JP3444323B2 - Contact charging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device used in an image forming apparatus such as a printer, a video printer, a facsimile, a copying machine, and a display. More specifically, it relates to a charging member to which a voltage is applied from the outside. The present invention relates to a contact charging device that charges or neutralizes an object to be charged by contacting the object to be charged.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 4-291374 discloses a contact charging device for charging or discharging a charged body by pressing a driven electrically conductive hollow body (tube) externally applied to the charged body to follow it. A gazette is proposed.

In the contact charging device disclosed in the above publication, a hollow surface layer is formed around a metal cored bar with a flexible material so as to have a roller shape. Alternatively, a tube member externally fitted to the conductive support member is included as a component, the conductive support member is brought into contact with the charged body through the tube member, and the tube member is driven to rotate as the charged body rotates. It is a thing.

[0004]

The contact charging device disclosed in the above publication has the following problems.

First, as the charging principle in the contact charging, there are a charging method and a discharging method in a minute gap. Generally, charging is performed based on the latter principle. Therefore, in order to make the charging potential uniform, it is important in contact charging to stably and uniformly maintain the shape of the minute voids. However, according to the configuration disclosed in the above publication, since the conductive hollow body is held by the thin disk at the end thereof, when the conductive hollow body is bent in the radial direction, the thin disk at the end is circular. In-plane bending and plane bending are simultaneously performed while the circumference is constrained. As a result, the deformation in the vicinity of the end of the conductive hollow body becomes unstable and the shape of the minute void becomes unstable, so that the charge distribution on the surface of the charged body becomes non-uniform. The same publication also discloses a structure in which a conductive hollow body is supported at its end by a radial elastic member. However, in this configuration, since the elastic member does not abut the entire inner surface of the hollow body, the deformed shape of the conductive hollow body differs between the place where the elastic member abuts and the place where the elastic member is separated. As a result, the shape of the minute voids changes at the circumferential pitch of the contact points of the elastic member, and the charging potential also changes at that cycle, causing periodic density unevenness in the image.

The present invention has been made in view of the above problems, and an object of the present invention is to bring a conductive tube into stable contact with an object to be charged, and
The object is to make the contacting force of the conductive tube against the charged body uniform and small. As a result, it is an object of the present invention to provide a contact charging device that can stably and uniformly charge an object to be charged.

[0007]

The present invention is a contact charging device characterized by the following constitution.

(1) In a contact charging device for charging or discharging a charged body by bringing the charged body into contact with the charged body to rotate the driven body, the charged body is composed of a conductive tube,
An elastic member made of an open-cell foaming member is interposed at both ends thereof, and the charging band is brought into contact with the member to be charged by a pressing unit, and the elastic member is in contact with the supporting member over the entire inner surface of the conductive tube. is doing.

(2) The charged body is pressed against the charged body by a position fixing preload method.

(3) The pressing means is a member for slidingly guiding the outer peripheral surface of the conductive tube.

(4) The pressing means comprises a shaft penetrating the inside of the conductive tube and its bearing.

(5) The conductive tube, the elastic body,
The contact interfaces between the shafts are fixed by press fit.

(6) The surface layer of the elastic body, which serves as the contact interface, is a solid layer, and the solid layer and the elastic body are the same.
To make the body .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings by taking a contact charging device used in an electrophotographic image forming apparatus as an example.

FIG. 1 is a schematic sectional view of a first embodiment of a charged body of a contact charging device according to the present invention. FIG. 2 is a side view. The conductive tube 1 is supported coaxially with the metal core 3 by the conductive elastic members 2 at both ends. The elastic member 2 is in contact with the entire inner surface of the conductive tube 1.

FIG. 3 is a side view showing a state in which the charging member shown in FIGS. 1 and 2 is brought into contact with the photosensitive member 4. The cored bar 3 is rotatably supported by a bearing (not shown), and the conductive tube 1 is brought into contact with the photoconductor 4 as a charged body so that the linear pressure is 50 g / cm or less. It is preferably 10 g / cm.

As will be described later in detail, as a typical structure of the present invention, the conductive tube 1 is a resin tube and the elastic member 2 is a foam member such as a so-called sponge. The conductive tube 1 itself is flexible with respect to radial deformation.
Further, since the elastic member 2 is also a so-called sponge, it can be configured flexibly, and the material itself is easily compressed and deformed in the radial direction, and the elastic member 2 is in contact with the entire inner surface of the conductive tube 1. The uneven or unstable deformation in the vicinity of the end of the conductive tube 1 as described above does not occur. As a result, the shape of the minute void for discharging for charging is always stable during the rotation of the conductive tube 1, and uniform charging is possible.

