JP2809023B2 - Fuel injection valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve.

[0002]

2. Description of the Related Art A fuel hole communicating with a pressure control chamber is opened at the center of the top surface of a needle insertion hole, and a pressure transmitting member for transmitting pressure in the pressure control chamber to the needle top surface is slidably disposed in the fuel hole. An annular back pressure chamber is formed between the top surface of the needle around the pressure transmitting member and the top surface of the needle insertion hole, and the volume of the pressure control chamber filled with fuel is controlled by an actuator to reduce the volume of the pressure control chamber. When it is increased, the needle rises to open the nozzle port, and at this time, the needle top surface contacts the peripheral portion of the needle insertion hole top surface, restricting the maximum lift amount of the needle, and reducing the volume of the pressure control chamber. A fuel injection valve in which the needle is urged in the valve closing direction via the pressure transmitting member when closed to close the nozzle port has already been proposed by the present applicant (Japanese Patent Application No. Hei 4-22290). No. reference).

[0003] In a fuel injection valve in which the opening / closing operation of a needle is controlled by controlling the volume of a pressure control chamber filled with fuel by an actuator, for example, the pressure control chamber is started to start fuel injection. Even if the volume is increased, the fuel pressure in the pressure control chamber drops rapidly because the needle does not immediately rise, so that the needle is urged at a high speed in the valve opening direction. When the needle is urged in the valve opening direction at a high speed, the needle collides with the peripheral edge of the needle insertion hole at a high speed. Will occur. However, when the needle bounces in this way, especially when the injection period is short, the needle closing operation is started while the needle bounces, so the needle closing time is scheduled. Therefore, there is a problem that the fuel injection amount is shifted from the normal fuel injection amount. In order to solve this problem, in the above-described fuel injection valve, the pressure transmitting member is slidably disposed in the fuel hole, and an annular back pressure is formed between the top surface of the needle around the pressure transmitting member and the top surface of the needle insertion hole. A chamber is formed and the back pressure chamber and the pressure control chamber are connected by a throttle passage. When the needle rises, fuel in the back pressure chamber gradually flows into the pressure control chamber via a throttle passage having a relatively large flow path resistance. By doing so, the rising speed of the needle is reduced. Accordingly, the rising speed of the needle at this time becomes proportional to the flow rate of the fuel flowing from the back pressure chamber through the throttle passage into the pressure control chamber.

[0004]

However, when the needle rises or descends as in the above-described fuel injection valve, the fuel in the back pressure chamber gradually flows out through the throttle passage into the pressure control chamber, and as a result, the needle If the ascending or descending speed is made to be proportional to the flow rate of the fuel flowing through the throttle passage, the throttle passage is formed by a minute gap between the pressure transmitting member and the fuel hole. On the other hand, it is difficult to keep this fuel flow constant, and as a result, the rising or lowering speed of the needle cannot be kept constant for each raising or lowering operation of the needle. As described above, if the rising or lowering speed of the needle is different for each raising or lowering operation of the needle, the time during which the needle is opening the nozzle opening will deviate from the normal opening time, so that the fuel injection amount at this time becomes normal. There is a problem that the fuel injection amount is shifted.

[0005]

According to the present invention, a back pressure chamber is formed on the top surface of a needle, and the back pressure chamber is connected to a pressure control chamber. When the volume of the filled 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 periphery of the top surface of the back pressure chamber. The maximum lift amount of the needle is regulated by contacting the part, 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. The annular chamber is formed between the downwardly directed annular surface and the upwardly directed annular surface formed on the inner peripheral surface of the needle insertion hole, and the annular chamber and the fuel reservoir are arranged in parallel with each other. Linked via the circulation can check valve towards.

