Technical Field
5 [0001] The present invention relates to an electric
motor including two bearing houses and an electrically
conductive member for electrically connecting those
bearing houses.
Background Art
10 [0002] As an electric motor, an inner-rotor electric
motor has been conventionally known, in which a
columnar rotor including a permanent magnet is disposed
coaxially with a cylindrical stator, which generates a
rotating magnetic field, on the inner diameter side of
15 the cylindrical stator. This electric motor is, for
example, used to rotationally drive a blower fan
mounted in an air conditioner.
[0003] When such an electric motor is driven by a
PWM inverter that performs high-frequency switching, a
20 potential difference (axis voltage) is caused between
the inner race and the outer race of a bearing. When
this axis voltage reaches a dielectric breakdown
voltage of an oil film within the bearing, a current
flows inside the bearing and causes electrolytic
25 corrosion in the bearing. In order to prevent the
electrolytic corrosion from occurring in the bearing,
20-00020IN
3
there is known an electric motor in which an
electrically conductive member electrically connects a
bearing provided at an end side of the electric motor
in a rotation axis direction and a bearing provided at
5 the other end side thereof.
The conventional technologies of fixing the
electrically conductive member to the outer
circumferential surface of the shell of the electric
motor include Patent Literature 1. Further, the
10 conventional technologies of embedding the electrically
conductive member into the electric motor include
Patent Literature 2.
Citation List
Patent Literature
15 [0004] Patent Literature 1: Japanese Patent
Application Laid-open No. 2007-20348
Patent Literature 2: Japanese Patent
Application Laid-open No. 2014-121100
Disclosure of Invention
20 Technical Problem
[0005] Here, if the electrically conductive member
is fixed to the outer circumferential surface of the
shell of the electric motor, assemblability of the
electric motor can be improved, but there is a
25 possibility that the electrically conductive member
drops from the outer circumferential surface. On the
20-00020IN
4
other hand, if the electrically conductive member is
embedded into the electric motor, the electrically
conductive member can be prevented from dropping from
the electric motor, but the assemblability of the
5 electric motor is lowered because the embedding step is
added.
[0006] In this regard, it is an object of the
present invention to provide an electric motor that
improves assemblability while preventing an
10 electrically conductive member from dropping from the
electric motor.
Solution to Problem
[0007] According to an aspect of the present
invention, there is provided an electric motor
15 including: a rotor; a shaft disposed along a rotation
axis of the rotor, the rotor being fixed to the shaft;
a first bearing provided at one end side of the shaft;
a second bearing provided at another end side of the
shaft; a shell that includes an annular portion and end
20 surface portions formed at both ends of the annular
portion and stores the rotor in an inside covered with
the annular portion and the end surface portions; an
electrically conductive member that electrically
connects the first bearing and the second bearing; and
25 a leg portion that protrudes outward in a radial
direction from an outer circumferential surface of the
20-00020IN
5
shell. The leg portion includes a mount hole to which a
vibrationproof member is to be attached. The mount hole
includes a fixing portion to which the electrically
conductive member is to be fixed.
5 [0008] According to the present invention, it is
possible to improve assemblability while preventing an
electrically conductive member from dropping from an
electric motor.
Brief Description of Drawings
10 [0009] [Fig. 1] Fig. 1 is an overall perspective
view of an electric motor according to the present
invention.
[Fig. 2] Fig. 2 is a transverse cross-sectional view
of the electric motor according to the present
15 invention.
[Fig. 3] Fig. 3 is a perspective view of a bracket of
the electric motor according to the present invention.
[Fig. 4] Fig. 4 is an overall perspective view of the
electric motor according to the present invention,
20 showing a state in which the bracket of Fig. 3 is
removed.
[Fig. 5] Fig. 5 is a cross-sectional view of a crosssection
taken along a slitted groove shown in Fig. 1.
[Fig. 6] Fig. 6 is an overall perspective view of the
25 electric motor according to the present invention as
viewed from an output side, showing a state in which a
20-00020IN
6
vibrationproof member and an electrically conductive
member are removed.
[Fig. 7] Fig. 7 is a perspective view showing a state
in which the vibrationproof member and the electrically
5 conductive member are attached in Fig. 6.
[Fig. 8] Fig. 8 is a perspective view of the
electrically conductive member of Fig. 5.
Mode(s) for Carrying Out the Invention
[0010] Next, an embodiment of the present invention
10 will be described with reference to the drawings. In
the following description about the drawings, the same
or similar portions will be denoted by the same or
similar reference symbols. It should be noted that the
drawings are schematic and may differ from reality.
15 Therefore, specific constituent parts should be
determined by referring to the following description.
[0011] Further, the embodiment to be described below
exemplifies apparatuses and methods for embodying the
technical idea of the present invention, and the
20 technical idea of the present invention does not
specify the shape, structure, arrangement, and the like
of the constituent parts to those described below.
Various modifications can be made to the technical idea
of the present invention within the technical scope
25 defined by the claims.
[0012] Hereinafter, an electric motor according to
20-00020IN
7
an embodiment of the present invention will be
described.
[0013]
Figs. 1 to 5 are views for describing a
5 configuration of an electric motor 1 of this embodiment.
As shown in those figures, this electric motor 1 is a
brushless DC motor, for example. The electric motor 1
is, for example, used to rotationally drive a blower
fan mounted in an outdoor unit of an air conditioner,
10 though not shown in the figures.
