JPH06175465A - Contact electrifying device - Google Patents

Abstract

PURPOSE:To provide a contact electrifying device which can satisfactorily electrify a member to be electrified such as a photosensitive drum without no electrifying noise and which can prevent leakage of current at each end part of an electrifying member having a flexible tube or the like being in con tact with the member to be electrified when a electrifying voltage is applied to the electrifying member. CONSTITUTION:In an electrifying roller 30 in which a core 11 formed thereon with conductive foamed sponge layers in parts near to both ends of the core 11, is located in a tube 31 constituting an electrifying part so that the tube 31 is supported by the sponge layer, the length A of an inner conductive layer 31a of the tube 31 is set to be shorter than the length B of a resistance layer 31b thereof. Accordingly, when a charge voltage is applied to the electrifying roller 30 through the intermediary of the core 11 so as to charge a photosensitive drum 1, leakage of current from the conductive layer 31a to the photosensitive drum 1 at both ends of the electrifying roller 30 can be prevented, and accordingly, the charge by the electrifying roller 30 using the tube 31 can be carried out with no leakage while preventing electrifying noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device for charging a charged member by applying a voltage to a charging member brought into contact with the charged member, and more particularly to a charging device having an improved charging member.

[0002]

2. Description of the Related Art As a method of charging an object to be charged, a voltage having a direct current voltage and an alternating voltage superimposed thereon is externally applied to a charging member made of a conductive member, and the charging member is brought into contact with the object to be charged. The present applicant has proposed a contact charging method for charging (see JP-A-3-174562).

In this method, for example, as shown in FIG. 8, a charging roller 10 as a charging member is brought into contact with the photosensitive drum 1, and an AC voltage Vac having a peak voltage Vpp that is at least twice the charging start voltage is applied to the charging roller 10. By applying a voltage (Vac + Vdc) that is a superposition of the DC voltage Vdc and the DC voltage Vdc, the photosensitive drum 1 can be uniformly charged.

The charging roller 10 includes a metal cored bar 11 and a charging section 12 made of a rubber material such as carbon-dispersed EPDM.
The charging roller 1 is provided through the electrode member 3 in which the above voltage is brought into contact with the core metal 11 by the external power source 4.
Applied to zero.

The photosensitive drum 1 is rotating as shown by an arrow, and after being uniformly charged by the charging roller 10, image information is written by the laser beam 5 to form an electrostatic latent image. The electrostatic latent image is developed by a developing device (not shown) having a developing sleeve 6 to be visualized as a toner image, and the toner image is transferred onto the transfer material 7 supplied between the photosensitive drum 1 and the transfer roller 8. , An image can be obtained on the transfer material.
After the transfer, the photosensitive drum 1 is prepared for the next image formation after cleaning and removing the residual toner by the cleaning blade 9 which is brought into contact with the photosensitive drum 1.

However, as a result of the research conducted by the present inventors,
When contact charging is performed using the charging device having the charging roller 10 as described above, there are the following problems. That is, the charging roller 10 and the photosensitive drum 1 vibrate due to the AC component Vac of the charging voltage applied to the electrode member 3 of the charging roller 10, and a vibration sound called "charging sound" is generated.

The mechanism of generation of this charging sound will be described with reference to FIGS. In FIG. 9, 1a is the photosensitive drum 1.
The aluminum base layer 1b is a photosensitive layer formed thereon, and the base layer 1a is grounded. Photosensitive drum 1 is 4
It is rotating at a speed of 0 mm / sec.

Since a voltage obtained by superimposing an AC voltage on the charging roller 10 is applied, the AC electric field causes the charging roller 10 to contact the charging unit 12 side at a certain moment, as shown in FIG. 9A. Positive charges induce negative charges on the base layer 1a side of the photosensitive drum 1. Since these charges attract each other, a force acts on the surface of the charging portion 12 in the direction of the arrow B in the figure, and is attracted to the photosensitive drum 1 to the outside from the position indicated by the solid line to the position indicated by the alternate long and short dash line. Deform. A force also acts on the photosensitive drum 1 in the direction of arrow C, but since the photosensitive drum 1 is a rigid body, it moves in the direction C without being deformed.

Next, when the polarity of the AC component begins to reverse,
As the direction of the alternating electric field reverses, the charging roller 1
Positive charge of the charging unit 12 of 0, the base layer 1a of the photosensitive drum 1
Of negative charges of the opposite polarity begin to be canceled by the induced opposite charges, and when the polarity of the AC component changes from just positive to negative, the positive charges on the charging unit 12 and the negative charges on the base layer 1a disappear. To do. As a result, the surface of the charging unit 12 is, as shown in FIG.
The position of the one-dot chain line returns to the original position of the solid line, and the photosensitive drum 1 attracted to the charging roller 10 also moves due to the elastic force of the charging roller 10 in the direction of arrow D.

