JPH11218999A - Electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain uniform and stable potential by means of electrification in stably rotating while holding an electrifying electrode in non-contact with the electric charge acceptor, in an electrifying device supporting the cylindrical electrifying electrode closely opposite to the electric charge acceptor. SOLUTION: This device is provided with the electrode supporting member 3 supporting the electrifying electrode 2 so as to face the electric charge acceptor 1 with a fine gap, inside the cylindrical electrifying electrode 2. The electrode supporting member 3 connected with a power source 4 is allowed to apply a voltage for electrifying on the electrifying electrode 2 across the electrode supporting member 3. When a given voltage is applied on the electrifying electrode 2, the electrifying electrode 2 is attracted to the electrode supporting member 3 side by the electrostatic force developed between the electrode supporting member 3, and driven in the rotary direction of the electric charge acceptor 1 by the electrostatic force developed between the electric charge acceptor 1. In such a manner, the electrifying electrode 2 is allowed to stably rotate which to keep a fine gap between the electric charge acceptor 1.

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 transferring charges to and from a predetermined charge receptor, and more specifically, to a device for charging the surface of a member to be charged such as a photoreceptor, and a photoreceptor. The present invention relates to a charging device applied to an electrophotographic recording device, an electrostatic recording device, and the like, including a device for removing charges accumulated on a charge-removing member such as a transfer member and an intermediate transfer member.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer to which an electrophotographic process is applied, for example, the above-described charging device, specifically, a charging device and a static eliminator have been widely used. In the above-described image forming apparatus, the surface of a charge receptor such as a photosensitive drum is charged by a charging device, and an image is exposed to form an electrostatic latent image on the surface of the charge receptor. Visualize the latent image to obtain a developed image, transfer the developed image to recording paper, etc.
An image is formed on the recording paper by a fixing process. Conventionally, as a charging device used in such an image forming apparatus, there are a non-contact charging system using corona discharge or the like and a contact charging system using a charging roll or the like using discharge in a minute gap.

In a charging device using corona discharge, a wire is stretched in a shield case so as to be close to or separated from the surface of a charge receptor, and a high voltage is applied to the wire to generate a corona discharge. To give a predetermined charge to the substrate. Such charging device, although excellent in charging uniformity, ozone, the discharge products such as NO _X occurs in large quantities, its address is required, size of the apparatus tends to cause high cost There is a disadvantage that. In addition, the electrode wire may be contaminated by dust in the air, toner, discharge products, fuser oil, or the like, resulting in non-uniform charging, which may cause a defect in an obtained image.

For this reason, recently, a contact charging system in which a charging electrode is brought into direct contact with a charge receptor to perform charging has been studied. In this charging device, a conductive member having semi-conductivity is arranged so as to be in contact with the surface of the charge receptor, and a voltage is applied to the conductive member to generate a discharge in a minute gap near the contact portion. Is what you do. Examples of the conductive member used in such an apparatus include a roll-shaped member and a brush-shaped member. This method has an advantage that the amount of generated ozone is extremely low because corona discharge is not used. Further, since it is in contact with the charge acceptor, it is suitable for reducing the size and weight of the apparatus. Currently, an image forming apparatus using a roll-type or brush-type charging device has been commercialized. In addition, cleaning blades having a charging function (JP-A-1-93760, JP-A-2-93760).
282279) or a charging device comprising a film-shaped charging member (see JP-A-4-249270).
Have been proposed, and research on the practical use of various contact charging devices has been promoted.

However, among the above-mentioned contact charging devices, those using a conductive elastic roll have a drawback that the structure tends to be complicated because a roll supporting device is required. In addition, in order to perform uniform charging, it is necessary to improve the adhesion to the charge acceptor to form stable minute voids, and to take measures such as lowering the hardness of rubber. Therefore, a large amount of process oil needs to be contained in the rubber, and this oil has a disadvantage that it tends to transfer to the charge acceptor and adversely affect the image quality. On the other hand, in order to solve such a defect, there is a method of increasing the outer shape accuracy of the roll, but it is very difficult to increase the outer shape accuracy of the elastic body, which leads to an increase in cost such as a decrease in yield.

[0006] In the charging device using a conductive brush, it is easier to make the contact uniform than the above-mentioned elastic roll, but it takes much time and effort to manufacture the brush, and the brush sweeping is difficult. However, there is a problem that the image tends to appear on the image as charging unevenness.

Further, in the method in which the blade-shaped charging electrode is also used as a cleaning blade, it is difficult to achieve both the cleaning accuracy and the setting of the minute gap required for discharge, and it is difficult to perform uniform and good charging. Even if the cleaning function is not used, the charging device is always stationary with respect to the charge receptor, so it is easy to accumulate dirt such as residual toner and external additives adhering to the charge receptor after transfer. There is a major drawback that image quality defects and abnormal discharge occur.

On the other hand, in a film-shaped charging device (for example, see Japanese Patent Application Laid-Open No. 4-249270), stable contact can be easily obtained with a simple structure as compared with other conductive members, and the cost of the members is low. Since the charging is performed while being pressed against the charge receptor, the charging potential tends to be unstable due to frictional charging or vibration of the charging electrode. Further, similarly to the blade-shaped charger, there is another problem that foreign matter such as toner adheres to the contact nip and the charged potential becomes uneven. As a means for improving such a problem, there is a method of applying a DC voltage in which an AC voltage is superimposed on the contact charging device. However, since the surface energy of the charge acceptor increases, cleaning failure may be caused. This causes a problem that generation and wear of the charge receptor become remarkable. In addition, there is a disadvantage that vibration according to the frequency of the alternating current occurs in the film-shaped member, and charging noise is generated. Further, when applying a DC voltage on which the AC voltage is superimposed as described above, there is a problem that the charging efficiency is extremely low. For example, when calculating the energy consumption efficiency, the ratio of the electrostatic energy for charging the charge receptor to the power consumption energy of the charger is:
The scorotron is 0.5%, and the charging roll to which a voltage obtained by superimposing an AC voltage on a DC voltage is 2.6%.

In order to solve such problems as low charging efficiency and accelerated deterioration of the charge acceptor, a DC voltage is applied by bringing the above semiconductive electrode into contact with the charge acceptor to charge the charge acceptor. The charging device to be used has been studied again. However, in such a method, the energy consumption efficiency is 27.
Although it is as large as 3%, the charging potential is uniquely determined by the discharge starting voltage and the resistance of the charging electrode.
There is a disadvantage that the charging potential becomes non-uniform due to resistance unevenness of the charging electrode or environmental fluctuation of the resistance. In particular, the polymer material used as the surface material of the charging electrode has a property that the resistance varies by about 0.5 to 1 digit and varies by about 2 digits depending on the temperature and humidity of the atmosphere. Furthermore, since the charged electrode is pressed against the charge receptor and brought into contact therewith, dirt such as toner, discharge products, dust in the air, and paper dust easily adheres to the surface of the charged electrode. And unstable discharge occur, and image defects such as fogging are likely to occur. This instability against dirt is particularly remarkable when a DC voltage is applied, and non-uniform charging due to a large amount of dirt is unsuitable especially for an image forming apparatus aiming at high image quality. There are also technical flaws.

In order to avoid the above-mentioned drawbacks, there have been proposed charging devices disclosed in JP-A-4-232977 and JP-A-5-72869. This charging device uses a charging electrode in which a flexible film-shaped member is formed in a cylindrical shape, and supports the charging electrode in contact with the peripheral surface of the support roller to contact the charge receiving member in a bent state. It is to let. The peripheral surface of the charging electrode is moved endlessly by the rotation of the support roller, and the moving direction is set to be the same direction at the contact portion with the charge receptor. In order to stably contact the charging electrode with the supporting roller, a pressing member for pressing the charging electrode against the peripheral surface of the supporting roller may be provided.

In such a charging device, there is an advantage that frictional charging between the charging electrode and the charge receptor is minimized, and occurrence of charging failure due to vibration can be eliminated. Further, foreign substances such as toner are unlikely to adhere, and the occurrence of uneven charging can be reduced. Also, even if foreign matter adheres, the charged electrode rotates, so that it does not stay at the same position,
It is possible to avoid the occurrence of vertical stripe-like image quality defects.

However, since the above-mentioned devices are similar to the above-described various charging devices in that they come into contact with the charge acceptors, poor charging occurs due to long-term use, resulting in the same deterioration in image quality. . In particular, in a cleanerless image forming apparatus that does not use a cleaning device, non-transferred toner and discharge products adhere to the charging device while being rubbed with the charging device. A major problem occurs. Further, an image on image (IOI) in which a plurality of color images are superimposed on a charge receptor and the images are collectively transferred to paper.
In an image forming apparatus, there is a fatal defect that a contact-type charging device including the above-mentioned device cannot be used because an image is disturbed when the image forming device comes into contact with a charge acceptor.

In order to solve such problems of the contact-type charging device, there have been proposed charging devices disclosed in JP-A-62-296174, JP-A-63-75760 and JP-A-1-292358. ing. In this charging device, a semiconductive flat plate or a curved plate is disposed in close proximity to a charge receptor, and discharge is generated in a minute gap to charge the charge receptor. Therefore,
Since the above-mentioned adverse effects caused by contact with the charge acceptor can be prevented, the present invention can be used in a cleanerless image forming apparatus and an IOI image forming apparatus.

[0014]

However, Japanese Patent Application Laid-Open Nos. 62-296174 and 63-7576 describe the above.
No. 0 and Japanese Patent Application Laid-Open No. 1-292358 have the following problems. In the above charging device, the distance between the charging device and the charge acceptor is 2000 μm
Very close to the following, the gap fluctuation due to slight eccentricity at the time of image formation, and the foreign matter on the charge acceptor flies to the charging device surface due to the electric field impact at the start or end of image formation . When the amount of deposits increases in this way, there is a disadvantage that charging failure occurs as in the case of the above-mentioned contact type charging device.

In order to avoid such a problem, the charging device disclosed in Japanese Patent Application Laid-Open No. 6-194933 proposes a configuration in which a rotating roll is arranged in a non-contact manner to reduce the occurrence of charging failure due to foreign matter adhesion. Have been. However, in the micro gap discharge to which a DC voltage is applied, when the distance between the charge receptor and the surface of the charging device changes by 1 μm, the potential fluctuates by about 3 V. Therefore, the fluctuation width must be suppressed to several μm or less. Therefore, there is a fatal drawback that it is almost impossible to hold a roll having such a driving source with such accuracy.

For this reason, it is conceivable to apply a voltage obtained by superimposing an AC voltage on a DC voltage instead of a DC voltage. However, since the member to be charged is greatly damaged as described above, the life is extremely shortened. In particular, it cannot be used at all in a cleanerless image forming apparatus or the like.

The present invention has been made in view of the above problems, and an object of the present invention is to rotate a charged electrode while keeping it in a stable and non-contact state with a charge receptor. An object of the present invention is to provide a charging device and a charging device for static elimination that can perform uniform and stable charging or static elimination, and that provide stable image quality for a long period of time.

