JP2003223040A - Brush electrifying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the occurrence of a white stripe due to irregular electrification peculiar to an image forming apparatus. <P>SOLUTION: The brush electrifying device provided in the image forming apparatus is constituted so that is performed simultaneously with electrification only on the upstream side from a brush 1 where the brush 1 abuts on the surface of a body to be electrified 7 first so as to remove the influence of projecting bristles on the upstream side from the brush 1 causing the occurrence of the white stripe. Namely, by intentionally radiating discharging light of a discharging lamp 12 arranged at the preceding stage of an electrification part even to the upstream part of the brush, the charge at the upstream part of the brush is eliminated. The brush 1 is constituted by flocking fibers on foundation 2 very densely and is ordinarily black, so that the discharging light of the lamp 12 does not enter inside the brush electrifier but excellently electrifies a part except the upstream side from the brush. Thus, since the irregular electrification on the upstream side from the brush is reduced, the influence of the projecting bristles on the upstream side from the brush causing the occurrence of the projecting bristles is removed and the occurrence of the white stripe is reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush charging device and an image forming apparatus relating to, for example, an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, as a charging device for electrophotography, a corona discharger using a scorotron has been the mainstream. However, since corona charging utilizes a discharging phenomenon, a large amount of ozone, which is harmful to the human body, is generated particularly when negatively charging. Also,
The applied voltage was relatively high at -4 to -5 kv, and most of the current also flowed to the case, so there was a drawback that the energy loss was large. In recent years, instead of corona charging,
Contact charging technology, in which ozone is hardly generated, has advanced. Typical examples are a roller charging method using a conductive roller and a brush charging method. Both of them are said to generate ozone less than 1/100 that of corona chargers.
In addition, the applied voltage is relatively low at about -1 kv, and no current flows to the case, so there is little loss.

[0003]

However, the roller charging method is vulnerable to dust such as toner and paper dust, and it immediately appears in the image as uneven charge. Further, considering the price of the conductive roller itself, it is disadvantageous in terms of cost. On the other hand, the brush charger is more effective than a roller against dirt such as toner and paper dust, and is cheap in price. Therefore, the brush charger is an effective charging means in a small and inexpensive device. However, because of the shape of the brush charger, many half-streaks are generated along the surface movement direction of the body to be charged when printing halftones in copying machines, printers, etc., especially in the electrophotographic process using the reversal development method. Will end up. The white streak in the negative charging reversal development method means that the surface potential of the body to be charged locally becomes higher on the negative side. This is a charging unevenness peculiar to the brush, and is particularly remarkable in the fixed conductive brush. Fixed brushes are made by implanting conductive contacts on the base.Metal fine wires and conductive fibers are known, but the latter is more common, with carbon dispersed in flexible rayon or nylon. Fibers are the mainstream. The surface of the brush is generally flat. On the other hand, the surface of the body to be charged in contact with it becomes a surface having a curvature when a drum is used. That is, by bringing a flat brush into contact with the surface of the charged body having a curvature, the brush bristles do not uniformly contact the surface of the charged body, which creates an abnormal charged state, and the potential is locally on the negative side. It is becoming a factor to increase the muscle. Then, in order to solve the problem, it is sufficient to give the brush itself substantially the same curvature as the charged body so that the tips of the brushes uniformly contact the surface of the charged body, but this is difficult to manufacture and the production cost is reduced. Considering it, there is no known method suitable for mass production.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a brush charging device and an image forming apparatus which can easily reduce the generation of halftone white streaks peculiar to the brush charging device. And

[0005]

In order to achieve the above object, the brush charging device of the present invention is a brush charging device in which a conductive brush is brought into contact with an object to be charged to charge the conductive brush. It is characterized in that only the upstream side of the conductive brush that first comes in contact with the surface of the charged body is charged and discharged at the same time. Here, if the charged body is a photoconductor, for example, static elimination light is used as the static elimination means.

Further, the image forming apparatus of the present invention is an image forming apparatus having a fixed conductive brush, wherein the conductive brush is brought into contact with the surface of the body to be charged in advance, and after the power of the apparatus is turned on, Before starting the use of the device, the charged body is moved in the plane for a certain time with respect to the conductive brush,
It is characterized in that the bristles of the conductive brush are set in a certain direction before being used. Further, the image forming apparatus of the present invention, when the surface of the member to be charged is moved,
A bias voltage is applied to the conductive brush.

