JPH0533673A - Two-four cycle changeable turbo-compound engine - Google Patents

Abstract

PURPOSE:To improve the extent of scavenging efficiency in a 2-4 cycle changeable engine. CONSTITUTION:An intake valve 2 and an exhaust valve 3 are installed in a cylinder head 1 while a scavenging hole 5 and an exhaust hole 6 being free of opening or closing by a slide valve 7 is installed in a cylinder liner 4. At the time of two cycle drive, fresh air is injected from this scavenging hole 5, and it is exhausted by both the valve 3 and the hole 6. At the time of four cycle drive, the scavenging hole 5 is closed by the slide valve 7, intake air takes place from the intake valve 2, and exhaust is carried out from both the valve 3 and the hole 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 2-4 cycle switching turbo compound engine, and more particularly to a 2-4 cycle switching turbo compound engine for smoothing the scavenging in the cylinder to improve the efficiency of the engine.

[0002]

2. Description of the Related Art A conventional piston reciprocating engine is a two-cycle engine that performs intake, compression, explosion, and exhaust processes by one reciprocating piston, that is, one revolution of a crankshaft.
It is roughly classified into a four-cycle engine that performs the above four steps during two reciprocations of the piston, that is, two revolutions of the crankshaft.

There are several types of the above-mentioned two-cycle engine. For example, in the uniflow type, an exhaust valve is arranged above the cylinder sleeve and a scavenging port is arranged below the exhaust valve so that the piston bottoms. When it is near the point position, in-cylinder combustion gas is ejected from this exhaust valve, and after a short delay, fresh air is pumped into the cylinder from the scavenging port, and the exhaust gas in the cylinder sleeve is sent to the cylinder by the pumped fresh air. The process of discharging the air from the exhaust valve above the sleeve and compressing the fresh air filled in the cylinder sleeve by the piston that has started to move upward and injecting the fuel near the top dead center of the piston is repeated. A two-cycle engine including such a uniflow type has a characteristic that an explosion is generated for each revolution of the crankshaft, so that a rotational fluctuation of the output shaft is small and a high torque can be generated.

On the other hand, in the four-cycle engine, since the intake and the exhaust are performed in independent steps, the exhaust gas and the fresh air are sufficiently replaced, and the exhaust gas at the time of low load and low speed operation is compared with the two-cycle engine. Is clean and has a characteristic that the fuel consumption rate is small especially when the engine speed is high.

[0005]

Recently, an engine has been developed which can be operated by switching between 2-cycle operation and 4-cycle operation by one engine and making full use of these advantages.
This engine obtains the scavenging air pressure during two-cycle operation by attaching a scavenging compressor to the crank chamber. Since the scavenging air pressure depends on the rotation of the engine, for example, when the engine is idling, The scavenging pressure is too low to perform sufficient scavenging when the load and rotation speed are low. Further, there is a problem that oil mist is mixed into the fresh air, and there is a problem that the size of the engine becomes large due to the attachment of the compressor. In addition, there is a problem that the open area of the exhaust valve is insufficient in high-speed operation and sufficient scavenging cannot be performed. Further, even during the four-cycle operation, the exhaust valve must be provided in the cylinder head having a limited space for arrangement, so that there is a problem that a sufficient exhaust area cannot be secured.

SUMMARY OF THE INVENTION The present invention is intended to provide a 2-4 cycle switching engine which is capable of performing smooth exhaust during the 2 cycle operation and the 4 cycle operation in the 2-4 cycle switching engine.

[0007]

In order to solve the above-mentioned problems, the present invention provides a turbo compound engine which is supplied with fresh air from a compressor driven by a turbine rotated by exhaust gas and which can be switched over for 2-4 cycles.
The cylinder head is provided with an exhaust valve and an intake valve that operates only during four-cycle operation, an exhaust hole and a scavenging hole communicating with the output side of the compressor are provided in the lower portion of the side wall of the cylinder liner, and the outer periphery of the cylinder liner is provided. The present invention provides a 2-4 cycle switching turbo compound engine characterized by being provided with a slide valve which is rotatable in a circumferential direction along the circumference and which makes the scavenging hole communicate with the output side of the compressor during scavenging.

[0008]

According to the present invention, the two-cycle operation is performed in a region where the engine speed is high and the load is small, and the high pressure gas in the cylinder is ejected from the exhaust hole of the cylinder side and the high pressure gas is ejected similarly from the exhaust valve in the initial stage of the exhaust operation. Let After that, the residual exhaust gas is pushed by the high-pressure fresh air introduced from the scavenging port provided on the side wall of the cylinder liner, and is discharged from the exhaust valve provided on the cylinder head. Four-cycle operation is performed in a region where the engine speed is relatively high, and exhaust is performed by both the exhaust valve provided on the cylinder head and the exhaust hole provided on the side wall of the cylinder liner.

