Liquid discharge head and liquid discharge device

Abstract

The present invention provides a liquid discharge head and a liquid discharge device using the same, which enable the discharge of air bubbles mixed into the pump chamber without complicating the device and without driving the diaphragm pump with high voltage. [Solution] The liquid discharge head 1 comprises a diaphragm pump 500, a pump chamber 503 that functions as a pump, a suction port 501 for drawing liquid from a downstream passage 102 into the pump chamber, and a discharge port for discharging the liquid inside the pump chamber to an upstream passage 101, wherein a bubble discharge port 520, different from the suction port and the discharge port, is connected to the pump chamber, and the bubble inside the pump chamber is discharged from the bubble discharge port by reducing the pressure of the bubble discharge port.

Description

Technical Field

[0001] The present invention relates to a liquid ejection head and a liquid ejection device.

Background Art

[0002] A liquid ejection head for ejecting a liquid is mounted on a liquid ejection device, and the liquid ejection device achieves a desired purpose by ejecting the liquid. For example, in an inkjet recording device, an inkjet head, which is a liquid ejection head, is mounted on a carriage, and recording such as an image or characters is performed on a recording medium by ejecting ink from a discharge unit provided in the inkjet head. Since the discharge port provided in the discharge element substrate is exposed to the outside air in order to eject the ink, there is a risk that the ink evaporates, thickens, and adheres depending on the type of the liquid (ink). In order to suppress this, a supply flow path for supplying the liquid to the discharge element substrate and a recovery flow path for recovering the liquid from the discharge element substrate are provided in the liquid ejection head, and a form in which the liquid is circulated by a circulation pump is known. By circulating the liquid, it is possible to reduce the risk of local adhesion due to the diffusion of the thickened liquid.

[0003] Furthermore, a configuration is known in which a diaphragm pump is installed at the liquid discharge head as a circulation pump, efficiently circulating the liquid within a small circulation path. Generally, a diaphragm pump comprises an actuator that converts input energy into physical energy, a diaphragm that deforms in accordance with the deformation of the actuator, and a pump chamber that deforms in accordance with the deformation of the diaphragm. In a diaphragm pump, the volume of the pump chamber continuously expands and contracts as the diaphragm deforms. At this time, the pressure in the pump chamber decreases or increases, causing repeated suction of fluid from outside the pump into the pump chamber and discharge of fluid to outside the pump. In addition, a diaphragm pump creates a one-way flow by placing check valves at the suction port where fluid is drawn into the pump chamber and the discharge port where fluid is discharged from the pump chamber. By repeatedly operating the diaphragm in this state, it becomes possible to suction and discharge fluid as a pump. Diaphragm pumps discharge fluid by causing pressure fluctuations due to changes in the volume of the pump chamber. If air bubbles contained in the liquid enter the pump chamber, the pressure fluctuations generated by the repeated expansion and contraction of the bubbles will decrease, which may reduce the efficiency of fluid transfer.

[0004] Patent Document 1 discloses a liquid discharge head equipped with a diaphragm pump for circulating liquid. In Patent Document 1, the actuator of the diaphragm pump is driven with a relatively high voltage of 120V to 300V, causing a large deformation of the pump chamber and resulting in high pressure fluctuations, which in turn discharges air bubbles mixed into the pump chamber. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-30350 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, as described in Patent Document 1, driving the actuator with a relatively high voltage to discharge air bubbles mixed into the pump chamber may affect the user. Furthermore, preventing this may require additional configurations such as interlocks, raising concerns about the complexity of the device.

[0007] In view of the above problems, the present invention aims to provide a liquid discharge head and a liquid discharge device using the same that can discharge air bubbles mixed into the pump chamber without complicating the device and without driving the diaphragm pump with high voltage. [Means for solving the problem]

[0008] The liquid discharge head of the present invention comprises a discharge unit for discharging liquid, an upstream passage for supplying liquid to the discharge unit, a downstream passage for recovering liquid from the discharge unit, and a diaphragm pump for transporting the liquid in the downstream passage to the upstream passage without passing through the discharge unit. The diaphragm pump comprises a pump chamber that functions as a pump, a suction port for drawing the liquid in the downstream passage into the pump chamber, and a discharge port for discharging the liquid inside the pump chamber to the upstream passage. The pump chamber is formed with a bubble discharge port different from the suction port and the discharge port, and when the bubble discharge port is depressurized, bubbles inside the pump chamber are discharged from the bubble discharge port. [Effects of the Invention]

[0009] The present invention aims to provide a liquid discharge head and a liquid discharge device using the same, which enable the discharge of air bubbles mixed into the pump chamber without complicating the device and without driving the diaphragm pump with high voltage. [Brief explanation of the drawing]

[0010] [Figure 1] Schematic diagram of a liquid dispensing device. [Figure 2] Exploded perspective view of the liquid dispensing head. [Figure 3] Schematic diagram of the circulation unit's appearance. [Figure 4] A schematic cross-sectional view showing the circulation path of the liquid discharge head. [Figure 5] Block diagram of the ink circulation path. [Figure 6] A schematic diagram of the drive mechanism of a diaphragm pump. [Figure 7] External view of a diaphragm pump. [Figure 8] Cross-sectional view of a diaphragm pump. [Figure 9] A schematic diagram showing the flow during bubble discharge. [Figure 10] Block diagram of the ink circulation path. [Figure 11] Cross-sectional view of a diaphragm pump. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are not intended to limit the scope of the present invention, and not all combinations of features described in these embodiments are necessarily essential to the solution of the present invention. The same reference numerals are used for identical components.

[0012] (First Embodiment) In this embodiment, the liquid ejection head is an inkjet head that ejects ink, and the liquid ejection device is an inkjet recording device, but it is not limited to these as long as it ejects liquid.