Furthermore, the negative peak of the AC component is reached,
When the direction of the alternating electric field is completely reversed, FIG.
As shown in FIG. 5, the charging portion 12 of the charging roller 10 is negatively charged, and the base layer 1a of the photosensitive drum 1 is positively charged.

Therefore, the force applied to the charging section 12 and the photosensitive drum 1 becomes exactly the same as that shown in FIG. 9A, and each of them moves in the same direction as that shown in FIG. 9A.

That is, in the vicinity of the peak value of the voltage applied to the charging roller 10, the charging roller 10 and the photosensitive drum 1 are attracted to each other as shown in FIG. The drum 1 moves in the C direction, but near the inflection point in the AC component of the applied voltage,
As shown in FIG. 10B, since the charging roller 10 and the photosensitive drum 1 do not exert a pulling force on each other, the charging roller 10 and the photosensitive drum 1 are separated from each other by the restoring force against the deformation of the surface of the charging roller 10. When a voltage in which an AC voltage is superimposed is applied to the charging roller 10, such a phenomenon is repeated, and as a result, "charging noise" is considered to occur.

Generally, the frequency of the AC component is f, and the charging unit 1
Assuming that the vibration frequency of 2 is F, as is clear from the above description, the charging unit 12 vibrates twice during one cycle of the AC component, and therefore both can be described as follows.

2f (Hz) = F (c / s)

[0015]

Therefore, in order to reduce the above-mentioned charging noise, the inventors of the present invention have filed Japanese Patent Application No. 3-568.
No. 59 proposed that the inside of the charging roller be hollow.

That is, as shown in FIG. 11, the charging roller 2
No. 0 has a hollow flexible tube 21 forming a charging portion, and inside the tube 21, a cored bar 11 around which a conductive foam sponge layer 22 having bubbles 22a is formed is arranged. It is formed in a structure having a hollow interior.

According to the charging roller 20 described above, the charging roller 20 and the photosensitive drum 1 are attracted to each other near the peak value of the voltage applied to the cored bar 11, but the charging roller 20 is flexible so that it is large. Deform. Further, in the vicinity of the inflection point of the AC component of the applied voltage, as shown in FIG. 11 (b), the charging roller 20 is not deformed because the forces do not act on each other. When a voltage in which an AC voltage is superimposed is applied to the charging roller 20, such a phenomenon is repeated, but when attention is paid to the distance t between the core metal 11 which is the center of gravity of the charging roller 20 and the photosensitive drum 1, the charging roller 20 is Because of its flexibility,
Even when changing from 1 (a) to FIG. 11 (b), the restoring force of the charging roller 20 does not have a force to move the photosensitive drum 1 and works only to restore the deformation of the charging roller 20, and the center of gravity of the charging roller 20 The distance t between the cored bar 11 and the surface of the photosensitive drum 1 does not always change and is constant. Therefore, the phenomenon here is only the deformation of the charging roller 20.
Also, there is no vibration of the photosensitive drum 1, and as a result, the charging noise is reduced.

The charging roller 10 of FIG. 10 and the charging roller 20 of FIG. 11 were used in an anechoic chamber to measure the charging sound when the photosensitive drum 1 was charged. The measurement is ISO 7779 6
It was performed according to the section. As a result, the conventional charging roller 10
When the charging roller 20 is used, the charging sound is 53.7 dB, whereas when the charging roller 20 is used, the charging sound is 43.6 dB.
I was able to lower it.

However, the flexible tube 21 constituting the charging portion has a two-layer structure in which the resistance layer 21b is formed on the conductive layer 21a, as shown in FIG. 12 which is a front view of the charging roller 20. Therefore, the end portion in the longitudinal direction of the charging roller 20 (the end portion in the same direction as the longitudinal direction of the photosensitive drum 1)
In the above, there is a drawback that a current leaks directly from the conductive layer 21a to the photosensitive drum 1 without passing through the resistance layer 21b and damages the photosensitive layer 1b of the photosensitive drum 1 to cause a defective image.

An object of the present invention is that when a charging voltage is applied to a charging member having a flexible tube or the like that is in contact with a member to be charged such as a photosensitive drum, current leakage may occur at the end of the charging member. It is another object of the present invention to provide a contact charging device capable of charging an object to be charged satisfactorily without generating a charging noise.

