Fluid jetting impact pin, nozzle and fluid jetting device

Abstract

This invention relates to a firing pin for fluid injection, wherein the firing pin is a hammer-head firing pin, and the head of the firing pin is composed of a cross-section that propels the fluid injection and a cylindrical surface that guides the fluid to exit in the opposite direction. The cross-section that propels the fluid injection is elliptical or similar to an elliptical cross-section, and the horizontal semi-axis length of the cross-section is greater than the vertical semi-axis length. Furthermore, the firing pin of this invention may also have a groove or ridge structure. This invention also provides a nozzle for fluid injection, characterized in that the nozzle has a structure in which the diameter gradually changes towards the outlet direction, with a larger diameter at the upstream end and a smaller diameter at the downstream end.

Description

Technical Field

[0001] This invention relates to a firing pin, nozzle, and fluid jetting device for fluid jetting, and more particularly to a hammer-head firing pin for high-viscosity fluids. Background Technology

[0002] A fluid micro-jet device is a device that precisely distributes fluid in a controlled manner. It is one of the key technologies in the microelectronics packaging industry. The fluid generates a pressure gradient under the action of the driving source, and is accelerated out of the nozzle under the action of the internal and external pressure difference to form a fluid jet, which finally falls on the substrate to form fluid points.

[0003] With the continuous development of ultra-micro machining technology, the size of precision components is becoming smaller and smaller. At the same time, the requirements for the micro-assembly and interconnection packaging technology of these precision components are also becoming increasingly stringent. Micro-jetting technology is currently one of the main methods of micro-assembly, thus playing a crucial role in the development of semiconductor, microelectronic packaging, and other fields. Jetting quality is mainly judged by the volume stability of the fluid point and whether it can be smoothly ejected from the nozzle. Many factors affect jetting quality, including fluid viscosity, control temperature, feed pressure, flow channel shape, valve stem stroke, and power source parameters. The following are publicly available technologies:

[0004] Patent CN102615018B, authorized by patent number CN102615018B, provides a micro-fluid quantitative distribution device. It uses a piezoelectric crystal as a driving source to drive a striker in a micro-reciprocating motion of 0.3–0.5 mm. The key flow channel of the injection valve is the distribution chamber between the striker head and the nozzle. The space between the striker and the chamber is filled with fluid. When the striker strikes the nozzle base, it cuts off the flow of the adhesive, simultaneously creating significant pressure in the nozzle, ejecting the adhesive to form droplets. Figures 6 and 7 in the specification are schematic diagrams of the fluid flow in the distribution chamber when the striker moves downward and upward, respectively. When the striker moves downward, part of the fluid flows downward and part flows upward. The fluid in the nozzle absorbs the momentum of the striker and is rapidly ejected to form droplets.

[0005] The patent with authorization announcement number CN106480433B provides a fluid jetting device. The flow channel is treated with a superhydrophobic coating. Optionally, the valve stem is designed as a stepped cylinder with a reduced size from top to bottom, and the taper of the inlet conical surface is designed to be 100-130°. By reducing the viscous resistance of the fluid along the flow direction, medium and high viscosity fluids are easier to jet.

[0006] The patent with authorization announcement number CN207357480U provides a split-type droplet distribution device. Figures 10 and 12 show two working states of the impact pin. The impact pin is driven to move up and down reciprocally by a stack of piezoelectric ceramics, generating instantaneous high pressure between the impact pin and the nozzle, which sprays the fluid out of the nozzle. In order to facilitate the spraying of fluids with high viscosity, the device includes a preheating device.

[0007] Existing flow channels only consider the fluid flow from the nozzle outwards, neglecting the impact of internal fluid flow on valve performance. When used for spraying small quantities of high-viscosity fluids, especially those with viscosities exceeding 100,000 mPa·s, the outlet kinetic energy of the fluid stream is insufficient, making it difficult to shear the fluid and resulting in challenging spraying conditions and inconsistent single-shot volume control. Current technologies employ methods such as heating the fluid and applying superhydrophobic coatings to the flow channel to facilitate nozzle ejection, but these methods are structurally complex and lack durability. Therefore, a simple, long-life spraying device is needed for spraying small quantities of high-viscosity fluids. Summary of the Invention

[0008] To address the problems of insufficient jetting kinetic energy (especially for high-viscosity fluids) and difficulty in controlling the single jetting volume in existing fluid jetting devices, this invention optimizes the design of the impact pin and nozzle structure of the fluid jetting device, which is beneficial for the micro-jetting of high-viscosity fluids.

