Pumps – Expansible chamber type – Pumping member position controlled port
Patent
1987-11-18
1989-05-16
Smith, Leonard E.
Pumps
Expansible chamber type
Pumping member position controlled port
123500, F02M 5924
Patent
active
048305871
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a fuel injection pump.
Known injection pump (DE-OS 34 28 174), have a control recess in a pump plunger which has, in addition to a helical groove for controlling the end of delivery during the pressure stroke of the pump plunger, an elongated groove connected with it, whose end edge remote of the pump work space controls the start of delivery. Moreover, the elongated groove serves to completely cancel the injection delivery at a determined relative rotational position of the pump plunger and the control slide so as to stop the internal combustion engine in a reliable and rapid manner. Compared with previously known fuel injection pumps, considerable operating advantages are achieved with such a construction of a control recess in the pump plunger skirt; but it has the disadvantage that, because of the large surface of the control recess which is acted upon by the injection pressure during the pressure stroke of the pump plunger, the prevailing pressure also acts on the portion of the inside of the control slide which overlaps this surface. If the control slide has a relatively thin wall for reasons relating to construction space, a deformation of the control slide occurs with an increase in friction during the pump plunger stroke, and the durability of the control slide is sharply reduced because of the load change occurring at every plunger stroke.
SUMMARY OF THE INVENTION
The fuel injection pump according to the invention, provides very great durability and service life of the control slide because of the relatively small surface of the control recess in the pump plunger, which surface is acted upon by pressure. Moreover, a preferred, relatively gradual pressure increase is achieved by means of the counterbore whose control edge controls the start of delivery when immersed in the slide. In addition, a quick drop in pressure is achieved during the control because of the central arrangement of the opening of the duct leading to the pump work space in the pump plunger, since unnecessary deflections of the control quantity between the duct in the pump plunger and the control borehole in the control slide are avoided to a great extent.
In an advantageous construction of the invention, any injection quantity delivery is prevented in the stop position of the pump plunger, even when the helical groove of the control recess is relatively flat, so that a reliable stopping of the internal combustion engine is also ensured in this case, as in the prior art. Finally, it has proved advantageous that the manufacturing of the cylindrical counterbores or pocket boreholes in the skirt of the pump plunger is less expensive than the production of elongated grooves.
BRIEF DESCRIPTION OF THE DRAWINGS
Three embodiment examples of the subject matter of the invention are shown in the drawing and described in more detail in the following. FIG. 1 shows a portion of a fuel injection pump in cross section; FIG. 2 shows a pump plunger of the fuel injection pump, according to FIG. 1, in enlarged scale; FIG. 3 shows the pump plunger, according to FIG. 2, in cross section in the plane III--III of FIG. 2; FIG. 4 shows a developed view of the outer surface area of the pump plunger in the control area according to FIG. 2; FIG. 5 shows a partial view of a pump plunger corresponding to FIG. 2, but for the second embodiment example; and FIG. 6 shows an constructional variant of the pump plunger shown in FIG. 2 for the third embodiment example.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Usually, a plurality of cylinder liners 2 are inserted in a row in a housing 1 of a fuel injection pump, pump plungers 3 being driven in these cylinder liners 2 by means of a camshaft, not shown, for its axial movement. A recess 4, which receives a control slide 5, which is axially displaceable on the pump plunger 3, is provided in the cylinder liner 2. The control slide 5 can be axially adjusted by means of a lever 6 for changing the time of the start of delivery, the lever 6 being supported in the
REFERENCES:
patent: 2890657 (1959-06-01), May et al.
patent: 4448167 (1984-05-01), Schmid et al.
patent: 4630586 (1986-12-01), Guntert et al.
patent: 4754737 (1988-07-01), Ishida et al.
Guntert Josef
Hafele Walter
Warga Johann
Robert & Bosch GmbH
Smith Leonard E.
Striker Michael J.
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