JP2017025926A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve which enables sprays injected from respective injection holes to have similar characteristics, even though inner diameters of the plurality of injection holes formed on a fuel injection valve are different from each other.SOLUTION: A fuel injection valve 10 has an inlet-side opening 156 on the same virtual circle around a central axis 18 of a nozzle body, and is provided with a first injection hole 155a and a second injection hole 155b which have reference inner diameters Dn1, Dn2 different from each other, as a plurality of injection holes 155. In this configuration, a L/D value of the first injection hole 155a obtained by dividing a flow channel length Ln1 of the first injection hole 155a by the reference inner diameter Dn1 of the first injection hole 155a agrees with a L/D value obtained by dividing a flow channel length Ln2 of the second injection hole 155b by the reference inner diameter Dn2 of the second injection hole 155b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel injection valve that injects fuel into a combustion chamber provided in an internal combustion engine.

  Conventionally, for example, in a fuel injection valve as disclosed in Patent Documents 1 and 2, a plurality of injection holes for injecting fuel into a combustion chamber are formed. In particular, in the fuel injection valve of Patent Document 2, the inner diameter of one nozzle hole is different from the inner diameters of the other nozzle holes among the plurality of nozzle holes formed. Thus, according to the structure which makes the internal diameter of a some injection hole mutually differ, the shape of the spray injected from a fuel injection valve becomes easy to adapt to the shape of the fuel chamber of an internal combustion engine.

Japanese Patent No. 5033335 JP 2008-202483 A

  However, when the inner diameter of one injection hole is different from the inner diameter of another injection hole as in the fuel injection valve disclosed in Patent Document 2, the characteristics of the spray injected from each injection hole may be different from each other. For this reason, a situation may occur in which the particle diameters of the fuels injected from the respective nozzle holes are different from each other, or the modes of spread of the sprays injected from the respective nozzle holes (hereinafter referred to as “spray change rates”) are different from each other.

  The present invention has been made in view of such problems, and an object thereof is to spray sprayed from each nozzle hole even if the inner diameters of the plurality of nozzle holes formed in the fuel injection valve are different from each other. It is an object of the present invention to provide a fuel injection valve capable of approximating these characteristics.

  To achieve the above object, a first invention is a fuel injection valve for injecting fuel from a plurality of injection holes (155) formed in a nozzle body toward a combustion chamber provided in an internal combustion engine, The plurality of nozzle holes have an inlet side opening (156) positioned on the same virtual circle (19) around the central axis (18) of the nozzle body, and have a reference inner diameter (Dn1, Dn2, Dn201, Dn202) includes different first nozzle holes (155a, 255a) and second nozzle holes (155b, 255b), and the first nozzle holes and the second nozzle holes are cylindrical hole shapes that extend while maintaining their respective reference inner diameters. The value obtained by dividing the channel length (Ln1, Ln201) of the first nozzle hole by the reference inner diameter (Dn1, Dn201) of the first nozzle hole is the channel length (Ln2, Ln202) of the second nozzle hole. Is the reference inner diameter of the second nozzle hole (Dn2, D It is characterized in that aligned to a value obtained by dividing by 202).

  A second invention is a fuel injection valve that injects fuel from a plurality of injection holes formed in a nozzle body into a combustion chamber provided in an internal combustion engine, wherein the plurality of injection holes are formed at the center of the nozzle body. An inlet side opening (356) is positioned on the same virtual circle (19) around the axis (18), and the first nozzle hole (355a) and the first nozzle holes having different reference inner diameters (Dn301, Dn302) are used. The first nozzle hole and the second nozzle hole have a tapered hole shape that expands from each reference inner diameter toward the fuel downstream side from the fuel upstream side, and includes two nozzle holes (355b). The value obtained by dividing the length (Ln301) by the reference inner diameter (Dn301) of the first injection hole and the value obtained by dividing the flow path length (Ln302) of the second injection hole by the reference inner diameter (Dn302) of the second injection hole are It is characterized by being aligned .

  The inventor of the present application has found that the atomization characteristics of the spray in the fuel injection valve are related to the ratio of the flow path length of the injection hole and the reference inner diameter. Therefore, in the first and second inventions, the values obtained by dividing the flow path length by the reference inner diameter are aligned with each other in the first nozzle hole and the second nozzle hole. Therefore, even if the reference inner diameters of these nozzle holes are different from each other, the atomization characteristics of the first nozzle hole and the second nozzle hole can be approximated to each other. According to the above, the fuel injection valve can reduce the variation in the particle diameter of the spray injected from each injection hole while forming the spray shape suitable for the fuel chamber of the internal combustion engine.

  Note that the reference numbers in the parentheses are merely examples of correspondences with specific configurations in the embodiments to be described later in order to facilitate understanding of the present invention, and limit the scope of the present invention. It is not a thing.

