Ultrasonic horn for fixing sound-absorbing material for vehicles, method for producing fixing structure for sound-absorbing material for vehicles, and fixing structure for sound-absorbing material for vehicles

Abstract

To provide an ultrasonic horn for fixing an automotive sound absorbing material, a method for producing a fixing structure for the automotive sound absorbing material, and a fixing structure for the automotive sound absorbing material, which fixes the automotive sound absorbing material by ultrasonic vibration at a deep position in a fiber-based base material and maintains stable fixing strength at a fixing point.SOLUTION: A ultrasonic horn 5 for fixing an automotive sound absorbing material is used to produce a fixing structure for the automotive sound absorbing material 3, in which a fixing part 14 of the automotive sound absorbing material 3 layered on a base material 2, which is a fiber molded body containing thermoplastic synthetic resin, is fixed to the base material 2. In a production of fixing structure of the sound absorbing material 3 for automotive use, the ultrasonic horn 5 includes: a pressing surface 23 for applying a pressing force to the fixing part 14 to push the fixing part 14 into the base material 2; and a transmission part 21 that realizes transmission of ultrasonic vibration from the pressing surface 23 toward the fixing part 14. The pressing surface 23 has a shape in which a displacement area 26 is set on a peripheral edge part such that a pressing depth of the fixing part 14 into the base material 2 becomes shallower toward an outer periphery.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic horn for fixing a sound-absorbing material to a vehicle, a method for producing a fixing structure for a sound-absorbing material to a vehicle, and a fixing structure for a sound-absorbing material to a vehicle. [Background technology]

[0002] Various interior and exterior vehicle materials have been known to have sound-absorbing materials attached to them to absorb noise from the outside of the vehicle into the interior of the vehicle. Ultrasonic welding is one method of attaching sound-absorbing materials. For example, Patent Document 1 discloses a vehicle ceiling material in which a felt made of a fibrous material is attached to the base material using a rod-shaped ultrasonic horn. In this ultrasonic welding, heat generated by vibration energy melts a portion of the laminate constituting the base material, generating molten resin. This molten resin entangles with the fibers constituting the felt and solidifies, thereby adhering the felt to the base material. Because the ultrasonic horn is pressed against the top surface of the felt and is pushed into the base material to a predetermined depth, the felt located directly below and near the ultrasonic horn is elastically compressed and deformed significantly.

[0003] Recently, in order to improve the sound absorption performance of the substrate, it has become common to increase the thickness of the fiber-based substrate and attach the sound-absorbing material to this thick portion by ultrasonic welding. In this case, in order to sufficiently transmit the vibration energy of the ultrasonic horn to the thick portion of the fiber web layer, it is necessary to press the ultrasonic horn deeper into the substrate. Furthermore, vehicle exterior materials such as undercovers are more susceptible to external influences than vehicle interior materials, and therefore require stable fixing strength for the sound-absorbing material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-272709 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when an ultrasonic horn is pushed deep into a fiber-based substrate to secure the sound-absorbing material, the force pulling the sound-absorbing material in the direction of the push increases, making it more likely to tear around the edge of the bonded portion. If an external load is applied to the bonded portion of the sound-absorbing material after a tear has occurred, the tear can cause the sound-absorbing material to tear. Furthermore, the location and extent of the tear vary, making the bond strength to the substrate unstable and leading to the problem of the sound-absorbing material easily falling off.

[0006] The present invention was devised in light of the above points, and the problem that the present invention aims to solve is to provide an ultrasonic horn for fixing an in-vehicle sound-absorbing material, a method for producing a fixing structure for an in-vehicle sound-absorbing material, and a fixing structure for an in-vehicle sound-absorbing material, which fix an in-vehicle sound-absorbing material at a deep position in a fiber-based base material using ultrasonic vibrations while maintaining stable fixing strength at the fixing point. [Means for solving the problem]

[0007] One feature of the ultrasonic horn for fixing in-vehicle sound-absorbing material that solves the above-mentioned problem is that it is an ultrasonic horn for fixing in-vehicle sound-absorbing material that is used to produce a fixing structure for in-vehicle sound-absorbing material in which a fixing portion of the in-vehicle sound-absorbing material that is layered on a base material that is a fiber molding containing a thermoplastic synthetic resin is fixed to the base material, and in producing the fixing structure for the in-vehicle sound-absorbing material, it has a pressing surface that applies a pressing force to the fixing portion to press the fixing portion into the base material, and a transmission portion that transmits ultrasonic vibrations from the pressing surface to the fixing portion, and the pressing surface has a shape in which a displacement area is set on its peripheral portion so that the pressing depth of the fixing portion into the base material becomes shallower towards the periphery.

