JP2811688B2 - Drive unit for image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus such as a copying machine, and more particularly, to an image forming unit such as a copying machine or a printer for copying a color document by electrophotography. The present invention relates to a driving device for an image forming apparatus for the purpose of achieving high precision and downsizing of the apparatus.

[Prior Art] Generally, as shown in FIG. 10, a cylindrical transfer means a (transfer drum) having an insulating flexible transfer medium is used as a multicolor image forming apparatus for electrophotographic copying of a color original. A charging device c, an optical system d serving as an electrostatic latent image forming unit, a developing device e, and a cleaner are provided on each of the plurality of image carriers b (photoconductors) arranged at equal intervals on the peripheral surface of the transfer drum a. An electrophotographic copying machine comprising a plurality of image forming units g provided with f is known. According to this conventional copying machine, for example, yellow, magenta, cyan or black is reproduced in the optical system d and the developing device e of each image forming unit g, and the transfer drum a faces each image forming unit g. The image is transferred onto the paper by the transfer corotron h.

On the other hand, the paper i to be transferred is sent out from the paper feeding unit k to the feed roll j and waits at the registration roll l. Then, a gripper (not shown) provided from the registration roll l to the transfer drum a at a predetermined timing. ), The sheet is conveyed to the transfer corotron side while being gripped by the transfer corotron h, and is sequentially changed to yellow, magenta, cyan, and black by the transfer corotron h while adjusting the timing with the lead edge of the visible image already formed on the photoconductor. After the corresponding multiple transfer, the sheet is conveyed to a fixing section n via a release guide m, and after the unfixed image is fixed in the fixing section n, the sheet is discharged to a discharge tray o.

The image forming apparatus configured as described above is required to have high performance because it is desirable to minimize the uneven speed and the displacement of the photosensitive member b in the image carrying unit. Therefore, a direct drive servomotor is generally used as a drive source of the photosensitive member b. However, since this servomotor requires advanced servo control, many control devices and their accessories are required. I do. In particular, in a multicolor image forming apparatus in which a plurality of image forming units g are arranged in tandem around the transfer drum a, there are problems that the entire apparatus becomes large and heavy, and that the cost increases. As a means for solving this problem, the use of a gear drive, a stepping motor, or the like as the drive source of the image bearing unit can reduce the size and weight.

[Problems to be Solved by the Invention] However, in the above-described gear drive and stepping motor, vibration is generated in the drive source, and the vibration becomes large before it is transmitted to the driven side.
Even if the displacement due to the vibration is small, there is a problem that the speed unevenness of the photoconductor b becomes large, a color shift occurs between the colors, and the image quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. It is an object of the present invention to form a drive source of an image carrier by a stepping motor or the like which can be reduced in size and to drive a driven portion of vibration generated in the drive source. It is an object of the present invention to provide a driving device for an image forming apparatus in which the transmission to the image forming apparatus is prevented by preventing transmission to the image forming apparatus.

[Means for Solving the Problems] To achieve the above object, a driving device according to the present invention comprises:
An image forming unit having at least an image carrier for forming a latent image and a developing unit for developing the latent image on the image carrier, and transferring a visible image formed by the image forming unit; In an image forming apparatus for transferring to
At least a vibration absorbing unit that absorbs vibration from the driving source is provided on a surface of a gear that forms a transmission system between a driving source of the image forming unit including a rotation driving unit of the image carrier and a driven side of the image forming unit. Things.

In the present invention, the driving source includes at least a rotation driving unit of the image carrier. For example, in addition to a driving unit such as a stepping motor for driving the image carrier to rotate, the image forming unit is moved relative to the transfer unit. All driving sources that affect the image forming unit, such as a driving unit for correction control and a driving unit for the transfer unit, are included.

Further, the vibration absorbing means may be of any type provided that it is provided on the surface of a gear forming a transmission system between the driving source and the driven side of the image forming unit. For example, the surface of the transmission gear may be attached to the vibration absorbing member. It may be formed by forming. In this case, the vibration absorbing means may be of any type as long as it has a certain degree of rigidity capable of accurately transmitting the power from the driving source, such as a soft material such as rubber or a material obtained by mixing rubber and plastic, or a metal material. A part of which is processed into a thin-walled shape so as to absorb vibration, a composite of metal and rubber in a sandwich form, or a metal with rubber coated on its surface can be used.

