Patent Description:
Toner is a developer and is accommodated in a developer cartridge. A developer cartridge is a consumable that is replaced when a developer contained therein is used up. A replacement time of the developer cartridge may be determined by detecting a remaining amount of the developer in the developer cartridge. <CIT> discloses a cylindrical toner container that has a toner discharge port for discharging toner, and a toner conveyance portion with projections provided in the inner wall of the toner container. A toner conveyane coil is provided inside of the toner container.

<FIG> is a schematic structural diagram of an electrophotographic printer (image forming apparatus) according to an example. Referring to <FIG>, the printer includes a main body <NUM> and a developer cartridge <NUM> that is attachable to/detachable from the main body <NUM>. The main body <NUM> includes a printing unit <NUM> printing an image on a print medium P by using an electrophotographic method. The printing unit <NUM> according to the present example prints a color image on a print medium P by using an electrophotographic method. The printing unit <NUM> may include a plurality of developing devices <NUM>, an exposure device <NUM>, a transfer unit, and a fixing unit <NUM>. The developer cartridge <NUM> accommodates a developer to be supplied to the printing unit <NUM>. The printer may include a plurality of developer cartridges <NUM> accommodating a developer. The plurality of developer cartridges <NUM> are respectively connected to the plurality of developing devices <NUM>, and a developer accommodated in the plurality of developer cartridges <NUM> is supplied to each of the plurality of developing devices <NUM>. A developer supplying unit <NUM> receives a developer from the developer cartridge <NUM> and supplies the same to the developing devices <NUM>. The developer supplying unit <NUM> is connected to the developing devices <NUM> via a supply pipeline <NUM>. Although not illustrated in the drawing, the developer supplying unit <NUM> may be omitted, and the supply pipeline <NUM> may directly connect the developer cartridge <NUM> to the developing devices <NUM>.

The plurality of developing devices <NUM> may include a plurality of developing devices 10C, <NUM>, 10Y, and <NUM> that are used to form toner images of cyan (C), magenta (M), yellow (Y), and black (K) colors, respectively. In addition, the plurality of developer cartridges <NUM> may include a plurality of developer cartridges 20C, <NUM>, 20Y, and <NUM> respectively accommodating developers of cyan (C), magenta (M), yellow (Y), and black (K) colors to be respectively supplied to the plurality of developing devices 10C, <NUM>, 10Y, and <NUM>. However, the scope of the disclosure is not limited thereto. The printer may further include other developer cartridges <NUM> and developing devices <NUM> to accommodate and develop developers of other various colors such as light magenta or white in addition to the above-described colors. Hereinafter, a printer including the plurality of developing devices 10C, <NUM>, 10Y, and <NUM> and the plurality of developer cartridges 20C, <NUM>, 20Y, and <NUM> will be described, and unless otherwise described, elements labeled C, M, Y, and K below respectively refer to elements for developing developers of cyan (C), magenta (M), yellow (Y), and black (K) colors.

The developing devices <NUM> may each include a photosensitive drum <NUM>, on a surface of which an electrostatic latent image is formed, and a developing roller <NUM> supplying a developer to the electrostatic latent image to develop the electrostatic latent image into a visible toner image. The photosensitive drum <NUM> is an example of a photosensitive body, on a surface of which an electrostatic latent image is formed, and may include a conductive metal pipe and a photosensitive layer formed on an outer circumference thereof. A charging roller <NUM> is an example of a charging device charging the photosensitive drum <NUM> to have a uniform surface potential. Instead of the charging roller <NUM>, a charging brush or a corona charging device or the like may also be used.

The developing devices <NUM> may further include a charging roller cleaner (not illustrated) removing a developer or foreign substances such as dust attached on the charging roller <NUM>, a cleaning member <NUM> removing a developer remaining on a surface of the photosensitive drum <NUM> after an intermediate transfer process to be described later, a regulation member regulating an amount of a developer supplied to a developing region in which the photosensitive drum <NUM> and the developing roller <NUM> face each other. The cleaning member <NUM> may be, for example, a cleaning blade that contacts a surface of the photosensitive drum <NUM> to scrape the developer. Although not illustrated in <FIG>, the cleaning member <NUM> may be a cleaning brush that rotates to contact a surface of the photosensitive drum <NUM> and scrape the developer.