[0008] One feature and advantage of the above configuration is that the pressing surface of the ultrasonic horn applies a pressing force to the fixed portion of the sound-absorbing material, pressing the fixed portion into the substrate. The fixed portion is fixed by the vibration energy of the ultrasonic vibrations modifying the substrate and the sound-absorbing material. The peripheral edge of the pressing surface has a displacement area where the pressing depth of the fixed portion into the substrate becomes shallower toward the periphery. The fixed portion pressed by the ultrasonic horn is recessed to match the shape of the pressing surface, so the pressing force is relatively smaller at the portion in contact with the displacement area of ​​the pressing surface, thereby easing the pulling force on the sound-absorbing material. Furthermore, the pressing surface transmits ultrasonic vibrations to the fixed portion even at shallow portions of its periphery, thereby fixing it. This allows the sound-absorbing material to be pressed into the substrate, which is a fiber molded body, to a depth where ultrasonic vibrations are sufficiently transmitted, thereby fixing the sound-absorbing material, and also prevents tearing from occurring at the peripheral edge of the fixed portion fixed by the ultrasonic horn.

[0009] In the ultrasonic horn for fixing a sound-absorbing material to be mounted on a vehicle, the displacement area may be configured to have a concave curved surface shape that is concave toward the opposite side to the base material when the pressing force is applied.

[0010] One feature and advantage of the above configuration is that the displacement area of ​​the pressing surface has a concave curved shape that is concave on the opposite side to the base material, which makes it possible to more gently pull the sound-absorbing material at the periphery of the fixing portion when a pressing force is applied to the fixing portion by the pressing surface.

[0011] One feature of the method for producing a fixed structure for an in-vehicle sound-absorbing material using the above-mentioned ultrasonic horn for fixing an in-vehicle sound-absorbing material is that it comprises a pressing step in which the pressing force is applied from the pressing surface of the ultrasonic horn to the fixing portion of the in-vehicle sound-absorbing material in a state where it is layered on the base material, thereby pressing the fixing portion into the base material, and a fixing step in which ultrasonic vibrations are transmitted from the transmission part of the ultrasonic horn to the fixing portion in a state where it has been pressed into the base material, thereby modifying and fixing at least a portion of the base material and the fixing portion by the ultrasonic vibrations.

[0012] One feature and advantage of the above production method is that an ultrasonic horn having a displacement area on its pressing surface is used to fix an in-vehicle sound-absorbing material to a substrate, which is a fiber molding. During the pressing process, the fixed portion of the sound-absorbing material pressed against the pressing surface receives a relatively gentle pressing force at the portion in contact with the displacement area. This also reduces the pulling force on the fixed portion, preventing tearing at the periphery of the fixed portion. Furthermore, during the fixing process, ultrasonic vibrations are transmitted to the substrate and the fixed portion via the pressing surface, and at least a portion of the substrate and the fixed portion are modified by the vibration energy of the ultrasonic vibrations. As a result, the fixed portion is fixed even in a shallow portion of its periphery, allowing for stable bonding strength to be maintained against external loads.

[0013] One feature of the fixing structure of the vehicle-mounted sound-absorbing material is that it has a substrate which is a fiber molding containing a thermoplastic synthetic resin, and the vehicle-mounted sound-absorbing material which is a laminate of a planar fiber web containing thermoplastic synthetic fibers and a nonwoven fabric, the substrate having a sound-absorbing surface which absorbs noise inside and outside the vehicle, and a pressure-bonded portion which is compressed in the thickness direction relatively more than the sound-absorbing surface, the vehicle-mounted sound-absorbing material having a fixing portion where the vehicle-mounted sound-absorbing material is fixed in a superimposed state to the sound-absorbing surface of the substrate, the fixing portion having a recess where the vehicle-mounted sound-absorbing material is pressed into the substrate, the recess being fixed by at least a portion of the substrate and the fixing portion being modified by ultrasonic vibration, and the recess having a displacement portion at the periphery where the depth of the recess becomes shallower towards the periphery.

