JPH04311667A - Initial fuel injection suppressing type fuel injection pump - Google Patents

Abstract

PURPOSE:To reduce diesel knocking and diesel engine noise by providing the plunger of an infection pump with a leak port switched before the opening of a spill port so as to suppress the initial fuel injection quantity. CONSTITUTION:A distributor-type fuel injection pump distributes and force-feeds fuel to each cylinder by the reciprocating rotation of one plunger 3. In this case, the plunger 3 of the VE-type injection pump is provided with a separate leak port 17 from a spill port 5, and an annular leak groove 18 and a leak passage 19 are further bored in a peripheral pump body 16. When the force-feeding of fuel is started, the wedge part of the leak port 17 is overlapped with the annular leak groove 18, so that a part of fuel force-fed into a distributing passage 11 from a fuel passage 4 in the plunger 3 leaks into pump 14 to lower fuel force-feeding pressure. Initial injection is thereby suppressed to decrease fuel injected before ignition and thereby to reduce diesel knocking and engine noise.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel feed rate control means for a distribution type fuel injection pump of a diesel engine, and more particularly to an initial fuel injection amount suppressing means for a VE type injection pump.

0002

BACKGROUND OF THE INVENTION FIG. 6 shows a sectional view of a main part of a fuel pressure distribution section 10 of a conventional VE injection pump. (Refer to "Diesel Fuel Injection," co-authored by Fujisawa and Kawai, Figure 4.62, published by Sankaido, June 1986.) To explain the outline, the feed pump 13 rotated by the drive shaft 15 pumps fuel from the fuel tank (not shown). Fuel is fed under pressure into the pump chamber 14 of the injection pump, and as the plunger 3 rotates and reciprocates, the fuel filling the pump chamber 14 flows into the pressure chamber 2 through the suction port 1 formed in the injection pump body 16. The compressed high-pressure fuel is then passed from the distribution passage 11 to the delivery valve 1.
2 and distributed to the injection nozzles (not shown) of each cylinder. During this period, the rotation and reciprocating movement of the plunger 3 is performed by the movement of the face cam 8 pressed against the roller 9 by the plunger spring 7, and the high-pressure fuel filling the fuel passage 4 in the plunger is transferred to the spill ring 6 during the forward movement of the plunger 3. Due to the relative positional relationship between the spill port 5 and the spill port 5, the spill port 5 is opened to the pump chamber 14, and the high-pressure fuel in the plunger fuel passage 4 flows out into the pump chamber 14, which has a lower pressure. The timing of the end of injection is determined.

Various methods for controlling the fuel feed rate of the injection pump have been conventionally proposed for the above structure. For example, in Japanese Patent Publication No. 1-52581, the pressure of the VE injection pump A means is disclosed in which a control valve having a relief passage is provided at the tip of the chamber 2, and the relief passage is opened and closed in response to increases and decreases in the load of the engine to control the fuel supply rate.

In a conventional injection pump, including the above disclosure, the relationship between fuel injection pressure and time during one stroke of the plunger is a diagram as shown in FIG. That is, the injection pressure when injection is performed from the delivery valve 12 to each injection nozzle rises to a predetermined maximum pressure in a short period of time, and thereafter the injection pressure increases to a predetermined maximum pressure in a short period of time.
Injection continues at a constant high pressure until the pump opens and the fuel flows into the pump chamber 14.

As shown in the above-mentioned injection pressure one-hour diagram, the injection pressure is high from the beginning of injection, so the initial injection amount is large, and for this reason, the amount of fuel injected before ignition increases. When the engine ignites, it burns rapidly, causing diesel knock and increasing engine noise.

In order to reduce this diesel knock, it is necessary to reduce the injection amount at the initial stage of injection to reduce the amount of end-burned fuel in the cylinder before ignition. It is better to lower it. In view of the above,
In the present invention, diesel knock is reduced by providing the injection pump with a means for suppressing initial injection.
The purpose is to reduce engine noise.

[0007]

[Operation] The plunger of the injection pump is provided with a leak port that opens and closes before the spill port opens, so during the stroke of the plunger, the leak port opens first and a portion of the high-pressure fuel in the fuel passage of the plunger flows from there. flows into the low-pressure pump chamber, and the oil pressure for sending fuel during the stroke of the plunger decreases by that amount.Therefore, the fuel injection pressure decreases, and the amount of fuel injected into each cylinder is reduced. After that, as the stroke progresses further and the leak port closes before the spill port opens, the injection pressure becomes high, and a predetermined high-pressure fuel is injected into each cylinder from the injection valve, resulting in normal combustion with little knocking. .

[0008]

[Embodiment] An embodiment of the present invention will be explained based on the drawings. FIG. 1 shows a first embodiment. In the figure, parts common to those in FIG. 6 are denoted by the same reference numerals, detailed explanations are omitted, and points different from the prior art will be mainly explained.

In this embodiment, as shown in FIG. 1, a leak port 17 separate from the spill port 5 is provided in the plunger 3 of the conventional VE injection pump in front of the spill port 5 (on the pressure chamber 2 side). Further, an annular leak groove 18 and a leak passage 19 are bored in the pump body 16 around the pump body 16.

