JPH103195A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of image caused by the rubbing between a photoreceptor drum and a transfer drum, at the time of installing a drum cartridge in a device main body. SOLUTION: A separating means for separating the transfer drum 2 from the photoreceptor drum 1 is constituted of an eccentric cam 25, a fitting hole 24, a pressing plate 26 and a spring 28. For the contact/separation states of the transfer drum 2 with/from the photoreceptor drum 1, driving by a single motor 12 can be attained and when rotational force is transmitted to the transfer drum 2 and the photoreceptor drum 1, first the transfer drum 2 is separated from the photoreceptor drum 1 by the separating means, then, both of them are rotated and after that, the transfer drum 2 is brought into contact with the photoreceptor drum 1. Thus, both of them are rotated without rubbing, to prevent the surface of the photoreceptor drum from being flawed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus using an electrophotographic process such as a color copying machine or a color laser printer.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional color image forming apparatus. In the figure, a photosensitive drum 1 which is an image carrier for forming a latent image serving as an image by sensitizing to a laser beam emitted from a scanner unit 8 is disposed substantially at the center of the apparatus. Around the developing cartridges 5 (5Y, 5Y, 4 colors) (yellow, magenta, cyan, black)
5M, 5C, 5B), a transfer drum 2 for transferring the developed image onto the photosensitive drum 1 by fixing the leading end of the fed transfer paper to the circumference by a gripper or the like, Further, a cleaner 6 for removing toner remaining on the photosensitive drum 1 at the time of transfer is provided.

A fixing device 3 is provided near the transfer drum 2 for fixing the toner to the transfer paper that has been transferred a plurality of times while being wound around the transfer drum 2 and is separated and guided. . The cleaner 6 is formed into a cartridge as a drum cartridge 7 integrally with the photosensitive drum 6 and the like, and is detachable in the drum axis direction with respect to the apparatus main body.

In the above-described schematic configuration, the transfer paper separated from the paper feed cassette 9 by the paper feed roller 12 one by one and sent out is sent to the transfer drum 2 at a timing by the registration roller 13 and transferred. The leading edge of the paper is gripped by a gripper (not shown). Further, the remaining portion of the transfer paper is electrostatically attracted to the surface of the transfer drum 2 by the attraction roller 10.

The transfer paper held on the transfer drum 2 passes through a transfer section between the photosensitive drum 1 and the transfer drum 2, and first a yellow toner image is transferred. Next, when the leading edge of the transfer paper comes to the transfer portion again, the magenta toner image is transferred, and similarly, the toner images of each color of cyan and black are transferred.
When the transfer of the final color toner image is completed, the transfer paper is moved to the separation claw 1.
The toner image is separated from the transfer drum 2 by 1 and is conveyed to a fixing device 3, and a multicolor image is obtained by fixing the toner images of each color in the fixing device 3. The above is the case where plain paper is used as the transfer paper.

Next, a case where an OHP sheet is used as transfer paper will be described. After the fourth color is transferred, OH
The P sheet moves without being separated and held by the transfer drum 2, and the transfer drum 2 is separated from the photosensitive drum 1 after the rear end of the transfer paper passes through the transfer unit. After the transfer drum 2 is separated from the photosensitive drum 1, the transfer paper passes between the two drums, is separated from the transfer drum 2 by the separation claw 11, and is conveyed to the fixing device 3, where the toner of each color is A multicolor image can be obtained by fixing the image. At this time, the peripheral speed of the transfer drum 2 is reduced to about half the speed just before the leading edge of the transfer paper enters the fixing device 3. The speed at which the transfer paper passes through the fixing device is about half the peripheral speed of the transfer drum 2 during transfer.

When the printout is completed, the transfer drum 2
Is separated from the photosensitive drum 1 and waits. And
When an image forming signal is input, the transfer drum 2 is brought into contact with the photosensitive drum 1.

Conventionally, for the purpose of facilitating maintenance and the like, a drum cartridge integrally incorporating a process device such as a photosensitive drum is detachably mounted to an apparatus main body. The transmission of the rotational force to the photosensitive drum in the drum cartridge is performed by meshing a driven gear provided integrally with the photosensitive drum and a drive gear on the apparatus main body side.

[0009]

However, in the conventional driving method, when the drum cartridge is mounted in the apparatus main body, it is not possible to accurately engage the driven gear of the photosensitive drum with the driving gear on the apparatus main body side. It is difficult, and the rotational accuracy of the photosensitive drum is surely lower than the rotational accuracy of the drive gear. Then, there is a problem that horizontal stripes such as density unevenness due to the gear engagement period occur in the formed image.