[0018]

According to a first aspect of the present invention, there is provided a charging device according to the first aspect of the present invention, comprising: a charge receiving member which is formed of a semiconductive material in a cylindrical shape and whose surface moves; A charging electrode that is opposed in a non-contact manner and that is rotatably supported in a circumferential direction; and a power supply that applies a charging voltage to the charging electrode; and near a facing portion between the charging electrode and the charge receptor. The surface of the charge acceptor is charged by causing a discharge within the minute gap, and the electrostatic force generated between the charge acceptor and the charging electrode causes movement of the surface of the charge acceptor. In this case, the charging electrode rotates and moves in the circumferential direction.

In such a charging device, the charging electrode is supported so as to face the charge receptor in a non-contact manner, and when a charging voltage is applied to the charging electrode, the charging electrode contacts the charge receptor. The charge receptor moves around in a certain direction due to the electrostatic force generated therebetween. At that time, a substantially uniform minute gap is obtained between the charging electrode and the charge receptor, and stable charging is performed. In addition, the electrostatic attraction area where the charging electrode comes close to the charge receptor increases due to the electrostatic force, and the discharge area holding an appropriate gap expands, so that a sufficient charging potential can be obtained.

The charging device according to the second aspect of the present invention is
The charging device according to claim 1, further comprising: a rotation stabilizing member that is in contact with an outer peripheral surface of the charging electrode and stabilizes rotation by regulating displacement of the charging electrode. is there.

In such a charging device, the rotation stabilizing member in contact with the outer peripheral surface of the charging electrode prevents the charging electrode from being excessively deformed by centrifugal force or the like, and stably approaches the charge receiving member. A force is applied to maintain the state. Therefore, the rotation of the charging electrode is stabilized, and a uniform charging potential is obtained. Further, the degree of freedom with respect to the installation position of the charging electrode is increased. Further, even when the straightness and roundness of the charging electrode are insufficient, power can be supplied stably, and high precision is not required in manufacturing, and cost can be reduced.

According to a third aspect of the present invention, there is provided a charging device,
3. The charging device according to claim 2, wherein the rotation stabilizing member has a shape such that a force that pushes the charging electrode toward the charge acceptor is increased at a portion in contact with both ends of the charging electrode. 4. This is a characteristic charging device.

In general, when a charged electrode made of a cylindrical thin member is used, if the potential of the charge receptor is uniformly removed in the axial direction, the charged electrode is rotated by the electrostatic force between the charge electrode and the charge receptor. At this time, the deformation of both end portions of the charging electrode tends to be larger than other portions. In particular, if the electrostatic force between the charging electrode and the charge receptor is large, the deformation of the both ends prevents the appropriate gap between the charging electrode and the charge receptor from being maintained, and fogging occurs on both sides of the paper due to uneven charging. Image quality defects occur. This tendency becomes more conspicuous as the hardness of the charging electrode is smaller. However, in the charging device of the present invention, since the pressing force against the charging electrode at both ends of the rotation stabilizing member is set to be larger than that at the center, excessive deformation occurs at both ends of the charging electrode. Can be prevented. For this reason, a uniform charging potential can be obtained, and generation of a fog-like image quality defect can be prevented.

According to a fourth aspect of the present invention, there is provided the charging device,
4. The charging device according to claim 2, wherein the rotation stabilizing member has an endless peripheral surface, and is supported so as to be able to rotate in a circumferential direction with the rotational movement of the charging electrode. 5. A charging device.

In such a charging device, since the rotation stabilizing member is provided so as to be rotatable in the circumferential direction, the rotation of the charging electrode can be performed more stably without obstructing the rotation of the charging electrode. It also has the advantage that the surface of the charging electrode is not easily damaged.

According to a fifth aspect of the present invention, there is provided a charging device,
The charging device according to claim 2, wherein the rotation stabilizing member is made of a conductive material,
A charging device is characterized in that a charging voltage is applied to the charging electrode via the rotation stabilizing member.

In such a charging device, the charging voltage is applied via the rotation stabilizing member which is in contact with the outer peripheral surface of the charging electrode.
Even if the position of the charging electrode fluctuates due to unevenness in film thickness and straightness, the position of the rotation stabilizing member in contact with the charging electrode does not change. it can. For this reason, it becomes possible to suppress the fluctuation of the resistance of the charging electrode, and it is possible to prevent the occurrence of uneven charging. In addition, by making the support member of the charging electrode insulative, fluctuations in the capacity between the charging electrode and the charge receptor near the discharge region are reduced, and a more stable charging potential can be obtained.

The charging device according to the invention according to claim 6 is:
6. The charging device according to claim 5, wherein a position where the rotation stabilizing member contacts the charging electrode is substantially equal in distance from both ends of a discharge region in a portion where the charging electrode and the charge receptor face each other. The charging device is set as follows.

The charge acceptor is charged while passing through the discharge area facing the charging electrode. By setting the power supply position of the rotation stabilizing member so that the distance from both ends of the discharge area is equal. In addition, the charge potential of the charge receptor when passing through the rear end of the discharge region can be made substantially constant. Therefore, the charging potential can be made more uniform.

The charging device according to the invention according to claim 7 is:
The charging device according to claim 5, wherein the rotation stabilizing member is supported such that a contact position with the charging electrode can be changed in a circumferential direction of the charging electrode. It is. That is, the power supply position by the rotation stabilizing member is installed so as to be changeable in the circumferential direction of the charging electrode.

In general, the charging property of a charging electrode is affected by the temperature or humidity near the charging device, so that the charging characteristics of the charge receptor with respect to the applied voltage also change. In a low-temperature and low-humidity environment, air is less likely to be ionized than in a high-temperature and high-humidity environment, and is hardly charged. Therefore, when the same voltage is applied, the charge potential of the charge receptor fluctuates. For this reason, this environmental change often has an adverse effect on image quality.
Therefore, the present invention controls the position of the rotation stabilizing member so that the distance from the contact portion with the charged electrode to the discharge region is reduced in a low-temperature and low-humidity environment, and the surface resistance of the charged electrode from the power supply position to the discharge region is reduced. Set to be smaller. Also, in a high temperature and high humidity environment, the position of the rotation stabilizing member is controlled so that the distance from the contact portion with the charging electrode to the discharge region becomes longer,
The resistance of the charging electrode from the power supply position to the discharge region is set to be large. This makes it possible to suppress a decrease in the charging potential in a low-temperature and low-humidity environment and a rise in the charging potential in a high-temperature and high-humidity environment, and to obtain a uniform and stable charging potential without being affected by environmental changes. it can.

The charging device according to the invention described in claim 8 is:
The charging device according to claim 5, wherein a plurality of the rotation stabilizing members are provided in a circumferential direction of the charging electrode, and the power source selects one of the plurality of rotation stabilizing members. A charging device for applying a voltage to the charging device.

In such a charging device, for example, in a low-temperature and low-humidity environment, the applied voltage is increased, the distance from the contact portion with the charging electrode to the discharge region is short, and the rotating device is arranged such that the resistance of the charging electrode is low. Use a stabilizing member.
On the other hand, in a high-temperature and high-humidity environment, a rotation stabilizing member is used in which the applied voltage is reduced, the distance from the contact portion with the charging electrode to the discharge region is long, and the resistance of the charging electrode is increased. As described above, the power supply position and the applied voltage can be selected according to the temperature and the humidity. For this reason, it is possible to prevent a change in the charging potential due to a change in the environment and to obtain a uniform and stable charging potential. Further, since there are a plurality of rotation stabilizing members, the rotation of the charging electrode is stabilized, and a more uniform charging potential can be obtained.

According to a ninth aspect of the present invention, there is provided the charging device,
A charging electrode formed of a semiconductive material in a cylindrical shape, a power supply for applying a charging voltage to the charging electrode,
Contact the charged electrode at a plurality of positions, the charged electrode,
Electrode support means for supporting the surface of the moving charge receptor in a non-contact manner in a non-contact manner and rotatably supporting in the circumferential direction; and This causes the surface of the charge acceptor to be charged, and the electrostatic force generated between the charge acceptor and the charged electrode causes the charged electrode to move around its surface as the charge acceptor surface moves. The charging device is characterized by rotating in a direction.

In such a charging device, the charging electrode can be regulated to an appropriate position by the electrode supporting means and can be rotated more stably, so that the charging electrode can be stably kept close to the charge receptor side. can do. Therefore, a more uniform charged electrode can be stably obtained.

The charging device according to a tenth aspect of the present invention is the charging device according to the ninth aspect, wherein the electrode supporting means is provided at a portion in contact with the charging electrode in a width direction of an outer peripheral surface of the charging electrode. Has a brush that is almost evenly contacted with the
A charging voltage is applied from the power supply to the charging electrode via the brush.

In the present invention, the charging electrode is supported by the brush, and the power is supplied to the charging electrode via the conductive brush. Therefore, the brush makes soft contact with the charging electrode,
Damage to the charging electrode can be prevented. In addition, foreign matter and dirt attached to the surface of the charged electrode can be scraped off by the brush, and the state of the charged electrode can be maintained in a good condition.

The charging device according to the eleventh aspect of the present invention is the charging device according to any one of the first to tenth aspects, wherein the charging electrode comprises an inner layer made of a material having a small electric resistance. And a surface layer having a higher resistance than the inner layer.

In such a charging device, when a voltage is applied to the charging electrode, a current flows through the low resistance inner layer,
Discharge occurs at a position close to the charge electrode and the charge receptor via a high-resistance surface layer. For this reason, even if the charging electrode vibrates and the distance from the power supply position to the discharge area changes, stable discharge can be performed, and fluctuation of the charging potential can be prevented. This is because the discharge is performed from the low-resistance inner layer through the high-resistance surface layer, resulting in a state similar to that in which a capacitor is inserted, which has the effect of smoothing out high-frequency current fluctuations. .

According to a twelfth aspect of the present invention, in the charging device according to any one of the first to eleventh aspects, the charging electrode comprises a flexible film-shaped member having a cylindrical shape. The charging device is characterized in that the charging device is formed in the charging device.

By using such a soft film-shaped charging electrode, it is possible to reduce the external accuracy such as straightness of the charging electrode, so that the manufacturing load can be reduced. Also, by changing the applied voltage,
Since the distance between the charging electrode and the charge receptor can be easily changed, there is also an advantage that it is possible to appropriately cope with environmental changes such as temperature and humidity.

According to a thirteenth aspect of the present invention, in the charging device according to any one of the first to twelfth aspects, the voltage applied to the charging electrode is:
A charging device, wherein the surface potential of the charge acceptor is set to be approximately 0V.

According to a fourteenth aspect of the present invention, in the charging device according to any one of the first to twelfth aspects, the charging electrode is formed on the image carrier by electrophotography. And a voltage applied to the charging electrode is set so that the surface potential of the transfer object is substantially 0 V. Charging device.

The above-described charging device functions as a charge removing device for removing a surface charge of a charge receiving member such as a photoreceptor or a transfer receiving member such as an intermediate transfer member. Although there is an optical charge eliminator as a charge eliminator for removing a charge acceptor such as a photoreceptor, there is a disadvantage that when the charge is removed by light, photo fatigue is promoted and the life of the photoreceptor is shortened. In the charging device of the present invention, since the charge is removed by discharging at minute intervals, such a disadvantage can be solved. Further, depending on the properties of the charge acceptor and the transfer receiving body, the DC voltage or the superimposed voltage of the DC and AC can be appropriately set, and the charge can be efficiently removed with a simple configuration.

