JPH0719081B2 - Image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer, and more particularly to an image forming apparatus that conveys a transfer sheet by using a belt-shaped conveying unit.

(Prior Art) Conventionally, in an apparatus of this type using an electrophotographic method, there is one that uses a belt as a means for conveying a transfer material. Compared to the case where the transfer material is conveyed by using a means such as a plurality of roller pairs, for example, this causes almost no conveyance failure such as skewing, and especially when electrostatic adsorption is also used, it is sudden. This is because stable transportation can be performed without causing displacement due to various obstacles.

(Problems to be Solved by the Invention) However, in such a conventional example, due to a speed difference between a conveyance belt that conveys a transfer material and an image carrier that forms an image, conveyance as described below is performed. The problem of floating the belt is occurring.

That is, considering the case where an image is formed using the image forming apparatus 100 as shown in FIG. 3, the scanner optical system 101
The image formed on the photosensitive drum 102 by the laser beam from the developing unit 103 is visualized by the cassette 104.
The transfer is carried out from the inside to the transfer material 106 which is carried in the direction of the arrow a by the carrying belt 105. At that time, the transfer charger 107 attracts the toner on the photosensitive drum 102 to the transfer material 106 to perform the above-mentioned transfer. Therefore, the conveyor belt 105 is also attracted to the photosensitive drum 102 side. In this case, arrow b
The peripheral speed Vd of the photosensitive drum 102 rotating in the direction
If the conveyance force due to the attraction of the photosensitive drum 102 is greater than the tension of the tension roller 108, the belt 105 will move toward the photosensitive drum 1 near the transfer position.
Along with 02, the tension roller 108 is moved rightward while being conveyed at the speed Vd.

The belt 105, which is the excess portion due to the movement of the tension roller 108, moves at a speed higher than the peripheral speed of the drive roller 109, and therefore, as shown by the dotted line in the figure, slack is generated on the side where the drive roller 109 is wound. However, when this is increased, the wrapping angle of the conveyor belt 105 with respect to the roller 109 is decreased, and the driving force is not transmitted to the conveyor belt 105. As a result, the conveyance of the transfer material 106 becomes unstable, and there is a problem that the transfer image is disturbed. In addition, if the electrostatic attraction force of the attraction charger 110 provided for securely fixing the transfer material 106 to the transport belt 105 is increased, the attraction force of the transport belt 105 at the time of transfer is also increased, which further disturbs the image. It was easy to occur. Further, the resultant force of the tangential direction conveying force of the photosensitive drum 102 via the transfer material 106 by the conveying belt 105 and the circumferential conveying force of the transfer material 106 by the photosensitive drum 102 is the peripheral speed of the photosensitive drum 102. Vd is the speed Vd of the conveyor belt 105
If it is larger than the above, the transfer material 106 is deflected in the direction in which the transfer material 106 is wound around the photosensitive drum 102, so that a jam may occur in which the transfer material 106 is wound around the photosensitive drum 102.

Further, as shown in FIG. 4, in an apparatus 200 having a plurality of image forming means 201 to 204 similar to the apparatus 100 and capable of forming a plurality of color images, between the photosensitive drums 205 to 208. Due to the difference in speed, at each transfer portion of the plurality of image forming units 201 to 204, the conveyor belt 209 is connected to the photosensitive drums 205 to 208.
When the transfer belt 209 is attracted to and follows the transfer driving roller 210, the transfer belt 209 is slacked not only on the transfer driving roller 210 but also between the transfer units, which not only causes the disorder of the transfer image as described above but also transfers each color. There is also a problem that the position is displaced.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and the object thereof is to prevent image defects and jams due to the slack of the belt-shaped conveying means and to obtain high-quality images. An object is to provide an image forming apparatus that can be formed.

