JPH09158734A - Direct injection combustion chamber of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the combustion efficiency by eliminating an air stagnation part to which the swirl flow is not applied in a cavity to promote the mixture of the air with the fuel in the cavity. SOLUTION: In a combustion chamber, a cavity 7 is arranged in a central part of a piston head top surface 4, and a valve recess 6 is arranged close to a circumferential edge of the piston head top surface 4 respectively, the cavity 7 is communicated with the valve recess 6, and the swirl flow 23 in introduced into the cavity 7 by the guide of an inner circumferential surface 12 of the valve recess. A raised part 10 is formed from a central part of an inner bottom of the cavity 7 to a cylinder head 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type combustion chamber of a diesel engine, and more particularly to a combustion chamber capable of increasing combustion efficiency.

[0002]

2. Description of the Related Art A conventional direct injection combustion chamber for a diesel engine is shown in FIG. This has the following basic structure as in the present invention. That is, the cylinder head 101 is provided with the fuel injection nozzle 102 and the swirl port 103, and the piston head top surface 10
4, leaving the squish surface 105, the valve recess 106
And a cavity 107 for combustion are recessed to form a cavity 1.
The fuel 108 is injected from the fuel injection nozzle 102 into the cavity 07, and the cavity 107 is inserted into the piston head top surface 1
In the center of 04, the valve recesses 106 are arranged near the periphery of the piston head top surface 104, respectively, and the cavity 107 and the valve recess 106 are communicated with each other so that the swirl flow 123 is guided by the valve recess inner peripheral surface 112. It is being introduced into.

In this type of combustion chamber, the intake air introduced into the cylinder from the swirl port 103 during the intake stroke causes
A swirl flow 123 around the cylinder center axis 109 is formed in the cylinder, and at the end of the compression process, the piston head top surface 104 approaches the cylinder head, so that the swirl flow 123 guides the valve recess inner peripheral surface 112. Is swiftly introduced into the cavity 107 to form a swirl flow 124 having the cavity center axis 122 as the swirl center in the cavity 107 and the squish surface 105.
A squish flow 125 is formed in the cavity 107, and the swirl flow 124 and the squish flow 125 mix air and fuel 108 in the cavity 107.

In this conventional technique, since the inner bottom surface of the cavity 107 is flat, a stagnant portion of air in which the swirl flow 124 does not act remains at the center of the cavity 107.

[0005]

In the above-mentioned conventional technique, since the stagnant portion of the air in which the swirling flow 124 does not act remains in the center of the cavity 107, the mixing of the air and the fuel 108 in the cavity 107 becomes insufficient. , The combustion efficiency is low.

An object of the present invention is to provide a direct injection type combustion chamber of a diesel engine which can improve combustion efficiency.

[0007]

[Means for Solving the Problems]

(First Invention) As shown in FIG. 1 (A) or 3, the first invention provides a cylinder head 1 with a fuel injection nozzle 2 and a swirl port 3, and a piston head top surface 4 with a squish surface 5. Remaining valve recess 6 and combustion cavity 7
Are provided so as to inject fuel 8 from the fuel injection nozzle 2 into the cavity 7, the cavity 7 is arranged at the center of the piston head top surface 4, and the valve recess 6 is arranged near the periphery of the piston head top surface 4. In addition, in the direct injection combustion chamber of the diesel engine in which the cavity 7 and the valve recess 6 are communicated with each other so that the swirl flow 23 is introduced into the cavity 7 by the guide of the valve recess inner peripheral surface 12, It is characterized by doing so.

That is, the ridge 10 is formed from the center of the inner bottom of the cavity 7 toward the cylinder head 1.

(Second Invention) In the second invention, as shown in FIG. 3, a swirl flow guide surface in which the cavity inner peripheral surface 11 and the valve recess inner peripheral surface 12 are directed tangentially to each other as shown in FIG. It is characterized by being connected by 13.

