JP2009139811A - Developing device for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a stable image by ensuring performance for toner replacement in a developing chamber, and maintaining toner performance in the entire image area for a long period of time. <P>SOLUTION: A partition wall 50 is disposed between the developing chamber storing the developing roller of a developing device and a toner supply chamber that has a stirring machine for supplying toner to the developing chamber. A plurality of openings 52 for supplying toner from the developing chamber to the toner supply chamber are formed in the partition wall 50. The plurality of openings 52 are formed so that the heights of the upper edges and lower edges of the adjacent openings 52 differ between each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device of an image forming apparatus used for a printing machine, a copying machine, a fax machine, a multifunction machine of these, and the like.

In the developing device of the image forming apparatus, toner is consumed according to the development of the electrostatic latent image on an image carrier such as a photosensitive drum. The developing device is provided with a toner replenishing chamber for storing toner and a developing chamber for supplying toner from the toner replenishing chamber. Conventionally, a partition wall 60 as shown in FIG. 7 is provided between the toner supply chamber and the developing chamber (see the partition wall 50 in FIG. 2), and the partition wall 60 has a width direction of the developing device. A plurality of rectangular openings 61 are formed at predetermined intervals.
The toner supply chamber is provided with a stirring member that can appropriately supply toner from the opening 61 in the developing chamber, and the toner is supplied from the toner supply chamber to the developing chamber by the rotational force of the stirring member.
JP-A-10-123836

  However, in the conventional developing device described above, when a developing operation is performed when a sufficient amount of unused toner is stored in the toner storage chamber, the amount of toner entering the developing chamber from the opening 61 by the toner mixer is reduced. The excess toner stays in the developing chamber. When the toner is further supplied into the developing chamber from the plurality of openings in a state where the excess toner is filled in the developing chamber, the toner pressure in the storage chamber increases. In addition, since toner is supplied at the center and both ends at the same time, it is difficult for the toner to spread laterally. In addition, the pressure at both ends in the developing chamber increases and the toner aggregates, and the toner quality deteriorates due to poor charging and aggregation due to the toner being subjected to stress for a long time, resulting in image defects such as image fog and black spots. Or the toner is insufficiently charged and soiled, resulting in a disadvantage that the print image quality is deteriorated.

  In order to solve this, in the technique of Patent Document 1, as shown in FIG. 8, among the plurality of openings of the partition wall 60, the lower edge portion of the opening 62 positioned at both ends thereof is extended downward. did. According to such a technique of Patent Document 1, toner is supplied first from the lower edge of the opening at both ends. Thereafter, the toner is supplied side by side from the entire supply roller openings 61 and 62 including the central opening 61. Then, the toner pressure in the developing chamber is rapidly increased by the replenishment of the toner, and most of the previously supplied toner returns from the openings 61 and 62 as it is. In particular, the openings 62 at both ends are larger than the other openings 61 so that the toner can easily move. When the toner is supplied to the upper part of the both end openings 62, the toner from the lower part is directly transferred from the developing chamber to the toner supply chamber. Will return as a shortcut. As a result, the toner located at both ends tends to be difficult to replace.

By the way, when printing paper, for example, with a printing machine capable of printing A4 paper, when printing B5 paper, both end areas of A4 wider than B5 are not printed at all. The toner consumption is generally less at both end portions than at the central portion, and it is difficult for toner to be replaced at both end positions in the developing chamber.
In this way, when toner replacement is difficult to occur, the toner quality is deteriorated due to unevenness in the toner particle size, charging failure and aggregation due to the toner being subjected to stress for a long time, and image defects such as image fog and black spots. May occur.
The present invention has been made in view of such circumstances. Even when the toner in the developing chamber is located at both ends of the developing chamber, the toner replacement performance is ensured and the toner is excessively stressed. An object of the present invention is to provide a developing device capable of forming a stable image while maintaining toner performance over a long period of time in the entire image area.

