112 may be disposed spaced apart in the up-down direction, and are not connected to the adjacent first release preventing members 112 on both sides in the up-down direction, and only the ends in the left-right direction may be supported by the first body 111.

Referring to FIGS. 5 and 7, the second filter frame 120 may be disposed on the other side (e.g., the rear side in FIG. 5) of the filter net 200. The second filter frame 120 may include a second body 121 and a second release preventing member 122.

A plurality of second chambers 121a in each of which the filter material 300 can be accommodated may be formed in the second body 121.

The second chamber 121a may be a space at least partially surrounded by the second body 121. The filter material 300 may be accommodated in the second chamber 121a. Further, the second chamber 121a may have, for example, a rectangular shape having the same size as the first chamber 111a. The second chamber 121a may include a second material space 121a-1 and a second empty space 121a-2.

The second material space 121a-1 may be a space filled with the filter material 300 in the second chamber 121a when the second filter frame 120 is erected vertically with respect to the ground. In this case, the second material space 121a-1 may include not only a space occupied by the filter material 300 in the second chamber 121a but also a minute space formed between the filter materials 300.

The second empty space 121a-2 may be a space in which the filter material 300 is absent in the second chamber 121a when the second filter frame 120 is erected vertically with respect to the ground. The second empty space 121a-2 may be provided above the second material space 121a-1 since the filter material 300 is located in a lower portion of the second chamber 121a by gravity when the second filter frame 120 is erected vertically with respect to the ground.

As such, the second material space 121a-1 and the second empty space 121a-2 may be partitioned by the filter material 300. In other words, the space in the second chamber 121a may be divided into the second material space 121a-1 and the second empty space 121a-2 by the space occupied by the filter material 300 in the second chamber 121a. In addition, the second material space 121a-1 may include not only the space occupied by the filter material 300 in the second chamber 121a but also a minute space formed between the filter materials 300. In addition, the spaces occupied by the second material space 121a-1 and the second empty space 121a-2 in the second chamber 121a may be changed in response to the movement of the filter material 300 by gravity when the second filter frame 120 is rotated.

The second release preventing member 122 may prevent the filter material 300 accommodated in the second chamber 121a from being released from the second chamber 121a. The second release preventing member 122 may include a plurality of second release preventing members. In addition, the plurality of second release preventing members 122 may extend in the same direction, for example, in the left-right direction.

Both ends of the plurality of second release preventing members 122 may be connected to the second body 121. For example, the plurality of second release preventing members 122 may be integrally connected to the second body 121 through injection molding. In addition, the ends of the plurality of second release preventing members 122 may be spaced apart from each other so as not to be connected to each other. For example, the plurality of second release preventing members 122 may be spaced apart from each other in the up-down direction. In this case, the second release preventing member 122 is not connected to the adjacent second release preventing members 122 on both sides in the up-down direction, and only both ends in the left-right directions may be supported by the second body 121. That is, a configuration for connecting the adjacent second release preventing members 122 in the up-down direction may be omitted.

Accordingly, the plurality of second release preventing members 122 and the second body 121 can be easily manufactured through injection molding, which reduces the manufacturing costs. In addition, since the plurality of second release preventing members 122 extend in the same direction and a configuration for connecting them to each other is omitted, differential pressure of air passing through the second filter frame 120 can be reduced.

In the above, the case where the plurality of second release preventing members 122 extend in the left-right direction has been described, but the extending direction is not limited to the left-right direction and the plurality of second release preventing members 122 may extend in the up-down direction as another example. In this case, the plurality of second release preventing members 122 may be spaced apart in the left-right direction, and are not connected to the adjacent second release preventing members 122 on both sides in the left-right direction, and only the ends in the up-down direction may be supported by the second body 121. Meanwhile, the direction in which the plurality of second release preventing members 122 extend may be substantially perpendicular to the direction in which the plurality of first release preventing members 112 extend, but is not limited thereto and may be the same direction.

Meanwhile, the first filter frame 110 and the second filter frame 120 may be configured such that a flow rate of air passing through the air filter 30 without being filtered by the filter material 300 is minimized. For example, the first filter frame 110 and the second filter frame 120 may be disposed so that the centers of the plurality of first chambers 111a are offset from the centers of the plurality of second chambers 121a in the up-down and left-right directions, respectively. Hereinafter, the description will be made on the assumption that the first filter frame 110 and the second filter frame 120 are erected vertically with respect to the ground.

Referring to FIG. 8, the first filter frame 110 and the second filter frame 120 may be disposed so that air passing through the air filter 30 flows through the first material space 111a-1 or the second material space 121a-1. For example, the first filter frame 110 and the second filter frame 120 are disposed so that at least a portion of the first empty space 111a-2 overlaps with at least a portion of the second material space 121a-1, and at least a portion of the first material space 111a-1 overlaps with at least a portion of the second empty space