FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ELECTRIC MOTOR;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

2
DESCRIPTION
5 Technical Field
[0001] The present disclosure relates to an electric motor.
Background Art
[0002] An electric motor includes a shaft, a rotor that is attached to and rotates
integrally with the shaft, and a stator that faces the rotor with a spacing therebetween in a
10 radial direction. Energizing the electric motor increases temperatures of the stator and
the rotor. In order to prevent occurrence of malfunctions due to an increase in a
temperature inside the electric motor, cooling of the inside of the electric motor is
performed by causing air blown by a blower disposed outside the electric motor to flow
through a ventilation path formed in a stator core. Patent Literature 1 discloses an
15 example of such kind of electric motor. According to the electric motor disclosed in
Patent Literature 1, air having flowed from an intake hole into the inside of the electric
motor passes through a ventilation hole formed in a stator and a flow path inside a casing,
and passes through another ventilation hole formed in the stator again, and then flows out
from an exhaust hole to the outside of the electric motor. This configuration enables
20 cooling of the inside of the electric motor.
Citation List
Patent Literature
[0003] Patent Literature 1: Unexamined Japanese Utility Model Application
Publication No. H02-110963
25 Summary of Invention
Technical Problem
[0004] In the electric motor disclosed in Patent Literature 1, as illustrated in FIG. 3,
3
the air having flowed from the intake hole into the inside of the electric motor, passed
through the ventilation hole formed in the stator core, and reached the casing, goes
toward a shaft, flows in a direction away from the shaft after reaching the vicinity of the
shaft, passes through the another ventilation hole formed in the stator core, and flows out
5 from the exhaust hole to the outside of the electric motor. According to this electric
motor, the flow of air having reached the casing, after going toward the shaft, bends back
in the direction away from the shaft, resulting in a high pressure drop in the flow path.
The high pressure drop leads to a small volume of air flowing into the electric motor,
resulting in a low cooling capacity of the electric motor.
10 [0005] The present disclosure is made in view of the aforementioned circumstances,
and an objective of the present disclosure is to provide an electric motor that has a high
cooling capacity.
Solution to Problem
[0006] To achieve the aforementioned objective, an electric motor according to the
15 present disclosure includes a shaft, a rotor, a stator, a first bracket, and a second bracket.
The shaft is rotatably supported for rotation around a rotation axis. The rotor is disposed
outwardly of the shaft in a radial direction and rotates integrally with the shaft. The
stator faces the rotor with a spacing therebetween in the radial direction. The first
bracket includes (i) an inflow path through which air of an outside flows into an inside
20 and (ii) an outflow path through which the air having flowed through the inflow path into
the inside flows out to the outside. The second bracket, with the first bracket,
sandwiches the rotor and the stator in a direction of the rotation axis. The stator includes
(i) a first ventilation path that penetrates the stator from an end to another end thereof in
the direction of the rotation axis and communicates with the inflow path and (ii) a second
25 ventilation path that penetrates the stator from the end to the another end thereof in the
direction of the rotation axis, communicates with the outflow path, and is positioned
spaced from the first ventilation path in a circumferential direction with respect to the
4
rotation axis. The second bracket includes a third ventilation path that forms a flow path
from the first ventilation path to the second ventilation path positioned opposite to the
first ventilation path with respect to a plane containing the rotation axis. The air having
flowed through the inflow path into the inside passes, in order, through the first
5 ventilation path, the third ventilation path, and the second ventilation path, and flows out
to the outside through the outflow path.
Advantageous Effects of Invention
[0007] According to the present disclosure, the air having flowed through the
inflow path into the inside passes, in order, through the first ventilation path, the third
10 ventilation path, and the second ventilation path, and flows out to the outside through the
outflow path. Since the air flows through the first ventilation path, the third ventilation
path, and the second ventilation path, in order, a cross-section of a flow path is smaller
than, while a surface area of the flow path being the same as, in a case in which a flow
path is formed unidirectionally, resulting in a high flowing speed of air and a high cooling
15 capacity of the electric motor. Further, a pressure drop is smaller than in a case in which
flow of air in a bracket goes toward a shaft, and bends back in a direction away from the
shaft. The cooling capacity of the electric motor increases due to an increase in a
volume of air flowing into the electric motor relative to a conventional electric motor.
