JP2004059203A - Image forming device, and belt type carrying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device, and a belt type carrying device, with improved follow-up performance of a tension roller to a belt. <P>SOLUTION: For increasing a friction coefficient of the tension roller 14b to an electrostatic carrying belt 11, a roller surface of the tension roller 14b is burnish-finished to have a mirror-finished surface of Rz2μm or less without having cutting marks. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile, and the like, and a belt transport device including a transport belt.
[0002]
[Prior art]
2. Description of the Related Art Some image forming apparatuses such as a printer, a copying machine, and a facsimile are provided with a belt conveyance device that drives a belt such as a photosensitive belt, a transfer belt, an intermediate transfer belt, and a transfer conveyance belt.
[0003]
For example, in a tandem-type color transfer device, a belt transfer device for driving a transfer transfer belt is provided. The tandem type color transport device is disclosed, for example, in Japanese Patent Application Laid-Open No. 09-288396.
[0004]
In such a belt conveyance device, a transfer conveyance belt, a driving roller for driving the transfer conveyance belt, a driven roller driven by the transfer conveyance belt, and a predetermined tension are applied to the transfer conveyance belt so that the transfer conveyance belt does not slack. A tension roller and the like are provided.
[0005]
In addition, it is important to drive the electrostatic transport belt without deviation or meandering in order to superimpose the toner images of each color. Therefore, as means for eliminating deviation and meandering, there is a device in which regulating flanges for preventing deviation are provided at both ends of the driven roller.
[0006]
Then, a tension roller is disposed upstream of the driven roller provided with the deviation restricting means so that the performance of the restricting flange can be easily obtained, that is, so that the belt can easily move right and left, and further, a winding angle around the tension roller is provided. Is set small.
[0007]
Note that the winding angle is an angle (angle of the arc with respect to the center of the tension roller) corresponding to an arc of a region (contact region) where the belt is wound around the tension roller.
[0008]
As described above, by setting the winding angle of the tension roller to be small, the ability of restricting the deviation is improved, but when the winding angle is small, the phenomenon that the tension roller does not follow the endless belt at the initial stage of the belt rotation may occur. .
[0009]
This occurs because the frictional force generated between the belt and the tension roller is not sufficient with respect to the inertia of the tension roller and the load due to the static friction of the bearing of the tension roller at the beginning of the belt rotation.
[0010]
If the non-following phenomenon is repeated due to the repetition of the start, a sliding scratch with the tension roller occurs in the belt circumferential direction on the back surface of the belt. When the winding angle is further reduced, the non-driven phenomenon occurs intermittently even at the beginning of the belt activation, and abrasion occurs.
[0011]
Further, the rotational torque of the sliding bearing portion of the tension roller increases due to durability. As a result, after the endurance, the non-driven phenomenon of the tension roller occurs irrespective of the belt winding angle, and abrasion may occur.
[0012]
If the back surface of the belt continues to be rubbed with the tension roller, the belt is shaved and uneven thickness of the belt appears on the image as uneven transfer.
[0013]
Further, as the belt backside scraping phenomenon progresses, the belt becomes wavy or wrinkled. The wrinkles form uneven rubbing on the photosensitive drum, and appear as a vertical pattern on the image as uneven development.
[0014]
[Problems to be solved by the invention]
As described above, in the related art, various adverse effects occur due to the tension roller not following the belt.
[0015]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and a belt conveying apparatus in which the followability of a tension roller to a belt is improved.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, the winding angle of the belt with respect to the tension roller for applying tension to the belt is set to 60 degrees or less, and the friction coefficient between the tension roller and the belt is increased. did.
[0017]
Here, the winding angle is an angle (an angle of an arc with respect to the center of the tension roller) corresponding to an arc of a region (contact region) where the belt is wound around the tension roller.
[0018]
In this way, by setting the winding angle of the belt around the tension roller to 60 degrees or less, the belt can easily slide left and right (axial direction of the roller) with respect to the tension roller, and the friction coefficient between the tension roller and the belt can be increased. As a result, the followability of the tension roller is improved.
[0019]
The present invention is characterized in that the friction coefficient between the tension roller and the belt is increased so that the surface roughness of the tension roller is set to Rz 2 μm or less.
[0020]
Here, the surface roughness Rz means a ten-point average roughness according to JIS B0601.
[0021]
Another aspect of the present invention is characterized in that the surface of the tension roller is made of an elastic material so as to increase the friction coefficient between the tension roller and the belt.
[0022]
Further, in the above invention, it is preferable that the belt is produced by pressure bonding with an outer mold and an inner mold whose surface is mirror-finished.
[0023]
Thereby, the surface condition of the belt inner surface is improved, and the friction coefficient between the tension roller and the belt is further increased.
