JPH026971A - Color image forming device - Google Patents

Abstract

PURPOSE:To achieve excellent copying by connecting plural transfer rollers to a rotary driving system and providing the system with a transmission system which synchronizes both transfer rollers and sets their mutual, relative rotational speed at almost zero. CONSTITUTION:When a motor 7 is activated, a transmission shaft 8 rotates with the aid of a driving gear 7a and an intermediate gear 8a, and the rotation is transmitted from operational gears 8b and 8c to flat gears 2a and 3a to rotate a transfer drum 1. At this time, transfer rollers 2 and 3 on both sides of the transfer drum 1 are rotated and driven, and ultimately they rotate synchronously. As a result, rotation of the same power is loaded to both sides of a transfer material 4 located inbetween, and therefore it rotates without being twisted. Consequently, fed paper passes transfer stages with the same posture, whereby copying free from color slippage and transfer error is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image forming apparatus for obtaining clear color images without color shift.

[Conventional technology]

2. Description of the Related Art As a color image forming apparatus, a tandem type apparatus has been generally used. In this tandem type color image forming apparatus, the leading edge of the paper is folded with a gripper and the image forming unit is bussed, so the trailing edge of the paper becomes a free edge, so the entire paper can be held in a --like position. It was difficult to transport the

To solve this problem, in recent years, image forming units have been arranged around a large transfer drum, as shown in Figure 3, in order to convey the paper while holding it in a negative position. It became so.

In the figure, there is a large transfer drum 5 inside the copying machine main body.
0 is provided, and yellow, magenta, cyan, and black image forming units 51 to 54 are arranged around it. These image forming units 51 to 54 include photoreceptors a,
Optical system, charger C, cleaning device d, and developing device e
The transfer drum 50 is further provided with a transfer device f for charging the paper and transferring the image on the photoreceptor a. Further, the paper P stored in the tray 55 is transferred from the feed roll 55a to the registration roll 56.
Its leading edge is held between the two, waiting for the start of the pass to the transfer process. Then, upon receiving a signal to start copying, the paper P is sent toward the transfer drum 50 and passes while being restrained and guided by the gripper 57.

Here, it is necessary to adsorb the paper P heading for the transfer process to the peripheral surface of the transfer drum 50, and the paper P is charged by the paper charger 58 before entering the image forming unit. Also, the paper P is attracted to the circumferential surface of the transfer drum 50 during transfer by the transfer device ff. Note that each image forming unit) 51
The paper P that has passed through 54 has its charge removed by a peeling static eliminator 59, is peeled from the peripheral surface of the transfer drum 50, is fixed by a fuse roller 60, and is then discharged to a paper discharge tray 61.

[Problem to be solved by the invention]

In the transfer process in which the paper P is passed along the circumferential surface of the transfer drum 50 as described above, a transfer material such as mesh or Mylar is provided on the circumferential surface of the transfer drum 50 in order to electrostatically attract and transfer the paper. is necessary.

FIG. 4 is a schematic vertical cross-sectional view of the transfer drum 50, in which transfer rollers 50a and 50b are arranged at both ends, and a transfer material 50c made of cylindrical mesh, Mylar, or the like is integrated between these rollers. Transfer roller 50a.

50b has its shaft portion supported by a bearing 50d, and rotational force is transmitted to one transfer roller 50a from a drive device 50e such as an electric motor. This rotational force is transmitted by using a chain, a belt, or the like, or by providing gears on the peripheral surface of the transfer roller 50a and arranging a gear train between the transfer roller 50a and the drive device.

However, the transfer roller 5 on one side from the drive device 50e
When rotation is transmitted to 0a, the transfer material 50C is not a completely rigid body, so it is twisted in the direction of rotation. In other words, no external driving force acts on the other transfer roller 50b, and the transfer roller 50C on the driving side is easily bent.
Therefore, when torque is applied to one end of the transfer material 50C, the transfer material 50C is twisted in the same way as a torsion bar.

If the transfer material 50c of the transfer drum 50 is twisted in this way, the uniformity of the posture of the paper P passing over the circumferential surface will be disrupted. This causes color misregistration and transfer errors in color images, resulting in problems with good image formation.