A developer accommodated in the developer cartridge <NUM>, that is, toner and carrier, is supplied to the developing devices <NUM>. The developing roller <NUM> may be spaced apart from the photosensitive drum <NUM>. A distance between an outer circumferential surface of the developing roller <NUM> and an outer circumferential surface of the photosensitive drum <NUM> may be, for example, about several tens to about several hundreds of microns. The developing roller <NUM> may be a magnetic roller. In addition, the developing roller <NUM> may have a form in which a magnet is disposed in a rotating developing sleeve. In the developing devices <NUM>, toner is mixed with a carrier, and the toner is attached to a surface of a magnetic carrier. The magnetic carrier is attached to a surface of the developing roller <NUM> and transported to the developing region in which the photosensitive drum <NUM> and the developing roller <NUM> face each other. A regulating member (not shown) regulates an amount of the developer transported to the developing region. Via a developing bias voltage applied between the developing roller <NUM> and the photosensitive drum <NUM>, the toner is supplied to the photosensitive drum <NUM> so as to develop an electrostatic latent image formed on a surface of the photosensitive drum <NUM> into a visible toner image.

The exposure device <NUM> radiates light modulated according to image information, onto the photosensitive drum <NUM>, to thereby form an electrostatic latent image on the photosensitive drum <NUM>. Examples of the exposure device <NUM> may be a laser scanning unit (LSU) using a laser diode as a light source or a light-emitting diode (LED) exposure device that uses an LED as a light source.

The transfer device transfers the toner image formed on the photosensitive drum <NUM>, onto a print medium P. In the present example, a transfer device that uses an intermediate transfer method is used. For example, the transfer device may include an intermediate transfer belt <NUM>, a plurality of intermediate transfer rollers <NUM>, and a transfer roller <NUM>.

The intermediate transfer belt <NUM> temporarily accommodates the toner image developed on the photosensitive drum <NUM> of the plurality of developing devices 10C, <NUM>, 10Y, and <NUM>. The plurality of intermediate transfer rollers <NUM> are disposed to face the photosensitive drum <NUM> of the plurality of developing devices 10C, <NUM>, 10Y, and <NUM>, with the intermediate transfer belt <NUM> therebetween. An intermediate transfer bias voltage used to intermediately transfer the toner image developed on the photosensitive drum <NUM>, to the intermediate transfer belt <NUM>, is applied to the plurality of intermediate transfer rollers <NUM>. Instead of the intermediate transfer rollers <NUM>, a corona transfer device or a pin scorotron transfer device may be used.

The transfer roller <NUM> is disposed to face the intermediate transfer belt <NUM>. A transfer bias voltage for transferring the toner image transferred to the intermediate transfer belt <NUM>, to the print medium P, is applied to the transfer roller <NUM>.

The fixing unit <NUM> fixes the toner image transferred to the print medium P, on the print medium P, by applying heat and/or pressure to the toner image. The form of the fixing unit <NUM> is not limited to that illustrated in <FIG>.

According to the above-described configuration, the exposure device <NUM> radiates light modulated according to image information of the colors onto the photosensitive drum <NUM> of the plurality of developing devices 10C, <NUM>, 10Y, and <NUM> to form an electrostatic latent image on the photosensitive drum <NUM>. The electrostatic latent image of the photosensitive drum <NUM> of the plurality of developing devices 10C, <NUM>, 10Y, and <NUM> is developed into a visible toner image by using the C, M, Y, and K developers supplied from the plurality of developer cartridges 20C, <NUM>, 20Y, and <NUM> to the plurality of developing devices 10C, <NUM>, 10Y, and <NUM>. The developed toner images are sequentially intermediately transferred to the intermediate transfer belt <NUM>. The print medium P loaded in a feeding unit <NUM> is transported along a feeding path <NUM> between the transfer roller <NUM> and the intermediate transfer belt <NUM>. Due to a transfer bias voltage applied to the transfer roller <NUM>, the toner images that are intermediately transferred onto the intermediate transfer belt <NUM> are transferred to the print medium P. When the print medium P passes through the fixing unit <NUM>, the toner images are fixed to the print medium P by heat and pressure. The print medium P, with which fixing is completed, is discharged using a discharge roller <NUM>.

The plurality of developer cartridges <NUM> are attachable to/detachable from the main body <NUM> and may be individually replaceable. When the developer accommodated in the developer cartridge <NUM> is completely consumed, the developer cartridge <NUM> may be replaced with a new developer cartridge <NUM>. When a mono-component development method is used, a developer accommodated in the developer cartridge <NUM> may be toner. When a dual-component development method is used, a developer accommodated in the developer cartridge <NUM> may be toner or toner and carrier. The developer cartridge <NUM> may also be referred to as a 'toner cartridge.