[0009]

EXAMPLE An example of the present invention will be described below. In FIG. 1, the cylinder head 1 includes an intake valve 2 and an exhaust valve 3.
Is provided. A scavenging hole 5 and an exhaust hole 6 are provided below the side wall of the cylinder liner 4. This scavenging hole 5
As is apparent from FIG. 3, a plurality of exhaust holes 6 are formed in the left half of the cylinder liner 4, and a plurality of exhaust holes 6 are formed in the right half of the cylinder liner 4. A slide valve 7 is fitted around the scavenging hole 5 and the exhaust hole 6 so as to be rotatable in the circumferential direction. The slide valve 7
Is provided with a scavenging port 8 facing the scavenging hole 5,
Further, an exhaust port 9 wide in the circumferential direction is provided at a portion facing the exhaust hole 6. Reference numerals 10 and 11 denote separators that separate the scavenging passage 12 and the exhaust passage 13, and a drive device for reciprocally rotating the slide valve 7 in the circumferential direction is housed inside. The scavenging passage 12 and the exhaust passage 13 are connected to a scavenging mother pipe 14 and an exhaust mother pipe 15, respectively, and the scavenging mother pipe 14 is connected to an intake mother pipe 16 connected to a turbocharger. The mother pipe 16 is connected to the intake port 17 of the cylinder head 1. The exhaust mother pipe 15 is an exhaust main pipe 1 led from an exhaust port 18 provided in the cylinder head 1.
9 is connected.

The tip of the main exhaust pipe 19 is connected to the exhaust turbine inlet of the turbocharger 20. Although not shown in FIG. 1, a compressor is connected to the turbocharger 20, and the fresh air discharged from the compressor by the rotation of the turbocharger 20 is supplied to the intake mother pipe 16. The exhaust turbine outlet of the turbocharger 20 is connected to the exhaust turbine inlet of another turbocharger 21. Although not shown in FIG. 1, a compressor is connected to the turbocharger 21 like the turbocharger 20, and the fresh air discharged from the compressor by the rotation of the turbocharger 20 is supplied to the intake mother pipe 16. Is configured to be. Reference numeral 22 is a crankcase, 23 is a piston, and 24 is a convex portion on the top surface of the piston to prevent the scavenging air from directly blowing toward the exhaust hole during the scavenging operation.

The operation of the embodiment of the present invention thus constructed will be described. When a relatively large load is applied such as when the vehicle approaches a slope and the engine speed becomes equal to or lower than a predetermined engine speed, an engine control device (not shown) issues a command for two-cycle operation of the engine. By this command, the intake valve 2 holds the closed state. Then, when the exhaust valve 3 is also closed and the air-fuel mixture in the cylinder liner 4 explodes and expands and the piston 17 approaches the bottom dead center, as shown in FIG. 2, first, the exhaust hole 6, the exhaust port 9, and the exhaust mother. Exhaust gas flows out through the route of the pipe 15, the exhaust valve 3 is opened later, and the exhaust gas in the cylinder liner 4 is exhausted to the exhaust port 18
Flow toward the turbocharger 20. At this time, the drive device in the separators 10 and 11 operates to rotate the slide valve 7 to take the position shown in FIG. Therefore, the high-pressure fresh air sent from the turbochargers 20 and 21 is sent into the cylinder liner 4 as scavenging, and therefore the exhaust gas in the cylinder liner 4 is scavenged in the exhaust valve 3 direction and the exhaust hole 6 direction to be turbocharged. The chargers 20 and 21 are driven.

In this scavenging process, the exhaust gas is exhausted from both the exhaust valve 3 and the exhaust hole 6, so that the exhaust area is sufficient and the scavenging is performed efficiently.

Next, when the load is not so great and the engine is rotating at a relatively high speed, such as when the vehicle is traveling on a highway, an engine control device (not shown) Issue a command for 4-cycle operation.
By this command, the intake valve 2 and the exhaust valve 3 are operated by the rotation of the engine. Then, as shown in FIG. 4, when the piston 23 starts descending from the top dead center position, the intake valve 2
Is opened, and fresh air is sucked into the cylinder liner 4 from the intake port 17. At this time, as shown in FIG. 5, the slide valve 7 is rotated so that the scavenging hole 5 and the scavenging port 8 are displaced from each other, and high-pressure fresh air from the turbocharger is transferred to the scavenging passage 12.
It has stopped at.

