JPH0719039A - Exhaust device for engine - Google Patents

Abstract

PURPOSE:To improve durability and reliability of a device by constituting an ejector by arranging a secondary air introducing pipe coaxially in order from outside so as to introduce secondary air to a mixing cylinder from outside. CONSTITUTION:An ejector 12 to supply mixture to catalyst 18 by mixing exhaust gas with secondary air introduced from outside, is provided in a muffler body 2 connected to the exhaust side of an engine. A turing cylinder 13 introduces exhaust gas from the opening part 13a arranged by an offset to the shaft center, and turns this exhaust gas. A mixing cylinder 14 takes in the exhaust gas turned in the turning cylinder 13 and secondary air, and mixes these together, and supply it to the catalyst 18. A secondary air introducing pipe 5 is arranged coaxially in order from outside so as to introduce the secondary air to the mixing cylinder 14 from outside, and the ejector 12 is constituted. In this way, since a proper quantity of secondary air can be introduced efficiently by optimizing the ejector, the deterioration in engine output or excessive activation of catalytic reaction can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system of an engine for purifying exhaust gas by introducing secondary air to promote an oxidation reaction on a catalyst.

[0002]

2. Description of the Related Art Conventionally, there is known a technique for promoting secondary exhaust gas purification reaction in a post-treatment device such as a catalyst or a thermal reactor by introducing secondary air into the exhaust gas of an engine operated at a rich air-fuel ratio. As a means for supplying the secondary air to the exhaust system, there is one that positively supplies the auxiliary air by using auxiliary equipment such as a pump.

However, the amount of secondary air introduced, which is commensurate with the amount of exhaust gas discharged, must be properly controlled by a control means such as a throttle valve, which complicates the control and increases the size of the entire apparatus, resulting in cost reduction. There is a problem that causes soaring prices.

On the other hand, the structure in which the secondary air is introduced by utilizing the ejector effect at the time of discharging the exhaust gas has a simple structure, and the secondary air corresponding to the discharge amount of the exhaust gas can be introduced. Because it can, it is used in many engines. For example, U.S. Pat. No. 3,468,124 discloses a technique in which secondary air is taken into each cylinder by an ejector effect on the upstream side of an exhaust manifold.

[0005]

By the way, when the secondary air is taken in by the ejector effect, it is necessary to set the specifications of the ejector in consideration of the displacement of the engine. Inadequate specifications for the secondary air will not be introduced efficiently. Further, as described in the above-mentioned prior art, an ejector is provided on the upstream side of the exhaust manifold, and a silencer is provided downstream of this ejector to reduce exhaust noise. The sufficient ejector effect cannot be obtained.

In this case, if a sufficient ejector effect is not obtained and an appropriate secondary air is not supplied, not only the suction noise of the secondary air increases but also a pulsating wave is generated in an extreme case. There is a risk that the exhaust gas will be released into the atmosphere by backflowing from the next air introduction pipe.

Further, when the amount of secondary air introduced is small, the engine output is lowered, and when excessive secondary air is introduced, the catalytic reaction is excessively activated and the temperature rises sharply. In addition to the fact that the muffler body is heated and deteriorates in durability due to oxidative deterioration, the temperature of the exhaust gas from the muffler rises, and strict attention to safety is required.

The present invention has been made in view of the above circumstances, and enhances the ejector effect to efficiently supply secondary air,
In addition, the exhaust gas temperature is lowered by suppressing the temperature rise in the vicinity of the catalyst part on the surface of the muffler body, and durability, reliability, and
It is an object of the present invention to provide an engine exhaust system that can improve safety.

[0009]

According to a first aspect of the present invention, an ejector is provided in a muffler body connected to an exhaust side of an engine for mixing exhaust gas and secondary air introduced from the outside and supplying the mixture to a catalyst. An exhaust system for an engine, in which exhaust gas is introduced from an opening provided offset to the center of the shaft,
A swirl cylinder for swirling this exhaust gas, and the exhaust gas swirled by the swirl cylinder and the secondary air are mixed in,
The ejector is configured by coaxially arranging a mixing cylinder for supplying to the catalyst and a secondary air introducing pipe for introducing secondary air into the mixing cylinder from the outside in order.