The method of holding the bearing for abutting against the photosensitive member 4 is roughly classified into a constant pressure preloading method using a pressure generating member such as a spring and a position fixing preloading method of fixing the position of the bearing. There are two types. The constant pressure preloading method is a general method when the roller-shaped parts are used in contact with each other. In the present invention, the conductive tube 1 itself is flexible with respect to radial deformation, and since the elastic member 2 is made of a foam material such as so-called sponge, this can also be configured flexibly. Being flexible means that the spring constant is small, and the load fluctuation due to displacement can be made small. Therefore, in the configuration shown in the present invention, the conductive tube 1 and the elastic member 2 can absorb the dimensional variation due to the component accuracy and the assembly accuracy, and can contact the charged body with a substantially uniform low load. Therefore, even if the position fixing preloading method is used, a good contact state can be realized, and this method is advantageous from the viewpoints of improving the assembling property and reducing the cost because the parts can be simplified.

Electrically, the conductive tube 1 and the core metal 3 are electrically connected by the conductive elastic member 2, so that an electrode (not shown) is brought into contact with the core metal 3 or a bearing (not shown) is made of a conductive material. A voltage or current required for charging can be applied to the conductive tube 1 by configuring it. A material obtained by foaming conductive rubber is suitable for the elastic member, and EPDM, urethane rubber, silicone rubber, or the like can be used, but the material is not limited to these.

The outer diameter of the elastic member 2 must be equal to or larger than the inner diameter of the conductive tube 1. The optimum diameter difference depends on the hardness of the member and the required crushing amount, but it is from 1 mm to 5 mm.
mm is suitable. Further, the fitting between the core metal 3 and the elastic member 2 is set so as not to move in the axial direction of the elastic member during use so that electrical conduction can be obtained. However, even if any fitting portion does not have a fixing means such as adhesion or welding. It can exert its function.

Here, it is desirable to determine the material of the conductive tube 1 so as to satisfy the following characteristics. 1) A substance that contaminates the photoconductor drum should not exude to the abutting surface of the tube on the photoconductor drum. 2) Strain is unlikely to remain after compression and release.

Taking these into consideration, resins such as nylon resin, polyester resin, polycarbonate resin, polyimide resin and the like, and rubber such as urethane rubber are particularly desirable.

The resistance value of the conductive tube is 10 ⁵
It is desirable to be in the range of 10 ⁹ Ω. If the resistance value is within this range, an image defect will not occur even if a defect (pinhole) exists on the photosensitive drum. In addition, there is no charging delay. The range of the resistance value varies depending on the peripheral speed of the photosensitive drum, and the upper limit of the resistance value becomes smaller as the peripheral speed increases.

Further, if the surface roughness of the conductive tube 1 on the surface contacting the photosensitive drum is 5 μm or less in Rz, more preferably 2 μm or less, it is desirable because the microscopic charging uniformity is further improved. The conductive tube used in the present invention does not have a manufacturing obstacle for achieving such a surface roughness and can be easily realized. As one example of the contact charging device, a charging roller is used, but it is very difficult to process such a surface roughness with a rubber roller at low cost.

The conductive tube 1 is formed by a known method, for example,
It can be manufactured by a melt extrusion method or a casting method. In addition, surface treatment (roughening the surface, forming a surface layer, etc.) may be performed as necessary.

In this embodiment, the conductive tube 1 is
A conductive nylon tube molded by the melt extrusion method was used.

When a voltage (current) is supplied to the conductive tube 1, an electrostatic attraction force acts on the contact portion between the conductive tube 1 and the photosensitive member 4. By the force obtained by multiplying the electrostatic attraction force by the friction coefficient between the conductive tube 1 and the photoconductor 4, the conductive tube 1 is driven to rotate as the photoconductor 4 rotates. Here, the electrostatic attraction force is 2 of the potential difference between the conductive tube 1 and the photoconductor 4.
Proportional to the square. As is well known, when the potential of the conductive tube 1 is Va and the post-charge potential of the photoconductor 4 is Vx, Vx = Va-Vth (where Va> Vth). Here, Vth is a discharge start voltage. That is, the potential difference between the conductive tube 1 and the photoconductor 4 becomes the discharge start voltage Vth.

