JP2008076499A - Transfer unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer unit in which high image quality is achieved by causing a dynamic absorption device, added as a subsidiary system, to dissipate vibration energy, thereby reducing a change in the tension of a roller and belt, which compose a main system, and hence image deterioration such as a stripe pattern or nonuniform color caused by shock jitter, and to provide an image forming apparatus. <P>SOLUTION: The tension roller 11 is disposed in contact with an intermediate transfer belt 10 such that using a spring or the like, fixed tension is applied to the intermediate transfer belt 10 in order to prevent an intermediate transfer belt 10 from slackening. By providing the tension roller 11 between the transfer roller 6 and the drive roller 5, as shown in FIG. 4, vibration caused by impact when paper 9 is brought into contact with the transfer roller 6 or ejected after conveyed is absorbed by the spring and the vibration is attenuated without being transmitted to the drive roller 5 directly as a result of a change in the tension of the intermediate transfer belt 10. In addition to that, the vibration of a specific frequency can also be absorbed by the dynamic absorption device 11a. Accordingly, the image quality can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transfer unit and an image forming apparatus, and more particularly to a vibration damping technique that absorbs vibration generated from each roller constituting the transfer unit.

  In recent years, documents processed in offices and the like have been rapidly colored, and image forming apparatuses such as copying machines, printers, and facsimiles that handle these documents have also been rapidly colored. Currently, these color devices tend to be improved in image quality and speeded up with the improvement and speed of office processing in offices and the like. As a color device that can meet such demands, for example, each color forming unit has black (K), yellow (Y), magenta (M), and cyan (C), and each image forming unit is formed. Various so-called tandem-type color image forming apparatuses that perform multiple transfer of images of different colors onto a transfer material or intermediate transfer member to be conveyed to form a color image have been proposed and commercialized.

  An example of this type of tandem color image forming apparatus is shown in FIG. As shown in FIG. 8, the tandem color image forming apparatus 100 includes a black image forming unit 1 that forms a black (K) image and a yellow image forming unit that forms a yellow (Y) image. There are four image forming units, Y2, a magenta image forming unit M3 that forms a magenta (M) image, and a cyan image forming unit C4 that forms a cyan (C) image. The four image forming units K, Y, M, and C are horizontally arranged with a certain distance from each other. An intermediate transfer belt 10 as an endless transfer material carrier is disposed below the four image forming units of black, yellow, magenta, and cyan. Each of the four image forming units includes a photoconductive drum. The surface of the photoconductive drum is uniformly charged, and then a laser beam for image formation is scanned and exposed in accordance with image information. A latent image is formed. The electrostatic latent image formed on the surface of the photosensitive drum is developed with each color toner of black, yellow, magenta, and cyan by a developer of each image forming unit, and becomes a visible toner image. The visible toner image is pre-transfer charged by the pre-transfer charger and then sequentially transferred onto the intermediate transfer belt. The intermediate transfer belt 10 onto which the toner images of the respective colors have been transferred is transferred to the paper 9 that is passed through at the position of the transfer roller 6 to form an image. In a color image forming apparatus including the transfer fixing unit 7, it is necessary to perform transfer fixing while bringing the recording paper 9 and the intermediate transfer belt 10 into contact with each other with a relatively high pressure. For this reason, when the recording paper 9 enters the transfer / fixing unit 7, a braking force is generated to stop the running of the belt 10 at the transfer / fixing unit 7 and the belt tension is rapidly increased. Tension decreases rapidly. As a result, shocking vibration is generated in the belt, and this vibration propagates through the belt 10 and is transmitted to the photoconductor that is in the process of image formation or primary transfer, causing local image degradation. Also, when the recording paper 9 is removed from the transfer and fixing unit 7, a vibration phenomenon occurs due to the release of the braking force, which similarly causes image deterioration. For this reason, “color misregistration” that causes misregistration between the colors of each other, “color unevenness” that slightly changes the hue, or a very ugly striped pattern occurs in the background color. There is a problem of causing shock jitter such as. As described above, it is important to suppress the vibration phenomenon of image forming belts such as an intermediate transfer belt and other photosensitive belts and paper conveying belts.

  In Patent Document 1, the belt is pressed against the image forming surface of the intermediate transfer belt by a tension roller from a portion other than the image formed on the surface of the intermediate transfer belt, and the belt is shocked by a spring provided in the translation direction of the tension roller. An image forming apparatus that absorbs vibration due to tension fluctuations and reduces image deterioration is disclosed.

