JPH09134056A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable image-quality over a long period of time by preventing the surface of a charge member from being soiled partially, thereby preventing charge irregularities. SOLUTION: The device is provided with an charge-member oscillating mechanism 30 composed of a cam 31 which oscillates charge roller 2, as the charge member, in the direction of the arrow C, an oscillating spring 32 which energizes the charge roller 2 so that one end of its conductive core 15 is pressed to the cam 31, or other component. Even in the case a part of the charge roller 2 in the direction of its length is noticeably soiled with toner, the occurrence of a streak-like image due to a charge irregularity can be prevented by oscillating the charge roller 2 in the direction of the arrow C, thereby dispersing the soil on the surface along the length of a photoreceptor 1.

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 and a printer, and more particularly to a contact charging type image forming apparatus.

[0002]

2. Description of the Related Art For example, an image forming apparatus such as an electrophotographic copying machine or an optical printer is provided with a device for charging a photosensitive member which is a charged member. A charging device having a contact charging means for charging the photoconductor in a contact state is attracting attention because it produces almost no harmful ozone or nitrogen oxides to the human body during charging.

However, in such a contact charging type charging device, since the charging member is in contact with the photoconductor, the toner image formed on the surface of the photoconductor is transferred onto the transfer paper, and then the surface is transferred. The toner remaining after cleaning by the cleaning unit adheres to the surface of a charging member such as a charging roller in a streak pattern, which tends to cause charging defects such as uneven charging.

Therefore, in order to solve such a problem,
It has been proposed that a cleaning member made of a sponge material is brought into contact with the charging roller to positively clean the surface of the charging roller (see, for example, Japanese Patent Laid-Open No. 3-100766).

[0005]

However, even if the conventional charging device of the contact charging type is provided with the cleaning member made of the sponge material as described above, the cleaning member is charged as shown in FIG. When the charging roller 62, which is a member, is always in sliding contact at the same position with respect to the longitudinal direction of the cleaning member 65, if the cleaning member 65 has a portion 65a with poor cleaning performance in the longitudinal direction, that portion will be used. Contamination due to the toner becomes conspicuous and the toner cannot be removed sufficiently, and streaks or strips of dirt 63 are accumulated on the portion of the charging roller 62 corresponding to that portion, which causes the photoreceptor 61. Therefore, there is a problem that a streak-shaped image may occur in the image transferred to the transfer paper due to uneven charging.

The present invention has been made in view of the above problems, and prevents uneven charging by preventing local stains on the surface of the charging member, thereby obtaining stable image quality for a long period of time. The purpose is to be able to.

[0007]

In order to achieve the above object, the present invention provides an image forming apparatus equipped with a contact charging means for charging a photosensitive member while the charging member is in contact with the photosensitive member. The charging member swinging means for swinging the member along the longitudinal direction of the photoconductor is provided. With this arrangement, the charging member rocking means can rock the charging member along the longitudinal direction of the photoconductor even when a portion of the charging member in the longitudinal direction is contaminated by toner. As a result, dirt on the surface of the charging member due to the toner is diffused in the longitudinal direction, so that it is possible to prevent the generation of streak images due to uneven charging.

Further, in the above image forming apparatus, it is preferable to provide means for controlling driving and stopping of the charging member swinging means. By doing so, for example, the charging member swinging means can be driven only when an image is formed on the photoconductor, so that the charging member swings as much as the time for swinging the charging member decreases. Since the wear of the mechanism and the charging member can be reduced, the durability is improved.

Further, the charging member swinging means includes a cam for swinging the charging member and a sliding contact member fixed to one end of the charging member and moved in the swinging direction while slidingly contacting the cam. The sliding contact member may be made of a material having lower wear resistance than the cam. In this case, the sliding contact member that comes into sliding contact with the cam is made of a material having lower wear resistance than the cam, so that the sliding contact member mainly wears during sliding contact. Since the sliding contact member is fixed to one end of the charging member, when the charging member reaches the end of its life and can be replaced, the sliding contact member can also be replaced, so that workability is improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a front view showing a charging device and a photoconductor of an electrophotographic image forming apparatus for explaining an embodiment of the invention, and FIG. 2 is a schematic configuration diagram showing an image forming unit of the image forming apparatus. is there. As shown in FIG. 2, this image forming apparatus is a contact charging type image forming apparatus that includes a charging roller 2 that is a charging member that uniformly charges the surface 1a of a drum-shaped photoreceptor 1 that is a member to be charged in a contact state. The charging roller 2 is driven by the rotation of the charging roller 2 in the direction indicated by the arrow A in FIG. .

The photosensitive member 1 is driven by a motor which is rotationally driven through a drum driving timing belt, a drum driving pulley (neither is shown), etc., and a charging roller 2 is constantly provided on the surface thereof as shown in FIG. Two bearings 17,
They are pressed against each other by the urging force of the pressure springs 12, 12 acting via 17 respectively.