The material of the charging electrode in the charging device of the invention according to the present invention may be any material as long as it has semiconductivity, such as polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, and polyolefin. Vinylidene chloride, polyimide, PEN, PEK, PES, PPS, PFA, PVd
Conductive powders such as carbon black, metal powder, and metal oxide are added to resins such as F, ETFE, and CTFE, or synthetic rubbers such as silicone rubber, EPDM, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, and nitrile rubber. Mixed ones can be used.
Also, epichlorohydrin rubber, chloroprene rubber, E
A polar rubber such as PDM rubber or a semiconductive inorganic material such as titanium oxide or amorphous silicon may be formed by depositing a thin film or a thick film on an insulating substrate. However, since a polar rubber or the like has a high adhesive force and a rough surface, a more uniform charging potential can be obtained by coating the surface with a low-adhesion material or the like.
In addition, it is also possible to suitably use a metal cylinder or the like that cannot be used in the conventional contact type but can be produced with high hardness but with high accuracy, and to prevent dielectric breakdown, Various materials can be suitably used by coating or vapor deposition.

[0046] At this time, it is necessary to adjust the mixing amount of the conductive particles such that the preferred volume resistivity, 10 ² Omega
· Spark discharge easily occurs in cm or less, 10 ¹¹ Ω · c
m or more tends to cause dot-like charging failure,
It is desirable to use in the range of 0 ³ Ω · cm to ^{10 10} Ω · cm. In particular, at 10 ⁴ Ω · cm to 10 ⁷ Ω · cm,
The charging voltage applied to the charging device can be set relatively low, and the process speed can be set to 150 mm / s.
When used in a high-speed machine of ec or more, it is most preferable because potential fluctuation can be suppressed.

The charging voltage applied to the charging electrode may be a DC voltage or a voltage obtained by superimposing an AC voltage that is twice or more the charging start voltage on the DC voltage. However, a voltage obtained by superimposing an AC voltage on a DC voltage increases the surface energy of the surface of the charge acceptor and the charging device, and further has a bad influence on the charge acceptor. Therefore, it is desirable to use a DC voltage.

The charging electrode is cylindrical and has a thickness of about 10 μm to 1 mm.
The optimum thickness varies depending on what is selected as the above-mentioned binder material and the condition (mainly the weight) at which rotation due to electrostatic attraction stops, and the like, but it can be generally said that the thinner the better. However, if the thickness is too small, the manufacturing load increases or the durability deteriorates. Therefore, as an approximate guide of the thickness, a combination of straightness, coaxiality, and Young's modulus may be used as an index. According to the present invention, the Young's modulus is 500 [kg / cm ² ] to 10,000.
In the case of a soft electrode formed to be [kg / cm ² ], the straightness can be suitably used as long as the straightness is 2 mm or less. For a relatively hard electrode having a Young's modulus of 10,000 [kg / cm ² ] or more, the straightness is 1 mm or less, although it depends on the required charge uniformity and the straightness of the charge receptor.
Preferably, it is set to 0.5 mm or less. However, in the case of the same material, the Young's modulus is a constant physical quantity even when the thickness is changed. However, from the viewpoint of actual hardness, the thinner the material, the softer the material. Therefore, by referring to the above-mentioned standard, when the Young's modulus is large, the flexibility can be obtained by reducing the thickness, and when the Young's modulus is small, the durability can be improved by increasing the thickness.

As a method of supplying a charging voltage to the charging electrode, a supporting member held in the charging electrode can be used as described later. A power supply electrode may be provided as described above. The material of the power supply electrode for supplying a charging voltage to the charging electrode may be any material having conductivity, such as polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, and PEN. , PE
K, PES, PPS, PFA, PVdF, ETFE, C
Resin such as TFE or synthetic rubber such as silicone rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, nitrile rubber or the like mixed with conductive powder such as carbon black or metal powder can be used. Further, a polar rubber such as epichlorohydrin rubber, chloroprene rubber, EPDM rubber, or a semiconductive inorganic material such as amorphous silicon may be formed by vapor-depositing a thin film or a thick film on an insulating substrate. However, since a polar rubber or the like has a high adhesive force, it is necessary to devise a method of coating the surface with a low-adhesion material or the like. further,
The material is not limited to the above-mentioned polymer materials, and for example, metals such as SUS, aluminum and brass, and conductive liquids such as water, alcohol, and liquid metal can also be used. However, when a conductive liquid is used, a mechanism for preventing the liquid from adhering to and scattering on the charged electrode and the like and evaporating is required.

The shape of the power supply electrode may be any shape as long as it can come into contact with the front surface or the back surface of the charging electrode. paddle,
A rotating body such as a block or a roll made of gel, resin, metal, or the like, or a brush-like member that reciprocates is preferably used. However, depending on the shape of the charging device,
In some cases, it is desirable that the pressure at the contact portion be small so as not to impair the rotational force due to the electrostatic attraction force. A brush, felt, nonwoven fabric, sponge, roll, or the like is preferably used.

Basically, if the resistance value of the power supply electrode is smaller than the resistance value of the charging electrode, the function can be sufficiently performed. However, considering the fluctuation of the resistance value due to the environmental change and the aging change, the smaller the resistance value is, the more stable power supply can be performed. In this experiment, the most stable result was obtained by adjusting the value to 10 ³ Ω · cm or less, but the present invention is not particularly limited to this range.

As an image forming apparatus in which the charging device according to the present invention is incorporated, a black-and-white, color copying machine, printer, or the like provided with a conventional photoconductor (charging target) cleaning device is suitable. Also, a cleanerless image forming apparatus without a cleaning device, or
Even when a pseudo cleaning device is provided, it can be suitably used. Furthermore, the toner image is sufficiently used as a charging device and a discharging device (including charging / discharging of the toner on the photoconductor) in the IOI process in which the toner images are successively superimposed on the photoconductor and finally transferred collectively to paper. be able to.

[0053]

Next, an embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention, wherein FIG. 1A is a cross-sectional view, and FIG. 1B is a side view.
Hereinafter, this is referred to as a first embodiment. This charging device 10
A charging electrode 2 which is supported at a position facing a charge receptor 1 movable in a certain direction, and which is formed in a cylindrical shape with a semiconductive thin member having a peripheral surface which can move endlessly; A cylindrical electrode support member that is inserted into the electrode and supports the charging electrode so as to be close to the charge receptor at a substantially equal distance in the longitudinal direction; Further, the electrode support member 3 is connected to a power supply 4 so that a charging voltage is applied to the charging electrode 2 via the electrode support member.

The charge acceptor 1 has, for example, a structure in which a photoconductive layer 1b is laminated on a cylindrical conductive substrate 1a, and the conductive substrate 1a is electrically grounded. Then, a discharge is generated in a minute gap near the contact portion with the charging electrode 2, so that the surface of the charge receptor 1 is charged.

The charging electrode 2 is formed such that the peripheral length of the film-shaped member is larger than the peripheral length of the electrode supporting member 3.
When no voltage is applied, the shape is slightly close to a perfect circle, though it is slightly deformed by its own weight. But,
As shown in FIG. 2A, when a voltage is applied to the charging electrode 2, an electrostatic force is generated between the charging electrode 2 and the electrode support member 3, and as shown in FIG. The shape is such that it is slightly pulled toward the body 1. The charging electrode 2 is always given a force to approach the charge receptor 1 by the electrostatic attraction force, and thus rotates following the rotation of the charge receptor 1. Although the operation of the charging electrode 2 will be described later, the more the softer charging electrode is used, the greater the deflection, and hardly deforms in a thin metal cylinder having high hardness. However, since the electrostatic attraction force is a physical quantity depending on the distance between the charge receptor 1 and the charging electrode 2, any electrode can be stabilized by appropriately adjusting the distance according to the hardness of the charging electrode 2. It becomes possible to rotate.

As the cylindrical member constituting the charging electrode 2, a semiconductive member obtained by applying the above-described semiconductive material to a metal cylinder having a thickness of about 30 to 200 μm is used. This cylindrical member is formed, for example, by mixing conductive particles such as carbon black in a film such as polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, and polyvinylidene fluoride, and has a preferable volume resistivity. Thus, the mixing amount of the conductive particles is adjusted. At this time,
Tends spark discharge occurs in the following 10 ² Ω · cm volume resistivity, for prone to dot-like charge failure is 10 ¹¹ Ω · cm or more, for use in the range of ^{10 3} ~10 10 Ω · cm desirable. In particular, in the case of 10 ³ to 10 ⁷ Ω · cm, the charging voltage to be used can be set relatively low, which is preferable in that power consumption can be saved.

The peripheral surface of the electrode support member 3 is formed of a conductive material so as to also supply power to the charging electrode 2. For example, a metal such as aluminum or SUS, or the volume resistivity of the charging electrode 2 A conductive polymer material formed to have a resistivity or less, for example, polyester, polyamide,
Polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, PE
N, PEK, PES, PPS, PFA, PVdF, ET
It is possible to use resin such as FE or CTFE or synthetic rubber such as silicone rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, nitrile rubber mixed with conductive powder such as carbon black or metal powder. it can. Further, a polar rubber such as epichlorohydrin rubber, chloroprene rubber, EPDM rubber, or a semiconductive inorganic material such as amorphous silicon may be formed by vapor-depositing a thin film or a thick film on an insulating substrate. As shown in FIG. 1B, the electrode support member 3
Is provided slightly longer than the total length in the longitudinal direction,
It is fixed and supported in the charging device so as not to rotate.

The power supply 4 can apply a DC voltage to the charging electrode 2 in the charging step of the charge receptor 1. Also,
As shown by a dotted line in the figure, a setting may be made so that a voltage obtained by superimposing an alternating current on a direct current is applied. The applied voltage of the power supply 4 will be described later.

In such a charging device, when a predetermined voltage is applied to the charging electrode 2 from the power supply 4 via the conductive electrode supporting member 3, as shown in FIG. And is attracted to the electrode support member 3 side by the electrostatic force generated between them. The charging electrode 2 is rotated by the electrostatic force generated between the charging electrode 2 and the charge receptor 1 as the charge receptor 1 moves in a certain direction. At this time,
Since the charging electrode 2 receives a substantially constant electrostatic attraction force in the longitudinal direction while being supported by the electrode support member 3, the charge receptor 1
In the vicinity of a point close to the above, a shape slightly swelled in the moving direction is obtained. A predetermined voltage is applied from the power supply 4 to the charging electrode 2, and a discharge occurs in a minute gap near the vicinity of the charging electrode 2 and the charge receptor 1, thereby causing ionization of air.
When the negative side of the power supply 4 is connected to the electrode support member 3, negative ions or electrons flow to the charge acceptor 1 side to charge it, and positive ions reach the charge electrode 2 side to neutralize. Is done.