In a second aspect based on the first aspect, the secondary air introducing pipe is penetrated through one end of the swirl cylinder to expose the secondary air outflow side opening end to the inside of the swirl cylinder. , The other end of the swirling cylinder penetrates the mixing cylinder, the exhaust gas inflow side opening end of the mixing cylinder, one end part that penetrates the secondary air introduction pipe of the swirling cylinder, or It is arranged on either side of the other end of the swirling cylinder that penetrates the mixing cylinder.

In a third aspect based on the first aspect, the secondary air outflow side opening end of the secondary air introducing pipe and the exhaust gas inflow side opening end of the mixing cylinder are arranged so as to overlap each other. Is.

A fourth aspect of the present invention is an engine exhaust system having an ejector in a muffler body connected to the exhaust side of the engine, which mixes exhaust gas and secondary air introduced from the outside and supplies it to a catalyst. Exhaust gas is introduced from an opening provided offset from the axis center, and a swirl cylinder for swirling this exhaust gas, and the exhaust gas swirled by the swirl cylinder and the secondary air are taken in and mixed. Then, a mixing cylinder for supplying to the catalyst and a secondary air introduction pipe for introducing secondary air from the outside to the mixing cylinder are coaxially arranged in order from the outside, and one end of the swirling cylinder is arranged. Part of the swirling cylinder through the secondary air introducing pipe to face the inside of the swirling cylinder, and the other end of the swirling cylinder penetrates the mixing cylinder to open the exhaust gas inflow side opening. The end of the secondary air introducing pipe is The air outflow side opening end is overlapped with the exhaust gas inflow side opening end of the mixing cylinder and the secondary air outflow side opening end of the secondary air introducing pipe. The ejector is arranged on either side of one end that penetrates the next air introduction pipe or the other end that penetrates the mixing cylinder of the swirling cylinder.

A fifth aspect of the present invention is an exhaust system for an engine, comprising a muffler body connected to the exhaust side of the engine, and an ejector for mixing exhaust gas and secondary air introduced from the outside and supplying the mixed catalyst to a catalyst. And a muffler chamber that expands the exhaust gas from the engine to reduce exhaust noise, an ejector chamber that accommodates the ejector that mixes the exhaust gas that has passed through the muffler chamber with secondary air introduced from the outside, and the ejector. Upstream of a catalyst chamber that adiabatically holds the catalyst that purifies exhaust gas from the chamber, and an exhaust chamber that swirls the exhaust gas purified in the catalyst chamber in the radial direction of the muffler body and discharges the exhaust gas to the outside. They are arranged in order from the side.

In a sixth aspect based on the fifth aspect, the ejector chamber is provided with a passage for swirling the exhaust gas from the muffling chamber and guiding it into the ejector.

[0015]

In the first aspect of the invention, when engine exhaust gas is introduced into the muffler body, the exhaust gas passes through the opening of the swivel cylinder of the ejector provided offset from the axial center, and the inside of the swirl cylinder To turn. Then, the swirled exhaust gas is mixed with the secondary air taken from the outside through the secondary air introduction pipe and supplied to the catalyst, and further purified by the catalyst and discharged.

According to a second aspect of the invention, in the ejector of the first aspect of the invention, the secondary air introducing pipe is penetrated through one end of the swirling cylinder to expose the open end of the secondary air outlet side to the inside of the swirling cylinder. The mixing cylinder is passed through the other end of the swirling cylinder, and the exhaust gas inflow side opening end of the mixing cylinder is connected to the one end of the swirling cylinder through the secondary air introduction pipe, or the mixing cylinder of the swirling cylinder is connected. The exhaust gas swirled by the swirling cylinder and the secondary air taken in from the secondary air introduction pipe, which are arranged on either side of the other end portion that penetrates, are mixed inside the mixture and supplied to the catalyst.

