JP2002364483A - Fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably hold a valve element of a control valve at an intermediate position to gradually and stably control the lift of a needle, in a constitution for controlling, by one control valve, two control chambers where fuel pressure in a direction closing the valve acts on the needle. SOLUTION: First and second pistons 21, 22 cooperated with the needle 1, and the first and second control chambers 50, 51 are disposed. In a valve chamber 31 of the control valve 3, a low pressure opening 33, and first and second openings 54a, 55a communicating with the first and second control chambers 50, 51 are disposed, so that the low pressure opening 33 communicates with the first opening 54a at a first lift position of the valve element 52 and the low pressure opening 33 communicates with the first and second openings 54a, 55a at a second lift position. A movable member 71 is brought into contact with the valve element 52 to support the valve element at the first lift position, and opens the second opening 55a when the movable member moves integrally with the valve element up to the second lift position, thereby the lift can be stably controlled and fuel pressure can be controlled with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device used in a fuel injection system of a diesel engine and capable of injecting fuel stepwise.

[0002]

2. Description of the Related Art Conventionally, reduction of harmful substances (NOx, HC, black smoke, etc.) in exhaust gas has been a major problem in a fuel injection system of a diesel engine. Further, high output and low fuel consumption are required. Therefore, a fuel injection device capable of changing the injection rate according to the operating conditions of the engine is required. As such a fuel injection valve,
For example, a control chamber that applies back pressure to a needle that opens and closes an injection hole, and a control valve that controls communication between the control chamber and the low-pressure passage are provided, and the opening area of the control valve is changed to increase or decrease the fuel pressure in the control chamber. Thus, a fuel injection device that lifts a needle stepwise is known (for example, US Pat.
No. 94903).

However, in the above conventional fuel injection device,
Since the fuel pressure in the control chamber changes depending on the opening area of the control valve, fuel properties, fuel temperature, and the like, it is difficult to stably control the needle. In order to improve this, there are fuel injectors that control the opening and closing independently by arranging control valves at the outlet and inlet of the control room, respectively. Problems arise.

In view of the above, a first and second control chambers for applying a fuel pressure are provided on upper surfaces of first and second pistons cooperating with a needle, and the fuel pressure is controlled by one control valve. Injection devices are being considered. For example, a first opening communicating with the first control chamber, a second opening communicating with the second control chamber, and a low-pressure opening communicating with the low-pressure fuel passage are provided in a valve chamber of the control valve. The second control chamber is communicated with the high-pressure fuel passage so that the valve body is connected to the low-pressure opening or the second pressure chamber.
The opening is opened and closed. When the valve body closes the low pressure opening, the first and second control chambers are at high pressure and the needle is closed. When the valve body closes the low pressure opening, the first and second control chambers are at high pressure and the needle is closed.

When the valve body closes the second opening, the second
Control room remains high pressure, but the low pressure opening and the first
The opening is opened and the pressure in the first control chamber becomes low. Thus, the needle lifts until the first piston abuts the second piston. On the other hand, when the valve body is lifted to the intermediate position to open both the low-pressure opening and the second opening, the first and second control chambers become low-pressure, and the first piston comes into contact with the second piston in the needle. Thereafter, the lift is further lifted together with the second piston. In this way, the needle can be lifted stepwise.

[0006]

However, in the fuel injection device having the above structure, it is not easy to stably hold the valve element of the control valve at the intermediate position. For this reason, the lift of the needle may become unstable, and the fuel injection amount may vary.

Accordingly, an object of the present invention is to provide a configuration in which two control chambers for applying a fuel pressure in a valve closing direction to a needle are controlled by one control valve, and the valve element of the control valve is stably held at an intermediate position. An object of the present invention is to provide a fuel injection device capable of controlling the fuel injection amount with high accuracy by controlling the needle lift stepwise and stably.

