JPH10247036A - Image forming device and processing cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely recover stuck contaminant from the surface of a photoreceptor drum to a developing sleeve by electrostatic force generated by a difference between the surface potential of the photoreceptor drum and developing bias by providing a charge imparting means imparting a charge to the stuck contaminant existing on the surface of a body to be electrified between a transferring means and an electrifying means. SOLUTION: DC voltage is applied to an elastic sheet 11 which is the charge imparting member or AC voltage is applied between the elastic sheet 11 and the photoreceptor drum 1 so that the stuck contaminant 10 such as residual toner left after transfer, whose polarity is inverted from a negative polarity to a positive polarity at the time of transferring and which remains on the surface of the photoreceptor drum 1 after transferring, may have the negative polarity. The stuck contaminant 10 such as the residual toner left after transfer electrified by a transferring part so as to have the positive polarity is changed so as to have the negative polarity by imparting the charge by the elastic sheet 11, and then, is electrified so as to have the same polarity as the photoreceptor drum 1 by the electrifying member 8 and is exposed. Thus, the positive polarity is surely changed to the negative polarity, so that the stuck contaminant 10 such as the residual toner left after transfer is surely recovered by a developing means 6 by a potential difference with the developing sleeve 2 and is reused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and a process cartridge.

[0002]

2. Description of the Related Art In a conventional image forming apparatus of this type, charging means for uniformly and uniformly charging the surface of a photosensitive drum as an image bearing member to be charged, and the surface of the photosensitive drum charged by the charging means Latent image forming means for forming an electrostatic latent image on the
Developing means for developing the electrostatic latent image to form a toner image;
Transfer means for transferring the toner image on the photosensitive drum to a transfer material, fixing means for fixing the toner image transferred on the transfer material to the transfer material, and toner remaining on the photosensitive drum surface after the transfer means. Cleaning means for cleaning.

In the above-described image forming apparatus, the toner remaining on the surface of the photosensitive drum after the transfer unit is collected by a cleaning unit, and the collected toner is stored in a waste container.

In recent years, there has been proposed a cleanerless process for realizing an extremely efficient image forming apparatus in which the cleaning means is omitted, the image forming apparatus is reduced in size, and maintenance such as disposal of toner is omitted. . In this cleanerless process, the toner is applied to the exposed portion of the photosensitive drum where the surface potential is attenuated by reversal development, and at the same time, the transfer residual toner and the like remaining in the non-exposed portion and adhered thinly are also attached. Collecting contaminants.

That is, the toner remaining on the surface of the photosensitive drum passes through the charging means, and is collected in the developing device by electrostatic force due to the difference between the charged surface potential of the photosensitive drum and the developing bias.

FIG. 5 is a configuration diagram showing a conventional image forming apparatus. In the figure, reference numeral 101 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier which is a member to be charged.
Is charged by a charging member 108 which is charging means connected to the charging member 108. Reference numeral 109 denotes a laser beam serving as an exposure unit. The surface potential of the portion of the photosensitive drum exposed to the laser beam attenuates, and image information is formed on the surface of the photosensitive drum as an electrostatic latent image. This electrostatic latent image is reversely developed by the developing sleeve 102 of the developing means 106. At this time, at the same time, the present image forming apparatus having no cleaning means removes the adhered contaminant 110, such as transfer residual toner, which is thinly adhered to the non-exposed portion to which the laser beam has not been irradiated. Is collected on the developing sleeve by electrostatic force due to the difference between the surface potential of the developing sleeve and the developing bias applied to the developing sleeve. A doctor blade 103 made of urethane rubber or the like whose base end is attached to the container of the developing means 106 is in elastic contact with the developing sleeve 102 so that the layer thickness of the toner on the surface of the developing sleeve is made a uniform predetermined value. .

The toner image developed by the toner is transferred to a transfer material 105 as an object to be charged, which is introduced from a paper supply unit (not shown) to a transfer unit between the photosensitive drum 101 and the transfer roller 104 at an appropriate timing. The transfer material 105 that has been transferred and passed through the transfer unit is separated from the photosensitive drum 101 and conveyed to an image fixing unit (not shown), and the transferred photosensitive drum 101 is repeatedly used for image formation.

