JPH04292569A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To improve sealing performance between a needle valve and a valve seat by achieving rapid and secure seating of the needle valve onto the valve seat when the fuel injection is completed. CONSTITUTION:An oiltight fuel recess 7 of which volume increases as a valve is closed is formed, and a through hole 27 connecting the fuel recess 7 and an oil recess 11f is provided to a needle valve 2 in a so-called seat hole nozzle which is provided with a nozzle body 1 where a fuel injection port 12 opens to a valve seat 11e, and the needle valve 2 which is inserted into the nozzle body 1 in a sliding manner. This constitution prevents any fuel leakage and suppresses fuel drip, leading to substantial suppression of HC generation and improvement of fuel consumption, and at the same time, nozzle deterioration or the like caused by carbon built up around the injection holes can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in fuel injection valves.

0002

2. Description of the Related Art A so-called hole type nozzle is known as a fuel injection valve used in a direct injection type internal combustion engine. Among the hole-type nozzles, there are those in which the fuel injection hole through which fuel is injected is directly blocked by a needle valve, and those in which the fuel injection hole for injecting fuel is not directly blocked. When an increase in HC due to sagging after fuel injection is a particular problem, a fuel injection valve called a so-called seat hole nozzle, in which the fuel injection hole is directly blocked by a needle valve, is often used. As a conventional sheet hole nozzle like this,
For example, there is one shown in FIG. (Jitsukai 63rd year)
-52970, etc.).

In FIG. 4, a needle valve 200 is attached to a nozzle body 100 having a tapered valve seat 102 having an oil reservoir 101 at the tip and a fuel injection hole 103 opening into the valve seat 102. They are movably fitted.

During fuel injection, the needle valve 200 moves upward in the figure, and the fuel flows from the gap 6 to the fuel injection hole 103 as shown by the arrow, and is injected from the fuel injection hole 103.

Next, when not injecting fuel, the needle valve 20
The valve portion 201, which is the tip of the valve 0, directly closes the fuel injection hole 103 by coming into close contact with the valve seat 102, so that fuel is not injected from the fuel injection hole 103.

Furthermore, by keeping the injection rate, which is the amount of fuel injected per unit time or unit crank angle, low at the beginning of injection, smoke generation is suppressed, and NOx, HC
An example of a conventional two-stage spring fuel injection valve that can reduce noise and keep the injection rate low at the initial stage of injection is the one shown in FIG. 5, for example. (Refer to Utility Model Application Publication No. 61-162572, etc.).

The valve portion 201 at the tip of the needle valve 200 is pressed against the valve seat 102 by the biasing force of the first spring 8a for the first stage valve opening pressure. 1st stage valve opening pressure
The second spring 8b for the second stage valve opening pressure, which is biased relatively more strongly than the spring 8a, biases the bush 9 in the valve closing direction. When the needle valve 200 is seated on the valve seat 102, the bushing 9 has a clearance h with the shoulder 202 of the needle valve. Based on such a configuration, as will be described later, the amount of movement of the needle valve 2 in the valve opening direction at the initial stage of injection is kept low, and the injection rate at the early stage of injection is kept low.

[0008]

However, in such a conventional seat hole nozzle, as shown in FIG. 4, when the needle valve 200 attempts to sit on the valve seat 102 at the end of fuel injection, the valve seat 102 and the valve Since the fuel interposed between the valve seat 201 and the oil reservoir 101 has no escape route and acts as a spring, the needle valve 200 is pushed back upwards with respect to the valve seat 102 and vibrates in the vertical direction, causing a delay in seating. In particular, in the seat hole type two-stage spring fuel injection valve shown in FIG. 5, when the valve is closed, the second spring 8b
Since the needle valve 200 is biased only by the first spring 8a, which biases the valve relatively weakly, the fuel interposed between the valve portion 201 and the valve seat 102 and the fuel accumulated in the oil reservoir 101 are removed. The force pushing out the fuel from the fuel injection hole 103 is weak, and seating of the valve portion 201 on the valve seat 102 is further delayed.