(Means for Solving the Problems) In order to achieve the above-mentioned object, in the present invention, an image carried by a moving image carrier is transferred by a belt-shaped transporting means that moves in the same direction as the image carrier. In the image forming apparatus for transferring to the transferred transfer material, Vd ≦ Vb is set, where Vd is the moving speed of the image carrier and Vb is the moving speed of the carrying unit.

It is also preferable to set the moving speed Vd of the image carrier and the moving speed Vb of the conveying means so that Vd ≦ Vb ≦ 1.005Vd.

(Operation) In the present invention having the above configuration, the relationship between the moving speed Vd of the image carrier and the transport speed Vb of the transport unit is set to Vd ≦ Vb,
Furthermore, since Vd ≤ Vb ≤ 1.005Vd is set, when the transfer means is attracted to the image carrier by the electrostatic attraction force during the transfer process, the transfer means transfers the image Since the carrier moves faster than the carrier, a force in the opposite direction to the carrying direction acts on the carrying means, and a force in the opposite direction to the moving direction acts on the driving means. Therefore,
Since the tension roller or the like for applying tension to the belt-shaped conveying means does not move and the conveying means does not have a remainder, the slack of the conveying means on the driving means is prevented. Further, due to the relationship of Vd ≦ Vb, the transfer material is prevented from being deflected in the direction in which the transfer material is wound around the image carrier, and the occurrence of a jam in which the transfer material is wound around the image carrier is prevented.

As a result, the transport unit is stably transported by the driving force of the drive unit, and the transfer material receives the image transferred on the image carrier while being transported at a constant speed.

(Example) Hereinafter, the present invention will be described based on illustrated examples.

FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. The full-color image forming apparatus 1 has an endless belt-shaped conveying belt B as a conveying means for conveying a transfer material S. Image forming means A ₁ , A ₂ , A ₃ , and A ₄ for forming images of cyan, magenta, yellow, and black are arranged on the upper surface side of the conveyor belt B at substantially equal intervals. Above the photosensitive drums D _{1 of} the image forming units A _{1 to} A ₄ by emitting a laser beam according to the image signal.
Scanners 11, 12, 13, and 14 that form latent images on D ₂ , D ₃ , and D ₄ are provided.

A cassette C containing a transfer material S is provided on the right side of the apparatus, and a pickup roller 2 for feeding the transfer material S into the apparatus and a registration roller 3 for guiding the transfer material S onto a conveyor belt B are provided inside the apparatus of the cassette C. There is.

Further, a fixing device 4 for fixing the image on the transfer material S conveyed by the conveyance belt B is provided inside the left side of the apparatus, and a tray for mounting the discharged fixed transfer paper is provided outside the left side of the apparatus. 5 is provided.

The conveyor belt B is wound around the driving roller 6 and the driven roller 7 and is given a predetermined tension by the tension roller 8. The drive roller 6 is connected to a drive motor (not shown) and rotates in the direction of arrow P to move the conveyor belt B in the direction of arrow Q at a predetermined speed Vb. Reference numeral 8 denotes an attraction charger for electrostatically attracting the transfer material S on the conveyor belt B so as not to shift it.

The image forming units A _{1 to} A ₄ have the same configuration and form an image corresponding to each color by a known electrophotographic process. In other words, around the photosensitive drum D ₁ to D _4, a primary charger 21, 22, 23, 24, developing device 31, 32, 33 and 34 corresponding to each color, a transfer charger 41, 42, 43 and 44 as well Cleaners 51, 52, 53, 54 are provided respectively, and the scanners 11 to 14 are provided in accordance with the color-separated image signals.
A color image corresponding to the laser beam emitted from the device is formed.

Here, the photosensitive drums D ₁ to D ₄ is connected to a drive motor (not shown), respectively so as to rotate in the direction of arrow R at a predetermined peripheral velocity Vd. Reference numerals 61, 62, 63 and 64 are lamps for making the surface charges of the photosensitive drums D _{1 to} D ₄ uniform after the image forming process and preparing for the next latent image formation.