According to the present invention, in order to solve the above problem, a fuel hole communicating with the pressure control chamber is opened at the center of the top surface of the needle insertion hole to transmit the pressure in the pressure control chamber to the needle top surface. A pressure transmitting member is slidably disposed in the fuel hole to form an annular back pressure chamber between a needle top surface around the pressure transmitting member and a needle insertion hole top surface. When the volume of the pressure control chamber is increased by controlling the volume by the actuator, the needle rises to open the nozzle port, and at this time, the top surface of the needle comes into contact with the peripheral portion of the top surface of the needle insertion hole, so that the maximum of the needle is reached. When the lift amount is regulated and the volume of the pressure control chamber is reduced, the needle is urged in the valve closing direction via the pressure transmitting member to close the nozzle port. A first throttle passage and an annular chamber in which an annular chamber is formed between a downward annular surface formed on the inner surface and an upward annular surface formed on the inner peripheral surface of the needle insertion hole, and the annular chamber and the fuel reservoir are arranged in parallel with each other. And a first check valve that can flow toward the fuel reservoir, and connects the back pressure chamber and the pressure control chamber to the pressure control chamber from the second throttle passage and the back pressure chamber which are arranged in parallel with each other. Through a second check valve that can be circulated.

[0007]

According to the first aspect of the invention, the rising and lowering speeds of the needle are proportional to the pressure difference between the fuel pressure in the fuel reservoir and the fuel pressure in the pressure control chamber. According to the first aspect of the invention, a large negative pressure is temporarily generated in the annular chamber when the needle is raised, so that a downward force acts on the downward annular surface of the needle, so that the rising speed of the needle is reduced. Can be

In the second aspect of the present invention, the rising and lowering speeds of the needle are proportional to the pressure difference between the fuel pressure in the fuel reservoir and the fuel pressure in the pressure control chamber. Claim 2
According to the invention described in (1), in addition to the fact that the rising speed of the needle is decreased due to the negative pressure generated in the annular chamber when the needle is raised, a large negative pressure is temporarily generated in the back pressure chamber when the needle is lowered. An upward force acts on the top surface of the needle, and the lowering speed of the needle is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 denotes a fuel injection valve housing, 2 denotes a nozzle holder having a nozzle orifice 3 at its tip, 4 denotes a needle arranged in the nozzle holder 2, and 5 denotes a housing. A fitted piston holder, 6 is a piston slidably inserted into a piston insertion hole 7 of the piston holder 5, 8 is a piezoelectric element formed of a laminate of disk-shaped piezoelectric element plates, and 9 is a guide for the piezoelectric element 8. And 10 indicate a piezoelectric element holder.

[0010] Piston holder 5 and piezoelectric element holder 1
No. 0 is fixed to a proper position in the housing 1 by a retainer 11 screwed to the housing 1, and the nozzle holder 2
Is fixed at a proper position in the housing 1 by a retainer 12 screwed to the housing 1. A pressure control chamber 13 defined by a lower end surface of the piston 6 is formed in a piston insertion hole 7 formed in the piston holder 5.
A fuel reservoir 16 is formed around the conical pressure receiving surface 15 of the needle 4. The fuel reservoir 16 is connected to the nozzle port 3 on the one hand, and to the fuel supply port 18 via a fuel supply pipe 18a on the other hand.

As shown in FIG. 2, a back pressure chamber 20 is formed on the top surface 19 of the needle 4. A fuel hole 22 extending upward from the center of the top surface 21 of the back pressure chamber 20 is formed,
The back pressure chamber 20 is connected to the pressure control chamber 13 via the fuel hole 22. A cylindrical enlarged head 23 is integrally formed on the top of the needle 4, and the enlarged head 23 is slidably inserted into a needle insertion hole 2 a formed in the nozzle holder 2. Further, the periphery of the top surface 21 of the back pressure chamber 20 is formed of an annular flat surface, and the periphery of the top surface 21 forms a needle lift restriction surface. Therefore, when the needle 4 moves up, the top surface 19 of the needle 4 comes into contact with the needle lift regulating surface 21 to regulate the maximum lift amount of the needle 4.

A downward annular surface 24 is formed on the outer peripheral surface of the enlarged head 23 of the needle 4, and an upward annular surface 25 facing the annular surface 24 of the needle 4 is formed on the inner peripheral surface of the needle insertion hole 2 a. You. Therefore, between the annular surface 24 of the needle 4 and the annular surface 25 of the needle insertion hole 2a, an annular chamber 26 whose volume increases when the needle is raised is formed.

