Knob Cap for High-Pressure Tank

Abstract

The present invention relates to a knob cap for a high-pressure tank, and discloses a knob cap for a high-pressure tank, which has a coupling groove formed on the underside of a body corresponding to a knob of a high-pressure tank liner, a peripheral wing portion extending outward from the lower end of the outer periphery of the body so as to contact the surface of the liner, and a thickness changing portion formed on the outer periphery of the body to change the thickness between the center line and the outer periphery.

Description

Technical Field

[0001] The present invention relates to a knob cap for a high-pressure tank, and more particularly to a knob cap for a high-pressure tank that serves as a coupling site with a shaft when manufacturing a high-pressure tank by winding composite material fibers on the surface of a liner by a filament winding method.

Background Art

[0002] Vehicles that use gaseous fuels, such as natural gas vehicles and hydrogen fuel cell vehicles, are equipped with high-pressure tanks for storing high-pressure gases such as hydrogen. In particular, as a high-pressure tank for storing high-pressure hydrogen gas, a high-pressure tank corresponding to Type 4 is used.

[0003] Generally, a Type 4 high-pressure tank is manufactured by forming a composite material layer on the surface of a liner made of a plastic material by a filament winding method. The liner is manufactured by bonding a metal boss and a knob to a plastic material such as a polyolefin-based resin or a polyamide-based resin. The composite material layer is formed by winding a composite material fiber in which carbon fiber or glass fiber is mixed with a polymer resin such as an epoxy resin on the surface of the liner.

[0004] In the case of a one-port type high-pressure tank, a port that is a head boss to which a valve for gas inlet and outlet such as hydrogen is coupled is formed on one side, and a knob that is a tail boss for fixing the tank is provided on the other side of the high-pressure tank. Conventionally, a method in which a metallic knob cap is externally coupled to the knob has been used.

[0005] The knob cap serves to be coupled and fixed to a fixed shaft to prevent the tank from shaking during the filament winding process. However, the entire knob cap is made of metal, which has become a factor that hinders the weight reduction of the high-pressure tank.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, the present invention has been devised to solve the above-described problems, and an object of the present invention is to provide a knob cap for a high-pressure tank that can be lightened while ensuring structural stability.

[0008] Another object of the present invention is to provide a knob cap for a high-pressure tank that can be provided with a reinforcing cap having impact resistance so as to improve the defensive effect against external impacts.

Means for Solving the Problems

[0009] To achieve the above object, an embodiment of the present invention provides a knob cap for a high-pressure tank, in which a coupling groove portion is formed on the lower surface of the body corresponding to a knob of a high-pressure tank liner, and a peripheral fin portion extending outward in contact with the surface of the liner is provided at the lower end of the outer peripheral surface of the body, and a thickness conversion portion for converting the thickness between the center line and the outer peripheral surface is formed on the outer peripheral surface of the body.

[0010] According to an embodiment of the present invention, a metal insert formed of a metal material coupled to the knob may be coupled to the coupling groove portion of the body.

[0011] According to an embodiment of the present invention, the metal insert may be formed in a cup shape having a hollow with a thread formed on the inner peripheral surface.

[0012] According to an embodiment of the present invention, one or more inner grooves extending downward from the upper surface of the body are formed in the body.

[0013] According to an embodiment of the present invention, a disc-shaped reinforcing cap with a hollow formed thereon and having coupling protrusions coupled to the inner grooves may be coupled to the upper surface of the body.

[0014] According to an embodiment of the present invention, the metal material of the metal insert includes aluminum, and the body is formed of a fiber-reinforced plastic reinforced with glass fiber or carbon fiber.

[0015] According to an embodiment of the present invention, the thickness conversion part may have a stepped shape with steps formed thereon.

[0016] According to an embodiment of the present invention, on the outer peripheral surface at the thickness conversion part, the outer peripheral surface may have an inclined surface shape such that the thickness of the body decreases as it goes upward, or a curved groove or a V-shaped groove shape that is recessed toward the center line.

