JPH04353222A - Four-cycle engine equipped with turbocharger - Google Patents

Abstract

PURPOSE:To provide a 4-cycle engine equipped with a turbocharger which reduces the compression work of a piston and sufficiently recovers the exhaust energy. CONSTITUTION:In a 4-cycle engine, the effective area of an exhaust passage is increased by forming an exhaust port 11 on a cylinder head 1 and forming an exhaust hole 4 in the lower part of a cylinder 10. The exhaust energy is recovered by feeding the exhaust gas having a high pressure and high speed which is supplied from the exhaust hole 4, into an impact turbines 6, and the exhaust gas is sent into a turbocharger 5. An exhaust manifold 3 connected to the exhaust port 11 is connected to the turbocharger 5. Almost all the exhaust gas supplied from the exhaust hole 4 is sent into the impact turbine 6, and the compression work of a piston 7 is reduced, and the reduction of the engine efficiency is prevented, and the residual gas remaining in the cylinder 10 is reduced, and the intake efficiency is improved.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art In general, an engine operates by sequentially repeating an explosion stroke (that is, an expansion stroke), an exhaust stroke, an intake stroke, and a compression stroke. There are two methods. A 4-cycle engine has an intake and exhaust port formed in the cylinder head, and each intake and exhaust port is equipped with an intake and exhaust valve. Each stroke is performed by one stroke of the piston, and in the exhaust stroke, the exhaust valve opens as the piston rises. The exhaust gas inside the cylinder is then discharged. Conventionally, engines with a turbocharger and an energy recovery turbine that are driven by exhaust energy have a turbocharger, an energy recovery turbine, etc. connected downstream of an exhaust pipe such as an exhaust manifold connected to an exhaust port, and the exhaust gas generated by the engine is The exhaust energy possessed by the exhaust gas is recovered by a turbocharger, an energy recovery turbine, etc., and used to drive a compressor, or is stored in a battery as electrical energy by a generator or electric motor.

In addition, in a four-stroke engine, during the explosion stroke (that is, expansion stroke), exhaust stroke, intake stroke, and compression stroke, the cylinder internal pressure, the opening area of the exhaust valve and the intake valve, and the valve timing are as shown in FIG. The trajectory shown in is shown. FIG. 6 is a graph illustrating the cylinder pressure, the opening area of the exhaust valve and the intake valve, and the valve timing with respect to the engine operating cycle. In FIG. 6, the vertical axis represents the cylinder internal pressure, the exhaust valve opening area, and the intake valve opening area, and the horizontal axis represents the operating cycle. At this time, if the opening timing of the exhaust valve is, for example, the end of the explosion stroke, that is, the crank angle is 180°, then
The exhaust valve opening area is now indicated by the symbol EPS, and the intake valve opening area is now indicated by the symbol IPS. At this time, the cylinder internal pressure draws a locus of symbol P, as shown by the dotted line. The exhaust pressure generated within the manifold is designated by the symbol MP.

[0004] Furthermore, in an engine that discharges exhaust gas through an exhaust port formed in the cylinder head, for example, if the exhaust valve opens at the end of the explosion stroke, that is, at a crank angle of 180°, the exhaust gas in the cylinder will be discharged. Only through the exhaust port, and the effective area of the exhaust passage is the area of the passage when the exhaust valve is opened. In addition, in a normal engine, for example, if the exhaust valve opens at the end of the explosion stroke, that is, at a crank angle of 180°, the cylinder pressure P will reach its maximum at the beginning of the explosion stroke as the fuel ignites.
The piston is pushed down to perform work and the cylinder pressure P decreases, and when the exhaust valve is opened, the exhaust gas in the cylinder is exhausted through the exhaust port formed in the cylinder head.
The cylinder pressure P decreases. Next, the exhaust gas in the cylinder is exhausted through the exhaust port as the piston rises during the exhaust stroke, but at the end of the exhaust stroke, the gas pressure in the exhaust manifold increases due to the arrangement of the turbocharger, and the cylinder internal pressure P increases. The pressure difference between the pressure and the manifold exhaust pressure MP becomes small, and the cylinder internal pressure P increases as indicated by HP without exhaust gas being discharged.

[0005] Further, as a turbo compound engine, there is one disclosed in Japanese Patent Application Laid-Open No. 63-9617. The turbo compound engine has a turbocharger and a turbine connected in series to a main exhaust passage of the engine, and a auxiliary exhaust passage that opens later than the main exhaust passage is connected to the main exhaust passage between the turbocharger and the turbine. ,
The auxiliary exhaust passage is provided with an on-off valve whose opening degree is adjusted based on the operating state of the engine.

