1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ROTATING ELECTRIC MACHINE
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
Technical Field
[0001] The present invention relates to a 5 rotating electric
machine in which a stator is provided on an outer side with respect
to a rotor in a radial direction.
Background Art
10 [0002] There has hitherto been known a rotating electric machine
including: a rotor; a stator provided on an outer side with respect
to the rotor in a radial direction of the rotor; and a motor frame,
which includes a tubular portion provided on an outer side with
respect to the stator in the radial direction of the rotor, and
15 has the stator fixed thereto. This rotating electric machine further
includes an intermediate member, which is provided on an outer
peripheral surface of the stator, and is press-fitted to an inner
peripheral surface of the tubular portion of the motor frame. With
the intermediate member being press-fitted to the inner peripheral
20 surface of the tubular portion of the motor frame, a tightening
force exerted on a stator core in the radial direction is improved.
With this, vibrations generated in the rotating electric machine
at the time of driving of the rotating electric machine can be
suppressed (for example, see Patent Literature 1).
25
3
Citation List
Patent Literature
[0003] [PTL 1] JP 4602329 B2
Summary 5 of Invention
Technical Problem
[0004] However, there has been a problem in that, with the
intermediate member provided between the outer peripheral surface
of the stator and the inner peripheral surface of the tubular portion
10 of the motor frame, an electric power steering motor device is
increased in size.
[0005] The present invention has been made to solve the problem
described above, and has an object to provide a rotating electric
machine capable of suppressing vibrations generated at the time
15 of driving and achieving downsizing.
Solution to Problem
[0006] According to one embodiment of the present invention,
there is provided a rotating electric machine, including: a rotor;
20 a stator including a stator core provided on an outer side with
respect to the rotor in a radial direction of the rotor; a motor
frame, which includes a tubular portion provided on an outer side
with respect to the stator core in the radial direction, and has
the stator fixed thereto; and an intermediate member, which is
25 provided on an outer peripheral surface of the stator core in the
4
radial direction, and is held in a state of being press-fitted to
an inner peripheral surface of the tubular portion in the radial
direction, wherein a stiffness of the intermediate member per unit
length is higher than a stiffness of the tubular portion per unit
5 length.
Advantageous Effects of Invention
[0007] In the rotating electric machine according to the present
invention, the intermediate member is provided on the outer
10 peripheral surface of the stator in the radial direction under the
state in which the intermediate member is press-fitted to the inner
peripheral surface of the tubular portion. With such a configuration,
a tightening force exerted on the stator core in the radial direction
is improved. As a result, vibrations generated in the rotating
15 electric machine at the time of driving of the rotating electric
machine can be suppressed. Moreover, according to the rotating
electric machine, a stiffness of the intermediate member per unit
length is higher than a stiffness of the tubular portion per unit
length. With this, a plate thickness of the tubular portion of the
20 motor frame can be reduced. As a result, downsizing of the rotating
electric machine can be achieved.
Brief Description of Drawings
[0008] FIG. 1 is a vertical sectional view for illustrating
25 an electric power steering motor device according to a first
5
embodiment of the present invention.
FIG. 2 is a sectional view for illustrating an electric power
steering motor device according to a second embodiment of the present
invention.
FIG. 3 is a side view for illustrating 5 a stator core, an
intermediate member, and a motor frame of an electric power steering
motor device according to a third embodiment of the present invention.
FIG. 4 is a sectional view for illustrating an electric power
steering motor device according to a fourth embodiment of the present
10 invention.
FIG. 5 is a perspective view for illustrating an intermediate
member of FIG. 4.
FIG. 6 is a sectional view for illustrating an electric power
steering motor device according to a fifth embodiment of the present
15 invention.
FIG. 7 is a perspective view for illustrating an intermediate
member of FIG. 6.
Description of Embodiments
20 [0009] First Embodiment
FIG. 1 is a vertical sectional view for illustrating an electric
power steering motor device according to a first embodiment of the
present invention. The electric power steering motor device is
described as an example of the rotating electric machine. The
25 electric power steering motor device mainly includes a motor portion
6
and an electronic control unit (not shown) configured to control
the motor portion. The motor portion is configured to assist a
steering effort of a steering portion of a vehicle. The electronic
control unit is hereinafter abbreviated as "ECU" (electronic control
unit). In FIG. 1, an illustration of the 5 ECU is omitted.
[0010] The motor portion includes a rotor 1 and a stator 2.
The stator 2 is provided on an outer side with respect to the rotor
1 in a radial direction of the rotor 1. Moreover, the motor portion
includes a motor frame 3 and an intermediate member 4. The motor
10 frame 3 is provided on an outer side with respect to the stator
2 in the radial direction of the rotor 1. The intermediate member
4 is provided between the stator 2 and the motor frame 3. In this
example, the radial direction corresponds to the radial direction
of the rotor 1.