[0009] The first aspect of the present invention provides a firing pin structure, wherein the firing pin is a hammer-head firing pin, and the radius of rotation of the hammer-head firing pin changes along the axis of rotation, with a larger radius of rotation on the firing pin head side and a smaller radius of rotation on the firing pin rod side. The side with the larger radius is called the firing pin head, and the side with the smaller radius is called the firing pin rod. Preferably, the radius of the head is 1.5-2.0 times the radius of the rod.

[0010] A second aspect of the present invention provides a firing pin head, the firing pin head being composed of a cross section for propelling fluid injection and a cylindrical surface for guiding fluid to be discharged in the opposite direction, wherein the cross section for propelling fluid injection is elliptical or similar to an elliptical cross section, and the horizontal semi-axis length of the cross section is greater than the vertical semi-axis length.

[0011] A third aspect of the present invention provides a firing pin structure with a "groove / protrusion structure".

[0012] The groove or ridge is one or a combination of rectangular, triangular, and arc-shaped cross-sections. The groove or ridge structure is a rotary groove or rotary ridge. Preferably, the "groove / ridge structure" is designed as a rotary groove or rotary ridge with a rectangular, triangular, arc-shaped, or other cross-section, i.e., the groove or ridge is axially symmetrically distributed along the rotation axis. Alternatively, it can be designed as a pit / protrusion, through hole, blind hole, or a combination of several forms, according to the working principle of the "groove / ridge structure".

[0013] Preferably, the depth of the "groove / protrusion structure" is 3% to 10% of the maximum diameter of the hammerhead striker head, particularly preferably 3% to 5%. The width of the groove / protrusion is 1 to 4 times the depth of the groove / protrusion, preferably 2 to 3 times. Within the preferred range, the overall effect is best. If the width is too wide and the depth is too shallow, the secondary flow effect is not obvious; conversely, the strength is affected, and the gaps are not easy to clean.

[0014] Preferably, the total number of grooves / protrusions is greater than or equal to 2, and particularly preferably, the total number of grooves / protrusions is greater than or equal to 3.

[0015] To prevent high-viscosity fluid from depositing and hardening, which could affect the jetting performance and facilitate the cleaning and maintenance of the firing pin, it is preferable to add a Teflon or other non-stick coating to the groove / ridge structure.

[0016] A fourth aspect of the present invention provides a hammerhead striking pin structure with a "groove / protrusion structure".

[0017] The "groove / protrusion structure" can be arranged on the head of the hammer striker, the rod of the hammer striker, or both. Preferably, it is arranged on the head of the hammer striker. More preferably, a rectangular groove / protrusion is arranged on the head of the hammer striker, and a pit / protrusion is arranged on the rod of the hammer striker.

[0018] A fifth aspect of the present invention provides a nozzle structure in which the nozzle portion of the flow channel is optimized from the conventional straight circular tube nozzle structure to a nozzle whose diameter decreases towards the outlet direction. The nozzle of the present invention has a diameter that gradually decreases towards the outlet direction, with a larger diameter upstream and a smaller diameter downstream. The nozzle of the present invention can also be a circular tube with a gradually decreasing diameter or a tapered tube with a gradually decreasing diameter.

[0019] Furthermore, the nozzle diameter gradient structure can be a two-stage step, preferably with a chamfer transition between the first and second stages to reduce local fluid resistance. More preferably, a rounded transition between the first and second stages minimizes local fluid resistance.

[0020] Preferably, the fillet radius should be between 0.2mm and 0.5mm, and particularly preferably between 0.2mm and 0.3mm. Within this preferred range, fluid resistance is minimized, spraying is smoother, and clogging is less likely.

[0021] Furthermore, the nozzle section's gradient structure can also be a series of three or more steps.

[0022] The sixth aspect of the present invention provides a conical spray cavity for fluid injection, wherein the conical cross-section has a cone angle denoted by α, and the cone angle is 60° < α < 95°. This provides a more balanced performance when the injection valve injects high-viscosity fluids. Preferably, the cone angle is 60° < α < 90°, and more preferably, it is 80° < α < 90°.

