JP2003302866A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning means for an auxiliary brush, in a C-roller cleaner-less electrifier. <P>SOLUTION: The device is provided with a means which separates a toner electrification quantitative control means (brush) and a residual transfer-toner uniformizing means (brush) from a photosensitive body. <P>COPYRIGHT: (C)2004,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. 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 that returns the transfer residual toner, so-called waste toner, collected by the cleaning device to the developing device and reuses it.

Further, the cleaner-less image in which the cleaning device 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 There is a forming device. Simultaneous development cleaning is the development of the electrostatic latent image by transferring the residual toner on the photosensitive body after transfer to the developing step after the next step, that is, by continuously charging and exposing the photosensitive body to form an electrostatic latent image. Existence on the surface (non-image area) of the photoconductor that should not be developed with toner due to 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) during the positive process. The transfer residual toner is collected by 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.

[0005]

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, even if the toner has a regular charging polarity, there is a toner whose charge polarity is reversed by being influenced by a transfer bias or peeling discharge, and a toner whose toner charge amount is reduced to reduce the amount of charge. Therefore, as the transfer residual toner, there are a mixture of a toner having a normal charge polarity, a reverse toner having a reverse polarity, and a toner having a small charge amount. When it passes through the charging unit, which is the contact nip part, it tends to adhere to 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 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 in the above a) is mixed in that the charging polarity is carried to the charging unit, the charging polarity is normal polarity, the charging polarity is reverse polarity, and the charging amount is small. 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 an image defect, 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 in the developing device. Was efficiently performed, and image stains due to poor collection were eliminated. However, due to the diversification of user needs in recent years, a large amount of transfer residual toner is generated at once due to continuous printing operation of images with high printing rate such as photographic images and multiple development method on the photoconductor due to colorization. As a result, the transfer residual toner accumulates between the transfer residual toner equalizing means and the toner charge amount control means, and when the number of passing sheets overlaps, the accumulated transfer residual toner passes through the toner charge amount control means at once and is developed. The image could not be completely collected by the device and an image defect occurred.

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 transfer residual developer to the charging means. It is a system that prevents the adhesion of the agent and efficiently collects the transfer residual developer by the developing means. Even when the paper passing durability is advanced, there is no charging failure or defective image due to the durability. An object of the present invention is to provide an image forming apparatus that takes advantage of the advantages of a cleanerless system.

[0012]

The present invention is an image forming apparatus having the following configuration.

(1) Image carrier, charging means for charging the surface of the image carrier, information writing means for forming an electrostatic latent image on the charged image carrier, and supply of developer to the electrostatic latent image. A developing means for visualizing the electrostatic latent image, a transferring means for transferring the visualized developer image onto a transfer material, and a developing means on the surface of the image carrier located upstream of the charging means and downstream of the transferring means. Developer charge amount control means for charging the developer on the developer surface,
A residual developer 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 a transfer material uniform. An image forming apparatus having an image uniformizing means, characterized in that means for contacting and separating the developer charge amount controlling means and the residual developer image uniformizing means from the image carrier are provided. apparatus.

(2) The image forming apparatus according to (1), wherein the charging means is contact charging.

(3) The image forming apparatus according to (2) or (3), wherein an oscillating electric field is applied to the charging means.

(4) The image forming apparatus according to any one of (1) to (3), wherein the information writing means is an exposing means.

(5) Image carrier, charging means for charging the surface of the image carrier, information writing means for forming an electrostatic latent image on the charged image carrier, and supply of a developer to the electrostatic latent image. Developing means for visualizing the electrostatic latent image, transfer means for transferring the visualized developer image to a transfer material, and developer located upstream of the charging means for charging the developer on the surface of the image carrier. A charge amount control means and a residual developer image located upstream of the developer charge amount control means and downstream of the transfer means and remaining on the surface of the image carrier after the developer image is transferred to the transfer material. In the image forming apparatus having a residual developer uniformizing means for uniformizing the
An image forming apparatus characterized in that the developer charge amount control means and the residual developer image uniformization means come into contact with and separate from the image carrier at the time of FF / ON.