It is sectional drawing which shows the fuel injection valve by 1st embodiment of this invention. It is sectional drawing which expands and shows the vicinity of a sack part. It is the III-III sectional view taken on the line of FIG. It is sectional drawing which expands and shows the vicinity of a 1st nozzle hole further. It is sectional drawing which expands and shows the vicinity of a 2nd nozzle hole further. It is a figure which shows the change of the characteristic of the spray accompanying the increase / decrease in L / D value in a cylindrical hole-shaped nozzle hole. It is sectional drawing which expands and shows the vicinity of the sack part of 2nd embodiment. It is sectional drawing which expands and shows the vicinity of a 1st nozzle hole further. It is sectional drawing which expands and shows the vicinity of a 2nd nozzle hole further. It is sectional drawing which expands and shows the vicinity of the 1st nozzle hole of 3rd embodiment. It is sectional drawing which expands and shows the vicinity of a 2nd nozzle hole. It is a figure which shows the change of the characteristic of the spray accompanying the increase / decrease in L / D value in the nozzle hole of a taper hole shape.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. Moreover, not only the combination of the configurations explicitly described in the description of each embodiment, but also the configuration of a plurality of embodiments can be partially combined even if they are not explicitly described, as long as there is no problem in the combination. And the combination where the structure described in several embodiment and the modification is not specified shall also be disclosed by the following description.

(First embodiment)
A fuel injection valve 10 according to the first embodiment of the present invention shown in FIG. 1 is installed in a gasoline engine as an internal combustion engine, and injects fuel into a combustion chamber (not shown) provided in the gasoline engine. In addition to this application form, for example, the fuel injection valve 10 may inject fuel into an intake passage communicating with a combustion chamber of a gasoline engine, or fuel into a combustion chamber of a diesel engine as an internal combustion engine. May be used.

  The fuel injection valve 10 includes a valve body 11, a fixed core 20, a movable core 30, a valve member 40, an elastic member 50, and a drive unit 60.

  The valve body 11 includes a core housing 12, an inlet member 13, a nozzle holder 14, a nozzle body 15, and the like. The core housing 12 is formed in a cylindrical shape, and includes a first magnetic portion 12a, a nonmagnetic portion 12b, and a second magnetic portion 12c in order from one end side in the axial direction toward the other end side. The magnetic portions 12a and 12c made of a magnetic material and the nonmagnetic portion 12b made of a nonmagnetic material are coupled by laser welding or the like. With such a coupling structure, the nonmagnetic portion 12b prevents the magnetic flux from being short-circuited between the first magnetic portion 12a and the second magnetic portion 12c.

  A cylindrical inlet member 13 is fixed to the axial end of the second magnetic portion 12c opposite to the nonmagnetic portion 12b. The inlet member 13 forms a fuel inlet 13a to which fuel is supplied from a fuel pump (not shown). In order to filter the fuel supplied to the fuel inlet 13 a and guide it into the core housing 12 on the downstream side, in the first embodiment, a fuel filter 16 is fixed to the inner peripheral side of the inlet member 13.

  A nozzle body 15 is fixed to an axial end of the first magnetic portion 12a opposite to the nonmagnetic portion 12b via a nozzle holder 14 formed in a cylindrical shape by a magnetic material. The nozzle body 15 is formed in a bottomed cylindrical shape, and a fuel passage 17 is formed on the inner peripheral side in cooperation with the core housing 12 and the nozzle holder 14. As shown in FIG. 2, the nozzle body 15 has a valve seat portion 150 and a sack portion 152.

  The valve seat portion 150 forms a valve seat surface 151 by an inner peripheral surface of a tapered surface that is reduced in diameter by a constant diameter reduction rate toward the fuel downstream side in the axial direction. The sack portion 152 is adjacent to the fuel downstream side of the valve seat portion 150 that forms the fuel passage 17 by the valve seat surface 151. The sack portion 152 has a cup-shaped recess 153 that opens toward the fuel passage 17 on the upstream side of the fuel. A nozzle hole 155 communicating with the sac chamber 154 is formed on the inner surface of the recess 153 forming the sac chamber 154. As shown in FIGS. 2 and 3, a plurality of nozzle holes 155 of the first embodiment are provided around the central axis 18 of the nozzle body 15 at intervals. Each inlet-side opening 156 of each nozzle hole 155 is located on the same virtual circle 19 around the central axis 18. Each nozzle hole 155 is inclined toward the outer peripheral side of the recess 153 toward the respective outlet side openings 157 on the fuel downstream side.

  As shown in FIG. 1, the fixed core 20 is formed in a cylindrical shape by a magnetic material, and is coaxially fixed to the inner peripheral surfaces of the nonmagnetic portion 12 b and the second magnetic portion 12 c in the core housing 12. The fixed core 20 is provided with a through hole 20a that penetrates the central portion in the radial direction in the axial direction. The fuel that flows into the through hole 20a from the fuel inlet 13a through the fuel filter 16 flows out of the through hole 20a toward the movable core 30 that is the downstream side.

