JP7463979B2 - Rotating Electric Machine - Google Patents

Description

The present invention relates to a rotating electric machine.

Conventionally, rotating electric machines are known that have multiple permanent magnets on the outer periphery of a rotor core. For example, in Patent Document 1, a non-magnetic ring is inserted to cover the outer periphery of the permanent magnets fixed to the outer periphery of the stator core.

Patent No. 5528552

In Patent Document 1, a non-magnetic ring with a polygonal cross section (e.g., a regular decagon) is formed by processing a flat plate into a ring shape. Here, if the rotor is, for example, a stage-skewed rotor, the magnets are arranged offset by the skew angle between the first and second stages, making it difficult to press-fit a polygonal cover.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a rotating electric machine that can properly fix magnets to a stage-skewed rotor.

The rotating electric machine of the present invention includes a housing (830), a stator (840), a shaft (870), a rotor (30), and a rotor cover (40). The stator is fixed to the housing so as not to rotate. The shaft is supported by the housing so as to be rotatable. The rotor has a rotor core (31, 32) and multiple stages of magnets (33, 34) arranged radially outward of the rotor core and shifted in the circumferential direction according to the skew angle, and rotates integrally with the shaft.

The rotor cover has a first large diameter portion (41) provided at one end in the axial direction, a second large diameter portion (42) provided at the other end in the axial direction, and a small diameter portion (45) provided between the first and second large diameter portions and having a smaller diameter than the first and second large diameter portions at the intermediate portion between the magnets adjacent in the axial direction , and is press-fitted and fixed to the radially outer side of the rotor. The magnets are fixed to the rotor core by the rotor cover. Both ends in the circumferential direction of each magnet are formed in a state in which an upright surface rising in a non-arcuate shape from the rotor core side remains, and when the rotor is projected in the axial direction, the end of the magnet fixed to one rotor core is formed inside the outer diameter of the magnet fixed to the other rotor core. This allows the rotor cover to properly hold multiple stages of magnets.

1 is a schematic configuration diagram showing a steering system according to an embodiment; FIG. 2 is a cross-sectional view of a drive arrangement according to one embodiment. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 2 is a side view of a rotor according to one embodiment. FIG. 2A is a plan view illustrating the arrangement of first-stage magnets, and FIG. 2B is a plan view illustrating the arrangement of second-stage magnets. FIG. 2 is an explanatory diagram illustrating the arrangement of first-stage magnets and second-stage magnets as viewed from the axial direction in one embodiment. FIG. 2 is a side view illustrating a rotor cover before press fitting according to one embodiment. FIG. 8 is a view taken in the direction of an arrow VIII in FIG. 7 . 5A and 5B are schematic diagrams illustrating a positional relationship between a rotor and a rotor cover according to one embodiment. FIG. 2 is a top view of a rotor and rotor cover according to one embodiment. 11 is a cross-sectional view taken along line XI-XI of FIG. This is a cross-sectional view taken along line XII-XII in Figure 11. This is a cross-sectional view taken along line XIII-XIII in Figure 11.

(One embodiment)
The rotating electric machine will be described below with reference to the drawings. One embodiment is shown in Fig. 1 to Fig. 13. As shown in Fig. 1, a drive device 10 includes an ECU 20 and a motor 80 as a rotating electric machine, and is applied to, for example, an electric power steering device 8 which is a steering device for assisting the steering operation of a vehicle.

Figure 1 shows the configuration of a steering system 90 equipped with an electric power steering device 8. The steering system 90 includes a steering wheel 91, which is a steering member, a steering shaft 92, a pinion gear 96, a rack shaft 97, wheels 98, and the electric power steering device 8.

The steering wheel 91 is connected to a steering shaft 92. A torque sensor 94 that detects the steering torque Ts is provided on the steering shaft 92. A pinion gear 96 is provided at the tip of the steering shaft 92. The pinion gear 96 meshes with a rack shaft 97. A pair of wheels 98 are connected to both ends of the rack shaft 97 via tie rods or the like.

