WO2012042901A1

WO2012042901A1 - Ink cartridge and recording apparatus using the same

Info

Publication number: WO2012042901A1
Application number: PCT/JP2011/005541
Authority: WO
Inventors: Hiroaki Yazawa; Hirofumi Kondo; Keiji Kura
Original assignee: Brother Kogyo Kabushiki Kaisha
Priority date: 2010-09-30
Filing date: 2011-09-30
Publication date: 2012-04-05
Also published as: JP2013176850A; JP5703666B2

Abstract

An ink cartridge configured to be mounted in a recording apparatus is provided. The ink cartridge includes: an ink chamber configured to store ink therein; a pyroelectric portion configured to output an electrical signal; and a first electrical interface configured to transmit the electrical signal from the pyroelectric portion.

Description

INK CARTRIDGE AND RECORDING APPARATUS USING THE SAME

The present invention relates to an ink cartridge and a recording apparatus provided with a cartridge accommodating portion adapted to accommodate the ink cartridge therein.

A well-known inkjet-type recording apparatus is configured to form (record) an image on a recording medium by ejecting ink droplets thereon. Such recording apparatus is provided with a cartridge accommodating portion. An ink cartridge is insertable into and removable from the cartridge accommodating portion.

Generally, an ink cartridge stores therein ink of a particular color, such as black, cyan, magenta and yellow. That is, each ink cartridge carries particular information in terms of color. In case that a recording apparatus is provided with a plurality of ink cartridge accommodating portions, there may be chances that an ink cartridge for black is inadvertently mounted in the cartridge accommodating portion adapted to accommodate an ink cartridge for cyan.

There has been proposed a recording apparatus that can detect wrong installation of ink cartridges. This recording apparatus can determine types of mounted ink cartridges by reading individual identification stored in an IC chip attached to each ink cartridge. Another proposed recording apparatus can detect types of mounted ink cartridges by detecting values of a resistor attached to each ink cartridge in order to detect wrong installation of the ink cartridges (Japanese Patent Application Publication No. H06-262771, for example).

There has been proposed another type of recording apparatus provided with a detection unit using a photointerrupter for detecting a residual amount of ink in an ink cartridge. The ink cartridge used for this recording apparatus is provided with a prism or a sensor arm that enables an intensity of light incident on a photodiode to change in accordance with movement of a shutter based on the residual amount of ink (Japanese Patent Application Publication no. 2005-125738, for example). The recording apparatus can determine whether the residual amount of ink is more than a prescribed amount by detecting a voltage outputted from the photointerrrupter.

However, the provision of the prism or the sensor arm results in a complex mechanical construction in the above-identified ink cartridge. Further, since the resistor or the IC chip needs to be attached to each ink cartridge, not only a complicated configuration becomes necessary for each cartridge, but also production costs of each ink cartridge would inevitably increase.

In view of the forgoing, it is an object of the present invention to provide a simple-structured ink cartridge that enables a recording apparatus to perform detection of a residual amount of ink and a type of the ink cartridge. The present invention also aims to provide a recording apparatus that can detect at least one of a residual amount of ink and a type of an ink cartridge mounted in the recording apparatus.

In order to achieve the above and other objects, the present invention provides an ink cartridge insertable into and removable from a cartridge accommodating section of a recording apparatus. The ink cartridge includes an ink chamber configured to store ink therein; a pyroelectric portion configured to output an electrical signal; and a first electrical interface. The first electrical interface transmits the electrical signal from the pyroelectric portion to the recording apparatus.

Preferably, the pyroelectric portion has a predetermined electrostatic capacitance determinative of a first signal as the electrical signal.

Preferably, the first signal is in a form of pulse trains having a frequency, the frequency being indicative of the electrostatic capacitance of the pyroelectric portion.

Preferably, the pyroelectric portion is charged in accordance with the electrostatic capacitance, the first signal being indicative of a voltage value developed at the pyroelectric portion.

Preferably, the ink cartridge further includes a heater configured to apply heat to the pyroelectric portion. The pyroelectric portion outputs a second signal in response to an amount of heat either applied to or preserved in the pyroelectric portion.

Preferably, the pyroelectric portion outputs the first signal before the second signal.

Preferably, the pyroelectric portion sequentially outputs the first signal and the second signal.

Preferably, the heater comprises an infrared ray emitter configured to apply heat to the pyroelectric portion.

Preferably, the infrared ray emitter is a resistor. And the ink cartridge further includes a heat transfer agent configured to transfer the heat from the resistor to the pyroelectric portion. The pyroelectric portion outputs the second signal in response to the amount of heat either applied thereto from the resistor or preserved in the pyroelectric portion.

Preferably, the infrared ray emitter is an infrared ray emitting diode configured to irradiate infrared ray. The infrared ray emitting diode is disposed to irradiate infrared ray toward the pyroelectric portion, and the pyroelectric portion is configured to output the second signal in response to the amount of heat either applied thereto or preserved in the pyroelectric portion.

Preferably, the pyroelectric portion is disposed to face the infrared ray emitting diode via the ink chamber.

Preferably, the pyroelectric portion is disposed at a position capable of being applied with heat by a heater disposed in the recording apparatus. The heater applies heat to the pyroelectric portion when the ink cartridge is mounted.

Preferably, the heater is a resistor. The pyroelectric portion outputs the second signal in response to the amount of heat either applied thereto from the resistor or preserved in the pyroelectric portion.

Preferably, the heater is an infrared ray emitting diode configured to irradiate infrared ray toward the pyroelectric portion, and the pyroelectric portion is configured to output the second signal in response to the amount of heat either applied thereto or preserved in the pyroelectric portion.

Preferably, the ink cartridge further includes a heat conductor configured to transfer heat between the pyroelectric portion and the ink in the ink chamber and positioned within the ink chamber.

Preferably, the heat conductor is in direct contact with the ink in the ink chamber to conduct heat to the ink when the amount of ink in the ink chamber is more than a predetermined amount.

Preferably, heat is conducted to the pyroelectric portion from the heat conductor when the amount of ink in the ink chamber is less than the predetermined amount and the heat conductor is exposed from the ink in the ink chamber.

According to another aspect of the present invention, there is provided a recording apparatus including: a cartridge accommodating section in which an ink cartridge is mountable; a second electrical interface provided on the cartridge accommodating section; and a controller. The second electrical interface is configured to contact with the first electrical interface when the ink cartridge is mounted in the cartridge accommodating section. The controller is configured to detect at least one of a type of the mounted ink cartridge and an amount of ink in the ink chamber based on the electrical signal outputted from the pyroelectric portion to the recording apparatus via the second electrical interface when the ink cartridge is mounted in the cartridge accommodating section.

Preferably, the controller detects the type of the mounted ink cartridge based on the first signal outputted from the pyroelectric portion via the second electrical interface.

Preferably, the cartridge accommodating section further includes a heater configured to apply heat to the pyroelectric portion, and the controller determines whether the amount of ink in the ink chamber is less than a predetermined amount based on the second signal.

Preferably, the heater is a resistor.

Preferably, the heater is an infrared ray emitting diode configured to irradiate infrared ray toward the pyroelectric portion when the ink cartridge has been mounted in the cartridge accommodating section.

Preferably, the recording apparatus further includes a storage configured to store a threshold value based on which whether the amount of ink in the ink chamber is less than the predetermined amount is determined. The controller determines whether the amount of ink in the ink chamber is less than the predetermined amount by comparing the second signal outputted from the pyroelectric portion with the threshold value stored in the storage.

The ink cartridge of the present invention allows the recording apparatus to determine types of the mounted ink cartridges based on differences in electrostatic capacitance of the pyroelectric portion provided on each ink cartridge. Further, the ink cartridge of the present invention also allows the recording apparatus to determine how much ink is left in each ink cartridge based on differences in the output voltage of the pyroelectric portion. The output voltage of the pyroelectric portion changes depending on an amount of heat applied thereto. The heat-dependent voltage change in the pyroelectric portion results from a change in the amount of ink in each ink cartridge. In other words, only one pyroelectric portion with a simple configuration provided on each ink cartridge enables the recording apparatus to perform two kinds of detection: types of ink cartridges and residual amounts of ink in the ink cartridges.