<FIG> is a perspective view of a developer cartridge <NUM> according to an example. <FIG> is a cross-sectional view of the developer cartridge <NUM> of <FIG> taken along X1-X1'. <FIG> is a cross-sectional view of the developer cartridge <NUM> of <FIG> taken along X2-X2'.

Referring to <FIG> and <FIG>, the developer cartridge <NUM> includes a housing <NUM>, a spring auger <NUM>, and a rotation member <NUM>.

A developer is accommodated in the housing <NUM>. The housing <NUM> includes a first end portion <NUM> and a second end portion <NUM> that are spaced apart from each other in a length direction B. A developer discharge outlet <NUM> through which a developer is discharged is provided at a position adjacent to one of the first end portion <NUM> and the second end portion <NUM>. In the present example, the developer discharge outlet <NUM> is located adjacent to the second end portion <NUM>. A shutter <NUM> selectively opening or closing the developer discharge outlet <NUM> may be provided in an outer portion of the developer discharge outlet <NUM>. A developer may be supplied to the developing devices <NUM> through the developer discharge outlet <NUM>. The supply pipeline <NUM> (<FIG>) may be connected to the developer discharge outlet <NUM>. The developer discharge outlet <NUM> may also be connected to the developer supplying unit <NUM> (<FIG>). In addition, although not illustrated in the drawings, the developer discharge outlet <NUM> may also be directly connected to the developing devices <NUM>.

The spring auger <NUM> is located inside the housing <NUM> and rotated to transport a developer to the developer discharge outlet <NUM>. The spring auger <NUM> has a spiral coil shape as illustrated in <FIG>. The rotation member <NUM> is located at the first end portion <NUM> of the housing <NUM>, and is connected to the spring auger <NUM> to rotate the spring auger <NUM>. One end <NUM> of the spring auger <NUM> is connected to the rotation member <NUM>.

A connection structure between the rotation member <NUM> and the spring auger <NUM> according to an example will be described with reference to <FIG> and <FIG>. The spring auger <NUM> may include a connection portion <NUM> connected to the rotation member <NUM>, an extension portion <NUM> extending from the connection portion <NUM> in a radial direction, and a spiral portion <NUM> extending from the extension portion <NUM> toward the second end portion <NUM> of the housing <NUM> in a length direction B in a spiral shape. The one end <NUM> of the spring auger <NUM> may include the connection portion <NUM> and the extension portion <NUM> described above. The other end <NUM> of the spring auger <NUM> is an end opposite to the one end <NUM> with the spiral portion <NUM> included therebetween.

The connection portion <NUM> may extend, for example, in an axial direction of the spring auger <NUM>. The connection portion <NUM> may be inserted into an insertion hole <NUM> provided in, for example, the rotation member <NUM>. The extension portion <NUM> is inserted into a slit <NUM> cut in the rotation member <NUM> in a radial direction. When the rotation member <NUM> is rotated, a sidewall of the slit <NUM> pushes the extension portion <NUM>, thereby rotating the spring auger <NUM>. The rotation member <NUM> may be, for example, a gear or a coupler. When the developer cartridge <NUM> is mounted in the main body <NUM>, the rotation member <NUM> may be connected to a developer supply motor (not shown) provided in the main body <NUM>. The rotation member <NUM> may be connected to a developer supply motor (not shown) provided in the developer cartridge <NUM>.

The other end <NUM> of the spring auger <NUM> may be a free end that is not restricted by the housing <NUM>. In other words, as illustrated in <FIG>, the other end <NUM> of the spring auger <NUM> may not be connected to the second end portion <NUM> of the housing <NUM> but may be located adjacent to the second end portion <NUM> of the housing <NUM>. As another example, the other end <NUM> of the spring auger <NUM> may be rotatably supported in the housing <NUM>. For example, as illustrated by a broken line in <FIG>, the other end <NUM> of the spring auger <NUM> may be rotatably supported by the second end portion <NUM> of the housing <NUM>.

When the spring auger <NUM> is rotated, the spiral portion <NUM> of the spring auger <NUM> contacts a bottom surface <NUM> of the housing <NUM>, transporting toner in the housing <NUM> in the length direction B toward the developer discharge outlet <NUM>. When the spring auger <NUM> is rotated, according to a rotational phase of the spring auger <NUM>, the spiral portion <NUM> of the spring auger <NUM> may be spaced apart from the bottom surface <NUM> of the housing <NUM>.

