192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-08-09
2002-06-25
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S10700R
Reexamination Certificate
active
06409004
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-006577, filed Jan. 14, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic clutch used in, for example, an automotive air conditioner.
DESCRIPTION OF THE RELATED ART
An electromagnetic clutch that can alternatively select transmittal or non-transmittal of power by means of electromagnetic force is constructed in the manner shown in
FIG. 7
, for example. The electromagnetic clutch
101
comprises a clutch rotor
102
rotatable by means of an external drive source (not shown), ring armature
103
opposed to one end face of the rotor
102
, ring exciting coil
104
, ring field
105
containing the coil
104
, return spring
113
, etc.
FIG. 7
shows a state in which current is supplied to the ring exciting coil
104
to generate a magnetic flux M that is diagrammatically indicated by a broken line.
As shown in
FIG. 9
, the clutch rotor
102
includes can outer tube portion
102
a
, an inner tube portion
102
b
, and a flange portion
102
c
that connects the tube portions
102
a
and
102
b
. The flange portion
102
c
is provided on one end portion of the clutch rotor
102
that faces the armature
103
. The front face of the flange portion
102
c
serves as a friction surface that touches the armature
103
.
As shown in
FIG. 8
, the flange portion
102
c
of the clutch rotor
102
is formed having arcuate outside slits
106
a
,
106
b
,
106
c
,
106
d
,
106
e
and
106
f
and arcuate inside slits
107
a
,
107
b
,
107
c
,
107
d
,
107
e
and
107
f
. Outside bridge portions
108
a
to
108
f
are arranged individually between the adjacent outside slits
106
a
to
106
f
. The outer peripheral portion of the flange portion
102
c
is supported on one end portion of the outer tube portion
102
a
by means of the bridge portions
108
a
to
108
f
. Further, inside bridge portions
109
a
to
109
f
are arranged individually between the adjacent inside slits
107
a
to
107
f
. The inner peripheral portion of the flange portion
102
c
is supported on one end portion of the inner tube portion
102
b
by means of the bridge portions
109
a
to
109
f.
When current is supplied from an external power source (not shown) to the exciting coil
104
, the coil
104
generates the magnetic flux M, as shown in FIG.
7
. The armature
103
is attracted to an end face of the clutch rotor
102
by means of an electromagnetic force based on the magnetic flux M. Thus, the rotor
102
and the armature
103
are connected magnetically to each other. When current supply to the coil
104
is interrupted, the magnetic flux M dies out, so that the armature
103
is separated from the end face of the rotor
102
by means of the elastic force of the return spring
113
. The coil
104
is held in the ring field
105
. The field
105
is held in a ring groove
110
that is defined by the respective inner surfaces of the outer tube portion
102
a
, inner tube portion
102
b
, and flange portion
102
c.
As shown in
FIG. 7
, the magnetic flux M gets out of the ring field
105
and gets into the outer tube portion
102
a
through a gap
111
a
between the field
105
and the outer tube portion
102
a
. The magnetic flux M in the outer tube portion
102
a
gets into the armature
103
through a first junction
111
b
between the clutch rotor
102
and the armature
103
. The magnetic flux M in the armature
103
gets into the flange portion
102
c
through a second junction
111
c
between the armature
103
and the flange portion
102
c
. The magnetic flux M in the flange portion
102
c
gets again into the armature
103
through a third junction
111
d
between the flange portion
102
c
and the armature
103
. The flux M in the armature
103
gets into the inner tube portion
102
b
through a fourth junction
111
e
between the armature
103
and the inner tube portion
102
b
. The flux M in the inner tube portion
102
b
returns to the ring field
105
through a gap
111
f
between the inner tube portion
102
b
and the field
105
. Thus, a closed magnetic circuit is formed in the clutch rotor
102
and the armature
103
.
When this magnetic circuit is formed in this manner, the clutch rotor
102
and the armature
103
frictionally engage each other in a manner such that their respective opposite surfaces are at least partially in contact with each other. This frictional engagement causes the rotor
102
and the armature
103
to rotate integrally with each other, whereupon power is transferred between them. When the power supply to the exciting coil
104
is interrupted, the magnetic flux M is canceled, so that the armature
103
is separated from the clutch rotor
102
, whereupon the power transmittal is interrupted.
When the clutch rotor
102
and the armature
103
are connected magnetically to each other, first, second, third, and fourth magnetic pole portions
112
a
,
112
b
,
112
c
and
112
d
are formed on the rotor
102
, ranging successively from the outer peripheral side to the inner peripheral side in the radial direction, as shown in
FIGS. 8 and 9
. The second magnetic pole portion
112
b
is supported on the outer tube portion
102
a
by means of the outside bridge portions
108
a
to
108
f
. The third magnetic pole portion
112
c
is supported on the inner tube portion
102
b
by means of the inside bridge portions
109
a
to
109
f
. The first magnetic pole portion
112
a
is supported on the outer tube portion
102
a
throughout its circumference. The fourth magnetic pole portion
112
d
is supported on the inner tube portion
102
b
throughout its circumference. Thus, the second and third magnetic pole portions
112
b
and
112
c
are lower in stiffness than the first and fourth magnetic pole portions
112
a
and
112
d
. Besides, the second and third magnetic pole portions
112
b
and
112
c
are formed on the flange portion
102
c
that is thinner than the tube portions
102
a
and
102
b
. The thin-walled flange portion
102
c
tends to be deformed into an outwardly convex undulatory shape by springback or the like that is caused when it is worked.
The pressure of contact between the flange portion
102
c
and the armature
103
is liable to increase when the clutch rotor
102
and the armature
103
are connected magnetically to each other. As mentioned before, moreover, the second and third magnetic pole portions
112
b
and
112
c
have low stiffness and easily become undulatory. When the rotor
102
and the armature
103
of the electromagnetic clutch
101
are connected magnetically to each other, therefore, the rotor
102
easily undergoes self-excited vibration. Thus, the second and third magnetic pole portions
112
b
and
112
c
vibrate during clutch operation, and noise is produced depending on the level of the vibration.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a low-noise electromagnetic clutch subject to less vibration during clutch operation.
In order to achieve the above object, an electromagnetic clutch according to the present invention comprises a clutch rotor having a flange portion, an armature opposed to the flange portion, and an exciting coil held in the clutch rotor and adapted to form in the clutch rotor and the armature a magnetic flux for attracting the armature to the flange portion when supplied with current. The flange portion includes arcuate outside slits and arcuate inside slits, formed individually on the respective circumferences of a plurality of concentric circles, and a plurality of ring magnetic pole portions formed separated in the radial direction of the flange portion by the outside slits and the inside slits. The flange portion has a step portion and a concave surface continuous with the step portion, formed in a region corresponding to a specific one of the magnetic pole portions formed between the outside slits and the i
Kawada Minoru
Tanigaki Ryuhei
Armstrong Westerman & Hattori, LLP
Bonck Rodney H.
Mitsubishi Heavy Industries Ltd.
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