JP2011196214A - Direct injection type combustion chamber of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct injection type combustion chamber of a diesel engine that can equalize a vaporization state of fuel inside a cavity at a time of fuel injection.SOLUTION: In the direct injection type combustion chamber of the diesel engine, compared to a narrow angle of the injection axis 6a of a fuel injection hole 6 on a front side with a tip-end extended line 5b of the central axis 5a of a fuel injector 5, a narrow angle of the injection axis 6a of a fuel injection hole 6 on the rear side therewith is set larger, the injection axis 6a of the fuel injection hole 6 on the front side orients toward the front side of the inner surface of a cavity 3 and the injection axis 6a of the fuel injection hole 6 on the rear side orients toward the rear side of the inner surface of the cavity 3. A bulged part 15 is formed in the rear side of the inner bottom surface 3a of the cavity 3, and a rear side tumble intake flow guide surface 16 extending in a lateral direction is formed in the rear surface of the bulged part 15.

Description

  The present invention relates to a direct injection combustion chamber of a diesel engine, and more particularly, to a direct injection combustion chamber of a diesel engine capable of uniformizing a fuel vaporization state in a cavity during fuel injection.

Conventionally, as a direct injection combustion chamber of a diesel engine, a piston is slidably fitted into a cylinder, a cavity is provided at the top of the piston, a fuel injector is disposed at the cylinder head, and a circumferential direction is provided at the tip of the fuel injector. A plurality of fuel injection holes are provided at predetermined intervals, the predetermined radial direction of the cylinder is the front-rear direction, one of which is the front side and the other is the rear side, and the tip of the fuel injector is located behind the central axis of the cavity. The center axis of the fuel injector is inclined forward and downward, and when the fuel is injected from each fuel injection hole, each injection axis is directed toward the inner surface of the cavity. Set the angle between the rear fuel injection hole and the injection axis of the front fuel injection hole to be larger than the front angle. Is injection axis of the fuel injection hole is directed to the front portion of the inner surface of the cavity, the injection axis of the post near the fuel injection hole is that as directed to deviation after the inner surface of the cavity.
According to this type of direct injection combustion chamber, the fuel distributed and injected from the fuel injector to the front and rear sides of the cavity receives the heat of the compressed air in the cavity and the heat of the inner surface of the cavity, and is vaporized. There is an advantage that the mixture is formed, self-ignition occurs, and combustion proceeds smoothly.
In this type of direct injection combustion chamber, the fuel injected from the front fuel injection hole to the front of the cavity is sandwiched between the extension line on the front end side of the central axis of the fuel injector and the injection axis of the fuel injection hole. Because the angle is small, the injection speed is high and the atomization is accelerated by the small flow resistance, whereas the fuel injected from the rear fuel injection hole to the rear of the cavity is in the center axis of the fuel injector. There is a tendency that the flow resistance is large, the injection speed is slow, and the atomization is stagnated as the angle between the distal end side extension line and the injection axis of the fuel injection hole is large.
However, this conventional technique has a problem because there is no means for promoting the vaporization of the fuel injected toward the rear of the cavity.

JP-A-6-221163 (see FIGS. 1 and 3)

<Problem> The fuel vaporization state in the cavity during fuel injection tends to be uneven.
Since there is no means for promoting the vaporization of the fuel injected toward the rear of the cavity, the vaporization of the rear fuel where the atomization stagnates is delayed, and the vaporization state of the fuel in the cavity during fuel injection tends to be uneven.
As a result, problems such as output reduction, fuel consumption deterioration, and exhaust gas deterioration occur.

  An object of the present invention is to provide a direct injection combustion chamber of a diesel engine that can uniformize the vaporization state of fuel in a cavity during fuel injection.

