JP2013108432A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve which can make a damper effect efficiently function by a simple structure.SOLUTION: In a needle 40 and a movable core 50, a first cylindrical clearance 101 is formed between a large diameter part 44 and a large diameter inner wall surface 51, a second cylindrical clearance 102 is formed between a small diameter part 43 and a small diameter inner wall surface 52, and a capacity-variable annular damper chamber 103 is formed between a needle step surface 45 and a core step surface 53. The needle 40 and the movable core 50 are formed so that an axial length L1 in the first clearance 101 is longer than an axial length L2 in the second clearance 102 when the capacity of the damper chamber 103 is minimum.

Description

  The present invention relates to a fuel injection valve that injects and supplies fuel to an internal combustion engine (hereinafter referred to as “engine”).

  Conventionally, a fuel injection valve having a configuration in which a movable core is provided so as to be movable relative to a needle is known. For example, in the fuel injection valves described in Patent Documents 1 and 2, a variable volume damper chamber is formed between the movable core and the needle to produce a damper effect, so that the needle is seated on the valve seat, and the movable core Attempts to prevent the movable core and needle from overshooting after the needle hits the stationary core. Here, the damper chamber has a cylindrical gap formed between the small diameter portion of the needle and the inner wall of the movable core, and a cylindrical shape formed between the large diameter portion of the needle and the inner wall of the movable core. The gap is connected.

  By the way, the amount of fluid flowing through the cylindrical gap, that is, the gap flow rate, is proportional to the first power of the inner diameter of the gap and the third power of the radial width of the gap, and inversely proportional to the axial length of the gap. The fuel injection valves of Patent Documents 1 and 2 are both fuel injection valves having a configuration in which the gap on the large diameter side is shorter than the gap on the small diameter side. Therefore, in order to efficiently exhibit the damper effect by the damper chamber, there is a problem that the radial width of the gap on the large diameter portion side in the cylindrical gap must be strictly managed.

  Moreover, in the fuel injection valve of patent document 1, the large diameter part of the needle is provided separately from the main body (small diameter part) of the needle. Moreover, in the fuel injection valve of Patent Document 2, the sleeve forming the inner wall of the movable core is provided separately from the main body of the movable core. Therefore, the configuration is complicated, the processing and assembly costs increase, and it may be difficult to manage the width of the cylindrical gap and the like.

JP-T-2006-509141 Utility Model Registration No. 2568515

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a fuel injection valve capable of efficiently functioning a damper effect with a simple configuration.

  The invention described in claim 1 includes a housing, a needle, a movable core, a fixed core, a coil, and a first biasing member. The housing is formed in a cylindrical shape and has a nozzle hole formed at one end in the axial direction, a valve seat formed around the nozzle hole, and a fuel passage through which fuel flows to the nozzle hole. doing. The needle is provided in the housing so as to be reciprocally movable. The needle has a rod-shaped main body, a seal portion formed at an end of the main body on the valve seat side, a cylindrical small diameter portion formed at an end opposite to the seal portion of the main body, and a seal portion of the small diameter portion A cylindrical large-diameter portion that is formed on the opposite side and has a larger outer diameter than the small-diameter portion, and an annular shape that is formed between the large-diameter portion and the small-diameter portion so as to be perpendicular to the axis of the large-diameter portion Needle step surface. Here, the “cylindrical shape” is not limited to a strict cylindrical shape, the inner diameter or the outer diameter is slightly different in the axial direction, and the shape of the inner wall or the outer wall viewed in the axial direction is slightly distorted from a perfect circle, etc. It is meant to include a substantially cylindrical shape. Further, the term “vertical” means not only strict vertical but also includes a case of a substantially vertical state that is inclined by a predetermined angle. The term “annular” means that the shape of the inner edge portion or outer edge portion includes a substantially circular shape such as a shape slightly distorted from a perfect circle. Hereinafter, the expressions “cylindrical”, “vertical”, and “annular” are used in the same meaning. The needle opens and closes the nozzle hole when the seal portion is separated from the valve seat or seated on the valve seat.

  The movable core includes a large-diameter inner wall surface whose inner diameter is larger than the outer diameter of the large-diameter portion of the needle, a small-diameter inner wall surface whose inner diameter is smaller than the large-diameter inner wall surface and smaller than the outer diameter of the small-diameter portion of the needle, and An annular core step surface is formed between the small-diameter inner wall surface and the large-diameter inner wall surface so as to be perpendicular to the axis of the wall surface. The movable core is provided so as to be relatively movable in the axial direction with respect to the needle in a state where the small diameter portion of the needle is positioned inside the small diameter inner wall surface and the large diameter portion of the needle is positioned inside the large diameter inner wall surface. The fixed core is formed in a cylindrical shape and is fixed in the housing. The coil attracts the movable core together with the needle in the valve opening direction by generating a magnetic attractive force between the movable core and the fixed core by energization. The first biasing member biases the needle in the valve closing direction.