Brief Description of Drawings
20 [0008] FIG. 1 is a perspective view of an electric motor according to Embodiment 1
of the present disclosure;
FIG. 2 is a cross-sectional view of the electric motor according to Embodiment 1;
FIG. 3 is a side view of the electric motor according to Embodiment 1;
FIG. 4 is a side view of a stator core according to Embodiment 1;
25 FIG. 5 is a cross-sectional view of a second bracket according to Embodiment 1;
FIG. 6 illustrates a flow of air in the electric motor according to Embodiment 1;
FIG. 7 illustrates a flow of air in the electric motor according to Embodiment 1;
5
FIG. 8 is a side view of an electric motor according to Embodiment 2;
FIG. 9 is a cross-sectional view of the electric motor according to Embodiment 2;
FIG. 10 is a side view of an electric motor according to Embodiment 3;
FIG. 11 is a side view of a stator core according to Embodiment 3;
5 FIG. 12 is a cross-sectional view of a second bracket according to Embodiment 3;
FIG. 13 is a side view of an electric motor according to Embodiment 4;
FIG. 14 is a side view of a stator core according to Embodiment 4;
FIG. 15 is a cross-sectional view of the electric motor according to Embodiment 4;
FIG. 16 is a cross-sectional view of the electric motor according to Embodiment 5;
10 and
FIG. 17 is a cross-sectional view of a frame according to Embodiment 5.
Description of Embodiments
[0009] Hereinafter, embodiments of an electric motor according to the present
disclosure are described in detail with reference to the drawings. In the drawings, the
15 same reference sign is assigned to the same or equivalent parts.
[0010] Embodiment 1
An electric motor according to Embodiment 1 is described using, as an example,
an electric motor used for driving a railroad vehicle. As illustrated in FIGS. 1 and 2, an
electric motor 1 according to Embodiment 1 includes a pair of frames 11, a shaft 15
20 positioned inwardly of the frames 11 in a radial direction, a rotor 16 that rotates integrally
with the shaft 15, and a stator 17 that is sandwiched and fixed by the pair of the frames 11.
In FIGS. 1 and 2, the Z-axis is a vertical direction, the Y-axis is parallel to a rotation axis
AX of the shaft 15, and the X-axis is orthogonal to the Y-axis and the Z-axis. In FIGS.
1 and 2, the dashed-dotted line indicates the rotation axis AX. Since the electric motor 1
25 is used as an electric motor for driving a railroad vehicle, the pair of the frames 11 is fixed
to a bogie of the railroad vehicle.
[0011] The rotor 16 is disposed outwardly of the shaft 15 in the radial direction.
6
The rotor 16 includes a rotor core 18 that is fitted to the shaft 15, and rotor conductors 19
that are received in grooves formed in an outer peripheral surface of the rotor core 18.
The stator 17 includes a stator core 20 that is sandwiched by the pair of the frames 11 in a
direction of the rotation axis AX, and stator conductors 21 that are received in grooves
5 formed in the stator core 20. The outer peripheral surface of the rotor core 18 and an
inner peripheral surface of the stator core 20 face each other with a spacing therebetween.
Further, the electric motor 1 includes a first bracket 13 and a second bracket 14 that
sandwich, in the direction of the rotation axis AX, the pair of the frames 11 that sandwich
and hold the stator core 20 in the direction of the rotation axis AX, and bearings 22 and
10 23 that rotatably support the shaft 15. The bearing 22 is held by the first bracket 13, and
the bearing 23 is held by the second bracket 14. The shaft 15 has one end that is close to
the second bracket 14 and is coupled to an axle of the railroad vehicle via non-illustrated
coupling and gear, and rotation of the shaft 15 generates motive power of the railroad
vehicle. The one end of the shaft 15 that is coupled to the axle is referred to as a driving
15 side, and the other end is referred to as a counter-driving side.
[0012] Cooling of the inside of the electric motor 1 is performed by causing air
blown by a non-illustrated blower disposed outside the electric motor 1 to flow through
the inside of the electric motor 1. A structure for cooling of the inside of the electric
motor 1 is described. The first bracket 13 includes an inflow path 24 through which air
20 flows into the inside of the electric motor 1, and an outflow path 25 through which the air
having flowed through the inflow path 24 into the inside of the electric motor 1 flows out.
Specifically, the inflow path 24 included in the first bracket 13 extends inwardly in the
radial direction from an upper end in the Z-axis direction. The inflow path 24 diverges
and extends in the direction of the rotation axis AX. Each of the frames 11 has a
25 through-hole 12 penetrating from one end to the other end thereof in the direction of the
rotation axis AX. For example, each of the frames 11 includes two tubes having
mutually different outer diameters and positioned with a spacing therebetween in the
7
radial direction, and a space between the two tubes forms the through-hole 12.
[0013] The stator core 20 includes a first ventilation path 26 penetrating from one
end to the other end thereof in the direction of the rotation axis AX and communicating
with the inflow path 24, and a second ventilation path 27 penetrating from one end to the
5 other end thereof in the direction of the rotation axis AX and communicating with the
outflow path 25. Specifically, the first ventilation path 26 is coupled with the inflow
path 24 via the through-hole 12, and the second ventilation path 27 is coupled with the
outflow path 25 via the through-hole 12. The second bracket 14 includes a third
ventilation path 28 that forms a flow path from the first ventilation path 26 to the second
10 ventilation path 27. The outflow path 25 included in the first bracket 13 at the lower
side thereof in the vertical direction is coupled with the second ventilation path 27 via the
through-hole 12 of the frame 11 and has, as illustrated in FIG. 3 that is a drawing of the
electric motor 1 as viewed in a positive Y-axis direction, a semicircular shape in a cross
section orthogonal to the rotation axis AX.