In order to achieve the above-mentioned object, the present invention comprises a developing roller for developing an electrostatic latent image on a photosensitive drum, and a supply roller for supplying a developing toner to the developing roller. A rotating shaft extending in the axial direction is provided, and a toner stirring member that stirs toner by rotating the rotating shaft and replenishes toner to the supply roller is provided in the toner replenishing chamber, and between the developing chamber and the toner replenishing chamber. Is an image forming apparatus in which a partition wall having a plurality of openings formed in the axial direction of the supply roller is formed, and toner is supplied from the openings to the developing chamber from the toner supply chamber by the toner stirring member. In the developing device, the height positions of the upper edge portion and the lower edge portion of the openings are changed with respect to the openings adjacent to the openings.
The said invention can be arrange | positioned in the position which the said some opening does not overlap with respect to the said adjacent opening and the height direction of the said partition wall.
Moreover, the said invention arrange | positions the opening located in the both ends of the said partition wall in a low position rather than the opening located in the center part of the said partition wall in the axial direction of the said supply roller among these openings. Can do.
Further, in the partition wall according to the invention, a part of the plurality of openings is formed at an upper position of the partition wall, and a plurality of remaining openings are formed at a lower position of the partition wall. The openings can be arranged in a staggered manner from one end to the other end of the partition wall in the axial direction of the supply roller.
In the above invention, the plurality of openings may have the same rectangular shape and the same size.

  In the present invention, a partition wall is formed between the developing chamber and the toner replenishing chamber, and openings for supplying toner from the developing chamber to the toner replenishing chamber are formed at a plurality of locations on the partition wall. Since the height positions of the upper edge portion and the lower edge portion of the openings are changed with respect to the adjacent openings, the flow of toner in the lateral direction can be formed. In addition, a rapid increase in the toner pressure in the developing chamber can be suppressed. As a result, heat generation due to stress and friction applied to the toner can be reduced, the separation and embedding of the toner surface treatment agent is reduced, and the carrier coating agent peeling and toner spent are reduced. As a result, the performance of the developer can be maintained for a long time.

The developing device of the image forming apparatus according to the first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a laser printer 1 (hereinafter simply referred to as “printer 1”) incorporating a developing device according to the present invention. The laser printer 1 includes a printer main body 2 which is a substantially rectangular parallelepiped apparatus main body. The printer main body 2 has the right side in FIG. 1 as the front of the apparatus, and a paper discharge tray 4 is formed on the upper surface of the printer main body 2. The paper discharge tray 4 is configured by an inclined surface that is gently inclined so that the front side is positioned higher, and a plane that continues to the front side of the inclined surface. As will be described later, the sheet discharge tray 4 supports a sheet discharged from the sheet discharge port 5 forward after image formation from below. A manual feed tray lid 6 is disposed on the front surface of the printer main body 2 so that the upper end side opens forward.

A photosensitive drum 7 serving as an image carrier is disposed in a substantially central region in the printer main body 2 so as to be rotated clockwise in FIG. Around the photosensitive drum 7, a main charging roller 8, a developing roller 44 of a developing device, a transfer roller 10, a cleaning roller 11 and a cleaning blade 12, a static eliminator (not shown), and the like are provided. A laser scanning unit LSU that converts input image information into laser light and irradiates the surface of the photosensitive drum 7 is disposed at an upper position in the printer main body 2.
As the photoreceptor of the photoreceptor drum 7, an a-Si system or OPC is used. When a charging bias is applied to the main charging roller 8 by a charging bias power supply device (not shown), the surface of the photosensitive drum 7 is uniformly charged. In this embodiment, a positive charging bias is applied, and the surface of the photosensitive drum 7 is uniformly positively charged.

The developing device 40 according to the present invention visualizes the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 7. As shown in FIG. 2, the developing device 40 is provided with a developing chamber 41 and a toner replenishing chamber 42. A developing roller 44 that rotates in a direction, a toner supply roller 45 that supplies toner to the peripheral surface of the developing roller 44, and a toner blade 46 that sets the thickness of the toner layer on the developing roller 44 to an appropriate thickness. I have.
The developing roller 44 is a cylindrical member disposed in parallel to the central axis of the photosensitive drum 7, and is rotatably supported by the casing 47 of the developing chamber 41. The developing roller 44 is energized by a driving source (not shown) and rotates in the direction of the arrow b in the drawing during the developing operation, so that the toner supplied from the toner supply roller uniformly adheres to the outer peripheral surface. In this state, the photosensitive drum 7 is brought close to and opposed to the toner, and the toner on the outer peripheral surface is adhered to the photosensitive drum 7.
The developing roller 44 is provided with a cylindrical supply roller 45 adjacent thereto, and the supply roller 45 is disposed so that the rotation axis thereof is parallel to the rotation axis of the development roller 44 and can be rotated by a driving source (not shown). It is arranged.

