Patent ID: 12204275

DETAILED DESCRIPTION

A developing cartridge according to one embodiment will be described with reference toFIGS.1through10(b).

FIG.1illustrates a laser printer1as an example of the image forming apparatus. The laser printer1primarily includes a housing2, a sheet-feeding unit3, an image-forming unit4, and a control unit CU.

The housing2has a front cover2A, and a discharge tray2B positioned at a top of the housing2. The sheet-feeding unit3and image-forming unit4are disposed in the housing2. By opening the front cover2A, a developing cartridge10described later can be detached from and attached to the housing2.

The sheet-feeding unit3accommodates sheets S. The sheet-feeding unit3is configured to feed one sheet at a time to the image-forming unit4.

The image-forming unit4includes a process cartridge4A, an exposure unit (not illustrated), a transfer roller4B, and a fixing unit4C.

The process cartridge4A includes a drum cartridge5, and the developing cartridge10. The developing cartridge10is detachably attached to the drum cartridge5. In a state where the developing cartridge10is attached to the drum cartridge5, the developing cartridge10and drum cartridge5can be detachably attached to the laser printer1as the process cartridge4A. The drum cartridge5includes a frame5A, and a photosensitive drum5B rotatably supported to the frame5A.

As illustrated inFIG.2, the developing cartridge10includes a casing11, a developing roller12, a supply roller13, and an agitator14.

The casing11includes a container11A as an example of a second frame, and a lid11B as an example of a first frame. The container11A of the casing11is configured to accommodate toner T. The toner T is an example of the developing agent.

The developing roller12includes a developing-roller shaft12A extending in a first direction, and a roller part12B. The roller part12B covers an outer circumferential surface of the developing-roller shaft12A. The roller part12B is formed of an electrically conductive rubber or the like. The developing roller12is rotatable about an axis of the developing-roller shaft12A. Put another way, the developing roller12is supported in the casing11so as to be rotatable about the axis of the developing-roller shaft12A. Hence, the roller part12B can rotate together with the developing-roller shaft12A. The control unit CU is configured to apply developing bias to the developing roller12.

The container11A and the lid11B of the casing11face each other in a second direction. The second direction crosses the first direction, and preferably is orthogonal to the first direction. The developing roller12is positioned at one side of the casing11in a third direction (hereinafter called a “first side”). The third direction crosses both the first and second directions, and is preferably orthogonal to both the first and second directions.

The supply roller13includes a supply-roller shaft13A extending in the first direction, and a roller part13B. The roller part13B covers an outer circumferential surface of the supply-roller shaft13A. The roller part13B is formed of a sponge material or the like. The supply roller13is rotatable about an axis of the supply-roller shaft13A. The roller part13B can rotate together with the supply-roller shaft13A.

The agitator14includes an agitator shaft14A, and a flexible sheet14B. The agitator shaft14A is rotatable about a second axis14X extending in the first direction. The agitator shaft14A is supported to the casing11so as to be rotatable about the second axis14X. The agitator14can rotate together with a coupling22described later. A base end of the flexible sheet14B is fixed to the agitator shaft14A, while a distal end of the flexible sheet14B can contact an inner surface of the casing11. The agitator14can agitate toner T in the casing11as the flexible sheet14B rotates.

As illustrated inFIG.1, the transfer roller4B faces the photosensitive drum5B. The transfer roller4B and photosensitive drum5B nip and convey the sheet S when the sheet S is interposed therebetween.

A charger (not illustrated) is configured to charge a surface of the photosensitive drum5B, after which the exposure unit (not illustrated) exposes the charged surface to light to form an electrostatic latent image thereon. The developing cartridge10supplies toner T to the latent image to form a toner image on the photosensitive drum5B. As a sheet S fed from the sheet-feeding unit3passes between the photosensitive drum5B and transfer roller4B, the toner image is transferred from the photosensitive drum5B onto the sheet S.

After the toner image is transferred onto the sheet S, the sheet S passes through the fixing unit4C, and the fixing unit4C thermally fixes the toner image to the sheet S. The sheet S is subsequently discharged from the housing2into the discharge tray2B.

The control unit CU is configured to control the overall operations of the laser printer1.

