JP2012036865A - Injection nozzle - Google Patents

Abstract

Disclosed is a low-cost and high-performance injection nozzle capable of preventing spray unevenness at a high spray angle and suppressing wasteful injection by injection amount control and preventing deterioration in fuel consumption and reduction in exhaust gas performance.
A valve needle and a nozzle body that accommodates the valve needle are displaceable. The nozzle body is formed with a fuel passage for introducing fuel into an injection hole. A conical surface of the valve seat 12 that opens and closes a part of the fuel passage 30 is provided between the nozzle body 10 and the nozzle body 10 having a conical surface 13 constituting the valve seat 12 and a concave wall surface 14 in which the injection holes 11a are opened. And an inner wall surface 16 having a cylindrical surface 15 extending substantially parallel to the axial direction between the conical surface 13 and the concave wall surface 14. In addition, the length of the cylindrical surface 15 in the axial direction is set within a range that exceeds 35% and is 50% or less with respect to the diameter Dsc of the suck chamber 17 formed by the concave wall surface 14 and the cylindrical surface 15. It is better.
[Selection] Figure 1

Description

  The present invention relates to an injection nozzle that injects a fluid, and more particularly to an injection nozzle that has a liquid pool chamber in which the injection hole is opened in the vicinity of an injection hole that injects liquid in a spray state.

  An injection nozzle having a liquid reservoir chamber (hereinafter referred to as a sac chamber) in which the nozzle hole is opened in the vicinity of the nozzle hole at the tip of the nozzle is used, for example, as a fuel injection nozzle of an internal combustion engine for a vehicle. In general, fuel spray is atomized in a fuel injection nozzle of a vehicle internal combustion engine.

  As this type of injection nozzle, for example, in a fuel injection nozzle of an internal combustion engine for a vehicle, an annular gap is formed between the outer peripheral surface on the tip side of the valve needle and the nozzle body, while at the center portion on the tip side of the valve needle. A fuel passage hole communicating with the nozzle hole is formed when the valve is opened, and the annular gap is changed by elastic deformation of the valve needle tip according to the fuel supply pressure to the fuel passage hole, so that the high pressure fuel is supplied to the low pressure portion. What prevents leakage is known (see, for example, Patent Document 1).

  In addition, a swirl passage that imparts a swirling force to the injected fuel is formed between the cylindrical member disposed near the tip of the needle and the nozzle body, and opens to the inner peripheral surface of the cylindrical member, so that the lift amount of the needle There is also known an injection nozzle in which the dynamic range of the injection amount is increased by reducing the passage cross-sectional area of the swirl passage when the valve is small and increasing the cross-sectional area of the swirl passage when the lift amount of the needle is large. (For example, refer to Patent Document 2).

  Further, the inlet portions of two adjacent nozzle holes are brought close to each other to form a swirl flow in each nozzle hole, so that fuel spray with a low penetration force and a high spray angle (wide spray angle) is formed in the low injection region. Have also been proposed (see, for example, Patent Document 3).

JP 2001-221132 A JP 10-288130 A JP 2003-161230 A

  However, in the conventional injection nozzle as described above, it is necessary to process a plurality of spray holes in the nozzle body, and when the spray angle is wide to promote atomization of the fuel spray, the total number of the spray holes is required. It is necessary to increase the opening area, and it is necessary to complicate the shape of the parts housed in the nozzle body in order to obtain the turning force of the fuel. There was a problem. In addition, it is difficult to ensure both the injection quantity in the high injection range and the high-precision injection quantity control in the low injection range, making it difficult to improve the fuel efficiency and exhaust gas performance of the internal combustion engine. was there.

  In addition, the nozzle hole opens into a sac chamber (liquid reservoir) provided inside the nozzle tip, and a conical valve seat inclined with respect to the inner peripheral wall surface of the sac chamber is arranged upstream of the sac chamber In this case, the volume of the sac chamber has been reduced to suppress sludge generation or improve the injection response (time required to refill the sac chamber with the fuel when the valve is opened). The fuel flow line flowing into the sack chamber is separated from the inner peripheral wall surface of the sac chamber, resulting in variations in the fuel stream line distribution at the nozzle hole inlet, which tends to cause a decrease in spray angle and uneven spraying. It was.

  Furthermore, in a direct injection gasoline engine that directly injects fuel into a cylinder, a slit nozzle that is excellent in penetrating power and can form a combustible mixture in the vicinity of a spark plug without assisting the airflow in the engine has begun to be used. Also in this slit nozzle, since the volume of the sac chamber is kept small, the fuel streamline flowing into the sac chamber is separated from the inner peripheral wall surface of the sac chamber, so that the fuel streamline at the entrance of the slit-shaped nozzle hole The distribution of the water was likely to vary, resulting in a decrease in spray angle and uneven spraying. For this reason, there is a possibility that engine oil may be diluted and exhaust gas performance may be deteriorated.

  Therefore, the present invention is capable of reliably preventing uneven spraying at a high spray angle, suppressing unnecessary fuel injection by highly accurate injection amount control, and preventing deterioration of fuel consumption and exhaust gas performance. A low-cost and high-performance injection nozzle that can be used.

