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DESCRIPTION JP2015053805

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DESCRIPTION JP2015053805
An object of the present invention is to provide a magnetic circuit capable of enhancing the
assembling accuracy. A magnetic circuit (2) is defined as a new magnetic circuit replaced from an
old magnetic circuit mainly made of a sintered magnet made of a neodymium magnet. The
magnetic circuit 2 includes, in addition to the area occupied by the sintered magnet of the old
magnetic circuit, a plastic magnet 21 of neodymium magnet in an amount covering the area
occupied by the inner yoke. The magnetic circuit 2 is obtained by integrally molding the plastic
magnet 21 with the outer yoke 23 by injection molding while the plastic magnet 21 is obtained
by injection molding using a synthetic resin containing neodymium powder. The shortfall of the
total magnetic flux amount for the same amount of sintered magnets was compensated by the
increased amount of plastic magnets. [Selected figure] Figure 4
Magnetic circuit
[0001]
The present invention relates to a magnetic circuit in which a plurality of parts including a
magnet are combined.
[0002]
Patent Document 1 discloses the configuration of a magnetic circuit of five parts including a
magnet.
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Intermediate members are joined to the upper and lower surfaces of the magnet, respectively, an
inner yoke is joined to the upper intermediate member, and an outer yoke is joined to the lower
intermediate member. The gap between the inner yoke and the outer yoke is called a gap. When
a coil is disposed in the gap and a current is supplied to the coil in a magnetic field, an
electromagnetic force is generated in the direction of the thumb according to Fleming's left-hand
rule. The electromagnetic force causes the actuator to move, for example, providing a function of
tactile feedback that applies a reaction force to the switch operation.
[0003]
JP 10-340809 A (paragraphs [0034], [Fig. 6])
[0004]
Since the coil is disposed in the gap portion, securing of the clearance between the coil and the
yoke is an essential condition.
However, because the magnetic circuit is composed of a plurality of parts, high accuracy is
required for each part tolerance and assembly tolerance, and it is a problem that it must be
cleared.
[0005]
The present invention has been made in view of such problems, and an object thereof is to
provide a magnetic circuit capable of enhancing the assembling accuracy.
[0006]
The magnetic circuit which solves the above-mentioned subject is a magnetic circuit which a
plurality of parts including a magnet are combined with, while forming a plastic magnet as
another magnet integrally with other parts as said magnet to make the magnetic circuit
concerned, the same amount of sintered magnets The main point is to make up for the shortfall
of the total magnetic flux amount with the increase of the plastic magnet.
[0007]
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According to this configuration, the assembling accuracy can be enhanced by integrally molding
a plurality of parts including the plastic magnet.
However, simply replacing the sintered magnet with a plastic magnet reduces the value of the
total magnetic flux in the comparison with the same amount, which causes a reduction in the
force generated by the actuator.
In this case, the insufficiency of the total magnetic flux can be compensated by increasing the
amount of the plastic magnet.
[0008]
With regard to the above magnetic circuit, the magnetic circuit is defined as a new magnetic
circuit to be replaced from the old magnetic circuit in which a sintered magnet and an inner yoke
and an outer yoke made of a magnetic material are combined, In addition, the plastic magnet
may be provided in an amount that covers the area occupied by the inner yoke.
[0009]
According to this configuration, the assembly accuracy can be improved by integral molding
while maintaining the actuator generation force by the old magnetic circuit of the threecomponent configuration.
With regard to the above magnetic circuit, the magnetic circuit is defined as a new magnetic
circuit to be replaced from the old magnetic circuit in which the sintered magnet and the inner
yoke and outer yoke made of magnetic material are combined, and the occupied area of the
sintered magnet In addition to both of the occupied regions of the inner yoke, the plastic magnet
may be provided in an amount that covers a partial region of the outer yoke.
