JPH084535A - Piston of direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To expedite inflow of air to the combustion chamber of a direct injection type diesel engine so as to improve its combustion performance. CONSTITUTION:A plurality of swirl guide grooves 6 are formed on the outer ring 5 of a piston head 2, the more each swirl guide groove 6 is advanced, in the peripheral direction A of the outer ring 5, the more they are downwardly deeply recessed and formed in a tapering sliding way shape approaching to a cavity 3, the inlet parts 6a of the swirl guide grooves 6 on a peripheral direction upper side are formed flush with head surfaces 7, and outlet parts on lower sides are communicated with the cavity 3. Directivity of air flow is enhanced, while air is guided along the peripheral direction A of the swirl guide grooves 6 and slides down along a tapering sliding way, and also the air flow is converged by throttle action so as to be introduced to the cavity 3. Hereby, the inflow of the air to a combustion chamber is expedited so that intake swirl can be strengthened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for a direct injection diesel engine, and by incorporating this piston in the engine, it promotes the inflow of air into the combustion chamber to strengthen the swirl and to mix air and fuel. We will provide products that are strong and can improve combustion performance.

[0002]

BACKGROUND OF THE INVENTION The basic structure of the piston of a direct injection diesel engine which is the subject of the present invention is, as shown in FIG. 1, FIG. 4 or FIG. 5, in the center of the piston head 2 of the piston 1 of the diesel engine E. The cavity 3 is of a type recessed downward.

[0003]

2. Description of the Related Art As prior art 1 of this type, as shown in Japanese Patent Application Laid-Open No. 3-168322 (see FIG. 4), the head surface 7 becomes closer to the outer peripheral portion of the cavity 3 of the piston head 2 in the inner diameter direction. A taper surface 50 is formed that is inclined from the bottom to the cavity 3 and a plurality of guide grooves 51 are engraved on the taper surface 50 from the radial direction of the cavity 3 as appropriate. 3 is provided with a convex portion 52 having a trapezoidal cross section so as to be opposed to No. 3.

In the prior art 1, when the piston 1 transitions to the top dead center, the passage of the squish flow 53 is narrowed by the proximity of the tapered surface 50 and the convex portion 52 to accelerate the flow, and the squish flow is also increased. Can be converged at each guide groove 51 to further enhance the speed increasing action, so that the mixing of fuel and air is promoted.

On the other hand, as the prior art 2, Japanese Patent Laid-Open No. 2-1
As shown in Japanese Patent Publication No. 49719 (see FIG. 5), a plurality of air supply holes 5 are provided on the outer peripheral side of the cavity 3 of the piston head 2.
4, the air supply holes 54 are connected to the central cavity 3 through the flame guide groove 55, and the flame guide groove 55 is formed to have a uniform depth and shallower than the air supply hole 54. There is one in which a convex portion 56 is provided on the lower surface of the cylinder head 10 so as to face the cavity 3 and oriented in the direction S of the intake swirl.

In the prior art 2, when the piston moves to the top dead center, the cavity 3 has the convex portion 5 on the cylinder head 10 side.
Since it is blocked by 6, the air shortage is caused and the generation of nitrogen oxides is suppressed. Further, at the time of expansion transition after passing through the top dead center, the flame and unburned vapor in the cavity 3 violently jet and meet the air in the air supply hole 54, and the second stage mixing is performed. In this case, the flame is selectively directed to the air supply hole 54 by the flame guide groove 55, so that the mixing speed is increased and high swirl strength is maintained.

[0007]

In the above-mentioned prior art 1,
Although the squish flow can be enhanced to some extent by providing the tapered surface 50 and the guide groove 51 on the outer peripheral side of the cavity 3, the tapered surface 50 is formed only at a local outer peripheral portion in contact with the piston head 2 and other head surfaces. Since it is not formed in 7, there is a limit to the speedup of the squish flow. Besides,
Since the prior art 1 is actually a mechanism for accelerating the squish flow by the combination of the convex portion 52 on the cylinder head 10 side and the cavity 3 on the piston 1 side, an ordinary smooth lower surface without the convex portion 52 is formed. Cylinder head 10 having
In combination with, the squish acceleration effect is further restricted.

