A high noise reduction automobile air conditioning duct and its forming mold and method

Abstract

A high noise reduction automobile air conditioning duct and its forming mold and method. The present invention belongs to the field of automobile air conditioning ducts. The present invention is to solve the technical problem that the existing PET air duct structure cannot meet the noise reduction requirements in the medium and low frequency bands and the noise reduction effect is not high. In the air duct of the present invention, an inner layer perforated PET upper part and an inner layer perforated PET lower part are provided between the outer layer PET upper part and the outer layer PET lower part, and the inner layer perforated PET upper part is provided with limiting holes, and the limiting holes are covered with a film, and a number of quality sheets are evenly and regularly arranged on the film through a glue layer. The mold of the present invention is composed of an independent upper punching mold and a lower punching mold, and the upper punching mold includes a cavity and an upper mold assembly, and the upper mold assembly is arranged in the cavity, and the lower punching mold structure is the same as the upper punching mold structure.

Description

Technical Field

[0001] The invention belongs to the field of automobile air-conditioning ducts, and in particular relates to a high-noise-reduction automobile air-conditioning duct and a molding die and a molding method thereof. Background Art

[0002] At present, the noise level at the air outlet of the air conditioning system in the cab is high, which affects the acoustic comfort of the entire vehicle. Since the air conditioning system blower, the noise source, is highly versatile and has a high cost of modification, it can only be rectified through the air conditioning duct, the path of noise propagation. In addition, due to the limited space in the cab and the limitations of the duct molding process and cost, it is impossible to add a resistive muffler. The only way to reduce the noise at the pipe mouth is to change the raw materials, that is, the structure, of the duct. Through analysis of the noise source, it was found that the full-band noise reduction capability is poor, and the low-frequency band noise contributes more. Therefore, the traditional single-layer PET pipeline is difficult to solve the problem, and an impedance composite structure is required for comprehensive and targeted noise reduction.

[0003] The existing HDPE material air duct molding method is generally blow molding (see Figure 1 ), the high-density polyethylene material itself does not have the property of being breathable, and there are no tiny pores inside the material, so it does not have the ability to absorb and transmit sound. After being made into an air duct, the cross-sectional area of ​​the pipe is constantly changing, and the expansion ratio is also changing. As a result, the acoustic impedance will also change. Since the cross-sectional area does not change very drastically, the sound energy loss is relatively small, so it has a weak noise reduction ability. Therefore, the air duct of HDPE material only has the properties of a resistant muffler. The noise at the pipe mouth is not significantly reduced. Another traditional PET material air duct structure is a single-layer PET (see Figure 2 ), the noise reduction effect is better than that of HDPE material air duct, and it has the full-band noise reduction ability of porous materials, but it is not very targeted and the sound transmission loss in the low-frequency band is low.

[0004] At present, the improvement of the noise reduction effect of the traditional PET air duct mainly focuses on changing the air duct structure to eliminate eddy currents and control pressure loss, so as to achieve the purpose of controlling noise. The existing invention patent with publication number CN110667373A discloses a PET pipeline and discloses a technical solution of reducing noise by setting a resonance cavity, and the utility model patent with publication number CN207420757U discloses a PET pipeline with a composite structure, which achieves the purpose of noise reduction by built-in braided tubes, and another utility model patent with publication number CN211343181U discloses a composite noise reduction intake pipeline, and specifically discloses that the PET lower shell is set as a porous structure, and elastic pads and shock-absorbing sheets are added to achieve comprehensive noise reduction, but the noise reduction effect of the above-mentioned prior art is still not obvious enough. Summary of the invention

[0005] The present invention provides a high-noise-reduction automobile air-conditioning air duct and a molding die and method thereof to solve the technical problem that the existing PET air duct structure cannot meet the requirements of noise reduction in the medium and low frequency bands and the noise reduction effect is not high.

[0006] A high noise reduction automobile air conditioning duct of the present invention comprises an outer PET upper part and an outer PET lower part, an inner perforated PET upper part and an inner perforated PET lower part are arranged between the outer PET upper part and the outer PET lower part, the lengths of the inner perforated PET upper part and the inner perforated PET lower part are shorter than the outer PET upper part, a limiting hole is arranged on the inner perforated PET upper part, the limiting hole is covered with a film, the film is located between the outer PET upper part and the inner perforated PET upper part, and a plurality of quality sheets are evenly and regularly arranged on the film by bonding with an adhesive layer.