In a third aspect of the invention, in the ejector of the first aspect of the invention, the secondary air outflow side opening end of the secondary air introducing pipe and the exhaust gas inflow side opening end of the mixing cylinder are arranged so as to overlap each other. The swirled exhaust gas is taken into the inside of the mixing cylinder through the gap in the overlapping portion.

In the fourth invention, when the exhaust gas of the engine is introduced into the main body of the muffler, the exhaust gas passes through the opening of the swivel cylinder of the ejector provided offset with respect to the shaft center, and the inside of the swirl cylinder is passed through. To turn. The swirled exhaust gas is taken into the mixture through the gap between the mixing cylinder inside the swirling cylinder and the secondary air introducing pipe, and the secondary air taken in through the secondary air introducing pipe is introduced. It is mixed and supplied to the catalyst, further purified by this catalyst and discharged.

In the fifth aspect of the invention, the exhaust gas of the engine is
First, exhaust noise is reduced by expanding in the muffler chamber inside the muffler body, then mixed with secondary air introduced from the outside in the ejector chamber and introduced into the catalyst chamber holding the catalyst adiabatically for purification. It Then, the exhaust gas purified in this catalyst chamber is swirled in the radial direction of the muffler body in the exhaust chamber and is discharged to the outside.

In a sixth aspect based on the fifth aspect, the exhaust gas introduced from the muffling chamber into the ejector chamber is swirled, guided into the ejector, and mixed with secondary air.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. The drawings show one embodiment of the present invention. FIG. 1 is a vertical cross-sectional view of an exhaust system, FIG. 2 is an external view of the exhaust system, FIG. 3 is a cross-sectional view of an exhaust gas introducing part, and FIG. 4 is an exhaust gas introducing part. Longitudinal section,
5 is a cross-sectional view of the ejector, FIG. 6 is a cross-sectional view of the immediate downstream side of the catalyst, FIG. 7 is a cross-sectional view of the gas outlet portion, FIG. 8 is an explanatory view showing an equivalent model of the ejector, and FIG. 9 is a diagram of the ejector inlet. FIG. 10 is an explanatory view showing the arrangement, FIG. 10 is an explanatory view showing the relationship between the flow velocity and throttle resistance, and the passage area of each part, and FIG. 11 is an explanation showing the relationship between the passage area between the swirling cylinder and the mixing cylinder and the amount of secondary air. Figure, Figure 1
2 is an explanatory view showing the relationship between the exhaust gas inflow side opening end position of the mixing cylinder and the secondary air amount, FIG. 13 is an explanatory view of an ejector in which the exhaust gas inflow side opening end position of the mixing cylinder is changed, and FIG. FIG. 15 is an explanatory diagram showing the relationship between the overlap amount of the secondary air introducing pipe and the mixing cylinder and the secondary air amount, and FIG. 15 is the relationship between the passage area of the overlapping portion of the secondary air introducing pipe and the mixing cylinder and the secondary air amount. FIG.

In FIG. 2, reference numeral 1 is an exhaust device,
A manifold pipe 3 extends from an upper side surface of a cylindrical muffler body 2 and is connected to an exhaust port of a general-purpose engine or the like (not shown) via a flange 4 at an inlet portion of the manifold pipe 3.

A secondary air introducing pipe 5 for taking in secondary air to an ejector 12 which will be described later is projected at the center of the upper end of the muffler main body 2, and the muffler main body 2
An exhaust port 6 opened in the circumferential direction at the lower end of the exhaust gas to release exhaust gas purified by a catalyst 18 described later to the atmosphere.
Is provided.

The muffler body 2 is, as shown in FIG.
The cup-shaped outer cylinders 2a and 2b are formed by facing each other and joining their peripheral edges, and an expansion chamber 7 and an ejector chamber 8 as a sound deadening chamber are sequentially provided in an upper space formed by the outer cylinder 2a. The catalyst chamber 9 and the exhaust chamber 10 are sequentially provided in the lower space formed by the outer cylinder 2b.

