JP2003295582A - Energizing method for electrifying member, electrifying device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize constitution for energizing an electrifying member to a body to be electrified, which is easily assembled and attached, by preventing the deflection of the electrifying member by energizing force and restraining faulty electrification without hindering miniaturization and lightness in weight in a proximate electrifying system. <P>SOLUTION: A projecting part 29c for holding an electrifying gap is formed at both ends of an electrifying roller 29, and an energizing means 30 is provided corresponding to each projecting part 29c. By pressing the projecting part 29c in a housing hole 30c-1, positional deviation in a radial direction and an axial direction is regulated, and the energizing means 30 is snap-fit and fixed in a housing through an attaching fixing part 30a in such a state. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for urging a charging member against an object to be charged such as a photoconductor, a charging device for carrying out the method for urging the charging member, a process cartridge having the charging device, and the charging device. The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, etc.

[0002]

2. Description of the Related Art In this type of image forming apparatus, an electrostatic latent image is formed on the surface of a photoconductor uniformly charged by a charging device based on image information of an original and the electrostatic latent image is developed. A toner image is visualized by a device, the toner image is transferred onto a recording medium, and the fixing device fixes the toner image on the recording medium. As a charging device, a voltage of several kV is applied to a wire of tungsten or the like for 10 to 30
A charging charger that charges the surface of the photoconductor through a space of mm has been used, but in recent years, for the reason that it is environmentally friendly, a metal cored bar of rubber or the like having a resistance value of 104 to 1012 Ω is used. The contact type roller charging method in which a roller having a resistance member is directly pressed against a photosensitive member to perform charging is the mainstream.

However, in contact-type roller charging, it is difficult to maintain the initial function of the roller because impurities such as toner and paper dust remaining on the surface of the photoconductor adhere to the roller surface through the contact portion. On the contrary, the impurities contained in the elastic layer of the charged body may be adhered to the charged body to be contaminated. In order to improve the problem, JP-A-58
-76851, JP2-148059, JP4-360167
In the publication, etc., a charging method (hereinafter referred to as a proximity charging method) in a non-contact (or proximity) state is proposed in which a minute gap is provided between a charged body (charging roller) and a charged body (photosensitive body). is doing.

For the roller charging, there is a DC charging method (hereinafter abbreviated as DC) in which only a DC voltage of a few hundreds V or more is applied,
There is an AC superimposition charging method (hereinafter abbreviated as AC) that applies an AC voltage of several hundreds of volts or more to a DC voltage, and in both cases, the ozone generation amount is one to two digits smaller than that of a charger. DC and AC have their respective advantages and disadvantages, and DC has the advantage that the ozone generation amount is one digit less than AC.
AC has the advantage over DC that it is easier to uniformly charge the surface of the photoconductor. In the market, there are many models that use AC mainly because it is easy to uniformly charge. However, the charging by AC has a problem in that the photosensitive member and the charging roller vibrate due to the influence of the AC voltage and generate noise. As one means to improve this problem, there is a method of increasing the pressure contact force to the photoconductor, and a method of pressing (biasing) the shafts provided at both ends of the charging roller is adopted.

[0005]

However, in the system in which the shafts at both ends of the charging roller are biased, both ends of the charging roller serve as fulcrums, and the central portion of the charging roller bends away from the photosensitive member. Defects are likely to occur. In the proximity charging method, as shown in FIG. 11, the convex portion 29c for holding the gap serves as a fulcrum to bend, and the size of the gap is the convex size of the convex portion 29c plus the amount of bending due to pressure contact. Therefore, charging failure is more likely to occur. In FIG. 11, reference numeral 29 is a charging roller, and 29a is a cored bar. Further, in order to reduce the amount of bending, the core metal 29a
It is necessary to increase the diameter of the, and inevitably there is a limit to reducing the diameter and weight. Further, generally, the urging means and a sliding member such as a bearing for receiving the urging force provided on the shaft of the charging roller are separate parts, and the number of assembling steps is large.
Further, in the proximity charging method, stains such as toner and paper powder adhere to the convex portions that are in contact with the body to be charged, and the stability of maintaining the gap for a long period of time cannot be said to be sufficient.

