Motor rotor and permanent magnet motor

Abstract

A motor rotor according to the present invention comprises a rotary shaft, a wire-shaped magnet, a holding ring, and a first soft material. The wire-shaped magnet is provided on the outer surface of the rotary shaft along the axial direction and extends at least partially along the circumferential direction of the rotary shaft. The holding ring holds the wire-shaped magnet on the rotary shaft from the outside in the radial direction. The first soft material is provided in a radial-direction gap between the rotary shaft and the wire-shaped magnet or between the wire-shaped magnet and the holding ring.

Description

Motor rotor and permanent magnet motor

[0001] This application claims priority to Japanese Patent Application No. 2024-090599, filed with the Japan Patent Office on June 4, 2024, the contents of which are incorporated herein by reference.

[0002] Permanent magnet motors are known that have rotors that use permanent magnets. To reduce eddy current loss, the motor rotors of these permanent magnet motors often use multiple bulk magnets. However, motor rotors that use multiple bulk magnets require a large number of assembly steps and are difficult to adjust for rotational balance.

[0003] One effective way to solve these problems is to use wire magnets instead of multiple bulk magnets. Wire magnets can be produced by compressing and molding magnetic powder into a jacket made of a non-magnetic material and then magnetizing it, or by sintering the magnetic powder. Wire magnets have small eddy current paths, making them suitable for suppressing eddy current loss, and by reducing the number of parts, they are advantageous for reducing the assembly labor required for motor rotors. Wire magnets can also easily be configured in a Halbach array, which can achieve high efficiency by concentrating the magnetic field on one side.

[0004] For example, Patent Documents 1 and 2 disclose assembly structures for magnets on a rotating shaft in a motor rotor, although they do not use wire magnets. Patent Document 1 discloses an assembly structure in which a cylindrical magnet attached to the rotating shaft is fixed to the rotating shaft by tightly fitting a reinforcing member made of a thin metal plate from the radial outside. Patent Document 2 also discloses an assembly structure in which a ring-shaped magnet is inserted into the rotating shaft and a wedge-shaped retaining ring is fitted from the radial outside.

[0005] JP2004-64887A JP10-210689A

[0006] While the above-mentioned Patent Documents 1 and 2 disclose an assembly structure in which magnets are fixed to the rotating shaft by reinforcing members and retaining rings, motor rotors with such assembly structures are required to minimize dimensional variations in the manufacturing process of each component. However, the aforementioned wire magnets are prone to large dimensional variations due to their shape characteristics, and reducing dimensional variations requires increasing manufacturing costs in order to improve processing precision.

[0007] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a motor rotor and a permanent magnet motor that allow wire-shaped magnets to be accurately assembled to a rotating shaft while keeping manufacturing costs down.

[0008] In order to solve the above problem, a motor rotor according to at least one embodiment of the present disclosure comprises: a rotating shaft; at least one wire magnet arranged axially on the outer surface of the rotating shaft and extending at least partially circumferentially around the rotating shaft; a retaining ring for holding the at least one wire magnet on the rotating shaft from the radially outside; and a first soft material arranged in at least one radial gap between the rotating shaft and the at least one wire magnet, or between the at least one wire magnet and the retaining ring.

[0009] In order to solve the above problems, a permanent magnet motor according to at least one embodiment of the present disclosure includes a motor rotor according to at least one embodiment of the present disclosure.

[0010] According to at least one embodiment of the present disclosure, it is possible to provide a motor rotor and a permanent magnet motor that allow wire magnets to be accurately assembled to a rotating shaft while reducing manufacturing costs.

[0011] 1 is a cross-sectional view taken along the axial direction of a motor rotor according to an embodiment; FIG. 2 is a perspective view showing the rotating shaft and wire magnets of FIG. 1; FIG. 3 is an enlarged cross-sectional view of region B of FIG. 1; FIG. 4 is another example of the cross-sectional shape of the wire magnet of FIG. 3; FIG. 5 is another example of the cross-sectional shape of the wire magnet of FIG. 3; FIG. 6 is another example of the cross-sectional shape of the wire magnet of FIG. 3; FIG. 7 is another example of the cross-sectional shape of the wire magnet of FIG. 3; FIG. 8 is a diagram showing the allowable thickness of the retaining ring from the perspective of the strength of the wire magnet (30 MPa) for each elastic modulus of the retaining ring, relative to the representative dimensions of the wire magnet and the diameter of the rotating shaft in the motor rotor shown in FIG. 3; FIG. 9 is a generalized diagram obtained by multiplying the vertical axis of FIG. 5A by the elastic modulus of the retaining ring; FIG. 10 is a graph showing the allowable range of the retaining ring thickness; FIG. 11 is a variation of FIG. 1; FIG. 8A is a cross-sectional view along line CC of FIG. 1; FIG. 8B is another variation of FIG. 1;

