JP2014194197A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variations of an injection mode in a fuel injection nozzle that injects a fuel to an internal combustion engine.SOLUTION: According to a nozzle 1, an opening 11a of an injection hole 11 exists closer to the front end in an axial direction than a tip 2d of a needle 2 when a seat part 13 is seated at a seat position 10. This relaxes the influence exerted on an injection mode by a flow state of a fuel in a sack chamber 21 so as to suppress variations of the injection mode.

Description

  The present invention relates to a fuel injection nozzle for injecting fuel (hereinafter sometimes abbreviated as a nozzle).

  2. Description of the Related Art Conventionally, for example, a fuel injection valve that injects and supplies fuel to an internal combustion engine includes a nozzle that injects fuel and an actuator that drives to open or close the nozzle. Further, a nozzle (fuel injection nozzle) used for a fuel injection valve is known that includes a cylindrical nozzle body and a needle that is accommodated in the inner periphery of the nozzle body so as to be movable in the axial direction. . The nozzle starts or stops fuel injection as the needle moves in the axial direction on the inner periphery of the nozzle body.

  That is, the inner wall of the nozzle body is provided with a seat position where the seat portion provided near the tip of the needle in the axial direction is separated, and further, the inner wall on the tip end side in the axial direction from the seat position is provided with fuel. A plurality of nozzle holes are opened. Then, when the seat portion is separated from the seat position, the fuel is guided from the inner periphery of the nozzle body to the outside through the injection hole (for example, see Patent Document 1).

By the way, in a fuel injection valve, it is ideal that the mode of injected spray does not fluctuate. In particular, among spray modes, the ability of spray to penetrate through space (spray penetration force) and the injection amount do not vary between individual nozzle holes during the same injection, and the same injection conditions appear even in the same nozzle hole. It is ideal that it does not change with time. Therefore, a sac chamber is provided as a space for forming an appropriate capacity on the tip end side in the axial direction from the sheet position on the inner periphery of the nozzle body, and the nozzle hole is opened in the sac chamber. As a result, the fuel flows between the seat portion and the seat position and flows into the sac chamber and is then injected from the injection hole.
However, it is extremely difficult to control the spray mode, and further improvement measures are required separately from the setting of the sack chamber.

JP 2010-180763 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to suppress fluctuations in the spray mode in a fuel injection nozzle that injects fuel into an internal combustion engine.

  According to the present invention, the fuel injection nozzle includes a cylindrical nozzle body and a needle that is accommodated in the inner periphery of the nozzle body so as to be movable in the axial direction. The fuel injection is started or stopped by moving in the direction. The fuel injection nozzle has the next seat position, injection hole, and specific relationship.

  First, the seat position is a part of the inner wall of the nozzle body, and the seat portion provided near the tip in the axial direction of the needle is detached. The nozzle hole opens in the inner wall of the nozzle body at the tip end side in the axial direction from the seat position, and guides the fuel from the inner periphery of the nozzle body to the outside by the seat portion being separated from the seat position. Furthermore, the specific relationship is an arrangement relationship when the seat portion is seated at the seat position, and the opening in the inner wall of the nozzle hole is located on the tip side in the axial direction rather than the tip in the axial direction of the needle. It is.

Thereby, the influence which the flow state of the fuel in the inner periphery of the nozzle body exerts on the spray mode can be alleviated, and the variation of the spray mode can be suppressed.
Here, for the purpose of suppressing fluctuations in the spray mode, the present inventors set the axial distance between the seat portion and the seat position (the lift amount of the needle) to the fuel flow state in the inner periphery of the nozzle body. (Hereinafter, for convenience of explanation, the movement toward the tip side with the tip side in the axial direction as the lower side is sometimes referred to as “lowering”, and the side opposite to the tip side as the upper side. The movement toward the opposite side of the tip side is sometimes called “raising”.)

In other words, the needle lift amount has a critical value at which the flow state in the region (corresponding to the sack chamber) on the tip side in the axial direction from the seat position on the inner periphery of the nozzle body changes greatly.
More specifically, when the lift amount is smaller than the critical value, the fuel that has flowed into the sac chamber through the space between the seat portion and the seat position mainly toward the inner peripheral side along the wall surface of the needle. Then, it turns and flows toward the outer peripheral side, and further rises along the inner wall of the nozzle body. That is, when the lift amount is smaller than the critical value, the flow state in the sac chamber forms a vortex so as to rise along the inner wall of the nozzle body.