  In the present invention, the needle and the movable core form a cylindrical first gap between the large-diameter portion and the large-diameter inner wall surface, and form a cylindrical second gap between the small-diameter portion and the small-diameter inner wall surface. An annular damper chamber having a variable volume is formed between the needle step surface and the core step surface. The damper effect of the damper chamber can prevent the movable core from overshooting in the valve closing direction after the needle is seated on the valve seat. Therefore, the amount of overshoot of the movable core after the needle valve is closed can be reduced, and the injection interval at the time of multistage injection can be shortened. Further, the amount of overshoot of the movable core after the needle valve is closed can be reduced, and the speed of the movable core can be further reduced at the time of re-raising. Therefore, irregular injection that can occur at the time of re-collision and wear of members due to the collision can be suppressed. . As a result, the reliability regarding the durability of the fuel injection valve can be improved.

  In the present invention, the needle and the movable core are formed such that the axial length of the first gap when the volume of the damper chamber is minimized is larger than the axial length of the second gap. By the way, the amount of fluid flowing through the cylindrical gap, that is, the gap flow rate, is proportional to the first power of the inner diameter of the gap and the third power of the radial width of the gap, and inversely proportional to the axial length of the gap. Therefore, in the present invention, when the volume of the damper chamber is minimized, the axial length of the first gap is larger than the axial length of the second gap. Can be made equal to the gap flow rate of the first gap and the gap flow rate of the second gap. Thereby, the damper effect by a damper chamber can be exhibited efficiently. Moreover, this invention is a structure which forms a damper chamber with two members, a movable core and a needle. Therefore, the damper effect can be efficiently exhibited with a simple configuration.

In the invention according to claim 2, the outer diameter of the large diameter portion of the needle is smaller than the inner diameter of the fixed core. Therefore, after the movable core collides with the fixed core, the needle can be overshot in the valve opening direction so that the large diameter portion enters the inside of the fixed core. Thereby, the impact load accompanying the collision with a movable core and a fixed core can be suppressed. As a result, it is possible to suppress the wear of the movable core and the fixed core due to the operation sound of the fuel injection valve and the collision.
Moreover, in this invention, after a movable core collides with a fixed core by the damper effect of a damper chamber, it can suppress that a needle overshoots in a valve opening direction excessively. Therefore, in the present invention, it is possible to improve the linearity of the injection amount by buffering the bounce of the needle and the movable core that may occur after the movable core collides with the fixed core.

By the way, in the case of a structure in which the small diameter portion and the large diameter portion of the needle are integrally formed so as to be directly connected, the outer wall in the vicinity of the large diameter portion of the large diameter side end portion of the small diameter portion has an outer diameter in the axial direction. It is difficult to process with high precision so that the is uniform.
Therefore, in the invention described in claim 3, the needle has a cylindrical connecting portion that connects the small diameter portion and the large diameter portion and has an outer diameter smaller than that of the small diameter portion. Thereby, an annular recess (groove) is formed between the small diameter portion and the large diameter portion. In this configuration, since the small-diameter portion and the large-diameter portion are separated by the recess, it is easy to process the outer wall of the small-diameter portion on the side of the large-diameter portion so that the outer diameter is uniform in the axial direction. Become. Therefore, when processing the needle, the inner diameter and the width of the second gap can be easily adjusted.

  The invention according to claim 4 further includes a second urging member that urges the movable core together with the needle in the valve opening direction. The positional relationship between the movable core and the needle and the volume change of the damper chamber can be stabilized by the urging force of the second urging member. Thereby, while being able to operate a fuel injection valve stably, an operation noise can be suppressed.

Sectional drawing which shows the fuel injection valve by 1st Embodiment of this invention. (A) is a fragmentary sectional view which shows the principal part of the fuel injection valve by 1st Embodiment of this invention, (B) is the BB sectional drawing of (A). It is a fragmentary sectional view showing an important section of a fuel injection valve by a 1st embodiment of the present invention, and is a figure showing the state where a needle has overshooted in the valve opening direction. It is a fragmentary sectional view showing an important section of a fuel injection valve by a 1st embodiment of the present invention, and is a figure showing a state where a movable core is overshooting in the valve closing direction. It is a schematic diagram for demonstrating the quantity of the fluid which flows through a cylindrical clearance gap, Comprising: (A) is a figure which shows the state where the outer side member and the inner side member are concentric, (B) is B of (A). -B line sectional drawing, (C) is a figure which shows the state from which the outer side member and the inner side member are eccentric, (D) is DD sectional view taken on the line of (C). The fragmentary sectional view which shows the principal part of the fuel injection valve by 2nd Embodiment of this invention. The fragmentary sectional view which shows the principal part of the fuel injection valve by 3rd Embodiment of this invention. The fragmentary sectional view which shows the principal part of the fuel injection valve by 4th Embodiment of this invention. The fragmentary sectional view which shows the principal part of the fuel injection valve by 5th Embodiment of this invention. The fragmentary sectional view which shows the principal part of the fuel injection valve by 6th Embodiment of this invention.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. Note that, in a plurality of embodiments, substantially the same components are denoted by the same reference numerals, and description thereof is omitted.
(First embodiment)
A fuel injection valve according to a first embodiment of the present invention is shown in FIG. The fuel injection valve 10 is used, for example, in a fuel injection device of a direct injection gasoline engine (not shown), and injects and supplies gasoline as fuel to the engine.

