JP3311440B2 - Transfer belt 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 transfer belt device used in an image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art Conventionally, a transfer belt device used in an image forming apparatus such as a copying machine or a printer rotates a transfer belt 1 around a driving roller 2 and a driven roller 3 as shown in FIG. The application roller 4 is brought into contact with the transfer belt 1 to supply a current from the power supply 5 to the transfer belt 1 via the application roller 4. Then, the drive roller 2 is grounded, and the transfer belt 1 is neutralized by irradiating light near the driven roller 3 with an eraser (see Japanese Patent Application Laid-Open No. 3-167579).

In this transfer belt device, the transfer paper 6 sent from the paper feeding unit is polarized by the charge applied from the application roller 4 via the transfer belt 1 to be polarized and the true charge on the transfer belt 1 is reduced. Static electricity is generated by the polarization charge of the transfer paper 6, and the transfer paper 6 is attracted to the transfer belt 1 by the static electricity. The transfer paper 6 is conveyed by the transfer belt 1 after the toner image is transferred from the photoreceptor 7, and is separated at the drive roller 2 by the curvature separation of the transfer paper 6 by the waist of the transfer paper 6.
Move away from

Further, in the transfer belt device, a configuration in which the driven roller 3 is grounded without grounding the driving roller 2 has been conventionally considered.

[0005]

In the transfer belt apparatus shown in FIG. 5, the drive roller 2 uses a rubber roller for preventing slip, and the rubber thereof uses conductive rubber. However, when a rubber roller using a conductive rubber is used as the driving roller 2, the cost becomes very high. Further, when a current is supplied to the transfer belt 1 via the application roller 4, the driven roller 3 has substantially the same potential as the application roller 4, so that the pre-transfer is performed before the nip portion between the photosensitive member 7 and the transfer belt 1. Then, dust and the like are transferred onto the transfer paper 6 to generate an abnormal image.

In a transfer belt device in which the driven roller 3 is grounded, the driven roller 3 is usually close to the transfer position, so that an excessive current flows through the driven roller 3 and the load on the power supply 5 increases. In addition, since the driven roller 3 uses a ball bearing or the like in consideration of the rotational load, the conduction is likely to be incomplete, and the charge removal of the transfer belt 1 is likely to be incomplete.

An object of the present invention is to provide a transfer belt device which can improve the above-mentioned drawbacks, reduce costs, prevent pre-transfer, and prevent an increase in power supply load, and can reliably remove charges from the transfer belt. Aim.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a transfer belt which is supported by a driving roller and a driven roller, rotates and has a predetermined resistance, and a transfer belt including the transfer belt. Charge providing means for providing a charge to the
A transfer member configured to clean a surface of the transfer belt; a toner image on an image carrier is transferred to a transfer material on the transfer belt and transferred by the transfer belt; In a transfer belt device that electrostatically sucks and conveys a material, the static elimination member is disposed upstream of the driven roller and downstream of the cleaning member with respect to a rotation direction of the transfer belt, and a peripheral length of the transfer belt is provided. Is L, the static elimination member is installed at a position of L / 2 or less upstream from the charge applying position of the charge applying means on the transfer belt with respect to the rotation direction of the transfer belt, and the driven roller is electrically conductive. electrically configured to float in sexual member, a length in a direction orthogonal to the rotation direction of the transfer belt l _1, before the portion in contact with the transfer belt of the driven roller The length of the orthogonal direction to l _2, when the length in the perpendicular direction of the portion in contact with the transfer belt of the neutralizing member was l _3, is obtained by constituting the _{l 1> l 2> l 3} .

According to a second aspect of the present invention, there is provided a transfer belt having a predetermined resistance value for transferring a toner image on an image carrier onto a transfer material, which is stretched over a driving roller and a driven roller. By making the difference between the current supplied to the transfer belt and the current fed back from the transfer belt via a transfer current feedback member constant, and making the current flowing from the transfer belt to the image carrier constant. In a transfer belt device configured to stably transfer a toner image, a member that contacts the back surface of the transfer belt at two or more locations is provided as the transfer current feedback member, and the driven roller is electrically connected to a conductive member. configured to float on, l ₁ the length in the direction perpendicular to the rotational direction of the transfer _belt, before the portion in contact with the transfer belt of the driven roller The length of the orthogonal direction to l _2, when the length in the perpendicular direction of the portion in contact with the transfer belt of the neutralizing member was l _3, is obtained by constituting the _{l 1> l 2> l 3} .