[Operation] As described above, the vibration absorbing means is interposed on the surface of the gear forming the transmission system between the driving source of the image forming unit including at least the rotation driving means of the image carrier and the driven side of the image forming unit. By causing the vibration generated by the driving source to be transmitted to the driven side, the vibration is absorbed by the vibration absorbing means, and by interposing such a vibration absorbing means in the driving system, driving other than the vibration source is performed. By lowering the natural frequency of the system, it is possible to prevent the drive system from resonating due to the vibration generated from the vibration source. As a result, the speed unevenness of the image carrier is prevented, and the image quality is also prevented from lowering.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a color image forming apparatus provided with a driving device of the present invention, FIG. 2 is an enlarged view of a main part thereof, and FIG. 3 is a longitudinal sectional view of FIG.

An image forming apparatus provided with a driving device according to the present invention includes a plurality of (four in the drawing, yellow, magenta, cyan, and black) image forming units 20 on a peripheral surface of a transfer drum 10 as a transfer unit. A paper feed unit 30 is provided on one side of the lower side of the transfer drum 10, and a fixing unit 40 and a discharge unit are provided on one side of the upper side of the transfer drum 10. A tray 42 is provided.

As shown in FIG. 2, the image forming unit 20 includes an image carrier that is disposed close to the transfer drum 10.
22 (photosensitive drum); a charger 24 disposed on the peripheral surface of the photosensitive drum 22 to charge the photosensitive drum 22;
An optical system 26 which is an electrostatic latent image forming means for writing a latent image thereon,
The image forming unit 20 comprises a developing device 28 which is a developing means for developing a latent image on the photosensitive drum 22 and a cleaner 29 which cleans toner remaining on the photosensitive drum 22. 22 and the developing device 28 are housed and held in the first frame 11. The first frame 11 is supported by the second frame 12 with support pins 13, and a projection 14 protruding outward is attached to the second frame 12.
The image forming unit 20 is formed so as to be slidably engaged with the guide rail 15 provided in the image forming apparatus and can be pulled out from the apparatus main body. The second frame 12 has a pivot width.
A support cam follower 18 protrudingly provided on the free end side of the apparatus is swingably mounted in a groove 19a of a grooved cam 19 for correction control, while being swingably mounted on a main frame 17 on the apparatus fixed side at 16. The grooved cam 19 is rotated by the operation of a correction control motor 61 which is operated by a signal from a position detection sensor 21 disposed at an appropriate position on the transfer drum 10, thereby causing the second rotation. The frame 12 is rocked and the position of the image forming unit 20 is controlled.

On the other hand, the photosensitive drum constituting the image forming unit 20
Reference numeral 22 denotes a photosensitive drum shaft 27 mounted on a drum body 25 having a diameter of, for example, 84 mm, which is connected to a stepping motor 60 as a drive source via a vibration absorbing means 50 (see FIGS. 3 and 4). . In this case, the vibration absorbing means 50
As shown in the figure, a connection shaft 54 connected and fixed to the photosensitive drum shaft 27 and the motor shaft 62 by a fixing screw 52 and a small-diameter step portion 55 formed at an intermediate portion of the connection shaft 54 are filled and bonded. It is formed of a hard rubber absorber 56. Also, vibration absorbing means
6, a pair of bottomed cylindrical connecting bodies 58, 58 connected and fixed to the photosensitive drum shaft 27 and the motor shaft 62 by fastening screws 52, as shown in FIG. It is formed of a hard rubber absorber 56 bonded between them.

In the drive unit of the photosensitive drum 22 configured as described above, for example, a five-phase stepping motor 60 that makes one rotation at 1000 pulses is used as a drive source. In this case, since the diameter of the photosensitive drum 22 is 84 mm and the surface speed is 80 mm / s,
The photosensitive drum 22 makes one rotation in about 3.3 seconds. In order to suppress the vibration of the motor 60, the step angle in one pulse is reduced by using a reduction gear. That is, by setting the gear ratio to about 1/1000, the amount of rotation of the photosensitive drum 22 in one pulse is 2.7 μm. By interposing the vibration absorbing means 50 in the transmission system between the driving source and the driven side thus configured, the vibration generated from the stepping motor 60 during driving is absorbed by the absorber 56. Due to 56, the natural frequency of the entire drive system other than the vibration source is reduced, and the natural frequency and the frequency of the vibration generated from the stepping motor 60 are greatly different from each other, and resonance does not occur.