  The movable core 30 is formed of a magnetic material in a stepped cylindrical shape, is coaxially disposed on the inner peripheral side of the core housing 12, and faces the fixed core 20 on the upstream side of the fuel in the axial direction. The movable core 30 is guided by the inner peripheral wall of the nonmagnetic portion 12b of the core housing 12, so that the movable core 30 can be accurately reciprocated on both sides in the axial direction. The movable core 30 has a first through hole 30a that penetrates the radial center portion in the axial direction and a second through hole 30b that penetrates the axial middle portion in the radial direction and communicates with the first through hole 30a. , Provided. The fuel flowing out from the through hole 20a of the fixed core 20 flows into the first through hole 30a of the movable core 30 on the downstream side, and flows out from the second through hole 30b to the fuel passage 17 in the core housing 12. Become.

  The valve member 40 is formed in a needle shape having a circular cross section by a non-magnetic material, and is coaxially disposed in the fuel passage 17 formed in the valve body 11 on the inner peripheral side by the elements 12, 14, 15. ing. The axial end of the upstream side of the fuel in the valve member 40 is coaxially fixed to the inner peripheral surface of the first through hole 30 a of the movable core 30. As shown in FIGS. 1 and 2, the axial end portion on the downstream side of the fuel in the valve member 40 forms a contact portion 41 whose diameter decreases toward the downstream side of the fuel in the axial direction. The abutting portion 41 is opposed to 151 so as to be abuttable. The valve member 40 causes the contact portion 41 to be separated from and seated on the valve seat surface 151 by displacement along a predetermined central axis 18. Thus, the fuel injection from the nozzle hole 155 is interrupted. Specifically, when the valve member 40 is opened so that the contact portion 41 is separated from the valve seat surface 151, fuel flows from the fuel passage 17 into the sac chamber 154 and is injected from each nozzle hole 155 into the combustion chamber. The On the other hand, when the valve member 40 is closed so that the contact portion 41 is seated on the valve seat surface 151, the fuel injection from each nozzle hole 155 to the combustion chamber is blocked.

  As shown in FIG. 1, the elastic member 50 is made of a metal compression coil spring, and is accommodated coaxially on the inner peripheral side of the through hole 20 a provided in the fixed core 20. One end of the elastic member 50 is locked to the axial end of the adjusting pipe 22 fixed to the inner peripheral surface of the through hole 20a. The other end of the elastic member 50 is locked to the inner surface of the first through hole 30 a of the movable core 30. With this locking structure, the elastic member 50 is elastically deformed by being compressed between the elements 22 and 30 sandwiching the elastic member 50. Therefore, the restoring force generated by the elastic deformation of the elastic member 50 becomes an urging force for urging the movable core 30 together with the valve member 40 toward the fuel downstream side.

  The drive unit 60 includes a coil 61, a resin bobbin 62, a magnetic yoke 63, a connector 64, and the like. The coil 61 is formed by winding a metal wire around a resin bobbin 62, and a magnetic yoke 63 is disposed on the outer peripheral side thereof. The coil 61 is coaxially fixed to the outer peripheral surfaces of the nonmagnetic portion 12 b and the second magnetic portion 12 c on the outer peripheral side of the fixed core 20 in the core housing 12 via a resin bobbin 62. The coil 61 is electrically connected to an external control circuit (not shown) via a terminal 64a provided on the connector 64, and energization is controlled by the control circuit.

  Here, when the coil 61 is excited by energization, the magnetic yoke 63, the nozzle holder 14, the first magnetic part 12a, the movable core 30, the fixed core 20, and the second magnetic part 12c form a magnetic circuit together. Flows. As a result, a magnetic attractive force that attracts the movable core 30 toward the fixed core 20 on the upstream side of the fuel is generated between the movable core 30 and the fixed core 20. On the other hand, when the coil 61 is demagnetized by stopping energization, the magnetic flux does not flow in the above-described magnetic circuit, so that the magnetic attractive force disappears between the movable core 30 and the fixed core 20.

  In the valve opening operation of the fuel injection valve 10 configured as described above, the magnetic attractive force acts on the movable core 30 by starting energization of the coil 61. Then, the movable core 30 together with the valve member 40 moves to the fixed core 20 side against the restoring force of the elastic member 50, and comes into contact with the fixed core 20 and stops. As a result, since the contact portion 41 is separated from the valve seat surface 151, fuel is injected from each nozzle hole 155.

  In the valve closing operation of the fuel injection valve 10 after such valve opening operation, the magnetic attraction force acting on the movable core 30 disappears by stopping the energization of the coil 61. Then, the movable core 30 together with the valve member 40 moves to the urging side by the restoring force of the elastic member 50, thereby bringing the valve member 40 into contact with the valve seat surface 151 and stopping. As a result, since the contact portion 41 is seated on the valve seat surface 151, fuel injection from each nozzle hole 155 is stopped.