15 [0011] The rotor 1 includes a shaft 11, a rotor core 12, and
a plurality of magnets 13. The shaft 11 serves as a center of rotation.
The rotor core 12 is fixed to an outer peripheral surface of the
shaft 11 in the radial direction. The plurality of magnets 13 are
joined to the rotor core 12.
20 [0012] The stator 2 includes a stator core 21, insulators 22,
and a plurality of coils 23. The insulators 22 are provided on the
stator core 21. The plurality of coils 23 are supported on the stator
core 21 through intermediation of the insulators 22. The stator
core 21 is provided on an outer side with respect to the rotor 1
25 in the radial direction. The stator core 21 is formed of a plurality
7
of electromagnetic steel sheets laminated on one another.
[0013] Moreover, the stator 2 includes terminals 24 and a holder
25. The terminals 24 receive currents fed from the ECU. The holder
25 is fixed to the motor frame 3, and has the terminals 24 fixed
thereto. The terminals 24 are electrically connected 5 to the coils
23, respectively.
[0014] The motor frame 3 is configured to protect the stator
2. The motor frame 3 includes a tubular portion 31 and a bottom
plate portion 32. The tubular portion 31 is provided on an outer
10 side with respect to the stator core 21 in the radial direction.
The bottom plate portion 32 is provided at one end portion of the
tubular portion 31 in an axial direction of the rotor 1. The tubular
portion 31 and the bottom plate portion 32 are formed integrally
with each other. The motor frame 3 is made of an aluminum-based
15 material. In this example, the axial direction corresponds to the
axial direction of the rotor 1.
[0015] The intermediate member 4 has an annular shape, and has
a cylindrical shape extending in the axial direction. The
intermediate member 4 is provided on an outer peripheral surface
20 of the stator core 21 in the radial direction. Moreover, the
intermediate member 4 is press-fitted to an inner peripheral surface
of the tubular portion 31 in the radial direction. That is, the
intermediate member 4 is provided on the outer peripheral surface
of the stator core 21 under a state in which the intermediate member
25 4 is press-fitted to the inner peripheral surface of the tubular
8
portion 31. The stator core 21 is press-fitted to an inner peripheral
surface of the intermediate member 4 in the radial direction.
[0016] A dimension of the intermediate member 4 in the axial
direction and a dimension of the stator core 21 in the axial direction
match each other. The intermediate member 4 is 5 provided so as to
cover an entire region in the axial direction with respect to the
outer peripheral surface of the stator core 21 in the radial direction.
[0017] Examples of a method of placing the intermediate member
4 between the stator core 21 and the tubular portion 31 include
10 a method of press-fitting the intermediate member 4 to the inner
peripheral surface of the tubular portion 31 in the radial direction
and thereafter press-fitting the stator core 21 to the inner
peripheral surface of the intermediate member 4 in the radial
direction. Moreover, examples of the method of placing the
15 intermediate member 4 between the stator core 21 and the tubular
portion 31 include a method of press-fitting the stator core 21
to the inner peripheral surface of the intermediate member 4 in
the radial direction and thereafter press-fitting the intermediate
member 4 to the inner peripheral surface of the tubular portion
20 31 in the radial direction.
[0018] Moreover, the motor portion further includes a bearing
5, a bearing holder 6, and a bearing 7. The bearing 5 is provided
at the bottom plate portion 32. The bearing holder 6 is provided
at the tubular portion 31. The bearing 7 is provided at the bearing
25 holder 6. The rotor core 12 and the stator core 21 are provided
9
between the bottom plate portion 32 and the bearing holder 6 in
the axial direction. The bearing 5 and the bearing 7 rotatably
support the shaft 11.
[0019] A rotation angle sensor (not shown) is provided to the
shaft 11. The rotation angle sensor is configured 5 to detect a
rotation angle of the shaft 11. Examples of the rotation angle sensor
include a resolver, a Hall integrated circuit (IC), and a
magnetoresistive (MR) sensor.
[0020] Moreover, the motor portion further includes a boss 8
10 provided at a distal end portion of the shaft 11. The boss 8 receives
a vehicle-side portion assembled thereto.
[0021] The stator core 21 typically has an annular shape.
Therefore, through feeding of currents through the coils 23, in
principle, an electromagnetic excitation force which deforms the
15 annular shape into an oval shape is generated in the stator core
21. Thus, with regard to the electric power steering motor device,
there is an issue of reducing vibrations generated in the stator
core 21 and noises generated by the vibrations. In the electric
power steering motor device according to the first embodiment, the
20 stator core 21 is press-fitted to the inner peripheral surface of
the intermediate member 4. With this, the stator core 21 is tightened
by the intermediate member 4 from the outer side toward the inner
side in the radial direction. Thus, the deformation of the stator
core 21 by the electromagnetic excitation force is suppressed. As
25 a result, the vibrations generated in the electric power steering
10
motor device and the noises generated by the vibrations are reduced.