In order to achieve the above object, the present invention is an injection nozzle comprising (1) a valve needle and a nozzle body that accommodates the valve needle so as to be displaceable in the axial direction. A jetting hole and a fluid passage for introducing the fluid into the nozzle hole are formed, and when the valve needle is displaced in the axial direction, a part of the fluid passage is opened and closed between the valve needle and the valve needle. A valve seat portion having a conical surface inclined with respect to the axial direction is provided, the nozzle body includes a conical surface constituting the valve seat portion, a concave wall surface in which the nozzle hole is opened, the conical surface and the concave portion. An inner wall surface having a cylindrical surface connected to the conical surface and the concave wall surface while extending substantially parallel to the axial direction between the wall surfaces is formed.
With this configuration, even if the fluid flowing into the sac chamber from the conical surface constituting the valve seat part peels off near the end of the cylindrical surface on the inlet side of the sac chamber, It is possible to ensure a state where the flow lines at the inlet portion are uniformly dispersed, for example, a state where the density of the fuel in which the gas phase and the liquid phase are mixed is uniformly distributed, and the spray unevenness is reduced at a large spray angle. be able to. Therefore, useless fuel injection can be suppressed by high-precision injection amount control, and a low-cost injection nozzle with improved performance that can prevent deterioration of fuel consumption and exhaust gas performance is obtained.
In the injection nozzle according to (1), preferably, (2) the length of the cylindrical surface in the axial direction is 35 with respect to the diameter of the sac chamber formed by the concave wall surface and the cylindrical surface. %, And is set within a range of 50% or less.

  With this configuration, the length of the cylindrical surface is close to the radius of the sac chamber, and it is possible to stably ensure a state where the streamlines at the inlet portion of the nozzle hole are evenly distributed.

  In the injection nozzle according to the above (1) or (2), (3) a radial distance between the outer peripheral surface of the valve needle and the inner wall surface of the nozzle body is on the downstream side of the valve seat portion. It is preferable that it becomes so large that it approaches the said nozzle hole within the said fluid channel | path. With this configuration, even if separation occurs near the end of the cylindrical surface on the inlet side of the sac chamber, a large vortex is less likely to occur in the sac chamber, and streamlined bundle-like bias and bending difficulty are suppressed, A state where the streamlines are uniformly distributed at the inlet of the nozzle hole is promoted.

  (4) In the injection nozzle according to any one of (1) to (3), (4) the valve needle is inserted from the conical surface of the nozzle body to the suck chamber side over the length of the cylindrical surface. It is preferable to have a protruding tip portion. With this configuration, even if the lift amount of the valve needle changes, the cross-sectional area of the fluid passage from the inlet side of the sac chamber to the inlet portion of the nozzle hole is maintained within an appropriate range according to the lift amount of the valve needle. be able to.

  In the injection nozzle according to the above (4), (5) the tip convex portion has an inclined direction of an outer peripheral surface with respect to the axial direction that is the same direction as the conical surface of the nozzle body, and with respect to the axial direction. It is preferable that the inclination angle of the outer peripheral surface is smaller than the inclination angle of the conical surface of the nozzle body. With this configuration, the fluid in the sac chamber is easily guided to the inlet portion of the nozzle hole with a uniform variation of streamlines.

  In the injection nozzle according to the above (4) or (5), (6) the concave wall surface of the nozzle body and the tip surface of the tip convex portion of the valve needle are each formed in a substantially hemispherical shape, It is preferable that the nozzle hole is opened on the concave wall surface at a position facing the tip surface of the tip convex portion. With this configuration, even if the nozzle hole has an axis that is inclined with respect to the axis of the valve needle, the cross-sectional area of the fluid passage from the inlet side of the sac chamber to the inlet of the nozzle hole is reduced to the valve needle. It can be easily set within an appropriate range according to the lift amount. In addition, the opening center of the nozzle hole on the concave wall surface may be located on the central axis of the valve needle and the nozzle body, or may be offset in the radial direction from the central axis.

  In the spray nozzle according to any one of (1) to (6), it is preferable that (7) the nozzle hole is a slit-shaped nozzle hole. With this configuration, atomization is promoted by the splitting of the fluid ejected from the slit-shaped nozzle hole due to the vibration of the liquid film and the shearing force from the surrounding gas, while a high penetrating spray can be formed. As a result, a portion having a high ejection angle is formed on both sides of the expansion direction of the gas-like nozzle hole, and the fluid flow velocity at both ends of the expansion direction is moderately suppressed, so that a preferable spray shape with a high penetration force can be obtained.

  In the injection nozzle according to (7) above, (8) the nozzle hole penetrates the wall portion on the tip end side of the nozzle body in a tilt axis direction inclined by a first tilt angle with respect to the axial direction. Preferably, both sides of the tilt axis direction and the direction orthogonal to the axial direction have a substantially sector shape that is widened by a second tilt angle larger than the first tilt angle. With this configuration, a uniform spray can be formed with a high spray angle (high dispersion) and a high penetration force. For example, in a cylinder of a spark ignition type internal combustion engine, the concentration is close to the spark plug without the assistance of airflow such as swirl. A controllable combustible mixture can be formed.

  In any of the injection nozzles according to (1) to (8), it is preferable that (9) the fuel of the internal combustion engine is injected into the cylinder of the internal combustion engine from the injection hole. With this configuration, it is possible to form a uniform fuel spray at a high spray angle, promote atomization of the fuel spray, and improve the fuel efficiency and exhaust purification performance of the internal combustion engine that performs in-cylinder injection.

  According to the present invention, the length of the cylindrical surface of the inner wall surface of the nozzle body is close to the radius of the sac chamber, so that the fluid flowing into the sac chamber from the conical surface constituting the valve seat portion is contained in the sac chamber. Even if separation occurs near the end of the cylindrical surface on the inlet side, the streamline at the inlet portion of the nozzle hole is ensured to be uniformly distributed, so the spray angle is high at a high spray angle. Providing a low-cost, high-performance injection nozzle that can be reliably prevented, can prevent unnecessary fuel injection by highly accurate injection amount control, and can prevent deterioration in fuel consumption and exhaust gas performance it can.

