Internal-combustion engines – Charge forming device – With fuel pump
Patent
1992-08-18
1993-09-14
Miller, Carl S.
Internal-combustion engines
Charge forming device
With fuel pump
123449, F02M 3704
Patent
active
052439437
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection pump for internal combustion engines.
More particularly, it relates to a fuel injection pump for internal combustion engines, which has a pump interior space constructed in a pump housing, a fuel delivery pump sucking fuel out of a fuel tank and delivering it into the pump interior space, a pressure control valve adjusting the fuel pressure in the pump interior space with a pump plunger executing at least an axial stroke movement, sucking the fuel out of the pump interior space during a suction stroke and apportioning the fuel injection pressure to at least one injection line during a delivery of a pressure stroke, a drive shaft rotating in a pump housing and driving the pump plunger to execute at least a stroke movement via a cam gear unit, and a hydraulic injection and adjusting mechanism for adjusting the start of the delivery stroke of the pump plunger with respect to the rotational position of the drive shaft and also with a control space and a spring space.
Such fuel injection pumps are known e.g. from GB 2 017 350 or DE 36 05 452 A1. Practical experience with these fuel injection pumps shows that unstable pressure vibrations frequently occur in the spring space of the hydraulic injection timing or adjusting mechanism used in such fuel injection pumps. These pressure vibrations trigger instability in the adjusting path of the injection adjusting piston, which results in defects in the operation of the fuel injection pump due to its displacing action on the cam gear unit.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fuel injection pump for internal combustion engines which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a fuel injection pump in which the spring space of the injection adjusting mechanism is connected to a pressure-side outlet of the fuel delivery pump via a second throttle, and the throttle cross-section of the second throttle is dimensioned so as to be smaller than the throttle cross-section of the first throttle between the spring space and the suction side inlet of the fuel delivery pump.
When the fuel injection pump is designed in accordance with the present invention, it has the advantage that a partial flow of fuel reaches the spring space by means of the throttled coupling of the spring space of the injection adjusting mechanism with the delivery or pressure side of the delivery pump and builds up a pressure level in the spring space which stabilizes pressure vibrations. An improvement in the injection adjusting function of the injection adjusting mechanism is accordingly achieved with respect to linearity, reproducibility and stability of the adjustment of the commencement of injection. For this purpose the spring space is partially uncoupled from the suction side of the delivery pump via a first throttle and is connected to the outlet of the delivery pump on the pressure side via a second throttle The throttle cross section of the first throttle is selected so as to be larger than that of the second throttle A good stabilization is achieved when the first throttle has a bore diameter of approximately 0.9 mm and the second throttle has a bore diameter of approximately 0.6 mm.
In a preferred embodiment form of the invention the throttled coupling of the spring space with the pressure side of the delivery pump is realized in a particularly advisable manner in that the throttle bore is introduced into the pressure piston of the pressure control valve and connects the pressure and spring chambers of the pressure piston. Thus, the spring chamber of the pressure control valve is not connected with the suction side of the delivery pump as was previously the case, but rather with the spring space of the injection adjusting mechanism. The necessary constructional modifications to the standard pump are accordingly min
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patent: 3633559 (1972-01-01), Eheim
patent: 4502449 (1985-03-01), Laufer
patent: 4589394 (1986-05-01), Ito
patent: 4619238 (1986-10-01), Hain
patent: 4733645 (1988-03-01), Hain
patent: 4796592 (1989-01-01), Hofer
patent: 5033441 (1991-07-01), Hain
patent: 5188083 (1993-02-01), Reisser
Bofinger Gunter
Hain Josef
Narr-Hess Manfred
Nothdurft Heinz
Russeler Karl-Friedrich
Miller Carl S.
Robert & Bosch GmbH
Striker Michael J.
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