[0013] <Liquid discharge device> Figure 1(a) is a schematic perspective view of an example configuration of a liquid ejection device using a liquid ejection head 1. The liquid ejection device of this embodiment is a serial scan type liquid ejection device 50. The liquid ejection head 1, which is an inkjet head, is mounted on a carriage 53, and the carriage 53 moves along a guide axis 51 in the main scanning direction (X direction). The recording medium P is transported by transport rollers 55, 56, 57, 58 in a sub-scanning direction (arrow Y) that intersects (orthogonal in this example) the main scanning direction.

[0014] In the present embodiment, a so-called serial type liquid ejection head that ejects ink while moving in the main scanning direction is taken as an example for explanation, but this is not the limit. That is, ejection ports are formed over the entire width direction of the recording medium P, and a so-called full-line type liquid ejection head that can eject over the entire width area of the recording medium P without moving in the main scanning direction may be used.

[0015] The liquid ejection head 1 includes an ink circulation unit 54 and a ejection unit 300 (Fig. 2). Although the specific configuration will be described later, the ejection unit 300 is provided with a plurality of ejection ports and energy generating elements (hereinafter referred to as ejection elements) for generating ejection energy for ejecting liquid from each ejection port. The ejection energy generating elements provided in the ejection unit 300 are driven by a head driver 1A (Fig. 1(b)) in response to an input signal from an electrical connection substrate. Electrical wiring, ink, and air pipes required for ejection are supplied to the carriage 53 through an ink supply tube 59.

[0016] Further, the liquid ejection device 50 is provided with an ink tank as a supply source of ink and an external pump. The ink stored in the ink tank is supplied to the circulation unit 54 through the ink supply tube 59 by the driving force of the external pump.

[0017] The liquid ejection device 50 forms a predetermined image on the recording medium P by repeating a recording scan in which the liquid ejection head 1 mounted on the carriage 53 ejects ink while moving in the main scanning direction and a conveyance operation for conveying the recording medium P in the sub-scanning direction. Note that the liquid ejection head 1 in the present embodiment can eject four types of inks, namely black (B), cyan (C), magenta (M), and yellow (Y), and can record a full-color image with these inks. However, the inks that can be ejected from the liquid ejection head 1 are not limited to the above four types of inks. The present disclosure is also applicable to liquid ejection heads for ejecting other types of inks. That is, the type and number of inks ejected from the liquid ejection head are not limited.

[0018] Also, a cap member (not shown) is disposed at a position deviated from the conveyance path of the recording medium P, and when the recording operation is not performed, it relatively moves to a position covering the face surface of the liquid ejection head 1 to prevent the drying of the ejection port and perform a suction operation for filling and recovery.

[0019] FIG. 1(b) is a block diagram showing a control system of the liquid ejection device 50. The CPU (control unit) 400 functions as control means for controlling the operations of each part of the liquid ejection device 50 based on programs such as processing procedures stored in the ROM 401. The RAM 402 is used as a work area and the like for the CPU (control unit) 400 to execute those processes. The CPU 400 receives image data from the host device 700 outside the liquid ejection device 50, controls the head driver 1A, and controls the driving of the ejection measures provided in the ejection unit 300. Further, the CPU 400 controls the carriage motor 403 for moving the carriage 53 via the motor driver 403A, and controls the conveyance motor 404 for conveying the recording medium P via the motor driver 404A.

[0020] <Basic Configuration of Liquid Ejection Head> Figure 2 is an exploded perspective view showing the liquid ejection head 1 of this embodiment. As shown in Figure 2, the liquid ejection head 1 has an ink circulation unit 54. The circulation unit 54 consists of circulation units 54m, 54y, 54k, and 54c, each corresponding to a different ink, and each circulation unit 54 is connected to a flow channel member 110. The method of connecting the circulation unit 54 and the flow channel member 110 may be a screw-fastening method with a sealing member sandwiched in between, or other connections such as welding. The flow channel member 110 has a joint 200 for receiving ink from the inkjet recording device body, and the joint 200 is in communication with each circulation unit 54a to 54d. When the liquid ejection head 1 is mounted on the liquid ejection device 50, supply tubes (not shown) corresponding to each ink are connected from the liquid ejection device body side to each joint 200. Each ink supplied from the supply tube is supplied to each circulation unit 54a to 54d via the joint 200 of the flow channel member 110. An ink discharge unit 300 is connected to the bottom surface of the flow channel member 110, and the ink supplied to the circulation unit 54 passes through the flow channel member 110 and is supplied to the ink discharge unit 300.

[0021] The ejection unit 300 includes an ejection element 310 equipped with an actuator for ejecting ink, a support member 320, an electrical wiring board 330 for sending electrical signals to the ejection element, and a cover member 340 covering the electrical wiring board. The ejection element 310 and the electrical wiring board 330 are adhesively fixed to the support member 320, and the cover member 340 is further adhesively bonded to cover the surface. The ejection element 310 and the electrical wiring board 330 are electrically connected by wire bonding, but the electrical connection method is not limited to this, and flying lead bonding or the like may also be used. The part of the cover member 340 corresponding to the ejection element 310 is an opening. The method of connecting the ejection unit 300 and the flow path member 110 may be by bonding with adhesive, or by fixing with screws with a sealing member sandwiched in between.

[0022] The discharge element 310 may be a thermoelectric element that converts given electrical energy into thermal energy to generate pressure for discharging liquid, or a piezoelectric element that converts given electrical energy into mechanical energy to generate pressure for discharging liquid. Furthermore, it is not particularly limited as long as it can generate energy for discharging liquid.

[0023] The side of the flow channel member 110 opposite the joint 200 is a contact surface, and the head electrical board 210, which receives electrical signals from the liquid discharge device 50, is connected to the contact surface. Electrical signals are sent from the head electrical board 210 to the discharge element 310 via the electrical wiring board 330 of the discharge unit 300. At this time, the connection between the head electrical board 210 and the flow channel member 110 may be fixed by crimping, adhesive, or double-sided tape. The electrical connection between the head electrical board 210 and the electrical wiring board 330 is made by ACF crimping, but it is not limited to this, and wire bonding or flying lead bonding may also be used.