The potential difference of the discharge gap shown in FIG. 3 is Vth.
If so, the battery is discharged, but on the contrary, it is discharged and charged in a certain discharge gap. Therefore, it is desirable that the discharge gap is evenly distributed when viewed from the photosensitive body surface 4. In the present invention, since the flexible foam member is used to support both ends of the conductive tube 1, unstable or discontinuous deformation may occur at both ends of the conductive tube 1 which is a problem in the conventional example. It is possible to form a stable and uniform discharge gap.

In order to increase the vertical drag by using the electrostatic attraction force acting between the conductive tube 1 and the photosensitive member 4, the conductive tube 1 has a Young's modulus of 1000 (kg / m 2).
m ² ) or less, thickness 300 (μm) or less, diameter 7 to 20
(Mm), a flexible material is preferable.

FIG. 4 shows a second contact charging device according to the present invention.
FIG. 3 is a schematic cross-sectional view near the end surface of the charged body according to the example. Here, the difference from the first embodiment will be mainly described.

As shown in FIG. 4, the elastic member 2 has a chamfered portion in contact with the end face of the conductive tube 1. As described above, since the elastic member 2 is made of sponge, if the elastic member 2 is pushed into the conductive tube 1 insufficiently, the elastic member 2 will protrude from the end surface of the conductive tube 1 and the photosensitive member If it is sandwiched between the contacting parts with and, charging failure or abnormality will occur. However, by chamfering as in this embodiment, it is possible to prevent the elastic member 2 from protruding, which facilitates assembly and increases reliability. The chamfering amount is preferably set to be equal to or larger than the fit between the conductive tube 1 and the elastic member 2.

FIG. 5 shows a third embodiment of the contact charging device according to the present invention.
FIG. 3 is a schematic cross-sectional view near the end surface of the charged body according to the example. Here, the difference from the first embodiment will be mainly described.

As shown in FIG. 5, the elastic member 2 is inserted in a state in which it is pushed inward from the end surface of the conductive tube 1 by a predetermined amount in the axial direction. As described above, since the elastic member 2 is made of sponge, if the elastic member 2 is not pushed into the conductive tube 1 sufficiently, the elastic member 2 is pressed from the end surface of the conductive tube 1.
If the toner sticks out at the contact portion with the photoconductor, it will result in poor charging or abnormal charging. However, by pushing the elastic member 2 sufficiently into the inside as in this embodiment, the elastic member 2 can be prevented from protruding, and the assembly becomes easier and the reliability is increased.

FIG. 6 shows a contact charging device according to a fourth embodiment of the present invention.
FIG. 3 is a side view of the charged body according to the example of FIG. FIG. 7 is a schematic cross-sectional view near the end surface of the same charged body. Here, the difference from the first embodiment will be mainly described.

In FIGS. 6 and 7, the surface layer of the elastic member 2 is the solid layer 5, and the solid layer 5 is integrated with the elastic member 2. The outer diameter of the solid layer 5 is approximately the same as the inner diameter of the conductive tube 1. Solid layer 5
The thickness of 0.1 to 3 mm can be used, and 0.1 to 1 mm is preferable. The elastic member having such a structure can be easily manufactured by molding a non-foaming rubber material on the outer periphery of a foaming rubber raw material by a coaxial molding method and then vulcanizing and foaming.
A wide variety of rubber materials such as EPDEM, urethane rubber, and silicone rubber can be used as the material.

The operation and effect of this embodiment will be described. FIG. 8 is a side view when the charged body is brought into contact with the photoconductor 4 without providing the solid layer 5. FIG. 9 is a side view when the charged body according to the present embodiment is brought into contact with the photoconductor 4. Conductive tube 1
When the elastic member 2 and the elastic member 2 are deformed in the radial direction, the conductive tube 1
It deforms without changing its circumference. On the other hand, since the elastic member 2 is a foamed member, it is deformed so that only the portion that receives the force is compressed. As a result, as shown in FIG. 8, when the deformation amount is increased, a gap 6 is formed between the conductive tube 1 and the elastic member 2. As a result, the conductive tube 1 and the elastic member 2 rotate while repeating contact and separation. However, during the repetition, the contact positions before the separation do not contact again without complete displacement, so that when the displacement occurs in the axial direction, the conductive tube 1 is displaced in the axial direction. This is the conductive tube 1 and the elastic member 2 as described above.
This is due to the different deformation modes of. According to the present embodiment, the solid layer 5 is deformed while maintaining its peripheral length, and is of course integral with the elastic body 2 so that it will not be displaced with respect to the elastic body. As a result, the deformation modes of the conductive tube 1 and the solid layer 5 coincide with each other, so that they do not separate from each other and the conductive tube 1 does not shift in the axial direction.

