Liquid droplet ejection device

Abstract

To enable liquid droplets whose diameters are smaller than an inner diameter of a discharge port to be discharged at a high liquid feeding speed.SOLUTION: A liquid droplet discharge device 10 comprises: a discharging member 12; a driving device 14 that moves the discharging member 12 back and forth; a liquid chamber 16 in which a tip end part 22 of the discharging member 12 is arranged and in which liquid to be discharged is arranged; a valve seat 18, configured at an inner bottom part of the liquid chamber 16, which the tip end part 22 of the discharging member 12 contacts when discharging liquid; and a discharging port 20 formed at the opposite side of the liquid chamber 16 side of the valve seat 18. The valve seat 18 is provided with a liquid storage part 36 whose cross sectional areas are smaller than cross sectional areas of the liquid chamber 16 and which has capacities which are 2.6-11 times discharge amounts of liquid per one-time forward and backward movement of the discharging member 12. An outlet liquid chamber 40 is provided between the liquid storage part 36 and the discharge port 20. A convex part 22A that can be fitted into the outlet liquid chamber 40 and a valve part 22B which can be fitted into the liquid storage part 36 and blocks a passage from the liquid chamber 16 to the outlet liquid chamber 40 are provided at the tip end part 22 of the discharging member 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a droplet ejection device. [Background technology]

[0002] A method for producing toner has been disclosed in which droplets are ejected from a nozzle and solidified in gas to form toner particles (see Patent Document 1). In this method, a throttle section arranged in the vicinity of the downstream part of the liquid ejection surface of the nozzle maintains or expands the passage cross-sectional area of ​​the airflow carrying the ejected droplets immediately after the droplets are ejected, temporarily slowing down the droplet flow speed, and then the passage cross-sectional area is reduced to re-accelerate the droplets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-245440 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional example, it is described that "the droplet diameter is about 10 μm for a nozzle diameter of 9 μm," meaning that the diameter of the ejected droplets is larger than the inner diameter of the nozzle.

[0005] In general, if you try to increase productivity by increasing the liquid delivery speed of the liquid discharged from the nozzle, the droplet diameter becomes larger, and if you try to reduce the droplet diameter, the liquid delivery speed decreases, resulting in low productivity. For this reason, it has been thought that it is theoretically impossible to use an intermittent discharge device (dispenser) to discharge droplets with a diameter smaller than the inner diameter of the nozzle.

[0006] An object of the present invention is to make it possible to eject droplets having a diameter smaller than the inner diameter of the ejection port at a high liquid delivery speed. [Means for solving the problem]

[0007] A droplet ejection device according to a first aspect includes an ejection member having a rod-shaped tip, a drive unit for moving the ejection member back and forth, a liquid chamber in which the tip of the ejection member is disposed and in which liquid to be ejected is disposed, a valve seat provided on the inner bottom of the liquid chamber and against which the tip of the ejection member abuts when the liquid is ejected, and an ejection port provided on the opposite side of the valve seat to the liquid chamber and serving as an outlet for the liquid from the liquid chamber to the outside, wherein the valve seat has: A liquid storage section is provided which has a cross-sectional area smaller than that of the liquid chamber and a volume 2.6 to 11 times the amount of liquid discharged per one advance / retract movement of the discharge member, and an outlet liquid chamber is provided between the liquid storage section and the discharge port which has a cross-sectional area smaller than that of the liquid storage section and a cross-sectional area larger than that of the discharge port, and the tip of the discharge member is provided with a convex section which can fit into the outlet liquid chamber, and a valve section which can fit into the liquid storage section and can block the flow path from the liquid chamber to the outlet liquid chamber.