<FIG> illustrates a change in a state of contact between the spiral portion <NUM> of the spring auger <NUM> and the bottom surface <NUM> of the housing <NUM> according to a rotational phase of the spring auger <NUM>. Referring to (a) of <FIG>, a position where the extension portion <NUM> of the spring auger <NUM> faces the bottom surface <NUM> is referred to as a reference rotational position of the spring auger <NUM>. Here, the spiral portion <NUM> is in contact with the bottom surface <NUM>. In this state, when the spring auger <NUM> starts rotating in a counterclockwise direction, the spiral portion <NUM> is moved in the length direction B. Here, as the spring auger <NUM> is twisted by rotational moment of the spring auger <NUM>, the spiral portion <NUM> starts being spaced apart from the bottom surface <NUM>. As the spring auger <NUM> passes the reference rotational position to a position where it is rotated by <NUM> degrees ((b) of <FIG>) and then to a position where it is rotated by <NUM> degrees ((c) of <FIG>), a distance between the spiral portion <NUM> and the bottom surface <NUM> may be gradually increased. The distance between the spiral portion <NUM> and the bottom surface <NUM> may be greatest when the spring auger <NUM> has reached a position where it is rotated by <NUM> degrees ((c) of <FIG>) from the reference rotational position. When a rotational position of the spring auger <NUM> passes the position where it is rotated by <NUM> degrees, illustrated in (c) of <FIG>, from the reference rotational position, the spiral portion <NUM> starts descending toward the bottom surface <NUM>. The spring auger <NUM> then passes the position where it is rotated by <NUM> degrees ((d) of <FIG>) from the reference rotational position and reaches again the reference rotational position illustrated in (a) of <FIG>.

When the bottom surface <NUM> is flat in the length direction B, a process that the spiral portion <NUM> is spaced apart from the bottom surface <NUM> and then contacts the bottom surface <NUM> again according to a rotational phase of the spring auger <NUM> is repeated during rotation of the spring auger <NUM>. Accordingly, a period of separation SP and a period of contact CP in the length direction B are repeated, and a repeat cycle of the period of separation SP and the period of contact CP is equal to a pitch PT of the spiral portion <NUM>.

As no developer is transported in the period of separation SP, at a time when the developer in the housing <NUM> is almost exhausted, the developer remains in an area of the bottom surface <NUM> corresponding to the period of separation SP. This developer is referred to as residual developer. The residual developer is present at various positions on the bottom surface <NUM> at certain distances in the length direction B, that is, at the pitch PT of the spiral portion <NUM>. Even when the spring auger <NUM> is rotated, the residual developer is not transported to the developer discharge outlet <NUM>, and thus is not used in printing.

Thus, a method to reduce an amount of residual developer is needed to increase a use efficiency of developer accommodated in the developer cartridge <NUM>. According to the developer cartridge <NUM> of the present example, a first portion <NUM> that is flat and a second portion <NUM> that is internally convex from the first portion <NUM> are formed on the bottom surface <NUM> of the housing <NUM>. The first portion <NUM> and the second portion <NUM> are repeatedly arranged in the length direction B. A repeated arrangement cycle of the first portion <NUM> and the second portion <NUM> is equal to a pitch of the spring auger <NUM>, that is, the pitch PT of the spiral portion <NUM>.

The first portion <NUM> may be formed to correspond to a period of contact CP, and the second portion <NUM> may be formed to correspond to a period of separation SP. According to this configuration, the spiral portion <NUM> may be maintained in a contacted state with respect to the second portion <NUM> that is internally convex, in the period of separation SP. Accordingly, a developer may be continuously transported toward the developer discharge outlet <NUM> also in the period of separation SP, thus reducing or preventing the occurrence of residual developer.

The first portion <NUM> and the second portion <NUM> are formed in synchronization with a rotational phase of the extension portion <NUM> of the spring auger <NUM>. For example, while the extension portion <NUM> is respectively located at a reference rotational position, a position rotated from the reference rotational position by <NUM> degrees, a position rotated from the reference rotational position by <NUM> degrees, and a position rotated from the reference rotational position by <NUM> degrees, respective positions where the spiral portion <NUM> faces the bottom surface <NUM> are respectively referred to as a first position CP-<NUM>, a second position CP-<NUM>, a third position CP-<NUM>, and a fourth position CP4. The second portion <NUM> may start from the first position CP-<NUM> corresponding to the reference rotational position of the extension portion <NUM>.

