JPH1150847A - Cylinder injection spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder injection spark ignition type internal combustion engine having high combustion efficiency and capable of realizing good combustion even if the bore is small. SOLUTION: Fuel injection valves 22 are provided on a cylinder head in the position either on one side or the other with a plane containing a cylinder axis X therebetween, and spark plugs 90 are provided on the cylinder head in the position almost opposite to the fuel injection valves 22 with the plane therebetween viewing from the cylinder axis X direction. The surface of pistons 12 are formed with a recessed part 16 from one side to the other with the plane therebetween for guiding fuel injected by the fuel injection valves 22 to the spark plugs 90 during a compression stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type spark ignition type internal combustion engine mounted on a vehicle, and more particularly to a direct injection gasoline engine having a small displacement.

[0002]

2. Related Background Art In recent years, in a spark ignition type internal combustion engine mounted on a vehicle, fuel is directly injected into a combustion chamber in place of a conventional intake pipe injection type in order to reduce harmful exhaust gas components and improve fuel efficiency. Various types of in-cylinder injection gasoline engines have been proposed, and examples of the configurations are disclosed in, for example, JP-A-5-240044.

In the cylinder injection gasoline engine disclosed in the above-mentioned publication, a cavity (dent) is provided at the top of the piston, and a small amount of fuel is injected into the cavity from a fuel injection valve during, for example, a compression stroke. Even in this case, it is possible to generate an air-fuel mixture having an air-fuel ratio close to the stoichiometric air-fuel ratio around the ignition plug (ignition plug) at the time of ignition by the swirling flow flowing over the cavity.

Accordingly, the direct injection gasoline engine is capable of igniting even with a lean air-fuel ratio as a whole and realizing stratified combustion with high combustion efficiency, and is capable of achieving carbon monoxide (CO) and It is possible to reduce the emission amount of harmful exhaust gas components such as hydrocarbons (HC), and to improve the fuel efficiency mainly at the time of idling operation or running at low load.

[0005]

In the direct injection gasoline engine disclosed in the above publication, a fuel injection valve is disposed near a cylinder wall surface on an intake port side so as to be able to inject fuel obliquely toward a combustion chamber. The ignition plug is disposed substantially at the center of the cylinder so as to be substantially upright facing the combustion chamber. When the piston is at the top dead center, one edge is located near the fuel injection valve and the other edge is ignited when the piston is at the top dead center according to the positions of the fuel injection valve and the spark plug. It is formed so as to be located near the plug.

However, such a configuration of the fuel injection valve and the spark plug is good when the engine displacement is large and the cylinder bore diameter is relatively large, but the engine displacement is small and the cylinder bore diameter is small. If is small,
There is a problem that the distance from the fuel injection valve to the spark plug becomes short, and a sufficient atomization time cannot be obtained until the injected fuel reaches the spark plug, so that the combustion efficiency is reduced and good combustion cannot be realized.

The present invention has been made in view of the above circumstances, and has as its object the in-cylinder injection type spark capable of realizing good combustion with high combustion efficiency even when the bore diameter is small. It is to provide an ignition type internal combustion engine.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, the fuel injection valve is provided on one side or the other side of a plane including a cylinder axis along the center axis of the cylinder. The ignition plug is provided on the cylinder head so as to be substantially opposite to the fuel injection valve across the plane when viewed from the cylinder axis direction. A recess is formed in the upper surface of the piston from the one side to the other side of the plane to guide the fuel injected by the fuel injection valve to the ignition plug during the compression stroke.

Thus, even in an internal combustion engine having a small bore diameter, the distance from the fuel injection valve to the spark plug is made relatively large, and the fuel injected from the fuel injection valve is formed on the upper surface of the piston. Since the fuel is guided well along the concave portion, when the fuel is injected in the compression stroke, the atomization time of the fuel is sufficiently obtained, and good stratified combustion with high combustion efficiency is realized.

Preferably, the concave portion is a curved long groove-shaped concave portion, whereby the fuel is smoothly guided to the spark plug, and stable stratified combustion is realized. According to the second aspect of the present invention, when the piston is at the top dead center position, one side edge of the recess is located near the fuel injection valve, and the other side edge of the spark plug is located on the other side. It is provided to be located in the vicinity.

Thus, the fuel injected from the fuel injection valve is reliably guided to the spark plug along the recess, and good stratified combustion is realized. According to the third aspect of the invention, the fuel injection valve is provided near the wall surface of the cylinder further away from the plane than one of the intake port and the exhaust port, while the ignition plug is provided at the intake port and the exhaust port. The port is provided near the wall surface of the cylinder further away from the plane than any one of the ports.

