JPH0533656A - Direct injection internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] In a direct injection diesel engine, to improve atomization of injected fuel and prevent cracks from occurring between valve portions of a cylinder head. [Structure] A pair of air supply valves are arranged on one side of the cylinder head inner wall surface 3a, and a pair of exhaust valves are arranged on the other side of the cylinder head inner wall surface 3a. The fuel injection valve 6 is arranged at the center of the cylinder head inner wall surface 3a. A cavity 14 is formed in the center of the top surface of the piston 2. Protrusions 18 are formed on the inter-valve portions 3b on the inner wall surface of the cylinder head located between the intake and exhaust valves. When the piston 2 is located near the top dead center, the fuel F ₁ is injected from each nozzle opening 16 of the fuel injection valve 6 toward each protrusion 18, and the fuel F ₂ that collides with the protrusion 18 and is reflected Diffuse into the cavity 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection internal combustion engine.

[0002]

2. Description of the Related Art A fuel injection valve is arranged in the center of the inner wall surface of a cylinder head, and a cavity is formed in the center of the top surface of the piston. A semi-circular concave section is formed, and the nozzle port of the fuel injection valve is radiated from the cavity side wall when the piston is located near top dead center to the area extending from the cavity side wall to the concave section on the cylinder head inner wall surface. A direct injection type diesel engine having a plurality of holes formed therein is known (see Japanese Utility Model Laid-Open No. 1-142525). In this direct-injection diesel engine, fuel is radially injected from the fuel injection valve toward the cavity side wall surface and the recess on the cylinder head inner wall surface near the end of the compression stroke, and the fuel and recessed portion that collide with the cavity side wall surface and reflect The fuel that has collided with and is reflected by the fuel is diffused while being mixed with each other inside the cavity, thus ensuring good mixing of the injected fuel and the air.

[0003]

By the way, in a direct injection internal combustion engine having an intake valve and an exhaust valve on the inner wall surface of the cylinder head, the intake valve and the exhaust valve are provided so that good intake efficiency and exhaust efficiency can be obtained. Since the opening area of the exhaust valve is made as large as possible, the wall width of the inter-valve portion of the cylinder head located between the intake valve and the exhaust valve is formed to be considerably narrow. Since heat is difficult to escape in the valve-to-valve portions having a narrow wall thickness, the valve-to-valve portion has a particularly high temperature, and as a result, there is a problem that cracks are easily generated in the valve-to-valve portion due to thermal stress. Even if you try to circulate the cooling water between the valves to solve this problem,
As described above, there is not enough space for circulating the cooling water because the wall width of the valve portion is narrow. On the other hand, if the injected fuel collides with the intervalve portion of the cylinder head inner wall surface exhibiting this high temperature, the intervalve portion can be cooled by the injected fuel, and the injected fuel receives heat from the intervalve portion. The atomization and atomization of the injected fuel can be improved.
However, in the above direct injection diesel engine, there is no suggestion of the positional relationship between the recess formed on the inner wall surface of the cylinder head and the intake valve and the exhaust valve. It does not suggest any positional relationship with the department.

[0004]

In order to solve the above problems, according to the present invention, an air supply valve and an exhaust valve are arranged on the inner wall surface of a cylinder head, and a cavity is formed at the center of the piston top surface. In a direct injection internal combustion engine in which fuel is supplied into the cavity from a fuel injection valve arranged on the cylinder head inner wall surface, between the valves on the cylinder head inner wall surface located between the intake valve and the exhaust valve. A protrusion or a recess is provided in the portion, and fuel is injected from the fuel injection valve toward the protrusion or the recess so that the fuel reflected by the collision with the protrusion or the recess is directed into the cavity.

Further, in order to solve the above problems, according to the present invention, an intake valve and an exhaust valve are arranged on the inner wall surface of the cylinder head, a cavity is formed at the center of the piston top surface, and the inner wall surface of the cylinder head is formed. In a direct injection internal combustion engine in which fuel is supplied into the cavity from a fuel injection valve arranged above, a fuel injection collision wall surface is provided on the side wall surface of the cavity or inside the cavity, and fuel injection collision occurs from the fuel injection valve. Fuel is injected toward the wall surface and injected fuel Collision A part of the fuel that collides against the wall surface and is reflected is directed to the intervalve portion of the inner wall surface of the cylinder head located between the intake valve and the exhaust valve, and the injected fuel is also injected. The remaining portion of the fuel that has collided against the collision wall surface and is reflected is directed into the cavity.

