JP3146936B2 - In-cylinder injection internal combustion 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 direct injection type internal combustion engine for directly injecting fuel into a combustion chamber, and more particularly, to a direct injection type internal combustion engine in which a lean air-fuel mixture is burned in a stable state. About.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection type gasoline engine, an engine in which fuel is injected into an intake port by an injector to supply the fuel is often used. In such an engine, in the intake port,
The intake air and fuel are mixed and ignited and burned in the combustion chamber.

On the other hand, in a diesel engine mainly using light oil or the like as fuel, fuel is directly injected into a combustion chamber, and the fuel is spontaneously ignited by compressed air in the combustion chamber to obtain power. By the way, even in the gasoline engine described above, a direct injection type internal combustion engine (for example, Japanese Patent Application Laid-Open No. 6-146886 and Japanese Utility Model Application Laid-Open No. 52334) has been proposed.

The direct injection type gasoline engine disclosed in Japanese Patent Application Laid-Open No. 6-146886 requires a spark plug as ignition means, and the arrangement of parts around the cylinder head is different from that of a diesel engine. . For example, it is configured as shown in FIGS. 7, 8, and 9, in which an upright intake port 101, a fuel injection valve 102 arranged on the intake side, and a curved combustion chamber 103 shifted toward the intake side are formed. Piston 104 and 4 valves (exhaust 2 valve, intake 2
The ignition valve 106 is disposed at the center of the valve 104. By switching the injection timing of injecting fuel toward the upper surface of the piston 104, an operation in which the fuel concentration distribution in the cylinder is controlled is performed.

In Japanese Utility Model Laid-Open No. 3-52334,
Shows a two-stroke engine direct injection type internal combustion engine. In order to improve the scavenging efficiency, a reverse tumble flow from the upper surface of the piston to the spark plug through the lower surface of the cylinder is provided so that the piston is near the bottom dead center. , Fuel is injected toward the upper surface of the piston from a fuel injection valve mounted directly downward between the intake and exhaust valves of the cylinder head to promote premixing.

[0006]

However, in the former engine, there is a problem that the spray wall control in the curved combustion chamber 103 can be performed only in the latter half of the compression stroke injection in which the piston 104 is relatively close to the compression top dead center. That is, when the pressure-accumulation type injector is operated by electronic control, the fuel is injected into the combustion chamber 1 in the middle to low speed range, as shown in FIG.
Although the fuel injection is performed efficiently within the fuel cell 03, it is necessary to complete the fuel injection in a short time in the high-speed range, so that it is necessary to perform the fuel injection in the first half of the compression stroke.

In such a case, as shown in FIG.
The fuel is injected at the position where the piston 104 is lowered, and the fuel is injected outside the combustion chamber 103, so that the fuel spray is not captured by the control wall surface of the piston and dissipates throughout the combustion chamber. , Cannot be stratified. When the ignition operation shown in FIG. 9 is performed in such a state, the air-fuel mixture is dispersed around the ignition plug 106, so that efficient combustion cannot be performed, and the super-lean mixture is not used. There is a problem that combustion is not established.

Further, in the latter engine, the fuel is injected downward in the vicinity of the bottom dead center at the piston position, so that the fuel is dispersed in the cylinder and the mixing is promoted, so that the stable combustion under the lean condition is achieved. There is a problem that it cannot be obtained. The present invention
An object of the present invention is to provide an in-cylinder injection type internal combustion engine that has been devised in view of such a problem and that can perform efficient fuel injection and lean combustion regardless of the engine speed.

[0009]

According to the first aspect of the present invention, there is provided an in-cylinder injection type internal combustion engine according to the present invention, which is formed between an upper surface of a piston inserted into a cylinder of an internal combustion engine and a lower surface of a cylinder head. A combustion chamber, an intake valve provided on one side of a virtual plane including a cylinder axis on a lower surface of a cylinder head forming the combustion chamber, and an intake valve provided on the other side of the cylinder head on the other side of the virtual plane. Exhaust valve and the upper
On the upper surface of the piston located on one side, the cylinder
Formed so as to present a downwardly convex curved surface when viewed perpendicular to the axis
And by recesses provided inclined exhaust valve side between the intake valve and the exhaust valve, pressure in the low-speed range within the internal combustion engine
In the latter half of the compression stroke, and in the high speed region of the internal combustion engine, the compression stroke
In the first half, and a fuel injection valve for injecting fuel toward the recess, respectively, and a spark plug disposed in the cylinder head portion opposite to the fuel injection valve across the axis of the intake valve
In addition, the wall surface of the recess is in the middle to low speed range of the internal combustion engine.
And reflects the fuel injected from the fuel injection valve in the high speed range.
It is characterized in that it is formed so as to be guided to the ignition plug .

