JPH0535049A - Electrifying device and process cartridge or image forming device having electrifying device - Google Patents

Abstract

PURPOSE:To obtain the electrifying device which is suitable for enhancing image quality and produces less noises by setting the ratio of the weight of an electrifying member and the weight of a body to be electrified higher than 1.25 and setting the weight of the body to be electrified at <1kg. CONSTITUTION:The ratio Wd/Wc of the weight Wc of the electrifying member and the weight Wd of the body to be electrified of the electrifying device having the electrifying member to be brought into contact with the body to be electrified in order to electrify the body to be electrified is set higher than 1.25 and the Wd is set at <1kg. The vibrating sounds to be generated are decreased in this way. The Wd/Wc is satisfactory with the value higher than 1.25 and is more preferably >=1.85. The effect of decreasing the vibrating sounds is not sufficient at <=1.25. The effect of decreasing the vibrating sounds is remarkable if the Wd is a >=1kg but caution is required in handling during the production process or at the time of transportation and use and in the worst case, a trouble arises. The method of decreasing Wc includes, for example, a method of forming the metallic part to be used heretofore to a hollow body and a method of changing the metal to a material having a smaller sp. gr., for example, resin, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electronic copying machine or an electrostatic recording apparatus, a process cartridge detachable from the apparatus, or a charging apparatus used in the apparatus.

[0002]

2. Description of the Related Art An image forming apparatus such as an electronic copying machine or an electrostatic recording apparatus includes a step of uniformly charging a body to be charged. Generally, a corona charging method is adopted as the charging processing means, but the corona charging method often generates corona products such as ozone and requires additional means / mechanisms for coping with the corona charging method. However, there are problems such as high cost and high cost.

Therefore, recently, a contact charging method has been studied in which a charging member is brought into contact with a member to be charged for charging.
It has been put to practical use in some areas.

The contact charging method uses a voltage (for example, 1 to 2 kV).
A direct current voltage or a superposed voltage of a direct current voltage and an alternating current voltage) is applied to the charging target with a predetermined pressing force to charge the charging target to a predetermined potential. By forming an AC voltage having a peak-to-peak voltage that is at least twice the charging start voltage when applied to the charging member between the charging member and the member to be charged, it is possible to make the charging of the member to be charged uniform. Since the generation of ozone is greatly reduced as compared with the corona charging method, there is an advantage that the corona charging method does not require additional means and mechanism indispensable.

[0005]

However, the contact charging device as described above is used as a charging unit of an image forming apparatus for forming an electrostatic latent image on a photosensitive member, which is a member to be charged, by line scanning, for example, a laser beam printer. If adopted, there are the following problems. When an image pattern is produced by repeatedly irradiating and non-irradiating a high-density laser with high density in the sub-scanning direction, when the frequency of the AC voltage applied to the contact charging member becomes close to the spatial frequency of the image pattern, moire fringes appear on the image surface May occur. This can be solved by increasing the frequency of the alternating current sufficiently, but since the contact charging member and the photoconductor are in contact with each other, vibration noise is likely to occur,
Particularly, in an office environment or the like, there is a drawback that it is extremely inconvenient for reducing noise during operation of a printer or the like.

[Object of the Invention] The present invention has been made in order to solve the above-mentioned problems associated with such a conventional charging method, and is suitable for high image quality and has low noise and a charging device. An object is to provide a process cartridge and an image forming apparatus.

[Structure of the Invention] The present invention is a charging device for charging a charging member by bringing the charging member into contact with the member to be charged. The ratio (Wd) of the weight (Wc) of the charging member to the weight (Wd) of the member to be charged. / Wc) is greater than 1.25 and Wd is 1k
It is achieved by setting it to be less than g.

[0008]

FIG. 1 shows an example of an image forming apparatus of the present invention.
It is a block diagram of an electrophotographic printer.

Reference numeral 1 denotes an electrophotographic photosensitive drum, in which a photosensitive material such as OPC, amorphous Se or amorphous Si is formed on a cylinder-shaped or belt-shaped substrate such as aluminum or nickel. In this embodiment, it has a cylindrical shape. The photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the laser scanner 3 performs raster scanning and exposure based on the image signal. The laser scanner 3 scans the blinking of the semiconductor laser with a polygon scanner and irradiates the photosensitive drum with an optical system. As a result, an electrostatic latent image is formed on the photosensitive drum 1. The produced electrostatic latent image is developed by the developing device 4. Development is
Jumping development, two-component development, FEED development, and the like are used, and reversal development is used in combination where recording is performed and a laser is turned on to attach toner to a latent image having a lower potential.

