JPH018649Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) This invention relates to an improvement in an engine exhaust system, particularly a structure that reduces vibration and noise in a catalytic converter.

(Prior art) Conventionally, a catalytic converter has been installed in the middle of the exhaust pipe to purify engine exhaust gas, and in order to prevent the temperature of the catalytic converter from rising too high due to the gas sent to the converter. Japanese Patent Publication No. 47-10889 proposes an overtemperature protection device provided upstream of the converter to reduce the amount of combustibles remaining in the exhaust gas. This involves cutting the exhaust pipe in the middle, forming a small-diameter nozzle at the tip, and forming a number of holes on the outer periphery.An annular chamber that covers the outer periphery of this cut part is inserted into the exhaust pipe downstream from the cut part. connection,
The reaction of the combustible material is caused by the turbulent flow and reduced pressure caused by the gas passing through the holes and nozzles.

By the way, the flow rate of exhaust gas increases rapidly during acceleration, which causes the case of the catalytic converter to expand and generate noise due to vibration. In other words, due to a sudden increase in exhaust energy, this is transmitted to the catalytic converter and generates noise. Therefore, reducing this energy can prevent the generation of noise, but conventionally this problem has been solved. No attention was paid to this issue, and therefore no countermeasures were considered.

(Purpose of the invention) This invention was made to solve this problem, and was designed to absorb the sudden increase in energy of exhaust gas and prevent the generation of noise due to vibration of the catalytic converter. It is something.

(Structure of the invention) This invention is an exhaust system for an engine in which a catalytic converter is installed in the middle of the exhaust pipe. , and an outer shell extending in the axial direction of the exhaust pipe is provided, and the upstream and downstream ends of this outer shell are fixed to the exhaust pipe to form an expansion chamber with a required space, and the exhaust pipe inside the expansion chamber extends from the upstream end. A large number of communication ports are opened in the axial direction of the exhaust pipe to connect the inside of the exhaust pipe and the expansion chamber to the downstream end. The exhaust pipe in the expansion chamber may be constructed of an integral pipe, but a connecting pipe may be interposed and a communication port may be formed in the connecting pipe. In the latter case, it is preferable that only one end of the connecting pipe is fixed to the exhaust pipe, and the other end is slidably fitted to the exhaust pipe so that thermal expansion can be absorbed.

(Example) In Figs. 1 to 3, an exhaust pipe 2 whose one end is connected to an engine 1 has a catalytic converter 3 attached to its downstream end, and an exhaust pipe on the upstream side of the catalytic converter 3 has a gas expanded A section 4 is provided.
The exhaust pipes 2 in this gas expansion section 4 are separated from each other and connected by a connecting pipe 5, one end of which is fixed to the exhaust pipe 2, and the other end of which is connected to the exhaust pipe 5. 2 and is slidably fitted to form a part of the exhaust pipe. An outer shell 6 is disposed on the outer periphery of the connecting pipe 5, both ends of the outer shell 6 are fixed to the outer periphery of the exhaust pipe 2, and a required space is created between the inside of the outer shell 6 and the inner surfaces of the connecting pipe 5 and the exhaust pipe 2. An expansion chamber 60 is formed. The expansion chamber 60 and the inside of the exhaust pipe communicate with each other through a number of holes (communication ports) 50 formed in the connecting pipe 5. The reason why the connecting pipe 5 and the exhaust pipe 2 are made slidable is to prevent thermal stress from occurring due to a temperature difference between the outer shell 6 and the connecting pipe 5.

A covering part 7 is disposed on the outer periphery of the outer shell 6, and the covering part 7 is made up of a heat insulating material 70 sandwiched between an inner plate 72 and an outer plate 73, and its longitudinal end is attached to the outer periphery of the exhaust pipe 2. It is loosely fitted. Moreover, the cover part 7 is constructed into two parts along the longitudinal direction, and the mutual joint part is joined by making a flange 71 protrude laterally and sandwiching this flange part between outer plates. A flange 61 is partially formed in the center of the outer shell 6, and the flange 61 is sandwiched and fixed between the flanges 71 to connect the outer shell 6 and the cover 7, thereby reducing the distance between them. I try to keep it constant. In other words, movement of the covering part 7 in the longitudinal direction and the width direction is prevented. By covering the circumference of the exhaust pipe with the cover 7 in this manner, a soundproofing effect is exhibited and heat is maintained.

