JPH06212973A - Direct injection diesel engine - Google Patents

Abstract

PURPOSE:To restrain generation of black smoke caused by improvement of nitrogen oxide in exhaust gas due to timing retard. CONSTITUTION:A combustion chamber 21 of a piston 21 is formed like such an undercut shape that the innermost part is spread to the outer peripheral side more than the inlet side, and a poppet valve-like projection 70 is formed substantially in the central part of the bottom of the combustion chamber 21. A throat part 71 is formed between the projection and the inlet part of the combustion chamber on the outer peripheral side of the projection 70.

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 to pressurizing fuel by a fuel injection pump and supplying the pressurized fuel to a fuel injection nozzle, which is formed at the top of a piston from its injection port. The present invention relates to a direct injection type diesel engine in which fuel is injected toward a combustion chamber that is open.

[0002]

2. Description of the Related Art In a direct-injection diesel engine, an intake valve is opened and intake air introduced into a cylinder is compressed by a piston moving to the top dead center to keep it at a high temperature so that the piston is almost at the top dead center. The fuel is injected from the fuel injection nozzle toward the combustion chamber formed at the top of the piton in synchronization with the arrival. The spray of fuel injected is spontaneously ignited by the heat of intake air, gas expansion is caused by combustion, and this gas expansion pushes the piston back to the bottom dead center side to take out the output. After this, the exhaust valve is opened so that the exhaust gas in the cylinder is exhausted through the exhaust port.

[0003]

A diesel engine designed to take out an output in this way has a problem in that exhaust gas contains a large amount of nitrogen oxides. An effective method for reducing nitrogen oxides in exhaust gas is to retard the timing retard, that is, the timing of fuel injection. However, when the timing retard is performed, there is a problem that the black smoke also deteriorates because the combustion state deteriorates. In addition, there are drawbacks that fuel efficiency deteriorates and engine efficiency decreases. However, with a direct-injection diesel engine that uses a piston with a conventional re-entrant type combustion chamber at the top, it is very difficult to suppress the generation of black smoke while reducing nitrogen oxides by timing retardation. there were.

The present invention has been made in view of the above problems, and it is possible to achieve both reduction of nitrogen oxides by timing retardation and reduction of black smoke by improvement of combustion. It is intended to provide an injection type diesel engine.

[0005]

According to the present invention, a fuel injection pump is used to pressurize fuel and supply the pressurized fuel to a fuel injection nozzle, and the fuel is injected from the injection port into a combustion chamber formed on the top of the piston. In a direct-injection diesel engine that injects fuel toward a combustion chamber, which is composed of a recess formed in the top of the piston, has an undercut shape in which the inner side of the piston expands toward the outer peripheral side. A direct injection diesel engine, characterized in that a protrusion is provided substantially in the center of the combustion chamber, and a throat is formed between the protrusion and the inlet of the combustion chamber. is there.

[0006]

When the spray of fuel is injected from the fuel injection nozzle toward the combustion chamber of the piston by the fuel injection nozzle in the process of moving the piston to the top dead center side, the spray of fuel is the projection of the combustion chamber. Becomes a vortex on the outer peripheral side of the piston, and when this vortex flows to the bottom dead center side of the piston, it becomes a turbulent jet while violently colliding with the throat on the outer peripheral side of the projection, improving combustion. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a main part of a diesel engine according to an embodiment of the present invention.
0 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 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.

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 the nozzle body 34, and 4 to 10 injection holes 35 are formed at the tip portion of the nozzle body 34. The nozzle body 34 is attached to the nozzle holder 37 by a retainer 36. A nozzle needle 38 is slidably held in the nozzle body 34. The upper end of the nozzle needle 38 is connected to the compression coil spring 4 in the nozzle holder 37 via the pressing rod 39.
It is designed to be pressed downward by 0. 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. A fuel sump 51 is formed at the end of the fuel passage 43.

The spring 40 pressing the pressing rod 39 has its upper end received by a 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 piston 12 incorporated in the cylinder 11 will be explained. As shown in FIG. 4, the piston 12 has an undercut combustion in which the inlet side is narrow and the inner side is widened to the outer peripheral side as shown in FIG. The room 21 is provided. Moreover, a poppet valve-shaped projection 70 is provided at the bottom of the center of the combustion chamber 21. Protrusion 70
Is made of a material different from that of the piston 12, for example, stainless steel or ceramic, and is joined to the bottom of the combustion chamber 21 of the piston 12 by a friction welding method.

