JPS6329769A - Picture forming device - Google Patents

Abstract

PURPOSE:To prevent toner and its carrier from being scattered, by bringing a shutter farther from the magnet of a developing agent carrying member as the shutter is moved when the shutter is moved from the covered location to an opened location of a developing roller. CONSTITUTION:When a shutter 7 is moved from the covered location to the opened location (the state shown in the figure) of a developing roller 4, the carrier on the shutter 7 slips on the shutter 7 and tends to stay at the location corresponding to the S1 pole of the roller 4, because the carrier is strongly attracted by the S1 pole. The carrier is intercepted by the protruding section 7a at the end section of the shutter 7 and deposited in the section 7a. When the carrier reaches the position shown in the figure, the carrier drops onto a receiving saucer 24. Since the deposited location of the carrier on the shutter 7 is at the midway of the S1 and N1 poles, the force attracting the carrier to the developing roller 4 side becomes weak and, since the rotating center O2 of the rising section 17b of the shutter 7 is eccentric to the axis O1 of the developing roller 4 and the shutter 7 is separated from the surface of the roller 4 as it is moved to the opened location of the roller 4, the force of a magnet becomes weaker and the carrier drops onto the saucer 24.

Description

[Detailed description of the invention]

-1 The present invention generally relates to an image forming apparatus equipped with a developing device for developing an electrostatic latent image on a latent image carrier, and particularly relates to a color image forming apparatus equipped with a plurality of developing devices. The present invention can be suitably applied not only to an image forming apparatus for two or three or more monochromatic colors, so-called multi-color image forming apparatus, but also to a full-color image forming bag. shall include color copying machines, computers, color printers constituting the output units of facsimile machines, and other various color printing devices.

[Yu Hisatachi] In recent years, electrophotographic copying equipment (hereinafter referred to as "copying equipment"), which is a type of image forming apparatus, has become more widely used for A1@. It is also possible to make copies using multicolor toners such as blue and green. Some such copying machines make copies of each color by replacing the developing device for each color, but recently, the number of copies of each color has been increased by replacing the developing device for each color. A four-page IP, multiple copying system is adopted, and two or more developing devices containing toner of different colors are installed in the copying device, making it possible to copy images of different colors with a simple button press on the control panel. became. Conventionally, this type of copying apparatus has been constructed as shown in FIG. That is, a document placement glass 101 is arranged above the main body 100 of the copying apparatus. An original 102 placed on the original placing glass 101 is illuminated by a lamp 103, and a light image of the original is irradiated onto a latent image carrier, that is, a photosensitive drum 111, by an optical system consisting of reflective mirrors 104 to 109 and a lens 110. be done. At this time, the lamp 103 and the reflecting mirror 104.105.1
06 moves at a predetermined speed in the direction of the arrow to scan the original 102. On the other hand, the photosensitive drum 111 is rotated in the direction of the arrow after its surface is uniformly charged by the charger 112, and a light image is irradiated at the exposure section as described above, and the surface of the photosensitive drum 111 is sequentially charged. An electrostatic image corresponding to the original image is formed. Further, color toner (for example, red,
A developer conveying member consisting of a magnetizable sleeve having a magnet inside, for example, a color developing device TL13 having a developing roller 113a, which stores black toner, and is similar to the developing roller 113a described above. A black developing device M114 having a developing roller 114a that can have a structure of . These developing devices M113 and 114 are movable in the direction of the arrow, and approach the photosensitive drum 111 according to a desired color image to visualize the electrostatic image on the drum. In FIG. 9, a color developing device M113 is a photosensitive drum 111.
Since the black developing device 114 is located close to the black developing device 114, a black image is formed on the photosensitive drum 111, and this black image is transferred to the transfer paper 117 by the transfer charger 115. Thereafter, the photosensitive drum ill goes to a cleaner 11B, where residual toner on the surface is removed, and the photosensitive drum ill moves on to the next step. Transfer paper 1'17 is loaded in a cassette 118 and fed to a pair of rollers 120 by a paper feed roller 119. The roller pair 120 is designed to separate only the topmost transfer paper 117 and feed it into the apparatus when the transfer paper 117 is fed in a pile.After passing through the roller pair 120, the transfer paper 11
7 is a registration roller 1 via guide plates 121 and 122.
