This application claims priority from Japanese Patent Application No. 2018-183247 filed on Sep. 28, 2018. The entire content of the priority application is incorporated herein by reference.
The present disclosure relates to a developing cartridge.
There is conventionally known an electro-photographic type image forming apparatus such as an LED printer. This type of image forming apparatus includes a frame provided with a photosensitive drum, and a developing cartridge attachable to and detachable from the frame. For example, prior art discloses a conventional image forming apparatus including a developing cartridge.
The developing cartridge disclosed in the prior art includes a casing, a developing roller, an agitator, and a supply roller. The casing can accommodate toner. The developing roller is rotatable about a rotation axis extending in a first direction. The agitator rotates about a rotation axis extending in the first direction to agitate the toner accommodated in the casing. The agitator is positioned spaced away from the developing roller in a second direction. The supply roller rotates about a rotation axis extending in the first direction to supply the toner to the developing roller. The supply roller is positioned between the developing roller and the agitator in the second direction.
However, in the developing cartridge disclosed in the prior art, in an internal space of the casing, there is a region where sufficient agitation of toner cannot be achieved by only rotation of the agitator. For example, toner stagnation may occur at a region ambient to the supply roller when residual amount of toner in the casing is low.
In view of the foregoing, it is an object of the present disclosure to provide a developing cartridge capable of sufficiently agitating toner in an internal space of a casing.
In order to attain the above and other objects, according to one aspect, the disclosure provides a developing cartridge including: a casing, a developing roller, a first agitator, a supply roller, and a second agitator. The casing is configured to accommodate toner. The developing roller is rotatable about a developing roller rotation axis extending in a first direction. The first agitator is configured to agitate the toner. The first agitator is rotatable about a first agitator rotation axis extending in the first direction. The supply roller is positioned between the first agitator and the developing roller. The supply roller is rotatable about a supply roller rotation axis extending in the first direction. The second agitator is positioned between the supply roller and the first agitator. The second agitator is rotatable about a second agitator rotation axis extending in the first direction. A rotation locus of the second agitator is positioned outside of a rotation locus of the first agitator.
The particular features and advantages of the disclosure as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which:
An embodiment of the present disclosure will be described while referring to the accompanying drawings.
A developing cartridge 2 according to the present embodiment includes a developing roller 22 and a first agitator 25 described later in detail. Here, as illustrated in
<1. Image Forming Apparatus>
The four developing cartridges 2 accommodate therein developing agents (for example, toners in the present embodiment) of different colors (for example, cyan, magenta, yellow, and black). The image forming apparatus 100 forms an image on a recording surface of a printing sheet using toners supplied from the four developing cartridges 2. However, the number of the developing cartridges 2 to be attached to the drum unit 1 is not restrictive. One to three developing cartridges 2 or not less than five developing cartridges 2 are available.
The controller 102 illustrated in
<2. Drum Unit>
The drum unit 1 illustrated in
The frame 12 is configured to hold the four photosensitive drums 11. The frame 12 includes four cartridge holding portions 120. The four cartridge holding portions 120 are arrayed with intervals therebetween. Each of the four developing cartridges 2 is attached to a corresponding one of the four cartridge holding portions 120.
<3. Details of Developing Cartridge>
The casing 21 illustrated in
As illustrated in
The developing roller 22 is rotatable about the developing roller rotation axis 22A extending in the first direction. As illustrated in
The developing roller 22 includes a developing roller body 221 and a developing roller shaft 222. The developing roller body 221 is a hollow cylindrical member extending in the first direction. The developing roller body 221 is made of an elastic material such as a rubber. The developing roller shaft 222 extends through the developing roller body 221 and is a solid cylindrical member extending along the developing roller rotation axis 22A. The developing roller shaft 222 is made of metal or electrically conductive resin.
The developing roller body 221 is fixed to the developing roller shaft 222 so as not to rotate relative to the developing roller shaft 222. The developing roller shaft 222 has one end portion in the first direction; the one end portion is positioned at the one side in the first direction. The one end portion in the first direction of the developing roller shaft 222 is fixed to the developing roller gear 223 so as not to rotate relative to the developing roller gear 223. With this configuration, when the developing roller gear 223 rotates, the developing roller shaft 222 also rotates and the developing roller body 221 is rotatable together with the developing roller shaft 222. As illustrated in
The supply roller 23 illustrated in
The supply roller body 231 is fixed to the supply roller shaft 232 so as not to rotate relative to the supply roller shaft 232. The supply roller shaft 232 has one end portion in the first direction; the one end portion is positioned at the one side in the first direction. The one end portion of the supply roller shaft 232 in the first direction is fixed to the supply roller gear 233 so as not to rotate relative to the supply roller gear 233. With this configuration, when the supply roller gear 233 rotates, the supply roller shaft 232 also rotates and the supply roller body 231 is rotatable together with the supply roller shaft 232.
