JP6299709B2 - Fuel injection nozzle - Google Patents

Description

  The present invention relates to a fuel injection nozzle that injects fuel into a combustion chamber of an engine.

Conventionally, there has been proposed a fuel injection nozzle that includes a nozzle body and a needle, and starts and stops fuel injection by separating and seating the needle with respect to the inner wall of the nozzle body (see, for example, Patent Document 1). ).
By the way, in the case of a large engine having a small surface area relative to the cylinder volume, fuel spray having a strong penetration characteristic is required as a spray characteristic of the fuel injected from the injection hole of the fuel injection nozzle. By strengthening the fuel spray penetration force in this way, the fuel spray reaches farther, so that the air utilization rate in the combustion chamber is increased and a good combustion state is obtained. Therefore, the engine output can be increased.

However, in the case of a small engine having a large surface area with respect to the cylinder volume, there is a problem that when the fuel spray collides with the wall surface of the combustion chamber by the fuel spray having a strong penetration characteristic, the cooling loss increases and the fuel consumption deteriorates.
In order to reduce the cooling loss, it is necessary to weaken the fuel spray penetration force. This makes it difficult for the fuel spray to reach the combustion chamber wall surface and reduces the amount of heat released from the combustion chamber wall surface to the cooling medium. Therefore, engine cooling loss can be reduced.
Therefore, in a small engine, it is desired to realize fuel spray with high dispersion characteristics.
Note that Patent Document 1 discloses that the spray penetration force is increased regardless of the amount of movement of the needle toward the rear end in the axial direction, but does not suggest any of the above requests or problems.

Japanese Patent Laying-Open No. 2015-034486

  The present invention has been made in view of the above problems, and an object of the present invention is to realize fuel spray with high dispersion characteristics in a small engine regardless of the amount of movement of the needle toward the rear end in the axial direction. It is an object of the present invention to provide a fuel injection nozzle that can be used.

According to the first aspect of the present invention, even if the needle moves to the rear end side in the axial direction, the tip part continues to abut against the bottom surface of the sac chamber, and the constricted portion always exists at the same position in the sac chamber. Thus, when the needle is separated from the inner wall of the nozzle body and opened, the fuel that has flowed into the sac chamber flows along the wall surface of the needle and the wall surface of the constricted portion of the tip part. And the fuel peeled from the wall surface of the constricted portion forms a vortex in the sac chamber.
On the other hand, the fuel that flows into the sac chamber and directly reaches the inlet of the nozzle hole takes in a part of the vortex formed in the sack chamber and forms a spiral flow in the nozzle hole. In the spiral flow in the nozzle hole, a component orthogonal to the nozzle axis of each of the plurality of nozzle holes is converted into a motion of expanding the jet at the outlet of the nozzle hole. For this reason, the fuel injected from the injection hole becomes a fuel spray with high dispersion characteristics.
Therefore, in a small engine, fuel spray with high dispersion characteristics can be realized regardless of the amount of movement of the needle toward the rear end side in the axial direction.

It is sectional drawing which showed the principal part of the fuel-injection nozzle (Embodiment 1). It is sectional drawing which showed the principal part of the fuel-injection nozzle (Embodiment 1). It is sectional drawing which showed the principal part of the fuel-injection nozzle (Embodiment 1). FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3 (Embodiment 1). It is explanatory drawing which showed typically the mode of the fuel flow in the sac chamber at the time of the low lift of a needle (Embodiment 1). It is explanatory drawing which showed typically the mode of the fuel flow in the sac chamber at the time of the high lift of a needle (Embodiment 1). It is sectional drawing which showed the principal part of the fuel-injection nozzle (Embodiment 2). FIG. 8 is a VIII-VIII cross-sectional view of FIG. 7 (Embodiment 2). It is sectional drawing which showed the principal part of the fuel-injection nozzle (Embodiment 3).

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.

[Configuration of Embodiment 1]
1 to 6 show Embodiment 1 to which the present invention is applied.

The fuel injection valve of this embodiment is mounted corresponding to each cylinder of a vehicle running engine such as an automobile.
Here, a direct injection diesel engine is employed as the engine.
The fuel injection valve includes a fuel injection nozzle 1 that directly injects fuel into the combustion chamber of the engine. The fuel injection nozzle 1 includes a needle 2 that can reciprocate in the axial direction, and a bottomed cylindrical nozzle body 3 that fits and supports the needle 2 so as to reciprocate.

