JPS59176419A - Two cycle engine with turbo supercharger - Google Patents

Abstract

PURPOSE:To enhance the supercharging efficiency with the aid of pulsated exhaust gas by closing the downstream end of an expansion chamber connected to an exhaust pipe and connecting a turbo-supercharger and a noise suppressing chamber to the site upper than the downstream end. CONSTITUTION:An exhaust port 12 is opened to discharge exhaust gas from a cylinder 8. Exhaust gas flows through an exhaust pipe 16 into an expansion chamber 18 and runs against a separation wall 20 to form reflection wave. By having the distance from the exhaust port 12 to the separation wall 20 correspond to the timing at which exhaust gas is pulsated, intake air may be prevented from blow bye. Since an exhaust passage 21 branches from the exhaust port at the upstream side of the separation wall 20 inside the expansion chamber 18, and has an exhaust turbine 23, high temperature and high pressure exhaust gas which flows into the expansion chamber 18 may be guided into the exhaust turbine 23. 19 indicates a noise suppressing chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stroke engine with a turbocharger.

As a two-stroke engine that performs supercharging using a tarp supercharger, for example, as shown in Japanese Utility Model Application Publication No. 57-186626, a tarp supercharger is installed at the downstream end of the exhaust pipe led out from the engine. A type equipped with an exhaust turbine is known.

However, in the configuration of this prior art, since the exhaust turbine is provided at the downstream end of the exhaust pipe, there is a problem in that the pressure attenuation of the exhaust gas up to the exhaust turbine is large and the turbine efficiency is reduced. In other words, in a two-stroke engine, the reflected waves of exhaust gas generated in the exhaust pipe have a large effect on the scavenging air in the cylinders and the filling efficiency of fresh air, so the downstream end of this exhaust pipe is narrowed to make effective use of the reflected waves. It has a large capacity chamber shape. therefore,
Since the exhaust gas that has passed through this large-capacity exhaust pipe is guided to the exhaust turbine, the exhaust gas temperature is naturally low and the pressure attenuation of the exhaust gas is large. As a result, a supercharging effect cannot be expected, particularly in a low rotation range where the exhaust flow rate is small relative to the internal capacity of the exhaust pipe, and the rise of supercharging pressure is also poor. As a countermeasure to this problem, it is possible to install an exhaust turbine in the upstream part of the exhaust pipe, but in this case, the exhaust turbine becomes an obstruction and the reflected waves of the exhaust cannot be used effectively, causing a problem that adversely affects engine performance. There is.

The present invention was made based on these circumstances, and
A turbo supercharger that can effectively utilize the reflected waves of the exhaust gas, and the pressure of the exhaust gas guided to the exhaust turbine is high enough to achieve both the supercharging effect of the turbocharger and the effective use of exhaust pulsation. The purpose is to provide a two-stroke engine equipped with

That is, in order to achieve the above object, the present invention closes the downstream end of the expansion chamber connected to the exhaust pipe, and connects the upstream side of the closed part of the expansion chamber and the muffling chamber connected downstream of the expansion chamber with an exhaust passage. The exhaust passage is connected to the exhaust passageway, and an exhaust turbine of a turbocharger is provided in the middle of the exhaust passage.

A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a motorcycle equipped with a two-stroke engine according to the present invention, where 1 is a frame, 2 is a 2-stroke single-cylinder engine, 3 is a front fork, 4 is a front wheel, 5 is a fuel tank, 6 is a rear arm, and 7 is a front fork. is the rear wheel.

The two-stroke engine 2 has an intake port 10 and a scavenging port 1 on the inner surface of the cylinder 8, which are opened and closed by a piston 9.
The intake port 1o is connected to a carburetor 14 via a reed valve 13. Further, an exhaust pipe 16 is led out from the exhaust port 2 toward the bottom of the crankcase 15, and a 77 collar 17 is integrally provided at the leading end of the exhaust pipe 16. The muffler 17 is made up of a 'fc expansion chamber 18 whose diameter increases as it goes downstream so that the passage area increases, and a tapered silencing chamber 19 that is integrally provided on the downstream side of this expansion chamber 18. A silencing chamber 19 portion extends rearward on the side of the rear wheel 7.

