Driving force transmission mechanism and image forming apparatus

A driving force transmission mechanism includes a body that includes a transmission member, which transmits a driving force and includes a rotatable first surface and two first projections, and an installation unit that includes a receiving member including a second surface, which faces the first surface and which is rotatable by receiving the force when the installation unit is installed, and two second projections, which receive the force from the first projections by contacting the first projections when the first surface rotates, and that is removably installed in the body in a direction, in which the second surface moves parallel to the first surface, to couple the transmission member and the receiving member. The body includes a contact member that contacts, to rotate the receiving member, one of the second projections when the installation unit is installed while a line segment connecting the second projections is intersecting an installation direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2015-060287 filed Mar. 24, 2015.

BACKGROUND

Technical Field

The present invention relates to a driving force transmission mechanism and an image forming apparatus.

SUMMARY

According to an aspect of the invention, there is provided a driving force transmission mechanism including a body including a transmission member that transmits a driving force and includes a first surface, which rotates, and two first projections that project from the first surface at positions, each of which is spaced apart from a center of rotation of the first surface and an installation unit that includes a receiving member including a second surface, which faces the first surface and which rotates as a result of receiving the driving force in a state where the installation unit is installed in the body, and two second projections, which project from the second surface at positions each of which is spaced apart from a center of rotation of the second surface and which receive the driving force from the first projections by being in contact with the first projections in accordance with rotation of the first surface, and that is configured to be removably installed in the body in a direction in which the second surface moves parallel to the first surface in such a manner that the transmission member and the receiving member are coupled to each other. The body further includes a contact member that is brought into contact with one of the second projections when the installation unit is installed in the body in a state where a line segment connecting the second projections intersects an installation direction in which the installation unit is installed in the body and that causes the receiving member to rotate.

DETAILED DESCRIPTION

An exemplary embodiment of the present invention will be described below.

FIG. 1is a schematic diagram illustrating a printer, which is an exemplary embodiment of an image forming apparatus of the present invention. A device, which is an exemplary embodiment of a driving force transmission device of the present invention, is incorporated within the printer.

A printer1illustrated inFIG. 1is a printer that employs an electrophotographic system and prints an image on one of sheets P, and a side surface of the printer1on the right side inFIG. 1is a front surface of the printer1. In the printer1, a process cartridge2is installed in a printer body11so as to be removable from the printer body11on the side on which the front surface of the printer1is present. In addition, a toner cartridge3is installed diagonally above a front surface of the process cartridge2so as to be removable from the printer body11on the side on which the front surface of the printer1is present.

Here, the printer body11corresponds to an example of a body, and the toner cartridge3corresponds to an example of an installation unit.

The toner cartridge3contains a replenishing toner, and this toner in the toner cartridge3is stirred as a result of rotation of a stirring member31, so that the toner is prevented from coagulating. A driving force is transmitted to the stirring member31from a motor111, which is provided in the printer body11, via a driving force transmission mechanism (not illustrated). The toner in the toner cartridge3is supplied to a developing unit21, which is included in the process cartridge2.

In addition to the developing unit21, the process cartridge2includes a photoconductor22, a charger23, and a cleaner24. A waste-toner containing chamber25that contains waste toner, which is scraped off from the photoconductor22by the cleaner24, is disposed between the developing unit21and the photoconductor22and the toner cartridge3.

The printer body11further includes an exposure unit112that radiates exposure light112aonto the photoconductor22and a transfer unit113that is disposed at a position facing the photoconductor22.

The photoconductor22is subjected to various operations described below while rotating in the direction of arrow A.

The charger23charges a surface of the photoconductor22to a predetermined potential.

The exposure unit112radiates the exposure light112a, which corresponds to an image signal, onto the charged surface of the photoconductor22so as to form an electrostatic latent image on the surface of the photoconductor22.

The developing unit21contains a developer containing a carrier and a toner and moves circularly in a direction perpendicular toFIG. 1as a result of rotation of two augers211and212. The developer in the developing unit21is delivered to a developing position facing the photoconductor22by a developing roller213that rotates in the direction of arrow B. An electrostatic latent image on the photoconductor22is developed with the toner, which is contained in the developer, and a toner image is formed on the photoconductor22. The toner image formed on the photoconductor22is transferred onto one of the sheets P, which is transported in a manner described later, by operation of the transfer unit113. The toner image on the sheet P is heated and pressurized by a fixing unit114provided in the printer body11and fixed onto the sheet P.

A sheet cartridge115is mounted in a lower portion of the printer body11in such a manner as to be capable of being drawn out toward the right side inFIG. 1, and the sheets P, on each of which an image is to be printed, are accommodated in the sheet cartridge115in such a manner as to be stacked on top of one another. When a printing operation is performed, one of the sheets P accommodated in the sheet cartridge115, the sheet P being at the top of the sheets P, is taken out by a take-out roller116. Even in the case where some of the sheets P are taken out while superposed with each other, separation rollers117separate the sheets P one by one with certainty, and only one of the sheets P is transported along a transport path d1and reaches registration rollers118. The registration rollers118correct the position of the sheet P, which has been transported, and send out the sheet P to a further downstream side by adjusting the timing of subsequent transportation of the sheet P. The registration rollers118send out the sheet P in accordance with the timing at which the toner image on the photoconductor22is transferred, and the toner image on the photoconductor22is transferred onto the sheet P. The sheet P, to which the toner image has been transferred, is further transported along a transport path d2in such a manner as to pass through the fixing unit114, the toner image is fixed onto the sheet P. The sheet P is ejected by sheet ejection rollers119into a sheet-ejection tray120that is provided in an upper portion of the printer body11.

In the case of printing an image on the two surfaces of the sheet P, a portion of the sheet P, which has an image printed on one surface thereof in a similar manner to the above, is sent out by the sheet ejection rollers119. After that, the sheet ejection rollers119rotate in a reverse direction, and the sheet P is transported along a transport path d3and reaches the registration rollers118again. Subsequently, the above-described printing operation is repeated, and the sheet P having images printed on the two surfaces thereof is ejected into the sheet-ejection tray120by the sheet ejection rollers119.

A cover121, which is a portion of a cover of the printer body11, is capable of being freely opened and closed in the direction of arrow C to arrow D, that is, toward the front surface of the printer1, with a hinge portion121aacting as a center. When a user opens the cover121and draws out the toner cartridge3by holding a handle39, which is included on the toner cartridge3, in their hand, the toner cartridge3is removed from the printer body11. When the user removes the process cartridge2from the printer body11, after the toner cartridge3has been removed from the printer body11, the user tilts a rotating lever29, which is included on the process cartridge2, in such a manner that the rotating lever29rotates in the direction of arrow E. The rotating lever29is rotatably mounted with a hinge portion29. However, during the period when the toner cartridge3is installed in the printer body11, the rotating lever29is maintained at a first position, which is illustrated inFIG. 1, due to the presence of the toner cartridge3.

When the process cartridge2is installed at a normal position, which is illustrated inFIG. 1, and the rotating lever29is located at the first position illustrated inFIG. 1, regardless of the existence of the toner cartridge3, part of a lower end portion of the process cartridge2is hooked on the printer body11, and accordingly, it is difficult to draw out the process cartridge2.

In the case of removing the process cartridge2from the printer body11, a user removes the toner cartridge3first. After that, the user tilts the rotating lever29in the direction of arrow E so as to bring the rotating lever29to a second position. Then, the process cartridge2is slightly raised by an eccentric cam (not illustrated) that is integrally formed with the rotating lever29. As a result, the part of the lower end portion of the process cartridge2, which has been hooked on the printer body11, is released. Finally, the user draws out the process cartridge2by using as a handle the rotating lever29, which has been tilted so as to be located at the second position as is, and the process cartridge2may be removed from the printer body11. In the case of installing the process cartridge2, the user performs an operation that is the reverse of the operation for removing the process cartridge2from the printer body11. In other words, the user presses the process cartridge2into the printer body11by using the rotating lever29of the process cartridge2as a handle and brings the rotating lever29to the first position illustrated inFIG. 1by rotating the rotating lever29in the direction of arrow F. Then, the part of the lower end portion of the process cartridge2is hooked on the printer body11and prevented from being released from the printer body11. After that, the user installs the toner cartridge3into the printer body11by holding the handle39of the toner cartridge3in their hand and closes the cover121of the printer body11in the direction of arrow D.

The printer body11includes a transmission member that transmits a driving force, which causes the stirring member31to rotate, from the motor111to the toner cartridge3. The toner cartridge3includes a receiving member that receives the driving force from the transmission member.

The structures of the transmission member and the receiving member and a structure associated therewith will be described below.

FIG. 2is a diagram illustrating a transmission member mounted on the printer body11.

FIG. 3is a diagram illustrating a receiving member mounted on the toner cartridge3.

Although the toner cartridge3in the printer1according to the present exemplary embodiment is configured to be installed in a diagonal direction from a top side to a bottom side as illustrated inFIG. 1, for ease of understanding,FIG. 2andFIG. 3illustrate the toner cartridge3as if the toner cartridge3is installed in the horizontal direction.

A transmission member40illustrated inFIG. 2has a circular-shaped first surface41. The first surface41receives a driving force from the motor111(seeFIG. 1) and rotates about a center of rotation40a, which is the center of the first surface41. The transmission member40includes two first projections42projecting from the first surface41at positions, each of which is spaced apart from the center of rotation40aof the first surface41in opposite directions. These two first projections42rotate around the center of rotation40aas a result of rotation of the first surface41. In the printer body11, a projection43, which has a portion on its bottom surface side formed in an arc shape, is disposed at a position closer than the transmission member40to the proximal side in an installation direction indicated by arrow G. Operation of the projection43will be described later. The projection43corresponds to an example of a contact member.

A receiving member50, which is mounted on the toner cartridge3and illustrated inFIG. 3, has a circular-shaped second surface51. When the toner cartridge3is installed in the printer body11, the second surface51is located at a position facing the first surface41(seeFIG. 2) of the transmission member40mounted on the printer body11. The second surface51receives a driving force from the transmission member40of the printer body11and rotates about a center of rotation50a, which is the center of the circular shape.

The receiving member50of the toner cartridge3includes two second projections52projecting from the second surface51at positions, each of which is spaced apart from the center of rotation50aof the second surface51in substantially opposite directions. Each of the two second projections52is brought into contact with a corresponding one of the two first projections42, which are included in the transmission member40of the printer body11. When the transmission member40rotates, the two second projections52receive a driving force from the corresponding two first projections42and rotate upon the rotations of the first projections42so that the second surface51rotates. This rotation is transmitted to the stirring member31, which is disposed in the toner cartridge3(seeFIG. 1), and consequently, the stirring member31rotates.

Coupling of the receiving member50to the transmission member40in the case of installing the toner cartridge3will now be described.

FIGS. 4A to 4Care schematic diagrams illustrating a state in which the receiving member50comes closer to the transmission member40as a result of an operation of installing the toner cartridge3.

Here, the transmission member40of the printer body11is stopped at a position where a line segment connecting the two first projections42is perpendicular to an insertion direction indicated by arrow G. The receiving member50of the toner cartridge3is also located at a position where a line segment connecting the two second projections52is perpendicular to the insertion direction indicated by arrow G. In the case where both the transmission member40and the receiving member50are located at the above-mentioned positions, when the toner cartridge3is installed in the direction of arrow G without taking any measures, the two second projections52abuts against the corresponding two first projections42at approximately the same time, and the installation of the toner cartridge3is obstructed. As a result, it is difficult to couple the receiving member50to the transmission member40. Accordingly, in the present exemplary embodiment, in the printer body11, the projection43is disposed at the position closer than the transmission member40to the proximal side in the installation direction (indicated by arrow G) (also seeFIG. 2).

In the case of installing the toner cartridge3, as illustrated inFIG. 4A, the receiving member50comes closer to the transmission member40in the direction of arrow G. Then, as illustrated inFIG. 4B, one of the two second projections52of the receiving member50abuts against the projection43of the printer body11, and the receiving member50rotates in the direction indicated by arrow H. Consequently, as illustrated inFIG. 4C, the toner cartridge3is inserted in such a manner that the second surface51reaches the normal position facing the first surface41while the second projections52avoid making contact with the first projections42.

FIGS. 5A and 5Bare schematic diagrams respectively illustrating the receiving member50and the transmission member40.

The shapes of the first projections42and the second projections52will now be described.

The transmission member40illustrated inFIG. 5Bwill be described first. Surfaces of the two first projections42of the transmission member40facing the center of rotation40aeach have an arc shape. In addition, each of the two first projections42has a first pointed portion42a, which is tapered in a direction away from the center of rotation40a.

The two second projections52of the receiving member50illustrated inFIG. 5Aare disposed at positions that are slightly offset with respect to the center of rotation50ain order to make a line segment connecting two contact points of the two second projections52and the two first projections42of the transmission member40pass through the center of rotation50a.

Portions of the second projections52that come into contact with the corresponding first projections42are each formed of a plane that is vertically oriented. On the other hand, each of the first projections42is brought into linear contact with the corresponding second projections52on a vertical boundary line between the portion of the first projection42having an arc shape and the first pointed portion42a. If each of the first projections42is formed in a plane so as to be brought into surface contact with the corresponding second projection52, contact positions will be displaced to a large extent in a radial direction with small tolerance. In the present exemplary embodiment, in order to suppress this from occurring, the first projections42are each formed in such a shape so as to come into linear contact with the corresponding second projection52.

Similar to the first projections42, each of the second projections52has a first pointed portion52a, which is tapered in a direction away from the center of rotation50a. In addition, each of the second projections52has a second pointed portion52b, which is tapered in a direction toward the center of rotation50a.

Here, the transmission member40and the receiving member50are located at positions where one of the second projections52that is positioned further toward the proximal side in the installation direction (direction of arrow G) and one of the first projections42that is positioned further toward the distal side in the installation direction (direction of arrow G) are arranged side by side in the installation direction (direction of arrow G). The one of the second projections52will hereinafter be referred to as a proximal second projection52, and the one of the first projections42will hereinafter be referred to as a distal first projection42.

While the transmission member40and the receiving member50are located at these positions, when the toner cartridge3is installed, and the receiving member50comes closer to the transmission member40, the first pointed portion52aof the proximal second projection52abuts against the first pointed portion42aof the distal first projection42. Here, since the distal first projection42and the proximal second projection52have the first pointed portion42a, which is tapered, and the first pointed portion52a, which is tapered, respectively, when the first pointed portion52acomes into contact with the first pointed portion42a, the receiving member50rotates in one of two directions. Consequently, when the toner cartridge3is inserted further in the installation direction (direction of arrow G), the receiving member50and the transmission member40are coupled to each other.

When the receiving member50rotates slightly as a result of the proximal second projection52coming into contact with the distal first projection42, and the toner cartridge3is inserted more deeply, or when the transmission member40is located at a position where the transmission member40reaches after rotating slightly from the position illustrated inFIG. 5B, and the toner cartridge3is inserted more deeply without contact between the proximal second projection52and the distal first projection42, a situation may be assumed in which the other one of the second projections52that is positioned further toward the distal side in the installation direction (direction of arrow G) comes into contact with the distal first projection42. The other one of the second projections52will hereinafter be referred to as a distal second projection52.

In this case, the second pointed portion52bof the distal second projection52facing the center of rotation50acomes into contact with the first pointed portion42aof the distal first projection42. Accordingly, also in this case, contact is made between portions each of which is tapered, and when the toner cartridge3is inserted further deeply as is, the receiving member50and the transmission member40are coupled to each other.

A relationship between the distance between the two first projections42, which are included in the transmission member40, and the distance between the two second projections52, which are included in the receiving member50, will now be described.

FIG. 6illustrates a comparative example and is a diagram illustrating a problem that may occur in the case where the distance between the two first projections42and the distance between the two second projections52are approximately equal to each other.

In order to transmit a driving force from the transmission member40to the receiving member50by correctly coupling the transmission member40and the receiving member50to each other, it is necessary that the two second projections52of the receiving member50move to positions opposite to each other with respect to the corresponding two first projections42of the transmission member40(on the same side in a rotation direction of the receiving member50).

Here, as illustrated inFIG. 6, the two first projections42and the two second projections52are positioned so as to be inclined to the installation direction (direction of arrow G).

In this case, the proximal second projection52(the second projection52in the lower right ofFIG. 6) abuts against a surface of the other one of the first projections42that is positioned further toward the proximal side in the installation direction (the first projection42in the lower right ofFIG. 6), the surface being located on the downstream side in a rotation direction of the transmission member40(direction indicated by arrow I). The other one of the first projections42will hereinafter be referred to as a proximal first projection42. Then, the receiving member50tries to rotate in a direction indicated by arrow H. However, the distal second projection52(the second projection52in the upper left ofFIG. 6) abuts against the distal first projections42(the first projection42in the upper left ofFIG. 6) this time, and it is difficult to correctly couple the transmission member40and the receiving member50to each other.

FIG. 7is a schematic diagram illustrating how to address the disadvantage illustrated inFIG. 6.

Here, a distance between a first end of one of the two first projections42, the first end being further away from the center of rotation40athan a second end of the first projection42, and a first end of the other one of the first projections42, the first end being closer to the center of rotation40athan a second end of the first projection42, is a first distance a. A distance between a first end of one of the two second projections52, the first end being further away from the center of rotation50athan a second end of the second projection52, and a first end of the other one of the second projections52, the first end being closer to the center of rotation50athan a second end of the second projection52, is a second distance b. When the first distance a and the second distance b are compared, a relationship of a>b is satisfied. However, since this is an outline of how to address the disadvantage illustrated inFIG. 6, there is a case where desirable results are not obtained even if the relationship of a>b is barely satisfied. Therefore, it is necessary that the difference between the first distance a and the second distance b be slightly larger in order to satisfy a relationship of a>b+c (c>0).

FIG. 8is a diagram illustrating the case of addressing the disadvantage illustrated inFIG. 6in the manner illustrated inFIG. 7.

InFIG. 8, regarding the transmission member40and the receiving member50, the two first projections42and the two second projections52are positioned so as to be oriented as illustrated inFIG. 8.

Assume that the toner cartridge3is installed in the installation direction (direction of arrow G), and the distal second projection52(the second projection52on the left side inFIG. 8) comes into contact with the distal first projections42(on the left side inFIG. 8) at a contact point X. Then, the receiving member50rotates in a direction indicated by arrow J. Here, a circle R2having a diameter equal to a distance b′ between the contact point X and a first end of the proximal second projection52(on the right side inFIG. 8), the first end being closer to the center of rotation50athan a second end of the proximal second projection52, is smaller than a circle R1having a diameter equal to a distance a′ between the contact point X and a first end of the proximal first projections42(on the right side inFIG. 8), the first end being closer to the center of rotation40athan a second end of the proximal first projection42. In other words, a relationship of a′>b′ is satisfied.

Note that, although in the present exemplary embodiment, the printer1has been described as an example of the driving force transmission device of the present invention, the present invention is not limited to the printer1and image forming apparatuses other than the printer1and may be widely applied to apparatuses each of which includes a body, which transmits a driving force, and an installation unit, which receives the driving force by being installed in the body.