As shown in FIG. 2, a developing device 6, a belt type transfer device 7, and a cleaning unit 8 are arranged around the photoconductor 1 for writing. Light from the device 9 is incident on the surface 1a of the photoconductor 1 and is uniformly negatively charged by the charging roller 2 to expose the charged charging surface to form an electrostatic latent image thereon. Is developed by the toner supplied by the developing sleeve 6a of the developing device 6 to form a toner image (visible image).

On the other hand, the transfer paper P in a paper feed cassette (not shown) is sent out one by one by a paper feed roller that rotates at a predetermined timing, and the transfer paper P is rotated by the registration roller 13 and the pressure roller 14 that rotates in pressure contact with it. Then, after being temporarily stopped and the timing is adjusted, the sheet is conveyed toward the transfer portion provided with the transfer device 7 at an accurate timing that matches the toner image on the photoconductor 1. A toner image is transferred to the upper surface side of the transfer paper P in FIG. 2, and the toner image is separated from the photoconductor 1 and conveyed to a fixing device (not shown). After the toner is fixed there, the transfer paper P is delivered to a discharge tray or the like outside the device. Is discharged.

The residual toner remaining on the photosensitive member 1 after the transfer is removed by the cleaning blade 8a of the cleaning unit 8, and the residual potential remaining on the photosensitive member 1 is removed by a discharge lamp (not shown). In preparation for the next charging by the charging roller 2.

The charging roller 2 is constructed by integrally mounting a conductive rubber roller portion 16 on the outer side of a conductive cored bar 15 made of iron or the like, and both ends of the conductive cored bar 15 are as shown in FIG. The bearings 17 are rotatably supported by respective bearings 17, and each of the bearings 17 is supported by the pressure spring 12 on the photoreceptor 1.
And the axis of the charging roller 2 is
The surface 1a of the photoconductor 1 is in contact with the surface 1a in a state parallel to the axis line of.

The conductive core metal 15 of the charging roller 2 includes
A negative charging bias voltage (for example, -500 V) is applied from the DC power source 20 through the power supply terminal 11, and the surface 1 of the photoconductor 1 that is negatively charged by the negative charging bias voltage is applied.
a is uniformly charged. The charging roller 2 is rocked by the charging member rocking mechanism 30 along the longitudinal direction of the photoconductor 1 (left-right direction in FIG. 1).

The charging member oscillating mechanism 30 is mounted on the cam 31 which is in sliding contact with one end of the conductive cored bar 15 of the charging roller 2 and the other end of the conductive cored bar 15 so that the charging roller 2 can be seen in FIG. A rocking spring 32, which is a compression coil spring that presses and urges rightward, and a cam drive gear 3 fixed to the cam 31.
3 and rotation drive means (not shown) for rotating the cam drive gear 33.

By the way, in the case of the contact charging type image forming apparatus in which the charging roller 2 is charged while contacting the surface 1a of the photoconductor 1, the fine particles not cleaned by the cleaning unit 8 shown in FIG. Toner or the like adheres to the charging roller 2 and stains it, which may deteriorate the charging performance. In that case, as described with reference to FIG. 5, if a part of the charging roller in the longitudinal direction is locally soiled, uneven charging occurs, and thus a streak-shaped image is likely to occur.

However, this image forming apparatus is provided with the charging member swinging mechanism 30 as described above, so that the charging roller 2 is swung along the longitudinal direction of the photosensitive member 1. It is possible to prevent streaky images from being formed. That is, even if the toner Tn ₁ may locally adhere to the surface 1a of the photoconductor 1 as shown in FIG. 1 without being completely cleaned by the cleaning unit 8, the cam of the charging member swinging mechanism 30 may be removed. Three
When 1 is rotated, the charging roller 2 in which one end of the conductive cored bar 15 is in sliding contact with the cam 31 is moved to the right in FIG. 1 by the urging force of the swing spring 32, and when it moves to the movement limit, Is moved to the left in the figure by the inclined cam surface of the cam 31, so that the rocking in the direction of arrow C is repeated.

Therefore, the toner Tn ₁ locally attached to the surface 1a of the photosensitive member 1 is thinned by being diffused into the toner Tn ₂ (shown by hatching) by the swing of the charging roller 2. The attached state adheres to the surface of the charging roller 2. As a result, uneven charging does not occur, and streaky images cannot be formed.

Although FIG. 1 shows an example in which the toner simply leaks from the cleaning unit 8 as a single streak, such toner leakage actually occurs at a plurality of points. However, since the toner leakage in any of the portions is diffused in the longitudinal direction of the charging roller 2 as described above, it becomes a thin uniform stain as a whole and covers the surface of the charging roller 2. Therefore, in this case as well, charging unevenness does not occur, so there is no effect on the image.

FIG. 3 is a front view similar to FIG. 1 for explaining the embodiment of the image forming apparatus provided with means for controlling the driving and stopping of the charging member swinging mechanism, and the portion corresponding to FIG. Are given the same reference numerals. This image forming apparatus includes:
A clutch 35 for rotating the cam 31 and stopping it, and a control device 50 for controlling the driving of the clutch 35 are provided.

