JPH0979038A - Cylinder injection type internal combustion engine and piston for cylinder injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the improvement of fuel consumption and of output compatible by setting the shape of a combustion chamber and the relative position relation of components of the combustion chamber in a cylinder injection type internal combustion engine in such a way as to optimize combustion efficiency. SOLUTION: A cylinder injection type internal combustion engine is provided with a combustion chamber 3, an intake valve 4 and an exhaust valve 5 disposed at the combustion chamber 3, and a fuel injection valve 1 for injecting fuel directly into the combustion chamber 3. The lower face of a cylinder head 8 is formed into pent-roof shape having an intake valve side inclined lower face 8a and an exhaust valve side inclined lower face 8b. A spark plug 6 is disposed near the top part of the upper face of the combustion chamber 3. The top face of a piston 2 is formed into pent-roof shape having an intake valve side inclined upper face 2a and an exhaust valve side inclined upper face 2b, and a recessed part 25 is formed at the intake valve side inclined upper face 2a so that the fuel injection valve 1 supplies injected fuel into the recessed part 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder injection type internal combustion engine and a piston for a cylinder injection type internal combustion engine which are of a spark ignition type and which directly inject fuel into a combustion chamber.

[0002]

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

The fuel injected into the intake port is supplied to the combustion chamber together with the air sucked in the intake stroke, mixed with the air, and ignited by the ignition plug to burn. On the other hand, in a diesel engine that mainly uses light oil or the like as fuel, fuel is directly injected into the combustion chamber, and this fuel is spontaneously ignited by compressed air in the combustion chamber.

In the gasoline engine as described above, a cylinder injection type internal combustion engine has been proposed which directly injects fuel into the combustion chamber to improve the responsiveness of the engine. In such an in-cylinder injection internal combustion engine, a vortex flow is formed in the cylinder, fuel is injected into the vortex flow, and a mixture layer of a required concentration (fuel concentration near the theoretical air-fuel ratio) is adjusted according to the position of the spark plug. Is formed and the fuel in the air-fuel mixture layer is supplied to the spark plug, combustion in a state where the fuel concentration is extremely low (high air-fuel ratio), that is, so-called layered lean combustion operation can be performed.

[0005]

By the way, in such an in-cylinder 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, and as a result, The advantage is that it is easy to increase the compression ratio. Therefore, in the in-cylinder injection 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, if the shape of the combustion chamber becomes complicated, the output characteristics and the fuel consumption performance of the engine will change greatly even if the shapes and volumes of the piston and the combustion chamber and the positions where the spark plugs are arranged are slightly changed. There is a problem of doing. Therefore, there is a demand to set the shape of the combustion chamber of the direct injection internal combustion engine and the relative positional relationship of the components of the combustion chamber to a state that optimizes the combustion efficiency.

Japanese Patent Laid-Open No. 4-228850 discloses a technique in which the fuel injected from the fuel injection valve does not hit the inner wall of the cylinder. However,
Such a technique focuses only on the direction of fuel injection from the fuel injection valve, and does not solve the above-mentioned problems.

Further, in Japanese Patent Laid-Open No. 4-58030,
A technique for suppressing the occurrence of self-ignition, knocking, and smoke in a cylinder injection internal combustion engine is disclosed. However, such a technique is merely for smoothly operating the engine, and again does not solve the above-mentioned problems. In addition, JP-A-4-
Japanese Patent No. 166612 discloses a technique for improving the ignitability of a cylinder injection type internal combustion engine during low load operation. However, such a technique requires that the combustion chamber and the combustion chamber be optimized so that the combustion efficiency is optimized. It does not form a piston or regulate the position of the ignition plug.

Further, in the above-mentioned technique, the piston is provided with the recessed portion in the upper portion to form the combustion chamber, but a large space is also formed between the top surface of the piston and the lower surface of the cylinder head. However, in such a combustion chamber shape, a sufficient compression ratio cannot be obtained, and there is a problem that it is difficult to achieve high output.

The present invention was devised to meet such demands and problems, and the combustion efficiency is optimized by the shape of the combustion chamber of the cylinder injection type internal combustion engine and the relative positional relationship of the components of the combustion chamber. An object of the present invention is to provide an in-cylinder injection internal combustion engine and a piston for an in-cylinder injection internal combustion engine, which are set in such a state and are capable of both improving fuel efficiency and improving output.

[0011]

Therefore, an in-cylinder injection type internal combustion engine of the present invention according to claim 1 has a combustion chamber which is vertically divided by a lower surface of a cylinder head and a top surface of a piston, and the combustion chamber. An intake valve arranged on one side of the upper surface of the chamber, an exhaust valve arranged on the other side of the upper surface of the combustion chamber, and a fuel injection valve arranged to inject fuel directly into the combustion chamber. In the in-cylinder injection type internal combustion engine, the lower surface of the cylinder head forming the upper surface of the combustion chamber has an inclined lower surface on the intake valve side formed on the one side and the exhaust valve side formed on the other side. An ignition plug is formed in a pent roof shape including an inclined lower surface, a spark plug is disposed near the top of the upper surface of the combustion chamber of the pent roof shape, and the top surface of the piston forming the lower surface of the combustion chamber is located on the intake valve side. To correspond to the inclined lower surface and the exhaust valve side inclined lower surface, respectively It is formed in the pent roof shape having the formed intake valve side inclined upper surface and exhaust valve side inclined upper surface, and at least a concave portion is provided on the intake valve side inclined upper surface of the piston top surface, and the fuel injection valve is provided with the concave portion. It is characterized in that it is provided so as to supply the injected fuel to.

According to the second aspect of the present invention, in addition to the structure of the first aspect, the in-cylinder injection type internal combustion engine of the present invention has the intake valve side inclined upper surface and the exhaust valve side inclined upper surface on the piston top surface. It is characterized in that a ridgeline that divides the upper surface is formed. Further, in the cylinder injection type internal combustion engine of the present invention described in claim 3, in addition to the configuration described in claim 2, the recess is formed so as to extend to the exhaust valve side inclined upper surface so as to divide the ridge line. It is characterized by

According to a fourth aspect of the present invention, in addition to the structure according to any one of the first to third aspects, the recess is formed by a spherical surface. It has a feature. Further, in addition to the configuration according to any one of claims 1 to 3, the cylinder injection type internal combustion engine of the present invention according to claim 5 has at least an outer peripheral end portion on one side of the piston top surface. A flat portion is formed, the concave portion is formed more gently than the flat portion, and an inflow portion when an intake air flow introduced into the combustion chamber flows into the concave portion and an intake air flow that has flowed into the concave portion are connected to the ignition plug. It is characterized in that it is composed of a gently swelled ridge that guides it toward the vicinity, and a connection part formed on a substantially flat surface that connects the inflow part and the swell.

According to a sixth aspect of the present invention, there is provided a cylinder injection type internal combustion engine in which a combustion chamber which is vertically divided by a lower surface of a cylinder head and a top surface of a piston, and one side of an upper surface of the combustion chamber. In-cylinder having an intake valve provided, an exhaust valve provided on the other side of the upper surface of the combustion chamber, and a fuel injection valve arranged to inject fuel directly into the combustion chamber In an injection type internal combustion engine, a lower surface of the cylinder head that forms an upper surface of the combustion chamber includes 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 in the vicinity of the top of the combustion chamber upper surface of the pentroof, and the piston top surface forming the lower surface of the combustion chamber is formed on the intake valve side inclined lower surface and the exhaust valve side. Intake valve side formed to correspond to the inclined lower surface The oblique top and exhaust valve-side inclined upper surface is formed in a mountain shape as substantially along the pentroof shape,
A recess formed by two spherical surfaces whose centers are adjacent to each other and a connecting surface that smoothly connects the two spherical surfaces is provided on the intake valve-side inclined upper surface of the piston top surface. I am trying.

According to a seventh aspect of the present invention, in addition to the structure of the sixth aspect, in the cylinder injection type internal combustion engine of the present invention, the centers of the two spherical surfaces are the piston pin's It is characterized in that they are set at positions that are offset in the opposite directions by the same distance with respect to an axis line that is orthogonal to the arrangement direction and that passes through the center of the piston.

