JP2009265249A - Conveying belt mechanism and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conveying belt mechanism having reduced speed variation, and to provide an image forming apparatus using the same, the apparatus obtaining a high-quality image by suppressing belt speed variation at a transfer part. <P>SOLUTION: In the conveying belt mechanism including an endless belt member and a driving means for driving the belt member and including a member for applying load variation by abutting against the belt member, the conveying belt mechanism comprises a load applying member stabilizing the belt running speed by imparting load resistance to the belt member. The conveying belt mechanism is used as an intermediate transfer belt of the image forming apparatus. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transport belt mechanism and an image forming apparatus, and more particularly to a general transport belt mechanism that dislikes speed fluctuations, a general image forming apparatus, and an image forming apparatus using a constant speed belt (intermediate transfer belt) as an intermediate transfer member. Is.

A conveyor belt mechanism using an endless belt that circulates is widely used, and many of them are required to have a small speed fluctuation. In an image forming apparatus, an intermediate transfer belt carries and conveys a toner image, but is required to have a small speed fluctuation in order to guarantee the quality of the formed image. As such a conventional intermediate transfer type image forming apparatus, for example, a photosensitive drum on which a toner image corresponding to an electrostatic latent image is formed, and an intermediate transfer in which the toner image on the photosensitive drum is transferred intermediately. A belt, a primary transfer device for transferring a toner image on the photosensitive drum to the intermediate transfer belt, and a secondary transfer device for secondary transfer of the toner images transferred on the intermediate transfer belt to a sheet collectively. (For example, refer to Patent Document 1).
This intermediate transfer belt has a multilayer structure, and the base layer is made of, for example, a fluororesin, PVDF sheet, or polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin. The toner image formed on the image carrier is primarily transferred to the intermediate transfer belt and then secondarily transferred onto the recording medium to form a color image. After the secondary transfer, the toner image remaining on the intermediate transfer belt is cleaned by a cleaning device (belt cleaning means).
As the cleaning device, a method of physically scraping off toner with a cleaning blade, a method of electrostatically removing residual toner using a brush roller, and the like are known. Due to the recent demand for higher image quality, toner particles have become smaller and spherical with polymerized toner, and it has become increasingly difficult to clean the toner remaining on the belt.
In the polymerized toner in which the wax component is uniformly dispersed in the toner, the wax component hardly deposits outside when adhering to the intermediate transfer belt, and the friction coefficient μs on the surface of the intermediate transfer belt tends to increase with time. There is something. Therefore, it is necessary to apply a lubricant in order to prevent blade entrainment and surface filming.

As a method of applying the lubricant, a method of applying the lubricant by bringing the lubricant into pressure contact with the brush roller and rotating the brush roller in contact with the intermediate transfer belt is generally used. As a driving source of the brush roller, a system in which a gear or coupling is transmitted from the machine body or a gear or the like is transmitted from one of the rollers around which the intermediate transfer belt is wound is considered.
By the way, the cleaning blade and the brush roller in contact with the belt are likely to change in the belt speed by giving a load fluctuation to the belt, and the belt speed fluctuation may be manifested as banding.
In particular, when the brush roller obtains driving from one of the rollers around which the intermediate transfer belt is wound, the fluctuation of the speed of the brush roller is directly transmitted to the driving source roller to be transmitted to the belt, resulting in an abnormal image such as banding. Probability is high. In particular, in a system in which driving is transmitted via a gear, the frequency of one gear pitch of the gear is easily manifested as banding.
In order to cope with this, as a method for stabilizing the running speed of the belt, an encoder is installed on at least one of the rollers around which the belt is wound or on the belt itself, and the belt driving roller is controlled based on the signal. There is a device that controls the rotation so that the belt runs at a constant speed.
Japanese Patent Laid-Open No. 5-323704

