JPH09212038A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device of a cleanerless system capable of preventing a contact electrifying member from being contaminated with toner and without causing defective electrification and degradation of output-image quality even when a large amount of untransferred toner reaches the contact electrifying member as in the case of restarting the device after the interruption of the operation of the device due to paper jamming during development and transfer. SOLUTION: A voltage to be applied to the contact electrifying member 31 is the voltage superimposing an ac voltage on a dc voltage at least at the time of image formation. As for the application of the voltage, at the time of the restart of the device in the case the operation of the device is interrupted due to a paper jam during development and transfer, the superimposition of the ac voltage on the dc voltage is stopped, or the device is restarted after an ac voltage smaller in amplitude than that of an ac voltage applied at the time of image formation is superimposed for a fixed period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for charging an image carrier on an image carrier, a process for writing information for forming an electrostatic latent image on the charged surface, and a process for developing the electrostatic latent image with toner. The present invention relates to an image forming apparatus in which image formation is performed by applying an image forming process having an image bearing member, and an image carrier is repeatedly used for image formation.

More specifically, the present invention relates to an image forming apparatus of a cleanerless system in which a developing means for developing an electrostatic latent image also serves as an image carrier cleaning means for collecting residual toner particles on the image carrier.

[0003]

2. Description of the Related Art FIG. 10 is a schematic diagram of a transfer type electrophotographic apparatus (copying machine, printer, facsimile, etc.) as a conventional example of an image forming apparatus.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which is driven to rotate at a predetermined peripheral speed in a clockwise direction indicated by an arrow. In the course of its rotation, the photosensitive drum 1 is subjected to static elimination exposure by the pre-exposure lamp 2 and subjected to uniform charging processing of a predetermined polarity and potential by a corona charger 3 as a charging means, and an image exposure means (not shown) By subjecting the image exposure L by image projection image forming exposure means, laser light scanning exposure means, etc.), the uniformly charged surface is selectively neutralized (or the potential is attenuated) in accordance with the exposure image pattern to form an electrostatic latent image. Is formed.
Then, the formed electrostatic latent image is developed as a toner image by a toner developing device 4 as a developing unit.

On the other hand, a transfer material P, which is a member to be charged, is fed from a paper feed mechanism (not shown) between the photosensitive drum 1 and a corona charger 7 as a transfer means at a predetermined control timing.
The toner image on the surface of the photosensitive drum 1 is electrostatically transferred to the front surface side of the transfer material P by charging the back surface of the transfer material P to the opposite polarity to the toner. Next, the transfer material P is electrostatically separated from the surface of the rotary photosensitive drum 1 by the separation charging device 8 and is introduced into the fixing means 6 to undergo fixing processing of the toner image and output as a copy or a print.

After the toner image is transferred onto the transfer material P, the surface of the photosensitive drum 1 is cleaned by a cleaning means (cleaner) 5 to remove residual toner after transfer, and is repeatedly used for image formation.

In the above, the charging means 3 for uniformly charging the photosensitive drum 1 may be a contact charging type charging device (magnetic brush charging, fur brush charging, roller charging, etc.) instead of the corona charging device. . The contact charging type charger has an advantage that generation of ozone and the like can be reduced. The transfer charger 7 can also be a transfer roller. Basically, an image is formed by the steps of charging, exposing, developing, transferring, fixing and cleaning as described above.

In recent years, miniaturization has progressed in such an apparatus, but there has been a limit only to miniaturization of the above-mentioned charging, exposing, developing, transferring, fixing, and cleaning process equipment. Further, the above-mentioned transfer residual toner is collected by the cleaner 5, but it is preferable that this waste toner is not in view of environmental protection.

Therefore, an image forming apparatus of a cleanerless system, in which the above-mentioned cleaner 5 is removed and cleaning is performed at the same time as development by the developing device 4 (collection of transfer residual toner), has also appeared.

Simultaneous development cleaning is the potential difference between the DC voltage applied to the developing device 4 and the surface potential of the photosensitive drum 1 at the time of developing the toner slightly remaining on the photosensitive drum after the transfer, fog. This is a method of collecting the potential difference Vback.

According to this method, since the transfer residual toner is collected and used in the subsequent steps, waste toner can be eliminated. In addition, the advantage in terms of space is great, and the size can be greatly reduced.

[0012]

However, in an image forming apparatus such as the conventional example, when the cleaner 5 was removed and an attempt was made to collect the residual toner after transfer at the time of development, it was found that a portion of the image which had no image had a previous image in the photosensitive drum cycle. Positive ghost has occurred.

This positive ghost reaches the transfer portion because the transfer residual toner of the previous image could not be collected in the developing portion, or because it was not collected sufficiently, the transfer material is originally a white background portion. Is a phenomenon that occurs when the toner is transferred to a certain place.

On the other hand, a contact charging type charging device is used as the charging means 3 of the photosensitive drum 1 as an image carrier.
By applying an alternating voltage to the contact charging member and causing the transfer residual toner to vibrate between the contact charging member and the photosensitive drum, the history of the transfer residual toner remaining in the state of the previous image is erased, and the residual toner remains on the photosensitive drum in a uniform state. It is possible to exhale. For this reason, the toner discharged in a thin layer is advantageous in the collectability at the time of development, and the image defect can be prevented.

However, even in this case, when the operation of the apparatus is interrupted (emergency stop of the apparatus due to a jam trouble or the like) due to a paper jam or the like during development or transfer, for example, when the apparatus is restarted, In this case, a large amount of untransferred toner remains, and when an alternating voltage is applied to the contact charging member as described above when the apparatus is restarted, the residual toner vibrates between the contact charging member and the photosensitive drum. This will cause movement, and excessively contaminate the contact charging member. Contamination of the toner on the contact charging member causes defective charging of the photosensitive drum as the image bearing member, thus deteriorating the quality of the output image.

Even if the operation of the apparatus is not interrupted due to a paper jam during development or transfer, the charging property and the output are the same as above even if the contact charging member is gradually contaminated by the transfer residual toner during image formation. Causes deterioration of image quality.