The downstream end of the expansion chamber 18 is closed by a flat partition wall 20 provided at the boundary between the expansion chamber 18 and the muffling chamber 19. It is independent. therefore,
When exhaust gas flows into the expansion chamber 18 through the exhaust pipe 16,
This exhaust gas expands within the expansion chamber 18, and a pressure wave generated when the exhaust gas flows in collides with the partition wall 2o, and due to this collision, a reflected wave of the exhaust gas that attempts to return to the exhaust port 12 side is formed within the expansion chamber 18. It looks like this. Further, the expansion chamber 18 and the silencing chamber 19 are communicated through an exhaust passage 2 which is separate from the 77r 17. One end of the exhaust passage 21 is connected to the upstream side of the partition wall 2o in the expansion chamber 18, and the other end is connected to the upstream position of the silencing chamber 19. Exhaust gas is guided to the silencing chamber 19 through this exhaust passage 21.

However, the turbo supercharger 2 is located in the middle of the exhaust passage 21.
2, and this turbo supercharger 22 is located exactly at the bottom of the space between the engine 2 and the rear wheel 7. As schematically illustrated in FIG. The exhaust inlet 28 is connected to the expansion chamber 18 through the upstream portion 29a of the exhaust passage 2.
The exhaust outlet 3o is also connected to the silencing chamber 19 through the downstream portion 29b of the exhaust passage 2. In addition, the intake inlet 31 of the compressor 25 is communicated with an air cleaner 33 provided below the fuel tank 5 through an intake introduction pipe 32, and the outside air sucked from the intake inlet 34 of the air cleaner 33 is filtered by an element 35. After that, the air is guided to the intake inlet 31. The intake outlet (not shown) of the compressor 25 is connected to an intake supply pipe 36.
'f: communicates with an intake chamber 37 via an intake passage 38, and this intake chamber 37 communicates with the carburetor 14 via an intake passage 38. Note that four normally closed on-off valves are provided in the bypass passage 4° that directly connects the exhaust gas inlet 28 of the exhaust turbine 23 and the downstream portion 29b of the exhaust passage 2.
This on-off valve 41 is opened and closed by a supercharging pressure actuator 42. The supercharging pressure actuator 42 is actuated by the intake pressure in the intake air supply pipe 36, and opens the on-off valve 41 when this intake pressure exceeds a predetermined value.

Next, the operation of the first embodiment based on such a configuration will be explained.

When the exhaust port 12 is now opened and exhaust is discharged from the cylinder 8, this exhaust passes through the exhaust pipe 16 to the expansion chamber 1.
At the same time, the pressure waves of the exhaust gas generated at the time of the inflow collide with the partition wall 20, and this collision causes the expansion chamber 18
There is an exhaust port 1 inside as shown by the dashed arrow in Figure 2.
A reflected wave of the exhaust gas that attempts to return toward the second side is formed.

The pressure at the outlet of the exhaust port 12 is increased by the reflected waves of the exhaust, so if the length from the exhaust port 12 to the partition wall 20 is set in accordance with the exhaust timing, the intake air filled in the cylinder 8 can be blown through. It can be prevented.

Therefore, the reflected waves of the exhaust gas can be effectively used to improve the intake efficiency, and the output can be improved.

On the other hand, since the exhaust passage 21 is branched and connected to the expansion chamber 18, which is divided from the silencing chamber 19, the high temperature, high pressure exhaust gas flowing into the expansion chamber 18 flows as shown by the solid line arrow in FIG. It flows into the exhaust passage 21 as it is. This exhaust gas is then introduced into the exhaust turbine 23 and the turbine wheel 2
Rotate 4. The rotation of the turbine wheel 24 is transmitted to the compressor impeller 26 through the drive shaft 27, so that the compressor impeller 26 is connected to the intake pipe 3.
2 and the air cleaner 33 , the outside air is pressurized and sent under pressure to the intake air supply pipe 36 .

