JPH103202A - Electrifier for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of the filming of toner on the surface of an electrifying roller by improving the contact state of the electrifying roller and a cleaning member at the electrifier of a roller electrifying system. SOLUTION: A recessed groove 34c is provided at a sponge 34a stuck on the inner surface of an electrifying roller case 31 out of the sponge 34a and felt 34b of the two-layer structure of a cleaning pad 34, so that a space S in a longitudinal direction is formed. When the cleaning pad 34 is brought into press-contact with the electrifying roller 19, the sponge 34a and the felt 34b are uniformly bent like the cylindrical outer peripheral surface of the electrifying roller 19 at a part provided with the recessed groove 34c. Thus, the difference in collapse quantity by the parts is hardly caused, and the variation of contact pressure is eliminated and the cleaning pad 34 and the electrifying roller 19 are brought into contact by proper pressure, so that the occurrence of the filming of the toner is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for an image forming apparatus, and more particularly to a charging device having improved contact between a charging roller and a member for cleaning the charging roller.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a facsimile, a photoreceptor, a developing device, a charging device and the like are housed in an integrated case to constitute an image forming unit, and an image forming unit is formed. It is becoming more common to reduce the size of the entire apparatus. In this type of image forming unit, a roller charging type charging device is often used.
Such a charging device is shown in FIGS. In this charging device, a charging roller 1 is held in a charging roller case 2, and springs 4, 4 are arranged between a bearing 3 of the charging roller 1 and a lower surface of the charging roller case 2, and a rotating arm (not shown) is provided as a whole. When the charging roller 1 comes into contact with the photoreceptor 5 by being pressed down, the charging roller 1 is evenly pressed against the photoreceptor 5 by the urging force of the spring 4 to rotate with the photoreceptor 5,
This is to uniformly charge the surface of the photoconductor 5.

A cleaning pad 6 is adhered to the lower surface of the charging roller case 2, and the charging roller case 2 is further pushed down by an arm (not shown) during a non-image forming step, so that the cleaning pad 6 made of a sponge or the like is transferred to the charging roller 1. , So that the toner and other foreign matter are removed from the surface of the charging roller 1 by sliding contact with the surface of the charging roller 1 which rotates with the photoreceptor 5. The arrow A in the figure indicates the photoconductor 5
, The arrow B indicates the rotation direction of the charging roller 1.

Incidentally, in such a charging device, it is necessary to take into consideration that toner filming does not occur on the surface of the charging roller 1 due to sliding contact with the cleaning pad 6. The contact pressure between the charging roller 1 and the cleaning pad 6 has a certain appropriate value, and toner filming is more likely to occur as the contact pressure between the charging roller 1 and the cleaning pad 6 increases. Charging becomes impossible, thereby causing a problem that image quality is impaired.

[0005] Cleaning pad 6 of this type of charging device
In general, a sponge and a felt having a two-layer structure, in which a sponge is attached to the inner surface of the charging roller case 2 with an adhesive tape or the like and the felt is brought into contact with the charging roller, are often used. Therefore, a countermeasure against the above-described filming of the toner may be considered in which the contact pressure between the charging roller 1 and the cleaning pad 6 is reduced by using a low-hardness sponge. However, a sponge having a low hardness has a crushing amount at the time of contact with the charging roller 1 (that is, an amount of biting into the charging roller 1), which tends to vary depending on the contact position with the charging roller 1. There is a problem that the contact pressure of the cleaning pad 6 is largely changed, and it has not been possible to sufficiently prevent toner filming.

Accordingly, the present invention provides a charging device for an image forming apparatus having a structure capable of improving the contact property between a charging roller and a cleaning member, properly contacting the charging roller with the cleaning member, and preventing occurrence of toner filming. The purpose is to provide.

[0007]

According to a first aspect of the present invention, there is provided a charging device for an image forming apparatus, comprising: a charging roller for pressing a photosensitive member to charge the photosensitive member in order to achieve the above object; And a cleaning member that cleans the charging roller while being pressed against the charging roller, wherein the cleaning member is provided on a surface of the holding member facing the charging roller.
Between the opposite side of the cleaning member and the holding member,
The cleaning member is provided with a space that allows the bending of the cleaning member.

