Title of Invention

LIQUID CARTRIDGE

Technical Field

[0001] The invention relates to a liquid cartridge that is detachably mounted in a liquid-ejecting device, such as an inkjet printer.

Background Art

[0002] In a liquid cartridge having a liquid chamber for storing liquid and a channel in communication with the liquid chamber, there is a known technology for disposing a movable magnetic body in the channel and for detecting movement of the magnetic body with magnetic field sensing means. For example, a known inkjet printer employs a liquid cartridge including a magnetized magnetic body (a rotor 8) disposed in a channel (ink supply path 6) that communicates with the liquid chamber, and magnetic field sensing means (a magnetic sensor) for detecting rotational motion of the magnetic body. The inkjet printer can determine the quantity of remaining ink in the cartridge based on the detected rotational motion.

Disclosure of Invention

Technical Problem

[0003] However, in the liquid cartridge described above, only the magnetic body is positioned in the channel, requiring the magnetic body to be highly magnetized in order to ensure accuracy in detecting the magnetic body. When the magnetic body is highly magnetized, foreign matter such as iron filings may be attracted to the magnetic body during manufacturing or reconditioning of the cartridge. Thus, by disposing the magnetic body in the ink channel while foreign matter is deposited thereon, the channel becomes contaminated. When this type of cartridge is mounted in a liquid-ejecting device such as an inkjet printer, the ejecting components of the device may become clogged with foreign matter, resulting in ejection problems.

[0004] Therefore, it is an object of the invention to provide a liquid cartridge capable of minimizing the introduction of foreign matter into a channel formed in the cartridge while ensuring accuracy in detecting a magnetic body disposed in the channel.

Solution to Problem

[0005] The invention provides a liquid cartridge including a storing unit, a fluid channel, a magnetic body, a magnetic field generating unit, and a detecting unit. The storing unit stores liquid. The fluid channel is in fluid communication with the storing unit. The magnetic body is configured to move in the fluid channel. The magnetic field generating unit is disposed outside of the fluid channel and generates magnetic field. The detecting unit is configured to detect magnetic field generated by the magnetic field generating unit and the magnetic body.

[0006] This structure ensures that the magnetic body can be detected with good precision, even when the magnetic body in itself is weakly magnetized (where "weakly magnetized" includes a magnetization of "0"). Further, the liquid cartridge minimizes contamination of the fluid channel.

[0007] Preferably, the magnetic body is movable between a first position and a second position. At the first position the magnetic body is positioned between the magnetic field generating unit and the detecting unit. At the second position the magnetic body is positioned outside of a region between the magnetic field generating unit and the detecting unit.

[0008] With this configuration, the difference in magnitude between electric signals outputted by the detecting unit when the magnetic body is in the open and closed states can be heightened to further improve detection precision.

[0009] Preferably, the magnetic body is movable in a first direction. The magnetic field generating unit opposes the detecting unit in a second direction orthogonal to the first direction. This configuration can increase output from the detecting unit, increasing the difference in magnitude of the electric signal outputted by the detecting unit when the magnetic body is in the open and closed states.

[0010] Preferably, when the magnetic body is at the first position, no part of the fluid channel is disposed between at least part of the magnetic body and at least part of the magnetic field generating unit. This configuration increases the output of the detecting unit, thereby enhancing the difference in magnitude of the electric signal outputted from the detecting unit when the magnetic body is in the open and closed states.

[0011] Preferably, when the magnet body is at the first position, no part of the fluid channel is disposed between at least part of the magnetic body and at least part of the detecting unit. This configuration increases the output of the detecting unit, thereby enhancing the difference in magnitude of the electric signal outputted from the detecting unit when the magnetic body is in the open and closed states.

[0012] Preferably, the magnetic body is not magnetized when the magnetic body is not in the magnetic field. The magnetic body is magnetized when the magnetic body is in the magnetic field. Accordingly, this configuration reliably suppresses the introduction of foreign matter into the fluid channel.

[0013] Preferably, the liquid cartridge further includes an adjusting unit that adjusts a distance between the magnetic field generating unit and the detecting unit. Accordingly, the relative distance between the detecting unit and the magnetic field generating unit can be adjusted by the adjusting unit.

[0014] Preferably, the magnetic body has a columnar -shape extending in the first direction. With this shape, the magnetic body can be moved smoothly. Further, since rotation of the magnetic body about its axis in the fluid chanel will not change the distance between the detecting unit and the magnetic field generating unit and thus will not have any effect on the output of the detecting unit, there is no need to provide any parts in the fluid channel to prevent rotation of the magnetic body.

[0015] Preferably, the magnetic body is movable in a first direction. The magnetic field generating unit opposes the detecting unit in a second direction orthogonal to the first direction. The liquid cartridge includes a wall defining the fluid channel. The wall has an inner surface opposing the fluid channel and a plurality of protrusions protruding from the inner surface into the fluid channel. The inner surface has a first part and a second part opposing each other. One of the two protrusions protrudes inward from the first part of the inner surface in a third direction orthogonal to both of the first direction and the second direction, and another one of the two protrusions protrudes inward from the second part in an opposite direction of the third direction. The magnetic body is disposed between the one of the plurality of protrusions and the another one of the plurality of protrusions such that the magnetic body is positioned by the one of the plurality of protrusions and the another one of the plurality of protrusions in the third direction.

[0016] Accordingly, the two protrusions maintain the magnetic body in position relative to the third direction, thereby preventing the magnetic body from moving in third direction within the fluid channel.

[0017] Preferably, the fluid channel has one end and another end. The one end is connected to the storing unit. The magnetic body is a valve that is movable between the first position and the second position. When the valve is positioned at the second position, the storing unit is in fluid communication with the another end. When the valve is positioned at the first position, the valve blocks fluid communication between the storing unit and the another end.

[0018] With this structure, the liquid cartridge can determine whether the storing unit is in fluid communication with the another end by detecting the magnetic body.

[0019] Preferably, when the valve is positioned at the first position, the magnetic field detecting unit detects a strength of magnetic field larger than a strength of the magnetic field when the valve is positioned at the second position. With this structure, the liquid cartridge can correctly determine that the valve is at the first position. Further, while the magnetic body is in the closed state, output from the detecting unit can be checked.

When the valve is positioned at the second position, the magnetic field detecting unit detects a strength of magnetic field larger than a strength of magnetic field when the valve is positioned at the first position. With this structure, the liquid cartridge can correctly determine that the valve is at the second position. Further, the valve is unlikely to be permanently magnetized even when the liquid cartridge has been stored for a long period of time with the magnetic body in the closed state.

[0020] Preferably, the liquid cartridge further includes a wall and an urging unit. The wall has an inner surface and a valve seat. The inner surface defines the fluid channel. The urging unit is disposed in the fluid channel and is configured to urge the magnetic body in a direction toward the valve seat. The magnetic body is moved to the first position by an urging force of the urging unit and contacts the valve seat such that the valve unit blocks the fluid communication between the another end and the storing unit. When the magnetic body is moved to the second position against the urging force of the urging unit, the magnetic body separates from the valve seat such that the liquid storing unit is in fluid communication with the another end.

