JPH055252Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection valve that controls fuel injection using an electrostrictive actuator containing a piezoelectric element.

[Conventional technology]

Various types of fuel injection valves for internal combustion engines are known in which an electrostrictive actuator is used to open and close a fuel injection control needle housed in the valve (for example, Japanese Patent Laid-Open No. 59-206668 (Japanese Patent Application Laid-Open No. 62-3166). An electrostrictive actuator using a piezoelectric element has a much shorter response time than a solenoid or the like, so it can improve fuel injection valve control responsiveness.

However, although the electrostrictive actuator has good responsiveness, it usually has a problem in that its own operating amount (expansion/contraction amount) cannot be made very large. To solve this problem, in the fuel injection valve disclosed in Japanese Patent Application Laid-open No. 59-206668, a pressure chamber filled with fuel is provided between the needle and the electrostrictive actuator. The fuel pressure in the pressure chamber is changed to operate the needle via the fuel pressure.

In this type of fuel injection valve, the needle is operated in the valve opening direction by the pressure receiving surface of the needle receiving fuel pressure in a fuel reservoir chamber in which supplied fuel is temporarily stored. In the valve closing direction, the extension action of the electrostrictive actuator is converted into pressure within the pressure chamber, and the needle is pushed in the valve closing direction by this pressure. The position of the needle is determined by the difference between the force acting in the valve opening direction and the force acting in the valve closing direction due to pressure chamber pressure, and is maintained at a balance point.

[Problem that the invention attempts to solve]

However, in the fuel injection valve as described above, a predetermined pressure must be generated in the pressure chamber in order to maintain a predetermined force in the needle valve closing direction. The pressure chamber is supplied with fuel through the clearance in the fuel injection valve, etc., and the pressure chamber is always filled with fuel so that the pressure can be maintained, but when starting, etc., the pressure chamber is filled with fuel. It may take time to apply pressure. This is because fuel is supplied to the pressure chamber through a relatively small clearance, but this clearance as a fuel supply path is necessary to prevent the pressure inside the pressure chamber from escaping. . On the other hand, since fuel is introduced into the fuel reservoir chamber facing the pressure-receiving surface of the needle without passing through the above-mentioned clearance, fuel pressure is applied faster than in the pressure chamber. As a result, especially during startup, there is an undesirable difference between the force in the needle valve opening direction via the needle pressure receiving surface due to the fuel pressure in the fuel reservoir chamber and the force in the needle valve closing direction via the pressure chamber pressure. In other words, there is a risk that an unintended imbalance may occur and the needle may open as a result of deviation from the control target.

The present invention focuses on these problems and quickly brings the fuel pressure inside the pressure chamber to a predetermined value or higher, prevents the needle from opening unintentionally during startup, and
The purpose is to ensure targeted fuel injection control.

[Means for solving problems]

The fuel injection valve of the present invention that meets this purpose includes a main body having a nozzle hole, a needle inserted into the main body so as to be able to open and close the nozzle hole, and having a pressure receiving surface for opening the nozzle hole, and a needle inside the main body. A fuel storage chamber is formed around the pressure receiving surface of the fuel chamber to temporarily accommodate the supplied fuel, an electrostrictive actuator using a piezoelectric element that operates to expand and contract, and the expansion and contraction operation of the electrostrictive actuator fills the inside. a pressure chamber that converts the generated fuel into a force in the opening/closing direction of the needle, in the vicinity of the pressure chamber in the fuel injector and upstream of the fuel reservoir chamber as seen in the fuel supply direction. The pressure chamber is temporarily filled with the supplied fuel and is provided with a pressure accumulator chamber that can replenish the pressure chamber with fuel. That is, a pressure accumulation chamber is provided in the vicinity of the pressure chamber, separate from the conventionally provided fuel reservoir chamber.

[Effect]

In such a fuel injection valve, at the time of startup, the pressure of the supplied fuel is first applied to the pressure accumulation chamber, and the pressure chamber is replenished with fuel from the pressure accumulation chamber, and the pressure in the pressure chamber is quickly increased. Fuel is also supplied to the fuel reservoir chamber located on the downstream side of the pressure accumulator chamber, increasing the fuel pressure, but as mentioned above, pressure is quickly introduced into the pressure chamber at the upstream position, so the pressure in the pressure chamber increases. The force that operates the needle in the valve-closing direction via fuel pressure has increased sufficiently, and even if fuel pressure builds up on the needle pressure-receiving surface in the fuel reservoir chamber in the needle valve-opening direction, the relationship between the two forces is no longer desirable. No imbalance occurs. Therefore, unintentional opening of the needle does not occur.

