Silencer for internal combustion engines

Abstract

To suppress the generation of abnormal noise at low temperatures and to prevent a silencer from becoming excessively hot. [Solution] The silencer 1 for an internal combustion engine comprises a silencer 3 into which exhaust gas from an internal combustion engine E is introduced via an exhaust passage 2, a cover member 5 with insulating properties arranged to cover the outer peripheral surface of the silencer 3, and a shape memory alloy member 9 attached to the cover member 5, and by utilizing the properties of the shape memory alloy member 9, the cover member 5 covers the outer peripheral surface of the silencer 3 at low temperatures, and the cover member 5 is spaced apart from the outer peripheral surface of the silencer 3 at high temperatures.

Description

[Technical Field]

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

[0002] 2. Description of the Related Art A vehicle equipped with an internal combustion engine is provided with a silencer into which engine exhaust gas is introduced via an exhaust passage. Patent Document 1 discloses an exhaust device for a motorcycle in which a heat insulating material is attached to the outer periphery of a muffler body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-273452 Summary of the Invention [Problem to be solved by the invention]

[0004] When the engine is started or at other cold times, if the hot exhaust gas from the engine is introduced into a cold silencer, the temperature distribution of the exhaust gas will become uneven. This temperature difference will cause a difference in the speed of sound, which in turn will generate shock waves that can cause high-frequency abnormal noise. By providing insulation around the periphery of the muffler, it is possible to prevent uneven temperature distribution of exhaust gases at low temperatures. However, depending on the degree of insulation effect, the muffler may become excessively hot after being warmed up, and the heat may weaken, deform, or damage the structural parts, leading to deterioration of the muffler.

[0005] The present invention has been made in view of the above circumstances, and has as its object to suppress the generation of abnormal noise at low temperatures and to prevent the silencer from becoming excessively hot. [Means for solving the problem]

[0006] The silencer for an internal combustion engine of the present invention comprises a silencer into which exhaust gas from the internal combustion engine is introduced through an exhaust passage, a cover member having an insulating effect arranged to cover the outer peripheral surface of the silencer, and a shape memory alloy member attached to the cover member, and is characterized in that, by utilizing the properties of the shape memory alloy member, the cover member covers the outer peripheral surface of the silencer at low temperatures and is spaced apart from the outer peripheral surface of the silencer at high temperatures. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the generation of abnormal noise at low temperatures and prevent the silencer from becoming excessively hot. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a silencer for an internal combustion engine according to an embodiment; [Figure 2] 1 is a diagram showing a schematic configuration of a silencer for an internal combustion engine according to an embodiment; [Figure 3] 10A and 10B are diagrams illustrating an example of a cover member. DETAILED DESCRIPTION OF THE INVENTION

[0009] A silencer (1) for an internal combustion engine according to one embodiment of the present invention comprises a silencer (3) into which exhaust gas from an internal combustion engine (E) is introduced via an exhaust passage (2), a cover member (5) having a heat insulating effect and arranged to cover the outer peripheral surface of the silencer (3), and a shape memory alloy member (9) attached to the cover member (5). Utilizing the properties of the shape memory alloy member (9), the cover member (5) covers the outer peripheral surface of the silencer (3) at low temperatures, and the cover member (5) is spaced apart from the outer peripheral surface of the silencer (3) at high temperatures. This makes it possible to suppress the generation of abnormal noise at low temperatures and to prevent the silencer (3) from becoming excessively hot. [Example]

[0010] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a diagram showing a schematic configuration of a silencer 1 for an internal combustion engine according to an embodiment, showing the state at high temperature. Fig. 2 is a diagram showing the schematic configuration of a silencer 1 for an internal combustion engine according to an embodiment, showing the state at low temperature. Fig. 3 is a diagram for explaining an example of a cover member 5. As shown in Figures 1 and 2, a vehicle such as an automobile equipped with an engine E, which is an internal combustion engine, is equipped with a silencer 1. The silencer 1 includes a silencer (also called a muffler) 3 into which exhaust gas from the engine E is introduced via an exhaust passage 2. The silencer 3 is cylindrical, and exhaust gas is introduced from the exhaust passage 2 connected to its front end and discharged from a pipe section 4 connected to its rear end. In the following, upstream and downstream are defined based on the flow of exhaust gas indicated by arrow A.

