JP3339959B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact brush charging device.
The present invention relates to an image forming apparatus using an electrophotographic method, such as an optical printer, a copying machine, a facsimile machine, and the like having a printer.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method, such as an optical printer or a copying machine, the surface of an image carrier such as a photosensitive drum or a photosensitive belt is charged by a charging device, and the charged area is exposed. An electrostatic latent image is formed by applying a toner to a visible image, transferred to a transfer sheet, and thermally fixed to perform a series of image forming processes.

[0003] Various types of charging devices are known. Roughly speaking, a corona charging device using corona discharge and a rotary charging member (roller type or brush type) or a fixed type charging member ( (Brush type, blade type).

[0004] The corona charging device has an advantage that stable charging can be performed. However, there is a problem that a large amount of ozone is generated due to a discharge phenomenon at the time of charging, which causes deterioration of an image carrier or adversely affects a human body. For this reason, attention has been paid to a contact charging device that generates a significantly smaller amount of ozone than a corona charging device.

[0005] Among them, for example, Japanese Utility Model Laid-Open No. 57-68242
As shown in FIG. 10 (a) or (b), a contact-type brush charging device as disclosed in Japanese Patent Application Laid-Open No. 58-121062 or Japanese Patent Application Laid-Open No. A brush charging member 43 formed in a brush shape by fixing the conductive fiber 41 to the fixing member 42 is brought into contact with the image carrier 1 rotating in a predetermined process direction (the direction of arrow A).
The voltage is applied to the brush charging member 43 to charge the surface of the image carrier 1. However, since the structure is relatively simple and the cost is low, the speed is slow and it is advantageous for a small-sized image forming apparatus. Is being promoted.

[0006] However, such a contact-type brush charging device is more likely to cause charging unevenness both initially and over time than a charging device using a rotary charging member. The initial charging unevenness is caused by the density unevenness of the brush charging member itself contacting the image carrier, that is, the magnitude of the contact probability per unit time. To prevent this, the fiber density of the brush charging member may be increased, or the contact length in the rotation direction of the image carrier may be increased.

[0007] The uneven charging over time is caused by a change in the resistance value between the image carrier and the brush charging member due to the presence of foreign matter between the charging member and the brush charging member. As a measure to prevent this, a method of increasing the resistance value of the brush charging member and reducing the amount of change in the resistance value in the absence and interposition of the foreign matter, or temporarily releasing the contact of the brush charging member with the image carrier to remove the foreign matter There is a method of removing.

[0008]

However, in the above-described conventional contact-type brush charging device, the following problems occur when the fiber (brush fiber) density of the brush charging member is increased. That is, assuming the state where the fiber density is the highest, the adjacent fibers are in close contact with each other, so that the brush fibers cannot bend in this state, and the contact with the image carrier is performed only at the fiber tips. As a result, charging unevenness is rather increased. From this, it can be seen that there is a limit in increasing the density of the brush fiber. In addition, as the density increases, it becomes more difficult to remove foreign matter that has once entered between the fibers.

In order to increase the contact length of the brush charging member in the direction of rotation of the image carrier, there are the following problems. That is, the contact-type brush charging device is suitable for a small and low-cost image forming apparatus. However, since the image carrier tends to be small in such an image forming apparatus, a brush having a large width in the moving direction of the image carrier is used. It is difficult to arrange the charging member, and the cost increases as the brush charging member increases.

Further, if the brush charging member is once released from contact with the image carrier to remove foreign matter, the structure becomes complicated, the cost increases, and the size of the image forming apparatus increases. .

[0011] The present invention has been made in view of the above, an image forming apparatus having such a contact-type brush band electrical location, without enlarging or complicating the configuration, initially to be An object is to prevent charging unevenness from occurring over time.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a brush charging member formed by fixing a large number of high resistance fibers to a fixing member and rotating in a predetermined process direction. An image forming apparatus provided with a contact-type brush charging device that makes contact with a body and applies a voltage to the brush charging member to charge the surface of the image carrier, wherein the contact point between the brush charging member and the image carrier is P. L1 is a tangent line of the image carrier passing through the contact point P, and L2 is a line along the direction of the high-resistance fiber near the fixing member of the brush charging member. L1 and L
2, the brush charging member is disposed so that θ <90 °, and the predetermined process is completed.
Later, the image carrier is rotated in the direction opposite to the process direction
Means for providing a brush charging member in the process direction of the image carrier
Arrange the cleaning blade on the more upstream side, and
Q is the point of contact between the cleaning blade and the image carrier,
When the contact point between the most upstream side of the electrical member and the image carrier is R,
The distance between the QRs on the surface of the image carrier
The amount of movement of the surface when rotating in the opposite direction increases.
That's what I did.