Therefore, the present invention relates to an image forming apparatus of a cleanerless system in which a contact charging type charging device is used as the charging means of the image bearing member and the developing means simultaneously cleans the developing means, due to paper jam during development or transfer. Even when a large amount of untransferred toner reaches the contact charging member such as when the device is restarted when the operation of the device is interrupted, toner contamination of the contact charging member is prevented and the charging state of the image carrier by the contact charging member is maintained for a long time. It is an object of the present invention to realize a practical image forming apparatus of a cleanerless system, which is devised so that it can be maintained satisfactorily over a period of time, and does not have a charging failure due to toner contamination of a contact charging member or a phenomenon of deterioration of output image quality.

[0018]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) A step of charging the image bearing member with respect to the image bearing member, an information writing process of forming an electrostatic latent image on the charged surface, and the electrostatic latent image is developed as a toner image by a developer. The image carrier is an image forming apparatus that is repeatedly used for image formation by applying an image forming process including a step of charging the image carrier, and the charging unit that charges the image carrier uses the charging member as the image carrier. Is a contact charging means for applying a voltage by contacting with the toner, the developing means for developing the electrostatic latent image also serves as an image carrier cleaning means for collecting the residual toner particles on the image carrier, and is applied to the contact charging member. The voltage applied should be a voltage obtained by superimposing an alternating voltage on a DC voltage at least during image formation, and at the time of restarting the device when the device operation is interrupted due to a paper jam during development or transfer, contact band Regarding the above-mentioned applied voltage to the member, the superimposition of the alternating voltage with respect to the DC voltage is stopped, or the alternating voltage with a weaker amplitude than the applied alternating voltage at the time of image formation is provided for a certain period of time to restart the apparatus. An image forming apparatus characterized in that:

(2) The image forming apparatus according to (1), characterized in that the voltage is applied to the developing means for developing the electrostatic latent image when the voltage is applied to the contact charging member.

(3) When the apparatus is activated, the applied voltage to the contact charging member is suspended from the superposition of the alternating voltage with respect to the direct current voltage, or the alternating voltage with a weaker amplitude than the applied alternating voltage at the time of image formation is superposed. The image forming apparatus described in (1) or (2) is characterized in that a certain period of time is set.

(4) Any one of (1) to (3), wherein the contact charging member is a brush member made of a conductive fiber, and the conductive fiber brush portion is in contact with the image carrier. The image forming apparatus described in 1.

(5) Any one of (1) to (3), wherein the contact charging member is a magnetic particle magnetic brush member, and the magnetic particle magnetic brush portion is in contact with the image carrier. The image forming apparatus described in 1.

(6) The image bearing member has a surface resistance of 10 ⁹ to 1
Characterized by having a low resistance layer of 0 ¹⁴ Ω · cm (1)
The image forming apparatus according to any one of (1) to (5).

(7) The developing means is a contact developing system in which the electrostatic latent image is developed with the developer being in contact with the image carrier, which is one of the features (1) to (6). An image forming apparatus according to any one of the above.

(8) The image forming apparatus according to any one of (1) to (7), wherein the developer contained in the developing means is a developer composed of toner particles and magnetic particles.

(9) The image formation according to any one of (1) to (8), wherein the toner particles in the developer contained in the developing means are toners produced by a polymerization method. apparatus.

(10) The image forming apparatus described in any one of (1) to (9), wherein the image bearing member is an electrophotographic photosensitive member.

(11) One of (1) to (10), wherein the information writing means for forming an electrostatic latent image on the charged surface of the image carrier is an image exposing means for the image carrier. The image forming apparatus according to item 1.

(12) The image forming apparatus described in any one of (1) to (11), wherein the toner image formed on the image carrier is transferred onto a transfer material by a transfer means.

(13) The contact charging member is provided in the process cartridge detachably mountable to the main body of the image forming apparatus together with at least the image bearing member, according to any one of (1) to (12). Image forming apparatus.

<Operation> a) In the image forming apparatus in which the developing means also serves as the cleaning means for the image bearing member, ozone is reduced by using the contact charging means as the charging means, and the image carrying is carried by the contact charging member. By charging the residual toner particles on the body to the normally-charged toner, it is possible to collect (clean) the residual toner at the same time of development by the developing means.

B) At the time of image formation, the charging uniformity is obtained by applying a bias in which an alternating voltage is superimposed on a DC voltage to the contact charging member.

C) At the time of restarting the device when the device operation is interrupted due to paper jam during development or transfer,
Regarding the above-mentioned applied voltage to the contact charging member, a period of time for suspending the superposition of the alternating voltage with respect to the DC voltage or superposing the alternating voltage with a weaker amplitude than the applied alternating voltage at the time of image formation is provided for a certain time, and the apparatus is re-installed. By activating the toner, the residual toner on the image bearing body is kept left on the image bearing body, and the mixed toner adhering to the contact charging member is transferred onto the image bearing body (toner ejection).

A voltage lower than the charging potential (a DC voltage component in the case of alternating voltage superposition) is applied to the toner remaining on the image carrier and the toner discharged from the contact charging member onto the image carrier. It is recovered by the developed developing means.

D) Further, not only when the apparatus is restarted when the operation of the apparatus is interrupted due to a paper jam or the like during development or transfer, but also when the apparatus is normally started (when the apparatus power is turned on), the contact charging member is always charged. Regarding the applied voltage, by stopping the superposition of the alternating voltage with respect to the DC voltage, or by setting the time for superposing the alternating voltage with a weaker amplitude than the applied alternating voltage at the time of image formation for a fixed time to start the device. The mixed toner adhering to the contact charging member is transferred onto the image carrier and collected by the developing means.

