JPH1113451A - Muffler equipped with variable throttle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict a back pressure to be lower than a maximum permitted pressure even if an exhaust flow rate is increased by communicating a room having a spring for energizing a flow rate control valve in a closing side with an atmosphere in a muffler provided with the flow rate control valve for making the opening area of an opening hole variable. SOLUTION: Exhaust gas from an engine flows into an exhaust introducing pipe 12, then flows out to an expansion room 8 after passing through a circular hole 12a, and then discharged through an exhaust discharge pipe 13. In this case, by a flow rate control valve 14 provided in the exhaust introducing pipe 12, an opening area when exhaust gas is flows out from the circular hole 12a to the expansion room 8 is adjusted. This flow rate control valve 14 is energized to an exhaust gas introducing side by a spring 15, and the initial contracting amount of the spring 15 is decided by a stopper 12b provided in the exhaust introducing pipe 12. Also, a side plate 16 is provided in the end part of the exhaust introducing pipe 12, a spring chamber 17 is formed between the side plate 16 and the flow rate control valve 14, an atmosphere communication room 16a is opened in the center of the side plate 16, and the spring chamber 17 is set at an atmosphere pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a muffler provided with a variable stop device.

[0002]

2. Description of the Related Art As a muffler having a variable aperture structure,
For example, the one disclosed in Japanese Utility Model Laid-Open No. 6-58114 is known. FIG. 9 shows a variable throttle structure of the exhaust muffler. An exhaust introduction pipe 2 is inserted into the muffler main body 1, and a spring 5 is provided in a spring chamber 6 between the side plate 3 of the exhaust introduction pipe 2 and the flow control valve 4. On the wall of the exhaust introduction pipe 2,
A large number of circular exhaust communication holes 2a are opened in the circumferential and axial directions. Exhaust gas from the engine flows into the exhaust introduction pipe 2, passes through the circular exhaust communication hole 2a, flows into the expansion chamber 7,
Further, it is emitted to the outside of the muffler through the tail tube 8. When the pressure in the exhaust gas introduction pipe 2 changes, the stroke of the spring 5 changes accordingly, and the total opening area (throttle) of the circular exhaust communication hole 2a changes. As a result, when the exhaust gas flow rate is small, the throttle is small, so that a reduction in the noise reduction effect due to insufficient throttle is prevented. Conversely, when the exhaust gas flow rate is large, the throttle is large, so that a decrease in engine output due to excessive throttle is suppressed. .

[0003]

However, in the conventional muffler variable throttle device, if the exhaust gas flow rate increases, the pressure in the exhaust gas inlet pipe 2 and the spring chamber 6 increase.
The pressure inside increases together. Therefore, the rate at which the force pressing the spring 5 increases, that is, the rate at which the pressure difference between the pressure in the exhaust gas inlet pipe 2 and the pressure in the spring chamber 6 increases, decreases with respect to the rate of increase in the exhaust gas flow rate. The rate of increase of the stroke is also reduced. As a result, as shown by the solid line in FIG. 10, the spring 5 does not stroke so that the back pressure is always smaller than the maximum allowable pressure P ^* , and the pressure in the exhaust gas introduction pipe 2 is increased due to excessive throttling. In some cases, as shown by the dotted line in FIG. 10, the pressure in the exhaust gas introduction pipe 2 exceeds the maximum allowable pressure P ^* , which causes problems such as a decrease in engine output and deterioration of fuel efficiency.

[0004] It is an object of the present invention to provide a muffler with a variable throttle device that ensures that the back pressure is always less than or equal to the maximum allowable pressure even when the exhaust gas flow rate increases.

