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US-12623453-B2 - Liquid droplet discharging apparatus

US12623453B2US 12623453 B2US12623453 B2US 12623453B2US-12623453-B2

Abstract

A liquid droplet discharging apparatus includes: a channel member having a nozzle and a pressure chamber; an actuator which applies pressure to liquid inside the pressure chamber; and a controller which applies a driving signal to the actuator. Within one discharging cycle, the driving signal includes: a main pulse for causing a liquid droplet to be discharged from the nozzle; and a cancel pulse which is applied to the actuator after the main pulse. In a case that a driving frequency of the driving signal is f (unit: kHz), a time from an end point of the main pulse to a start point of the cancel pulse is Tw (unit: μsec) and a width of the cancel pulse is Tc (unit: μsec), the following expressions (1) and (2) hold: 50≤f≤−11.3×(Tw+Tc)+120 . . . (1); and Tw+Tc≤5.2 . . . (2).

Inventors

  • Takaaki YOSHINO
  • Toru Kakiuchi

Assignees

  • BROTHER KOGYO KABUSHIKI KAISHA

Dates

Publication Date
20260512
Application Date
20231130
Priority Date
20230222

Claims (10)

  1. 1 . A liquid droplet discharging apparatus, comprising: a channel member having a nozzle and a pressure chamber communicating with the nozzle; an actuator configured to apply pressure to liquid inside the pressure chamber; and a controller configured to apply a driving signal to the actuator, wherein within one discharging cycle for forming one dot, the driving signal includes: a main pulse for causing a liquid droplet of the liquid to be discharged from the nozzle; and a cancel pulse which is applied to the actuator after the main pulse, the cancel pulse being a pulse for canceling a pressure wave, inside the pressure chamber, generated by application of the main pulse, the controller is configured to drive the actuator in a pull-strike system of increasing volume of the pressure chamber from a predetermined volume and then decreasing the volume to be not more than the predetermined volume to thereby cause the liquid droplet to be discharged from the nozzle, and in a case that a driving frequency of the driving signal is f (unit: kHz), a time from an end point of the main pulse up to a start point of the cancel pulse is Tw (unit: usec) and a width of the cancel pulse is Tc (unit: usec), the following expressions (1) and (2) hold: 5 ⁢ 0 ≤ f ≤ - 11.3 × ( T ⁢ w + T ⁢ c ) + 120 ; ( 1 ) and Tw + T ⁢ c ≤ 5.2 . ( 2 )
  2. 2 . The liquid droplet discharging apparatus according to claim 1 , wherein the following expression (3) holds: Tc ≤ - 0.4 ⁢ Tw + 4.3 . ( 3 )
  3. 3 . The liquid droplet discharging apparatus according to claim 1 , wherein each of the main pulse and the cancel pulse is rectangular.
  4. 4 . The liquid droplet discharging apparatus according to claim 1 , wherein a recording resolution which is a resolution of an image to be recorded by the liquid droplet is not less than 1200 dpi.
  5. 5 . The liquid droplet discharging apparatus according to claim 4 , wherein the channel member has a plurality of nozzles including the nozzle, the nozzles being aligned in a first direction at a density of not less than 50 dpi and constructing a plurality of nozzle rows arranged side by side in a second direction crossing the first direction, and positions in the first direction of the nozzles are shifted between the nozzle rows.
  6. 6 . The liquid droplet discharging apparatus according to claim 1 , wherein in a case that a width of the main pulse is Tm (unit: usec) and a round trip propagation time of the pressure wave in an individual channel including the pressure chamber and the nozzle is AL (Acoustic Length; unit: μsec), the following expression (4) holds: A ⁢ L × 0 . 7 ≤ T ⁢ m ≤ A ⁢ L × 1.3 . ( 4 )
  7. 7 . The liquid droplet discharging apparatus according to claim 6 , wherein the AL is not more than 6 μsec.
  8. 8 . The liquid droplet discharging apparatus according to claim 1 , wherein a member constructing the nozzle is made of metal.
  9. 9 . The liquid droplet discharging apparatus according to claim 1 , wherein the actuator is a piezoelectric element of a unimorph type.
  10. 10 . The liquid droplet discharging apparatus according to claim 1 , wherein the channel member has a surface in which the pressure chamber is opened, the liquid droplet discharging apparatus further comprises a sealing member arranged on the surface of the channel member and configured to seal the pressure chamber, and the actuator is a stacked body which is adhered to a surface, of the sealing member, on a side opposite to the channel member and which includes a piezoelectric layer and an electrode.