(Third Invention) In the third invention, as shown in FIG. 1A or 3, in the first or second invention, only one valve recess 6 is provided, and the direction parallel to the cylinder center axis 9 is provided. , The imaginary recess line 15 extending from the cylinder center axis 9 toward the recess center axis 14 of the valve recess 6, and the reference imaginary line extending from the cylinder center axis 9 to the opposite side of the recess center radiating line 15 16, a lower limit imaginary line 17 that is advanced from the reference imaginary imaginary line 16 in the swirl flow swirl direction, and an upper limit imaginary line 18 that is advanced from the lower radiant line 17 in the swirl flow swirl direction. Assuming that, it is characterized as follows.

That is, the advancing angle 19 of the lower limit imaginary line 17 from the reference imaginary imaginary line 16 is set to 30 °, and the advancing angle 20 of the upper limit imaginary line 18 from the reference imaginary imaginary line 16 is 15.
The cavity center axis 2 is eccentric from the cylinder center axis 9 in a fan-shaped region 21 having a center angle of 120 ° sandwiched between the lower limit phantom imaginary line 17 and the upper limit imaginary phantom line 18
2 is arranged.

[0012]

[Action]

(First Invention) In this type of combustion chamber, as shown in FIG. 1 (A) or FIG. 3, the cylinder center axis 9 is swirled in the cylinder by the intake air introduced into the cylinder from the swirl port 3 in the intake stroke. A central swirl flow 23 is formed, and at the end of the compression process, the piston head top surface 4 approaches the cylinder head 1, so that the swirl flow 23 is introduced into the cavity 7 promptly by the guide of the valve recess inner peripheral surface 12. As a result, a swirl flow 24 with the center axis 22 of the cavity as the swirl center is formed in the cavity 7, and a squish flow 25 is formed in the cavity 7 by the squish surface 5, and the swirl flow 24 and the squish flow 25 cause the cavity 7 to move. Air and fuel 8 are mixed therein.

In the first aspect of the invention, the cavity 7
Since the ridge 10 is formed from the central portion of the inner bottom of the cavity toward the cylinder head, there is no stagnant portion of the air in the center of the cavity 7 where the swirling flow 24 does not act.

(Second Invention) In addition to the operation of the first invention, the second invention operates as follows. That is, as shown in FIG. 3, the swirl flow 23 introduced into the valve recess 6
However, the swirling flow 24 in the cavity 7 is quickly guided into the cavity 7 along the swirl flow guide surface 13, and the flow velocity of the swirling flow 24 in the cavity 7 increases.

(Third invention) In addition to the operation of the first invention or the second invention, the third invention operates as follows. That is, as shown in FIG. 1 (A) or FIG. 3, the reference radiation virtual line 16 extends from the valve recess 6 along the swirl flow swirling direction.
When the squish surface 5 is divided into a front half portion 26 leading to the reference radial imaginary line 16 and a rear half portion 27 reaching the valve recess 6 along the swirl flow swirling direction, the eccentricity of the cavity center axis line 22 from the cylinder center axis line 9 is eccentric. If the distance is constant, the area of the front half portion 26 is maximized when the cavity center axis 22 is located on the right-angled radial imaginary line 28 that is advanced 90 ° from the reference radial imaginary line 16 to the downstream side of the swirl flow, and The area of the latter half 27 is minimized.

For this reason, when the cavity center axis 22 is arranged in the fan-shaped region 21 having a central angle of 120 °, which spreads uniformly from the imaginary line of orthogonal radiation 28 to the upstream side and the downstream side of the swirl flow 23, the front half portion 26 is formed. Area is sufficiently large, the area of the second half 27 is sufficiently small,
As the squish flow 25 formed by is accelerated,
The squish flow 25 formed in the latter half portion 27 is slowed down. Therefore, the swirling flow 24 having a high swirling force immediately after being introduced from the valve recess 6 into the cavity 7 and the high-speed squish flow 25 are combined in a well-balanced manner, and the swirling force is swirled in the cavity 7 for about a half turn so that the swirling force is slightly increased. The lowered swirl flow 24 and the low-speed squish flow 25 are combined in a well-balanced manner, and the squish flow 25 is less likely to cause turbulence in the swirl flow 24, thereby suppressing a decrease in the swirling force.