The supply roller 45 is a cylindrical member having substantially the same length as the developing roller 44 and is in contact with the outer peripheral surface of the developing roller with a predetermined pressing force. During the developing operation, the toner rotates in the direction of arrow c in the figure, and the toner supplied from the toner replenishing unit 3 is attached to the developing roller 44. At this time, the toner supply roller 45 rotates in the same direction as the developing roller 44 (in the opposite direction at the nip portion), abuts against the developing roller 44 in a pressed state, and slides on the outer peripheral surface to each other. The toner can be attached to the toner.
Above the developing roller 44, a toner blade 46 is disposed inside the housing 47 in a state where it is implanted. The toner blade 46 has substantially the same width as the developing roller 44, and is disposed in a direction facing the rotation direction b of the developing roller 44. In this way, the toner adhering to the outer peripheral surface of the developing roller 44 can be favorably thinned.

The toner supply chamber 42 is provided in the container main body 48, and the container main body 48 may be fixed to the housing 47 of the developing chamber 41 or may be detachable from the housing 47. The toner supply chamber 42 is a space formed in a predetermined size, and the stirrer 49 and toner are stored in this space. The stirrer 49 includes a rotating shaft 49a located substantially at the center of the toner supply chamber 42, and a stirring member 49b that rotates about the rotating shaft 49a. The rotating shaft 49a of the stirrer 49 is disposed in parallel with the developing roller 44 described above, and is rotatably supported in the direction of arrow a by a driving source (not shown). During the developing operation, it rotates in the direction of the arrow d in the figure, and the stirring member 49b rotates accordingly, and rotates so as to scoop up the toner in the toner supply chamber 42.
A partition wall 50 is provided between the toner supply chamber 42 and the developing chamber 41 to partition them in the front-rear direction. The flat partition wall 50 extends in the same direction as the rotation axis of the supply roller 45, and The wall surface is formed in the vertical direction.

As shown in FIG. 3, a plurality (seven in this embodiment) of openings 52 a to 52 g (these openings 52 a to 52 g are collectively referred to as openings 52) are formed in the partition wall 50. The openings 52 are formed with an interval from one end to the other end of the partition wall 50, and in the present embodiment, the openings 52 a to 52 d positioned oddly from the left and right ends of the partition wall 50 are below the partition wall 50. The openings 52e to 52g located on the side and even-numbered from one end are located above the partition wall 50 and are arranged in a staggered manner toward the width direction of the partition wall 50 (the axial direction of the supply roller 45). Yes. Accordingly, the upper edge positions of the openings 52e to 52g are higher than the upper edge positions of the openings 52a to 52d, and the lower edge positions of the openings 52e to 52g are higher than the lower edge positions of the openings 52a to 52d. In position. That is, the plurality of openings 52 are formed so as to change the height positions of the upper and lower edges of the openings 52a to 52d with respect to the adjacent openings 52e to 52g of the openings 52a to 52d.
The upper edge positions of the openings 52a to 52d are higher than the lower edge positions of the openings 52e to 52g, and the lower openings 52a to 52d and the upper openings 52e to 52g are overrun in the vertical direction. Wrapping.
The positions of the lower edge portions of the lower openings 52 a to 52 d are arranged so as to be located above the upper position of the supply roller 45.

  In the developing device 40 having such a partition wall 50, when the developing bias is applied to the developing roller 44 by the developing bias power supply device, the photosensitive drum 7 shown in FIG. 1 is exposed by the laser scanning unit LSU. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 7 is developed. In the embodiment, toner that is a one-component developer having magnetism charged to the same positive polarity as the polarity of the charging bias is reversely developed with respect to the electrostatic latent image formed on the surface of the photosensitive drum 7. It is configured.

