Ball bearing

Details Ball bearing Ball bearing

2002-03-28

2004-01-27

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

C384S516000

Reexamination Certificate

active

06682223

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a ball bearing used in various motors, which are used for a general industrial purpose. More particularly, the invention relates to a ball bearing which reduces the noise, vibration, fretting damage (abrasion) and torque of the ball bearing, and improves the acoustic durability of the cage noise.
BACKGROUND OF THE INVENTION
An example of such for the general industrial purpose is a motor device for driving an air conditioning apparatus (referred to as an air conditioner). Recently, the air conditioner has been improved to have high performances and a multifunctionality. The air conditioner is operated in the following way, for example. Under control of the inverter unit, the air conditioner is operated at high speed to effect a rapid cooling and to lower room temperature in the shortest possible time. Then, it is operated at low speed to keep the room at constant temperature. In such circumstances, when the air conditioner is operated at the low speed, low noise operation is required, viz., it is operated generating reduced noises of the air blowing, the motor rotation and the like. In the low speed operation, the cooling efficiency within the apparatus decreases, the temperature of the rolling bearing incorporated into the motor increases to sometimes reach 100 to 120° C. In this condition, it is difficult to secure a thickness of the oil film formed by the lubrication, the grease packed in the ball bearing is liable to deteriorate. With progress of the deterioration, noise will be generated.
In the outdoor unit used for the air conditioner, the initial noise (cage noise) of the bearing sometimes is required to reduce at the start operation in low temperature environment, e.g., in winter season. Furthermore, the motor units of air-conditioners with rolling bearings installed therein are sometimes transported over long distances from a motor manufacturer to end users by a truck. In such a long distance transportation, the truck traces the fine unevenness of roads, and the associated movement is transmitted to the rolling bearing in the form of repetitive impact loads, which cause the rolling element of the rolling bearing to repeatedly put into microscopic contact with the raceway surface. Such microscopic contacts sometimes cause a fretting damage (abrasion) on the raceway surface, and the damage acts as a source of noise.
Taking account of environmental regulations as well as the achieving of high performances and multifunctionality, efforts have been made to downsize the motor and to realize the lower output of the motor in order to reduce the heat generation of the motor. For this reason, it is recognized that the torque characteristic has a vital function in the rolling bearings having those uses. The dynamic frictional torque of the rolling bearing is caused by the frictions by a minute slip on the rolling contact surface, sliding friction at the sliding contact part in the bearing, and viscosity resistance of the grease. It is known that the viscosity resistance of the grease is affected by the kinematic viscosity of the base oil and the worked penetration of the grease. Accordingly, the kinematic viscosity of the base oil is based on a shearing resistance of the oil when a fluid lubricating film is formed. In this sense, reduction of the kinematic viscosity plays an important role in reducing the dynamic frictional torque of the rolling bearing. The grease worked penetration affects the channeling performance when it is sheared within the bearing when the bearing rotates. In this sense, the approach of reducing the worked penetration of the grease presents an effective solution to the reducing of the dynamic frictional torque of the rolling bearing.
When the kinematic viscosity of the base oil is reduced, because sometimes the motor of the air conditioner is rotated at relatively low speed under the inverter control, it is difficult to secure the thickness of the oil film. Generally, the oil of low kinematic viscosity is low in heat resistance, and a problem arises in the acoustic durability. The reduction of the worked penetration of the grease results in the addition amount of the thickener. In this case, the amount of the base oil decreases relative to the amount of other compositions in the grease, and the resisting force of the grease to the mechanical shear increases. As a result, an amount of supplying of the base oil to the lubricating surface of the bearing reduces, and it is impossible to stably maintain the lubricating property of the oil for a long term.
Thus, there is a limit in reducing the kinematic viscosity and the worked penetration of the grease. In the rolling bearing having the uses mentioned above, the following values are considered appropriate: the kinematic viscosity of the base oil is 10 to 500 mm
2
/s at 40° C., the worked penetration of the grease is NLGI grades No. 2 to 3, or the thickener is contained in an amount of 5 to 20% by mass based on the total amount of the grease composition. Particularly, in the motor which requires the low noise characteristic, i.e., acoustic durability, a grease is generally used which prepared by blending a fatty acid lithium salt as a thickener into an ester as a base oil. The heat resistance of an ester oil is higher than that of the mineral oil. The ester oil contains a polar group in the molecular structure. The polar group functions to increase the sorbability to the metallic surface, to improve the friction characteristic and the acoustic durability. Further, where the reduction of the fretting damage (abrasion) is required, it is effective to use a base oil of high oil film forming property and relatively high viscosity.
For example, a ball bearing as shown in
FIG. 1
is known for the rolling bearing having the uses stated above. The ball bearing is constructed such that an inner ring
2
having inner raceway
1
formed on its outer peripheral surface and an outer ring
4
having an outer raceway
3
formed on its inner peripheral surface are coaxially disposed. A plurality of balls
5
,
5
are rotatably disposed between the inner raceway
1
and the outer raceway
3
. In the illustrated case, the inner raceway
1
and the outer raceway
3
are both of the deep groove type. The balls
5
,
5
are rotatably retained in pockets
7
,
7
provided in a cage
6
.
The cage
6
is called a wave press cage (a corrugated press cage). To form the cage
6
, a metal plate is molded into an element
8
, wavy and annular in shape, by press molding, and a couple of elements
8
,
8
so shaped are combined. Concave parts
9
,
9
, semicylindrical in shape, are formed at a plurality of positions on the element
8
as viewed circumferentially. Those concave parts
9
,
9
are used for forming the pockets
7
,
7
. The couple of elements
8
,
8
are butted against each other at positions apart from the concave parts
9
,
9
thereof. Those butted parts are joined and fixed by a plurality of rivets
10
to thereby form a cage
6
, annular in shape. The thus formed cage
6
includes pockets
7
,
7
arranged at plural positions as viewed circumferentially. A middle part of the inner surface of the concave part
9
is spherically concaved to be arcuate in cross section, with the radius of curvature being slightly larger than that of the outer surface of each ball
5
. Accordingly, when the couple of elements
8
,
8
are butted against each other, the concave parts
9
,
9
are combined to form a pocket
7
.
When the ball bearing is used, the inner ring
2
and the outer ring
4
are rotatable relative to each other with the rolling of the balls
5
,
5
. The balls
5
,
5
revolve around the inner ring
2
while rolling about its axis. The cage
6
moves (rotates) around the inner ring
2
at a speed equal to the revolving speed of each ball
5
.
A space between the outer peripheral surface of the inner ring
2
and the inner peripheral surface of the outer ring
4
is packed with a lubricant, such as grease or another lubricant, to thereby make the relative rotat

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