As a result, the distance from the fuel injection valve to the spark plug is increased, so that the fuel is sufficiently atomized when the fuel is injected in the compression stroke, and the intake port and the exhaust port are connected to the cylinder axis. As a result, the intake and exhaust efficiency is improved, and good stratified combustion is realized.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, there is shown a longitudinal sectional view of a SOHC (single overhead camshaft) type direct injection gasoline engine according to the present invention mounted on a vehicle. Referring to FIG. 2, a rocker cover is removed. FIG. 1 is a top view of a direct injection gasoline engine in a state, and an SO according to the present invention will be described below with reference to FIGS.
The configuration of the HC type direct injection gasoline engine will be described in detail. The SOHC in-cylinder gasoline engine is, for example, a four-valve four-cylinder gasoline engine having a small displacement, and all four cylinders can perform fuel injection not only in the intake stroke but also in the compression stroke. Here, one of the four cylinders will be described as a representative.

As shown in FIG. 1, an SOHC type direct injection gasoline engine (hereinafter, simply referred to as an engine) 1 has a cylinder head 4 and a rocker cover 6 on a cylinder block 2 like a normal gasoline engine. Each of them is placed in order and fixed by a bolt or the like.
As shown in the figure, a piston 12 is inserted into a cylindrical cylinder 10 of the cylinder block 2. The piston 12 is connected to a crankshaft (not shown) via a connecting rod 14, and reciprocates by sliding in the cylinder 10 according to rotation of the crankshaft. A cavity (recess) 16 is formed on the top surface of the piston 12. The piston 12
Since the engine 1 has a small displacement, the bore diameter is relatively small.

Referring to FIG. 3, there is shown a perspective view of the piston 12. As shown in FIG. 3, the cavity 16 formed at the top of the piston 12 has a curved bottom surface and is formed in a long groove shape. ing. More specifically, when the piston 12 is at the top dead center, the cavity 16 has one edge 16a of the cavity 16 located near the injection portion 22a of the fuel injection valve 22 described later, and the other edge 16b has the edge 16b described later. The spark plug 90 is formed so as to be located near the spark generating portion 90a. That is, the cavity 16 is provided so that the fuel injected from the fuel injection valve 22 is guided to the spark generating portion 90 a of the spark plug 90 along the cavity 16.

On the other hand, the cylinder head 4 is provided with a fuel injection valve (injector) 22 for directly injecting fuel toward a combustion chamber 20 formed by being divided by the lower surface of the cylinder head 4 and the top surface of the piston 12. Is provided.
More specifically, the fuel injection valve 22 is located at a position corresponding to the vicinity of the outer peripheral wall (near the wall surface) of the cylinder 10 when viewed from the center line Y (see FIG. 2) of the engine 1 connecting the central axes of the cylinders. The cylinder head 4 is attached to the cylinder head 4 with bolts 23 at a predetermined angle so as to be able to inject fuel obliquely with respect to the center axis of 10, ie, the cylinder axis X. The predetermined angle is an angle at which fuel can be injected along the bottom surface of the cavity 16 when the piston 12 is near the top dead center. The fuel injection valve 22 can satisfactorily supply the fuel to the cylinder 10 not only during the intake stroke but also during the compression stroke when the pressure in the combustion chamber 20 becomes high.
The allowable fuel injection pressure is set to a high pressure (for example, 50 kgf / cm ² or more) so that the fuel can be supplied to the inside.

A cam shaft 30 is rotatably supported on the cylinder head 4 along the center line Y. Specifically, the camshaft 30 includes a plurality of shaft support portions 32 formed between the cylinders and at both ends of the cylinder head 4.
The cylinder head 4 is rotatably supported by the cylinder head 4 while being held by cam caps 34 provided corresponding to the support portions 32. The cam cap 34 is fixed to the support 32 with a pair of bolts 38, 38, respectively.

Further, a pair of intake ports 44, 44 are formed in the cylinder head 4. More specifically, a pair of intake ports 40 are formed on the lower surface of the cylinder head 4 at one side of a base surface (plane) including the cylinder axis X and the center line Y. 44
Each of the lower ends (one end) is open to the combustion chamber 20 at the pair of intake ports 40, 40, while each upper end (the other end) is open.
Is provided so as to open on the upper surface of the rocker cover 6.

