JPH07317542A - Cylinder direct injection type engine - Google Patents

Abstract

PURPOSE:To provide a small-sized compressive ignition type engine equipped with a fuel injection nozzle having a high injection pressure, wherein the fuel is injected uniformly into the combustion chamber and dispersed so that fuel sticking to the wall surface is prevented. CONSTITUTION:A combustion chamber 7 is formed by recesses 7a, 7b provided at the opposing surfaces of a cylinder head 5 and a piston 3, in such a shape as segment shells spreading downward aslant on the counter-side of piston 3 to the base point in which the position aslant over the cylinder head 5 and dislocated aside from the area right over the cylinder bore is used as the base point, and the jet 8a of a hole type fuel injection nozzle 8 having a high directionality and having an injection pattern similar to the shape of the combustion chamber 7 is located at this base point. The jet 8a is formed continuously in the combustion chamber spreading direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a combustion chamber by a recess formed in the upper surface of a piston that moves up and down in a cylinder and a recess formed in a surface of a cylinder head that faces the upper surface of the piston. , An in-cylinder direct injection engine having a fuel injection valve in the upper part of its combustion chamber.

[0002]

2. Description of the Related Art In recent years, as exhaust gas regulations have been tightened, there has been an increasing demand for increasing fuel injection pressure, especially in compression ignition engines. Therefore, the penetrating force of the fuel spray is increased and it is difficult to uniformly diffuse the spray in the conventional combustion chamber shape. In the reciprocating engine, the naturally aspirated type,
As shown in FIG. 5, a substantially spherical combustion chamber 7 is formed by a pair of concave portions 7a and 7b formed on the respective facing surfaces of the piston 3 and the cylinder head 5, and a swirling high swirl promotes mixing with air. Technology for achieving the above (Japanese Patent Laid-Open No. 59-60024)
In the in-cylinder direct injection engine, as shown in FIG. 6, an opening smaller than the bore diameter is formed between the flat combustion chamber 7 formed in the cylinder head 5 and the cylinder chamber 1a. A technique in which a partition wall 12 having 12a is provided and the injection nozzle 8 is arranged in the upper center (Japanese Patent Laid-Open No. 63-5062).
No. 1) or as shown in FIG. 7, a conical recess 7a is formed in the cylinder head 5, a fuel diffusion groove 13 is formed in the upper surface of the piston 3, and the injection port of the unit injector 14 is formed in the recess. The technique of arranging at the apex of 7a (disclosed in Japanese Patent Laid-Open No. 64-35011), and further, as shown in FIG. 8, four valves 15, 15, ... Are V-shaped in a recess 7a formed in the lower surface of the cylinder head 5. And place it in
A technique in which the unit injector 14 is arranged in the central portion of the piston 3, the top surface of the piston 3 is conically recessed, and the outer periphery of the piston 3 has a toroidal shape (see Japanese Utility Model Publication No. 2-1423).
A structure is known in which a combustion chamber is formed across the cylinder head 5 and the piston 3.

[0003]

In the conventional technology developed so far, in the case of the compression ignition type engine, when the displacement is small (bore diameter is 100 mm or less), the combustion chamber which is sufficient in the injection direction can be obtained. It is difficult to secure the volume, and the fuel adheres to the wall surface, leading to a decrease in combustion efficiency. Also, because the inner wall area of the combustion chamber is small and there is no room to increase the valve diameter,
Intake and exhaust efficiency is poor, and high output cannot be obtained. If it is expanded upward to increase the volume of the combustion chamber,
Since the cylinder head became huge and the mountability deteriorated, it was not possible to manufacture a small engine with high performance and excellent mountability. In addition, in the case of the conventional combustion chamber shape, the pin type nozzle is preferably used to uniformly supply the spray into the combustion chamber, but since the heat capacity of the pin portion is large, the fuel and the like are easily cooled, and the smoke There is a possibility that the occurrence of a crack may occur or the nozzle hole may be clogged.

[0004]

SUMMARY OF THE INVENTION The present invention is an in-cylinder direct injection type engine capable of ensuring a large-capacity combustion chamber without sacrificing mountability even if the engine displacement is small. Is that the combustion chamber is formed to bulge laterally from the area directly above the cylinder bore, and the fuel injection valve is arranged in the bulging portion, and the combustion chamber is inclined with respect to the nozzle of the fuel injection valve. Forming a fan-shaped pattern that spreads downward in the horizontal direction, making the fuel injection valve a Hall-type fuel injection nozzle, and continuously forming an injection port at the tip of the nozzle along the expansion direction of the combustion chamber You can

It is desirable that the inner wall surface of the combustion chamber on the cylinder head side be coated with a heat insulating material. The vertical direction in the present invention is an expression when the cylinder is in a vertical posture, and when the cylinder is tilted or in a horizontal posture, the reciprocating movement direction of the piston is understood as a vertical direction.