[0005]

[Means for Solving the Problems]

(1) One embodiment will be described with reference to FIG. 1. According to the first aspect of the present invention, a muffler main body 11 forming at least one expansion chamber and a plurality of opening holes 12a in a wall surface are provided for exhaust gas from an engine. An exhaust introduction pipe 12 for introducing the inside of the muffler main body 11 through the exhaust pipe, an exhaust discharge pipe 13 for discharging the exhaust gas from the engine introduced to the inside of the muffler main body 11 to the outside, and a sliding inside the exhaust introduction pipe 12. Moving, opening hole 12a
Flow control valve 14 that makes the opening area of
a) is applied to a muffler with a variable throttling device having a spring 15 which urges the flow control valve 14 to the closing side so that the opening area of a becomes a minimum value and which expands and contracts according to the magnitude of exhaust pressure from the engine. The above object is achieved by making the chamber 17 provided with the spring 15 communicate with the atmosphere. (2) According to a second aspect of the present invention, in the variable aperture device for the muffler according to the first aspect, as shown in FIG. 3, the shape of the opening is a staggered slot hole 21a. (3) As shown in FIG. 4, the muffler main body 11 forming at least one expansion chamber, an exhaust introduction pipe 34 for introducing exhaust gas from an engine into the muffler main body 11, It has an end face that abuts on the end face of the exhaust introduction pipe 34, and slides in a direction perpendicular to the end face to slide the exhaust introduction pipe 3.
A flow control valve 33 for varying the gap between the end face of the flow control valve 4 and
A spring 15 which urges the flow control valve 33 to the closing side so that the distance of the gap becomes a minimum value, and which expands and contracts in accordance with the magnitude of exhaust pressure from the engine; The above object is attained by communicating with the atmosphere. (4) According to a fourth aspect of the present invention, in the muffler variable throttle device according to the first or third aspect, as shown in FIG.
2 is provided to change the initial contraction amount of the spring 15. (5) According to a fifth aspect of the present invention, in the muffler variable throttle device according to the first or third aspect, the sliding portion 51a of the flow control valve 51 has an arc shape as shown in FIG. With the minimum contact area.

[0006] In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments are used to make the present invention easier to understand. However, the present invention is not limited to this.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. -First Embodiment- FIG. 1 is a sectional view showing a first embodiment of a muffler according to the present invention. In FIG. 1, M is a muffler, and an exhaust introduction pipe 12 and an exhaust discharge pipe 1 are provided inside a main body 11 thereof.
3 is inserted. A plurality of circular holes 12 a are opened in the circumferential wall and the axial direction on the peripheral wall of the exhaust gas introduction pipe 12, and expand from the circular holes 12 a of the exhaust gas introduction pipe 12 by a flow control valve 14 provided inside the exhaust gas introduction pipe 12. The opening area when the exhaust gas flows into the chamber 8 is adjusted. Flow control valve 14
Are urged toward the exhaust gas introduction port by a spring 15, and the initial contraction amount of the spring 15 is determined by a stopper 12 b provided inside the exhaust introduction pipe 12. The exhaust introduction pipe 12 penetrates the muffler main body 11, and a side plate 16 is provided at an end of the muffler main body 11. A spring chamber 1 is provided between the side plate 16 and the flow control valve 14.
7 are formed. At the center of the side plate 16, the air communication hole 1
6a is opened, and the spring chamber 17 is set to the atmospheric pressure.

Here, in order to enhance the silencing effect, the back pressure should be as large as possible, for example, equal to the maximum allowable pressure. Therefore, for example, the initial contraction amount of the spring is set to be equal to the maximum allowable pressure.

Next, the operation of the first embodiment will be described. The exhaust from the engine (not shown) is
2, where the opening area is reduced by the circular holes 12a and compressed. The compressed exhaust gas flows into the expansion chamber 8 through the circular hole 12a and is expanded, and then the exhaust discharge pipe 1
3 and is released outside the muffler. Through such a process of compression and expansion of the exhaust gas, the exhaust gas is silenced.

The total opening area of the circular hole 12a (hereinafter, referred to as a stop) changes according to the stroke of the spring 15, and the stroke Δx of the spring 15 is expressed by the following equation.