The laser printer1is further includes a device-side developing electrode8as an example of a first electrical component, a device-side supply electrode9as an example of a second electrical component, and a sensor7. The device-side developing electrode8is configured to apply a developing bias to a developing electrode35described later in response to a command from the control unit CU. In a case where the developing cartridge10is attached to the laser printer1, the device-side developing electrode8is positioned to face the developing electrode35. Specifically, the device-side developing electrode8is positioned to face a second electrical contact35B (described later) of the developing electrode35in a case where the developing cartridge10is attached to the laser printer1. More specifically, the device-side developing electrode8is positioned to face a developing contact surface35D (described later) of the second electrical contact35B in a case where the developing cartridge10is attached to the laser printer1.

The device-side supply electrode9is configured to apply a supply bias to a supply electrode36described later in response to a command from the control unit CU. In a case where the developing cartridge10is attached to the laser printer1, the device-side supply electrode9is positioned to face the supply electrode36. Specifically, the device-side supply electrode9is positioned to face a second electrical contact36B (described later) of the supply electrode36in a case where the developing cartridge10is attached to the laser printer1. More specifically, the device-side supply electrode9is positioned to face a supply contact surface36D (described later) of the second electrical contact36B in case where the developing cartridge10is attached to the laser printer1.

The sensor7is configured to detect whether the developing cartridge10is a new product (i.e., whether the developing cartridge10is unused) and/or identifies specifications of the developing cartridge10. The sensor7includes a lever7A that is pivotably supported to the housing2, and an optical sensor7B. The lever7A is disposed in a position for contacting protrusions that rotate together with a detection gear33described later. The optical sensor7B is connected to the control unit CU and is configured to output detection signals to the control unit CU. The control unit CU can determine specifications and the like of the developing cartridge10on a basis of the signals received from the optical sensor7B. Specifically, the optical sensor7B detects displacement of the lever7A and transmits the detection signals to the control unit CU on a basis of this displacement. More specifically, the optical sensor7B employs a sensor unit that includes a light-emitting element and a light-receiving element, for example. The sensor7will be described later in greater detail.

Next, the structure of the developing cartridge10will be described in greater detail.FIGS.3and4illustrate the structure of the developing cartridge10at one end of the casing11in the first direction (hereinafter called a “first end”). At the first end of the casing11, the developing cartridge10includes a first gear cover21, the coupling22, a developing gear23, a supply gear24, a first agitator gear25, an idle gear26, a first bearing27, and a cap28.

The first gear cover21supports the idle gear26via a shaft (not illustrated). The first gear cover21covers at least one gear positioned at the first end of the casing11. The first gear cover21is fixed to an outer surface11C of the casing11by screws29.

Note that the term “gear” in the present specification is not limited to a gear member having gear teeth that transmits rotational force through the gear teeth, but may include a member that transmits rotational force through friction.

The coupling22is rotatable about a first axis22A extending in the first direction. The coupling22is positioned at the first end of the casing11relative to the first direction. That is the coupling22is positioned at the outer surface11C. The coupling22can rotate in response to a drive force. That is, the coupling22can receive a drive force from the laser printer1. The coupling22can rotate by engaging with a drive member (not illustrated) provided in the laser printer1. The coupling22includes a recessed part22B (FIG.4) that is recessed in the first direction. The recessed part22B can receive and engage with the drive member. Specifically, the recessed part22B can engage with the drive member of the laser printer1to receive a drive force from the drive member.

The developing gear23is mounted to the developing-roller shaft12A and can rotate together with the coupling22. The developing gear23is positioned at the first end of the casing11in the first direction. That is, the developing gear23is positioned at the outer surface11C.

The supply gear24is mounted to the supply-roller shaft13A and can rotate together with the coupling22. The supply gear24is positioned at the first end of the casing11in the first direction. That is, the supply gear24is positioned at the outer surface11C.

The first agitator gear25is positioned at the first end of the casing11in the first direction. That is, the first agitator gear25is positioned at the outer surface11C. The first agitator gear25is mounted to the agitator shaft14A of the agitator14. The first agitator gear25can rotate together with the agitator14in response to rotation of the coupling22.