According to a third aspect of the present invention, there is provided a transfer belt which is supported by a driving roller and a driven roller, rotates and has a predetermined resistance, a charge applying means for applying a charge to the transfer belt, and the transfer belt. A transfer belt device for transferring a toner image on an image carrier to a transfer material on the transfer belt, and electrostatically attracting and transferring the transfer material by the transfer belt. Potential V of driven roller
Is set to | V | ≦ 1.5 [KV], the driven roller is electrically floated by a conductive member, and the length in a direction orthogonal to the rotation direction of the transfer belt is l ₁ . When the length of the portion in contact with the transfer belt in the orthogonal direction is l ₂ , and the length of the portion of the charge removing member in contact with the transfer belt in the orthogonal direction is l ₃ , l ₁ > l
_2> are those that you have configured _{l 3.}

[0011]

According to the first aspect of the present invention, the charge removing member removes charge from the transfer belt upstream of the driven roller and downstream of the cleaning member in the rotation direction of the transfer belt. When the circumferential length of the transfer belt is L, the charge removing member removes the charge from the transfer belt at a position L / 2 or less upstream from the charge application position of the transfer belt by the charge application means in the rotation direction of the transfer belt. The length in the direction orthogonal to the rotation direction of the transfer belt is l ₁ , the length in the orthogonal direction of a portion of the driven roller in contact with the transfer belt is l ₂ , and the length of the portion of the charge removing member in contact with the transfer belt in the orthogonal direction. when the length was _{l 3, l} 1> _l
Has a _2> l _3, the driven roller is electrically floating.

According to the second aspect of the present invention, the transfer current feedback member contacts the back surface of the transfer belt at two or more locations, and the current is fed back from the transfer belt via the transfer current feedback member. The length in the direction orthogonal to the rotation direction of the transfer belt is l ₁ , the length in the orthogonal direction of a portion of the driven roller in contact with the transfer belt is l ₂ , and the length of the portion of the charge removing member in contact with the transfer belt in the orthogonal direction. when the length was _{l 3,} has a _{l 1> l 2> l 3} , the driven roller is electrically floating.

According to the third aspect of the invention, the potential V of the driven roller satisfies | V | ≦ 1.5 [KV]. The length in the direction orthogonal to the rotation direction of the transfer belt is l ₁ , the length in the orthogonal direction of a portion of the driven roller in contact with the transfer belt is l ₂ , and the length of the portion of the charge removing member in contact with the transfer belt in the orthogonal direction. when the length was _{l 3,} it has a _{l 1> l 2> l 3} ,
The driven roller is in an electrically floating state.

[0014]

FIG. 1 shows a first embodiment of the present invention. This first
The embodiment is used as a transfer device of an image forming apparatus. In an image forming apparatus, an image carrier 18 composed of a drum-shaped photoreceptor is uniformly charged by a charging device and then subjected to image exposure by an exposure device to form an electrostatic latent image. After the latent image is developed by the developing device to become a toner image and the surface potential is reduced by light irradiation of the pre-transfer static elimination lamp, the toner image is transferred to the transfer paper by the transfer belt device of the first embodiment and is cleaned by the cleaning device. Is done.

In the first embodiment, the transfer belt 11
It is wrapped around the drive roller 12 and the driven roller 13, and is supported by these with an appropriate tension to be rotated and driven, and is brought into contact with the photosensitive member 18. An application roller 14 for applying a transfer bias to the transfer belt 11 contacts the back surface of the transfer belt 11 and rotates with the rotation of the transfer belt 11. The static elimination member 21 is made of sheet metal, and the transfer belt 11
It is installed near the upstream side of the driven roller 13 with respect to the rotation direction.

The power supply 17 is provided with a power supply 14 from the power supply.
And a current I supplied from the power supply to the transfer belt 11 through the application roller 14 by the current control unit.
₁ and, by the difference by comparing a current I ₂ which is fed back through the discharging member 21 (I ₁ -I ₂₎ to control the output power to be constant value K from the transfer belt 11,
With the current flowing from the transfer belt 11 to the photoreceptor 18 being a constant value, the transfer of the toner image is always performed under stable transfer conditions.

A cleaning member 22 composed of a cleaning blade comes into contact with the transfer belt 11 upstream of the transfer paper separating position with respect to the rotation direction of the transfer belt 11 to scrape off unnecessary toner on the transfer belt 11 and to scrape the toner. The dropped toner is collected in a toner collection tank (not shown). The drive roller 12 is made of EPBM so as not to slip.
And the like, and the photosensitive member 1 is driven by a driving source (not shown).
8 at the same linear speed. The driven roller 13 is made of metal such as stainless steel and is in an electrically floating state.

