JPH07199596A - Electrifying device of image forming device - Google Patents

Abstract

PURPOSE:To prevent an electrifying noise from occurring by providing a covering member for covering an electrifying roller on the rear side, in an electrifying device provided with the electrifying roller as an electrifying member to a photoreceptor drum for electrifying the photoreceptor drum. CONSTITUTION:To the photoreceptor drum 1 for forming an image applying an electrophotographic method, the electrifying roller 10 is arranged in a state in contact with the electrifying position by a prescribed pressing force and the surface of the photoreceptor drum is electrified by applying the voltage superposed with the AC component to the electrifying roller 10. To the electrifying roller 10, the covering member 15 made of a polyacetal resin (POM) is arranged in a state of admitting the electrifying roller 10 to go through the recessed groove 16 of the covering member 15 and a part of the electrifying roller 10 exposed from the upper part opening, is pressed to the photoreceptor drum 1. Thus, the vibration of the photoreceptor drum 1 and the electrifying roller 10 caused by the AC component applied at the time of electrifying the photoreceptor drum 1 is prevented so as to reduce the electrifying noise.

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 electrophotographic copying machine, a laser beam printer, an electrostatic recording device, etc. The present invention relates to a contact type charging member for charging or discharging a surface of a body.

[0002]

2. Description of the Related Art An image forming method in which a toner image is formed on the surface of an image carrier using an electrophotographic method, such as an electrophotographic copying machine, a laser beam printer, and an electrostatic recording device, and the toner image is transferred onto a sheet. In the apparatus, a photosensitive drum is used as the image carrier. And
Arranging a corotron member for the photosensitive drum,
The surface of the photosensitive drum is uniformly charged by the discharge from the corotron. However, when the corotron is used, it is necessary to apply a high voltage of several kV in order to charge the surface of the photosensitive drum to a predetermined potential, and ozone is generated by the corona discharge, and ozone forms an image. There is a problem that it causes deterioration of the rubber and the photoconductor provided inside the apparatus. Therefore, in the image forming apparatus using the corotron as described above, in addition to selecting the material and shape of the members used in the machine, providing an exhaust fan for discharging ozone to the outside of the machine, It is necessary to provide auxiliary means such as detoxifying ozone contained in.

Further, in a device provided with corona discharge means,
If dust and fixing oil in the air are floating in the machine,
There is also a problem that the corotron wire becomes dirty, the photosensitive drum is not uniformly charged, and image unevenness or the like is likely to occur. Therefore, in addition to regularly cleaning the corotron wire to prevent uneven discharge, a cleaning device or the like is provided on the corotron wire to periodically clean the wire. There is a case. However, providing the cleaning means or the like for the corotron wire is also an extra device, which causes a problem in space, and an extra device for a small photosensitive drum or the like. Attaching the sigma also causes a problem such as an increase in constraint conditions when designing the device. In order to eliminate the inconvenience in the case of using the corotron wire as described above, a means for using a charging member such as a charging roller and charging the photosensitive drum in a state of being in contact with the photosensitive drum has attracted attention.

As an image forming apparatus using the charging member, for example, an apparatus as shown in FIG. 6 is used. In the apparatus shown in FIG. 6, the developing device 3, the cleaning device 5, the image writing means, and the like are arranged around the photosensitive drum 1. Further, a charging roller 10 for uniformly charging the photosensitive drum and a transfer roller 2 for transferring a toner image onto a sheet are provided, and a cleaning member 14 is arranged on the charging roller 10. Be able to clean the roller surface. The developing device 3
Arranges the developing roller 4 at a position corresponding to the photosensitive drum, and causes the toner carried on the surface of the developing roller to fly to the photosensitive drum to form a toner image. Further, the cleaning device 5 is provided with a blade 6 in contact with the surface of the photoconductor drum 1 so as to scrape off the toner remaining after the image transfer, and the film seal 7 is arranged in the opening portion on the moving path side of the sheet. Then, the toner cloud does not leak out from the toner collected in the housing of the cleaning device. Then, after uniformly charging the surface of the photosensitive drum by the charging roller, the image information is written by laser light to form an electrostatic latent image, and toner is supplied from the developing device to the electrostatic latent image. Then, the toner image is visualized, and at the image transfer position, the toner image is transferred onto the paper from the back surface of the paper by discharging the transfer roller 2.