[0014] As shown in Figs. 1 and 2, the electric motor
1 of this embodiment includes a stator 2, a rotor 3, a
motor shell (casing, shell) 10, a bracket 41, and an
electrically conductive member 5.
15 Hereinafter, an inner-rotor permanent magnet
electric motor 1 will be described as an example, in
which a columnar rotor 3 including a permanent magnet
portion 31 is rotatably disposed inward in the radial
direction of a cylindrical stator 2 that generates a
20 rotating magnetic field.
[0015]
As shown in Fig. 2, the rotor 3 includes an
annular permanent magnet portion 31 and a coupling
portion 35, which is disposed on the inner diameter
25 side relative to the permanent magnet portion 31 and
couples the permanent magnet portion 31 and a shaft 32
20-00020IN
8
to each other. The shaft 32 is disposed along the
center axis of the columnar rotor 3 and also fixed to
the rotor 3. In this embodiment, the permanent magnet
portion 31 and the coupling portion 35 of the rotor 3
5 are formed by integral molding of a resin material in
which a ferrite magnetic substance is mixed. After the
molding, only the permanent magnet portion 31 is
magnetized to cause the permanent magnet portion 31 to
function as a ferrite bonded magnet. Further, the
10 permanent magnet portion 31 is magnetized to be a polar
anisotropic magnet in which a south pole and a north
pole alternately appear in the circumferential
direction thereof. Thus, a part of a yoke for
concentrating the flow of the magnetic flux of the
15 permanent magnet portion 31 becomes unnecessary, and
the leakage flux can be suppressed.
Note that the permanent magnet portion 31 and the
coupling portion 35 may be formed separately. For
example, the rotor 3 may be a so-called surface magnet
20 (SPM) rotor, in which a plurality of ferrite sintered
magnets (corresponding to the permanent magnet portion
31), which are obtained by sintering a powder-like
ferrite magnetic substance in a mold, are annularly
attached to the outer circumferential surface of a
25 rotor core (corresponding to the coupling portion 35).
[0016] The stator 2 includes a stator core 21
20-00020IN
9
including a cylindrical yoke portion (not shown) and a
plurality of teeth portions (not shown) extending from
the yoke portion to the inner diameter side, and
winding (not shown) wound around the teeth portions via
5 an insulator. The stator 2 is covered with the motor
shell 10 (main body) formed of resin by resin integral
molding, except for the inner circumferential surface
of the stator core 21 (see Figs. 2 and 4). Specifically,
the motor shell 10 covers the stator 2 including the
10 stator core 21 and the winding, and stores the rotor 3
therein. As shown in Figs. 1 and 2, the stator 2 is
disposed on the outer circumferential side of the rotor
3 (outward in the radial direction of the permanent
magnet electric motor 1). Further, the stator core 21
15 of the stator 2 is disposed such that the teeth
portions of the stator core 21 face the permanent
magnet portion 31 of the rotor 3 in the radial
direction. In other words, the stator 2 is disposed
such that the annular permanent magnet portion 31 of
20 the rotor 3 faces the stator core 21 of the stator 2 in
the radial direction.
[0017] The motor shell 10 as a main body may have
any shape, but it is formed into, for example, a
bottomed cylindrical shape having an opening O on one
25 side (the opposite output side of the shaft 32) in the
axis direction of the center axis of the permanent
20-00020IN
10
magnet electric motor 1, that is, the rotation axis of
the rotor 3 (hereinafter, rotation axis C). In this
embodiment, the motor shell 10 includes an annular
portion 12, the opening O, and an end surface portion
5 (bottom surface) 13 formed at the end portion on the
opposite side of the opening O (the output side of the
shaft 32). Note that the motor shell 10 need not be
formed of an insulating material such as resin as a
whole, and may be partially formed of metal of an
10 electrically conductive material. Further, this
embodiment exemplifies the case where the outer
appearance of the motor shell 10 has a columnar shape,
but the outer appearance of the motor shell 10 may be a
quadrangular prism shape or hexagonal column shape.
15 [0018] The rotor 3 is rotatably disposed on the
inner circumferential side of the stator core 21 of the
stator 2 with a predetermined clearance (gap) from the
stator core 21. As shown in Figs. 2, 4, and 5, the
permanent magnet portion 31 disposed in an annular
20 shape is disposed on the outer side (outer
circumference side) in the radial direction of the
rotor 3 so as to face the stator core 21.
[0019] The rotor 3 is fixed to the circumference of
the shaft 32. The shaft 32 is rotatably supported
25 (held) by a first bearing 33 and a second bearing 34
fixed to the outer circumferential surface of the shaft
20-00020IN
11
32. Further, the first bearing 33 is stored (held) in a
first bearing storing portion 42 to be described later,
and the second bearing 34 is stored (held) in a second
bearing storing portion 43 to be described later, so
5 that the rotor 3 is rotatably supported. The first
bearing storing portion 42 and the second bearing
storing portion 43 are formed of, for example, a
magnetic substance of chromium-nickel-based stainless
steel.
10 [0020]
As shown in Figs. 2, 3, and 5, the first bearing
33 is fixed to one end side (opposite output side) of
the shaft 32 at the inner race side of the first
bearing 33. The second bearing 34 is fixed to the other
15 end side (output side) of the shaft 32 at the inner
race side of the second bearing 34. The first bearing
33 and the second bearing 34 (a pair of bearings)
cooperate to rotatably support the shaft 32 and the
rotor 3 coupled to the shaft 32. For example, a ball
20 bearing is used for each of the first bearing 33 and
the second bearing 34.
