JP2526618Y2 - Fuel injection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fuel injection device for an internal combustion engine.

[Conventional technology]

A needle having a through hole penetrating the cylinder head formed in the cylinder head, a tip of the fuel injection valve fitted in the through hole, a needle insertion hole formed in the tip, and a needle inserted into the needle insertion hole. A fuel passage formed between the needle insertion hole and the needle insertion hole, a conical valve seat that expands outward at the open end of the needle insertion hole, and a valve body that can be seated on the valve seat at the tip of the needle. A fuel injection valve is known in which an outer end surface of a valve body is exposed in a combustion chamber (see Japanese Utility Model Laid-Open No. 58-2363). In this fuel injection valve, the entire outer peripheral surface of the front end portion is brought into close contact with the inner peripheral surface of the through hole, or the entire outer peripheral surface of the front end portion is arranged at a distance from the inner peripheral surface of the through hole.

[Problems to be solved by the invention]

By the way, if the fuel around the needle is heated appropriately while the research on such a fuel injection valve is repeated, the injected fuel boils when the pressure applied to the fuel is reduced by injection of the fuel. The fuel is boiled under reduced pressure,
As a result, it was found that good atomization of the fuel was obtained. In this case, if the fuel around the needle is excessively heated, the fuel around the needle will boil in the fuel injection valve. Thus, when the fuel boils in the fuel injection valve, the fuel injection amount is greatly reduced. Boiling the fuel around the needle is not desirable.

Incidentally, in an internal combustion engine, as the engine load increases, the combustion temperature increases and the temperature of the cylinder head also increases. Therefore, as described in Japanese Utility Model Application Laid-Open No. 58-2363, when the entire outer peripheral surface of the front end portion of the fuel injection valve is brought into close contact with the inner peripheral surface of the through hole formed in the cylinder head, heat transfer from the cylinder head causes The temperature of the fuel injection valve increases as the engine load increases. Therefore, if the fuel is appropriately heated so as to generate good reduced-pressure boiling during low-load operation of the engine using this fuel injection valve, the fuel will boil in the fuel injection valve during high-load operation of the engine. If the fuel is moderately heated to generate good reduced pressure boiling during load operation, good reduced pressure boiling cannot be generated because the fuel in the fuel injection valve is not sufficiently heated during low engine load operation. Cause problems.

On the other hand, as described in Japanese Utility Model Application Laid-Open No. 58-2363, when the entire outer peripheral surface of the front end portion of the fuel injection valve is arranged at a distance from the inner peripheral surface of the through hole formed in the cylinder head, fuel Since the injection valve is less affected by the temperature of the cylinder head, it is possible to suppress the fuel in the fuel injection valve from boiling during the high-load operation of the engine.

However, particularly in a direct injection internal combustion engine, the fuel injection direction has a great influence on the combustion, and if the fuel injection direction deviates even slightly from a predetermined normal direction, good combustion may not be obtained. Therefore, as described above, when the entire outer peripheral surface of the tip end portion of the fuel injection valve is arranged at a distance from the inner peripheral surface of the through hole, it is possible to suppress the fuel in the fuel injection valve from boiling, but the fuel injection direction is set in advance. It is difficult to set the prescribed normal direction, which causes a problem that expected good combustion cannot be obtained.

[Means for solving the problem]

In order to solve the above-mentioned problems, according to the present invention, a through-hole penetrating the inner wall of the combustion chamber is formed, the tip of the fuel injection valve is fitted into the through-hole, and a needle is inserted into the tip. Forming a hole, forming a fuel passage between the needle inserted into the needle insertion hole and the needle insertion hole, and forming a conical valve seat that expands outward at the open end of the needle insertion hole; In a fuel injection device in which a valve body that can be seated on a valve seat is formed at a tip end of a needle, and an outer end surface of the valve body is exposed in a combustion chamber, an enormous portion is formed on a needle that is spaced from the valve body. A hollow cylindrical heat insulating member is inserted between the through hole and the tip of the fuel injection valve around the needle located upstream of the enormous portion in the flow direction of the fuel around the needle so that the injected fuel is boiled under reduced pressure. ing.

[Action]

The fuel flowing in the fuel passage around the needle passes through the bulge and approaches the valve body and is heated to near the boiling temperature, and then this fuel is boiled under reduced pressure as soon as it is injected.