[0006]

[Problems to be Solved by the Invention] However, in an engine having a turbocharger and an energy recovery turbine, since a load is applied to rotate the turbocharger turbine and the energy recovery turbine, the exhaust gas such as the exhaust manifold connected to the exhaust port is The exhaust pressure MP within the pipe increases, and the back pressure that opposes the discharge of exhaust gas from within the cylinder increases. Therefore, as the piston rises, the combustion gas pressure P in the cylinder and the gas pressure M in the manifold
A phenomenon occurs in which the pressure difference with P becomes small and combustion gas is not sufficiently exhausted from the cylinder to the manifold. In particular, in engines that discharge exhaust gas from the cylinder by opening an exhaust valve from an exhaust port formed in the cylinder head, if the exhaust gas is discharged as the piston rises, the presence of a turbocharger, energy recovery turbine, etc. Since the exhaust pressure MP of the manifold is high, the compression work of the piston increases during the exhaust stroke, and the flow rate per hour through the exhaust valve decreases, leading to an increase in the cylinder pressure, that is, the cylinder pressure P, which reduces engine efficiency. There is a problem that the amount decreases.

Furthermore, near the top dead center of the exhaust stroke, the lift of the exhaust valve becomes smaller, so the flow rate of combustion gas that can be discharged through the exhaust valve decreases in response to the decrease in cylinder internal volume as the piston rises. The pressure P in the cylinder increases rapidly near the end of the exhaust stroke as shown by HP in FIG. As a result, the piston performs compression work at a pressure higher than the exhaust pressure of the engine, resulting in a decrease in engine efficiency and a decrease in suction efficiency due to an increase in residual gas remaining in the cylinder. Further, the outflow speed of exhaust gas is proportional to the ratio of cylinder internal pressure/exhaust pressure, and when the exhaust pressure is high, the outflow speed of exhaust gas decreases. In particular, in engines such as adiabatic engines and high-output diesel engines, when the boost is increased and the amount of working gas is large, the exhaust gas is not sufficiently exhausted through the normal exhaust valve.

The turbo compound engine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 63-9617 discharges exhaust gas through the sub-exhaust passage by adjusting the opening degree of the on-off valve according to the operating condition of the engine. In the vicinity of the top dead center of the piston, the pressure inside the cylinder increases as described above, and as a result, the piston performs compression work, making it impossible to solve the above problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems by providing an exhaust port in the cylinder head and an exhaust hole in the lower part of the cylinder to increase the effective area of the exhaust passage. The effective exhaust area in It is an object of the present invention to provide a four-stroke engine with a turbocharger that reduces compression work, prevents a decrease in engine efficiency, and improves suction efficiency by reducing residual gas remaining in a cylinder.

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is,
This invention provides an exhaust manifold communicating with an exhaust port formed in a cylinder head, a turbocharger communicating with the exhaust manifold, an exhaust hole formed in the lower part of the cylinder that opens near the bottom dead center of the piston, and an exhaust passage communicating with the exhaust hole. The present invention relates to a four-stroke engine having a turbocharger having an impulse turbine communicating with the exhaust passage, and an exhaust pipe communicating an outlet of the impulse turbine upstream of the turbocharger.

[0011] Furthermore, in this four-cycle engine having a turbocharger, the turbocharger is used for generating electricity and
It is equipped with an electric motor.

Furthermore, in this four-stroke engine with a turbocharger, the timing of opening of the exhaust valve disposed at the exhaust port is delayed from the opening of the exhaust hole.

[0013]

[Operation] The four-stroke engine with a turbocharger according to the present invention is constructed as described above and operates as follows. That is, in addition to the exhaust port formed in the cylinder head, this four-cycle engine with a turbocharger has an exhaust hole that opens near the bottom dead center of the piston formed in the lower part of the cylinder, and communicates the exhaust port with the turbocharger. Since the exhaust hole is connected to the impulse turbine and the impulse turbine is connected to the turbocharger, the exhaust hole opens near the bottom dead center of the piston, thereby increasing the effective exhaust area for discharging exhaust gas by the amount of the exhaust hole. As the pressure increases, the exhaust gas in the cylinder passes through the exhaust hole, passes through the impulse turbine, and exhaust energy is recovered. Further, the impulse turbine does not have a nozzle, so there is no need for a pressure ratio, there is no pumping loss due to an increase in combustion gas pressure in the cylinder, and exhaust energy can be effectively recovered. Furthermore, at the beginning of the exhaust stroke, most of the exhaust gas in the cylinder, for example 70%, is exhausted from the exhaust hole, so the amount of exhaust gas in the cylinder is reduced and the exhaust gas pressure is lowered. Even at the end of the exhaust stroke when the piston rises, the combustion gas pressure does not become very high, and the compression work of the piston is reduced.