15 [0014] As illustrated in FIG. 4 that is a drawing of the stator core 20 as viewed in a
negative Y-axis direction, the stator core 20 includes the first ventilation path 26 and the
second ventilation path 27 positioned opposite to the first ventilation path 26 with respect
to an XY plane containing the rotation axis AX. Specifically, the stator core 20 includes
the first ventilation path 26 and the second ventilation path 27 positioned symmetrically
20 to the first ventilation path 26 with respect to the XY plane containing the rotation axis
AX. More specifically, multiple first ventilation paths 26 are positioned in the
vertical-direction upper half of the stator core 20, with spacings in a circumferential
direction. Multiple second ventilation paths 27 are positioned in the vertical-direction
lower half of the stator core 20, with spacings in the circumferential direction. In other
25 words, the second ventilation paths 27 are positioned symmetrically to the first
ventilation paths 26 with respect to the XY plane containing the rotation axis AX.
[0015] As illustrated in FIG. 5 that is a cross-sectional view taken along the A-A
8
line in FIG. 2, the second bracket 14 includes the third ventilation path 28 that forms the
flow path from the first ventilation path 26 to the second ventilation path 27 positioned
symmetrically to the first ventilation paths 26 with respect to the XY plane containing the
rotation axis AX. For smooth flow of air from the first ventilation path 26 to the second
5 ventilation path 27, the second bracket 14 includes, in the third ventilation path 28, air
flow baffle plates 29 extending in the Z-axis direction.
[0016] Flows of air in the electric motor 1 having the aforementioned configuration
are explained using FIGS. 6 and 7. In FIGS. 6 and 7, the flows of air are illustrated
using solid arrows. The air blown by the blower disposed outside the electric motor 1
10 flows into the inside of the electric motor 1 through the inflow path 24, as illustrated in
FIG. 6. That is to say, the air blown by the blower passes through the inflow path 24
and reaches the through-hole 12. The air having flowed into the first ventilation path 26
through the through-hole 12 flows through the first ventilation path 26 from the
counter-driving side to the driving side. The air having reached the third ventilation
15 path 28 through the first ventilation path 26 flows through the third ventilation path 28 in
a negative Z-axis direction along the air flow baffle plates 29 extending parallel to the
Z-axis direction as illustrated in FIG. 7. The air having reached the second ventilation
path 27 through the third ventilation path 28 flows through the second ventilation path 27
from the driving side to the counter-driving side, as illustrated in FIG. 6. The air having
20 passed through the second ventilation path 27 flows out to the outside of the electric
motor 1 through the outflow path 25. At the inflow path 24, a part of the air flows in the
negative Z-axis direction and reaches the vicinity of the bearing 22. Flowing of the air
through the inside of the electric motor 1 as described above cools the rotor 16, the stator
17, the bearings 22 and 23, and the like.
25 [0017] In the third ventilation path 28, the air flows unidirectionally, that is, in the
negative Z-axis direction. Thus, the electric motor 1 has a smaller pressure drop in a
flow path than a conventional electric motor in which flow of air in a bracket at a driving
9
side goes toward a shaft, and bends back in a direction away from the shaft, if conditions
other than specified above are the same. Additionally, in comparison to a conventional
electric motor in which air flows unidirectionally through a ventilation path of a stator
core, the electric motor 1 has the same heat radiation area while being smaller in a
5 cross-section of a flow path than the conventional electric motor, and the electric motor 1
is higher in speed of air flowing in the flow path and higher in cooling capacity than the
conventional electric motor, if conditions other than specified above are the same.
[0018] As described above, the electric motor 1 according to Embodiment 1
includes a flow path that passes through the first ventilation path 26, the third ventilation
10 path 28, and the second ventilation path 27, in order, and in which no bending back
occurs in the third ventilation path 28. This enables a pressure drop in the electric motor
1 that is smaller than that in the conventional electric motor, leading to an improvement
in cooling capacity of the electric motor 1.
[0019] Embodiment 2
15 The first bracket 13 may have any shape through which the air flows into the
inside of an electric motor, through which the air having flowed in flows out, and that
leads to a pressure drop that is smaller than that in a conventional electric motor. In
Embodiment 2, an example electric motor is described that has a configuration in which
the inflow path 24 extends inwardly in the radial direction from the Z-axis upper end of
20 the first bracket 13 and further extends beyond the rotation axis AX. An electric motor
2 according to Embodiment 2 that is illustrated in FIGS. 8 and 9 includes, instead of the
first bracket 13 included in the electric motor 1 according to Embodiment 1, a first
bracket 30. The first bracket 30 includes an inflow path 24 that extends inwardly in the
radial direction from the Z-axis direction upper end and further extends beyond the
25 rotation axis AX. The inflow path 24 extends in the direction of the rotation axis AX
and is coupled with the first ventilation path 26. Further, the first bracket 30 includes, at
the lower side thereof in the vertical direction, an outflow path 25 that communicates
10
with the second ventilation path 27.
