JP2002242652A - Exhaust muffler for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To open/close a valve element at an exhaust pipe opening inside a casing such that both of quietness at low engine speed and exhaust loss at high engine speed are reduced. SOLUTION: The valve element 4 is pivotally supported via a shaft 5 to a valve seat 2 of the exhaust pipe 1, and a tapered diameter enlarging part 3 provided to the valve seat 2 is sealed with a tapered seat surface 6 of the valve element 4. The pivotal support shaft 5 of the valve element 4 is positioned outside the exhaust pipe 1 and more upstream side in an A direction of an exhaust flow than the valve element 4. A lower edge of the seat surface 6 at starting of opening of the valve element 4 shows a locus designated by β, and the lower edge of the seat surface is displaced to an inside (right side) in a direction perpendicular to an axis of the exhaust pipe 1 which approaches the turning pivotal support shaft at opening turning of the valve element 4. Accordingly, an enlarging change rate of a gap between the diameter enlarging part 3 and the seat surface 6 at open turning of the valve element 4 is increased, whereby a state in which a force in a valve closing direction acts on the valve element 4 is not held in a long time due to a negative pressure generated by an exhaust flow passing the gap. Accordingly, the valve element 4 largely opens at a stretch if once the valve element starts opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle exhaust silencer for reducing noise generated from an exhaust system of a vehicle engine.

[0002]

2. Description of the Related Art Conventionally, as a vehicle exhaust silencer, as described in, for example, International Publication WO95 / 13460, an opening of an exhaust pipe in a housing of the exhaust silencer is opened and closed to open and close the exhaust pipe. A valve element rotatably provided in a direction approaching and moving away from the part is pivotally provided, and the valve element is rotationally biased in a direction approaching the opening of the exhaust pipe to close the opening. Things are known.

This exhaust silencer opens and closes an opening of an exhaust pipe by rotating the valve body in accordance with the exhaust pressure of the engine, so that a plurality of exhaust gas filters provided in a housing of the exhaust silencer are provided. The purpose of the present invention is to reduce the exhaust noise when the engine is running at a low engine speed with a low exhaust flow rate, and to reduce the exhaust noise and the exhaust loss when the engine is running at a high engine speed with a large exhaust flow rate.

[0004] By the way, when the above-mentioned valve element is pivotally supported on the opening of the exhaust pipe, the gas sealing property at the time of closing the valve element has been conventionally known as described in the above-mentioned literature and Japanese Patent Application Laid-Open No. 11-324638. It has been proposed to do this as shown in FIG.

That is, the valve seat 32 provided at the opening of the exhaust pipe 31 is provided with an enlarged diameter portion 33 having a tapered shape larger than the inner diameter of the exhaust pipe 31. A valve body 35 is rotatably supported and provided on the valve seat 32 via a rotation pivot shaft 34. The valve body 35 rotates in a direction approaching and away from the enlarged-diameter portion 33. Open and close this. The valve body 35 is
A return spring (not shown) urges the rotation toward the enlarged diameter portion 33 and normally closes the enlarged diameter portion 33 against the exhaust flow. The valve body 35 further has a seat surface 36 having a shape corresponding to the enlarged diameter portion 33, and the seat surface 36 contacts and closes the enlarged diameter portion 33.

[0006]

However, in the conventional exhaust silencer, the pivot shaft 34 of the valve body 35 is connected to the exhaust pipe 3.
Since it was installed downstream of the large diameter portion 33 in the exhaust flow direction, it was confirmed that the following problems would occur.

That is, when the exhaust flow rate is relatively low and the engine speed is relatively low, the valve body 35 is open as shown in FIG. 8, and the gap formed between the enlarged diameter portion 33 and the seat surface 36 is small. narrow. Accordingly, the flow velocity V when the exhaust flow A flows through the narrow gap becomes very fast, and a fluid force (negative pressure) is generated in this gap, and a force B in the valve closing direction acts on the valve body 35. For this reason, the exhaust gas flow rate subsequently increases, and the valve element 35 is difficult to open even if the valve element 35 receives a force in the valve opening direction with the dynamic pressure.