In contrast to the structure disclosed in Japanese Unexamined Patent Publication No. 59-206668, in which fuel is introduced into the pressure chamber from the fuel reservoir through a clearance, the present invention introduces fuel into the pressure chamber separately from the fuel reservoir on the upstream side of the fuel reservoir. A pressure accumulation chamber is provided to completely separate the functions of the pressure accumulation chamber, which quickly introduces fuel pressure into the pressure chamber, and the fuel reservoir chamber, which applies fuel pressure to the needle pressure receiving surface and controls the needle valve opening during normal operation. This has a major feature that reliably prevents the needle from opening unintentionally during startup.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 shows a fuel injection valve according to a first embodiment of the present invention. In the figure, 1 indicates the entire fuel injection valve. Fuel from a fuel tank 2 is pumped to the fuel injection valve 1 by a pump 3, and a tank 4 (which serves as a pressure accumulation chamber) provided in the middle is used to pump the fuel into the fuel injection valve 1. The pulsation of the pump 3 is absorbed.

Reference numeral 5 indicates a main body having a nozzle hole 6, and a needle 7 is inserted into the main body 5 so that the nozzle hole 6 can be opened and closed. In this embodiment, the operation of the needle 7 is controlled via a push rod 8, and a body 9 and a body 10 are connected to the main body 5 (on the upper side of the figure). , 10, a push rod 8 is slidably inserted therein. body 9 and body 10
and are connected by a retaining nut 11.

A fuel supply path 12 from the tank 4 is connected to a high pressure fuel passage 13 within the fuel injection valve 1, and the high pressure fuel passage 13 communicates with a fuel reservoir chamber 14 formed within the main body 5. A pressure receiving surface 15 of the needle 7 faces the fuel reservoir chamber 14, and the needle 7 is actuated (lifted) in the valve opening direction by the fuel pressure within the fuel reservoir chamber 14 acting on the pressure receiving surface 15. There is.

An electrostrictive actuator 16 having a built-in piezoelectric element that operates to expand and contract is attached to the upper end of the body 10. The space between the electrostrictive actuator 16 and the upper end of the push rod 8 is filled with fuel.
A pressure chamber 17 is formed in which the expansion and contraction operation of the electrostrictive actuator 16 is converted into a force in the sliding direction of the push rod 8, that is, a force in the opening and closing direction of the needle 7, through the pressure of the filled fuel. The shape of the pressure chamber 17 is such that the area on the electrostrictive actuator 16 side is larger than the area on the push rod 8 side.
The amount of expansion and contraction of the electrostrictive actuator 16 can be expanded and transmitted to the push rod 8.

At a position upstream of the fuel reservoir chamber 14 in the fuel injection valve 1 in the high-pressure fuel passage 13 and near the pressure chamber 17, there is a pressure accumulation having a much larger volume than the fuel reservoir chamber 14. A chamber 18 is provided. The pressure accumulation chamber 18 is a push rod 8.
The pressure accumulating chamber 18 and the pressure chamber 17 are in communication with each other via a clearance 19 between the push rod 8 and the inner peripheral surface of the hole in the body 10 . This clearance 19 is a relatively small clearance, and allows fuel to be supplied from the pressure accumulation chamber 18 to the pressure chamber 17 via the clearance 19, and the pressure accumulation chamber 18
of fuel pressure can be introduced into the pressure chamber 17, and the fuel in the pressure chamber 17 does not easily escape to the pressure accumulation chamber 18 side.

In a multi-cylinder internal combustion engine, as shown in the figure, the fuel supply path 12 from the tank 4 is branched for each cylinder, and the supplied fuel is distributed to fuel injection valves (not shown) for each cylinder.