When the driver turns the steering wheel 91, the steering shaft 92 connected to the steering wheel 91 rotates. The rotational motion of the steering shaft 92 is converted into linear motion of a rack shaft 97 by a pinion gear 96. A pair of wheels 98 are steered to an angle that corresponds to the amount of displacement of the rack shaft 97.

The electric power steering device 8 includes a motor 80, a reduction gear 89 as a power transmission unit that reduces the speed of the rotation of the motor 80 and transmits it to the steering shaft 92, and an ECU 20. That is, the electric power steering device 8 of this embodiment is a so-called "column assist type," and the steering shaft 92 can be said to be the driven object. It may also be a so-called "rack assist type" that transmits the rotation of the motor 80 to a rack shaft 97.

As shown in Figures 1 to 3, the motor 80 outputs some or all of the torque required for steering, and is driven by power supplied from a battery (not shown), causing the reduction gear 89 to rotate forward and backward.

As shown in Figures 2 and 3, the drive unit 10 is a so-called "mechatronically integrated" type, with the ECU 20 provided on one side of the motor 80 in the axial direction. The mechatronically integrated type allows the ECU 20 and the motor 80 to be efficiently arranged in a vehicle with limited mounting space. The ECU 20 is arranged coaxially with the axis Ax of the shaft 870, on the opposite side to the output shaft of the motor 80. The ECU 20 may be provided on the output shaft side of the motor 80, or may be provided separately from the motor 80.

The motor 80 includes a stator 840, a rotor 30, and a housing 830 that houses them. The stator 840 is fixed to the housing 830, and motor windings 801 and 802 are wound around the stator 840. The rotor 30 is provided radially inside the stator 840 and is rotatable relative to the stator 840.

The shaft 870 is fitted into the rotor 30 and rotates integrally with the rotor 30. The shaft 870 is rotatably supported in the housing 830 by bearings 835 and 836. The end of the shaft 870 on the ECU 20 side protrudes from the housing 830 towards the ECU 20 side. A magnet 875 is provided on the end of the shaft 870 on the ECU 20 side. The magnet 857 is held on the shaft 870 by a magnet holder 876.

The housing 830 has a cylindrical case 834, a rear frame end 837 provided at one end of the case 834, and a front frame end 838 provided at the other end of the case 834. The rear frame end 837 is formed with lead wire insertion holes through which lead wires 803, 804 connected to each phase of the motor windings 801, 802 are inserted, and the lead wires 803, 804 are taken out to the ECU 20 side.

The ECU 20 includes a control board 230, a power board 235, power modules 241 and 242, and a heat sink 245. The control board 230 is formed in a substantially rectangular shape and is fixed to the surface of the heat sink 245 facing the motor 80 with bolts or the like. The power board 235 is formed in a substantially rectangular shape and is fixed to the surface of the heat sink 245 opposite the motor 80 with bolts or the like.

The heat sink 245 is fixed to the rear frame end 837. The heat sink 63 and the rear frame end 837 may be integrated or separate. The heat sink 245 is made of a metal with good thermal conductivity, such as aluminum, and the power modules 241 and 242 are provided on the side surface so as to be able to dissipate heat. That is, in this embodiment, the power modules 241 and 242 are arranged vertically along the axial direction of the motor 80.

The power modules 241 and 242 are provided with switching elements and the like that constitute an inverter for controlling the current supply to the motor windings 801 and 802, respectively, and are connected to the motor windings 801 and 802 via lead wires 803 and 804. The power modules 241 and 242 are also connected to the control board 230 and the power board 235.

The cover 21 is formed in a generally bottomed cylindrical shape and fits onto the radially outer side of the rear frame end 837. The cover 21 is provided to cover the boards 230, 235 and the power modules 241, 242. A rotation angle sensor 53 is mounted on the surface of the control board 230 facing the motor 80, in a position opposite the magnet 875. The connector unit 22 is fixed to the cover 21 with screws or the like.