As illustrated in
The first agitator 25 illustrated in
As illustrated in
The tip end portion of the first agitator fin 253 contacts the inner surface of the casing 21. When the first agitator gear 254 rotates in a clockwise direction as viewed from the one side in the first direction, the first agitator shaft 251 also rotates and the first agitator fin 253 also rotates together with the fin support portion 252 about the first agitator rotation axis 25A. During this rotation of the first agitator fin 253, the tip end portion of the first agitator fin 253 is flexed and deformed by contact with the inner surface of the casing 21.
The second agitator 26 is configured to agitate toner accommodated in the casing 21. The second agitator 26 is rotatable about a second agitator rotation axis 26A extending in the first direction. As illustrated in
As illustrated in
The second agitator shaft 261 has one end portion in the first direction; the one end portion is positioned at the one side in the first direction. The one end portion of the second agitator shaft 261 in the first direction is fixed to the second agitator gear 264 so as not to rotate relative to the second agitator gear 264. When the second agitator gear 264 rotates, the second agitator shaft 261 also rotates and the second agitator fin 263 also rotates together with the agitating portion 262 about the second agitator rotation axis 26A.
As illustrated in
The idle gear 27 includes a first idle gear portion 27a, a second idle gear portion 27b, and a third idle gear portion 27c. As illustrated in
In
The coupling 24 illustrated in
The idle gear 27 illustrated in
The first idle gear portion 27a, the second idle gear portion 27b, and the third idle gear portion 27c have diameters different from one another. The second idle gear portion 27b is positioned closer to the first outer surface 211 of the casing 21 in the first direction than both of the first idle gear portion 27a and the third idle gear portion 27c are to the first outer surface 211. Specifically, the second idle gear portion 27b is accommodated in a recessed portion 211a of the first outer surface 211 of the casing 21. The third idle gear portion 27c is positioned between the first idle gear portion 27a and the second idle gear portion 27b in the first direction. The third idle gear portion 27c is in meshing engagement with the first agitator gear 254. The first idle gear portion 27a is in meshing engagement with the coupling gear portion of the coupling 24. The second idle gear portion 27b is in meshing engagement with the first drive gear 28.
The first drive gear 28 and the second drive gear 29 illustrated in
The support member 31 illustrated in
The support member 31 partitions the internal space of the gear case 32 into one side space and the other side space in the first direction; the one side space is positioned at the one side in the first direction and the other side space positioned at the other side in the first direction. Specifically, the coupling 24, the developing roller gear 223, and the supply roller gear 233 are positioned in the one side space in the first direction of the support member 31. The support member 31 has a circular hole for allowing the developing roller shaft 222 and the supply roller shaft 232 to extend through the support member 31. On the other hand, the first drive gear 28, the second drive gear 29, and the second agitator gear 264 are positioned in the other side space in the first direction of the support member 31. Specifically, in a state where the first drive gear 28, the second drive gear 29, and the second agitator gear 264 are accommodated in the recessed portion 211a of the first outer surface 211 of the casing 21, the recessed portion 211a is partly covered with the support member 31 from the one side in the first direction. The recessed portion 211a is recessed in the direction from the one side to the other side in the first direction. The second idle gear portion 27b of the idle gear 27 is also accommodated in the recessed portion 211a.
In the image forming apparatus 100 constructed described above, when the coupling 24 rotates about the coupling axis 241 in response to the driving force from the drive shaft, the developing roller gear 223, the supply roller gear 233, and the idle gear 27 which are in meshing engagement with the coupling 24 rotate. By the rotation of the idle gear 27, the first agitator gear 254 in meshing engagement with the idle gear 27 also rotates. Further, by the rotation of the idle gear 27, the first drive gear 28 in meshing engagement with the idle gear 27 rotates. Upon the rotation of the first drive gear 28, the second drive gear 29 in meshing engagement with the first drive gear 28 rotates. In accordance with this rotation of the second drive gear 29, the second agitator gear 264 in meshing engagement with the second drive gear 29 also rotates.
