JPH05214948A - Two-stroke engine with turbo-charger - Google Patents

Abstract

PURPOSE:To provide a two-stroke engine having a turbo-charger effectively recovering exhaust energy. CONSTITUTION:An exhaust port 4 is formed at the lower section of a cylinder 10, and the exhaust port 4 is communicated to an exhaust passage 8 or an exhaust passage 11 by the action of a selector valve 3. The exhaust passage 8 is communicated to the upstream side of a turbo-charger 5, and the exhaust passage 11 is communicated to the downstream side of the turbo-charger 5. The exhaust port 4 is communicated to the exhaust passage 8 when the cylinder pressure is high, the exhaust port 4 is communicated to the exhaust passage 8 when the cylinder pressure is low, and the high-pressure exhaust energy at the initial stage of the exhaust stroke in the turbo-charger 5 can be effectively recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine having a turbocharger driven by the exhaust energy of the engine.

[0002]

2. Description of the Related Art Generally, regarding the operation of an engine, the operations of an explosion stroke (that is, an expansion stroke), an exhaust stroke, an intake stroke, and a compression stroke are sequentially repeated. There are two methods. In a two-stroke engine, an exhaust port is formed in the cylinder head or the lower part of the cylinder, a scavenging port is provided in the lower part of the cylinder, and one stroke is completed by two stalks of the piston. be able to. Conventionally, an engine having a turbocharger driven by exhaust energy and an energy recovery device has a turbocharger and an energy recovery device connected downstream of an exhaust pipe such as an exhaust manifold connected to an exhaust port, so that exhaust energy generated by the engine is It is recovered by a turbocharger or energy recovery device and drives a compressor, or is recovered as electric energy by a generator / motor.

Further, as an exhaust energy recovery system for an engine, there is one disclosed in Japanese Patent Application Laid-Open No. 59-20526. The exhaust energy recovery system of the engine is
It suppresses the dissipation of heat generated inside and recovers the energy of the exhaust gas.The rotary shafts of the DC generator are directly connected to the turbine shafts of the multiple exhaust turbines that are sequentially installed at the tip of the engine exhaust manifold. In addition, the rotating shaft of the DC motor is connected to the rotating shaft of the engine, the electric energy generated from the DC generator is applied to the DC motor to drive it, and the output of the DC motor is fed back to the output shaft of the engine. Is.

Further, Japanese Patent Laid-Open No. 3-50363 discloses that
A two-stroke adiabatic engine is disclosed. In the two-stroke heat insulation engine, the lower surface of the head and the upper portion of the liner are constructed in a heat insulating structure, an exhaust valve is arranged in an exhaust port formed in the lower surface of the head, and a heat insulating gasket is arranged at the boundary between the upper portion of the liner and the lower portion of the liner. However, many intake ports are formed in the lower part of the liner, and the intake ports are opened to intake ports formed in the outer periphery of the lower part of the liner.

[0005]

By the way, in a two-stroke engine, when a turbocharger is provided, it is impossible from the two-stroke principle to make the exhaust pressure higher than the scavenging pressure. However, the cylinder pressure immediately before the exhaust stroke is several kg / cm ² or more, and if the high cylinder pressure is utilized, it is possible to effectively recover the exhaust energy by the exhaust turbine. However, in reality, the pressure once expands to the pressure on the upstream side of the exhaust turbine, and the pressure expands to the atmospheric pressure. Only the pressure difference can be recovered by the exhaust turbine. Further, when considering increasing the pressure on the upstream side of the exhaust turbine and increasing the amount of recovery thereof, in a two-stroke engine, the scavenging air pressure needs to be increased to a pressure higher than the pressure on the upstream side of the exhaust turbine. The required energy is increased, and the total energy recovery efficiency is not improved.