A transport path 15 for transporting paper is disposed at a substantially central portion of the printer main body 2 in the vertical direction, and a paper feed cassette 16 is mounted at the lower end. The conveyance path 15 passes between the photosensitive drum 7 and the transfer roller 10 and extends substantially horizontally in the tangential direction thereof. The upstream end region of the transport path 15 is inverted downward and connected to the paper feed cassette 16. On the upstream side of the photosensitive drum 7 in the conveyance path 15, a separation roller pair 18, a conveyance roller pair 19, and a registration roller pair 20 are disposed along the conveyance path 15 in that order from upstream to downstream. Yes. On the upstream side of the pair of registration rollers 20 in the conveyance path 15, a sheet detection sensor S that can detect the sheet P being conveyed is disposed.
In the paper feed cassette 16, a bottom plate 22 that is a paper placement plate supported at one end so as to be rotatable around the shaft 21, a compression coil spring 28 that pushes the other end of the bottom plate 22 upward, and the like are disposed. . The upper surface of the leading end of the paper P stacked and accommodated on the bottom plate 22 is pressed against a pickup roller 23 provided in the printer main body 2.

A fixing device 24 is disposed on the downstream side of the photosensitive drum 7 in the conveyance path 15. The fixing device 24 includes a heat roller 25 and a pressure roller 26 pressed against the heat roller 25 from below.
On the downstream side of the fixing device 24 in the conveyance path 15, a conveyance roller pair 27 is disposed. The conveying roller pair 27 includes a driving roller 30 and a driven roller 31 that is pressed against the driving roller 30. A discharge conveyance path 29 is disposed on the downstream side of the conveyance roller pair 27. The discharge conveyance path 29 extends upward along the inner side of the rear wall of the printer main body 2, and is curved to the front side of the printer main body 2 at the upper end portion and connected to the discharge port 5. A pair of conveyance rollers 32 is disposed at a substantially central position in the vertical direction of the discharge conveyance path 29, and a pair of discharge rollers 33 is disposed at the upper end (downstream end). Each of the conveyance roller pair 32 and the discharge roller pair 33 includes a driving roller and a driven roller pressed against the driving roller.

  With this configuration, when the printer 1 transmits a print signal to the printer 1, the paper P is pulled out from the paper feed cassette 16 by the pickup roller 23. Then, when the sheet P is conveyed to the conveyance path 15 and conveyed to the photosensitive drum 7, the surface of the photosensitive drum 7 uniformly charged by the charging roller 8 is exposed by the laser scanning unit LSU. An electrostatic latent image is formed, and the electrostatic latent image is developed by a developing device to become a toner image.

  At this time, in the developing device 40, the toner is lifted upward along the partition wall 50 by the film 49c attached to the tip of the toner stirring member 49b by the clockwise rotation of the stirring member 49b. In the partition wall 50, the above-described opening 52 is formed. First, toner is supplied from the openings 52 a to 52 d arranged below to the developing chamber 41. At this time, since the distance between the openings 52a to 52d to which the toner is supplied is increased, a part of the toner supplied into the developing chamber 41 easily moves in the lateral direction. That is, the opening 52a easily moves toward the opening 52e, the opening 52b easily moves toward the opening 52e or 52f, the opening 52c easily moves toward the opening 52f or 52g, and the opening 52d moves toward the opening 52g. It becomes easy. Further, a part of the toner is moved upward or agitated as the supply roller 45 rotates.

When a large amount of toner is put in the developing device 40, the toner is first supplied by an amount corresponding to the openings 52a to 52d which are almost half (4/7, exactly) of the entire area of the opening 52. Therefore, it is possible to prevent a rapid increase in the toner pressure in the developing chamber 41.
By further rotation of the stirring member 49b, toner is supplied to the upper edges of the lower openings 52a to 52d, and at the same time, toner is supplied to the upper openings 52e to 52g. At this time, toner is temporarily supplied from the entire opening 52, but no toner is supplied from the lower ends of the openings 52a to 52d, so that a sudden increase in toner pressure is buffered. Next, when the film 49c exceeds the upper edge of the lower openings 52a to 52d, toner is supplied to the developing chamber 41 only from the upper openings 52e to 52g.

At this time, since the distance between the openings 52e to 52g to which the toner is supplied is increased, a part of the toner supplied into the developing chamber 41 is easily moved in the lateral direction. That is, it becomes easy to move from the opening 52e to the opening 52a or 52b, from the opening 52f to the opening 52b or 52c, and from the opening 52g to the opening 52c or 52d.
Thus, by suppressing the toner pressure in the developing chamber 41 from rising or suddenly rising, it is possible to reduce heat generated by stress and friction applied to the toner, and also to reduce the removal and embedding of the toner surface treatment agent. . As a result, the performance of the developer can be maintained for a long time.

