JP2002371851A - Indirect diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce toxic exhaust substance such as smoke and increase high thermal efficiency. SOLUTION: This indirect diesel engine is constituted in such a way that an auxiliary chamber 6 is provided inside a piston 5, a hole 8 in which a fuel injection nozzle 4 mounted on a cylinder head 3 in the vicinity of top dead center is inserted is provided in a top plate 6a in the auxiliary chamber, and a plurality of communication ports 10 communicating the auxiliary chamber 6 with a main combustion chamber 9 facing a top part of the piston are radially arranged around the auxiliary chamber. The communication port 10 is provided in a shoulder part 6b of the auxiliary chamber, its direction is offset close to a side wall from a central line 0 of the auxiliary chamber, and it is obliquely and downward inclined toward a bottom face 12 of the auxiliary chamber crossing the central line 0 of the auxiliary chamber. Moreover, a part around a lower part 16 of the auxiliary chamber is formed into a circular arc smooth shape which is large as much as possible from the bottom face 12 of the auxiliary chamber to the side wall 17. Furthermore, fuel (b) is injected between adjacent communication ports or toward below each communication port from the fuel injection nozzle 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sub-chamber diesel engine having a sub-chamber in a piston.

[0002]

2. Description of the Related Art Conventionally, a hollow sub-chamber is provided inside a piston, and a hole is formed in a top plate of the sub-chamber near the top dead center of the piston, through which a fuel injection nozzle mounted on a cylinder head enters. 2. Description of the Related Art A sub-chamber diesel engine is known in which a plurality of communication ports are radially arranged around a chamber to communicate a sub-chamber and a main combustion chamber facing the top of a piston.

[0003]

However, in the conventional subchamber diesel engine, the air flowing from the main combustion chamber into the subchamber during the compression stroke is relatively small because the angle of inclination of the communication port with respect to the top of the piston is relatively small. The drawback is that the swirl created by the flow is uneven before reaching the lower part of the subchamber.

For this reason, the air flow partially has a weak region, and the mixing of the fuel and the air that has reached that portion deteriorates, delaying the generation of smoke or the outflow of the combustion gas into the main combustion chamber. There is a problem that is easily generated.

[0005] Further, because the vertical flow of the air flow is weak, the fuel or the combustion gas that has reached the bottom of the sub-chamber stays at the bottom of the sub-chamber to generate smoke or to move the combustion gas to the main combustion chamber. In some cases, the performance was deteriorated due to the outflow delay. In particular, in the case of the fuel injection direction in which a large amount of fuel spray collides with the side wall of the sub-chamber, after the collision, the injected fuel tends to reach the bottom of the sub-chamber along the side wall, and the above-mentioned effects tend to appear more. .

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a sub-chamber diesel engine having a sub-chamber in a piston, which has less harmful emissions such as smoke and high heat. An object of the present invention is to provide an efficient sub-chamber diesel engine.

[0007]

Means for Solving the Problems To solve the above problems, the present invention is configured as follows.

That is, (1) a hollow sub-chamber is provided inside the piston, and a hole is formed in the top plate of the sub-chamber near the top dead center of the piston, into which the fuel injection nozzle mounted on the cylinder head enters. In a sub-chamber diesel engine in which a plurality of communication ports communicating the sub-chamber and the main combustion chamber facing the top of the piston are arranged radially around the sub-chamber, the communication ports are provided on shoulders of the sub-chamber. The direction is offset toward the side wall from the center line of the sub-chamber, and further tilted obliquely downward toward the bottom surface of the sub-chamber beyond the center line of the sub-chamber. A sub-chamber type characterized in that it is formed in an arc-shaped smooth shape as large as possible from the front to the side wall, and that fuel is injected from a fuel injection nozzle between adjacent communication ports or downward of each communication port. With a diesel engine That.

(2) The sub-chamber diesel engine according to (1), wherein a bottom surface of the sub-chamber is projected in a conical shape.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a sub-chamber type diesel engine according to the present invention, and FIG. 2 is a sectional view taken along line AA 'of FIG.

As shown in FIG. 1, this sub-chamber diesel engine has a cylinder block 2 having a cylinder 1.
And a cylinder head 3 fixed to the cylinder block 2
A fuel injection nozzle 4 mounted on the cylinder head 3 and a piston 5 reciprocating in the cylinder 1.