[0021] The bracket 41 includes the first bearing
storing portion 42 that is formed of a magnetic
substance and stores the first bearing 33, and a non25
magnetic portion 44 (end surface portion) formed of a
non-magnetic substance (e.g., resin). In the motor
20-00020IN
12
shell 10 (main body) of the permanent magnet electric
motor 1, the bracket 41 is disposed at an end in the
rotation axis C direction, that is, disposed on the
opposite output side of the shaft 32. The non-magnetic
5 portion (end surface portion) 44 of the bracket 41
includes a connection portion 45 connected to the first
bearing storing portion 42 (see Figs. 2, 3, and 5). The
non-magnetic portion (end surface portion) 44 of the
bracket 41 is integrally formed with the first bearing
10 storing portion 42, which is a magnetic portion, by
insert molding. The non-magnetic portion (end surface
portion) 44 is connected to the first bearing storing
portion 42 at the connection portion 45.
The bracket 41 is attached to the end portion of
15 the motor shell 10 (main body) on the opposite output
side by using screws to serve as a lid for covering the
opening O of the motor shell 10 (main body). Note that
the opening O of the motor shell 10 (main body) may be
provided toward the output side. In this case, the
20 bracket 41 is disposed not on the opposite output side
of the shaft 32 but on the output side of the shaft 32.
[0022] The non-magnetic portion 44 (end surface
portion) of the bracket 41 is formed into a
substantially circular plate shape having the outer
25 shape in the radial direction, which expands to the
outer circumferential surface of the motor shell 10 in
20-00020IN
13
the radial direction. Further, the non-magnetic portion
44 (end surface portion) of the bracket 41 forms a
resin shell of the permanent magnet electric motor 1
together with the motor shell 10. Additionally, the
5 non-magnetic portion 44 includes protrusions 410, which
protrude outward in the radial direction relative to
the outer circumferential surface of the motor shell 10
as viewed from the rotation axis C direction. The
protrusions 410 each abut on the basal end portion of a
10 leg portion 107 of the motor shell 10. The leg portion
107 will be described later. The protrusion 410 of the
bracket 41 is disposed so as to overlap with the leg
portion 107 in the rotation axis C direction.
[0023] The protrusions 410 of the bracket 41 are
15 formed as many as the leg portions 107 provided to the
motor shell 10 (three positions). For example, the
protrusions 410 are each formed into a trapezoidal
shape as viewed from the rotation axis C direction and
each include, at the center portion thereof, a screw
20 through hole 413 penetrating in the rotation axis C
direction.
[0024] Note that the bracket 41 includes a slitted
groove 416 for providing an electrically conductive
member 5 for measures against electrolytic corrosion,
25 which will be described later, on the outer surface
side exposed to the outside in the permanent magnet
20-00020IN
14
electric motor 1 after assembling (see Figs. 1 and 3).
The slitted groove 416 extends outward in the
radial direction from the center portion of the bracket
41 (tubular connection portion 45 of the non-magnetic
5 portion 44 to be described later) to the outer
circumferential surface of the bracket 41, and further
extends in the axis direction from there to the
position abutting on the motor shell 10.
[0025] The bracket 41 is fitted into the motor shell
10 10 (main body) and then screwed at leg-portion-side
fastening portions (screw holes) 103 (to be described
later) of the leg portions 107 of the motor shell 10
via the screw through holes 413 (see Fig. 1).
Further, the first bearing storing portion
15 (bearing house portion) 42 for storing the first
bearing 33 on the inner side (output side) of the
permanent magnet electric motor 1 is disposed at the
center portion of the circular plate shape bracket 41.
The first bearing storing portion 42 is formed into,
20 for example, a substantially bottomed cylindrical shape
by press working. Further, the non-magnetic portion 44
of the bracket 41 includes, at the inner diameter side
thereof, the tubular connection portion 45 connected to
the first bearing storing portion 42 (see Figs. 2 and
25 5).
[0026] The second bearing storing portion (bearing
20-00020IN
15
house portion) 43 for storing the second bearing 34 on
the inner side (opposite output side) of the electric
motor 1 is disposed at the center portion of the output
side end portion of the motor shell 10 (see Figs. 2, 5,
5 and 6). The second bearing storing portion 43 is formed
into, for example, a substantially bottomed cylindrical
shape similarly to the first bearing storing portion 42.
The second bearing storing portion 43 is disposed
inward (inner diameter side) relative to the annular
10 permanent magnet portion 31 in the radial direction of
the rotor 3. The end surface portion 13 of the motor
shell 10 includes a connection portion 14 that is
connected to a flange portion 432 (to be described
later) of the second bearing storing portion 43.
15 [0027] As shown in Figs. 2 and 5, the first bearing
storing portion 42 includes a tubular portion 421 that
holds the outer race side of the first bearing 33 from
the radial direction, an annular flange portion 422
that extends outward (outer circumferential side) in
20 the radial direction of the rotor 3 from one end
portion of the tubular portion 421 in the rotation axis
C direction, and a coronal portion 423 that extends
inward (inner circumferential side) in the radial
direction from the other end portion of the tubular
25 portion 421 in the rotation axis C direction. The
coronal portion 423 covers the other end side of the
20-00020IN
16
first bearing 33 in the rotation axis C direction. The
outer circumferential edge of the annular flange
portion 422 is located inward (inner circumferential
side) in the radial direction of the rotor 3 relative
5 to the permanent magnet portion 31. In other words, the
first bearing storing portion 42 is formed so as not to
overlap with the permanent magnet portion 31 as viewed
from the rotation axis C direction of the rotor 3.