Another object of the present invention is to charge a charging member, which has a flexible tube in contact with an object to be charged such as a photosensitive drum, and a core metal is not provided in the tube, to charge the object to be charged. It is an object of the present invention to provide a contact charging device capable of satisfactorily applying a voltage with a simple mechanism to charge an object to be charged satisfactorily and without generating a charging sound.

[0022]

The above object is achieved by the contact charging device according to the present invention. In summary, the present invention provides a conductive flexible layer provided around a core in which a mandrel rotatably supported is disposed in a flexible tube having at least a conductive layer and a resistance layer outside thereof. The tube is supported from the inside by means of which the power source for charging the body to be charged with which the tube is in contact by applying a charging voltage to the tube is connected to the core metal, and in the same direction as the longitudinal direction of the tube. In the contact charging device, the conductive layer is shorter than the resistance layer.

According to the present invention, an endless flexible belt having at least a conductive layer and a resistance layer outside the conductive layer can be used instead of the tube. The belt is rotatably supported by a supporting member and an abutting member arranged inside the belt, and abuts on the member to be charged by the abutting member. A power source for applying a charging voltage to the belt is connected to the support. Instead of the above belt, it is also possible to use an endless flexible belt having at least a resistance layer. The belt is rotatably supported by an abutting member having a support and a conductive layer disposed inside the belt, and a power source for applying a charging voltage to the belt is connected to the abutting member for abutting the belt against a member to be charged. It In each case, the conductive layer is made shorter than the resistance layer in the same direction as the width direction of the belt.

Further, according to the present invention, a flexible tube having at least a conductive layer and a resistance layer outside thereof is inserted into a holding guide having one side opened, the tube being supported by the holding guide, and It is designed to come into contact with the body to be charged on the one side that is opened,
Then, the conductive layer is exposed in the vicinity of both ends of the tube, an electrode member having elasticity is brought into contact with the exposed conductive layer, and the charged body with which the tube is brought into contact is charged with a charging voltage to the tube. In the contact charging device, a power source that is charged by being applied is connected to the electrode member.

[0025]

【Example】

Embodiment 1 FIG. 1 is a sectional view showing a main part of an embodiment of the contact charging device of the present invention. As shown in FIG. 1, the contact charging device of this embodiment includes a charging roller 30 as a charging member, and the charging roller 30 has a hollow flexible tube 31 forming a charging portion, and a core inside the tube 31. A conductive foam sponge layer 2 in which gold 11 is provided, and bubbles 22a, which are conductive flexible layers, are provided around the entire length of the core metal 11 in the longitudinal direction.
2 is provided, and the flexible tube 31 is supported by the conductive sponge layer 22. An electrode member (not shown) is brought into contact with the core metal 11, and a power source (not shown) is connected to the electrode member.

The flexible tube 31 has a three-layer structure in which a resistance layer 31b is provided on an inner conductive layer 31a having a hollow portion inside, and a protective layer 31c is provided thereon.

The conductive layer 31a of the tube 31 is the resistance layer 3
It is an electrode layer for applying a uniform voltage to 1b, and its volume resistivity is adjusted to be conductive or semi-conductive, which is 10 ⁶ Ω · cm or less. As the material of the conductive layer 31a, a conductive resin, a resin in which conductive particles are dispersed in an insulating resin or a non-conductive resin, a rubber or an elastomer in which conductive particles are dispersed, or a semiconductive resin or conductive particles in this is used. A dispersed resin fat or the like can be used.

The resistance layer 31b is for charging the photosensitive drum 1 which is the member to be charged with which the tube 31 is in contact, and is formed so as to have a higher resistance than the conductive layer 31a. Its volume resistivity is adjusted to 10 ⁴ to 10 ¹² Ω · cm, preferably 10 ⁷ to 10 ¹⁰ Ω · cm. As the material of the resistance layer 31b, similarly to the above, a resin in which conductive particles are dispersed in a conductive resin, an insulating resin or a non-conductive resin, a rubber or elastomer in which conductive particles are dispersed, or a semi-conductive resin or this A resin or the like in which conductive particles are dispersed can be used.

The protective layer 31c is a layer for preventing adhesion of contaminants that may exude from the resistance layer 31b to the photosensitive drum 1. Although the protective layer 31c is not always necessary, when the contaminant leaks from the resistance layer 31b, the protective layer 31c can prevent the contaminant from adhering to the photosensitive drum 1 and the photosensitive drum 1 due to the contaminant. It is possible to prevent cracks and fusion of contaminants. The protective layer 31c is made of a material such as resin.