FIG. 4 shows another embodiment of this invention, in which an outer shell 6 is disposed around the outer periphery of a connecting pipe 5 having a large number of holes (communication ports) 50, and an expansion chamber 60 is placed inside the outer shell 6.
is formed and the outer shell 6 is covered by the covering part 7, which is similar to the above embodiment, but this structure differs in that the outer shell 6 is attached to the exhaust pipe 2 so that it can expand and contract. There is. That is, one end of the outer shell 6 is directly fixed to the outer periphery of the exhaust pipe 2, and the other end is connected to the flexible tube 62.
The other end is fixed to the outer periphery of the exhaust pipe 2. Therefore, in this structure, the connecting pipe 5 slides with respect to the exhaust pipe 2 at the fitting part due to a change in temperature, and the outer shell 6 also expands and contracts due to the difference in thermal expansion with the cover part 7 due to the expansion and contraction of the flexible tube 62. It is possible to prevent thermal stress from occurring. Note that the exhaust pipe 2 may be integrally continued inside the outer shell 6 without providing the connecting pipe 5, and the hole 50 may be formed therein.

(Effect of the invention) In the above configuration, exhaust gas from the engine 1 is sent to the catalytic converter 3 through the exhaust pipe 2, but if the exhaust gas increases rapidly during acceleration etc., the hole in the connecting pipe 5 Exhaust gas is released into the expansion chamber 60 through 50, thereby absorbing the energy of the exhaust gas and preventing a sudden increase in the exhaust gas being sent to the catalytic converter 3. The exhaust gas sent into the expansion chamber 60 passes through the same hole 50 to the connecting pipe 5.
However, the energy of the exhaust gas is reduced due to the buffering effect caused by the exhaust gas flowing in and out of the expansion chamber 60. Therefore, the exhaust gas sent to the catalytic converter 3 is returned to the catalytic converter 3 even during acceleration.
The case does not expand rapidly and therefore does not generate vibration or noise.

Note that there is a temperature difference between the connecting pipe 5, which forms part of the exhaust pipe, and the outer shell 6 on the outside thereof, since the degree of heating by the exhaust gas is different, but the connecting pipe 5
Since the exhaust pipe 2 and the exhaust pipe 2 are slidably fitted, the difference in thermal expansion is absorbed and no thermal stress is generated. Furthermore, in the configuration shown in FIG. 4, since the outer shell 6 is also attached so as to be expandable and retractable, the difference in thermal expansion between the outer shell 6 and the cover 7 is also absorbed. In addition, by providing the covering portion 7, noise caused by exhaust gas flowing in and out of the expansion chamber 60 is also absorbed, and the effect of keeping the exhaust gas appropriately warm is also exhibited.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an embodiment of this invention, Figure 2 is a sectional view showing an embodiment of this invention.
The figure is a partially cutaway plan view, FIG. 3 is a sectional view taken along the line -- in FIG. 1, and FIG. 4 is a sectional view showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Engine, 2... Exhaust pipe, 3... Catalytic converter, 4... Gas expansion part, 5... Connecting pipe, 6... Outer shell, 50... Hole (communication port), 60... Expansion chamber,

Claims (1)

[Scope of utility model registration request] In an engine exhaust system with a catalytic converter installed in the middle of the exhaust pipe, there is a catalytic converter on the outer periphery of the exhaust pipe upstream of the catalytic converter that has virtually no enlarged diameter section and has a diameter larger than that of the exhaust pipe and extends in the axial direction of the exhaust pipe. An outer shell is provided, and the upstream and downstream ends of this outer shell are fixed to an exhaust pipe to form an expansion chamber with a required space, and the exhaust pipe inside the expansion chamber is continuous from the upstream end to the downstream end, and the exhaust pipe is An engine exhaust system characterized in that a large number of communication ports communicating with an expansion chamber are opened in the axial direction of an exhaust pipe.