JP5507950B2 - Method for manufacturing sound absorbing member - Google Patents

Description

The present invention relates to a method for manufacturing a sound absorbing member that absorbs noise emitted from a noise source.

  In an engine room of an automobile, an engine and various auxiliary devices are arranged, and these engines and auxiliary devices are so-called noise sources that generate noise. For this reason, a sound absorbing member that absorbs noise radiated from a noise source is mounted on the back surface of the bonnet located in the upper part of the engine room and facing the engine room, and on the lower side of the engine room of the vehicle body. Among these, the sound absorbing member disposed below the engine room of the vehicle body is generally called an “engine undercover”, and has a sound absorbing function for absorbing noise and the flow of air flowing into the vehicle body during traveling. It also has a rectifying function that adjusts.

  FIG. 8 is a perspective view schematically showing a sound absorbing member 10 provided for implementation as an engine undercover, and FIG. 9 shows a use state in which the sound absorbing member 10 is disposed below the engine room ER. It is. The sound absorbing member 10 is formed using a known blow molding technique. When the sound absorbing member 10 is disposed below the engine room ER, the first wall 12 and the engine room ER located on the lower side which is the road surface side. 2nd wall part 14 located in the upper side which is a side is provided. The 1st wall part 12 is formed in the smooth surface structure, and a rectification | straightening function is expressed, and the 2nd wall part 14 is formed in uneven | corrugated shape. The first wall portion 12 and the convex portion of the second wall portion 14 are brought into close contact with each other, and the concave portion of the second wall portion 14 is covered with the first wall portion 12 so that the hollow sound absorption projecting toward the engine room ER side. A large number of chambers 16 are formed. As shown in FIG. 10, each of the sound absorbing chambers 16 has a cubic shape with a flat top portion, and the top portion (the bottom of each concave portion of the second wall portion 14) vibrates with sound waves from a noise source. It is a plate surface 16A. That is, the sound absorbing member 10 is configured such that the diaphragm surface 16A of each sound absorbing chamber 16 vibrates and absorbs sound due to sound waves from a noise source.

  FIG. 10 is a partial perspective view of the sound absorbing member 10 and a molding die M1 for molding the sound absorbing member 10. FIG. The mold M1 has a mold configuration corresponding to blow molding, and includes a first mold 20 and a second mold 22 that sandwich a molding material (parison) P that has been softened by heating and expanded into a hollow shape from the left and right directions. (In FIGS. 10 to 12, the first mold 20 and the second mold 22 are displayed so as to be sandwiched from above and below for the convenience of display of the drawings). The first mold 20 is provided with a first molding surface 24 that defines the shape of the first wall portion 12 of the sound absorbing member 10. Further, the second mold 22 is provided with a second molding surface 26 that defines the shape of the second wall portion 14 of the sound absorbing member 10, and the second molding surface 26 is used to mold each sound absorbing chamber 16. A molding recess 28 is formed which is recessed in accordance with the sound absorbing chamber 16 and opens toward the first mold 20. 10 and 11, in the second mold 22, in the vicinity of the four corners of the molding top surface 28A for molding the diaphragm surface 16A of each molding recess 28, the molding recess 28 and the outside of the mold are provided. Exhaust holes 30 are formed in the respective openings.

  FIG. 12 is an explanatory view showing a method of forming the sound absorbing member 10 using the forming die M1 shown in FIGS. The molding material P, which has been blown into a hollow shape by sending air into it, is sandwiched from the left and right by the second mold 22 and the first mold 20 of the molding die M1 (FIG. 12 (a)), and further air is introduced into the molding material P. Then, a portion P1 of the molding material P corresponding to the molding concave portion 28 (hereinafter referred to as “small chamber molding portion”) P1 is pushed into the molding concave portion 28 by the pressure of the air. As a result, the air remaining in each molding recess 28 (including gas other than air) is pushed by the small chamber molding portion P1 that expands into the molding recess 28 and is discharged to the outside of the mold through the exhaust holes 30 (FIG. 12 (b)). When all the air in the molding recess 28 is discharged to the outside through the exhaust holes 30, the small chamber molding portion P <b> 1 is pressed against the inner wall surface in the molding recess 28 to mold the sound absorbing chamber 16. If the molding surface of the mold M1 is cooled in this state to solidify the molding material P, the sound absorbing member 10 including the sound absorbing chamber 16 is molded. Such a mold and a molding method are disclosed in Patent Document 1, for example.