It is a principal part expanded sectional view of the injection nozzle which concerns on one Embodiment of this invention. It is a principal part schematic block diagram of the injection nozzle of one Embodiment of this invention containing the II-II arrow sectional drawing of FIG. Fig.3 (a) is explanatory drawing explaining the change of the cross-sectional area in each position of the fluid channel | path in the injection nozzle which concerns on one Embodiment of this invention, FIG.3 (b) is one Embodiment which has an injection hole. FIG. 6 is an explanatory diagram of a plurality of cylindrical surfaces defined on the JK surface, which is an expanded surface of the nozzle hole according to the shape of the tip of the injection nozzle, and the spray angle direction and the JK flow velocity and the jet angle at the nozzle hole outlet side. is there. FIG. 4A is an explanatory diagram of streamline distribution at the injection hole inlet portion of the injection nozzle according to the embodiment of the present invention, and FIG. 4B is a view at the injection hole inlet portion of the injection nozzle of the comparative example. It is explanatory drawing of streamline distribution. FIG. 5A is a graph showing the effect of suppressing the JK flow velocity at both ends of the slit-shaped nozzle hole in the expansion direction of the injection nozzle according to the embodiment of the present invention, and the vertical axis represents the JK flow velocity ratio relative to the comparative example. The axis indicates the spray angle expressed in units of the number of divided arrows, and FIG. 5B is a graph showing the effect of increasing the spray angle in the injection nozzle of one embodiment of the present invention, and the vertical axis is a comparison. The spray angle ratio with respect to the example is shown, and the horizontal axis indicates the spray angle represented by the unit of the number of divided arrows. The graph which shows the relationship of the increase effect of the spray angle with respect to the length H1 of the cylindrical surface in the injection nozzle of one Embodiment of this invention with respect to the length, a vertical axis | shaft is a jet angle ratio with respect to a comparative example, and a horizontal axis is cylindrical. The surface length H1 is shown.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show a schematic configuration of an injection nozzle according to an embodiment of the present invention.

  The injection nozzle according to the present embodiment is provided in a cylinder in a dual-injection gasoline engine (internal combustion engine; hereinafter simply referred to as an engine) in which the present invention performs port injection and in-cylinder injection (direct injection in a cylinder). The present invention is applied to an in-cylinder injector (fuel injection valve) that directly injects fuel, and is provided corresponding to each cylinder of the engine. However, the present invention can be applied to injectors other than the direct injection type, and can also be applied to other injection nozzles that inject a fluid in a spray form.

  First, the configuration of the present embodiment will be described.

  As shown in FIGS. 1 and 2, the injector 1 constituting the injection nozzle of the present embodiment includes a tip portion 11 in which a slit-like injection hole 11 a is formed and a substantially conical surface valve seat portion located in the vicinity thereof. A bottomed cylindrical nozzle body 10 having 12 (a portion indicated by cross-hatching in FIG. 2), a valve body portion 21 that can be seated on the valve seat portion 12, and a shaft portion that supports the valve body portion 21 on the distal end side. And a valve needle 20 accommodated in the nozzle body 10 so as to be displaceable in the axial direction. Between the nozzle body 10 and the valve needle 20 of the injector 1, there is formed a fuel passage 30 (fluid passage) through which gasoline as fuel (fluid) can be introduced and ejected from the nozzle hole 11a. The passage 30 has an annular cross section at least in the vicinity of the valve body 21.

  The tip portion 11 of the nozzle body 10 is located inwardly of each cylinder 2, for example, approximately in the radius, on the upper side of the combustion chamber (not shown in detail) in each cylinder 2 of the engine (slightly above the piston head at the end of the compression stroke). A convex shape is formed so as to protrude and expose obliquely downward in the direction, and a thin fan-shaped injection hole 11a is opened in a rectangular shape on the tip end surface 11b.

  Further, the valve seat portion 12 of the nozzle body 10 serves as a valve seat that opens and closes a part of the fuel passage 30 with the valve body portion 21 of the valve needle 20 when the valve needle 20 is displaced in the axial direction. The nozzle body 10 is formed in a concave conical surface inclined at a constant angle (for example, 45 °) with respect to the axial direction of the nozzle body 10 (the extending direction of the central axis Cn). Then, the conical valve face 21a, which is a part of the outer peripheral surface of the valve body part 21 of the valve needle 20, is engaged with and disengaged from the valve seat part 12, so that a part of the fuel passage 30 is airtight. It is designed to be closed and opened.

  More specifically, the nozzle body 10 includes a conical surface 13 partly formed by the valve seat portion 12, a concave spherical concave wall surface 14 in which an injection hole is opened, and a conical surface 13 and a concave wall surface 14. And a cylindrical surface 15 that extends substantially parallel to the axial direction of the nozzle body 10 and is connected to the conical surface 13 and the concave wall surface 14 at both ends thereof. The conical surface 13, the concave wall surface 14 and the cylindrical surface 15 constitute a downstream passage section from the vicinity of the valve seat portion 12 to the nozzle hole 11 a in the inner wall surface 16 of the nozzle body 10.

  In addition, the concave wall surface 14 and the cylindrical surface 15 of the nozzle body 10 have a rectangular cross section along the central axis Cn between the conical surface 13 and the nozzle hole 11a, and a substantially rectangular shape on the side of the nozzle hole 11a. A sac chamber 17 having a semicircular cross section is formed.