(6) The image forming apparatus according to (5), wherein the charging means is contact charging.

(7) The image forming apparatus according to (5) or (6), wherein an oscillating electric field is applied to the charging means.

(8) The image forming apparatus according to any one of (5) to (7), wherein the information writing unit is an exposing unit.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) An image forming apparatus (image recording apparatus) according to an embodiment 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.

In the photosensitive drum 1, as shown in the layer structure model of FIG. 2, an undercoat layer for suppressing the interference of light on the surface of the aluminum cylinder (conductive drum substrate) 1a 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 at both ends of a cored bar 2a by bearing members (not shown), 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.
By applying a charging bias voltage of a predetermined condition, the peripheral surface of the rotary 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 a DC voltage (Vdc) and an AC voltage (V
ac) is an oscillating voltage that is superimposed.

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 longitudinal length of the charging roller 2 is 320 mm, and the core metal (supporting member) 2a as shown in the layer structure model diagram 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 10 ² to 10 ⁵ Ωcm, layer thickness 700 μm d. Surface layer 2d: Dispersion of tin oxide and carbon in fluorine-containing resin resin, volume resistance 10 ⁷ to 10 ¹⁰ Ωcm, surface roughness (JIS standard 10-point average surface roughness Ra) 1.5 μm, layer thickness 10 μ
m In FIG. 2, 2f is a charging roller cleaning member, which in this example is a flexible cleaning film. 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 supporting 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 is 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 which has been charged, 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 closest to the photosensitive drum 1 (S-Dg
(hereinafter referred to as ap) is kept at 350 μm so as to be close to the photosensitive drum 1 and face it. The portion where the photosensitive drum 1 and the developing sleeve 4a face each other is the developer 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 a direct current voltage (Vdc) and an alternating current voltage (V).
ac) is an oscillating voltage that is superimposed. 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 section 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 charge amount 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 developing container 4a
The toner concentration of the two-component developer 4e therein is detected by, for example, an optical toner concentration sensor (not shown), and the toner hopper 4g is drive-controlled in accordance with the detected information so that the toner in the toner hopper is stored in the developing container 4a. The two-component developer 4e is replenished. 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 section d is the rotating photosensitive drum 1
The transfer bias is applied between the transfer roller 5 and the transfer roller 5 between the transfer roller 5 and the transfer roller 5. During this period, the transfer bias of +2 kV is applied to the transfer roller 5 from the power source S3. As a result, the toner image on the surface of the photosensitive drum 1 is sequentially electrostatically transferred onto the surface of the transfer material P that is nipped and conveyed at the transfer portion d.

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) Cleanerless System and Toner Charge Amount Control The printer of this example is cleanerless, and is dedicated for 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 post-exposure portion b as the photosensitive drum 1 continues to rotate, and is simultaneously cleaned (collected) by the developing device 3 for developing. Is done (cleanerless system).

In this 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. It is advantageous for collecting the 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 includes those having a normal charge polarity, those having a reverse charge polarity (reverse toner), and those having a small charge amount, among which the reverse toner and the toner having a small charge amount. Adheres to the charging roller 2 when passing through the charging portion a, so that the charging roller undesirably contaminates the toner and causes charging failure.

Further, in order to effectively carry out simultaneous cleaning of the transfer residual toner on the surface of the photosensitive drum 1 by the developing device 3, the charge polarity of the transfer residual toner on the photosensitive drum carried to the developing section c is set. It is necessary that the polarity is normal and that the amount of charge is the amount of charge of the toner that can develop the electrostatic latent image on the photosensitive drum by the developing device. Inverted toner and toner having an unsuitable charge amount cannot be removed / collected from the photosensitive drum by the developing device, resulting in defective images.

Also, 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 this embodiment, the transfer residual toner (residual developer image) equalizing means 8 for uniformizing the transfer residual toner on the photosensitive drum 1 at a position downstream of the transfer portion d in the photosensitive drum rotation direction. Is provided at the downstream side of the transfer residual toner equalizing means 8 in the direction of rotation of the photosensitive drum.
A toner (developer) charge amount control means 7 for adjusting the charge polarity of the transfer residual toner to the negative polarity, which is the normal polarity, is provided at a position upstream of the photosensitive drum rotation direction.