Japanese National Patent Publication No. 10-504406

  By the way, in the conventional mold M1 described above, the exhaust hole 30 formed in the molding top surface 28A of the molding recess 28 is an aperture having a diameter of 0.3 to 0.5 mm. This is because if the opening size of the exhaust hole 30 is further increased, the molding material P protrudes into the exhaust hole 30 when the sound absorbing member 10 is blow-molded, and a pin-like burr is formed on the diaphragm surface 16A of the sound absorbing chamber 16. Because it is done. Therefore, in the conventional molding die M1, the area ratio (hereinafter referred to as “mold porosity R1”) of the total opening area S2 including the opening area of each exhaust hole 30 to the area S1 of the molding top surface 28A is extremely small. Yes. As an example, when the molding top surface 28A is a square of 16.5 mm × 16.5 mm and the opening size of each of the four exhaust holes 30 is 0.5 mm in diameter, the mold porosity R1 is only 0.288%. . For this reason, when the sound absorbing member 10 is blow-molded from the molding material P, the air in the molding material 28 is quickly transferred to the outside of the mold through the exhaust holes 30 with the pressure of the air fed into the molding material P. It cannot be discharged, and the expansion deformation of the small chamber molding portion P1 is delayed.

  As described above, when the expansion and deformation of the small chamber forming portion P1 is slow, the entire small chamber forming portion P1 extends uniformly, so that the vibration plate surface 16A, the side wall surface 16B, and the vibration constituting the sound absorbing small chamber 16 are vibrated. The boundary edge portion 16C between the plate surface 16A and the side wall surface 16B is formed to have substantially the same thickness. For this reason, the flexibility of the boundary edge portion 16C is impaired, and the vibration of the diaphragm surface 16A due to the deformation of the boundary edge portion 16C is suppressed. Therefore, the noise from the noise source cannot be efficiently absorbed, and the sound absorption performance is improved. A problem that degrades occurs. Further, since it takes time to expand and deform the small chamber forming portion P1, the time required for forming the sound absorbing member 10 becomes long, and there is a problem that the forming efficiency is lowered.

  If the exhaust holes 30 are additionally provided for each molding recess 28, the amount of air discharged in the molding recess 28 is increased and the exhaust efficiency is improved, so that the above problem can be solved. However, each exhaust hole 30 is directly formed one by one on the wall portion of the second mold 22 using a laser drilling machine or the like. Therefore, if the number of the exhaust holes 30 is increased, the number of drilling operations is increased, and the time required for manufacturing the mold M1 is lengthened. Thus, there is a problem that the cost for manufacturing the mold M1 is greatly increased.

In this invention, by using a mold manufacturing cost inexpensive molds, and an object thereof is to provide a method of manufacturing a sound absorbing member that can be efficiently molded sound-absorbing member absorbing performance is improved.

In order to solve the above problems and achieve the intended purpose, the invention according to claim 1 of the present application provides:
It has a hollow sound-absorbing chamber defined by covering the opening of a recess formed by recessing one opposing wall with the other wall, and absorbs sound by vibration of the diaphragm surface forming the bottom of the recess A method for producing a sound absorbing member by blow molding,
The mold used for the blow molding is
A molding recess recessed from the molding surface defining the opening edge of the recess, and having a flat molding top surface at the bottom ;
Open to the forming top surface corresponding to the diaphragm surface in the forming recess, the aperture communicates with the outside of the forming die,
The fitted together with opening the mold top surface, and a vent member having a plurality of exhaust ports capable of discharging communicates with the mold outside from the molding recess an air of the molding recess to the outside,
Wherein the molding material is fed into the air in the interior of the molding material is set in a mold inflated to the molding in the recess, the air in molding in the recess, the end face of the opening total area facing the mold top surface of the vent member by discharged through the exhaust port is set to 1% to 15% of the area range molding top, including the boundary edge between the diaphragm surface and the side wall surface continuous with the diaphragm plane The sound absorbing chamber that is thinner than the diaphragm surface is formed .

Therefore, according to the invention according to claim 1, the molding top for blow molding includes the total opening area of the exhaust port provided in the vent member, including the end surface facing the molding top surface of the vent member. By setting it in the range of 1 to 15% of the area, the air in the molding recess can be quickly discharged to the outside of the mold through the exhaust port . Thus, the molding material that expands to the forming recess during blow molding using the mold, in contact with the previously molded top surface of the molding recess, may be subsequently contacted with the non-forming top surface of the forming recess. Accordingly, in the sound absorbing chamber formed by the molding recess, the thickness of the boundary edge around the diaphragm surface is smaller than the thickness of the diaphragm surface formed by the molding top surface, and the diaphragm surface easily vibrates. Thus, a sound absorbing member with improved sound absorbing performance can be formed. Further, since air can be quickly discharged from the molding recess, the molding time of the sound absorbing chamber can be shortened and the molding efficiency of the sound absorbing member can be improved. Furthermore, with a vent member provided with a plurality of exhaust ports, a single opening is formed by forming an opening corresponding to the vent member in the mold and attaching the vent member to the opening. A molding die having a plurality of exhaust ports can be manufactured simply by molding the mold, and the number of manufacturing steps for the molding die can be reduced and the cost for manufacturing the die can be reduced.

