JP3530720B2 - Transfer belt and image forming apparatus - 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 used in an electrophotographic image forming apparatus and an image forming apparatus equipped with the transfer belt.

[0002]

2. Description of the Related Art Image forming apparatuses include various methods such as an electrophotographic method, a thermal transfer method, and an inkjet method.
Among these, the electrophotographic image forming apparatus is
It is superior to other methods in terms of high image quality and high quietness, and has become popular in recent years.

There are various types of electrophotographic image forming apparatuses. For example, a multi-developing type in which a color image is superposed on the surface of an image carrier and then collectively transferred to form an image, and a development and transfer type are used. Multiple transfer method that repeats the cycle of
There is an intermediate transfer method in which a developed image (toner image) of each color is sequentially transferred onto an intermediate transfer body and then transferred collectively onto a transfer material. Among them, the intermediate transfer method is attracting attention because it does not cause color mixture and can be applied to various media.

FIG. 8 is a schematic block diagram showing an example of a conventional intermediate transfer type image forming apparatus. In the figure, a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum)
On the peripheral surface of 1, along the rotation direction (direction of arrow a),
A charging device 2, a laser exposure optical system 3 for irradiating the rotary drum 1 with the laser light L, a developing device 5, an intermediate transfer belt 6, a photosensitive drum cleaner 16 and a charge eliminating exposure device 17 are arranged.

The yellow developing device 5a, the cyan developing device 5b, the magenta developing device 5c, and the black developing device 5d mounted on the rotating body 5A of the developing device 5 are rotated in the direction of arrow b by a drive mechanism (not shown). It is configured to selectively abut the photosensitive drum 1.

The intermediate transfer belt 6 is wound around a drive roller 8, a counter roller 9 and a tension roller 10 and stretched, and rotates in the direction of arrow c. At the primary transfer portion where the intermediate transfer belt 6 contacts the photosensitive drum 1, a primary transfer roller 11 is arranged with the intermediate transfer belt 6 interposed, and a bias power source 12 is connected to the primary transfer roller 11. There is. A secondary transfer roller 7 is arranged on the counter roller 9 with the intermediate transfer belt 6 interposed therebetween to form a secondary transfer portion. A bias power supply 13 is connected to the secondary transfer roller 7.

An intermediate transfer belt cleaner 14 for removing secondary transfer residual toner from the intermediate transfer belt 6 and a charge eliminator 15 are arranged on the outer peripheral surface of the intermediate transfer belt 6 between the opposing roller 9 and the tension roller 10. There is.

In the image forming apparatus thus constructed, the photosensitive drum 1 is uniformly charged by the charger 2, and the laser light L is emitted from the laser exposure optical system 3 to form an electrostatic latent image. Then, the electrostatic latent image formed on the photosensitive drum 1 is developed for each color by the yellow developing device 5a, the cyan developing device 5b, the magenta developing device 5c, and the black developing device 5d of the developing device 5, and the intermediate image is sequentially printed. Primary transfer is performed on the transfer belt 6, and a four-color superimposed color image is formed.

Then, the secondary transfer roller 7 comes into contact with the intermediate transfer belt 6 via the transfer material P which is a recording medium, and the color images are secondarily transferred onto the transfer material P all together.

The above-mentioned primary transfer step and secondary transfer step will be described in more detail.

(Primary Transfer Step) When the photosensitive drum 1 is a negative polarity OPC photosensitive member, a negative polarity toner is used for developing the electrostatic latent image. Therefore, the transfer bias applied to the primary transfer roller 11 by the bias power supply 12 has a positive polarity.

The intermediate transfer belt 6 usually has a thickness of 100.
~ 200 μm, volume resistivity 1e11 to 1e16 Ωcm
A resin film adjusted to some extent (for example, PVdF, nylon, PET, polycarbonate) is used. In this way, by using a thin film as the intermediate transfer belt 6, the electrostatic capacitance at the primary transfer portion is increased (equation 10).
Since 0 to several thousand pF), a stable transfer current can be obtained.

As the primary transfer roller 11, it is general to use a roller having a volume resistivity of 1e5 Ωcm or less at the transfer portion.