Therefore, according to the present invention, there are provided a charging member urging method, a charging device, a process cartridge, and an image forming apparatus which can solve the above problems in the proximity charging system and can fully utilize the advantages of the proximity charging system. Providing is its main purpose.

[0007]

In order to achieve the above object, in the invention described in claim 1, the charging member having a convex portion on the outer surface is biased to come into contact with the member to be charged, and In the biasing method of the charging member for maintaining a minute discharge gap between the surface and the surface of the body to be charged, the portion corresponding to the convex portion of the charging member is biased.

According to the second aspect of the present invention, a charging member having an outer surface with a convex portion for maintaining a minute discharge gap between the surface of the member to be charged and the charging member is urged to the member to be charged. In the charging device having the biasing means, the biasing means has a configuration of biasing a portion of the charging member corresponding to the convex portion.

According to a third aspect of the present invention, in the charging device according to the second aspect, the urging means is an attachment fixing portion and is supported by the attachment fixing portion and can be brought into contact with and separated from the charged body. The charging member has a convex holding portion that holds the convex portion, and an elastic member that biases the convex holding portion toward the body to be charged, and the convex holding portion is the convex portion of the charging member. The configuration is such that the portion of the portion can be pushed in and fitted in the direction orthogonal to the axial direction of the charging member.

According to a fourth aspect of the present invention, in the charging device according to the third aspect, the charging member has a roller shape, and the convex portion is provided in an annular shape in the circumferential direction, and the convex portion holding portion is provided. Has a configuration in which a cleaning member for cleaning the outer peripheral surface of the convex portion is provided.

According to a fifth aspect of the present invention, in a process cartridge that integrally includes an image carrier and a charging device that performs a charging process on the surface of the image carrier, the charging device includes:
The configuration is as described in any one of claims 2 to 4.

According to a sixth aspect of the present invention, in an image forming apparatus having an image bearing member and a charging device for performing a charging process on the surface of the image bearing member, the charging device is the second to fourth aspects.
It is the one described in any one of the above.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.
It will be described with reference to FIG. First, the outline of the configuration of the copying machine 1 as the image forming apparatus in this embodiment will be described with reference to FIG. An image forming unit 2 is arranged substantially in the center of the in-body discharge type copying machine 1, and a paper feeding unit 3 is arranged immediately below the image forming unit 2. If necessary, you can add another paper feeder to the bottom. Above the image forming section 2, a reading section 5 for reading a document with a discharged sheet storage section 4 interposed therebetween.
Is provided. A space between the image forming section 2 and the reading section 5 is formed as a discharged sheet storage section 4, and a recording medium on which an image is formed (hereinafter referred to as a sheet) is discharged and stored. In the image forming unit 2, the photoconductor 6 is provided around the drum-shaped photoconductor 6.
Device 7 for charging the surface of the photoconductor, an exposure device 8 for irradiating the surface of the photoconductor 6 with a laser beam based on image information, and an electrostatic latent image formed by being exposed on the surface of the photoconductor 6 are visualized. A developing device 9, a transfer device 10 for transferring the toner image developed on the photoconductor 6 to a sheet, a cleaning device 11 for removing and collecting the toner remaining on the surface of the photoconductor 6 after the transfer, and the like are arranged.

