JP2004054083A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus constituted so that the installation of a coupling mechanism for bringing a developing roller in contact with an image carrier is unnecessary, and also, the developing roller can be rotated before a developing process. <P>SOLUTION: The image forming apparatus is provided with the image carrier, several developing units separately including a developing roller for developing a toner image on the image carrier, a developing roller gear arranged in the developing unit so as to drive the developing roller, a developing unit holding member for holding and successively moving the several developing units so that the units may be positioned facing the image carrier while rotating around a rotary shaft, a drive gear for transmitting a driving force generated by a driving means to the developing roller gear, the developing roller gear is engaged with the drive gear when the image carrier and the developing roller are positioned facing each other with the rotation of the developing unit holding member. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image forming apparatus such as a color copying machine or a color printer, which has a driving mechanism for driving a developing roller of a developing unit and performs image formation using an electrophotographic system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is a color image forming apparatus which has a developing device in a rotary and performs development while rotating the rotary. As such an image forming apparatus, as shown in JP-A-11-52715 and FIG. 7, there is an image forming apparatus having a carousel 103 as a rotary developing cartridge switching mechanism in a developing cartridge configuration detachable from an apparatus main body.
[0003]
With reference to FIG. 8, a description will be given of the operation of releasing the connection of the developing drive by the lever unit 337. In the configuration of the developing cartridge, the drive coupling portions 314 and 410 are provided at the swing center of the developing cartridge in order to surely drive and connect the developing roller. At the other end of the lever unit 337, a dog 337b is provided as an operation member for the drive connection member (drive coupling unit) 314. When connecting the drive coupling portions 314 and 410, the coupling 314a and 410a of the coupling were performed by the dog 337b of the lever unit 337 on the apparatus main body side.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional color image forming apparatus, in order to drive the developing roller, it is necessary to rotate the rotary until the developing unit comes to the developing position and to couple the coupling mechanism by the dog 337b fixed to the main body. Accordingly, the width of the device is increased accordingly, and the volume of the entire device is increased. Further, the cost is increased because a coupling mechanism is required. Further, since the coupling mechanism for driving the developing roller operates only at the position of the dog 337b on the main body side, the developing roller can be driven only at the developing position. For this reason, there has been a problem that the developing roller cannot be rotated before the development, and the development process is greatly restricted.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which does not require a coupling mechanism for development and can rotate a developing roller before development.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a typical configuration of the present invention is an image carrier, a plurality of developing units including a developing roller for developing a toner image on the image carrier, and disposed in the developing unit. A developing roller gear for driving the developing roller, a developing unit holding member for holding the plurality of developing units, rotating the developing unit around a rotation axis and sequentially moving the developing units to a position facing the image carrier, A driving gear for transmitting a driving force generated by the means to the developing roller gear, and rotating the developing unit holding member so that when the image carrier and the developing roller come to a position facing each other, the developing unit It is characterized in that the roller gear and the drive gear mesh with each other.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The configuration of the embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a rotary type full color laser beam printer in an electrophotographic image forming apparatus embodying the present invention. First, after describing the schematic configuration and operation of the image forming apparatus, a detailed description of the periphery of the rotary (developing unit holding member) 4 which is a feature of the present invention will be given.
[0008]
(Image forming device)
The image forming apparatus A of the present invention is roughly classified into an image forming section for forming an image and a transfer material transporting section. The image forming unit includes a rotary unit 4 having developing units (developing units) 4Y, 4M, 4C, and 4Bk for forming toner images on a photosensitive drum 1 serving as an image carrier, and performs exposure to the developing units. An exposing unit 3, an intermediate transfer body 5 having an intermediate transfer belt 5a for temporarily carrying the toner image formed on the photosensitive drum 1 by a primary transfer unit 5j, and a transfer material S for transferring the toner image carried on the intermediate transfer belt 5a And a fixing device 8 for fixing the transferred toner image.
[0009]
The transfer material transport unit includes a feeding unit 18 for feeding the transfer material S stacked in the cassette 19 and a registration roller for correcting skew of the transfer material S in front of the secondary transfer unit 11. Pair 7, a transport belt unit 12 for transporting the transfer material S after the transfer by the secondary transfer means 11, a transport roller 13 for transporting the transfer material S after the fixing of the toner image by the fixing device 8 downstream, And a discharge roller pair 9 for discharging the transfer material S to a discharge tray 10 outside the apparatus via a discharge guide 15.
