192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
2002-05-16
2004-12-14
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S11000B
Reexamination Certificate
active
06830137
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pulley unit having a one-way clutch. The pulley unit can be mounted in an auxiliary machine which is driven by a crankshaft of an engine of an automobile or the like through a belt. Examples of auxiliary machine are an air-conditioner compressor, a water pump, an alternator, a cooling fan and the like of an automobile.
BACKGROUND OF THE INVENTION
Various auxiliary machines mounted in automobile engines are driven by an engine crankshaft through a belt. Amongst the auxiliary machines, an alternator is driven by an engine crankshaft so as to generate electricity. When the alternator is coupled with the engine crankshaft so as to simultaneously rotate, as the number of rotation of the crankshaft decreases, the power generating efficiency decreases. In order to prevent the decrease of the power generating efficiency, an alternator having a one-way clutch in a pulley portion thereof has been devised. As to the alternator, when the rotational speed of the crankshaft lowers, the rotation of a rotor of the alternator is continued by inertial force so as to improve the power generating efficiency thereof.
FIG. 10
shows a pulley unit. The pulley unit is equipped with a pulley
1
, a rotor shaft
2
, a one-way clutch
3
and a deep groove ball bearing
44
and a needle roller bearing
45
. A cam face
10
is formed intermediate the axial direction of an outer peripheral surface of a rotor shaft
2
. A belt
6
is wound around an outer periphery of the pulley
1
. When the belt
6
is driven by an engine crankshaft of an automobile not shown in a figure, the pulley
1
is rotationally driven. The rotor shaft
2
is fixed to a rotor of an alternator. The one-way clutch
3
has a cage
12
and a plurality of rollers
13
which are housed in a plurality of pockets of the cage
12
one each. The rollers
13
are always pushed to a narrow side (lock side) of a wedge-like space by a coil spring not shown in a figure. The wedge-like space is an annular space in a circumferential direction formed between an inner peripheral surface of an outer ring
11
and the cam face
10
of the rotor shaft
2
so as to roll the rollers
13
. The wedge-like space is narrowed to the lock side. The one-way clutch
3
, the deep groove ball bearing
44
and the needle roller bearing
45
are sealed by a pair of seal rings
20
,
21
and a seal annular body
22
and lubricated by a common lubricant.
In operation, when a rotational speed of the pulley
1
becomes relatively faster than the same of the rotor shaft
2
, the rollers
13
of the one-way clutch
3
are rolled to the narrow side of the wedge-like space and so as to be in a locked state. The locked state is a state in which the outer ring
11
and the rotor shaft
2
can be integrally rotated via the rollers
13
. The outer ring
11
and the pulley
1
are integrally arranged. As a result, the pulley
1
and the rotor shaft
2
are integrally rotated in the locked state so that a rotational power can be transmitted from the pulley
1
to the rotor shaft
2
.
When the rotational speed of the pulley
1
becomes relatively slower than the same of the rotor
2
, the rollers
13
of the one-way clutch
3
are rolled to a broad side (free side) which is the apposite side from the narrow side of the wedge-like space. As a result, the pulley unit becomes in a free state. The free state is a state in which the outer ring
11
and the rotor shaft
2
can freely rotate to each other. Thus, transmission of a rotational power from the pulley
1
to the rotor shaft
2
is intercepted. In the case where the rotor shaft
2
is being rotated prior to the interception, the rotor shaft
2
continues its rotation only by its own rotational inertial force after the interception.
Referring to
FIGS. 10 and 11
, the deep groove ball bearing
44
will be described. The bearing
44
takes an axial load. The bearing
44
is equipped with an inner ring
50
, an outer ring
51
, a cage
56
and a plurality of balls
52
. The inner ring
50
and the outer ring
51
respectively have raceway grooves
53
and
54
. The raceway grooves
53
and
54
correspond to an arc of a circle
55
indicated by an imaginary line larger than a diameter of the balls
52
. In a case that a curvature radius of the raceway grooves
53
and
54
is R and a diameter of the balls
52
is D, a raceway curvature (%) of the raceway grooves
53
and
54
is expressed as the formula (1).
Raceway curvature=(
R/D
)×100 (1)
According to the formula (1), when the raceway curvature is 50%, the radius of the balls
52
(D/2) and the curvature radius (R) of the raceway grooves
53
and
54
are identical. Therefore, when the raceway curvature is 50%, the balls
52
are fitted to the raceway grooves
53
and
54
with no gap. In this manner, when the raceway curvature is 50%, an axial deviation of the bearing
11
becomes completely nil. In this state, the balls
52
are fitted to the raceway grooves
53
and
54
with no gap. Therefore, there are possibilities of a generation of a seizure on the raceway grooves
53
and
54
and of an undesirable influence on a service life of a lubricant due to a contact friction between the balls
52
and the raceway grooves
53
and
54
. In order to deal with this, the above-mentioned raceway curvature is set to a range of 52.0-52.5% for the raceway groove
53
of the inner ring
50
, and to a range of 53.0-53.5% for the raceway groove
54
of the outer ring
51
.
As shown in
FIG. 12
, the bearing
44
needs to be mounted by force-fitting between the pulley
1
and the rotor shaft
2
. For the reason thereof, a radial internal clearance of the bearing
44
is set to a few times as large as a standard radial internal clearance with regard to a tolerance. For example, in case of the bearing
44
having bearing designation 6807 in JIS (Japan Industrial Standard), a radial internal clearance before mounting thereof is set to 50-100 &mgr;m. When the bearing
44
is force-fitted between the pulley
1
and the rotor shaft
2
, the radial internal clearance decreases. Therefore, the radial internal clearance after mounting of the ball bearing
44
is set to a range of approximately 21-52 &mgr;m.
In the case where the deep groove ball bearing
44
, in which the raceway curvature of the raceway groove
53
is a range of 52.0-52.5%, the raceway curvature of the raceway groove
54
is a range of 53.0-53.5%, and the radial internal clearance before mounting thereof is a range of 75-99 &mgr;m, is mounted by force-fitting between the pulley
1
and the rotor shaft
2
, the radial internal clearance after mounting thereof is a range of 21-52 &mgr;m and the axial internal clearance thereof is a range of 140-239 &mgr;m, as shown in Table 7.
TABLE 7
radial internal
clearance after
axial internal
mounting [&mgr;m]
clearance [&mgr;m]
21~52
140~239
The axial internal clearance, as shown in
FIG. 13
, denotes the axial deviation of the inner and outer rings
50
and
51
based upon raceway curvatures and the radial internal clearance after mounting of raceway grooves
53
and
54
.
SUMMARY OF THE INVENTION
A main object of this invention is to provide a pulley unit capable of decreasing an axial deviation between a pulley and a shaft.
Other objects, features and advantages of the present invention will be apparent from the following description.
In summary, a pulley unit according to the invention comprises a pulley; a shaft which can be relatively rotated with the pulley and which is concentrically arranged inner side of the pulley; a one-way clutch which is interposed in an annular space between the pulley and the shaft; and a ball bearing which is disposed adjacent to the one-way clutch in an axial direction in the annular space.
As for the pulley unit of the invention, firstly, raceway curvatures of both inner and outer rings of the ball bearing are set to not less than 50.5% and not more than 52.0%. Secondly, a radial internal clearance after mounting of the ball bearing is set to less than 20 &m
Jordan and Hamburg LLP
Koyo Seiko Co. Ltd.
Lorence Richard M.
LandOfFree
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