JP3148868B2 - Exhaust purification system for two-cycle 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 for a two-cycle engine provided with a catalytic converter in a muffler.

[0002]

2. Description of the Related Art A conventional exhaust gas purifying apparatus of this type includes:
For example, there is one disclosed in Japanese Utility Model Laid-Open Publication No. 53-72012.

[0003] In the exhaust gas purifying apparatus disclosed in this publication, a main catalyst (catalytic converter) is interposed in a portion of the muffler on the downstream side of the exhaust flow so as to partition the inside of the muffler. Since the main catalyst is located away from the engine, the exhaust gas introduced is relatively low in temperature and the purification performance is reduced, but in this device, the part closer to the engine than the main catalyst is used to compensate for the decrease. Was equipped with a cylindrical auxiliary catalyst.

[0004]

However, if the auxiliary catalyst is arranged close to the engine as described above, there is a limit in increasing the engine output. It is considered that this is because when the engine speed is in a high rotation range, the flow of exhaust gas is easily disturbed by the sub-catalyst, and the exhaust resistance increases.

That is, in order to obtain high purification performance from a low rotation speed region where the exhaust gas temperature is low, it is necessary to dispose the catalyst close to the engine. In such a case, when the engine speed increases, the output of the engine greatly decreases. turn into. In other words, if one muffler is used over the entire range of the engine speed, either the purification performance in the low speed range or the engine output in the high speed range is sacrificed.

[0006]

An exhaust emission control device for a two-stroke engine according to the present invention comprises an exhaust port of a cylinder block.
Exhaust passage communicating with the cylinder head
The passage for the rotation region and the passage for the high rotation region
A low-rotation range passage located on the opposite side of the
Formed at the upstream end of the high-speed range passage,
High when the engine speed is above a predetermined speed
Open the passage for the rotation range to increase the degree of opening and advance the exhaust timing.
High when the engine speed is lower than the set speed.
An exhaust valve that closes the rotation range passage and delays exhaust
An exhaust passage for the high rotation range that communicates with the passage for the high rotation range.
And a low-speed exhaust passage communicating with the low-speed region passage.
Chambers with roads arranged side by side inside are cylinder blocks
Connected to the downstream end of this chamber.
Connect the merging section to flow, and connect the rear catalytic converter to this merging section.
And the exhaust passage for the low speed range
The front catalytic converter is interposed in the part near the gin .

[0007]

When the engine speed is in the low speed range, the entire amount of exhaust gas discharged from the engine is guided to the low speed range exhaust passage of the muffler and purified by the catalytic converter.
When the engine speed is in the high speed range, the exhaust gas flows through both the low speed range exhaust passage and the high speed range exhaust passage of the muffler, and the exhaust gas flowing through the low speed range exhaust passage is purified by the catalytic converter. You. Also, the exhaust timing
Utilizing an exhaust valve configured to speed up according to the rotation speed,
Exhaust gas flows to the front catalytic converter at low speed.
In addition, the exhaust resistance should be reduced at high revolutions
Can be.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a side view of a motorcycle provided with a two-cycle engine exhaust purification device according to the present invention according to the present invention, and FIG. 2 is a cross-sectional view showing a cylinder part of a two-cycle engine used in the exhaust purification device according to the present invention. FIG. 3 is a side view of a muffler used in an exhaust emission control device for a two-stroke engine according to the present invention. In FIG. FIG. 4 shows A of the engine exhaust port in FIG.
It is an arrow view.

In these figures, reference numeral 1 denotes a motorcycle, 2
Denotes an engine of the motorcycle 1 and 3 denotes a muffler connected to the engine 2. The engine 2 is a two-stroke engine, and the cylinder 5 on the crankcase 4 is provided with an exhaust valve device 6 that changes the exhaust timing according to the engine speed.

The cylinder portion of the engine 2 is configured as shown in FIG. In FIG. 2, reference numeral 7 denotes a piston which is vertically movably fitted in a cylinder block 5a of the cylinder 5, reference numeral 8 denotes a connecting rod, and reference numeral 9 denotes a spark plug attached to a cylinder head 5b of the cylinder 5. Also,
Reference numeral 10 denotes a scavenging passage formed in the cylinder block 5a.

The exhaust valve device 6 comprises an exhaust valve 12 facing an exhaust port 11 opened in the cylinder block 5a, and a drive unit provided with a servomotor (not shown) connected to the exhaust valve 12. Have been. The exhaust valve 12 is formed in a substantially drum shape as a whole, and is rotatably supported by the cylinder block 5a with the direction perpendicular to the plane of FIG. 2 as the axial direction. The exhaust valve 12 has a notch 12a which forms a part of a side wall and an upper wall of an exhaust passage described later.

