JPH0876554A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image-forming device which easily controls a carry belt in the direction of its deviation, at the same time, minimizes meandering of the transfer-material carry belt, and prevents color slippage of an image on a transfer-material in the direction of main scan. CONSTITUTION: The device is equipped with the carry belt 12 which carries the transfer material to a plurality of photosensitive drums 2 in order, a carry means consisting of a drive roller 16 and tapered follower-roller 17, between which the carry belt 12 is stretched; a plurality of transfer means 5 which transfers images, formed on the photoreceptor drum 2, to the transfer material carried by the carry means, and a first and second follower-roller compression- spring 18 which energizes the large-diameter part and small-diameter part of the follower-roller 17 to apply tension to the carry belt 12, the energizing force of the small-diameter part being smaller than that of the large-diameter part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a full color copying machine,
The present invention relates to an image forming apparatus, such as a business color copying machine, which forms an image on copy paper using a plurality of photoconductors.

[0002]

2. Description of the Related Art In recent years, depending on the color orientation of an office,
Full color copiers have appeared. One of the systems of this full-color copying machine is a 4-tandem photosensitive drum tandem system. In this system, four photoconductor drums are arranged in parallel, and a toner image is formed on each photoconductor drum by using yellow, magenta, cyan, and black toners, and the toners are sequentially formed on one transfer material. In this method, the images are transferred and the colors are overlaid to obtain a full-color image.

In the four-tandem tandem system, the transfer material placed on the conveyor belt successively contacts the four photosensitive drums to transfer the toner image. In addition, when a black image alone is formed at times other than the formation of a full-color image, the toner image is not formed on the three drums of yellow, magenta, and cyan, but only the toner image is formed by the black toner. Do. Therefore, only the toner image with the black toner is transferred to the transfer material, and a black-only image is obtained.

By the way, in this type of image forming apparatus, there is a problem that color deviation occurs in an obtained image due to meandering and deviation of the transfer material conveying belt. Therefore,
Conventionally, belt-shaped detent guide members are fixedly provided on both side portions of the transfer material conveyance belt, and these guide members prevent the conveyance belt from meandering and shifting.

The dimension between the detent guide members is made equal to the length of the roller portion of the driving roller and the driven roller that stretches the transfer material, and the detent guide member fixed to the transfer material conveying belt when the belt is driven is The driven roller slides on the end surface of the roller portion, whereby the deviation and meandering of the conveyor belt are regulated.

However, it is difficult to fix the detent guide member of the transfer material conveying belt so that the inner dimensions of both side guide members are equal to the roller portion length of the driven roller. Actually impossible. The problem that the belt meanders due to the slight gap between the roller and the guide member (that is,
If the widths do not match, the belt may meander in a wide area, and the guide member may pass over the roller in a narrow area). this is,
This is because guide members are required on both sides of the belt in order for the belt to make a meandering motion while moving toward one side. Therefore, it has been difficult to effectively suppress the color shift due to the meandering and deviation of the conveyor belt by the conventional method.

[0007]

In the conventional method, the transfer material is conveyed to the four photoconductor drums by the transfer material conveying belt, but if the transfer material conveying belt meanders, the transfer material conforms to this. It becomes a meandering state and color shift occurs.

At the same time, deviation of the transfer material conveying belt occurs. It is difficult to predict in advance which direction the deviation of the deviation will be caused by the transfer material conveying belt, which makes the meandering / deviation control more difficult.

The present invention was made on the basis of the finding newly found by the inventor, and it is possible to easily control the deviation direction of the transfer material conveying belt and at the same time easily meander the transfer material conveying belt. An object of the present invention is to provide an image forming apparatus in which the color misregistration of an image in the main scanning direction of a transfer material is solved by suppressing the amount to an extremely small range that does not affect the quality of a color image.

[0010]

In order to solve the above problems, the present invention provides a plurality of image carriers for carrying images, a plurality of image forming means for forming images on these image carriers, and Conveying belts for sequentially conveying the transfer material to the individual image carriers, conveying means composed of a drive roller for hanging the conveyor belts and a taper driven roller, and formed on each of the image carriers. A plurality of transfer means for respectively transferring the image to the transfer material conveyed by the conveying means, and a large diameter portion and a small diameter portion side of the driven roller are respectively biased to apply tension to the conveyor belt, First and second tension applying means for making the biasing force on the small diameter portion side smaller than the biasing force on the large diameter portion side.

A plurality of image carriers for carrying images,
A plurality of image forming means for forming an image on these image carriers,
Conveying belts for sequentially conveying the transfer material to the plurality of image carriers, conveying means composed of a driving roller and a taper driven roller for hanging the conveying belts, and a conveying means on each of the image carriers. A plurality of transfer means for transferring the formed image to the transfer material conveyed by the conveying means, and a large diameter portion and a small diameter portion side of the driven roller are respectively biased to apply tension to the conveyor belt. However, the driven roller comprises the first and second tension applying means for making the urging force on the small diameter portion side smaller than the urging force on the large diameter portion side, and the driven roller has the formula T = (D−d) / L.
(However, T is the taper amount of the driven roller, D is the diameter on the large diameter side, d is the diameter on the small diameter side, and L is the length of the roller portion.) The taper is 2.31 × 10 ⁻³ or more, and The coefficient of static friction with the conveyor belt is 0.26 or less.

A plurality of image carriers for carrying images,
A plurality of image forming means for forming an image on these image carriers,
Conveying belts for sequentially conveying the transfer material to the plurality of image carriers, conveying means composed of a driving roller and a taper driven roller for hanging the conveying belts, and a conveying means on each of the image carriers. A plurality of transfer means for transferring the formed image to the transfer material conveyed by the conveying means, and a large diameter portion and a small diameter portion side of the driven roller are respectively biased to apply tension to the conveyor belt. One of the first and second tension applying means for making the urging force on the small diameter portion side smaller than the urging force on the large diameter portion side, and the conveyor belt located on the small diameter portion side of the driven roller. And a guide member for slidingly guiding the end face side.