[0024]
As the belt constituting the present invention, a belt-shaped transfer member for transferring a toner image formed on an image carrier can be suitably applied.
[0025]
Here, the belt-shaped transfer body is an intermediate transfer body for temporarily holding the toner image and transporting it to a sheet or the like, and a transfer for transporting the sheet to a transfer unit to transfer the toner image onto the sheet. It shall include any of the conveyor belts.
[0026]
As described above, by applying the present invention to the belt-shaped transfer member, the followability of the tension roller to the belt-shaped transfer member is improved, and the deterioration of the quality of the belt-shaped transfer member can be suppressed. Therefore, it contributes to the improvement of image quality.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless otherwise specified. Absent.
[0028]
In the following description, an image forming apparatus including a device for driving an electrostatic transport belt as a belt-shaped transfer member will be described as a belt transport device. Therefore, by describing the embodiment of the image forming apparatus of the present invention, the embodiment of the belt conveying apparatus of the present invention will be described at the same time.
[0029]
An image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
[0030]
2. Description of the Related Art In recent years, with the spread of an electrophotographic color image forming apparatus, in addition to a demand for a print quality of a color image, a demand for a high-speed color output has been increased. In order to meet this demand, several proposals have been made for an image forming system, and among them, there is a so-called tandem type. That is, images of Bk (black) toner, C (cyan) toner, M (magenta) toner and Y (yellow) are formed on each drum-shaped image carrier, and are transferred onto a transfer material conveyed by an electrostatic conveyance belt. On the other hand, this is a color image forming system in which transfer is sequentially performed by respective transfer units and finally fixed on a transfer material.
[0031]
FIG. 1 is a side sectional view showing an example of a tandem type color image forming apparatus.
[0032]
In this color image forming apparatus, a transfer unit 5 is mounted on a lower portion of a right side surface of a main body device. The sheet S as a transfer material set in the transfer unit 5 is taken out one by one by a paper feed roller 18 and fed to an image forming unit by a feed roller (roll pair) 19.
[0033]
In the image forming section, an electrostatic transport belt 11 for transporting the transfer material is stretched flat in the paper transport direction by a plurality of rotating rollers, and at the most upstream portion thereof, the upper surface side (outer surface side) of the electrostatic transport belt 11 ) Is provided with a suction roller 22. By applying a bias to the attraction roller 22, the transfer material is electrostatically attracted to the electrostatic transport belt 11.
[0034]
Further, four drum-shaped image carriers (hereinafter, referred to as photosensitive drums) 1a to 1d are arranged linearly in opposition to the belt conveying surface to constitute an image forming unit. Chargers 4a to 4d and developing units 7a to 7d are arranged on each of the photosensitive drums 1a to 1d so as to sequentially surround the peripheral surface thereof. Further, transfer members 12a to 12d are disposed at positions sandwiching the transport surface of the electrostatic transport belt 11 with respect to each of the photosensitive drums 1a to 1d.
[0035]
Bk (black) toner, M (magenta) toner, Y (yellow) toner, and C (cyan) toner are accommodated in the housing of each of the above-described developing units from the downstream side (upper side in the figure).
[0036]
A predetermined gap is provided between the charging device and the developing device, and exposure and irradiation are performed on the peripheral surfaces of the photosensitive drums 1a to 1d from the scanner units 3a to 3d as exposure means through the gap.
[0037]
In this color image forming apparatus, the electrostatic transport belt 11 circulates clockwise in the drawing to transport the transfer material. On the other hand, each charger uniformly charges the peripheral surface of the corresponding photosensitive drum with a predetermined charge, and the scanner units 3a to 3d image the uniformly charged peripheral surfaces of the photosensitive drums 1a to 1d. Exposure is performed according to information to form an electrostatic latent image. Then, the developing device transfers the toner to the low potential portion of the electrostatic latent image to form a toner image (development).
[0038]
The toner images formed (developed) on the peripheral surfaces of the respective photosensitive drums are attracted to the charges generated on the transferred transfer material by the transfer electric field formed by the corresponding transfer members, and are transferred to the transfer material surface. Transcribed. The transfer material onto which the toner image has been transferred is discharged outside the machine by a discharge roller pair 23 after the toner image is thermally fixed on the surface of the transfer material by a fixing unit 20 including a pressure roller and a heat roller.
[0039]
Here, the image forming apparatus in the present embodiment shown in FIG. 1 is more specifically a color laser beam printer employing an electrophotographic image forming process. Hereinafter, the sheet conveying system will be described in more detail.