[0024] <Circulation Unit> Figure 3 is a schematic diagram of the external appearance of one circulation unit 54 corresponding to one type of ink applied to the recording device of this embodiment. The circulation unit 54 has a diaphragm pump 500. In addition, it is preferable that the circulation unit 54 also has a filter 23, a first pressure regulating means 120 and a second pressure regulating means 150.

[0025] <Circulation path within the liquid dispensing head> Figure 4 is a schematic longitudinal cross-sectional view showing the circulation path of one type of ink (one color ink) configured within the body discharge head 1. Note that, in order to more clearly explain the circulation path, the relative positions of each component (first pressure adjustment means 120, second pressure adjustment means 150, diaphragm pump 500, etc.) in Figure 5 have been simplified. Therefore, the relative positions of each component differ from those in Figure 6, which will be described later. Figure 5 is a schematic block diagram showing the circulation path shown in Figure 4. As shown in Figures 4 and 5, the first pressure adjustment means 120 includes a first valve chamber 121 and a first pressure control chamber 122. The first pressure control chamber 122 adjusts the pressure in the supply passage 130 between the first pressure control chamber 122 in the upstream passage 101 and the discharge unit 300. The second pressure adjustment means 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure adjustment means 120 is configured to have a relatively higher control pressure than the second pressure adjustment means 150. In this embodiment, the two pressure adjustment means 120 and 150 are used to achieve circulation within a constant pressure range in the circulation path. Furthermore, the ink is configured to flow through the pressure chamber 12 at a flow rate corresponding to the pressure difference between the first pressure adjustment means 120 and the second pressure adjustment means 150. The circulation path in the liquid discharge head 1 and the flow of ink within the circulation path will be described below with reference to Figures 4 and 5. The arrows in each figure indicate the direction of ink flow.

[0026] First, the connection status of each component in the liquid ejection head 1 will be explained. The external pump 21, which sends ink contained in the ink tank 2 (Figure 5) located outside the liquid ejection head 1 to the liquid ejection head 1, is connected to the circulation unit 54 via the ink supply tube 59 (Figure 1). A filter 23 is provided in the ink flow path (discharge flow path) located upstream of the circulation unit 54. The ink supply path (discharge flow path) located downstream of the filter 23 is connected to the first valve chamber 121 of the first pressure adjustment means 120. The first valve chamber 121 communicates with the first pressure control chamber 122 via a communication port 191A that can be opened and closed by the valve 190A shown in Figure 5. The discharge flow path is a flow path that discharges the liquid in the ink tank 2 located outside the liquid ejection head 1 to the liquid ejection head 1 in order to supply it to the pressure chamber 12.

[0027] The first pressure control chamber 122 is connected to the supply channel 130, the bypass channel 160, and the pump outlet channel 180 of the diaphragm pump 500. The supply channel 130 passes through the channel member 110 and is connected to the common supply channel 18 via the aforementioned ink supply port provided in the discharge unit 300. The bypass channel 160 is connected to the second valve chamber 151 provided in the second pressure adjustment means 150. The second valve chamber 151 communicates with the second pressure control chamber 152 via a communication port 191B that is opened and closed by the valve 190B shown in Figure 4. Figures 4 and 5 show an example in which one end of the bypass channel 160 is connected to the first pressure control chamber 122 of the first pressure adjustment means 120, and the other end of the bypass channel 160 is connected to the second valve chamber 151 of the second pressure adjustment means 150. Alternatively, one end of the bypass channel 160 may be connected to the supply channel 130, and the other end of the bypass channel may be connected to the second valve chamber 151.

[0028] The second pressure control chamber 152 is connected to the recovery channel 140. The recovery channel 140 is connected to the common recovery channel 19 via the channel member 110 and the aforementioned ink recovery port provided in the discharge unit 300. Furthermore, the second pressure control chamber 152 is connected to the diaphragm pump 500 via the pump inlet channel 170.

[0029] Next, the flow of ink in the liquid discharge head 1 having the above configuration will be described. The ink supplied to the circulation unit 54 passes through the filter 23 to remove foreign matter such as dust and air bubbles, and then is discharged into the first valve chamber 121 provided in the first pressure adjustment means 120. The pressure of the ink decreases due to the pressure loss when passing through the filter 23, but the pressure of the ink at this stage is positive. After that, the ink discharged into the first valve chamber 121 passes through the communication port 191A and is discharged into the first pressure control chamber 122 when the valve 190A is open. Due to the pressure loss when passing through the communication port 191A, the pressure of the ink discharged into the first pressure control chamber 122 switches from positive to negative. Next, the flow of ink in the circulation path will be described. The diaphragm pump 500 operates to send ink drawn in from the pump inlet passage 170, which is on its upstream side, to the pump outlet passage 180, which is on its downstream side. Therefore, when the pump is driven, the ink supplied to the first pressure control chamber 122 is discharged into the supply channel 130 and the bypass channel 160 together with the ink delivered from the pump outlet channel 180.

[0030] As will be described in more detail later, in this embodiment, a piezoelectric diaphragm pump is used as the liquid-dispensing diaphragm pump, which uses a piezoelectric element attached to the diaphragm as the driving source. The piezoelectric diaphragm pump is a pump that dispenses liquid by changing the volume inside the pump chamber by inputting a driving voltage to the piezoelectric element, causing two check valves to move alternately due to pressure fluctuations. The driving voltage is supplied to the diaphragm pump 500 by the pump drive circuit 213. The ink discharged into the supply channel 130 is discharged from the ink supply port of the discharge unit 300 through the common supply channel 18 to the pressure chamber 12, and some of the ink is discharged from the discharge port 13 by driving (heating) the energy generating element 15. The remaining ink that was not used for discharge flows through the pressure chamber 12, passes through the common recovery channel 19, and is discharged into the recovery channel 140 connected to the discharge unit 300. The ink discharged into the recovery channel 140 is discharged into the second pressure control chamber 152 of the second pressure adjustment means 150. Meanwhile, the ink discharged from the first pressure control chamber 122 to the bypass channel 160 is discharged to the second valve chamber 151, then passes through the communication port 191B and is discharged to the second pressure control chamber 152. The ink discharged to the second pressure control chamber 152 via the bypass channel 160 and the ink recovered from the recovery channel 140 are drawn into the diaphragm pump 500 via the pump inlet channel 170 by the drive of the diaphragm pump 500. The ink drawn into the diaphragm pump 500 is then sent to the pump outlet channel 180 and discharged again to the first pressure control chamber 122. Subsequently, the ink discharged from the first pressure control chamber 122 to the second pressure control chamber 152 via the supply channel 130 and the discharge unit 300, and the ink discharged to the second pressure control chamber 152 via the bypass channel 160 are discharged to the diaphragm pump 500. Then, they are sent from the diaphragm pump 500 to the first pressure control chamber 122. In this way, the ink is circulated within the circulation path.