Further, a plurality of image carriers for carrying images, a plurality of image forming means for forming images on these image carriers, and a conveyor belt for sequentially transferring the transfer material to the plurality of image carriers. A transporting means composed of a driving roller and a taper driven roller for hanging up the transporting belt, and an image formed on each of the image carriers on a transfer material transported by the transporting means. A plurality of transfer means for transferring and a large-diameter portion and a small-diameter portion side of the driven roller are urged to apply tension to the conveyor belt, and the urging force on the small-diameter portion side is applied to the large-diameter portion side. The first and second tension applying means, which are smaller than the force, are integrally provided on the end face side of the conveyor belt located on the large diameter side of the driven roller, and the driven belt is driven when the conveyor belt is running. A guide that slides on the large diameter portion of the roller to guide the conveyor belt. Made by and a wood.

A plurality of image carriers for carrying images,
A plurality of image forming means for forming an image on these image carriers,
Conveying belts for sequentially conveying the transfer material to the plurality of image carriers, conveying means composed of a driving roller and a taper driven roller for hanging the conveying belts, and a conveying means on each of the image carriers. A plurality of transfer means for transferring the formed image to the transfer material conveyed by the conveying means, and a large diameter portion and a small diameter portion side of the driven roller are respectively biased to apply tension to the conveyor belt. The first and second tension applying means for making the biasing force on the small diameter portion side smaller than the biasing force on the large diameter portion side. The difference is the formula {(Pa-Pb) / Pb} × 100 ≧ 10
(However, Pa is the magnitude of the applied load by the first tension applying means, Pb is the magnitude of the applied load by the second tension applying means, and is a value obtained by Pa.> Pb).

[0015]

According to the first aspect of the present invention, the driven roller that hangs the conveyor belt is formed in a taper shape, and the large diameter portion and the small diameter portion side of the driven roller are urged to apply tension to the conveyor belt. By setting the urging force of the second tension applying means to the small diameter portion side to be smaller than the urging force to the large diameter portion side, the conveyor belt is stably biased toward the small diameter portion side of the driven roller. ,
Control the direction of deviation.

Further, one end surface side of the conveyor belt located on the small diameter side of the driven roller is slidably contacted with the guide member to guide the conveyor belt at a low cost and easily with high reliability of deviation and meandering of the conveyor belt at the same time. Suppress with sex. Further, by integrally providing the guide member on the end surface side of the conveyor belt located on the large diameter side of the driven roller, the structure is simplified and the cost is reduced.

[0017]

The present invention will be described below with reference to an embodiment shown in the drawings. The inventor first conducted an experiment for controlling the deviation of the belt. The outline of this experimental apparatus is shown in FIG.

In the figure, 12 is a transfer material conveying belt which constitutes a conveying means, 16 is a belt driving roller, 17 is a tapered driven roller having an inclination, and 31 is movable in a direction parallel to the central axis of rotation of the belt driving roller 16. The deviation control plate 19 and the reference numeral 19 are deviation force measuring sensors.

The endless transfer material conveying belt 12 is drawn around by a driving roller 16 and a taper driven roller 17, and the taper driven roller 17 has its bearing 21 pushed outward by a driven roller compression spring 18 as a hearing imparting means. As a result, tension is generated on the conveyor belt 12.

By setting the driven roller 17 as a taper roller and arranging the deviation control plate 31 on the small diameter side, the conveyor belt 12 gradually slides to the small diameter side of the taper roller 17 and the deviation advances. This biasing force is the regulation plate 31.
The biasing force measuring sensor 19 can measure this size. Further, the roller length of the taper roller 17 is designed to be equal to or larger than the width of the belt 12, so that the taper effect acts on the entire width of the belt 12.

The taper driven roller 17 does not always cause the belt 12 to slip regardless of the taper size. Also, this slip means the taper driven roller 17
It is also affected by the friction coefficient of the belt 12. At the same time, the friction causes the pressure contact state between the taper driven roller 17 and the belt 12, that is, the belt applied load.

Therefore, in order to clarify these influences,
(1) Coefficient of static friction between the belt 12 and the taper roller 17,
The force was measured based on three parameters: (2) the taper size of the taper roller 17 and (3) the applied load of the belt 12.

Here, the definition of words is clarified. The taper size is indicated by a value obtained by dividing the difference between the diameter D of the taper roller 17 on the large diameter side and the diameter d on the small diameter side by the length of the roller portion. That is, the taper T = (D−d) / L.

The change of the static friction coefficient depends on the taper roller 1.
It was realized by changing the surface condition of 7. Furthermore, belt 1
The applied load W of 2 is the sum of the magnitudes of the forces acting from the driven roller compression springs 18 on both sides of the belt 12 arranged to apply tension to the belt 12 described above (belt). Tension is W / 2).

The adjustment of the belt applied load is performed by converting several kinds of compression springs 18. Now,
The size of each parameter is (1) five types of friction coefficient: 0.24,0.25,0.26,0.27,0.28, (2) taper size: 0.77,1.54,2.31,3.08,3.85 (×
10-3), 5 types, (3) Belt application load: 2.5,2.75,3.0,3.25,3.5Kg 5
It was a kind.

Graphs summarizing the results of this experiment are shown in FIGS. The belt applied load is the applied load of each graph,
The X-axis shows the coefficient of static friction, the Y-axis shows the magnitude of taper, and the Z-axis shows the magnitude of force.

From this graph, there are the following matters. (1) When focusing on the belt applying load, the belt 12 approaches the small diameter side of the taper roller 17 when the belt applying load is 3 kg or more.