[0007] It is further defined that the diameter of the holes in the upper part of the inner perforated PET layer and the lower part of the inner perforated PET layer is 6-12 mm, and the perforation rate is 5% to 50%.

[0008] It is further defined that the film thickness is 13 μm.

[0009] It is further defined that the thickness of the glue layer is 17 μm.

[0010] It is further defined that the film is 40 mm away from the air duct opening.

[0011] It is further defined that the mass sheet is semicircular in shape and has a diameter of 12 mm.

[0012] It is further defined that the number of quality sheets is 12, which are divided into three groups. The thickness of the three groups increases successively, and the thickness within each group is the same.

[0013] It is further defined that the thickness of the first set of quality sheets is 0.5 mm.

[0014] It is further defined that the thickness of the second set of quality sheets is 1 mm.

[0015] It is further defined that the thickness of the third set of quality sheets is 1.5 mm.

[0016] The molding die of the high noise reduction automobile air conditioning duct of the present invention is composed of an independent upper punching die and a lower punching die;

[0017] The upper punching die comprises a cavity and an upper die assembly, wherein the upper die assembly is arranged in the cavity;

[0018] The upper mold assembly includes an outer PET concave mold, an inner PET concave mold, a punching convex mold, a punching concave mold, an inner PET convex mold, and an outer PET convex mold, which are arranged in sequence from bottom to top;

[0019] The right side of the inner PET female mold, the left side of the inner PET male mold, the front side of the punching male mold and the rear side of the punching female mold are respectively provided with hydraulic cylinders;

[0020] The inner PET female mold and the inner PET male mold are slidably connected to the cavity through the slide rails arranged on the front and rear sides thereof.

[0021] The punching punch and the punching die are slidably connected to the cavity through slide rails arranged on the left and right sides thereof;

[0022] The structure of the lower punching die is the same as that of the upper punching die.

[0023] The working principle of the high noise reduction automobile air conditioning duct forming mold of the present invention is as follows:

[0024] The inner PET raw material sheet is placed in the punching die to punch out the holes. After the punching is completed, the punching die is slid out of the die by the hydraulic cylinder. At the same time, the manipulator places the punched sheet in the middle of the inner PET molding die. The inner PET molding die is molded under the push of the hydraulic equipment. At the same time, the punched sheet is clamped in the middle of the mold. The inner PET perforated structure is completed. The molding die is then slid out of the mold by the hydraulic cylinder. At the same time, the molded inner PET layer slides out with the mold, and the molding temperature is maintained at 100°C to prevent the hardening of the inner PET from affecting the secondary composite. Then, the outer PET sheet is placed in the molding die by the manipulator. The outer PET molding die is molded under the push of the hydraulic equipment. At the same time, the manipulator takes out the pressed inner PET from the inner PET mold and the composite film quality sheet and puts them into the outer PET molding die according to the air duct structure. The inner and outer layers are fused together by hot pressing to obtain a half shell of the PET air duct. The other half of the PET air duct shell is molded according to the above process. Finally, the two are composited to obtain the high noise reduction automobile air conditioning air duct of the present invention.

[0025] The high noise reduction automobile air conditioning duct mold of the present invention solves the following problems of the existing double-layer PET structure mold:

[0026] (1) In the existing double-layer PET structure mold, the inner and outer PET need to be molded separately, the number of molds is large, the cost is high, and the efficiency is low.

[0027] (2) The double-layer PET structure mold requires a separate set of punching dies. However, after forming, many holes in the inner layer of PET are at a negative angle to the punching direction. It is impossible to punch holes at negative angles. Only some flat holes can be punched. This will affect the transmission loss and thus the acoustic effect.

[0028] (3) After the double-layer PET structure mold is formed and punched, the two need to be vibration welded together, and a separate vibration mold needs to be made.