As described above, in the above-described charging device, uniform fine voids are obtained between the charging electrode and the charge receptor, and stable charging is performed. Further, as shown in FIG. 3, the electrostatic attraction area where the charging electrode 2 comes close to the charge receptor 1 increases due to the electrostatic force, and the discharge area holding an appropriate gap expands, so that a sufficient charging potential is obtained. be able to. further,
By using a semiconductive member for the charging electrode 2, it is possible to prevent an excessive current from flowing to any part of the gap, and it is possible to uniformly charge the charge receptor 1. In FIG. 3, the charging electrode 2 is shown to be largely bent in order to explain the action of the electrostatic attraction force. However, the amount of bending varies depending on the hardness of the charging electrode 2, Obviously, a thin cylinder hardly bends.

Next, the results of carrying out a charging test of the charging device using a charging test device as shown in FIG. 4 will be described. This charging test apparatus has a surface potential sensor 11 for detecting the potential of the surface of the charge receptor 1 and a charge removing lamp 13 for removing the surface around the charge receptor 1. A total of 12 are connected. The charging device 10 of the present embodiment is arranged on the upstream side of the surface potential sensor 11 in the rotation direction of the charge receptor 1, and the charging electrode 2 is supported so as to be close to the surface of the charge receptor 1.
A DC power supply 14 is connected to the electrode support member 3 so that a DC charging voltage is applied. This DC power supply 1
Reference numeral 4 denotes a device that can arbitrarily change the voltage. The surface potential of the charge receptor 1 that changes with the voltage is measured by a surface voltmeter 12.

The above-mentioned charged electrode 2 was formed by using a polyvinylidene fluoride paint and an acrylic paint so as to have a volume resistivity of 10 ⁵ Ω · cm and 10 ⁷ Ω · cm, respectively, to a thickness of 100 μm. Hollow thin cylindrical SUS
And one formed by vapor-depositing a-Si on a hollow thin cylindrical glass having a thickness of 1 mm so as to have the same volume resistivity. This charged electrode 2
Is 12.5 mm, and Φ1
0 aluminum column was used.

FIG. 5 shows the relationship between the applied voltage when a DC voltage is applied to the charging electrode 2 and the surface potential of the charge receptor 1 in the charging test using the charging test apparatus. In this figure, 0 to -20
When a DC voltage of 00 V was applied, the surface potential of the charge receptor 1 started to increase from an applied voltage of about -1000 V,
It was confirmed that the applied voltage of 2000 V reached about -1000 V. During this time, no abnormal discharge was caused by the charging device 10. Also, with respect to the combination of the material and dimensions of the charging electrode 2 or the dimensions of the electrode support member 3, good results were obtained in all of the above cases.

When the rotation speed of the charging device 2 when the charge receptor 1 was rotating was measured, as shown in FIG. It starts to rotate following the charge receiver 1 and reaches about -500 V
Until then, the rotation became unstable, and the stationary and the rotation were repeated irregularly. When the applied voltage was further increased, rotation started stably at around -800 V, and thereafter, good rotation at a constant speed was obtained. That is, it was confirmed that when an appropriate applied voltage was set, the rotation was stabilized by the electrostatic force with the charge acceptor 1 and uniform charging was performed. In the above test, the rotation speed of the charging electrode was set to 1
It was determined from the average value of 0 rotations. Since such a charging device does not require a special mechanism for rotating the charging electrode 2, there is an advantage that the device can be downsized.

Further, as shown by the generally known Paschen equation, the firing voltage is a function of the gap length, and the larger the gap length, the higher the firing voltage. FIG. 7 shows this relationship. For example, the discharge starting voltage when the charging electrode 2 is in contact with the charge receptor 1 is about -600 V, but when the gap length is 0.1 mm, the discharge starting voltage is about -1000 V. Therefore, when discharging is performed at the same applied voltage, the further the charging electrode 2 is away from the charge receptor 1, the lower the charging potential. Therefore, from the viewpoint of reducing the applied voltage, it can be said that it is better to arrange them as close as possible. In the present embodiment, FIG.
As shown in FIG. 7, since the charging start voltage is -1000 V, it can be said from FIG. 7 that the gap between the charging electrode 2 and the charge receptor 1 is about 0.1 mm. The gap is not particularly limited to this distance, and it has been confirmed in experiments that even when the gap is about 2 mm, substantially the same charge uniformity can be obtained.

FIG. 8 is a schematic configuration diagram showing an image forming apparatus to which the charging device 10 is applied. The image forming apparatus includes a photoreceptor (charge acceptor) 20 on which a latent image is formed by irradiating an image light after uniform charging, and a book for charging the surface of the photoreceptor 20 around the photoreceptor 20. In addition to the charging device 10 of the embodiment, an exposure device 21, a developing device 22,
It has a transfer roller 25, a cleaning device 27, and a charge removing lamp 28. The apparatus further includes a paper cassette 23 for storing paper 24, a fixing device 26 for fixing a toner image, and the like.

In such an image forming apparatus, the charging device 1
After the photosensitive member 20 is charged to a predetermined potential by 0, a laser beam corresponding to the image information is irradiated by the exposure device 21 to form an electrostatic latent image on the surface of the photosensitive member 20. This electrostatic latent image is developed by the developing device 22 to form a visible image due to toner adhesion. Further, the paper 24 is transported from the paper cassette 23 along the paper guide 29 between the photoconductor 20 and the transfer roller 25, and the transfer roller 25 transfers the toner image onto the paper 24. The transferred toner image is fixed by the fixing device 26 to form one copy image. On the other hand, as the photosensitive member 20 rotates, the photosensitive member 2
The toner remaining on the surface of the photoconductor 20 is cleaned by the cleaning device 27, and after the surface of the photoconductor 20 is neutralized by the neutralization lamp 28, the charging process by the charging device 10 is started again. Note that the voltage applied to the charging device 10 in the above-described process includes-
A DC voltage of 1400 V or a voltage in which an AC component of a peak-to-peak voltage of 2100 V is superimposed on a DC component of -400 V is set, whereby the charge potential of the charge receptor 1 becomes approximately -400.
V. A print image was formed using such an image forming apparatus, and a reliability test of the charging device 10 was performed. As a result, a good image having a uniform charging potential and no image quality defects was obtained as shown in FIG. It was confirmed that it could be obtained.

Next, in order to examine the influence of the positional relationship between the charge receptor 1 and the charging device 10 on the charging characteristics, the charging device was changed to four positions around the charge receptor 1 as shown in FIG. 10 were installed, and the same charging test and copying test as described above were performed for each of them. As a result, the rotation of the charging electrode 2 becomes unstable when it is arranged on the side of the charge receptor 1 as in (b) or (d), or when it is arranged below as in (c). Was. Particularly at the position (c), the power supply failure became remarkable, and horizontal black lines were generated at intervals of the circumference of the charging electrode 2 as shown in FIG. on the other hand,
In the case of the arrangement above as shown in FIG. 10A, the power supply is stabilized and the rotation of the charging electrode 2 is also stabilized, so that a good image without image quality defects was obtained.

The charging device 10 is applied to an image forming apparatus as shown in FIG. 8. For example, the charging device may be integrated with a toner cartridge or the like, and may be detachably supported by the image forming device. Good. Thus, if the used cartridge is collected and only the charging electrode 2 is replaced at the factory, the charging device can be reused, which is effective for recycling and can reduce the cost.

Further, as shown in FIG. 11, the charging device 10 can be similarly applied to a cleanerless image forming apparatus which does not use a cleaning device. The process of this image forming apparatus is almost the same as that of FIG. 8 described above, but the untransferred toner remaining on the charge receptor 30 passes through the charging device 10 as it is, and is collected by the developing device 32. Alternatively, the transfer device 35 performs transfer close to 100%, thereby reducing untransferred toner as much as possible. In such an image forming apparatus, from the viewpoint of adhesion of foreign matter, an apparatus that is arranged in non-contact with the photoconductor 30 as the charging apparatus described in the present embodiment is most suitable.
By applying the present invention, it can be said that the merits such as low cost, ozone-less, small size, and low voltage are significantly higher than those of the charging device conventionally performed by the scorotron.

FIG. 12 is a schematic structural view showing a charging device according to an embodiment of the present invention.
FIG. 12A is a cross-sectional view, and FIG. 12B is a side view. This charging device includes a rotation stabilizing member 45 supported above the electrode support member 43 at a predetermined interval in addition to the charging device 10 shown in FIG. This rotation stabilizing member 4
Numeral 5 has a substantially uniform rectangular cross section in the longitudinal direction (direction substantially perpendicular to the direction of travel of the charge receptor), and comes into contact with the outer peripheral surface of the charging electrode 42 to lightly move the charging electrode 42 toward the charge receptor. It is designed to be pressed. As a material for forming the rotation stabilizing member 45, a soft material, a material having high smoothness, a material having a small surface energy, and the like are desirable. For example, a sponge formed by firing polyethylene, polyurethane, silicone, or the like is used. In addition, a material made of an elastic material such as a felt, a brush, a foam, and a nonwoven fabric is preferably used, but is not particularly limited thereto. For example, rubber, gel, blade, paddle, resin,
A rotating body such as a block or a roll made of metal or the like, a member that reciprocates, and the like are also preferably used. Examples of the material of the brush include a polymer material such as rayon, acrylic, nylon, polypropylene, and polyethylene terephthalate. The rotation stabilizing member 45 made of such a material is supported at a position such that the charging electrode 42 is not strongly pressed against the electrode support member 43 and is in contact with the outer peripheral surface of the charging electrode 42. The other structure of the charging device is the same as that of the charging device shown in FIG.

In such a charging device, when a voltage is applied to the charging electrode 42, the charging electrode 42 is moved by the electrostatic attraction generated between the charging electrode 42 and the electrode supporting member 43.
, And is pulled in the moving direction of the charge receptor 41 by the electrostatic attraction force with the charge receptor 41. At the same time, the rotation stabilizing member 45 in contact with the outer peripheral surface of the charging electrode 42 prevents the charging electrode 42 from being excessively deformed by centrifugal force or the like, and stably comes close to the charge receptor 41 side. Is applied to keep the At this time, the force applied to the charging electrode 42 is, as shown in FIG. 12A, a force F _E that tends to rotate along the charge receiving member 41 due to an electrostatic attraction force with the charge receiving member 41 and a charging electrode 41. A frictional force F _H acting between the electrode support member 43 and the electrode support member 43;
The frictional force F _S acting between the rotation stabilizing member 45 and
The direction of each force is as shown in the figure. Therefore,
The larger the F _E than the sum of the F _S and F _H, the charging electrode 4
It turns out that 2 rotates. In fact, F _E is the charged electrode 4
2, since F _H depends on the surface state of the electrode support member 43 and the charging electrode 42,
If the applied voltage and the distance between the charging electrode 42 and the charge receptor 41 at the time of applying the voltage, and the setting conditions of the electrode support member 43 and the charging electrode 42 are equal, the material and position of the rotation stabilizing member 45 satisfy the above relationship. It can be seen that setting should be made.

In such a charging device, the rotation stabilizing member 45 comes into contact with the charging electrode 42 so that the charging electrode 4
It was confirmed that the rotation of No. 2 was stabilized and a uniform charging potential was obtained. It was also confirmed that stable charging was performed regardless of the position of the charging device around the charge receptor 41. Furthermore, even when the straightness and roundness of the charging electrode 42 are insufficient, power can be supplied stably, and high precision is not required in manufacturing, and cost reduction can be realized. Also, even when a superimposed voltage of DC and AC is applied, the rotation of which is likely to be unstable as compared with the DC voltage, stable charging can be performed. Therefore, there is also an effect that charging noise can be reduced.

