JP5838701B2 - Fuel injection valve - Google Patents

Description

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

  As a conventional fuel injection valve, as shown in FIG. 11, a sack portion 21 surrounded by a sack peripheral wall surface 210 and a sack bottom wall surface 211 is provided downstream of the seat surface 20 of the nozzle body 2. Further, there is known one in which the opening on the inlet side of the nozzle hole 22 is opened (see, for example, Patent Document 1).

  Then, fluid polishing is applied to the boundary portion between the sack portion 21 and the nozzle hole 22 to form an R surface at the inlet side opening of the nozzle hole 22, thereby increasing the flow coefficient to suppress a decrease in the injection speed, and high penetration. Is to be realized. By realizing high penetration, a low-emission and high-power internal combustion engine is realized.

JP 2005-315136 A

  However, although the conventional fuel injection valve can achieve high penetration in the high lift region of the needle 1, there is a problem that the penetration during the initial lift, that is, in the low lift region is small.

  As shown in FIG. 11, in the low lift region, the fuel flowing through the needle seat portion 13 and flowing to the sack portion 21 is pulled by the wall surface of the needle 1 and flows along the wall surface of the needle 1. Even when the flow is separated from the sheet surface 20 of the nozzle body 2 and reaches the inlet side opening of the nozzle hole 22, the fuel flow is also separated, so that the fuel has an R surface at the inlet side opening of the nozzle hole 22. This is because the flow cannot smoothly flow along the flow path, and the flow loss increases.

  An object of the present invention is to increase a flow coefficient in a low lift region in a fuel injection valve in which an inlet side opening of a nozzle hole is opened on a circumferential wall surface of a sack.

In order to achieve the above object, the invention according to claim 1 is a fuel injection valve in which the needle (1) reciprocates in the nozzle body (2), and the nozzle body (2) has a tapered body seat surface ( 20), a sack portion (21) provided on the downstream side of the body seat surface (20) and surrounded by the sac peripheral wall surface (210) and the sack bottom wall surface (211), and an entrance to the sac peripheral wall surface (210) The side opening is provided with an injection hole (22) that communicates the sac part (21) with the outside and serves as a fuel outlet, and the needle (1) has two tapered surfaces (11, 12). The needle seat portion (13) formed at the boundary portion that opens and closes the nozzle hole (22) in contact with and away from the body seat surface (20), and the downstream side of the two tapered surfaces (11, 12) of the needle (1) Formed on the tapered surface (12) of the needle Than isolation portions (13) provided with a needle groove (14) extending from the downstream side in the closed state to the position facing the inlet side opening of the injection hole (22), nozzle holes (22), a plurality comprises The needle groove portion (14) is a long groove that is long in the fuel flow direction, and is provided in the circumferential direction of the downstream tapered surface (12) in the same number as the nozzle holes (22), and the nozzle body (2) and the needle (1) is provided with a relative rotation prevention mechanism (15, 24) for preventing relative rotation of the nozzle body (2) and the needle (1).

  According to this, in the low lift region, since the flow velocity of the fuel flowing in the needle groove portion (14) is reduced, the force that pulls the fuel flow toward the wall surface of the needle (1) is reduced, and the body seat surface ( 20), the fuel flows smoothly into the nozzle hole (22), and the flow coefficient in the low lift region can be increased.

Further, the relative rotation prevention mechanism (15, 24) maintains the positional relationship in which the inlet side opening of the nozzle hole (22) and the needle groove (14) face each other, thereby increasing the flow coefficient in the low lift region. It can be obtained continuously .

In the invention according to claim 2 , in the fuel injection valve according to claim 1, when the diameter of the injection hole (22) is Di and the height of the needle groove (14) is Hn, Hn ≧ 1/3. It is characterized by × Di.

  According to this, the flow velocity of the fuel flowing through the needle groove portion (14) can be reliably reduced, and the fuel flow can be more reliably prevented from peeling from the body seat surface (20).

As in the third aspect of the invention, in the fuel injection valve of the first or second aspect, when the diameter of the sack peripheral wall surface (210) is Ds and the length of the needle groove (14) is Ln, Ln ≧ 1/2 × Ds.

As in the invention according to claim 4 , in the fuel injection valve according to any one of claims 1 to 3 , the diameter of the injection hole (22) is Di, and the width of the needle groove (14) is Wn. In this case, Wn ≧ Di.

As in the invention described in claim 5, in the fuel injection valve according to any one of claims 1 to 4, the diameter of the nozzle hole (22) and Di, needle groove from the needle seat (13) ( When the distance to the upstream end of 14) is Yn, Yn ≧ Di can be satisfied.

