JPH11295951A - Driving device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make setting of inertia mass possible to be arranged for preventing rotary unevenness amplification of a driving motor, in the case of using as plural independent driving devices at plural driving speed in an image forming device, and to enable reducing such as the number of components. SOLUTION: By this image forming device of such as a copying machine performing record of the image by forming the image on a photoreceptor 1 in repeating respective processing stage of electrifying, writing, developing, transferring, cleaning, discharging or the like, and transferring the image on a paper sheet, in the case of using as the plural independent driving devices at the plural driving speed, the rotary speed of the driving motor 10 is made to coincide with the rotary speed of the higher speed side by changing the number of gear teeth on the output gear 13 of the driving motor 10 provided with the least teeth number.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to charging, writing,
Copiers, printers, facsimile machines, printing machines, etc. that form images on the image carrier by repeating the steps of development, transfer, cleaning, charge removal, etc., and sequentially transfer and fix the images on paper to record on paper The present invention also relates to a driving device of an image forming apparatus applicable to a photoconductor driving unit of an image forming apparatus such as a multifunction peripheral.

[0002]

2. Description of the Related Art In order to reduce costs by suppressing an increase in the number of parts, two or more types of image forming apparatuses having different copy and print speeds are designed using the same drive system structure. It shall be. At this time, for example, assuming that the paper feed speed is 200 mm / sec, the rotation speed of the drive motor is 1500 rpm, and the paper feed speed is 240 mm / sec.
Seconds, the rotation speed of the drive motor is 1800 rpm (= 1
(500 rpm × 240/200). On the other hand, the drive motor has one rotation unevenness per one rotation,
The rotation unevenness frequency (speed fluctuation frequency) is also 25 Hz (=
1500 rpm / 60 seconds), 30 Hz (= 1800 rpm)
m / 60 seconds).

The photoreceptor receives a direct force from a drive path for transmitting a driving force and an indirect force from a portion contacting the photoreceptor such as a transfer belt, a charging roller, or a transfer paper. Rotation tends to be uneven. The frequency of the rotation unevenness is often about 20 to 150 Hz, and the pitch of the unevenness becomes 2 to 10 mm when converted into a pitch. In particular, a pitch of 2 to 5 mm is very sensitive to human vision, and becomes more noticeable when generated on an image.

[0004] When the flywheel is mounted, the rotation unevenness frequency characteristic of the photoreceptor moves to a lower frequency side within the range of 20 to 150 Hz. No longer appear. on the other hand,
As the frequency characteristic moves to the lower frequency side, the uneven rotation at 25 Hz and 30 Hz of the drive motor described above is amplified. Therefore, it is necessary to take measures to prevent this amplification.

When the same drive system structure is used, it is necessary to increase the inertial mass of the flywheel so that the photosensitive member frequency characteristic is on the lower frequency side than any of the rotation unevenness frequencies of 25 Hz and 30 Hz. The inertial mass is enlarged so that the uneven frequency is not amplified. However, this results in excessive mass for the rotation unevenness frequency of 30 Hz, which leads to a significant increase in weight and cost. Further, when the inertial mass becomes excessive, an unfavorable state occurs in which the load on the drive motor increases, that is, the motor rise time increases, and the rush current to the motor increases.

Accordingly, the present invention makes it possible to greatly improve the above-mentioned problems with respect to load and cost by making the above-mentioned drive motor rotation speed at a paper feed speed of 200 mm / sec equal to the drive motor rotation speed at 240 mm / sec. It is an object of the present invention to provide a driving device for an image forming apparatus that can perform the above.

[0007]

According to a first aspect of the present invention, a drive motor for driving a photosensitive drum and the drive motor for driving a photosensitive drum are provided to achieve the above object. An image forming apparatus having a photosensitive drum gear train for transmitting the driving force of the photosensitive drum to the photosensitive drum, wherein the drive motor and the gear train have a driving unit connected thereto, and perform operations such as copying and printing. In a driving device used for two or more types of image forming apparatuses having different speeds,
It is characterized in that the number of rotations of each drive motor approaches one type.

