JP2000097031A - Direct injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish enhancement of the fuel economy and the enhancement of the output compatibly by of a direct injection type internal combustion engine by setting the shape of the combustion chamber and the relative positional relationship of constituent parts of the combustion chamber so that the combustion efficiency becomes the highest. SOLUTION: An direct injection type internal combustion engine to inject the fuel directly into a combustion chamber 3 is structured so that the undersurface of a cylinder head 8 is made in a pentroof shape, the top face of each piston 2 is made in a crest shape alongside the pentroof shape, and that a recess 25 is formed at least in the inclined oversurface on the intake valve side of the top face of the piston 2, wherein the ratio of Va and Vb to the total capacity of the combustion chamber 3 Va+Vb+Vb when the piston 2 lies at the upper dead point should be between 0.4 and 0.6, where Va represents the capacity portion inside the recess 25 and Vb represents the capacity portion between the cylinder head 8 undersurface and the piston 2 oversurface located over the recess 25 among the capacity of the combustion chamber 3 when the piston 2 lies at the upper dead point.

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 which is of a spark ignition type and directly injects fuel into a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, a fuel injection device (injector) has been widely used in a fuel supply system of a gasoline engine which mainly uses gasoline as a fuel among internal combustion engines. In such a gasoline engine, the operation of the injector is controlled by a control unit such as a controller,
At a predetermined timing, a predetermined amount of fuel is injected into the intake port.

[0003] The fuel injected into the intake port is supplied into the combustion chamber together with the air sucked in the intake stroke, mixed with the air, ignited by a spark plug, and burned. 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.

In the meantime, there has been proposed an in-cylinder internal combustion engine in which the fuel is injected directly into the combustion chamber of the above gasoline engine to improve the responsiveness of the engine. In such an in-cylinder injection internal combustion engine, a vortex is formed in the cylinder, fuel is injected into the vortex, and an air-fuel mixture having a required concentration (fuel concentration near the stoichiometric air-fuel ratio) is adjusted according to the position of the ignition plug. By supplying the fuel in the gaseous mixture layer to the ignition plug, it is possible to perform combustion in a state where the fuel concentration is extremely low (high air-fuel ratio) as a whole, that is, a so-called stratified lean combustion operation.

[0005]

By the way, in such a direct injection type internal combustion engine, since the intake air in the combustion chamber is cooled by the fuel injected into the cylinder, knocking can be suppressed. There is an advantage that the compression ratio can be easily increased. Therefore, in the cylinder injection type internal combustion engine, it is important to design the shape of the combustion chamber formed by the piston, the lower surface of the cylinder head, and the like so as to take advantage of this advantage.

However, when the shape of the combustion chamber becomes complicated, the output characteristics and fuel efficiency of the engine greatly change only by slightly changing the shape and volume of the piston and the combustion chamber, and the arrangement of the spark plug. There is a problem of doing it. Therefore, there is a demand to set the shape of the combustion chamber of the in-cylinder injection type internal combustion engine and the relative positional relationship of the components of the combustion chamber so that the combustion efficiency is optimized.

Japanese Patent Application Laid-Open No. 4-228850 discloses a technique in which fuel injected from a fuel injection valve does not hit the inner wall of a cylinder. However,
Such a technique focuses only on the direction of fuel injection from the fuel injection valve, and does not solve the above-described problem. Japanese Patent Application Laid-Open No. 4-58030 discloses a technique for suppressing the occurrence of self-ignition, knocking and smoke in an in-cylinder injection type internal combustion engine. However, such a technique is merely for smoothly operating the engine, and also does not solve the above-mentioned problem.

Japanese Patent Application Laid-Open No. 4-166612 discloses a technique for improving the ignitability of a direct injection internal combustion engine during low load operation. It is not intended to form a combustion chamber or a piston or to regulate the position of the spark plug so as to be optimal. Further, in the above-described technology, a combustion chamber is formed by forming a concave portion in the upper portion of the piston, but a large space is formed between the top surface of the piston and the lower surface of the cylinder head. However, such a combustion chamber shape has a problem that a sufficient compression ratio cannot be obtained, and it is difficult to increase the output.

The present invention has been devised in order to meet such demands and problems, and the combustion efficiency is optimized based on the shape of the combustion chamber and the relative positional relationship of the components of the combustion chamber of the direct injection internal combustion engine. It is an object of the present invention to provide an in-cylinder injection type internal combustion engine which is set in such a state so that both fuel efficiency and output can be improved.

[0010]

In the cylinder injection type internal combustion engine according to the present invention, the lower surface of the cylinder head is formed in a pent roof shape, and the spark plug is arranged near the top of the upper surface of the pent roof shaped combustion chamber. At the same time, the top surface of the piston forming the lower surface of the combustion chamber is formed in a mountain shape substantially following the pent roof shape. A recess is provided on at least the intake valve-side inclined upper surface of the piston top surface, and of the volume of the combustion chamber when the piston is at the top dead center position, the volume in the recess and the piston upper surface above the recess and the cylinder head lower surface The ratio between the volume in between and the total volume of the combustion chamber when the piston is at the top dead center position is set between 0.4 and 0.6.
With such a configuration, each volume ratio in the combustion chamber can be optimized, and both high fuel efficiency and high output can be achieved.

According to a second aspect of the present invention, there is provided the in-cylinder injection type internal combustion engine according to the first aspect of the present invention, wherein a flat portion is formed at least at an outer peripheral end on one side of the piston top surface, and the concave portion is formed. An inflow portion that is formed more gently than the flat portion and that is introduced into the combustion chamber when the intake air flows into the concave portion, and a gently raised portion that guides the intake air flow that has flowed into the concave portion toward the vicinity of the ignition plug. And a connecting portion connecting the inflow portion and the protruding portion, the formation of a longitudinal vortex (tumble flow) in the combustion chamber is promoted, and stratified combustion is easily performed.

According to a third aspect of the present invention, in the cylinder injection type internal combustion engine of the first aspect, the inclined lower surface on the intake valve side and the inclined lower surface on the exhaust valve side forming the upper surface of the combustion chamber are arranged. By forming each of them substantially flat, the formation of the longitudinal vortex generated in the combustion chamber is promoted, and the longitudinal vortex is strengthened. According to a fourth aspect of the present invention, in the configuration of the first aspect, the inclined upper surface of the piston on the exhaust valve side is set to a smaller inclination angle than the lower surface of the cylinder head on the exhaust valve side. At the same time, it is formed so that the mutual distance between the exhaust valve-side inclined lower surface of the cylinder head and the exhaust valve-side inclined upper surface of the piston expands toward the center of the combustion chamber. By forming a substantially wedge-shaped flame entry space, the flame is uniformly propagated in the combustion chamber, and uniform combustion is performed.

According to a fifth aspect of the present invention, in the cylinder injection type internal combustion engine according to the first aspect, when the piston is at the top dead center, the distance between the piston and the exhaust valve is reduced. , So as to be smaller than the distance between adjacent parts of the piston and the intake valve. Thereby, the surface area in the combustion chamber is reduced and the heat loss is reduced without substantially changing the volume ratio of the entire combustion chamber.

According to a sixth aspect of the present invention, in the cylinder injection type internal combustion engine of the first aspect, the concave portion is formed by a spherical surface, so that the surface area of the concave portion with respect to the volume of the concave portion of the piston is minimized. Becomes Further, the formation of a vortex flow, that is, a tumble flow, due to the intake air flow in the combustion chamber is promoted. According to a seventh aspect of the present invention, in the direct injection internal combustion engine of the present invention,
By forming the concave portion as a part of a virtual spherical surface having a center at the upper part of the piston on the intake valve side, by configuring the apex of the piston and the lower end of the inclined surface on the intake valve side of the piston to be included in the virtual spherical surface, The spark plug can be easily arranged in the recess. Also, generation of a tumble flow is promoted.