According to an eighth aspect of the present invention, there is provided a cylinder injection internal combustion engine according to the eighth aspect, in addition to the structure according to any of the fourth, sixth and seventh aspects, wherein the recess is on the intake valve side of the piston. It is formed as a part of a virtual spherical surface having a center in the upper part, and the apex of the piston and the lower end of the intake valve side inclined upper surface of the piston are
It is characterized in that it is configured to be included in the virtual spherical surface.

According to a ninth aspect of the present invention, there is provided a cylinder injection internal combustion engine according to the present invention, in addition to the configuration according to any one of the fourth to sixth aspects, wherein the piston is at a top dead center position. An injection port of the fuel injection valve and a valve element of the intake valve are included in the virtual spherical surface, and an ignition point of a discharge electrode of an ignition plug is included in the recess. Is characterized by.

According to a tenth aspect of the present invention, in addition to the structure according to any of the first to ninth aspects, the cylinder injection type internal combustion engine according to the present invention further comprises: The inclination angle of the cylinder head is set to be smaller than that of the exhaust valve side lower surface, and the exhaust valve side inclined lower surface of the cylinder head and the exhaust valve side inclined upper surface of the piston are disposed toward each other toward the center of the combustion chamber. It is characterized in that a flame penetration space is formed so as to widen the distance and has a substantially wedge-shaped cross section at the top dead center position of the piston.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 11, in addition to the structure as set forth in any one of claims 1 to 10, combustion is performed when the piston is at the top dead center position. Of the chamber volume, the volume inside the recess and the volume between the piston upper surface and the cylinder head lower surface above the recess,
The ratio to the total volume of the combustion chamber when the piston is at the top dead center position is set to 0.4 to 0.6.

According to a twelfth aspect of the present invention, in addition to the structure according to any one of the first to eleventh aspects, the cylinder injection type internal combustion engine according to the present invention, when the piston is at the top dead center position, It is characterized in that the discharge electrode of the spark plug and the surface of the recess are arranged so as to be close to each other. A cylinder injection internal combustion engine according to a thirteenth aspect of the present invention, in addition to the configuration according to any one of the first to twelfth aspects, has the piston and the piston when the piston is at a top dead center position. It is characterized in that the interval between the portion close to the exhaust valve is set to 5 mm to 8 mm.

According to the fourteenth aspect of the present invention, in addition to the structure according to any one of the first to sixth aspects, the cylinder injection type internal combustion engine according to the present invention, when the piston is at the top dead center, It is characterized in that it is arranged such that a distance between a portion close to the exhaust valve and the exhaust valve is smaller than a distance between a portion closer to the piston and the intake valve. A cylinder injection type internal combustion engine according to a fifteenth aspect of the present invention, in addition to the configuration according to any one of the first to sixth aspects, further includes: an intake valve side inclined lower surface that forms an upper surface of the combustion chamber; The inclined lower surface on the exhaust valve side is formed substantially flat, respectively.

A piston for an in-cylinder injection type internal combustion engine according to a sixteenth aspect of the present invention is a combustion chamber which is vertically divided by a lower surface of a cylinder head and a top surface of the piston, and an upper surface of the combustion chamber. An intake valve disposed on a side of the combustion chamber, an exhaust valve disposed on the other side of the upper surface of the combustion chamber, and a fuel injection valve disposed so as to directly inject fuel into the combustion chamber. The cylinder head lower surface forming the upper surface of the combustion chamber 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. In a piston used in a cylinder injection type internal combustion engine arranged near the top of the upper surface of the combustion chamber having the pent roof shape, the piston top surface forming the lower surface of the combustion chamber has To correspond to the inclined lower surface of the exhaust valve side It is formed in the pent roof shape having the formed intake valve side inclined upper surface and exhaust valve side inclined upper surface, and at least a concave portion is provided on the intake valve side inclined upper surface of the piston top surface. .

Further, the piston for an in-cylinder injection type internal combustion engine according to a seventeenth aspect of the present invention is characterized in that, in addition to the structure according to the sixteenth aspect, the recess is formed in a spherical shape. . The piston for a cylinder injection type internal combustion engine according to the present invention of claim 18 is characterized in that, in addition to the configuration of claim 16, the bottom surface of the recess is formed to be substantially flat.

In addition to the structure according to claim 16, the piston for an in-cylinder injection type internal combustion engine of the present invention according to claim 19 secures a space in the vicinity of the spark plug adjacent to the recess. It is characterized in that a recess for forming is formed. A piston for a direct injection internal combustion engine according to a twentieth aspect of the present invention is, in addition to the structure according to the sixteenth aspect, an exhaust valve that is adjacent to the recess and is disposed on the exhaust valve side inclined lower surface of the piston. It is characterized in that a recess is formed to secure a nearby space.

According to a twenty-first aspect of the present invention, there is provided a piston for an in-cylinder injection type internal combustion engine, which comprises a combustion chamber defined by a lower surface of a cylinder head and a top surface of the piston, and an upper surface of the combustion chamber. An intake valve disposed on a side of the combustion chamber, an exhaust valve disposed on the other side of the upper surface of the combustion chamber, and a fuel injection valve disposed so as to directly inject fuel into the combustion chamber. The cylinder head lower surface forming the upper surface of the combustion chamber 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. In a piston used in a cylinder injection type internal combustion engine arranged near the top of the upper surface of the combustion chamber having the pent roof shape, the piston top surface forming the lower surface of the combustion chamber has To correspond to the inclined lower surface of the exhaust valve side The intake valve-side inclined upper surface and the exhaust valve-side inclined upper surface are formed into a mountain shape that substantially follows the pent roof shape, and the centers are adjacent to each other on the intake valve-side inclined upper surface of the piston top surface. It is characterized in that a concave portion formed by two spherical surfaces and a connecting surface for smoothly connecting the two spherical surfaces is provided.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. First, a cylinder injection type internal combustion engine and a piston for a cylinder injection type internal combustion engine as a first embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing the structure of a combustion chamber thereof, and FIG. ) To (c) and FIGS. 15 to 22 are schematic views showing the shape of the piston as the main part thereof, and FIG. 3 is a view showing the relative positional relationship between the top surface of the piston and the lower surface of the cylinder head. FIG. 4 is a schematic diagram for explaining the ratio of the total volume of the combustion chamber to the volume of the recessed portion of the piston, and FIGS. 5A and 5B show changes in the volume ratio of the recessed portion of the piston. Graphs for explaining changes in the characteristics of the accompanying engine, FIGS. 6, 7, and 23 to 46 are schematic diagrams showing modified examples thereof, and FIGS. 8 and 9 are for explaining the operation thereof. The graph and Fig. 10 show changes in fuel consumption and HC emissions due to differences in the shape of the combustion chamber. Is a graph showing characteristics.

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

The upper surface side 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 such that its tip end side faces the combustion chamber 3, and the injector 1 injects fuel directly into the combustion chamber 3.

Next, the shape of the piston 2 will be described. As shown in FIGS. 1, 2A to 2C and 15 to 22, the top surface of the piston 2 forming the lower surface of the combustion chamber 3 is described. An intake valve-side inclined upper surface 2a and an exhaust valve-side inclined upper surface 2b that are inclined toward the center of the piston 2 are formed at the intake valve-side inclined lower surface 8a and the exhaust valve-side inclined lower surface 8b, respectively. , These inclined upper surfaces 2a, 2b
The top surface of the piston 2 is formed in a mountain shape that substantially conforms to the pent roof shape. In addition, these inclined upper surfaces 2a,
2b is defined by a ridgeline formed on the top surface of the piston.

A concave portion (hereinafter, simply referred to as a cavity) 25 as shown in FIGS. 1 and 2A to 2C is formed on the intake valve side inclined upper surface 2a of the piston 2. 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 also formed in a spherical shape that is curved downward in a convex shape, and is formed on the intake valve 4 side of the piston 2. Virtual spherical surface 25a having a center at the top
It is formed as a part of.

Further, an intake port (see FIG. 12) opening to the combustion chamber 3 is extended above the intake valve 4 so as to be substantially upright, and an intake flow is made through the intake port. The intake air flows toward the piston 2 below and is guided along the cavity 25 of the piston 2 to flow upward to form a tumble flow (longitudinal vortex flow).

