JPS63183265A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To enable quick decrease of injection rate at be completion of combustion force feed in a fuel injection pump having a control sleeve for controlling injection quantity externally fitted to a plunger of the pump by forming the upper end lower end edges of a lead and a spill port which freely communicate with each other parallel to each other. CONSTITUTION:A fuel injection pump has a high pressure chamber 7 formed between a plunger 4 fitted in a plunger barrel 3 In a pump body 1 and a delivery valve 6 disposed in a valve housing 5. A control sleeve 17 is slidably fitted in the plunger 4 and moved up and down by drive of a stepping motor or the like through a control rod 19 and an engaging pin 20, whereby the communicating state of a spill port 23 of the control sleeve 17 with a lead 21 of the plunger 4 is controlled to adjust injection quantity. In this case, the upper and lower end edges of the lead 21 and an opening portion 23a of the spill port 23 are formed parallel to each other to quickly increase the opening area of the spill port 23 after the end of fuel force feed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection pump used in a compression single-ignition internal combustion engine.

(Prior Art) Conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 60-128939, a control sleeve is fitted onto a plunger which is reciprocated by a cam, and a lead formed on the plunger and a control sleeve are formed on the control sleeve. It is known that the position of the plunger where the plunger communicates with the spill port is the end of pumping. The control sleeve is moved up and down by a stepping motor, and the injection rate is controlled by changing the end of pumping, thereby reducing fuel consumption, exhaust gas, noise, etc.

(Problems to be Solved by the Invention) However, even if the injection rate is controlled in this way, it is difficult to reduce the amount of NOx in the exhaust gas.

Therefore, the inventor of the present application conducted various experiments by changing the injection rate characteristics in order to reduce No. 8, and as a result, discovered that it is sufficient to rapidly reduce the injection rate at the end of pumping.

(Means for Solving the Problems) A feature of the present invention is that the lower end edge or upper end edge of the lead and the upper end edge or lower end edge of the spill port are made substantially parallel.

(Function) Therefore, after the end of pumping, the lower or upper edge of the parallel lead is connected to the upper or lower edge of the spill port, causing the spill port to suddenly open. This is something that can solve problems.

(Example) In FIG. 2, the fuel injection pump has a pump body l, a vertical hole 2 is formed in this pump body l, a plunger barrel 3 is fixed to the body l within this vertical hole 2, and this pump body l is formed with a vertical hole 2. A plunger 4 is slidably inserted into a plunger barrel 3. The upper end of this plunger 4 is inserted into a valve housing 5 fixed to the main body 1.
A delivery valve 6 is provided therein, a high pressure chamber 7 is formed between the plunger 4 and the delivery valve 6, and a fuel outlet 8 is formed in the main body 1 above the delivery valve 6.

The lower end of the plunger 3 is connected to a cam 10 formed on a cam shaft 9.
via the tappet 11.

The cam 10 consists of a tangential cam, for example, and the return spring 1
2 to cause the plunger 3 to reciprocate along the contour of the cam 10.

Further, the plunger 3 is formed with a face portion 13, and this face portion 13 engages with a rotating sleeve 14 that is fitted onto the plunger barrel 3.

A retaining protrusion 15 is fixed to the flange portion of the rotating sleeve 14, and an injection amount adjusting rod 16 is attached to the retaining protrusion 15.
The plunger 4 is rotated in response to the movement of the rod 16, and the relative circumferential position of the plunger 4 and a control sleeve 17, which will be described below, can be changed.

The control sleeve 17 is located in a fuel reservoir chamber 18 that communicates with a fuel inlet (not shown) formed in the main body 1, and is slidably fitted onto the plunger 4. In addition, the main body 1
A control rod 19 driven by, for example, a stepping motor is inserted in the lateral direction, and an engagement pin 20 provided on this control rod 19 engages with the control sleeve 17, allowing the control sleeve 17 to move up and down. It is.

As shown in FIG. 1 and FIG. 3, the upper end edge of the control sleeve 17 is formed with a diagonal cutout 21, and the lower end edge of the control sleeve 17 is formed with a notch 21.
2 is formed in a step shape.

Further, a spill port 23 and a suction boat 24 are formed vertically in the plunger 4, and the spill port 23 and suction boat 24 are connected to the high pressure chamber mentioned above through a communication hole 25 formed in the axial direction of the plunger 4. It communicates with 7. The spill port 23 includes a parallelogram-shaped opening 23a formed by diagonally cutting out the peripheral surface of the plunger 40, and a through hole 23b connecting the opening 23a and the communication hole 25. The lead 21 and the upper and lower edges of the opening 23a of the spill port 23 are formed parallel to each other.

In the above configuration, when the camshaft 9 rotates in response to torque from the internal combustion engine, the plunger 4 reciprocates along the contour curve of the cam lO. At the beginning of the plunger 4 rising from the bottom dead center, the high pressure chamber 7 is connected to the communication hole 2 of the plunger 4.
5 and the suction boat 24 to the fuel reservoir chamber 18, so that no fuel is pumped. Then, as shown by the solid line in FIGS. 1 and 3, when the plunger 4 rises and the suction boat 24 is closed by the lower end edge of the control sleeve 17, the position of the plunger 4 at this time is the beginning of pressure feeding. ), the fuel in the high pressure chamber 7 is trapped, its pressure rises, and the delivery valve 6 is opened to start the actual pumping of fuel. The distance from the bottom dead center of the plunger 4 to the start of pumping is the prestroke.