[0021] With this configuration, the fluid communication between the fluid storing unit and the another end can be achieved by the movement of the magnetic body.

Preferably, the liquid cartridge includes a wall defining the fluid channel. The wall includes a first wall part and a second wall part. The first wall part includes a first inner surface and a first outer surface. The second wall part includes a second inner surface and a second outer surface. The first inner surface opposes the second inner surface. The magnetic body contacts the first inner surface at a first contact point and the magnetic body contacts the second inner surface at a second contact point. The magnetic field generating unit is disposed at a side of the first outer surface and the detecting unit is disposed at a side of the second outer surface. The wall further includes a first protrusion and a second protrusion opposing the first protrusion. The first protrusion protrudes in a prescribed direction that is orthogonal to a line between the first contact point and the second contact point, and the second protrusion protrudes in an opposite direction of the prescribed direction.

Accordingly, because a length between the magnetic field generating unit and the detecting becomes short, magnetic field generated by the magnetic field generating unit and the magnetic body is effectively detected by the detecting unit. Further, the magnetic body is accurately positioned in the prescribed direction and a direction parallel to the line between the first contact point and the second contact point. Advantageous Effects

[0022] This structure ensures that the magnetic body can be detected with good precision, even when the magnetic body in itself is weakly magnetized (where "weakly magnetized" includes a magnetization of "0"). Further, the liquid cartridge minimizes contamination of the fluid channel.

Brief Description of Drawings

In the drawings:

[0023] Fig. 1 is a perspective view of an inkjet printer according to a first embodiment of the invention;

[0024] Fig. 2 is a side view illustrating the general internal structure of the printer;

[0025] Fig.3 is a perspective view showing an ink cartridge according to the first embodiment;

[0026] Fig. 4 is a schematic diagram showing the general internal structure of the ink cartridge;

[0027] Fig. 5 is a cross-sectional view taken along the line V-V in Fig. 4;

[0028] Fig. 6(a) is a partial cross-sectional view of the ink cartridge taken along the line VI(a)(b)-VI(a)(b) in Fig. 5 when the valve is in a closed state;

[0029] Fig. 6(b) is a partial cross-sectional view of the ink cartridge taken along the line VI(a)(b)-VI(a)(b) in Fig. 5 when the valve is in an open state;

[0030] Fig. 6(c) is a partial cross-sectional view of the ink cartridge taken along the line VI(c)(d)-VI(c)(d) in Fig. 5 when the valve is in the closed state;

[0031] Fig. 6(d) is a partial cross-sectional view of the ink cartridge taken along the line VI(c)(d)-VI(c)(d) in Fig. 5 when the valve is in the open state;

[0032] Fig. 7 is a block diagram illustrating a circuit of a Hall element:

[0033] Fig. 8(a) is an explanatory diagram illustrating a process of mounting the ink cartridge in the printer;

[0034] Fig. 8(b) is an explanatory diagram illustrating the process mounting the ink cartridge to the printer;

[0035] Fig. 9 is a block diagram showing the electrical structure of the cartridge and the printer;

[0036] Fig. 10 is a flowchart illustrating steps in a process executed by a controller of the printer when the ink cartridge is mounted in the printer;

[0037] Fig. 11 is a graph showing the relationship between movement of the valve and an output from the Hall element in the cartridge;

[0038] Fig. 12(a) is a partial cross-sectional view of an ink cartridge according to a second embodiment when an valve is in a closed state ;

[0039] Fig. 12(b) is a partial cross-sectional view of the cartridge according to the second embodiment when the valve is in an open state;

[0040] Fig. 13 is a graph showing the relationship between movement of the valve and an output from a Hall element in the cartridge according to the second embodiment;

[0041] Fig. 14 is a cross-sectional view of an outlet tube according to a third embodiment;

[0042] Fig. 15(a) is a partial cross-sectional view of an ink cartridge according to a fourth embodiment when an valve is in a closed state ;

[0043] Fig. 15(b) is a partial cross-sectional view of the cartridge according to the fourth embodiment when the valve is in an open state;

[0044] Fig. 16 is a graph showing the relationship between movement of the valve and an output from a Hall element in the cartridge according to the fourth embodiment;

[0045] Fig. 17 is a cross-sectional view of an outlet tube according to a fifth embodiment;

[0046] Fig. 18(a) is a partial cross-sectional view of an ink cartridge according to a modification when an valve is in a closed state; and

[0047] Fig. 18(b) is a partial cross-sectional view of the cartridge according to the modification when the valve is in an open state.

Explanation of Reference

1 liquid-ejecting device

40 liquid cartridge

42 storing unit

43 a fluid channel

62 magnetic body

71 detecting unit

72 generating unit

63 urging unit

44 adjusting unit

Best Mode for Carrying Out the Invention

[0048] Next, embodiments of the invention will be described while referring to the accompanying drawings.

[0049] First, the general structure of an inkjet printer 1 will be described with reference to Fig. 1. The inkjet printer 1 employs ink cartridges 40 according to a first embodiment of the invention. The ink cartridges 40 are detachably mounted in the inkjet printer 1.

[0050] As shown in Fig. 1, the inkjet printer 1 has a casing la formed in the shape of a rectangular parallelepiped. A paper discharge unit 31 is provided on a top plate constituting the casing la. Three openings lOd, 10b, and 10c are formed in order from top to bottom in the front surface of the casing la (the surface on the near left side in Fig. 1). The opening 10b is provided for inserting a sheet-feeding unit lb into the casing la, while the opening 10c is formed for inserting an ink unit lc into the casing la. A door Id is fitted into the opening lOd and is capable of pivoting about a horizontal axis passing through its lower edge. The door Id is provided in the casing la at a position confronting a conveying unit 21 described later (see Fig. 2) in a main scanning direction of the inkjet printer 1 (a direction orthogonal to the front surface of the casing la).

[0051] Next, the internal structure of the inkjet printer 1 will be described with reference to Fig. 2.

[0052] As shown in Fig. 2, the interior of the casing la is partitioned into three spaces A, B, and C in order from top to bottom. Within the space A are disposed four inkjet heads 2 that eject ink droplets in the respective colors magenta, cyan, yellow, and black; a conveying unit 21 that conveys sheets of a paper P; and a controller 100 that controls operations of various components in the inkjet printer 1. The sheet- feeding unit lb is disposed in the space B, and the ink unit lc is disposed in the space C. As indicated by the bold arrows in Fig. 2, a paper-conveying path is also formed in the inkjet printer 1 for guiding sheets of paper P conveyed from the sheet-feeding unit lb to the paper discharge unit 31.

[0053] In addition to a central processing unit (CPU), the controller 100 includes a read-only memory (ROM), a random access memory (RAM; including nonvolatile RAM), and an interface. The ROM stores programs executed by the CPU, various fixed data, and the like. The RAM temporarily stores data (image data and the like) required by the CPU when executing programs. Through its interface, the controller 100 exchanges data with a sensor unit 70 of an ink cartridge 40 described later and exchanges data with external devices such as a PC connected to the inkjet printer 1.