Invention specific matters of the invention according to claim 1 are as follows.
As illustrated in FIGS. 1A to 1C, a piston (2) is slidably fitted in a cylinder (1), a cavity (3) is provided at the top of the piston (2), and a cylinder head is provided. (4), a fuel injector (5) is disposed, and a plurality of fuel injection holes (6) are provided at the tip of the fuel injector (5) at predetermined intervals in the circumferential direction.
As illustrated in FIGS. 1A and 1B, a predetermined radial direction of the cylinder (1) is a front-rear direction, one of which is a front side and the other is a rear side.
The tip of the fuel injector (5) is biased to the rear of the center axis (3b) of the cavity (3), and the center axis (5a) of the fuel injector (5) is inclined toward the front bottom dead center. When injecting fuel from the injection hole (6), each injection axis (6a) is directed toward the inner surface of the cavity (3).
As illustrated in FIG. 1B, the included angle between the distal end extension line (5b) of the central axis (5a) of the fuel injector (5) and the injection axis (6a) of the front fuel injection hole (6). The angle between the rear fuel injection hole (6) and the injection axis (6a) is set larger, and the front fuel injection hole (6) has the injection axis (6a) as the inner surface of the cavity (3). In the direct injection combustion chamber of the diesel engine, the injection axis (6a) of the rear fuel injection hole (6) is directed to the rear of the inner surface of the cavity (3).
As illustrated in FIG. 1B, a raised portion (15) is provided on the rear side of the inner bottom surface (3a) of the cavity (3), and a rearward tumble intake air that is long in the left-right direction is provided on the rear surface of the raised portion (15). A direct injection combustion chamber of a diesel engine, characterized in that a flow guide surface (16) is formed.

(Invention of Claim 1)
The invention according to claim 1 has the following effects.
<< Effect >> The vaporization state of the fuel in the cavity during combustion can be made uniform.
As illustrated in FIG. 1 (B), a raised portion (15) is provided on the rear side of the inner bottom surface (3a) of the cavity (3), and a rearward tumble intake air extending in the left-right direction on the rear surface of the raised portion (15). Since the flow guide surface (16) is formed, the rear tumble intake air flow (18) generated when the piston (2) rises is caused by the rear tumble intake air flow guide surface (16) and the cavity (3) opposed thereto. In the space of a narrow short path between the inner peripheral surface (3c), the vaporization of the rear fuel where the atomization stops and the atomization stops is promoted, the vaporization state approaches the vaporization state of the front fuel, The fuel vaporization state in the cavity (3) at the time of fuel injection can be made uniform.
Thereby, output improvement, fuel consumption improvement, and exhaust gas improvement can be aimed at.

(Invention of Claim 2)
The invention according to claim 2 has the following effect in addition to the effect of the invention according to claim 1.
<< Effect >> The fuel vaporization state in the cavity at the time of combustion injection can be made more uniform.
As illustrated in FIG. 1B, the separation distance between the rear tumble intake flow guide surface (16) and the inner peripheral surface (3c) of the cavity (3) facing the rear tumble intake flow guide surface is defined as the front tumble intake flow guide surface. The curvature of the rear tumble intake flow guide surface (16) is made smaller than the separation distance between (17) and the inner peripheral surface (3c) of the cavity (3) opposite to the front tumble intake flow guide surface ( 17), the front tumble intake air flow (19) generated when the piston (2) ascends causes the front tumble intake air flow guide surface (17) and the inner periphery of the cavity (3) opposite to the front tumble intake air flow guide surface (17). In a space with a wide long path with the surface (3c), it turns a few, suppresses the vaporization of the front fuel where atomization is promoted, and matches the vaporization state with the vaporization state of the rear fuel The fuel vaporization state in the cavity (3) during fuel injection can be made more uniform. That.

It is a figure explaining the direct injection type combustion chamber of the diesel engine which concerns on embodiment of this invention, FIG. 1 (A) is a cross-sectional top view, FIG.1 (B) is the BB sectional drawing of FIG. FIG. 1C is a cross-sectional view taken along the line CC of FIG. 2A and 2B are views for explaining a front end portion of a fuel injector used in the direct injection combustion chamber of FIG. 1, FIG. 2A is a longitudinal side view, FIG. 2B is a cross-sectional view taken along line BB in FIG. FIG. 2C is a cross-sectional view taken along the line CC of FIG.

