JPH0642351A - Direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To decrease black smoke and particulates in exhaust gas when timing retard for delaying the timing of fuel injection is actuated so as to decrease quantity of nitrogen oxide in the exhaust gas, in a direct injection type diesel engine. CONSTITUTION:A troidal type auxiliary combustion chamber 22 is formed in the central part of the bottom part of a main combustion chamber 21 formed on the top part of a piston 12, and fuel is injected into the main and auxiliary chambers 21, 22 respectively through a fuel injection nozzle 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection diesel engine, and more particularly, a combustion chamber having a recess is formed on the top surface of a piston, and fuel is injected into the combustion chamber of the piston by a fuel injection nozzle. Direct injection diesel engine.

[0002]

2. Description of the Related Art In a diesel engine, by moving a piston to the top dead center side, intake air in the cylinder is compressed and kept in a high temperature state, and fuel is injected in synchronization with the piston almost reaching top dead center. The fuel is injected from the nozzle, and the fuel spray is spontaneously ignited by the heat of intake air to perform combustion.

The fuel spray injected from the fuel injection nozzle is mixed with intake air in a combustion chamber formed by a recess formed on the top surface of the piston to form a mixture, and this mixture is burned. ing.

[0004]

The conventional combustion chamber formed on the top surface of the piston is a toroidal type in which the outer peripheral wall is scooped out or an open chamber type having a substantially cup shape, which is relatively simple. It has a unique shape. Therefore, according to such a conventional combustion chamber, the fuel spray and the air are not always mixed well, and there is a limit to the utilization of the air in the combustion chamber. Moreover, in order to lower the combustion temperature and reduce the content of nitrogen oxides in the exhaust gas, the timing retard for retarding the fuel injection is performed, and the time for promoting the mixing of fuel and air is reduced. Therefore, there is a problem that a large amount of black smoke and particulates are generated.

The present invention has been made in view of the above problems, and promotes mixing of air and fuel spray in the combustion chamber of a direct injection diesel engine, thereby improving combustion. It is intended to provide a direct injection diesel engine.

[0006]

SUMMARY OF THE INVENTION The present invention is a direct injection diesel engine in which a main combustion chamber consisting of a recess is formed on the top surface of a piston, and fuel is injected into the main combustion chamber by a fuel injection nozzle. A sub-combustion chamber consisting of a recess smaller than the main combustion chamber is formed in the substantially central portion of the bottom of the main combustion chamber, and the fuel is also injected into the sub-combustion chamber by the fuel injection nozzle. The present invention relates to a characteristic direct injection diesel engine.

[0007]

[Function] Not only the main combustion chamber is provided by the fuel injection nozzle,
Fuel is also injected into the auxiliary combustion chamber formed in the substantially central portion of the bottom of the main combustion chamber, and such fuel spray is mixed with air and burned. In particular, the flame in the main combustion chamber and the flame in the auxiliary combustion chamber collide with each other in the substantially central portion of the combustion chamber, which improves the utilization efficiency of air and improves combustion.

[0008]

1 shows a main part of a diesel engine equipped with a fuel injection device according to an embodiment of the present invention, in which a cylinder block 10 is provided with a cylinder 11 consisting of a through hole. A piston 12 is slidably arranged in the cylinder 11. The piston 12 is connected to the connecting rod 14 by a piston pin 13.

The upper opening of the cylinder 11 is closed by a cylinder head 15, and the cylinder head 15 has an intake port 16 and an exhaust port 1.
7 and 7 are formed respectively. These intake ports 1
6 and the exhaust port 17 are opened and closed by an intake valve 18 and an exhaust valve 19, respectively. A fuel injection nozzle 20 is attached to the cylinder head 15 so as to inject fuel toward a combustion chamber 21 formed on the top surface of the piston 12.

As shown in FIGS. 4 and 5, at the top of the piston 12, a toroidal type combustion chamber 21 is formed in which the side wall portion is inserted and is undercut. Moreover, the main combustion chamber 21 is provided at the center of the bottom of the combustion chamber 21.
A smaller sub combustion chamber 22 is formed. The auxiliary combustion chamber 22 is formed in advance on the auxiliary piece 23, and the auxiliary piece 23 is fixed to the bottom of the main combustion chamber 21. As the material of the auxiliary piece 23, for example, stainless steel or ceramics is used.

The fuel injection nozzle 20, as shown in FIG.
It is connected to the corresponding pump unit 26 of the fuel injection pump 25 by the injection pipe 24. Fuel injection pump 25
Is equipped with a mechanical governor 27, and the mechanical governor 27 moves a control rack 28 to adjust the supply amount of fuel injected at one time. The fuel injection pump 25 has a cam shaft 29, and a cam 30 attached to the cam shaft 29 drives each pump unit 26. A timer 31 is provided on the camshaft 29, and the timing of injection is adjusted by the timer 31.