[0020] Since the inflow path 24 extends inwardly in the radial direction from the
upper end of the first bracket 30 in the vertical direction and further extends beyond the
rotation axis AX, a part of air in the inflow path 24 reaches a lower end of the bearing 22
5 in the vertical direction and cools the lower end of the bearing 22.
[0021] As described above, due to the inclusion of the first bracket 30, the electric
motor 2 according to Embodiment 2 cools the bearing 22 more in the electric motor 1.
This enables an improvement in efficiency of cooling by the electric motor 2.
[0022] Embodiment 3
10 According to Embodiments 1 and 2, multiple first ventilation paths 26 are
positioned in the upper side of the stator core 20 in the vertical direction, with spacings in
the circumferential direction, and multiple second ventilation paths 27 are positioned in
the lower side of the stator core 20 in the vertical direction, with spacings in the
circumferential direction. With regard to an arrangement of the first ventilation path and
15 the second ventilation path, any arrangement may be employed that enables a pressure
drop in a flow path that is smaller than in the case of using a conventional electric motor.
In Embodiment 3, an example electric motor is described that includes multiple first
ventilation path groups that each include multiple first ventilation paths, and multiple
second ventilation path groups that each include multiple second ventilation paths. An
20 electric motor 3 according to Embodiment 3 that is illustrated in FIG. 10 includes, instead
of the first bracket 13 included in the electric motor 1 according to Embodiment 1, a first
bracket 31. The first bracket 31 includes two outflow paths 25a and 25b positioned
symmetrically with respect to the rotation axis AX. The outflow path 25a is coupled
with, via the through-hole 12 of the frame 11, second ventilation paths 27 included in a
25 second ventilation path group 27a described below, and the outflow path 25b is coupled
with, via the through-hole 12 of the frame 11, second ventilation paths 27 included in a
second ventilation path group 27b described below.
11
[0023] As illustrated in FIG. 11 that is a drawing of the stator core 20 as viewed in
the negative Y-axis direction, the stator core 20 includes multiple first ventilation path
groups 26a and 26b that each include multiple first ventilation paths 26, and multiple
second ventilation path groups 27a and 27b that each include multiple second ventilation
5 paths 27. The first ventilation path groups 26a and 26b and the second ventilation path
groups 27a and 27b are equal in number, and the first ventilation path groups 26a and 26b
and the second ventilation path groups 27a and 27b are positioned alternately in the
circumferential direction. Specifically, as illustrated in FIG. 11, the first ventilation path
group 26a, the second ventilation path group 27a, the first ventilation path group 26b, and
10 the second ventilation path group 27b, are disposed, in order, clockwise in the
circumferential direction. Further, the first ventilation path groups 26a and 26b are
positioned symmetrically with respect to the rotation axis AX, and the second ventilation
path groups 27a and 27b are positioned symmetrically with respect to the rotation axis
AX. More specifically, the first ventilation path group 26a is formed in the stator core
15 20 at a part on a positive Z-axis direction side with respect to the rotation axis AX and on
a negative X-axis direction side with respect to the rotation axis AX, whereas the first
ventilation path group 26b is formed in the stator core 20 at a part on a negative Z-axis
direction side with respect to the rotation axis AX and on a positive X-axis direction side
with respect to the rotation axis AX. Both of the first ventilation paths 26 included in
20 the first ventilation path group 26a and the first ventilation paths 26 included in the first
ventilation path group 26b are coupled with the inflow path 24 via the through-hole 12.
The second ventilation paths 27 included in the second ventilation path group 27a are
coupled with the outflow path 25a via the through-hole 12, and the second ventilation
paths 27 included in the second ventilation path group 27b are coupled with the outflow
25 path 25b via the through-hole 12.
[0024] In FIG. 12 that is a cross-sectional view of the second bracket 14 as viewed
in the negative Y-axis direction, flows of air are illustrated using solid arrows. The
12
second bracket 14 includes (i) a third ventilation path 28a that forms a flow path from the
first ventilation paths 26 included in the first ventilation path group 26a to the second
ventilation paths 27 included in the second ventilation path group 27a, and (ii) a third
ventilation path 28b that forms a flow path from the first ventilation paths 26 included in
5 the first ventilation path group 26b to the second ventilation paths 27 included in the
second ventilation path group 27b. A partition wall 32 separates the third ventilation
path 28a from the third ventilation path 28b, and thus no flow of air occurs between the
third ventilation paths 28a and 28b. As illustrated in FIG. 12, the first ventilation paths
26 included in the first ventilation path group 26a and the second ventilation paths 27
10 included in the second ventilation path group 27a are positioned symmetrically with
respect to the XY plane containing the rotation axis AX, and the first ventilation paths 26
included in the first ventilation path group 26b and the second ventilation paths 27
included in the second ventilation path group 27b are positioned symmetrically with
respect to the XY plane containing the rotation axis AX.
