and the residual developer image uniformizing means, wherein the contacting on the image bearing member.

As a result, the cleaning device in the image forming apparatus is abolished, and the transfer residual toner on the photoconductor after the transfer step is removed and collected from the photoconductor by the "developing device simultaneous cleaning" and reused. A cleanerless system can be achieved.

According to a second aspect of the invention, there is provided an image forming apparatus characterized in that the process cartridge according to the first aspect is detachably provided in the main body of the image forming apparatus, and the invention according to the third aspect is. 3. The image forming apparatus according to claim 2, wherein the main body of the image forming apparatus includes a pressing member that presses the developer charge amount control unit and the residual developer uniformizing unit against the image carrier. .

With these configurations, density unevenness that occurs after the process cartridge is installed in the image forming apparatus main body is eliminated, and good and stable images can be maintained.

According to a fourth aspect of the invention, there is provided the image forming apparatus according to the second or third aspect, wherein the image forming apparatus is cleanerless.

According to this structure, the structure of the image forming apparatus main body is simplified.

An invention according to claim 5 is the image forming apparatus according to any one of claims 2 to 4, wherein the charging means is contact charging. The image forming apparatus according to claim 2, wherein an oscillating electric field is applied to the charging unit.

According to these configurations, the photosensitive drum can be charged to a predetermined potential, and at the same time, the charge amount can be controlled to be appropriate for developing the electrostatic latent image on the photosensitive drum. Thus, the transfer residual toner can be efficiently collected.

According to a seventh aspect of the present invention, the information writing means is an exposing means.
The image forming apparatus according to any one of the above.

According to this structure, it is possible to sequentially form electrostatic latent images corresponding to the image information that is obtained by scanning and exposing the surface of the photosensitive drum.

[0027]

DETAILED DESCRIPTION OF THE INVENTION An image forming apparatus according to an embodiment of the present invention will be described below.

FIG. 1 is a schematic structural model diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process, a contact charging type, an anti-development image type, a cleanerless type, and a maximum sheet size of A3 size.

(1) Overall Schematic Configuration of Printer a) The image carrier 1 is a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier. This photosensitive drum 1
Is a negatively chargeable organic photoconductor (OPC) with an outer diameter of 50 mm
And is driven to rotate in the counterclockwise direction indicated by the arrow with a process speed (peripheral speed) of 100 mm / sec about the central support shaft.

As shown in the layer structure model of FIG. 2, this photosensitive drum 1 has a subbing layer on the surface of an aluminum cylinder (conductive drum substrate) 1a for suppressing light interference and improving the adhesiveness of the upper layer. 1b, a photocharge generation layer 1c, and a charge transport layer 1d are applied in this order from the bottom.

B) The charging device 2 is a contact charging device (contact charging device) as a charging device for uniformly charging the peripheral surface of the photosensitive drum 1, and this example is a charging roller (roller charging device).

The charging roller 2 is rotatably held by bearing members (not shown) at both ends of the cored bar 2a, and is urged toward the photosensitive drum by a pressing spring 2e so as to be applied to the surface of the photosensitive drum 1. They are pressed against each other with a predetermined pressing force, and are rotated by the rotation of the photosensitive drum 1. The pressure contact portion between the photosensitive drum 1 and the charging roller 2 is a charging portion (charging nip portion) a.

A power source S1 is applied to the core metal 2a of the charging roller 2.
When the charging bias voltage of a predetermined condition is applied, the peripheral surface of the rotating photosensitive drum 1 is contact-charged with a predetermined polarity and potential. In this example, the charging bias voltage for the charging roller 2 is an oscillating voltage obtained by superimposing a DC voltage (Vdc) and an AC voltage (Vac).

More specifically, DC voltage: -500V AC voltage: frequency f1000Hz, peak-to-peak voltage Vpp
This is an oscillating voltage in which 1400 V and a sine wave are superposed, and the peripheral surface of the photosensitive drum 1 is uniformly contact-charged to -500 V (dark potential Vd).