[0010]
(Developer)
In the present embodiment, a developing device shown in FIG. 7 employing a non-magnetic one-component contact developing system will be described as an example. Since the developing units 4Y, 4M, 4C, and 4Bk all have the same configuration, the yellow developing unit 4Y is shown here. The developing device 4Y includes a developing roller 41Y that contacts and develops the photosensitive drum 1, an elastic roller 54Y that conveys toner from the toner container 52Y to the developing roller 41Y, and a stirring member 53Y that stirs the toner in the toner container 52Y. Consists of
[0011]
(Outline of image forming operation of color image forming apparatus)
Next, an outline of an image forming operation of the color image forming apparatus of the present embodiment will be described by taking development of yellow toner as an example. The photosensitive drum 1 is rotated in the direction of the arrow (counterclockwise) in FIG. 1 in synchronization with the rotation of the intermediate transfer belt 5 a, and the surface of the photosensitive drum 1 is uniformly charged by the charging device 2. After the photosensitive drum 1 is uniformly charged, the exposure unit 3 irradiates a yellow image with light to form a yellow electrostatic latent image on the photosensitive drum 1. At the same time as the formation of the electrostatic latent image, the rotary 4 is driven to place the yellow developing unit 4Y at the developing position, and the charging of the photosensitive drum 1 is performed so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. A voltage having the same polarity as the polarity and substantially the same potential is applied to cause the yellow toner to adhere to the electrostatic latent image for development. Thereafter, a voltage having a polarity opposite to that of the toner is applied to a pressing roller (primary transfer roller) 5j of the intermediate transfer body 5, and the yellow toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a.
[0012]
When the primary transfer of the yellow toner image is completed as described above, the next developing device is rotated to the position facing the photosensitive drum 1. After being rotated and moved to the developing position facing the photosensitive drum 1, the developing unit forms an electrostatic latent image for each of magenta M, cyan S, and black Bk in the same manner as in the case of yellow Y. , Development and primary transfer are sequentially performed, and four color toner images are superimposed on the intermediate transfer belt 5a. During this time, the secondary transfer roller 11 is not in contact with the intermediate transfer belt 5a, so that the toner image is not transferred to the transfer material S. At this time, the charging roller 5f as a cleaning unit is also in a non-contact state with the intermediate transfer belt 5a.
[0013]
When the formation of the toner images of four colors on the intermediate transfer belt 5a is completed, the secondary transfer roller 11 is pressed against the intermediate transfer belt 5a (the state shown in FIG. 1), and the supply is performed in synchronization with the rotation of the intermediate transfer belt 5a. The transfer material S which has been waiting at a predetermined position near the registration roller pair 7 as the feeding means is sent to the nip portion between the intermediate transfer belt 5a and the secondary transfer means 11. In this case, immediately before the registration roller pair 7, a pre-registration sensor 14 for detecting the leading end of the transfer material S, interrupting the rotational driving force of the registration roller pair 7, and waiting the transfer material S at a predetermined position is provided. I have. Further, a voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 11, and the toner image on the intermediate transfer belt 5a is secondarily transferred onto the surface of the transfer material S conveyed in a lump. .
[0014]
The transfer material S thus secondary-transferred reaches the fixing device 8 via the transport belt unit 12, where the toner images of a plurality of colors are fixed, and then transported by the transport roller 13 to the discharge guide 15. The sheet is conveyed along with the sheet and is discharged to a discharge tray 10 above the color image forming apparatus A by the discharge roller pair 9 to complete the image formation. The control of each means is performed by the control means 17.
[0015]
(Rotary and developing roller drive)
Next, an example of a rotary developing device driving mechanism according to the present invention will be described in detail with reference to FIGS. 2 to 5 are longitudinal sectional views showing the schematic configuration of the rotary-side developing drive system during the development according to the present invention (view from the left side when viewed from the front of the apparatus). The present embodiment employs a contact development method in which the developing roller 41Y, the elastic roller 54Y, and the stirring member 53Y of the developing device 4Y shown in FIG. ing.