[0029] The molding method of a high noise reduction automobile air conditioning duct of the present invention is carried out according to the following steps:

[0030] S1: placing the inner PET sheet between the punching punch and the punching die, closing the die and punching, and starting the hydraulic cylinders on the punching punch and the punching die after punching, so as to slide the punch and the punching die out;

[0031] S2: placing the punched sheet between the inner PET concave mold and the inner PET convex mold, closing the molds and hot pressing to obtain the inner perforated PET upper part;

[0032] S3: Start the hydraulic cylinders on the inner PET concave mold and the inner PET convex mold to slide out the inner PET concave mold and the inner PET convex mold, and the upper part of the inner perforated PET slides out with the inner PET concave mold and keeps warm;

[0033] S4: bonding the quality sheet to the preheated film through the adhesive layer;

[0034] S5: placing the outer PET sheet between the outer PET concave mold and the outer PET convex mold, closing the molds and hot pressing to obtain the upper part of the outer PET layer;

[0035] S6: Assemble the film with the quality sheet and the upper part of the inner perforated PET layer for heat preservation with the upper part of the outer PET layer, and heat-press and laminate them to obtain the upper half shell of the PET air duct;

[0036] S7: According to the steps of S1-S3 and S5-6, the outer PET lower part and the inner perforated PET lower part are prepared by using the lower punching mold, and then the inner and outer layers are compounded by hot pressing to obtain the PET air duct lower half shell;

[0037] S8: The upper shell of the PET air duct and the lower shell of the PET air duct are composited by vibration friction welding to obtain a high noise reduction automobile air conditioning air duct.

[0038] It is further defined that the hot pressing temperature in S2 is 280° C. and the time is 30-40 s.

[0039] It is further defined that in S4 the film is preheated at 140-060°C for 8-12 min.

[0040] It is further defined that the hot pressing temperature in S5 is 250° C. and the time is 30-40 s.

[0041] It is further defined that the hot pressing temperature in S6 is 200° C. and the time is 30-40 s.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] The method of the present invention realizes broadband noise reduction of the PET air duct by adding upper and lower double micro-perforated plates and using thin film resonators and thin film quality sheets in coordination. The composite structure PET material air duct of the present invention has high sound transmission loss, wide frequency band coverage, sound waves transition in media of different densities, and maximum sound energy loss. The specific advantages are as follows:

[0044] 1) The present invention adds upper and lower double micro-perforated plates in the original PET pipeline, and utilizes the resonance between the upper part of the inner perforated PET and the lower part of the inner perforated PET and the internal pores of the PET fiber to convert part of the kinetic energy into heat energy for consumption, so increasing its area can effectively improve the noise reduction level; at the same time, by limiting the pore size to micropores to improve the sound absorption coefficient, in addition, the low perforation rate can increase the sound absorption frequency band width.

[0045] 2) The present invention embeds a film structure at a local position on the upper part of the perforated PET in the inner layer of the composite structure PET material air duct, which significantly improves the sound absorption effect. At the same time, by adding mass sheets with different wall thicknesses to the film, the mass sheets and the film undergo a piston-like overall movement. This movement causes a displacement discontinuity area to be generated between the connection between the mass sheet and the film and the part of the film that is not attached with the mass sheet, so that more sound energy is converted into elastic strain energy of the film in these narrow and long areas, thereby further improving the low-frequency sound transmission loss, having a strong low-frequency targeting, and enhancing the overall sound absorption coefficient of the composite structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the air duct structure of the existing blow-molded HDPE material;

[0047] Figure 2 It is a schematic diagram of the existing single-layer PET air duct structure;

[0048] Figure 3 This is a schematic diagram of a high noise reduction automobile air conditioning duct structure of the present invention;

[0049] Figure 4 Schematic diagram of the positional relationship of the film;

[0050] Figure 5 It is a schematic structural diagram of an upper mold assembly of an upper punching mold in a high noise reduction automobile air conditioner air duct forming mold of the present invention;

[0051] Figure 6 It is a schematic structural diagram of a lower mold assembly of a lower punching mold in a high noise reduction automobile air conditioner air duct forming mold of the present invention;

[0052] Figure 7 The transmission loss curves of the automobile air conditioning duct in the low-frequency band of Example 3, Control Group 1 and Control Group 2 are shown;

[0053] Figure 8 for Figure 7 Enlarged view of the middle mark (low frequency);

[0054] Among them, 01-the upper part of the outer PET layer, 02-the lower part of the outer PET layer;

[0055] 1-upper part of inner perforated PET layer, 2-lower part of inner perforated PET layer, 3-limiting hole, 4-film, 5-quality sheet;

[0056] 6-external PET concave mold, 7-internal PET concave mold, 8-punching convex mold, 9-punching concave mold, 10-internal PET convex mold, 11-external PET convex mold;

[0057] 12-inner PET sheet, 13-outer PET sheet;

[0058] 14-external PET concave mold, 15-internal PET concave mold, 16-punching convex mold, 17-punching concave mold, 18-internal PET convex mold, 19-external PET convex mold;

[0059] 20-inner PET sheet, 21-outer PET sheet;

[0060] A, B, C, D, E, F, and H are all hydraulic cylinders;

[0061] 70, 80, 90, 100, 150, 160, 170, and 180 are all slide rails. DETAILED DESCRIPTION

[0062] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0064] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0066] In the description of the present invention, the terms "comprises", "including", "having", "containing" or any other variations thereof are used to cover a non-exclusive inclusion. For example, a composition, step, method, article or apparatus comprising the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, step, method, article or apparatus.