In Patent Document 2, when a recording medium is fed into a transfer nip formed between a transfer backup roller and a transfer pinch roller in a transfer portion, a braking force is generated to stop the running of the belt photoreceptor. Then, the belt tension on the belt tension side suddenly increases, the belt tension on the belt slack side tries to decrease sharply, and when the belt tension on the belt tension side increases, the second tension roller is restrained from being displaced, and the belt When the belt tension on the slack side decreases, the position sensor detects the displacement of the first tension roller, and the speed servo control circuit increases the rotation speed of the transfer backup roller to suppress the decrease in belt tension. An image forming apparatus that reduces image deterioration due to belt tension variation by maintaining a roller in a fixed position is disclosed.
JP-A-2005-338884 JP-A-5-224572

However, the conventional technique disclosed in Patent Document 1 absorbs the vibration due to the shock tension fluctuation of the belt with the spring provided in the translation direction of the tension roller, but absorbs the vibration by the change in the tension of the spring. There is a problem that it cannot be done.
Further, the conventional technique disclosed in Patent Document 2 has a problem that the configuration becomes complicated because the rotational speed of the transfer backup roller is increased by the position sensor to control the belt tension.

  The present invention has been made in view of the above problems, and the dynamic vibration absorber added as a sub-system by using the dynamic vibration absorber for the roller in the transfer unit is a vibration energy. A transfer unit and an image forming apparatus that reduce the tension fluctuation of the main system rollers and belts and reduce image deterioration caused by uneven color and stripes called shock jitter, thereby improving image quality. The purpose is to provide.

In order to solve such a problem, the present invention provides an intermediate transfer belt in which a toner image of each color formed by an image forming unit for each color of black, yellow, magenta, and cyan is stretched by a plurality of rollers. The transfer unit that performs multiple transfer above includes a dynamic vibration absorber having an elastic body made of a spring and a damper and an inertial body made of a rigid body in order to absorb vibrations generated from the rollers. To do.
According to a second aspect of the present invention, the dynamic vibration absorber is provided on a transfer roller provided at a position where the toner image formed on the intermediate transfer belt is transferred to a transfer material.
According to a third aspect of the present invention, the dynamic vibration absorber is provided on a driving roller that transmits driving force to rotate the intermediate transfer belt.

According to a fourth aspect of the present invention, a tension roller for applying tension to the intermediate transfer belt is further provided between the transfer roller and the driving roller, and the dynamic vibration absorber is provided on the tension roller.
According to a fifth aspect of the present invention, the inertial body has a disk shape.
According to a sixth aspect of the present invention, the dynamic vibration absorber is provided at the center of each rotation shaft of the transfer roller, the driving roller, or the tension roller.
According to a seventh aspect of the present invention, the rigidity of the elastic body is variable.

According to an eighth aspect of the present invention, the frequency of the torsional vibration determined by the torsion spring constant k and the inertial body J of the elastic body is a frequency of vibration caused by impact generated during transfer onto paper or tension variation of the transfer belt It corresponds to.
According to a ninth aspect of the present invention, a plurality of the dynamic vibration absorbers are provided.
A tenth aspect includes the transfer unit according to any one of the first to ninth aspects.

  According to the present invention, in the transfer unit, in order to absorb the vibration generated from the rollers arranged around the intermediate transfer belt, the dynamic vibration absorber having an elastic body made of a spring and a damper and an inertial body made of a rigid body. Therefore, it is possible to improve the image quality by reducing fluctuations in the tension of the rollers and belts and reducing image deterioration caused by uneven color and stripes called shock jitter.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is a schematic view in which a dynamic vibration absorber made of an elastic body and an inertial body is provided on a roller. The dynamic vibration absorber 150 includes an elastic body 61 and an inertial body 60.
FIG. 2 is a diagram showing an outline of the structure of the dynamic vibration absorber. In FIG. 2, m1 is a main system 64, m2 is an additional system 63, and both are connected by a spring k2 and a damper c2. The dynamic vibration absorber 150 dissipates the vibration energy given to the main system 64 as the additional system 63 vibrates, and as a result, the vibration of the main system 64 is reduced. The main system 64 in the present invention is a transfer / tension / drive roller, and the additional system 63 is an inertia body 60 connected to an elastic body 61 serving as a spring and a damper.