FIG. 2 is a side view showing the charging roller 30 with the protective layer 31c removed. In the present invention, as shown in FIG. 2, in the conductive layer 31a, the length A along the longitudinal direction of the charging roller 30 (the same direction as the longitudinal direction of the photosensitive drum 1) is calculated from the length B of the resistance layer 31b. Shorten the resistance layer 3
Both ends of the conductive layer 31a are located inside of both ends of 1b.

Therefore, according to the contact charging device of this embodiment,
In order to charge the photosensitive drum 1, when a charging voltage is applied to the charging roller 30 from an external power source through the core metal 11, the conductive layer 3 is formed at the longitudinal end of the charging roller 30.
It is possible to prevent the current from directly leaking from the photosensitive drum 1 to the photosensitive drum 1, and it is possible to charge the photosensitive drum 1 favorably and form an image.

Embodiment 2 FIG. 3 is a sectional view showing the main part of another embodiment of the contact charging device of the present invention. The contact charging device of this embodiment has an endless flexible charging belt 40 as a charging member. The charging belt 40 is wound around a pair of metal support shafts 41 arranged at intervals in the circumferential direction of the photosensitive drum 1 and an abutting member 42 arranged in a position close to the photosensitive drum 1 between them. ing.

At the time of charging the photosensitive drum 1, a charging voltage is applied to the charging belt 40 via the supporting shaft 41 by an external power source connected to the supporting shaft 41, and the charging member 40 is pressed by the contact member 42. The charging belt 40 is brought into contact with the photosensitive drum 1. In order to suppress the generation of charging noise of the contact member 42 during charging, the contact member 42 has a contact portion 42b made of a flexible foam material on the support member 42a.

Also in this embodiment, the charging belt 40 is
Similar to the tube 31 of Example 1 shown in FIGS. 1 and 2, the resistance layer 40b is formed on the endless conductive layer 40a which is the inner layer.
And a protective layer 40c is provided on the resistance layer 40b.

Similarly, the conductive layer 40a of the charging belt 40
Is conductive or semiconductive with a volume resistivity of 10 ⁶ Ω · cm or less, and the resistance layer 40 b has a volume resistivity of 10 ⁴ to 1
0 ¹² Ω · cm, preferably 10 ⁷ to 10 ¹⁰ Ω · cm, and the materials of the conductive layer 40 a and the resistance layer 40 b are
Conductive resin, resin in which conductive particles are dispersed in insulating resin or non-conductive resin, rubber or elastomer in which conductive particles are dispersed, or semi-conductive resin or resin fat in which conductive particles are dispersed therein is used. ing. A protective layer 40 for preventing contaminants from the resistance layer 40b from adhering to the photosensitive drum 1.
c is also made of a material such as resin as in the first embodiment.

According to the present embodiment, the conductive layer 40a of the charging belt 40 has a width direction (photosensitive drum) as shown in FIG. 4 which is a side view of the charging belt 40 with the protective layer 40c removed. Length A along the longitudinal direction of 1)
Is shorter than the length B of the resistance layer 40b.

Therefore, also in the contact charging device of this embodiment, when a charging voltage is applied to the charging belt 40 via the support shaft 41 in order to charge the photosensitive drum 1, the charging belt 40 is applied to the end portion in the width direction of the charging belt 40. The current can be prevented from directly leaking from the conductive layer 40a to the photosensitive drum 1, and the photosensitive drum 1 can be properly charged to form an image.

Embodiment 3 FIG. 5 is a sectional view showing the main part of still another embodiment of the contact charging device of the present invention. In the contact charging device of this embodiment, the inner resistance layer 40b and the protective layer 40 thereon are used as the charging member.
endless flexible charging belt 40A having a two-layer structure composed of
The charging belt 40A is wound around a pair of metal support shafts 41 and abutting members 42.

In this embodiment, since the charging belt 40A does not have a conductive layer, the support shaft 41 of the charging belt 40A is not used.
Instead, a voltage is applied to the abutting member 42 that abuts the charging belt 40A on the photosensitive drum 1. Therefore, the abutting member 42 has the abutting portion 42b made of a conductive material on the supporting member 42a. The contact portion 42b is formed so as to also serve as a conductive layer. Further, in order to suppress the generation of charging noise of the contact member 42 during charging, the contact portion 42b also needs to be formed of a flexible material. For this reason, in this embodiment, the contact portion 42b is formed using a conductive sponge.