Therefore, an object of the present invention is to solve the above problems, and in a two-stroke engine in which a scavenging port and an exhaust port are formed in the lower part of a cylinder formed in a cylinder block, the exhaust formed in the lower part of the cylinder is exhausted. The port divides into communication with the first exhaust passage and the second exhaust passage, communicates with the first exhaust passage upstream of the turbocharger, and communicates the second exhaust passage downstream of the turbocharger with the exhaust port and the first exhaust passage. The communication with the exhaust passage or the second exhaust passage is switched by a switching valve such as a rotary valve, and only the exhaust gas whose cylinder pressure is higher than the scavenging pressure is sent to the turbocharger through the first exhaust passage to effectively recover the exhaust energy. The purpose is to provide a two-stroke engine with a turbocharger.

[0007]

In order to achieve the above object, the present invention is configured as follows. That is,
The present invention relates to a two-stroke engine having a turbocharger having a scavenging port and an exhaust port formed in a lower portion of a cylinder formed in a cylinder block, and a first stroke communicating with the exhaust port and upstream of the turbocharger. An exhaust passage, a second exhaust passage communicating with the exhaust port and downstream of the turbocharger, and the exhaust port are switched to communicate with either the first exhaust passage or the second exhaust passage. A two-stroke engine having a turbocharger characterized by having a switching valve.

Further, in the two-stroke engine having the turbocharger, the switching valve is operated in synchronization with the rotation of the engine so that the exhaust port and the first exhaust passage communicate with each other in the first half of the exhaust stroke. In the latter half of the stroke, the exhaust port and the second exhaust passage are operated to communicate with each other.

[0009]

The two-stroke engine having the turbocharger according to the present invention is constructed as described above and operates as follows. That is, 2 with this turbocharger
In the stroke engine, an exhaust port is formed in a lower portion of a cylinder, the exhaust port is connected to an upstream side of the turbocharger by a first exhaust passage, and the exhaust port is connected to a downstream side of the turbocharger by a second exhaust passage, Further, since the exhaust valve has a switching valve that is switched so as to communicate with either the first exhaust passage or the second exhaust passage, only exhaust gas having a pressure higher than the scavenging pressure is sent to the upstream side of the turbocharger. be able to.

That is, by opening the exhaust port near the bottom dead center of the piston, the exhaust gas in the cylinder is exhausted to the turbine upstream side of the turbocharger through the first exhaust passage, and the exhaust gas is exhausted even if the exhaust pressure is large. Since high-pressure gas from the engine blowdown flows out from the port in a short time, the turbine of the turbocharger can be driven, the compressor can be driven, and if the turbocharger is equipped with a generator / motor, the generator / motor can be used. It can be recovered as electric energy, and the energy of the exhaust gas can be effectively recovered.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a two-stroke engine having a turbocharger according to the present invention will be described below with reference to the drawings. 1 is a schematic sectional view showing an embodiment of a two-stroke engine having a turbocharger according to the present invention,
2 is a schematic cross-sectional view showing a state in which the opening / closing valve in the two-stroke engine of FIG. 1 has the second exhaust passage opened, and FIG.
Is an explanatory view showing a turbocharger provided in the engine of FIG. 1, FIG. 4 is an explanatory view showing an energy recovery turbine provided in the engine of FIG. 1, and FIG. 5 is an example of operation of a two-stroke engine having this turbocharger. FIG.

As shown in the figure, a two-stroke engine having this turbocharger has a turbocharger 5 and an energy recovery device 6 driven by the exhaust energy of the engine. This two-stroke engine rotates a cylinder block 2, a cylinder head 1 fixed to the cylinder block 2, a cylinder 10 formed in the cylinder block 2, a piston 7 reciprocating in the cylinder 10, and a reciprocating motion of the piston 7. It has a connecting rod and a crankshaft that convert it into motion. In FIG. 1, the cylinder 10 formed in the cylinder block 2 is schematically illustrated. A fuel injection nozzle 9 is arranged in the cylinder head 1.

