JP2002285851A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a supercharging amount to improve thermal efficiency in an internal combustion engine provided with a suction valve, an exhaust valve, and a pressure accumulation valve capable of being opened and closed in a cylinder head provided with a combustion chamber continuous with a cylinder bore, a suction port and an exhaust port opened in the combustion chamber, a pressure accumulation chamber, and a pressure accumulation port connecting the pressure accumulation chamber with the combustion chamber. SOLUTION: The suction valve is fully closed until a piston reaches a bottom dead center, and the pressure accumulation valve is opened during a first period in an expansion stroke of the engine and is opened during a second period over a compression stroke from before the bottom dead center to after the bottom dead center in the next suction stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber connected to a cylinder bore into which a piston is slidably fitted, an intake port and an exhaust port opening to the combustion chamber, a pressure accumulator,
An internal combustion engine in which an intake valve, an exhaust valve, and an accumulator valve for opening and closing the intake port, the exhaust port, and the accumulator port, respectively, are provided in a cylinder head provided with an accumulator port that connects the accumulator and the combustion chamber. Related to institutions.

[0002]

2. Description of the Related Art Conventionally, such an internal combustion engine is already known, for example, from Japanese Patent Application Laid-Open No. 2000-282867, and a combustion gas is taken into a pressure accumulation chamber by opening a pressure accumulation valve for a certain period in an expansion stroke of the engine. By opening the accumulator valve for a certain period of time in the compression stroke, the burned gas is injected from the accumulator into the combustion chamber, thereby increasing the compression pressure of the gas in the combustion chamber and increasing the output of the engine.

[0003]

However, in the prior art described above, the intake valve is slightly opened even if it passes through the bottom dead center of the piston and enters the compression stroke. The valve is opened for a certain period in the compression stroke after the valve is closed. For this reason, the pressure accumulating valve is opened in a state where the pressure in the combustion chamber has already started to increase, and when the pressure accumulating valve is opened, the pressure difference between the pressure accumulating chamber and the combustion chamber is relatively small. In addition, since the valve opening period of the accumulator is relatively short, the effect of increasing the compression pressure and temperature of the gas in the combustion chamber is insufficient, and it is necessary to increase the supercharging amount in order to further improve the thermal efficiency.

[0004] The present invention has been made in view of such circumstances, and has as its object to provide an internal combustion engine having an improved thermal efficiency by increasing a supercharging amount.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a combustion chamber connected to a cylinder bore into which a piston is slidably fitted, an intake port opened to the combustion chamber, and An intake valve, an exhaust valve, and an accumulator valve that open and close the intake port, the exhaust port, and the accumulator port, respectively, open and close in a cylinder head that is provided with an exhaust port, an accumulator, and an accumulator port that connects the accumulator and the combustion chamber. In an operably disposed internal combustion engine, the intake valve is fully closed by the time the piston reaches a bottom dead center, the pressure accumulator valve is opened for a first period during an expansion stroke of the engine, and the next intake operation is performed. The valve is opened only for a second period from before the bottom dead center in the stroke to the compression stroke past the bottom dead center.

According to such a configuration, the intake valve is fully closed by the time the piston reaches the bottom dead center,
By limiting the amount of intake air and increasing the expansion ratio over the compression ratio, thermal efficiency can be improved. In addition, since the intake valve is fully closed before the piston reaches the bottom dead center, the valve opening timing of the accumulator can be determined before the bottom dead center of the piston in the intake stroke. Since the valve is closed in the compression stroke past the dead center, the burned gas in the accumulator is injected into the combustion chamber before the pressure in the combustion chamber starts to increase, and the opening angle of the accumulator is relatively large. It is possible to increase the supercharging amount and further improve the thermal efficiency.

[0007] The invention according to claim 2 provides the above-described claim 1.
In addition to the configuration of the invention described above, the intake port is formed in a shape that generates a swirl flow in the combustion chamber, and directly below an opening end of the intake port to the combustion chamber along a flow direction of the swirl flow in the combustion chamber. According to such a configuration, by closing the intake valve relatively quickly, the swirl flow in the already formed combustion chamber causes the pressure accumulation port to be formed in the pressure accumulation port so as to open to the combustion chamber. Utilizing the acting negative pressure, the accumulated pressure in the accumulator is effectively applied to the combustion chamber, and the thermal efficiency can be further improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the attached drawings.