The outside air pressurized by the compressor 25 is sent to the intake chamber 37, and is forcibly supplied to the intake port IQ via the intake passage 38 and the carburetor 39.

In this way, the exhaust passage 21 is branched and connected to the upstream side of the partition wall 20 in the expansion chamber 18, and the exhaust turbine 23 is provided in the exhaust passage 21. This means that the exhaust gas will be guided as it is. As a result, the exhaust turbine 23 is substantially brought closer to the exhaust port 12, and a small amount of pressure attenuation of the exhaust gas is required, so a large driving force can be obtained, and the supercharging efficiency is significantly improved.

In this way, according to the above configuration, the supercharging efficiency can be increased while effectively utilizing the reflected waves of the exhaust gas and the exhaust pulsation.
Engine output can be improved over the entire rotation range from low rotation range to high rotation range.

In addition, since the exhaust turbine 2sVi is installed in a position different from the exhaust flow path within the muffler 17, the
2 is not restricted by the position of the muffler 17. Therefore, there is a large degree of freedom in the installation location of the turbo supercharger 22, which is particularly advantageous in motorcycles where the installation location is limited due to serious problems with the space available on the vehicle body.

In addition, in the first embodiment described above, the expansion chamber and the silencing chamber were integrally formed in a common muffler, but the expansion chamber and the silencing chamber are separated from each other, with only the expansion chamber inside the muffler, and this muffler and A separate silencer may be provided. Further, the partition wall is not limited to a flat plate shape, but may be curved into a spherical shape.

On the other hand, the present invention is not limited to the first embodiment described above, and second to seventh embodiments of the present invention are shown from FIG. 3 onwards. However, in these second to seventh embodiments, the same components as those in the first embodiment described above are given the same numbers, and the explanation thereof will be omitted.

In the second embodiment of the present invention shown in FIG. 3, an exhaust pipe 16 is branched into two parts in the middle, and one branch end 51 is equipped with a large-capacity expansion chamber 18 that emphasizes performance in a high rotation range. muffler 1
7 is connected to the other branch end 52, and a 77 roller 54 is connected to the other branch end 52, which has an expansion chamber 53 with a smaller capacity than the expansion chamber 18 described above, which emphasizes performance in the low and medium rotation range. The downstream end of this expansion chamber 53 for low and medium rotations is closed by a lid 55, and the upstream side of the downstream end of this expansion chamber 53 is communicated with the upstream portion 29m of the exhaust passage 21 via a communication passage 56. .

Further, a control valve 57 is provided at a branch portion of the exhaust pipe 16 to switch communication between both mufflers 17 54 and the exhaust port 12 , and this control valve 57 is switched and operated by a supercharging pressure actuator 58 . The supercharging pressure actuator 58 controls the control valve 57 so as to communicate the exhaust port 12 with the muffler 54 for low and medium rotation when the supercharging pressure does not reach a certain value.
, and when the boost pressure reaches a certain value due to an increase in the engine speed, the exhaust port 12 and the high speed 7
The control valve 57 is operated to communicate with the exhaust gas 72-17, thereby switching the flow path of the exhaust gas.

According to the configuration of the second embodiment, the exhaust gas can be guided to the expansion chamber 18 or 53 with an internal capacity commensurate with the flow rate, so that the pressure attenuation of the exhaust gas is small over the entire rotation range and the exhaust gas is Not only can the charging effect be further enhanced, but also the build-up of supercharging pressure in the low rotation range can be improved.

In addition, in the low rotation range, the pressure □ of the reflected wave of the exhaust gas becomes large, so it is possible to reliably prevent fresh air from blowing through, contributing to improved output in the low rotation range. In this case, instead of the boost pressure actuator, for example, the engine speed can be controlled by ignition or
It is also possible to use a pulse motor or a solenoid that is detected from the groove and whose rotation is controlled according to this detection signal.