According to an eighth aspect of the present invention, there is provided the in-cylinder injection type internal combustion engine according to the sixth aspect of the present invention, wherein the injection port of the fuel injection valve and the valve body of the intake valve are located at the top dead center position of the piston. Are contained in the virtual spherical surface, and the ignition point of the discharge electrode of the ignition plug is contained in the concave portion, whereby an air-fuel mixture having a high fuel concentration can be generated in the concave portion.

According to a ninth aspect of the present invention, there is provided the in-cylinder injection type internal combustion engine according to the first aspect of the present invention, wherein the ridge defining the intake valve side inclined upper surface and the exhaust valve side inclined upper surface is formed on the piston top surface. And the recess extends beyond the ridge line and extends from the intake valve side inclined upper surface to the exhaust valve side inclined upper surface. This makes it easy to optimally set the ratio between the volume of the recess in the combustion chamber and the volume of the entire combustion chamber.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. First, a description will be given of a direct injection internal combustion engine as a first embodiment of the present invention. FIG. 1 is a schematic sectional view showing the configuration of a combustion chamber, and FIGS.
(C), FIGS. 15 to 22 are schematic diagrams each showing a shape of a piston as a main part thereof, and FIG. 3 is a diagram showing a relative positional relationship between a top surface of the piston and a lower surface of a cylinder head. 4 is a schematic view for explaining the ratio of the total volume of the combustion chamber to the volume of the concave portion of the piston, and FIGS. 5 (a) and 5 (b) show the engine accompanying the change in the volume ratio of the concave shape of the piston. 6, FIG. 7, and FIGS. 23 to 46 are schematic diagrams showing modifications thereof, and FIGS. 8 and 9 are graphs for explaining the operation thereof. FIG. 10 shows the fuel efficiency and H due to the difference in the shape of the combustion chamber.
It is a graph which shows the change characteristic of C discharge.

As shown in FIG. 1, a combustion chamber 3 of this engine is formed by a lower surface of a cylinder head 8 and a top surface of a piston 2. An intake valve 4 is provided on one side of the upper surface of the combustion chamber 3. However, an exhaust valve 5 is disposed on the other side.
The lower surface of the cylinder head 8, that is, the upper surface of the combustion chamber 3, on the side where the intake valve 4 is disposed, has an intake valve-side inclined lower surface 8a inclined from the top to the end of the combustion chamber 3.
The exhaust valve 5 is provided with an exhaust valve-side inclined lower surface 8b on the side where the exhaust valve 5 is provided.

The upper surface of the combustion chamber 3 is formed in a pent roof shape as shown in FIG. 1 by these inclined lower surfaces 8a and 8b. A fuel injection valve (hereinafter simply referred to as an injector) 1 is attached to the cylinder head 8. The injector 1 is arranged so that the tip side faces the combustion chamber 3, and fuel is directly injected into the combustion chamber 3 by the injector 1.

Next, the shape of the piston 2 will be described. The top surface of the piston 2 forming the lower surface of the combustion chamber 3 is shown in FIGS. The intake valve side inclined lower surface 8a and the exhaust valve side inclined upper surface 2b which are inclined toward the center side of the piston 2 are formed corresponding to the intake valve side inclined lower surface 8a and the exhaust valve side inclined lower surface 8b, respectively. By these inclined upper surfaces 2a and 2b,
The top surface of the piston 2 is formed in a mountain shape substantially along the pent roof shape. In addition, these inclined upper surfaces 2a,
2b is defined by a ridgeline formed on the piston top surface.

A concave portion (hereinafter simply referred to as a cavity) 25 as shown in FIGS. 1 and 2 (a) to 2 (c) is formed on the inclined upper surface 2a of the piston 2 on the intake valve side. The cavity 25 is formed so as to extend to the exhaust valve side inclined upper surface 2b so as to divide the ridge line, and is formed in a spherical shape curved downward and convexly. A virtual spherical surface 25a having a center at the top
It is formed as a part of.

An intake port 9 (see FIG. 12) opening to the combustion chamber 3 extends substantially upright above the intake valve 4, and the intake air flows through the combustion port 3 through this intake port. The intake air flows toward the lower piston 2 and is guided along the cavity 25 of the piston 2 to flow upward to form a tumble flow (longitudinal vortex).

In particular, the inclined lower surfaces 8a, 8b of the combustion chamber 3
Is formed substantially flat, that is, by continuously connecting the lower surfaces 8a and 8b of the cylinder head 8 and the lower surfaces of the intake valve 4 and the exhaust valve 5, the flow of the tumble flow becomes smooth, The flow will be strengthened. Also,
The lower surface of the cylinder head 8 is formed in the pent roof shape as described above mainly for the following reasons.

That is, in such an in-cylinder injection type engine, the fuel injection timing is largely changed depending on the engine speed and the engine load, and it is necessary to establish the fuel injection even during the compression stroke. For this purpose, it is preferable to generate a strong flow continuously without disturbing the intake flow in the combustion chamber 3. Therefore, in the present embodiment, in order to maintain the tumble flow generated in the combustion chamber 3 particularly until the latter half of the compression stroke, the intake valve side lower surface 8a and the exhaust valve side inclined lower surface 8b of the cylinder head 8 are formed in a pent roof shape. The flow of the tumble flow from the piston 2 toward the lower surface 8b on the exhaust valve side and the flow from the slope 8a on the intake valve side to the piston 2 are made smooth, and the tumble flow is maintained until the latter half of the compression stroke.

Also, by forming the intake port 9 substantially upright, the resistance at the time of intake is reduced and a strong intake flow is introduced into the combustion chamber 3, whereby a strong vertical vortex flow (tumble flow) is generated in the combustion chamber 3. ) Is formed. Further, the intake valve-side inclined lower surface 8a of the cylinder head 8 has a pent roof shape in which the intake valve 4 can be arranged to be inclined, thereby increasing the degree of freedom of the layout of the intake port 9.

The setting of the volume of the cavity 25 has a large effect on the engine performance. For example, if the volume of the cavity 25 is too large with respect to the total volume of the combustion chamber 3, a graph shown in FIG. As described above, although it is advantageous to perform the stratified combustion, the surface area of the combustion chamber 3 is increased and the heat loss is increased. Although fuel efficiency is improved by this, as shown in the graph of FIG.
It is considered that the maximum output and the maximum torque are reduced.

If the volume of the cavity 25 is too small relative to the total volume of the combustion chamber 3, the maximum output and the maximum torque are improved as shown in the graph of FIG. As a result, a low tumble flow cannot be formed, and as shown in the graph of FIG. Therefore, in the in-cylinder injection type internal combustion engine of the present invention, the volume of the cavity 25 is set to have a predetermined ratio to the volume of the entire combustion chamber 3 in order to achieve both output performance and fuel efficiency of the engine. Have been.

Here, the setting of this volume ratio will be described with reference to FIG. 4. The volume of the cavity 25 is Va, and the intake valve side inclined lower surface 8a when the piston 2 is at the top dead center position.
Let Vb be the volume between the intake valve side inclined upper surface 2a and Vc be the volume between the exhaust valve side inclined lower surface 8b and the exhaust valve side inclined upper surface 2b when the piston 2 is at the top dead center position.
The value of (Va + Vb) / (Va + Vb + Vc) is 0.4
It is set to be between 0.6 and 0.6.

In the present embodiment, in order to form such a combustion chamber 3, the top surface of the piston 2 is formed in a mountain shape substantially following the pent roof shape of the cylinder head 8. That is, when the top surface of the piston 2 is formed in a pent roof shape in this manner, the space surrounded by the piston 2 and the cylinder head 8 can be reduced when the piston 2 rises, and the total volume of the combustion chamber 3 can be reduced. , The ratio of the volume of the cavity 25 to the ratio can be increased.