The fuel injection valve 10 includes a housing 20, a needle 40, a movable core 50, a fixed core 60, a coil 70, a spring 81 as a first urging member, a spring 82 as a second urging member, and the like.
As shown in FIG. 1, the housing 20 includes a first cylinder member 21, a second cylinder member 22, a third cylinder member 23, and an injection nozzle 30. The first cylinder member 21, the second cylinder member 22, and the third cylinder member 23 are all formed in a substantially cylindrical shape, and are coaxial in the order of the first cylinder member 21, the second cylinder member 22, and the third cylinder member 23. Arranged and connected to each other.

  The 1st cylinder member 21 and the 3rd cylinder member 23 are formed, for example with magnetic materials, such as ferritic stainless steel, and the magnetic stabilization process is performed. The first cylinder member 21 and the third cylinder member 23 have a relatively low hardness. On the other hand, the second cylindrical member 22 is formed of a nonmagnetic material such as austenitic stainless steel, for example. The hardness of the second cylinder member 22 is higher than the hardness of the first cylinder member 21 and the third cylinder member 23.

  The injection nozzle 30 is provided at the end of the first cylinder member 21 opposite to the second cylinder member 22. The injection nozzle 30 is made of a metal such as martensitic stainless steel. The injection nozzle 30 is subjected to a quenching process so as to have a predetermined hardness.

  The injection nozzle 30 is formed in a substantially bottomed cylindrical shape and has a bottom portion 31 and a cylindrical portion 32. The bottom portion 31 closes one end portion of the cylindrical portion 32. An injection hole 311 that connects the inner wall and the outer wall is formed in the bottom 31. An annular valve seat 312 is formed on the inner wall of the bottom 31 so as to surround the nozzle hole 311. The cylinder portion 32 is connected to the first cylinder member 21 such that the outer wall is fitted to the inner wall of the first cylinder member 21. The fitting part of the cylinder part 32 and the 1st cylinder member 21 is welded.

The needle 40 is formed in a rod shape from a metal such as martensitic stainless steel. The needle 40 is subjected to a quenching process so as to have a predetermined hardness. The hardness of the needle 40 is set substantially equal to the hardness of the injection nozzle 30.
The needle 40 is accommodated in the housing 20 so as to be capable of reciprocating in the axial direction. The needle 40 includes a main body 41, a seal portion 42, a small diameter portion 43, a large diameter portion 44, a needle step surface 45, and the like. The main body 41 is formed in a substantially cylindrical rod shape. The seal portion 42 is formed at the end of the main body 41 on the valve seat 312 side, and can contact the valve seat 312. The small diameter portion 43 is formed on the opposite side of the seal portion 42 of the main body 41. The large diameter portion 44 is formed on the opposite side of the seal portion 42 of the small diameter portion 43. The large diameter portion 44 has a larger outer diameter than the small diameter portion 43. In the present embodiment, the large diameter portion 44 is formed integrally with the small diameter portion 43 so as to be in contact with the small diameter portion 43 (see FIG. 2). Thereby, an annular needle step surface 45 is formed between the large diameter portion 44 and the small diameter portion 43 so as to be perpendicular to the axis of the large diameter portion 44. In other words, the exposed portion of the end surface of the large diameter portion 44 on the seal portion 42 side forms the needle step surface 45.

  Further, a sliding contact portion 46 is formed in the vicinity of the seal portion 42 of the main body 41. The sliding contact portion 46 is formed in a substantially cylindrical shape, and a part of the outer wall 461 is chamfered. The slidable contact portion 46 can be slidably contacted with the inner wall 321 of the cylindrical portion 32 of the injection nozzle 30 at a portion where the outer wall 461 is not chamfered. As a result, the needle 40 is guided to reciprocate at the tip of the nozzle hole 311 side.

  The needle 40 opens and closes the nozzle hole 311 when the seal portion 42 is separated (separated) from the valve seat 312 or seated (abutted) on the valve seat 312. Hereinafter, the direction in which the needle 40 is separated from the valve seat 312 is referred to as the valve opening direction, and the direction in which the needle 40 is seated on the valve seat 312 is referred to as the valve closing direction. The small diameter portion 43 and the large diameter portion 44 of the needle 40 are formed in a hollow cylindrical shape. The small diameter portion 43 is formed with a hole 47 that connects the inner wall and the outer wall.

  The movable core 50 is formed in a substantially cylindrical shape by a magnetic material such as ferritic stainless steel. The movable core 50 is subjected to a magnetic stabilization process. The hardness of the movable core 50 is relatively low and is substantially equal to the hardness of the first cylindrical member 21 and the third cylindrical member 23 of the housing 20.

The movable core 50 has a large-diameter inner wall surface 51, a small-diameter inner wall surface 52, a core step surface 53, and the like. The large-diameter inner wall surface 51 is formed on the inner wall of the end portion of the movable core 50 opposite to the seal portion 42. The large-diameter inner wall surface 51 has an inner diameter larger than the outer diameter of the large-diameter portion 44 of the needle 40. The small-diameter inner wall surface 52 is formed on the inner wall on the seal portion 42 side with respect to the large-diameter inner wall surface 51 among the inner walls of the movable core 50. The small diameter inner wall surface 52 has a smaller inner diameter than the large diameter inner wall surface 51 and a larger inner diameter than the outer diameter of the small diameter portion 43 of the needle 40. Thereby, an annular core step surface 53 is formed between the small-diameter inner wall surface 52 and the large-diameter inner wall surface 51 so as to be perpendicular to the axis of the small-diameter inner wall surface 52.
The movable core 50 is provided to be movable relative to the needle 40 in the axial direction in a state where the small diameter portion 43 is positioned inside the small diameter inner wall surface 52 and the large diameter portion 44 is positioned inside the large diameter inner wall surface 51. .