The toner image thus supplied to the photosensitive drum 7 is transferred onto one side of the paper P conveyed from the paper feed cassette 16 at a predetermined timing by the transfer roller 10.
The sheet P on which the toner image has been transferred is guided by the conveyance path 15 and conveyed to the fixing device 24, and is thermally fixed while passing through the fixing device 24. The sheet P on which the toner image is fixed is one sheet in a face-down state from the discharge port 5 to the discharge tray 4 through the discharge conveyance path 29 by the conveyance roller pair 27, the conveyance roller pair 32, and the discharge roller pair 33. Alternatively, two or more sheets are continuously discharged to the discharge tray 4.

Next, a second embodiment of the developing device of the image forming apparatus of the present invention will be described.
In the present embodiment, only the shape of the partition wall 50 is different from that of the first embodiment, and therefore only the partition wall will be described (the same applies to the following other embodiments).
As shown in FIG. 4, a plurality (seven in this embodiment) of openings 53 a to 53 g (these openings 53 a to 53 g are collectively referred to as openings 53) are formed in the partition wall 50. The opening 53 is formed at an interval from one end of the partition wall 50 toward the other end. In the present embodiment, the opening 53 extends from the opening 53a located at one end of the partition wall 50 to the opening 53g at the other end. The openings are sequentially arranged so that the position of the opening becomes higher upward.
Therefore, the position of the upper edge of each opening 53 is lower in the opening 53a on one end side and gradually increases toward the opening 53g on the other end side. Similarly, the position of the lower edge of each opening 53 is the opening on the one end side. 53a is low and becomes higher sequentially toward the opening 53g on the other end side. Thus, the plurality of openings 53 are formed so as to change the height positions of the upper and lower edges of the openings 53a to 53g with respect to the openings 53 adjacent to each other.
And the upper edge part position and lower edge part position of the adjacent opening 53 overlap in the up-down direction.
The position of the lower edge portion of the lower opening 53 a is arranged so as to be positioned above the upper position of the supply roller 45.

In such a partition wall 50, the toner is lifted upward along the partition wall 50 by the film 49c attached to the tip of the toner stirring member 49b by the clockwise rotation of the stirring member 49b. First, toner is supplied toward the developing chamber 41 from the opening 53a disposed below. Next, as the film 49c is raised, toner is supplied from the overlapping portion of the opening 53b adjacent to the opening 53a. When the supply of the toner to the opening 53a is stopped, the supply of the single toner to the opening 53b is next performed, and then the toner is supplied to the developing chamber from the overlapping portion of the opening 53b and the opening 53c. The toner is sequentially supplied from the order of the openings 53d, 53e, and 53f toward the opening 53g.
In this embodiment, by raising the opening 53 upward, there is an effect of eliminating a sudden change in the toner pressure in the developing chamber 41 and maintaining a substantially constant toner pressure during toner supply.
Further, since the step is formed in the vertical direction with respect to the adjacent openings 53, the toner supplied into the developing chamber 41 is easily moved in the horizontal direction.

Next, a third embodiment of the developing device of the image forming apparatus of the present invention will be described.
As shown in FIG. 5, the partition wall 50 is formed with a plurality (seven in this embodiment) of openings 54 a to 54 g (these openings 54 a to 54 g are collectively referred to as openings 54). The opening 54 is formed with a space from the left and right end portions to the other end portion of the partition wall 50. In this embodiment, the opening 54a located at the center portion of the partition wall 50 is disposed at the highest position, and The left and right adjacent openings 54b and 54c are arranged low, the openings 54d and 54e located outside the openings 54b and 54c are arranged at lower positions, and arranged at both ends of the partition wall 50 located outside the openings 54b and 54c. It is a pyramid shape in which the openings 54f and 54g are arranged at the lowest position.
Such an opening 54 is disposed such that the lower edge and the upper edge of the adjacent openings 54 overlap each other, and each opening 54 is located above the openings 54a to 54g with respect to the adjacent openings 54 of each opening. It is formed so that the height positions of the edge part and the lower edge part are changed.

The positions of the lower edge portions of the openings 54 f and 54 g located at both ends of the partition wall 50 are arranged so as to be located substantially above the upper position of the supply roller 45.
In the present embodiment, the central opening 54a is disposed at a high position, and the outer openings 54b to 54g are lowered to eliminate a sudden change in the toner pressure in the developing chamber 41, so that the toner supply is substantially constant during toner supply. The toner pressure is maintained.
In addition, there is an effect that the toner in the lower layer portion close to the supply roller is easily moved at both ends of the developing chamber 41 where toner consumption is low.
Further, since the step is formed in the vertical direction with respect to the adjacent openings 54, the toner supplied into the developing chamber 41 is easily moved in the horizontal direction.