The sub-chamber diesel engine further has a hollow sub-chamber 6 inside the piston 5 and a sub-chamber 6.
Near the top dead center of the piston 5 has a hole 8 into which the fuel injection nozzle 4 attached to the cylinder head 3 enters,
Further, a plurality of communication ports 10 are provided radially around the sub-chamber 6 to communicate the sub-chamber 6 with the main combustion chamber 9 facing the piston top 7.

According to the present invention, as shown in FIG. 1, the communication port 10 is formed around the upper part of the sub-chamber 6, ie, the shoulder 6b.
And the direction of the communication port 10 from the center axis O of the sub-chamber 6 so that the air a flowing from the main combustion chamber 9 to the sub-chamber 6 during the compression process does not collide with each other at the center line O of the sub-chamber 6. It is offset laterally (see FIG. 2). That is, as shown in FIG.
Is translated by L just beside L. However, it is not limited to this example. The point is that air a flowing from the main combustion chamber 9 into the sub-chamber 6 during the compression process should not collide with each other at the central axis O of the sub-chamber 6.

Further, as shown in FIG.
The sub chamber 6 is inclined obliquely downward toward a substantially horizontal bottom surface 12. For example, the communication port 10a has its center line 13
The intersection 14 between the sub-chamber and the bottom surface 12 of the sub-chamber
The sub chamber is inclined so as to be located on the side beyond the radial straight line 11a (see FIG. 2) of the sub-chamber which is orthogonal to. The inclination angle θ is set with respect to the horizontal surface 15, that is, the bottom surface 12 of the sub-chamber so that the flow velocity of the air a flowing into the sub-chamber 6 from the communication port 10 is not greatly attenuated by the collision with the bottom surface 12 of the sub-chamber. About 4
Set to 5 degrees or less.

When the height of the sub-chamber 6 is high, FIG.
As shown in FIG. 5, the bottom surface 12 'of the sub chamber 6 is made to protrude in a conical shape so that the inclination angle θ of the communication port 10 with respect to the conical bottom surface 12' falls within a set range. In the figure, α is
It shows the leg opening angle of the conical bottom surface 12 '.

Returning to FIG. 1, the lower periphery 16 of the sub-chamber 6 is formed as large as possible in the shape of a circular arc from the bottom surface 12 of the sub-chamber to the side wall 17 of the sub-chamber.

Further, the fuel b is injected from the fuel injection nozzle 4 toward a space between the adjacent communication ports 10. However, if desired, the fuel b may be injected from the fuel injection nozzle 4 downwardly of each communication port 10.
In short, the fuel 4 injected from the fuel injection nozzle 4 is
Downstream along the side wall 17.

Next, the operation of the sub-chamber diesel engine will be described.

As shown in FIGS. 4A and 4B, the air a flowing from the main combustion chamber 9 to the sub-chamber 6 during the compression stroke is such that the communication port 10 is offset from the central axis O of the sub-chamber 6. Therefore, the air reaches the bottom surface 12 of the sub-chamber 6 without interfering with the air a flowing from the adjacent communication port 10.

The air a reaching the bottom surface 12 of the sub-chamber 6 flows along the side wall 17 from the bottom surface 12 of the sub-chamber 6 without substantially attenuating the flow velocity because the inclination angle θ of the communication port 10 is relatively small. On the side wall 17 of the sub-chamber 6, as shown in FIG. 4A, an upward vertical flow c is formed.

Further, since the communication port 10 is offset from the central axis O of the sub chamber 6 as described above,
As shown in FIG. 4B, a swirl d is also generated, and a three-dimensional uniform air flow is formed in the sub-chamber 6.

On the other hand, as shown in FIG. 4A, the fuel b is injected from the fuel injection nozzle 4 toward the side wall 17 between the adjacent communication ports 10, so that the fuel b collides with the side wall 17 of the sub chamber 6. The fuel b and the combustion gas flow along the side wall 17 toward the lower part of the sub-chamber 6 as shown by the arrow e.