[0040]
The sheets S stacked on the feed cassette 17 are separated one by one by a feed roller (pickup roller) 18 and sent out to a feed roller 19. The sheet S sent to the feed roller 19 is fed to the electrostatic transfer belt 11 as a belt-shaped transfer member. Note that the electrostatic transport belt 11 can also be called a recording material transport unit, a transfer belt, or an endless belt.
[0041]
On the other hand, scanner units 3a, 3b provided with rotating polygon mirrors 9a, 9b, 9c, 9d and reflecting mirrors 10a, 10b, 10c, 10d for photosensitive drums 1a, 1b, 1c, 1d uniformly charged. , 3c, and 3d, light corresponding to the image information is exposed, and a latent image is formed on each photosensitive drum surface.
[0042]
Each of the latent images is developed by developing units 7a, 7b, 7c, and 7d for applying yellow, magenta, cyan, and black toners, respectively, and is converted into a visible image. Then, this visible image is transferred onto the sheet S conveyed by the electrostatic conveyance belt 11.
[0043]
The electrostatic transport belt 11 can be composed of a film-like member having a volume resistivity of, for example, 10 ¹² Ω · cm or less and having a thickness of about 110 μm. The electrostatic transport belt 11 is wound around a downstream drive roller 13, an upstream driven roller 14a, 15 and a tension roller 14b, which constitute a belt suspension member, and transports the sheet (arrow X). Direction). The volume resistivity is a value obtained by applying a voltage of 100 V with a high resistance meter R8340 manufactured by ADVANTEST using a measurement probe conforming to JIS method K6911.
[0044]
Each of these rollers is rotatably held at both ends between bearings (not shown) and is disposed substantially in parallel.
[0045]
The driving roller 13 is formed of a metal roller having a rubber layer having a large friction coefficient on its surface, and has a diameter of 30 mm. The driving roller 13 is driven to rotate at a predetermined speed in a sheet conveying direction by a driving source. The driven roller 14a has a function of restricting a problem such as a deviation or meandering that has occurred on the electrostatic transport belt 11.
[0046]
When the drive roller 13 is driven to rotate in the direction of transporting the sheet by the drive source, the driving force is transmitted to the electrostatic transport belt 11 by the frictional force between the outer peripheral surface of the drive roller 13 and the inner peripheral surface of the electrostatic transport belt 11. Is done. Then, the electrostatic transport belt 11 is driven to rotate between the four members of the drive roller 13, the driven rollers 14a and 15 and the tension roller 14b in the direction of transporting the sheet.
[0047]
The sheet S to which the toner image has been transferred is peeled off from the photosensitive drum 1d by the separation charger, and is conveyed to the pair of fixing rollers 21a and 21b. On the other hand, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is scraped off by a cleaning device provided in contact with the photosensitive drums 1a to 1d to prepare for the next image formation. The sheet S conveyed to the fixing roller pair 21 is fixed with the toner image by the fixing roller pair 21, and is discharged outside the image forming apparatus by the discharge roller pair 23.
[0048]
Next, the transfer unit which is a feature of the present embodiment will be described in detail.
[0049]
In the present embodiment, the tension roller 14b has a mechanism for controlling the circumference of the electrostatic transport belt 11. More specifically, the winding angle of the electrostatic transport belt is 60 degrees or less so that the electrostatic transport belt 11 is always urged in the direction in which the electrostatic transport belt 11 is stretched by a spring, and the deviation of the electrostatic transport belt 11 is easily controlled. , Preferably about 40 degrees.
[0050]
In the present embodiment, the tension roller 14b is disposed upstream of the driven roller 14a in the transport direction. As for the mechanism for controlling the circumference, the tension roller 14b is held by an arm-type holding member 30a, and the tension roller 14b is rotationally moved about a rotation shaft provided on the arm-type holding member 30a, and is a biasing means. The electrostatic torsion belt 11 is urged by the torsion coil spring 30b.
[0051]
Here, as the torsion coil spring 30b, a spring having a low spring constant is adopted, and the center of rotation of the arm-type holding member 30a is arranged near the belt surface. Instead, substantially the same spring force acts.
[0052]
In order to increase the friction coefficient between the tension roller 14b having such a mechanism and the electrostatic transport belt 11, in the present embodiment, the roller surface of the tension roller 14b is subjected to burnishing, so that Rz 2 μm or less having no cutting edge is formed. Mirror surface. Here, the surface roughness Rz means a ten-point average roughness according to JIS B0601.
[0053]
The burnishing is a processing method in which a roller is moved while being pressed against the surface of a workpiece to generate plastic deformation on the surface, thereby obtaining a smooth and highly accurate surface. This processing method is used when finishing to a roughness of about Rz 0.2 to 3.2, and is excellent in cost performance among means for processing to a similar roughness. When the roller length is about several hundreds of millimeters, it was used in the present embodiment because a single work has several seconds and mass productivity.
