JPS63271388A - Image forming device - Google Patents

Abstract

PURPOSE:To surely remove high-frequency abnormal noises uncomfortable to the ears so that a silent operation can be made by inserting a vibration damping member such as foamed urethane into a photosensitive drum in contact with wit the inside wall surface of the photosensitive drum. CONSTITUTION:The vibration damping member 11 such as foamed polyurethane is provided on the photosensitive drum 1 in contact with the inside wall surface of the drum 1. The abnormal noises uncomfortable to the ears are generated when the friction force acting between the drum 1 and a cleaning blade is negative attenuation. If, however, the vibration damping member such as foamed polyurethane is inserted into the photosensitive drum in contact with the inside wall surface thereof, the member 11 oscillates with the inside wall of the drum 1 tending to oscillate and imparts positive attenuation to the drum 1 and, therefore, the oscillation beginning to be generated in the drum is sharply attenuated. The self-excitated oscillation is eventually not generated and the abnormal noises are thoroughly prevented.

Description

[Detailed Description of the Invention] rObject of the Invention] (Industrial Application Field) The present invention relates to image forming apparatuses such as laser printers and electronic copying machines, and particularly relates to image forming apparatuses such as laser printers and electronic copying machines, and in particular to the development of a developing image remaining on the surface of a photosensitive drum after image transfer. The present invention relates to an image forming apparatus including a cleaning device that scrapes off toner with a cleaning blade.

(Prior Art) In image forming apparatuses such as laser printers and electronic copying machines, photoconductors are used as printing media. This photoconductor is applied to the outer peripheral surface of a cylindrical photosensitive drum made of a conductor such as aluminum.

Taking a laser printer as an example, the printing process will be described. First, the photoconductor is uniformly charged. For example, in the case of an organic photoconductor (OPC)
Charging is performed to a negative potential of 00V. Next, line scanning is performed while turning the laser beam on and off in accordance with the printed dot data, and by sending the photoconductor at a constant speed in a direction perpendicular to this line scanning, two-dimensional light is produced on the photoconductor. form an image. This two-dimensional optical image is an electrostatic latent image in which the charged potential of the portion irradiated with the laser beam is reduced.

A charged developer (toner) is then contacted onto the surface of the photoconductor. For example, when a developer of the same polarity as the electrostatic potential on the photoconductor is brought into contact, the developer will adhere to the de-charged areas of the photoconductor.

Such a development process forms a visible developer image on the surface of the photoconductor.

Thereafter, a sheet of paper is applied to the front surface of the photoconductor, and a potential opposite to the charged potential of the developer is applied from the back side of the sheet to transfer the developer on the photoconductor to the sheet of paper. Then, heat or pressure is applied to the developer image transferred to the paper to fix the image on the paper. The developer remaining on the photoconductor without being transferred to the paper is scraped off and cleaned by a cleaning blade brought into contact with the photoconductor, and the process returns to the charging step again.

In this way, image forming devices such as laser printers perform printing through charging, exposure, development, fixing, and cleaning processes, so compared to impact printers, they can print arbitrary characters, graphics, etc. faster and with higher quality. It has the characteristics of being able to print with low noise.

(Problem to be Solved by the Invention) However, although such image forming apparatuses are capable of low-noise operation in principle, they have the disadvantage that they sometimes generate abnormal high-frequency noise that is very harsh to the ears. . This noise usually has a clear ``chee'' tone and is caused by other mechanical noises, such as motors, gears, paper feed, etc. No effective countermeasures have been taken, and there has been a strong desire to reduce or even eliminate such abnormal noise. The present invention has been made in view of these points, and it is an object of the present invention to provide an image forming apparatus that can effectively remove abnormal high-frequency noise using simple means. .

[Structure of the Invention] (Means for Solving the Problem) The present inventor has discovered that abnormal high-frequency noise in an image forming apparatus such as a laser printer can cause friction between the photosensitive drum and the cleaning blade during the cleaning process. It was discovered that self-excited vibration occurs in the photosensitive drum due to the force, and that the sound of this self-excited vibration is abnormal high-frequency noise. Such a vibration system is a torsional vibration of the photosensitive drum, and its vibration mode is an even-order mode. This is related to the fact that the photosensitive drum is a thin cylinder with flanged structures at both ends, and a frictional force uniformly distributed in the axial direction acts on the cylindrical surface in the circumferential direction. In this case, energy tends to enter the photosensitive drum in even-order mode torsional vibration, and furthermore, when the frictional force acting on it has negative damping, that is, when the first derivative number of friction with respect to the sliding speed is negative. The present inventor has discovered that this frictional force becomes the limit of energy supply, and that self-excited vibration occurs in the even-order mode of torsional vibration in the photosensitive drum as described above. Since the vibration frequency is in the audible frequency range, it becomes noise.

