JP7281581B2 - engine cover - Google Patents

Description

The present invention relates to an engine cover installed in an engine room.

In the engine room, an engine cover is installed to cover the engine in order to reduce the sound emitted from the engine. The engine cover has a sound absorbing layer made of non-woven fabric or foam to prevent transmission of sound emitted from the engine.

WO2016/006073

In order to further reduce the sound emitted from the engine, it is necessary to increase the surface density of the sound absorbing layer, and this is addressed by increasing the thickness of the sound absorbing layer. However, since the space of the engine room is limited, it is difficult to ensure the thickness of the sound absorbing layer, and it is not possible to obtain an engine cover with sufficient performance of preventing transmitted sound.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-described problems associated with the prior art, and an object of the present invention is to provide an engine cover excellent in transmission sound prevention performance.

In order to overcome the above problems and achieve the intended purpose, the engine cover of the invention according to claim 1 of the present application comprises:
An engine cover that covers an engine,
a cover body made of an elastic foam;
a support body having a partition defining a space penetrating the engine cover in the front and back directions, the partition being embedded in the cover body and integrated with the cover body,
The gist is that the foam of the cover body closing the space defined by the partition forms a resonance part.
According to the first aspect of the invention, the resonance part resonates when sound is incident and attenuates the transmitted sound, thereby exhibiting high transmission sound prevention performance.

A gist of the invention according to claim 2 is that the resonance section is held by the partition section in the periphery of the foam except for the wall surfaces facing the front and back of the engine cover.
According to the second aspect of the invention, the resonance section can be appropriately resonated.

In the invention according to claim 3, the gist is that the support body is provided with a plurality of the partitions which define the space with the same opening shape and the same opening size so as to be adjacent to each other.
According to the third aspect of the present invention, it is possible to generate resonance in which the phases are opposite to each other in the adjacent resonating portions, so it is possible to improve the transmission sound prevention performance.

In the invention according to claim 4, the gist is that the support body is provided with the partition portion that defines the space so that the openings facing the front and back of the engine cover have the same shape and the same opening area. do.
According to the fourth aspect of the invention, it is possible to easily generate resonance in the resonance section.

The gist of the invention according to claim 5 is that at least one of the end faces in the front-back direction of the partition is covered with the foam.
According to the fifth aspect of the invention, by covering the end surface of the partition with the cover body, the cover body is less likely to come off the partition, and the transmission sound prevention performance can be ensured for a long period of time.

The invention according to claim 6 is characterized in that the support is a molded resin product that is harder than the cover body, and is integrally formed with an attachment portion for attachment to an installation target.
According to the sixth aspect of the invention, since the mounting portion is formed using the supporting body which is a resin molded product harder than the cover main body, the engine cover can be securely fixed.

In the invention according to claim 7, the gist is that the partition section is a frame-shaped piece defining the space by plate-shaped pieces extending so as to intersect each other.
According to the seventh aspect of the present invention, since it is possible to set a large number of resonance parts corresponding to the partition parts, it is possible to improve the transmission sound prevention performance.

In the invention according to claim 8, the support is provided with an extension portion extending in a direction intersecting with the front and back direction,
The gist is that the extending portion is embedded in the foam forming the cover main body.
According to the eighth aspect of the invention, the extending portion makes it difficult for the cover main body to come off from the support.

In the invention according to claim 9, the extending portion is formed so as to extend from a wall of the partition portion facing the space, and is embedded in the foam that closes the space. do.
According to the ninth aspect of the invention, the extending portion makes it difficult for the foam that is arranged in the space of the partition to become the resonance portion to come off the partition.

The engine cover according to the present invention is excellent in transmission sound prevention performance.

1 is a cross-sectional view showing an engine cover according to a preferred embodiment of the present invention; FIG. FIG. 2 is a schematic perspective view showing the essential parts of the engine cover of the embodiment; FIG. 3 is a schematic perspective view showing a main part of a support of an example; It is explanatory drawing which shows the manufacturing process of the engine cover of an Example. It is explanatory drawing which shows the manufacturing process of the engine cover of an Example. FIG. 4 is an image diagram showing resonance of a resonator; FIG. 2 is an explanatory diagram showing a testing device for sound transmission loss; 4 is a graph showing test results related to sound transmission loss. FIG. 11 is a cross-sectional view showing a main part of an engine cover of a modified example; FIG. 11 is a cross-sectional view showing a main part of an engine cover of another modified example;