[0017]

【The invention's effect】

(First Invention) In the first invention, the swirling flow 2 is generated in the cavity 7.
Since the stagnant portion of the air in which 4 does not act is eliminated, the mixing of the air and the fuel 8 in the cavity 7 is promoted, and the combustion efficiency is increased.

(Second Invention) In addition to the effects of the first invention, the second invention has the following effects. That is, the cavity 7
Since the flow velocity of the swirling flow 24 in the inside increases, the mixing of the air and the fuel 8 in the cavity 7 is further promoted, and the combustion efficiency is further increased.

(Third Invention) In addition to the effects of the first invention or the second invention, the third invention has the following effect. That is, the squish flow 25 hardly disturbs the swirl flow 24, and the reduction of the swirling force is suppressed, so that the mixing of the air and the fuel 8 in the cavity 7 is further promoted, and the combustion efficiency is further enhanced.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. In the first embodiment shown in FIGS. 1 and 2,
It uses a single cylinder horizontal diesel engine. The structure of this engine is as follows. That is, FIG.
As shown in FIG.
Is provided in a horizontal direction, and the cylinder head 1 is attached to one end of the cylinder block 29. A piston head 32 is fitted in the cylinder 30. A push rod insertion hole 34 is formed between the cylinder block 29 and the cylinder head 1, and a push rod 35 is inserted therein. The cylinder head 1 has an intake swirl port 3, an exhaust port 31, and a nozzle insertion hole 33.
And the fuel injection nozzle 2 is inserted into the nozzle insertion hole 33 and fixed.

As shown in FIG. 1, a valve recess 6 and a combustion cavity 7 are recessed in the piston head top surface 4 leaving a squish surface 5, and the fuel injection nozzle 2 to fuel 8 are introduced into the cavity 7. And the cavity 7 is arranged at the center of the piston head top surface 4 and the valve recess 6 is arranged near the peripheral edge of the piston head top surface 4, and the cavity 7 and the valve recess 6 are communicated with each other to form a swirl. The flow 23 is the inner surface 1 of the valve recess.
It is adapted to be introduced into the cavity 7 by the guide of 2.

In this type of combustion chamber, the intake air introduced into the cylinder from the swirl port 3 during the intake stroke forms a swirl flow 23 centered around the cylinder center axis 9 in the cylinder, and at the end of the compression stroke. Because the piston head top surface 4 approaches the cylinder head 1, the swirl flow 23 is guided by the inner peripheral surface 12 of the valve recess and the cavity 7
Is swiftly introduced into the cavity 7, and a swirl flow 24 having the cavity center axis 22 as a swirl center is formed in the cavity 7. Further, the squish surface 5 forms a squish flow 25 in the cavity 7. Flow 2
5 mixes air and fuel 8 in the cavity 7.

In this embodiment, the swirl flow 24 does not act on the central portion of the cavity 7 because the raised portion 10 is formed from the center of the inner bottom of the cavity 7 toward the cylinder head 1 in order to improve the combustion efficiency. The stagnant portion of air is eliminated, the mixing of air and fuel in the cavity 7 is promoted, and the combustion efficiency is increased.

The valve recess 6 has a circular shape. The valve recess 6 is a valve recess for an intake valve, and no valve recess for an exhaust valve is provided. The fuel 8 injected from the fuel injection nozzle 2 has a cavity center axis line 22.
It is directed from the vicinity to the cavity inner peripheral surface 11. The cavity 7 has a cavity center axis 22 parallel to the cylinder center axis 9, and the cavity inner peripheral surface 11 is a truncated cone surface whose diameter gradually increases as it approaches the inner bottom surface of the cavity 7. The peripheral surface of the raised portion 10 is a conical surface whose diameter gradually increases as it approaches the cylinder head 1. As shown in FIG. 1D, since the cavity inner peripheral surface 11 and the peripheral surface of the raised portion 10 are concentric circles centering on the cavity central axis 22 on an imaginary cross section orthogonal to the cylinder central axis 9. The swirling flow 24 swirls in the cavity 7 with less resistance.