[0014] One feature and advantage of the above configuration is that the vehicle-mounted sound-absorbing material is fixed to the sound-absorbing surface of the substrate, which has a relatively thick plate thickness. The fixing portion has a recess formed by being pressed into the substrate to a set depth. The recess has a displacement portion at its peripheral edge, where the depth of the recess becomes shallower toward the periphery. The shape of this recess gently suppresses the force pulling the sound-absorbing material at the peripheral edge, suppressing the occurrence of tears at the fixed edge of the sound-absorbing material. Furthermore, ultrasonic vibrations are transmitted throughout the entire recess, including the displacement portion, and the substrate and the fixing portion are modified and fixed by the vibration energy of the ultrasonic vibrations. As a result, the sound-absorbing material is fixed to the substrate, which is a fiber molded body, at a depth position where ultrasonic vibrations can be sufficiently transmitted, and the fixing strength of the sound-absorbing material is maintained stable against external loads.

[0015] In the fixing structure of the on-vehicle sound-absorbing material, the displacement portion may have a convex curved surface shape that is convex toward the opposite side to the base material.

[0016] One feature and advantage of the above configuration is that the displacement portion in the recess of the fixing portion has a convex curved shape that is convex on the opposite side to the base material, which makes it possible to more gently pull the sound-absorbing material that has been pressed to a set depth into the base material at the periphery of the fixing portion. [Effects of the Invention]

[0017] By adopting the above-described configuration or production method, the present invention can provide an ultrasonic horn for fixing on-vehicle sound-absorbing material, a method for producing a fixing structure for on-vehicle sound-absorbing material, and a fixing structure for on-vehicle sound-absorbing material, which fixes the on-vehicle sound-absorbing material at a deep position in a fiber-based base material using ultrasonic vibrations while maintaining stable fixing strength at the fixing point. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an overall perspective view of a substrate and a sound-absorbing material that constitute a vehicle exterior material according to an embodiment. [Figure 2] FIG. 2 is a side view schematically showing a fastening portion of the exterior material for a vehicle. [Figure 3] FIG. 4 is a plan view schematically showing a fixing portion. [Figure 4] FIG. 2 is a side view of the tool horn according to the embodiment. [Figure 5] FIG. 4 is a view showing a pressing surface as viewed from the axial direction of the tool horn. [Figure 6] 10A to 10C are diagrams schematically illustrating a process of layering a sound-absorbing material on a substrate. [Figure 7] FIG. 10 is a diagram illustrating a state in which the sound-absorbing material is pressed into the substrate by the tool horn. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0020] <Fixing structure for in-vehicle sound-absorbing material> The structure of a vehicle exterior material 1 will be described as an example of the fixing structure of the vehicle-mounted sound-absorbing material according to this embodiment. Examples of the vehicle exterior material 1 include a body undercover and an engine undercover. For example, a body undercover is attached to the lower part of a vehicle so as to cover the underside of the vehicle in order to reduce the air resistance of the airflow flowing below the vehicle. As shown in FIG. 1 , the vehicle exterior material 1 has a substrate 2 which is a fiber molded body containing a thermoplastic synthetic resin, and a sound-absorbing material 3 (vehicle-mounted sound-absorbing material) which is a laminate of a planar fiber web containing thermoplastic synthetic fibers and a nonwoven fabric. The sound-absorbing material 3 is fixed to the substrate 2 so as to be positioned between the vehicle underside and the substrate 2.

[0021] The substrate 2 is a fiber molding formed into a three-dimensional planar shape, including a fiber layer having a thermoplastic synthetic resin and a fiber reinforcing material. A nonwoven fabric made of a thermoplastic synthetic resin or the like may be laminated on one or both sides of the fiber layer as appropriate. The fiber layer can be formed by either a dry method, such as cross-layering or air-laying, or a wet method, such as papermaking. The thermoplastic synthetic resin used in the dry method may be a thermoplastic synthetic fiber such as polyethylene fiber, polyester fiber, or polypropylene fiber. The thermoplastic synthetic resin used in the wet method (papermaking) may be a powder of polyethylene, polyester, polypropylene, or the like. The fiber reinforcing material may be glass fiber, basalt fiber, carbon fiber, or natural fibers such as kenaf (western hemp) or bamboo.