The developed toner image is transferred to a transfer material. The transfer material is contained in the cassette 5 and is fed one by one by the paper feed roller 6. When a print signal is sent from the host computer, the paper is fed by the paper feed roller 6, and the toner image is transferred onto the transfer material by the transfer roller 8 in synchronization with the image signal by the timing roller 7. The transfer roller 8 is an electrically conductive elastic body having a low hardness, and is electrostatically transferred by a bias electric field in a nip portion formed by the photosensitive drum 1 and the transfer roller 8.

The transfer material on which the toner image has been transferred is fixed by the fixing device 9, sent out of the apparatus by the paper discharge roller 10, and discharged to the paper discharge tray 11. On the other hand, the toner remaining after the transfer is cleaned by the cleaner 12 by the blade.

FIG. 2 is a side view of a process cartridge which can be attached to and detached from the image forming apparatus shown in FIG. 1. The process cartridge C supports a photosensitive drum 1, a charging roller 2 as a charging member, a developing device 4, and a cleaner 12. ing. Further, the process cartridge C is provided with a shutter 14 for protecting the photosensitive drum 1. Here, the process cartridge C may include at least the photosensitive drum 1 which is an image carrier and the charging roller 2 which is a charging member.

(Embodiment 1) FIG. 3 is a side view of a charging device for charging an image carrier, which is a member to be charged.

A photosensitive drum 1 was prepared by providing an organic photosensitive layer 1a on the surface of an aluminum cylinder 1b which is a grounded conductive substrate having an outer diameter of 30 mm and an inner diameter of 28.5 mm.
Next, a brass rod having a diameter of 22 mm and EPDM rubber are integrally molded to form a rubber roller 1c having an outer diameter of 28.7 mm and a length of 60 mm.
After inserting the inside of the photosensitive drum 1,
The weight Wd of was measured to be 250 g. A gear flange is bonded in the longitudinal direction of this drum 1 (direction perpendicular to the paper surface of FIG. 3), and LBP-A404 is attached as shown in FIG.
It was attached to the position of the photosensitive drum used for (Canon page printer).

Further, a stainless cored bar 2 having a diameter of 6 mm
c and the conductive EPDM rubber 2b were integrally molded to prepare a conductive roller having an outer diameter of 12 mm. Further, on this surface, a surface layer 1a was provided by dipping with a coating material of methylolated nylon dissolved in methanol, followed by drying to obtain a charging roller 2 which is a contact charging member in contact with the photosensitive drum 1. The weight Wc of the charging roller was measured and found to be 71 g. This charging roller was attached to the position of the primary charger used in LBP-A404 as shown in FIG.

A vibration sound when an AC voltage of 2 kV, a frequency of 500 Hz, and a DC voltage of -700 V was applied as a bias to the charging device, ISO 777 was used in an anechoic chamber.
When measured in accordance with the sixth item of No. 9, it was good at 50 dB. The results are shown in Table-1.

As described above, the oscillating voltage obtained by superimposing the DC voltage and the AC voltage is applied between the photosensitive drum 1 and the charging roller 2 by the power source 15, and the oscillating voltage is applied between the photosensitive drum 1 and the charging roller 2. An oscillating electric field is formed, and the charge on the surface of the electrophotographic photosensitive member converges to a voltage substantially equal to the DC voltage.

The oscillating voltage is the same as that disclosed in Japanese Patent Laid-Open No. 63-14966.
As also shown in No. 8, the charging roller 2 as a charging member and the photosensitive drum 1 as a member to be charged have a peak-to-peak voltage that is at least twice the charging start voltage when a DC voltage is applied to the charging member. By forming an oscillating electric field between them, the photosensitive drum 1 can be uniformly charged. A rectangular wave, a triangular wave, a sine wave, or the like can be used as the oscillating voltage. However, since the sine wave does not include a harmonic component, the sine wave is preferable because it produces the smallest charging sound under the same conditions. Further, the oscillating voltage may be a pulse waveform formed by turning on / off the DC power supply, and may be a waveform in which the voltage periodically changes with time.

(Comparative Example 1) The procedure of Example 1 was repeated except that the rubber roller was not inserted inside the photosensitive drum. The vibration sound at this time is very noisy at 71 dB,
There was a problem in practice. The results are shown in Table-1.

(Example 2) The same procedure as in Example 1 was carried out except that a rubber roller having a length of 15 mm was used.
The vibration sound at this time was 59 dB, and the effect of reducing the vibration sound was recognized. The results are shown in Table-1.

(Comparative Example 2) The procedure of Example 1 was repeated except that a rubber roller having a length of 10 mm was used.
The vibration sound at this time was as loud as 65 dB, which was a practical problem. The results are shown in Table-1.

(Embodiment 3) Diameter 28.5 mm, length 50
When vibration was performed in the same manner as in Example 1 except that a rod made of aluminum having a thickness of mm was used, the vibration noise was as good as 55 dB. The results are shown in Table-1.