[0014] Furthermore, in the four-cycle engine having this turbocharger, the turbocharger is used for generating electricity and
Since it is equipped with an electric motor, the exhaust energy of the exhaust gas that has passed through the impulse turbine operates the compressor of the turbocharger and is recovered as electric energy by the generator/electric motor, and the remaining energy is discharged from the exhaust port. The exhaust gas also operates the compressor of the turbocharger, and the exhaust energy is recovered as electrical energy by the generator/motor.

Furthermore, in this engine having a turbocharger and a recovery turbine, the exhaust valve is opened later than the opening of the exhaust hole, so that the combustion gas pressure in the cylinder is dispersed and does not decrease. The high-pressure gas is fed into the impulse turbine while being maintained, and exhaust energy can be effectively recovered.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a four-cycle engine having a turbocharger according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of a four-stroke engine with a turbocharger according to the present invention, and FIG.
is an explanatory diagram showing the turbocharger installed in the engine of FIG. 1, FIG. 3 is an explanatory diagram showing the impulse turbine installed at the bottom of the cylinder of the engine of FIG. 1, and FIG. 4 is an explanatory diagram showing the exhaust gas injection velocity and exhaust gas of the engine of FIG. Graph showing pressure relationship and Figure 5
2 is a graph illustrating the cylinder internal pressure, the opening area of the exhaust valve and the intake valve, and the valve timing for the operating cycle of the engine shown in FIG. 1. FIG.

As shown in the figure, this four-stroke engine with a turbocharger has a turbocharger 5 driven by engine exhaust energy and an impulse turbine 6 which is an energy recovery turbine. This four-stroke engine includes a cylinder block 2, a cylinder head 1 fixed to the cylinder block 2, and a cylinder liner 2L fitted into a hole formed in the cylinder block 2.
, a cylinder 10 formed by the cylinder liner 2L, a piston 7 that reciprocates within the cylinder 10, and a fuel injection nozzle 18 disposed in the cylinder head 1. The cylinder head 1 has an exhaust port 11 and an intake port 1.
2 is formed, an exhaust valve 9 is arranged at the exhaust port 11, and an intake valve 13 is arranged at the intake port 12. Exhaust port 1 formed in cylinder head 1
1 is connected to the exhaust manifold 3 with a manifold gasket 19 interposed therebetween.

This four-stroke engine with a turbocharger has a plurality of exhaust holes (four for each cylinder in FIG. 3) that open in the lower part of the cylinder 10 and near the bottom dead center of the piston, which are formed in the cylinder liner 2L. 4, the exhaust hole 4 is connected to an impulse turbine 6 with blades 27 through an exhaust passage 16, and the outlet 23 of the impulse turbine 6 is connected to a turbine scroll 29 of a turbine 20 in a turbocharger 5 through an exhaust pipe 14. Furthermore, the exhaust manifold 3 is connected to the turbine scroll 29 of the turbine 20.
It is characterized by being connected to. Further, as shown in FIG. 3, the exhaust hole 4 formed at the lower part of the cylinder 10 communicates with the inlet of the impulse turbine 6 through an exhaust passage 16. In order to make the areas the same, an exhaust manifold rib 8 is formed in the exhaust passage 16 and extends along the flow line of the exhaust gas discharged from the exhaust hole 4. These exhaust manifold ribs 8
If the passage cross-sectional area of each passage 17 divided by is made the same,
Expansion of the exhaust gas in the exhaust passage 16 is prevented, and the exhaust gas maintains a high speed and high pressure state to drive the impulse turbine 6.
blades 27 to effectively drive the impulse turbine 6. In addition, each exhaust hole 4 is provided with a reed valve 2.
8 are provided, and each reed valve 28 connects the exhaust passage 1
The exhaust gas is configured to prevent backflow of exhaust gas from the cylinder 6 into the cylinder 10. In some cases, a rotary valve that can open and close each exhaust hole 4 may be provided instead of the reed valve 28, and similar to the reed valve 28, a rotary valve can be provided to prevent backflow of exhaust gas from the exhaust passage 16 into the cylinder 10. Can be configured.

