JPS6051101B2 - Photoreceptor drum drive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive drum driving device.

Generally, in a device applying electrophotography such as an electrophotographic copying device, a photoreceptor having a photoconductive layer is formed in the shape of a drum, and as the photoreceptor is rotated, an electrostatic layer corresponding to the original is formed on the surface of the photoreceptor. form an image.

Therefore, a drive motor is used not only to rotate the photoreceptor but also to move the document table or the exposure optical system. In a conventional electrophotographic copying apparatus, a single drive motor is used to rotate the photosensitive drum and move the exposure optical system. By the way, the circumferential speed of the photoreceptor drum and the moving speed of the exposure optical system must move at the same speed and in synchronization. If they are not synchronized, jitter will occur in the image on the photoreceptor drum. , the image quality will deteriorate significantly. In this type of system that uses a single drive source, various parts such as chains, gears, and sprockets are used as drive transmission means, and the accuracy of these parts cannot be made very high. It was extremely difficult to synchronize. On the other hand, for the purpose of downsizing electrophotographic copying devices, Japanese Patent Laid-Open No. 54-67437 discloses a method in which a drive motor is disposed inside a photoreceptor drum and the photoreceptor drum is rotationally driven by this drive motor. proposed by.

In such a system, the photoconductor drum can be rotated by a drive motor inside the photoconductor drum, and the document table or the exposure optical system can be driven independently by another drive motor, but the above-mentioned drive system It is undesirable because it has the following disadvantages.

First, the fact that the drive motor is placed inside the photoreceptor drum limits the size of the drive motor itself, making it difficult to make the motor multi-phase, and the photoreceptor drum is driven using a mechanical deceleration mechanism. .

Therefore, since gears, sprockets, chains, etc. are used, speed non-uniformity occurs, which leads to deterioration of image quality due to occurrence of jitter, etc. In addition, because the drive motor is placed inside the photoreceptor drum and there are restrictions on the size of the motor, there is no margin for motor torque even though large torque is required to drive the photoreceptor drum. Therefore, the temperature inside the photoreceptor drum increases due to the heat generated by the motor.

As a result, the temperature of the surface of the photoreceptor also increases, resulting in image unevenness and unstable images. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a novel photosensitive drum drive device that directly drives a photosensitive drum.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an electrophotographic copying machine to which the present invention can be applied.

In the figure, reference numeral 1 indicates a photosensitive drum, which has a photosensitive layer on its surface and rotates counterclockwise. Photosensitive drum 1
First, it is uniformly charged by the charging device 2 and reaches the exposed area. Then, the slit exposure optical system 3 irradiates a light image of the document on the document table 4 to form an electrostatic latent image on the photoreceptor drum 1. The slit exposure optical system 3 includes a first reflecting mirror 5 that moves in the direction of the arrow a parallel to the original platen 4 at a speed V, and a first reflecting mirror 5 that moves in the same direction as the first reflecting mirror 5 at a half speed X.
It is composed of a second reflecting mirror 6 that moves synchronously with each other, an in-mirror lens 7, a fixed reflecting mirror 8, and an illumination lamp (not shown). This slit exposure optical system 3 is reciprocated by a drive device (not shown). The electrostatic latent image thus formed is visualized by the developing device 9. Then, the transfer paper sent from the paper feeding device 10 comes into contact with the photoreceptor drum 1 at the transfer section, and the visible image on the photoreceptor drum 1 is transferred onto the transfer paper by the transfer device 11. Next, the charge on the transfer paper is removed from the surface of the transfer paper by the charge removal/separation device 12, thereby separating the transfer paper from the photoreceptor drum 1. This transfer paper is sent out to a paper discharge tray (not shown) via the fixing device 13. On the other hand, after residual developer is removed from the photosensitive drum 1 by the cleaning device 14, unnecessary charges are removed by the static eliminator 15, and the above series of copying cycles is repeated again. In the embodiment shown below, the photosensitive drum of a copying machine using the photosensitive drum as described above is directly driven.

FIG. 2 shows an embodiment of the present invention.

