US-20260124838-A1 - LIQUID DISCHARGE HEAD AND LIQUID DISCHARGE APPARATUS

US20260124838A1US 20260124838 A1US20260124838 A1US 20260124838A1US-20260124838-A1

Abstract

A liquid discharge head includes a discharge unit for discharging liquid, an upstream flow path for supplying liquid to the discharge unit, a downstream flow path for collecting liquid from the discharge unit, and a diaphragm pump for sending liquid in the downstream flow path to the upstream flow path not via the discharge unit. The diaphragm pump includes a pump chamber for functioning as a pump, a suction hole for suctioning the liquid in the downstream flow path into the pump chamber, and a discharge hole for discharging the liquid in the pump chamber to the upstream flow path. The pump chamber is formed with an air bubble discharge hole different from the suction hole and the discharge hole. Air bubbles in the pump chamber are discharged outside through the air bubble discharge hole by reducing a pressure in the air bubble discharge hole.

Inventors

Takeho Miyashita

Assignees

CANON KABUSHIKI KAISHA

Dates

Publication Date: 20260507
Application Date: 20251023
Priority Date: 20241105

Claims (19)

1 . A liquid discharge head comprising: a discharge unit configured to discharge liquid; an upstream flow path configured to supply liquid to the discharge unit; a downstream flow path configured to collect liquid from the discharge unit; and a diaphragm pump configured to send liquid in the downstream flow path to the upstream flow path not via the discharge unit, wherein the diaphragm pump includes a pump chamber configured to function as a pump, a suction hole configured to suction the liquid in the downstream flow path into the pump chamber, and a discharge hole configured to discharge the liquid in the pump chamber to the upstream flow path, wherein the pump chamber is formed with an air bubble discharge hole different from the suction hole and the discharge hole, and wherein air bubbles in the pump chamber are discharged outside through the air bubble discharge hole by reducing a pressure in the air bubble discharge hole.
2 . The liquid discharge head according to claim 1 , wherein the diaphragm pump includes, a first check valve configured to open and close the suction hole, a second check valve configured to open and close the discharge hole, and a third check valve configured to open and close the air bubble discharge hole.
3 . The liquid discharge head according to claim 2 , wherein the diaphragm pump includes, a piezoelectric member configured to deform by applying a voltage, a diaphragm configured to displace along with a deformation of the piezoelectric member, and wherein the pump chamber functions as a pump by varying an inner volume of the pump chamber by a displacement of the diaphragm.
4 . The liquid discharge head according to claim 2 , wherein an opening pressure of the third check valve is larger than an opening pressure of the second check valve.
5 . The liquid discharge head according to claim 4 , wherein the opening pressure of the third check valve is 10 kPa or more.
6 . The liquid discharge head according to claim 2 , wherein the second check valve is in a closed state when the third check valve is in an open state.
7 . The liquid discharge head according to claim 1 , wherein, in a state where the liquid discharge head is in a use state, the air bubble discharge hole is located vertically above the discharge hole.
8 . The liquid discharge head according to claim 1 , wherein, in a state where the liquid discharge head is in a use state, the air bubble discharge hole is located vertically above the suction hole.
9 . The liquid discharge head according to claim 8 , wherein, in a state where the liquid discharge head is in the use state, the air bubble discharge hole is located vertically above the discharge hole.
10 . The liquid discharge head according to claim 1 , further comprising a pressure reduction unit configured to reduce a pressure in the air bubble discharge hole.
11 . The liquid discharge head according to claim 10 , further comprising an air bubble discharge flow path configured to connect the air bubble discharge hole and the pressure reduction unit, wherein the air bubble discharge flow path is provided with a reservoir portion configured to reserve liquid suctioned by the pressure reduction unit.
12 . The liquid discharge head according to claim 10 , wherein the pressure reduction unit is different from the diaphragm pump.
13 . A liquid discharge apparatus comprising: a liquid discharge head including, a discharge unit configured to discharge liquid, an upstream flow path configured to supply liquid to the discharge unit, a downstream flow path configured to collect liquid from the discharge unit, and a diaphragm pump configured to send liquid in the downstream flow path to the upstream flow path not via the discharge unit, wherein the diaphragm pump includes, a pump chamber configured to function as a pump, a suction hole configured to suction the liquid in the downstream flow path into the pump chamber, and a discharge hole configured to discharge the liquid in the pump chamber to the upstream flow path, wherein the pump chamber is formed with an air bubble discharge hole different from the suction hole and the discharge hole, and wherein air bubbles in the pump chamber are discharged outside through the air bubble discharge hole by reducing a pressure in the air bubble discharge hole, and a pressure reduction unit provided outside the liquid discharge head to reduce the pressure in the air bubble discharge hole.
14 . The liquid discharge apparatus according to claim 13 , further comprising an air bubble discharge flow path configured to connect the air bubble discharge hole and the pressure reduction unit, wherein the air bubble discharge flow path is provided with a reservoir portion configured to reserve liquid suctioned by the pressure reduction unit.
15 . The liquid discharge apparatus according to claim 14 , wherein the pressure reduction unit is different from the diaphragm pump.
16 . A liquid discharge head comprising: a discharge unit configured to discharge liquid; an upstream flow path configured to supply liquid to the discharge unit; a downstream flow path configured to collect liquid from the discharge unit; and a diaphragm pump including a pump chamber configured to send liquid in the downstream flow path to the upstream flow path not via the discharge unit, wherein an air bubble discharge flow path is connected to the upstream flow path, wherein air bubbles in the pump chamber are discharged outside through the air bubble discharge flow path via the upstream flow path by causing a pressure in the air bubble discharge flow path to be lower than a pressure in the pump chamber, and wherein the upstream flow path is provided with a regulation valve configured to prevent the liquid from being suctioned to the air bubble discharge flow path from the discharge unit, not via the diaphragm pump.
17 . The liquid discharge head according to claim 16 , further comprising a pressure reduction unit configured to reduce a pressure in the air bubble discharge flow path.
18 . The liquid discharge head according to claim 16 , wherein the upstream flow path is provided with a pressure control chamber, wherein the pressure control chamber adjusts a pressure in a flow path between the pressure control chamber and the discharge unit in the upstream flow path, and wherein the regulation valve is provided between the diaphragm pump and the pressure control chamber in the upstream flow path.
19 . The liquid discharge head according to claim 18 , wherein the air bubble discharge flow path is connected between the diaphragm pump and the regulation valve in the upstream flow path.