As shown in Figs. 4 and 5, the rotor 30 has rotor cores 31, 32 and magnets 33, 34. The rotor cores 31, 32 are formed in a generally regular octagonal shape in a plan view, and are formed by stacking thin plates made of, for example, iron or the like. In this embodiment, the rotor core 32 is provided on the motor 80 side, and the rotor core 31 is provided on the connector unit 22 side. The first-stage magnets 33 are segment-type magnets whose radially outer side is formed in an arc shape, and are fixed to the radially outer side of the rotor core 31. The second-stage magnets 34 are segment-type magnets whose radially outer side is formed in an arc shape, and are fixed to the radially outer side of the rotor core 32. In this embodiment, there are eight first-stage magnets 33 and eight second-stage magnets 34.

The motor 80 is a so-called SPM motor in which the magnets 33, 34 are attached to the outer circumferential surfaces of the rotor cores 31, 202, respectively. As shown in FIG. 5, the first stage magnet 33 and the second stage magnet 34 are arranged with their radial positions shifted in the circumferential direction by the skew angle θs. In other words, the rotor 30 is a stage skew rotor. The magnets 33, 34 are fixed to the rotor cores 31, 32 by the rotor cover 40, which is pressed into the radially outward side (see FIG. 9 to FIG. 13). In this embodiment, no adhesive material such as adhesive is provided between the magnets 33, 34 and the rotor cores 31, 32, and they are fixed without adhesive.

As shown in FIG. 6, the outer circumferential end of each magnet 33, 34 is chamfered. In addition, the radius of curvature of magnets 33, 34 is made large so that the end of magnet 33 is inside the outer diameter of magnet 34 when rotor 30 is projected in the axial direction, preventing interference with rotor cover 40. This reduces the step between first-stage magnet 33 and second-stage magnet 34, reducing the amount of snagging when rotor cover 40 is pressed in the axial direction, making it easier to press in.

As shown in Figures 7 and 8, the rotor cover 40 is made of a non-magnetic material and is formed in a substantially cylindrical shape. The rotor cover 40 is formed to a thickness that allows it to be deformed by being pressed into the rotor 30 and does not buckle when pressed. The rotor cover 40 has an inner diameter 401 that is circular before being pressed into the rotor 30. The rotor cover 40 is a stepped cylindrical member that has, from one axial side, a first large diameter portion 41, a small diameter portion 45, a second large diameter portion 42, and a tapered portion 43. The magnets 33, 34 are fixed to the rotor cores 31, 32 by pressing the rotor cover 40 into the rotor 30 from the tapered portion 43 side.

The small diameter portion 45 is provided in the center in the axial direction so as to straddle the first stage magnet 33 and the second stage magnet 34. The large diameter portions 41, 42 are provided on both sides of the small diameter portion 45 in the axial direction. The tapered portion 43 is formed so as to expand radially outward from the second large diameter portion 42. This makes it easier to press-fit the rotor cover 40 by pressing it in from the tapered portion 43 side. To prevent the magnets 33, 34 from being exposed, both axial ends of the rotor cover 40 are bent radially inward after being pressed into the rotor 30.

As shown in FIG. 9, the small diameter portion length L1 is the axial length of the small diameter portion 45, and the rotor length L2 is the axial length of the rotor 30. The small diameter portion length L1 is formed to be more than half the rotor length L2 (Equation (1)). The rotor length L2 can also be considered as the length from one end side of the first stage magnet 33 to the other end side of the second stage magnet 34. In this embodiment, the first stage magnet 33 and the second stage magnet 34 have the same axial length and are provided on both sides of the axial center position C of the rotor 30. Since the axial center position of the small diameter portion 45 is set to coincide with the axial center position C of the rotor 30, the small diameter portion 45 can hold more than half of the axial length of the magnets 33 and 34. This makes it possible to suppress the inclination of the magnets 33 and 34. In FIG. 9, for the purpose of explanation, the difference between the large diameter portions 41 and 42 and the small diameter portion 45 is emphasized so as to make it clear. Also, in Figure 11 described below, the steps between the large diameter portions 41 and 42 and the small diameter portion 45 have been omitted.