The secondary air introducing pipe 5 is axially inserted into the expansion chamber 7 and extends into the ejector chamber 8, and the manifold pipe 3 extends from the radial direction, as shown in FIG. As shown in FIG. 3 which is a cross section taken along the line AA (longitudinal cross section of the exhaust gas introduction part) and FIG. 4 which is a cross section taken along the line C-C of FIG. 3 (transverse cross section of the exhaust gas introduction part), Is abutted and joined to the inner wall of the outer cylinder 2a. A hole 3a for discharging exhaust gas into the expansion chamber 7 is formed in a radial direction at a portion of the manifold pipe 3 facing the expansion chamber 7, and the secondary air introduction pipe 5 is provided with the hole 3a. A hole 3b to be inserted is formed.

Further, the ejector chamber 8 is provided with a BB line in FIG.
As shown in FIG. 1 which is a line cross section (longitudinal cross section of the exhaust device 1), the ejector outer cylinder 11 separates the swirl cylinder 1 for swirling exhaust gas into the ejector outer cylinder 11.
3, and a mixing cylinder 1 for mixing exhaust gas and secondary air
An ejector 12 in which 4 and the secondary air introduction pipe 5 for supplying secondary air to the mixing cylinder 14 are arranged concentrically in order from the outside is housed.

The ejector outer cylinder 11 is formed into a substantially cup shape having a predetermined gap with respect to the inner diameter of the outer cylinder 2a, and has a cylindrical portion fitted to the inner wall of the outer cylinder 2a at the lower part. The flanges on the periphery of the cylindrical portion are the outer cylinders 2a, 2b
The expansion chamber 7 and the catalyst chamber 9 are sandwiched between the peripheral chambers facing each other.
It forms the boundary with.

Further, the ejector outer cylinder 11 has a structure shown in FIG.
5, which is a cross-sectional view (cross-section of the ejector) taken along line D-D of FIG. 5, a part of the cylindrical surface having a predetermined gap with respect to the inner diameter of the outer cylinder 2a is brought into contact with the inner wall of the outer cylinder 2a. A protrusion is formed, and an exhaust gas inlet 11a communicating with the expansion chamber 7 is formed on a side wall extending from the protrusion to the cylindrical surface.
Is opened.

Further, as shown in FIG. 1, the swivel cylinder 13 is formed in a substantially cup shape and has a flange, and the secondary air introducing pipe 5 is penetrated and fixed at the center of the end surface of the cup shape. And the ejector outer cylinder 1 around the end face.
The end faces of No. 1 are joined. Furthermore, the mixing cylinder 14
Has a flange at the lower open end of the cylinder, and this flange and the flange of the swivel cylinder 13 are overlapped with each other and are joined to a step plane portion of the ejector outer cylinder 11 from the upper cylinder to the lower cylinder. There is.

The secondary air outlet side opening end of the secondary air introducing pipe 5 is slightly overlapped with the exhaust gas inlet side opening end of the mixing cylinder 14 having a diameter larger than that of the secondary air introducing pipe 5. The mixing cylinder 14, the swirl cylinder 13, and the cylindrical portion of the ejector outer cylinder 11 are coaxial with each other with respect to the secondary air introduction pipe 5 arranged at the axial center of the muffler body 2. Is arranged.

As shown in FIG. 5, the swirl cylinder 13 has a passage 15 formed between the ejector outer cylinder 11 and the swirl cylinder 13 and a space between the swirl cylinder 13 and the mixing cylinder 14. Opening 13 communicating with a passage 16 formed in
a is provided as an ejector inlet offset with respect to the axis center. Specifically, a part of the cylindrical side wall of the revolving cylinder 13 is cut in a shape with an H-shaped sideways, and one piece is bent outward in the tangential direction of the cylindrical surface, and the other is bent inward so that the opening 13a is formed. Has been formed.

Here, the basic constituent elements of the ejector 12 for efficiently introducing the secondary air will be described. An appropriate amount of secondary air introduced into the ejector 12 is 10% to 40% of the engine displacement per unit time.
It has been experimentally confirmed that the above is a proper amount, and as shown in FIG. 10, if the passage area of each part is too small, it becomes throttling resistance of the exhaust gas, and if too large, the flow velocity of the exhaust gas decreases. Therefore, the ejector 12 is in the optimum range with respect to the contradictory factors of the flow velocity and the resistance, and the specifications of the following parts are determined so that the secondary air can be introduced most efficiently.