The fuel injection nozzle 1 of this embodiment is particularly effective for a small engine having a large surface area relative to the cylinder volume. The fuel injection nozzle 1 includes a tip hole 5 opened at the tip surface of the needle 2, a tip component (hereinafter referred to as a guide pin) 6 slidably held on the inner peripheral surface of the tip hole 5, and the guide. A coil spring (hereinafter referred to as a spring) 7 that urges the pin 6 toward the front end in the axial direction is provided.
Details of the tip hole 5, the guide pin 6, and the spring 7 will be described later.

The needle 2 has a sliding portion supported on the sliding end of the nozzle body 3 so as to be reciprocally slidable on the rear end side in the axial direction. In addition, illustration of the sliding part of the needle 2 and the sliding hole of the nozzle body 3 is omitted.
The needle 2 includes an annular seat portion 9 that can be seated on the inner wall of the nozzle body 3. The needle 2 includes a cylindrical main body 11 on the rear end side in the axial direction from the seat portion 9. Further, the needle 2 includes a truncated cone-shaped reduced diameter portion 12 on the distal end side in the axial direction from the seat portion 9.
Further, the urging force of the return spring acts on the needle 2.
The return spring is not shown.

A bottomed cylindrical sack portion 13 is provided on the tip end side in the axial direction of the nozzle body 3. The sack portion 13 is provided with a plurality of nozzle holes 14 and a sac chamber 15.
A seat surface 16 is provided on the inner wall of the nozzle body 3. Further, a fuel flow path 17 is provided between the needle 2 and the nozzle body 3 for introducing high-pressure fuel from a high-pressure generator such as a supply pump or a common rail.

The plurality of nozzle holes 14 are formed at equal intervals in the circumferential direction. These nozzle holes 14 communicate with the inside and outside of the sack portion 13. For example, 6 to 10 nozzle holes 14 are provided.
In the plurality of nozzle holes 14, nozzle hole inlets 21 are opened on the inner wall of the sack portion 13. These injection holes 14 inject fuel from the injection hole outlets 22 into the cylinders of the engine. Each nozzle hole 14 is a straight nozzle hole whose flow path area does not change from the nozzle hole inlet 21 toward the nozzle hole outlet 22. Each nozzle hole 14 is inclined by a predetermined angle downward in the figure with respect to a radial direction perpendicular to an axis (hereinafter referred to as nozzle axis) Y of the nozzle body 3.

The suck chamber 15 is located downstream of the fuel flow path 17. The sac chamber 15 is a distribution chamber in which fuel that flows in an annular shape in the fuel flow path 17 is collected and temporarily stored, and then distributed to the nozzle holes 14 evenly.
The sac chamber 15 has, as inner walls of the sack portion 13, a cylindrical peripheral wall surface 23 centered on the nozzle axis Y and a spherical bottom surface 24 centered on the sack center on the nozzle axis Y. .
The sac chamber 15 is provided with an entrance-side opening at an annular ridge line 25 formed at the downstream end of the seat surface 16.
Further, the inlet diameter of the sack chamber 15 is φds as shown in FIG.

The seat surface 16 has a conical shape in which the inner diameter gradually decreases toward the downstream side. The seat portion 9 of the needle 2 is seated on and off the seat surface 16.
The fuel flow path 17 is formed between the outer peripheral surface of the needle 2 and the inner peripheral surface of the nozzle body 3. The fuel flow path 17 communicates the fuel reservoir chamber of the nozzle body 3 and the nozzle hole 14.
The nozzle body 3 is connected to an actuator that drives the needle 2 to open. As the actuator, a solenoid actuator or a piezo actuator is employed.
The illustration of the actuator is omitted.

The needle 2 opens and closes on the seat surface 16 to open and close the fuel flow path 17.
The sheet portion 9 is formed between the main body portion 11 and the reduced diameter portion 12.
The main body 11 has an outer peripheral surface that forms a fuel flow path 17 between the main body 11 and the nozzle body 3. Further, a conical surface 31 is formed on the outer peripheral surface of the main body 11 on the front end side in the axial direction.
Conical surfaces 32 and 33 are formed on the outer peripheral surface of the reduced diameter portion 12 such that the outer diameter gradually decreases toward the distal end in the axial direction.