  The distance in the radial direction (left-right direction in FIG. 1) between the outer peripheral surface 20a of the valve needle 20 and the inner wall surface 16 of the nozzle body 10 approaches the nozzle hole 11a in the fuel passage 30 on the downstream side of the valve seat portion 12. It is getting bigger.

  As schematically shown in FIG. 3A, the fuel passage 30 formed between the outer peripheral surface 20a of the valve needle 20 and the inner wall surface 16 of the nozzle body 10 is located downstream of the valve seat portion 12 (passage position). The passage cross-sectional area in the section on the downstream side from P0 is smaller than the passage cross-sectional area in the section on the upstream side from the valve seat portion 12. Further, the fuel passage 30 is located on the downstream side of the valve seat portion 12, particularly in the sac chamber 17, and has a fixed passage area that is sufficiently larger than the cross-sectional area of the injection hole 11 a until reaching the positions P5 a and P5 b of the inlet portion of the injection hole 11 a. It is formed to become.

  A broken line S1 shown at the center of FIG. 3A is a cross-sectional area of the fuel passage 30 in the vicinity of the valve seat portion 12 when the valve is opened at a larger opening than the open state shown by the solid line in FIG. The two-dot chain line S2 shown at the center of FIG. 3A is substantially closed at a smaller opening than the valve open state shown by the solid line in FIG. 1 (in FIG. 1). The change in the cross-sectional area of the fuel passage 30 in the vicinity of the valve seat portion 12 at the time of the valve body position indicated by a two-dot difference line in FIG. Further, passage positions P0 to P6a (P6b) shown in FIG. 3A correspond to passage positions P0 to P6a (P6b) shown in FIG.

  Further, the nozzle hole 11a of the tip portion 11 of the nozzle body 10 has a cone wall portion constituting the tip portion 11 of the nozzle body 10 at a first inclination angle α (see FIG. 2) with respect to the axial direction of the nozzle body 10. While passing through the inclined axis direction with a substantially constant slit thickness t, the first axis is formed on both sides of the inclined axis direction and the direction perpendicular to the axial direction of the valve needle 20 (left and right direction in FIG. 1). It has a substantially fan-shaped slit shape widened by a second inclination angle β larger than the inclination angle α. Note that the first inclination angle α is further applied to the central axis Cn of the injector 1 that is directed obliquely downward in the substantially radial direction (for example, 30 ° downward) with respect to the cylinder inner wall of the engine, for example. Is an angle of inclination closer to the upper surface of the piston head in the later stage of the compression stroke (not shown), ie, an angle within 10 °.

  Further, the valve seat portion 12 has a conical seat surface 12a (valve seat surface) having a diameter Dv1 on the outer and upstream end sides and a diameter Dv2 on the inner and downstream end sides around the central axis Cn of the nozzle body 10. 2; and the diameter Dv2 on the inner side and the downstream end side of the seat surface 12a is larger than the sack diameter Dsc.

  Further, the nozzle body 10 is formed with a needle storage hole 18 having an inner diameter larger than the diameter Dv1 on the outer side and upstream end side of the valve seat portion 12, and is formed in a substantially cylindrical cylindrical inner wall surface 18a of the needle storage hole 18. On the other hand, the seat surface 12a is formed by a part of the conical surface 13 inclined on the conical surface at an inclination angle of 45 °, for example. In addition, although the connection part of the cylindrical inner wall surface 18a of the nozzle body 10 and the conical surface 13 and the connection part of the conical surface 13 and the cylindrical surface 15 are bent in the drawing, they may be curved.

  The valve face 21 a of the valve body 21 provided on the distal end side of the valve needle 20 is inclined with respect to the central axis of the valve needle 20 that coincides with the central axis Cn of the nozzle body 10 (hereinafter, both are referred to as the central axis Cn). θv1 is formed. Further, the valve body portion 21 of the valve needle 20 has an intermediate inclination that forms an inclination angle θv2 in the same direction as the inclination angle θv1 with respect to the central axis Cn of the valve needle 20 on the tip side of the valve needle 20 relative to the valve face 21a. It has a surface 21b and a tip-side inclined surface 21c that forms a smaller inclination angle θv3 in the same direction as the inclination angle θv1 with respect to the central axis Cn on the tip side of the valve needle 20 than the intermediate inclined surface 21b. That is, the valve body portion 21 has a smaller diameter as it approaches the nozzle hole 11a on the distal end side of the valve needle 20 facing the nozzle hole 11a.

  Here, the intermediate inclined surface 21b of the valve body 21 is located within the range of the conical surface 13 in the axial direction of the nozzle body 10 when the lift amount of the valve needle 20 is large, but when the lift amount of the valve needle 20 is small. The tip of the intermediate inclined surface 21b enters the sac chamber 17 beyond the position P2 where the inner wall surface 16 bends from the conical surface 13 to the cylindrical surface 15 in the axial direction of the nozzle body 10. Further, the tip side inclined surface 21c of the valve body 21 is in a state in which at least a part thereof is always inserted into the sac chamber 17 regardless of the lift amount of the valve needle 20, and the cylindrical surface 15 A part of the fuel passage 30 is formed between the two. Further, the connecting portion between the intermediate inclined surface 21 b and the distal side inclined surface 21 c of the valve body 21 is about the distance between the distal side inclined surface 21 c of the valve body 21 and the cylindrical surface 15 on the inlet side of the sack chamber 17. It is an annular curved surface curved with a curvature radius of.