Further, when a load fluctuation occurs on the photosensitive drum,
There is also a problem that the speed fluctuation occurs on the photosensitive drum due to the backlash between the driving gear and the driven gear. For this reason, when the latent image recording density is increased, density unevenness and pitch unevenness of a formed image become more conspicuous, and when a plurality of color toners are superimposed and transferred, a color shift occurs, so that it is difficult to achieve high definition and full color. There was a problem.

Therefore, in order to solve the above-mentioned problems, a connecting portion is provided on the apparatus body side for connecting to the drum rotating shaft of the photosensitive drum, and the positioning of the photosensitive drum and the rotational force to the photosensitive drum are provided at the connecting portion. And at the same time,
By removing the play between the member that transmits the rotational force to the photosensitive drum and the drum shaft of the photosensitive drum,
In mounting the drum cartridge, image quality is improved by eliminating engagement of gears and transmitting the rotation accuracy of the connecting portion to the photosensitive drum almost directly.

FIG. 6 schematically shows the above method. In the figure, the drum cartridge is mounted in the longitudinal direction of the photosensitive drum 1. A rotating shaft 100 extending in the longitudinal direction is attached to the photosensitive drum 1, and the rotating shaft 100 is
A shaft portion 100a for positioning the device main body and a cracked portion 100 which is a fitting portion for receiving a rotational force transmitted from the device main body.
b.

A drive shaft 5 serving as a connecting portion is provided on the main body of the apparatus.
The drive shaft 50 is provided with a fitting hole 51 for positioning the photosensitive drum 1 and a drive pin 52 as a drive member for transmitting a rotational force to the photosensitive drum 1. The drive shaft 50 is configured to rotate integrally with the drive shaft 50 and to be movable in the axial direction within the fitting hole 51 of the drive shaft 50 by a coil spring 53 serving as an urging means.

Therefore, in the above-described configuration, when the drum cartridge is inserted into the apparatus main body, when the tip portion 100b of the photosensitive drum rotary shaft 100 and the drive pin 5 of the drive shaft 50
2 is fitted, and the rotational force from the apparatus main body is transmitted to the photosensitive drum 1 via the drive pin 52 and the crack 100b.

However, if the phase of the drive pin 52 of the apparatus main body does not coincide with the phase of the crack 100b of the rotary shaft 100 of the photosensitive drum 1 when the drum cartridge is inserted into the apparatus main body, the drive pin 52 100 without being fitted to the crack 100b,
It is pushed into the drive shaft 50. In that state,
When the photosensitive drum 1 and the transfer drum 2 are to be rotated, only the transfer drum 2 rotates until the phase of the drive pin 52 coincides with the phase of the crack 100b of the rotating shaft 100 of the photosensitive drum 1. The surface of the photosensitive drum 1 is rubbed against the surface of the transfer drum 2, and the surface of the photosensitive drum is damaged. As a result, there is a problem that image deterioration is caused by the scratch.

The transmission of the rotational force to the photosensitive drum 1 and the transfer drum 2 is performed from the same drive source, and the transmission of the rotational force to the photosensitive drum 1 and the transfer drum 2 is performed by contacting the photosensitive drum 1 with the photosensitive drum 1. If it is performed in a state where the contact force is applied, there is also a problem that the torque applied to the drive source is increased due to a friction load due to the contact force.

Accordingly, a main object of the present invention is to provide a color image which can prevent image deterioration due to rubbing of the image carrier by the transfer material carrier when the drum cartridge including the image carrier is inserted into the apparatus main body. It is to provide a forming device.

Another object of the present invention is to provide a color image forming apparatus capable of reducing the torque applied to the drive source when transmitting torque from the same drive source to the image carrier and the transfer material carrier. is there.

[0019]

The above object is achieved by a color image forming apparatus according to the present invention. In summary, the present invention is directed to a drum cartridge having at least an image carrier, which is detachable from an apparatus main body, and a toner image developed on the image carrier is repeatedly applied to a transfer material wound around a transfer material carrier. In a color image forming apparatus for transferring, there is provided separation means for separating and contacting the transfer material carrier with the image carrier, and in a contact state and a separated state between the transfer material carrier and the image carrier. In both states, transmission of rotational force from the same drive source to the transfer material carrier and the image carrier is possible, and when transmitting rotational force to the transfer material carrier and the image carrier, First, the transfer material carrier is separated from the image carrier by a separation unit, and then the transfer material carrier and the image carrier are rotated, and then the transfer material carrier and the image carrier are brought into contact with each other. The feature is to let That is a color image forming apparatus.

When the power of the apparatus main body is turned on, the transfer material carrier is separated from the image carrier, and a connecting portion connected to the drive source, which is connected to a rotation shaft of the image carrier, is rotated to rotate the transfer member. After the rotational force can be transmitted to the image carrier, the transfer material carrier is preferably brought into contact with the image carrier.