[0067] In the description of the present invention, the indefinite articles "a" and "an" before an element or component have no limitation on the quantity requirement (i.e. the number of occurrences) of the element or component. Therefore, "a" or "an" should be interpreted as including one or at least one, and an element or component in the singular form also includes the plural form, unless the quantity obviously refers to the singular form only.

[0068] Embodiment 1:

[0069] Combined with Figure 3-4 The high noise reduction automobile air conditioning duct of this embodiment includes an outer PET upper portion 01 and an outer PET lower portion 02.

[0070] An inner layer perforated PET upper part 1 and an inner layer perforated PET lower part 2 are provided between the outer layer PET upper part 01 and the outer layer PET lower part 02.

[0071] The length of the inner layer perforated PET upper part 1 and the inner layer perforated PET lower part 2 is shorter than the outer layer PET upper part 01.

[0072] The upper part 1 of the inner perforated PET layer is provided with a limiting hole 3.

[0073] The limiting hole 3 is covered with a film 4.

[0074] The film 4 is located between the outer PET upper part 01 and the inner perforated PET upper part 1.

[0075] A plurality of quality sheets 5 are evenly and regularly arranged on the film 4 by bonding with an adhesive layer;

[0076] The diameter of the hole in the upper part 1 of the inner perforated PET layer is 8 mm, and the perforation rate is 30%;

[0077] The diameter of the hole in the lower part 2 of the inner perforated PET layer is 8 mm, and the perforation rate is 30%;

[0078] Film 4 has a thickness of 13 μm;

[0079] The size of film 4 is 144mm×66mm;

[0080] Film 4 is 40 mm away from the air duct opening;

[0081] The thickness of the adhesive layer is 17 μm;

[0082] The mass piece 5 is semicircular in shape and has a diameter of 12 mm;

[0083] The number of quality sheets 5 is 12, divided into three groups, the number of each group is equal, the thickness of the three groups increases in sequence, and the thickness within the group is the same;

[0084] The thickness of the first set of quality sheets 5 is 0.5 mm;

[0085] The thickness of the second set of quality sheets 5 is 1 mm;

[0086] The thickness of the third set of mass sheets 5 is 1.5 mm;

[0087] The upper and lower spacing of the mass pieces 5 is 20 mm;

[0088] The left-right spacing between the mass sheets 5 is 33 mm.

[0089] Embodiment 2:

[0090] Combination Figure 5-6 The high noise reduction automobile air conditioning duct forming mold of this embodiment is composed of an independent upper punching mold and a lower punching mold.

[0091] The upper punching die comprises a cavity and an upper die assembly, wherein the upper die assembly is arranged in the cavity;

[0092] Upper mold assembly (such as Figure 5 The PET die 10 includes an outer PET die 6, an inner PET die 7, a punching die 8, a punching die 9, an inner PET die 10, and an outer PET die 11, which are arranged in sequence from bottom to top;

[0093] The surface of the outer PET female mold 6 is provided with a contoured cavity, and the surface of the outer PET male mold 11 is provided with a contoured protrusion;

[0094] The surface of the inner PET female mold 7 is provided with a contoured cavity, and the surface of the inner PET male mold 10 is provided with a contoured protrusion;

[0095] A hydraulic cylinder A is provided on the right side of the inner PET concave mold 7;

[0096] A hydraulic cylinder B is provided on the left side of the inner PET male mold 10;

[0097] A hydraulic cylinder C is provided on the front side of the punching punch 8;

[0098] A hydraulic cylinder D is provided at the rear side of the punching die 9;

[0099] The inner PET concave mold 7 is slidably connected to the cavity through the slide rails 70 provided on the front and rear sides thereof.

[0100] The inner PET male mold 10 is slidably connected to the cavity through the slide rails 100 provided on the front and rear sides thereof.