Fig. 1 is a schematic cross-sectional view of a recording apparatus according to an embodiment of the present invention, in which an ink cartridge according to the embodiment is accommodated in a cartridge mounting section of the recording apparatus; Fig. 2 is a schematic perspective view of the ink cartridge according to the embodiment, wherein the ink cartridge according to the embodiment includes a sensor chip on which a pyroelectric portion having a prescribed electrostatic capacitance is mounted; Fig. 3 is a partially-enlarged vertical cross-sectional view of the ink cartridge according to the embodiment taken along a plane III-III in Fig. 2; Fig. 4 is an electric circuit diagram of a detection scheme configured when the ink cartridge of the embodiment is mounted in the recording apparatus according to the embodiment, wherein the electric circuit is configured of a first detection circuit (RC circuit) and a second detection circuit; Fig. 5 is another electric circuit diagram of a detection scheme configured when the ink cartridge of the embodiment is mounted in the recording apparatus according to the embodiment, wherein the electrical circuit is configured of another first detection circuit (oscillation circuit) and the second detection circuit; Fig. 6 is a block diagram showing an internal control system of the recording apparatus according to the embodiment; Fig. 7A is a flowchart of a process executed for detecting the electrostatic capacitance of the pyroelectric portion using the first detection circuit of Fig. 4; Fig. 7B is a graph showing how each pyroelectric portion is charged in accordance with its electrostatic capacitance during the detection process of Fig. 7A; Fig. 8A is a flowchart of a process executed for detecting the electrostatic capacitance of the pyroelectric portion using the first detection circuit of Fig. 5; Fig. 8B is an explanatory view illustrating with what kind of frequencies pulses are outputted from each pyroelectric portion in accordance with its electrostatic capacitance during the detection process of Fig. 8A; Fig. 9 is a flowchart of a process executed for detecting residual amount of ink in the ink cartridge using the second detection circuit; Fig. 10 is a perspective view of a sensor chip attached to an ink cartridge according to a first modification of the embodiment; Fig. 11 is a partially-enlarged vertical cross-sectional view of an ink cartridge according to a second modification of the embodiment; and Fig. 12 is a partially-enlarged vertical cross-sectional view of an ink cartridge according to a third modification of the embodiment.

40 cartridge accommodating section
44 first electrical interface
45 third electrical interface
60 ink cartridge
61 cartridge casing
71 pyroelectric portion
72 pyroelectric element
73 film electrode
74 sensor board
75 second electrical interface
76 resistor
77 fourth electrical interface
78 heat conductor
81 controller

An ink cartridge 60 according to an embodiment of the present invention and a recording apparatus 1 in which the ink cartridge 60 is detachably mountable will be described with reference to Figs. 1 through 9.

First, a general configuration of the recording apparatus 1 will be described with reference to Fig. 1.

The recording apparatus 1 includes a casing (not shown) within which a printing unit 16, a sheet feed cassette 15 and a discharge tray 17 are provided. The sheet feed cassette 15 accommodates therein recording mediums 14 in a stacked state. The printing unit 16 functions to form an image on each recording medium 14 conveyed from the sheet feed cassette 15. The image-formed recording medium 14 is then discharged onto the discharge tray 17.

The recording apparatus 1 also includes a controller 81 (see Fig. 6) for controlling various operations of the recording apparatus 1. The controller 81 also serves to detect a type and a residual amount of ink of the mounted ink cartridge 60, as will be described later. The term "type" as used herein is intended to mean what kind of ink is contained in the ink cartridge 60, for example. Accordingly, a cyan ink cartridge 60 and a black ink cartridge 60 are treated as different types of ink cartridges in the present embodiment. Instead, ink cartridges 60 storing ink of the same color but made of different chromatic materials may be treated as different types of ink cartridges.

The printing unit 16 includes a conveying section 30, a recording head 20, a cartridge accommodating section 40 and a driving section (not shown).

The conveying section 30 is configured to convey the recording medium 14 accommodated in the sheet feed cassette 15. The conveying section 30 includes a sheet feed roller 32, a pair of conveyor rollers 33, a platen 35 and a pair of discharge rollers 34. The sheet feed roller 32 is configured to convey the recording medium 14 stacked in the sheet feed cassette 15 to a sheet conveying path 31. The pair of conveyor rollers 33 and the pair of discharge rollers 34 are configured to convey the recording medium 14 conveyed by the sheet feed roller 32. The platen 35 is positioned between the pair of conveyor rollers 33 and the pair of discharge rollers 34 in the sheet conveying path 31, as shown in Fig. 1.

The pair of conveyor rollers 33 is configured of a drive roller 33A and a follower roller 33B. The pair of discharge rollers 34 is configured of a drive discharge roller 34A and a follower discharge roller 34B. The drive roller 33A and the drive discharge roller 34A are driven by the driving section (not shown), and the follower roller 33B and the follower discharge roller 34B are configured to rotate following rotation of the drive roller 33A and the drive discharge roller 34A respectively. The recording medium 14 is conveyed over the platen 35 by at least one of the pairs of conveyor rollers 33 and the discharge rollers 34.

The recording head 20 is positioned above the platen 35. The recording head 20 includes a plurality of sub-tanks 21, a plurality of nozzles 22 and a plurality of piezoelectric elements 23 (see Fig. 6).

Each sub-tank 21 serves to temporarily store ink supplied from corresponding ink cartridge 60. The ink stored in each sub-tank 21 is then supplied to the plurality of nozzles 22.

Each nozzle 22 has an ink discharge outlet (not shown) facing toward the platen 35 positioned below. In response to print data, the piezoelectric elements 23 are selectively deformed such that the corresponding nozzles 22 can eject ink therefrom toward the recording medium 14 conveyed over the platen 35. In the present embodiment, the controller 81 controls whether to activate the piezoelectric elements 23 for ejecting the ink from the nozzles 22. The controller 81 may alternatively employ a heater to generate heat for producing bubbles in the ink such that the ink is ejected from the nozzles 22.

The recording head 20 is supported to a carriage (not shown). This carriage is configured to move in a direction perpendicular to a conveying direction of the recording medium 14 (a left-to-right direction in Fig. 1) as well as to a height direction of the recording apparatus 1 (a vertical direction in Fig. 1), that is, in a direction perpendicular to the sheet of Fig. 1. The carriage is driven by the driving section (not shown). An image can be recorded on an entire surface of the recording medium 14 due to the movement of the recording head 20 against the recording medium 14 conveyed to the platen 35 by the conveying section 30.

The driving section (not shown) includes a plurality of motors 19 (Fig. 6) and a driving force transmission mechanism (not shown) for transmitting a driving force of the motors 19 to the conveying section 30 and so on. The motors 19 are driven by a motor drive circuit 85 (also see Fig. 6) that is controlled by the controller 81, as will be described later.

The controller 81 is configured to control movements of the recording head 20 and the carriage. The controller 81 controls the recording medium 14 to intermittently move over the platen 35. While the recording medium 14 is stopped moving on the platen 35, the controller 81 controls the recording head 20 to eject ink droplets onto the recording medium 14 that is stationary on the platen 35 to record an image on the recording medium 14. The controller 81 controls the motors 19 to rotate the pair of discharge rollers 34 in order to discharge the image-recorded recording medium 14 onto the discharge tray 17.

As shown in Fig. 1, the cartridge accommodating section 40 has a box-shaped casing. The casing has one open surface through which the ink cartridges 60 can be inserted. A cover (not shown) is movably provided at the cartridge accommodating section 40 for opening and closing the open surface. The casing has an internal space that is divided into smaller spaces partitioned by a plurality of partitioning walls. The cartridge accommodating section 40 accommodates therein the ink cartridges 60 each storing ink of one of the colors among cyan, magenta, yellow and black.

The cartridge accommodating section 40 includes an ink tube 43 for supplying ink stored in each ink cartridge 60 to the recording head 20, a pair of first electrical interfaces 44 and a pair of third electrical interfaces 45 for achieving electrical connection between each ink cartridge 60 and the cartridge accommodating section 40.