[0023] The present invention has the following advantages over the prior art:

[0024] (1) The radius of rotation of the hammer head of the hammer-head ejector is relatively increased, and the lower diameter of rotation is larger, allowing for a larger arc of the ejector head. This increases the contact area with the fluid, increases the "effective fluid" pressure gradient, and improves the fluid jet kinetic energy, which is beneficial for the jetting of high-viscosity fluids. The "hammer head" structure increases the fluid jet kinetic energy, making the ejected fluid easier to shear. Therefore, the nozzle diameter can be made smaller without worrying about increased resistance and jetting difficulties caused by an excessively small nozzle diameter. Compared with traditional technology, the diameter of a single fluid point that can be jetted is smaller.

[0025] (2) The elliptical cross-section of the firing pin head has the beneficial effect of increasing the pressure gradient in the jet channel and increasing the kinetic energy of the jet fluid.

[0026] (3) The "groove / convex ridge structure" increases the kinetic energy of the "effective fluid" through the "secondary flow" effect. The structure is compact and significantly improves the jet kinetic energy. During operation, the rate of change of fluid shear velocity increases. For shear-thinned fluids, this is equivalent to reducing the local viscosity of high-viscosity fluids, which is beneficial for the jetting of high-viscosity fluids.

[0027] (4) The surface area of ​​the hammerhead striker with a "grooved / protruding ridge structure" is larger than that of a simple cylindrical striker, making it easier to arrange more "grooved / protruding ridge structures". For the same type of injection valve, without changing the tail structure of the striker, only the "hammerhead" part needs to be changed to change the injection performance, thus improving the versatility of injection valve parts. During operation, the grooved / protruding ridge structure on the hammerhead agitates the fluid, reduces the viscosity of non-Newtonian fluids, and improves the injection performance of high-viscosity fluids.

[0028] (5) The upstream part of the nozzle has a larger diameter, which can reduce the flow resistance of the fluid. The downstream part of the nozzle has a smaller diameter, which is used to form a smaller fluid jet. This is beneficial to control the single-point diameter of the fluid. The beneficial effect is that it can spray a smaller fluid jet to achieve precision spraying, without causing excessive flow resistance and making spraying difficult.

[0029] (6) The nozzle and device described in this invention are independent structures in the fluid jetting device. By simultaneously optimizing the impact needle head structure and the nozzle structure, a better high-viscosity fluid jetting effect can be achieved. Attached Figure Description

[0030] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram illustrating the principle of calculating the volume of pressurized fluid when the firing pin is raised, as described in Example 1 of the present invention.

[0032] Figure 1a This is a schematic diagram illustrating the principle of calculating the volume of pressurized fluid when the striking pin is raised, as shown in Example 2 of the present invention.

[0033] Figure 1b This is a schematic diagram illustrating the principle of calculating the volume of pressurized fluid when the striking pin is raised, as shown in Example 2 of the present invention.

[0034] Figure 2 This is a schematic diagram illustrating the principle of calculating the volume of pressurized fluid when the firing pin falls, as described in Example 1 of this invention.

[0035] Figure 2a This is a schematic diagram illustrating the principle of calculating the volume of pressurized fluid when the striking pin falls, as shown in Example 2 of this invention.

[0036] Figure 2b This is a schematic diagram illustrating the principle of calculating the volume of pressurized fluid when the striking pin falls, as shown in Example 2 of this invention.

[0037] Figure 3 This is a graph showing the relationship between the effective fluid volume change and the firing pin radius in Example 1 of the present invention.

[0038] Figure 4 This is a graph showing the relationship between the effective fluid volume change and the firing pin stroke in Example 1 of the present invention.

[0039] Figure 5a This is a comparison of the flow channel profile pressure cloud diagrams of Examples 1 and 2 of the present invention.

[0040] Figure 5b This is a comparison of the flow channel cross-sectional streamline diagrams of Examples 1 and 2 of the present invention.

[0041] Figure 6a This is a schematic diagram of the flow channel cross-sectional structure of the firing pin head (ordinary firing pin) according to an example of the present invention.

[0042] Figure 6bThis is a schematic diagram of the flow channel cross-sectional structure of the firing pin head (hammer firing pin) according to an embodiment of the present invention.

[0043] Figure 7a This is a partial detailed schematic diagram of the groove structure in Example 3 of the present invention.

[0044] Figure 7b This is a partial detail diagram of the convex ridge structure in Example 3 of the present invention.

