JP2695814B2 - Fuel injection pump for internal combustion engines - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a fuel injection pump for an internal combustion engine of the type defined in the preamble of the claims.

[Conventional technology]

In fuel injection pumps of this type, it is known to extend the lower part-load range and the injection period during no-load operation in order to improve the quiet operation of the diesel engine. For this reason, a known fuel injection pump (West German Patent Application Publication No.
In Japanese Patent No. 3013087), a relief passage communicating with a pump working chamber is provided, the opening of which is controlled by the pump piston when the pump piston has advanced a predetermined preliminary stroke for generating an injection pressure. Through the released relief passage,
A portion of the fuel returns from the pumping chamber to the low pressure chamber. At full load or at higher partial loads, the relief passage is blocked by the control slider.

[Construction Means of the Invention]

The configuration of the present invention is described in the characterizing part of the claims.

[Action / Effect]

The fuel injection pump according to the present invention has an advantage that the injection period can be extended by the discharge start control when the rotation speed is small and the discharge amount per pump piston stroke is small. If the first control hole is covered by the adjusting slider in any stroke position of the pump piston, the fuel discharge is started by closing the second control hole. Until the top dead center of the pump piston, fuel is discharged at a slow speed. In the case of a high rotation speed or a large amount of fuel (at full load), the adjustment slider is moved and adjusted over the entire stroke of the pump piston, while the second control hole is covered, while the first slider is moved from the control slider. When the control hole is released, the fuel discharge ends. The fuel is then discharged at a high speed. The desired short injection period is achieved at full load. The movement adjustment of the adjustment slider from the discharge start control to the discharge end control is performed between two injections.

Injection start deviation caused by the ejection at the various cam portions can be sufficiently controlled by the injection start control. At the start position of the adjustment slider, both control holes remain closed over the entire stroke of the pump piston,
The maximum fuel amount (starting amount) is injected. At both end positions of the adjusting slider, fuel discharge is reliably suppressed in each case.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

The distribution pump type fuel injection pump shown in a partial vertical cross section in FIG. 1 has a housing 10 surrounding a pump inner chamber, that is, a low pressure chamber 11, in which the fuel is supplied from a fuel tank via a feed pump (not shown). Is supplied. As is well known, the pressure in the low-pressure chamber is controlled by the pressure control valve according to the rotation speed, and the pressure in the low-pressure chamber 11 increases as the rotation speed increases.

A cylinder liner 13 is fitted in a hole 12 provided in the housing 10, and a pump piston is provided in the cylinder liner.
14 operates to limit the pump working chamber 15 together with the cylinder liner 13. The pump piston 14 is rotated at the same time as the reciprocating motion via a drive shaft 16 and a cam drive device 17 which are schematically shown. Until the pump piston 14 performs the suction stroke (downward movement in FIG. 1) and occupies the bottom dead center position, the pump working chamber 15 includes the suction passage 19 from the low pressure chamber 11 and the outer peripheral surface of the pump piston. The fuel is supplied through the vertical groove 18 provided in the fuel cell.

A vertical passage 20 that opens into the pump working chamber 15 extends inside the pump piston 14. The horizontal hole 21 branches off from the vertical passage 20,
The lateral hole opens into a distribution longitudinal groove 22 on the outer peripheral surface of the pump piston 14. During the compression stroke (upward movement in FIG. 1) of the pump piston 14, the pump piston 14 rotates,
Since the suction passage 19 is closed and one of the many pressurizing passages 23 is controlled to open via the distribution longitudinal groove 22, fuel under high pressure is discharged from the pump working chamber 15 to the vertical passage 20, the horizontal hole. The pressurizing passage 23 can be reached via 21 and the distribution flute 22. Pressurizing passage 23
Are respectively connected to the discharge pipes connected to the injection nozzles of the internal combustion engine via check valves. A first control hole 24 and a second control hole 25 further branch off from the vertical passage 20, and these control holes are opened on the outer peripheral surface of the pump piston 14. Both control holes 24,2
5 extend at a distance from each other at a piston portion of a pump piston 14 which projects from the cylinder liner 13 and enters the low-pressure chamber 11. Mounted on said piston portion of the pump piston 14 is an axially movable adjusting slider 26 which opens or closes both control holes 24,25. In this case, the axial distance between the two control holes 24, 25 is reduced by the maximum stroke of the pump piston 14,
Is smaller than the length in the axial direction. Adjustment slider 26
Release of the first control hole 24 or the second control hole 25 by
Since the communication between the pump operation chamber and the low-pressure chamber 11 is established, the fuel can flow out of the pump operation chamber 15 to the low-pressure chamber 11 each time. At that time, the release of the first control hole 24 defines a discharge end period in which the fuel supply to the pressurized passage whose opening is controlled is cut off,
On the other hand, the closing of the second control hole 25 by the adjustment slider 26 causes the pressurized passage 23 from the pump working chamber 15 to be opened.
A discharge start period for starting fuel discharge to the fuel cell is defined.