Next, a detailed configuration of the ink cartridge 60 according to the embodiment will be described with reference to Figs. 2 and 3.

The ink cartridge 60 includes a cartridge casing 61 defining therein an ink chamber (not shown) for storing ink, and a sensor chip 70 whose outputs are used for detecting the color (type) and the residual amount of ink in the ink cartridge 60.

As shown in Fig. 2, the cartridge casing 61 has a flat rectangular parallelepiped shape whose thickness is shorter than its depth and height. The cartridge casing 61 is formed, for example, by attaching a film to a frame. When mounted in the cartridge accommodating section 40, the ink cartridge 60 is held in a mounting position shown in Fig. 2.

Hereinafter, terms "upward", "downward", "upper", "lower", "above", "below", "beneath" and the like will be used throughout the description assuming that the ink cartridge 60 is in the mounting position. The cartridge casing 61 has a thickness in a widthwise direction 7, a depth in a depth direction 8 and a height in a height direction 9 perpendicular to the widthwise direction 7 and the depth direction 8. In the embodiment, in the mounting position, the widthwise direction 7 corresponds to a horizontal direction, and the height direction 9 is coincident with the vertical direction of the recording apparatus 1.

The cartridge casing 61 has a surface 61A on which an ink outlet port 65 is formed. In the mounting position, the ink outlet port 65 is connected to the ink tube 43 such that the ink accommodated in the cartridge casing 61 flows into the sub-tank 21 of the same color via the ink tube 43. On the surface 61A, a sensor board 74 of the sensor chip 70 (described next) is fixed. Hereinafter, the surface 61A of the cartridge casing 61 will be referred to as an attachment surface 61A.

On the attachment surface 61A, a pair of positioning claws 63 and a pair of engaging claws 64 are provided for holding the sensor board 74, as shown in Fig. 2. The positioning claws 63 are disposed in separation from each other in the widthwise direction 7. The pair of engaging claws 64 is disposed such that the engaging claws 64 are in separation from each other in the widthwise direction 7 and spaced away from the positioning claws 63 in the height direction 9. Each positioning claw 63 has a base portion and a claw portion 63A protruding from the base portion toward the opposing engaging claw 64. Likewise, each engaging claw 64 has a base portion and a claw portion 64A protruding from the base portion toward the opposing positioning claw 63. The engaging claw 64 is made of a synthetic resin and has a resiliency. For fixing the sensor board 74 on the attachment surface 61A, the engaging claws 64 resiliently deform such that the sensor board 74 can be fitted in a space formed between the positioning claws 63 and the engaging claws 64. The sensor board 74 may be welded to the attachment surface 61A or may be attached to the attachment surface 61A by an adhesive agent.

The sensor chip 70 includes the sensor board 74 and a heat conductor 78.

As shown in Fig. 2, the sensor board 74 includes a pyroelectric portion 71, a resistor (thermoelectronic element) 76, a pair of second electrical interfaces 75, a pair of fourth electrical interfaces 77, and circuit patterns P1, P2.

The sensor board 74 is made of an electrically insulative material such as glass epoxy and ceramics. The sensor board 74 is formed in a rectangular plate shape, having a pair of

flat surfaces

74A, 74B opposing to each other in the depth direction 8. Hereinafter, as shown in Fig. 3, one of the flat surface 74B in direct confrontation with the attachment surface 61A is referred to as a contact surface 74B, whereas another flat surface 74A on which the pyroelectric portion 71 is disposed is referred to as a mounting surface 74A. The sensor board 74 is held to the cartridge casing 61 by being engaged between the pairs of positioning claws 63 and the engaging claws 64. The sensor board 74 corresponds to the claimed heat transfer agent.

The pyroelectric portion 71 is disposed on the mounting surface 74A of the sensor board 74. As shown in Fig. 3, the pyroelectric portion 71 has a three-layered structure, including a film-like pyroelectric element 72 (dielectric material) and a pair of

film electrodes

73A, 73B interposing the pyroelectric element 72 therebetween in the depth direction 8. In Figs. 2 and 3, the pyroelectric element 72 is shown to have a certain thickness, but in reality the pyroelectric element 72 has a thin film-like shape. The pyroelectric portion 71 has a prescribed electrostatic capacitance. The pyroelectric portion 71 is held to the sensor board 74 (the mounting surface 74A) by an insulating thin film, for example, an organic insulation film such as polyimide resin film, or an inorganic insulation film such as SiO₂ thin film and Si₃N₄ thin film.

The pyroelectric element 72 is formed in a rectangular film-like shape and is made of lead zirconium titanate, for example. The pyroelectric element 72 exhibits the pyroelectric effect according to which a change in temperature causes intrinsic polarization. As the pyroelectric element 72, the following pyroelectric materials are available other than lead zirconium titanate: inorganic materials such as lithium titanate, other lead titanate, tourmaline (cyclo-silicate mineral including boron) and lithium tantalate, or organic materials such as triglycine sulfate (TGS) and polyvinylidene fluoride (PVDF).

Each of the

film electrodes

73A, 73B is formed in a rectangular film-like shape, and is vapor-deposited (evaporated) to the pyroelectric element 72. The film electrode 73A, which constitutes a top surface of the pyroelectric portion 71, is made of a NiCr (Nichrome) thin-film whose infrared reflectance is low in order to realize enhanced efficiency in absorption of infrared rays transmitted to the pyroelectric element 72. The film electrode 73B, which is in contact with the mounting surface 74A of the sensor board 74 via the insulating film (not shown), is made of a Pt (platinum) thin film.

The pyroelectric portion 71 is disposed on the mounting surface 74A at a position closer to the pair of engaging claws 64 than to the pair of positioning claws 63 in the height direction 9 (i.e., at an upper portion of the mounting surface 74A in Fig. 2). Each

film electrode

73A, 73B of the pyroelectric portion 71 is connected to the circuit pattern P1 provided on the sensor board 74 by means of wire bonding, for example.

The

film electrodes

73A, 73B are not necessarily vapor-deposited (evaporated) to the pyroelectric element 72. Instead, each of the

film electrodes

73A, 73B may be integrally formed with the circuit pattern P1 and attached to the pyroelectric element 72 by an electrically-conductive adhesive agent or by means of wire bonding.

The film electrode 73A is virtually grounded, as shown in Figs. 4 and 5. The circuit pattern P1 is arranged on the mounting surface 74A such that the circuit pattern P1 has a portion extending in the widthwise direction 7.

The electrostatic capacitance of the pyroelectric portion 71 can vary depending on an electric permittivity of the pyroelectric element 72, a distance between the

film electrodes

73A, 73B (a thickness of the pyroelectric element 72) and an area of the

film electrodes

73A, 73B. In other words, the electrostatic capacitance of the pyroelectric portion 71 can be changed by changing the material constituting the pyroelectric portion 71, or, instead of changing the material, by changing the thickness of the pyroelectric element 72 or the area of the

film electrodes

73A, 73B. In the present embodiment, each ink cartridge 60 is designed to have the pyroelectric portion 71 whose electrostatic capacitance is different from one another, depending on colors of ink or types of chromatic materials of ink stored in the ink cartridges 60. That is, the electrostatic capacitance of each pyroelectric portion 71 can be set to a particular value that is unique (peculiar) to each ink cartridge 60.

The pair of second electrical interfaces 75 is disposed on the mounting surface 74A each at a position closer to the positioning claws 63 than to the engaging claws 64 in the height direction 9 (at a lower portion of the mounting surface 74A) but offset from each positioning claw 63 in the widthwise direction 7. In other words, the second electrical interfaces 75 are exposed on the attachment surface 61A of the cartridge casing 61 at which the ink outlet port 65 is formed. When the ink cartridge 60 is mounted in the cartridge accommodating section 40, the second electrical interfaces 75 are respectively brought into abutment with the first electrical interfaces 44 provided on the cartridge accommodating section 40. Each second electrical interface 75 is connected to either one of the

film electrodes

73A, 73B via the circuit pattern P1, as described earlier.