The cylinder head 4 is also formed with a pair of exhaust ports 46. For more information,
A pair of exhaust ports 42, 42 are formed on the lower surface of the cylinder head 4 at the other side of the base surface, and one end of each of the exhaust ports 46, 46 has one end thereof.
2, the other end is open on the side surface of the rocker cover 6 while the other end is open toward the combustion chamber 20.

The intake ports 40, 40 are provided with a pair of intake valves 50, 50 for communicating and shutting off the intake ports 44, 44 and the combustion chamber 20, while the exhaust port 4 is provided.
A pair of exhaust valves 52, 52 for communicating and shutting off the exhaust ports 46, 46 and the combustion chamber 20 are provided in the exhaust ports 2, 42. As shown in the figure, the intake valves 50, 50 and the exhaust valves 52, 52 also have a cylinder axis X, based on the positional relationship between the intake ports 44, 44 and the exhaust ports 46, 46.
And the base surface including the center line Y is provided on the cylinder head 4. Specifically, these intake valves 5
0, 50 and the exhaust valves 52, 52 each have a predetermined angle with respect to the base surface when viewed from the center line Y direction, that is, the intake valves 50, 50 and the exhaust valves 52, 52 As shown in FIG. 1, the cylinder head 4 extends so as to be separated from each other.

Incidentally, the intake valves 50, 50 and the exhaust valves 52, 52 are not special, but are similar to those normally used in an internal combustion engine. Therefore, the spring seats 54, 54 and the spring seats 5 are respectively provided on the heads of the intake valves 50, 50 and the exhaust valves 52, 52.
6, 56 are provided, and these spring seats 5
Coil springs 6, 54, and spring seats 56, 56 and the cylinder head 4, the intake valves 50, 50 and the exhaust valves 52, 52 are fitted around the coil springs 6, respectively.
0, 60 and coil springs 62, 62 are contracted. Therefore, usually, the intake valves 50, 50 and the exhaust valves 52, 5
Reference numeral 2 denotes a state in which the intake ports 40, 40 and the exhaust ports 42, 42 are closed by being urged by the coil springs 60, 60 and the coil springs 62, 62.

The camshaft 30 has a cam portion 30a and a pair of cam portions 30b, 30b corresponding to the intake valves 50, 50 and the exhaust valves 52, 52, respectively.
Are formed. A T-shaped rocker arm 70 extending between the intake ports 44, 44 is provided between the cam portion 30a and the intake valves 50, 50.
Rocker arms 72, 72 are provided between the cam portions 30b, 30b and the exhaust valves 52, 52.

More specifically, as shown in the drawing, a rocker shaft 74 and a rocker shaft 76 are supported by the cam cap 34 in parallel with the camshaft 30.
The rocker arm 70 and the rocker arm 72 are swingably supported by the rocker shaft 74 and the rocker shaft 76, respectively. As for the rocker arm 70, the roller 8 provided on one end side of the rocker arm 70
0 is in contact with the cam portion 30a, and each tip of a pair of valve adjusters 84, 84 provided on the other end side is an intake valve 5
It is arranged so that it may contact the heads of 0 and 50, respectively. Further, regarding the rocker arm 72, rollers 82, 8 provided on one end side of the rocker arms 72, 72, respectively.
2 is provided so as to abut against the cam portions 30b, 30b, and one ends of a pair of valve adjusters 86, 86 provided at the other end thereof are in contact with the heads of the exhaust valves 52, 52, respectively.

Therefore, when the camshaft 30 rotates,
The rocker arm 70 and the rocker arms 72, 72 swing around the rocker shafts 74, 76 in accordance with the shapes of the cam portions 30a and the cam portions 30b, 30b, so that the intake valves 50, 50 and the exhaust valves 52, 52 are coiled. The opening / closing operation is performed against the urging forces of the springs 60, 60 and the coil springs 62, 62.

The cylinder head 4 is provided with an ignition plug (ignition plug) 90 so as to face the fuel injection valve 22 with the base surface interposed therebetween. Specifically, the ignition plug 90 is located near the outer peripheral wall of the cylinder 10 (near the wall surface).
, The fuel injection valve 22 and the spark plug 90 are mounted on an orthogonal line Z (see FIG. 2) which is orthogonal to the center line Y when viewed from the cylinder axis X direction, and are opposed to each other with the base surface interposed therebetween. The spark generation portion 90a at the tip of the cylinder head 4 projects toward the combustion chamber 20.

