JP3459862B2 - Charging device for image forming apparatus - Google Patents

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, an image forming unit is constructed by housing a photoconductor, a developing device, a charging device and the like in an integrated case to form an image. It is becoming increasingly common to contribute to miniaturization of the entire device. In this type of image forming unit, a roller charging type charging device is often used.
In many of such charging devices, the charging roller is constantly urged so as to be pressed against the photoconductor, and a cleaning member separately held so as to be able to contact and separate from the charging roller is urged against the charging roller when necessary. The cleaning is performed by pressing them against each other.

By the way, in such a charging device, it is necessary to consider the rotatability of the charging roller due to the sliding contact with the cleaning member. That is, when cleaning is performed by pressing the cleaning member against the charging roller that is rotated by the photosensitive member, a frictional force acts in the direction in which the cleaning member stops the rotation of the charging roller. Is required to be larger than the frictional force of the cleaning member. Of course, the force with which the photoconductor rotates the charging roller is determined by the friction coefficient between the photoconductor and the surface of the charging roller and the pressure contact force of the charging roller to the surface of the photoconductor,
In the first place, since the charging device must charge the photoconductor satisfactorily, the degree of freedom in designing the surface material of the charging roller and the pressure contact force of the charging roller to the photoconductor is small. Therefore, conventionally, it was not possible to employ a cleaning member made of a material having a large friction coefficient with respect to the surface of the charging roller, and therefore, there was a limit to improving the cleaning ability. Further, since the cleaning member having a large friction coefficient generates a comparatively large noise when it comes into sliding contact with the charging roller, there is a problem in using it in the office.

Therefore, the present invention provides a charging device for an image forming apparatus capable of improving the contact property between the charging roller and the photosensitive member, appropriately contacting the charging roller and the cleaning member, and exhibiting sufficient cleaning performance. With the goal.

[0005]

In order to achieve the above-mentioned object, the charging device for an image forming apparatus according to the present invention has a structure in which the photosensitive member is pressed against the photosensitive member and is driven and rotated. A charging roller for charging and a cleaning member for cleaning the charging roller by pressing the charging roller are provided, and the cleaning member contacts the charging roller.
And the direction in which the charging roller contacts the photoconductor is the same direction.
In a charging device for an image forming apparatus, the charging roller
And charging roller case for holding the cleaning member
An urging means for urging the charging roller in a direction away from the cleaning member, and the cleaning member
Note that the charging roller is pressed against the charging roller,
Press in the direction of contact, and the pressing force can be changed
And a charging means, wherein the charging roller is attached to the photosensitive member.
In the charging mode for charging, the pressing means is
The charging roller is pressed against the photosensitive member by the urging force of the urging means.
In the cleaning mode, press with contact pressure
The pressing means resists the urging force of the urging means.
The cleaning member is the charging roller, and the charging roller is
It is special to press with a pressing force that presses together with the above photoreceptor.
To collect.

According to the second aspect of the present invention, the cleaning
Member and charging roller case holding the charging roller
And the pressing means moves the charging roller case.
The charging roller is pressed against the photoconductor and
Do not press the leaning member against the charging roller.
Characterize.

The invention according to claim 3 relates to the above-mentioned cleaning.
At least the surface of the plug member that contacts the charging roller is
It is characterized by being made of plastic material.

According to the fourth aspect , the sponge material is
The number of cells is 20 to 60.

According to a fifth aspect of the present invention, the cleaning member has a two-layer structure of a sponge material and a felt material that is in sliding contact with the surface of the charging roller.

The invention according to claim 6 is characterized in that the thickness of the sponge material is three times or more the thickness of the nonwoven fabric.

[0011]

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a charging device of an image forming apparatus according to the present invention will be described below with reference to the drawings. First, the configuration of the image forming unit of the image forming apparatus using the charging device according to the present invention will be described. 1 is a perspective view of an image forming unit using a charging device according to the present invention, FIG. 2 is a cross-sectional view showing the image forming unit, transfer / separation device, fixing device, etc. of FIG. 1, and FIG. FIG. 3 is an exploded perspective view of a charging device used in the image unit. In these figures, 10 is an image forming unit, 11 is a transfer / separation device, 12 is a fixing device,
The image forming unit 10 is formed in a cartridge shape and can be attached to and detached from the main body of the image forming apparatus (not shown). The transfer / separation device 11 is provided with a transfer roller 13 and is rotatable in a vertical direction in the drawing by a rotation fulcrum 14. The fixing device 12 includes a pressure roller 15 and a heating roller 1.
6 and 6.