The adjusting slider 26 engages with an adjusting lever for axially shifting the adjusting slider 26 on the pump piston 14 in relation to the load and the rotational speed of the internal combustion engine.

Therefore, the adjustment pin mounted on the end face of the adjustment mechanism shaft 29
A rotary magnet adjustment mechanism 28, known per se, which acts on the adjustment slider 26 via 30 is used. Rotating magnet adjustment mechanism 28
Is controlled by the electric control device 31 according to operating parameters such as torque request, rotation speed, pressure, temperature, etc.
As described below, control is performed to obtain a different fuel injection amount for each rotation angle in various operation ranges.

In FIG. 2, an adjusting slider 26 is shown together with the pump piston 14.
The enlarged view of FIG. At that time, the pump piston 14
Occupies the bottom dead center position in the upper half figure and occupies the top dead center position in the lower half figure. Moreover, the position of the adjustment slider 26 corresponds to a cold start of the engine when the engine is cold. That is, during the maximum piston stroke, the maximum amount of fuel is delivered to the pressurized passage 23 whose opening is controlled while both control holes 24 and 25 remain closed. Now, when the rotation speed is low and the discharge amount per discharge stroke of the pump piston 14 is small, the adjustment slider 26 moves through the first control hole 24, and when the rotation speed is high and the discharge amount per discharge stroke of the pump piston 14 is small. If larger,
The second control hole 25 is controlled to close at any stroke position of the pump piston 14. In the former case, the adjustment slider 26 is shifted to the right, to a greater or lesser degree, as seen in FIG. 2, with the second control hole 25 being adjusted by the adjustment slider 26 during the course of the pump piston 14 stroke. As soon as it is covered, fuel discharge starts. At this time, the piston stroke curve as a function of the drive rotation angle becomes sufficiently flat at the end of the top dead center of the drive cam of the pump piston 14, and the fuel reaches the top dead center of the pump piston 14. It is discharged at a low speed until it reaches. In the latter case, the adjustment slider 26 is shifted to the left in FIG. As soon as the first control hole 24 comes out of the adjustment slider 26, the fuel discharge by the pump piston 14 ends. Since fuel is discharged at a high speed, a desired short injection period is obtained at full load. In this case, substantially the entire part of the piston stroke curve of the pump piston 14 extending at the maximum steepness is exerted over the rotation angle. On the other hand, in the case of the former discharge start control, an extremely long injection period is obtained. The adjustment slider 26 is adjusted from the discharge start control to the discharge end control between the two injections.

In FIG. 3, the discharge start control range A and the discharge end control range B
Are shown diagrammatically. Here, the diagram shows the course of the discharge volume FV per stroke of the pump piston 14 as a function of the rotational speed n. The discharge start control range A is in a rotational speed range lower than approximately 1500 min ^-1 and reaches a discharge volume equal to about half of the amount of fuel discharged at full load.

[Brief description of the drawings]

1 is a partial longitudinal sectional view of a distribution pump type fuel injection pump for a diesel internal combustion engine, and FIG. 2 is a pump at a bottom dead center position (upper half view) and a top dead center position (lower half view). FIG. 3 is an enlarged view of the piston and the adjustment slider, and FIG. 3 is a diagram of the discharge volume as a function of the rotational speed n of the diesel internal combustion engine in order to illustrate the adjustment range of the discharge start adjustment and the discharge end adjustment.
In the figure, 10 ... housing, 11 ... low-pressure chamber, 13 ...
Cylinder liner, 14 Pump piston, 15 Pump working chamber, 20 Vertical passage, 21 Horizontal hole, 24 First control hole, 25 Second control hole, 26 Adjustment slider

Claims (1)

(57) [Claims] A pump working chamber, limited by a driven pump piston, provided for delivering an amount of fuel under high pressure to at least one injection nozzle of an internal combustion engine;
Connecting the pump working chamber to a low pressure chamber filled with fuel,
A first control hole (24) opened on the outer periphery of the pump piston, and closing and opening the first control hole, wherein the opening of the first control hole defines the end of discharge, and slides in the axial direction along the pump piston. A movable adjustment slider, an adjustment lever engaging the adjustment slider for sliding the adjustment slider along the pump piston according to a load and a rotation speed of the internal combustion engine;
A second control hole (25) communicating with the pump working chamber (15) is provided at an axial distance from the control hole, and the second control hole is provided in the adjustment slider (26). In a fuel injection pump for an internal combustion engine, which can be released and closed by sliding in the axial direction and the start of discharge is defined by closing the second control hole, the axial distance between the two control holes (24, 25) is The adjustment slider (26) is designed to be smaller than the axial length of the adjustment slider (26) reduced by the maximum stroke of the pump piston (14), and the adjustment slider (26) has a low rotation speed and discharges the pump piston (14). When the discharge amount per stroke is small, the first control hole (24) is used. When the rotation speed is high and the discharge amount per discharge stroke of the pump piston (14) is large, the second control hole (24) is used. 25) at any stroke of the pump piston (14) Characterized by a chain, a fuel injection pump for an internal combustion engine.