JPS5996475A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To approach injection properties to an ideal value, by installing a throttle mechanism which limits the substantial opening area of a fuel passage to a micro value in a primary injection area. CONSTITUTION:A throttle mechanism 9 is constituted such that a middle-sized column part 15, loosely engaged with the inner periphery of a shaft hole 11 with a fine annular gap 14, is formed between a large column part 12 of a needle valve 6, slidably mating with the shaft hole 11 in a nozzle body 2, and a taper part 13 of the needle valve 6 situated in a fuel chamber 3, an annular groove 16, communicated to the fuel chamber 3 through the annular gap 14, is provided in the vicinity of the lower end of the shaft hole 11, and a high-pressure fuel A, introduced from the start end of the fuel passage 1, can be guided to the fuel chamber 3 through the annular groove 16 and the annular gap 14. This constitution shows properties in that an injection rate is controlled to a low value until the lift amount of the needle valve 6 exceeds a specified value, and after exceeding the specified value, the injection rate is rapidly increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a fuel injection nozzle 1 used in a diesel engine E.

In general diesel engines, it is extremely important to control the fuel injection rate as a countermeasure for knocking noise, and the ideal injection rate is as shown by the solid line a in Figure 1.
It is desirable that the initial value of Iζ be lower and then higher by one.

Conventionally, Iζ, so-called throttle-type or bottle-type fuel injection nozzles have often been used to obtain such injection rate characteristics, but in reality, it is often not possible to obtain the ideal injection rate characteristics as described above. do not have. That is, in this type of injection nozzle, a needle valve is lifted by the pressure of high-pressure fuel introduced into a fuel chamber 1ζ through a fuel passage, and the fuel in the fuel chamber is injected into a predetermined amount through a nozzle that opens by a lift amount of the needle valve. In the case where the injection can be made in one direction, a small diameter cylindrical part provided at the tip of the needle valve is loosely fitted in the nozzle through an annular gap, and the initial stage when the needle valve starts to lift. The structure is such that a small amount of fuel ft can be preliminarily injected through the annular gap. However, in conventional systems, the high-pressure fuel supplied from the injection pump is directly supplied to the fuel chamber through a simple boat-shaped fuel passage, so pressure waves generated within the fuel supply system are avoided. As a result, the pressure in the fuel chamber tends to increase rapidly by 1ζ, which tends to cause the needle valve to jump up and lift rapidly. As a result, the period during which the throttling effect by the tip of the needle valve is exerted becomes extremely short, resulting in a fuel injection rate characteristic that is far from ideal, i.e., an undesired fuel injection rate as shown by the broken line in Figure 1. In many cases, only injection rate characteristics can be obtained.

In addition, as a prior art related to this type of nozzle,
As shown in No. 0-106520, there is also a needle valve in which a concave portion is provided in the small-diameter cylindrical portion of the needle valve to further enhance the throttling effect in the initial injection stage. However, this method only enhances the throttling effect at the tip of the needle valve, and is not effective in preventing the needle valve from jumping up. Even the throttling effect, which has been painstakingly enhanced, is only available for a very short period of time, resulting in the disadvantage that, as mentioned above, only poor fuel injection rate characteristics can be obtained.

The present invention has been made in view of the above-mentioned circumstances, and is aimed at reducing the substantial open area of the fuel passage to a minute value in the initial injection region m until the lift amount of the needle valve exceeds a predetermined value. 1
The present invention provides a fuel injection nozzle that effectively eliminates the above-mentioned disadvantages and can obtain ideal injection rate characteristics by providing a throttle mechanism that limits this.

An embodiment of the present invention will be described below with reference to FIG.

The high-pressure fuel A discharged from a fuel injection pump (not shown) is introduced into the fuel chamber 8 formed inside the nozzle body 2 through the fuel passage 1.
is configured to be able to be injected to the outside of the nozzle body 2 through a nozzle 5 formed in the center of the valve seat portion 4. A needle valve 6 is provided on the valve seat portion 4 so as to be able to come into contact with and separate from the valve seat portion 4, and the needle valve 6 connects and disconnects the communication state between the jet nozzle 5 and the fuel chamber 8. The needle valve 6 is pressed against the valve seat 4I by a spring (not shown), and is lifted by the pressure only when high-pressure fuel A is introduced into the fuel chamber 8. It's starting to move away from 4. Further, a small diameter cylindrical portion 7 is integrally provided at the tip of the needle valve 6. Then, this small-diameter cylindrical portion 7 is loosely fitted through a minute annular gap 8 in the inner layer of the nozzle 5, and a minute amount of fuel is poured into the annular gap 8 in the initial stage when the needle valve 6 is about to separate from the valve seat portion 4. The nozzle body 2 is configured to be able to be preliminarily injected to the outside of the nozzle body 2 through the nozzle body 2.

In such a fuel injection nozzle Cζ, the fuel passage 1
A throttle mechanism 9 is provided at the terminal end of the fuel passage 1 to limit the substantial open area of the fuel passage 1 to a small value in the initial injection region until the lift amount of the needle valve 6 exceeds a predetermined value. To be more specific, the aperture mechanism 9 has a shaft hole 11 in the nozzle body 2.
There is a small annular gap between the large-diameter cylindrical part 12 of the needle valve 6 that can be slid into the inner circumference of the shaft hole 11 and the tapered part 18 of the needle valve 6 that faces the fuel chamber 8. When forming a medium-diameter cylindrical portion 15 that fits loosely through the shaft hole 1,
An annular groove 16 communicating with the fuel chamber 8 via the annular gap 14 is provided near the lower end of the fuel passage 1, and high-pressure fuel A introduced from the starting end side of the fuel passage 1 passes through the annular groove 16 and the annular gap 14. 5- The fuel can be led to the fuel chamber 8.