[0017] According to an embodiment of the present invention, a hollow fixing groove to which a fixing shaft can be coupled during the filament winding process is formed at the center of the upper surface of the body. A metal bushing may be coupled to the fixing groove.

Effect of the Invention

[0018] According to the knob cap for a high-pressure tank of the present invention having the configuration as described above, since it can be formed of a plastic material such as a fiber-reinforced plastic, the weight reduction effect of the high-pressure tank can be enhanced.

[0019] Further, according to the present invention, by forming a thickness conversion part such as a stepped shape on the outer peripheral surface of the knob cap so as to control the generation of strong internal stress of the high-pressure tank, breakage of the knob cap and the high-pressure tank can be prevented.

[0020] According to the present invention, since it is possible to provide a reinforcing cap having impact resistance on the outside of the knob cap, there is an effect of protecting it from a drop test and external impact.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0022] The present invention can be subjected to various modifications and can have various forms. Therefore, embodiments will be described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention. Similar reference numerals are used for similar components in describing each drawing.

[0023] The above terms are used only for the purpose of distinguishing one component from another. The terms used in this application are merely used to describe a specific embodiment and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates a different meaning.

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings as follows.

[0025] FIG. 1 is a configuration diagram of a high-pressure tank liner according to the present invention.

[0026] A high-pressure tank for storing high-pressure gases such as hydrogen includes a liner 110 and a composite material layer formed by filament winding a fiber-reinforced composite material on the outer surface of the liner. The liner stores high-pressure gas in the internal space and maintains the gas tightness, and the composite material layer serves to support the stress acting in the circumferential direction of the liner due to the internal pressure of the gas.

[0027] The liner 110 is manufactured by blow molding, rotational molding, injection molding, etc. using plastic materials such as polyolefin resins and polyamide resins for weight reduction.

[0028] The composite material layer (see Fig. 3, 120) is formed by wrapping a fiber-reinforced composite material in which carbon fibers or glass fibers are mixed with a polymer resin such as an epoxy resin around the surface of the liner 110 to maintain strength.

[0029] The high-pressure tank 100 manufactured in this way is used for the purpose of compressing and storing various fluids including liquefied petroleum gas (LPG), compressed natural gas (CNG), light hydrocarbons (methane, propane, butane), and hydrogen gas.

[0030] A valve is coupled to one side of the liner 110 to form a port 101 through which gas fuel can enter and exit, and a knob 111 for fixing purposes is provided on the other side. A knob cap 200 as shown in Figs. 2 to 3 is coupled to the knob 111.

[0031] Figs. 2 and 3 are a cross-sectional perspective view and a cross-sectional view showing a knob cap for a high-pressure tank according to the present invention. For easier explanation, the composite material layer 120 is shown in FIG. 3 instead of FIG. 2.

[0032] The knob cap 200 according to an embodiment of the present invention includes a body 201 coupled to the knob 111 of the liner 110 of the high-pressure tank 100. According to an embodiment of the present invention, the body 201 can be formed of a plastic material and can further include a metal insert 211 made of a metal material.

[0033] According to an embodiment of the present invention, a fiber-reinforced plastic in which fibers are included in a plastic resin is used as the plastic material of the knob cap body 201. As the plastic resin, a polyolefin-based resin ( HDPE system) or a polyamide-based (such as PA6, PA66) and a compound material based on this or a combination of the resins can be used, and as the fiber, carbon fiber or glass fiber in the form of long fiber or short fiber can be used. The fiber-reinforced plastic according to the present invention can be a long fiber-reinforced plastic (LFT; long fiber thermoplastic) or a short fiber-reinforced plastic (SFT; short fiber thermoplastic). When the fiber-reinforced plastic is applied, it is advantageous that the weight ratio of the fiber is composed of 2 to 70%.