Next, a fourth embodiment of the developing device of the image forming apparatus of the present invention will be described.
The partition wall 50 shown in FIG. 6 is arranged close to the opening 52 in the first embodiment. The difference is that the lower openings 52a to 52d and the upper openings 52e to 52g in the first embodiment are different. Whereas the positions overlap in the vertical direction, the present embodiment is different in that there is no portion overlapping the lower openings 55a to 55d and the upper openings 55e to 55g.
Therefore, the timing when the toner is supplied to the developing chamber 41 is supplied in two steps. After the toner is first supplied from the lower openings 55a to 55d, the timing is shifted and the developing chamber is then supplied from the upper openings 55e to 55g. 41. Thus, in this embodiment, since toner is supplied in two steps, there is an effect that toner pressure is not suddenly applied.
Further, since the step is formed in the vertical direction with respect to the adjacent openings 55, the toner supplied into the developing chamber 41 is easily moved in the horizontal direction.
In particular, there are marginal areas at both ends as in general document printing, and toner tends to stay without being consumed at both ends in the developing chamber 41, especially when printing on small size paper. The flow is effective in preventing toner retention.

The embodiments of the present invention have been described above. However, of course, the present invention can be variously modified or changed based on the technical idea of the present invention.
For example, in the first to fourth embodiments, the openings are all the same shape and the same size of a rectangle, but the shape may be a circle, an ellipse, a trapezoid, or a polygon more than a triangle. The size of each opening can be changed as long as the upper edge portion and the lower edge portion are positioned. Furthermore, the intervals between the openings may be equal or may be appropriately changed.

1 is a schematic cross-sectional view of a printer employing a developing device of an image forming apparatus according to each embodiment of the present invention. It is an expanded sectional view of the developing device of FIG. It is a front view of the partition wall of the developing device of the 1st Embodiment of this invention. It is a front view of the partition wall of the developing device of the 2nd Embodiment of this invention. It is a front view of the partition wall of the developing device of the 3rd Embodiment of this invention. It is a front view of the partition wall of the developing device of the 4th Embodiment of this invention. It is a front view of the partition wall of the developing device by a prior art example. It is a front view of the partition wall of the developing device by another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Printer main body 40 Developing device 41 Developing chamber 42 Toner supply chamber 44 Developing roller 45 Supply roller 47 Housing 48 Container body 49 Stirrer 50 Partition walls 52-55 (52a-52g, 53a-53g, 54a-54g, 55a- 55g)
Opening

Claims (5)

The developing chamber includes a developing roller for developing the electrostatic latent image on the photosensitive drum and a supply roller for supplying developing toner to the developing roller.
A rotation shaft extending in the axial direction of the supply roller, and a toner stirring member for stirring the toner by rotation of the rotation shaft and supplying the toner to the supply roller is provided in the toner supply chamber;
A partition wall having a plurality of openings formed in the axial direction of the supply roller is formed between the developing chamber and the toner supply chamber, and toner is removed from the opening by the toner stirring member. In the developing device of the image forming apparatus supplied to the developing chamber,
The developing device of an image forming apparatus, wherein the plurality of openings are different in height position of an upper edge portion and a lower edge portion of the opening from an opening adjacent to the opening.   The developing device of an image forming apparatus according to claim 1, wherein the plurality of openings are arranged at positions that do not overlap the adjacent openings and in a height direction of the partition wall.   Among the plurality of openings, the openings located at both ends of the partition wall are arranged at a lower position than the opening located at the center of the partition wall in the axial direction of the supply roller. The developing device for an image forming apparatus according to claim 1.   In the partition wall, a part of the plurality of openings is formed at a position above the partition wall, and the remaining plurality of openings are formed at a position below the partition wall, and the plurality of openings are the supply rollers. 3. The developing device for an image forming apparatus according to 1 or 2, wherein the partition wall is arranged in a staggered manner from one end to the other end of the partition wall in the axial direction.   5. The developing device of an image forming apparatus according to claim 1, wherein each of the plurality of openings has the same rectangular shape and the same size. 6.

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