A hollow cylindrical valve member 27 is slidably inserted between the needle 4 and the needle insertion hole 2a located between the fuel reservoir 16 and the annular chamber 26. A pressure receiving surface 28 facing the annular chamber 26 is formed around the top surface of the valve member 27, and a compression spring for urging the valve member 27 upward between the bottom surface of the valve member 27 and the fuel reservoir 16. 29 are arranged. The cross section of the needle 4 surrounded by the valve member 27 has a shape cut in the axial direction along two parallel chords as shown in FIG. A fuel passage 30 is defined between the inner peripheral surfaces. The flow passage area of the fuel passage 30 is larger than the flow passage area of the throttle passage 31 described later, and therefore, the flow passage resistance of the fuel passage 30 is smaller than the flow passage resistance of the throttle passage 31. The fuel passage 30 is communicated on the one hand with the annular chamber 26 and on the other hand with the fuel reservoir 16.

The fuel pressure in the annular chamber 26 causes the valve member 27
When the pressure acting on the pressure receiving surface 28 is smaller than the pressure acting on the bottom surface of the valve member 27 due to the fuel pressure in the fuel reservoir 16 and the compression spring 29, as shown in FIG. When the top surface contacts the annular surface 24 of the needle 4, the fuel passage 30 located on the annular chamber 26 side is formed.
Opening 30a is closed. On the other hand, when the pressure acting on the pressure receiving surface 28 of the valve member 27 by the fuel pressure in the annular chamber 26 becomes larger than the pressure acting on the bottom surface of the valve member 27 by the fuel pressure in the fuel reservoir 16 and the compression spring 29. As shown in FIG. 3B, the valve member 27 is displaced downward relative to the needle 4, thereby opening the opening 30a of the fuel passage 30 located on the annular chamber 26 side. The fuel in the fuel tank 26 can flow into the fuel reservoir 16 through the fuel passage 30. Thus, the valve member 27 functions as a check valve.

On the other hand, an annular gap 31 is formed between the outer peripheral surface of the valve member 27 and the inner peripheral surface of the nozzle holder 2 as shown in FIGS.
And an orifice passage communicating with the annular chamber 26 is formed. Therefore, the fuel reservoir 16 and the annular chamber 26 are connected via the fuel passage 30 and the throttle passage 31 arranged in parallel with each other.

Further, an annular gap 32 is formed between the enlarged head 23 located between the back pressure chamber 20 and the annular chamber 26 and the needle insertion hole 2a, and the gap 32 is formed between the back pressure chamber 20 and the annular chamber 26. Are formed to communicate with the throttle passage. Therefore, a part of the high-pressure fuel supplied into the fuel reservoir 16 via the fuel supply pipe 18a is supplied into the annular chamber 26 via the throttle passage 31, and a part of the fuel supplied into the annular chamber 26 is supplied. The air is supplied into the back pressure chamber 20 and the pressure control chamber 13 through the throttle passage 32.

As shown in FIG. 1, a compression spring 33 is disposed between the bottom surface of the piston 6 and the top surface 19 of the needle 4.
The compression spring 33 urges the needle 4 downward by the spring force, and prevents the needle 4 from accidentally rising and opening the nozzle port 3 particularly when the valve is closed.

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. Even when 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 back pressure chamber 20 sharply decreases.
Therefore, the needle 4 is raised by the fuel pressure applied to the pressure receiving surface 15. As a result, the needle 4 becomes the nozzle port 3
Is opened to start fuel injection.

When the needle 4 starts rising, the annular chamber 26
Increases in volume. While the needle 4 is rising, FIG.
As shown in (A), since the top surface of the valve member 27 is in contact with the annular surface 24 of the needle 4 and closes the opening 30a of the fuel passage 30 located on the annular chamber 26 side, almost no annular chamber 26 is provided. No fuel flows in and the annular chamber 2
Since the volume of 6 increases, a negative pressure is generated in the annular chamber 26. As a result, this negative pressure causes the annular surface 2 of the needle 4 to move.
4, a downward force acts on the needle 4. In addition, the valve member 27
The upward force acts on the pressure receiving surface 28 of the
The top surface is more firmly in contact with the annular surface 24 of the needle 4. As the needle 4 rises, the pressure control chamber 1
3 and the fuel pressure in the back pressure chamber 20 slightly increases, and when the needle 4 rises, the opening 30a is always closed by the valve member 27, so that as the needle 4 rises, the negative pressure in the annular chamber 26 increases. As a result, the valve opening speed of the needle 4 is reduced. Next, as shown in FIG. 2B, the needle 4 comes into contact with the needle lift regulating surface 21 to regulate the lift of the needle 4. However, the rising speed of the needle 4 at this time is slow, and thus the needle lift regulating surface 21 It is possible to prevent rebound from colliding.
As a result, deterioration of the accuracy of the injection amount can be prevented.