The fuel injection nozzle 20, as shown in FIG.
The tip portion is composed of a nozzle body 34, and a main jet port 35 and an auxiliary jet port 52 are formed at the tip portion of the nozzle body 34 (see FIG. 6). And the nozzle body 34
Is attached to a nozzle holder 37 by a retainer 36. A nozzle needle 38 is slidably held in the nozzle body 34. And this nozzle needle 3
The upper end of 8 is pressed downward by a compression coil spring 40 in the nozzle holder 37 via a pressing rod 39. As a result, the nozzle needle 38 is pressure-bonded to the valve seat 41 formed on the nozzle body 34 to shut off the fuel. Further, the nozzle holder 37 is formed with a fuel passage 42 communicating with the injection pipe 24. The fuel passage 42 communicates with the fuel passage 43 of the nozzle body 34. Fuel passage 4
A fuel sump 51 is formed at the end of 3.

The upper end of the spring 40 pressing the pressing rod 39 is received by the spring receiver 44. An adjusting screw 45 is attached to the upper end of the spring receiver 44. The adjusting screw 45 is screwed with a female screw 46 formed on the inner peripheral surface of the nozzle holder 37. Further, a protrusion 48 is formed on the side surface side of the nozzle holder 37, and a male screw 49 is formed on the protrusion 48, and a connection nut 50 screwed with the male screw 49.
The injection pipe 24 is connected to the nozzle holder 37.

Next, the structure of each pump unit of the fuel injection pump 25 will be described. As shown in FIG. 3, a tappet 55 is attached to the lower end of the plunger 54.
The tappet 55 is pressed downward by the compression coil spring 56, and thereby pressed against the outer peripheral surface of the cam 30. A spill port 58 is formed in the barrel 57 in which the plunger 54 is slidably fitted, and an inclined groove 59 is formed in the outer peripheral surface of the plunger 54 so as to substantially face the spill port 58. ing.

A pinion 60 is rotatably supported on the outer peripheral side of the barrel 57. A control sleeve 61 is fixed to the pinion 60 and a notch 62 formed in the control sleeve 61.
Receives the engagement plate 63. The engagement plate 63 is fixed to the plunger 54.

A delivery valve 64 is provided on the outlet side of each pump unit 26, and is arranged on a valve seat 66 provided at the bottom of the casing 65.
The coil spring 67 presses the delivery valve 64 toward the valve seat 66.

Next, the outline of the operation of the direct injection diesel engine having the above-mentioned structure will be described.

The timer 31 is controlled by a part of the output of the engine.
When the camshaft 29 is driven via the camshaft 29, the cam 30 having the shape shown in FIG. 3 pushes up the roller of the tappet 55, which causes the plunger 54 to move.
Move up in 7. Then, the top surface of the plunger 54 closes the spill port 58 and starts the pressure feeding of the fuel. When the plunger 54 moves further upward, the inclined groove 5
9 aligns with the spill port 58, whereby the pressure in the space above the plunger 54 escapes to the spill port 58 side through the inclined groove 59, and the pumping of fuel is completed.

Mechanical governor 2 of fuel injection pump 25
When the 7 moves the control rack 28, the pinion 60 is rotated, which causes the control sleeve 6 to move.
1 will be rotated. The rotation of the control sleeve 61 is transmitted to the plunger 54 via the notch 62 and the engaging plate 63, and the plunger 54 is rotated in the barrel 57. Therefore spill port 5
8, the effective stroke determined by the position of the inclined groove 59 aligned with 8 is changed, the fuel is metered,
The supply amount of fuel injected at one time is controlled. The timer 31 provided on the camshaft 29 of the fuel injection pump 25 controls the phase angle of the camshaft 29 and adjusts the fuel injection timing.

When the plunger 54 pumps fuel in the barrel 57, the delivery valve 64 is opened and the fuel is pumped to the fuel injection nozzle 20 through the injection pipe 24. The fuel passage 4 of the fuel injection nozzle 20 shown in FIG.
When fuel pressure is applied to the fuel sump 51 through 2 and 43, the nozzle needle 38 moves through the rod 39 into the spring 4
0 is compressed and moves upward, whereby the tip end side portion of the nozzle needle 38 separates from the valve seat 41, and fuel is injected through the injection port 35. When the pressure feed of the fuel is completed, the elastic restoring force of the spring 40 pushes the nozzle needle 38 downward via the rod 39, and the tip end thereof is pressed against the valve seat 41 to stop the fuel injection.

The fuel is sprayed from the main injection port 35 and the auxiliary injection port 52 of the fuel injection nozzle 20 through the piston 12 shown in FIG.
The fuel is injected toward the combustion chambers 21 and 22 formed on the top surface of the. Then, this fuel spray is spontaneously ignited by the heat of the compressed intake air, combustion occurs in the cylinder 11, the piston 12 is pushed downward, and the output of the engine is taken out. And after this, the exhaust valve 19
Is opened and exhaust gas is exhausted through the exhaust port 17.

The combustion chamber 21 at the top of the piston 12 into which the fuel spray is injected by the fuel injection nozzle 20 is shown in FIG.
As shown in FIG. 5 and FIG. 5, the outer peripheral portion has an undercut toroidal shape. Moreover, the auxiliary combustion chamber 22 is provided at the bottom of the main combustion chamber 21 by the auxiliary piece 23. That is, the piston 12 includes combustion chambers 21 and 22 having a double structure.

