JPH05231264A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To prevent the occurrence of secondary injection phenomenon by a method wherein a fuel pressure in a pressure control chamber is decreased through reduction of the volume of the pressure control chamber to lower a needle, and during the stop of injection of fuel, the closing speed of the needle. CONSTITUTION:A slide member 23 is integrally formed on the top surface of a needle 4, and the slide member 23 is slidably inserted in a fuel hole 22 through which a back pressure chamber 20 is communicated to a pressure control chamber 13. When a piezoelectric element 8 is contracted to raise a piston 6 and a fuel pressure in a pressure control chamber 13 is reduced and the needle 4 is raised, a fuel pressure in an annular chamber 24 formed around the slide member 23 is increased and the increase speed of the needle 4 is reduced. On the contrary, when the piezoelectric element 8 is expanded to increase a fuel pressure in the pressure control chamber 13 and the needle 4 is lowered, a negative pressure is generated in the annular chamber 24 around the slide member 23, resulting in reduction of the opening speed of the needle 4. Thus, secondary injection phenomenon is prevented from occurring.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel injection valve.

[0002]

2. Description of the Related Art A back pressure chamber is formed on the top surface of a needle, and the central portion of the top surface of the back pressure chamber, which faces the top surface of the needle, is connected to a pressure control chamber through a fuel hole and filled with fuel. When the volume of the pressure control chamber is controlled by an actuator to increase the volume of the pressure control chamber, the needle rises to open the nozzle port, and at this time, the top surface of the needle is the peripheral portion of the back pressure chamber top surface. There is known a fuel injection valve that abuts against the needle to regulate the maximum lift amount of the needle, and when the volume of the pressure control chamber is reduced, the needle is urged in the valve closing direction to close the nozzle port. 60-1369
(See the official gazette).

In this fuel injection valve, when the volume of the pressure control chamber is increased and the fuel pressure acting on the top surface of the needle is decreased, the needle rises, and as a result, the needle opens the nozzle opening, so that fuel injection is performed. Be started. Then, when the volume of the pressure control chamber is decreased, the fuel pressure acting on the top surface of the needle, that is, the fuel pressure in the back pressure chamber is increased. As a result, the needle urges in the valve closing direction to close the nozzle port, and thus the fuel injection is stopped.

[0004]

By the way, in this fuel injection valve, the needle does not immediately descend even if the volume of the pressure control chamber is reduced in order to stop the fuel injection, so that the fuel pressure in the back pressure chamber suddenly increases. Rise to. As a result, the fuel pressure in the back pressure chamber becomes high, so that the needle is urged at a high speed in the valve closing direction. However, when the needle is biased at a high speed in the valve closing direction in this way, the needle collides with the valve seat at a high speed, so that the reaction force of the collision action causes the needle to close and then open again. Unfavorable,
A so-called secondary injection phenomenon will occur.

[0005]

In order to solve the above problems, according to the present invention, a back pressure chamber is formed on the top surface of the needle and the top surface of the back pressure chamber facing the top surface of the needle is formed. The central part is connected to the pressure control chamber through the fuel hole, and when the volume of the pressure control chamber filled with fuel is controlled by the actuator and the volume of the pressure control chamber is increased, the needle rises and the nozzle port is opened. At the same time as opening, the top surface of the needle abuts the peripheral edge of the top surface of the back pressure chamber to regulate the maximum lift amount of the needle, and when the volume of the pressure control chamber is reduced, the needle is biased in the valve closing direction. In the fuel injection valve that closes the nozzle opening by being slidably inserted into the fuel hole, at least when the needle descends, a sliding member that is integrally connected to the center of the top surface of the needle and descends together with the needle is slidably inserted. Sliding part And so as to form an annular chamber which is separated from the pressure control chamber by a sliding member between the needle top surface peripheral portion and the back pressure chamber top surface perimeter around.

Further, according to the present invention, in order to solve the above problems, the sliding member is fixed to the center of the top surface of the needle. Further, according to the present invention, in order to solve the above problems, the cross-sectional area of the fuel hole located between the pressure control chamber and the sliding member is made smaller than the cross-sectional area of the fuel hole portion on which the sliding member slides. There is.