It reaches 23. The registration roller 123 starts rotating at the timing when the developed image on the photosensitive drum 111 and the transfer paper 117 match, and sends the transfer paper 117 to the surface of the photosensitive drum 111 via an upper transfer guide 124 and a lower transfer guide 125. -Then, the transfer paper 11 on which the image has been transferred as described above.
7 is separated from the surface of the photosensitive drum 111 by a separation charger 126 and sent to a fixing device 128 via a conveying section 127. The image on the transfer paper 117 is fixed as a permanent image by a fixing device 128, and then sent to a discharge section 129 and delivered to a tray 13.
Ejected to 0. In this copying apparatus, when developing with one developing device 114, the developing roller 114a is brought close to the photosensitive drum through a certain gap, but the other developing device l13 is placed close to the photosensitive drum 11.
1 and evacuated to a position away from the The reason for this is that, for example, when the developer in the developing device ail13 located upstream of the photosensitive drum 111 is a so-called one-component developer in which iron powder is coated with resin, the amount of the developer adsorbed on the photosensitive drum 111 is This is to avoid the problem of so-called mixed color development, in which a portion of the developing roller 114a of the lower developing device 114 is attracted by a built-in magnet, resulting in a mixture of different colored developers. In addition, when the developer in the developing device [113] is a two-component developer consisting of a magnetic powder carrier and a resin toner, when the magnetic brush rubs the surface of the photosensitive drum 111, a small amount of carrier is deposited on the surface of the photosensitive drum 111. adhere to. When the photosensitive drum 111 reaches the position of the developing device 114, this carrier is attracted to the developing roller 114a. In this case, the developing device 114
There is no problem if the developer is the same as the developer in the developing device 113. If the developer is a one-component developer, its carrier will be attached around the developing roller 114a. The carrier is captured between the developing roller 114a and a magnetic blade (not shown) that regulates the coating height of the developer on the developing roller 114a, and the coating height is reduced by the amount of the carrier. As a result, a problem arises in that a good developing effect is hindered. In order to avoid the various inconveniences mentioned above, the developing device 114
is retracted to a position away from the photosensitive drum when the developing device 113 is placed in the developing operation position. [Ll]However, in the image forming apparatus having the above configuration, there is a problem in that if a sufficient distance is secured for one of the developing devices to be retracted from the photosensitive drum, there will be wasted space and the apparatus will become larger. Therefore, a rotatable shutter was installed in the developing device, and when the developing operation was not performed, the developing roller was covered with this shutter, and when the developing operation was performed, the shutter was retracted to a desired position to expose the developing roller and enable development. something is proposed. However, the conventional shutter rotates close to the photosensitive drum when moving, which has the problem of damaging the photosensitive drum and furthermore causing toner and carrier attached to the shutter to scatter again. . The present invention was made in view of the above-mentioned problem, and its purpose is to improve the driving mode of the shutter so that it can be used in a narrow space without damaging the latent image carrier such as the photosensitive drum. Another object of the present invention is to provide an image forming apparatus that can open and close the shutter while preventing toner, carrier, etc. attached to the shutter from scattering. [lJ The above-mentioned purpose of accounting is achieved in an image forming apparatus according to the present invention. In summary, the present invention provides a developer transport member with a built-in magnet, a coating position that covers the exposed portion of the developer transport member facing the latent image carrier, and a coating position that covers the exposed portion of the developer transport member that supports the latent image. In an image forming company YI, which is equipped with a developing device having a shutter that is movable between an open position that exposes the body, when the shutter moves from the covered position to the open position, the shutter moves from the covered position to the open position. According to a preferred embodiment of the present invention, the developer conveying member is a developing roller having a magnet inside. The center of rotation of the shutter when the shutter moves from the covering position to the open position is eccentric to the rotational axis of the developing roller. Example of Disaster The image forming apparatus according to the present invention will be explained in more detail below with reference to the drawings. An embodiment of the present invention is illustrated in FIGS. 1-4. In this embodiment, the present invention is embodied in the two-color electrophotographic copying apparatus described above in connection with FIG.