The volume resistivity of the contact portion 42b is the same as that of the conductive layer 40b of the charging belt 40 of the second embodiment, and is 10 ⁶ Ω · cm or less. Charging belt 40
The resistance layer 40b of A has a volume resistivity of 1 as before.
Conductive or semi-conductive of 0 ⁶ Ω · cm or less, made of a resin in which conductive particles are dispersed in a conductive resin, an insulating resin or a non-conductive resin, and the protective layer 40c is made of a material such as resin. There is.

Also in this embodiment, as shown in FIG. 6 which is a side view of the charging belt 40A with the protective layer 40c removed, a conductive layer similar to the resistance layer 40b of the charging belt 40 of the second embodiment is used. Abutting portion 4 of the abutting member 42 serving as
2b has a length A in the longitudinal direction (the same direction as the longitudinal direction of the photosensitive drum 1) shorter than a length B in the width direction (the same direction as the longitudinal direction of the photosensitive drum 1) of the resistance layer 40b of the charging belt 40A. I am doing it.

Therefore, the charging belt 4 is connected via the contact member 42.
When a voltage is applied to 0A to charge the photosensitive drum 1, it is possible to prevent a current from directly leaking from the conductive contact portion 42b to the photosensitive drum 1 at the widthwise end of the charging belt 40A. 1 can be charged well and an image can be formed.

Embodiment 4 In this embodiment, an example of using the contact charging device according to the present invention in a process cartridge will be described. The process cartridge is shown in FIG.

As shown in FIG. 7, the process cartridge includes a contact charging device having the charging roller 30 of the first embodiment in the periphery of the photosensitive drum 1 in the cover 15 as a center.
A developing unit 16 including a developing sleeve 6 and an elastic blade 11, and a cleaning blade 9 are arranged, and the photosensitive drum 1 is a drum shutter 1 attached to a cover 15.
Protected by 3. A toner container 14 containing magnetic toner 14a is installed adjacent to the developing unit 16 and a toner reservoir 12 for collecting the toner collected by the cleaning blade 9 is provided above the toner container 14.

After the photosensitive drum 1 is uniformly charged by the charging roller 30, the laser beam 5 is irradiated from the outside of the cartridge through the passage between the toner reservoir 12 and the toner container 14 to form the photosensitive drum 1. The electrostatic latent image is developed by the developing unit 16 and visualized as a toner image.
The developing unit 16 carries the toner 14a conveyed from the toner container 14 on the developing sleeve 6 and conveys the toner 14a toward the developing portion facing the photosensitive drum 1 while regulating the toner layer having a uniform thickness by the elastic blade 11. The developing unit uses the toner to develop the electrostatic latent image on the photosensitive drum 1.

The toner image obtained by the development is transferred onto a transfer material (not shown) supplied to the photosensitive drum 1 by opening the drum shutter 13, and the untransferred toner on the photosensitive drum 1 is cleaned as described above. The blade 9 cleans and collects.

As shown in FIGS. 1 and 2, the tube 31 of the charging roller 30 is formed in a three-layer structure of a conductive layer 31a, a resistance layer 31b and a protective layer 31c.
The tube 31 is supported by the conductive foam sponge layer 22 formed around the cored bar 11 disposed in the tube 1. The length A of the conductive layer 31a of the tube 31 is the resistance layer 31.
It is made shorter than the length B of b.

A charging voltage is applied to the charging roller 30 through the core 11 of the charging roller 30, and the charging roller 30 causes the photosensitive drum 1 to move.
At the end of the charging roller 30 in the longitudinal direction during charging, current is prevented from directly leaking from the conductive layer 31a to the photosensitive drum 1. Therefore, according to the present embodiment, there is no charging noise of the charging roller 30. Thus, a very compact process cartridge can be achieved in which the photosensitive drum 1 can be satisfactorily charged and high-quality images can be obtained without the occurrence of current leakage at the ends.

As described above, according to the first to fourth embodiments, the tube having at least the conductive layer and the resistance layer outside the conductive layer, which is charged by contacting the charged body such as the photosensitive drum of the charging device, is provided. A charging member, or at least a charging member having a belt having a resistance layer, and a conductive layer separate from the charging layer is brought into contact with the charging member at the time of charging, the length of the conductive layer is shorter than the length of the resistance layer. Therefore, the charged body can be favorably charged without causing the charging noise of the charging member and the leakage of the electric current at the end portion.