The invention described in claim 2
The forming top surface is a square .

The invention according to claim 3
The gist of each exhaust port is a slit hole having a width of 0.3 mm or less or a pore having an opening diameter of 0.3 mm or less.
Therefore, according to the invention of claim 3, when the sound absorbing chamber is formed by the forming recess, the molding material is prevented from projecting into the exhaust port and solidifying, and the burr is formed on the diaphragm surface of the formed sound absorbing chamber. Not formed.

The invention according to claim 4
The vent member, the disposed one on molded top surface of the forming recess, the area including the exhaust port of the end face facing the molding top surface of each vent member, including said end surface of said forming top surface larger than the area of the circle inscribed in a square area corresponding to 1/4 of the area was, and summarized in that is set smaller than the area of the shaped top surface.
Therefore, according to the invention according to claim 4, in the case of disposing one vent member forming the ceiling surface of the forming recess, it is disposed a vent member in any position in the shaped top surface, it can be located the vent member in the vicinity of the center or central portion of the shaped top surface. Thus, at the time of molding the sound absorbing member, when discharging air from the molding recess by molded material which expands into the molding recess, because the air is rapidly discharged from the vicinity of the center portion of the molding top surface, the molding material central portion of the portion that expands to the forming recesses can be contacted with the molded top surface quickly in.

According to the method for manufacturing a sound absorbing member according to the present invention, it is possible to efficiently form a sound absorbing member with improved sound absorbing performance by using a molding die that is inexpensive to manufacture a mold . Further, the molding time of the sound absorbing member can be shortened and the molding efficiency can be improved.

It is the fragmentary sectional perspective view which showed the principal part structure of the shaping | molding die used for the manufacturing method of the sound absorption member of an Example , and showed the principal part of the sound absorption member shape | molded by this shaping | molding die. (a) is explanatory sectional drawing which shows the shaping | molding die used for the manufacturing method of the sound-absorbing member of an Example in the state before a 1st type | mold and 2nd type | mold pinch | mold a shaping | molding raw material, (b) is ( It is the IIb-IIb arrow directional view of a). It is explanatory drawing regarding a vent porosity. It is explanatory drawing regarding a mold porosity. (a) is explanatory drawing which prescribes | regulates the size of this vent member in the case of arrange | positioning one vent member on a shaping | molding top surface, (b) is arranging a vent member in any position of a shaping | molding top surface. It is explanatory drawing which shows that even if it provides, this vent member is located in the center part of a shaping | molding top surface, or the center part vicinity. It is explanatory drawing which showed the method of blow-molding a sound-absorbing member from a molding material with the shaping | molding die of an Example over time. It is explanatory drawing which shows another example of the arrangement | positioning aspect of the vent member with respect to a shaping | molding top surface. It is the perspective view which showed schematically the engine undercover as a sound-absorbing member. It is sectional drawing which shows the use condition which has arrange | positioned the engine undercover as a sound absorption member under the engine room. It is the fragmentary sectional perspective view which showed the principal part structure of the conventional shaping | molding die, and showed the principal part of the sound-absorbing member shape | molded by this shaping | molding die. (a) is explanatory sectional drawing shown in the state before the 1st type | mold and 2nd type | mold of the conventional shaping | molding mold pinched | molding a shaping | molding raw material, (b) is a XIb-XIb arrow directional view of (a). is there. It is explanatory drawing which showed the method of blow-molding a sound-absorbing member from a shaping | molding raw material with the conventional shaping | molding die in time.

Next, a method for manufacturing a sound absorbing member according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments. In the embodiment, the engine undercover shown in FIGS. 8 and 9 is exemplified as the sound absorbing member, and is indicated by the same reference numeral.

FIG. 1 is a partial cross-sectional perspective view showing a main part structure of a molding die M used in the manufacturing method of the embodiment and a main part of a sound absorbing member 10 molded by the molding die M. The sound absorbing member 10 includes a first wall portion 12 that faces the road surface side and a second wall portion 14 that faces the engine room ER side when disposed below the engine room ER. The 1st wall part 12 has a smooth surface structure and can express a rectification function. The second wall portion 14 is formed in a concavo-convex shape, and the concave portion is in close contact with the first wall portion 12 and protrudes to the engine room ER side by the first wall portion 12 and the concave portion of the second wall portion 14. A large number of hollow sound absorbing chambers 16 are formed.