[0010]
According to this configuration, the assembly accuracy can be improved by integral molding
while maintaining the actuator generation force by the old magnetic circuit of the threecomponent configuration. With respect to the above magnetic circuit, when current is supplied to
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a coil disposed in a magnetic field generated by the magnetic circuit, its own movement is
permitted by the electromagnetic force generated in the direction of the thumb according to
Fleming's left-hand rule. It is also possible to provide an axial hole through which the mandrel
allows movement of the magnetic circuit by force.
[0011]
According to this configuration, positioning can be facilitated by passing the mandrel through the
axial hole of the magnetic circuit.
[0012]
According to the present invention, assembling accuracy can be enhanced.
[0013]
FIG. 1 is an exploded perspective view showing a main part configuration of an actuator
including a magnetic circuit according to a first embodiment.
Sectional drawing which shows the structure of a former magnetic circuit.
Sectional drawing which shows the orientation in a former magnetic circuit. Sectional drawing
which shows the structure of the magnetic circuit by 1st Embodiment with orientation. The table
which compares and shows the residual magnetic flux density for every magnet. Sectional
drawing which shows the structure of the magnetic circuit by 2nd Embodiment with orientation.
Sectional drawing which shows the structure of the magnetic circuit by 3rd Embodiment with
orientation.
[0014]
First Embodiment The first embodiment of the magnetic circuit will be described below. As
shown in FIG. 1, the magnetic circuit 2 constitutes the actuator 1 together with the coil ASSY 3.
The magnetic circuit 2 is defined as a new magnetic circuit which is replaced from the old
magnetic circuit mainly composed of a sintered magnet.
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[0015]
As shown in FIG. 2, in the old magnetic circuit 2F, a sintered magnet 21F made of neodymium
magnet and an inner yoke 22F made of magnetic material and an outer yoke 23F are assembled.
The outer yoke 23F serving as a base has a disk-shaped bottom wall and a peripheral wall along
the outer edge, and has a U-shaped cross section. A sintered magnet 21F is bonded to the center
of the inner bottom surface of the outer yoke 23F. The sintered magnet 21F has a disk shape
which is slightly smaller than the bottom wall of the outer yoke 23F. On the upper surface of the
sintered magnet 21F, an inner yoke 22F having a disk shape having the same diameter is
adhered. A gap between each outer peripheral surface of the sintered magnet 21F and the inner
yoke 22F and the inner peripheral surface of the peripheral wall of the outer yoke 23F is defined
as a gap 24F.
[0016]
As shown in FIG. 3, the old magnetic circuit 2F is set to the obtained orientation of the direction
of the magnetic field from the bottom to the top of the sintered magnet 21F. The magnetic field
generated by the sintered magnet 21F is guided from the inner yoke 22F to the peripheral wall
of the outer yoke 23F via the gap 24F, and conforms to the shape of the outer yoke 23F, and
reaches the sintered magnet 21F soon from the bottom wall.
[0017]
As shown in FIG. 4, the magnetic circuit 2 replaced from the old magnetic circuit 2F is a plastic
magnet 21 by a neodymium magnet of an amount extending to the occupied area of the inner
yoke 22F in addition to the occupied area of the sintered magnet 21F of the old magnetic circuit
2F. Is equipped. The magnetic circuit 2 is obtained by integrally molding the plastic magnet 21
with the outer yoke 23 equivalent to the outer yoke 23F by the injection molding while the
plastic magnet 21 is obtained by the injection molding using a synthetic resin containing a
neodymium powder. A gap between the outer peripheral surface of the plastic magnet 21 and
the inner peripheral surface of the peripheral wall of the outer yoke 23 is defined as a gap 24
equivalent to the gap 24F. In the magnetic circuit 2, the direction of the magnetic field is
obtained from the bottom to the top near the radial center of the plastic magnet 21, and at the
top of the plastic magnet 21, the orientation of the magnetic field is obtained from the inside to
the outside ing. The magnetic field generated by the plastic magnet 21 is guided from the upper
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outer periphery of the plastic magnet 21 to the peripheral wall of the outer yoke 23 via the gap
24 and conforms to the shape of the outer yoke 23 and eventually reaches the plastic magnet 21
from the bottom wall.