[0028] Specifically, the first bearing storing
10 portion 42 (bearing house portion of the bracket 41 is
disposed inward (inner diameter side) in the radial
direction of the rotor 3 relative to the permanent
magnet portion 31, as viewed from the rotation axis C
direction. Further, the outer circumferential edge
15 portion (edge portion on the outer diameter side) of
the flange portion 422 of the first bearing storing
portion 42 (bearing house portion) is covered with
resin that is a non-magnetic substance. Specifically,
in the bracket 41, the outer circumferential edge
20 portion of the flange portion 422 of the first bearing
storing portion 42 is covered with the non-magnetic
portion 44 made of resin.
[0029] As described above, the bracket 41 is formed
by the first bearing storing portion (magnetic portion)
25 42, which is one of the pair of bearing storing
portions (bearing house portions), and the non-magnetic
20-00020IN
17
portion 44 (end surface portion). The first bearing
storing portion (magnetic portion) 42 is disposed on
the inner diameter side relative to the permanent
magnet portion 31 in the radial direction of the rotor
5 3, and thus can prevent the flange portion 422 of the
first bearing storing portion 42 serving as a magnetic
portion from facing the permanent magnet portion 31 in
the rotation axis C direction. This makes it possible
to suppress a leakage flux flowing from the permanent
10 magnet portion 31 to the first bearing storing portion
(magnetic portion) 42. Furthermore, in the first
bearing storing portion (magnetic portion) 42, the
outer circumferential edge portion of the flange
portion 422, which is disposed close to the permanent
15 magnet portion 31 of the rotor 3, is covered with the
non-magnetic portion 44. This makes it possible to
block the path of the leakage flux flowing from the
permanent magnet portion 31 to the first bearing
storing portion (bearing house portion) 42 formed of a
20 magnetic substance by the non-magnetic portion 44
formed of a non-magnetic substance, and thus further
possible to suppress the leakage flux flowing from the
permanent magnet portion 31 to the first bearing
storing portion 42.
25 [0030] Note that such a structure for suppressing
the leakage flux can be applied to not only the first
20-00020IN
18
bearing storing portion 42 side but also the second
bearing storing portion 43 side. At that time, the
second bearing storing portion 43 is formed into the
shape similar to that of the first bearing storing
5 portion 42 and includes a tubular portion 431 that
holds the outer race side of the second bearing 34 from
the radial direction, an annular flange portion 432
that extends outward in the radial direction of the
rotor 3 from one end portion of the tubular portion 431
10 in the rotation axis C direction, and a coronal portion
433 that extends inward in the radial direction from
the other end portion of the tubular portion 431 in the
rotation axis C direction. Additionally, the second
bearing storing portion 43 is disposed on the inner
15 diameter side relative to the permanent magnet portion
31 in the radial direction of the rotor 3. Further, the
outer circumferential edge portion of the flange
portion 422 of the second bearing storing portion 43 is
covered with the end surface portion 13 (connection
20 portion 14) of the resin motor shell 10 that is a nonmagnetic
substance. This makes it possible to suppress
the leakage flux flowing from the permanent magnet 31
to the second bearing storing portion 43.
[0031] The non-magnetic portion (end surface
25 portion) 44 of the bracket 41 includes the connection
portion 45 connected to the first bearing storing
20-00020IN
19
portion (bearing house portion) 42. The connection
portion 45 is formed into a substantially tubular shape,
and the flange portion 422 of the first bearing storing
portion (bearing house portion) 42 is inserted into and
5 fixed to the side surface of the tubular connection
portion 45 on the inner diameter side. Here, the
tubular portion 421 of the first bearing storing
portion 42 is not in contact with the non-magnetic
portion 44 of the bracket 41 (is not covered with the
10 non-magnetic portion 44), and only the outer
circumferential edge portion of the flange portion 422
is joined (connected) to the connection portion 45 of
the non-magnetic portion 44 so as to be covered
therewith. Further, a clearance portion (air gap) AG1
15 is formed between the tubular portion 421 of the first
bearing storing portion 42 and the tubular connection
portion 45 of the non-magnetic portion 44. With this
configuration, the deformation of the motor shell 10
due to heat, shock, or the like hardly affects the
20 first bearing 33. Furthermore, the contact area between
the connection portion 45 of the bracket 41 and the
flange portion 422 of the first bearing storing portion
42 can be reduced, and thus the heat generated at the
winding wound in the stator core 21 can be prevented
25 from being transmitted to the first bearing 33 via the
bracket 41. This makes it possible to suppress an
20-00020IN
20
increase in temperature of the first bearing 33 and
prevent the first bearing 33 from deteriorating.