The image forming apparatus of the present invention is an image forming apparatus equipped with a brush charging device for bringing a fixed conductive brush to which a bias voltage is applied into contact with the surface of a member to be charged. An alternating bias voltage is superposed and applied, and the alternating bias voltage is set to be less than a region where the charged body uniformly starts converged charging.

[0008]

Therefore, according to the present invention, it is possible to reduce the occurrence of white streaks due to the uneven charging characteristic of the image forming apparatus.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows a method of cutting the bristle tips of a brush in the process of manufacturing the brush. Examples of the material of the brush bristles include those in which carbon is dispersed in rayon and nylon, and when those fibers are sewn to the conductive base fabric, the brush surface is cut as a finishing process. . Therefore, the base cloth 2 on which the conductive fibers 1 are implanted has a member 3 having substantially the same curvature as the surface of the charged body at the portion where the brush charger contacts the surface of the charged body from the surface of the base cloth side. Is set to. Then, as shown in FIG. 1B, the conductive fibers 1 are each cut into a predetermined length by horizontally cutting the hair tips with the cutter 4. After that, when the brush is removed from the curvature member 3 and the base cloth is returned to the original horizontal state, the brush bristles are cut into a curvature in the opposite direction to the attached curvature member as shown in FIG. 1 (c). . That is, it is possible to cut the brush surface having substantially the same curvature as that of the body to be charged by an extremely simple method. Further, since the curvature of the tip end surface of the conductive fiber obtained at this time is larger than the curvature of the support member 3 by the length of the fiber, the curvature of the support member is set to be slightly smaller than the charged body curvature. By doing so, it is possible to form a conductive fiber surface having a curvature closer to that of the charged body.

In the brush bristle cutting step in the brush manufacturing method, in many cases, the supporting member 3 is provided on the drum 5 made of metal or the like as shown in FIG. The base fabric 2 was attached and the drum 5 was rotated to cut the conductive fibers by the cutter 4 installed outside the drum 5, thereby obtaining a substantially flat brush surface. However, in this method, the brush cut surface is strictly a convex shape, and thus it is not possible to evenly contact the bristle tips of the brush with the surface of the body to be charged. Therefore, in the step of cutting the hair tips, as shown in FIG. 2B, the base cloth 2 on which the fibers 1 have been planted is attached to the inside of the drum 5 provided with the support members 3 on both sides, and the drum 5 is rotated. The tip of the hair is cut by the cutter 4 installed inside the drum 5 to make the conductive fiber surface concave. Furthermore, here, the curvature of the conductive fiber surface can be increased by making the support member 3 to which the base fabric 2 on which the fibers 1 have been transplanted attached have a curvature opposite to that of the drum 5. It is possible to obtain brush surfaces having almost the same curvature. Similarly, also in FIG. 2A, the same effect can be obtained by increasing the curvature of the support member 3. It goes without saying that the same effect can be obtained by rotating the gutter instead of the cylindrical drum.