The conveyor belt mechanism is required to have a small speed fluctuation. In particular, an intermediate transfer belt mechanism of an image forming apparatus is required to have high low speed fluctuation performance. However, as described above, in the case where the belt is driven at a constant speed by controlling the rotation of the belt driving roller based on the signal of the encoder installed on the belt, the high-frequency speed fluctuation that is manifested as banding is Encoder resolution is insufficient and sufficient control cannot be realized, and in the worst case, speed fluctuations may even be promoted.
In particular, in the case of an apparatus having a mechanism in which a photoconductor not used for image formation is separated from the transfer belt surface in order to improve the life of the photoconductor, the load resistance to the belt when the photoconductor is separated from the transfer belt. The banding is likely to deteriorate because of the decrease.
The present invention has been made in consideration of the above-described circumstances, and has a high-performance conveyance belt mechanism with little speed fluctuation and a belt speed fluctuation at the transfer portion is suppressed by using this, so that high image quality without banding can be obtained. An object of the present invention is to provide an image forming apparatus capable of obtaining a stable image.

In order to solve the above-mentioned problem, the conveying belt mechanism according to the present invention according to claim 1 drives an endless belt-like member stretched and supported by a plurality of rotatable rollers, and the belt-like member. A conveying belt mechanism having a driving means and a member that abuts against the belt-like member and gives a load fluctuation, and applies a load resistance to the belt-like member so as to stabilize a belt traveling speed. It has the member.
According to a second aspect of the present invention, there is provided an endless belt-like member stretched and supported by a plurality of rotatable rollers, a driving means for driving the belt-like member, and the belt-like member. In the image forming apparatus configured to include a conveyance belt mechanism having a load variation member, the conveyance belt mechanism stabilizes the belt traveling speed by applying a load resistance to the belt-shaped member. It is characterized by having.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the load applying member is a counter member that is biased toward the load applying member at a position where the belt-shaped member is inserted. It is characterized by having.
According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the belt-shaped member is an intermediate transfer belt. According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the member that gives the load fluctuation is a blade.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the second to fifth aspects, the member that gives the load fluctuation is a brush roller. According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the brush roller is a lubricant application brush. According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth or seventh aspect, the brush roller rotates using at least one of the support rollers around which the belt-shaped member is wound as a driving source. It is characterized by that.
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the fourth to eighth aspects, the load applying member is installed downstream of the member that applies the load fluctuation and upstream of the primary transfer unit. It is characterized by. A tenth aspect of the present invention is the image forming apparatus according to any one of the fourth to ninth aspects, wherein the load applying member is controlled to rotate at a constant speed with the belt-shaped member. And the rotational speed fluctuation is controlled to be 0.2% or less.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the fourth to tenth aspects of the present invention, the image forming apparatus includes a mechanism in which a non-imaged photosensitive member is separated from the intermediate transfer belt. The load applying member is in contact with the intermediate transfer belt and applies load resistance only when at least one photoconductor is separated from the belt. According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the driving force applied to the load applying member is transmitted from a driving mechanism of a photosensitive member.

According to the conveyor belt mechanism of the present invention, the belt running can be stabilized by attenuating the vibration generated by the member that gives load fluctuation to the belt by the member that gives load resistance to the belt.
The image forming apparatus according to claim 2 prevents the occurrence of banding and improves the image quality by attenuating the vibration generated by the member that applies load resistance to the belt and stabilizing the belt running by the member that applies load resistance to the belt. Is possible.
In the image forming apparatus according to the third aspect, the adhesion between the member that gives load resistance to the belt by the facing member and the belt increases, and the belt does not slip.
The image forming apparatus according to claim 4 is a case where the belt is an intermediate transfer belt, and a belt with high rigidity and small expansion / contraction is often used for reasons such as color misregistration, and vibration is difficult to attenuate, and the belt Therefore, the effect of the present invention is remarkably obtained.
In the image forming apparatus according to the fifth aspect, the member that gives load fluctuation is a blade, and the blade repeats stick-slip by contacting the belt, so that vibration is generated and the load is easily given to the belt. Load fluctuation can be reduced effectively.
In the image forming apparatus according to the sixth aspect, when the member that gives load fluctuation is a brush roller, the load transmitted to the belt differs depending on whether the brushed portion contacts the belt or the non-planted portion of the brush roller. Although it is easy to give a load fluctuation to the belt, the invention can effectively reduce the load fluctuation.

