Internal combustion engine connecting rod

Details Internal combustion engine connecting rod Internal combustion engine connecting rod

2002-04-12

2003-10-28

Yuen, Henry C. (Department: 3747)

Internal-combustion engines

Transmission mechanism from piston

Crankshaft and connecting rod

Reexamination Certificate

active

06637400

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an internal combustion engine connecting rod whose end is divided and disposed circumferentially with respect to a hole formed therein, and which has a slide metal piece mounted in the hole. More particularly, the invention relates to a technique for preventing relative rotation of the slide metal piece with respect to the hole.
BACKGROUND ART
FIG. 10A
is a perspective view showing a large end of the main body of the internal combustion engine connecting rod (referred to simply as “connecting rod” hereinafter) having the structure described above. A hole
2
is formed in the center of the large end
1
. The large end
1
is divided into a rod portion
3
and a cap portion
4
which are disposed as two semi-circles in the longitudinal direction of the hole
2
, and the rod portion
3
and the cap portion
4
are mounted with bolts which are not shown in the drawing. At an inner periphery of one mating surface vicinity of the rod portion
3
and the cap portion
4
, as shown in an enlarged view in
FIG. 10B
, grooves
5
which are in the circumferential direction and which gradually deepen until the mating surface is reached, are formed so as to be on different sides from each other, and such that the mating surface is disposed therebetween. The slide metal piece
10
shown in
FIG. 11
is mounted in the hole
2
of the connecting rod body having the structure described above.
As shown in
FIG. 11A
, the slide metal piece
10
comprises two ring halves
10
a
and
10
b
obtained by dividing the ring. At one mating portion of the ring halves
10
a
and
10
b
, nails
11
which extend from the outer periphery side are formed so as to be opposite to each other. The slide metal piece
10
is fit into the hole
2
by the nails
11
being accommodated in the grooves
5
of the connecting rods, and the slide metal piece is mounted into the hole
2
with a fixed tightness by tightening the bolts. Furthermore, relative movement of the slide metal piece
10
is prevented by the end surfaces of the nails
11
which are accommodated in the grooves
5
, being caused to abut the end surface of the rod portion
3
or the cap portion
4
.
In this invention, the rod portion
3
and the cap portion
4
are formed separately by sintering, forging, casting or the like, but they may also be formed integrally. In the case where the rod portion
3
and the cap portion
4
are formed integrally, the connecting rod may be formed first, and then the hole and the grooves are mechanically machined. The rod portion and the cap portion are then divided by being split so as to break, and thus have a similar structure to that described above, and then the slide metal piece is mounted. In this case, the machining of grooves like those shown in
FIG. 10B
is difficult. As a result, as shown by the broken lines in the same drawing, the connecting rod is machined to form grooves which straddle the rod portion
3
and the cap portion
4
. Furthermore, for both the embodiment having the rod portion
3
and the cap portion
4
formed separately, and for that having the integral structure, which was divided by being mechanically machined and then carrying out a breaking-split, the slide metal piece may be mounted without providing grooves for fixing the slide metal piece.
FIG. 12A
is a cross sectional view showing the breaking-split type connecting rod described above in a state in which the crank pin
15
is mounted. Because the nail
11
of the slide metal piece
10
does not abut the end surface inside the groove
5
, as shown in
FIG. 12B
, the slide metal piece
10
may rotate due to deformation of the large end
1
caused by load being exerted on the connecting rod. In addition, by being deformed from the unloaded state in
FIG. 13A
, to the state in
FIG. 13B
in which the large end was deformed in the longitudinal direction thereof, as shown in
FIG. 13C
, the nail
11
is pressed in the direction of the arrow and there is a danger that the base plate B will eventually breaking due to fatigue. Also, broken pieces from the nail
11
may become caught between the crank pin
15
and the slide metal piece
10
, and in the worst case, the slide metal piece
10
and the crank pin
15
may heat up.
In addition, as shown in
FIG. 14A
, a slide metal piece
10
having no nail may also be used. In this case, it is easier for the large end to deform due to load applied to the connecting rod than in the case described above in which the slide metal piece is provided with nails. As shown in
FIG. 14A
, crush relief portions
20
are formed at both ends of the ring halves
10
a
and
10
b
which comprise the slide metal piece
10
. The crush relief portion
20
is formed such that its thickness decreases as the end thereof is approached, by causing the diameter of the inner peripheral surface to gradually increase as the end is approached. As shown in
FIG. 14B
, in the connecting rod in which the rod portion
3
and the cap portion
4
are separately formed, when these two portions are mounted, the joint surface may be slid. In this case, the crush relief portions
20
prevent localized contact between the slide metal piece
10
and the crank pin
15
.
Furthermore, if the crush height (the height of the slide metal piece which projects from the hole in the large end in an unloaded state) is excessive, due to the elastic deformation of the mating portion of the ring halves
10
a
and
10
b
, the crush height portion distends toward the inner side, and the effective inner diameter of the shaft receiving metal piece is decreased. In that case also, the crush relief portion
20
functions to prevent localized contact between the slide metal piece
10
and the crank pin
15
.
However, when the slide metal piece
10
rotates for the above described reason, the crush relief portion
20
is not able to function to prevent the localized contact between the slide metal piece
10
and the crank pin
15
. That is to say, the crush relief portion
20
functions to prevent localized contact between the slide metal piece
10
and the crank pin
15
along the direction of the joint surface of the rod portion
3
and the cap portion
4
. Accordingly, when as shown in
FIG. 14C
, the slide metal piece
10
rotates and the phase is slid, the portion which is slid and distends towards the inner side becomes close to the crank pin
15
side, and thus there is localized contact between the sliding portion and the crank pin
15
. Furthermore, when the large end
1
in an unloaded state shown in
FIG. 13A
is deformed in the longitudinal direction so as to be in the state shown in the
FIG. 13B
, localized contact is more intense, and this may cause great damage to the inner peripheral surface of the slide metal piece
10
.
Furthermore, this problem is common to all configurations of the slide metal piece, and due to deformation and the like of the large end caused by load being applied to the connecting rod, relative micro slippage of the slide metal piece and the hole in the large end with respect to each other is caused. Thus, fretting is generated when the outer peripheral surface of the slide metal piece and the inner peripheral surface of the hole contact. That is to say, when the large end
1
deforms in the longitudinal direction as shown in
FIG. 13B
, because the deformation of the hole
2
of the large end
1
of the slide metal piece
10
is not in exactly the same manner, relative micro slippage of the slide metal piece
10
and the hole
2
with respect to each other is caused. In addition wear dust, generated due to fretting, accumulates between the slide metal piece
10
and the crank pin
15
, and this damages the slide surface. Also, minute cracks caused by fretting at the inner surface of the hole
2
develop, and in the worst case, there is the danger that the connecting rod will be damaged.
Thus, an object of the present invention is to provide a connecting rod in which rotation and relative slippage of the slide metal piece is restricted, and the problems described above ar

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