As shown in FIG. 5, the fuel injection nozzle 20 injects fuel not only into the main combustion chamber 21 but also into the auxiliary combustion chamber 22. As shown in FIG. 6, an auxiliary injection port 52 is provided obliquely downward along with the injection port 35 at the tip of the nozzle body 34, and the fuel injected by this auxiliary injection port 52 is supplied to the auxiliary combustion chamber 22. It is like this. Moreover, the diameter of the auxiliary injection port 52 is smaller than that of the main injection port 35, so that the amount of fuel sprayed to the side of the auxiliary combustion chamber 22 becomes smaller than the amount of fuel sprayed to the side of the main combustion chamber 21. ing.

Injecting fuel into the main combustion chamber 21 and the auxiliary combustion chamber 22 in this way improves the utilization rate of air particularly on the bottom side of the main combustion chamber 21. Further, the flame generated on the outer peripheral wall side of the main combustion chamber 21 is diffused toward the center side, and such a flame collides with the flame emerging from the sub combustion chamber 22 at the inlet portion of the sub combustion chamber 22 and becomes air. Make the combustion gas collision more active. This will further improve the utilization rate of air.

The piston 12 having the combustion chambers 21 and 22 as described above is particularly suitable for a diesel engine in which a timing retard is performed in order to suppress the combustion temperature and reduce the nitrogen oxides in the exhaust gas. This is because when such timing retardation is performed, the mixing promotion time of the fuel spray and the air is reduced, which reduces the utilization rate of the air. It becomes possible to prevent such a decrease in the utilization rate of air by the existence of the auxiliary combustion chamber 22 described above, and it is possible to reduce the nitrogen oxides in the exhaust gas and suppress the generation of black smoke and particulates. become.

[0026]

[Modification] The present invention has been described above with reference to the illustrated embodiment, but the present invention is not limited to the above embodiment.
Various modifications can be made based on the technical idea of the present invention.
For example, in the above embodiment, the toroidal-type auxiliary combustion chamber 22 is formed at the bottom of the toroidal-type main combustion chamber 21, but the toroidal-type auxiliary combustion chamber is formed at the bottom of the open-chamber-type main combustion chamber. It may be provided.

[0027]

As described above, according to the present invention, the sub-combustion chamber having a recess smaller than the main combustion chamber is formed in the substantially central portion of the bottom of the main combustion chamber formed at the top of the piston. The fuel is injected not only into the main combustion chamber but also into the auxiliary combustion chamber by the combustion injection nozzle.

Therefore, the air in the vicinity of the central portion of the main combustion chamber, which has not been effectively used in the past, is mixed with the fuel spray injected into the auxiliary combustion chamber, whereby the air in this portion is effectively used. It will be. Moreover, the flame that spreads from the outer peripheral side to the center side of the main combustion chamber will collide violently with the flame from the auxiliary combustion chamber at the outlet of the auxiliary combustion chamber.
As a result, the collision between the combustion gas and the air is further activated and the utilization of the air is further promoted. Therefore, it is possible to reduce the amount of black smoke and particulates in the exhaust gas when timing retard is performed in order to suppress the combustion temperature and reduce the amount of nitrogen oxides in the exhaust gas. Will lead to the promotion of.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a direct injection diesel engine according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a fuel injection nozzle.

FIG. 3 is a perspective view of a main part of a fuel injection pump.

FIG. 4 is a plan view of a piston.

5 is a sectional view taken along line VV in FIG.

FIG. 6 is an enlarged vertical sectional view showing the structure of the tip portion of the fuel injection nozzle.

[Explanation of symbols]

 10 cylinder block 11 cylinder 12 piston 13 piston pin 14 connecting rod 15 cylinder head 16 intake port 17 exhaust port 18 intake valve 19 exhaust valve 20 fuel injection nozzle 21 combustion chamber 22 auxiliary combustion chamber 23 auxiliary piece 24 injection pipe 25 fuel injection pump 26 pump Unit 27 Mechanical governor 28 Control rack 29 Cam shaft 30 Cam 31 Timer 34 Nozzle body 35 Main injection hole 36 Retainer 37 Nozzle holder 38 Nozzle needle 39 Push rod 40 Spring 41 Valve seat 42, 43 Fuel passage 44 Spring bearing 45 Adjusting screw 46 Female screw 47 Cap 48 Projection 49 Male screw 50 Connection nut 51 Fuel sump 52 Auxiliary nozzle 54 Plunger 55 Tappet 56 Coil spring 57 Barrel 58 Spill port 59 Inclined groove 60 Pinion 61 Control sleeve 62 Notch 63 Engagement plate 64 Delivery valve 65 Casing 66 Valve seat 67 Coil spring

Claims (1)

[Claims] 1. A direct injection diesel engine in which a main combustion chamber consisting of a recess is formed on the top surface of a piston, and fuel is injected into the main combustion chamber by a fuel injection nozzle. A direct-injection diesel engine, characterized in that a sub-combustion chamber consisting of a recess smaller than the main combustion chamber is formed substantially in the center and fuel is also injected into the sub-combustion chamber by the fuel injection nozzle. .