534A of the development unit 53 fits into the through hole 5512A. The protrusion 534A will be described later.

As shown in FIG. 6, the side plate 551B is located at the other end of the frame 55 in the first direction. The side plate 551B is located away from the side plate 551A in the first direction. The side plate 551B extends in the second direction and the third direction. The side plate 551B supports the other end of the photosensitive drum 51 and the other end of the development unit 53. The side plate 551B has two through holes 5511B and 5512B.

The through hole 5511B is located away from the photosensitive drum 51 in the fourth direction (see FIG. 8). The through hole 5511B extends in the fourth direction. The through hole 5511B is an elongated hole. A protrusion 533B of the development unit 53 fits into the through hole 5511B. The protrusion 533B will be described later.

The through hole 5512B is located away from the through hole 5511B in the fourth direction. The through hole 5512B is located between the photosensitive drum 51 and the through hole 5511B in the fourth direction. The through hole 5512B extends in the fourth direction. The through hole 5512B is an elongated hole. A protrusion 534B of the development unit 53 fits into the through hole 5512B. The protrusion 534B will be described later.

2.1.2 Waste Toner Container 552

As shown in FIG. 6, the waste toner container 552 is located between the side plate 551A and the side plate 551B in the first direction. The waste toner container 552 extends in the first direction. One end of the waste toner container 552 in the first direction is connected to the side plate 551A. The other end of the waste toner container 552 in the first direction is connected to the side plate 551B. As shown in FIG. 7, the waste toner container 552 has an opening 552A. The waste toner container 552 stores waste toner.

2.1.3 Drum Cleaning Member 553

The drum cleaning member 553 is attached to the waste toner container 552. The drum cleaning member 553 extends in the first direction. The drum cleaning member 553 has a plate shape. The drum cleaning member 553 cleans the circumferential surface of the photosensitive drum 51. Specifically, an edge of the drum cleaning member 553 contacts the surface of the photosensitive drum 51. As the photosensitive drum 51 rotates, the waste toner on the surface of the photosensitive drum 51 contacts the edge of the drum cleaning member 553 and is removed from the surface of the photosensitive drum 51. The removed waste toner is stored in the waste toner container 552 through the opening 552A.

2.2 Details of Development Unit 53

As shown in FIG. 6, the development unit 53 is located between the side plate 551A and the side plate 551B in the first direction. Specifically, the development housing 531 is located between the side plate 551A and the side plate 551B in the first direction. As shown in FIGS. 6 and 7, the development unit 53 includes two protrusions 533A and 534A (see FIG. 6), two protrusions 533B and 534B (see FIG. 6), a first agitator 535 (see FIG. 7), and a second agitator 536 (see FIG. 7) in addition to the development housing 531 and the development roller 532 described above.

2.2.1 Details of Development Housing 531

As shown in FIGS. 9 and 10, the development housing 531 includes two side walls 5311A and 5311B, a first wall 5312 (see FIG. 9), a second wall 5313 (see FIG. 10), a protrusion 5314 (see FIG. 10), a third wall 5315, and a wall 5316 (see FIG. 7).

2.2.1.1 Side Walls 5311A and 5311B

As shown in FIG. 10, the side wall 5311A is located at one end of the development housing 531 in the first direction. The side wall 5311A supports one end of the development roller 532. The side wall 5311A extends in the second direction and the third direction.

The side wall 5311B is located at the other end of the development housing 531 in the first direction. The side wall 5311B is located away from the side wall 5311A in the first direction. The side wall 5311B supports the other end of the development roller 532. The side wall 5311B extends in the second direction and the third direction.

2.2.1.2 First Wall 5312

As shown in FIG. 9, the first wall 5312 is located between the side wall 5311A and the side wall 5311B in the first direction. The first wall 5312 extends in the first direction and the second direction. One end of the first wall 5312 in the first direction is connected to the side wall 5311A. The other end of the first wall 5312 in the first direction is connected to the side wall 5311B. As shown in FIG. 7, the first wall 5312 is located at one end of the development housing 531 in the third direction. As shown in FIGS. 7 and 9, the first wall 5312 has a reception port 5310. In other words, the development housing 531 has the reception port 5310.