The conical surface 31 is set to an inclination angle at which the gap with the seat surface 16 gradually decreases toward the downstream side.
The conical surfaces 32 and 33 are set to an inclination angle at which the gap with the seat surface 16 gradually increases toward the downstream side.
The conical surfaces 31 to 33 are relief surfaces for preventing interference with the seat surface 16 when the seat portion 9 is seated on the seat surface 16.
The conical surface 32 has a steeper inclination angle than the conical surface 31, and is gentler than the conical surface 33.
The conical surfaces 31 to 33 have different inclination angles.
Further, the diameter of the relief portion of the reduced diameter portion 12 of the needle 2 is φdn as shown in FIG. Further, the relief angle θ of the reduced diameter portion 12 of the needle 2 is larger than 90 °. For example, θ = 150 ° to 160 °. The relief angle θ is an inclination angle of the conical surface 33 at the tip of the needle 2.

In the fuel injection nozzle 1, when the seat portion 9 is seated on the seat surface 16, the fuel flow path 17 is blocked. Thereby, fuel injection from the plurality of nozzle holes 14 into the combustion chamber is not performed.
In the fuel injection nozzle 1, the fuel flow path 17 is opened when the seat portion 9 is lifted from the seat surface 16. As a result, fuel is introduced from the fuel flow path 17 to the sac chamber 15. For this reason, fuel is injected from the plurality of nozzle holes 14 into the combustion chamber.
In the fuel injection nozzle 1, the lift amount of the needle 2 changes from the fully closed position to the full lift position throughout the fuel injection period.

[Features of Embodiment 1]
Here, the side on which the needle 2 moves toward the rear end side in the axial direction may be referred to as the upper side, and the side on which the needle 2 moves toward the front end side in the axial direction may be referred to as the lower side.
A tip hole 5 that is recessed toward the rear end side in the axial direction is formed at the tip of the needle 2. The tip hole 5 is a sliding hole through which the axial rear end side of the guide pin 6 slides. A storage chamber 41 is formed in the tip hole 5 to store the spring 7 in a compressed state in the axial direction.
A spring 7 that urges the guide pin 6 toward the distal end in the axial direction is accommodated in the accommodation chamber 41. The spring 7 is set between the bottom surface of the tip hole 5 and the guide pin 6.

The rear end side of the guide pin 6 in the axial direction is held in the front end hole 5 so as to be able to reciprocate.
The guide pin 6 is provided as a separate part from the nozzle body 3. The guide pin 6 has a cylindrical shape and a cross-sectional shape perpendicular to the axial direction is circular. The guide pin 6 is formed in a predetermined shape by cutting a cylindrical metal material. Thereby, the cutting process of a complicated shape is made easy by forming the guide pin 6 with the nozzle body 3 and a separate component.

  The inner wall of the needle 2 has a plurality of fuel passages 42 communicating with the sac chamber 15 and the storage chamber 41 in order to ensure fuel flow between the sac chamber 15 and the storage chamber 41 when the needle 2 moves in the axial direction. Is formed. As a result, the fuel easily enters and exits into the storage chamber 41, and the fuel pressure in the storage chamber 41 and the fuel pressure in the sac chamber 15 are kept equal. Further, the movement of the needle 2 with respect to the guide pin 6 toward the rear end side in the axial direction becomes smooth.

The guide pin 6 is provided on the sliding portion 51 that is in sliding contact with the inner peripheral surface of the tip hole 5, the constricted portion 52 provided on the axially distal end side of the sliding portion 51, and the axially distal end side of the constricted portion 52. A contact portion 53 is provided.
The sliding length α of the sliding portion 51 is larger than the full lift amount of the needle 2 as shown in FIG. That is, the sliding portion 51 is prevented from coming off from the tip of the needle 2.
A cylindrical shaft portion 55 that guides the inner diameter of the spring 7 is provided on the rear end side in the axial direction of the sliding portion 51.

The constricted portion 52 is constricted radially inward from the sliding portion 51. The constricted portion 52 is always present at the same position in the sack chamber 15 even when the needle 2 moves toward the rear end side in the axial direction.
Here, as shown in FIG. 5, when the axial length of the constricted portion 52 is L, and the axial component along the axial direction in the hole diameter of the injection hole inlet 21 is φDy, the relationship of L> φDy is established. Satisfies.