[0031] The flow path connecting the diaphragm pump 500 and the discharge unit 300, and for supplying liquid to the discharge unit 300, is referred to as the upstream flow path 101. Specifically, the upstream flow path 101 includes the pump outlet flow path 180, the first pressure control chamber 122, and the supply flow path 130.

[0032] Furthermore, the flow path connecting the diaphragm pump 500 and the discharge unit 300, and primarily for recovering liquid from the discharge unit 300, is referred to as the downstream flow path 102. Specifically, the downstream flow path 102 includes the pump inlet flow path 170, the second pressure control chamber 152, and the recovery flow path 140.

[0033] In other words, the diaphragm pump 500 is a pump for transferring liquid from the downstream channel 102 to the upstream channel 101 without going through the discharge unit 300.

[0034] As described above, in this embodiment, the diaphragm pump 500 makes it possible to circulate the liquid along the circulation path formed in the liquid discharge head 1. This makes it possible to suppress the thickening of the ink and the accumulation of sedimentary components of the colorant ink within the discharge unit 300, and to maintain good ink fluidity in the discharge unit 300 and good discharge characteristics at the discharge port.

[0035] Furthermore, since the circulation path in this embodiment is completed within the liquid ejection head 1, the length of the circulation path can be significantly shortened compared to the case where ink is circulated between the ink tank 2 located outside the liquid ejection head and the liquid ejection head 1. As a result, ink circulation can be performed with a small circulation pump.

[0036] Furthermore, the connection channel between the liquid ejection head 1 and the ink tank 2 is configured to include only a channel for supplying ink. In other words, a channel for recovering ink from the liquid ejection head 1 to the ink tank 2 is not required. Therefore, only an ink supply tube is needed to connect the ink tank 2 and the liquid ejection head 1, and there is no need for an ink recovery tube. Consequently, the internal structure of the liquid ejection device 50 can be simplified by reducing the number of tubes, enabling miniaturization of the entire device. Furthermore, by reducing the number of tubes, it is possible to reduce ink pressure fluctuations caused by the oscillation of the tubes during the main scanning of the liquid ejection head 1. In addition, the oscillation of the tubes during the main scanning of the liquid ejection head 1 becomes a driving load for the carriage motor that drives the carriage 53. Therefore, by reducing the number of tubes, the driving load of the carriage motor is reduced, making it possible to simplify the main scanning mechanism including the carriage motor. Furthermore, since it is not necessary to recover ink from the liquid ejection head to the ink tank, it is also possible to miniaturize the external pump 21. Thus, according to this embodiment, it is possible to miniaturize the liquid dispensing device 50 and reduce its cost.

[0037] <Explanation of the diaphragm pump drive mechanism> Figure 6 is a schematic diagram of the drive mechanism of the diaphragm pump. A drive signal is sent from the CPU 400 mounted on the main board 230 in the liquid discharge device to the carriage board 220 via an FFC. Furthermore, the control signal and reference voltage of the pump drive circuit are sent from the carriage board 220 to the head electrical board 210 via an electrical connection part 212 with contact connections. Here, the pump drive circuit 213 is mounted on the head electrical board 210. The pump drive signal output from the pump drive circuit is output to the diaphragm pump 500 via harness wiring 211, which drives the diaphragm pump 500 and circulates the liquid. The pump drive circuit 213 may also be provided in other parts such as the carriage board 220 or the main board 230.

[0038] <Diaphragm pump> Next, with reference to Figures 7 and 8, the configuration and operation of the diaphragm pump 500 built into the liquid discharge head 1 described above will be explained in detail.

[0039] Figure 7 is an external perspective view of the diaphragm pump 500. Figure 7(a) is an external perspective view showing the front side of the diaphragm pump 500, and Figure 7(b) is an external perspective view showing the rear side of the diaphragm pump 500. The outer shell of the diaphragm pump 500 is composed of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 is composed of a housing body 505a and a flow path connecting member 505b that is adhesively fixed to the outer surface of the housing body 505a. In this embodiment, the housing body 505a and the flow path connecting member 505b are each provided with three through holes communicating with each other at different positions.

[0040] The through-hole at the first position is a suction hole 501 for drawing the liquid from the downstream flow path 102 into the pump chamber 503, which will be described later. The through-hole at the second position is a discharge hole 502 for discharging the liquid from inside the pump chamber 503 into the upstream flow path. Furthermore, as will be described in detail later, in the invention according to this embodiment, a through-hole different from the suction hole 501 and the discharge hole 502 is also provided at the third position, which is a bubble discharge hole 520 for discharging bubbles from inside the pump chamber 503 by reducing the pressure.

[0041] The suction port 501 is connected to the pump inlet passage 170, which is connected to the second pressure control chamber 152, and the discharge port 502 is connected to the pump outlet passage 180, which is connected to the first pressure control chamber 122. During ink circulation, the ink supplied from the suction port 501 passes through the pump chamber 503 (see Figure 8) described later and is discharged from the discharge port 502.

