JP2003138943A - Two-cycle internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the speed of a uniflow two-cycle internal combustion engine having a poppet exhaust valve 6 installed at the top part of a cylinder 2 incorporating a piston 3 and a scavenging port 8 provided in the lower part of the cylinder. SOLUTION: A second exhaust valve (rotary valve) opening only for a period L2 smaller than the valve-open period L3 of the poppet exhaust valve 6 in the open period is disposed in an exhaust passage 11 from the poppet exhaust valve 6. The exhausting of exhaust gas is controlled by the second exhaust valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniflow type two-cycle internal combustion engine among two-cycle internal combustion engines.

[0002]

2. Description of the Related Art As is well known in the art, a uniflow type two-cycle internal combustion engine of this kind is synchronized with the crankshaft at the top of a cylinder containing a piston that reciprocates in conjunction with the crankshaft. A poppet exhaust valve that is opened and closed by a cam shaft that rotates at the same speed is installed, while a scavenging port that is opened and closed by reciprocating motion near the bottom dead center of the piston is opened in the cylinder at the bottom of the cylinder. The exhaust gas in the cylinder is pushed out from the poppet exhaust valve by the intake air introduced into the cylinder from the scavenging port.

Further, Japanese Patent Laid-Open No. 4-362 as prior art.
Japanese Laid-Open Patent Publication No. 225 proposes to apply an exhaust turbocharger in which a compressor is directly connected to an exhaust turbine to the uniflow type two-cycle internal combustion engine.

That is, in this prior art, the exhaust passage from the poppet exhaust valve is provided at the exhaust gas inlet of the exhaust turbine of the exhaust turbocharger, and the compressed intake passage from the compressor of the exhaust turbocharger is provided. The connection is made to each of the scavenging ports.

[0005]

However, in a two-cycle internal combustion engine, the opening operation of the poppet exhaust valve at the top of the cylinder is prevented by performing each stroke of two cycles while the crankshaft makes one revolution. It is configured to be performed for each rotation of the crankshaft, and for each rotation of the exhaust valve camshaft that rotates at the same speed in synchronization with the crankshaft.

As described above, the rotation speed of the exhaust valve camshaft of the two-cycle internal combustion engine is the same as that of the crankshaft, and is twice that of the camshaft of the four-cycle internal combustion engine. The angle at which the poppet exhaust valve is opened and operated, that is, the opening operation angle is as narrow as half that in the case of four cycles, and the rising gradient of the cam profile on this exhaust valve cam shaft becomes steep, and the exhaust gas at the poppet exhaust valve is exhausted. Since the followability of the opening / closing operation with respect to the rotational speed of the valve camshaft is lower than in the case of four cycles, the maximum rotational speed of this two-cycle internal combustion engine is lower than that of the four-cycle internal combustion engine, and the maximum rotational speed is increased. There was a problem that I could not.

An exhaust turbocharger is applied to the two-cycle internal combustion engine, and an exhaust passage from a poppet exhaust valve of the exhaust turbocharger is provided at an exhaust gas inlet of an exhaust turbine of the exhaust turbocharger. When the intake air passage from the compressor of the compressor is connected to the scavenging port, exhaust energy can be recovered by applying this exhaust turbocharger, so the pumping loss due to the increase in exhaust pressure is a negative component. Although it can greatly contribute to the performance improvement of the internal combustion engine, on the other hand, the exhaust turbocharger does not operate sufficiently in the low load operating range, so the intake air compressed by the compressor is Since the pressure is low, the scavenging property by pushing the compressed intake air cannot be effectively exhibited.

Therefore, as another prior art, Japanese Patent Laid-Open No.
JP-A 1-132462, when applying an exhaust turbocharger, provides a supercharger driven by an internal combustion engine in a compression intake passage from a compressor to the scavenging port in the exhaust turbocharger. Is proposing that.

By installing this supercharger, the pressure of the intake air to the scavenging port can be increased, so that the scavenging performance can be improved in the operating region where the load is small.

On the other hand, however, the supercharger installed here must be made quite large in order to improve the scavenging property in the low load region, and in the low load region, the output of the internal combustion engine is Since the ratio of the load required to drive the supercharger increases,
There is a problem that not only the fuel consumption is deteriorated, but also the installation of the large-sized supercharger causes the internal combustion engine to become large and expensive.

SUMMARY OF THE INVENTION The present invention has a technical object to solve the above-mentioned problems in a uniflow type two-cycle internal combustion engine.

