JP3402310B2 - Sliding member and photosensitive drum assembly - Google Patents

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 such as an electrophotographic copying machine, a laser printer, etc., and more particularly, an image forming apparatus provided with a charging device for charging a photosensitive member by contacting the photosensitive member. The present invention relates to a sliding contact member and a photosensitive drum assembly that are components of the apparatus.

[0002]

2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses have been widely used. This electrophotographic image forming apparatus normally has a photosensitive member (photosensitive drum) configured in a drum shape.
Is uniformly charged, and light carrying the information of the image recorded on the document is applied to the photosensitive drum to form an electrostatic latent image on the photosensitive drum. Is a device for obtaining a print (copy) image by developing the toner image and transferring the toner image directly or through a transfer drum onto a sheet.

A corotron has been widely used as a charging device for uniformly charging the photosensitive drum in the electrophotographic image forming apparatus. This corotron has a structure in which, for example, a tungsten wire having a diameter of 50 to 100 μm is arranged at a distance of about 1 cm from the surface of the photosensitive drum, and the wire is shielded by a metal such as aluminum.

This corotron is an effective device for uniformly charging, but it is necessary to apply a high voltage of several kV to this corotron in order to charge the photoconductor drum to a predetermined surface potential, and ozone is generated by corona discharge. Occurs,
There is a problem of causing deterioration of rubber parts and photoconductor drums.

Therefore, it is necessary to consider the material and shape and install an exhaust fan so as not to be affected by ozone. Further, since the wire of the corotron is easily soiled by dust in the air or the fuser oil and the image is likely to be uneven, some image forming apparatuses have a wire cleaning device.

Therefore, as a charging device that replaces the corotron, a charging device of the type that contacts the photosensitive member and charges the photosensitive member has attracted attention.

This contact charging type charging device is provided with a contact charging member, for example, a charging roll, which comes into direct contact with the photosensitive member, and the contact charging member has a predetermined peak-to-peak voltage in the DC voltage V _DC. A voltage V _DC + V _AC on which the _AC voltage V _AC is superimposed is applied, and the contact charging member to which the voltage V _DC + V _AC is applied contacts the photoconductor to charge the photoconductor.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus equipped with a contact charging type charging device.

The photosensitive drum 11 is rotated in the direction of arrow A shown in the drawing, and the photosensitive drum 11 is uniformly contact-charged by the charging device 12. The charging device 12 is provided with a charging roll 121 that is rotatably supported about an axis parallel to the axis of the photoconductor drum 11. The charging roll 121 is a photoconductor by a pressure spring (not shown). The drum 11 is pressed and urged to come into linear contact with the photosensitive drum 11, and is rotated in the direction of arrow B following the rotation of the photosensitive drum 11. A predetermined voltage (DC voltage + AC voltage) from a voltage application power source (not shown) is applied to the charging roll 121 via a leaf spring-shaped electrode 122, whereby the surface of the photoconductor drum 11 is exposed. It is charged to the required potential. The charging device 12 includes a charging roll 12
A cleaning pad 123 is provided to keep the surface of No. 1 always cleaned.

An image is recorded by the laser beam 13 on the area of the photosensitive drum 11 charged by the charging device 12 to form an electrostatic latent image, and the electrostatic latent image is developed by the developing device 14.
Is developed by the toner carried by the developing roller 141 rotating in the direction of arrow C, and the toner image thereof is transferred to
5, the toner image transferred to the transfer roll 151 and then transferred to the transfer roll 151 is transferred onto a sheet (not shown).

On the other hand, the photoconductor roll 11 is cleaned for the next image formation by the cleaner 16 arranged further downstream than the transfer device 15.

[0012]

One of the problems of the charging device of the type in which the contact charging member, for example, the charging roll is brought into direct contact with the photosensitive drum and the AC voltage is applied to charge the photosensitive drum as described above. As an example, noise called charging noise is generated during charging.

This charging sound is triggered by the AC voltage applied to the charging roll 121, positive and negative charges are generated at the contact point between the charging roll 121 and the photosensitive drum 11, and are attracted to each other, and this is repeated. This is caused by the charging roll 121 and the photosensitive drum 11 vibrating and hitting each other. The mechanism of generation of this vibration is disclosed in JP-A-4-86682.