  When the valve needle 20 is axially displaced so that the valve body 21 approaches the tip 11 of the nozzle body 10 that is the inner bottom of the needle housing hole 18, the valve face 21 a of the valve body 21 is valve seat 12. The sheet surface 12a. When the valve body portion 21 and the valve seat portion 12 come into contact with each other, the fuel passage 30 therebetween is hermetically closed in the vicinity of the injection hole 11a.

  The axial length (height) Hb0 of the valve seat portion 12 of the nozzle body 10 is substantially equal to the axial length (height) Hv0 of the valve face 21a of the valve needle 20, and from the valve seat portion 12 The height Hb1 of the lower portion 13e of the conical surface 13 up to the inlet of the sack chamber 17 is equal to the axial length Hv1 of the intermediate inclined surface 21b of the valve needle 20.

  The inclination angle θv1 of the valve face 21a with respect to the central axis Cn is slightly larger (for example, by a difference of 1 ° or less) than the inclination angle θs of the conical surface 13 with respect to the central axis Cn. The seat surface 12a of the valve seat portion 12 is in pressure contact with each other at the outer and upstream end portions thereof. Further, the inclination angle θv2 of the intermediate inclined surface 21b with respect to the central axis Cn is sufficiently larger than the inclination angle θv1 of the conical surface 13 with respect to the central axis Cn.

  The length Hb2 of the cylindrical surface 15 in the axial direction of the nozzle body 10 is the diameter of the sac chamber 17 formed by the substantially concave spherical wall surface 14 and the substantially cylindrical surface 15 (hereinafter referred to as sac). The diameter is referred to; FIG. 2) The length exceeds 35% with respect to Dsc and is set within a range of 50% or less with respect to the diameter of the sack chamber 17. Here, the depth of the sac chamber 17 corresponds to the sum of the length Hb2 of the cylindrical surface 15 and the curvature radius Rsc of the concave wall surface 14, and the curvature radius Rsc of the concave wall surface 14 is approximately 1 / of the sac diameter Dsc. 2 in length.

  On the other hand, the tip side inclined surface 21c of the valve body portion 21 of the valve needle 20 is inserted into the sack chamber 17 side from the conical surface 13 of the nozzle body 10 so as to extend beyond the length of the cylindrical surface 15. This tip-side inclined surface 21c is inclined in the same direction as the conical surface 13 of the nozzle body 10 with respect to the axial direction of the valve needle 20 (the central axis direction of the shaft portion 22). . Here, the inclination angle θv3 of the tip side inclined surface 21c with respect to the axial direction of the valve needle 20 is smaller than the inclination angle θs of the conical surface 13 of the nozzle body 10, but the inner wall surface of the nozzle body 10 facing in the radial direction. 16 is an angle at which the valve face 21a of the valve needle 20 is inclined inward with respect to the seat surface 12a of the valve seat portion 12 (for example, 1 °). (Below) is larger.

  The concave wall surface 14 of the nozzle body 10 and the tip surface 21d of the tip convex portion 21p of the valve needle 20 are formed in a substantially hemispherical shape having different radii, and the inner end of the slit-shaped injection hole 11a is In addition, an opening is formed on the concave wall surface 14 at a position facing the tip surface 21d (see FIG. 1) of the tip convex portion 21p.

  The separation distance Hb3 from the center position of curvature of the concave wall surface 14 in the axial direction of the nozzle body 10 to both end positions in the opening width direction of the nozzle hole 11a on the concave wall surface 14 is the sac chamber 17 when the valve needle 20 is in the closed position. Is set so as to be larger than the axial height Hv2 from the inlet to the apex of the tip surface 21d of the tip convex portion 21p.

  Further, the nozzle body 10 and the valve needle 20 are shown only in their respective tip portions in FIG. 1, but the upper end portion or the axial intermediate portion of the valve needle 20 is, for example, between the valve needle 20 and the nozzle body 10. 2 is always urged to one side in the axial direction of the valve needle 20, for example, the lower side in FIG. 2 which is the valve closing direction.

  More specifically, an electromagnetic coil (which may be a piezo element) 42 is accommodated in the upper end portion (the vertical direction means the vertical direction in FIG. 2) or the axial intermediate portion of the nozzle body 10, and the inner side thereof. Further, a movable plunger 43 attached to the upper end portion or the axially intermediate portion of the valve needle 20 and a fixed plunger 44 fixed to the nozzle body 10 side are housed. The compression spring 41 is contracted between the movable plunger 43 and the fixed plunger 44 to urge the valve needle 20 in the valve closing direction. Further, when the electromagnetic coil 42 is energized through a lead wire (not shown), a magnetic circuit is formed through the movable plunger 43 and the fixed plunger 44 so that the valve needle 20 is resisted against the urging force of the compression spring 41 by the movable plunger 43. The valve opening / closing drive means 40 is configured by the compression spring 41, the electromagnetic coil 42, the movable plunger 43, and the fixed plunger 44. The electromagnetic coil 42 of the valve opening / closing drive means 40 is energized so that the valve opening according to the required fuel injection amount is obtained by a valve opening signal from an electronic control unit (hereinafter referred to as ECU) (not shown). The duty is controlled. Since such a valve opening / closing drive system itself is known, it will not be described in further detail.