[0008] In this droplet ejection device, a liquid storage section with a cross-sectional area smaller than that of the liquid chamber is provided on the valve seat. In addition, a convex section and a valve section are provided on the tip of the ejection member. The ejection member is moved back and forth by the drive device, so that the liquid in the liquid chamber is ejected from the ejection port. Specifically, when the ejection member retreats, the liquid is supplied to the liquid storage section, and when the ejection member advances, the liquid is ejected from the ejection port. When the convex section of the ejection member enters the outlet liquid chamber, the liquid in the outlet liquid chamber is ejected from the ejection port. In addition, the valve section of the ejection member narrows and blocks the flow path from the liquid chamber to the outlet liquid chamber. This increases the pressure in the outlet liquid chamber, accelerating the ejection of the liquid. In other words, the ejection speed accelerates in stages during one ejection of liquid. In addition, since the liquid storage section has a volume 2.6 to 11 times the amount of liquid ejected per one forward and backward movement of the ejection member, the liquid is first ejected in a straight line at a high liquid delivery speed, and then breaks down in the air into numerous droplets smaller than the inner diameter of the ejection outlet.

[0009] In a second aspect, in the droplet ejection device according to the first aspect, the valve portion comes into contact with a bottom portion of the liquid storage portion, thereby blocking the flow path from the liquid chamber to the outlet liquid chamber.

[0010] In this droplet ejection device, the valve unit abuts against the bottom of the liquid storage unit to block the flow path from the liquid chamber to the outlet liquid chamber. By increasing the pressure in the outlet liquid chamber in this way, the ejection speed of the liquid can be accelerated in stages.

[0011] In a third aspect, in the droplet ejection device according to the first or second aspect, the outlet liquid chamber and the ejection port are in constant communication with each other.

[0012] In this droplet ejection device, the outlet liquid chamber and the ejection port are constantly in communication with each other, so that liquid whose pressure has been increased by the action of the valve portion of the ejection member is smoothly ejected from the ejection port. Effect of the Invention

[0013] According to the present invention, droplets having a diameter smaller than the inner diameter of the ejection port can be ejected at a high liquid sending speed. [Brief description of the drawings]

[0014] [Figure 1] 1A and 1B are a cross-sectional view and a block diagram showing a droplet ejection device according to an embodiment of the present invention; [Diagram 2] 2 is an enlarged cross-sectional view of a portion B in FIG. 1, showing a state in which the discharge member is in contact with a valve seat. [Diagram 3] 11 is an enlarged cross-sectional view showing a state in which the discharge member is retracted into the liquid chamber. FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a state in which liquid is discharged from a nozzle. [Diagram 5] 5 is an enlarged cross-sectional view showing a state in which the liquid ejected in FIG. 4 has changed into droplets. FIG. [Figure 6] 4 is a timing chart during operation of the droplet ejection device. [Figure 7] FIG. 4 is a cross-sectional view showing a main part of a droplet ejection device according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same or similar components. Note that duplicated descriptions and reference numerals in the embodiments described below may be omitted. In addition, all drawings used in the following description are schematic, and the dimensional relationship of each element, the ratio of each element, etc. shown in the drawings do not necessarily match the actual ones. In addition, the dimensional relationship of each element, the ratio of each element, etc. between multiple drawings do not necessarily match.

[0016] In FIG. 1, a droplet ejection device 10 according to this embodiment includes an ejection member 12, a drive device 14, a liquid chamber 16, a valve seat 18, and an ejection port 20.

[0017] The discharge member 12 is a member having a rod-shaped tip 22, and is supported in the case 24 so as to be movable up and down in the vertical direction. A piston 26 is provided in a cylinder 25 of the case 24 so as to be slidable up and down. This piston 26 is attached to the discharge member 12. A compressed fluid, for example, air, is supplied from the drive device 14 to the lower side of the piston 26 in the cylinder 25. A compression spring 28, for example, is attached to the upper end of the discharge member 12 in the case 24. This compression spring 28 is interposed, for example, between the ceiling of the case 24 and a spring receiver 30 provided on the discharge member 12, and urges the discharge member 12 downward (in the forward direction).