15 [0025] In the third ventilation path 28a, the air flows unidirectionally, that is, in the
negative Z-axis direction, and in the third ventilation path 28b, the air flows
unidirectionally, that is, in the positive Z-axis direction. Thus, the electric motor 3 has a
smaller pressure drop in a flow path than a conventional electric motor in which flow of
air in a bracket at a driving side goes toward a shaft, and bends back in a direction away
20 from the shaft, if conditions other than specified above are the same. Additionally, in
comparison to a conventional electric motor in which air flows unidirectionally through a
ventilation path of a stator core, the electric motor 3 has the same heat radiation area
while being smaller in a cross-section of a flow path than the conventional electric motor,
and the electric motor 3 is higher in speed of air flowing in the flow path and higher in
25 cooling capacity than the conventional electric motor, if conditions other than specified
above are the same.
[0026] The air blown by the blower and having flowed through the inflow path 24
13
into the inside of the electric motor 3 passes, in order, through the first ventilation paths
26 included in the first ventilation path group 26a, the third ventilation path 28a, and the
second ventilation paths 27 included in the second ventilation path group 27a, and flows
out to the outside of the electric motor 3 through the outflow path 25a. Alternatively,
5 the air blown by the blower and having flowed through the inflow path 24 into the inside
of the electric motor 3 passes, in order, through the first ventilation paths 26 included in
the first ventilation path group 26b, the third ventilation path 28b, and the second
ventilation paths 27 included in the second ventilation path group 27b, and flows out to
the outside of the electric motor 3 through the outflow path 25b. Since the air having
10 flowed into the inside of the electric motor 3 flows while undergoing heat exchange,
temperature of the air increases while the air flows through the inside of the electric
motor 3. That is to say, temperatures of air located in the first ventilation paths 26
included in the first ventilation path group 26a and in the first ventilation paths 26
included in the first ventilation path group 26b are lower than temperatures of air located
15 in the second ventilation paths 27 included in the second ventilation path group 27a and
in the second ventilation paths 27 included in the second ventilation path group 27b.
Since the first ventilation path groups 26a and 26b are positioned symmetrically with
respect to the plane containing the rotation axis AX, variance in temperatures in the stator
core 20 in the circumferential direction is reduced.
20 [0027] As described above, according to the electric motor 3 according to
Embodiment 3 of the present disclosure, the first ventilation path groups 26a and 26b of
the stator core 20 are positioned symmetrically with respect to the plane containing the
rotation axis AX. This enables reduction of variance in temperatures in the stator core
20 in the circumferential direction, and thus, enables reduction of occurrence of a
25 malfunction of the electric motor 3 that is caused by the occurrence of extremely high
temperature at a part of the stator core 20.
[0028] Embodiment 4
14
The numbers of the first ventilation path groups and the second ventilation path
groups may be freely selected. In Embodiment 4, an example electric motor is
described that includes three first ventilation path groups and three second ventilation
path groups. An electric motor 4 according to Embodiment 4 that is illustrated in FIG.
5 13 includes, instead of the first bracket 13 included in the electric motor 1 according to
Embodiment 1, a first bracket 33. The first bracket 33 includes three outflow paths 25a,
25b, and 25c positioned with spacings in the circumferential direction. The outflow
path 25a is coupled with, via the through-hole 12 of the frame 11, second ventilation
paths 27 included in a second ventilation path group 27a described below. The outflow
10 path 25b is coupled with, via the through-hole 12 of the frame 11, second ventilation
paths 27 included in a second ventilation path group 27b described below. The outflow
path 25c is coupled with, via the through-hole 12 of the frame 11, second ventilation
paths 27 included in a second ventilation path group 27c described below.
[0029] As illustrated in FIG. 14 that is a drawing of the stator core 20 as viewed in
15 the negative Y-axis direction, the stator core 20 includes multiple first ventilation path
groups 26a, 26b, and 26c that each include multiple first ventilation paths 26, and
multiple second ventilation path groups 27a, 27b, and 27c that each include multiple
second ventilation paths 27. The first ventilation path groups 26a, 26b, and 26c, and the
second ventilation path groups 27a, 27b, and 27c, are positioned alternately in the
20 circumferential direction. Specifically, as illustrated in FIG. 14, the first ventilation path
group 26a, the second ventilation path group 27a, the first ventilation path group 26b, the
second ventilation path group 27c, the first ventilation path group 26c, the second
ventilation path group 27b, are disposed, in order, counterclockwise in the circumferential
direction. Further, each of the second ventilation path groups 27a, 27b, and 27c is
25 positioned symmetrically, with respect to the XY plane containing the rotation axis AX,
to a corresponding one of the first ventilation path groups 26a, 26b, and 26c. The first
ventilation paths 26 included in the first ventilation path group 26a, the first ventilation
15
paths 26 included in the first ventilation path group 26b, and the first ventilation paths 26
included in the first ventilation path group 26c are each coupled with the inflow path 24
via the through-hole 12. The second ventilation paths 27 included in the second
ventilation path group 27a are coupled with the outflow path 25a via the through-hole 12,
5 the second ventilation paths included in the second ventilation path group 27b are
coupled with the outflow path 25b via the through-hole 12, and the second ventilation
paths 27 included in the second ventilation path group 27c are coupled with the outflow
path 25c via the through-hole 12.
