JPH0370094B2 - - Google Patents

Description

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

Supercharging was performed using a turbo supercharger 2
As a cycle engine, for example,
As shown in Japanese Patent No. 186626, it is known that an exhaust turbine of a turbocharger is provided at the downstream end of an exhaust pipe led out from an engine.

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 naturally decreases and the pressure attenuation of the exhaust gas increases. 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 gets in the way and makes it impossible to effectively utilize the reflected waves of the exhaust, which has a negative effect on engine performance. .

The present invention has been made based on these circumstances, and it is possible to effectively utilize the reflected waves of the exhaust gas, and the pressure of the exhaust gas guided to the exhaust turbine is also sufficiently high, so that the supercharging effect by the turbocharger and the exhaust pulsation can be improved. The purpose of the present invention is to provide a two-stroke engine equipped with a turbocharger that can achieve both effective utilization of fuel and fuel.

That is, in order to achieve the above object, the present invention
The downstream end of the expansion chamber connected to the exhaust pipe is closed, and an exhaust passage connects the upstream side of the closed part of the expansion chamber to the silencing chamber connected downstream of the expansion chamber, and a turbo supercharger is installed in the middle of this exhaust passage. It is characterized by being equipped with an exhaust turbine.

The first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.
This will be explained based on the diagram.

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

The two-stroke engine 2 has an intake port 1 on the inner surface of a cylinder 8 that is opened and closed by a piston 9.
0, a scavenging port 11 and an exhaust port 12, and the intake port 10 is connected to a carburetor 14 via a reed valve 13. Also exhaust port 12
An exhaust pipe 16 extends downward from the crankcase 15, and a muffler 17 is integrally provided at the end of the exhaust pipe 16. The muffler 17 is composed of an expansion chamber 18 whose diameter increases so that the passage area increases as it goes downstream, and a tapered silencing chamber 19 that is integrally provided on the downstream side of the expansion chamber 18. This 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. The area is partitioned independently. Therefore, when exhaust gas flows into the expansion chamber 18 through the exhaust pipe 16, the exhaust gas expands within the expansion chamber 18, and the pressure waves generated when the exhaust gas flows in collide with the partition wall 20, and this collision causes the inside of the expansion chamber 18 to expand. Reflected waves of the exhaust gas attempting to return to the exhaust port 12 side are formed. Also, such an expansion chamber 1
8 and the muffling chamber 19 are communicated with each other through an exhaust passage 21 that is separate from the muffler 17. Exhaust passage 21
has one end connected to the upstream side of the partition wall 20 in the expansion chamber 18 and the other end connected to the upstream direction of the silencing chamber 19, and the expansion chamber 1
The high-temperature, high-pressure exhaust gas that has flowed into the chamber 8 is guided to the silencing chamber 19 through the exhaust passage 21 .

A turbo supercharger 22 is disposed in the middle of the exhaust passage 21, and this turbo supercharger 22 is located just below the space between the engine 2 and the rear wheel 7. . As schematically shown in FIG. 2, the turbo supercharger 22 is constructed by integrally connecting a turbine wheel 24 in an exhaust turbine 23 and a compressor impeller 26 in a compressor 25 by a drive shaft 27. The exhaust inlet 28 is connected to the expansion chamber 18 through the upstream portion 29a of the exhaust passage 21, and is connected to the exhaust outlet 30.
Similarly, it is connected to the silencing chamber 19 through the downstream portion 29b of the exhaust passage 21. Also Compressa 25
The intake inlet 31 of is connected through an intake introduction pipe 32 to an air cleaner 33 provided below the fuel tank 5, and the outside air sucked from the intake inlet 34 of this air cleaner 33 is filtered by an element 35, and then The air is guided to the intake inlet 31 .
An intake outlet (not shown) of the compressor 25 is communicated with an intake chamber 37 via an intake supply pipe 36, and the intake chamber 37 is communicated with the carburetor 14 via an intake passage 38. A normally closed on-off valve 41 is provided in the bypass passage 40 that directly connects the exhaust gas inlet 28 of the exhaust turbine 23 and the downstream portion 29b of the exhaust passage 21, and this on-off valve 41 is connected to the boost pressure actuator 42. It is opened and closed by twisting. The boost pressure actuator 42 is operated by the intake pressure in the intake air supply pipe 36,
When this intake pressure exceeds a predetermined value, the on-off valve 41 is opened.