(Secondary Transfer Step) In the secondary transfer section, the counter roller 9 serving as a counter electrode is grounded, and a positive transfer bias is applied to the secondary transfer roller 7 by the bias power source 13. Then, in this state, the transfer material P is passed through the secondary transfer portion to perform the secondary transfer. Note that an appropriate bias may be applied instead of grounding the opposing roller 9.

After the secondary transfer step is completed, the toner (secondary transfer residual toner) remaining on the surface of the intermediate transfer belt 6 after the secondary transfer is removed by the intermediate transfer belt cleaner 14. Further, after that, the intermediate transfer belt 6 is removed from the static eliminator 15
To eliminate static electricity. As the static eliminator 15, AC corona charging is often used. Further, in order to improve the static elimination efficiency, an electrode 18 is generally provided at a position facing the static eliminator 15 via the intermediate transfer belt 6. Note that the toner remaining on the photosensitive drum 1 (primary transfer residual toner) even after the completion of the primary transfer process is collected by the photosensitive drum cleaner 16, and the photosensitive drum 1 is initialized by the static eliminator and exposed to the next stage. Prepare for image forming operation.

By the way, as the intermediate transfer belt 6, there is a belt using a rubber belt having a core in addition to the above-mentioned resin film. The rubber belt is mainly used when high durability is required. As shown in FIG. 9, the intermediate transfer belt 6 formed of a rubber belt includes
A rib 20 is provided on the back surface, and the rib 20 is used to drive the driving roller 8,
There is also one in which the meandering of the intermediate transfer belt 6 is prevented by fitting the tension roller 10 in a groove 8a provided at an end portion (end portion of the driving roller 8 in the figure).

[0017]

By the way, in the case of using the conventional intermediate transfer belt 6 composed of the rubber belt having the ribs 20 on the back surface as described above, as shown in FIG.
During the image forming operation, the intermediate transfer belt 6 may have a difference in parallelism between the driving roller 8 and the tension roller 10, a variation in the diameter of the driving roller 8 in the longitudinal direction, or the like.
A large force is applied in the longitudinal direction of the drive roller 8.

Further, the conventional intermediate transfer belt 6 has a hardness in order to stabilize the contact nip with the photosensitive drum 1, the transfer material P and the like, to prevent the occurrence of the dropout in the transfer, and to prevent the sliding with the drive roller 8. The rubber is small and has a large coefficient of dynamic friction.

Therefore, the rib 20 of the intermediate transfer belt 6
Of the transfer roller 8 is pressed against the side surface 8b of the groove 8a of the drive roller 8 by the force acting in the longitudinal direction of the drive roller 8 to be worn by rubbing, and the rib 20 is disengaged from the groove 8a to remove the wheel. This causes inconvenience such as inoperability.

Therefore, an object of the present invention is to provide an intermediate transfer belt having ribs, which can prevent the ribs from coming off, and an image forming apparatus provided with the transfer belt.

[0021]

The invention according to claim 1 is
Endless belt for transferring the toner image on the image carrier
And the belt has a belt flat portion and ribs,
The belt is stretched around a plurality of rollers and the ribs are regulated.
In the belt where the meandering is prevented by
The belt flat portion has a core body that covers the entire circumference of the belt flat portion.
And a portion forming the rib of the belt flat portion
Is characterized in that the core does not exist.

The invention according to claim 2 is a toner on an image carrier.
-An endless belt for transferring an image,
The belt has a flat surface portion and ribs, and the belt has a plurality of
By being stretched around the roller and the rib being regulated
In a belt in which meandering is prevented, the belt flat portion
Has a core that extends over the entire circumference of the belt flat portion, and
The denseness of the core body in the portion of the flat surface forming the rib.
The degree is characterized by being smaller than the other parts.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the belt according to, the flat surface portion of the belt is a rubber layer.
And the rib is made of a rubber material,
The hardness of the rubber forming the ribs is greater than the hardness of the rubber layer.
Is also large.