Thus, the compression ratio of the engine can be increased, and the output can be greatly improved. By setting the volume ratio of the cavity 25 to the above-mentioned predetermined value, it is possible to achieve a good balance between improvement in fuel efficiency and high output. In addition to this, the shape of the cavity 25 is shown in FIG.
By forming a spherical shape as shown in (a) to (c),
There is an advantage that the cavity surface area with respect to the cavity volume Va of the piston 2 can be minimized. By minimizing the cavity surface area in this way, heat loss can be reduced and combustion efficiency can be improved.

Further, by forming the cavity 25 in a spherical shape, there is an advantage that a vortex flow, that is, a tumble flow due to the intake flow is easily formed in the combustion chamber 3. Further, as shown in FIG. 1, the above-described virtual spherical surface 25a is
Is set so that the apex of the piston 2 and the lower end of the intake valve-side inclined upper surface 2 a of the piston 2 are included in the cavity 25.

Further, when the piston 2 reaches the top dead center position, the injector 1, the intake valve 4 and the virtual valve are arranged such that the injection port of the injector 1 and the valve element of the intake valve 4 are respectively positioned within the virtual spherical surface 25a. The positional relationship of the spherical surface 25a is set. And, as described above, the injector 1 and the intake valve 4
By arranging the cavities, it is ensured that the cavities 25
The fuel concentration in the inside is in a high state.

In such a direct injection type internal combustion engine, the fuel injection timing and the fuel injection amount of the injector 1 are controlled by a controller (not shown) according to the operating condition of the engine. In some situations, fuel injection is performed during the compression stroke. in this case,
In the combustion chamber 3, the air-fuel mixture is formed in a layered form of air and fuel, and the fuel (shaded portion in FIG. 1) exists in the cavity 25 in a relatively large amount. Therefore, unlike a normal internal combustion engine in which a substantially uniform air-fuel mixture exists in the combustion chamber, in a normal spark plug for an internal combustion engine, the electrode does not reach a position where a sufficient concentration of a combustible air-fuel mixture exists, and combustion occurs. It is conceivable that the efficiency is reduced.

Therefore, in the in-cylinder injection type internal combustion engine of the present invention, the position of the ignition plug 6 and the length of the electrode 6a are set so as to be optimal for fuel combustion in order to reliably burn the fuel. I have. That is, when the piston 2 rises to the top dead center position, the center of the ignition plug 6 is so positioned that the electrode 6a of the ignition plug 6 is securely positioned on the cavity 25 side while avoiding interference between the piston 2 and the ignition plug 6. The ignition plug 6 is disposed with the shaft inclined at a predetermined angle θ toward the exhaust valve 5 with respect to the cylinder center axis CL.

The cylinder head 8 is provided with a spark plug mounting portion 28 for mounting the spark plug 6.
A spark plug mounting surface 27 for regulating the mounting position of the spark plug 6 is formed in the spark plug mounting portion 28, and this mounting surface 27 is also a predetermined amount D with respect to a conventional internal combustion engine.
1 (for example, D1 = 2 mm) is provided closer to the combustion chamber 3 side.

Thus, the ignition plug 6 is attached to the cylinder head 8 so as to approach the cavity 25 side. In this case, the screw portion below the ignition plug 6 is exposed to the inside of the combustion chamber 3 by a predetermined amount D1, and when the engine is operated in such a state, carbon or the like adheres to the lower portion of the ignition plug 6. Resulting in. Then, when carbon or the like adheres to the screw portion below the ignition plug 6, the ignition plug 6 is moved to the cylinder head 8.
It is conceivable that it becomes difficult to remove from the device, and the workability is reduced.

Therefore, in this in-cylinder injection type internal combustion engine, as shown in FIG. 1, a thickened portion 29 is formed around the lower portion of the spark plug mounting portion 28 to protect the lower portion of the spark plug 6. . This prevents carbon or the like from adhering to the lower portion of the ignition plug 6, thereby improving the workability when replacing the ignition plug 6 and the durability of the ignition plug 6.
Further, by providing such an overlaid portion 29, the heat applied to the ignition plug 6 can be released to the cylinder head 8 via the overlaid portion 29, so that the durability of the ignition plug 6 against heat is improved. It has become.

Further, the length of the electrode 6a of the ignition plug 6 is formed to be longer than that of a normal ignition plug by a predetermined amount, so that the electrode 6a is located at a portion where the fuel concentration is high when the fuel is ignited. It becomes. The mounting surface 27 of the ignition plug 6 is formed at the same position as that of the conventional internal combustion engine, and only the electrode 6a of the ignition plug 6 is formed to be longer by a predetermined amount D1 by that amount. It is also conceivable to provide a structure in which the light-emitting element is disposed in a portion having a high density. That is, the fuel is reliably ignited only by the configuration in which only the electrode 6a is extremely long. In this case, the above-mentioned overlaid portion 29 becomes unnecessary, but if only the length of the electrode 6a is formed extremely long in this way, the durability of the electrode 6a may be reduced.

On the other hand, in the present invention, the ignition plug 6
Of the electrode 6 near the combustion chamber 3 side.
Since the ignition portion is brought closer to the inside of the cavity 25 in a two-stage configuration in which the length of a is formed long, while ensuring that the electrode 6a is located in the portion where the fuel concentration is high in the cavity 25, There is an advantage that the durability of the spark plug 6 is not impaired. As a result, the fuel can be reliably ignited, and the combustion efficiency can be improved.

The value of the gap (indicated by D2 in FIG. 1) between the discharge electrode 6a of the spark plug 6 and the surface of the cavity 25 also affects the engine output and fuel efficiency. Must be set. That is, if the gap D2 is too large, the electrode 6a of the ignition plug 6 will not sufficiently reach the fuel riding on the intake tumble flow formed in the combustion chamber 3, and the combustion efficiency will deteriorate. If the discharge electrode 6a is too close to the surface of the cavity 25, the electrode 6a may interfere with the piston 2.

Therefore, in the in-cylinder injection type internal combustion engine, the distance D2 between the discharge electrode 6a and the surface of the cavity 25 at the top dead center position of the piston 2 is set to an optimum value (for example, D2 = 1 to 1).
(About 2 mm) so that high combustion efficiency can be obtained while avoiding interference with the piston 2 sufficiently. Further, in such a direct injection internal combustion engine, the interval between the adjacent portions of the piston 2 and the exhaust valve 4 (this is called an exhaust-side gap and is indicated by D3 in FIG. 1) greatly affects the performance of the engine. For example, as shown at points C and D in the graph of FIG.
If the exhaust-side gap D3 is too large, the fuel sprayed from the injector 1 during the compression stroke will be diffused outside the cavity 25, and fuel efficiency will be deteriorated.

On the other hand, as shown at points A and B, when the exhaust-side gap D3 is too small, the flame in the space on the exhaust valve 5 side during the full-open operation (ie, during fuel injection during the intake stroke) is sufficient. It is not propagated and the output drops. Therefore, in the in-cylinder injection type internal combustion engine of the present invention, the exhaust-side gap D3 is set to an optimum value such that the fuel consumption and the output can be balanced and efficient combustion can be realized (in the vicinity of the symbol ☆ in FIG. 8, D3). = 5-8 mm).

As described above, by forming the cavity 25 in a spherical shape and arranging the cavity 25 and the spark plug 6 so that the positional relationship between the cavity 25 and the spark plug 6 becomes optimal, the fuel injected toward the cavity 25 is ignited during ignition. Cavity 2
5 to promote stratification of the intake air and the fuel, and moreover, reliable ignition and combustion are performed.