  Next, the configuration near the recess 153 shown in FIGS. 2 and 3 will be described in detail. The bottom wall 160 of the recess 153 is formed to face the valve member 40 having the contact portion 41 seated on the valve seat surface 151 with a distance. With such a facing structure, a sac chamber 154 communicating with each nozzle hole 155 is formed between the tip surface 42 of the valve member 40 and the bottom wall 160 when the contact portion 41 is seated on the valve seat surface 151. . The volume of the sac chamber 154 is regulated so as to suppress the entry of foreign matter (contamination) in the fuel.

  A central surface portion 161 and a tapered surface portion 162 are formed on the bottom surface of the bottom wall 160. Further, a connection surface 168 is formed on the outer peripheral side of the bottom surface. The central surface portion 161 is a flat surface formed in a perfect circle shape, and is positioned coaxially with the central axis 18. The taper surface portion 162 is formed in a tapered surface shape whose diameter is reduced at a constant diameter reduction rate toward the center surface portion 161 on the fuel downstream side in the axial direction. The connection surface 168 is formed in a concave curved surface shape whose diameter reduction rate increases toward the downstream side of the fuel, and connects the outer peripheral side of the tapered surface portion 162 and the inner peripheral side of the valve seat surface 151.

  A plurality of nozzle holes 155 including a first nozzle hole 155a and a second nozzle hole 155b are formed in the bottom wall 160 described above. Both the first nozzle hole 155a and the second nozzle hole 155b are formed in a cylindrical hole shape. The first injection hole 155a and the second injection hole 155b extend in the bottom wall 160 in a posture in which the respective central axes (hereinafter referred to as “injection hole axis”) intersect the tapered surface portion 162. Each nozzle hole axis 159a, 159b obliquely intersects the tapered surface portion 162, and is inclined toward the outer peripheral side of the nozzle body 15 from the inlet side opening 156 toward the outlet side opening 157. Here, the inner diameter maintained substantially constant in the first nozzle hole 155a shown in FIG. 4 is defined as a reference inner diameter Dn1. Similarly, the inner diameter maintained substantially constant in the second nozzle hole 155b shown in FIG. 5 is defined as a reference inner diameter Dn2. As shown in FIGS. 4 and 5, the reference inner diameter Dn1 of the first injection hole 155a is larger than the reference inner diameter Dn2 of the second injection hole 155b.

  Furthermore, the channel length of the first nozzle hole 155a is Ln1, and the channel length of the second nozzle hole 155b is Ln2. In the first embodiment, the flow path length Ln1 of the first injection hole 155a is longer than the flow path length Ln2 of the second injection hole 155b. With this configuration, the value obtained by dividing the flow path length Ln1 in the first nozzle hole 155a by the reference inner diameter Dn1 (hereinafter referred to as “L / D value”) is the flow path length Ln2 in the second nozzle hole 155b. It is aligned with the L / D value divided by Dn2.

  In order to realize the shapes of the first injection hole 155a and the second injection hole 155b, the first wall 164 and the second diameter expansion are formed in the bottom wall 160 so as to be continuous with the holes 155a and 155b. A hole 165 is formed. The first enlarged hole 164 and the second enlarged hole 165 shown in FIGS. 2, 4, and 5 are counterbore holes formed from the outer surface side of the bottom wall 160 toward the suck chamber 154.

  4 is formed in the shape of a cylindrical hole extending along the nozzle hole axis 159a, and is located coaxially with the first nozzle hole 155a. With such a shape and arrangement, the first enlarged diameter hole 164 provided on the fuel downstream side of the first injection hole 155 a allows the first injection hole 155 a to communicate with the outside of the nozzle body 15. The inner diameter De1 of the first enlarged hole 164 is larger than the reference inner diameter Dn1 of the first nozzle hole 155a so that the channel area of the enlarged hole 164 is larger than the channel area of the first nozzle hole 155a. It is prescribed. The flow path length Le1 of the first enlarged diameter hole 164 is the difference between the wall thickness of the bottom wall 160 along the injection hole axis 159a of the first injection hole 155a and the flow path length Ln1 of the first injection hole 155a. To compensate for the difference between the flow path length Ln1 and the wall thickness.

  5 is formed in the shape of a cylindrical hole extending along the nozzle hole axis 159b, and is positioned coaxially with the second nozzle hole 155b. The second diameter expansion hole 165 provided on the fuel downstream side of the second injection hole 155b by this shape and arrangement communicates the second injection hole 155b to the outside of the nozzle body 15. The inner diameter De2 of the second enlarged diameter hole 165 is larger than the reference inner diameter Dn2 of the second injection hole 155b so that the flow area of the enlarged diameter hole 165 is larger than the flow area of the second injection hole 155b. It is prescribed. The flow path length Le2 of the second enlarged diameter hole 165 is the difference between the wall thickness of the bottom wall 160 along the injection hole axis 159b of the second injection hole 155b and the flow path length Ln2 of the second injection hole 155b. To compensate for the difference between the flow path length Ln2 and the wall thickness of the bottom wall 160.