Conventionally, various measures have been taken to reduce the charging noise, but the one in which a weight is arranged inside the photosensitive drum has been put into practical use, and it is also effective in reducing the charging noise. It has been confirmed that it is large (see JP-A-5-35167 and JP-A-5-35048).

However, if a weight, which is heavy enough to sufficiently reduce the charging noise, is placed inside the photoconductor drum, the weight of the photoconductor drum increases, and there is a problem that the handling and operation thereof are difficult. In addition, it is necessary to use a weight made of a material having the same temperature expansion coefficient as that of the photoconductor drum as the weight to be placed inside, and it is difficult to select a cheap material. There is also a manufacturing problem that the tolerance between the inner diameter of the photosensitive drum and the outer diameter of the weight is strict because the toner is fixed with an adhesive.

Japanese Unexamined Patent Publication (Kokai) No. 5-35166 proposes disposing a weight member surrounded by a rubber layer inside the photosensitive member. Since the circumference is surrounded by rubber, the material of the weight itself is considerably free. However, in order to be integrated with the photoconductor without the weight vibrating inside the photoconductor, it is necessary to use a rubber that is hard to some extent. The crossing with the inner diameter of the body drum is severe, and it is difficult to insert the weight into the photoconductor even if the outer diameter of the rubber is slightly large. There is little effect to reduce. Further, since the weight is inserted inside the photoconductor, the problem that the photoconductor is heavy and the operation is difficult remains as it is.

As described above, the conventional countermeasure against charging noise is to increase the weight of the photoconductor, and the conventional proposal is to devise means for increasing the weight of the photoconductor or a method of disposing a weight inside the photoconductor. is there.

Japanese Unexamined Patent Publication (Kokai) No. 3-45981 proposes to bond a plurality of vibration inhibitors with an adhesive in order to prevent resonance in the lengthwise direction of the photosensitive drum. It is caused by another mechanism, and even if the resonance is prevented, the charging sound itself does not decrease.

In view of the above circumstances, the present invention makes it possible to sufficiently reduce the charging sound without increasing the weight of the photosensitive member to the extent that the charging noise can be sufficiently reduced by the weight. An object is to provide a member and a photosensitive drum assembly.

[0020]

A sliding contact member of the present invention that achieves the above object is a sliding contact member provided inside a photosensitive drum, wherein the sliding contact member extends in the longitudinal direction of the photosensitive drum. It has a cylindrical shape having a slit and a constricted portion extending in the longitudinal direction .

Further, the photosensitive drum assembly of the present invention which achieves the above object, is provided with a photosensitive drum, a slit extending in the longitudinal direction for pressing against the inner wall surface of the photosensitive drum with a predetermined frictional force, and the longitudinal direction. And a cylindrical slidable contact member having a constricted portion extending in the direction.

Here, in the above-described photosensitive drum assembly of the present invention, the sliding contact member has, for example, a force required to relatively move the photosensitive drum and the sliding contact member of 0.5 kg.
It is configured to press against the inner wall surface of the photosensitive drum with a frictional force of f or more and 12.5 kg · f or less.

Since the noise at the time of charging generated by the contact charging member and the photoconductor vibrating each other is mainly dominated by the vibration of the photoconductor drum made of metal, the vibration of the photoconductor drum is suppressed. Is effective. As previously mentioned,
Conventionally, the mass of the photosensitive drum has been increased in order to suppress vibration.

On the other hand, the present invention is characterized in that the sliding contact member is arranged inside the photosensitive drum so as to be pressed against the inner wall of the photosensitive drum with a predetermined frictional force.

The sliding contact member does not have to be heavy enough to reduce the charging noise by increasing the weight of the photosensitive drum, and for example, a cylinder which does not substantially increase the weight of the photosensitive drum. It may be made of a light resin. The fact that the sliding contact member does not reduce the charging noise due to its weight means that the sliding contact member is strongly pressed against the photosensitive drum so as not to slide with the inner wall of the photosensitive drum, or It is confirmed that when the sliding contact member is adhered to the photosensitive drum, the charging sound is generated to the same extent as when the sliding contact member is not arranged inside the photosensitive drum.

The present invention aims to reduce the charging noise by disposing the above-mentioned sliding contact member inside the photoconductor drum, and it is not necessary to significantly increase the weight of the photoconductor, and the photoconductor is easy to handle and operate. A body drum assembly is constructed.