[0012]

In order to achieve this technical object, the first aspect of the present invention is that "the top of a cylinder having a piston that reciprocates in conjunction with the crankshaft is synchronized with the crankshaft. In a uniflow type two-cycle internal combustion engine in which a poppet exhaust valve that opens and operates with an exhaust valve cam shaft that rotates at the same speed is provided in the lower part of the cylinder, a scavenging port into the cylinder is used. In the exhaust passage of No. 2, a second exhaust valve is provided which is configured to be opened and operated only during a period narrower than the opening period of the poppet exhaust valve. ”

According to a second aspect of the present invention, "In the first aspect, the exhaust passage from the poppet exhaust valve is provided at an exhaust gas inlet of an exhaust turbine of an exhaust turbocharger, and the exhaust turbocharger is installed. The discharge port of the compressor in the feeder is connected to each of the scavenging ports, and the second exhaust valve is configured as a rotary valve that rotates at the same speed in synchronization with the crankshaft. The rotary valve and the exhaust valve The cam camshaft is provided with a phase varying means for displacing the opening timing of the rotary valve and the opening timing of the poppet exhaust valve relative to the crankshaft. ”

[0014]

In the structure described in claim 1, the exhaust gas from the cylinder is discharged through the exhaust passage through the poppet exhaust valve and the second exhaust passage in the exhaust passage.
It is performed when both of the exhaust valves are both open, and in this case, the opening period of the second exhaust valve is set to a narrower period within the opening period of the poppet exhaust valve. Exhaust gas discharge is controlled not by the poppet exhaust valve but exclusively by the second exhaust valve. Therefore, the poppet exhaust valve is used in the cylinder during the compression stroke and the explosion stroke. It is sufficient that the pressure is not released and that the pressure is closed to withstand this pressure.

This makes it possible to increase the opening angle of the poppet exhaust valve in one revolution of the exhaust valve cam shaft, that is, the opening operation angle, and make the rising gradient of the cam profile of the exhaust valve cam shaft gentle. Therefore, the followability of the opening / closing operation with respect to the rotation speed of the exhaust valve cam shaft in the poppet exhaust valve is improved, and the maximum rotation speed of the two-cycle internal combustion engine can be greatly improved.

Further, in the structure described in claim 2, the exhaust gas from the exhaust passage flows to the exhaust turbine of the exhaust turbocharger to drive the exhaust turbocharger, while the exhaust gas is exhausted. The intake air compressed by the compressor by driving the turbocharger is introduced into the cylinder through the scavenging port, and the compressed intake air is pushed to scaveng the inside of the cylinder.

The exhaust energy of the exhaust gas discharged from the cylinder is proportional to the temperature of the exhaust gas, and the higher the temperature of the exhaust gas, the greater the exhaust energy that can be applied to the exhaust turbocharger. On the other hand, the temperature of the exhaust gas is such that the earlier the exhaust gas is discharged,
Get higher

Therefore, the opening timing of the rotary valve and the opening timing of the poppet exhaust valve are displaced by the phase varying means so as to approach the top dead center in proportion to the decrease in the load, and the exhaust gas in the cylinder is exhausted. By accelerating the timing of starting the exhaust gas, it is possible to supply the exhaust gas having a high temperature, that is, the exhaust gas having a large exhaust energy, to the exhaust turbocharger in the low load operation range. It is possible to surely reduce the decrease in the operation of the supercharger in the low load operation range, and thus the decrease in the intake pressure compressed by the compressor in the low load operation range.

As a result, it is possible to surely reduce the decrease in the scavenging efficiency due to the pushing of the compressed intake air from the compressor in the exhaust turbocharger into the cylinder via the scavenging port in the low load operating region. , This much,
The supercharger installed to secure the scavenging efficiency can be downsized, and in some cases, the supercharger can be abolished.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings of FIGS.

In the figure, reference numeral 1 indicates a cylinder block in a compression ignition type uniflow type two-cycle internal combustion engine. The cylinder block 1 has a built-in piston 3 which reciprocates in conjunction with a crankshaft (not shown). It is equipped with a cylinder 2, and the top surface of the piston 3 is
The combustion chamber 4 is recessed.

On the other hand, a cylinder head 5 is fastened to the upper surface of the cylinder block 1 so as to close the top of the cylinder 2. The cylinder head 5 has a poppet exhaust valve 6 and a fuel injection valve 7. Is provided so as to be seen in a substantially central portion of the cylinder 2 in a plan view.

A plurality of scavenging ports 8 are formed in the lower portion of the cylinder 2, and each scavenging port 8 is reciprocally moved by the piston 3 in the same manner as in a normal two-cycle internal combustion engine. Time A before bottom dead center at piston 3
Timing B (approx. 45 degrees before bottom dead center at crank angle) to B after bottom dead center (approx. 45 degrees after bottom dead center at crank angle)
Up to the period L1.

The inner bottom surface 8a of each of the scavenging ports 8 coincides with the top surface 3a of the piston 3 at the bottom dead center.