The guide pin 6 has a minimum diameter portion 56 having a minimum cross-sectional area perpendicular to the axial direction in the constricted portion 52. As shown in FIG. 5, the minimum diameter portion 56 is thinner than the sliding diameter φdo of the sliding portion 51.
Further, the guide pin 6 has a maximum diameter portion 57 having a maximum cross-sectional area perpendicular to the axial direction in the contact portion 53. The maximum diameter portion 57 is in contact with the bottom surface 24 below the lower end of the nozzle hole inlet 21.

In the guide pin 6, a concave curved surface from the upper end of the constricted portion 52 to the maximum diameter portion 57 of the contact portion 53 serves as a vortex formation guide 59 that generates a vortex in the fuel flow toward the nozzle hole 14 in the sac chamber 15. The minimum diameter portion 56 is included in the constricted portion 52. Further, the constricted portion 52 includes a projection shape of the nozzle hole inlet 21 formed when the opening cross section of the nozzle hole inlet 21 is projected in the nozzle hole axial direction of each of the plurality of nozzle holes 14.
The contact portion 53 is provided at the tip of the guide pin 6. The contact surface shape of the contact portion 53 is a hemispherical shape corresponding to the bottom surface shape of the bottom surface 24 of the sack chamber 15.
The contact portion 53 is always abutted against the bottom surface 24 of the sack chamber 15 by the urging force of the spring 7. The abutment portion 53 has a larger diameter than both ends of the constricted portion 52 in the axial direction. The wall surface of the contact portion 53 is a concave curved surface that is smoothly connected to the concave curved surface of the constricted portion 52. Further, the curvature of the concave curved surface of the constricted portion 52 is different from the curvature of the concave curved surface of the contact portion 53. Further, the curvature of the concave curved surface of the contact portion 53 may be continuously changed. As the curvature of the concave curved surface is increased, a stronger vertical vortex can be formed in the sac chamber 15.

The reduced diameter portion 12 of the needle 2 has a relief portion for preventing interference with the seat surface 16, the relief portion diameter dn is larger than the inlet diameter ds of the sack chamber 15, and the relief angle is more than 90 °. large.
As a result, the flow of fuel that has passed through the seat portion 9 of the needle 2 from the beginning of fuel injection is separated from the conical surface 32 of the needle 2 at the entrance of the sac chamber 15, and the nozzle holes 14 are formed along the wall surface of the sac chamber 15. To reach. Further, a part of the flow that has passed through the sheet portion 9 flows along the wall surface of the constricted portion 52 and is separated from the wall surface of the constricted portion 52 to form a vortex.

Here, the operation in which the needle 2 moves from the valve closed state in which the seat portion 9 is seated on the seat surface 16 to the rear end side in the axial direction is referred to as lift. Further, the vortex formed in the sac chamber 15 may be referred to as a sac vortex. Moreover, the conical surfaces 32 and 33 of the reduced diameter part 12 may be called a needle surface.
Next, the state of fuel flow in the sac chamber 15 when the lift amount of the needle 2 is low will be described with reference to FIG.
At the time of low lift, the flow rate of the fuel flowing from the fuel flow path 17 into the sac chamber 15 becomes faster than at the time of high lift. Most of the fuel that has flowed into the sac chamber 15 from the fuel flow path 17 is separated from the needle surface at the inlet of the sac chamber 15, and flows along the peripheral wall surface 23 of the sac chamber 15 toward the distal end side in the axial direction of the sac chamber 15. . At this time, since the flow velocity of the fuel flowing into the sac chamber 15 is high, the resistance when separating from the needle surface and flowing into the nozzle hole 14 is large, and along the peripheral wall surface 23 of the sac chamber 15 as compared with the time of high lift. The rate of flowing fuel is reduced.