[0008]

Since the conventional image forming apparatus is constructed as described above, the difference between the surface potential of the non-exposed portion of the charged photosensitive drum 101 and the developing bias applied to the developing sleeve 102 is obtained. In order to recover the toner to the developing sleeve by the electrostatic force, it is necessary to return the toner inverted to the positive polarity by the transfer to the original negative polarity. However, the charging member 10 is brought into contact with or close to the photosensitive drum 101.
In the method of charging by applying an oscillating voltage to the charging member 8, the charging uniformity is superior and the adhesion of the contaminants 110 such as transfer residual toner to the charging member 108 is reduced as compared with the case of applying only the direct current. The adhered contaminant 110 such as transfer residual toner that has been inverted to the positive electrode cannot be returned to the negative polarity, and remains in the dark portion potential portion with the attached contaminant 110 being inverted to the positive electrode. For this reason, the contaminant 110 attached to the positive electrode adheres to the surface of the photosensitive drum 101 charged to the negative electrode with a strong electrostatic absorption force, and the dark portion potential (−700 V) of the photosensitive drum 101 and the surface potential of the developing sleeve 102 (−500 V). With the electrostatic force caused by the potential difference of (2), there is a problem that the contaminant 110 of the positive polarity cannot be collected in the developing sleeve 102.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an electric charge is applied to an adhering contaminant such as a transfer residual toner by a charge applying member so that the adhering contaminant such as the transfer residual toner is provided. It is an object of the present invention to reliably recover the toner from the surface of the photosensitive drum to the developing sleeve by the electrostatic force caused by the difference between the surface potential of the photosensitive drum and the developing bias applied to the developing bias.

In addition, the structure is simplified by sharing the high-voltage power supply for the charge applying member and the high-voltage power supply for the charging means, and the durable and mechanical rubbing force is imparted to the charge applying member to collect adhered contaminants. The aim is to increase efficiency.

It is another object of the present invention to prevent a current leak to a photosensitive drum and to make the structure excellent in user-friendly handling.

[0012]

According to the first aspect of the present invention, there is provided an image forming apparatus comprising: charging means for charging a surface of an object to be charged in contact with or in proximity to an object to be charged; Latent image forming means for forming an electrostatic latent image, developing means for developing the electrostatic latent image on the surface of the member to be charged to form a toner image, transfer means for transferring the toner image to a transfer material, In an image forming apparatus having a fixing unit for fixing a transfer toner image on the transfer material, a charge applying unit for applying a charge to an adhering contaminant existing on the surface of the member to be charged is provided between the transfer unit and the charging unit. It is provided.

According to a second aspect of the present invention, an image forming apparatus applies an oscillating voltage applied to a charging unit to a charge applying member via a diode.

The charge applying means of the image forming apparatus according to the third aspect of the present invention uses an elastic sheet.

The charge applying means of the image forming apparatus according to the present invention uses an elastic roller.

According to a fifth aspect of the present invention, as the charge applying means of the image forming apparatus, a fur brush roller is used.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect of the invention, the electric charge applying means has a resistance of 10 ⁵ to 10 ⁹ Ω · cm.
Is used.

According to a seventh aspect of the present invention, there is provided a process cartridge comprising:
7. The image forming apparatus according to claim 1, wherein the charge applying unit is integrated with at least one of a charging unit, a member to be charged, and a developing unit. It can be freely attached.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

Embodiment 1 FIG. 1 shows an image forming apparatus using an electrophotographic process according to a first embodiment of the present invention.
Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier 1 which is a member to be charged;
The surface of the photosensitive drum 1 is uniformly charged by a charging member 8 serving as a charging unit. This charging is performed by applying a vibration voltage Vpp of 2 k between the photosensitive drum 1 and the charging member 8 from the power supply 81.
V, a superimposed voltage having a DC voltage of -720 V is applied, and the charging member 8 is brought into contact with or close to the photosensitive drum 1 to charge the photosensitive drum. In this case, the charging potential (dark portion potential)
Was -700V.

Reference numeral 9 denotes a laser beam serving as an exposure unit, whereby image information is formed on the photosensitive drum 1 as an electrostatic latent image, and the light portion irradiated with the laser beam has a potential of -150 V
Becomes This electrostatic latent image is developed (developing bias -500 V) by the developing sleeve 2 of the developing means 6 which is close to or in contact with the photosensitive drum 1, and a toner image is formed. in this case,
A doctor blade 4 made of urethane rubber or the like whose base end is attached to the developing sleeve container is in elastic contact with the developing sleeve 2 so that the thickness of the toner layer on the surface of the developing sleeve 2 is made uniform to a predetermined value of -7 μC / g. As the developer, a toner obtained by polymerizing and pulverizing a magnetic material or a non-magnetic material can be used.

After development, the formed toner image is transferred to a transfer material 5 introduced into a transfer portion between the photosensitive drum 1 and the transfer roller 4 at an appropriate timing from a paper feed portion (not shown), The transfer material 5 that has passed through the transfer unit is separated from the photosensitive drum 1 and transported to an image fixing unit (not shown), and the photosensitive drum 1 after transfer is repeatedly used for image formation.