(A) When the opening 13a of the swirl cylinder 13 which is the ejector inlet is equivalently expressed by the diameter d1 and the area S1, if the inlet area S1 is too small, it becomes throttle resistance of the exhaust gas, and if it is too large, the exhaust gas is exhausted. Gas flow velocity is reduced and swirl cylinder 1
The degree of swirl in the passage 16 between the No. 3 and the mixing cylinder 14 decreases.

When the ejector inlet area S1 is within the range of the following equation (1) with respect to the engine piston area S0 (piston diameter D0), the ejector inlet area S1 is in the optimum range shown in FIG. The area of is equivalently set in this range.

0.05S0 <S1 <0.13S0 (1) (0.2D0 <d1 <0.35D0) (b) The offset amount δ1 of the ejector inlet with respect to the center of the ejector axis is an important factor that causes a swirling flow. Therefore, when the ejector inlet diameter d1 is set to 1/2, the swirling flow can be generated most smoothly, and the offset amount δ1 from the equation (1) is within the range of the following equation (2). Is set.

0.1D0 <δ1 (= d1 / 2) <0.18D0 (2) Further, the position δ2 of the exhaust gas inflow side opening end of the mixing cylinder 14 with respect to the ejector inlet is set to δ2> d1 / 2. . That is, by not including the axial position of the exhaust gas inflow portion of the mixing cylinder 14 in the ejector inlet opening, the exhaust gas that has flowed into the ejector is surely along the wall surface of the swirl cylinder 13, and the swirl flow is effectively generated. Let it happen.

(C) The swirling speed is determined by the size of the sectional area S2 of the passage 16 between the swirling cylinder 13 and the mixing cylinder 14. When the passage 15 is narrow, the flow velocity of the exhaust gas becomes large, but it becomes exhaust resistance and the engine output decreases.

It has been experimentally confirmed that this cross-sectional area S2 is in the vicinity of the maximum secondary air amount shown by the broken line in FIG. 11 when it is within the range of the following formula (3) with respect to the piston area S0 of the engine. Since the offset amount δ1 in the previous section is set to d1 / 2, the diameter d2 of the swivel cylinder 13 is d2≈2d1.
Therefore, the diameter d3 of the mixing cylinder 14 is set.

0.15S0 <S2 <O. 38S0 (3) (0.4D0 <d2 (≈2d1) <0.7D0 0.3D0 <d3 <0.55D0) (d) The exhaust gas inflow side end of the mixing cylinder 14 and the swirling cylinder 13
If the band-shaped area S3 formed by the gap δ3 with the end portion of the secondary air introduction pipe 5 on the side is small, it causes throttle resistance and the engine output decreases. This strip-shaped area S3 is
When it is within the range of the formula (4), the secondary air amount can be introduced efficiently.

0.05S0 <S3 <0.13S0 (4) The gap δ3 within the range of the formula (4) is such that the position of the exhaust gas inflow side end of the mixing cylinder 14 is the secondary air introduction pipe 5. Although it is on the side of the penetrating end and has the largest secondary air amount as shown in FIG. 12, the secondary air amount can be increased next even at the position of the gap δ3 ′. Therefore, as shown in FIG. 13, the ejector 12 may be configured by setting the exhaust gas inflow side end position of the mixing cylinder 14 to the opposite end side (gap δ3 ′).

(E) The overlap amount δ4 between the secondary air outflow side opening end of the secondary air introducing pipe 5 and the exhaust gas inflow side opening end of the mixing cylinder 14 determines the direction of the exhaust gas flow. When the overlap is provided, as shown in FIG. 14, the amount of secondary air rapidly increases. Therefore, it is sufficient if δ4> 0, that is, if there is an overlap with a predetermined value or less.

(F) If the area S4 of the annular gap caused by the overlap is small, it causes throttling resistance, leading to a decrease in engine output, and if it is too large, the flow velocity decreases.
If the area S4 is smaller than the passage area of the manifold pipe 3, the output is reduced, and if it is large, the negative pressure generated is reduced.