[0022] The sound-absorbing material 3 has a planar fiber web containing thermoplastic synthetic fibers, and a planar nonwoven fabric containing thermoplastic synthetic fibers laminated on both sides of the planar fiber web as a cover layer. The sound-absorbing material 3 is molded into a shape corresponding to the substrate 2 to which it is attached, and the fiber web is compressed in the thickness direction along the entire periphery. The thermoplastic synthetic fiber can be selected from the group consisting of polyethylene fiber, polypropylene fiber, polystyrene fiber, polyester fiber, etc., and mixtures thereof. The nonwoven fabric of the cover layer may be treated with a water-repellent finish.

[0023] The base material 2 has a sound-absorbing surface 10 that absorbs noise from inside and outside the vehicle, and a pressure-bonded portion 12 that is compressed in the thickness direction relative to the sound-absorbing surface 10. The pressure-bonded portion 12 is stronger than the sound-absorbing surface 10 and maintains the rigidity of the fiber molding. The pressure-bonded portion 12 is provided on the surface of the base material 2 that conforms to the vehicle underside, as well as on a flange portion that bends from the outer periphery of the base material 2 toward the vehicle and connects to the vehicle underside. By providing the base material 2, which is a fiber molding, with the sound-absorbing surface 10 and pressure-bonded portion 12 of different thicknesses, it is possible to achieve both sound absorption function and shape retention of the base material 2. The shape of the base material 2 and the arrangement of the sound-absorbing surface 10 and pressure-bonded portion 12 are appropriately determined depending on the shape of the vehicle underside. A sound-absorbing material 3 is fixed to the sound-absorbing surface 10 in a state where it is overlapped on the surface of the base material 2 that faces the vehicle underside. The sound-absorbing material 3 has multiple fixing portions 14 along its outer periphery and is fixed to the sound-absorbing surface 10 at the fixing portions 14.

[0024] As shown in Figures 2 and 3, the fixing portion 14 has a recess 15 formed by pressing the sound-absorbing material 3 into the base material 2. The recess 15 has a circular shape in a plan view and has a bottom surface portion 17 and a displacement portion 18. The bottom surface portion 17 is the deepest part of the recess 15 and has a circular flat surface shape. The displacement portion 18 is a portion at the periphery of the recess 15 where the depth of the recess 15 becomes shallower toward the periphery, and has a convex curved shape that is convex toward the opposite side to the base material 2. The shape of the displacement portion 18 can be selected as appropriate, for example, a rounded surface, an R-surface, a spoon-shaped surface (fillet), an angular surface, a C-surface, etc.

[0025] The recess 15 is fixed to the base material 2 by modifying at least a portion of the fixing portion 14 with ultrasonic vibrations. Specifically, the thermoplastic synthetic resin contained in the base material 2 and the thermoplastic synthetic fiber contained in the sound-absorbing material 3 are thermally melted and solidified by the vibration energy of the ultrasonic vibrations, thereby fusing the resin. Here, the portion of the base material 2 and the fixing portion 14 modified by the ultrasonic vibrations is referred to as a modified portion 15a. The modified portion 15a is formed across the bottom portion 17 and the displacement portion 18.

[0026] <Configuration of ultrasonic horn for fixing sound absorbing material in vehicles> Next, the ultrasonic horn for fixing an in-vehicle sound-absorbing material according to this embodiment will be described using a tool horn 5 for ultrasonic welding as an example. Tool horn 5 is used to produce a fixing structure for an in-vehicle sound-absorbing material, in which a fixing portion 14 of sound-absorbing material 3, which is layered on a base material 2 that is a fiber molding containing a thermoplastic synthetic resin, is fixed to the base material 2.