Further, according to the present invention, in order to solve the above-mentioned problems, the sliding member is formed separately from the needle, and the sliding member is constantly pressed against the central portion of the top surface of the piston by the spring force to slide. A throttle passage extending from the upper end surface to the lower end surface of the sliding member is formed in the member.

[0008]

According to the first aspect of the invention, when the volume of the pressure control chamber is reduced and the fuel pressure in the pressure control chamber rises, the needle descends. At this time, since a large negative pressure is temporarily generated in the annular chamber around the sliding member, an upward force acts on the needle due to this negative pressure, and thus the descending speed of the needle is reduced.

According to the second aspect of the invention as well, when the needle descends, a large negative pressure is temporarily generated in the annular chamber around the sliding member, so that the descending speed of the needle is reduced. Further, in the invention according to claim 2, when the fuel pressure in the pressure control chamber is lowered and the needle is raised, a large positive pressure is temporarily generated in the annular chamber around the sliding member, whereby the rising speed of the needle is increased. Is reduced.

Also in the invention according to claim 3, when the needle descends, a large negative pressure is temporarily generated in the annular chamber around the sliding member, so that the descending speed of the needle is reduced. Further, in the invention of claim 3, since the cross-sectional area of the fuel hole located between the pressure control chamber and the sliding member is smaller than the cross-sectional area of the fuel hole portion where the sliding member is located, the fuel pressure in the pressure control chamber is When the fuel flows at a high speed in the fuel hole portion with a small cross-sectional area when it rises, and the fuel pressure in the fuel hole portion where the sliding member is located does not reduce the cross-sectional area due to the inertia of the fuel at this time, It will be higher than that. This stabilizes the time when the needle starts descending.

According to the fourth aspect of the invention, when the volume of the pressure control chamber is reduced and the fuel pressure in the pressure control chamber rises, the needle descends with the sliding member pressed against the needle top surface. Therefore, also in the invention described in claim 4, when the needle descends, a large negative pressure is temporarily generated in the annular chamber around the sliding member, so that the descending speed of the needle is reduced. Further, in the invention according to claim 4, when the fuel pressure in the pressure control chamber is reduced, the sliding member is separated from the needle top surface, and the fuel in the annular chamber around the sliding member passes through the throttle passage formed in the sliding member. Through the fuel holes. The outflow velocity at this time changes depending on the cross-sectional area of the throttle passage, and when the cross-sectional area of the throttle passage is large, the outflow velocity is high, so the fuel pressure in the annular chamber immediately decreases and the needle rapidly rises. When the cross-sectional area of the throttle passage is small, the outflow velocity is slow, so the fuel pressure in the annular chamber slowly drops and the needle rises at a relatively low speed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is a fuel injection valve housing, 2 is a nozzle holder having a nozzle port 3 at its tip, 4 is a needle arranged in the nozzle holder 2, and 5 is a housing fitted in the housing 1. The attached piston holder, 6 is a piston slidably inserted in the piston insertion hole 7 of the piston holder 5, 8 is a piezoelectric element made of a laminated body of disk-shaped piezoelectric element plates, and 9 is a guide for the piezoelectric element 8. Sleeves 10 for indicating the piezoelectric element holders, respectively.

Piston holder 5 and piezoelectric element holder 1
0 is fixed to a regular position in the housing 1 by a retainer 11 screwed to the housing 1, and the nozzle holder 2
Is fixed to a regular position in the housing 1 by a retainer 12 screwed to the housing 1. A pressure control chamber 13 defined by the lower end surface of the piston 6 is formed in the piston insertion hole 7 formed in the piston holder 5, and a plate for pressing the piston 6 upward is formed in the pressure control chamber 13. The spring 14 is inserted.