On the other hand, due to the above-described arrangement of the rotation pivot shaft 34, when the valve body 35 starts to open, the lower edge of the seat surface 36 draws a locus indicated by α in FIG. The exhaust pipe 3 moves the lower edge of the seat surface away from the rotation pivot shaft 34 with the movement.
1 while being displaced outward in the direction perpendicular to the axis. For this reason, when the valve body 35 is opened and rotated, the enlarged diameter portion 33 and the seat surface 3
6, the rate of change in the expansion of the gap is small, and the state in which the force B in the valve closing direction acts on the valve body 35 with the negative pressure described above continues for a long time. As a result, even if the exhaust flow rate increases due to an increase in the engine speed, the valve body 35 does not easily open, or the opening degree is not sufficient even when the engine speed is increased. And the exhaust flow noise increases.

In order to solve this problem, the valve closing force of the return spring acting on the valve body 35 is weakened so that the valve body 35 opens earlier when the exhaust flow rate increases due to an increase in the engine speed. Thus, it is conceivable to solve the problem that the exhaust loss increases and the exhaust flow noise increases under a high engine speed.

However, if the return spring force of the valve body 35 is weakened, the valve body 35 opens with a slight increase in rotation at low engine speed, and the valve body 35 opens as expected at a low engine speed. The noise reduction effect cannot be achieved, and silence at low engine speed cannot be ensured. Therefore, when adjusting the return spring force of the valve body 35, if this is strengthened to ensure quietness at low engine speed, exhaust loss and exhaust flow noise increase under high engine speed. Conversely, if the return spring force of the valve body 35 is weakened to improve exhaust loss and exhaust flow noise at high engine speeds, it becomes impossible to ensure quietness at low engine speeds. I had to sacrifice either one.

According to the first aspect of the present invention, the valve body is closed with a strong closing force during a low engine rotation with a small exhaust flow rate, but the engine speed increases (the exhaust flow rate increases).
If the valve element opens at a stretch from a state where the valve element is slightly opened to secure a sufficient valve element opening, it is possible to improve exhaust loss at high engine rotation, improve exhaust noise, and reduce engine rotation. An object of the present invention is to propose a vehicle exhaust silencer that realizes the above-described problem by realizing this idea based on the fact that silence at the same time can be achieved.

According to a second aspect of the present invention, it is possible to simply and inexpensively mold the enlarged diameter portion and the seat surface of the valve element to be provided at the opening of the exhaust pipe in order to realize the operation and effect of the first aspect. It is an object of the present invention to propose a vehicle exhaust silencer as described above.

A third aspect of the present invention is to propose an exhaust muffler for a vehicle having a shape of a diameter-enlarged portion and a valve body seat surface in which the function and effect of the first invention are further remarkable. And

According to a fourth aspect of the present invention, there is provided an exhaust muffler for a vehicle in which the enlarged diameter portion and the valve body seat surface are easily formed and the opening of the valve body can be easily adjusted. With the goal.

According to a fifth aspect of the present invention, the degree of freedom in selecting the pivotal position of the valve body for achieving the operation and effect of the first invention can be increased, and the workability of mounting the valve body is improved. It is an object of the present invention to propose an exhaust muffler for a vehicle which is made to be exhausted.

[0016]

To achieve these objects, a vehicle exhaust silencer according to a first aspect of the present invention has a valve body at an opening of an exhaust pipe in a housing of the exhaust silencer, and a valve body close to the opening. In a vehicle exhaust silencer in which the opening is closed by closing the opening by biasing the valve body in the direction approaching the opening of the exhaust pipe, the valve body being rotatably supported in a direction in which the opening and the direction away from the opening are provided. At the opening of the exhaust pipe, a large-diameter portion larger than the inner diameter of the exhaust pipe is provided, and a seat surface corresponding to the shape of the large-diameter portion is provided on the valve body, and the pivot shaft of the valve body is closed. It is characterized by being arranged on the upstream side in the exhaust flow direction from the position of the valve body in the state.

According to a second aspect of the present invention, there is provided a vehicle exhaust silencer according to the first aspect, wherein the enlarged portion has a tapered surface, and the seat surface has a tapered surface shape corresponding to the enlarged portion. Is what you do.

According to a third aspect of the present invention, in the vehicle exhaust silencer according to the first aspect, the enlarged diameter portion is formed as a convex spherical surface, and the seat surface is formed as a concave spherical shape corresponding to the enlarged diameter portion. Is what you do.

According to a fourth aspect of the present invention, there is provided a vehicle exhaust silencer according to any one of the first to third aspects, wherein the enlarged diameter portion and the seat surface are located within a plane perpendicular to the axis of the exhaust pipe. It is a feature.