[0006]

[Function] Since a part of the combustion chamber is bulged laterally from the area directly above the cylinder bore, a large distance can be secured in the injection direction even in a low space, and a wide combustion chamber and a large valve opening area are secured. Even if the injection nozzle having a high injection pressure is adopted for the small engine, the fuel is less likely to adhere to the wall surface, and the combustion efficiency is not reduced. In addition, by forming the combustion chamber in a fan-shaped pattern that spreads in the horizontal direction diagonally downward from the nozzle of the fuel injection valve, it is possible to use a Hall-type nozzle with a smaller heat capacity than a pin-type nozzle. ,
The clogging of the injection hole is eliminated and the injection hole at the tip of the nozzle is continuously formed along the expansion direction of the combustion chamber, so that oxygen in the combustion chamber is effectively utilized without waste.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which a direct injection type cylinder engine according to the present invention is implemented in a compression ignition type engine will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a cylinder block, which is provided with a vertically long cylinder chamber 1a corresponding to the number of cylinders, around which a water jacket 2 for circulating cooling water is provided. Has become. Reference numeral 3 denotes a piston which is housed in the cylinder chamber 1a so as to be reciprocally movable in the vertical direction. The piston 3 is mounted on the piston pin 3a and the piston pin 3a which are installed in a direction orthogonal to the reciprocating direction of the piston 3. It is connected to a crankshaft (not shown) via a connecting rod 4 which is axially mounted. Piston rings 3b, 3b, 3b are fitted to the peripheral surface of the piston 3 by using ring grooves.

Reference numeral 5 denotes a cylinder head, which is assembled to the cylinder block 1 so as to cover the upper surface of the opening of the cylinder chamber 1a, and a gasket 6 is interposed on the contact surface. The cylinder head 5 has a two-part structure. Recesses 7a and 7b are formed on the facing surfaces of the cylinder head 5 and the piston 3, respectively. When the piston 3 reaches the top dead center position as shown in the drawing, the recess 7a and the recess 7b A combustion chamber 7 is formed which bulges laterally from an area immediately above the cylinder bore. As shown in FIG. 2, the combustion chamber 7 formed by the recessed portions 7a and 7b has a diagonally upper side of the cylinder head 5 which is located at a position deviated laterally from an area immediately above the cylinder bore, and is diagonally lower on the opposite side. The cylinder head 5 has a shape like a fan-shaped bivalve, and a hole-type injection nozzle 8 has an injection port 8a whose injection direction is obliquely downward of the combustion chamber 7, as shown in FIG. It is installed in a vertical position facing the base point.

The injection nozzle 8 is equipped with a type having a high injection pressure, has a strong directivity, and a fuel is formed in the shape of the combustion chamber 7 from an injection port 8a which is continuously formed along the spreading direction of the combustion chamber. It is injected in a pattern similar to. That is, the combustion chamber 7 has a shape that substantially matches the shape of the injection pattern of the installed injection nozzle 8. The injection port 8a includes, for example, a type in which needle holes 9, 9, ... Are arranged side by side in a row (FIG. 4a) and a type in which only one slit 10 is formed (FIG. 4b). 9 and slits 10 are provided in a plurality of rows (FIGS. 4c and d), and further, a pattern such as a composite type in which those needle holes and slits are combined is conceivable, and the injection pattern of the fuel injected from these injection ports is It is not limited to the shape shown in the embodiment such as a fan-shaped bivalve, it is also possible to adopt a spray nozzle, or a spray nozzle having a spray pattern such as a bifurcated or eight-handed split tip, In this case, the combustion chamber ideally has a shape similar to the outer shape of those injection patterns. By using the hole type nozzle with a small heat capacity, the temperature of fuel and the like is less likely to drop, smoke is not generated, and the nozzle hole is not clogged.
In the case of a slit like d, oxygen in the combustion chamber is effectively used. On the inner wall surface of the combustion chamber 7, a ceramic coating layer 11 as a heat insulating material is provided on the cylinder head 5 side, that is, on the inner wall surface of the recess 7a.