The image forming unit 10 shown in the drawing comprises a case 17 around the photosensitive member and an upper cover 37, inside which a photosensitive member 18 and a charging roller 19 constituting a charging device are provided.
A developing device 20, a cleaning device 21, and a toner recycle 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, etc. are provided. Also the upper cover 3
Reference numeral 7 is attached so as to cover the case 17 around the photoconductor, and prevents the hand of an operator or a service person from coming into contact with the photoconductor 18, the charging roller 19, and the like.

As shown in FIG. 3, the charging roller 19 of the charging device has a small hygroscopic property on the outer periphery of the metal cored bar 27.
A conductive rubber having a stable resistance value (for example, epichlorohydrin rubber) 28 is molded, and the conductive rubber 2
8 with the surface of 8 in contact with the surface of the photoconductor 18
By applying a high voltage to 7, the surface of the photoconductor 18 is uniformly charged. Both ends of the cored bar 27 of the charging roller 19 are rotatably held by bearings 29, 29.
Each bearing 29 is attached by a 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 photoconductor 18 with a predetermined pressure.

A cleaning pad 34 for cleaning the surface of the charging roller 19 is attached to the inner surface of the charging roller case 31 which is a holding member of the charging roller 19 with an adhesive such as a double-sided tape. The charging roller 19 keeps in contact with the surface of the photoconductor 18 during the charging operation, and as is well known, the surface of the photoconductor 18 is easily contaminated by minute toner adhering to the surface of the photoconductor 18, causing uneven charging. By cleaning the cleaning pad 34 by pressing it and removing the adhered toner, it is possible to prevent charging unevenness that occurs when the charging roller 19 is soiled.

Further, the inside of both ends of the charging roller case 31 in the longitudinal direction and the case 1 around the photoconductor of the image forming unit 10 are provided.
The springs 36, 36 are respectively interposed between the spring receivers 35, 35 provided in 7, so that the entire charging device is separated from the photoconductor 18 in a state other than the charging operation and the cleaning of the charging roller 19. The charging roller case 31 is biased upward in the drawing by the biasing force of the spring 36.

In the figure, reference numerals 40 and 40 denote a pair of swingable pressure arms which constitute a mechanism for contacting / separating the charging roller 19 with respect to the photosensitive member 18 and pressing it. As shown in FIG. 1, both arms 40 are connected by a rotation shaft 99, and are eccentrically rotatably supported on the main body of the image forming apparatus (not shown) and linked to the end of one arm 40. By rotating the cam 100 by a driving means such as an electromagnetic clutch, these arms 40 can be rotated around the rotation shaft 99. By pressing the upper surface of the charging roller case 31 with the tip of the arm 40, the charging roller 19 together with the charging roller 19 can be pressed toward the photoconductor 18, and if 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 photoconductor 18 by the urging force of the spring 36. Reference numeral 101 in the drawing is a holder of a static elimination lamp (not shown), which is made of a highly rigid metal or the like and is fixed to the tip end side of the arm 40 in parallel with the rotation shaft 99.

An image forming operation using the image forming unit thus constructed will be briefly described. First, with the main body of the image forming apparatus attached at a predetermined position, the photoconductor 18 becomes rotatable in the direction of the arrow in FIG. 1 by a drive source (not shown), and when the image forming operation starts, The surface of 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 0 to -150 V, for example. Next, a high voltage is applied to the charging roller 19 which is in contact with the surface of the photoconductor 18 to charge the photoconductor 18, and the surface potential thereof is set to, for example, about -1100V. Then, by exposing the charged potential surface, the surface potential of an image becomes 0 to
-290V latent image portion is formed.