[0012] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the configurations described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0013] FIG. 1 is a cross-sectional view along the axial direction of a motor rotor 1 according to one embodiment, FIG. 2 is a perspective view showing the rotating shaft 2 and wire-shaped magnets 4 of FIG. 1, and FIG. 3 is an enlarged cross-sectional view of region B of FIG. 1.

[0014] The motor rotor 1 is a rotor used in an inner rotor type permanent magnet motor, in which the motor rotor is placed inside the stator. In a permanent magnet motor, a permanent magnet is used in the motor rotor 1, and a secondary current does not flow through the motor rotor 1. This eliminates rotation loss, resulting in energy savings and excellent efficiency.

[0015] The motor rotor 1 comprises a rotating shaft 2, a wire magnet 4, a retaining ring 6, and a pair of end plates 8.

[0016] The rotating shaft 2 is a shaft that can rotate when the permanent magnet motor is driven, and has a shaft body 2a extending along the axial direction and an expanded diameter portion 2b fixed around the shaft body 2a. The shaft body 2a has a substantially constant radius and is rotatably supported by a bearing (not shown). The expanded diameter portion 2b is attached to the center of the shaft body 2a excluding both end sides, and has a substantially constant diameter d that is larger than the shaft body 2a.

[0017] The wire magnet 4 is a type of longitudinal permanent magnet and is spirally (wound) on the radially outer side of the enlarged diameter portion 2b of the rotating shaft 2. In this embodiment, the wire magnet 4 has a sufficiently large length along its longitudinal direction and is wound around the enlarged diameter portion 2b multiple times. The wire magnets 4 wound around the enlarged diameter portion 2b are tightly packed so that adjacent side surfaces along the axial direction are in contact with each other. The longitudinally shaped wire magnet 4 has a small eddy current path, making it suitable for suppressing eddy current loss, and it is easy to realize a Halbach array that concentrates the magnetic field on one side and achieves high efficiency.

[0018] It should be noted that, instead of the wire magnet 4 wound around the rotating shaft 2 as described above, a plurality of ring-shaped magnets or wire magnets 4 may be used. In this case, each ring-shaped magnet is attached along the circumferential direction of the rotating shaft 2, and is arranged along the axial direction so that adjacent ring-shaped magnets are in contact with each other.

[0019] 1 and 3, the wire magnet 4 of this embodiment is composed of a jacket 4a that defines the outer shell, and magnetic powder 4b housed within the jacket 4a. The jacket 4a is made of a non-magnetic material. The magnetic powder 4b is made by compressing magnetic powder, which is a powdered magnetic material, and is housed within the jacket 4a.

[0020] In the embodiment shown in FIGS. 1 and 3 , the wire magnet 4 has a substantially square cross section perpendicular to the longitudinal direction, but other cross sections may be used. For example, as shown in FIG. 4A , a rectangular cross section allows the wire magnets 4 to be arranged without gaps, thereby favorably improving the performance of a permanent magnet motor incorporating the motor rotor 1. As shown in FIG. 4B , an elliptical cross section is easier to manufacture than a rectangular cross section and favorably reduces manufacturing costs. As shown in FIGS. 4C and 4D , a trapezoidal or parallelogram cross section has lower radial rigidity than a rectangular cross section. Therefore, when the wire magnet 4 is wound around the rotating shaft 2, it is easier to equalize the variation in the pressing load exerted by the retaining ring 6 disposed radially outward, as described below. Although the structural strength may be lower than when the cross section is square, the variation in the pressing load can be reduced by increasing the thickness of the first soft material 10 (described below) or by using a first soft material 10 with a low elastic modulus. The soft material 10 is made of a material having a lower modulus of elasticity than the surrounding members such as the rotating shaft 2 and the retaining ring 6, and for example, an adhesive, a resin material, or the like can be used.