Here, since the passage area of the manifold pipe 3 is usually made equivalent to the ejector inlet area S1,
Experimentally, the following equation (5) is established.

0.65S1 <S4 <1.7S1 (5) Therefore, for the piston area S0 of the engine, from the equation (1), 0.65 × 0.05S0 <S4 <1.7 × 0. 13S0 That is, the following expression (6) is established.

0.03S0 <S4 <0.22S0 (6) (g) If the opening area S5 of the secondary air introducing pipe 5 is small, the amount of secondary air introduced is small. Therefore, when the range of the area S5 (the diameter d4 of the secondary air introduction pipe 5) is set within the range of the following formula (7), the mixing cylinder 14 and the secondary air set under the condition of the above formula (6) are set. It has been experimentally confirmed that the secondary air amount is close to the maximum value shown by the broken line in FIG. 15 with respect to the area S4 of the annular gap in the overlapping portion of the introduction pipe 5.

0.0055S0 <S5 <0.07S0 (7) (0.07D0 <d4 <0.26D0) The ejector 12 has the specifications determined in the above (a) to (g).
By configuring the above, it is possible to obtain an optimum amount of secondary air and prevent the engine output from decreasing.

On the other hand, as shown in FIG. 1, in the catalyst chamber 9, a catalyst (oxidation catalyst) 18 having a small flow path resistance is housed and held in a catalyst holder 17, and the catalyst 18 has a downstream side. In addition, a partition plate 19 having a plurality of vent holes 19a formed therein is joined to the inner wall of the outer cylinder 2b to form a boundary with the exhaust chamber 10. Although the partition plate 19 lowers the exhaust gas temperature after the exhaust gas reacts with the catalyst 18, the partition plate 19 need not have a strict condition of heat resistance.

The catalyst holder 17 has a flange extending from a housing portion for housing the catalyst 18, and this flange is formed at the opposite peripheral edge portions of the outer cylinders 2a and 2b together with the flange of the ejector outer cylinder 11. The storage unit is held between the outer cylinder 2b and a predetermined gap and is suspended in the catalyst chamber 9. That is, the catalyst 18 is connected to the muffler body 2
Is adiabatically retained, so that the reaction heat generated in the catalyst 18 is adiabatically insulated and the outer cylinder 2b is not locally heated.

Further, in the exhaust chamber 10, a partition plate 22 stands up between an upper plate 20 having its periphery joined to the inner wall of the outer cylinder 2b and a bottom plate 21 having its periphery joined to the inner wall of the bottom of the outer cylinder 2b. It is arranged to form the exhaust passage 10a. This exhaust passage 10a is a sectional view taken along the line FF of FIG. 1 (a transverse section immediately downstream of the catalyst) and a sectional view taken along a line GG of FIG. 1 (the transverse cross section of the gas outlet portion). As shown in
When viewed from the catalyst chamber 9 side, it is formed in a substantially inverted C shape to reach the cutout portion of the outer cylinder 2b, and the exhaust port plate 23 is joined to this cutout portion to form the exhaust port 6. It has become.

Next, the operation of the embodiment having the above construction will be described.

When the engine is started, the exhaust gas discharged from the engine is guided from the manifold pipe 3 into the muffler body 2, and the holes 3 bored in the manifold pipe 3 are introduced.
a, 3b are discharged into the expansion chamber 7 and expanded (expanded),
Exhaust noise is reduced.

Next, as shown in FIG. 5, the exhaust gas in the expansion chamber 7 is introduced into the passage 15 between the ejector outer cylinder 11 and the swirl cylinder 13 from the exhaust gas inlet 11a of the ejector outer cylinder 11 and swirls. Then, it is introduced into the turning cylinder 13 through the opening 13a of the turning cylinder 13. At this time, since the opening 13a is offset with respect to the axis center of the swivel cylinder 13,
The exhaust gas introduced into the swirl cylinder 13 swirls in a passage 16 between the swirl cylinder 13 and the mixing cylinder 14 while increasing the flow velocity.