When this latent image portion moves to the position of the developing sleeve 23 of the developing device 20 due to the rotation of the photosensitive member 18, the latent image portion is held on the surface of the developing sleeve 23 which is biased, for example, at about -800V. The formed toner adheres and the latent image portion is developed to form 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 photoconductor 18 are aligned at the position of the transfer roller 13. The toner image on the photoconductor 18 is transferred to the transfer paper P by the transfer roller 13 with the timing adjusted. The transfer paper P is conveyed between the pressure roller 15 and the heating roller 16 of the fixing device 12, where the toner transferred by heat and pressure is fused to the transfer paper P, and is transferred to a discharge tray or the like (not shown) outside the machine. Discharge.

The residual toner remaining on the photoconductor 18 after the image transfer is scraped off by the cleaning blade 25 of the cleaning device 21, and it is assumed that almost no toner adheres to and remains on the surface of the photoconductor 18 in the next image forming step. Move to. The residual toner collected by the cleaning device 21 is transferred to the developing device 20 by the toner recycling belt 22.
Of the agent stirring member 43.
And the toner is recycled by supplying it to the developing sleeve 23 again. In the figure, 41 is the cleaning blade 2.
5 holders.

FIG. 4 shows the operation and positional relationship of the charging roller 19, charging roller case 31, and arm 40 during each operation of the image forming unit as described above. In the apparatus of this embodiment, the arm 40 constituting the pressing means presses the photosensitive member 18 side more strongly when cleaning the charging roller 19 with the cleaning pad 34 than when the charging roller 19 charges the photosensitive member 18. The body 18 and the charging roller 19 and the charging roller 19 and the cleaning pad 34 are brought into pressure contact with each other.

A cleaning pad 6 is attached 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 the non-image forming process to bring the cleaning pad 6 into contact with the charging roller 1. An appropriate amount of bite is set, and 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 rotation of the photoconductor 5.

That is, first, when the photosensitive member 18 shown in FIG. 4A is not charged, the arm 40 is in a state of being rotated upward by the eccentric cam 100, and the charging roller 19 and the charging roller 40 are charged. The roller case 31 is separated from the surface of the photoconductor 18 by a spring 36. FIG. 5 is a front sectional view (A) and a side sectional view (B) schematically showing this state. Note that arrow A in FIG. 5 indicates the rotation direction of the photoconductor 18, and arrow B indicates the rotation direction of the charging roller 19.

Next, in the charging mode shown in FIG. 4B, in which the photosensitive member 18 is charged, the arm 40 moves the eccentric cam 10.
0, the charging roller case 31 is pushed down against the biasing force of the spring 36, and the charging roller 19 is pushed by the biasing force of the spring 33 against the surface of the photoconductor 18. Contact with each other and rotate together with the photoconductor 18. In this state, the surface of the photoconductor 18 is charged. FIG. 6 is a front sectional view (A) and a side sectional view (B) schematically showing this state. As is apparent from comparison with FIG. 5, the spring 33 is compressed and contracted, and the repulsive force determined by the spring constant causes the charging roller 19 to press against the photoconductor 18.

Further, the charging roller 19 shown in FIG.
In the cleaning mode to clean the surface of
The arm 40 is in a state of being rotated most downward by the eccentric cam 100, and the charging roller 19 strongly presses the photosensitive member 18.
When the cleaning pad 34 is pressed against the surface of the charging roller 19, the cleaning pad 34 comes into contact with the surface of the charging roller 19 so as to come into contact with the surface of the charging roller 19, and the cleaning pad 34 comes into sliding contact with the surface of the charging roller 19 that rotates together with the photoconductor 18 to clean and remove toner and the like. There is. FIG. 7 is a front sectional view (A) and a side sectional view (B) schematically showing this state. More spring 33 than the state of FIG.
Is pressed and contracted, and the repulsive force causes the charging roller 19 to further strongly press against the photoconductor 18. The above-mentioned modes are alternately repeated according to the cam curve of the eccentric cam 100.