The needle 40 and the movable core 50 are provided so that the needle step surface 45 and the core step surface 53 can come into contact with each other. Here, the needle 40 and the movable core 50 form a cylindrical first gap 101 between the large diameter portion 44 and the large diameter inner wall surface 51, and are cylindrical between the small diameter portion 43 and the small diameter inner wall surface 52. The second gap 102 is formed (see FIGS. 2A and 2B). When the movable core 50 moves relative to the needle 40 in the axial direction, the large-diameter inner wall surface 51 and the small-diameter inner wall surface 52 and the large-diameter portion 44 and the outer wall of the small-diameter portion 43 can come into sliding contact.
In the present embodiment, the axial length of the large-diameter portion 44 of the needle 40 is substantially the same as the axial length of the large-diameter inner wall surface 51 of the movable core 50. Therefore, when the needle step surface 45 and the core step surface 53 are in contact with each other, the end surface of the large diameter portion 44 opposite to the injection nozzle 30 and the end surface of the movable core 50 opposite to the injection nozzle 30 are provided. Are located on substantially the same plane.

  3 and 4, when the needle step surface 45 and the core step surface 53 are separated from each other, the needle step surface 45, the core step surface 53, the large-diameter inner wall surface 51, and the outer wall of the small-diameter portion 43 are surrounded. An annular space is formed. This space is referred to as a damper chamber 103. The volume of the damper chamber 103 changes according to the distance between the needle step surface 45 and the core step surface 53, that is, the relative position between the needle 40 and the movable core 50. That is, the needle 40 and the movable core 50 form an annular damper chamber 103 having a variable volume between the needle step surface 45 and the core step surface 53. When the needle step surface 45 and the core step surface 53 are in contact with each other, the volume of the damper chamber 103 is zero.

  As shown in FIG. 2, the movable core 50 is formed so that the outer diameter is smaller than the inner diameter of the housing 20, that is, the end of the first cylinder member 21 on the second cylinder member 22 side, and the inner diameter of the second cylinder member 22. Yes. Further, the end of the movable core 50 on the seal portion 42 side has an inner diameter that is larger than the inner diameters of the large-diameter inner wall surface 51 and the small-diameter inner wall surface 52. Thereby, an annular step surface 54 is formed on the seal portion 42 side of the small-diameter inner wall surface 52 so as to be perpendicular to the axis of the small-diameter inner wall surface 52. The movable core 50 is formed with a plurality of through holes 55 that connect the end face on the seal portion 42 side and the end face on the opposite side of the seal portion 42. In addition, the movable core 50 has an annular projecting portion 56 formed so as to project annularly from the outer wall in the radially outward direction.

  The fixed core 60 is formed in a substantially cylindrical shape by a magnetic material such as ferritic stainless steel. The fixed core 60 is subjected to a magnetic stabilization process. The fixed core 60 has a relatively low hardness and is approximately equal to the hardness of the movable core 50. The fixed core 60 is provided so as to be fixed inside the housing 20. The fixed core 60 and the third cylinder member 23 of the housing 20 are welded.

  The coil 70 is formed in a substantially cylindrical shape, and is provided so as to surround the outer side in the radial direction of the second cylindrical member 22 and the third cylindrical member 23 of the housing 20. The coil 70 generates a magnetic force when electric power is supplied (energized). When a magnetic force is generated in the coil 70, a magnetic circuit is formed in the fixed core 60, the movable core 50, the first cylindrical member 21, and the third cylindrical member 23. As a result, a magnetic attractive force is generated between the fixed core 60 and the movable core 50, and the movable core 50 is attracted to the fixed core 60. At this time, since the core step surface 53 of the movable core 50 contacts the needle step surface 45 of the needle 40, the needle 40 moves together with the movable core 50 toward the fixed core 60, that is, in the valve opening direction. As a result, the seal portion 42 is separated from the valve seat 312 and the nozzle hole 311 is opened.

  The spring 81 is provided so that one end is in contact with the end of the needle 40 on the large diameter portion 44 side. The other end of the spring 81 is in contact with one end of the adjusting pipe 11 that is press-fitted and fixed inside the fixed core 60. The spring 81 has a force that extends in the axial direction. Thereby, the spring 81 urges the needle 40 together with the movable core 50 in the valve closing direction.

One end of the spring 82 is provided so as to contact the stepped surface 54 of the movable core 50. The other end of the spring 82 is in contact with an annular step surface 211 formed inside the first cylindrical member 21 of the housing 20. The spring 82 has a force extending in the axial direction. As a result, the spring 82 urges the movable core 50 together with the needle 40 in the valve opening direction.
In the present embodiment, the urging force of the spring 81 is set larger than the urging force of the spring 82. Therefore, in a state where power is not supplied (energized) to the coil 70, the seal portion 42 of the needle 40 is in a state of being seated on the valve seat 312, that is, a valve-closed state.