[0054]
Thereby, the friction coefficient between the tension roller and the electrostatic transport belt becomes 0.36.
[0055]
In addition, since the purpose is to increase the friction coefficient between the tension roller and the electrostatic transport belt, the roller surface is coated with rubber, and the surface of the tension roller is made of an elastic material, or is coated with resin, so that the friction coefficient is increased. Can also be increased.
[0056]
In this embodiment, since the roller needs to be dropped to the ground, it is more cost-effective to increase the friction coefficient while keeping the metal roller.
[0057]
Further, as a means for improving the followability of the tension roller with respect to the electrostatic transport belt, there is a method of managing the surface property of the back surface of the belt with which the roller comes into contact. This technique will be described.
[0058]
The forming of the electrostatic transport belt is performed using inner and outer dies having different coefficients of thermal expansion. First, a sheet-like belt material is sandwiched between an inner mold and an outer mold, and heat is applied to the mold, whereby the inner mold having a high coefficient of thermal expansion approaches the outer mold, and the belt is pressed and formed. Therefore, irregularities on the surface of the inner mold that forms the inside of the endless belt are transferred to the back surface of the belt.
[0059]
Therefore, it is possible to increase the friction coefficient between the tension roller and the back surface of the belt by making the inner die surface a mirror surface state.
[0060]
As a means for improving the followability of the tension roller with respect to the electrostatic transport belt, there is a method in which the tension roller bearing has a mechanical configuration with low sliding resistance.
[0061]
In this embodiment, the sliding resistance is kept low before and after the endurance by inserting conductive ball bearings at both ends of the bearing portion.
[0062]
As another inexpensive means for reducing the sliding resistance, there is a method of applying grease to the sliding portion. In this embodiment, a ball bearing that is stable over time was used because it is a portion where toner scattering is possible.
[0063]
With the above-described configuration, it is possible to reduce slippage in the electrostatic transport belt (endless belt) and the tension roller having a constant tension mechanism.
[0064]
As a result, damage to the electrostatic transport belt can be minimized, and the unit life can be extended. Also, by reducing belt wear and belt wrinkles, it has become possible to provide high-quality images throughout life.
[0065]
【The invention's effect】
As described above, according to the present invention, the followability of the tension roller to the belt is improved.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an image forming apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1a, 1b, 1c, 1d Photoconductor drums 3a, 3b, 3c, 3d Scanner units 4a, 4b, 4c, 4d Charger 5 Transfer units 7a, 7b, 7c, 7d Developing devices 9a, 9b, 9c, 9d Rotating polygon mirror 10a, 10b, 10c, 10d Reflecting mirror 11 Electrostatic transport belt 12a Transfer member 13 Drive roller 14a Follower roller 14b Tension roller 15 Follower roller 17 Feed cassette 18 Feed roller 19 Feed roller 20 Fixing sections 21a, 21b Fixing roller pair 22 Suction roller 23 Discharge roller pair 23 Discharge roller pair 30a Arm type holding member 30b Coil spring

Claims (6)

A belt-shaped transfer member for transferring the toner image formed on the image carrier,
A driving roller for driving the belt-shaped transfer member,
A tension roller for applying tension to the belt-shaped transfer body, and an image forming apparatus comprising:
While setting the winding angle of the belt-shaped transfer body around the tension roller to 60 degrees or less,
An image forming apparatus, wherein the surface roughness of the tension roller is set to Rz 2 μm or less. A belt-shaped transfer member for transferring the toner image formed on the image carrier,
A driving roller for driving the belt-shaped transfer member,
A tension roller for applying tension to the belt-shaped transfer body, and an image forming apparatus comprising:
While setting the winding angle of the belt-shaped transfer body around the tension roller to 60 degrees or less,
An image forming apparatus, wherein the surface of the tension roller is made of an elastic material. 3. The image forming apparatus according to claim 1, wherein the belt-shaped transfer body is manufactured by pressure bonding using an outer mold and an inner mold having a mirror-finished surface. 4. A conveyor belt,
A driving roller for driving the transport belt,
A tension roller that applies tension to the transport belt, and a belt transport device including:
While setting the winding angle of the transport belt around the tension roller to 60 degrees or less,
A belt conveying device, wherein the surface roughness of the tension roller is set to Rz 2 μm or less. A conveyor belt,
A driving roller for driving the transport belt,
A tension roller that applies tension to the transport belt, and a belt transport device including:
While setting the winding angle of the transport belt around the tension roller to 60 degrees or less,
A belt conveying device, wherein the surface of the tension roller is formed of an elastic body. The belt conveying device according to claim 4, wherein the conveyor belt is manufactured by pressure bonding using an outer die and an inner die whose surface is mirror-finished.

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