JP2002258706A - Image forming device and cleaning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and a cleaning device which prevent the occurrence of insufficient cleaning and dirt in a machine to form images of high quality for a long period of time. SOLUTION: The image forming device is provided with a latent image carrier which is rotated and driven, an electrifier, a developing device, a transfer device, and a cleaning device. The electrifier and the transfer device face the latent image carrier and are arranged so as to extend in their axial directions. The cleaning device has a cleaning blade, a cleaning roll which is arranged so as to extend in the axial direction of the latent image carrier, and a bias voltage applying means, and the effective cleaning areas, effective transfer area, and effective electrification area of the cleaning device satisfy a prescribed relation in the axial direction of the latent image carrier. With respect to the cleaning device, a part corresponding to the effective electrification area in the breadthwise direction of the cleaning roll is made conductive, and a part placed on the outside of its both outside ends is made insulating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus and a cleaning device mounted on the image forming apparatus.

[0002]

2. Description of the Related Art As a cleaning method in an electrophotographic process, for example, a blade made of an elastic material is brought into contact with the surface of a latent image carrier to thereby remove residual toner such as untransferred toner and transfer residual toner on the latent image carrier. A blade cleaning method for removing is used. 2. Description of the Related Art In recent years, in an electrophotographic image forming apparatus, there has been a demand for a reduction in the particle size of toner particles from the viewpoint of high image quality. Is preferably used.

[0003] With the reduction in the size of toner particles,
Since the adhesive force between the toner particles and the latent image carrier increases, it becomes difficult to remove the residual toner on the latent image carrier. In particular, when a so-called polymerized toner manufactured by a polymerization method is used, the shape of the toner particles becomes nearly spherical, so that the toner particles roll on the latent image carrier and pass through the cleaning blade, a so-called “ There is a problem that a cleaning failure called “slippage” easily occurs, and it becomes more difficult to remove the residual toner on the latent image carrier.

[0004] In order to prevent the occurrence of such defective cleaning, a cleaning method using both mechanical cleaning with a cleaning blade and electrostatic cleaning is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-179675. I have. Specifically, a brush roller made of a conductive material and capable of applying a voltage is installed at a position upstream of the cleaning blade with respect to the moving direction of the latent image carrier. An appropriate bias voltage having a polarity opposite to that of the above residual toner is applied, and the cleaning performance is improved by a mechanical cleaning effect by a cleaning blade and an electrostatic cleaning effect by a brush roller. .

However, the toner used to visualize the latent image formed on the latent image carrier adheres over a wider area than the image forming area of the latent image carrier due to scattering from a developing device. Therefore, even in the above-described cleaning method, it is actually difficult to remove the toner on the latent image carrier scattered over a wide range. For such a problem,
By simply increasing the width of the brush roller to increase the cleaning area in the axial direction of the latent image carrier,
In the latent image carrier, the area charged by the brush roller in the opposite polarity to the polarity of the residual toner becomes too large, and in the area charged by the brush roller and not charged again by the charging device, the toner is deposited. This causes dirt and dielectric breakdown of the photosensitive layer of the latent image carrier, and as a result, dirt in the apparatus and poor cleaning tend to occur.
Such a problem becomes conspicuous when a reversal developing method, which is predominant in current digital machines and the like, is used.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made based on the above circumstances, and its object is to provide:
Provided is an image forming apparatus capable of reliably removing residual toner on a latent image carrier, preventing generation of stains in the apparatus, and forming a high-quality image for a long period of time. It is in. Another object of the present invention is to provide a cleaning device having high cleaning performance and not causing in-machine contamination of the mounted image forming apparatus.

[0007]

According to the present invention, there is provided an image forming apparatus comprising: a latent image carrier that is driven to rotate; and a latent image carrier that is arranged to face the latent image carrier and extend in the axial direction thereof. A developing device that visualizes the latent image on the latent image carrier using a toner, and a developing device that is arranged to extend in the axial direction opposite to the latent image carrier. A transfer device that transfers the toner image on the latent image carrier to the recording material in the transfer region, and a cleaning device that removes the toner on the latent image carrier that has passed through the transfer region,
The cleaning device includes a cleaning blade that contacts the surface of the latent image carrier, and a cleaning blade that contacts the surface of the latent image carrier at a position upstream of the cleaning blade with respect to the moving direction of the latent image carrier. A cleaning roller disposed so as to extend in the axial direction of the image carrier, and a bias voltage applying unit that applies a bias voltage to the cleaning roller; and in the axial direction of the latent image carrier,
Set the effective cleaning area by the cleaning roller to W
1. When the effective transfer area of the transfer device is W2 and the effective charge area of the charging device is W3, the following formulas (1) and (2) are satisfied.

