JP2001027167A - Fuel injection valve for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve for an internal combustion engine to stabilize the spray shape. SOLUTION: A nozzle hole 16 provided in a valve element 11 of a fuel injection valve has the specified slit width, and the slit length W is gradually longer from a sack part 12 side to the outer side, and the section along the forming direction is substantially fan-shaped. In addition, an inlet part 18 and an outlet part 19 are respectively formed so that the lines L1, L2 to connect a circumferential edge of the inlet part 18 of the nozzle hole 16 to a circumferential edge of the outlet part 19 are across each other at the specified angle θ2 at a point P on the axis C on the upstream side of the center O of the sack part 12. Both sides 16a, 16b of the nozzle hole 16 in the extending direction of the slit are formed in the arc shape whose section is bulged inward of the lines L1, L2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an internal combustion engine having a slit-shaped injection hole.

[0002]

2. Description of the Related Art As a fuel injection valve used in a direct injection internal combustion engine, for example, those described in Japanese Patent Application Laid-Open Nos. 9-126095 and 9-158736 are known. FIG. 7 shows a cross-sectional structure of such a fuel injection valve, and FIG. 8 shows an enlarged view of a portion surrounded by a broken line in FIG. FIG. 9 shows a cross-sectional structure along the line 9-9 in FIG.

As shown in these figures, a slit 31 is formed in a valve body 31 of a fuel injection valve 30. The injection hole 32 communicates with a sack portion 33 formed in the valve body 31. When the needle valve 35 separates from the valve seat 37,
The fuel flowing into the sack portion 33 from the fuel passage 39 is injected from the injection hole 32. The fuel thus injected is collected around the spark plug using the top surface of the engine piston, and is ignited by the spark plug.

The injection hole 32 has a slit length W (FIG. 9).
Has a fan-shaped cross-sectional shape that gradually increases toward the downstream. For this reason, the spray injected from the injection hole 32 has a flat fan shape. By making the fuel spray into such a flat fan shape, the contact area between the spray and the air can be increased to promote the atomization (vaporization).

[0005]

However, in such a fuel injection valve 30, since the inlet portion 34 of the injection hole 32 is an edge, the fuel flowing from the sack portion 33 into the injection hole 32 does not pass through the inlet portion. At 34, large peeling occurs. For this reason, the spread angle θf of the spray cannot be increased, and as shown by the two-dot chain line in FIG. 9, the spray shape cannot be expanded to a desired shape. In particular, since many vortices are generated in the vicinity of the entrance portion 34 which is an edge, the spray is influenced by these vortices, and inevitably the shape becomes unstable.

Further, since the cross-sectional area of the injection hole 32 gradually increases from the inlet portion 34 to the outlet portion 38, the fuel is uniformly distributed in the width B direction of the injection hole 32 (see FIG. 8). As a result, fuel becomes extremely thin (low-pressure portion) near the inner wall surface of the injection hole 32 as compared with the central portion of the flow. For this reason, when the fuel injection is performed intermittently and the fuel pressure in the sack portion 33 fluctuates, the fuel injection becomes susceptible to the influence, and as shown by the one-dot chain line or two-dot chain line in FIG. The direction is not determined, and this shape becomes unstable.

In particular, when the injection hole 32 is formed to be inclined with respect to the axial direction C of the valve body 31, the flow rate of fuel from the sack portion 33 into the injection hole 32 is different in the width B direction. Therefore, the fluctuation of the fuel injection direction and the instability of the spray shape are further promoted.

The present invention has been made in view of such circumstances, and has as its object to provide a fuel injection valve for an internal combustion engine that can stabilize the spray shape.

[0009]

The means for achieving the above object and the effects thereof will be described below. The invention according to claim 1 is a needle valve provided reciprocally in a valve body, and a sack portion formed in a distal end portion of the valve body.
A slit-shaped opening at the distal end of the valve body, the slit length of which extends toward the outside of the distal end of the valve body. In the fuel injection valve for an internal combustion engine, which is configured to inject from the injection hole based on a reciprocating operation, a gist of the invention is that a side surface of an inner wall of the injection hole is formed to have a convex cross-sectional shape bulging inward.