The charging roller 2 has a longitudinal length of 320 mm and has a core metal (support member) 2a as shown in the layer structure model of FIG.
It has a three-layer structure in which a lower layer 2b, an intermediate layer 2c, and a surface layer 2d are sequentially laminated from the bottom to the outer periphery. The lower layer 2b is a foam sponge layer for reducing charging noise, and the surface layer 2d is a protective layer provided to prevent leakage even if there is a defect such as a pinhole on the photosensitive drum 1. .

More specifically, the specifications of the charging roller 2 of this example are as follows. a. Core 2a; stainless round bar with a diameter of 6 mm b. Lower layer 2b; foamed EPDM of carbon dispersion, specific gravity 0.5 g / cm ³ , volume resistance value 10 ² to 10 ⁹ Ωcm,
Layer thickness 3.0 mm, length 320 mm c. Intermediate layer 2c; carbon-dispersed NBR rubber, volume resistance value of 10 ² to 10 ⁵ Ωcm, layer thickness of 700 μm d. Surface layer 2d; tin oxide and carbon dispersed in resin of fluorine compound, volume resistance value of 10 ⁷ to 10 ¹⁰ Ωcm, surface roughness (JIS
Standard 10 points average surface roughness Ra) 1.5 μm, layer thickness 10
μm

In FIG. 2, 2f is a charging roller cleaning member, which is a flexible cleaning film in this example. The cleaning film 2f is arranged in parallel with the longitudinal direction of the charging roller 2 and has one end fixed to a supporting member 2g that reciprocates a certain amount in the longitudinal direction, and is connected to the charging roller 2 on the surface near the free end side. Arranged to form a contact nip. The support member 2g is driven by a drive motor of the printer through a gear train to reciprocate a predetermined amount in the longitudinal direction, and the charging roller surface layer 2d.
Are rubbed with the cleaning film 2f. As a result, contaminants (fine toner, external additives, etc.) on the surface of the charging roller 2d are removed.

C) The information writing means 3 is an exposure device as an information writing means for forming an electrostatic latent image on the surface of the photosensitive drum 1 that has been subjected to the charging process, and this example is a laser beam scanner using a semiconductor laser. . Laser light modulated corresponding to the image signal sent to the printer side from the host processing such as an image reading device (not shown) is output to expose the uniformly charged surface of the rotary photosensitive drum 1 to the exposure position b.
In, laser scanning exposure L (image exposure) is performed. The laser scanning exposure L lowers the potential of the surface of the photosensitive drum 1 irradiated with the laser beam, so that electrostatic latent images corresponding to the scanned and exposed image information are sequentially formed on the surface of the rotating photosensitive drum 1. Go.

D) The developing means 4 is a developing device (developing device) as a developing means for supplying the developer Z (toner) to the electrostatic latent image on the photosensitive drum 1 to visualize the electrostatic latent image. Is a reversal developing device of a two-component magnetic brush developing system.

4a is a developing container. Reference numeral 4b is a non-magnetic developing sleeve, and the developing sleeve 4b is rotatably arranged in the developing container 4a with a part of the outer peripheral surface thereof exposed to the outside. 4c is a magnet roller fixed non-rotatably and inserted in the developing sleeve 4b, 4d is a developer coating blade, 4e is a two-component developer housed in the developing container 4a, and 4f is a bottom part in the developing container 4a. The developer agitating member 4g provided is a toner hopper, and contains replenishment toner.

The two-component developer 4e in the developing container 4a is a mixture of toner and magnetic carrier, and is a developer stirring member 4f.
Is stirred by. In this example, the magnetic carrier has a resistance of about 10 ¹³ Ωcm and a particle size of 40 μm. The toner is negatively charged by friction with the magnetic carrier.

The developing sleeve 4b is disposed facing the photosensitive drum 1 while keeping the closest distance (referred to as S-Dgap) to the photosensitive drum 1 at 350 μm. The facing portion between the photosensitive drum 1 and the developing sleeve 4b is the developing portion c. The developing sleeve 4b is rotationally driven in the developing portion c in the direction opposite to the traveling direction of the photosensitive drum 1. On the outer peripheral surface of the developing sleeve 4b, a part of the two-component developer 4e in the developing container 4a is adsorbed and held as a magnetic brush layer by the magnetic force of the magnet roller 4c in the sleeve, and is rotatably conveyed as the sleeve rotates. A predetermined thin layer is formed by the developer coating blade 4d, and the surface of the photosensitive drum 1 is brought into contact with the developing portion c to appropriately rub the surface of the photosensitive drum. A predetermined developing bias is applied to the developing sleeve 4b from the power source S2. In this example, the developing bias voltage for the developing sleeve 4b is an oscillating voltage obtained by superimposing a DC voltage (Vdc) and an AC voltage (Vac). More specifically, it is an oscillating voltage obtained by superimposing a DC voltage of −350V and an AC voltage of 1600V.

