Fuel injection pump for internal combustion engines

Internal-combustion engines – Charge forming device – With fuel pump

Patent

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Details

123449, F02M 3704

Patent

active

050851969

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention is based on a fuel injection pump as defined hereinafter. Such a pump is known from German Patent Disclosure Document DE-OS 31 48 214. In it, the pressure valve provided in the relief line of the restoring chamber is controllable as a function of temperature, so that it is closed in cold starting of the engine and opened no later than once the engine is at operating temperature. The pressure valve is embodied as a check valve that is capable of opening at a maximum pressure and is pushed open by a thermostatically controlled element. As long as the pressure valve is closed, the same pressure, determined by the feed rate of the fuel feed pump, is established in both the pressure chamber and the restoring chamber, and also becomes operative at the injection timing adjuster and adjusts it toward "early". This special shift to early is cancelled at the end of the warmup phase by opening of the pressure valve, and subsequently the pressure acting upon the injection timing adjuster is controlled in a known manner as a function of rpm by the pressure control valve. The special shift toward early effects an improvement of cold starting behavior and of engine operation in the warmup phase.
A disadvantage in the known apparatus is that when the fuel injection pump is stopped a small remaining gap of the outflow throttle from the pressure chamber to the relief chamber remains open at the pressure control valve. When the fuel injection pump starts up the feed pump delivery rate is inadequate for immediately generating the required pressure at low rpm in the startup phase of the engine or fuel injection pump in the pressure chamber or restoring chamber in such a way that the special shift to early is simultaneously achieved for cold starting. The desired pressure does not become established until later, with increasing rpm and an increasing quantity supplied by the feed pump.


ADVANTAGES OF THE INVENTION

The fuel injection pump according to the invention has an advantage that the outflow throttle on the pressure control valve is closed both quickly and securely upon cold starting and that the aforementioned pressure for the shift to early upon cold starting is consistently attainable.
By means of the provisions recited herein, advantageous further features of and improvements to the fuel injection pump disclosed are possible.


DRAWING

Two exemplary embodiments of the invention are shown in simplified form in the drawing and described in further detail below.
FIG. 1 shows a schematic view of a first exemplary embodiment of the fuel injection pump according to the invention;
FIG. 2 shows a second exemplary embodiment of the invention; and
FIG. 3 shows the course of pressure in the pressure chamber upstream of the pressure control valve or of the control pressure that is operative at the injection timing adjuster, in various functional positions.


DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows only part of a distributor-type fuel injection pump 1, having an injection timing adjuster 2 which has an injection adjuster piston 4 that is displaceable in a cylinder 3 and is acted upon by one face end by a restoring spring 5; the restoring spring is supported fixedly on one face end of the cylinder 3, and an injection adjuster work chamber 6 is defined in the cylinder 3 on its other face end. Via a throttle bore 7 in the injection adjuster piston, the injection adjuster work chamber 6 communicates with a suction chamber 9 in the interior of the fuel injection pump. The suction chamber 9 is supplied with fuel by a feed pump 10, driven in synchronism with the fuel injection pump 1, via a pressure line 11; the feed pump draws the fuel from an fuel supply tank 13 via a, intake line 12. A bypass line 15 in which a pressure control valve 16 is disposed is provided parallel to the feed pump 10. The pressure control valve has an adjustable wall in the form of a control piston 17, which slides tightly in a cylinder 18 and on one side defines a pressure chamber 19, into which the bypass line 15 discha

REFERENCES:
patent: 4334514 (1982-06-01), Konrath
patent: 4359994 (1982-11-01), Hofer
patent: 4366795 (1983-01-01), Laveer
patent: 4475519 (1984-10-01), Eheim
patent: 4510908 (1985-04-01), Eisele
patent: 4522181 (1985-06-01), Oreiner
patent: 4619238 (1986-10-01), Hain
patent: 4733645 (1988-03-01), Hain
patent: 4796592 (1989-01-01), Hofer
patent: 5033441 (1991-07-01), Hain

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