  As shown in FIG. 1, a substantially cylindrical fuel introduction pipe 12 is press-fitted and welded to the end of the third cylinder member 23 opposite to the second cylinder member 22. A filter 13 is provided inside the fuel introduction pipe 12. The filter 13 collects foreign matters in the fuel that has flowed from the introduction port 14 of the fuel introduction pipe 12.

  The radially outer sides of the fuel introduction pipe 12 and the third cylinder member 23 are molded with resin. A connector 15 is formed in the mold part. The connector 15 is insert-molded with a terminal 16 for supplying electric power to the coil 70. Further, a cylindrical holder 17 is provided outside the coil 70 in the radial direction so as to cover the coil 70.

  The fuel that has flowed from the introduction port 14 of the fuel introduction pipe 12 flows between the fixed core 60, the adjusting pipe 11, the inside of the large diameter portion 44 and the small diameter portion 43 of the needle 40, the hole 47, the first cylindrical member 21 and the needle 40. In the meantime, it circulates between the injection nozzle 30 and the needle 40 and is guided to the injection hole 311. That is, a fuel passage 18 through which fuel flows is formed inside the housing 20. When the fuel injection valve 10 is operated, the periphery of the movable core 50 is filled with fuel. Further, when the fuel injection valve 10 is operated, the fuel flows through the through hole 55 of the movable core 50. Therefore, the movable core 50 can move smoothly in the axial direction inside the housing 20.

As described above, when the needle 40 reciprocates within the housing 20, the sliding contact portion 42 (the end portion on the seal portion 42 side) is supported by the cylindrical portion 32 of the injection nozzle 30.
Further, as described above, the outer diameter of the movable core 50 is formed smaller than the inner diameter of the housing 20, that is, the end of the first cylinder member 21 on the second cylinder member 22 side, and the inner diameter of the second cylinder member 22. Yes. When the movable core 50 reciprocates within the housing 20, the annular projecting portion 56 can come into sliding contact with the inner wall of the housing 20, particularly the inner wall of the second cylindrical member 22. At this time, the large-diameter inner wall surface 51 and the small-diameter inner wall surface 52 of the movable core 50 can be in sliding contact with the large-diameter portion 44 of the needle 40 and the outer wall of the small-diameter portion 43.

Thus, in this embodiment, the needle 40 has the sliding contact portion 42 (end portion on the seal portion 42 side) supported by the inner wall of the housing 20 (injection nozzle 30), and the end portion on the large diameter portion 44 side movable. While being supported by the inner wall of the housing 20 (second cylindrical member 22) via the core 50, the inner side of the housing 20 is reciprocated.
Further, when the movable core 50 is attracted toward the fixed core 60 (in the valve opening direction) by a magnetic attraction force, the end surface on the fixed core 60 side collides with the end surface on the movable core 50 side of the fixed core 60. As a result, the movable core 50 is restricted from moving in the valve opening direction (see FIG. 3). That is, the fixed core 60 functions as a stopper for the movable core 50.

In the present embodiment, in the needle 40 and the movable core 50, the axial length L1 of the first gap 101 when the volume of the damper chamber 103 is minimized (see FIG. 2) is the axial length of the second gap 102. It is formed to be larger than the length L2.
As shown in FIGS. 2 to 4, the first gap 101 and the second gap 102 are connected to the damper chamber 103. When the movable core 50 and the needle 40 move relative to each other in the direction in which the core step surface 53 and the needle step surface 45 are separated from each other (see FIGS. 3 and 4), the volume of the damper chamber 103 increases. Therefore, at this time, the fuel in the space on the fixed core 60 side of the movable core 50 flows into the damper chamber 103 via the first gap 101. On the other hand, the fuel in the space on the opposite side of the movable core 50 from the fixed core 60 flows into the damper chamber 103 via the second gap 102.

Here, the amount of fluid flowing through the cylindrical gap, that is, the gap flow rate will be described with reference to FIG.
As shown in FIGS. 5A and 5B, when the cylindrical outer member 200 and the cylindrical inner member 201 are concentric, they are formed between the outer member 200 and the inner member 201. The radial width of the cylindrical gap 202 is constant in the circumferential direction. The radial width of the gap 202 (the difference between the inner diameter of the outer member 200 and the outer diameter of the inner member 201 divided by 2) is h, the inner diameter of the gap 202 (outer diameter of the inner member 201) is d, and the gap When the axial length of 202 is l, the differential pressure between the space 203 and the space 204 connected to both ends of the gap 202 is Δp, and the viscosity coefficient of the fluid is μ, the fluid flows from the space 203 toward the space 204 through the gap 202. The amount Q of fluid is derived from Equation 1 below.
Q = π × d × h ³ / (12 × μ × l) × Δp Equation 1

On the other hand, as shown in FIGS. 5C and 5D, when the cylindrical outer member 200 and the cylindrical inner member 201 are eccentric, the radial width of the cylindrical gap 202 is circumferential. It is different. When the amount of eccentricity of the inner member 201 with respect to the outer member 200 at this time is represented by e, the amount Q of the fluid flowing through the gap 202 from the space 203 toward the space 204 is derived by the following equation 2.
Q = π × d × h ³ /(12×μ×l)×Δp{1+1.5(e/h) ² } Equation 2
From Equations 1 and 2, the gap flow rate of the generally cylindrical gap is proportional to the first power of the inner diameter of the gap and the third power of the radial width of the gap, and may be inversely proportional to the axial length of the gap. Recognize.