Thus, the toner in the developer coated on the surface of the rotating developing sleeve 4b as a thin layer and conveyed to the developing portion c is converted into an electrostatic latent image on the surface of the photosensitive drum 1 by the electric field due to the developing bias. Correspondingly and selectively adhering, the electrostatic latent image is developed as a toner image. In the case of this example, toner adheres to the exposed bright portion of the surface of the photosensitive drum 1 and the electrostatic latent image is reversely developed. At this time, the amount of charge of the toner developed on the photosensitive drum is -25 μC / g.

The thin developer layer on the developing sleeve 4b that has passed through the developing section c is returned to the developer reservoir section in the developing container 4a as the developing sleeve continues to rotate.

In order to maintain the toner concentration of the two-component developer 4e in the developing container 4a within a predetermined substantially constant range, the toner concentration of the two-component developer 4e in the developing container 4a is, for example, an optical toner (not shown). Detected by the density sensor, the toner hopper 4g is drive-controlled according to the detected information, and the toner in the toner hopper is replenished to the two-component developer 4e in the developing container 4a. The toner supplied to the two-component developer 4e is stirred by the stirring member 4f.

E) Transfer means / fixing means 5 is a transfer device, and in this example is a transfer roller. The transfer roller 5 is pressed against the photosensitive drum 1 with a predetermined pressing force, and the press contact nip portion is the transfer portion d. A transfer material (transferred member, recording material) P is fed to the transfer section d from a paper feed mechanism section (not shown) at a predetermined control timing.

The transfer material P fed to the transfer portion d is nipped and conveyed between the rotating photosensitive drum 1 and the transfer roller 5, and during that time, the transfer roller 5 is supplied to the transfer roller 5 from the power source S3 and the negative polarity of the toner is the normal charging polarity. In this example, +2 kV is applied to transfer the transfer portion d.
The toner images on the surface of the photosensitive drum 1 are sequentially electrostatically transferred to the surface of the transfer material P that is nipped and conveyed.

The transfer material P which has received the transfer of the toner image through the transfer portion d is sequentially separated from the surface of the rotary photosensitive drum 1 and conveyed to the fixing device 6 (for example, a heat roller fixing device) to fix the toner image. The image is received and output as an image-formed product (print, copy).

(2) Cleaner-less system and toner charge amount control The printer of this example is cleaner-less and is dedicated to removing a small amount of transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image onto the transfer material P. No cleaning device provided. The transfer residual toner on the surface of the photosensitive drum 1 after the transfer is carried to the developing portion c through the charging portion a and the dew portion b as the photosensitive drum 1 continues to rotate, and is simultaneously cleaned (recovered) by the developing device 4 for developing. Is done (cleanerless system).

In the present embodiment, the developing sleeve 4b of the developing device 4 is rotated in the developing portion c in the direction opposite to the traveling direction of the surface of the photosensitive drum 1 as described above. This is advantageous for collecting the transfer residual toner.

Since the transfer residual toner on the surface of the photosensitive drum 1 passes through the exposure portion b, the exposure process is performed on the transfer residual toner. However, since the amount of transfer residual toner is small, a great influence does not appear.

However, as described above, the transfer residual toner has a normal charging polarity, a reverse charging polarity (reversing toner),
Some toners having a small charge amount are mixed, and the reversal toner and the toner having a small charge amount adhere to the charging roller 2 when passing through the charging portion a, so that the charging roller is contaminated more than an allowable amount and charged. It will cause defects.