L1 ≧ (1/2) × L2 ... (1)

For example, if the inner circumference of the rotor cover is polygonal, for example, when the convex portion of the first stage magnet 33 is aligned with the corner of the inner circumference of the cover and pressed in, the convex portion of the second stage magnet 33 and the convex portion of the rotor cover will not be aligned, making the press-in difficult.

Therefore, in this embodiment, by making the inner diameter 401 of the rotor cover 40 before press-fitting a circle, it is possible to press-fit while deforming to match the outer diameter of the magnets 33, 34. Therefore, the inner diameter 401 of the rotor cover 40 after press-fitting is not a simple circle, but a shape that follows the outer edges of the magnets 33, 34. In addition, by making the radius of curvature of each magnet 33, 34 as large as possible, the step between the first stage magnet 33 and the second stage magnet 34 is reduced, and the second stage magnet 34 is less likely to get caught, making it easier to press-fit.

Figure 12 is a cross-sectional view of the first large diameter portion 41, and Figure 13 is a cross-sectional view of the small diameter portion 45. Note that Figures 12 and 13 are diagrams for explaining the definitions of the circumscribing circle radius φR0 of the rotor 30, the small diameter portion minimum radius φR1, and the large diameter portion minimum radius φR2, and do not necessarily correspond to the actual sizes. In addition, the size of the second large diameter portion 42 is the same as that of the first large diameter portion 41, so the description is omitted. As shown in Figures 12 and 13, when the rotor cover 40 is pressed in, the rotor cover 40 is aligned along the outer diameter at the center of each magnet 33 and separated at the middle portion.

The distance between the axis Ax and the top of the magnet 33 is the circumscribed circle radius φR0, the minimum radius of the rotor cover 40 at the small diameter portion 45 is the small diameter minimum radius φR1, and the minimum radius of the rotor cover 40 at the large diameter portion 41 is the large diameter minimum radius φR2. The minimum radius of the rotor cover 40 at the large diameter portion 41 and the small diameter portion 45 is the length connecting the center point of the abutment point with the tops of two circumferentially adjacent magnets 33 and the axis Ax. In this embodiment, the large diameter minimum radius φR2 is equal to or smaller than the circumscribed circle radius φR0, and the small diameter minimum radius φR1 is smaller than the large diameter minimum radius φR2 (see formula (2)). The small diameter minimum radius φR1 is formed to a size that allows the rotor 30 to be inserted by deformation due to press-fitting and allows the magnets 33, 34 to be held by residual stress. If φR2 = φR0, the large diameter portions 41, 42 are perfect circles.

φR1<φR2≦φR0 ... (2)

In this embodiment, the rotor cover 40 is cylindrical, with a small diameter section 45 in the axial center and large diameter sections 41, 42 at both ends, and the magnets 33, 34 are fixed to the rotor cores 31, 32 without adhesive by press-fitting the rotor cover 40 into the rotor 30. This makes it possible to minimize the portion of the rotor cover 40 that is press-fitted into the magnets 33, 34, making assembly easier.

The rotor 30 of this embodiment is a staged skewed rotor, and by making the center of the rotor cover 40 a small diameter section 45, both the first stage magnet 33 and the second stage magnet 34 can be fixed simultaneously. In addition, by making the axially outer sides of the rotor cover 40 into large diameter sections 41 and 42, the rotor cover 40 can be formed by deep drawing.

As described above, the motor 80 includes a housing 830, a stator 840, a shaft 870, a rotor 30, and a rotor cover 40. The stator 840 is fixed to the housing 830 so as not to rotate. The shaft 870 is supported rotatably by the housing 830.

The rotor 30 has rotor cores 31, 32 and multiple stages of magnets 33, 34 arranged radially outside the rotor cores 31, 32, shifted in the circumferential direction according to the skew angle, and rotates integrally with the shaft 870. In this embodiment, the rotor cores 31, 32 are arranged shifted in the circumferential direction according to the skew angle, and the magnets 33, 34 are arranged shifted by the skew angle by providing magnets 33, 34 on the outside of the rotor cores 31, 32, respectively.