When the needle 4 comes into contact with the needle lift restricting surface 21, the fuel in the fuel reservoir 16 gradually flows out into the annular chamber 26 through the throttle passage 31, so that the annular chamber 2
The fuel pressure in 6 becomes substantially equal to the fuel pressure in fuel reservoir 16. At this time, the fuel in the annular chamber 26 is supplied to the enlarged head 2.
The fuel gradually flows into the fuel holes 22 through the three orifices 32 around the three, so that the fuel pressure in the pressure control chamber 13 and the fuel holes 22 becomes substantially equal to the fuel pressure in the annular chamber 26.

On the other hand, when the piezoelectric element 8 is charged with electric charge and the piezoelectric element 8 extends in the axial direction, the piston 6 is lowered, and as a result, the volume of the pressure control chamber 13 is reduced. Even if the volume of the pressure control chamber 13 is reduced, the needle 4 does not immediately descend, so that the fuel pressure in the pressure control chamber 13 and the fuel in the fuel hole 22 increases. As a result, the needle 4 is urged in the valve closing direction, so that the needle 4 starts descending.

When the needle 4 starts descending, the annular chamber 26
The internal fuel is compressed, and the pressure in the annular chamber 26 becomes high. As a result, the downward force acting on the pressure receiving surface 28 of the valve member 27 by the fuel pressure in the annular chamber 26 is directed upward on the bottom surface of the valve member 27 by the fuel pressure in the fuel reservoir 16 and the spring force of the compression spring 29. Fig. 3
As shown in (B), the valve member 27 is displaced downward relative to the needle 4 to open the opening 30a of the fuel passage 30. Therefore, the fuel in the annular chamber 26 flows out into the fuel reservoir 16 through the fuel passage 30 having a small flow path resistance. For this reason, the descending speed of the needle 4 is not proportional to the flow rate of the fuel flowing into the fuel reservoir 16 through the throttle passage 31 having a large flow path resistance as in the above-described conventional fuel injection valve, and Since the pressure becomes proportional to the pressure difference between the fuel pressure and the fuel pressure in the pressure control chamber 13, the descent speed of the needle 4 can be kept constant.

The fuel in the annular chamber 26 flows out into the fuel reservoir 16, and a downward force acting on the pressure receiving surface 28 of the valve member 27 by the fuel pressure in the annular chamber 26 reduces the fuel pressure in the fuel reservoir 16 and the compression spring. When the upward force acting on the bottom surface of the valve member 27 becomes smaller due to the spring force of 29, the top surface of the valve member 27 again contacts the annular surface 24 of the needle 4 to close the opening 30a of the fuel passage 30.

When the needle 4 comes into contact with the valve seat and the fuel injection is stopped, the fuel in the back pressure chamber 20 flows into the annular chamber 26 through the throttle passage 32 around the enlarged head 23, and as a result, The fuel pressure in the pressure chamber 20 is substantially equal to the fuel pressure in the annular chamber 26.

FIGS. 5 and 6 show another embodiment. In this embodiment, the same components as those in the embodiment shown in FIGS. 1 to 4 are denoted by the same reference numerals.

Referring to FIGS. 5 and 6, in this embodiment, a downward annular surface 24 is formed on the outer peripheral surface of the enlarged head 23 of the needle 4, and the annular surface of the needle 4 is formed on the inner peripheral surface of the needle insertion hole 2a. Upward annular surface 25 facing surface 24
Is formed. Therefore, between the annular surface 24 of the needle 4 and the annular surface 25 of the needle insertion hole 2a, an annular chamber 26 whose volume increases when the needle is raised is formed.