Further, in order to effectively perform the simultaneous cleaning of the transfer residual toner on the surface of the photosensitive drum 1 by the developing device 4, the photosensitive drum 1 carried to the developing section c is carried out.
It is necessary that the charge polarity of the transfer residual toner is a normal polarity and that the charge amount is the charge amount of the toner capable of developing the electrostatic latent image on the photosensitive drum 1 by the developing device 4.
Reversed toner and toner having an unsuitable charge amount cannot be removed / collected from the photosensitive drum 1 to the developing device 4, resulting in a defective image.

In addition, with the diversification of user needs in recent years,
The continuous printing operation of images having a high printing rate such as photographic images causes a large amount of transfer residual toner at one time, which further aggravates the above problems.

Therefore, in the present embodiment, the transfer portion d
A transfer residual toner (residual developer image) equalizing means 8 for uniformizing the transfer residual toner on the photosensitive drum 1 is provided at a position downstream of the photosensitive drum 1 in the rotational direction of the photosensitive drum. The toner (developer) charge amount for aligning the charge polarity of the transfer residual toner to the negative polarity, which is the normal polarity, at a position downstream of the photosensitive drum rotation direction 8 and upstream of the charging portion a in the photosensitive drum rotation direction. A control means 7 is provided.

By providing the transfer residual toner equalizing means 8, the pattern transfer residual toner on the photosensitive drum 1 which is carried from the transfer portion d to the toner charge amount control means 7 has a large amount of toner, even if the toner amount is large. Are dispersed and distributed on the surface of the photosensitive drum 1 and are not patterned, so that the toner is not concentrated on a part of the toner charge amount control means 7, and the toner of the transfer residual amount by the toner charge amount control means 7 as a whole. The normal polarity charging process is always sufficiently performed to effectively prevent the transfer residual toner from adhering to the charging roller 2. Generation of a ghost image of the transfer residual toner image pattern is strictly prevented.

In the present embodiment, the transfer residual toner equalizing means 8 and the toner charge amount controlling means 7 are brush-like members having appropriate conductivity, and the brush portion is brought into contact with the surface of the photosensitive drum 1. It is provided. Reference numeral f is a contact portion between the transfer residual toner uniformizing means 8 and the surface of the photosensitive drum 1. Reference numeral e is a contact portion between the toner charge amount control means 7 and the surface of the photosensitive drum 1.

The transfer residual toner equalizing means 8 is grounded and the toner charge amount controlling means 7 is applied with a negative voltage from the power source S4.

The transfer residual toner remaining on the photosensitive drum 1 after the toner image is transferred onto the transfer material P at the transfer portion d is transferred to the transfer residual toner equalizing means 8 by the subsequent rotation of the photosensitive drum 1.
To the contact portion f between the photosensitive drum 1 and the transfer drum, and the toner is once sucked by the transfer residual toner equalizing means 8. Here, since the amount of toner that the transfer residual toner equalizing means 8 can hold is limited, after the saturation state is reached, the toner is gradually released and adhered to the surface of the photosensitive drum 1 and conveyed. The toner attachment state on one surface, that is, the distribution of the toner attached to the photosensitive drum 1 surface is made uniform.

The transfer residual toner on the surface of the photosensitive drum 1 uniformized by the transfer residual toner equalizing means 8 reaches the contact portion e between the toner charge amount control means 7 and the photosensitive drum 1 by the subsequent rotation of the photosensitive drum 1. The transfer residual toner on the photosensitive drum 1 passing through the toner charge amount control means 7 is made to have a negative charge polarity, which is a normal polarity.

By aligning the charge polarity of the transfer residual toner to the negative polarity which is the normal polarity, when the charging portion a located further downstream is charged on the surface of the photosensitive drum 1 from above the transfer residual toner, Increase the tolerance to the photosensitive drum 1,
The transfer residual toner is prevented from adhering to the charging roller 2.

Therefore, the amount of charge required for the transfer residual toner needs to be 2.2 times or more as compared with the amount of charge of the toner during development.

FIG. 3 shows the relationship between the voltage applied to the toner charge amount control means 7 and the toner charge amount after passing through the toner charge control means 7. When no voltage is applied to the toner charge amount control means 7, as described above, the transfer residual toner is affected by the negative toner of the image portion, the positive toner of the non-image portion, and the positive voltage of the transfer. Since the toner includes the toner whose polarity is reversed to the positive polarity, the charge amount is indefinite. Further, it can be seen that by applying a voltage to the toner charge amount control means 7, the toner charge amount after passing through the toner charge amount control means 7 is increased and is saturated at a certain value or more. In the toner used in this embodiment, the charge amount when saturated is −90 μC / g.
Met.