(2) Focusing on the coefficient of static friction, the belt 12 approaches the smaller diameter side of the taper roller 17 when the coefficient of static friction is 0.26 or less. (3) When focusing on the size of the taper roller 17, the belt 12 is closer to the small diameter side of the taper roller 17 when the taper size is 2.31 × 10 −3 or more.

(4) Focusing on the belt applying load, if the belt applying load is 3 kg or more, the obtained deviation force does not change with the change of the belt applying load.
A nearly constant bias can be obtained.

(5) Focusing on the coefficient of static friction, if the coefficient of static friction is 0.26 or less, the obtained deviating force does not change with a change in the magnitude of the coefficient of static friction, and a definite deviating force can be obtained. .

(6) Focusing on the size of the taper roller 17, if the size of the taper is 2.31 × 10 ⁻³ or more, the change in the amount of deviation force according to the change in the size of the taper can be obtained. To be

The phenomenon (4) can be explained as follows. That is, when the applied load of the belt is less than 3 kg, the rollers 12 and the belt 12 do not come into close contact with each other and stable running of the belt 12 cannot be performed, so that the deviation direction control toward the taper roller cannot be performed. On the other hand, when the applied belt load becomes 3 kg, the rollers 12 and the belt 12 come into close contact with each other, and the taper roller 1
The effect of No. 7 depends on the taper size and the static friction coefficient size. When the applied belt load exceeds 3 kg, a stable contact (sliding) state has already occurred between each roller and the belt 12, and therefore the magnitude of the deviation force does not change depending on the applied belt load. Absent.

Next, the phenomenon (5) can be explained as follows. That is, when the coefficient of static friction exceeds 0.26, a stable sliding state does not occur between the belt 12 and the taper roller 17, and when the coefficient of static friction becomes 0.26, a stable sliding state occurs between the belt 12 and the taper roller 17. Occurs. When the coefficient of static friction is 0.26 or less, a stable sliding state has already occurred, so that the magnitude of the force does not change depending on the magnitude of the coefficient of static friction.

The phenomenon (6) can be explained as follows. Up to a taper size of 2.31 × 10 ^-3 , the belt's own offset force is greater and cannot be controlled by the taper inclination, but the taper size is 2.31 × 1.
When it becomes 0 ⁻³ , the biasing force of the belt 12 increases the force sliding on the taper, so that the taper depends on the taper direction rather than the belt's own deviation direction. When the size of the taper exceeds 2.31 × 10 ⁻³ , the amount of slippage of the belt 12 becomes remarkable according to the size, and a leaning force corresponding to the size of the taper is obtained.

As described above in detail, the results are summarized as follows. The taper size is 2.31 × 10 ⁻³ or more, and the belt 12 and the taper roller having the static friction coefficient of 0.26 or less are used. By setting the load to 3 kg or more, the deviation direction of the belt 12 can be controlled so that the belt 12 approaches the smaller diameter side of the taper roller 17.

Next, an experiment using the Taguchi method was conducted in order to improve the stability of the deviation direction control by this method.
This Taguchi method is an experimental method of quality control engineering. For example, when a certain device A makes a motion B, the parameters constituting the device A for performing a stable motion B in a conceivable usage environment are optimized. It is an experimental method to select the conditions.

In other words, it has a feature that noise that deteriorates the function is positively taken in during the evaluation, and strong functionality against the noise is economically created. The parameters in the experiment are as follows. Control factors are (1) taper size, (2) belt applied load, (3) belt thickness, (4)
There are four types of applied load balance, and the respective values are (1) taper size = 0, 2.31, 3.85 × 10
-3 (2) Belt applied load = 3.0, 3.5, 4.0 kg (3) Belt thickness = 75 μm, 100 μm (4) Applied load balance = Rear 10% increase, Rear 20%
The rear 30% increase.

Error factors that cause noise are (1) temperature and humidity, (2) roller surface condition, (3) applied load variation, (4) photoconductor drum axis parallelism, and (5) transfer roller axis parallelism. , (6) There are 6 types of belt circumference difference, and each value is (1) Temperature / humidity = high temperature and high humidity (30 ° C-85%), low temperature and low humidity (10 ° C-20%) (2) Roller surface condition = No toner stains, toner stains (3) Applied load variation = 30% large front side, 30% large rear side (4) Parallelism of photosensitive drum axis = 0.2mm upstream on the front side, 0.2mm upstream on the rear side ( 5) Transfer roller axis parallelism = front side 0.2mm upstream,
Rear side 0.2mm upstream (6) Belt circumference difference = long side front, long side rear.

Now, the control factor is assigned to the orthogonal L18 and the error factor is assigned to the orthogonal L8, and an experiment table based on a direct product is prepared, and an experiment is performed in accordance with this. Table 1 shows an orthogonal table of the experiment by the direct product.

[0040]

[Table 1]

According to this orthogonal table, 144 experiments were carried out. The output value of the experiment is the transfer material conveying belt 12
Was used to push the regulation plate 31, that is, a biasing force. The outline of the experimental apparatus is shown in FIG. When the transfer material conveyance belt 12 comes close to the direction of the regulation plate 31 and pushes the regulation plate 31, the deviation force measuring sensor 19 on which the regulation plate 31 is fixedly arranged is pushed, whereby the transfer material conveyance belt 12 is regulated. The force pressing the plate 31 can be measured. The regulation plate 31 has a structure that is movable in a direction perpendicular to the rotation axis of the drive roller. The measurement results are shown in Table 2 in a simplified form.

[0042]

[Table 2]

As described above, the bias force (unit: g) was used as the output value in the actual experiment, but even if the numerical value is shown, the explanation is quite specialized, so the bias force obtained is obtained. It does not indicate the numerical result of, but indicates whether or not the deviation direction could be controlled. That is, when the transfer material conveyance belt is conveyed under the conditions of the parameters shown in the orthogonal table, if the deviation direction can be controlled, the deviation force is measured as a result. In this case, Table 2
On the contrary, when the transfer material conveyance belt is conveyed under the conditions of the parameters shown in the orthogonal table, the deviation force cannot be measured as a result unless the deviation direction can be controlled. In this case, in Table 2, the result is shown by a cross. Next, Table 3 shows a variance analysis table of the applied load balance calculated based on the measured values of the bias force obtained in this experiment.

