JPH0746243B2 - Rotary developing device for image forming apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrostatic latent image formed on a latent image carrier having a plurality of developing devices containing a developer and each developing device occupying a predetermined phenomenon position. So that the development operation to visualize the
The developing unit is rotatably supported at a predetermined position facing the latent image carrier and is supported so that it can be pulled out from the predetermined position. When the unit is pulled out from the predetermined position, the developing unit is carried. The present invention relates to a rotary developing device of an image forming apparatus capable of removing the unit from the unit carrier.

2. Description of the Related Art A rotary developing device of the above type in an image forming apparatus such as a copying machine or a printer is conventionally known. In this type of developing device, the developing unit set at a predetermined position in the main body of the image forming apparatus is rotated to position a predetermined developing device at the developing position, and the electrostatic latent image formed on the latent image carrier is formed. Is visualized by the developing device. Therefore, it is necessary to rotatably support the developing unit. At this time, at least one of the end walls located at the longitudinal end of the developing unit is formed with a cylindrical outer peripheral surface, and the outer periphery thereof is formed. If the surface is rotatably supported by at least three support pieces, the developing unit can be kept in a stable state even if the developing device or other device element is located outside this end wall in the longitudinal direction of the developing unit. This is advantageous because it can be rotatably supported.

However, like the developing unit of the type described at the beginning, it is constructed so that it can be pulled out from a predetermined position in the main body of the image forming apparatus, and the developing unit pulled out can be detached from the unit carrier that carries it. If it is configured to, the end wall of this developing unit,
When supported by at least three support pieces as described above,
This may be an obstacle, and it may become impossible to remove the developing unit from the unit carrier.

The present invention is based on the above-mentioned novel recognition, and is capable of rotatably supporting a developing unit in a stable state, and when the unit is pulled out, it can be detached from the carrier unit without trouble. It is an object to provide a developing device of the type described at the beginning.

Configuration The present invention, first, of the both end walls located at the longitudinal end of the developing unit, the outer peripheral surface of at least one end wall is formed into a cylindrical shape, and when the developing unit is set to the above-mentioned predetermined position, A first feature of the present invention is that the outer peripheral surface of at least one end wall is rotatably supported by the support piece at at least three places. With this configuration, even if a soft element is arranged outside the end wall of the developing unit in the longitudinal direction of the unit, the unit can be supported in a stable state without any trouble. The present invention is further characterized in that at least one of the support pieces is supported by the image forming apparatus main body. As a result, when the developing unit is pulled out from a predetermined position inside the image forming apparatus main body,
The unit is released from the restraint by the supporting piece supported by the image forming area main body, and the unit can be freely removed from the unit carrier. Further, according to the present invention, when the developing unit is pulled out or returned to the predetermined position, at least one supporting piece supported by the image forming apparatus main body is separated from the developing unit, and the developing unit is set to the predetermined position. Another feature is that a contacting / separating means for contacting the supporting piece supported by the main body of the image forming apparatus with the outer peripheral surface of the end wall of the developing unit is provided.
With this configuration, the developing unit can be freely pulled out or returned to a predetermined position in the image forming apparatus main body without being disturbed by the support portion piece provided in the image forming apparatus main body.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

The rotary developing device shown in FIG. 1 has a developing unit 1 which is supported by a main body 2 of a copying machine, which is an example of an image forming area main body, so as to be freely drawn out as described later. FIG. 1 shows a state in which the developing unit 1 is set at a predetermined position in the body of the copying machine (from the copying machine body 2 to the developing unit 1).
(See Fig. 2 for the state of pulling out). The developing unit 1 has a plurality of developing machines 3, 3R, 3B in the illustrated example, and the developer chambers 4, 4R, 4B of the developing machines 3, 3R, 3B are made of a non-magnetic material such as aluminum. Partition walls of the casing member 5 consisting of
It is divided by 6,6R, 6B and two end walls 7,8 (see FIGS. 2 and 3) fixed to each end portion in the longitudinal direction.

The developer chambers 4, 4R, 4B of the developing devices 3, 3R, 3B contain developers 9, 9R, 9B of different colors, and in this example, these developers are black, red, and blue, respectively. Suppose there is. It is also possible to store cyan, yellow, and magenta toner developers in each developer chamber to form a full-color image. It is also possible to store the same color developer in each developer chamber and selectively use this. Although a one-component developer containing no carrier may be used as the developer, in the example shown in the figure, a two-component developer having a carrier and a toner, at least a part of which is a self-control developer. Is used.