  On the other hand, when the lift amount is larger than the critical value, the fuel that has flowed into the sac chamber through between the seat portion and the seat position mainly descends along the inner wall of the nozzle body, and then swirls. It flows toward the inner peripheral side, and further rises along the wall surface of the needle toward the outer peripheral side. In other words, when the lift amount is larger than the critical value, the flow state in the sac chamber forms a vortex so as to descend along the inner wall of the nozzle body.

Thereby, when the lift amount is smaller than the critical value, the flow rising in the sac chamber flows into the nozzle hole, and when the lift amount is larger than the critical value, the flow descending in the sac chamber flows into the nozzle hole. For this reason, the inflow mode to the nozzle hole changes greatly with the critical value as a boundary, and as a result, the spray mode changes greatly with the critical value as the boundary.
Therefore, when the seat portion is seated at the seat position (that is, when the nozzle is closed), “the opening in the inner wall of the nozzle hole is more axial than the axial tip of the needle. Adopt a specific relationship that exists on the side.

Thus, when the lift amount is smaller than the critical value, the influence of the upward flow on the inflow mode can be mitigated, and when the lift amount is larger than the critical value, the influence of the downward flow on the inflow mode can be mitigated. Can do. For this reason, since the change of the inflow aspect on the boundary of a critical value can be suppressed, the change of the spray aspect on the boundary of a critical value can be suppressed as a result.
As described above, the influence of the fuel flow state in the sac chamber on the spray mode can be mitigated, and the variation of the spray mode can be suppressed.

It is sectional drawing which shows the whole fuel-injection nozzle (Example 1). (Example 1) which is the fragmentary sectional view in the specific cross section which shows the principal part of a fuel-injection nozzle. (A) is explanatory drawing which shows eddy current when the lift amount of a needle is smaller than a critical value, (b) is explanatory drawing which shows vortex flow when the lift amount of a needle is larger than a critical value (Example) 1). (Example 2) which is the fragmentary sectional view in the specific cross section which shows the principal part of a fuel-injection nozzle. (Example 3) which is the fragmentary sectional view in the specific cross section which shows the principal part of a fuel-injection nozzle. (Example 4) which is the fragmentary sectional view in the specific cross section which shows the principal part of a fuel-injection nozzle. (Example 5) which is the fragmentary sectional view in the specific cross section which shows the principal part of a fuel-injection nozzle.

  Hereinafter, modes for carrying out the invention will be described based on examples.

[Configuration of Example 1]
The configuration of the fuel injection nozzle 1 (hereinafter referred to as nozzle 1) of the first embodiment will be described with reference to the drawings.
The nozzle 1 is opened to inject fuel, and constitutes a fuel injection valve together with an actuator (not shown) that drives the nozzle 1 to open or close. The fuel injection valve is mounted on, for example, an internal combustion engine (not shown), and is used to directly inject high-pressure fuel exceeding 100 MPa into the cylinder.

The actuator drives the valve body by increasing / decreasing the back pressure acting on the valve body (needle 2 described later) of the nozzle 1, for example, and generates magnetism by energizing a coil (not shown). The back pressure is increased or decreased by opening and closing a back pressure chamber (not shown) using force.
The fuel injection valve is, for example, a fuel supply pump (not shown) that discharges the fuel at a high pressure, and a pressure accumulation container (not shown) that accumulates the fuel discharged from the fuel supply pump in a high pressure state. At the same time, an accumulator fuel supply device is constructed, and high-pressure fuel is distributed from the accumulator vessel and injected into the cylinder.

  As shown in FIG. 1, the nozzle 1 includes a cylindrical nozzle body 3 and a needle 2 as a valve body that is accommodated in the inner periphery of the nozzle body 3 so as to be movable in the axial direction. The nozzle 1 starts or stops fuel injection when the needle 2 moves in the axial direction on the inner periphery of the nozzle body 3.

