Rotating electric machines

Abstract

To provide a rotary electric machine which allows improvement in assemblability of a rotor through reduction of the total number of magnets, while suppressing a rise in suction force caused by corners of a stair-like shape formed by a stator and a rotor.SOLUTION: A rotary electric machine comprises: a stator having a stator core around which an armature coil is wound; and a rotor which is rotatably disposed via a predetermined radial gap from the stator, and which has a magnet and a rotor core facing the stator. Facing surfaces of the rotor and the stator core has a stair-like shape in cross section which radially expands along a rotation axis direction of the rotor. The magnet is inserted along the rotation axis direction of the rotor into the rotor core.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine. [Background technology]

[0002] Conventionally, there have been known rotating electric machines that can obtain output characteristics according to the rotation speed by adjusting the output at low and high speeds of the rotating electric machine. Various structures of such rotating electric machines are known, and for example, there is known a rotating electric machine that has a stator, a rotor that is rotatably provided coaxially with the stator, and a moving means that changes the axial position of the stator relative to the rotor, and that has an armature coil and a core provided on the stator, and a magnet that faces the core.

[0003] With such a rotating electric machine, during low-speed rotation, the stator is moved axially by a movement mechanism so that the opposing area between the stator and rotor is increased, thereby increasing the effective magnetic flux passing through the stator and achieving high torque, and during high-speed rotation, the stator is moved so that the opposing area between the stator and rotor is reduced, thereby reducing the effective magnetic flux passing through the stator, thereby achieving high-speed rotation.

[0004] Furthermore, various configurations are known to further increase the variable range of the output characteristics as the stator moves along the axial direction. For example, as described in Patent Document 1, the opposing surfaces of the stator and magnet are configured in a stepped shape to reduce the opposing area of the stator and magnet as the stator moves, thereby effectively reducing the magnetic flux acting on the stator as the stator moves along the axial direction, thereby increasing the variable range of the output characteristics. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-141900 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional rotating electric machines, when the rotor magnets are formed in a stepped shape and the stator is moved to insert or remove from the rotor using a moving mechanism, it has been found that the attractive force increases when the corners of the stator and magnet face each other during the insertion or removal operation.

[0007] To suppress this increase in attractive force, a conventional method is to tape the corners of the rotor magnets to prevent the corners of the stator and magnets from coming close to each other. Another known rotor structure is the rotor core structure shown in Figure 10, in which multiple magnets 101 with tapered surfaces are attached to a rotor core with a stepped inner diameter surface.

[0008] However, with conventional structures, complex processing was required to manufacture magnets with tapered surfaces, and because a large number of magnets had to be attached, there were issues such as large variations in magnetic force and the time and effort required to adjust the position when attaching the magnets.

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide a rotating electric machine that has a moving mechanism that can move either a stator or a rotor having facing surfaces in a stepped shape so as to insert or remove one of them, but that can suppress the increase in attractive force caused by the facing corners of the stepped shapes of the stator and rotor, reduce the total number of magnets, and improve the assembly ease of the rotor. [Means for solving the problem]

[0010] The rotating electric machine according to the present invention, which solves the above-mentioned problems, comprises a stator having a stator core wound with an armature coil, and a rotor which is rotatably arranged with a predetermined gap in the radial direction relative to the stator and has a magnet and a rotor core which faces the stator, wherein the mutually facing surfaces of the rotor and the stator core are formed in a stepped cross section which expands radially along the direction of the rotation axis of the rotor, and the magnet is inserted into the rotor core along the direction of the rotation axis of the rotor. The axial intervals of the stepped cross-section of the rotor are formed at unequal intervals different from the axial intervals of the stepped cross-section of the stator core. It is characterized by the following.