[0027] The tool horn 5 is made of a metal material and is formed into a rod-like shape that is long in the axial direction. As shown in Figures 4 and 5, the tool horn 5 has a transmission unit 21 that transmits ultrasonic vibrations input from the ultrasonic vibrator in the axial direction. The transmission unit 21 has a cylindrical large-diameter portion 21a that is connected to the ultrasonic vibrator and a small-diameter portion 21c that extends from the large-diameter portion 21a toward the tip 21b so that its outer diameter becomes smaller than that of the large-diameter portion 21a. The tool horn 5 has a pressing surface 23 at the tip 21b of the transmission unit 21. The pressing surface 23 is the surface that faces the surface of the sound-absorbing material 3 when producing a fixed structure for the sound-absorbing material 3 (vehicle-mounted sound-absorbing material). The pressing surface 23 applies a pressing force to the fixing portion 14 to press the fixing portion 14 into the substrate 2. The transmission unit 21 transmits the ultrasonic vibrations from the pressing surface 23 toward the fixing portion 14.

[0028] The pressing surface 23 has an end surface portion 25 and a displacement area 26. The end surface portion 25 has a circular flat shape when viewed from the axial direction of the tool horn 5, and is the portion where the fixing portion 14 is pressed deepest into the substrate 2. The displacement area 26 is set at the peripheral edge of the pressing surface 23, i.e., on the outer periphery of the end surface portion 25, and is shaped so that the pressing depth of the fixing portion 14 into the substrate 2 becomes shallower toward the periphery. In this embodiment, the displacement area 26 has a concave curved shape that is concave toward the opposite side from the substrate 2 when a pressing force is applied to the fixing portion 14. The shape of the displacement area 26 can be selected as appropriate, for example, a spoon-shaped surface (fillet), a rounded surface, an R-shaped surface, an angular surface, a C-shaped surface, etc.

[0029] By providing the displacement area 26 on the pressing surface 23 of the tool horn 5, the recess 15 of the fixing portion 14 is formed into an expanded shape so that its depth becomes shallower from the bottom surface 17 toward the outer periphery. Therefore, when the tool horn 5 presses the sound-absorbing material 3 into the substrate 2, the force pulling the sound-absorbing material 3 is gentler, thereby suppressing the occurrence of tearing at the peripheral portion of the recess 15. Furthermore, the modified portion 15a is formed by ultrasonic welding not only at the bottom surface 17 but also at the peripheral portion of the recess 15, i.e., the displacement portion 18. Therefore, even if tearing occurs in the displacement portion 18, the fixing portion 14 is welded over the entire recess 15, including the displacement portion 18, so the fixing strength can be maintained. In this way, the pressing surface 23 is shaped so that the portion where tearing occurs in the fixing portion 14 is contained inside the recess 15.

[0030] The shape and size of tool horn 5 are set appropriately depending on the materials, thicknesses, etc. of base material 2 and sound-absorbing material 3. For example, the diameter, width, depth, etc. of recess 15 are set relative to the thickness of sound-absorbing surface 10 of base material 2 so that vibration energy is transmitted sufficiently and fixing portion 14 and base material 2 are thermally welded. The shape and size of pressing surface 23 of tool horn 5 are set according to the size of recess 15. Furthermore, the planar shape of end surface portion 25 is not limited to a circle, and any other shape may be selected.

[0031] <Process for producing the fixing structure of in-vehicle sound-absorbing material> Next, a process for producing the fixing structure for the in-vehicle sound-absorbing material according to the above embodiment will be described. The fiber molded body constituting the substrate 2 of the vehicle exterior material 1 is formed into a three-dimensional surface shape that conforms to the vehicle underside through a heating process in which a laminate formed by laminating another nonwoven fabric onto a fiber layer containing a thermoplastic synthetic resin and a fiber reinforcement material is heat-softened, and a press molding process in which the laminate heated in the heating process is clamped on both sides between press molds and pressurized while being cooled. In the press molding process, the sound-absorbing surface 10 and the pressure-bonding portion 12 are formed. The sound-absorbing surface 10 is a surface that absorbs noise inside and outside the vehicle. The pressure-bonding portion 12 is a portion that is compressed in the thickness direction relatively more than the sound-absorbing surface 10. The pressure-bonding portion 12 is provided on the surface of the substrate 2 that conforms to the vehicle underside, as well as on a flange portion that bends from the outer periphery of the substrate 2 toward the vehicle and connects to the vehicle underside.