1 to 4 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional front view of an internal combustion engine, and FIG.
FIG. 3 is a bottom view of the cylinder head as viewed from the line 3-3 in FIG. 1, and FIG. 4 is an opening / closing operation characteristic diagram of the intake valve, the exhaust valve, and the accumulator valve.

Referring first to FIG. 1 and FIG.
The engine body Ea includes a crankcase 10 and a cylinder block 11 coupled to an upper surface of the crankcase 10.
And a cylinder head 12 coupled to an upper end surface of the cylinder block 11. A crankshaft 13 rotatably supported by the crankcase 10 and a cylinder bore 11 a provided in the cylinder block 11 slidably fitted. The piston 14 is connected via a connecting rod 28.

The cylinder head 12 has a cylinder bore 1
1a, a combustion chamber 12a connected to the combustion chamber 1a is provided.
The ignition plug 15 is attached to the cylinder head 12 so that the electrode 15a faces the center of the ceiling surface 2a.

Referring also to FIG.
2 is provided with an intake port 16 and an exhaust port 17 which are spirally formed so as to form a swirl flow 29 as shown by an arrow in FIG. 3 in the combustion chamber 12a.
Valve seats 18 and 19 are formed at the open ends of the intake port 16 and the exhaust port 17 to the combustion chamber 12a. An intake valve 20 and an exhaust valve 21 can be seated on these valve seats 18, 19, respectively.

The intake valve 20 and the exhaust valve 21 are arranged in a V-shape so that the distance between the axes of the valves 20 and 21 expands upward, and is arranged on the cylinder head 12 so as to be capable of opening and closing. Valve springs 25 and 26 are provided between the cylinder head 12 and the intake valve 20 and the exhaust valve 21 to urge the valves 20 and 21 in the valve closing direction.

A camshaft 22 rotatably supported by the cylinder head 12 is disposed between the valve heads of the intake valve 20 and the exhaust valve 21. The camshaft 22 is provided with an intake cam 22a and an exhaust cam 22b,
The intake cam 22a and the exhaust cam 22b and the intake valve 20 and the exhaust valve 21 are interlocked and connected via an intake rocker arm 23 and an exhaust rocker arm 24.

The rotational power of the crankshaft 13 is transmitted to the camshaft 22 via a timing transmission 27 at a reduction ratio of 1/2, and the intake valve 20 and the exhaust valve 21
The intake and exhaust cams 22a and 22b and the intake and exhaust rocker arms 22 and 23 cooperate with each other according to the rotation of the camshaft 22 to be opened and closed at the opening and closing timings shown in FIG.

As shown by the solid line in FIG. 4, the intake cam 22a reduces the valve opening lift of the intake valve 20 as compared with the open / close operation characteristic of the conventional intake valve shown by the broken line in FIG. Moreover, the intake valve 20 is formed so as to be fully closed before the piston 14 reaches the bottom dead center.

Further, the cylinder head 12 has a pressure accumulating chamber 3
0 and a pressure accumulating port 31 connecting the pressure accumulating chamber 30 and the combustion chamber 12a.
Along the flow direction of the swirl flow 29 formed in 2a, the intake port 16 is formed so as to open to the combustion chamber 12a immediately below the opening end to the combustion chamber 12a.

A valve seat 32 is formed at the opening end of the pressure accumulating port 31 to the combustion chamber 12a, and a pressure accumulating valve 33 which can be seated on the valve seat 32 is disposed on the cylinder head 12 so as to be capable of opening and closing. Cylinder head 12 and accumulator valve 33
A valve spring 35 for urging the accumulator valve 33 in the valve closing direction is provided therebetween.