[0044]

[Table 3]

In this table, the contribution rate is 17.98%, which shows that the degree of influence is high. Next, a factor effect diagram of the applied load balance calculated based on the measured bias force values obtained in this experiment is shown. In this graph, the horizontal axis represents the magnitude of the applied load balance parameter, and the vertical axis represents the calculation result of the S / N ratio. That is, the higher the S / N ratio, the higher the stability.

Next, gain calculation was performed under the current condition and the optimum condition. The applied load balance was calculated by selecting the case where the rear side was increased by 10%. This is the lowest value in this experiment, as can be seen from FIG.
This is because it is already known that even better conditions can be obtained by increasing the percentage by 30%.

Estimated gain value under optimal conditions: 11.371 db Estimated gain value under current conditions: 6.192 db From this, the gain difference is the difference between the gains under the current condition and the optimal condition = 11.371-6.1.
92 = 5.17db 10log X = 5.179 Therefore, X = 10 ^0.5179 = 3.30 In other words, if the optimum conditions (applied load balance rear side 10% increase state) are set, the current conditions (no applied load balance)
From this, it can be seen that the reliability can be improved 3.3 times.

Next, a confirmation experiment was conducted under the optimum conditions and the current conditions. This is an experiment to see if the estimated reliability improvement is really obtained. Table 4 shows an orthogonal table showing a combination of experimental parameters of this confirmation experiment.

[0049]

[Table 4]

The measurement results are shown in Table 5 in the same manner as Table 2 above.

[0051]

[Table 5]

As described above, the bias force (unit: g) was used as the output value in the actual experiment, but even if the numerical value is shown, the explanation is quite specialized, so the bias force obtained is obtained. It does not indicate the numerical result of, but indicates whether or not the deviation direction could be controlled. That is, when the transfer material conveyance belt is conveyed under the conditions of the parameters shown in the orthogonal table, if the deviation direction can be controlled, the deviation force is measured as a result. In this case, Table 5
Next, we calculated the gain under the current and optimum conditions obtained in this confirmation experiment. The applied load balance was calculated by selecting the case where the rear side was increased by 10%. This is the lowest value in this experiment, as can be seen from FIG. 9, and it is already known that if the other values are increased by 20% and 30%, a better condition can be obtained.

Gain under optimum condition: 18.93db Gain under current condition: 12.04db From this, the difference in gain is the difference between current condition and optimum condition = 18.93-12.0
4 = 6.89db 10log X = 6.89 Therefore, X = 10 ^0.5179 = 4.9 In other words, if the optimum conditions (applied load balance rear side 10% increase state) are set, the current condition (no applied load balance)
From this, it was confirmed that the reliability improvement rate of 3.3 times, which was expected to be 4.9 times, was able to be obtained.

As described in detail above, the results are summarized as follows. The taper size is 2.31 × 10 ⁻³ or more and the transfer material conveying belt 12 and the taper roller 17 having the static friction coefficient of 0.26 or less are used. By increasing the applied load on the diameter side by 10% or more of the applied load on the small diameter side, and preferably by setting the applied load on the transfer material conveying belt to 3 kg or more, the transfer material conveying belt 12 is stably placed on the small diameter side of the taper roller 17. It is possible to control the deviation direction of the transfer material conveyance belt 12 so that the transfer material conveyance belt 12 approaches.

Next, an embodiment of the invention based on this finding will be described with reference to the drawings. First, as an example to which the present invention is applied, an outline of a four-tandem tandem type full-color image forming apparatus will be described.

FIG. 1 is a schematic view of a 4-drum tandem type full-color image forming apparatus. This image forming apparatus includes four sets of recording units (individual scanning head unit and equal-magnification imaging optical system) and four sets of image forming units (photosensitive drums) in which an electrophotographic system capable of forming an image on a transfer material is combined.・ It consists of a charging device, a developing device, a transfer device, a cleaning device, and a static eliminator.

First, the solid scanning head 1Y outputs exposure light to the yellow photosensitive drum 2Y according to the yellow image data sent. This individual scanning head 1Y has a structure in which minute light emitting portions are arranged at equal intervals on a line in the main scanning direction, and according to a pattern to be printed, an ON-OFF signal sent from a printing control portion is transmitted. Accordingly, the individual light emitting portions of the main scanning direction line are turned on, and the light of the light emitting portions is imaged in a one-to-one manner. Do.
Specifically, the solid scanning head 1Y has a resolution of 4000P.
The LED head array of I is used, and the selfoc lens array is used for the same-magnification imaging optical system.

Around the yellow photosensitive drum 2Y, a charging device 3Y for charging the surface of the photosensitive drum, a yellow developing device 4Y, a yellow transfer device 5Y, a yellow cleaning device 6Y and a yellow discharging device 7Y are arranged.

The yellow photosensitive drum 2Y is rotationally driven at a peripheral speed of V0 by a drive motor (not shown). The surface of the yellow photoconductor drum 2Y is charged by a charging device 3Y which is provided in contact with the surface of the photoconductor drum and includes a conductive charging roller. The charging roller is rotated by coming into contact with the drum surface.

The surface of the photosensitive drum 2Y is formed of an organic photoconductor. This photoconductor usually has a high resistance, but has a property that the specific resistance of the light irradiation portion changes when light is irradiated. Therefore, by irradiating the surface of the charged yellow photoconductor drum 2Y with light according to the yellow print pattern through the unit-magnification imaging optical system from the individual scanning head 1Y, the latent image of the yellow print pattern is formed on the yellow photoconductor drum. It is formed on the surface of 2Y.