On the other hand, a fuel reservoir 16 is formed around the conical pressure receiving surface 15 of the needle 4. This fuel pool 16
Is connected to the nozzle port 3 on the one hand and to the fuel supply port 18 on the other hand. As shown in FIGS. 1 and 2 (A), a back pressure chamber 20 is formed on the top surface 19 of the needle 4, and a fuel hole 22 extending upward is formed in the central portion of the top surface 21 of the back pressure chamber 20. It is formed. The fuel hole 22 is formed in the pressure control chamber 1
Connected within 3. Further, the peripheral portion of the top surface 21 of the back pressure chamber 20 is formed of an annular flat surface. Needle 4
A cylindrical sliding member 23 is integrally formed on the top surface 19 of the sliding member 23, and the sliding member 23 is slidably inserted into the fuel hole 22. Therefore, the back pressure chamber 20 around the sliding member 23
An annular chamber 24 is formed between the periphery of the top surface 21 of the needle 4 and the periphery of the top surface 19 of the needle 4.

On the other hand, an annular gap 25 is formed between the enlarged portion of the needle 4 located between the fuel reservoir 16 and the annular chamber 24 and the nozzle holder 2, and this gap 25 is formed between the fuel reservoir 16 and the annular chamber 24. Forming a throttle passage communicating with the peripheral portion of the top surface of the. Therefore, a part of the high-pressure fuel supplied from the fuel supply port 18 into the fuel reservoir 16 is partially discharged into the throttle passage 25.
Is supplied into the annular chamber 24 via. The pressure control chamber 13 and the fuel hole 22 are also filled with high-pressure fuel.

When the electric charge charged in the piezoelectric element 8 is discharged and the piezoelectric element 8 contracts in the axial direction, the piston 6 is raised as shown in FIG. 2 (B). Even if the piston 6 is raised, the needle 4 does not immediately rise, and at this time, the fuel pressure in the pressure control chamber 13 and the fuel hole 22 sharply drops. Therefore, when the fuel pressure in the pressure control chamber 13 decreases, the fuel pressure applied to the top surface of the sliding member 23 immediately decreases. When the fuel pressure applied to the top surface of the sliding member 23 decreases, the needle 4 is raised by the fuel pressure applied to the pressure receiving surface 15, and as a result, the needle 4 opens the nozzle port 3 to start fuel injection.

When the needle 4 rises, the fuel inside the annular chamber 24 is compressed and the inside of the annular chamber 24 becomes high pressure. As a result, when the needle 4 moves up, the fuel in the annular chamber 24 exerts a downward force on the needle 4. Next, the fuel in the annular chamber 24 flows into the fuel hole 22 through the gap between the sliding member 23 and the fuel hole 22, and the needle 4 rises accordingly. Therefore, the ascending speed of the needle 4 is reduced. Next, the needle 4 comes into contact with the top surface of the annular chamber 24 that regulates the maximum lift amount of the needle 4 as shown in FIG. 2B, but the speed of the needle 4 at this time is low,
Thus, the needle 4 is prevented from hitting and bouncing against the top surface of the annular chamber 24.

On the other hand, when the piezoelectric element 8 is charged with electric charge and the piezoelectric element 8 expands in the axial direction, the piston 6 is lowered as shown in FIG. 2 (A), and as a result, the volume of the pressure control chamber 13 decreases. Be punished. Even if the volume of the pressure control chamber 13 is reduced, the needle 4 does not immediately descend,
Thus, the fuel pressure in the pressure control chamber 13 and the fuel hole 22 increases. As a result, the needle 4 is biased in the valve closing direction,
Thus, the needle 4 starts descending.

When the needle 4 starts descending, the annular chamber 24
Greatly increases the volume of. While the needle 4 is descending, almost no fuel flows into the annular chamber 24, and as described above, the volume of the annular chamber 24 greatly increases, so that the inside of the annular chamber 24 becomes a negative pressure. As a result, this negative pressure exerts an upward force on the needle 4. The fuel pressure in the pressure control chamber 13 and the fuel hole 22 slightly decreases as the needle 4 descends, and the negative pressure in the annular chamber 24 increases as the needle 4 descends, so that the valve closing speed of the needle 4 decreases. Be done. As a result, the speed at which the needle 4 comes into contact with the valve seat becomes slower, so that the needle 4 does not bounce at the valve seat, and thus it is possible to prevent the secondary injection phenomenon from occurring.