FIG. 10 is a schematic sectional view of the vicinity of the end surface of the charged body of the fifth embodiment of the contact charging device according to the present invention. Here, the difference from the first embodiment will be mainly described.

In this embodiment, the elastic member 2 that contacts the core metal 3
The surface layer is a solid layer 7. The manufacturing method and material of such an elastic member 2 are the same as those described in the fourth embodiment. Since the solid layer 7 is much less likely to be deformed than the foamed member, by setting the inner diameter of the solid layer 7 and the outer diameter of the cored bar 3 to be a tight fit, a strong restraining force is generated between the two and elastic Since the member 2 and the cored bar 3 can be sufficiently fixed without being bonded, the stability of electrical conduction, the assembling workability, and the reliability during use are improved. If the charged body is no longer needed,
Since no adhesive is used, the workability of sorting by material is good. Of course, this embodiment can be used in combination with the other embodiments already described, and it is more preferable.

FIG. 11 is a schematic sectional view of the vicinity of the end surface of the charged body of the sixth embodiment of the contact charging device according to the present invention. Here, the difference from the first embodiment will be mainly described.

For the reason that the elastic member 2 supports the conductive tube 1, the outer diameter of the elastic member 2 must be equal to or larger than the inner diameter of the conductive tube 1. In this embodiment, both sides of the outer diameter ridge of the elastic member 2 are chamfered. By doing so, since the guide surface is formed by chamfering when the elastic member 2 is inserted into the conductive tube 1, it is easy to insert and the assemblability is improved. This embodiment can also be used in combination with other embodiments.

FIG. 12 is a schematic sectional view of a charged body of a seventh embodiment of the contact charging device according to the present invention. Here, the difference from the first embodiment will be mainly described.

In this embodiment, the elastic member 2 is also inserted near the center of the conductive tube 1 in the axial direction. The current path for charging is from the elastic members 2 at both ends to the conductive tube 1.
Since a current flows in the axial direction of, the length of the conductive tube 1 becomes longer, the charged potential of the photoconductor may become lower near the center due to the voltage drop due to the resistance of the conductive tube 1 itself. By inserting the elastic member 2 as a current path near the center as in the present embodiment, the above-mentioned problem can be avoided.

FIG. 13 is a schematic sectional view of an eighth embodiment of the contact charging device according to the present invention. FIG. 14 is a side view. Here, the difference from the first embodiment will be mainly described.

In this embodiment, the means for pressing the charged body against the photoconductor is different. The charged body is composed of only the conductive tube 1 and the elastic member 2. As shown in the figure, a guide 8 having a shape for guiding a part of the outer peripheral surface of both ends of the conductive tube 1 is used to press the photoconductor 4.

At this time, since the charging current is directly supplied from the guide 8 to the conductive tube 1, a conductive material having a low friction coefficient is required as the material of the guide 8. Specifically, conductive polyacetal, nylon, polypropylene, polyethylene, fluororesin and the like can be used, but are not limited thereto. The guide 8 restricts the movement of the conductive tube 1 in the radial direction and the axial direction. Moreover, the elastic member 2 does not need to be conductive. With such a structure, the core metal is not required and the cost can be reduced.

Further, the elastic member 2 is used for all the examples.
It is effective to improve the environmental stability of the contact charging device of the present invention by using as an open-cell foaming member. That is,
According to the present invention, since the space formed by the conductive tube 1, the elastic member 2, and the core metal 3 is a closed space, the conductive tube 1 may expand or contract due to changes in temperature or atmospheric pressure. However, since the air in the conductive tube 1 is communicated with the atmosphere by using the elastic member 2 as a foamed member having open cells, the shape of the conductive tube does not change in response to changes in temperature and atmospheric pressure, and as a result, charging also occurs. It will be good.

