JPS6343407Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The invention is mainly applicable to diesel engines,
The present invention relates to a fuel injection valve for injecting and supplying fuel to the combustion chamber.

[Conventional technology]

One of the causes of knotting in diesel engines is the large injection rate at the beginning of fuel injection supply, and to eliminate this factor, it is effective to control the rising speed of the needle valve low in the initial stage of injection. It is known.

Therefore, Japanese Patent Application Laid-Open No. 55-23375 as a prior art discloses that a valve body of a fuel injection valve is connected to a spring chamber housing a nozzle spring that presses and biases a needle valve in the valve closing direction through a throttle orifice. Tsutsumi is proposing to install an accumulator to do this.

According to this configuration, at the start of fuel injection, when the needle valve moves upward in the valve opening direction while resisting its nozzle spring and pushing out the fuel oil in the spring chamber to the accimulator, the fuel flowing from the spring chamber to the accimulator By applying a large resistance to the oil by the throttle orifice and regulating the rising speed of the needle valve, the rising speed of the needle valve in the initial stage of injection can be controlled to be low, so that fuel injection can be started. It is possible to eliminate the knocking factor caused by a large injection rate.

[Problem that the invention attempts to solve]

However, the restrictor orifice in this prior art also provides a large resistance to the flow of fuel oil from the accumulator toward the spring chamber when the needle valve moves downward in the valve closing direction due to the nozzle spring force. Therefore, when the needle valve closes, the pressure inside the splash chamber becomes a large negative pressure below atmospheric pressure,
Air bubbles are generated within the spring chamber, significantly interfering with subsequent fuel injection.

The present invention aims to solve this problem.

[Means for solving problems]

To achieve this object, the present invention provides a fuel injection valve having a needle valve, a nozzle spring that presses and biases the needle valve in a closing direction, and a spring chamber that accommodates the nozzle spring. A back chamber communicating with the spring chamber via a communication passage is formed in the back chamber, and when the pressure in the back chamber increases, the communication passage is closed, and when the pressure in the back chamber decreases, the communication passage is closed. A control valve that opens a passage is provided, and the control valve is provided with a throttle orifice that communicates the back chamber and the spring chamber.

[Effect of invention]

With this configuration, when the needle valve opens during fuel injection supply, the pressure in the back chamber provided at the back of the needle valve increases, and the control valve closes the communication passage, allowing the fuel oil in the back chamber to flow through the throttle orifice. The throttle orifice provides a large resistance to the flow of fuel oil into the spring chamber, making it possible to restrict the upward speed of the needle valve to a low value.

Furthermore, when the needle valve closes when fuel injection is stopped, the pressure in the rear chamber decreases, the control valve opens, and the fuel oil in the spring chamber flows through the communication passage into the rear chamber without flow resistance. There is no speed restriction applied to the valve closing operation, and no large negative pressure is generated in the back chamber.

[Effect of idea]

Therefore, according to the present invention, by regulating the rising speed when the needle valve is opened, the timing of the maximum lift can be moved away from the timing of the beginning of fuel injection, so the injection rate at the beginning of fuel injection can be reduced. While it is possible to reliably suppress knocking caused by a large injection rate at the beginning of fuel injection, when the needle valve closes, the speed regulation is released by opening the control valve, so the needle valve closes quickly. At the same time, a large negative pressure is not generated in the back chamber and the spring chamber, so there is almost no risk of bubbles being generated, and the fuel can be injected stably.

〔Example〕

Below, we will explain the drawings when the embodiment of the present invention is applied to a pintle type fuel injection valve.
In the drawings, reference numeral 1 indicates a valve body in a fuel injection valve, and inside the valve body 1 there is a needle valve 2 that opens and closes the nozzle hole 3, and a spring receiver that contacts the needle valve 2 with a small diameter portion 4 at its upper end. 5, a nozzle spring 6 for normally pressing in the closing direction, a spring chamber 7 housing the nozzle spring 6, and a hole through which pressurized fuel from a fuel injection pump (not shown) is supplied to the tip of the needle valve 2. 8 and a fuel storage chamber 9 into which the fuel is introduced. When the pressure in the fuel reservoir chamber 9 exceeds a value set by the nozzle spring 6, the needle valve 2 moves upward against the nozzle spring 6 and opens, so that fuel is injected and supplied from the nozzle hole 3. There is.