[0032] The substrate 2 and sound-absorbing material 3 of the vehicle exterior material 1 are bonded together through a pressing process and a bonding process using the tool horn 5. Specifically, as shown in FIG. 6, the substrate 2, which is a fiber molding, is placed on a base (not shown), and the sound-absorbing material 3 is layered on the sound-absorbing surface 10 of the substrate 2. The sound-absorbing material 3 has a bonding portion 14 along its outer periphery. In the pressing process, as shown in FIG. 7, a pressing force is applied in the thickness direction from the pressing surface 23 of the tool horn 5 to the bonding portion 14 of the sound-absorbing material 3 layered on the substrate 2. The pressing force presses the bonding portion 14 into the substrate 2, forming a recess 15 in the bonding portion 14 where it comes into contact with the pressing surface 23.

[0033] In the bonding process, ultrasonic vibrations are transmitted from the transmission part 21 of the tool horn 5 via the pressing surface 23 to the bonding part 14, which has been pressed into the base material 2 by the tool horn 5. The vibration energy of the ultrasonic vibrations modifies and bonds at least a portion of the base material 2 and the bonding part 14 in the recess 15. That is, ultrasonic welding is performed, in which the thermoplastic synthetic resin contained in the base material 2 and the thermoplastic synthetic fiber contained in the sound-absorbing material 3 are thermally melted and solidified by the vibration energy.

[0034] In the ultrasonically welded fixing portion 14, a bottom surface portion 17, which is the deepest portion of the recess 15, is formed in the area in contact with the end surface portion 25 of the pressing surface 23, and a displacement portion 18, where the depth of the recess 15 becomes shallower toward the periphery, is formed in the area in contact with the displacement area 26. The bottom surface portion 17 has a circular flat shape. The displacement portion 18 has a convex curved shape that is convex toward the side opposite the substrate 2. Referring to Figure 2, a modified portion 15a, where the substrate 2 and the fixing portion 14 are modified and fixed, is formed across the bottom surface portion 17 and the displacement portion 18.

[0035] According to the configuration of the above embodiment, the pressing surface 23 of the tool horn 5 (ultrasonic horn for fixing a sound-absorbing material to an automobile) applies a pressing force to the fixing portion 14 of the sound-absorbing material 3 (the sound-absorbing material to be mounted on an automobile) to press the fixing portion 14 into the substrate 2. The fixing portion 14 is fixed by the vibration energy of the ultrasonic vibrations modifying the substrate 2 and the sound-absorbing material 3. The peripheral portion of the pressing surface 23 has a displacement area 26 in which the pressing depth of the fixing portion 14 into the substrate 2 becomes shallower toward the periphery. The fixing portion 14 pressed into the tool horn 5 is recessed to match the shape of the pressing surface 23, so that the pressing force is relatively small at the portion of the pressing surface 23 that contacts the displacement area 26, thereby easing the force pulling the sound-absorbing material 3. Furthermore, the pressing surface 23 transmits ultrasonic vibrations to the fixing portion 14 even in the shallow portion of its periphery, thereby fixing the fixing portion 14. This allows the sound-absorbing material 3 to be pushed into the base material 2, which is a fiber molding, to a depth where ultrasonic vibrations can be sufficiently transmitted, thereby fixing the sound-absorbing material 3 and preventing tears from occurring around the edges of the fixed portion 14 fixed by the tool horn 5.

[0036] Furthermore, the displacement area 26 of the tool horn 5 has a concave curved surface shape that is concave toward the side opposite to the substrate 2 when a pressing force is applied. This makes it possible to more gently pull the sound-absorbing material 3 at the periphery of the fixing portion 14 when a pressing force is applied to the fixing portion 14 of the sound-absorbing material 3 by the pressing surface 23.