  Next, each L / D value of the first nozzle hole 155a and the second nozzle hole 155b will be described in detail with reference to FIG. In FIG. 6, a pair of broken lines arranged with a solid line in between indicate the upper and lower limits of variation.

  As shown in FIG. 6A, the atomization characteristics of the spray in the fuel injection valve 10 are related to the ratio of the flow path length of the injection hole and the reference inner diameter. Specifically, as the L / D value at the nozzle hole decreases, the particle size of the spray also decreases. Therefore, each L / D value of each nozzle hole 155a, 155b in the first embodiment is defined such that the upper limit of the particle size causing the variation does not exceed a predetermined value.

  In addition, as shown in FIG. 6B, the L / D value is related to the contraction rate of the spray injected from the injection hole. The shrinkage rate of the spray indicates that the smaller the numerical value, the more difficult the spray shrinks and diffuses. The larger the L / D value, the longer the flow path length of the nozzle hole, so that the fuel is rectified. Therefore, the spray sprayed becomes easy to fly along the nozzle hole axis. For these reasons, the shrinkage rate of the spray increases as the L / D value increases. However, the shrinkage rate of the spray becomes almost constant when the L / D value exceeds a specific value. Each L / D value of each nozzle hole 155a, 155b in the first embodiment is defined to be 1.45 or more at which the increase in the spray shrinkage rate is saturated.

  Further, as shown in FIG. 6C, the L / D value is related to the length of the spray injected from the injection hole. As described above, the fuel flowing through the nozzle hole is rectified as the L / D value increases. Therefore, the length of the spray sprayed becomes longer as the L / D value increases. Therefore, each L / D value of each nozzle hole 155a, 155b of the first embodiment is defined to be 1.85 or less so that the spray length does not exceed a predetermined value. Here, the predetermined value that defines the upper limit of the spray length is set such that the tip of the spray does not reach the cylinder wall surface and the piston top surface that define the combustion chamber.

  In the first embodiment described so far, each L / D value of the first nozzle hole 155a and the second nozzle hole 155b is an intermediate value between the two boundary values (1.45, 1.85) described above. It is about 1.65. Therefore, even if the reference inner diameters Dn1 and Dn2 are different from each other, the atomization characteristics of the first injection hole 155a and the second injection hole 155b can be approximated to each other. Therefore, the fuel injection valve 10 can reduce the variation in the particle diameter of the spray injected from the injection holes 155a and 155b, while forming a spray shape suitable for the fuel chamber of the internal combustion engine to which the fuel injection valve 10 is attached.

  In addition, in the first embodiment, since the L / D values of the first injection hole 155a and the second injection hole 155b both exceed 1.45, sufficient rectification is performed for the fuel flowing through the injection holes 155a and 155b. An effect can be produced. Therefore, the spray injected from each nozzle hole 155a, 155b will fly stably in the direction toward each nozzle hole axis 159a, 159b. According to the above, the rate of change of the spray injected from each nozzle hole 155a, 155b is close to each other and becomes a stable value. Therefore, the fuel injection valve 10 can stably form a spray having a shape suitable for the fuel chamber of the internal combustion engine.

  Further, according to the first embodiment, since the L / D values of the first injection hole 155a and the second injection hole 155b are both 1.85 or less, the fuel flowing through the injection holes 155a and 155b is excessively rectified. This situation can be avoided. Therefore, the length of the spray injected from each nozzle hole 155a, 155b can be suppressed so as not to adhere to the cylinder wall surface and the piston top surface. Therefore, the fuel injection valve 10 can form a spray having a more optimal shape in the fuel chamber of the internal combustion engine to which it is attached.

  Furthermore, in the first embodiment, the difference between the flow path lengths Ln1 and Ln2 and the wall thickness of the bottom wall 160 is complemented by the respective enlarged diameter holes 164 and 165. Therefore, even if the wall thickness of the bottom wall 160 is constant, each flow path length Ln1, Ln2 can be defined so that each L / D value in each nozzle hole 155a, 155b is optimized. As described above, the configuration in which the respective diameter-enlarged holes 164 and 165 are provided to adjust the flow path lengths Ln1 and Ln2 is particularly suitable for the fuel injection valve 10 that optimizes the L / D values of the respective nozzle holes 155a and 155b. It is suitable.

  In addition, in the first embodiment, since each of the enlarged diameter holes 164 and 165 is formed on the fuel downstream side of each of the injection holes 155a and 155b, the flow of the fuel to flow into each of the injection holes 155a and 155b is expanded. The situation of being disturbed in the diameter holes 164 and 165 can be avoided. According to the above, the fuel in the sac chamber 154 can smoothly flow into the nozzle holes 155a and 155b, so that the shape of the spray injected from these nozzle holes 155a and 155b can be further stabilized. .

  In addition, in the first embodiment, since each of the enlarged diameter holes 164 and 165 is arranged coaxially with each of the injection holes 155a and 155b, the spray injected from each of the injection holes 155a and 155b It can scatter without hitting the inner peripheral wall surface of 164,165. Therefore, a situation in which the shape of the spray is disturbed due to the formation of the respective enlarged diameter holes 164 and 165 is avoided.