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 to the lower surfaces of the intake valve 4 and the exhaust valve 5, the flow of the tumble flow becomes smooth and the tumble flow becomes smooth. The flow will be strengthened. Also,
The reason why the lower surface of the cylinder head 8 has the pent roof shape as described above is mainly because of 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 continuously generate a strong flow in the combustion chamber 3 without disturbing the intake flow. Therefore, in the present embodiment, in order to maintain the tumble flow generated in the combustion chamber 3 especially in 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 have a pent roof shape. The flow of the tumble flow from the piston 2 toward the exhaust valve side lower surface 8b and the flow from the intake valve side slope 8a to the piston 2 are made smooth, and the tumble flow is maintained until the latter half of the compression stroke.

Further, 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 in an inclined manner, thereby increasing the degree of freedom in layout of the intake port 9.

The setting of the volume of the cavity 25 has a great influence 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, the graph of FIG. As described above, it is advantageous to perform the stratified combustion, but the surface area of the combustion chamber 3 becomes large and the heat loss becomes large. Then, although the fuel economy is improved by this, as shown in the graph of FIG.
It is possible that the maximum output and maximum torque will decrease.

If the volume of the cavity 25 is too small with respect 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. However, a tumble flow cannot be formed, and as shown in the graph of FIG. 5A, fuel consumption is reduced. Therefore, in the direct injection internal combustion engine of the present invention, the volume of the cavity 25 is set to a predetermined ratio with respect to the volume of the entire combustion chamber 3 in order to achieve both output performance and fuel efficiency of the engine. Has been done.

The setting of this volume ratio will now 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.

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 so as to substantially follow the pent roof shape of the cylinder head 8. That is, when the top surface of the piston 2 is formed in the pent roof shape as described above, the space surrounded by the piston 2 and the cylinder head 8 can be reduced when the piston 2 is raised, and the total volume of the combustion chamber 3 can be reduced. The volume ratio of the cavity 25 to the cavity can be increased.

As a result, the compression ratio of this 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 of fuel consumption and high output. In addition to this, the shape of the cavity 25 is shown in FIG.
By forming the 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. Then, 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 swirl flow due to the intake air flow, that is, a tumble flow can be easily formed in the combustion chamber 3. In addition, the above-mentioned virtual spherical surface 25a, as shown in FIG.
In the cross section of the central axis of the above, 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 set to be 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 so that the injection port of the injector 1 and the valve element of the intake valve 4 are located inside the virtual spherical surface 25a. The positional relationship of the spherical surface 25a is set. Then, in this way, the injector 1 and the intake valve 4 are
By arranging, the cavity 25 can be reliably
The fuel concentration inside is high.

In such an in-cylinder 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. Depending on the situation, fuel injection is performed in the compression stroke. in this case,
In the combustion chamber 3, the air-fuel mixture is formed as a layer of air and fuel, and the fuel (hatched portion in FIG. 1) is present 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 an ordinary internal combustion engine spark plug, the electrode does not reach the position where a combustible air-fuel mixture of sufficient concentration exists, and It is possible that the efficiency will be reduced.

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

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

Thus, the spark plug 6 is attached to the cylinder head 8 so as to approach the cavity 25 side. In this case, the screw portion at the bottom of the spark 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 and the like adhere to the bottom of the spark plug 6. Resulting in. When carbon or the like adheres to the threaded portion at the bottom of the spark plug 6, the spark plug 6 causes the cylinder head 8 to move.
It may be difficult to remove it from the machine and workability may decrease.

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

Also, the length of the electrode 6a of the spark plug 6 is formed to be a predetermined amount longer than that of the normal spark plug, so that the electrode 6a is positioned at the portion where the fuel concentration is high at the time of ignition of the fuel. It will be. The mounting surface 27 of the spark plug 6 is formed at a position similar to that of a conventional internal combustion engine, and only the electrode 6a of the spark plug 6 is formed longer by a predetermined amount D1 so that the electrode 6a is kept in the fuel inside the cavity 25. A configuration in which it is arranged in a high density portion is also conceivable. 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 built-up portion 29 becomes unnecessary, but if the length of the electrode 6a alone is made extremely long in this way, the durability of the electrode 6a may be reduced.

On the other hand, in the present invention, the spark plug 6
The mounting surface 27 of the electrode is brought closer to the combustion chamber 3 side, and the electrode 6
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 to be long, while ensuring that the electrode 6a is located in the portion of the cavity 25 where the fuel concentration is high, There is an advantage that the durability of the spark plug 6 is not impaired. Then, by this, the fuel can be reliably ignited and the combustion efficiency can be improved.

Further, the value of the clearance (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 output of the engine and the fuel consumption. Must be set. That is, if the gap D2 is too large, the fuel carried on the intake tumble flow formed in the combustion chamber 3 does not reach the electrode 6a of the spark plug 6 sufficiently, and the combustion efficiency deteriorates. If the discharge electrode 6a and the surface of the cavity 25 are too close to each other, the electrode 6a and the piston 2 may interfere with each other.

Therefore, in the in-cylinder injection 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).
2 mm) so that high combustion efficiency can be obtained while sufficiently avoiding interference with the piston 2. Further, in such an in-cylinder injection internal combustion engine, the distance between the piston 2 and the exhaust valve 4 in the vicinity thereof (this is called the exhaust side clearance, indicated by D3 in FIG. 1) also greatly affects the performance of the engine. For example, as shown by 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 diffuses to the outside of the cavity 25, which deteriorates fuel efficiency.

On the other hand, as shown at points A and B, if the exhaust side gap D3 is too small, flames are sufficiently generated in the space on the exhaust valve 5 side during full open operation (that is, during fuel injection in the intake stroke). It is not propagated and the output drops. Therefore, in the in-cylinder injection internal combustion engine of the present invention, an optimum value (in the vicinity of the star mark, D3 shown in FIG. 8; = 5 to 8 mm).

By forming the cavity 25 in a spherical shape and arranging it so that the positional relationship between the cavity 25 and the spark plug 6 is optimized, the fuel injected toward the cavity 25 is ignited at the time of ignition. Cavity 2
It is possible to promote the stratification of the intake air and the fuel by allowing the fuel to stay in the inside of the fuel cell 5 and to perform reliable ignition and combustion.

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

The reason why the substantially wedge-shaped flame entry space 26 is formed on the exhaust valve 4 side of the combustion chamber 3 is as follows. That is, in the combustion chamber 3 of the in-cylinder injection 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 to be substantially parallel to each other. Since the space formed by these surfaces 2b and 8b is formed narrow, the flame propagation to this space after fuel ignition tends to be delayed. Therefore, 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. Total volume (V in Figure 4
An optimum volume ratio exists between the (a + Vb + Vc portion) and the volume (Va + Vb) of the cavity 25 and its upper space.

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

According to such a flame infiltration space 26, first, the flame that has started combustion around the electrode 6a 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 toward the center of the combustion chamber 3, and even on the end side of the combustion chamber 3 with a relatively narrow gap, the flame propagates 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 of the combustion chamber 3 on the side of the exhaust valve 5 into a substantially wedge shape, the volume of the space of the combustion chamber 3 on the side of the exhaust valve 5 is not changed, and the cavity ratio It also has the advantage of not affecting the settings.
Since the cylinder injection type internal combustion engine and the piston for the cylinder injection type internal combustion engine according to the first embodiment of the present invention are configured as described above, the following effects can be obtained.

First, on the intake valve side inclined upper surface 2a of the piston 2, a spherical cavity 25 which is curved downward in a convex shape as shown in FIGS. 2 (a) to 2 (c) is formed. There is an advantage that the fuel efficiency can be improved.

That is, by forming the shape of the cavity 25 to be spherical, the surface area of the cavity for the cavity volume Va of the piston 2 can be minimized. As a result, heat loss can be reduced and combustion efficiency can be improved. Further, by forming the cavity 25 in a spherical shape, the formation of a vortex flow due to the intake flow, that is, a tumble flow, is promoted in the combustion chamber 3, and there is an advantage that stratified combustion is easily performed. further,
By forming the inclined lower surfaces 8a and 8b of the combustion chamber 3 to be substantially flat, the formation of the tumble flow is strengthened.

