JPH0533743A - Fuel injection device - Google Patents

Abstract

PURPOSE:To stabilize an idling operation by preventing growth of liquid drops adhered to an injector or its holder during the idling operation. CONSTITUTION:An injector 6 is arranged on an upstream side of a throttle valve of an intake passage of an engine through a holder 5. An outer periphery 6A-1 on an end of a nozzle of the injector 6 and an outer periphery 5A of an end of the holder 5 on an outside of the surface 6A-1 are tapered surfaces. The nozzle side tapered surface 6A-1 is projected in respect to the holder side tapered surface 5A with a boundary stepped difference S being substantially zero or minute difference of nearly zero. Thus, the tapered surfaces 6A-1 and 5A are substantially continuously formed and the end of the tapered surface reaches a nozzle port 6B. Atomized fuel adhered to an outer wall of the injector holder 5 is introduced to the nozzle port 6B continuously along the tapered surface 5A and the tapered surface 6A-1, joined by a fuel flow injected from the nozzle port 6B for injection, and thus growth of liquid drops is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector (fuel injection valve), and more particularly to a fuel injection device for an engine in which the injector is arranged upstream of a throttle valve.

[0002]

2. Description of the Related Art For example, in a fuel injection device used for a gasoline engine of an automobile, an injector is arranged in an intake passage upstream of a throttle valve and used commonly for each cylinder.

By the way, since the throttle valve is almost fully closed during idle operation, fuel mist fills the throttle valve upstream side in the intake passage. Therefore, in the device in which the injector is arranged upstream of the throttle valve, the fuel mist is deposited as droplets on the inner wall of the intake passage on the upstream side of the throttle valve, the outer wall of the holder supporting the injector, the outer peripheral surface of the injector tip, and the like.

Of these, the fuel adhered to the inner wall of the intake passage continuously flows down through the wall and enters the downstream side of the intake passage through the gap between the throttle valve and the inner wall of the intake passage.
There is no problem because it is continuously vaporized on the downstream side of the intake passage in the low pressure state.

On the other hand, as for the fuel mist adhering to the injector holder and the injector, the adhering liquid flow stays at a portion where the angle of the outer circumference of the holder suddenly changes or at the boundary between the injector and the injector holder, and it grows. As a result, the air-fuel ratio of the fuel suddenly changes due to intermittent spillage, which causes instability in idle operation.

Therefore, conventionally, as shown in FIG. 6, the outer peripheral surface 20A of the tip end of the nozzle of the injector 20 is formed in a tapered shape to prevent fuel droplets from accumulating on the tip end surface of the injector (see, for example, Japanese Unexamined Patent Publication As disclosed in Japanese Laid-Open Patent Publication No. 57-191455), as shown in FIG.
Nozzle tip 30A of No. 0 is projected from the holder 31 and is exposed to the air flow flowing toward the intake port side to the projected nozzle tip 30A to prevent large droplets of fuel from adhering to and growing at the nozzle tip opening. (For example, disclosed in Japanese Laid-Open Patent Publication No. 59-226272) has been proposed.

[0007]

However, even if the nozzle tip end outer peripheral surface 20A is formed in a tapered shape as shown in FIG. 6 in the above liquid drop retention means, the nozzle tip end is conventionally formed. A recess is formed between the outer circumference 20A and the injector holder 21 so as to be surrounded by a one-dot chain line circle, and the adhered fuel flowing through the holder 21 is accumulated in this part, which causes droplet growth.

Further, in the system of exposing the nozzle tip 30A to the air flow as shown in FIG. 7, when the injector is arranged on the upstream side of the throttle valve, the air flow velocity on the upstream side of the throttle valve is low during idle operation. The fuel attached to the tip of the injector cannot be blown off by the air flow, and it is sufficient to prevent droplet growth at the position surrounded by the dashed-dotted line circle in the figure (the gap between the holder 31 and the injector 30, the edge of the nozzle tip 30A, etc.). Was not.

The present invention has been made in view of the above points, and it is an object of the present invention to prevent fuel mist from adhering to the injector and injector holder during idle operation.
The purpose of this is to effectively prevent the droplet growth of the adhered fuel and stabilize the idle operation.

[0010]

In order to achieve the above object, the present invention basically proposes the following means for solving the problems, and in order to make the contents easy to understand, the embodiment of FIG. The description will be given by citing the reference numeral.