When the needle 4 abuts on the valve seat and the fuel injection is stopped, the fuel in the fuel hole 22 gradually flows out into the annular chamber 24 through the periphery of the outer peripheral surface of the sliding member 23. The fuel pressure in the pressure control chamber 13 and the fuel hole 22 becomes substantially equal to the fuel pressure in the annular chamber 24. FIG. 3 shows another embodiment. 3 (A) shows the time when the piston 6 is lowered, and FIG. 3 (B) shows the time when the piston 6 is raised.

In this embodiment, the sliding member 23 is the needle 4
The sliding member 23 is always pressed against the central portion of the top surface of the needle 4 by the spring force of the compression spring 26 inserted in the fuel hole 22. In this embodiment, when the piston 6 descends, the sliding member 23 descends integrally with the needle 4, so that a large negative pressure is generated in the annular chamber 24, and thus the descending speed of the needle 4 is reduced. .. On the other hand, when the piston 6 moves up, the movement of the sliding member 23 varies depending on the strength of the spring force of the compression spring 26.

That is, when the spring force of the compression spring 26 is strong, the slider 23 continues to be pressed against the top surface of the needle 23 even if the piston 6 rises from the state shown in FIG. Next, when the needle 23 moves up, the sliding member 23 moves up accordingly. On the other hand, when the spring force of the compression spring 26 is weak, when the piston 6 rises from the state shown in FIG. 3A, the sliding member 23 also rises accordingly, and then the needle 4 rises.

FIG. 4 shows another embodiment. Note that FIG.
4A shows the time when the piston 6 is lowered, and FIG. 4B shows the time when the piston 6 is raised. In this embodiment, as in the embodiment shown in FIGS. 1 and 2, the sliding member 23 is integrally formed on the top surface of the needle 4, so basically the needle 4 is shown in FIGS. 1 and 2. The same movement as in the embodiment is performed. That is, FIG.
When the piston 6 is raised from the state shown in (A), when the needle 4 starts to rise, the fuel pressure in the annular chamber 24 rises, so that the rising speed of the needle 4 is reduced, and FIG. When the piston 6 is lowered from the state shown, while the needle 4 is descending, the annular chamber 2
Since a large negative pressure is generated in the needle 4, the descending speed of the needle 4 is reduced.

However, in this embodiment, the pressure control chamber 1
3 and the sliding member 23, the diameter of the fuel hole portion 22a located between the sliding member 23 and the sliding member 23 is smaller than the diameter of the fuel hole portion 22b on which the sliding member 23 slides.
The throttle passage 22 between the fuel hole portion 22b on which the sliding member 3 slides.
a is provided, and the operation of the needle 4 is slightly different from the operation of the needle 4 shown in FIGS. 1 and 2 due to the provision of the throttle passage 22a.

That is, the pressure control chamber 13 and the fuel hole portion 2
When two chambers such as 2b are connected by a conduit such as the throttle passage 22a, when the pressure in one chamber is increased, the pressure in each chamber oscillates and gradually reaches an equilibrium state. That is, when the pressure in one room is increased, the fuel in this room flows at a high speed in the pipeline, and the pressure in the other room becomes a pressure at the equilibrium state due to the inertia of the fuel flowing in the pipeline. Will also be temporarily higher. In other words, when two rooms are connected by a pipeline, the pressure in one room is increased when the pressure in the other room is not provided, that is, when the two rooms are directly connected. Can be high. Therefore, when the throttle passage 22a as shown in FIG. 4 is provided, when the piston 6 descends from the state shown in FIG. 4 (B), the fuel pressure in the fuel hole portion 22b is reduced by the throttle passage 22b.
In comparison with the case where the throttle passage 22b is not provided, the needle 4 is biased with a large force in the valve closing direction as compared with the case where the throttle passage 22b is not provided.