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

When the exhaust port 12 is opened and the exhaust gas is discharged from the cylinder 8, the exhaust gas flows into the expansion chamber 18 through the exhaust pipe 16, and the pressure waves of the exhaust gas generated at the time of this inflow collide with the partition wall 20.
Due to this collision, a reflected wave of the exhaust gas is formed in the expansion chamber 18, as shown by the broken line arrow in FIG. 2, which attempts to return toward the exhaust port 12 side. 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 It is possible to prevent blow-through. 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 separated from the silencing chamber 19, the high temperature and 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. And this exhaust is the exhaust turbine 23
is introduced into the turbine wheel 24 to rotate the turbine wheel 24. The rotation of this turbine wheel 24 is caused by the drive shaft 2
7 to the compressor impeller 26, the compressor impeller 26 sucks in the outside air through the intake air introduction pipe 32 and the air cleaner 33, pressurizes this outside air, and sends it 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 forcibly supplied to the intake port 10 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 this exhaust passage 21, so that the exhaust turbine 23 is equipped with the high temperature and high pressure that has flowed into the expansion chamber 18. The exhaust gas will be guided as is. Therefore, the exhaust turbine 23 is substantially brought closer to the exhaust port 12, and pressure attenuation of the exhaust gas is reduced, so a large driving force can be obtained, and the supercharging efficiency is significantly improved.

In this way, according to the above configuration, it is possible to increase supercharging efficiency while effectively utilizing the reflected waves of the exhaust gas, that is, exhaust pulsation, and improve engine output over the entire rotation range from low rotation range to high rotation range. can be done.

Further, since the exhaust turbine 23 is provided at a position different from the exhaust flow path within the muffler 17, the installation location of the turbocharger 22 is not restricted by the position of the muffler 17. Therefore, the degree of freedom in the installation location of the turbo supercharger 22 is increased, which is particularly advantageous in motorcycles where installation locations are limited due to space issues around 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, that is, only the expansion chamber is inside the muffler, and this muffler is 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, these second to seventh
In the embodiment, the same components as those in the first embodiment described above are given the same numbers, and the explanation thereof will be omitted.

A second embodiment of the present invention shown in FIG.
6 is branched into two from the middle, and one branch end 51 has a large-capacity expansion chamber 1 that emphasizes performance in the high rotation range.
8 is connected to the muffler 17, and the other branch end 52 is connected to a muffler 54 having an expansion chamber 53 having a smaller capacity than the expansion chamber 18, which emphasizes performance in a low 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 29a of the exhaust passage 21 via a communication passage 56. ing. Further, a control valve 57 is provided at the branch part of the exhaust pipe 16 to switch communication between the mufflers 17 and 54 and the exhaust port 12.
This control valve 57 is switched and operated by a supercharging pressure actuator 58. Boost pressure actuator 58
If the boost pressure does not reach a certain value, the control valve 57 is operated so that the exhaust port 12 and the muffler 54 for low and medium speeds communicate with each other, and the boost pressure is kept constant by increasing the engine speed by 2. When this value is reached, the control valve 57 is operated to connect the exhaust port 12 and the high-speed muffler 17, thereby switching the exhaust flow path.

According to the configuration of the second embodiment, since the exhaust gas can be guided to the expansion chamber 18 or 53 with an internal capacity commensurate with the flow rate, the pressure attenuation of the exhaust gas is reduced over the entire rotation range, and the supercharging Not only can the effect be further enhanced, but also the build-up of supercharging pressure in the low rotation range can be improved. Furthermore, since the pressure of the reflected waves from the exhaust gas increases in the low rotation range, it is possible to more 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, a pulse motor or a solenoid that detects the engine rotational speed from an ignition pulse and whose rotation is controlled in accordance with this detection signal may be used.

On the other hand, FIG. 4 shows a third embodiment of the present invention, in which the exhaust passage 21 in the expansion chamber 18
A pair of butterfly valves 61 and 62 are provided downstream of the branch position of the exhaust gas and are spaced apart in the flow direction of the exhaust gas, and these butterfly valves 61 and 62 are connected to the boost pressure actuators 63 and 64 or the pulse motor or solenoid, respectively. Therefore, by switching to the open or closed position, the pipe length from the exhaust port 12 to the downstream end of the expansion chamber 18 can be changed depending on the operating condition of the engine 2. According to this configuration, the pulsating effect of the exhaust gas can be fully exerted over the entire rotation range, and together with the supercharging effect, high output can be obtained.

Furthermore, 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 the intake passage 38 is similarly branched and connected with an intake inflow chamber 73 having a constant capacity, and this exhaust port 12
Opening/closing valves 74 and 7 provided in the communication portions between the exhaust inflow chamber 72 and the intake passage 38 and the intake inflow chamber 73, respectively.
5 and the control valve 71 are connected to the supercharging pressure actuator 7.
6 to open and close in conjunction with each other. The supercharging pressure actuator 76 opens the on-off valves 74 and 75 in a low rotation range where the supercharging pressure does not reach a certain value to communicate the exhaust port 12 with the exhaust inflow chamber 72 and the intake passage 38 with the intake inflow chamber 73. At the same time, the control valve 71 is rotated by a certain angle to advance its outer peripheral surface from the top dead center side of the exhaust port 12 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 when the boost pressure reaches a certain value, the on-off valve 74,
75 to close the exhaust inflow chamber 72 and the intake inflow chamber 73, and at the same time, the control valve 71 is moved back to the top dead center side, and the opening height of the exhaust port 12 is increased to advance the exhaust timing. There is.