In addition, in the four-cycle engine having this turbocharger, the turbocharger 5 sends exhaust gas from the engine through the exhaust hole 4 to the turbine 20, rotates the turbine 20, thereby rotating the shaft 26, The compressor 22 is rotated to supercharge the engine with intake air, and the generator/motor 21 is rotated to operate the generator/motor 21 as a generator to regenerate energy.

Therefore, in this four-stroke engine with a turbocharger, when the piston 7 descends in the cylinder 10 and reaches the vicinity of the piston bottom dead center (in FIG. 5, the crank angle is 125° during the explosion stroke), the exhaust hole 4 opens. When opened, the cylinder 10 communicates with the exhaust passage 16, and the combustion gas in the cylinder 10 is sent from the exhaust hole 4 through the exhaust passage 16 to the impulse turbine 6, where the exhaust energy of the exhaust gas is recovered. . Next, the impulse turbine 6
The exhaust gas that has passed through is sent from the outlet 23 through the exhaust pipe 14 to the turbine scroll 29 of the turbine 20 in the turbocharger 5. The exhaust valve 9 opens later than the opening of the exhaust port 4 (in FIG. 5, at the end of the explosion stroke, that is, at a crank angle of 180°), and the exhaust gas flows through the exhaust port 1.
1 to the exhaust manifold 3 and sent to the turbine scroll 29 of the turbine 20 of the turbocharger 5.

Therefore, in this four-stroke engine with a turbocharger, the exhaust hole 4 opens near the bottom dead center of the piston, and most of the combustion gas in the cylinder 10 is sent to the impulse turbine 6 through the exhaust hole 4. However, since the impulse turbine 6 does not have a nozzle, the cylinder 1
There is no need for a pressure difference, that is, a pressure ratio, between the gas pressure within 0 and the gas pressure on the outlet 23 side of the impulse turbine 6, and there is no pumping loss due to an increase in engine exhaust pressure, and the impulse turbine 6 effectively recovers exhaust energy. be able to. Further, the exhaust gas discharged from the exhaust hole 4 is transferred to an impulse turbine 6.
After driving, the exhaust gas is sent from the outlet 23 of the impulse turbine 6 to the turbine 20 of the turbocharger 5, and after driving the turbine 20, the exhaust gas is exhausted to the outside. Therefore, the effective exhaust area for discharging exhaust gas increases by 4 times the exhaust hole, and the exhaust gas in the cylinder 10 is discharged to the impulse turbine 6 through the exhaust hole 4, and the exhaust gas is discharged from the exhaust hole 4 to the engine regardless of the exhaust pressure. As the high pressure gas from the blowdown flows out in a short time, the blades 2 of the impulse turbine 6
7 can be effectively rotated. Next, the exhaust gas that has passed through the impulse turbine 6 is transferred to the turbine 2 of the turbocharger 5.
0, which drives the turbine 20 and the compressor 22, and can be recovered as electrical energy by the generator/motor 21 provided in the turbocharger 5.

In the above-mentioned operation of the four-stroke engine with this turbocharger, what are the engine exhaust pressure P and the jet speed C during blowdown for each position along the flow of exhaust gas for the exhaust gas discharged from the exhaust hole 4? ,
The result is as shown in FIG. FIG. 4 is a graph showing the evolution of exhaust gas ejection speed and exhaust pressure of exhaust gas discharged from the exhaust hole in this four-stroke engine. Exhaust hole 4
Regarding the exhaust gas discharged from the engine, at the position of the exhaust hole 4, the engine exhaust pressure P is the exhaust pressure P1, and the jetting speed C during blowdown is the jetting speed C1. Exhaust gas is discharged from the exhaust hole 4 and sent to the impulse turbine 6,
At the exit position that has passed through the impulse turbine 6, the engine exhaust pressure P is the exhaust pressure P2, which is the same value as the exhaust pressure P1, but the injection speed C during blowdown is reduced by the impulse turbine 6 and is changed from the injection speed C1. The ejection speed becomes C2. Next, the exhaust gas is sent to the turbine scroll 29 of the turbocharger 5, and at the turbine scroll 29, that is, at the nozzle position, the engine exhaust pressure P is reduced from the exhaust pressure P2 to the exhaust pressure P3, and the ejection speed C is reduced by that amount. From the jetting speed C2 to the jetting speed C3
and is sent to the turbine 20. Therefore, the exhaust gas acts on the rotor blades of the turbine 20 in the turbocharger 5, and the exhaust pressure P3 and the injection speed C3 are consumed, and at the outlet 15 of the turbine 20, the exhaust pressure P3 is reduced to the exhaust pressure P4, and the injection speed is reduced. The ejection speed is reduced from C3 to C4. That is, exhaust pressure P4 and injection speed C
4 is the exhaust pressure and ejection speed of the muffler installed in the engine. Note that the exhaust pressure and injection speed shown by dotted lines in FIG. 4 are for the case where the exhaust gas in the cylinder 10 is discharged through the exhaust port 11 formed in the cylinder head 1.