[0008]

According to a first aspect of the present invention, there is provided a fuel injection device comprising a needle for opening and closing an injection hole by sliding in a valve body, and a first piston cooperating with the needle in an axial direction. A first control chamber and a second control chamber for applying a fuel pressure in the valve closing direction of the needle to the first piston and the second piston, respectively;
A first chamber that communicates with the first control chamber is provided in a valve chamber that houses the valve body.
An opening, a second opening communicating with the second control chamber, and a control valve provided with a low-pressure opening communicating with the low-pressure fuel passage are provided.

The valve element of the control valve is lifted in a stepwise manner by a driving means to switch a communication state between the first opening and the second opening and the low-pressure opening.
The needle is lifted stepwise by changing the fuel pressure in the first control chamber and the second control chamber. Further, the movable member provided in the valve chamber abuts on the first lift position of the valve body when the valve body is lifted by the driving means, and the valve body is larger than the first lift position. It moves integrally with the valve body until it moves to the second lift position.

In the above configuration, when the valve is lifted to the first lift position by the driving means, the movable member contacts and supports the valve at this position.
When the valve is further driven by the driving means, the movable member moves together with the valve, and the valve is lifted to the second lift position. Thus, by the movable member,
Since the valve body can be stably held at the first lift position, the controllability of the fuel pressure in the first and second control chambers is improved, and the lift of the needle is controlled stepwise and stably. Thus, a desired injection rate can be achieved.

Preferably, as the movable member moves integrally with the valve body, the first member moves.
The communication state between the opening or the second opening and the valve chamber is switched. Thereby, the first or second control chamber and the valve chamber can be easily communicated or disconnected according to the lift of the valve body, and the configuration can be made compact.

According to the third aspect of the present invention, the first control room includes:
The second control chamber is provided above the second piston between the first piston and the second piston that move up and down integrally with the needle. The control valve communicates the first opening with the low-pressure opening when the valve body is at the first lift position, and the first opening part when the valve body is at the second lift position. And the second opening communicates with the low-pressure opening.

In the above structure, when the valve body is lifted to the first lift position, the first opening communicates with the low-pressure opening, so that the pressure in the first control chamber decreases, and the first piston moves. Can be lifted together with the needle. When the valve body is lifted to the second lift position,
Since the first and second openings communicate with the low-pressure opening, the pressures in the first and second control chambers decrease, and both the first and second pistons can be lifted. Therefore, the needle can be lifted stepwise in cooperation with the first and second pistons.

According to a fourth aspect of the present invention, in addition to the configuration of the third aspect, the movable member cuts off communication between the second opening and the valve chamber at an initial position, and moves integrally with the valve body. Accordingly, the second opening and the valve chamber communicate with each other.

At this time, up to the first lift position, the movable member cuts off the communication between the second opening and the valve chamber, so that the second control chamber does not communicate with the low-pressure fuel passage and the pressure decreases. do not do. When the valve body is at the second lift position, the second opening is opened with the movement of the movable member, so that the pressure in the second control chamber becomes low and the second piston can be lifted. Therefore, the pressure in the second control chamber can be easily controlled according to the lift of the valve body.

According to a fifth aspect of the present invention, in the configuration of the fourth aspect, the movable member partitions the valve chamber into a first chamber accommodating the valve element and a second chamber communicating with the high-pressure fuel passage. are doing. The movable member is provided with a passage that communicates the first chamber and the second chamber and that is interrupted by contact with the valve body.

In the above configuration, since the second chamber communicates with the high-pressure fuel passage, the valve element closes the low-pressure opening,
When the first opening is opened, high-pressure fuel can be supplied to the first control chamber via the passage and the first chamber. When the valve body lifts to the first lift position and opens the low-pressure opening, the high-pressure fuel flows out of the high-pressure fuel passage to the low-pressure opening because the valve abuts on the movable member and closes the passage. Absent.

Alternatively, as in the sixth aspect of the present invention, the movable member includes a first valve housing in which the valve body is accommodated.
A configuration may be adopted in which the chamber is divided into a chamber and a second chamber communicating with the low-pressure fuel passage, and the above-described passage of claim 5 is not provided. In this case, the first control chamber communicates with the high-pressure fuel passage,
High-pressure fuel can be supplied to the first control chamber.