[0042] Figure 8 is a cross-sectional view of the diaphragm pump 500 shown in Figure 7(a) along the line IX-IX. A diaphragm 506 is joined to the inner surface of the pump housing 505, and a pump chamber 503, which functions as a pump, is formed between the diaphragm 506 and a recess formed in the inner surface of the pump housing 505. The pump chamber 503 communicates with a suction port 501 and a discharge port 502 formed in the pump housing 505. A first check valve 504a for opening and closing the suction port 501 is provided in the middle portion of the suction port 501, and a second check valve 504b for opening and closing the discharge port 502 is provided in the middle portion of the discharge port 502. Specifically, the first check valve 504a is positioned so that a part of it can move to the left in the figure within a space 512a formed in the middle portion of the suction port 501. Furthermore, the second check valve 504b is positioned so that a portion of it can move to the right in the figure within the space 512b, which is formed in the middle portion of the discharge hole 502.

[0043] A piezoelectric element 509, which deforms when a voltage is applied, is attached to the diaphragm 506. When the piezoelectric element 509 deforms, the diaphragm 506 is displaced along with it. When the diaphragm 506 is displaced in a concave shape relative to the pump chamber 503, the volume of the pump chamber 503 increases, causing the pump chamber 503 to be depressurized. At this time, the first check valve 504a moves away from the opening of the suction hole 501 in the space 512a (i.e., it moves to the left in the figure). When the first check valve 504a moves away from the opening of the suction hole 501 in the space 512a, it becomes an open state that allows ink to be discharged from the suction hole 501. On the other hand, at this time, when the pump chamber 503 is depressurized, the second check valve 504b comes into close contact with the wall surface around the opening of the pump housing 505, becoming a closed state that blocks the discharge of ink from the discharge hole 502.

[0044] Furthermore, when the diaphragm 506 is displaced convexly relative to the pump chamber 503, the volume of the pump chamber 503 decreases, causing the pump chamber 503 to be pressurized. At this time, the first check valve 504a comes into close contact with the wall surface surrounding the opening of the suction hole 501. As a result, it enters a closed state that blocks the flow of ink through the suction hole 501. Meanwhile, at this time, the second check valve 504b moves away from the opening of the pump housing 505 towards the space 512b (i.e., moves to the right in the figure), and enters a closed state that allows the discharge of ink through the discharge hole 502.

[0045] Furthermore, the material of the first check valve 504a and the second check valve 504b may be any material that can deform in accordance with the pressure in the pump chamber 503, and can be formed from elastic materials such as EPDM or elastomer, or from films or thin sheets of polypropylene, etc. However, it is not limited to these.

[0046] As mentioned above, the pump chamber 503 is formed by the joint between the pump housing 505 and the diaphragm 506. Therefore, the pressure in the pump chamber 503 changes as the diaphragm 506 deforms. For example, if the diaphragm 506 is displaced toward the pump housing 505 (displaced to the right in the figure) and the volume of the pump chamber 503 decreases, the pressure inside the pump chamber 503 increases. This causes the second check valve 504b, which is positioned opposite the discharge port 502, to open, and the ink in the pump chamber 503 is discharged. At this time, the first check valve 504a, which is positioned opposite the suction port 501, is in close contact with the wall surface around the suction port 501, so backflow of ink from the pump chamber 503 to the suction port 501 is suppressed. Conversely, if the diaphragm 506 is displaced in a direction that expands the volume of the pump chamber 503, the pressure in the pump chamber 503 decreases. As a result, the first check valve 504a, positioned opposite the suction port 501, opens, and ink is supplied to the pump chamber 503. At this time, the second check valve 504b, positioned at the discharge port 502, comes into close contact with the surrounding wall surface of the opening formed in the pump housing 505, thereby closing the opening. Therefore, backflow of ink from the discharge port 502 to the pump chamber 503 is suppressed. In this way, the diaphragm pump 500 performs ink suction and discharge by deforming the diaphragm 506 and changing the pressure inside the pump chamber 503.

[0047] <Air bubble removal configuration for diaphragm pumps> As described above, if air bubbles enter the pump chamber 503, even if the diaphragm 506 is displaced, the repeated expansion and contraction of the air bubbles reduces the pressure fluctuations within the pump chamber 503, thus decreasing the fluid transfer efficiency.

[0048] Therefore, in this embodiment of the invention, a bubble discharge hole 520 is formed in both the housing body 505a and the flow path connecting member 505b as a through hole different from the suction hole 501 and the discharge hole 502. A third check valve 504c for opening and closing the bubble discharge hole 520 is provided in the middle portion of the bubble discharge hole 520. Specifically, the check valve 504c is positioned so that a part of it can move to the right in the figure in a space 512c formed in the middle portion of the discharge hole 520.

[0049] The bubble discharge hole 520 is connected to a bubble discharge channel 530 formed inside the head, and the bubble discharge channel 530 is further connected to a suction channel 540 that is connected to the main body. On the opposite end of the suction channel 540 from the end connected to the bubble discharge channel 530, a suction pump 550 (pressure reducing means) on the main body side is connected.

[0050] Next, we will explain the flow during bubble removal. Figure 9 shows the airflow during bubble removal. First, as in normal operation, ink is supplied to the head 1 from the ink tank 2 by the external pump 21. At the same time, the suction pump 550 of the main unit reduces the pressure inside the bubble discharge hole 520 via the suction passage 540 and the bubble discharge passage 530. At this time, the check valve 504c on the side opposite the pump 500 (right side in the figure) is reduced in pressure, so the check valve 504c moves to the bubble discharge passage 530 side (right side in the figure) in space 512c, and the bubble discharge passage 530 and the pump chamber 503 communicate through the bubble discharge hole 520. Since the bubble discharge hole 520 is reduced in pressure by the suction pump 550, the bubbles present in the pump chamber 503 are discharged from the bubble discharge hole 520 into the bubble discharge passage 530.