[0010] According to the above configuration, since the inner wall side surface of the injection hole is formed in a convex shape in cross section which swells inward, fuel flowing into the injection hole from the sac portion gradually flows along the inner wall side surface of the injection hole. The flow direction can be changed. Therefore,
The occurrence of separation is suppressed, the separation point moves to the downstream side of the injection hole, and the occurrence of vortices in the injection hole is suppressed, so that the position fluctuation of the separation point is also suppressed. . Further, in the vicinity of the outlet of the injection hole, the opening area becomes large, so that the fuel is drawn to the inner wall side surface of the injection hole.

As a result, the spread angle of the spray can be increased, and the shape can be stabilized. According to a second aspect of the present invention, there is provided a needle valve provided reciprocally in a valve body, a sack portion formed in a distal end portion of the valve body, and a slit-shaped opening in the distal end portion of the valve body. An injection hole having a fan-shaped cross-section, the slit length of which extends toward the outside of the distal end portion of the valve body, and the fuel in the sack portion is injected from the injection hole based on the reciprocating operation of the needle valve. In the fuel injection valve for an internal combustion engine described above, the gist is that the slit width of the injection hole is gradually reduced from the opening on the sack side to the opening on the outside.

According to the above construction, the difference between the opening area on the sack portion side and the opening area on the outside of the injection hole is reduced, and the fuel flowing in the injection hole becomes more uniform in the width direction. Therefore, even if the pressure in the sack portion fluctuates, it is hardly affected by the fluctuation. As a result, the fuel injection direction can be stabilized, and the spray shape can be stabilized.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is applied to a fuel injection valve of a direct injection internal combustion engine will be described with reference to FIGS. I do.

First, an outline of a fuel injection valve according to this embodiment will be described with reference to FIGS. FIG. 1 shows a cross-sectional structure of a tip portion of the fuel injection valve, and FIG. 2 shows a cross-sectional structure along line 2-2 in FIG.

As shown in these figures, the fuel injection valve 10 includes a valve body 11 to which fuel is supplied, a needle valve 14 that can reciprocate along a central axis C of the valve body 11, and a valve. Sack portion 12 formed in the tip of body 11, valve body 11
Is provided with an injection hole 16 or the like that is opened at the tip end of the nozzle.

The sack portion 12 is provided at the center axis C of the valve body 11.
It is formed in a substantially hemispherical shape with the upper point O as the center.
A fuel passage 17 for supplying fuel to the sac portion 12 is formed between the inner peripheral surface of the valve body 11 and the outer peripheral surface of the needle valve 14, and the passage 17 is connected to a delivery pipe (not shown). It is connected. Further, the needle valve 1 is provided on the inner wall of the valve body 11.
A valve seat 13 is formed between the fuel passage 17 and the sack portion 12 so that the distal end portion 15 of the fourth member 4 can be detached and seated.

In the fuel injection valve 10, when the tip 15 of the needle valve 14 moves away from the valve seat 13, the fuel passage 17
And the sack portion 12 are communicated with each other, and fuel is supplied to the sack portion 12 from the fuel passage 17. As a result, the sack section 12
The fuel pressure in the sac portion 12 is increased, and the fuel in the sack portion 12 is injected from an injection hole 16 into an engine combustion chamber (not shown).

On the other hand, when the distal end portion 15 of the needle valve 14 comes into contact with the valve seat 13, the communication between the fuel passage 17 and the sack portion 12 is interrupted, the fuel pressure in the sack portion 12 is reduced, and the fuel injection is also performed. Stopped.

The injection hole 16 is a slit-like hole having a rectangular cross section at a portion through which fuel passes, and has a predetermined angle θ with respect to the center axis C of the valve body 11 as shown in FIG.
It is formed along a direction inclined by one. By the way,
By inclining the forming direction of the injection hole 16 in this manner, fuel injected from the injection hole 16 can be supplied to an engine piston (not shown).
At the top surface of the fuel cell and can be collected near a spark plug (not shown).

The injection hole 16 has a constant slit width B.
(See FIG. 1), and the slit length W (see FIG. 2) is formed so as to gradually increase from the sack portion 12 side toward the outside. Thus, the slit length W
Is set, the injection hole 16 has a substantially fan-shaped cross section along the forming direction.