A two-stroke engine having this turbocharger is particularly equipped with an exhaust port 4 and a scavenging port 12 which are open at the bottom of the cylinder 10 and near the piston bottom dead center.
Is formed. Further, the exhaust port 4 is connected to the upstream side of the turbocharger 5, that is, the turbine scroll 14 of the turbine 20 through an exhaust passage 8 which is a first exhaust passage. Further, the exhaust port 4 is connected to an upstream side of the energy recovery device 6, that is, a turbine scroll 17 of the power generation turbine 25, on the downstream side of the turbocharger 5 through an exhaust passage 11 which is a second exhaust passage. The outlet of the turbine 20 of the turbocharger 5 is connected to a turbine scroll 17 of the energy recovery device 6 through an exhaust pipe, that is, an exhaust passage 16. Of course, in some cases, the exhaust passage 11 may communicate with the exhaust passage 18 on the downstream side of the energy recovery device 6.

Further, in the two-stroke engine having this turbocharger, a switching valve 3 which is a rotary valve is provided at the outlet of the exhaust port 4 and the exhaust port is rotated by the rotational operation of the switching valve 3 (counterclockwise in the figure). 4 is communicated with either the exhaust passage 8 or the exhaust passage 11. In particular, the switching valve 3 is operated in synchronization with the rotation of the engine. As shown in FIG. 1, the exhaust port 4 communicates with the exhaust passage 8 in the first half of the exhaust stroke, and as shown in FIG. The exhaust port 4 is communicated with the exhaust passage 11 near the bottom dead center BDC, that is, in the latter half of the exhaust stroke. That is, the exhaust port 4 communicates with the exhaust passage 8 when the in-cylinder pressure is high above a predetermined pressure in the exhaust stroke, and communicates with the exhaust passage 11 when the in-cylinder pressure is low below a predetermined pressure. Therefore, when the piston 7 descends in the cylinder 10 and near the piston bottom dead center, the exhaust port 4 opens and the combustion gas in the cylinder is exhausted from the exhaust port 4 or the exhaust passage 8 depending on the turning position of the switching valve 3. It is sent to the passage 11.

The switching valve 3 can be constructed so as to operate at the same speed in synchronization with the engine rotation. Alternatively, the controller may be configured to control in response to engine operating conditions. Also, turbocharger 5
The air pressurized by the compressor 19 of the
Through the intake manifold through the intercooler or the like, and from the intake manifold to the scavenging port 1 through the intake manifold.
2, then sent into the cylinder.

Further, as shown in FIG. 3, the turbocharger 5 incorporated in this two-stroke engine has a turbine 20, a compressor 19 connected to a shaft 23 fixed to the turbine 20, and a power generation / provided on the shaft 23. It has an electric motor 21. The turbine scroll 14 on the inlet side of the turbine 20 communicates with the exhaust pipe, that is, the exhaust passage 8. The exhaust passage 16 on the outlet side of the turbine 20 is
It communicates with the turbine scroll 17 on the inlet side of the power generation turbine 25 of the energy recovery device 6 shown in FIG. The exhaust passage 18 on the outlet side of the power generation turbine 25 is open to the atmosphere through, for example, an exhaust gas purifying device. In the energy recovery device 6, a generator 27 is provided on a shaft 22 fixed to a generator turbine 25, and the generator 2
The exhaust energy is collected at 7.

The operation timing of the two-stroke engine configured as described above will be described with reference to FIG.
FIG. 5 is a timing diagram for explaining an embodiment of the operation of the two-stroke engine having this turbocharger.
In FIG. 5, the reference symbol P indicates the displacement of the piston 7 when the piston 7 reciprocates in the cylinder 10, and the top dead center is T.
DC and bottom dead center are indicated by BDC. Furthermore, in FIG. 5, the exhaust port 4 in this two-stroke engine is shown.
Is the openable period of A, the open period of the scavenging port 12 is B, the open period of the switching valve 3 on the exhaust passage 8 side is C, the open period of the switching valve 3 on the exhaust passage 11 side is D, and the exhaust A symbol E indicates a closed period in which the port 4 is openable but closed by the switching valve 3. Therefore, when the switching valve 3 is closed, the exhaust port 4 is closed, and the open period of the exhaust port 4 is shortened.

