JP7770862B2 - 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 - Google Patents

Description

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

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 fibrous felt is attached to the base material using a rod-shaped ultrasonic horn. In this ultrasonic welding process, heat generated by vibration energy melts part of the laminate that makes up the base material, generating molten resin. This molten resin entangles with the fibers that make up 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 to a predetermined depth into the base material, the felt located directly below and near the ultrasonic horn is subjected to significant elastic compression deformation.

Recently, in order to improve the sound absorption performance of the base material, it has become common to increase the thickness of the fiber-based base material and then attach the sound-absorbing material to this thicker section using ultrasonic welding. In this case, in order to fully transmit the vibration energy of the ultrasonic horn in the thicker section of the fiber web layer, the ultrasonic horn must be pushed deeper into the base material. Furthermore, vehicle exterior materials such as undercovers are more susceptible to external influences than vehicle interior materials, and so stable fixing strength for the sound-absorbing material is required.

Japanese Patent Application Laid-Open No. 2006-272709

However, when an ultrasonic horn is pushed deep into the fiber-based substrate to secure the sound-absorbing material, the pulling force on the sound-absorbing material increases in the direction it is pushed, making it more likely to tear around the edges of the bonded area. If an external load is then applied to the bonded area of the sound-absorbing material when a tear has occurred, the tear can serve as the starting point for the sound-absorbing material to tear apart. Furthermore, because the location and extent of this tear vary, the strength of the bond to the substrate becomes unstable, posing the problem of the sound-absorbing material easily falling off.

The present invention was conceived in light of these issues, and the problem it aims to solve is to provide an ultrasonic horn for fixing vehicle-mounted sound-absorbing material, a method for producing a fixing structure for vehicle-mounted sound-absorbing material, and a fixing structure for vehicle-mounted sound-absorbing material that uses ultrasonic vibrations to fix vehicle-mounted sound-absorbing material deep within a fiber-based substrate while maintaining stable fixing strength at the fixing point.

One feature of the ultrasonic horn for fixing in-vehicle sound-absorbing material that solves the above problem is that it is used to produce a fixed structure for in-vehicle sound-absorbing material, in which a fixing portion of the in-vehicle sound-absorbing material layered on a substrate that is a fiber molding containing a thermoplastic synthetic resin is fixed to the substrate. During the production of the fixed structure for the in-vehicle sound-absorbing material, the horn has a pressing surface that applies a pressing force to the fixing portion to press the fixing portion into the substrate, and a transmission portion that transmits ultrasonic vibrations from the pressing surface to the fixing portion. The pressing surface has a shape with a displacement area set on its periphery, where the pressing depth of the fixing portion into the substrate becomes shallower toward the periphery.

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 it into the substrate. The fixed portion is bonded 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 depth to which the fixed portion is pressed 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 portion in contact with the displacement area of the pressing surface experiences relatively less pressing force, thereby easing the pulling force on the sound-absorbing material. Furthermore, the pressing surface transmits ultrasonic vibrations to the fixed portion even in shallow areas of its periphery, thereby bonding 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, bonding the sound-absorbing material, and preventing tears from occurring around the periphery of the fixed portion bonded by the ultrasonic horn.

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

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. This makes it possible to more gently pull the sound-absorbing material at the periphery of the fixing portion when a pressing force is applied by the pressing surface to the fixing portion of the sound-absorbing material.

One feature of the method for producing a fixed structure for vehicle-mounted sound-absorbing material using the ultrasonic horn for fixing vehicle-mounted sound-absorbing material described above is that it includes a pressing step in which the pressing force is applied from the pressing surface of the ultrasonic horn to the fixing portion of the vehicle-mounted sound-absorbing material that 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 that has been pressed into the base material, thereby modifying and fixing at least a portion of the base material and the fixing portion with the ultrasonic vibrations.

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

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

One feature and advantage of the above configuration is that the vehicle-mounted sound-absorbing material is fixed to the relatively thick sound-absorbing surface of the substrate. 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 periphery, where the depth of the recess becomes shallower toward the periphery. The shape of this recess gently suppresses the force pulling on the sound-absorbing material at the periphery, preventing tearing at the periphery of the fixing portion of the sound-absorbing material. Furthermore, ultrasonic vibrations are transmitted throughout the entire recess, including the displacement portion, and the substrate and fixing portion are modified and fixed by the vibration energy of the ultrasonic vibrations. This allows the sound-absorbing material to be fixed to the substrate, which is a fiber molded body, at a depth that allows ultrasonic vibrations to be sufficiently transmitted, while maintaining stable adhesion strength of the sound-absorbing material against external loads.