[0021] The retaining ring 6 is configured to hold the wire magnets 4 attached to the rotating shaft 2 from the radially outer side. The retaining ring 6 is a substantially cylindrical member attached to the rotating shaft 2. A pair of end plates 8 is attached to the rotating shaft 2 to support the wire magnets 4 from both ends along the axial direction. Each of the pair of end plates 8 has a substantially circular disk shape, with the inner diameter side fixed to the rotating shaft 2 and the aforementioned retaining ring 6 fixed by press fit to the radially outer end face. In other words, the retaining ring 6, which holds the wire magnets 4 so as to cover them, is engaged with the rotating shaft 2 via the end plates 8, thereby realizing a motor rotor 1 with a structure that is highly stable even when rotating at high speeds.

[0022] A radial gap filled with a first soft material 10 is provided between the retaining ring 6 and the wire-shaped magnet 4 (outer diameter side) or between the wire-shaped magnet 4 (inner diameter side) and the rotating shaft 2. In this embodiment, the radial gaps shown include both a first radial gap 12a between the retaining ring 6 and the wire-shaped magnet 4 (outer diameter side) and a second radial gap 12b between the wire-shaped magnet 4 (inner diameter side) and the rotating shaft 2. The first soft material 10 is made of a soft material with a lower elastic modulus than surrounding members such as the rotating shaft 2, the wire-shaped magnet 4, and the retaining ring 6, and for example, an adhesive or resin can be used.

[0023] As described above, when the retaining ring 6 that holds the wire-shaped magnet 4 is press-fitted onto a pair of end plates 8 provided on the rotating shaft 2, the wire-shaped magnet 4 is subjected to a pressing load from both the inside and outside in the radial direction by the retaining ring 6. This pressing load has a distribution that corresponds to the dimensional variation of the wire-shaped magnet 4, so if the dimensional variation of the wire-shaped magnet 4 is large, an excessive pressing load may be applied to the wire-shaped magnet 4. In this embodiment, by filling the radial gaps 12 (the first radial gap 12a and the second radial gap 12b) with the first soft material 10, even if the dimensional variation of the wire-shaped magnet 4 is large, the dimensional variation is absorbed by the compressive deformation of the first soft material 10, and the pressing load acting on the wire-shaped magnet 4 can be suitably kept within an allowable range.

[0024] As described above, a configuration in which the first soft material 10 can absorb dimensional variations in the wire magnets 4 can be achieved by designing the thickness t of the retaining ring 6 to fall within an appropriate tolerance range. The tolerance range for the thickness t of the retaining ring 6 is defined by the following equation using the maximum thickness tmax and the minimum thickness tmin: tmin≦t≦tmax (1) A specific method for calculating the maximum thickness tmax and the minimum thickness tmin will be explained below.

[0025] First, we will explain how to calculate the maximum plate thickness tmax, which is the upper limit of the allowable range. The larger the elastic modulus E of the material constituting the retaining ring 6 that holds the wire-shaped magnet 4, and the larger the plate thickness t, the larger the pressing load that the wire-shaped magnet 4 held inside will be. In the structure of this embodiment, the radial stress σ that occurs when the retaining ring 6 is fitted with an interference between the retaining ring 6 and the first soft material 10 is ｒ , circumferential stress σ θ and the deformation amount u are expressed by the following governing equations: By solving this governing equation by applying the force balance conditions and displacement conditions at the boundaries of each component, the stress generated in each component can be determined and the pressing load applied to the wire-shaped magnet 4 can be calculated.

[0026] Here, assuming that the strength of the wire magnet 4 is 30 MPa and the thickness ts of the first soft material 10 is 0.2 mm, relative to the representative dimension s (radial length) of the wire magnet 4, the plate thickness t of the retaining ring 6 can be determined as shown in Figure 5A for each elastic modulus E of the retaining ring 6, as a condition under which the stress calculated using the above formulas (2-1) and (2-2) is equal to or less than the allowable value for the wire magnet 4. Note that in Figure 5A, the graph is exemplarily shown with the horizontal axis s / d in the range of 0.06≦s / d≦0.13, which is expected in an actual machine, but values ​​outside this range are also included in the present invention.

[0027] 5A, if the value on the vertical axis is multiplied by the elastic modulus E of the retaining ring 6 and generalized, it is expressed as the dashed line in Fig. 5B (t / d × E × s / d = 0.2). If the wire magnet 4 is stronger or if the thickness ts of the first soft material 10 is greater, the allowable plate thickness t of the retaining ring 6 will be larger, so the maximum plate thickness tmax within the expected range was determined as shown by the solid line (t / d × E × s / d = 0.4).