[0045] Figure 8a This is a local velocity vector diagram of the fluid in the groove structure of Example 3 of the present invention.

[0046] Figure 8b This is a cloud map showing the rate of change of local shear velocity of the fluid in the groove structure of Example 3 of the present invention.

[0047] Figure 9 This is a schematic diagram of the nozzle flow channel cross-sectional structure of Example 4 of the present invention. Detailed Implementation

[0048] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and the design principles of flow channel geometry parameters. However, the present invention should be understood as not being limited to the embodiments described below, and the technical concept of the present invention can be implemented in combination with other known technologies or other technologies with the same function as those known technologies.

[0049] Example 1: "Hammer" firing pin

[0050] like Figure 6b As shown, this embodiment provides a "hammerhead" striking pin structure, wherein the radius of rotation of the "hammerhead" striking pin changes along the axis of rotation, like the head of a hammer, on the side that impacts the fluid (i.e., Figure 6b The firing pin head section has a larger radius of rotation, while on the other side (i.e., Figure 6b The firing pin rod portion has a small radius of rotation, with the head radius being 1.5-2.0 times the radius of the rod portion. The larger side is referred to as the "hammer head" portion, and the "hammer head" firing pin structure of this invention is as follows: Figure 6b Compared with ordinary firing pins Figure 6a As shown. The design principle is as follows:

[0051] Figure 1 , Figure 2 This is a schematic diagram of the calculation principle for the "effective fluid" of the flow channel in a jet valve with a ball-shaped ejector head. During ejection, the ejector moves vertically downwards. Figure 1 Before the firing pin strikes, Figure 2 This is after the firing pin strikes. The state of the firing pin of the injection device before strike is as follows: Figure 1 As shown in the figure, the space between the firing pin and the conical surface (hereinafter referred to as "conical surface") is filled with fluid. The state of the firing pin after impact is as follows. Figure 2 As shown, the fluid flow state during the impact is as follows: Figure 5b As shown, when the firing pin strikes the fluid, the fluid flows relative to the firing pin under the influence of the pressure gradient. A portion of the fluid flows along the direction of the firing pin's movement and is ejected from the nozzle; this is called "effective fluid." The other portion flows back in the opposite direction of the firing pin's movement after being displaced by the firing pin; this is called "ineffective fluid." The following section combines... Figure 1 The process of volume change of the "effective fluid" is described.

[0052] Figure 1 The diagram shows a cross-sectional view of the flow channel of a jet valve with a spherical impact pin head passing through the axis of rotation. The cross-section of the impact pin head is an arc with radius R, and the cone angle of the two conical walls is α (0° < α < 180°). Figure 1 (For the special case where α = 90°), point O is the center of the arc of the firing pin head, point A is the intersection of the conical wall (the nozzle is located at point A), and point B is the intersection of the rotation axis and the section of the firing pin head. Draw a perpendicular line from point O to the wall, with the foot of the perpendicular at point P. The intersection of this perpendicular line OP and the section of the firing pin head is at point q. Draw a vertical line from point q intersecting the wall at point C, and a horizontal line from point q intersecting the rotation axis at point d. The length of line qc is the firing pin stroke s, and the length of line bd is the height H of the pin's spherical crown. The following uses... Figure 1 Taking the circular firing pin cross-section shown as an example, the relationship formula is derived as follows:

[0053] The "effective fluid" volume is the rotatable volume of quadrilateral bqpa about the axis of rotation oa, and the rotatable volume of triangular bdq about the axis of rotation oa is called the "needle cap". The figure enclosed by the three points pqc is called the "small triangle". When the firing pin moves downward, the volume of the "needle cap" remains unchanged, the area of ​​the "small triangle" decreases, and the firing pin stroke s gradually decreases until it reaches the limit position ( Figure 2 Points p, q, and c coincide, and the area of ​​the small triangle is 0.

[0054] The effective fluid volume before impact (denoted as V) 有效流体 The volume (denoted as V) of a polygon adqp can be rotated about an axis of rotation. adqp Subtract the volume of the needle cap (denoted as V) 针头球冠 ), where V adqp It is easy to calculate, and the derivation process is omitted.

[0055] For a spherical striking needle, establish a rectangular coordinate system at the center point o of the spherical cap, with the horizontal axis as the x-axis and the vertical axis as the y-axis, and calculate the volume formula of the spherical cap of the needle.

