JPH0424707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus equipped with a mobile developing device, and particularly to an image forming apparatus equipped with a rotary developing device using powder developer (hereinafter referred to as toner).

Image forming devices such as color copiers print originals in red,
In order to separate the colors into three colors, green and blue, and develop an optical image corresponding to each color with toners of cyan, magenta, and yellow, which are complementary colors of each color, a plurality of developing units are required. In this case, configuring the developing units separately and arranging them in parallel around the electrostatic latent image holder increases the size of the apparatus. Therefore, a rotary type developing device has been proposed, which includes a plurality of developing devices, has a developing port for each developing device on the circumferential surface, and is rotatably provided close to the electrostatic latent image holder. Although this rotary developing device is extremely effective for miniaturization, there is a problem in that toner leaks and scatters from a developing port that is not used for development.

If the developer that leaks and scatters from each developing device during movement of each developing device adheres to the developing roller of the other developing device,
Not only toner of that color but also toner of other colors adheres to the latent image that should be developed in a desired color, making it impossible to obtain a clear image.

An object of the present invention is to prevent a developed image from deteriorating due to developer of another color adhering to a developing device selected for developing a latent image.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the outline of a color copying machine. A document placement glass 2 is provided on the top surface of the copying machine main body 1, and a document 3 placed on this glass 2 is placed on a light source 4.
While irradiating, move mirrors 5, 6, lens 7,
An exposure optical system comprising fixed mirrors 8 and 9 slit-exposes the original image onto a photoreceptor 10 serving as an electrostatic latent image holder. In this case, the moving speed of the moving mirror 6 is 1/2V with respect to the moving speed V of the moving mirror 5.
It is. A primary charger 1 is provided around the photoreceptor 10.
1, Secondary charging simultaneous exposure device 12, Full exposure lamp 1
3. A rotary developing device 14, a transfer charger 17 that transfers the visible image on the photoreceptor 10 to the paper P on the surface of the transfer member 16 such as a transfer drum, and a cleaning blade 18 that cleans the surface of the photoreceptor are sequentially installed. It is located.

The above paper P is fed from the cassette 19 to the paper feed roller 20.
is sent out to one sheet by the guide plate pair 21, 2.
2. The photoreceptor 10 is guided by the roller pair 23
The paper P passes between the paper P and the transfer member 16, passes through the guide plate 24, the pair of fixing rollers 25, and the pair of delivery rollers 26, and is discharged onto the discharge tray 27, where a permanent visible image is formed on the paper P.

As shown in FIGS. 2 to 6, the rotary developing device 14 is composed of an outer casing 29 having a developing port 28 in the longitudinal direction, and a rotating body 30 rotatably mounted within the outer casing. . This rotating body has radial partition plates 32a to 32d between both end plates 31a and 31b.
Developing rollers 34a to 34d are provided in each of the partitioned chambers 33a to 33d, blades 36a to 36d apply toners 35a to 35d in a uniform thin layer on the peripheral surface of the developing roller, and the developing roller is connected to the developing port 28.
Scrapers 37a to 37d, which serve as shielding members, are separated from the developing roller when facing the developing roller, and come into contact with the developing roller when the developing roller is in another position.
A developing device is configured for each of the partition chambers 33a to 33d.

The rotating shaft 38 of the rotary body 30 penetrates the outer casing 29 and protrudes to the outside, and a gear 39 attached to this protruding portion is meshed with a gear 41 attached to a first speech shaft 40 of the main body of the copying machine. . Further, shafts 34a-a to 34d of the developing rollers 34a to 34d
-d passes through the end plate 31a, and the gear 4 is inserted into the penetrating portion.
2a to 42d are attached respectively. On the other hand, the gear 4 attached to the second driving shaft 43 of the copying machine main body
4 enters into the outer casing 29 through a hole 45 made in the end plate of the outer casing 29, and is engaged with a gear on a developing roller shaft located opposite the developing port 28. 46
is an internal gear fixed to the main body of the copying machine or the outer casing 29, which is engaged by the rotation of the rotating body 30 with the gear on the shaft of the developing roller immediately before moving to the position facing the developing port 28 (developing position). located at the location.

Hereinafter, the state of each developing device in each position of the rotary developing device having the above structure will be explained. Now, the first
When power is applied to the driving shaft 40, the gears 41, 3
9, the rotating body 30 is rotationally driven in the direction of the arrow in FIG. At this time, the developing devices (33b to 33d in the illustrated example) that do not contribute to development enter the outer casing 29,
The scrapers 37b to 37d of these developing devices are pushed by the inner wall of the outer casing so that their tips end at the developing rollers 34b to 37d.
34d, and the developing device, that is, the partition chamber 33b.
Prevents leakage and mixing of toner within ~33d.