FIG. 9 shows such a spherical cavity 25.
5 is a graph showing a comparison between a piston 2 having a cavity having a different shape and a piston 2 having a cavity having another shape, with respect to fuel consumption and maximum torque (indicated by points A and B in the figure) of a cavity having another shape in cross section. Thus, in the piston 2 having the spherical cavity 25, both the fuel consumption and the maximum torque can be improved as shown at the point C.

Further, such a spherical cavity 25
In addition to two pairs of pistons each having a flame, a flame penetration space 26 in which the cross-sectional shape of the combustion chamber 3 on the exhaust valve 5 side is formed into a substantially wedge shape
As shown by point D, the provision of is advantageous in that the maximum torque is further improved. Further, as shown in FIG. 10, by providing such a substantially wedge-shaped flame penetration space 26, the fuel consumption rate can be reduced in almost the entire region, and the amount of THC (total amount of hydrocarbons) emitted can be reduced. It also has the advantage that it can be reduced.

In the in-cylinder injection internal combustion engine, the mounting surface 27 of the spark plug 6 is moved by a predetermined amount D1 (for example, D1 = 2 m).
m) only near the combustion chamber 3 side, and the spark plug 6
The two-stage structure in which the discharge electrode 6a is formed by a predetermined amount longer than that of the conventional one, and the ignition portion of the electrode 6a is located in the portion of the cavity 25 where the fuel concentration is high, so that the fuel can be reliably discharged. There is an advantage that the durability of the electrode 6a of the spark plug 6 is not impaired while enabling ignition.

Further, in such a spark plug 6, since it is only necessary to form the electrode 6a part by a predetermined length as compared with the conventional spark plug, there is an advantage that it can be realized at a low cost. Further, on the surface where the combustion chamber 3 of the cylinder head 8 is formed, the built-up portion 2 is provided around the attachment portion 28 of the spark plug 6.
9 is provided, even if the lower end of the spark plug 6 moves to the combustion chamber 3 side by the predetermined amount D1, the lower end of the spark plug 6 is not directly exposed to the combustion chamber 3.

Therefore, carbon or the like is prevented from adhering to the threaded portion of the lower portion of the spark plug 6, and the workability of replacing the spark plug 6 is improved. Also, the lower part of the spark plug 6
Since it is protected by the built-up portion 29, there is an advantage that the durability of the spark plug 6 itself is improved. Furthermore, since the heat applied to the spark plug 6 can be released to the cylinder head 8 via the built-up portion 29, there is an advantage that durability against heat is also improved.

On the other hand, the cavity 25 of the piston 2 is provided with the apex of the piston 2 and the intake valve side inclined upper surface 2a of the piston 2.
By forming the lower end of the spark plug so as to be included in the virtual spherical surface 25a, the spark plug 6 can be easily arranged in the cavity 25. There is also an advantage that the generation of the tumble flow can be promoted. Further, when the piston 2 reaches the top dead center position, the injector 1, the intake valve 4 and the virtual spherical surface 25a are positioned so that the injection port of the injector 1 and the valve body of the intake valve 4 are positioned inside the virtual spherical surface 25a. Since the relationship is set, it is possible to generate the air-fuel mixture having a high fuel concentration in the cavity 25.

The intake valve side inclined lower surface 8a when the volume Va of the cavity 25 and the piston 2 are at the top dead center position
Vb between the intake valve side inclined upper surface 2a and the combustion chamber 3
The optimum volume ratio of the total volume Va + Vb + Vc is
For example, (Va + Vb) / (Va + Vb + Vc) = 0.
Since it is set to a value between 4 and 0.6,
There is an advantage that it is possible to achieve a good balance between improvement of fuel consumption and improvement of output.

That is, as shown in FIGS. 5 (a) and 5 (b), if the cavity volume ratio is too large, the maximum torque and the maximum output decrease, and if 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 improved fuel consumption and improved output.

Further, as shown by a star in the graph of FIG. 8, the exhaust side clearance D3 is set to an optimum value (D3 = 5 to 8 mm), so that a combustion state with high thermal efficiency can be realized. After all, there is an advantage that the maximum output can be improved. In addition, the discharge electrode 6 of the spark 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 with the piston 2 of the spark plug 6. have.

Further, by forming the lower surface of the cylinder head 8 in a pent roof shape, it is possible to maintain a strong vertical vortex flow even during the compression stroke, and it is possible to perform stable fuel injection 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 formed by being divided by the ridge line of the piston top surface, the combustion chamber 3 has a shape such that 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, the first to third modified examples of the direct injection internal combustion engine according to the first embodiment will be described.
6, FIG. 7, and FIG. 23 to FIG. 30 are diagrams showing a first modification example thereof, which is different from the above-described first embodiment only in the shape of the recess 25. That is, in this first modified example, the shape of the recess 25 is different from that shown in FIGS.
As shown in (a) to (c), the cavities 25A and 25B having a substantially rectangular cross section are formed.

The piston 2 having these cavities 25A and 25B will be briefly described. A flat portion 41 perpendicular to the moving direction of the piston 2 is formed on the outer peripheral end portion 40 of the piston top surface on the intake valve 4 side. Has been done. Also,
The intake flow is supplied to the cavities 25A and 25B.
5A, the inflow part 42 which guides in 25B, and the cavity 2
5A, 25B, a raised portion 43 that guides the intake air flow toward the vicinity of the ignition plug 6, and a connecting portion 44 that connects the inflow portion 42 and the raised portion 43 and is formed on a substantially flat surface. Has been done.

As a result, the intake air flows in through the inflow portion 42 formed gently between the flat portion 41 and the bottom surface (connecting portion) 44 of the cavities 25A and 25B, and then is directed at the raised portion 43. Is changed to an upward direction toward the vicinity of the spark plug 6, whereby a tumble flow is formed. Therefore, such a cavity 25A,
Even a cylinder injection internal combustion engine having 25B has an advantage of being excellent in fuel consumption and output as compared with the conventional cylinder injection internal combustion engine.

Further, FIGS. 31 to 38 are views showing a second modified example of the direct injection internal combustion engine as the first embodiment, in which ignition is performed with respect to the configuration of the first embodiment described above. The only difference is that a recess for ensuring a space near the plug is formed adjacent to the cavity 25 of the piston. In addition, FIGS.
FIG. 8 is a diagram showing a third modified example of the direct injection internal combustion engine as the first embodiment, for ensuring a clearance between the piston and the exhaust valve on the exhaust valve side inclined upper surface 2b of the piston 2. The recess is formed separately from the cavity 25.

Even in the in-cylinder injection type internal combustion engine having the pistons configured as in the second and third modified examples as described above, the conventional in-cylinder in-cylinder can be used as in the first modified example. It has an advantage over the injection type internal combustion engine in terms of fuel efficiency and output. Next, the cylinder injection type internal combustion engine and the piston for the cylinder injection type internal combustion engine as the second embodiment of the present invention will be described. FIG. 11 and FIGS. 47 to 54 are schematic views showing the piston as a main part thereof. is there. In addition, this second
In the embodiment, only the shape of the recess of the piston 2 is formed differently from the first embodiment, and the other configurations are common to the above-described first embodiment.

As shown in FIGS. 11 (a) to 11 (c), the top surface of the piston 2 on the intake valve 4 side is formed with a cavity 25C which is curved downward in a convex shape.

As shown in FIG. 11C, the cavity 25C has two phantom spherical surfaces 25b and 25c whose centers are adjacent to each other at the upper portion on the intake valve 4 side and a smooth space between these two spherical surfaces 25b and 25c. And a connection surface 25d that is connected to. As shown in FIG. 11A, the centers of these phantom spherical surfaces 25b, 25c are
Are set at positions offset by the same distance in opposite directions with respect to the axis line orthogonal to the arrangement direction.

The connecting surface 25d is composed of two spherical surfaces 2
It is formed as a cylindrical surface connecting the lower portions of 5b and 25c. 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 to be relatively small.

Therefore, the fuel consumption can be improved with almost no reduction in fuel loss, that is, with almost no reduction in output characteristics. Further, by forming the cavity 25C in a substantially spherical shape, there is also an advantage that the formation of a vortex flow due to the intake flow, that is, a tumble flow, is promoted in the combustion chamber 3.