  In the first embodiment, the bottom wall 160 corresponds to an “injection hole wall” recited in the claims.

(Second embodiment)
The second embodiment of the present invention shown in FIGS. 7 to 9 is a modification of the first embodiment. In the bottom wall 260 of the nozzle body 215 according to the second embodiment, a first injection hole 255a and a second injection hole 255b corresponding to the injection holes 155a and 155b (see FIG. 2) of the first embodiment are formed. Yes. In the following description, in the bottom wall 260, a region that penetrates the first injection hole 255a is referred to as a first region 260a, and a region that penetrates the second injection hole 255b is referred to as a second region 260b. Also in the second embodiment, the L / D value (= Ln201 / Dn201) of the first nozzle hole 255a and the L / D value (= Ln202 / Dn202) of the second nozzle hole 255b are aligned with each other. For example, it is set to about 1.65 as in the embodiment.

  On the other hand, configurations corresponding to the first diameter expansion hole 164 and the second diameter expansion hole 165 (see FIG. 2) of the first embodiment are omitted from the bottom wall 260. In the second embodiment, in order to realize the flow path lengths Ln201 and Ln202 of the first injection hole 255a and the second injection hole 255b, the wall thicknesses of the first area 260a and the second area 260b are respectively set to the flow paths. It is defined to correspond to the lengths Ln201 and Ln202. As described above, the wall thicknesses t1 and t2 of the first region 260a and the second region 260b which are different from each other are adjusted by scraping the outer surface of the nozzle body 215 formed to have a substantially constant wall thickness. Specifically, as shown in FIGS. 8 and 9, the thickness at which the nozzle body 215 is cut to form the second region 260b, rather than the thickness tc1 at which the nozzle body 215 is cut to form the first region 260a. tc2 is increased. Through such a cutting process, the nozzle holes 255a and 255b having different flow path lengths Ln201 and Ln202 are realized. The wall thicknesses t1 and t2 and the cutting thicknesses tc1 and tc2 are defined along the nozzle hole axes 259a and 259b.

  Even in the second embodiment described so far, the same effects as in the first embodiment can be obtained by aligning the L / D values of the first injection hole 255a and the second injection hole 255b within a predetermined range. It becomes. Therefore, even if the reference inner diameters Dn201 and Dn202 of the respective nozzle holes 255a and 255b are different from each other, it is possible to approximate the characteristics of the sprays ejected therefrom.

  In addition, the flow path lengths Ln201 and Ln202 are made different by making the wall thicknesses t1 and t2 of the first region 260a and the second region 260b penetrating the nozzle holes 255a and 255b as in the second embodiment. The difference may be realized. With such a configuration, the feasibility of a configuration in which each L / D value is optimized further improves. In the second embodiment, the bottom wall 260 corresponds to an “injection hole wall” recited in the claims.

(Third embodiment)
The third embodiment of the present invention shown in FIGS. 10 and 11 is another modification of the first embodiment. In the bottom wall 360 of the third embodiment, a through hole made up of the first injection hole 355a and the first enlarged diameter hole 364 and a through hole made up of the second injection hole 355b and the second enlarged diameter hole 365 are formed. Yes. The first injection hole 355a and the second injection hole 355b are tapered hole shapes that expand from the respective reference inner diameters Dn301 and Dn302 from the inlet side opening 356 on the fuel upstream side toward the outlet side opening 357 on the fuel downstream side. Is formed. Also in the third embodiment, the L / D value (= Ln301 / Dn301) of the first injection hole 355a and the L / D value (= Ln302 / Dn302) of the second injection hole 355b are aligned with each other.

  On the other hand, the first diameter expansion hole 364 and the second diameter expansion hole 365 correspond to the diameter expansion holes 164 and 165 (see FIG. 4) of the first embodiment, and the injection hole axis lines 359a of the injection holes 355a and 355b. , 359b are arranged coaxially. The inner diameters De301 and De302 of the respective enlarged diameter holes 364 and 365 are larger than the respective reference inner diameters Dn301 and Dn302 of the respective injection holes 355a and 355b. The flow path length Le301 of the first diameter expansion hole 364 complements the difference between the flow path length Ln301 of the first injection hole 355a and the wall thickness of the bottom wall 360. Similarly, the channel length Le302 of the second enlarged diameter hole 365 complements the difference between the channel length Ln302 of the second nozzle hole 355b and the wall thickness of the bottom wall 360.

  Next, the L / D value in the tapered hole like the nozzle holes 355a and 355b of the third embodiment will be described in detail below with reference to FIG.