On the other hand, a part of the fuel that has flowed into the sac chamber 15 from the fuel flow path 17 forms a flow along the vortex formation guide 59 of the guide pin 6, particularly the wall surface of the constricted portion 52. At this time, the constricted portion 52 is always present at the same position in the sack chamber 15.
Then, the fuel is peeled off from the concave curved surface of the contact portion 53 on the downstream side of the constricted portion 52 to form a vertical vortex with a small bend.
Here, such a vortex in the sack is formed even with a fuel injection nozzle having a conventional shape. However, in the fuel injection nozzle 1 of the present embodiment, the presence of the vortex forming guide 59 forms a stronger vortex than the conventional fuel injection nozzle.
Moreover, since the inflow speed into the sac chamber 15 is higher than that in the high lift state and the flow rate along the peripheral wall surface 23 of the sac chamber 15 is small, a stronger vortex is formed.
A part of the vortex formed in the sac chamber 15 flows into the injection hole 14 from the injection hole inlet 21 while being taken into the flow along the peripheral wall surface 23 of the sac chamber 15.

As a result, the fuel passing through each nozzle hole 14 has a spiral shape that combines a velocity component parallel to the nozzle axis of each of the plurality of nozzle holes 14 and two spiral flows rotating within each nozzle hole cross section. Form a flow with velocity vectors. Among these, the two vortex flows rotating within each nozzle hole cross section are derived from the fact that the vortex formed in the sac chamber 15 is taken into the flow along the peripheral wall surface 23 of the sac chamber 15. At this time, since the vortex formed in the sac chamber 15 is strong, the two vortex flows rotating in the cross section of each nozzle hole are stronger than those of the conventional fuel injection nozzle.
Moreover, the component orthogonal to the nozzle hole axis of the spiral flow in each nozzle hole 14 is converted into a motion of expanding the jet at the nozzle hole outlet 22.
Accordingly, the fuel passing through each nozzle hole 14 becomes a jet having a larger velocity component perpendicular to the injection direction than the jet formed by the conventional fuel injection nozzle at the nozzle hole outlet 22. A fuel spray having a large spray angle and a high dispersion characteristic is injected from 14 into the combustion chamber.

Next, the state of the fuel flow in the sac chamber 15 when the lift amount of the needle 2 is high will be described with reference to FIG.
At the time of high lift, the flow rate of the fuel flowing from the fuel flow path 17 into the sac chamber 15 becomes slower than at the time of low lift. At this time, the constricted portion 52 is always present at the same position in the sack chamber 15. Therefore, the fuel is separated from the needle surface at the inlet of the sac chamber 15, and the flow along the peripheral wall surface 23 of the sac chamber 15 and the fuel from the fuel flow path 17 are separated at the lower end of the conical surface 32 of the needle 2. The flow branches along the vortex forming guide 59 of the guide pin 6. At this time, the ratio of the flow that branches is larger in the flow along the peripheral wall surface 23 than in the low lift state.

The fuel flowing along the vortex forming guide 59 of the guide pin 6, particularly the wall surface of the constricted portion 52, peels off from the concave curved surface of the contact portion 53 on the downstream side of the constricted portion 52, thereby generating a vertical vortex with a small bend. Form. In the fuel injection nozzle of the conventional shape, the wall guide that contributes to the vortex formation only exists at the bottom surface of the sac in a high lift state, so the vortex in the sac becomes very weak. On the other hand, in the fuel injection nozzle 1 of the present embodiment, since the vortex formation guide 59 is present in the sac chamber 15, a vortex flow is easily formed in the sac chamber 15 even in a high lift state.
On the other hand, most of the fuel separated from the needle surface at the entrance of the sac chamber 15 flows along the peripheral wall surface 23 of the sac chamber 15 toward the distal end side in the axial direction of the sac chamber 15. Then, the fuel flows into the injection hole 14 from the injection hole inlet 21 while taking in a part of the vortex formed in the sack chamber 15 as in the case of the low lift.
Thereby, the fuel passing through each nozzle hole 14 forms a flow having a spiral velocity vector. Since this spiral flow still has vortex in the sac even in a high lift state, the two vortex flow components rotating in the cross section of the nozzle hole with respect to the conventional fuel injection nozzle become large.
Therefore, the velocity component orthogonal to the injection direction of the fuel that passes through each nozzle hole 14 and increases, the spray angle from each nozzle hole 14 into the combustion chamber is large, and fuel spray with high dispersion characteristics is produced. Be injected.