[0051] As described above, the diaphragm pump 500 according to this embodiment has a bubble discharge hole 520 for discharging bubbles that have entered the pump chamber 503, so it is possible to discharge bubbles that have entered the pump chamber 503 even without driving the diaphragm pump 500 at a high voltage.

[0052] Furthermore, when bubbles in the pump chamber 503 are discharged into the bubble discharge channel 530, the pressure inside the pump chamber 503 is reduced, causing the first check valve 504a of the suction port 501 to move towards the pump chamber 503 in space 512a and open, creating communication between the pump inlet channel 170 and the inside of the pump chamber 503. The pump inlet channel 170 is also reduced in pressure. At this time, since the inside of the pump chamber 503 is under reduced pressure, the second check valve 504b is closed. As described above, since the pump inlet channel 170 is connected to the second pressure control chamber 152, the pressure inside the second pressure control chamber 152 is also reduced, causing valve 190B to open and connect to the first pressure adjustment means 120 and the ink tank 2 beyond it via the bypass channel 160. Therefore, by continuing suction by the suction pump 550, ink from the ink tank 2 is eventually drawn into the pump chamber 503. Even after the bubbles in the pump chamber 503 have been discharged, by continuing to operate the suction pump 550, bubbles in the downstream channel 102 and the upstream channel 101 can also be discharged to the outside of the circulation channel through the bubble discharge hole 520.

[0053] (Modified version of the first embodiment) In removing air bubbles from a diaphragm pump, a mechanism for detecting ink is provided between the air bubble discharge hole 520 and the suction pump 550. This allows the suction operation to be stopped when ink is detected. This prevents the suction pump 550 from drawing in ink. Alternatively, a similar effect can be achieved by pre-determining the time it takes for ink to reach the pump chamber 503 and performing suction only during that time.

[0054] Furthermore, even when using the ink detection mechanism and suction time setting described above, a certain amount of ink may still be drawn from the diaphragm pump 500 to the suction pump 550. For this reason, it is preferable to have an ink return mechanism that places a storage section (not shown) for storing the ink drawn into the suction pump 550 in the middle of the bubble discharge channel 530 or the suction channel 540, and supplies the ink stored in the storage section back to the ink tank 2 or the discharge unit.

[0055] In this embodiment, the suction pump 550 (pressure reducing means) is provided outside the liquid discharge head 1 of the liquid discharge device 50, but it may also be provided inside the liquid discharge head. In this case, the bubble discharge channel 530, the bubble suction channel, and the recovery storage section will also be provided in the liquid discharge head. When the suction pump 550 is provided in the liquid discharge device 50, it is possible to miniaturize the liquid discharge head 1. On the other hand, when the suction pump 550 is provided in the liquid discharge head 1, the recovery storage section is also mounted in the liquid discharge head, making it easier to supply the ink in the storage section to the discharge unit by the ink return mechanism.

[0056] Furthermore, it is preferable that the opening pressure of the third check valve 504c is greater than the opening pressure of the second check valve 504b located in the discharge hole 502. This ensures that when the diaphragm 506 is displaced towards the pump housing 505 (displaced to the right in the figure) during ink circulation (when the diaphragm pump is driven), and the pressure inside the pump chamber rises, the second check valve 504b opens before the third check valve 504c. Since the second check valve 504b opens first, the pressure inside the pump chamber 503 decreases, reducing the likelihood of the third check valve 504c opening, and also reducing the likelihood of ink being discharged from the bubble discharge hole 520 when the diaphragm pump is driven.

[0057] Furthermore, in order to obtain such effects, instead of making the material and rigidity of the third check valve 504c and the second check valve 504b different, a configuration may be used in which a biasing member such as a spring is used to make it difficult for the check valve 504c of the bubble discharge hole 520 to deform. Since it is preferable that the third check valve 504c opens only when releasing bubbles and does not open when the diaphragm pump is driven, it is preferable that the opening pressure of the third check valve 504c is 10 kPa or more.

[0058] To improve the efficiency of bubble discharge from the pump chamber 503, it is preferable that the bubble discharge hole 520 is located vertically above the suction hole 501 and discharge hole 502 when the liquid discharge head is in use. Since buoyancy acts on the bubbles in the pump chamber 503, keeping the bubbles in the pump chamber 503 near the bubble discharge hole 520 makes it easier to discharge them.

[0059] Similarly, when the liquid discharge head is in use, it is preferable that the discharge port 502 is located vertically above the suction port 501. Having the discharge port 502 vertically above the suction port 501 makes it easier for air bubbles in the pump chamber 503 to be discharged through the discharge port 502 as well.

[0060] In this embodiment, the diaphragm pump 500 is configured such that the bubble discharge hole 520 is formed on the same surface as the suction hole 501 and the discharge hole 502. However, the bubble discharge hole may be located on a different surface from the suction hole 501 and the discharge hole 502, as long as it is in communication with the pump chamber.

[0061] Even when a circulation pump is installed in the liquid discharge head 1, if the circulation pump is the diaphragm pump 500 according to this embodiment, it is possible to circulate the liquid while minimizing the impact on the size of the liquid discharge head. Furthermore, since the diaphragm pump 500 according to this embodiment has a bubble discharge hole 520 for discharging air bubbles mixed into the pump chamber 503, it is possible to discharge air bubbles mixed into the pump chamber without driving the diaphragm pump at a high voltage.

[0062] In this embodiment, it is assumed that the diaphragm pump 500 is mounted on the liquid discharge head 1, but the diaphragm pump 500 may also be mounted on the liquid discharge device 50.

[0063] (Second embodiment) Next, the liquid discharge head 1 and liquid discharge device 50 according to the second embodiment will be described. The second embodiment mainly differs from the first embodiment in that the diaphragm pump 500 does not have a bubble discharge hole 520 for discharging bubbles from the pump chamber 503, and a bubble discharge passage 530 is connected to the pump outlet passage 180. In the following description, only the parts that differ mainly from the first embodiment will be described, and parts that are the same as the first embodiment will not be described.