[0028] Next, we will explain the method for calculating the minimum thickness tmin, which is the lower limit of the allowable range. During rotation, the wire magnet 4 is subjected to centrifugal force, and the pressing load it receives from the radially inner side decreases. Therefore, the minimum thickness tmin of the retaining ring 6 can be determined as a condition for generating an appropriate pressing load so that the pressing load does not become zero during rotation. The centrifugal force F acting on the wire magnet 4 rotating at the rotation speed N of the motor rotor 1 and angular velocity ω (= 2πN / 60 [rad / s]) is expressed by the following equation: F = 2πω ２ ρs × (r о ３ -r ｉ ３ ) / 3 (3) where ρ is the density of the wire magnet 4, and r о is the outer radius of the wire magnet 4, r ｉ is the inner radius (= d / 2) of the wire-shaped magnet 4. As a result, the change in surface pressure Δpi of the wire-shaped magnet 4 during rotation is expressed by the following equation: Δpi=F / (πds) (4)

[0029] According to the above formula (3), the centrifugal force F is a function of the square of the rotation speed and the radius r ｉ , r о The centrifugal force F is proportional to the cube of the rotation speed N and the radius r ｉ , r о When setting the inner radius r ｉ The rotation speed N is set relative to the rotation speed N, and the change in surface pressure Δpi is calculated. Under conditions where the centrifugal force F is constant in this way, the larger the diameter d of the expanded diameter portion 2b, the smaller the change in surface pressure. As an example, under conditions where d = 92 mm, s / d = 0.087, and the rotation speed is 14,000 rpm, the change in surface pressure Δpi is approximately 5 MPa. Since the surface pressure is approximately proportional to the plate thickness t of the retaining ring 6, the plate thickness t of the retaining ring 6 must be 1 / 6 of the condition indicated by the dashed line in Figure 5B in order to maintain the surface pressure.

[0030] As another way of thinking about the setting of the diameter d and rotation speed N of the expanded diameter portion 2b, from the above equations (3) and (4), the surface pressure change Δpi is proportional to the cube of the rotation speed N and the cube of the diameter d. When the rotation speed N and diameter d are set so that the surface pressure change Δpi is constant, the rotation speed N is set relative to the diameter d. Assuming a surface pressure change Δpi = 20 MPa, the surface pressure is approximately proportional to the thickness t of the retaining ring 6, and therefore, the surface pressure can be maintained if the thickness t of the retaining ring 6 is 2 / 3 of the condition indicated by the dashed line in Figure 5B. From an examination based on the above two conditions for setting the diameter d and rotation speed N, the minimum thickness tmin of the retaining ring 6 that encompasses both is set to 1 / 6 of the dashed line shown in Figure 5B.

[0031] From such considerations, the maximum plate thickness tmax is set to 0.4d / (s / d) / E and the minimum plate thickness tmin is set to 0.033d / (s / d) / E, and by substituting these into the above formula (1), the allowable range of plate thickness t of the retaining ring 6 is expressed by the following formula: 0.033d / (s / d) / E≦t≦0.4d / (s / d) / E (5) Therefore, by setting the plate thickness t of the retaining ring 6 to satisfy the above formula (5), the pressing load received by the wire-shaped magnet 4 can be kept within an appropriate range.

[0032] The material of the retaining ring 6 is preferably non-magnetic and has an elastic modulus E of 20 to 200 GPa. Specific examples of the material that can be used for the retaining ring 6 include high-strength Ni-based alloys, Ti alloys, and CFRP.

[0033] Figure 7 shows a modification of Figure 3. In this modification, the motor rotor 1 further includes a second soft material 16 provided in the axial gap 14 between the end plate 8 and the wire-shaped magnet 4. By providing the second soft material 16 in this manner, when the end plate 8 is pressed against and fixed to the wire-shaped magnet 4, the second soft material 16 is preferentially compressed and deformed, thereby preventing the creation of an unnecessary gap between the two and preventing the wire-shaped magnet 4 from receiving an excessive pressing load from the end plate 8. In other words, by providing the second soft material 16 so as to fill the axial gap 14 that occurs when the length of the wire-shaped magnet 4 on the rotating shaft 2 is set shorter than the distance between the pair of end plates 8, the creation of the axial gap 14 and the excessive pressing load from the end plate 8 can be prevented.