〔Example〕

4 and 5, reference numeral 1 denotes a two-stroke internal combustion engine body, 2 denotes a cylinder block, 3 denotes a piston,
Is a cylinder head, 5 is a combustion chamber, 6 is a pair of air supply valves, 7
Is an air supply port, 8 is a pair of exhaust valves, 9 is an exhaust port, 10
Denotes an ignition plug, and a mask wall 11 is formed on the inner wall surface of the cylinder head 4 so as to cover the opening of the supply valve 6 on the exhaust valve 8 side during the full opening period of the supply valve 6. In the embodiment shown in FIGS. 4 and 5, the exhaust valve 8 opens before the air supply valve 6 and closes first. When the air supply valve 6 is opened, fresh air flows into the combustion chamber 5 from the opening of the air supply valve 6 on the side opposite to the mask wall 11, and this fresh air then flows along the inner wall surface of the cylinder bore below the air supply valve 6. After descending, it proceeds along the top surface of the piston 3 as shown by the arrow W. By providing the mask wall 11 in this manner, fresh air flows in a loop in the combustion chamber 5 and thus good exhaust is performed. A fuel injection valve 20 is arranged around the inner wall surface of the cylinder head 4 on the side of the supply valve 6. For example, after the exhaust valve 8 is closed, fuel is injected from the fuel injection valve 20 into the combustion chamber 5. .

Referring to FIG. 1, the combustion injection valve 20 includes a housing body.
The cylinder head 4 has a front end 21 and a front end 19. The front end 19 is fitted into a through hole 18 formed through the cylinder head 4. This tip portion 19 has a protruding end portion 21a protruding from the housing body 21.
And a nozzle member 22 fixed to the protruding end 21a. The fuel injection valve 20 has a protruding end 21b protruding from the housing body 21 on the side opposite to the protruding end 21a, and a solenoid provided on the protruding end 21b. And a housing 24 fixed via a holder 23. On the other hand, the through hole 18 is a large diameter hole 25,
The small-diameter hole 26 opens into the combustion chamber 5, and the medium-diameter hole 27 is located between the large-diameter hole 25 and the small-diameter hole 26.
The small diameter hole 26 and the medium diameter hole 27 are aligned with each other. The protruding end 21a of the housing body 21 is fitted into the large-diameter hole 25 via a hollow cylindrical heat-insulating member 15 made of, for example, bakelite. Nozzle members 22 are fitted at intervals. As shown in FIG. 2, the hollow cylindrical heat insulating member 15 has a slit 15a extending in the longitudinal direction, and the outer peripheral surface and the inner peripheral surface of the heat insulating member 15 are the inner peripheral surface and the protruding end of the large diameter hole 25. It is in close contact with the outer peripheral surface of the portion 21a. The housing body 21 has a flange 21c extending in the lateral direction, and the fuel injection valve 20 is fixed to the cylinder head 4 by fastening the flange 21c to the cylinder head 4 with a bolt 17 via a heat insulating member 16. . An annular flange 22 is provided on the outer peripheral surface of the nozzle member 22.
a is formed, and the outer peripheral surface of the annular flange 22a is brought into close contact with the inner peripheral surface of the medium diameter hole 27. In addition, a seal ring 28 is inserted between a step formed between the intermediate hole 27 and the small hole 26 and the annular flange 22a.

A needle insertion hole 30 is formed in the nozzle member 22, and a needle 31 is inserted into the needle insertion hole 30. A conical valve seat 32 that expands outward is formed at the open end of the needle insertion hole 30, and a valve body 33 that can be seated on the valve seat 32 is integrally formed at the tip of the needle 31. . The outer end surface of the valve element 33 is exposed inside the combustion chamber 5. The portion of the needle 31 opposite to the valve element 33 protrudes from the nozzle member 22, and a spring retainer 34 is attached to the protruding portion of the needle 31. A compression spring 35 is inserted between the spring retainer 34 and the nozzle member 22, and the valve body 33 is normally seated on the valve seat 32 by the spring force of the compression spring 35. On the other hand, a movable core 36 is slidably inserted into the housing 24, and the movable core 36 is pressed against the end face of the needle 31 by the spring force of a compression spring 37.

As shown in FIGS. 1 and 3 (A), an enlarged portion 38 is formed on the needle 31 spaced from the valve body 33. The enlarged portion 38 has a cylindrical outer peripheral surface, and the cylindrical outer peripheral surface has a diameter slightly smaller than that of the needle insertion hole 30. Therefore, an annular fuel passage 39 is formed between the enlarged portion 38 and the needle insertion hole 30, and the flow passage area of the annular fuel passage 39 is such that the flow between the valve body 33 and the valve seat 22 when the valve body 33 is opened. It is formed smaller than the road area. Accordingly, the annular fuel passage 39 forms a fuel metering throttle passage. An annular fuel reservoir 40 is formed around the needle 31 between the fuel metering throttle passage 39 and the valve element 33, and the volume of the fuel reservoir 40 is substantially equal to the volume occupied by fuel when the fuel injection amount is minimum. ing. In the embodiment shown in FIG.
The diameter of a is formed substantially equal to the diameter of the needle insertion hole 30, and a plurality of spiral grooves 41 are formed on the outer peripheral surface of the enlarged portion 38a. In this embodiment, these spiral grooves 41 form a fuel metering throttle passage.
Similarly, the volume of the fuel reservoir 40 formed between the valve body 41 and the valve body 33 is substantially equal to the volume occupied by fuel when the fuel injection amount is minimum.

