JP4070552B2 - Color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an image forming apparatus that forms images with different colors on each image carrier arranged in succession, and forms one color image by sequentially superimposing images formed on each image carrier. About.
[0002]
[Prior art]
Conventionally, a plurality of photoconductors (image carriers) are arranged in parallel, and a visible image of a different color is formed on each photoconductor by a charging device, an exposure device, and a developing device. After the images are sequentially transferred, the images are fixed by a fixing device, or the visible images of the colors formed on the respective photosensitive members are sequentially superimposed on the intermediate transfer member for primary transfer, and then the superimposed visible images are batched. An image forming apparatus that obtains a color image by performing secondary transfer onto a transfer material and fixing with a fixing device is known.
[0003]
In particular, the former color image forming apparatus is called a tandem method because a developing device (charging device, exposure device, etc.) centering on a photosensitive member is arranged in parallel on an intermediate transfer member.
[0004]
In general, in a color image forming apparatus, a full color image is formed by superposing four color developing particles (toners) of yellow, magenta, cyan, and black. In the tandem system, a photoconductor is used according to the toner of each color. Therefore, the working efficiency is superior to that of a one-drum type color image forming apparatus in which toner images are sequentially superimposed on a single photosensitive member and then transferred to an intermediate transfer member at a time.
[0005]
However, in such a conventional color image forming apparatus, periodic driving unevenness in each rotating body (photosensitive member, transfer belt driving roller, etc.) has been a problem, and this unevenness is caused in each photosensitive member and each belt nip portion. There is a problem in that a faithful color image cannot be reproduced because a color shift occurs between the colors when the images are reproduced by superimposing the colors.
[0006]
On the other hand, in order to solve the above problem, a mark that rotates in synchronization with the photoconductor is detected by a sensor, and alignment stop control is performed so that the photoconductor stop position is in a predetermined positional relationship based on the detected result. It has been proposed to provide a rotation stop means for performing the reproduction faithfully as one color image corresponding to a periodic drive fluctuation (see, for example, Patent Document 1).
[0007]
[Patent Document 1]
JP 2000-330450 A
[Problems to be solved by the invention]
However, in the invention described in the above publication, when the transfer belt is used, there are many cases in which the speed fluctuation of the transfer belt that does not appear in a cycle occurs. Therefore, if the force from the image carrier that the belt receives at the transfer nip of each color does not match, the frictional force acts on the belt between the transfer nips of each color, and the belt speed passing through the image carrier of each color does not match. In some cases, color misregistration occurs.
[0009]
In view of the above, an object of the present invention is to obtain a beautiful color image by suppressing the transfer deviation by suppressing the speed fluctuation of the transfer belt.
[0010]
[Means for Solving the Problems]
According to the first aspect of the present invention, a color image forming apparatus that visualizes a plurality of image carriers and an electrostatic latent image formed on the image carrier and sequentially transfers the visible images to an intermediate transfer member. The intermediate transfer member is stretched over the transfer belt, a transfer belt drive roller for rotating the transfer belt, a driven pulley provided coaxially with the transfer belt drive roller, a drive pulley provided in a drive motor, and the pulleys. The load member is arranged so that a relationship of 2T / d> Ft is established, where T is the torque of the drive pulley, d is the diameter of the drive pulley, and Ft is the inflection point load of the drive transmission belt. It is characterized by providing.
[0011]
According to the first aspect of the present invention, when the image forming cycle is started, the plurality of image carriers (photoconductors) rotate in a predetermined direction and the transfer belt also starts running, and each color is transferred onto the transfer belt. The toner image is transferred in a superimposed manner. The transfer belt is driven by rotation of a transfer belt drive roller, and this transfer belt drive roller is driven by drive transmission of a drive pulley, a driven pulley, and a drive transmission belt stretched around these pulleys. That is, when the drive pulley provided in the drive motor rotates, the driven pulley rotates through the drive transmission belt. Due to the rotation of the driven pulley, the transfer belt runs due to the rotation of the transfer bell and the drive roller provided on the same axis of the pulley.