[0054] The sheet-feeding unit lb includes a paper tray 23, and a feeding roller 25. The paper tray 23 can be mounted in and removed from the casing la along the main scanning direction. The paper tray 23 is box-shaped with an open top and can store sheets of paper P in a variety of sizes. The feeding roller 25 is driven to rotate by a feeding motor 125 (see Fig. 9) under control of the controller 100 in order to feed the topmost sheet of paper P in the paper tray 23. A sheet fed by the feeding roller 25 is guided along guides 27a and 27b, and a pair of conveying rollers 26 grip and convey the sheet to the conveying unit 21.

[0055] The conveying unit 21 includes two belt rollers 6 and 7 and an endless conveying belt 8 looped around the belt rollers 6 and 7 and stretched therebetween. The belt roller 7 is the drive roller. A conveying motor 127 (see Fig. 9) coupled with a shaft of the belt roller 7 drives the belt roller 7 to rotate clockwise in Fig. 2 under control of the controller 100. The belt roller 6 is a follow roller that rotates clockwise in Fig. 2 when the conveying belt 8 is circulated by the rotating belt roller 7.

[0056] A platen 19 having a rectangular parallelepiped shape is disposed within the loop of the conveying belt 8 at a position opposite the four inkjet heads 2 so that an outer surface 8a on the upper loop portion of the conveying belt 8 is maintained parallel to bottom surfaces 2a of the four inkjet heads 2, with a slight gap formed between the bottom surfaces 2a and the outer surface 8a. The bottom surfaces 2a of the inkjet heads 2 are ejection surfaces in which are formed a plurality of ejection holes for ejecting ink droplets.

[0057] The outer surface 8a of the conveying belt 8 is coated with mildly adhesive silicone. When a sheet of paper P is conveyed from the sheet- feeding unit lb onto the conveying unit 21, a nip roller 4 disposed above the belt roller 6 holds the sheet against the outer surface 8 a of the conveying belt 8. Thereafter, the conveying belt 8 conveys the sheet in a sub scanning direction indicated by the bold arrows, while the sheet is held on the outer surface 8a by its adhesive coating.

[0058] The sub scanning direction in the embodiment is parallel to the direction that the conveying unit 21 conveys the paper P. The main scanning direction follows a horizontal plane orthogonal to the sub scanning direction.

[0059] As the sheet of paper P held on the outer surface 8a of the conveying belt 8 passes directly beneath the four inkjet heads 2, the controller 100 sequentially controls the inkjet heads 2 to eject ink droplets in their respective colors through their bottom surfaces 2a onto the top surface of the paper P, thereby forming a desired color image on the paper P. A separating plate 5 disposed above the belt roller 7 separates the sheet from the outer surface 8a of the conveying belt 8 after the sheet has passed beneath the inkjet heads 2. Guides 29a and 29b disposed downstream of the separating plate 5 guide the sheet upward toward an opening 30 formed in the top of the casing la, while two pairs of conveying rollers 28 grip and convey the sheet toward and through the opening 30 and discharge the sheet into the paper discharge unit 31. A feeding motor 128 (see Fig. 9) controlled by the controller 100 drives one of the conveying rollers 28 in each pair to rotate.

[0060] Each of the inkjet heads 2 is a line-type print head elongated in the main scanning direction (the direction orthogonal to the plane of the paper in Fig. 1). Externally, the inkjet head 2 is shaped substantially like a rectangular parallelepiped. The four inkjet heads 2 are arranged at a prescribed pitch in the sub scanning direction and are supported in the casing la on a frame 3. A joint is provided on the top surface of each inkjet head 2 for attaching a flexible tube. A plurality of ejection holes is formed in the bottom surface 2a of each inkjet head 2. Ink cartridges 40 provided one for each of the inkjet heads 2 supply ink to the corresponding inkjet heads 2 through the flexible tubes and joints. An ink channel is formed in each inkjet head 2 for conveying the ink supplied from the ink cartridge 40 to the ejection holes.

[0061] The ink unit lc includes a cartridge tray 35, and four of the ink cartridges 40 arranged in a row within the cartridge tray 35. The leftmost ink cartridge 40 shown in Fig. 2 stores black ink. This leftmost ink cartridge 40 has a larger dimension in the sub scanning direction and, hence, a greater ink capacity than the other three ink cartridges 40. The remaining ink cartridges 40 have an identical dimension in the sub scanning direction and an identical ink capacity among one another. These three ink cartridges 40 respectively store ink in the colors magenta, cyan, and yellow. Ink stored in each of the ink cartridges 40 is supplied to a corresponding inkjet head 2 via a flexible tube and joint.

[0062] With the ink cartridges 40 arranged in the cartridge tray 35, the cartridge tray 35 can be mounted in and removed from the casing la in the sub scanning direction. Accordingly, a user of the inkjet printer 1 can selectively replace the four ink cartridges 40 in the cartridge tray 35 after removing the cartridge tray 35 from the casing la.

[0063] Next, the structure of the ink cartridges 40 will be described with reference to Figs. 3 through 6(d). The four ink cartridges 40 arranged in the cartridge tray 35 have the same structure, except that the ink cartridge 40 storing black ink has a larger dimension in the sub scanning direction and a greater ink storage capacity than the ink cartridges 40 for the other colors, as described above.

[0064] Each ink cartridge 40 includes a case 41, a reservoir 42, an outlet tube 43, a stopper 50, a valve 60, a sensor unit 70 (see Fig. 5), a contact 142, and a power input unit 147 (see Figs. 3, 4, and 9).

[0065] The case 41 has a rectangular parallelepiped shape (see Figs. 3 and 4). The reservoir 42 is provided inside the case 41 (see Fig. 4). Inner walls (inner surfaces) of the outlet tube 43 define an outlet path 43 a (see Fig. 6(a)) through which ink stored in the reservoir 42 is discharged (supplied to the inkjet head 2). The stopper 50 and the valve 60 are disposed in the outlet path 43a (see Fig. 6(a)).

[0066] As shown in Fig. 4, the interior of the case 41 is partitioned into two chambers 41a and 41b. The reservoir 42 is provided in the chamber 41a on the right of the chamber 41b shown in Fig. 4, while the outlet tube 43 is provided in the other chamber 41b.

[0067] The reservoir 42 is a baglike member with an opening formed therein and serves to store ink. A base end (right end of Fig. 6(a)) of the outlet tube 43 is connected to the opening in the reservoir 42.

[0068] Fig. 5 is a cross-sectional view taken along the line V-V illustrating a region IV of the ink cartridge 40. Fig. 6(a) is a cross-sectional view taken along the line VI(a)(b)-VI(a)(b) when the valve 60 is in a closed state (when the valve 60 is positioned at a first position) whereas Fig. 6(b) is a cross-sectional view taken along the line VI(a)(b)-VI(a)(b) when the valve 60 is in an open state (when the valve 60 is positioned at a second position). Fig. 6(c) is a cross-sectional view taken along the line VI(c)(d)-VI(c)(d) when the valve 60 is in the closed state (positioned at a second position) whereas Fig. 6(d) is a cross-sectional view taken along the line VI(a)(b)- VI(a)(b) when the valve 60 is in the open state.

