JP7213693B2 - Sound insulation structure for internal combustion engines - Google Patents

Description

The present invention relates to a sound insulation structure for an internal combustion engine in an automobile or the like.

2. Description of the Related Art An internal combustion engine in an automobile or the like has a relatively thin oil pan on the bottom and a front cover on the front to cover a timing chain or timing belt that drives a camshaft. Since the oil pan and the front cover have a relatively wide and low-rigidity surface, they receive excitation force due to combustion and explosion of the internal combustion engine, vibrate the membrane, and become a kind of sound source.

Therefore, as disclosed in Patent Document 1, it has been proposed to cover the internal combustion engine with a sound insulating cover made of a material having sound absorbing or sound insulating properties.

JP-A-10-205352

A front cover for covering the timing chain and timing belt is attached to the mounting surface on the front surface of the internal combustion engine body in such a manner as to seal the space between the front cover and the mounting surface, and seals the lubricating oil that scatters in the internal space. As the sealing performance deteriorates over time, lubricating oil may seep out from the boundary between the front cover and its mounting surface. Here, if the lower surface and the front surface of the internal combustion engine are covered with the sound insulating cover, there is a concern that it may be delayed to discover that the lubricating oil is leaking from the boundary between the front cover and its mounting surface. In addition, it is necessary to remove the sound insulation cover in order to check whether or not the lubricating oil is oozing out, which deteriorates maintainability.

A sound insulation structure for an internal combustion engine according to the present invention includes a flexible lower sound insulation cover disposed under an internal combustion engine body so as to cover an oil pan attached to the lower surface of the internal combustion engine body; a flexible front sound insulation cover arranged at the front of the internal combustion engine body so as to cover the front cover attached to the front. The front edge portion of the lower sound insulation cover and the lower edge portion of the front sound insulation cover overlap each other as free ends along mating surfaces parallel to the mounting surface of the oil pan. The front edge of the side sound insulation cover and the lower edge of the front sound insulation cover are configured to be deformable outward or inward using a finger or a jig, and to return to their initial states when the finger or jig is released. there is The overlapping portion between the two is positioned below the mounting surface of the front cover, and the front edge portion of the lower sound insulation cover and the lower edge portion of the front sound insulation cover at the overlapping portion are deformed outward or inward . , the boundary between the lower edge of the front cover and the mounting surface of the front cover can be visually recognized.

According to such a configuration, since the lower sound insulation cover and the front sound insulation cover cover the oil pan and the front cover, which are the sources of sound generation, the sound can be absorbed or insulated, and the front edge portion and the front side of the lower sound insulation cover can be Since the lower edge of the sound insulation cover overlaps, the noise leaking to the outside is reduced. When checking whether or not lubricating oil is seeping out from the boundary between the front cover and its mounting surface, use fingers or an appropriate jig to deform the overlapped portion, which is a free end, to remove the inside. It suffices to take a peek, and inspection becomes easy.

1 is a front view of an internal combustion engine provided with a sound insulation structure according to the present invention; FIG. The perspective view of the same internal combustion engine. FIG. 2 is an exploded perspective view of the internal combustion engine; Sectional drawing of a lower side sound insulation cover and a front side sound insulation cover. Sectional drawing which shows the layered structure of a sound insulation cover. The bottom view which looked at the lower side sound insulation cover and the front side sound insulation cover from the downward direction. The perspective view which looked at the lower side sound insulation cover and the front side sound insulation cover from the inside.

An embodiment of the present invention will be described in detail below with reference to the drawings. 1 is a front view of an internal combustion engine equipped with a sound insulation structure according to the present invention, FIG. 2 is a perspective view, and FIG. 3 is an exploded perspective view showing the sound insulation structure. The internal combustion engine of the embodiment is an in-line multi-cylinder (for example, 3-cylinder or 4-cylinder) internal combustion engine. is configured. The cylinder block 2 includes a plurality of cylinders (not shown) and a water jacket surrounding the cylinders. The cylinder head 3 is fixed on the top surface of the cylinder block 2, forms a combustion chamber (not shown) by covering the upper end of the cylinder, and has an intake port and an exhaust port (not shown) inside. The cylinder head 3 supports a pair of camshafts (an intake valve side camshaft and an exhaust valve side camshaft) (not shown), and a cylinder head cover 5 is attached to the top opening of the cylinder head 3 .