[0034] According to the knob cap 200 of the present invention, a metal insert 211 can be provided with a metal, for example, aluminum (Al) at a portion where the knob 111 of the high-pressure tank liner 110 is coupled. By forming the body 201 with a plastic material and coupling it with the metal insert 211, it is possible to improve the durability of the portion coupled with the knob 111 of the liner 110 while reducing the weight. The knob cap 200 according to an embodiment of the present invention can be manufactured by an insert injection molding method in which the metal insert 211 is inserted into a mold and a plastic material is injected when the metal insert 211 is included.

[0035] Referring to FIGS. 2 and 3, in the knob cap 200 according to an embodiment of the present invention, a coupling groove portion 210 is formed at the center of the lower surface corresponding to the knob 111 in the body 201, and the metal insert 211 is provided in the coupling groove portion 210.

[0036] The metal insert 211 is a part where the knob 111 of the liner 110 is inserted and coupled, and is formed in a hollow cup shape with a thread formed on the inner peripheral surface. Therefore, it can be coupled to the knob 111 of the liner 110 having a thread formed on the outer peripheral surface by a screw fastening method. Since the metal insert 211 is integrally formed with the body 201, the knob cap 200 can be coupled to the knob 111 of the liner 110 by a screw fastening method. The metal insert 211 increases the durability of the knob cap 200.

[0037] The body 201 of the knob cap 200 is provided with a peripheral fin portion 220 extending outward at the lower end of the outer peripheral surface. The peripheral fin portion 220 extends in a curved connection with the outer peripheral surface of the body 201 and the outer surface of the liner 110, and the entire bottom surface is in close contact with the liner 110.

[0038] A plurality of inner grooves 230 are formed in the body 201 of the knob cap 200. The inner groove 230 is a columnar groove extending downward from the upper surface of the body 201, that is, having an open upper end and extending downward. The inner groove 230 is formed in a cylindrical or polygonal column shape. The plurality of inner grooves 230 can be arranged annularly surrounding the center line of the body 201, but are arranged in a form in which a plurality are spaced apart at equal intervals in the circumferential direction and a plurality are spaced apart in the radial direction.

[0039] The inner groove 230 functions to prevent shrinkage from occurring during demolding with a mold after injection molding. That is, when the knob cap is demolded with a mold after molding, shape deformation may occur due to a relatively large amount of cooling shrinkage in the central portion, but the plurality of inner grooves 230 function to prevent shape deformation due to shrinkage.

[0040] According to the present invention, a reinforcing material is attached to the inner groove 230. That is, when there is a risk of a decrease in physical properties due to the inner groove 230, a reinforcing material having a shape corresponding to the inner groove 230, for example, a cylindrical reinforcing material, can be inserted into the inner groove 230 to prevent a decrease in physical properties.

[0041] According to the present invention, a hollow fixing groove 240 for fixing a fixing shaft (not shown) necessary for the filament winding process is formed at the center of the upper surface of the body 201 of the knob cap 200. A metal bushing 250 is provided inside the fixing groove 240 to enhance the bonding force with the fixing shaft.

[0042] The metal bushing 250 applied to the fixing groove 240 also strengthens the bonding force with the fixing shaft and functions to prevent breakage due to strong tension during the filament winding operation.

[0043] According to an embodiment of the present invention, a thickness conversion portion 260 is formed on the outer peripheral surface of the body 201 of the knob cap 200. The thickness conversion portion 260 changes the thickness of the body defined between the center line and the outer peripheral surface so that the outer peripheral surface has different thicknesses at least in part in the height direction. The center line is a line passing through the center of the knob cap in the height direction. The thickness conversion portion 260 improves the supporting force against internal stress.

[0044] According to an embodiment of the present invention, as can be seen from FIGS. 2 and 3, the thickness conversion portion 260 formed on the outer peripheral surface of the body 201 of the knob cap 200 may have a stepped shape with a step 262 formed. By providing the thickness conversion portion 260 with the step 262, a reduced outer diameter portion 261 with a relatively reduced thickness is provided at the upper end of the outer peripheral surface.