[0006]

According to the first aspect of the present invention, the fuel injected from the fuel injection valve collides with and is reflected by the projections or recesses provided in the intervalve portion of the inner wall surface of the cylinder head, and the reflected fuel is diffused. Head into the cavity. In the invention described in claim 2, the fuel injected from the fuel injection valve collides against the injected fuel collision wall surface and is reflected, and a part of the reflected fuel is directed toward the intervalve portion of the cylinder head inner wall surface and is reflected. The remaining part of the is diffused into the cavity.

[0007]

1 to 3 show a case where the present invention is applied to a direct injection type two-cycle diesel engine. 1 and 2
1 is a cylinder block, 2 is a piston that reciprocates in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, and 4 is formed between the inner wall surface 3 a of the cylinder head 3 and the piston 2. The respective combustion chambers are shown. A fuel injection valve 6 is arranged at the center of the cylinder head inner wall surface 3a. Also, the inner wall surface 3a of the cylinder head
A pair of air supply valves 8 are arranged on one side, and a pair of exhaust valves 9 are arranged on the other side of the cylinder head inner wall surface 3a. In the cylinder head 3, an air supply port 11 is formed for the air supply valve 8 and an exhaust port 12 is formed for the exhaust valve 9.

On the other hand, a cavity 14 is formed at the center of the top surface of the piston 2. As shown in FIG. 1, the side wall surface 14a of the cavity 14 has a substantially cylindrical shape that slightly expands downward, and the bottom wall surface 14b of the cavity 14 has a shape in which its central portion is slightly raised as compared with the peripheral portion. . As can be seen from FIGS. 1 and 2, the cavity 14 and the fuel injection valve 6 are both arranged on the cylinder axis.

Further, substantially hemispherical projections 18 are formed on the intervalve portions 3b of the cylinder head inner wall surface 3a located between the intake valve 8 and the exhaust valve 9, respectively. These four protrusions 18 are slightly inside the peripheral portion of the cavity 14 formed on the top surface of the piston 2, that is, the fuel injection valve 6
It is formed so as to be located on the side. At the tip of the fuel injection valve 6, there are four nozzle openings 16 facing the protrusions 18.
Are radially formed, and fuel is injected from the nozzle openings 16 toward the corresponding protrusions 18, respectively.

FIG. 3 shows an example of fuel injection timing from the fuel injection valve 6. In FIG. 3, I _r shows an example of fuel injection timing during engine operation with a small fuel injection amount, for example, engine low rotation and low load operation, and I _h during engine operation with a large fuel injection amount, for example engine high rotation. An example of fuel injection timing at the time of high load operation is shown. From FIG. 3, the fuel injection I _r during engine operation with a small fuel injection amount is the top dead center TDC.
It started at a point just before the TDC and was almost at TDC.
It can be seen that it will be terminated at the time of. On the other hand, it can be seen that the fuel injection I _h injection end timing with injection start timing is advanced as compared with the fuel injection I _r during the fuel injection amount is large engine operation is slow. This fuel injection I
_It can be seen that at _h , the injection period before top dead center and the injection period after top dead center are almost equal.

As shown in FIGS. 1 and 2, when the piston 2 is positioned near the top dead center, it is formed from each nozzle port 16 of the fuel injection valve 6 on each valve interspace 3b on the inner wall surface of the cylinder head. The fuel F ₁ is injected toward the protrusion 18.
The injected fuel F ₁ collides with each protrusion 18 and is reflected in a wide range toward the cavity 14 as indicated by F ₂ in FIG. 1, and thus the fuel F ₂ is spread over a wide area in the cavity 14. Be spread. As a result, the fuel F ₂ and the air in the cavity 14 are mixed well.