Further, as in the invention of claim 7, the movable member may divide the valve chamber into a first chamber in which the valve body is accommodated and a second chamber communicating with the low-pressure fuel passage. Good. In this case, a similar effect can be obtained by providing the movable member with a passage that communicates the first chamber with the high-pressure fuel passage and that is disconnected by contact with the valve body.

Further, the movable member has a passage communicating between the valve chamber and the high-pressure fuel passage, the communication being interrupted by contact with the valve body. The valve member provided between the second opening and the second control chamber may be opened as the movable member moves integrally with the valve body.

According to a ninth aspect of the present invention, in the above construction, the second control chamber communicates with a high-pressure fuel passage. Specifically, it is preferable that the second control chamber is always in communication with the high-pressure fuel passage, and the second opening communicating with the valve chamber is opened and closed by the valve body or the movable member.

According to a tenth aspect of the present invention, there is provided a spring member for urging the movable member toward the valve body. By appropriately adjusting the set load of the spring member, the valve body is securely held at the first lift position, and is quickly moved to the second lift position to accurately perform variable control of the needle. Can be.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. Here, the present invention is applied to a diesel engine common rail fuel injection system, and FIG. 1 shows a schematic configuration of an injector 1 as a fuel injection device for injecting high pressure fuel supplied from a common rail into each cylinder of the engine. Show. In FIG.
The injector 1 has a first piston 21 and a second piston 22 slidably disposed in the first housing 10,
A first control room 50 and a second control room 51 are provided in contact with the respective upper surfaces, and the first and second control rooms 50 and 5 are provided.
1, the fuel pressure is controlled, the needle 2 slidably disposed in the valve body 13 below the fuel pressure is variably lifted, and the injection rate can be arbitrarily set.

The fuel pressure in the first control chamber 50 and the second control chamber 51 is controlled by the control valve 3 provided in the second housing 11.
It is controlled by opening and closing by the piezoelectric element 4. The second housing 11 is disposed above the first housing 10 with a plate 39 interposed therebetween, and the valve body 13 is provided below the first housing 10 with the chip packing 14 interposed therebetween. These first and second housings 10, 11,
The retaining nut 12 is mounted on the outer periphery of the plate 39, the tip packing 14, and the valve body 13 and fastened to each other in an oil-tight manner. The details of the configuration of each unit will be described below.

A high-pressure fuel passage 60 extends in the injector 1 in the up-down direction.
1 is open to the upper side wall and communicates with a common rail (not shown). The lower end of the high-pressure fuel passage 60 has a plate 39,
The first housing 10 passes through the inside of the tip packing 14 and communicates with the fuel reservoir 16 provided in the valve body 13.
The fuel reservoir 16 is formed around an intermediate portion of the small-diameter needle 2, and applies an upward (valve-opening) fuel pressure to the needle 2. When the formed injection hole 13a is opened,
High-pressure fuel supplied to the fuel pool 16 from the common rail is injected.

A tip packing 1 is provided on the upper surface of the needle 2.
A rod 23 accommodated in the inside 4 is in contact, and a needle spring 15 disposed around the first piston 21 urges the needle 2 downward (to close the valve) via the rod 23. The lower end surface of the first piston 21 is in contact with the upper end surface of the rod 23 serving as a spring holder, and a first control chamber 50 is formed between the upper end surface of the first piston 21 and the lower end surface of the second piston 22. I have. The second control room 51
It is formed between the upper end surface of the second piston 22 and the lower end surface of the plate 30. The first and second control chambers 50 and 51 apply a downward (pressure closing direction of the needle 2) fuel pressure to the first and second pistons 21 and 22.