Furthermore, this four-stroke engine with a turbocharger communicates the exhaust manifold 3 with the turbocharger 5, and sends the remaining exhaust gas exhausted from the exhaust port 11 to the turbine 20 of the turbocharger 5.
Even if the combustion gas pressure in the cylinder 10 decreases near the top dead center of the exhaust stroke, the exhaust pressure in the exhaust manifold 3 is considerably low, so the exhaust gas is discharged sufficiently smoothly and the exhaust energy is sufficiently transferred to the turbocharger 5. can be recovered. That is, most of the exhaust gas, for example 70%, is exhausted from the exhaust hole 4 at the beginning of the exhaust stroke, so the amount of exhaust gas inside the cylinder 10 is reduced, and even when the piston rises during the exhaust stroke, combustion gas The pressure is not very high (PX shown by the dotted line in Figure 5).
), the compression work of the piston 7 is reduced.

In other words, as shown in FIG. 5, the four-stroke engine with this turbocharger has an effective exhaust area of four exhaust ports, as shown in FIG. The effective exhaust area increases, and the effective exhaust area becomes the sum of the effective exhaust area EPS of the exhaust port 11 and the effective exhaust area EHS of the exhaust hole 4, and the effective exhaust area is significantly increased. Moreover, a large number of exhaust holes 4 provided at the bottom of the cylinder 10 can be provided in the circumferential direction of the cylinder 10 (four for each cylinder in FIG. 3), and a large amount of exhaust gas can be passed from the exhaust holes 4 to the exhaust passage 1 in a short time.
6 to the impulse turbine 6.

Therefore, this four-stroke engine with a turbocharger discharges the exhaust gas in the cylinder 10 through the exhaust port 11 formed in the cylinder head 1 and the exhaust hole 4 formed in the lower part of the cylinder 10, as shown in FIG.
As shown by the dotted lines P and PX, the combustion gas pressure in the cylinder 10 decreases, and in the subsequent exhaust stroke, the amount of combustion gas in the cylinder has already decreased, so even if the piston moves up, the exhaust gas pressure will not decrease. is not expensive. That is, cylinder 1
By providing the exhaust hole 4 at the bottom of the cylinder 10, the cylinder pressure inside the cylinder 10 decreases from the cylinder pressure P0 to the cylinder pressure PX, and the compression work of the piston 7 during the exhaust stroke becomes W as indicated by the diagonal line.
It will be reduced by X. In a conventional four-stroke engine with a turbocharger, as shown in FIG. 5 or FIG. When port 11 and exhaust hole 4 are opened, the cylinder pressure becomes PX, and in this 4-stroke engine with a turbocharger, the symbol W shown by diagonal lines is
The compression work of the piston 7 will be reduced by X.

Furthermore, in this four-stroke engine with a turbocharger, the exhaust gas in the cylinder 10 is sent through the exhaust hole 4 to the impulse turbine 6 where the exhaust energy is recovered, and then the exhaust gas that has passed through the impulse turbine 6 is is sent to the turbine 20 of the turbocharger 5, so the exhaust energy is recovered by the generator/motor 21 of the turbocharger 5, and also by operating the compressor 22, and the exhaust gas in the cylinder 10 is then transferred to the exhaust valve 9. Exhaust port 11 and exhaust manifold 3 when open
The exhaust energy of the exhaust gas is sufficiently recovered by the turbocharger 5.