By the way, the opening area of the air supply valve 8 and the opening area of the exhaust valve 9 are set to be as large as possible in order to obtain good air supply efficiency and exhaust efficiency. The wall width of each intervalve portion of the cylinder head 3 located is formed to be considerably narrow as shown in FIG. Since heat is hard to escape in these valve-to-valve portions having a narrow wall thickness, the valve-to-valve portion exhibits a particularly high temperature. In the embodiment shown in FIGS. 1 and 2, the injected fuel F is injected into the projection 18 formed on the intervalve portion 3b on the inner wall surface of the cylinder head which exhibits a particularly high temperature.
_{Since 1 is made} to collide, the injected fuel receives heat from the protrusion 18, and as a result, atomization and atomization of the fuel are promoted. Such finely atomized fuel is shown in FIG.
Since it is diffused into the cavity 14 as indicated by F ₂ in (1), a good air-fuel mixture can be formed in the cavity 14. On the other hand, the inter-valve portion of the cylinder head 3 is cooled by the injected fuel F ₁ colliding with the protrusion 18,
In this way, cracks are prevented from being generated in the inter-valve portion of the cylinder head 3 due to thermal stress.

FIG. 4 shows a second embodiment. In the embodiment shown in FIG. 4, recesses 20 are formed on the respective intervalve portions 3b of the cylinder head inner wall surface 3a located between the intake valve 8 and the exhaust valve 9, and the piston 2 is located near the top dead center. The fuel F ₁ is injected from each nozzle port 16 of the fuel injection valve 6 toward each recess 20 at the time of being located at. FIG. 5 shows a third embodiment. In the embodiment shown in FIG. 5, three air supply valves 8 and two exhaust valves 9 are arranged on the cylinder head inner wall surface 3a, and the protrusions 2 are formed on the inter-valve portions 3b of the cylinder head inner wall surface.
2 is formed. Five nozzle openings 16 are radially formed at the tip of the fuel injection valve 6 toward these projections 22, and the corresponding projections 2 are formed from these nozzle openings 16.
Fuel F ₁ is injected toward each of the two.

A fourth embodiment is shown in FIGS. 6 to 8. Figure 1
2 and the embodiment shown in FIG. 4 and FIG.
In the embodiment shown in FIG. 7, the projections 18, 22 or the recesses 20 are formed on the intervalve portion 3b on the inner wall surface of the cylinder head, but in the embodiment shown in FIGS. 6 to 8, the intervalve portion on the inner wall surface of the cylinder head is formed. No protrusion or recess is formed on 3b, and the cylinder head inner wall surface 3a is flat over the entire surface. On the other hand, on the upper portion of the side wall surface 14a of the cavity 14 formed on the top surface of the piston 2, there are formed four substantially hemispherical projections 24 that constitute the injected fuel collision wall surface. Each protrusion 24 is located immediately below each intervalve portion 3b on the inner wall surface of the cylinder head. The tip of the fuel injection valve 6 has a protrusion 24 when the piston 2 is located near the top dead center.
The four nozzle openings 16 are radially formed toward each of the nozzles, and the fuel is injected from each of the nozzle openings 16 toward the corresponding protrusion 24.

During operation of the engine with a small amount of fuel injection, for example, under low engine speed and low load operation, as shown in FIG. 3, the fuel injection I _r is started a little before the top dead center TDC, and the top dead center TDC is almost reached. At the point of time, the fuel injection I _r is ended. The state of fuel injection at this time is shown in FIG. At this time, the fuel F ₁ injected from each nozzle opening 16 of the fuel injection valve 6 collides with a portion below the center of each hemispherical projection 24 as shown in FIG. Therefore,
Each injected fuel F ₁ that collides with each protrusion 24 receives the cavity 1
4 is not reflected to the outside of the cavity 4 and all of the fuel is removed from the cavity 1 as indicated by F ₃ in FIG.
It is reflected in a wide area toward the inside of 4. Since the injected fuel collides with the protrusions 24 in this way, atomization of the fuel is promoted and the fuel is diffused over a wide area in the cavity 14, so that the fuel and the air in the cavity 14 are well conditioned. To be mixed.

On the other hand, at the time of engine operation with a large fuel injection amount, for example, at high engine speed and high load operation, as indicated by I _h in FIG. 3, the injection start timing is advanced as compared with the engine operation with a small fuel injection amount. The injection end timing is delayed. FIG. 7 shows the state of the fuel injection when the piston 2 is located slightly below the top dead center in the initial and final stages of the fuel injection timing I _h . The fuel injection timing I
The state of fuel injection in the middle period of _h , that is, when the piston 2 is located substantially at the top dead center is similar to the case of fuel injection I _r during engine operation in which the fuel injection amount is small as shown in FIG.

