Connecting rod for hermetic refrigerating compressor

Details Connecting rod for hermetic refrigerating compressor Connecting rod for hermetic refrigerating compressor

2000-02-11

2001-08-14

Ryznic, John E. (Department: 3745)

Expansible chamber devices

Resilient means interposed between working member and...

C074S57900F

Reexamination Certificate

active

06272971

ABSTRACT:

The invention concerns a connecting rod for a hermetic refrigerating compressor, in which a shaft is connected with a piston via a crank and a connecting rod, said piston making a forward and back stroke, the connecting rod being connected to the crank by means of a first bearing and the to the piston by means of a connecting link, the connecting rod having means for preventing direct transfer of compressive stress between the common movement centre of the crank and the connecting rod and the common movement centre of the connecting rod and the piston.
U.S. Pat. No. 2,846,897 concerns a connecting rod for a combustion engine, in which the crank bearing comprises two halves assembled with bolts. The connecting rod consists of two longitudinally extending flanges assembled with a central rib. On its transition to the crank bearing the central rib has an arched opening limited on both sides by the longitudinally extending flanges.
DE 32 38 489 A1 also concerns a connecting rod for a combustion engine with a crank bearing comprising a roller bearing, the problem to be solved being to secure the distribution of compressive stresses over several rollers. This problem is solved in that the connection between the bearings of the connecting rod is formed by two flanges, which are mutually connected by a bridge, openings being made between the flanges and the bridge. Thus, it is obtained that compressive stresses are not directly transferred between the movement centres of the connecting rod, and that the stresses are distributed between several rollers. It is also described that the bearing ring is resilient. However, a resilient bearing ring will yield to pressures, when it is not supported by the flanges. Thus, the forces will concentrate at the flanges, and the compressive stresses between the flanges will be substantially reduced. The problem is solved in that with the two flanges the stresses can, in the worst case, run through two rollers.
In both documents mentioned above, the compressive stresses run in the flanges, which are tangentially connected with the bearings. Thus, there is hardly any direct transfer of compressive stresses between the movement centres, and the load on the bearings at the direct connecting line is very small. This gives an increased load of the bearings in other parts of the bearing circumference, where increased wear may cause a reduction of the life.
FIG. 1
shows a computer-simulated calculation of compressive stresses in a crank bearing, which is connected with the connecting rod piston bearing by tangentially arranged flanges.
It is the purpose of the invention to realise an increased life of the connecting rod for a hermetic refrigerating compressor using only simple means.
This task can be solved with a connecting rod as described in the introduction, in that the connecting rod is provided with a cut-out, which cut-out is arranged at a distance to the bearing surface of the first bearing, the distance amounting to 15% to 30% of the diameter of the first bearing, the relation between the area of the first bearing opening and the area of the cut-out being 0.1% to 5%.
This gives an even distribution of the compressive stress over a larger share of the bearing surface, which results in reduced wear on the connecting rod crank bearing. Only an adaptation of both placing and size of the cut-out will give an optimum solution. If overcompensating, a drop may occur at the direct connecting line between the movement centres of the connecting rod, and at the same time two new stress concentrations giving wear problems may occur.
Advantageously, the invention can be made so that the largest transverse measure of the cut-out is 5% to 15% of the inner diameter of the first bearing of the connecting rod. This will give a relief of compressive stresses without causing the formation of new pressure peaks with distance to the plane of symmetry.
Advantageously, the outer contour of the connecting rod around the cut-out is formed by a first concave line, which extends into a second convex line. Thus, the compressive stresses can run along the outside of the connecting rod without being deflected by sharp edges.
Advantageously, the material surrounding the cut-out facing the outer contour is thicker than the largest transverse measure of the cut-out. Thus, the compressive stresses can be distributed over a larger angle.
Advantageously, the cut-out is arranged at a distance from the circumference of the first bearing, which distance is larger than the largest transverse measure of the cut-out. Thus, compressive stresses are enabled to act directly under the bore.
Advantageously, the convex line of the outer contour forms an angle &agr; with the outer ring of the first bearing. Thus, production conditions are considered, if the connecting rod has to be made as a sintering workpiece. The angle may also be necessary out of regard for the room in a hermetic compressor.
Advantageously, the cut-out is arranged on the connecting rod in a position displaced to one of the sides in relation to the direct connecting line between the centres of the bearings. Thus, a reduction of the peak of the compressive stresses can be obtained. A friction in the connecting rod bearings may cause a displacement of the compressive stresses from the symmetry line of the connecting rod in the direction of the edge of the connecting rod. To ensure a reduction of compressive stresses, the optimum arrangement and the shape of the cut-out can be calculated to be displaced in relation to the symmetry line. The outer shape of the connecting rod can also be optimised in a way that the sides of the connecting rod deviate from each other.
In the following the invention is explained on the basis of drawings, showing:
FIG. 1
a computer calculated curve of the compressive stresses of the state of the art
FIG. 2
a top-view of the connecting rod
FIG. 3
a section through the connecting rod
FIG. 4
a section of a connecting rod for a hermetic compressor from the state of the art
FIG. 5
a section of a connecting rod with changed outer contour
FIG. 6
a section of a connecting rod with changed outer contour and a through-going cut-out.
FIG. 7
curves of the radial load for the
FIGS. 4
,
5
and
6
FIG. 8
a top view of a connecting rod, the cut-out being shown as an ellipse displaced from the symmetry line of the connecting rod
FIG. 9
a section through the connecting rod from FIG.
8
.


REFERENCES:
patent: 800592 (1905-09-01), Phillips et al.
patent: 2846897 (1958-08-01), Schall
patent: 5140869 (1992-08-01), Mrdjenovich et al.
patent: 5865092 (1999-02-01), Woudwyk
patent: 951201 (1949-10-01), None
patent: 1193651 (1959-11-01), None
patent: 1-275949-A (1989-11-01), None

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