Next, before the transfer residual toner enters the charge amount a,
FIG. 4 is a graph showing the relationship between the transfer residual toner charge amount and the adhesion amount to the charging roller 2 when the transfer residual toner amount is 1.
Shown in. It can be seen that the adhesion amount is decreased by increasing the charge amount of the transfer residual toner. Further, at this time, the occurrence of a poorly charged image due to the adhesion of the transfer residual toner to the charging roller 2 occurred at a charge amount of the transfer residual toner of −55 μC / g or less.

Therefore, in order to prevent the transfer residual toner from adhering to the charging roller 2 and suppress the occurrence of a charging failure image, the charge amount of the transfer residual toner is compared with the toner charge amount at the time of development. It turns out that it is necessary to double or more.

In the present embodiment, the voltage applied to the toner charge control means 7 is -800 V, and the charge amount of the transfer residual toner after passing through the toner charge amount means 7 is -70 μC /
It was set to g.

Next, the recovery of the transfer residual toner in the developing step will be described.

As described above, the developing device 4 is of a cleanerless type in which the transfer residual toner is cleaned simultaneously with the development.
As described above, the amount of developed toner charge on the photosensitive drum 1 is -25 μC / g in the present embodiment.
Table 1 shows the relationship between the transfer residual toner and the amount of charge for collecting by the developing device 4 under the developing conditions in the present embodiment.

[0069]

[Table 1]

The toner charge amount for collecting the transfer residual toner on the photosensitive drum 1 by the developing device 4 is 0.5 to 1.8 as compared with the toner charge amount (-25 μC / g) at the time of development.
It needs to be doubled.

However, in order to prevent the toner from adhering to the charging roller 2 as described above, the transfer residual toner that is negatively charged to a large negative polarity of −70 μC / g by the toner charge amount control means 7 is used in the developing device 4. In order to recover, it is necessary to remove the charge.

Here, the relationship between the toner charge amount after the toner on the photosensitive drum 1 having the charge amount of −70 μC / g after passing through the charge roller 2 and the Vpp of the AC voltage applied to the charge roller 2 is shown in FIG. Shown in. It can be seen that power is being received as Vpp of the alternating voltage is increased.

The charging roller 2 is charged with an AC voltage (frequency f1000 Hz, in order to charge the peripheral surface of the photosensitive drum 1).
By applying Vpp1400V), the transfer residual toner is subjected to AC charge removal. Therefore, the charging portion a
After passing through, the toner charge amount is −30 μC / g. In the developing process, the untransferred toner on the photosensitive drum 1, which should not be developed with the toner, is caused by the developing device 4 due to the above reason.
Will be collected.

In this way, the charge amount of the transfer residual toner on the photosensitive drum 1 carried from the transfer part d to the charging part a is adjusted to the negative polarity of the normal polarity by the toner charge amount control means 7, and the charging process is performed. While preventing the residual toner from adhering to the charging roller 2, the charging roller 2 charges the photosensitive drum 1 to a predetermined potential, and at the same time, the toner charging amount control means 7 is charged to a negative polarity of normal polarity. By controlling the charge amount of the transfer residual toner to an appropriate charge amount by which the developing device 4 can develop the electrostatic latent image on the photosensitive drum, the transfer device can efficiently collect the transfer residual toner.

When such a cleanerless image forming apparatus uses a process cartridge in which the image carrier, the charging means, and the developing means are integrated, the density of the image is formed on the image immediately after the cartridge is installed in the main body of the image forming apparatus. The unevenness occurred. This image unevenness is particularly noticeable after the process cartridge left in a low humidity environment for a long time is installed in the main body of the image forming apparatus in a high humidity environment, and the uneven density occurs until the image passing durability exceeds 100 sheets. Continued.

This density unevenness is caused by the toner charge amount control means 7
When the brush member of the transfer residual toner equalizing means 8 is in contact with the photoconductor and an environmental change occurs in which water easily contacts the photoconductor, the water is adsorbed to the brush member in the contacting portion, Since water adheres to the photoconductor on the area (1), a partial resistance difference occurs between the area where the brush member is in contact and the area where the brush member is not in contact, and this occurs.