A cam follower 36 abutting on the valve head of the pressure accumulating valve 33 is slidably fitted to the cylinder head 12, and the pressure accumulating cam 2 fixed to one end of the camshaft 22.
2c abuts and engages with the cam follower 36.

In accordance with the rotation of the camshaft 22, the accumulator valve 33 is driven to open and close as shown in FIG. At the same time, the valve is opened for a second period B from before the bottom dead center of the piston 14 in the next intake stroke to the compression stroke after the bottom dead center. In addition, the pressure accumulating cam 22c has a second pressure which is longer than the valve opening period B 'of the conventional pressure accumulating valve, which is indicated by a broken line in FIG.
, The pressure accumulator valve 33 is opened only during the period B.
The lift amount L of No. 3 is formed to be larger than the lift amount L 'of the conventional accumulator shown by the broken line in FIG.

Further, the cylinder head 12 has a pressure accumulating chamber 3
0, a fuel injection valve 36 for directly injecting fuel is attached,
As shown in FIG. 4, the fuel injection by the fuel injection valve 36 is performed during the closing of the pressure accumulating valve 33, preferably in the exhaust stroke.
In the period C.

Next, the operation of the present embodiment will be described.
Is opened during the first period A, a part of the burned gas in the combustion chamber 12a is charged from the pressure accumulating port 31 into the pressure accumulating chamber 30 by the pressure of the gas itself. Next, in the exhaust stroke, the fuel injection valve 36 operates only for the third period C, and the engine E
The fuel directly injected into the pressure accumulating chamber 30 by an amount corresponding to the operating state of the above-mentioned fuel gas comes into contact with the burned gas in a relatively high temperature state to be in a vaporized state.

Next, when shifting from the exhaust stroke to the intake stroke, the piston 14 descends and the intake valve 20 opens, so that air is sucked from the intake port 16 into the combustion chamber 12a to form a swirl flow 29, and the intake valve After the valve 20 is closed, the pressure accumulating valve 33 is opened only for the second period B. As a result, the burned gas stored in the pressure accumulating valve 30 has its own pressure and the fuel in the vaporized state together with the fuel in the pressure accumulating port 3.
1 into the combustion chamber 12a to form an air-fuel mixture containing vaporized fuel in the combustion chamber 12a, and further increase the compression pressure and temperature of the air-fuel mixture.
There can be exhibited EGR effect of reducing the NO _X in the exhaust gas as well as exhibit high output.

In addition, the intake valve 20 is fully closed by the time the piston 14 reaches the bottom dead center, thereby limiting the amount of intake air, increasing the expansion ratio over the compression ratio, and improving thermal efficiency. be able to.

Since the intake valve 20 is fully closed before the piston 14 reaches the bottom dead center, the valve opening timing of the pressure accumulator valve 33 can be determined before the bottom dead center of the piston 14 in the intake stroke. In addition, since the pressure accumulating valve 33 is closed in the compression stroke after the bottom dead center, the combustion chamber 12
Before the pressure in a starts increasing, the burned gas in the accumulator 30 is injected into the combustion chamber 12a, and a second period that is longer than the valve-opening period B 'of the conventional accumulator shown by a broken line in FIG. B
Only by opening the accumulator valve 33, the opening angle of the accumulator valve 33 can be made relatively large, and the lift amount L can be made larger than the conventional lift amount L 'by increasing the open angle. Becomes As a result, the supercharging amount is increased, and the thermal efficiency can be further improved.

Further, a pressure accumulating port 31 connecting between the pressure accumulating chamber 30 and the combustion chamber 12a is provided immediately below an opening end of the intake port 16 to the combustion chamber 12a along a flow direction of a swirl flow 29 formed in the combustion chamber 12a. The opening of the combustion chamber 12a at a relatively low pressure makes it possible to use the negative pressure acting on the pressure accumulation port 31 by the swirl flow in the combustion chamber 12a already formed by closing the intake valve 20 relatively quickly. The accumulated pressure in the inside effectively acts on the combustion chamber 12a, and the thermal efficiency can be further improved.