The resistor 76 is positioned at a substantially center of the mounting surface 74A as an example of the claimed heater or the claimed infrared ray emitter. As the resistor 76, a plate-shaped resistor is used in order to enhance heat conduction to the sensor board 74. The resistor 76 has both widthwise ends in the widthwise direction 7 each connected to either one of the fourth electrical interfaces 77 via the circuit pattern P2, as shown in Fig. 2.

The pair of fourth electrical interfaces 77 is arranged between the pair of second electrical interfaces 75 in the widthwise direction 7 such that the fourth electrical interfaces 77 are disposed in opposition to each other and each at a position offset from the positioning claw 63. In other words, the fourth electrical interfaces 77 are exposed on the attachment surface 61A of the cartridge casing 61 at which the ink outlet port 65 is formed. When the ink cartridge 60 is mounted in the cartridge accommodating section 40, the fourth electrical interfaces 77 are respectively brought into abutment with the third electrical interfaces 45 provided on the cartridge accommodating section 40. Each fourth electrical interface 77 is connected to either one of the widthwise ends of the resistor 76 via the circuit pattern P2. The circuit pattern P2 is arranged on the mounting surface 74A such that the circuit pattern P2 has a portion extending along the circuit pattern P1.

In the present embodiment, the pyroelectric portion 71, the resistor 76, the circuit patterns P1, P2, the second electrical interfaces 75 and the fourth electrical interfaces 77 are all mounted on the mounting surface 74A of the sensor board 74. However, the pyroelectric portion 71 and the resistor 76 may be arranged on the mounting surface 74A, whereas the circuit patterns P1, P2, the second electrical interfaces 75 and the fourth electrical interfaces 77 may be mounted on the contact surface 74B opposite to the mounting surface 74A.

The heat conductor 78 is a thin-plate (or a film-like) shaped member for conducting heat applied from the resistor 76 to the ink stored in the ink chamber. The heat conductor 78 is an example of the claimed heat conductor. As shown in Fig. 2, the heat conductor 78 includes a penetrating portion 78A (as a base portion) and a protruding portion 78B protruding from the penetrating portion 78A.

The penetrating portion 78A penetrates through the attachment surface 61A of the cartridge casing 61 (see Fig. 3) and has a tip end portion from which the protruding portion 78B protrudes downward as shown in Fig. 2.

More specifically, as shown in Fig. 3, the penetrating portion 78A is provided to be in direct contact with the sensor board 74. Alternatively, the penetrating portion 78A may be disposed to be adjacent to the sensor board 74. The protruding portion 78B has a bottom end that is positioned at a lower portion of the cartridge casing 61 in the mounting position. The heat conductor 78 is fabricated by a material having a relatively high thermal conductivity, such as copper foil and aluminum foil. As such, since formed as a thin-plate made of a material having a high thermal conductivity, the heat conductor 78 is allowed to have an improved thermal conductivity.

The heat conductor 78 serves to conduct heat applied from the resistor 76, via the sensor board 74, to the ink stored in the ink chamber defined in the cartridge casing 61.

More precisely, the heat applied from the resistor 76 is conducted to both of the heat conductor 78 and the pyroelectric portion 71. When there is a sufficient amount of ink remaining in the ink chamber, the heat conducted (transferred) to the heat conductor 78 via the sensor board 74 is conducted to the ink since the heat conductor 78 is generally soaked in the ink. At the same time, the pyroelectric portion 71 is also applied with heat from the resistor 76 either via the sensor board 74 (heat transfer or thermal conduction) or via an air layer existing between the resistor 76 and the pyroelectric portion 71 (heat radiation). In other words, the sensor board 74 and the air layer function as a medium for transferring heat (heat transfer agent). But the pyroelectric portion 71 is cooled down by the ink stored in the ink chamber since the sufficient amount of ink can absorb the heat conducted to the pyroelectric portion 71 in addition to the heat directly conducted from the heat conductor 78. The pyroelectric portion 71 therefore exhibits little change in temperature.

In other words, when the amount of ink is sufficient, the heat generated at the resistor 76 can be ultimately released to the ink, thereby suppressing heat from being conducted to the pyroelectric portion 71. The amount of heat conducted to the pyroelectric portion 71 when a current flows into the resistor 76 is smaller than that conducted to the ink, since the amount of heat conducted to the ink is a combination of the amount of heat conducted directly from the heat conductor 78 and the amount of heat conducted from the pyroelectric portion 71 via the sensor board 74. Since little amount of heat is applied, the pyroelectric portion 71 has preserved little amount of heat to develop a voltage between the

film electrodes

73A, 73B.

However, when the amount of ink in the ink chamber becomes smaller, the heat conductor 78 gradually starts to be exposed from the ink. When the ink further decreases and the bottom end of the heat conductor 78 is completely exposed from the ink, heat can no longer be conducted to the ink from the heat conductor 78. As a result, the heat conducted to the heat conductor 78, which had been conducted to the ink while the heat conductor 78 was in contact with the ink, is now conducted to the pyroelectric portion 71 via the sensor board 74. Likewise, the heat conducted to the pyroelectric portion 71 can no longer be conducted to the ink, either. Therefore, the temperature of the pyroelectric portion 71 starts to rise due to the heat conducted from the resistor 76 and the heat transferred from the heat conductor 78 via the sensor board 74.

In other words, the greater amount of heat is now conducted to the pyroelectric portion 71 than to the heat conductor 78 exposed from the ink, causing the temperature of the pyroelectric portion 71 to increase significantly. As a result, due to the pyroelectric effect, a voltage is developed between the pair of

film electrodes

73A, 73B. The voltage is then outputted to the controller 81 for detecting the residual amount of ink in the ink cartridge 60.

In this way, since the protruding portion 78B extends in the height direction 9 to have its bottom end positioned at the lower portion of the cartridge casing 61 in the mounting position, the recording apparatus 1 can detect that the amount of ink left in the cartridge casing 61 falls below a prescribed amount by detecting the output voltage from the pyroelectric portion 71.

Next, an electrical connection between the mounted ink cartridge 60 and the recording apparatus 1 (serving as a detection scheme 50) will be described with reference to Figs. 4 and 5.

The detection scheme 50 is configured of a first detection circuit 51, a second detection circuit 52 and a toggle switch 53. The first detection circuit 51 is provided for detecting the electrostatic capacitance of the pyroelectric portion 71 to thereby identify the type (color) of the ink cartridge. It should be noted that the pyroelectric portion 71 is electrically equivalent to a capacitor. In the description of the circuits shown in Figs. 4 and 5, the pyroelectric portion 71 may be referred to as a capacitor 71 where necessary. The second detection circuit 52 is provided for detecting the voltage developed across the capacitor 71 to thereby indicate the residual amount ink in the ink cartridge 60. The toggle switch 53 is illustrated to include a first-detection side fixed contact, a second-detection side fixed contact, and a wiper contact that can trip between the two fixed contacts. The first detection circuit 51 or the second detection circuit 52, whichever is selected by the switch 53, is connected to the pyroelectric portion 71. The switch 53 is operated in accordance with signals from the controller 81. An electromagnetic switch or a semiconductor switch is available as the switch 53.

The first detection circuit 51 is closed when the wiper contact of the switch 53 is toggled to the first-detection side contact. The first detection circuit 51 is configured of the capacitor 71, and a resistor R1 having one terminal connected to the non-grounded side electrode 73B of the capacitor 71 and another terminal connected to a first drive circuit 82. As will be described later with reference to Fig. 6, the first drive circuit 82 is a part of a control circuit 80 and outputs, under the aegis of the controller 81, a pulse signal having a voltage level V_IN with a predetermined duration. A totem-pole output circuit well known in the art can be used for the first drive circuit 82. An output from the first detection circuit 51 is derived from an output terminal V1_OUT connected to a node between the resistor R1 and the none-grounded side electrode 73B of the capacitor 71.