Further, the spark plug 90 is attached to the cylinder head 4 at a predetermined angle with respect to the cylinder axis X when viewed from the center line Y direction.
The angle is set so that the spark plug 90 can be appropriately disposed along the exhaust ports 46, 46. Actually, as shown in FIG. 1, a straight pipe functioning as an insertion guide for the ignition plug 90, that is, a guide tube 94 is provided at the above-mentioned predetermined angle, and the ignition plug 90 is provided with the guide tube 94. And can be attached to the cylinder head 4.

FIG. 4 shows the operation and effect of the SOHC type direct injection gasoline engine constructed as described above.
This will be described with reference to FIG. Here, a case where the fuel is injected in the compression stroke will be described as an example. In the present embodiment, since the intake ports 44, 44 are erected substantially along the cylinder axis X, the intake air flows through the intake ports 44, 44 as the piston 12 descends during the intake stroke. The fuel enters the combustion chamber 20 along the wall surface of the cylinder 10.

Thereafter, the process proceeds to the compression stroke, in which the piston 12
Rises, with the rise, the intake air is wound up along the curved bottom surface of the cavity 16 provided on the top surface of the piston 12. At this time, the intake air is swirled in the cavity 16 as a vertical swirling flow in the cylinder 10 as shown by an arrow in FIG. And piston 1
When the fuel cell 2 reaches the vicinity of the top dead center, the fuel is injected from the fuel injection valve 22 along the curved bottom surface of the cavity 16, that is, in the same direction as the reverse tumble flow 100, as shown in FIG. You. As a result, the fuel is supplied to the cavity 16.
The fuel gas is mixed with the intake air to form a fuel spray 102 and reaches the spark generating portion 90 a of the spark plug 90. At this time, since the distance from the fuel injection valve 22 to the spark generating portion 90a is substantially equal to the bore diameter of the cylinder 10, sufficient time is obtained for atomizing the fuel. Therefore, when the fuel spray 102 reaches the spark generating section 90a, the fuel is in a state of being atomized so as to be appropriate for combustion, so that good combustion can be obtained.

By the way, when the fuel reaches the spark generating portion 90a of the spark plug 90 in such a state that the fuel is substantially confined in the cavity 16 together with the reverse tumble flow 100, that is, in a stratified state, the fuel is injected. Even if the amount is small, that is, the air-fuel ratio is lean as a whole (lean)
Even in the vicinity of the spark generating portion 90a, the air-fuel ratio is set to a relatively high (stoichiometric air-fuel ratio or rich) state. Therefore,
Thereafter, when the piston 12 is further moved to the vicinity of the top dead center, the ignition is performed by the spark plug 90, but the ignitability is good around the spark generating portion 90a.
Therefore, extremely good and efficient combustion, that is, stratified combustion is realized without occurrence of misfire (lean misfire) or the like. The operation and effect of stratified combustion are known, and a detailed description thereof is omitted here.

Thus, in a SOHC type direct injection gasoline engine, even if the displacement is small and the bore diameter is small, the atomization time is secured and the combustion efficiency is improved to improve the hydrocarbon (HC) Harmful exhaust gas components such as carbon monoxide (CO) can be reduced, and fuel consumption can be suppressed to a very low level to improve fuel efficiency. Here, the case where the fuel is injected in the compression stroke has been described as an example, but the use of the piston 12 having the cavity 16 having the above shape is also effective in the case where the fuel is injected in the intake stroke. is there. That is, the cavity 16
Is formed so as to extend substantially equal to the bore diameter of the cylinder 10, so that when the piston 12 descends, the reverse tumble flow 10
0 can be satisfactorily generated. For example, when a small amount of fuel is injected in the intake stroke and operation is performed at a lean air-fuel ratio, a mixture suitable for combustion can be satisfactorily generated. Thus, fuel efficiency can be improved.

As described above, in the in-cylinder injection gasoline engine according to the present invention, the fuel injection valve 22 and the spark plug 90 are positioned at the position corresponding to the vicinity of the outer peripheral wall of the cylinder 10 (the vicinity of the wall surface). The piston 12 is mounted on the cylinder head 4 so as to face each other with the base surface therebetween when viewed from the X direction. A cavity 16 having a curved bottom surface and a long groove shape is provided on the top surface of the piston 12. Like that.

Therefore, even in the case of an internal combustion engine having a small displacement and a small bore diameter, the reverse tumble flow 100 can be favorably generated in the combustion chamber 20, and the fuel injection is performed in the compression stroke. Can sufficiently secure the atomization time of the fuel and appropriately concentrate the fuel spray 102 in an appropriate atomized state having a high air-fuel ratio around the ignition plug 90, and achieve extremely good stratified combustion without misfiring or the like. Can be realized. As a result, generation of harmful exhaust gas components can be suppressed and fuel efficiency can be improved.