[0034] The second soft material 16 may be provided in at least a part of the axial gap 14. In other words, the second soft material 16 may be provided in the entire axial gap 14, or may be provided in part of the axial gap 14.

[0035] Figure 8A is a modified example of Figure 1, and Figure 8B is a cross-sectional view taken along line CC of Figure 8A. In this modified example, the wire magnet 4 has a configuration in which magnetic powder 4b is housed in a jacket 4a, as described above, but a key groove 18 is provided on the side of the jacket 4a that faces the rotating shaft 2. The key groove 18 is formed to extend axially over the entire area of ​​the rotating shaft 2 where the wire magnet 4 is provided. A rod-shaped key 20 having a corresponding shape is inserted into this key groove 18, making it possible to transmit torque from the wire magnet 4 to the rotating shaft 2.

[0036] In this modification, the side of the jacket 4a that constitutes the wire magnet 4 that faces the rotating shaft 2 (i.e., the radially inner side) is configured to be thicker than the other sides. This makes it possible to suppress a decrease in the rigidity of the jacket 4a, even when the key grooves 18 are formed in the jacket 4a as described above, and to achieve a motor rotor 1 with a stable structure.

[0037] Figure 9 shows another modified example of Figure 1. This modified example differs from the modified example shown in Figure 8A in that the key groove 18 is formed only in a portion of the wire magnet 4 adjacent to the end plate 8 (the axial end). Accordingly, the jacket 4a of the wire magnet 4 is also configured so that the side facing the rotating shaft 2 (i.e., the radially inner side) is thicker than the other sides only in the portion adjacent to the end plate 8. Due to this range of key groove 18, the key 20 inserted into the key groove 18 is also shorter than in the modified example shown in Figure 8A. According to this modified example, the area where the key groove 18 is provided is smaller, which minimizes the reduction in strength and the processing burden caused by forming the key groove 18 in the jacket 4a of the wire magnet 4.

[0038] In other embodiments, the wire magnet 4 may be configured as a sintered magnet. Figure 10 shows another variation of Figure 1. In this variation, the wire magnet 4 is configured as a sintered magnet, eliminating the need for an outer shell structure like the jacket 4a of the previous embodiment. Because such wire magnets 4 without a jacket 4a have relatively low strength, it is necessary to reduce dimensional variation to prevent excessive pressing loads from acting on some magnets. Specifically, the outer shape must be finished by machining. If the pressing load variation due to dimensional variation is still large, it is effective to increase the thickness of the first soft material 10 compared to when the jacket 4a is included, or to use a soft material with a low elastic modulus as the first soft material 10. Furthermore, wire magnets 4 configured as sintered magnets have stronger magnetic force than wire magnets 4 with a jacket 4a, which is advantageous for improving the performance of permanent magnet motors.

[0039] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0040] The contents described in each of the above embodiments can be understood, for example, as follows.

[0041] (1) A motor rotor according to one embodiment comprises: a rotating shaft; at least one wire magnet arranged axially on the outer surface of the rotating shaft and extending at least partially circumferentially around the rotating shaft; a retaining ring for holding the at least one wire magnet on the rotating shaft from the radially outer side; and a first soft material arranged in a radial gap at least either between the rotating shaft and the at least one wire magnet or between the at least one wire magnet and the retaining ring.

[0042] According to the above aspect (1), a first soft material is provided in a radial gap between the rotating shaft and the wire-shaped magnet or between the wire-shaped magnet and the retaining ring. The first soft material is a material with a lower elastic modulus than the rotating shaft and the retaining ring of the motor rotor. When the wire-shaped magnet is held (squeezed) from the radial outside by the retaining ring on the rotating shaft, the first soft material is preferentially compressively deformed, thereby equalizing the pressing load applied to the wire-shaped magnet. As a result, even if there is dimensional variation in the wire-shaped magnet, the dimensional variation is absorbed by the compressive deformation of the first soft material, allowing for accurate assembly of the motor rotor.

[0043] (2) In another aspect, in the above aspect (1), an end plate is further provided that is attached to the rotating shaft and supports the at least one wire magnet from the axial direction, and the radially outer end surface of the end plate is supported by the retaining ring.

[0044] According to the above aspect (2), the wire magnets attached to the rotating shaft are supported at their axial ends by end plates. The end plates are attached to the rotating shaft at their radially inner sides and supported at their radially outer sides by the retaining ring, thereby realizing a motor rotor with a stable configuration.