Although the developing devices 3, 3R, 3B shown in FIGS. 1 to 3 are arranged radially about the central axis O of the developing unit 1,
Since all of the structures are the same, in the following description, the configuration of the first developing device 3 will be mainly described and the other developing devices 3 will be described.
With respect to the respective portions of R and 3B, the reference numerals assigned to the respective elements of the first developing device 3 are denoted by R and B, and the duplicate description thereof will be omitted.

The developing unit 1 is rotatably supported around its central axis O, and each developing device (more precisely, a developing roller described later) rotates to a predetermined developing position to perform a developing operation. First
The figure shows a state in which the first developing device 3 occupies the developing position. Reference numeral 88 denotes a drive motor for rotating the developing unit 1 around its center O.

In FIG. 1, the developer transport member provided in the first developing device 3, in the example shown, the developing roller 10 is partially exposed from the opening formed by the two partition walls 6 and 6R (see FIG. 2). Also, the developing roller 10 occupies a predetermined developing position with respect to the latent image carrier rotatably supported by the main body 2 of the copying machine, in this example, the photosensitive drum 11. The developing roller 10 is positioned parallel to the photosensitive drum 11 with a predetermined minute gap. A latent image carrier composed of a photosensitive belt may be used instead of the photosensitive drum, and it is well known that a latent image carrier composed of a dielectric belt or a dielectric drum is used depending on the model of the image forming apparatus. On the street.

An impeller 16 having a large number of blades 15 is provided inside the developer chamber 4.
The impeller 16 is rotationally driven in the counterclockwise direction in FIG. 1, whereby the developer in the developer chamber 4, that is, the toner and the carrier are supplied to the developing roller 10 while being agitated. The toner is triboelectrically charged to a predetermined polarity by the stirring.

Inside the developing roller 10, a magnet 21 having a magnetic pole composed of an S pole and an N pole is fixedly arranged in the casing member 5 of the developing unit 1 as shown by S and N in FIG. As a result, when the developing roller 10 is rotationally driven counterclockwise in FIG. 1, the developer 9 supplied to the developing roller 10 is magnetized.
It is carried on the surface of the developing roller 10 by the magnetic force of 21 and is conveyed counterclockwise. The developer conveyed is subjected to a scraping action by a doctor blade 22 fixed to the casing member 5, and a predetermined amount of the developer passing through the blade 22 is sent to the photosensitive drum 11 with its layer thickness regulated.

On the other hand, the photosensitive drum 11 is driven to rotate clockwise in FIG. 1, and an electrostatic latent image corresponding to an original (not shown) image is known on its surface by charging / exposure means not shown. Is formed. When this latent image reaches the opposing developing area D between the photoconductor drum 11 and the developing roller 10, the charged toner in the developer also conveyed to this area D is electrostatically transferred to the electrostatic latent image to form the latent image. Is visualized. The visible image is transferred onto a transfer paper (not shown) by a transfer device (not shown), and the transferred visible image is fixed by a fixing device (not shown). Development area D
The developer that has passed through is returned to the inside of the developer chamber 4 again,
It is mixed with other developers in this chamber and used again.

The other developing units 3R and 3B also occupy the predetermined developing position, and the developing operation is performed in exactly the same manner as described above. In this way, each developing device 3, 3R, 3B occupies a predetermined developing position so that the developing operation for visualizing the electrostatic latent image formed on the latent image carrier composed of the photosensitive drum 11 can be performed. ,
The developing unit 1 is rotatably supported at a predetermined position facing the photoconductor drum 11.

When the above-described developing operation is performed, the toner in the developer chamber 4 is sequentially consumed, so that the toner supply devices 44 and 4 shown in FIG.
Toner is supplied from 4R and 44B to each developer chamber. In FIG. 1, only the positions of the toner supply devices 44, 44R and 44B are shown by chain lines.

Next, the configuration relating to the support of the developing unit 1 will be described.