In the fixing structure of the above-mentioned in-vehicle sound-absorbing material, the displacement portion may be configured to have a convex curved surface shape that is convex toward the side opposite the base material.

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 of the base material. This makes it possible to more gently pull the sound-absorbing material, which has been pressed to a set depth into the base material, at the periphery of the fixing portion.

By adopting the above-described configuration or production method, the present invention can provide an ultrasonic horn for fixing vehicle-mounted sound-absorbing material, a method for producing a fixing structure for vehicle-mounted sound-absorbing material, and a fixing structure for vehicle-mounted sound-absorbing material that uses ultrasonic vibrations to fix vehicle-mounted sound-absorbing material deep within a fiber-based substrate while maintaining stable adhesion strength at the fixing point.

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

Embodiments of the present invention will be described below with reference to Figures 1 to 7.

<Fixing structure of in-vehicle sound-absorbing material>
The structure of a vehicle exterior material 1 will be described as an example of a fixing structure for an in-vehicle 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 air resistance of the airflow flowing below the vehicle. As shown in FIG. 1 , the vehicle exterior material 1 includes a substrate 2 that is a fiber molded body containing a thermoplastic synthetic resin, and a sound-absorbing material 3 (in-vehicle sound-absorbing material) that 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.

The substrate 2 is a fiber molded body formed into a three-dimensional surface shape, including a fiber layer having a thermoplastic synthetic resin and a fiber reinforcement 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 using 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. When using the wet method (papermaking), the thermoplastic synthetic resin may be a powder of polyethylene, polyester, polypropylene, or the like. The fiber reinforcement may be glass fiber, basalt fiber, carbon fiber, or natural fibers such as kenaf (western hemp) or bamboo.

The sound-absorbing material 3 comprises a planar fiber web containing thermoplastic synthetic fibers, with a planar nonwoven fabric containing thermoplastic synthetic fibers laminated on both sides as a cover layer. The sound-absorbing material 3 is molded to 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.

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 edge 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 sound-absorbing surfaces 10 and pressure-bonded portions 12 of different thicknesses, the base material 2 can achieve both sound absorption function and shape retention. 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 superimposed 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 edge and is fixed to the sound-absorbing surface 10 at the fixing portions 14.

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 is circular in plan view and has a bottom surface 17 and a displacement portion 18. The bottom surface 17 is the deepest part of the recess 15 and has a circular flat surface. The displacement portion 18 is the part 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 from 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.

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

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

The tool horn 5 is made of a metal material and is shaped like a long rod in the axial direction. As shown in Figures 4 and 5, the tool horn 5 has a transmission section 21 that transmits ultrasonic vibrations input from the ultrasonic vibrator in the axial direction. The transmission section 21 has a cylindrical large-diameter section 21a that connects to the ultrasonic vibrator, and a small-diameter section 21c that extends from the large-diameter section 21a toward the tip 21b so that its outer diameter is smaller than that of the large-diameter section 21a. The tool horn 5 has a pressing surface 23 at the tip 21b of the transmission section 21. The pressing surface 23 faces the surface of the sound-absorbing material 3 during the production of the fixed structure of the sound-absorbing material 3 (vehicle-mounted sound-absorbing material). The pressing surface 23 applies a pressing force to the fixed section 14, pressing the fixed section 14 into the base material 2. The transmission section 21 transmits ultrasonic vibrations from the pressing surface 23 toward the fixed section 14.

The pressing surface 23 has an end surface 25 and a displacement area 26. The end surface 25 has a circular flat shape when viewed from the axial direction of the tool horn 5, and is the area where the fixing portion 14 is pressed deepest into the substrate 2. The displacement area 26 is set on the periphery of the pressing surface 23, i.e., on the outer periphery of the end surface 25, and is shaped so that the depth at which the fixing portion 14 is pressed into the substrate 2 becomes shallower toward the periphery. In this embodiment, the fixing portion 14 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, a R-shaped surface, a squared surface, a C-shaped surface, etc.

By providing a 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 with a depth that decreases 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, preventing tears from occurring around the periphery of the recess 15. Furthermore, a modified portion 15a is formed by ultrasonic welding not only on the bottom surface 17 but also on the periphery of the recess 15, i.e., the displacement portion 18. Therefore, even if tears occur in the displacement portion 18, the fixing portion 14 is welded across the entire recess 15, including the displacement portion 18, and therefore the fixing strength can be maintained. In this way, the pressing surface 23 is shaped so that the location of the tear in the fixing portion 14 is contained within the recess 15.