E) Thus, even when a large amount of untransferred toner reaches the contact charging member, such as when the device is restarted when the operation of the device is interrupted due to paper jam during development or transfer, the toner adheres to the contact charging member. The toner can be efficiently discharged and collected, the toner of the contact charging member can be prevented from being contaminated, and a good charge state can be realized for a long period in the image forming apparatus of the cleanerless system.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 6) (1) Schematic configuration of an example of an image forming apparatus FIG. 1 is a schematic configuration 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, and a cleanerless system apparatus that uses a contact charging type charging device as a charging unit of an image carrier and performs simultaneous development cleaning by a developing unit. Is.

A is a laser beam printer, and B is an image reading device (image scanner) mounted on the printer.

A. Image Reading Device B In the image reading device B, 10 is an original platen glass fixedly arranged on the upper surface of the device, and the original G is placed on the upper surface of the original platen glass with the surface to be copied facing down. Cover the original with a document pressure plate (not shown) and set it.

An image reading unit 9 is provided with a document irradiation lamp 9a, a short focus lens array 9b, a CCD sensor 9c and the like. When a copy button (not shown) is pressed, this unit 9 is driven forward along the lower surface of the glass from the home position shown by the solid line on the right side of the glass 10 on the lower side of the platen glass 10 to the left side. When the forward end point of is reached, it is driven backward and returned to the home position indicated by the first solid line.

In the forward drive process of the unit 9, the downward image surface of the set original G placed on the original table glass 10 is sequentially illuminated and scanned by the original irradiation lamp 9a of the unit 9 from the right side to the left side. The light reflected from the document surface of the illumination scanning light is imaged and incident on the CCD sensor 9c by the short focus lens array 9b.

The CCD sensor 9c comprises a light receiving section, a transfer section and an output section. The light signal is converted into a charge signal in the CCD light receiving unit, and the transfer unit sequentially transfers the light signal to the output unit in synchronization with the clock pulse. The output unit converts the charge signal into a voltage signal, amplifies the signal, reduces the impedance, and outputs the voltage signal. The analog signal thus obtained is subjected to well-known image processing to be converted into a digital signal, and the printer A
Send to

That is, the image information of the original G is photoelectrically read by the image reading device B as a time series electric digital pixel signal (image signal).

B. Printer A In the printer A, 1 is a rotating drum type electrophotographic photosensitive member (photosensitive drum) as an image bearing member. The photosensitive drum 1 is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed about a central support shaft, in this example, a rotational speed of 150 mm / s. Next, in the case of the present example, the charging means 31 receives a uniform negative charging process (about -650 V).
The charging means 31 in this example is a fur brush charger (contact charging member) as a contact charging type charging means, and a predetermined charging bias (alternating voltage + DC voltage) is applied by the charging bias applying power source S1.

A laser scanning unit (laser scanner) 100 is provided on the uniformly charged surface of the rotary photosensitive drum 1.
Output from the image reading device B to the printer A
The scanning exposure L by the laser light modulated according to the image signal sent to the
On the surface, an electrostatic latent image corresponding to the image information of the document G photoelectrically read by the image reading device B is sequentially formed.

The electrostatic latent image formed on the surface of the rotating photosensitive drum 1 is sequentially developed as a toner image by the developing means 4 in the case of reversal development. S2 is a power source for applying a predetermined developing bias (alternating voltage + DC voltage) to the developing sleeve of the developing device 4.

On the other hand, the transfer material P stored in the paper feed cassette 11 is fed out one by one by the paper feed roller 12 and fed into the printer A, and is transferred to the photosensitive drum 1 by the registration roller 13 at a predetermined control timing. The sheet is fed to a transfer unit 72 which is a contact nip portion with a transfer roller 71 as a transfer unit. A transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 71 from the transfer bias applying power source S3 at a predetermined control timing, and the toner image on the surface of the photosensitive drum 1 is formed on the surface of the transfer material P fed to the transfer unit 72. Electrostatically transferred.

The transfer material P which has received the transfer of the toner image through the transfer portion 72 is sequentially separated from the surface of the photosensitive drum 1 and is transferred to the fixing device 6 by the transfer device 14, where the toner image is thermally fixed and copied. Or it is output as a print.

After the toner image is transferred onto the transfer material P, the surface of the rotating photosensitive drum 1 is repeatedly used for image formation.

(2) Photosensitive Drum 1 As the photosensitive drum 1 as the image bearing member, a commonly used organic photosensitive member or the like can be used, but preferably, a low resistance surface layer is formed on the organic photosensitive member. It has a surface resistance of 10 ⁹ to 1 such as those that it has and amorphous silicon photoconductors.
Having a low resistance layer of 0 ¹⁴ Ω · cm can realize charge injection charging and is effective in preventing ozone generation. Further, the chargeability can be improved.

In this example, conductive particles (SnO ₂ ) were dispersed as a charge injection layer on the surface of the organic photoreceptor, and the surface resistance was about 10 ¹³ Ω · cm and the outer diameter was 60 mmφ.

(3) Laser Scanning Section 100 FIG. 2 shows a schematic configuration of the laser scanning section 100. When laser scanning exposure is performed on the surface to be scanned 1 (the surface of the rotating photosensitive drum) by the laser scanning unit 100, first, the solid-state laser element 102 blinks at a predetermined timing by the light emission signal generator 101 based on the input image signal. ON / OFF). And the solid-state laser element 10
2 is converted into a substantially parallel light beam by a collimator lens system 103, and further scanned in a direction of an arrow c by a rotating polygon mirror 104 rotating at a high speed in a direction of an arrow b, and fθ lens groups 105a and 105b.・ 10
An image is formed in a spot shape on the surface to be scanned 1 by 5c. By such laser light scanning, an exposure distribution for one scan of an image is formed on the surface to be scanned 1, and the surface to be scanned 1 is scrolled by a predetermined amount perpendicular to the scanning direction for each scan.
An exposure distribution according to the image signal is obtained on the surface 1 to be scanned.

(4) Fur brush charger 31 The fur brush charger 31 as a contact charging member is a rotary roller type in which a conductive fiber brush portion (fur brush) is disposed in contact with the photosensitive drum 1, and At the contact portion (charging portion, charging area) with the drum 1, the rotational speed 1 of the photosensitive drum 1 is counter to the rotational direction of the photosensitive drum 1.
It is rotated at a rotation speed of 300 mm / sec with respect to 50 mm / sec.