As shown in FIGS. 1 and 3, between the exhaust valve-side inclined upper surface 2 b of the piston 2 and the exhaust valve-side lower surface 8 b of the cylinder head 8, the ignited flame enters the combustion chamber 3. A flame penetration space 26 is formed so as to spread uniformly. Here, the exhaust valve side inclined upper surface 2b is connected to the exhaust valve side lower surface 8
is set to a smaller inclination angle than b.
As shown in FIG. 3, the above-described flame infiltration space 26 is formed in a shape in which the distance between the surfaces 2 b and 8 b increases toward the center of the combustion chamber 3, that is, a space having a substantially wedge-shaped cross section. ing.

The substantially wedge-shaped flame penetration space 26 is formed on the exhaust valve 4 side of the combustion chamber 3 for the following reason. That is, in the combustion chamber 3 of the in-cylinder injection type internal combustion engine in which the cavity 25 is formed as described above, the exhaust valve side inclined upper surface 2b and the exhaust valve side lower surface 8b are usually formed so as to be substantially parallel to each other. Since the space formed by these surfaces 2b and 8b is formed narrow, the propagation of the flame into this space after fuel ignition tends to be delayed. In order to make the flame propagation in the combustion chamber 3 uniform, it is conceivable to simply widen the space between the exhaust-valve-side inclined upper surface 2b and the exhaust-valve-side lower surface 8b. 4 (V in FIG. 4)
An optimum volume ratio exists between the (a + Vb + Vc portion) and the volume of the cavity 25 and its upper space (Va + Vb).

Therefore, if the space of the combustion chamber 3 on the side of the exhaust valve 5 is simply widened, it becomes difficult to set the volume ratio of the cavity 25 to an optimum value, and the performance of the engine is rather deteriorated. It is also possible. Therefore, as described above, a substantially wedge-shaped flame infiltration space 26 is formed in the space on the exhaust valve 5 side of the combustion chamber 3 in which the gap on the center side is made large and the gap on the end portion on the exhaust valve 5 side is reduced accordingly. -ing

According to the flame infiltration space 26, first, the flame which has started burning around the vicinity of the electrode 6 a of the ignition plug 6 has a relatively wide gap in the space on the exhaust valve 5 side of the combustion chamber 3. The flame surely spreads to the center side of the combustion chamber 3 and the flame propagates to the end portion of the combustion chamber 3 with a relatively small gap without delay with respect to the other parts of the combustion chamber 3 and uniform combustion without unevenness Can be realized.

Further, by forming the cross section of the space on the exhaust valve 5 side of the combustion chamber 3 into a substantially wedge shape, the volume of the space on the exhaust valve 5 side of the combustion chamber 3 is not changed, and the cavity ratio is not changed. It also has the advantage of not affecting the settings at all.
As the first embodiment of the present invention, the in-cylinder injection type internal combustion engine is configured as described above, so that the following effects can be obtained.

First, a spherical cavity 25 is formed on the intake valve-side inclined upper surface 2a of the piston 2 as shown in FIGS. There is an advantage that fuel economy can be improved. That is, by forming the shape of the cavity 25 into a spherical shape, the cavity surface area with respect to the cavity volume Va of the piston 2 can be minimized. Thereby, heat loss can be reduced, and combustion efficiency can be improved.

Also, by forming the cavity 25 in a spherical shape, the formation of a vortex flow, that is, a tumble flow by the intake air flow in the combustion chamber 3 is promoted, and there is an advantage that stratified combustion is easily performed. Furthermore, the inclined lower surfaces 8a, 8b of the combustion chamber 3
Is formed substantially flat, the formation of the tumble flow is strengthened. FIG. 9 shows such a spherical cavity 2.
5 is a graph showing a comparison between the piston 2 having the cavity 5 and the piston 2 having the cavity of another shape, and shows the fuel consumption and the maximum torque of the cavity having a cross section of another shape (points A,
In contrast to the point B), the piston 2 having the spherical cavity 25 can improve both the fuel consumption and the maximum torque as shown in the point C.

Also, such a spherical cavity 25
In addition to the two pairs of pistons having the above, a flame entry space 26 in which the cross-sectional shape of the combustion chamber 3 on the side of the exhaust valve 5 is formed in a substantially wedge shape.
Is advantageous in that the maximum torque is further improved as shown at point D. Further, as shown in FIG. 10, by providing such a substantially wedge-shaped flame infiltration space 26, the fuel consumption rate can be reduced substantially over the entire area, and the THC (total hydrocarbon amount) emission amount is reduced. Also has the advantage that it can be reduced.

In the in-cylinder injection type internal combustion engine, the mounting surface 27 of the ignition plug 6 is fixed at a predetermined amount D1 (for example, D1 = 2 m).
m) closer to the combustion chamber 3 side and the spark plug 6
Is formed in a two-stage configuration in which the discharge electrode 6a is formed to be longer than the conventional discharge electrode by a predetermined amount, and the ignition portion of the electrode 6a is located in the portion where the fuel concentration is high in the cavity 25. There is an advantage that the durability of the electrode 6a of the ignition plug 6 is not impaired while enabling ignition.

Further, such an ignition plug 6 has an advantage that it can be realized at a low cost because it is only necessary to form the electrode 6a longer by a predetermined amount than the conventional ignition plug. In addition, on the formation surface of the combustion chamber 3 of the cylinder head 8, the build-up portion 2 is provided around the mounting portion 28 of the ignition plug 6.
9, even if the lower end of the ignition plug 6 moves toward the combustion chamber 3 by a predetermined amount D1, the lower end of the ignition plug 6 is not directly exposed to the combustion chamber 3.

Accordingly, adhesion of carbon or the like to the screw portion below the ignition plug 6 is prevented, and workability such as replacement of the ignition plug 6 is improved. Also, the lower part of the ignition plug 6
Since it is protected by the overlay portion 29, there is an advantage that the durability of the spark plug 6 itself is also improved. Furthermore, since the heat applied to the ignition plug 6 can be released to the cylinder head 8 via the overlay portion 29, there is an advantage that the durability against heat is improved.

On the other hand, the cavity 25 of the piston 2 is divided into the top of the piston 2 and the upper surface 2a of the piston 2 on the intake valve side.
Is formed so as to be included in the imaginary spherical surface 25a, so that the ignition plug 6 can be easily arranged in the cavity 25. There is also an advantage that generation of a tumble flow can be promoted. Further, when the piston 2 reaches the top dead center position, the positions of the injector 1, the intake valve 4 and the virtual spherical surface 25a are set so that the injection port of the injector 1 and the valve element of the intake valve 4 are respectively positioned within the virtual spherical surface 25a. Since the relationship is set, an air-fuel mixture with a high fuel concentration can be generated in the cavity 25.

When the volume Va of the cavity 25 and the piston 2 are at the top dead center position, the intake valve side inclined lower surface 8a
Vb between the fuel cell and the intake valve side inclined upper surface 2a and the combustion chamber 3
The volume ratio with the total volume Va + Vb + Vc is an optimal value,
For example, (Va + Vb) / (Va + Vb + Vc) = 0.
Since it is set to be a value between 4 and 0.6,
There is an advantage that the improvement in fuel efficiency and the improvement in output can be achieved in a well-balanced manner.

That is, as shown in FIGS. 5A and 5B, when the cavity volume ratio is too large, the maximum torque and the maximum output decrease, and when the cavity volume ratio is too small, the fuel consumption decreases. However, as described above, by setting the cavity volume ratio to an optimum value, it is possible to achieve both improvement in fuel efficiency and improvement in output.

Further, as shown by a mark in the graph of FIG. 8, by setting the exhaust-side gap D3 to an optimum value (D3 = 5 to 8 mm), a combustion state with high thermal efficiency can be realized. Again, there is an advantage that the maximum output can be improved. Also, the discharge electrode 6 of the ignition plug 6
By setting the gap D2 between a and the surface of the cavity 25 to an optimum value (for example, D2 = 1 to 2 mm), it is possible to obtain high combustion efficiency while sufficiently avoiding interference of the ignition plug 6 with the piston 2. have.