Here, the needle 2 has a sliding shaft portion 2a that is slidably supported in the axial direction by the nozzle body 3, and a conical tip portion 2b that substantially functions as a valve portion. A cylindrical portion 2c that is long in the axial direction is formed between the portion 2a and the tip portion 2b.
The inner periphery of the nozzle body 3 has a cylindrical shape that is long in the axial direction, and the tip is closed. A part of the inner periphery of the nozzle body 3 is locally enlarged in the radial direction to form a fuel reservoir 4 in which fuel to be injected is temporarily stored.

  A region on the axially rear end side of the fuel reservoir 4 in the inner periphery of the nozzle body 3 forms a sliding hole 5 for slidably supporting the sliding shaft portion 2a. The region on the front end side in the direction accommodates the front end portion 2b and the cylindrical portion 2c to form an annular cylindrical fuel passage 6. In addition, a fuel passage 7 for guiding the fuel received from the pressure accumulating vessel to the fuel reservoir 4 is connected to the fuel reservoir 4 separately in the nozzle body 3.

Hereinafter, a characteristic configuration of the nozzle 1 will be described with reference to FIG.
The nozzle 1 includes a seat position 10 and an injection hole 11 as a characteristic configuration, and further, an arrangement relationship when the seat portion 13 is seated at the seat position 10 (when the nozzle 1 is closed). And a first structure that defines the specific relationship and the shape of the inner wall in the vicinity of the tip of the nozzle body 3.

First, the sheet position 10 is a part of the inner wall near the tip of the nozzle body 3, and the sheet portion 13 provided at the tip 2b is detached.
Here, the outer peripheral surface of the front end portion 2b is, for example, one in which three different conical surfaces 14a, 14b, and 14c are coaxially continuous from the front end to the axial rear end side, and the conical surfaces 14a to 14c are the respective buses. The angle formed between the needle 2 and the axis α of the needle 2 increases toward the distal end side. The intersecting line 15a between the conical surfaces 14a and 14b and the intersecting line 15b between the conical surfaces 14b and 14c are circles perpendicular to the axis α, the intersecting line 15b functions as the sheet portion 13, and the sheet position 10 is circular. It is.

  Further, the nozzle hole 11 opens to the inner wall of the nozzle body 3 on the tip end side in the axial direction with respect to the sheet position 10, and the seat portion 13 is separated from the sheet position 10, so that fuel flows from the inner periphery of the nozzle body 3 to the outside. Lead. That is, when the seat portion 13 is separated from the seat position 10, a gap is formed between the seat portion 13 and the seat position 10, and fuel is introduced from the fuel passage 6 into the nozzle hole 11 through this gap. Injected to the outside of the nozzle body 3.

  Further, the specific relationship is that when the seat portion 13 is seated at the seat position 10, the opening 11 a in the inner wall of the injection hole 11 exists on the tip end side in the axial direction with respect to the tip end 2 d in the axial direction of the needle 2. That's it. Therefore, the opening 11a is always present at the front end side in the axial direction from the front end 2d regardless of whether the seat portion 13 is seated at the seat position 10 or away from the seat position 10.

  Further, the first structure defines the relationship between the sheet surface that is the portion including the sheet position 10 and the nozzle hole opening surface that is the portion including the opening 11a in the inner wall near the tip of the nozzle body 3. is there. More specifically, according to the first structure, the sheet surface and the nozzle hole opening surface are defined as follows. First, the sheet surface is provided as a conical surface that is coaxial with the axis β and has a smaller diameter toward the tip end in the axial direction, and the tip is a circle. Further, the nozzle hole opening surface is coaxial with the axis β and has a diameter equal to or less than the diameter of the front end of the sheet surface, or is continuous with the front end side in the axial direction of the cylindrical surface, and the diameter of the cylindrical surface It is a hemispherical surface having the same diameter and forming a convex on the tip side in the axial direction.

More specifically, the inner wall in the vicinity of the tip of the nozzle body 3 has the following conical surface 17, cylindrical surface 18, and hemispherical surface 19, and the inner peripheral tip of the nozzle body 3 is closed in a bag shape.
The conical surface 17 is provided coaxially with the axis β, has a smaller diameter toward the tip in the axial direction, and has a circle 20 at the tip. The conical surface 17 is a seat surface including the seat position 10.