Furthermore, what is shown in FIG. 6 is disclosed in Japanese Utility Model Application Publication No. 63-52970 in an attempt to solve such problems, in which a through hole 203 connecting the oil reservoir 101 and the gap 6 is It is provided in the needle valve 200. Based on such a configuration, the valve seat 102 and the valve portion 201 are separated at the end of fuel injection.
The fuel present between the through hole 2 and the oil reservoir 101 is
03 as shown by the arrow. However, the pressure within the gap 6 immediately after the end of fuel injection has not decreased enough to guide the fuel in this way, and the needle valve 200 cannot be seated on the valve seat 102 immediately.

As explained above, if the needle valve is not seated reliably on the valve seat, the injected fuel will not be cut properly at the end of fuel injection, resulting in dripping of fuel from the fuel injection hole. There were problems such as deterioration of the nozzle body due to carbon adhesion around the fuel injection hole, and a high proportion of unburned fuel, resulting in poor fuel efficiency and high exhaust gas concentration.

[0011] The present invention has been made in view of these conventional problems, and is designed to actively remove the fuel interposed between the valve portion and the valve seat and the fuel accumulated in the oil pool at the end of fuel injection. It is an object of the present invention to provide a fuel injection valve that solves the above-mentioned problems by configuring a fuel reservoir that sucks out fuel in a manner that allows the needle valve to be seated on the valve seat more quickly and more reliably.

0012

[Means for Solving the Problems] A nozzle body having a valve seat through which a fuel injection hole opens, and a needle valve slidably fitted into a needle valve sliding hole of the nozzle body, In a fuel injection valve whose tip opens and closes the fuel injection hole by seating on and separating from the valve seat, the rear end side of the sliding part of the needle valve with the nozzle body has a cross-sectional area larger than that of the needle valve sliding hole. An oil-tight means is provided for sealing a fuel reservoir formed of a small guide part and a space surrounded by the guide part and the needle valve sliding hole, and an oil-tight means is provided at the tip of the fuel reservoir and the valve seat. A through hole connecting the reservoir was provided in the needle valve.

[0013]

[Operation] Based on the above structure, fuel injection is started when the needle valve is separated from the valve seat, and fuel injection is ended when the needle valve is seated on the valve seat and shuts off the fuel injection hole.

In a needle valve, the volume of the fuel reservoir, which is partially formed by the surface created by the difference in cross-sectional area between the sliding part with the nozzle body and the guide part, changes according to the opening and closing of the needle valve, and the volume changes depending on the opening and closing of the needle valve. increases as the person is seated, and decreases as the distance increases. For this reason, the pressure inside the fuel reservoir, which is kept oil-tight, is lower as the needle valve is seated, and becomes higher as it is separated from the needle valve, compared to that at the tip of the needle valve.

Therefore, when the fuel injection ends, the fuel interposed between the tip of the needle valve and the valve seat and the fuel accumulated in the oil reservoir are sucked out through the through hole, and conversely, the fuel is sucked into the fuel reservoir. The discharged fuel is discharged at the same time as fuel injection starts.

As described above, by removing the fuel interposed between the tip of the needle valve and the valve seat and the fuel accumulated in the oil pool at the end of fuel injection, the needle valve can be seated on the valve seat more quickly. Moreover, it can be carried out more reliably, and the sagging of fuel after the injection is completed can be improved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, and is a partially enlarged view of a two-stage spring fuel injection valve described in the prior art.

First, to explain the configuration, the nozzle body 1
A needle valve fitting hole 11 is formed inside the needle valve fitting hole 11, and the needle valve 2 that fits into the needle valve fitting hole 11 is operated by a first spring for the first stage valve opening pressure (not shown), so that the nozzle It is pressed against a valve seat 11e formed at the tip of the body 1.