According to a second aspect of the present invention, the space is formed by providing a concave groove on the side of the cleaning member facing the holding member.

According to a third aspect of the present invention, the space is formed by providing a pair of protrusions on the opposing surface of the holding member.

[0010] According to a fourth aspect of the present invention, the space is formed by providing a recess in the opposing surface of the holding member.

According to a fifth aspect of the present invention, one side edge of the cleaning member is fixed to an opposing surface of the holding member at one side of the recess, and the other side edge of the cleaning member is a free end. And formed so as to be able to enter the above-mentioned depression.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a charging device for an image forming apparatus according to the present invention will be described below with reference to the drawings. First, the configuration of an image forming unit of an image forming apparatus using the charging device according to the present invention will be described. FIG. 1 is a sectional view showing an image forming unit, a transfer / separation device, a fixing device and the like using the charging device according to the present invention, and FIG. 2 is an exploded perspective view of the charging device shown in FIG. In these figures, reference numeral 10 denotes an image forming unit, 11 denotes a transfer / separation device, and 12 denotes a fixing device. The image forming unit 10 is formed in a cartridge shape and is detachably attached to an image forming apparatus main body (not shown). It is possible.
Further, the transfer / separation device 11 includes a transfer roller 13 and is rotatable in a vertical direction in FIG.
The fixing device 12 includes a pressure roller 15 and a heating roller 16.

The illustrated imaging unit 10 comprises a case around a photoreceptor surrounding case 17 and an upper cover 37, inside which a photoreceptor 18, a charging roller 19 constituting a charging device,
The developing device 20, the cleaning device 21, a toner recycling belt 22 for feeding the residual toner collected by the cleaning device 21 to the developing device 11, a toner conveying screw 42, an agent stirring member 43, and the like are provided. Upper cover 3
Reference numeral 7 is attached so as to cover the case 17 around the photosensitive member, and prevents the hand of an operator or a service person from contacting the photosensitive member 18 and the charging roller 19.

As shown in FIG. 2, the charging roller 19 of the charging device has a small hygroscopic property on the outer periphery of the metal core 27,
It is formed by molding a conductive rubber (e.g., epichlorohydrin rubber) 28 having a stable resistance value.
8 is brought into contact with the surface of the photoreceptor 18 and
By applying a high voltage to the photoconductor 7, the surface of the photoconductor 18 is uniformly charged. Both ends of the core metal 27 of the charging roller 19 are rotatably held by bearings 29, 29,
Each of the bearings 29 is attached to the charging roller case 31 so as to be movable in the vertical direction in the figure, and a pressure spring 33 is interposed between the bearing 29 and the inner surface of the charging roller case 31. The charging roller 19 can be pressed against the photosensitive member 18 with a predetermined pressure.

A cleaning pad 34 for cleaning the surface of the charging roller 19 is provided with an adhesive such as a double-sided tape on an inner surface of the charging roller case 31, which is a holding member of the charging roller 19, facing the charging roller 19. It is pasted. The charging roller 19 keeps in contact with the surface of the photoconductor 18 during the charging operation.
Although the surface is easily stained by minute toner adhering to the surface of No. 8 and charging unevenness is caused, the charging roller 19 is cleaned by pressing the cleaning pad 34 against the surface and removing the adhering toner, whereby the charging roller 19 becomes dirty. In this case, it is possible to prevent charging unevenness that may occur in the case where the charging is performed.

Further, the inside of both ends in the longitudinal direction of the charging roller case 31 and the photosensitive member surrounding case 1 of the image forming unit 10 are formed.
7, springs 36, 36 are interposed between the spring receivers 35, 35, respectively, so that the entire charging device is separated from the photoreceptor 18 in a state other than during the charging operation and when the charging roller 19 is cleaned. The charging roller case 31 is urged upward in the drawing by the urging force of the spring 36. In the figure, reference numerals 40 and 40 denote a pair of swingable pressure arms which constitute a contact / separation mechanism for bringing the charging roller 19 into and out of contact with the photosensitive member 18.
1 by pressing the upper surface of the charging roller case 31
When the pressing arm 40 is separated from the upper surface of the charging roller case 31, the charging roller 19 and the charging roller case 31 are separated from the photosensitive member 18 by the urging force of the spring 36. Has become.