  As shown in FIG. 1, each sound absorbing chamber 16 has a cubic shape (cubic shape), and is substantially perpendicular to the diaphragm surface 16A from the periphery of the diaphragm surface 16A having a flat top and the periphery of the diaphragm surface 16A. And a bottom wall surface 16D formed from a part of the first wall portion 12 to form a hollow closed space. In the sound absorbing chamber 16 of the sound absorbing member 10 of the embodiment, as shown in FIG. 1 and FIG. 6C, the boundary edge 16C around the diaphragm surface 16A is formed thinner than the diaphragm surface 16A. By increasing the flexibility of the boundary edge portion 16C to facilitate the vibration of the diaphragm surface 16A, the structure can absorb noise efficiently. In this way, the diaphragm surface 16A can be thick and the boundary edge 16C can be formed thinly because of the mold configuration of the mold M of the embodiment described later. In addition, the thickness of the diaphragm surface 16A is ¼ to ½ of the thickness of the portion of the second wall portion 14 joined to the first wall portion 12. Further, the thickness of the boundary edge portion 16C is 1/10 to 1/5 of the thickness of the second wall portion 14 joined to the first wall portion 12, and 1/6 to 2 of the thickness of the diaphragm surface 16A. / 3.

  The protruding height H of the sound absorbing chamber 16 is set to ¼ of the wavelength of the noise in the frequency band to be absorbed, or an odd multiple thereof (see FIG. 1). The sound absorbing chamber 16 is not limited to a cubic shape, and may be formed in various shapes such as a cylindrical shape and a polygonal column shape.

  As shown in FIGS. 1 and 2, the mold M of the embodiment has a mold configuration corresponding to blow molding, and sandwiches a molding material (parison) P softened by heating and expanded in a hollow shape from the left and right directions. The first mold 40 and the second mold 42 are provided (in FIG. 1, FIG. 2, and FIG. 6, the first mold 40 and the second mold 42 are sandwiched from above and below for the convenience of display of the drawings. it's shown). The first mold 40 is provided with a first molding surface 44 that defines the shape of the first wall portion 12 of the sound absorbing member 10. The second mold 42 is provided with a second molding surface 46 that defines the shape of the second wall portion 14 of the sound absorbing member 10. On the second molding surface 46 of the second mold 42, a molding recess 48 is formed that is recessed in accordance with the sound absorbing chamber 16 and opens toward the first mold 40 in order to mold each sound absorbing chamber 16. Yes. Each molding recess 48 includes a molding top surface 48A corresponding to the diaphragm surface 16A of the sound absorbing chamber 16, and a molding side surface 48B corresponding to the side wall surface 16B of the sound absorbing chamber 16.

  As shown in FIGS. 1 and 2, in the second mold 42, a circular opening that communicates the molding recess 48 and the outside of the mold is formed in the wall portion corresponding to the molding top surface 48 </ b> A of each molding recess 48. Department 50 is established. The opening 50 is formed to fit and attach a vent member 60 described later, and has a size that matches the outer shape of the vent member 60. The opening 50 may be formed at the same time as the second mold 42 is manufactured, or may be formed in a subsequent process using a cutting tool or the like.

  The vent member 60 of the embodiment has a slit shape penetrating through the main body 62 so as to open to end faces 62A and 62A opposed to both ends of the columnar main body 62 made of iron, copper, an iron alloy, stainless steel, or the like. This is a so-called slit vent provided with a plurality of exhaust ports 64 (seven in the embodiment). Each exhaust port 64 has an opening width W in the short side direction of 0.3 mm or less, and is arranged in parallel at intervals of 1 to 2 mm (see FIG. 3). 1 and 2, the vent member 60 has one end surface 62A aligned with the molding top surface 48A of the molding recess 48 and the other end surface 62A exposed to the outside of the second mold 42. The outer peripheral surface 62 </ b> B is fitted into the opening 50 in a state where the outer peripheral surface 62 </ b> B is in close contact with the inner peripheral surface of the opening 50. The outer peripheral surface 62B of the main body 62 is knurled, and when the vent member 60 is fitted into the opening 50, the outer peripheral surface 62B bites into the inner peripheral surface of the opening 50, and the vent The member 60 is prevented from easily falling off from the opening 50.

As shown in FIG. 3, the vent member 60 has a total opening area of each exhaust port 64 opened to the end surface 62A with respect to an area S3 of the end surface 62A facing the molding recess 48 (the sum of the opening areas of the seven exhaust ports 64). ) “Vent porosity R2” indicating the ratio of S2 is set in a range of 1 to 60%. For example, in the columnar vent member 60 having a diameter of 15 mm, the area of the end face 62A facing the molding recess 48 is 176.63 mm ² , so the total opening area S2 of each exhaust port 64 is 1.77 to 106.03 mm ² . Set by range. Note that if the vent porosity R2 is less than 1%, the exhaust efficiency may decrease and the problems inherent in the conventional mold M1 may not be solved. Further, when the vent porosity R2 is larger than 60%, the strength of the main body 62 is reduced, and when the vent member 60 is fitted into the opening 50 of the second mold 42, each exhaust port 64 is Narrowing distortion may occur in the main body 62. In other words, the vent member 60 can achieve both improvement in exhaust efficiency and prevention of distortion of the main body 62 by setting the vent porosity R2 to 1 to 60%.