In the fuel injection valve configured as described above, the fuel sent from the tank 4 via the fuel supply path 12 is first transferred to the pressure accumulation chamber 18 in the fuel injection valve 1.
supplied within. Fuel is also supplied to the fuel reservoir chamber 14 from the pressure accumulation chamber 18 through the high-pressure fuel passage 13, but since the pressure accumulation chamber 18 is provided near the pressure chamber 17, it is also supplied to the pressure chamber 17 via the clearance 19. be done. Since the pressure accumulation chamber 18 is formed to have a relatively large volume, even if some fuel is supplied to the pressure chamber 17, the pressure inside the pressure chamber 18 does not decrease so much, and therefore the pressure inside the pressure chamber 18 Stand up quickly. In addition, inside the pressure accumulation chamber 18,
Since it is already filled with fuel before starting and the pressure accumulation chamber 18 has a relatively large volume,
Even if the fuel supply path 12 is relatively long and there is a pressure loss during this period, the fuel pressure within the pressure accumulator chamber 18 rises quickly, and as described above, the pressure within the pressure chamber 18 rises quickly.

As a result, during startup, a force in the needle valve opening direction via the needle pressure receiving surface 15 due to the fuel pressure introduced into the fuel reservoir chamber 14, and a force in the needle valve closing direction via the pressure inside the pressure chamber 18. Between,
Undesirable reversal phenomena do not occur and unintended opening movements of the needle 7 are prevented.

Second Embodiment Next, FIG. 2 shows a fuel injection valve 21 according to a second embodiment of the present invention.

In this embodiment, a check valve 25 is provided in the fuel passage 24 between the pressure accumulation chamber 22 and the fuel reservoir chamber 23, which opens the passage only when the upstream pressure of the passage reaches a predetermined value or higher. . By providing the check valve 25, the fuel accumulation chamber 22 is filled with a predetermined amount of fuel until the pressure chamber 22 reaches a predetermined pressure or higher, and the pressure chamber 26 is filled with a predetermined amount of fuel. Since it does not communicate with the chamber 23, the timing at which pressure is applied to the pressure receiving surface 28 of the needle 27 is forcibly delayed, and unintended valve opening of the needle is more reliably prevented. Other configurations and operations are similar to those of the first embodiment.

[Effect of idea]

As explained above, when using the fuel injection valve of the present invention, a pressure accumulation chamber is provided inside the fuel injection valve separately from the conventional fuel reservoir chamber, and fuel pressure of a predetermined value or higher is quickly introduced into the pressure chamber. As a result, it is possible to prevent an undesirable imbalance between the force in the needle valve opening direction via the needle pressure receiving surface and the force in the needle valve closing direction via the pressure chamber pressure at the time of startup. Unintentional opening of the needle valve can be reliably prevented.

Therefore, highly responsive fuel injection control using the electrostrictive actuator can be guaranteed without causing any inconvenience.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a fuel injection valve according to a first embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a fuel injection valve according to a second embodiment of the present invention. 1, 21...Fuel injection valve, 2...Fuel tank,
3... Pump, 5... Main body, 6... Nozzle hole,
7, 27... Needle, 8... Push rod,
12...Fuel supply passage, 13...High pressure fuel passage, 1
4, 23... Fuel reservoir chamber, 15, 28... Pressure receiving surface, 16... Electrostrictive actuator, 17, 26
... Pressure chamber, 18, 22 ... Pressure accumulation chamber, 19 ... Clearance, 24 ... Fuel passage, 25 ... Check valve.

Claims (1)

[Scope of utility model registration request] A main body having a nozzle hole, a needle inserted into the main body so that the nozzle hole can be opened and closed and having a pressure receiving surface for opening operation, and a needle formed around the pressure receiving surface of the needle in the main body and supplying a fuel storage chamber that temporarily accommodates the incoming fuel; an electrostrictive actuator using a piezoelectric element that operates to expand and contract; and the expansion and contraction of the electrostrictive actuator to the needle via the fuel filled inside. and a pressure chamber that converts force into an opening/closing direction, the fuel is supplied to a position near the pressure chamber in the fuel injection valve and upstream of the fuel reservoir chamber when viewed in the fuel supply direction. 1. A fuel injection valve characterized in that a pressure accumulation chamber is provided which is temporarily filled with incoming fuel and capable of replenishing the pressure chamber with fuel.