[0008]

Equation (1) W2 <W1 Equation (2) | W3-W1 | ≦ 30 [mm]

In the image forming apparatus of the present invention, it is preferable that the bias voltage applying means in the cleaning device is a constant current power supply. Further, in the above image forming apparatus, the toner used for visualizing the latent image can be composed of toner particles having a volume average particle diameter of 8.5 μm or less obtained by a polymerization method, Further, the CV value of toner particles having a volume average particle size in the range of 2 to 32 μm can be 20% or less. Further, in the above-described image forming apparatus, the developing device may be configured to visualize the latent image formed on the latent image carrier by a reversal developing method.

An image forming apparatus according to the present invention comprises: a latent image carrier rotatably driven; and a charging device for charging the latent image carrier, which is disposed to face the latent image carrier and extend in the axial direction thereof. A developing device that visualizes the latent image on the latent image carrier using toner, and a developing device that is arranged to face the latent image carrier and extend in the axial direction thereof. A transfer device for transferring a toner image onto a recording material in a transfer region; and a cleaning device for removing toner on the latent image carrier that has passed through the transfer region, wherein the cleaning device includes a surface of the latent image carrier. A cleaning blade that contacts the surface of the latent image carrier at a position upstream of the cleaning blade with respect to the moving direction of the latent image carrier and extends in the axial direction of the latent image carrier. Cleaning row And a bias voltage applying means for applying a bias voltage to the cleaning roller. The cleaning roller has a portion located in a width direction thereof located outside a portion corresponding to an effective charging area by the charging device. It is insulative.

In the above image forming apparatus, it is preferable that the bias voltage applying means in the cleaning device is a constant current power supply. Further, in the above image forming apparatus, the toner used for visualizing the latent image can be composed of toner particles having a volume average particle diameter of 8.5 μm or less obtained by a polymerization method, Further, the developing device may be configured to visualize the latent image formed on the latent image carrier by a reversal developing method.

A cleaning device according to the present invention includes a cleaning blade that contacts a surface of a latent image carrier that is driven to rotate, and a latent image carrier at a position upstream of the cleaning blade in the moving direction of the latent image carrier. A cleaning roller disposed in contact with the surface of the latent image carrier and extending in the axial direction of the latent image carrier, and bias voltage applying means for applying a bias voltage to the cleaning roller. In the direction, the portion corresponding to the effective charging area where the surface of the latent image carrier is charged by the charging device is conductive, and the portion located outside both outer ends of the portion corresponding to the effective charging area. Is insulative.

[0013]

According to the image forming apparatus of the present invention, electrostatic cleaning by a cleaning roller is performed in addition to mechanical cleaning by a cleaning blade. The residual toner on the image carrier can be reliably removed,
Moreover, since the effective cleaning area W1 by the cleaning roller is set in a specific range, the removal electric field formed between the latent image carrier and the cleaning roller is reduced by a predetermined area with respect to the axial direction of the latent image carrier. As a result, it is possible to reliably prevent the occurrence of contamination in the apparatus due to toner adhesion and defective cleaning due to dielectric breakdown of the photosensitive layer of the latent image carrier.

According to the cleaning device of the present invention, in the width direction of the cleaning roller, the portion located outside both outer ends of the portion corresponding to the charged area of the latent image carrier is made insulative. Since the latent image carrier is not charged beyond the effective charging area by the cleaning roller, there is no occurrence of contamination inside the apparatus due to toner adhesion or cleaning failure due to dielectric breakdown of the latent image carrier. A cleaning effect is exhibited.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory view schematically showing the configuration of an example of the image forming apparatus of the present invention, and FIG.
FIG. 4 is an explanatory diagram showing an enlarged view of the cleaning device in FIG. In this image forming apparatus, a drum-shaped photosensitive member 10 as a latent image carrier that is driven to rotate,
A charging device 11 for uniformly charging the surface of the photoconductor 10, an exposure device 12 for exposing the surface of the photoreceptor 10 charged by the charging device 11 to form an electrostatic latent image, and an exposure device 12 formed by the exposure device 12 A developing device 13 for visualizing the electrostatic latent image using a developer containing toner, a transfer device 14 for transferring a toner image formed on the photoconductor 10 to a recording material in a transfer area, and a photoconductor The image forming apparatus includes a separating device 15 for separating a recording material that is in close contact with the photoconductor 10, and a cleaning device 20 for removing toner on the photoconductor 10 that has passed through the transfer area.
In FIG. 1, reference numeral 16 denotes a fixing device for fixing a toner image transferred to a recording material.

The photoreceptor 10 is made of an organic photoreceptor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate. In FIG. 1, it is arranged so as to extend in a direction perpendicular to the paper surface).

The charging device 11 is composed of, for example, a scorotron charger having a control grid and a discharge electrode, and is arranged so as to extend in the axial direction thereof (in FIG. 1, the direction perpendicular to the plane of FIG. 1) opposite to the photoreceptor 10. Have been.