[0101] The punching punch 8 is slidably connected to the cavity through the slide rails 80 arranged on the left and right sides thereof.

[0102] The punching die 9 is slidably connected to the cavity through the slide rails 90 arranged on the left and right sides thereof;

[0103] The lower punching die comprises a cavity and a lower die assembly, and the lower die assembly is arranged in the cavity;

[0104] Lower mold assembly (such as Figure 6 ) includes an outer PET concave mold 14, an inner PET concave mold 15, a punching convex mold 16, a punching concave mold 17, an inner PET convex mold 18, and an outer PET convex mold 19 which are arranged in sequence from bottom to top;

[0105] The surface of the outer PET female mold 14 is provided with a contoured cavity, and the surface of the outer PET male mold 19 is provided with a contoured protrusion;

[0106] The surface of the inner PET female mold 15 is provided with a contoured cavity, and the surface of the inner PET male mold 18 is provided with a contoured protrusion;

[0107] A hydraulic cylinder E is provided on the left side of the inner PET female mold 15;

[0108] A hydraulic cylinder F is provided on the right side of the inner PET male mold 18;

[0109] A hydraulic cylinder (not shown in the figure) is provided at the rear side of the punching punch 16;

[0110] A hydraulic cylinder H is provided on the front side of the punching die 17;

[0111] The inner PET female mold 15 is slidably connected to the cavity through the slide rails 150 provided on the front and rear sides thereof.

[0112] The inner PET male mold 18 is slidably connected to the cavity through the slide rails 180 provided on the front and rear sides thereof.

[0113] The punching punch 16 is slidably connected to the cavity through the slide rails 160 arranged on the left and right sides thereof.

[0114] The punching die 17 is slidably connected to the cavity through slide rails 170 arranged on the left and right sides thereof.

[0115] Embodiment 3:

[0116] Combination Figure 3-6 , a method for forming the high noise reduction automobile air conditioning duct as described in Example 1 by using the mold as described in Example 2:

[0117] S1: placing the inner PET sheet 12 between the punching punch 8 and the punching die 9, closing the die and punching, and after punching, starting the hydraulic cylinder C on the punching punch 8 and the hydraulic cylinder D on the punching die 9 to slide the punching punch 8 and the punching die 9 out;

[0118] S2: placing the punched sheet between the inner PET female mold 7 and the inner PET male mold 10, closing the molds and hot pressing at 280° C. for 30 seconds to obtain the inner layer perforated PET upper part 1;

[0119] S3: Start the hydraulic cylinder A on the inner PET female mold 7 and the hydraulic cylinder B on the inner PET male mold 10, slide the inner PET female mold 7 and the inner PET male mold 10 out, and the inner perforated PET upper part 1 slides out with the inner PET female mold 7 and is kept warm at 100°C;

[0120] S4: bonding the quality sheet 5 to the preheated film 4 through the adhesive layer;

[0121] Film 4 was preheated at 150°C for 10 min;

[0122] S5: placing the outer PET sheet 13 between the outer PET concave mold 6 and the outer PET convex mold 11, closing the molds and hot pressing at 250° C. for 40 seconds to obtain the outer PET upper part 01;

[0123] S6: Assemble the film 4 with the quality sheet 5 attached thereto, the heat-insulating inner perforated PET upper part 1 and the outer PET upper part 01 according to the air duct structure, and then heat-press them at 200° C. for 35 seconds to obtain the PET air duct upper half shell;

[0124] S7: placing the inner PET sheet 20 between the punching punch 16 and the punching die 17, closing the die and punching, and after punching, starting the hydraulic cylinder on the punching punch 16 and the hydraulic cylinder H on the punching die 17 to slide the punching punch 16 and the punching die 17 out;

[0125] S8: placing the punched sheet between the inner PET female mold 15 and the inner PET male mold 18, closing the molds and hot pressing at 280° C. for 30 seconds to obtain the inner layer perforated PET lower part 2;

[0126] S9: Start the hydraulic cylinder E on the inner PET female mold 15 and the hydraulic cylinder F on the inner PET male mold 18 to slide the inner PET female mold 15 and the inner PET male mold 18 out, and the inner perforated PET lower part 2 slides out with the inner PET female mold 15 and is kept at 100°C;

[0127] S10: placing the outer PET sheet 21 between the outer PET concave mold 14 and the outer PET convex mold 19, closing the molds and hot pressing at 250° C. for 40 seconds to obtain the outer PET lower part 02;