Therefore, in the present embodiment, when the process cartridge is outside the main body of the image forming apparatus, the toner charge amount control means 7 and the transfer residual toner equalizing means 8 are brought into contact with and separated from the photoconductor. Only when the process cartridge is installed in the main body of the image forming apparatus, the toner charge amount controlling means 7 and the transfer residual toner equalizing means 8 are used as means for contacting the photoconductor. Specific examples are shown in FIGS.

As shown in FIG. 6, the brush is removed from the photosensitive member before the process cartridge is installed. The closest distance D between the brush and the photoconductor was 500 μm.

As shown in FIG. 7, the brush pressing member H is installed inside the image forming apparatus main body, and when the process cartridge is installed in the image forming apparatus main body, the toner charge amount control means 7 and the transfer residual toner are made uniform. The means 8 contacts the regular grounding positions e and f by the brush pressing member H.

As a result of such a structure, the density unevenness that occurred after the process cartridge was installed in the main body of the image forming apparatus was eliminated, and good and stable images were maintained.

(Others) 1) The transfer residual toner equalizing means 8 and the toner charge amount control means 7 are brush-like members in the embodiment, but any form such as a brush rotating body, an elastic roller body, and a sheet-like member is used. Can be a member of.

2) The image bearing member has a surface resistance of 10 ⁹ to 10 10.
^It may be a direct injection type having a charge injection layer of ¹⁴ Ω · cm. Even when the charge injection layer is not used, the same effect can be obtained even when the charge transport layer is in the above resistance range. Surface volume resistance is about 10 ¹³ Ω
An amorphous silicon photoconductor having a size of cm may be used.

3) As the flexible contact charging member, in addition to the charging roller, a fur brush, felt, cloth or the like having a shape and material can be used. Moreover, more appropriate elasticity, conductivity, surface property, and durability can be obtained by combining various materials.

4) As the waveform of the alternating voltage component (AC component, voltage whose voltage value changes cyclically) of the oscillating electric field applied to the contact charging member and the developing member, a sine wave, a rectangular wave, a triangular wave or the like can be appropriately used. Is. It may be a rectangular wave formed by periodically turning on / off the DC power supply.

5) The image exposing means as the information writing means for the charged surface of the photoconductor as the image carrier is not limited to the laser scanning means of the embodiment, but may be a digital light emitting element array such as an LED. It may be exposure means. It may be an analog image exposure means using a halogen lamp, a fluorescent lamp or the like as a document illumination light source. in short,
Anything can be used as long as it can form an electrostatic latent image corresponding to image information.

6) The image carrier may be an electrostatic recording dielectric or the like. In this case, after uniformly charging the dielectric surface,
The charged surface is selectively neutralized by a neutralizing means such as a neutralizing needle head or an electron gun to write and form an electrostatic latent image corresponding to target image information.

7) The toner developing system and means for the electrostatic latent image are arbitrary. The reversal development method or the regular development method may be used.

Generally, in the method of developing an electrostatic latent image, a non-magnetic toner is coated with a blade or the like on a developer carrying and conveying member such as a sleeve, and a magnetic toner is coated on the developer carrying and carrying member. A method for developing an electrostatic latent image by applying it to the image carrier in a non-contact state by coating with a magnetic force and developing the electrostatic latent image on the developer carrying member as described above. A method in which a coated toner is applied to an image carrier in a contact state to develop an electrostatic latent image (one-component contact development) and a method in which a magnetic carrier is mixed with toner particles is used as a developer (two-component development). Used as a developer) to be conveyed by magnetic force and applied to the image carrier in a contact state to develop an electrostatic latent image (two-component contact development), and the above two-component developer to the image carrier. Applied in a non-contact state It is roughly divided into four types of methods (2-component non-contact development) for developing the latent image.

8) The transfer means is not limited to the roller transfer of the embodiment, but may be blade transfer, belt transfer, other contact transfer charging system, or non-contact transfer charging system using a corona charger. .

9) The present invention can be applied not only to the formation of a single color image using an intermediate transfer member such as a transfer drum or a transfer belt, but also to an image forming apparatus for forming a multicolor or full color image by multiple transfer or the like.

[0091]

According to the invention described in each claim of the present application, the process cartridge and the image forming apparatus using the process cartridge can continuously perform stable and favorable image formation without density unevenness.

Further, according to the first aspect of the present invention, the cleaning device in the image forming apparatus is eliminated, and the transfer residual toner on the photoconductor after the transfer process is removed and collected from the photoconductor by the "developing device simultaneous cleaning" in the developing device. A cleanerless system that can be reused can be achieved.

According to the invention described in claims 2 and 3, density unevenness that occurs after the process cartridge is installed in the main body of the image forming apparatus is eliminated, and a good and stable image can be maintained.

According to the invention described in claim 4, the structure of the image forming apparatus main body is simplified.

According to the fifth and sixth aspects of the invention, the photosensitive drum can be charged to a predetermined potential, and at the same time, the charge amount is controlled to be appropriate for developing the electrostatic latent image on the photosensitive drum. Therefore, the transfer residual toner can be efficiently collected.

According to the seventh aspect of the invention, it is possible to sequentially form an electrostatic latent image corresponding to the image information scanned and exposed on the surface of the photosensitive drum.

[Brief description of drawings]

FIG. 1 is a schematic configuration model diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a layer configuration of a photosensitive drum and a charging roller in FIG.

FIG. 3 is a diagram showing a relationship between an applied voltage to a toner charge amount control unit and a charge amount of transfer residual toner after passing through the toner charge amount control unit according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a charge amount of transfer residual toner and a toner adhesion amount on a charging roller according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a toner charge amount after passing through a charging roller and Vpp of an applied AC voltage according to an embodiment of the present invention.

FIG. 6 is a model diagram of a process cartridge before being installed in the image forming apparatus that is an embodiment of the present invention.

FIG. 7 is a model diagram of a process cartridge after being installed in the image forming apparatus that is an embodiment of the present invention.

[Explanation of symbols] 1 Photosensitive drum (image carrier) 2 charging roller 3 Laser beam scanner 4 Developing device 5 Transfer roller 6 fixing device 7 Toner charge amount control means (developer charge amount control means) 8 Transfer residual toner uniformizing means (residual developer uniformizing means) S1 to S4 Bias voltage application power supply

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H071 BA04 BA13 BA27 BA29 DA06                       DA07                 2H077 AA11 AA37 AB01 AB14 AB18                       AC16 AD02 AD06 AD13 AD18                       AD23 AD36 DA10 DA42 DB02                       EA03                 2H134 GA01 GB02 HF13 JA11 KG01                       KG03 KG05 KG07 KH01

Claims (7)

[Claims] 1. An image carrier, a charging unit that charges the surface of the image carrier, an information writing unit that forms an electrostatic latent image on the charged image carrier, and a developer is supplied to the electrostatic latent image. A developing means for visualizing the electrostatic latent image, a transfer means for transferring the visualized image onto a transfer material, and a fixing means are detachable from the main body of the image forming apparatus and upstream from the charging means. And a developer charge amount control unit located downstream of the transfer unit for charging the developer on the developer surface on the image carrier surface, and upstream of the developer charge amount control unit and downstream of the transfer unit. And a residual developer image uniformizing means for uniformizing a residual developer image remaining on the surface of the image carrier after the developer is transferred to the transfer material. Installed inside the device body The process cartridge characterized in that the developer charge amount control means and the residual developer image uniformization means come into contact with each other on the image carrier only when the above-mentioned operation is performed. 2. An image forming apparatus, wherein the process cartridge according to claim 1 is removably provided in an image forming apparatus main body. 3. The image forming apparatus body according to claim 2, further comprising a pressing member that presses the developer charge amount control unit and the residual developer uniformizing unit against the image carrier. Image forming apparatus. 4. The image forming apparatus according to claim 2, wherein the image forming apparatus is cleanerless. 5. The image forming apparatus according to claim 2, wherein the charging unit is contact charging. 6. The image forming apparatus according to claim 2, wherein an oscillating electric field is applied to the charging unit. 7. The image forming apparatus according to claim 2, wherein the information writing unit is an exposure unit.