Cover member for internal combustion engine

Abstract

To provide a cover member for an internal combustion engine capable of improving silencing performance.SOLUTION: A cover member 1 comprises a plate body 2 formed of resin in a plate shape, and having a plurality of fixing parts 21 fixed to an object to be fixed. A thin part 3 is formed in the plate body 2 at a position adjacent to a strain node A caused by vibration displacing along a plate thickness direction with the plurality of fixing parts 21 as fixed ends.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cover member for an internal combustion engine. [Background technology]

[0002] Conventionally, a vibration-damping plate made of multiple laminated steel plates has been proposed as a plate to be attached to an automobile engine or the like (see, for example, Patent Document 1). In the vibration-damping plate described in Patent Document 1, vibration energy is consumed by friction generated between the steel plates during vibration, thereby suppressing radiated sound. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-106809 Summary of the Invention [Problem to be solved by the invention]

[0004] Methods for dissipating vibrational energy include not only generating friction between components as described in Patent Document 1, but also constructing a plate-shaped component out of resin and generating dynamic strain (hereinafter simply referred to as "strain") within the component. In this case, making the plate-shaped component more deformable and increasing the amount of strain increases the consumption of vibrational energy, but the amplitude of the component itself increases, which can cause noise. On the other hand, making the plate-shaped component less deformable suppresses the vibration of the component itself, but the amount of strain generated is small, making it difficult to achieve a vibration damping effect. Thus, it has been difficult to achieve both a vibration damping effect and suppression of the component's own vibration.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a cover member for an internal combustion engine that can improve noise reduction performance. [Means for solving the problem]

[0006] In order to solve the above problems, the cover member for an internal combustion engine according to the present invention comprises a plate-shaped body made of resin and having a plurality of fixing portions that are fixed to an object to be fixed to, and the plate body is characterized in that a thin-walled portion is formed in a position adjacent to a node of strain caused by vibration that displaces along the plate thickness direction with the plurality of fixing portions as fixed ends.

[0007] According to this embodiment, the thin-walled portion can make it easier for the plate body to deform at positions adjacent to the strain nodes (positions where the strain amount is 0 during vibration). This increases the strain amount, increases the consumption of vibration energy, and makes it easier to attenuate vibration, improving the sound deadening effect. In this case, it is not necessary to make the entire plate body thinner to increase the strain amount, and the amplitude of the cover member itself can be prevented from increasing, making it easier to achieve the sound deadening effect.

[0008] A pair of the thin-walled portions may be formed at positions sandwiching the strain node. According to this aspect, the amount of strain can be increased on both sides of the strain node, and the sound deadening effect can be further improved.

[0009] The thin-walled portions may be formed by forming recesses on both sides of the plate body. According to this aspect, the depth of each recess can be reduced, improving workability. Furthermore, the formation of the recesses can prevent asymmetry from occurring in the plate body, and changes in vibration characteristics due to the provision of the thin-walled portions can be suppressed.

[0010] The thin-walled portion may be formed at a position adjacent to a node of strain caused by the natural vibration of the plate body at 700 to 1300 Hz. According to this aspect, when the cover member is, for example, a front cover of an engine, it is possible to easily reduce noise generated by the engine and noise radiated from the front cover due to engine vibration. [Effects of the Invention]

[0011] According to the cover member for an internal combustion engine of the present invention, the thin-walled portion is formed in a position adjacent to the node of strain, thereby making it possible to improve the sound deadening performance. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a cover member for an internal combustion engine according to an embodiment of the present invention. [Figure 2] 1A and 1B are a cross-sectional view and a graph of strain distribution, each of which schematically shows a cover member for an internal combustion engine according to an embodiment of the present invention; [Figure 3] 4 is a cross-sectional view schematically showing a cover member for an internal combustion engine of Comparative Example 1 and a graph of strain distribution. [Figure 4] 10 is a cross-sectional view schematically showing a cover member for an internal combustion engine of Comparative Example 2 and a graph of strain distribution. [Figure 5] 10 is a graph showing the vibration transmissibility characteristics of the cover member for an internal combustion engine according to the embodiment of the present invention and the cover member for an internal combustion engine of Comparative Example 3. [Figure 6] 10 is a graph showing noise characteristics of a cover member for an internal combustion engine according to an embodiment of the present invention and a cover member for an internal combustion engine of Comparative Example 3. [Figure 7] 10A and 10B are a cross-sectional view and a graph of strain distribution, each showing a schematic diagram of a cover member for an internal combustion engine according to a modified example of the present invention; [Figure 8] FIG. 10 is a cross-sectional view schematically showing a main portion of a cover member for an internal combustion engine according to another modified example of the present invention. [Figure 9] FIG. 10 is a cross-sectional view schematically showing a main portion of a cover member for an internal combustion engine according to another modified example of the present invention. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a main portion of a cover member for an internal combustion engine according to another modified example of the present invention. [Figure 11] FIG. 10 is a cross-sectional view schematically showing a main portion of a cover member for an internal combustion engine according to another modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a perspective view showing a cover member 1 for an internal combustion engine according to an embodiment of the present invention.