As shown in FIGS. 1 and 2, the slider 62 is pulled out to the front side (direction of arrow G in FIG. 2) of the copying machine main body 2 by a slide guide device 61 known per se, or conversely, to the back side (direction G). Similarly, it is slidably supported by the copying machine main body 2 so as to be pushed in the direction of arrow H). This slider
The developing unit storage table 63 is supported by the slider 62, and the slider 62
The storage table 63 constitutes a unit carrier for slidably supporting the developing unit 1 on the main body 2 of the copying machine. As a result, the developing unit 1 is supported so that it can be pulled out from the above-mentioned predetermined position facing the photosensitive drum 11.
Further, as will be described later, when the developing unit 1 is pulled out from the predetermined position, the developing unit 1 can be removed from the unit carrier that supports the developing unit 1. The unit carrier may not be divided into the storage table 63 and the slider, but may be configured as an integrated carrier.

The slider 62 includes a support plate 64 on the front side and a support plate 65 on the back side (the third side).
(See also the drawing), and a base plate 66 connecting them, and both supporting plates 64, 65 have respective ends of first to third connecting rods 67, 68, 69 extending parallel to each other in the sliding direction of the slider 62. The parts are fixed to each other, and both support plates 64, 65 are reinforced by these connecting rods 67, 68, 69.

The storage base 63 also has a front support arm 70 and a rear support arm 71.
(Fig. 3), and the lower cover 72 is attached to these arms 70 and 71.
Is stuck. Both supporting arms 70, 71 and the lower cover 72 are pivotally supported by a third connecting rod 69 of the slider 62 so as to be rotatable in the direction of arrow I. An upper cover 75 is pivotally supported on the storage base 63 via a pivot pin 73 so as to be rotatable in the arrow J direction.
The upper cover 75 is normally held in the closed position shown in FIGS. 1 and 3 (the position shown by the chain line in FIG. 2).

On the other hand, the outer peripheral surface of the front end wall 7 in the developing unit 1 is formed in a cylindrical shape, and the outer peripheral surface of the rear end wall 8 is also cylindrical. Upper part 7a, 71 of both support arms 70,71 of the storage stand 63
The a is formed in an arc shape that fits the outer peripheral surfaces of the end walls 7 and 8. Further, a plurality of, in the illustrated example, two supporting roller pieces 76, 77 are rotatably supported by the supporting arm 70 on the front side, and the outer peripheral surface of the end wall 7 on the front side of the developing unit 1 is rotatably supported. Are supported in two places by these support rollers 76, 77. When the developing unit 1 is pulled out from the main body 2 of the copying machine by the slider 62, the cylindrical end wall 8 on the back side of the developing unit 1 has an arc-shaped upper portion 71a of the support arm 71 on the back side as shown in FIG. Is rotatably supported by. With these configurations, the developing unit 1 can rotate around its central axis O while being supported by the storage table 63.

The developing unit 1 supported by the storage base 63 is pulled out from a predetermined position in the copying machine main body 1 by pulling out or pushing the slider 62 in the direction of the arrow G as described above, or in the copying machine main body 1 It is set back in place. That is, when setting the developing unit 1,
It is sufficient to push the slider 62 in the direction of the arrow H (FIG. 2) while the developing unit 1 is carried by 63. Immediately before the completion of this pushing operation, the positioning pin 78, which is the end wall 8 on the back side of the developing unit 1 and which is projected on the central axis O of the unit 1, has a side plate on the back side of the copying machine main body 2 ( It is fitted into a positioning hole (not shown) formed in a not shown) or a hole of a bearing (also not shown) fitted therein, so that the back side of the developing unit 1 is located in the main body of the copying machine. 2. Therefore, the main body 2 is positioned with respect to the photosensitive drum 11 supported at a predetermined position. At this time, in this example, as can be seen from FIG. 1, the depth reduction 8 on the inner side slightly rises from the support arm 71 of the storage table 63. Therefore, the rear side of the developing unit 1 is rotatably supported by the copying machine main body 2 via the positioning pin 78, and is positioned with respect to the photosensitive drum 11. On the other hand, the end wall 7 on the front side is still rotatably supported by the two support rollers 76 and 77 even after the developing unit 1 is set, but the pin protruding from the support arm 70 on the front side of the storage base 63 is provided. 82 (second
Is fitted in a positioning hole formed in the front side plate 83 of the copying machine main body 2 or in the center hole of the receiving member 85 fitted in this, and the front side of the storage base 63 is set to the photosensitive drum 11. Positioned relative to. Therefore, the front end wall 7 of the developing unit 1 supported on the front side of the storage base is positioned with respect to the photoconductor drum 11 via the storage base 63, and as a result, the front and rear sides of the development unit 1 (that is, the rear side). The whole) is positioned at a predetermined position parallel to the photosensitive drum 11. Also, on the back side of the storage base 63, a pin 86 (FIG. 3) protruding from the support arm 71 is fitted into a hole (not shown) formed in the side plate on the back side of the main body, so that the storage base 63 is covered. The back side is fixedly positioned and supported by the main body 2 of the copying machine.