The developing device 13 includes a developing sleeve 13A which is arranged to face the photoreceptor 10 via a developing area, and a DC developing bias having the same polarity as the charging polarity of the charging device 11 is provided on the developing sleeve 13A. Alternatively, a developing bias in which a DC voltage having the same polarity as the charging polarity of the charging device 11 is superimposed on the AC voltage is applied.
Is performed to cause the toner to adhere to the exposed area.

The transfer device 14 is composed of, for example, a corona charger, and is arranged so as to face the photoreceptor 10 and extend in the axial direction thereof.

The cleaning device 20 is made of an elastic material such as urethane rubber. The cleaning device 20 has a plate-shaped cleaning blade 21 whose leading edge is in contact with the surface of the photoreceptor 10 and extends in the axial direction thereof. A cleaning roller 22 which is in contact with the surface of the photoreceptor 10 at a position upstream of the blade 21 with respect to the moving direction of the photoreceptor 10 and extends in the axial direction thereof, and applies a bias voltage to the cleaning roller 22. Bias voltage applying means 23. In FIG. 2, 24
Is a scraper provided on the cleaning roller 22, whereby the toner on the cleaning roller 22 is collected and sent to the developing device 13 by a collection roller 25 arranged to extend to face the cleaning roller 22.

The cleaning blade 21 has a base end portion held by, for example, a fixed blade holder 26. The elasticity of the cleaning blade 21 itself makes the photoreceptor 10 substantially constant over the entire area in the axial direction. It is in a state of being pressed against by a load.

The contact load of the cleaning blade 21 on the photosensitive member 10 is preferably 0.1 to 30 g / cm, more preferably 1 to 25 g / cm. If the contact load is smaller than 0.1 g / cm, the cleaning power is insufficient, and the image is easily stained. On the other hand, when the contact load is larger than 30 g / cm, the abrasion of the photoreceptor 10 becomes large, and the image is easily blurred.
The contact load can be measured by pressing the leading edge of the cleaning blade 21 against the balance, or by electrically arranging a sensor such as a load cell at a contact position between the photosensitive member 10 and the leading edge of the cleaning blade 21. And the like.

The contact angle θ of the cleaning blade 21 to the photosensitive member 10 is preferably 0 to 40 °, and particularly preferably 0 to 25 °. Contact angle θ is 0
If it is smaller than °, the cleaning power is reduced, and image stains are likely to occur. On the other hand, the contact angle θ is 40 °
If it is larger, the so-called “blade turn-up” in which the leading edge of the cleaning blade 21 reverses following the photoconductor 10 easily occurs. Here, "Photoconductor 1
The contact angle θ with respect to the cleaning blade 2
The contact surface N1 of the cleaning blade 21 and the photoconductor 1 at a position P where the leading edge of the photoconductor 1 contacts the photoconductor 10
The angle formed by the tangent plane N2 of 0.

The JIS A hardness of the cleaning blade 21 is preferably 20 to 90 °, particularly preferably 60 to 80 °. When the JIS A hardness is less than 20 °, the cleaning blade 21 is too soft, and the blade is easily turned. Meanwhile, JIS
When the A hardness is more than 90 °, it is difficult to follow slight irregularities and foreign matters on the photoreceptor 10, and “slippage” of toner particles is likely to occur. Here, JIS
A hardness is measured based on JIS K-6253.

The thickness and free length of the cleaning blade 21 are not particularly limited as long as the contact load and contact angle θ of the cleaning blade 21 are within the above ranges. From the viewpoint of preventing the occurrence of turning over, the thickness of the cleaning blade 21 is 1 to
It is preferably 3 mm, more preferably 1.5 to
It is preferably 2.5 mm, and the free length is preferably 2 to 20 mm, more preferably 3 to 15 mm.
The “free length” is the length of a portion that is not restrained by the blade holder 26, that is, the length from the lower end surface of the blade holder 26 to the tip of the blade 21.
The width dimension of the cleaning blade 21 is preferably basically the same as the width dimension of the cleaning roller 22, which will be described later. However, due to mechanical design conditions, even if there is a difference of about 5 mm between both ends at each end. There is no practical problem.

The cleaning roller 22 is made of an elastic material from the viewpoint of obtaining a good contact state with the photoreceptor 10, and the material of the elastic material is a conventionally known rubber material such as silicone rubber or polyurethane. Alternatively, a foam or a foam coated with a resin or the like can be used. The cleaning roller 22 is conductive or semiconductive, and preferably has a surface resistance of 10 ² to 10 ¹⁰ Ωcm. If the surface resistance is smaller than 10 ² Ωcm, banding or the like due to electric discharge is likely to occur.
On the other hand, if it is larger than 10 ¹⁰ Ωcm, a potential difference required for removing the toner cannot be obtained, and cleaning failure tends to occur. Here, the surface resistance is determined by, for example, carbon,
Add conductive materials such as metals and conductive polymers,
It can be adjusted by introducing a polar group into the rubber-like polymer constituting the elastic material.