As shown in FIG. 9, the reception port 5310 is located away from the development roller 532 in the second direction. The reception port 5310 is located at the other end of the development housing 531 in the second direction. The reception port 5310 is located at a center portion of the development housing 531 in the first direction. The reception port 5310 is not limited to this configuration. In this embodiment, the reception port 5310 has a circular shape.

As shown in FIG. 1, in a state where the process cartridge 5 is attached to the image forming apparatus 1, the reception port 5310 is located on the opposite side of the fuser 7 with respect to the exposure device 6 in the second direction. In a state where the process cartridge 5 is attached to the image forming apparatus 1, the reception port 5310 faces upward. As shown in FIG. 3, in a state where the process cartridge 5 is attached to the image forming apparatus 1, the second cover 32 is located at the second cover open position, and the toner container B is connected to the reception port 5310, the reception port 5310 receives toner from the toner container B.

2.2.1.3 Second Wall 5313

As shown in FIG. 7, the second wall 5313 is located on the other side of the first wall 5312 in the third direction. The second wall 5313 is located away from the first wall 5312 in the third direction. In a state where the process cartridge 5 is attached to the image forming apparatus 1, the second wall 5313 is located below the first wall 5312. As shown in FIG. 10, the second wall 5313 is located between the side wall 5311A and the side wall 5311B in the first direction. The second wall 5313 extends in the first direction and the second direction. One end of the second wall 5313 in the first direction is connected to the side wall 5311A. The other end of the second wall 5313 in the first direction is connected to the side wall 5311B. The second wall 5313 has a first inner surface SI and a second inner surface S2.

The first inner surface S1 is located at the other end of the second wall 5313 in the second direction. The first inner surface S1 is located away from the development roller 532 in the second direction. The first inner surface S1 extends in the first direction. Toward the development roller 532, the first inner surface S1 separates farther from the first wall 5312. In a state where the reception port 5310 faces upward, the first inner surface S1 slopes downward toward the development roller 532. In a state where the reception port 5310 faces upward, the gradient of the first inner surface S1 is greater than an angle of repose of the toner.

The second inner surface S2 is located between the first inner surface S1 and the development roller 532 in the second direction. The second inner surface S2 extends in the first direction. Toward the development roller 532, the second inner surface S2 separates farther from the first wall 5312. In a state where the reception port 5310 faces upward, the second inner surface S2 slopes downward toward the development roller 532. In a state where the reception port 5310 faces upward, the gradient of the second inner surface S2 is greater than the angle of repose of the toner. In a state where the reception port 5310 faces upward, the gradient of the second inner surface S2 is greater than the gradient of the first inner surface S1.

2.2.1.4 Protruding Portion 5314

The protruding portion 5314 is located below the reception port 5310 (see FIG. 9) inside the development housing 531. The protruding portion 5314 protrudes from the first inner surface S1 of the second wall 5313 toward the first wall 5312 (see FIG. 9) in the third direction. The protruding portion 5314 has an apex T and a slope S3. That is, the development housing 531 has the slope S3. The slope S3 is located below the reception port 5310 inside the development housing 531. In this embodiment, the slope S3 includes two first slopes S31 and S32 and a second slope S33. The protruding portion 5314 has a triangular pyramid shape including the first slopes S31 and S32 and the second slope S33.

The apex T is located at one end of the protruding portion 5314 in the third direction. The apex T is located away from the first inner surface S1 of the second wall 5313 in the third direction. The apex T is the intersection of a line L1 where the first slope S31 and the first slope S32 intersect, a line L2 where the first slope S32 and the second slope S33 intersect, and a line L3 where the first slope S31 and the second slope S33 intersect. As shown in FIG. 6, when the protruding portion 5314 is viewed from above through the reception port 5310, the apex T is located within the reception port 5310.