[0016]
When a full-color image is formed, the operation of the developing device driving mechanism on the rotary 4 side before and after developing the yellow color is described below. Here, the case where the yellow toner image is developed on the photosensitive drum 1 will be described as an example. However, the same operation is performed when developing other colors, that is, magenta, cyan, and black toner images. Do.
[0017]
First, as shown in FIG. 2, in a standby state of the developing operation, the developing device 4 </ b> Y containing the yellow toner is at a position separated from the photosensitive drum 1. When the development is started, the rotary 4 rotates in the direction shown in FIG. 2, and the developing device 4 </ b> Y held by the rotary 4 approaches the position facing the photosensitive drum 1.
[0018]
Here, it is necessary for the developing roller gear 42Y connected to the developing roller 41Y of the developing device 4Y to smoothly enter the position facing the photosensitive drum 1 from below the rotary 4. For this reason, the present embodiment employs the following means. First, the drive motor (drive means) 31 on the main body is rotated in the direction (counterclockwise) shown in FIG. When the rotary 4 rotates in the direction of FIG. 2 and the developing roller gear 42 </ b> Y meshes with the drive gear 35, the developing device 4 </ b> Y advances to a position facing the photosensitive drum 1. At that position, the rotation of the rotary 4 is stopped, the rotation is locked by the rotation stopping mechanism, and the rotation of the drive motor 31 on the main body side is also temporarily stopped.
[0019]
As shown in FIG. 3, the drive motor 31 once stopped rotates in the opposite direction (clockwise) to that in FIG. 2 to rotate the gear trains 32 to 35 on the rotary 4 side. Then, the developing roller gear 42Y on the side of the developing device 4Y connected to the drive gear 35 rotates, and the developing roller 41Y connected to the developing roller gear 42Y, the elastic roller 54Y (not shown), and the stirring member 53Y rotate. At this time, the position of the rotary 4 is at a position facing the photosensitive drum 1 as shown in the figure.
[0020]
The developing roller 41Y is accelerated at a constant speed and rotated at a constant speed by the drive motor 31 on the main body side. Next, the developing roller 41Y is rotated by a rotary contacting / separating mechanism (oscillating mechanism) (not shown) by swinging the entire rotary around the swing shaft 36 above the rotary 4 as shown in FIG. Contact 1 Then, the yellow toner on the developing roller 41Y develops the electrostatic latent image on the photosensitive drum 1. Thus, a yellow toner image is formed on the photosensitive drum 1.
[0021]
After the development by the developing device 4Y is completed, the developing device 4Y is separated from the photosensitive drum 1 by the rotary contact / separation mechanism and returned to a position facing the photosensitive drum 1. After temporarily stopping the drive motor 31 on the main body side for driving the developing roller 41Y, the developing unit 4Y is made to escape from a position facing the photosensitive drum 1 as shown in FIG. Then, while rotating the drive motor 31 on the main body side in the direction shown in FIG. 5 (counterclockwise) and rotating the gear trains 32 to 35 on the rotary side in the direction shown in FIG. Then, the rotary is rotated in the direction shown in FIG. Then, the developing device 4Y escapes from a position facing the photosensitive drum 1.
[0022]
Of the rotary gear trains 32 to 35 for driving the developing roller gear 42Y on the developing device 4Y side, the rotation shaft of one gear 32 is coaxial with the swing shaft 36 of the swing mechanism. That is, the swing mechanism of the rotary 4 engages with the gear on the drive shaft of the drive motor 31 on the main body side while using the swing shaft 36 as the central axis. Therefore, even when the entire rotary 4 is swung between the separated position shown in FIG. 3 and the contact position shown in FIG. 4, the developing roller 41Y can be driven to rotate. Further, the developing roller 41Y can be sufficiently rotated before the development.
[0023]
(Other embodiments)
In the above-described embodiment, the configuration is such that the drive motor 31 is rotated when the rotary 4 is rotated and the developing roller 41Y of the developing device 4Y enters the position facing the photosensitive drum 1, but is not limited thereto. Instead, the gear train may be driven to rotate before entering the position facing the photosensitive drum 1. With such a configuration, the developing rollers 41Y, 41M, 41C, and 41Bk can be sufficiently rotated.