Embodiment 5 FIGS. 13A and 13B are views showing the main part of still another embodiment of the contact charging device of the present invention, FIG. 13A being a sectional view and FIG. 13B being a side view. The contact charging device of this embodiment includes a charging roller 50 as a charging member, and the charging roller 50 has a hollow flexible tube 51 forming a charging portion.

In this embodiment, in order to prevent the charging roller 50 from generating a charging noise, a cored bar having a conductive foam sponge layer is disposed in a flexible tube 51 forming a charging portion to form a sponge layer. A major feature is that the core metal itself is eliminated in the tube 51 instead of supporting the tube 51 by. Therefore, as it is,
Since the tube 51 moves in the rotation direction of the photosensitive drum 1, the entire charging roller 50 is housed in a guide 59 having a U-shaped cross-section whose lower side is opened for the purpose of preventing the movement. In the charging roller 50, the tube 51 contacts the photosensitive drum 1 at the opening below the guide 59, and the charging roller 50 rotates following the rotation of the photosensitive drum 1.

The tube 51 has a two-layer structure in which a resistance layer 51b is provided on an annular conductive layer 51a having a hollow portion, and the conductive layer 51a has a volume resistivity of 10 ⁶ Ω. The resistance layer 51b has a volume resistivity of 10 ⁴ to 10 ¹² Ω · cm, preferably 10 ⁷ to 10 ¹⁰ Ω · cm. The conductive layer 51a and the resistance layer 51b are made of a conductive resin, an insulating resin or a non-conductive resin in which conductive particles are dispersed,
A rubber or elastomer in which conductive particles are dispersed, a semiconductive resin, or a resin fat in which conductive particles are dispersed therein is used.

According to this embodiment, in order to apply the charging voltage to the tube 51 of the charging roller 50, the resistance layer is formed at a position corresponding to the outside of the image forming portion 1'of the photosensitive drum 1 of the tube 51. 51b is shaved to expose the conductive layer 51a, and the exposed conductive layer 51a is brought into contact with the electrode member 58 attached to the inside of the upper surface of the guide 59.
In this example, the conductive layer 51a is also partially cut to have a small diameter, and the electrode member 58 is brought into contact with the reduced diameter conductive layer 51a.

The electrode member 58 has a substantially L shape as shown in FIGS. 13 (a) and 13 (b) in order to impart elasticity to itself.
It is formed in a smooth curved shape with a letter shape, and the vicinity of its tip is curved and contacts according to the curvature of the conductive layer 51a. The external power source 4 is connected to the electrode member 58. The tube 5 of the charging roller 50 for charging the photosensitive drum 1
1, the charging voltage from the external power source 4 via the electrode member 58 in contact with the conductive layer 51a, for example, 2.0 kVpp, 6
An AC bias of 00 Hz is applied.

As described above, in the present embodiment, the charging roller 50 exposes a part of the conductive layer 51a of the tube 51 in order to apply the charging voltage to the tube 51, and the electrode member 58 is applied to this. A voltage is applied in contact with each other.

If this is a conventional example using a hollow roller, as shown in FIGS. 14 (a) and 14 (b), the charging roller 6 is used.
Since the cored bar 11 having the conductive foam sponge layer 22 in the vicinity of both ends thereof is arranged in the flexible tube 61 composed of the conductive layer 61a of 0 and the resistance layer 61b thereon, Electrode member 6 also serving as a pressing member from above
8 is brought into contact with the core metal 11, and the tube 6 is inserted through the core metal 11.
1 can be applied with a charging voltage. However, generally speaking, the conductive foam sponge layer 22 is formed on the core metal 11, or the sponge layer 22 is inserted into the tube 61 so that The method of adhering to the periphery is expensive to manufacture.

According to the present embodiment, as described above, the charging voltage can be applied to the tube 51 without using the cored bar for the charging roller 50, and the photosensitive drum 1 can be charged only by the tube 51. Charging can be performed without producing noise. In addition, the manufacturing cost of the charging roller 50 can be reduced because the conductive foam sponge layer is not required to be formed unlike the case where the core metal is used.

Embodiment 6 FIG. 15 is a view showing still another main part of the contact charging device of the present invention, FIG. 15 (a) is a sectional view and FIG. 15 (b) is a side view. In the present embodiment, unlike the case of the embodiment 5 shown in FIG. 13, only the resistance layer 51b is shaved near the end of the flexible tube 51 forming the charging portion to expose the conductive layer 51a in a large diameter. A major feature is that the charging roller 50A is provided.

