JP3021111B2 - Exhaust gas purifier for two-stroke internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus in which a catalyst is provided in a muffler of a two-cycle internal combustion engine mounted on a small vehicle such as a motorcycle.

[0002]

2. Description of the Related Art A conventional exhaust gas purifying apparatus is configured as shown in FIG. In FIG. 5, the upstream end of the exhaust pipe portion 04 of the first muffler 03 is connected to the exhaust port 02 of the two-cycle internal combustion engine 01, and the first muffler 03
Then, along the exhaust flow, the exhaust pipe part 04 and the expanded pipe part 0
5, the tubular portion 06, and the contracted tube portion 07 are integrally connected. Further, a tail pipe 08 facing the cylindrical portion 06 is integrally fitted into a downstream end of the contracted tube portion 07 of the first muffler 03, and a second muffler 09 is attached to a downstream end of the tail pipe 08.
And an exhaust gas permeable catalyst 010 is attached to the upstream end of the tail pipe 08.
When the exhaust gas passes through the inside of the exhaust gas permeable catalyst 010, harmful gases such as carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) in the exhaust gas are exhausted. , And are purified by redox.

[0003]

Since the temperature of the exhaust gas in the first muffler 03 decreases linearly as the distance from the exhaust port 02 increases, as shown in FIG. If the exhaust gas permeable catalyst 010 is disposed on the side, the exhaust gas purification performance at the time of starting the cold machine may decrease. To avoid this,
When the exhaust gas permeable catalyst 010 is disposed close to the exhaust port 02, the dynamic effect of the exhaust is significantly impaired, and the output of the internal combustion engine 01 is greatly reduced.

[0004] The present invention relates to an improvement of an exhaust gas purifying apparatus for a two-cycle internal combustion engine which overcomes such difficulties, and an exhaust pipe connected to an exhaust port of the two-cycle internal combustion engine comprises an inner pipe and an outer pipe. And a control valve is provided in an exhaust passage downstream of an exhaust port of the two-cycle internal combustion engine, wherein a control valve is provided in the exhaust gas purification device, wherein a catalyst is provided in an annular passage surrounded by the inner pipe and the outer pipe. A bypass passage communicating with the annular passage from an upstream portion of the control valve in the passage is provided.

According to the present invention, the control valve is closed in a certain operation state such as a cold start or a low load operation, and the exhaust gas flows through the bypass passage. It is led to the annular passage, and is brought into contact with the catalyst in the annular passage, oxidized and reduced, and sufficiently purified.

In an operation state other than the above-mentioned certain operation state, the control valve of the exhaust passage is opened, and most of the exhaust gas flows in the exhaust passage with low flow resistance, and power loss is reduced. , Can generate a large output.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in FIGS. 1 and 2 will be described below. Reference numeral 1 denotes a two-stroke internal combustion engine mounted on an off-road motorcycle (not shown). The two-stroke internal combustion engine 2 is connected to an exhaust port 2 of the two-stroke internal combustion engine 1 so that an exhaust passage 31 of an exhaust pipe mounting portion 30 communicates with the exhaust port. An exhaust pipe attachment part 30 is attached to the cycle internal combustion engine 1, a control valve 32 is provided in the exhaust passage 31 so as to be openable and closable, and a bypass passage 33 is formed from an upstream portion of the exhaust passage 31 from the control valve 32. The exhaust pipe mounting section 30 detects the temperature of the cooling water passing through the two-stroke internal combustion engine 1 and closes the control valve 32 when the temperature is lower than a certain temperature, and closes the control valve 32 when the temperature is higher than a certain temperature. A thermostat 34 for opening 32 is attached. Further, an upstream end of an exhaust pipe 35 is connected to the exhaust pipe mounting portion 30. The exhaust pipe 35 includes an inner pipe 37 provided with a number of small holes 36 and an outer pipe 38 having a larger diameter. The inside of the inner tube 37 communicates with the exhaust passage 31, and the annular passage 39 surrounded by the inner tube 37 and the outer tube 38 communicates with the bypass passage 33, and a catalyst 40 is provided in the annular passage 39.

The downstream end of the exhaust pipe 35 is connected to a connecting portion 41.
Is connected to the exhaust pipe portion 42 on the upstream side of the muffler 3.

Since the embodiment shown in FIGS. 1 and 2 is constructed as described above, the cooling water temperature is low, the control valve 32 is closed and the two-cycle internal combustion engine 1 The exhaust gas discharged from the bypass passage 33
Flows into the annular passage 39 from the inside, and is brought into contact with the catalyst 40 in the annular passage 39 to be oxidized and reduced, thereby being reliably purified. When the required time has elapsed since the start, the two-stroke internal combustion engine 1
Is heated, and the exhaust pipe 35 is sufficiently heated,
The control valve 32 in the closed state is opened by the operation of the thermostat 34, and most of the exhaust gas flows into the muffler 3 through the inner pipe 37, and a similar purifying action is performed in the muffler 3. Then, in a normal operation state in which a large amount of exhaust gas is discharged compared with the time of starting, most of the exhaust gas passes through the inner pipe 37 having a small flow resistance without flowing through the annular passage 39 having a large flow resistance. The power loss is small and a large output can be generated.

Further, in the embodiment shown in FIGS. 1 and 2, a plurality of small holes 36 are provided in the inner tube 37. However, as shown in FIGS. 3 and 4, the small holes 36 are provided in the inner tube 37. Without
A small hole 36 may be provided in the connecting portion 41 between the portion where the inner tube 37 and the outer tube 38 are fitted to the connecting portion 41. In this embodiment, at the time of cold start, the catalyst 40 converts all the exhaust gas. The passage through the existing annular passage 39 allows the exhaust gas to be more reliably purified.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal side view illustrating an embodiment of an exhaust gas purifying apparatus for a two-cycle internal combustion engine according to the present invention when a cold start is performed.

FIG. 2 is an enlarged longitudinal sectional side view of a main part during normal operation in the embodiment shown in FIG.

FIG. 3 is a partial longitudinal side view at the time of starting a cold machine in still another embodiment of the present invention.

FIG. 4 is a partially longitudinal side view of the embodiment shown in FIG. 3 during normal operation.

FIG. 5 is a partial longitudinal side view of a conventional exhaust gas purifying apparatus for a two-cycle internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 2 cycle internal combustion engine, 2 ... exhaust port, 30 ... exhaust pipe attachment part, 31 ... exhaust passage, 32 ... control valve, 33 ... bypass passage, 34 ... thermostat, 35 ... exhaust pipe, 3
6 ... small hole, 37 ... inner pipe, 38 ... outer pipe, 39 ... annular passage,
40 ... catalyst, 41 ... connection part, 42 ... muffler.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-18612 (JP, A) Japanese Utility Model Showa 50-48011 (JP, U) Japanese Utility Model Showa 49-33215 (JP, U) Japanese Utility Model Showa 51- 1613 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) F01N 3/24 F01N 3/20

Claims (1)

(57) [Claims] 1. A two-stroke internal combustion engine connected to an exhaust port.
Exhaust pipe consists of an inner pipe and an outer pipe,
A catalyst is provided in an annular passage surrounded by the inner pipe and the outer pipe.
Exhaust gas purifying device, the exhaust passage downstream of the exhaust port of the two-cycle internal combustion engine
A control valve is provided, and an upstream portion of the exhaust passage from the control valve;
And a bypass passage communicating with the annular passage is provided .