The lower block 4 is attached to the lower edge of the skirt portion 2a of the cylinder block 2, and together with the cylinder block 2, forms a crankcase serving as a space in which the crankshaft rotates. A part of the lower surface of the lower block 4, more specifically, a front end portion of the lower surface is opened in a substantially rectangular shape. An oil pan 6 is attached to the lower surface of the lower block 4 so as to cover this opening (see FIGS. 3 and 4). The oil pan 6 is made of, for example, a metal plate press-molded product, a hard synthetic resin molded product, or a thin aluminum die-cast, and is formed in a substantially rectangular dish shape corresponding to the shape of the opening. The oil pan 6 is thinner than the lower block 4 and has relatively low rigidity, and therefore tends to cause membrane vibration.

Although the lower block 4 and the oil pan 6 are sometimes referred to as "oil pan upper" and "oil pan lower", in this embodiment, the oil pan 6 corresponds to the "oil pan" in the claims.

The front end of the crankshaft protrudes forward from the front surface 1a of the internal combustion engine body 1, and a crank pulley 7 is attached thereto (see FIGS. 3 and 4). A front cover 8 is attached to the front surface 1a of the internal combustion engine body 1 to cover a winding transmission member such as a timing chain (not shown) (see FIGS. 3 and 4). The crank pulley 7 is located forward of the front cover 8 and is not covered with the front cover 8 . In other words, the front end of the crankshaft passes through the front cover 8, and the crank pulley 7 is attached to its tip. A timing chain (not shown) is wound between a crank sprocket at the end of the crankshaft and a cam sprocket at the end of the camshaft (both not shown), and rotates the camshaft at half the rotational speed of the crankshaft. I am driving with it. The crank pulley 7 drives auxiliary equipment (such as a water pump) (not shown) via a belt.

The front cover 8 is made of a hard synthetic resin molding, a press molding of a metal plate, a thin aluminum die-cast, or the like, and is formed in a cover shape along the running path of the timing chain. Lubricating oil is scattered in the space inside the front cover 8 in which the timing chain runs. A sealing material (such as a liquid gasket or a molded gasket) is interposed between the . The front cover 8 is thinner than the cylinder block 2, the cylinder head 3, or the lower block 4, which constitute the internal combustion engine body 1, and has relatively low rigidity. A position near the crank pulley 7 (shown as point P1 in FIG. 1), which is a particularly wide surface, is a point where the sound pressure level due to membrane vibration is high.

Incidentally, the internal combustion engine is generally called the front side of the internal combustion engine on the side of the crank pulley 7 regardless of the mounting posture of the vehicle, and the side opposite to the crank pulley 7 (the side to which the transmission (not shown) is connected) is the side of the internal combustion engine. called posterior.

The sound insulation structure of the embodiment includes a lower sound insulation cover 11 arranged at the lower part of the internal combustion engine body 1 so as to cover the oil pan 6, and a front side sound insulation cover 11 arranged at the front part of the internal combustion engine body 1 so as to cover the front cover 8. a sound insulation cover 12; 3 to 7 show these sound insulation covers 11 and 12. FIG. Although not shown, it is desirable to further combine two side sound insulation covers that respectively cover both side surfaces of the internal combustion engine body 1 .

These sound insulating covers 11 and 12 are made of a flexible sound absorbing material such as nonwoven fabric or urethane foam. In one embodiment, as shown in FIG. 5, an inner sound absorbing layer 31 made of a relatively low density nonwoven fabric, an outer sound insulating layer 32 made of a relatively high density nonwoven fabric, and inner and outer surface layers are formed. The sound insulation covers 11 and 12 are formed by using a sheet material having a four-layer structure consisting of thin skin layers 33 and 34 which are formed into a predetermined cover shape. For example, a sheet material made of the nonwoven fabric described above is impregnated with a thermosetting resin and hot-pressed to form a predetermined shape. The sheet material has a thickness of, for example, about 25 mm to 30 mm. Therefore, the general portion (for example, the central portion of the wide surface) of the sound insulation covers 11, 12 that are used without being compressed during pressing has a thickness of about 25 mm. have.

The lower sound insulation cover 11 has a deep plate shape with an open upper surface so as to form an inner space 11a large enough to cover the oil pan 6 with an appropriate gap. It is fixed to the lower block 4 at four locations (indicated by circles 14) via bolts (not shown). The four sides surrounding the inner space 11a are in the shape of a continuous flange, and the three sides except for the front edge portion 11c are in contact with the lower surface of the lower block 4. As shown in FIG. In FIG. 6, point P2 indicates the point where the sound pressure level is highest when the oil pan 6 vibrates. The lower sound insulation cover 11 needs to cover at least the periphery of this point P2 from below. The lower sound insulation cover 11 of the embodiment covers the entire oil pan 6 including the point P2 where the sound pressure level is high.