[0045] Although FIGS. 2 and 3 illustrate the formation of one step, it can be formed such that the thickness decreases in a manner in which steps are continuously formed.

[0046] The thickness conversion portion 260 formed on the outer peripheral surface of the knob cap 200 allows the composite material layer 120 to be reinforced during the manufacture of the high-pressure tank. Since the composite material layer 120 can be reinforced and stress can be supported, it functions to improve the structural stability of the knob cap 200.

[0047] According to an embodiment of the present invention, the thickness conversion unit 260 is not limited to a stepped shape and can be formed in various shapes.

[0048] FIG. 4 is a partial cross-sectional view for explaining an embodiment of a thickness conversion unit formed on an outer peripheral surface of a knob cap according to an embodiment of the present invention.

[0049] Referring to FIG. 4(a), the thickness conversion unit 260 is formed in an inclined surface shape. The outer peripheral surface has an inclined surface shape at the thickness conversion unit 260 such that the thickness of the body decreases as it goes upward. Therefore, the upper end of the inclined surface is close to the center line, and the lower end is relatively far from the center line. When the thickness conversion unit 260 shown in FIG. 4(a) is formed and when it is formed on the entire height of the outer peripheral surface, the body has a trapezoidal cross-section with a narrow width at the upper end and a wide width at the lower end.

[0050] Referring to FIG. 4(b), the thickness conversion unit 260 is formed in a curved groove shape. The curved groove is formed in a shape where the middle part is recessed toward the center line. Therefore, when the curved groove is formed on the outer peripheral surface, the thickness of the body is the thinnest at the middle part. Referring to FIG. 4(c), the thickness conversion unit 260 can be in the groove shape of a V-shaped groove where the middle part is recessed toward the center line. Therefore, the thickness of the body is the thinnest at the middle part. Although it is shown in FIGS. 4(b) and (c) that the recessed part toward the center line is formed in the middle part, the position can be changed. Also, the inclined surface, the curved groove, and the V-shaped groove can be formed over the entire height direction of the outer peripheral surface of the body, but can be formed in some parts. The thickness conversion unit 260 as described above functions to improve the bonding force with the composite material layer 120 and suppress deformation against the stress acting in the outer direction of the liner 110.

[0051] According to an embodiment of the present invention, a reinforcing cap 300 that covers the upper surface of the knob cap 200 is further included. The reinforcing cap 300 is formed in a hollow thin disk shape having a diameter or width larger than the diameter or width of the body 201 of the knob cap 200. The reinforcing cap 300 includes a hollow 310, and coupling protrusions 320 corresponding to the inner grooves 230 are formed on the lower surface. The coupling protrusions 320 are inserted and coupled to the inner grooves 230.

[0052] The reinforcing cap 300 is formed of EPP foam (Expanded Polypropylene foam) and has excellent resilience against repetitive impacts and deformations. When exposed to extreme temperatures, it maintains high dimensional stability and is excellent in impact resistance, repetitive cushioning, flexibility, chemical resistance, etc. Such a reinforcing cap 300 can enhance the drop test of the high-pressure tank 100 and the response force against external impacts.

[0053] Hereinafter, with reference to Table 1, FIGS. 5 and 6, the weight reduction effect of the knob cap according to the present invention and the structural stability based on the explanation result of the stress distribution are provided.

[0054] Examples realized the knob caps shown in FIGS. 2 and 3. The reference examples are the same as the examples, but regarding the straight shape in which the thickness conversion part is not applied to the outer peripheral surface. The comparative examples are conventional knob caps formed of a metal material.

[0055] In the examples and reference examples, aluminum (specifically, Al6061-T61) material was used for the metal insert, and long fiber reinforced plastic was used for the body in which the metal insert was inserted into the coupling groove. Specifically, PA6 was used as the matrix resin, and 50 wt% of GF was included.

[0056] First, when examining the weight reduction rate with reference to Table 1, it is as follows.