The connecting portion has a fitting hole into which the rotating shaft of the image carrier is fitted, and a driving member which is fitted to the fitting portion of the rotating shaft of the image carrier to transmit a rotational force. It is preferable that the driving member is urged by urging means to be movable in the longitudinal direction of the connecting portion, and is rotated integrally with the connecting portion.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the embodiment described below, it is assumed that the present invention is embodied in the color image forming apparatus shown in FIG. Therefore, a detailed description of the overall configuration and functions of the color image forming apparatus will be omitted, and features of the present invention will be described.

First, the mounting state of the drum cartridge 7, the apparatus main body and the drum cartridge will be described with reference to FIGS.

As shown in FIGS. 3 and 4, the drum cartridge 7 has the photosensitive drum 1 and the like integrally formed as described above, and extends in the longitudinal direction of the photosensitive drum 1 from the front side plate 34 side of the apparatus main body. Is inserted and mounted along the device body At this time, the positioning pin 36 provided at the rear end of the drum cartridge 7 in the insertion direction is fitted into the positioning hole 35 formed in the front plate 34 of the main body, and further, as shown in FIG. Rotation shaft 100 is the drive shaft 5 of the apparatus main body.
0, the drum cartridge 7 is positioned at a predetermined position in the apparatus main body.

Next, referring to FIG. 1 and FIG.
And the drive system of the transfer drum 2 will be described.

In FIG. 1, a drive gear 13 is fixed to a rotating shaft 12a of a motor 12 which is a drive source of the transfer drum 2 and the photosensitive drum 1, and a first gear 2 is attached to the drive gear 13.
The gear 14a of the step gear 14 meshes with the first gear 2a.
The photosensitive drum gear 15 is meshed with the small gear 14b of the step gear 14. Here, the photosensitive drum gear 15 is
When the phase of the drive pin 52 of the drive shaft 50 coincides with the phase of the crack 100b of the rotary shaft 100 of the photosensitive drum 1 when the drive shaft 52 shown in FIG. To rotate.

The driving gear 13 includes a second two-stage gear 16.
, And the small gear 16 b of the two-stage gear 16 is meshed with the intermediate gear 17. Intermediate gear 1
A rotating shaft 19 is integrally attached to the driving gear 7, and a driving gear 18 into which a one-way clutch 20 is press-fitted is attached to the rotating shaft 19.
Are integrally mounted.

The drive gear 18 is provided on a flange portion of the transfer drum 2 and rotates integrally with the transfer drum gear 21.
Are engaged.

The transfer drum 2 rotates around a fixed shaft 22 via a bearing.
Are slidably positioned on both side plates (not shown). A fitting hole 24 for the fixed shaft 22 is formed in the side plate in an elliptical shape so that the transfer drum 2 is positioned on a straight line L ₁ connecting the rotation center of the photosensitive drum 1 and the rotation center of the transfer drum 2. Has become.

The fixed shaft 22 is held between the eccentric cam 25 as a separating means and the pressing plate 26 by being pressed against the eccentric cam 25 by the pressing plate 26. The holding plate 26 is rotatable about a support shaft 27.
Is pulled in the direction of the fixed shaft 22 by a spring 28, one end of which is supported by the opposing portion and the other end of which is supported by the side plate.

The tangential direction of the pitch circle between the transfer drum gear 21 and the drive gear 18 provided on the flange portion of the transfer drum 2 and the separation direction between the photosensitive drum 1 and the transfer drum 2 are substantially parallel to each other. .

In the above configuration, the rotational force of the motor 12 is transmitted to the drive gear 13, the first two-stage gear 14, and the photosensitive drum gear 15 to rotate the photosensitive drum 1, and the rotational force of the motor 12 Is transmitted to the driving gear 13, the second two-stage gear 16, and the intermediate gear 17, and rotates the rotating shaft 19 in the direction of arrow A. When the rotation shaft 19 rotates in the direction of arrow A, the one-way clutch 20 meshes with the rotation shaft 19, and the rotational force is transmitted to the drive gear 18 and the transfer drum gear 21 to rotate the transfer drum 2 in the direction of arrow B.

As shown in FIG. 2, the eccentric cam 25 is rotated by a drive source (not shown), and as a result, even when the transfer drum 2 is separated from the photosensitive drum 1 by W = 5 mm, the drive gear 18 is rotated. Since the drive gear 18 moves in the tangential direction of the pitch circle of the transfer drum gear 21 and the transfer drum gear 21, the meshing of the two gears continues without being separated. Further, at the time of jam clearance, the eccentric cam 25 is rotated by a separation lever (not shown) to move the transfer drum 2 from the photosensitive drum 1 as shown in FIG.
Apart.