The piezoelectric element 4 housed in the second housing 11 has a well-known structure, and is formed by alternately laminating piezoelectric layers and electrode layers, and the magnitude of the voltage applied by a signal from an external control device. Displaced in the axial direction accordingly. Since the upper end of the piezoelectric element 4 is defined by the second housing 11, the displacement of the piezoelectric element 4 is transmitted to the large-diameter piston 41 which is in contact with the lower end surface and displaced downward. Large diameter piston 4
1 is set so as to be urged upward by a disc spring 43 disposed in a hydraulic chamber 42 therebelow to follow the expansion and contraction of the piezoelectric element 4. The hydraulic chamber 42 is formed between the large-diameter piston 41 and the small-diameter piston 44 and
(Cross-sectional area AH1) is converted to hydraulic pressure and the small-diameter piston 4
4 (cross-sectional area AH2), and the transmission magnification is AH1 / AH2.

The amount of upward movement of the small-diameter piston 44 is regulated by a stopper 45, and the small-diameter piston 44
A spring 46 is disposed around the small diameter portion 47 in the lower half, and urges the small diameter piston 44 upward. The spill chamber 48 in which the spring 46 is disposed is connected to the lower end of a low-pressure fuel passage 63 extending vertically in the second housing 11, and the upper end of the low-pressure fuel passage 63 is connected to the upper side wall of the second housing 11. It is open and communicates with a fuel tank (not shown).

As shown in FIG. 2, the control valve 3 is formed at an abutting portion between the second housing 11 and the plate 39, and the movable member 7
1, a valve chamber 31 partitioned into an upper chamber 31a as a first chamber and a lower chamber 31b as a second chamber, and an upper chamber 3 of the valve chamber 31.
1 a, which has a hemispherical valve body 32 driven by a small-diameter piston 44. Upper chamber 3 of valve chamber 31
The first chamber 1a and the lower chamber 31b communicate with each other by a passage 73 penetrating through the center of the movable member 71, and the upper chamber 31a communicates with the first control passage 64 via a first communication passage 64 connected to a first opening 64a opened to the side wall. It is always in communication with the room 50. In addition, a second communication passage 65 communicating with the second control chamber 51 is connected to a second opening 65a provided in an upper side wall of the lower chamber 31b. The lower chamber 31b and the second control chamber 51 communicate with the high-pressure fuel passage 60 through orifice passages 61 and 66, respectively.

At the center of the top surface of the upper chamber 31a, a low-pressure opening 33 which is opened and closed by a valve 32 is opened. The low-pressure opening 33 communicates with a low-pressure fuel passage 63 through a spill chamber 48. The small-diameter piston 44 has the tip of the small-diameter portion 47 abutting on the valve body 32 through the low-pressure opening 33 and the piezoelectric element 4.
In the illustrated state where no current is supplied to the valve body 32, the valve body 32 closes the low-pressure opening 33.

The movable member 71 has a T-shaped cross section and is inserted into a lower chamber 31b having a larger diameter than the upper chamber 31a, and is urged upward by a spring 72 which is a spring member disposed in the lower chamber 31b. The upper chamber 31a and the lower chamber 3
1b is in contact with the step surface 74 of the connection portion. In this state, the upper side surface of the movable member 71 is
The second opening 65a leading to the second control room 5 is closed.
The communication between 1 and the valve chamber 31 is shut off.

Therefore, in the initial state in which the valve body 32 closes the low-pressure opening 33, the first control chamber 50 connects the orifice passage 61 to the lower chamber 31b, the passage 73, and the upper chamber 31a.
The pressure is increased by the high-pressure fuel introduced through the first opening 64a and the first communication passage 64. The second control room 5
1 also has a high pressure due to the high-pressure fuel introduced from the orifice passage 61 because the second opening 65a is closed. Needle 2 includes first and second pistons 2
The fuel pressure of the first and second control chambers 50 and 51 acting downward via the first and second 22, and the urging force of the needle spring 15 lowers (see FIG. 1), and the injection hole 13a is closed.

