192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-07-10
2002-07-16
Bonick, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S084960
Reexamination Certificate
active
06419066
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic coupling apparatus for intermittently transmitting a rotational torque by utilizing an electromagnetic force, and more particularly to, for example, an electromagnetic coupling apparatus provided with a first rotary member for forming a magnetic circuit, a magnetically exciting coil provided rotatably relatively inside of the first rotary member, a yoke provided rotatably relatively to the first rotary member for constituting a part of the magnetic circuit of the first rotary member, and a second rotary member provided to face the first rotary member in an axial direction and having a movable member and provided to be movable in the axial direction for constituting a part of the magnetic circuit.
2. Description of the Related Art
A conventional electromagnetic coupling apparatus will now be described.
In a paper feed mechanism for a copying machine, a facsimile or the like, a paper feed roller is rotated from a predetermined rotational position by a predetermined angle, for example, one turn to feed a piece of recording paper into an interior of the apparatus. The electromagnetic coupling apparatus for performing engagement operation and interruption operation of a clutch is applied in accordance with a control of electric supply to electromagnets as a drive apparatus of a paper feed roller shaft in the paper feed mechanism.
FIG. 6
is a fragmentary side elevational view showing one example of such an electromagnetic coupling apparatus.
In
FIG. 6
, reference numeral
1
denotes the first rotary member. This rotary member is in the form of a ring for forming the magnetic circuit having a U-shape in cross section and is composed of a cup-shaped rotor
3
and a first shaft
2
made of oil impregnated sintered alloy into which a suitable amount of oil is impregnated.
Reference numeral
4
designates the magnetically exciting coil. This magnetically exciting coil
4
is an annular coil that is disposed inside of the first rotary member
1
, i.e., between the first shaft
2
and the rotor
3
to be movable relative to the first rotary member
1
and wound around a bobbin
12
that is a winding frame.
A yoke
5
is disposed on the opening end side of the first rotary member
1
, i.e., on the open side of the gap between the first shaft
2
and the rotor
3
to form a part of the magnetic circuit, mounted to be slidable, i.e., movable in the axial direction and rotatable relative to the first shaft
2
and made of oil impregnated sintered alloy into which a suitable mount of oil is impregnated.
A second rotary member
6
is disposed to face the first rotary member
1
in the axial direction, fixed to a gear portion
7
through a leaf spring
8
to form a part of the magnetic circuit and composed of a movable member
9
that is movable in the axial direction.
A second shaft
10
is made of oil impregnated sintered alloy into which a suitable amount of oil is impregnated, clamps the rotor
3
in cooperation with the first shaft
2
. The first shaft
2
and the second shaft
10
are formed into one piece by press-fitting or by invasion of a projection (not shown).
A rotation preventing projection
5
a
that forms a rotation preventing means relative to the first rotary member
1
is provided at a part of the yoke
5
and is connected to or engaged with an outside stationary portion (not shown) so that the yoke
5
and the magnetically exciting coil
4
are prevented from rotating together with the first shaft
2
.
Also, the movable member
9
is positioned to have a gap G between the movable member
9
and the side surface of the rotor
3
in the case where one end of the gear portion
7
is brought into contact with a side surface of the rotor
3
.
A plurality of windows (not shown) are formed in the side wall portion that serves as a frictional surface with the rotor
3
to increase the magnetic resistance to decrease a part passing through the side wall portion from an inner diameter side to an outer diameter side of the rotor
3
and to increase a part passing through the movable member
9
out of the magnetic flux &PHgr; to be described later.
Also, the above-described first shaft
2
, second shaft
10
and yoke
5
are formed of the oil impregnated sintered alloy into which the oil is impregnated in order to form the magnetic circuit and the rotor
3
and the movable member
9
are made of magnetic material, for example, iron plates.
The operation of this electromagnetic coupling apparatus will now be described.
When the rotational torque of the drive shaft (not shown) is transmitted to the second rotary member
6
through the gear portion
7
, the second rotary member
6
inclusive of the movable member
9
is rotated around the second shaft
10
.
Subsequently, when the current is caused to flow through the magnetically exciting coil
4
as the magnetically exciting means to magnetically excite the coil, the magnetic flux &PHgr; passing through the first shaft
2
, the side wall portion of the rotor
3
, the movable member
9
, the cylindrical portion of the rotor
3
and the yoke
5
is generated to form the magnetic circuit.
The movable member
9
is attracted to the side wall portion of the rotor
3
against the spring force of the leaf spring
8
by the thus generated magnetic force. The rotational torque is transmitted between side surfaces of the movable member
9
and the side wall portion of the rotor
3
by the force that is determined by the attractive force and the frictional coefficient between the movable member
9
and the rotor
3
.
Accordingly, the rotational torque given to the second rotary member
6
is transmitted to the first shaft
2
through the leaf spring
8
, the movable member
9
and the rotor
3
so that the load shaft of the load device (not shown) engaged with the first shaft
2
is drivingly rotated.
On the other hand, when the electric supply to the magnetically exciting coil
4
is interrupted, the electromagnetic force is eliminated and the movable member
9
is separated away from the rotor
3
by the restoration force of the leaf spring
8
. As a result, the rotational torque of the second rotary member
6
is not transmitted to the first shaft
2
and is not transmitted to the load shaft (not shown). Thereafter, the load device (not shown) is naturally stopped by, for example, a mechanical frictional force or the like.
As described above, in the conventional electromagnetic coupling apparatus, the first shaft
2
and the yoke
5
are made of oil impregnated sintered alloy into which the suitable amount of oil is impregnated. For this reason, there is a limit to durability (anti-sliding property). There is a problem that a disadvantage of sticking or the like is generated due to the degradation of the oil or the shortage of the oil, resulting in locking or that the inertia rotation of the load is remarkable, or that the amount of wear of the sliding portions is increased.
Also, the yoke
5
made of the oil impregnated sintered alloy tends to be magnetically balanced with rotor
3
to be attracted toward the rotor
3
and to be subjected to a thrust load. The magnetic exciting coil
4
is pushed toward the side wall portion of the rotor
3
so that the bobbin
12
that is the winding frame of the magnetically exciting coil
4
is frictionally moved on and along the side wall portion of the rotor
3
to increase the frictional wear amount of the end face of the bobbin
12
. Furthermore, there is a problem that a stick slip is generated between the side surfaces of the bobbin
12
and the rotor
3
by the frictional wear powder so that the bobbin is resonant and generates abnormal noise.
Also, when the yoke
5
tilts when the yoke S is attracted toward the rotor
3
, the sliding portion thereof with the first shaft
2
is abnormally worn.
Also, since the first shaft
2
, the second shaft
10
and the yoke
5
are made of oil impregnated sintered material, these components are porous. Due to the existence of these pores, the density is lowere
Kittaka Yoshiaki
Tanaka Hiroshi
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