  Further, as shown in FIG. 3, the vent member 60 has an opening region S4 formed by sequentially connecting the end edges of the seven slit-like exhaust ports 64 with an area S3 of the end surface 62A of the main body 62. It is set to 80 to 90%. That is, the vent member 60 is provided with the exhaust ports 64 over substantially the entire end surface 62A on the assumption that the vent porosity R2 is set to 1 to 60%. Therefore, when the vent member 60 is fitted into the opening 50, the exhaust port 64 can be exposed to the molding recess 48 in a wide range.

  Further, in the molding die M of the embodiment, as shown in FIG. 4, the area ratio between the area S1 of the molding top surface 48A and the total opening area S2 obtained by summing the opening areas of the exhaust ports 64 formed in the vent member 60. The “mold porosity R1” is set to 1 to 15%. That is, in the mold M of the example, the mold void ratio R1 is set to be considerably larger than that of the conventional mold M1 shown in FIG. For this reason, when the sound absorbing member 10 is blow-molded from the molding material P, the air in the molding recess 48 is quickly brought out of the mold via the exhaust ports 64 by the pressure of the air fed into the molding material P. And can be discharged smoothly.

  The vent member 60 is not limited to the slit vent shown in FIG. 1, but is a mesh vent in which a large number of linear pores opening on both outer end faces 62A and 62A of the main body 62 are formed. It is also possible to employ a porous metal vent or the like made of a sintered product having fine metal holes (5 to 20 μm). However, in the case of a vent member made of a mesh vent, it is desirable to use a vent member having pores formed with an opening diameter of 0.3 mm or less. Further, in the case of a vent member composed of a slit vent and a mesh vent, one having an opening width W or an opening diameter of the exhaust port 64 of 0.03 mm or more can be used. Further, a vent member 60 having a main body 62 having an outer diameter of 2.5 mm or more is selected and used according to the size of the molding top surface 48A.

  Further, in the molding die M of the embodiment, as shown in FIG. 5A, the area S2 of the end surface 62A facing the molding recess 48 of the vent member 60 is 1 / S1 of the area S1 of the molding top surface 48A of the molding recess 48. 4 may be set larger than an area S5 of a circle inscribed in a square having an area corresponding to 4, and smaller than an area S1 of the molding top surface 48A. As a result, when one vent member 60 is disposed on the molding top surface 48A of each molding recess 48, as shown in FIG. 5 (b), the vent member 60 is positioned at any position on the molding top surface 48A. Even if it arrange | positions, the vent member 60 can be located in the center part C of the shaping | molding top surface 48A, or the vicinity of the center part C. FIG. Therefore, when the sound absorbing member 10 is blow-molded, when the air in the molding concave portion 48 is discharged by the small chamber molding portion P1 of the molding material P that expands into the molding concave portion 48, the air is quickly supplied from the center of the molding top surface 48A. Since it is discharged, the small chamber molding portion P1 that expands into the molding recess 48 can be brought into contact with the molding top surface 48A quickly.

( Manufacturing method)
Next, a method of manufacturing the sound absorbing member 10 using the mold M configured as described above will be described with reference to FIG.

  The molding material P, which has been softened by heating and sent into the interior and blown into a hollow shape, is sandwiched between the first mold 40 and the second mold 42 of the mold M from the left and right sides (FIG. 6A). After closing the mold, air is further fed into the molding material P, and the small chamber molding portion P1 corresponding to the molding recess 48 of the molding material P is expanded into the molding recess 48 by the pressure of the air.

  Then, the air present in each molding recess 48 is discharged out of the mold through each exhaust port 64 of the vent member 60 at the small chamber molding portion P1 that expands and deforms into the molding recess 48 (FIG. 6B). . At this time, by setting the mold porosity R1 within the above-described range, the air in the molding recess 48 can be quickly and smoothly discharged to the outside of the mold by the pressure of the air fed into the molding material P. it can. As a result, the small chamber molding portion P1 is quickly expanded and deformed into the molding concave portion 48, and first, the central portion of the small chamber molding portion P1 is brought into contact with the molding top surface 48A of the molding concave portion 48 (FIG. 6B). Since the central portion of the small chamber molding portion P1 in contact with the molding top surface 48A hardly stretches after contact with the molding top surface 48A, the central portion is maintained at the thickness at the time of contact with the molding top surface 48A.