Regarding the rotation speed, the higher the charging uniformity, the better the charging uniformity. Further, the higher the brush density of the fur brush, the higher the uniformity, and the better charging property is obtained at 100,000 brushes / inch ² or more.

The amplitude of the alternating voltage component of the bias applied to the fur brush charger 31 and the first-round charging potential are as shown in FIG. 3. By increasing the amplitude of the alternating voltage, applied DC (direct current) The difference between the bias and the charging potential in the first round is small. Along with this, the uniformity of charging is improved.

In this example, a good charging property could be obtained by applying to the fur brush charger 31 a bias in which a DC voltage of -700 V and an alternating voltage of 1000 Hz and 1000 V were superposed.

(5) Developing Means 4 Generally, in the method of developing an electrostatic latent image, a non-magnetic toner is coated on a sleeve with a blade or the like, and a magnetic toner is coated by a magnetic force and conveyed to a photosensitive drum. In contrast, a method of developing in a non-contact state (one-component non-contact development), a method of developing the toner coated as described above in a state of contact with the photosensitive drum (one-component contact development), and a method of developing toner particles A method in which a mixture of magnetic carriers is used as a developer and is conveyed by magnetic force to develop in contact with the photosensitive drum (two-component contact development), and the above two-component developer is brought into non-contact state. The method is roughly classified into four types, i.e., a method of developing by two-component development (two-component non-contact development).

In this example, a mixture of non-magnetic toner particles and magnetic carrier particles is used as a developer,
Using a two-component contact developing method in which the developer is held on a developer carrier as a magnetic brush layer by magnetic force, transported to a developing unit, and brought into contact with the surface of the photosensitive drum 1 to develop an electrostatic latent image as a toner image. I have.

This is because it is advantageous from the viewpoints of high image quality and high stability of images and mechanical recoverability by the magnetic brush when recovering the residual toner on the photosensitive drum 1.

FIG. 4 is a schematic diagram of the two-component contact developing type (two-component magnetic brush developing) developing device 4 used in this example.

41 is a developing container, 42 is a developing sleeve as a developer carrying member, 43 is a magnet roller as a magnetic field generating means fixedly arranged in the developing sleeve 42, and 44 is a thin layer of the developer on the surface of the developing sleeve. To form a developer layer thickness controlling blade, 45 is a developer stirring and conveying screw, and 46 is a two-component developer housed in the developing container 41, and mixes non-magnetic toner particles t and magnetic carrier particles c. It was done. 47 is a toner replenishing section.

The developing sleeve 42 has a closest distance (gap) to the photosensitive drum 1 of about 5 at least during development.
The developer magnetic brush thin layer 46 a carried on the outer surface of the developing sleeve 42 is set to be in contact with the surface of the photosensitive drum 1. A contact portion between the developer magnetic brush layer 46a and the photosensitive drum 1 is a developing portion (developing area).

The developing sleeve 42 is driven in the counterclockwise direction indicated by an arrow at a predetermined rotation speed around the fixed magnet roller 43, and the magnetic force of the magnet roller 43 causes the developer 46 to be applied to the outer surface of the sleeve inside the developing container 41. A magnetic brush is formed. The developer magnetic brush is conveyed along with the rotation of the sleeve 42, and is regulated by the blade 44 in the layer thickness to be carried out as a developer magnetic brush thin layer 46a having a predetermined layer thickness to the outside of the developing container and conveyed to the developing section to be photosensitive drum. The first surface is brought into contact with the first surface, and the sleeve 42 is subsequently rotated to be conveyed back into the developing container 41.

Between the developing sleeve 42 and the conductive drum base of the photosensitive drum 1, a developing bias applying power source S2 applies a developing bias of a DC voltage and an alternating voltage.

In this example, DC voltage: -500V, alternating voltage; amplitude Vpp = 1500V, frequency Vf = 20
A developing bias of 00 Hz is applied, and the toner t in the developer magnetic brush thin layer 46 a on the developing sleeve 42 side selectively adheres to the electrostatic latent image on the photosensitive drum 1 side in the developing section, so that the electrostatic latent image is It is developed as an image.

Generally, in the two-component developing method, when an alternating voltage is applied, the developing efficiency is increased and the image is of high quality, but on the contrary, there is a risk that fogging is likely to occur. For this reason, fog is generally prevented by providing a potential difference between the DC voltage applied to the developing device 4 and the surface potential of the photosensitive drum 1.

The toner concentration (mixing ratio with the carrier) of the developer 46 in the developing container 41 gradually decreases as the toner is consumed for developing the electrostatic latent image. The toner concentration of the developer 46 in the developing container 41 is detected by a detection unit (not shown), and when the toner concentration falls to a predetermined allowable lower limit concentration, the toner replenishing unit 47.
Is supplied to the developer 46 in the developing container 41, and the toner replenishment is controlled so that the toner concentration of the developer 46 in the developing container 41 is always kept within a predetermined allowable range.

The two-component developer 46 used in this example is toner particles t; average particle size 6 μ manufactured by a pulverizing method.
m negatively charged toner to which titanium oxide having an average particle size of 20 nm was added externally at a weight ratio of 1% Carrier c; a magnetic carrier having a saturation magnetization of 205 emu / cm ^{3 and} an average particle size of 35 μm was mixed in a weight ratio of 6:94 It was done.

Here, as the volume average particle diameter of the toner, for example, one measured by the following measuring method is used.

As a measuring device, a Coulter counter T
Using an A-II type (manufactured by Coulter), an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-i personal computer (manufactured by Canon) are connected, and primary electrolyte is sodium chloride. 1% NaC
Adjust the aqueous solution.

The measuring method is as follows:
In 150 ml, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample was suspended was subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and a particle size distribution of particles of 2 to 40 μm was obtained by using a 100 μm aperture as an aperture by the Coulter Counter TA-II type. To determine the volume distribution. The volume average particle diameter of the sample is obtained from the obtained volume distribution.