According to a second aspect of the present invention, in order to make the rotation speeds of the drive motors of two or more types of image forming apparatuses having different operation speeds such as copying and printing the same or substantially the same, the driving motors have the same teeth. It is characterized in that the specifications of the output shaft of the drive motor having a small number and the first reduction gear meshing with the output shaft are changed so that the rotation speed reduction ratio of the drive motor is increased.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of an image forming apparatus to which a driving device according to the present invention is applied. The image forming apparatus shown here is configured as a copying machine, and a drum-shaped photosensitive member 1 as an example of an image carrier is rotatably supported by a frame of an image forming apparatus main body (not shown), and is driven by a driving device described later. In FIG. 1, it is driven to rotate clockwise. The surface of the photoconductor 1 is uniformly charged to a predetermined polarity by the charging device 2, and the charged surface is irradiated with the light-modulated laser light L emitted from the optical writing device 3, whereby the surface of the photoconductor 1 is irradiated. A predetermined electrostatic latent image is formed on the image. This electrostatic latent image is visualized by toner when passing through a position facing the developing device 4. On the other hand, a recording sheet P is fed from a sheet feeding device (not shown), and the recording sheet P is sent to a transfer position 6 at a predetermined timing by a pair of registration rollers 5, where a toner image on the photoconductor 1 is recorded. The image is transferred onto the sheet P. The recording paper P on which the toner image has been transferred is sent to a fixing device (not shown) by the transfer belt 7, where the toner image is fixed on the recording paper P. After the toner image is fixed, the recording paper P is discharged outside the apparatus and stacked on a discharge tray (not shown). Further, the transfer residual toner adhering to the surface of the photoconductor 1 after the transfer of the toner image is removed by the cleaning device 8, and the surface of the photoconductor 1 is cleaned. Thereafter, the surface of the photoreceptor 1 is subjected to a charge removing operation by light from the charge removing lamp 9.

FIG. 2 is a partial sectional view showing an example of a drive motor 10 for rotating the photosensitive member 1 and a drive unit for transmitting the rotation to the photosensitive member 1. FIG. It is a front view showing the arrangement state of. Drive motor 1
Numeral 0 is fixedly supported by a bracket 12 fixed to a frame 11 of the image forming apparatus main body, and an output gear 13 is meshed with a first reduction gear 14 made of resin. The first reduction gear 14 is rotatably supported by a shaft 15 fixed to the bracket 12 and meshes with a second gear 16 made of resin.
The second gear 16 is fixed to a shaft 17 rotatably supported on the bracket 12 via bearings. A timing pulley 18 is fixed to one end of the shaft 17 concentrically with the second gear 16. I have. This timing pulley 18
An endless timing belt 21 is wound around another timing pulley 19 fixed to a support shaft 22 for fixedly supporting the photoconductor 1. A flange 25 is fixed to the support shaft 22, and a flywheel 26 is fastened to the flange 25 with screws or the like. These photoreceptor 1 and support shaft 2
2. The timing pulley 19, the flange 25, and the flywheel 26 are arranged concentrically with each other.

One end of the support shaft 22 is rotatably supported by a photoconductor holder 24 via two bearings 23 (one of which is an energizing bearing and the photoconductor 1 is grounded from the support shaft 22). The holder 24 is fixed to the frame 11 of the image forming apparatus main body. The other end (not shown) of the support shaft 22 is also rotatably supported by the frame 11 via a bearing (not shown).

When the drive motor 10 operates and the output gear 13 rotates, the rotation is transmitted to the timing pulley 18 via the first and second gears 14, 16 and the shaft 17, and the rotation is transmitted to the timing belt. The light is transmitted to the photoconductor 1 via the timing pulley 19 and the support shaft 22, and the photoconductor 1 rotates clockwise in FIG.

Here, the inertial masses of the photoreceptor 1, the support shaft 22, the flange 25, and the flywheel 26 (hereinafter, referred to as a photosensitive system) are all added amounts. When the photoconductor 1 rotates, the value of the natural frequency of the rotation unevenness of the system is determined according to the magnitude of the inertial mass. The magnitude of the natural frequency decreases as the inertial mass increases, and increases as the inertial mass decreases. For example, assuming that the magnitude of the natural vibration of the photosensitive system is 20 Hz and only the photosensitive system is directly driven by an external force (assuming that there is no drive motor, belt, and gear), the rotational unevenness frequency component is as shown in FIG. Become like In FIG. 4, the horizontal axis represents the frequency, and the vertical axis represents the magnitude of the rotation unevenness frequency component of only the photosensitive system. As can be seen from FIG. 4, the frequency becomes higher or lower than 20 Hz depending on the magnitude of the inertial mass of the photoconductor, flywheel, or the like.

When the photosensitive member 1 is driven via the drive motor 10, the gears 13 to 16 and the timing belt 21 in such a drive system, the rotational unevenness frequency component is as shown in FIG. In FIG. 5, the number of rotations of the drive motor 10 is converted into a frequency, and the horizontal axis represents the frequency. The rotation unevenness component of the photoconductor 1 coincides with the natural frequency of the photosensitive system at a rotation frequency where the rotation frequency of the drive motor 10 is 20 Hz, that is, 1200 rpm (= 20 Hz × 60 sec), and is amplified to a maximum. Therefore, the rotation speed of the drive motor 10 is set to 12
It cannot be used as 00 rpm or a value very close to it.

Here, the rotational speed of the drive motor 10 is set to 25 Hz.
(1500 rpm) and 30 Hz (1800 rpm), and the magnitude of the rotation unevenness frequency component on the photoconductor 1 for each frequency (rotation speed) is compared.
When a motor 10 of 25 Hz (1500 rpm) close to z is used, the rotation unevenness component on the photoconductor 1 is amplified and increased. On the other hand, when the motor 10 having the rotation speed of 30 Hz (1800 rpm) is used, the amplification of the rotation unevenness component is small because the frequency is apart from 20 Hz.