A length of the second portion <NUM> may be longer than a length of the first portion <NUM>. Accordingly, the bottom surface <NUM> may be in stable contact with the spiral portion <NUM>, thereby effectively reducing or preventing the occurrence of residual developer. In other words, with respect to a rotational phase of the extension portion <NUM>, a section from the reference rotational position to the position rotated by <NUM> degrees is a section where the spiral portion <NUM> is spaced apart from the bottom surface <NUM>, and thus, the second portion <NUM> may be formed from the first position CP-<NUM> and at least to the third position CP-<NUM>. A protrusion amount of the second portion <NUM> may be in a smooth curve shape which gradually increases from the first position CP-<NUM> and then gradually decreases again until the third position CP-<NUM> is reached.

When a rotational phase of the extension portion <NUM> exceeds the <NUM>-degree rotated position, the spiral portion <NUM> may descend toward the bottom surface <NUM> and contact the bottom surface <NUM> in a certain rotational position. The second portion <NUM> may be formed up to the fourth position CP-<NUM> to minimize an amount of residual developer. A protrusion amount of the second portion <NUM> may be in a smooth curve shape which gradually increases from the first position CP-<NUM> and then gradually decreases again until the fourth position CP-<NUM> is reached.

Referring to <FIG>, a regulation protrusion <NUM> protruding downwards to regulate an upward flow of the spring auger <NUM> is provided on an upper wall <NUM> of the housing <NUM>. The regulation protrusion <NUM> is spaced apart from the spiral portion <NUM> of the spring auger <NUM> by a distance d. The distance d may be, for example, <NUM> or less. A protrusion amount of the second portion <NUM> may be the distance d or less.

As the extension portion <NUM> affects generation of the period of separation SP, the period of separation SP is likely to occur at a portion of the housing <NUM> close to the first end portion <NUM>. When the other end <NUM> of the spring auger <NUM> is a free end, the other end <NUM> may sag toward the bottom surface <NUM> due to gravity, and thus, the period of separation SP is less likely to occur at a portion of the housing <NUM> close to the second end portion <NUM>. Also when the other end <NUM> of the spring auger <NUM> is rotatably supported by the housing <NUM>, the period of separation SP may be less generated at a portion of the housing <NUM> close to the second end portion <NUM>. Considering these characteristics, the first portion <NUM> and the second portion <NUM> may be repeatedly arranged at least from the first end portion <NUM> of the housing <NUM> to a section corresponding to a half or more of a distance between the first end portion <NUM> and the second end portion <NUM>. The first portion <NUM> and the second portion <NUM> may also be repeatedly arranged in the entire section between the first end portion <NUM> and the second end portion <NUM> of the housing <NUM>.

As a method of reducing or eliminating an amount of residual developer in the period of separation SP, moving the period of separation SP may be considered. As described above, a plurality of periods of separation SP are formed in the length direction B of the housing <NUM> on a cycle corresponding to the pitch PT of the spiral portion <NUM> of the spring auger <NUM>. Accordingly, by modifying the pitch PT of the spiral portion <NUM> of the spring auger <NUM>, a position of the period of separation SP may be varied, and a developer remaining in the period of separation SP in a position before the position thereof is varied may be transported to the developer discharge outlet <NUM>.

<FIG> is a perspective view of a developer cartridge <NUM> according to an example. Referring to <FIG>, the developer cartridge <NUM> includes a housing <NUM>, a spring auger <NUM>, and a rotation member <NUM>.

A developer is accommodated in the housing <NUM>. The housing <NUM> includes a first end portion <NUM> and a second end portion <NUM> in a length direction B. A bottom surface <NUM> of the housing <NUM> is flat. A developer discharge outlet <NUM> through which a developer is discharged is provided at a position adjacent to one of the first end portion <NUM> and the second end portion <NUM>. In the present example, the developer discharge outlet <NUM> is located adjacent to the second end portion <NUM>. A shutter <NUM> selectively opening or closing the developer discharge outlet <NUM> may be provided in an outer portion of the developer discharge outlet <NUM>. A developer may be supplied to the developing devices <NUM> through the developer discharge outlet <NUM>. The supply pipeline <NUM> (<FIG>) may be connected to the developer discharge outlet <NUM>. The developer discharge outlet <NUM> may be connected to the developer supplying unit <NUM> (<FIG>). In addition, although not illustrated in the drawings, the developer discharge outlet <NUM> may also be directly connected to the developing devices <NUM>.

The spring auger <NUM> is located inside the housing <NUM> and rotated in a forward direction A1 to transport a developer to the developer discharge outlet <NUM>. The spring auger <NUM> has a spiral coil shape as illustrated in <FIG>.