The electrostatic latent image is an image formed on the surface of the photoconductor drum by charging, and the specific resistance of the irradiated surface of the photoconductor is lowered by the light irradiation from the solid scanning head 1Y. It is formed by the electric charges charged on the surface of the photoconductor drum flowing, while the electric charges of the portion not irradiated with light from the solid scanning head 1Y remain (negative latent image).

The light of the solid scanning head 1Y is linearly imaged at the exposure position of the yellow photoconductor drum 2Y thus charged, and the latent image is formed on the yellow photoconductor drum 2Y. Rotate at speed. Then, at this position, the latent image on the yellow photoconductor drum 2Y becomes a visible toner image by the yellow developing device 4Y.

In the yellow developing device 4Y, a yellow toner containing a yellow dye and made of resin is prepared. The yellow toner is frictionally charged by being agitated inside the yellow developing device 4Y, and the yellow photosensitive drum 2Y.
It has the same polarity as the upper charged electrostatic charge. As the surface of the yellow photosensitive drum 2Y passes through the yellow developing device 4Y, only the latent image portion from which the charge has been removed,
The yellow toner electrostatically adheres and the latent image is developed by the yellow toner (reversal phenomenon).

The yellow photosensitive drum 2Y on which the yellow toner image is formed continues to rotate at the outer circumference V0, and at the transfer position, the transfer material 8 on the conveyor belt 12 is timely supplied by the paper feeding system. The image is transferred onto the upper surface by the yellow transfer device 5Y.

The paper feeding system is composed of a pickup roller 9, a feed roller 10 and a registration roller 11.
The transfer material 8 lifted from the paper feed cassette 23 by the pickup roller 9 is moved by the feed roller 10
Only one sheet is conveyed to the registration roller 11. The registration roller 11 aligns the posture of the transfer material 8 and then feeds it onto the transfer material transport belt 12. The peripheral speed of the registration roller 11 and the peripheral speed of the transfer material conveying belt 12 are set to be the same as the peripheral speed V0 of the photosensitive drum. The transfer material 8 is partially held by the registration roller 11, and the transfer material transport belt 12 is moved at a speed V0 equal to that of the yellow photosensitive drum 2Y.
At the same time, it is sent to the transfer position of the yellow photosensitive drum 2Y.

The yellow toner image in contact with the transfer material 8 is transferred from the yellow photosensitive drum 2Y to the transfer material 8 by the yellow transfer device 5Y, and a yellow toner image having a print pattern based on the yellow print signal is transferred. It is formed on the transfer material 8.

The yellow transfer device 5Y is composed of a transfer roller having semiconductivity. The transfer roller is electrostatically attached to the yellow photosensitive drum 2Y from the back side of the transfer material transport belt 12. An electric field having a polarity opposite to that of the yellow toner is supplied. This electric field acts on the yellow toner through the transfer material transport belt 12 and the transfer material 8 and transfers the yellow toner onto the transfer material 8 from the yellow transfer device 5Y.

The transfer material 8 to which the yellow toner has been transferred is then supplied to the magenta recording section / image forming section, the cyan recording section / image forming section, and the black recording section / image forming section.

Each recording section and the image forming section are made up of the same constituent members and operations described above in which yellow is replaced with magenta, cyan, and black, so that these explanations will be simplified for the sake of simplicity. Descriptions of the recording unit and the image forming unit are omitted. The transfer material 8 on which the color-superimposed image has been formed is sent to the fixing device 13 after passing through the yellow transfer portion, the magenta transfer portion, the cyan transfer portion, and the black transfer portion.

The fixing device 13 is composed of a heat roller incorporating a heater, and by heating the toner image just on the transfer material 8 by the electric charge,
The color-superposed toners are melted and permanently fixed to the transfer material 8. The transfer material 8 that has been fixed is sent out by the delivery roller 14
As a result, the paper is discharged onto the paper discharge tray 15.

On the other hand, the photosensitive drums (2Y / 2M / 2C / 2Bk) of the respective colors which have passed the transfer position are rotationally driven as they are at the outer peripheral speed V0, and by the cleaning device (6Y / 6M / 6C / 6Bk). Clean the residual toner and paper dust, and use the static eliminator lamp of the static eliminator (7Y / 7M / 7C / 7Bk) to clean the photosensitive drum (2Y / 2M /
2C / 2Bk) surface potential is leveled to a constant level, and if necessary, again
Enter the series of processes from the charging device (3Y / 3M / 3C / 3Bk).

The transfer material carrying belt 12 carrying the transfer material 8 has an endless structure and is held by a driving roller 16 on the fixing device 13 side and a driven roller 17 on the transfer material supply port side. The driving force of the driving roller 16 is transmitted from a driving motor (not shown), and as described above, the driving roller 16 is driven so that the outer peripheral speed V0 of the photosensitive drum and the outer peripheral speed of the belt become constant. On the other hand, the driven roller 17
Has a mechanism capable of moving in a direction parallel to the transfer material conveying direction on the shafts on both sides of the roller, and presses the transfer material conveying belt 12 by a compression spring 18 in a direction opposite to the transfer material conveying direction so as to apply a tensile load to the transfer material conveying belt 12. Has been done. Driven roller 17
The mechanism for moving the driven roller 17 in a direction parallel to the transfer material conveying direction is an elongated hole (not shown) provided in the frame, and a driven roller holding member 21 that slides the elongated hole and allows the driven roller 17 to rotate. Composed of. The transfer material conveying belt 12 sends the transfer material 8 to the fixing device 13 and then cleans the residual toner and powder paper adhering to the belt surface by the belt cleaning device 22, and if necessary,
The next transfer material 8 is conveyed.

In the case of monochrome printing, the above-mentioned
Image formation is performed by an arbitrary monochrome recording unit / image forming unit.
At this time, the recording unit / image forming unit other than the selected color does not operate.