The developer circulation system in the developing device 4 will be described. First, as the developing sleeve 42 rotates, the developer 46 drawn up by the N ₃ pole of the magnet roller 43 is transported from the S ₂ pole to the N ₁ pole,
A thin layer 46 a of the developer 46 is formed on the developing sleeve 42 by being regulated by the regulating blade 44 arranged perpendicularly to the developing sleeve 42. Developer layer 46a which is a thin layer formed brush is formed by the conveyed to the developing main pole S ₁ of the developing unit magnetic force. The electrostatic latent image on the photosensitive drum 1 is developed as a toner image by the developer layer 46a formed in the shape of a spike, and is left on the photosensitive drum 1 as a transfer residue in the pre-image forming step and remains as a contact charging member. The toner that has been normally charged (negative) by the brush charger 31 is the developer layer 4 on the developing sleeve 42.
6a is recovered. After that, the developer on the developing sleeve 42 is developed by the repulsive magnetic field of the N ₂ pole and the N ₃ pole,
Will be returned within.

(6) Transfer Means In this example, the transfer means is the transfer roller 71, and the pressure contact nip portion as the transfer portion 72 is formed by contacting the photosensitive drum 1 in a predetermined manner.

The transfer roller 71 of the present example comprises a core made of a conductive rigid material such as a metal having an outer diameter of 8φ, urethane, EPD and the like.
A conductive material such as carbon is dispersed in M (ethylene propylene dimethyl rubber) to have a resistance value of 10 ⁵ to 10 ¹⁰ Ω.
Cm, composed of a conductive elastic layer formed of a foamed elastic body adjusted to Asker C hardness of about 20 to 50 degrees,
The outer diameter is 16φ. At the time of transfer, about +4 kV of DC voltage is applied as a transfer bias from the transfer bias applying power source S3 to the core of the transfer roller, and negative polarity toner particles forming a toner image are transferred between the photosensitive drum 1 and the transfer roller 71. Electrostatic transfer is performed by forming a transfer electric field in the direction of transfer to the material P.

(7) Exhaustion of toner from the contact charging member (fur brush charger) 31 Simultaneous development cleaning by the developing means 4 (toner recovery) Transfer remaining on the surface of the photosensitive drum 1 after transfer of the toner image onto the transfer material P. Toner remains. The printer of this example is a cleaner-less device of a simultaneous cleaning system that removes the transfer residual toner by making the developing device 4 also serve as a cleaner without disposing a dedicated cleaner (cleaning device).

In many cases, the transfer residual toner has its charge polarity reversed due to peeling discharge at the time of transfer, and thus the toner whose polarity has been reversed cannot be collected simultaneously with development.

The transfer residual toner reaches the charging portion from the transfer portion as the photosensitive drum 1 rotates. The toner that has reached the charging portion is made into a normally charged toner by rubbing against the brush of the fur brush charger 31, which is a contact charging member.

At the same time, the photosensitive drum 1-
Due to the vibration effect of the electric field between the fur brush chargers 31, the toner is collected and discharged to the fur brush charger 31, and the toner that has been normally charged is transferred to the photosensitive drum 1.
It is discharged to the upper side, and simultaneous development recovery is performed in the developing section.

The bias applied to the fur brush charger 31, chargeability, and toner discharge will be described.

When the alternating voltage is superposed, the chargeability is good, so a potential difference for collecting the toner on the photosensitive drum 1 can be secured at the time of development, but the difference between the applied voltage and the charging potential is small, so The amount of toner discharged into the brush charger 31 is small.

When only a DC voltage is applied,
Since the charging property is poor, the difference between the applied voltage and the charging potential is large, and the amount of toner discharged into the fur brush charger 31 is large. However, the charging property is poor, so the toner on the photosensitive drum 1 is collected during development. Therefore, not only the electric potential difference cannot be secured, but also the image quality is adversely affected by uneven charging.

Therefore, applying only the DC voltage to the fur brush charger 31 at the time of image formation leads to an image defect, and superposition of the alternating voltage is essential.

For the above reasons, the fur brush charger 31
When the charging is performed by superposing the alternating voltage on the toner, the toner is discharged little by little from the fur brush charger 31 even when the alternating voltage is applied during the normal operation. A small amount can be maintained and a good image can be obtained.

However, in the current image forming apparatus,
There is a case where the main assembly of the apparatus is stopped during the development or transfer, such as a jam due to poor conveyance of paper (transfer material). In such a case, a large amount of untransferred toner is present on the photosensitive drum 1. When the apparatus is restarted after the required treatment such as removal of jammed paper and an alternating voltage is applied to the fur brush charger 31 as in the image formation, the untransferred toner is not transferred as shown in the model diagram of FIG. In the charging section, the oscillating electric field reciprocates between the photosensitive drum 1 and the fur brush charger 31 to contaminate the fur brush charger 31 with toner.

On the other hand, as in the present invention, when only the DC voltage (or the bias in which the alternating voltage of which the amplitude is weakened is superimposed) is applied to the fur brush charger 31 when the apparatus is restarted, no transfer is performed. Since the residual toner of No. 1 is a toner charged to a regular polarity, in the case of a normal charged state where | applied bias-charging potential |> 0, as shown in the model diagram of FIG. Therefore, the amount of toner that contaminates the fur brush charger 31 when passing through the charging unit is extremely small.

The toner that has passed through the charging section is collected by applying a voltage lower than the charging potential to the developing device 4, and the photosensitive drum 1 is sufficiently cleaned.

Here, in the present embodiment, by applying the direct current voltage only to the fur brush charger 31 when the apparatus is restarted, the toner on the fur brush of the charger 31 is transferred onto the photosensitive drum. I spit out evenly,
Even if the alternating voltage is not completely stopped, the amplitude of the alternating voltage is reduced to 200 V, for example, and the amplitude is weakened as compared with during image formation, whereby the toner can be biased toward the photosensitive drum side. This is because, as the amplitude is weakened, the charging ability is lowered as shown in FIG. 3. Therefore, the potential difference | applied bias-charging potential | for biasing the toner in the direction of the photosensitive drum is increased, and the toner discharging effect is increased. Was confirmed to be obtained.