In this embodiment, an electrophotographic photosensitive drum l is provided, and various means necessary for electrophotographic image formation are provided around the photosensitive drum l, similar to the arrangement shown in FIG. 9. Only the developing device portion is shown. A black toner (mag-toner) developing device 2 is disposed on the downstream side with respect to the rotational direction indicated by A of the photosensitive drum l, and a color toner developing device 3 containing a two-component developer is disposed on the upstream side thereof. . Each of the developing devices 2.3 has a developer conveying member, in this example a developing roller 4.5 consisting of a non-magnetic sleeve with a built-in magnet. FIG. 1 shows the black toner developing device 2 in the developing operating position and the color toner developing device 3 in the non-developing position, and FIG. 2 shows the color toner developing device 3 in the developing operating position and the black toner developing device 3 in the developing operating position. The developing device 2 is shown in the developing operating position. Referring to FIG. 1, the color toner developing device M3 is detachably attached to a support rail R having a roughly U-shaped cross section, and the rail R is held on the side plate of the main body in a well-known manner so as to be freely movable in X directions. ing. Further, a spring 6 is connected to a projection P formed integrally with the support rail R, and is biased in the direction of arrow B. Therefore, the one-color toner developing device 3 is moved in the direction away from the photosensitive drum 1, and is stopped in contact with the stopper 21. On the other hand, the black toner developing device 2 is swingably supported around a pivot shaft 18. In this embodiment, the developing device 2 is rotated around the rotating shaft 18 in a direction away from the photosensitive drum 1 due to the action of gravity. It is structured with a tendency to move. In FIG. 1, a protrusion 8a formed at one end of the developer container 8 is pressed by a cam 11, rotates clockwise about a shaft 18, and is moved toward the photosensitive drum l. Cam 11
can be a normal eccentric cam that rotates around a rotating shaft, but in this embodiment, a groove 11a is formed in the eccentric cam 11, and a mouth-shaped shaft 12 is fitted into the groove. Shaft 11 and groove 1
A spring 13 is disposed between the shafts 1a, and the cam 11 is configured to be able to slide in the direction of arrow C with respect to the shaft 12. Blooming,
During the developing operation of the black toner developing device 2, the projection 8a of the developer container 8 of the developing device 2 is pressed in the solid line direction of arrow C by the compression spring 13, so that the developing device 2 is brought close to the photosensitive drum 1. In this state, the developing roller 4 of the black toner developing device 2 is set so that the exposed portion 4a facing toward the photosensitive drum l from the opening 8a of the developer container 8 is maintained at a predetermined distance from the photosensitive drum l. In this copying apparatus, the black toner developing device is normally set to be in an operating state as shown in FIG.
The cam 11 that was pressing the projection 8a rotates counterclockwise together with the rotation shaft 12, and is released from contact with the projection 8a. When the cam 11 is rotated counterclockwise, it engages one 7-m 14a of a bell crank-shaped actuating member 14 rotatably mounted around a shaft 16. The cam 11 rotates the actuating member 14 clockwise around the shaft 16. As the actuating member 14 rotates clockwise, the other arm 14b engages with the protrusion 8a of the black toner developing device 2. The developing device 2 is rotated counterclockwise around the shaft 18. As a result, the black toner developing device 2 is placed at a developing non-operating position separated from the photosensitive tram 1 (Fig. 5S2). On the other hand, due to such rotation of the black toner developing device 2, the protrusion 8b formed at the other end of the developing container 8 is moved to the color toner developing device 3.
2), and move the rail R and the developing device 3 to the left side (in the opposite direction of arrow B) in FIG. 1 (FIG. 2). According to the present invention, when the black toner developing device Wt2 located below is placed in the developing non-operating position as shown in FIG. 2, the exposed portion 4a of the developing roller 4 of the developing device 2 is covered. A shutter 7 is provided for this purpose. The shutter 7
has a curved cross section so as to cover the exposed portion 4a of the developing roller 4, and the exposed portion 4a of the developing roller 4 is The developing roller is configured to be movable to the open position M (FIG. 1). To explain the shutter 7 in more detail with reference to FIGS. 3 to 5, the shutter 7 is formed of an arc-shaped plate extending along the longitudinal direction of the developing roller 4 as described above. A protrusion 7a extending in the longitudinal direction is formed at one end. Further, fan-shaped rising portions 7b, 7b are integrally provided on both sides of the arc-shaped plate. Each rising portion 7b
A bearing hole 7c is bored in the eccentric shaft 22a having a rotation center 02 offset by a distance e from the center OI of the shaft 22, which is the axis of the developing roller 4a and the rotation center.
