JP2006242159A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group injection hole type fuel injection valve capable of securing strong accomplishing force in injection. <P>SOLUTION: As a direction for giving accomplishing force to injection, a plurality of directions are set, while displacing them from each other in the circumferential direction around a needle valve 151. About each of the plurality of directions, reference lines L, L... expressing each of directions are specified, and a plurality of injection holes 152a, 152a... are formed at an acute angle against each of the reference line L and arranged in the circumferential direction around each of the reference line L. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve, and in particular, in a multi-injection type fuel injection valve in which a plurality of injection holes are formed in a circumferential direction centering on a needle valve, the penetration force of spray is enhanced. For technology.

It is well known that a multi-injection type fuel injection valve is employed for fuel miniaturization. Among the multi-injection type fuel injection valves, the following group injection-hole type fuel injection valves are known, particularly for the purpose of uniform fuel distribution in spraying. That is, a plurality of directions are set by shifting in the circumferential direction centering on the needle valve as a direction for giving a penetrating force to the spray, and a nozzle hole group composed of a plurality of small nozzle holes for each of the plurality of directions. Is provided (Patent Document 1). In this structure, the nozzle holes of each nozzle hole group are arranged in a circle at a position on an axis indicating a direction in which a penetrating force is given and a position on a circumference with reference to this axis.
JP-A-62-087665 (FIG. 2)

  However, this known group injection hole type fuel injection valve has the following problems in injection characteristics. That is, in this, in each nozzle hole group, a plurality of nozzle holes are arranged in a circle shape including the position on the axis. For this reason, the distribution of fuel in the spray is made uniform compared to the general multi-hole type in which the nozzle holes are provided only in the position on the axis indicating the direction for each direction in which the penetrating force is given. Can be promoted. However, since the spray spread angle is merely increased, the spray penetration force is reduced, and the mixing of fuel and air does not proceed sufficiently, so that the generation of soot can be suppressed satisfactorily. There is a case that cannot be done.

  An object of the present invention is to secure a strong penetration force of spray and suppress the generation of soot in a group injection hole type fuel injection valve.

  The present invention provides a multi-injection type fuel injection valve. The apparatus according to the present invention is a fuel injection valve in which fuel is injected from a plurality of injection holes arranged in a circumferential direction centering on a needle valve, and as a reference line indicating a direction in which a penetration force is given to the spray, First and second reference lines are set by shifting in the circumferential direction around the needle valve, and the first reference line is a first reference line formed of a plurality of nozzle holes formed at positions excluding the first reference line. The first nozzle hole group is provided, and the second nozzle hole group including a plurality of nozzle holes formed at positions other than the second reference line is provided with respect to the second reference line. Each nozzle hole of the hole group forms an acute angle with respect to the first reference line, and forms an opening end aligned in the circumferential direction with the first reference line as the center. The hole makes an acute angle with respect to the second reference line, and forms an opening end aligned in the circumferential direction around the second reference line. It is intended.

  According to the present invention, with respect to a plurality of reference lines (that is, the first and second reference lines) indicating the direction in which the penetration force is given to the spray, the position on each reference line is removed and an acute angle with respect to each reference line. The nozzles are arranged in the circumferential direction to promote uniform fuel distribution in the spray, and sprays that travel on each reference line are formed. This spray provides a strong penetration force for the entire spray. Obtainable.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of an internal combustion engine 1 including a fuel injection valve 101 according to a first embodiment of the present invention.
An internal combustion engine (hereinafter referred to as “engine”) 1 is a so-called HCCI (or premixed compression ignition) type diesel engine in which premixing of combustion is promoted. In the engine 1, the fuel injection valve 101 is disposed on the cylinder center axis m, and is disposed on the cylinder head H so as to face the upper center of the combustion chamber 102. The fuel is directly injected into the combustion chamber 102 by the fuel injection valve 101, and the injected fuel forms a hollow cone spray as a whole.

  A piston 103 is inserted into the cylinder block B, and a space formed between the crown surface of the piston 103 and the lower surface of the cylinder head H becomes the combustion chamber 102. The cylinder head H is formed with an intake port 104 on one side with respect to the cylinder center axis m, and the intake port 104 is connected to an intake manifold (not shown) to form an intake passage. The intake port 104 is opened and closed by an intake valve 105. On the other hand, an exhaust port 106 is formed on the other side with respect to the cylinder center axis m, and the exhaust port 106 is connected to an exhaust manifold (not shown) to form an exhaust passage. The exhaust port 106 is opened and closed by an exhaust valve 107. The intake valve 105 and the exhaust valve 107 are driven by an intake cam and an exhaust cam (not shown) arranged above the valves 105 and 107, respectively.