The image forming apparatus according to claim 7 is a case where the brush roller is a lubricant application brush, and the lubricant is in pressure contact with the brush roller. As a result, speed fluctuations are likely to occur in the brush roller. Therefore, the device of the present invention is more effective.
In the image forming apparatus according to claim 8, since the brush roller is driven from one of the rollers around which the belt is wound, the speed fluctuation of the brush roller is directly transmitted to the roller around which the belt is wound. The apparatus of the present invention is effective.
In the image forming apparatus according to the ninth aspect, the member that applies load resistance is disposed downstream of the member that applies load variation and upstream of the primary transfer portion, and this can suppress fluctuations in belt speed at the transfer portion. The member which gives load resistance exhibits a great effect.
11. The image forming apparatus according to claim 10, wherein a driving force is applied to a load applying member that applies load resistance to the belt to prevent an increase in belt driving torque, and in particular, a speed variation that does not reveal a speed variation of the load applying member in an image. By restraining to 0.2% or less, the load applying member itself is prevented from giving a speed fluctuation to the belt.
In the image forming apparatus according to the eleventh aspect, when the photosensitive members are separated from each other, the load resistance applied to the belt is smaller than when all the photosensitive members are in contact with each other. For this reason, the present apparatus works effectively to prevent belt speed fluctuations. Further, by using this apparatus only when the photosensitive members are separated from each other, an increase in power of the entire apparatus is prevented.
The image forming apparatus according to a twelfth aspect is configured so that the driving means of the driving member also serves as the photosensitive member driving, and it is not necessary to have a separate driving means for the load applying member, and the configuration is simple and low-cost. realizable.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram showing a schematic configuration of a tandem indirect transfer type electrophotographic image forming apparatus (color printer) according to an embodiment of the present invention in a cross-sectional view.
The image forming apparatus main body is provided with an endless belt-shaped intermediate transfer member 11 in the center. The intermediate transfer body 11 has a multilayer structure, and the base layer is made of, for example, a fluororesin, a PVDF sheet, or a polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin. As shown in FIG. 1, in the illustrated example, the intermediate transfer member 11 can be rotated and conveyed counterclockwise in the drawing by being wound around the support rollers 10, 12, 34, and 35 (34 is a drive roller). In this embodiment, an intermediate transfer body cleaning device 25 for removing residual toner remaining on the intermediate transfer body 11 after image transfer is provided on the left of the support roller 10. The intermediate transfer portion directly related to the present invention will be described in more detail later.
Further, on the intermediate transfer member 11 stretched between the support roller 12 and the support roller 35, four image forming units (a, b, c, d) of magenta, cyan, yellow, and black are arranged along the transport direction. ) Are arranged side by side to constitute a tandem image forming apparatus.

An exposure apparatus 4 is further provided below the tandem image forming apparatus as shown in FIG. On the other hand, a secondary transfer device is provided on the opposite side of the support roller 35 downstream of the primary transfer roller group 20 in the driving direction of the intermediate transfer body 11. In the illustrated example, the secondary transfer device is configured by spanning a secondary transfer belt 100, which is an endless belt, between two rollers 111 and 112, and is pressed against the support roller 35 via the intermediate transfer body 11. Then, the superimposed toner image on the intermediate transfer body 11 is batch-transferred onto the sheet conveyed by the secondary transfer belt 100.
A fixing device 30 for fixing the transferred image on the sheet is provided on the upper portion of the secondary transfer device. The fixing device 30 is configured by pressing a fixing pressure roller against the fixing roller. The secondary transfer device described above is also provided with a sheet transport function for transporting the image-transferred sheet to the fixing device 30. Of course, a transfer roller or a non-contact charger may be arranged as the secondary transfer device. However, in such a case, it is difficult to provide this sheet conveyance function together, so an appropriate conveyance means is separately provided.
A lower part of the printer is provided with a paper feeding unit. The paper feed unit includes a paper feed roller 27, a registration roller 28, a transport path 29, and the like that transport the recording medium from the paper feed cassettes 26-1 and 26-2 to the secondary transfer region.

