Liquid discharge device and head unit

{
  "publication_number": "US9744761B2",
  "country": "US",
  "kind": "B2",
  "title": "Liquid discharge device and head unit",
  "abstract": "A liquid discharge device includes a modulation circuit that generates a modulation signal obtained by pulse-modulating a source signal by self oscillation, a transistor pair which includes a high side transistor and a low side transistor and which generates an amplified modulation signal by amplifying the modulation signal, a demodulator which includes an inductor and a capacitor and which generates a drive signal by smoothing the amplified modulation signal, an piezoelectric element that is displaced when the drive signal is applied, a cavity inside which a liquid droplet is filled and whose internal volume is changed by the displacement of the piezoelectric element, and a nozzle provided to discharge liquid inside the cavity according to the change of the internal volume of the cavity. A distance between the high side transistor and the capacitor is longer than a distance between the inductor and the capacitor.",
  "claims": [
    "1. A liquid discharge device, comprising: a modulation circuit that generates a modulation signal obtained by pulse-modulating a source signal by self oscillation; a transistor pair which includes a high side transistor and a low side transistor and which generates an amplified modulation signal by amplifying the modulation signal; a demodulator which includes an inductor and a capacitor and which generates a drive signal by smoothing the amplified modulation signal; an piezoelectric element that is displaced when the drive signal is applied; a cavity inside which a liquid droplet is filled and whose internal volume is changed by the displacement of the piezoelectric element; and a nozzle provided to discharge liquid inside the cavity according to the change of the internal volume of the cavity, wherein a distance between the high side transistor and the capacitor is longer than a distance between the inductor and the capacitor.",
    "2. The liquid discharge device according to claim 1, wherein the distance between the inductor and the capacitor is longer than or equal to 3 mm.",
    "3. The liquid discharge device according to claim 1, wherein the distance between the inductor and the capacitor is shorter than or equal to 6 mm.",
    "4. The liquid discharge device according to claim 1, wherein a distance between the low side transistor and the capacitor is shorter than a distance between the high side transistor and the capacitor.",
    "5. The liquid discharge device according to claim 1, wherein a frequency of the self oscillation is greater than or equal to 1 MHz and smaller than or equal to 8 MHz.",
    "6. A head unit, comprising: an piezoelectric element that is displaced when a drive signal is applied; a cavity inside which a liquid droplet is filled and whose internal volume is changed by the displacement of the piezoelectric element; and a nozzle provided to discharge liquid inside the cavity according to the change of the internal volume of the cavity, wherein the drive signal is obtained by smoothing an amplified modulation signal by a demodulator including an inductor and a capacitor, the amplified modulation signal is generated by amplifying a modulation signal by a transistor pair including a high side transistor and a low side transistor, the modulation signal is generated by pulse-modulating a source signal by self oscillation of a modulation circuit, and a distance between the high side transistor and the capacitor is longer than a distance between the inductor and the capacitor."
  ],
  "description_excerpt": "The entire disclosure of Japanese Patent Application No. 2015-132438, filed Jul. 1, 2015 is expressly incorporated by reference herein.\n\n1. Technical Field\n\nThe present invention relates to a liquid discharge device and a head unit.\n\n2. Related Art\n\nAs an ink jet printer that prints images and texts by discharging ink, a printer that uses piezoelectric elements is known. The piezoelectric element is provided corresponding to each of a plurality of nozzles in a head unit. Each piezoelectric element is driven according to a drive signal, so that a predetermined amount of ink (liquid) is discharged from a nozzle at a predetermined timing, and a dot is formed. The piezoelectric element is a capacitive load such as a capacitor from an electrical point of view, so that a sufficient amount of current has to be supplied to drive the piezoelectric element of each nozzle.\n\nTherefore, a drive signal amplified by an amplifier circuit is supplied to the head unit to drive the piezoelectric element. As the amplifier circuit, there is a method where a source signal before amplification is amplified by a class AB amplifier. However, this method is not energy-efficient. Therefore, in recent years, a method using a class D amplifier is proposed (see JP-A-2010-114711).",
  "cpc": [
    "B41J 2/04541",
    "B41J 2/0455",
    "B41J 2/04581",
    "B41J 2/04588",
    "B41J 2202/11"
  ],
  "ipc": [
    "B41J 2/045",
    "H10N 30/20",
    "H10N 30/80"
  ],
  "assignees": [
    "Seiko Epson Corp"
  ],
  "inventors": [
    "Dai Nozawa"
  ],
  "filing_date": "2016-05-03",
  "publication_date": "2017-08-29",
  "grant_date": "2017-08-29",
  "priority_date": "2015-07-01",
  "application_number": "US-201615145155-A",
  "family_id": "56555165",
  "cited_by_count": 1,
  "citations": [
    "JP2010114711A",
    "US20120182339A1",
    "JP2013118628A",
    "US20140354352A1",
    "US20130241983A1",
    "US20140285579A1"
  ]
}