On the other hand, as shown in FIG. 6B, in the state where the central portion of the small chamber molding portion P1 is in contact with the molding top surface 48A, the portion surrounding the central portion in the small chamber molding portion P1 is still the molding side surface of the molding recess 48. It is not in contact with 48B. Therefore, the air surrounding the central portion is brought into contact with the molding side surface 48B while being stretched by the air fed into the molding material P. The portion surrounding the central portion of the small chamber forming portion P1 comes into contact with the forming side surface 48B of the forming recess 48, whereby the side wall surface 16B and the boundary edge portion 16C are formed. At this time, as is apparent from FIGS. 6B and 6C, the deformation amount of the portion surrounding the central portion is the largest at the portion that becomes the boundary edge portion 16C. Is the smallest. That is, according to the molding method using the molding die M of the embodiment, the sound absorbing chamber 16 formed by the molding recess 48 is formed with the thickest diaphragm surface 16A, and then the side wall surface 16B and the boundary edge portion 16C in this order. It is thinly formed.

The inventor of the present application blow-molded the sound absorbing member 10 from the molding material P using the molding die M under the following conditions of the molding die M of the example.
(Embodiment 1)
・ Area S1: 272.25 mm ² (16.5 × 16.5 mm square) of the molding top surface 48A of the molding recess 48
・ Vent member 60
・ Number of units: 1 ・ Diameter: 15 mm
-Area S3 of end face 62A: 176.63mm ²
-Exhaust port 64: slit hole (width 0.2 mm) x 7-Total opening area S2 of the exhaust port 64: 10.5 mm ²
・ Vent porosity R2: 5.9%
-Mold porosity: 3.9%
When the sound absorbing member 10 is blow-molded from the molding material P in the molding die M having the above-described configuration, the sound absorbing member 10 having the sound absorbing chambers 16 in which the thickness of the boundary edge portion 16C is smaller than the thickness of the diaphragm surface 16A is obtained. An improvement in performance can be expected. Further, the molding time is shortened when the sound absorbing member 10 is molded using the molding die M of the embodiment, compared with the case where the sound absorbing member 10 is molded using the conventional molding die M1 shown in FIG. As a result, improvement in molding efficiency was confirmed.

(Embodiment 2)
・ Area S1: 272.25 mm ² (16.5 × 16.5 mm square) of the molding top surface 48A of the molding recess 48
・ Vent member 60
・ Number of units: 4 ・ Diameter: 4 mm
-End face area S3: 12.56 mm ²
-Exhaust port 64: slit hole (width 0.2 mm) x 3-Total opening area S2 of the exhaust port 64: 4.0 mm ²
・ Vent porosity R2: 31.8%
-Mold porosity: 5.9% ((4.0 × 4) ÷ 272.25 × 100)
When the sound absorbing member 10 is blow-molded from the molding material P in the molding die M having the above-described configuration, the sound absorbing member 10 having the sound absorbing chambers 16 in which the thickness of the boundary edge portion 16C is smaller than the thickness of the diaphragm surface 16A is obtained. An improvement in performance can be expected. Further, the molding time is shortened when the sound absorbing member 10 is molded using the molding die M of the embodiment, compared with the case where the sound absorbing member 10 is molded using the conventional molding die M1 shown in FIG. As a result, improvement in molding efficiency was confirmed.