It is preferable to set the angle θ to 10 ° ≦ θ ≦ 60 ° or to form the tip of the high-resistance fiber in a loop.

[0014]

[0015]

According to the image forming apparatus of the present invention, the tangent of the image carrier passing through the contact point P between the brush charging member and the image carrier is set to L.
1. L2 is a line along the direction of the high resistance fiber near the fixing member of the brush charging member, and θ is an angle formed between L1 and L2 on the downstream side in the process direction from the contact point P of the image carrier. Since the brush charging member is disposed so that θ <90 ° (contact with the image carrier is in counter contact), foreign matter is less likely to be caught between the tip of the brush charging member and the image carrier. After the completion of the predetermined process, the image carrier is
The brush is rotated in the opposite direction to the
The trailing contact occurs between the image carrier and the image carrier.
The tip of the brush charging member may bite foreign matter.
However, it can be removed after the completion of the predetermined process. Further
At the upstream of the brush charging member in the process direction of the image carrier.
Place a cleaning blade on the side and clean it
The contact point between the blade and the image carrier is Q,
When the contact point between the most upstream side and the image carrier is R,
Move the image carrier in the opposite direction from the length between the QRs on the surface of the body
Increased the amount of movement of the surface when rotated to
Therefore, foreign matter removed from the tip of the brush charging member is cleaned.
Brush can be reliably collected by the
Re-adhesion to the tip of the charging member is eliminated. Therefore, the long
It is possible to obtain a stable charged potential without unevenness over the period.
Wear.

When the angle θ is set to 10 ° ≦ θ ≦ 60 °, the fixing member of the brush charging member approaches the image carrier to cause a leak, or the high-resistance fiber of the brush charging member is inverted to cause image leakage. The contact with the carrier does not come into trailing contact. Further, if the tip of the high-resistance fiber of the brush charging member is formed in a loop shape, the contact length of the high-resistance fiber to the image carrier per one high-resistance fiber is increased, and a more stable charging potential can be obtained.

[0017]

[0018]

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the periphery of an image carrier of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a relationship between the image carrier and a brush charging member. Corresponding parts have the same reference characters allotted.

In this image forming apparatus, reference numeral 1 denotes a drum-shaped image carrier whose surface is formed of a photoconductor, around which a contact-type brush charger 2, an eraser 3, a developing device 4, and a transfer device 5 are provided. , And the cleaning unit 6 are sequentially arranged.

As shown in FIG. 2, the contact-type brush charging device 2 drives a brush charging member 13 formed by fixing a large number of high-resistance fibers 11 to a fixing member (holder) 12 to form a brush during image formation. The motor is brought into contact with the image carrier 1 rotating in the direction of arrow A (predetermined process direction) by a motor,
A high voltage is applied to the brush charging member 13 by a DC power supply (HV) 14 to charge the surface of the image carrier 1.

The charged surface of the image carrier 1 is exposed to light from an exposure device (not shown) to form an electrostatic latent image thereon, and the latent image is removed by an eraser 3 to remove unnecessary potential. The toner is adhered by a developing roller 4a in the developing device 4 to form an image, and the toner image is fed from a paper feeding unit (not shown) and sent to a transfer unit at a predetermined timing by a pair of registration rollers 10. The image is transferred by the transfer device 5.

That is, the transfer roller 21 of the transfer device 5
Means that a high voltage is applied to the metal core 23 by the DC power supply 22 to contact the surface of the image carrier 1, rotate around the image carrier 1 rotating in the direction of arrow A, and rotate at a constant speed. To transfer the toner image on the surface to the paper.