  In the present embodiment, the combustion mode is switched between HCCI combustion and typical compression ignition (hereinafter referred to as “compression ignition”) combustion that starts combustion before the end of fuel injection in accordance with the operating state of the engine 1. . When the engine 1 is in a relatively low rotation and low load side region, the former is based on HCCI combustion, and when it is in a region other than this, it is based on the latter compression ignition combustion. In the case of HCCI combustion, a large amount of burned gas is circulated in the cylinder by internal EGR and the like, and the fuel injection timing is retarded from that in the case of compression ignition combustion. By HCCI combustion, the generation of nitrogen oxides and soot that are inherently in a trade-off relationship can be simultaneously reduced. In order to implement internal EGR, in this embodiment, a variable mechanism is adopted for the intake cam, and the overlap amount between the intake valve open period and the exhaust valve open period is changed.

  The operation of the fuel injection valve 101 is controlled by an engine control unit (hereinafter referred to as “ECU”) 201. The ECU 201 detects a signal from the accelerator sensor 251 that detects the amount of depression of the accelerator pedal and a signal from the crank angle sensor 252 that detects the unit crank angle and the reference crank angle (based on this signal, the engine speed is detected. ) Etc. are input. The ECU 201 controls the fuel injection amount and injection timing by the fuel injection valve 101 based on various input signals.

FIG. 2 shows the configuration of the nozzle portion of the fuel injection valve 101. FIG. 2 (a) shows the nozzle portion in a cross-section by a plane including the central axis (hereinafter referred to as “needle valve central axis”) n of the needle valve 151, and FIG. It is shown enlarged.
The fuel injection valve 101 is a multi-injection type fuel injection valve, and has a plurality of injection holes 152a, 152a,... Arranged in a circumferential direction around the needle valve 151. A hollow is formed in the inside of the main body 152 in the axial direction, and a needle valve 151 is coaxially inserted into the hollow, and the fuel communicated with the injection hole 152a by the peripheral surface of the needle valve 151 and the inner surface of the main body 152. The internal passage 153 is formed. The needle valve 151 is driven based on a signal from the ECU 201, and a solenoid (not shown) is excited based on this signal, so that the needle valve 151 is attracted to the solenoid and rises on the central axis n of the needle valve. Open. The fuel is supplied by the fuel pump 108 via the pipe 109 and is injected into the combustion chamber 102 via the internal passage 153 and the injection hole 152a.

  In the present embodiment, a plurality of directions are set by shifting in the circumferential direction around the needle valve 151 as directions in which the spray of the injected fuel has a penetrating force. Reference lines L, L... Are set. Each reference line L forms an acute angle with respect to the needle valve central axis n, and is radially shifted by a predetermined angle (here, 60 °) in the circumferential direction around the needle valve 151. . A plurality of nozzle holes 152a, 152a,... Are arranged in parallel at the distal end of the main body 152 in the circumferential direction centering on a reference line L that defines the direction for each direction in which a penetrating force is given. A nozzle hole group g, g... Is formed for each line L. The nozzle hole 152a of each nozzle hole group g forms an opening end aligned on the circumference centered on the reference line L on the end surface of the main body 152. Each nozzle hole 152a (center axis is indicated by C) is inclined at an angle θ of 20 to 45 ° with respect to the reference line L, and is formed with a hole diameter φ of 0.1 mm or less. Such a setting regarding the angle θ and the hole diameter φ is considered necessary for forming the spray S2 having a strong penetrating force by the entrainment of the spray described later. In the present embodiment, the phase α of the circumferential injection hole 152a centering on the reference line L is matched in all the injection hole groups g.

FIG. 3 shows a spray formation process by the fuel injection valve 101.
In the initial stage of injection, the fuel spray S1 injected from each injection hole 152a forms a hollow cone-shaped spray centering on a reference line L indicating the direction in which the penetration force is given (FIG. 3A). ). Here, each injection hole 152a is formed to be inclined with respect to the reference line L, and the diameter φ of each injection hole 152a is set to a small value so that the fuel is sufficiently miniaturized, whereby the internal passage 153 is formed. When the pressure of the fuel in the inside is sufficiently increased, a swirl flow F is formed in which air around the cone-shaped spray is entrained immediately after the start of injection. Due to this swirl flow F, the subsequent spray S1 is entrained in the cone-shaped spray together with the surrounding air while accelerating (FIG. 3B). The entrained spray forms a substantially solid spray S2 that travels on the reference line L and has a small fuel concentration difference. This spray S2 overtakes the preceding spray S1 by the end of the injection, whereby a strong penetrating force as the entire spray is given by this spray S2 (FIG. 3 (c)), due to insufficient mixing of fuel and air. Soot generation is suppressed. At the end of injection, a hollow cone spray diffused in a relatively wide range of the combustion chamber 102 is formed by the spray S2 from each nozzle hole group g (FIG. 3 (d)).