[0056] Formula 1:

[0057] Special, when Figure 1 When the cone angle α of the middle wall is 90°, it can be deduced that:

[0058]

[0059] Formula 2:

[0060] Similarly, calculating the volume of the remaining parts and rearranging, we obtain the algebraic relationship between the "effective fluid" volume Veffective fluid before impact and the impact pin stroke s (or the impact pin head radius R):

[0061] Formula 3: V 有效流体 =a1s 3 +b1s 2 +c1s+d1

[0062] Formula 3′: V 有效流体 =a2R 3 +b2R 2 +c2R+d2

[0063]

[0064]

[0065] Specifically, when the wall cone angle α = 90°

[0066]

[0067]

[0068] The formula for calculating the volumetric "effective fluid" ΔV effective fluid before and after the impact is as follows:

[0069] Formula 4: ΔV 有效流体 =a3R 3 +b3R 2 +c3R+d3

[0070] Formula 4': ΔV 有效流体 =a4s 3 +b4s 2 +c4s+d4

[0071] a3 = 0,

[0072]

[0073] Specifically, when the wall cone angle α = 90°

[0074] a3 = 0,

[0075] d4 = 0

[0076] Differentiating both sides of Equation 4 with respect to α, we get:

[0077] Formula 5:

[0078] Formula 2 is a special form of Formula 1, Formula 3 and Formula 3' are different expressions of the same formula, and Formula 4 and Formula 4' are different expressions of the same formula.

[0079] According to Formula 4, with the firing pin radius R as the independent variable, we obtain... Figure 3 The function curves shown in the figure are as follows: the curve with dashed line and hollow circle represents the striker stroke s = 0.1 mm, and the curve with solid line and solid circle represents the striker stroke s = 0.2 mm.

[0080] According to formula 4', with the striker stroke s as the independent variable, we obtain... Figure 4 The function curves shown in the figure represent the impact pin radius R = 2 mm (dashed line + hollow circle) and the impact pin radius R = 3 mm (solid line + solid circle). From... Figure 4 The trends of the two curves show that the effective fluid volume change is positively correlated with the length of the firing pin stroke; that is, the greater the firing pin stroke (or the height the firing pin is raised), the greater the effective fluid volume change and the easier the ejection. Comparing the coordinate points of the two curves reveals that the effective fluid volume change is positively correlated with the firing pin radius R; that is, the larger the firing pin radius, the greater the effective fluid volume change and the easier the ejection.

[0081] in Figure 3 and Figure 4 Only two curves with different parameters were plotted. Similarly, a family of curves with different parameters can be plotted using the above formula.

[0082] According to formula 4, refer to Figure 3 The curve shown indicates that the effective fluid volume change ΔV increases monotonically with the impeller radius R. This means that increasing the impeller radius within the same space can improve the valve body's injection capability. Based on this principle... Figure 6a The conventional firing pin structure shown is modified by increasing the radius of the firing pin head to obtain... Figure 6b The "hammerhead" firing pin structure shown.

[0083] It is easy to see from Formula 5 that when α = 0°, ΔV effective fluid takes the maximum value. ΔV effective fluid increases monotonically with α. When α = 90°, the rate of change of ΔV effective fluid is the largest. In order to make the performance of the injection valve more balanced when injecting high viscosity fluid, α is designed to be a small value near 90°. Preferably, it is 60° < α < 90°, and particularly preferably it is 80° < α < 90°.

[0084] The "hammer" impact pin structure increases the pressure gradient of the fluid in the nozzle and increases the fluid exit velocity, making it more effective when spraying high-viscosity fluids.

[0085] Example 2: Oval hammerhead firing pin

[0086] Figure 1a , Figure 2a , Figure 1b , Figure 2b This is a schematic diagram illustrating the calculation principle of the "effective fluid" in the flow channel of a jet valve with an ellipsoidal ejector head. (For example...) Figure 1a and Figure 2a As shown, the length of the transverse semi-axis of the elliptical cross-section is greater than the length of the longitudinal semi-axis; as Figure 1b and Figure 2b As shown, the length of the transverse semi-axis of the elliptical cross-section is less than the length of the longitudinal semi-axis. Because... Figure 1 (The firing pin head is a sphere) can be considered as... Figure 1a The special form (the firing pin head is an ellipsoid) follows the same design principle as the spherical cross-section described above, except that a semi-axis parameter is added. The specific design process is as follows:

[0087] Figure 1a The diagram shows a cross-sectional view of the jet valve flow channel through the axis of rotation, where the head of the ejector pin is an ellipsoid. The cross-section of the ejector pin head is an ellipse, with point O as the center of the ellipse. A rectangular coordinate system is established with point O as the origin. The cone angle of the wall is α, and the slope of the right-side conical wall line is k. The right-side conical wall line is moved parallel to the ellipse and becomes tangent to it at point q, with the coordinates of point q being q(x0, y0). A perpendicular line segment qp is drawn from point q to the conical wall, with the foot of the perpendicular being p.