Description

REFERENCE TO RELATED APPLICATIONS This application claims priority from Japanese Patent Application No. 2023-026399 filed on Feb. 22, 2023. The entire content of the priority application is incorporated herein by reference. BACKGROUND ART Conventionally, there is a known ink jetting apparatus (liquid droplet discharging apparatus) configured to apply, to an actuator, a driving signal having a total of three pulse signals which are two jetting pulse signals and one non-jetting pulse signal, with respect to a printing command per one dot (within one discharging cycle). With this, a pressure wave is generated in an ink channel and ink droplets are discharged from a nozzle. SUMMARY In the recent years, the liquid droplet discharging apparatus is required to drive the actuator at a high frequency, from a viewpoint of realizing a high-speed recording. In a case that the frequency of the driving signal is approximately 20 kHz, it is possible to discharge liquid droplets stably from the nozzle by the driving signal in the above-described conventional ink jetting apparatus. In a case that the frequency of the driving signal is raised higher, however, the discharge becomes unstable with the driving signal in the above-described conventional ink jetting apparatus. Further, depending on the configuration of the driving signal, it is not possible to adjust an amount of the liquid droplet discharged from the nozzle, thereby making it impossible to realize any gradation expression (half-toning). An object of the present disclosure is to provide a liquid droplet discharging apparatus capable of realizing the stable discharge and the gradation expression by a driving with a high frequency. According to an aspect of the present disclosure, there is provided a liquid droplet discharging apparatus including: a channel member having a nozzle and a pressure chamber communicating with the nozzle; an actuator configured to apply pressure to liquid inside the pressure chamber; and a controller configured to apply a driving signal to the actuator, wherein within one discharging cycle for forming one dot, the driving signal includes: a main pulse for causing a liquid droplet of the liquid to be discharged from the nozzle; and a cancel pulse which is applied to the actuator after the main pulse, the cancel pulse being a pulse for canceling a pressure wave, inside the pressure chamber, generated by application of the main pulse, the controller is configured to drive the actuator in a pull-strike system of increasing volume of the pressure chamber from a predetermined volume and then decreasing the volume to be not more than the predetermined volume to thereby cause the liquid droplet to be discharged from the nozzle, and in a case that a driving frequency of the driving signal is f (unit: kHz), a time from an end point of the main pulse up to a start point of the cancel pulse is Tw (unit: μsec) and a width of the cancel pulse is Tc (unit: μsec), the following expressions (1) and (2) hold: 50≤f≤−11.3×(Tw+Tc)+120 . . . (1); and Tw+Tc≤5.2 . . . (2). BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view schematically depicting a printer according to an embodiment of the present disclosure. FIG. 2 is a plan view of a head included in the printer. FIG. 3 is a cross-sectional view of the head along a III-III line of FIG. 2. FIG. 4 is a block diagram depicting an electrical configuration of the printer. FIG. 5 is a graph indicating a driving signal to be supplied by a driver IC of the head to an actuator. FIG. 6 is a graph indicating a relationship between Tw+Tc indicated in FIG. 5 and a threshold frequency FI. FIG. 7 is a graph indicating a relationship between Tw+Tc indicated in FIG. 5 and volume of an ink droplet. FIG. 8 is a graph indicating a relationship between Tw and Tc, in a case that an unintended ink droplet is discharged in accordance with application of a cancel pulse Pc depicted in FIG. 5. FIG. 9 is a graph indicating a driving signal according to a modification of the present disclosure. DESCRIPTION As depicted in FIG. 1, a printer 1 according to an embodiment of the present disclosure is provided with a head 3, a carriage 2 capable of moving in a scanning direction (a direction orthogonal to the vertical direction) while holding the head 3, a platen 6 configured to support a paper sheet P below the head 3 and the carriage 2, a conveying mechanism 4 configured to convey the paper sheet P in a conveying direction (a direction orthogonal to the scanning direction and the vertical direction), and a controller 100. A plurality of nozzles 31 is formed in a lower surface of the head 3. The carriage 2 is supported by a pair of guide rails 7 and 8 extending in the scanning direction. In a case that a carriage motor 2M (see FIG. 4) is driven by a control of the controller 100, the carriage 2 is thereby moved in the scanning direction along the pair of guide rails 7 and 8. The conveying mechanism 4 includes two roller pairs 11 and 12 which