BEST MODE FOR CARRYING OUT THE INVENTION Next, an engine cover according to the present invention will be described below with reference to preferred embodiments and with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the engine cover 20 includes a cover body 22 made of foam and a support 24 integrated with the cover body 22 . The engine cover 20 is a plate-like body whose shape is set according to the space of the engine room 10 and the external shape of the engine 12 , and is installed in the engine room 10 with the back side facing the engine 12 . The engine cover 20 is arranged between the engine 12 and the engine hood 14 so as to cover the engine 12, and prevents the sound emitted from the engine 12 from being transmitted in the thickness direction from the back side to the front side.

The cover main body 22 is formed into a plate-like shape that constitutes the main body of the engine cover 20 and is made of an elastic foam. As the foam, for example, a soft foam that is soft and has resilience, a semi-rigid foam that has properties intermediate between a hard foam that is hard and has no resilience and the soft foam and has a certain degree of resilience. A rigid foam can also be used as long as it has elasticity. As the foam forming the cover main body 22, a urethane-based or olefin-based foam can be used, and among these, a soft or semi-rigid polyurethane foam is suitable. The cover main body 22 adopts a closed-cell polyurethane foam, which makes it easier to achieve the required rigidity and sound transmission prevention performance. may be In addition, the cover body 22 preferably has a covering layer (not shown) made of a skin layer, an in-mold coat, or the like on the surface. There are advantages such as being able to improve and being able to clean the appearance.

As shown in FIGS. 1 and 2, the support 24 is embedded in the cover main body 22 in its entirety or most of the main body except for the mounting portion 26, which will be described later. The support body 24 may be arranged corresponding to a partial area of the cover body 22 or may be arranged over the entire cover body 22 . A support 24 is arranged in the central portion where transmission sound prevention performance is required. The support 24 is a resin molded product made of polyamide (nylon) or the like, and has higher rigidity than the cover main body 22 , and also functions as a skeleton of the cover main body 22 .

As shown in FIGS. 2 and 3, the support 24 has a partition 28 that defines a space penetrating the engine cover 20 in the front and back directions. As for the shape, a polygon such as a quadrangle, a hexagon, or a round shape can be adopted, but a regular quadrangle as in the embodiment is preferable. The support 24 of the embodiment has a frame-like shape in which plate-shaped pieces 24a extending in a grid shape that intersect with each other form a partition 28 surrounding the space. They are arranged in a grid pattern. The support 24 is provided with a plurality of partitions 28 adjacent to each other that define a space with the same opening shape and the same opening size (opening area). Thus, in the support 24, the partitions 28 having the same opening shape and opening size are preferably formed side by side. In addition, the partition 28 preferably defines a space such that the openings facing the front and back of the engine cover 20 have the same shape and the same opening area (size). The partition part 28 of the embodiment has the same shape and size for the opening on the front side and the opening on the back side, and has a cylindrical shape in which the size of the space penetrating in the front and back direction does not change. The plate-like pieces 24a forming the partitioning portion 28 are arranged in an upright posture in the front and back directions, and adjacent spaces are provided with the plate-like pieces 24a interposed therebetween in the thickness direction. Further, the plate-like piece 24a forming the partition portion 28 is set harder than the cover main body 22. As shown in FIG.

The support member 24 is integrally formed with a mounting portion 26 for mounting and fixing the engine cover 20 to an installation target such as the engine 12 . The mounting portion 26 of the embodiment is formed in a plate-like shape extending outward from a plate-like piece 24a constituting the main body of the support 24 and protruding outside the cover main body 22. A through hole 26a is formed to pass through.

As shown in FIGS. 1 and 2 , the engine cover 20 has a resonance portion 30 formed by the foam of the cover body 22 that closes the space defined by the partition portion 28 . In other words, the resonance section 30 is made of a foam that forms a region of the cover body 22 that closes the space defined by the partition section 28 . The partition portion 28 embedded in the foam is joined to the foam, and the periphery of the resonance portion 30 is held by the partition portion 28 except for the wall surfaces facing the front and back of the engine cover 20 in the foam. The engine cover 20 is provided with a resonance section 30 corresponding to each of the plurality of partitions 28 provided on the support 24, and corresponding to the partitions 28 having the same opening shape and opening size and arranged side by side. , the resonators 30 having the same wall surface shape and the same wall surface size are arranged side by side. A plurality of resonance portions 30 are provided in the engine cover 20 so as to be adjacent to each other with a plate-like piece 24a constituting the partition portion 28 interposed therebetween. The resonance section 30 has front and back wall surfaces of the same shape and size corresponding to the partition section 28 having the same opening shape and opening area (size) on the front and back sides.