FIG. 13 is a perspective view showing an electrode supporting member 53 used in a charging device according to another embodiment of the present invention. This charging device has a rib-shaped electrode support member 53 in which cylindrical members are arranged at equal intervals on a support shaft 53a, instead of the electrode support member 43 used in the charging device shown in FIG. This electrode support member 53
The peripheral surface of the cylindrical member comes into contact with the charging electrode when a voltage is applied, and the contact area with the charging electrode is set to be smaller than that of the charging device shown in FIG.
As a material of the electrode support member 53, a material formed by mixing conductive carbon black powder or the like with aluminum, EPDM, and fluororesin so as to have a smaller volume resistivity than the charged electrode was used. The material of the electrode support member 53 is not limited to these three types, and the various conductive materials described above can be used. The other structure of the charging device is the same as that of the charging device shown in FIG.

In order to grasp the effects of the shape and the material of the electrode support member 53 in such a charging device, the evaluation results are shown by changing the size and the installation position of the rotation stabilizing member. As shown in FIG. 14, the width (length in the moving direction of the charging electrode) C of the rotation stabilizing member is 2 mm, 4 mm, 6 mm.
mm. The installation position is determined by three steps of a distance a between the peripheral surface of the rotation stabilizing member 55 and the electrode support member 53 and a distance b between the center line of the rotation stabilization member 55 and the center line of the electrode support member 53. Was set to. Polyurethane foam was used as the material of the rotation stabilizing member 55. Further, for comparison, similar experiments were performed for the cylindrical support member as shown in FIG. 12 in addition to the rib-like support member of the present embodiment for the shape of the electrode support member.

Table 1 shows the results of the charging test and the printing test performed for each of them. (Below)

[Table 1]

In this table, a comparison between the aluminum rib roller and the aluminum roller shows that the use of the aluminum rib roller broadens the range in which good results can be obtained with respect to the size and the installation position of the rotation stabilizing member. Was done. In addition, even when a fluoroplastic roller having high lubricity was used, almost the same effect as that of the aluminum rib roller was observed. on the other hand,
When the EPDM roller having a large friction is used, it is understood that the settable range of the rotation stabilizing member is narrowed and the setting must be strictly performed. From the above results, by reducing the frictional force between the charging electrode and the electrode support member,
It was confirmed that by providing the rotation stabilizing member, the range in which good results could be obtained was widened, and that stable charging was performed. Further, by providing the rotation stabilizing member on the right side in FIG. 14 (the front side in the table) with respect to the center line of the supporting member, the rotation stability of the charging electrode is improved, and a more uniform charging potential can be obtained. all right. In this case, instead of sandwiching the charging electrode between the electrode support member and the rotation stabilizing member, the charging electrode may be installed so as to be separated from the electrode supporting member and the rotation stabilizing member so that the charging electrode does not jump upward due to the rotation.

FIG. 15A is a schematic structural view showing a charging device according to an embodiment of the third aspect of the present invention, and FIG. 15B is a rotation stabilizing member used in this charging device. It is a schematic perspective view which shows 65. In this charging device, instead of the rotation stabilizing member 45 used in the charging device shown in FIG. 12, the thickness T1 at both ends in the longitudinal direction is made larger than the thickness T2 at the center, and both ends protrude. The rotation stabilizing member 65 formed as described above is provided. The rotation stabilizing member 65 is supported such that protruding portions at both ends thereof come into contact with both ends of the charging electrode 62, and the effect of pressing the charging electrodes 62 at both ends against the charge receptor 61 is more effective than at the center. Is also set to be large. As the material of the rotation stabilizing member 65, the same material as the rotation stabilizing member 45 shown in FIG. 12, such as a foaming material, can be used. Also, a firing member having a different thickness or a material having a different hardness is used in combination. May be used.

In the present embodiment, the conditions of the rotation stabilizing member 65 are set as follows. Material of rotation stabilizing member: urethane foam Gap with electrode supporting member 63 at center: 0.75 mm Gap with electrode supporting member 63 at both ends: 0.25 mm Width W of rotation stabilizing member: 4 mm Rotation stabilizing member The thickness T1 at both ends of the rotation stabilizing member: 2.5 mm The thickness T2 at the center of the rotation stabilizing member: 2 mm The other structure of this charging device is the same as that of the charging device shown in FIG.

Next, the operation of such a charging device will be described. In general, when a charged electrode made of a cylindrical thin member is used, if the potential of the charge receptor is uniformly removed in the axial direction, when the charged electrode is rotated by an electrostatic force between the charge receptor and the charge receptor. In addition, the deformation of both end portions of the charging electrode tends to be larger than other portions. In particular, if the electrostatic force between the charging electrode and the charge receptor is large, deformation of the both ends prevents the proper gap between the charging electrode and the charge receptor from being maintained. Image quality defects may occur. This tendency becomes more conspicuous as the hardness of the charging electrode is smaller. However, in the charging device of the present embodiment, since the effect of pressing the charging electrode 62 at both end portions of the rotation stabilizing member 65 is set to be greater than that at the center portion, the charging electrode 62
Excessive deformation can be prevented from occurring at both end portions of the. For this reason, a uniform charging potential can be obtained, and generation of a fog-like image quality defect can be prevented.

When a print test was performed using such a charging device, it was confirmed that no fog-like image quality defects occurred on both sides of the paper, and an image of good image quality was obtained. Although a firing member is used for the rotation stabilizing member 65, a brush-like member or the like is used in addition to the one shown in FIG.
Various materials and shapes described in the embodiment shown in FIG. 2 can be used, and the same effect can be obtained. Particularly in the case of a brush, two types of brush members having different lengths of bristle feet may be combined.

FIG. 16 shows a rotation stabilizing member 70 used in a charging device according to another embodiment of the third aspect of the present invention.
FIG. This rotation stabilizing member 70
Unlike the rotation stabilizing member 65 shown in FIG. 15, the width (length in the rotation direction of the charging electrode) W1 at both ends is changed to the width W2 at the center.
In this case, the contact area between the rotation stabilizing member and the charging electrode is made wider at both ends than at the center of the charging electrode. At the same time, the thickness T1 at both ends in the longitudinal direction is made larger than the thickness T2 at the center,
Both ends are formed so as to protrude. In the present embodiment, the thickness of the rotation stabilizing member 70 is T1 of 2.5 mm, T1
2 is set to 2 mm, and the width is 8 mm for W1 and 4 mm for W2.
Set to. The material of the rotation stabilizing member 70 is shown in FIG.
Can be used as the rotation stabilizing member 65, and firing members having different lengths and thicknesses may be combined. The configuration of the charging device to which the rotation stabilizing member 70 is applied is the same as the charging device shown in FIG.

In such a charging device as well, the effect of pressing against the charge receptor at both ends of the charging electrode can be made larger than that at the center, and the occurrence of fog-like image quality defects at the end of the sheet can be prevented. it can. In addition, there is also an effect of preventing lateral displacement of the charging electrode, and stable charging can be performed. When a print test was performed on the case where such a rotation stabilizing member 70 was used, it was confirmed that an image with good image quality was obtained. For comparison, when a print test was performed using a rotation stabilizing member with the same pressing force or contact width at both ends as the center, the width of the charging electrode was not much larger than the width of the paper Is
A slight horizontal streak-like fog occurred on both sides of the paper.

FIG. 17 is a schematic structural view showing a charging device according to an embodiment of the present invention. This charging device has a cylindrical electrode support member 7 made of an insulating material.
3, a plate-shaped rotation stabilizing member 75 made of a conductive material
The power supply 74 is connected to the rotation stabilizing member 75.
Is connected. The shapes of the electrode support member 73 and the rotation stabilizing member 75 are the same as those shown in FIG. 12, and other configurations of this charging device are the same as those of the charging device shown in FIG.

When a print test was performed using such a charging device, it was confirmed that a good image could be obtained as described above. Further, since the electrode support member 73 does not need to mix conductive powder such as carbon, the frictional force with the charging electrode 72 can be further reduced, and the charging electrode can be rotated more stably. There is also an advantage.

Further, it has been found that when power is supplied from outside the charging electrode, the unevenness of the charging potential is improved, and in particular, high-frequency noise-like unevenness is almost eliminated. The effect of the present embodiment will be described with reference to FIG. That is, in the case of the charging device shown in FIG.
Since the charged electrode is rotated by the electrostatic attraction with the charge acceptor, the solid and dashed lines in FIG. 28A indicate unevenness in the rigidity, eccentricity, film thickness, and straightness of the charged electrode. As shown, the position of the charging electrode fluctuates, and the power supply unit near the discharge region fluctuates from C to D. Therefore, the resistance value seen from the discharge region changes, and the unevenness of the potential increases. Further, since the charged electrode and the conductive electrode support member in the vicinity of the discharge region adhere to or separate from each other, both gaps fluctuate in the range of the vertical line shown in FIG. Will occur. Therefore, high-frequency noise is further increased. However, in this embodiment, since the voltage is applied from the outside of the charging electrode, the distance from the power supply unit to the discharge region can be kept substantially constant, and the fluctuation of the resistance can be suppressed. Further, by making the electrode support member insulative, it is possible to reduce the fluctuation of the capacity near the discharge region. For the above two reasons, a more stable charging potential can be obtained.

FIG. 18 is a schematic structural view showing a charging device according to an embodiment of the present invention described in claim 4 or 5, wherein FIG. 18 (a) is a sectional view, and FIG. It is a side view. This charging device is supported at a position facing a charge receptor 81 movable in the direction of the arrow in the figure, and has a cylindrically formed charging electrode having a semiconductive member having an endlessly movable peripheral surface. 82, and a cylindrical electrode support member 83 inserted into the charging electrode 82 and supporting the charging electrode 82 so as to be in contact with the charge acceptor 81.
Further, a rotation stabilizing member 85 also serving as a power supply electrode connected to the DC power supply 84 is provided. The rotation stabilizing member 85 is disposed so as to sandwich the charging electrode 82 with the electrode supporting member 83.

The charging electrode 82 and the electrode supporting member 83 are the same as those in the embodiment shown in FIG. 1, and the charging electrode 82 is moved in the direction of the arrow in FIG. It is spinning. Rotation stabilizing member 85
Is a conductive rubber roll formed by dispersing carbon in EPDM so as to have a volume resistivity of about 10 ³ Ω · cm. And is driven to contact the charging electrode 82 with a force F. In order to stabilize the rotation of the charging electrode 82, the magnitude of the force F
It is better that the electrostatic attraction force acting between the charging electrode 82 and the charge receptor 81 be smaller.

