JPH0656524B2 - Image forming device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an image forming apparatus such as an electronic copying machine, and more particularly to an image forming apparatus having two developing devices.

[Technical background of the invention and its problems]

Recently, electronic copying machines capable of two-color development have been widely used. In this electronic copying machine, first and second developing devices are arranged in the vicinity of the photoconductor, and for example, the first developing device performs color development and the second developing device performs black development. .

The first and second developing devices each include a developing roller formed by externally fitting a magnet roller having a plurality of magnetic pole portions with a rotating sleeve, and the rotation of the rotating sleeve causes the magnetic brush of the developer to move onto the photosensitive member. The latent image is slidably contacted with the latent image and developed.

The first and second developing devices are selectively switched for use.

However, in the prior art, a motor capable of rotating in the forward and reverse directions is required as a means for selectively driving the first and second developing devices, and its power is intermittently supplied to the first and second developing devices. Requires a one-way clutch for effective transmission, and a drive means for rotating the magnet roller to cut the magnetic brush of the developing device that is not in use, resulting in a large number of parts. However, there was an inconvenience that the cost became high.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a developing device capable of selectively switching between the first and second developing devices with a simple structure. It is the one to be provided.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention provides a rotatable image carrier, cleaning means for cleaning the surface of the image carrier, and a first developing device provided in the vicinity of the image carrier. A second developing device provided in the vicinity of the image carrier and at a position downstream of the first developing device in the rotational direction of the image carrier, and the first and second developing devices. Switching means for selectively moving the image bearing member in a direction toward and away from the image bearing member to relatively change the distance of the gap between the image bearing member and the image bearing member; When switching from the developing device to the second developing device, both the first and second developing devices are separated from the image carrier, and the image carrier is the first developing device and the second developing device. To rotate the cleaning unit to clean the surface of the image carrier. By doing so, it is possible to eliminate the need for a special forward / reverse rotatable motor, a one-way clutch, or a means for rotating the magnet roller for magnetic brush cutting for switching the first and second developing devices. This makes it possible to prevent the developer of the previous developing device attached to the image carrier from mixing into the next developing device, and prevent the image carrier from being scratched when the developing device is attached or detached. It was done.

Example of Invention

The present invention will be described below with reference to an embodiment shown in the drawings. In the figure, reference numeral 1 denotes a main body of an electronic copying machine, and a photosensitive drum 2 as an image bearing member is rotatably provided at a substantially central portion of the main body 1. A charger 3, a developing device 4, transfer peeling chargers 5a and 5b, and a cleaning device 6 are arranged around the photosensitive drum 2 along the rotation direction thereof. An original table glass 7 is provided on the upper surface of the main body 1, and an optical system 8 is provided on the lower side of the original table glass 7. The optical system 8 includes a lamp 9, first to third reflecting mirrors 10, 11 and 12, a lens 65 and a fourth mirror.
The reflecting mirrors 66 and 67 are used. In addition, the first and second units are detachably attached to one side of the main body 1.
The paper feed cassettes 14 and 15 are mounted, and the papers P and P ′ in the first and second paper feed cassettes 14 and 15 are taken out one by one by take-out rollers 68 and 69. The papers P and P ′ thus taken out are conveyed by the conveying path 16
Is conveyed along the conveying path 16 and the feed roller 1
7a, 17b, registration roller 18, transfer / separation charger 5a, 5b, conveyor belt 19, fixing roller 20
And a discharge roller 21 is provided. 22 is a paper discharge tray.

Thus, when copying a document, the document placed on the document table 7 is scanned with light from the lamp 9 of the optical system, and the reflected light is reflected by the first to third reflecting mirrors 10, 11, 12, and
An image is formed on the photosensitive drum 2 via the lens 65 and the fourth and fifth reflection mirrors 67. The surface of the photosensitive drum 2 is uniformly charged by the charger 3, and an electrostatic latent image is formed by the above image formation. This electrostatic latent image is sent to the developing device 4 by the rotation of the photosensitive drum 2 and, after being developed with a red or black toner as described later, transferred,
It is sent to the peeling charger 5a, 5b side. On the other hand, at this time, the paper P is fed from the first or second paper feeding cassette.
Alternatively, P'is fed and the feed roller 17a or 1
After being sent to the registration roller 18 by 7b and aligned, it is sent between the photosensitive drum 2 and the transfer / separation chargers 5a and 5b. Transfer charger 5 to this paper P (P ')
By the action of a, the original image on the photosensitive drum 2 is transferred,
After that, by the action of the peeling changer 5b, it is peeled from the photosensitive drum 2 and sent to the fixing roller 20 via the conveying belt 19. Here, the image is fixed on the paper P (P ′) and is discharged to the paper discharge tray 22 via the paper discharge roller 21. After the image is transferred onto the paper P (P '), when the photoconductor drum 2 is further rotated and reaches the position of the cleaning device 6, the action of the cleaning device 6 causes residual toner on the surface of the photoconductor drum 2. Are removed. The cleaning device 6 is in contact with the surface of the photoconductor drum 2 at least during the image forming operation, and cleans the surface of the photoconductor drum 2 by rotating the photoconductor drum 2.