As shown in FIG. 1 , the engine cover 20 is configured such that at least one of the front side end face and the back side end face of the partition portion 28 is covered with a foam that forms the cover body 22 . In the embodiment, the front side of the partitioning portion 28 is covered with foam, while the rear end surface of the partitioning portion 28 and the rear wall surface of the cover main body 22 are aligned. Thus, the thickness Sh of the support 24 is set thinner than the thickness Bh of the cover body 22 . Here, it is preferable that the coating thickness D of the foam covering the end face of the partition 28 is 1.5 times or less than the plate thickness t of the plate-like piece 24a forming the partition 28, so as to prevent adverse effects between the adjacent resonance portions 30. is preferable from the viewpoint of reducing

The engine cover 20 can be manufactured, for example, as follows. The support 24 is obtained by molding such as injection molding. A support 24 made of resin is set in a mold 32 (FIG. 4(a)). Here, support projections 36 protruding upward from the lower mold surface 34 are provided on the lower mold surface 34 of the molding die 32 at predetermined locations while being spaced apart from each other. Thus, the support 24 is set with a gap between it and the lower mold surface 34 (FIG. 4(b)). The cover main body 22 is obtained by injecting the foam raw material into the cavity 38 of the closed mold 32 and foaming and molding the foam raw material in the cavity 38 (FIG. 5(a)). In this way, by molding with the support 24 inserted, the engine cover 20 in which the support 24 is embedded and integrated with the cover body 22 is obtained (FIG. 5(b)). When the engine cover 20 is obtained by molding the cover main body 22 in a molding die 32 in which the support 24 is set, the foam is joined to the support 24 so that the four sides of the resonance part 30 made of the foam are the supports. It is held in 24 compartments 28 .

As shown in FIG. 6, the resonance section 30 resonates on the wall surface of the cover body 22 (foam) forming the resonance section 30 when sound of a target frequency is incident. Here, while the periphery (four sides) of the resonance section 30 is held and constrained by the partition section 28, the wall surfaces of the front and back surfaces are set in a free state. can be properly resonated. When the wall surface on the back side of the cover body 22 is deformed to be recessed to the front side, the resonance part 30 is deformed so that the wall surface on the front side of the cover body 22 is bulged to the front side. Further, when the wall surface on the back side of the cover body 22 is deformed to swell to the back side, the resonance part 30 is deformed so that the wall surface on the front side of the cover body 22 is recessed to the back side. In this way, the resonance section 30 resonates when sound is incident, canceling the sound on both the front side wall surface and the rear side wall surface of the cover body 22, and at the same time reducing the sound on the rear side, which is the noise generating side. has the effect of lowering the sound of Further, in another resonance section 30 adjacent to a certain resonance section 30 , the wall surface of the cover body 22 forming the other resonance section 30 resonates in the opposite phase to the wall surface of the cover body 22 forming the resonance section 30 . In this way, the adjacent resonance portions 30 resonate in opposite phases when sound is incident, so that the sounds cancel each other out and the effect of lowering the sound as a whole is produced.

The distance between the opposing plate-like pieces 24a, 24a of the partition 28 is determined from the conditions of the foam forming the cover body 22, such as density, Young's modulus, and Poisson's ratio, and the conditions of the sound to be reduced (for example, frequency 800 Hz to 1 kHz). P (the size of the compartment 28) can be determined. That is, by setting the wall surfaces of the front and back surfaces of the resonance section 30 to the size calculated from the above conditions, the resonance section 30 can resonate more appropriately with the target sound and improve the transmission loss of the sound.