When the piezoelectric element 4 is energized and extended, the valve element 32 is pushed down by the small-diameter piston 44, the low-pressure opening 33 is opened, and the fuel in the valve chamber 31 is discharged.
After that, the fuel is discharged to the low-pressure fuel passage 63. Here, the lift position of the valve body 32 is in contact with the movable member 71 and the passage 73.
And a second lift (full lift) position where the movable member 71 is further pushed down to open the second opening 65a.

When the valve body 32 is lifted to the first lift position, the flat bottom surface of the valve body 32 comes into contact with the movable member 71 and closes the passage 73 as shown in FIG. As a result, communication between the upper chamber 31a and the lower chamber 31b is cut off, and the low-pressure opening 33 is opened, so that the first control chamber communicating with the upper chamber 31a via the first opening 64a and the first communication passage 64. 50 becomes low pressure. Since the movable member 71 is at the same initial position as in FIG. 2, the second communication path 65 remains closed, and the pressure in the second control chamber 51 is high. Accordingly, the total force for urging the needle 2 in the valve closing direction becomes lower than the fuel pressure in the fuel pool 16 acting in the valve opening direction, and the needle 2 starts lifting together with the first piston 21, and the first piston 21 lifts.
When the upper end surface of the piston 21 contacts the lower end surface of the second piston 22, the lift stops (first lift h1, see FIG. 1).

Next, when the voltage applied to the piezoelectric element 4 is increased, the valve body 32 moves against the movable stopper 7 against the spring 72.
1 is depressed and moves downward integrally. Valve body 32
When lifted to the lift position, the second opening 65a reaching the second control chamber 51 is opened, as shown in FIG. Thus, the second control chamber 51 communicates with the low-pressure opening 33 via the second communication passage 65 and the upper chamber 31a, and the pressure is reduced. The first control chamber 50 includes a first opening 64 as in FIG.
a, which communicates with the upper chamber 31a via the first communication passage 64, and has a low pressure. Therefore, as the first piston 21 pushes up the second piston 22 after the first piston 21 comes into contact with the second piston 22, the needle 2 further continues to lift, and the upper end surface of the needle 2 faces the tip. It stops when it comes into contact with the lower end surface of the packing 14 (second lift h2, see FIG. 1).

Next, the operation of the injector 1 having the above configuration will be described with reference to FIG. When an engine control device (not shown) calculates the fuel injection rate according to the engine operating conditions, the lift amount of the needle 2 and the piezoelectric element
Is set, and electric charges are supplied to the piezoelectric element 4 from the driving power supply.

As shown in FIG. 5A, when the lift amount of the needle 2 is set to the first lift h1, the driving voltage of the piezoelectric element 4 is set to V1, and the piezoelectric element 4 is driven so as to give a small displacement. In FIG. 1, as the piezoelectric element 4 expands, the large-diameter piston 41 descends against the disc spring 43 and pressurizes the fuel in the hydraulic chamber 42. When the fuel pressure in the hydraulic chamber 42 rises, the small-diameter piston 44 descends against the spring 46, and the valve body 32
To open the low-pressure opening 33. As shown in FIG. 3, the valve body 32 is lifted to the first lift position where it comes into contact with the movable member 71 (lift amount H1).

Here, since the spring force of the spring 72 for urging the movable member 71 upward is set to be larger than the force applied to the valve body 32 due to the extension of the piezoelectric element 4, the movable member 71 is at the initial position. . That is, the valve element 32 is supported by the movable member 71 and stops at the first lift position. Valve room 33
The low pressure opening 33 and the first opening 64 a reaching the first control chamber 50 are open, and the second opening 65 a reaching the second control chamber 51 is closed by the movable member 71. The first control chamber 50 is connected to the low-pressure fuel passage 6 through the valve chamber 33.
Pressure of the first control chamber 50 (PC1) to communicate with 3
When the force acting downward on the needle 2 falls below the force acting upward, the needle 2 starts lifting and fuel is injected from the injection hole 13a.