[0018] The driving device 14 is a device for moving the discharge member 12 back and forth, and includes, for example, a control unit (not shown) and a solenoid valve 32. The control unit is configured to issue a signal S for opening and closing the solenoid valve 32 at a predetermined timing. When the solenoid valve 32 is opened, air A is supplied to the cylinder 25.

[0019] 2 and 3, the liquid chamber 16 is, for example, a cylindrical space in which the tip portion 22 of the discharge member 12 is disposed and in which the liquid to be discharged is disposed, and is provided in the lower part of the case 24. The inner diameter of the liquid chamber 16 is set to be slightly larger than the outer diameter of the tip portion 22. The liquid chamber 16 is adapted to be supplied with liquid from a liquid storage portion 34 (FIG. 1).

[0020] The valve seat 18 is provided at the inner bottom of the liquid chamber 16, and is a portion against which the tip 22 of the discharging member 12 abuts when discharging liquid. The valve seat 18 is provided with a liquid storage section 36. The liquid storage section 36 has a smaller cross-sectional area than the liquid chamber 16, and has a volume that is 2.6 to 11 times, preferably 2.7 to 10 times, and more preferably 2.7 to 5 times the volume of the liquid discharged per one forward and backward movement of the discharging member 12. The liquid storage section 36 is, for example, a circular countersunk portion formed in the valve seat 18.

[0021] Here, the cross-sectional area of ​​the liquid chamber 16 is the area of ​​a cross section obtained by cutting the liquid chamber 16 in the radial direction (horizontal direction). Similarly, the cross-sectional area of ​​the liquid storage section 36 is the area of ​​a cross section obtained by cutting the liquid storage section 36 in the radial direction (horizontal direction).

[0022] The discharge port 20 is provided on the opposite side of the valve seat 18 to the liquid chamber 16 side, and serves as an outlet for the liquid from the liquid chamber 16 to the outside. The outside is the air. As shown in FIG. 2, a nozzle 38 having, for example, a cylindrical shape is provided at the tip of the discharge port 20. The liquid is discharged from the lower end of the nozzle 38. The inner diameter of the discharge port 20 including the nozzle 38 is, for example, 1.6 times or less the average droplet diameter.

[0023] As shown in FIG. 3, an outlet liquid chamber 40 is provided between the liquid storage section 36 and the discharge port 20. The outlet liquid chamber 40 is set to have a smaller cross-sectional area than the liquid storage section 36 and a larger cross-sectional area than the discharge port 20. A majority of the wall surface of the outlet liquid chamber 40 is, for example, a conical surface that narrows in diameter downward. The wall surface of the outlet liquid chamber 40 is not limited to a conical surface, and may be, for example, a cylindrical surface. Of the wall surface of the outlet liquid chamber 40, a portion (lower end) adjacent to the discharge port 20 is, for example, a cylindrical surface.

[0024] 3, the discharge member 12 is retracted into the liquid chamber 16, but the discharge member 12 during use is configured to advance and retreat within the range of the depth h of the liquid storage section 36. This is because the liquid storage section 36 has a volume that is 2.6 to 11 times the amount of liquid discharged per one advance and retreat of the discharge member 12, in other words, the amount of liquid discharged per one advance and retreat of the discharge member 12 is 1 / 11 to 1 / 2.6 of the volume of the liquid storage section 36.

[0025] The tip 22 of the discharge member 12 is provided with a protrusion 22A that can fit into the outlet liquid chamber 40, and a valve portion 22B that can fit into the liquid storage portion 36 and close the flow path from the liquid chamber 16 to the outlet liquid chamber 40. The protrusion 22A is formed in a tapered shape, for example a truncated cone shape, that fits into the outlet liquid chamber 40. Comparing the conical surface of the liquid storage portion 36 and the conical surface of the protrusion 22A, the angle of the protrusion 22A with respect to the horizontal direction is set to be larger.

