JPH0219532Y2 - - Google Patents

Description

[Detailed description of the invention] a. Purpose of the invention (industrial application field) The automobile silencer according to this invention is used to attenuate noise components in the exhaust gas emitted from the engine for driving the vehicle. do.

(Prior art) In the middle of the exhaust pipe for dispersing the exhaust gas emitted from the driving engine of the automobile into the atmosphere,
A muffler is provided to attenuate noise components contained in the exhaust gas. This type of muffler has a flow path with a changing cross-sectional area and a bend inside the casing, and while the exhaust gas passes through the muffler, it expands, contracts, resonates, or has a silencing effect due to interference. receive.

However, in the case of automobile silencers, the engine speed changes greatly from 700 to 800 rpm to 6000 to 7000 rpm, and the amount of exhaust gas sent into the silencer changes accordingly, resulting in the following disadvantages. occurs. That is, in order to obtain a sufficient noise damping effect, the flow path area must be set to an appropriate value for the exhaust flow rate, and the flow path area must not be made too large or too small.
For this reason, a silencer that can effectively silence noise when the engine is rotating at low speeds will degrade its performance when the engine rotates at high speeds; In the case of a silencer, performance at low speeds is insufficient.

For example, as shown in FIG. 10, in the case of a silencer with two outlet pipes 3a and 3b that dissipate the exhaust gas sent into the casing 2 from one inlet pipe 1 into the atmosphere, one outlet pipe 3b is closed and exhaust gas is sent out only from one outlet pipe 3a, as shown by the solid line a in Fig. 11, the noise in the exhaust air released into the atmosphere at low speeds is small, but at high speeds, the noise is small. As the noise increases, the noise reduction performance becomes unsatisfactory. On the contrary, the two outlet pipes 3a, 3
If exhaust gas is allowed to flow through both of b.
As shown by the broken line b in the figure, although the silencing performance at high speeds improves, the performance at low speeds deteriorates.

In order to deal with such problems,
167216, as shown in FIG. 12, a plate 5 is provided at the inlet opening of one of the two outlet pipes 3a and 3b which are parallel to each other, and which opens and closes the opening using an actuator 4. A silencer is shown. In this muffler, when the engine speed is low and the amount of exhaust gas sent into the muffler is small, negative pressure is not introduced to the actuator, and the plate 5 pressed by the compression spring is moved to one outlet pipe 3a.
When the engine speed is high and the amount of exhaust gas is large, negative pressure is introduced into the actuator 4, causing the plate 5 to close the compression spring 12. The inlet opening of the outlet pipe 3a is opened by moving against the elastic force, and the exhaust gas is
The books act to be discharged through the outlet pipes 3a, 3b.

(Problem to be solved by the invention) However, in the case of the conventional muffler configured and operated as described above, since the mutually parallel flow paths are provided independently by the two outlet pipes 3a and 3b, the muffler The assembling of the muffler becomes troublesome, and the muffler becomes large, making it difficult to assemble it under the floor of an automobile.

Furthermore, while resonance chambers are effective in attenuating the low-frequency noise that occurs when the engine rotates at low speeds, such resonance chambers are not very effective at attenuating the high-frequency noise that occurs when the engine rotates at high speeds. Useless.

Therefore, a resonance chamber is formed inside the muffler only when the engine rotates at low speeds, and attenuates low frequency noise.
When the engine rotates at high speeds, this resonance chamber space is used as an exhaust flow path to increase the exhaust flow area and prevent the generation of jet noise, thereby creating a compact muffler that exhibits stable performance over the entire frequency range. can get.

The present invention aims to provide such a silencer for automobiles.

b. Structure of the invention (means for solving the problem) The automobile silencer of the invention divides the inside of one exhaust pipe into two in cross section to provide two flow paths parallel to each other. A through hole communicating with only one of the two flow paths is provided in the middle of the conduit, and a valve body is provided to open and close the end opening on the exhaust inflow side of the one exhaust conduit. This valve body has a valve rod on one side of a valve plate that faces and can close the end opening on the exhaust inflow side of the exhaust conduit, and this valve rod is attached to a guide tube fixed to the casing. One end of the bellows made of heat-resistant material surrounding the valve stem is hermetically joined to the outer circumferential surface of the guide cylinder and the outer circumferential surface of the valve body at the other end. There is. The inside of this bellows is communicated with a negative pressure source through an air passage provided in the guide tube. Furthermore, a compression spring is provided inside the bellows to extend the length of the bellows.

(Function) The automobile silencer of the present invention is constructed as described above, but when the engine speed is low and the amount of exhaust gas sent into the silencer is small, the inside of the bellows can be used as a negative pressure source. By not allowing the air to pass through to the valve, or by keeping the negative pressure of the negative pressure source low, the valve plate is pushed by the elasticity of the compression spring and closes the opening on the exhaust gas introduction side of the exhaust conduit. Therefore, the exhaust gas enters one of the channels through a hole provided in the middle of the exhaust conduit and is discharged. The space from the through hole to the end of the exhaust gas introduction pipe acts as a resonance chamber and contributes to attenuation of low frequency noise.

Next, when the engine speed is high and the amount of exhaust gas fed into the muffler increases, the inside of the bellows is communicated with a negative pressure source having sufficient negative pressure. As a result, the bellows is compressed by the exhaust pressure, and the valve plate separates from the exhaust inlet side opening end of the exhaust conduit against the elasticity of the compression spring. Therefore, when the engine rotates at low speeds, the exhaust gas is discharged through two parallel flow paths, including the resonance chamber space.

(Example) Next, the present invention will be explained in more detail by explaining the illustrated embodiment.

FIG. 1 shows the overall structure of the silencer of the present invention. Of the inlet pipe 1 and the outlet pipe 3 inserted into the casing 2 from opposite directions, the inside of the outlet pipe 3 is partitioned into two sections, and the inside of the outlet pipe 3 is two channels 1
8 and 19 are provided, and furthermore, the inlet end opening of this outlet pipe 3 can be opened and closed according to the engine speed, and the two flow channels 18 and 1 are provided on the side of the outlet pipe 3.
A through hole communicating only with one of the channels 18 is bored.

Various structures can be considered in order to divide the inside of the outlet pipe 3 into two in cross-section and provide two mutually parallel channels 18 and 19. For example, as shown in FIG. An outer tube 21 with a large number of through holes 20, 20 and an inner tube 22 with no holes are connected to the stay 2.
3 or a similar outer tube 2
1 has an inner tube 2 with a cocoon-shaped cross section as shown in Fig. 3.
2 or an inner tube 22 having a substantially triangular cross section as shown in FIG. Furthermore, as shown in FIG. 5, a flat partition plate 24 is provided inside the outlet pipe 3.
By dividing the flow path into two by
8 and 19, and one flow path 1 is provided on one side of the outlet pipe 3.
Through holes 20, 20 communicating only with 8 may be bored.

Further, a valve mechanism for opening and closing the inlet end opening of the outlet pipe 3 is constructed as shown in FIGS. 6 to 9.

First, to explain in order starting from the case of the first embodiment shown in FIGS. Cylinder part 8 that opens only inward
A valve rod 10 of a mushroom-shaped valve body 9 is slidably inserted into the cylinder portion 8.
At the end of the valve rod 10, there is a valve plate 1 that faces the opening at the inlet end of the outlet pipe 3 and can close this opening.
1 is formed, and a compression spring 12 is provided between this valve plate 11 and the end face of the guide tube 7, giving elasticity to this valve plate 11 toward the end opening of the outlet pipe 3. Further, a bellows 13 is provided around the compression spring 12.
It is surrounded by This bellows 13 is made of a heat-resistant material such as a stainless steel plate.
One end is attached to the outer peripheral surface of the guide tube 7, and the other end is attached to the valve body 9.
are airtightly joined to the outer circumferential surface of each. The bellows 13 is attached to a portion of the guide tube 7 which is airtightly joined to one end of the bellows 13 in a portion that is removed from the cylinder portion 8.
Ventilation passages 14, 14 for communicating the interior with a negative pressure source
Further, a hose 15 airtightly joined to the outer end of the casing of the guide tube 7 is connected to a negative pressure source such as an intake manifold directly or via a solenoid valve.

In the automobile silencer of the present invention configured as described above, when the engine speed is low and the amount of exhaust gas sent to the silencer is small, the solenoid valve in the middle of the hose 15 is closed. Since no negative pressure is introduced into the bellows 13 or only a weak negative pressure is introduced into the bellows 13 compared to the elasticity of the compression spring 12, the bellows 1
3 will not be shortened in length by atmospheric pressure,
The valve plate 11 of the valve body 9 closes the end opening of the outlet pipe 3 due to the elasticity of the compression spring 12. Therefore, the exhaust gas sent into the muffler casing 2 from the inlet pipe 1 flows only into one flow path 18 through the through holes 20, 20 bored in the side surface of the outlet pipe 3. It is discharged only through channel 18.
Therefore, the sound pressure in the exhaust gas after passing through the muffler changes as shown by the solid line a in FIG. 11 as the engine speed changes. Further, at this time, the space 25 located upstream of the exhaust hole 20 in the flow path 18 acts as a resonance chamber, effectively attenuating the low frequency component of the noise.

Next, when the engine speed is high and the amount of exhaust gas sent to the muffler increases, the solenoid valve in the middle of the hose 15 is opened, or the negative pressure of the negative pressure source becomes large, so that there is sufficient pressure inside the bellows 13. A large negative pressure is introduced into the bellows 13, and the bellows 13 is pushed by atmospheric pressure and contracts as shown in FIG. For this reason, the valve plate 11 of the valve body 9
is separated from the end opening of the outlet pipe 3, and the exhaust gas is discharged not only through one flow path 18 but also through the other flow path 19. Therefore, the sound pressure in the exhaust gas after passing through the muffler changes as shown by the broken line b in FIG. 11 as the engine speed changes.

Therefore, the engine rotation speed x (Fig. 11) is determined so that the silencing performance is the same when the exhaust gas is discharged through only one flow path 18 and when it is discharged through both flow paths 18 and 19. When operating at a speed lower than this rotation speed x, the valve body 9 closes the outlet pipe 3.
By closing the opening at the end of the engine and opening the valve body 9 during high-speed operation, it is possible to obtain optimal noise reduction performance depending on the operating conditions of the engine. Opening and closing the valve body 9 before and after x rotation in this way can be easily done by opening and closing a solenoid valve provided in the middle of the hose 15 according to the engine speed, and also by using the intake manifold as a negative pressure source. By using the negative pressure of the negative pressure source, by appropriately determining the elasticity of the compression spring 12 that presses the valve body 9 against the end opening of the outlet pipe 3, the valve body 9 is pressed against the outlet pipe 3 before and after x rotation. The end openings of 3 can be opened and closed. The negative pressure required to open the valve body 9 can be easily adjusted by changing the diameter of the bellows 13 or by changing the elasticity of the compression spring 12.

Next, FIG. 8 shows a second embodiment of the structure of the valve body. In this embodiment, the cylinder part 8 into which the valve rod 10 is inserted is used as a part of the negative pressure introducing path, and the negative pressure introduced into the cylinder part 8 from the ventilation path 14 is further transferred to the valve rod 10. Air passage 1 formed in
6 into the bellows 13. Other configurations and operations are the same as in the first embodiment described above.

Further, the compression spring for pressing the valve body 9 against the open end of the outlet pipe 3 may have a large diameter so as to come into contact with the inner circumferential surface of the bellows 13, as shown in FIG.

c. Effects of the invention Since the automobile silencer of the invention is configured and operates as described above, it is possible to obtain optimal noise reduction performance depending on the engine speed. In addition, since the movable parts of the valve structure for opening and closing and the compression springs are covered with bellows, the movable parts may become clogged with soot mixed in with the exhaust gas, or the compression springs may be directly exposed to high-temperature exhaust gases. Never. Furthermore, since there is only one outlet pipe, the silencer is easy to assemble and does not require a particularly large installation space.

In addition, in the above explanation, the inside of the outlet pipe was divided into two to create two flow paths, and the opening at the end of the exit pipe was opened and closed. The present invention is not limited to a pipe, and for example, a pipe communicating between the first expansion chamber and the second expansion chamber may be divided into two, and the opening and closing of the exhaust upstream end opening of this pipe may be controlled.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing the overall structure of the silencer of the present invention, Figs. 2 to 5 are enlarged sectional views taken along line A-A in Fig. 1 showing four examples of the structure of the exhaust pipe, and Figs. 6 to 7 are 6 is a sectional view corresponding to section B in FIG. 1 showing the first embodiment of the valve mechanism; FIG. 6 is a state at low engine speed;
The figures also show the conditions at high rotation speeds. FIG. 8 is a diagram similar to FIG. 6 showing the second embodiment;
Fig. 9 is a view similar to Figs. 6 to 8 showing a third embodiment with some parts omitted; Fig. 10 is a schematic sectional view showing a first example of a conventional muffler; and Fig. 11 is an outlet pipe. FIG. 12 is a cross-sectional view showing a second example of a conventional muffler. 1: Inlet pipe, 2: Casing, 3, 3a, 3
b: Outlet pipe, 4: Actuator, 5: Plate, 6:
End plate, 7: Guide cylinder, 8: Cylinder part, 9: Valve body,
10: Valve rod, 11: Valve plate, 12: Compression spring, 1
3: Bellows, 14: Ventilation path, 15: Hose, 16:
Ventilation path, 18, 19: Channel, 20: Through hole, 21:
Outer pipe, 22: Inner pipe, 23: Stay, 24: Partition plate, 25: Space.

Claims (1)

[Scope of utility model registration request] By partitioning the inside of the exhaust conduit of a silencer installed in the middle of the exhaust pipe that dissipates the exhaust gas of the automobile engine into the atmosphere by dividing the cross section, two parallel flow paths are formed, and the above-mentioned A muffler is provided with a through hole communicating only with one flow path on the side surface of the exhaust pipe, and a valve body for opening and closing an opening at an end of the exhaust pipe on the exhaust upstream side, the valve body being provided with a valve body that opens and closes an opening at an end of the exhaust pipe on the upstream side of the exhaust gas, the valve body communicating with only one flow path. A valve rod is provided on one side of the valve plate that faces and can close the end opening of the passage, and this valve rod is slidably engaged with a guide tube fixed to the casing, and the valve rod is surrounded by a valve rod. A compression spring is provided inside the bellows made of heat-resistant material, which is airtightly joined to the guide cylinder at one end and to the valve lever at the other end, and the inside of the bellows is freely connected to a negative pressure source. A silencer for automobiles.