In this embodiment, fuel is directly injected from the fuel injection valve 36 into the pressure accumulating chamber 30 during the exhaust stroke immediately after the pressure accumulating valve 33 is closed. A sufficient time can be secured, and the fuel can be sufficiently vaporized in the pressure accumulating chamber 30.

When fuel is directly injected into the pressure accumulating chamber 30 during the long closing period of the pressure accumulating valve 33, the injection time C can be sufficiently ensured, and the combustion chamber 12a is closed at the end of the compression stroke. The injection pressure can be reduced as compared with a general in-cylinder injection in which fuel is directly injected instantaneously, and the configuration of the fuel supply system including the fuel injection valve 36 can be simplified, and the cost can be reduced. It becomes possible.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible.

For example, in the above embodiment, the fuel is directly injected into the accumulator 30. However, the present invention can be applied to an internal combustion engine in which the fuel is injected into the intake port 16. Further, the intake valve 20 and the exhaust valve 21 are not limited to the two-valve type as in the above-described embodiment.
The present invention is also applicable to a two-valve or four-valve internal combustion engine.

The present invention can be applied to an internal combustion engine in which the operating characteristics of the intake valve 20 and the exhaust valve 21 are changed according to the operating conditions. A part of the supercharging timing due to the opening of the valve is overlapped with the intake stroke when the load is low, so that the in-cylinder pressure can be prevented from lowering, and the pumping loss can be reduced by increasing the throttle opening. it can.

[0032]

As described above, according to the first aspect of the present invention, by closing the intake valve early, the expansion ratio can be higher than the compression ratio to improve the thermal efficiency, and the pressure in the combustion chamber can be reduced. The burned gas in the accumulator is injected into the combustion chamber before the gas starts to rise, and the opening angle of the accumulator can be made relatively large, so that the supercharging amount can be increased and the thermal efficiency can be further improved.

According to the second aspect of the present invention, the accumulated pressure in the accumulator can be effectively applied to the combustion chamber, and the thermal efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of an internal combustion engine.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a bottom view of the cylinder head as viewed from the line 3-3 in FIG. 1;

FIG. 4 is an opening / closing operation characteristic diagram of an intake valve, an exhaust valve, and a pressure accumulation valve.

[Explanation of symbols]

 11a Cylinder bore 12 Cylinder head 12a Combustion chamber 14 Piston 16 Intake port 17 Exhaust port 20 Intake valve 21 Exhaust valve 30 Accumulation chamber 31 ・ ・ ・ accumulation port 33 ・ ・ ・ accumulation valve E ・ ・ ・ internal combustion engine

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G023 AA01 AA05 AB03 AC02 AC04 AD03 AD06 AG03 3G092 AA01 AA06 AA10 AA12 DA12 DA13 DE03S FA01 FA21 FA24

Claims (2)

[Claims] A combustion chamber (12a) connected to a cylinder bore (11a) into which a piston (14) is slidably fitted.
, An intake port (16) and an exhaust port (17) opening to the combustion chamber (12a), a pressure accumulation chamber (30), and a pressure accumulation port (31) connecting the pressure accumulation chamber (30) and the combustion chamber (12a). The intake valve (20) for opening and closing the intake port (16), the exhaust port (17) and the pressure accumulation port (31) respectively, the exhaust valve (21) and the pressure accumulation valve (33) are provided on the cylinder head (12) provided with In the internal combustion engine, which is provided so as to be able to open and close, the intake valve (20) is fully closed by the time the piston (14) reaches the bottom dead center, and the pressure accumulating valve (33) is set in the expansion stroke of the engine. An internal combustion engine that opens for a first period and opens for a second period from before the bottom dead center in the next intake stroke to a compression stroke that has passed the bottom dead center. 2. The combustion chamber (1), wherein the intake port (16) is provided in a combustion chamber (1).
2a), the swirl flow is formed in the combustion chamber (12a), along the flow direction of the swirl flow in the combustion chamber (12a), just below the opening end of the intake port (16) to the combustion chamber (12a). The internal combustion engine according to claim 1, wherein the pressure accumulation port (31) is formed so as to open to (12a).