Therefore, according to the shaping | molding die M of the sound-absorbing member of Embodiment 1, there exist the following effects.
(1) Since the air in the molding recess 48 can be quickly and smoothly discharged to the outside of the molding die M through each exhaust port 64 provided in the vent member 60, the air expands into the molding recess 48 in the molding material P. The small chamber molding portion P1 comes into contact with the molding top surface 48A of the molding recess 48 first, and then comes into contact with the molding side surface 48B. Accordingly, the sound absorbing chamber 16 formed by the forming recess 48 has a thickness of the boundary edge 16C around the diaphragm surface 16A smaller than the thickness of the diaphragm surface 16A formed by the molding top surface 48A. The sound absorbing member 10 having the improved vibration absorbing performance due to the vibration of the diaphragm surface 16A can be formed.
(2) When the sound absorbing member 10 is blow-molded, air can be quickly discharged from the molding recess 48 by the expansion and deformation of the molding material P into the molding recess 48, so that the molding time of the sound absorbing chamber 16 is shortened, and the sound absorbing member The molding efficiency of 10 can be improved.
(3) The area S3 including the exhaust port 64 of the end surface 62A of the vent member 60 is set larger than the area of a circle inscribed in a square having an area corresponding to ¼ of the area including the end surface 62A of the molding top surface 48A. As a result, when one vent member 60 is disposed, the central portion C or the central portion C of the molding top surface 48A can be disposed at any position on the molding top surface 48A. The vent member 60 can be positioned in the vicinity. Thereby, when the sound absorbing member 10 is molded, when the air of the molding recess 48 is exhausted by the molding material P that expands into the molding recess 48, air is quickly exhausted from the center of the molding top surface 48A. The small chamber molding portion P1 of the molding material P can be quickly brought into contact with the molding top surface 48A.
(4) Since the mold void ratio R1 is in the range of 1 to 15%, the air in the molding recess 48 of the molding die M can be quickly discharged to the outside of the mold when the sound absorbing member 10 is molded.
(5) Since the vent porosity R2 is in the range of 1 to 60%, when the sound absorbing chamber 16 is molded by the molding recess 48, the discharge of air from the molding recess 48 is not hindered. . Moreover, since the strength reduction of the vent member 60 is suppressed, it can be prevented that the vent member 60 attached to the opening 50 is deformed and the exhaust port 64 is narrowed.
(6) Since the width or opening diameter of each exhaust port 64 is set to 0.3 mm or less, the molding material P is prevented from protruding into the exhaust port 64 when the sound absorbing chamber 16 is molded by the molding recess 48. It is possible to prevent burrs from being formed on the diaphragm surface 16A of the sound absorbing chamber 16.
(7) With the vent member 60 provided with a plurality of exhaust ports 64 being prepared, an opening 50 corresponding to the vent member 60 is formed in the mold M, and the vent member 60 is attached to the opening 50. As a result, the molding die M (with a plurality of exhaust ports 64) having a higher mold void ratio R1 can be easily manufactured by simply forming one opening 50, and the number of manufacturing steps for the molding die M can be greatly reduced. As a result, mold production costs can be reduced.

Moreover, according to the shaping | molding die M of the sound absorption member of Embodiment 2, there exist the following effects.
(1) Since the air in the molding recess 48 can be quickly and smoothly discharged to the outside of the molding die M through each exhaust port 64 provided in the vent member 60, the air expands into the molding recess 48 in the molding material P. The small chamber molding portion P1 comes into contact with the molding top surface 48A of the molding recess 48 first, and then comes into contact with the molding side surface 48B. Accordingly, the sound absorbing chamber 16 formed by the forming recess 48 has a thickness of the boundary edge 16C around the diaphragm surface 16A smaller than the thickness of the diaphragm surface 16A formed by the molding top surface 48A. The sound absorbing member 10 having the improved vibration absorbing performance due to the vibration of the diaphragm surface 16A can be formed.
(2) When the sound absorbing member 10 is blow-molded, air can be quickly discharged from the molding recess 48 by the expansion and deformation of the molding material P into the molding recess 48, so that the molding time of the sound absorbing chamber 16 is shortened, and the sound absorbing member The molding efficiency of 10 can be improved.
(3) Since the mold porosity R1 is in the range of 1 to 15%, the air in the molding concave portion 48 of the molding die M can be quickly discharged to the outside of the mold when the sound absorbing member 10 is molded.
(4) Since the vent porosity R2 is in the range of 1 to 60%, when the sound absorbing chamber 16 is molded by the molding recess 48, the discharge of air from the molding recess 48 is not hindered. . Moreover, since the strength reduction of the vent member 60 is suppressed, it can be prevented that the vent member 60 attached to the opening 50 is deformed and the exhaust port 64 is narrowed.
(5) Since the width or opening diameter of each exhaust port 64 is set to 0.3 mm or less, the molding material P is prevented from projecting into the exhaust port 64 when the sound absorbing chamber 16 is molded by the molding recess 48. It is possible to prevent burrs from being formed on the diaphragm surface 16A of the sound absorbing chamber 16.
(6) With four vent members 60 provided with a plurality of exhaust ports 64 being prepared, four openings 50 corresponding to each vent member 60 are formed in the mold M, and the openings 50 are formed in the openings 50. By mounting the vent member 60, the mold M (having a plurality of exhaust ports 64) having a higher mold void ratio R <b> 1 can be easily manufactured simply by molding one opening 50. That is, since four openings 50 can be drilled in one step by an electric discharge machine equipped with electrodes having four protrusions, one small exhaust hole is formed at a time by a laser drilling machine. Compared with the conventional mold M1 to be drilled, the number of manufacturing steps can be greatly reduced, and the mold manufacturing cost can be reduced.