In the image forming apparatus shown in FIG. 6, the charging roller 10 for charging the photosensitive drum 1 corresponds to the entire image forming area of the photosensitive drum 1 as shown in FIG. It is configured as a long one. Then, the charging roller 10 is attached to the photosensitive drum 1.
Using a spring or the like arranged on the shaft members on both sides, they are brought into contact with each other with a predetermined pressing force to follow the rotation of the photosensitive drum, and the operation of charging the surface of the photosensitive drum while rotating is performed. The charging roller 10 is configured as shown in FIG. 8. An elastic body 12 is integrally provided on a cored bar 11 made of a material such as iron or stainless steel, and a cover member 13 is provided on the surface thereof. ing. The elastic body 12
Uses EPDM rubber or the like in which carbon or the like is dispersed,
The cover member 13 provided on the surface is made of a resin such as nylon in which carbon or the like is dispersed in order to prevent a pinhole leak.

In the apparatus configured as described above, both ends of the cored bar 11 of the charging roller 10 are supported by bearings so that the charging roller 10 is pressed against the photosensitive drum in a state in which it is allowed to rotate freely. Then, a preset DC voltage Vdc and an AC voltage Vac having a peak-to-peak voltage Vpp which is more than twice the charging start voltage of the body to be charged are superimposed on the charging member of the charging roller 10 to obtain a voltage Vdc + Vac. By applying through the core metal 11, the photosensitive drum is charged. Therefore, by uniformly charging the surface of the photoconductor drum by charging the surface of the photoconductor drum by using the charging roller, electrostatic charges can be obtained by scanning light of image information in the subsequent process. The latent image can be formed in good condition.

[0007]

However, when the charging roller as described above is used to charge the photosensitive drum, an unpleasant charging sound is generated by the photosensitive drum due to the oscillating voltage component, and an image is generated. There is a problem that it is one of the causes of the noise of the forming apparatus. The noise due to the charging sound is
As shown in FIG. 9, by applying the AC component voltage Vac to the charging roller 10 that is pressed against the photosensitive drum 1, by applying periodic vibration to the photosensitive drum 1 via the charging roller. Occur. Then, as in the example shown in FIG. 9, the photosensitive drum 1 is indicated by a chain line 1a.
By repeating expansion and contraction between the state of 1 and the state of 1b, vibration with a frequency twice the frequency of the AC component is generated,
The air around the photoconductor drum is vibrated and transmitted outside the machine as charging noise.

In order to solve the above-mentioned problems, for example, as disclosed in Japanese Patent Laid-Open No. 4-44060, it has been proposed to dispose a member that outputs a sound wave that cancels charging noise. . In the conventional example, a sound source that generates a sound wave having a phase opposite to that of the charging noise is provided so that the vibration sound can be canceled.When the frequency of the vibration sound changes, a sound wave for canceling the vibration sound is generated. Is configured to change the frequency of the. However, in the case of using the means as shown in the conventional example, in addition to providing a means for measuring the frequency of charging noise, it is necessary to separately arrange a device for outputting a sound wave having a phase opposite to the charging noise. In addition to the complicated structure of the device, there is a concern that problems such as troublesome maintenance may occur.

[0009]

It is an object of the present invention to solve the problem of charging noise in an image forming apparatus using a charging member as described above, and to provide a covering member having a concave groove along the surface shape of the charging roller. For the purpose of providing a means for covering the portion behind the charging roller, even if the charging roller vibrates, the covering member suppresses the vibration,
It is an object of the present invention to provide a device that can prevent charging noise from being output outside the machine.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a charging member of an image forming apparatus which contacts the surface of an image carrier and charges the surface of the image carrier. In the present invention,
A covering member is provided on the opposite side of the image bearing member of the charging member from the center of the shaft and provided with a groove corresponding to the surface shape of the charging member. Further, in the present invention, the charging member may be configured as a conductive roller, and the concave groove of the covering member arranged with respect to the roller may be formed within a range of 60 ° or more of the central angle of the roller. Further, in the present invention, the covering member can be arranged at one or more places in a part of the charging member.

[0011]

In the charging device of the image forming apparatus of the present invention configured as described above, the covering member provided with the concave groove corresponding to the arc of the charging roller is arranged on the charging roller pressed against the photosensitive drum. When the charging roller vibrates, the vibration can be suppressed by the covering member. By suppressing the vibration of the charging roller, the degree of freedom of the vibration of the photosensitive drum is reduced, and the vibrations of both the charging member and the photosensitive drum are prevented from being transmitted to the air. be able to. Further, in the present invention, the covering member is made of urethane resin, polyacetal resin, or the like to cover a portion other than the portion where the charging roller is in contact with the photosensitive drum, and the angle behind the photosensitive drum is 60 °. It is possible to provide a concave groove that covers the above range. Further, the range in which the covering member is arranged with respect to the charging roller is the entire length direction of the charging roller, or only a part of the central portion, and the covering member is arranged at a plurality of positions in the length direction. It is possible to exert the coating action by.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A charging device for an image forming apparatus of the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 shows a configuration of the photosensitive drum 1, a charging roller 10 as a charging member, and a covering member 15 arranged with respect to the charging roller in an apparatus configured similar to the example of FIG. ing. In the example of FIG. 1, the charging roller 10 has the same configuration as that shown in FIG. 8, and is provided with a means for applying a voltage in which an AC component is superimposed on a core metal (support shaft). Then, a means for charging the photoconductor drum via a conductive rubber member is configured. In addition, the charging roller 10
The covering member 15 arranged corresponding to the back (the direction in which the charging roller is pressed against the photosensitive drum) is made of a plastic material such as polyacetal resin (POM), and a part of the outer circumference of the charging roller is left. It is configured to be accommodated in the concave groove 16 while covering the other portion.