The rotation member <NUM> is located at the first end portion <NUM> of the housing <NUM>, and is connected to the spring auger <NUM> to rotate the spring auger <NUM> in the forward direction A1. A one end <NUM> of the spring auger <NUM> is connected to the rotation member <NUM>. The rotation member <NUM> includes a first support portion <NUM> supporting the one end <NUM> of the spring auger <NUM> and a second support portion <NUM> located in the forward direction A1 of the first support portion <NUM> and having a position in an axial direction C different from a position of the first support portion <NUM>. The second support portion <NUM> may be closer to the first end portion <NUM> in the axial direction C than the first support portion <NUM>. The spring auger <NUM> is supported in a compressed state between the rotation member <NUM> and the second end portion <NUM> of the housing <NUM> such that the one end <NUM> of the spring auger <NUM> is deviated from the first support portion <NUM> and supported by the second support portion <NUM> when the rotation member <NUM> is rotated in a reverse direction A2 opposite to the forward direction A1.

The developer cartridge <NUM> may further include a one-directional bearing <NUM> that is located at the second end portion <NUM> of the housing <NUM> to support the other end <NUM> of the spring auger <NUM> and allows rotation of the spring auger <NUM> in the forward direction A1. The one-directional bearing <NUM> does not allow rotation of the spring auger <NUM> in the reverse direction A2. Thus, when the rotation member <NUM> is rotated in the reverse direction A2, the first end <NUM> of the spring auger <NUM> may be easily deviated from the first support portion <NUM> and supported by the second support portion <NUM>.

The rotation member <NUM> may be, for example, a gear or a coupler. When the developer cartridge <NUM> is mounted in the main body <NUM>, the rotation member <NUM> may be connected to a developer supply motor (not shown) provided in the main body <NUM>. The rotation member <NUM> may be connected to a developer supply motor (not shown) provided in the developer cartridge <NUM>.

<FIG> is a perspective view illustrating a connection structure between the rotation member <NUM> and the one end <NUM> of the spring auger <NUM>, according to an example, where the one end <NUM> of the spring auger <NUM> is supported by the first support portion <NUM>. <FIG> is a perspective view illustrating a connection structure between the rotation member <NUM> and the one end <NUM> of the spring auger <NUM>, according to an example, where the one end <NUM> of the spring auger <NUM> is supported by the second support portion <NUM>.

Referring to <FIG> and <FIG>, while the one end <NUM> of the spring auger <NUM> is supported by the first support portion <NUM> (marked by a solid line in <FIG>), a pitch of the spring auger <NUM> is PT. In this state, when the rotation member <NUM> is rotated in the forward direction A1, a wall <NUM> of the first support portion <NUM> in the reverse direction A2 pushes the one end <NUM> of the spring auger <NUM> in the forward direction A1. The spring auger <NUM> is rotated in the forward direction A1 and thereby transports a developer to the developer discharge outlet <NUM>. As the bottom surface <NUM> is flat, as described with reference to <FIG>, a period of separation SP and a period of contact CP are formed at pitches PT of the spiral portion <NUM>. Accordingly, a developer may remain in an area of the bottom surface <NUM> corresponding to the period of separation SP.

In the state as illustrated in <FIG>, the rotation member <NUM> is rotated in the reverse direction A2. As the spring auger <NUM> is supported in a compressed state between the rotation member <NUM> and the second end portion <NUM> of the housing <NUM>, the spring auger <NUM> is not rotated. When the rotation member <NUM> is rotated in the reverse direction A2, the one end <NUM> of the spring auger <NUM> is deviated from the first support portion <NUM> and supported by the second support portion <NUM> as illustrated in <FIG>. As the second support portion <NUM> is closer to the first end portion <NUM> in the axial direction C than the first support portion <NUM>, as marked by a broken line in <FIG>, the spring auger <NUM> is tensioned in the length direction B. In this state, when the rotation member <NUM> is rotated again in the forward direction A1, a wall <NUM> of the second support portion <NUM> in the reverse direction A2 pushes the one end <NUM> of the spring auger <NUM> in the forward direction A1. The spring auger <NUM> is rotated in the forward direction A1 and thereby transports a developer to the developer discharge outlet <NUM>.