[0088] Let the length of the horizontal semi-axis of the ellipse be *a*, and the length of the vertical semi-axis be *b*. Then, the functional relationship of the ellipse can be expressed in a rectangular coordinate system as follows:

[0089] Formula 6:

[0090] Applying the implicit function differentiation rule, by differentiating and simplifying both sides of the ellipse equation, the slope formula of the conical wall can be expressed as:

[0091] Formula 7:

[0092] Combining formulas 6 and 7, we can solve for the coordinates q(x0, y0) of point q, which can be expressed as:

[0093]

[0094] Specifically, when the cone angle α = 90°, the slope k = 1, and the coordinates of point q (x0, y0) can be expressed as:

[0095]

[0096] The volume of rotation of the needle ellipsoidal cap is:

[0097] Formula 8:

[0098] Substituting the coordinates of point q (x0, y0) into formula 8, we get:

[0099] Formula 9:

[0100] Specifically, when a = b, formula 9 and formula 2 are equivalent, that is...

[0101]

[0102] Regarding the volume change of "effective fluid" ΔV, the effective fluid can be organized into the format shown in Formula 4 according to the calculation principle of this embodiment, where the variables are s, a, and b, which will not be elaborated here. According to the calculation method of "effective fluid" volume change ΔV in Embodiment 1, it is easy to see that when the ratio of a to b is larger, ΔV is larger. That is, when using an elliptical cross-section ejector pin with a longer horizontal semi-axis, ΔV is larger, the pressure gradient in the jet channel is also larger, and the kinetic energy of the ejected fluid is greater.

[0103] Figure 5a To compare the pressure contour maps of the ejector jet channel obtained using flow field simulation software, all geometric parameters were identical except for the ejector head cross-section. The contour maps, from left to right, depict an ejector with a circular cross-section, an ejector with an elliptical cross-section with a longer horizontal semi-axis, and an ejector with an elliptical cross-section with a longer vertical semi-axis. The comparison of the pressure contour maps shows that, with other parameters remaining the same, the ejector with an elliptical cross-section and a longer horizontal semi-axis exhibits the largest pressure gradient within the jet channel, thus resulting in the greatest kinetic energy of the ejected fluid.

[0104] Figure 5b To compare the streamline diagrams of the ejector jet channel obtained using flow field simulation software, the "effective fluid" flows downward along the nozzle, while the "ineffective fluid" flows upward.

[0105] This embodiment is a detailed description of a typical example of a method for calculating the volume of "effective fluid". In practical use, the calculation can be performed according to the calculation principle of the embodiment for any arbitrarily defined function curve of the impact pin. That is, the impact pin of the present invention can also be any curve instead of an ellipse, as long as the interface shape is designed to resemble an ellipse according to the principle of the present invention, wherein the semi-axis length of the ellipse along the horizontal direction is longer than the semi-axis length of the ellipse along the vertical direction.

[0106] Example 3: Hammer striker with "groove / protrusion structure"

[0107] Figure 7a , Figure 7b This is a partial schematic diagram of the impact pin head in this embodiment, showing several typical impact pin head structures. The impact pin head is designed with grooves / protrusions, pits / protrusions, round holes, or one or more combinations of the above structures.

[0108] The working principle of the "groove / convex ridge structure" described in this invention is as follows: When the striker moves downward, most of the "ineffective fluid" flows in the opposite direction of the striker's movement, becoming the "main flow." Since the fluid near the "groove / convex ridge structure" is driven by the striker, it becomes a "secondary flow." Because the "secondary flow" and the "main flow" are in opposite directions, the "main flow" is displaced, reducing the flow area of ​​the main flow and thus indirectly increasing the kinetic energy of the "effective fluid." High-viscosity fluids are generally polymeric fluids with shear-thinning effects. When such fluids are sprayed, the "groove / convex ridge structure" increases the local shear rate of the fluid, thereby reducing the apparent viscosity, increasing fluid flowability, and increasing the exit kinetic energy of the fluid jet at the nozzle, which is beneficial for fluid spraying and results in better performance.