[0037] In the process of producing the above-mentioned fixed structure for the sound-absorbing material 3, the sound-absorbing material 3 is fixed to the substrate 2, which is a fiber molding, using a tool horn 5 having a displacement area 26 on the pressing surface 23. During the pressing process, the fixed portion 14 of the sound-absorbing material 3 pressed against the pressing surface 23 receives a relatively gentle pressing force at the portion in contact with the displacement area 26. This also reduces the pulling force on the fixed portion 14, preventing tearing at the periphery of the fixed portion 14. Furthermore, during the fixing process, ultrasonic vibrations are transmitted to the substrate 2 and the fixed portion 14 via the pressing surface 23, and at least a portion of the substrate 2 and the fixed portion 14 is modified by the vibration energy of the ultrasonic vibrations. As a result, the fixed portion 14 is fixed even in a shallow portion of its periphery, allowing it to maintain a stable fixing strength against external loads.

[0038] In the fixing structure of the sound-absorbing material 3, the sound-absorbing material 3 is fixed to the sound-absorbing surface 10 of the substrate 2, which has a relatively thick plate thickness. The fixing portion 14 has a recess 15 formed by being pressed into the substrate 2 to a set depth. The recess 15 has a displacement portion 18 at its periphery, where the depth of the recess 15 becomes shallower toward the periphery. The shape of the recess 15 gently suppresses the force pulling the sound-absorbing material 3 at the periphery, thereby suppressing the occurrence of tearing at the periphery of the fixing portion 14 of the sound-absorbing material 3. Furthermore, ultrasonic vibrations are transmitted throughout the entire recess 15, including the displacement portion 18, and the substrate 2 and the fixing portion 14 are modified and fixed by the vibration energy of the ultrasonic vibrations. As a result, the sound-absorbing material 3 is fixed to the substrate 2, which is a fiber molded body, at a depth position where ultrasonic vibrations can be sufficiently transmitted, and the fixing strength of the sound-absorbing material 3 is maintained stable against external loads.

[0039] Furthermore, in the fixing structure of the sound-absorbing material 3, the displacement portion 18 in the recess 15 of the fixing portion 14 has a convex curved shape that is convex on the opposite side to the base material 2. This makes it possible to more gently pull the sound-absorbing material 3, which has been pressed to a set depth into the base material 2, at the periphery of the fixing portion 14.

[0040] A displacement area 26 provided on the pressing surface 23 of the tool horn 5 forms a displacement portion 18 on the periphery of the recess 15. The displacement portion 18 is formed in an expanded shape such that the depth of the recess 15 becomes shallower from the bottom surface 17 toward the outer periphery. This prevents the sound-absorbing material 3 from being suddenly pulled and tearing at the displacement portion 18 when the tool horn 5 presses the sound-absorbing material 3 into the substrate 2, thereby improving the bonding strength of the fixed portion 14. Furthermore, ultrasonic vibrations are transmitted to the displacement portion 18 via the pressing surface 23 not only at the bottom surface 17 but also at the fixed portion 14, forming a welded modified portion 15a. As a result, even if a tear occurs in the displacement portion 18, the location of the tear will be contained within the recess 15, i.e., within the range to be welded, thereby maintaining stable bonding strength.

[0041] The depth (height) of the displacement area 26 of the tool horn 5 is set to correspond to the depth of the recess 15. This makes it easy to visually check the depth of the pressing into the base material 2, even when ultrasonic welding is performed manually, and allows welding to be performed at an appropriate depth. This reduces variation in the depth of the recess 15, and stabilizes the bonding strength.

[0042] The ultrasonic horn for fixing an in-vehicle sound-absorbing material, the method for producing a fixing structure for an in-vehicle sound-absorbing material, and the fixing structure for an in-vehicle sound-absorbing material according to the present invention are not limited to the appearances and configurations described in the above embodiments, and can be embodied in various other forms by various modifications, additions, deletions, and combinations of configurations without departing from the spirit of the present invention. For example, although the fixing structure for an in-vehicle sound-absorbing material according to the present embodiment shows an example in which the sound-absorbing material is fixed to an exterior material for a vehicle, the invention is not limited to this and can also be applied to an interior material for a vehicle that uses a fiber-based base material. [Explanation of symbols]