Next, the developing device 4 will be described in detail. The developing device 4 includes first and second developing devices 23,
It is composed of 24. Developing rollers 25 and 26 are provided in the first and second developing units 23 and 24, respectively, and these developing rollers 25 and 26 are a magnet roller 27 having a plurality of magnetic pole portions as shown in FIG. ,
A rotating sleeve 28 fitted on the magnet roller 27.
It is composed of and. Further, the first developing device 2
3 contains a toner 29 as a red developer,
Black toner 30 is stored in the second developing device 24. The first and second developing units 23 and 24 can be alternately moved in a direction in which they come in contact with and separate from the photosensitive drum 2 by a switching mechanism described later.

As shown in FIGS. 2 to 6, the switching mechanism includes a first switching mechanism.
And a pair of pins 31, 32 and 33, 34 projecting inward from one side in the longitudinal direction of the second developing device 23, 24 corresponding to the front frame 60 of the copying machine body 1, while the rear frame is provided. Rotating shaft end portions 27a and 27b of the respective magnet rollers 27 and pins 35 and 36 are provided on the other side portion in the longitudinal direction corresponding to (not shown), and the respective pins 31 and 33 and the rotating shaft 27a are provided.
And 27a are fitted to guides 37, 38 and 39, 40 fixed to the front frame 60 and a rear frame (not shown), respectively, and the pins 32 and 34 and the pins 35 and 36 are fixed to the Heront frame 60. And a link 41 rotatably and movably attached to each elongated hole 61 of the rear side frame (not shown) through a guide bush 62 in an engaged state as shown as an example in FIGS. 3 and 4. 42 and link 4
As a spigot structure fitted to 3 and 44, respectively, the first and second developing devices 23 and 24 can be movably approached to the photosensitive drum 2 in a direction of approaching and separating. Further, each of the links, for example, the link 42, has a dharma groove portion 42a.
The guide bush 62 is movably fitted to the 2a, and the first and second developing units 23, 2 are moved to the left by the biasing force of the spring 63, that is, with respect to the photosensitive drum 2.
4 is urged in the direction to be pressed. Further, the links 41 and 43 for moving the first developing device 23 are connected to the shaft 47 via the levers 45 and 46, while the links 42, 43 for moving the second developing device 24.
44 is connected to a shaft 50 via levers 48 and 49, and these shafts 47 and 50 are connected to the guide arm 5
It is engaged with the cam 53 via 1, 52. This cam 5
3 is a reduction gear 5 as shown in FIG. 5 and FIG.
It is rotated by a drive motor 56 via 4, 55, and the roller 51 of the guide arm 51, 52 is inserted in the cam groove 53a.
a and 52a are engaged and forcedly pushed down by the convex portions 53b alternately to reciprocate the shafts 47 and 50 to alternately move the first and second developing units 23 and 24 to the photosensitive drum 2 side. It is switched so that it is pressed against. In addition, the cam 53 rotates in one direction, and the switch 57 detects the initial position of the first or second
The position of the convex portion 53b for switching the developing devices 23 and 24 can be selected.

That is, the above-mentioned first and second developing units 23 and 24
The driving state of the second developing device 24 will be described with reference to FIG.
2 is pushed down, lever 48-link 42-pin 34
The thrust is transmitted to and the pin 33 is pressed against the guide 38. At this time, with respect to the stroke S _A 'of the ring 42, the stroke S _A of the pin 33 is greater (S _A <
S _A ′), so that the second developing device 24 is always pressed against the photosensitive drum 2 side by the urging force of the spring 63. On the contrary, the first developing device 23 moves in a direction in which the guide arm 51 is pushed up by the cam 53, the thrust is transmitted to the lever 45-link 41-pin 32, and the first developing device 23 is separated from the photosensitive drum 2. Also link 4
1 stroke S _B 'stroke S _B of the pin 32 relative to the greater (S _B <S _B'). Also, as shown in FIG.
The height of the convex portion 53b of the cam 53 is h, and the guide arm 51
When the length of (52) is set to l ₁ and the length of the lever 46 (49) is set to l ₂ , the movement stroke of the link 41 (42) is Therefore, it becomes easy to set the stroke of the link.

By the way, as shown in FIGS. 3 and 4, for example, when the link 42 is on the right side, that is, when the second developing device 24 is separated from the photosensitive drum 2, the guide bush 62 and the link 42 are separated.
Contact at the end of the long hole 42a of the link 42,
Move to the right together with the gap δ
₁ differs from the gaps δ _{1 to} δ ₄ shown in FIGS. 7 to 9 even when the link 42 approaches the leftmost end.
It is provided with a margin so that it does not abut against the long hole 61 of 0 and project. Although only the mechanism on the front side is shown in the above embodiment, the mechanism and the operation on the rear side are the same, and the description thereof will be omitted.