In the above configuration, when a signal indicating that an image should be formed is input, the transfer material S in the cassette C is fed into the apparatus main body by the pickup roller 2 and the registration roller 3
Then, it is placed on the conveyor belt B with the timing adjusted. Then, the transfer material S is electrostatically attracted by the attraction charger 8 and moves at a speed Vb together with the conveyor belt B without causing a positional shift during transportation.

On the other hand, the image signal is decomposed into signals corresponding to each color of cyan, magenta, yellow, and black. For example, a cyan image signal is input to the scanner 11. The scanner 11 emits a laser beam according to this image signal, and the photosensitive drum D ₁ uniformly charged by the primary charger 21.
Is exposed to form a latent image. The photosensitive drum D ₁ is rotating at a peripheral velocity Vd in the direction of arrow R, the latent image on the drum D ₁ is visualized by the developing device 31, and the transfer charging device 41 transfers the transfer material S on the conveying belt B. This image is transferred to. After that, the surface of the photosensitive drum D ₁ is cleaned by the cleaner 51, and the surface potential on the drum surface is uniformly reduced by the illumination of the lamp 61 to prepare for the next latent image formation. Magenta,
For the respective colors of yellow and black, after the corresponding image signals are sent to the scanners 12, 13 and 14, the respective image forming means
In A ₂ , A ₃ , and A ₄ , image formation is performed through the same process as the process in the image forming unit A ₁ .

During the above-described image formation, the transfer material S is transported by the transport belt B, images of each color are sequentially transferred, and then separated from the transport belt B by the curvature separation of the driving roller 6,
It is sent to the fixing device 4. Further, the transfer material S undergoes image fixing by the fixing device 4, and is discharged onto the tray 5.

By the way, in this embodiment, in order to prevent the image disturbance due to the deviation during the transfer of the transfer material S, each photosensitive drum is
The peripheral speed Vd of D _{1 to} D ₄ and the transfer speed Vb of the transfer belt B are
Each drive motor (not shown) so as to satisfy the relationship of Vd ≦ Vb
Drive speed is set in advance. In this case, Vd and Vb are 1,0
It is desirable to set the range of 00Vd <Vb ≦ 1,005Vd.

That is, with such a configuration, when the conveyor belt B is attracted to each of the photosensitive drums D _{1 to} D ₄ by electrostatic attraction at the time of image transfer in each of the image forming units A _{1 to} A ₄ , At the transfer position, the conveyor belt B is the photosensitive drum D ₁
~D is moving faster than _4, for better frictional driving force by the drive roller 6 than the conveying force by the electrostatic attraction force is large, the arrow P direction opposite force acts on the conveyor belt B, the driving roller 6 A force in the direction opposite to the rotation direction acts on the. Therefore, the tension roller 9 does not move, and the conveyor belt B does not have a remainder.
The slack of the belt B above is prevented.

As a result, the conveyor belt B is always stably conveyed by the driving force of the driving roller 6, and the transfer material S can be transferred at a constant speed at the transfer portion of each of the image forming units A _{1 to} A ₄ , resulting in an image shift. It is possible to prevent the occurrence of defective images such as.

Further, since it is possible to prevent the slack of the conveyor belt B between the image forming means A _{1 to} A _4, it is possible to obtain a good image output without a color shift without causing a position shift of the transfer image at each transfer portion. be able to.

In the present embodiment, in order to set the transport speed Vb of the transport belt B and the peripheral speed Vd of the photosensitive drums D _{1 to} D ₄ to Vb ≧ Vd,
Although the driving roller 6 and the motors for driving the photosensitive drums D _{1 to} D ₄ are separately provided and individually controlled, the present invention is not limited to this, and the same driving source and gear are used. The conveyor belt B and the photosensitive drums D _{1 to} D ₄ may be driven so as to satisfy the above relationship by changing the reduction ratio. Further, the transport speed Vb of the belt B may be adjusted by selecting the diameter of the drive roller 6 that drives the transport belt B.

