JPH0519575Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a fuel injection valve for an internal combustion engine.

[Conventional technology]

As described in JP-A-48-4823 and JP-A-60-1369, if an electrostrictive actuator is used instead of a solenoid, a fuel injection valve with high-speed response and high controllability can be obtained. I can do it. Although the electrostrictive actuator has high-speed response, the amount of displacement is small, so as shown in both of the above publications, a pressure chamber is provided to amplify the displacement of the electrostrictive actuator and transmit it to the needle. This pressure chamber is filled with fuel.

[Problem that the invention attempts to solve]

When the amount of oil in the pressure chamber decreases, there is a problem that the needle opens even if the electrostrictive actuator is controlled to close the needle. This means that it is constantly filled. However, if the pressure chamber is filled with fuel,
When the engine starts, the pressure chamber is empty and the supplied fuel pressure is low, so it takes time to fill the pressure chamber with fuel, and the rise in pressure in the hydraulic chamber is delayed, resulting in an abnormality in which the valve opens even when the valve is controlled to close. Injection occurs. In order to prevent this, the fuel filling speed at startup can be increased by increasing the area of the passage leading from the fuel supply port to the pressure chamber. However, it is generally desirable that the pressure chamber be a sealed chamber, and if the area of this passage is increased, pressure fluctuations in the pressure chamber will increase during operation, and controllability will deteriorate.
Therefore, it is required to perform rapid filling at startup, and to perform a small amount of filling to compensate for leakage during operation.

[Means for solving problems]

The fuel injection valve according to the present invention includes a main body having a fuel supply port and a nozzle, a needle valve housed in the main body for opening and closing the nozzle, an accumulator for accumulating fuel at a predetermined pressure inside, and an accumulator for accumulating fuel at a predetermined pressure inside. a first fuel passage communicating between the mulator and the nozzle;
an oil reservoir provided in the middle of the first fuel passage and biasing the needle valve in the opening direction; a pressure chamber biasing the needle valve in the closing direction; and the pressure chamber and the accumulator. an electrostrictive actuator that controls the pressure within the pressure chamber; Switching the area of the second fuel passage to a first predetermined area and changing the area of the second fuel passage to a second predetermined area smaller than the first predetermined area when the fuel pressure of the accumulator is higher than the predetermined pressure. The fuel filling control valve is characterized in that it is equipped with a fuel filling control valve that switches to the fuel filling control valve.

〔Example〕

1 to 3, the main body of the fuel injection valve includes an injector main body 10 located at the center when viewed in the axial direction, a nozzle main body 12 located at the tip side,
It consists of a cylinder body 14 located on the rear end side,
Furthermore, a case 18 housing an electrostrictive element actuator 16 is attached to the cylinder body 14.
The nozzle body 12 is connected to the injector body 10 via a lower distance piece 20 and fastened by a retaining nut 22. The cylinder body 14 is connected to the injector body 10 via an attachment distance piece 24, and is integrated between the injector body 10 and the case 18, which are arranged to sandwich both sides of the cylinder body, by fastening them to the housing 26. is achieved.

The nozzle body 12 has a nozzle 28 for fuel injection.
is provided and houses a needle 30 that is engageable in a seat around the spout 28 . needle 3
A pressure pin 32 and a push rod 34 are disposed on the same axis as the pin 0, and can be brought into contact with each other between their end surfaces. Furthermore, the compression spring 36
is the pressure pin 32 in the valve closing direction of the needle 30.
is arranged so as to energize the