Therefore, in the present invention, a vibration damping member such as foamed polyurethane is provided inside the photosensitive drum in contact with the inner wall surface of the photosensitive drum.

(Function) When the frictional force acting between the photosensitive drum and the cleaning blade is negatively damped, self-excited vibration occurs due to even-order torsional vibration in which energy easily enters the photosensitive drum as described above, causing an emergency. However, if a vibration damping member such as foamed polyurethane is inserted into the photosensitive drum in contact with the inner wall surface of the photosensitive drum, this vibration damping member may slide against the inner wall of the photosensitive drum that is about to vibrate. However, positive damping is applied to the photosensitive drum, so that vibrations that are about to occur in the photosensitive drum are rapidly attenuated, and as a result, self-excited vibrations do not occur, and abnormal noise is fundamentally prevented.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 denotes a photosensitive drum, and around this photosensitive drum 1, a charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a peeling device 6, and an afterimage erasing device 7 are arranged in the direction of rotation of the photosensitive drum 1. They are arranged sequentially. The cleaning device 7 has a cleaning blade 9 that comes into contact with the circumferential surface of the photosensitive drum 1, and due to this contact, the developer remaining on the surface of the photosensitive drum 1 is removed as the photosensitive drum 1 rotates. It is scraped off and cleaned.

The photosensitive drum 1 is formed into a cylindrical shape as shown in FIGS. 1 and 2, and a driving gear 10 is attached to one end of the photosensitive drum 1. A driving force from a driving source (not shown) is applied to the driving gear 10. The above-mentioned photoconductor is uniformly applied to the outer peripheral surface of the photosensitive drum 1. A vibration damping member 11 is provided inside the photosensitive drum 1 in contact with the inner wall surface of the photosensitive drum 1. This damping member 11 is made of polyurethane foam, for example. The damping member 11 may be provided over the entire length of the photosensitive drum 1 or may be provided on a portion of the entire length.

Therefore, during the cleaning process of the photosensitive drum 1, if the frictional force acting between the photosensitive drum 1 and the cleaning blade 9 is negatively damped, as described above, energy is likely to enter the photosensitive drum 1 at an even-numbered order. Self-excited vibration occurs due to torsional vibration, which generates extremely harsh and abnormal noise.

However, in the present invention in which a vibration damping member 11 made of foamed polyurethane or the like is inserted into the photosensitive drum 1, when the photosensitive drum 1 tries to vibrate, the vibration damping member 11 slides on the inner wall of the photosensitive drum 1. Positive damping is applied to the photosensitive drum 1, and as a result, vibrations that begin to occur in the photosensitive drum 1 are rapidly attenuated, so that self-excited vibrations do not occur, and abnormal noise can be fundamentally prevented.

A photosensitive drum in which a vibration damping member 11 is not inserted].

When we analyzed the frequency of the sound generated during the cleaning process, we found that the frequency was 10 as shown in Figure 4(a).
．． Abnormal high frequency noise of 65KHz occurred. On the other hand, in the case of the photosensitive drum 1 with the vibration damping member 11 inserted inside, the frequency is 10.65 KHz, as shown in FIG.
No abnormal noise was generated and it was completely eliminated.

[Effects of the Invention] As explained above, according to the present invention, a vibration damping member such as foamed urethane is inserted into the inside of the photosensitive drum in contact with the inner wall surface of the photosensitive drum. This has the effect of reliably removing abnormal noise and achieving quiet operation.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a sectional view of a photosensitive drum, FIG. 2 is a perspective view of the same, FIG. 3 is a sectional view of the main parts of a laser printer, and FIG. It is an analysis diagram. 1... Photosensitive drum, 7... Cleaning device, 9...
... Cleaning blade, 11... Vibration damping member. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (4)

[Claims] (1) In an image forming apparatus that has a process of applying a developer to a photosensitive drum to form a desired image, and a process of transferring the image formed in this process to a recording material, the inside of the photosensitive drum is An image forming apparatus characterized in that a vibration damping member is provided in contact with an inner wall surface of the photosensitive drum. (2) The image forming apparatus according to claim 1, wherein the braking member is provided over the entire length of the photosensitive drum. (3) The image forming apparatus according to claim 1, wherein the braking member is provided at a portion of the entire length of the photosensitive drum. (4) The image forming apparatus according to claim 1, 2, or 3, wherein the vibration damping member is made of polyurethane foam.