are rotatably fitted. The shaft 22 and the eccentric shaft 22a are integrally formed. Further, a long hole 7d is bored in the rising portion 7b, and the long hole 7d is formed in the rising portion 7b.
d is engaged with pin loa. The pin lOa is integrally implanted in a boss portion (FIG. 5) of the gear 10 rotatably supported by the shaft 22. The gear 10 and the shutter 7 are rotated as described below. A sector gear 17 is rotatably attached to a rotation support shaft 18 of the black toner developing device 2. Also, the large gear 15a and the small gear 1
A relay gear 15 that is integrated with the gear 5b is rotatably provided in the developing device through a shaft 16, and a large gear 15a is integrated with the gear 10.
Further, the small gears 15b mesh with the sector gears 17, respectively. The sector gear is urged in the direction of the arrow in FIG. 4 by a spring 19, and its rotation amount is determined by the engagement of a stopper 17a embedded in the gear 17 with an opening 20 in the side plate of the main body of the device. Regulated. In such a state, that is, the black toner developing device t2 is in the first state.
In the developing operating position shown in FIG. 4 and FIG. 4, the shutter 7 is moved below the arcuate stage portion 9 of the developing container 8 so as not to cover the exposed portion 4a of the developing roller 4. The shutter 7 is located approximately 1 to 2 times from the outer station of the stage section 9.
They are disposed movably and removably at positions spaced apart by mm, occupy only a small space, and are designed not to interfere with the developing operation of the developing device 2. The color toner is selected and the black toner developing device is placed on the photosensitive drum.
When the intermediate gear 15 and the gear 10, which are engaged with the sector gear 17 which is held in a substantially fixed state, rotate in the direction of arrow C in FIG. , 8 and a gear 10 by a pin lOa, the shutter 7 also rotates in the direction of arrow C. By rotating the shutter 7 clockwise, the exposed portion 4a of the developing roller 4 of the black toner developing device is covered by the shutter as described above. At this time, the shutter 7 rotates until its protrusion 7a abuts one end 22a of the cover 22, so the exposed portion 4a is completely covered. In the M type 117, the projection 7a of the shutter 7 is connected to the cover 22.
After the shutter 7 comes into contact with one end 22a and stops rotating, when the black toner developing device 2 further rotates slightly, it resists the biasing force of the spring 19 and moves to the right in FIG. Rotate slightly. Further, since the shutter 7 rotates around the rotation center Oz eccentrically toward the movement position with respect to the axis 01 of the developing roller 4, the shutter 7 moves closer to the developing roller 4 when the exposed portion 4a of the developing roller 4 is covered. brought to a state of In this embodiment, the black toner developing device 2 has a four-pole magnet fixed in the developing roller 4 (see FIG. 2). The magnetic blade 23 that regulates the thickness is disposed facing the magnetic blade 23, and the S and pole poles are disposed facing the photosensitive drum l. Further, the NZ pole is located below the developing roller 4 and acts as a seal to prevent the mag toner from spilling from the lower opening of the developing container 8, and the Sz pole promotes adhesion of the mag toner to the developing roller 4. It functions to increase frictional charging between the magnetic toner and the developing roller 4. The shutter 7 described above has a protrusion 7a formed at the front end that comes into contact with one end 22a of the cover 22, and the protrusion has the following effect. In this copying apparatus, when color toner development is performed using the arrangement of the developing devices as shown in FIG. 2, a small amount of carrier adheres to the photosensitive drum. The carrier is
When the photosensitive drum 1 rotates in the direction indicated by the arrow in FIG. It is deposited on the coated shutter 7. When this shutter 7 moves from the developing roller covering position M (FIG. 2) to the developing roller releasing position (FIG. 1), the carriers on the shutter 7 are strongly attracted to the S electrode, so the carriers on the shutter 7 are The robot tries to remain in the position corresponding to S1 by sliding or rolling. The carriers are blocked by a protrusion 7a formed at the end of the shutter 7, and are deposited next to the protrusion 7a. When the carrier moves together with the protrusion 7a and reaches the position shown in FIG. 1, it falls onto the tray 24 which is removably installed in the main body of the apparatus for the reason described below. The first reason is that the carrier deposition position in the shutter 7 corresponds to an intermediate position between the S1 pole and the N pole, so the lines of magnetic force are tangential to the surface of the developing roller 4. This is because the force that attracts the carrier to the developing roller 4 becomes weaker. The second reason is that the rotation center 0 of the rising portion 17b of the shutter 7 is eccentric to the axis o1 of the developing roller 4. Therefore, as the shutter 7 moves to the developing roller release position, it becomes separated from the developing roller surface, and the magnetic force of the magnet becomes weaker.As explained above, in the above embodiment, the carrier fall prevention means are: Although the description has been made in relation to the shutter 7 having the protrusion 7a, the invention is not limited thereto, and for example, FIGS.
