Rotating electric machine

Abstract

In a rotating electric machine in which the rotor is mounted to be axially movable relative to the stator, the present invention provides a rotating electric machine that can suppress the increase in iron loss while suppressing manufacturing costs, even when the rotor is withdrawn from the stator. [Solution] A rotating electric machine comprising a rotating shaft, a rotor having permanent magnets that apply rotational force to the rotating shaft and is mounted so as to be axially movable relative to the rotating shaft, a moving mechanism for moving the rotor in the axial direction, and a stator having coils and being arranged radially with a gap with the outer circumference of the rotor, wherein the stator comprises a first electromagnetic steel sheet and a second electromagnetic steel sheet laminated in the direction of the rotor withdrawal of the first electromagnetic steel sheet, and the second electromagnetic steel sheet has lower iron loss than the first electromagnetic steel sheet.

Description

Technical Field

[0001] The present invention relates to a rotating electrical machine.

Background Art

[0002] In recent years, a rotating electrical machine capable of obtaining output characteristics according to the rotation speed by adjusting the output at low speed and high speed of the rotating electrical machine is known. Specifically, a rotating electrical machine capable of changing the axial relative position of the rotor with respect to the stator according to the rotation speed of the rotating electrical machine is known. Although various structures of such a rotating electrical machine are known, for example, a stator in which a coil is wound around a stator core, a magnet is embedded inside a rotor core made of a magnetic material, and the rotor rotates facing radially outward or radially inward with respect to the stator, and an actuator that changes the axial relative position of the rotor with respect to the stator and adjusts the magnetic flux of the magnet that intersects with the coil, and the rotor is provided with a magnetic flux shielding portion that shields the axial magnetic flux at least on the stator side in the radial direction with respect to the magnet.

[0003] According to such a rotating electrical machine, it is possible to prevent the magnetic flux from leaking axially from the exposed portion of the rotor when the rotor is axially exposed from the stator to the stator.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with conventional rotating electric machines, while it is possible to prevent magnetic flux from leaking axially from the exposed portion of the rotor to the stator when the rotor is exposed axially from the stator, as shown in Figure 4, the direction of the magnetic flux changes from the exposed portion of the rotor 120 to the stator 110, causing it to flow from the axial direction of the stator core 110, which increases eddy current C. This increase in eddy current C leads to an increase in iron loss.

[0006] Furthermore, while the rotating electric machine described in Patent Document 1 prevents magnetic flux from leaking from the exposed portion of the rotor to the stator by providing a magnetic flux shielding section on the rotor, it has the problem that it does not address the increase in iron loss due to the increase in eddy currents caused by the change in the direction of the magnetic flux from the exposed portion.

[0007] Another possibility is to construct the stator using low-iron-loss electrical steel sheets, but constructing the entire stator core from low-iron-loss material would increase costs.

[0008] The present invention has been made to solve the above problems, and aims to provide a rotating electric machine in which the rotor is mounted to the stator so as to be movable in the axial direction, that can suppress the increase in iron loss while suppressing manufacturing costs, even when the rotor is withdrawn from the stator. [Means for solving the problem]

[0009] The present invention, which solves the above problems, is a rotating electric machine comprising: a rotating shaft; a rotor having permanent magnets that applies rotational force to the rotating shaft and is assembled to be axially movable with respect to the rotating shaft; a moving mechanism for moving the rotor in the axial direction; and a stator having coils and being arranged with a radial gap with respect to the outer circumference of the rotor, wherein the stator comprises a first electromagnetic steel sheet and a second electromagnetic steel sheet laminated in the direction of the rotor withdrawal of the first electromagnetic steel sheet, and the second electromagnetic steel sheet has lower iron loss than the first electromagnetic steel sheet.

[0010] Furthermore, the rotating electric machine according to the present invention comprises a stator having coils, a rotor having permanent magnets and being arranged radially with a gap between it and the outer circumference of the stator, and a moving mechanism for moving the stator in the axial direction of the rotor's rotation axis, wherein the stator comprises a first electromagnetic steel sheet and a second electromagnetic steel sheet laminated on the side of the first electromagnetic steel sheet opposite to the direction of extraction from the stator, and the second electromagnetic steel sheet has lower iron loss than the first electromagnetic steel sheet. [Effects of the Invention]

[0011] According to the rotating electric machine of the present invention, the stator comprises a first electromagnetic steel sheet and a second electromagnetic steel sheet laminated on the first electromagnetic steel sheet in the direction of withdrawal of the rotor or stator, or on the opposite side of the withdrawal direction. Since the second electromagnetic steel sheet has lower iron loss than the first electromagnetic steel sheet, even when the rotor is withdrawn from the stator, or the stator is withdrawn from the rotor, the increase in eddy currents due to the magnetic flux from the exposed portion of the rotor can be suppressed, thereby reducing iron loss.

