JP3298361B2 - In-cylinder injection internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type internal combustion engine which is of a spark ignition type and directly injects fuel into a combustion chamber.

[0002]

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

[0003] The fuel injected into the intake port is supplied into the combustion chamber together with the air sucked in the intake stroke, mixed with the air, ignited by a spark plug, and burned. On the other hand, in a diesel engine mainly using light oil or the like as fuel, fuel is directly injected into a combustion chamber, and the fuel is spontaneously ignited by compressed air in the combustion chamber.

In the meantime, there has been proposed an in-cylinder internal combustion engine in which the fuel is injected directly into the combustion chamber of the above gasoline engine to improve the responsiveness of the engine. Here, such a direct injection type internal combustion engine will be briefly described with reference to the drawings. FIG. 11 is a schematic sectional view showing a conventionally proposed direct injection type internal combustion engine as described above. In the figure, reference numeral 1 denotes an injector, 2 denotes a piston, 3 denotes a combustion chamber, 4 denotes an intake valve, 5 denotes an exhaust valve, 6 denotes a spark plug, 7 denotes a cylinder block, 8 denotes a cylinder head, and 9 denotes an intake port. Reference numeral 10 denotes an exhaust port.

In this direct injection type internal combustion engine, the injection hole of the injector 1 is provided directly in the combustion chamber 3, and the fuel is directly injected into the combustion chamber 3. Further, the injector 1 is controlled by, for example, a controller (not shown), and an appropriate amount of fuel is injected from the injector 1 at an appropriate timing. Then, the fuel is mixed in the combustion chamber 3 with air sucked from an intake port 9 provided substantially upright above the intake valve 4 to generate an air-fuel mixture. afterwards,
The mixture is ignited by a spark plug 6 in the combustion chamber 3,
After expansion (explosion), the gas is discharged from the exhaust port 10.

In such an in-cylinder injection type internal combustion engine, a longitudinal vortex can be formed in a cylinder and fuel can be injected into the longitudinal vortex. It becomes possible. Then, an air-fuel mixture having a required concentration (fuel concentration near the stoichiometric air-fuel ratio) is formed in accordance with the position of the ignition plug 6, and the fuel in the air-fuel mixture is supplied to the ignition plug 6. (High air-fuel ratio), that is, a so-called stratified lean combustion operation can be performed.

[0007]

By the way, ordinary MP
In the I (multipoint injection) engine,
Since a substantially uniform air-fuel mixture is sucked into the cylinder,
During the compression stroke, a combustible air-fuel mixture exists around the ignition plug, and combustion is performed efficiently. On the other hand, in the above-described in-cylinder injection type engine, the fuel injection timing is controlled according to the operation state of the engine, and the fuel injection may be performed in the compression stroke. In this case, the air-fuel mixture is formed in a layered form of air and fuel in the combustion chamber as described above, and at a normal ignition plug ignition position, a sufficient concentration of the combustible mixture at the discharge electrode position of the ignition plug at the time of ignition. May not exist. Therefore, in such a case, there is a problem that the combustion efficiency is impaired.

In Japanese Utility Model Laid-Open Publication No. 4-27120, a concave groove is formed on the top surface of the piston from below the spark plug to below the fuel injection valve, and the injected fuel along the injection axis of the fuel injection valve is formed at an acute angle. A technique is disclosed in which the shape of the concave inner wall surface and the fuel injection timing are set so as to collide with the concave inner wall surface of the concave groove. Also, Japanese Patent Application Laid-Open No. Hei 4-22422
No. 9 discloses a groove on the top surface of the piston extending from below the spark plug to below the fuel injection valve, a concave portion on the top surface of the piston below the spark plug, opening above the groove, and a groove. There is disclosed a technology in which a step formed in an arc shape is provided between the fuel injection valve and the recess so that fuel from the fuel injection valve is collected around an ignition plug.

However, in such a technique, it is necessary to form two concave portions in the piston.
The surface area of the piston becomes large. This allows
There is a possibility that heat loss increases and output decreases. Japanese Patent Application Laid-Open No. 6-10674 discloses that the fuel injection direction of a fuel injection valve is set to two directions having different fuel amounts, and the ratio of the fuel amount injected in these two directions is determined according to the load state of the engine. Techniques for changing are disclosed. However, there is a problem that it is quite difficult and impractical to finely control the proportion of fuel injected in two directions in this way. Further, since a special fuel injection valve is required, there is a problem that the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a direct injection internal combustion engine in which the fuel in a combustion chamber is reliably ignited at a low cost and combustion efficiency is improved. The purpose is to do.