[0128] S11: Assemble the heat-insulating inner perforated PET lower part 2 and the outer PET lower part 02 according to the air duct structure, and then heat-press them at 200° C. for 35 seconds to obtain the PET air duct lower half shell;

[0129] S12: The upper shell of the PET air duct obtained in S6 and the lower shell of the PET air duct obtained in S11 are combined by vibration friction welding. The lower shell of the PET air duct is fixed, and the upper shell of the PET air duct vibrates left and right. Friction heat is generated by the welding edge until the welding surface melts, thereby obtaining a high-noise reduction automobile air conditioning duct.

[0130] Control group 1:

[0131] Combined with Figure 2 In this embodiment, an automobile air conditioning duct comprises an outer PET upper portion and an outer PET lower portion, and the outer PET upper portion and the outer PET lower portion are composited by vibration friction welding to obtain the automobile air conditioning duct.

[0132] Control group 2:

[0133] An automobile air-conditioning duct of the present embodiment includes an outer PET upper part and an outer PET lower part, an inner perforated PET upper part and an inner perforated PET lower part are arranged between the outer PET upper part and the outer PET lower part, the lengths of the inner perforated PET upper part and the inner perforated PET lower part are shorter than the outer PET upper part, the outer PET upper part and the inner perforated PET upper part are composited by hot pressing, the outer PET lower part and the inner perforated PET lower part are composited by hot pressing, and finally the automobile air-conditioning duct is obtained by vibration friction welding.

[0134] Transmission loss test:

[0135] The transmission loss test was conducted on the high noise reduction automobile air conditioning duct obtained in Example 3 and the automobile air conditioning ducts of control group 1 and control group 2. The specific process is as follows:

[0136] Test method: GBZ 27764-2011, Measurement of sound transmission loss in impedance tubes - transfer matrix method, impedance tube inner diameter 100mm, sensor spacing 70mm, transmission loss test see Figure 7-8 ,

[0137] Depend on Figure 7 It can be seen that the transmission loss of the high noise reduction automobile air conditioning duct obtained in Example 3 of the present invention in the range of 500 Hz to 2500 Hz is significantly higher than the transmission loss of the automobile air conditioning duct structures in the control group 1 and the control group 2.

[0138] Depend on Figure 8 It can be seen that the transmission loss of the film structure below 500Hz is significantly improved by more than 5dB, and the low-frequency effect is significantly higher than the double-layer PET built-in perforation solution of control group 2.

[0139] In summary, the combination of the thin film mass sheet structure and the double-layer PET built-in perforated structure can not only reduce low-frequency noise, but also widen the mid-frequency band and increase the transmission loss amplitude. The two complement each other and truly achieve the effect of targeted noise reduction in the entire frequency band.