According to the engine cover 20, since it is provided with the resonance section 30 that resonates with the incidence of sound, the sound that is about to pass through the cover body 22 is suppressed by the resonance section 30 in addition to the sound insulation effect due to the density and thickness of the cover body 22. It can be damped by 30 resonances. Therefore, the engine cover 20 exhibits high transmitted sound prevention performance due to the resonating resonance part 30 in spite of the thickness of the cover body 22 . Since the engine cover 20 has a high transmission sound prevention performance even though it is thin, it can be arranged in a narrower space than before. In addition, since the engine cover 20 can ensure a predetermined transmission sound prevention performance even if it is thin, a space can be provided in the engine room 10 even if it is arranged, and the transmission sound prevention performance can be maintained. An adverse effect on cooling of the engine 12 can be suppressed.

The engine cover 20 can adjust the frequency of the sound resonated by the resonance section 30 provided corresponding to the partitioning portion 28 by adjusting the interval between the plate-like pieces 24a forming the partitioning portion 28. . Therefore, the engine cover 20 can easily improve the transmission loss of a specific frequency band in a specific range by setting the partition 28, and has a high degree of freedom in design. Since the cover body 22 of the engine cover 20 is supported by the support member 24, it is possible to use the cover body 22 made of a relatively soft foam, and it is possible to prevent transmission of low frequency sound.

In the engine cover 20, the front end surface of the partition 28 of the support 22 is covered with the foam forming the cover body 22, so that the cover body 22 is difficult to separate from the support 22 and is affected by temperature changes. it gets harder. Since such an engine cover 20 is excellent in durability, it is possible to secure transmission sound prevention performance over a long period of time. In addition, by setting the end face of the partitioned portion 28 of the support 22 in the engine cover 20 so as to cover the end surface of the partitioned portion 28 with the foam, the foam raw material does not flow between the mold surface and the partitioned portion 28 during insert molding with the molding die 32 . A flow gap can be secured, and molding of the cover main body 22 can be facilitated.

If the front and rear wall surfaces of the adjacent resonant portions 30, 30 have the same shape and size, the adjacent resonant portions 30, 30 can easily generate resonance in which the phases are opposite to each other. Due to such combined action of the adjacent resonance portions 30, 30, the transmission sound prevention performance of the engine cover 20 can be improved. Further, when the resonance section 30 has the same size for the wall surface on the front side and the wall surface on the back side, the resonance section 30 is likely to resonate, so that the transmitted sound prevention performance can be improved.

As described above, the support 24 has a frame-like shape in which the plate-shaped pieces 24a extending so as to intersect each other form the partitions 28, so that the resonance portions 30 provided corresponding to the partitions 28 are placed in the cover main body. 22 can be set per unit area. As a result, the transmission sound prevention performance of the engine cover 20 can be improved. Moreover, the adjacent resonance portions 30, 30 with the plate-like piece 24a interposed therebetween can be set close to each other, and the adjacent resonance portions 30, 30 can easily resonate in opposite phases.

Since the engine cover 20 forms the mounting portion 26 using the supporting body 24, which is a resin molded product harder than the cover main body 22 made of foam, the engine cover 20 is securely fixed to the installation target such as the engine 12. be able to. In addition, since the engine cover 20 has the mounting portion 26 formed integrally with the support 24, there is no need to form a portion for mounting on the cover main body 22, and there is no need to form a separate part for mounting the engine cover 20 alone. The number of members can be reduced, and the cost can be reduced.

(Transmitted sound prevention performance test)
An engine cover of the example was produced, and its transmission sound prevention performance was examined. In the engine cover of the example, the cover body is made of polyurethane foam having a density of 0.15 g/cm 3 , a Young's modulus of 110 kPa, and a Poisson's ratio of 0.16. In the support of the example, plate-like pieces with a plate thickness of 2 mm are formed in a frame shape extending vertically and horizontally in a grid pattern, and the plate-like pieces arranged at intervals of 15 mm define a square opening. are provided multiple times. Here, in the engine cover of the embodiment, a resonance part is set for 800 Hz to 1000 Hz, which is the frequency band of sound emitted by the engine. In the engine cover of the example, the thickness of the cover body is 12.5 mm, and the thickness of the support is 10 mm. The wall surface on the back side of the cover body and the end face on the back side of the support are aligned, and the end face on the front side of the support is covered with a foam with a coating thickness of 2.5 mm. The engine cover of the embodiment is integrated by molding the cover main body with a mold into which the supporting body is inserted. The engine cover of the comparative example was composed only of a cover body made of polyurethane foam having a density of 0.15 g/cm 3 , a Young's modulus of 110 kPa, and a Poisson's ratio of 0.16. The thickness of Comparative Example 1 is 10 mm, the thickness of Comparative Example 2 is 20 mm, the thickness of Comparative Example 3 is 30 mm, and the thickness of Comparative Example 4 is 40 mm.