In the figure, reference numerals 16 and 17 are frames of the copying machine, and the rotation shaft 18 of the photoreceptor drum 1 is attached to the frames 16 and 17.
is rotatably supported by bearings 19 and 20.
The photosensitive drum 1 has a rotor 21 fitted to one end thereof and a flange 22 fitted to the other end thereof, and the rotating shaft 18
It rotates as one. This rotor 21 is configured as a rotor of a motor, as will be described later, and also has a function as a flange. A stator 23 is fixed to a support member 24 attached to the frame 16 on the outer periphery of the rotor 21 and spaced apart from it by a predetermined distance.
The stator 23 is composed of a stator core 25 and a stator winding 26. This stator core 25 and stator winding 2
6 is multi-phase, and when a power source is connected to the stator winding 26, the rotor 21 rotates in a fixed direction. Generally, the outer diameter of the photoreceptor drum 1 is relatively large, and it is easy to make the stator 23 multi-phase.

Therefore, it is possible to provide the photosensitive drum 1 with the required rotational speed without providing a special mechanical speed reduction mechanism. Therefore, speed unevenness caused by mechanisms such as gears, sprockets, chains, etc. does not occur, and smooth rotation can be performed. FIG. 3 is an enlarged sectional view of the photosensitive drum driving device shown in FIG. 2 above.

In the figure, the photosensitive drum 1 is composed of a cylindrical aluminum drum 27, and a rotor 21 is fitted into one end thereof. This rotor 21 consists of a flange-shaped aluminum die-cast 28 fitted to the end of the aluminum drum 27, and a rotor made of a magnetic material embedded in the aluminum die-cast 28 at intervals. It is composed of an iron core 29. As mentioned above, the fixed core 25 and the stator winding 26 are multiphase, and when an AC power source (not shown) is connected, a rotating magnetic field is formed therein, and the rotor 2
1 is rotated in a fixed direction by the rotating magnetic field.
In this case, if the rotor is a hysteresis ring made of permanent magnets, the hysteresis ring is magnetized by the rotating magnetic field of the stator, and rotation in synchronization with the rotating magnetic field can also be obtained. In this example, the photoreceptor drum is rotationally driven using an AC power supply, but it is also possible to have a structure in which the rotor can rotate in the same way even if a DC power supply is connected to the stator winding. Easy to configure.

That is, if the rotor is composed of a permanent magnet and magnetized in advance, the photosensitive drum can be rotationally driven even by a DC power source. In another embodiment, the rotor core is formed with a large number of salient poles, the stator core is also formed with corresponding salient poles and windings, and this is connected to a power source. This allows the photosensitive drum to be driven to rotate.

The rotational speed of the photosensitive drum 1 is set in advance so that its circumferential speed is the same as the moving speed (2) of the first reflecting mirror 5 of the slit exposure optical system 3. As described above, a large torque is required to drive the photoreceptor drum, but since the diameter of the rotor can be made large, the required torque can be easily obtained.

Therefore, since the photoreceptor drum can be directly driven, a mechanical deceleration mechanism is not required, and smooth rotation without speed unevenness can be achieved. In addition, as the required torque can be easily obtained as mentioned above, there is less heat generation from the drive device, and since the rotor, stator core, stator winding, etc. are built outside the photoreceptor drum, the cooling effect is low. Therefore, there is no adverse effect on the photosensitive layer of the photosensitive drum due to heat generation, and good image quality can be maintained.
Of course, there is almost no jitter in the image due to speed unevenness. There is a concern that the magnetic field generated by the rotor 21 and the stator 23 may have an adverse effect on the magnetic brush in the developing device 9 and the developer on the photoreceptor drum. However, since the rotor and stator are provided at the end of the photoreceptor drum, that is, at a position away from the image forming area, the magnetic field generated by them has almost no adverse effect. However, if the rotor and the image forming area must be brought close to each other in order to reduce the size of the apparatus, it is necessary to cut off the influence of the magnetic field. A person skilled in the art can easily implement the magnetic seal means for blocking the magnetic field and the means for preventing developer from entering the rotor or stator, and if necessary, one with an appropriate configuration can be selected. Ru.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an electrophotographic copying machine, Fig. 2 is a side view of a photosensitive drum drive device showing an embodiment of the present invention, and Fig. 3 is a partial side view with only the main parts of the drive device enlarged. FIG. 1... Photosensitive drum, 3... Slit exposure optical system, 18... Rotating shaft, 21...
- Rotor, 23... Stator, 25... Stator core, 26... Stator winding wire, 29... Rotor core.

Claims (1)

[Claims] 1. A photoreceptor drum on which an electrostatic latent image is formed, a rotor formed at one end of the photoreceptor drum, and a multi-phase fixing device arranged around the rotor at a predetermined distance. A photoreceptor drum driving device having a stator comprising an iron core and a stator winding, the photoreceptor drum being directly driven by the stator.