  1 to 2 are views for explaining a direct injection combustion chamber of a diesel engine according to an embodiment of the present invention.

  As shown in FIGS. 1A to 1C, a piston (2) is slidably fitted into a cylinder (1), a cavity (3) is provided at the top of the piston (2), and a cylinder head ( 4), a fuel injector (5) is arranged, and a plurality of fuel injection holes (6) are provided at a distal end portion of the fuel injector (5) at a predetermined interval in the circumferential direction.

As shown in FIGS. 1A to 1C, the cavity (3) has a toroidal shape with a cylindrical peripheral wall, but may have a reentrant shape with a narrowed opening (3b). The central axis (3b) of the cavity (3) is biased rearward from the central axis (1a) of the cylinder (1). The tip of the fuel injector (5) is also biased rearward from the central axis (1a) of the cylinder (1), as is the central axis (3b) of the cavity (3).
As shown in FIGS. 2 (A) to (C), a nozzle (10) is provided at the tip of the fuel injector (5), and a valve opening working chamber (11) and a fuel branch chamber (12) are provided in the nozzle (10). A valve seat (13) is provided at the boundary between the valve opening working chamber (11) and the fuel flow dividing chamber (12), and a needle valve (14) energized by a nozzle spring (not shown) is provided on the valve seat (13). ) And a plurality of fuel injection holes (6) are led out from the fuel diversion chamber (12). When fuel is pumped from the fuel injection pump (not shown) to the valve opening working chamber (11), the needle valve (14) is opened against the urging force of the nozzle spring, and the fuel is opened to the valve opening working chamber (11). The fuel is simultaneously injected from the plurality of fuel injection holes (6) through the fuel diversion chamber (12).
As shown in FIG. 2 (B), a plurality of fuel injection holes (6) are arranged at equal intervals on the entire circumference of the tip of the fuel injector (5), and are parallel to the central axis (5a) of the fuel injector (5). Looking in the direction, the injection axis (6a) of the fuel injection hole (6) is directed to radiate from the central axis (5a) of the fuel injector (5). Specifically, a total of four fuel injection holes (6) are arranged every 90 ° on the entire circumference of the tip of the fuel injector (5).

  As shown in FIG. 1B, the predetermined radial direction of the cylinder (1) is the front-rear direction, one of which is the front side and the other is the rear side, and the tip of the fuel injector (5) is the center of the cavity (3). The center axis (5a) of the fuel injector (5) is inclined closer to the front bottom dead center than the axis (3b), and when the fuel is injected from each fuel injection hole (6), each injection axis ( 6a) is directed to the inner surface of the cavity (3) as follows.

As shown in FIG. 2 (A), the angle between the extension line (5b) at the front end of the central axis (5a) of the fuel injector (5) and the injection axis (6a) of the front fuel injection hole (6). Also, the angle between the rear fuel injection hole (6) and the injection axis (6a) is set to be large so that the front fuel injection hole (6) has the injection axis (6a) on the inner surface of the cavity (3). The injection axis (6a) of the rear fuel injection hole (6) is directed toward the front and is directed toward the rear of the inner surface of the cavity (3).
1A to 1C, the point shown at the tip of each injection axis 6a is the intersection of each injection axis 6a and the inner bottom surface 3a of the cavity 3.

  As shown in FIG. 1 (B), the central axis (5a) of the fuel injector (5) is inclined at an angle of 60 ° with respect to the cylinder central axis (1a), as shown in FIGS. 2 (A) and (C). In addition, the included angle between the tip extension line (5b) of the central axis (5a) of the fuel injector (5) and the injection axis (6a) of each fuel injection hole (6) is 30 ° on the front side and 90 ° on the rear side. The horizontal side is set to 45 °.

