CAGE FOR ROLLER BEARINGS
FIELD OF THE INVENTION
The present invention relates to a cage for roller bearings and particularly to a cage for roller bearings used on crankshaft/connecting rod mechanisms.
BACKGROUND OF THE INVENTION
Roller bearing is widely used on crankshaft/connecting rod mechanisms. The roller bearing with the rollers at the diameter smaller than 6mm (included) also is called as needle roller bearing. In the present invention both roller bearing and needle roller bearing adopt the same construction, thus the roller bearing discussed hereinafter also includes the needle roller bearing.
Refer to FIG. 1 for an application example of a conventional roller bearing 10 used in the internal combustion engine of motorcycles, lawn mowers and the like. It is located at the conjunction of a hole 21 at one end of a connecting rod 20 and a crank pin 40. The roller bearing 10 is positioned at an eccentric location of a crankshaft 30 which is consisting of two circular disks. The crankshaft 30 has an axle 31 on each of two sides. The roller bearing 10 has rolling elements 12 and cage 11. The hole 21 has an inner surface serving as outer raceway 22 of the roller bearing 10. The crank pin 40 serves as an inner raceway of the roller bearing 10.
Refer to FIGS. 2 through 5 for the construction of the
roller bearing 10 used on a mechanism of crankshaft 30/connecting rod 20. It includes an annular cage 11 made of metal and rolling elements 12. The commonly used cage 11 is annular can be divided into an one piece type cage 11 with recession on outer surface 13 (referring to FIG. 2), or an one piece type cage 11 with a flat outer surface 13 (referring FIG. 3), or a split type cage 11 ( consisting of two semi-circular rings ) with recession on outer surface 13 (referring to FIG. 4), or a split type cage 11 with a flat outer surface 13 (referring FIG. 5).
As the roller bearing 10 for the crankshaft/ connecting rod mechanism is located at the conjunction of connecting rod 20 and the crank pin 40. When the crankshaft 30 rotates, the roller bearing 10 is driven to perform two types of motions: first, spinning about the crank pin 40 as the center; second, moving along with crank pin 40 to rotate about the axle 31 of the crankshaft 30.
As the roller bearing 10 is eccentric relative to the axle 31 of the crankshaft 30, the second motion generates a centrifugal force on the roller bearing 10. As a result the cage 11 is constantly rubbing against the inner surface of the hole 21 that also serves as the outer raceway 22 of the bearing. The rubbing behavior will cause wear on the outer raceway 22. To reduce the wear, the conventional method is to electroplate a copper layer or a sliver layer on a copper layer on the outer
surface 13 of the cage 11. Such an approach allows the softer copper/silver layer to be consumed to defer the wear on the outer raceway 22.
However the process of electroplating copper layer or a silver layer on the copper layer is expensive. Moreover electroplating process may generate hydrogen embrittlement (HE) problem. It frequently causes fracture of cage 11 while bearing is running.
There is still a lot of room for improvement. The applicant has a lot of experiences in this field and consecrates himself to research and improve. Finally, he found this invention. SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a cage that has a Polyetheretherketones (PEEK) containing coating layer on the cage surface thereof to reduce cost and prevent the HE problem. The cage thus formed also is more durable.
The cage according to the invention includes a body and a Polyetheretherketones (PEEK) containing coating layer covering the outer surface of the body. The Polyetheretherketones (PEEK) containing coating layer is formed at a thickness between 1µm and 50 µm. Additive(s) may be added to the coating layer, such as Polytetrafluoroethylene (PTFE), Graphite, Molybdenum Disulfide (MoS2) or a compound thereof.
The body of cage is annular and can be a one piece type or a split type. The outer surface of the body of cage can be with
recession or flat.
Taking the advantage of the properties of Polyetheretherketones (PEEK) containing coating layer, such as low hardness (much lower than HV700-840 of the ordinary bearing outer raceway), low coefficient of friction, non-stick, abrasion resistance, oil resisting, and also high temperature applicable, the coating layer can remain on the surface of cage for a long period of time to extend the life span and defer wear on the outer raceway of the bearing.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a roller bearing in an application example.
FIG. 2 is a roller bearing with a one piece type cage (has recession on outer surface of cage ).
FIG. 3 is a roller bearing with a one piece type cage (outer surface of cage is flat).
FIG. 4 is a roller bearing with a split type cage ( has recession on outer surface of cage ).
FIG. 5 is a roller bearing with a split type cage (outer surface of cage is flat ). FIG. 6 is a cross section of the roller bearing of the invention.