The front sound insulation cover 12 is formed in a dish-like or cover-like shape so as to form an inner space 12a that opens toward the front surface 1a of the internal combustion engine body 1, which serves as a mounting surface. It has a size that can cover the area of the part. In addition, the central portion serves as a belt accommodating portion 12b so as to cover the crank pulley 7 together with an accessory drive belt (not shown) that is wound around the crank pulley 7, and is shaped along the running path of the accessory drive belt. bulging forward. The depth of the inner space 12a (the depth measured in the longitudinal direction of the internal combustion engine) is deep at the belt accommodating portion 12b, as shown in FIG.

As shown in FIG. 1, the front sound insulation cover 12 is fixed to the internal combustion engine body 1 via bolts (not shown) at two upper and lower diagonal points (points indicated by circles 15). In this embodiment, the front sound insulation cover 12 covers most of the lower side of the front cover 8 and part of the upper side of the front cover 8 is exposed without being covered. It is also possible to configure so as to cover the entire front cover 8 as . The front sound insulation cover 12 needs to cover at least the vicinity of the point P1 where the sound pressure level of the front cover 8 is the highest. A lower edge portion 12c of the front sound insulation cover 12 has a substantially linear shape when viewed from the front as shown in FIG. The lower edge portion 12c is located below the lower surface of the internal combustion engine body 1 (mounting surface of the oil pan 6), and is therefore not in contact with the front surface 1a of the internal combustion engine body 1. As shown in FIG.

When both the lower sound insulation cover 11 and the front sound insulation cover 12 are attached to the internal combustion engine body 1, the front edge portion 11c of the lower sound insulation cover 11 and the front sound insulation cover 12 are separated from each other as shown in FIGS. overlaps with the lower edge 12c to form an overlapping portion 17. As shown in FIG. In one example, the front edge portion 11c of the lower sound insulation cover 11 overlaps with the lower edge portion 12c of the front sound insulation cover 12 so as to be relatively upward. Conversely, the lower edge 12c of the front sound insulation cover 12 may face upward.

As shown in FIG. 6, the overlapping portion 17 extends substantially uniformly over substantially the entire width of the lower sound insulation cover 11 (dimension in the left-right direction on the paper surface of FIG. 6). In addition, in the overlapping portion 17, the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12 overlap each other over a length L of 10 mm to 20 mm, for example, in the longitudinal direction of the internal combustion engine. there is

FIG. 4 shows an example of the cross-sectional structure of the overlapping portion 17. As shown in FIG. As shown in the figure, the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12 that constitute the overlapping portion 17 are both free ends that are not fixed to the internal combustion engine body 1. . In other words, the front edge portion 11c of the lower sound insulation cover 11 protrudes forward from the fixing point (bolt position of the circle 14) of the lower sound insulation cover 11, and the lower edge portion 12c of the front sound insulation cover 12 It is located below the fixing point of the front sound insulation cover 12 (bolt position of circle 15). As shown in FIG. 4, they overlap each other along a mating surface parallel to the mounting surface 4a of the oil pan 6. As shown in FIG. That is, the lower surface 11d of the front edge portion 11c of the lower sound insulation cover 11 and the upper surface 12d of the lower edge portion 12c of the front sound insulation cover 12 extend parallel to the mounting surface 4a and face each other. The mating surfaces are defined by these facing surfaces 11d and 12d. Here, in the illustrated example, the facing surfaces 11d and 12d of the overlapping portion 17 are not in contact with each other, and have a gap 18 so that air can flow between the inside and the outside. In one example, gap 18 has dimensions in the range of 1 mm to 10 mm.

Further, the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12, which constitute the overlapping portion 17, are compared with the thicknesses of the general portions of the lower sound insulation cover 11 and the front sound insulation cover 12, respectively. and partially thinned. For example, if the thickness of the general portion is about 25 mm, each is compressed to a thickness of about 5 to 15 mm.

As shown in FIG. 4 , the overlapping portion 17 is positioned below the mounting surface of the internal combustion engine body 1 to which the front cover 8 is mounted, that is, the front surface 1a of the internal combustion engine body 1 . The overlap portion 17 is formed by deforming the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12, which constitute the overlap portion 17, outward or inward. The boundary between the lower edge and the mounting surface of the front cover 8 (the front surface 1a of the internal combustion engine body 1) can be visually recognized by an operator from the outside. For example, by expanding both of them outward and creating a space between them, visual recognition becomes possible.