[0014] A cover member 1 for an internal combustion engine according to an embodiment of the present invention includes a plate-shaped resin body 2 having a plurality of fixing portions 21 that are fixed to an object to be fixed (an engine). A thin-walled portion 3 is formed in the plate body 2 at a position adjacent to a node A of strain caused by vibration that displaces along the plate thickness direction with the plurality of fixing portions 21 as fixed ends.

[0015] The cover member 1 is a front cover attached to an engine body, such as a timing chain cover for the engine, etc. In the illustrated example, the cover member 1 is formed with a through hole O through which a crankshaft passes.

[0016] The cover member 1 includes a plate body 2 that is entirely made of a resin such as PA (polyamide) or PP (polypropylene) and has a flat plate shape. The plate body 2 may extend along a plane, or may have some degree of deflection relative to the plane in its natural state (undeformed state). A direction perpendicular to such a plane is called the "plate thickness direction." A plurality of fixing portions 21 are formed along the outer periphery of the plate body 2. The fixing portions 21 are formed in the shape of through-holes, through which fastening members such as screws are inserted, and the plate body 2 is fixed to a target object by these fastening members. Note that the fixing structure of the fixing portions 21 is not limited to this, and various fixing structures can be adopted.

[0017] When the cover member 1 is fixed to a fixed object and sound is emitted from a sound source such as an engine or engine vibrations are transmitted to the cover member 1, the cover member 1 vibrates, generating radiated sound. Specifically, the fixed portion 21 serves as the fixed end, and vibrations occur in which each portion of the plate body 2 is displaced along the plate thickness direction. In FIG. 1, the outer periphery of the plate body 2 serves as the fixed end, and the portion surrounded by this outer periphery is displaced. The vibration mode at this time depends on the wavelength of the radiated sound. Below, the strain node A corresponding to the fundamental vibration and the thin-walled portion 3 are illustrated and explained. The plate body 2 has not only the thin-walled portion 3 corresponding to the strain node A of the fundamental vibration, but also thin-walled portions corresponding to strain nodes generated by other vibration modes (particularly the natural vibration in the 700 to 1300 Hz frequency range, which will be described later).

[0018] FIG. 2 is a schematic cross-sectional view of the cover member 1 and a graph of strain distribution. From top to bottom, FIG. 2 shows the plate body 2 in its natural state, the plate body 2 undergoing fundamental vibration, and the amount of strain at that time. When the plate body 2 undergoes fundamental vibration, both ends become fixed ends (nodes of vibration) and the center becomes the antinode of vibration. At this time, a compressive moment (negative strain) occurs near the fixed ends, and a tensile moment (positive strain) occurs in the center, and the amount of strain becomes zero (no strain occurs) at the position where these switch. In other words, this position where no strain occurs is strain node A. A strain node is a position where the amount of strain is zero, and is different from a vibration node where the amount of displacement is zero.

[0019] The cross-sectional view shown in Fig. 2 shows the state in which the plate body 2 is cut so as to pass through the two fixing parts 21 and intersect with the strain node A. The strain node A has an arc shape as shown in Fig. 1, and appears in two places in the cross-sectional view of Fig. 2.

[0020] The plate body 2 has recesses 22, 23 formed on both sides at positions adjacent to the strain node A. The recesses 22, 23 are arranged on the central side (opposite the fixed end) of the strain node A. The recess 22 is formed by a pair of side surfaces 221 along the plate thickness direction and a bottom surface 222 connecting these surfaces, and has a cross-sectional shape surrounded by three straight lines. The recess 23 has a shape similar to that of the recess 22. The recesses 22, 23 are arc-shaped grooves inside the arc-shaped strain node A. The recesses 22, 23 and the thin-walled portion 3 described later may have a continuous arc shape or an intermittent arc shape.