[0012]
In the present invention, since the load member is provided so that the relationship of 2T / d> Ft is established, a tension equal to or greater than the inflection point load acts on the drive transmission belt, thereby making it possible to suppress the amount of expansion and contraction of the belt. . Accordingly, transfer deviation due to expansion and contraction of the transfer belt is hardly caused, and as a result, a beautiful color image can be obtained.
[0013]
According to a second aspect of the present invention, there is provided a color image forming apparatus that visualizes a plurality of image carriers and an electrostatic latent image formed on the image carrier and sequentially transfers the visible images to an intermediate transfer member. The intermediate transfer member is stretched over the transfer belt, a transfer belt drive roller for rotating the transfer belt, a driven pulley provided coaxially with the transfer belt drive roller, a drive pulley provided in a drive motor, and the pulleys. A drive transmission belt, a tension pulley for applying tension to the drive transmission belt, the drive pulley torque T, the drive pulley diameter d, the inflection point load of the drive transmission belt Ft, and the drive transmission by the tension pulley A load member is provided so that a relationship of 2T / d> Ft−Fb is established when the tension applied to the belt is Fb.
[0014]
According to the second aspect of the present invention, in addition to the load member according to the first aspect, a tension pulley is provided so that a tension greater than the inflection point load acts on the drive transmission belt. Similarly to the first aspect of the invention, transfer deviation due to expansion and contraction of the drive transmission belt is less likely to occur, and a beautiful color image can be obtained. The drive transmission belt is provided with a tension pulley separately from the load member. Since the belt tension is applied, the load member is not excessively burdened and the life of the load member can be extended.
[0015]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the load member is provided on the transfer belt driving roller.
[0016]
In the third aspect of the invention, the same effect as that of the first or second aspect of the invention can be achieved, and the load member is provided on the transfer belt drive roller. For example, the load member is provided on the drive pulley. Compared to the above, slip hardly occurs between the transfer belt driving roller and the transfer belt.
[0017]
According to a fourth aspect of the present invention, a color image forming apparatus that visualizes a plurality of image carriers and an electrostatic latent image formed on the image carrier and sequentially transfers the visible images to an intermediate transfer member. The intermediate transfer member is stretched over the transfer belt, a transfer belt drive roller for rotating the transfer belt, a driven pulley provided coaxially with the transfer belt drive roller, a drive pulley provided in a drive motor, and the pulleys. A drive transmission belt and a tension pulley that applies tension to the drive transmission belt, where Ft is an inflection point load of the drive transmission belt, and Fb is a tension received by the drive transmission belt by the tension pulley, Fb ≧ Ft Tension is applied to the drive transmission belt so that the relationship is established.
[0018]
In the invention described in claim 4, since the tension is applied to the drive transmission belt so that the relationship of Fb ≧ Ft is established in the tension pulley, the transfer caused by the expansion / contraction of the transfer belt is the same as in the invention described in claim 1. It is possible to obtain a beautiful color image with little deviation, and no torque limiter is required. Therefore, the configuration is simple and the cost can be reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing a part of an intermediate transfer member of the color copying machine according to FIG. 2, and FIG. 2 is a sectional view schematically showing a part of the color copying machine according to the present invention.
[0020]
The color copying machine 100 visualizes an electrostatic latent image formed on a paper feed unit 3 that accommodates transfer paper, an electrophotographic process unit 5 that performs image formation, and an image carrier (photoconductor) 13. The image forming apparatus includes an intermediate transfer body 7 that sequentially transfers a visible image, a fixing device 9 that heats and pressurizes the transfer paper, and a paper discharge unit 11 that discharges the fixed transfer paper.
[0021]
The electrophotographic process unit 5 includes four electrophotographic process units 5M, 5C, 5Y, and 5K for magenta, cyan, yellow, and black in order, and each process unit mainly includes a plurality of photoconductors 13. Around the photoconductor 13, a charger 15, an exposure device 17, a developing device 19, a transfer device 21, and a photoconductor cleaner 23 are arranged in this order.
[0022]
In the present embodiment, a system that prints directly on transfer paper will be described. However, as long as it is a tandem system, a configuration having primary transfer and secondary transfer may be used.
[0023]
A transfer belt 31 is stretched around the intermediate transfer member 7 by two support rollers 33 and 35. In the actual transfer process, the transfer paper is nipped and conveyed between the photosensitive member 13 and the transfer device 21, and the developer image formed and supported on the surface of the photosensitive member 13 on the surface side is successively subjected to electrostatic force and pressing force. Are transferred.
[0024]
One of the support rollers is a transfer belt drive roller (hereinafter referred to as drive roller) 33 that drives the transfer belt 31, and the transfer belt 31 travels in a predetermined direction by the rotation of the drive roller 33. One end of the drive roller 31 is provided with a transmission means for transmitting the drive. The transmission means includes a drive pulley 41, a driven pulley 43, and a drive transmission belt 45 stretched around these pulleys.
[0025]
Next, the drive transmission belt 45 will be described. In the tandem color image forming apparatus as described above, the printing speed is fast, but on the other hand, there may be a positional shift at the time of transfer. Conventionally, this positional deviation was prevented by a method of correcting the writing timing, but the positional deviation was not eliminated even if it was corrected with high accuracy. This was thought to be caused by the unstable running speed of the transfer belt 31.
[0026]
Specifically, the speed fluctuation occurs at the nip between the photosensitive member 13 and the transfer device 21 of the transfer belt 31, and the cause thereof is that both electrostatic action and mechanical action interact at the transfer nip. This is because the frictional force between the transfer belt 31 and the photosensitive member 13 changes. Further, in the case of the tandem system, since the plurality of photosensitive members 13 are in contact with the transfer belt 31, the above-described phenomenon occurs at the same time. Therefore, when each color operates sequentially, the transfer is performed each time. The speed variation of the belt 31 occurs.
[0027]
Specifically, (1) the attraction force due to the electrostatic action at the nip between the transfer belt 31 and the photoconductor 13 is changed by the potential difference generated on the photoconductor 13 in the charging step, whereby the photoconductor 13 and the transfer belt. The frictional force with 31 changes. (2) In the developing process, when the developing roller starts to rotate, a small amount of toner adheres to the photosensitive member 13, and when the toner reaches the transfer nip, the toner becomes a lubricant, and the photosensitive member 13 and the transfer belt 31. Changes in the friction force. (3) In the transfer process, the attracting force due to the electrostatic action at the nip between the transfer belt 31 and the photosensitive member 13 changes depending on the magnitude and timing of the applied voltage, and the frictional force changes. (4) When rotation of the fur brush or the like is started in the cleaning process, the photosensitive member 13 slightly changes in speed. Variations in the speed of the transfer belt 31 occur due to causes such as (1) to (4).
[0028]
Next, there is a problem as to where the speed fluctuation of the transfer belt 31 occurs. Initially, it is estimated that the speed fluctuation occurs in the transfer belt 31 due to slippage of the transfer belt 31 and the driving roller 33 due to load fluctuation. . Therefore, for each of the transfer belt 31 and the driving roller 33, the fluctuations in the belt surface position and the roller position were measured simultaneously.
[0029]
FIG. 3 is a graph showing the measurement results of the belt surface position and roller position fluctuation for each of the transfer belt 31 and the driving roller 33, where the vertical axis represents the fluctuation amount and the horizontal axis represents the length of one A3 sheet. It shows. Also, the alternate long and two short dashes line (A) indicates the belt surface position, and the dotted line (B) indicates the roller position fluctuation. As a result, as shown in FIG. 3, there was no difference in fluctuation between the two, and it was found that the speed fluctuation was not caused by slippage of the transfer belt 15 and the driving roller 33.
[0030]
Therefore, it was speculated that there might be a cause for the drive source that drives the drive roller 33. FIG. 4 shows changes in the amount of load and the amount of elongation applied to the belt. As shown in FIG. Then, the amount of elongation becomes smaller. From this, it was estimated that the elongation of the drive transmission belt 45 was the cause of the speed fluctuation. Then, the tension of the drive transmission belt 45 was increased so that a load Ft equal to or greater than the inflection point load was applied to the drive transmission belt 45, and the simultaneous measurement of the positional fluctuations of the transfer belt 31 and the drive roller 33 was performed again. As a result, as shown by the one-dot chain line (c) and straight line (d) in FIG.