By providing the transfer residual toner uniforming 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 even if the toner amount is large. Since the toner is dispersed and distributed on the surface of the photosensitive drum 1 and is not patterned, the toner is prevented from concentrating on a part of the toner charge amount control means 7, and the transfer charge residual toner of the toner charge amount control means 7 is entirely normalized. The 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 uniformizing means 8 and the toner charge amount controlling means 7 are brush-like members having appropriate conductivity, and the brush portion is arranged by contacting the surface of the photosensitive drum 1. It is set up. f is a transfer residual toner equalizing means 8
And the contact portion of 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 a negative voltage is applied to the toner charge amount control means 7 from a power source S4. The transfer residual toner remaining on the photosensitive drum 1 after the toner image is transferred to the transfer agent P at the transfer portion d reaches the contact portion f between the transfer residual toner equalizing means 8 and the photosensitive drum 1 by the subsequent rotation of the photosensitive drum 1.
The transfer residual toner is once sucked into the uniformizing 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. 1
The adhered state of the toner on the surface, that is, the distribution of the toner adhered on the surface of the photosensitive drum 1 is made uniform.

The transfer residual toner on the surface of the photosensitive drum uniformized by the transfer residual toner equalizing means 8 continues to the photosensitive drum 1.
Rotation reaches the contact portion e between the toner charge amount control means 7 and the photosensitive drum 1, and the transfer residual toner on the photosensitive drum 1 passing through the toner charge amount control means 7 has a negative polarity whose charge polarity is normal polarity. Are aligned with. By aligning the charge polarity of the transfer residual toner to the negative polarity which is the normal polarity, when the surface of the photosensitive drum 1 is charged from above the transfer residual toner with the charge a located further downstream, the charge is transferred to the photosensitive drum 1. Of the transfer residual toner is prevented from adhering to the charging roller 2.

Therefore, the amount of charge required for the transfer residual toner is 2.2 times or more as compared with the amount of charge of the toner at the time of development. Here, 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 is shown in FIG. 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 example, the charge amount when saturated was −90 μC / g.

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 poorly charged image, the charge amount of the transfer residual toner is 2.2 times as large as the toner charge amount at the time of development. It is understood that the above is necessary.

In this embodiment, the voltage applied to the toner charge control means 7 is -800 V, and the toner charge amount means 7 is used.
The charge amount of the transfer residual toner after passing through was set to -70 μC / g. Next, the recovery of the transfer residual toner in the developing step will be described. As described above, the developing device 4 is a cleanerless system that cleans the transfer residual toner at the same time as the development. As described above, the developed toner charge amount on the photosensitive drum 1 is −25 μC / g in this 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 this embodiment.
Shown in.

[0053]

[Table 1] The toner charge amount for the transfer residual toner on the photosensitive drum 1 to be collected by the developing device 4 is the toner charge amount at the time of development (-2
It is necessary to be 0.5 to 1.8 times as high as 5 μC / g).

However, in order to prevent the toner from adhering to the charging roller 2 as described above, the transfer residual toner largely negatively charged with −70 μC / g by the toner charge amount control means 7 is developed. In order to recover in No. 4, it is necessary to remove the charge. Where the charge is −
FIG. 5 shows the relationship between the toner charge amount after 70 μC / g of toner on the photosensitive drum 1 has passed through the charging roller 2 and Vpp of the AC voltage applied to the charging roller 2. 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 portion d to the charging portion a is adjusted to the negative polarity of the normal polarity by the toner charge amount control means 7, and the transfer processing 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.