That is, according to the present invention, in the fuel injection device in which the injector 6 is arranged upstream of the throttle valve in the intake passage of the engine via the injector holder 5, the outer periphery 6A-1 of the tip end of the nozzle portion of the injector 6 is connected to the fuel injection hole 6B. Of the injector holder 5 located outside of the nozzle holder 5 is tapered toward the nozzle fitting hole 5B provided in the center of the injector holder 5, and the outer circumference of the tip end of the nozzle portion is In order that the tapered surface 6A-1 and the tapered surface 5A on the outer periphery of the tip of the injector holder are almost continuous, the boundary step S between the tapered surfaces 6A-1 and 5A is set to zero or a minute difference close to this. The tip outer peripheral tapered surface 6A-1 is made to protrude from the injector holder tip outer peripheral tapered surface 5A.

[0012]

As described above, the nozzle tip end outer peripheral tapered surface 6A-1 of the injector 6 is set so that the boundary step S with respect to the tip outer peripheral tapered surface 5A of the injector holder 5 becomes almost zero or a minute difference close thereto. By making them protrude, both the tapered surfaces 6A-1 and 5A become a substantially continuous surface, and the tip of the tapered surface reaches the fuel injection hole 6B.

As a result, even if the fuel mist that fills the upstream side of the throttle valve during idle operation adheres to the outer surface of the injector holder 5, the holder-side tapered surface 5A and the nozzle-part tapered surface 6A-1 are connected almost continuously. The adhered fuel is smoothly guided to the fuel injection hole 6B of the injector, and the fuel injection hole 6B
Is injected together with the fuel flow being injected from.

Since the above-described operation is continuously performed, it is possible to prevent the fuel attached to the outer surface of the injector holder and the fuel attached to the outer surface of the injector from growing into large drops, and to drop as droplets on the throttle valve surface. prevent.

In order to satisfy the above operation, as described above, the tapered surface 6A-1 on the outer periphery of the tip of the nozzle of the injector 6 is replaced by the tapered surface 5 on the outer periphery of the injector holder.
It is necessary to project the boundary step S from A so that the boundary step S becomes zero or a minute step close to this.

On the contrary, when the nozzle portion tip outer peripheral taper surface 6A-1 has a step difference S'lower than the holder taper surface 5A as shown in FIG. 3, the taper surface 6A-1 becomes a recess with respect to the taper surface 5A, and the injector holder 5 The fuel adhering to the outer surface grows into large drops at the edge portion 5'of the holder and drops.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partial sectional view showing a main part of a first embodiment of the present invention, and FIG. 2 is a vertical sectional view of a fuel injection device according to the first embodiment.

Prior to the description of the essential parts of this embodiment, the overall construction will be described with reference to FIG.

In FIG. 2, reference numeral 1 denotes a throttle body which is a part of an intake passage of the engine. A throttle valve 3 is arranged in the internal intake passage 2 so as to be openable and closable via a shaft 4. A throttle valve 3 is provided upstream of the throttle valve 3. An injector 6 serving as a dot type fuel injection device is arranged while being supported by an injector holder 5.

The injector 6 is housed in the injector holder 5, and a cap 11 serving as an injector holder is attached to the upper portion of the holder 5. The injector 6 is assembled to the holder 5 by sandwiching the injector 6 with a lower seat 10 and an upper seat 9 made of an elastic material such as rubber, and pushing the upper seat 9 with an injector cap 11.

A passage 7 for measuring an intake air flow rate is formed on a side wall of the throttle body 1 in parallel with the intake air passage 2, and a hot-wire type flow rate measuring element 8 disposed in the passage 7 is provided to prevent the ventilation flow rate of the passage 7. The flow rate of intake air passing through the intake passage 2 is indirectly measured.

The injector 6 is of a single-point type as an example, and an amount of fuel corresponding to the operating state of the engine is injected into the intake passage 2.

In the present embodiment, as shown in FIG. 1, the tip outer circumference 6A-1 of the nozzle portion 6A of the injector 6 is formed in a tapered shape extending to the edge of the nozzle hole (fuel injection hole) 6B. 6A-1 faces the intake passage 2. The injector holder tip outer circumference 5A is also positioned outside the nozzle tip tip outer circumference tapered surface 6A-1, and the holder tip outer circumference 5A is tapered toward the nozzle fitting hole 5B provided at the center thereof. Further, the nozzle portion tip outer peripheral taper surface 6A-1 and the injector holder tip outer peripheral taper surface 5
Both taper surfaces 6A-1, 6A-1, such that A and A are almost continuous surfaces.
The boundary step S of 5A is made to be zero or a minute difference close to this, and the nozzle portion tip outer peripheral taper surface 6A-1 is projected from the injector holder tip outer peripheral taper surface 5A.

Specifically, the size of the boundary step S is controlled by controlling the thickness variation of the upper seat 9 and the lower seat 10 with respect to the load and the inlay length L of the injector retainer 11 as shown in FIG. The range is 0 to 0.5 mm.