[0021] The plate body 2 has a substantially constant plate thickness except for the portions where the recesses 22, 23 are formed. As a result, the portion of the plate body 2 between the recesses 22, 23 (the portion sandwiched between their bottom surfaces) has a smaller plate thickness than the other portions, forming the thin-walled portion 3. The thin-walled portion 3 is formed at a position adjacent to the strain node A. Here, "adjacent position" means, for example, within 5 mm from the strain node A (for example, within 2% of the distance between the fixed ends).

[0022] The thinner the plate body 2, the more easily it deforms and the greater the amount of strain. Therefore, as shown in the graph in Figure 2, the amount of strain is greater at the position where the thin-walled portion 3 is formed (the position adjacent to the strain node A).

[0023] Here, we will explain a comparative example in which no thin-walled portion is formed (the entire plate body has a substantially constant plate thickness). Figure 3 is a cross-sectional view and a graph of strain distribution that schematically shows a cover member for an internal combustion engine of Comparative Example 1. Figure 3 shows the plate body 4 in its natural state, the state of the plate body 4 undergoing fundamental vibration, and the amount of strain at that time for the cover member of Comparative Example 1 in which the plate body 4 has a relatively large plate thickness. Figure 4 is a cross-sectional view and a graph of strain distribution that schematically shows a cover member for an internal combustion engine of Comparative Example 2. Figure 4 shows the plate body 5 in its natural state, the state of the plate body 5 undergoing fundamental vibration, and the amount of strain at that time for the cover member of Comparative Example 2 in which the plate body 5 has a relatively small plate thickness.

[0024] In Comparative Example 1, although the amplitude of the plate body 4 can be suppressed, the amount of strain is relatively small and vibration energy is not easily consumed. On the other hand, in Comparative Example 2, the amount of strain is relatively large and vibration energy is easily consumed, but the amplitude of the plate body 5 is large, and the vibration of the plate body 5 itself can become a cause of noise generation.

[0025] In contrast to such comparative examples 1 and 2, the cover member 1 of this embodiment can increase the amount of strain while suppressing the amplitude of the plate body 2. This makes it easier to consume vibration energy and to attenuate vibration.

[0026] Fig. 5 is a graph of the vibration transmissibility characteristics of the cover member 1 and the cover member for an internal combustion engine of Comparative Example 3. The graph in Fig. 5 shows the vibration transmissibility (amplitude) characteristics of the cover member 1 of this embodiment and the cover member of Comparative Example 3. The cover member of Comparative Example 3 does not have a thin-walled portion formed therein, and is otherwise similar to the cover member 1 of this embodiment in terms of thickness, etc. It can be seen that the amplitude of the cover member 1 of this embodiment is reduced compared to the cover member of Comparative Example 3, particularly at the resonance frequency.

[0027] Fig. 6 is a graph of noise characteristics of the cover member 1 and a cover member for an internal combustion engine of Comparative Example 3. Fig. 6 shows the noise characteristics of the cover member 1 of this embodiment and the cover member of Comparative Example 3. With the cover member 1 of this embodiment, by reducing the amplitude as described above, a noise reduction effect can be obtained compared to the cover member of Comparative Example 3, particularly in the region surrounded by the dashed line (700 to 1300 Hz).

[0028] Thus, according to the cover member 1 according to the embodiment of the present invention, the thin-walled portion 3 is formed in a position adjacent to the strain node A, which makes it easier for the plate body 2 to deform and increases the amount of strain. This makes it easier to attenuate vibrations and improves the sound-deadening effect. Furthermore, by forming the thin-walled portion 3 in a position adjacent to the strain node A, it is possible to suppress a decrease in the rigidity of the entire cover member 1 compared to when the thin-walled portion 3 is formed in another position. Furthermore, by forming the plate body 2 from resin, it is possible to reduce the weight of the cover member 1.

[0029] Furthermore, by forming the recesses 22, 23 on both sides of the plate body 2, the depth of each of the recesses 22, 23 can be reduced, improving processability. Furthermore, the formation of the recesses 22, 23 prevents asymmetry from occurring in the plate body 2, and can suppress changes in vibration characteristics caused by providing the thin-walled portion 3.

[0030] Furthermore, by forming a thin-walled portion adjacent to the node of strain caused by the natural vibration of the plate body 2 at 700 to 1300 Hz, when the cover member 1 is, for example, the front cover of an engine, it is possible to easily reduce the noise generated by the engine and the noise radiated from the front cover due to engine vibration.

[0031] The present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention, and the following modifications are also included in the present invention. For example, in the above-described embodiment of the present invention, the thin-walled portion 3 is formed only on the central side of the strain node A, but the thin-walled portion may be formed only on the fixed end side.