In the above-mentioned prior art 2, the main purpose is to suppress the production of nitrogen oxides, and the flame guide groove 55 guides the flame from the cavity 3 toward the air supply hole 54, so that the two stages at the time of expansion transition. It promotes eye mixing. Therefore, in the mixing process of the fuel and the air before and after the transition to the top dead center, there is a limit to the sufficient promotion of this mixing. Further, in the prior art 2 as well, as in the prior art 1, since the convex portion 56 on the cylinder head 10 side is combined with the concave portions 54, 55 on the piston 1 side, the swirl speed-up action is largely restricted. The present invention relates to a direct injection diesel engine, and has a technical problem to develop a piston capable of promoting the inflow of air into a combustion chamber to improve combustion performance.

[0009]

Means for achieving the above object will be described below with reference to FIGS. 1 to 3 showing an embodiment. That is, the present invention relates to the piston of the direct injection diesel engine having the basic structure described above, wherein the piston head 2
A plurality of swirl guide grooves 6 are formed in a strip-shaped outer ring portion 5 between the outer peripheral edge 4 and the cavity 3, and each swirl guide groove 6 is deeply recessed downward as it goes in the circumferential direction A of the outer ring portion 5. At the same time, the vortex flow guide groove 6 is formed in the shape of a tapered slide that approaches the cavity 3 and is located on the upper side of the circumferential direction A thereof.
Of the vortex flow guide groove 6 located on the lower side of the circumferential direction A of the piston head 2 is formed so as to have an inlet portion 6a which is as wide as the outer ring portion 5 in the radial direction and which is flush with the head surface 7. Is communicated with the cavity 3.

[0010]

The piston 1 is incorporated in a diesel engine with the circumferential direction A of the vortex flow guide groove 6 aligned with the swirl direction. Therefore, the operation of this diesel engine will be described.

The air that has entered the combustion chamber through the intake port is
First, it is received in the inlet portion 6a of the vortex flow guide groove 6 which is formed in the outer ring portion 5 of the piston head 2 to its full width and is flush with the head surface 7. Therefore, the air is guided toward the vortex flow outlet portion 6b so as to slide down the slide of the first throttle, along the circumferential direction A of the vortex flow guide groove 6.
During this time, the flow direction of the intake swirl is enhanced, and the flow is converged (that is, accelerated) by its throttling action and introduced into the cavity 3. Therefore, unlike the above-mentioned prior art 1 or 2 in which a special cylinder head 10 having a protruding portion is combined with the piston 1, regardless of the form of the cylinder head 10 to be combined, the inflow of air into the combustion chamber is promoted. The intake swirl can be strengthened, and the mixture of air and fuel can be strongly promoted.

[0012]

Since the air that has entered the combustion chamber is strongly guided to the cavity of the piston by the swirl guide groove, it is possible to strongly mix the air and the fuel and improve the combustion performance. Thus, harmful components in the exhaust (soot, CO, NO _X, SO _X, etc.)
The fuel consumption rate is improved and
The maximum output of the diesel engine can be increased.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a main part of a piston of a vertical direct injection diesel engine, FIG. 2 is a plan view of the piston, and FIG. 3 is a vertical sectional view of a main part of the diesel engine.

As shown in FIG. 3, the cylinder head 10 is assembled on the upper side of the cylinder 11 of the vertical direct injection diesel engine E, and the fuel injection pump 12 is brought from above the cylinder head 10 into the combustion chamber 13 and close to the cylinder 11. It rushes toward the center of the combustion chamber 13 so as to tilt. The intake port 15 is opened in the cylinder head 10 and the intake port 15
The intake valve 16 is opened and closed at the outlet 15a of the.

As shown in FIGS. 1 to 3, the cylinder 1
1, a cylinder bore 14 is formed, a piston 1 is vertically slidably fitted in the cylinder bore 14, and a cavity 3 is formed downward in the center of the piston head 2. The outer peripheral portion 3a of the cavity 3 is depressed downward from the head surface 7 of the piston head 2 in a curved shape, and a conical mound is projected in the central portion 3b thereof, and the injection hole 12a of the fuel injection pump 12 is It is directed to this cavity 3.

As shown in FIGS. 1 to 3, three swirl guide grooves 6 are formed in a belt-shaped outer ring portion 5 between the outer peripheral edge 4 of the piston head 2 and the cavity 3. As shown in FIGS. 1 and 2, each vortex flow guide groove 6 is deeply recessed downward as it goes in the circumferential direction A (specifically, leftward direction) of the outer ring portion 5 and approaches the cavity 3. In addition, it is formed in the shape of a tapered slide. However, the direction of the intake swirl is, for example,
Although it is determined by the direction in which air enters the combustion chamber 13 from the swirl chamber of the intake port 15, the circumferential direction A in which the swirl guide groove 6 is narrowed is set so as to coincide with this swirl direction.