[0109] Figure 8a The diagram shows the flow trend of the "ineffective fluid" at a certain moment when the striker falls. The velocity vector lines in the figure represent the "secondary flow" of the local fluid near the "groove / convex structure" of the striker head, calculated by the flow field simulation software. From the magnified view, it can be seen that obvious "secondary flow" appears on both sides of the "groove / convex structure", which reduces the width of the "main flow" channel.

[0110] Figure 8b The diagram shows a comparison of the change in the local shear velocity rate of the fluid near the groove before and after adding the "groove / protrusion structure". The left image shows the change before adding the groove, and the right image shows the change after adding the groove. Specifically, after adding the "groove / protrusion structure", the change rate of the fluid shear velocity increases. For shear-thinned fluids, this is equivalent to reducing the local viscosity of high-viscosity fluids, which is beneficial for fluid jetting.

[0111] Example 4: Circular tube nozzle with gradually changing diameter

[0112] like Figure 9 As shown, this embodiment provides an optimized nozzle structure, which optimizes the nozzle portion of the flow channel from the existing straight circular tube nozzle structure to a circular tube nozzle with a gradually changing diameter. The upstream portion of the nozzle has a larger diameter, while the downstream portion has a smaller diameter. The nozzle portion is designed according to the principle of minimizing local fluid loss, allowing for a smooth transition in the flow channel.

[0113] Preferably, the nozzle diameter gradient structure is a two-stage step, with a chamfer transition between the first and second stages to reduce local fluid resistance; more preferably, a rounded corner transition is used between the first and second stages.

[0114] Preferably, the fillet radius should be between 0.2 and 0.5, and particularly preferably, the fillet radius should be between 0.2 and 0.3.

Claims

1. A firing pin for fluid injection, characterized in that, The striking pin is a hammer-head striking pin, the radius of rotation of which changes along the axis of rotation, and the radius of rotation of the striking pin head is larger than that of the striking pin rod; the striking pin head is composed of a cross section that propels the fluid jet and a cylindrical surface that guides the fluid to be discharged in the opposite direction, the cross section that propels the fluid jet is elliptical or similar to an elliptical cross section, and the horizontal semi-axis length of the cross section is greater than the vertical semi-axis length; The firing pin head has a groove or ridge structure; the groove or ridge structure is a rotary groove or a rotary ridge. During operation, the grooves or protrusions on the hammerhead agitate the fluid, reducing its viscosity and improving the jetting performance of high-viscosity fluids.

2. The firing pin for fluid injection according to claim 1, characterized in that, The rotation radius of the firing pin head is 1.5-2.0 times that of the firing pin rod.

3. The firing pin for fluid injection according to claim 1, characterized in that, The depth of the groove or ridge structure is 3% to 10% of the maximum diameter of the hammerhead head.

4. The firing pin for fluid injection according to claim 1, characterized in that, The total number of grooves or protrusions is greater than or equal to 3.

5. The firing pin for fluid injection according to claim 1, characterized in that, The width of the groove or protrusion is 1 to 4 times the depth of the groove or protrusion.

6. The firing pin for fluid injection according to claim 1, characterized in that, The width of the groove or protrusion is 2 to 3 times the depth of the groove or protrusion.

7. A fluid jetting device, comprising a firing pin, a jet chamber, and a nozzle, characterized in that, The firing pin is the fluid jet firing pin according to any one of claims 1-6.

8. The fluid jetting device according to claim 7, characterized in that, The nozzle has a diameter that gradually changes towards the outlet direction, with a larger diameter at the upstream end and a smaller diameter at the downstream end.

9. The fluid jetting device according to claim 8, characterized in that, The nozzle has a diameter gradient structure consisting of two steps.

10. The fluid jetting device according to claim 9, characterized in that, The two steps are transitioned by chamfering or rounding.

11. The fluid jetting device according to claim 10, characterized in that, The fillet radius should be any value between 0.2 mm and 0.5 mm.

12. The fluid jetting device according to claim 7, characterized in that, The spray chamber is a conical spray chamber, and the cone angle of the conical cross section of the conical spray chamber is any value between 60° and 95°.

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