  The fuel passage 30 communicates with a delivery pipe (not shown), and fuel discharged from a fuel pump (not shown) via the delivery pipe is accumulated and stored in the delivery pipe, and a predetermined fuel pressure is stored in the fuel passage 30. It comes to be supplied with. Therefore, when the ECU performs energization control with a duty ratio corresponding to the required fuel injection amount on the electromagnetic coil 42 of the valve opening / closing drive means 40, the fuel is injected by the injector 1 into the cylinders of the plurality of cylinders of the engine. Further, a required amount of fuel is selectively injected into the intake port corresponding to each cylinder by a port injection injector (not shown).

  The ECU includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup memory using a nonvolatile memory, an input interface circuit and an output interface circuit (not shown), and the like. It is configured. The input interface circuit of the ECU is connected to an air flow meter, a rotation speed sensor, a throttle sensor, and a sensor group such as an oxygen sensor, a cylinder discrimination sensor, an intake air temperature sensor, and a water temperature sensor (not shown). The sensor information is taken into the ECU. In addition, an injector, an igniter that drives a spark plug (not shown), a drive circuit for the fuel pump, and the like are connected to the output interface circuit of the ECU.

  Next, the operation of this embodiment will be described.

  In the fuel injection valve of the present embodiment configured as described above, fuel discharged from a fuel pump (not shown) is supplied into the fuel passage 30 through the delivery pipe at a predetermined fuel pressure, while the ECU performs injection timing. When the energization control is performed on the valve opening / closing drive means 40 of the injector 1 at a duty ratio corresponding to the required injection amount, a required amount of fuel is injected from the injector 1 into the corresponding cylinder.

  That is, first, the electromagnetic coil 42 of the valve opening / closing drive means 40 is energized by the valve opening signal from the ECU, and the valve body 21 of the valve needle 20 and the tip end portion 11 of the nozzle body 10 are in contact with each other. In the state shown by the two-dot chain line in FIG. 1, the valve opening operation is started by raising the valve needle 20, and the valve face 21 a of the valve body portion 21 is separated from the seat surface 12 a of the valve seat portion 12 and passes through the fuel passage 30. The sac chamber 17 is filled with fuel, and fuel is injected into the combustion chamber from the nozzle hole 11a.

  At this time, since the length of the cylindrical surface 15 located on the inlet side of the sac chamber 17 is close to the radius Rsc of the sac chamber 17, the sac chamber 17 extends from the conical surface 13 constituting the valve seat portion 12. Even if the fluid flowing into the inside of the sack chamber 17 peels or vortexes near the end of the cylindrical surface 15 on the inlet side of the sac chamber 17, the streamlines near the inlet of the nozzle hole 11a are uniformly distributed. It is possible to ensure a state in which, for example, the density of the fuel in which the gas phase and the liquid phase are mixed is relatively uniformly distributed, and the substantially fan-shaped spray ejected from the nozzle hole 11a is ejected at a large spray angle. Unevenness of spraying can be reduced. Therefore, useless fuel injection can be suppressed by highly accurate injection amount control, and the low-cost injector 1 can prevent deterioration in fuel consumption and exhaust gas performance.

  Further, in the present embodiment, the radial distance between the outer peripheral surface 20 a of the valve needle 20 and the inner wall surface 16 of the nozzle body 10 approaches the nozzle hole 11 a in the fuel passage 30 on the downstream side of the valve seat portion 12. The required passage sectional area is such that the sectional area of the fuel passage 30 downstream from the valve seat portion 12 gradually increases until it reaches the vicinity of the injection hole 11a regardless of the lift amount of the valve needle 20. Therefore, even if separation occurs near the end of the cylindrical surface 15 on the inlet side of the sac chamber 17, a large vortex is less likely to be generated in the sac chamber 17, and the streamline bundles are bent and bent. By suppressing the difficulty, a state where the streamlines are uniformly distributed at the inlet portion of the nozzle hole 11a is promoted.

  As shown in FIG. 3 (b), depending on the shape of the tip 11 of the injector 1 (injection nozzle) of the present embodiment having the injection hole 11a, it is defined on the JK surface that is the expansion surface of the injection hole 11a. 4A and 4B are obtained by analyzing and examining the JK flow velocity and the jetting angle on the outlet side of the nozzle hole 11a in comparison with the comparative example in consideration of the plurality of cylindrical surfaces and the spray jetting direction. The result was as shown in.

  The streamline distribution at the inlet of the injection hole 11a of the injection nozzle 1 according to the present embodiment is shown in FIG. 4A, and the streamline distribution at the injection hole of the injection nozzle of the comparative example is shown in FIG. 4B. ing.

  As is clear from these figures, in the comparative example shown in FIG. 4B, the flow component as indicated by the white arrow pointing downward in the figure is generated due to the influence of the streamline bundle near the seat surface exit b1. It becomes stronger, the streamline is biased toward the center of the nozzle hole in the expanding direction, and the spray unevenness at both ends of the nozzle hole in the expanding direction becomes large. On the other hand, in the present embodiment, as shown in FIG. 4A, the influence of the streamline bundle near the sheet surface exit a1 on the flow component of the white arrow is suppressed, and the streamline toward the nozzle hole 11a side. Thus, it is possible to obtain a state in which streamlines are evenly distributed at the inlet of the nozzle hole 11a.