The poppet exhaust valve 6 is driven by an exhaust valve cam shaft 9 that rotates at the same speed in synchronization with the crank shaft by interlocking with the crank shaft and the like. It is configured to open only once during one rotation of the cam shaft 9 for use, and furthermore, fuel is injected into the cylinder 2 from the fuel injection valve 7 at a time around the top dead center of the piston 3 and The fuel is configured to explode and burn by compression ignition.

Reference numeral 10 denotes an exhaust turbo supercharger in which a blower type compressor 10b is directly connected to the exhaust turbine 10a, and an exhaust gas inlet of the exhaust turbine 10a of the exhaust turbo supercharger 10 is An exhaust passage 11 from the poppet exhaust valve 6 is connected to an exhaust pipe 12 to the atmosphere at an exhaust gas outlet of an exhaust turbine 10a, and an air cleaner 13 is connected to a suction side of the compressor 10b. An atmospheric air suction pipe line 14 is connected to the discharge port of the compressor 10b, and a compression intake pipe line 16 to a chamber 15 surrounding the scavenging ports 8 is connected to the discharge port of the compressor 10b.

On the other hand, in the middle of the exhaust passage 11 from the poppet exhaust valve 6, a rotary valve 17 which is one embodiment as a second exhaust valve is provided, and the rotary valve 17 is the exhaust valve. Gear pair 18 from the camshaft 9 for
The rotary valve 17 is configured to rotate at the same speed in synchronization with the crankshaft by transmission of rotation via 19, and further, the rotary valve 17 includes one of the crankshaft and the rotary valve 17 during one rotation. A passage 17a for opening the exhaust passage 11 so as to communicate with the exhaust passage 11 only once is formed as a recess.

In this case, in an operating region where the accelerator opening is almost full and the load is high, the exhaust passage 11 is formed by the rotary valve 17 in the piston 3 similarly to the poppet exhaust valve in a normal two-cycle internal combustion engine. From time C before bottom dead center (around 70 degrees before bottom dead center in crank angle) to time D after bottom dead center (about 30 to 6 after bottom dead center in crank angle)
Period L2 (near crank angle is approximately 10)
(A period of 0 to 130 degrees) is set to open, while the poppet exhaust valve 6 is set to the bottom dead center from the time E before the bottom dead center of the piston 3 (around the crank angle of about 70 degrees before the bottom dead center). It is set to open a period L3 (a period of about 160 degrees at the crank angle) until a later time F (around 90 degrees after the bottom dead center at the crank angle).

That is, the open period L3 of the poppet exhaust valve 6 is increased to about 160 degrees, while the open period L2 of the rotary valve 17 is increased.
Like the poppet exhaust valve in a normal two-cycle internal combustion engine, which is narrower than the open period L3 of the poppet exhaust valve 6, the angle is set to approximately 100 to 130 degrees.

The time D when the rotary valve 17 is closed is about 30 degrees after the bottom dead center when the effect of supercharging from the scavenging port 8 is important, and the bottom dead center when the scavenging effect is important. After about 60 degrees.

The opening timing E of the poppet exhaust valve 6 and the opening timing C of the rotary valve 16 are set to be substantially the same.

A phase varying means 21 is provided between the exhaust valve camshaft 9 and the power transmission wheel 20 from the crankshaft to the camshaft 9, and the phase varying means 2 is provided.
According to 1, the opening and closing timing of the poppet exhaust valve 6 with respect to the crankshaft is configured to be advanced and displaced relatively to the front side with respect to the rotational direction in inverse proportion to the accelerator opening degree, and accordingly, the load. There is.

The phase varying means 21 may be, for example, Japanese Patent Laid-Open Nos. 4-109007 and 8-21.
A conventionally known hydraulic valve timing mechanism described in JP-A No. 0158 and JP-A-8-218823 is used.

In this structure, the poppet exhaust valve 6 and the rotary valve 17 are opened during the downward movement of the piston 3 due to the explosion in the cylinder 2, so that the exhaust gas in the cylinder 2 is exhausted through the exhaust passage 11 to the exhaust turbo. While flowing into the exhaust turbine 10a in the supercharger 10 to drive the exhaust turbo supercharger 10, the intake air compressed by the compressor 10b by the drive of the exhaust turbo supercharger 10 is transferred to each scavenging port 8. At the moment each scavenging port 8 is opened by the downward movement of the piston 3 when being sent to the chamber 15 surrounding the outside, the compressed intake air stored in the chamber 15 is transferred from each scavenging port 8 to the inside of the cylinder 2. Is rapidly introduced into the cylinder 2 and the scavenging of the inside of the cylinder 2 is performed by pushing in the compressed intake air.