[Effect of Embodiment 1]
As described above, in the fuel injection nozzle 1 of the present embodiment, the guide pin 6 is slidably held in the tip hole 5 of the needle 2. The contact portion 53 continues to abut against the bottom surface 24 of the sack chamber 15 at all times by the biasing force of the spring 7. The constricted part 52 is always present at the same position in the sack chamber 15.
As a result, the constricted portion 52 of the guide pin 6 is always at the same position regardless of the lift amount of the needle 2, so that a vortex is stably formed. Further, since the volume increase of the sac space during the lift of the needle 2 is smaller than that of the conventional shape, a strong vortex is formed in the small space.

Here, the flow of the vortex flowing along the wall surface of the constricted portion 52, that is, the flow formed outward from the center of the vortex is separated from the wall surface of the constricted portion 52 while reaching the injection hole inlet 21. Such a vortex flow is called a strong vortex.
As a result, the constricted portion 52 is always present at the same position in the sack chamber 15, so that a strong vortex is formed by the constricted portion 52, and the strong vortex can be maintained even if the lift amount of the needle 2 changes. .
Therefore, in a small engine, fuel spray with high dispersion characteristics can be realized regardless of the amount of movement of the needle 2 toward the rear end side in the axial direction.

  Further, the conical surface 33 of the needle 2 and the sliding surface of the guide pin 6 continue smoothly and continuously. As a result, the fuel flow is stably supplied from the inlet of the sac chamber 15 and there is no point at which it suddenly separates from the conical surface 33 of the needle 2 or the sliding surface of the guide pin 6. It is possible to suppress variations in fuel spray for each. Moreover, the fuel spray dispersion | variation for every nozzle hole 14 can also be suppressed.

  The sliding length α of the sliding portion 51 of the guide pin 6 is larger than the full lift amount of the needle 2. Thus, the tip of the needle 2 is always on the sliding surface of the guide pin 6 during the fuel injection period. Accordingly, the fuel flow is stably supplied from the inlet of the sac chamber 15 and there is no point at which the needle 2 suddenly peels off from the conical surface 33 of the needle 2 or the sliding surface of the sliding portion 51 of the guide pin 6. The fuel spray variation for each injection of 1 can be suppressed. Moreover, the fuel spray dispersion | variation for every nozzle hole 14 can also be suppressed.

[Configuration of Embodiment 2]
7 and 8 show Embodiment 2 to which the present invention is applied. Here, the same reference numerals as those in the first embodiment indicate the same configuration or function, and a description thereof will be omitted.

In order to ensure the fuel flow between the sac chamber 15 and the storage chamber 41 when the needle 2 moves in the axial direction, the sac chamber 15 and the storage chamber 41 are communicated with the outer periphery of the sliding portion 51 of the present embodiment. A plurality of fuel passages 43 are formed.
As described above, the fuel injection nozzle 1 of the present embodiment has the same effects as those of the first embodiment.

[Configuration of Embodiment 3]
FIG. 9 shows a third embodiment to which the present invention is applied. Here, the same reference numerals as those in Embodiments 1 and 2 indicate the same configuration or function, and the description thereof will be omitted.

The guide pin 6 of this embodiment has a coupling portion 54 on the tip end side in the axial direction of the contact portion 53. The coupling portion 54 is provided at the tip of the guide pin 6.
In addition, the sack portion 13 is formed with a fitting hole 63 that opens at the bottom surface 24 of the sack chamber 15 and is recessed toward the tip end side in the axial direction.
The coupling portion 54 is press-fitted and fitted into the fitting hole 63. As a result, the guide pin 6 is fixed to the bottom surface 24 of the sack chamber 15.
The guide pin 6 is connected to the nozzle body 3 after the guide pin 6 is cut. Further, the spring 7 is not necessary.
As described above, the fuel injection nozzle 1 of the present embodiment has the same effects as those of the first and second embodiments.

[Modification]
In the present embodiment, an example in which the present invention is applied to the fuel injection nozzle 1 that directly injects high-pressure fuel introduced from a supply pump or a common rail into the combustion chamber of the engine has been described. Fuel is pumped into the fuel reservoir chamber from a fuel injection pump such as a distributed fuel pump. When the fuel pressure in the fuel reservoir chamber exceeds the urging force of the return spring, the needle opens and the direct injection engine You may apply to the fuel-injection nozzle injected directly into a combustion chamber.