[0022] A linear expansion coefficient of the intermediate
member 4 and a linear expansion coefficient of the stator core 21
are equal to each other. With this, in a case in which the electric
power steering motor device is driven, when a 5 temperature change
occurs in the electric power steering motor device, a change in
interference between the intermediate member 4 and the stator core
21 is suppressed. As a result, a tightening force exerted on the
stator core 21 by the intermediate member 4 is maintained. Thus,
10 the suppression of the deformation of the stator core 21 is maintained.
As a result, in the case in which the electric power steering motor
device is driven, when the temperature change occurs in the electric
power steering motor device, the reduction of the vibrations
generated in the electric power steering motor device and the noises
15 generated by the vibrations is maintained.
[0023] The intermediate member 4 is press-fitted to the inner
peripheral surface of the tubular portion 31 of the motor frame
3. With this, the tightening force exerted on the stator core 21
from the outer side toward the inner side in the radial direction
20 becomes stronger.
[0024] As a method of increasing the tightening force exerted
on the stator core 21 from the outer side toward the inner side
in the radial direction, it is conceivable to increase a plate
thickness of the tubular portion 31 of the motor frame 3. The increase
25 in plate thickness of the tubular portion 31 increases a stiffness
11
of the tubular portion 31. However, the increase in plate thickness
of the tubular portion 31 may cause a problem in that a dimension
of the electric power steering motor device in the radial direction
increases. The electric power steering motor device is onboard
equipment. Thus, there is limitation on the electric 5 power steering
motor device in terms of mountability. That is, importance is given
on downsizing of the electric power steering motor device. As a
result, the increase in dimension of the electric power steering
motor device in the radial direction may pose a significant demerit.
10 [0025] In consideration of a stiffness of a structure provided
on the outer side of the stator core 21 in the radial direction
in a simple manner, the stiffness of the structure is obtained by
the expression of E×I. In this expression, "E" represents a Young's
modulus, and "I" represents geometrical moment of inertia.
15 [0026] In the electric power steering motor device according
to the first embodiment, the intermediate member 4 and the tubular
portion 31 are provided on the outer side of the stator core 21
in the radial direction. A value of the stiffness of the structure
provided on the outer side of the stator core 21 in the radial direction
20 corresponds to a sum total value of the stiffness of the intermediate
member 4 and the stiffness of the tubular portion 31. When the Young's
modulus E of any one of the intermediate member 4 and the tubular
portion 31 is set higher, the geometrical moment of inertia of the
intermediate member 4 and the tubular portion 31 can be reduced
25 correspondingly.
12
[0027] In the electric power steering motor device according
to the first embodiment, the stiffness of the intermediate member
4 per unit length is higher than the stiffness of the tubular portion
31 per unit length. With this, the geometrical moment of inertia
of the tubular portion 31 can be reduced. As a 5 result, the plate
thickness of the tubular portion 31 can be reduced. Thus, downsizing
of the electric power steering motor device can be achieved. Examples
of a material having a higher stiffness per unit length include
an iron-based material and an SUS material.
10 [0028] When the stator core 21 is a segmented core divided into
a plurality of portions in a circumferential direction, the stiffness
of the stator core 21 is lower as compared to the case in which
the stator core 21 is an integrated core which is not divided into
a plurality of portions in the circumferential direction. However,
15 the intermediate member 4 tightens the stator core 21 from the outer
side toward the inner side in the radial direction. With this, the
stiffness of the stator 2 is set higher. As a result, the vibrations
generated in the electric power steering motor device and the noises
generated by the vibrations are reduced.
20 [0029] The stator core 21 is formed of a plurality of
electromagnetic steel sheets laminated on one another. Therefore,
in the case in which the stator core 21 is press-fitted to the inner
peripheral surface of the tubular portion 31 of the motor frame
3, when a step is formed on the outer peripheral surface of the
25 stator core 21, there is a risk in that damage such as shaving occurs
13
on the motor frame 3. In particular, when a hardness of the stator
core 21 is higher than a hardness of the motor frame 3, the risk
of causing damage on motor frame 3 is higher. Therefore, in the
related art, shrink fitting is adopted when the stator core 21 is
press-fitted to the inner peripheral surface of the 5 tubular portion
31 of the motor frame 3. However, the shrink fitting increases cost
for equipment. As a result, there is a problem in that the
manufacturing cost for the electric power steering motor device
increases.
10 [0030] In the electric power steering motor device according
to the first embodiment, the intermediate member 4 is provided between
the stator core 21 and the tubular portion 31 of the motor frame
3. With this, as a material of the motor frame 3, there is used
an aluminum-based material having a hardness lower than that of
15 the electromagnetic steel sheets used for the stator core 21. As
a result, reduction in overall weight of the electric power steering
motor device can be achieved.