The photoconductor 6, the charging device 7, the developing device 9, the cleaning device 11 and the like are incorporated in one unit as a process cartridge 12 which is detachable from the main body of the device. A fixing device 13 for fixing the toner on the paper on which the toner image is obtained is arranged downstream in the paper conveyance path. The sheet that has passed through the fixing device 13 has a pair of discharge rollers 14
After that, the paper is discharged and stored in the discharged paper storage unit 4. In the paper feeding unit 3, the paper 16 is accommodated in the paper feeding cassette 15, and the paper feeding rollers 17 rotate to feed the paper one by one from the highest one and convey it to the registration roller pair 18.
The sheet is temporarily stopped by the pair of registration rollers 18, the skew displacement is corrected, and then the rotation of the sheet is controlled at the timing when the positional relationship between the toner image on the surface of the photoconductor 6 and the leading edge of the sheet becomes a predetermined position. It is conveyed to the transfer site by the pair 18.

In the reading section 5, the contact glass 19
In order to read and scan a document (not shown) placed on the document, a document traveling light source 20 and a reading traveling body 24 including mirrors 21, 22, and 23 reciprocate. The image information scanned by the reading traveling body 24 is read by the lens 25.
It is read as an image signal in a CCD (charge coupled device) 26 installed in the rear of the. The read image signal is digitized and image-processed. Based on the image-processed signal, the laser diode 27 of the exposure device 8 emits light to form an electrostatic latent image on the surface of the photoconductor 6. The optical signal from the laser diode 27 is transmitted to the polygon mirror 2
It reaches the photoconductor 6 through 8 and a lens.

As shown in FIG. 6, the charging device 7 has a charging roller 29 as a charging member and an urging means 30 for pressing and urging the charging roller 29 against the photosensitive member 6. The means 30 is fixed to the fixing member 31 of the process cartridge 12. As shown in FIGS. 1 and 2, the charging roller 29 has, for example, 104 to 1 on the outer peripheral surface of a metal cored bar 29a.
It has a structure in which a medium resistance layer 29b such as rubber having a resistance value of 012 Ω is fleshed out, and convex portions 29c for holding a discharge gap between the surface of the photoconductor 6 are formed at both ends in an annular shape. ing. The convex portion 29c is in contact with the photoconductor 6 and is rotated by a frictional force as the photoconductor 6 rotates. By applying a voltage to the cored bar 29a, the surface of the photoconductor 6 is charged to a predetermined potential.

The urging means 30 is the process cartridge 1
It has an attachment fixing portion 30a fixed to the second fixing member 31 by a snap fit method, and a convex portion holding portion 30c supported by the attachment fixing portion 30a via two spring portions 30b as elastic members. . Mounting and fixing portion 30a, spring portion 30
The b and the convex portion holding portion 30c are integrally formed of resin. Engagement protrusions 30a-1 having hooks are formed on both sides of the upper surface of the attachment fixing portion 30a as an attachment portion to the housing, and correspondingly, the engaging portion 30a of the process cartridge 12 is engaged with the fixing portion 31a. A receiving portion (not shown) is formed. When the attachment fixing portion 30a is pushed into the engagement receiving portion, the engagement protrusion 30
The a-1 enters while elastically deforming outward, and the hook portion fits to the engagement receiving portion by the elastic force. This one-touch operation completes the attachment and fixing of the biasing means 30 in the process cartridge 12.

The convex portion holding portion 30c has a housing hole 30c-1 for housing the convex portion 29c of the charging roller 29, and the housing hole 30c-1 is partially opened. The charging roller 29 is inserted into the accommodation hole 30c-1 by pushing the convex portion 29c in the direction orthogonal to the axial direction of the charging roller 29. The width d of the opening 30c-4 is equal to the width of the charging roller 2 after accommodation.
It is set to be narrower than the outer diameter of the convex portion 29c so that 9 does not come off. In addition, the opening 30c-4 has a tapered guide surface 30c-2 that expands outward, which facilitates the pressing of the charging roller 29 and also allows the accommodation hole 3 to be accommodated.
0c-1 spreads easily due to the elastic deformability of the resin. The accommodation hole 30c-1 has an accommodation width slightly wider than the width s of the convex portion 29c and a diameter slightly larger than the outer diameter of the convex portion 29c, and the shaft of the charging roller 29 is provided on both sides thereof. The side edge 30c-3 that regulates the deviation in the direction is formed in an annular shape. The inner surface of the accommodation hole 30c-1 is a sliding surface that contacts the convex portion 29c.