The opening area of the annular gap 14 is the annular gap 1
The pressure loss in the 4th section is set to a value smaller than the pressure loss in the 8th section I of the annular gap. Reference numeral 17 is a check valve for directly returning the fuel in the fuel chamber 8 to the fuel passage 1, and the ball 18 is brought into elastic contact with the seat portion 2 (H4) by a spring 19r. The valve 17 is provided to quickly seat the needle valve 6.

With such a configuration, the high-pressure fuel introduced into the fuel chamber 8 is basically operated in the same way as a conventional throttle type or bottle type fuel injection valve, and the high-pressure fuel is pumped through the nozzle 5 and out of the nozzle body 2. In other words, the injection rate Cζ is injected into the combustion chamber of a diesel engine (not shown), and the injection rate at this time is suppressed to a low value until the lift amount of the needle valve 6 exceeds a certain value, and then rapidly increases. It exhibits the characteristic of becoming higher. Moreover, in the present invention, a throttle mechanism 9 is provided on the upstream side of the fuel chamber 8, and the substantial flow of the fuel passage 1 is provided in the initial injection region until the lift amount of the needle valve 6 exceeds a certain value l. 1 to limit the open circuit area to a small value [this]
It's straining. That is, in this embodiment, until the lift amount of the needle valve 6 exceeds the above-mentioned constant value l, there is a small gap between the medium diameter cylindrical part 15 of the needle valve 6 and the inner peripheral surface of the shaft hole 11 of the nozzle body 2. An annular gap 14 is formed so that the high-pressure fuel A introduced into the fuel passage 1 is guided into the fuel chamber 8 through the annular groove 16 and the annular gap 14 sequentially. Therefore, the high pressure fuel A is in the fuel chamber 3.
A large pressure loss is involved until the pressure reaches 1ζ.

As a result, even if there is a large pressure fluctuation in the high-pressure fuel introduced into the fuel passage 11ζ, the pressure inside the fuel chamber 3 will rise relatively smoothly, and the pressure in the fuel chamber 3 will rise relatively smoothly, causing the needle valve 6 to jump up. It is possible to eliminate the phenomenon of lifting. That is, it becomes possible to lift the needle valve 6 at a stable speed.

Therefore, sufficient time is secured for controlling the injection rate through the small-diameter cylindrical portion 7I of the needle valve 6, and the initial injection rate rises smoothly. It is possible to obtain a characteristic similar to that of the injection rate characteristic f.

Partly, when the lift amount of the I'nl needle valve 6 exceeds a certain value, the tapered portion 18 of the needle valve 6 faces the annular groove 16, which causes high pressure in the fuel passage 1. Fuel A is introduced into the fuel chamber 3 without resistance. Furthermore, when the fuel injection period ends and the needle valve 6 is seated, a portion of the fuel A in the fuel chamber B is directly returned to the fuel passage 1 via the check valve 17. Therefore, the seating of the needle valve 6 is quickly completed.

The present invention is not limited to throttle type or bottle type injection nozzles, but can be applied to all types of injection nozzles such as direct injection nozzles.

Furthermore, the configuration of the diaphragm mechanism is of course not limited to that of the embodiment described above, and may be as shown in FIG. 8, for example. That is, the aperture mechanism 9 shown in FIG.
' is a shallow annular groove 21 that forms a small annular gap 14' between the inner circumference 1 of the shaft hole 11 of the nozzle body 2 and the needle valve 6, and an annular groove 22 that communicates with the fuel passage IIL. At the same time, the needle valve 6 has a boat 2B with one end facing the annular groove 21 and the other end communicating with the fuel chamber 8Iζ, so that the lift amount of the needle valve 6 is constant. Until the value l!I is exceeded, the high-pressure fuel A introduced into the fuel passage 1 is guided into the boat 28 through a minute annular gap 14' and into the fuel chamber 8. It has become.

Further, although a check valve provided between the fuel chamber and the fuel passage is not necessarily necessary, if such a check valve is provided, the needle valve can be seated quickly. It is possible to eliminate the inconvenience that the fuel injection state is disturbed due to sluggishness and thermal efficiency is reduced.

Since the present invention has the above-described configuration, it is possible to lift the needle valve smoothly at a stable speed in the initial injection region, and therefore it is possible to obtain a fuel that can bring the characteristics of the initial injection rate closer to the ideal. Let's take a look at what spray nozzles we can provide.

[Brief explanation of the drawing]

9- FIG. 1 is a diagram for explaining injection rate characteristics, FIG. 2 is a cross-sectional view showing one embodiment of the present invention, and FIG. 8 is a cross-sectional view showing another embodiment of the present invention. 1... Fuel passage 8... Fuel chamber 5... Nozzle 6... Needle valve 9.9'... Throttle mechanism agent Patent attorney Hiroshi Akazawa 10-

Claims (1)

[Claims] The needle valve is lifted by the pressure of high-pressure fuel introduced into the fuel chamber through the fuel passage, and the high-pressure fuel in the fuel chamber is injected in a predetermined direction through a nozzle opening from the lift of the needle valve. In the fuel injection nozzle configured as shown in FIG. A fuel injection nozzle characterized by: