JPH07189701A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To accelerate the mixing of fuel spray and air so as to attain desirable combustion by optimizing the flow of air in process of combustion. CONSTITUTION:Protruding parts 71, 72 are provided at the approximately control part of the bottom part of a combustion chamber 21 formed of a recessed part formed at the top face of a piston 12. These protruding parts 71, 72 are formed into the shape of cones put one over the other in two stages, and the vertical angle of the cone 72 on the lower side is to be larger than that of the cone 71 on the upper side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine, and more particularly to a piston for an internal combustion engine which has a combustion chamber having a concave portion on its top surface and is suitable for a direct injection diesel engine.

[0002]

2. Description of the Related Art A direct injection diesel engine uses a fuel injection nozzle to raise the pressure of fuel to inject fuel spray from a nozzle into a combustion chamber consisting of a recess formed on the top surface of a piston. While mixing with the air, the heat of the intake air causes the fuel spray to ignite spontaneously and burn.

[0003]

As described above, the piston used in the diesel engine is provided with a combustion chamber having a recess on the top surface thereof. This combustion chamber was constructed, for example, in a toroidal type or a reentrant type. However, according to the conventional toroidal type or reentrant type combustion chamber, the air flow in the combustion process cannot be optimally performed, and the oil droplets of the fuel spray and the air cannot be sufficiently mixed. Therefore, there is a drawback that the exhaust gas contains black smoke and particulates.

The present invention has been made in view of the above problems, and makes it possible to optimize the flow of air in the combustion process, thereby promoting the mixing of air and fuel spray. An object of the present invention is to provide a piston for an internal combustion engine, which enables good combustion.

[0005]

According to the present invention, there is provided a piston for an internal combustion engine having a combustion chamber having a concave portion on a top surface thereof, wherein the concave portion forming the combustion chamber has a protrusion substantially at the center thereof, and the protrusion is provided. Relates to a piston for an internal combustion engine, wherein the cone has a shape in which the cones are stacked in two stages, and the vertex angle of the lower cone is larger than the vertex angle of the upper cone.

[0006]

The flow of air from the outer peripheral side of the combustion chamber consisting of the concave portion formed on the top surface of the piston to the bottom portion has a shape in which cones are superposed in two steps at the substantially central portion of the bottom portion, and By the projection where the apex angle of the lower cone is larger than the apex angle, it is changed to the air flow from the upper side to the outer peripheral side,
Such air flow promotes the mixing of fuel and air.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an essential part of a diesel engine equipped with a piston for an internal combustion engine 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. And piston 1
2 is connected to a 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, the combustion chamber 21 formed of a recess formed on the top surface of the piston 12 has a protrusion at its bottom and substantially in the center thereof. This protrusion has two cones, as shown in FIG.
It has a stacked shape. That is, the shape is such that the cone 71 having a small apex angle θ _{1 on} the upper side is overlapped with the cone 72 having a large apex angle θ ₂ .

The fuel injection nozzle 20, as shown in FIG.
It is connected to the corresponding pump unit 26 of the column fuel injection pump 25 by the injection pipe 24. The fuel injection pump 25 includes a mechanical governor 27, and the mechanical governor 27 moves a control rack 28 to
The amount of fuel that is injected each time is adjusted. The fuel injection pump 25 includes a cam shaft 29, and a cam 30 attached to the cam shaft 29.
Drive 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 plurality of injection holes 35 are formed at each of the injection positions of 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 pressed downward by the compression coil spring 40 in the nozzle holder 37 via the 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. A fuel sump 51 is formed at the end of the fuel passage 43.

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 this protrusion 48, and the injection pipe 24 is connected to the nozzle holder 37 by a connection nut 50 screwed with the male screw 49. It is supposed to be done.

Next, the structure of each pump unit 26 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 delivery valve 64 is pressed toward the valve seat 66 by the coil spring 67.

Next, an outline of the operation of the diesel engine configured as above will be described.

The timer 31 is controlled by a part of the output of the engine.
When the cam shaft 29 of the column fuel injection pump 25 is driven via the cam, the cam 30 pushes up the roller of the tappet 55, which causes the plunger 54 to move upward in the barrel 57. Then, the peripheral 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 59 eventually 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 fuel is pumped. finish.

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 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 the diesel engine which takes out the output in this way, the piston 12 is provided with the combustion chamber 21 as shown in FIGS. 4 and 5, and the cone is arranged in two stages in the center of the bottom. A protrusion having a shape is formed. That is, it has a shape in which the conical protrusion 71 having a small apex value of θ ₁ is superposed on the upper side of the lower conical protrusion 72 having a large apex angle θ ₂ . By providing the protrusions with such a shape, the flow of air in the combustion process is optimized, which promotes the mixing of the air and the fuel spray, and the exhaust gas does not contain black smoke or particulates. Combustion is achieved.

The apex angle θ ₁ of the upper conical protrusion 71 is preferably in the range of 90 to 150 °, and the apex angle θ ₂ of the lower conical protrusion 72 is in the range of 130 to 180 °. Is preferred. On the other hand, the angle θ ₃ formed by the generatrixes of the two conical protrusions
Should be within the range of 45 ° at maximum.

Direct injection type diesel engine piston 12
The combustion chamber 21 is usually provided with a conical protrusion at the center of the combustion chamber, but it was not always shaped to optimize the air flow. In the piston 12 according to the present embodiment, in particular, as shown in FIG. 5, the conical protrusions 71, 72 are vertically stacked in two stages to form the combustion chamber 2
As shown in FIG. 6, the vortex flow of air in 1 is stronger than in the case of the one-step conical protrusion. That is, a strong air flow as indicated by an arrow in FIG. 4 is generated, and such air flow promotes mixing of the fuel spray and air, thereby improving combustion. This will reduce black smoke.

That is, a stronger vortex flow is obtained by improving the shape of the projection at the bottom of the combustion chamber 21, and such strong vortex flow promotes the mixing of air and fuel to improve combustion, The amount of black smoke and particulates in the exhaust gas is reduced, which greatly contributes to the improvement of exhaust gas.

[0025]

As described above, according to the present invention, the protrusion is formed in the substantially central portion of the bottom surface of the recess forming the combustion chamber formed on the top surface of the piston, and the protrusion forms a cone in two stages. It is a shape that is overlapped, and the apex angle of the lower cone is larger than the apex angle of the upper cone.

By forming the protrusion having such a shape, a stronger vortex flow is generated to promote the mixing of the fuel spray and the air to improve the combustion and reduce the smoke concentration in the exhaust gas. It will be possible.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a direct injection diesel engine equipped with a piston 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 vertical sectional view of a piston.

FIG. 5 is a side view showing a shape of a protrusion formed at a substantially central portion of a bottom portion of a combustion chamber of a piston.

FIG. 6 is a graph showing a change in vortex strength with respect to the shape of a protrusion.

[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 52 One-way valve 54 Plunger 55 Tappet 56 Coil spring 57 Barrel 58 Spill port 59 Sloping groove 60 Anions 61 the control sleeve 62 the notch 63 engagement plate 64 Deriberibarubu 65 casing 66 valve seat 67 coil spring 71 yen conical projection (top) 72 yen conical projection (bottom)

Claims (1)

[Claims] 1. A piston for an internal combustion engine having a combustion chamber having a concave portion on its top surface, wherein the concave portion forming the combustion chamber has a protrusion at substantially the center thereof, and the protrusion has a conical stack in two stages. A piston for an internal combustion engine, which is shaped and in which the apex angle of the lower cone is larger than the apex angle of the upper cone.