[0026] The valve portion 22B is, for example, an end surface located at the base end of the protrusion 22A. When the valve portion 22B abuts against the bottom of the liquid storage portion 36, the flow path from the liquid chamber 16 to the outlet liquid chamber 40 is blocked. When the flow path from the liquid chamber 16 to the outlet liquid chamber 40 is blocked, the tip of the protrusion 22A approaches the discharge port 20 but does not reach it, and the discharge port 20 is not blocked by the protrusion 22A. As a result, the outlet liquid chamber 40 and the discharge port 20 are constantly in communication with each other.

[0027] (action) The present embodiment is configured as described above, and its operation will be described below. In Fig. 4 and Fig. 5, in the droplet discharge device 10 according to the present embodiment, the valve seat 18 is provided with a liquid storage section 36 having a cross-sectional area smaller than that of the liquid chamber 16. In addition, a convex section 22A and a valve section 22B are provided at the tip section 22 of the discharge member 12. The discharge member 12 is moved forward and backward by the drive unit 14, so that the liquid in the liquid chamber 16 is discharged from the discharge port 20. Specifically, when the discharge member 12 retreats, the liquid is supplied from the liquid storage section 34 to the liquid storage section 36, and when the discharge member 12 advances, the liquid is discharged from the discharge port 20. When the convex section 22A of the discharge member 12 advances in the outlet liquid chamber 40, the liquid in the outlet liquid chamber 40 is discharged from the discharge port 20.

[0028] Furthermore, the flow path from the liquid chamber 16 to the outlet liquid chamber 40 is narrowed and blocked by the valve portion 22B of the discharge member 12. Specifically, the flow path from the liquid chamber 16 to the outlet liquid chamber 40 is blocked by the valve portion 22B abutting the bottom of the liquid storage portion 36. This increases the pressure in the outlet liquid chamber 40, accelerating the discharge of the liquid. In other words, the discharge speed accelerates in stages during one discharge of the liquid. Furthermore, since the outlet liquid chamber 40 and the discharge port 20 are constantly in communication with each other, the liquid whose pressure has been increased by the action of the valve portion 22B of the discharge member 12 is smoothly discharged from the discharge port 20.

[0029] In addition, since the liquid storage section 36 has a volume that is 2.6 to 11 times the amount of liquid ejected per one forward and backward movement of the ejection member 12, the liquid is first ejected from the nozzle 38 at a high liquid delivery speed in a linear series (liquid thread W1 in Figure 4), and then breaks down in the air into numerous droplets that are smaller than the inner diameter of the ejection port 20 (nozzle 38) (droplets W2 in Figure 5).

[0030] In this manner, according to this embodiment, droplets having a diameter smaller than the inner diameter of the ejection port 20 (nozzle 38) can be ejected at a high liquid sending speed.

[0031] Here, a specific example of droplet creation will be described using numerical values. First, the average droplet diameter is set to 200 μm or less, and the number of divisions is set to 100 or more (1). Then, the droplet volume x the number of divisions = "total amount discharged per one discharge" is calculated. The number of divisions can be determined from the discharge speed, the relative speed of the discharge speed to the air flow, the inner diameter of the discharge nozzle, the viscosity of the discharged liquid, and its density. As described above, the liquid storage section 36 has a volume 2.6 to 11 times the amount of liquid discharged per one forward and backward movement of the discharge member 12 (2). The liquid stored in this liquid storage section 36 is pushed out by the discharge member 12 and discharged in a thread-like shape with a length of 10 to 100 mm through the nozzle 38, which is thicker than the average droplet diameter (thread-like liquid W1 in FIG. 4) (3).

[0032] When these conditions (1) to (3) are satisfied, the liquid pushed by the discharge member 12 is accelerated in multiple stages and is discharged from the nozzle in the form of a thread. This thread then breaks up in the air, yielding fine particles having the set average droplet diameter (droplet W2 in Figure 5).