In FIG. 1, 4 kg / cm ² to 20 kg / cm
^{About 2} low pressure fuel is supplied. The low-pressure fuel passes through the filter 43, passes around the movable core 36, and is fed into the fuel chamber 44 in the housing body 21. This fuel then passes through a passage 45 formed in the spring retainer 34,
The fuel is passed through the fuel passage between the needle 31 and the needle insertion hole 30 and then into the fuel reservoir 40 through the fuel metering throttle passages 39 and 41 (FIG. 3). When the solenoid 23a disposed in the solenoid holder 23 is urged, the movable core 36 moves toward the needle 31, so that the valve element 33 separates from the valve seat 32. At this time, the fuel measured by the fuel metering throttle passages 39 and 41 is ejected into the combustion chamber 5 from between the valve body 33 and the valve seat 23. The amount of fuel flowing in the fuel metering throttle passages 39 and 41 within a unit time during fuel injection is constant, so the fuel injection amount is controlled by controlling the valve opening time of the needle valve body 33. can do.

As shown in FIG. 1 and FIG.
Is exposed in the combustion chamber 5, so that the outer end surface of the needle valve body 33 is strongly heated by the combustion heat. In particular, the temperature of the needle valve body 33 becomes considerably high in the two-cycle internal combustion engine since the explosion cycle is shorter than that in the four-cycle internal combustion engine. As a result, the temperature of the fuel in the fuel reservoir 40 increases, and the temperature of the fuel in the fuel reservoir 40 is increased to near the boiling temperature. Further, the fuel located upstream of the enlarged portions 38, 38a is separated from the needle valve body 33, and the heat insulating member 15 is inserted between the protruding end 21a and the large-diameter hole 25. Not much heat is transmitted to the nozzle member 22. Therefore, the fuel located upstream of the enlarged portions 38 and 38a is maintained at a temperature slightly lower than the fuel temperature in the fuel reservoir 40, and thus the fuel does not boil in the nozzle member 22.

When fuel injection is started, first, fuel heated to near the boiling temperature in the fuel reservoir 40 is injected. This fuel boils under reduced pressure immediately after injection, and is thus finely atomized. Next, fuel upstream of the expanding portions 38, 38a sent into the fuel reservoir 40 is injected. This fuel also receives heat as it passes through the fuel reservoir 40 and is thus boiled under reduced pressure.

Also, the hollow cylindrical heat insulating member 15 inserted between the protruding end portion 21a and the large diameter portion 25 allows the axis of the fuel injection valve 20 to have a large diameter hole.
Exactly coincides with 25 axes. As a result, the fuel injection direction can be set to a predetermined normal direction.

[Effect of the invention]

It is possible to satisfactorily boil the injected fuel under reduced pressure while preventing the fuel from boiling in the fuel injection valve. Further, the fuel injection direction can be accurately set to a predetermined regular direction.

[Brief description of the drawings]

1 is a side cross-sectional view of a fuel injection valve, FIG. 2 is a perspective view of a heat insulating member, FIG. 3 is an enlarged side cross-sectional view around a needle tip, FIG. 4 is a side cross-sectional view of a two-cycle internal combustion engine, FIG. 5 is a bottom view of the cylinder head of FIG. 15, 16 ... heat insulation member, 18 ... through hole, 19 ... tip, 30
... Needle insertion hole, 31 ... Needle, 32 ... Valve seat, 33
…… Valve, 38,38a… Very large part, 39,41 …… Throttle passage for fuel measurement, 40 …… Fuel pool.

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication F02M 61/14 310 F02M 61/14 310A (72) Inventor Masahiko Masuchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Vehicle (72) Inventor Masanori Kanamaru 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hideto Takeda 1-1-1 Showacho, Kariya City, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Nobuo Lee 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References Japanese Utility Model Showa 60-41576 (JP, U) Japanese Utility Model Showa 58-134669 (JP, U) -127870 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] A through hole penetrating the inner wall of the combustion chamber, a tip of a fuel injection valve is fitted into the through hole, a needle insertion hole is formed in the tip, and the needle is formed. A fuel passage is formed between the needle inserted into the insertion hole and the needle insertion hole, a conical valve seat that expands outward at the open end of the needle insertion hole, and the fuel passage is formed at the tip of the needle. In a fuel injection device in which a valve body that can be seated on a valve seat is formed and an outer end surface of the valve body is exposed in a combustion chamber, an enormous portion is formed on a needle that is spaced from the valve body, and fuel around the needle is formed. An internal combustion engine in which a hollow cylindrical heat insulating member is inserted between the through hole and the tip of the fuel injection valve around the needle located upstream of the enlarged portion in the flow direction of the injection fuel to decompress and boil the injected fuel. For fuel injection.