[0012] Furthermore, since the amount of low-iron-loss material used can be reduced, the increase in manufacturing costs for rotating electric machines can be suppressed. [Brief explanation of the drawing]

[0013] [Figure 1] A cross-sectional view of a rotating electric machine according to an embodiment of the present invention. [Figure 2] Enlarged view of section A in Figure 1. [Figure 3] A schematic diagram showing the rotor of a rotating electric machine according to an embodiment of the present invention in a withdrawn state. [Figure 4] A schematic diagram showing a conventional rotating electric machine with its rotor removed. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the rotating electric machine according to the present invention will be described with reference to the drawings. Note that the following embodiments are not intended to limit the inventions described in each claim, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0015] Figure 1 is a cross-sectional view of a rotating electric machine according to an embodiment of the present invention, Figure 2 is an enlarged view of part A in Figure 1, and Figure 3 is a schematic diagram showing the state in which the rotor of the rotating electric machine according to an embodiment of the present invention has been withdrawn.

[0016] The rotating electric motor 1 according to this embodiment is suitably used as a so-called in-wheel motor incorporated into the wheels of automobiles and the like. The wheel has a tire incorporated into the wheel, and the rotating electric motor 1 is built into the wheel.

[0017] As shown in Figure 1, the rotating electric machine 1 according to this embodiment comprises a stator 10 and a housing 40 that houses a rotor 20 rotatable relative to the stator 10. The stator 10 is positioned with a radial gap between it and the outer circumference of the rotor 20. The rotor 20 comprises a rotating shaft 22 and bolts 23 that rotate together with the rotating shaft 22. A wheel (not shown) is attached to the bolts 23.

[0018] As shown in Figure 3, the stator 10 has coils 12, which are made by winding wire around a stator core 11, arranged in the circumferential direction. The stator core 11 is made up of a first electromagnetic steel sheet 13 and a second electromagnetic steel sheet 14 stacked along the axial direction of the rotation axis 22. The second electromagnetic steel sheet 14 is positioned on the side of the first electromagnetic steel sheet 13 that is in the withdrawal direction D of the rotor 20, which will be described later. Here, the withdrawal direction D of the rotor 20 refers to the direction in which the rotor 20 is pulled out of the stator 10 by the moving mechanism 50.

[0019] The first electromagnetic steel sheet 13 is preferably a conventionally well-known electromagnetic steel sheet. The second electromagnetic steel sheet 14 is configured to have lower iron loss than the first electromagnetic steel sheet 13. For example, it is preferable to use a low iron loss material with lower iron loss than the electromagnetic steel sheet used for the first electromagnetic steel sheet 13 for the second electromagnetic steel sheet 14. Further, the second electromagnetic steel sheet 14 is not limited to the low iron loss material. For example, powder cores, amorphous materials, etc. are preferably used. In addition, an electromagnetic steel sheet similar to the first electromagnetic steel sheet 13 may be used and formed thinner than the first electromagnetic steel sheet 13.

[0020] Also, the first electromagnetic steel sheet 13 and the second electromagnetic steel sheet 14 can be joined by various conventionally well-known joining methods. For example, it is preferable that they are fixed to each other by adhesion using an adhesive, caulking, or the like.

[0021] As shown in FIG. 1, the rotor 20 includes a rotor main body 24 assembled to the moving mechanism 50 and permanent magnets 21 provided on the outer side in the circumferential direction of the rotor main body 24 and facing the stator 10. A plurality of permanent magnets 21 are arranged along the circumferential direction so that the polarities of the opposing surfaces with the stator 10 are reversed from each other as N·S·N.... Further, the stator 10 is provided with cooling means (not shown) for cooling.

[0022] As shown in FIG. 2, the moving mechanism 50 includes a spline nut member 53 assembled to be axially movable in a spline groove 31a formed along the axial direction on the rotating shaft 22, a screw shaft member 51 assembled to the outer periphery of the spline nut member 53 via a bearing 56, and a screw nut member 52 rotatably assembled to the screw shaft member 51.