The drive unit of the exhaust valve device 6 turns the exhaust valve 12 counterclockwise in FIG. 2 from the fully closed position shown by the solid line in FIG. 2 when the engine speed reaches a predetermined speed. As the engine speed increases from the fully closed position to the fully open position indicated by the two-dot chain line in FIG.
It is configured to increase the opening degree.

That is, as the opening degree of the exhaust valve 12 is increased, the substantial upper edge of the exhaust port 11 gradually moves upward, so that the exhaust timing is such that the exhaust valve 12 is in the fully closed state. Sometimes slowest and fastest when fully open. By opening and closing the exhaust valve 12 in this manner, a high torque is obtained when the engine speed is low and in the middle rotation range, and a high output is obtained when the engine rotation speed is in the high rotation range.

An exhaust passage communicated with the exhaust port 11 is:
In this engine 2, the upper side (cylinder head) in FIG.
5b) and a lower side of the high-speed range passage 13 (opposite to the cylinder head 5b).
Is formed from a passage 15 for the high rotation region and a passage 15 for the low rotation region which is isolated via a partition wall 14.
The exhaust valve 12 is disposed on the upstream end side of the high-speed range passage 13, and the high-speed range passage 13 is closed by the exhaust valve 12 when the exhaust valve 12 is fully closed. It is configured.

That is, when the exhaust valve 12 rotates according to the engine speed, the high-speed range passage 13 opens and closes.

As shown in FIG. 3, the muffler 3 includes a chamber 16 connected to the engine 2 and a silencer 17 connected to the rear end of the chamber 16. The chamber section 16 according to the present invention
Constructs a chamber. The interior of the chamber portion 16 is defined by an exhaust passage 18 for a high revolution region and an exhaust passage 19 for a low revolution region. When the muffler 3 is attached to the engine 2, the exhaust passage 18 for a high revolution region is formed. , The low-speed exhaust passage 19 is connected to the high-speed
It is constituted so that it may be connected to passage 15 for low revolution ranges, respectively.

The outer wall of the chamber portion 16 bulges partially upward (toward the engine 2) at a location on the upstream side of the exhaust flow from the relatively large-diameter expansion chamber forming portion 16a in the chamber portion 16. And the exhaust passage 19 for the low rotation range.
A space having a larger diameter than other parts is formed therein, and a front catalytic converter 20 described later is interposed in the space. The catalytic converter 20 is provided in the exhaust passage 1 for the low rotation speed region.
9 is mounted to partition the front and rear.

The silencer 17 is provided with a sound absorbing material such as glass wool (not shown). An exhaust pipe 17a is provided at the rear, and the silencer 1 is provided inside.
7, the rear catalytic converter 21
Is interposed. After in this silencer 17
The high-speed exhaust gas upstream of the side catalytic converter 21
So that the passage 18 and the exhaust passage 19 for the low-speed range merge.
Has become. This junction is indicated by reference numeral 22 in FIG.

The front catalytic converter 20 and the rear catalytic converter 21 have the same structure, and are formed in a columnar shape having a substantially honeycomb shape. The front and rear catalytic converters 20 and 21 may be formed as shown in FIG.

FIG. 5 is a sectional view showing another example of the catalytic converter, and FIG. 5 shows a sectional view taken along line VV in FIG. The catalytic converter shown in FIG. 5 is formed in a columnar shape having a substantially honeycomb-shaped cross section by winding a flat plate A and a corrugated plate B, each of which has a foil shape, in a spiral shape so as to overlap each other.

The front and rear catalytic converters 20, 21
In order to assemble, first, a flat plate or a corrugated plate B is laminated with a thin flat brazing material on both sides of the plate, and the other plates are aligned with their tips aligned and overlapped. A band-like honeycomb member is formed by sandwiching the jigs. Then, the flat plate A and the corrugated plate B are wound together with the brazing material, and the cylindrical shape is heated in a furnace and brazed and formed.

After the honeycomb-shaped member is spirally wound to form a columnar member, the columnar member is separated from a catalyst metal (for example, platinum, palladium, rhodium, copper, chromium, iron, nickel, etc.) and alumina. The catalyst material is immersed in the mixed suspension and supported on the columnar member. Thereafter, the front and rear catalytic converters 20 and 21 are completed by reducing and drying the columnar members.