[0031] As described above, according to the electric power
steering motor device of the first embodiment of the present invention,
20 the intermediate member 4 is provided on the outer peripheral surface
of the stator 2 in the radial direction under the state in which
the intermediate member 4 is press-fitted to the inner peripheral
surface of the tubular portion 31. With this, the tightening force
exerted on the stator core 21 in the radial direction is improved.
25 As a result, the vibrations generated in the electric power steering
14
motor device at the time of driving of the electric power steering
motor device and the noises generated by the vibrations can be
suppressed. Moreover, according to the electric power steering
motor device, the stiffness of the intermediate member 4 per unit
length is higher than the stiffness of the tubular 5 portion 31 per
unit length. With this, even when the plate thickness of the tubular
portion 31 of the motor frame 3 is reduced, an appropriate stiffness
can be obtained as a whole. As a result, downsizing of the electric
power steering motor device can be achieved.
10 [0032] Moreover, the linear expansion coefficient of the
intermediate member 4 is equal to the linear expansion coefficient
of the stator core 21. With this, even when the temperature change
occurs in the electric power steering motor device, suppression
of deformation of the stator core 21 can be maintained.
15 [0033] Moreover, the motor frame 3 is made of an aluminum-based
material. With this, reduction in overall weight of the electric
power steering motor device can be achieved.
[0034] Second Embodiment
FIG. 2 is a sectional view for illustrating an electric power
20 steering motor device according to a second embodiment of the present
invention. The stator core 21 includes twelve teeth 211. The twelve
teeth 211 are arranged at equal intervals in the circumferential
direction. The rotor 1 includes ten magnets 13. The ten magnets
13 are magnetized so that N poles and S poles are alternately arranged
25 in the circumferential direction. In this electric power steering
15
motor device, the number of poles is ten, and the number of slots
is twelve. The coils 23 are provided to the twelve teeth 211,
respectively. The twelve coils 23 are arranged so that each pair
of coils 23 located at positions apart from each other by a mechanical
angle of 180 degrees have the same phase. In other 5 words, the twelve
coils 23 are arranged so that each of the pairs of coils 23 located
at opposed positions have the same phase. In this example, the number
of slots is twelve. Thus, each of the pairs of coils 23 apart from
each other by six slots in the circumferential direction have the
10 same phase.
[0035] In the electric power steering motor device according
to the second embodiment, the number of poles is ten, and the number
of slots is twelve. With this, a winding factor with respect to
a fundamental wave is large, and a winding factor with respect to
15 a higher harmonic wave is small. Thus, occurrence of torque ripple
can be reduced while generating a large torque with a smaller amount
of magnets. As a result, an electric power steering motor device
exhibiting a high performance can be supplied with less cost. However,
in the electric power steering motor device having the combination
20 of ten poles and twelve slots and the above-mentioned arrangement
of the coils 23, in principle, an electromagnetic force which causes
deformation of the shape of the stator core 21 from the annular
shape to the oval shape is generated. Thus, the stator core 21 is
liable to be deformed into the oval shape, and the amount of
25 deformation of the stator core 21 is liable to be large.
16
[0036] In the electric power steering motor device according
to the second embodiment, a sum total value of a stiffness value
of the tubular portion 31 of the motor frame 3 and a stiffness value
of the intermediate member 4 corresponds to a stiffness value of
the member which tightens the stator core 21 from 5 the outer side
toward the inner side in the radial direction. With this, as compared
to the case in which only the motor frame 3 tightens the stator
core 21 from the outer side toward the inner side in the radial
direction, the stiffness of the stator core 21 becomes higher. As
10 a result, the deformation of the stator core 21 into the oval shape
is suppressed. Thus, the vibrations of the electric power steering
motor device being a demerit can be suppressed while utilizing the
merit of the electric power steering motor device with ten poles
and twelve slots. Other configurations are the same as those of
15 the first embodiment.
[0037] As described above, according to the electric power
steering motor device of the second embodiment of the present
invention, the number of slots of the stator 2 is twelve, and the
number of poles of the rotor 1 is ten. With this, the electric power
20 steering motor device exhibiting a high performance can be supplied
with less cost, and the vibrations of the electric power steering
motor device can be suppressed.
[0038] Third Embodiment
FIG. 3 is a side view for illustrating a stator core, an
25 intermediate member, and a motor frame of an electric power steering
17
motor device according to a third embodiment of the present invention.
In FIG. 3, the motor frame 3 is illustrated in sectional view. When
a length of the stator core 21 in the axial direction is represented
by L1, and a length of the intermediate member 4 in the axial direction
is represented by L2, a relationship between L1 5 and L2 satisfies
L1/2