According to this embodiment, since the exposed conductive layer 51a and the photosensitive drum 1 are close to each other in the tube 51 of the charging roller 50A, the external power source is connected via the electrode member 58 which is brought into contact with the conductive layer 51a. When the charging voltage is applied from No. 4, there is a risk of leakage from the conductive layer 51a to the photosensitive drum 1. Therefore, the base layer of the corresponding portion 1c of the photosensitive drum 1 is shaved to reduce the diameter of the corresponding portion 1c, thereby making the distance between them the first and solving the problem of leakage.

According to the charging roller 50A in which only the resistance layer 51b of the tube 51 is shaved to form the conductive layer 51a with a large diameter as in the present embodiment, the strength is increased, so that the charging roller requires high strength. This is an effective measure in some cases.

Also in this embodiment, as in the case of the fifth embodiment, a charging voltage is applied to the tube 51 without using a cored bar for the charging roller 50A, and the photosensitive drum 1 is charged without producing a charging noise. In addition, the manufacturing cost of the charging roller 50A can be reduced because the conductive foam sponge layer is not required to be formed unlike the case where the core metal is used.

Embodiment 7 FIGS. 16A and 16B are views showing the main part of still another embodiment of the contact charging device of the present invention. FIG. 16A is a sectional view and FIG. 16B is a side view. In this embodiment, the fifth embodiment shown in FIG.
Similarly to the above, the resistance layer 51b and the conductive layer 51a are partially scraped near the end of the flexible tube 51 forming the charging section, and the charging roller 50B is provided in which the conductive layer 51a is exposed to a small diameter. The feature is that the diameter of the corresponding portion 1c of 1 is also reduced.

This is effective when the voltage applied to the charging roller 50B is relatively large and it is necessary to increase the distance between the conductive layer 51a of the tube 51 and the photosensitive layer on the surface of the photosensitive drum 1.

Also in this embodiment, as in the case of the fifth embodiment, the charging voltage is applied to the tube 51 without using the cored bar for the charging roller 50B, and the photosensitive drum 1 is charged without generating a charging sound. In addition, the manufacturing cost of the charging roller 50B can be reduced.

Embodiment 8 FIGS. 17A and 17B are views showing the main part of still another embodiment of the contact charging device of the present invention, FIG. 17A being a sectional view and FIG. 17B being a side view. In this embodiment, in the fifth embodiment of FIG. 13, an electrode member 58A formed in a substantially downward L shape is provided as an electrode member of the charging roller 50, and the electrode member 58 is provided.
One end of the L-shape of A is fixed to a nearby fixing member 55, the opening of the L-shape is brought into contact with the exposed conductive layer 50a of the tube 51 of the charging roller 50, and the tube 51 is moved in the rotation direction of the photosensitive drum 1. The feature is that it also serves as the guide 59 of FIG.

According to this embodiment, in addition to the same effects as the eighth embodiment, there is an advantage that the number of parts of the contact charging device can be reduced by one.

Embodiment 9 FIG. 18 is a sectional view showing a process cartridge provided with the contact charging device according to the present invention. This embodiment is characterized in that a contact charging device provided with the charging roller 50 of the embodiment 5 of FIG. 13 is used as a contact charging device in a process cartridge. Other configurations of the process cartridge are basically the same as those of the cartridge of the fourth embodiment of FIG. 7, and the same reference numerals as those in FIG. 18 denote the same members in FIG. In FIG. 18, reference numeral 7 is a transfer material that is supplied to the photosensitive drum by opening a shutter (not shown), and 8 is a transfer roller that transfers the toner image on the photosensitive drum 1 onto the supplied transfer material.

According to the present embodiment, since the contact charging device having the charging roller 50 of the fifth embodiment is used in the process cartridge, the charging noise at the time of charging the photosensitive drum 1 can be eliminated, and the process cartridge The problems of mass productivity and cost reduction, which are important factors, can be improved.

As described above, according to Examples 5 to 9, the tube having at least the conductive layer and the resistance layer outside the conductive layer, which is charged by contacting the charged body such as the photosensitive drum of the charging device, is provided. In the charging member, the charging voltage is applied to the charging member via the electrode member which exposes the conductive layer and is brought into contact with the conductive layer. It is possible to charge the body to be charged without the occurrence of the phenomenon and to reduce the cost of the charging member.

[0070]

As described above, according to the contact charging device of the present invention, when a charging voltage is applied to a charging member having a flexible tube or the like which is in contact with an object to be charged such as a photosensitive drum, the charging is performed. It is possible to charge the body to be charged satisfactorily and without generating a charging sound without causing current leakage at the end of the member.