  As shown in FIG. 12A, the atomization characteristics of the spray are related to the L / D value even if the nozzle hole has a tapered hole shape. The particle diameter of the spray in the tapered hole shape temporarily decreases as the L / D value decreases. However, when the L / D value becomes smaller than a specific inflection point (L / D value = about 2.5), the spray particle size gradually increases. This is presumably because the spray region formed into a liquid film is difficult to be formed because the flow path length is short. More specifically, in order to atomize the fuel, it is necessary to form a region in which the fuel is formed into a liquid film in the outer peripheral portion of the spray. However, when the flow path length is shortened, the fuel flow becomes difficult along the inner peripheral wall surface of the nozzle hole whose inner diameter changes. For this reason, it becomes difficult to form a spray region formed into a liquid film, and the particle size of the spray becomes large. The range of each L / D value of each nozzle hole 355a, 355b in the third embodiment is defined so as to sandwich the above-mentioned L / D value indicating the minimum value.

  As shown in FIG. 12B, even if the injection hole has a tapered hole shape, the L / D value is related to the contraction rate of the spray injected from the injection hole. As in the first embodiment, the shrinkage rate of the spray in the tapered hole shape becomes substantially constant when the L / D value exceeds a specific value. Each L / D value of each nozzle hole 355a, 355b in the third embodiment is defined to be 2.0 or more at which the increase in the spray shrinkage rate is saturated.

  As shown in FIG. 12C, the rate of change of the spray length with respect to the L / D value when the nozzle hole has a tapered hole shape is smaller than that when the nozzle hole has a cylindrical hole shape. . Therefore, even if the L / D value is increased, the spray length does not easily exceed a predetermined value that defines the upper limit of the spray length. Therefore, each L / D value of each nozzle hole 355a, 355b of the third embodiment is, for example, 3.0 so that the minimum value shown in FIG. 12 (A) is sandwiched in the center together with the lower limit value shown in FIG. 12 (B). Stipulated in

  In the third embodiment described so far, each L / D value of the first nozzle hole 355a and the second nozzle hole 355b is an intermediate value between the two boundary values (2.0, 3.0) described above. Thus, the particle size of the spray is the smallest, for example, about 2.5. Thus, by aligning the L / D values of the first injection hole 355a and the second injection hole 355b within a predetermined range, the same effect as in the first embodiment can be obtained. Therefore, even if the reference inner diameters Dn301 and Dn302 of the nozzle holes 355a and 355b are different from each other, it is possible to approximate the characteristics of the sprays ejected from them. In the third embodiment, the bottom wall 360 corresponds to an “injection hole wall” recited in the claims.

(Other embodiments)
Although a plurality of embodiments according to the present invention have been described above, the present invention is not construed as being limited to the above embodiments, and can be applied to various embodiments and combinations without departing from the gist of the present invention. can do.

  In the above embodiment, the L / D values of the two nozzle holes having different reference inner diameters are aligned. However, three or more nozzle holes with different reference inner diameters may have the same L / D value. In addition, the L / D values of the nozzle holes do not have to be exactly the same, and need only be aligned with each other to the extent that the spray characteristics can be approximated. Further, although it is desirable that the L / D values of all the nozzle holes formed in the nozzle body are uniform, the L / D values of some of the nozzle holes are not consistent with the L / D values of the other nozzle holes. May be.

  In the said embodiment, each L / D value was prescribed | regulated within the range of the upper limit and lower limit prescribed | regulated based on the shape of the nozzle hole. However, each L / D value of each nozzle hole may be aligned with each other outside the range of the upper limit value and the lower limit value. Further, each L / D value of each nozzle hole may be defined as a different value within the range of the upper limit value and the lower limit value.

  In the above embodiment, the plurality of nozzle holes are arranged along the same virtual circle 19 (see FIG. 3). However, the positions where the inlet openings of the plurality of nozzle holes are provided depend on the required spray shape. May be changed as appropriate. For example, a small-diameter second nozzle hole may be arranged on the inner peripheral side of the large-diameter first nozzle hole. Alternatively, the first nozzle holes and the second nozzle holes may be alternately arranged in the circumferential direction. In addition, the shape of each nozzle hole may be changed as appropriate as long as the shapes are similar to each other. For example, in the tapered hole-shaped nozzle hole as in the third embodiment, the taper angle of the inner wall surface may be changed as appropriate. Specifically, the nozzle hole may be formed in a tapered hole shape whose diameter decreases from the inlet side opening toward the outlet side opening. In addition, the shape of the cross section of each nozzle hole may not be a perfect circle, but may be an ellipse or the like.

  In the first and third embodiments, the axial direction of the enlarged diameter hole is directed in the same direction as the nozzle hole axis. However, the axial direction of the diameter expansion hole may intersect the nozzle hole axis. Further, the center of the diameter-expanded hole may be positioned so as to be shifted from the nozzle hole axis. Furthermore, the diameter expansion hole is not limited to the cylindrical hole shape as described above, and is a tapered hole shape whose diameter is increased toward the fuel downstream side, or a hemispherical shape in which the outer surface of the nozzle body is recessed. Also good. Moreover, the diameter expansion hole may be provided in a form communicating with the sac chamber not on the fuel downstream side of the nozzle hole but on the fuel upstream side of the nozzle hole.