A hollow cylindrical first valve member 27 is slidably inserted between the needle 4 and the needle insertion hole 2a located between the fuel reservoir 16 and the annular chamber 26. A pressure receiving surface 28 facing the annular chamber 26 is provided around the top surface of the first valve member 27.
Are formed, and the bottom of the first valve member 27 and the fuel reservoir 1 are formed.
A compression spring 29 for urging the first valve member 27 upward is disposed between the six. The cross section of the needle 4 surrounded by the first valve member 27 has a shape cut in the axial direction along two parallel chords as shown in FIG. A first fuel passage 30 is defined between the inner peripheral surfaces of the one valve member 27. The flow passage area of the first fuel passage 30 is larger than the flow passage area of a first throttle passage 31 which will be described later. Therefore, the flow passage resistance of the first fuel passage 30 is larger than the flow passage resistance of the first throttle passage 31. It is getting smaller. The first fuel passage 30 is communicated on the one hand with the annular chamber 26 and on the other hand with the fuel reservoir 16.

The pressure acting on the pressure receiving surface 28 of the first valve member 27 by the fuel pressure in the annular chamber 26 is higher than the pressure acting on the bottom surface of the first valve member 27 by the fuel pressure in the fuel reservoir 16 and the compression spring 29. 6A, the top surface of the first valve member 27 abuts against the annular surface 24 of the needle 4 to close the opening 30a of the first fuel passage 30 located on the annular chamber 26 side, as shown in FIG. It is closed. on the other hand,
The pressure acting on the pressure receiving surface 28 of the first valve member 27 by the fuel pressure in the annular chamber 26 becomes larger than the pressure acting on the bottom surface of the first valve member 27 by the fuel pressure in the fuel reservoir 16 and the compression spring 29. 6B, the first valve member 27 is displaced downward relative to the needle 4 as shown in FIG.
The opening 30a of the fuel passage 30 is opened, so that the fuel in the annular chamber 26 is supplied to the fuel pool 1 through the first fuel passage 30.
6 can flow. Thus, the first valve member 2
7 acts as a check valve.

As shown in FIGS. 4 to 6, an annular gap 3 is provided between the outer peripheral surface of the first valve member 27 and the inner peripheral surface of the nozzle holder 2.
The gap 31 forms a first throttle passage communicating between the fuel reservoir 16 and the annular chamber 26.
Therefore, the fuel reservoir 16 and the annular chamber 26 are connected via the first fuel passage 30 and the first throttle passage 31 arranged in parallel with each other.

On the other hand, referring to FIGS. 5 and 6, a second valve member 37 is slidably inserted into the fuel hole 22. When the fuel pressure in the pressure control chamber 13 and the fuel hole 22 is increased, the second valve member 37 urges the needle 4 downward by bringing its bottom surface into contact with the top surface 19 of the needle 4, It functions as a pressure transmitting member for transmitting the fuel pressure in the pressure control chamber 13 and the fuel hole 22 to the needle 4. At this time, an annular back pressure chamber 20 is provided between the top surface 19 of the needle 4 around the second valve member 37 and the needle insertion hole 2a.
Is formed.

The back pressure chamber 2 is provided around the bottom surface of the second valve member 34.
0 is formed, and the second valve member 37
A compression spring 39 for urging the second valve member 37 downward is arranged between the top surface of the piston 6 and the bottom surface of the piston 6. Also, the second
A second fuel passage 40 extending from the upper end surface to the lower end surface is formed inside the valve member 37. This second fuel passage 4
The flow passage area of 0 is larger than the flow passage area of the second throttle passage 41 described later, and therefore the flow passage resistance of the second fuel passage 40 is smaller than the flow passage resistance of the second throttle passage 41.
The second fuel passage 40 is communicated on the one hand with the back pressure chamber 20 and on the other hand with the fuel hole 22.

The pressure acting on the pressure receiving surface 38 of the second valve member 37 by the fuel pressure in the back pressure chamber 20 acts on the top surface of the second valve member 37 by the fuel pressure in the fuel hole 22 and the compression spring 39. When the pressure is smaller than the pressure, as shown in FIG.
, The opening 40 a of the second fuel passage 40 located on the back pressure chamber 20 side is closed. On the other hand, the pressure acting on the pressure receiving surface 38 of the second valve member 37 by the fuel pressure in the back pressure chamber 20 is the pressure acting on the top surface of the second valve member 37 by the fuel pressure in the fuel hole 22 and the compression spring 39. When it becomes larger than the second, as shown in FIG.
When the valve member 37 is displaced upward relative to the needle 4, the second fuel passage 4 located on the back pressure chamber 20 side
The opening 40a is opened, so that the fuel in the back pressure chamber 20 can flow into the fuel hole 22 through the second fuel passage 40. As described above, in the present embodiment, the second valve member 37 functions as a pressure transmitting member that transmits the fuel pressure in the pressure control chamber 13 and the fuel hole 22 to the needle 4 and also functions as a check valve.