Under the above configuration, the following operations are performed when the apparatus is started. 1) The eccentric cam 25 is rotated to separate the transfer drum 2 from the photosensitive drum 1 as shown in FIG. 2) By rotating the motor 12 to rotate the drive shaft 50 by 180 degrees or more, the drive pin 52 and the rotating shaft 10 of the photosensitive drum 1 are rotated.
The zero crack portion 100b is fitted (see FIG. 6). 3) As shown in FIG. 1, the eccentric cam 25 is rotated to bring the transfer drum 2 into contact with the photosensitive drum 1.

By performing such an operation when the apparatus is started up, the surface of the photosensitive drum 1 is not rubbed by the surface of the transfer drum 2, and the surface of the photosensitive drum can be prevented from being damaged.

When the photosensitive drum 1 and the transfer drum 2 are rotated, the following operation is performed. 1) The eccentric cam 25 is rotated to separate the transfer drum 2 from the photosensitive drum 1 as shown in FIG. (FIG. 6) 2) The motor 12 is rotated. 3) As shown in FIG. 1, the transfer drum 2 is brought into contact with the photosensitive drum 1 by rotating the eccentric cam 25.

By performing such an operation when the photosensitive drum 1 and the transfer drum 2 are rotated, the frictional load between the photosensitive drum surface and the transfer drum surface is eliminated when the motor is started, so that the motor torque can be reduced. Can be.

[0038]

As is apparent from the above description, the color image forming apparatus according to the present invention has the separating means for separating and abutting the transfer material carrier with respect to the image carrier. In both the contact state and the separated state of the image carrier and the image carrier, it is possible to transmit the rotational force from the same drive source to the transfer material carrier and the image carrier, and the transfer material carrier and When transmitting the rotational force to the image carrier, the separating means first separates the transfer material carrier from the image carrier, then rotates the transfer material carrier and the image carrier, and then The transfer material carrier and the image carrier are brought into contact with each other to cause the transfer material carrier to rub against the image carrier when the drum cartridge including the image carrier is inserted into the apparatus main body. High quality, preventing image deterioration Image can be obtained.

Further, when transmitting a rotational force to the image carrier and the transfer material carrier from the same drive source, the torque applied to the drive source can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a drive system of a photosensitive drum and a transfer drum.

FIG. 2 is an explanatory diagram illustrating a state in which a transfer drum is separated from a photosensitive drum.

FIG. 3 is a perspective view showing a drum cartridge according to one embodiment.

FIG. 4 is a perspective view showing a state where the drum cartridge of FIG. 1 is positioned in the apparatus main body.

FIG. 5 is an overall configuration diagram illustrating an example of a conventional color image forming apparatus.

6 is a perspective view showing a rotation shaft of the photosensitive drum of FIG. 5 and a connection shaft on the apparatus main body side.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (image carrier) 2 transfer drum (transfer material carrier) 50 connecting shaft (connecting portion) 51 fitting hole 52 drive pin (drive member) 53 coil spring (biasing means) 7 drum cartridge 100 rotating shaft 100b Fitting portion

Claims (3)

[Claims] 1. A color that detachably attaches a drum cartridge having at least an image carrier to an apparatus main body and repeatedly transfers a toner image developed on the image carrier to a transfer material wound around a transfer material carrier. In the image forming apparatus, the image forming apparatus further includes a separation unit that separates and abuts the transfer material carrier with respect to the image carrier, and includes both a contact state and a separated state between the transfer material carrier and the image carrier. In both cases, the rotational force can be transmitted from the same drive source to the transfer material carrier and the image carrier, and when the rotational force is transmitted to the transfer material carrier and the image carrier, First, separating the transfer material carrier from the image carrier, then rotating the transfer material carrier and the image carrier, and then bringing the transfer material carrier and the image carrier into contact with each other Mosquito characterized by Over the image forming apparatus. 2. When the power of the apparatus main body is turned on, the transfer material carrier is separated from the image carrier, and a connecting portion connected to the drive source, which is connected to a rotation shaft of the image carrier, is rotated. 2. The color image forming apparatus according to claim 1, wherein the transfer material carrier is brought into contact with the image carrier after a rotational force can be transmitted to the image carrier. 3. The connecting portion includes a fitting hole into which a rotation shaft of the image carrier is fitted, and a driving member that fits into a fitting portion of the rotation shaft of the image carrier to transmit a rotational force. 3. The collar according to claim 2, wherein the driving member is urged by urging means to be movable in the longitudinal direction of the connecting portion, and is rotatable integrally with the connecting portion. Image forming device.