Further, by forming the lower surface of the cylinder head 8 in a pent roof shape, a strong vertical vortex can be maintained even during the compression stroke, and the fuel injection can be stably performed during the compression stroke. is there. Further, since the intake valve-side inclined upper surface 2a and the exhaust valve-side inclined upper surface 2b are defined by the ridge line of the piston top surface, the shapes of the combustion chambers 3 are the intake valve-side inclined lower surface 8a and the exhaust valve-side inclined lower surface. 8b can have different shapes, and the role of the combustion chamber 3 can be shared between the intake valve 4 side and the exhaust valve 5 side.

Next, first to third modifications of the direct injection internal combustion engine as the first embodiment will be described.
FIGS. 6, 7, and 23 to 30 are views showing a first modification thereof, and are different from the first embodiment only in the shape of the concave portion 25. That is, in the first modified example, the shape of the concave portion 25 is different from that shown in FIGS.
As shown in (a) to (c), the cavities 25A and 25B have a substantially rectangular cross section.

The piston 2 having the cavities 25A and 25B will be briefly described. A flat portion 41 perpendicular to the direction of movement of the piston 2 is formed at the outer peripheral end 40 of the piston on the intake valve 4 side. Have been. Also,
In the cavities 25A and 25B, the intake air flow is
5A, 25B, and the cavity 2
A raised portion 43 for guiding the intake air flow flowing into the inside of 5A, 25B toward the vicinity of the spark plug 6 and a connecting portion 44 connecting the inflow portion 42 and the raised portion 43 and formed on a substantially flat surface. Have been.

As a result, the intake air flows in through the inflow portion 42 that is gently formed between the flat portion 41 and the bottom surface (connection portion) 44 of the cavities 25A and 25B. To the vicinity of the spark plug 6, thereby forming a tumble flow. Therefore, such cavities 25A,
Even a direct injection internal combustion engine having 25B has the advantage of being superior in fuel efficiency and output over a conventional direct injection internal combustion engine.

FIGS. 31 to 38 are views showing a second modification of the in-cylinder injection type internal combustion engine according to the first embodiment. The only difference is that a recess for securing a space near the plug is formed adjacent to the cavity 25 of the piston. Also, FIGS.
FIG. 5 is a view showing a third modification of the direct injection internal combustion engine as the first embodiment, in which a clearance between the piston and the exhaust valve is ensured on the exhaust valve-side inclined upper surface 2b of the piston 2; The recess is formed separately from the cavity 25.

In the direct injection type internal combustion engine having the pistons constructed as in the second and third modified examples, similarly to the first modified example described above, the conventional in-cylinder injection type internal combustion engine is used. It has an advantage over an injection type internal combustion engine in terms of fuel efficiency and output. Next, a cylinder injection type internal combustion engine as a second embodiment of the present invention will be described.
7 to 54 are schematic views showing pistons as main parts thereof. Note that, in the second embodiment, only the shape of the concave portion of the piston 2 is formed differently from the first embodiment, and other configurations are common to the above-described first embodiment.

As shown in FIGS. 11 (a) to 11 (c), a cavity 25C bent downward and convex is formed on the top surface of the piston 2 on the side of the intake valve 4. This cavity 25C
As shown in FIG. 11C, two virtual spheres 25b and 25c whose centers are adjacent to each other are provided on the upper part on the intake valve 4 side.
A connection surface 25d for smoothly connecting between these two spherical surfaces 25b and 25c is formed.

As shown in FIG. 11 (a), the centers of these virtual spherical surfaces 25b and 25c are offset by the same distance from each other with respect to the axis perpendicular to the direction in which the piston pins 30 are provided. Set to position. The connection surface 25d is formed of two spherical surfaces 25b, 2b.
5c is formed as a cylindrical surface connecting the lower portions. Therefore, the sectional shape of the combustion chamber 3 is substantially the same as that of the first embodiment.

According to such a cavity 25C, the cavity volume of the piston 2 can be increased, and the cavity surface area with respect to the cavity volume can be formed relatively small. Therefore,
It is possible to improve the fuel efficiency with almost no decrease in the fuel loss, that is, with almost no decrease in the output characteristics.

Further, since the shape of the cavity 25C is formed to be substantially spherical, there is an advantage that the formation of a vortex flow, that is, a tumble flow by the intake air flow in the combustion chamber 3 is promoted. The in-cylinder injection type internal combustion engine according to the second embodiment of the present invention is configured as described above.
The intake air flow that has flowed into the combustion chamber 3 through the air passage is guided to a cavity 25C formed in the piston 2 to form a tumble flow, and a stratified mixture is formed by injecting fuel into the tumble flow. Is done.

Here, the two virtual spheres 25b and 25c forming the cavity 25C are connected to the piston pins 30.
Are formed along the disposition direction, so that they are formed as spherical cavities in the direction in which the intake air flows, that is, in the direction in which the tumble flow is formed [FIG. 11 (b)].
reference〕. Therefore, stratified combustion can be performed as in the first embodiment.

Further, in the above-described cavity 25C, the cavity surface area can be formed relatively small while increasing the cavity volume of the piston 2, so that fuel efficiency can be improved without substantially lowering output characteristics. There is an advantage. Note that the connection surface 25d is not limited to a cylindrical surface, but may be 2
As long as the two spherical surfaces 25b and 25c can be smoothly connected, the surfaces may have other shapes.

Next, an in-cylinder injection type internal combustion engine according to a third embodiment of the present invention will be described. FIG. 12 is a schematic sectional view showing the configuration of a combustion chamber. In the present embodiment, as shown in FIG. 12, the configuration is basically the same as in the first embodiment. That is, the upper surface of the combustion chamber 3 is formed in a pent roof shape by the lower surface of the cylinder head 8, and the top surface of the piston 2 is also formed in a mountain shape corresponding to the pent roof shape of the cylinder head 8. The piston 2 is provided with a cavity 25 formed in a spherical shape.

The injection hole of the injector 1 is
The fuel is directly injected into the combustion chamber 3. Also, the injector 1
For example, it is controlled by a controller (not shown) so that an appropriate amount of fuel is injected from the injector 1 at an appropriate timing. Then, the fuel is injected toward the cavity 25 of the piston 2, and the air and the fuel mixed in the combustion chamber 3 are mixed with air sucked from an intake port 9 provided substantially upright above the intake valve 4. Thus, an air-fuel mixture is generated. Thereafter, the air-fuel mixture is ignited by the ignition plug 6 in the combustion chamber 3, expands (explodes), and is discharged from the exhaust port 10. In the drawings, reference numeral 7 denotes a cylinder block, and reference numeral 8 denotes a cylinder head.

On the other hand, in the third embodiment, the values for setting the mounting position of the spark plug 6, the amount of protrusion, the setting of the cavity volume ratio, and the like are not strictly defined, and this point is different from the first embodiment. Is different. Therefore, there is an advantage that dimensional management at the time of assembling the engine or manufacturing the parts can be made easier than in the first and second embodiments. That is, since the shape of the combustion chamber 3 is not strictly defined, it is easy to manage the dimensions of the components that make up the engine, especially the components related to the shape of the combustion chamber, and also to easily manage the assembling accuracy during engine assembly. .

By the way, even if the shape of the combustion chamber 3 is not strictly defined as described above, the concave portion 25 of the piston 2 is made spherical and the top surface of the piston 2 is made pent roof type. It has the following functions and effects. That is, when the intake air flow is introduced into the combustion chamber 3 through the intake port 9 extending substantially upright above the intake valve 4, the intake air flows toward the lower piston 2 and then into a spherical shape. The tumble flow (longitudinal vortex) is formed by being guided upward along the cavity 25. Then, by injecting fuel into the tumble flow, a stratified mixture is formed.