More preferably, the bias applied with the DC voltage or the alternating voltage of which the amplitude is weakened is applied to the fur brush charger 31 not only when the apparatus is restarted but also when the apparatus is normally started. Sufficient time for discharging the toner mixed in the fur brush charger 31 and collecting it in the developing device 4 can be obtained, and the life of the fur brush charger 31 can be greatly extended.

<Embodiment 2> (FIGS. 7 to 9) In this embodiment, in the printer of Embodiment 1 described above, the fur brush contact charging device as the charging means is replaced with a magnetic brush contact charging device. Since the other device configurations and process devices are the same, repetitive description will be omitted.

FIG. 7A and FIG. 8A are schematic configuration diagrams of the magnetic brush contact charging device used in this example. Reference numeral 32 is a magnetic brush charger as a contact charging member.

The magnetic brush charger 32 has an outer diameter of 20 m.
m non-magnetic sleeve 32a, a magnet roller 32b as a magnetic field generating means fixedly arranged in the non-magnetic sleeve, and a magnetic force magnetically held by the magnetic force of the internal magnet roller 32b on the outer peripheral surface of the non-magnetic sleeve 32a. The magnetic brush layer 32c of particles (magnetic carrier) or the like is formed, and the magnetic brush layer 32c is placed in contact with the surface of the photosensitive drum 1 to form a charging portion.

The non-magnetic sleeve 32a is rotated in the contact portion with the photosensitive drum 1 at a rotational speed of 225 mm / sec with respect to the rotational speed of the photosensitive drum 1 of 150 mm / sec counter to the rotational direction of the photosensitive drum 1. With the rotation of the sleeve, the magnetic brush 32c is also rotatably conveyed and rubs the surface of the photosensitive drum 1. By applying a predetermined charging bias from the charging bias power source S1 to the non-magnetic sleeve 32a of the magnetic brush charger 32, electric charges are given from the magnetic particles onto the photosensitive drum 1, and the surface of the photosensitive drum 1 corresponds to the charging voltage. Is charged to the potential.

The magnetic particles constituting the magnetic brush 32c are preferably those having an average particle size of 10 to 100 μm, a saturation magnetization of 20 to 250 emu / cm ^{3 and a} resistance of 10 ² to 10 ¹⁰ Ω · cm.

In this example, a ferrite carrier having an average particle size of 25 μm, a saturation magnetization of 200 emu / cm ³ , and a resistance of 5 × 10 ⁶ Ω · cm was used.

Here, the resistance value of the carrier has a bottom area of 22.
After putting 2 g of the carrier into an 8 mm ² metal cell, 6.6
The measurement is performed by applying a weight of Kg / cm ² and applying a voltage of 100V.

The higher the rotating speed of the magnetic brush charger 32, the better the charging uniformity tends to be. However, the magnetic brush contact charging system has a denser contact state than the far brush contact charging system. The speed can be slightly slowed.

In this example, the charging bias for the magnetic brush charger 32 is a combination of the DC voltage V _DC and the alternating voltage V _AC . The amplitude of the alternating voltage component and the first-round charging potential are as shown in FIG. 9, and the difference between the applied DC voltage and the first-round charging potential is reduced by increasing the amplitude of the alternating voltage. Along with this, the uniformity of charging is improved. In this example, a good charging property could be obtained by applying a DC voltage V _DC ; -700 V, an alternating voltage V _AC ; 1000 Hz, 1000 V to the magnetic brush charger 32.

Also in the case of this example, the transfer residual toner that has reached the charging portion from the transfer portion is made into a normally charged toner by sliding friction with the magnetic brush charger 32.

At the same time, the AC voltage component applied to the magnetic brush charger 32 causes the electric field between the photosensitive drum 1 and the magnetic brush charger 32 to vibrate, whereby the transfer residual toner to the magnetic brush charger 32 is collected and discharged. Then, the transfer residual toner that has been normally charged is discharged onto the photosensitive drum 1, and the developing device 4 performs simultaneous development collection (cleaning).

When charging is performed by superposing an alternating voltage on the magnetic brush charger 32, during normal operation, the toner is discharged little by little from the magnetic brush charger 32 even when the alternating voltage is applied. Therefore, the amount of toner mixed is kept small and a good image can be obtained.

The magnetic brush charger 32 has a wider tolerance (latitude) for toner contamination than the fur brush charger 31, but when a large amount of toner is mixed in, the AC bias is superposed on the charging bias. In some cases, the charging uniformity may be reduced.

When an alternating voltage is applied to the magnetic brush charger 32 in the same manner as during image formation when the image forming apparatus main body is stopped during development or transfer due to a jam or the like and the apparatus is restarted, the model diagram of FIG. As described above, the untransferred toner reciprocates between the photosensitive drum 1 and the magnetic brush charger 32 in the charging section due to an oscillating electric field, and the toner contaminates the magnetic brush charger 32.

On the other hand, as in the present invention, when only the DC voltage (or the bias in which the alternating voltage with the weakened amplitude is superimposed) is applied to the magnetic brush charger 32 when the apparatus is restarted, no transfer is performed. Since the residual toner of is a toner charged to a regular polarity, in the case of a normal charged state where | applied bias-charge potential |> 0, as shown in the model diagram of FIG. Therefore, the amount of toner that contaminates the magnetic brush charger 32 when passing through the charging unit is extremely small.

The toner that has passed through the charging section is collected by applying a voltage lower than the charging potential to the developing device 4, and the surface of the photosensitive drum 1 is sufficiently cleaned.