[0011]

Therefore, in the direct injection internal combustion engine according to the first aspect of the present invention, fuel is directly injected into the combustion chamber, and the fuel injected into the combustion chamber is burned.
A spark plug with a discharge electrode protruding
In withered-cylinder injection type internal combustion engine, the intake port or downward
On the spherical surface formed continuously from the lower part of the spark plug
And a fuel injection valve for injecting fuel into the recess, a mounting portion for mounting the spark plug on a cylinder head is formed, and a part of the mounting portion is a cylinder. The piston is formed so as to protrude into the combustion chamber from the combustion chamber forming surface of the head so that the discharge electrode of the ignition plug is located in the recess of the piston when the piston is raised to the top dead center position. It is characterized by being arranged.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the in-cylinder injection type internal combustion engine of the present invention has a padding around the mounting portion on the combustion chamber forming surface of the cylinder head. It is characterized in that a part is formed. According to a third aspect of the present invention, there is provided the in-cylinder injection type internal combustion engine of the present invention, in addition to the configuration of the first or second aspect, further comprising a part of the mounting portion.
Is more protruding into the combustion chamber than the combustion chamber forming surface of the cylinder head.
And the discharge of the spark plug
The electrode protrudes from the spark plug body,
When the piston rises to the top dead center position, the spark plug is released.
The electrode is disposed so as to be located in the recess of the piston .

[0013]

[0014]

According to the first aspect of the present invention, the fuel is directly injected into the combustion chamber by the fuel injection valve mounted on the mounting portion formed on the cylinder head. At this time, the fuel is supplied from below the intake port to the ignition plug.
Is injected toward a concave portion on a spherical surface that is formed continuously below the ring . It also burns fuel injected into the combustion chamber.
The piston rises to the top dead center position because part of the spark plug with the discharge electrode protruding from the cylinder head protrudes into the combustion chamber beyond the combustion chamber forming surface of the cylinder head. Then, the discharge electrode of the ignition plug is located in the recess of the piston, and when the discharge is performed by the ignition plug, the highly concentrated fuel present in the recess is reliably ignited. As a result, combustion efficiency is improved, and both output and fuel efficiency can be achieved.

In the above-described in-cylinder injection type internal combustion engine according to the second aspect of the present invention, the built-up portion formed around the mounting portion on the combustion chamber forming surface of the cylinder head forms the combustion chamber on the outer peripheral portion of the ignition plug. Exposure to is suppressed. This prevents carbon or the like from adhering to the ignition plug, and facilitates operations such as replacement of the ignition plug. In addition, since the lower portion of the spark plug is protected by the overlay, the durability of the spark plug itself is also improved. Further, the heat applied to the ignition plug can be released to the cylinder head via the built-up portion, thereby improving the durability against heat.

In the cylinder injection type internal combustion engine according to the third aspect of the present invention, a part of the combustion chamber forming surface of the cylinder head is closer to the surface than the combustion chamber forming surface of the cylinder head.
The mounting part is formed so as to protrude into the combustion chamber, and the ignition plug
By projecting the discharge electrode from the lug body, the piston
When rising to the top dead center position, the discharge electrode of the spark plug
Located in the recess of the
Make it fire.

[0017]

EXAMPLES In the following, the drawings and will be described in-cylinder injection type internal combustion engine as an embodiment of the present invention, FIG. 1 is a schematic sectional view showing a configuration of the combustion chamber, FIG. 2 (a) ~ (C)
Fig. 3 is a schematic view showing the shape of a piston as its main part,
FIG. 4 is a diagram 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 between the total volume of the combustion chamber and the volume of the concave portion of the piston.
(A) and (b) are graphs for explaining the change in the characteristics of the engine accompanying the change in the volume ratio of the concave shape of the piston, FIGS. 6 (a) to 6 (c) and FIGS. (C) is a schematic diagram showing another example of the concave shape of the piston, FIGS. 8 and 9 are graphs for explaining the operation thereof,
FIG. 10 is a graph showing a change characteristic of fuel consumption and HC emission amount due to a difference in the shape of the combustion chamber.

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

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

The top surface of the piston 2 forming the lower surface of the combustion chamber 3 is inclined toward the center of the piston 2 corresponding to the intake valve-side inclined lower surface 8a and the exhaust valve-side inclined lower surface 8b, respectively. An intake valve side inclined upper surface 2a and an exhaust valve side inclined upper surface 2b are formed, and these inclined upper surfaces 2a, 2b are formed.
By b, the top surface of the piston 2 is formed in a mountain shape almost along the pent roof shape.

On the intake valve-side inclined upper surface 2a of the piston 2, there is formed a concave portion (hereinafter simply referred to as a cavity) 25 as shown in FIGS. 1 and 2 (a) to 2 (c). The cavity 25 is formed in a spherical shape curved downwardly convexly, and is formed as a part of an imaginary spherical surface 25 a having a center at an upper portion of the piston 2 on the intake valve 4 side.