When FIG. 2 show another embodiment of the image forming apparatus according to the present invention, the in embodiments the same parts will be denoted by the same reference numerals, the present embodiment, the photosensitive drum D ₁ instead of to D ₄ is that it uses a belt-shaped photoreceptor differs from the previous examples. That is, in this embodiment, each image forming unit
At the positions of the photosensitive drums D _{1 to} D ₄ of A _{1 to} A ₄ , photosensitive belts 81, 82, 83, 84 wound around a plurality of rollers are provided,
Each of the photosensitive belts 81 to 84 has an endless belt-shaped base material coated with a photosensitive member. Then, a laser beam corresponding to each color is emitted from each of the scanners 11 to 14 onto each of the photosensitive belts 81 to 84, and an image is formed through the same process as in the above embodiment. In this case, the relationship between the moving speed Vd of each of the photosensitive belts 81 to 84 and the conveyor belt Vb is set so that Vd ≦ Vb.

By using such photosensitive belts 81 to 84, the process elements of the image forming units A _{1 to} A ₄ can be arranged relatively freely, and the backup rollers 91 to
Since 94 does not require a large-diameter roller, the length of the apparatus main body in the width direction can be shortened as compared with the one using a photosensitive drum.

In the present embodiment having the above configuration, each photosensitive belt
The moving speed Vd of 81 to 84 and the carrying speed Vb of the carrying belt B are
By setting so as to satisfy the relationship of Vd ≦ Vb, the transfer material S can be stably conveyed as in the above embodiment, and the photosensitive belts 81 to 84 are prevented from sagging on the downstream side with respect to the conveyor belt B. can do. The rest of the configuration and operation are the same as in the above-mentioned embodiment, so the explanation is omitted.

In each of the above-described embodiments, the four-color image forming apparatus using the laser scanner has been described as an example, but the present invention is not limited to this, and a so-called analog type copying machine or image carrier is used. It is needless to say that the present invention can be applied to devices other than four.

(Effects of the Invention) In the present invention having the above-described configuration and operation, since the moving speed Vd of the image carrier and the transport speed Vb of the transport unit are set so that Vd ≦ Vb, The transfer image is prevented from being disturbed due to the slack of the conveying means to form a high-quality image, and the transfer material is not deflected in the direction of winding around the image carrier, and the jam occurs when the transfer material winds around the image carrier. There is an effect that can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a vertical sectional view showing a schematic configuration of another embodiment of the present invention, and FIG. FIG. 4 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a conventional example, and FIG. 4 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to another conventional example. Explanation of reference numerals 6 ... Driving roller (driving means) 11,12,13,14 ... Scanner 41,42,43,44 ... Transfer charger A ₁ , A ₂ , A ₃ , A ₄ ... Image forming means B ... Conveyor belt (Conveying means) D ₁ , D ₂ , D ₃ , D ₄ ... Photosensitive drum (image carrier) S ... Transfer material

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasushi Murayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Yoshihiko Hirose 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Kunihiko Matsuzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP 62-161156 (JP, A) JP 62-242965 (JP) , A) Japanese Patent Laid-Open No. 63-12569 (JP, A)

Claims (3)

[Claims] 1. An image forming apparatus for transferring an image carried by a moving image carrier onto a transfer material carried by a belt-like carrying means moving in the same direction as the image carrier, said image carrying device comprising: An image forming apparatus, wherein Vd ≦ Vb is set, where Vd is a moving speed and Vb is a moving speed of the conveying unit. 2. The moving speed Vd of the image carrier and the moving speed Vb of the conveying means are set so as to satisfy Vd ≦ Vb ≦ 1.005Vd. Image forming apparatus. 3. A structure in which images carried by a plurality of image carriers moving in the same direction are successively transferred onto a transfer material carried by a belt-shaped carrying means moving in the same direction as the image carriers. The image forming apparatus according to claim 1 or 2.