The side edge 30c-3 is projected in the radial direction,
The protrusion amount is set to a size that intersects the side surface of the convex portion 29c. Therefore, the convex portion 29c pushed into the accommodation hole 30c-1 is regulated on both sides in the axial direction by the side edges 30c-3, and the displacement of the charging roller 29 with respect to the biasing means 30 in the axial direction is regulated. As described above, since the radial slip-off is also restricted, the convex portion 29c is inserted into the accommodation hole 30c-1.
After being fitted in, the displacement of the biasing means 30 and the charging roller 29 is restricted. Therefore, the operator only needs to hold the biasing means 30 and fix it to the fixing portion 31 of the process cartridge 12 after fitting the convex portion 29c, which facilitates the fixing work.

That is, the diameter of the accommodation hole 30c-1 is set to be slightly larger than the outer diameter of the convex portion 29c so that the charging roller 29 can be slanted without the side edge 30c-3. If the charging roller 29 is inclined, the biasing means 30 and the charging roller 29 need to be held by hand because they fall out of the biasing means 30, but in the present embodiment, even if the charging roller 29 is inclined, Since the displacement of the charging roller 29 does not occur, after assembling the biasing means 30 and the charging roller 29, the charging roller 29 can be fixed without worrying about the slipping out and without being firmly held by both hands. In the present embodiment, since the convex portion 29c of the charging roller 29 is used as it is, no special additional work is required for preventing the charging roller 29 from coming off in the axial direction. The side edge 30c-3 can restrict the positional deviation even if it is formed only on the side closer to the axial end portion or on the side closer to the central portion in the axial direction in each biasing means 30. The axial retaining structure is not limited to the above-described shape, but can be arbitrarily formed by relatively providing, for example, a concave and convex engaging structure between the biasing means 30 and the charging roller 29.

As shown in FIG. 1, in the convex portion holding portion 30c, a cleaning member 32 for cleaning the outer peripheral surface of the convex portion 29c so as to project to the sliding surface of the accommodation hole 30c-1.
Is provided. FIG. 3 is a sectional view taken along arrow A1 in FIG. The convex portion 29c of the charging roller 29 is provided in the accommodation hole 30.
Although it slides on the inner surface of c-1, the outer surface of the medium resistance layer 29b does not slide on the side edge 30c-3. FIG. 4 is a sectional view taken along arrow A2 in FIG. At this portion, the outer peripheral surface of the convex portion 29c is cleaned of dirt by the cleaning member 32. The cleaning member 32 may be made of any material as long as it can easily remove stains such as toner and paper dust on sponges, brushes, felts, blades and the like. As shown in FIG. 5, the urging means 30 includes the convex portions 29 of the charging roller 29.
The spring portion 3 of the biasing means 30 is provided corresponding to c.
Due to the elastic deformation of 0b, the urging force G acts on the portion of the convex portion 29c. That is, the charging roller 29 is pressed against the photoconductor 6 at a predetermined pressure with the convex portion 29c as a force point. Therefore, the bending of the charging roller 29 as shown in FIG. 10 is prevented,
The discharge gap g is held uniformly over the entire axial direction.

The urging force G needs to be strong so that noise due to AC can be suppressed, and it is preferable that G> VAC / 2 is satisfied in order to reduce the noise level to 50 (dB) or less. By providing the process cartridge with the biasing means 30, it is possible to reduce the size and weight of the process cartridge, reduce the number of parts, improve recyclability, and improve quality. Further, by providing the image forming apparatus, it is possible to reduce the size and weight of the image forming apparatus, reduce the number of parts, improve recyclability, and improve quality. Further, since the biasing means 30 in the present embodiment uses the roller portion of the charging roller 29 directly as the rotating shaft, it is not necessary to provide a shaft portion on the charging roller as in the conventional case, which leads to cost reduction and the roller portion By taking the datum, there is an advantage that the deflection and cylindricity of the roller portion can be directly measured in the inspection process.