Next, an 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 fixed to the camshaft 29 pushes up the roller of the tappet 55, whereby the plunger 54 moves upward in the barrel 57. 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,
Eventually, the inclined groove 59 is aligned with the spill port 58, so that the pressure in the space above the plunger 54 is increased.
Through the spill port 58 side, 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 changes, and 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 the 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 by the injection port 3 of the fuel injection nozzle 20.
5, the fuel is injected toward the combustion chamber 21 formed on the top surface of the piston 12 shown in FIG. 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.
After this, the exhaust valve 19 is opened, and exhaust gas is discharged through the exhaust port 17.

In such a direct-injection diesel engine, if the timing retard is carried out in order to reduce the nitrogen oxides in the exhaust gas, black smoke and fuel efficiency will deteriorate. Therefore, in this engine, in order to make the combustion immediately after the piston 12 reaches the top dead center and to promote the combustion,
The shape of the combustion chamber 21 of the piston 12 is a swirl chamber type, and the throat portion 71 is provided on the outer peripheral side of the protrusion 70 in order to perform high temperature combustion by ejecting a flame.

When the piston 12 moves to the top dead center side,
Immediately before reaching the top dead center, fuel is injected from the injection port of the fuel injection nozzle 20 as shown in FIG. This injection port becomes a swirl in the swirl chamber 21 formed by the combustion chamber 21 through the throat portion 71. And after this, the piston 12
As shown in FIG. 6, when the turbulent flame in the swirl chamber 21 starts moving to the bottom dead center side, the throat portion 7 on the outer peripheral side of the projection 70 is generated.
The fuel is sprayed upward from the inlet of the combustion chamber 21 while violently colliding with each other through 1. Thus, re-combustion of the fuel spray is performed, and soot which should be black smoke is re-combusted at this time.

As described above, the swirl chamber is provided at the bottom of the combustion chamber 21 of the piston 12 and on the outer peripheral side of the protrusion 70, and the throat portion 71 is provided between the outer peripheral side of the protrusion 70 and the inlet portion of the combustion chamber 21. By forming the, the re-combustion is achieved by the unburned portion of the fuel spray, the heat generation rate is improved, and the efficiency is improved.

Although the projection 70 is made of stainless steel in this embodiment, a ceramic material may be used instead of the projection 70 made of such stainless steel, or the projection 70 may be made of stainless steel. The protrusions 70 can be joined by various methods other than friction welding, for example, various structures such as casting together at the time of casting or fixing with screws later. Further, the piston 12 provided with such a protrusion 70 can be applied to a piston made of cast iron as well as a piston made of an aluminum alloy.

[0025]

As described above, according to the present invention, the combustion chamber composed of the concave portion formed at the top of the piston is formed into an undercut shape in which the inner side is widened toward the outer peripheral side than the inlet, and the combustion chamber is formed. Is provided at a substantially central portion thereof, and a throat portion is formed between the projection and the inlet portion of the combustion chamber.

Therefore, according to the present invention, the inside of the combustion chamber on the outer peripheral side of the protrusion becomes the swirl chamber, and the spray of fuel can be mixed well with the intake air in this swirl chamber. Moreover, when the combustion gas generated by the combustion of the air-fuel mixture is ejected from the swirl chamber consisting of the combustion chamber, it is violently generated at the throat portion formed on the outer peripheral side of the protrusion and between the combustion chamber and the inlet portion of the combustion chamber. It becomes possible to re-combust, which suppresses the generation of black smoke and improves the thermal efficiency.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a direct injection diesel engine.

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

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

FIG. 4 is a perspective view in which a part of a piston is cut away.

FIG. 5 is a cross-sectional view of essential parts showing a state of vortex flow.

FIG. 6 is a cross-sectional view of essential parts showing reburning due to turbulent flow.

[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 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 Main Body 35 Nozzle 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 Thread 47 Cap 48 Projection 49 Male Thread 50 Connection Nut 51 Fuel sump 54 Plunger 55 Tappet 56 Coil spring 57 Barrel 58 Spill port 59 Inclined groove 60 Pinion 61 Cement engaging roll sleeve 62 notch 63 Plywood 64 Deriberibarubu 65 casing 66 valve seat 67 coil spring 70 projection 71 throat

Claims (1)

[Claims] 1. A fuel injection pump pressurizes fuel and supplies the pressurized fuel to a fuel injection nozzle,
In a direct-injection diesel engine in which fuel is injected from the injection port toward the combustion chamber formed at the top of the piston, the combustion chamber consisting of the recess formed at the top of the piston is located deeper than the inlet. Has a shape of an undercut that spreads to the outer peripheral side, a protrusion is provided substantially in the center of the combustion chamber, and a slot is formed between the protrusion and the inlet of the combustion chamber. A direct-injection diesel engine characterized by the above.