Further, the exhaust gas swirled in the passage 16 in the swirling cylinder 13 is mixed through the annular gap formed between the opening end of the mixing cylinder 14 and the opening end of the secondary air introducing pipe 5 into the mixing cylinder 1
4 Invades inside. As a result, the flow velocity of the exhaust gas is further increased and a negative pressure is generated, the fresh air (secondary air) outside is sucked from the secondary air introduction pipe 5, and the exhaust gas and the secondary air are sucked in the mixing cylinder 14. Are mixed and discharged into the catalyst chamber 9, and the catalyst 18 purifies toxic HC and CO.

In this case, since the specifications are set so that the ejector 12 can efficiently introduce the secondary air, the output of the engine is not lowered, and the expansion chamber 7 having a large resistance is used as the ejector. Since it is arranged on the upstream side of 12, the engine noise can be efficiently reduced, the exhaust pressure of the engine can be effectively utilized to further enhance the ejector effect, and an optimum amount of the secondary air can be generated. The durability and the reliability of the muffler body 2 can be significantly improved without supplying the catalyst 18 with an excessive oxidation reaction.

Further, since the catalyst 18 is adiabatically retained inside the muffler body 2, heat damage due to the reaction heat of the catalyst 18 is prevented. That is, the temperature rise in the vicinity of the catalyst chamber 9 on the surface of the muffler body 2 is suppressed, the surface temperature of the muffler body 2 is made uniform, and the entire muffler is kept at a relatively low temperature.

Thereafter, the purified exhaust gas is separated by the partition plate 19
The gas is discharged from the exhaust port 6 into the atmosphere by flowing out from the vent hole 19a formed in the exhaust gas to the exhaust chamber 10 formed in the downstream of the muffler body 2, passing through the exhaust passage 10a, and swirling in the radial direction. In this case, since the exhaust gas is swirled in the exhaust passage 10a having a long passage length, the exhaust heat is transferred to the surface of the muffler body 2, the exhaust gas temperature is lowered, and the muffler outlet temperature can be lowered, which is safe. Can be increased.

[0057]

As described above, according to the present invention, it is possible to optimize the ejector and efficiently introduce an appropriate amount of secondary air, and prevent engine output reduction and excessive activation of catalytic reaction. can do. Further, the exhaust gas temperature can be lowered by suppressing the temperature rise in the vicinity of the catalyst portion on the surface of the muffler body. Therefore, it is possible to improve the durability and reliability of the device, and further, it is possible to obtain excellent effects such as the safety.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an exhaust device.

[Figure 2] External view of the exhaust system

[Fig. 3] Cross-section of exhaust gas introduction part

FIG. 4 is a vertical cross-sectional view of an exhaust gas introduction section.

FIG. 5 is a cross section of the ejector.

FIG. 6 is a cross-sectional view immediately downstream of the catalyst.

FIG. 7 is a cross-sectional view of the gas outlet section.

FIG. 8 is an explanatory diagram showing an equivalent model of an ejector.

FIG. 9 is an explanatory view showing an arrangement of ejector inlets.

FIG. 10 is an explanation showing the relationship between the flow velocity and throttle resistance and the passage area of each part.

FIG. 11 is an explanatory diagram showing the relationship between the passage area between the swirling cylinder and the mixing cylinder and the amount of secondary air.

FIG. 12 is an explanatory diagram showing the relationship between the exhaust gas inflow side opening end position of the mixing cylinder and the amount of secondary air.

FIG. 13 is an explanatory diagram of an ejector in which the exhaust gas inflow side opening end position of the mixing cylinder is changed.

FIG. 14 is an explanatory diagram showing the relationship between the amount of overlap of the secondary air introduction pipe and the mixing cylinder and the amount of secondary air.

FIG. 15 is an explanatory view showing the relationship between the passage area of the overlapping portion of the secondary air introducing pipe and the mixing cylinder and the amount of secondary air.