The invention according to claim 4 is an image carrier,
Multiple rollers for transferring the toner image on the image carrier
And an endless belt stretched around the
It has a belt flat portion and a rib, and the rib is restricted.
Image formation that prevents the belt from meandering due to
In the device, the belt flat portion is the belt flat portion.
Having a core over the entire circumference, the rib of the belt flat portion
The core is not present in the formed part
And

The invention according to claim 5 is an image carrier,
Multiple rollers for transferring the toner image on the image carrier
And an endless belt stretched around the
It has a belt flat portion and a rib, and the rib is restricted.
Image formation that prevents the belt from meandering due to
In the device, the belt flat portion is the belt flat portion.
Having a core over the entire circumference, the rib of the belt flat portion
The density of the core body of the forming part is higher than that of other parts.
Characterized by being small. The invention according to claim 6 is a claim
The image forming apparatus according to Item 4 or 5, wherein the bell
The flat surface has a rubber layer, and the rib is made of rubber material.
The hardness of the rubber forming the ribs is
It is characterized in that it is larger than the hardness of the rubber layer.

[0026]

[0027]

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic configuration diagram showing an image forming apparatus (a laser beam printer in a full color mode in this embodiment) using a transfer belt according to the present invention as an intermediate transfer belt. Is. It should be noted that members having the same functions as those of the conventional image forming apparatus shown in FIG. 8 are designated by the same reference numerals, and overlapping description will be omitted.

The image forming apparatus of the present embodiment is the same as the conventional example except for the structure of the intermediate transfer belt 6. In the present embodiment, the image forming operation is performed in the same manner as the above-mentioned conventional image forming apparatus. Done. In this embodiment, the description of the image forming operation is omitted.

As shown in FIGS. 1 and 2, one end of the intermediate transfer belt 6 on the back side of the belt flat portion 21 is provided at the end of the drive roller 8 and the tension roller 10 as described above. A rib 20 that fits in the groove 8a (see FIG. 9) is formed.

In the present embodiment, the hardness of the rubber forming the rib 20 (JIS-A) is made higher than the hardness of the rubber forming the belt flat portion 21 (JIS-A). Specifically, in this embodiment, the rib 20 has a hardness (JIS
-A) 75 degree epichlorodrine rubber or NBR rubber is used, and the flat surface portion 21 of the belt has hardness (JIS-A).
A 65-degree epiclodrine rubber or NBR rubber was used.

As described above, the rib 20 provided on the back side of the belt flat portion 21 of the intermediate transfer belt 6 is attached to the belt flat portion 21.
As shown in FIG. 10, even if the rib 20 is pressed against the side surface 8b of the groove 8a of the drive roller 8 by using a rubber having a hardness higher than that of the drive roller 8, abrasion of the rib 20 is reduced and the rib 20 is removed from the groove 8a. Since it is possible to prevent the looping, it is possible to stabilize the contact nip with the photosensitive drum 1, the transfer material P, and the like, and to prevent the occurrence of voids in the transfer.

(Second Embodiment) In the present embodiment,
As shown in FIG. 3, the core body 22 is put in the substantially central portion in the thickness direction along the entire circumference of the belt flat surface portion 21 of the intermediate transfer belt 6 used in the first embodiment. However, the core 22 is not included in the side end portion 21a of the belt flat portion 21 where the rib 20 is provided. Further, similarly to the above, the hardness of the rubber forming the rib 20 is made larger than the hardness of the rubber forming the belt flat surface portion 21. The structure of the image forming apparatus including the intermediate transfer belt 6 is the same as that of the first embodiment. As the core body 22, for example, a plain woven cloth or a thread wound in a spiral shape can be used.

By inserting the core 22 into the belt flat portion 21 of the intermediate transfer belt 6, it is possible to reduce the stress relaxation of the intermediate transfer belt 6 due to the endurance of use, but as shown in FIG. When the core body 22 is inserted along the entire circumference of the belt 21 from the central portion in the thickness direction to the front surface side (or the back surface side), warpage occurs on the side end portion side of the flat belt portion 21 where the rib 20 is provided. When this warp occurs, the rib 20 locally contacts the side surface 8b of the groove 8a of the drive roller 8, and the rubbing force received by the rib 20 is concentrated and increased. Therefore, the rubber hardness of the rib 20 is increased. However, the rib 20 is worn.