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

<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 conforming to the vehicle underside through a heating process in which a laminate formed by laminating another nonwoven fabric to 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 cooling. 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 relative to the sound-absorbing surface 10. The pressure-bonding portion 12 is provided on the surface of the substrate 2 conforming 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.

The base material 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 base material 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 base material 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 base material 2. The pressing force presses the bonding portion 14 into the base material 2, forming a recess 15 in the bonding portion 14 where it comes into contact with the pressing surface 23.

In the bonding process, ultrasonic vibrations are transmitted from the transmission section 21 of the tool horn 5 via the pressing surface 23 to the bonding section 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 section 14 in the recess 15. In other words, 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.

In the ultrasonically welded fixing portion 14, a bottom surface portion 17, where the recess 15 is deepest, 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 fixing portion 14 are modified and fixed, is formed across the bottom surface portion 17 and displacement portion 18.

According to the configuration of the above embodiment, the pressing surface 23 of the tool horn 5 (ultrasonic horn for fixing in-vehicle sound-absorbing material) applies a pressing force to the fixing portion 14 of the sound-absorbing material 3 (in-vehicle sound-absorbing material) 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 edge 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 it. This allows the sound-absorbing material 3 to be pushed into the base material 2, which is a fiber molding, to a depth that allows ultrasonic vibrations to be sufficiently transmitted, and fixes the sound-absorbing material 3, while also preventing tears from occurring around the edges of the fixed portion 14 fixed by the tool horn 5.

In addition, the displacement area 26 of the tool horn 5 has a concave curved surface shape that is concave toward the side opposite 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 by the pressing surface 23 to the fixing portion 14 of the sound-absorbing material 3.

In the process of producing the above-mentioned fixed structure for the sound-absorbing material 3, a tool horn 5 having a displacement area 26 on the pressing surface 23 is used to fix the sound-absorbing material 3 to the substrate 2, which is a fiber molding. 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 tears from occurring around the edges 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 shallow areas around its edges, allowing it to maintain stable bond strength against external loads.

The sound-absorbing material 3 is fixed to the relatively thick sound-absorbing surface 10 of the substrate 2. 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 reduces the pulling force on the sound-absorbing material 3 at the periphery, preventing tearing around 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 denatured and fixed by the vibration energy of the ultrasonic vibrations. This allows the sound-absorbing material 3 to be fixed to the substrate 2, which is a fiber molded body, at a depth that allows ultrasonic vibrations to be sufficiently transmitted, while maintaining a stable adhesion strength of the sound-absorbing material 3 against external loads.

Furthermore, with regard to 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 from 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.

A displacement area 26 provided on the pressing surface 23 of the tool horn 5 forms a displacement portion 18 around the periphery of the recess 15. The displacement portion 18 is formed in an expanded shape so that the depth of the recess 15 decreases 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 to the bottom surface 17 of the fixed portion 14 but also to the bottom surface 17, forming a welded modified portion 15a. As a result, even if a tear occurs in the displacement portion 18, the tear location will be contained within the recess 15, i.e., within the welded area, maintaining stable bonding strength.

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 insertion into the base material 2, even when ultrasonic welding is performed manually, and ensures welding at the appropriate depth. This reduces variation in the depth of the recess 15, ensuring stable bonding strength.

The ultrasonic horn for fixing in-vehicle sound-absorbing material, the method for producing a fixing structure for in-vehicle sound-absorbing material, and the fixing structure for in-vehicle sound-absorbing material according to the present invention are not limited to the appearance and configuration described in the above embodiment, and can be implemented in a variety of other forms through various modifications, additions, deletions, and combinations of configurations without departing from the spirit of the present invention. For example, while the fixing structure for in-vehicle sound-absorbing material in this embodiment shows an example in which sound-absorbing material is fixed to a vehicle exterior material, the present invention is not limited to this and can also be applied to vehicle interior materials using a fiber-based base material.

1 Vehicle exterior material 2 Base material 3 Sound-absorbing material (vehicle sound-absorbing material)
5. Tool horn (ultrasonic horn for fixing sound-absorbing material for vehicles)
10 sound absorbing surface 12 pressure-bonded portion 14 fixed portion 15 recessed portion 15a modified portion 17 bottom surface portion 18 displacement portion 21 transmission portion 23 pressing surface 25 end surface portion 26 displacement area

Claims (4)

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 . 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. 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. 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.