Further, in such a transfer drum 50, a beam portion is provided between the transfer rollers 5Qa and 50b at both ends constituting the drum to connect them, so that the transfer drum 50 is rotated integrally. . However, due to the presence of this beam, the paper charger 58 shown in FIG.
Even if it is charged by , this part will not be charged and the paper will not be attracted. Therefore, paper must be sucked while avoiding the beam part, and even when paper P of various sizes is used, the printing speed must be unified to the speed when using the maximum size paper, that is, a low speed. There is a need.

For this reason, there is a problem in that the printing speed of the apparatus as a whole becomes slow.

Therefore, an object of the present invention is to obtain a good color image by preventing twisting or other deformation from occurring in the transfer material. Another purpose is to eliminate the need for a beam portion of the transfer drum and to be able to set the optimum printing speed for each paper size.

[Means to solve the problem]

In order to achieve the above object, the color image forming apparatus of the present invention includes a transfer drum having transfer rollers at both ends and a cylindrical transfer material disposed coaxially therebetween, and has a transfer drum arranged around the transfer drum. In an image forming apparatus in which one or more image forming units are arranged, both of the transfer rollers are connected to a rotational drive system, and the rotational drive system synchronizes both of the transfer rollers and reduces their relative rotational speed to approximately zero. It is characterized by having a transmission system.

[Effect]

In the color image forming apparatus of the present invention, the transfer rollers disposed at both ends of the transfer drum are rotated, respectively, and these transfer rollers are rotated synchronously and at the same speed. Therefore, the same torque acts on both ends of the transfer material located between the transfer rollers, and no torsional stress is generated in the direction in which the transfer material rotates.

〔Example〕

Hereinafter, features of the present invention will be specifically explained with reference to embodiments shown in the drawings.

FIG. 1 is a schematic vertical sectional view showing a transfer drum to be incorporated into an image forming apparatus of the present invention together with its drive system.

As shown in FIG. 3, the transfer drum 1 is rotatably incorporated into the main body of the copying machine with a plurality of image forming units arranged around its circumferential surface. As a whole, a pair of transfer rollers 2.3 are coaxially arranged at both left and right ends, as in the conventional example,
A cylindrical transfer material 4 such as mesh or mylar is integrated between these. A paper charger, a transfer device, etc. shown in FIG. 3 are arranged inside the transfer material 4, and perform electrostatic attraction of the fed paper and transfer from the photoreceptor.

The transfer rollers 2 and 3 have the same shape, and are cylindrical bodies of different diameters, with the side where the transfer material 4 is integrated being larger and the outer end smaller, as shown in FIG. Further, spur gears 2a and 3a are formed on the peripheral surface of the outer end, and the transfer rollers 2 and 3 are connected to the support member 6 of the copying machine main body via bearings 5 provided inside the small diameter portion.
Supported by

Further, an electric motor 7 for rotating the transfer drum 1 is disposed in the main body of the copying machine, and rotational force is transmitted through a gear train. That is, a transmission shaft 8 is provided parallel to the axis of the transfer drum l, a driving gear 7a provided on the output shaft of the electric motor 7 is meshed with an intermediate gear 8a provided on one end of the transmission shaft 8, and an operating gear of the transmission shaft 8 is meshed with an intermediate gear 8a provided on one end of the transmission shaft 8. 3b and 3c are spur gears 2 of transfer rollers 2 and 3, respectively.
Provide a drive system that meshes with a and 3a.

In such a drive system, it is necessary to set the arrangement of each member with high precision so that the transfer drum l rotates appropriately. For this reason, the transmission shaft 8 is installed so as to be exactly parallel to the axis of the transfer drum 1 by means of a bearing or the like (not shown), and is also provided with operating gears 8b, 8c and a spur gear 2a.
, Select gears such as Modineal to reduce backlash when meshing with 3a. Further, when the two transfer rollers 2.3 are rotated simultaneously from the transmission shaft 8, the rotation angles of these transfer rollers 2.3 per unit time are also configured to be the same. In other words, the operating gear 3b, ge
By transmitting the rotational force from the transfer rollers 2 and 3, the transfer rollers 2 and 3 rotate synchronously, so that no phase difference occurs between them.

As a result, when the transfer drum I rotates, the rotational deviation between the transfer rollers 2 and 3 is prevented from occurring, and the relative rotational speed between the two is brought to zero, thereby preventing twisting of the transfer material 4 in the rotational direction. prevent.