As shown in FIG. 10, the first slope S31 is a side surface of the protruding portion 5314 on one side in the first direction. The first slope S31 is located between the apex T and the side wall 5311A in the first direction. In a state where the reception port 5310 faces upward, the first slope S31 slopes downward from the apex T toward the side wall 5311A. In other words, in a state where the reception port 5310 faces upward, the first slope S31 slopes downward away from the reception port 5310 in the first direction. That is, the slope S3 includes a first slope portion P1 that slopes downward away from the reception port 5310 in the first direction, and the first slope S31 serves as the first slope portion P1. In a state where the reception port 5310 faces upward, the gradient of the first slope S31 is greater than the angle of repose of the toner. That is, in a state where the reception port 5310 faces upward, the gradient of the first slope portion P1 is greater than the angle of repose of the toner. The first slope S31 extends in the second direction. The first slope S31 is a flat surface. The upper end of the first slope S31 is connected to the first slope S32. The lower end of the first slope S31 is connected to the first inner surface S1 of the second wall 5313. One end of the first slope S31 in the second direction is connected to the second slope S33.

The first slope S32 is the side surface on the other side of the protruding portion 5314 in the first direction. The first slope S32 is located between the apex T and the side wall 5311B in the first direction. In a state where the reception port 5310 faces upward, the first slope S32 slopes downward from the apex T toward the side wall 5311B. In other words, in a state where the reception port 5310 faces upward, the first slope S32 slopes downward away from the reception port 5310 in the first direction. The gradient of the first slope S32 is greater than the angle of repose of the toner. The first slope S32 extends in the second direction. The first slope S32 is a flat surface. The upper end of the first slope S32 is connected to the first slope S31. The lower end of the first slope S32 is connected to the first inner surface S1 of the second wall 5313. One end of the first slope S32 in the second direction is connected to the second slope S33.

The second slope S33 is a side surface of the protruding portion 5314 on one side in the second direction. The second slope S33 is located between the apex T and the development roller 532 in the second direction. In a state where the reception port 5310 faces upward, the second slope S33 slopes downward from the apex T toward the development roller 532. That is, the slope S3 includes a second slope portion P2 that slopes downward toward the development roller 532 in the second direction, and the second slope S33 serves as the second slope portion P2. In a state where the reception port 5310 faces upward, the gradient of the second slope S33 is greater than the angle of repose of the toner. That is, the gradient of the second slope portion P2 is greater than the angle of repose of the toner. In the present embodiment, the gradient of the second slope S33 is the same as the gradient of the second inner surface S2 of the second wall 5313. The second slope S33 extends in the first direction. The second slope S33 is a flat surface. One end of the second slope S33 in the first direction is connected to the first slope S31. The other end of the second slope S33 in the first direction is connected to the first slope S32. The lower end of the second slope S33 is connected to the second inner surface S2 of the second wall 5313.

2.2.1.5 Third Wall 5315

The third wall 5315 is located at the other end of the development housing 531 in the second direction. The third wall 5315 is located between the first wall 5312 and the second wall 5313 in the third direction. The third wall 5315 extends in the first direction and the third direction.

2.2.1.6 Wall 5316

As shown in FIG. 7, the wall 5316 is located within the development housing 531. The wall 5316 is located between the protruding portion 5314 and the development roller 532 in the second direction. The wall 5316 is located between the slope S3 and the development roller 532 in the second direction. In a state where the reception port 5310 faces upward, the wall 5316 protrudes upward from the second wall 5313 toward the first wall 5312. The wall 5316 extends in the first direction.

2.2.2 Protrusions 533A and 534A

As shown in FIG. 6, the protrusion 533A is located away from the photosensitive drum 51 in the fourth direction (see FIG. 8). The protrusion 533A is located at one end of the development unit 53 in the first direction. The protrusion 533A extends in the first direction. In this embodiment, the protrusion 533A extends from one outer surface of the development housing 531 in the first direction. The protrusion 533A may be attached to one outer surface of the development housing 531 in the first direction. The protrusion 533A has a cylindrical shape. The protrusion 533A fits into the through hole 5511A of the side plate 551A.