[0011] Furthermore, a rotating electric machine according to the present invention that solves the above-mentioned problems comprises a stator having a stator core wound with an armature coil, and a rotor that is arranged to be freely rotatable relative to the stator via a predetermined radial gap and has a magnet and a rotor core that faces the stator, wherein the opposing surfaces of the rotor and the stator core are formed into a cross-sectional stepped shape that extends radially along the direction of the rotor's rotational axis, and the axial spacing of the cross-sectional stepped shape of the rotor is formed at unequal intervals that are different from the axial spacing of the cross-sectional stepped shape of the stator core. [Effects of the Invention]

[0012] The rotating electric machine of the present invention has a rotor core structure in which a plate-shaped magnet with an arc-shaped cross section is inserted into a rotor core whose inner diameter surface is formed in a stepped shape, which makes it easier to manufacture the magnets and reduces the total number of magnets, thereby reducing assembly labor. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an axial cross-sectional view of a rotating electric machine according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional perspective view showing a cross-sectional state of a stator and a rotor of a rotating electric machine according to an embodiment of the present invention; [Figure 3] 1 is a cross-sectional perspective view showing a cross-sectional state of a rotor core of a rotating electrical machine according to an embodiment of the present invention; [Figure 4]1 is a perspective view showing a method for attaching a magnet to a rotating electric machine according to an embodiment of the present invention; [Figure 5] 1 is a cross-sectional perspective view showing a cross-sectional state of a stator of a rotating electric machine according to an embodiment of the present invention; [Figure 6] FIG. 3 is an enlarged cross-sectional view of part A in FIG. 2. [Figure 7] 6 is a graph showing the attractive force of a rotating electric machine according to an embodiment of the present invention and a conventional rotating electric machine. [Figure 8] 6 is a graph showing torque of an embodiment of the present invention and a conventional rotating electric machine. [Figure 9] 6 is a graph showing changes over time in torque of an embodiment of the present invention and a conventional rotating electric machine; [Figure 10] FIG. 10 is a perspective view showing a method for attaching a magnet in a conventional embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of a rotating electrical machine according to the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0015] Figure 1 is an axial cross-sectional view of a rotating electric machine according to an embodiment of the present invention, Figure 2 is a cross-sectional oblique view showing the cross-sectional state of the stator and rotor of a rotating electric machine according to an embodiment of the present invention, Figure 3 is a cross-sectional oblique view showing the cross-sectional state of the rotor core of a rotating electric machine according to an embodiment of the present invention, Figure 4 is a cross-sectional oblique view showing a method of mounting magnets for a rotating electric machine according to an embodiment of the present invention, Figure 5 is a cross-sectional oblique view showing the cross-sectional state of the stator of a rotating electric machine according to an embodiment of the present invention, Figure 6 is an enlarged cross-sectional view of part A in Figure 2, and Figure 10 is a perspective view showing a method of mounting magnets in a conventional example.

[0016] 1, a rotating electric machine 10 according to this embodiment is suitable for use as a so-called in-wheel motor that is incorporated into a wheel 1 of an automobile or the like. The wheel 1 is attached to the body of the automobile and includes an axle 4 that rotatably supports the wheel 1, a wheel 3, and a tire 2 made of an elastic material such as rubber attached to the outer circumferential surface of the wheel 3.

[0017] The rotating electric machine 10 according to this embodiment is disposed inside the wheel 3, and by transmitting the rotational force of the rotating electric machine 10 to the wheel 3, a driving force for the automobile to which the rotating electric machine 10 is attached is generated.

[0018] The wheel housing 15 is a pair of hollow disk-shaped members that are assembled to sandwich the rotor core 13 in the axial direction. A moving mechanism 20, which will be described later, is housed inside the wheel housing 15. Furthermore, the wheel housing 15 is assembled to be rotatable about the axle 4 by hub members 16 that are assembled to both ends in the axial direction.

[0019] Furthermore, the stator 11 is attached to a movement mechanism 20 that is movable in the axial direction of the axle 4. The movement mechanism 20 is provided with the axle 4 arranged coaxially with the central axis of rotation of the stator 11, and includes a ball spline nut member 24 non-rotatably attached to the outer circumferential surface of the axle 4, and a ball screw nut member 25 rotatably attached to the outer circumferential surface of the axle 4.

[0020] The ball screw nut member 25 is accommodated in the wheel housing 15, and is configured so that a rotational force is applied to it by a drive motor (not shown) serving as a drive source having a gear attached to its output shaft. With this configuration, when the drive motor rotates, the gear attached to the output shaft rotates, and the gear meshes with the outer peripheral surface of the ball screw nut member 25, thereby transmitting the rotational force of the drive motor to the ball screw nut member 25.