Further, by disposing the fuel injection valve 22 and the spark plug 90 outside the intake ports 44, 44 and the exhaust ports 46, 46 further away from the base surface, the intake ports 44, 44 The ports 46 and 46 can be formed relatively upright, and the intake and exhaust efficiency can be improved. In the above embodiment, the SOHC
Although the in-cylinder injection gasoline engine has been described, the engine 1 may be any internal combustion engine regardless of the structure of the valve mechanism. That is, the present invention can be suitably applied to a DOHC type direct injection gasoline engine having a small displacement and a small bore diameter.

[0034]

As described above in detail, according to the in-cylinder injection type spark ignition type internal combustion engine of the first aspect of the present invention, even if the internal combustion engine has a small bore diameter, the fuel injection valve can be used. The distance to the spark plug can be made relatively large, and the fuel injected from the fuel injection valve can be guided well along the recess formed on the upper surface of the piston. Therefore, when the fuel is injected in the compression stroke, a sufficient atomization time of the fuel can be obtained, and good stratified combustion with high combustion efficiency can be realized.

According to the in-cylinder injection spark ignition type internal combustion engine of the second aspect, the fuel injected from the fuel injection valve can be reliably guided to the ignition plug along the concave portion, and good stratified combustion is realized. be able to. Further, according to the in-cylinder injection type spark ignition internal combustion engine of the third aspect, the distance from the fuel injection valve to the spark plug can be increased, and the atomization time of the fuel when the fuel is injected in the compression stroke can be sufficiently increased. In addition to this, the intake port and the exhaust port can be arranged as close to the cylinder axis as possible and upright, so that the intake and exhaust efficiency can be improved and good stratified combustion can be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a direct injection gasoline engine according to the present invention.

FIG. 2 is a top view of the direct injection gasoline engine shown in FIG. 1 with a rocker cover removed.

FIG. 3 is a perspective view showing a piston in FIG. 1;

FIG. 4 is a diagram illustrating the operation of the direct injection gasoline engine according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine (SOHC type direct injection gasoline engine) 2 cylinder block 4 cylinder head 6 rocker cover 10 cylinder 12 piston 16 cavity (recess) 20 combustion chamber 22 fuel injection valve 30 camshaft 40 intake port 42 exhaust port 44 intake port 46 exhaust Port 50 Intake valve 52 Exhaust valve 70 Rocker arm 72 Rocker arm 74 Rocker shaft 76 Rocker shaft 90 Ignition plug (Ignition plug) 94 Guide tube

Continued on the front page (72) Inventor Kazuhiro Ichimoto 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Industry Co., Ltd. (72) Inventor Tomo Yokoyama 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industries Inside the corporation

Claims (3)

[Claims] 1. A piston inserted into a cylinder, a combustion chamber formed between an upper surface of the piston and a lower surface of a cylinder head, and a plane having one end including a cylinder axis extending along a center axis of the cylinder. An intake port formed in the cylinder head so as to be located on one side of the cylinder head and open to the combustion chamber; and an intake port formed on the cylinder head such that one end is located on the other side and opens to the combustion chamber across the plane. A formed exhaust port, a fuel injection valve that is provided on the cylinder head at one of one side and the other side across the plane, and directly injects fuel into the combustion chamber; and the cylinder axial direction. An ignition plug that is provided on the cylinder head so as to substantially face the fuel injection valve with the plane interposed therebetween, and ignites toward the combustion chamber; And a concave portion formed from one side to the other side across the plane, and guiding the fuel injected by the fuel injection valve to the spark plug during a compression stroke. Type internal combustion engine. 2. The recess is such that when the piston is at a top dead center position, one edge of the recess is located near the fuel injection valve and the other edge of the recess is located at the top of the ignition plug. The in-cylinder injection spark ignition type internal combustion engine according to claim 1, wherein the engine is formed so as to be located in the vicinity of the engine. 3. The fuel injection valve is provided near a wall surface of the cylinder further away from the plane than one of the intake port and the exhaust port, and the ignition plug is provided in the intake port. The in-cylinder injection type spark ignition type internal combustion engine according to claim 1 or 2, wherein the cylinder is provided near a wall surface of the cylinder further away from the plane than one of the other of the exhaust ports. engine.