Further, by forming the top surface of the piston 2 in a mountain shape substantially following the pent roof shape of the cylinder head 8, the space surrounded and bent by the piston 2 and the cylinder head 8 when the piston 2 rises. Can be reduced. As a result, the compression ratio of the engine can be increased, and the engine output can be greatly improved.

Therefore, it is possible to reduce the manufacturing cost while realizing the contradictory elements of low fuel consumption and high output at a high level. Next, a description will be given of a direct injection internal combustion engine as a fourth embodiment of the present invention.
FIG. 13 is a schematic sectional view showing the shape of a combustion chamber as a main part thereof, and FIG. 14 is a schematic plan view showing a piston as a main part thereof.

In the fourth embodiment, the combustion chamber 3 is configured in substantially the same manner as in the first embodiment described above, and only the following configuration is different. That is, in the fourth embodiment, as shown in FIG. 13, the gap between the top surface of the piston 2 and the lower surface of the cylinder head 8 is different between the intake valve 4 side and the exhaust valve 5 side. The gap a on the valve 4 side is set to be larger than the gap b on the exhaust valve 5 side.

The difference between the gap a and the gap b is not so large, and does not significantly affect the volume ratio described in the first embodiment. That is, the volume of the cavity 25 is Va, the volume between the intake valve side inclined lower surface 8a and the intake valve side inclined upper surface 2a when the piston 2 is at the top dead center position is Vb, and the piston 2 is at the top dead center position. Assuming that the volume between the exhaust valve side inclined lower surface 2b and the exhaust valve side inclined upper surface 2b at a given time is Vc, (Va + Vb) / (Va + V
The value of (b + Vc) is 0.4 to 0.4 as in the first embodiment.
It is set to be between 0.6.

The shape of the cavity 25 is also spherical. This is because, as described in the first embodiment, by forming the cavity 25 in a spherical shape, the cavity surface area with respect to the cavity volume Va of the piston 2 can be minimized. By minimizing the cavity surface area, heat loss can be reduced and combustion efficiency can be improved.

Now, the reason why the gap a on the intake valve 4 side is set larger than the gap b on the exhaust valve 5 side will be described. That is, as described in detail in the first embodiment, as the surface area of the combustion chamber 3 decreases, the heat loss decreases and the combustion efficiency can be improved. Therefore, the volume and the compression ratio of the combustion chamber 3 are changed. Without reducing the surface area of the combustion chamber 3.

However, as described above, in the direct injection type internal combustion engine, the output characteristics and fuel efficiency of the engine are greatly increased depending on the shapes and volumes of the piston 2 and the combustion chamber 3 and the arrangement position of the ignition plug 6. If the shape of the combustion chamber of the first embodiment is largely changed, there is a possibility that the balance between the output characteristics and the fuel consumption performance may be lost. Therefore, in order to reduce the surface area without substantially changing the shape of the combustion chamber 3 as described in the first embodiment, the upper surface 2a of the piston 2 on the intake valve side is compared with that described in the first embodiment. The exhaust valve-side inclined upper surface 2b is configured to be slightly closer to the exhaust valve 5 than that described in the first embodiment. That is, the relationship a> b is established between the intake valve gap a and the exhaust valve side gap b in the combustion chamber 3.

According to such a configuration, the surface area of the upper surface 2b on the exhaust valve side of the piston 2 hardly changes, but the surface area of the upper surface 2a on the intake valve side increases at a larger rate than the change in the surface area of the upper surface 2b on the exhaust valve side. Will decrease. This is because most of the cavity 25 is provided on the intake valve side of the piston 2 as shown in FIG. This is because the surface area of the cavity 25 (particularly, the surface area in the vertical direction with respect to the intake valve side upper surface 2a) also decreases. In other words, between the intake valve side upper surface 2a and the exhaust valve side upper surface 2b, the surface area that changes when the surfaces are moved in the up-down direction is larger in the intake valve side upper surface 2a.

Further, of the surface area of the upper surface 2a of the piston 2 on the intake valve side, the area facing the lower surface of the cylinder head (FIG. 1)
4 reference area S ₁₎ of the cylinder in the area opposed to (see the area S ₂ of FIG. 14) in the head lower surface, an amount corresponding intake valve side upper surface 2a in the presence of the cavity 25 of the surface area of the exhaust valve-side top surface 2b In order to change the intake valve gap a and the exhaust valve side gap b while securing the same compression ratio as that of the first embodiment, the intake valve 4 on the intake valve side upper surface 2a needs to be changed. It is necessary to make the distance to be larger than the distance to bring the exhaust valve side inclined upper surface 2b closer to the exhaust valve 5. Therefore, even with such a configuration, the amount of decrease in the total surface area of the intake valve side upper surface 2a is further larger than the increase in surface area of the exhaust valve side upper surface 2b. In order to secure a compression ratio equivalent to that of the first embodiment with such a configuration, the amount of moving the intake valve side upper surface 2a away from the intake valve 4 is the amount of bringing the exhaust valve side upper surface 2b closer to the exhaust valve 5. About 2
About double.

In this way, by setting the intake valve gap a to be larger than the exhaust valve side gap b, the surface area of the combustion chamber 3 can be further reduced, and the heat loss can be reduced. Thus, the combustion efficiency can be improved. Note that the two-dot chain line in FIGS. 13 and 14 is the top surface shape of the piston 2 corresponding to the first embodiment.

Since the in-cylinder injection type internal combustion engine according to the fourth embodiment of the present invention is configured as described above, it has the same functions and effects as those of the first embodiment, and also has the following functions. , Has an effect. That is, by setting the intake valve gap a to be larger than the exhaust valve side gap b, the surface area of the combustion chamber 3 can be further reduced, the heat loss can be reduced, and the combustion efficiency can be improved. You can do it. Note that, with such a configuration, in the fourth embodiment, for example, the fuel efficiency is increased by about 2% with respect to the fuel efficiency of the first embodiment.

The shape of the piston 2, that is, the shape of the combustion chamber 3 in which a> b between the intake valve gap a and the exhaust valve side gap b is applied to the second embodiment. You may. In the case where the second embodiment is configured as described above, the surface area of the combustion chamber 3 can be reduced as described above, and the heat loss can be reduced. This has the advantage that the combustion efficiency can be improved.

In this case, since the area of the intake valve side upper surface 2a facing the cylinder head lower surface is smaller than that of the first embodiment, the amount of moving the intake valve side upper surface 2a away from the intake valve 4 must be reduced. , Can be made larger than the piston 2 of the first embodiment, and the effect of reducing the heat loss becomes more remarkable.

[0088]

As described above in detail, according to the in-cylinder injection type internal combustion engine of the first aspect of the present invention, the combustion chamber divided up and down by the lower surface of the cylinder head and the top surface of the piston;
An intake valve disposed on one side of the upper surface of the combustion chamber, an exhaust valve disposed on the other side of the upper surface of the combustion chamber, and a fuel disposed to inject fuel directly into the combustion chamber In a direct injection type internal combustion engine having an injection valve, a lower surface of the cylinder head forming an upper surface of the combustion chamber is formed on an intake valve side inclined lower surface formed on one side and an exhaust gas formed on the other side. A pentroof shape formed of a valve-side inclined lower surface, a spark plug is disposed near the top of the upper surface of the pentroof-shaped combustion chamber upper surface, and the piston top surface forming the lower surface of the combustion chamber is provided with the intake air. The piston is formed in a mountain shape substantially along the pent roof shape having an intake valve side inclined upper surface and an exhaust valve side inclined upper surface formed so as to correspond to the valve side inclined lower surface and the exhaust valve side inclined lower surface, respectively. Top surface of intake valve side inclined top surface A recess is provided, and of the volume of the combustion chamber when the piston is at the top dead center position, the volume in the recess and the volume between the upper surface of the piston above the recess and the lower surface of the cylinder head; Is set between 0.4 and 0.6 with respect to the total volume of the combustion chamber when it is at the top dead center position, the concave volume with respect to the total volume is suitable for performing stratified combustion. It can be set, and the increase in the surface area of the combustion chamber can be avoided as much as possible. As a result, the fuel efficiency is improved, the maximum output and the maximum torque are improved by avoiding an increase in heat loss, and the advantage that the engine output performance and the fuel efficiency performance of the direct injection internal combustion engine can be achieved at the same time. is there.