[0024]
【The invention's effect】
As described above, according to the present invention, an image carrier, a plurality of developing units including a developing roller for developing a toner image on the image carrier, and a developing unit disposed in the developing unit and driving the developing roller are provided. A roller gear, a developing unit holding member that holds the plurality of developing units, rotates about a rotation axis and sequentially moves the developing units to a position facing the image carrier, and a driving force generated by a driving unit. A drive gear for transmitting to the developing roller gear, and rotating the developing unit holding member, when the image carrier and the developing roller come to a position facing each other, the developing roller gear and the drive gear are It is a configuration that meshes. The image forming apparatus further includes a swinging mechanism that swings the developing unit holding member and causes the developing roller that moves together with the developing unit holding member to contact and separate from the image carrier.
[0025]
With the above configuration, it is possible to provide an image forming apparatus having a configuration that does not require a coupling mechanism for development and that can rotate the development roller before development.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an electrophotographic color image forming apparatus.
FIG. 2 is a longitudinal sectional view of a rotary developing roller driving system (when the rotary roller enters a position facing a photosensitive drum).
FIG. 3 is a longitudinal sectional view of a rotary developing roller driving system (a position facing a photosensitive drum).
FIG. 4 is a longitudinal sectional view of a rotary developing roller driving system (a contact position with a photosensitive drum: a developing position).
FIG. 5 is a longitudinal sectional view of a rotary developing roller driving system embodying the present invention (escape from a position facing a photosensitive drum).
FIG. 6 is a configuration diagram of a developing device used in the image forming apparatus.
FIG. 7 is a configuration diagram of a conventional image forming apparatus.
FIG. 8 is an explanatory view of a conventional developing roller drive system coupling.
[Explanation of symbols]
A: image forming apparatus, S: transfer material,
DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum 2 ... Charging device
3: Exposure means, 4: Rotary,
4Y, 4M, 4C, 4Bk ... developing unit,
5: Intermediate transfer member, 5a: Intermediate transfer belt,
5f: charging roller, 5j: primary transfer means,
6: developing device, 7: registration roller pair, 8: fixing device,
9: discharge roller pair, 10: discharge tray, 11: secondary transfer means,
12: conveyor belt unit, 13: conveyor roller, 14: sensor before registration
15 ... discharge guide, 17 ... control means, 18 ... feeding means,
19 ... cassette, 31 ... drive motor, 32 ... gear, 33 ... gear,
34 ... gear, 35 ... drive gear, 36 ... swing shaft,
41Y, 41M, 41C, 41Bk ... developing roller,
42Y, 42M, 42C, 42Bk ... developing roller gear,
52Y, 52M, 52C, 52Bk ... toner container,
53Y, 53M, 53C, 53Bk ... stirring member,
54Y, 54M, 54C, 54Bk ... elastic roller

Claims (4)

An image carrier;
A plurality of developing units including a developing roller for developing a toner image on the image carrier,
A developing roller gear disposed in the developing unit to drive the developing roller;
A developing unit holding member that holds the plurality of developing units and rotates the developing unit around a rotation axis to sequentially move the developing units to a position facing the image carrier;
A driving gear for transmitting a driving force generated by a driving unit to the developing roller gear,
The image forming apparatus is characterized in that the developing roller gear and the driving gear mesh with each other when the developing unit holding member is rotated and the image carrier and the developing roller come to a position where they face each other. An image carrier;
A plurality of developing units including a developing roller for developing a toner image on the image carrier,
A developing roller gear disposed in the developing unit to drive the developing roller;
A developing unit holding member that holds the plurality of developing units and rotates the developing unit around a rotation axis to sequentially move the developing units to a position facing the image carrier;
A driving gear for transmitting a driving force generated by a driving unit to the developing roller gear,
An image forming apparatus, wherein the developing roller gear and the driving gear are engaged before the developing unit holding member is rotated and the image carrier and the developing roller come to a position where they face each other. 3. The image forming apparatus according to claim 1, further comprising a swing mechanism configured to swing the developing unit holding member and contact and separate the developing roller that moves together with the developing unit holding member from the image carrier. 4. The image forming apparatus according to any one of the preceding claims. A swing shaft of the swing mechanism is located above the developing unit holding member and is coaxial with any one of rotation shafts of a gear train provided between the driving unit and the driving roller. The image forming apparatus according to claim 3, wherein:

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