Using such a charging device, a charging test was performed by the charging test device shown in FIG.
Good results were obtained in the same manner as in the embodiment. FIG.
When a print test was performed using the image forming apparatus shown in FIG. 1 and the cleanerless image forming apparatus shown in FIG. 11, it was confirmed that a good image free from image quality defects such as fog was obtained. In addition, since the rotation stabilizing member 85 is made of a conductive rubber material, the rotation stabilizing member 85 can be softly contacted with the charged electrode, and thus has an effect of not easily damaging the electrode surface. Furthermore, since the rotation stabilizing member is freely rotatably installed, the rotation of the charging electrode 82 is not hindered even if the charging electrode 82 is sandwiched between the rotation stabilizing member and the support member 83, so that the rotation stabilizing member is more stable. It turned out that there was also an advantage that it became possible to rotate.

In this embodiment, a roll formed by dispersing carbon in EPDM is used. However, the present invention is not limited to this configuration. Various materials and shapes that have been used can be used. In this experiment, the charging voltage is supplied from the surface of the charging electrode 82. However, as in the charging device shown in FIG.
It is obvious that the same effect can be obtained even if is molded using a conductive material and power is supplied from the inner surface of the charging electrode 82.

FIG. 19A is a schematic configuration diagram showing a charging device according to an embodiment of the present invention. This charging device has substantially the same configuration as the charging device shown in FIG.
Different position, the discharge starting position and length of the circumferential direction from A _1, approximately equal position and circumferential position of the discharge stop position A ₂ between the charging electrode 92 and the charge receptor 91, the rotation stabilizing The supporting member 95 is supported so as to be in contact with the charging electrode 92. The other configuration of this charging device is the same as that of the charging device shown in FIG.

In such a charging device, the charge acceptor 91
Is the position facing the charging electrode 92, but charged is during passage through the discharge stop position A ₂ from the discharge start position A _1, until the rotation stabilizing member 95 from the discharge start position A ₁ and the discharge stop position A ₂ can be a by substantially equal to the circumferential direction of the distance, the surface potential of the charge receptor 91 as it passes through the discharge stop position a ₂ substantially uniform. For this reason, it is possible to more reliably prevent the fluctuation of the charging potential.

Further, as in the charging device shown in FIG.
Applying a voltage obtained by superimposing a circumferential distance from the discharge start position B _1, with approximately equal position in the circumferential direction of the distance from the discharge stop position B _2, the rotation stabilizing member 98 is charging electrode 9
It is also possible to adopt a configuration that makes contact with 2. The voltage applied from the power supplies 96 and 97 is, for example, −400.
DC component of V, peak-to-peak voltage 2.1k as AC component
V, a voltage obtained by superimposing a sin wave having a frequency of 400 Hz is set. Accordingly, even when a voltage obtained by superimposing an alternating current on a direct current is applied, the charging potential of the charge receptor 91 when passing through the discharge stop position B2 can be made substantially uniform, and fluctuation of the charging potential can be prevented. it can. With the above configuration, a constant voltage can always be applied even when the surface resistance value of the charging electrode 92 partially varies, so that a stable charging potential is obtained. be able to.

FIG. 20 is a schematic diagram showing a charging device according to an embodiment of the present invention. This charging device is configured such that the contact position with the charging electrode 102 can move in the circumferential direction of the charging electrode instead of the fixed power supply electrode / rotation stabilizing member 75 used in the charging device shown in FIG. The held roll-shaped power supply electrode 105 is provided.

The rotation stabilizing member 105 is provided with the charging electrode 1.
The movable member 107 is connected to a movable member 107 via a support rod 108 above the support member 02, and the movable member 107 slides on a rail 106 fixed and supported in the apparatus, so that the peripheral surface of the charging electrode 102 is moved. It is designed to move. And
The surrounding temperature and humidity are detected by a sensor (not shown) or the like, and the driving of the movable member 107 is controlled based on the detected temperature and humidity, and the rotation stabilization is performed so that the contact portion between the rotation stabilizing member 105 and the charging electrode 102 is at an appropriate position. The movement of the forming member 105 is controlled. The position of the rotation stabilizing member 105 is controlled as follows.

Since the charging property of the charging electrode 102 is affected by the temperature or humidity near the charging device, the charging characteristics shown in FIG. 5 also change. In a low-temperature and low-humidity environment, air is less likely to be ionized than in a high-temperature and high-humidity environment, and is less likely to be charged. For this reason, this environmental change often has an adverse effect on image quality. In the present embodiment, in order to suppress such fluctuations in the charging potential, at low temperature and low humidity, the rotation from the contact portion with the charging electrode 102 to the discharge start position is shortened as shown by the solid line in FIG. The position of the stabilizing member 105 is controlled so that the surface resistance of the charging electrode from the power supply position to the discharge region is set to be small. In a high-temperature and high-humidity environment, the position of the rotation stabilizing member 105 is controlled so that the distance from the contact portion with the charging electrode 102 to the discharge start position is increased as indicated by the dotted line in FIG. The setting is made so that the resistance of the charging electrode up to the discharge region increases. The other structure of this charging device is the same as that of the charging device shown in FIG.

In such a charging device, the power supply position can be controlled according to the surrounding environment, and the charging potential can be prevented from fluctuating due to changes in temperature and humidity. In this device, since the rotation stabilizing member also serving as the power supply electrode moves according to the environment, depending on the setting conditions, the rotation may be unstable even if the power supply condition is good. In the case where such a condition is generated and the material of the charging electrode is selected, the rotation stabilizing member 105 in FIG. It is advisable to install another member for the purpose of stabilization.

In the present embodiment, the rotation stabilizing member 105 is moved by detecting the temperature or the humidity. However, the present invention is not limited to this control method. For example, there is a case where the rotation of the charging electrode 102 becomes unstable during long-term use, or an unstable movement occurs at the start of rotation. In such a case, the rotation state of the charging electrode or the potential on the charge acceptor may be monitored in advance, and the rotation stabilizing member 105 may be controlled according to the state.

Using such a charging device, a charging test was performed by the charging test device shown in FIG. 4. As a result, stable charging characteristics were obtained from a high-temperature, high-humidity environment to a low-temperature, low-humidity environment, and the difference in charging potential was 10 V. Improved to a degree. A print test was performed using the image forming apparatus shown in FIG. 8 and the cleaner-less image forming apparatus shown in FIG.
It was confirmed that a good image free from image quality defects such as fog was obtained.

FIG. 21 is a schematic structural view showing a charging device according to an embodiment of the present invention. This charging device is different from the rotation stabilizing member 75 and the power supply 74 used in the charging device shown in FIG.
And three roll-shaped rotation stabilizing members 115a, 115b, and 115c that also serve as power supply electrodes, and an applied voltage switching device 116 that selects one of the rotation stabilizing members and applies a potential thereto. And three power supplies 114.

The rotation stabilizing members 115a, 115b,
Reference numeral 115c is made of a conductive rubber roll having the same configuration as the rotation stabilizing member 105 shown in FIG. 20, and is supported so as to be driven to rotate while being in contact with the charging electrode 112 with a force F in the direction of the arrow shown in the figure. In order to stabilize the rotation of the charging electrode 112, the magnitude of the force F is preferably smaller than the electrostatic attractive force acting between the charging electrode 112 and the charge receptor 111.

The power supply 114 is an applied voltage switching device 1
16, connected to the rotation stabilizing member 115,
Different charging voltages can be independently applied to the three rotation stabilizing members. Applied voltage switching device 1
Reference numeral 16 denotes a rotation stabilizing member 115 which is always one kind of applied voltage and an electrode according to a detection signal (not shown) such as temperature and humidity.
Is configured to be selectable. In the present embodiment, at low temperature and low humidity, the applied voltage is increased, the distance from the contact portion with the charging electrode 112 to the discharge region is short, and the rotation stabilizing member 115a is arranged so as to reduce the resistance of the charging electrode.
In high temperature and high humidity, the applied voltage is reduced, and the distance from the contact portion with the charging electrode 112 to the discharge region is long, and the rotation stabilizing member 115c arranged so as to increase the resistance of the charging electrode is used. To be selected. The rotation stabilizing member 115b is set to be used in a normal environment.

When a charging test was performed by using the charging device shown in FIG. 4 with such a charging device, stable charging characteristics were exhibited from a high-temperature and high-humidity environment to a low-temperature and low-humidity environment. Improved to the following. A print test was performed using the image forming apparatus shown in FIG. 8 and the cleaner-less image forming apparatus shown in FIG. 11, and it was confirmed that a good image free from image quality defects such as fog was obtained. . Further, the rotation stabilizing member 11
5, a single rotation stabilizing member serves as the charging electrode 1
When power is supplied to the power supply 12, the other two perform the same role as the rotation stabilizing member shown in the previous embodiment.
There is also an effect that the charging electrode 112 rotates stably and becomes a more uniform charging potential.

In this embodiment, a plurality of power supply electrodes and a plurality of applied voltages are used. However, the configuration for eliminating the influence of the environment dependence of the charging characteristics is not limited to the configuration shown in FIG. . That is, the same effect can be obtained by controlling the resistance value from the discharge region to the power supply unit depending on each environment. Therefore, in addition to FIG. 21, for example, one type of DC power supply and a plurality of power supply electrodes, a configuration of one type of power supply and one type of power supply electrode, and a means of changing the contact point between the power supply electrode and the charging electrode are used. Also has a sufficient effect.

From the above results, the configuration shown in FIG. 21 increases the number of contacts with the surface of the charging electrode.
There is a disadvantage that the rotation of the charging electrode is easily hindered, but by setting it at an appropriate position, the rotation is also stable,
It has been found that an excellent charging device having no environmental dependency can be provided.

FIG. 22 is a schematic diagram showing a charging device according to an embodiment of the present invention. This charging device includes a charging electrode 122 having substantially the same configuration as the charging electrode shown in the above-described embodiment, and a frame 127 fixedly supported so as to cover the outside of the charging electrode 122 with the charging electrode 122 inserted therein. have. Furthermore, this frame 12
Reference numeral 7 is connected to a power supply 124 and applies a charging voltage to the charging electrode 122.

The material used for the frame 127 may be any material having conductivity, such as polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, PEN, and PEK. , PE
A resin such as S, PPS, PFA, PVdF, ETFE, or CTFE, or a synthetic rubber such as silicone rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, or nitrile rubber is coated with conductive powder such as carbon black or metal powder. Mixed ones can be used. Further, a polar rubber such as epichlorohydrin rubber, chloroprene rubber, EPDM rubber, or a semiconductive inorganic material such as amorphous silicon may be formed by vapor-depositing a thin film or a thick film on an insulating substrate. However, since a polar rubber or the like has a high adhesive force, it is necessary to devise a method of coating the surface with a low-adhesion material or the like.

The shape of the frame 127 is such that the charging electrode 12
Any shape may be used as long as it does not drop or move around unnecessarily. For example, a mesh-shaped frame, a structure in which only both ends of the charging electrode 122 are hung, a frame formed in a circular shape, and the like are given.
Also, a sponge or the like is attached to the inside to
2 may be configured to stabilize the rotation.

When a charging test was carried out using such a charging device by using a charging test device shown in FIG. 4, extremely stable charging characteristics were shown. A print test was performed using the image forming apparatus shown in FIG. 8 and the cleaner-less image forming apparatus shown in FIG. 11, and it was confirmed that a good image free from image quality defects such as fog was obtained. . Since the function of regulating the position of the charging electrode 122 was high, it was confirmed that more stable rotation was performed.