The idle gear26is positioned to face the first end of the casing11in the first direction. That is, the idle gear26is positioned to face the outer surface11C. The idle gear26includes a large-diameter part26A that engages with gear teeth of the coupling22, and a small-diameter part26B that engages with gear teeth of the first agitator gear25. As described above, the idle gear26is rotatably supported on the shaft (not illustrated) in the first gear cover21. The idle gear26transmits the rotation of the coupling22to the first agitator gear25while reducing the speed of rotation. The large-diameter part26A is separated farther from the casing11than the small-diameter part26B is from the casing11in the first direction.

The first bearing27supports the coupling22, the developing gear23, and the supply gear24.

The first bearing27is fixed to the first end of the casing11in the first direction.

The cap28covers a first end of the developing-roller shaft12A in the first direction. Note that the first gear cover21and cap28may be formed of different types of resin.

FIGS.5and6illustrate the structure of the developing cartridge10at the other end of the casing11in the first direction (hereinafter called a “second end”). At the second end, the developing cartridge10includes a second gear cover31as an example of a gear cover, a second agitator gear32, the above-mentioned detection gear33, a second bearing34, the above-mentioned developing electrode35, and the above-mentioned supply electrode36.

The second gear cover31covers at least a portion of the detection gear33. The second gear cover31has an opening31A that exposes a portion of the detection gear33to an outside. The second gear cover31also includes a shaft31B extending in the first direction. The second gear cover31accommodates therein a torsion spring37as an example of a spring. The torsion spring37will be described later in greater detail.

The second agitator gear32is positioned at the second end of the casing11in the first direction. That is, the second agitator gear32is positioned at an outer surface11E of the casing11. The outer surface11E is positioned at the second end of the container11A in the first direction. The second agitator32is mounted to the agitator shaft14A of the agitator14and can rotate together with the agitator14. The second agitator gear32includes gear teeth around its entire circumference. The second agitator gear32is positioned at the container11A and is rotatably supported to the container11A.

The detection gear33is positioned at the second end of the casing11in the first direction. That is, the detection gear33is positioned at the outer surface11E. The detection gear33engages with the second agitator gear32and can rotate together with the second agitator gear32. The detection gear33has a first hole33C. The shaft31B of the second gear cover31is inserted into the first hole33C so that the detection gear33can rotate about the shaft31B. The lid11B of the casing11includes a side wall11D at the second end of the casing11in the first direction. The side wall11D has a support hole133. The distal end of the shaft31B is inserted into and supported by the support hole133. The detection gear33is capable of rotating irreversibly from a first position to a second position. The detection gear33rotates in the clockwise direction inFIG.6.

The detection gear33includes a first protrusion41, a second protrusion42, and a third protrusion43. The first protrusion41, second protrusion42, and third protrusion43can move along with the rotation of the detection gear33, and preferably can rotate together with the detection gear33. In the present embodiment, the detection gear33includes the first protrusion41, second protrusion42, and third protrusion43. In other words, the detection gear33is integrally formed with the first protrusion41, second protrusion42, and third protrusion43. Note that the detection gear33need not include three protrusions, but may include one or two of the first protrusion41, second protrusion42and third protrusion43.

The first protrusion41, second protrusion42, and third protrusion43are positioned at intervals along the rotating direction of the detection gear33. More specifically, the first protrusion41, second protrusion42, and third protrusion43are arranged in the clockwise direction inFIG.6in the order given and are spaced apart from each other in the rotating direction. Each of the first protrusion41, second protrusion42, and third protrusion43extends outward in radial directions of the detection gear33. The distal end of each of the first protrusion41, second protrusion42, and third protrusion43is positioned at the outer circumference of the detection gear33. That is, the distal end of the first protrusion41, second protrusion42, and third protrusion43are positioned farthest from the rotational center of the detection gear33. The distal ends of the first protrusion41and second protrusion42have a prescribed length in the rotating direction, while the distal end of the third protrusion43is longer in the rotating direction than the first protrusion41and second protrusion42.