[0011] Here, a pair of cover members 5A, 5B are arranged to cover the outer peripheral surface of the silencer 3, and are each movably connected to the silencer 3. Specifically, the cover member 5A on the upstream side (toward the engine E) and the cover member 5B on the downstream side are arranged to cover the outer peripheral surface of the silencer 3. In this embodiment, the cover members 5A, 5B have the same shape, and hereinafter, when there is no need to distinguish between them for the sake of explanation, they will be referred to as cover members 5. As shown in FIG. 3 , the cover member 5 is a plate material curved to fit the outer peripheral surface of the silencer 3, and a bearing portion 6 is provided at its end 5b. Furthermore, a heat insulating material 7 is provided on the inside of the cover member 5 (the side facing the silencer 3). The heat insulating material 7 also has a plate shape curved to fit the outer peripheral surface of the silencer 3.

[0012] The upstream cover member 5A is attached to the front end of the silencer 3 via a shaft 8 so as to be able to swing freely, with the end 5b where the pivotal support portion 6 is located facing upstream. The downstream cover member 5B is attached to the rear end of the silencer 3 via a shaft 8 so as to be able to swing freely, with the end 5b where the pivotal support portion 6 is located facing downstream.

[0013] The pair of cover members 5A, 5B are connected by a connecting member 9 made of a shape memory alloy. Specifically, the connecting member 9 made of a shape memory alloy connects the mutually facing ends 5a of the pair of cover members 5A, 5B, i.e., the end 5a of the upstream cover member 5A facing the downstream side and the end 5a of the downstream cover member 5B facing the upstream side. Shape memory alloys have the property of being deformed below a predetermined temperature, but recovering to their original shape when the temperature reaches or exceeds the predetermined temperature. The connecting member 9 has a leg 9a on the upstream cover member 5A side and a leg 9b on the downstream cover member 5B side, and can be deformed between a state in which the legs 9a, 9b are open (see FIG. 1) and a state in which the legs 9a, 9b are closed (see FIG. 2). In this embodiment, the connecting member 9 corresponds to the shape memory alloy member defined in the present invention.

[0014] A pair of such cover members 5A, 5B is taken as one set, and a plurality of pairs of cover members 5A, 5B are arranged in the circumferential direction of the silencer 3.

[0015] In the silencer 1 configured as described above, when the temperature is low, such as during engine start-up, as shown in FIG. 2, the connecting member 9 closes, the pair of cover members 5A, 5B come close to the outer peripheral surface of the silencer 3 to cover the outer peripheral surface, and the heat insulating material 7 comes into contact with the outer peripheral surface. For example, a biasing member (not shown) applies a biasing force to each of the cover members 5A, 5B in a direction to bring them close to the outer peripheral surface of the silencer 3, thereby deforming the connecting member 9 into a closed state. In this way, when the silencer 3 is cold, the cover members 5A, 5B, which have a thermal insulating effect, cover the outer peripheral surface of the silencer 3, so that the structural components of the silencer 3 are warmed up quickly, and the occurrence of uneven temperature distribution in the exhaust gas is suppressed. This prevents a difference in sound speed due to a temperature difference, thereby suppressing the occurrence of abnormal noise.

[0016] When the temperature of the connecting member 9 reaches a predetermined level or higher, the property of the shape memory alloy to return to its original shape causes the connecting member 9 to open, and the pair of cover members 5A, 5B move away from the outer peripheral surface of the silencer 3 against the opposing force of a biasing member (not shown), so that the heat insulating material 7 is no longer in contact with the outer peripheral surface. When the silencer 3 is heated in this way, a space is secured between the heat insulating material 7 of the cover members 5A, 5B and the outer peripheral surface of the silencer 3, preventing the silencer 3 from becoming excessively hot. This prevents the structural components from losing strength, deforming, or breaking due to heat, and prevents deterioration of the silencer.

[0017] 2, with the pair of cover members 5A, 5B covering the outer peripheral surface of the silencer 3, the lower parts of the legs 9a, 9b of the connecting member 9 are in contact with the outer peripheral surface of the silencer 3. This makes it easier for heat from the silencer 3 to be transferred to the connecting member 9, enabling more appropriate temperature control of the silencer 3.

[0018] In the examples, the shape memory alloy constituting the connecting member 9 is exemplified as a unidirectional alloy that has the property of recovering to its original shape when the temperature reaches or exceeds a predetermined value, but the present invention is not limited to this. Bidirectional shape memory alloys that assume a low-temperature memory shape at low temperatures and a high-temperature memory shape at high temperatures have been put into practical use, and these may also be used. That is, the connecting member 9 has a bidirectional property of deforming to a closed state (see FIG. 2) at low temperatures and to an open state (see FIG. 1) at high temperatures, even without using a biasing member as in the examples.

[0019] Furthermore, in the embodiment, the cover member 5 is a curved plate material, but this is not limiting. For example, the cover member 5 may be a flat plate material. In this case, the heat insulating material 7 provided inside the cover member 5 is also flat, but for example, the surface of the heat insulating material 7 facing the silencer 3 may be formed with a curved surface that matches the outer peripheral surface of the silencer 3.

[0020] In addition, in the embodiment, the heat insulating material 7 is provided inside the cover member 5, but the present invention is not limited to this. For example, the cover member 5 itself may be made of a material that has a heat insulating effect.

[0021] Furthermore, in the embodiment, a pair of cover members 5A, 5B are arranged in the longitudinal direction (front-rear direction) of the silencer 3, and only one connecting member 9 is arranged in the center of the silencer 3 in the longitudinal direction, but the present invention is not limited to this. In this case, the amount of displacement when the cover member 5 swings becomes large, so in order to avoid this, multiple pairs of cover members 5A, 5B may be arranged in the longitudinal direction (front-rear direction) of the silencer 3. This reduces the amount of change when the cover member 5 swings, making it possible to avoid interference with the road surface or other components, for example.

[0022] Although the embodiments of the present invention have been described in detail above with reference to the drawings, each embodiment merely shows a specific example of how the present invention can be implemented. The technical scope of the present invention is not limited to each embodiment. Various modifications of the present invention are possible within the scope of the gist of the present invention, and these modifications are also included within the technical scope of the present invention. In the embodiment, a configuration including a pair of cover members 5A and 5B has been described, but the present invention is not limited to this. It is also possible to provide cover members that do not form a pair, and utilize the properties of the shape memory alloy member provided in the cover members so that the cover members cover the outer peripheral surface of the silencer at low temperatures and are separated from the outer peripheral surface of the silencer at high temperatures. [Explanation of symbols]

[0023] 1: silencer, 2: exhaust passage, 3: silencer, 4: pipe section, 5 (5A, 5B): cover member, 5a, 5b: end portion, 6: shaft support section, 7: heat insulating material, 8: shaft, 9: connecting member, 9a, 9b: legs

Claims

1. a muffler into which exhaust gas from the internal combustion engine is introduced via an exhaust passage; a cover member having a heat insulating effect, which is arranged so as to cover an outer peripheral surface of the silencer; a shape memory alloy member provided on the cover member, A silencer for an internal combustion engine, characterized in that, by utilizing the characteristics of the shape memory alloy member, the cover member covers the outer surface of the silencer at low temperatures, and the cover member is separated from the outer surface of the silencer at high temperatures.

2. a muffler into which exhaust gas from the internal combustion engine is introduced via an exhaust passage; At least a pair of cover members arranged to cover the outer peripheral surface of the silencer, each of which is movably connected to the silencer and has a heat insulating effect; a shape memory alloy member connecting the pair of cover members, A silencer for an internal combustion engine, characterized in that, by utilizing the characteristics of the shape memory alloy member, the pair of cover members cover the outer surface of the silencer at low temperatures, and the pair of cover members are separated from the outer surface of the silencer at high temperatures.

3. 3. A silencer for an internal combustion engine according to claim 1, wherein the shape memory alloy member contacts the outer peripheral surface of the silencer at low temperatures.

4. 3. A silencer for an internal combustion engine according to claim 1, wherein a heat insulating material is provided inside the cover member.

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