By the way, in the apparatus of this embodiment, since the pressure contact force between the photoconductor 18, the charging roller 19 and the cleaning pad 34 is changed according to the operating state as described above, the cleaning pad 34 has a large friction coefficient. A sponge alone can be used. However, if it is too hard (the number of cells is large), a large noise is generated when it rubs against the charging roller 19, and if it is too soft (the number of cells is small), the amount of crushing at the time of contact with the charging roller 19 (that is, the charging roller 1). It is not preferable because the contact pressure between the charging roller 1 and the cleaning pad 6 is greatly changed even if the amount of bite into the charging pad 1 easily varies. According to a study made by the inventors of the present application, the number of cells is about 20 to 60, preferably a value in the vicinity of 50 (for example, 50
It is good to set about ± 3). If such a sponge is adopted, there is no variation in contact pressure, the cleaning pad 34 and the charging roller 19 come into contact with each other at an appropriate pressure, and noise is not generated much. The sponge is preferably a continuous cell type that allows the removed toner and the like to enter the inside without stopping near the surface.

In the apparatus of the present embodiment, the cleaning pad 34 may have a two-layer structure of sponge and non-woven fabric, and the non-woven fabric may be brought into contact with the charging roller 19. Although the frictional force of non-woven fabric is not so large as that of sponge, a sponge having a suitable hardness is selected to increase the amount of biting during press contact, and the pressing force of the arm 40 during cleaning depends on the cam curve of the eccentric cam 100. Adjust it. The cleaning pad 3 is made by combining a sponge with about 50 cells and a non-woven fabric.
No. 4 is made, a contact pressure of 30 g / cm ² and 10,000 sheets of A4 paper are copied, and the toner remaining on the surface of the charging roller 19 is removed by tape transfer during that time, and the density of the tape is adjusted. Upon measurement, as shown in FIG. 8 (A), good results were obtained when the thickness of the sponge was 3 times or more the thickness of the nonwoven fabric. The pressure contact force of 30 g / cm ² was selected in order to satisfy both the filming property and the cleaning property of the toner in the experiment of the present inventors, as shown in FIG. 8B.

The charging device of the present invention is not limited to the one in which the direction of pressure contact of the charging roller with the photoconductor and the direction of pressure contact of the cleaning member with the charging roller coincide with each other as in the above-described embodiment. It does not matter if the pressure contact direction is deviated. The cleaning member is not limited to a sponge alone or a combination of a sponge and a non-woven fabric, but if the cleaning member is not a combination of a non-woven fabric, at least the surface contacting the charging roller is made of sponge.

[0030]

As described above, in the charging device of the image forming apparatus according to the first aspect of the present invention, the charging roller charges the photosensitive member.
In the charging mode to perform the
The charging roller is pressed against the photoconductor by the force.
In pressing and cleaning mode, pressing means is attached.
The cleaning member is a charging roller against the biasing force of the biasing means.
The charging roller is pressed against the photoconductor together
Attach the cleaning member by pressing it against the charging roller.
Clean the charging roller in the direction in which it stops rotating along with the photoreceptor.
There is no problem even if friction force is applied by the
Of the cleaning member
The degree of freedom in quality selection has increased, making it difficult to use
The effect that Ponji can also be used as a cleaning member
There is.

In the charging device of the image forming apparatus according to the second aspect, the pressing means moves the charging roller case and senses it.
Pressing the charging roller against the optical body and charging roller of the cleaning member
Since the pressure is applied to the roller,
In addition, it is easier to change the pressure contact force.
It has the effect of growing.

According to a third aspect of the present invention, in the charging device of the image forming apparatus , at least the charging roller of the cleaning member is brought into contact with the charging device .
Since the surface is made of sponge material,
In addition to the effect, it can exert a great cleaning ability
Has the effect of becoming.

A charging device for an image forming apparatus according to claim 4.
Since the number of cells of the sponge material is 20 to 60,
Sufficient cleaning ability even with sponge material alone
In addition to the above, the noise generated during sliding contact with the charging roller is also
The effect is that you can lose
It

In the charging device of the image forming apparatus according to the fifth aspect, since the cleaning member is composed of a two-layer structure of sponge material and felt material, the nip width can be increased without increasing the pressure contact force by bending the sponge material. It is possible to increase the size, and it is possible to obtain sufficient cleaning ability even when using a non-woven fabric having a not so large friction coefficient, and it is possible to substantially eliminate the generation of noise during sliding contact with the charging roller.