The needle valve fitting hole 11 includes, in order from the top in FIG. 1, a seal ring insertion hole 11a and a needle valve sliding hole 11b.
It is composed of an oil reservoir chamber 11c, a fuel guide hole 11d, and a tapered valve seat 11e having an oil reservoir 11f at its tip, and a fuel injection hole 12 is opened in the valve seat 11e. Here, the inner diameter of the seal ring insertion hole 11a is larger than the inner diameter of the needle valve sliding hole 11b, and a surface A is formed by the difference in these diameters.

The needle valve 2 is formed from a tapered valve portion 21 from its tip, a fuel guide portion 22, a pressure receiving surface 23, and a sliding portion 24 with the nozzle body, and further includes a guide portion 25 on the rear end side. A spring guide portion 26 is formed. Here, the outer diameter of the guide part 25 is the sliding part 24 with the nozzle body.
is smaller than the outer diameter of B, and due to the difference in these diameters, the rear end surface B
form. Also, inside the needle valve 2, there is an oil reservoir 11.
A through hole 27 is formed so that f communicates with a fuel reservoir 7, which will be described later.
is formed.

The sliding portion 24 with the nozzle body is slidably fitted into the needle valve sliding hole 11b, and the valve portion 21 shuts off the fuel injection hole 12 by seating on the valve seat 11e. Furthermore, the fuel reservoir chamber 11c is formed so as to surround a pressure receiving surface 23 formed on the needle valve 2, and communicates with an injection pump (not shown) via the fuel passage 13. Also, when the needle valve 2 lifts, the fuel reservoir chamber 11
the fuel guide hole 11 so that c and the fuel injection hole 12 communicate with each other.
The inner diameter of d is larger than the outer diameter of the fuel guide portion 22 into which it is inserted.

Next, the seal ring 3, which is an oil-tight means,
When the nozzle body 1 is attached to the nozzle holder 4, it is pressed against the surface A via the disc spring 5, thereby sealing the surface A and the outer peripheral surface of the guide portion 25.

The fuel reservoir 7 has a cross-sectional area of the needle valve sliding hole 11b.
It consists of a space surrounded by a smaller guide portion 25, the needle valve sliding hole 11b, the rear end surface B, and a seal ring 3, and is kept oil-tight by the seal ring 3. In the figure, the volume of the fuel reservoir 7 changes according to the amount of vertical movement of the needle valve 2, that is, according to the movement of the rear end surface B, and is maximum when the needle valve 2 is seated, and minimum when the needle valve 2 is at maximum lift. It is what it is. Further, the point at which the rear end surface B contacts the seal ring 3 is the maximum lift of the needle valve 2, and further lift is regulated.

Next, the operation will be explained.

Due to the pressure of the fuel led from the injection pump to the fuel reservoir chamber 11c through the fuel passage 13, a biasing force is exerted on the pressure receiving surface 23 of the needle valve to lift the needle valve 2. , exceeds the biasing force in the valve closing direction of the first spring acting on the needle valve 2, the needle valve 2 starts to lift,
By lifting the oil reservoir chamber 11c and the fuel injection hole 1
2 are in communication with each other, and fuel is injected from the fuel injection hole 12 through the gap 6. As shown in area L of FIG. 3, the lift of the needle valve 2 is the position where the biasing force of the second spring (not shown) begins to act on the needle valve 2 (the position where the needle valve has been lifted by h in FIG. 5). The fuel becomes dull once, and the injection rate at the initial stage of injection is kept low. When the fuel pressure further increases and the urging force in the valve opening direction exceeds the urging force of the first spring and the second spring in the valve closing direction, the needle valve 2 is further lifted.

[0027] Then, after the pressure feeding of fuel is completed, the fuel storage chamber 1
When the fuel pressure in 1c decreases, the needle valve 2 is pushed back by the force of the spring and is seated on the valve seat 11e, at the same time the injection ends.