As another configuration, as shown in FIG. 23, the frame 128 can be provided only in the non-image forming areas at both ends of the charging electrode 122. In general, when used for a long period of time, fine scratches may be formed on the surface of the charging electrode 122 due to rubbing. However, with the configuration shown in FIG. There is a great advantage that it can be used stably for a long period of time without scratches or the like.

FIG. 24 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention. This charging device is provided at a position facing a charge receptor 131 that can move in the direction of the arrow in the figure, and is a charging electrode formed by forming a thin cylindrical member into a cylindrical shape so as to have a peripheral surface that can move endlessly. 132, and a frame 136 fixed so as to cover the outside of the charging electrode 132 and supporting the charging electrode 132 so as to face the charge receptor 131 in a non-contact manner. Further, a brush-like power supply electrode 137 connected to the DC power supply 134 is provided inside the frame 136, and a brush-like support member for preventing the charging electrode 132 from moving in the frame 136. 133 is installed inside the frame 136.

The charging electrode 132 is the same as that of the embodiment shown in FIG.
Numeral 32 rotates in the direction of the arrow in the figure while approaching the charge receptor 131. The power supply electrode 137 has a volume resistance of 10 ³ Ω · cm by dispersing carbon in rayon.
It is a conductive brush formed so as to have a degree of rotation, and is fixed to the frame in a shape lying slightly in the rotation direction so as not to hinder the rotation of the charging electrode 132. The material used for the brush-like power supply electrode 137 is not limited to rayon, but may be any material such as polyester or nylon as long as it can be formed into a fibrous shape. The support member 133 is made of fibrous material such as rayon or nylon, and is fixed to the frame in a shape slightly laid in the rotation direction, similarly to the power supply electrode. Also, the frame 136 is
It may be formed of any material as long as it is an insulating material, for example, polyester, polyamide, polyimide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, acrylic,
A polymer material such as POM, phenol, and fluororesin is preferably used. Further, in the case where the charge receiving member 131 is installed at a sufficient distance so as not to be discharged, a conductive material such as polyester, polyamide, polyethylene, polycarbonate, polyolefin, or polyurethane may be used in addition to the insulating material. , Polyvinylidene fluoride, polyimide, PEN, PEK, PES, PPS, PFA, PVd
Use resin such as F, ETFE, CTFE, etc., or synthetic rubber such as silicone rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, nitrile rubber mixed with conductive powder such as carbon black or metal powder. be able to. Further, a polar rubber such as epichlorohydrin rubber, chloroprene rubber, EPDM rubber, or a semiconductive inorganic material such as amorphous silicon may be formed by vapor-depositing a thin film or a thick film on an insulating substrate.

Using such a charging device, a charging test was performed by the charging test device shown in FIG.
Good results were obtained in the same manner as in the embodiment. FIG.
A print test was performed using the image forming apparatus shown in FIG. 1 and the cleaner-less image forming apparatus shown in FIG. 11, and it was confirmed that a good image free from image quality defects such as fog was obtained. In addition, since the power supply electrode 137 is formed of a conductive brush, the power supply electrode 137 can be softly contacted with the charging electrode 132, and thus has the effect of not easily damaging the electrode surface. Further, the support member 133 is
It also has the effect of scraping off foreign matter and dirt attached to the top,
Another feature is that the life of the charging device is prolonged. This can be said to be an effect particularly effective for a cleaner-less image forming apparatus to which dirt easily adheres. In addition, since the function of regulating the position of the charging electrode 132 is high, and the power supply electrode 137 and the support member 133 also have the effect of stabilizing the rotation of the charging electrode 132, more stable rotation is performed and favorable charging is performed. It was confirmed that uniformity was obtained.

Further, in this embodiment, a brush-like member is used inside the frame 136. However, the present invention is not limited to this shape. The same effect can be obtained by using the above member or the like. However, as described above, the brush-like one is particularly excellent in the effect of removing the foreign matter attached to the surface of the charging electrode 132.

FIG. 25 is a schematic structural view showing a charging device according to an embodiment of the present invention. This charging device has a thin cylindrical charging electrode 142 and a cylindrical support member 143 inserted into the charging electrode 142 and supporting the charging electrode 142 so as to be arranged close to the charge receptor 141. doing.

The charging electrode 142 is formed on the inner layer 1 having a low resistance.
42a and a high-resistance outer layer 142b. The low-resistance inner layer 142a contacts the electrode supporting member 143 also serving as a power supply electrode, and the high-resistance outer layer 142b faces the charge acceptor 141. It has become. For the low resistance inner layer 142a constituting the charging electrode, various materials shown in the above-described embodiment can be used. However, the same material may be used as the material forming the high resistance outer layer 142b. However, polar rubber materials such as epichlorohydrin rubber, chloroprene rubber, and EPDM rubber and ionic conductive materials are preferable. In the present embodiment, epichlorohydrin rubber is used as the charging electrode, the volume resistivity of the inner layer 142a is 10 ³ Ω · cm,
b has a volume resistivity of 10 ¹⁰ Ω · cm and thicknesses of 50
It is set to μm. Since the polar rubber has a high adhesive force, the surface of the outer layer 142b is coated with a fluorine-based low-adhesion material. The other configuration of the charging device is the same as that of the charging device shown in FIG.

In such a charging device, when a voltage is applied to the charging electrode 142 from the power source 144 via the electrode support member 143 also serving as a power supply electrode, the low resistance inner layer 142
a, a discharge is generated through the outer layer 142b in a region near the high-resistance outer layer 142b and the charge receptor 141, and a discharge current flows. Along with this,
The charging electrode 142 is pulled toward the charge receptor 141 by electrostatic attraction generated between the charge receptor 141 and the charging electrode 142, and rotates following the orbital movement of the charge receptor 141.

In such a charging device, the charging electrode 142
Even if the distance from the contact portion with the electrode supporting member 143 to the discharge region changes due to vibration, stable discharge is possible,
Variations in the charged potential can be prevented. This is because the discharge is performed from the low-resistance inner layer 142a to the high-resistance outer layer 142b, so that a state similar to that of the case where a capacitor is interposed is obtained, which has an effect of smoothing a high-frequency current fluctuation. It is. The adverse effects that occur when the charging electrode 142 vibrates and the distance from the contact portion with the electrode support member 143 to the discharge region changes are as shown in the embodiment of FIG.

Using such a charging device, a charging test was performed by the charging test device shown in FIG.
Good results were obtained in the same manner as in the embodiment. FIG.
A print test was performed using the image forming apparatus shown in FIG. 1 and the cleaner-less image forming apparatus shown in FIG. 11, and it was confirmed that a good image free from image quality defects such as fog was obtained. Further, since the electrode support member 143 disposed inside the charging electrode 142 also serves as a power supply,
There is also an effect that stable charging can be performed for a long period without damaging the outer surface 142b of the charging electrode.

FIG. 26 is a schematic structural view showing a charging device according to an embodiment of the present invention. This charging device has substantially the same configuration as the charging device shown in FIG. 1, but uses a flexible film-shaped member made of a polymer material as a material used for the charging electrode 152. Unlike the electrode having relatively high hardness, the charging electrode 152 is considerably bent by the electrostatic attraction as shown in FIG. Therefore, the electrode support member 15
Care must be taken because the charging electrode 152 contacts the charge receptor 151 when the voltage is applied unless 3 is separated in advance.

The use of such a soft charging electrode makes it possible to reduce the outer shape accuracy such as the straightness of the charging electrode, and thus has a great advantage that the manufacturing load is reduced. Further, since the distance between the charging electrode 152 and the charge acceptor 151 can be easily changed by changing the applied voltage, it is possible to provide a charging device excellent in environmental characteristics and the like.

In the present embodiment, the volume resistivity was adjusted to 10 ⁶ Ω · cm by mixing carbon black into polycarbonate, nylon, and PVdF.
A 2.5 mm film-shaped member is used. The film-like member constituting the charging electrode is not particularly limited to this, but a flexible semiconductive member having a thickness of about 30 to 200 μm is preferably used. This film-shaped member is obtained by mixing conductive particles such as carbon black into a film formed of a polymer material such as polyester, polyamide, polyimide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, and acrylic. Formed and have a preferred volume resistivity (10 ³
Ω · cm to ^{10 10} Ω · cm). Further, the tensile modulus is 10 to 280.
What is set to about kg / mm ² is good. In addition,
Other configurations of this charging device are the same as those of the charging device shown in FIG.

Using such a charging device, a charging test was performed by the charging test device shown in FIG.
As a result, good results were obtained as in the charging device shown in FIG. Further, when a print test was performed using the image forming apparatus shown in FIG. 8 and the cleanerless image forming apparatus shown in FIG. 11, it was confirmed that a good image free from image quality defects such as fog was obtained.

FIG. 27 is a schematic configuration diagram showing an image forming apparatus to which the charging device according to one embodiment of the present invention is applied. This image forming apparatus is a color tandem type image forming apparatus, and includes four image forming units 162a, 162b, 162c, 16
2d. The configuration of these image forming units is the same as that of FIG. 8, but each developing device contains toner of four colors of yellow, magenta, cyan, and black, respectively. The image forming apparatus is provided with an intermediate transfer belt 167 stretched around a roll 168 as a transfer object. The intermediate transfer belt 167 includes a yellow unit 162a, a magenta unit 162b, a cyan unit 162c, and a black unit. It extends across the unit 162d and is driven to circulate. When transferring from each unit to the intermediate transfer belt 167, a transfer voltage is applied to the transfer devices 165a to 165d. Further, four image forming units 1
The photoconductors 62a, 162b, 162c, 162d and the intermediate transfer belt 167 are provided with charging devices 161a, 161b, 161c, 161d, 161e according to the present invention, respectively. However, in the present embodiment, this charging device functions as a static eliminator for removing electric charges remaining on the photoconductor and the intermediate transfer belt 167, and is separately provided for charging the photoconductor.

In this image forming apparatus, the toner of each color is primarily transferred onto the intermediate transfer belt 167 moving in the direction of the arrow in FIG. The secondary transfer is performed collectively. Paper 163
Moves along the paper path 164 and is fixed by the fixing device 166 to complete the print image. On the other hand, the image forming units 162a, 162b, 162 after transferring the toner
For c and 162d, residual toner is removed by a cleaning device (not shown). The residual charges are eliminated by the electrification charging devices 161a, 161b, 161c, and 161d of the present invention, and the invasion potential into the charging device is 0V.
Is homogenized. Charge removing devices 161a, 161b,
+950 from a power source (not shown)
A voltage of about V to +1000 V is applied. Also,
The intermediate transfer body 167 after the secondary transfer is the image forming unit 1
Before invading 61a, the charging device 161e for static elimination of the present invention is used.
As a result, residual charges are eliminated. Charging device 161 for static elimination
An AC voltage having a peak-to-peak voltage of about 2.2 kV is applied to e from an AC power supply (not shown).