As shown in FIGS. 5 and 6, an annular gap 41 is formed between the outer peripheral surface of the second valve member 37 and the inner peripheral surface of the piston holder 5, and this gap 41 is formed between the fuel hole 22 and the back pressure. A second throttle passage communicating between the chambers 20 is formed.
Therefore, the fuel hole 22 and the back pressure chamber 20 are connected via the second fuel passage 40 and the second throttle passage 41 arranged in parallel with each other.

An annular gap 32 is provided between the enlarged head 23 located between the back pressure chamber 20 and the annular chamber 26 and the needle insertion hole 2a.
This gap 32 forms a throttle passage that connects the back pressure chamber 20 and the annular chamber 26. Therefore, a part of the high-pressure fuel supplied into the fuel reservoir 16 via the fuel supply pipe 18a is supplied into the annular chamber 26 via the first throttle passage 31, and a part of the fuel supplied into the annular chamber 26 is provided. Is supplied into the back pressure chamber 20 through the throttle passage 32, and a part of the fuel supplied into the back pressure chamber 20 is supplied into the fuel hole 22 and the pressure control chamber 13 through the second throttle passage 41. Is done.

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. 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 rapidly decreases.
Therefore, the needle 4 is raised by the fuel pressure applied to the pressure receiving surface 15. As a result, the needle 4 becomes the nozzle port 3
Is opened to start fuel injection.

When the needle 4 starts to rise, the annular chamber 26
Increases in volume. While the needle 4 is rising, FIG.
As shown in (A), the top surface of the first valve member 27 contacts the annular surface 24 of the needle 4 and the first valve member 27 is located on the annular chamber 26 side.
Since the opening 30a of the fuel passage 30 is closed, almost no fuel flows into the annular chamber 26, and a negative pressure is generated in the annular chamber 26 because the volume of the annular chamber 26 increases as described above. I do. As a result, a downward force acts on the annular surface 24 of the needle 4 due to the negative pressure, and thus a downward force acts on the needle 4. Further, an upward force acts on the pressure receiving surface 28 of the first valve member 27 due to the negative pressure, so that the top surface of the first valve member 27 is more firmly abutted against the annular surface 24 of the needle 4. As a result, when the needle 4 rises, the opening 30a is always closed by the first valve member 27.
The negative pressure in the inside becomes large, so that the valve opening speed of the needle 4 is reduced.

At this time, the fuel in the back pressure chamber 20 is compressed, and the pressure in the back pressure chamber 20 becomes high. As a result, the back pressure chamber 20
The upward force acting on the pressure receiving surface 38 of the second valve member 37 due to the fuel pressure in the inside of the fuel valve 22 increases the fuel pressure in the fuel hole 22 and the compression spring 39.
When the downward force acting on the top surface of the second valve member 37 becomes larger due to the spring force of the second valve member 37, the second valve member 37 moves relative to the needle 4 as shown in FIG. It is displaced upward to open the opening 40a of the second fuel passage 40. Therefore, the fuel in the back pressure chamber 20 flows into the fuel hole 22 through the second fuel passage 40 having a small flow path resistance. For this reason, the rising speed of the needle 4 is limited to the second flow rate having a large flow path resistance as in the above-described conventional fuel injection valve.
The needle is not proportional to the flow rate of the fuel flowing into the fuel hole 22 through the throttle passage 41, but proportional to the pressure difference between the fuel pressure in the fuel reservoir 16 and the fuel pressure in the pressure control chamber 13. 4 can be kept constant.
Note that the fuel in the back pressure chamber 20 flows out into the fuel hole 22, and the fuel pressure in the back pressure chamber 20 causes the pressure receiving surface 3 of the second valve member 37.
When the upward force acting on the second valve member 37 becomes smaller than the downward force acting on the top surface of the second valve member 37 due to the fuel pressure in the fuel hole 22 and the spring force of the compression spring 39, the second force is again applied.
The bottom surface of the valve member 37 contacts the top surface 19 of the needle 4 and the second
The opening 40a of the fuel passage 40 is closed.