In a case where the above-described gears engage, in accordance with the numbers of teeth of the gears, the second agitator gear 264 rotates at a rotation frequency greater than a rotation frequency of the first agitator gear 254. In the present embodiment, the rotation frequency of the second agitator gear 264 is about three to four times as great as the rotation frequency of the first agitator gear 254. However, the numbers of teeth of the gears and diameters of the gears are set so that a peripheral speed of the second agitator 26 is greater than or equal to a peripheral speed of the supply roller 23.
Note that no gear is provided between the idle gear 27 and the first agitator gear 254. On the other hand, an even number of gears (in the present embodiment, the first drive gear 28 and the second drive gear 29) are provided between the idle gear 27 and the second agitator gear 264. Therefore, the first agitator gear 254 and the second agitator gear 264 rotate in the same rotating direction (in the present embodiment, clockwise direction as viewed from the one side in the first direction).
In the printing process in the image forming apparatus 100, the outer circumferential surface of the photosensitive drum 11 is uniformly charged and then exposed by a laser beam or an LED beam, whereby an electrostatic latent image based on input image data is formed on the outer circumferential surface of the photosensitive drum 11. Further, while toner in the casing 21 is agitated by the rotating first agitator 25 and the rotating second agitator 26, the toner is supplied to the outer circumferential surface of the supply roller 23 and then supplied to the outer circumferential surface of the developing roller 22 from the outer circumferential surface of the supply roller 23. Subsequently, by the rotation of the developing roller 22, a thin layer of the toner is carried on the outer circumferential surface of the developing roller body 221.
The toner carried on the outer circumferential surface of the developing roller 22 is supplied to the electrostatic latent image formed on the outer circumferential surface of the photosensitive drum 11. Hence, the electrostatic latent image becomes a visible toner image on the outer circumferential surface of the photosensitive drum 11. The toner image is transferred onto a recording surface of a printing sheet, and then the toner image is thermally fixed, terminating the printing process.
As described above, the developing cartridge 2 according to the embodiment includes the casing 21, the developing roller 22, the first agitator 25, the supply roller 23, and the second agitator 26. Here, a rotation locus of the second agitator fin 263 of the second agitator 26 is positioned outside of a rotation locus of the first agitator fin 253 of the first agitator 25. Hence, in the internal space of the casing 21, toner positioned at a region where sufficient agitation of the toner cannot be achieved by only rotation of the first agitator 25 can be agitated by rotation of the second agitator 26. Accordingly, sufficient agitation of toner can be performed even if remaining amount of the toner in the internal space of the casing 21 becomes low.
Further, in the developing cartridge 2 according to the embodiment, the second agitator 26 is positioned closer to the supply roller 23 in the second direction than the first agitator 25 is to the supply roller 23. Hence, toner stagnating around the supply roller 23 can be agitated by rotation of the second agitator 26. Accordingly, stagnation of a toner flow around the supply roller 23 in the internal space of the casing 21 can be restrained.
Further, in the developing cartridge 2 according to the embodiment, the first agitator 25 and the second agitator 26 rotate in the same rotating direction. Hence, a toner flow formed by rotation of the second agitator 26 can be easily merged into a toner flow formed by rotation of the first agitator 25. As a result, toner stagnating in the casing 21 can be introduced into the agitating region of the first agitator 25, thereby sufficiently performing agitation of toner in its entirety.
Further, the developing cartridge 2 according to the embodiment includes the coupling 24, the developing roller gear 223, the supply roller gear 233, the first agitator gear 254, the second agitator gear 264, the idle gear 27, the first drive gear 28, and the second drive gear 29. In this way, the developing cartridge 2 includes an even number of drive gears, namely, the first drive gear 28 and the second drive gear 29. Hence, the first agitator 25 and the second agitator 26 can be rotated with a constant speed ratio. Further, the first agitator 25 and the second agitator 26 rotate in the same rotating direction when viewed in the first direction. Thus, a toner flow formed by agitation by the second agitator 26 can be easily merged with a toner flow formed by agitation by the first agitator 25. In another aspect, in a region between the outer circumferential surface of the second agitator 26 and the outer circumferential surface of the supply roller 23, the rotating directions of the second agitator 26 and the supply roller 23 are the same direction when viewed in the first direction. As a result, toner can be easily supplied to the outer circumferential surface of the supply roller 23 by rotation of the second agitator 26.