According to the cylinder injection type internal combustion engine of the present invention described in claim 2, in addition to the structure of claim 1,
A flat portion is formed at least on the outer peripheral end on one side of the piston top surface, and the concave portion is formed to be gentler than the flat portion and the inflow when the intake air introduced into the combustion chamber flows into the concave portion. And a connection portion connecting the inflow portion and the raised portion, and a gently raised portion for guiding the intake air flowing into the concave portion toward the vicinity of the ignition plug. There is an advantage that a longitudinal vortex (tumble flow) can be reliably formed in the combustion chamber.

According to a third aspect of the present invention, there is provided a cylinder injection type internal combustion engine,
The configuration in which the intake valve-side inclined lower surface and the exhaust valve-side inclined lower surface forming the upper surface of the combustion chamber are formed substantially flat, respectively, facilitates the formation of a vertical vortex generated in the combustion chamber. This has the advantage that the longitudinal vortex can be enhanced. Thereby, there is an advantage that more stable stratified combustion can be performed.

Further, according to the in-cylinder injection type internal combustion engine of the present invention described in claim 4, in addition to the configuration described in claim 1,
The exhaust valve-side inclined upper surface of the piston is set to a smaller inclination angle than the exhaust valve-side lower surface of the cylinder head, and the exhaust valve-side inclined lower surface of the cylinder head and the exhaust valve-side inclined upper surface of the piston. Is formed so as to increase the mutual distance toward the center side of the combustion chamber, and at the top dead center position of the piston, a flame entry space having a substantially wedge-shaped cross section is formed. There is an advantage that the flame can be evenly propagated, and uniform combustion can be realized. Further, there is an advantage that the volume of the space on the exhaust valve side of the combustion chamber is not changed, and the setting of the volume ratio of the concave portion is not affected at all.

Further, according to the in-cylinder injection type internal combustion engine of the present invention described in claim 5, in addition to the structure of claim 1 described above,
When the piston is at the top dead center, the distance between the piston and the exhaust valve is close to the distance between the piston and the intake valve. Since the surface area of the combustion chamber can be reduced without substantially changing the volume ratio of the entire combustion chamber, heat loss is reduced. This improves combustion efficiency,
There is an advantage that high output and high fuel efficiency can be achieved at a high level.

Further, according to the in-cylinder injection type internal combustion engine of the present invention described in claim 6, in addition to the configuration described in claim 1,
With the configuration in which the concave portion is formed by a spherical surface, the surface area of the concave portion with respect to the volume of the concave portion of the piston can be minimized. This also has the advantage that heat loss can be reduced and combustion efficiency can be improved. Further, by forming the concave portion in a spherical shape, the formation of a vortex flow, that is, a tumble flow by the intake air flow in the combustion chamber is promoted, and there is an advantage that stratified combustion is easily performed.

Further, according to the in-cylinder injection type internal combustion engine of the present invention described in claim 7, in addition to the structure of claim 6,
The recess is formed as a part of an imaginary sphere having a center on the intake valve side upper portion of the piston, and the apex of the piston and the lower end of the intake valve side inclined upper surface of the piston are included in the imaginary spherical surface. With the configuration, there is an advantage that the spark plug can be easily arranged in the recess. There is also an advantage that generation of a tumble flow can be promoted.

According to the in-cylinder injection type internal combustion engine of the present invention described in claim 8, in addition to the configuration described in claim 6,
When the piston is at the top dead center position, the injection port of the fuel injection valve and the valve body of the intake valve are respectively included in the virtual spherical surface, and the ignition point of the discharge electrode of the ignition plug is in the concave portion. By being included, there is an advantage that a mixture with a high fuel concentration can be generated in the recess. This has the advantage that the combustion efficiency can be increased.

Further, according to the in-cylinder injection type internal combustion engine of the present invention described in claim 9, in addition to the structure of claim 1,
A ridgeline is formed on the piston top surface to partition the intake valve-side inclined upper surface and the exhaust valve-side inclined upper surface, and the concave portion exceeds the ridgeline and extends from the intake valve-side inclined upper surface to the exhaust valve-side inclined upper surface. With the configuration that extends to
It is easy to optimally set the ratio between the volume of the concave portion in the combustion chamber and the volume of the entire combustion chamber, and there is an advantage that both high fuel efficiency and high output can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a combustion chamber in a direct injection internal combustion engine as a first embodiment of the present invention.

FIGS. 2A and 2B are schematic views showing the shape of a piston as a main part in a direct injection internal combustion engine as a first embodiment of the present invention, wherein FIG. 2A is a top view and FIG. ,
(C) is an A1-A1 sectional view in (b).

FIG. 3 is a diagram showing a relative positional relationship between a top surface of a piston and a lower surface of a cylinder head in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining a ratio of a total volume of a combustion chamber to a volume of a concave portion of a piston in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 5 is a graph for explaining a change in the characteristic of the direct injection internal combustion engine according to the first embodiment of the present invention in accordance with a change in the volume ratio of the concave shape of the piston in the internal combustion engine.

FIG. 6 is a schematic diagram of a piston for illustrating another example of the concave shape of the piston in the direct injection internal combustion engine as the first embodiment of the present invention, wherein (a) is a top view thereof;
(B) is the front view, (c) is A3-A in (b).
It is three sectional drawing.

FIG. 7 is a schematic diagram of a piston for illustrating another example of the concave shape of the piston in the direct injection internal combustion engine as the first embodiment of the present invention, wherein (a) is a top view thereof;
(B) is the front view, (c) is A4-A in (b).
It is four sectional drawing.

FIG. 8 is a graph for explaining the operation of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 9 is a graph for explaining an operation in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 10 is a graph showing a change characteristic of fuel consumption and HC emission due to a difference in shape of a combustion chamber in the direct injection internal combustion engine as the first embodiment of the present invention.

11A and 11B are schematic views showing the shape of a piston as a main part in a direct injection internal combustion engine according to a second embodiment of the present invention, wherein FIG. 11A is a top view thereof, and FIG. 11B is a front view thereof. And (c) are A2-A2 sectional views in (b).

FIG. 12 is a schematic sectional view showing a configuration of a combustion chamber in a direct injection internal combustion engine as a third embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view showing a configuration of a combustion chamber in a direct injection internal combustion engine as a fourth embodiment of the present invention.

FIG. 14 is a schematic plan view showing the shape of a piston in a direct injection internal combustion engine as a fourth embodiment of the present invention.

FIG. 15 is a plan view showing a piston shape in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 16 is a front view showing a piston shape in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 17 is a bottom view showing a piston shape in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 18 is a left side view showing a piston shape in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 19 is a right side view showing a piston shape in the direct injection internal combustion engine as the first embodiment of the present invention.

20 is a rear view showing a piston shape in the direct injection internal combustion engine as the first embodiment of the present invention, which is a view symmetrical to the front view shown in FIG. 16;

21 is a cross-sectional view showing a piston shape in the in-cylinder injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along line AA in a right side view shown in FIG. 19;

FIG. 22 is a cross-sectional view showing a piston shape in the in-cylinder injection internal combustion engine as the first embodiment of the present invention, and is a BB cross-sectional view in the front view shown in FIG.