[0032] In this embodiment, the second bearing
storing portion 43, which is the other one of the pair
5 of bearing storing portions (bearing house portions),
also has the structure similar to that of the first
bearing storing portion 42. Specifically, the motor
shell 10 is formed into a bottomed cylindrical shape
and includes the annular portion 12 of the motor shell
10 10, which is integrally formed with the stator 2, and
the end surface portion 13 of the motor shell 10, which
is connected to the end portion of the annular portion
12 and expands inward (inner circumferential side) in
the radial direction. Additionally, the end surface
15 portion 13 of the motor shell 10 includes the
cylindrical connection portion 14 connected to the
second bearing storing portion 43. Further, similarly
to the first bearing storing portion 42, the second
bearing storing portion 43, which is the other one of
20 the pair of bearing storing portions, includes the
tubular portion 431 and the flange portion 432
extending outward in the radial direction from the
tubular portion 431, and only the outer circumferential
edge portion of the flange portion 432 is inserted into
25 and fixed to the side surface of the connection portion
14 of the resin shell (motor shell 10) on the inner
20-00020IN
21
diameter side. Further, a clearance portion (air gap)
AG2 is formed between the tubular portion 431 of the
second bearing storing portion 43 and the connection
portion 14 of the resin shell (motor shell 10).
5 [0033] With this configuration, the deformation of
the motor shell 10 due to heat, shock, or the like
hardly affects the second bearing 34. Furthermore, the
contact area between the connection portion 14 of the
motor shell 10 and the flange portion 432 of the second
10 bearing storing portion 43 can be reduced, and thus the
heat generated at the winding wound in the stator core
21 can be prevented from being transmitted to the
second bearing 34 via the resin shell 10. This makes it
possible to suppress an increase in temperature of the
15 first bearing 33 and prevent the first bearing 33 from
deteriorating.
[0034] Further, as described above, the rotor 3
includes the coupling portion 35, to which the shaft 32
is fixed and which couples the permanent magnet portion
20 31 and the shaft 32 to each other. The permanent magnet
portion 31 is disposed so as to face the cylindrical
stator core 21 in the radial direction. The coupling
portion 35 is disposed on the inner diameter side of
the permanent magnet portion 31 annularly disposed. As
25 shown in Figs. 2 and 4, the coupling portion 35
includes a recess 36 that is recessed in the axis
20-00020IN
22
direction of the rotation axis C (rotation axis C
direction). The recess 36 is formed such that the
thickness of the coupling portion 35 in the rotation
axis C direction at the position at which the recess 36
5 is formed is smaller than the thickness of the
permanent magnet portion 31 in the rotation axis C
direction. Additionally, the flange portion 422 of the
first bearing storing portion 42 is disposed so as to
overlap with the recess 36 in the rotation axis C
10 direction.
[0035] This makes it possible to form the annular
recess 36 recessed toward the rotation axis C direction
in the rotor 3, so that the flange portion 422 of the
first bearing storing portion 42 can be disposed within
15 the recess 36.
In such a manner, a part of the first bearing
storing portion 42 (flange portion 422) can enter the
annular recess 36 recessed in the axis direction of the
rotation axis C, thus reducing the thickness of the
20 permanent magnet electric motor 1 in the rotation axis
C direction and downsizing the permanent magnet
electric motor 1 in the rotation axis C direction.
[0036] As shown in Fig. 4, terminal pins 26
electrically connected to the winding (not shown) of
25 the stator core 21, and bosses 27 each serving as a
guide used when a substrate (not shown) is attached are
20-00020IN
23
provided at the end portion (upper end portion in Fig.
4) of the stator 2 on the opposite output side in the
rotation axis C direction.
The bracket 41 functions as an insulation cover
5 for preventing the terminal pins 26 from being exposed
to the outside of the permanent magnet electric motor 1.
In this embodiment, the terminal pins 26 are
provided at three positions, and the bracket 41 is
attached to the motor shell 10 so as to cover up those
10 three positions.
[0037] The bracket 41 includes a cover main body 414
to be attached along the upper end surface of the
stator 2 and a fitting portion 415 integrally formed
with the cover main body 414. The cover main body 414
15 and the fitting portion 415 correspond to the nonmagnetic
portion 44 (end surface portion).
The cover main body 414 is formed into a
substantially circular plate shape as a whole. As shown
in Fig. 3, the fitting portion 415 is formed as an
20 annular protrusion disposed at the outer
circumferential edge portion of the cover main body 414.
The fitting portion 415 is fitted into the end portion
of the motor shell 10 on the opposite output side
(upper end surface of the motor shell 10 in Fig. 4)
25 from the rotation axis C direction, so that the motor
shell 10 (main body) and the bracket 41 are aligned
20-00020IN
24
with each other, and the first bearing 33 is stored in
the first bearing storing portion 42 of the bracket 41
as shown in Fig. 2.
[0038]
5 The motor shell 10 (main body) of the electric
motor 1 includes the plurality of leg portions 107
protruding outward (outer diameter side) in the radial
direction from the outer circumferential surface of the
tubular motor shell 10 (outer circumferential surface
10 of annular portion 12), on one end side in the rotation
axis C direction (end portion on the opposite output
side) (see Figs. 1, 2, and 4 to 7). Three leg portions
107 are arranged at regular intervals in the
circumferential direction of the electric motor 1, for
15 example.
The plurality of leg portions 107 each protrude
into a trapezoidal shape in the outer diameter
direction of the electric motor 1 and each have a
predetermined thickness in the rotation axis C
20 direction. Note that any number of leg portions 107,
such as two or six leg portions 107, may be provided,
and the plurality of leg portions 107 need not be
arranged at regular intervals.