Description

BACKGROUND Field of the Technology The present disclosure relates to a liquid discharge head and a liquid discharge apparatus. Description of the Related Art A liquid discharge apparatus includes a liquid discharge head for discharging liquid to achieve a desired purpose thereby. For example, an inkjet recording apparatus is mounted with an inkjet head serving as a liquid discharge head on a carriage to record images, characters, and the like on a recording medium, by discharging ink from a discharge unit included in the ink jet head. Since discharge ports provided in a discharge element substrate for discharging ink contact the ambient air, there is a risk that the ink may evaporate to be thickened and solidified, depending on a type of the liquid (ink). To suppress this risk, there is known a configuration for providing in the liquid discharge head a supply path for supplying liquid to the discharge element substrate, and a collection path for collecting liquid from the discharge element substrate, and circulating the liquid with a circulation pump. By circulating the liquid, since the thickened liquid spreads, it is possible to reduce the risk of the local solidification of the ink. Further, there is also known a configuration in which a diaphragm pump is provided in a liquid discharge head as a circulation pump to effectively circulate liquid in a small circulation route. In general, the diaphragm pump includes an actuator for converting an input energy into a physical energy, a diaphragm deforming along with the deformation of the actuator, and a pump chamber deforming along with the deformation of the diaphragm. In the diaphragm pump, the inner volume of the pump chamber repeatedly expands and contracts along with the deformation of the diaphragm. At this time, since the pressure in the pump chamber increases or decreases, the fluid is repeatedly suctioned from outside the pump into the pump chamber, and discharged outside the pump. Further, in the diaphragm pump, a unidirectional flow of the fluid is created by providing check valves in a suction port for suctioning the fluid into the pump chamber therethrough, and in a discharge port for discharging the fluid from the pump chamber therethrough. By repeatedly operating the diaphragm in this state, the diaphragm pump can suction and discharge the fluid as a pump. Since the diaphragm pump suctions and discharges the fluid by causing the pressure variation by changing the inner volume of the pump chamber, when air bubbles contained in the liquid enter the pump chamber, the liquid sending efficiency may deteriorate because the pressure variation becomes small due to the repeated expansions and contractions of the air bubbles. Japanese Patent Laid-open No. 2018-30350 describes a liquid discharge head having a diaphragm pump mounted thereon as a diaphragm pump for circulating liquid. In Japanese Patent Laid-open No. 2018-30350, a pump chamber is largely deformed to cause a high-pressure variation to discharge air bubbles having entered the pump chamber, by driving an actuator of the diaphragm pump with a relatively high voltage (e.g., 120 V(volts) to 300 V). However, in a case where the actuator is driven by the relatively high voltage to discharge air bubbles having entered the pump chamber as described in Japanese Patent Laid-open No. 2018-30350, it may influence users. To prevent the influence, an additional configuration, for example, an interlock mechanism may be used, and there is a concern of complicating the apparatus. SUMMARY In consideration of the above issues, the present disclosure is directed to a liquid discharge head capable of discharging air bubbles having entered a pump chamber, without complicating the apparatus and driving a diaphragm pump with a high voltage, and a liquid discharge apparatus employing the liquid discharge head. According to some embodiments of the present disclosure, a liquid discharge head includes a discharge unit configured to discharge liquid, an upstream flow path configured to supply liquid to the discharge unit, a downstream flow path configured to collect liquid from the discharge unit, and a diaphragm pump configured to send liquid in the downstream flow path to the upstream flow path not via the discharge unit. The diaphragm pump includes a pump chamber configured to function as a pump, a suction hole configured to suction the liquid in the downstream flow path into the pump chamber, and a discharge hole configured to discharge the liquid in the pump chamber to the upstream flow path. The pump chamber is formed with an air bubble discharge hole different from the suction hole and the discharge hole. Air bubbles in the pump chamber are discharged through the air bubble discharge hole by reducing a pressure in the air bubble discharge hole. Features of the present disclosure will become apparent from the following description of embodiments with reference to the attached drawings. The following description of