Although not shown, an intake port (see FIG. 11 ) opening into the combustion chamber 3 extends substantially upright above the intake valve 4, and the intake air flows through this intake port. When taken into the combustion chamber 3, the intake air flows toward the lower piston 2, and then is guided along the cavity 25 of the piston 2 and flows upward to form a tumble flow (longitudinal vortex flow). I have.

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

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

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

Thus, by setting the volume ratio of the cavity 25 to a predetermined value, it is possible to achieve a good balance between an improvement in fuel efficiency and an increase in output. Incidentally, the shape of the concave portion 25 is not limited to a spherical cavity, and may be, for example, as shown in FIGS.
Although cavities 25A and 25B having a substantially rectangular cross section as shown in (a) to (c) are conceivable, the cavities 25A and 25B having such a shape are somewhat disadvantageous in terms of fuel efficiency and output.

Therefore, in the direct injection internal combustion engine of the present invention, the shape of the cavity 25 is formed into a spherical shape as shown in FIGS. 2 (a) to 2 (c). The shape of the cavity 25 has an advantage that the cavity surface area with respect to the cavity volume Va of the piston 2 can be minimized. By minimizing the cavity surface area in this way, heat loss can be reduced and combustion efficiency can be improved.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

According to the flame infiltration space 26, first, the flame which has started burning around the vicinity of the electrode 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 to the center side of the combustion chamber 3 and the flame propagates to the end portion of the combustion chamber 3 with a relatively small gap without delay with respect to the other parts of the combustion chamber 3 and uniform combustion without unevenness Can be realized.

Further, by forming the space cross section of the combustion chamber 3 on the side of the exhaust valve 5 in 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 is not changed. It also has the advantage of not affecting the settings at all.
Cylinder injection type internal combustion engine as a real施例of the present invention, which is configured as described above, it is possible to obtain the following effects.

First, a spherical cavity 25 is formed on the intake valve-side inclined upper surface 2a of the piston 2 as shown in FIGS. 2 (a) to 2 (c). 6
The advantage that the output and fuel efficiency can be improved with respect to the piston 2 having the cavities 25A and 25B whose cross sections are substantially rectangular as shown in (a) to (c) and FIGS. 7 (a) to (c). is there.

That is, by forming the shape of the cavity 25 into a spherical shape, the cavity surface area with respect to the cavity volume Va of the piston 2 can be minimized. Thereby, heat loss can be reduced, and combustion efficiency can be improved. In addition, by forming the cavity 25 in a spherical shape, the formation of a vortex flow, that is, a tumble flow due to the intake air flow in the combustion chamber 3 is promoted, and there is an advantage that stratified combustion is easily performed.

FIG. 9 shows such a spherical cavity 25.
And a cavity 25 having a substantially rectangular cross section
5A and 5B are graphs showing a comparison with a piston 2 having A and 25B.
For the fuel consumption and the maximum torque (shown by points A and B in the figure), the piston 2 having the spherical cavity 25
As shown at point C, both fuel economy and maximum torque can be improved.

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

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

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

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

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

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

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

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

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

As described above in detail, according to the in-cylinder injection type internal combustion engine of the present invention, fuel is directly injected into the combustion chamber, and the fuel injected into the combustion chamber is burned.
A spark plug with a discharge electrode protruding
In includes a cylinder injection type internal combustion engine, the intake port lower
From the bottom to the spark plug
A piston having a recess above the top surface, and a fuel injection valve for injecting fuel toward the inside of the recess, is formed a mounting portion for mounting the ignition plug in shea cylinder head, a portion of the mounting portion Is formed so as to protrude into the combustion chamber from the combustion chamber forming surface of the cylinder head, and the discharge electrode of the ignition plug is located in the recess of the piston when the piston is raised to the top dead center position. With such a configuration, the discharge electrode can be disposed in the vicinity of the recess by using a conventionally used normal ignition plug. Thereby, there is an advantage that the discharge electrode is surely located in the portion where the fuel concentration is high, and the combustion efficiency can be improved at low cost. Also in the combustion chamber
It is easy to form a bubble flow and spray
The injected fuel is stratified by this tumble flow,
Reliable ignition by the discharge electrode of the ignition plug located in the part
Is effected.