The force for urging the needle 4 in the valve closing direction is determined by the pressure difference between the fuel pressure in the fuel hole portion 22b and the fuel pressure in the fuel pool 16, and the fuel pressure in the fuel pool 16 is the fuel pressure. Although it is pulsating due to the pressure wave generated by the injection action, when the fuel pressure in the fuel hole portion 22b is increased, the urging force of the needle 4 in the valve closing direction is increased by the amount by which the fuel pressure is increased. Will not be affected by.
As a result, the time from the expansion of the piezoelectric element 8 to the stop of the fuel injection is always constant, and thus a good injection amount adjustment accuracy can be obtained. In addition,
In this case, the descending speed of the needle 4 in the initial stage of descending becomes faster, but when the needle 4 descends, a large negative pressure is generated in the annular chamber 24, so that the collision speed of the needle 4 with respect to the valve seat is reduced, thus Rebound of the needle 4 at the valve seat is suppressed. Therefore, even if the urging force of the needle 4 in the valve closing direction is increased, the needle 4 does not bounce from the valve seat, thus preventing generation of secondary injection while ensuring good injection amount adjustment accuracy. You will be able to

FIG. 5 and FIG. 6 show still another embodiment.
Note that FIG. 5 shows the entire fuel injection valve, and FIG.
Indicates that the piston 6 has descended.
(B) shows that the piston 6 has risen. In this embodiment, the sliding member 23 is formed separately from the needle 4, and the sliding member 23 has a hollow cylindrical shape. The sliding member 23 is constantly pressed against the central portion of the top surface of the needle 4 by the spring force of the compression spring 26 arranged in the fuel hole 22, and the sliding member 23 defines the annular chamber 24. A pin 27 is fixed on the top surface 19 of the needle 4 to prevent the lower end of the compression spring 26 from falling off the top of the sliding member 23.
As shown in FIG. 6 (A), the sliding member 23 has a small diameter portion at its lower portion, and an annular pressure receiving surface 28 is formed at the upper end of this small diameter portion.

When the electric charge charged in the piezoelectric element 8 is discharged and the piezoelectric element 8 contracts in the axial direction, the piston 6 is raised as shown in FIG. 6 (B). Even if the piston 6 is raised, the needle 4 does not immediately rise, so that at this time, the fuel pressure in the pressure control chamber 13 and the fuel hole 22 drops sharply and becomes considerably lower than the fuel pressure in the annular chamber 24. As a result, the sliding member 23 is immediately raised by the fuel pressure in the annular chamber 24 acting on the pressure receiving surface 28 of the sliding member 23, that is, the sliding member 23 is immediately separated from the top surface 19 of the needle 4, and As a result, the fuel pressure in the annular chamber 24 also drops sharply. Therefore, when the fuel pressure in the pressure control chamber 13 decreases, the fuel pressure applied to the entire top surface 19 of the needle 4 immediately decreases.

When the fuel pressure applied to the top surface 19 of the needle 4 is lowered, the needle 4 is raised by the fuel pressure applied to the pressure receiving surface 15, and as a result, the needle 4 opens the nozzle port 3 to start fuel injection. .. When the needle 4 rises, the fuel pressure in the pressure control chamber 13 and the fuel hole 22 slightly rises, and when the fuel pressure in the annular chamber 24 becomes higher than the fuel pressure in the pressure control chamber 13 and the fuel hole 22 at this time, the sliding occurs. Since the moving member 23 moves away from the top surface 19 of the needle 4, the fuel pressure in the annular chamber 24 is maintained at a pressure substantially equal to the fuel pressure in the pressure control chamber 13 and the fuel hole 22 while the needle 4 is rising. .. That is, in this embodiment, when the needle 4 rises, the pressure acting on the top surface 19 of the needle 4 becomes almost equal to that when the sliding member 23 is not provided, and thus the needle 4 is rapidly raised. become. Next, as shown in FIG. 6B, the needle 4 comes into contact with the peripheral portion of the top surface 21 of the back pressure chamber 20 that regulates the maximum lift amount of the needle 4 and stops.