Further, the method of supplying an electric current to the conductive tube is not limited to this embodiment. For example, an electrode may be provided in contact with the conductive tube 1 and a voltage may be applied to it.

The structure of the conductive tube may be a multi-layer structure in which metal is vapor-deposited on the back surface. In this case, current (voltage) is applied from the electrode that contacts a part of the back surface of the conductive tube.
Can be supplied. Further, by making the conductive tube high in resistance and thin, it is possible to reduce the leak current flowing into the minute defects of the photoconductor 4 and prevent the occurrence of charging failure.

The present invention will be described in more detail below with reference to specific examples.

<Specific Example> The above-mentioned fifth embodiment (FIG. 10).
Based on the above, image formation was performed.

As the conductive tube 1, carbon black was added to adjust the resistance value to 107Ω, the diameter was 14 mm,
Thickness 100 μm, Young's modulus 110 kg / mm 2, length 2
A 30 mm nylon tube was prepared.

As the elastic member 2, an EPDM sponge having a solid surface and an inner diameter of 5 mm and an outer diameter of 15 mm was prepared. The rubber hardness was 30 degrees in Asker C.
As the core metal 3, a shaft made of stainless steel and having a diameter of 6 mm was used.

As the photosensitive member 4, a drum in which a function-separated negatively chargeable organic photoconductive layer was formed in a thickness of 20 μm on an aluminum tube having a diameter of 60 mm was used and rotated at a peripheral speed of 30 mm / sec. Then, a DC voltage of -1150 V was applied to the core metal 3 to charge the photosensitive drum. At this time, a surface potential meter was installed at a position 1 sec after charging, and the surface potential after charging was measured. The potential of the photoconductor 4 after charging is -600.
It was V.

Further, the contact charging device was mounted on a 600 DPI image forming apparatus to form a dot pattern (1 dot on, 3 dot off pattern) image on A4 size plain paper. The formed image was evaluated.

The surface potential showed a constant value without fluctuation. Further, since the dot pattern was uniform with no density unevenness, it was estimated from the print results that the surface potential unevenness was within ± 30V.

Further, no dot or line loss of the image was observed, and the toner was hardly attached to the non-image area.

Further, image formation was performed on 10,000 sheets of A4 size, and the scratches on the surface of the conductive tube 1 and the photosensitive member 4 were
Almost never. Then, the image quality after 10,000 sheets was as good as the initial one.

In the above embodiments, the application to the contact charging device for the photoconductor of the image forming apparatus has been described as an example, but the present invention is not limited to this, and functions by charging or discharging, including a transfer device and a discharging device. It can be applied to a wide range of devices and parts.

[0059]

As described above, according to the present invention, in the contact charging device for charging or discharging the charged body, the conductive tube to which a voltage is applied from the outside is driven to the charged body. Both ends of the tube are supported by a flexible elastic member such as a foaming member, and the elastic member makes contact with the entire circumference of the inner surface of the conductive tube at the supporting portion, so that the conductive tube can be stably contacted with the body to be charged. ,Also,
It has become possible to stably form the discharge gap between the conductive tube and the body to be charged. As a result, it has become possible to provide a contact charging device that can stably and uniformly charge an object to be charged.

According to the present invention, by using the conductive tube as the charging member, the surface roughness of the charging member surface can be easily smoothed, and the charging uniformity in a minute range can be improved. Further, the conductive tube itself is flexible with respect to radial deformation, and since the elastic member is made of a foam material such as so-called sponge, this can also be configured flexibly. Such flexibility means that the spring constant is small, and the load fluctuation due to the displacement can be reduced. Therefore, the conductive tube and the elastic member can absorb the dimensional variation due to the component precision and the assembly precision, and can contact the charged body with a substantially uniform low load. Therefore, even if the position fixing preloading method is used, a good contact state can be realized, and this method is advantageous from the viewpoints of improving the assembling property and reducing the cost because the parts can be simplified. Moreover, the environmental stability of the contact charging device can be improved by forming the elastic member as an open-cell foaming member. That is, since the space formed by the conductive tube, the elastic member, and the core metal is a closed space, the conductive tube may expand or contract due to changes in temperature or atmospheric pressure. Since the air and the atmosphere in the conductive tube communicate with each other by forming the member, the shape of the conductive tube does not change in response to changes in temperature and atmospheric pressure, and as a result, charging becomes good.