Moreover, the cylindrical surface 18 is provided coaxially with the axis β, has the same diameter as the circle 20, and continues from the circle 20 to the tip side in the axial direction. Further, the hemispherical surface 19 has the same diameter as the cylindrical surface 18 and is continuous with the cylindrical surface 18 so as to form a convex on the tip end side in the axial direction. And the opening 11a in the inner wall of the nozzle hole 11 is provided so that it may straddle the cylindrical surface 18 and the hemispherical surface 19, and the cylindrical surface 18 and the hemispherical surface 19 are the nozzle hole opening surfaces.
In addition, the inner peripheral area | region of the axial direction front end side from the sheet | seat position 10 forms the sac chamber 21, and the injection hole 11 opens to the sac chamber 21 in an injection hole opening surface.

[Effect of Example 1]
The nozzle 1 of Example 1 has the following specific relationship. That is, the specific relationship is an arrangement relationship when the seat portion 13 is seated at the seat position 10, and the opening 11a is present on the tip side in the axial direction with respect to the tip 2d.
Thereby, the influence which the fluid state of the fuel in the sack chamber 21 has on the spray mode can be alleviated, and the variation of the spray mode can be suppressed.

  Here, for the purpose of suppressing fluctuations in the spray mode, when attention is paid to the axial distance (the lift amount of the needle 2) between the seat portion 13 and the seat position 10, the lift amount of the needle 2 includes the suck chamber 21. There is a critical value at which the flow state changes greatly (hereinafter, for convenience of explanation, “down” means that the needle 2 and the nozzle body 3 operate toward the tip side with the tip end side in the axial direction as the lower side. And moving toward the opposite side of the tip side with the side opposite to the tip side as the upper side may be referred to as “raising”.)

  More specifically, when the lift amount is smaller than the critical value, the fuel that has flowed into the sac chamber 21 between the seat portion 13 and the seat position 10 mainly passes along the inner wall of the needle 2. It descends toward the side, then turns and flows toward the outer peripheral side, and further rises along the inner wall forming the sack chamber 21. That is, when the lift amount is smaller than the critical value, the flow state in the sac chamber 21 forms a vortex so as to rise along the inner wall of the nozzle body 3 (see FIG. 3A).

  In contrast, when the lift amount is larger than the critical value, the fuel that has flowed into the sac chamber 21 through between the seat portion 13 and the seat position 10 mainly descends along the inner wall that forms the sac chamber 21. Then, it turns and flows toward the inner peripheral side, and further rises along the wall surface of the needle 2 toward the outer peripheral side. That is, when the lift amount is larger than the critical value, the flow state in the sac chamber 21 forms a vortex so as to descend along the inner wall of the nozzle body 3 (see FIG. 3B).

As a result, when the lift amount is smaller than the critical value, the flow rising in the sac chamber 21 flows into the nozzle hole 11, and when the lift amount is larger than the critical value, the flow descending in the sack chamber 21 enters the nozzle hole 11. Inflow. For this reason, the inflow mode to the nozzle hole 11 changes greatly with the critical value as a boundary, and as a result, the spray mode changes greatly with the critical value as the boundary.
Therefore, as an arrangement relationship when the seat portion 13 is seated at the seat position 10 (that is, when the nozzle 1 is closed), the opening 11a is present on the tip side in the axial direction with respect to the tip 2d. Adopt specific relationships.

By adopting the specific relationship, when the lift amount is smaller than the critical value, the opening 11a can be brought close to the position in the sack chamber 21 where the flow of fuel turns from the flow toward the outer peripheral side to the upward flow. Thereby, the influence which an upflow has on an inflow aspect can be relieved.
That is, as shown in FIG. 3A, in a virtual state where the opening 11a overlaps the tip 2d in the axial direction, the position where the upward flow turns and the opening 11a are far from each other, so the fuel flows as an upward flow. After being prepared, it reaches the opening 11 a and is introduced into the nozzle hole 11. For this reason, it is thought that the influence which an upflow has on an inflow aspect is large.

  On the other hand, by providing the opening 11a closer to the tip end in the axial direction than the tip 2d, the opening 11a is brought closer to the position where it turns to the upward flow. Thus, the fuel can reach the opening 11a and be introduced into the nozzle hole 11 before the flow is sufficiently adjusted as an upward flow. For this reason, the influence which an upflow has on an inflow aspect can be relieved by employ | adopting specific relationship.

