Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2002-09-17
2003-04-22
Moller, Richard A. (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
Reexamination Certificate
active
06550333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sliding rotation members for highly reliable continuously variable transmission (CVT) for use in a toroidal CVT, such as a disk and power roller bearing, and an evaluation method of the members.
2. Description of the Related Art
For an input/output disk and power roller bearing for use in a toroidal continuously variable transmission (CVT), whose use environments include a high load and high surface pressure and which are positioned with important protective components, there have been proposed a large number of techniques for enhancement of durability in order to prevent breakage and flaking in a short time. For example, in Jpn. Pat. Appln. KOKAI Publication No. 2001-032900 (hereinafter referred to as Prior Document 1), there are disclosed chemical components of alloy steels for use in the input/output disk and power roller bearing, and a carbon amount, nitrogen amount, surface hardness, and the like of a function surface are limited, and preferable alloy components, heat treatment quality, and the like for enhancing the durability.
Moreover, in Jpn. Pat. Appln. KOKAI Publication No. 2001-026840 (hereinafter referred to as Prior Document 2), it is disclosed that a high-cleanliness steel is used in order to prevent breakage and flaking from being generated starting at a large nonmetal inclusion in a steel in a short time. Furthermore, a method of performing an ultrasonic flaw detection/inspection is used to guarantee that the large nonmetal inclusions do not exist in a traction surface
62
and surface layer portion of the input/output disk shown in
FIG. 9
, and a traction surface
67
and surface layer portion of an inner ring of the power roller bearing shown in FIG.
10
. For example, it is guaranteed that the nonmetal inclusion having a maximum size of 0.1 mm or more does not exist within 0.5 mm from the surface in a disclosed member for CVT.
Moreover, for the use environments of a toroidal continuously variable transmission disk and power roller, high torque transmission capabilities are required from properties described later as compared with other types of continuously variable transmissions. It is necessary to apply a highly durable material which is not broken by a very large bend stress and repeated stress. To solve the problem, the present inventors have developed and proposed a management method of a steel which satisfies durability necessary especially for the CVT disk and power roller in Jpn. Pat. Appln. KOKAI Publication No. 11-193855 (hereinafter referred to as Prior Document 3).
To detect an inner defect of a steel material for use as a material of a bearing ring, only a defect inspection has heretofore been performed by an ultrasonic inspection in a steel manufacturing process. The ultrasonic inspection comprises: transmitting an ultrasonic wave to the inside of a rolled steel material from an outer peripheral surface thereof in water or on a base to detect a flaw. For example, a normal wave method described in “page 31, No. 6, Vol. 46, Tokushuko, Tokushuko Club Association” (hereinafter referred to as Prior Document 4), and the like are known.
In the inspection of defects (nonmetal inclusions) of the steel material in a steel maker, only large defects each having a width of several hundreds of micrometers and a length of several millimeters or more are detected because of the properties of the inspection. Additionally, a representative inspection (sampling inspection) is performed so that the high-cleanliness steel is entirely managed. However, the presence/absence of harmful inclusions has not been grasped or guaranteed with respect to all the steel materials (total inspection) in the existing technique.
Moreover, in recent years, it has been possible to detect even the nonmetal inclusion, for example, having a micro size of about 0.01 mm (10 &mgr;m) using a high frequency in the ultrasonic inspection in a background of progress of a nondestructive inspection technique. However, in the ultrasonic inspection, when the frequency is increased, attenuation of the ultrasonic wave inside the steel material increases, and the method is not practical. Especially when the surface of the steel material becomes rough, the attenuation of the ultrasonic wave further increases. Therefore, for a practical range of the size of the inclusion, in which the total inspection of a product is possible, only a large defect having a width of several hundreds of micrometers and a length of several millimeters or more is detected in the existing circumstances.
The toroidal continuously variable transmission (CVT) disk and power roller bearing member having large defects inside (particularly in the vicinities of surfaces) are sometimes broken in a relatively short time, when repeatedly undergoing bend stresses. Particularly a rolling member of the large CVT repeatedly undergoes a high bend stress, and therefore tends to flaking or crack starting at a position deeper than a maximum stress generated position in which a conventional general-purpose rolling bearing has heretofore undergone the stress. Concretely, in input/output disks
31
,
32
of the large CVT, a large repeated bend stress is added to portions (traction surface
62
and surface layer portion) shown by diagonal lines in
FIG. 11
, and a high tensile stress is generated. Moreover, in the inner ring of the power roller bearing of the large CVT, the large repeated bend stress is added to portions (traction surface
67
, inner peripheral surface
68
, rolling surface
69
, and surface layer portion) shown by the diagonal lines in
FIG. 12
, and the high tensile stress is generated. Therefore, the flaking or cracks are easily generated starting at these surfaces
62
,
67
,
68
,
69
and surface layer portions.
Additionally, in Prior Document 1 described above, it is proposed that the alloy components are optimized and heat treatment quality is specified in order to prevent the generation of the flaking or cracks. Moreover, in the invention of Prior Document 1, the traction surfaces
62
and surface layer portions of the input/output disks
31
,
32
shown in
FIG. 11
are strengthened, and the traction surfaces
67
, inner peripheral surfaces
68
, rolling surfaces
69
, and surface layer portions of power roller inner rings
36
a,
37
a
shown in
FIG. 12
are strengthened, so that the entire strength is enhanced. However, it is not proposed to improve the large inclusion at which the flaking or crack starts.
Moreover, in Prior Document 2 described above, it is proposed that among the traction surfaces
62
, inner peripheral surfaces
63
, and surface layer portions of the input/output disks
31
,
32
shown in
FIG. 11
, and the traction surfaces
67
, inner peripheral surfaces
68
, and rolling surfaces 69 of the power roller inner rings
36
a,
37
a
shown in
FIG. 12
, particularly the large inclusions of the surface layer portions corresponding to the traction surfaces
62
,
67
are detected and guaranteed in order to prevent the breakage or the flaking in the short time. However, in the invention of Prior Document 2, only the surface layer portions of the traction surfaces
62
,
67
are objects of a precision inspection (or the total inspection), but the surface layer portions of the surfaces
63
,
68
,
69
other than the traction surfaces are not the objects of the precision inspection (or the total inspection).
A future demand for the CVT lies not only in long life and breakage prevention of the disk and power roller but also in eradication of accidental generation of a short-life bearing. This is a demand for a highly reliable member for the CVT which has no possibility of generation of short-life components even under conditions further stricter than before, with future elongation of guarantee period of a car.
The present invention has been developed to solve the above-described problems, and an object thereof is to provide a long-life sliding rotation member for CVT in which flaking is not easily generated in a sliding
Christensen O'Connor Johnson & Kindness PLLC
Moller Richard A.
NSK Ltd.
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