Next, the meandering / deviation direction control and the meandering suppressing system using the meandering regulating plate according to the present invention will be described. As described above, the offset direction of the transfer material conveying belt can be stably controlled by using the taper roller and the applied load balance under the above conditions. With this taper roller method, the direction in which the transfer material transport belt deviates is toward the smaller diameter side of the taper roller. As a method of suppressing the meandering amount by using this property, there is a method of using a deviation regulating plate as shown in FIG. In the figure, 12 is a transfer material transport belt, 16 is a drive roller to the transfer material transport belt,
Reference numeral 17 is a taper driven roller, and 31 is a deviation regulation plate which is a meandering regulation plate. The endless transfer material conveying belt 12 is drawn around by the driving roller 16 and the driven roller 17, and as described above, the tapered driven roller 17 receives the bearing 21 by the driven roller compression springs 18a and 18b.
The a and 21b are pushed outward, which causes the transfer material transport belt 12 to generate tension. As described above, the driven roller compression spring 18a for pressing the front side bearing 21a of the taper driven roller 17 and the driven roller compression spring 18b for pressing the rear side bearing 21b of the tapered driven roller have a belt pressing force of 10% or more. There is a difference. In the case of this embodiment, since the large diameter side of the taper driven roller 17 is arranged on the back side in the drawing and the small diameter side of the taper driven roller 17 is arranged on the front side in the drawing, the rear side bearing 21b of the taper driven roller 17 is pushed. Driven roller compression spring 1
8b is a front side bearing 21 of the taper driven roller 17.
10% on the driven roller compression spring 18a side that pushes a
The one with the high pressing force is used. The taper driven roller 17a has a taper size of 2.31 ×
The roller has a diameter of 10 ⁻³ or more, and as described above, the front side in the drawing is the small diameter side of the taper roller, and the back side in the drawing is the large diameter side of the taper roller. Also, this taper driven roller 1
The roller surface state of the taper driven roller 17 is processed so that the coefficient of static friction between the transfer belt 7 and the transfer material conveying belt 12 is 0.26 or less. Further, the driven roller compression spring 18
The a and 18b are adjusted so that the total applied load on the front side and the back side in the figure is 3 kg or more. On the other hand, the deviation regulating plate 31 is arranged in a fixed state on the front side of the belt driving roller 16 in the figure (the small diameter side of the taper driven roller 17, the side on which the transfer material conveying belt applying load is small).

The transfer material carrying belt 12 having such a structure
The operating state is as follows. When the transfer material conveying belt 12 is conveyed by the rotation of the belt driving roller 16, the transfer material conveying belt 12 is gradually moved toward the small diameter side of the taper driven roller 17a by the taper driven roller 17 and the driven roller compression spring 18b in which the applied load balance is taken into consideration. That is, the deviation progresses toward the front side. As the deviation of the transfer material carrying belt 12 advances, it contacts the deviation regulating plate 31 fixedly arranged on the front side of the belt driving roller 16 in the figure, and is always slid and carried. become. Since the deviation regulating plate 31 is fixed in a stationary state, when the deviation of the transfer material conveying belt 12 advances by a certain amount, the pushing force of the deviation regulating plate 31 and the reaction generated thereby balance each other and the deviation is stopped. To do. On the other hand, the transfer material transport belt 12
Since the meandering force of is generally smaller than the offset force of the transfer material transport belt 12, the meandering force is included in the action of the offset force and the reaction force when the offset force is balanced. Does not happen. FIG. 11 shows the result of measuring the meandering / deviation amount of the transfer material transport belt 12 based on this configuration.

That is, the deviation regulating plate 31 is arranged on the smaller diameter side of the taper driven roller 17, and the taper driven roller 17 is arranged.
By largely distributing the applied load balance of the driven roller compression spring 18b on the large diameter side of the transfer material conveying belt 1
The deviation direction of 2 can be controlled, and thus the deviation of the transfer material conveying belt 12 and the meandering movement of the transfer material conveying belt 12 can be suppressed.

Next, a description will be given of a second embodiment of the method for controlling the deviation direction and a meandering suppressing method using the deviation preventing guide 24 which is a meandering restricting member arranged on the transfer material conveying belt 12. As described in detail above, the offset direction of the transfer material transport belt 12 can be controlled by using the taper roller and the transfer material transport belt applied load balance under the above conditions. By using this taper roller and the transfer material transfer belt applied load balance, the transfer material transfer belt 12 is offset toward the smaller diameter side of the taper roller. As a method of suppressing the amount of meandering by using this property, there is a method of using a detent guide as shown in FIG. In the figure, 12 is a transfer material transport belt, 16 is a transfer material transport belt driving roller, 17 is a taper driven roller, and 24 is a detent guide provided integrally with the transfer material transport belt on the large diameter side of the taper driven roller 17a. .

The endless transfer material conveying belt 12 is drawn around by the belt driving roller 16 and the driven roller 17, and the taper driven roller 17 has its bearing 21 supported by the driven roller compression springs 18a and 18b as described above.
The a and 21b are pushed outward, which causes the transfer material transport belt 12 to generate tension. As described above, the driven roller compression spring 18a for pressing the front side bearing 21a of the tapered driven roller and the driven roller compression spring 18b for pressing the rear side bearing 21b of the tapered driven roller 17 have a belt pressing force of 10% or more. There is a difference. In the case of this embodiment, since the large diameter side of the taper driven roller 17 is arranged on the back side in the drawing and the small diameter side of the taper driven roller 17 is arranged on the front side in the drawing, the rear side bearing 21b of the taper driven roller 17 is pushed. Driven roller compression spring 1
8b is a front side bearing 21 of the taper driven roller 17.
10% more than the driven roller compression spring 18a that pushes a
The one with the high pressing force is used. Further, this taper driven roller 17 is a roller having a taper size of 2.31 × 10 ⁻³ or more as in FIG. 10, and as described above, the front side in the figure is the taper roller small diameter side, The inner diameter side is the larger diameter side of the taper roller. The roller surface state of the taper roller is processed so that the coefficient of static friction between the taper driven roller 17 and the transfer material carrying belt 12 is 0.26 or less. Further, the driven roller compression springs 18a and 18b are adjusted so that the total applied load on the front side and the back side in the drawing is 3 kg or more. On the other hand, the deviation prevention guide 24 is arranged integrally with the transfer material conveying belt 12 on the large diameter side of the taper driven roller 17.