Thereafter, the sheet on which the toner image has been transferred is conveyed to a fixing device (not shown), where it is subjected to a heat fixing process to obtain an image forming sheet (copy sheet or the like). on the other hand,
The toner remaining on the surface of the image carrier 1 is removed by a polyurethane rubber cleaning blade 6a provided in the cleaning unit 6 to prepare for the next image forming process.

It should be noted that the DC power supply 14 is preferably
High resistance fiber (hereinafter referred to as “brush fiber”) of the brush charging member 13
Even if the contact resistance between 11) and the image carrier 1 changes,
This is a constant current power supply in which the value of the current flowing during this period does not change.
In addition, a stable charging potential can be obtained by superimposing an alternating current on a direct current.

The fixing member (holder) 12 of the brush charging member 13 is made of a conductive material such as aluminum. The brush fibers 11 may be various known fibers, for example, carbon-containing acrylic fibers (trade name: SA-7) manufactured by Toray Industries, Inc. This fiber has a thickness of ³ to 15 denier and a volume resistance of 10 ³ to 10 ^8.
Ω / cm has been put to practical use.

The manufacturing method of the brush charging member 13 will be briefly described. For example, as shown in FIG. 3A, the brush fiber 11 is folded and bent at a constant width, and one side thereof is interposed between a plurality of fibers 15. Then, it is knitted into a conductive (for example, aluminum plate) fixing member 12 which is bent as shown in FIG. A brush charging member (loop brush) 1 having a tip 11 formed in a loop shape
3 is completed.

Compared to the brush charging member (straight brush) 17 in which the tip of the brush fiber 16 is formed in a straight hair shape as shown in FIGS. The brush charging member 13 which is a loop brush as shown in FIG.
5, the total contact length in the longitudinal direction of each loop portion becomes large, and when the image carrier 1 is moved in the direction of arrow A as shown in FIG. 5, the contact area with the surface thereof becomes considerably large. Charging unevenness is less likely to occur.

The brush charging member 13 (brush fiber 1)
1) is in contact with the image carrier 1 in a so-called counter direction. Hereinafter, the counter contact will be described in detail with reference to FIG. In order to facilitate understanding, the image carrier 1 is shown as a plane in FIG.

In this embodiment, as shown in FIG. 6A, the contact point between the brush charging member 13 and the image carrier 1 is P, and the tangent line of the image carrier 1 passing through the contact point P is L. ₁ ,
A line along the direction of the brush fiber (high resistance fiber) 11 near the fixing member 12 of the brush charging member 13 is denoted by L _2, and L ₁ and L are located downstream from the contact point P of the image carrier 1 in the direction of arrow A. ₂ is θ, the brush charging member 1 is set so that θ <90 ° (counter contact with the image carrier 1).
3 is arranged.

In the conventional contact-type brush charging device, the angle θ is θ ≧ 90 ° (contact with the image carrier 1 is in trailing contact).
Since the brush charging member 13 was arranged so that
Foreign matter (toner or paper dust passing through the cleaning blade) sent from the upstream side of the brush charging member 13 in the direction of arrow A of the image carrier 1 is formed by the brush charging member 13 and the image carrier 1. In the worst case, the toner is stuck to the fiber, and the contact between the brush charging member 13 and the image carrier 1 becomes non-uniform.

On the other hand, in the contact type brush charging device 2 in this embodiment, since the contact between the brush charging member 13 and the image carrier 1 is a counter contact, the contact between the tip of the brush charging member 13 and the image carrier 1 is performed. Foreign matter is hardly caught in the brush, and most of the foreign matter is repelled by the brush fibers 11, so that a stable charging potential without unevenness can be obtained for a long period of time.

When the angle θ is set to 10 ° ≦ θ ≦ 60 °, the fixing member 12 of the brush charging member 13 approaches the image carrier 1 to cause a leak, or a virtual line shown in FIG. As shown by, the brush fibers 11 do not reverse and the contact with the image carrier 1 does not come into trailing contact. Further, the amount of the brush fibers 11 biting into the image carrier 1 (see FIG. 6)
(a), assuming that the brush fibers 11 do not bend as shown by the imaginary line in FIG. When ≧ 0.5 mm, uneven charging and reversal of the brush fibers 11 can be reliably prevented.

