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A liquid-amount detecting apparatus detects the amount of a liquid in containers. The liquid-amount detecting apparatus includes a liquid detecting circuit and a determining unit. The liquid detecting circuit includes electrode units disposed so as to be in contact with the liquid in the containers,

A liquid-amount detecting apparatus detects the amount of a liquid in containers. The liquid-amount detecting apparatus includes a liquid detecting circuit and a determining unit. The liquid detecting circuit includes electrode units disposed so as to be in contact with the liquid in the containers, which becomes electrically conductive when in contact with the liquid, an impedance, and an AC-signal source. An AC signal not containing a DC component is input from the AC-signal source to the electrode units through the source impedance, and a signal representing the status of electric connection of the electrode units is output. Furthermore, based on the output signal, a binary signal representing the presence or absence of electrical connection of the electrode units is output. The determining unit determines the presence or absence of the liquid at the electrode units based on the binary signal output from the liquid detecting circuit.

대표청구항 ▼

1. A liquid-amount detecting apparatus for detecting the amount of a liquid contained in at least one container, the liquid detecting apparatus comprising:a liquid detecting circuit comprising an electrode unit formed by a pair of electrodes that is to be disposed in contact at least partially with

1. A liquid-amount detecting apparatus for detecting the amount of a liquid contained in at least one container, the liquid detecting apparatus comprising:a liquid detecting circuit comprising an electrode unit formed by a pair of electrodes that is to be disposed in contact at least partially with the liquid in the container, the pair of electrodes being electrically connected to each other when the pair of electrodes is in contact with the liquid; a source impedance; and an alternating-current signal source;wherein the liquid detecting circuit inputs an alternating-current signal not containing a direct-current component to the electrode unit through the source impedance, outputs a signal representing a status of electrical connection between the pair of electrodes, and outputs a binary signal representing the presence or absence of an electrical connection between the pair of electrodes based on the output signal; anda determining means for determining the presence or absence of the liquid at the electrode unit based on the binary signal output from the liquid detecting circuit and wherein the electrode unit is provided in each of a plurality of containers, and wherein the liquid detecting circuit sequentially outputs, by time division, signals representing a status of electrical connection between each of the respective pairs of electrodes in the plurality of containers.2. A liquid-amount detecting apparatus according to claim 1, wherein the binary signal representing the presence or absence of an electrical connection between the pair of electrodes is output based on a period of the alternating signal generated by the alternating-current signal source.3. A liquid-amount detecting apparatus according to claim 1, wherein the liquid detecting circuit generates a clock signal for outputting the binary signal representing the presence or absence of electrical connection between the pair of electrodes, and exercises control so that the alternating-current signal generated by the alternating-current signal source and the clock signal are synchronized with each other.4. A liquid-amount detecting apparatus according to claim 1, wherein a plurality of the electrode units are provided in the single container and disposed at a plurality of positions in a direction of lowering of a liquid surface in accordance with decrease of the liquid in the container, wherein the liquid detecting circuit outputs binary signals representing the presence or absence of electrical connection between the respective pairs of electrodes, and wherein the determining means determines, in a stepwise manner, the remaining amount of the liquid in the container based on the binary signals associated with the respective pairs of electrodes.5. A liquid-amount detecting apparatus according to claim 1, wherein a plurality of the electrode units are provided in the single container and disposed at a plurality of positions in a direction of lowering of a liquid surface in accordance with decrease of the liquid in the container, wherein the liquid detecting circuit outputs, based on a period of the alternating-current signal generated by the alternating-current signal source, binary signals representing the presence or absence of electrical connection between each respective pair of electrodes, wherein the determining means determines, in a stepwise manner, the remaining amount of the liquid in the container based on the binary signals associated with each respective pair of electrodes, and wherein the alternating-current signal source is connected to the plurality of electrode units such that a connection of the alternating-current signal source with one of the plurality of electrode units can be switched to a connection with another one of the plurality of electrode units, the connection between the alternating-current signal source and each of the plurality of electrode units being switched