Further, by adopting the specific relationship, when the lift amount is larger than the critical value, the opening 11a can be brought close to a position in the sac chamber 21 where the flow of the fuel turns from the downward flow toward the inner peripheral side. Thereby, the influence which a downward flow has on an inflow aspect can be relieved.
That is, as shown in FIG. 3B, in the virtual state where the opening 11a overlaps the tip 2d in the axial direction, the position of turning from the downward flow is far from the opening 11a, so that the fuel flows as a downward flow. Before the disturbance starts, the opening 11a is reached and introduced into the nozzle hole 11. For this reason, it is thought that the influence which a downflow has on an inflow aspect is large.

On the other hand, by providing the opening 11a closer to the tip end side in the axial direction than the tip 2d, the opening 11a is brought closer to the position where it turns from the downward flow. Thereby, after the flow starts to be disturbed as a downward flow, the fuel can reach the opening 11 a and be introduced into the injection hole 11. For this reason, the influence which a downward flow has on an inflow aspect can be relieved by employ | adopting specific relationship.
By the above, since the change of the inflow mode on the boundary of a critical value can be suppressed, as a result, the change of the spray mode on the boundary of a critical value can be suppressed. For this reason, the influence which the flow state of the fuel in the sac chamber 21 has on the spray mode can be mitigated, and the variation of the spray mode can be suppressed.

[Example 2]
As shown in FIG. 4, the nozzle 1 according to the second embodiment is obtained by shortening the most distal end portion 2 e having a conical surface 14 a in the tip portion 2 b in the axial direction as compared with the nozzle 1 according to the first embodiment. That is, the specific relationship of Example 1 was formed by bringing the opening 11a closer to the tip of the sack chamber 21 in the axial direction without shortening the most distal portion 2e in the axial direction as compared with the prior art. The specific relationship of Example 2 is formed by shortening the most distal portion 2e in the axial direction.

Example 3
According to the nozzle 1 of the third embodiment, as shown in FIG. 5, the tip 2b does not have the conical surface 14a (no tip 2e), and the tip of the needle 2 is perpendicular to the axis α. A circular plane 23. The specific relationship of the second embodiment is formed by providing the tip of the needle 2 on the flat surface 23.

Example 4
The nozzle 1 of the fourth embodiment has the same specific relationship as that of the first to third embodiments. In addition, the nozzle 1 of the fourth embodiment includes the following second structure as a structure that defines the shape of the inner wall near the tip of the nozzle body 3.
Here, the second structure defines the relationship between the sheet surface and the nozzle hole opening surface as in the first structure. However, according to the second structure, as shown in FIG. The hole opening surface is a common conical surface 17, and both the sheet position 10 and the opening 11 a exist in the common conical surface 17.

That is, the second structure is such that the seat surface is provided as a conical surface 17 coaxial with the axis β, the diameter is smaller toward the tip end side in the axial direction, and the opening 11a exists in the seat surface.
The most advanced portion 2e is shortened in the axial direction as compared with the nozzle 1 of the first embodiment. Further, a relief 25 by grinding is formed at the tip of the sack chamber 21.

Example 5
The nozzle 1 of the fifth embodiment has the same specific relationship as that of the first to fourth embodiments. Moreover, the nozzle 1 of Example 5 is provided with the following 3rd structure as a structure which prescribes | regulates the shape of the inner wall near the front-end | tip of the nozzle body 3. FIG.
Here, the third structure defines the relationship between the sheet surface and the nozzle hole opening surface as in the first and second structures, but according to the third structure, as shown in FIG. The surface and the nozzle hole opening surface are two different conical surfaces. More specifically, according to the third structure, the sheet surface and the nozzle hole opening surface are defined as follows. That is, according to the third structure, the seat surface is provided as a conical surface coaxial with the axis β, and has a smaller diameter toward the tip end side in the axial direction, and the tip is a circle. Further, the nozzle hole opening surface has an angle formed between the axis β and the generatrix smaller than that of the seat surface, and is provided as a conical surface coaxial with the axis β and has a smaller diameter toward the tip end in the axial direction.

