JP2799917B2 - 2-4 cycle switching turbo compound engine - Google Patents

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 engine, and more particularly, to a 2-4 cycle switching turbo compound engine which smoothly scavenges cylinders to improve engine efficiency.

[0002]

2. Description of the Related Art A conventional piston reciprocating engine is a two-stroke engine that performs a stroke of suction, compression, explosion, and exhaust in one reciprocation of a piston, that is, one revolution of a crankshaft.
It is roughly classified into a four-stroke engine that performs the above-described four strokes during two reciprocations of the piston, that is, two revolutions of the crankshaft.

There are several types of the above two-stroke engines. For example, in a uniflow type engine, an exhaust valve is disposed above a cylinder sleeve, and a scavenging port is disposed below the exhaust valve so that a piston is positioned near a bottom dead center position. At this time, the in-cylinder combustion gas is ejected from this exhaust valve, and after a short time, fresh air is pumped into the cylinder from the scavenging port, and the exhausted gas in the cylinder sleeve is sent to the upper part of the cylinder sleeve by the pumped fresh air. The process of discharging fresh air from the exhaust valve and compressing fresh air filled in the cylinder sleeve by the piston that has started to move upward, and injecting fuel near the top dead center of the piston is repeated. Since the two-stroke engine including the uniflow type explodes every rotation of the crankshaft, the two-stroke engine has a characteristic that the rotation fluctuation of the output shaft is small and a high torque can be generated.

On the other hand, in a four-cycle engine, intake and exhaust are performed in independent strokes, so that exhaust gas and fresh air are sufficiently replaced, and exhaust gas during low-load low-speed operation is lower than in a two-cycle engine. Has a characteristic that the fuel consumption is small especially when the engine speed is high.

[0005]

Recently, an engine has been developed which can switch between two-cycle operation and four-cycle operation with one engine and operate with the advantages of these two engines.
This engine obtains a scavenging pressure during two-cycle operation by attaching a scavenging compressor to the crank chamber. However, since the scavenging pressure depends on the rotation of the engine, for example, as in the case of idling, When the load and the number of revolutions are low, the scavenging pressure is low and sufficient scavenging cannot be performed. Further, there is a problem that oil mist is mixed into fresh air, and there is a problem that an engine becomes large due to the addition of a compressor. In addition, in high-speed operation, there is a problem that the open area of the exhaust valve is insufficient and sufficient scavenging and exhaust cannot be performed. Further, even during the four-cycle operation, there is a problem that a sufficient exhaust area cannot be ensured because the exhaust valve must be provided in the cylinder head having a limited arrangement space.

An object of the present invention is to provide a 2-4 cycle switching engine capable of performing smooth scavenging and exhausting during the above 2 cycle operation and 4 cycle operation.

[0007]

SUMMARY OF THE INVENTION 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 is capable of switching between 2-4 cycles.
The cylinder head is provided with an exhaust valve and an intake valve that operates only during four-cycle operation, and an exhaust hole and a scavenging hole that communicates with the output side of the compressor are provided at the lower part of the side wall of the cylinder liner. The present invention provides a 2-4 cycle switching turbo compound engine characterized in that a slide valve is provided, which is rotatable in a circumferential direction along the periphery thereof and which connects the scavenging hole to the output side of the compressor during scavenging.

[0008]

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

[0009]

An embodiment of the present invention will be described below. In FIG. 1, an intake valve 2 and an exhaust valve 3 are provided on a cylinder head 1.
Is provided. A scavenging hole 5 and an exhaust hole 6 are provided in a lower portion of the side wall of the cylinder liner 4. This scavenging hole 5
As shown in 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 outer circumference of 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 which is wide in the circumferential direction is provided at a portion facing the exhaust port 6. Reference numerals 10 and 11 denote separators for separating the scavenging passage 12 and the exhaust passage 13, and a driving device for reciprocatingly rotating the slide valve 7 in the circumferential direction is accommodated therein. In addition, the scavenging passage 12 and the exhaust passage 13 are connected to a scavenging mother pipe 14 and an exhaust mother pipe 15, respectively. The scavenging mother pipe 14 is connected to an intake mother pipe 16 connected to a turbocharger. The mother pipe 16 is connected to an intake port 17 of the cylinder head 1. The exhaust main pipe 15 is an exhaust main pipe 1 guided from an exhaust port 18 provided in the cylinder head 1.
9 is connected.

The leading end of the exhaust main pipe 19 is connected to an exhaust turbine inlet of a turbocharger 20. Although not shown in FIG. 1, a compressor is connected to the turbocharger 20, and fresh air discharged from the compressor by 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 similarly to the turbocharger 20, and fresh air discharged from the compressor by rotation of the turbocharger 20 is supplied to the intake mother pipe 16. It is configured to be. Reference numeral 22 denotes a crankcase, reference numeral 23 denotes a piston, and reference numeral 24 denotes a projection on the top surface of the piston, which is for preventing scavenging air from flowing directly toward an exhaust hole during a scavenging operation.