As shown in FIG. 1 (B), a raised portion (15) is provided on the rear side of the inner bottom surface (3a) of the cavity (3), and a rearward tumble intake flow extending in the left-right direction on the rear surface of the raised portion (15). A guide surface (16) is formed.
An arrow (16) in FIG. 1 (A) indicates a swirl intake flow. This swirl intake flow (16) is formed in the cavity (3) by the introduction of intake air through the intake swirl port (not shown).

  As shown in FIG. 2 (B), the rear tumble intake flow guide surface (16) is formed in an arc shape closer to the bottom dead center as viewed from the side, and the front surface of the raised portion (15). The front tumble intake flow guide surface (17) that is long in the left-right direction is formed, and the front tumble intake flow guide surface (17) has an arc shape that is closer to the bottom dead center as it goes forward as viewed from the side. The separation distance between the rear tumble intake flow guide surface (16) and the inner peripheral surface (3c) of the cavity (3) facing the rear tumble intake flow guide surface (17) is opposed to the front tumble intake flow guide surface (17). The curvature of the rear tumble intake flow guide surface (16) is made larger than the curvature of the front tumble intake flow guide surface (17) by making it smaller than the distance from the inner peripheral surface (3c) of the cavity (3). ing.

(1) Cylinder
(1a) Cylinder center axis
(2) Piston
(3) Cavity
(3a) Inner bottom
(3b) Cavity center axis
(3c) Cavity inner surface
(4) Cylinder head
(5) Fuel injector
(5a) Center axis
(5b) Extension line on the tip side
(6) Fuel injection hole
(6a) Injection axis
(15) Raised part
(16) Rear tumble intake flow guide surface
(17) Front tumble intake flow guide surface

Claims (2)

A piston (2) is slidably fitted in the cylinder (1), a cavity (3) is provided at the top of the piston (2), a fuel injector (5) is disposed on the cylinder head (4), and a fuel injector A plurality of fuel injection holes (6) are provided at the tip of (5) at predetermined intervals in the circumferential direction,
The predetermined radial direction of the cylinder (1) is the front-rear direction, one of which is the front side and the other is the rear side.
The tip of the fuel injector (5) is biased to the rear of the center axis (3b) of the cavity (3), and the center axis (5a) of the fuel injector (5) is inclined toward the front bottom dead center. When injecting fuel from the injection hole (6), each injection axis (6a) is directed toward the inner surface of the cavity (3).
The fuel injection hole (6) located at the rear of the fuel injector (5) is located closer to the rear side than the angle between the extension line (5b) at the front end of the central axis (5a) of the fuel injector (5a) and the injection axis (6a) ) With the injection axis (6a) is set large, the injection axis (6a) of the front fuel injection hole (6) is directed toward the front of the inner surface of the cavity (3), and the rear fuel In a direct injection combustion chamber of a diesel engine in which the injection axis (6a) of the injection hole (6) is directed toward the rear of the inner surface of the cavity (3),
A raised portion (15) is provided on the rear side of the inner bottom surface (3a) of the cavity (3), and a rearward tumble intake flow guide surface (16) that is long in the left-right direction is formed on the rear surface of the raised portion (15). A diesel engine direct injection combustion chamber. In the direct injection combustion chamber of the diesel engine according to claim 1,
The rear tumble intake flow guide surface (16) is formed in an arc shape closer to the bottom dead center as it goes rearward as viewed from the side,
A front tumble intake flow guide surface (17) that is long in the left-right direction is formed on the front surface of the raised portion (15), and the front tumble intake flow guide surface (17) is lowered toward the front as viewed from the side. Formed in an arc shape near the dead center,
The separation distance between the rear tumble intake flow guide surface (16) and the inner peripheral surface (3c) of the cavity (3) opposed to the rear tumble intake flow guide surface (16) is defined as the cavity (3 ) Smaller than the distance from the inner peripheral surface (3c),
A direct injection combustion chamber of a diesel engine, characterized in that the curvature of the rear tumble intake flow guide surface (16) is larger than the curvature of the front tumble intake flow guide surface (17).

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