[0140] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for forming a high noise reduction automobile air conditioning duct, characterized in that: The high noise reduction automobile air conditioning duct comprises an outer PET upper part and an outer PET lower part, an inner perforated PET upper part (1) and an inner perforated PET lower part (2) are arranged between the outer PET upper part and the outer PET lower part, the inner perforated PET upper part (1) and the inner perforated PET lower part (2) are shorter than the outer PET upper part, a limiting hole (3) is provided on the inner perforated PET upper part (1), a film (4) is covered on the limiting hole (3), the film (4) is located between the outer PET upper part and the inner perforated PET upper part (1), and a plurality of mass sheets (5) are evenly and regularly arranged on the film (4) by bonding with an adhesive layer; The molding die of the high noise reduction automobile air conditioning duct is composed of an independent upper punching die and a lower punching die. The upper punching die includes a cavity and an upper die assembly. The upper die assembly is arranged in the cavity. The upper die assembly includes an outer PET concave die (6), an inner PET concave die (7), a punching convex die (8), a punching concave die (9), an inner PET convex die (10), and an outer PET convex die (11) arranged in sequence from bottom to top. Hydraulic cylinders are respectively provided on the right side of the inner PET concave die (7), the left side of the inner PET convex die (10), the front side of the punching convex die (8), and the rear side of the punching concave die (9). The inner PET concave die (7) and the inner PET convex die (10) are slidably connected to the cavity via slide rails arranged on their front and rear side surfaces. The punching convex die (8) and the punching concave die (9) are slidably connected to the cavity via slide rails arranged on their left and right side surfaces. The lower punching die comprises a cavity and a lower die assembly, wherein the lower die assembly is arranged in the cavity; the lower die assembly comprises a lower outer PET die (14), a lower inner PET die (15), a lower punching convex die (16), a lower punching die (17), a lower inner PET convex die (18), and a lower outer PET convex die (19) which are arranged in sequence from bottom to top; hydraulic cylinders are respectively arranged on the left side of the lower inner PET die (15), the right side of the lower inner PET convex die (18), the rear side of the lower punching convex die (16), and the front side of the lower punching die (17); the lower inner PET die (15) and the lower inner PET convex die (18) are slidably connected to the cavity via slide rails arranged on their front and rear side surfaces, and the lower punching convex die (16) and the lower punching die (17) are slidably connected to the cavity via slide rails arranged on their left and right side surfaces; The molding method of the high noise reduction automobile air conditioning duct: S1: placing the inner PET sheet (12) between the punching punch (8) and the punching die (9), closing the die to punch, and after punching, starting the hydraulic cylinders on the punching punch (8) and the punching die (9) to slide them out; S2: placing the punched sheet between an inner PET concave mold (7) and an inner PET convex mold (10), closing the molds and performing hot pressing to obtain an inner layer perforated PET upper part (1); S3: activating the hydraulic cylinders on the inner PET female mold (7) and the inner PET male mold (10) to slide them out, and the inner perforated PET upper part (1) slides out along with the inner PET female mold (7) and is kept warm; S4: bonding the quality sheet (5) to the preheated film (4) through the adhesive layer; S5: placing the outer PET sheet (13) between the outer PET concave mold (6) and the outer PET convex mold (11), closing the molds and performing hot pressing to obtain the outer PET upper part (01); S6: Assemble the film (4) with the quality sheet (5) and the heat-insulating inner perforated PET upper part (1) and the outer PET upper part (01), and heat-press and laminate them to obtain the PET air duct upper half shell; S7: placing the lower inner layer PET sheet (20) between the lower punching punch (16) and the lower punching die (17), closing the die to punch, and after punching, starting the hydraulic cylinders on the lower punching punch (16) and the lower punching die (17) to slide it out; S8: placing the punched sheet between the lower inner PET concave mold (15) and the lower inner PET convex mold (18), closing the molds and performing hot pressing to obtain the inner layer perforated PET lower part (2); S9: activating the hydraulic cylinders on the lower inner PET female mold (15) and the lower inner PET male mold (18) to slide them out, and the inner perforated PET lower part (2) slides out along with the lower inner PET female mold (15) and is kept warm; S10: placing the lower outer layer PET sheet (21) between the lower outer PET concave mold (14) and the lower outer PET convex mold (19), closing the molds and performing hot pressing to obtain the outer layer PET lower part (02); S11: Assembling the heat-insulating inner perforated PET lower part (2) and the outer PET lower part (02) according to the air duct structure, and hot-pressing and laminating them to obtain the PET air duct lower half shell; S12: The upper shell of the PET air duct and the lower shell of the PET air duct are composited by vibration friction welding to obtain a high noise reduction automobile air conditioning air duct.

2. The molding method according to claim 1, characterized in that: The hot pressing temperature in S2 is 280°C, the hot pressing temperature in S5 is 250°C, and the hot pressing temperature in S6 is 200°C, and the time is 30-40s.

3. The molding method according to claim 1, characterized in that: The film (4) in S4 is preheated at 150°C for 8-12 minutes.

4. The molding method according to claim 1, characterized in that: The diameter of the holes in the inner layer perforated PET upper part (1) and the inner layer perforated PET lower part (2) is 6-12 mm, and the perforation rate is 5%-50%.

5. The molding method according to claim 1, characterized in that: The film (4) has a thickness of 13 μm, the adhesive layer has a thickness of 17 μm, and the film (4) is 40 mm away from the air duct opening.

6. The molding method according to claim 1, characterized in that: The mass sheet (5) is semicircular in shape and has a diameter of 12 mm.

7. The molding method according to claim 1, characterized in that: The number of quality sheets (5) is 12, which are divided into three groups. The thickness of the three groups increases in sequence, and the thickness within each group is the same.

8. The molding method according to claim 1, characterized in that: The thickness of the first set of quality sheets is 0.5 mm, the thickness of the second set of quality sheets is 1 mm, and the thickness of the third set of quality sheets is 1.5 mm.

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