The transfer drum 1 has a structure in which transfer rollers 2 and 3 are arranged at both ends and the transfer material 4 is wound between them. Incidentally, in order to facilitate the attachment and detachment of the transfer rollers 2 and 3 from the main body of the machine, a stay 1a as shown in FIG. 1 may be provided. The stays 1a connect the transfer rollers 2.3, and the number of stays 1a may be as long as it can provide appropriate strength.

Providing such a stay 1a means that the transfer rollers 2 and 3, which are located apart from each other, are integrated, so that the transfer rollers 2 and 3 can be easily handled when being attached and detached. Note that this stay 1a is attached only when the transfer rollers 2 and 3 are attached and detached, and is removed during normal operation.

In the above configuration, when the electric motor 7 is operated, the transmission shaft 8 is rotated by the driving gear 7a and the intermediate gear 8a, and the rotation is transmitted from the operating gears 8b and 8c to the spur gears 2a and 3a, and the transfer drum 1 is rotated. At this time, the transfer rollers 2 and 3 at both ends of the transfer drum 1 are driven to rotate, and these rotate synchronously.

Therefore, since the same rotational force is applied to both ends of the transfer material 4 located in the middle, the transfer material 4 rotates without twisting. For this reason, the supplied paper passes through the transfer process in a --like posture, making it possible to copy without color misregistration or transfer errors.

Furthermore, since the beam portion that was conventionally required is no longer necessary, it becomes possible to attract the paper over the entire circumference of the transfer drum l. That is, since there is no restriction on the paper suction position, the optimum printing speed can be set for each paper size.

For example, in the case of small-sized sheets, by arranging a large number of sheets on the transfer drum 1, the printing speed of the entire apparatus can be increased.

In the embodiment, two transfer rollers 2 are connected by a gear train.
．． Although the transfer rollers 2 and 3 are rotationally driven,
Other drive systems can also be used as long as they rotate synchronously. For example, the electric motor 70 rotations are driven by a chain, a timing belt, a flat belt, and a V-belt. It is also oil-free that helical gears, worms, etc. can be used in place of the spur gears 2a and 3a of the gear train.

Furthermore, in FIG. 2, transfer rollers 2, 3 and spur gears 2a, 3
Although a is integrally formed, these can also be made into separate bodies.

Further, in the above embodiment, four image forming units are arranged around the transfer drum 1, but it is clear that the effects of the present invention can be obtained even when only one image forming unit is arranged. .

〔Effect of the invention〕

As explained above, in the color image forming apparatus of the present invention, both of the transfer rollers provided at both ends of the transfer drum are rotated synchronously by the rotation drive system, so that the relative rotational speed of these transfer rollers becomes zero. I have to. Therefore, compared to the conventional case where only one transfer roller is driven to rotate, the transfer material such as a flexible material placed between the transfer rollers is not twisted in the rotation direction. Therefore, the supplied paper always passes through the transfer process in a negative position, and it is possible to obtain a good copy image without color shift or transfer errors.

Furthermore, since there is no beam part of the transfer drum, there are no restrictions on the paper suction position, and the optimum printing speed can be set for each paper size.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal cross-sectional view showing a transfer drum together with its drive system, showing one embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view of a transfer roller, and FIG. 3 is a schematic side view of a transfer drum-type multiple transfer device. 4 are schematic diagrams showing a conventional transfer drum and its drive system. l: Transfer drum 1a Nisty 2: Transfer roller 2a: Spur gear 3: Transfer roller 3a: Spur gear 4: Transfer material 5: Bearing 6: Support member 7: Electric motor 7a: 8a: 50: 51° 55 = 56: 58: 60: a: C: e: P: Drive gear 8: Transmission shaft intermediate gear 3b, 3c: Operating gear transfer drum (conventional example) 52, 53.54: Image forming unit tray
55a: Feed roll resist roll 57: Gripper paper charger 59: Peeling static eliminator fuser roll 61: Paper discharge tray photoreceptor b: Optical system charger d: Cleaning device developer
f: Transfer device paper

Claims (1)

[Claims] 1. An image forming apparatus comprising a transfer drum having transfer rollers at both ends and a cylindrical transfer material coaxially arranged therebetween, and one or more image forming units disposed around the transfer drum. A color image forming apparatus, characterized in that both of the transfer rollers are connected to a rotational drive system, and the rotational drive system has a transmission system that synchronizes both of the transfer rollers and makes their relative rotational speeds approximately zero.