In this two-stroke engine, when the piston 7 becomes close to the top dead center TDC in the compression stroke and the cylinder air is compressed to a high temperature and high pressure, fuel is injected from the fuel injection nozzle 9 into the cylinder and compressed. Mixed with air and burned,
In the combustion stroke, the piston 7 descends. When the piston top surface 15 of the piston 7 begins to wrap with the upper portion 13 of the exhaust port 4, that is, when the exhaust port 4 begins to open in the cylinder and the exhaust stroke begins, the switching valve 3 becomes the position shown in FIG. At the beginning of the exhaust stroke, the exhaust passage 8 is opened, and the high-temperature and high-pressure combustion gas in the cylinder is exhausted to the exhaust passage 8 through the exhaust port 4 and the switching valve 3, and then the turbocharger 5
It is sent to the turbine 20 of. In this case, the pressure in the exhaust passage 8 has a high exhaust pressure because the turbocharger 5 and the energy recovery device 6 are provided, but the in-cylinder pressure becomes higher than the exhaust pressure. Because
Most of the combustion gas in the cylinder is turbocharged in a short time.
Outflows to.

Further, the piston 7 descends, and the piston top surface 1
Since the switching valve 3 is rotating at the timing when 5 starts to wrap with the upper portion 26 of the scavenging port 12, that is, at the timing when the scavenging port 12 starts to open in the cylinder, the switching valve 3 comes to the position shown in FIG. The exhaust passage 8 is closed so that the exhaust port 4 communicates with the exhaust passage 11. When the exhaust port 4 communicates with the exhaust passage 11, the combustion gas in the cylinder is exhausted through the exhaust passage 11 and fresh air is introduced into the cylinder through the scavenging port 12 so that the exhaust gas is pushed out by the fresh air. The residual gas in the cylinder is exhaust passage 11
Exhausted from. The exhaust gas discharged from the exhaust passage 11 is exhausted to the exhaust passage 11 on the downstream side of the turbocharger 5 or the exhaust passage 18 on the downstream side of the energy recovery device 6. Further, as the piston 7 rises, the scavenging port 1
2 is closed, and at this time, the switching valve 3 closes the exhaust port 4. Of course, the closing timing of the exhaust port 4 of the switching valve 3 can be controlled before or after closing the scavenging port 12.

In the two-stroke engine having this turbocharger, the pressure of each portion at the timing of opening the exhaust passage 8, opening the exhaust passage 11, and opening the scavenging port 12 by the operation of the switching valve 3 is examined. The pressure of 8 is the highest, the pressure of the scavenging port 12 continues, and the pressure of the exhaust passage 11 is low. Therefore,
If the switching valve 3 is not provided in the exhaust port 4, a phenomenon occurs in which exhaust gas flows back into the cylinder due to the pressure in the exhaust passage 8.
Since it is closed by, the backflow phenomenon of exhaust gas into the cylinder does not occur. The pressure in the exhaust passage 11 is the same as that of the scavenging port 1.
The pressure is lower than the pressure in 2 and the scavenging and intake strokes are performed well. Subsequently, the piston 7 rises again, the scavenging / intake stroke by the exhaust passage 11 and the scavenging port 12 is completed, and the compression stroke is started. During the scavenging / intake stroke and the compression stroke, the switching valve 3 is closed.

Therefore, in the two-stroke engine having this turbocharger, the switching valve 3 opens near the piston bottom dead center and the exhaust port 4 communicates with the inside of the exhaust passage 8, whereby the inside of the cylinder passes through the exhaust port 4. The combustion gas is exhausted to the upstream side of the turbine 20 of the turbocharger 5, and the exhaust gas drives the turbine 20 and then the turbine 20
Energy recovery device 6 through the exhaust passage 16 from the outlet of the
Of the exhaust gas, the exhaust gas is driven to the power generation turbine 25 and then exhausted to the outside. Therefore,
The exhaust gas in the cylinder is exhausted to the upstream side of the turbine 20 of the turbocharger 5 through the exhaust port 4, and even if the exhaust pressure is high, the high pressure gas for blowdown of the engine flows out from the exhaust port 4 in a short time. It is possible to drive the turbine 20 of No. 5 and drive the compressor 19, and at the same time, it can be recovered as electric energy by the power generator / motor 21 provided in the turbocharger 5.