The concave groove 16 provided in the covering member 15 is formed as a hole having a shape substantially matching the outer shape of the charging roller, and the outer peripheral portion of the charging roller is configured to slide inside the concave groove. . The charging roller 10 housed in the covering member 15 is provided such that only a portion corresponding to the photosensitive drum 1 is exposed by a predetermined angle θa. Angle θa at which the upper part of the charging roller is exposed from the covering member
When the covering member 15 is made of a relatively hard plastic material, the angle can be set to a large angle, but it is preferable that the shaft member of the charging roller can be held inside the covering member.

The photosensitive drum 1 and the charging roller 10 can be rotated with the covering member 15 arranged. Further, in the means for holding the charging roller by the covering member of the present invention, when the charging roller is rotated inside the concave groove 16 of the covering member 15, the plastic member forming the covering member has a relatively small friction coefficient. With this configuration, it is possible to prevent the rotation resistance of the charging roller from adversely affecting the rotation of the photoconductor drum or adversely affecting the uniform charging of the photoconductor drum. Therefore, in the example of FIG. 1, when a voltage in which an AC component is superimposed is applied to the photosensitive drum, even if vibration occurs in the charging roller or the photosensitive drum, the expansion and contraction of the photosensitive drum is large. It is possible to prevent the noise from being generated, and the charging noise generated from the image forming apparatus can be reduced.

Apart from the case of FIG. 1, in the present invention, as shown in FIG. 2, the covering member 15a can be made of a relatively soft plastic material such as urethane rubber. As in the case of FIG. 1, the covering member 15a for holding the charging roller 10 is provided with a concave groove 16a for accommodating the charging roller. The concave groove 16a is a photosensitive drum of the charging roller. The portion corresponding to is exposed by an angle θb smaller than that in the case of FIG. Then, the exposure range of the charging roller 10 is set narrow, and the charging roller is pressed toward the photosensitive drum 1, so that the charging roller is rotated following the rotation of the photosensitive drum to rotate the surface of the photosensitive drum. Being able to charge uniformly and being able to deal with the charging noise problem.

In the present invention, as shown in FIG. 3, the covering member 15 covers a part of the charging roller in the longitudinal direction.
It is also possible to dispose b and configure a means for suppressing the vibration of the charging roller and the photosensitive drum. In the example shown in FIG. 3, as in the case of FIG.
The charging roller 10 is made of a plastic material such as M, and is provided in a state where the charging roller 10 is inserted into the groove provided in the covering member. Further, even if vibration or the like occurs in the charging roller supported by the covering member, the vibration is suppressed by the covering member, so that the vibration of the roller is not amplified and output as noise to the outside. To be

Further, in the example shown in FIG. 3, the case where one covering member is arranged in the central portion of the charging roller has been described, but the covering member 15b has a predetermined lengthwise direction of the charging roller. It is possible to dispose a plurality of them at intervals of, and to dispose at an optimum position for suppressing the noise in accordance with the condition of vibration generated from the photosensitive drum. Therefore, even when the narrow covering member as shown in FIG. 3 is arranged on the charging roller, it is possible to prevent the charging noise from being generated from the photosensitive drum and the charging roller. The covering member shown in each of FIGS. 1 to 3 can be fixedly provided to a fixed frame disposed behind the charging roller, and even when the covering member is provided at a fixed position, vibration is prevented. It is possible to maintain the noise suppression performance in a good state.