It is preferable that the cleaning roller 22 rotates so that the contact portion with the photosensitive member 10 moves in the same direction as the moving direction of the photosensitive member 10. When the contact portion with the photoreceptor 10 is rotated so as to move in the opposite direction, if excessive toner is present on the surface of the photoreceptor 10, the toner removed by the cleaning roller 22 is spilled and the recording material is spilled. Or soil the equipment. Further, it is preferable that the linear velocity ratio (Vr / Vp) between the linear velocity (Vr) of the cleaning roller 22 and the linear velocity (Vp) of the photoconductor 10 is 0.5 to 2. If the linear velocity ratio is smaller than 0.5, the cleaning power is reduced, and image stains are likely to occur. On the other hand, when the linear velocity ratio is larger than 2, scratches and the like are likely to be generated on the surface of the photoconductor 10 when foreign matter or the like is sandwiched.

As described above, the cleaning roller 22
Is connected to a bias voltage applying means 23, and a bias voltage having a polarity opposite to that of the toner used for visualizing the electrostatic latent image on the photoreceptor 10, for example, when the toner is negatively charged. A current controlled by the control unit 27 is applied so that a positive bias voltage is applied to the cleaning roller 22. As a result, the toner is electrostatically attracted to the cleaning roller 22 and is removed from the photoconductor 10. Preferably, the bias voltage applying means 23 is a constant current power supply.

The current value applied to the cleaning roller 22 by the bias voltage applying means 23 varies depending on the thickness of the photosensitive layer of the photoconductor 10 and the surface resistance of the cleaning roller 22, but may be 1 to 50 μA in absolute value. preferable. If the current value is smaller than 1 μA, it becomes difficult to perform sufficient cleaning. On the other hand, when the current value is 50
When it is larger than μA, discharge or the like is likely to occur.
For example, the thickness of the photosensitive layer of the photoconductor 10 is 15 to 30 μm,
The surface resistance of the cleaning roller 22 is 10 ² to 10 ¹⁰ Ω
cm, the current value applied to the cleaning roller 22 is preferably 5 to 40 μA in absolute value.

In the image forming apparatus of the present invention, as shown in FIG.
When the effective cleaning area by the cleaning roller 22 is W1 and the effective transfer area by the transfer device 14 is W2, the effective cleaning area W1 is set to be larger than the effective transfer area W2. As a result, the toner scattered outside the effective transfer area W2 and adhered to the photoconductor 10 can be reliably removed by the cleaning roller 22. Here, the “effective cleaning area W1” refers to the width in the width direction of the photoconductor 10 where the removal electric field formed between the photoconductor 10 and the cleaning roller 22 effectively acts, and the “effective transfer area W2”. "Means a width in the width direction of the photoconductor 10 in which the discharge by the transfer device 14 effectively acts. When the transfer device 14 is of a contact type, the width of the transfer device that is actually in contact with the surface of the photoconductor 10 is the effective transfer area W2.

It is preferable that the effective cleaning area W1 is larger than the effective transfer area W2 by at least 3 mm or more, preferably 7 mm or more at each of both ends. As a result, the toner scattered over a wide range in the width direction of the photoconductor 10 can be removed. On the other hand, when the effective transfer area W2 is equal to or larger than the effective cleaning area W1, the toner scattered outside the effective transfer area W2 and adhered to the photoreceptor 10 cannot be removed, and contamination to the band electrodes and the optical system can be prevented. And image defects such as fog and white stripes occur.

When the effective charging area by the charging device 11 in the width direction of the photoreceptor 10 is W3, the absolute value | W3-W1 | ≦ 30 of the difference between the effective charging area W3 and the effective cleaning area W1 is satisfied. You. Thereby, a predetermined area can be reliably recharged by the charging device 11, and
It is possible to reliably prevent poor cleaning due to dielectric breakdown of the photosensitive layer of the photoreceptor 10 and occurrence of contamination inside the apparatus due to toner adhesion. Here, the “effective charging area W3” refers to a width in which the discharge by the charging device 11 in the width direction of the photoconductor 10 effectively acts. When the charging device 11 is of a contact type, the width of the charging device that actually contacts the surface of the photoconductor 10 is the effective charging area W3.

An example of a dimension example in the above-described image forming apparatus is as follows.
2 is 300 mm, the effective cleaning area W1
Is set to 306 mm or more, which is larger than the effective transfer area W2 by at least 3 mm at both ends thereof, and when the effective cleaning area W1 is 306 mm,
The effective charging area W3 of the charging device 11 is 276 to 336.
mm. In practice, the cleaning roller 22
In order to make the oppositely charged area (W4 in FIG. 3), which is an area charged by the charging device 11 and not recharged by the charging device 11, extremely small, the effective charged area W3 has a size very close to the effective cleaning area W1, Alternatively, it is preferably set to be equal to or more than the effective cleaning area W1.