Referring to <FIG>, while the one end <NUM> of the spring auger <NUM> is supported by the second support portion <NUM>, a pitch of the spring auger <NUM> is PT1, and PT < PT1. While the one end <NUM> of the spring auger <NUM> is supported by the second support portion <NUM>, a period of separation SP1 and a period of contact CP2 are respectively different from the period of separation SP and the period of contact CP while the one end <NUM> of the spring auger <NUM> is supported by the first support portion <NUM>. A portion of the period of separation SP overlaps the period of contact CP1. Thus, at least a portion of the developer remaining in the area corresponding to the period of separation SP of the bottom surface <NUM> may be transported to the developer discharge outlet <NUM>, and a use efficiency of the developer may be increased accordingly.

In the rotation member <NUM>, a plurality of first supporting portions <NUM> and a plurality of second supporting portion <NUM> may be alternately arranged in a circumferential direction. <FIG> illustrates a rotation member <NUM> according to an example, showing a rotational phase of the rotation member <NUM> respectively at <NUM> degrees, <NUM> degrees, <NUM> degrees, and <NUM> degrees. Referring to <FIG>, the first support portion <NUM> and the second support portion <NUM> are apart at <NUM> degrees, and two pairs of the first support portion <NUM> and the second support portion <NUM> are arranged in a circumferential direction. A wall <NUM> of the second support portion <NUM> in the forward direction A1 is inclined with respect to the axial direction C such that, when the rotation member <NUM> is rotated in the reverse direction A2, the one end <NUM> of the spring auger <NUM> is deviated from the second support portion <NUM> and supported by the first support portion <NUM> located in the forward direction A1. According to this configuration, by rotating the rotation member <NUM> in the reverse direction A2, the one end <NUM> of the spring auger <NUM> is sequentially supported by the first support portion <NUM>, the second support portion <NUM>, the first support portion <NUM>, and the second support portion <NUM> such that a section where a developer remains on the bottom surface <NUM> may be sequentially varied from a period of separation SP, a period of separation SP1, and the period of separation SP. Thus, an amount of a developer remaining in the period of separation SP and the period of separation SP1 may be reduced to further increase a use efficiency of the developer.

The first support portion <NUM> may have a concave shape having the wall <NUM> in the reverse direction A2 and the wall <NUM> in the forward direction A1 as illustrated by a solid line in <FIG>. In this case, when the rotation member <NUM> is rotated in the reverse direction A2, the one end <NUM> of the spring auger <NUM> is deviated from the first support portion <NUM> over the wall <NUM> to be supported by the second support portion <NUM>. A shape of the first support portion <NUM> may include the wall <NUM> in the reverse direction A2 as marked by a broken line illustrated in <FIG>, and the wall <NUM> in the forward direction A1 may be omitted.

<FIG> is a block diagram illustrating an image forming apparatus including the developer cartridge <NUM> illustrated in <FIG>, according to an example. Referring to <FIG>, the image forming apparatus includes a printing unit <NUM> printing an image on a print medium P by receiving a developer from the developer cartridge <NUM>, a developer remaining amount detector <NUM> detecting a remaining amount of a developer of the developer cartridge <NUM>, a driving motor <NUM> rotating the rotation member <NUM>, and a controller <NUM> controlling the driving motor <NUM> such that the rotation member <NUM> is rotated in the reverse direction A2 and then rotated again in the forward direction A1 when a detected remaining amount of developer is equal to or less than a reference remaining amount.

The printing unit <NUM> may print an image on the print medium P by using an electrophotographic method, and may have the structure illustrated in and described with reference to <FIG>.

The driving motor <NUM> may be a motor used to drive components of the printing unit <NUM>. In this case, when the developer cartridge <NUM> is mounted in the printing unit <NUM>, the rotation member <NUM> may be connected to the driving motor <NUM> and rotated. The driving motor <NUM> may be a motor provided in the developer cartridge <NUM> to rotate the rotation member <NUM>. In this case, when the developer cartridge <NUM> is mounted in the printing unit <NUM>, the driving motor <NUM> may be connected to the controller <NUM>.

The developer remaining amount detector <NUM> may detect a developer remaining amount of the developer cartridge <NUM> by using various methods. For example, a method of detecting a developer remaining amount from an amount of consumed developer based on the number of printing pixels, a method of detecting a developer remaining amount from an amount of consumed developer based on a driving time of the driving motor <NUM> for supplying a developer to the printing unit <NUM>, or the like may be used. The above-described methods do not include actual measurement of a consumed amount of developer, but include predicting an amount of consumed developer based on the number of printing pixels and a driving time of the driving motor <NUM> and detecting a developer remaining amount based on the predicted amount of consumed developer.