According to this embodiment, the following effects can be obtained.
That is, in this embodiment, in the multi-hole injection type fuel injection valve 101, the reference line L is set for each direction in which the penetration force is given to the spray, and the position on the reference line L is removed for each of these directions. A plurality of injection holes 152a having an acute angle with respect to the reference line L are arranged in the circumferential direction. For this reason, a swirl flow F is formed immediately after the start of injection, and the swirl flow F causes the subsequent spray to enter the inside of the cone formed by the preceding spray. Since a small spray is formed, it is possible to promote uniform fuel distribution throughout the spray. Further, the spray S2 formed by the entrainment by the swirl flow F has a stronger penetration force than the preceding spray S1, and overtakes the preceding spray S1 by the end of the injection. And soot generation can be suppressed. In particular, in the case of HCCI combustion, the soot reduction effect can be further emphasized in combination with premixing of combustion.

Hereinafter, another embodiment of the present invention will be described.
FIG. 4 is an enlarged view of the tip of the nozzle portion of the fuel injection valve according to the second embodiment of the present invention.
In this embodiment, it is intended to suppress the spray interference between the adjacent nozzle hole groups g and g and to develop the swirl flow F with certainty. That is, in this embodiment, in each nozzle hole group g, the hole diameter φ of the nozzle hole 152a and the interval ρ between the adjacent nozzle holes 152a and 152a are changed in the circumferential direction around the reference line L, and the hole diameter is changed. φ is set to a smaller value for the nozzle hole 152a closer to a line (hereinafter referred to as “original line”) x perpendicular to the needle valve central axis n, and the interval ρ is also a position closer to the original line x. It is set to a smaller value for. FIG. 5 shows the hole diameter φ of the injection hole 152a at the position of the angle α from the original line x and the interval ρ between the injection hole 152a and the adjacent injection hole 152a. The hole diameter φ is set to the smallest value at the position (α = 0, 180 °) on the original line x, and is set to the largest value at the position where the angle α is 90,270 °. It is gradually changed between. Similarly, the interval ρ is set to the smallest value at the position on the original line x, and is set to the largest value at the position where the angle α is 90,270 °. In other words, the number μ of the injection holes 152a per range is set to the largest value at the position on the original line x, and is set to the smallest value at the position where the angle α is 90,270 °. In the present embodiment, the center angle of an arc cut by two points on the central axis of the adjacent nozzle holes 152a and 152a is adopted as the interval ρ. The configuration other than the setting of the hole diameter φ and the interval ρ is the same as that of the first embodiment.

  The effects obtained by this embodiment will be described with reference to FIGS. FIG. 6 shows that, in the case of the first embodiment, the sprays S1 and S1 interfere with each other between the adjacent nozzle hole groups g and g, and the swirl flow F does not develop sufficiently and proceeds on the reference line L. The state in which the spray S2 is not formed well is shown. On the other hand, FIG. 7 shows a state in which the interference of the sprays S1 and S1 is suppressed, the swirl flow F is developed, and the spray S2 is formed satisfactorily by adopting this embodiment.

  In the case of FIG. 6 in which the hole diameter φ and the interval ρ are constant in the circumferential direction, the sprays S1 and S1 tend to interfere with each other between the adjacent nozzle hole groups g and g. When the sprays S1 and S1 actually interfere with each other, it becomes difficult to take in the surrounding air in the interference region, so that the entrainment of the subsequent spray becomes weak due to the undeveloped swirl flow F, and the penetration force of the spray S2 is obtained with sufficient strength. I can't. Further, a fuel concentration difference is caused in the spray, and the amount of soot is increased by the fuel concentrated in the interference region. On the other hand, by adopting this embodiment, in the case of FIG. 7 in which the hole diameter φ and the interval ρ are changed in the circumferential direction, the interference of the sprays S1 and S1 can be suppressed, and the swirling flow F is reliably developed. Thus, the penetration force of the spray S2 can be obtained with sufficient strength. This effect is because by setting the nozzle hole φ to a small value in a region where interference is likely to occur, fuel miniaturization is promoted, and kinetic energy imparted to the surrounding air increases. In this case, the interval ρ is set to a small value and the number μ of the injection holes 152a per range is increased, so that the pressure drop at the initial stage of injection becomes large and the entrainment of the spray becomes strong.

  8 and 9 show the configuration of the nozzle portion of the fuel injection valve according to the third and fourth embodiments of the present invention, respectively. FIG. 8A shows the tip of the nozzle part of the fuel injection valve, and FIG. 8B shows the tip in an enlarged manner. On the other hand, FIG. 9A shows the nozzle portion of the fuel injection valve in a cross section by a plane including the needle valve central axis n, and FIG. 9B shows the tip of the nozzle portion.