In the example illustrated above, the developing unit 1 set in the main body of the copying machine has the storage table 63 whose rear side is positioned in the main body 2 of the copying machine and whose front side is positioned in the main body 2 of the copying machine. It is positioned on the main body 2 via. As a result, the entire developing unit 1 is positioned with respect to the photosensitive drum 11, but when the storage base 63 is inserted and set in the main body of the copying machine, the entire storage base 63 is moved by the above-mentioned pins 82 and 86. A support roller similar to the rollers 76 and 77 on the front side is provided on the support arm 71 on the back side of the storage base 63, which is positioned with respect to the main body 2 of the copying machine. End wall 8 of the developing unit 1 is rotatably supported by the supporting roller of the back side supporting arm 71, and the entire developing unit 1 (back side and front side) is transferred to the main body 2 of the copying machine through the storage base 63, and thus the photoconductor. It can also be positioned with respect to the drum 11.

As will be described later, at least one movable support roller 87 (FIG. 2) movably supported by the side plate 83 on the front side of the copying machine main body 2 is used to support the front side. It is configured to press the upper part of the side end wall 7. Therefore, the end wall 7 of the developing unit 1 set at a predetermined position in the main body of the copying machine has three support rollers 76, 77, 87.
Supported from three sides by, the developing unit 1 is able to rotate about its central axis O while keeping its position correct.

A circumferential groove is formed in the end wall 7, and a support roller is provided here.
76, 77 may be fitted, similarly, a groove may be provided in the end wall on the back side, and the support arm 71 on the back side (or a support portion such as a support roller) may be fitted therein. With this configuration, the developing unit can be positioned in the front-rear direction with respect to the unit carrier.

In this example, since the toner supply devices 44, 44R, 44B are provided in the space on the front side of the developing unit 1 as described above, as compared with the case where the toner supply devices are provided on the outer side in the radial direction of each developing device, Since the entire developing device can be made compact, and the toner supply devices 44, 44R, 44B are provided in a large space on the front side of the developing unit 1, the amount of toner to be replenished,
That is, the capacity of the toner tank can be increased. When the toner supply devices 44, 44R, and 44B are arranged in front of the developing unit 1 in this way, the toner conveying supply pipe and the like project from the end wall 7 of the developing unit 1. However, in the illustrated configuration, as described above, the outer peripheral surface of the end wall 7 is formed into a cylindrical shape, and this peripheral surface is supported by the supporting portion piece composed of the three supporting rollers 76, 77, 87. It is possible to support the developing unit 1 rotatably in a stable state of three points even if there is a supply pipe or the like outside the side.

Instead of the support rollers 76, 77, 87, the end wall 7 may be rotatably supported by a support piece made of, for example, a pin. The number of supporting pieces supporting the end wall 7 by the supporting pieces may be more than three. Further, in the example of the drawing, the back side of the developing unit 1 set in the copying machine main body 2 rotatably supports the unit 1 by fitting the positioning pin 78 into the positioning hole. As described above, the support piece may be rotatably supported. Further, the end wall of the developing unit 1 in the longitudinal direction is a cylindrical supported surface,
Since this is supported by the support piece, it is not necessary to provide a special supported member in the developing unit, and the increase in cost can be suppressed. Further, the outer diameters of the end walls 7 and 8 are relatively large, but if the end walls are supported by bearings that are in contact with the entire circumference of the end walls, the entire structure becomes large, but the end walls are not The structure can be made compact if supported by the support pieces.

