JPH0143444Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a silencer for automobiles, etc. Conventionally, as this type of device, for example, as shown in the longitudinal sectional view of FIG. 1, there is known a structure in which the flow path 8 is closed without the on-off valve 9 and a structure in which the flow path 8 is opened. However, in such a structure, when the cavity 4 is made to function as a low-frequency resonant chamber by the closed flow path 8, the silencing property is relatively good on the low-speed side, but has the disadvantage that it deteriorates on the high-speed side. On the other hand, when the cavity 4 is made to function as an expansion chamber by opening the flow path 8, the noise silencing characteristics on the high rotation side are good, but there is a drawback that the noise silencing characteristics on the low rotation side deteriorate. In order to improve the muffler capacity, the capacity of the muffler inevitably increases, which not only makes it difficult to mount the muffler on a vehicle, but also increases the weight, which is disadvantageous in terms of cost. The present invention was proposed in view of the above circumstances, and the purpose is to provide a noise reduction device that is small and lightweight and has good noise reduction characteristics over a wide rotational speed range from low to high engine rotation speeds. Silencing an engine having an expansion chamber, a resonance chamber, an exhaust introduction pipe communicating with the expansion chamber, an exhaust outlet pipe communicating with the expansion chamber, and a tuning pipe communicating the expansion chamber and the resonance chamber. The device includes an on-off valve inserted between the resonance chamber and the expansion chamber in parallel with the tuning pipe, and an on-off valve that detects the engine speed and closes the on-off valve when the engine speed is below a set value. The engine is characterized by comprising a valve opening/closing means that opens the opening/closing valve when the engine speed exceeds the set value. To explain the present invention with reference to the drawings, FIG. 1 is a longitudinal sectional view showing the first embodiment thereof, FIG. 2 is an enlarged longitudinal sectional view showing the on-off valve of FIG. A characteristic diagram showing the relationship between the speed and the sound pressure level, FIG. 4 is a longitudinal sectional view showing the second embodiment, and FIG. 5 is a characteristic diagram showing the relationship between the engine rotation speed and the sound pressure level according to FIG. 4. It is. First, in the first embodiment shown in FIGS. 1 and 2, 1 is a silencer main body, and the main body 1 is divided into three chambers: a cavity 4, a first expansion chamber 5, and a second expansion chamber 6. , 6 communicate through a flow path 7, and between the cavity 4 and the first expansion chamber 5 through a flow path 8, the flow path 8 can be opened and closed as needed by an on-off valve 9. As will be described later, the opening and closing of the on-off valve 9 is controlled by a solenoid, a solenoid and a
This is done using hydraulic pressure, motors, etc. 2 passes through the second and first expansion chambers 6 and 5, and the tip end is connected to the cavity 4.
This is an exhaust introduction pipe that opens inward, and a portion of the exhaust introduction pipe 2 located inside the first expansion chamber 5 is provided with a large number of small holes 2a, and the exhaust gas flowing through the exhaust introduction pipe 2 passes through the small holes 2a. It is designed to enter the first expansion chamber 5. Reference numeral 3 denotes an exhaust outlet pipe, which is installed so that it passes through the cavity 4 and the first expansion chamber 5 and its tip opens into the second expansion chamber 6.The small hole 3a is a hole that improves the noise reduction effect, and is installed as necessary. This shall be provided accordingly. Reference numeral 9 denotes an on-off valve that is fitted into the flow path 8 and opens and closes it, and as shown in FIG. 2, the valve casing 12
An opening 19 is provided at the front end of the valve casing 12, and a valve guide 18 is provided at the rear of the valve casing 12.
A valve cone 14 is attached to the tip of the valve shaft 15 inserted into the valve casing 12, and a spring cover 16 is attached to the middle part, and a return spring 17 is interposed between the spring cover 16 and the valve guide 18, and the valve shaft 15 is inserted into the valve shaft 12. The rear end of 15 is attached to a cable hinge 2 to a control cable 21 connected to a solenoid 22.
0. A solenoid 22 operates the control cable 21 according to the magnitude of the engine rotation speed via the engine rotation speed sensor 24 and the control unit 23. That is, when the engine speed is below the set value, the control unit 23 closes the solenoid 2.