The transmission sound prevention performance was evaluated by normal incidence sound transmission loss (sound transmission loss tube transfer matrix method: conforming to ASTM E2611-09). Specifically, the sample X of the example and the comparative example was set in the device main body 42 of the test device 40 shown in FIG. Sound pressure is measured with a microphone 46 installed at a position. Reference numeral 48 denotes a sound absorbing material that closes the side of the device main body 42 opposite to the speaker 44 . Then, the transmission loss is obtained by calculating the complex transfer function using a 4-channel digital frequency analyzer. The test equipment used was Brüel & Kjær Japan 4206T for large pipes with a diameter of 100 mm, and the software used was 7758 PULSE. FIG. 8 shows the results of the transmitted sound prevention performance test.

As shown in FIG. 8, it can be seen that the transmission loss of the engine cover of Example is greater than that of Comparative Example 3, which is composed only of the cover body with a thickness of 30 mm. In addition, the engine cover of the example shows a large transmission loss in the target frequency band of 800 Hz to 1000 Hz, approaching that of Comparative Example 4, which consists only of a cover body with a thickness of 40 mm. As described above, it can be confirmed that the engine cover of the example exerts an excellent transmitted sound prevention performance even if the thickness is thin.

(Change example)
The configuration is not limited to the one described above, and can be modified, for example, as follows.
(1) In the embodiment, the support is arranged in a partial range of the engine cover, but the support is not limited to this, and the support may be arranged over the entire engine cover.
(2) In the embodiment, one end surface of the support is covered with the foam, but as shown in FIG. 9, both the front and back end surfaces of the support may be covered with the foam. At this time, if the entire support body except for the mounting portion is covered with the foam, the cover body becomes more difficult to peel off from the support body, and the durability can be improved. In addition, in FIG. 9, the same code|symbol as an Example is attached|subjected to the structure similar to an Example. Further, the support may protrude from the front and back wall surfaces of the cover body.
(3) The support is not limited to a frame-like shape as in the embodiment, and may have, for example, a configuration in which openings formed through a plate material serve as partitions.
(4) As shown in FIG. 10, the support member 24 may be provided with extending portions 25a and 25b extending in a direction intersecting the front and back direction of the engine cover 20. As shown in FIG. The extending portions 25 a and 25 b formed on the support 24 are embedded in the foam forming the cover body 22 . For example, as the extending portions 25a and 25b, a plate piece that is provided integrally with the plate-like piece 24a in the middle portion in the front and back direction of the plate-like piece 24a and extends in the thickness direction of the plate-like piece 24a is adopted. can do. The inwardly extending portion 25a is formed to extend from the wall of the plate-like piece 24a facing the space in the partition portion 28, and is embedded in the foam that closes the space. According to such an inwardly extending portion 25a, the foam that is arranged in the space of the partition portion 28 and becomes the resonance portion 30 can be made difficult to come off the partition portion 28, and the foam can be appropriately used as the resonance portion. can function. Moreover, since the outwardly extending portion 25 b provided to extend outward from the outer peripheral surface of the support 24 is embedded in the foam forming the cover body 22 , the cover body 22 can be removed from the support 24 . can be made difficult. In the modification, the configuration including both the inwardly extending portion 25a and the outwardly extending portion 25b is illustrated, but the configuration is not limited to this, and only one of the inwardly extending portion 25a and the outwardly extending portion 25b may be provided. . In addition, in FIG. 10, the same code|symbol as an Example is attached|subjected to the structure similar to an Example.

20 engine cover, 22 cover body, 24 support, 24a plate-like piece,
25a inner extending portion (extending portion), 25b outer extending portion (extending portion), 26 mounting portion,
28 division part, 30 resonance part

Claims (2)

An engine cover that covers an engine,
a cover body made of an elastic foam;
a support body having a partition defining a space penetrating the engine cover in the front and back directions, the partition being embedded in the cover body and integrated with the cover body,
An engine cover according to claim 1, wherein the cover main body closing the space defined by the partition is a resonating part in which front and rear wall surfaces of the foam body resonate when sound is incident. 2. The engine cover of claim 1, wherein said foam comprises closed cells .

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