The developer remaining amount detector <NUM> may directly detect a remaining amount of developer inside the developer cartridge <NUM>. In this case, the developer remaining amount detector <NUM> may include a developer remaining amount sensor (not shown) arranged adjacent to the developer discharge outlet <NUM> of the housing <NUM> to generate an electrical detection signal based on a developer remaining amount. The developer remaining amount sensor may be located downstream of the developer discharge outlet <NUM> with respect to a direction in which a developer is transported by the spring auger <NUM>. The structure of the developer remaining amount sensor is not particularly limited. The developer remaining amount sensor may include a circuit used to detect a variation in inductance based on a remaining amount of developer. For example, the developer remaining amount sensor may include an L-C circuit. When a conductor approaches a coil of the L-C circuit, inductance of the L-C circuit is varied. As a carrier accommodated in a developer contains an iron component, inductance of the L-C circuit is varied based on an amount of developer near the developer remaining amount sensor. Thus, a developer remaining amount may be detected based on the variation in the inductance.

The developer remaining amount detector <NUM> may also detect a developer remaining amount of the developer cartridge <NUM> by performing both a method of detecting a developer remaining amount based on a predicted amount of consumed developer and a method of detecting a developer remaining amount by using the developer remaining amount sensor.

The developer remaining amount detector <NUM> sends a detection signal corresponding to a developer remaining amount to the controller <NUM>. The controller <NUM> compares the detected developer remaining amount with a preset reference remaining amount. The reference remaining amount may be, for example, about <NUM>% of an initial amount of developer accommodated in the developer cartridge <NUM>. When the detected developer remaining amount is equal to or less than the preset reference remaining amount, the controller <NUM> controls the driving motor <NUM> such that the rotation member <NUM> is rotated in the reverse direction A2. Then the one end <NUM> of the spring auger <NUM> is deviated from the first support portion <NUM> and supported by the second support portion <NUM>, and a pitch of the spring auger <NUM> is varied. Next, the controller <NUM> controls the driving motor <NUM> such that the rotation member <NUM> is rotated in the forward direction A1 again. Then, as described above, at least a portion of developer remaining in an area corresponding to the period of separation SP of the bottom surface <NUM> of the housing <NUM> may be transported to the developer discharge outlet <NUM>, thereby increasing a use efficiency of the developer. In addition, when the rotation member <NUM> in the form as illustrated in <FIG> is included, and a detected developer remaining amount is equal to or less than a preset reference remaining amount, rotation of the rotation member <NUM> in the forward direction A1 and rotation of the rotation member <NUM> in the reverse direction A2 may be repeated to transport a developer remaining in an area corresponding to the period of separation SP and the period of separation SP1 of the bottom surface <NUM> of the housing <NUM> to the developer discharge outlet <NUM>, thereby further increasing a use efficiency of the developer.

Claim 1:
A developer cartridge (<NUM>), comprising:
a housing (<NUM>) accommodating a developer, the housing (<NUM>) including a first end portion (<NUM>) and a second end portion (<NUM>), the first end portion (<NUM>) and the second end portion (<NUM>) being respectively located at opposite ends of the housing (<NUM>) in a lengthwise direction (B), the housing (<NUM>) is to discharge the developer through a developer discharge outlet (<NUM>) coupled to the housing and adjacent to one of the first end portion (<NUM>) and the second end portion (<NUM>);
a spring auger (<NUM>) located inside the housing (<NUM>) and to rotate to transport the developer to the developer discharge outlet (<NUM>); and
a rotation member (<NUM>) located at the first end portion (<NUM>) of the housing (<NUM>) and connected to a first end of the spring auger (<NUM>) to rotate the spring auger (<NUM>),
wherein a bottom surface (<NUM>) of the housing (<NUM>) includes a plurality of first portions (<NUM>) and a plurality of second portions (<NUM>), the first portions (<NUM>) being flat and the second portions (<NUM>) being internally convex from the first portions (<NUM>), a first portion (<NUM>) of the plurality of first portions (<NUM>) being adjacent to a respective second portion (<NUM>) of the plurality of second portions (<NUM>), the first portions (<NUM>) and the second portions (<NUM>) are repeatedly arranged on the bottom surface (<NUM>) of the housing (<NUM>) in the lengthwise direction (B),
wherein the developer cartridge (<NUM>) is configured such that the state of contact between the spiral portion (<NUM>) of the spring auger (<NUM>) and the bottom surface (<NUM>) of the housing (<NUM>) is changed according to a rotational phase of the spring auger (<NUM>).