Here, the reason why it is better to set 10 ° ≦ θ will be described in more detail. The fixing member 13 for fixing the brush fibers 11 always has a thickness equal to or greater than a certain width.
Is considerably close to the image carrier 1, so that not only the arrangement becomes difficult, but also leakage occurs between the image carrier 1 due to conductivity, and a stable charging potential cannot be obtained. However,
If the above-described problem does not occur even when the angle θ of the fixing member 12 is set to 10 ° or less, the fixing member 12 may be provided at an angle θ at which the problem does not occur. It should be noted that a maximum voltage of 3 KV is applied to the fixing member 12 of this embodiment.

Next, the reason why it is better to set θ ≦ 60 ° will be described in more detail. When the angle θ is larger than 60 °, the brush fibers 11 are inverted and the contact with the image carrier 1 is likely to be in trailing contact. However, this case also differs depending on the fiber material. For example, when the brush fiber 11 is formed using the above-mentioned carbon-containing acrylic fiber manufactured by Toray Industries, Inc., the carbon-containing acrylic fiber is soft, so that the length and bite amount of the brush fiber 11 are set to 10 mm and 1 mm, respectively. When the carrier 1 is driven at a linear velocity of 100 mm / s for 10 minutes, when the angle θ is 70 ° or more, almost half of the fibers are inverted, but when the angle θ is 60 °, such inversion is unlikely to occur.

Next, the reason why it is preferable to set m ≧ 0.5 mm will be briefly described in more detail. If the amount m of the brush fibers 11 that bite into the image carrier 1 is small, the contact length (area) between the brush fibers 11 and the image carrier 1 is small, so that charging unevenness is likely to occur, or the brush fibers 11 carry the image. It is caught and inverted by the frictional force with the body 1 and comes into trailing contact, so that foreign matter is easily trapped.

In view of the brush forming accuracy of the brush fibers 11 and the component accuracy in arrangement, the minimum value of the depth m for preventing inversion is limited to 0.5 mm. Brush fiber 1
When the biting amount m of 1 is 0.2 to 0.3 mm, the biting amount m may actually be a small value such as 0 to 0.2 due to variation. Problems may arise. In addition, as shown in FIG. 7, by stacking the brush charging members 13 in two stages or in three or more stages, it is possible to more reliably prevent charging unevenness.

FIG. 8 is a block diagram schematically showing a control system of the image forming apparatus.
An image forming process including a microcomputer including an AM, an I / O, etc., and inputting respective signals from an operation panel 32 and sensors / switches 33 to include a contact-type brush charging device 2 shown in FIG. The device 34 and sequence devices 35 such as a motor, a solenoid, and a fixing heater are controlled.

FIG. 9 is a flowchart showing a process according to the present invention by the control unit 31 of FIG. This routine starts when an image forming request is made, performs a predetermined image forming process as described above, and after the process is completed, moves the image carrier 1 in the direction opposite to the process direction (the direction indicated by arrow A). It rotates (reverse rotation), and after a lapse of a predetermined time, stops the rotation.

That is, as shown in FIG. 1, the contact point between the cleaning blade 6a and the image carrier 1 arranged upstream of the brush charging member 13 in the process direction of the image carrier 1 is denoted by Q, and the brush charging member 13 And the image carrier 1
When the point of contact with R is R, Q on the surface of the image carrier 1
The image carrier 1 is reversed for a predetermined time so that the amount of movement of the surface when the image carrier 1 is rotated in the reverse direction becomes larger than the length between R.

After the predetermined image forming process is completed, the image carrier 1 is rotated in the direction opposite to the process direction, so that the brush charging member 13 and the image carrier 1 are rotated.
As a result, the tip of the brush charging member 13 may be caught by a foreign matter, which can be removed after the above process, and a more stable charging potential can be obtained. it can. Further, since the reverse rotation is performed for a predetermined time, the foreign matter removed from the tip of the brush charging member 13 can be collected by the cleaning blade 6a, and the re-adhesion to the tip of the brush charging member 13 is eliminated.

