Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1995-06-29
1997-01-14
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
417402, F02M 4100
Patent
active
055929206
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is directed to a distributor-type fuel injection pump for internal combustion engines. In a distributor-type fuel injection pump of this kind known from EP-B 0 382 388, a drive shaft drives a rotor which is guided in a casing and in which two pump-plunger pairs each guided in a cylinder bore are arranged in a plane radial relative to the drive shaft. The cylinder bores arranged in a common radial plane of the rotor here intersect at right angles and the individual pump plungers thus delimit with their radially inward-facing end faces a common pump working space in the overlapping region of the cylinder bores. The ends of the pump plungers, which project from the cylinder bores, run by means of a roller tappet along a fixed cam track of a cam ring guided in the casing, with the result that, during a rotary motion of the rotor, they have a reciprocating motion imparted to them, opening the connection of the cylinder bore to a filling line starting from a low-pressure space during the radially outward suction-stroke movement, which line is then closed by the pump plungers during the subsequent delivery stroke. The fuel compressed in the common pump working space during the delivery stroke then passes via a high-pressure passage in the rotor to a distributor hole which leads off radially from said passage and, during the rotary motion of the rotor, comes into overlap with the individual high-pressure delivery lines leading to the injection locations.
The pump-plunger pairs in the two cylinder bores are here designed in such a way that a longer plunger pair guided in a first cylinder bore projects with its pump working-space end into the second cylinder bore, and the shorter guided plunger pair does not reach the first cylinder bore even in its maximum delivery-stroke position.
However, the known distributor-type fuel injection pump has the disadvantage that the cam lift, which is the same for all the pump plungers, must be less than half the diameter of the cylinder bores, which are each made of equal size. This is necessary in this case to ensure that the long plungers still project into the second cylinder bore, even in their maximum suction-stroke position, in order reliably to prevent the shorter plungers from sliding by themselves between the long plungers when the internal combustion engine is switched off and the pump working space is unpressurized, since this otherwise leads to the mechanical destruction of the distributor-type injection pump during its operation. However, this imposes structural limits on the delivery stroke of the pump plungers, limiting the performance parameters of the entire pump.
ADVANTAGES OF THE INVENTION
In contrast, the distributor-type fuel injection pump according to the invention has the advantage that the shorter pump plungers can be reliably prevented from sliding unintentionally into the cylinder bore between the long pump plungers by means of a stop on their end projecting out of the cylinder bore.
This eliminates the need that the long pump plungers should project continuously into the cylinder bore guiding the short pump plungers, allowing the cam lift to be made greater than half the diameter of the cylinder bore to give a bigger delivery-stroke movement. This increase in the delivery stroke can advantageously be converted into an increase in the injection pressure or a larger delivery quantity.
The stop on the short pump plungers is advantageously arranged in such a way that it permits them to enter the cylinder bore guiding them until their pump working-space end approaches to within a short distance of the second cylinder bore and it is thus possible to achieve large delivery-stroke lengths.
The stop on the short pump plungers can be embodied in a simple manner by a collar or a retaining ring guided in an annular groove in the body of the short plungers, which then interact in a simple manner with the end wall of the cylinder bore.
Further advantages and advantageous developments of the subject-matter of the invention can be taken from
REFERENCES:
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patent: 4575316 (1986-03-01), Mowbray
patent: 4604980 (1986-08-01), LeBlanc
patent: 4840162 (1989-06-01), Brunel
patent: 4889096 (1989-12-01), Brunel
patent: 5044898 (1991-09-01), Harris
patent: 5050558 (1991-09-01), Brunel
patent: 5215060 (1993-06-01), Flopfer
patent: 5443048 (1995-08-01), Nicol
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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