In a case where the developing cartridge10is unused (i.e., a new product), the detection gear33is in the position illustrated inFIGS.8(a) and8(b)relative to the second gear cover31. Hereinafter, this position of the detection gear33will be referred to as a first position. Note that the detection gear33is in the first position in a case where the developing cartridge10is in an unused state. In a case where the detection gear33is in the first position, the distal end of the first protrusion41is exposed to an outside through the opening31A. Further, in a case where the detection gear33is in the first position, the distal end of the first protrusion41contacts the lever7A and maintains the lever7A between the light-emitting element and light-receiving element of the optical sensor7B, as illustrated inFIG.8(a). Consequently, the lever7A blocks light emitted from the light-emitting element. The detection gear33includes a gear section33A. The gear section33A includes a plurality of gear teeth and the gear section33A is provided at a portion of the circumference of the detection gear33. The detection gear33also includes a toothless section33B. The toothless section33B is provided at the remaining circumference of the detection gear33and the toothless section33B is a region with no gear teeth. The detection gear33also includes a fourth protrusion33D, and a fifth protrusion33E. Each of the fourth protrusion33D and fifth protrusion33E protrudes radially outward from the peripheral edge of the first hole33C. The torsion spring37includes a coil part37A, a first arm37B, and a second arm37C. The first arm37B and second arm37C both extend from the coil part37A. The second arm37C contacts and catches a portion of the second gear cover31. In a case where the detection gear33is in the first position, the first arm37B contacts the fourth protrusion33D and urges the detection gear33such that the leading gear tooth in the rotating direction of the gear section33A (counterclockwise inFIG.8(b)) is pressed against the gear teeth of the second agitator gear32. Hence, the second agitator gear32meshes with at least one of the gear teeth of the gear section33A in a case where the detection gear33is positioned at the first position. The torsion spring37holds the detection gear33in a prescribed posture relative to the shaft31B.

The detection gear33is configured to rotate from the first position illustrated inFIGS.8(a) and8(b), through the positions illustrated inFIGS.9(a),9(b) and9(c)to a second position illustrated inFIG.10(a), where the detection gear33comes to a halt. Hence, the detection gear33can rotate from the first position to the second position. In a case where the detection gear33is in the second position illustrated inFIG.10(b), the first arm37B of the torsion spring37contacts both the fourth protrusion33D and fifth protrusion33E and maintains the detection gear33in the state illustrated inFIG.10(b)relative to the shaft31B. In a case where the detection gear33is in the second position as illustrated inFIG.10(b), the second protrusion42is in substantially the same position as the first protrusion41when the detection gear33is in the first position as illustrated inFIG.8(a). In a case where the detection gear33is in the second position, the distal end of the second protrusion42contacts the lever7A and maintains the lever7A at a position between the light-emitting element and light-receiving element, as illustrated inFIG.10(a). Consequently, the lever7A blocks light emitted from the light-emitting element.

Further, the detection gear33rotates from the first position to the second position through third positions illustrated inFIGS.9(a) and9(c). In the third positions, the detection gear33does not contact any part of the laser printer1(and particularly the lever7A). As illustrated inFIGS.9(a) and9(c), the lever7A is not in contact with the distal end of any of the first protrusion41, second protrusion42, and third protrusion43in a case where the detection gear33is in the third positions. Hence, the lever7A is not positioned between the light-emitting element and light-receiving element. Consequently, the lever7A does not block light emitted from the light-emitting element, and the light-receiving element can receive the emitted light.

As described above, the laser printer1can identify specifications of the developing cartridge10based on detection signals obtained from the optical sensor7B in a case where the light-receiving element receives light and in a case where the light-receiving element does not receive light.

Further, in the present embodiment, the distal end of the first protrusion41contacts the lever7A in a case where the detection gear33is in the initial position, and the distal end of the second protrusion42contacts the lever7A when the detection gear33is in the second position. Accordingly, the laser printer1can determine whether the developing cartridge10is attached to the laser printer1through use of the first protrusion41and second protrusion42.

Turning back toFIG.6, the second bearing34includes a first support part34A, and a second support part34B. The first support part34A rotatably supports the developing-roller shaft12A. The second support part34B rotatably supports the supply-roller shaft13A. The second bearing34is fixed to the outer surface11E at the second end of the container11A of the casing11while supporting the developing-roller shaft12A and supply-roller shaft13A.

As illustrated inFIG.6, the developing electrode35is positioned at the second end of the casing11in the first direction. In other words, the developing electrode35is positioned at the outer surface11E. The developing electrode35is configured to supply power to the developing-roller shaft12A. The developing electrode35is formed of an electrically conductive resin, for example.