[0023] The rotating shaft 22 is a member that rotates about the axis together with the rotor 20 and is rotatably supported by a rotary bearing 57 attached to the housing 40.

[0024] The screw shaft member 51 has a helical screw groove formed on its outer circumference and is hollow in the center, through which a bearing 56, a spline nut member 53, and a rotating shaft 31 can be inserted. The screw shaft member 51 also has a guide portion 59 that extends along the axial direction. The screw nut member 52 is composed of multiple (for example, two) parts along the axial direction. However, the screw nut member 52 may be formed as a single unit without being divided along the axial direction.

[0025] The guide portion 59 is preferably formed in pairs along the horizontal direction. The guide portion 59 is guided by a cam follower 58, which is a sliding portion attached to the housing 40, and constitutes a rotation prevention means.

[0026] The screw nut member 52 has a screw groove and a corresponding nut-side screw groove formed on its inner circumferential surface, and rolling elements 54 are arranged spirally between the screw groove and the nut-side screw groove. In addition, a gear section (not shown) that meshes with the drive motor 60 is attached to the end of the screw nut member 52.

[0027] The spline nut member 53 is a cylindrical member having a nut-side spline groove formed therein that corresponds to the spline groove 31a, and the rotor body 24 is assembled to its outer circumferential surface. Multiple rolling elements 55 are arranged axially between the spline groove 31a and the nut-side spline groove.

[0028] The cam follower 58 is a bearing with a shaft, and has a shaft fixed to the housing 40 and a bearing rotatably mounted around the shaft. The outer surface of the bearing abuts against the upper surface of the guide portion 59 described above, and guides the axial movement of the screw shaft member 51 via the guide portion 59. Preferably, the guide portion 59 is formed in a pair in a direction horizontal to the ground, and by being arranged horizontally in this way, when the vehicle is subjected to an impact from the ground, the guide portion 59 and the cam follower 58 can appropriately load the impact.

[0029] Next, the operation of the rotating electric machine 1 according to this embodiment will be described. When current is passed through the coil 12 of the stator 10, the rotor 20 rotates relative to the stator 10 due to interaction with the magnetic field provided by the permanent magnets 21 arranged on the rotor 20.

[0030] In this case, when the rotor 20 is inserted as far as possible into the stator 10, the contact area between the stator 10 and the rotor 20 is at its largest, and the output characteristics of the rotating electric machine 1 become high torque, low rotation type. This state is most suitable for situations where high torque is required but the speed is slow, such as when starting an automobile.

[0031] Furthermore, in this state, the back electromotive force increases, so power supply to the stator 10 is stopped, and power can be efficiently generated during deceleration to brake the wheels, making it possible to operate as a highly efficient regenerative brake.

[0032] Next, the operation of the moving mechanism 50 will be explained. Since the rotor body 24 is attached to the spline nut member 53, the rotation of the rotor body 24 is transmitted to the rotating shaft 22 via the spline nut member 53 and the spline groove 31a. In addition, since a bearing 56 is interposed between the spline nut member 53 and the screw shaft member 51, the rotation of the rotor 20 is not transmitted to the screw shaft member 51, but is blocked by the bearing 56.

[0033] The drive motor 60 is driven, and the gear portion attached to the screw nut member 52 is rotated, thereby moving the screw shaft member 51 in the axial direction. At this time, since the spline nut member 53 and the rotating shaft 22 are assembled via the spline groove 31a, the spline nut member 53 moves axially together with the rotor body 24.

[0034] At this time, as shown in Figure 3, by pulling the rotor 20 out of the stator 10 in the pulling direction D, the area of ​​contact between the permanent magnets 21 of the rotor 20 and the stator 10 becomes the smallest. In this state, the back electromotive force decreases, and the output characteristics of the rotating electric machine 1 become low torque, high rotation type. In this state, with the rotor 20 pulled out of the stator 10 in the pulling direction D, the output characteristics are best suited for high-speed operation where torque is not required.

[0035] Furthermore, in this state, as shown in Figure 3, the magnetic flux φ emitted from the permanent magnets 21 of the rotor 20 flows in a curved manner. However, since a second electromagnetic steel sheet 14 made of low iron loss material is arranged on the side of the stator core 11 that receives the magnetic flux φ, it is possible to reduce eddy current losses even when the direction of the flow of the magnetic flux φ changes, thereby enabling higher efficiency and higher output of the rotating electric machine 1 according to this embodiment.