[0018]
As shown in FIG. 5, when the residual magnetic flux density for each magnet is compared, the
value of the neodymium magnet (plastic magnet 21) by bonding is smaller than that of the
neodymium magnet (sintered magnet 21F) by sintering. That is, simply replacing the sintered
magnet with a plastic magnet reduces the value of the total magnetic flux amount in comparison
with the same amount. For this reason, in this example, in addition to the area occupied by the
sintered magnet 21F of the old magnetic circuit 2F, the plastic magnet 21 is used in an amount
extending to the area occupied by the inner yoke 22F. As a result, the shortage of the total
magnetic flux amount for the same amount of sintered magnets is compensated by the increased
amount of the plastic magnet. In addition to the distribution of the magnets derived from the
amount of the plastic magnet 21, the orientation of the plastic magnet 21 compensates for the
shortage of the total amount of magnetic flux for the same amount of the sintered magnet.
[0019]
Returning to FIG. 1, the coil ASSY 3 mainly includes the coil 32 wound around the bobbin 31.
The inner diameter of the bobbin 31 is slightly larger than the outer diameter of the plastic
magnet 21, and the outer diameter of the coil 32 is slightly smaller than the inner diameter of
the peripheral wall of the outer yoke 23. Thus, the coil 32 is disposed in the gap 24 with
clearances between the bobbin 31 and the plastic magnet 21 and between the coil 32 and the
peripheral wall of the outer yoke 23 respectively. When a current is supplied from a current
source (not shown) to the coil 32 in a magnetic field, an electromagnetic force is generated in the
direction of the thumb according to Fleming's left-hand rule.
[0020]
Referring to FIG. 4, in the vicinity of gap 24 on the left side, the direction of the magnetic field is
from the right to the left, so the direction of the current supplied to coil 32 is from the front to
the back of the paper. On the premise of this, electromagnetic force is generated in the direction
from the bottom to the top. On the other hand, in the vicinity of the gap 24 on the right side, the
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direction of the magnetic field is from the left to the right, and the direction of the current
supplied to the coil 32 under the above assumption is from the back to the front of the sheet.
Therefore, an electromagnetic force is generated in the same direction from the bottom to the
top. As a result, the magnetic circuit 2 and the coil ASSY 3 relatively linearly move in the vertical
direction due to the electromagnetic force. For example, in a configuration in which the magnetic
circuit 2 can be displaced while the coil ASSY 3 is fixed, the magnetic circuit 2 performs a
downward motion from the top to the bottom in a direction opposite to the direction of the
electromagnetic force from the bottom to the top. On the other hand, in a configuration in which
the coil ASSY 3 can be displaced while the magnetic circuit 2 is fixed, the coil ASSY 3 moves
upward from the bottom in accordance with the direction of the electromagnetic force from the
bottom to the top.
[0021]
Next, the operation of the magnetic circuit 2 will be described. The magnetic circuit 2 is formed
by integrally molding a plastic magnet 21 with an outer yoke 23 by injection molding. For this
reason, even if the assembly accuracy depends on the dimensional tolerance of the molding die,
high accuracy can be easily cleared as compared with the old magnetic circuit 2F in which each
component is assembled by bonding while manufacturing a plurality of components individually.
As a result, while the gap 24 in which the coil 32 is disposed can be optimized, a necessary and
sufficient clearance between the coil 32 and the coil 32 can be secured.
[0022]
As described above, according to the first embodiment, the following effects can be achieved. (1)
Assembling accuracy can be improved by integrally molding a plurality of parts including the
plastic magnet 21.
[0023]
(2) The magnetic circuit 2 includes the plastic magnet 21 in an amount that covers the area
occupied by the inner yoke 22F, in addition to the area occupied by the sintered magnet 21F.
Therefore, the assembly accuracy can be enhanced by integral molding while maintaining the
actuator generation force by the old magnetic circuit 2F of the three-part configuration.
