Pulley, ball bearing and belt transmitting device

Details Pulley, ball bearing and belt transmitting device Pulley, ball bearing and belt transmitting device

1998-05-05

2001-05-08

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Positive drive pulley or guide roll

With particular belt

C474S148000, C474S149000

Reexamination Certificate

active

06227994

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention generally relates to a pulley and a ball bearing for a pulley. In particular, the invention relates to a ball bearing for use in a timing belt of an engine of an automobile, and a pulley to be contacted with a belt for driving accessory of an automobile.
In a timing belt for an engine of an automobile, or an accessory driving belt, a pulley is arranged so as to increase an angle of contact of a belt for the purpose of applying an appropriate tension to the belt.
FIG. 12
shows a constructional example of a timing belt. This timing belt includes a belt E which is stretched around a driving pulley A secured to a crankshaft, a driven pulley B, B secured to a camshaft, a tensioner pulley C rotatably mounted on a stationary shaft, and an idler pulley D mounted on a stationary shaft. Among the above-mentioned pulleys, the pulleys C and D mounted on the respective stationary shafts are usually constituted by a ball bearing supported pulley. The ball bearing is fitted within the inner diameter of the pulley. It is noted that the stationary shaft for the tensioner pulley C is displaceably supported in elongated openings provided in a frame for supporting the tensioner pulley. By this, tension adjustment of the belt is permitted.
Such a kind of pulley may include a pulley in which a peripheral surface of the pulley to be engaged by a belt is provided directly around the outer diameter of an outer ring of a ball bearing (called a hat type outer ring). It is noted, however, that a pulley of the type shown in
FIG. 13
is frequently used. This pulley includes a pulley body
11
having a peripheral surface
11
c
and a ball bearing
12
which are engaged with each other as a unit.
The pulley body
11
is pressed from a steel plate. The pulley body
11
includes an outer cylindrical portion
11
a
around which a belt is extended, and an inner cylindrical portion
11
b
fitted over an outer ring
12
a
of the ball bearing
12
. A peripheral surface
11
c
of the pulley is provided around the outer diameter of the outer cylindrical portion
11
a.
The ball bearing
12
includes the outer ring
12
a
fitted within the inner cylindrical portion
11
b
of the pulley body
11
, an inner ring
12
b
fitted over a stationary shaft (not shown), a retainer
12
d
for retaining a plurality of balls
12
c
provided in a space between the raceway surfaces of the inner and outer rings
12
b
and
12
a
, and a seal
12
e
for sealing a grease.
In the above-mentioned pulley, and when the pulley body
11
is rotated by a rotational driving force from the belt, the outer ring
12
a
of the ball bearing
12
a
fitted within the pulley body is rotated integrally with the pulley body
11
.
In the above-mentioned pulley, the ball bearing
12
is of a outer ring rotation type, and usually, a deep groove ball bearing is used provided with zero contact angle.
When the above-mentioned pulley is driven under cold ambient, abnormal noise (hoot sound) may be caused, depending upon a given specification of the pulley and/or operational condition. Such abnormal sound under cold condition, i. e., abnormal noise under cold ambient is not always caused during use. Occurrence of such abnormal noise under cold ambient greatly depends upon a given ambient temperature. Thus, it occurs only in a very limited area (for example, Hokkaido Prefecture in Japan). Such abnormal noise under cold ambient occurs in a brief time (within one minute at the longest) after an engine start of an automobile. Thereafter, no abnormal noise is caused. Abnormal noise is frequently caused when a deep groove ball bearing of a single row type is used as a ball bearing. Occurrence of abnormal noise is reduced when an angular ball bearing of a plural row type is used.
Abnormal noise under cold ambient has a complexed nature as mentioned above, so that it is difficult to reproduce such abnormal noise under cold ambient. Accordingly, the cause or mechanism for the occurrence of abnormal noise has not been definitely clarified. As far as a pulley for use with an automobile is concerned, it is operated at a high temperature and at a high speed. Thus, durability is one of the important factors for such pulleys. Accordingly, any counter-measures leading to a reduction in durability could not be employed.
For the reasons given above, no particular means for elimination of such abnormal noise under cold ambient has been proposed heretofore.
Conventionally, a grease having a superior property at lower temperature (being able to form uniform oil film in the contact portions between the rolling element and the raceway surfaces of the inner and outer rings) has been proposed in order to eliminate abnormal noise under cold ambient. This counter-measure is intended to restrict occurrence of abnormal noise under cold ambient by increasing lubrication ability of a grease under cold ambient, and expected to give a relatively high effect. It is noted, however, that such a grease has an lower viscosity, so as to provide an insufficient lubrication ability at high temperature. This may lead to a reduced durability.
Accordingly, it is the main object of the invention to provide means, keeping the function of a pulley, for effectively restricting or preventing occurrence of abnormal noise under cold ambient, while, at the same time, satisfying durability and cost effectiveness.
SUMMARY OF THE INVENTION
Generally speaking, oil film on a raceway surface tends to become uneven and irregular during cold ambient, due to the increase in viscosity of base oil of a grease. When such unevenness and irregularity of the oil film occur, the friction coefficient between a rolling element and the raceway surface is caused to be periodically changed within a small range, so as to cause self-excited vibration of the rolling element.
The applicant has discovered several mechanisms to be occurred during a test for reproducing abnormal noise under cold ambient.
1. When abnormal noise occurred under cold ambient, a pulley (outer ring) was being oscillated in the axial direction. The frequency component at that time corresponded to the acoustic frequency of the abnormal noise (hoot sound) under cold ambient.
2. When no abnormal noise occurred under cold ambient, the above frequency component could not be found.
3. The frequency component when abnormal noise occurred under cold ambient, the same phase is recognized at two measuring points 180 degrees on the end face of the pulley.
Although a mechanism in which abnormal noise under cold ambient occurs has not been completely analyzed, it is considered from the above results that the abnormal noise under cold ambient is caused mainly by the fact that resonance of vibration of the pulley system is caused by self-excited vibration of the rolling element, so that the outer ring is caused to be oscillated in the axial direction (translational movement)
The present invention is aimed, based on the above assumption, at provision of a construction or arrangement for effectively restricting axial vibration of the outer ring due to the self-excited vibration of the rolling element, in order to eliminate abnormal noise under cold ambient.
Accordingly, the present invention provides a pulley including a pulley body having a peripheral surface which is contacted with a belt to be driven by an engine of an automobile. The pulley body is fitted on the outer diameter of an outer ring of a ball bearing. The ball bearing is arranged in a single row, so as to give a contact angle. By this, behavior of the rolling element, in particular, the behavior in the axial direction may be restricted, so that the self-excited vibration of the rolling element is effectively restricted. By this, frequency components in the axial direction of the pulley may be restricted. The term “single row” is meant to express a ball bearing having a single row of rolling element. The term “contact angle” is meant to indicate an angle to be defined by a line along which a load is applied to the rolling element and a plane perpendicular to the central

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