Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
1999-08-12
2001-03-20
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
Reexamination Certificate
active
06202620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lubricating structure for an internal combustion engine and more particularly, it relates to a lubricant passage structure formed in a crankshaft of the engine.
2. Description of the Related Art
Generally, lubricating oil in the internal combustion engine is sucked up from an oil pan through the intermediary of a strainer by an oil pump. Thereafter, the pressure of lubricating oil is controlled by a pressure governor and subsequently, the oil is fed to a main gallery. Formed to branch off from the main gallery are respective oil holes (or lubricant passages) through which the lubricating oil is supplied to respective lubricating sections, for example, a moving valve system, the crank shaft and so on.
As one of the oil hole structures provided in the crankshaft, there is known a general H-shaped lubricating structure where parallel oil holes (i.e. parallel lubricant passages) are respectively formed in both each crank journal and each crank pin so as to be perpendicular to a line connecting a center of the crank journal with a center of the crank pin in the axial view of the crankshaft. In this lubricating structure, an additional oil hole is formed so as to connect the oil hole of the crank journal with the oil hole of the crank pin at respective intermediate portions thereof (Japanese Unexamined Patent Publication No. 7-27126).
SUMMARY OF THE INVENTION
Further, there is also proposed an oblique oil hole structure which has the advantage of both simplicity in the configuration of oil holes and superior formability of the oil holes.
FIG. 1
is a schematic view for explanation of the above-mentioned oblique oil hole structure. In the figure, reference numeral
1
denotes a crankshaft. In the crankshaft
1
, a first oil hole
4
is formed to extend from the outer peripheral face of a crank journal
2
to the outer peripheral face of a crank pin
3
while penetrating both crank journal
2
and crank pin
3
. Furthermore, the crankshaft
1
is provided with a second oil hole
5
which has one end communicating with a part of the first oil hole
4
positioned in the crank journal
2
and the other end opening onto the outer face of the crank journal
2
.
Now, if the opening of the oil hole in the crank journal is positioned at an area of thin oil-film thickness (e.g. less than approx. 2 &mgr;m) resulting from the approaching of the outer peripheral face of the crank journal to the inner face of a main metal for bearing the journal, there will be caused a condition equivalent to a case where the width of the main metal is reduced by the opening of the oil hole. Consequently, it may cause the oil-film pressure to be elevated radically and the minimum oil-film thickness to be decreased.
Taking such an apprehensive situation into consideration, it has been proposed, as a general design technique against the crankshaft
1
employing the above-mentioned oblique oil hole structure, to allow the arrangement of the second oil hole
5
in the crank journal
2
to resemble that of the general H-shaped oil hole structure in a manner that the frequency where the oil hole in the crank journal
2
opens at the area of thin oil-film thickness is substantially equal to that of the general H-shaped oil hole structure thereby to maintain the wear-resistant and seizure resistant capacities affecting the reliability of the main metal.
In detail, assuming that, under condition of the crank pin
3
of a straight 4-cylinder engine occupying upward in the vertical direction, the vertical upside point is set at an angle of 0 degree and the clockwise direction from the point is set to the positive direction, it is being supposed to position one opening
5
a
of the second oil hole
5
opening the outer face of the crank journal
2
at an angle of approx. +45 degrees in angle and position the other opening
5
b
opening on the outer face of the crank journal
2
and also communicating with the first oil hole
4
at an angle of +200 degrees (see FIG.
1
).
In the shown arrangement, however, the opening
5
a
of the second oil hole
5
is positioned apart from a portion along a straight line C connecting a center A of the crank pin with a center B of the crank journal
2
and also included in a area having an oil clearance C
2
broader than the oil clearance C
1
between the outer face of the crank journal
2
and the inner face of the main metal
6
and along the line C. Therefore, the lubricating oil is apt to escape from an oil groove
6
A on the main metal
6
laterally, so that the oil pressure applied on the second oil hole
5
is lowered.
Thus, it means that the pressure of lubricating oil passing from the second oil hole
5
to the side of the crank pin
3
via the first oil hole
4
, that is, the oil pressure supplied to a connecting-rod metal disposed on a bearing part of a connecting rod supporting the crank pin
3
gets low.
Especially in the oblique oil hole structure, since the oil hole
4
is adapted so that the only one end on the crank pin's side opens to the inner face of the connecting-rod metal, the seizure is easy to occur to the connecting-rod metal originally requiring seriousness in lubricating.
Accordingly, as a matter of fact, it is difficult to apply the oblique oil hole structure involving the above-mentioned problem on a high-powered engine.
Under such a situation, with the improvement of positioning an oil hole formed in the crank journal, an object of the present invention is to provide a lubricating structure for an internal combustion engine, which is capable of increasing the oil pressure acting on the oil hole formed in the crank journal thereby to enhance the performance to supply the lubricating oil to the bearing part of the connecting rod while maintaining both wear-resistance and seizure-resistance influencing on the reliability of the journal bearing part, similarly to those in the conventional structure.
According to the invention, the above-mentioned object is accomplished by a lubricating structure for an internal combustion engine, comprising:
a crankshaft having a plurality of crank journals and a plurality of crank pins each disposed between the adjoining crank journals;
a plurality of oil holes formed in the crankshaft, for supplying lubricating oil to both of a journal bearing part provided in the internal combustion engine for bearing each of the crank journals and a connecting-rod bearing part provided in the internal combustion engine for bearing each of the crank pins; and
wherein the oil holes formed in the crank journals are formed so that, in view of the axial direction of the crankshaft, at least one opening of each oil hole, which opens onto the outer peripheral face of each of the crank journals, substantially lies on a straight line for connecting respective centers of the adjoining crank pin and crank journal with each other.
The above and other features and advantages of this invention will become apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference to the attached drawings showing one preferred embodiment of the invention.
REFERENCES:
patent: 4622933 (1986-11-01), Fukuo et al.
patent: 5163341 (1992-11-01), Murrish et al.
patent: 5799547 (1998-09-01), Agarrat
patent: 7-27126 (1995-01-01), None
Ali Hyder
Foley & Lardner
Kamen Noah P.
Nissan Motor Co,. Ltd.
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