The in-cylinder injection type internal combustion engine and the piston for the in-cylinder injection type internal combustion engine according to the second embodiment of the present invention are configured as described above, and therefore, the combustion chamber 3 is connected via the intake valve 4.
The intake flow that has flowed in is guided to the cavity 25C formed in the piston 2 to form a tumble flow, and fuel is injected into this tumble flow to form a stratified mixture.

Here, the two two phantom spherical surfaces 25b and 25c forming the cavity 25C are the piston pin 30
Since they are adjacent to each other in the arrangement direction, they are formed as spherical cavities in the inflow direction of the intake air flow, that is, the direction in which the tumble flow is formed [FIG. 11 (b)].
reference〕. Therefore, the stratified combustion can be performed as in the first embodiment.

Further, in the above-mentioned cavity 25C, the cavity surface area of the piston 2 can be made relatively small while the cavity volume of the piston 2 is made relatively large, so that the fuel efficiency can be improved with almost no deterioration in the output characteristics. There is an advantage. The connecting surface 25d is not limited to the cylindrical surface, and is not limited to the cylindrical surface.
If the two spherical surfaces 25b and 25c can be smoothly connected to each other, the surfaces may have other shapes.

Next, a cylinder injection type internal combustion engine and a piston for a cylinder injection type internal combustion engine as a third embodiment of the present invention will be described. FIG. 12 is a schematic sectional view showing the structure of the combustion chamber. is there. In this embodiment, as shown in FIG. 12, the configuration is basically the same as that of 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 directly connected to the combustion chamber 3
The fuel is directly injected into the combustion chamber 3. In addition, the injector 1
For example, controlled by a controller (not shown), the injector 1 injects an appropriate amount of fuel at an appropriate timing. Then, this fuel is injected toward the cavity 25 of the piston 2, and the air sucked from the intake port 9 provided substantially upright above the intake valve 4 and the fuel are mixed in the combustion chamber 3. A mixture is generated. Then, the air-fuel mixture is ignited by the ignition plug 6 in the combustion chamber 3, expanded (exploded), and then discharged from the exhaust port 10. In the figure, 7 is a cylinder block, and 8 is a cylinder head.

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

By the way, even when the shape of the combustion chamber 3 is not strictly defined in this way, the recess 25 of the piston 2 is made spherical and the top surface of the piston 2 is made into a pent roof type as follows. There is such an action and effect. That is, when the intake flow is taken into the combustion chamber 3 through the intake port 9 that extends substantially upright above the intake valve 4, the intake flow flows toward the piston 2 below and then becomes spherical. A tumble flow (longitudinal vortex flow) is formed by being guided upward along the cavity 25. By injecting fuel into this tumble flow, a stratified mixture is formed.

Further, by forming the top surface of the piston 2 into a mountain shape that substantially conforms to the pent roof shape of the cylinder head 8, a space surrounded 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, the manufacturing cost can be reduced while satisfying the contradictory factors of low fuel consumption and high output at a high level. Next, a cylinder injection internal combustion engine and a piston for a cylinder injection internal combustion engine as a fourth embodiment of the present invention will be described. FIG. 13 is a schematic cross-sectional view showing a combustion chamber shape as a main part thereof, FIG. 14 is a schematic plan view showing a piston as a main part thereof.

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

The difference between the gap a and the gap b is not so large and does not exert a great influence on 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 cavity 25 is also formed into a spherical shape. This is because, as described in the first embodiment, by forming the cavity 25 in the spherical shape, the cavity surface area with respect to the cavity volume Va of the piston 2 can be minimized. Then, by minimizing the surface area of the cavity, 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 becomes smaller, the heat loss becomes smaller 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 in-cylinder injection type internal combustion engine, the output characteristics and the fuel consumption performance of the engine are large depending on the shapes and volumes of the piston 2 and the combustion chamber 3 and the positions where the spark plugs 6 are arranged. If the shape of the combustion chamber in the first embodiment is significantly changed, the balance between the output characteristics and the fuel efficiency may be impaired. Therefore, in order to reduce the surface area without changing the shape of the combustion chamber 3 as described in the first embodiment, the intake valve side upper surface 2a of the piston 2 is compared with that described in the first embodiment. And the exhaust valve side inclined upper surface 2b is slightly closer to the exhaust valve 5 as compared with the one described in the first embodiment. That is, in the combustion chamber 3, the relation of a> b is established between the intake valve gap a and the exhaust valve side gap b.

According to this structure, the surface area of the exhaust valve side upper surface 2b of the piston 2 hardly changes, but the surface area of the intake valve side upper surface 2a is larger than that of the exhaust valve side upper surface 2b. 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. 14. Therefore, when the upper surface 2a of the piston 2 on the intake valve side is moved downward, this amount is reduced by this amount. 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) is also reduced. That is, the intake valve-side upper surface 2a and the exhaust valve-side upper surface 2b have a larger surface area that changes when the surfaces are moved in the vertical direction on the intake valve-side upper surface 2a.

Further, of the surface area of the intake valve side upper surface 2a of the piston 2, the area facing the cylinder head lower surface (see 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 Therefore, in order to change the intake valve gap a and the exhaust valve side gap b while ensuring the same compression ratio as in the first embodiment, the intake valve 4 on the intake valve side upper surface 2a is It is necessary to make the distance away from the exhaust valve-side inclined upper surface 2b closer to the exhaust valve 5. Therefore, also from such a configuration, the amount of decrease in the total surface area of the intake valve side upper surface 2a becomes larger than the amount of increase in the surface area of the exhaust valve side upper surface 2b. In order to secure the same compression ratio as that of the first embodiment with such a configuration, the amount by which the intake valve side upper surface 2a is moved away from the intake valve 4 is the amount by which the exhaust valve side upper surface 2b is brought closer to the exhaust valve 5. About 2
It will be 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. The combustion efficiency can be improved. 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 cylinder injection type internal combustion engine and the piston for the cylinder injection type internal combustion engine according to the fourth embodiment of the present invention are configured as described above, the same operation and effect as those of the first embodiment described above. In addition, it has the following actions and effects. 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, heat loss can be reduced, and combustion efficiency can be improved. It is possible. With such a configuration, the fuel efficiency of the fourth embodiment is increased by, for example, about 2% with respect to the fuel efficiency of the first embodiment.

Further, such a shape of the piston 2, that is, the shape of the combustion chamber 3 in which a> b between the intake valve clearance a and the exhaust valve side clearance b is applied to the second embodiment. May be. Even when the second embodiment is configured in this way, the surface area of the combustion chamber 3 can be reduced and the heat loss can be reduced, as described above. Then, there is an advantage that the combustion efficiency can be improved.

In this case, the area of the intake valve side upper surface 2a facing the lower surface of the cylinder head is smaller than that of the first embodiment. Therefore, the amount by which the intake valve side upper surface 2a is separated from the intake valve 4 is set. The piston 2 can be made larger than the piston 2 of the first embodiment, and the effect of reducing heat loss becomes more remarkable.

[0100]

As described in detail above, according to the in-cylinder injection type internal combustion engine of the present invention as set forth in claim 1, a combustion chamber which is vertically divided by the lower surface of the cylinder head and the top surface of the piston,
An intake valve arranged on one side of the upper surface of the combustion chamber, an exhaust valve arranged on the other side of the upper surface of the combustion chamber, and a fuel arranged to inject fuel directly into the combustion chamber. In a cylinder injection type internal combustion engine having an injection valve, the cylinder head lower surface forming the upper surface of the combustion chamber has an intake valve side inclined lower surface formed on the one side and an exhaust gas formed on the other side. The ignition plug is disposed in the vicinity of the top of the upper surface of the combustion chamber having the pent roof shape, and the piston top surface forming the lower surface of the combustion chamber has The pentroof shape having an intake valve side inclined upper surface and an exhaust valve side inclined upper surface formed corresponding to the valve side inclined lower surface and the exhaust valve side inclined lower surface, respectively, at least the intake valve side of the piston top surface The sloped upper surface is provided with a recess Fuel injection valve, the configuration that is provided to supply the injected fuel recess, high-cylinder injection type internal combustion engine compression ratio can be realized, it is possible to greatly improve the output. That is, since the ratio of the volume of the recess of the piston to the volume of the entire combustion chamber can be increased, the compression ratio can be set high and the output can be increased.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 2, in addition to the configuration of claim 1,
With the configuration in which a ridge line that partitions the intake valve-side inclined upper surface and the exhaust valve-side inclined upper surface is formed on the piston top surface, the combustion chamber has a shape corresponding to each of the intake valve side and the exhaust valve side, There is an advantage that the role of the combustion chamber can be shared between the intake valve side and the exhaust valve side.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 3, in addition to the structure of claim 2,
Since the recess is formed so as to extend to the exhaust valve side inclined upper surface so as to divide the ridge line, it becomes easy to optimally set the ratio of the volume of the recess in the combustion chamber to the volume of the entire combustion chamber. The advantage is that both high fuel efficiency and high output can be achieved at the same time.