As described above, since the air a forms a flow flowing upward along the side wall 17 of the sub-chamber 6, the air a and the fuel b and the combustion gas after colliding with the side wall 17 of the sub-chamber 6 It collides and blocks the flow of the fuel b and the combustion gas toward the lower part of the sub-chamber 6. As a result, the fuel b and the combustion gas are
The air a does not reach the bottom surface 12 of the sub-chamber 6, and the air a
Only exists.

Since the communication port 10 is provided at the shoulder 6b of the sub-chamber 6, after the upward air a, the downward fuel b and the combustion gas collide with each other at the upper part of the sub-chamber 6, they are mixed. While burning, the fuel is immediately jetted into the main combustion chamber 4 as shown by an arrow g.
Completely burn. The air a at the bottom of the sub-chamber is blown out into the main combustion chamber 9 from the hole 8 and the communication port 10 at the latter stage of the combustion, and promotes the secondary combustion in the main combustion chamber 9, thereby realizing good combustion.
In FIG. 4A, f indicates a mixed combustion section.

As described above, according to the present invention, since the fuel and the fuel gas do not reach the bottom surface 12 of the sub chamber 6, low smoke can be realized. Further, in the sub-chamber 6, the fuel and the combustion gas do not greatly diffuse into the sub-chamber 6 but richly burn near the communication port 10 and recombust in the main combustion chamber 9, so that low NOx and low smoke are realized. it can.

Further, since the combustion gas is quickly spouted from the sub-chamber 6, it burns rapidly and high heat efficiency can be obtained. Further, by promoting the mixing by the three-dimensional air flow, the operation at a low excess air ratio becomes possible, and the output is improved.

[0028]

As described above, according to the present invention, since the fuel and the fuel gas do not reach the bottom of the sub chamber, low smoke can be realized. Further, in the sub-chamber, fuel and combustion gas do not greatly diffuse into the sub-chamber, but perform rich combustion near the communication port and re-combust in the main combustion chamber, so that low NOx and low smoke can be realized.

Further, since the combustion gas is quickly spouted from the sub-chamber, it burns rapidly and high heat efficiency can be obtained. Further, by promoting the mixing by the three-dimensional air flow, the operation at a low excess air ratio becomes possible, and the output is improved.

Further, even if the area ratio of the communication port is increased (for example,
(1.5% to 2.3%), the air flow in the sub-chamber becomes uniform, so that the throttle loss is reduced and the output is improved. Further, low excess air ratio operation can be performed at low speed rotation where it is difficult to increase the supercharging pressure, and low speed torque can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a sub-chamber diesel engine according to the present invention.

FIG. 2 is a sectional view taken along the line AA 'of FIG.

FIG. 3 is a longitudinal section showing another example of the bottom shape of the sub chamber.

FIGS. 4 (a) and 4 (b) are explanatory diagrams of the operation of the sub-chamber diesel engine according to the present invention.

[Explanation of symbols]

 Reference Signs List 3 cylinder head 4 fuel injection nozzle 5 piston 6 sub-chamber 6a sub-chamber top plate 6b sub-chamber shoulder 7 piston top 8 hole 9 main combustion chamber 10 communication port 12 sub-chamber bottom surface 16 sub-chamber lower periphery 17 sub-chamber Side wall of b Fuel O Center line of sub chamber

Claims (2)

[Claims] 1. A hollow sub-chamber is provided inside a piston, and a hole is formed in a top plate of the sub-chamber near a top dead center of the piston, into which a fuel injection nozzle mounted on a cylinder head enters.
Further, in a sub-chamber diesel engine in which a plurality of communication ports for communicating the sub-chamber and the main combustion chamber facing the top of the piston are arranged radially around the sub-chamber, the communication ports are provided on shoulders of the sub-chamber. At the same time, the direction is offset from the center line of the sub-chamber toward the side wall, and further inclined obliquely downward toward the bottom surface of the sub-chamber beyond the center line of the sub-chamber. Characterized in that the fuel injection nozzle is formed into a shape as large as possible from the bottom surface to the side wall and is as smooth as possible, and the fuel is injected from a fuel injection nozzle between adjacent communication ports or downward of each communication port. Room type diesel engine. 2. The sub-chamber diesel engine according to claim 1, wherein a bottom surface of the sub-chamber protrudes in a conical shape.