The transfer material carrying belt 12 having such a structure
The operating state is as follows. When the transfer material conveying belt 12 is conveyed by the rotation of the belt driving roller 16, the taper driven roller 17 and the driven roller compression spring 18b in which the applied load balance is taken into account causes the transfer material conveying belt 12 to gradually decrease in diameter. The deviation progresses to the side, that is, the front side. As the transfer material conveying belt 12 shifts to one side, the deviation preventing guide 2 provided integrally with the transfer material conveying belt 12 on the back side in the drawing.
4 comes into contact with the end surface of the taper driven roller 17 on the large diameter side and is always slid to be conveyed. Since the deviation prevention guide 24 is disposed integrally with the transfer material conveyance belt 12, when the deviation of the transfer material conveyance belt 12 by a certain amount progresses, the force of the deviation prevention guide 24 and the end surface of the taper driven roller 17 on the large diameter side is increased. And become in equilibrium and the one-sided stop.

On the other hand, since the meandering force of the transfer material conveying belt 12 is generally smaller than the biasing force of the transfer material conveying belt 12, the meandering force is included in the acting force and the reaction force of the deviating force when the deviating force is balanced. There is no meandering of the transfer material transport belt 12 that is included. FIG. 13 shows the results of measurement of the meandering amount / deviation amount of the transfer material conveying belt 12 based on this configuration.

That is, the detent guide 24 is formed integrally with the transfer material conveying belt 12, is arranged on the large diameter side of the taper driven roller 17, and the driven roller compression spring 18b of the large diameter side of the taper driven roller 17 is provided. By largely distributing the applied load balance, the offset direction of the transfer material transport belt 12 can be controlled, and thereby the progress of the offset of the transfer material transport belt 12 and the meandering travel of the transfer material transport belt 12 can be suppressed. .

When the taper driven roller 17 is used, the taper driven roller 17 is arranged on the large diameter side and the small diameter side with respect to the belt driving roller 16 so that the transfer side of the transfer material conveying belt 12 contacts the photosensitive drum. It is installed at an angle of 1/2 the diameter. This is because if the rotation center axes of the belt driving roller 16 and the taper driven roller 17 are set parallel to each other, the small diameter side of the taper driven roller 17 will not come into contact with the photosensitive drum, resulting in defective transfer. This state is shown in FIG.

As described above in detail, the taper size is set to 2.31 × 10 ⁻³ or more, and the transfer material conveying belt 12 and the taper driven roller 17 having the static friction coefficient of 0.26 or less are used to apply the image on the large diameter side. Increase the load by 10% or more of the applied load on the small diameter side, preferably the applied load of the transfer material transport belt 3
By setting it to be equal to or more than kg, it is possible to control the deviation direction of the transfer material conveying belt 12 so that the transfer material conveying belt 12 can stably approach the smaller diameter side of the taper driven roller 17. Also,
At the same time, by disposing the offset control plate 31 on the small diameter side of the taper driven roller 17, it is possible to inexpensively and easily suppress the offset and meandering of the transfer material transport belt 12 at the same time with high reliability. Further, by forming the offset guide 24 integrally with the transfer material transport belt 12 on the large diameter side of the taper driven roller 17, the same effect can be easily obtained at low cost.

[0084]

As described above, according to the present invention, the driven roller that hangs the conveyor belt is formed in a taper shape, and the large diameter portion and the small diameter portion side of the driven roller are biased respectively. Since the urging force of the first and second tension applying means for applying the tension to the conveyor belt to the small diameter portion side is smaller than the urging force on the large diameter portion side, the conveyor belt is stably driven. The deviation direction can be controlled so as to approach the smaller diameter portion side.

The driven roller has the formula T = (D-d) / L.
(However, T is the taper amount of the driven roller, D is the diameter on the large diameter side, d is the diameter on the small diameter side, and L is the length of the roller portion.) The taper is 2.31 × 10 ⁻³ or more, and Since the coefficient of static friction with the conveyor belt is 0.26 or less, it is possible to more reliably control the deviation direction so that the conveyor belt is stably and closer to the small diameter portion side of the driven roller.

Further, since the guide member for slidingly guiding the one end face side of the conveyor belt located on the small diameter side of the driven roller is provided, the conveyor belt can be inexpensively and easily displaced and meandered with high reliability. Can be suppressed with. In addition, the driven roll
Since the guide member is integrally provided on the end surface side of the conveyor belt located on the large diameter side of the la, the structure can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a four-tandem tandem type full-color image forming apparatus that is an embodiment of the present invention.

FIG. 2 is a perspective view showing a deviation force measuring device for measuring the deviation force of a conveyor belt used in the image forming apparatus of FIG.

FIG. 3 shows an experimental result of investigating the influence of the taper size and the coefficient of static friction on the magnitude of the transfer material transport belt offset force at a load of the transfer material transport belt of 2.5 kg by the offset force measuring device of FIG. Fig.

FIG. 4 shows an experimental result obtained by investigating the influence of the taper size and the coefficient of static friction on the transfer material transfer belt deviation force with a transfer material transfer belt load of 2.75 kg by the deviation force measuring device of FIG. Fig.

FIG. 5 shows an experimental result obtained by examining the influence of the taper size and the coefficient of static friction on the magnitude of the transfer material transport belt offset force at a load of the transfer material transport belt of 3.0 kg by the offset force measuring device of FIG. Fig.