According to the cylinder injection type internal combustion engine of the present invention described in claim 4, in addition to the structure described in any one of claims 1 to 3, the recess is formed by a spherical surface. The configuration can minimize the surface area of the recess relative to the volume of the recess of the piston. Also, this 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, there is an advantage that the formation of a vortex flow due to the intake air flow, that is, a tumble flow is promoted in the combustion chamber, and the stratified combustion is facilitated.

According to the cylinder injection type internal combustion engine of the present invention described in claim 5, in addition to the structure described in any one of claims 1 to 3, at least the one side of the top surface of the piston is provided. A flat portion is formed at the outer peripheral end, the concave portion is formed more gently than the flat portion, and the intake flow introduced into the combustion chamber flows into the concave portion and the intake air flowing into the concave portion. The combustion chamber has a configuration in which it is composed of a gently raised ridge that guides the flow toward the vicinity of the spark plug, and a connection portion formed on a substantially flat surface that connects the inflow portion and the ridge. There is an advantage that a tumble flow can be reliably formed with.

According to the sixth aspect of the cylinder injection type internal combustion engine of the present invention, one of the combustion chamber defined by the lower surface of the cylinder head and the top surface of the piston and the upper surface of the combustion chamber is defined. An intake valve disposed on the side, an exhaust valve disposed on the other side of the upper surface of the combustion chamber, and a fuel injection valve disposed so as to directly inject fuel into the combustion chamber. In a cylinder injection internal combustion engine, the lower surface of the cylinder head forming the upper surface of the combustion chamber is composed of an inclined lower surface on the intake valve side formed on the one side and an inclined lower surface on the exhaust valve side formed on the other side. The ignition plug is formed in a pent roof shape, the ignition plug is disposed near the top of the upper surface of the combustion chamber in the pent roof shape, and the top surface of the piston forming the lower surface of the combustion chamber has a lower inclined surface on the intake valve side and the exhaust gas. Suctions formed to correspond to the valve-side inclined lower surface The sloping upper surface on the valve side and the sloping upper surface on the exhaust valve side are formed in a mountain shape that substantially conforms to the pent roof shape. With the configuration in which the concave portion formed by the connecting surface that smoothly connects the two spherical surfaces is provided, the surface area of the concave portion can be formed to be relatively small while the volume of the concave portion of the piston is increased, and the output characteristics can be improved. There is an advantage that the fuel efficiency can be improved with almost no decrease.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 7, in addition to the structure of claim 6,
The centers of the two spherical surfaces are, in a top view of the piston,
The pistons are formed symmetrically with respect to each other by the positions that are orthogonal to the arrangement direction of the piston pins and are offset by the same distance in opposite directions with respect to the axis passing through the center of the pistons. be able to. This has the advantage that there is no variation in combustion within the combustion chamber and the combustion state of the fuel is stable.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 8, in addition to the structure as set forth in any one of claims 4, 6, and 7, the concave portion is the intake air of the piston. Ignition is formed as a part of a virtual spherical surface centered on the valve side upper part, and the apex of the piston and the lower end of the intake valve side inclined upper surface of the piston are configured to be included in the virtual spherical surface. There is an advantage that the plug can be easily arranged in the recess. There is also an advantage that the generation of the tumble flow can be promoted.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 9, in addition to the structure as set forth in any one of claims 4, 6 to 8, the piston is located at the top dead center position. In some cases, the injection port of the fuel injection valve and the valve element of the intake valve are included in the virtual spherical surface, and the ignition point of the discharge electrode of the spark plug is included in the recess. As a result, there is an advantage that an air-fuel mixture having a high fuel concentration can be generated in the recess. Then, there is an advantage that the combustion efficiency can be increased.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 10, in addition to the structure as set forth in any of claims 1 to 9, the inclined upper surface of the piston on the exhaust valve side is An inclination angle smaller than that of the exhaust valve side lower surface of the cylinder head, and toward the center side of the combustion chamber by the exhaust valve side inclined lower surface of the cylinder head and the exhaust valve side inclined upper surface of the piston. It is formed so that the mutual distance widens,
With the configuration in which the flame penetration space having a substantially wedge-shaped cross section is formed at the top dead center position of the piston, the flame can be uniformly propagated in the combustion chamber, and uniform combustion can be realized. There are advantages. 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 recess is not affected at all.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 11, when the piston is at the top dead center position in addition to the structure as set forth in any one of claims 1 to 10 above. Of the combustion chamber volume, the volume between the recess and the space between the piston upper surface and the cylinder head lower surface above the recess, and the total volume of the combustion chamber when the piston is at the top dead center position. With the configuration in which the ratio of and is set between 0.4 and 0.6, each volume ratio in the combustion chamber can be set to an optimum value, and high fuel efficiency and high output can both be achieved.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 12, in addition to the structure as set forth in any one of claims 1 to 11, when the piston is at the top dead center position. The configuration in which the discharge electrode of the spark plug and the surface of the recess are arranged close to each other has an advantage that the improvement of fuel consumption and the improvement of output can be achieved in a well-balanced manner.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 13, when the piston is at the top dead center position in addition to the structure as set forth in any of claims 1 to 12, , The distance between the piston and the exhaust valve is 5 mm
With the configuration of between 8 mm and 8 mm, there is an advantage that the fuel injected toward the concave portion can be retained in the concave portion at the time of ignition, and stratification of the intake air and the fuel can be promoted. In addition, this has the advantage that a combustion state with high thermal efficiency can be realized and the maximum output can be improved.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 14, in addition to the structure as set forth in any of claims 1 to 6, when the piston is at the top dead center, The volume ratio of the entire combustion chamber is almost changed by the configuration in which the interval between the piston and the exhaust valve is smaller than the interval between the piston and the intake valve. The heat loss can be reduced because the surface area inside the combustion chamber can be reduced without the need. As a result, there is an advantage that combustion efficiency is improved, and high output and high fuel efficiency can be compatible at a high level.

According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 15, in addition to the structure as set forth in any one of claims 1 to 6, the intake air forming the upper surface of the combustion chamber is formed. With the configuration in which the valve-side inclined lower surface and the exhaust valve-side inclined lower surface are formed substantially flat, it is possible to promote the formation of the vertical vortex flow generated in the combustion chamber and to strengthen the vertical vortex flow. This has the advantage that more stable stratified combustion can be performed.

According to the piston for a cylinder injection type internal combustion engine of the present invention as defined in claim 16, a combustion chamber which is vertically divided by a lower surface of the cylinder head and a top surface of the piston, and an upper surface of the combustion chamber. An intake valve disposed on one side of the combustion chamber, an exhaust valve disposed on the other side of the upper surface of the combustion chamber, and a fuel injection valve disposed to directly inject fuel into the combustion chamber. The cylinder head lower surface forming the upper surface of the combustion chamber 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 ignition is performed. In a piston used in an in-cylinder injection type internal combustion engine in which a plug is arranged near the top of the upper surface of the combustion chamber having the pent roof shape, the piston top surface forming the lower surface of the combustion chamber has a lower surface inclined toward the intake valve. And the inclined lower surface on the exhaust valve side. Is formed into the pent-roof shape with the formed intake valve side inclined upper surface and the exhaust valve-side inclined upper surface as at least the intake valve side inclined upper surface of the piston top surface, the configuration of the recess is provided,
It is possible to achieve both low fuel consumption and high output.

