JP2012154251A - Muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler in which a sound pressure level of discharge sound can be lowered by cooling exhaust.SOLUTION: A thermoacoustic cooling device 10 is provided to a discharge pipe 3 through which the exhaust from an engine circulates. The thermoacoustic cooling device 10 includes a loop pipe 11 in which working gas is sealed, a thermoacoustic generation part 12A connected to the loop pipe 11 to generate pulsation by thermoacoustic oscillation in the working gas, and a heat pump 12B operated by generation of the pulsation. The thermoacoustic generation part 12A and the heat pump 12B are respectively provided with a heat storage part 14 and a cooling storage part 16, and have heat exchangers 13A, 15A in the high temperature side and heat exchangers 13B, 15B in the low temperature side positioned in both sides thereof. The heat exchanger 13A in the high temperature side is connected to the discharge pipe 3 at a first position in a flow direction of the exhaust, and the heat exchanger 15B in the low temperature side is connected to a second position in a downstream side of the first position. The heat exchanger 13B in the low temperature side and the heat exchanger 15A in the high temperature side are cooled by removing heat with atmosphere or engine cooling water.

Description

  The present invention relates to an automobile exhaust silencer.

Conventionally, as an automobile exhaust silencer, as shown in FIG. 2 of Patent Document 1, as its basic type, (a) extended type, (b), (b ′) extended resonant type, (c) resonant type, (D) Absorption type, (e) Interference type, and (f) Resistance type.
However, it is generally known that the sound pressure level of the exhaust sound can be reduced by lowering the temperature of the exhaust gas before the exhaust gas is released into the atmosphere from the outlet of the exhaust pipe.
Patent Document 2 describes a technique of a loop tube air column acoustic wave refrigerator using a thermoacoustic phenomenon.

Japanese Patent No. 3337556 Japanese Patent No. 3015786

  However, cooling the exhaust gas using power to lower the temperature of the exhaust gas increases the fuel consumption of the vehicle. In addition, the method of cooling the exhaust gas by air cooling using the wind when the automobile is running does not function efficiently for reducing the exhaust noise while the vehicle is stopped, and because of the heat exchange between the exhaust gas and the atmosphere. As a result, the volume of the cooling part increases and the volume of the exhaust system increases significantly.

  The present invention solves the above-described conventional problems, and can reduce the sound pressure level of the exhaust sound by efficiently cooling the exhaust gas itself with a simple structure and no dynamic mechanism. An object of the present invention is to provide an exhaust silencer that can be used.

  In order to solve the above-mentioned problem, an exhaust silencer of the invention according to claim 1 is provided in an exhaust pipe through which exhaust gas from an engine circulates to reduce exhaust noise, and is filled with working gas. A thermoacoustic cooling device having a loop-shaped pipe, a wave generating means for generating a wave due to thermoacoustic self-excited vibration in the working gas, and a heat pump that operates by the generation of the wave, the wave generating means and the heat pump Each having a stack and a high temperature side heat exchanger and a low temperature side heat exchanger located on both sides of the stack, and connecting the high temperature side heat exchanger of the wave generating means to the first part of the exhaust pipe in the flow direction of the exhaust gas In addition, the low temperature side heat exchanger of the heat pump is connected to the second portion of the exhaust pipe downstream of the first portion in the flow direction of the exhaust gas, and the low temperature side heat exchanger of the wave generating means and the high temperature of the heat pump are connected. The heat exchanger is heat-removed and cooled with air or engine cooling water, supplies the heat of the exhaust gas in the first part of the exhaust pipe to the high-temperature side heat exchanger of the wave generating means, and serves as the low-temperature side heat exchanger of the heat pump. The exhaust gas in the second part is cooled by the generated cold heat.

  According to the first aspect of the present invention, the temperature of the exhaust gas flowing in the exhaust pipe is efficiently reduced by the thermoacoustic cooling device having a simple structure wave generating means and a heat pump that does not have a dynamic mechanism. The sound pressure level can be lowered. For example, when the main muffler is provided on the downstream side of the second part of the exhaust pipe, the temperature of the exhaust gas flowing into the main muffler is reduced as compared with the conventional case, and the life of the main muffler is further extended.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the thermoacoustic cooling device has a flow direction of the exhaust gas rather than the catalyst device that purifies the exhaust gas connected to the exhaust pipe. It arrange | positions in the downstream of this, It is characterized by the above-mentioned.