In the above embodiment, the case where the vibration absorbing unit 50 is formed by the connecting shaft 54, the connecting body 58, and the absorbing body 56 which form a connecting portion between the photosensitive drum shaft 27 and the motor shaft 62 has been described. It is not necessary to form a part of the transmission shaft 64 into a small diameter shape as shown in FIG.
Alternatively, the vibration of the driving source may be absorbed. Also, the power from the motor 60 is supplied to the photosensitive drum 22 on the driven side.
In the case where a transmission gear is interposed in the transmission system for transmitting the drive gear, a part of the drive gear 66 and the driven gear 68 is formed by a hard rubber absorber 56 as shown in FIG.
Similarly, vibration from the drive source can be absorbed by the absorber 56. In this case, the driving gear 66 or the sliding gear 68
May be coated with a rubber absorber 56 (see FIG. 9).

In the above embodiment, the case where the vibration absorbing means 50 is interposed in the transmission system between the drive source and the driven side of the photosensitive drum 22 has been described. Transmission between a motor 61 as a drive source and a transmission system on the photosensitive drum 22 side of the main frame 17, that is, the image forming unit 20, or between a drive source of the transfer drum 10 and an image forming unit such as the transfer drum 10 as a driven side Vibration absorbing means 50 may be interposed in the system. Further, even if a vibration absorbing means 50 made of, for example, a hard rubber bellows is interposed between the drive side and the fixed side in the mounting portion (bearing portion 70) on the device fixed side of the transmission system, the vibration from the drive source can be reduced. Can be absorbed.

The transfer drum 10 has an insulating mesh 10b (or an insulating synthetic resin film) stretched over an opening formed on the peripheral surface of the cylindrical base 10a, and a paper 32 on a part of the outer periphery of the cylindrical base 10a. A gripper (not shown) for gripping the distal end of the camera is opened and closed by a cam mechanism or the like (not shown). And the insulating mesh of this transfer drum 10
A transfer corotron 34 is provided on the inner side of 10b so as to face the photosensitive drum 22.

On the other hand, a paper supply unit for supplying the paper 32 to the transfer drum 10 side
A feed roll 31 is disposed on the feed roll 31, and the paper 32 conveyed from the paper feed unit 30 by the feed roll 31 is supplied to the transfer drum 10 side after being kept on standby by a registration roll 33, and is supplied to the electrostatic tack corotron 35. Is transported on the transfer drum 10 by electrostatic attraction. The paper 32 conveyed by the transfer drum 10 is a transfer corotron.
After being transferred by the transfer roller 34, the transfer roller is separated from the transfer drum 10 by the separation corotron 36, and is conveyed to the fixing unit 40.
The unfixed visible image, that is, the unfixed toner image on the sheet 32 is fixed by the heating roll 41a and the pressure roll 41b, and the sheet is discharged onto the discharge tray.

[Effects of the Invention] As described above, according to the driving device of the present invention, the transmission system between the driving source of the image forming unit including at least the rotation driving unit of the image carrier and the driven side of the image forming unit. By interposing the vibration absorbing means on the surface of the gear constituting, the vibration generated at the drive source is absorbed by the vibration absorbing means when it is transmitted to the driven side, and such a vibration absorbing means is Lowering the natural frequency of the drive system other than the vibration source by interposing it in the drive system prevents the drive system from resonating due to the vibration generated from the vibration source, thereby preventing unevenness in the speed of the image carrier and lowering the image quality. Can also be prevented. Further, since a small and inexpensive stepping motor or the like can be used as the drive source, the size and weight of the device can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus provided with the driving device of the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, FIG. 3 is a longitudinal sectional view of FIG. 2, and FIG. FIG. 5 is a cross-sectional view showing a first embodiment of the driving device of the present invention, FIG. 5 is a cross-sectional view of the vibration absorbing means of the present invention, and FIGS. 6 to 9 are cross-sectional views showing another embodiment of the vibration absorbing means. FIG. 10 is a schematic sectional view showing the structure of the multicolor image forming apparatus. Description of symbols (10) Transfer drum (transfer means) (20) Image forming unit (22) Photoconductor (image carrier) (24) Charger (26) Optical system (28) Developing device (developing means) (34) Transfer corotron (50) Vibration absorbing means (54) Connection shaft (56) Vibration absorber (58) Connection body (60) Stepping motor (drive source) (61) Correction control motor (drive source) (64) Transmission shaft (65) Small diameter section (66) Drive gear (68) Driven gear

Claims (1)

(57) [Claims] 1. An image forming unit having at least an image carrier for forming a latent image and a developing means for visualizing the latent image on the image carrier is formed by the image forming unit. In a copying machine or the like that transfers a visible image to a transfer unit, at least a surface of a gear that forms a transmission system between a driving source of an image forming unit including a rotation driving unit of the image carrier and a driven side of the image forming unit. A driving apparatus for an image forming apparatus, comprising: a vibration absorbing unit configured to absorb vibration from a driving source.