The needle 2 pushes up the first piston 21 via the rod 23 and lifts up integrally. However, since the pressure (PC2) in the second control chamber 51 remains high, the lift amount of the needle 2 becomes h1. Then, the first piston 21 comes into contact with the second piston 22, and the lift stops. At this time, the force in the injection hole closing direction that the needle 2 receives due to the fuel pressure in the second control chamber 51 is greater than the force pushing up the needle 2, and the needle 2 does not lift to the first lift h1 or more.

As shown in FIG. 5B, when the lift amount of the needle 2 is set to the second lift h2 (> hV1), the drive voltage of the piezoelectric element 4 is set to V2 (> V1) so that a large displacement is applied. The piezoelectric element 4 is driven. When the large-diameter piston 41 descends against the disc spring 43 in accordance with the extension of the piezoelectric element 4, the fuel in the hydraulic chamber 42 is pressurized to increase the fuel pressure. Under the fuel pressure, the small-diameter piston 44
6, the valve body 32 is lifted. As a result, similarly to FIG. 5A, as the pressure (PC1) in the first control chamber 50 decreases, the needle 2 lifts together with the first piston 21 and fuel is injected from the injection hole 13a.

The valve body 32 is moved to the first lift position (lift amount H
When lifted to 1), the movable member 71 comes into contact with the movable member 71 and temporarily stops. However, when the force applied to the valve body 32 by the extension of the piezoelectric element 4 exceeds the spring force of the spring 72, the movable member 71 It descends with 71. As a result, as shown in FIG. 4, as a result, the valve body 32 is lifted to a second lift position where the second opening 521 closed by the movable member 71 is opened (lift amount H2).

At this time, the low pressure opening 33 is provided in the valve chamber 33.
And the first opening 64a and the second opening 65a are open. That is, since the second control chamber 51 communicates with the low-pressure fuel passage 63 via the valve chamber 33 in addition to the first control chamber 50, the pressure (PC2) in the second control chamber 51 decreases, and the second piston The fuel pressure acting downward on 22 decreases. Therefore, the needle 2 and the first piston 21 push up the second piston 22 to further lift, and when the lift amount of the needle 2 becomes h2, the upper end surface of the needle 2 comes into contact with the lower end surface of the tip packing 14 and stops. .

Further, as shown in FIG. 5C, the driving voltage of the piezoelectric element 4 can be switched during the ejection. Here, for example, in the initial stage of the injection, the drive voltage of the piezoelectric element 4 is set to V
As 1, the needle 2 is lifted to the first lift h1, and then the drive voltage is switched to V2 to further lift the needle 2 to the second lift h2 (boot injection rate). By doing so, the injection rate can be obtained according to the operating conditions.

As described above, the driving voltage of the piezoelectric element 4 is controlled to lift the valve body 32 in a stepwise manner, so that the high-pressure fuel passage 60, the low-pressure fuel passage 63, the first control chamber 50, and the second control The communication between the first control room 5 and the communication with the room 51 is switched.
The needle 2 can be lifted in a stepwise manner by lowering the fuel pressure of only 0 or both the first control chamber 50 and the second control chamber 51.

Since the movable member 71 is provided in the valve chamber 33 so as to come into contact with the valve body 32 at the first lift position, the valve body 32 can always be held at a constant intermediate lift position. Therefore, the fuel pressure in the two control chambers (the first control chamber 50 and the second control chamber 51) can be controlled stably by one valve body 32, and a desired injection rate can be realized, and the fuel injection can be performed. Variation in the amount can be prevented.

FIG. 6 shows a second embodiment of the present invention. In the present embodiment, in the control valve 3, the passage 73 that connects the upper chamber 31 a and the lower chamber 31 b of the valve chamber 31 is not provided, and instead of connecting the lower chamber 31 b to the high-pressure fuel passage 60, a passage 34 is used. The spill chamber 48 is connected to the low-pressure fuel passage 63. Further, an orifice passage 67 for communicating the first control chamber 50 with the high-pressure fuel passage 60 is provided.