On the other hand, when the developing roller moves inside the outer casing after development, the toner that had adhered to the surface of the developing roller adheres to the inner wall surface of the outer casing. The toner that has adhered to the wall surface will adhere to the developing roller of each developing device. However, the gear 42a of the developing roller shaft of the developing device (33a in the illustrated example) immediately before moving to the developing position (the position closest to the photoreceptor 10) meshes with the internal gear 46,
Due to the rotation of the rotating body 30, the developing roller 34a is pre-rotated by at least an angle α in the counterclockwise direction indicated by the arrow, and the scraper 37a that is in pressure contact with the developing roller is rotated.
As a result, the mixed color toner adhering to the developing roller is scraped off. The scraped toner 49 is removed from the outer casing 29.
The toner falls naturally into the toner reservoir 29a formed in the toner reservoir 29a.

Then, when the developing roller 34a of the developing device 33a reaches a predetermined developing position as shown in FIG. The rotating body 30 is stopped by stopping the power. At this time, the gear 42a of the developing roller shaft is disengaged from the internal gear 46 that pre-rotates the developing roller as described above, and meshes with the gear 44 of the second driving shaft 43, and the scraper 37a is released from the inner wall of the outer casing and its It is restored by elastic restoring force, and a gap g is created between its tip and the developing roller 34a.

Therefore, when power is applied to the second driving shaft 43 via the chain 50 and sprocket 51, the gear 4
4 and 42a, the developing roller 34a rotates in the direction of the arrow in FIG.
A is regulated into a uniform thin layer by a blade 36a, and transported to a position facing the photoreceptor 10 for development. This development may be either contact development in which a developing roller is brought into contact with the photoreceptor, or jumping development in which toner is caused to fly into the gap formed between the two. During development, the toner remaining on the surface of the developing roller returns into the developing device 33a through the gap g.

When the development by the developing unit 33a is completed, power is again applied to the first driving shaft 40 to rotate the rotating body 30, and the next developing unit 33b is operated in the same manner as described above.
The control means sequentially controls the image forming apparatus so that the image forming apparatus is moved to the developing position and development is performed.

If there is a risk that the scraper may damage the surface of the photoreceptor 10 when the rotating body 30 rotates, the diameter of both ends of the photoreceptor 10 should be made slightly larger than the diameter of the photoreceptor in the jumping developing device, as shown in FIG. If the large diameter portions 10a are brought into contact with the developing roller, the large diameter portions can press both ends of the scraper and prevent the scraper from coming into contact with the latent image holder.

In addition, as shown in FIG. 7, a developing opening 28 having a width Wo larger than the photoreceptor width D and smaller than the scraper length is provided in the outer casing 29, and the scraper is removed by the notch 52 only when the developing roller is at the developing position. If a predetermined gap g is maintained, there is no need to worry about damaging the surface of the photoreceptor.

As described above, in this embodiment, a rotary body in which a plurality of developing devices are provided at approximately equal intervals on the circumference is rotatably provided in an outer casing having a developing port in the longitudinal direction, and the developing device other than the developing device facing the developing port is provided. is located inside the outer casing, and each developing device located inside this outer casing has a structure in which the tip of the scraper comes into contact with the developing roller, so the developing device can be used by loading and unloading the copying machine with the outer casing intact. Can be thrown away. Since the toner in each developing device is naturally agitated by the rotation of the rotating body, no special toner agitating mechanism is required. It is possible to prevent leakage and mixing of toner from each developing device within the outer casing.

Note that the developing units 33 a to 33 d may be independently constructed and arranged side by side on the circumference of the rotating body 30 . Further, the toner reservoir 29a may be separated from the outer casing 29 and configured independently.

As explained above, according to the present invention, the developing roller of the developing device moves to the developing position while being pre-rotated just before reaching the developing position, and at this time, the developer is removed from the developing roller. Since the developer is removed and discharged, even if developer of another color is attached to the developing roller, it is removed before the start of development, and therefore a clear image with good reproducibility can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an outline of a color copying machine to which the present invention is applied, FIG. 2 is a perspective view of a developing device, FIG. 3 is an end view thereof, and FIG. 4 is a vertical cross-sectional plan view of FIG. 5 and 6 are cross-sectional views of the developing device for explaining the selection operation of the developing device, and FIG. 7 is a perspective view showing another embodiment of the developing device. 28 is a developing port, 29 is an outer casing, 30 is a rotating body, 3
3a to 33d are developing devices (partition chambers), 34a to 34
d is a developing roller, 36a to 36d are blades, 3
7a to 37d are scrapers.

Claims (1)

[Scope of Claims] 1. An image carrier, a means for forming a latent image on the image carrier, and a developing means for developing the latent image formed on the image carrier, which carries a developer. a plurality of developing means each having a developing roller that supplies developer to the latent image and movable to a developing position for developing the latent image; An image forming apparatus comprising: means for preliminary rotation of the developing roller; and means for removing developer from the developing roller and discharging it to the outside during the preliminary rotation of the developing roller.