The developing electrode35includes a first electrical contact35A, the above-mentioned second electrical contact35B, and a coupling part35C. The first electrical contact35A contacts the developing-roller shaft12A. The second electrical contact35B can contact the device-side developing electrode8(FIG.1) in a case where the developing cartridge10is attached to the laser printer1. The coupling part35C connects the first electrical contact35A to the second electrical contact35B and is electrically connected to both the first electrical contact35A and second electrical contact35B.

The first electrical contact35A has a second hole35E. The developing-roller shaft12A is inserted into the second hole35E. The second hole35E is preferably a circular-shaped hole. In a case where the developing-roller shaft12A is inserted into the second hole35E, the first electrical contact35A contacts a portion of the developing-roller shaft12A. Specifically, the first electrical contact35A contacts the circumferential surface of the developing-roller shaft12A while the developing-roller shaft12A is inserted in the second hole35E. The second electrical contact35B of the developing electrode35includes the above-mentioned developing contact surface35D. The developing contact surface35D extends in the second and third directions.

The supply electrode36is positioned at the second end of the casing11in the first direction. That is, the supply electrode36is positioned at the outer surface11E. The supply electrode36supplies power to the supply-roller shaft13A. The supply electrode36is formed of an electrically conductive resin, for example. The supply electrode36includes a first electrical contact36A, the above-mentioned second electrical contact36B, and a coupling part36C. The first electrical contact36A contacts the supply-roller shaft13A. The second electrical contact36B can contact the device-side supply electrode9(FIG.1) in a case where the developing cartridge10is attached to the laser printer1. The coupling part36C connects the first electrical contact36A and second electrical contact36B and is electrically connected to both the first electrical contact36A and second electrical contact36B.

The first electrical contact36A has a third hole36E. The supply-roller shaft13A is inserted into the third hole36E. The third hole36E is preferably a circular-shaped hole. In a case where the supply-roller shaft13A is inserted into the third hole36E, the first electrical contact36A contacts a portion of the supply-roller shaft13A. Specifically, the first electrical contact36A contacts the circumferential surface of the supply-roller shaft13A while the supply-roller shaft13A is inserted into the third hole36E. The second electrical contact36B of the supply electrode36includes the above-mentioned supply contact surface36D. The supply contact surface36D extends in the second and third directions.

Together with the second bearing34, the developing electrode35and supply electrode36are fixed to the outer surface11E positioned at the second end of the casing11with screws38.

As illustrated inFIGS.5and7, the second electrical contact35B of the developing electrode35is positioned closer to the developing roller shaft12A than the second agitator gear32is to the developing-roller shaft12A in the third direction. Further, the second electrical contact35B of the developing electrode35is positioned farther from the developing roller shaft12A than the first electrical contact35A is from the developing-roller shaft12A in both the second and third directions.

Further, the second electrical contact36B of the supply electrode36is positioned closer to the developing roller shaft12A than the second agitator gear32is to the developing-roller shaft12A in the third direction. In addition, the second electrical contact36B of the supply electrode36is positioned farther from the developing roller shaft12A than the second electrical contact35B of the developing electrode35is from the developing-roller shaft12A in both the second and third directions.

The detection gear33is positioned farther from the developing-roller shaft12A than the second electrical contact36B of the supply electrode36is from the developing-roller shaft12A in the third direction. Further, when the detection gear33is in the first position as illustrated inFIG.9(a), the distal end of the first protrusion41is positioned farther from the developing-roller shaft12A than the second electrical contact36B of the supply electrode36is from the developing-roller shaft12A in both the second and third directions. In a case where the detection gear33is in the second position as illustrated inFIG.10(a), the distal end of the second protrusion42is at approximately the same position as the first protrusion41in a case where the detection gear33is in the first position. Therefore, in a case where the detection gear33is in the second position, the distal end of the second protrusion42is positioned farther from the developing-roller shaft12A than the second electrical contact36B of the supply electrode36is from the developing-roller shaft12A in both the second and third directions.

Thus, the second electrical contact35B of the developing electrode35, the second electrical contact36B of the supply electrode36, and the distal end of the first protrusion41are at different positions in the second and third directions in a case where the detection gear33is in the first position. Further, the second electrical contact35B of the developing electrode35, the second electrical contact36B of the supply electrode36, and the distal end of the second protrusion42are at different positions in the second and third directions in a case where the detection gear33is in the second position.