The method of supporting the catalyst material on the columnar member is not limited to the above-described method, and various conventional methods such as a method of first supporting only alumina and then supporting the catalytic metal may be employed. can do. FIG. 5 shows front and rear catalytic converters 20, 21.
The central portion is enlarged and drawn for easy understanding in explaining the configuration of the above, and the dimensions such as the thickness of the constituent members are different from those of the actual one.

That is, the exhaust gas guided to the exhaust passage 18 for the high rotation region of the muffler 3 is purified and discharged through the rear catalytic converter 21 in the silencer 17. Further, the exhaust gas guided to the low-rotational-range exhaust passage 19 is purified by passing through the front-side catalytic converter 20, is purified again through the rear-side catalytic converter 21 in the silencer 17, and is discharged. .

In the exhaust gas purifying apparatus for a two-stroke engine configured as described above, when the engine speed is in a low rotation range, the exhaust valve 12 of the exhaust valve device 6 is closed as shown by a solid line in FIG. Therefore, the entire amount of exhaust gas discharged from the engine 2 passes through the muffler 3
To the low-rotational-range exhaust passage 19. Then, the exhaust gas is purified by the front catalytic converter 20 and the rear catalytic converter 21 and discharged from the muffler 3.

That is, since relatively low temperature exhaust gas discharged when the engine speed is low can be guided to the front catalytic converter 20 with a small temperature decrease, the front catalytic converter 20 is purified at an early stage after the engine is started. It can be heated to a temperature, and high purification performance can be obtained from an early stage. Since the total amount of exhaust gas is relatively small when the engine speed is in the low rotational speed range, even if all the exhaust gas is passed through the front catalytic converter 20, the exhaust resistance is small,
The amount of decrease in engine output is also small.

When the engine speed exceeds the predetermined engine speed and the exhaust valve 12 opens, the exhaust gas is
Of the low rotation speed range 15 and the high rotation speed range passage 13 to the muffler 3. The exhaust gas guided to the low-rotational-range exhaust passage 19 in the muffler 3 is supplied to the front catalytic converter 20 and the rear catalytic converter 2 in the same manner as described above.
1 and is discharged to the outside of the muffler 3.

On the other hand, the exhaust gas guided to the high-speed exhaust passage 18 in the muffler 3 flows into the silencer 17 through the chamber section 16 where the low-speed exhaust passage 1
9 and is sent to the rear catalytic converter 21. Then, the gas is purified through the rear catalytic converter 21 and discharged to the outside of the muffler 3.

That is, when the engine speed is in the high rotation range, the exhaust gas discharged from the engine 2 is supplied to the high rotation range exhaust passage 18 and the low rotation range exhaust passage 1 in the muffler 3.
9, a part of the exhaust gas passes through the front catalytic converter 20, and most of the exhaust gas passes through the front catalytic converter 2.
It will be discharged without passing through zero.

Therefore, in the exhaust gas purifying apparatus for a two-stroke engine according to the present invention, when the engine speed is in the low speed region, the exhaust gas is purified by the front catalytic converter 20,
When the engine speed is in the high rotation range, the increase in exhaust resistance can be suppressed because part of the exhaust passes through the front catalytic converter 20 and most of the exhaust is discharged without passing through the front catalytic converter 20. .

In this embodiment, the exhaust gas flows only through the low-speed exhaust passage 19 in the muffler 3 and the exhaust gas flows through both the low-speed exhaust passage 19 and the high-speed exhaust passage 18. Since the switching when flowing is performed using the exhaust valve device 6 for controlling the exhaust timing of the engine 2, there is no need to provide a dedicated switching valve for switching the exhaust passage. That is, since the function of controlling the exhaust timing and the function of switching the exhaust passage can be provided to the exhaust valve 12, an increase in the number of parts can be suppressed.

In the present embodiment, since the rear catalytic converter 21 is also provided in the silencer 17, even when the engine speed is in the high rotation range, exhaust gas is exhausted from the muffler 3 in a state where the entire amount is purified. Become so. Also after
The side catalytic converter 21 is located at the rear end of the high-speed exhaust passage 18.
The rear catalytic converter 21
The exhaust is not disturbed in the chamber 16
Since no resistance is caused by this, the chamber 1
6 is not hindered.

Further, by dividing the inside of the muffler 3 into two passages for a low rotation region and a high rotation region, it becomes easy to manufacture a muffler suitable for engine characteristics .

