JP2010174727A - Muffler for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffler for a vehicle, improving sound deadening performances while inhibiting a degradation of travelling performance. <P>SOLUTION: This muffler has a structure which is provided with: an outer tube 28; an inner tube 38; and a sound absorbing material 35 with which the inside of a filling space 34 formed between the outer tube 28 and the inner tube 38, is filled, has: a large diameter part 26 at an exhaust direction upstream side of the inner tube 38; and a small diameter part 29 at an exhaust direction downstream side, and also has punching holes 37 formed on the small diameter part 29, but no punching hole at the large diameter part 26. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle muffler that purifies and silences exhaust gas discharged from a vehicle engine.

  Conventionally, a vehicle muffler (exhaust muffler) used in a motorcycle or the like has an output performance that efficiently discharges exhaust gas exhausted from an engine, and an exhaust sound caused by exhaust of exhaust gas that has been increased in pressure and temperature. It is required to satisfy the two performances of silencing performance.

  Moreover, in recent years when noise regulations have been strengthened, there has been an increasing demand for improvement in noise reduction performance, and in particular, regulations for noise regulations have been strengthened in competition motocrossers (off-road bikes) as well as ordinary cars. Yes.

  At this time, it is desired to improve the silencing performance while maintaining the output performance. However, considering only the output performance, it is most preferable that the exhaust muffler is arranged in a straight line.

  However, if the exhaust muffler extends in a straight line, the exhaust muffler cannot be accommodated in the motorcycle body. Therefore, in order to reduce exhaust resistance, the exhaust muffler can only extend toward the rear of the vehicle body so as not to bend as rapidly as possible.

  In practice, it is often difficult to extend the exhaust muffler toward the rear of the vehicle without suddenly bending the exhaust muffler in relation to the front wheels or the bank angle.

  Normally, the muffler with the ideal length for engine performance does not fit in the shape of the motorcycle as it is, and the muffler with the length close to the best in the performance is kept in the shape of the motorcycle while maintaining the smooth shape as much as possible. This design is very difficult compared to the muffler design of a passenger car.

  Especially for racing motocrossers, the exhaust muffler needs to be placed high so as to avoid obstacles protruding from the ground, so it is very important to ensure output performance and noise reduction performance. It is difficult to.

  Therefore, a silencer for a vehicle muffler is composed of an outer cylinder and an inner cylinder made of stainless steel, and glass wool, stainless wool (SUS wool), aluminum, which is a material capable of absorbing sound waves between the outer cylinder and the inner cylinder. There is known a vehicle muffler that is configured so as to closely contact a sound-absorbing material made of wool, ferrite, or the like and particularly efficiently absorb high-frequency sound (exhaust sound in a high frequency range) (for example, Patent Document 1). reference).

  In the vehicle muffler disclosed in Patent Document 1, a number of punching holes communicating the inside and the outside are formed on the peripheral surface of the inner cylinder, and a punching cone is disposed inside the inner cylinder.

  In addition, this punching cone has a cone shape made of stainless steel, for example, and a punching hole is formed in the region of the side surface of the cone shape, mainly to ensure a sound reduction effect for high-frequency sound (for example, cylinder skipping sound). Yes.

JP 2007-292049 A

  However, in the case of the muffler for a vehicle configured as described above, for example, when a muffler structure in which a sound absorbing material is filled between the outer cylinder and the inner cylinder made of punching metal is adopted, the noise reduction performance is improved. In order to achieve this, it is common to reduce the diameter of the inlet tube, inner cylinder, and outlet tube.

  However, if the diameter of the inlet pipe, inner cylinder, and outlet pipe is reduced in order to improve the silencing effect, driving characteristics such as throttle response will be greatly reduced, maintaining (or improving) the output performance and improving the silencing performance. There is a problem that it is difficult to achieve both.

  In addition, the exhaust gas that flows into the outside of the punching cone may have inertia acting on the molecules contained in the exhaust gas, and its main flow flows directly downstream of the silencer without passing through the punching hole. In fact, the reality is that the sound reduction effect of high-frequency sound is not as secure as expected.