in synchronization with the period of the alternating-current signal.6. A liquid-amount detecting apparatus according to claim 1, wherein a plurality of the electrode units are provided in the single container and disposed at a plurality of positions in a direction of lowering of a liquid surface in accordance with decrease of the liquid in the container, wherein the liquid detecting circuit outputs binary signals representing the presence or absence of electrical connection between the respective pairs of electrodes, wherein the determining means determines, in a stepwise manner, the remaining amount of the liquid in the container based on the binary signals associated with the respective pairs of electrodes, wherein the liquid detecting circuit generates a clock signal for outputting the binary signals representing the presence or absence of electrical connection between the respective pairs of electrodes, and exercises control so that the alternating-current signal generated by the alternating-current signal source and the clock signal will be synchronized with each other, and wherein the alternating-current signal source is connected to the plurality of electrode units such that a connection of the alternating-current signal source with one of the plurality of electrode units can be switched to a connection with another one of the plurality of electrode units, the connection between the alternating-current signal source and each of the plurality of electrode units being switched in synchronization with the clock signal.7. A liquid-amount detecting apparatus according to claim 1, wherein the electrode unit of the liquid detecting circuit is disposed inside the container, and wherein parts of the liquid detecting circuit other than the electrode unit and the determining means are disposed outside the container.8. A liquid-amount detecting apparatus according to claim 1, wherein a plurality of the electrode units are provided, and wherein impedance characteristics of the plurality of electrode units are common so as to facilitate determination for binarization.9. A liquid-amount detecting apparatus according to claim 1, wherein the liquid detecting circuit outputs the binary signal representing the presence or absence of electrical connection between the pair of electrodes using at least one of a positive-polarity signal and a negative-polarity signal of the alternating-current signal.10. A liquid-amount detecting apparatus according to claim 1, wherein the liquid detecting circuit is allowed to disconnect the alternating-current signal source from a node of the electrode unit to which the alternating-current signal is input.11. A liquid-amount detecting apparatus according to claim 1, wherein the liquid detecting circuit is allowed to disconnect the alternating-current signal source from a node of the electrode unit to which the alternating-current signal is input, and to thereby connect the alternating-current signal source to a grounding point or a connection at a predetermined potential.12. A liquid-amount detecting method for detecting an amount of a liquid contained in at least one container, wherein an alternating-current signal not containing a direct-current component is input from an alternating-current signal source to an unit through a source impedance, the electrode unit being formed by a pair of electrodes that is to be disposed in contact at least partially with the liquid in the container, the pair of electrodes being electrically connected to each other when the pair of electrodes is in contact with the liquid, wherein a signal representing a status of electrical connection between the pair of electrodes is output, wherein a binary signal representing the presence or absence of electrical connection between the pair of electrodes is output based on the output signal, and wherein the presence or absence of the liquid at the electrode unit is determined based on the binary signal, andwherein the electrode unit is provided in each of a plurality of containers, and wherein the liquid detecting circuit sequentially outputs, by time division, signals representing a status of electrical connection between each of the respective pairs of electrodes in the plurality of containers.13. A liquid-amount detecting method according to claim 12, wherein the binary signal representing the presence or absence of electrical connection between the pair of electrodes is output based on a period of the alternating signal generated by the alternating-current signal source.14. A liquid-amount detecting method according to claim 12, wherein a clock signal for outputting the binary signal representing the presence or absence of electrical connection between the pair of electrodes is generated, and wherein control is exercised so that the alternating-current signal generated by the alternating-current signal source and the clock signal will be synchronized.15. A liquid-amount detecting method according to claim 12, wherein a plurality of the electrode units are provided in the single container and disposed at a plurality of positions in a direction of lowering of a liquid surface in accordance with decrease of the liquid in the container, wherein binary signals representing the presence or absence of electrical connection between the respective pairs of electrodes are output, and wherein the remaining amount of the liquid in the container is determined in a stepwise manner based on the binary signals associated with the respective pairs of electrodes.