  In the present embodiment, the valve needle 20 further has a tip convex portion 21p inserted over the length of the cylindrical surface 15 from the conical surface 13 of the nozzle body 10 to the sac chamber 17 side. Even if the amount of lift of 20 changes, the cross-sectional area of the fuel passage 30 from the inlet side of the sack chamber 17 to the inlet of the nozzle hole 11a is maintained within an appropriate range corresponding to the amount of lift of the valve needle 20. Can do. And the inclination direction with respect to the central axis Cn of the tip side inclined surface 21c which is an outer peripheral surface of the tip convex part 21p is the same direction as the inclination direction of the conical surface 13 of the nozzle body 10 with respect to the center axis Cn, and the inclination angle is Since the inclination angle θs of the conical surface 13 of the nozzle body 10 is smaller, the fluid in the sac chamber 17 is easily guided to the inlet portion of the nozzle hole 11a in a state where the flow lines are uniformly dispersed.

  In addition, the concave wall surface 14 of the nozzle body 10 and the tip surface 21d of the tip convex portion 21p of the valve needle 20 are each formed in a substantially hemispherical shape, and the injection hole 11a faces the tip surface 21d of the tip convex portion 21p. Since the nozzle hole 11a has an axis inclined with respect to the central axis Cn, the area between the inlet side of the sack chamber 17 and the inlet part of the nozzle hole 11a is opened. The cross-sectional area of the fuel passage 30 can be easily set within an appropriate range corresponding to the lift amount of the valve needle 20.

  In the present embodiment, in particular, since the nozzle hole 11a has a slit shape, atomization is promoted by splitting due to liquid film vibration of fuel injected from the slit-shaped nozzle hole 11a and shearing force from surrounding gas. On the other hand, a spray with high penetrating force can be formed. In addition, as shown in FIG. 5 (b), the jet angle ratio with the comparative example is shown in FIG. 5 (b). As shown in FIG. 5 (a), the fuel flow rate is moderately suppressed in the vicinity of both ends in the spreading direction (region surrounded by the dotted line Z1 in the figure). However, it is possible to obtain a preferable spray shape that can suppress the adhesion of the injected fuel to the wall surface.

  In addition, the nozzle hole 11a penetrates the tip end portion 11 of the nozzle body 10 in the tilt axis direction inclined by the first tilt angle α with respect to the central axis Cn, and both sides in the tilt axis direction and the direction orthogonal to the axial direction. Are substantially fan-shaped and expanded by a second inclination angle β larger than the first inclination angle α, so that a uniform spray can be formed with a high spray angle (high dispersion) and a high penetration force. In the cylinder of the ignition internal combustion engine, it is possible to form a combustible air-fuel mixture that can be precisely controlled in the vicinity of the spark plug without the assistance of airflow such as swirl.

  Further, the fuel consumption of an engine that injects fuel from the nozzle hole 11a of the injector 1 into the cylinder of the engine, forms a uniform fuel spray at a high spray angle, promotes atomization of the fuel spray, and performs in-cylinder injection. And exhaust purification performance can be improved.

  FIG. 6 shows how the jet angle changes at the outlet of the nozzle hole 11a in the specific spray angle direction (near arrow division number 21) when the axial length Hb2 of the cylindrical surface 15 of the injector 1 is changed. The vertical axis represents the ratio of the ejection angle with the comparative example in which the axial length Hb2 of the cylindrical surface 15 is equivalent to the conventional value (less than 35% with respect to the sack diameter). The horizontal axis is the size of the axial length Hb2 of the cylindrical surface 15. In addition, the dashed-two dotted line in a figure is the curve regression of the analytical data shown by a point.

  As is apparent from this figure, when the axial length Hb2 of the cylindrical surface 15 is made larger than the conventional one and the ratio of the axial length Hb2 to the sack diameter Ds is set to a size greater than or equal to r1, the slit-like shape is obtained. The expansion effect of the ejection angle on both sides of the expansion direction of the nozzle hole 11a clearly appears. However, when the ratio of the axial length Hb2 to the sack diameter Ds increases to exceed r2 in the figure, the effect of expanding the ejection angle on both sides of the expansion direction of the slit-shaped injection hole 11a starts to decrease, and the sac chamber Disadvantages due to the increase in the volume of 17 (for example, an increase in fuel filling time at the start of injection and an increase in deposit) appear. Therefore, when the ratios r1 and r2 of the axial length Hb2 with respect to the sack diameter Ds are observed for a plurality of specific spray angle directions, it is preferable that the ratio r1 is 35% or more and the ratio r2 is less than 50%. High ejection angle ratios were obtained within a range of numbers. Therefore, the length Hb2 of the cylindrical surface 15 in the axial direction of the nozzle body 10 is more than 35%, more preferably more than 45% with respect to the diameter Dsc of the sac chamber 17, and this sac The length is set within a range of 50% or less with respect to the diameter Dsc. Generally, when the volatility of the fluid is high, the cavitation generation sensitivity in the injector 1 tends to decrease according to the supply pressure of the fuel, but a large change in the preferable range of the set length Hb2 of the cylindrical surface 15 There is no.

  As described above, in the present embodiment, the length Hb2 of the cylindrical surface 15 of the inner wall surface 16 of the nozzle body 10 is close to the radius Rsc of the sac chamber 17, so that the conical surface constituting the valve seat portion 12 is formed. 13, even if the fuel flowing into the sac chamber 17 peels off near the end of the cylindrical surface 15 on the inlet side of the sac chamber 17, the streamline at the inlet portion of the nozzle hole 11 a is uniformly distributed. Since it ensures, it is a high spray angle and can prevent the spray nonuniformity reliably. Therefore, it is possible to provide a low-cost and high-performance injection nozzle 1 that can suppress useless fuel injection by highly accurate injection amount control and can prevent deterioration in fuel consumption and exhaust gas performance.