On the other hand, when the first or second developing device 23, 24 is pressed against the photosensitive drum 2, the links 41, 42, 43, 44 move to the left as shown in FIGS. 2 and 3. Then, the pin 31 or 33 of the first or second developing device 23, 24 and the rotary shaft 27a, 27a are guided by the guides 37 to 37.
When it comes into contact with 40, the movement of the guide bush 62 also stops at that time, but the movement of the links 41 to 44 tries to move further to the left, and thereafter, the guide bush 62 is moved by the biasing force of the sprig 63 to the photosensitive drum. By being pushed toward the second side, gaps δ ₃ and δ ₄ are generated between the guide bush 62 and the links 41 and 42, whereby the first and second developing units 23 and 24 are provided at both ends in the longitudinal direction. Guides 37 to 40 selectively only by the urging force of the spring 63 from the section
The guide rails 37 to 40, that is, the photosensitive drum 2 can be accurately positioned.

Thus, FIG. 7 shows the copying state by the second developing device 24, and FIG. 8 shows the copying state by the first developing device 23. A gap S ₁ or S ₂ is relatively formed between the magnet roller 27 of each developing device and the photosensitive drum 2 so that the non-contact state can be maintained.

Further, FIG. 9 shows the developing devices 23 and 2 of FIG.
4 As both away from the photosensitive drum 2 the gap S _3, S
₄ shows a state in which No. ₄ is formed. That is, after the photosensitive drum 2 is stopped, the first developing device 23 to the second developing device 2
When switching to 4, even if the first developing device 23 located upstream with respect to the rotation direction of the photosensitive drum 2 is separated, the toner 29 of the first developing device 23 remains on the photosensitive drum 2 in the first direction. Since the developing device 23 and the second developing device 24 adhere to each other over the section O ₁ from the contact positions a and b to the cleaning position c, the state is kept as it is in the downstream direction with respect to the rotation direction of the photosensitive drum 2. When the second developing device 24 located at
The toner 29 of the first developing device 23 is prevented from being mixed into the second developing device 24, and at least the first developing device 2
The photosensitive drum 2 is rotated while keeping both developing devices 23 and 24 in a non-contact state for a distance of O ₂ or more from the contact position a of No. 3 to the contact position b of the second developing device 24. . In this case, in practice, the rotation range of the photosensitive drum 2 is a half rotation or more larger than the section O ₂ .
It is usual to make one rotation or more, and the above operation is not necessary when switching from the second developing device 24 to the first developing device 23.

Therefore, the first and second developing units 23 and 24 can be selectively operated without the need for a drive motor capable of rotating in the forward and reverse directions and a one-way clutch.
Toner 29 without rotating magnet roller 27
Alternatively, the supply of 30 can be stopped and the structure can be significantly simplified.

The present invention is not limited to the above-mentioned embodiment,
Of course, various modifications can be made within the scope of the gist.

〔The invention's effect〕

As described above, according to the present invention, the first and second developing devices are selectively moved by the moving means, one of the developing devices is brought close to the image carrier, and the other developing device is separated from each other. The movement of the first and second developing devices selectively connects and disconnects them with the driving means to operate them, so that there is no need for a motor, a one-way clutch, etc. capable of rotating in the forward and reverse directions as the driving means as in the prior art. The first and second developing devices can be selectively operated, and
The drive means of the magnet roller for cutting the magnetic brush of the developer is not required, and the structure is remarkably simplified.
Cost can be reduced. Further, when switching between the first and second developing units, both developing units are separated from the image carrier, and the image carrier is rotated in a cleaning state over a predetermined range. The toner before adhering to the toner can be prevented from being mixed into the next developing device, and the operation of attaching and detaching the developing device can be facilitated, and the image carrier can be prevented from being damaged.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a block diagram showing switching means of a developing device, and FIGS. 3 and 4 are image bearing members of the developing device. FIG. 5 and FIG. 6 are views showing the driving means of the developing device, and FIGS. 7 and 8 are schematic explanatory views of the essential parts showing the developing state, and FIG. FIG. 4 is a schematic explanatory view of a main part showing a state where the developing device is separated from the image carrier at the time of switching. 2 ... Photosensitive drum (image carrier), 4 ... Developing device, 6 ...
... Cleaning device, 23, 24 ... Developing device, 27 ...
Magnet roller, 47, 50 ... Shaft, 53 ...
Cam 56, drive motor, S _{1 to} S _4, gap,
_{O 1,} O ₂ ...... section, a, b ...... contact position, c ...... cleaning position.

Claims (1)

[Claims] 1. A rotatable image carrier, cleaning means for cleaning the surface of the image carrier, a first developing device provided in the vicinity of the image carrier, and a first developing device in the vicinity of the image carrier. A second developing device provided at a position downstream of the first developing device in the rotation direction of the image carrier.
And a switching means for selectively moving the first and second developing devices in a direction in which the first and second developing devices are brought into contact with and separated from the image carrier to relatively change the distance of the gap between the image carrier and the image carrier. When the switching means switches at least from the first developing device to the second developing device, both the first and second developing devices are separated from the image carrier and the image carrier is carried out. An image forming apparatus, characterized in that the body is rotated by a distance equal to or more than the distance between the first developing device and the second developing device to clean the surface of the image carrier by the cleaning means.