Further, in the cross section shown in FIG. 2, the injection hole 16 has a periphery of an opening 18 (hereinafter, referred to as an "entrance") on the side of the sack portion 12 and an opening (hereinafter, referred to as an "outlet") on the outside. The inlet 18 and the outlet 19 are arranged such that straight lines L1 and L2 connecting the periphery of the sack 19 intersect at a predetermined angle θ2 at a point P on the center axis C upstream of the center O of the sack 12. Each is formed. Then, both side surfaces 16a, 16b of the injection hole 16 in the direction in which the slit extends.
(Left and right side surfaces in FIG. 2) are those whose cross-sectional shape is the straight line L
1, L2, it is formed in an arc shape bulging inward.
Incidentally, the amount of fuel flowing from the sack portion 12 into the injection hole 16 is determined by the opening area of the inlet portion 18.

The injection hole 16 having the above shape can be formed in the valve body 11 by, for example, electric discharge machining. Next, a method of forming the injection hole 16 will be described.
This will be described with reference to FIG.

First, a plate-shaped electrode A having a mountain-shaped tip is brought close to the surface of the valve body 11 placed in insulating oil,
A predetermined voltage is applied between the valve body 11 and the valve body 11. Then, while the electrode A is moved toward the valve body 11 at a predetermined feed speed, electric discharge machining is performed so that the surface portion of the valve body 11 close to the electrode A follows the shape of the electrode A (FIG. 3A). ).

When the valve element 11 is processed in this manner, the peripheral portion on the distal end side of the electrode A gradually forms an arc shape toward the inside along with the processing (FIG. 3B). When the electrode A is further moved and the processing of the valve body 11 is advanced, both side surfaces 16a and 16b of the injection hole 16 are formed in an arc-shaped cross section following the shape of the electrode A (FIG. 3C). ).

Here, each side surface 16a, 16b of the injection hole 16
Can be changed according to the hardness of the material of the electrode A. For example, by using a metal having relatively low hardness such as copper or aluminum as the electrode A,
The degree of swelling of 6a and 16b can be increased, and conversely, the degree of swelling can be reduced by using a metal having relatively high hardness such as stainless steel.

The fuel injection valve 10 of the present embodiment described above
In this embodiment, since the both side surfaces 16a and 16b of the injection hole 16 are formed to have a convex cross-sectional shape bulging inward, the fuel flowing from the sack portion 12 into the injection hole 16 gradually flows along the side surfaces 16a and 16b. Can be changed to For this reason, the occurrence of peeling near the entrance 18 is suppressed,
The peeling point K (see FIG. 2) moves to a position on the downstream side. Moreover, since the flow direction of the fuel does not suddenly change, the generation of vortices in the injection holes 16 is suppressed, and the position fluctuation of the separation point K is also suppressed. As a result, the spray shape becomes stable.

Further, since the opening area is large near the outlet 19, the separated fuel is attracted to the both side surfaces 16a and 16b of the injection hole 16 and spreads. As a result, the fuel injected from the injection hole 16 is as shown in FIG.
As shown by the two-dot chain lines in (a) and (b), there is no deviation toward the center, and the spray becomes a substantially triangular spray as shown by the solid line. It becomes substantially uniform in the region where the light is emitted.

As described in detail above, according to the fuel injection valve 10 of this embodiment, the following excellent effects can be obtained. (1) The spray shape can be stabilized, and
The spread angle of the spray can be increased.

(Second Embodiment) Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment.

FIG. 5 shows a cross-sectional structure of the injection hole 16 in the fuel injection valve 10 of the present embodiment, and corresponds to an enlarged cross-sectional view in a broken line portion of FIG. As shown in FIG. 5, the injection hole 16 is formed on both side surfaces 1 in the width direction.
6c and 16d are formed so as to be closer to the center line of the injection hole 16 toward the downstream side. Therefore, the slit width B of the injection hole 16 gradually decreases from the inlet 18 to the outlet 19 (Bin> Bout). Incidentally, the injection hole 16 having such a shape can be formed in the valve body 11 by, for example, laser processing.

By having the injection hole 16 having such a shape, the difference in the opening area between the inlet portion 18 and the outlet portion 19 is reduced as compared with the configuration in which the slit width B is constant. Become. Thereby, the fuel flowing in the injection hole 16 becomes more uniform in the width direction. As a result, a very thin portion of the fuel does not occur near both side surfaces 16c and 16d of the injection hole 16, and the sack portion 12
Even if the internal pressure fluctuates, the spray becomes less susceptible. In addition, since there is no need to change the opening area of the inlet section 18, there is no effect on fuel metering.