[0069] The outlet tube 43 has a diameter-restricting part 43x near the distal end of the outlet tube 43. The diameter-restricting part 43x has an inward step 43z as a valve seat of the valve 60. Here, the inward step 43z extends inward in the radial direction of the outlet tube 43 at the inner wall (inner surface) of the outlet tube 43. An opening 43y is defined at the distal end side of the diameter-restricting part 43x. The opening 43y has a smaller diameter than the diameter of the outlet path 43a on the base end side of the diameter-restricting part 43x.

[0070] The outlet tube 43 is formed of polyethylene, for example. As shown in Fig. 4, a distal end (left end of Fig. 4) of the outlet tube 43 protrudes out of the case 41. The stopper 50 is formed of a rubber or other elastic member and is fitted into this distal end of the outlet tube 43 in a compressed state so as to block the exit end of the outlet path 43a (see Figs. 6(a)-6(d)). A cap 46 is fitted over the outside of this distal end of the outlet tube 43 and the stopper 50. A hole 46a is formed in the center of the cap 46, exposing an endface (a surface opposite the surface facing the valve 60) of the stopper 50.

[0071] As shown in Fig. 6(a), the valve 60 is provided inside the outlet tube

43 and includes an O-ring 61, a valve body 62, and a coil spring 63.

[0072] The valve body 62 is formed of a non-magnetized magnetic material, such as stainless steel, Grade 430 (SUS430). That is, the valve body 62 is not magnetized when the valve body 62 is not in the magnetic field whereas the valve 72 is magnetized when the valve body 62 is in the magnetic field. As shown in Figs. 5 and 6(a)-6(d), the valve body 62 is columnar in shape, with its axis extending in the main scanning direction. [0073] As shown in Fig. 5, the portion of the outlet tube 43 in which the valve body 62 is disposed is cylindrical in shape, with a flattened top wall 431 , a flattened bottom wall 432, and side walls 433, 434. The top wall 431 has an inner surface 431a and an outer surface 431b, and the bottom wall 432 has an inner surface 432a and an outer surface 432b. The top portion of the valve body 62 contacts the inner surface 43 la at a contact point Pa and the bottom portion of the valve body 62 contacts the inner surface 432a at a contact point Pb. A cross section of the outlet tube 43 taken orthogonal to the main scanning direction is elongated in the sub scanning direction. One protrusion 43p is formed on each inner side wall of the outlet tube 43 with respect to the sub scanning direction and protrudes inward in the sub scanning direction. That is, the two protrusions protrude inward from opposite surfaces of the inner side walls 433, 434. Each protrusion 43p extends in the main scanning direction along the inside wall over the range in which the valve body 62 moves. The two protrusions 43p contacts the valve body 62 at a contact points PI and P2 such that the valve body is positioned in the sub scanning direction. The valve body 62 is positioned in the center of the outlet path 43 a in a cross-sectional view, held between the protrusions 43p and the top wall 431 and the bottom wall 432 of the outlet tube 43. A fluid channel is formed in a region between the valve body 62 and the outlet tube 43, excluding the regions in which the valve body 62 contacts the protrusions 43p (left and right sides in Fig. 5) and upper and lower walls of the outlet tube 43.

[0074] The O-ring 61 is formed of a rubber or other elastic material and is fixed to the front surface of the valve body 62 (the surface opposing the stopper 50). One end of the coil spring 63 is fixed to a base end 43 f that protrudes inside in the outlet tube 43, while the other end contacts the rear surface of the valve body 62. The coil spring 63 constantly urges the valve body 62 toward the O-ring 61 and toward the inward step 43z.

[0075] When the valve 60 is in the closed state for closing the outlet path

43a, as shown in Figs. 6(a) and 6(c), the O-ring 61 contacts the inward step 43z and seals the opening 43 y. With this construction, the O-ring 61 interrupts communication between the space formed from the base end of the outlet path 43a to the diameter- restricting part 43x and the space formed from the diameter-restricting part 43x to the stopper 50, thereby interrupting external communication with the reservoir 42 via the outlet path 43 a. At this time, the O-ring 61 is elastically deformed by the urging force of the coil spring 63. On the other hand, the valve 60 is in the open state shown in Figs. 6(b) and 6(d), the O-ring 61 separates from the inward step 43 z, thereby enabling the external communication with the reservoir 42 via the outlet path 43 a.

[0076] The sensor unit 70 includes a Hall element 71, and a magnet 72. The sensor unit 70 is electrically connected to the contact 142 and the power input unit 147. The magnet 72 produces a magnetic field. The Hall element 71 and the magnet 72 is disposed outside of the outlet path 43a. In this example, the top of the magnet 72 is the north pole and the bottom is the south pole. However, the top of the magnet 72 may be the south pole the bottom of the magnet 72 may be the north pole.

[0077] The Hall element 71 is a magnetic sensor that detects a magnetic field.

The Hall element 71 converts the magnetic field to an electric signal and outputs this electric signal to the controller 100 via the contact 142. In the embodiment, the electric signal that the Hall element 71 outputs to the controller 100 specifies a voltage proportional to the magnitude (strength) of the magnetic field and fluctuates with movement of the valve body 62. The Hall element 71 is disposed at a position for detecting the magnetic field produced by the magnet 72 and the valve body 62 (see Fig. 6(a)). The Hall element 71 is packaged with an amplifier circuit 81, for example, to configure a circuit such as that shown in Fig. 7. The Hall element 71 outputs an analog voltage proportional to the magnetic field (magnetic flux density).

[0078] As shown in Figs. 5 and 6(a), the Hall element 71 and the magnet 72 are respectively fixed in the upper and lower walls of the outlet tube 43 and oppose each other vertically. When the valve 60 is in the closed state shown in Fig. 6(a), the Hall element 71 and the magnet 72 are positioned on opposite sides of the valve body 62 (i.e., the valve body 62 is positioned between the Hall element 71 and the magnet 72). At this time, the magnetic field produced by the magnet 72 is efficiently applied to the Hall element 71 through the valve body 62. Consequently, the Hall element 71 detects a large strength of the magnetic field and outputs a signal specifying a high voltage. In other words, the strength of the magnetic field when the valve is in the closed state is larger than the strength of the magnetic field when the valve is in the open state.

[0079] As shown in Fig. 5, the top portion of the valve body 62 contacts the inner surface 431a at a contact point Pa and the bottom portion of the valve body 62 contacts the inner surface 432a at a contact point Pb. In other words, when the valve 60 is in the closed state, no part of the outlet path 43a is disposed between a part (top surface) of the valve body 62 and a part of the Hall element 71. Further, when the valve 60 is in the closed state, no part of the outlet path 43 a is disposed between a part (bottom surface) of the valve body 62 and a part of the magnet 72. Accordingly, a vertical length between the Hall element 71 and the magnet 72 becomes short. Thus, magnetic field generated by the magnet 72 and the valve body 62 is effectively detected by the Hall element 71 while the valve body 62 is accurately positioned in the vertical direction by the inner surfaces 431a and 431b. Moreover, as shown in Fig. 5, the contact points Pa, PI, Pb, P2 are substantially equiangularly arranged in a circumferential direction of the valve body 62 (at each 90 degree). Accordingly, the valve 62 is accurately positioned in the main scanning direction and the sub scanning direction.