[0030] In FIG. 15 that is a cross-sectional view of the second bracket 14 as viewed
10 in the negative Y-axis direction, flows of air are illustrated using solid arrows. The
second bracket 14 includes a third ventilation path 28a that forms a flow path from the
first ventilation paths 26 included in the first ventilation path group 26a to the second
ventilation paths 27 included in the second ventilation path group 27a, a third ventilation
path 28b that forms a flow path from the first ventilation paths 26 included in the first
15 ventilation path group 26b to the second ventilation paths 27 included in the second
ventilation path group 27b, and a third ventilation path 28c that forms a flow path from
the first ventilation paths 26 included in the first ventilation path group 26c to the second
ventilation paths 27 included in the second ventilation path group 27c. The partition
wall 32 separates the third ventilation paths 28a, 28b, and 28c from each other, and thus
20 no flow of air occurs among the third ventilation paths 28a, 28b, and 28c. As illustrated
in FIG. 15, the first ventilation paths 26 included in the first ventilation path group 26a
and the second ventilation paths 27 included in the second ventilation path group 27a are
positioned symmetrically with respect to the XY plane containing the rotation axis AX,
the first ventilation paths 26 included in the first ventilation path group 26b and the
25 second ventilation paths 27 included in the second ventilation path group 27b are
positioned symmetrically with respect to the XY plane containing the rotation axis AX,
and the first ventilation paths 26 included in the first ventilation path group 26c and the
16
second ventilation paths 27 included in the second ventilation path group 27c are
positioned symmetrically with respect to the XY plane containing the rotation axis AX.
[0031] Air flow is unidirectional in the positive Z-axis direction in the third
ventilation path 28a, air flow is unidirectional in the negative-Z-axis direction in the third
5 ventilation path 28b, and air flow is unidirectional in the positive Z-axis direction in the
third ventilation path 28c. Thus, the electric motor 4 has a smaller pressure drop in the
flow path than the conventional electric motor in which flow of air in a bracket at a
driving side goes toward the shaft, and bends back in a direction away from the shaft, if
conditions other than specified above are the same,. Additionally, in comparison to a
10 conventional electric motor in which air flows unidirectionally through a ventilation path
of a stator core, the electric motor 4 has the same heat radiation area while being smaller
in a cross-section of a flow path than the conventional electric motor, and the electric
motor 4 is higher in speed of air flowing in a flow path and higher in cooling capacity
than the conventional electric motor, if conditions other than specified above are the
15 same.
[0032] The air blown by the blower and having flowed through the inflow path 24
into the inside of the electric motor 4 passes, in order, through the first ventilation paths
26 included in the first ventilation path group 26a, the third ventilation path 28a, and the
second ventilation paths 27 included in the second ventilation path group 27a, and flows
20 out to the outside of the electric motor 4 through the outflow path 25a. Alternatively,
the air blown by the blower and having flowed through the inflow path 24 into the inside
of the electric motor 4 passes, in order, through the first ventilation paths 26 included in
the first ventilation path group 26b, the third ventilation path 28b, and the second
ventilation paths 27 included in the second ventilation path group 27b, and flows out to
25 the outside of the electric motor 4 through the outflow path 25b. Alternatively, the air
blown by the blower having flowed through the inflow path 24 into the inside of the
electric motor 4 passes, in order, through the first ventilation paths 26 included in the first
17
ventilation path group 26c, the third ventilation path 28c, and the second ventilation paths
27 included in the second ventilation path group 27c, and flows out to the outside of the
electric motor 4 through the outflow path 25c. Since the air having flowed into the
inside of the electric motor 4 flows while undergoing heat exchange, temperature of the
5 air increases while the air flows through the inside of the electric motor 4. That is to say,
temperatures of air located in the first ventilation paths 26 included in the first ventilation
path group 26a, in the first ventilation paths 26 included in the first ventilation path group
26b, and in the first ventilation paths 26 included in the first ventilation path group 26c,
are lower than temperatures of air located in the second ventilation paths 27 included in
10 the second ventilation path group 27a, in the second ventilation paths 27 included in the
second ventilation path group 27b, and in the second ventilation paths 27 included in the
second ventilation path group 27c. Since the first ventilation path groups 26a, 26b, and
26c are positioned with spacings in the circumferential direction, variance in temperatures
in the stator core 20 in the circumferential direction is reduced.