The operation of the embodiment of the present invention configured as described above will be described. When a relatively large load is applied, such as when the vehicle approaches a hill, and the engine speed falls below a predetermined speed, an engine control device (not shown) issues a command for two-cycle operation of the engine. With this command, the intake valve 2 is kept closed. 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 vicinity of the bottom dead center, as shown in FIG. Exhaust gas flows out through the route of the pipe 15, and the exhaust valve 3 is opened later, and the exhaust gas in the cylinder liner 4 is discharged to the exhaust port 18.
From the turbocharger 20. At this time, the drive devices in the separators 10 and 11 operate to rotate the slide valve 7 to take the position shown in FIG. For this reason, high-pressure fresh air sent from the turbochargers 20 and 21 is sent into the cylinder liner 4 as scavenging gas. Therefore, exhaust gas in the cylinder liner 4 is scavenged in the exhaust valve 3 direction and the exhaust hole 6 direction and 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 large and the engine is rotating at a relatively high speed, such as when the vehicle is running on a highway, an engine control device (not shown) uses Issues a 4-cycle operation command.
With 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 to descend from the top dead center position, the intake valve 2
Is opened, and fresh air is drawn into the cylinder liner 4 from the intake port 17. At this time, as shown in FIG. 5, the slide valve 7 rotates and the scavenging hole 5 and the scavenging port 8 are displaced from each other, and high-pressure fresh air from the turbocharger is supplied to the scavenging passage 12.
Stopped at.

When the piston 23 moves upward after reaching the bottom dead center, the intake valve 2 is closed, the air in the cylinder liner 4 is compressed, and the fuel injection is started when the piston 23 rises near the top dead center. Once done, the mixture will explode and enter the expansion cycle. Due to this explosion and expansion, the piston 23 descends,
When reaching the vicinity of the bottom dead center, the exhaust valve 3 opens and the upper edge of the piston 23 descends below the exhaust hole 6, so that 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 four-cycle operation, the exhaust gas is exhausted from both the exhaust valve 3 and the exhaust hole 6, and it is possible to obtain a sufficient exhaust area required for the exhaust.

The relationship between the exhaust area and the work required for exhaust during the four-cycle operation will be described 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 starts at a crank angle 125. 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 exhausts as the piston 23 rises from the bottom dead center. Since the hole 6 is closed by the piston 23, the number of holes 6 decreases. The exhaust area at this time is the sum (curve C) of the exhaust valve 3 (curve A) and the exhaust hole 6 (curve B). After the exhaust hole 6 is closed by the piston 23, exhaust is performed only from the exhaust valve 3 until exhaust top dead center (crank angle 380 degrees).

As described above, by exhausting 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 when there is no exhaust hole 6 is obtained. The work required for exhaust is reduced only in the portion surrounded by the pressure (curve D). Line G is the exhaust gas exhaust pressure.

[0017]

As described above in detail, according to the present invention, the intake valve and the exhaust valve are provided on the cylinder head, and the scavenging holes and the exhaust holes are provided on the side wall of the cylinder liner so that the scavenging holes can be opened and closed. The exhaust in the scavenging process or the exhaust process during the two-cycle operation and the four-cycle operation can be performed through both the exhaust valve and the exhaust hole. As a result, the scavenging efficiency and the exhaust efficiency can be improved by making the exhaust area sufficient, and the exhaust work during four-cycle operation can be reduced and the engine efficiency can be improved.

[Brief description of the drawings]

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

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

FIG. 3 is a transverse sectional view taken along line AA of FIG. 2;

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

FIG. 5 is a transverse sectional view taken along line BB in FIG. 4;

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

[Explanation of symbols]

 1 ... Cylinder head 2 ... Intake valve 3 ... Exhaust valve 4 ... Cylinder liner 5 ... Scavenging hole 6 ... Exhaust hole 7 ... ······································································ Exhaust port ··············································································································· Turbocharger 21 ··· Turbocharger 22 ··· Crankcase 23 ··· Piston

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02B 29/08 F02B 29/08 B

Claims (1)

(57) [Claims] 1. A turbo compound engine which is supplied with fresh air from a compressor driven by a turbine rotated by exhaust gas and is capable of switching between two and four cycles.
The cylinder head is provided with an exhaust valve and an intake valve that operates only during four-cycle operation, and an exhaust hole and a scavenging hole that communicates with the output side of the compressor are provided at the lower part of the side wall of the cylinder liner. 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 connects the scavenging hole to the output side of the compressor during scavenging.