The first detection circuit 51 forms an RC circuit in which the capacitor 71 is gradually charged in response to the pulse signal applied from the first drive circuit 82. The voltage developed across the capacitor 71 is detected at a relevant time t1 before the capacitor is fully charged and the resultant voltage is outputted to an A/D converter 89 (described later) of the controller 81 through the output terminal V1_OUT. In the transition period before the capacitor 71 is fully charged, the voltage across the capacitor 71 differs depending upon the electrostatic capacitance. The voltage across the capacitor 71 and the electrostatic capacitance thereof are in an exponential curve relation. More specifically, the smaller the electrostatic capacitance is, the higher the voltage is developed across the capacitor. Among capacitors different in electrostatic capacitance, the capacitor with the smallest electrostatic capacitance C1 develops the highest voltage thereacross and the capacitor with the second smallest electrostatic capacitance C2 develops the second highest voltage thereacross at time t1 as shown in Fig. 7B. The difference delta V between the highest and the second highest voltages enables the two types of capacitors different in electrostatic capacitance to distinguish. The above-described voltage-and-capacitance relation is true with respect to the remaining two capacitors having electrostatic capacitances C3 and C4 shown in Fig. 7B. Thus, the type (color) of the ink cartridge 60 can be identified by the voltage detected at time t1.

The second detection circuit 52 is closed when the wiper contact of the switch 53 is toggled to the second-detection side contact. The second detection circuit 52 is configured of a DC power source E, resistors R2, R3, and a field-effect transistor (FET). The second detection circuit 52 serves as an amplifier circuit. More specifically, the FET has a gate to which a voltage developed across the resistor R2 is applied, a drain connected to one terminal of the resistor R3, and a source connected to the negative terminal of the DC power source E. The resistor R3 is connected between the positive terminal of the DC power source E and the drain of the FET. The output terminal V2_OUT is derived from a node connecting the resistor R3 and the drain of the FET. In operation, when a voltage is applied to the gate of the FET, the latter is rendered conductive and its ON resistance changes depending upon the gate voltage. The voltage derived from the output terminal V2_OUT is amplified with respect to the gate voltage equal to the voltage developed across the capacitor 71. In this way, the output voltage generated at the pyroelectric portion 71 due to heat conducted from the resistor 76 is amplified by the amplifier circuit and then outputted to the controller 81 for detection of the residual amount ink in the ink cartridge 60.

Fig. 5 shows another example of the first detection circuit. In this example, an oscillation circuit is used in the first detection circuit and is referred to either as a first detection circuit 54 or an oscillation circuit 54. The configuration of the second detection circuit 52 is the same as that shown in Fig. 4. The first detection circuit (oscillation circuit) 54 shown in Fig. 5 includes the capacitor 71, a resistor R4 and an inverter (INV). The resistor R4 and inverter are connected in parallel and this parallel-connection circuit is connected to the non-grounded side electrode 73B of the capacitor 71. The output of the inverter is used as the output V1_OUT of the first detection circuit 54. The first detection circuit (oscillation circuit) 54 generates pulse trains having a frequency determined depending upon the electrostatic capacitance of the capacitor 71. Therefore, the frequency of the pulse trains can identifies the color or type of the cartridge 60.

The inverter has two threshold values V_T+ and V_T- where V_T+ is greater than V_T-. Before turning on a power source (not shown) of the oscillation circuit 54, no electric charges are accumulated in the capacitor 71, so that the voltage across the capacitor 71 is zero. In this case, the input to the inverter is treated as being at a low level and thus the output of the inverter is at a high level. When the capacitor 71 is gradually charged and the voltage across the capacitor 71 has reached the upper threshold value V_T+, then the input to the inverter is treated as being changed from the low level to the high level, causing the output of the inverter to change from the high level to a low level. The electric charges accumulated in the capacitor 71 are then discharged through the resistor R4 and the voltage across the capacitor 71 is gradually lowered. When the voltage across the capacitor 71 has lowered to the lower threshold value V_T-, the input to the inverter is treated as being changed from the high level to the low level, causing the inverter output to change from the low level to the high level. In this way, pulse trains are outputted from the output terminal V1_OUT of the oscillation circuit 54 to the A/D converter 89. The frequency of the pulse trains outputted therefrom changes depending upon the electrostatic capacitance of the capacitor 71. Accordingly, the ink cartridges having their own electrostatic capacitance can be identified from the frequency of the oscillated pulse trains.

Next, an internal control system of the recording apparatus 1 will be described with reference to Fig. 6.

The recording apparatus 1 includes the control circuit 80 which controls power supply to the first detection circuit 51, the resistor 76, the motors 19 and the piezoelectric elements 23.

The control circuit 80 includes the controller 81, the motor drive circuit 85 for driving the motors 19, a piezoelectric element drive circuit 86 for driving the piezoelectric elements 23, the first drive circuit 82 for driving the first detection circuit 51, and a second drive circuit 83 for supplying power to the resistor 76. The controller 81 controls whether to drive the first drive circuit 82, the second drive circuit 83, the motor drive circuit 85 and the piezoelectric element drive circuit 86.

The controller 81 includes a storage 84, a timer 87, a counter 88 and the A/D converter 89. The storage 84 stores therein a first determination table and a second determination table. The first determination table contains predetermined values (to be referred to as first values) for determining types of the ink cartridges 60 mounted in the cartridge accommodating section 40. The second determination table contains a prescribed value (to be referred to as a second value) as a threshold value for determining the residual amount of ink in each ink cartridge 60. The A/D converter 89 serves to convert analog signals outputted from the first detection circuit 51 into digital signals. The timer 87 and the counter 88 will be necessary when the recording apparatus 1 performs detection of the type of the ink cartridge 60 mounted therein and detection of the residual amount of ink in the ink cartridge 60, as will be described next.

How the recording apparatus 1 will determine the type (color) of the ink cartridge 60 mounted therein will first be described. In the present embodiment, the detection of the electrostatic capacitance of the pyroelectric portion 71 is performed using the first detection circuit 51 shown in Fig. 4. However, as described earlier, the electrostatic capacitance of the pyroelectric portion 71 can also be detected by using the oscillation circuit 54 shown in Fig. 5. Hereinafter, therefore, a process for detecting the electrostatic capacitance of the pyroelectric portion 71 using the first detection circuit 51 of Fig. 4 will first be described with reference to Figs. 7A and 7B. Then, another process for detecting the electrostatic capacitance of the pyroelectric portion 71 using the first detection circuit (oscillation circuit) 54 of Fig. 5 will be described with reference to Figs. 8A and 8B.

Referring to Fig. 7A, when a cover (not shown) of the cartridge accommodating section 40 is opened for replacing the ink cartridge 60 with a new one, a process for detecting the electrostatic capacitance of the pyroelectric portion 71 of the newly mounted ink cartridge 60 is initiated. This process does not proceed, however, until the cover is closed (S1:NO). When the cover is closed (S1:YES), the switch 53 closes the first detection circuit 51 to be operative and the controller 81 controls the first drive circuit 82 to apply a voltage V_IN to the first detection circuit 51. The first drive circuit 82 applies the stepped voltage V_IN to the first detection circuit 51 (S2). Due to the voltage V_IN applied to the pyroelectric portion 71, the latter is gradually charged.

Fig. 7B shows how each pyroelectric portion 71 corresponding to each color is charged depending on the electrostatic capacitance thereof. In Fig. 7B, each pyroelectric portion 71 associated with each color is given an electrostatic capacitance C1, C2, C3 and C4, where C1 is the smallest, while C4 is the greatest. The electrostatic capacitance C1 represents the ink cartridge 60 for black, C2 for yellow, C3 for cyan and C4 for magenta. As shown in Fig. 7B, the voltages V_C1-C4 outputted from the output terminal V1_OUT at time t1 are different from one another depending upon the electrostatic capacitances C1-C4. When the controller 81 detects the voltage V_C1-C4at time t1 in S3, in S4 the controller 81 compares the detected voltage V_C1-C4associated with each electrostatic capacitance C1-C4 with each first value listed in the first determination table and determines in S5 whether the mounted new ink cartridge 60 is proper.

If the detected voltage V_C1-C4does not match any of the first values (S5:NO), the controller 81 determines that the mounted ink cartridge is irrelevant, notifying a user that the irrelevant ink cartridge is mounted, for example, by using a display (S7). If the mounted ink cartridge 60 is determined to be correct (S5:YES), the controller 81 launches various initial operations necessary for the recording apparatus 1 to perform an image recording operation on the recording medium 14, such as positioning of the carriage and an purge operation. At this time, the controller 81 can now move on to the detection of the amount of ink left in the mounted ink cartridge 60 (S6).