  In view of the above circumstances, an object of the present invention is to provide a muffler for a vehicle that can improve the silencing performance while suppressing a decrease in running performance.

  A muffler for a vehicle according to the present invention is a muffler for a vehicle comprising an outer cylinder, an inner cylinder, and a sound absorbing material filled in a filling space formed between the outer cylinder and the inner cylinder. The upstream side of the inner cylinder in the exhaust direction is a large diameter portion, the downstream side in the exhaust direction is a small diameter portion, a punching hole is formed in the small diameter portion, and the punching hole is not formed in the large diameter portion. A vehicle muffler.

  According to the vehicle muffler of the present invention, by setting the upstream side in the exhaust direction of the inner cylinder as the large diameter portion, it is possible to improve the noise reduction performance while suppressing a decrease in running performance.

  The vehicle muffler according to claim 2, wherein an inner diameter of the large-diameter portion is substantially equal to an inner diameter of an exhaust pipe communicating with an exhaust port.

  According to the muffler for a vehicle according to claim 2, by making the large-diameter portion of the inner cylinder substantially equal to the inner diameter of the exhaust pipe, there is no generation of a path restriction with a narrow cross-sectional area in the exhaust path. The exhaust gas can be guided toward the small diameter portion of the inner cylinder, and output characteristics with good responsiveness to the throttle operation can be maintained.

  The vehicle muffler according to claim 3, wherein a length along the axial direction of the small diameter portion is longer than a length along the axial direction of the large diameter portion. .

  According to the muffler for a vehicle according to the third aspect, the communication section for communicating the inner space of the inner cylinder and the filling space can be set long, and the sound deadening performance by the sound absorbing material can be improved.

  The vehicle muffler according to claim 4, wherein the upstream portion of the small diameter end portion located upstream of the small diameter portion in the exhaust direction is upstream of the downstream large diameter end portion downstream of the large diameter portion in the exhaust direction. The extension part which extended in the side and overlapped with the said downstream large diameter end part along an axial direction was formed, The punching hole was formed in the said extension part, The Claim 3 characterized by the above-mentioned. Muffler for vehicles.

  According to the muffler for a vehicle according to claim 4, after the exhaust gas is once branched at the upstream end of the small diameter portion, exhaust interference can be generated by merging the branched exhaust gases with each other. Can be improved.

  The muffler for a vehicle according to claim 5, wherein the downstream large-diameter end is joined to the outer peripheral surface of the small-diameter upstream portion downstream of the extending portion in the exhaust direction, and the extending portion and the large portion The vehicle muffler according to claim 4, wherein a closed space for closing the downstream large-diameter end portion in the exhaust direction is formed between the diameter portion and the diameter portion.

  According to the muffler for a vehicle according to claim 5, all of the branched exhaust gas passes through the punching hole of the extension part by forming a closed space between the extension part and the large diameter part. Thus, the exhaust interference effect can be improved.

  6. The vehicle muffler according to claim 6, wherein the small-diameter portion is formed with a non-hole portion in which the punching hole is not formed at a joint portion with the downstream large-diameter end portion. The vehicle muffler described in 1.

  According to the muffler for a vehicle according to claim 6, the non-hole portion that makes the inner space of the inner cylinder located at the joint portion between the downstream-side large-diameter end portion and the small-diameter portion and the filling space a state of being in a sympathetic communication state. The exhaust gas branched from the non-hole portion upstream in the exhaust direction can be merged at the non-hole portion, and the merged section can be set longer along the axial direction. The interference effect can be reliably ensured.

  The muffler for a vehicle according to the present invention has a smaller diameter than the muffler inlet pipe, and the front end of the inner cylinder faces the inside of the muffler inlet pipe so as to be positioned forward of the rear end of the muffler inlet pipe. In addition, the silencing performance can be improved while suppressing a decrease in running performance.

1 is a side view of a motorcycle (a racing motocrosser) that employs a vehicle muffler according to an embodiment of the present invention. It is sectional drawing of the principal part of the muffler for vehicles which concerns on one Embodiment of this invention. It is an expanded sectional view of the important section of the muffler for vehicles concerning one embodiment of the present invention.