[0045] (3) In another aspect, in the aspect (1) or (2), the radial gap is provided between the rotating shaft and the at least one wire-shaped magnet.

[0046] According to the above aspect (3), the first soft material is provided in the radial gap between the rotating shaft and the wire-shaped magnet, so that the first soft material located radially inward of the wire-shaped magnet can preferably bear the pressing load from the wire-shaped magnet.

[0047] (4) In another aspect, in the above aspect (1) or (2), the radial gap is provided between the at least one wire magnet and the retaining ring.

[0048] According to the above aspect (4), the first soft material is provided in the radial gap between the wire-shaped magnet and the retaining ring, so that the first soft material located radially outward from the wire-shaped magnet can preferably bear the pressing load from the wire-shaped magnet.

[0049] (5) In another aspect, in any one of the above aspects (1) to (4), the plate thickness t of the retaining ring is configured to satisfy the following formula, where d is the diameter of the rotation shaft, s is the maximum radial dimension of the at least one wire magnet in a cross section perpendicular to the rotation shaft, and E is the elastic modulus of the retaining ring: 0.033d / (s / d) / E≦t≦0.4d / (s / d) / E

[0050] According to the above aspect (5), by setting the plate thickness of the retaining ring so as to satisfy the above formula, the pressing load received by the wire-shaped magnet can be kept within an appropriate allowable range.

[0051] (6) In another aspect, in the above aspect (2), a second soft material is further provided in an axial gap between the end plate and the at least one wire-shaped magnet.

[0052] According to the above aspect (6), by providing a second soft material between the end plate and the wire-shaped magnet, when the end plate is pressed against the wire-shaped magnet and fixed, the second soft material is preferentially compressed and deformed, thereby preventing unnecessary gaps from being created between the two and preventing the wire-shaped magnet from being subjected to excessive pressing load from the end plate.

[0053] (7) In another aspect, in any one of the above aspects (1) to (6), the at least one wire magnet includes: a jacket made of a non-magnetic material; and a magnetic powder body contained in the jacket and including compression-molded magnetic powder.

[0054] According to the above aspect (7), the wire magnet is configured by housing a magnetic powder body in which magnetic powder is compressed and molded within a jacket. Wire magnets with this configuration have lower strength than sintered magnets, so if there is a large variation in their dimensions, the wire magnet may be subjected to a large pressing load, which could result in crushing. In the motor rotor of this aspect, by providing the first soft material in the radial gap as described above, even when wire magnets with this configuration are used, the first soft material absorbs the dimensional variation of the wire magnet, thereby preferably preventing the wire magnet from being crushed due to an excessive pressing load acting on it.

[0055] (8) In another aspect, in the aspect (7) above, a key groove into which a key for transmitting torque to the rotary shaft can be inserted is provided on the side of the jacket facing the rotary shaft.

[0056] According to the above aspect (8), the torque from the rotating shaft can be suitably transmitted by inserting a key into a key groove provided in the jacket that constitutes the wire magnet.

[0057] (9) In another aspect, in the aspect (8), the jacket is configured so that the side facing the rotating shaft is thicker than the other sides.

[0058] According to the above aspect (9), the jacket constituting the wire magnet is configured so that the side facing the rotating shaft where the key groove is provided is thicker than the other sides, thereby suppressing a decrease in the jacket rigidity even when the key groove is formed, and realizing a motor rotor with a stable structure.

[0059] (10) In another aspect, in the above aspect (8) or (9), the key groove is provided over the entirety of the at least one wire magnet.

[0060] According to the above aspect (10), by providing a key groove over the entire wire magnet, torque can be suitably transmitted to the rotating shaft.

[0061] (11) In another aspect, in the aspect (8) or (9), the key groove is provided at an axial end of the at least one wire magnet.

[0062] According to the above aspect (11), by providing a key groove only at the axial end of the wire-shaped magnet, it is possible to minimize the reduction in strength and the processing burden caused by forming a key groove in the jacket of the wire-shaped magnet.

[0063] (12) In another aspect, in any one of the above aspects (1) to (6), the at least one wire magnet is a sintered magnet.

[0064] According to the above aspect (12), the wire magnet is made of a sintered magnet formed by sintering magnetic powder. Such a wire magnet without a jacket structure can improve motor performance by obtaining a strong magnetic force.

[0065] (13) In another aspect, in any one of the above aspects (1) to (12), the at least one wire magnet has a cross section perpendicular to the axial direction that is either rectangular, elliptical, trapezoidal, or parallelogrammatic.