In the first embodiment, as shown in FIG. 1 (A), only one valve recess 6 is provided, and when viewed in a direction parallel to the cylinder center axis 9, the recess center axis of the valve recess 6 from the cylinder center axis 9 is seen. 14, a virtual imaginary line 15 extending toward the recess center, a reference virtual imaginary line 16 extending from the cylinder center axis 9 to the opposite side of the radial imaginary line 15 facing the recess center, and a virtual phantom line 16 extending from the reference virtual imaginary line 16 in the swirl swirling direction. The lower limit imaginary phantom line 17 that is angled and the upper limit imaginary phantom line 18 that is further advanced in the swirl flow swirling direction than the lower limit imaginary phantom line 17 are assumed.

The advancing angle 19 of the lower limit imaginary line 17 from the reference imaginary imaginary line 16 is set to 30 °, and the advancing angle 20 of the upper limit imaginary line 18 from the reference imaginary imaginary line 16 is set to 150.
And a cavity center axis line 22 decentered from the cylinder center axis line 9 in a fan-shaped region 21 having a center angle of 120 ° sandwiched between the lower limit phantom imaginary line 17 and the upper limit imaginary phantom line 18.
Was placed.

According to such a configuration, the valve recess 6
When the squish surface 5 is divided into the front half portion 26 extending from the reference imaginary line 16 along the swirl swirl direction to the rear half portion 27 extending from the reference radial imaginary line 16 to the valve recess 6 along the swirl swirl direction. If the eccentric distance of the cavity center axis line 22 from the cylinder center axis line 9 is constant, the cavity center axis line 22 is positioned on the right angle imaginary line 28 that is advanced 90 degrees to the swirl flow downstream side from the reference radiation imaginary line 16. At this time, the area of the first half portion 26 is maximized and the area of the second half portion 27 is minimized.

Therefore, when the cavity center axis line 22 is arranged in the fan-shaped region 21 having a central angle of 120 °, which spreads evenly from the imaginary line of right-angled radiation 28 to the upstream side and the downstream side of the swirl flow 23, the front half portion 26 is formed. Area is sufficiently large, the area of the second half 27 is sufficiently small,
As the squish flow 25 formed by is accelerated,
The squish flow 25 formed in the latter half portion 27 is slowed down. Therefore, the swirling flow 24 having a high swirling force immediately after being introduced from the valve recess 6 into the cavity 7 and the high-speed squish flow 25 are combined in a well-balanced manner, and the swirling force is slightly swirled in the cavity 7 by making a half turn. The lowered swirl flow 24 and the low-speed squish flow 25 are combined in a well-balanced manner, and the squish flow 25 is less likely to cause turbulence in the swirl flow 24, thereby suppressing a decrease in the swirling force. Therefore, the mixing of the air and the fuel 8 in the cavity 7 is further promoted, and the combustion efficiency is further enhanced.

More preferably, the advancing angle 19 of the lower limit imaginary line 17 from the reference imaginary imaginary line 16 is set to 45 °, and the advancing angle 20 of the upper limit imaginary line 18 from the reference imaginary imaginary line 16 is set.
Is set to 135 °, and a cavity center axis line 22 eccentric from the cylinder center axis line 9 is arranged in a fan-shaped region 21 having a center angle of 90 ° sandwiched between the lower limit imaginary line 17 and the upper limit imaginary line 18.

In the second embodiment shown in FIG. 3, the cavity inner peripheral surface 11 in the first embodiment shown in FIGS. 1 and 2 is used.
The valve recess inner peripheral surface 12 and the valve recess inner peripheral surface 12 are connected to each other by a swirl flow guide surface 13 directed in a tangential direction thereof. The other configuration is the same as that of the first embodiment. In FIG. 3, the same elements as those of the first embodiment are denoted by the same reference numerals. With such a configuration, the swirl flow 23 introduced into the valve recess 6 is quickly guided into the cavity 7 along the swirl flow guide surface 13, and the flow velocity of the swirl flow 24 in the cavity 7 increases. Therefore, the mixing of the air and the fuel 8 in the cavity 7 is further promoted, and the combustion efficiency is further enhanced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a combustion chamber according to a first embodiment, and FIG.
1A is a front view of the top surface of the piston head, FIG. 1B is a sectional view taken along line BB in FIG. 1A, and FIG. 1C is a sectional view taken along line CC in FIG. 1A. FIG. 1D is a sectional view taken along the line D-D of FIG.