  Next, an embodiment of a vehicle muffler according to the present invention will be described with reference to the drawings. The following embodiments are preferred specific examples of the vehicle muffler of the present invention, and may have various technically preferred limitations. However, the technical scope of the present invention is particularly limited to the present invention. As long as there is no description which limits, it is not limited to these aspects. Further, before and after in the following description, the vehicle traveling direction will be used as a reference, and upstream and downstream will be described based on the exhaust direction.

  As shown in FIG. 1, a motorcycle 11 according to the present invention includes an engine 13 mounted at the lower center of a body frame 12, a fuel tank 14 disposed above the body frame 12, and a front portion of the body frame 12. The head pipe 15 connected to the head pipe 15, the handle 16 provided on the head pipe 15, the front fork 18 provided on the head pipe 15 for rotatably supporting the front wheel 17, and swinging to the lower center of the body frame 12 A swing arm 20 that is disposed so as to rotatably support the rear wheel 19, a seat 21 that is supported by a seat rail (not shown) that extends to the rear portion of the vehicle body frame 12, and a rear end of the seat 21 A rear fender 22 extending so as to cover the rear wheel 19 and a cylinder head 23 of the engine 13 and extending downward from the rear fender 22. It was the vehicle muffler 24, and a.

  The motorcycle 11 according to the present embodiment employs well-known components for the vehicle body components 12 to 23 excluding the vehicle muffler 24. Therefore, in the following description, the motorcycle 11 will be described specifically for the vehicle muffler 24. To do.

  The vehicle muffler 24 is connected to the cylinder head 23 of the engine 13 and communicates with an exhaust port (not shown), and the exhaust pipe 25 exhaust direction (see arrow A in FIG. 2, the same applies hereinafter) downstream. An outer cylinder 28 connected to the exhaust pipe 25 via an outer cylinder connection bracket 27 upstream of the downstream exhaust pipe end 26, a punching pipe 29 connected to the downstream exhaust pipe end 26, and punching Provided on the outer periphery of the punching pipe 29, the tail connection pipe 30 disposed downstream of the pipe 29, the tail cover 32 connected to the downstream tail pipe end 30 a of the tail connection pipe 30 via the cover connection bracket 31, and the punching pipe 29. And a sound absorbing material 35 such as glass wool filled in a filling space 34 formed inside the outer cylinder 28.

  The downstream exhaust pipe end portion 26 of the exhaust pipe 25 functions as a large diameter portion by facing the upstream side of the outer cylinder 28 in a state of being integrally formed with the exhaust pipe 25 (in the following description, The “downstream exhaust pipe end portion 26” is referred to as a “large diameter portion 26”). At this time, the large-diameter portion 26 faces the inside of the outer cylinder 28 with the same diameter as the exhaust pipe 25 positioned on the upstream side (outside) of the outer cylinder 28. A connecting flange 26b is formed integrally with the downstream large-diameter end portion 26a of the large-diameter portion 26.

  The outer cylinder connection bracket 27 has a substantially bottomed cylindrical shape with a one-side cross-sectional crank shape, and its inner peripheral side is welded and fixed to the outer periphery of the exhaust pipe 25 and is separated from the outer periphery of the exhaust pipe 25. An upstream side outer cylinder end portion 28 a of the outer cylinder 28 is fixed via a rivet 36 on the outer peripheral side. Thereby, the outer cylinder connection bracket 27 closes the upstream outer cylinder end portion 28 a of the outer cylinder 28.

  The outer cylinder 28 forms a so-called silencer outer shape with the tail cover 32 connected to the downstream outer cylinder end portion 28b. The outer cylinder 28 is integrally formed with an expanded portion 28c that is coaxially expanded from the upstream outer cylinder end portion 28a.