According to the cylinder injection type internal combustion engine piston of the present invention described in claim 17, in addition to the structure described in claim 16, the concave portion is formed in a spherical shape. The compression ratio can be increased while reducing the heat loss. According to the piston for an in-cylinder injection type internal combustion engine of the present invention described in claim 18, in addition to the structure described in claim 16, the bottom surface of the recess is formed to be substantially flat. Can be reduced.

According to the cylinder injection type internal combustion engine piston of the present invention as set forth in claim 19, in addition to the structure of claim 16, a space adjacent to the recess is provided in the vicinity of the spark plug. Due to the configuration in which the recess for ensuring is formed, reliable ignition can be realized and misfire can be eliminated. Further, according to the piston for a direct injection internal combustion engine of the present invention as set forth in claim 20, in addition to the configuration of claim 16, the piston is provided adjacent to the recess and on the exhaust valve side inclined lower surface of the piston. With the configuration in which the recess is formed, a sufficient clearance with the exhaust valve can be secured.

According to the piston for a cylinder injection type internal combustion engine of the present invention as set forth in claim 21, a combustion chamber which is vertically divided by a lower surface of the cylinder head and a top surface of the piston, and an upper surface of the combustion chamber. An intake valve disposed on one side of the combustion chamber, an exhaust valve disposed on the other side of the upper surface of the combustion chamber, and a fuel injection valve disposed to directly inject fuel into the combustion chamber. The cylinder head lower surface forming the upper surface of the combustion chamber 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 ignition is performed. In a piston used in an in-cylinder injection type internal combustion engine in which a plug is arranged near the top of the upper surface of the combustion chamber having the pent roof shape, the piston top surface forming the lower surface of the combustion chamber has a lower surface inclined toward the intake valve. And the inclined lower surface on the exhaust valve side. The intake valve-side inclined upper surface and the exhaust valve-side inclined upper surface are formed in a mountain shape that substantially follows the pent roof shape, and the centers are adjacent to the intake valve-side inclined upper surface of the piston top surface. Due to the configuration in which the concave portion formed by the two spherical surfaces that are formed and the connecting surface that smoothly connects these two spherical surfaces is provided, the surface area of the concave portion is formed to be relatively small while the volume of the concave portion of the piston is increased. Therefore, there is an advantage that fuel efficiency can be improved with almost no deterioration in output characteristics.

[Brief description of drawings]

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

2A and 2B are schematic diagrams showing the shape of a piston as a main part in a cylinder injection type internal combustion engine as a first embodiment of the present invention, in which FIG. 2A is a top view thereof, 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 bottom surface of a cylinder head in a direct injection internal combustion engine as a first embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining a ratio between the total volume of the combustion chamber and the volume of the recess of the 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 characteristics of the engine with a change in the volume ratio of the recessed shape of the piston in the direct injection internal combustion engine as the first embodiment of the present invention.

FIG. 6 is a schematic view of a piston for showing another example of the concave shape of the piston in the direct injection internal combustion engine as the first embodiment of the present invention, (a) is a top view thereof,
(B) is the front view, (c) is A3-A in (b).
It is 3 sectional drawing.

FIG. 7 is a schematic view of a piston for showing another example of the recessed shape of the piston in the direct injection internal combustion engine as the first embodiment of the present invention, (a) is a top view thereof,
(B) is the front view, (c) is A4-A in (b).
FIG. 4 is a sectional view.

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 the operation of the direct injection internal combustion engine as the first embodiment of the present invention.

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

FIG. 11 is a schematic view showing a shape of a piston as a main part in a cylinder injection type internal combustion engine as a second embodiment of the present invention, in which (a) is a top view and (b) is a front view thereof. , (C) is an A2-A2 sectional view in (b).

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

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

FIG. 15 is a plan view showing a piston shape of a cylinder injection type internal combustion engine piston according to a first embodiment of the present invention.

FIG. 16 is a front view showing the piston shape of the cylinder injection type internal combustion engine piston according to the first embodiment of the present invention.

FIG. 17 is a bottom view showing the piston shape of the cylinder injection type internal combustion engine piston according to the first embodiment of the invention.

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

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

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

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

22 is a cross-sectional view showing the piston shape of the cylinder injection type internal combustion engine piston 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 cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 24 is a front view showing a piston shape of a first modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 25 is a bottom view showing the piston shape of a first modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

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

FIG. 27 is a right side view showing the piston shape of a first modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

28 is a rear view showing the piston shape of a first modification of the piston for a cylinder injection internal combustion engine as the first embodiment of the present invention, the rear view being symmetrical to the front view shown in FIG. 24. It is a figure that appears in.

29 is a cross-sectional view showing a piston shape of a first modified example of the cylinder injection type internal combustion engine piston according to the first embodiment of the present invention, and taken along the line AA in the right side view shown in FIG. 27. FIG. It is a figure.

30 is a cross-sectional view showing a piston shape of a second modification of the piston for a cylinder injection internal combustion engine as the first embodiment of the present invention, and B in the front view shown in FIG. 24.
It is a -B sectional view.

FIG. 31 is a plan view showing a piston shape of a second modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 32 is a front view showing a piston shape of a second modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 33 is a bottom view showing the piston shape of a second modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 34 is a left side view showing the piston shape of a second modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 35 is a right side view showing a piston shape of a second modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 36 is a rear view showing a piston shape of a second modification of the in-cylinder injection internal combustion engine piston according to the first embodiment of the present invention, the rear view being symmetrical to the front view shown in FIG. 32. It is a figure that appears in.

37 is a sectional view showing a piston shape of a second modified example of the cylinder injection type internal combustion engine piston according to the first embodiment of the invention, and is a sectional view taken along the line AA in the right side view shown in FIG. 35. It is a figure.

38 is a sectional view showing a piston shape of a second modification of the in-cylinder injection type internal combustion engine piston according to the first embodiment of the present invention, and B in the front view shown in FIG. 32. FIG.
It is a -B sectional view.

FIG. 39 is a plan view showing a piston shape of a third modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

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

FIG. 41 is a bottom view showing a piston shape of a third modified example of the cylinder injection type internal combustion engine piston according to the first embodiment of the invention.

FIG. 42 is a left side view showing the piston shape of a third modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

FIG. 43 is a right side view showing the piston shape of a third modified example of the cylinder injection type internal combustion engine piston as the first embodiment of the invention.

44 is a rear view showing the piston shape of a third modified example of the piston for a cylinder injection internal combustion engine as the first embodiment of the present invention, the rear view being symmetrical to the front view shown in FIG. 40. It is a figure that appears in.

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

FIG. 46 is a sectional view showing a piston shape of a third modification of the in-cylinder injection type internal combustion engine piston according to the first embodiment of the present invention, and B in the front view shown in FIG. 40.
It is a -B sectional view.

FIG. 47 is a plan view showing a piston shape of a cylinder injection type internal combustion engine piston according to a second embodiment of the present invention.

FIG. 48 is a front view showing a piston shape of a cylinder injection type internal combustion engine piston according to a second embodiment of the present invention.

FIG. 49 is a bottom view showing a piston shape of a cylinder injection type internal combustion engine piston according to a second embodiment of the present invention.

FIG. 50 is a left side view showing the piston shape of a cylinder injection type internal combustion engine piston according to a second embodiment of the present invention.

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

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

53 is a sectional view showing a piston shape of a cylinder injection type internal combustion engine piston according to a second embodiment of the invention, and is a sectional view taken along the line AA in the right side view shown in FIG. 51.