According to the present invention, the electrically conductive tube, the elastic member, the core metal and the like can be constructed as a charged body by press-fitting without using a strong joining method such as adhesion or welding. It has good properties, and it is now possible to easily separate materials by material when the charged body is no longer needed.

According to the present invention, the surface layer of the elastic member that abuts the conductive tube is made into a solid layer, and this solid layer is integrally formed with the elastic member, so that the conductive tube does not increase in parts and cost. It was possible to prevent the deviation.

According to the present invention, the surface layer of the elastic member that abuts against the core metal is made into a solid layer, and this solid layer is integrally formed with the elastic member, whereby the holding force of the elastic member to the core metal is increased and the assembly stability is improved. And the reliability of electrical continuity is also improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a charged body of a first embodiment of a contact charging device according to the present invention.

FIG. 2 is a side view of the charged body of the first embodiment of the contact charging device according to the present invention.

FIG. 3 is a side view in which the charged body of the first embodiment of the contact charging device according to the present invention is brought into contact with the photoconductor.

FIG. 4 is a schematic cross-sectional view in the vicinity of an end surface of a charged body of a second embodiment of the contact charging device according to the present invention.

FIG. 5 is a schematic sectional view of the vicinity of an end surface of a charged body of a third embodiment of the contact charging device according to the present invention.

FIG. 6 is a side view of a charged body of a fourth embodiment of the contact charging device according to the present invention.

FIG. 7 is a schematic cross-sectional view of the vicinity of an end surface of a charged body of a fourth embodiment of the contact charging device according to the present invention.

FIG. 8 is a side view in which the charged body of the first embodiment of the contact charging device according to the present invention is brought into contact with the photoconductor.

FIG. 9 is a side view of a contact charging device according to a fourth embodiment of the present invention in which a charging member is brought into contact with a photosensitive member.

FIG. 10 is a schematic cross-sectional view in the vicinity of an end surface of a charged body of a contact charging device according to a fifth exemplary embodiment of the present invention.

FIG. 11 is a schematic sectional view of the vicinity of an end surface of a charged body of a sixth embodiment of the contact charging device according to the present invention.

FIG. 12 is a schematic sectional view of a charged body of a seventh embodiment of the contact charging device according to the present invention.

FIG. 13 is a schematic sectional view of an eighth embodiment of the contact charging device according to the present invention.

FIG. 14 is a side view of an eighth embodiment of the contact charging device according to the present invention.

[Explanation of symbols]

1 ... Conductive tube 2 ... Elastic member 3 ... core 4 ... Photoreceptor 5 ... Solid layer 6 ... Clearance 7 ... Solid layer 8 ... Guide

Continuation of front page (56) Reference JP-A-3-171079 (JP, A) JP-A-5-265305 (JP, A) JP-A-7-43985 (JP, A) JP-A-4-256983 (JP , A) JP 3-100677 (JP, A) JP 6-43733 (JP, A) JP 7-43984 (JP, A) JP 6-123309 (JP, A) 5-36453 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (8)

(57) [Claims] 1. A contact charging device for charging or discharging a charged body by bringing the charged body into contact with the charged body and rotating the driven body in a driven manner. An elastic member made of a foamed member is intervened, and the charged body is brought into contact with the charged body by a pressing means, and the elastic member has the conductive portion at its supporting portion.
A contact charging device, which is in contact with the entire inner surface of a flexible tube . 2. The charged body is subjected to the position fixing preload method by the above-mentioned method.
The contact charging device according to claim 1, wherein the contact charging device is pressed against an object to be charged . 3. The contact charging device according to claim 1, wherein the pressing unit is a member that slides and guides the outer peripheral surface of the conductive tube. 4. The contact charging device according to claim 1, wherein the pressing unit includes a shaft that penetrates through the conductive tube and a bearing thereof. 5. The contact charging device according to claim 4, wherein the shaft is press-fitted into the elastic body. 6. The outer diameter of the elastic body is the inner diameter of the conductive tube.
The contact charging device according to claim 1 or 2 , wherein the diameter is set to be equal to or larger than the diameter, and the elastic body is press-fitted into the conductive tube. 7. The contact charging device according to claim 4, wherein a surface layer of an inner peripheral surface of the elastic body is a solid layer, and the solid layer is integrated with the elastic body . 8. The contact charging device according to claim 1, wherein the outer peripheral surface layer of the elastic body is a solid layer, and the solid layer is integrated with the elastic body .