Further, the outer peripheral taper surface 6A-1 at the tip of the nozzle portion
The gap (fitting gap) G at the boundary with the outer peripheral tapered surface 5A of the injector holder is set in the range of 0 to 0.2 mm, and the apex angle between both tapered surfaces 6A-1 and 5A is 100 ° to 12 mm.
It forms a 0 ° conical surface.

According to the above configuration, the injector 6
Even if the injected fuel particles adhere to the outer surface of the injector holder 5 and become a fuel liquid flow, the taper surface 5 is almost continuous.
It smoothly flows to the nozzle hole 6B side through A.6A-1, and when it reaches the nozzle hole 6B, it is atomized again by the force of the fuel flow injected from the nozzle hole 6B. Since this action is continuously performed, the fuel adhering to the outer surface of the injector holder 5 does not grow into large drops, and the dropping of the fuel can be prevented.

As a result, even during idle operation, a normal air-fuel ratio is maintained to ensure smooth operation.

FIG. 5 shows a second embodiment of the present invention and is a view of the tip outer peripheral surface 5A of the injector holder 5 and the nozzle portion tip outer peripheral surface 6A-1 of the injector 6 as viewed from below.

These outer peripheral surfaces are formed in a substantially continuous taper shape as in the first embodiment.
Radial grooves 1 centered on the nozzle holes 6B in A and 6A-1
2 is formed.

According to this embodiment, when the fuel particles injected from the injector 6 adhere to the outer surface of the injector holder 5, they flow along the holder tip outer peripheral taper surface 5A and the nozzle tip outer peripheral taper surface 6A-1. At that time, it is guided by the radial groove 12 and smoothly guided to the nozzle hole 6B of the injector, and the same effect as the first embodiment is obtained.

[0032]

According to the present invention, in the fuel injection system of the type in which the injector is arranged on the upstream side of the throttle valve, fuel dripping can be prevented even during idling when the air flow velocity in the intake passage is low, so that stable engine rotation is achieved. Can be planned.

Further, since no special parts are used for preventing fuel dripping, there is an effect of cost reduction for improving performance.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an essential part of a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing the overall configuration of the first embodiment.

FIG. 3 is an explanatory diagram showing an example of a problem to be solved by the present invention.

FIG. 4 is a partial sectional view showing a part of the first embodiment.

FIG. 5 is a bottom view of the injector and its holder used in the second embodiment of the present invention.

FIG. 6 is a partial cross-sectional view showing an example of a conventional fuel injection device.

FIG. 7 is a partial cross-sectional view showing an example of a conventional fuel injection device.

[Explanation of symbols]

1 ... Throttle body 2 ... Intake passage 3 ... Throttle valve 5 ... Injector holder 5A ... Injector holder tip outer peripheral taper surface 6 ... Injector 6A ... Nozzle part 6A-1 ... Nozzle tip outer peripheral taper surface 6B ... Fuel injection hole (nozzle hole) 12 ... Directional groove

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoichi Fukuda             2520, Takaba, Katsuda City, Ibaraki Prefecture             Hitachi Sawa Factory (72) Inventor Toru Ishikawa             2520, Takaba, Katsuda City, Ibaraki Prefecture             Hitachi Sawa Factory

Claims (4)

[Claims] 1. A fuel injection device in which an injector is arranged upstream of a throttle valve in an intake passage of an engine via an injector holder, wherein a tip end outer periphery of the injector is tapered to a rim of a fuel injection hole. The outer circumference of the injector holder tip located outside of the nozzle holder is tapered toward the nozzle fitting hole provided in the center, and the tapered surface of the outer circumference of the nozzle tip and the outer circumference of the injector holder are tapered. So that the surface and the surface are almost continuous,
A fuel injection device characterized in that the nozzle step tip outer peripheral taper surface is projected from the injector holder tip outer peripheral taper surface with a minute difference of zero or a boundary difference between the two tapered surfaces. 2. The nozzle portion tip outer peripheral taper surface according to claim 1, wherein the nozzle holder tip tip outer peripheral taper surface protrudes with a boundary step of 0.5 mm or less with respect to the injector holder tip outer peripheral taper surface, and Gap at the boundary with the outer peripheral tapered surface of the injector holder (fitting gap)
Of 0.2 mm or less. 3. The conical surface having an apex angle of 100 ° to 120 ° is formed by the nozzle portion tip outer peripheral taper surface and the injector holder tip outer peripheral taper surface according to claim 1 or 2. Fuel injection device. 4. The nozzle assembly according to claim 1, wherein the nozzle portion tip outer peripheral taper surface and the injector holder tip outer peripheral taper surface are radial with respect to a fuel injection hole of the nozzle portion. A fuel injection device having a groove formed therein.