FIG. 2 shows a partially enlarged view of FIG. 1, in which (a) is a detailed view of section A in FIG.
c) is a plan view (top view) of plunger 3; (d) is (c)
An enlarged plan view of part D, that is, the leak port 17 is shown. The leak port 17 is located on the outer periphery of the plunger as shown in Fig. 2(c).
As shown in (d), the tip 1 has a wedge-shaped opening that narrows toward the rear of the plunger 3 (toward the spill port 5 side).
It has a 7b shape. The center of the hole of the leak port 17 communicates with the fuel passage 4 at the center of the plunger. The annular leak groove 18 is formed in the body 16 and overlaps with the wedge-shaped starting portion 17a of the leak port 17 when the plunger 3 is in the rearmost position at the beginning of fuel pumping. Further, the annular leak groove 18 communicates with the pump chamber 14 through a leak passage 19.

FIG. 3 shows the operation of the injection pump with the above configuration.
This is explained by: FIG. 3(a) shows the state at the beginning of pressure feeding of fuel, showing the wedge-shaped portion of the leak port 17 and the annular leak groove 1.
8 overlap here, and part of the fuel that is being pumped from the fuel passage 4 in the plunger 3 to the distribution passage 11 leaks from here into the pump chamber 14, reducing the pressure of the fuel being pumped and flowing to the injection nozzle. Less fuel is pumped.

As the plunger 3 advances further and the pumping stroke progresses, the shape of the leak port 17 at the overlapping portion of the wedge-shaped portion of the leak port 17 and the annular leak groove 18 changes to the shape shown in FIG. As shown in d), the opening area becomes narrower as it moves from 17a to 17b, and the amount of fuel leaked into the pump chamber 14 decreases, so that relatively less fuel is pumped through the distribution passage 11 toward the injection nozzle. The amount of will gradually increase.

As the pumping stroke progresses further and the overlap between the wedge-shaped portion of the leak port 17 and the annular leak groove 18 disappears, the leak to the pump chamber 14 disappears, resulting in a state as shown in FIG. The plunger 3 pumps high-pressure fuel to the injection nozzle.

[0014] Then, when the pumping stroke of the plunger 3 further advances, the spill port 5 opens as shown in FIG. 3(d), and the high-pressure fuel inside the plunger 3 is pushed back into the pump chamber 14, ending the pumping of fuel. .

It should be noted that the shape of the outlet of the leak port 17 need not be limited to the wedge shape shown in FIGS. It may be of any shape.

Furthermore, the relationship between the annular leak groove and the wedge shape of the leak port may be reversed, and the annular groove may be provided on the plunger and the wedge shape may be provided on the pump body side.

The relationship between fuel injection pressure and time according to the above embodiment is shown in a diagram as shown in FIG. In the figure, a conventional relationship diagram at the initial stage of injection is shown by a dotted line, which is the same diagram as in FIG. As shown here, according to this embodiment, the injection amount is the lowest at the beginning of the injection, gradually increases to reach a predetermined maximum injection pressure, and the injection ends after a predetermined period of time has elapsed. By reducing the pumping pressure at the initial stage of injection in this manner, initial injection can be suppressed, thereby reducing the amount of fuel injected before ignition and reducing diesel knock and engine noise.

[0018]

[Effects of the Invention] By implementing the present invention, the following effects can be achieved. (1) Since the amount of fuel injected before the diesel engine ignites is reduced, the occurrence of diesel knock is suppressed,
Engine noise can be reduced. (2) Since fuel is gradually increased and supplied into the cylinder, sudden combustion is eliminated, combustion pressure is reduced, and engine reliability is improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a fuel pressure distribution section of a VE type fuel injection pump according to a first embodiment of the present invention.

2 shows partially enlarged views of FIG. 1, (a) is a detailed view of part A in FIG. 1, (b) is a BB sectional view of (a), and (c) is a
) is a plan view of the plunger shown in (d) is an enlarged view of section D in (c).

FIG. 3 shows an explanatory diagram of the action of the injection pump shown in FIG. 1,
(a) shows a state where the leak port is wide open at the beginning of pressure feeding of fuel, (b) shows a state where the leak port becomes narrow during pressure feeding, and (c) shows a state where the leak port is closed and pressure feeding of high-pressure fuel is performed. (d) is an explanatory diagram showing the movement of each port and the flow of fuel in a state where the spill port is open and pressure feeding of fuel is completed.

FIG. 4 is a diagram showing the relationship between fuel injection pressure and time in the above embodiment.

FIG. 5 is a diagram showing the relationship between fuel injection pressure and time of a VE type fuel injection pump according to the prior art.

FIG. 6 is a sectional view of a main part of a fuel pressure distribution section of a VE fuel injection pump according to the prior art.

[Explanation of symbols]

3...Plunger 5... Spill port 6... Spilling 10...Fuel pressure distribution section 14...Pump room 16...Pump body 17...Leak port 18...Annular leak groove 19...Leak passage

Claims (1)

[Claims] 1. A distribution type fuel injection pump that distributes and pressure-feeds fuel to each cylinder by reciprocating and rotating motion of a single plunger, wherein the plunger of the injection pump is provided with a leak port that opens and closes before opening a spill port. A distribution type fuel injection pump for a diesel engine, characterized in that the injection pump is configured to reduce an initial fuel injection amount.