In the apparatus of the present invention configured as described above, when a covering member for covering the back of the charging roller is arranged in correspondence with the image area width of the photosensitive drum as shown in FIGS. Assuming the models shown in FIGS. 4 and 5, the noise suppressing effect was confirmed. In the example shown in FIGS. 4 and 5, the covering member 15c is made of POM, and means for covering the charging roller 10 from behind is formed by the covering member 15c, and the concave groove 16c provided in the covering member 15c is relatively formed. The groove 16c is formed in a shallow groove shape, and the concave groove 16c is in contact with the portion behind the arc surface of the charging roller within a small angle θ. Also, as shown in FIGS.
In the example shown in, the following conditions are set.・ Photoconductor drum φ30mm organic photoconductor ・ Rotation speed 56mm / sec ・ Charging roll φ12mm elastic body (core is made of φ6mm stainless steel) ・ Applied voltage Vdc = -350V, Vac = 200Hz-
200 μA to 500 Hz-500 μA, ・ Pressing force of shaft, 500 g weight on one side, set the conditions as described above, arrange the covering member behind the charging roller, and cover the charging roller with the concave groove of the covering member 15c. When the angle θ for covering the charging roller by the groove of the covering member is set to 60 ° or more, the noise level is reduced as compared with the case where only the both ends of the shaft member of the charging roller are supported by the biasing means. Can be made. For example, in the case of a device having a charging noise of 65 dB, the noise level is 55 in the example in which the countermeasure as shown in FIG. 1 is taken.
It is possible to reduce the noise level to dB, and in the case of the covering member using urethane rubber or the like as shown in FIG. 2, the noise level can be reduced to 52 dB. Furthermore, when the covering member as shown in FIG. 3 is used, the noise level is 53 dB.
Could be reduced to a certain degree. Further, as shown in FIGS. 4 and 5, even when the concave groove 16c provided in the covering member 15c is configured as a shallow groove and a device for covering from behind the charging roller is configured, the photosensitive drum and the charging roller are also formed. It was possible to suppress the noise level generated from the noise level to about 53 dB. In the example of FIG. 5, it was found that the noise suppressing effect can be obtained if the angle θ of the concave groove of the covering member corresponding to the charging roller is 60 ° or more.

As described above, in the apparatus provided with the means for covering the charging roller from behind, the diameter and material of the photosensitive drum and the charging roller can be set arbitrarily. As for the covering member that covers the charging roller from the rear side, any material can be used as long as it has a property of not being greatly worn by sliding on the charging roller. In the combination of the covering member and the charging roller, if the friction resistance when the charging roller slides in the groove is large, the charging roller is rubbed on the surface of the photosensitive drum. Combining materials that cause conditions is not a good idea. However, when a cover member made of nylon or the like is provided on the surface of the charging roller, the wear resistance of the surface of the charging roller can be set well, and therefore the material of the covering member is not particularly limited.

[0020]

As described above, in the charging device of the image forming apparatus of the present invention, when the charging member by the charging roller is arranged on the photosensitive drum, the outer peripheral portion of the charging roller is spread over a predetermined range. By disposing the covering member in the state of covering, the charging noise generated from the charging roller and the photosensitive drum can be reduced. Further, in the device of the present invention, the effect of covering from the back of the charging roller with the covering member is imparted, and the charging roller and the photosensitive drum can reduce the occurrence of vibration due to the application of the voltage in which the AC component is superimposed, The noise level can be reduced by about 10 dB. An arbitrary plastic member is used as the covering member arranged on the charging roller, and the charging roller is slid in the groove provided in the covering member, and the portion of the charging roller that is in contact with the photosensitive drum is Only by providing a mechanism for covering the back, noise countermeasures can be easily taken.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a noise countermeasure member of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of a fourth exemplary embodiment of the present invention.

5 is a front view of the device of FIG.

FIG. 6 is an explanatory diagram showing a configuration of an image forming apparatus to which the present invention can be applied.

FIG. 7 is an explanatory diagram of a conventional device that does not take measures against noise.

FIG. 8 is a sectional view of a conventional charging roller.

FIG. 9 is an explanatory diagram showing a vibration state of a photosensitive drum and a charging roller.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 photoconductor drum, 2 transfer roller, 3 developing device, 4 developing roller, 5 cleaning device, 10 charging roller, 11 core metal, 12
Elastic body, 13 cover member, 14 cleaning member,
15 coating member, 16 concave groove.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kumiko Miyazawa 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Hiroyuki Akanuma 2274, Hongo Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Kenichi Sanshin 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Hiroshi Ogo 2274, Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (3)

[Claims] 1. A charging member of an image forming apparatus, which contacts the surface of an image carrier to charge the surface of the image carrier, wherein the charging member has a surface opposite to an axis center of the image carrier. A charging device for an image forming apparatus, wherein a covering member having a groove corresponding to the surface shape of the charging member is arranged. 2. The charging member is configured as a conductive roller, and the concave groove of the covering member arranged with respect to the roller is formed within a range of 60 ° or more of the central angle of the roller. Item 2. The charging device of the image forming apparatus according to Item 1. 3. The charging device for an image forming apparatus according to claim 1, wherein the coating member is arranged at one or more places in a part of the charging member.