Next, the process for detecting the electrostatic capacitance of the pyroelectric portion 71 using the oscillation circuit 54 of Fig. 5 will be described with reference to Figs. 8A and 8B.

As in the detection process of Fig. 7A, the detection of the electrostatic capacitance using the oscillation circuit 54 is initiated when the cover (not shown) of the cartridge accommodating section 40 is opened. Until the cover is closed, the process does not proceed (S101:NO).

When the cover is closed (S101:YES), the switch 53 closes the oscillation circuit 54 to be operative and the controller 81 controls the first drive circuit 82 to apply a voltage V_IN to the oscillation circuit 54 and waits for the oscillation circuit 54 to be stabilized (S102).

Once the oscillation circuit 54 is stabilized, the timer 87 is started and the controller 81 resets the counter 88 (S103). The counter 88 is incremented each time when a rising edge of a pulse is detected (S104, S105), and the controller 81 checks whether a predetermined period of time t2 has elapsed using the timer 87. If the timer 87 indicates that the predetermined period of time t2has not yet elapsed (S106:NO), the controller 81 moves back to S104 to see whether another rising edge of the pulse is detected, and increments the counter 88 by one when detecting another rising edge of the pulse (S105). In this way, the controller 81 continues the steps S104-S106 until the predetermined period of time t2has elapsed.

When the predetermined period of time t2has elapsed (S106:YES), in S107 the controller 81 calculates a frequency (or period) of the pulse trains based on how many times the rising edge of the pulse trains has been counted (i.e. a value of the counter 88) during the predetermined period of time t2.

Fig. 8B shows four kinds of frequencies (waveforms) outputted from the output terminal V1_OUT in accordance with each electrostatic capacitance (i), (ii), (iii) and (iv). As described above, each pulse represented by each wave form is outputted in accordance with the electrostatic capacitance of each pyroelectric portion 71. In other words, detecting the frequency (waveform) of each pulse leads to detection of colors of the mounted ink cartridge 60.

The first determination table stores first values each representing each frequency (waveforms (i) through (iv)) and associated with one of the four colors of black, yellow, cyan and magenta. For example, as shown in Fig. 8B, if the pulse trains outputted from the output terminal V1_OUT are detected to have a frequency represented by the waveform (iii), this means that the color of the mounted ink cartridge 60 is determined to be cyan.

In S108, the controller 81 compares the detected frequency (the value of the counter 88) with the first values stored in the first determination table to determine whether the mounted ink cartridge 60 is proper.

If the detected frequency does not match any of the first values (S109:NO), the controller 81 determines that the mounted ink cartridge is irrelevant, notifying a user that the irrelevant ink cartridge is mounted, for example, by using a display (S112). If the mounted ink cartridge 60 is determined to be correct (S109:YES), the controller 81 launches various initial operations necessary for the recording apparatus 1 to perform an image recording operation on the recording medium 14, such as positioning of the carriage and the purge operation. At this time, the controller 81 can now move on to the detection of the amount of ink left in the mounted ink cartridge 60 (S110).

On the other hand, in S104, if no rising edge is detected (S104:NO), whether the predetermined period of time t2 has elapsed is detected in S111. If the predetermined period of time t2has not yet elapsed (S111:NO), the flow goes back to S104 to see whether the rising edge of the pulse is detected. If no rising edge is detected even after the predetermined period of time t2has elapsed (S111:YES), the controller 81 jumps to S107 to calculate the frequency of the output pulse.

A process to detect the residual amount of ink is configured to be initiated after the ink cartridge 60 mounted in the cartridge accommodating section 40 is determined to be proper (after S6 or S110), or an image forming operation is instructed by the user. Hereinafter, the process for detecting the residual amount of ink will be described with reference to Fig. 9.

When the residual amount of ink detection is initiated, the controller 81 controls the switch 53 such that the pyroelectric portion 71 is connected to the second detection circuit 52 (S201). The controller 81 then controls the second drive circuit 83 to supply power to the resistor 76 (S202). In S203, the timer 87 is started. Once the timer 87 starts to run, in S204 the controller 81 detects a voltage V_Noutputted from the output terminal V2_OUTand calculates a sum voltage V_SUM, which is a sum of the latest output voltage V_N and a voltage V_N-1 outputted immediately before the output voltage V_N, until a predetermined period of time t3 has elapsed.

When the predetermined period of time t3 elapsed (S205:YES), the controller 81 compares the sum voltage V_SUM with the second value (threshold value) stored in the second determination table in S206 to determine whether or not the residual amount of ink is smaller than a prescribed amount (i.e., whether or not the ink cartridge 60 is near empty). The sum voltage V_SUM becomes greater than the second value in S207 when the residual amount of ink is smaller than the prescribed amount since the liquid surface of the ink left in the mounted ink cartridge 60 falls below the bottom end of the protruding portion 78B of the heat conductor 78 (i.e., the heat conductor 78 is exposed from the ink). In other words, the heat generated at by the resistor 76 is no longer absorbed by the ink, but is conducted to the pyroelectric portion 71 via the sensor board 74.

When the sum voltage V_SUM is smaller than or equal to the second value (S207:NO), the controller 81 determines in S208 that there still remains enough amount of ink in the mounted ink cartridge 60. The recording apparatus 1 can therefore perform the image recording operation in accordance with instructions inputted by an input button (not shown) or via an external device such as a personal computer.

On the other hand, when the sum voltage V_SUM is greater than the second value (S207:YES), the controller 81 determines that the residual amount of ink is smaller than the prescribed amount (the mounted ink cartridge 60 is near empty). The controller 81 therefore informs the user in S209 that the ink is running out soon and prompts replacement of the mounted ink cartridge 60. When determining that the residual amount of ink is less than the prescribed amount, the controller 81 starts performing a well-known dot-counting, i.e., counting how many dots have been printed, in order to grasp how much more ink is left until the ink is used up. Alternatively, the user may be notified, by the display for example, that the amount of ink is determined to be actually empty.

As described above, the ink cartridge 60 according to the embodiment is given an electrically specific value depending on the electrostatic capacitance of the pyroelectric portion 71. Therefore, the ink cartridge 60 can allow the recording apparatus 1 to determine the type of the mounted ink cartridge 60 by reading the specific value individually determined for each ink cartridge 60. Further, with provision of the resistor 76, the sensor board 74 and the heat conductor 78, the ink cartridge 60 according to the embodiment can change the output voltage from the pyroelectric portion 71 depending on whether or not the residual amount of ink is less than the prescribed amount. Therefore, the recording apparatus 1 can determine whether the residual amount of ink is less than or not less than the prescribed amount based on the voltage outputted from the pyroelectric portion 71. In other words, the ink cartridge 60 according to the embodiment enables the recording apparatus 1 to determine both the type and the residual amount of the ink cartridge 60 mounted in the recording apparatus 1. That is, with such a simple circuit configuration attached to the ink cartridge 60, the recording apparatus 1 of the present embodiment can detect not only the type of the ink cartridge 60 mounted therein but also whether the residual amount of ink in the mounted ink cartridge 60 is less than the prescribed amount.

Further, in the present embodiment, the heat conductor 78 can serve to suppress the voltage output from the pyroelectric portion 71 as long as the residual amount of ink is more than or equal to the prescribed amount. In other words, the provision of the heat conductor 78 can enlarge the difference in the voltage output of the pyroelectric portion 71 depending on whether or not the residual amount of ink is less than the prescribed amount. Therefore, the recording apparatus 1 can determine, with accuracy, whether or not the residual amount of ink is less than the prescribed amount.

Further, in the present embodiment, a portion of the heat conductor 78 is positioned within the cartridge casing 61 and is in direct contact with the ink. Therefore, the ink cartridge 60 enables the recording apparatus 1 to detect, with further accuracy, whether or not the residual amount of ink is less than the prescribed amount. Alternatively, the heat conductor 78 may be brought into contact with the ink indirectly via a film, for example. Still alternatively, the heat conductor 78 can be dispensed with. When the heat conductor 78 is not provided, the sensor board 74 may be brought into direct contact with the ink.