Next, operation of the developing cartridge10thus constructed will be described. As illustrated inFIG.1, the developing cartridge10is attached to the laser printer1by inserting the developing cartridge10such that the developing roller12is a leading end in the third direction, i.e., in the inserting direction.

Through this operation, the developing contact surface35D of the developing cartridge10contacts the device-side developing electrode8, and the supply contact surface36D contacts the device-side supply electrode9. At this time, each of the developing contact surface35D and supply contact surface36D extends in both the second and third directions. Therefore, contact between the second electrical contact35B and the device-side developing electrode8and between the second electrical contact36B and the device-side supply electrode9is smooth. Since the positions of the second electrical contact35B and the second electrical contact36B are offset in both the second and third directions, the device-side supply electrode9is prevented from scraping against the second electrical contact35B and the device-side developing electrode8is prevented from scraping against the second electrical contact36B.

In a case where the developing cartridge10is unused as illustrated inFIG.1, i.e., when the detection gear33is in the first position, the distal end of the first protrusion41is exposed through the opening31A. Accordingly, the distal end of the first protrusion41contacts and pivots the lever7A. In a case where the optical sensor7B detects this displacement of the lever7A, the control unit CU can determine that the developing cartridge10is attached to the laser printer1, as described earlier. Here, the second protrusion42is not exposed through the opening31A in a case where the detection gear33is in the first position and, hence, does not contact the lever7A. Since the distal end of the first protrusion41is offset from the second electrical contact35B of the developing electrode35in both second and third directions, this construction prevents the device-side developing electrode8from contacting the first protrusion41and prevents the lever7A from contacting the second electrical contact35B.

In response to a command from the control unit CU, the laser printer1begins driving the coupling22through the drive member (not illustrated). As illustrated inFIG.4, rotation of the coupling22is transmitted via the idle gear26to the first agitator gear25and rotates the first agitator gear25. In a case where the first agitator gear25rotates, the second agitator gear32provided at the second end of the developing cartridge10is rotated via the agitator14.

In a case where an unused developing cartridge10is attached to the housing2, the detection gear33is positioned at the first position illustrated inFIGS.8(a) and8(b). In a case where the second agitator gear32rotates in this state, the second agitator gear32transmits a drive force to the gear teeth on the detection gear33meshed with the second agitator gear32, causing the detection gear33to rotate.

In a case where the detection gear33rotates, the lever7A becomes positioned between the first protrusion41and third protrusion43as illustrated inFIG.9(a). In other words, none of the first protrusion41, second protrusion42, and third protrusion43contacts the lever7A. Consequently, the lever7A is no longer positioned between the light-emitting element and light-receiving element of the optical sensor7B, and the signal that the control unit CU receives from the optical sensor7B changes.FIG.9(a)shows the detection gear33in one of the third positions.

As the detection gear33continues to rotate, the third protrusion43becomes exposed through the opening31A and contacts the lever7A as illustrated inFIG.9(b). This contact moves the lever7A back to a position between the light-emitting element and light-receiving element of the optical sensor7B. Accordingly, the signal that the control unit CU receives from the optical sensor7B changes again.

As the detection gear33continues to rotate, the lever7A becomes positioned between the third protrusion43and second protrusion42as illustrated inFIG.9(c). At this time, none of the first protrusion41, second protrusion42, and third protrusion43contacts the lever7A. Accordingly, the lever7A is no longer positioned between the light-emitting element and light-receiving element of the optical sensor7B, and the signal that the control unit CU receives from the optical sensor7B changes again.FIG.9(c)shows the detection gear33in the remaining one of the third positions.

As the detection gear33continues to rotate, the second protrusion42becomes exposed through the opening31A and contacts the lever7A as illustrated inFIG.10(a). This contact moves the lever7A to a position between the light-emitting element and light-receiving element of the optical sensor7B, once again changing the signal that the control unit CU receives from the optical sensor7B.FIGS.10(a) and10(b)show the detection gear33in the second position. As illustrated inFIG.10(b), in a case where the detection gear33is in the second position, the second agitator gear32faces the toothless section33B of the detection gear33and, hence, is not meshed with any of the plurality of gear teeth of the gear section33A. Since the torsion spring37maintains the posture of the detection gear33at this time, the detection gear33does not rotate thereafter, even when the second agitator gear32rotates.