FIG. 6 shows an experimental result obtained by examining the influence of the taper size and the coefficient of static friction on the magnitude of the transfer material transport belt offset force under a load of the transfer material transport belt of 3.25 kg by the offset force measuring device of FIG. Fig.

FIG. 7 shows an experimental result of investigating the influence of the taper size and the coefficient of static friction on the magnitude of the transfer material transport belt offset force at a load of the transfer material transport belt of 3.5 kg by the offset force measuring device of FIG. Fig.

FIG. 8 is a perspective view showing an apparatus used in an experiment by the Taguchi method, which is an embodiment of the present invention.

FIG. 9 is a diagram (S / N ratio) showing a factor effect of an experimental result by the apparatus of FIG.

FIG. 10 is a perspective view showing a transfer material transporting belt transporting device of an offset regulation plate system which is an embodiment of the present invention.

FIG. 11 is a diagram showing the deviation / meandering amount of the conveyor belt when the deviation regulating plate of FIG. 10 is used.

FIG. 12 is a perspective view showing a transfer material transport belt transport device of a detent guide type which is another embodiment of the present invention.

FIG. 13 is a diagram showing the deviation / meandering amount of the conveyor belt when the deviation prevention guide system of FIG. 12 is used.

14A and 14B show states of a driving roller and a driven roller of the belt conveying device of FIG. 12, FIG. 14A being a front view thereof, and FIG. 14B being a side view thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Individual scanning head, 2 ... Photosensitive drum, 3 ... Charging device, 4 ... Developing device, 5 ... Transfer device, 6 ... Cleaning device, 7 ... Eliminating device, 8 ... Transfer material, 12 ... Transfer material conveying belt, 16 ... Drive roller, 17 ... Tapered driven roller, 18
a: driven roller compression spring (first biasing means), 1
8b: driven roller compression spring (second biasing means),
24 ... Offset prevention guide (guide member), 31 ... Offset control plate (guide member).

Claims (5)

[Claims] 1. A plurality of image carriers that carry images, a plurality of image forming means that form images on these image carriers, and a conveyor belt that sequentially conveys a transfer material to the plurality of image carriers. A transporting means composed of a drive roller and a taper-like driven roller for hanging up the transporting belt, and an image formed on each of the image carriers on a transfer material transported by the transporting means. A plurality of transfer means for transferring and a large-diameter portion and a small-diameter portion side of the driven roller are urged to apply tension to the conveyor belt, and the urging force of the small-diameter portion side is applied to the large-diameter portion side. First and second less than power
An image forming apparatus, comprising: 2. A plurality of image carriers that carry images, a plurality of image forming means that form images on these image carriers, and a conveyor belt that sequentially conveys a transfer material to the plurality of image carriers. A transporting means composed of a drive roller and a taper-like driven roller for hanging up the transporting belt, and an image formed on each of the image carriers on a transfer material transported by the transporting means. A plurality of transfer means for transferring and a large-diameter portion and a small-diameter portion side of the driven roller are urged to apply tension to the conveyor belt, and the urging force of the small-diameter portion side is applied to the large-diameter portion side. First and second less than power
The driven roller is of the formula T = (D-d) / L (where T is the taper amount of the driven roller, D is the diameter on the large diameter side, d is the diameter on the small diameter side, L Is the length of the roller portion) and the taper is 2.31.
× 10 ⁻³ or more, the coefficient of static friction with the conveyor belt was 0.
An image forming apparatus having 26 or less. 3. A plurality of image carriers for carrying images, a plurality of image forming means for forming images on these image carriers, and a conveyor belt for sequentially transferring a transfer material to the plurality of image carriers. A transporting means composed of a drive roller and a taper-like driven roller for hanging up the transporting belt, and an image formed on each of the image carriers on a transfer material transported by the transporting means. A plurality of transfer means for transferring and a large-diameter portion and a small-diameter portion side of the driven roller are urged to apply tension to the conveyor belt, and the urging force of the small-diameter portion side is applied to the large-diameter portion side. First and second less than power
And a guide member for guiding one end surface side of the conveyor belt, which is located on the small diameter side of the driven roller, in sliding contact with each other. 4. A plurality of image carriers that carry images, a plurality of image forming means that form images on these image carriers, and a conveyor belt that sequentially conveys a transfer material to the plurality of image carriers. A transporting means composed of a drive roller and a taper-like driven roller for hanging up the transporting belt, and an image formed on each of the image carriers on a transfer material transported by the transporting means. A plurality of transfer means for transferring and a large-diameter portion and a small-diameter portion side of the driven roller are urged to apply tension to the conveyor belt, and the urging force of the small-diameter portion side is applied to the large-diameter portion side. First and second less than power
Of the tension roller and the end surface side of the conveyor belt located on the large diameter portion side of the driven roller, and slides on the large diameter portion of the driven roller when the conveyor belt is running. And a guide member for guiding the conveyor belt. 5. A plurality of image carriers for carrying images, a plurality of image forming means for forming images on these image carriers, and a conveyor belt for sequentially transferring a transfer material to the plurality of image carriers. A transporting means composed of a drive roller and a taper-like driven roller for hanging up the transporting belt, and an image formed on each of the image carriers on a transfer material transported by the transporting means. A plurality of transfer means for transferring and a large-diameter portion and a small-diameter portion side of the driven roller are urged to apply tension to the conveyor belt, and the urging force of the small-diameter portion side is applied to the large-diameter portion side. First and second less than power
And a difference in biasing force between the first and second tension applying means is expressed by the formula {(Pa-Pb) / Pb} × 100 ≧ 10 (where Pa is
Is the magnitude of the load applied by the first tension applying means, Pb is the magnitude of the load applied by the second tension applying means, and Pa.
> Pb), the image forming apparatus.