[0032] FIG. 7 is a cross-sectional view and a graph of strain distribution illustrating a modified cover member for an internal combustion engine according to the present invention. In this modified example, a pair of thin-walled portions 3, 3A are formed at positions sandwiching strain node A. Like thin-walled portion 3, thin-walled portion 3A may be formed by recesses on both sides. For other vibration modes, thin-walled portions may also be formed on both sides of the strain node. This configuration increases the strain amount on both sides of strain node A, making it easier to damp vibrations and further improve the silencing effect. Furthermore, both positive and negative strains can be increased on both sides of strain node A, making it easier to ensure a total strain amount compared to a configuration in which either positive or negative strain is generated at two locations.

[0033] In the above-described embodiment of the present invention, the thin-walled portion 3 is formed by forming the recesses 22 and 23 on both sides, but as shown in Fig. 8, the thin-walled portion 3B may be formed by forming the recess 24 on only one side of the plate body 2. In this case, the side on which the recess 24 is formed may be the side facing the sound source, or the opposite side.

[0034] In the above-described embodiment of the present invention, the recesses 22 and 23 have a pair of side surfaces and a bottom surface and a cross-sectional shape surrounded by three straight lines. However, the recesses may have other shapes. For example, as shown in FIG. 9, the thin-walled portion 3C may be formed by forming recesses 25 and 26 having a V-shaped cross-sectional shape (surrounded by two straight lines). As shown in FIG. 10, a tapered portion 223 may be added between the side surface 221 and the bottom surface 222 of the recess 22 in the above-described embodiment (the same applies to the recess 23). As shown in FIG. 11, the thin-walled portion 3D may be formed by forming recesses 27 and 28 by continuously forming a plurality of recessed portions. In the example shown in FIG. 11, each recessed portion has a V-shaped cross-section, similar to the recesses 25 and 26 in FIG. 9.

[0035] Furthermore, the thin-walled portion is not limited to being formed by a localized recess. That is, the thin-walled portion may be formed by forming a portion where the thickness gradually decreases. Furthermore, the thin-walled portion only needs to be formed at a position adjacent to at least the strain node, and may be formed so as to straddle the strain node (that is, the thin-walled portion may also be formed at the strain node).

[0036] In the embodiment of the present invention and the modified examples shown in FIGS. 7 to 11, the positions, numbers, shapes, etc. of the thin-walled portions and recesses are exemplified, but these elements may be combined as appropriate.

[0037] In the above-described embodiment of the present invention, the thin-walled portions are formed adjacent to the nodes of strain caused by the natural vibration of the plate body 2 in the range of 700 to 1300 Hz. However, the thin-walled portions may be formed adjacent to the nodes of strain in an appropriate frequency range depending on the application of the cover member. For example, if the cover member is an engine oil pan, it is preferable that the thin-walled portions be formed adjacent to the nodes of strain caused by the natural vibration in the range of 300 to 1500 Hz. Furthermore, if the cover member is an engine cylinder head cover, it is preferable that the thin-walled portions be formed adjacent to the nodes of strain caused by the natural vibration in the range of 300 to 1500 Hz.

[0038] Although the embodiments of the present invention have been described above, the present invention is not limited to the cover member for an internal combustion engine according to the above embodiments, and includes all aspects encompassed by the concept and scope of the present invention. Furthermore, the various configurations may be appropriately and selectively combined to achieve at least some of the above-described problems and advantages. For example, the shape, material, arrangement, size, etc. of each component in the above embodiments may be appropriately modified depending on the specific use of the present invention. [Explanation of symbols]

[0039] 1...cover member, 2...plate body, 21...fixing portion, 22-28...recess, 3, 3A, 3B, 3D...thin portion, A...strain node

Claims

1. The plate body is formed in a plate shape from resin and has a plurality of fixing portions to be fixed to a fixing object, A cover member for an internal combustion engine, characterized in that a thin-walled portion is formed in the plate body at a position adjacent to a node of strain caused by vibration that displaces along the plate thickness direction with the multiple fixed portions as fixed ends.

2. 2. The cover member for an internal combustion engine according to claim 1, wherein a pair of said thin-walled portions are formed at positions sandwiching said strain node.

3. 3. The cover member for an internal combustion engine according to claim 1, wherein said thin-walled portion is formed by forming recesses on both sides of said plate body.

4. The cover member for an internal combustion engine according to any one of claims 1 to 3, characterized in that the thin-walled portion is formed at a position adjacent to a node of strain caused by a natural vibration of the plate body at 700 to 1300 Hz.

Images