The invention according to claim 6, in the fuel injection valve according to any one of claims 1 to 5, wherein the bottom surface of the needle groove (14) is curved. According to this, the flow coefficient in the low lift region can be further increased.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing which shows the principal part of the fuel injection valve which concerns on 1st Embodiment of this invention. It is sectional drawing which follows the AA line of FIG. It is a B arrow line view of FIG. It is sectional drawing which follows the CC line of FIG. It is sectional drawing which expands and shows the principal part of the fuel injection valve of FIG. It is sectional drawing of the principal part with which it uses for operation | movement description of the fuel injection valve of FIG. It is a figure which shows the relationship between the maximum injection pressure and the groove length Lb in the fuel injection valve of FIG. It is sectional drawing which shows the fuel injection valve which concerns on 2nd Embodiment of this invention. It is sectional drawing which expands and shows the principal part of the fuel injection valve of FIG. It is an expanded sectional view of the D section of FIG. It is sectional drawing which shows the principal part of the conventional fuel injection valve.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
A first embodiment of the present invention will be described. 1 is a cross-sectional view showing a main part of the fuel injection valve according to the first embodiment, FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1, FIG. 3 is a view taken in the direction of arrow B in FIG. It is sectional drawing which follows the CC line of 3. FIG.

  The fuel injection valve of the present embodiment is mounted in each cylinder of an internal combustion engine (hereinafter referred to as an engine) such as a multi-cylinder diesel engine (not shown), and directly injects and supplies high-pressure fuel into the combustion chamber of each cylinder of the engine. is there.

  As shown in FIGS. 1 to 4, the fuel injection valve includes a substantially cylindrical needle 1 and a substantially cylindrical nozzle body 2 that accommodates the needle 1 therein. The needle 1 is slidably held by the nozzle body 2 so as to reciprocate in the nozzle body 2 along the axial direction of the needle 1 and the nozzle body 2 (the vertical direction in the drawing of FIG. 1; hereinafter simply referred to as the axial direction). It has become.

  The needle 1 includes a cylindrical needle shaft portion 10 extending in the axial direction, and a tapered needle first taper surface 11 formed on the fuel flow downstream side (the lower side in FIG. 1) of the needle shaft portion 10. And a tapered needle second tapered surface 12 formed on the downstream side of the fuel flow of the needle first tapered surface 11.

  The needle first taper surface 11 and the needle second taper surface 12 have a smaller diameter along the fuel flow direction. The taper angle of the needle second taper surface 12 is larger than the taper angle of the needle first taper surface 11.

  And the needle seat part 13 which is an annular ridgeline is formed in the boundary part of the needle 1st taper surface 11 and the needle 2nd taper surface 12, This needle seat part 13 is the body sheet surface 20 (detailed later) of the nozzle body 2 The nozzle hole 2 (details will be described later) of the nozzle body 2 is opened and closed.

  The nozzle body 2 has a tapered body seat surface 20 whose diameter decreases along the fuel flow direction, a sack portion 21 which is a space provided on the downstream side of the fuel flow of the body seat surface 20, and the sack portion 21. A plurality of nozzle holes 22 that communicate with the outside and serve as fuel outlets are provided.

  More specifically, the sac portion 21 is located at the cylindrical sack peripheral wall surface 210 extending in the axial direction from the fuel flow downstream end portion of the body seat surface 20 and the fuel flow downstream end portion of the sac peripheral wall surface 210. It is a space surrounded by a tapered sack bottom wall surface 211.

  Further, the nozzle hole 22 has a circular cross-sectional shape, an opening on the inlet side thereof opens to the sack peripheral wall surface 210, and an R surface is formed on the opening on the inlet side. Further, the nozzle hole 22 extends substantially along the radial direction of the needle 1 and the nozzle body 2 (hereinafter simply referred to as the radial direction). In the present embodiment, two injection holes 22 are illustrated, but generally 6 to 10 injection holes 22 are provided.

  When the portion of the body seat surface 20 with which the needle seat portion 13 abuts is the body seat portion, the body seat surface 20 and the sac peripheral wall surface 210 have openings on the inlet side of the injection holes 22 from the downstream side of the body seat portion. A body groove portion 23 extending to the nozzle hole 22 and connected to the nozzle hole 22 is formed. The body groove portions 23 are provided in the same number as the nozzle holes 22, and one body groove portion 23 is connected to one nozzle hole 22. As shown in FIG. 4, the body groove portion 23 has a substantially semicircular cross section. Therefore, the bottom surface of the body groove portion 23 is a curved surface, more specifically, an arc shape.