The operation of the above-described image forming apparatus will be described. The surface of the photoreceptor 10 that is rotationally driven is
The surface of the photoreceptor 10 is selectively irradiated with light by the exposure device 12 so that the potential of the irradiated portion (exposed area) is reduced to form a document image. A corresponding electrostatic latent image is formed. The surface of the developing sleeve 13A constituting the developing device 13 also has the same polarity (for example, negative polarity) as the surface potential of the photoconductor 10 due to a developing bias applied from a power supply (not shown).
The developer containing the toner charged to the same polarity (for example, negative polarity) as the surface potential of the developing sleeve 13A is transported to the developing area. The surface potential [Vh] in the non-exposed area of the photoconductor 10, the surface potential [Vl] in the exposed area of the photoconductor 10, and the surface potential [Vd] of the developing sleeve 13A have the same polarity, The value is [Vh]>[Vd]> [Vl]. Therefore, in the developing area, the toner on the developing sleeve 13A adheres to the exposed area of the photoconductor 10 and the reversal development is performed. The toner image formed on the photoconductor 10 is transferred to a recording material by a transfer device 14, and the recording material on which the toner image has been transferred is separated from the surface of the photoconductor 10 by a separation device 15, A fixing process is performed.

On the other hand, a bias voltage corresponding to the magnitude of the current controlled by the control device 27 is applied to the cleaning roller 22 constituting the cleaning device 20 by the bias voltage applying means, whereby the photosensitive member which has passed through the transfer area is exposed. The polarity of the residual toner on the body 10 is charged to the opposite polarity (for example, positive polarity), and most of the residual toner on the photoconductor 10 is electrostatically removed. Then, the cleaning roller 22
After the residual toner that has passed through is mechanically removed by the cleaning blade 21, the photosensitive member 10 is
, And the above operation is repeated as necessary. The collected residual toner is sent to the developing device 13 by the collection roller 25 and reused.

According to the above-described image forming apparatus, electrostatic cleaning by the cleaning roller 22 is performed in addition to mechanical cleaning by the cleaning blade 21, so that a high cleaning effect is basically obtained. The cleaning roller 2 can be reliably used to remove the residual toner on the photoconductor 10.
Since the second effective cleaning area W1 is set in a specific range, the removal electric field formed between the photoconductor 10 and the cleaning roller 22 can act on a predetermined area in the width direction of the photoconductor 10. As a result, it is possible to reliably prevent the occurrence of contamination inside the apparatus due to toner adhesion and cleaning failure due to dielectric breakdown of the photosensitive layer of the photoconductor 10.

More specifically, since the effective cleaning area W1 is larger than the effective transfer area W2 by the transfer device 14, the toner scattered outside the effective transfer area W2 in the width direction of the photoreceptor 10 and adhered thereto can be prevented. As a result, the toner can be reliably removed, and the effective cleaning area W1 is | W3-
W1 | ≦ 30 is an area charged by the cleaning roller 22 in the photoconductor 10,
An area that is not recharged by the charging device 11, that is, an oppositely charged area that is charged to a polarity opposite to that of the toner can be made extremely small. As a result, toner adheres and accumulates in the oppositely charged area, The layer can be prevented from causing dielectric breakdown, whereby high cleaning performance can be maintained over a long period of time, and a high-quality image can be formed.

When the bias voltage applying means 23 in the cleaning device 20 is a constant current power supply,
There always occurs a potential difference between the surface of the cleaning roller 22 and the surface of the photoreceptor 10 for flowing a constant current, and this potential difference is generated in a state where it is always constant according to the surface potential of the photoreceptor 10. Therefore, as compared with the case where a constant voltage power supply is used, it is possible to reliably prevent the occurrence of unevenness and poor cleaning due to the potential level and polarity of the photoconductor 10.

In the image forming apparatus of the present invention, as shown in FIG. 4, the cleaning roller 30 constituting the cleaning device 20 has the conductive portion 3 in the width direction.
1 and an insulating portion 32 located outside both outer ends of the conductive portion 31. Specifically, the cleaning roller 30 has a portion corresponding to the effective charging area W3 of the charging device 11 made of a conductive or semi-conductive material, and has a portion outside the portion corresponding to the effective charging area W3. The extending portions are made of an insulating material, and the cleaning roller constituent materials having different surface resistances are electrically conductive portions 31.
In order to prevent the electric discharge from occurring, it is joined via, for example, an insulating buffer member 33.

The surface resistance of the insulating portion 32 is 10 ¹¹ Ωc
m or more, more preferably 10 ¹³ Ω
cm or more. Thereby, the cleaning roller 30
Can be reliably prevented from being discharged due to the current applied to the photoconductor 10 and the accumulation of charges on the photoconductor 10. The surface resistance is determined by installing a cleaning roller 30 on a conductive flat plate and applying a constant voltage (V) to the cleaning roller 30 to obtain a current value (I) obtained from the flat plate. And the contact width (W) between the flat plate and the cleaning roller 30 can be determined by (V / IW).