  FIG. 3 is a diagram illustrating a state in which a vibration absorber is attached to the transfer roller and vibration is suppressed when paper enters. The same components will be described with the same reference numerals as in FIG. That is, it is necessary to perform transfer fixing while the recording paper 9 and the intermediate transfer belt 10 are in contact with each other at a relatively high pressure. When the recording paper 9 enters the transfer roller 6, the transfer roller 6 generates a braking force for stopping the running of the belt 10, the belt tension increases rapidly, and the belt tension on the belt slack side decreases rapidly. To do. As a result, shocking vibration is generated in the belt, and this vibration propagates through the belt 10 and is transmitted to the photoconductor that is in the process of image formation or primary transfer, causing local image degradation. Also, when the recording paper 9 is removed from the transfer roller 6, a vibration phenomenon occurs due to the release of the braking force, which similarly causes image degradation. Therefore, by connecting the elastic body 61 to the shaft of the transfer roller 6, vibration generated in the transfer roller 6 by the inertia of the inertia body 60 provided on the shaft can be dispersed. In addition to this, a dynamic vibration absorber 150 may be provided on the driving roller 5 that transmits driving force to rotate the intermediate transfer belt 10.

  FIG. 4 is a schematic view in which a tension roller for applying tension to the intermediate transfer belt is provided between the transfer roller and the drive roller. The tension roller 11 is in contact with the intermediate transfer belt 10 so as to give a certain tension with a spring or the like so as not to loosen the intermediate transfer belt 10. By providing the tension roller 11 between the transfer roller 6 and the drive roller 5 as shown in FIG. 4, vibration generated by an impact when the paper 9 is conveyed and contacts or is ejected to the transfer roller 6 is prevented. The vibration is not directly transmitted to the driving roller 5 due to the tension fluctuation of 10, and is not only the effect of absorbing the vibration by the spring, but also the vibration of the specific frequency can be reduced by the dynamic vibration absorber 11a, and the image quality can be improved. Become.

In addition, when the inertial body 60 of the dynamic vibration absorber 150 mounted to reduce rotational vibration in FIG. 1 has a distribution in the circumferential direction, the roller 62 causes eccentricity and causes fluctuation in the rotational speed of the roller 62. End up. Therefore, the inertial body 60 constituting the dynamic vibration absorber 150 has a disk shape and is attached to the center of the rotating shaft of the roller 62 to be attached, so that the dynamic vibration absorber 150 can be formed without eccentricity, which occurs as a side effect. It is possible to prevent speed fluctuation and vibration.
Further, since the rigidity of the elastic body 61 constituting the dynamic vibration absorber 150 is variable, even when the vibration frequency of the main roller 62 changes, the rigidity of the elastic body can be changed and optimized. is there. As a method of making the rigidity variable, the elastic body 61 can be changed and controlled by a method of controlling the torque in the rotational direction with current or voltage using a brake using electromagnetic force or the like.

  As an application example, FIG. 5 is a diagram showing a result of comparison of speed fluctuation when a paper enters a transfer roller rotating at a constant speed, when a dynamic vibration absorber is used and when it is not used. . The dotted line 66 in FIG. 5 is the result without the dynamic vibration absorber 150, and the solid line 65 is the result with the dynamic vibration absorber 150. When the dynamic vibration absorber 150 is not provided, the damping vibration of 80 Hz is shown with respect to the impact vibration caused by the entry of paper. However, when the dynamic vibration absorber 150 designed to reduce this frequency is attached, the vibration vibration absorber 150 is mounted in a short time. It can be seen that the vibration is attenuated and the amplitude is also reduced. Thus, the frequency of torsional vibration determined by the torsion spring constant k of the elastic body and the inertial body J coincides with the frequency of vibration caused by impact generated during transfer onto paper or tension variation of the transfer belt. By setting the dynamic vibration absorber in this way, it is possible to reduce vibrations, thereby efficiently reducing image degradation such as shock jitter and improving image quality.

  FIG. 6 is a schematic view of a transfer unit provided with a plurality of dynamic vibration absorbers. By using a dynamic vibration absorber for each roller as shown in FIG. 6, it is possible to reduce the vibration generated in each roller, and to reduce image degradation such as shock jitter by reducing the vibration. It is possible. In this embodiment, the transfer roller 6, the tension roller 11, and the driving roller 5 are provided with dynamic vibration absorbers 6a, 11a, and 5a, respectively.