The protrusion 534A is located between the photosensitive drum 51 and the protrusion 533A in the fourth direction. The protrusion 534A is located at one end of the development unit 53 in the first direction. The protrusion 534A extends in the first direction. In this embodiment, the protrusion 534A extends from one outer surface of the development housing 531 in the first direction. The protrusion 534A may be attached to one outer surface of the development housing 531 in the first direction. The protrusion 534A has a cylindrical shape. The protrusion 534A may be one end of a shaft of the development roller 532. The protrusion 534A fits into the through hole 5512A of the side plate 551A.

2.2.3 Protrusions 533B and 534B

The protrusion 533B is located away from the photosensitive drum 51 in the fourth direction. The protrusion 533B is located at the other end of the development unit 53 in the first direction. The protrusion 533B extends in the first direction. In this embodiment, the protrusion 533B extends from the other outer surface of the development housing 531 in the first direction. The protrusion 533B may be attached to the other outer surface of the development housing 531 in the first direction. The protrusion 533B has a cylindrical shape. The protrusion 533B fits into the through hole 5511B of the side plate 551B.

The protrusion 534B is located between the photosensitive drum 51 and the protrusion 533B in the fourth direction. The protrusion 534B is located at the other end of the development unit 53 in the first direction. The protrusion 534B extends in the first direction. In this embodiment, the protrusion 534B extends from the other outer surface of the development housing 531 in the first direction. The protrusion 534B may be attached to the other outer surface of the development housing 531 in the first direction. The protrusion 534B has a cylindrical shape. The protrusion 534B may be the other end of the shaft of the development roller 532. The protrusion 534B fits into the through hole 5512B of the side plate 551B.

In a state where the protrusion 533A fits into the through hole 5511A of the side plate 551A, the protrusion 534A fits into the through hole 5512A of the side plate 551A, the protrusion 533B fits into the through hole 5511B of the side plate 551B, and the protrusion 534B fits into the through hole 5512B of the side plate 551B, the development unit 53 is movable relative to the photosensitive drum 51.

2.2.4 First Agitator 535

As shown in FIG. 7, the first agitator 535 is located inside the development housing 531. The first agitator 535 is located between the protruding portion 5314 and the wall 5316 in the second direction. The first agitator 535 is located between the slope S3 and the development roller 532 in the second direction. The first agitator 535 conveys the toner in the development housing 531 toward the development roller 532.

2.2.5 Second Agitator 536

The second agitator 536 is located inside the development housing 531. The second agitator 536 is located between the wall 5316 and the developer roller 532 in the second direction. The second agitator 536 is located between the first agitator 535 and the development roller 532 in the second direction. The second agitator 536 conveys the toner in the development housing 531 toward the development roller 532 in cooperation with the first agitator 535.

3. EFFECTS

(1) According to the image forming apparatus 1 and the process cartridge 5, as shown in FIG. 10, the development unit 53 includes the slope S3 located below the reception port 5310 (see FIG. 9) in the development housing 531. The slope S3 includes the first slopes S31 and S32 and the second slope S33. Each of the first slopes S31 and S32 slopes downward away from the reception port 5310 in the first direction. The second slope S33 slopes downward toward the development roller 532 in the second direction.

Thus, the toner supplied into the development housing 531 through the reception port 5310 flows in directions away from the reception port 5310 in the first direction due to the slope S3 located below the reception port 5310 and flows in a direction toward the development roller 532 in the second direction.

Thus, by supplying toner from the reception port 5310 into the development housing 531, the toner flows toward the development roller 532 while being distributed throughout the entirety of the development housing 531 in the first direction.

As a result, it is unnecessary to spread the toner to the entirety of the development housing 531 after the toner is supplied, and the development unit 53 is smoothly supplied with toner.

(2) According to the image forming apparatus 1 and the process cartridge 5, the gradient of the first slopes S31 and S32 is greater than the angle of repose of the toner. Thus, the first slopes S31 and S32 allow the toner to flow in the first direction.

(3) According to the image forming apparatus 1 and the process cartridge 5, the gradient of the second slope S33 is greater than the angle of repose of the toner. Thus, the second slope S33 allows the toner to flow in the second direction.