In this embodiment, the example in which the present invention is applied to the fuel injection nozzle 1 of the type in which the needle 2 lifts from the fully closed position to the full lift position at the time of fuel injection has been described. When the injection quantity is smaller than the predetermined value, the needle 2 is lifted from the fully closed position to the low lift position, and when the required injection quantity of the engine is larger than the predetermined value, the needle 2 is lifted from the fully closed position. You may apply to the fuel injection nozzle of the lift amount variable type which the needle 2 lifts to a position. Alternatively, the present invention may be applied to a lift amount variable fuel injection nozzle in which the maximum lift amount changes during the fuel injection period.
Even in the case of the fuel injection nozzle 1 in which the needle 2 is lifted from the fully closed position to the full lift position, if the energization time for the actuator is short, the actuator moves from the fully closed position to the full lift position toward the rear end in the axial direction. However, the needle 2 may be lifted only to the low lift position.

Further, as an actuator for opening the needle 2 of the fuel injection nozzle 1, a piezo actuator for adjusting the fuel pressure in the control chamber provided immediately above the needle and controlling the opening / closing operation of the needle 2 may be employed. Further, a solenoid valve for adjusting the fuel pressure in the control chamber and controlling the opening / closing operation of the needle 2 may be employed.
Further, as an actuator for driving the needle 2 of the fuel injection nozzle 1 to open, the needle 2 is directly opened by a driving force of a solenoid actuator or a piezoelectric actuator, and is closed by a biasing force of a return spring. Also good.
In this embodiment, a direct injection diesel engine is employed as the direct injection engine, but a direct injection gasoline engine may be employed as the direct injection engine.
The present invention is not limited to the above-described embodiment, and can be implemented with various modifications.

DESCRIPTION OF SYMBOLS 1 Fuel injection nozzle 2 Needle 3 Nozzle body 5 Tip hole 6 Guide pin (tip component)
7 Spring
13 Suck part 14 Injection hole 15 Suck chamber

Claims (5)

A cylindrical nozzle body (3) having a nozzle hole (14) and a sac chamber (15) in which an inlet (21) of the nozzle hole is opened at the tip;
A needle (2) accommodated in the nozzle body so as to be movable in the axial direction,
In the fuel injection nozzle (1) that starts and stops fuel injection by the needle being detached from and seating on the inner wall (16) of the nozzle body and moving in the axial direction,
A hole (5) provided in the tip (12) of the needle and recessed in the axial rear end;
A tip part (6) that is slidably held on the inner peripheral surface of the hole and protrudes into the sac chamber;
The tip part is provided on a sliding portion (51) slidably in contact with the inner peripheral surface of the hole, and on the tip end side in the axial direction of the sliding portion, and is bound radially inward from the sliding portion. It has a constricted part (52),
Even if the needle moves in the axial direction, the tip part continues to abut against the bottom surface (24) of the sac chamber, and the constricted part is always present at the same position in the sac chamber. Fuel injection nozzle. The fuel injection nozzle according to claim 1,
A spring (7) housed in the hole and biasing the tip part toward the tip side in the axial direction;
The tip component is disposed such that the tip end side in the axial direction protrudes into the sac chamber, and the rear end side in the axial direction is slidably held in the hole.
The tip (53) of the tip part is abutted against the bottom surface of the sac chamber by the biasing force of the spring. The fuel injection nozzle according to claim 1,
The tip component is disposed such that the tip end side in the axial direction protrudes into the sac chamber, and the rear end side in the axial direction is slidably held in the hole.
The fuel injection nozzle according to claim 1, wherein a tip (54) of the tip part is fixed to a bottom surface of the sack chamber. The fuel injection nozzle according to any one of claims 1 to 3,
The axial length of the constricted portion is L,
When the axial component along the axial direction in the hole diameter at the inlet of the nozzle hole is φDy,
A fuel injection nozzle characterized by satisfying a relationship of L> φDy. The fuel injection nozzle according to any one of claims 1 to 4,
The tip part has a minimum diameter part (56) in which the cross-sectional area perpendicular to the axial direction is the smallest in the constricted part,
The constricted part including the minimum diameter part includes a projected shape of the inlet of the nozzle hole formed when an opening cross section of the inlet of the nozzle hole is projected in the direction of the nozzle axis of each of the plurality of nozzle holes. A fuel injection nozzle characterized by that.

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