  In the above-described embodiment, the opening center of the injection hole 11a on the concave wall surface 14 is located on the central axis Cn of the valve needle 20 and the nozzle body 10, but the injection hole 11a on the concave wall surface 14 The center of the opening may be located on the central axis Cn, or may be offset in the radial direction from the central axis Cn.

  The thickness difference t between the slit-shaped nozzle holes 11a is set according to the fuel pressure and the required penetration force (spraying distance), and the second inclination angle β in the expanding direction is the first inclination angle α. Larger than 90 °. However, in FIG. 1, as long as Hv2 <Hb2 + Hb3 is established, the inclination angle of the inner wall surface at both ends in the expanding direction of the slit-shaped nozzle hole 11a may be 90 ° with respect to the central axis Cn.

  In the above-described embodiment, the present invention is applied to an in-cylinder injector in a dual-injection engine. However, the present invention can also be applied to a port-injector, or a slit nozzle. The present invention can also be applied to an injection nozzle having other shapes of nozzle holes.

  In the above-described embodiment, the injector 1 is positioned on the upper side of the combustion chamber (not shown in detail) in the cylinder 2, that is, slightly above the piston head at the end of the compression stroke, and substantially in the radial direction of the cylinder 2. However, it may be installed downward (in the direction from the cylinder head side toward the piston head) near the top of the combustion chamber.

  As described above, according to the present invention, the fluid flowing into the sac chamber from the conical surface constituting the valve seat portion so that the length of the cylindrical surface of the inner wall surface of the nozzle body is close to the radius of the sac chamber. However, even if separation occurs near the end of the cylindrical surface on the inlet side of the sac chamber, the streamline at the inlet of the nozzle hole is ensured to be uniformly distributed, so that the spray angle is high. A low-cost, high-performance injection nozzle that can reliably prevent uneven spraying, suppress unnecessary fuel injection by highly accurate injection amount control, and prevent deterioration of fuel consumption and exhaust gas performance. This is advantageous in that it can be provided, and is useful for all injection nozzles having a liquid reservoir chamber in which the nozzle holes are opened in the vicinity of the nozzle holes for spraying the liquid in the form of a spray.

1 Injector (injection nozzle)
2 cylinder 10 nozzle body 11 tip 11a nozzle hole 11b tip 12 valve seat 12a seat (valve seat)
13 Conical surface (conical surface)
13e lower part 14 concave wall surface 15 cylindrical surface 16 inner wall surface 17 sack chamber 18 needle accommodation hole 18a cylindrical inner wall surface 20 valve needle 20a outer peripheral surface 21 valve body portion 21a valve face 21b intermediate inclined surface 21c front end side inclined surface 21d front end surface 21p Tip convex portion 22 Shaft portion 30 Fuel passage (fluid passage)
40 Valve opening / closing drive means Hb2 Axial length of cylindrical surface θs Inclination angle of seat surface θv1, θv2, θv3 Inclination angle α First inclination angle β Second inclination angle

Claims (9)

An injection nozzle comprising a valve needle and a nozzle body that accommodates the valve needle in an axially displaceable manner,
The nozzle body is formed with a nozzle hole for ejecting a fluid and a fluid passage for introducing the fluid into the nozzle hole, and the fluid between the valve needle and the valve needle when the valve needle is displaced in the axial direction. A conical valve seat portion inclined with respect to the axial direction so as to open and close a part of the passage is provided,
The nozzle body extends substantially parallel to the axial direction between the conical surface constituting the valve seat, the concave wall surface where the nozzle hole is opened, and the conical surface and the concave wall surface. An injection nozzle comprising an inner wall surface having a surface and a cylindrical surface connected to the concave wall surface.   The length of the cylindrical surface in the axial direction is set in a range exceeding 35% and not more than 50% with respect to the diameter of the sac chamber formed by the concave wall surface and the cylindrical surface. The spray nozzle according to claim 1.   A radial separation distance between the outer peripheral surface of the valve needle and the inner wall surface of the nozzle body is increased as it approaches the nozzle hole in the fluid passage on the downstream side of the valve seat portion. The injection nozzle according to claim 1 or 2.   4. The valve needle has a tip-like convex inclined surface portion that is inserted on the side of the sack chamber from the conical surface of the nozzle body over the length of the cylindrical surface. The injection nozzle according to claim 1.   The tip convex portion has an inclination direction of the outer peripheral surface with respect to the axial direction in the same direction as the conical surface of the nozzle body, and an inclination angle of the outer peripheral surface with respect to the axial direction is an inclination of the conical surface of the nozzle body. The spray nozzle according to claim 4, wherein the spray nozzle is smaller than an angle.   The concave wall surface of the nozzle body and the tip surface of the tip convex portion of the valve needle are each formed in a substantially hemispherical shape, and the concave wall surface is located at a position where the nozzle hole faces the tip surface of the tip convex portion. The spray nozzle according to claim 4 or 5, wherein the spray nozzle is opened upward.   The injection nozzle according to any one of claims 1 to 6, wherein the injection hole is a slit-shaped injection hole.   The nozzle hole penetrates the wall portion on the tip end side of the nozzle body in a tilt axis direction inclined by a first tilt angle with respect to the axial direction, and is orthogonal to the tilt axis direction and the axial direction. The injection nozzle according to claim 7, wherein each side has a substantially fan shape that is widened by a second inclination angle larger than the first inclination angle.   The injection nozzle according to any one of claims 1 to 8, wherein fuel of the internal combustion engine is injected into the cylinder of the internal combustion engine from the injection hole.

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