According to a second aspect of the present invention, in the cylinder injection type internal combustion engine according to the first aspect, the fuel injection valve is inclined substantially parallel to an axis of the exhaust valve. Features. Further, the in-cylinder injection type internal combustion engine of the present invention according to claim 3 is an engine according to claim 1,
The recess is formed to promote the vortex flow of the intake air.

According to a fourth aspect of the present invention, there is provided the in-cylinder injection type internal combustion engine according to the first aspect, wherein a tip of the ignition plug is disposed in the recess at a compression top dead center of the piston. and that it is characterized by that.

Furthermore, direct injection internal combustion engine of the present invention of claim 5, wherein, for claim 1 or 3 engine according intake air system is opened and closed by the intake valve, which is introduced into the combustion chamber the flow through the recess from the underside the cylinder head and the longitudinal vortex toward the spark plug from the exhaust valve side
It is characterized in that it is configured so as to form Te.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view schematically showing a main part of a direct injection type internal combustion engine according to an embodiment of the present invention; FIG.
Is a schematic front view showing the lower surface of the cylinder head, FIG.
4 is a schematic diagram showing the operating state, and FIG. 5 is a graph showing its combustion characteristics.

As shown in FIG. 1, in the cylinder injection type internal combustion engine, an engine body is constituted by a cylinder head 1 and a cylinder block 3, and a piston 2 is inserted into a cylinder 3A of the cylinder block 3. ing. Also,
As shown in FIG. 2, the cylinder head 1 of the internal combustion engine has two intake valves (see reference numerals 9 and 9 in FIG. 2) and two exhaust valves (see reference numerals 8 and 8 in FIG. 2). It is configured as a valve-type internal combustion engine.

A combustion chamber 7 is formed between the upper surface of the piston 2 and the lower surface 1A of the cylinder head 1. The cylinder head 1 of the combustion chamber 7 has a standard non-standing intake passage. The intake port 4 and the exhaust port 5 of the exhaust passage are connected to each other. An intake valve 9 and an exhaust valve 8 are installed at the combustion chamber openings 4A and 5A of the intake and exhaust ports 4 and 5, respectively, and the combustion chamber openings 4A and 5A are formed by the intake and exhaust valves 9 and 8, respectively. It can be opened and closed.

Here, the intake valve 9 has a virtual plane P including a cylinder axis on the lower surface of the cylinder head 1 forming the combustion chamber 7.
, And the exhaust valve 8 is provided on the lower surface of the cylinder head 1 on the other side across the virtual plane P.
A fuel injection valve 10 is provided between the intake valve 9 and the exhaust valve 8 so as to be inclined toward the exhaust valve 8.
It is configured to inject fuel toward the upper surface of the.

Further, an ignition plug 1 is provided on a cylinder head portion opposite to the fuel injection valve 10 with respect to the axis L of the intake valve 9.
1 is provided. Since the fuel injection valve 10 is installed so as to be substantially parallel to the axis M of the exhaust valve 8, the fuel pipe (not shown) is separated from the exhaust port 5 side,
It can be mounted on the upper surface side of the cylinder head 1 that is hardly heated. Further, as shown in FIG. 6, after the cylinder head 1 is fixed to the fuel injection hole 10A and the exhaust valve guide hole 8A using the cylinder head mounting jig 105 that matches the inclination angle in the processing step, the hole processing is performed. And are formed in the same step.

Further, a recess 13 having a downwardly convex curved surface when viewed perpendicularly to the cylinder axis is formed on the upper surface of the piston 2 located on one side in order to promote the swirling flow of the intake air. Are configured to inject fuel toward the recess 13. Thereby, this piston 2
Form a combustion chamber-shaped piston with a curved intake side.

Further, the wall surface 12 of the recess 13 is arranged so as to reflect and guide the injected fuel and guide the injected fuel toward the ignition plug 11. The ignition plug 11 is disposed such that its tip reaches the recess 13 at the compression top dead center of the piston 2. The intake system opened and closed by the intake valve 9 forms a vertical vortex flow (forward tumble flow) of the intake air introduced into the combustion chamber 7 from the lower surface 1A of the cylinder head to the ignition plug 11 via the upper surface of the piston 2. It is configured to be.

Here, the intake system is formed by the intake port 4 and the combustion chamber 7, and is configured to generate a counter-clockwise forward tumble flow in FIG. I have. The operation as shown in FIG. 3 is performed by the above configuration. That is, when the engine is operated in a high speed range, fuel is injected from the fuel injection valve 10 in the first half of the compression stroke in which the piston 2 is relatively lower.