Here, in this example, by applying a DC voltage only to the magnetic brush charger 32 when the apparatus is restarted, the toner on the magnetic brush of the charger 32 is made uniform on the photosensitive drum. However, even if the alternating voltage is not completely stopped, for example, the amplitude of the alternating voltage is 20
By lowering the amplitude as compared with the time of image formation, such as dropping it to 0 V, it becomes possible to bias the toner to the photosensitive drum side. This is because, as the amplitude is weakened, the charging ability is lowered as shown in FIG. 9, and therefore, the potential difference | applied bias-charging potential | for biasing the toner toward the photosensitive drum is increased, and the toner discharging effect is increased. Was confirmed to be obtained.

More preferably, the bias applied with the DC voltage or the alternating voltage with weakened amplitude is applied to the magnetic brush charger 32 not only when the apparatus is restarted but also when the apparatus is normally started. Sufficient time for discharging the toner mixed in the magnetic brush charger 32 and collecting it in the developing device 4 can be obtained, and the life of the magnetic brush charger 32 can be greatly extended.

Further, the magnetic brush charger 32 in this example.
Is a non-magnetic sleeve rotation system in which the magnet roller 32b is fixed, but the magnetic brush charger 32 is not limited to this configuration. For example, a system in which the magnet roller 32b rotates in the same configuration, or only the magnet roller 32b. Even in a system in which the magnet roller itself rotates in the configuration, it can be realized by subjecting the roller surface to a conductive treatment.

<Embodiment 3> In this embodiment, the toner used as the developer in the apparatus of Embodiments 1 and 2 is a toner produced by a polymerization method.
The control is the same as that of the devices of the first and second embodiments, and thus the repetitive description will be omitted.

In the apparatus of Embodiments 1 and 2, the toner particles t of the developer 46 are toners produced by the pulverization method, but in this example, the average particle diameter 6 μm produced by the suspension polymerization method is used. Average particle size 2 for spherical toner
An externally added 1% by weight ratio of 0 nm titanium oxide was used.

The magnetic carrier c has a saturation magnetization of 2
A magnetic carrier having an average particle diameter of 35 μm of 05 emu / cm ³ was used.

The toner t and the carrier c are in a weight ratio of 6:
The mixture of 94 was used as the developer 46.

Since the toner produced by the polymerization method has a shape close to a sphere, the external additive is uniformly coated. For this reason,
Very good releasability from the photosensitive drum. For example, when comparing transfer efficiency (toner amount transferred per unit area on paper / toner amount per unit area on photosensitive drum) between pulverized toner and polymerized toner, pulverized toner was 90%, When the polymerized toner was used, the efficiency was as high as 97%. Further, the fogging is also better than that of the pulverized toner, and when the polymerized toner is used, Vback =
Even at 50 V, fogging could be prevented.

When the same examination as in Embodiments 1 and 2 was carried out using such a polymerized toner, in this example, the transfer residual toner is in a very small amount, and in addition, it has a high releasability. Therefore, in the case of adopting the cleanerless system configuration of simultaneous cleaning for development, the toner collecting property is further improved and the image defect does not occur at all.

Further, when the image forming apparatus main body is stopped during development or transfer due to a paper jam or the like due to poor conveyance of paper, crushed toner is used because of good releasability from the photosensitive drum. As a result, the collectability during development is improved. Therefore, for example, if it is necessary to rotate the photosensitive drum several revolutions in order to recover the untransferred pulverized toner, it can be confirmed that when the polymerized toner is used, it can be recovered in one to two revolutions. It was Therefore, when the apparatus is restarted, a DC voltage or an alternating bias with a weakened amplitude is applied to collect untransferred residual toner in the developing device 4, and the cleaning time on the photosensitive drum is shortened to start a normal image forming process. It becomes possible.

<Modifications, etc.> 1) The present invention is not limited to the apparatus configurations of the first and second embodiments, and in an image forming apparatus in which a developing device also serves as a cleaner means, for example, as a contact charging member, a conductive material is used. A charging roller using a conductive rubber or a conductive sponge, a charging device configured not to rotate even with a magnetic brush or a fur brush, and the like are possible, and can be applied to all contact type charging devices.

2) As for the photoconductor as the image bearing member,
It is desirable to have a low resistance layer with a surface resistance of 10 ⁹ to 10 ¹⁴ Ω · cm from the viewpoint of preventing charge generation and ozone generation. However, even for organic photoreceptors other than the above, contact charger contamination prevention is also possible. With respect to, a sufficient effect can be obtained.

3) Further, the image exposing means as the information writing means for the charged surface of the image carrier is limited to the laser scanning exposing means for forming a digital latent image as shown in the embodiment. Instead of ordinary analog image exposure or other light emitting element such as LED, a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter can form an electrostatic latent image corresponding to image information. It doesn't matter if it is a thing.

Further, the image carrier may be an electrostatic recording dielectric or the like. In this case, after the primary surface of the dielectric surface is uniformly charged to a predetermined polarity and potential, the target electrostatic latent image is written and formed by selectively neutralizing with a neutralizing means such as a neutralizing needle head or an electron gun.

4) As for the developing method, only the two-component developing method has been described in the embodiment, but other developing methods are also effective. Preferably, the one-component contact development or the two-component contact development, in which the developer is developed in contact with the image bearing member, is effective in further enhancing the simultaneous toner recovery effect during development.

When the polymerized toner is used as the toner particles in the developer as in the third embodiment, the above-mentioned 1 is used.
A sufficient toner recovery effect can be obtained not only in the component contact development and the two component contact development but also in other development methods such as the one component non-contact development and the two component non-contact development.

Of course, the regular developing method may be used.

5) As the transfer method, not only the roller transfer shown in the embodiment, but also blade transfer and other contact transfer charging methods, and further, a transfer drum, a transfer belt, an intermediate transfer member, or the like can be used. It goes without saying that it is applicable not only to image formation but also to an image forming apparatus that forms a multicolor or full-color image by multiple transfer or the like.

6) As the waveform of the alternating voltage applied to the contact charging member and the developing means, a sine wave, a rectangular wave, a triangular wave or the like can be appropriately used. Further, it may be a rectangular wave formed by periodically turning on / off the DC power supply. As described above, a bias whose voltage value periodically changes can be used as the waveform of the alternating voltage.