On the other hand, FIG. 4 shows a third embodiment of the present invention, in which a pair of exhaust passages 21 in the expansion chamber 18 are arranged downstream of the branching position of the exhaust passage 21 and spaced apart in the flow direction of the exhaust gas. Butterfly valves 61 and 62 are provided, and these butterfly valves 61 and 62 are switched to the open or closed position by the boost pressure actuator 63, 64 or the above-mentioned master motor or solenoid, thereby changing the operating status of the engine 2. The pipe length from the exhaust port 12 to the downstream end of the expansion chamber 18 is changed accordingly. According to this configuration, the exhaust pulsation effect can be fully exerted over the entire rotation range, and in combination with the supercharging effect, high output can be obtained.

Further, FIG. 5 shows a fourth embodiment of the present invention.

In this fourth embodiment, a rotary control valve 71 for changing the exhaust timing is provided at the end of the exhaust port 12 facing the cylinder 8, and an exhaust inflow chamber 72 of a constant capacity is branched and connected to the exhaust port 12. , and intake passage 38
Similarly, an intake inflow chamber 73 of a constant capacity is branch-connected to the exhaust port 12, the exhaust inflow chamber 72, and the intake passage 38.
and fc8 closing valve 7 provided in the communication portion with the intake inflow chamber 73.
4, 75 and the control valve 71 are connected to the supercharging pressure actuator 7.
6 to open and close in conjunction with each other.

In a low rotation range where the boost pressure does not reach a certain value, the boost pressure actuator 76 opens the on-off valve 74.75 to communicate the exhaust port 12 with the exhaust inflow chamber 72 and the intake passage 3B with the intake inflow chamber 73. At the same time, the control valve 71 is rotated by a certain angle to advance from the top dead center side of the exhaust port 12 on its outer peripheral surface to the bottom dead center side, thereby reducing the opening height of the exhaust port 12 and delaying the exhaust timing. ing. In addition, in the high speed range where the boost pressure has reached a certain value, the on-off valves 74 and 75 are closed to close the exhaust inflow chamber 72 and the intake inflow chamber 73, and the control valve 21 is retreated to the top dead center side, causing the exhaust The opening height of the port 12 is increased to speed up the exhaust timing.

According to the fourth embodiment with such a configuration, the exhaust timing is delayed in the low rotation range, and the exhaust gas exploded in the cylinder 8 expands and is discharged after sufficiently pushing down the piston 9, so that the work lid is closed. increases, and the intake passage 38 and exhaust pipe 1
Since the substantial pipe length of the engine 6 increases in accordance with the exhaust flow rate, the pulsating effect of intake and exhaust can be effectively used, and the output can be improved even in the low rotation range where no supercharging effect can be expected. On the other hand, in the high rotation range, the exhaust timing becomes earlier and the opening area of the exhaust port 12 increases, increasing the exhaust efficiency. The pulsation effect can be used effectively, and in combination with the supercharging effect, high output can be obtained.

In the fourth embodiment described above, the two on-off valves and the control valve are operated in conjunction with one boost pressure actuator, but they may be operated independently, or their driving The source is not limited to the boost pressure actuator; for example, the engine rotation speed may be detected from the ignition pulse, and a pulse smoke or solenoid whose rotation is controlled in accordance with this detection signal may be used for opening and closing operation.

6 and 7 show a fifth embodiment of the present invention. This fifth embodiment includes an exhaust pipe 16 and a muffler 17.
A fibrous catalyst 82 is attached to the entire inner wall surface of the upstream portion 29a of the expansion chamber 18 and the exhaust passage 21 via a punching metal 81. According to this configuration, the catalyst 82
Even though the exhaust gas flow and reflected waves are not obstructed, the catalyst 82fi receives heat from the exhaust gas immediately after being discharged from the exhaust port 12, so the startup leading to the start of the oxidation reaction is prevented. becomes faster. Therefore, the oil in the exhaust gas is combusted, resulting in less white smoke and the purification efficiency is improved, as well as the exhaust temperature increases due to the oxidation reaction, which leads to higher temperature exhaust gas being guided to the exhaust turbine 23. , turbine efficiency can be increased.