In such a cleanerless image forming apparatus, when 100% image duty (solid) sheet passing durability was accumulated, image smearing occurred when the number of sheets exceeded 1,000. As a result of intensive research, the above-mentioned image stain passes through the transfer residual toner equalizing means 8 and does not pass through the toner charge amount control means 7, that is, the transfer residual toner equalizing means 8 and the toner charge amount control means 7. The transfer residual toner accumulated in the meantime exceeds the limit that can be retained, and the toner charge amount control normally enters the nip portion of the toner 7 all at once, and all the toner is not accurately charged, and the amount is too large to be collected by the developing device 4. It was found that stains appear on the image.

Therefore, in this embodiment, regardless of the image duty, the transfer residual toner equalizing means 8 and the toner charge amount controlling means 7 are brought into contact with and separated from the photoconductor 1 once for every 100 sheets of paper passing durability. Was rotated several times to collect the transfer residual toner accumulated between the transfer residual toner uniformizing means 8 and the toner charge amount control means 7 at the developing section and transferred to the transfer section (contact / separation mode).

As a result, image stains due to the transfer residual toner accumulated between the transfer residual toner equalizing means 8 and the toner charge amount control means 7 do not occur, and up to 50,000 sheets of images can be obtained with a paper passing durability of 5% in image duty. There was no defect and a good and stable image was maintained.

(Embodiment 2) When Jam (the operation stops during the image formation due to an error such as a paper jam) occurs during the paper passing durability, the toner which is not transferred at all remains on the photoconductor 1. A larger amount of transfer residual toner than the normal transfer residual toner accumulates between the transfer residual toner equalizing unit 8 and the toner charge amount control unit 7. After the end of the Jam processing, the same image defect as that in the example 1 occurred in the first image after the main body power was turned off and then on again.

Therefore, in this embodiment, Jam occurs,
Regardless of whether or not the main body is turned off / on, the transfer residual toner equalizing means 8 and the toner charge amount control means 7 are brought into contact with and separated from the photoconductor 1 (contact / separation mode), and the photoconductor 1 is rotated several times. Then, a contact / separation mode was set in which the transfer residual toner accumulated between the transfer residual toner equalizing means 8 and the toner charge amount control means 7 was collected at the developing portion and transferred to the transfer portion. As a result, even if the operation is forcibly stopped during image formation, image stains due to the transfer residual toner accumulated between the transfer residual toner equalizing unit 8 and the toner charge amount control unit 7 do not occur, and a good image is formed. Maintained.

(Others) 1) The transfer residual toner equalizing means 8 and the toner charge amount controlling means 7 are brush-like members in the embodiment, but may have any form such as a brush rotating body, an elastic roller body and a sheet-like member. It can be a member.

2) The image bearing member has a surface resistance of 10 ⁹ to 10 ¹⁴
It may be a direct injection type having a charge injection layer of 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. An amorphous silicon photoreceptor having a surface layer having a volume resistance of about 10 ¹³ Ω · 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 periodically) of the oscillating electric field applied to the contact charging member or 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) In addition to the laser scanning means of the embodiment, the image exposing means as the information writing means for the charged surface of the photoconductor as the image carrier is, for example, digital exposure using a solid light emitting element array such as an LED. It may be a 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, what is necessary is just to 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 on a developer carrying and conveying member such as a sleeve with a blade or the like, 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 methods, or non-contact transfer charging method using a corona charger. .

9) The present invention can be applied to an image forming apparatus for forming a multicolor image or a full color image by multiple transfer as well as a single color image formation by using an intermediate transfer member such as a transfer drum or a transfer belt.

[0072]

EFFECT OF THE INVENTION By adopting the following constitution as the image forming apparatus in the present invention, stable and favorable image formation can be continuously carried out.

(1) Image carrier, charging means for charging the surface of the image carrier, information writing means for forming an electrostatic latent image on the charged image carrier, and supply of developer to the electrostatic latent image. A developing means for visualizing the electrostatic latent image, a transferring means for transferring the visualized developer image onto a transfer material, and a developing means on the surface of the image carrier located upstream of the charging means and downstream of the transferring means. Developer charge amount control means for charging the developer on the developer surface,
A residual developer 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 a transfer material uniform. An image forming apparatus having an image uniformizing means, characterized in that means for contacting and separating the developer charge amount controlling means and the residual developer image uniformizing means from the image carrier are provided. apparatus.