The configuration shown in the figure can also be used. In these modified examples, the same members and parts as in the above-mentioned embodiments are given the same reference numerals, and detailed explanation thereof will be omitted. In the embodiment shown in FIG. 6, the carrier fall prevention means is the shutter 7 It can also be configured with a plurality of protrusions (projections) 25 extending parallel to each other in the longitudinal direction on the surface of the golf pole.
It can also be constructed by forming a recess 26. FIG. 7 shows another modification of the carrier fall prevention means,
This carrier fall prevention means is formed by providing electrostatic flocking 27 on the surface of the shutter 7 extending in the longitudinal direction thereof. In each of the above-mentioned modifications shown in FIGS. 6 and 7, the carrier captured on the shutter 7 does not move on the surface of the shutter 7, so the falling position of the carrier is compared to the above embodiment. Then, it will fall onto the tray 24 over a rather wide range. Therefore, it is necessary to take this point into account when arranging the magnetic poles of the developing roller. Further, although the shutter 7 has been described as rotating around the rotation center oZ in FIG. 3, the shutter 7 has rotation centers 03 and 04 as shown in FIG. 8, and the arm 29 rotates around the rotation center 03. The front end of the shutter 7 rotates via the arm 30, and the rear end of the shutter 7 rotates about the rotation center 04 via the arm 30. With this configuration, the shutter is largely separated from the developing roller, especially in the carrier release position, and the carrier is placed in the tray 2.
4 can be easily released. 11 vertical differences] The image forming apparatus according to the present invention configured as described above has the following features:
It has an extremely simple configuration and occupies only a small amount of space.
Layer 11! 'The shutter can be driven without damaging the carrier, and furthermore, it is possible to effectively prevent the magnetic powder carrier scattered from one developing device from getting mixed into other developing devices. At the same time, it is possible to maintain a good developing effect, obtain high quality images, and improve the reliability of the image forming apparatus. Moreover, it can also meet the demand for miniaturization.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device portion of an image forming apparatus according to the present invention, in which the black toner developing device is in a developing operation position. FIG. 2 is a sectional view of the developing device portion of the image forming apparatus according to the present invention, similar to FIG. 1, in which the color toner developing device is in the developing operation position. FIG. 3 is a partial side view showing the shutter. FIG. 4 is a partial side view showing the driving portion of the shutter. FIG. 5 is a sectional view of the driving portion of the shutter. 6 and 7 are cross-sectional views showing modified examples of the shutter. FIG. 8 is a sectional view showing a modification of the shutter rotation means. FIG. 9 is a cross-sectional view of a two-color electrophotographic copying apparatus. 2.3: Developing device 4.5: Developing roller 4a: Developing roller exposed portion 7: Shutter 7a, 25.26.27: Fall prevention means Fig. 1 Fig. 3 Fig. 5

Claims (1)

[Scope of Claims] 1) A developer conveying member with a built-in magnet, a covering position that covers the exposed portion of the developer conveying member facing the latent image carrier, and a latent image covering the exposed portion of the developer conveying member. In an image forming apparatus including a developing device having a shutter movable between an open position and an open position where the carrier is exposed, when the shutter moves from the covered position to the open position, the shutter moves from the covered position to the open position. An image forming apparatus characterized in that the developer conveying member moves further away from the magnet as it moves. 2) A patent in which the developer conveying member is a developing roller with a magnet inside, and the center of rotation of the shutter when the shutter moves from the covered position to the open position is eccentric to the rotational axis of the developing roller. An apparatus according to claim 1. 3) The magnet of the developer transporting member has a plurality of magnetic poles, and at least one of the poles is fixed to the exposed portion side of the developer transporting member, as described in claim 1 or 2. equipment.