[0057]

Table 1

[0058] As can be seen from Table 1, when forming a knob cap by insert injection molding of a metal insert and plastic as in the examples of the present invention, a weight reduction effect of 40% or more can be obtained compared to the comparative examples, which acts as a factor that can improve the weight efficiency of container products.

[0059] FIG. 5 is a diagram showing the result of interpreting the stress distribution for the knob cap for a high-pressure tank according to an embodiment of the present invention, and FIG. 6 is a diagram showing the result of interpreting the stress distribution for the knob cap for a high-pressure tank according to a reference example.

[0060] It was assumed that the liner was made of a PA-based resin and formed by a blow molding method. It can be formed by a rotation molding or injection molding method. After forming the liner, the knob caps according to the examples and reference examples were attached to the screw-type protrusions, and a composite material layer was formed by the filament winding method. The stress distribution was interpreted assuming the case where a gas such as hydrogen was injected at high pressure inside after complete curing, and the presence or absence of deformation of the knob at the minimum design burst pressure (1,750 bar) was interpreted. Damage occurs when the stress value exceeds the tensile strength value of each material (Reference: Al6061-T61: 310 Mpa, PA6 + GF50wt%: 230 Mpa)

[0061] Comparing FIG. 5 and FIG. 6, as can be seen from FIG. 5, in the embodiment, it can be seen that a safety margin of +85% for the plastic material and +9% for the aluminum material can be ensured, and sufficient structural stability can be ensured at the peripheral part of the blade.

[0062] Thus, it can be seen that in the case of the embodiment of the present invention, while achieving weight reduction, excellent structural properties are exhibited.

[0063] The above description of the present invention is for illustrative purposes, and those of ordinary skill in the technical field to which the present invention pertains can understand that the present invention can be easily deformed into other specific forms without changing the technical idea and essential features of the present invention. Therefore, it must be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts are construed to be included within the scope of the present invention.

Description of Symbols

[0064] 100 High-pressure tank 110 Liner 111 Knob 120 Composite material layer 200 Knob cap 201 Body 210 Coupling groove part 211 Metal insert 220 Peripheral fin part 230 Inner groove 240 Fixing groove 250 Bushing 260 Thickness conversion part 300 Reinforcing cap 310 Hollow 320 Coupling protrusion

Claims

1. A coupling groove corresponding to a knob of a high-pressure tank liner is formed on the lower surface of the body, and a peripheral blade portion extending outward at the lower end of the outer peripheral surface of the body so as to contact the surface of the liner is provided, and a thickness conversion portion for changing the thickness between the center line and the outer peripheral surface is formed on the outer peripheral surface of the body, a metal insert formed of a metal material coupled to the knob is inserted into the coupling groove, the body, a hollow fixing groove extending downward from the center of the upper surface of the body and fixing a fixing shaft used in a filament winding process, and one or more inner grooves located outside the fixing groove on the upper surface of the body and extending downward are included, and a reinforcing cap having a hollow formed with a coupling protrusion coupled to the inner groove is coupled to the upper surface of the body, a knob cap for a high-pressure tank.

2. The knob cap for a high-pressure tank according to claim 1, wherein the metal insert has a cup shape with a hollow formed with a thread on the inner peripheral surface.

3. The body is formed of a fiber-reinforced plastic reinforced with glass fiber or carbon fiber, and the metal material of the metal insert includes aluminum, the knob cap for a high-pressure tank according to claim 1.

4. The knob cap for a high-pressure tank according to claim 1, wherein the thickness conversion portion has a stepped shape with a step formed.

5. The knob cap for a high-pressure tank according to claim 1, wherein the outer peripheral surface at the thickness conversion portion has an inclined surface shape in which the thickness of the body decreases upward, or a curved groove or a V-shaped groove shape recessed toward the center line.

6. The knob cap for a high-pressure tank according to claim 1, wherein the fixing groove enables the fixing shaft to be coupled when performing a filament winding process.

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