With this configuration, the same effect as in the first embodiment can be obtained. Further, when the pressure in the lower chamber 31b becomes low and the valve body 32 is brought into the second lift position, the fuel pressure of the high-pressure fuel passage 60 does not act on the valve body 32, so that there is an advantage that the drive voltage can be reduced.

Alternatively, as shown in FIG. 7 as a third embodiment, the movable member 71 is formed in a cylindrical lower half by the lower chamber 3.
1b, the passage 73 formed in the movable member 71 is L-shaped. And the upper end is the valve chamber 31
Can be directly connected to the orifice passage 61 at the lower end of the upper chamber 31a. The lower chamber 31 b of the valve chamber 31 communicates with the spill chamber 48 that reaches the low-pressure fuel passage 63 through the passage 34.

FIG. 8 shows a fourth embodiment of the present invention.
In the present embodiment, the inside of the valve chamber 31 is not partitioned, and the movable member 71 having a T-shaped cross section is disposed in the lower half of the valve chamber 31 with an interval from the inner peripheral surface. The lower end of the movable member 71 is a plate 39
And abuts a plate-shaped valve member 75 provided in contact with the upper surface of the second control chamber 51. On plate 39,
A second communication path 65 is provided between the bottom surface of the valve chamber 31 and the upper surface of the second control chamber 51 through the plate 39, and the valve member 75 is connected to the second control chamber 51 of the second communication chamber 65. The opening 65b is closed. The opening 65a of the second communication passage 65 to the valve chamber 31 is always open.

In the above configuration, when the valve body 32 is lifted, it comes into contact with the movable member 71 at the first lift position, and then,
The movable member 71 is lowered integrally while being pushed down. At this time, since the lower end of the movable member 71 pushes down the valve member 75, the opening 65b on the second control chamber side of the second communication passage 65 is opened, and the valve chamber 31 and the second control chamber 51 communicate with each other. Even with such a configuration, a similar effect can be obtained.

FIG. 9 shows a fifth embodiment of the present invention.
In the present embodiment, the movable member 71 has a substantially cylindrical shape, and the upper end thereof is disposed in the valve chamber 31, and the lower end thereof is
It penetrates through the plate 39 and the second control chamber 51 and is slidably fitted into a cylinder provided in the second piston 22. A spring chamber 76 in which a spring 72 is disposed is formed below the movable member 71.
The passage 34 communicates with the low-pressure fuel passage 63. The movable member 71 functions as a valve member that opens and closes between the valve chamber 31 and the second control chamber 51 while the flange 71 a provided on the outer periphery of the intermediate portion contacts the lower end surface of the plate 39 to restrict upward displacement. I do. A part above the flange 71a is a small diameter portion 71b, and forms a second communication path 65 with the inner peripheral surface of the plate 39. The first control chamber 50 communicates with the high-pressure fuel passage 60 through an orifice passage 67.

In the above configuration, when the valve body 32 is lifted, it comes into contact with the movable member 71 at the first lift position, and then,
The movable member 71 is lowered integrally while being pushed down. At this time, the flange 71a of the movable member 71 is separated from the lower end face of the plate 39, and the valve chamber 31 and the second control chamber 51 are connected via the second communication path 65 between the small diameter portion 71b and the inner peripheral surface of the plate 39.
Communicate. Even with such a configuration, a similar effect can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a fuel injection device according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the fuel injection device according to the first embodiment.

FIG. 3 is an enlarged sectional view of a main part of the fuel injection device, showing a state in which the valve body is at a first lift position in the first embodiment.

FIG. 4 is an enlarged cross-sectional view of a main part of the fuel injection device showing a state in which the valve body is at a second lift position in the first embodiment.

FIG. 5 is a time chart showing the behavior of each part of the fuel injection device according to the first embodiment during a step lift.

FIG. 6 is an overall sectional view of a fuel injection device according to a second embodiment of the present invention.

FIG. 7 is an overall sectional view of a fuel injection device according to a third embodiment of the present invention.