Next, as shown in FIG. 5B, the needle 4 comes into contact with the needle lift regulating surface 21 to regulate the lift of the needle 4. However, the rising speed of the needle 4 at this time is slow, and thus the needle lift regulation is performed. Rebound can be prevented from colliding with the surface 21. As a result, deterioration of the accuracy of the injection amount can be prevented.

When the needle 4 comes into contact with the needle lift regulating surface 21, the fuel in the fuel reservoir 16 is removed from the first throttle passage 31.
Through the annular chamber 26 so that the fuel pressure in the annular chamber 26 is substantially equal to the fuel pressure in the fuel reservoir 16. Further, at this time, the fuel in the annular chamber 26 gradually flows out into the fuel hole 22 through the throttle passage 32 and the second throttle passage 41 around the enlarged head 23, and accordingly, the fuel in the pressure control chamber 13 and the fuel hole 22 in the fuel hole 22. The fuel pressure is substantially equal to the fuel pressure in the annular chamber 26.

On the other hand, when the piezoelectric element 8 is charged with electric charge and the piezoelectric element 8 extends in the axial direction, the piston 6 is lowered, and as a result, the volume of the pressure control chamber 13 is reduced. Even if the volume of the pressure control chamber 13 is reduced, the needle 4 does not immediately descend, so that the fuel pressure in the pressure control chamber 13 and the fuel in the fuel hole 22 increases. As a result, the needle 4 is urged in the valve closing direction, so that the needle 4 starts descending.

When the needle 4 starts descending, the back pressure chamber 20
Increases in volume. While the needle 4 is moving down, FIG.
As shown in (B), since the bottom surface of the second valve member 37 contacts the top surface 19 of the needle 4 and closes the opening 40a of the second fuel passage 40 located on the back pressure chamber 20 side, the back pressure is reduced. Room 2
At 0, almost no fuel flows, and a negative pressure is generated in the back pressure chamber 20 because the volume of the back pressure chamber 20 increases as described above. As a result, an upward force acts on the top surface 19 of the needle 4 due to the negative pressure, and thus an upward force acts on the needle 4. In addition, a downward force acts on the pressure receiving surface 38 of the second valve member 37 due to the negative pressure, so that the bottom surface of the second valve member 37 is more firmly contacted with the top surface 19 of the needle 4. As a result, when the needle 4 descends, the opening 40a is always closed by the second valve member 37, so that as the needle 4 descends, the negative pressure in the back pressure chamber 20 increases. Is reduced.

At this time, the fuel in the annular chamber 26 is compressed, and the pressure in the annular chamber 26 becomes high. As a result, the annular chamber 26
The downward force acting on the pressure receiving surface 28 of the first valve member 27 due to the fuel pressure in the internal space, the upward force acting on the bottom surface of the first valve member 27 due to the fuel pressure in the fuel reservoir 16 and the spring force of the compression spring 29. When it becomes larger than FIG.
The first valve member 27 is displaced downward relative to the needle 4 as shown in FIG.
Will be opened. Therefore, the fuel in the annular chamber 26 flows into the fuel reservoir 16 through the first fuel passage 30 having a small flow path resistance. Therefore, the descending speed of the needle 4 is
The fuel pressure in the fuel reservoir 16 and the pressure control chamber 13 are not proportional to the flow rate of the fuel flowing into the fuel reservoir 16 through the first throttle passage 31 having a large flow path resistance as in the conventional fuel injection valve described above. The lowering speed of the needle 4 can be maintained constant because the pressure becomes proportional to the pressure difference between the fuel pressure in the needle 4 and the inner fuel pressure. The fuel in the annular chamber 26 is stored in the fuel pool 1
6, and the downward force acting on the pressure receiving surface 28 of the first valve member 27 by the fuel pressure in the annular chamber 26 is reduced by the fuel pressure in the fuel reservoir 16 and the spring force of the compression spring 29.
When the force acting on the top surface of the valve member 27 becomes smaller than the upward force, the top surface of the first valve member 27 again contacts the annular surface 24 of the needle 4 to close the opening 30a of the first fuel passage 30.