At this time, the fuel interposed between the valve portion 21 and the valve seat 11e and the fuel accumulated in the oil reservoir 11f are compressed by the biasing force of the spring. Further, since the volume of the fuel reservoir 7, which is kept oil-tight, increases as the needle valve 2 is seated, the pressure inside the fuel reservoir 7 becomes lower than that at the tip of the needle valve 2. Therefore, as shown by the arrow in FIG. 2, the fuel interposed between the valve portion 21 and the valve seat 11e and the fuel accumulated in the oil reservoir 11f pass through the through hole 27 to the fuel reservoir 7 at the end of fuel injection. The fuel is sucked out through the fuel reservoir 7, and conversely, the fuel sucked out into the fuel reservoir 7, whose volume decreases with distance, is discharged at the same time as fuel injection starts.

In this manner, by removing the fuel present in the oil pool 11f or between the valve portion 21 and the valve seat 11e at the end of fuel injection, the first spring is biased relatively weakly compared to the second spring. Even in a seat hole type two-stage spring fuel injection valve that biases the needle valve 2 only by a spring, the valve seat 11e of the needle valve 2 is It is possible to seat the user more quickly and more reliably.

In other words, a seat hole nozzle that can improve the tailing of fuel at the end of injection, and a two-stage spring fuel that can reduce smoke generation, NOx, HC, and noise by keeping the injection rate low at the beginning of injection. The advantages of both injection valves can be obtained at the same time.

Although this embodiment uses a two-stage spring fuel injection valve, the present invention is not limited to this, and can also be applied to a one-stage spring fuel injection valve.

[0032]

[Effects of the Invention] As explained above, according to the present invention, a guide portion having a cross-sectional area smaller than the needle valve fitting hole is formed on the rear end side of the sliding portion of the needle valve with the nozzle body. , providing an oil-tight means for sealing a fuel reservoir consisting of a space surrounded by the guide portion and the needle valve sliding hole, and a through hole connecting the fuel reservoir and an oil reservoir provided at the tip of the valve seat. is provided in the needle valve, so at the end of fuel injection, the fuel interposed between the tip of the needle valve and the valve seat and the fuel accumulated in the oil pool are sucked out into the oil pool, thereby preventing the needle valve from opening. Seating on the valve seat can be done more quickly and more reliably,
Since the sealing performance between the needle valve and the valve seat is improved, fuel leakage is eliminated and fuel dripping can be suppressed. Therefore, H.C.
The occurrence of carbon can be significantly suppressed, fuel efficiency can be improved, and deterioration of the nozzle due to carbon sticking around the nozzle hole can be prevented.

[Brief explanation of drawings]

FIG. 1 is an enlarged partial sectional view of a fuel injection valve showing an embodiment of the present invention.

FIG. 2 is an enlarged partial cross-sectional view illustrating the movement of fuel at the end of fuel injection.

FIG. 3 is a diagram illustrating the lift situation of the needle valve in the conventional example and the present invention.

FIG. 4 is a sectional view showing a conventional sheet hole nozzle.

FIG. 5 is a sectional view showing a conventional two-stage spring fuel injection valve.

FIG. 6 is a sectional view showing a conventional sheet hole nozzle.

[Explanation of symbols]

1 Nozzle body 11 Needle valve fitting hole 11b Needle valve sliding hole 11e Valve seat 11f Oil reservoir 12 Fuel injection hole 2 Needle valve 21 Valve part 24 Sliding part with nozzle body 25 Guide part 27 Through hole 3 Seal ring (oil secret means) 4
Nozzle holder 5 Belleville spring 7 Fuel reservoir

Claims (1)

[Claims] 1. A nozzle body having a valve seat through which a fuel injection hole opens, and a needle valve slidably fitted into a needle valve sliding hole of the nozzle body, the tip of the needle valve being connected to the valve seat. Sit down/
In the fuel injection valve that opens and closes the fuel injection hole by separating the fuel injection hole, a guide portion having a cross-sectional area smaller than that of the needle valve sliding hole is formed on the rear end side of the sliding portion of the needle valve with the nozzle body, and An oil-tight means is provided for sealing a fuel reservoir consisting of a space surrounded by a guide portion and the needle valve sliding hole, and a through hole connecting the fuel reservoir and an oil reservoir provided at the tip of the valve seat is provided. A fuel injection valve characterized by being provided in a needle valve.