FIG. 2 is an explanatory view of a main part of an engine including a combustion chamber according to the first embodiment, FIG. 2 (A) is a vertical side view, and FIG. 2 (B) is FIG.
It is a BB sectional view taken on the line of (A).

FIG. 3 is a front view of the top surface of a piston head used in the combustion chamber of the second embodiment.

FIG. 4 is a diagram illustrating a conventional combustion chamber, and FIG.
Is a front view of the top surface of the piston head, and FIG.
It is a BB sectional view taken on the line of (A).

[Explanation of symbols]

1 ... Cylinder head, 2 ... Fuel injection nozzle, 3 ... Swirl port, 4 ... Piston head top surface, 5 ... Squish surface, 6 ... Valve recess, 7 ... Cavity, 8 ... Fuel, 9
... Cylinder center axis line, 10 ... Raised part, 11 ... Cavity inner peripheral surface, 12 ... Valve recess inner peripheral surface, 13 ... Swirl flow guide surface, 14 ... Recess center axis line, 15 ... Recess center radiating virtual line, 16 ... Reference radiation Virtual line, 17 ... Lower limit virtual line, 18 ... Upper limit virtual line, 19/20 ... Advance angle, 2
1 ... fan-shaped region, 22 ... cavity center axis line, 23 ... swirl flow.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F02F 3/28 F02F 3/28 B

Claims (3)

[Claims] A fuel injection nozzle is provided on a cylinder head (1).
(2) and swirl port (3) are provided, and the valve recess (6) is left on the piston head top surface (4) leaving the squish surface (5).
And the cavity (7) for combustion are recessed, and the cavity (7)
The fuel (8) is injected from the fuel injection nozzle (2), the cavity (7) is located at the center of the piston head top surface (4), and the valve recess (6) is located at the periphery of the piston head top surface (4). The cavities (7) and the valve recesses (6) are connected to each other, and the swirl flow (2
3) Guide the inner surface of the valve recess (12) to the cavity
In the direct injection combustion chamber of the diesel engine, which is adapted to be introduced into (7), the ridge (10) is formed from the center of the inner bottom of the cavity (7) toward the cylinder head (1). The direct injection type combustion chamber of the diesel engine. 2. A direct injection type combustion chamber of a diesel engine according to claim 1, wherein the cavity inner peripheral surface (11)
A direct injection combustion chamber for a diesel engine, characterized in that the valve recess inner peripheral surface (12) and the valve recess inner peripheral surface (12) are connected by a swirl flow guide surface (13) directed in a tangential direction thereof. 3. The direct injection combustion chamber for a diesel engine according to claim 1 or 2, wherein only one valve recess (6) is provided, and the cylinder center is viewed in a direction parallel to the cylinder center axis (9). Valve recess from axis (9)
(6) Recess center imaginary imaginary line (15) extending toward the recess center axis (14) and reference imaginary imaginary line extending from the cylinder center axis (9) to the opposite side of the recess center facing imaginary line (15). (16), the lower limit radial phantom line (17) advanced from the reference radial phantom line (16) in the swirl flow swirl direction, and the lower limit radial phantom line (17) further advanced in the swirl flow swirl direction than this lower limit radial phantom line (17). Assuming that the upper limit virtual phantom line (18), the advance angle (19) of the lower limit virtual phantom line (17) from the reference virtual phantom line (16) is set to 30 ° The advancing angle (20) of the imaginary radiation line (18) is set to 150 °,
A cavity center axis (22) eccentric from the cylinder center axis 9 is located in a fan-shaped region (21) having a central angle of 120 ° sandwiched between the lower limit imaginary line (17) and the upper limit imaginary line (18).
The direct injection combustion chamber of a diesel engine is characterized in that