Next, the operation of the first embodiment will be described.
The contact portion between the photosensitive member 18 and the transfer belt 11 has a width of 4 to 12
mm nip is formed. When transfer paper fed from a paper supply unit (not shown) at a timing synchronized with the toner image on the photoreceptor 18 enters the nip, the power supply device 17 is activated.
Then, a transfer bias is applied to the application roller 14 to apply a charge having a polarity opposite to that of the toner on the photoconductor 11 to the transfer belt 11, and the toner image on the photoconductor 11 is transferred to the transfer paper on the transfer belt 11.

In this example, the surface of the photoconductor 11 is charged to -800 V by a charging device, and an electrostatic latent image is formed by image exposure by an exposure device. After the surface potential is lowered by a pre-transfer static elimination lamp (not shown),
When the negative high voltage is applied to the application roller 14, the toner is transferred to the transfer paper on the transfer belt 11.

The transfer belt 11 electrostatically attracts and conveys the transfer paper fed from the paper feeding unit, and the transfer paper is separated at the position of the drive roller 12 by curvature separation due to the waist of the transfer paper. The transfer paper is discharged after the toner is fixed by the fixing device. The transfer belt 11 has a surface electric resistance of 1 × 10
⁹ to 1 × 10 ¹² Ω, and the electric resistance on the inner surface side is 1 × 10 ⁷
A medium resistance of ５5 × 10 ⁸ Ω is used.

Here, the power supply device 17 supplies the application roller 14
The current output to the transfer belt 11 via the I _1,
The power supply 17 from the transfer belt 11 via the charge removing member 21
A current feedback When _{I 2,} the power supply 17 is _{I 1} -
I ₂ = Iout: controlled by the current control means _{I 1} such that (Iout constant). As a result, by electrically setting the transfer belt 11 and all the members in contact with the transfer belt 11 to float, Iout becomes a current value flowing toward the photoconductor 18 due to the transfer of the toner. The charge removing member 21 is a transfer belt 11
The transfer belt 11 is formed in such a shape as to come into contact at two places with different rotation directions. It is hard to be.

FIG. 2 shows the dimensional relationship of the first embodiment. Since the transfer belt 11 is an elastic body, it is driven downstream of the transfer unit in the rotation direction. Photoreceptor 18 and transfer belt 11
Is in contact with the transfer section, but if the potential of the transfer belt 11 is high in front of the transfer section, a discharge occurs between the toner on the photoconductor 11 and the transfer belt 11 before transfer, resulting in an abnormal image. Occurs. Therefore, it is necessary to lower the potential of the transfer belt 11 before the transfer.

In the first embodiment, in order to lower the potential of the transfer belt 11 before the transfer by bringing the charge removing member 21 as close to the transfer position as possible, the charge removing member 21 is moved upstream of the driven roller 13 with respect to the rotation direction of the transfer belt 11. It is installed near the side. Therefore, when the circumferential length of the transfer belt 11 is L,
Let the distance x between the application roller 14 and the charge removing member 21 be x ≦ L
/ 2.

In this embodiment, when the potential of the driven roller 13 is lowered, the abnormal image is dramatically improved. FIG.
Indicates the potential of the driven roller 13 and an abnormal image (called a print).
The relationship with the rank of is shown. As can be seen from FIG. 3, when the potential of the driven roller 13 is set to −1.5 KV or less (the power supply device 1).
When the transfer bias is applied to the application roller 14 from the roller 7 and the transfer bias is set to +1.5 KV or less when the transfer bias is positive), the rank of the abnormal image may be lowered. Is achieved near the upstream side of the driven roller 13 with respect to the rotation direction of the driven roller 13.

In the first embodiment, the toner adheres to the transfer belt 11 from the nip between the photosensitive member 18 and the transfer belt 11 to the cleaning position of the cleaning blade 22. Since the toner is disposed upstream of the driven roller 13 and downstream of the cleaning blade 22 with respect to the rotation direction, the toner on the transfer belt 11 is less likely to enter between the charge removing member 21 and the transfer belt 11. It is possible to prevent the transfer belt 11 from being insufficiently neutralized due to a change in the contact state with the toner due to the toner.