Further, in the developing cartridge 2 according to the embodiment, the developing roller gear 223 and the supply roller gear 233 are positioned at the one side portion in the first direction of the support member 31, whereas the first drive gear 28, the second drive gear 29, and the second agitator gear 264 are positioned at the other side portion in the first direction of the support member 31. With this configuration, the developing roller gear 223, the supply roller gear 233, the first drive gear 28, the second drive gear 29, and the second agitator gear 264 can be divided into the one side portion and the other side portion in the first direction of the support member 31 and each disposed at the corresponding one of the two side portions. As a result, high layout density of the gears can be realized in a limited space, thereby rendering the developing cartridge 2 compact.
Further, in the developing cartridge 2 according to the embodiment, the first outer surface 211 of the casing 21 has the recessed portion 211a recessed in the direction from the one side to the other side in the first direction. The first drive gear 28, the second drive gear 29, and the second agitator gear 264 are accommodated in the recessed portion 211a. With this structure, the first drive gear 28, the second drive gear 29, and the second agitator gear 264 can be additionally accommodated in the gear case 32 with almost no modification to the conventional layout of gears, such as the coupling 24, the developing roller gear 223, and the supply roller gear 233. Hence, the second agitator 26 can be easily employed in the developing cartridge 2.
Further, in the developing cartridge 2 according to the present embodiment, the rotation frequency of the second agitator 26 is greater than the rotation frequency of the first agitator 25. Further, a diameter of the second agitator fin 263 about the second agitator rotation axis 26A is smaller than a diameter of the first agitator fin 253 about the first agitator rotation axis 25A. Hence, by rotation of the second agitator 26 which is smaller than the first agitator 25 and rotates at a higher speed than the first agitator 25, toner stagnating in the internal space of the casing 21 can be easily introduced to the wider agitating region of the first agitator 25.
Further, in the developing cartridge 2 according to the present embodiment, the peripheral speed of the second agitator 26 (i.e., the moving speed of the second agitator fin 263) is greater than or equal to the peripheral speed of the supply roller 23 (i.e., the moving speed of the outer circumferential surface of the supply roller body 231). Hence, shortage of toner supply to the supply roller 23 can be prevented.
Further, in the developing cartridge 2 according to the embodiment, the first agitator fin 253 and the second agitator fin 263 do not contact each other. With this configuration, generation of an intricate toner flow in the internal space of the casing 21 due to interference between the first agitator fin 253 and the second agitator fin 263 can be prevented, thereby facilitating uniform agitation of toner.
Further, in the developing cartridge 2 according to the present embodiment, the first agitator fin 253 is a sheet-shaped film. Hence, by rotation of the first agitator 25, the tip end portion of the first agitator fin 253 can be flexed while contacting the inner surface of the casing 21. Accordingly, toner adhering to the inner surface of the casing 21 can be scraped off. As a result, the toner in the casing 21 can be mixed further uniformly. In other words, toner stagnation can be suppressed over the entire internal space of the casing 21.
Further, in the developing cartridge 2 according to the embodiment, the second agitator 26 has a polygonal column shape whose corner portions each function as the second agitator fin 263. Hence, the second agitator fin 263 having high rigidity can be realized.
<4. Modifications>
While the description has been made in detail with reference to the specific embodiment, it would be apparent to those skilled in the art that many modifications and variations may be made thereto. Various modifications of the above-described embodiment will be simply described next.
Although the second agitator 26 has a triangular prism shape rotatable about the second agitator rotation axis 26A in the above-described embodiment, the shape of the second agitator 26 is not limited to the triangular prism shape. For example, the second agitator 26 may have a pentagonal prism shape or hexagonal prism shape, in place of the triangular prism shape.
Further, the shape of the second agitator 26 is not limited to any polygonal prism shape. For example, the second agitator fin 263 of the second agitator 26 may include: a rotary member rotatable about the second agitator rotation axis 26A; and a plurality of fin portions each extending radially outwardly from the rotary member. The fin portions may have a flat shape or curved shape. According to this modification, the surface area of the second agitator fin 263 can be increased. As a result, toner stagnating in the internal space of the casing 21 can be sufficiently agitated by the second agitator fin 263.
In the above-described embodiment, the first agitator fin 253 is a sheet-shaped film. However, a plastic thin plate may be available as the first agitator fin 253.
The developing roller gear 223, the supply roller gear 233, the first agitator gear 254, the second agitator gear 264, the coupling 24, the idle gear 27, the first drive gear 28, and the second drive gear 29 may be positioned at the second outer surface 212 that is an outer surface of the casing 21 at the other side in the first direction.
Further, the detailed configuration of the developing cartridge may be suitably modified. Additionally, various features appearing in the above embodiment and modifications thereof may be suitably combined together as long as no contradiction arises.
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