Example 4 Chloroprene rubber (CR) was molded into a cylindrical shape having a diameter of 28.7 mm and a length of 100 mm by press molding. A heavy-weight insertion photosensitive drum was prepared in the same manner as in Example 3 except that this cylindrical CR molded product was used instead of the rubber roller. When the same operation as in Example 1 was carried out except that this photosensitive drum was used, the vibration noise was 57 dB, which was at a level having no problem in practical use. The results are shown in Table-1.

(Example 5) The same procedure as in Example 1 was carried out except that the thickness of the aluminum cylinder used for the photosensitive member was 3 mm and no heavy object was inserted.
The vibration sound at this time was as good as 53 dB. Table of results
Shown in 1.

Example 6 Instead of the stainless steel cored bar (diameter 6 mm) used in the charging roller used in Example 1, an aluminum cylinder having an outer diameter of 6 mm and an inner diameter of 4 mm was used as the cored bar. In addition, when the same operation as in Example 1 was performed except that a photosensitive drum in which a heavy object was not inserted was used, the vibration noise was 59 dB, and the effect of reducing the vibration noise was recognized. The results are shown in Table-1.

(Embodiment 7) Instead of the conductive rubber used in the charging roller used in Embodiment 1, the density is 0.
Except that a conductive sponge of ³ g / cm ³ was used and a photosensitive drum in which a heavy object was not used was used, the vibration sound was 59 dB, and the vibration noise reduction effect was recognized. Was given. The results are shown in Table-1.

[0027]

[Table 1]

The vibration noise in the contact charging method is because the vibration voltage is applied when the charging member and the body to be charged are in contact with each other.
The cause is the vibration generated by the exciting force of the applied oscillating voltage, and it is considered that the vibration is caused by the charging member "beating" the charged body with the AC voltage frequency, the electric field force and the restoring force of the elastic body. ing.

From the above experimental results, it was found that the vibration noise generated by the application of the AC voltage can be reduced by increasing the ratio (Wd / Wc) of the weight of the charging member to be tapped and the weight of the charged member to be tapped. . Wd / Wc may be larger than 1.25, but is preferably 1.85 or more, and when 1.25 or less, the vibration noise reduction effect is not sufficient, and when Wd is 1 kg or more, the vibration noise reduction effect is remarkable. However, the amount is preferably less than 1 kg because it requires caution in the manufacturing process, handling during transportation and use, and causes troubles in extreme cases.

In order to increase Wd / Wc, it is natural to increase Wd or decrease Wc. As a method of increasing Wd. For example, there is a method of increasing the thickness of the body to be charged or changing the material, and a method of inserting a heavy object inside the body to be charged. Examples of the kind of the heavy object include a metal, an elastic body, and a composite body of these. Examples thereof include liquids such as water and silicone oil, and inorganic substances such as clay and gypsum, and they may be inserted as they are. However, in some cases, they may be previously sealed in a resin tube or the like and then inserted. If necessary, the inserted heavy object may be fixed by adhesion or the like.

Next, as a method of reducing Wc, for example, a metal part used in the charging member is made hollow, a metal is changed to a resin having a lower specific gravity, or the elastic part is made low. For example, a method of using a sponge or the like having a specific gravity can be used.

[0032]

As described above, by increasing Wd / Wc, vibration noise can be reduced even when the printer or the like is in operation, so that a charging device suitable for high image quality and low noise can be obtained.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a side view showing an embodiment of the process cartridge of the present invention.

FIG. 3 is a schematic view showing an example of a contact charging device using a heavy-weight insertion type photosensitive drum of the present invention.

[Explanation of symbols]

1 photosensitive drum 1a Photosensitive layer 1b base 1c heavy goods 2 Contact charging member 2a surface layer 2b conductive rubber 2c core metal 15 power supply

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Matsuda             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Hiroaki Miyake             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Manabu Takano             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Masahiro Goto             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation

Claims (3)

[Claims] 1. In a charging device having a charging member that contacts a charged body for charging the charged body, a ratio (W) of a weight (Wc) of the charging member and a weight (Wd) of the charged body.
d / Wc) is greater than 1.25 and Wd is less than 1 kg. 2. A process cartridge attachable to and detachable from an image forming apparatus, the process cartridge having an image carrier and a charging member contacting the image carrier for charging the image carrier, wherein the charging member. Weight (W
c) and the weight (Wd) of the image carrier (Wd / W
c) is greater than 1.25 and Wd is less than 1 kg. 3. An image forming apparatus comprising: an image carrier, an image forming means for forming an image on the image carrier, and a charging member contacting the image carrier for charging the image carrier. The ratio (Wd / Wc) of the weight (Wc) of the charging member to the weight (Wd) of the image carrier is larger than 1.25,
An image forming apparatus having a Wd of less than 1 kg.