Further, the two-stroke engine according to the present invention is not limited to a single-cylinder engine, and FIG. 8 shows a sixth embodiment in which the engine is a multi-cylinder engine. In this sixth embodiment, the left and right cylinders 2
, 2' are connected to exhaust pipes 16, J6', respectively, with mufflers 17, J7', and exhaust passages 2 branched from the respective expansion chambers 1B, J8'.
J, upstream part 29a of 21'.

29a' is connected to the exhaust gas inlet 28 of the exhaust turbine 23. Further, the exhaust outlet 30 of the exhaust turbine 23 is located at the downstream portions 29b, 29 of the exhaust passages 2J, 2J', respectively.
Muffler Z 7, J 7' muffler chamber 1 through b'
9 and 19'.

Furthermore, in the sixth embodiment described above, the gift muffler 17, J7' was connected to each cylinder 2゜2'.
As in the seventh embodiment shown in FIG. 9, the exhaust pipes 16 + 16' led out from each cylinder 2.2' may be gathered together and connected to one muffler 17. In this case, as shown by the imaginary line in Fig. 9, the exhaust passage 2 is connected to the exhaust pipe 1.
6 and 16' may be branched immediately after the aggregation part.

In addition, in each of the above-mentioned embodiments, the compressor of the Tase supercharger was provided upstream of the carburetor, but for example, a compressor may be provided between the carburetor and the intake port to directly pressurize the air-fuel mixture and supply it to the intake port. You may also do this.

The means for supplying fuel is not limited to a carburetor, but a fuel injection nozzle may also be used.

According to the present invention described in detail above, when exhaust gas flows into the expansion chamber, the pressure wave of this exhaust gas collides with the closed part at the downstream end of the expansion chamber, and a reflected wave that tries to return to the exhaust port side is formed in the expansion chamber. Therefore, this reflected wave can be effectively used to improve intake efficiency. Moreover, since the exhaust gas flows into the exhaust passage from the upstream side of the downstream end of the expansion chamber, the high temperature and high pressure exhaust gas is directly guided to the exhaust turbine. Therefore, the exhaust turbine is substantially brought closer to the exhaust port, and pressure attenuation of the exhaust gas is reduced, so a large driving force can be obtained, and the supercharging efficiency is significantly improved. Therefore, it is possible to make effective use of the pulsation effect of the exhaust gas and improve supercharging efficiency, and high output can be obtained over the entire rotation range.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention;
The figure is a side view of the motorcycle, FIG. 2 is a sectional view, FIG. 3 is a sectional view showing a second embodiment of the present invention, and FIG. 4 is a third embodiment of the present invention.
5 is a cross-sectional view showing a fourth embodiment of the present invention; FIGS. 6 and 7 are a cross-sectional view showing a fifth embodiment of the present invention; FIG. 6 is a cross-sectional view, and FIG. The figures are a sectional view taken along the line ■-■ in FIG. 6, FIG. 8 is a schematic diagram showing the sixth embodiment of the present invention, and FIG. 9 is a schematic diagram showing the seventh embodiment of the present invention. . 2...2-cycle engine, 9...Piston, 10
...Intake port, 12...Exhaust boat, 16...
Exhaust pipe, 18... expansion chamber, 19... muffling chamber, 21.
...exhaust passage, 22...tar is supercharger, 23...exhaust turbine, 25...compressor.

Claims (1)

[Claims] In a two-stroke engine equipped with a tarp supercharger, which rotates an exhaust turbine by the exhaust flow from an exhaust port opened and closed by a piston, and supercharges intake air to the intake port by driving a compressor with this exhaust turbine, the above-mentioned exhaust The downstream end of the expansion chamber connected to the exhaust pipe led out from the port is closed, and the upstream side of the closed part of this expansion chamber is connected to the silencing chamber connected downstream of this expansion chamber by an exhaust passage. A two-cycle ennon equipped with a tarp supercharger, characterized in that the exhaust turbine of the above-mentioned tarp supercharger is provided.