15 [0033] As described above, according to the electric motor 4 according to
Embodiment 4 of the present disclosure, the first ventilation path groups 26a, 26b, and
26c of the stator core 20 are positioned with spacings in the circumferential direction.
This enables more reduction, than the electric motor 4, of variance in temperatures in the
stator core 20 in the circumferential direction, and thus, enables reduction of occurrence
20 of a malfunction of the electric motor 4 that is caused by the occurrence of extremely
high temperature at a part of the stator core 20.
[0034] Embodiment 5
The flow path for air in the electric motor may have any shape that leads to cooling
of the inside of the electric motor by the air flowing in the motor and that leads to a
25 pressure drop that is smaller than that in a conventional electric motor. In Embodiment
5, an example electric motor is described in which a frame includes a first ventilation path
and a second ventilation path. The electric motor 5 illustrated in FIG. 16 incudes,
18
instead of the pair of the frames 11 included in the electric motor 1 according to
Embodiment 1, a tubular frame 34. The frame 34 includes a first ventilation path 35
communicating with the inflow path 24, and a second ventilation path 36 communicating
with the outflow path 25. In the electric motor 5, the stator core 20 does not include a
5 ventilation path. Heat generated in the stator core 20 is transferred via the frame 34 to
air flowing through the first ventilation path 35 and the second ventilation path 36. The
first bracket 13 and the second bracket 14 are fixed on end surfaces of the frame 11 in the
direction of the rotation axis AX.
[0035] As illustrated in FIG. 17 that is a cross-sectional view of the frame 34 taken
10 along the B-B line in FIG. 16, multiple first ventilation paths 35 are positioned in the
vertical-direction upper half of the frame 34, with spacings in the circumferential
direction. Multiple second ventilation paths 36 are positioned in the vertical-direction
lower half on the frame 34, with spacings in the circumferential direction. As illustrated
in FIG. 16, the second bracket 14 includes the third ventilation path 28 that forms a flow
15 path from the first ventilation paths 35 to the second ventilation paths 36. The second
bracket 14 is similar in shape to that of Embodiment 1.
[0036] The air blown by the blower having flowed through the inflow path 24 into
the inside of the electric motor 5 passes, in order, through the first ventilation paths 35,
the third ventilation path 28, and the second ventilation paths 36, and flows out to the
20 outside of the electric motor 5 through the outflow path 25.
[0037] As described above, in the electric motor 5 according to the present
embodiment, the frame 34 includes the first ventilation paths 35 and the second
ventilation paths 36. This eliminates the need for processing for forming a through-hole
in the stator core 20, and thus enables simplification of the manufacturing process.
25 [0038] The present disclosure is not limited by the aforementioned embodiments.
Any of the aforementioned embodiments may be freely combined. For example, the
electric motor 5 may include the first bracket 30, and the frame 34 may include, similarly
19
to Embodiment 3, multiple first ventilation paths 35 that are positioned symmetrically
with respect to the XY plane containing the rotation axis AX and multiple second
ventilation paths 36 that are positioned symmetrically with respect to the XY plane
containing the rotation axis AX.
5 [0039] Any arrangement that enables formation of a flow path in which flow of air
does not bend back in the third ventilation path 28 may be employed for the first
ventilation path 26 and the second ventilation path 27. For example, the first ventilation
path 26 and the second ventilation path 27 may be positioned symmetrically with respect
to a YZ plane containing the rotation axis AX, or may be positioned symmetrically with
10 respect to a plane that contains the rotation axis AX and forms a predetermined angle
with the XY plane containing the rotation axis AX. The first ventilation path 26 and the
second ventilation path 27 need not be positioned symmetrically with respect to the YZ
plane containing the rotation axis AX, and may be positioned asymmetrically with
respect to the YZ plane containing the rotation axis AX.
15 Further, the first ventilation path groups 26a and 26b and the second ventilation
path groups 27a and 27b need not be equal in number, and the number of the first
ventilation path groups 26a and 26b and the number of the second ventilation path groups
27a and 27b may be different.
[0040] The direction of the inflow path 24 opening is not limited to the vertical
20 direction, and any direction that allows air from the blower disposed outside to flow into
the inside of the electric motors 1–5 can be employed. For example, the direction of the
inflow path 24 opening may be the direction of the rotation axis AX. The blower
disposed outside the electric motors 1–5 may be a fan that rotates in conjunction with the
rotation of the shaft 15. Further, in the electric motor 5, the first bracket 13 and the
25 second bracket 14 may be fixed, via fixing members, on end surfaces of the frames 11 in
the direction of the rotation axis AX.