The control device 50 includes a central processing unit (CPU) having various judgment and processing functions, a ROM storing each processing program and fixed data, a RAM serving as a data memory for storing the processing data, and an input / output. Circuit (I /
O) and a clutch 35
And a drive circuit for driving the.

In this embodiment, the control device 50 controls the clutch 35 so as to transmit the rotational force from the drive shaft 36 to the drive gear 37 only when an image is formed on the photosensitive member 1, for example. As a result, the drive gear 37 is rotated to rotate the cam drive gear 33 so that the charging roller 2 is swung in the direction of arrow C, and the swing time of the charging roller 2 is reduced, so that the cam of the cam 31 is reduced. Since the surface is less worn, the durability of the charging member swinging mechanism 30 is improved.
Although the example in which the clutch 35 is provided is shown in FIG. 3, the means for controlling the driving and stopping of the charging member rocking mechanism 30 directly transmits the rotational force of the motor to the drive gear 37 without passing through the clutch. It may be one that does. In that case, the controlling means controls the rotation and stop of the motor.

FIG. 4 is a schematic view showing a cam sliding contact portion for explaining an embodiment in which a sliding contact member made of a material having lower wear resistance than the cam is fixed to one end of the charging roller. In this embodiment, the charging member swing mechanism includes a charging roller 2
And a sliding contact member 41 that is fixed to one end of the conductive cored bar 15 of the charging roller 2 and is slidably contacted with the cam 31 and that is moved in the swinging direction indicated by arrow C. The sliding contact member 41 is formed of a material having lower wear resistance than at least the sliding contact surface 31a of the cam 31.

In this way, the sliding contact surface 31 of the cam 31
When a and the sliding contact member 41 are in sliding contact with each other, since the sliding contact member 41 is formed of a material having lower wear resistance than the cam 31, it is mainly the sliding contact member 41 that wears and the cam wears. 31
The sliding contact surface 31a of the above is hardly worn. Since the sliding contact member 41 is fixed to one end of the conductive cored bar 15 of the charging roller 2, when the charging roller 2 reaches the end of its life and is replaced, the sliding contact member 41 is also replaced. Therefore, as compared with the case where the sliding contact member 41 is replaced alone, the labor is saved and the workability is improved.

Although the respective embodiments have been described above,
In each of the embodiments, the case where the charging roller 2 is rotated while being pressed against the photoconductor 1 by the frictional force with the photoconductor 1 has been described. However, in the present invention, the charge roller 2 is rotated by its own drive source. The same can be applied to the image forming apparatus of this type.

[0028]

As described above, according to the present invention, the charging member oscillating means oscillates the charging member along the longitudinal direction of the photosensitive member, so that toner or the like is locally deposited on the surface of the charging member. Even if it adheres, it can be diffused in the longitudinal direction of the photoconductor, preventing streak images due to uneven charging and providing stable image quality over a long period of time. To be

Further, by providing a means for controlling the driving and stopping of the charging member swinging means, the charging member swinging means can be driven only when necessary, so that the time for swinging the charging member is increased. The wear of the charging member and the like can be reduced as much as it is reduced, and the life of the charging member rocking means can be extended.

Further, the charging member swinging means includes a cam,
A charging member fixed to one end of the charging member and moved in the swinging direction while slidingly contacting the cam, and the sliding contact member is formed of a material having lower wear resistance than the cam. For example, it is the sliding contact member that wears, the cam hardly wears, the life of the cam extends, and the sliding contact member can be replaced together when the charging member is replaced, so that the parts replacement work is facilitated.

[Brief description of the drawings]

FIG. 1 is a front view showing a charging device and a photoconductor of an electrophotographic image forming apparatus for explaining an embodiment of the invention.

FIG. 2 is a schematic configuration diagram showing an image forming unit of the image forming apparatus.

FIG. 3 is a front view similar to FIG. 1 for explaining an embodiment of an image forming apparatus provided with means for controlling driving and stopping of a charging member swinging mechanism.

FIG. 4 is a schematic view showing a cam sliding contact portion for explaining an embodiment in which a sliding contact member made of a material having lower wear resistance than the cam is fixed to one end of the charging roller.

FIG. 5 is a front view showing a state in which toner is locally accumulated in a streak shape on the surface of a charging roller in a conventional contact charging type image forming apparatus.

[Explanation of symbols]

 1: Photoconductor 2: Charging roller (charging member) 15: Conductive core metal 30: Charging member swinging mechanism 31: Cam 35: Clutch 41: Sliding contact member 50: Control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Megumi Otoshi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. An image forming apparatus comprising a contact charging means for charging a photosensitive member in a state where the charging member is in contact with the photosensitive member, wherein the charging member is swung along the longitudinal direction of the photosensitive member. An image forming apparatus comprising member swinging means. 2. The image forming apparatus according to claim 1, wherein
An image forming apparatus comprising means for controlling driving and stopping of the charging member swinging means. 3. The charging member swinging means is a cam for swinging the charging member, and a sliding contact member fixed to one end of the charging member and moved in the swinging direction while slidingly contacting the cam. 3. The sliding contact member is formed of a material having lower wear resistance than the cam.
The image forming apparatus as described in the above.