[0080] When the valve 60 is shifted from its closed state shown in Fig. 6(a) to its open state shown in Figs. 6(b) for opening the outlet path 43a, the magnetic field detected by the Hall element 71 decreases as the valve body 62 moves toward a position not confronting the Hall element 71 and the magnet 72 vertically (i.e., a position not between the Hall element 71 and the magnet 72), reducing the voltage indicated by the signal outputted from the Hall element 71.

[0081] The controller 100 determines whether the valve 60 is in the open state or the closed state based on the voltage specified by the signal received from the Hall element 71.

[0082] While the Hall element 71 is directly fixed to the outer surface 43 lb, the magnet 72 is fixed to the outer surface 432b via a spacer 44, as shown in Fig. 5. The spacer 44 is formed of a non-magnetic material. The magnet 72 is fixed to the bottom surface of the spacer 44. Both the magnet 72 and the spacer 44 are plate-shaped and have the same length in the sub scanning direction. The relative vertical distance between the Hall element 71 and the magnet 72 can be adjusted by modifying the number of spacers 44 provided on the lower wall of the outlet tube 43.

[0083] As shown in Fig. 8(a), the contact 142 of the ink cartridge 40 is disposed on the outer surface of the case 41. As mentioned above, the contact 142 is electrically connected to the sensor unit 70 and serves as an interface of the ink cartridge 40 for communicating with the controller 100.

[0084] The power input unit 147 is exposed on the outer surface of the case

41 at a position near the contact 142. As mentioned above, the power input unit 147 is electrically connected to the sensor unit 70 and functions to supply power to the sensor unit 70 from the inkjet printer 1 side.

[0085] As shown in Fig. 8(a), the inkjet printer 1 is also provided with a contact 152, a power output unit 157, and a support body 154 for each ink cartridge 40, as well as a moving mechanism 155 and a power supply 158 (see Fig. 9).

[0086] The contact 152 is disposed on a wall surface of the casing la at a position opposing the contact 142 on the corresponding ink cartridge 40 when the ink cartridge 40 is mounted in the inkjet printer 1. The contact 152 functions as an interface of the controller 100 for communicating with the corresponding ink cartridge 40 when electrically connected to the contact 142 on the ink cartridge 40.

[0087] The power output unit 157 is exposed in a wall surface of the casing la at a position opposing the power input unit 147 of the corresponding ink cartridge 40 when the ink cartridge 40 is mounted in the inkjet printer 1. The power output unit 157 is electrically connected to the power supply 158 and functions to supply power from the power supply 158 to the sensor unit 70 of the ink cartridge 40 when electrically connected to the power input unit 147.

[0088] The support body 154 is disposed in a wall surface of the casing la at a position opposing the cap 46 of the corresponding ink cartridge 40 when the ink cartridge 40 is mounted in the inkjet printer 1. The support body 154 functions to support a hollow needle 153 and can be moved relative to the casing la in the main scanning direction for inserting the hollow needle 153 into and extracting the hollow needle 153 from the ink cartridge 40 (Figs. 6(a)-6(d)).

[0089] The hollow needle 153 is fixed to the support body 154 and is in communication with the flexible tube attached to the joint of the corresponding inkjet head 2. As shown in Fig. 6(b), the hollow needle 153 extends in the main scanning direction. A fluid channel 153a is formed inside the hollow needle 153 along its longitudinal dimension and is in fluid communication with the flexible tube attached to the joint of the corresponding inkjet head 2. A hole 153b is formed near the distal end of the hollow needle 153 for providing external communication with the channel 153a.

[0090] The moving mechanism 155 (Fig. 9) is disposed in the casing la and functions to move the support body 154 and the hollow needle 153 fixed to the support body 154 in the main scanning direction.

[0091] The power supply 158 (Fig. 9) is disposed in the casing la and provides power to various components of the inkjet printer 1 and to the sensor unit 70 in each ink cartridge 40.

[0092] Next, operations for mounting the ink cartridges 40 in the inkjet printer 1 will be described with reference to Figs. 5 through 11. In Fig. 9 the bold lines indicate power supply lines, while the fine lines indicate signal lines.

[0093] Before an ink cartridge 40 is mounted in the inkjet printer 1, the valve

60 is maintained in the closed state shown in Fig. 6(a). At this stage, the hollow needle 153 has not yet been inserted into the ink cartridge 40, the contact 142 has not yet been electrically connected to the contact 152, and the power input unit 147 has not yet been electrically connected to the power output unit 157 shown in Fig. 9. Hence, at this stage, the ink cartridge 40 and the inkjet printer 1 cannot exchange signals, and power is not being supplied to the sensor unit 70.

[0094] To mount a cartridge in the inkjet printer 1, the user of the inkjet printer 1 places the ink cartridge 40 in the cartridge tray 35 (see Fig. 2) and subsequently inserts the cartridge tray 35 into the space C of the casing la by moving the cartridge tray 35 in the main scanning direction indicated by the white arrow in Fig. 8(a). Initially, this operation causes the contact 142 of the ink cartridge 40 to make contact with the contact 152 on the inkjet printer 1 side, as shown in Fig. 8(a), forming an electrical connection between the ink cartridge 40 and inkjet printer 1. Accordingly, the ink cartridge 40 and the inkjet printer 1 can now exchange signals.

[0095] At the same time the contacts 142 and 152 come into contact, the power input unit 147 of the ink cartridge 40 contacts the power output unit 157 of the inkjet printer 1, as shown in Fig. 8(a). This contact forms an electrical connection that allows the power supply 158 in the inkjet printer 1 (see Fig. 9) to supply power to the sensor unit 70 via the power output unit 157 and the power input unit 147.

[0096] At this stage, the ink cartridge 40 remains separated from the hollow needle 153. Therefore, the reservoir 42 is not in communication with the ink channel formed in the corresponding inkjet head 2.

[0097] Fig. 10 illustrates steps in a control process performed by the controller 100 when an ink cartridge 40 is mounted in the inkjet printer 1. In SI of Fig. 10, the controller 100 determines whether an ink cartridge 40 has been electrically connected to the inkjet printer 1. Upon detecting an ink cartridge 40 being electrically connected to the inkjet printer 1 (SI : YES), in S2 the controller 100 controls the moving mechanism 155 (see Fig. 9) to begin moving the support body 154 and the hollow needle 153 supported by the support body 154 in the main scanning direction indicated by the black arrow in Fig. 8(b). After initiating the operation to move the hollow needle 153 in S2, in S3 the controller 100 determines whether the valve 60 has switched to its open state based on the value outputted from the Hall element 71 and the like.

[0098] As the moving mechanism 155 begins moving the hollow needle 153 in S2, as illustrated in Fig. 6(b), the hollow needle 153 first passes through the hole 46a formed in the cap 46 and penetrates the approximate center region of the stopper 50 in the main scanning direction. When the hollow needle 153 is inserted through the stopper 50 until the hole 153b on the distal end thereof is positioned inside the outlet path 43a, the channel 153a formed in the hollow needle 153 is in fluid communication with the outlet path 43a via the hole 153b. Although a penetration hole is formed in the stopper 50 by the hollow needle 153 through this operation, the elasticity of the stopper 50 allows the region of the stopper 50 surrounding the penetration hole to form a tight seal with the outer surface of the hollow needle 153, thereby preventing ink from leaking out through the penetration hole between the stopper 50 and the hollow needle 153.