2, the solenoid 22 is not activated, and the return spring 17 urges the valve shaft 15 to the left, so that the valve cone 14 establishes communication between the cavity 4 and the second expansion chamber 5. When the valve is closed and the engine speed exceeds the set value, the control unit 23 outputs a high-level signal to the solenoid 22, which activates and pulls the valve shaft 15 to the right against the return spring 17. , the cavity 4 and the first expansion chamber 5 communicate through the opening 19. In this structure, the engine rotation speed is now set to 3000 rpm by the control unit 23.
When set to , the on-off valve 9 is set to
The cavity 4 functions as a resonance chamber when the engine speed is 3000 rpm or less, and as an expansion chamber when the engine speed exceeds 3000 rpm. First, when the engine speed is 3000 rpm or less, exhaust gas enters the first expansion chamber 5 from the exhaust introduction pipe 2 through the small hole 2a as shown by the arrow, and at this time, the noise that enters from the inlet of the exhaust introduction pipe 2 The pressure energy (mainly low-frequency pulsating sound) is directly weakened in the cavity 5 that functions as a resonance chamber, and the exhaust gas exiting from the small hole 2a expands in the first expansion chamber 5 and the sound waves are attenuated. After being muted in expansion room 5,
The exhaust gas is throttled by the flow path 7 and enters the second expansion chamber 6, where it expands again, and the sound waves are further attenuated and discharged to the outside from the exhaust outlet pipe 9. Next, when the engine speed exceeds 3000 rpm,
Since the cavity 4 functions as an expansion chamber, part of the exhaust gas flowing in from the exhaust introduction pipe 2 passes through the small hole 2a and expands in the first expansion chamber 5 as shown by the arrow, but the main flow is inside the cavity 4. After the exhaust gas is expanded in the flow path 8, the sound wave is attenuated, and the sound is muffled in the cavity 4, it is throttled in the flow path 8 and enters the first expansion chamber 5, where it expands again. The sound wave is squeezed and enters the second expansion chamber 6, where it further expands, and the sound wave gradually attenuates until it reaches the exhaust outlet pipe 9.
More is discharged to the outside. According to such a structure, by opening and closing the channel 8 with the on-off valve 9, the cavity 4 can function as both a resonance chamber and an expansion chamber.
As shown by the solid line in FIG. 3, a small-capacity muffler can exhibit extremely good silencing characteristics over a wide range from low-frequency pulse noise to high-frequency sound. In addition, by opening the flow path 8 in the high rotational speed range, the flow of exhaust gas can pass through both the flow path 8 and the small hole 2a, so the flow of exhaust gas is extremely good, and as a result, the muffler The effect of reducing resistance can also be achieved. Note that the resonance frequency when the cavity 4 acts as a resonance chamber is:

[Formula] becomes. However, V: volume of the cavity 4, l: tuning length of the exhaust gas introduction pipe 3, S: cross-sectional area of the exhaust gas introduction pipe 3, and C: speed of sound. Next, in the second embodiment shown in FIG. 4, 31 is a main body of the silencer, and the main body 31 is divided into four chambers: a resonance chamber 34, a first expansion chamber 35, a second expansion chamber 36, and a third expansion chamber 37. A flow path 39 is provided between the first expansion chamber 35 and the second expansion chamber 36.
A punching separator 4 is provided between the third expansion chamber 37 and the third expansion chamber 37.
3. Reference numeral 32 denotes an exhaust introduction pipe that passes through the third and second expansion chambers 37 and 36 and has a tip opening into the first expansion chamber 35;
A small hole 38 is provided in the portion located within the second expansion chamber 36.
The exhaust gas flowing into the exhaust introduction pipe 32 expands in the second expansion chamber 36 through the small hole 38, and the sound waves are attenuated. Reference numeral 33 denotes an exhaust outlet pipe, which is installed so that it passes through the resonance chamber 34, the first expansion chamber 35, and the second expansion chamber 36, and its tip opens into the third expansion chamber 37. 40 and 41 are tuning pipes communicating with the resonance chamber 34;
As in the first embodiment, the opening located in the first resonance chamber 34 is opened and closed by the on-off valve 9. Now, if the on-off valve 9 is set to close when the engine speed is 2500 rpm or less and open when the engine speed exceeds 2500 rpm, the resonance frequency of the resonance chamber 34 will be the tuning pipe when the engine speed is 2500 rpm or less, as shown in the formula below. 40 and resonance chamber 34, and when the engine speed exceeds 2500 rpm, it is determined by tuning pipes 40, 41 and resonance chamber 34. When the engine rotation speed is 2500rpm or less If the engine speed exceeds 2500rpm Here, V: Volume of the resonance chamber 34 S ₁ : Cross-sectional area of the tuning pipe 40 l ₁ : Length of the tuning pipe 40 S ₂ : Cross-sectional area of the tuning pipe 41 l ₂ : Length of the tuning pipe 41 C: Speed of sound In such a structure, the exhaust Gas flows in from the exhaust introduction pipe 32 as shown by the arrow, and enters the small hole 3.
8 and expands in the second expansion chamber 36 and first expansion chamber 35, and at that time, the sound pressure energy that enters from the inlet of the exhaust introduction pipe 32 is directly weakened in the resonance chamber 34, and is Since the resonant frequency is set, extremely good sound deadening characteristics can be obtained. Then, the exhaust gas is throttled by the flow path 39 and enters the second expansion chamber 36, where it expands again and the sound waves are further attenuated.The exhaust gas then passes through the punching separator 43 and enters the third expansion chamber 37. Here, the sound waves are also attenuated and then discharged to the outside from the exhaust outlet pipe 33. According to this structure, the resonance frequency of the resonance chamber 34 can be changed in two ways by opening and closing the tuning pipe 41 with the opening/closing valve 9, and furthermore, by providing a large number of tuning pipes and opening/closing valves, it is possible to change the resonance frequency of the resonance chamber 34 in two ways. Since the resonant frequency of the muffler can be freely set, a small-capacity muffler can exhibit extremely good silencing characteristics over a wide range of engine speeds, as shown in FIG. In addition, in the above figure, the on-off valve 9 is provided on the tuning pipe 41, but the tuning pipe 40
In this case, the resonant frequency when the engine speed is 2500 rpm or less is becomes. In short, according to the present invention, an expansion chamber, a resonance chamber,
An engine muffler comprising: an exhaust inlet pipe communicating with the expansion chamber; an exhaust outlet pipe communicating with the expansion chamber; and a tuning pipe communicating the expansion chamber with the resonance chamber. is an on-off valve inserted between the resonance chamber and the expansion chamber in parallel, and detects the engine rotation speed, and closes the on-off valve when the engine rotation speed is below the set value, and the engine rotation speed is adjusted to the above set value. By providing a valve opening/closing means that opens the above-mentioned opening/closing valve when the limit is exceeded,
The present invention is extremely useful industrially because it provides a high-performance, small, lightweight, and low-cost silencing device.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention;
Fig. 2 is an enlarged longitudinal cross-sectional view showing the on-off valve in Fig. 1, Fig. 3 is a characteristic diagram showing the relationship between engine speed and sound pressure level according to Fig. 1, and Fig. 4 shows the second embodiment thereof. The longitudinal sectional view shown in FIG. 5 is a characteristic diagram showing the relationship between the engine rotation speed and the pressing level according to FIG. 4. 1... Silencer main body, 2... Exhaust introduction pipe, 2a...
...Small hole, 3...Exhaust outlet pipe, 3a...Small hole, 4...
...Cavity, 5...First expansion chamber, 6...Second expansion chamber,
7...Flow path, 8...Flow path, 9...Opening/closing valve, 11...
...Return pipe, 12...Valve casing,
13... Valve cap, 14... Valve cone, 15... Valve shaft, 16... Spring cover, 17... Return spring, 18...
... Valve guide, 19 ... Opening, 20 ... Cable hinge, 21 ... Control cable, 2
2... Solenoid, 23... Control unit, 24... Rotation speed sensor, 31... Silencer body, 32... Exhaust inlet pipe, 33... Exhaust outlet pipe, 34... Resonance chamber, 35... First Expansion room, 36
...Second expansion room, 37...Third expansion room, 38...
Small hole, 39... Channel, 40... Tuning pipe, 41... Tuning pipe, 43... Punching metal separator.

Claims (1)

[Scope of utility model registration request] An engine having an expansion chamber, a resonance chamber, an exhaust introduction pipe communicating with the expansion chamber, an exhaust outlet pipe communicating with the expansion chamber, and a tuning pipe communicating the upward expansion chamber with the resonance chamber. In the silencer, an on-off valve inserted between the resonance chamber and the expansion chamber in parallel with the tuning pipe;
A silencer characterized by comprising a valve opening/closing means that detects the engine rotation speed, closes the on-off valve when the engine rotation speed is below a set value, and opens the on-off valve when the engine speed exceeds the set value. .