In the charging device of the image forming apparatus according to the sixth aspect, the thickness of the sponge material is three times or more the thickness of the non-woven fabric, so that the effect common to the fifth aspect can be further improved. There is an effect that.

[0036]

[Brief description of drawings]

FIG. 1 is a perspective view of an image forming unit using a charging device according to the present invention.

FIG. 2 is a cross-sectional view showing an image forming unit, a transfer / separation device, a fixing device and the like of FIG.

FIG. 3 is an exploded perspective view of a charging device used in the image forming unit of FIG.

FIG. 4 is a cross-sectional view showing the operation of an embodiment of the charging device according to the present invention.

FIG. 5 is a front sectional view (A) and a side sectional view (B) schematically showing the state of FIG. 4 (A).

FIG. 6 is a front sectional view (A) and a side sectional view (B) schematically showing the state of FIG. 4 (B).

FIG. 7 is a front sectional view (A) and a side sectional view (B) schematically showing the state of FIG. 4 (C).

FIG. 8 is a graph (B) showing experimental results regarding the relationship between the thickness ratio and the cleaning property (A) and the relationship between the pressure contact force, the cleaning property, and the filming in a cleaning pad having a two-layer structure of sponge and nonwoven fabric. Is.

[Explanation of symbols]

10 Imaging unit 11 Transfer device 12 Fixing device 13 Transfer roller 14 Rotation fulcrum 15 Pressure roller 16 heating roller 17 Case of image forming unit

Front page continuation (72) Inventor Shigeru Watanabe 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company within Ricoh (72) Inventor Kenzo Tatsumi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company In Ricoh (72) Inventor Toshitaka Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh (72) Inventor Takeo Suda 1-3-6 Nakamagome, Tokyo Ota-ku, Tokyo Stock company (72) Inventor Hiroshi Yoshinaga 1-3-6 Nakamagome, Ota-ku, Tokyo Incorporated in Ricoh Company (72) Inventor Mayumi Ohori 1-3-3 Nakamagome, Ota-ku, Tokyo In Ricoh (56) ) Reference JP-A-7-110640 (JP, A) JP-A-6-3930 (JP, A) JP-A-8-22172 (JP, A) JP-A-7-325461 (JP, A) JP-A-7-325461 (JP, A) 8-62948 (JP, A) JP-A-8-110683 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (6)

(57) [Claims] 1. A charging roller, comprising: a charging roller for charging the photosensitive element while pressingly contacting the photosensitive element and rotating while being driven; and a cleaning member for cleaning the charging roller by pressingly contacting the charging roller. Contact
Direction is the same as the charging roller contacting the photoconductor
In the charging device of the image forming apparatus is, the charging Low
And a charging roller case that holds the cleaning member and the cleaning member.
And a biasing means for biasing the charging roller in a direction away from the cleaning member, and the cleaning member.
The charging roller is pressed against the charging roller so that the charging roller contacts the photoreceptor.
Press in the direction of pressure contact, and the pressing force can be changed
And a charging unit, the charging roller is
In the charging mode for charging to
The charging roller is applied to the photosensitive member by the urging force of the urging means.
Press in the pressing force of pressure contact, and put in the cleaning mode.
The pressing means resists the urging force of the urging means.
The cleaning member is attached to the charging roller and the charging roller.
Is pressed against the photoconductor with the pressing force.
Charging device for the image forming apparatus. 2. A charging roller case holding the cleaning member and the charging roller, wherein the pressing means moves the charging roller case to press the charging roller against the photoconductor and charge the cleaning member. The charging device of the image forming apparatus according to claim 1 , wherein the charging device is pressed against the roller. 3. A charging device for an image forming apparatus according to claim 1 or 2 surface in contact to at least the charging roller of the cleaning member is characterized in that it consists of a sponge material. 4. The number of cells of the sponge material is 20 to 60.
The image forming apparatus according to claim 3, wherein
Charging device. Wherein said cleaning member comprises a sponge material, a charging device of an image forming apparatus according to claim 1 or 2, characterized in that a two-layer structure of the felt material to slide on the surface of the charging roller. 6. The charging device for an image forming apparatus according to claim 5, wherein the thickness of the sponge material is three times or more the thickness of the nonwoven fabric.