The length of the insulating portion 32 is preferably in the range of 2 to 80 mm, so that it is possible to reliably prevent the collected toner from blowing out to the photoconductor 10 and adhering to the photoconductor 10 again. can do.

According to the above-described image forming apparatus, the portions located outside both outer ends of the conductive portion 31 corresponding to the effective charging area W3 in the width direction of the cleaning roller 30 are insulative. On the surface of the photoreceptor 10, there is no formation of an oppositely charged area that is charged by the cleaning roller 30 and is not recharged by the charging device 11. That is, since the surface of the photoreceptor 10 is reliably recharged by the charging device 11, there is no occurrence of contamination inside the apparatus due to toner adhesion or cleaning failure due to dielectric breakdown of the photosensitive layer. Therefore, high cleaning performance is maintained for a long time. Thus, a high quality image can be formed. Further, since the insulating portion 32 is formed on the cleaning roller 30, the toner once collected is blown out again to the photoconductor 10 side, and
0 can be prevented from adhering.

As described above, according to the image forming apparatus of the present invention, in addition to the mechanical cleaning by the cleaning blade 21, the electrostatic cleaning by the cleaning roller 30 is executed. High cleaning performance can be stably exhibited over a long period of time without increasing the contact load of the cleaning blade 21. Therefore, with a conventional cleaning device, the contact load of the cleaning blade 21 can be increased. This is extremely effective when an organic photoreceptor, which has been difficult to exhibit stable cleaning performance over a long period of time, is used as a latent image carrier.

Further, according to the present invention, even when a toner having a small particle diameter which is liable to cause a cleaning failure such as "slimming" or a polymerized toner having a nearly spherical shape manufactured by a polymerization method is used. Extremely effective. In particular,
What consists of toner particles having a volume average particle size of 8.5 μm or less, further 6.5 μm or less, a polymerized toner having a nearly spherical shape, or a volume average particle size of 2 to 32 μm
Even if toner having a CV value of the toner particles in the range of 20% or less is used, an appropriate removal electric field is applied to the toner by the cleaning roller 30, Can be reliably removed. Here, the “CV value” indicates the sharpness of the particle size distribution of the toner particles, and is obtained by the following equation.

[0045]

CV value = (standard deviation of particle diameter / arithmetic diameter) × 100 [%]

[0046]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. <Embodiment 1> According to the configuration of the image forming apparatus shown in FIG.
The photoreceptor, developing device, toner, cleaning roller, cleaning blade, etc. were set as follows.

(1) Photoreceptor The photoreceptor (10) has a drum-like shape in which a 25 μm-thick photosensitive layer made of polycarbonate containing a phthalocyanine pigment is formed on the outer peripheral surface of a drum-shaped metal base made of aluminum. Was used. (2) Charging device A scorotron charger was used as the charging device (11). The effective charging area (W3) of the charging device (11) is 3
18 mm. (3) Developing device The developing device (13) has a linear velocity of 370 mm / min.
A developing sleeve (13A) that is rotationally driven by a bias voltage having the same polarity as the surface potential of the photoconductor (10) is applied to the developing sleeve (13A), and reverse development is performed by a two-component developer. Using. The toner constituting the two-component developer is composed of toner particles having a volume average particle diameter of 6.5 μm manufactured by an emulsion polymerization method and has negative chargeability. (4) Cleaning Roller A cleaning roller (22) made of conductive urethane and having a surface resistance of 10 ⁴ Ωcm was used.
The effective cleaning area (W1) of the cleaning roller (22) is 320 mm. The cleaning roller (22) has a contact portion with the photoconductor (10) at the photoconductor (1).
0), and the linear velocity ratio (Vr / Vp) between the linear velocity (Vr) of the cleaning roller 22 and the linear velocity (Vp) of the photoconductor 10 is set to 1.1. Set. (5) Cleaning blade The cleaning blade (21) is made of urethane rubber and has a JIS A hardness of 70 ° and a thickness of 2.00 m.
m and a free length of 10 mm were used. The contact angle (θ) with respect to the photoreceptor (10) was set at 10 °, and the contact load was set at 20 g / cm. (6) Others The transfer device (14) has an effective transfer area (W2) of 300 m.
m was used.

In the above, the surface potential [Vh] of the photoconductor (10) in the non-exposed area is -750V, and the surface potential [Vl] of the photoconductor (10) in the exposed area is -100V.
A developing bias of -600 V was applied to the developing sleeve (13A). Also, the cleaning roller (2) is applied by bias voltage applying means (23) composed of a constant current power supply.
By applying +20 μA to 2), the surface potential becomes +
It was charged to 600 V.