[0066] According to the above aspect (13), the cross-sectional shape of the wire magnet can be various shapes, such as a rectangle, an ellipse, a trapezoid, or a parallelogram. For example, if the cross-sectional shape is a rectangle (including a square), the wire magnets can be arranged without gaps, improving the performance of the permanent magnet motor equipped with the motor rotor. Furthermore, if the cross-sectional shape is an ellipse (including a circle), it is easier to manufacture than a rectangle, and manufacturing costs can be reduced. Furthermore, if the cross-sectional shape is a trapezoid or parallelogram, the radial rigidity is lower than if it is a rectangle, which has the effect of equalizing variations in pressing load due to dimensional variations of the wire magnet.

[0067] (14) In another aspect, in any one of the above aspects (1) to (13), the at least one wire magnet is wound spirally around the rotation axis.

[0068] According to the above aspect (14), in a motor rotor using a wire-shaped magnet configured by winding the wire-shaped magnet spirally around a rotating shaft, by providing a first soft material in the radial gap, the pressing load received by the wire-shaped magnet can be suitably equalized.

[0069] (15) A permanent magnet motor according to one aspect includes the motor rotor according to any one of the above aspects (1) to (14).

[0070] According to the above aspect (15), by having the motor rotor described above, it is possible to preferably realize a permanent magnet motor that can be assembled with high precision while suppressing manufacturing costs.

[0071] REFERENCE SIGNS LIST 1 Motor rotor 2 Rotating shaft 2a Shaft body 2b Expanded diameter portion 4 Wire magnet 4a Jacket 4b Magnetic powder 6 Retaining ring 8 End plate 10 First soft material 12 Radial gap 12a First radial gap 12b Second radial gap 14 Axial gap 16 Second soft material 18 Keyway 20 Key

Claims

1. A motor rotor comprising: a rotating shaft; at least one wire magnet provided axially on an outer surface of the rotating shaft and extending at least partially circumferentially around the rotating shaft; a retaining ring for holding the at least one wire magnet on the rotating shaft from the radially outer side; and a first soft material provided in a radial gap between the rotating shaft and the at least one wire magnet, or between the at least one wire magnet and the retaining ring.

2. The motor rotor according to claim 1, further comprising an end plate attached to the rotating shaft for axially supporting the at least one wire magnet, the end plate having a radially outer end surface supported by the retaining ring.

3. The motor rotor according to claim 1 or 2, wherein the radial gap is provided between the rotating shaft and the at least one wire-shaped magnet.

4. The motor rotor of claim 1 or 2, wherein the radial gap is provided between the at least one wire magnet and the retaining ring.

5. The motor rotor according to claim 1 or 2, wherein the thickness t of the retaining ring is configured to satisfy the following formula, using the diameter d of the rotating shaft, the maximum radial dimension s of the at least one wire magnet in a cross section perpendicular to the rotating shaft, and the elastic modulus E of the retaining ring: 0.033d / (s / d) / E≦t≦0.4d / (s / d) / E 6. The motor rotor of claim 2, further comprising a second soft material disposed in an axial gap between said end plate and said at least one wire magnet.

7. The motor rotor according to claim 1 or 2, wherein the at least one wire-shaped magnet comprises: a jacket made of a non-magnetic material; and a magnetic powder body that is housed in the jacket and includes compression-molded magnetic powder.

8. A motor rotor according to claim 7, wherein the jacket is provided on the side facing the rotary shaft with a key groove into which a key for transmitting torque to the rotary shaft can be inserted.

9. The motor rotor according to claim 8, wherein the jacket is configured so that the side facing the rotating shaft is thicker than the other sides.

10. The motor rotor of claim 8, wherein said keyway extends through said at least one wire magnet.

11. The motor rotor of claim 8, wherein the keyway is provided at an axial end of the at least one wire magnet.

12. The motor rotor according to claim 1 or 2, wherein said at least one wire magnet is a sintered magnet.

13. A motor rotor according to claim 1 or 2, wherein the at least one wire-shaped magnet has a cross section perpendicular to the axial direction that is either rectangular, elliptical, trapezoidal or parallelogrammatic in shape.

14. The motor rotor according to claim 1 or 2, wherein said at least one wire magnet is wound helically about said rotational axis.

15. A permanent magnet motor having a motor rotor according to claim 1 or 2.

Images