As shown in FIG. 2, when the vortex flow guide groove 6 is viewed in plan, it has a shape in which the base of an elongated triangle is not moved but its apex is twisted and swung in a certain direction. Therefore, as shown in FIG. 1, the inlet portion 6a of the swirl guide groove 6 located on the upper side of the swirl direction A has the full width in the radial direction of the outer ring portion 5 and is flush with the head surface 7 of the piston head 2. Formed in a uniform shape. Further, the outlet portion 6b of the vortex flow guide groove 6 located on the lower side of the swirl direction A has the cavity 3
Be communicated to. Moreover, when the piston head 2 is viewed in a plan view, the inlet portion 6a of each vortex flow guide groove 6 is arranged so as to contact the outlet portion 6b of the adjacent vortex flow guide groove 6.

The function of the direct injection diesel engine incorporating the piston of this embodiment will be described. Inlet 6a of swirl guide groove 6 recessed in piston head 2
Is formed so as to fill the width of the belt-shaped outer ring portion 5 and to be flush with the head surface 7, so that the air that has entered the combustion chamber 13 through the intake port 15 is first guided by these three vortex flow guides. It is received in the inlet portion 6a of the groove 6, respectively.

For this reason, the air flows along the swirl direction A of the vortex flow guide groove 6 while moving along the swirl direction A (see FIGS. 1 and 2).
It is guided to the outlet portion 6b of the vortex flow guide groove 6 in a state of sliding down. During this time, the direction of the flow of the air is enhanced, and the flow is converged (that is, accelerated) by the throttling action of the vortex flow guide groove 6 to move from the outlet portion 6b of the vortex flow guide groove 6 to the cavity 3. be introduced. Therefore, the guide action of the vortex flow guide groove 6 and the throttle action can promote the inflow of air to strengthen the intake swirl, so that the fuel injected from the fuel injection pump 12 toward the cavity 3 is mixed with the air. The combustion performance of the diesel engine E can be enhanced strongly, and the amount of harmful components in the exhaust gas can be reduced.

Since the present invention is characterized in that the outer ring portion 5 of the piston head 2 is provided with a squeezing slide groove-like vortex guide groove 6 in advance, the number of the guide groove 6 is two or two. Three or more may be used. Further, the inlet portion 6a of each vortex flow guide groove 6 may be separated without contacting the outlet portion 6b of the adjacent vortex flow guide groove 6. On the other hand, the present invention is not limited to a vertical diesel engine in which the cylinder bore is oriented vertically,
It can also be applied to horizontal engines with the cylinder bore facing sideways.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a piston of a vertical direct injection diesel engine.

FIG. 2 is a plan view of the piston.

FIG. 3 is a longitudinal sectional view of a main part of the diesel engine.

FIG. 4 shows Prior Art 1, FIG. 4A is a longitudinal sectional view of a main part of a direct injection diesel engine, and FIG. 4B is a perspective view of a main part of a piston head.

FIG. 5 shows Prior Art 2, FIG. 5A is a longitudinal sectional view of a main part of a direct injection diesel engine, and FIG. 5B is a plan view of a piston head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piston, 2 ... Piston head, 3 ... Cavity, 4 ... Piston outer peripheral edge, 5 ... Piston head outer ring part, 6 ... Vortex guide groove, 6a ... Vortex guide groove inlet part, 6b
... outlet of swirl guide groove, 7 ... head surface, A ... circumferential direction of outer ring, E ... direct injection diesel engine.

Claims (1)

[Claims] 1. A piston (1) for a diesel engine (E)
In a piston of a direct injection diesel engine in which a cavity (3) is recessed downward in the center of the piston head (2), the outer peripheral edge (4) of the piston head (2) and the cavity
A plurality of swirl guide grooves (6) are formed in the strip-shaped outer ring part (5) between (3) and
And each vortex flow guide groove (6) is deeply recessed downward as it goes in the circumferential direction (A) of the outer ring portion (5), and is formed in a pre-sliding slide shape so as to approach the cavity (3). The inlet portion (6a) of the vortex flow guide groove (6) located on the upper side of the circumferential direction (A) is filled with the radial width of the outer ring portion (5) and the head surface of the piston head (2) ( 7) is formed so as to be flush with, and the outlet portion 6 (b) of the vortex flow guide groove (6) located on the lower side of the circumferential direction (A) is communicated with the cavity (3). Injection diesel engine piston.