Next, a method for obtaining the same effect without cutting the conductive fiber surface into a concave shape will be described. As described above, one of the causes of white streaks in the halftone image during brush charging is that the contact state of the tips of the fibers with respect to the surface of the charged body has a great influence. In the conventional charging brush, as shown in FIG. 3 (a), the surface of the conductive fiber is flat, and when it is brought into contact with the surface of the charged object having a curvature with a predetermined bite amount. As shown in FIG. 3 (b), in the contact area between the conductive fiber 1 and the body to be charged 7, the hair tips on the upstream side in the surface movement direction of the body to be charged are opposite to the rotation of the body to be charged. You will be standing. In this state, when halftone images are output using the electrophotographic process of the reversal development method, many white streaks occur,
White streaks are particularly noticeable when printing is performed after leaving the brush charger in contact with the member to be charged. White streak mainly occurs in a high humidity environment (RH85%) and a low humidity environment (RH20
%), High humidity results in continuous white streaks, and low humidity results in short sharp white streaks. In order to prevent the generation of white streaks in a low temperature environment, it is effective to minimize the amount of brush fibers that bite into the body to be charged. The brush charger having the same curvature as the surface of the body to be charged can stabilize the amount of bite to be small in the entire contact width and further increase the apparent fiber density, which is effective in reducing streaks. The white streaks are particularly noticeable on the first several tens of prints made after the brush charger is brought into contact with the surface of the member to be charged. This is considered to occur because the reversely fluffed fibers try to flow to the downstream side in the surface movement direction due to the rotation of the body to be charged, and become inconspicuous after printing several hundred sheets. Therefore, in order to eliminate the fibers in the state of reverse fluffing in the initial state, the fibers of the fixed conductive brush are
Inclination treatment was performed in advance so that the tips of the hairs were uniformly fluttered in the forward direction with respect to the surface moving direction of the charged body 7. The angle of slant is shown in Fig. 4.
As shown in (a), when the fiber on the most upstream side with respect to the surface moving direction of the charged body 7 contacts the surface of the charged body,
It only has to flow to the downstream side in the surface movement direction of the charged body 7. That is, in FIG. 4A, the angle formed by the base cloth and the brush fiber is θ ₁ , the radius of the body to be charged is a, the length of the bristles of the brush is b,
The distance from the intersection of the vertical line drawn from the center of the charged body to the brush surface and the brush base cloth to the end of the brush on the upstream side of the charged body,
When the flock width of the so-called upstream brush is c, co
It suffices to satisfy the relationship such as sθ ₁ > c / (a + b).
As a result, as shown in FIG. 4 (b), the brush bristles flow uniformly on the downstream side of the surface-to-be-charged body 7 in the direction of surface movement, and there is no reverse bristling fiber. In the experiment, it was confirmed that the white streaks in the low humidity after being left were remarkably reduced as compared with the brush not subjected to the bristling treatment. This slanted hair treatment method includes a cylindrical container 8 as shown in FIG.
It is possible to sandwich the base cloth 2 in which the conductive fibers 1 are planted between the cylindrical members 9 having a diameter smaller than that, and rotate either or both of the members. Alternatively, as shown in FIG. 5B, it is also possible to gradually press the plate-shaped member 10 against the fixed conductive brush from the upstream side where the bristles are slanted.

Further, as a method of eliminating the bristles and curving of the brush fiber itself, the following methods are available. As shown in FIG. 6 (a), this is a support member 6 in which the base fabric 2 in which the conductive fibers 1 are implanted is angled at one or more locations in a direction along the curvature of the surface of the body to be charged. By mounting, according to this method, there is no need to perform cutting or beveling on the curvature which is a problem in manufacturing.

In FIG. 6A, the radius of the member 7 to be charged is a, the fiber length of the brush is b, and the surface movement direction of the member 7 to be charged of the brush is from the vertex of the angle θ ₂ of the brush supporting member. When the width to the upstream side of is d,
The angle θ ₂ flutters to the downstream side of the surface moving direction of the charged body.
To set. That is, by defining the value of θ ₂ so as to satisfy tan θ ₂ <(a + b) / d, the tip of the brush does not come into contact with the surface of the body to be charged in a reverse bristling manner. As a result, there are no bristles that are raised up against the charged body on the upstream side of the brush, and the white lines in the initial state of low humidity are reduced. Moreover, according to this method, as shown in FIG.
As shown in (b), since the density of the amount of the fibers at the upstream side of the contact area between the conductive fiber 1 and the member to be charged with respect to the member to be charged becomes large, stable charging can be performed with a small charging width. It will be possible. In addition, when such a brush charger is used in an electrophotographic apparatus, an angle is provided in advance in a part of the process cartridge as shown in FIG. 7, and the brush charger is attached to the base cloth together therewith. It is also possible to make easily with. Even in such a method, halftone white streaks printed after being left standing were significantly reduced.

Further, it is possible to reduce white streaks by using the conventional brush and the brush supporting member. This can be achieved by first, in the conventional brush charging device as described above, removing charges simultaneously with charging only on the brush upstream side where the conductive brush first contacts the surface of the body to be charged. It has already been explained that the protruding hair on the upstream side of the brush affects the cause of the white streaks. Therefore, particularly in the apparatus using the electrophotographic method, as shown in FIG. 8, the static elimination light by the static elimination lamp 12 existing in the preceding stage of the charging section is intentionally applied to the first half of the brush to eliminate the static electricity in the upstream part of the brush. Will end up. FIG. 8 shows an example of an electrophotographic process cartridge processed as described above.
Here, since the brush fibers 1 are densely planted on the base cloth 2 and are usually black, the charge removal light by the charge removal lamp 12 does not enter the inside of the brush charger, but the brush upstream side is removed. Good charging is performed in the part. As a result, uneven charging on the upstream side of the brush is reduced.