By the way, the above-mentioned warp on the side end portion of the flat belt portion 21 occurs in the heating step during manufacturing. That is, when the belt flat portion 21 containing the core 22 is heated, both the rubber forming the belt flat portion 21 and the core 22 contract. However, the rubber has a larger contracting force. Therefore, as shown in FIG.
The front surface portion 21b is warped to the front surface side (the upper side in the figure) of the belt flat portion 21, and the back surface portion 21c is bent to the rear surface side (the lower side of the figure) of the belt flat portion 21 from the core 22. To do.

Then, the belt flat portion 21 as a whole warps from the core body 22 toward the thicker side. In the intermediate transfer belt 6 shown in FIG. 5, the thickness d of the surface portion 21 b is larger than that of the core body 22.
The relationship between 1 and the thickness d2 of the back surface portion 21c of the core body 22 is d1 <d2. Therefore, as shown in FIG. 6, the side end portion side of the intermediate transfer belt 6 is warped to the back surface side provided with the rib 20. In addition, the entire circumference of the belt flat portion 21 (rib 20
If the core body 22 is inserted in the central portion in the thickness direction along the side end portion side where the core body 22 is provided, warpage does not occur, but the core body 22 is always kept in the belt flat surface portion due to variations in processing accuracy during manufacturing. It is difficult to insert 21 in the central portion in the thickness direction.

Therefore, in the present embodiment, as shown in FIG. 3, the side end portion 2 of the belt flat portion 21 provided with the rib 20 is provided.
Since the core body 22 is not put in 1a, the belt flat surface portion 21
It is possible to suppress the occurrence of warp at the side end portion of the. Therefore, as shown in FIG. 4, the rib 20 is prevented from locally contacting the side surface 8b of the groove 8a of the drive roller 8,
Since it is possible to reduce wear of the ribs 20 and prevent derailment from the groove 8a, it is possible to stabilize the contact nip with the photosensitive drum 1, the transfer material P and the like, and to prevent the occurrence of a void in the transfer. You can

The reduction of stress relaxation by the core 22 is
It was equivalent to the case where the core body 22 was inserted to the side end portion of the belt flat portion 21.

Further, the warp of the side end portion of the belt flat surface portion 21 is such that, when the core body 22 is inserted to the side end portion of the belt flat surface portion 21, the density of the core body 22 put in this side end portion (used) Thread thickness or number of threads existing per unit area)
Can be reduced by making it smaller than the portion other than the side end portions of the belt flat portion 21. Also in this case, the same effect as described above can be obtained.

(Third Embodiment) In this embodiment, an intermediate transfer belt as shown in FIG. 7 is used as an intermediate transfer belt of an image forming apparatus having the same configuration as that of the first embodiment shown in FIG. The transfer belt 6 was used. Other configurations are similar to those of the first embodiment.

In the intermediate transfer belt 6 according to this embodiment, the dynamic friction coefficient of the rubber forming the rib 20 is calculated as follows.
It is smaller than the dynamic friction coefficient of the rubber constituting No. 1.
Specifically, in the present embodiment, the ribs 20 are made of epichlorodrin rubber or NBR rubber having a dynamic friction coefficient of 1.0, and the belt flat portion 21 is made of epiclodrin rubber or NBR rubber of a dynamic friction coefficient of 2.0. Rubber was used.

To measure the dynamic friction coefficient between the rib 20 and the belt flat portion 21 of the intermediate transfer belt 6, H of Shinto Kagaku Co., Ltd. was used.
EIDON-14DR was used. For more information, HEIDO
A PET sheet is wrapped around the ASTM indenter of N-14DR to make a measurement object, and a rubber sample sheet and AS are used.
A vertical load of 200 gf was applied between the TM plane indenters, and the dynamic friction coefficient of the PET sheet and the rubber sample sheet was measured when the sample sheet was moved in the horizontal direction at a speed of 100 mm / min.