Using the above image forming apparatus, 20
By performing a real-image test for printing all sheets, evaluation was made as to whether or not the inside of the apparatus had been stained and whether or not cleaning had occurred. The actual shooting test was carried out in a normal temperature and normal humidity environment (temperature 20 ° C., relative humidity 50%) from 0 to 100,000 sheets.
The printing was performed in a high-temperature and high-humidity environment (temperature: 30 ° C., relative humidity: 80%) from 0,000 to 200,000 sheets. Table 1 shows the results.

<Comparative Examples 1 to 3> According to Table 1, W
Except that 1, W2 and W3 were changed, the same actual shooting test as in Example 1 was performed. Table 1 shows the results.

[0051]

[Table 1]

As described above, according to the image forming apparatus of the present invention according to the first embodiment, it was confirmed that a high-quality image could be obtained for a long period of time without occurrence of cleaning failure and contamination in the apparatus. . On the other hand, in the image forming apparatuses according to Comparative Examples 1 to 3, in-machine dirt has occurred, and in Comparative Examples 1 and 2, strip-shaped cleaning failure has occurred. , Was found to be impractical.

<Embodiment 2> An insulating portion (32) protruding outward from both outer ends of the conductive portion (31) corresponding to the effective charging area W3 of the charging device (11) is formed by 10 mm. An image forming apparatus similar to that of the first embodiment is configured except that the cleaning roller (30) is used and the effective charging area W3 of the charging device (11) is set to 302 mm.
A real-photo test was performed to print 200,000 sheets under the conditions shown below, and evaluation was performed to determine whether or not the inside of the machine and the occurrence of cleaning failure were found. It was confirmed that a high image was formed.

In the actual test, up to 100,000 sheets were printed in a normal temperature and normal humidity environment (temperature: 20 ° C., relative humidity: 50%), and from 100,000 sheets to 150,000 sheets were printed in a low-temperature, low-humidity environment (temperature: 10 ° C., relative humidity) 20%), 150,000 to 200,000 sheets were printed in a high-temperature, high-humidity environment (temperature: 30 ° C., relative humidity: 80%).

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. (1) The charging device may be of either a non-contact type or a contact type, and may be constituted by, for example, a roller to which a voltage can be applied. In this case, the effective charging area is It is the width that is actually in contact with the surface of the photoconductor. (2) The cleaning blade is supported in the cleaning device by a rotatable blade that is rotatable around an axis parallel to the rotation axis of the photoconductor and applies a constant pressing force to the cleaning blade by a spring or gravity. It is also possible to use a holder. (3) To remove the toner and the like transferred to the cleaning roller, a roller or a brush can be used in addition to the scraper. (4) The toner used in the present invention can be used for both a one-component developer and a two-component developer.
Further, it can be used as either a magnetic toner or a non-magnetic toner. Further, the developing method of the latent image is not limited to the reversal developing method. (5) The insulating portion of the cleaning roller can have various configurations. For example, the entire roller is formed of the same conductive / semiconductive material, and the portion corresponding to the effective charging area by the charging device is formed. It is also possible to adopt a configuration in which a portion located outside of both outer ends is covered with an insulating coating or a tube.

[0056]

According to the image forming apparatus of the present invention, in addition to the mechanical cleaning by the cleaning blade,
Since the electrostatic cleaning is performed by the cleaning roller, basically, a high cleaning effect is exhibited, the residual toner on the latent image carrier can be reliably removed, and the effective cleaning area W1 by the cleaning roller is reduced. Since it is set to a specific range, the removal electric field formed between the latent image carrier and the cleaning roller can act on a predetermined region in the axial direction of the latent image carrier, and as a result, toner Occurrence of cleaning failure due to in-machine contamination and dielectric breakdown of the photosensitive layer of the latent image carrier is reliably prevented, and a high-quality image can be stably formed over a long period of time.

According to the image forming apparatus of the present invention, since the bias voltage applying means is a constant current power supply, a constant current always flows between the surface of the cleaning roller and the surface of the latent image carrier. And the potential difference of
Since this potential difference always occurs in a state that is constant according to the surface potential of the latent image carrier, compared to the case where a constant voltage power supply is used, unevenness due to the potential level and polarity of the latent image carrier and cleaning failure are reduced. Occurrence can be reliably prevented.

Further, according to the image forming apparatus of the present invention,
In the width direction of the cleaning roller, since the portions located outside both outer ends of the portion corresponding to the effective charging area are insulative, on the surface of the latent image carrier,
Since a reverse charging area which is not charged by the charging device and is not recharged by the charging device is not formed, no cleaning failure due to contamination inside the apparatus due to toner adhesion or dielectric breakdown of the photosensitive layer occurs, Therefore, high cleaning performance is maintained over a long period, and an image with high image quality can be formed. Also,
By forming the insulating portion on the cleaning roller, it is possible to reliably prevent the toner once collected from blowing out toward the latent image carrier and adhering to the latent image carrier again.