[0027]

[Effects of the Invention] A four-stroke engine with a turbocharger according to the present invention is constructed as described above.
It has the following effects. That is, this four-cycle engine with a turbocharger has an exhaust manifold communicating with an exhaust port formed in the cylinder head, a turbocharger communicating with the exhaust manifold, an exhaust hole formed in the lower part of the cylinder that opens near the bottom dead center of the piston, Since it has an exhaust passage communicating with the exhaust hole, an impulse turbine communicating with the exhaust passage, and an exhaust pipe communicating the outlet of the impulse turbine upstream of the turbocharger, the exhaust hole opens near the bottom dead center of the piston. As a result, the effective exhaust area increases by the amount of the exhaust hole, and the exhaust gas in the cylinder is discharged to the impulse turbine through the exhaust hole, thereby driving the impulse turbine. Since the impulse turbine does not have a nozzle, the impulse turbine does not require a pressure ratio, the exhaust pressure does not increase, there is no pumping loss, and the exhaust energy can be effectively recovered by the generator/motor. Then,
The exhaust gas that has passed through the impulse turbine is sent to the turbocharger through the exhaust pipe, and the exhaust gas drives the turbine of the turbocharger to drive the compressor. Recover energy as electrical energy.

Therefore, in this four-cycle engine with a turbocharger, the exhaust gas in the cylinder passes through the exhaust port and the exhaust hole, and the absolute amount of exhaust gas decreases at the end of the explosion stroke and at the beginning of the exhaust stroke, causing the piston to rise. Even when the combustion gas pressure in the cylinder does not rise much, the compression work of the piston is reduced, and the pressure in the cylinder is particularly low at the end of the exhaust stroke, so there is little residual gas remaining in the cylinder, and in the subsequent intake stroke. Sufficient intake air can be introduced into the cylinder to improve intake efficiency.

In particular, when a four-stroke engine with a turbocharger is applied to an adiabatic engine or a high-output diesel engine, the four-stroke engine has a high boost and a large amount of working gas. However, the exhaust gas inside the cylinder is well discharged,
Since the cylinder internal pressure near the end of the exhaust stroke can be kept low, the compression work of the piston during the exhaust stroke can be reduced, and the suction efficiency can also be improved. Moreover, the exhaust energy discharged from inside the cylinder can be sufficiently recovered by the impulse turbine communicating with the exhaust hole formed at the bottom of the cylinder and the turbocharger provided downstream of the exhaust manifold. It can increase engine efficiency and reduce fuel consumption.

Furthermore, in this four-cycle engine with a turbocharger, the exhaust valve disposed at the exhaust port opens later than the opening of the exhaust hole, so that the exhaust gas in the cylinder initially flows through the exhaust hole. The pressure of the combustion gas in the cylinder is dispersed and the exhaust gas maintains a high pressure and high speed state, and then passes through the exhaust hole and the exhaust passage to the impulse turbine. The exhaust energy that is sent and contained in the exhaust gas can be effectively recovered.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a four-stroke engine with a turbocharger according to the present invention.

FIG. 2 is an explanatory diagram showing a turbocharger provided in the engine of FIG. 1.

FIG. 3 is an explanatory diagram showing an impulse turbine provided under the cylinder of the engine in FIG. 1;

FIG. 4 is a graph showing the evolution of exhaust gas jetting speed and exhaust pressure of exhaust gas discharged from an exhaust hole in the four-cycle engine shown in FIG. 1;

FIG. 5 is a graph illustrating cylinder pressure, exhaust valve and intake valve opening areas, and valve timing for the operating cycle of the engine in FIG. 1;

FIG. 6 is a graph illustrating cylinder internal pressure, exhaust valve and intake valve opening areas, and valve timing for the operating cycle of a conventional engine.

[Explanation of symbols]

1 Cylinder head 2 Cylinder block 3 Exhaust manifold 4 Exhaust hole 5 Turbocharger 6 Impulse turbine 7 Piston 9 Exhaust valve 10 Cylinder 11 Exhaust port 14 Exhaust pipe 16 Exhaust passage 20 Turbine

Claims (3)

[Claims] Claim 1: An exhaust manifold communicating with an exhaust port formed in a cylinder head, a turbocharger communicating with the exhaust manifold, an exhaust hole formed in the lower part of the cylinder that opens near the bottom dead center of the piston, and an exhaust communicating with the exhaust hole. A four-stroke engine having a turbocharger having a passage, an impulse turbine communicating with the exhaust passage, and an exhaust pipe communicating an outlet of the impulse turbine upstream of the turbocharger. 2. The four-stroke engine with a turbocharger according to claim 1, wherein the turbocharger includes a generator/electric motor. 3. The four-stroke engine with a turbocharger according to claim 1, wherein the exhaust valve disposed at the exhaust port opens later than the exhaust hole.