At this time, the fuel injection valve 10 injects fuel from a central position on the lower surface of the cylinder head 1. Here, since the fuel injection valve 10 is inclined to the exhaust valve 8 side and the recess 13 is formed on the upper surface of the piston 2 on the intake valve 9 side, the injected fuel is stored in the recess 13. I will head.

After reaching the recess 13, the wall 1
As shown in FIG. 4, the injected fuel is guided to the position of the spark plug 11,
Immediately before ignition, a rich mixture is formed. In this state, the ignition operation by the ignition plug 11 is performed, so that efficient combustion is performed.

By the way, the intake air flows into the combustion chamber 7 from the combustion chamber opening 4A. However, depending on the direction and speed component of the inflow and the shape of the combustion chamber 7, a vertical eddy current is generated as shown by an arrow X in FIG. appear. That is, a tumble flow is generated in the forward direction (counterclockwise in the figure) to assist fuel transport and reach the position of the spark plug 11 while being efficiently mixed with the injected fuel injected from the fuel injection valve 10. Becomes

As a result, sufficient mixing and stratification with the fuel are achieved, and stable combustion is performed even in a high-speed operation of the engine. By the way, considering the low-speed operation of the engine, in such a speed range,
In the latter half of the compression stroke (the piston position is shown in FIG. 4), fuel is injected from the fuel injection valve 10, whereby the injected fuel is also guided to the position of the spark plug 11 and immediately before ignition. A rich mixture is formed, resulting in stable combustion of the engine.

Such improvement in combustion characteristics is considered in the graph shown in FIG. That is, FIG. 5 shows each characteristic by taking the air-fuel ratio on the horizontal axis and the indicated mean effective pressure and the combustion fluctuation rate on the vertical axis. The dotted line in the figure indicates the case of the conventional intake pipe injection, the dashed line indicates the case of the structure shown in FIGS. 6 and 7, and the solid line indicates the case of the present embodiment.

As can be seen from the drawing, in the case of the present embodiment, a stable indicated mean effective pressure is obtained up to the lean side, and the combustion fluctuation rate is kept low until the lean operation, whereby a stable lean operation is realized. Is done. In addition to having the standard intake port 4 as described above, the injection valve 10 is disposed at the center of the combustion chamber 7 with a slight inclination toward the exhaust side with respect to the intake-side curved combustion chamber-shaped piston 2, and the ignition plug 11 is arranged from the intake side. By adopting the inclined arrangement, the fuel spray collides with the piston 10 during the compression stroke and the fuel concentration distribution in the cylinder can be controlled, so that the combustion stability in the high speed operation range is improved, This enables ultra-lean combustion operation in the entire operation range including the region, thereby improving fuel efficiency.

The fuel injection hole 10 for the fuel injection valve 10
Since A and the exhaust valve guide hole 8A can be formed in the same process, man-hours required for manufacturing (man-hours for cutting) are reduced, and cost reduction is realized.

[0028]

As described above in detail, according to the in-cylinder injection type internal combustion engine according to the first aspect of the present invention, the upper surface of the piston and the cylinder head inserted into the cylinder of the internal combustion engine. A combustion chamber formed between the lower surface of the cylinder, an intake valve provided on one side of a virtual plane including a cylinder axis on a lower surface of a cylinder head forming the combustion chamber, and an intake valve provided on the other side of the virtual plane. An exhaust valve provided on the lower surface of the cylinder head,
On the upper surface of the piston located on one side, the syringe
A shape that exhibits a downwardly convex curved surface when viewed in a plane orthogonal to the da axis.
And made a recess provided obliquely to the exhaust valve side between the intake valve and the exhaust valve, in the low speed range in the said internal combustion engine
In the latter half of the compression stroke, and in the high speed region of the internal combustion engine, the compression stroke
In the first half, a fuel injection valve for injecting fuel toward the recess, and an ignition plug disposed on the cylinder head portion opposite to the fuel injection valve with respect to the axis of the intake valve.
And the wall of the recess is in the middle to low speed range of the internal combustion engine.
And reflects the fuel injected from the fuel injection valve in the high speed range
With a simple configuration that Ru is formed so as to be guided to the ignition plug, to form a rich mixture of via a recess in the vicinity of the spark plug
Therefore, there is an advantage that the combustion stability in the high-speed operation range is improved, the ultra-lean combustion operation in the entire operation range including this speed range is realized, and the fuel efficiency is improved.

According to the cylinder injection type internal combustion engine of the present invention, the fuel injection valve is inclined substantially parallel to the axis of the exhaust valve. With such a simple configuration, the fuel injection hole for the fuel injection valve and the exhaust valve guide hole can be formed in the same process, so that the number of steps is reduced and the cost is reduced. Further, according to the in-cylinder injection type internal combustion engine of the present invention described in claim 3, with respect to the engine described in claim 1, the recess is formed through the recess because the recess is formed to promote the vortex flow of the intake air. A rich air-fuel mixture can be formed near the ignition plug, improving combustion stability in the high-speed operation range, enabling ultra-lean combustion operation in the entire operation range including this speed range, and reducing fuel consumption. There are advantages to be improved.