As described above, by using rubber having a dynamic friction coefficient smaller than that of the flat portion 21 on the belt surface, the rib 20 is formed on the side surface 8b of the groove 8a of the drive roller 8 as shown in FIG. Even when it is pressed, it is possible to reduce the abrasion of the rib 20 and prevent it from being detached from the groove 8a. Therefore, the contact nip between the photosensitive drum 1 and the transfer material P, etc. is stabilized, and the dropout of transfer occurs. It is possible to prevent the occurrence of slippage, and to suppress the slippage with the driving roller 8 to obtain stable rotation of the intermediate transfer belt 6.

In each of the above-described embodiments, the present invention is applied to the intermediate transfer belt of the image forming apparatus. However, the present invention is not limited to the intermediate transfer belt, and a normal transfer belt, Is applicable to all belts.

[0046]

As described above, according to the present invention, the hardness of the rubber forming the rib is made larger than the hardness of the rubber layer of the belt flat surface portion, or the dynamic friction coefficient of the rubber forming the rib is set to the belt flat surface. By making it smaller than the dynamic friction coefficient of the rubber layer of the portion, even if the rib is pressed against the side surface of the groove of the roller, it is possible to reduce the abrasion of the rib and prevent the wheel from slipping out of the groove. Transfer is possible, and a good image can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus including an intermediate transfer belt according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing an intermediate transfer belt according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing an intermediate transfer belt according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a warped state of the intermediate transfer belt.

FIG. 5 is a diagram for explaining the occurrence of warp of the intermediate transfer belt.

FIG. 6 is a diagram showing a warped state of the intermediate transfer belt.

FIG. 7 is a perspective view showing an intermediate transfer belt according to a third embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing an image forming apparatus including a conventional intermediate transfer belt.

FIG. 9 is a view showing a state in which a rib of a conventional intermediate transfer belt is fitted in a groove of a drive roller.

FIG. 10 is a diagram showing a state in which a rib of a conventional intermediate transfer belt is in contact with a side surface of a groove of a drive roller.

[Explanation of symbols]

1 Photosensitive drum (image carrier) 2 charger 5 Development device 6 Intermediate transfer belt (transfer belt) 7 Secondary transfer roller 8 drive rollers 20 ribs 21 Belt flat part 22 core

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (6)

(57) [Claims] 1. For transferring the toner image on the image carrier
The belt is an endless belt, and the belt is
The belt is stretched over a plurality of rollers,
A bell that prevents meandering by regulating the ribs
In the The belt flat portion is a core that extends over the entire circumference of the belt flat portion.
And a portion forming the rib of the belt flat portion
The bell is characterized in that the core does not exist in the minute
To. 2. For transferring the toner image on the image carrier
The belt is an endless belt, and the belt is
The belt is stretched over a plurality of rollers,
A bell that prevents meandering by regulating the ribs
In the The belt flat portion is a core that extends over the entire circumference of the belt flat portion.
And a portion forming the rib of the belt flat portion
The density of the core body is smaller than that of other parts.
Belt to collect. 3. The belt flat portion has a rubber layer.
The rib is made of a rubber material.
The hardness of the constituent rubber must be greater than the hardness of the rubber layer.
The belt according to claim 1 or 2, characterized in that. 4. Image carrier and toner image on the image carrier
Endless, stretched over multiple rollers for transferring
A belt, the belt having a belt flat portion and ribs.
And the rib is regulated so that
In an image forming apparatus that prevents the belt from meandering, The belt flat portion is a core that extends over the entire circumference of the belt flat portion.
And a portion forming the rib of the belt flat portion
Image formation characterized in that the core does not exist in the
apparatus. 5. Image carrier and toner image on the image carrier
Endless, stretched over multiple rollers for transferring
A belt, the belt having a belt flat portion and ribs.
And the rib is regulated so that
In an image forming apparatus that prevents the belt from meandering, The belt flat portion is a core that extends over the entire circumference of the belt flat portion.
And a portion forming the rib of the belt flat portion
The density of the core body is smaller than that of other parts.
Image forming apparatus to be used. 6. The belt flat portion has a rubber layer.
The rib is made of a rubber material.
The hardness of the constituent rubber must be greater than the hardness of the rubber layer.
The image forming apparatus according to claim 4 or 5, characterized in that
Place