DESCRIPTION of CODES in DRAWINGS
10: roller bearing
11: cage
12: rolling elements
13: outer surface of cage
20: connecting rod
21: hole (at one end of connecting rod)
22: outer raceway
30: crankshaft
31: axle of the crankshaft
40: crank pin
100:cage
110: body of cage
120: coating layer
200: rolling elements
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENT
Please refer to FIG. 6 for the cross section of the roller bearing of the invention.
The cage 100 of the invention includes a body 110 to hold the rolling elements 200. The rolling elements 200 may be needle rollers at a diameter smaller than 6mm or rollers at a diameter greater than 6mm. In addition, the body 110 has the outer surface covered by a Polyetheretherketones (PEEK) containing coating layer 120 which is formed at a thickness
between 1 µm and 50 µm. Moreover, additive(s) may be added to the coating layer, such as PTFE, graphite, MoS2 or a compound thereof.
The body 110 of the cage 100 is annular and can be one piece type with recession on outer surface or one piece type with flat outer surface, or a split type, consisting of two semi-circular rings, with recession on outer surface or a split type with flat outer surface.
Compared with the conventional technique which has a electroplated silver layer on a plated copper layer on cage, the Polyetheretherketones (PEEK) containing coating layer 120 can remain on cage 100 for longer period of time and can more effectively defer the wear on the outer raceway. Test results of the conventional technique and the invention are shown as follows:
Test piece A: The outer surface of the cage is electroplated with copper at a thickness of 1µm and further electroplated with silver at a thickness of 10µm, with the total plating layer at a thickness of 20µm.
Test piece B: The outer surface of the cage is covered by a Polyetheretherketones (PEEK) containing coating layer 120 at a thickness of lOum.
Test conditions: The bearing rotates at 9000RPM, the centrifugal force of the cage exerting on the outer raceway is 95 Newtons, the relative speed between the cage and the outer raceway is 7.2 m/sec, lubrication oil temperature is 80°C, and the hardness of
the bearing outer raceway is HV720-750.
Test results after 100 hours testing duration:
1. Test piece A: The plated silver layer on the outer surface of the cage has been totally worn out, and a portion of the plated copper layer has been worn out also. The maximum wear on the bearing outer raceway is about 2um.
2. Test piece B: The Polyetheretherketones (PEEK) containing coating layer on the outer surface of the cage remains intact, and the maximum wear on the bearing outer raceway is less than lµm.
In short, the test results indicate that the Polyetheretherketones (PEEK) containing coating layer 120 of the invention can remain on the outer surface of the cage longer than the conventional copper plus silver plating. Also, the Polyetheretherketones (PEEK) containing coating layer can more effectively defer the wear on the outer raceway.
Summarizing, the cage 100 of the invention, whether adopted on the needle roller bearing with the needle rollers at the diameter smaller than 6mm or the roller bearing with the rollers at the diameter greater than 6mm, through the Polyetheretherketones (PEEK) containing coating layer 120 which has a lower hardness (much lower than HV700-840 of the ordinary bearing outer raceway) and a low coefficient of friction, and is non-stick, abrasion resistance, oil resisting and also high temperature applicable, can improve the life span of cage and
defer wear on the bearing outer raceway.
While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.

We Claim:
1. A cage for roller bearings, comprising:
a body of the cage; and
a coating layer containing Polyetheretherketones (PEEK) to cover an outer surface of the body.
2. The cage of claim 1, wherein the body of cage is an one piece annular construction.
3. The cage of claim 2, wherein the outer surface of the cage is formed with recession or a flat surface.
4. The cage of claim 1, wherein the body of cage is a split annular construction.
5. The cage of claim 4, wherein the outer surface of the cage is formed with recession or a flat surface.
6. The cage of claim 1, wherein the coating layer is formed at a thickness between lµm and 50 µm.
7. The cage of claim 1, wherein the coating layer further includes additive(s) which is selected from the group consisting of Polytetrafluoroethylene (PTFE), Graphite, Molybdenum disulfide (M0S2) and a compound thereof.
8. The cage of claim 1, wherein the cage holds needle rolling elements, the diameter of rolling elements is smaller than 6mm.
9. The cage of claim 1, wherein the cage holds rolling
elements, the diameter of rolling elements is greater than
6mm.
10. The cage of claim 1, wherein the containing of
Polyetheretherketones (PEEK) in coating layer is between 5% and
100% by weight.
11. A cage for roller bearings, substantially as herein described,
particularly with reference to and as illustrated in accompanying
drawings.