Next, an outline of the image forming operation of the image forming apparatus will be described. When a start switch (not shown) is pressed, the support roller 34 is rotationally driven by a drive motor (not shown), the other three support rollers 10, 12, and 35 are driven to rotate, and the intermediate transfer member 11 is rotationally driven and conveyed. At the same time, the photosensitive member 1 is rotated by the individual image forming units a, b, c, and d, and the surface of the photosensitive member 1 is uniformly charged by the charging device 3 as the photosensitive member 1 rotates.
Next, the image data is irradiated with writing light by a laser from the exposure device 4 to form an electrostatic latent image on each photoconductor 1. Thereafter, toner is attached by each developing device 5 to visualize the electrostatic latent image, thereby forming magenta, cyan, yellow, and black single-color images on each photoconductor 1. Then, along with the conveyance of the intermediate transfer body 11, those single color images are sequentially transferred to form a composite color image superimposed on the intermediate transfer body 11.
On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 27 of the paper feed table is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 26-1 and 26-2 provided in multiple stages in the paper bank. The paper is separated one by one by a separation roller and put into a paper feed path 29, conveyed by a transport roller, guided to a paper feed path 29 in the copying machine main body, and abutted against a registration roller 28 and stopped.
Then, the registration roller 28 is rotated in synchronization with the composite color image on the intermediate transfer body 11, the sheet is fed between the intermediate transfer body 11 and the secondary transfer device, and is transferred by the secondary transfer device to be transferred onto the sheet. Record a color image on

The sheet (recording medium) after the secondary transfer is conveyed by the secondary transfer device and sent to the fixing device 30, and heat and pressure are applied by the fixing device 30 to fix the transferred image, and then the discharge roller 32. Are discharged and stacked on the discharge tray 40.
On the other hand, the intermediate transfer body 11 after the image is transferred is subjected to removal of residual toner remaining after the image transfer by the intermediate transfer body cleaning device 25, and is prepared for another image formation by the tandem image forming apparatus.
Next, the structure of the intermediate transfer portion that characterizes the present invention will be described in more detail below. As shown in FIG. 1, in this embodiment, an endless belt-like intermediate transfer belt 11 constituting an intermediate transfer portion is wound around support rollers 10, 12, 34, and 35, and is counterclockwise in the figure. It can be rotated around. Of the support rollers, the roller 34 is a drive roller. The support roller 10 also serves as a cleaning counter roller, and an intermediate transfer member cleaning device 25 for removing residual toner remaining on the intermediate transfer belt 11 after the secondary image transfer is provided on the left. As will be described later, the cleaning device 25 includes a cleaning blade 21 and a brush roller 22 which are main members that abut against the intermediate transfer belt (belt-like member) 11 and give a load fluctuation.
The support rollers 12 and 35 are driven rollers and have a function of stabilizing the primary transfer nip. The support roller (cleaning counter roller) 10 also serves as a tension roller in this configuration, and functions as a pressing member that applies a constant tension to the intermediate transfer belt 11. Four rollers 20 aligned on the inner peripheral side are primary transfer (opposite) rollers, and four rollers 20 are provided corresponding to the respective image forming means of black, yellow, magenta, and cyan.

The cleaning device 25 includes a cleaning blade 21 and a brush roller (a rotatable roller-shaped application brush) 22. The brush roller 22 is accompanied by a solid lubricant (not shown) and a pressure spring (not shown) that urges the solid lubricant toward the brush roller 22. The cleaning blade 21 contacts the intermediate transfer belt 11 and scrapes off the transfer residual toner from the surface thereof. The brush roller 22 scrapes off and applies the solid lubricant pressed by the pressure spring to the intermediate transfer belt 11 while rotating. As described above, the belt cleaning device 25 has both a function as a cleaning device for cleaning the transfer residual toner on the intermediate transfer belt 11 and a function as a lubricant application device for applying the lubricant to the surface of the intermediate transfer belt 11. Yes.
In the embodiment device, as a major feature, a load applying member is provided in contact with the belt, and a load resistance is applied to the belt by the load applying member, thereby stabilizing the belt running. That is, as shown in FIG. 1, the intermediate transfer belt 11 is located at a position downstream of the member giving the load fluctuation and upstream of the primary transfer portion on the circumferential movement path of the intermediate transfer belt 11 as a belt-like member. As a roller-shaped load applying member for stabilizing the traveling speed, for example, a metal cylindrical load resistance roller 23A having a sufficient mass (sufficient rotational moment of inertia) is rotatably supported and installed. It is.
Further, a pressure roller 23B as a facing member (pressure member) is disposed on the inner peripheral side facing the load resistance roller 23A across the intermediate transfer belt 11. The pressure roller 23B is urged by the pressure spring 24 and comes into contact with the intermediate transfer belt 11 from the inner peripheral side to bring the intermediate transfer belt 11 and the load resistance roller into close contact with each other.
The load resistance roller 23A rotates while applying a slight load along with the movement (circulation) of the intermediate transfer belt 11, and when the movement speed of the intermediate transfer belt 11 is minutely changed, the intermediate transfer belt in contact with the load resistance roller 23A is rotated. 11 is given a load resistance that resists fine speed fluctuations. That is, the load resistance roller 23A rotates in close contact with the intermediate transfer belt 11 and slightly loads the drive of the intermediate transfer belt 11 in the circumferential direction. It becomes a big braking load. As a result, the running speed of the intermediate transfer belt 11 is stabilized.

FIG. 2 shows a case where there is a load resistance in which a brush roller is brought into contact with the intermediate transfer belt as a member that gives a load fluctuation to the intermediate transfer belt, and a case where there is no load resistance (experiment). In the case of the case where the brush roller is not brought into contact for the purpose), the result of analyzing the speed fluctuation generated in the intermediate transfer belt by decomposing it into frequency components is shown. The roller member (corresponding to the load resistance roller 23A) provided at this time has a diameter of 40 × length of 345 mm and a mass of 300 gf, and the pressure roller (23B) is 3N in order to increase adhesion at the opposite position. Pressed with force.
In the characteristic diagram of FIG. 2, when there is load resistance, the driving load of the belt is increased by about 0.1 kgf · cm. It can be seen that the maximum peak is smaller when the load resistance is applied, and the frequency peak is shifted to the lower frequency side.
In addition, when it is considered that the load applying member functions as a kind of flywheel (flywheel), the moment of inertia is considered as an index of performance. In the case of a roller member, the moment of inertia is proportional to the square of the radius and proportional to the first power of the mass. In consideration of these, an appropriate shape and mass can be determined. For example, if the φ40 roller obtained experimental values is reduced to 1/2 of φ20, the same function as the above-described load applying member can be achieved if the mass is set to 1200 gf, which is four times as large.