In this case, as shown in FIG. 2, in order to make the adhered contaminants 10 such as untransferred toner remaining on the surface of the photosensitive drum even after the transfer from the negative electrode to the positive electrode during the transfer, have the negative polarity, as shown in FIG.
It is necessary to apply a DC voltage or an AC voltage between the elastic sheet 11 and the photosensitive drum 1 that is less than the discharge starting voltage (Vth) to the elastic sheet, which is a charge providing member having a resistance of 10 ⁵ to 10 ⁹ Ω · cm. .

In the illustrated example, an AC voltage higher than the discharge starting voltage Vth is applied to the elastic sheet 11 from the power supply 81 for applying a voltage to the charging member 8 via the diode 20 and the electrode plate 21. Wave rectification becomes an AC voltage lower than the discharge start voltage Vth. Therefore, the adhered contaminants 10 such as transfer residual toner charged to the positive polarity in the transfer portion 10
Is converted into a negative polarity by applying a charge by the elastic sheet 11. Thereafter, the adhered contaminants 10 such as transfer residual toner are charged by the charging member 8 to the same polarity as the photosensitive drum 1 and exposed.

The density of the contaminants 10 such as transfer residual toner for one round covering the surface of the photosensitive drum 1 is 0.1 mg / c.
The average particle size is 10 μm or less at m ² or less. Also, 60
The spot diameter of the laser beam 9 for realizing 0 DPI is 75 to 90 μm. According to the experiment, the density of the adhered contaminants 10 such as transfer residual toner for one round of the photosensitive drum is 0.2 m.
When it was not more than g / cm ² , there was no image disturbance due to light shielding. As a result, the image information is converted into an electrostatic latent image on the photosensitive drum 1.
Formed on top.

Next, the adhered contaminants 10 such as untransferred toner existing in the non-image area (dark area) are removed from the developing bias (−50).
0 V) and the potential difference between the dark portion potential (−700 V) and collected by the developing unit 6, and the electrostatic latent image is developed by the developing sleeve 2 of the developing unit 6. The adhered contaminants 10 such as the collected transfer residual toner are reused.

Thereafter, as described above, the developed toner image is transferred to the transfer material 5 at the transfer portion, the transferred transfer material 5 is fixed at the fixing portion, and the photosensitive drum 1 is repeatedly formed into an image. Provided.

As described above, according to the first embodiment, the charge applying member applies the charge to the adhered contaminant 10 such as the transfer residual toner, and the polarity is reliably converted from the positive electrode to the negative electrode. Adhered contaminants 10 such as transfer residual toner are reliably collected and reused by the developing means 6 due to a potential difference from the developing sleeve 2, thereby greatly increasing toner use efficiency.
In addition, a stable high-quality image can be obtained.

Embodiment 2 FIG. 3 shows an image forming apparatus using an electrophotographic process according to a second embodiment of the present invention.
In the figure, reference numeral 12 denotes an elastic roller which is a charge applying member having a resistance of 10 ⁵ to 10 ⁹ Ω · cm.
An AC voltage higher than the discharge start voltage Vth similar to that of the charging member 8 is applied to the power supply 2 via the diode 30 by the power supply 81, but is half-wave rectified by the diode 30 to become an AC voltage lower than the discharge start voltage Vth. Therefore, the contaminant 10 such as the transfer residual toner charged to the positive polarity in the transfer unit is charged by the elastic roller 12 that rotates following the photosensitive drum 1 and is surely converted to the negative polarity. Subsequent operations are the same as those in the first embodiment shown in FIG. 1, and therefore, the same portions are denoted by the same reference characters and description thereof will not be repeated.

As described above, according to the second embodiment, the polarity of the adhered contaminants 10 such as untransferred toner is ensured by using the elastic roller 12 that rotates following the photosensitive drum 1 as the charge applying member. The contaminants 10 such as transfer residual toner can be recovered by the developing means 6 due to the potential difference from the developing sleeve 2 and reused, thereby greatly increasing the toner use efficiency and stabilizing the toner. High quality images can be obtained. In addition, since the elastic drum serving as the charge applying member is driven to rotate with respect to the photosensitive drum 1, adhesion of the contaminants 10 such as transfer residual toner is reduced.

Embodiment 3 FIG. 4 shows an image forming apparatus using an electrophotographic process according to a third embodiment of the present invention.
In the drawing, reference numeral 13 denotes a fur brush roller 13 which is a charge applying member having a resistance of 10 ⁵ to 10 ⁹ Ω · cm, and the fur brush roller 13 has a discharge starting voltage Vth similar to that of the charging member 8 via a diode 40. The above AC voltage is applied by the power supply 81, but is half-wave rectified by the diode 40 to become an AC voltage lower than the discharge start voltage Vth.
Accordingly, the contaminant 10 such as the transfer residual toner charged to the positive polarity in the transfer portion is charged by the fur brush roller 13 rotating with a peripheral speed difference in the forward direction or the counter direction to the photosensitive drum 1, and the negative polarity is applied. Is converted to Subsequent operations are the same as those of the first embodiment shown in FIG. 1, and therefore, the same portions are denoted by the same reference characters and description thereof will not be repeated.