After the image carrier 1 is rotated in the reverse direction and foreign matter passes under the cleaning blade 6a, the image carrier 1 is rotated forward to remove the foreign matter from the cleaning blade 6a.
As a result, the cleaning blade 6a can be brought into contact with the counter in the same manner as the brush charging member 13.

[0043]

As it has been described above, according to the present invention, the field of the present invention
According to the image forming apparatus, since the brush charging member is disposed so that the contact between the brush charging member and the image carrier becomes a counter contact, foreign matter is caught between the tip of the brush charging member and the image carrier. It is difficult to make the configuration complicated and large .

After the predetermined process is completed, the image carrier is rotated in a direction opposite to the process direction, so that the contact between the brush charging member and the image carrier comes into trailing contact, and the tip of the brush charging member causes foreign matter. even if such biting and Ru can remove it after completion of the predetermined process. Further
At the upstream of the brush charging member in the process direction of the image carrier.
Place a cleaning blade on the side and clean it
The contact point between the blade and the image carrier is Q,
When the contact point between the most upstream side and the image carrier is R,
Move the image carrier in the opposite direction from the length between the QRs on the surface of the body
Increased the amount of movement of the surface when rotated to
Therefore, foreign matter removed from the tip of the brush charging member is cleaned.
The brush can be reliably collected by the
Re-adhesion to the tip of the charging member is eliminated. Therefore, the first
Obtain stable charge potential without unevenness both periodically and over time
be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing the periphery of an image carrier of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a relationship between a brush charging member of the contact type brush charging device and an image carrier.

FIG. 3 is an explanatory diagram for explaining a method of manufacturing a brush charging member.

FIG. 4 is an explanatory diagram for explaining the operation of the brush charging member.

FIG. 5 is another explanatory diagram for explaining the operation of the brush charging member.

FIG. 6 is still another explanatory diagram for explaining the operation of the brush charging member.

FIG. 7 is a diagram showing an example in which brush charging members are similarly stacked in two stages.

FIG. 8 is a block diagram illustrating a control system of the image forming apparatus of FIG. 1;

FIG. 9 is a flowchart showing processing according to the present invention by the control unit.

FIG. 10 is a diagram showing a relationship between a brush charging member and an image carrier of a conventional contact brush charging device.

[Explanation of symbols]

 1: Image carrier 2: Contact brush charging device 4: Developing device 6: Cleaning unit 6a: Cleaning blade 11: High resistance fiber (brush fiber) 12: Fixed member 13: Brush charging member 14: DC power supply 31: Control unit 34: Image forming process device 35: Sequence device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/02

Claims (3)

(57) [Claims] 1. A method in which a large number of high resistance fibers are fixed to a fixing member.
The brush charging member formed in the shape of a brush
Contacting the image carrier rotating in the opposite direction, and the brush charging member thereof
Contact to apply voltage to the surface of the image carrier
Brush chargerImage forming apparatus provided withThe contact point between the brush charging member and the image carrier is denoted by P.
The tangent line of the image carrier passing through the corresponding contact point P is L1,
The high-resistance fiber near the fixing member of the brush charging member
A line along the direction is defined as L2, and the contact point P of the image carrier is referred to as L2.
Angle between L1 and L2 on the downstream side in the process direction.
, The brush band so that θ <90 °.
Arrange electrical componentsAlong with After completion of the predetermined process, the image carrier is
A means for rotating in the opposite direction to the direction is provided, The brush charging member in the process direction of the image carrier
Arrange the cleaning blade on the more upstream side, The contact point between the cleaning blade and the image carrier is determined.
Q, the most upstream side of the brush charging member and the image carrier
When the contact point is R, QR on the surface of the image carrier
When the image carrier is rotated in the opposite direction from the length between
So that the amount of movement of the surface is large Characterized by
Image forming device. 2. The image forming apparatus according to claim 1, wherein the angle θ satisfies 10 ° ≦ θ ≦ 60 °. 3. A have your <br/> the image forming apparatus according to claim 1 or 2, wherein the image forming apparatus is characterized in that the front end of the high resistance fibers formed in a loop shape.