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[0024]
(3) While the plastic magnet 21 of neodymium magnet is integrally molded with other parts to
form the magnetic circuit 2, the shortage of the total magnetic flux amount to the same amount
of sintered magnet is compensated by the increase of the plastic magnet. Therefore, the
assembling accuracy can be enhanced by integral molding, and the generated force of the
actuator 1 can be made equal to that of the old magnetic circuit 2F using the sintered magnet
21F.
[0025]
(4) The distribution and orientation of the plastic magnet 21 can maintain the actuator
generation force. Second Embodiment Next, a second embodiment of the magnetic circuit will be
described.
[0026]
As shown in FIG. 6, the magnetic circuit 2A is defined as a new magnetic circuit to be replaced
from the old magnetic circuit 2F. The magnetic circuit 2A includes a plastic magnet 21A made of
a neodymium magnet in an amount covering a partial region of the outer yoke 23F, in addition to
both the region occupied by the sintered magnet 21F and the region occupied by the inner yoke
22F. That is, in addition to the area occupied by the plastic magnet 21 according to the first
embodiment, the plastic magnet 21A occupies a partial area of the peripheral wall of the outer
yoke 23. The magnetic circuit 2A is integrally molded by injection molding. For convenience, a
region equivalent to the outer yoke 23 including the region occupied by the plastic magnet 21A
is defined as the outer yoke 23A. In addition, a gap 24A equivalent to the gap 24 is also defined.
Of the peripheral wall of the outer yoke 23A, the portion occupied by the plastic magnet 21A is
set to the obtained orientation of the direction of the magnetic field from the top to the bottom.
As a result, the amount of magnet is increased with the addition of the above portion, and the
insufficient amount of the total magnetic flux amount for the same amount of sintered magnet is
compensated by the orientation of the portion as well, and the actuator higher than the first
embodiment The power is obtained.
[0027]
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As described above, according to the second embodiment, in addition to the same effects as the
effects (1) to (4) of the first embodiment, the following effects can be achieved. (5) The magnetic
circuit 2A includes the plastic magnet 21A in an amount that covers a partial region of the outer
yoke 23F, in addition to both the region occupied by the sintered magnet 21F and the region
occupied by the inner yoke 22F. Therefore, the assembly accuracy can be enhanced by integral
molding while maintaining the actuator generation force by the old magnetic circuit 2F of the
three-part configuration.
[0028]
Third Embodiment Next, a third embodiment of the magnetic circuit will be described. As shown
in FIG. 7, the magnetic circuit 2B has an outer diameter equivalent to that of the old magnetic
circuit 2F, and includes an axial hole 20B penetrating in the vertical direction at the radial center.
A shaft (not shown) provided in the coil ASSY 3 and disposed at the radial center of the bobbin
31 is passed through the shaft hole 20B. Thereby, the movement of the magnetic circuit 2B or
the coil ASSY 3 by the electromagnetic force is permitted. The magnetic circuit 2B is added to the
area excluding the area of the axial hole 20B from the area corresponding to the three of the area
occupied by the sintered magnet 21F and the area occupied by the inner yoke 22F and a partial
area of the bottom wall of the outer yoke 23F, A plastic magnet 21B made of a neodymium
magnet is provided in an amount covering a partial area of the peripheral wall of the outer yoke
23F. That is, the plastic magnet 21B occupies the area excluding the area of the shaft hole 20B
from the area corresponding to both the occupied area of the plastic magnet 21A according to
the second embodiment and the partial area of the bottom wall of the outer yoke 23A. . The
magnetic circuit 2B is integrally molded by injection molding. For convenience, an area
equivalent to the outer yoke 23 including the area occupied by the plastic magnet 21B is defined
as an outer yoke 23B. In addition, a gap 24B equivalent to the gap 24 is also defined. In the
portion of the bottom wall of the outer yoke 23B occupied by the plastic magnet 21B, the
direction of the magnetic field is obtained from the outer side to the inner side, and is set to the
obtained orientation of the magnetic field direction from the lower side to the upper side . As a
result, the shortage of the amount of magnet due to the axial hole 20B is compensated with the
addition of the above-mentioned portion, and the deficiency of the total amount of magnetic flux
for the same amount of sintered magnet is also compensated by the orientation of that portion.