Next, the needle 4 comes into contact with the valve seat and the fuel injection is stopped. However, the needle 4 does not rebound at the valve seat because the descending speed of the needle 4 is low at this time. The phenomenon can be prevented from occurring.

When the needle 4 comes into contact with the valve seat, the fuel holes 22
The fuel in the inside gradually flows into the back pressure chamber 20 through the second throttle passage 41, so that the fuel pressure in the back pressure chamber 20 becomes substantially equal to the fuel pressure in the pressure control chamber 13 and the fuel hole 22.

[0045]

As described above, since the needle moves up and down in proportion to the pressure difference between the fuel pressure in the fuel reservoir and the fuel pressure in the pressure control chamber, the rising and lowering speed of the needle can be kept constant. In addition, during fuel injection, the valve opening speed of the needle is slowed to prevent deterioration of the injection amount accuracy, and when the fuel injection is stopped, the valve closing speed of the needle is slowed to prevent the occurrence of the secondary injection phenomenon.

[Brief description of the 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 portion A of the fuel injection valve similar to FIG. 2;

FIG. 4 is a partial sectional view of the fuel injector taken along line IV-IV in FIG. 2;

FIG. 5 is an enlarged side sectional view of a part of a fuel injection valve showing another embodiment.

FIG. 6 is an enlarged side sectional view of a part of the fuel injection valve similar to FIG. 5;

[Explanation of symbols]

 4 Needle 20 Back pressure chamber 24 Annular surface of needle insertion hole 25 Annular surface of needle 26 Annular chamber 27 Valve member 30 Fuel passage 31 Throttle passage

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-1369 (JP, A) JP-A-60-53660 (JP, A) JP-A-2-125960 (JP, A) JP-A-5-205 231264 (JP, A) Fully open 1982-139666 (JP, U) Fully open 1986-122372 (JP, U) Fully open 1987-20165 (JP, U) Fully open, 3-68559 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 47/00-47/02 F02M 51/00 F02M 51/06 F02M 61/10 F02M 61/20

Claims (2)

(57) [Claims] 1. A back pressure chamber is formed on a top surface of a needle, the back pressure chamber is connected to a pressure control chamber, and a volume of the pressure control chamber filled with fuel is controlled by an actuator to form the pressure control chamber. When the volume is increased, the needle rises to open the nozzle port, and at this time the top surface of the needle comes into contact with the peripheral portion of the top surface of the back pressure chamber to regulate the maximum lift amount of the needle. When the volume is reduced, the needle is urged in the valve closing direction to close the nozzle port. In the fuel injection valve, a downward annular surface formed on the outer peripheral surface of the needle and an upward annular surface formed on the inner peripheral surface of the needle insertion hole. A fuel injection valve in which an annular chamber is formed between the surfaces and the annular chamber and the fuel reservoir are connected via a throttle passage arranged in parallel with each other and a check valve which can flow from the annular chamber toward the fuel reservoir. 2. A fuel hole communicating with the pressure control chamber is opened at the center of the top surface of the needle insertion hole, and a pressure transmitting member for transmitting the pressure in the pressure control chamber to the needle top surface is slidably disposed in the fuel hole. An annular back pressure chamber is formed between the top surface of the needle around the pressure transmitting member and the top surface of the needle insertion hole, and the volume of the pressure control chamber filled with fuel is controlled by an actuator to reduce the volume of the pressure control chamber. When it is increased, the needle rises to open the nozzle port, and at this time, the needle top surface contacts the peripheral portion of the needle insertion hole top surface, restricting the maximum lift amount of the needle, and reducing the volume of the pressure control chamber. When pressed, the needle is urged in the valve closing direction via the pressure transmitting member to close the nozzle port. In the fuel injection valve, a downward annular surface formed on the outer peripheral surface of the needle and the inner periphery of the needle insertion hole are formed. An annular chamber is formed between the upwardly-facing annular surfaces formed on the surface, and the annular chamber and the fuel reservoir are arranged in parallel with a first throttle passage and a first reverse flowable from the annular chamber to the fuel reservoir. A second check passage, which is connected via a stop valve, and connects the back pressure chamber and the pressure control chamber to each other in parallel with each other, and a second check valve that can flow from the back pressure chamber to the pressure control chamber; The fuel injection valve connected via.