Further, the recording apparatus 1 of the present embodiment is provided with the detection scheme 50 and the controller 81 so that the recording apparatus 1 can detect the type of the mounted ink cartridge 60 as well as the residual amount of the ink in the mounted ink cartridge 60. The recording apparatus 1 of the present embodiment can also detect wrong installation of the ink cartridge 60 and prompt the user to replace the mounted ink cartridge 60.

Further, the pyroelectric portion 71, the resistor 76, the second electrical interfaces 75 and the fourth electrical interfaces 77 are all mounted on the sensor board 74 to form a single chip. Therefore, the configuration of the ink cartridge 60 can be made simpler.

Further, the switch 53 is provided for enabling either one of the first detection circuit 51 or the second detection circuit 52 to be switched and connected to the pyroelectric portion 71. Therefore, depending on what is to be detected, switching between the first detection circuit 51 and the second detection circuit 52 can be performed to obtain the desired output voltage at the pyroelectric portion 71, leading to accurate detection of the output voltage at the pyroelectric portion 71. Occurrence of wrong detection can therefore be reduced.

Further, the electrostatic capacitance of the pyroelectric portion 71 is detected at the RC circuit (the first detection circuit 51) in the present embodiment. The first detection circuit 51 can be formed simply by connecting the resistor R1 to the pyroelectric portion 71. The configuration of the first detection circuit 51 is thus simpler. Further, the first detection circuit 51 and the second detection circuit 52 share the pyroelectric portion 71 to form an electrical circuit configuration that allows the electrostatic capacitance and the output voltage of the pyroelectric portion 71 to be detected. Such circuit configuration enables at least one of color identification and residual amount of ink to be detected.

Note that in the present embodiment, the pyroelectric portion 71 can become compact, being formed of the thin film-like shaped pyroelectric element 72 and the

film electrodes

73A, 73B. However, the present invention is not limited to this configuration. For example, as long as the pyroelectric portion 71 can serve as a capacitor to have a prescribed electrostatic capacitance and to generate the pyroelectric effect, the shape and the size of the pyroelectric portion 71 can be changed appropriately.

Instead of the resistor 76 of the present embodiment, a material capable of generating heat when applied with a current, or an infrared-emitting diode may be used as a heater.

Further, in the present embodiment, the heat conductor 78 (the penetrating portion 78A) penetrates the cartridge casing 61 (the attachment surface 61A) so as to realize heat conduction from the resistor 76 to the ink. However, the heat conductor 78 may have a size, a shape and a location different from those of the present embodiment, provided that the heat conductor 78 can change the amount of heat to be transmitted from the resistor 76 to the pyroelectric portion 71 in accordance with the residual amount of ink in the ink cartridge 60.

Further, although the RC circuit (the first detection circuit 51) and the CR oscillation circuit (the first detection circuit 54) are employed for detecting the electrostatic capacitance of the pyroelectric portion 71, other well-known detection circuits may be employed as the first detection circuit 51, as long as the electrostatic capacitance of the pyroelectric portion 71 can be detected.

Further, the amplifier circuit using the FET is used as the second detection circuit 52 for detecting the output voltage of the pyroelectric portion 71 in the present embodiment. However, other amplifier circuits, such as one including an operational amplifier may be employed. A noise filter may be provided for removing noises generated at the amplifier circuit.

Further, although the heat conductor 78 of the present embodiment includes the penetrating portion 78A and the protruding portion 78B, the heat conductor 78 may be formed in a rod-like shape or a thin plate-like (or film-like) shape extending in the horizontal direction. With this configuration, an area of contact between the heat conductor 78 and the ink can vary significantly depending on whether the residual amount of ink is less than or not less than the prescribed amount. As a result, the recording apparatus 1 can readily and accurately detect that the residual amount of ink is less than the prescribed amount.

Further, although the recording apparatus 1 according to the embodiment detects whether or not the residual amount of ink is less than the predetermined amount, the recording apparatus 1 may be configured to determine the residual amount of ink at multiple stages instead of one. In this case, the second determination table prestores a plurality of predetermined values (second values) associated with a plurality of levels of the amount of ink in the ink cartridge 60.

Various modifications are conceivable.

Fig. 10 shows a sensor board 174 of a sensor chip 170 attached to an ink cartridge 160 according to a first modification of the present embodiment.

In the first modification, the resistor 76 mounted on the sensor board 74 of the embodiment is now provided on the cartridge accommodating section 40 and referred to as a resistor 176 (not shown).

The sensor board 174 of the first modification is formed with a heat receiving area 179 with which the resistor 176 disposed on the cartridge accommodating section 40 is brought into direct contact when the ink cartridge 160 is mounted in the cartridge accommodating section 40. Note that, the resistor 176 may not necessarily be in direct contact with the heat receiving area 179, but a separate member to which heat from the resistor 176 is conducted may also be provided so as to be in contact with the heat receiving area 179.

Since the resistor 176 is provided in the cartridge accommodating section 40, the fourth electrical interfaces 77 of the embodiment are no longer necessary to be provided at the sensor board 174 in the first modification. Therefore, the sensor board 174 of the first modification can realize a configuration simpler than that of the sensor board 74 of the embodiment. As a result, the configuration of the ink cartridge 160 can also be made simpler.

Fig. 11 shows a sensor board 274 mounted on an ink cartridge 260 according to a second modification of the embodiment.

Instead of the resistor 76 of the embodiment, an infrared-ray emitting diode 294 is provided as the claimed heater or the claimed infrared ray emitter in the second modification. The infrared-ray emitting diode 294 may be arranged on the sensor board 274, or on the cartridge accommodating section 40. The infrared-ray emitting diode 294 is adapted to irradiate infrared ray directly toward the pyroelectric portion 71, more specifically, to a side surface of the pyroelectric portion 71 or to the film electrode 73A (the top surface of the pyroelectric portion 71). When the infrared ray irradiated from the infrared-ray emitting diode 294 is incident on the pyroelectric portion 71, heat is generated at the pyroelectric portion 71 (heat radiation). Due to an air layer existing between the pyroelectric portion 71 and the infrared-ray emitting diode 294, the air layer also serves a medium for conducting heat.

The sensor board 274 is disposed such that the sensor board 274 is in direct contact with the ink accommodated within the cartridge casing 61, as shown in Fig. 11. Therefore, heat applied to the pyroelectric portion 71 due to incidence of the infrared ray thereon can be released to the ink via the sensor board 274. Alternatively, the heat conductor 78 may also be provided within the ink cartridge 260, as in the embodiment. If this is the case, the heat applied to the pyroelectric portion 71 due to incidence of infrared ray can be released to the ink via the sensor board 274 and the heat conductor 78.

In the second embodiment, a control circuit 280 includes a diode drive circuit (not shown), instead of the second drive circuit 83, for driving the infrared-emitting diode 294. The diode drive circuit can be a constant voltage circuit or a constant current circuit.

When detecting the residual amount of ink in the ink cartridge 260, the controller 81 drives the infrared-ray emitting diode 294 to irradiate the infrared ray to the pyroelectric portion 71, as shown in a dotted line in Fig. 11. When there is enough ink left in the ink cartridge 260, the pyroelectric portion 71 can be cooled down by the ink even if the pyroelectric portion 71 is applied with heat resulting from incidence of infrared ray on the pyroelectric portion 71. Therefore, there is little change in temperature of the pyroelectric portion 71, and few output voltage is produced at the pyroelectric portion 71.

When the amount of ink decreases to fall below the prescribed amount, the pyroelectric portion 71 no longer contacts the ink and therefore cannot be cooled down by the ink. As a result, the temperature of the pyroelectric portion 71 starts rising and the polarization structure of the pyroelectric portion 71 is caused to change, developing a voltage between the

film electrodes

73A, 73B. In this way, the voltage outputted from the pyroelectric portion 71 changes in accordance with a change in the amount of ink in the ink cartridge 260. The controller 81 detects the output voltage of the pyroelectric portion 71 by using the second detection circuit 52, and determines how much ink is left in the ink cartridge 260. In the second modification, determination on the type of the ink cartridge 260 is performed in the same manner as in the embodiment.