The fuel F ₁ injected from each nozzle opening 16 of the fuel injection valve 6 at the early and final stages of the fuel injection timing I _h is slightly more than the center of each hemispherical projection 24 as shown in FIG. It collides with the protrusion 24 centering on the upper position. Therefore, a part of the injected fuel that collides with the protrusion 24 is shown in FIG.
In FIG. 7, the remaining portion of the injected fuel that is reflected toward the intervalve portion 3b of the inner wall surface of the cylinder head while being diffused and reflected by the protrusion 24 is indicated by F ₄ in FIG.
_As shown by ₅ , the light is reflected toward the inside of the cavity 14 while being diffused. The reflected fuel portion F ₄ collides with the intervalve portion 3b on the inner wall surface of the cylinder head to be reflected, and then advances toward the inside of the cavity 14 while diffusing. At this time, since the intervalve portion 3b on the inner wall surface of the cylinder head exhibits a particularly high temperature as described above, the fuel portion F ₄ receives heat from the intervalve portion 3b when it collides with the intervalve portion 3b, and as a result, the fine particles of fuel are Atomization and atomization are promoted. On the other hand, the inter-valve portion of the cylinder head 3 is cooled by the fuel portion F ₄ , thus preventing the inter-valve portion of the cylinder head 3 from cracking due to thermal stress.

By the way, in the present embodiment, as described above, when the engine is operated with a small fuel injection amount, all the injected fuel that has collided with the projection 24 over the entire injection period of the fuel injection I _r is reflected toward the inside of the cavity 14. (See FIG. 6), the intervalve portion of the cylinder head 3 is not cooled by the fuel. This is because it is not necessary to cool the intervalve portion of the cylinder head 3 when the engine is operated with a small amount of fuel injection, because the intervalve portion of the cylinder head 3 does not reach such a high temperature that cracks occur.

FIG. 9 shows a fifth embodiment. In the embodiment shown in FIG. 9, four substantially hemispherical recesses 26 forming the injected fuel collision wall surface are formed on the upper portion of the cavity side wall surface 14a. Each recess 26 is located immediately below each intervalve portion 3b on the inner wall surface of the cylinder head. As shown in FIG. 9, when the piston 2 is located near the top dead center, the fuel F ₁ is injected from each nozzle opening 16 of the fuel injection valve 6 toward each recess 26. A part of the injected fuel colliding with each recess 26 is diffused and reflected toward the intervalve portion 3b on the inner wall surface of the cylinder head as shown by F ₄ in FIG. The remaining portion is reflected while being diffused into the cavity 14 as indicated by F ₅ in FIG. In the embodiment shown in FIGS. 6 to 8, as described above, when the engine is operating with a small amount of fuel injection, the fuel reflected by colliding with the protrusion 24 does not hit the intervalve portion 3b on the inner wall surface of the cylinder head. (See Figure 6)
However, in this embodiment, as can be seen from FIG. 9, even when the engine is operated with a small amount of fuel injection, a part of the fuel F ₄ reflected by colliding with the recess 26 collides with the intervalve portion 3b on the inner wall surface of the cylinder head. ing.

FIG. 10 shows a sixth embodiment. In the embodiment shown in FIG. 10, three air supply valves 8 and two exhaust valves 9 are arranged on the cylinder head inner wall surface 3a. In addition, a ring-shaped protrusion 28 that forms the injected fuel collision wall surface is formed on the upper portion of the cavity side wall surface 14a. The ring-shaped protrusion 28 has a substantially semicircular cross-sectional shape over the entire circumference thereof. At the tip of the fuel injection valve 6, there is a protrusion 28 located immediately below each intervalve portion 3b on the inner wall surface of the cylinder head.
Five nozzle openings 16 are formed radially toward the portion, and when the piston 2 is located near the top dead center, the projections 28 located directly below the intervalve portions 3b from the nozzle openings 16 are located.
Fuel F ₁ is injected toward the portion.