According to the fourth embodiment with such a configuration, in the low rotation range, the exhaust timing is delayed and the exhaust gas exploded in the cylinder 8 expands and is exhausted after sufficiently pushing down the piston 9, increasing the amount of work. Furthermore, since the actual pipe lengths of the intake passage 38 and the exhaust pipe 16 increase in accordance with the exhaust flow rate, the pulsating effect of intake and exhaust can be effectively utilized, and the output can be improved even in the low rotation range where no supercharging effect can be expected. can. On the other hand, in a high rotation range, the exhaust timing becomes earlier and the opening area of the exhaust port 12 increases, so the exhaust efficiency increases.
Since the pipe length changes to a capacity commensurate with the exhaust flow rate, the pulsating effect of intake and exhaust can be effectively used, and together with the supercharging effect, high output can be obtained.

In addition, in the fourth embodiment described above, the two on-off valves and the control valve are operated in conjunction with one supercharging pressure actuator, but they may be operated independently, or The driving source is not limited to the supercharging pressure actuator, but may be opened and closed using, for example, a pulse motor or a solenoid whose rotation is controlled by detecting the engine rotational speed from an ignition pulse in response to this detection signal.

6 and 7 show a fifth embodiment of the present invention. In this fifth embodiment, the exhaust pipe 1
6. Expansion chamber 18 of muffler 17 and exhaust passage 2
A fibrous catalyst 82 is attached to the entire inner wall surface of the upstream side 29a of 1 through a punching metal 81. According to this configuration, even though the catalyst 82 is provided, the flow of exhaust gas and reflected waves are not obstructed, and since the catalyst 82 receives heat from the exhaust gas immediately after being discharged from the exhaust port 12, the oxidation reaction takes place. The rise leading to the start is faster. Therefore, the oil in the exhaust is burned, reducing the amount of white smoke.
Not only does the purification efficiency improve, but since the exhaust temperature increases due to the oxidation reaction, higher temperature exhaust gas is guided to the exhaust turbine 23, and the 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, mufflers 17, 17' are connected to exhaust pipes 16, 16' led out from left and right cylinders 2, 2', respectively, and exhaust passages branched from respective expansion chambers 18, 18'. 21, 21' upstream parts 29a, 2
9a' 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 portion 29b of the exhaust passage 21, 21', respectively.
Muffler 17, 17' muffler chamber 1 through 29b'
9 and 19'.

Furthermore, in the sixth embodiment described above, each cylinder 2,
Although mufflers 17 and 17' are connected to the cylinders 2' and 2', respectively, as in the seventh embodiment shown in FIG.
The exhaust pipes 16, 16' led out from the exhaust pipe 2' may be gathered together and connected to one muffler 17. In this case, the exhaust passage 21 may be branched immediately after the gathering portion of the exhaust pipes 16, 16', as shown by the imaginary line in FIG.

In each of the above-mentioned embodiments, a turbocharger compressor is 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.

Further, the fuel supply means is not limited to the 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 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 drawings]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a side view of a motorcycle, FIG. 2 is a sectional view, and FIG. 3 is a sectional view showing a second embodiment of the invention. ,
FIG. 4 is a sectional view showing the third embodiment of the present invention, and FIG.
The figure is a sectional view showing a fourth embodiment of the present invention, FIGS. 6 and 7 show a fifth embodiment of the invention, FIG. 6 is a sectional view, and FIG. 8 is a schematic diagram showing a sixth embodiment of the present invention, and FIG. 9 is a schematic diagram showing a seventh embodiment of the present invention. 2...2-stroke engine, 9...piston,
10...Intake port, 12...Exhaust port, 16
...exhaust pipe, 18...expansion chamber, 19...muffling chamber,
21...Exhaust passage, 22...Turbo supercharger, 23
...Exhaust turbine, 25...Compressor.

Claims (1)

[Claims] 1 A two-stroke engine equipped with a turbocharger that rotates an exhaust turbine using the exhaust flow from an exhaust port that is opened and closed by a piston, and uses this exhaust turbine to drive a compressor to supercharge intake air to the intake port. In the engine, the downstream end of the expansion chamber connected to the exhaust pipe led out from the exhaust port is closed, and the upstream side of the closed part of the expansion chamber and the muffling chamber connected downstream of the expansion chamber are connected by an exhaust passage. A two-stroke engine equipped with a turbocharger, characterized in that the exhaust passage is provided with an exhaust turbine of the turbocharger.