Measurement results of the VAC-G (AC superimposed charging-urging force) characteristics, and the gap size between the photoconductor and the charging roller and the actual sheet passing in the initial stage of the conventional urging structure and the urging structure of this embodiment. The results of measuring the gap size after 20k (20,000) sheets are shown below. 1. VAC-G characteristics The outline is shown in FIG. The horizontal axis is the peak to
The voltage width of the peak (between peaks), the vertical axis is the biasing force. Ricoh's IPSIO NX410 was used for the measurement, and 50 (d
If there is noise above B), it is "NG", and if it is below 50 (dB), it is "O."
K. "2. Gap size measurement (initial and after 20 k sheets of actual paper run) (Sample) Conventional biasing configuration, biasing configuration of this embodiment (fixed condition) Charging roller: (outer diameter 12 mm ) × 340mm Charging roller core metal diameter: 8mm Energizing force: 1000gf Convex part dimension: 50μm

As a result, it can be seen that in the conventional biasing structure, as shown in FIG. 9, the gap in the central portion is widest. 80 μm or more in the initial state, 100 μm due to stains on the protrusions after 20 k sheets of actual paper run
It becomes the above gap. On the other hand, in the biasing structure of the present embodiment (the present invention), as shown in FIG. 10, there is no bulge in the central portion, and it is found that the gap is stably maintained even after 20 k sheets of actual paper feed run. .

In the above embodiment, the urging means 30 is integrally formed, but the mounting and fixing portion 30a and the spring portion 30 are provided.
b, the convex portion holding portion 30c is formed of a separate component,
The structure may be integrally assembled. Spring part 30
For b, a leaf spring or a spring can be adopted. The mounting / fixing portion 30a may be fixed by a screw or the like. In the case of integrally molding and adopting the snap-fit fixing method as described above, it is possible to reduce the number of parts, facilitate manufacturing, reduce costs associated therewith, and improve fixing operability. Further, since the charging roller 29 can be fixed to the biasing means 30 by a one-touch pushing operation, the assembling easiness of the charging device 7 can be improved. Side edge 30
c-3 must lock at least one side surface of the convex portion 29c of the charging roller 29. It is preferable to lock from both sides (one side surface in each biasing means 30), and it is more preferable to lock both side surfaces of the convex portion 29c as described above. The reason is that the parts can be downsized, and the force for pushing the opening 30c-4 when the roller is fitted is small.

[0026]

According to the present invention, a charging member having a convex portion on its outer surface is urged to abut against a member to be charged, and the space between the surface of the charging member and the surface of the member to be charged. In the biasing method of the charging member for maintaining the minute discharge gap, since the portion of the charging member corresponding to the convex portion is biased, the charging member does not bend even if the biasing force is increased. ,
The discharge gap can be made uniform and charging failure can be suppressed. Also,
Since it is not necessary to make the core metal of the charging member large, downsizing,
The weight can be reduced.

According to the invention of claim 2, 5 or 6,
In a charging device having a charging member having an outer surface with a convex portion for maintaining a minute discharge gap between the surface of the member to be charged and a biasing unit for biasing the charging member to the member to be charged,
Since the urging means has a structure for urging the portion of the charging member corresponding to the convex portion, the charging member does not bend even if the urging force is increased, and the discharge gap is reduced. It is possible to make it uniform and to suppress charging failure. Further, since it is not necessary to make the core metal of the charging member large, it is possible to reduce the size and weight.