54 is a cross-sectional view showing the piston shape of the cylinder injection type internal combustion engine piston 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]

 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 Recess or cavity 25a to 25c Virtual spherical surface 25d Connection surface 26 Flame penetration space 27 Spark plug mounting surface 28 Spark plug mounting portion 29 Buildup portion 30 Piston pin 40 Peripheral end portion 41 Flat part 42 Inflow part 43 Raised part 44 Connection part (bottom surface) CL Cylinder center axis

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kei Kawabe 5-3-8, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (72) Inventor Katsunori Ueda 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Automobile Industry Co., Ltd. (72) Inventor Nobuaki Murakami 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corp. (72) Inventor Hideyuki Oda 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation Co., Ltd. (72) Inventor Kyoya Igarashi 5-3-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation

Claims (21)

[Claims] 1. A combustion chamber that is vertically divided 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. An in-cylinder injection internal combustion engine having an exhaust valve disposed in the combustion chamber and a fuel injection valve disposed so as to inject fuel directly into the combustion chamber, the cylinder forming an upper surface of the combustion chamber. The lower surface of the head is formed in a pent roof shape including an inclined lower surface on the intake valve side formed on the one side and an inclined lower surface on the exhaust valve side formed on the other side, and an ignition plug is formed on the upper surface of the combustion chamber in the pent roof shape. An intake valve-side inclined upper surface which is arranged near the top and is formed so that the piston top surface forming the lower surface of the combustion chamber corresponds to the intake valve-side inclined lower surface and the exhaust valve-side inclined lower surface, respectively. And the pentle having an inclined upper surface on the exhaust valve side A concave portion is provided at least on the intake valve side inclined upper surface of the piston top surface, and the fuel injection valve is provided so as to supply the injected fuel to the concave portion. , A cylinder injection internal combustion engine. 2. The in-cylinder injection internal combustion engine according to claim 1, wherein a ridgeline is formed on the top surface of the piston to divide the intake valve-side inclined upper surface and the exhaust valve-side inclined upper surface. . 3. The in-cylinder injection internal combustion engine according to claim 2, wherein the recess is formed to extend to the exhaust valve side inclined upper surface so as to divide the ridge line. 4. The in-cylinder injection internal combustion engine according to claim 1, wherein the recess is formed by a spherical surface. 5. A flat portion is formed at least on the outer peripheral end portion on the one side of the piston top surface, and the concave portion is formed so as to be gentle from the flat portion, and the intake flow introduced into the combustion chamber enters the concave portion. Formed on an inflow portion at the time of inflow, a gently raised ridge that guides the intake air flow that has flowed into the recess toward the vicinity of the spark plug, and a substantially flat surface that connects the inflow portion and the ridge. The in-cylinder injection internal combustion engine according to any one of claims 1 to 3, characterized in that the in-cylinder injection internal combustion engine is configured with a connected portion. 6. A combustion chamber that is vertically divided 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. An in-cylinder injection internal combustion engine having an exhaust valve disposed in the combustion chamber and a fuel injection valve disposed so as to inject fuel directly into the combustion chamber, the cylinder forming an upper surface of the combustion chamber. The lower surface of the head is formed in a pent roof shape including an inclined lower surface on the intake valve side formed on the one side and an inclined lower surface on the exhaust valve side formed on the other side, and an ignition plug is formed on the upper surface of the combustion chamber in the pent roof shape. An intake valve-side inclined upper surface which is arranged near the top and is formed so that the piston top surface forming the lower surface of the combustion chamber corresponds to the intake valve-side inclined lower surface and the exhaust valve-side inclined lower surface, respectively. And the pent roof due to the inclined upper surface on the exhaust valve side It is formed in a mountain shape that almost conforms to the shape, and on the inclined upper surface on the intake valve side of the piston top surface, from two spherical surfaces whose centers are adjacent to each other and a connecting surface which smoothly connects these two spherical surfaces. An in-cylinder injection internal combustion engine having a formed recess. 7. The centers of the two spherical surfaces are, in a top view of the piston, orthogonal to the direction in which the piston pin is arranged and offset from each other by the same distance with respect to an axis passing through the center of the piston. 7. The in-cylinder injection internal combustion engine according to claim 6, wherein the in-cylinder injection type internal combustion engine is set at a predetermined position. 8. The recess is formed as a part of an imaginary spherical surface centered on an upper portion of the piston on the intake valve side, and the apex of the piston and the lower end of the inclined upper surface of the piston on the intake valve side,
The in-cylinder injection internal combustion engine according to any one of claims 4, 6 and 7, characterized in that it is included in the virtual spherical surface. 9. 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 included in the virtual spherical surface, respectively, and the ignition point of the discharge electrode of the spark plug is included. 9. The in-cylinder injection internal combustion engine according to any one of claims 4, 6 to 8, characterized in that is included in the recess. 10. The exhaust valve side inclined upper surface of the piston,
The inclination angle of the cylinder head is set to be smaller than that of the exhaust valve side lower surface of the cylinder head. The cylinder according to any one of claims 1 to 9, characterized in that a flame penetration space having a substantially wedge-shaped cross section is formed at a position of the top dead center of the piston so as to widen the distance. Internal injection internal combustion engine. 11. A combustion chamber volume when the piston is at a top dead center position, a volume inside the recess and a volume between the piston upper surface above the recess and the cylinder head lower surface, and the piston. Is set at a top dead center position with respect to the total volume of the combustion chamber, and the ratio is set to 0.4 to 0.6. Cylinder injection type internal combustion engine. 12. When the piston is at the top dead center position,
The discharge electrode of the spark plug and the surface of the recess are arranged so as to be close to each other.
1. A cylinder injection internal combustion engine according to any one of 1. 13. When the piston is at the top dead center position,
The in-cylinder injection internal combustion engine according to any one of claims 1 to 12, characterized in that the interval between the piston and the exhaust valve is set to be between 5 mm and 8 mm. 14. When the piston is at the top dead center, the distance between the piston and the exhaust valve is smaller than the distance between the piston and the intake valve. The in-cylinder injection internal combustion engine according to any one of claims 1 to 6, which is characterized in that. 15. 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 formed substantially flat, respectively. The in-cylinder injection type internal combustion engine according to claim 1. 16. A combustion chamber that is vertically divided 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. And a fuel injection valve disposed so as to inject fuel directly into the combustion chamber, and the cylinder head lower surface forming the upper surface of the combustion chamber is formed on the one side. A cylinder in which a sloping lower surface on the intake valve side and a lower sloping lower surface on the exhaust valve side formed on the other side are formed in a pent roof shape, and an ignition plug is disposed near the top of the combustion chamber upper surface of the pent roof shape. In a piston used for an injection type internal combustion engine, an intake valve side inclined surface formed so that the piston top surface forming the lower surface of the combustion chamber corresponds to the intake valve side inclined lower surface and the exhaust valve side inclined lower surface, respectively. The upper surface and the exhaust valve side inclined upper surface Is formed in a Ntorufu shape,
A cylinder injection type internal combustion engine piston, characterized in that a recess is provided at least on the intake valve side inclined upper surface of the piston top surface. 17. The cylinder injection type internal combustion engine piston according to claim 16, wherein the recess is formed in a spherical shape. 18. The cylinder injection type internal combustion engine piston according to claim 16, wherein a bottom surface of the recess is formed to be substantially flat. 19. The piston for a cylinder injection internal combustion engine according to claim 16, wherein a recess is formed adjacent to the recess to secure a space near the spark plug. 20. A recess for securing a space near the exhaust valve is formed on the exhaust valve side inclined lower surface of the piston adjacent to the recess, and the recess is formed. Cylinder injection type piston for internal combustion engine. 21. A combustion chamber which is vertically divided 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. And a fuel injection valve disposed so as to inject fuel directly into the combustion chamber, and the cylinder head lower surface forming the upper surface of the combustion chamber is formed on the one side. A cylinder in which a sloping lower surface on the intake valve side and a lower sloping lower surface on the exhaust valve side formed on the other side are formed in a pent roof shape, and an ignition plug is disposed near the top of the combustion chamber upper surface of the pent roof shape. In a piston used for an injection type internal combustion engine, an intake valve side inclined surface formed so that the piston top surface forming the lower surface of the combustion chamber corresponds to the intake valve side inclined lower surface and the exhaust valve side inclined lower surface, respectively. Due to the upper surface and the inclined upper surface on the exhaust valve side, Is formed in a mountain shape as substantially along the Torufu shape, the intake valve side inclined upper surface of the piston top surface, the two flanked the central one another spherical and of these 2
A cylinder injection type internal combustion engine piston, characterized in that a recess formed by a connection surface that smoothly connects two spherical surfaces is provided.