  Therefore, in this embodiment, at least when the volume of the damper chamber 103 is minimized (see FIG. 2), the axial length L1 of the first gap 101 is larger than the axial length L2 of the second gap 102. Since it is large, the gap flow rate of the first gap 101 and the second gap are not particularly strictly controlled without strictly managing the radial width (the outer diameter of the large diameter portion 44 and the inner diameter of the large inner wall surface 51). The gap flow rate of the gap 102 can be made equal.

Next, the operation of the fuel injection valve 10 will be described.
When the coil 70 is energized, the movable core 50 is attracted to the fixed core 60. As a result, the needle 40 moves to the fixed core 60 side together with the movable core 50, and the seal portion 42 moves away from the valve seat 312. Thereby, the nozzle hole 311 will be in the open state (valve open state). The fuel flowing in from the inlet 14 of the fuel introduction pipe 12 flows through the fuel passage 18 and is injected from the injection hole 311.

  When the movable core 50 is attracted by the coil 70 and further moves to the fixed core 60 side, the movable core 50 collides with the fixed core 60 and is restricted from moving in the valve opening direction. When the movable core 50 collides with the fixed core 60, the needle 40 overshoots in the valve opening direction so that the large-diameter portion 44 enters the inside of the fixed core 60 while resisting the biasing force of the spring 81 due to inertia (FIG. 3). At this time, since the volume of the damper chamber 103 increases, the fuel in the space on the fixed core 60 side of the movable core 50 flows into the damper chamber 103 via the first gap 101. At the same time, the fuel in the space opposite to the fixed core 60 of the movable core 50 flows into the damper chamber 103 via the second gap 102. It is possible to suppress the needle 40 from overshooting in the valve opening direction due to the damper effect generated at this time.

Subsequently, when the power supply to the coil 70 is turned off, the seal portion 42 of the needle 40 is seated on the valve seat 312 and closed. Thereby, fuel injection is interrupted | blocked.
When the needle 40 is closed by turning off the power supply to the coil 70, the movable core 50 overshoots in the valve closing direction against the urging force of the spring 82 due to inertia (see FIG. 4). At this time, since the volume of the damper chamber 103 increases, the fuel in the space on the fixed core 60 side of the movable core 50 flows into the damper chamber 103 via the first gap 101. At the same time, the fuel in the space opposite to the fixed core 60 of the movable core 50 flows into the damper chamber 103 via the second gap 102. Due to the damper effect generated at this time, the overshoot of the movable core 50 in the valve closing direction can be suppressed.
The damper effect also occurs when the fuel flows out of the damper chamber 103 via the first gap 101 and the second gap 102 (when the volume of the damper chamber 103 decreases).

  As described above, in this embodiment, the needle 40 and the movable core 50 form the cylindrical first gap 101 between the large-diameter portion 44 and the large-diameter inner wall surface 51, and the small-diameter portion 43 and the small-diameter inside A cylindrical second gap 102 is formed between the wall surface 52 and an annular damper chamber 103 having a variable volume is formed between the needle step surface 45 and the core step surface 53. Due to the damper effect of the damper chamber 103, it is possible to prevent the movable core 50 from excessively overshooting in the valve closing direction after the needle 40 is seated on the valve seat 312. Therefore, the amount of overshoot of the movable core 50 after the valve closing of the needle 40 can be reduced, and the injection interval at the time of multistage injection can be shortened. Furthermore, since the amount of overshoot of the movable core 50 after the valve closing of the needle 40 can be reduced and the speed of the movable core 50 can be further reduced at the time of re-raising, irregular injection that can occur at the time of re-collision and wear of members due to collision are suppressed. be able to. As a result, the reliability regarding the durability of the fuel injection valve 10 can be improved.

  Further, in the present embodiment, the needle 40 and the movable core 50 are configured such that the axial length L1 of the first gap 101 when the volume of the damper chamber 103 is minimum is greater than the axial length L2 of the second gap 102. Is also formed to be large. The gap flow rate of the cylindrical gap is proportional to the first power of the inner diameter of the gap and the third power of the radial width of the gap, and inversely proportional to the axial length of the gap. Therefore, in the present embodiment, the clearance flow rate of the first clearance 101 and the clearance flow rate of the second clearance 102 can be made equal without particularly managing the width of the first clearance 101 in the radial direction. Thereby, the damper effect by the damper chamber 103 can be exhibited efficiently. Further, in the present embodiment, the damper chamber 103 is formed by two members of the movable core 50 and the needle 40. Therefore, the damper effect can be efficiently exhibited with a simple configuration.

  In the present embodiment, the large diameter portion 44 of the needle 40 is formed so that the outer diameter is smaller than the inner diameter of the fixed core 60. Therefore, after the movable core 50 collides with the fixed core 60, the needle 40 can be overshot in the valve opening direction so that the large diameter portion 44 enters the inside of the fixed core 60. Thereby, the impact load accompanying the collision between the movable core 50 and the fixed core 60 can be suppressed. As a result, it is possible to suppress the wear of the movable core 50 and the fixed core 60 due to the operation sound of the fuel injection valve 10 and the collision.