Δx = {A (P _B −P ₀ ) −k · x ₀ } / k where A: pressure receiving area of flow control valve P _B : back pressure P ₀ : spring chamber pressure k: spring constant x ₀ : initial contraction amount of the spring That is, the stroke Δx of the spring 15 is
The pressure is proportional to a value obtained by subtracting the initial load of the spring from the pressure difference between the pressure in the pressure chamber 2 (hereinafter referred to as the back pressure) and the spring chamber 17. Since the spring chamber 17 is always at atmospheric pressure, when the back pressure is larger than the initial load of the spring, the stroke Δx of the spring 15 increases in proportion to the increase of the back pressure. Here, the initial contraction amount x ₀ of the spring because the set equal to the maximum allowable pressure, at the time of a small low idle rotation of for example exhaust flow rate shown in a ₁ in FIG. 2, the spring 15 remains the smaller aperture without stroke There, at the time of large rated rotation of the example exhaust flow rate shown in a ₂ of FIG. 2, the spring 15 as the back pressure is maintained at the maximum allowable pressure stroke, the diaphragm is increased.

According to the first embodiment, since the spring chamber 7 is always kept at the atmospheric pressure, after the back pressure reaches the maximum allowable pressure, the spring 15 strokes in proportion to the increase of the back pressure. as a result,
During low idle rotation with a small exhaust flow rate, the throttle is small and the back pressure is at its allowable value P ^* , so that the noise reduction effect can be enhanced. Also, at the time of rated rotation with a large exhaust flow rate, the spring 15 strokes in proportion to the exhaust flow rate and the throttle area becomes large, so that the back pressure can be made equal to the maximum allowable pressure P ^* , without adversely affecting the engine output. The silencing effect can be maximized. That is, the maximum noise reduction effect can be obtained without adversely affecting the engine output over the entire range of the engine speed from a low rotation speed to a high rotation speed.

Generally, when the spring is used at a high temperature for a long time, the set of the spring becomes a problem. However, according to the first embodiment, the temperature of the spring chamber 17 is low because the spring chamber 17 is at atmospheric pressure. As a result, the creep life and repetitive life of the spring are not reduced even without using expensive high-temperature spring material.

If the spring 15 is initially set to start the stroke before the back pressure reaches the maximum allowable pressure P ^* , the back pressure increases as the spring stroke Δx increases as shown by the solid line in FIG. It approaches the allowable pressure P ^* .

Second Embodiment FIG. 3 is a partial cross-sectional view of an exhaust gas introduction pipe according to a second embodiment of the muffler according to the present invention. The other configuration of the muffler (not shown) is the same as that of FIG. In FIG. 3, a plurality of slot holes 2 staggered in the circumferential and axial directions are formed in the peripheral wall of the exhaust introduction pipe 12.
1a is provided.

In the second embodiment, as in the first embodiment, even if the exhaust gas flow from the engine increases, the back pressure is controlled by the stroke of the spring 15, and is always set to be equal to or less than the maximum allowable pressure. Is done. According to the second embodiment, the throttle holes are formed in the staggered slot holes 21a.
The diaphragm continuously changes according to the stroke of the spring 15. Therefore, fine setting of the back pressure is possible.

Third Embodiment FIG. 4 is a partial cross-sectional view of an exhaust pipe according to a third embodiment of the muffler according to the present invention. The other configuration of the muffler (not shown) is the same as that of FIG. In FIG. 4, a spring chamber ring 31 is fixed to the muffler main body 11 through a part of the muffler main body 11, and a side plate 32 having an atmosphere communication hole 32 a is joined to one end thereof. A chamber 17 is formed. The flow control valve 33, one end of which is inserted into the outer periphery of the spring chamber pipe 31 and is slidable, is urged by the spring 15 toward the exhaust gas introduction side. The opening area of the exhaust introduction pipe 34 is zero.

In the third embodiment, when the spring 15 strokes due to the back pressure, a gap is formed between the end face of the exhaust pipe 34 and the flow control valve 33, and the length of the gap increases as the back pressure increases. Become. Further, according to the third embodiment, since the initial throttle is zero, the back pressure can be maximized even at a low flow rate, and the noise reduction effect can be maximized. Further, the rate of increase of the throttle with respect to the stroke amount of the spring is larger than that of FIG.
Since the aperture can be increased even for a small stroke, the spring constant can be set large, and the degree of freedom in spring design is expanded.

In the third embodiment, FIG.
The notch 34a is formed at the end of the exhaust introduction pipe 34 as shown in FIG.
May be opened. Thereby, even if the stroke of the spring is delayed due to the increase of the back pressure,
Since the back pressure can be reduced to a predetermined value, there is no adverse effect on engine performance.

Fourth Embodiment FIG. 6 is a partial sectional view of a spring chamber according to a third embodiment of the muffler according to the present invention. The other configuration of the muffler (not shown) is the same as that of FIG. 1 and the description thereof is omitted. A flange 41 is provided concentrically with the exhaust introduction pipe 12 at a part of the muffler main body 11 at the end of the exhaust introduction pipe 12, and a spacer 42 having a predetermined thickness L is provided on the flange 41 via a gasket 43. It is fastened by bolts 44. An atmosphere communication hole 42a is opened in the center of the spacer 42, and the spring chamber 17 is always at atmospheric pressure.

In the fourth embodiment, since the initial contraction amount of the spring 15 can be changed by changing the thickness L of the spacer 42, the relationship between the back pressure and the spring stroke can be easily changed. . Therefore, when trying to apply the same muffler to engines having different displacements, it is necessary to change the relationship between the back pressure and the spring stroke. However, according to the third embodiment, the spacers 42 having different heights L are different.
This makes it easy to do this, and as a result, many muffler parts can be shared even in engines with different displacements, and costs can be reduced.

Fifth Embodiment FIG. 7 is a partial sectional view of an exhaust gas introduction pipe according to a fourth embodiment of the muffler according to the present invention. The other configuration of the muffler (not shown) is the same as that of FIG. In FIG. 5, the longitudinal cross-sectional shape of the outer peripheral portion of the flow control valve 51 is an arc shape, and has a sliding portion 51 a in a part thereof, and the sliding portion 51 a is in line contact with the inner wall of the exhaust gas introduction pipe 12. I have.

According to the fifth embodiment, the exhaust introduction pipe 1
Since the contact area between the inner wall 2 and the sliding portion 51a of the flow control valve 51 is small, frictional resistance when the flow control valve 51 slides due to an increase in the exhaust flow rate can be reduced, and stick-slip can be prevented. The spring 15 can smoothly stroke so as to obtain a predetermined stroke at a predetermined back pressure.

Sixth Embodiment FIG. 8 is a partial sectional view of an exhaust gas introduction pipe according to a sixth embodiment of the muffler according to the present invention. The other configuration of the muffler (not shown) is the same as that of FIG. 1 and the description is omitted. 8, a side plate 62 having an atmosphere communication hole 62a is provided at an end of a spring chamber pipe 61 in which the spring 15 is installed.
Is fixed, and the spring chamber 17 is formed by the flow control valve 63. The flow control valve 63 is slidable by being inserted into the inner walls of the spring chamber pipe 61 and the exhaust introduction pipe 64.
5 is urged toward the exhaust gas introduction side, and the initial position is determined by the stopper 62b. A plurality of cutout holes 64a are opened at the end of the exhaust introduction pipe 64 in the circumferential direction.

According to the sixth embodiment, since the plurality of cutout holes 64a have a slit shape, the aperture changes continuously according to the stroke of the spring 15. Therefore, fine setting of the back pressure is possible.

In the above embodiment, there is only one exhaust introduction pipe and one exhaust discharge pipe, but a plurality of these may be provided. Although the expansion chamber 8 is applied to one case, the present invention is similarly applied to a case where the inside of the muffler is partitioned into a plurality of rooms and there are a plurality of expansion chambers.

[0026]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the present invention, since the spring chamber is set to the atmospheric pressure, the spring strokes in proportion to the increase in the back pressure. This is the allowable value, and the silencing effect can be enhanced. Also, at the time of rated rotation with a large exhaust flow rate, the spring strokes according to the exhaust flow rate and the throttle becomes large, making it possible to make the back pressure equal to the maximum allowable back pressure, without affecting the engine output and reducing the noise reduction effect. It can be maximized. (2) According to the second aspect of the present invention, since the throttle holes are slot holes arranged in a staggered arrangement, the throttle changes continuously according to the stroke of the spring, so that it is possible to finely set the back pressure. (3) According to the third aspect of the invention, since the initial throttle is zero, the back pressure can be maximized even at a low flow rate, and the noise reduction effect can be maximized. In addition, since the rate of increase of the diaphragm with respect to the stroke amount of the spring becomes the maximum, the spring constant can be set large, and the degree of freedom in spring design is expanded. (4) According to the fourth aspect of the invention, by changing the thickness of the spacer, the relationship between the back pressure and the spring stroke can be changed, and the same muffler is applied to engines having different displacements. Will also be easily possible. (5) According to the invention of claim 5, since the contact area between the inner wall of the exhaust introduction pipe and the sliding portion of the flow control valve is small, the frictional resistance when the flow control valve slides due to an increase in the exhaust flow rate is reduced. It is smaller and can prevent sticks.

[Brief description of the drawings]

FIG. 1 is a sectional view of a muffler according to a first embodiment.

FIG. 2 is a diagram illustrating a relationship between a back pressure and a spring stroke according to the first embodiment.

FIG. 3 is a partial cross-sectional view of an exhaust gas introduction pipe according to a second embodiment.

FIG. 4 is a partial cross-sectional view of an exhaust gas introduction pipe according to a third embodiment.

FIG. 5 is a partial cross-sectional view of an exhaust gas introduction pipe as a modified example according to the third embodiment.

FIG. 6 is a partial cross-sectional view of a spring chamber according to a fourth embodiment.

FIG. 7 is a partial cross-sectional view of an exhaust gas introduction pipe according to a fifth embodiment.

FIG. 8 is a partial cross-sectional view of an exhaust gas introduction pipe according to a sixth embodiment.

FIG. 9 shows a conventional variable exhaust throttle device.

FIG. 10 is a diagram showing a relationship between a back pressure and a spring stroke according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Muffler main body 12 Exhaust introduction pipe 12a Opening hole 13 Exhaust discharge pipe 14 Flow control valve 15 Spring 17 Spring chamber 21a Slot hole 34 Exhaust introduction pipe 33 Flow control valve 42 Spacer 51 Flow control valve 51a Sliding part

Claims (5)

[Claims] 1. A muffler main body forming at least one expansion chamber; an exhaust introduction pipe for introducing exhaust gas from an engine into the inside of the muffler main body through a plurality of opening holes in a wall surface; An exhaust discharge pipe that discharges exhaust gas from the engine introduced into the outside to the outside; a flow control valve that slides inside the exhaust introduction pipe to change an opening area of the opening; and an opening of the opening. A muffler with a variable throttle device, comprising: a spring that urges the flow control valve to the closed side so that the area becomes a minimum value and that expands and contracts according to the magnitude of exhaust pressure from the engine. A muffler with a variable throttle device, characterized in that the chamber communicates with the atmosphere. 2. The muffler according to claim 1, wherein the shape of the opening is a staggered slot. 3. A muffler main body forming at least one expansion chamber, an exhaust introduction pipe for introducing exhaust gas from an engine into the muffler main body, and an end face contacting an end face of the exhaust introduction pipe, A flow control valve that slides in a direction perpendicular to the end face to change a gap between the end face of the exhaust pipe and the flow control valve, and closes the flow control valve so that a distance of the gap becomes a minimum value. A muffler with a variable throttle device, comprising: a spring that is energized and expands / contracts in accordance with the magnitude of exhaust pressure from the engine, and wherein a chamber provided with the spring is communicated with the atmosphere. 4. The variable throttle device for a muffler according to claim 1, wherein an exchangeable spacer is provided at an end of the exhaust introduction pipe in contact with the spring, and an initial contraction amount of the spring is changed. A muffler with a variable diaphragm device characterized by the following. 5. The variable throttle device for a muffler according to claim 1, wherein a sliding portion of the flow control valve is formed in an arc shape, and a contact area with an inner wall of the exhaust introduction pipe is minimized. Muffler with a variable aperture device.