[0039] As shown in Figs. 1, 4, and 7, each leg
25 portion 107, which is formed into a trapezoidal shape,
is formed such that the length of the leg portion 107
20-00020IN
25
in the circumferential direction becomes shorter
outward (outer diameter side) in the radial direction
of the electric motor 1. This makes it possible to
ensure the strength of the leg portion 107 and also
5 effectively use a dead space formed in the leg portion
107. The dead space will be described later.
[0040] Each leg portion 107 includes the legportion-
side fastening portion 103 and a vibrationproof
member placing portion 104 in which a vibrationproof
10 member 6 is to be disposed. The vibrationproof member
placing portion 104 is formed at the center portion of
the leg portion 107 in the circumferential direction of
the electric motor 1.
[0041] Examples of the vibrationproof member 6
15 include vibrationproof rubbers and bushings, each of
which is molded into a hollow bobbin shape or a
cylindrical shape. The vibrationproof member 6 of the
embodiment is formed into a bobbin shape and includes a
central core portion 61, flange portions 62 formed at
20 both ends of the central core portion 61 in the
rotation axis C direction, and an insertion hole 63
into which a fastening member is to be inserted (see
Figs. 5 and 7). Note that the bobbin-shaped
vibrationproof member 6 may have a hexagonal shape or a
25 square shape as viewed from the rotation axis C
direction (as viewed from the top). A fastening member
20-00020IN
26
(not shown) (e.g., screw) for attaching the permanent
magnet electric motor 1 to a target object (e.g.,
casing of air conditioner), to which the permanent
magnet electric motor 1 is to be fixed, is inserted
5 into the insertion hole 63 of the vibrationproof member
6 in the rotation axis C direction. The vibrationproof
member 6 is formed of an elastic material such as
ethylene propylene diene rubber (EPDM) or chloroprene
rubber (CR).
10 [0042] The leg-portion-side fastening portion 103 is,
for example, a screw hole or an embedded nut, to which
a fastening member (screw or the like) (not shown) is
to be fastened. The leg-portion-side fastening portion
103 formed in the leg portion 107 and the screw through
15 hole 413 formed in the bracket 41 are fastened via a
fastening member, and thus the leg-portion-side
fastening portion 103 is fixed at a position that does
not overlap with the vibrationproof member 6
(vibrationproof member placing portion 104). This makes
20 it possible to effectively use the region in each leg
portion 107 where the vibrationproof member 6 is not
disposed (dead space), and to thus suppress an increase
in size of each leg portion 107.
[0043] The vibrationproof member placing portion 104
25 formed in the leg portion 107 includes a mount hole
104A penetrating in the rotation axis C direction, into
20-00020IN
27
which the central core portion 61 of the vibrationproof
member 6 is to be fitted (attached), and a cutout
portion 104B that connects the outer edge of the leg
portion 107 and the mount hole 104A to each other to
5 fit (attach) the vibrationproof member 6 into the mount
hole 104A from the outer diameter side. This makes it
possible to fit the central core portion 61 of the
vibrationproof member 6 into the mount hole 104A via
the cutout portion 104B.
10 Additionally, the vibrationproof member 6 attached
to the vibrationproof member placing portion 104 is
restricted to move in the thickness direction of the
leg portion 107 (rotation axis C direction) by the
flange portions 62 of the vibrationproof member 6.
15 [0044] Note that the vibrationproof member placing
portion 104 need not include the cutout portion 104B
connected to the outer circumferential edge of the leg
portion 107, and may be a mount hole 104A constituted
as a mere through hole penetrating in the rotation axis
20 C direction. In this case, the vibrationproof member 6
is inserted into the mount hole 104A, which is formed
as a through hole, in the rotation axis C direction.
[0045] The vibrationproof member placing portion 104
may include a recess portion 106 recessed on one side
25 of the leg portion 107 in the rotation axis C direction
(the output side of the shaft 32) along with the shape
20-00020IN
28
of the vibrationproof member 6. This makes it possible
to ensure the thickness of the leg portion 107 to
maintain the strength and also to simplify the shape of
the vibrationproof member 6.
5 [0046] Here, when the electric motor 1 is driven by
a PWM inverter that performs high-frequency switching,
the potential of the neutral point of the winding does
not become zero, and a voltage called common mode
voltage is generated. Due to the common mode voltage,
10 the stray capacity within the electric motor 1 causes
the potential difference (axis voltage) between the
inner race and the outer race of each of the first
bearing 33 and the second bearing 34. When this axis
voltage reaches a dielectric breakdown voltage of the
15 oil film within the bearing, a current flows inside the
bearing and causes electrolytic corrosion in the
bearing. In order to prevent the electrolytic corrosion
from occurring in the bearings, the electric motor 1 of
this embodiment includes the electrically conductive
20 member 5 for electrical conduction between the first
bearing storing portion 42 and the second bearing
storing portion 43, in which the two bearings are
stored, respectively.
[0047] The electrically conductive member 5 is
25 formed by, for example, processing an electrically
conductive material into a strip shape or wire shape.
20-00020IN
29
In this embodiment, the electrically conductive member
5 is formed by, for example, punching a steel plate
having a thickness of approximately 0.3 mm into a strip
shape and bending the obtained steel plate into a
5 squared U shape (U shape) along the outer surfaces of
the motor shell 10 and the bracket 41 (see Figs. 5 and
8). The electrically conductive member 5 allows the
potentials of the first bearing 33 and the second
bearing 34 on the outer race side to be the same by
10 electrically connecting the first bearing storing
portion 42 in which the first bearing 33 is stored, and
the second bearing storing portion 43 in which the
second bearing 34 is stored, so that the occurrence of
electrolytic corrosion can be suppressed by reducing
15 the potential difference between the inner and outer
races of each bearing.