When the piston 23 reaches the bottom dead center and then moves upward, the intake valve 2 is closed, the air in the cylinder liner 4 is compressed, and fuel is injected when the piston 23 rises to near the top dead center. Once done, the mixture explodes and enters the expansion cycle. Due to this explosive expansion, the piston 23 descends,
When the exhaust valve 3 is opened near the bottom dead center and the upper edge of the piston 23 descends below the exhaust hole 6, the exhaust gas is exhausted from the exhaust hole 6 and the exhaust port 9 toward the exhaust mother pipe 15. .. In this way, during the 4-cycle operation, the exhaust gas is exhausted from both the exhaust valve 3 and the exhaust hole 6, and a sufficient exhaust area required for exhaust can be taken.

Explaining the relationship between the exhaust area and the work required for exhaust during the four-cycle operation with reference to FIG. 6, the piston 23 descends from the top dead center of the explosion and the exhaust of the exhaust valve 3 from the crank angle 125 point. As the area (curve A) increases, the exhaust area (curve B) of the exhaust hole 6 increases, the piston 23 reaches its maximum at the bottom dead center (crank angle 180 degrees), and the exhaust increases as the piston 23 rises from the bottom dead center. The number is reduced because the hole 6 is closed by the piston 23. The exhaust area at this time is the total of the exhaust valve 3 (curve A) and the exhaust hole 6 (curve B) (curve C). Then, after the exhaust hole 6 is closed by the piston 23, the exhaust valve 3 only exhausts the gas to the exhaust top dead center (crank angle 380 degrees).

As described above, by exhausting gas from both the exhaust valve 3 and the exhaust hole 6, the pressure in the cylinder liner 4 becomes low as shown by the curve E, and the pressure in the cylinder liner without the exhaust hole 6 is reduced. Only the portion surrounded by the pressure (curve D) reduces the work required for exhaust. Line G is the exhaust pressure of exhaust gas.

[0017]

As described above in detail, according to the present invention, the cylinder head is provided with the intake valve and the exhaust valve, and the side wall of the cylinder liner is provided with the scavenging hole and the exhaust hole so that the scavenging hole can be opened and closed. Exhaust in the scavenging process during the 2-cycle operation and the 4-cycle operation can be performed by both the exhaust valve and the exhaust hole. As a result, the exhaust area can be made sufficient to improve the scavenging efficiency, and at the same time, the exhaust work during the 4-cycle operation can be reduced to improve the engine efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a state during a two-cycle operation.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view showing a state during a 4-cycle operation.

5 is a cross-sectional view taken along the line BB of FIG.

FIG. 6 is a diagram showing the relationship between the exhaust area and the work required for exhaust during 4-cycle operation.

[Explanation of symbols]

 1-Cylinder head 2--Intake valve 3--Exhaust valve 4--Cylinder liner 5--Scavenging hole 6-Exhaust hole 7-・ ・ ・ ・ Slide valve 8 ・ ・ ・ Scavenging port 9 ・ ・ ・ Exhaust port 10 ・ ・ ・ ・ Separator 11 ・ ・ ・ ・ Separator 12 ・ ・ ・ ・ Scavenging passage 13 ・ ・ ・ ・ Exhaust passage 14 ・・ ・ ・ Scavenging mother pipe 15 ・ ・ ・ Exhaust mother pipe 16 ・ ・ ・ ・ Intake mother pipe 17 ・ ・ ・ ・ Intake port 18 ・ ・ ・ ・ ・ ・ Exhaust port 19 ・ ・ ・ ・ ・ ・ Exhaust main pipe 20 ・ ・ ・ Turbocharger 21 ... ・ Turbocharger 22 ・ ・ ・ ・ ・ ・ Crankcase 23 ・ ・ ・ ・ Piston

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area F02B 29/08 D 7367-3G

Claims (1)

Claim: What is claimed is: 1. A turbo compound engine which is supplied with fresh air from a compressor driven by a turbine rotated by exhaust gas and which is switchable for 2-4 cycles,
The cylinder head is provided with an exhaust valve and an intake valve that operates only during four-cycle operation, an exhaust hole and a scavenging hole communicating with the output side of the compressor are provided in the lower portion of the side wall of the cylinder liner, and the outer periphery of the cylinder liner is provided. A 2-4 cycle switching turbo compound engine, characterized in that it is provided with a slide valve which is rotatable in the circumferential direction along the same and which makes the scavenging hole communicate with the output side of the compressor during scavenging.