[Explanation of symbols]

 2 Muffler body 5 Secondary air introduction pipe 7 Expansion chamber (silence chamber) 8 Ejector chamber 9 Catalyst chamber 10 Exhaust chamber 12 Ejector 13 Swirling cylinder 13a Opening 14 Mixing cylinder 15 Passage 18 Catalyst

Claims (6)

[Claims] 1. A muffler body connected to an exhaust side of an engine
An engine exhaust system equipped with an ejector (12) inside (2) that mixes exhaust gas with secondary air introduced from the outside and supplies it to the catalyst (18). The exhaust gas is introduced from the opening (13a) provided in the swirl cylinder (13) for swirling the exhaust gas, and the exhaust gas swirled by the swirl cylinder (13) and the secondary air are taken in and mixed. The mixing cylinder (1 for supplying to the catalyst (18).
4), and the ejector (12) is configured by coaxially arranging a secondary air introduction pipe (5) for introducing secondary air into the mixing cylinder (14) from the outside in order from the outside. A characteristic engine exhaust system. 2. The secondary air introduction pipe (5) is passed through one end of the swirl cylinder (13) to expose the secondary air outflow side opening end to the inside of the swirl cylinder (13), The swivel tube (1
3) Penetrating the mixing cylinder (14) to the other end of the mixing cylinder (14), the exhaust gas inflow side opening end of the mixing cylinder (14) is
(13) Arranged on either side of one end that penetrates the secondary air introduction pipe (5) or the other end that penetrates the mixing cylinder (14) of the swirling cylinder (13). The exhaust system for an engine according to claim 1, wherein: 3. The secondary air outflow side opening end of the secondary air introducing pipe (5) and the exhaust gas inflow side opening end of the mixing cylinder (14) are arranged so as to overlap each other. The exhaust system for an engine according to claim 1. 4. A muffler body connected to an exhaust side of an engine
An engine exhaust system equipped with an ejector (12) inside (2) that mixes exhaust gas with secondary air introduced from the outside and supplies it to the catalyst (18). The exhaust gas is introduced from the opening (13a) provided in the swirl cylinder (13) for swirling the exhaust gas, and the exhaust gas swirled by the swirl cylinder (13) and the secondary air are taken in and mixed. The mixing cylinder (1 for supplying to the catalyst (18).
4) and a secondary air introduction pipe (5) for introducing secondary air from the outside into the mixing cylinder (14) are coaxially arranged in order from the outside, and one end of the swirling cylinder (13) Part of the secondary air introduction pipe
The secondary air outflow side opening end is penetrated through (5) and the revolving cylinder (13)
While facing the inside, the other end of the swirling cylinder (13) penetrates the mixing cylinder (14) and the exhaust gas inflow side opening end has a secondary air outflow side of the secondary air introducing pipe (5). The exhaust gas inflow side opening end of the mixing cylinder (14) and the secondary air outflow side opening end of the secondary air introduction pipe (5) are overlapped with the opening end, and the swirling cylinder (13) Arranged on either side of one end that penetrates the secondary air introduction pipe (5) or the other end that penetrates the mixing cylinder (14) of the swirling cylinder (13). The exhaust device for an engine is characterized by comprising the ejector (12). 5. A muffler body connected to an exhaust side of an engine
(2) An engine exhaust system equipped with an ejector (12) that mixes exhaust gas with secondary air introduced from the outside and supplies it to the catalyst (18), and expands exhaust gas from the engine. And a muffler chamber (7) for reducing exhaust noise, and an ejector chamber (8) accommodating the ejector (12) for mixing the exhaust gas passing through the muffler chamber (7) with secondary air introduced from the outside, The catalyst for purifying exhaust gas from the ejector chamber (8)
A catalyst chamber (9) for holding (18) adiabatically, and an exhaust chamber (10) for discharging exhaust gas purified in the catalyst chamber (9) to the outside by swirling in the radial direction of the muffler body. An exhaust system for an engine, characterized in that the engine is arranged in order from the upstream side. 6. The ejector chamber (8) is provided with a passage (15) for swirling exhaust gas from the muffler chamber (7) and guiding the exhaust gas into the ejector (12). Exhaust system for the engine described.