As described above, when the number of rotations of the drive motor 10 is two or more, an inertial mass must be added (to reduce the thickness of the flywheel) in order to prevent rotation unevenness of the motor having a low rotation number. Therefore, the frequency of the drive motor 10 having a low rotation speed is made equal to that of the other drive motor 10 having a high rotation speed, so that the frequency of the drive motor 10 is reduced from the natural frequency of the photosensitive system. Separation and amplification of the rotation unevenness component can be reduced.

Next, a method for adjusting the number of rotations of the driving motor 10 in the driving device of the image forming apparatus according to the embodiment of the present invention will be described. The output gear 13 of the drive motor 10 is made of a metal such as S45C, but the first and second gears 14, 16 are made of a resin molded product as described above. The photoreceptor 1 constitutes one of the driven members that is driven to rotate through these gears 14 and 16. Further, in the driving device shown in FIG. 2, two gears 14 and 16 made of resin are provided. However, the driving device can be configured using one or three or more resin gears.

The distance between the shafts of the output gear 13 and the resin gear 14 is constant in two types of image forming apparatuses having different paper feed speeds. At present, the number of teeth of the output gear 13 of the drive motor at 1500 rpm and 1800 rpm is 12 teeth, which is the same.
If the number of teeth of the output gear 13 at 500 rpm is simply 10 teeth, the paper feed speed is reduced by 20% to 160 m / sec. Therefore, by increasing the rotation speed of the drive motor by 20% to 1800 rpm, the paper feed speed becomes 200 mm /
Hold seconds. Since the number of teeth of the output gear 13 is reduced by two (the number of teeth of the gear 14 remains the same), the distance between the shafts (the gear 1
In order to satisfy the condition that the distance between the center of the gear 3 and the center of the gear 14 is fixed, the gear specifications are modified. That is, since the number of teeth of the gear 13 is reduced, the transfer coefficient of the gear 13 is increased to the plus side. Also, the twist angle is increased by about 3 to 5 degrees (the optimum value is determined by the gear tooth ratio). Thereby, the rotation speed of the drive motor 10 can be changed. 20
If the speed is changed by about%, it is effective to change the number of teeth of the motor output gear 13 having the smallest number of teeth in the driving device.

[0019]

According to the driving device for an image forming apparatus according to the first aspect of the present invention, as described above, when used as two or more independent driving devices at two or more driving speeds,
By adjusting the rotation speed of the drive motor, especially the rotation speed on the high-speed side, the setting of the inertial mass for preventing motor rotation unevenness amplification can be arranged in one type, reducing the number of parts, the weight of the low-speed drive device, This has the effect of enabling cost reduction.

In the image forming apparatus driving apparatus according to the second aspect, as described above, in order to increase the rotation speed of the driving motor without changing the copying or printing speed,
Reduce the number of teeth on the drive motor output shaft with the least number of teeth,
By increasing the rotational speed reduction ratio of the drive motor, in addition to the above-described common effects, there is an effect that the number of changed parts can be suppressed to two or less.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an image forming apparatus to which a driving device according to the present invention is applied.

FIG. 2 is a partial cross-sectional view illustrating an example of a driving device including a driving motor that rotationally drives the photoconductor of FIG.

FIG. 3 is a front view showing an arrangement state of each element of the driving device of FIG. 2;

FIG. 4 is a diagram showing a relationship between the magnitude of a rotation unevenness component of only the photoconductor drive system shown in FIGS.

FIG. 5 is a diagram showing a relationship between the magnitude of the rotation unevenness component of the photoconductor shown in FIGS. 1 to 3 and the frequency of a drive motor forming the photoconductor drive system shown in FIGS.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 charging device 3 optical writing device 4 developing device 5 registration roller pair 6 transfer position 7 transfer belt 8 cleaning device 9 static elimination lamp 10 drive motor 11 frame 12 bracket 13 output gear 14 first reduction gear 15 shaft 16 second gear 17 axis 18, 19 timing pulley 21 timing belt 22 support shaft 23 bearing 24 photoconductor holder 25 flange 26 flywheel L laser beam P recording paper

Claims (2)

[Claims] 1. A drive motor for driving a photosensitive drum, and a photosensitive drum gear train for transmitting a driving force of the drive motor to the photosensitive drum, wherein the drive motor and the gear train are connected. Image forming apparatuses having different driving units, wherein the driving speed of each driving motor is close to one type in a driving apparatus used for two or more types of image forming apparatuses having different operation speeds such as copying and printing. A driving device for an image forming apparatus. 2. An output of a drive motor having a small number of teeth among the drive motors in order to make the rotation speeds of drive motors of two or more types of image forming apparatuses having different operation speeds such as copying and printing the same or substantially the same. 2. The driving device for an image forming apparatus according to claim 1, wherein specifications of the shaft and the first reduction gear meshing with the output shaft are changed so that a rotation speed reduction ratio of the driving motor is increased.