[0099] As the moving mechanism 155 continues to move the hollow needle

153, the distal end of the hollow needle 153 contacts the valve body 62 and continues inward into the outlet path 43a, pushing the valve body 62 also inward into the outlet path 43 a. The O-ring 61 moves together with the valve body 62 and separates from the inward step 43z (see Figs. 6(b) and 6(d)). At this time, the valve 60 shifts from the closed state to the open state.

[0100] When the valve 60 is in the open state, the space in the outlet path

43a from its base end to the diameter-restricting part 43x is in communication with the space from the diameter-restricting part 43x to the stopper 50, allowing external communicatioii with the reservoir 42 through the outlet path 43 a. In other words, when the hollow needle 153 is inserted through the stopper 50 until the valve 60 is in the open state shown in Figs. 6(b) and 6(d), the reservoir 42 is in fluid communication with the ink channel formed in the inkjet head 2 through the outlet path 43a, the channel 153a, and the like.

[0101] The graph in Fig. 11 shows the relationship between movement of the valve 60 and the output value from the Hall element 71. The horizontal axis in the graph denotes the distance over which the valve body 62 has moved away from the stopper 50 (the inward wall 43 z) in the main scanning direction from the first position shown in Fig. 6(a) when the valve 60 is in the closed state. When the output value from the Hall element 71 reaches a threshold value Vt, the controller 100 determines that the valve 60 has shifted from the open state to the closed state.

[0102] Returning to the flowchart in Fig. 10, when the controller 100 determines in S3 that the valve 60 has switched to the open state (S3: YES), in S4 the controller 100 begins a print control process and subsequently ends the current routine. In the print control process of S4, the controller 100 performs processes required when print commands are received from external devices, such as driving the feeding motor 125, the conveying motor 127, and the feeding motor 128 (see Fig. 9), as well as the inkjet heads 2 and the like.

[0103] However, while the controller 100 determines in S3 that the valve 60 has not shifted to the open state (S3: NO), the controller 100 continually repeats the determination in S3 while also determining in S5 whether a prescribed time has elapsed. If the prescribed time elapses before the valve 60 is shifted to the open state (S5: YES), in S6 the controller 100 issues an error notification to the user by displaying an image on a display of the inkjet printer 1, outputting sounds, or the like, and in S7 halts operations of the components in the inkjet printer 1, thereby restricting the execution of printing operations on the inkjet printer 1. This error may occur due to a malfunction of the sensor unit 70, the stopper 50, the valve 60, the hollow needle 153, or the like.

[0104] The controller 100 performs the series of processes described in Fig.

10 for each ink cartridge 40.

[0105] When removing or replacing a cartridge, the user of the inkjet printer

1 first removes the cartridge tray 35 from the casing la. Through this operation, all four ink cartridges 40 are simultaneously separated from their respective support body 154, the contact 152, and the power output unit 157, thereby interrupting the electrical connections between the contact 142 and the contact 152 and between the power input unit 147 and the power output unit 157 for each ink cartridge 40; disabling the ability of each ink cartridge 40 to exchange signals with the inkjet printer 1; and interrupting the supply of power to the sensor unit 70 in each ink cartridge 40. In addition, as the hollow needle 153 moves leftward in Fig. 6(b) relative to the ink cartridge 40, the urging force of the coil spring 63 moves the valve body 62 leftward in Fig. 6(b) together with the O-ring 61. Accordingly, as shown in Fig. 6(a), the O-ring 61 contacts the inner wall 43z, switching the valve 60 from the open state to the closed state. After the hollow needle 153 is extracted from the stopper 50, the portion of the stopper 50 surrounding the penetration hole springs back to its original state due to the elasticity of the stopper 50, reducing the size of the hole sufficiently to prevent ink leakage.

[0106] Providing the magnet 72 separate from the valve body 62 (the magnetic body) in the ink cartridge 40 according to the embodiment described above ensures that the valve body 62 (valve 60) can be detected with good precision, even when the valve body 62 is weakly magnetized in itself (where "weakly magnetized" in the embodiment includes a magnetization of "0"). Further, since the magnet 72 is not provided inside the outlet path 43a and the valve body 62 that is provided in the outlet path 43a is weakly magnetized, this construction suppresses the introduction of foreign matter into the outlet path 43a. Hence, the ink cartridge 40 of the embodiment ensures good precision in detecting the valve body 62 (valve 60) and minimizes contamination of the outlet path 43 a.

[0107] The valve body 62 can be moved between the first position between the Hall element 71 and the magnet 72 (the position of the valve body 62 when the valve 60 is in the closed state shown in Figs. 6(a) and 6(c)) and the second position not between the Hall element 71 and the magnet 72 (the position of the valve body 62 when the valve 60 is in the open state shown in Figs. 6(b) and 6(d)). With this configuration, the difference in magnitude between electric signals outputted by the Hall element 71 when the valve 60 is in the open and closed states can be heightened to further improve detection precision.

[0108] The magnet 72 is disposed in a position opposing the Hall element 71 along a direction (vertically in the embodiment) orthogonal to the direction in which the valve body 62 is moved. This configuration can increase output from the Hall element 71, increasing the difference in magnitude of the electric signal outputted by the Hall element 71 when the valve 60 is in the open and closed states.

[0109] As shown in Fig. 5, the valve body 62 is held between the upper and lower walls of the outlet tube 43. When the valve body 62 is in the first position between the Hall element 71 and the magnet 72 (when the valve 60 is in the closed state shown in Fig. 6(a)), no part of the outlet path 43 a is disposed between a part (top surface) of the valve body 62 and a part of the Hall element 71, and no part of the outlet path 43a is disposed between a part (bottom surface) of the valve body 62 and a part of the magnet 72. This configuration increases the output of the Hall element 71, thereby further enhancing the difference in magnitude of the electric signal outputted from the Hall element 71 when the valve 60 is in the open and closed states.

[0110] In the embodiment, the valve body 62 is not magnetized, thereby reliably suppressing the introduction of foreign matter into the outlet path 43 a.

[0111] As described above, the spacer 44 is provided for adjusting the relative distance between the Hall element 71 and the magnet 72 (see Fig. 5). Accordingly, the relative distance between the Hall element 71 and the magnet 72 can be adjusted to enhance the difference in magnitude of the electric signal outputted by the Hall element 71 when the valve 60 is in the open and closed states.

[0112] In the embodiment, the valve body 62 is columnar in shape, with the axis of the column extending along the direction that the valve body 62 moves. With this shape, the valve body 62 can be moved smoothly. Further, since rotation of the valve body 62 about its axis in the outlet path 43a will not change the distance between the Hall element 71 and the magnet 72 and thus will not have any effect on the output of the Hall element 71, there is no need to provide any parts on the inner surface of the wall defining the outlet path 43a to prevent rotation of the valve body 62.