As described in detail above, according to the fuel injection valve 10 of this embodiment, the following excellent effects can be obtained. (2) The spray shape can be stabilized, and
Fluctuations in the fuel injection direction can be suppressed.

(Other Embodiments) In each of the above embodiments, for example, the configuration can be appropriately changed as follows.

(A) In the second embodiment, FIG.
As shown in FIG. 5 (corresponding to a cross-sectional view taken along line 6-6 in FIG. 5), the injection hole 16 of the fuel injection valve 10 may have a shape in which the slit width B at the center thereof is further reduced.

With this configuration, in addition to the effects described in the second embodiment, more fuel can be flowed to both ends of the injection hole 16 and the spread angle of the spray can be further increased. Will be able to do it.

(B) The fuel injection valve may have the configuration shown in each of the first embodiment and the second embodiment. That is, the injection hole of the fuel injection valve is formed to have a convex cross section in which both side surfaces in the slit length direction swell inward, and the slit width is set to be thinner toward the downstream side.

With such a configuration, the effects described in (1) and (2) can be obtained in each of the above embodiments. (C) The configurations shown in the other embodiments (a) and (b) may be combined. That is, the injection hole of the fuel injection valve has a cross-sectional convex shape in which both side surfaces in the slit length direction bulge inward, and further, when the slit width is reduced toward the downstream side, the central portion of the injection hole is made thinner. .

With such a configuration, in addition to the effects described in the other embodiments (b), the spread angle of the spray can be further increased. (D) Each of the above embodiments and other embodiments (a),
In (b) and (c), the injection hole 16 is provided at the position shown in FIGS. 1, 5 and 6 (a position inclined at a predetermined angle θ1 with respect to the central axis C of the valve body 11). The position can be changed as appropriate. For example, the injection hole 16 may be formed along the central axis C.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sectional structure of a tip portion of a fuel injection valve according to a first embodiment.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a process chart for explaining a process of forming an injection hole.

FIG. 4 is an explanatory diagram for explaining a shape of a spray and a flow rate distribution thereof.

FIG. 5 is a cross-sectional view illustrating a cross-sectional structure of a tip portion of a fuel injection valve according to a second embodiment.

FIG. 6 is a sectional view showing a sectional shape of an injection hole according to another embodiment (a).

FIG. 7 is a cross-sectional view showing a cross-sectional structure of a tip portion of a fuel injection valve in a conventional configuration.

FIG. 8 is an enlarged sectional view showing the inside of a broken line part in FIG. 7;

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

[Explanation of symbols]

10 ... fuel injection valve, 11 ... valve element, 12 ... sack part,
13 ... valve seat, 14 ... needle valve, 15 ... tip, 16 ... injection hole, 16a, 16b, 16c, 16d ... side surface (of injection hole), 17 ... fuel Passage, 18: entrance, 19: exit, B: slit width, W: slit length.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeno Furuno 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Masanori Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yukio Mori 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 3G066 AA02 AB02 AD12 BA01 BA03 CC14 CC21

Claims (2)

[Claims] A needle valve provided reciprocally within a valve body;
A sack portion formed in the distal end portion of the valve body, and an injection hole having a fan-shaped cross section that is opened in a slit shape at the distal end portion of the valve body and has a slit length that extends toward the outside of the distal end portion of the valve body. A fuel injection valve for an internal combustion engine that injects the fuel in the sac portion from the injection hole based on the reciprocating operation of the needle valve. A fuel injection valve for an internal combustion engine, wherein the fuel injection valve is formed. 2. A needle valve provided reciprocally within a valve body;
A sack portion formed in the distal end portion of the valve body, and an injection hole having a fan-shaped cross section that is opened in a slit shape at the distal end portion of the valve body and has a slit length that extends toward the outside of the distal end portion of the valve body. In the fuel injection valve for an internal combustion engine, wherein the fuel in the sac portion is injected from the injection hole based on the reciprocating operation of the needle valve, the slit width of the injection hole is set from the opening on the sack side. A fuel injection valve for an internal combustion engine, wherein the fuel injection valve is gradually thinned toward an outer opening.