As the intermediate transfer belt 167, a polymer film made of polyimide, polycarbonate, PVdF or the like, or a synthetic rubber made of silicone rubber or fluorine rubber added with a conductive filler such as carbon black to make it conductive is used. . The transfer devices 165a to 165e are devices made by adding a conductive filler such as carbon black to synthetic rubber such as silicone rubber, EPDM, urethane rubber or the like to make them conductive, and have a diameter of about 10 to 30 mm. A voltage of about +0.5 to 1.5 kV is applied to the transfer devices 165a to 165d from a power supply (not shown), and the image forming units 162a, 162b, 162c,
From 162d, the toner image is transferred by electrostatic force. On the other hand, a transfer device 165 for transferring to the paper 163
A voltage of about +1.5 to 3.0 kV is applied to e from a power supply (not shown), so that multiple toner images are collectively transferred from the intermediate transfer belt 167 to the paper 163 by electrostatic force. ing. Other image forming unit 16
The structures and materials in 2a, 162b, 162c and 162d are the same as those in the apparatus shown in FIG.

In general, when a DC voltage is applied to the charging device of the image forming apparatus, there is a disadvantage that the charging potential is apt to fluctuate due to the pattern of the penetration potential, and image quality defects such as ghosts are likely to occur. Therefore, especially in an image forming apparatus requiring high image quality such as a color image, it is necessary to provide a light neutralization device or a neutralization device by discharge upstream of the charging device. When static electricity is removed from the photoconductor, light fatigue is accelerated, and light fatigue is accelerated.
There is a disadvantage that the life of the photoconductor is shortened. Therefore, a discharge type static eliminator as shown in the present embodiment is also used, but when an AC voltage is applied, the surface energy of the photoreceptor surface increases as described above, which has various adverse effects on other processes. Would. Therefore, it is necessary to devise a method of applying a DC voltage so as not to deteriorate the photoconductor as much as possible.

On the other hand, since the intermediate transfer belt is formed of an insulating or high-resistance material, there is a drawback that the residual potential becomes large after repeating the transfer many times, and the transfer failure is likely to occur. Since the transfer belt generally has no photoconductivity unlike the photoreceptor, it is necessary to remove electricity by a discharge device. However, unlike the photoconductor, the residual potential on the transfer belt generally fluctuates greatly from plus to minus, and the magnitude sometimes exceeds 2000 V. Therefore, in order to remove static electricity from the transfer belt or the like, a robustness that can always keep the voltage around 0 V with respect to any penetration potential is required. Therefore, it is necessary to use AC discharge instead of DC voltage. Further, the transfer object such as the transfer belt has almost no adverse effect even if the surface energy is increased, and therefore, the AC discharge is optimal. As described above, by using the charging device according to the present invention as a charging device for removing charges on a photosensitive member and a transfer-receiving member, it is possible to efficiently remove charges with a simple configuration.

Using such an image forming apparatus, a charging test was performed by a charging test apparatus shown in FIG.
It was confirmed that the invasion potential into the charging device was almost uniformly 0 V, and a result equivalent to that of the erase lamp was obtained. Further, when a print test was performed using the image forming apparatus of FIG. 27, it was confirmed that a good color image free from image quality defects such as fog was obtained. From the above results, it has been clarified that the charging device of the present invention is very effective as a charging device for neutralizing the photosensitive member and the intermediate transfer belt.

As in the first embodiment, the image forming apparatus can be applied to a cleanerless image forming apparatus shown in FIG. 11 which does not use a cleaning device. The cleanerless device can be used as a color image forming device by applying to such a tandem type image forming device.

[0131]

As described above, according to the charging device according to the present invention, since the charging electrode is arranged in non-contact with the charge receptor, adhesion of foreign matter to the charging electrode is greatly reduced. be able to. This makes it possible to stably maintain a discharge region with the charge acceptor, and to obtain a uniform charging potential. Further, even if the accuracy such as the degree of straightness and coaxiality of the charging electrode is somewhat poor, a sufficiently uniform charging potential can be obtained, so that the yield can be improved. In addition, there is an advantage that a wide range of materials from hard to soft can be used for the hardness of the charging electrode. Furthermore, since it is not in contact with the charge acceptor, it does not damage the charge acceptor and can realize a charging device that can be suitably used for a cleanerless device and a color image forming device. .
In addition, high performance can be exhibited not only as a charging device but also as a charge removing device for removing charges.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 2 is a view showing the charging device shown in FIG. 1 when a voltage is applied to a charging electrode and when the voltage is not applied;

FIG. 3 is a view showing a state in which the charging electrode is rotated by electrostatic attraction in the charging device shown in FIG. 1;

FIG. 4 is a schematic configuration diagram showing a charging test device for performing a test of the charging device.

5 is a diagram showing test results of the charging device shown in FIG. 1 and showing a relationship between a DC voltage applied to the charging device and a surface potential of a charged charge receptor.

FIG. 6 is a diagram showing test results of the charging device shown in FIG. 1 and showing a relationship between a DC voltage applied to the charging electrode and a rotation speed of the charging electrode.

FIG. 7 is a diagram showing a relationship between a gap initiation derived from Paschen's law and a discharge starting voltage.

FIG. 8 is a schematic configuration diagram of an image forming apparatus configured using the charging device of FIG. 1;

9 is a diagram illustrating an example of an image obtained by using the image forming apparatus illustrated in FIG.

10 is a diagram showing a state where the installation location of the charging device shown in FIG. 1 is changed.

11 is a schematic configuration diagram of a cleaner-less type image forming apparatus configured using the charging device of FIG. 1;

FIG. 12 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 13 is a view showing another embodiment of the charging electrode support member applied to the charging device of FIG. 12;

FIG. 14 is a diagram illustrating setting conditions applied to the charging device of FIG. 12;

FIG. 15 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 16 is a schematic configuration diagram showing another shape of the rotation stabilizing member applied to FIG. 15;

FIG. 17 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 18 is a schematic configuration diagram showing a charging device according to an embodiment of the invention described in claim 4 or 5;

FIG. 19 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 20 is a schematic configuration diagram illustrating a charging device according to an embodiment of the present invention.

FIG. 21 is a schematic configuration diagram illustrating a charging device according to an embodiment of the present invention.

FIG. 22 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 23 is a schematic configuration diagram showing a charging device according to another embodiment of the present invention.

FIG. 24 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 25 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 26 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 27 is a schematic configuration diagram showing a charging device, a charging device for static elimination, and a tandem-type image forming apparatus into which the charging device and the charging device according to an embodiment of the present invention are incorporated;

FIG. 28 is a view for explaining the mechanism of the invention described in claim 2;

[Explanation of symbols]

1, 41, 51, 61, 71, 81, 91, 101, 1
11, 121, 131, 141, 151 Charge acceptor 2, 42, 52, 62, 72, 82, 92, 102, 1
12, 122, 132, 142, 152 Charging electrode 3, 43, 53, 63, 73, 83, 93, 103, 1,
13, 123, 133, 143, 153 Electrode support member 4, 44, 74, 84, 94, 104, 114, 124
134, 144, 154 DC power supply 45, 55, 65, 70, 75, 85, 95, 98, 1
05, 115 Rotation stabilizing member 10 Charging device 11 Surface potential sensor 12 Surface potential meter 13 Static elimination lamp 14 DC power supply 20, 30 Photoconductor 21, 31 Exposure device 22, 32 Developing device 23, 33 Paper cassette 24, 34 Paper 25, 35 Transfer device 26, 36 Fixing device 27 Cleaning device 28, 38 Static elimination lamp 29, 39 Paper path 96 DC power supply 97 AC power supply 106 Rail 107 Movable member 108 Support rod 116 Applied voltage switching device 127, 128, 136 Frame body 137 Power supply electrode 161 Charging device for static elimination 162 Image forming unit 163 Paper 164 Paper path 165 Transfer device 166 Fixing device 167 Intermediate transfer belt 168 Roll

Claims (14)

[Claims] 1. A charging electrode which is formed in a cylindrical shape from a semiconductive material, has a surface opposed to a moving charge receptor in a non-contact manner, and is supported rotatably in a circumferential direction. A power supply for applying a voltage of the charge receptor, and causing a discharge in a minute gap near a facing portion between the charging electrode and the charge receptor to charge the surface of the charge receptor, and A charging device, wherein the charging electrode rotates and moves in the circumferential direction along with the movement of the surface of the charge receptor due to electrostatic force generated between the charging electrode and the charging electrode. 2. The charging device according to claim 1, further comprising: a rotation stabilizing member that is in contact with an outer peripheral surface of the charging electrode and stabilizes rotation by regulating displacement of the charging electrode. Charging device. 3. The charging device according to claim 2, wherein the rotation stabilizing member is configured such that, at a portion in contact with both ends of the charging electrode, a force for pushing the charging electrode toward the charge receptor increases. A charging device having a shape. 4. The charging device according to claim 2, wherein the rotation stabilizing member has an endless peripheral surface, and rotates in a circumferential direction with the rotational movement of the charging electrode. A charging device characterized in that the charging device is supported as possible. 5. The charging device according to claim 2, wherein the rotation stabilizing member is made of a conductive material, and the charging electrode is charged through the rotation stabilizing member. A charging device characterized by applying a voltage of 6. The charging device according to claim 5, wherein the position at which the rotation stabilizing member contacts the charging electrode is:
A charging device characterized in that the distance from both ends of a discharge region in a portion where the charging electrode and the charge receptor face each other is substantially equal. 7. The charging device according to claim 5, wherein the rotation stabilizing member is supported such that a contact position with the charging electrode can be changed in a circumferential direction of the charging electrode. Characteristic charging device. 8. The charging device according to claim 5, wherein a plurality of the rotation stabilizing members are provided in a circumferential direction of the charging electrode, and the power source is provided in the plurality of rotation stabilizing members. A charging device characterized in that one is selected and a voltage is applied. 9. A charging electrode formed of a semiconductive material in a cylindrical shape, a power supply for applying a charging voltage to the charging electrode, and contacting the charging electrode at a plurality of positions; Electrode support means for supporting the surface of the moving charge receptor in a non-contact manner so as to be rotatable in a circumferential direction, wherein discharge is performed in a minute gap near a facing portion between the charging electrode and the charge receptor. This causes the surface of the charge receptor to be charged, and the electrostatic force generated between the charge receptor and the charged electrode causes the charged electrode to move around its surface as the charge receptor surface moves. A charging device characterized by rotating in a direction. 10. The charging device according to claim 9, wherein the electrode supporting means has a brush which is brought into contact with the contact portion with the charging electrode substantially uniformly in a width direction of an outer peripheral surface of the charging electrode. And a charging voltage is applied to the charging electrode from the power supply via the brush. 11. The charging device according to claim 1, wherein the charging electrode includes an inner layer made of a material having a small electric resistance and a surface layer having a higher resistance than the inner layer. A charging device comprising: 12. The charging device according to claim 1, wherein the charging electrode is formed by forming a flexible film-shaped member into a cylindrical shape. Charging device. 13. The charging device according to claim 1, wherein a voltage applied to the charging electrode is set such that a surface potential of the charge receptor is substantially 0V. A charging device. 14. The charging device according to claim 1, wherein the charging electrode is a member to which a toner image formed on an image carrier by electrophotography is transferred. A charging device, wherein the charging device is disposed so as to face and oppose to the charging electrode, and a voltage applied to the charging electrode is set so that a surface potential of the transfer object is substantially 0 V.