On the other hand, when the piezoelectric element 8 is charged with electric charge and the piezoelectric element 8 expands in the axial direction, the piston 6 is lowered as shown in FIG. 6 (A), and as a result, the volume of the pressure control chamber 13 decreases. Be punished. Even if the volume of the pressure control chamber 13 is reduced, the needle 4 does not immediately descend,
Thus, the fuel pressure in the pressure control chamber 13 and the fuel hole 22 increases. At this time, the sliding member 23 strongly presses against the top surface 19 of the needle 4 by the fuel pressure applied to the top surface of the sliding member 23. Further, the increased fuel pressure acts on the needle top surface 19 through the circular hole 29 formed at the center of the sliding member 23. As a result, the needle 4 is biased in the valve closing direction, and thus the needle 4 starts descending.

When the needle 4 starts descending, the annular chamber 24
Greatly increases the volume of. While the needle 4 is descending, the sliding member 23 continues to be strongly pressed against the top surface 19 of the needle 4, so that almost no fuel flows into the annular chamber 24. Since the volume greatly increases, the inside of the annular chamber 24 becomes a negative pressure. As a result, this negative pressure exerts an upward force on the needle 4.
The fuel pressure in the pressure control chamber 13 and the fuel hole 22 slightly decreases as the needle 4 descends, and the negative pressure in the annular chamber 24 increases as the needle 4 descends, so that the valve closing speed of the needle 4 decreases. Be done. As a result, the speed at which the needle 4 comes into contact with the valve seat becomes slower, so that the needle 4 does not bounce at the valve seat, thus
It is possible to prevent the next injection phenomenon from occurring.

When the needle 4 comes into contact with the valve seat and the fuel injection is stopped, the fuel in the pressure control chamber 13 and the fuel hole 22 gradually flows into the annular chamber 24 around the outer peripheral surface of the sliding member 23. Therefore, the fuel pressure in the pressure control chamber 13 and the fuel hole 22 becomes substantially equal to the fuel pressure in the annular chamber 24. FIG. 7 shows another embodiment of the sliding member 23. In this embodiment, the sliding member 23 is formed of a hollow cylindrical body having a uniform sectional shape over its entire length. Even if the sliding member 23 having such a shape is used, the fuel pressure in the annular chamber 24 considerably acts between the sliding member 23 and the top surface 19 of the needle 4, so that the fuel pressure in the pressure control chamber 13 decreases. At times, the sliding member 23 separates from the top surface of the needle 4, and thus the reduced fuel pressure acts on the entire top surface 19 of the needle 4.

FIG. 8 shows still another embodiment of the sliding member 23. In this embodiment, a small diameter portion is also formed above the sliding member 23, and the compression spring 2 is formed by this small diameter portion.
The lower end of 6 is prevented from falling off. Therefore, in this embodiment, it is not necessary to provide the pin 27 as shown in FIGS. FIG. 9 shows still another embodiment. Note that FIG.
9A shows the piston 6 lowered, and FIG. 9B shows the piston 6 raised.

In this embodiment, as in the embodiment shown in FIGS. 5 and 6, the sliding member 23 is formed separately from the needle 4, and the circular hole 29 is formed in the sliding member 23. In the embodiment, unlike the embodiment shown in FIGS. 5 and 6, the throttle passage 30 is formed in the circular hole 29. Even if such a throttle passage 30 is provided, when the piston 6 descends from the state shown in FIG. 9B, the sliding member 23 is pressed against the top surface 19 of the needle 4, so that the annular chamber 24 has A large negative pressure is generated, so that the descending speed of the needle 4 is reduced. Therefore, the operation of the needle 4 when the needle 4 descends is the same as that of the embodiment shown in FIGS. 5 and 6.

However, when the throttle passage 30 is provided in the circular hole 29, the operation of the needle 4 when the needle 4 rises is slightly different from the embodiment shown in FIGS. 5 and 6. That is,
When the piston 6 rises and the fuel pressure in the pressure control chamber 13 decreases, the fuel pressure in the circular hole 29 below the throttle passage 30, which is still high, causes the sliding member 23 to move the needle 4
Away from the top surface 19 of the throttle passage 30 and thus the fuel in the circular hole 29 below the throttle passage 30 and the fuel in the annular chamber 24
And starts to flow into the fuel hole 22 through. However, in this case, the throttling passage 30 causes the throttling passage 3 to move.
The fuel pressure in the lower circular hole 29 and the fuel pressure in the annular chamber 24, that is, the fuel pressure acting on the entire top surface of the needle 4, decreases relatively slowly, and thus the rising speed of the needle 4 decreases. Will be In this case, the rising speed of the needle 4 can be arbitrarily changed by changing the cross-sectional area of the throttle passage 30. Therefore, in this embodiment, not only the rising speed of the needle 4 can be slowed to prevent the rebound of the needle 4, but also the rising of the fuel injection rate at the time of opening the fuel injection can be arbitrarily changed by changing the cross-sectional area of the throttle passage 30. Can be changed.