According to a fifth aspect of the present invention, there is provided a vehicle exhaust silencer according to any one of the first to fourth aspects, wherein a pivot shaft of the valve body is located outside the exhaust pipe. Things.

[0021]

According to the first aspect of the present invention, there is provided a vehicle exhaust silencer,
When the engine speed increases and the exhaust flow rate increases, the flow velocity causes the valve body pivotally supported at the opening of the exhaust pipe to open and rotate against the above-mentioned rotational urging force, and when the engine speed is low and the engine speed is high. A plurality of exhaust passages provided in the housing of the exhaust silencer are switched between when the engine is running, so that the exhaust noise is reduced when the engine is running at a low engine speed where the exhaust flow is small, and the exhaust noise is reduced when the engine is running at a high engine flow where the exhaust flow is large. It can aim at loss reduction.

By the way, in the first invention, in particular, an enlarged portion larger than the inner diameter of the exhaust pipe is provided at the opening of the exhaust pipe, and a seat surface corresponding to the shape of the enlarged portion is provided on the valve body.
Since the pivoting shaft of the valve body is arranged on the upstream side in the exhaust flow direction from the position of the valve body in the closed state, the valve body moves the seat surface closer to the pivoting shaft of the valve body as the valve body rotates. The exhaust pipe is rotated while being displaced in a direction perpendicular to the axis of the exhaust pipe, and the rate of expansion change of the gap between the enlarged diameter portion and the valve seat surface when the valve is opened is large. As a result, immediately after the valve element starts to open and rotate, the exhaust flow velocity in the gap between the enlarged diameter portion and the valve element sheet surface decreases, and the negative pressure is eliminated, thereby reducing the valve closing force of the valve element. It disappears and the valve can be opened at a stretch.

Therefore, according to the first aspect of the invention, the valve body with a strong valve closing force is closed during low engine rotation when the exhaust flow rate is small, but the valve body is closed with an increase in the engine speed (increased exhaust flow rate). From a slightly open state, the valve body opens at a stretch and a sufficient valve body opening can be secured, and the biasing force of the valve body closing direction rotation is set large to achieve quietness at low engine rotation Even so, it is possible to improve exhaust loss and exhaust flow noise at high engine speed, and to achieve both quietness at low engine speed and improvement of exhaust loss and exhaust flow noise at high engine speed. Can be.

In the second invention, the enlarged diameter portion is formed by a tapered surface, and the valve element seat surface is formed to have a tapered surface shape corresponding to the enlarged diameter portion. It is possible to simply and inexpensively mold the enlarged diameter portion to be provided at the opening of the pipe and the seat surface of the valve body.

In the third aspect of the present invention, the enlarged diameter portion is formed as a convex spherical surface, and the valve element seat surface is formed as a concave spherical shape corresponding to the enlarged diameter portion. In addition to the large change rate of the gap between the valve body seat surface and the valve body seat surface as in the first invention, when the valve body opening is small, exhaust gas is exhausted through the narrow gap between the enlarged diameter portion and the valve body seat surface. Since the fluid flows along the spherical shape, an increase in pressure loss due to separation can be suppressed, and the operation and effect of the first invention can be made more remarkable.

In the fourth aspect of the present invention, the enlarged diameter portion and the valve element seat surface are located in the plane perpendicular to the axis of the exhaust pipe, so that the enlarged diameter portion and the valve element seat surface can be easily formed.
Advantageously in terms of cost, and by changing the length of the gap between the enlarged diameter portion and the valve body seat surface, the magnitude of the valve closing force due to the negative pressure caused by the exhaust flow passing therethrough is adjusted. This makes it possible to adjust the manner in which the valve element is opened without increasing the urging force acting on the valve element in the valve closing direction.

In the fifth invention, since the pivot shaft of the valve body is located outside the exhaust pipe, selection of the pivot position of the valve body for achieving the operation and effect of the first invention is achieved. And the workability of mounting the valve body can be improved.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a main part of an exhaust silencer for a vehicle according to an embodiment of the present invention. A valve seat 2 is provided at an opening of an exhaust pipe 1 in a casing (not shown) of the exhaust silencer. 2, a tapered enlarged portion 3 larger than the inner diameter of the exhaust pipe 1 is set. The valve seat 2 is further provided with a valve body 4 opposite to the valve body 4 so as to open and close the valve body 2 at the enlarged diameter portion 3. It is pivotally supported on the valve seat 2 via the pivot shaft 5.

The valve element 4 has a tapered seat surface 6 corresponding to the shape of the enlarged diameter portion 3, and the seat surface 6 contacts the enlarged diameter portion 3 so that the enlarged diameter portion 3 can be closed. The valve body 4 is rotationally urged by a well-known return spring (not shown) in a direction approaching the enlarged diameter portion 3 of the valve seat 2, whereby the enlarged diameter portion 3 is normally closed by the valve body 4 as shown in the figure. Shall be kept.

Here, the above-described urging force of the valve body 4 in the valve closing direction due to the return spring force is such that the valve body 4 is opened even by the dynamic pressure from the exhaust flow A in a predetermined low engine rotation region where the exhaust flow rate is small. The valve body 4 has a force not to be moved, and in the other relatively high engine rotation range where the exhaust flow rate is large, the valve element 4 is opened and rotated against the return spring force by the dynamic pressure from the exhaust flow A. Shall be. Further, in the present embodiment, the rotary pivot shaft 5 that rotatably supports the valve element 4 on the valve seat 2 of the exhaust pipe 1 is further moved in the exhaust flow (A) direction than the position of the valve element 4 in the closed state. It is located upstream and outside the exhaust pipe 1.

The operation of the exhaust silencer according to the above embodiment will now be described. Under a low engine speed where the exhaust flow rate is small, the dynamic pressure of the exhaust flow cannot open the valve body 4 against the valve closing force of the return spring. And the required quietness in the low engine speed range can be ensured as predetermined. Note that the return spring force of the valve element 4 is determined to be a spring force that ensures that the valve element 4 maintains the closed position in a low engine rotation range where the valve element 4 needs to be closed for the quietness.

When the exhaust flow rate increases as the engine speed increases, the dynamic pressure of the exhaust flow starts to open the valve body 4 against the closing force of the return spring as shown in FIG. However, at this time, the gap between the enlarged diameter portion 3 and the valve body seat surface 6 is still narrow, and the flow velocity V when the exhaust flow A flows through the narrow gap is still small.
Is very fast, a fluid force (negative pressure) is generated in this gap, and a force B in the valve closing direction acts on the valve body 4. For this reason, the valve element 4 is in a situation where it is difficult to increase the opening degree at the beginning of opening,
Keep this state for a while.

By the way, due to the above-mentioned arrangement of the pivot shaft 5, when the valve body 4 starts to open, the lower edge of the seat surface 6 draws a locus indicated by β in FIG. With the movement, the seat surface turns while displacing the lower edge of the sheet surface inward in the direction perpendicular to the axis of the exhaust pipe 1 approaching the turning pivot shaft 5 (to the right in FIG. 3). Therefore, the enlarged diameter portion 3 and the seat surface 6 when the valve body 4 is opened and rotated.
9 is larger than that described above with reference to FIG. 9, and the state of FIG. 2 in which the force B in the valve closing direction acts on the valve body 4 by the above-described negative pressure does not last for a long time.

Further, when the opening degree of the valve element 4 is slightly increased from the start of opening in FIG. 2, the locus indicated by β in FIG. 4), the flow of exhaust gas changes from a flow along the valve body seat surface 6 to a flow away from the valve body seat surface 6 as shown by C in FIG. Stagnation D of exhaust is generated in the vicinity of. Thus, the flow velocity of the exhaust gas flowing around the valve body seat surface 6 becomes slow, so that the fluid force (negative pressure) acting on the valve body seat surface 6 sharply decreases, and the negative pressure exerts on the valve body 4. As a result of the valve closing force rapidly disappearing, the dynamic pressure from the exhaust flow causes the valve body 4 to open greatly at a stretch.

As described above, in the present embodiment, the valve body 4 is closed with a strong valve closing force during a low engine rotation with a small exhaust flow rate, but the valve body 4 is closed with an increase in the engine speed (increase in the exhaust flow rate). When the valve 4 is slightly opened, the valve 4 can be opened at a stretch to ensure a sufficient valve opening, and high-speed exhaust at a high engine speed increases exhaust loss and exhaust flow noise. Can be avoided, and it is possible to achieve both improvement of exhaust loss and exhaust flow noise at high engine rotation and quietness at low engine rotation.

Further, in the present embodiment, since the pivot shaft 5 of the valve body 4 is located outside the exhaust pipe 1, the pivot position of the valve body 4 for achieving the above operation and effect is achieved. The degree of freedom in the selection of the valve body 4 can be increased, and the workability of mounting the valve body 4 can be improved. In addition, since the enlarged diameter portion 3 and the valve element seat surface 6 are formed to have a simple tapered shape so that the above-described effects can be obtained, the processing is easy and the cost is greatly improved.

FIG. 5 shows a main part of an exhaust silencer according to another embodiment of the present invention. In this embodiment, the enlarged diameter portion 3 is formed by a convex spherical surface, and the valve body seat surface 6 is Enlarged part 3
Are formed in a concave spherical shape corresponding to According to this configuration, the rate of change of the gap between the enlarged diameter portion 3 and the valve body seat surface 6 when the valve body 4 is opened and rotated is increased as in the above-described embodiment. When the body opening is small, the exhaust gas flows through the narrow gap between the enlarged diameter portion 3 and the valve body seat surface 6 along the above-mentioned spherical shape, so that an increase in pressure loss due to peeling can be suppressed. The function and effect can be made more remarkable.

FIG. 6 shows still another embodiment of the present invention. In this embodiment, the enlarged diameter portion 3 and the valve body seat surface 6 are arranged in a plane perpendicular to the axis of the exhaust pipe 1. .
According to this configuration, the enlarged diameter portion 3 and the valve body seat surface 6 are more easily formed, which is advantageous in cost, and the length of the gap between the enlarged diameter portion 3 and the valve body seat surface 6 is changed. This makes it possible to adjust the magnitude of the valve closing force due to the negative pressure caused by the exhaust gas passing therethrough, and to increase the valve closing direction rotation urging force of the valve body 4 by the return spring without increasing the valve closing direction. Opening can be adjusted

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an exhaust silencer according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view showing the exhaust silencer according to the embodiment in a state where a valve body starts opening.

FIG. 3 is an operation explanatory view showing the exhaust silencer according to the embodiment in a state where a valve body is further opened.

FIG. 4 is an operation explanatory view showing the exhaust silencer according to the embodiment together with the exhaust flow when the valve is in the same open state as in FIG. 3;

FIG. 5 is a sectional view showing a main part of an exhaust silencer according to another embodiment of the present invention.

FIG. 6 is a sectional view showing a main part of an exhaust silencer according to still another embodiment of the present invention.

FIG. 7 is a sectional view showing a main part of a conventional exhaust silencer.

FIG. 8 is an operation explanatory view showing the conventional exhaust muffler in a state where a valve element starts to open.

FIG. 9 is an operation explanatory diagram showing an opening rotation locus of a valve body in the conventional exhaust muffler. DESCRIPTION OF SYMBOLS 1 Exhaust pipe 2 Valve seat 3 Large diameter part 4 Valve element 5 Rotating pivot 6 Seat surface A Exhaust flow

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazushige Maeda 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa F-term in Nissan Motor Co., Ltd. (reference) 3G004 AA01 BA01 BA03 CA04 DA11 DA24

Claims (5)

[Claims] 1. A valve body is provided at an opening of an exhaust pipe in a housing of an exhaust muffler so as to be rotatably supported in a direction approaching and moving away from the opening, and the valve body is provided with the exhaust gas. In a vehicle exhaust silencer in which the opening is closed by rotating and biasing in a direction approaching the opening of the pipe, the opening of the exhaust pipe is provided with an enlarged diameter portion larger than the inner diameter of the exhaust pipe. A vehicle, wherein a seat surface corresponding to the shape of the enlarged diameter portion is provided on a valve body, and a rotation pivot shaft of the valve body is disposed upstream of the position of the closed valve body in the exhaust flow direction. Exhaust silencer. 2. The vehicle exhaust silencer according to claim 1, wherein said enlarged diameter portion has a tapered surface, and said seat surface has a tapered surface shape corresponding to said enlarged diameter portion. 3. The exhaust muffler for a vehicle according to claim 1, wherein the enlarged diameter portion has a convex spherical surface, and the seat surface has a concave spherical shape corresponding to the enlarged diameter portion. 4. The vehicle exhaust silencer according to claim 1, wherein said enlarged diameter portion and a seat surface are located in a plane perpendicular to an axis of said exhaust pipe. apparatus. 5. The exhaust muffler for a vehicle according to claim 1, wherein a rotation pivot shaft of the valve body is located outside the exhaust pipe.