An actuator generation force equivalent to that of the embodiment can be obtained.
[0029]
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As described above, according to the third embodiment, in addition to the same effects as the
effects (1) to (5) of the above-described embodiments, the following effects can be achieved. (6)
Positioning can be facilitated by passing the mandrel through the axial hole 20B of the magnetic
circuit 2B.
[0030]
The above embodiments can be modified and embodied as follows. In the third embodiment, the
plastic magnet 21B on the peripheral wall of the outer yoke 23B may be omitted. In this case, an
actuator generation force equivalent to that of the first embodiment can be obtained.
[0031]
-As a new magnetic circuit replaced from the old magnetic circuit 2F mainly made of a sintered
magnet 21F made of neodymium magnet, it may be embodied in a magnetic circuit made mainly
of a plastic magnet made of samarium iron magnet.
[0032]
As shown in FIG. 5, the value of the residual magnetic flux density of the samarium iron magnet
(plastic magnet) by bonding is smaller than that of the neodymium magnet (sintered magnet
21F) by sintering.
That is, simply replacing the neodymium magnet by sintering with a samarium iron magnet by
bonding reduces the value of the total magnetic flux in comparison with the same amount.
Therefore, according to the above-described embodiments, the plastic magnet made of samarium
iron magnet is integrally molded with other parts to form a magnetic circuit, and the shortage of
the total magnetic flux amount with respect to the same amount of sintered magnet is increased
by the plastic magnet Replacement with the old magnetic circuit 2F is possible.
[0033]
According to this configuration, the assembling accuracy is improved by integral molding, and
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the force generated by the actuator can be made equal to that of the old magnetic circuit using
the sintered magnet, and the weight can be reduced. In the case of samarium iron magnet, the
specific gravity is about 1/4 of iron.
[0034]
Next, technical ideas that can be grasped from the above-described embodiments and other
examples will be described. (A) In the magnetic circuit, the magnetic circuit is defined as a new
magnetic circuit to be replaced from the old magnetic circuit in which a plurality of parts
including a sintered magnet by neodymium magnet are combined, and the plastic magnet by
neodymium magnet is And the shortage of the total magnetic flux amount for the same amount
of sintered magnets was compensated by the increased amount of the plastic magnet while being
integrally molded into the magnetic circuit.
[0035]
According to this configuration, the assembling accuracy can be improved by integral molding,
and the force generated by the actuator can be made equal to that of the old magnetic circuit
using the sintered magnet. (B) In the magnetic circuit, the magnetic circuit is defined as a new
magnetic circuit to be replaced from an old magnetic circuit in which a plurality of parts
including sintered magnets by neodymium magnets are combined, and plastic magnets by
samarium iron magnets While making the magnetic circuit integrally with the parts and making
up the magnetic circuit, the insufficient amount of the total magnetic flux amount with respect to
the same amount of the sintered magnet is compensated by the increased amount of the plastic
magnet.
[0036]
According to this configuration, the assembling accuracy is improved by integral molding, and
the force generated by the actuator can be made equal to that of the old magnetic circuit using
the sintered magnet, and the weight can be reduced. In the case of samarium iron magnet, the
specific gravity is about 1/4 of iron.
[0037]
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(C) In a magnetic circuit, compensating for the shortage of the total magnetic flux amount for the
same amount of sintered magnets by both the distribution of magnets derived from the amount
of plastic magnets and the orientation of the magnets derived from the direction of the magnetic
field.
[0038]
According to this configuration, the actuator generation force can be maintained by the
distribution and orientation of the magnets.
[0039]
DESCRIPTION OF SYMBOLS 1 ... Actuator 2, 2A, 2B ... Magnetic circuit, 3 ... Coil ASSY, 20B ...
Axial hole, 21, 21A, 21B ... Plastic magnet (magnet), 23, 23A, 23B ... Outer yoke, 24, 24A, 24B ...
Gap, 31 ... bobbin, 32 ... coil.
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