192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
2001-11-01
2003-06-03
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S11000B
Reexamination Certificate
active
06571924
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-334605 filed on Nov. 1, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pulley unit provided with a one-way clutch.
2. Description of the Related Art
Various accessories installed on a vehicular engine are driven by a belt which receives its rotational energy from the engine's crankshaft. However, in the case of an alternating current (AC) generator used as an accessory connected in synchronous rotation to the crankshaft of the engine, a decrease in the number of revolutions of the crankshaft is normally experienced, which results in a diminished power generating capacity of the AC generator, during certain modes of the AC generator or its associated driving mechanism.
For avoiding the inconvenience of a reduction of rotational capacity, there is known a method wherein a pulley unit with a one-way clutch is used for the AC generator to improve the generating efficiency during periods of a decreased number of revolutions of the crankshaft.
FIG. 5
is a partial cross-sectional view of a conventional pulley unit incorporating a one-way clutch
120
. The conventional pulley unit shown in
FIG. 5
comprises a pulley
100
and a shaft
110
which are arranged concentrically and a one-way clutch
120
disposed in an axially intermediate position within a space formed between the pulley
100
and the shaft
110
. The one-way clutch
120
comprises an outer ring
122
fixed to the pulley
100
, an inner ring
124
fixed to the shaft
110
, and a plurality of cylindrical rollers
126
sandwiched in between the outer ring
122
and the inner ring
124
.
FIG. 3
, also a conventional pulley arrangement, shows that between the outer ring
122
and inner ring
124
, there are formed wedge-like spaces in multiple positions in the circumferential direction, and the rollers
126
are disposed within those wedge-like spaces, whereby there is formed the one-way clutch
120
which can transfer a rotational driving force in only one direction.
With this pulley unit, a locked state (power transfer state) of the one-way clutch
120
and a free state (power transfer cut-off state) of the one-way clutch
120
are switched from one to the other in accordance with a difference in rotation between a rotor integral with the shaft
110
and the pulley
100
. Thus, it is possible to transfer power between the pulley
100
and the rotor and cut off the transfer. Two bearings
130
are provided, respectively, at both axial ends of the one-way clutch
120
to ensure smooth, relative rotation between the pulley
100
and the rotor and lighten the load applied to the clutch from a belt.
In the above conventional pulley unit, when the pulley
100
is rotated by a belt which is secured in the channels of the outer periphery of the pulley
100
, a radial load is exerted from the pulley
100
on the rollers
126
of the one-way clutch
120
and also on the bearings
130
disposed on both sides of the rollers. In such a state of use, a clearance allowance between the pulley
100
and the outer ring
122
of the one-way clutch
120
is increased by the radial load exerted from the belt, because the outer ring
122
of the one-way clutch
120
is apt to be distorted radially inwards. Consequently, the wedge-like spaces formed in plural positions in the circumferential direction of the one-way clutch
120
become smaller in radial size and the rollers
126
are displaced which cause the state of the clutch to change. With a decreasing radial size, the wedge angle of each wedge-like space is apt to become small. For example, if the wedge angle becomes smaller than a predetermined lower-limit value, the rollers
126
of the one-way clutch
120
are fixed in the locked state, with no change-over being made to the free state. Thus, the conventional pulley unit has the problem that long-term operational stability can not be achieved due to a deformation of the one-way clutch caused by the radial load from the belt.
Continuing with the conventional pulley unit,
FIG. 3
provides a visual example of the outer ring
122
when it is distorted radially inward. Distortion occurs when the wedge angle of each wedge-like space changes from an angle &thgr;
1
in the absence of a distortion of the outer ring
122
to an angle &thgr;
2
in the presence of distortion of the outer ring
122
. It follows that the number of revolutions at a change-over between a locked state and a free state will vary depending on the degree of distortion of the outer ring, thereby creating unstable pulley operation.
Moreover, in the above conventional pulley unit, since two bearings
130
are provided at both axial ends of the one-way clutch
120
, the number of components used is large and the assembly performance is poor.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-mentioned problems, therefore, it is an object of the present invention to provide a pulley unit which ensures long-term operational stability even with the use of a one-way clutch. It is another object of the present invention to provide a pulley unit with a reduced number of components to thereby attain a reduction in part cost and improvement in assembly performance.
For solving the above-mentioned problems, the pulley unit of the present invention is provided with a one-way clutch between a pulley and a shaft which are concentrically disposed. The one-way clutch comprises an inner ring formed integrally with the pulley, an outer ring formed integrally with the shaft, and rollers accommodated within wedge-like spaces formed between the inner ring and the outer ring. Since the inner ring of the one-way clutch and the pulley are integral with each other, a radial load from the pulley is not transferred to the outer ring and the rollers which are disposed radially outside of the inner ring. This prevents distortion of the outer ring. Consequently, the shape of the wedge-like spaces can be held constant and it is also possible to essentially hold constant the number of revolutions of the pulley, which accommodates transitioning between the locked state and the free state (and vice versa) with movement of the rollers, thus making it possible to ensure long-term operational stability of the pulley. Moreover, since the radial load from the pulley is not imposed on the rollers, it is possible to reduce the roller diameter and it becomes possible to reduce the size of the entire pulley unit.
It is preferable that the pulley and the inner ring be U-shaped and that the one-way clutch be disposed in an annular space inside the pulley. By forming the pulley and the inner ring integrally in a U shape, an interior annular U-shaped space necessary for disposing the one-way clutch is created.
Continuing, it is preferable that two bearings be disposed radially inside of the one-way clutch to receive a load from the pulley. Thus, a load from the pulley can be received directly by the outer ring and the inner ring, which is integral with the pulley, without going through the rollers, etc. in the one-way clutch. In this way the load can be transferred to the shaft by disposing one bearing radially inside of the inner ring and one between the pulley and the outer ring. This positioning in the bearings makes it possible to improve the assembly performance.
It is preferable that clutch cam portions which form the wedge-like spaces have rounded cam surfaces. An inner peripheral surface of the outer ring and/or an outer peripheral surface of the inner ring, opposed to the clutch cam portions, are/is a curved surface and therefore, by forming the clutch cam portions so as to have rounded surfaces, the radial width of each wedge-like space can be changed gently in connection with movement of the rollers in the circumferential direction and it is possible to realize a firmly locked state when the rollers have moved to a particular position.
It is preferable that a retaining piece fo
Mizutani Akihiro
Murata Nakato
Denso Corporation
Lorence Richard M.
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