[0033] The amount of liquid discharged per one movement of the discharge member 12 can be determined by the mechanical structure and various set values, for example, by setting the volume pushed out by the discharge member 12 as the stroke length per one movement. Alternatively, the amount of liquid discharged per one movement of the discharge member 12 can be calculated from the amount discharged per minute (g / min) and the discharge time per one movement (msec).

[0034] 1 and 6, the operation of each part of the droplet discharge device 10 will be described. The signal S sent from the control unit to the solenoid valve 32 is, for example, ON for 2.00 ms and OFF for 4.00 ms. This waveform becomes rectangular. Accordingly, air A is supplied to the cylinder 25. This waveform becomes trapezoidal. The piston 26 is pressed by the air A, causing the position of the discharge member 12 to retreat (rise). As the discharge member 12 retreats, liquid is supplied from the liquid storage section 34 to the liquid chamber 16. At this time, liquid is also supplied to the liquid storage section 36 and the outlet liquid chamber 40 (see FIG. 2).

[0035] When the supply of air A stops, the position of the discharge member 12 advances (descends). Since the discharge member 12 is biased by the compression spring 28, it advances faster than it retreats. This causes the liquid to be discharged from the nozzle 38 through the discharge port 20. For the "liquid volume at the discharge port" and the "liquid volume at the nozzle" in FIG. 6, a comparative example and an embodiment are shown. The comparative example has a configuration in which the valve seat 18 does not have a liquid storage section as shown in FIG. 7. The embodiment has a liquid storage section 36 as shown in FIG. 2 to FIG. 5. The "liquid volume at the discharge port" and the "liquid volume at the nozzle" increase more sharply in the embodiment than in the comparative example. In particular, the "liquid volume at the nozzle" is discharged more sharply and in a larger amount than in the comparative example. The "liquid volume at the discharge port" is the amount of liquid pushed out to the discharge port 20. The "liquid volume at the nozzle" is the amount of liquid discharged to the outside from the nozzle 38 at the end of the discharge port 20.

[0036] [Test example] As described above, in this embodiment, the liquid storage portion has a volume that is 2.6 to 11 times the amount of liquid discharged per one advance / retract movement of the discharge member. In other words, the ratio between the volume of the liquid storage portion and the amount of liquid discharged per one advance / retract movement of the discharge member (hereinafter simply referred to as "volume ratio") is 2.6 to 11. Configurations in which this ratio falls within the range of 2.6 to 11 are shown in Table 1 as Examples 1 to 8. Configurations in which the ratio falls outside the range of 2.6 to 11 are shown in Table 2 as Comparative Examples 1 to 8.

[0037] Where: Liquid chamber diameter: 3.5mm Outer diameter of the valve at the tip of the discharge member: 3.0 mm Inner diameter of the nozzle: 260μm Inner diameter of the liquid reservoir: 3mm It is.

[0038] The calculation of the discharge amount (droplet weight), the calculation of the volume of the liquid storage section, an example of a method for measuring the discharge speed from the discharge nozzle, and the evaluation of the droplets will be described.

[0039] (Calculation of discharge amount (droplet weight)) The amount of sol liquid (g) put into the droplet discharge device is recorded, and the time it takes to discharge the sol liquid from the device until it runs out is also recorded. Alternatively, the amount of sol liquid collected at the discharge port after discharge for one minute or more is measured using an electronic balance, and the discharge time (minutes) is recorded. The amount of sol discharged per minute (g / min) is calculated from the amount of sol discharged (g) and the discharge time (min). A high-speed camera is used to measure the time per discharge. The discharge is filmed at 1 / 4000 fps, the number of frames at the beginning and end of each discharge is counted, and the number of discharge frames (f) / 4000 (f / sec) = discharge time (sec) is calculated. Calculate the discharge amount (g) per one shot = discharge amount (g / min) / 60 (sec) x discharge time per one shot (sec). Calculate the amount discharged (mL) per time (g) x specific gravity of sol liquid (g / mL) = amount discharged (mL) per time. Convert the unit from mL to m3.