According to the cylinder injection type internal combustion engine of the present invention described in claim 2, in addition to the configuration of claim 1,
With the configuration in which the build-up portion is formed around the mounting portion on the combustion chamber forming surface of the cylinder head, the lower end portion of the spark plug is prevented from being directly exposed to the combustion chamber,
Adhesion of carbon or the like to the screw portion below the spark plug is prevented. Thereby, there is an advantage that workability such as replacement of a spark plug is improved. Also, the lower part of the spark plug
There is an advantage that the durability of the spark plug itself is also improved by being protected by the built-up portion. Furthermore, since the heat applied to the ignition plug can be released to the cylinder head through the build-up portion, there is an advantage that the durability against heat can be improved.

[0065]

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, a part of the mounting portion has a combustion chamber forming surface of a cylinder head. And the discharge electrode of the spark plug protrudes from the spark plug body, so that the discharge of the spark plug when the piston rises to the top dead center position. With the configuration in which the electrode is disposed near the concave portion of the piston, the discharge electrode can be reliably disposed in a portion where the fuel concentration is high while maintaining the durability of the discharge electrode of the ignition plug. There is an advantage that the combustion efficiency can be improved.

[Brief description of the drawings]

1 is a schematic sectional view showing the configuration of a combustion chamber in the cylinder injection type internal combustion engine as a real施例of the present invention.

[Figure 2] A schematic view showing the shape of a piston as a main part of a cylinder injection type internal combustion engine as a real施例the present invention, (a) is its top view, (b) is a front view thereof, (C)
FIG. 2 is a sectional view taken along line A1-A1 in FIG.

It is a diagram illustrating a relative positional relationship between the lower surface of the piston top surface and the cylinder head of the cylinder injection type internal combustion engine as a real施例of the present invention; FIG.

4 is a schematic diagram for explaining the volume and the ratio of the concave portion of the total volume and the piston of the combustion chamber in the cylinder injection type internal combustion engine as a real施例of the present invention.

5 is a graph for explaining a change in the characteristics of the engine with changes in the volume ratio of the concave shape of the piston in the cylinder injection type internal combustion engine as a real施例of the present invention.

[6] A schematic view of a piston for illustrating another example of a concave shape of the piston in the cylinder injection type internal combustion engine as a real施例the present invention, (a) is a top view thereof, (b) Is a front view thereof, and (c) is a sectional view taken along line A3-A3 in (b).

[Figure 7] A schematic view of a piston for illustrating another example of a concave shape of the piston in the cylinder injection type internal combustion engine as a real施例the present invention, (a) is a top view thereof, (b) Is a front view thereof, and (c) is a sectional view taken along line A4-A4 in (b).

8 is a graph for explaining the operation in the direct injection type internal combustion engine as a real施例of the present invention.

9 is a graph for explaining the operation in the direct injection type internal combustion engine as a real施例of the present invention.

10 is a graph showing a change characteristic of fuel consumption and HC emissions due to the difference in the shape of the combustion chamber in the cylinder injection type internal combustion engine as a real施例of the present invention.

FIG. 11 shows a configuration of a combustion chamber of a conventional direct injection internal combustion engine.
It is a typical sectional view shown.

Continued on the front page (72) Inventor Kenji Goshima 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Kyoya Igarashi 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi (56) References JP-A-5-65811 (JP, A) JP-A-5-86992 (JP, A) JP-A-5-44473 (JP, A) JP-A-4-224229 ( JP, A) JP-A-6-10674 (JP, A) JP-A-5-240047 (JP, A) JP-A 5-1826 (JP, U) JP-A 1-124042 (JP, U) JP-A Hei 4-27120 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 23/10 F02F 3/28 F02F 13/00 301

Claims (3)

(57) [Claims] 1. A fuel directly into the combustion chamber is injected, combustion
Discharge to burn the fuel injected into the room
In an in- cylinder injection type internal combustion engine equipped with a spark plug provided with a protruding electric electrode , continuously from below the intake port to below the spark plug.
A piston having a recess on the formed spherical in the top surface, and a fuel injection valve for injecting fuel toward the inside of the recess, the mounting portion for mounting the ignition plug in shea cylinder head is formed, with said mounting A part of the portion is formed so as to protrude into the combustion chamber from the combustion chamber forming surface of the cylinder head, and the discharge electrode of the ignition plug is connected to the concave portion of the piston when the piston rises to the top dead center position. An in- cylinder injection type internal combustion engine, which is disposed so as to be located inside the internal combustion engine. 2. The direct injection internal combustion engine according to claim 1, wherein a built-up portion is formed around the mounting portion on a combustion chamber forming surface of the cylinder head. 3. A part of the mounting part is a cylinder head combustion.
It is formed so as to protrude into the combustion chamber from the chamber formation surface.
And the discharge electrode of the spark plug is
By projecting from the body, the piston moves to the top dead center position.
When the discharge electrode of the spark plug rises,
3. The direct injection internal combustion engine according to claim 1, wherein the internal combustion engine is disposed so as to be located in the recess .