FIG. 4 shows a part of the second embodiment of the present invention.
In the second embodiment, the distance between the application roller 14 and the charge removing member 21 in the first embodiment is x as shown in FIG. Transfer belt 11 is l ₁ is the length in the direction perpendicular to the direction of rotation, the driven roller 13 is a transfer belt 1
The length of the portion in contact with the transfer belt 11 in the direction orthogonal to the rotation direction of the transfer belt 11 is l ₂ , and the charge removing member 21 is the portion of the portion in contact with the transfer belt 11 in the direction orthogonal to the rotation direction of the transfer belt 11. There is a _{l 3.} Length l of the driven roller 13
_The reason ₂ is shorter than the length l ₁ of the transfer belt 11 is to prevent the transfer belt 11 from shifting. The length l ₂ of length l ₃ of the discharging member 21 is a driven roller _13, a shorter of than the length l ₁ is the transfer belt 11 in order to reduce the cost.

The length l ₃ of the charge removing member 21 is adjusted by the driven roller 13.
In order to make the length l ₂ shorter than the length l ₁ of the transfer belt 11, a condition that the driven roller 13 is made of a conductive member and is electrically floated is required. In this case, the condition is satisfied, and the driven roller 13 is made of aluminum. The reason why this condition is necessary is that if the driven roller 13 is made of, for example, an insulator, a current flows from the application roller 14 to the charge removing member 21. (The potential between the application roller 14 and the driven roller 13) is not uniform due to unevenness in the longitudinal direction.

[0028]

As described above, according to the first aspect of the present invention, a transfer belt which is supported by a driving roller and a driven roller and rotates and has a predetermined resistance, and applies a charge to the transfer belt. A transfer unit configured to transfer a toner image on the image carrier to a transfer material on the transfer belt, the charge transfer unit including: a charge applying unit; a charge removing member for removing charge from the transfer belt; and a cleaning member for cleaning a surface of the transfer belt. In the transfer belt device that electrostatically sucks and conveys the transfer material by the transfer belt, the static elimination member is disposed upstream of the driven roller and downstream of the cleaning member with respect to the rotation direction of the transfer belt. The toner hardly enters between the transfer belt and the charge removing member, and the charge removal of the transfer belt can be reliably performed. When the circumferential length of the transfer belt is L, the charge removing member is moved to a position L / 2 or less upstream from the charge applying position of the transfer belt by the charge applying unit with respect to the rotation direction of the transfer belt. Since this is installed, the potential of the transfer belt before transfer can be reduced, and occurrence of an abnormal image due to discharge before transfer can be prevented. In addition, since the driven roller is not used as a charge removing member, it is possible to prevent an increase in the load on the power supply, and it is possible to reliably remove charge from the transfer belt. Further, the driven roller is electrically floated by a conductive member, and a length in a direction perpendicular to a rotation direction of the transfer belt is l ₁ , and a length of the driven roller in contact with the transfer belt is perpendicular to the length of the driven roller. Assuming that the length in the direction is l ₂ and the length in the orthogonal direction of a portion of the charge removing member that contacts the transfer belt is l ₃ , l ₁ > l ₂
> Since it is configured to l _3, without discharging member is potential of the transfer portion of the shorter and the transfer belt in the perpendicular direction becomes non-uniform, it is possible to reduce the cost.

According to the second aspect of the present invention, there is provided a transfer belt having a predetermined resistance value for transferring a toner image on an image carrier onto a transfer material, which is stretched over a driving roller and a driven roller. The difference between the current supplied to the transfer belt and the current fed back from the transfer belt via the transfer current feedback member is kept constant to keep the current flowing from the transfer belt to the image carrier constant. Thus, in the transfer belt device configured to stably transfer the toner image, the transfer current feedback member includes a member that comes into contact with the back surface side of the transfer belt at two or more locations. A rubber roller that does not use rubber can be used, and the cost can be reduced. Further, the driven roller is electrically floated by a conductive member, and a length in a direction orthogonal to a rotation direction of the transfer belt is l ₁ , and a length of the driven roller in contact with the transfer belt is orthogonal. Assuming that the length in the direction is l ₂ and the length in the orthogonal direction of a portion of the charge removing member that contacts the transfer belt is l ₃ , l ₁ > l ₂ >
since it is configured to l _3, the potential of the transfer portion of the short even if the transfer belt charge eliminating member in the orthogonal direction without nonuniform, the cost can be reduced.