7) The contact charging member may be provided in a process cartridge which is detachable from the main body of the image forming apparatus together with at least the image carrier.

8) Further, the electrophotographic photosensitive member as the image bearing member or the electrostatic recording dielectric member is made into a rotating belt type, and charging / charging
A toner image corresponding to the required image information is formed by means of the latent image forming / developing process, the toner image forming section is positioned on the reading display section for image display, and after the display, the toner image is transferred to a transfer material. There is also an image display device in which the image carrier is repeatedly removed from the surface of the image carrier without being used, and the image carrier is repeatedly used for forming a display image. The present invention is also effective in the case where a toner image after display is removed by cleaning with developing means at the same time as developing in such an image display device to form a cleanerless system device.

[0128]

As described above, according to the present invention, the image forming apparatus of the cleanerless system in which the contact charging type charging means is used as the charging means of the image bearing member and the developing means simultaneously cleans the developing or Even when a large amount of untransferred toner reaches the contact charging member such as when the device is restarted when the operation of the device is interrupted due to paper jam during transfer, the toner is discharged from the contact charging member and collected by the developing unit. It can be effectively carried out, and it is possible to prevent toner contamination of the contact charging member and maintain a good charged state for a long time, and there is no charging failure or deterioration of output image quality due to toner contamination of the contact charging member. Therefore, it is possible to realize a practical cleanerless system image forming apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cleanerless image forming apparatus according to a first embodiment.

FIG. 2 is a schematic diagram of a laser scanner unit.

FIG. 3 is a graph of applied alternating voltage and charging potential in the fur brush charger.

FIG. 4 is a structural model diagram of a developing device.

FIG. 5 is a schematic diagram illustrating a force or movement applied to untransferred toner on a photosensitive drum when a DC voltage is applied to a fur brush charger.

FIG. 6 is a schematic diagram illustrating a force or movement applied to untransferred toner on a photosensitive drum when an alternating voltage superposition bias is applied to a fur brush charger.

FIG. 7 is a schematic diagram illustrating a force or movement applied to untransferred toner on a photosensitive drum when a DC voltage is applied to a magnetic brush charger.

FIG. 8 is a schematic diagram illustrating a force or movement applied to untransferred toner on a photosensitive drum when an alternating voltage superimposed bias is applied to a magnetic brush charger.

FIG. 9 is a graph of applied alternating voltage and charging potential in a magnetic brush charger.

FIG. 10 is a schematic diagram of a conventional image forming apparatus.

[Explanation of symbols]

A printer body B image reading device 1 image carrier (photosensitive drum) 3, 31 and 32 charging means (corona charger, fur brush charger, magnetic brush charger) 4 developing means (two-component magnetic brush developing device) 5 cleaner 7 ・ 71 Transfer means (transfer corona charger, transfer roller)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location G03G 21/10 G03G 21/00 312 (72) Inventor Ryo Inoue 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 Canon Inc.

Claims (13)

[Claims] 1. A process of charging the image carrier with respect to the image carrier, an information writing process of forming an electrostatic latent image on the charged surface, and developing the electrostatic latent image as a toner image with a developer. The image carrier is an image forming apparatus for repeatedly performing image formation by applying an image forming process having steps, and the charging means for charging the image carrier is configured such that the charging member changes the charging member to the image carrier. It is a contact charging means for contacting and applying a voltage, the developing means for developing the electrostatic latent image also serves as an image carrier cleaning means for collecting the residual toner particles on the image carrier, and is applied to the contact charging member. The voltage to be applied must be a voltage obtained by superimposing an alternating voltage on a DC voltage at least during image formation, and contact charging should be performed when the device is restarted when the device operation is interrupted due to a paper jam during development or transfer Regarding the above-mentioned applied voltage to the material, stop the superposition of the alternating voltage with respect to the DC voltage, or restart the device with a certain period of time for superposing the alternating voltage with a weaker amplitude than the applied alternating voltage during image formation An image forming apparatus characterized in that: 2. The image forming apparatus according to claim 1, wherein when the voltage is applied to the contact charging member, the voltage is applied to the developing means for developing the electrostatic latent image. 3. When the apparatus is activated, the superposition of the alternating voltage with respect to the DC voltage with respect to the applied voltage to the contact charging member is stopped, or the superposition of the alternating voltage with a weaker amplitude than the applied alternating voltage at the time of image formation is performed. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided with a fixed time. 4. The contact charging member is a brush member made of a conductive fiber, and the conductive fiber brush portion is in contact with the image carrier, according to any one of claims 1 to 3. Image forming device. 5. The contact charging member is a magnetic particle magnetic brush member, and the magnetic particle magnetic brush portion is in contact with the image carrier.
An image forming apparatus according to any one of the preceding claims. 6. The image bearing member has a surface resistance of 10 ⁹ to 10 ^14.
The image forming apparatus according to claim 1, further comprising a low resistance layer having an Ω · cm. 7. The developing device is a contact developing system in which an electrostatic latent image is developed with a developer in contact with an image carrier. The image forming apparatus according to item 1. 8. The image forming apparatus according to claim 1, wherein the developer contained in the developing means is a developer composed of toner particles and magnetic particles. 9. The image forming apparatus according to claim 1, wherein the toner particles in the developer accommodated in the developing means are toners produced by a polymerization method. 10. The image forming apparatus according to claim 1, wherein the image bearing member is an electrophotographic photosensitive member. 11. The image writing means for forming an electrostatic latent image on the charged surface of the image carrier is image exposing means for the image carrier, according to claim 1. Image forming apparatus. 12. The image forming apparatus according to claim 1, wherein the toner image formed on the image carrier is transferred to a transfer material by a transfer unit. 13. The image forming apparatus according to claim 1, wherein the contact charging member is provided on the image forming apparatus main body together with at least the image carrier in a detachable process cartridge. .