[0030] Then, according to the cylinder injection type internal combustion engine of the present invention described in claim 4, the engine according to claim 1, the tip of the spark plug in the compression top dead center of the piston arrangement in the recess With a simple configuration, the ignition plug is located at the position where the rich mixture is formed via the recess, so that the combustion stability in the high-speed operation range is improved. In addition, ultra-lean combustion operation can be performed in the entire operation range, and there is an advantage that fuel efficiency is improved.

[0031]

Furthermore, according to the cylinder injection type internal combustion engine of the present invention according to claim 5, for claim 1 or 3 engine according intake system is opened and closed by the intake valve is introduced into the combustion chamber concave the intake flow from the lower surface above the cylinder head that
Via Tokoro with a simple configuration in order to form configured as a vertical vortex toward the spark plug from the exhaust valve side, in addition to the rich mixture of via a recess, vertical vortices are generated As a result, efficient mixing of fuel and assistance of fuel transport to the vicinity of the spark plug are realized, and a mixture having a uniform lean air-fuel ratio can be formed, and combustion stability in a high-speed operation range is improved. There is an advantage that ultra-lean combustion operation is realized in the entire operation range including the speed range, and fuel efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a configuration of a main part of a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 2 is a schematic front view showing a cylinder head lower surface of a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 3 is a schematic diagram showing an operating state of a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 4 is a schematic diagram showing an operation state of a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 5 is a graph showing fuel characteristics of a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 6 is a view showing a process of forming a fuel injection hole and an exhaust valve guide hole.

FIG. 7 is a schematic diagram showing an operation state of a conventional direct injection internal combustion engine.

FIG. 8 is a schematic diagram showing an operation state of a conventional direct injection internal combustion engine.

FIG. 9 is a schematic diagram showing an operation state of a conventional direct injection internal combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 1A Cylinder head lower surface 2 Piston 3 Cylinder block 3A Cylinder 4 Intake port 4A Intake passage combustion chamber opening 5 Exhaust port 5A Exhaust passage combustion chamber opening 7 Combustion chamber 8 Exhaust valve 8A Exhaust valve guide hole 9 Intake valve 10 Fuel injection valve Reference Signs List 10A Fuel injection hole 11 Spark plug 12 Wall surface 13 Depression 101 Intake port 102 Fuel injection valve 103 Combustion chamber 104 Piston

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-42352 (JP, A) JP-A-5-240044 (JP, A) JP-A-5-240047 (JP, A) 215878 (JP, A) JP-A-5-60038 (JP, A) JP-A-6-146886 (JP, A) JP-A-3-52334 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 23/10

Claims (5)

(57) [Claims] 1. A combustion chamber formed between an upper surface of a piston inserted into a cylinder of an internal combustion engine and a lower surface of a cylinder head, and a virtual plane including a cylinder axis on a lower surface of a cylinder head forming the combustion chamber. An intake valve provided on one side of the cylinder head, an exhaust valve provided on the lower surface of the cylinder head on the other side of the imaginary plane, and an upper surface of the piston located on the one side;
A shape that exhibits a downwardly convex curved surface when viewed in a plane orthogonal to the da axis.
The recess formed is provided between the intake valve and the exhaust valve so as to be inclined toward the exhaust valve, and in the middle and low speed range of the internal combustion engine, in the latter half of the compression stroke,
In the high speed region of the internal combustion engine,
Re a fuel injection valve for injecting fuel toward the recess, provided with an ignition plug disposed in the cylinder head portion opposite to the fuel injection valve across the axis of the intake valve, the recess The wall of the above-mentioned internal combustion engine is in the middle and low speed range and high speed range
The fuel injected from the fuel injection valve is reflected at the ignition plug
An in-cylinder injection type internal combustion engine characterized by being formed to guide . 2. The direct injection internal combustion engine according to claim 1, wherein said fuel injection valve is inclined substantially parallel to an axis of said exhaust valve. 3. The recess is formed to promote air vortex flow.
The in- cylinder injection type internal combustion engine according to claim 1, wherein: Wherein the tip of the spark plug in the compression top dead center of the piston, characterized in that it is disposed in the recess, a cylinder injection type internal combustion engine according to claim 1. 5. An intake system which is opened and closed by said intake valve,
Characterized in that the intake air flow introduced into the combustion chamber is configured so as to form a vertical vortex flow toward the ignition plug via the recess from the exhaust valve side from the lower surface above the cylinder head, according to claim 1 Or a direct injection internal combustion engine according to 3.