  In these embodiments, as in the previous second embodiment, the purpose is to suppress spray interference between adjacent nozzle hole groups g, g. In the third embodiment, the reference line L In the fourth embodiment, the reference lines L and L of the adjacent nozzle hole groups g and g are set as the needles in the fourth embodiment. It is set by shifting in the direction of the valve center axis n. In the third embodiment, the phase of the nozzle holes 152a, 152a is set to be shifted by α / 2 between the adjacent nozzle hole groups g, g (FIG. 8B). In the fourth embodiment, While the phases of the nozzle holes 152a are matched in all the nozzle hole groups g, the reference lines L and L are set so as to be shifted by a distance l in the direction of the needle valve central axis n.

According to these embodiments, it is easy to cause the intake of air in a region where the spray is adjacent, and the swirl flow F can be reliably developed, so that the undeveloped swirl flow F due to the interference of the spray is avoided and strong. The penetrating force spray S2 can be formed satisfactorily.
In addition, although the case where the HCCI type diesel engine was employ | adopted as an internal combustion engine was demonstrated above as an example, this invention is applicable not only to this but to an HCCI type gasoline engine. When applied to gasoline engines, in order to ensure compression ignition, the in-cylinder temperature at the start of compression is increased by internal EGR, etc., and a spark plug is installed to ensure a practical operating range, and HCCI combustion It is preferable to switch the combustion mode between homogeneous combustion and homogeneous combustion.

Further, when a gasoline engine is employed as the internal combustion engine, it is effective to adopt a direct injection type due to the characteristics of the fuel injection valve capable of obtaining uniform fuel distribution and spray penetration.
Further, the pressure of the fuel supplied to the fuel injection valve is changed according to the operating state, and an injection mode mainly for ensuring penetration force and an injection mode mainly for widening the spread angle are, for example, combustion modes You may make it switch corresponding to.

Configuration of internal combustion engine according to first embodiment of the present invention Configuration of nozzle portion of fuel injection valve according to same embodiment as above Spray formation process by fuel injection valve according to the embodiment Configuration of nozzle portion of fuel injection valve according to second embodiment of present invention Setting of hole diameter and interval of fuel injection valve Spray interference between adjacent nozzle holes Spray formed by the fuel injection valve according to the second embodiment Configuration of nozzle portion of fuel injection valve according to third embodiment of the present invention Configuration of nozzle portion of fuel injection valve according to fourth embodiment of present invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 101 ... Fuel injection valve, 102 ... Combustion chamber, 103 ... Piston, 104 ... Intake port, 105 ... Intake valve, 106 ... Exhaust port, 107 ... Exhaust valve, 151 ... Needle valve, 152 ... Fuel injection valve , ... engine control unit, 251 ... accelerator sensor, 252 ... crank angle sensor, H ... cylinder head, B ... cylinder block, L ... reference line, S1, S2 ... spray, F ... air Flow, g ... nozzle hole group, m ... cylinder central axis, n ... needle valve central axis.

Claims (7)

A fuel injection valve in which fuel is injected from a plurality of injection holes arranged in a circumferential direction around a needle valve,
As a reference line indicating a direction in which a penetrating force is given to the spray, the first and second reference lines are set by shifting in the circumferential direction around the needle valve,
With respect to the first reference line, a first nozzle hole group including a plurality of nozzle holes formed at positions other than on the first reference line is provided,
With respect to the second reference line, a second nozzle hole group comprising a plurality of nozzle holes formed at positions other than on the second reference line is provided,
Each nozzle hole of the first nozzle hole group forms an acute angle with respect to the first reference line, and forms an opening end aligned in the circumferential direction around the first reference line,
Each of the nozzle holes of the second nozzle hole group has an acute angle with respect to the second reference line and a fuel injection valve that forms an opening end aligned in the circumferential direction centering on the second reference line.   2. The fuel injection valve according to claim 1, wherein in the first and second nozzle hole groups, an angle formed by the nozzle hole with respect to each reference line is 20 to 45 °.   The fuel injection valve according to claim 1 or 2, wherein in the first and second nozzle hole groups, a hole diameter of the nozzle hole is 0.1 mm or less.   In the first and second nozzle hole groups, the hole diameter of the nozzle hole forming each nozzle hole group is smaller as the nozzle hole is closer to a line connecting two points on the reference line of both nozzle hole groups. 4. The fuel injection valve according to any one of 3.   In the first and second nozzle hole groups, the distance between adjacent nozzle holes forming each nozzle hole group is closer to a line connecting two points on the reference line of both nozzle hole groups. The fuel injection valve according to any one of claims 1 to 4, wherein the fuel injection valve is small.   The fuel injection valve according to any one of claims 1 to 5, wherein a phase of a circumferential nozzle hole centered on the first or second reference line is set to be shifted for each nozzle hole group.   The fuel injection valve according to any one of claims 1 to 5, wherein the first and second reference lines are set to be shifted in a direction of a central axis of the needle valve.

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