[0036] Furthermore, compared to constructing the entire stator core 11 from low-iron-loss material, by placing a second electromagnetic steel sheet 14 made of low-iron-loss material only on the pull-out direction D side of the stator core 11, it is possible to minimize the cost increase and torque reduction caused by using low-iron-loss material, thereby achieving both cost reduction and higher output than before.

[0037] Furthermore, since the moving mechanism 50 can move the rotor 20 steplessly in the axial direction, the position of the rotor 20 can be adjusted to a position corresponding to the required output characteristics by controlling the amount of rotation of the drive motor 60.

[0038] In the embodiment described above, the rotating electric machine 1 has been described in cases where rolling elements 54 and 55 are interposed between the screw shaft member 51 and the screw nut member 52, and between the spline groove 31a and the spline nut member 53, and in cases where a rolling guide is applied in which the guide portion 59 is guided by a cam follower 58. However, these may also be sliding guides in which the members are in direct sliding contact with each other without the use of rolling elements. Furthermore, although the case where a pair of guide portions 59 are formed in the horizontal direction has been described, the number of guide portions 59 may be two or more, for example, multiple guide portions may be formed at equal intervals in the circumferential direction of the screw shaft member 51. In addition, although the case where a pair (two) of guide portions 59 are formed on the screw shaft member 51 has been described, there may be two or more guide portions 59 formed on the screw shaft member 51. In this case, it is preferable that the cam follower 58 guides at least two of the guide portions 59 from the same direction. In this case, it is preferable that the two guide portions 59 are arranged symmetrically around the axis.

[0039] Furthermore, although the rotating electric machine 1 according to the present embodiment described above is a so-called inner rotor type rotating electric machine in which the rotor 20 is arranged on the inner circumference side of the stator 10 and the rotor 20 is moved along the axial direction of the rotating shaft 22, it may also be applied to a so-called outer rotor type rotating electric machine in which the rotor is arranged on the outer circumference side of the stator and the stator is moved along the axial direction. When applied to an outer rotor type rotating electric machine, it is preferable that the second electromagnetic steel sheet, which has lower iron loss than the first electromagnetic steel sheet, is arranged on the opposite side of the stator's pull-out direction. It is clear from the description of the claims that such modified or improved forms may also be included in the technical scope of the present invention. [Explanation of Symbols]

[0040] 1 Rotating electric machine, 10 Stator, 12 Coil, 13 First electrical steel sheet, 14 Second electrical steel sheet, 20 Rotor, 22 Rotating shaft, 50 Moving mechanism, D Pulling direction.

Claims

1. The axis of rotation and A rotor having a permanent magnet, which applies rotational force to the rotating shaft and is mounted so as to be axially movable relative to the rotating shaft, A moving mechanism for moving the rotor in the axial direction, A rotating electric machine having a stator having a coil and being arranged radially with a gap between it and the outer circumference of the rotor, The stator comprises a first electromagnetic steel sheet and a second electromagnetic steel sheet laminated in the direction of the rotor withdrawal of the first electromagnetic steel sheet. A rotating electric machine characterized in that the second electrical steel sheet has lower iron loss than the first electrical steel sheet.

2. In the rotating electric machine described in claim 1, A rotating electric machine characterized in that the second electrical steel sheet is formed of a low-iron-loss material which has lower iron loss than the first electrical steel sheet.

3. In the rotating electric machine described in claim 1, The rotating electric machine is characterized in that the second electromagnetic steel sheet is made of a compacted magnetic core or amorphous material.

4. In the rotating electric machine described in claim 1, The rotating electric machine is characterized in that the second electrical steel sheet has a thinner axial thickness than the first electrical steel sheet.

5. A stator having a coil, The rotor comprises a permanent magnet and is positioned radially away from the outer circumference of the stator, A rotating electric machine having a moving mechanism for moving the stator in the axial direction of the rotor's rotation axis, The stator comprises a first electromagnetic steel sheet and a second electromagnetic steel sheet laminated on the side of the first electromagnetic steel sheet opposite to the direction in which the stator is pulled out. A rotating electric machine characterized in that the second electrical steel sheet has lower iron loss than the first electrical steel sheet.

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