  The details of the body groove portion 23 will be described mainly with reference to FIG. FIG. 5 is an enlarged sectional view showing the vicinity of the body groove 23.

  In the fuel injection valve of the present embodiment, the dimensions of each part of the body groove portion 23 are set as follows in order to realize high penetration of fuel spray in the low lift region.

  First, when the diameter of the nozzle hole 22 is Di and the height of the body groove portion 23 is Hb, Hb ≧ 1/3 × Di is set. Incidentally, Hb = 1/3 × Di is most desirable.

  When the diameter of the sack peripheral wall surface 210 is Ds and the length of the portion formed on the body sheet surface 20 in the body groove portion 23 is Lb, Lb ≧ 1/2 × Ds is set.

  When the width of the body groove portion 23 is Wb (see FIG. 3), Wb ≧ Di is set. Further, when the distance from the body sheet portion to the upstream end of the body groove portion 23 is Yb, Yb ≧ Di is set.

  Next, the operation of the fuel injection valve of the present embodiment will be described based on FIG. FIG. 6 is an enlarged cross-sectional view showing the vicinity of the body groove 23 in the low lift region, and arrows in the figure indicate the flow of fuel.

  As shown in FIG. 6, in the low lift region, the fuel that passes through the needle seat portion 13 and flows to the sack portion 21 is pulled by the wall surface of the region a in the needle second taper surface 12, and upstream in the body groove portion 23. It peels from the bottom surface of the body groove part 23 once in the area | region b.

  However, the fuel flowing in the body groove portion 23 decreases in flow velocity and spreads to the bottom surface side of the body groove portion 23, and adheres to the bottom surface of the body groove portion 23 in the downstream region c in the body groove portion 23 (that is, peeling is eliminated). Thereby, the fuel flows smoothly from the body groove portion 23 to the nozzle hole 22. Therefore, it is possible to increase the flow coefficient in the low lift region, and to achieve high penetration of fuel spray in the low lift region.

  In the high lift region, the gap between the body seat surface 20 and the needle second taper surface 12 becomes large. Therefore, the force that pulls the fuel to the needle second taper surface 12 side is a fuel that flows in a portion close to the body seat surface 20. It does not reach. Therefore, fuel separation does not occur on the body seat surface 20 or the bottom surface of the body groove 23, and high penetration of fuel spray in the high lift region can be realized.

  The higher the maximum injection pressure, the higher the flow rate of the fuel in the body groove portion 23, and the longer the distance from when the fuel flow peels from the bottom surface of the body groove portion 23 to the bottom surface of the body groove portion 23, As shown in FIG. 7, by increasing the groove length Lb as the maximum injection pressure increases, the fuel flow is reliably attached to the bottom surface of the body groove 23 in the downstream region c of the body groove 23. Can do.

(Second Embodiment)
A second embodiment of the present invention will be described. 8 is a cross-sectional view showing a fuel injection valve according to the second embodiment, FIG. 9 is an enlarged cross-sectional view showing a main part of the fuel injection valve of FIG. 8, and FIG. 10 is an enlarged cross-sectional view of a D portion of FIG. is there. Only the parts different from the first embodiment will be described below.

  The fuel injection valve of the present embodiment eliminates the body groove 23 in the fuel injection valve of the first embodiment, and instead provides a groove on the needle to realize high penetration of fuel spray in the low lift region. It is.

  As shown in FIGS. 8 to 10, the needle 1 has the same number (four in this example) of needle groove portions as the nozzle holes 22 on the needle second tapered surface 12 located on the downstream side of the fuel flow with respect to the needle seat portion 13. 14 is formed. The needle groove portion 14 extends from the downstream side of the needle seat portion 13 to a position facing the inlet side opening of the injection hole 22 in the valve-closed state. The needle groove portion 14 has a substantially semicircular cross section. Therefore, the bottom surface of the needle groove portion 14 is a curved surface, and more specifically, an arc shape.

  The needle 1 includes a protruding piece 15 that extends in the axial direction and protrudes radially outward at a portion that is slidably held by the nozzle body 2. On the other hand, the nozzle body 2 is formed with a guide groove 24 that extends in the axial direction and is recessed radially outward in a portion that holds the needle 1 slidably.