FIG. 7 is an overall configuration diagram of an image forming apparatus provided with the dynamic vibration absorber of the present invention, and shows a tandem indirect transfer type color image forming apparatus. Reference numeral 100 is a copying machine main body, 200 is a paper feed table on which it is placed, 300 is a scanner mounted on the copying machine main body 100, and 400 is an automatic document feeder (ADF) further mounted thereon.
The copying machine main body 100 is provided with an endless belt-shaped intermediate transfer member 10 in the center. The intermediate transfer member 10 is wound around three support rollers (stretching rollers) 14, 15, and 16 so as to be able to rotate and convey clockwise in the drawing. In this illustrated example, an intermediate transfer body cleaning device 17 for removing residual toner remaining on the intermediate transfer body 10 after image transfer is provided on the left side of the second support roller 15 of the three support rollers. On the intermediate transfer member 10 stretched between the first support roller 14 and the second support roller 15 among the three support rollers, four of black, cyan, magenta, and yellow are arranged along the transport direction. The tandem image forming unit 20 is configured by arranging two image forming units 18 side by side.

  An exposure apparatus 21 is further provided immediately above the tandem image forming unit 20 as shown in FIG. On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer body 10 from the tandem image forming unit 20. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24, which is an endless belt, between two rollers 23, and is pressed against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to a recording sheet. Next to the secondary transfer device 22, a fixing device 25 for fixing the transfer image on the recording paper is provided. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. The secondary transfer device 22 described above also has a recording paper transport function for transporting the recording paper after image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be arranged as the secondary transfer device 22.

  In the illustrated example, a recording sheet that reverses the recording sheet so as to record an image on both sides of the recording sheet in parallel with the tandem image forming unit 20 described above under the secondary transfer device 22 and the fixing device 25 described above. A reversing device 28 is provided. The description of the operation is the same as that of a known color image forming apparatus, and is omitted here.

It is the schematic which provided the dynamic vibration damper which consists of an elastic body and an inertial body in the roller of this invention. It is a figure which shows the outline of the structure of a dynamic vibration absorber. It is a figure which shows a mode that a vibration damper is attached to a transfer roller, and a vibration is suppressed when paper enters. FIG. 3 is a schematic view in which a tension roller that applies tension to an intermediate transfer belt is provided between a transfer roller and a driving roller. It is a figure which shows the result of having compared the speed fluctuation | variation when a paper rushes into the transfer roller rotating at a fixed speed about the case where it does not use with the case where a dynamic vibration absorber is used. It is a schematic diagram of a transfer unit provided with a plurality of dynamic vibration absorbers. 1 is an overall configuration diagram of an image forming apparatus including a dynamic vibration absorber according to the present invention. It is a schematic block diagram of the conventional tandem type color image forming apparatus.

Explanation of symbols

  5 driving roller, 6 transfer roller, 8 driven roller, 9 paper, 10 intermediate transfer belt, 11 tension roller, 150 dynamic vibration absorber

Claims (10)

In a transfer unit that multiplex-transfers each color toner image formed by an image forming unit for each color of black, yellow, magenta, and cyan onto an intermediate transfer belt stretched by a plurality of rollers,
A transfer unit comprising a dynamic vibration absorber having an elastic body made of a spring and a damper and an inertial body made of a rigid body in order to absorb vibration generated from each roller.   The transfer unit according to claim 1, wherein the dynamic vibration absorber is provided on a transfer roller provided at a position where a toner image formed on the intermediate transfer belt is transferred to a transfer material.   The transfer unit according to claim 1, wherein the dynamic vibration absorber is provided on a driving roller that transmits driving to rotate the intermediate transfer belt.   The tension roller for applying tension to the intermediate transfer belt is further provided between the transfer roller and the driving roller, and the dynamic vibration absorber is provided on the tension roller. Transcription unit.   The transfer unit according to claim 1, wherein the inertial body has a disk shape.   The transfer unit according to any one of claims 1 to 5, wherein the dynamic vibration absorber is provided at the center of each rotation shaft of the transfer roller, the drive roller, or the tension roller.   The transfer unit according to claim 1, wherein rigidity of the elastic body is variable.   The frequency of torsional vibration determined by the torsion spring constant k of the elastic body and the inertial body J matches the frequency of vibration caused by impact generated at the time of transfer to paper or tension variation of the transfer belt. The transfer unit according to claim 7, wherein   The transfer unit according to claim 1, comprising a plurality of the dynamic vibration absorbers.   An image forming apparatus comprising the transfer unit according to claim 1.

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