[0048] The electrically conductive member 5 includes
a pair of connection end portions 51 and 51 that are
connected to the bearing storing portions 42 and 43, a
20 pair of end-surface-side placing portions 52 and 52
disposed on the end surface portions of the shell of
the electric motor 1 to extend in the radial direction,
and an outer-circumferential-surface-side placing
portion 53 disposed on the outer circumferential
25 surface of the shell of the electric motor 1 along the
rotation axis C direction. Note that this embodiment
20-00020IN
30
exemplifies the case where the electrically conductive
member 5 is formed from a single strip-shaped member,
but a plurality of electrically conductive members may
be connected to form the electrically conductive member
5 5.
[0049] As described above, in the electric motor 1
of this embodiment, slitted grooves 108 and 416 are
formed in the motor shell 10 and the bracket 41,
respectively (see Figs. 1 and 5 to 7). Additionally,
10 when the bracket 41 is fitted into the motor shell 10,
the slitted groove 416 of the bracket 41 and the
slitted groove 108 formed in the outer surface of the
motor shell 10 become continuous.
[0050] As shown in Figs. 5 and 7, the electrically
15 conductive member 5 is disposed in the outer surface of
the electric motor 1 so as to extend from the position
of the flange portion 422 of the first bearing storing
portion 42 to the position of the flange portion 432 of
the second bearing storing portion 43 through the
20 slitted groove 416 of the bracket 41, the slitted
groove 105 of the leg portion 107, which will be
described later, and the slitted groove 108 of the
motor shell 10. The electrically conductive member 5 is
disposed in the slitted grooves (416, 105, 108), so
25 that the electrically conductive member 5 can be
prevented from protruding from the surface of the shell
20-00020IN
31
of the electric motor 1 and from dropping from the
electric motor 1.
[0051] Here, any one of the three leg portions 107
includes the slitted groove (electrically-conductive-
5 member fixing portion) 105 formed at a position with
the minimum distance from the rotation axis C in the
mount hole 104A of the vibrationproof member placing
portion 104. This slitted groove 105 is a groove having
a concave shape, V-shape, or the like, which is formed
10 to be continuous with the mount hole 104A so as to be
recessed from the edge of the mount hole 104A toward
the inner diameter side.
With this configuration, the edge of the mount
hole 104A serves as a guide for guiding the outer15
circumferential-surface-side placing portion 53 of the
electrically conductive member 5 to the slitted groove
105, which facilitates the positioning of the
electrically conductive member 5. Further, the slitted
groove 105 serving as an electrically-conductive-member
20 fixing portion is formed in the leg portion 107
protruding from the outer circumference of the motor
shell 10 in the outer diameter direction, so that a
deeper groove than a groove directly provided on the
side surface of the motor shell 10 can be formed, and
25 the electrically conductive member 5 is more difficult
to drop from the electric motor 1.
20-00020IN
32
[0052] Further, as described above, the
vibrationproof member placing portion 104 includes the
cutout portion 104B, which is obtained by partially
cutting out the leg portion 107 such that the outer
5 circumferential surface of the leg portion 107 and the
mount hole 104A are continuous. This makes it possible
to easily arrange the electrically conductive member 5
in the electrically-conductive-member fixing portion
(slitted groove) 105 provided to the mount hole 104A,
10 from the outer circumferential side of the leg portion
107 via the cutout portion 104B, in a similar manner
that attaches the vibrationproof member 6 to the mount
hole 104A. In other words, since the electrically
conductive member 5 is attached to the electrically15
conductive-member fixing portion 105 so as to be laid
from the outside of the electric motor 1, the
electrically conductive member 5 is easily attached to
the electric motor 1.
[0053] Furthermore, before the vibrationproof member
20 6 is fitted into the vibrationproof member placing
portion 104 (mount hole 104A) of the leg portion 107,
the outer-circumferential-surface-side placing portion
53 of the electrically conductive member 5 is inserted
into the above-mentioned slitted groove 105 in advance,
25 and then the vibrationproof member 6 is fitted into the
vibrationproof member placing portion 104 (mount hole
20-00020IN
33
104A), so that the electrically conductive member 5 is
restricted to move in the outer diameter direction by
the vibrationproof member 6. Further, the electrically
conductive member 5 is restricted to move in the
5 circumferential direction by the slitted groove
(electrically-conductive-member fixing portion) 105
formed to be continuous with the mount hole 104A.
Specifically, the vibrationproof member 6 and the
slitted groove 105 cooperate to restrict the movement
10 of the electrically conductive member 5, and thus the
electrically conductive member 5 can be prevented from
dropping from the electric motor 1.
[0054] The connection end portions 51 and 51 that
are both ends of the electrically conductive member 5
15 are bent along the tubular connection portions (45, 14)
of the resin shell and the tubular portions (421, 431)
of the bearing house portions (42, 43), and then pressfitted
into and fixed to clearance portions AG1 and AG2
formed outside the tubular portions 421 and 431 of the
20 bearing house portions 42 and 43, respectively (see
Figs. 1 and 5 to 7). With this configuration, the
electrically conductive member 5 for preventing
electrolytic corrosion can be easily fixed to the
bearing house portions 42 and 43 by using the clearance
25 portions AG1 and AG2. Additionally, the connection end
portions 51 and 51 of the electrically conductive
20-00020IN
34
member 5 are fixed to the flange portions 422 and 432
of the bearing house portions 42 and 43, respectively,
in the abutting state, and thus the first bearing 33
and the second bearing 34 are electrically connected.