In an engine in which the combustion chamber is formed in this way, the fuel injection pattern and the shape of the combustion chamber are substantially the same, so the fuel injected at high pressure is also diffused uniformly in the combustion chamber, and the fuel is deposited on the wall surface. Is adhered, and an ideal combustion state is realized even in a small direct injection cylinder engine. Moreover, since the fuel injection direction is inclined with respect to the vertical direction, the height of the cylinder head is lowered correspondingly, which is advantageous in design for the demand for miniaturization, and the injection nozzle is arranged in a horizontal position. The cylinder head can be made thinner. Even for a small engine with a bore diameter of 100 mm or less, the valve opening area can be increased, and the ceramic coating layer provided on the inner wall of the combustion chamber can also prevent the influence of cooling water in the water jacket. Since it is hard to receive and the ignition timing is very little delayed, there is an advantage that the combustion state becomes close to complete combustion and the emission of hydrocarbon compounds (hydrocarbons) and harmful gas (nitrogen oxides) is reduced.

The combustion chamber structure of the direct injection type cylinder engine of the present invention exerts a remarkable effect in a small compression ignition engine, but can be applied to a large engine or an electric ignition engine.

[0012]

According to the present invention, by adopting the inclined combustion chamber, even if a fuel injection nozzle having a high injection pressure is attached to a small in-cylinder direct injection engine having a small bore diameter, a combustion chamber inner wall at the time of fuel injection is provided. It is possible to expect the state to be close to complete combustion, and to reduce the emission of diesel black smoke and hydrocarbons. Further, since the height of the cylinder head is low, it is suitable for downsizing the entire engine, and the restrictions on the size of the combustion chamber are reduced, and the mountability is improved. Furthermore, by providing a ceramic coating layer on the inner wall surface of the combustion chamber, it is less affected by cooling water, the ignition delay time is shorter, the emission of nitrogen oxides is drastically reduced, and the combustion noise is quiet. There is. Furthermore, it becomes possible to use a hole-type nozzle, and it becomes difficult for clogging of the injection hole to occur.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a combustion chamber portion of a direct injection type cylinder engine according to the present invention.

FIG. 2 is an explanatory view of the shape of a combustion chamber.

FIG. 3 is an explanatory diagram showing a state in which the Hall-type fuel injection nozzle is arranged with its injection port facing the combustion chamber.

FIG. 4 is an explanatory view illustrating an injection port of a fuel injection nozzle.

FIG. 5 is an explanatory diagram of a conventional example.

FIG. 6 is an explanatory diagram of a conventional example.

FIG. 7 is an explanatory diagram of a conventional example.

FIG. 8 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1 ... Cylinder block, 1a ... Cylinder chamber, 2 ...
Water jacket, 3 ・ ・ Piston, 3a ・ ・ Piston pin, 3b ・ ・ Piston ring, 4 ・ ・ Connecting rod, 5 ・ ・ Cylinder head, 6 ・ ・ Gasket, 7 ・
・ Combustion chambers, 7a, 7b ... Recesses, 8 ... Injection nozzles, 8
a ... Nozzle, 9 ... Needle hole, 10 ... Slit, 11 ...
Coating layer, 12 ... Partition wall, 12a ... Opening, 1
3 ... Fuel diffusion groove, 14 ... Unit injector, 1
5 ... Valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Sato 1 Toyota-cho, Toyota-shi, Aichi Toyota Automobile Co., Ltd.

Claims (3)

[Claims] 1. A combustion chamber is formed by a recess formed in an upper surface of a piston that moves up and down in a cylinder and a recess formed in a surface of a cylinder head that faces the upper surface of the piston, and an upper portion of the combustion chamber. In a direct injection engine having a fuel injection valve in a cylinder, a part of the combustion chamber is formed to bulge laterally from an area directly above the cylinder bore, and the fuel injection valve is arranged in the bulging portion. Direct injection engine. 2. The combustion chamber is formed in a fan-shaped pattern that extends in a horizontal direction diagonally downward from the nozzle of the fuel injection valve as a base point, and the fuel injection valve is a Hall-type fuel injection nozzle, and the nozzle thereof is provided. The in-cylinder direct injection engine according to claim 1, wherein the injection port at the tip is continuously formed along the spreading direction of the combustion chamber. 3. The in-cylinder direct injection engine according to claim 1, wherein an inner wall surface of the combustion chamber on the cylinder head side is coated with a heat insulating material.