As described above, according to the third embodiment, the fur brush roller 1 rotates the charge applying member relative to the photosensitive drum 1 in a forward direction or a counter direction with a peripheral speed difference.
By setting the number to 3, adhesion contaminants such as transfer residual toner 10
Can be scraped off by a mechanical rubbing force. As a result, the chance of applying a charge increases, and the effect of applying a charge improves. Therefore, even if the amount of adhered contaminants 10 such as transfer residual toner increases unexpectedly, its polarity is surely converted, collected and reused by the developing means, and the toner use efficiency is greatly increased; A stable high-quality image can be obtained.

Embodiment 4 FIG. The charge applying unit 11 (12, 13) described in each of the above-described embodiments and at least one of the charging unit 8, the member to be charged 1, and the developing unit 6 are integrally accommodated.
It is detachably attached to the image forming apparatus main body,
A configuration that is excellent in user-friendly handling can be achieved.

[0034]

As described above, according to the first aspect of the present invention, since the charge applying member applies the charge to the adhered contaminant such as the toner remaining after transfer, the charge applying means and the object to be charged can be charged. Even if an oscillating voltage higher than the firing voltage is applied to
There is an effect that the polarity of the adhered contaminants such as the transfer residual toner is converted, and the collected contaminants can be reliably collected by the developing means and reused.

According to the second aspect of the present invention, since the oscillating voltage applied to the charging means is applied to the charge applying means via the diode, a high voltage applied to the charge applying means and the charging member is applied. There is an effect that the power supply can be shared.

According to the third aspect of the present invention, since the charge applying member is formed of an elastic sheet, the structure can be simplified and the cost can be reduced.

According to the fourth aspect of the present invention, since the charge applying member is constituted by the elastic roller, there is an effect that durability can be provided.

According to the fifth aspect of the present invention, since the charge applying member is constituted by the fur brush roller, contaminants such as transfer residual toner can be scraped off from the surface of the member by mechanical rubbing force. This has the effect of improving the charge imparting effect.

According to the sixth aspect of the present invention, since the charge applying member is configured to have a resistance of 10 ⁵ Ω · cm to 10 ⁹ Ω · cm, there is an effect that a current leak to the photosensitive drum as a member to be charged can be prevented. .

According to the seventh aspect of the present invention, at least one of the charging means, the charging means, the member to be charged, and the developing means is integrally accommodated, and is configured to be detachably attached to the image forming apparatus main body. There is an effect that the configuration can be made excellent in user-friendly handling.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a voltage applied to a charge providing member and a charge applied to an adhered contaminant such as a transfer residual toner.

FIG. 3 is a sectional view of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a sectional view of an image forming apparatus according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a conventional image forming apparatus.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (subject to be charged), 6 toner hopper (developing unit), 8 charging member (charging unit), 10 attached contaminants such as transfer residual toner, 11 elastic sheet, 12 elastic roller, 13 fur brush roller, 20, 30, 40 diodes.

Claims (7)

[Claims] A charging unit configured to charge a surface of the charged body in contact with or close to the charged body; a latent image forming unit configured to form an electrostatic latent image on the charged body surface; An image having developing means for developing a latent image on the surface to form a toner image, transferring means for transferring the toner image to a transfer material, and fixing means for fixing the transferred toner image on the transfer material The image forming apparatus according to claim 1, further comprising a charge applying means for applying a charge to the contaminant adhering to the surface of the member to be charged, between the transfer means and the charging means. 2. The image forming apparatus according to claim 1, wherein the oscillating voltage applied to the charging unit is applied to the charge applying member via a diode. 3. The image forming apparatus according to claim 1, wherein the charge applying unit is an elastic sheet. 4. The image forming apparatus according to claim 1, wherein the charge applying unit is an elastic roller. 5. The image forming apparatus according to claim 1, wherein the charge applying means is a fur brush roller. 6. The charge applying means has a resistance of 10 ⁵ to 10 ⁹ Ω.
The image forming apparatus according to any one of claims 1 to 5, wherein the image forming apparatus is (cm). 7. An image forming apparatus main body in which the charge applying means according to claim 1 and at least one of a charging means, a charged member, and a developing means are integrally accommodated. A process cartridge which is configured to be detachable from the process cartridge.