In the above-described embodiment apparatus, the member that gives the load resistance is installed downstream of the member that gives the load fluctuation and upstream of the primary transfer portion, and has a great effect of suppressing the speed fluctuation. This is because fluctuations in belt speed can be suppressed before the intermediate transfer belt reaches the transfer portion.
Further, as in the embodiment, the load applying member that applies load resistance to the belt (here, the intermediate transfer belt) is disposed by combining the opposing members as described above at the position where the belt is inserted. As a result, the adhesion between the belt and the member that gives load resistance to the belt increases and the belt does not slip, so the effect is increased. In addition, it is possible to use a method of applying a bias between the facing member and the load applying member and electrostatically adsorbing it to the belt in addition to bringing the facing member into pressure contact with the facing member. .
At this time, it is confirmed that by suppressing the speed fluctuation of the member that gives load resistance to the belt to 0.2% or less, it is possible to prevent the member giving the load resistance itself from giving speed fluctuation to the belt and appearing in the image. ing. The characteristic data of FIG. 3 shows the data that makes it desirable to set the speed fluctuation to 0.2% or less. When the speed fluctuation is decomposed into each frequency, the speed fluctuation rate and the banding rank are correlated, and the speed fluctuation rate is 0.15% or less, rank 4 or higher, and the speed fluctuation rate 0.2 or higher, rank 3 or less. It becomes easy to manifest. In addition, as a load provision member, you may use the form which does not depend on the moment of inertia of a rotation direction.

[Modification 1]
By the way, as mentioned above, as a method for stabilizing the running speed of the already known belt, an encoder is installed on at least one of the rollers around which the belt is wound or on the belt itself, and based on the signal. There is a device that controls the rotation of the belt driving roller so that the belt travels at a constant speed. However, it has already been mentioned that high-frequency speed fluctuations manifested as banding cannot be controlled with the resolution of existing general-purpose encoders, and may promote speed fluctuations in the worst case.
The load applying member (load resistance member) according to the present invention as described in the above embodiment can also be applied to an apparatus having a configuration using the known technology encoder. By providing a load resistance, the speed fluctuation can be shifted to the low frequency side. If the speed fluctuation is low frequency, it can be controlled by an existing general encoder, so that the control performance is further improved. The application is sufficiently effective.

[Second Embodiment]
By the way, if a load resistance is simply applied to the belt such as the intermediate transfer belt 11, the driving torque of the belt at the time of start-up increases, the belt becomes loose and tension, and it may take time until the belt travel is stabilized. There is sex. In addition, when the belt is stopped, the roller that gives load resistance to the belt has inertia, so that there is a possibility that a brake is required for the load resistance particularly in a high-speed machine. In order to avoid these inconveniences, a controlled driving force is also applied to the load applying member itself that applies load resistance to the intermediate transfer belt 11, thereby preventing an increase in belt driving torque and following the belt speed. It is preferable to be configured. Therefore, a control technique for driving the load applying member to cause the outer peripheral speed to follow the belt speed is known, and is not particularly illustrated here.

[Third Embodiment]
The invention of the present application can also be applied to an image forming apparatus having a mechanism in which a non-imaged photoconductor is separated from a belt, and functions effectively. This case will be described as a third embodiment. In the apparatus having this configuration, when the photosensitive member is separated, the load resistance applied to the belt is smaller than when all the photosensitive members are in contact with each other. The effect by this invention is remarkable. Since the overall configuration of the apparatus of this embodiment is substantially the same as that shown in FIG. 1, the entire illustration is omitted, and only the features of this embodiment are shown in FIGS. 4 and 5 (when the photosensitive member is separated). It will be described in detail.
FIG. 4 is a main part configuration diagram schematically showing main parts of the present embodiment in a state where the intermediate transfer belt 11 is in contact with all the photoconductors. Among the photoconductors of the toner image forming units a to d, those of a to c are color photoconductors, and those of the toner image forming unit d are Bk photoconductors. Other reference numerals are also attached in accordance with FIG. 1, and description of equivalent parts is omitted. Since each color photosensitive member other than the photosensitive member 1 for Bk (d portion) is not used for image formation at the time of black image formation, the main portion configuration diagram of FIG. As shown in the separated state), each color photosensitive member has a mechanism for separating from the intermediate transfer belt 11 (which is well-known and the detailed configuration is not shown or described). In this embodiment, only when the color photosensitive member 1 (of the toner image forming units a to c) is separated from the intermediate transfer belt 11 and the belt load resistance is reduced, the load applying member to which the controlled driving force is applied is intermediate. It contacts the transfer belt 11 and is driven at the same speed as the belt (meaning a speed fluctuation rate of 0.2% or less). Here, the apparatus shown in the figure is configured such that the driving force of the load applying member is obtained from the rotating portion of the driving mechanism of the photosensitive member 1 (of the toner image forming means a) during driving through clutch switching. (It is a known technique, and illustration and description of a specific configuration are omitted).
At this time, since the respective photoreceptors 1 of the toner image forming units a to c are not driven, even if the load applying member and the driving load member are driven, the power consumption of the entire driving mechanism hardly increases. Thus, by using the function of the present invention only when the photosensitive members are separated from each other, an increase in power consumption of the entire apparatus can be prevented. Further, the driving of the brush roller 22 as a driving load member is also obtained from the driving force of the photosensitive member 1 of the same toner image forming means a.