[0040] (Calculation of liquid storage volume) The dimensions of the discharge member or valve seat and the discharge port are measured using an optical microscope, and the volume is calculated. (Method for measuring discharge speed from discharge nozzle)

[0041] A high-speed camera is used to measure the length of the droplet per ejection. The ejection is filmed at 1 / 4000 fps, the number of frames at the beginning and end of each ejection is counted, and the droplet length (mm) / (number of ejection frames (f) / 4000 (f / sec)) = speed (mm / sec) is calculated.

[0042] (Droplet evaluation) The droplets were evaluated by solidifying in the air, collecting them, and determining the average particle size. 5: Good: Very few large particles, and the particle size distribution is close to normal distribution. 4: Good: The proportion of slightly larger particles is high, but the particle size distribution is generally close to normal distribution. 3: Poor Not bimodal, but the proportion of large particles is high. 2: Poor: Few coarse particles, but bimodal. 1: Poor - A large proportion of coarse particles is present, and the result is bimodal.

[0043] From Tables 1 and 2, it can be seen that in the examples (ratios of 2.6 to 11), good droplets were obtained and the yield was high, but in the comparative examples (ratios less than 2.6 or greater than 11), good droplets were not obtained and the yield was low.

[0044] [Table 1]

[0045] [Table 2]

[0046] As an example, the liquid storage section is 3 mm in diameter and 0.1 mm deep. 160 μm droplets (1.29 nL) are ejected. When splitting 100 times, the total ejection volume per ejection is 0.129 μL, and the droplets are ejected from a nozzle with an inner diameter of 260 μm to a liquid column length of 30 mm. The droplets are solidified in the air and collected, and the average particle diameter is calculated to be 160 μm, which is a good result.

[0047] In addition, droplets of 160 μm (1.29 nL) were ejected using a liquid storage section of the same volume. When split into 212 droplets, the total ejection volume per ejection was 0.256 μL, and the droplets were ejected from a nozzle with an inner diameter of 260 μm to a liquid column length of 60 mm. The droplets were solidified in the air and collected, and the average particle diameter was calculated to be 160 μm, which was a good result. [Explanation of symbols]

[0048] 10 Droplet discharge device 12 Discharge member 14 Drive unit 16 Liquid chamber 18 Valve seat 20 outlet 22 Tip 22A Convex 22B Valve part 36 Liquid storage section 38 Nozzles 40 outlet liquid chamber

Claims

1. A discharge member having a rod-shaped tip portion; A drive device that moves the discharge member forward and backward; a liquid chamber in which the tip of the discharge member is disposed and in which liquid to be discharged is disposed; a valve seat provided on an inner bottom of the liquid chamber, the valve seat being in contact with the tip of the discharge member when the liquid is discharged; a discharge port provided on a side of the valve seat opposite to the liquid chamber, the discharge port being an outlet port for the liquid from the liquid chamber to the outside; In a droplet ejection device comprising: a liquid storage section having a cross-sectional area smaller than that of the liquid chamber and a volume 2.6 to 11 times the amount of the liquid discharged per one movement of the discharge member; an outlet liquid chamber having a cross-sectional area smaller than that of the liquid storage portion and larger than that of the discharge port is provided between the liquid storage portion and the discharge port; A droplet ejection device, wherein the tip of the ejection member is provided with a convex portion capable of fitting into the outlet liquid chamber, and a valve portion capable of fitting into the liquid storage portion and blocking the flow path from the liquid chamber to the outlet liquid chamber.

2. The droplet ejection device according to claim 1 , wherein the flow path from the liquid chamber to the outlet liquid chamber is blocked by the valve portion abutting against a bottom of the liquid storage portion.

3. 3. The droplet ejection device according to claim 1, wherein the outlet liquid chamber and the ejection port are constantly in communication with each other.

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