In the valve body 1, a needle valve 2 is provided.
Fuel oil leaking from the fuel reservoir chamber 9 through the sliding part on the outer periphery of the needle valve 2 flows into the upper end portion, that is, the back surface portion, and flows into the spring chamber 7 via the communication passage 10. Communicating back chamber 11
A ring-shaped control valve 12 is provided in the back chamber 11 so as to fit over the small diameter portion 4 of the needle valve 2.
3, the communication passage 10 between the back chamber 11 and the spring chamber 7 is pressed in the direction of closing, while this control valve 12
A restrictor orifice 1 having an appropriate passage area is provided between the inner circumferential surface of the needle valve 2 and the outer circumferential surface of the small diameter portion 4 of the needle valve 2.
4.

In this configuration, when supplying fuel by injection,
When the pressure in the fuel reservoir chamber 9 exceeds the set value of the nozzle spring 6, the needle valve 2 resists the nozzle spring 6 and moves upward while pushing out the fuel oil in the back chamber 11 to the spring chamber 7 and opens. , control valve 12 of the back chamber 11
closes the communication passage 10 to the spring chamber 7 by the spring 13 and the pressure increase in the back chamber 11,
The fuel oil in the back chamber 11 only flows through the restrictor orifice 14 formed between the inner periphery of the control valve 12 and the outer periphery of the small diameter portion 4 of the needle valve 2, and at this time it is subject to large flow resistance. , the rising speed of the needle valve 2 is determined by the throttle orifice 14.
The time at which the needle valve body 2 reaches its maximum lift is moved away from the time at the beginning of fuel injection toward the time at which the fuel injection ends.

Then, when the pressure in the fuel reservoir chamber 9 decreases, the needle valve 2 descends to close due to the force of the nozzle spring 6. At this time, the pressure in the back chamber 11 decreases due to the lowering of the needle valve 2, and a pressure difference is generated between the back chamber 11 and the spring chamber 7, and this pressure difference causes the control valve 12 to
opens against the spring 13, and the fuel oil in the spring chamber 7 flows into the rear chamber 11 without flow resistance. Therefore, the closing operation of the needle valve 2 is not subject to any speed restriction and is instantaneous. At the same time, the back chamber 11 is closed.
Also, no large negative pressure is generated in the spring chamber 7, and therefore no air bubbles are generated at all.

Furthermore, regulating the rising speed of the needle valve 2 during the opening operation also serves to prevent the needle valve 2 from vertically vibrating due to pulsations in the fuel oil from the fuel injection pump.

In this case, the opening characteristics of the needle valve 2 can be set arbitrarily by the cross-sectional area of the throttle orifice 14.
In addition, by providing a plurality of vertical grooves 15 only on the outer periphery of the root portion of the small diameter portion 4 in the needle valve 2, or by forming only the root portion of the small diameter portion 4 into an even smaller diameter,
The length l of the throttle orifice 14 between the inner peripheral surface of the control valve 12 and the maximum lift L of the needle valve 2
If it is configured to be shorter, the opening speed of the needle valve 2 will be restricted only in the lift section of length l in the throttle orifice 14, and after this section, the opening speed will no longer be restricted. , since the needle valve 2 rapidly opens to the maximum lift L, the throttle orifice 1
The length l in 4 can also be set to any desired characteristic.Furthermore, the present invention is applicable not only to the pintle type fuel injection valve of the above embodiment but also to other types of fuel injection valves. It goes without saying that it can be done.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the main part of the fuel injection valve, and FIG.
FIG. 3 is an enlarged cross-sectional view. 1... Valve body, 2... Needle valve, 3... Nozzle hole, 6... Nozzle spring, 7... Spring chamber, 10...
Communication passage, 11... Rear chamber, 12... Control valve, 1
3... Spring, 14... Squeezing orifice.

Claims (1)

[Scope of utility model registration request] In a fuel injection valve having a needle valve, a nozzle spring that presses and biases the needle valve in a closing direction, and a spring chamber that accommodates the nozzle spring, a fuel injection valve is provided at a back surface of the needle valve and connected to the spring chamber through a communication passage. forming a communicating rear chamber, and providing in the rear chamber a control valve that closes the communication passage when the pressure in the rear chamber increases and opens the communication passage when the pressure in the rear chamber decreases; A fuel injection valve for an internal combustion engine, wherein the control valve is provided with a throttle orifice that communicates between a back chamber and a spring chamber.