Through the operation process described above, the output from the optical sensor7B changes four times after the detection gear33begins to rotate. The pattern of these changes in output (e.g., the lengths of the OFF signals or ON signals, the number of changes, or differences in the timing of the changes) can be varied by modifying the number of protrusions that rotate together with the detection gear33and the lengths of the protrusions in the rotating direction. By establishing correlations between signal patterns and specifications of developing cartridges10in advance, the control unit CU can identify specifications of the developing cartridge10.

In a case where a used developing cartridge10is attached to the housing2of the laser printer1, the detection gear33is already positioned in the second position. In this case, the distal end of the second protrusion42is at the same approximate position as the first protrusion41of an unused developing cartridge10, as described above. Hence, in a case where a used developing cartridge10is attached to the housing2, the distal end of the second protrusion42contacts the lever7A, enabling the control unit CU to detect that a developing cartridge10is attached to the housing2. Note that the first protrusion41may be partially exposed through the opening31A in a case where the detection gear33is in the second position. However, the first protrusion41does not contact the lever7A since the first protrusion41is separated away from the second protrusion42.

With the developing cartridge10according to the embodiment described above, the second electrical contact35B of the developing electrode35, the second electrical contact36B of the supply electrode36, and the distal end of the first protrusion41are at different positions in the second and third directions in a case where the developing cartridge10is in an unused state. This arrangement prevents the distal end of the first protrusion41from scraping against the device-side developing electrode8, prevents the second electrical contact35B from scraping against the lever7A, and prevents the second electrical contact36B from scraping against the lever7A, for example. Further, the second electrical contact35B, second electrical contact36B, and distal end of the second protrusion42are also arranged at different positions in the second and third directions after the developing cartridge10is used. Therefore, this arrangement prevents the distal end of the second protrusion42from scraping against the device-side developing electrode8, prevents the second electrical contact35B from scraping against the lever7A, and prevents the second electrical contact36B from scraping against the lever7A, for example.

Various modifications are conceivable.

In the embodiment described above, the first protrusion41, the second protrusion42, and the third protrusion43can rotate together with the detection gear33, but the embodiment is not limited to this arrangement. For example, each of the protrusions may not be rotatable together with the detection gear, but may be provided separately from the detection gear, and the detection gear may be provided with a cam. Specifically, the detection gear moves together with the rotation of a coupling. While rotating, the detection gear shifts between a state in which the cam contacts a protrusion and a state in which the cam does not contact a protrusion. In this way, the protrusions are moved through contact with the cam. However, the protrusions may also be moved linearly as long as the protrusions can move the lever7A.

In the embodiment described above, the developing electrode35and supply electrode36are formed of an electrically conductive resin, but the composition of these components is not particularly limited. For example, the developing electrode35or the supply electrode36may be configured of a metal plate rather than an electrically conductive resin. In this case, one end portion of the metal plate serves as the first electrical contact35A of the developing electrode35or the first electrical contact36A of the supply electrode36, while the other end portion of the metal plate serves as the second electrical contact35B of the developing electrode35or the second electrical contact36B of the supply electrode36. Alternatively, the developing electrode35or supply electrode36may be configured of a metal plate combined with a coil spring. Further, the first electrical contact35A of the developing electrode35may be electrically connected to the developing-roller shaft12A through a metallic member. More specifically, the first electrical contact35A and developing-roller shaft12A are electrically connected via a spring, preferably coil spring. Further, the first electrical contact36A of the supply electrode36may be electrically connected to the supply-roller shaft13A via a metallic member. More specifically, the first electrical contact36A and supply-roller shaft13A are electrically connected via a spring, preferably coil spring.

In the embodiment described above, the developing cartridge10is configured as a separate component from the drum cartridge5, but the two components may be integrally configured.

In the embodiment described above, a monochrome laser printer is used as an example of the image forming apparatus, but the image forming apparatus may be a color image forming apparatus. Further, the exposure unit in the image forming apparatus may employ LED light rather than laser light. Further, the image forming apparatus may be a photocopier or multifunction device, for example.

While the description has been made in detail with reference to the embodiment(s) thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the disclosure.