  Further, in the present embodiment, the damper effect of the damper chamber 103 can suppress the needle 40 from excessively overshooting in the valve opening direction after the movable core 50 collides with the fixed core 60. Therefore, in this embodiment, the bounce of the needle 40 and the movable core 50 that may occur after the movable core 50 collides with the fixed core 60 is buffered, so that the linearity of the injection amount can be improved.

  In addition, the present embodiment further includes a spring 82 that urges the movable core 50 together with the needle 40 in the valve opening direction. The positional relationship between the movable core 50 and the needle 40 and the volume change of the damper chamber 103 can be stabilized by the urging force of the spring 82. Thereby, while being able to operate the fuel injection valve 10 stably, an operation sound can be suppressed.

(Second Embodiment)
A fuel injection valve according to a second embodiment of the present invention will be described with reference to FIG. In 2nd Embodiment, the magnitude | size (outer diameter) of the large diameter part 44 of the needle 40 differs from 1st Embodiment.

  In the second embodiment, the large diameter portion 44 is formed so that the outer diameter is larger than the inner diameter of the fixed core 60. That is, the large diameter portion 44 of the second embodiment has a larger outer diameter than the large diameter portion 44 of the first embodiment. The large-diameter inner wall surface 51 of the second embodiment is also formed with a larger inner diameter than the large-diameter inner wall surface 51 of the first embodiment. Therefore, in the second embodiment, the needle step surface 45 and the core step surface 53 are also larger in area than the first embodiment.

  In the present embodiment, when the needle 40 is sucked together with the movable core 50 by the coil 70, the large diameter portion 44 collides with the fixed core 60, so that the needle 40 does not overshoot in the valve opening direction. However, since the areas of the needle step surface 45 and the core step surface 53 are large compared to the first embodiment, the volume change rate of the damper chamber 103 per relative movement amount of the movable core 50 with respect to the needle 40 can be increased. Therefore, the damper effect can be exhibited more efficiently.

(Third embodiment)
A fuel injection valve according to a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the configuration of the needle 40 is different from that of the first embodiment.

  In the third embodiment, the needle 40 has a cylindrical connecting portion 48 that connects the small diameter portion 43 and the large diameter portion 44 and has a smaller outer diameter than the small diameter portion 43. Thereby, an annular recess (groove) 49 is formed between the small diameter portion 43 and the large diameter portion 44. In this configuration, since the small diameter portion 43 and the large diameter portion 44 are separated by the recess 49, the outer wall of the end portion on the large diameter portion 44 side of the small diameter portion 43 is processed so that the outer diameter is uniform in the axial direction. It becomes easy. Therefore, when machining the needle 40, the inner diameter and the radial width of the second gap 102 can be easily adjusted. Also in the present embodiment, the axial length L1 of the first gap 101 when the volume of the damper chamber 103 is minimized (see FIG. 7) is larger than the axial length L2 of the second gap 102. large.

(Fourth embodiment)
A fuel injection valve according to a fourth embodiment of the present invention will be described with reference to FIG. In 4th Embodiment, the magnitude | size (length of an axial direction) of the large diameter part 44 of the needle 40 differs from 1st Embodiment.

In the fourth embodiment, the axial length of the large-diameter portion 44 of the needle 40 is smaller than the axial length of the large-diameter inner wall surface 51 of the movable core 50. Therefore, in a state where the needle step surface 45 and the core step surface 53 are in contact with each other, the end surface on the fuel introduction pipe 12 side of the large diameter portion 44 is larger than the end surface on the fuel introduction pipe 12 side of the movable core 50. Located on the side. Also in the present embodiment, the axial length L1 of the first gap 101 when the volume of the damper chamber 103 is minimized (see FIG. 8) is larger than the axial length L2 of the second gap 102. large.
In the present embodiment, during operation of the fuel injection valve, it is possible to prevent the end portion of the spring 81 from being displaced in the radial direction and thereby urging the end surface on the fixed core 60 side of the movable core 50 in the valve closing direction. it can.

(Fifth embodiment)
A fuel injection valve according to a fifth embodiment of the present invention will be described with reference to FIG. In 5th Embodiment, the magnitude | size (length of an axial direction) of the large diameter part 44 of the needle 40 differs from 1st Embodiment and 4th Embodiment.

In the fifth embodiment, the axial length of the large-diameter portion 44 of the needle 40 is larger than the axial length of the large-diameter inner wall surface 51 of the movable core 50. Therefore, in a state where the needle step surface 45 and the core step surface 53 are in contact with each other, the end surface of the large diameter portion 44 on the fuel introduction pipe 12 side is more than the end surface of the movable core 50 on the fixed core 60 side. Located on the side. Further, in the state where the needle 40 is closed, the end portion of the large diameter portion 44 on the fuel introduction pipe 12 side is located inside the fixed core 60. Also in the present embodiment, the axial length L1 of the first gap 101 when the volume of the damper chamber 103 is minimized (see FIG. 9) is larger than the axial length L2 of the second gap 102. large.
In the present embodiment, as in the fourth embodiment, during operation of the fuel injection valve, the end portion of the spring 81 is biased in the valve closing direction by shifting the end portion of the spring 81 in the radial direction. Can be suppressed.

(Sixth embodiment)
A fuel injection valve according to a sixth embodiment of the present invention will be described with reference to FIG. In 6th Embodiment, the magnitude | size (outer diameter) of the large diameter part 44 of the needle 40 differs from 5th Embodiment.