[0031]
FIG. 5 shows the relationship of the force applied to the drive transmission belt 45, where T is the torque applied to the drive pulley 41, d is the diameter of the pulley 41, and F is the tension applied to the drive transmission belt 45. The relationship of F = 2T / d is established. Here, by making the tension F applied to the drive transmission belt 45 larger than the load Ft greater than or equal to the inflection point load (2T / d> Ft), the belt position fluctuation can be suppressed, and the speed fluctuation of the transfer belt 31 can be reduced. Can be suppressed.
[0032]
In the present embodiment, a torque limiter 47 (load member) that applies load torque to the other end of the drive roller 33 is provided so that the tension F applied to the drive transmission belt 45 is larger than the load Ft that is greater than the inflection point load. It was. The torque limiter 47 is fixed to the main body.
[0033]
Next, the operation of the present embodiment will be described based on the configuration described above. When the image forming cycle is started, the plurality of photoreceptors 13 rotate in a predetermined direction and the transfer belt 31 also rotates, and the toner images of the respective colors are transferred onto the transfer belt 31 in an overlapping manner. As a result, a color toner image is transferred onto the transfer paper, and the image is fixed on the transfer paper by being heated and pressed by the fixing device 9 and discharged from the paper discharge unit 11.
[0034]
The transfer belt 31 travels as the drive roller 33 rotates, and the drive roller 33 is driven by drive transmission of a transmission means including a drive pulley 41, a driven pulley 43, and a drive transmission belt 45 stretched around these pulleys. Done. That is, when the drive pulley 41 provided in the drive motor rotates, the driven pulley 43 rotates via the drive transmission belt 45. By the rotation of the driven pulley 43, the transfer belt 31 travels by the rotation of the driving roller 33 provided on the same axis of the pulley.
[0035]
In the present invention, the torque limiter 47 is provided so that a load equal to or greater than the inflection point load of the belt acts on the drive transmission belt 45, so that tension can be applied to the belt, thereby suppressing the amount of expansion and contraction of the belt. Is possible. Therefore, transfer deviation due to the elongation of the transfer belt is less likely to occur, and a beautiful color image can be obtained.
[0036]
Next, other embodiments will be described. In the description, portions similar to those described above are denoted by the same reference numerals, and description thereof is omitted. In the first embodiment, the torque limiter 47 is provided to apply load tension to the drive transmission belt 45. In the second embodiment, in addition to the torque limiter 47, tension is further applied to the drive transmission belt 45. Therefore, a tension pulley 51 was provided.
[0037]
The tension pulley 51 directly applies tension to the drive transmission belt 45 as shown in FIG. When the tension applied to the belt by the tension pulley 51 is Fb, the torque is applied so that a load larger than the value obtained by subtracting the tension Fb received by the tension pulley 51 from the load Ft greater than the inflection point load (Ft−Fb) is applied. The limiter 47 is set.
[0038]
As described above, according to the second embodiment, since the tension load applied to the drive transmission belt 45 by the torque limiter 47 is reduced, the torque limiter 47 is not excessively loaded, and the torque limiter 47 The service life can be extended.
[0039]
The third embodiment is different from the first and second embodiments in that only the tension pulley 51 is used without using the torque limiter 47. When only the tension pulley 51 is used, when the tension received by the belt by the tension pulley 51 is Fb, the Fb is set to be equal to or greater than the load Ft greater than the inflection point load (Fb ≧ Ft). Thus, since only the tension pulley 51 is used, the torque limiter 47 is not required, and the configuration is simple and the cost can be reduced.
[0040]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, although the description has been made assuming the color copying machine 100, it may be related to a printer, a FAX, or the like.
[0041]
Further, the method of applying a load to the drive transmission belt 45 is not limited to the torque limiter 47 and the tension pulley 51, and the load may be applied directly to the transfer belt 31. For example, as shown in FIG. 7, the roller 61 may be provided in contact with the reverse rotation roller 63, or the roller 71 may be provided with a blade 73 as shown in FIG.
[0042]
【The invention's effect】
In the first aspect of the present invention, since the load member is provided so that the load greater than the inflection point load acts on the drive transmission belt, the belt is always in a tensioned state, whereby the amount of expansion and contraction of the belt can be suppressed. It becomes. Therefore, transfer deviation due to expansion and contraction of the transfer belt is less likely to occur, and a beautiful color image can be obtained.