As described above, the outer peripheral surface of at least one of the both end walls located at the longitudinal end of the developing unit is formed into a cylindrical shape, and when the developing unit is set at the predetermined position, at least one of the end walls is formed. The outer peripheral surface of the end wall is rotatably supported by the support pieces at at least three places, and at least one of the support pieces is supported by the copying machine main body, that is, the image forming apparatus main body. In the illustrated example, a supporting piece other than the supporting piece made of the supporting roller 87 supported by the main body of the copying machine, that is, a supporting piece made of the supporting rollers 76 and 77 is supported by the unit carrier. Moreover, the end wall 7 on the front side in the pulling-out direction of the developing unit 1
When the developing unit 1 is set at a position inside the main body of the copying machine, the outer peripheral surface of the end wall 7 on the front side is supported by the unit rollers.
It is rotatably supported by a plurality of support pieces composed of at least one support roller 87 supported by the main body 2 of the copying machine.

The developer unit cleans, inspects, or adjusts its elements regularly or as needed (e.g. doctor blades 22,2).
It is necessary to adjust the 2R and 22B differently) or to repair it. In such a case, the slider 62 is pulled out to the front side, the developing unit 1 is taken out of the copying machine main body, and the upper cover 75 is placed on the second side. It is possible to perform predetermined work such as maintenance and inspection by lifting it to the open position shown by the solid line in the figure. Therefore, even if the weight of the developing device is large, the worker can easily perform the work without soiling his hands and clothes with the developer. At this time, the developing unit 1 including the plurality of developing devices 3, 3R, 3B needs to be inspected and repaired not only on one side but also on the entire circumference thereof, as described above. Even when the slider 62 is pulled out, the end walls 7 and 8 of the developing unit 1 are stored in the storage table 63.
Since it is rotatably supported by the two support rollers 76 and 77 and the upper part 71a of the support arm 71 on the far side, the unit 1 can be freely rotated while being placed on the storage base 63. Therefore, any part of the outer circumference can be easily oriented toward the operator, and the required work can be performed easily and efficiently.

If the upper cover 75 is opened as shown in FIG. 2, the drawer developing unit 1 can be freely removed from the storage table 63. At that time, since the supporting roller 87 is supported by the copying machine main body 2 and is located away from the pulled-out developing unit 1 and does not restrain the developing unit 1 at all, it is disturbed by the roller 87. Without developing unit 1
Can be removed from 63. When returning the developing unit 1 to a predetermined position in the main body of the copying machine, the upper cover 75 is returned to the position shown by the chain line in FIG.

By the way, if the support roller 87 is fixedly supported on the body of the copying machine, when the developing unit 1 is pulled out of the body of the copying machine or pushed in, the storage base 63 and the developing unit 1 may interfere with the roller 87. There is. Therefore, in this example, when the developing unit 1 is pulled out or returned to the above-mentioned predetermined position, at least one supporting part piece, that is, the supporting roller 87, which is considered by the copying machine main body 2, is set to the developing unit 1
When the developing unit 1 is set at a predetermined position in the main body of the copying machine, the supporting roller 87 supported by the main body 2 of the copying machine is brought into contact with the outer peripheral surface of the end wall 7 of the developing unit 1. Separation means is provided. A specific configuration example of this contacting / separating means is as follows.

In FIG. 4, the side plate 83 on the front side of the copying machine main body 2 is
A rotating arm 100 is rotatably supported in a horizontal plane in the direction of arrow K via a bracket 99, and this arm 100 is biased toward the front side by a torsion coil spring 101 as shown by a solid line in FIG. There is. One end of a first link 102 is pivotally attached to the tip end region of the rotating arm 100, and one end of a second link 103 is pivotally attached to the other end of the link 102.
The other end of 03 is pivotally attached to a support member 104 that rotatably supports the movable support roller 87 via a pivot pin 105. The support member 104 is pivotally supported by a support bracket 106 fixed to the front side plate 83 of the main body of the copying machine via a pin 107 so as to be rotatable in the arrow P direction. The pin 107 is located below the portion where the second link 103 is pivotally attached to the support member 104. A pressure roller 108 is supported on the lower part of the tip of the rotating arm 100.