This prestroke is adjusted by changing the vertical position of the control sleeve 17.

Then, when the plunger 4 further rises, the upper edge of the opening 23a of the spill port 23 of the plunger 4 touches the lead 21 of the control sleeve 17 (the position of the plunger 4 at this time is the end of pressure feeding), and the high pressure chamber 7 is the communication hole 2
5 and the spill port 23, the fuel in the high pressure chamber 7 flows back into the fuel reservoir chamber 18, and the pressure of the fuel in the high pressure chamber 7 decreases rapidly, causing the actual pumping of fuel to be interrupted. finish. Plunger 4 from the start of pressure feeding to the end of pressure feeding
The distance δ (shown in FIG. 3) is the effective stroke.

This effective stroke δ is adjusted by changing the position of the plunger 4 in the rotational direction. Note that when the plunger 4 is rotated to the two-dot chain line in FIG. 3, the suction port 24 is closed and the spill port 23 is opened at the same time, so that the fuel is not pumped and no injection occurs. In this embodiment, the rotational position of the control sleeve 17 is fixed and the injection amount is controlled by rotating the plunger 4, but conversely, the rotational position of the plunger 4 is fixed. The control sleeve 17 may also be rotated.

As described above, the lead 21 and the upper edge of the opening 23a of the spill port 23 are parallel to each other.

Therefore, since the opening area of the spill port 23 per unit stroke of the plunger 4 after the end of pumping increases rapidly, the recirculation speed of the fuel from the high pressure chamber 7 to the fuel reservoir chamber 18 increases.

Therefore, as shown in FIG. 4, in which the cam angle θ is plotted on the horizontal axis, in the past, the injection rate decreased gradually after the end of pumping θ2', whereas in this invention, the injection rate decreased gradually after the end of pumping θ1. After that, the injection rate decreased rapidly.

In addition, in this invention, since the injection amount decreases by the amount that the injection rate decreases sharply compared to the conventional one, the characteristic line of the conventional method and the characteristic line of the present invention are surrounded by the characteristic line of the present invention, as shown by diagonal lines in FIG. It is necessary to delay the end of pumping until θ so that the upper surface aBl and the lower area B2 are equal. As a result, we will be using a cam part that is faster, so
This allows a high injection rate as a whole.

FIG. 5 shows the change in NOx value with respect to the injection amount when the spill port is square in shape as in the present invention and in the conventional circular shape.

As a result, it became clear that NOX could be reduced by 24% or more at the maximum point.

In FIG. 6, a second embodiment of the invention is shown in which a lead 21 is formed in the plunger 4 and a spill port 23 is formed in the control sleeve 17. The lead 21 is connected to a suction port 24 through a vertical groove 26 for realizing a no-injection state, and this suction port 24 communicates with a high pressure chamber through a communication hole (not shown).

The spill port 23 is formed as a triangle circumscribing a conventional circular shape shown by a dotted line (when the diameter of the plunger 4 is 8 to 1411, it is set to 3.5 mm). The upper end edge of the lead 21 and the lower end edge of the spill port 23 are made parallel, and the same operation and effect as in the first embodiment described above is achieved.

FIG. 7 shows a third embodiment in which the spill port is shaped like a parallelogram, and FIG. 8 shows a fourth embodiment in which the spill port is shaped like a semicircle. Other points in the third and fourth embodiments are the same as in the second embodiment, so the same numbers are attached to the drawings and the explanation thereof will be omitted.

(Effects of the Invention) As described above, according to the present invention, since the lead and the spill port are made parallel, the injection rate at the end of pumping can be rapidly reduced, and as a result, NOx can be reduced. be able to. Further, even if the parallelism is slightly deviated, it does not have much effect on the control of the injection amount and injection timing, so precision for forming leads and spill ports is not required, and it can be manufactured easily.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of a first embodiment of the present invention;
Fig. 2 is a sectional view showing the entire same as above, Fig. 3 is a conceptual diagram showing the state at the end of pumping in comparison with the conventional one, Fig. 4 is a diagram showing the injection rate characteristics in comparison with the conventional one, and Fig. 5 The figure is a diagram showing the change in NOX value with respect to the injection amount compared to the conventional one, Figure 6 is a sectional view showing the main part of the second embodiment, and Figure 7 is the main part of the third embodiment. Cross-sectional view, FIG. 8 is a cross-sectional view showing the main part of the fourth embodiment. 4... Plunger, 17... Control sleeve, 21...
... Reed, 23... Spill Port. Figure 1 Figure 2 River Figure 4 Cam angle (e) □ Figure 5 Injection amount -

Claims (1)

[Claims] A control sleeve is fitted onto the plunger, a lead is formed on one side of the plunger and the control sleeve, and a spill port is formed on the other side, and the fuel injection ends at a position of the plunger where the lead and the spill port communicate with each other. A fuel injection pump characterized in that the lower end edge or upper end edge of the lead and the upper end edge or lower end edge of the spill port are substantially parallel to each other.