(2) The image forming apparatus according to (1), wherein the charging means is contact charging.

(3) The image forming apparatus according to (2) or (3), characterized in that an oscillating electric field is applied to the charging means.

(4) The image forming apparatus according to any one of (1) to (3), wherein the information writing unit is an exposing unit.

(5) Image carrier, charging means for charging the surface of the image carrier, information writing means for forming an electrostatic latent image on the charged image carrier, and supply of developer to the electrostatic latent image. Developing means for visualizing the electrostatic latent image, transfer means for transferring the visualized developer image to a transfer material, and developer located upstream of the charging means for charging the developer on the surface of the image carrier. A charge amount control means and a residual developer image located upstream of the developer charge amount control means and downstream of the transfer means and remaining on the surface of the image carrier after the developer image is transferred to the transfer material. In the image forming apparatus having a residual developer uniformizing means for uniformizing the
An image forming apparatus characterized in that the developer charge amount control means and the residual developer image uniformization means come into contact with and separate from the image carrier at the time of FF / ON.

(6) The image forming apparatus according to (5), wherein the charging means is contact charging.

(7) The image forming apparatus according to (5) or (6), characterized in that an oscillating electric field is applied to the charging means.

(8) The image forming apparatus according to any one of (5) to (7), wherein the information writing unit is an exposing unit.

[Brief description of drawings]

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

[Fig. 2] Model diagram of layer structure of photosensitive drum and charging roller

FIG. 3 is a diagram showing a relationship between a voltage applied to a toner charge amount control unit and a charge amount of transfer residual toner.

FIG. 4 is a graph showing the relationship between the amount of residual transfer toner and the amount of toner adhered to the charging roller

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.

[Explanation of Codes] 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 equalizing means (residual developer equalizing means) S1 to S4 ... Bias voltage application power source

Claims (8)

[Claims] 1. An image carrier, charging means for charging the surface of the image carrier, information writing means for forming an electrostatic latent image on the charged image carrier, and a developer for the electrostatic latent image. A developing unit for visualizing the electrostatic latent image, a transfer unit for transferring the visualized developer image to a transfer material, and a developer on the surface of the image carrier, which is located upstream of the charging unit and downstream of the transfer unit. A developer charge amount control means for charging the developer on the surface, and an image carrier after the developer is transferred to the transfer material, which is located upstream of the developer charge amount control means and downstream of the transfer means. In an image forming apparatus having a residual developer image uniformizing means for uniformizing a residual developer image remaining on a body surface, the developer charge amount controlling means and the residual developer image uniformizing means are provided on the image carrier. An image forming apparatus comprising means for contacting and separating from the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the charging unit is contact charging. 3. The image forming apparatus according to claim 2, wherein an oscillating electric field is applied to the charging unit. 4. The image forming apparatus according to claim 1, wherein the information writing unit is an exposure unit. 5. An image carrier, charging means for charging the surface of the image carrier, information writing means for forming an electrostatic latent image on the charged image carrier, and supplying a developer to the electrostatic latent image. Developing means for visualizing the electrostatic latent image, transfer means for transferring the visualized developer image onto a transfer material, and developer charging for charging the developer on the surface of the image carrier, which is located upstream of the charging means. An amount control means and a residual developer image which is located upstream of the developer charge amount control means and downstream of the transfer means and which remains on the surface of the image carrier after transferring the developer image to a transfer material. In an image forming apparatus having a residual developer uniformizing means for uniformizing, the power source of the image forming apparatus main body is turned off.
The image forming apparatus is characterized in that the developer charge amount control means and the residual developer image uniformization means come into contact with and separate from the image carrier at the time of turning on. 6. The image forming apparatus according to claim 5, wherein the charging unit is contact charging. 7. The image forming apparatus according to claim 5, wherein an oscillating electric field is applied to the charging unit. 8. The image forming apparatus according to claim 5, wherein the information writing unit is an exposure unit.