The rotor cover 40 has a first large diameter portion 41 provided at one axial end, a second large diameter portion 42 provided at the other axial end, and a small diameter portion 45 provided between the first large diameter portion 41 and the second large diameter portion 42, which is smaller in diameter than the first large diameter portion 41 and the second large diameter portion 42, at the intermediate portion between the axially adjacent magnets 33, 34, and is press-fitted and fixed to the radially outer side of the rotor. This allows multiple stages of magnets 33, 34 to be appropriately held by one rotor cover 40. In addition, by making both axial ends large diameter, the press-fit load can be reduced.

If the circumscribing circle radius of the rotor 30 is φR0, the minimum radius of the small diameter portion 45 is φR1, and the minimum radius of the first large diameter portion 41 and the second large diameter portion 42 is φR2, then φR1 < φR2 ≦ φR0. This allows the magnets 33 and 34 to be properly held in the small diameter portion 45 by residual stress.

The axial length of the small diameter portion 45 is at least half the axial length of the rotor 30. It is preferable that the axial center position of the small diameter portion 45 coincides with the midpoint of the magnets 33, 34. If the rotor 30 is a two-stage skewed rotor, the small diameter portion 45 can hold more than half of the magnets 33, 34, so that a single rotor cover 40 can hold the magnets 33, 34 in a balanced manner while suppressing tilt.

Both circumferential ends of each magnet 33, 34 are chamfered. This reduces the step between the first stage magnet 33 and the second stage magnet 34, reducing snagging when the rotor cover 40 is pressed in, making assembly easier.

Other Embodiments
In the above embodiment, a tapered portion is provided at an axial end of the rotor cover. In other embodiments, a tapered portion may not be provided. In the above embodiment, the magnet is held to the rotor by the rotor cover without adhesive. In other embodiments, the magnet may be adhered to the rotor using an adhesive member such as an adhesive, and then held by the rotor cover.

In the above embodiment, each stage is composed of eight magnets. In other embodiments, the number of magnets in each stage may be other than eight. The rotor in the above embodiment is a two-stage skewed rotor. In other embodiments, the number of stages in the skewed rotor may be three or more.

In the above embodiment, the rotating electric machine is applied to an electric power steering device. In other embodiments, the rotating electric machine may be applied to a device other than an electric power steering device, such as a steering device or a reaction device in a steer-by-wire system. As described above, the present invention is not limited to the above embodiment, and can be implemented in various forms without departing from the spirit of the invention.

REFERENCE SIGNS LIST 10: Drive device 30: Rotor 31, 32: Rotor core 33, 34: Magnet 40: Rotor cover 41: First large diameter portion 42: Second large diameter portion 45: Small diameter portion 80: Motor 840: Stator 870: Shaft

Claims (3)

A housing (830);
A stator (840) fixed non-rotatably to the housing;
A shaft (870) rotatably supported in the housing;
a rotor (30) having a rotor core (31, 32) and multiple stages of magnets (33, 34) provided radially outward of the rotor core and shifted in a circumferential direction according to a skew angle, the rotor (30) rotating integrally with the shaft;
a rotor cover (40) having a first large diameter portion (41) provided at one end in the axial direction, a second large diameter portion (42) provided at the other end in the axial direction, and a small diameter portion (45) provided between the first large diameter portion and the second large diameter portion and having a smaller diameter than the first large diameter portion and the second large diameter portion at an intermediate portion between adjacent magnets in the axial direction, the rotor cover (40) being press-fitted and fixed to the radial outside of the rotor;
Equipped with
the magnet is fixed to the rotor core by the rotor cover,
A rotating electric machine in which both circumferential ends of each of the magnets leave an upright surface that rises non-arcuately from the rotor core side, and when the rotor is projected in the axial direction, the end of the magnet fixed to one of the rotor cores is formed inside the outer diameter of the magnet fixed to the other rotor core . The rotating electric machine according to claim 1, wherein the circumscribing circle radius of the rotor is φR0, the minimum radius of the small diameter portion is φR1, and the minimum radius of the first large diameter portion and the second large diameter portion is φR2, and φR1<φR2≦φR0. The rotating electric machine according to claim 1 or 2, wherein the axial length of the small diameter portion is at least half the axial length of the rotor.

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