Moreover, according to the manufacturing method of the sound absorption member using the said shaping | molding die M, there exist the following effects.
(1) When the sound absorbing member 10 is blow-molded from the molding material P, the air in the molding recess 48 can be quickly and smoothly discharged to the outside of the mold by the pressure of the air sent to the molding material P. Thus, the sound absorbing chamber 16 can be formed into an appropriate shape, and the sound absorbing member 10 with improved sound absorbing performance can be formed.
(2) When the sound absorbing member 10 is blow-molded, the air in the molding recess 48 can be quickly discharged, so that the molding time of the sound absorbing member 10 can be shortened and the molding efficiency of the sound absorbing member 10 can be improved.

(Example of change)
The manufacturing method of the sound absorbing member of the present application can be variously changed.
(1) The vent member 60 is not limited to the slit vent illustrated in the embodiment, and a mesh vent having a large number of linear pores or a minute (5 to 20 μm) void of a porous crystalline metal at the center of the main body. A porous metal vent made of a sintered product having holes can be used.
(2) The number of the vent members 60 disposed for each molding recess 48 is not limited to one, and the number of vent members 60 is not limited to one when the mold porosity R1 and the vent porosity R2 are within the above ranges. It may be more than one. Further, when a plurality of vent members 60 are provided, as shown in FIG. 7, it is possible to set various positions for the forming top surface 48A. For example, FIG. 7A shows an example in which two vent members 60, 60 are disposed at two locations facing each other across the center portion, with the molding top surface 48A divided into four. FIG. 7B shows an example in which a total of five vent members 60 are arranged on two diagonal lines intersecting each other on the rectangular shaped top surface 48A. FIG. 7C shows an example in which a total of three vent members 60 are disposed on each apex of a regular triangle on a rectangular shaped top surface 48A.
(3) Although FIG. 7 illustrates an example in which a plurality of vent members 60 having the same size are disposed, a plurality of vent members 60 having different sizes may be disposed.
(4) A spiral male screw is formed on the outer peripheral surface 62B of the main body 62 of the vent member 60, and a spiral female screw is formed on the inner peripheral surface of the opening 50 provided in the second mold 42 of the molding die M. You may comprise so that the vent member 60 may be screwed with respect to the opening part 50, and may be fixed. In such a form, the vent member 60 can be easily attached and detached, and maintenance and replacement work of the vent member 60 can be easily performed.
(5) The vent member 60 is not limited to a cylindrical shape, and may be a prismatic shape or a disc shape.
(6) The sound absorbing member targeted by the present application is not limited to the engine under cover exemplified in the embodiment, but is disposed on the sound absorbing member disposed on the back surface of the engine hood in the body of the automobile or another part of the vehicle body. And a sound absorbing member provided in various machines and devices other than automobiles.

10 sound absorbing member, 12 first wall (the other wall), 14 second wall (one wall)
16 sound absorption chamber, 16A diaphragm surface, 16B sidewall surfaces, 16C boundary edge 46 forming surface 48 forming the recess, 48A forming the ceiling surface, 50 opening, 60 a vent member 62A end face 64 outlet, M mold, P molding material, opening the total area of area S2 each outlet of S1 forming top surface 48A, S3 area of the end face 62A of the vent member 60, the area of the S5 yen

Claims (4)

It has a hollow sound-absorbing chamber defined by covering the opening of a recess formed by recessing one opposing wall with the other wall, and absorbs sound by vibration of the diaphragm surface forming the bottom of the recess A method for producing a sound absorbing member by blow molding,
The mold used for the blow molding is
A molding recess recessed from the molding surface defining the opening edge of the recess, and having a flat molding top surface at the bottom ;
Open to the forming top surface corresponding to the diaphragm surface in the forming recess, the aperture communicates with the outside of the forming die,
The fitted together with opening the mold top surface, and a vent member having a plurality of exhaust ports capable of discharging communicates with the mold outside from the molding recess an air of the molding recess to the outside,
Wherein the molding material is fed into the air in the interior of the molding material is set in a mold inflated to the molding in the recess, the air in molding in the recess, the end face of the opening total area facing the mold top surface of the vent member by discharged through the exhaust port is set to 1% to 15% of the area range molding top, including the boundary edge between the diaphragm surface and the side wall surface continuous with the diaphragm plane The method of manufacturing a sound absorbing member, wherein the sound absorbing chamber is formed thinner than the diaphragm surface . The method for manufacturing a sound absorbing member according to claim 1 , wherein the molded top surface is square . 3. The method for producing a sound absorbing member according to claim 1, wherein each of the exhaust ports is a slit hole having a width of 0.3 mm or less or a pore having an opening diameter of 0.3 mm or less. The vent member, the disposed one on molded top surface of the forming recess, the area including the exhaust port of the end face facing the molding top surface of each vent member, including said end surface of said forming top surface It was greater than the area of the circle inscribed in a square area corresponding to 1/4 of the area, the production of sound-absorbing member according to any one of claims 1 to 3 is set smaller than the area of the shaped top surface Way .

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