[0034]

As described above, the exhaust gas purifying apparatus for a two-stroke engine according to the present invention has a function of exhausting a cylinder block.
The exhaust passage communicating with the air vent is located on the cylinder head side.
And the cylinder from the high-speed passage
A low-rotation range passage located on the opposite side of the head through a partition
And the upper end of the high-speed range passage.
When the engine speed is higher than the predetermined speed
The opening for the high rotation range is opened in
Early, when the engine speed is lower than the set speed
Exhaust valve that closes the high-speed passage and delays the exhaust timing
And a high-speed exhaust gas communicating with the high-speed region passage.
A passage, and low-speed exhaust gas communicating with the low-speed region passage.
Cylinder block with chambers with passages inside
At the downstream end of this chamber.
Connect the merging section to join, and connect the rear catalyst converter to this merging section.
And the exhaust passage for the low speed range.
The front catalytic converter was installed at the part near the engine.
Therefore, according to this exhaust gas purification apparatus, it is possible to prevent
When the engine speed is in the low speed range, the exhaust
The exhaust gas flows through the exhaust passage for the low speed range of the engine. For this low rotation range
Install the front catalytic converter in the exhaust passage near the engine.
Since it is interposed, immediately after starting, the front catalytic converter
Can be heated to the purification temperature. On the other hand,
When the engine's rotation range is in the high rotation range, most of the exhaust
Flows through the high-speed exhaust passage of the chamber and
It flows into the rear catalytic converter provided at the junction. This and
Exhaust temperature rises as the engine speed increases.
At the same time, the initial exhaust
As the temperature rises particularly due to the inflow of exhaust, the rear catalyst core
The inverter is far away from the cylinder block
High purification performance despite being located at the rear end of the bar
Ability can be obtained .

The chamber is designed to increase the output.
Although set, the rear catalytic converter is for high speed
It is provided at the rear end of the exhaust passage.
The exhaust does not disturb the exhaust inside the chamber.
And does not create any resistance,
The operation of the key is not hindered. Therefore, the present invention
According to, the purification performance from low rotation range to high rotation range
To improve and increase engine power.
Can be compatible.

Furthermore, according to the present invention, the passage for the low rotation range is provided.
Exhaust air flow at low revolutions
Exhaust at high revolutions where exhaust flows through both the
The exhaust mode can be switched by the exhaust valve for exhaust timing control.
Can be. In other words, the exhaust timing is
Skillfully utilize the exhaust valve that is configured to respond quickly to
Exhaust gas flows to the front catalytic converter at low speed.
In addition, the exhaust resistance should be reduced at high revolutions
Can be. For this reason, the exhaust mode at low rotation and the high
No special valve is required to switch between
And the number of parts can be reduced, so a simple structure
Realizing an exhaust purification system with high purification performance
Can be. In addition, the exhaust valve is provided in the cylinder block.
Exhaust passage for the high speed range and the exhaust passage for the low speed range
Is formed in the chamber,
Can be

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle equipped with a two-stroke engine exhaust purification device according to the present invention.

FIG. 2 is a cross-sectional view showing a cylinder part of a two-stroke engine used in the exhaust emission control device according to the present invention.

FIG. 3 is a side view of a muffler used in an exhaust emission control device for a two-cycle engine according to the present invention.

FIG. 4 is a view of the engine exhaust port in FIG.

FIG. 5 is an enlarged sectional view showing another example of the catalytic converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motorcycle 2 2 cycle engine 3 Muffler 6 Exhaust valve device 12 Exhaust valve 13 High rotation range passage 15 Low rotation range passage 18 High rotation range exhaust passage 19 Low rotation range exhaust passage 20 Front catalytic converter

Claims (1)

(57) [Claims] An exhaust system communicating with an exhaust port of a cylinder block.
The air passage is located on the cylinder head side for the high rotation range.
And the side opposite to the cylinder head from this high rotation range passage
Formed separately from the passage for the low rotation range located through the partition wall
The engine rotation is provided at the upstream end of the high speed passage.
When the number is higher than a predetermined number of rotations, the passage for high rotation range
Open the valve to advance the exhaust
When the number of revolutions is lower than the set number of revolutions,
An exhaust valve that closes and delays exhaust time the most is provided.
An exhaust passage for the high rotation range that communicates with the passage for the shift range;
A low-rotation range exhaust passage that communicates with the
Connect the installed chamber to the cylinder block, and
At the downstream end of the chamber, the junction where the two exhaust passages join
Connect the rear catalytic converter at this junction
In both cases, the portion of the exhaust passage for the low rotation range near the engine.
An exhaust purification device for a two-stroke engine , wherein a front catalytic converter is interposed .