[0113] Although no space is provided above and below the valve body 62 in the outlet path 43a, as shown in Fig. 5, channels are formed on both sides of the valve body 62 with respect to the sub scanning direction. However, the protrusions 43p provided on the inside of the outlet tube 43 maintain the valve body 62 in position relative to the sub scanning direction, thereby preventing the valve body 62 from moving in any direction within the outlet tube 43 other than its intended direction of movement (the main scanning direction).

[0114] The electric signal outputted by the Hall element 71 is higher when the valve 60 is in the closed state than when the valve 60 is in the open state. Therefore, the controller 100 can check output from the Hall element 71 while the valve 60 is in the closed state (i.e., without performing a process to shift the valve 60 into the open state), simplifying the process for checking output from the Hall element 71.

[0115] In the embodiment, the controller 100 checks output from the Hall element 71 after the ink cartridge 40 is electrically connected to the inkjet printer 1 and before the hollow needle 153 has been inserted into the stopper 50. If output of a prescribed value or greater is not obtained in this operation, the controller 100 can take measures to report an error or the like, thereby avoiding problems that may occur when using a Hall element 71 that is not performing properly. Problems may arise when the Hall element 71 is unable to detect the valve 60 properly. For example, the Hall element 71 erroneously detects the valve 60 in the closed state despite the valve 60 being in the open state and thus, the controller 100 cannot perform ink ejecting operations (or print control process). Or, the Hall element 71 erroneously detects the valve in the open state despite the valve 60 being in the closed state and thus, the controller 100 initiate the ink ejecting operations, resulting in ejection problems.

[0116] Next, an ink cartridge according to a second embodiment of the invention will be described with reference to Figs. 12 and 13. The cartridge according to the second embodiment differs from the ink cartridge 40 described in the first embodiment in the positions of the Hall element 71 and the magnet 72. The remaining structure is essentially identical to the ink cartridge 40 according to the first embodiment. The following description will focus on the differences from the first embodiment.

[0117] In the second embodiment, both the Hall element 71 and magnet 72 are separated farther from the stopper 50 in the main scanning direction than in the first embodiment (see Fig. 5). When the valve 60 is in the closed state shown in the closed position shown in Fig. 12(a), the Hall element 71 and magnet 72 do not vertically oppose the valve body 62 (i.e., the valve body 62 is not positioned between the Hall element 71 and magnet 72). At this time, the Hall element 71 detects a faint strength of the magnetic field and outputs a signal indicating a low voltage. In other words, the strength of the magnetic field when the valve 60 is in the closed state is smaller than the strength of the magnetic field when the valve in the open state.

[0118] When the valve 60 is shifted from the closed position shown in Fig.

12(a) to the open position shown in Fig. 12(b), the magnetic field generated by the magnet 72 is more efficiently applied to the Hall element 71 via the valve body 62 as the valve body 62 moves to a position vertically opposed by the Hall element 71 and magnet 72 (i.e., a position between the Hall element 71 and magnet 72). Hence, the strength of the magnetic field detected by the Hall element 71 increases, and the voltage indicated by the signal outputted from the Hall element 71 increases.

[0119] The graph in Fig. 13 shows the relationship between the movement of the valve 60 and the output value from the Hall element 71 for the cartridge according to the second embodiment. The horizontal axis of this graph denotes the distance that the valve body 62 has moved away from the stopper 50 in the main scanning direction from the position in which the valve 60 is in the closed state shown in Fig. 12(a). When the output value from the Hall element 71 reaches the threshold value Vt, the controller 100 determines that the valve 60 has switched from the closed state to the open state.

[0120] In addition to the effects described in the first embodiment owing to a similar structure, the cartridge according to the second embodiment obtains the following effects owing to a structure different from the first embodiment. That is, the electric signal outputted by the Hall element 71 is smaller when the valve 60 is in the closed state than when the valve 60 is in the open state. The magnetic field in the region of the valve body 62 is weaker when the valve 60 is in the closed state. Therefore, the valve body 62 is unlikely to be permanently magnetized even when the cartridge has been stored for a long period of time with the valve 60 in the closed state. The precision of the Hall element 71 in detecting the valve body 62 worsens if the valve body 62 becomes magnetized. However, since the construction according to the second embodiment suppresses magnetization of the valve body 62, detecting precision is sufficiently maintained.

[0121] Next, an ink cartridge according to a third embodiment of the invention will be described with reference to Fig. 14. The cartridge according to the third embodiment differs from the ink cartridge 40 according to the first embodiment in the structure of the valve body and the outlet tube, while the remaining structure is essentially identical to that of the ink cartridge 40 according to the first embodiment. The following description will focus on the differences from the first embodiment.

[0122] In the third embodiment, the cartridge has a valve body 362 that is pillar-shaped, with its axis extending in the main scanning direction. A cross section of the valve body 362 taken orthogonal to the main scanning direction is not circular, but is elongated vertically.

[0123] The valve body 362 is provided in an outlet path 343a formed inside an outlet tube 343. The portion of the outlet tube 343 in which the valve body 362 is provided is substantially cylindrical in shape. Four protrusions 343p are formed on the inner surface of the outlet tube 343 and protrude inward. The protrusions 343p are arranged at equal intervals along the inner circumference of the outlet tube 343. Each protrusion 343p extends in the main scanning direction along the inner wall surface of the outlet tube 343 over the range in which the valve body 362 moves. The valve body 362 is held between the protrusions 343p and the upper and lower walls of the outlet tube 343, positioning the valve body 362 in the center of the outlet path 343a in a cross-sectional view and restricting rotation of the valve body 362. Channels are formed between the valve body 362 and the outlet tube 343 (left and right sides in Fig. 14), that is a region in the outlet tube 343 excluding the region of the valve body 343 and the regions of the outlet path 343a in which the valve body 362 contacts the protrusions 343p and the upper and lower walls of the outlet tube 343.

[0124] In addition to the effects described in the first embodiment owing to a similar structure, the cartridge according to the third embodiment obtains the following effects owing to a structure different from the first embodiment. Specifically, the valve body 362 has a pillar shape, with its axis aligned in the main scanning direction and a cross section of the valve body 362 taken orthogonal to the direction in which the valve body 362 moves (main scanning direction) is elongated vertically. This construction ensures that space is not formed between the valve body 362 and the Hall element 71 and between the valve body 362 and the magnet 72, without requiring that the outlet tube 343 have a complex shape (in other words, the outlet tube 343 can even be formed in a cylindrical shape, as in the first embodiment). Therefore, the cartridge according to the third embodiment can obtain the above effects by not interposing a channel between the valve body 362 and the Hall element 71 and between the valve body 362 and the magnet 72, while preventing the shape of the outlet tube 343 from becoming complex.

[0125] Next, an ink cartridge according to a fourth embodiment of the invention will be described with reference to Figs. 15(a), 15(b), and 16. The cartridge according to the fourth embodiment differs from the ink cartridge 40 described in the first embodiment in the positions and structures of the Hall element 71 and the magnet 72. The remaining structure is essentially identical to the ink cartridge 40 according to the first embodiment. The following description will focus on the differences from the first embodiment.