5 [0055] Note that the means for fixing both end
portions of the electrically conductive member 5 to the
bearing house portions is not limited to the means
described above. For example, the connection end
portions 51 and 51 of the electrically conductive
10 member 5 may be fixed to the bearing house portions 42
and 43 with a caulking member (not shown).
[0056] Further, the electrically conductive member 5
is not limited to be formed into the squared U shape as
a whole and only needs to include the outer15
circumferential-surface-side placing portion 53, which
is to be fixed to the mount hole 104A formed in the leg
portion 107. For example, if the metal bearing house
portions (first bearing storing portion 42 and second
bearing storing portion 43) are formed to extend to the
20 outer circumferential surface of the cylindrical motor
shell 10, the electrically conductive member 5 only
needs to include the outer-circumferential-surface-side
placing portion 53 along the side surface (outer
circumferential surface of annular portion 12) of the
25 motor shell 10, and does not need to include the endsurface-
side placing portions 52 along the end surfaces
20-00020IN
35
(end surface portions 13, 44) of the electric motor 1.
[0057] As described above, the electric motor 1
includes: the rotor 3; the shaft 32 disposed along the
rotation axis C of the rotor 3, the rotor 3 being fixed
5 to the shaft 32; the first bearing 33 provided at one
end side of the shaft 32; the second bearing 34
provided at the other end side of the shaft 32; the
shell 10 and 41 that includes the annular portion 12
and the end surface portions 13 and 44 formed at both
10 ends of the annular portion 12 in the rotation axis C
direction and stores the rotor 3 in the inside covered
with the annular portion 12 and the end surface
portions 13 and 44; the electrically conductive member
5 that electrically connects the first bearing 33 and
15 the second bearing 34; and the leg portions 107
protruding outward in the radial direction from the
outer circumferential surface of the shell 10. The leg
portion 107 includes the mount hole 104A to which the
vibrationproof member 6 is to be attached. The mount
20 hole 104A includes the electrically-conductive-member
fixing portion (slitted groove) 105 to which the
electrically conductive member 5 is to be fixed.
This makes it possible to fix the electrically
conductive member 5 to the electric motor 1 by using
25 the slitted groove (electrically-conductive-member
fixing portion) 105 provided to the mount hole 104A,
20-00020IN
36
and thus to easily attach the electrically conductive
member 5 to the electric motor 1 and also prevent the
electrically conductive member 5 from dropping from the
electric motor 1.
5 [0058] Note that the electrically-conductive-member
fixing portion 105 provided to the mount hole 104A need
not include the slitted groove in which the edge of the
mount hole 104A is cut out. At that time, the
electrically conductive member 5 is fixed while being
10 sandwiched between the edge of the circular mount hole
104A and the vibrationproof member 6. In this case as
well, it is possible to easily fix the electrically
conductive member 5 by using the mount hole 104A and
the vibrationproof member 6 attached to the mount hole
15 104A and also to prevent the electrically conductive
member 5 from dropping from the electric motor 1.
Reference Signs List
[0059]
1 electric motor
20 10 motor shell (shell)
12 annular portion
13 end surface portion
104 vibrationproof member placing portion
104A mount hole
25 104B cutout portion
105 slitted groove (electrically-conductive-member
20-00020IN
37
fixing portion)
107 leg portion
2 stator
3 rotor
5 32 shaft
33 first bearing
34 second bearing
41 bracket
44 end surface portion
10 5 electrically conductive member
53 outer-circumferential-surface-side placing portion
6 vibrationproof member

Claims
[1] An electric motor, comprising:
a rotor;
a shaft disposed along a rotation axis of the
5 rotor, the rotor being fixed to the shaft;
a first bearing provided at one end side of the
shaft;
a second bearing provided at another end side of
the shaft;
10 a shell that includes an annular portion and end
surface portions formed at both ends of the annular
portion in a direction of the rotation axis and stores
the rotor in an inside covered with the annular portion
and the end surface portions;
15 an electrically conductive member that
electrically connects the first bearing and the second
bearing; and
a leg portion that protrudes outward in a radial
direction from an outer circumferential surface of the
20 shell, wherein
the leg portion includes a mount hole to which a
vibrationproof member is to be attached, and
the mount hole includes a fixing portion to which
the electrically conductive member is to be fixed.
25 [2] The electric motor according to claim 1, wherein
the electrically conductive member includes an
20-00020IN
39
outer-circumferential-surface-side placing portion that
is disposed on the outer circumferential surface of the
shell along an axis direction of the rotation axis, and
the outer-circumferential-surface-side placing
5 portion of the electrically conductive member is fixed
to the fixing portion.
[3] The electric motor according to claim 1 or 2,
wherein
the fixing portion is a groove formed to be
10 continuous with the mount hole.
[4] The electric motor according to claim 3, wherein
the fixing portion is formed at a position with a
minimum distance from the rotation axis in the mount
hole.
15 [5] The electric motor according to any one of claims
1 to 4, wherein
a part of the mount hole on an outer diameter side
is cut out, and an outer circumferential surface of the
leg portion and the mount hole are continuous.