In the present invention, the material and shape of the sliding contact member are not particularly limited, but as the sliding contact member, a cylindrical resin having slits and constrictions extending in the longitudinal direction of the photosensitive drum is formed. Is preferably provided. The outer diameter of the resin is formed to be slightly larger than the inner diameter of the photosensitive drum, and since the slit and the constricted portion are formed, the resin is bent in the direction of reducing the diameter of the resin so that the sliding contact member is moved to the photosensitive drum. It can be easily inserted into, and the workability of assembling is improved. The sliding contact member inserted into the photoconductor drum presses the inner wall of the photoconductor drum so that the desired frictional force is generated as the diameter of the slide contact member tends to increase.

Although it is necessary for the sliding contact member to press the inner wall of the photosensitive drum with a predetermined frictional force, what degree of frictional force is appropriate depends on the material and shape of the photosensitive drum. It is specified. As an example, according to an experiment by the present inventor, when the predetermined frictional force is defined as a force required to relatively move the photosensitive drum and the sliding contact member, the force is 0.5 kg · f or more. When it was 0.5 kg · f or less, the charging noise could be reduced by 5 dB or more.

If the force is less than 0.5 kg · f, the sliding contact member will move too easily.
When it exceeds kg · f, the sliding contact member hardly slides on the inner wall of the photoconductor drum and is almost integrated with the photoconductor drum. Therefore, in any case, the effect of reducing the charging sound was less than 5 dB. Further, within the range of 0.5 kg · f to 12.5 kg · f, the charging noise reducing effect reaches about 9 dB in the range of 1.0 kg · f or more and 8.5 kg · f or less, which is more preferable. Results were obtained.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 2 is a longitudinal sectional view of a photosensitive drum assembly in an embodiment of an image forming apparatus incorporating the sliding contact member and the photosensitive drum assembly of the present invention.

A sliding contact member 111 is installed inside the cylindrical photosensitive drum 11, and the photosensitive drum 1 is also installed.
Both ends of 1 are closed by flanges 112.

FIG. 3 is a view showing an example of the shape of the sliding contact member as seen in the direction of arrow XX shown in FIG.

The sliding contact member 111 shown in FIG. 3 is formed with a slit 111a extending in the longitudinal direction thereof, and further, a constricted portion 111b extending in the longitudinal direction is formed on the opposite side of the slit 111a. , Is formed so as to be easily bent in the radial direction.

This sliding contact member 111 is made of acrylic,
It can be formed of a resin such as ABS or glass-filled polycarbonate. Alternatively, the sliding contact member 111 may be formed of metal such as stainless steel or hard rubber. Sliding member 11
No. 1 has its outer diameter dimension, surface roughness, etc., set in advance so that when it is placed inside the photoconductor drum 11, it makes contact with the inner wall of the photoconductor drum 11 with a predetermined frictional force. There is.

FIG. 4 is a graph showing an example of the relationship between the frictional force of the sliding contact member with the inner wall of the photosensitive drum and the noise reduction effect of the charging sound.

The experimental conditions are described below.

Photoreceptor drum: outer diameter 30 mmφ, inner diameter 28.5 mm
φ, length 350mm organic photoconductor ・ Surface velocity of photoconductor drum: 136mm / sec ・ Charging roll: 14mmφ outer diameter, 330mm length elastic body (with 8mmφ stainless steel core) ・ Applied voltage: 520V (DC ) + 800Hz ・ 1.0m
A (AC) -Sliding contact member: An inner diameter of 26.5 mm, a length of 100 mm, and various acrylic outer diameters were manufactured and tested.

Measurement of frictional force: Dynamic frictional force required to move the sliding contact member relative to the photosensitive drum by pushing the sliding contact member arranged inside the photosensitive drum in the direction of arrow D in FIG. 1 and charging Sound measurement: The sound level meter was fixed so as to face the photoconductor drum, and the frictional force and the charging sound were measured under the above experimental conditions, and the results shown in FIG. 3 were obtained.

From the graph of FIG. 3, there is an appropriate range for the frictional force. Even if the frictional force is too small, the noise reduction effect is small, but if the frictional force is too large, the noise reduction effect is attenuated. I understand. From this point, it is understood that the sliding contact member 111 does not reduce the charging sound due to its weight.