More specifically, the inner wall near the tip of the nozzle body 3 has the following first and second conical surfaces 17a and 17b.
The first and second conical surfaces 17 a and 17 b are coaxial with the axis β of the nozzle body 3, and the first conical surface 17 a has a smaller diameter toward the tip end side in the axial direction, and the tip is a circle 20. Further, the second conical surface 17b is continuous with the tip end side in the axial direction of the circle 20, and the angle formed between the axis β and the generatrix is smaller than that of the first conical surface 17a. The seat position 10 is provided on the first conical surface 17a, and the first conical surface 17a is a seat surface. The opening 11a is provided in the second conical surface 17b, and the second conical surface 17b is a nozzle hole opening surface.
The most advanced portion 2e is shortened in the axial direction as compared with the nozzle 1 of the first embodiment.

[Modification]
The aspect of the nozzle 1 is not limited to an Example, A various modification can be considered. For example, in the nozzle 1 having the second and third structures, a specific relationship may be formed by making the tip of the needle 2 a flat surface 23, and the tip portion 2e is shortened much in the axial direction compared to the conventional one. The specific relationship may be formed by bringing the opening 11a closer to the tip of the sack chamber 21 in the axial direction without doing so.

DESCRIPTION OF SYMBOLS 1 Nozzle (fuel injection nozzle) 2 Needle 2d Tip 3 Nozzle body 10 Sheet position 11 Injection hole 11a Opening 13 Sheet part

Claims (4)

A cylindrical nozzle body (3) and a needle (2) accommodated in the inner periphery of the nozzle body (3) so as to be movable in the axial direction, the needle (2) being the nozzle body ( In the fuel injection nozzle (1) that starts or stops fuel injection by moving in the axial direction on the inner circumference of 3),
A seat position (10) at which a seat portion (13) that is a part of the inner wall of the nozzle body (3) and is provided near the tip of the needle (2) in the axial direction;
The nozzle body (3) is opened to the inner wall of the nozzle body (3) on the front end side in the axial direction from the sheet position (10), and the seat portion (13) is separated from the sheet position (10). Nozzle hole (11) for guiding fuel from the inner periphery to the outside;
The seat portion (13) is in an arrangement relationship when seated at the seat position (10), and the opening (11a) in the inner wall of the nozzle hole (11) is an axial tip of the needle (2). A fuel injection nozzle (1) provided with a specific relationship existing on the tip end side in the axial direction from (2d). The fuel injection nozzle (1) according to claim 1,
Of the inner wall, the sheet surface is a structure that defines the shape of the wall portion where the sheet position (10) and the opening (11a) are present, and is the portion of the wall portion that includes the sheet position (10). Is a conical surface (17) that is coaxial with the axis (β) of the nozzle body (3), has a smaller diameter toward the tip end in the axial direction, has a tip (20), and includes the opening (11a). The nozzle hole opening surface is a cylindrical surface (18) that is coaxial with the axis (β) and has a diameter equal to or smaller than the diameter of the front end of the sheet surface, or the front end side in the axial direction of the cylindrical surface (18). And a fuel injection nozzle (1) having a first structure which is a hemispherical surface (19) having a diameter equal to the diameter of the cylindrical surface (18) and forming a convex on the tip end side in the axial direction. The fuel injection nozzle (1) according to claim 1,
Of the inner wall, the sheet surface is a structure that defines the shape of the wall portion where the sheet position (10) and the opening (11a) are present, and is the portion of the wall portion that includes the sheet position (10). Is provided as a conical surface (17) coaxial with the axis (β) of the nozzle body (3) and has a smaller diameter toward the tip end in the axial direction, and the opening (11a) also has a second structure existing on the seat surface. Fuel injection nozzle (1). The fuel injection nozzle (1) according to claim 1,
Of the inner wall, the sheet surface is a structure that defines the shape of the wall portion where the sheet position (10) and the opening (11a) are present, and is the portion of the wall portion that includes the sheet position (10). Is a conical surface (17a) that is coaxial with the axis (β) of the nozzle body (3), has a smaller diameter toward the tip end in the axial direction, has a tip (20), and includes the opening (11a). The nozzle hole opening surface is provided as a conical surface (17b) having an angle formed between the axis (β) and the generatrix smaller than that of the seat surface and coaxial with the axis (β). A fuel injection nozzle (1) having a third structure having a smaller diameter toward the front end in the direction.

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