According to the invention of claim 3, 5 or 6,
3. The charging device according to claim 2, wherein the urging means holds a mounting fixing portion and a portion of the convex portion of the charging member which is supported by the mounting fixing portion and is capable of coming into contact with and separating from the body to be charged. A convex holding unit and an elastic member for urging the convex holding unit toward the body to be charged are provided, and the convex holding unit has the convex portion of the charging member in the axial direction of the charging member. Since the charging member is configured so that it can be pushed in and fitted in the orthogonal direction, the charging member does not bend even if the biasing force is increased, the discharge gap can be made uniform, and charging failure can be suppressed. Further, since it is not necessary to make the core metal of the charging member large, it is possible to reduce the size and weight.

According to the invention described in claim 4, 5 or 6,
The charging device according to claim 3, wherein the charging member has a roller shape, the convex portion is provided in an annular shape in a circumferential direction, and the convex portion holding portion cleans an outer peripheral surface of the convex portion. Since the member is provided, even if dirt such as paper powder or toner adheres to the convex portion during long-term use of the charging member, the charging member can be cleaned and the discharge gap can be uniformly maintained, and the charging member can be protected from impurities. It is possible to prevent the charged body from being contaminated.

[Brief description of drawings]

FIG. 1 is a front view of a charging unit according to an embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a cross-sectional view taken along arrow A1 of FIG.

FIG. 4 is a cross-sectional view taken along arrow A2 of FIG.

FIG. 5 is a cross-sectional view showing a biased state of a charging member with respect to a photoconductor.

FIG. 6 is an enlarged front view of the process cartridge.

FIG. 7 is a schematic front view of a copying machine as an image forming apparatus.

FIG. 8 is a graph showing VAC-G characteristics.

FIG. 9 is a graph showing the relationship between the gap size and the distance from the end of the charging roller in the conventional biasing structure.

FIG. 10 is a graph showing the relationship between the gap size and the distance from the end of the charging roller in this embodiment.

FIG. 11 is a cross-sectional view showing a conventional biasing state of a charging member with respect to a photoconductor.

[Explanation of symbols]

6 Photoreceptor as charged body 12 process cartridges 29 Charging roller as charging member 29c convex g Discharge gap 20 Biasing means 30a Mounting and fixing part 30b Spring part as elastic member 30c convex part holding part 32 Cleaning member

Claims (6)

[Claims] 1. A charging device for urging a charging member having a convex portion on its outer surface to bring it into contact with an object to be charged so that a minute discharge gap is maintained between the surface of the charging member and the surface of the object to be charged. In the member biasing method, the charging member biasing method is characterized in that a portion of the charging member corresponding to the convex portion is biased. 2. A charging member having an outer surface having a convex portion for holding a minute discharge gap between the charging member and the surface of the member to be charged, and an urging means for urging the charging member to the member to be charged. In the charging device, the urging means has a structure for urging a portion of the charging member corresponding to the convex portion. 3. The charging device according to claim 2, wherein the urging means is an attachment fixing portion and the protrusion of the charging member is supported by the attachment fixing portion and can be brought into contact with and separated from the charged body. Of the charging member, and an elastic member for urging the projection holding member toward the body to be charged.The projection holding member is configured to charge the protruding portion of the charging member to the charging member. A charging device having a configuration capable of being pushed in in a direction orthogonal to an axial direction of a member and fitted therein. 4. The charging device according to claim 3, wherein the charging member has a roller shape, the convex portion is provided in an annular shape in a circumferential direction, and the convex portion holding portion has an outer periphery of the convex portion. A charging device comprising a cleaning member for cleaning the surface. 5. A process cartridge integrally comprising an image bearing member and a charging device for charging the surface of the image bearing member, wherein the charging device is according to any one of claims 2 to 4. Process cartridge characterized by being. 6. An image forming apparatus having an image carrier and a charging device for charging the surface of the image carrier, wherein the charging device is the device according to any one of claims 2 to 4. An image forming apparatus characterized in that there is.