According to the third aspect of the present invention, a transfer belt which is supported and rotated by a driving roller and a driven roller and has a predetermined resistance, a charge applying means for applying a charge to the transfer belt, A transfer belt device for transferring a toner image on an image carrier to a transfer material on the transfer belt, and electrostatically attracting and transferring the transfer material by the transfer belt. Since the potential V of the driven roller is set to | V | ≦ 1.5 [KV], occurrence of an abnormal image due to discharge before transfer can be prevented. Also,
The driven roller is electrically floated by a conductive member, and the length of the driven roller in a direction orthogonal to the rotation direction is l ₁ , and a portion of the driven roller in contact with the transfer belt in the orthogonal direction. The length is l ₂ , and the length of the portion of the charge removing member in contact with the transfer belt in the orthogonal direction is l _3.
In this case, since l ₁ > l ₂ > l ₃ , the potential of the transfer portion of the transfer belt does not become uneven even if the charge removing member is short in the orthogonal direction, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a dimensional relationship of the first embodiment.

FIG. 3 is a characteristic diagram showing a relationship between a driven roller potential and a print according to the first embodiment.

FIG. 4 is a schematic view showing a part of a second embodiment of the present invention.

FIG. 5 is a schematic view showing a conventional transfer belt device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 transfer belt 12 drive roller 13 driven roller 14 applying roller 17 power supply device 21 static elimination member 22 cleaning member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Kagita 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. No. 3 in Tohoku Ricoh Co., Ltd. (56) References JP-A-3-231274 (JP, A) JP-A-4-184378 (JP, A) JP-A 1-154075 (JP, A) JP Hei 5-113725 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16

Claims (3)

(57) [Claims] The invention is supported by a driving roller and a driven roller.
Transfer belt with predetermined resistance
Charge transfer means for providing charge to the transfer belt, and the transfer belt
Cleaning the surface of the transfer belt with the charge removing member for charge removal
And a cleaning member for cleaning the toner on the image carrier.
Transferring an image to a transfer material on the transfer belt,
Transfer belt device that electrostatically sucks and transports the transfer material
In which the charge removing member is rotated in the rotation direction of the transfer belt.
The cleaning section upstream of the driven roller with respect to
It was installed downstream of the material, and the circumference of the transfer belt was L.
When the discharging member is moved with respect to the rotation direction of the transfer belt.
The charge applying position of the transfer belt by the charge applying means.
Installed at a position of L / 2 or less upstream from the
Roller is electrically floated with conductive members, and
The length in the direction perpendicular to the rotation direction of the transfer belt is l ₁ ,
The portion of the driven roller that contacts the transfer belt is
The length in the orthogonal direction is l ₂ , and the transfer belt of the charge removing member is
And the length in the perpendicular direction of the portion in contact with the l ₃ and
_Can, transfer, characterized by being configured to _{l 1>} l _2> l ₃
Belt device. 2. A driving roller and a driven roller.
Also, for transferring the toner image on the image carrier onto the transfer material,
A transfer belt having a predetermined resistance value;
Current supplied to the transfer belt and the transfer current filter from the transfer belt.
Current fed back through the feedback member
From the transfer belt to the image carrier
The transfer of the toner image is stabilized by keeping the flowing current constant.
In the transfer belt device, the transfer
Back side of the transfer belt as a current feedback member
The driven roller, comprising a member that contacts at two or more places on the side
Is electrically floated by a conductive member,
The length in the direction orthogonal to the rotation direction of the copying belt is l ₁ ,
The orthogonality of the portion of the driven roller that contacts the transfer belt
The length in the direction of l ₂ is in contact with the transfer belt of the discharging member.
When the length in the perpendicular direction of the portion of touch was l _3, l
Transfer belt, characterized by being configured to _{1> l} 2> _{l 3}
apparatus. 3. A roller supported by a driving roller and a driven roller.
Transfer belt with predetermined resistance
Charge transfer means for providing charge to the transfer belt, and the transfer belt
A charge removing member for removing charge, and a toner image on the image carrier is moved forward.
The image is transferred to the transfer material on the transfer belt and is transferred by the transfer belt.
A transfer belt device that electrostatically suctions and transfers the transfer material
And the potential V of the driven roller is | V | ≦ 1.5 [K
V], and the driven roller is electrically flowed by a conductive member.
The transfer belt is configured to be perpendicular to the rotation direction of the transfer belt.
The length of the transfer belt of the driven roller is l ₁
The length in the perpendicular direction of the portion which contacts l _2, wherein the neutralizing and
The portion of the member that contacts the transfer belt in the orthogonal direction
When the length was _{l 3,} this constituted a _{l 1>} l _2> l ₃
And a transfer belt device.