Assuming that the criterion for judging that the sound reduction effect is sufficiently effective is 5 dB, 0.5 kg is used in the above experimental example.
-Frictional force within the range of f to 12.5 kg-f is appropriate, and further, with the frictional force within the range of 1.0 kg-f to 8.5 kg-f, a noise reduction effect of about 9 dB was confirmed.

The above embodiment is an example in which the frictional force is changed by changing the outer diameter dimension of the substantially C-shaped pipe-like (see FIG. 3) sliding contact member made of acrylic. Even when the frictional force is changed by changing the wall thickness of the outer diameter dimension of, the almost same result as the graph shown in FIG. 4 was obtained. Further, similar results were obtained even when the material of the sliding contact member was changed to ABS, polycarbonate with glass, stainless steel, hard rubber or the like. However, as a general tendency, the sound reduction effect of resin is slightly larger than that of metal, and the material of the sliding contact member is somewhat related.

FIG. 5 is a schematic view showing another example of the photosensitive drum assembly of the present invention.

In the photosensitive drum assembly shown in this example, the portion of the flange 112 inserted into the photosensitive drum 11 serves as a sliding contact member. With the configuration shown in FIG. 5A, when the flange 112 is attached to the photoconductor drum 11, the flange 112 is resisted against its frictional force.
It is necessary to insert the part of the sliding contact member of the above into the photoconductor drum 11, but if it is constructed as shown in FIG. 5B, the diameter of the flange 112 is expanded after it is inserted into the photoconductor drum 11, The work of attaching 112 to the photoconductor drum 11 becomes easier.

As shown in FIGS. 5A and 5B, the sliding contact member according to the present invention does not need to be provided as an independent member alone.

The sliding contact member according to the present invention may press the inner wall of the photosensitive drum with a predetermined frictional force, and if the slit and the constricted portion are formed, the cross section as shown in FIG. The material is not limited to the C-shaped one, and the material thereof is not particularly limited, and a material that is light, easy to process, and easy to assemble can be selected.

[0047]

As described above, according to the present invention,
It is possible to effectively reduce the charge amount without significantly increasing the weight of the photosensitive drum.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus including a contact charging type charging device.

FIG. 2 is a longitudinal sectional view of a photosensitive drum assembly of an embodiment of an image forming apparatus incorporating the sliding contact member and the photosensitive drum assembly of the present invention.

FIG. 3 is a diagram showing an example of the shape of a sliding contact member as seen in the direction of arrow XX shown in FIG.

FIG. 4 is a graph showing an example of the relationship between the frictional force of the sliding contact member with the inner wall of the photosensitive drum and the noise reduction effect of the charging sound.

FIG. 5 is a schematic view showing another example of the photosensitive drum assembly of the present invention.

[Explanation of symbols]

11 Photosensitive drum 111 Sliding contact member 112 flange 12 Charging device 121 charging roll

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuji Katsuno 2274 Hongo, Ebina-shi, Kanagawa Fuji Zerox Co., Ltd.Inside the Ebina business office (72) Akio Arai 2274 Hongo, Ebina-shi, Kanagawa Inside Fuji Xerox Co., Ltd. Ebina Works (56) Reference JP-A-6-19377 (JP, A) JP-A-50-150424 (JP, A) JP-A-5-35166 (JP, A) JP-A-63-271388 (JP, A) Actual development Sho 63-181116 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 21/00 350

Claims (3)

(57) [Claims] 1. A sliding member provided inside the photosensitive drum, the sliding member has a cylindrical shape constricted portion extending slit and the longitudinal direction are formed extending in the longitudinal direction of the photosensitive drum A sliding contact member characterized by the above. [2 claim] and the photosensitive drum is pressed against a predetermined frictional force to the inner wall surface of the photosensitive drum, and the sliding member of the cylindrical neck portion extending slit and the longitudinal direction are formed extending in the longitudinal direction A photoconductor drum assembly comprising: 3. A force required for the sliding contact member to relatively move the photosensitive drum and the sliding contact member is 0.5 k.
With a friction force of g · f or more and 12.5 kg · f or less,
The photosensitive drum assembly according to claim 2, wherein the photosensitive drum assembly is pressed against the inner wall surface of the photosensitive drum.