  In the sixth embodiment, the large-diameter portion 44 is formed so that the outer diameter is equal to the inner diameter of the fixed core 60 or slightly smaller than the inner diameter of the fixed core 60. Therefore, when the needle 40 reciprocates inside the housing 20, the outer wall of the large diameter portion 44 comes into sliding contact with the inner wall of the fixed core 60. That is, the needle 40 is supported by the fixed core 60 so that the end on the large diameter portion 44 side can be reciprocated. Therefore, the posture of the needle 40 during the reciprocating movement is stabilized. As a result, local wear due to sliding contact between the outer wall of the large-diameter portion 44 and the outer wall of the small-diameter portion 43 and the large-diameter inner wall surface 51 and the small-diameter inner wall surface 52 due to relative movement between the needle 40 and the movable core 50 is suppressed. can do.

  Further, in the present embodiment, since the end of the needle 40 on the large diameter portion 44 side is supported by the fixed core 60, the outer wall (annular protrusion 56) of the movable core 50 is prevented from sliding on the inner wall of the housing 20. it can. Therefore, wear due to sliding contact between the movable core 50 and the housing 20 can be suppressed.

(Other embodiments)
In another embodiment of the present invention, the spring 82 as the second urging member may not be provided.

  In the above-mentioned embodiment, the example which forms a housing, a needle, a movable core, and a fixed core with stainless steel was shown. On the other hand, in another embodiment of the present invention, the housing, the needle, the movable core, and the fixed core may be formed of a metal other than stainless steel, such as iron. Further, the hardness of each member may be set in any way. Moreover, the 1st cylinder member and the injection nozzle may be integrally formed with the same material.

  Moreover, in the above-mentioned embodiment, the small diameter part of the needle, the large diameter part, and the connection part showed the example formed in a hollow cylinder shape. On the other hand, in other embodiments of the present invention, the small diameter part, the large diameter part and the connection part of the needle may be formed in a solid cylindrical shape.

The fuel injection valve of the present invention is not limited to a direct injection type gasoline engine, and may be applied to, for example, a port injection type gasoline engine or a diesel engine.
Thus, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve 18 ... Fuel passage 20 ... Housing 21 ... First cylinder member (housing)
22 .... Second cylinder member (housing)
23... Third cylinder member (housing)
30... Injection nozzle (housing)
311 ... Injection hole 312 ... Valve seat 40 ... Needle 41 ... Body 42 ... Seal part 43 ... Small diameter part 44 ... Large diameter part 45 ... Needle step surface 50 ... movable core 51 ... large diameter inner wall surface 52 ... small diameter inner wall surface 53 ... core step surface 60 ... fixed core 70 ... coil 81 .... Spring (first biasing member)
101 ... 1st gap 102 ... 2nd gap 103 ... Damper chamber

Claims (4)

A nozzle hole formed at one end in the axial direction, into which fuel is injected, a valve seat formed around the nozzle hole, and a cylindrical housing having a fuel passage through which fuel flows to the nozzle hole;
A rod-shaped main body, a seal portion formed at an end portion of the main body on the valve seat side, and a cylinder formed at an end portion of the main body opposite to the seal portion. A small diameter portion, a cylindrical large diameter portion formed on the opposite side of the small diameter portion from the seal portion and having a larger outer diameter than the small diameter portion, and the large diameter portion so as to be perpendicular to the axis of the large diameter portion. A needle that has an annular needle step surface formed between a diameter portion and the small diameter portion, and opens and closes the nozzle hole when the seal portion is separated from the valve seat or seated on the valve seat; ,
A large-diameter inner wall surface whose inner diameter is larger than the outer diameter of the large-diameter portion, a small-diameter inner wall surface whose inner diameter is smaller than the large-diameter inner wall surface and smaller than the outer diameter of the small-diameter portion, and perpendicular to the axis of the small-diameter inner wall surface An annular core step surface formed between the small-diameter inner wall surface and the large-diameter inner wall surface so that the small-diameter portion is located inside the small-diameter inner wall surface and inside the large-diameter inner wall surface A movable core provided so as to be relatively movable in the axial direction with respect to the needle in a state where the large diameter portion is located at
A cylindrical fixed core provided so as to be fixed in the housing;
A coil that attracts the movable core together with the needle in the valve opening direction by generating a magnetic attractive force between the movable core and the fixed core by energization;
A first urging member for urging the needle in the valve closing direction,
The needle and the movable core form a cylindrical first gap between the large-diameter portion and the large-diameter inner wall surface, and a cylindrical second gap between the small-diameter portion and the small-diameter inner wall surface. Forming an annular damper chamber having a variable volume between the needle step surface and the core step surface, and the axial length of the first gap when the volume of the damper chamber is minimized. Is formed so as to be larger than the axial length of the second gap.   The fuel injection valve according to claim 1, wherein the large-diameter portion has an outer diameter smaller than an inner diameter of the fixed core.   3. The fuel injection valve according to claim 1, wherein the needle has a cylindrical connection portion that connects the small diameter portion and the large diameter portion and has an outer diameter smaller than that of the small diameter portion.   The fuel injection valve according to any one of claims 1 to 3, further comprising a second urging member that urges the movable core together with the needle in a valve opening direction.

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