A piston 38 is fitted into the cylinder body 14. The piston 38 is pushed toward the electrostrictive actuator 16 by a disk spring 40, and the opposite end of the electrostrictive actuator 16 is brought into contact with the case 18. The electrostrictive actuator 16 is formed into a cylindrical body by laminating a plurality of disc-shaped elements, and is moved to a predetermined length in the direction of the piston 38 by applying a voltage of 500 V from a control device (not shown). It extends and moves the piston 38, e.g.
By applying 200V, it degenerates and returns to its original length.
At this time, the piston 38 is returned by the spring force of the disc spring 40 following the electrostrictive actuator. There is a space between the lower end of the piston 38 and the atsupada stance piece 24 due to the cylinder bore diameter, and this space is
A pressure chamber is formed together with a small hole 42 formed through the center of the pressure chamber and a space defined by the bore diameter between the attachment distance piece 24 and the push rod 34 (hereinafter, 42 is used as the reference numeral for the pressure chamber). Since the pressure receiving area at the upper end of the push rod 34 is smaller than the pressure receiving area at the lower end of the piston 38 and the diameter of the small hole 42 is small, a small displacement of the piston 38 following the electrostrictive actuator 16 becomes a larger displacement, and the push rod 34 is further transmitted to the needle 3 via the pressure pin 32.
0 can be communicated.

A fuel supply port 44 is provided in the injector body 10, and fuel is supplied from an accumulator 46 that accumulates fuel at a predetermined pressure. The accumulator 46 stores fuel supplied from a high-pressure pump (not shown) at a predetermined high pressure. This fuel supply port 44
A first fuel passage 48 connecting the nozzle 28 and the nozzle 28 is
A fuel reservoir 50 is formed through the injector body 10, the lower distance piece 20, and the nozzle body 12, and surrounds the tapered portion of the needle 30 at the middle portion of the nozzle body 12. Further, a second fuel passage 52 connecting the fuel supply port 44 and the pressure chamber 42 is formed through the injector body 10. The second fuel passage 52 opens into the pressure chamber 42 through a groove formed in the lower surface of the upper distance piece 24 in the radial direction.

A fuel filling control valve 54 is arranged in the middle of the second fuel passage 52. The fuel filling control valve 54 is connected to the valve body 5
6 and a spring 58. The valve body 56 has a cylindrical shape and is slidably inserted into a correspondingly formed bore wall, with a port 60 extending halfway through its center.
, a port 62 extending diametrically from the port 60 , and a circumferential groove 64 passing through an outer opening of the port 62 , the port 60 being connected to the second fuel passage 5 .
It is always connected to the fuel supply port 44 side of No. 2. Circumferential groove 64
can communicate with the pressure chamber 42 side of the second fuel passage 52 that opens in the bore wall containing the valve body 56 .
That is, when the fuel supply pressure is lower than the set pressure of the spring 58 disposed on the blind side of the valve body 56, the spring 58
Due to the urging force of
A large amount of fuel can be filled into the pressure chamber 42 through the passages 0 and 62, and when the pressure of the fuel becomes greater than the set pressure of the spring 58, the spring 58 is compressed and the valve body 56
, thereby causing misalignment between the circumferential groove 64 and the bore wall opening, so that there is no flow of fuel through the ports 60, 62, and fuel to the pressure chamber 42 is directed between the valve body 56 and its bore wall. Only a small amount will pass through the clearance. However, the pressure chamber 42
Considering that the leakage of fuel mainly occurs from the clearance between the push rod 34 and its sliding bore wall, when the fuel supply pressure is high, the fuel leakage occurs from the clearance between the valve body 56 and its bore wall. It is sufficient to fill the pressure chamber 42 and the first fuel passage 48, thereby separating the pressure chamber 42 and the first fuel passage 48.
2. Pressure fluctuation becomes smaller. Furthermore, the space on the spring 58 side that accommodates the valve body 56 is connected to a return passage 66. The clearance between push rod 34 and its bore wall is also connected to return passage 68.

Furthermore, a check valve 70 is arranged between the pressure chamber 42 and the fuel filling control valve 54. This check valve 70
This allows only fuel to flow toward the pressure chamber 42 through the second fuel passage 52. This check valve 70 is arranged as close as possible to the pressure chamber 42 to reduce the volume of the pressure chamber 42 during compression, to make pressure changes in the pressure chamber 42 more sensitive, and to improve the valve closing response of the needle 30. It is.