[0064] Figure 10 is a schematic block diagram showing the circulation path in the second embodiment. Figure 11 is a schematic cross-sectional view of the diaphragm pump 500 in the second embodiment. As shown in Figure 11, the diaphragm pump 500 in this embodiment has a suction port 501 and a discharge port 502, similar to the first embodiment, but does not have a bubble discharge port 520. Instead, as shown in Figure 10, a bubble discharge channel 530 is connected to the pump outlet channel 180 of the upstream channel 101, and the bubble discharge channel 530 is connected to the suction pump 550 (pressure reducing means) via the suction channel 540, similar to the first embodiment.

[0065] When the suction pump 550 is driven, the suction passage 540, the bubble discharge passage 530, and the pump outlet passage 180 are depressurized, and the check valve 504b that closes the discharge hole 502 opens. As a result, the inside of the pump chamber 503 is depressurized, and the bubbles inside the pump chamber 503 are drawn into the suction pump 550 via the discharge hole 502, the pump outlet passage 180, the bubble discharge passage 530, and the suction passage 540. This allows the bubbles inside the pump chamber 503 to be discharged. Since the bubbles inside the pump chamber 503 are discharged by the suction pump 550, which is external to the diaphragm pump 500, it is possible to discharge bubbles mixed in the pump chamber 503 without driving the diaphragm pump 500 at high voltage.

[0066] Here, the upstream flow path 101 is provided with a regulating valve 600 to restrict the discharge of liquid from the discharge unit 300 to the bubble discharge flow path 530 without passing through the diaphragm pump 500. In other words, the regulating valve 600 is located in the upstream flow path 101 between the diaphragm pump 500 and the pressure control chamber 122. The configuration of the regulating valve 600 is not limited as long as it allows the flow of liquid from the diaphragm pump 500 to the second pressure control chamber 152 and suppresses the flow in the reverse direction.

[0067] The second embodiment also makes it possible to discharge air bubbles mixed into the pump chamber without complicating the apparatus and without driving the diaphragm pump with high voltage.

[0068] To summarize this disclosure, it includes the following methods and structure:

[0069] (Composition 1) A dispensing unit for dispensing liquid, An upstream channel for supplying liquid to the aforementioned discharge unit, A downstream channel for recovering liquid from the aforementioned discharge unit, The system includes a diaphragm pump for transferring the liquid from the downstream channel to the upstream channel without passing through the discharge unit, The aforementioned diaphragm pump is A pump room that functions as a pump, A suction port for drawing the liquid from the downstream channel into the pump chamber, A discharge port for discharging the liquid inside the pump chamber into the upstream flow path, A liquid dispensing head equipped with, The pump chamber is provided with a bubble discharge port that is different from the suction port and the discharge port. A liquid dispensing head characterized in that, when the pressure of the bubble discharge hole is reduced, bubbles inside the pump chamber are discharged to the outside through the bubble discharge hole.

[0070] (Configuration 2) The aforementioned diaphragm pump is A first check valve for opening and closing the suction hole, A second check valve for opening and closing the aforementioned discharge hole, A third check valve for opening and closing the aforementioned bubble discharge hole, A liquid dispensing head as described in configuration 1, having the following features.

[0071] (Composition 3) The aforementioned diaphragm pump is A piezoelectric material that deforms upon application of voltage, A diaphragm that is displaced in accordance with the deformation of the piezoelectric element, It has, A liquid discharge head according to configuration 1 or 2, wherein the volume of the pump chamber is changed by the displacement of the diaphragm, thereby causing the pump chamber to function as a pump.

[0072] (Composition 4) The liquid discharge head according to configuration 2, wherein the opening pressure of the third check valve is greater than the opening pressure of the second check valve.

[0073] (Composition 5) The liquid discharge head according to configuration 2 or 4, wherein the opening pressure of the third check valve is 10 kPa or more.

[0074] (Composition 6) A liquid discharge head according to any one of configurations 2, 4, or 5, wherein when the third check valve is open, the second check valve is closed.

[0075] (Composition 7) In the operating state of the liquid dispensing head, The liquid discharge head according to any one of configurations 1 to 6, wherein the bubble discharge hole is located vertically above the discharge hole.

[0076] (Composition 8) In the operating state of the liquid dispensing head, The liquid discharge head according to any one of configurations 1 to 7, wherein the discharge port is located vertically above the suction port.

[0077] (Composition 9) In the operating state of the liquid dispensing head, The liquid discharge head according to configuration 8, wherein the bubble discharge hole is located vertically above the discharge hole.

[0078] (Composition 10) A liquid discharge head according to any one of configurations 1 to 9, having a depressurizing means for reducing the pressure of the bubble discharge hole.

[0079] (Composition 11) It has a bubble discharge channel connecting the bubble discharge hole and the depressurization means, The liquid discharge head according to configuration 10, wherein the bubble discharge channel is provided with a storage section for storing the liquid sucked in by the depressurization means.

[0080] (Composition 12) The pressure reducing means is a liquid discharge head according to configuration 10 or 11, which is different from the diaphragm pump.

[0081] (Composition 13) The liquid dispensing head described in Configuration 1, A liquid dispensing device characterized by having a depressurizing means provided outside the liquid dispensing head for reducing the pressure of the bubble discharge hole.

[0082] (Composition 14) It has a bubble discharge channel connecting the bubble discharge hole and the depressurization means, The liquid discharge device according to configuration 13, wherein the bubble discharge channel is provided with a storage section for storing the liquid sucked in by the depressurization means.

[0083] (Composition 15) The liquid discharge device according to configuration 13 or 14, wherein the pressure reducing means is different from the diaphragm pump.