  In the second embodiment, the nozzle holes having different channel lengths are realized by changing the cutting thickness for cutting the outer surface of the nozzle body for each region. With such a configuration, a radial step surface is not formed between the nozzle hole and the enlarged hole. Therefore, a situation in which deposits accumulate on the outer peripheral portion of the step surface can be avoided. Thus, the method of providing a difference between the wall thickness of the first region and the wall thickness of the second region in the nozzle body is not limited to the above-described cutting. For example, a difference in wall thickness between the first region and the second region may already be provided when the nozzle body is molded. Furthermore, if the wall thickness before cutting in the first region already corresponds to the flow path length of the first nozzle hole, only the second region of the first region and the second region may be formed by cutting. Good.

10 fuel injection valve, 155 injection hole, 155a, 255a, 355a first injection hole, 155b, 255b, 355b second injection hole, 160, 260, 360 bottom wall (injection hole wall), 164, 364 first expansion hole 165, 365 Second diameter expansion hole, 260a First region, 260b Second region, Dn1, Dn2, Dn201, Dn202, Dn301, Dn302 Reference inner diameter of injection hole, Ln1, Ln2, Ln201, Ln202, Ln301, Ln302 injection hole Channel length, Le1, Le2, Le301, Le302 channel length of the expanded hole

Claims (6)

A fuel injection valve that injects fuel from a plurality of nozzle holes (155) formed in a nozzle body into a combustion chamber provided in an internal combustion engine,
The plurality of nozzle holes have an inlet-side opening (156) positioned on the same virtual circle (19) around the central axis (18) of the nozzle body, and have a reference inner diameter (Dn1, Dn2, Dn1, Dn2, Dn201, Dn202) includes different first nozzle holes (155a, 255a) and second nozzle holes (155b, 255b),
The first nozzle hole and the second nozzle hole have a cylindrical hole shape that extends while maintaining the reference inner diameter,
The value obtained by dividing the channel length (Ln1, Ln201) of the first nozzle hole by the reference inner diameter (Dn1, Dn201) of the first nozzle hole is the channel length (Ln2, Ln202) of the second nozzle hole. The fuel injection valve is characterized in that the value is divided by a reference inner diameter (Dn2, Dn202) of the second injection hole. A fuel injection valve that injects fuel from a plurality of injection holes formed in a nozzle body toward a combustion chamber provided in an internal combustion engine,
The plurality of nozzle holes have an inlet side opening (356) located on the same virtual circle (19) around the central axis (18) of the nozzle body, and have a reference inner diameter (Dn301, Dn302) as a reference. Includes different first nozzle holes (355a) and second nozzle holes (355b),
The first nozzle hole and the second nozzle hole have a tapered hole shape that expands from each reference inner diameter toward the fuel downstream side from the fuel upstream side,
The value obtained by dividing the flow path length (Ln301) of the first nozzle hole by the reference inner diameter (Dn301) of the first nozzle hole, and the channel length (Ln302) of the second nozzle hole are set to the second nozzle hole. The fuel injection valve is characterized in that the values divided by the reference inner diameter (Dn302) are aligned. A fuel injection valve comprising a nozzle hole wall (160, 360) in which the plurality of nozzle holes are formed,
The nozzle hole wall is
The nozzle hole penetrates the nozzle hole wall while being continuous with the first nozzle hole, the channel area is larger than the first nozzle hole, and the channel length of the first nozzle hole and the wall thickness of the nozzle hole wall are A first diameter-enlarged hole (164, 364) that defines a flow path length (Le1, Le301) so as to compensate for the difference;
The nozzle hole passes through the nozzle hole wall while being continuous with the second nozzle hole, the channel area is made larger than the second nozzle hole, and the channel length of the second nozzle hole and the wall thickness of the nozzle hole wall are The fuel injection valve according to claim 1 or 2, characterized in that a second diameter expansion hole (165, 365) having a flow path length (Le2, Le302) defined so as to compensate for the difference is formed. . The first diameter expansion hole is formed on the fuel downstream side of the first nozzle hole,
The fuel injection valve according to claim 3, wherein the second enlarged diameter hole is formed on the fuel downstream side of the second injection hole. Both said 1st diameter expansion hole and said 2nd diameter expansion hole are cylindrical hole shapes,
The first diameter expansion hole is located coaxially with the first nozzle hole,
5. The fuel injection valve according to claim 3, wherein the second diameter expansion hole is located coaxially with the second injection hole. A fuel injection valve comprising a nozzle hole wall (260) having a first region (260a) that penetrates the first nozzle hole and a second region (260b) that penetrates the second nozzle hole,
The wall thickness (t1) of the first region and the wall thickness (t2) of the second region are the channel length (Ln201) of the first nozzle hole and the channel length (Ln202) of the second nozzle hole, respectively. 3. The fuel injection valve according to claim 1, wherein the fuel injection valves are different from each other.

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