(4) According to the image forming apparatus 1 and the process cartridge 5, as shown in FIG. 7, the development housing 531 includes the wall 5316 located between the slope S3 and the development roller 532 in the second direction.

Thus, the wall 5316 suppresses that the toner flowed toward the development roller 532 on the slope S3 leaks out from the periphery of the development roller due to the momentum of the toner.

(5) According to the image forming apparatus 1 and the process cartridge 5, as shown in FIG. 9, the reception port 5310 is located at a center portion of the development housing 531 in the first direction.

Thus, the toner flows from the center portion of the development housing 531 toward both sides in the first direction.

This suppresses unevenness in the amount of toner in the development housing 531 in the first direction.

(6) According to the image forming apparatus 1 and the process cartridge 5, as shown in FIG. 6, when the protruding portion 5314 is viewed from above through the reception port 5310, the apex T of the protruding portion 5314 is located within the reception port 5310.

Thus, the toner supplied into the development housing 531 through the reception port 5310 reliably hits the slope S3.

4. MODIFICATIONS

While the invention has been described in conjunction with various example structures outlined above and illustrated in the figures, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that may be presently unforeseen, may become apparent to those having at least ordinary skill in the art. Accordingly, the example embodiments of the disclosure, as set forth above, are intended to be illustrative of the invention, and not limiting the invention. Various changes may be made without departing from the spirit and scope of the disclosure. Thus, the disclosure is intended to embrace all known or later developed alternatives, modifications, variations, improvements, and/or substantial equivalents. Some specific examples of potential alternatives, modifications, or variations in the described invention are provided below. Modifications will be described with reference to FIGS. 11 to 23. In the description of the modifications, the same reference numerals are given to the same members as in the above-described embodiment, and the descriptions thereof are omitted.

(1) As shown in FIG. 11, the process cartridge 5 may be configured to recover waste toner in the waste toner container 552 into the development housing 531. In this case, the process cartridge 5 mixes the collected waste toner with the toner in the development housing 531 and uses the mixed toner again for image formation. Specifically, the process cartridge 5 includes a waste toner pipe 56, a conveyance member 57, and a seal member 58 (see FIG. 12).

One end of the waste toner pipe 56 is connected to the waste toner container 552. The other end of the waste toner pipe 56 is connected to a center portion of the development housing 531 in the first direction via the seal member 58. The other end of the waste toner pipe 56 is located between the reception port 5310 and the development roller 532 in the second direction. More specifically, the other end of the waste toner pipe 56 is located between the reception port 5310 and the wall 5316 (see FIG. 12) in the second direction. As shown in FIG. 12, the waste toner pipe 56 has a waste toner discharge port 561. The waste toner discharge port 561 discharges the toner in the waste toner pipe 56. The waste toner discharge port 561 communicates with a waste toner reception port 530 of the development housing 531. With this configuration, the waste toner discharged from the waste toner discharge port 561 passes through the waste toner reception port 530 and enters the development housing 531.

The conveyance member 57 is located inside the waste toner container 552 and the waste toner pipe 56. The conveyance member 57 conveys the waste toner in the waste toner container 552 toward the waste toner discharge port 561. The conveyance member 57 is a shaftless screw, for example.

As shown in FIG. 12, the seal member 58 is located between the other end of the waste toner pipe 56 and the development housing 531. The seal member 58 is located around the waste toner discharge port 561 of the waste toner pipe 56 and the waste toner reception port 530 of the development housing 531. The seal member 58 seals between the other end of the waste toner pipe 56 and the development housing 531.

In this modification, too, effects similar to those of the above-described embodiment are obtained. According to this modification, waste toner is reused for image formation. At that time, the wall 5316 suppresses the waste toner being directly supplied to the development roller 532. Thus, the waste toner is mixed with new toner supplied from the toner reception port 5310 and then supplied to the development roller 532. This suppresses an influence of the waste toner on the print quality.

(2) The shape of the protruding portion 5314 is not limited. For example, as shown in FIG. 13, the slope S3 may be a curved surface. Specifically, in this modification, the second slope S33 is a curved surface having the same shape as a surface of a cone. No side is formed at the connection portion between the first slope S