Note that a driving force may be obtained from the photosensitive member of the toner image forming unit b or c instead of the photosensitive member 1 of the toner image forming unit a. This configuration has an advantage that it is not necessary to specially have the load resistance roller 23A and the drive means of the brush roller 22 which is a member for applying load resistance by combining the drive means of the drive member with the drive means of the photosensitive member. The driving using the driving means of the photosensitive member may be only one of the load resistance roller 23A and the brush roller 22.
As described so far, in each of the above-described embodiments, the belt running is stabilized by applying a load resistance to the belt. In particular, by installing a member that gives load resistance downstream of the member that gives load fluctuations and upstream of the primary transfer part, belt speed fluctuations at the transfer part are sufficiently suppressed, so high-quality images without banding can be obtained. It is done.
In addition, since the belt driving torque is increased simply by applying a load resistance to the belt, a device has been proposed in which a member for applying the load resistance rotates at a constant speed with the belt. In this case, the rotational speed is preferably set to a speed fluctuation of 0.2% or less, which is an upper limit value that does not appear in the image, in order to prevent the member that gives load resistance itself from giving a speed fluctuation to the belt. Sufficient results can be obtained.

In another embodiment, only when the at least one photoconductor is separated from the belt, the member for applying load resistance comes into contact with the belt to stabilize the belt speed fluctuation. In the apparatus configured as described above, since the driving force of the photoconductor that is not imaged is used to drive the member that gives the load resistance, an increase in power of the entire apparatus can be prevented. Further, as a drive source for the load resistance, it is not necessary to have a drive means for a member that provides the load resistance by using a photoconductor drive device that is not imaged. Similarly, the load resistance roller 23A driven while controlling the speed can utilize the driving force of the photosensitive member that has not formed an image, and does not involve the addition of driving means and increase in power.
The present invention is effective for general belt drive mechanisms, but is particularly suitable for application to the intermediate transfer belt in the image forming apparatus mentioned as the embodiment. In the case of an intermediate transfer belt, a belt with high rigidity and small expansion / contraction is often used for reasons such as color misregistration, so vibration due to load fluctuations is difficult to attenuate, and belt speed fluctuations are easily manifested directly in the image. The configuration application of the present invention is extremely effective.

In the case of an intermediate transfer belt, a brush roller or a blade is incorporated as a member that gives a load variation to the intermediate transfer belt and causes a speed variation in a normal configuration. In the case where the member that gives load fluctuation is a blade, vibration is generated because stick-slip is repeated by the blade coming into contact with the belt, and load fluctuation is easily given to the belt. In addition, when the member that gives load fluctuation is a brush roller, the load transmitted to the belt differs depending on whether the brush roller flocked portion is in contact with the belt or the non-flocked portion is in contact with the belt. According to the present invention, it is possible to appropriately reduce the speed fluctuation of the intermediate transfer belt caused by these load fluctuations.
In particular, a brush roller is used as the lubricant roller, and since the lubricant is in pressure contact with the brush roller, the lubricant bites into or gets on the brush roller due to rotation of the brush roller. It is easy to generate. Therefore, the application of the present invention is more effective. In addition, since the brush roller is driven from one of the rollers around which the belt is wound, the speed fluctuation of the brush roller is easily transmitted to the roller around which the belt is wound, so that the belt speed fluctuation is likely to occur. From this point, the application of the present invention is extremely effective.
Each embodiment described above shows an example of a preferred embodiment of the present invention, and the present invention is not limited to the embodiment, and various modifications may be made without departing from the scope of the invention. Is possible. In addition, not only the intermediate belt according to the embodiment but also an image forming apparatus and other general belt driving mechanisms are effective and reduce speed fluctuations.