[0021] The axle 4 is a hollow shaft with a through hole 21 formed in the axial direction, and has a ball spline groove (not shown) formed along the axial direction on one axial end of the outer surface, and a spiral ball screw groove 23 formed on the other end. The ball spline groove and ball screw groove 23 are formed adjacent to each other so as to overlap near the center of the axle 4.

[0022] A pair of rolling grooves 29, in which rolling elements (described later) can roll, are formed on the outer surface of the axle 4. The rolling grooves 29 are formed along the circumferential direction of the axle 4, and are formed on the axial end side of the axle 4. In other words, the rolling grooves 29 are located closer to the axial end than the ball spline grooves and the ball screw grooves 23, and the ball spline grooves and the ball screw grooves 23 are located between the pair of rolling grooves 29.

[0023] The ball spline nut member 24 is a cylindrical member, and the axle shaft 4 is inserted into the inner periphery of the ball spline nut member 24. Second ball spline grooves corresponding to the ball spline grooves of the axle shaft 4 are formed on the inner periphery of the ball spline nut member 24, and rolling elements (not shown) or the like are interposed between the ball spline grooves and the second ball spline grooves, thereby assembling the ball spline nut member 24 to be movable in the axial direction of the axle shaft 4. The ball spline nut member 24 is also attached to the stator 11.

[0024] Ball screw nut member 25 is an annular member having a spiral second ball screw groove (not shown) formed on its inner periphery that corresponds to ball screw groove 23, and a gear that meshes with a gear attached to the output shaft of the drive motor is attached to its outer periphery. By interposing rolling elements (not shown) between the second ball screw groove and ball screw groove 23, ball screw nut member 25 is rotatably assembled to axle 4.

[0025] In addition, a second rolling groove 33 corresponding to the rolling groove 29 formed on the outer surface of the axle 4 is formed on the inner surface of the insertion hole of the hub member 16 into which the axle 4 is inserted, and a plurality of rolling elements 32 are arranged between the rolling groove 29 and the second rolling groove 33.

[0026] In the rotating electric machine 10 according to this embodiment configured as described above, when the drive motor of the movement mechanism 20 is rotated to rotate the ball screw nut member 25 via a gear attached to the output shaft of the drive motor, the ball screw nut member 25 moves in the axial direction along the ball screw groove 23 formed in the axle 4. The ball screw nut member 25 is assembled to the ball spline nut member 24, and therefore moves in the axial direction together with the stator 11.

[0027] In this way, the rotating electric machine 10 according to this embodiment is capable of moving the stator 11 in the axial direction so as to be inserted into or removed from the rotor 12 by rotating the ball screw nut member 25 using the drive motor of the movement mechanism 20, and therefore the output characteristics can be varied depending on the relative position of the stator 11 with respect to the rotor 12. Note that in this specification, the insertion and removal direction of the stator 11 is defined as the direction in which the stator 11 moves from left to right in Fig. 1 as the extraction direction, and as the direction in which it moves from right to left as the insertion direction.

[0028] As shown in Fig. 2, rotor 12 is rotatably disposed relative to stator 11 via a predetermined gap, and includes rotor core 13 made of a conductive metal or the like, and magnets 14. As shown in Fig. 1, rotor core 13 is assembled in wheel housing 15 attached to wheel 3, and wheel 3 rotates as rotor 12 rotates.

[0029] The surface of rotor core 13 facing stator 11 is formed in a stepped shape that expands radially along the axial direction of stator 11. For example, as shown in Fig. 3, the stepped shape has five steps consisting of a first rotation-side step portion 13a, a second rotation-side step portion 13b, a third rotation-side step portion 13c, a fourth rotation-side step portion 13d, and a fifth rotation-side step portion 13e. The stepped shapes are formed at unequal intervals so that the axial lengths are L1 to L5, respectively. Here, it is preferable that the stepped shape of rotor core 13 is formed so as to expand along the drawing direction.

[0030] 3, rotor core 13 is formed with slits 13f penetrating first rotation-side step portion 13a, second rotation-side step portion 13b, third rotation-side step portion 13c, and fourth rotation-side step portion 13d. Slits 13f are arc-shaped slits corresponding to the cross-sectional shape of magnets 14, and the inner surface of slit 13f located on the outer side in the radial direction is formed to connect with the inner diameter surface of fifth rotation-side step portion 13e.