According to such a configuration, the sound due to the vibration of the membranes of the oil pan 6 and the front cover 8, which receives the excitation force due to the combustion and explosion of the internal combustion engine, is generated by the lower sound insulation cover covering the oil pan 6 and the front cover 8. 11 and the front sound insulation cover 12 provide sound insulation and absorption. At the boundary between the two, the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12 overlap over a relatively long length L with a gap 18 as an overlapping portion 17. Therefore, air can flow while suppressing leakage of sound from the inside of the sound insulation covers 11 and 12 to the outside, and the heat inside the sound insulation covers 11 and 12 can be released to the outside. Therefore, it is possible to prevent the inside of the sound insulation covers 11 and 12 from becoming excessively hot. Here, the size of the gap 18 and the length L of the overlapping portion 17 are set in consideration of the expected frequency of sound, that is, the wavelength. In one example, it is set to correspond to a sound of 2000 Hz.

Furthermore, in the above configuration, the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12, which constitute the overlapping portion 17, are removed by fingers or an appropriate jig during regular inspections. By deforming outward or inward, the boundary between the lower edge of the front cover 8 and the mounting surface of the front cover 8 (the front surface 1a of the internal combustion engine body 1) can be visually recognized from the outside. It is possible to easily check the presence or absence of bleeding of lubricating oil between the surfaces (that is, poor sealing). Both the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12, which constitute the overlapping portion 17, are free ends protruding from fixed points by bolts, so that they can be easily mounted. It can be transformed. Of course, when the fingers are released, the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12, which constitute the overlapping portion 17, return to the initial state, that is, the state in which they face each other with the gap 18 interposed therebetween. do. Since the front edge portion 11c of the lower sound insulation cover 11 and the lower edge portion 12c of the front sound insulation cover 12 are thinner than the thickness of the general portion, they can be deformed with fingers or the like to reshape the interior. Visual recognition becomes easy.

Therefore, it is possible to inspect and confirm deterioration of the sealing performance of the front cover 8 without removing the sound insulation covers 11 and 12 .

In the above-described embodiment, the overlapping portion 17 has the gap 18, which is advantageous in releasing internal heat.

REFERENCE SIGNS LIST 1 Internal combustion engine body 2 Cylinder block 3 Cylinder head 4 Lower block 6 Oil pan 8 Front cover 11 Lower sound insulation cover 11c Front edge 12 Front sound insulation cover 12c Lower edge 17 Overlapping portion 18 Gap

Claims (6)

A flexible lower sound insulation cover arranged at the lower part of the internal combustion engine body so as to cover the oil pan attached to the lower surface of the internal combustion engine body, and a front cover attached to the front surface of the internal combustion engine body so as to cover the front cover. a flexible front sound insulation cover arranged in front of the internal combustion engine body;
A front edge portion of the lower sound insulation cover and a lower edge portion of the front sound insulation cover overlap each other as free ends along a mating surface parallel to the mounting surface of the oil pan. The front edge of the cover and the lower edge of the front sound insulation cover are configured to be deformable outward or inward using a finger or a jig and to return to their initial states when the finger or jig is released,
The overlapping portion between the two is positioned below the mounting surface of the front cover, and the front edge portion of the lower sound insulation cover and the lower edge portion of the front sound insulation cover at the overlapping portion are deformed outward or inward . A sound insulation structure for an internal combustion engine, wherein a boundary between a lower edge of the front cover and a mounting surface of the front cover can be visually recognized. The front edge portion of the lower sound insulation cover and the lower edge portion of the front sound insulation cover, which constitute the overlapping portion, are partially thinner than the general thickness of the lower sound insulation cover or the front sound insulation cover. 2. A sound insulation structure for an internal combustion engine according to claim 1, characterized in that: 3. The sound insulation structure for an internal combustion engine according to claim 1, wherein the overlapping portion has a gap along the mating surface to allow air to flow. 4. The sound insulation structure for an internal combustion engine according to claim 3, wherein the size of said gap is 1 mm to 10 mm. The overlapping portion is characterized in that the front edge portion of the lower sound insulation cover and the lower edge portion of the front sound insulation cover overlap each other over a length of 10 mm to 20 mm in the longitudinal direction of the internal combustion engine. Item 5. A sound insulation structure for an internal combustion engine according to any one of Items 1 to 4. 6. The sound insulation structure for an internal combustion engine according to claim 1, wherein said lower sound insulation cover and said front sound insulation cover are made of non-woven fabric or urethane foam.

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