FIG. 23 is a plan view showing a piston shape of a first modified example of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 24 is a front view showing a piston shape of a first modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 25 is a bottom view showing a piston shape of a first modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 26 is a left side view showing a piston shape of a first modified example of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 27 is a right side view showing a piston shape of a first modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 28 is a rear view showing a piston shape of a first modification of the direct injection internal combustion engine as the first embodiment of the present invention, and the rear view appears symmetrically with the front view shown in FIG. 24; FIG.

29 is a cross-sectional view showing a piston shape of a first modification of the direct injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along line AA in a right side view shown in FIG. 27. is there.

30 is a cross-sectional view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along line BB in the front view shown in FIG. 24. .

FIG. 31 is a plan view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 32 is a front view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 33 is a bottom view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 34 is a left side view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 35 is a right side view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention.

36 is a rear view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention, and the rear view appears symmetrically with the front view shown in FIG. 32. FIG.

FIG. 37 is a cross-sectional view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along line AA in a right side view shown in FIG. 35. is there.

FIG. 38 is a cross-sectional view showing a piston shape of a second modification of the direct injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along line BB in the front view shown in FIG. 32; .

FIG. 39 is a plan view showing a piston shape of a third modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 40 is a front view showing a piston shape of a third modified example in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 41 is a bottom view showing a piston shape of a third modified example of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 42 is a left side view showing a piston shape of a third modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 43 is a right side view showing a piston shape of a third modification of the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 44 is a rear view showing a piston shape of a third modification of the direct injection internal combustion engine as the first embodiment of the present invention, and the rear view appears symmetrically with the front view shown in FIG. 40; FIG.

45 is a cross-sectional view showing a piston shape of a third modification of the direct injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along line AA in a right side view shown in FIG. 43. is there.

46 is a cross-sectional view showing a piston shape of a third modification of the direct injection internal combustion engine as the first embodiment of the present invention, and is a cross-sectional view taken along the line BB in the front view shown in FIG. 40. .

FIG. 47 is a plan view showing a piston shape in a direct injection internal combustion engine as a second embodiment of the present invention.

FIG. 48 is a front view showing a piston shape in a direct injection internal combustion engine as a second embodiment of the present invention.

FIG. 49 is a bottom view showing a piston shape in a direct injection internal combustion engine as a second embodiment of the present invention.

FIG. 50 is a left side view showing a piston shape in a direct injection internal combustion engine as a second embodiment of the present invention.

FIG. 51 is a right side view showing a piston shape in a direct injection internal combustion engine according to a second embodiment of the present invention.

FIG. 52 is a rear view showing a piston shape in the direct injection internal combustion engine as the second embodiment of the present invention, and is a view symmetrical to the front view shown in FIG. 48.

FIG. 53 is a cross-sectional view showing a piston shape in a direct injection internal combustion engine as a second embodiment of the present invention, and is a cross-sectional view taken along the line AA in the right side view shown in FIG. 51.

FIG. 54 is a cross-sectional view showing a piston shape in the in-cylinder injection internal combustion engine as the second embodiment of the present invention, and is a BB cross-sectional view in the front view shown in FIG. 48.

[Explanation of symbols]

 Reference Signs List 1 fuel injection valve or injector 2 piston 2a intake valve side inclined upper surface 2b exhaust valve side inclined upper surface 3 combustion chamber 4 intake valve 5 exhaust valve 6 spark plug 6a discharge electrode 7 cylinder block 8 cylinder head 8a intake valve side inclined lower surface 8b exhaust valve Side inclined lower surface 9 Intake port 10 Exhaust port 25, 25A to 25C Concave or cavity 25a to 25c Virtual spherical surface 25d Connection surface 26 Flame infiltration space 27 Ignition plug mounting surface 28 Ignition plug mounting portion 29 Overlay portion 30 Piston pin 40 Outer peripheral end 41 Flat portion 42 Inflow portion 43 Raised portion 44 Connection portion (bottom surface) CL Cylinder central axis

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Goshima 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Takashi Kawabe 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Inside the Automotive Industry Co., Ltd. (72) Katsunori Ueda 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industry Co., Ltd. (72) Nobuaki Murakami 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Inside (72) Inventor Hideyuki Oda 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industry Co., Ltd. (72) Keiya Igarashi 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industrial Co., Ltd. In company

Claims (9)

[Claims] A combustion chamber divided into upper and lower sides by a lower surface of a cylinder head and a top surface of a piston; an intake valve disposed on one side of an upper surface of the combustion chamber; and another side of an upper surface of the combustion chamber. A cylinder forming an upper surface of the combustion chamber, comprising an exhaust valve disposed in the combustion chamber and a fuel injection valve disposed to inject fuel directly into the combustion chamber. A lower surface of the head is formed in a pent roof shape including an intake valve side inclined lower surface formed on the one side and an exhaust valve side inclined lower surface formed on the other side, and a spark plug is formed on the pent roof shaped combustion chamber upper surface. An intake valve-side inclined upper surface which is disposed near the top and which is formed so that the piston top surface forming the lower surface of the combustion chamber respectively corresponds to the intake valve-side inclined lower surface and the exhaust valve-side inclined lower surface. And an exhaust valve-side inclined upper surface The piston is formed in a mountain shape substantially following the shape of the piston, and a recess is provided at least on the intake valve-side inclined upper surface of the top of the piston. Of the volume of the combustion chamber when the piston is at the top dead center position, And the ratio between the volume between the upper surface of the piston above the recess and the lower surface of the cylinder head and the total volume of the combustion chamber when the piston is at the top dead center position is 0.4 to 0. An in-cylinder injection type internal combustion engine, which is set between 6 and 6. 2. A flat portion is formed at least on the outer peripheral end on one side of the piston top surface, and the concave portion is formed to be gentler than the flat portion, and the intake air introduced into the combustion chamber flows into the concave portion. An inflow portion at the time of inflow, a gently raised ridge that guides the intake air flowing into the recess toward the vicinity of the ignition plug, and a connection portion that connects the inflow portion and the ridge. The in-cylinder injection type internal combustion engine according to claim 1, wherein: 3. The in-cylinder according to claim 1, wherein the intake valve side inclined lower surface and the exhaust valve side inclined lower surface forming the upper surface of the combustion chamber are formed substantially flat. Injection type internal combustion engine. 4. The exhaust valve-side inclined upper surface of the piston is set to a smaller inclination angle than the exhaust valve-side lower surface of the cylinder head, and the exhaust valve-side inclined lower surface of the cylinder head and the exhaust of the piston are set. The valve-side inclined upper surface is formed so as to increase the mutual distance toward the center side of the combustion chamber, and a flame entry space having a substantially wedge-shaped cross section is formed at the top dead center position of the piston. The in-cylinder injection type internal combustion engine according to claim 1, characterized in that: 5. When the piston is at the top dead center, the interval between the piston and the exhaust valve is smaller than the interval between the piston and the intake valve. The in-cylinder injection type internal combustion engine according to claim 1, wherein: 6. The direct injection internal combustion engine according to claim 1, wherein said recess is formed by a spherical surface. 7. The concave portion is formed as a part of an imaginary spherical surface centered on an upper portion of the piston on the intake valve side, and a vertex of the piston and a lower end of the inclined upper surface on the intake valve side of the piston are
7. The direct injection internal combustion engine according to claim 6, wherein the internal combustion engine is configured to be included in the virtual spherical surface. 8. When the piston is at the top dead center position, the injection port of the fuel injection valve and the valve body of the intake valve are respectively included in the virtual spherical surface, and the ignition point of the discharge electrode of the spark plug 7. The direct injection internal combustion engine according to claim 6, wherein the internal combustion engine is configured to be included in the recess. 9. A ridgeline that defines the intake valve side inclined upper surface and the exhaust valve side inclined upper surface is formed on the piston top surface, and the recess extends beyond the ridgeline and extends from the intake valve side inclined upper surface. 2. The direct injection internal combustion engine according to claim 1, wherein the internal combustion engine extends to the exhaust valve side inclined upper surface.