  According to the second aspect of the present invention, since the thermoacoustic cooling device is disposed downstream of the catalyst device for purifying the exhaust gas in the flow direction of the exhaust gas, the exhaust gas exhausted from the engine is thermoacoustic. It is possible to prevent the catalyst device from reaching the catalyst device before being cooled by the cooling device and preventing the temperature of the catalyst device from rising when the engine is started.

  According to the present invention, it is possible to provide an exhaust silencer that can reduce the sound pressure level of exhaust sound by efficiently cooling the exhaust gas itself with a simple structure and no dynamic mechanism. .

1 is an overall schematic configuration diagram of an exhaust system including an exhaust silencer according to the present embodiment. It is a schematic block diagram of the thermoacoustic cooling device in FIG. (A) is AA arrow sectional drawing of the thermoacoustic generating part in FIG. 2, (b) is BB arrow sectional drawing of the heat pump in FIG. (A) is AA arrow sectional drawing of the modification of the thermoacoustic generating part in FIG. 2, (b) is BB arrow sectional drawing of the modification of the heat pump in FIG.

  Below, the whole outline | summary of the exhaust system containing the exhaust silencer 1 which concerns on embodiment of this invention is demonstrated. FIG. 1 is an overall schematic configuration diagram of an exhaust system including an exhaust silencer according to the present embodiment, FIG. 2 is a schematic configuration diagram of a thermoacoustic cooling device in FIG. 1, and FIG. 2 is a cross-sectional view taken along the line AA of the thermoacoustic generator in FIG. 2, and FIG. 2B is a cross-sectional view taken along the line BB of the heat pump in FIG.

  As shown in FIG. 1, the exhaust pipe 3 of the exhaust system is connected to an exhaust manifold (not shown) by fastening a flange with bolts, allows exhaust gas to flow through the catalyst device 5, and further downstream in an intermediate portion called a conventional sub-muffler 6. A thermoacoustic cooling device 10 is provided. A main muffler 7 is connected to the downstream side of the sub muffler 6 by fastening a flange with bolts.

The thermoacoustic cooling device 10 is mainly configured by connecting a thermoacoustic generator (wave generation means) 12A and a heat pump 12B with a loop pipe (loop-shaped pipe) 11. In the loop tube 11, an inert gas as a working gas, for example, a helium gas having a predetermined pressure is sealed.
The working gas may be an inert gas having another component, for example, nitrogen, argon, a mixed gas of helium and argon, or the like as described in Patent Document 2.

The thermoacoustic generator 12 </ b> A is provided in a portion (first portion) of the exhaust pipe 3 located on the downstream side of the catalyst device 5, and is a heat storage portion provided in the straight pipe portion 11 a (see FIG. 2) of the loop pipe 11. (Stack) 14 and a high temperature side heat exchanger 13A for exchanging heat of the exhaust gas between one end side of the heat storage unit 14 and a low temperature side for heat exchange between the other end side of the heat storage unit 14 and the outside air And a heat exchanger 13B.
The heat storage unit 14 has a thermal gradient between the high temperature side heat exchanger 13A and the low temperature side heat exchanger 13B, thereby converting thermal energy into acoustic energy, and thermoacoustic (wave) is generated by self-excitation. A traveling wave propagates from the straight tube portion 11a of FIG. 2 to the connecting tube portion 11b and the straight tube portion 11c in the direction indicated by the arrow 31 (see FIG. 2) from the high temperature side heat exchanger 13A side of the tube portion 11a. And it is transmitted to the cool storage part 16 of the heat pump 12B (refer FIG. 2).

  The heat pump 12B is provided in a portion (second portion) of the exhaust pipe 3 located downstream in the exhaust gas flow direction from the first portion, and the straight pipe portion 11c of the loop pipe 11 (see FIG. 2). The regenerator (stack) 16 provided in the above, the high-temperature side heat exchanger 15A for exchanging heat between one end of the regenerator 16 and the atmosphere, the other end of the regenerator 16 and the exhaust pipe 3 described above. And a low temperature side heat exchanger 15B for exchanging heat with the two parts. When the high temperature side heat exchanger 15A exchanges heat with the outside air, the cold storage unit 16 sandwiched between the high temperature side heat exchanger 15A and the low temperature side heat exchanger 15B has a thermal gradient. . The cold storage unit 16 converts the acoustic energy into heat energy and transports heat from the low temperature side heat exchanger 15B to the high temperature side heat exchanger 15A. The low temperature side heat exchanger 15B The heat of the exhaust gas is absorbed at the part 2. This endothermic function will be described later.

  The loop tube 11 of the thermoacoustic cooling device 10 of the present embodiment is basically composed of a stainless steel tube that is piped in a substantially rectangular shape except for the heat exchange function portion, and the heat storage portion of the thermoacoustic generator 12A. 14 and the heat storage unit 16 of the heat pump 12B are configured to store, for example, ceramics 25 and 26 (see FIGS. 3A and 3B) having a honeycomb structure with a cylindrical outer shape. And each is accommodated in the stainless steel pipe | tube which comprises the straight pipe parts 11a and 11c. The ceramics 25 and 26 have a large number of small parallel passages 25a and 26a (see FIGS. 3A and 3B) parallel to the axial direction of the straight tube portions 11a and 11c. The parallel passages 25a and 26a have a hydrodynamic passage diameter that is sufficiently smaller than the wavelength of the sound wave propagating through the working gas in the loop tube 11 as a medium. For example, it is a narrow passage of about one-third of the wavelength of a sound wave.

As shown in FIG. 3A, the high temperature side heat exchanger 13A of the thermoacoustic generator 12A is fixed to the outer peripheral side of the exhaust pipe 3 by close welding, for example, made of copper alloy. Cylindrical heat conduction member 21A, straight tube portion 11a on one end side of ceramic 25 (one end side of heat storage portion 14) and one end side thereof are joined with dissimilar metals, for example, a copper-shaped tube heat conduction member 21B, The heat exchange member 22 stored in the tubular heat conduction member 21B, and the heat conduction member 21C that connects the heat conduction member 21A and the heat conduction member 21B so as to be capable of conducting heat are included. The other end side of the tubular heat conducting member 21B is joined to the straight tube portion 11a with a different metal.
The heat exchanging member 22 is, for example, a structure in which a large number of thin metal plates are arranged at minute intervals, and is configured so that the acoustic wave of the working gas is transmitted to the small parallel passage 25a of the ceramic 25. The plurality of thin metal plates contacted with one end side of the ceramic 25 so that heat conduction to the ceramic 25 is possible.

As shown to (a) of FIG. 3, the low temperature side heat exchanger 13B of the thermoacoustic generating part 12A has its one end side on the straight tube part 11a on the other end side (the other end side of the heat storage part 14) of the ceramic 25. For example, the heat conductive member 23 is formed of a copper alloy and has a fin shape with a cooling fin, and a heat exchange member 24 stored in the heat conductive member 23. The heat conducting member 23 has a large number of cooling fins 23a in the circumferential direction on the outer peripheral side thereof, and is configured to increase the heat exchange surface area with the atmosphere by the cooling fins 23a. The other end side of the heat conducting member 23 is joined to the straight tube portion 11a by dissimilar metal.
The heat exchanging member 24 is, for example, a structure in which a large number of thin metal plates are arranged at minute intervals, and the acoustic wave of the working gas is transmitted to the small parallel passage 25a of the ceramic 25. A number of the thin metal plates thus brought into contact with the other end of the ceramic 25 are configured to conduct heat from the ceramic 25.

As shown in FIG. 3 (b), the high temperature side heat exchanger 15A of the heat pump 12B has one end side joined to the straight tube portion 11c on one end side of the ceramic 26 (one end side of the cold storage unit 16). For example, it is composed of a pipe-shaped heat conductive member 23 with a cooling fin made of a copper alloy and a heat exchange member 24 stored in the heat conductive member 23. The heat conducting member 23 has a large number of cooling fins 23a in the circumferential direction on the outer peripheral side thereof, and is configured to increase the heat exchange surface area with the atmosphere by the cooling fins 23a. The other end of the heat conducting member 23 is joined to the straight tube portion 11c with a different metal.
The heat exchange member 24 is, for example, a structure in which a large number of thin metal plates are arranged at a minute interval, and is configured so that the acoustic wave of the working gas is transmitted to the small parallel passage 26a of the ceramic 26. The multiple thin metal plates thus made contact with one end of the ceramic 26 so that heat can be conducted from the ceramic 26.

As shown in FIG. 3 (b), the low temperature side heat exchanger 15B of the heat pump 12B is fixed to the outer peripheral side of the exhaust pipe 3 by brazing or the like, for example, in a cylindrical shape made of copper alloy. The heat conducting member 21A, the straight tube portion 11c on the other end side of the ceramic 26 (the other end side of the cold storage unit 16) and the one end side thereof are joined with different metals, for example, a copper-shaped tube-shaped heat conducting member 21B, tube The heat exchange member 22 stored in the heat conduction member 21B having a shape, and the heat conduction member 21C that connects the heat conduction member 21A and the heat conduction member 21B so as to be capable of conducting heat are included. The other end side of the tubular heat conductive member 21B is joined to the straight tube portion 11c with a different metal.
The heat exchanging member 22 is, for example, a structure in which a large number of thin metal plates are arranged at a minute interval, and the acoustic wave of the working gas is transmitted to the small parallel passage 26a of the ceramic 26. A number of the thin metal plates thus brought into contact with the other end of the ceramic 26 are configured to conduct heat to the ceramic 26.

  According to this embodiment, like the technique described in FIG. 1 of Patent Document 2, the high temperature side heat exchanger 13A of the thermoacoustic generator 12A transmits the heat of the exhaust gas from the first part of the exhaust pipe 3. As a result, the temperature of the low-temperature side heat exchanger 13B is removed and cooled by heat exchange with the atmosphere. Therefore, the wall of the small parallel passage 25a of the ceramic 25 of the heat storage unit 14 is placed on the wall of the high-temperature side heat exchanger 13A. A steep temperature gradient is generated in the axial direction toward the low temperature side heat exchanger 13B. Since the lengths of the straight pipe portions 11a and 11c and the lengths of the connecting pipe portions 11b and 11d are set to predetermined values and the working gas pressure is appropriately set and sealed, a small parallel passage of the ceramic 25 The thermal energy given to the working gas in 25a is converted into pressure by the wall of the small parallel passage 25a of the ceramic 25, and self-excited vibration is generated from the fluctuating pressure, and the thermal energy is converted into acoustic energy. Then, a traveling wave and a standing wave sound wave (wave) traveling in the direction indicated by the arrow 31 in FIG. 2 are generated from the high temperature side heat exchanger 13A side of the small parallel passage 25a of the ceramic 25.

  The sound wave propagating through the loop tube 11 passes through the wall of the small parallel passage 26a of the ceramic 26 of the heat pump 12B. Here, when sound waves enter the small parallel passage 26a of the ceramic 26 from the high-temperature side heat exchanger 15A side, conversion from acoustic energy to thermal energy and acoustic energy to acoustic energy between the working gas and the wall of the parallel passage 26a. The conversion to energy is repeated. In the process, the ceramics 26 transports heat from the low-temperature side heat exchanger 15B side to the high-temperature side heat exchanger 15A side, and at the high-temperature side heat exchanger 15A of the heat pump 12B, heat is removed and cooled by heat exchange with the atmosphere. The As a result, the low temperature side heat exchanger 15B can absorb the heat of the exhaust gas from the second part of the exhaust pipe 3.

According to this embodiment, the thermoacoustic cooling device 10 can reduce the temperature of the exhaust gas in the process of converting the thermal energy of the exhaust gas into acoustic energy by the thermoacoustic generator 12A at the first part of the exhaust pipe 3. Furthermore, the temperature of the exhaust gas can be reduced even in the process of absorbing the heat energy of the exhaust gas by the heat pump 12B at the second portion of the exhaust pipe 3.
Thus, the thermoacoustic cooling device 10 effectively reduces the temperature of the exhaust gas in two stages at the first and second portions of the exhaust pipe 3 without requiring any power. Can be silenced. In addition, since the temperature of the exhaust gas reaching the main muffler 7 (see FIG. 1) can be expected to be lower than before, the temperature required for the heat-resistant material of the main muffler 7 and the required specifications for oxidation resistance can be reduced. Helps reduce costs.

  Further, since the thermoacoustic cooling device 10 is installed downstream of the catalyst device 5 provided in the exhaust pipe 3 in the flow direction of the exhaust gas, it prevents an early temperature rise of the catalyst device 5 at the time of engine start. And the exhaust gas purification function of the catalyst device 5 is not hindered.

  Furthermore, since the exhaust gas has less pressure loss than the case where the exhaust gas is silenced by passing through a member having many small-diameter holes in a conventional sub-muffler and repeating expansion, the overall back pressure of the exhaust system is reduced. It becomes possible to make it lower than before, and it may contribute to an increase in engine output.

<Modification>
Next, modified examples of the thermoacoustic generator 12A and the heat pump 12B will be described with reference to FIG. 4A is a cross-sectional view taken along the line AA of the modified example of the thermoacoustic generator in FIG. 2, and FIG. 4B is a cross-sectional view taken along the line BB of the modified example of the heat pump in FIG.
In the present modification, the loop pipe 11 (see FIG. 1) is formed of a thin stainless steel pipe, and therefore, as shown in FIGS. 3A and 3B of the embodiment, the high temperature side heat exchanger 13A, The low temperature side heat exchanger 13B, the high temperature side heat exchanger 15A, and the low temperature side heat exchanger 15B do not have a structure in which different kinds of metals are joined to the straight tube portion 11a and the straight tube portion 11c, but as shown in FIG. A structure in which the heat conducting members 21B and 23 are brazed and welded to the outer peripheral side of the portion 11a and the straight tube portion 11c may be employed.

  In the present embodiment and the modified example, the ceramics 25 having a honeycomb structure is used as the heat storage unit 14, but the present invention is not limited thereto. As described in Patent Document 2, a large number of stainless steel mesh thin plates are arranged at minute intervals. Or a sintered metal having a plurality of narrow passages. Similarly, the ceramics 26 having a honeycomb structure is used as the cold storage unit 16, but is not limited thereto. The shape is a mesh, sphere, plate, or plate rounded into a cylindrical shape using stainless steel, copper, lead, or the like, Various things such as a plate processed by etching can be used. However, it is only necessary that a large number of narrow passages capable of propagating acoustic waves are secured between the high temperature side heat exchanger 15A and the low temperature side heat exchanger 15B using the working gas as a medium.

  Furthermore, in the present embodiment and the modification, the low temperature side heat exchanger 13B and the high temperature side heat exchanger 15A are configured to radiate heat to the atmosphere, but the present invention is not limited thereto. It is good also as a structure which circulates engine cooling water on the outer peripheral side of the heat conductive member 23, and radiates heat. In this case, even when the vehicle is not in a running state or when the atmospheric temperature is high, sufficient heat dissipation from the cooling fins 23a can be expected, and the noise reduction effect by the thermoacoustic cooling device 10 is enhanced.

DESCRIPTION OF SYMBOLS 1 Exhaust silencer 3 Exhaust pipe 5 Catalytic device 6 Sub muffler 7 Main muffler 10 Thermoacoustic cooling device 11 Loop pipe (loop-like piping)
11a, 11c Straight tube portion 11b, 11d Connecting tube portion 12A Thermoacoustic generator (wave generating means)
12B Heat pump 13A High temperature side heat exchanger 13B Low temperature side heat exchanger 14 Heat storage part (stack)
15A High temperature side heat exchanger 15B Low temperature side heat exchanger 16 Cold storage unit (stack)
21A, 21B, 21C Heat conduction member 22 Heat exchange member 23 Heat conduction member 23a Cooling fin 24 Heat exchange member 25 Heat storage member (stack)
25a Parallel passage 26 Cold storage member (stack)
26a Parallel passage

Claims (2)

An exhaust silencer that is provided in an exhaust pipe through which exhaust gas from an engine flows and reduces exhaust noise,
A thermoacoustic cooling device having a loop-shaped pipe filled with a working gas, a wave generating means for generating a wave by thermoacoustic self-excited vibration in the working gas, and a heat pump that operates by the generation of the wave,
The wave generating means and the heat pump each have a stack and a high temperature side heat exchanger and a low temperature side heat exchanger located on both sides thereof,
Connecting the high temperature side heat exchanger of the wave generating means to a first portion of the exhaust pipe in the flow direction of the exhaust gas;
Connecting a low temperature side heat exchanger of the heat pump to a second part of the exhaust pipe downstream of the first part in the flow direction of the exhaust gas,
The low temperature side heat exchanger of the wave generating means and the high temperature side heat exchanger of the heat pump are cooled by removing heat with the atmosphere or engine cooling water,
The heat of the exhaust gas in the first part of the exhaust pipe is supplied to the high temperature side heat exchanger of the wave generating means, and the cold heat generated in the low temperature side heat exchanger of the heat pump causes the heat in the second part. An exhaust silencer for cooling exhaust gas.   2. The exhaust silencer according to claim 1, wherein the thermoacoustic cooling device is disposed downstream of the catalyst device that purifies the exhaust gas connected to the exhaust pipe in the flow direction of the exhaust gas.

Images