[0031] The stepped shape of rotor core 13 is preferably formed by stacking a plurality of annular rings with different inner diameters in the direction of the rotation axis, as shown in Fig. 3. Furthermore, the method is not limited to stacking a plurality of annular rings, and the stepped shape may also be formed by, for example, casting or cutting.

[0032] As shown in Fig. 4, magnet 14 is a plate-shaped magnet whose cross section is an arc shape coaxial with rotor 12, and is inserted into slit 13f of rotor core 13. By attaching magnet 14 in this manner, a staircase shape is formed on the inner diameter surface of rotor 12, combining multiple steps formed on rotor core 13 with partially exposed surfaces of magnet 14. Magnets 14 include north-pole magnets 14N and south-pole magnets 14S, which are arranged alternately in the circumferential direction of rotor core 13.

[0033] Here, in this embodiment, a plate-shaped magnet 14 having an arc shape is combined with an arc-shaped slit 13f, but the shapes of the magnet and slit are not limited to this, and the same effect can be obtained by combining a plate-shaped magnet having a linear shape with a linear slit.

[0034] In this way, by forming magnet 14 into a plate shape, it is possible to easily manufacture magnet 14. Furthermore, in the configuration of a conventional rotor, as shown in Fig. 10, multiple magnets 101 are required for one magnetic pole, and position adjustment is required when attaching magnets 101, but in this embodiment, one plate-shaped magnet 14 is inserted into rotor core 13 for one magnetic pole, so the total number of magnets can be reduced, and position adjustment during assembly is no longer necessary, resulting in a reduction in assembly man-hours.

[0035] 4, a groove 17 extending in the axial direction is formed on the surface of rotor core 13 facing stator 11 at a position corresponding to the gap between north-pole magnet 14N and south-pole magnet 14S. This groove 17 forms an air gap between north-pole magnet 14N and south-pole magnet 14S, preventing short-circuiting of magnetic flux.

[0036] 2, the stator 11 has an armature coil 11b wound around a stator core 11a and arranged in the circumferential direction. Note that the armature coil can be wound using any of various conventionally known winding methods.

[0037] As shown in FIG. 5, the stator core 11a includes a plurality of stator core base portions 41 extending radially in the radial direction and around which the armature coils 11b are wound, and flange portions 42 extending circumferentially from the end portions of the stator core base portions 41.

[0038] The surface of the flange 42 facing the rotor core 13 is formed in a stepped shape that expands radially along the axial direction to correspond to the stepped shape of the rotor 12, for example, a three-step shape consisting of a fixed-side first step 42a, a fixed-side second step 42b, and a fixed-side third step 42c. Preferably, this stepped shape is formed with axial lengths L6 to L8 that are approximately equally spaced. Here, like the stepped portion of the rotor core 13, the stepped shape of the flange 42 is preferably formed to expand along the drawing direction.

[0039] The stepped shape of the stator core 11a is preferably formed by stacking a plurality of stator core base segments, each having a different shape of flange 42, in the rotation axis direction, as shown in Fig. 5. Furthermore, the step shape is not limited to stacking a plurality of stator core base segments, and may also be formed by, for example, casting or cutting.

[0040] 6, with such rotor 12 and stator 11, the stepped shape of rotor 12 and the stepped shape of stator 11 have different numbers of steps, and the axial lengths L1 to L5 of the steps of the stepped shape of rotor 12 are different from each other, so that even when stator 11 is moved in the axial direction by movement mechanism 20, it is possible to prevent multiple corners of the steps of the stepped shape of rotor 12 from facing each other at the same time. In this way, by varying the timing at which the corners of the stepped shapes of stator 11 and rotor 12 face each other, it is possible to distribute the timing at which the attractive force increases and reduce the maximum value of the attractive force.