1 is an overall configuration diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention in a cross-sectional view. FIG. 6 is a characteristic diagram showing the results of an experiment comparing the speed variation rate of the intermediate transfer belt in the first embodiment with respect to the presence or absence of load resistance. FIG. 6 is a characteristic diagram illustrating a speed variation rate of an intermediate transfer belt and a banding rank, which are shown in association with the first embodiment. It is the principal part block diagram which showed the principal part of 3rd Embodiment typically. It is a principal part block diagram which showed typically the principal part (photosensitive body separation state) of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor, a, b, c, d Toner image formation means, 3 charging device, 4 exposure device, 5 developing device, 10 support roller, 11 intermediate transfer belt, 12 support roller, 20 primary transfer roller, 21 cleaning blade, 22 Brush roller (lubricant roller), 23A Load resistance roller, 23B Opposing member (pressure roller), 24 Pressure spring, 25 Cleaning device (belt cleaning means), 26 Paper feed cassette, 27 Paper feed roller, 28 Registration roller , 30 Fixing device, 34, 35 Support roller, 100 Secondary transfer belt

Claims (12)

A conveyor belt having an endless belt-like member stretched and supported by a plurality of rotatable rollers, a driving means for driving the belt-like member, and a member that abuts against the belt-like member and gives a load fluctuation Mechanism,
A conveying belt mechanism comprising a load applying member that stabilizes a belt traveling speed by applying a load resistance to the belt-shaped member. A conveyor belt having an endless belt-like member stretched and supported by a plurality of rotatable rollers, a driving means for driving the belt-like member, and a member that abuts against the belt-like member and gives a load fluctuation In an image forming apparatus including a mechanism,
The image forming apparatus, wherein the transport belt mechanism includes a load applying member that stabilizes a belt traveling speed by applying a load resistance to the belt-shaped member.   The image forming apparatus according to claim 2, wherein the load applying member includes an opposing member biased toward the load applying member at a position where the belt-shaped member is inserted.   The image forming apparatus according to claim 2, wherein the belt-shaped member is an intermediate transfer belt.   The image forming apparatus according to claim 2, wherein the member that gives the load fluctuation is a blade.   The image forming apparatus according to claim 2, wherein the member that gives the load fluctuation is a brush roller.   The image forming apparatus according to claim 6, wherein the brush roller is a lubricant application brush.   8. The image forming apparatus according to claim 6, wherein the brush roller is rotated by using at least one of support rollers, around which the belt-like member is wound, as a driving source.   The image forming apparatus according to claim 4, wherein the load applying member is disposed downstream of the member that applies the load fluctuation and upstream of the primary transfer unit.   10. A drive control means for controlling the load applying member to rotate at a constant speed with the belt-shaped member, wherein the rotational speed fluctuation is controlled to 0.2% or less. The image forming apparatus according to any one of the above.   A photosensitive member that is not imaged is provided with a mechanism for separating from the intermediate transfer belt, and the load applying member abuts on the intermediate transfer belt only when at least one photosensitive member is separated from the belt. The image forming apparatus according to claim 4, wherein a resistance is given.   The image forming apparatus according to claim 11, wherein the driving force applied to the load applying member is transmitted from a driving mechanism of a photosensitive member.

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