[0084] (Composition 16) A dispensing unit for dispensing liquid, An upstream channel for supplying liquid to the aforementioned discharge unit, A downstream channel for recovering liquid from the aforementioned discharge unit, A liquid discharge head having a diaphragm pump equipped with a pump chamber for transferring the liquid in the downstream channel to the upstream channel without passing through the discharge unit, A bubble discharge channel is connected to the aforementioned upstream channel. As the pressure in the bubble discharge channel is reduced compared to the pump chamber, bubbles inside the pump chamber are discharged to the outside through the bubble discharge channel via the upstream channel. A liquid discharge head characterized in that the upstream flow path is provided with a regulating valve for restricting the suction of liquid from the discharge unit to the bubble discharge flow path without going through the diaphragm pump.

[0085] (Composition 17) A liquid discharge head according to configuration 16, having a pressure reducing means for reducing the pressure of the bubble discharge channel.

[0086] (Composition 18) A pressure control chamber is provided in the aforementioned upstream channel. The pressure control chamber adjusts the pressure in the upstream flow path between the pressure control chamber and the discharge unit. The regulating valve is a liquid discharge head according to configuration 16 or 17, provided in the upstream flow path between the diaphragm pump and the pressure control chamber.

[0087] (Composition 19) The bubble discharge channel is connected between the diaphragm pump and the regulating valve in the upstream channel, and is a liquid discharge head according to any one of configurations 16 to 18.

[0088] (Composition 20) The liquid discharge head described in configuration 16, A liquid dispensing device characterized by having a depressurization means provided outside the liquid dispensing head for reducing the pressure of the bubble discharge channel. [Explanation of symbols]

[0089] 1. Liquid dispensing head 101 Upstream flow path 102 Downstream channel 300 Discharge Unit 500 diaphragm pump 501 Suction hole 502 Discharge hole 503 Pump Room 520 Bubble discharge holes

Claims

1. A dispensing unit for dispensing liquid, An upstream channel for supplying liquid to the aforementioned discharge unit, A downstream channel for recovering liquid from the aforementioned discharge unit, The system includes a diaphragm pump for transferring the liquid from the downstream channel to the upstream channel without passing through the discharge unit, The aforementioned diaphragm pump is A pump room that functions as a pump, A suction port for drawing the liquid from the downstream channel into the pump chamber, A discharge port for discharging the liquid inside the pump chamber into the upstream flow path, A liquid dispensing head equipped with, The pump chamber is provided with a bubble discharge port that is different from the suction port and the discharge port. A liquid dispensing head characterized in that, when the pressure of the bubble discharge hole is reduced, bubbles inside the pump chamber are discharged to the outside through the bubble discharge hole.

2. The aforementioned diaphragm pump is A first check valve for opening and closing the suction hole, A second check valve for opening and closing the aforementioned discharge hole, A third check valve for opening and closing the aforementioned bubble discharge hole, A liquid dispensing head according to claim 1, having the following features.

3. The aforementioned diaphragm pump is A piezoelectric material that deforms upon application of voltage, A diaphragm that is displaced in accordance with the deformation of the piezoelectric element, It has, The liquid discharge head according to claim 2, wherein the volume of the pump chamber is changed by the displacement of the diaphragm, thereby causing the pump chamber to function as a pump.

4. The liquid discharge head according to claim 2, wherein the opening pressure of the third check valve is greater than the 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 when the third check valve is in an open state, the second check valve is in a closed state.

7. In the operating state of the liquid dispensing head, The liquid discharge head according to claim 1, wherein the bubble discharge hole is located vertically above the discharge hole.

8. In the operating state of the liquid dispensing head, The liquid discharge head according to claim 1, wherein the discharge hole is located vertically above the suction hole.

9. In the operating state of the liquid dispensing head, The liquid discharge head according to claim 8, wherein the bubble discharge hole is located vertically above the discharge hole.

10. The liquid discharge head according to claim 1, further comprising a depressurization means for reducing the pressure of the bubble discharge hole.

11. It has a bubble discharge channel connecting the bubble discharge hole and the depressurization means, The liquid discharge head according to claim 10, wherein the bubble discharge channel is provided with a storage section for storing the liquid sucked in by the depressurization means.

12. The liquid discharge head according to claim 10, wherein the pressure reducing means is different from the diaphragm pump.

13. The liquid dispensing head according to claim 1, A liquid dispensing device characterized by having a depressurizing means provided outside the liquid dispensing head for reducing the pressure of the bubble discharge hole.

14. It has a bubble discharge channel connecting the bubble discharge hole and the depressurization means, The liquid discharge device according to claim 12, wherein the bubble discharge channel is provided with a storage section for storing the liquid sucked in by the depressurization means.

15. The liquid discharge device according to claim 13, wherein the pressure reducing means is different from the diaphragm pump.

16. A dispensing unit for dispensing liquid, An upstream channel for supplying liquid to the aforementioned discharge unit, A downstream channel for recovering liquid from the aforementioned discharge unit, A liquid discharge head having a diaphragm pump equipped with a pump chamber for transferring the liquid in the downstream channel to the upstream channel without passing through the discharge unit, A bubble discharge channel is connected to the aforementioned upstream channel. As the pressure in the bubble discharge channel is reduced compared to the pump chamber, bubbles inside the pump chamber are discharged to the outside through the bubble discharge channel via the upstream channel. A liquid discharge head characterized in that the upstream flow path is provided with a regulating valve for restricting the suction of liquid from the discharge unit to the bubble discharge flow path without going through the diaphragm pump.

17. The liquid discharge head according to claim 16, further comprising a pressure reducing means for reducing the pressure of the bubble discharge channel.

18. A pressure control chamber is provided in the aforementioned upstream channel. The pressure control chamber adjusts the pressure in the upstream flow path between the pressure control chamber and the discharge unit. The liquid discharge head according to claim 16, wherein the restricting valve is provided in the upstream flow path between the diaphragm pump and the pressure control chamber.

19. The liquid discharge head according to claim 18, wherein the bubble discharge channel is connected between the diaphragm pump and the regulating valve in the upstream channel.

20. The liquid dispensing head according to claim 16, A liquid dispensing device characterized by having a depressurization means provided outside the liquid dispensing head for reducing the pressure of the bubble discharge channel.

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