  The punching pipe 29 is composed of a metal porous cylindrical body in which a large number of punching holes 37 communicating with the inside and the outside are formed. The punching pipe 29 functions as a small-diameter portion by making the diameter smaller than that of the large-diameter portion 26 (hereinafter, “punching pipe 29” is referred to as “small-diameter portion 29”). Therefore, the large-diameter portion 26 composed of the exhaust pipe end portion 26 on the downstream side of the exhaust pipe 25 and the small-diameter portion 29 composed of the punching pipe 29 are arranged coaxially in a state of being separated from the inner periphery of the outer cylinder 28. A cylinder 38 is formed, and a space between the outer cylinder 28 and the inner cylinder 38 is a filling space 34. Furthermore, the length L1 along the axial direction of the small diameter portion 29 is set to be longer than the length L2 along the axial direction of the large diameter portion 26. Further, the small diameter end upstream portion 29a of the small diameter portion 29 extends to the upstream side in the exhaust direction from the downstream large diameter end portion 26a of the large diameter portion 26 to form an extension portion 29b. Thereby, the extension part 29b and the downstream large-diameter end part 26a are overlapped along the axial direction. Similarly to the small-diameter portion 29, a punching hole 37 is formed in the extending portion 29b over a good circumference. Further, a connection flange 26b formed on the downstream large-diameter end portion 26a is welded to the outer peripheral surface of the small-diameter end upstream portion 29a of the small-diameter portion 29. Therefore, a closed space 39 is formed between the downstream large-diameter end portion 26a and the extending portion 29b so as to be separated by a difference in diameter. Further, a non-hole portion 29c in which no punching hole 37 is formed is formed in the vicinity of the joint portion between the small diameter end upstream portion 29a and the connection flange 26b. The non-hole portion 29c may be formed by forming the punching hole 37 over the entire area of the small diameter portion 29 including the extending portion 29b and closing the punching hole 37 with the connection flange 26b. In addition, the extension part 29b is so good that it extends toward the upstream of the large diameter part 26. FIG. At this time, it is preferable that the expanding portion 28c has been expanded at least upstream of the connection flange 26b in order to ensure a sound deadening region in the thickness direction of the filling space 34, from the tip of the extending portion 29b. It is desirable that the expansion has been completed on the upstream side.

  The tail connection pipe 30 is fixed to the downstream small-diameter end portion 29d with the upstream tail pipe end portion 30b facing the downstream small-diameter end portion 29d of the small-diameter portion 29. Further, the downstream tail pipe end 30a of the tail connection pipe 30 has a larger diameter than the upstream tail pipe end 30b.

  The cover connection bracket 31 has a substantially bottomed cylindrical shape with a U-shaped cross section on one side, and its inner peripheral side is welded and fixed to the outer periphery of the tail connection pipe 30 so as to be separated from the outer periphery of the tail connection pipe 30. Further, on the outer peripheral side, the downstream outer cylinder end portion 28 b of the outer cylinder 28 and the tail cover 32 are fixed via a rivet 40. Further, the cover connection bracket 31 has a plurality of holes formed at intervals in the circumferential direction.

  The tail cover 32 includes an outer cylinder 41 whose upstream side is fixed to the cover connection bracket 31 and an inner cylinder 42 whose upstream side is connected to the tail connection pipe 30, and the downstream side and inner cylinder of the outer cylinder 41. The space 43 is formed in cooperation with the cover connection bracket 31 by joining the downstream side of the body 42. Since the space portion 43 communicates with the filling space 34 by the hole formed in the cover connection bracket 31, the sound absorbing effect is further improved by filling the space portion 43 with the sound absorbing material 35.

  In the present embodiment, the cylindrical sound absorber 33 includes a wire mesh 44 formed of a three-layered cylindrical body that is separated from the inside and the outside, and a stainless wool 45 provided between the wire meshes 44. . The cylindrical sound absorber 33 is fixed by welding its inner periphery to the outer periphery of the connection flange 26b. Therefore, the inner periphery of the cylindrical sound absorber 33 and the outer periphery of the small diameter portion 29 are separated (cavity) by the thickness of the connection flange 26b.