[0043] 1. Exterior materials for vehicles 2 Base material 3. Sound-absorbing materials (vehicle sound-absorbing materials) 5 Tool horn (ultrasonic horn for fixing sound absorbing material for vehicles) 10 Sound-absorbing surface 12 Crimping section 14 Fixing part 15 recess 15a Denatured part 17 Bottom part 18 Displacement section 21 Transmission section 23 Pressing surface 25 End section 26 Displacement Area

Claims

1. A metallic ultrasonic horn for fixing an on-vehicle sound-absorbing material, used to produce a fixing structure for an on-vehicle sound-absorbing material, the on-vehicle sound-absorbing material being a laminate of a planar fiber web containing thermoplastic synthetic fibers and a nonwoven fabric, overlaid on a substrate being a fiber molded body containing a fiber layer having a thermoplastic synthetic resin and a fiber reinforcing material, the fixing portion of the on-vehicle sound-absorbing material being fixed to the substrate at a recess where the fixing portion is pressed into the substrate to a set depth, a pressing surface that applies a pressing force to the fastening portion to press the fastening portion into the base material when producing the fastening structure for the in-vehicle sound-absorbing material; a transmission section that has the pressing surface at a tip end and realizes transmission of ultrasonic vibration from the pressing surface toward the fixing section, the pressing surface has a planar shape and is configured to have an end surface portion, which is a portion where the pressing depth of the fixing portion into the base material is deepest, and a displacement area, on the outer periphery side of the end surface portion, which is configured so that the pressing depth of the fixing portion into the base material becomes shallower toward the outer periphery; The displacement area has a concave curved shape that becomes concave toward the opposite side of the base material when the pressing force is applied, and has a spoon-shaped surface that is concave from the outer periphery of the displacement area toward the inner periphery, and the outer edge of the tip is chamfered, and the ultrasonic horn for fixing sound-absorbing material to an automobile has a shape with a set height that corresponds to the set depth of the base material.

2. A method for producing a fixing structure for a sound-absorbing material for a vehicle, using the ultrasonic horn for fixing a sound-absorbing material for a vehicle according to claim 1, comprising: a pressing step of applying the pressing force from the pressing surface of the ultrasonic horn to the fixing portion of the in-vehicle sound-absorbing material that is superimposed on the base material, thereby pressing the fixing portion into the base material, thereby forming the recess at the portion of the fixing portion that comes into contact with the pressing surface; a step of transmitting ultrasonic vibrations from the transmission part of the ultrasonic horn to the fixing part pressed into the base material, and using the vibration energy of the ultrasonic vibrations to thermally melt and solidify the thermoplastic synthetic resin contained in the base material and the thermoplastic synthetic fiber contained in the vehicle sound-absorbing material at the boundary between the base material and the fixing part, the step being carried out over the bottom part that is in contact with the end face part in the recess, as well as over the displacement part that is in contact with the displacement area, thereby welding the base material and the fixing part.

3. A fixing structure for an in-vehicle sound-absorbing material, a substrate that is a fiber molded body containing a thermoplastic synthetic resin; The sound-absorbing material for vehicles is a laminate of a planar fiber web containing thermoplastic synthetic fibers and a nonwoven fabric, the base material has a sound absorbing surface that absorbs noise inside and outside the vehicle, and a crimped portion that is compressed in a thickness direction relative to the sound absorbing surface and maintains the rigidity of the fiber molding and the shape of the base material, the on-vehicle sound-absorbing material has a fixing portion to which the on-vehicle sound-absorbing material is fixed in a superposed state to the sound absorbing surface of the base material, the fixing portion has a recess formed by pressing the vehicle-mounted sound-absorbing material into the base material, the recess is fixed to the substrate by a modified portion, which is a portion where at least a part of the fixing portion is modified by ultrasonic vibration, and has a displacement portion at the periphery of the recess, the depth of the recess becoming shallower toward the periphery, A fixing structure for an in-vehicle sound-absorbing material, in which the modified portion is formed by welding the base material and the fixed portion together with a molten and solidified mixture of the thermoplastic synthetic resin and the thermoplastic synthetic fiber at the boundary between the base material and the fixed portion, and is formed over the entire recess.

4. 4. The fixing structure for a sound-absorbing material for use in a vehicle according to claim 3, The displacement portion has a convex curved surface shape that is convex toward the opposite side from the base material.

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