FIG. 11 shows a seventh embodiment. In the embodiment shown in FIG. 11, a ring-shaped ring member 30 is arranged in the upper portion inside the cavity 14.
Is the bottom wall surface 1 of the cavity through the plurality of support rods 31.
It is fixed on 4b. As can be seen from FIG. 11, the ring member 30 is arranged on the cylinder axis, and the inner peripheral wall surface of the ring member 30 forming the injected fuel collision wall surface has a substantially semicircular cross-sectional shape over the entire circumference. As shown in FIG. 11, when the piston 2 is located near the top dead center, from the nozzle openings 16 of the fuel injection valve 6 to the inside of the ring member 30 located immediately below the intervalve portions 3b on the inner wall surface of the cylinder head. The fuel F ₁ is injected toward the peripheral wall surface portion. A part of the injected fuel that has collided with each inner peripheral wall surface portion of the ring member 30 is reflected while being diffused toward the intervalve portion 3b of the cylinder head inner wall surface as indicated by F ₄ in FIG. The remaining portion of the injected fuel that has collided with each inner peripheral wall surface of the cavity 1 is the cavity 1 as shown by F ₅ in FIG.
It is reflected while diffusing toward the inside of 4.

Although the present invention has been described so far as applied to a direct injection type two-cycle diesel engine, the present invention can also be applied to a direct injection type four-cycle diesel engine.

[0023]

EFFECTS OF THE INVENTION By colliding the injected fuel with the intervalve portion of the inner wall surface of the cylinder head exhibiting a high temperature, atomization and atomization of the fuel can be improved. Further, since the intervalve portion of the cylinder head is cooled by the injected fuel, it is possible to prevent the intervalve portion from cracking.

[Brief description of drawings]

FIG. 1 is a side sectional view of a direct injection two-cycle diesel engine.

FIG. 2 is a bottom view of a cylinder head.

FIG. 3 is a diagram showing a fuel injection timing.

FIG. 4 is a side sectional view of a direct injection type two-cycle diesel engine showing a second embodiment.

FIG. 5 is a bottom view of a cylinder head showing a third embodiment.

FIG. 6 is a side sectional view of a direct injection two-cycle diesel engine showing a state of fuel injection when the piston is located at the top dead center in the fourth embodiment.

FIG. 7 is a side sectional view of a direct injection two-cycle diesel engine showing a state of fuel injection when the piston is located slightly below the top dead center.

FIG. 8 is a bottom view of the cylinder head.

FIG. 9 is a side sectional view of a direct injection two-cycle diesel engine showing a fifth embodiment.

FIG. 10 is a bottom view of a cylinder head showing a sixth embodiment.

FIG. 11 is a side sectional view of a direct injection type cycle diesel engine showing a seventh embodiment.

[Explanation of symbols]

2 ... piston 3 ... Cylinder head 3a ... Cylinder head inner wall surface 3b ... Intervalve portion of cylinder head inner wall surface 6 ... Fuel injection valve 8 ... Air supply valve 9 ... Exhaust valve 14 ... Cavity 14a ... Cavity side wall surface 18 ... Projection 20 ... Recess 22 ... Projection 24 ... Projection 26 ... Recess 28 ... Projection 30 ... Ring member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Sato             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd.

Claims (2)

[Claims] 1. An air supply valve and an exhaust valve are arranged on an inner wall surface of a cylinder head, a cavity is formed in a central portion of a piston top surface, and a cavity is formed from a fuel injection valve arranged on the inner wall surface of the cylinder head. In a direct injection internal combustion engine for supplying fuel, a protrusion or a recess is provided in an intervalve portion of an inner wall surface of a cylinder head located between valves of an intake valve and an exhaust valve, and the protrusion portion or the recess is provided from the fuel injection valve. A direct injection internal combustion engine in which fuel is injected toward a concave portion and collides with a projection or a concave portion and reflects the reflected fuel toward the inside of the cavity. 2. An air supply valve and an exhaust valve are arranged on an inner wall surface of a cylinder head, a cavity is formed in a central portion of a piston top surface, and a cavity is formed from a fuel injection valve arranged on the inner wall surface of the cylinder head. In a direct injection internal combustion engine adapted to supply fuel, an injection fuel collision wall surface is provided on the side wall surface of the cavity or inside the cavity, and fuel is injected from the fuel injection valve toward the injection fuel collision wall surface. A portion of the fuel reflected by colliding with the injected fuel collision wall surface is directed toward the intervalve portion of the cylinder head inner wall surface located between the valves of the air supply valve and the exhaust valve and collided with the injected fuel collision wall surface and reflected. A direct injection internal combustion engine in which the remainder of the fuel is directed into the cavity.