Next, another method of reducing white streaks using a conventional brush charger will be described. It is an image forming device that uses a fixed brush as a charging device.The brush charging device is brought into contact with the surface of the charged object in advance, and the charged object is brushed for several minutes before the device is turned on after the power is turned on. With respect to the brush fiber, the brush fiber is moved in a plane, and the brush fiber is preliminarily used in a certain direction. Further, at that time, it is more effective to apply a predetermined bias to the brush.

In the experiment, the resolution is 300 dpi and the initiation speed is 8
A reversal development type laser printer of sheets / minute was used. The member to be charged uses a negatively charged organic photosensitive drum. The brush charger uses a fiber in which carbon is dispersed in rayon, and the resistance value of the entire brush is about 10 5 Ω. Printed from the beginning with a new fixed brush charger in a low-humidity environment. Half of the halftone dot area ratio is 50% after rotating the photoconductor without passing electricity for 12 minutes (about 100 sheets) without passing electricity. White lines in the halftone image of the one printed with the tone image and the one rotating the photoconductor without passing the paper for 12 minutes while applying a constant voltage bias of -0.5 to -1.3 kv to the brush. Indicates the status.
In addition, the brush charger introduced in the explanation so far, which has a curvature matched to the body to be charged, and the brush that has been subjected to bevel treatment,
The following table shows the results of the brushes that were intentionally irradiated with the static elimination light on the upstream side, when compared at the same time.

[0017]

[Table 1] The width of all the brushes is 9 mm and the length of the fibers is 4 mm. The amount of bite into the photoconductor was set as shallow as possible within the range in which the entire surface of the brushed brush fiber was in contact with the photoconductor. The photoconductor diameter is 30 mmφ. According to this, when a brush attached to a member having the same curvature as the photoconductor is used, there are few white stripes, but printing is performed after rotating the photoconductor without passing about 100 sheets while energizing a normal brush. It can be seen that the white streak is reduced almost in the same way. Further, it can be seen that the white stripes are reduced to some extent even if the brush is not energized. That is, by contacting the surface of the photoconductor with the fixed brush and rotating it for several minutes in advance,
The bristles have a certain tendency in a certain direction, and the same effect as that obtained when the bristles are treated can be obtained. Regarding the bias for energizing, no significant difference was observed at 0.5 kv or less as compared with the case where no energizing was performed, but at 0.8 kv or more, white streaks were further reduced. Normally used bias is -1.0 kv
Since it is only about 80% of the normal voltage, it is effective in reducing white streaks.

Regarding the brush which has been subjected to the bristling treatment,
The number of streaks is small when the angle is within the angle of slant, and the number of white lines is large when the condition is out of the range as compared with the former. The same applies to the brush attached to the angled member. When the brush is in the range of the condition, the streak is reduced, but when the brush is out of the range, the streak is generated more than in the range. But,
In all cases, white streaks were apparently reduced compared to the initial state of the brush without any measures. In addition, even in the brush charger in which the charge removing light was irradiated to the upstream side of the brush, the white streak was less than that in the case of no countermeasure, and the effect was seen.

Next, there is a method of reducing white streaks other than uniformly contacting the brush fibers with the member to be charged. In this method, in addition to direct current, an AC bias less than the voltage at which the body to be charged uniformly starts convergent charging is superimposed on the brush charger. This will also be described by taking the above-described reversal development type laser printer as an example. The member to be charged is a negatively charged photosensitive drum, and the charging is performed on the negative side. If the surface potential of the photosensitive member is high on the negative side, it becomes white on the image, and if it is close to the positive side, it becomes black on the image. Here, the higher the negative voltage is, the higher the potential is, and the larger the potential is.

When a DC bias is applied to the brush charger, it becomes as shown in FIG. According to this, the surface potential of the photoconductor starts to rise suddenly when the applied voltage of the brush becomes about −500 V, and rises almost linearly, and when the brush charger is applied −1000 V, the surface potential of the photoconductor is about −50.
It is charged to 0v. That is, the brush applied voltage at the start of charging of the photosensitive member is about -500 V, and the photosensitive member is charged for the first time with a potential difference of this level with the brush charger, and the potential difference is maintained even if the brush applied voltage changes. It is kept almost constant. And this is a characteristic peculiar to discharge development. Further, even in brush charging, a very small amount of ozone is generated in the immediate vicinity of the charger (about 10 ⁻³ of corona electricity), and it is considered that charging by discharge is also dominant in brush charging. Here, the white streaks are the areas where the surface potential is locally higher than other areas due to the charge development that does not rely on normal discharge due to defective fibers or waste hair in the brush charger. That is already explained. And the surface potential, which has been once high, can no longer be reduced only by DC bias.