Further, by connecting the exhaust passage 11 to the upstream side of the energy recovery device 6, the energy recovery device 6 recovers the exhaust energy of the remaining exhaust gas exhausted from the exhaust port 4.

[0023]

The two-stroke engine having the turbocharger according to the present invention is constructed as described above and has the following effects. That is, in the two-stroke engine having this turbocharger, the first exhaust passage communicating with the exhaust port formed in the lower portion of the cylinder communicates with the upstream side of the turbocharger, and the second exhaust passage communicating with the exhaust port has the above-mentioned second exhaust passage. Since a switching valve that communicates with the downstream side of the turbocharger and is switched so that the exhaust port communicates with either the first exhaust passage or the second exhaust passage is provided, high-pressure exhaust gas in the early stage of the exhaust stroke is provided. Exhaust energy can be effectively recovered by being sent to the turbocharger through the switching valve and the first exhaust passage.

That is, in the early stage of the exhaust stroke, the exhaust gas in the cylinder can be exhausted to the turbine upstream side of the turbocharger through the first exhaust passage through the switching valve opened from the exhaust port, and the exhaust pressure is large even if the exhaust pressure is large. High-pressure gas from the engine blowdown flows out from the exhaust port in a short time, so that the turbine can be driven, the compressor can be driven, and the turbocharger can generate electricity.
When an electric motor is provided, it can be recovered as electric energy by the generator / motor.

Further, if an energy recovery device is provided downstream of the turbocharger, after driving the turbocharger, the exhaust gas is sent to the energy recovery device to drive the power generation turbine of the energy recovery device. Exhaust energy can be recovered.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a two-stroke engine having a turbocharger according to the present invention and showing a state where a switching valve and a high pressure side exhaust passage are in communication with each other.

FIG. 2 is a schematic cross-sectional view showing a state in which a switching valve and a low pressure side exhaust passage communicate with each other in the two-stroke engine of FIG.

FIG. 3 is a schematic explanatory view showing an example of a turbocharger having a generator / motor incorporated in the two-stroke engine of FIG.

FIG. 4 is a schematic explanatory diagram showing an example of an energy recovery device incorporated in the two-stroke engine of FIG.

FIG. 5 is a timing diagram showing an example of the operation of a two-stroke engine having this turbocharger.

[Explanation of symbols]

 1 Cylinder Head 2 Cylinder Block 3 Switching Valve 4 Exhaust Port 5 Turbocharger 6 Energy Recovery Device 7 Piston 8 Exhaust Passage (First Exhaust Passage) 10 Cylinder 11 Exhaust Passage (Second Exhaust Passage) 12 Scavenging Port 15 Piston Top

Claims (2)

[Claims] 1. A two-stroke engine having a turbocharger having a scavenging port and an exhaust port formed in a lower portion of a cylinder formed in a cylinder block, the two-stroke engine communicating with the exhaust port and upstream of the turbocharger. 1 exhaust passage, a second exhaust passage communicating with the exhaust port and downstream of the turbocharger, and the exhaust port switched to communicate with either the first exhaust passage or the second exhaust passage A two-stroke engine with a turbocharger, which has a switching valve that is operated. 2. The switching valve is operated in synchronization with the rotation of the engine, connects the exhaust port and the first exhaust passage in the first half of the exhaust stroke, and connects the exhaust port and the second port in the latter half of the exhaust stroke. The two-stroke engine having a turbocharger according to claim 1, wherein the two-stroke engine communicates with an exhaust passage.