JP2577271Y2 - Fuel injection pump - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for a diesel engine or the like, and more particularly to a technique for suppressing an initial injection amount.

[0002]

2. Description of the Related Art Conventionally, a fuel injection pump having a structure in which a feed hole is provided on a circumferential surface of a plunger barrel, and the feed hole is closed by a plunger fitted and held in the plunger barrel to start fuel pressure feed. This is known (see Japanese Utility Model Laid-Open No. 2-43460).

[0003]

An invention is the way, in order to effectively reduce the NO _X and noises discharged from a diesel engine, an initial injection rate of the fuel kept as low, it is effective to suppress the combustion temperature However, since the conventional fuel injection pump uses a cylindrical plunger whose outer diameter matches the inner diameter of the plunger barrel, the initial fuel injection rate cannot be suppressed at all, and NO _X Was not able to be effectively reduced.

Conventionally, the outer diameter of the top of the plunger is formed in a conical tapered surface that becomes smaller in diameter as it goes to the top surface, thereby deteriorating the sealing performance at the start of the initial fuel pumping, thereby reducing the initial fuel injection rate. In some cases, the temperature is kept low (see JP-A-3-210061). However, in this case, the amount of fuel leakage changes before the top of the plunger passes through the feed hole and is not constant, and the injection rate during the initial low injection rate period is not smoothed. The amount is poor.

In view of the above, the present invention has been made in view of the above circumstances.
The aim is to improve x and noise reduction.

[0006]

According to the fuel injection pump of the present invention, a feed hole is provided in a peripheral wall of a plunger barrel.
In a fuel injection pump configured to start fuel pumping by closing the feed hole with the plunger fitted and held in the plunger barrel, the plunger barrel inner peripheral surface immediately above the feed hole may be moved in the plunger ascending direction. An annular groove having a conical tapered surface on the inner peripheral surface whose diameter becomes larger as it goes was formed.

[0007]

In the fuel feeding period after the feed hole is closed, there is a slight clearance between the plunger and the barrel, fuel leaks therefrom, and a rise in fuel pressure is suppressed, so that the injection amount at the beginning of the injection is suppressed. Also, the clearance amount is constant until the plunger passes through the concave groove, the amount of fuel leakage is constant, the injection rate during the initial low injection rate period is smoothed, and the initial injection amount is well cut, Therefore, low N
Ox and noise can be effectively reduced.

[0008]

FIG. 1 shows a plunger barrel 1 in which
A plunger 3 is provided which is reciprocated upward and downward by a cam 2 which rotates synchronously with the engine. That is, the plunger 3 is pushed up by the cam 2 via the tappet 4 and pushed back by the plunger spring 5. A feed hole 6 is provided on the peripheral wall of the plunger barrel 1, and when the plunger 3 rises and closes the feed hole 6, fuel pumping is started, and the oblique notch 7 on the outer peripheral surface of the plunger 3 forms the feed hole 6. Pumping of fuel ends when we meet.

When the plunger 3 feeds the fuel to increase the pressure and becomes larger than the resistance of the delivery valve spring 8, the delivery valve 9 is pushed open to send the fuel to the fuel injection nozzle via the nozzle pipe. Is configured. A control rack 10 that moves left and right by operation of a control lever, and a control sleeve 12 to which a pinion 11 that meshes with the control rack 10 are provided. The control sleeve 12 is combined with a claw 3a of the plunger 3 to It rotates with the plunger 3. Therefore, by operating the control lever, the control rack 10 is moved right and left, and the plunger 3 is rotated together with the control sleeve 12, whereby the position of the notch 7 is changed, and the effective stroke of the plunger 3 is changed. The adjustment of the fuel delivery amount is performed according to (3).

As shown in FIG. 2, the inner peripheral surface of the plunger barrel 1 immediately above the feed hole 6 has a conical tapered surface 13a whose diameter increases toward the ascending direction of the plunger 3. An annular groove 13 is formed on the surface. In such a configuration, after the feed hole 6 is closed by the plunger 3, the pumping of the fuel is started. In the fuel feeding period, there is a slight clearance between the outer peripheral surface of the plunger 3 and the boundary between the concave groove 13 and the feed hole 6, and fuel leaks therefrom to suppress an increase in fuel pressure. The injection amount at the beginning of the injection is suppressed, and the clearance amount is constant and the fuel leakage amount is constant until the plunger 3 finishes passing through the concave groove 13.

As a result, the relationship between the crank angle and the fuel injection pressure of the fuel injection pump is as shown in the characteristic diagram of FIG.
At the beginning of the injection start, the fuel injection amount is the same as the conventional fuel injection amount without fuel leakage, but at the end of the initial injection start, the fuel injection amount is much lower than the conventional fuel injection amount. Therefore, as is clear from the characteristic diagram of FIG. 3, the injection rate in the low injection rate period is smoothed, and the initial injection amount is well cut.
Low NOx and low noise can be effectively achieved.

It should be noted that the present invention is not limited to the configuration of the embodiment, and various changes can be made based on the claims of the utility model registration.

[0013]

As described above, according to the present invention, in the fuel injection pump, the inner peripheral surface of the plunger barrel immediately above the feed hole is provided with the conical tapered surface whose diameter increases as the plunger rises. Since the annular concave groove on the surface is formed, the rise in fuel pressure is suppressed during the fuel pumping period after the feed hole is closed, the injection amount at the beginning of injection is suppressed, and especially the injection rate during the low injection rate period is smoothed And also
The cutoff of the initial injection amount is good, so that the NOx reduction and noise reduction can be effectively achieved, and the practical effect is large.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a fuel injection pump according to the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the groove according to the embodiment.

FIG. 3 is a characteristic diagram of a fuel injection pressure in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plunger barrel 3 Plunger 6 Feed hole 13 Concave groove 13a Conical taper surface

Claims (1)

(57) [Scope of request for utility model registration] 1. A fuel injection pump having a configuration in which a feed hole is provided in a peripheral wall of a plunger barrel, and pressure feed of fuel is started by closing the feed hole with a plunger fitted and held in the plunger barrel. A fuel injection pump, wherein an annular concave groove having a conical tapered surface whose diameter increases toward the plunger rising direction is formed in the inner peripheral surface of the plunger barrel immediately above the plunger barrel.