An image forming operation using the image forming unit configured as described above will be briefly described. First, with the image forming apparatus main body mounted at a predetermined position, the photosensitive member 18 can be rotated in a direction indicated by an arrow in FIG. 1 by a driving source (not shown). The surface is neutralized by irradiating static elimination light from a static elimination lamp (not shown), and the surface potential is averaged to a reference potential of, for example, 0 to -150V. Next, a high voltage is applied to the charging roller 19 which is in contact with the surface of the photoreceptor 18 to charge the photoreceptor 18, and the surface potential is set to, for example, about -1100V. Then, the charged potential surface is exposed, and the surface potential to form an image is, for example, 0 to 0.
A latent image portion of -290 V is formed.

When the latent image portion is moved to the position of the developing sleeve 23 of the developing device 20 by the rotation of the photosensitive member 18, the latent image portion is held on the surface of the developing sleeve 23 in which a bias of, for example, about -800 V is applied. The latent toner adheres, and the latent image portion is developed to become a toner image (visible image).

On the other hand, the transfer paper P fed from a paper feed unit (not shown) is moved by the registration roller pair 24 so that the front end of the transfer paper P and the front end of the toner image on the photosensitive member 18 coincide with each other at the position of the transfer roller 13. The timing is adjusted, and the toner image on the photoconductor 18 is transferred to the transfer paper P by the transfer roller 13. The transfer paper P is conveyed between the pressure roller 15 and the heating roller 16 of the fixing device 12, where the transferred toner is fused to the transfer paper P by heat and pressure, and is transferred to a discharge tray (not shown) outside the apparatus. Discharge.

The residual toner remaining on the photoreceptor 18 after the image is transferred is scraped off by a cleaning blade 25 of a cleaning device 21. Move to The residual toner collected by the cleaning device 21 is transferred to the developing device 20 by the toner recycling belt 22.
The developer is transported to the developer agitating section 26 and collected.
And the toner is recycled by supplying the toner to the developing sleeve 23 again. In the figure, 41 is the cleaning blade 2
5 holder.

By the way, in the present embodiment, FIG.
2 and, more specifically, as shown in FIG. 3, the structure of the cleaning pad 34 on the charging roller case 31 is improved. That is, the cleaning pad 34 of the present embodiment has a two-layer structure of the sponge 34a and the felt 34b,
A concave groove 34c is formed in the sponge 34a so as to provide a space S along the longitudinal direction between the inner surfaces of the charging roller case 31 to be stuck. Therefore, when the cleaning pad 34 is pressed against the charging roller 19 by pressing down the charging roller case 31, the sponge 34a and the felt 34b are bent so as to enter the space S as shown in FIG. At this time, in the portion where the concave groove 34c is provided to form the space S, the sponge 34a and the felt 34b bend almost uniformly following the cylindrical outer peripheral surface of the charging roller 19, so that the sponge 34a has a low hardness. However, there is almost no difference in the amount of crushing depending on the part. Although there is a slight difference in the amount of bending at the portion near both side edges (the left and right side edges in FIG. 3) of the cleaning pad 34, the contact pressure due to the variation in the amount of deflection is larger than the variation in the contact pressure due to the variation in the amount of collapse. Is very small. Therefore, there is no variation in the contact pressure due to the difference in the crushing amount, and the cleaning pad 34 and the charging roller 19 come into contact with an appropriate pressure as a whole, so that toner filming is less likely to occur.

FIG. 4 is a sectional view showing a second embodiment of the charging device of the present invention. In the present embodiment, a space S is formed by providing a pair of ridges 31a, 31a on the inner surface of the charging roller case 31 to which the cleaning pad 34 is attached. Also in this example, the state and operation when the cleaning pad 34 is pressed against the charging roller 19 by pressing down the charging roller case 31 are the same as those in the previous embodiment.

FIG. 5 is a sectional view showing a third embodiment of the charging device of the present invention. In the present embodiment, a space S is formed by providing a single recess 31b in the charging roller case 31 to which the cleaning pad 34 is attached. Also in this example, the state and operation when the cleaning pad 34 is pressed against the charging roller 19 by pressing down the charging roller case 31 are the same as those in the previous embodiment. In this embodiment, as shown in FIG. 6, the cleaning pad 34 does not extend over the entire width of the depression 31 b, and one side edge of the depression 31 b is located on the upstream side in the rotation direction B of the charging roller 19. And the downstream end of the charging roller 19 in the rotation direction B may be a free end. In this way, the free end side bends into the space S when pressed against the charging roller 19, and the sponge 34a and the felt 34b bend almost uniformly. In this case, if the width of the cleaning pad 34 is set such that the free end of the cleaning pad 34 extends slightly from the center of the recess 31b to the other side edge, a sufficient contact length can be secured.

In the embodiment described above, only the cleaning pad having a two-layer structure of sponge and felt has been described. However, the present invention is not limited to this. It can be applied to the case where it is used. Although only an example in which the charging roller case also serves as a cleaning pad holding member has been described, the cleaning pad holding member and the charging roller case may be separate members and may be separately supported or fixed, The present invention is not limited to the structure shown in the illustrated example.

[0025]

As described above, the charging device of the image forming apparatus according to the present invention comprises a cleaning member for pressing and cleaning the charging roller and a holding member for providing the cleaning member on the surface facing the charging roller. In the meantime, since a space is provided to allow the cleaning member to bend, the amount of crushing of the cleaning member, that is, the amount of bite when the charging roller and the cleaning member are pressed against each other becomes substantially uniform over the entire contact portion, so that the contact properties of both members are reduced. This has the effect of reliably preventing the occurrence of toner filming on the surface of the charging roller.

According to a second aspect of the present invention, there is provided a charging device for an image forming apparatus, comprising:
Since the holding member is provided with a space that allows the cleaning member to bend by providing a pair of protrusions or depressions, the manufacturing is simple, and the strength of the charging roller case is not reduced.

[Brief description of the drawings]

FIG. 1 shows an image forming unit using a charging device according to the present invention;
FIG. 3 is a cross-sectional view illustrating a transfer / separation device, a fixing device, and the like.

FIG. 2 is an exploded perspective view of the charging device shown in FIG.

FIG. 3 is a sectional view showing a first embodiment of a charging device according to the present invention.

FIG. 4 is a sectional view showing a second embodiment of the charging device according to the present invention.

FIG. 5 is a sectional view showing a third embodiment of the charging device according to the present invention.

FIG. 6 is a sectional view showing a modification of the embodiment of FIG. 5;

FIG. 7 is a side sectional view showing a configuration of a conventional charging device.

FIG. 8 is a front sectional view of the charging device of FIG. 7;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 image forming unit 11 transfer device 12 fixing device 13 transfer roller 14 rotation fulcrum 15 pressure roller 16 heating roller 17 image forming unit case 18 photoconductor 19 charging roller 20 developing device 21 cleaning device 22 toner recycling belt 23 developing sleeve 24 Registration roller pair 25 Cleaning blade 26 Developer stirring section 27 Core bar 28 Conductive rubber 29 Bearing 31 Charging roller case 31a Ridge 31b Depression 33 Pressure spring 34 Cleaning pad 34a Sponge 34b Felt 34c Recessed groove 35 Spring receiver 36 Spring 37 Upper Cover 41 Holder for cleaning blade 42 Toner transport screw 43 Agent stirring member A Rotation direction of photoconductor B Rotation direction of charging roller P Transfer paper S Space

Claims (5)

[Claims] A charging roller for pressing the photosensitive member to charge the photosensitive member; and a cleaning member for cleaning the charging roller while pressing the charging roller. In a charging device of an image forming apparatus provided on a surface facing a roller, a space is provided between a surface of the cleaning member and a surface of the holding member that allows bending of the cleaning member. Device charging device. 2. The charging device for an image forming apparatus according to claim 1, wherein a concave groove is provided on the cleaning member on a side facing the holding member to form the space. 3. The space is formed by providing a pair of ridges on an opposing surface of the holding member.
Charging device for an image forming apparatus. 4. The charging device for an image forming apparatus according to claim 1, wherein the space is formed by forming a depression in the opposing surface of the holding member. 5. One side edge of the cleaning member is fixed to the opposing surface of the holding member at one side of the depression, and the other side edge of the cleaning member is a free end, and can be inserted into the depression. 2. The charging device for an image forming apparatus according to claim 1, wherein the charging device is formed as described above.