According to the cleaning device of the present invention, in the width direction of the cleaning roller, a portion located outside both outer ends of a portion corresponding to the charged area of the latent image carrier is insulative. Since the latent image carrier is not charged beyond the effective charging area by the cleaning roller, there is no occurrence of contamination inside the apparatus due to toner adhesion or cleaning failure due to dielectric breakdown of the latent image carrier. A cleaning effect can be exhibited.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of an example of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing an enlarged configuration of a cleaning device in FIG. 1;

FIG. 3 is an explanatory perspective view showing an example of a relationship among three members, an effective cleaning area by a cleaning roller, an effective transfer area by a transfer device, and an effective charging area by a charging device.

FIG. 4 is an explanatory diagram showing another configuration example of the cleaning roller.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor 11 charging device 12 exposing device 13 developing device 13A developing sleeve 14 transfer device 15 separating device 16 fixing device 20 cleaning device 21 cleaning blade 22 cleaning roller 23 bias voltage applying means 24 scraper 25 recovery roller 26 blade holder 27 control means 30 Cleaning roller 31 Conductive part 32 Insulating part 33 Buffer member W1 Effective cleaning area W2 Effective transfer area W3 Effective charging area W4 Reverse charging area

Claims (10)

[Claims] 1. A latent image carrier that is driven to rotate, and is arranged to face the latent image carrier and extend in the axial direction thereof.
A charging device for charging the latent image carrier, a developing device for visualizing the latent image on the latent image carrier using toner, and a device facing the latent image carrier and extending in the axial direction thereof. A transfer device that transfers the toner image on the latent image carrier to a recording material in a transfer area, and a cleaning device that removes the toner on the latent image carrier that has passed through the transfer area. The apparatus includes a cleaning blade that contacts the surface of the latent image carrier, and a cleaning blade that contacts the surface of the latent image carrier at a position upstream of the cleaning blade with respect to the moving direction of the latent image carrier. A cleaning roller disposed to extend in the axial direction of the carrier; and a bias voltage applying unit for applying a bias voltage to the cleaning roller. When the effective cleaning area by the ning roller is W1, the effective transfer area by the transfer device is W2, and the effective charging area by the charging device is W3, the following formulas (1) and (2) are satisfied. apparatus. Equation (1) W2 <W1 Equation (2) | W3-W1 | ≦ 30 [mm] 2. A cleaning apparatus according to claim 1, wherein said bias voltage applying means is a constant current power supply.
4. The image forming apparatus according to claim 1. 3. A toner used for visualizing a latent image,
The image forming apparatus according to claim 1, wherein the image forming apparatus comprises toner particles having a volume average particle diameter of 8.5 μm or less obtained by a polymerization method. 4. A toner used for visualizing a latent image,
4. The image forming apparatus according to claim 1, wherein the CV value of the toner particles having a volume average particle size in a range of 2 to 32 [mu] m is 20% or less. 5. The developing device according to claim 1, wherein the developing device visualizes the latent image formed on the latent image carrier by a reversal developing method. Image forming apparatus. 6. A latent image carrier that is driven to rotate, and is arranged to face the latent image carrier and extend in the axial direction thereof.
A charging device for charging the latent image carrier, a developing device for visualizing the latent image on the latent image carrier using toner, and a device facing the latent image carrier and extending in the axial direction thereof. A transfer device that transfers the toner image on the latent image carrier to a recording material in a transfer area, and a cleaning device that removes the toner on the latent image carrier that has passed through the transfer area. The apparatus includes a cleaning blade that contacts the surface of the latent image carrier, and a cleaning blade that contacts the surface of the latent image carrier at a position upstream of the cleaning blade with respect to the moving direction of the latent image carrier. A cleaning roller disposed so as to extend in the axial direction of the carrier; and a bias voltage applying unit configured to apply a bias voltage to the cleaning roller. Oite, the image forming apparatus portion located outward from the portion corresponding to the effective charging area by the charging device is characterized in that insulating. 7. The cleaning device according to claim 6, wherein the bias voltage applying means is a constant current power supply.
4. The image forming apparatus according to claim 1. 8. A toner used for visualizing a latent image,
The image forming apparatus according to claim 6, wherein the image forming apparatus comprises toner particles having a volume average particle diameter of 8.5 μm or less obtained by a polymerization method. 9. The developing device according to claim 6, wherein the developing device visualizes the latent image formed on the latent image carrier by a reversal developing method. Image forming apparatus. 10. A cleaning blade in contact with the surface of a rotationally driven latent image carrier, and a cleaning blade in contact with the surface of the latent image carrier at a position upstream of the cleaning blade in the moving direction of the latent image carrier. A cleaning roller disposed so as to extend in the axial direction of the latent image carrier, and a bias voltage applying unit for applying a bias voltage to the cleaning roller. The portion corresponding to the effective charging area where the surface of the image carrier is charged by the charging device is conductive, and the portion located outside both outer ends of the portion corresponding to the effective charging area is insulating. A cleaning device, comprising: