JP2003138931A - Exhaust gas purification device - Google Patents

Abstract

(57) [Problem] To provide an exhaust gas purification device capable of reducing high-frequency radiation sound over a wide area. SOLUTION: An exhaust gas purification device 10 provided with a two-layer case exhaust gas purification device case 11 composed of an inner case 12 and an outer case 13, wherein the exhaust gas purification device case is a reducer on the upstream side of the monolith carrier and a reducer on the downstream side A plurality of convex portions 15 or concave portions 16 are formed on at least one of the inner case 12 and the outer case 13 so as to have a space portion 17 between the inner and outer cases in at least one of the inner case 12 and the inner case 12. A plurality of holes 18 communicating with the exhaust gas flow path in the inner case 12 are formed, and the inner case 12 and the outer case 13 are slidably adhered to each other except at least a portion where the space 17 is formed. Exhaust gas purification device 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device capable of reducing radiated sound in a high frequency range, and particularly to a case (casing) structure thereof.

[0002]

2. Description of the Related Art A catalytic converter in which a converter case is made of a steel plate is known in order to improve warm-up characteristics and reduce weight.
The steel plate catalytic converter case is formed of a thin plate to reduce the heat capacity and improve the warm-up characteristics. However, when the plate is thinned, the rigidity is reduced and the high frequency exhaust pulsation easily causes vibration, which causes a problem of radiated sound. In order to reduce the radiated sound from the catalytic converter, as disclosed in Japanese Unexamined Patent Publication No. 9-310614, the case of the catalytic converter arranged under the vehicle floor is made into multiple tubes to reduce the sound by the sound insulation effect of each tube, or Alternatively, in the catalytic converter directly below the exhaust manifold, the case of the monolith carrier holding part may be made into a double-layered pipe (where the pipes are slidably adhered to each other) to reduce high-frequency noise by friction damping between the inner pipe and the outer pipe. It is valid.

[0003]

However, the conventional method for reducing the radiated sound in the catalytic converter case has the following problems. The conventional radiated sound reduction measure uses one kind of radiated sound reduction principle although the radiated sound reduction principle has a difference in sound insulation effect of pipes or frictional attenuation between pipes. Therefore, although it is effective to reduce the radiation sound in the region where the one kind of radiation noise reduction principle works effectively, it is not possible to reduce the radiation sound well over a wide frequency region outside the region. Further, the conventional measures against radiated sound have not taken measures against the high frequency radiated sound on the upstream side of the monolith carrier. On the upstream side of the monolith carrier of the catalytic converter, since the high frequency component of the exhaust pulsation is not yet taken by the monolith carrier, the exhaust pulsation has a strong high frequency component, and the high frequency radiated sound on the upstream side of the monolith carrier is particularly It becomes a problem. An object of the present invention is to provide an exhaust emission control device that can reduce high frequency radiation noise over a wide area. An object of the present invention is to provide an exhaust emission control device capable of reducing high-frequency radiation noise over a wide area and also reducing emission noise of exhaust pulsation containing a large amount of high-frequency components on the upstream side of a monolith carrier.

[0004]

The present invention which achieves the above object is as follows. (1) An exhaust purification device including a two-layer case exhaust purification device case including an inner case and an outer case, wherein the exhaust purification device case is at least one of a reducer on an upstream side and a reducer on a downstream side of the monolith carrier. In between, the space portion is formed between the inner and outer cases (between the two-layer case), the inner case is formed with a plurality of holes that communicate the space portion and the exhaust gas flow passage in the inner case, The exhaust gas purification device, wherein the inner case and the outer case are slidably adhered to each other except at least a portion where the space is formed. (2) The exhaust emission control device is a catalytic converter connected to an exhaust manifold of an internal combustion engine, and the space is formed between the inner and outer cases of a reducer on the upstream side of a monolith carrier of the catalytic converter. Exhaust purification device.

In the exhaust gas purifying apparatus of the above (1), since the inner case and the outer case are slidably attached to each other, vibration of the inner case caused by exhaust pulsation causes the inner case and the outer case to slide at the contact portion. Since it is weakened by the friction damping due to and transmitted to the outer case, the radiation sound can be reduced by the friction damping, and the space between the inner case and the outer case and the structure of the multiple holes in the inner case contribute to the space. And the multiple holes serve as a muffler similar to the Helmholtz resonator, reducing the radiated sound. Therefore, there are two types of radiated sound reduction effects that have different principles, and by varying the radiated sound reduction areas (adjustable by changing the volume of the space, the diameter of the holes, etc.), the effect is achieved over a wide range of high frequencies. Radiation noise can be reduced. In the exhaust emission control device of the above (2), since the space is formed between the inner and outer cases of the reducer on the upstream side of the monolith carrier of the catalytic converter, the exhaust pulsation radiates on the upstream side of the monolith carrier containing a large amount of high frequency components. The sound can be effectively reduced.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an exhaust emission control device of the present invention will be described with reference to FIGS. 1 and 2 show Embodiment 1 of the present invention, and FIGS. 3 and 4 show Embodiment 2 of the present invention. Components common to or similar to the first and second embodiments of the present invention are denoted by the same reference numerals in the first and second embodiments of the present invention.

First, the first and second embodiments of the present invention are common or similar (though not necessarily required).
The configuration will be described with reference to FIGS. 1 and 2. The exhaust gas purification device 10 of the present invention is an exhaust gas purification device provided in an exhaust system of an internal combustion engine of an automobile, and includes a catalytic converter or a diesel particulate purification device. When the exhaust purification device is a catalytic converter, if the catalytic converter is a catalyst converter directly below the exhaust manifold, a great effect of reducing radiation noise can be obtained. However, the catalytic converter may be arranged under the vehicle floor.

The exhaust gas purifying apparatus 10 of the present invention is provided with a two-layer case exhaust gas purifying apparatus case 11 consisting of an inner case 12 and an outer case 13 made of metal (for example, steel plate), and an air-permeable monolith carrier 14 inside. Holding Here, the two-layer case refers to a case in which the inner and outer cases are in close contact with each other except for a space portion described later, and is distinguished from a double case having a space between the inner and outer cases. The monolith carrier 14 has air permeability and is formed, for example, in a honeycomb shape. When the exhaust purification device case 11 is a catalytic converter, the monolith carrier 14 carries a catalyst, and when the exhaust purification device case 11 is a diesel particulate purification device, the monolith carrier 14 is a diesel particulate trap.

The inner case is formed so that the exhaust purification apparatus case 11 has a space 17 between the inner and outer cases on at least one of the upstream side (FIGS. 1 and 2) and the downstream side (FIGS. 3 and 4) of the monolith carrier. A plurality of convex portions 15 or concave portions 16 are formed on at least one of 12 and the outer case 13.
The space portion 17 formed by the plurality of convex portions 15 or the plurality of concave portions 16 is divided into a plurality of space portion elements 17a in the circumferential direction. The contact portions 20 between the inner case 12 and the outer case 13 are slidable with respect to each other in a region where the space 17 is present. Figure 1,
The example of FIG. 2 shows a case where the outer case 13 maintains a circular shape and a plurality of recesses 16 are formed in the inner case 12, but instead of this, the inner case 12 maintains a circular shape and the outer case Alternatively, a plurality of convex portions 15 may be formed.

A plurality of holes 18 are formed in the inner case 12 to connect the space 17 and the exhaust gas passage 19 in the inner case 12. The hole 18 and the space 17 form a kind of Helmholtz silencer. The holes 18 may have the same diameter or different diameters. By adjusting the diameter of the hole 18 and the volume of the space 17, or the hole 1
By making the diameters of 8 different from each other, the hole 18 and the space portion 1
It is possible to adjust the frequency of the sound to be silenced by the volumetric silencer composed of 7 and 7. The frequency range of the sound silenced by this volumetric silencer is wider and wider than that in the case of a single hole due to the plurality of holes 18 or the different diameters of the holes 18. Over, the radiated sound is reduced. However, compared to the case with a single hole,
The radiated sound reduction effect is weak, and a shallow radiated sound reduction effect is obtained over a wide frequency range.

The inner case 12 and the outer case 13 have at least a space 17 formed therein (the space 17 separates the inner case 12 and the outer case 13).
Except that they are slidably adhered to each other. The outer case 13 is manufactured by bending a flat plate and butt-welding the ends. The inner case 12 is fitted in the outer case 13, and may be partially welded or spot-welded. In the majority of the area, the expansion spring is biased and slidably adheres to the outer case 13. Therefore, when the inner case 12 vibrates, the inner case 12 and the outer case 13 frictionally slide at the contact portion 20 to absorb vibration energy.

In the exhaust manifold portion of the internal combustion engine, exhaust pulsation has a large amount of high frequency components (for example, 1 kHz).
The above is included, but since it is attenuated by the monolith carrier 14, the radiation sound of high frequency on the upstream side of the monolith carrier 14 becomes a particular problem. Therefore, the exhaust gas purification device 10 is a catalytic converter directly below the exhaust manifold connected to the exhaust manifold of the internal combustion engine,
In addition, when the space 17 is located upstream of the monolith carrier 14, the exhaust emission control device 10 of the present invention has a large radiation noise reducing action.

However, the exhaust emission control device 10 may be a catalytic converter arranged under the floor of the vehicle. In addition, the space portion 17 is a reducer 21 on the upstream side of the monolith carrier 14.
(The reducer on the upstream side expands in the exhaust flow direction)
It is not limited to the one formed between the inner and outer cases 12 and 13, and the inner and outer cases 12 of the reducer 22 on the downstream side of the monolith carrier 14 (the reducer on the downstream side has a reduced diameter in the exhaust flow direction). 13 may be formed between the inner and outer cases 12 and 13 of the reducer 21 on the upstream side of the monolith carrier 14 and between the inner and outer cases 12 and 13 of the reducer 22 on the downstream side of the monolith carrier 14. May be done.

Next, the operation of the components common to or similar to the first and second embodiments of the present invention will be described. In the exhaust emission control device 10 of the present invention, due to the slidable close contact structure between the inner case 12 and the outer case 13, vibration of the inner case 12 due to exhaust pulsation is generated at the contact portion 20 at the inner case 12.
The friction between the inner case 12 and the outer case 13 is weakened by the frictional damping due to the sliding between the outer case 13 and the outer case 13 and is transmitted to the outer case 13.
Due to the structure of the space 17 between and the plurality of holes 18 of the inner case 12, the space 17 and the plurality of holes 18 perform a silencing effect similar to a Helmholtz resonator, and the radiated sound is reduced. Therefore, there are two types of radiated sound reducing actions of the friction damping and the volumetric silencer which are different in principle, and by making the radiated sound reducing regions different (especially, the volume of the space portion 17, the diameter of the hole 18, etc.). The radiation noise reduction region of the volumetric silencer can be easily adjusted by changing), and the radiation noise can be effectively reduced over a wide high frequency region, for example, 1 to 10 kHz or more.

In the range of 1 kHz to 5 kHz, the friction damping is mainly effective for reducing the radiated sound, but at 5 kHz or higher, the space 17 and the hole 1 are formed.
The effect of reducing the radiated sound by No. 8 is increased, and the effect is almost the same as that of the radiated sound by friction damping. Therefore, the space part 1
When 7 is formed between the inner and outer cases 12 and 13 of the reducer 21 on the upstream side of the monolith carrier 14 of the catalytic converter, the radiated sound on the upstream side of the monolith carrier in which exhaust pulsation contains a large amount of high frequency region components is effective. Can be reduced. Further, the space portion 18 is formed in the reducers 21 and 22 having high rigidity of the outer case 13, so that the outer case 1
Radiated sound due to the vibration of 3 is reduced.

Next, the structure and operation of each embodiment of the present invention will be described. In the first embodiment of the present invention, as shown in FIGS. 1 and 2, the exhaust purification device 10 is a catalytic converter directly below the exhaust manifold of the internal combustion engine, and the space 17 is inside or outside the reducer 21 on the upstream side of the monolith carrier 14. It is formed between the cases 12 and 13. Recess 1 in inner case 12
6 is formed, and a space 17 is formed between the inner and outer cases 12, 13. The hole 18 is formed in the inner case 12 of the reducer 21 on the upstream side of the monolith carrier 14. With respect to the operation, since the muffler including the space 17 and the hole 18 is located on the upstream side of the monolith carrier 14, exhaust pulsation containing a large amount of high frequency components on the upstream side of the monolith carrier 14 can be effectively reduced.

In the second embodiment of the present invention, as shown in FIGS. 3 and 4, the exhaust purification device 10 is a catalytic converter directly below the exhaust manifold of the internal combustion engine, and the space 17 is a reducer on the downstream side of the monolith carrier 14. It is formed between 22 inner and outer cases 12 and 13. A convex portion 15 is formed on the outer case 13 so that a space 17 is formed between the inner and outer cases 12, 13.
Is formed. The hole 18 is formed in the inner case 12 of the reducer 22 on the downstream side of the monolith carrier 14. With respect to the operation, since the silencer including the space 17 and the hole 18 is located on the downstream side of the monolith carrier 14, even if a high frequency component remains in the exhaust pulsation on the downstream side of the monolith carrier 14, it is effective. It can be reduced.

[0018]

According to the exhaust emission control device of the first aspect, since there are two kinds of radiated sound reducing actions having different principles, the radiated sound can be effectively reduced over a wide high frequency range. According to the exhaust gas purifying apparatus of claim 2, since the space is formed between the inner and outer cases of the reducer on the upstream side of the monolith carrier of the catalytic converter, the exhaust pulsation is located on the upstream side of the monolith carrier containing a large amount of high frequency components. Radiated sound can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an exhaust emission control device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG.

FIG. 3 is a sectional view of an exhaust emission control device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view taken along the line A-A ′ of FIG.

[Explanation of symbols]

10 Exhaust gas purification device 11 Exhaust gas purifier case 12 inner case 13 outer case 14 Monolith carrier 15 convex 16 recess 17 Space Department 17a spatial element 18 holes 19 Exhaust gas flow path 20 Contact part 21 Reducer on the upstream side 22 Downstream reducer

Claims (2)

[Claims] 1. An exhaust gas purification device having a two-layered exhaust gas purification device case consisting of an inner case and an outer case made of steel plate, and holding an air-permeable monolith carrier inside, wherein said exhaust gas purification device case is said A plurality of protrusions or recesses are formed in at least one of the inner case and the outer case so as to have a space between the inner and outer cases in at least one of the reducer on the upstream side of the monolith carrier and the reducer on the downstream side. A plurality of holes are formed in the inner case to connect the space portion and the exhaust gas flow passage in the inner case, and the inner case and the outer case are mutually except at least a portion where the space portion is formed. Exhaust gas purification device that is slidably attached. 2. The exhaust emission control device is a catalytic converter connected to an exhaust manifold of an internal combustion engine, and the space portion is formed between inner and outer cases of a reducer upstream of a monolith carrier of the catalytic converter. The exhaust emission control device according to 1.