FIG. 8 is an overall sectional view of a fuel injection device according to a fourth embodiment of the present invention.

FIG. 9 is an overall sectional view of a fuel injection device according to a fifth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 injector (fuel injection device) 13a injection hole 16 fuel reservoir 2 needle 21 first piston 22 second piston 3 control valve 31 valve chamber 31a upper chamber (first chamber) 31b lower chamber (second chamber) 32 valve body 33 low pressure Opening 41 Piezoelectric element (driving means) 41 Large-diameter piston 42 Hydraulic chamber 44 Small-diameter piston 50 First control chamber 51 Second control chamber 60 High-pressure fuel passage 63 Low-pressure fuel passage 64 First communication passage 64a First opening 65 Second Communication passage 65a Second opening 71 Movable member 72 Spring (spring member) 73 Passage

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihisa Yamamoto 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Toshio Kondo 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture F term (reference) 3G066 AA07 AB02 AC09 AD12 BA51 CC06T CC08T CC14 CC67 CC68U CC70 CE13 CE27 CE34

Claims (10)

[Claims] 1. A needle for opening and closing an injection hole by sliding in a valve body, a first piston and a second piston cooperating with the needle in an axial direction, and a first piston and a second piston, respectively. A first control chamber and a second control chamber for applying a fuel pressure in the valve closing direction of the needle, and a first chamber communicating with the first control chamber to a valve chamber accommodating a valve element.
An opening, a second opening communicating with the second control chamber, and a control valve provided with a low-pressure opening communicating with the low-pressure fuel passage, wherein the valve body of the control valve is lifted stepwise by driving means. By doing so, the first opening and the second opening,
A fuel injection device that switches a communication state with the low-pressure opening, changes fuel pressure in the first control chamber and the second control chamber, and lifts the needle in a stepwise manner. When the valve body is lifted, a movable member is provided which abuts on the valve body at a first lift position of the valve body and moves integrally with the valve body to a second lift position larger than the first lift position. A fuel injection device characterized in that: 2. The communication device according to claim 1, wherein the movable member switches a communication state between the first opening or the second opening and the valve chamber as the movable member moves integrally with the valve body. Fuel injection device. 3. The first control chamber is provided between the first piston and the second piston which moves up and down integrally with the needle, and the second control chamber is provided above the second piston. The control valve communicates the first opening with the low-pressure opening when the valve body is at the first lift position, and when the valve body is at the second lift position, the first opening. The fuel injection device according to claim 1 or 2, wherein the low pressure opening communicates with the second opening and the second opening. 4. The movable member cuts off communication between the second opening and the valve chamber at an initial position, and moves together with the valve body to move the second opening and the valve chamber together. The fuel injection device according to claim 3, wherein the fuel injection device communicates. 5. The movable member partitions the valve chamber into a first chamber accommodating the valve body and a second chamber communicating with a high-pressure fuel passage. Room and second
5. The fuel injection device according to claim 4, further comprising a passage communicating with the chamber and being interrupted by contact with the valve element. 6. The movable member divides the valve chamber into a first chamber in which the valve body is accommodated and a second chamber communicating with a low-pressure fuel passage. The fuel injection device according to claim 4, which is in communication with the passage. 7. The movable member partitions the valve chamber into a first chamber in which the valve body is accommodated and a second chamber communicating with a low-pressure fuel passage. 5. The fuel injection device according to claim 4, further comprising a passage communicating between the chamber and the high-pressure fuel passage, the passage being interrupted by contact with the valve body. 8. The movable member has a passage communicating between the valve chamber and the high-pressure fuel passage, the passage being interrupted by contact with the valve body, and the movable member being integral with the valve body. With the movement, the second opening and the second
The fuel injection device according to claim 4, wherein a valve member provided between the control chambers is opened. 9. The fuel injection device according to claim 4, wherein the second control chamber communicates with a high-pressure fuel passage. 10. The fuel injection device according to claim 1, further comprising a spring member for urging the movable member toward the valve body.