Fuel injection pump for internal combustion engines

Details Fuel injection pump for internal combustion engines Fuel injection pump for internal combustion engines

1987-10-13

1989-06-27

Smith, Leonard E.

Pumps

Expansible chamber type

Pumping member position controlled port

123495, F02M 5924, F02M 5944

Patent

active

048424978

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a fuel injection pump for internal combustion engines. In such spool-controlled injection pumps, exact and also synchronous guidance of the control spools is of importance for the injection quality and hence for the combustion quality in the engine. Higher loads on the torque shaft, such as can occur in the case of abrupt twisting, for example, can cause a slight bending of the torque shaft, which not only causes errors in the synchronisation between the individual control spools but can also cause substantially increased friction at the bearings of the torque shaft. Since the twisting of the shaft takes place by means of a governor whose adjustment forces are sensitive and depend on rotational speed, variable frictional forces have particularly disadvantageous effects on the control quality.
As in almost all injection pumps of this type, the bearing of the torque shaft on the drive side in a known injection pump (U.S. Pat. No. 3,667,437) is also designed as a simple sliding bearing which simultaneously forms a type of oil barrier in the direction of the governor.
Apart from these sealing and frictional problems, there are also problems in the manufacture of such bearings because the casing bores for accepting the bearing bushes must be absolutely coaxial with the torque shaft in order to avoid bearing stresses which either lead to intolerable additional frictional forces or to deflections and lack of axial sealing at the bearing when torque is applied.


SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved fuel injection pump.
The fuel injection pump according to the invention has, in contrast to conventional pumps, the advantage that no bending stresses can be transmitted to the bearing because of the cardanic rotational connection between the two shaft parts. The bearing of the second shaft part on the drive side of the torque shaft, in particular, can operate without stress and therefore almost without friction. Because of the absence of transverse forces, the bearing between the second shaft part and the pump casing can be designed with a very fine fit, such as is usual, for example, between injection pump pistons and cylinders, so that there is a substantial sealing against an outflow of fuel from the injection pump into the governor.
According to an advantageous embodiment of the invention, one shaft part has, as an axial guide, an end trunnion extending in the shaft axis on the coupling side, which end trunnion is located in a corresponding blind hole on the end of the other shaft part, it being possible to design this end trunnion so that it is slightly crowned. Distortion-free bearing support of the first shaft part is achieved by this type of the guide for the free end of the first shaft part without slight alignment errors between the two shaft axes having disadvantageous effects in the form of distortions.
According to a further embodiment of the invention, the shaft parts each have an extended section on the ends facing towards one another, for example a collar, on which drive claws or--recesses for the rotational connection are present. This extended section, for example a large collar, to which is added an axial nose which engages in a corresponding recess in the opposite collar, provides a favorable lever arm for the drive without disadvantageous transverse forces.
According to an important embodiment of the invention, the second shaft part is supported in a central bore of a bearing bush which is arranged to seal radially by sealing rings in a pump casing bore and such that an oil ring groove with a leakage hole leading towards the outside is present in the central bore. It is also advantageous to guide the second shaft part in this central bore in the manner of an injection pump element seal. Since there are practically no axial motions of the second shaft part, little fuel will leak between the shaft and the bore if there is a good fit. Even these small quantities, however, are caught by the oil ring groo

REFERENCES:
patent: 2110314 (1938-03-01), Wisner
patent: 3385221 (1968-05-01), Parks
patent: 4576130 (1986-03-01), Hafele et al.

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