  In the above configuration, the exhaust gas that has flowed into the large-diameter portion 26 branches to the inside and the outside of the extending portion 29b of the small-diameter portion 29, and the main flow of the exhaust gas that has flowed directly into the inside and branched to the outside. The exhaust gas that flows inward (mainly) later through the punching hole 37 can be merged, and the exhaust gas interference can be caused by the merge of these exhaust gases, so that the silencing performance can be greatly improved.

  In particular, by forming the closed space 39 at the downstream end of the large diameter portion 26, the exhaust gas branched to the outside of the extending portion 29b can be surely passed through the punching hole 37. The silencing performance due to the exhaust interference can be further improved.

  Moreover, since the large diameter part 26 is formed in the upstream part of the inner cylinder 38, the sound deadening performance can be enhanced while the middle and low torques are greatly improved.

  Further, since the non-hole portion 29c not formed with the punching hole 37 is formed in the vicinity of the connection portion between the small diameter end portion upstream portion 29a and the connection flange 26b, exhaust interference can be reliably generated in this formation region. As a result, it is possible to ensure an improvement in the sound deadening performance.

  On the contrary, when the punching hole 37 is formed in the formation region of the non-hole portion 29c, the exhaust gas is branched again before the exhaust gas is sufficiently merged, so that the silencing performance is reduced.

  In addition, since the sound absorbing material 35 is also filled around the large diameter portion 26, the capacity of the sound absorbing material 35 can be sufficiently secured, and further improvement in the sound deadening performance can be ensured.

  The shape of the inner cylinder 38 is not limited to a cylinder, but at least one end side of the inner cylinder 38 is a frustoconical type, or by multiplexing the downstream end of the inner cylinder 38, the inner cylinder 38 is formed from the outer periphery of the upstream end. It is possible to increase the flow rate of exhaust gas that interferes with exhaust in the inner circumferential direction, and it is possible to attenuate the energy of the exhaust gas while suppressing an increase in exhaust pressure, and to further reduce the silencing performance while suppressing a decrease in running performance Can be improved.

24 ... Vehicle muffler 25 ... Exhaust pipe 26 ... Downstream exhaust pipe end (large diameter part)
26a ... downstream large diameter end portion 26b ... connection flange 28 ... outer cylinder 28a ... upstream side outer cylinder end portion 28b ... downstream side outer cylinder end portion 28c ... widening portion 29 ... punching pipe (small diameter portion)
29a ... Small diameter end portion upstream side portion 29b ... Extension portion 29c ... Non-hole portion 34 ... Filling space 35 ... Sound absorbing material 37 ... Punching hole 38 ... Inner cylinder 39 ... Closure space

Claims (6)

  A muffler for a vehicle comprising an outer cylinder, an inner cylinder, and a sound absorbing material filled in a filling space formed between the outer cylinder and the inner cylinder, upstream of the inner cylinder in the exhaust direction A vehicle muffler characterized in that the side is a large diameter portion, the downstream side in the exhaust direction is a small diameter portion, a punching hole is formed in the small diameter portion, and the punching hole is not formed in the large diameter portion.   The muffler for a vehicle according to claim 1, wherein an inner diameter of the large diameter portion is substantially equal to an inner diameter of an exhaust pipe communicating with an exhaust port.   The vehicle muffler according to claim 2, wherein a length along the axial direction of the small diameter portion is longer than a length along the axial direction of the large diameter portion.   An upstream portion of a small-diameter end portion located upstream of the small-diameter portion in the exhaust direction extends from the downstream large-diameter end portion of the large-diameter portion on the downstream side in the exhaust direction so as to extend upstream in the exhaust direction. The vehicle muffler according to claim 3, wherein an extending portion that overlaps the end portion along the axial direction is formed, and a punching hole is formed in the extending portion.   The downstream large-diameter end is joined to the outer peripheral surface of the small-diameter upstream portion downstream of the extending portion in the exhaust direction, and the downstream large-diameter portion is interposed between the extending portion and the large-diameter portion. The vehicle muffler according to claim 4, wherein a closed space for closing the end portion in the exhaust direction is formed.   The muffler for a vehicle according to claim 5, wherein the small diameter portion is formed with a non-hole portion in which the punching hole is not formed at a joint portion with the downstream large diameter end portion.

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