FIG. 10 shows another embodiment of the sliding member 23 of FIG. It should be noted that FIG. 10A shows the piston 6 lowered, and FIG. 10B shows the piston 6 raised. In this embodiment, a conical pressure receiving surface 28 is formed at the lower end of the outer peripheral surface of the sliding member 23. Therefore, when the fuel pressure in the pressure control chamber 6 decreases, the sliding member 23 causes the sliding member 23 to move by the fuel pressure in the pressure receiving surface 28 in addition to the fuel pressure in the circular hole 29 below the throttle passage 30.
Away from the top of. The other operation of the needle 4 is the same as that of the embodiment shown in FIG.

[0037]

EFFECTS OF THE INVENTION When the fuel injection is stopped, the needle closing speed can be slowed to prevent the secondary injection phenomenon from occurring.

[Brief description of drawings]

FIG. 1 is a side sectional view of a fuel injection valve.

FIG. 2 is an enlarged side sectional view of a portion A of the fuel injection valve shown in FIG.

FIG. 3 is an enlarged side sectional view of a part of a fuel injection valve showing another embodiment.

FIG. 4 is an enlarged side sectional view of a part of a fuel injection valve showing still another embodiment.

FIG. 5 is a side sectional view showing still another embodiment of the fuel injection valve.

6 is an enlarged side sectional view of a portion A of the fuel injection valve shown in FIG.

FIG. 7 is an enlarged side sectional view of a part of the fuel injection valve showing still another embodiment.

FIG. 8 is an enlarged side sectional view of a part of the fuel injection valve showing still another embodiment.

FIG. 9 is an enlarged side sectional view of a part of the fuel injection valve showing still another embodiment.

FIG. 10 is an enlarged side sectional view of a part of the fuel injection valve showing still another embodiment.

[Explanation of symbols]

 4 ... Needle 6 ... Piston 8 ... Piezoelectric element 13 ... Pressure control chamber 20 ... Back pressure chamber 22 ... Fuel hole 23 ... Sliding member 24 ... Annular chamber

Claims (4)

[Claims] 1. A back pressure chamber is formed on the top surface of a needle, and a central portion of the top surface of the back pressure chamber facing the top surface of the needle is connected to a pressure control chamber via a fuel hole and filled with fuel. When the volume of the pressure control chamber is controlled by an actuator to increase the volume of the pressure control chamber, the needle rises to open the nozzle port, and at this time, the top surface of the needle is the peripheral portion of the back pressure chamber top surface. When the maximum lift amount of the needle is abutted against the fuel injection valve and the volume of the pressure control chamber is reduced, the needle is biased in the valve closing direction to close the nozzle opening. A sliding member, which is integrally connected to the central portion of the top surface of the needle and descends together with the needle, is slidably inserted into the fuel hole, and the peripheral portion of the needle top surface around the sliding member and the back pressure chamber top surface. Between the peripheral parts A fuel injection valve configured to form an annular chamber separated from a pressure control chamber by a moving member. 2. The fuel injection valve according to claim 1, wherein the sliding member is fixed to the central portion of the top surface of the needle. 3. The fuel according to claim 1, wherein a cross-sectional area of the fuel hole located between the pressure control chamber and the sliding member is smaller than a cross-sectional area of a fuel hole portion on which the sliding member slides. Injection valve. 4. The sliding member is formed separately from the needle, and the sliding member is constantly pressed against the central portion of the top surface of the piston by a spring force so that the sliding member has an upper end surface in the sliding member. The fuel injection valve according to claim 1, wherein a throttle passage extending from the bottom to the bottom surface is formed.