Next, the effect will be explained.

As mentioned above, the electrostrictive actuator 16
When 500V is applied, a predetermined elongation in the axial direction occurs due to the electrostrictive effect, which overcomes the spring force of the disc spring 40 to push down the piston 38 and increase the pressure in the pressure chamber 42. When the pressure in the pressure chamber 42 increases, the needle 30 is pushed down via the push rod 34 and the pressure pin 32 and comes into close contact with the seat. At this time, a pushing up force due to fuel pressure is acting on the tapered part of the needle 30, but the pressure receiving area is equivalent to the pushing down pressure receiving area of the upper end of the push rod 34, and the compression effect of the pressure chamber 42 The push-down force is stronger by that amount, and the needle 30 can be closed. Also, the pressure in the pressure chamber 42 is
4 and its bore wall, the pressure in the pressure chamber 42 will not drop below the fuel supply pressure, and the downward force of the spring 36 will keep the needle 30 closed. be able to. Conversely, if -200V is applied to the electrostrictive actuator 16,
The electrostrictive actuator 16 contracts and the piston 38
follows this and retreats, making the pressure chamber 42 a negative pressure, and the needle 30 opens under the upward force of the fuel acting on its tapered portion.

When starting the engine, the pressure of the fuel supplied from the fuel pump or accumulator 46 is low, and the valve body 56 of the fuel filling control valve 54 is pushed by the spring 58 to allow fuel to flow through the ports 60 and 62. position and the time for fuel to pass through the second fuel passage 52 to the pressure chamber 42 and the first fuel passage 48
The time it takes to reach the oil pool 50 is approximately equal, and the time between the upper end of the push rod 34 and the needle
Since the tapered portion can receive mutually balanced fuel pressure without delay, reliable fuel injection can be performed under the control of the electrostrictive actuator 16.

[Effect of idea]

As explained above, according to the present invention, the area of the second fuel passage increases when the pressure of the accumulator decreases, so a large amount of fuel can be filled into the pressure chamber when the electrostrictive actuator retracts. The pressure in the pressure chamber can be quickly increased, and the needle can be closed when the electrostrictive actuator is extended.
Furthermore, after the pressure in the accumulator becomes sufficiently high, the area of the second fuel passage becomes smaller, so the amount of fuel filled in the pressure chamber is suppressed when the electrostrictive actuator retracts, and the pressure in the pressure chamber increases. This prevents the needle valve from being left closed due to excessive movement. In this way, the pressure chamber is reliably filled with fuel, and highly reliable fuel injection is possible.

[Brief explanation of the drawing]

1 is a sectional view of a fuel injection valve according to the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is an enlarged view of the valve body of FIG. 2. 10... Injector body, 12... Nozzle body, 14... Cylinder body, 16... Electrostrictive actuator, 28... Spout, 30... Needle,
34...Push rod, 38...Piston, 4
2... Pressure chamber, 44... Fuel supply port, 48... First fuel passage, 52... Second fuel passage, 54...
...Fuel filling control valve.

Claims (1)

[Scope of utility model registration request] A main body having a fuel supply port and a nozzle, a needle valve housed in the main body that opens and closes the nozzle, an accumulator that stores fuel at a predetermined pressure therein, and communication between the accumulator and the nozzle. a first fuel passage; an oil pool provided in the middle of the first fuel passage for urging the needle valve in the opening direction; a pressure chamber for urging the needle valve in the closing direction; a second fuel passage that communicates between the chamber and the accumulator; an electrostrictive actuator that controls the pressure within the pressure chamber; is lower than a predetermined pressure, the area of the second fuel passage is switched to the first predetermined area, and when the fuel pressure of the accumulator is higher than the predetermined pressure, the area of the second fuel passage is changed to the first predetermined area. A fuel injection valve comprising a fuel filling control valve that switches to a smaller second predetermined area.