[0043]
In the second aspect of the invention, similarly to the first aspect of the invention, transfer deviation due to expansion and contraction of the transfer belt is less likely to occur, and a beautiful color image can be obtained. Since the tension pulley is provided separately from the load member to apply tension to the belt, the load member is not excessively burdened and the life of the load member can be extended.
[0044]
The invention according to claim 3 has the same effect as that of the invention according to claim 1 or 2, and the load member is provided on the transfer belt drive roller, so that slip occurs between the transfer belt drive roller and the transfer belt. Is unlikely to occur.
[0045]
In the invention described in claim 4, similarly to the invention described in claim 1, transfer deviation due to expansion and contraction of the transfer belt is less likely to occur, and a beautiful color image can be obtained and a torque limiter is required. Therefore, the configuration is simple and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a part of an intermediate transfer member according to FIG. 2 in an extracted manner.
FIG. 2 is a cross-sectional view schematically showing a part of a color copying machine according to the present invention.
FIG. 3 is a graph showing a belt surface position and a roller position variation for each of a transfer belt and a driving roller.
FIG. 4 is a graph showing changes in load and elongation applied to a belt.
FIG. 5 is a configuration diagram showing an operational relationship of forces applied to a drive transmission belt.
FIG. 6 is a configuration diagram showing a state in which a tension and pulley is used as a load member.
FIG. 7 is a schematic configuration diagram illustrating an intermediate transfer member according to another embodiment.
FIG. 8 is a schematic configuration diagram illustrating an intermediate transfer member according to another embodiment.
[Explanation of symbols]
1 Color copier (image forming device)
7 Intermediate transfer member 13 Photoconductor (image carrier)
31 Transfer belt 33 Drive roller (transfer belt drive roller)
41 Drive pulley 43 Driven pulley 45 Drive transmission belt 47 Torque limiter (load member)
51 Tension pulley 100 Color copier (color image forming device)

Claims (4)

  In a color image forming apparatus that visualizes a plurality of image carriers and an electrostatic latent image formed on the image carrier and sequentially transfers the visible images to the intermediate transfer member, the intermediate transfer member is a transfer belt. A transfer belt drive roller for rotating the transfer belt, a driven pulley provided coaxially with the transfer belt drive roller, a drive pulley provided for the drive motor, and a drive transmission belt stretched over these pulleys, Color image formation characterized in that a load member is provided so that a relationship of 2T / d> Ft is established, where T is the pulley torque, d is the drive pulley diameter, and Ft is the inflection point load of the drive transmission belt. apparatus.   In a color image forming apparatus that visualizes a plurality of image carriers and an electrostatic latent image formed on the image carrier and sequentially transfers the visible images to the intermediate transfer member, the intermediate transfer member is a transfer belt. A transfer belt drive roller for rotating the transfer belt, a driven pulley provided coaxially with the transfer belt drive roller, a drive pulley provided on the drive motor, a drive transmission belt stretched around these pulleys, and a drive transmission belt A tension pulley for applying tension to the drive pulley, T as the torque of the drive pulley, d as the diameter of the drive pulley, Ft as the inflection point load of the drive transmission belt, and Fb as the tension applied to the drive transmission belt by the tension pulley. 2. A color image forming apparatus, wherein a load member is provided so that a relationship of 2T / d> Ft−Fb is established.   3. The color image forming apparatus according to claim 1, wherein the load member is provided on a transfer belt driving roller. In a color image forming apparatus that visualizes a plurality of image carriers and an electrostatic latent image formed on the image carrier and sequentially transfers the visible images to the intermediate transfer member, the intermediate transfer member is a transfer belt. A transfer belt drive roller for rotating the transfer belt, a driven pulley provided coaxially with the transfer belt drive roller, a drive pulley provided on the drive motor, a drive transmission belt stretched around these pulleys, and a drive transmission belt A tension pulley for applying tension to the drive transmission belt so that the inflection point load of the drive transmission belt is Ft and the tension applied to the drive transmission belt by the tension pulley is Fb. A color image forming apparatus characterized by applying tension.

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