  Then, the protruding piece 15 is slidably inserted into the guide groove 24 to prevent relative rotation between the needle 1 and the nozzle body 2. Further, the projecting piece 15 and the guide groove 24 constituting the relative rotation preventing mechanism are positioned in the circumferential direction so that the opening on the inlet side of the nozzle hole 22 and the needle groove portion 14 face each other when the valve is closed.

  In the fuel injection valve of the present embodiment, the dimensions of each part of the needle groove portion 14 are set as follows in order to realize high penetration of fuel spray in the low lift region.

  First, when the diameter of the nozzle hole 22 is Di and the height of the needle groove portion 14 is Hn, Hn ≧ 1/3 × Di is set. When the diameter of the sac peripheral wall surface 210 is Ds and the length of the needle groove portion 14 is Ln, Ln ≧ 1/2 × Ds is set.

  When the width of the needle groove portion 14 is Wn, Wn ≧ Di is set. Further, when the distance from the needle seat portion 13 to the upstream end of the needle groove portion 14 is Yn, Yn ≧ Di is set.

  Next, the operation of the fuel injection valve of this embodiment will be described. In the low lift region, the flow rate of the fuel flowing in the needle groove portion 14 is reduced. Therefore, in the portion of the needle second tapered surface 12 where the needle groove portion 14 is formed, the fuel flow is directed to the wall surface side of the needle second tapered surface 12. The pulling force becomes smaller. Accordingly, in the vicinity of the portion of the body seat surface 20 that faces the needle groove portion 14, the fuel flow is not separated from the body seat surface 20, thereby allowing the fuel to flow smoothly into the nozzle hole 22 and reducing the lift. The flow coefficient in the region can be increased. Therefore, it is possible to increase the flow coefficient in the low lift region, and to achieve high penetration of fuel spray in the low lift region.

  Further, the protrusion 15 and the guide groove 24 can maintain the positional relationship in which the inlet side opening of the nozzle hole 22 and the needle groove 14 face each other, and can continuously obtain the effect of increasing the flow coefficient in the low lift region. it can.

  In addition, each said embodiment can be arbitrarily combined in the range which can be implemented.

DESCRIPTION OF SYMBOLS 1 Needle 2 Nozzle body 11 Tapered surface 12 Tapered surface 13 Needle seat part 20 Body sheet surface 21 Sack part 22 Injection hole 23 Body groove part 210 Sack peripheral wall surface 211 Sack bottom wall surface

Claims (6)

A fuel injection valve in which a needle (1) reciprocates in a nozzle body (2),
The nozzle body (2) is provided on the downstream side of the tapered body sheet surface (20) and the body sheet surface (20), and is surrounded by a sack peripheral wall surface (210) and a sack bottom wall surface (211). The sac portion (21), and an inlet opening on the sac peripheral wall surface (210), and an injection hole (22) that communicates the sac portion (21) with the outside and serves as a fuel outlet. ,
The needle (1) is formed at a boundary portion between two tapered surfaces (11, 12), and a needle seat portion (13) that opens and closes the nozzle hole (22) in contact with and away from the body seat surface (20). , The two tapered surfaces (11, 12) of the needle (1) are formed on the downstream tapered surface (12), and the nozzle hole ( 22) a needle groove (14) extending to a position facing the inlet side opening of (22),
A plurality of the nozzle holes (22) are provided,
The needle groove portion (14) is a long groove that is long in the fuel flow direction, and is provided in the same number as the nozzle holes (22) in the circumferential direction of the downstream tapered surface (12).
The fuel injection valve according to claim 1, wherein the nozzle body (2) and the needle (1) include a relative rotation prevention mechanism (15, 24) for preventing relative rotation of the nozzle body (2) and the needle (1). The diameter of the injection hole (22) and Di, when the height of the needle groove (14) and Hn, the fuel injection valve according to claim 1, characterized in that the Hn ≧ 1/3 × Di . The diameter of the sack circumferential wall surface (210) and Ds, the length of the needle groove (14) when the Ln, according to claim 1 or 2, characterized in that the Ln ≧ 1/2 × Ds Fuel injection valve. The fuel according to any one of claims 1 to 3 , wherein Wn≥Di, where Di is the diameter of the nozzle hole (22) and Wn is the width of the needle groove (14). Injection valve. The diameter of the nozzle hole (22) is Di, and when the distance from the needle seat portion (13) to the upstream end of the needle groove portion (14) is Yn, Yn ≧ Di. 1 to the fuel injection valve according to any one of 4. The fuel injection valve according to any one of claims 1 to 5 , wherein a bottom surface of the needle groove portion (14) is a curved surface.

Images