[0126] In the fourth embodiment, the Hall element 71 is disposed at a position in the main scanning direction exactly between the valve body 62 in the closed state shown in Fig. 15(a) and the valve body 62 shown in the open state shown in Fig. 15(b). The magnet 72 is longer in the main scanning direction than the magnet according to the first embodiment and extends in this direction over the entire range in which the valve body 62 moves. In this example, the south pole of the magnet 72 is positioned on the side nearest the stopper 50 in the main scanning direction and the north pole on the opposite side. However, the north pole of the magnet 72 may be positioned on the side nearest the stopper 50 in the main scanning direction and the south pole on the opposite side.

[0127] When the valve 60 is in the closed state shown in Fig. 15(a), approximately half of each of the Hall element 71 and the magnet 72 on the side in the main scanning direction nearest the stopper 50 vertically opposes the valve body 62 (i.e., the valve body 62 is positioned between the Hall element 71 and the magnet 72. The magnet 72 vertically opposes the entire valve body 62. When the south pole of the magnet 72 is positioned on the side nearest the stopper 50 in the main scanning direction and the north pole on the opposite side, the magnetic field generated by the magnet 72 is applied to the Hall element 71 via the valve body 62 in the direction indicated by arrows in Fig. 15(a) (the substantially upper direction in the example shown in Fig. 15(a)).

[0128] When the valve 60 is in the open state shown in Fig. 15(b), approximately half of each of the Hall element 71 and the magnet 72 on the side in the main scanning direction farthest from the stopper 50 vertically opposes the valve body 62 (i.e., the valve body 62 is positioned between the Hall element 71 and the magnet 72). The magnet 72 vertically opposes the entire valve body 62. When the south pole of the magnet 72 is on the side in the main scanning direction nearest the stopper 50 and the north pole is on the side farthest from the stopper 50, the magnetic field generated by the magnet 72 is applied to the Hall element 71 via the valve 60 in the direction indicated by arrows shown in Fig. 15(b) (the substantially lower direction in the example shown in Fig. 15(b)).

[0129] In this way, the direction of the magnetic field applied to the Hall element 71 is reversed when the valve 60 is in the closed state shown in Fig. 15(a) and in the open state shown in Fig. 15(b). As a result, the Hall element 71 outputs a positive value when the valve 60 is in the closed state and a negative value when the valve 60 is in the open state (see Fig. 16). Consequently, the magnitude of the electric signal outputted by the Hall element 71 differs greatly when the valve 60 is in the closed state and the open state, thereby enhancing detection precision.

[0130] In addition to the effects obtained in the first embodiment owing to its similar structure, the cartridge according to the fourth embodiment further enhances the precision at which the Hall element 71 can detect the valve body 62.

[0131] Next, an ink cartridge according to a fifth embodiment of the invention will be described with reference to Fig. 17. The cartridge according to the fifth embodiment differs from the ink cartridge 40 according to the first embodiment only in the position of the magnet 72, while the remaining structure is essentially identical to that of the ink cartridge 40 according to the first embodiment. The following description will focus on the differences from the first embodiment.

[0132] In the fifth embodiment, the magnet 72 is fixed to the side wall rather than the bottom wall of the frame 3. Hence, the magnet 72 is not positioned vertically opposite the Hall element 71, but is positioned 90 degrees from the Hall element 71 along the circumference of the outlet tube 43.

[0133] The cartridge according to the fifth embodiment obtains the same effects described in the first embodiment owing to its similar structure (i.e., providing the magnet 72 separate from the valve body 62 (the magnetic body) ensures that the valve body 62 (valve 60) can be detected with good precision, while suppressing the introduction of foreign matter into the outlet path 43 a).

[0134] While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the scope of the invention which is defined by the attached claims.

[0135] The structure of the cartridge according to the invention may be modified in a variety of ways. That is, it is possible to suitably modify the configuration

(shape, position, and the like) of the reservoir 42, the case 41, the outlet path 43 a, the stopper 50, the valve 60, the sensor unit 70, and the like. It is also possible to add new components and to eliminate some of the components described in the embodiments.

[0136] The number of valves incorporated in the cartridge is also arbitrary. Further, while the valve in the embodiments is formed by combining a magnetic body with a non-magnetic body, the valve may be configured of only the magnetic body instead.

[0137] Instead of providing a valve that serves to open and close the channel, as described in the embodiments, the magnetic body may be configured of any type of valve that serves to adjust flow. Further, the magnetic body is not limited to a valve structure, but may be any member, provided that the magnetic body can move within the channel that communicates with the liquid chamber.

[0138] The magnetic body (valve 60) used in the cartridge according to the invention may be either magnetized or not magnetized. In other words, while the invention can reduce magnetization of the body, a magnetized magnetic body also falls within the technical scope of the invention.

[0139] Space constituting part of the channel in which the magnetic body (valve 60) is disposed may be formed in either one or both of the regions between the magnetic body and the Hall element 71 and between the magnetic body and the magnet 72 when the magnetic body is in the first position.

[0140] The shape of the magnetic body (valve 60) may be arbitrarily modified. For example, the magnetic body may have a rectangular cross section. Further, the magnetic body need not have a pillar shape, but may be a spherical body, rectangular parallelepiped, or the like.

[0141] The Hall element 71 may be disposed in any position, including the positions described in the embodiments, provided that the position allows the Hall element 71 to detect a magnetic field created by the magnet 72 and the magnetic body (valve 60).

[0142] While the spacer 44 and the like serve as means for adjusting the relative distance between the Hall element 71 and the magnet 72 in the embodiments, any type of member or means capable of adjusting this relative distance may be employed. Alternatively, the means for adjusting this relative distance may be omitted.

[0143] The hollow needle 153 may be inserted into the outlet path 43a automatically by the controller 100, as described in the embodiments, or manually by the user of the liquid-ejecting device.

[0144] The timing at which the ink cartridge 40 (liquid cartridge) and the printer 1 (liquid-ejecting device) are enabled to exchange signals and the timing at which the printer 1 is capable of supplying power to the ink cartridge 40 may be arbitrarily modified and are not limited to the timings described in the embodiments. In addition, the positions of the contacts 142 and 152, power input unit 147, the power output unit 157, and the like on the ink cartridge 70 and the printer 1 may be arbitrarily modified.

[0145] The type of liquid stored in the liquid cartridge is not limited to ink, but may be a liquid used to coat the printing medium prior to printing in order to enhance image quality, a cleaning liquid for cleaning the conveying belt, or the like.

[0146] The liquid cartridge according to the invention is not limited to a cartridge mounted in a printer, but may be a cartridge mounted in a facsimile machine, a copy machine, or other liquid-ejecting device. Further, the print head 2 of the printer 1 (liquid-ejecting device) may be a serial type head rather than a line-type head. The number of print heads 2 incorporated in the printer 1 is not limited to four, provided that there is at least one.

[0147] In the first embodiment, the Hall element 71 and the magnet 72 are respectively fixed in the upper and lower walls of the outlet tube 43. However, as shown in Figs. 18(a) and 18(b), the Hall element 71 and the magnet 72 may be respectively embedded in the upper and lower walls of the outlet tube 43.