Fig. 12 shows a sensor board 374 and an infrared-ray emitting diode 394 provided in an ink cartridge 360 according to a third modification of the embodiment.

In the third modification, a pyroelectric portion 371 and the infrared-ray emitting diode 394 constitute a photointerrupter. More specifically, as show in Fig. 12, the pyroelectric portion 371 is disposed on a contact surface 374B of the sensor board 374 to face the infrared-ray emitting diode 394 such that the ink stored within a cartridge casing 361 is interposed between the pyroelectric portion 371 and the infrared-ray emitting diode 394 when the amount of ink is more than or equal to the prescribed amount. In the third modification, walls of the cartridge casing 361 are formed of a resin or a film capable of transmitting light.

When the sufficient amount of ink is left in the cartridge casing 361, the infrared ray emitted from the infrared-ray emitting diode 394 is absorbed or reflected by the ink. Therefore, little infrared ray can be incident on the pyroelectric portion 371 and no output voltage is produced at the pyroelectric portion 371. However, the residual amount of ink becomes less than the prescribed amount, the infrared ray irradiated from the infrared-ray emitting diode 394 is neither absorbed nor reflected by the ink, but incident on the pyroelectric portion 371. As a result, the pyroelectric portion 371 produces an output voltage.

In the third modification, a control circuit 380 includes a diode drive circuit (not shown) for driving the infrared-ray emitting diode 394, instead of the second drive circuit 83, as in the second modification. The controller 81 controls the diode drive circuit to drive the infrared-ray emitting diode 394 to emit an infrared ray toward the pyroelectric portion 371 and subsequently detects the output voltage or a rate of change in the output voltage of the pyroelectric portion 371 by the second detection circuit 52, thereby making a determination on whether the residual amount of ink in the ink cartridge 360 is less than or not less than the prescribed amount. Determination on the type of the ink cartridge 360 is performed in the same manner as in the embodiment.

Although the present invention has been described with respect to the specific embodiment and modifications, it will be appreciated by one skilled in the art that a variety of changes may be made without departing from the scope of the invention.

The ink cartridge of the present invention is widely applicable to inkjet type printers for home and office uses.

Claims

An ink cartridge (60, 160, 260, 360) configured to be mounted in a recording apparatus (1), the ink cartridge comprising:
an ink chamber configured to store ink therein;
a pyroelectric portion (71, 371) configured to output an electrical signal; and
a first electrical interface (75) configured to transmit the electrical signal from the pyroelectric portion (71, 371) to the recording apparatus (1).
The ink cartridge according to claim 1, wherein the pyroelectric portion (71, 371) has an electrostatic capacitance determinative of a first signal as the electrical signal.
The ink cartridge according to claim 2, wherein the first signal is in a form of pulse trains having a frequency, the frequency being indicative of the electrostatic capacitance of the pyroelectric portion (71).
The ink cartridge according to claim 2, wherein the pyroelectric portion (71) is charged in accordance with the electrostatic capacitance, the first signal being indicative of a voltage value developed at the pyroelectric portion (71).
The ink cartridge according to claim 2, further comprising a heater (76, 294, 394) configured to apply heat to the pyroelectric portion (71, 371), the pyroelectric portion (71, 371) outputting a second signal in response to an amount of heat either applied to or preserved in the pyroelectric portion (71, 371).
The ink cartridge according to claim 5, wherein the pyroelectric portion (71, 371) outputs the first signal before the second signal.
The ink cartridge according to claim 5, wherein the pyroelectric portion (71, 371) sequentially outputs the first signal and the second signal.
The ink cartridge according to claim 5, wherein the heater comprises an infrared ray emitter configured to apply heat to the pyroelectric portion (71, 371).
The ink cartridge according to claim 8, wherein the infrared ray emitter is a resistor (76), and
wherein the ink cartridge further comprises a heat transfer agent (74) configured to transfer the heat from the resistor to the pyroelectric portion (71), the pyroelectric portion (71) outputting the second signal in response to the amount of heat either applied thereto from the resistor (76) or preserved in the pyroelectric portion (71, 371).
The ink cartridge according to claim 8, wherein the infrared ray emitter is an infrared ray emitting diode (294, 394) configured to irradiate infrared ray, the infrared ray emitting diode (294, 394) being disposed to irradiate infrared ray toward the pyroelectric portion (71, 371), and
wherein the pyroelectric portion (71, 371) is configured to output the second signal in response to the amount of heat either applied thereto or preserved in the pyroelectric portion (71, 371).
The ink cartridge according to claim 10, wherein the pyroelectric portion (371) is disposed to face the infrared ray emitting diode (394) via the ink chamber.
The ink cartridge according to claim 1, wherein the pyroelectric portion (71) is disposed at a position capable of being applied with heat by a heater (176, 294) disposed in the recording apparatus, the heater (176, 294) applying heat to the pyroelectric portion (71) when the ink cartridge is mounted.
The ink cartridge according to claim 12, wherein the heater is a resistor (176), the pyroelectric portion (71) outputting the second signal in response to the amount of heat either applied thereto from the resistor (176) or preserved in the pyroelectric portion (71).
The ink cartridge according to claim 12, wherein the heater is an infrared ray emitting diode (294) configured to irradiate infrared ray toward the pyroelectric portion (71), and
wherein the pyroelectric portion (71) is configured to output the second signal in response to the amount of heat either applied thereto or preserved in the pyroelectric portion (71).
The ink cartridge according to any one of claims 1 through 14, further comprising a heat conductor (78) configured to transfer heat between the pyroelectric portion (71) and the ink in the ink chamber and positioned within the ink chamber.
The ink cartridge according to claim 15, wherein the heat conductor (78) is in direct contact with the ink in the ink chamber to conduct heat to the ink when the amount of ink in the ink chamber is more than a predetermined amount.
The ink cartridge according to claim 16, wherein heat is conducted to the pyroelectric portion (71) from the heat conductor (78) when the amount of ink in the ink chamber is less than the predetermined amount and the heat conductor (78) is exposed from the ink in the ink chamber.
A recording apparatus (1) comprising:
a cartridge accommodating section (40) in which an ink cartridge (60, 160, 260, 360) according to any one of claims 1 through 17 is mountable;
a second electrical interface (44) provided on the cartridge accommodating section (40) and configured to contact with the first electrical interface (75) when the ink cartridge (60, 160, 260, 360) is mounted in the cartridge accommodating section (40); and
a controller (81) configured to detect at least one of a type of the mounted ink cartridge (60, 160, 260, 360) and an amount of ink in the ink chamber based on the electrical signal outputted from the pyroelectric portion (71) to the recording apparatus (1) via the second electrical interface (44) when the ink cartridge (60, 160, 260, 360) is mounted in the cartridge accommodating section (40).
The recording apparatus according to claim 18, wherein the controller (81) detects the type of the mounted ink cartridge (60, 160, 260, 360) based on the first signal outputted from the pyroelectric portion (71) via the second electrical interface (44).
The recording apparatus according to claim 19, wherein the cartridge accommodating section (40) further includes a heater (176, 294) configured to apply heat to the pyroelectric portion (71), and
wherein the controller (81) determines whether the amount of ink in the ink chamber is less than a predetermined amount based on the second signal.
The recording apparatus according to claim 20, wherein the heater is a resistor (176).
The recording apparatus according to claim 20, wherein the heater is an infrared ray emitting diode (294) configured to irradiate infrared ray toward the pyroelectric portion (71) when the ink cartridge (260) has been mounted in the cartridge accommodating section (40).
The recording apparatus according to claim 20, further comprising a storage (84) configured to store a threshold value based on which whether the amount of ink in the ink chamber is less than the predetermined amount is determined,
wherein the controller (81) determines whether the amount of ink in the ink chamber is less than the predetermined amount by comparing the second signal outputted from the pyroelectric portion (71, 371) with the threshold value stored in the storage (84).