Next, when the DC bias is fixed at -500 V and the AC bias is gradually superposed thereon, the surface potential of the photoconductor changes as shown in FIG. According to FIG. 10, the surface potential rises with a constant inclination up to an AC voltage of about 400V. The surface potential at this time is only DC, and is almost equal to the value when the maximum value of the voltage when AC is superimposed on DC is applied to the brush charger.
The surface potential of the photoconductor when charged only with direct current is shown by a dotted line. However, when the AC voltage exceeds 400 V, the slope becomes very small and gradually rises, but within the so-called convergence range. Here, FIG. 11 shows a conceptual diagram of the brush application bias and the surface potential of the photoconductor when the AC voltage in the area of the convergent charging area is 600 v. According to FIG. 11, the maximum value of the brush bias is about -1340v.
(−500−600 × 1.4), and the photosensitive member then has a difference of about 500 v from the applied bias and −80.
It is charged to about 0v. On the other hand, the minimum value of the brush bias is about + 340v (-500 + 600x1.4), and the photoreceptor is charged to about -150v from the same theory. That is, the charging by the positive and negative discharges is repeatedly performed over the entire area where the brush charger and the photoconductor are in contact with each other. The final surface potential of the photoconductor is ultimately determined by the brush bias in the portion where the brush charger is finally in contact with the photoconductor. On the most downstream side where the brush charger separates from the photoconductor, the brush fibers are not in a completely linear state along the axial direction of the photoconductor, and some fibers protrude depending on the location. That is, the surface potential is affected by those fibers and is scattered in the range of −150 to −800 v, and is not uniform. Even if a halftone image is printed under such conditions, a portion having a high surface potential becomes white and a portion having a low surface potential becomes black, and a good image cannot be obtained.

On the other hand, in FIG. 10, a linear portion having a large inclination, that is, an AC voltage which is a region below the convergence region is 350 V
In the case of, the result is as shown in FIG. Fig. 12 shows DC voltage
According to this, when the AC voltage 350v is superimposed on 550v, the maximum value of the brush bias is -1040v (-
550-350 × 1.4), at which time the photoreceptor is charged to approximately −550. Even if a minimum value of the brush bias of −60 V is applied thereto, the potential difference from the photoconductor is already about 500 V, and almost no discharge to the positive side occurs. That is, the surface potential of the photoconductor charged when the brush bias has the maximum value is almost unchanged during the contact between the brush and the charged body, and is stored as it is.
The final potential converges to about -550v. That is, as in the case where only the direct current is applied to the brush charger, the potential of the portion charged to an appropriate surface potential is not lowered. The region where the AC voltage is less than 400 V shown in FIG. 10 is a region where the charging due to discharge on the positive side does not occur, that is, the so-called AC voltage is less than when the photosensitive member starts convergent charging. Considering the white streak part here, since the white streak is a part where the surface potential is locally high, the potential difference is 500 v when only the white streak part has the minimum value of the brush bias, and the discharge start here is started. The voltage will be exceeded. Then, it is discharged to the positive side and the potential drops, and then it settles down when the potential difference reaches 500 v. That is, only the white streak part has a reduced potential and the streak decreases. Also,
At this time, even if charging which is not due to normal discharge is generated on the positive side and a portion having a low surface potential is generated, it is restored to a normal potential when a maximum value of -1040v is applied thereafter. That is, even if such abnormal charging does not occur on the most downstream side of the brush, uneven charging does not occur, and black streaks as well as white streaks hardly increase.

The results of actually printing and evaluating halftone images using a laser printer are shown below. The environment was hot and humid, and the brush charger used was a new type of conventional type, and various biases were changed and experiments were conducted. The printer used was the one described above, and the fifth image was evaluated after the brush charger was attached.

[0024]

[Table 2] In the case of the brush charger used in the experiment, 300 V to 400 V was appropriate for the AC bias superimposed on the DC. That is, the condition immediately before the photosensitive body starts the convergent charging is preferable. This is slightly different from the charging start voltage of −500 V in FIG. This is because the charging start voltage of the white streaks is also included in the surface potential and measured,
Actually, the charging start voltage of the white streak portion is shifted by about 200 V in the positive direction due to charging other than normal discharge. The area immediately before the start of the convergent charging is the area immediately before the inclination of the straight line changes in FIG. 10, and a great effect can be seen in reducing the white streaks in this area. In other words, by setting the areas other than the muscles to the potential at the boundary where the potential is lowered by the discharge, even the subtle white muscles where the potential is slightly increased can be reduced by the positive discharge. Because you can.