According to another aspect of the contact charging device of the present invention, a charging member having a flexible tube in contact with an object to be charged such as a photosensitive drum and having no cored bar inside the tube is covered with the charging member. The charging voltage for charging the charged body can be satisfactorily applied by a simple mechanism to charge the charged body satisfactorily and without generating a charging noise.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of an embodiment of a contact charging device of the present invention.

FIG. 2 is a side view showing a state in which a protective layer of a charging roller provided in the contact charging device of FIG. 1 is peeled off.

FIG. 3 is a sectional view showing a main part of another embodiment of the contact charging device of the present invention.

FIG. 4 is a side view showing a state in which a protective layer of a charging belt provided in the contact charging device of FIG. 3 is peeled off.

FIG. 5 is a cross-sectional view showing a main part of still another embodiment of the contact charging device of the present invention.

FIG. 6 is a side view showing a state in which a protective layer of a charging belt provided in the contact charging device of FIG. 5 is peeled off.

FIG. 7 is a cross-sectional view showing a process cartridge provided with the contact charging device of the present invention.

FIG. 8 is a cross-sectional view schematically showing an image forming apparatus provided with a contact charging device having a conventional charging roller.

9 is an explanatory diagram showing a mechanism of generating a charging sound at the time of charging by the charging roller of FIG.

FIG. 10 is an explanatory diagram showing the deformation of the charging roller that occurs during the generation mechanism of FIG.

FIG. 11 is an explanatory diagram showing a mechanism of preventing generation of charging noise in a conventional hollow type charging roller that prevents charging noise.

12 is an enlarged front view showing the charging roller of FIG. 11. FIG.

FIG. 13 is a diagram showing a main part in still another embodiment of the contact charging device of the present invention.

FIG. 14 is a diagram showing another example of a contact charging device having a conventional charging roller.

FIG. 15 is a diagram showing a main part in still another embodiment of the contact charging device of the present invention.

FIG. 16 is a diagram showing a main part in still another embodiment of the contact charging device of the present invention.

FIG. 17 is a diagram showing a main part in still another embodiment of the contact charging device of the present invention.

FIG. 18 is a cross-sectional view showing a process cartridge including a contact charging device according to another embodiment of the present invention.

[Explanation of symbols]

 1 Photosensitive Drum 4 Power Supply 11 Core Bar 22 Conductive Foam Sponge Layer 30 Charging Roller 50, 50A, 50B Charging Roller 31a, 40a, 50a Conductive Layer 31b, 40b, 50b Resistive Layer 31c, 40c Protective Layer 40, 40A Charging Belt 41 Support Shaft 42 Contact member 42b Contact part 58, 58A Electrode member 59 Guide

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michihito Yamazaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazushige Sakurai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroki Kisu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A rotatably supported core metal is disposed in a flexible tube having at least a conductive layer and a resistance layer outside the conductive layer, and the conductive flexible layer is provided around the core metal to provide the conductive flexible layer. A tube is supported from the inside, and a power source for charging the charged body with which the tube is brought into contact by applying a charging voltage to the tube is connected to the core metal,
The contact charging device is characterized in that the conductive layer is shorter than the resistance layer in the same direction as the longitudinal direction of the tube. 2. An endless flexible belt having at least a conductive layer and a resistance layer outside thereof is rotatably supported by a support member and an abutting member disposed inside the belt, and the belt is abutted with the abutting member. A member is brought into contact with the member to be charged, and a power source for charging the member to be contacted with the belt by applying a charging voltage to the belt is connected to the support, and a width direction of the belt. The contact charging device, wherein the conductive layer is shorter than the resistance layer in the same direction. 3. An endless flexible belt having at least a resistance layer is rotatably supported by an abutment member having a support and a conductive layer disposed inside the belt, and the belt is abutted by the abutment member. A power source, which is in contact with the member to be charged and charges the belt by contacting the belt by applying a charging voltage to the belt, is connected to the contact member, and is the same as the width direction of the belt. The contact charging device is characterized in that a conductive layer of the abutting member is shorter than a resistance layer of the belt in a direction. 4. A flexible tube having at least a conductive layer and a resistance layer outside thereof is inserted into a holding guide which is open on one side, said tube being supported by said holding guide and said opening of said holding guide. The one side is to be contacted with the body to be charged, and the conductive layer is exposed near both ends of the tube,
An electrode member having elasticity is brought into contact with the exposed conductive layer, and a power source for charging the charged body with which the tube is brought into contact by applying a charging voltage to the tube is connected to the electrode member. A contact charging device characterized in that