When the storage table 63 and the developing unit 1 are pulled out,
By the action of the spring 101, the rotating arm 100 occupies the position shown by the solid line in FIG. 4, and at this time, the movable support roller 87 is also retracted to the position shown by the solid line outside the movement path of the storage table 63. Therefore, if the slider 62 and the storage base 63 are pushed together with the developing unit 1 in this state, they will not interfere with the movable support roller 87. Immediately before the storage table 63 reaches the final position on the back side, the pressing member 109 (see also FIG. 2) attached to the slider 62 pushes the pressed roller 108 inward. As a result, the rotating arm 100 is rotated to the position shown by the chain line, the supporting member 104 is pushed leftward in FIG. 4 via the two links 102 and 103, and rotates around the pin 107 in the counterclockwise direction. Therefore, the movable support roller 87 descends downward, and at this time, the end wall 7 on the front side reaches below the roller 87, so that the roller 87 can be pressed against the peripheral surface of the end wall 7.

When the developing unit 1 is pulled out, the reverse operation is performed. Therefore, at this time also, the movable supporting roller 87 moves the developing unit 1
It does not interfere with the storage table 63.

Of course, the present invention can be widely applied to image forming apparatuses other than the copying machine, for example, developing devices such as printers.

Advantageous Effects of Invention The present invention forms the outer peripheral surface of at least one of the end walls located at the longitudinal end of the developing unit into a cylindrical shape, and sets the developing unit at a predetermined position in the main body of the image forming apparatus. Since the outer peripheral surface of at least one of the end walls is supported by the supporting piece at least at three points, the developing unit or other device may be located outside the developing unit end wall in the longitudinal direction of the unit. Even if the element is located, the developing unit can be surely rotatably supported. Moreover, since the portion supported by the support piece is the end wall of the developing unit, there is no need to provide a dedicated supported member, and the cost of the developing unit can be reduced. It is also possible to prevent the structure from becoming large.

Further, since at least one of the support pieces is supported by the image forming apparatus main body, when the developing unit is pulled out, it can be freely removed from the unit carrier. Moreover, when the developing unit is pulled out or returned to the above-mentioned predetermined position, at least one supporting portion piece supported by the image forming apparatus main body is separated from the developing unit,
When the developing unit is set at a predetermined position, a contacting / separating unit for contacting the supporting piece supported by the image forming apparatus main body with the outer peripheral surface of the end wall of the developing unit is provided. During the reverse setting operation, the unit can be moved without being disturbed by the support piece.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view when the developing unit is set at a predetermined position in the copying machine main body, and FIG. 2 is a perspective view showing a state in which the developing unit is pulled out from the copying machine main body and removed from the storage stand. FIG. 3 is a perspective view of the unit carrier as seen from the rear side with the developing unit removed, and FIG. 4 is a perspective view showing a configuration example of a contacting / separating means for vertically moving a movable supporting roller. Is. 1 ... Development unit, 3,3R, 3B ... Developer 7,8 ... End wall, 9,9R, 9B ... Developer

Claims (3)

[Claims] 1. A developing operation comprising a plurality of developing devices containing a developer, each developing device occupying a predetermined developing position to visualize an electrostatic latent image formed on a latent image carrier. In order to perform the above, a developing unit rotatably supported at a predetermined position facing the latent image carrier and supported so as to be able to be pulled out from the predetermined position is provided, and the unit is pulled out from the predetermined position. At this time, in a rotary developing device of an image forming apparatus capable of removing the unit from a unit carrier that carries the same, at least one end wall of both end walls located at the longitudinal end of the developing unit. The outer peripheral surface is formed into a cylindrical shape,
When the developing unit is set at the predetermined position, the outer peripheral surface of the at least one end wall is rotatably supported by the support piece at at least three places, and at least one of the support piece is an image forming apparatus. When the developing unit is supported by the main body and is pulled out or returned to the predetermined position, at least one of the supporting piece supported by the main body of the image forming apparatus is separated from the developing unit, and the developing unit is moved to the predetermined position. The developing device, comprising a contacting / separating means for contacting the supporting piece supported by the image forming apparatus main body with the outer peripheral surface of the end wall of the developing unit when set. 2. The developing device according to claim 1, wherein a supporting member other than the supporting member supported by the image forming apparatus main body is supported by the unit carrier. 3. An outer peripheral surface of an end wall on the front side in the drawing direction of the developing unit is formed into a cylindrical shape, and when the developing unit is set at a predetermined position, the outer peripheral surface of the end wall on the front side is a unit. 3. The developing device according to claim 1, wherein the developing device is rotatably supported by a plurality of supporting pieces supported by a carrier and at least one supporting piece supported by the image forming apparatus main body. .