Regarding the frequency, although it is related to the followability of the frequency of the brush, 100 Hz to 800 Hz was an appropriate value for the brush that was tested. When the frequency of the brush is lowered to 200 Hz, the portion where the electric potential becomes high due to the influence of defective fibers and waste bristles slightly mixed in the brush does not become streak-like but halftone dot-like. Then, the area between the high-potential halftone dot portions has a normal surface potential, and as a result, the area of the high-potential white streak portion decreases. In addition, since it becomes a halftone dot pattern, uneven charging such as streaks is difficult to catch with the naked eye. As a result, the muscles themselves become less noticeable. However, even if the frequency is high, it is not ineffective, and the white streak is considerably reduced as compared with the case where only the DC bias is applied.

As described above, by superimposing a proper AC bias on the DC bias, there is no portion where the potential is locally high on the surface of the photoconductor. That is, in addition to the white streak in the low humidity environment, the continuous white streak generated in the high humidity environment can be significantly reduced.

[0027]

According to the present invention, it is possible to reduce white streaks on a halftone image due to uneven charging peculiar to a fixed-type conductive brush charger.

[Brief description of drawings]

1A, 1B, and 1C are schematic views showing the order of brush cutting according to an embodiment of the present invention.

2A is a schematic view showing an example of a conventional brush cut shown for comparison, and FIG. 2B is a schematic view of a brush cut method according to an embodiment of the present invention.

3A and 3B are schematic diagrams showing a contact state of a conventional fixed brush for comparison.

4 (a) and 4 (b) are schematic diagrams showing the conditions for the slanting treatment performed in the above-described embodiment.

5 (a) and 5 (b) are schematic views of an example of the method of the above-mentioned slant treatment.

6A and 6B are schematic views showing a state in which a brush is attached to an angled member.

FIG. 7 is a front view of an embodiment in which the angled member is part of a process cartridge.

FIG. 8 is a front view of another embodiment of the process cartridge.

FIG. 9 is a diagram showing a charging characteristic of a fixed brush when a DC bias is applied.

FIG. 10 is a diagram showing a charging characteristic of a fixed brush when an alternating bias is applied to a direct bias.

FIG. 11 is a conceptual diagram in the case where AC 600V is superimposed and applied to DC 500V.

FIG. 12 is a conceptual diagram in the case where an alternating current of 350 V is superposed on a direct current of 550 V.

[Explanation of symbols]

1 ... Brush, 2 ... Brush base cloth, 3 ... Support member, 4 ... Cutter, 5 ... Drum, 6 ... Brush support member, 7 ... Charged member, 8 ... Cylindrical drum, 9 ... Cylindrical drum, 10 ... Press plate, 11 ... Process cartridge, 12 ... Static elimination lamp.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Yoshida             70 Yanagicho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture             Toshiba Yanagimachi Factory (72) Inventor Shigeru Fujiwara             70 Yanagicho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture             Toshiba Yanagimachi Factory (72) Inventor Masashi Takahashi             70 Yanagicho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture             Toshiba Yanagimachi Factory F-term (reference) 2H200 FA16 FA17 GA23 GB02 HA03                       HA29 HB07 HB20 HB39 HB45                       HB46 HB48 MA04 MB01 NA06                       NA09

Claims (4)

[Claims] 1. A brush charging device for charging a conductive brush by bringing it into contact with a body to be charged, in which charge is removed simultaneously with charging only on the upstream side of the conductive brush where the conductive brush first contacts the surface of the body to be charged. The brush charging device is characterized in that 2. An image forming apparatus provided with a fixed conductive brush, wherein the conductive brush is previously brought into contact with the surface of the body to be charged,
After turning on the power of the device and before starting use of the device,
An image forming apparatus, wherein the charged body is moved in a plane with respect to the conductive brush for a certain period of time, and the bristles of the conductive brush are given a habit in a certain direction before the use is started. 3. The image forming apparatus according to claim 2, wherein a bias voltage is applied to the conductive brush when the surface of the body to be charged is moved. 4. An image forming apparatus equipped with a brush charging device for bringing a fixed type conductive brush to which a bias voltage is applied into contact with the surface of an object to be charged, wherein direct current and alternating current bias voltages are superimposed and applied to the conductive brush. The image forming apparatus is characterized in that the AC bias voltage is less than a region where the charged body starts uniformly converged charging.