[0041] The frames 11 may be omitted from the electric motors 1–4. In this case,
20
each of the first brackets 13, 30, 31, 33, and the second bracket 14 are positioned to
sandwich the stator core 20.
[0042] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
5 persons skilled in the art will recognize that changes may be made in form and detail
without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
10 equivalents to which such claims are entitled.
Reference Signs List
[0043] 1, 2, 3, 4, 5 Electric motor
11, 34 Frame
12 Through-hole
15 13, 30, 31, 33 First bracket
14 Second bracket
15 Shaft
16 Rotor
17 Stator
20 18 Rotor core
19 Rotor conductor
20 Stator core
21 Stator conductor
22, 23 Bearing
25 24 Inflow path
25, 25a, 25b, 25c Outflow path
26, 25, 35 First ventilation path
21
26a, 26b, 26c First ventilation path group
27, 36 Second ventilation path
27a, 27b, 27c Second ventilation path group
28, 28a, 28b, 28c Third ventilation path
5 29 Air flow baffle plate
32 Partition wall
AX Rotation axis
22
We Claim :
1. An electric motor comprising:
a shaft that is rotatably supported for rotation around a rotation axis;
a rotor that is disposed outwardly of the shaft in a radial direction and rotates
5 integrally with the shaft;
a stator that faces the rotor with a spacing therebetween in the radial direction;
a first bracket that includes (i) an inflow path through which air of an outside flows
into an inside and (ii) an outflow path through which the air having flowed through the
inflow path into the inside flows out to the outside; and
10 a second bracket that, with the first bracket, sandwiches the rotor and the stator in a
direction of the rotation axis, wherein
the stator includes (i) a first ventilation path that penetrates the stator from an end
to another end thereof in the direction of the rotation axis and communicates with the
inflow path and (ii) a second ventilation path that penetrates the stator from the end to the
15 another end thereof in the direction of the rotation axis, communicates with the outflow
path, and is positioned spaced from the first ventilation path in a circumferential direction
with respect to the rotation axis,
the second bracket includes a third ventilation path that forms a flow path from the
first ventilation path to the second ventilation path positioned opposite to the first
20 ventilation path with respect to a plane containing the rotation axis, and
the air having flowed through the inflow path into the inside passes, in order,
through the first ventilation path, the third ventilation path, and the second ventilation
path, and flows out to the outside through the outflow path.
25 2. The electric motor according to claim 1, wherein
the stator includes
first ventilation path groups that each include a plurality of the first
23
ventilation paths positioned adjacent to each other in the circumferential direction, and
second ventilation path groups that each include a plurality of the second
ventilation paths positioned adjacent to each other in the circumferential direction and are
equal in number to the first ventilation path groups, and
5 the first ventilation path groups and the second ventilation path groups are
positioned alternately in the circumferential direction.
3. An electric motor comprising:
a shaft that is rotatably supported for rotation around a rotation axis;
10 a rotor that is disposed outwardly of the shaft in a radial direction and rotates
integrally with the shaft;
a stator that faces the rotor with a spacing therebetween in the radial direction;
a tubular frame that encompasses the rotor and the stator;
a first bracket that includes (i) an inflow path through which air of an outside flows
15 into an inside and (ii) an outflow path through which the air having flowed through the
inflow path into the inside flows out to the outside; and
a second bracket that, with the first bracket, sandwiches the rotor and the stator in a
direction of the rotation axis, wherein
the first bracket and the second bracket are fixed to the frame at positions
20 sandwiching the frame in the direction of the rotation axis,
the frame includes (i) a first ventilation path that communicates with the inflow
path and (ii) a second ventilation path that communicates with the outflow path and is
positioned spaced from the first ventilation path in a circumferential direction with
respect to the rotation axis,
25 the second bracket includes a third ventilation path that forms a flow path from the
first ventilation path to the second ventilation path positioned opposite to the first
ventilation path with respect to a plane containing the rotation axis, and
24
the air having flowed through the inflow path into the inside passes, in order,
through the first ventilation path, the third ventilation path, and the second ventilation
path, and flows out to the outside through the outflow path.
5 4. The electric motor according to claim 3, wherein
the frame includes
first ventilation path groups that each include a plurality of the first
ventilation paths positioned adjacent to each other in the circumferential direction, and
second ventilation path groups that each include a plurality of the second
10 ventilation paths positioned adjacent to each other in the circumferential direction and are
equal in number to the first ventilation path groups, and
the first ventilation path groups and the second ventilation path groups are
positioned alternately in the circumferential direction.
15 5. The electric motor according to any one of claims 1 to 4, wherein the inflow
path included in the first bracket extends inwardly in the radial direction, from an outer
peripheral surface of the first bracket to the rotation axis.
6. The electric motor according to any one of claims 1 to 5, wherein the second
20 bracket includes, in the third ventilation path, air flow baffle plates extending in a
direction orthogonal to the plane containing the rotation axis.