The exhaust gas from the cylinder 2 is discharged through the exhaust passage 11 when both the poppet exhaust valve 6 and the rotary valve 17 in the exhaust passage 11 are open. In this case, the opening period L2 of the rotary valve 17 is set to be narrower than the opening period L3 of the poppet exhaust valve 6 so that the exhaust gas is discharged by the poppet exhaust valve 6. Since it is controlled exclusively by the rotary valve 17 without being controlled, the poppet exhaust valve 6 does not release the pressure in the cylinder and withstands this pressure in the compression stroke and the explosion stroke. It is enough to just close it.

Accordingly, in one rotation of the exhaust valve camshaft 9, the angle at which the poppet exhaust valve 6 is opened, that is, the opening operation angle θ is set to the open period L3 of the poppet exhaust valve 6 (about 160 in crank angle). Since the cam profile of the exhaust valve camshaft 9a can be gradually increased, the rising slope of the cam profile of the cam 9a of the exhaust valve camshaft can be made gentle. The followability of opening and closing operations can be greatly improved.

The open period L3 of the poppet exhaust valve 6 and the open period L2 of the rotary valve 17 are the positions shown by the solid line in FIG. 3 in the high load operation range where the accelerator opening is almost full. However, in the medium-load operation range where the accelerator opening is medium, the phase varying means 21 causes Δθ1 to be greater than when the accelerator opening is almost full, as shown by the alternate long and short dash line in FIG. In the low load operation range in which the accelerator opening is reduced, the phase changing means 21 causes
As indicated by the alternate long and short dash line, the displacement is made so as to advance by Δθ2 even more than when the accelerator opening is almost full.

As a result, the opening timing C of the rotary valve 17 and the opening timing E of the poppet exhaust valve 6 are gradually advanced to C ', E', C ", E" in the low load operating region, and the cylinder is opened. Since it is possible to advance the timing of starting the exhaust of the exhaust gas in 2, the exhaust gas having a high temperature, that is, the exhaust gas having a large exhaust energy, with respect to the exhaust turbocharger 10 in the operation region where the load is low. Therefore, it is possible to surely prevent the operation of the exhaust turbocharger 10 from being reduced in an operation range where the load is low.

In the above embodiment, the fuel is injected and supplied from the fuel injection valve 7 into the cylinder 2 before the top dead center of the histone 3, and the fuel is compression ignited. The present invention is not limited to this compression ignition type two-cycle internal combustion engine, and is similarly applicable to a spark ignition type two-cycle internal combustion engine using the spark plug 22 provided as shown by the chain double-dashed line in FIG. Needless to say.

In either case of compression ignition or spark ignition, the temperature of the exhaust gas is raised by additionally supplying the fuel into the cylinder 2 near the closing timing D of the rotary valve 17. , Exhaust turbine 10
The efficiency of a can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of an essential part showing an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a diagram showing a two-cycle process.

[Explanation of symbols]

1 cylinder block 2 cylinders 3 pistons 5 cylinder head 6 Poppet exhaust valve 7 Fuel injection valve 8 scavenging port 9 Exhaust valve camshaft 10 Exhaust turbocharger 10a exhaust turbine 10b compressor 11 exhaust passage 17 Rotary valve 21 Phase changing means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 9/04 F02D 9/04 H 9/16 9/16 13/02 13/02 A B G 23/00 23/00 AK F term (reference) 3G005 DA04 EA04 EA16 FA05 GD13 HA09 JA02 3G065 AA02 AA03 AA09 CA00 EA07 EA10 GA10 GA46 HA05 JA01 KA02 3G092 AA01 AA02 AA03 AA11 AA18 DA02 DA08 DA12 DA14 DB03 FA12 FA14 DB03 FA12

Claims (2)

[Claims] Claim: What is claimed is: 1. A poppet exhaust valve, which is opened and operated by an exhaust valve cam shaft that rotates at the same speed in synchronism with the crankshaft, at the top of a cylinder containing a piston that reciprocates in conjunction with the crankshaft. In a uniflow type two-cycle internal combustion engine having a scavenging port into the cylinder in the lower part of the cylinder, in the exhaust passage from the poppet exhaust valve, only a narrower period within the open period of the poppet exhaust valve. A two-cycle internal combustion engine having a second exhaust valve that is operated to open. 2. The exhaust passage from the poppet exhaust valve to the exhaust gas inlet of the exhaust turbine of the exhaust turbocharger, and the discharge port of the compressor of the exhaust turbocharger according to claim 1. , The second exhaust valve is connected to each of the scavenging ports, and the second exhaust valve is configured as a rotary valve that rotates at the same speed in synchronization with a crankshaft, and the rotary valve and the exhaust valve cam shaft open the rotary valve. The two-cycle internal combustion engine is provided with a phase varying means for displacing the timing and the opening timing of the poppet exhaust valve relative to the crankshaft.