[0041] In this embodiment, the rotor 12 has a five-step stepped shape made up of the rotor core 13 and the magnets 14, and the stator 11 has a three-step stepped shape made up of the stator core 11a, but the number of steps in each step shape may be increased or decreased as appropriate. The magnitude relationship between the number of steps in the rotor 12 and the number of steps in the stator 11 may be reversed, such as by reducing the number of steps in the rotor 12 and increasing the number of steps in the stator 11. In this embodiment, the axial lengths L6 to L8 of the stepped shapes of the stator 11 are formed at approximately equal intervals, but they may be formed at unequal intervals as long as the corners of the stepped shapes of the stator 11 and the rotor 12 face each other at different times during axial movement of the stator 11.

[0042] In this way, by configuring the stator 11 to be axially insertable and removable from the rotor 12 using the movement mechanism 20, when the stator 11 is fully inserted into the rotor 12, the opposing area between the stator 11 and the rotor 12 is largest and the gap between the stator 11 and the rotor 12 is also smallest, so the output characteristics of the rotating electric machine 10 are high torque and low rotation. In this state, the output characteristics are most suitable for situations where high torque is required but the speed is slow, such as when starting a car.

[0043] In addition, in this state, the back electromotive force increases, so the power supply to the armature coil 11b is stopped, and when deceleration occurs to brake the wheel 1, the back electromotive force increases, allowing for efficient power generation, making it possible to function as a highly efficient regenerative brake.

[0044] When the drive motor of the movement mechanism 20 is rotated to apply a rotational force to the ball screw nut member 25, the ball screw nut member 25 rotates along the ball screw groove 23 of the axle 4 and moves in the axial direction. When the movement mechanism 20 is driven in this manner, the stator 11 is pulled out most from the rotor 12, the opposing area between the stator 11 and the rotor 12 is smallest, and the gap between the stator 11 and the rotor 12 is largest. In this state, the back electromotive force decreases, and the output characteristics of the rotating electric machine 10 become low torque and high rotation. With the stator 11 pulled out most from the rotor 12 in this manner, the output characteristics are suitable for high-speed driving when torque is not required.

[0045] The rotating electric machine 10 of this embodiment is held in rotation relative to the axle 4 by hub members 16 arranged at both axial ends of the wheel 3. Therefore, by making the hub members 16 smaller, the weight of the rotating electric machine 10 can be reduced, and as a result of the weight reduction, the time required to reach the required rotation speed can be shortened, thereby improving response performance.

[0046] Furthermore, in the rotating electric machine 10 according to this embodiment, the rotating shaft and the drive shaft are arranged coaxially, which makes it possible to reduce the size of the rotating electric machine 10. Furthermore, in addition to the deceleration effect provided by the ball screw nut member 25 and the ball screw groove 23 formed on the outer surface of the axle 4, when the stator 11 is moved in the axial direction by the movement mechanism 20, it is possible to suppress an increase in the attractive force that opposes the force in the movement direction, so it is possible to reduce the output of the drive motor, and by reducing the size of the drive motor, it is possible to further reduce the size of the rotating electric machine 10.

[0047] Furthermore, since the movement mechanism 20 moves the stator 11 using the ball screw nut member 25 and the ball spline nut member 24, it is possible to control the movement of the stator 11 with a small amount of energy. Also, since the amount of movement by the movement mechanism 20 is controlled by the amount of rotation of the ball screw nut member 25, it is possible to drive the rotating electric machine 10 with the most suitable output characteristics by arbitrarily setting the position of the stator 11 according to the required output characteristics.

[0048] Next, the effects of the present invention will be confirmed by referring to the results of measuring the attractive force and torque of the rotating electric machine 10 according to this embodiment and a conventional rotating electric machine.

[0049] 7 is a graph showing the relationship between the amount of axial movement (hereinafter referred to as the withdrawal amount) of the stator 11 relative to the rotor 12 and the attractive force. In this measurement, the state in which the stator 11 is fully inserted into the rotor 12 is set as the withdrawal amount of 0 mm, and the stator 11 is gradually moved in the axial direction so as to be withdrawn from the rotor 12, and the attractive force is measured.

[0050] 7, it can be seen that the maximum value of the attractive force is lower in the measured values of the rotating electric machine 10 according to this embodiment than in the measured values of the conventional rotating electric machine. Furthermore, the range between the minimum and maximum attractive force values is narrower in the measured values of the rotating electric machine 10 according to this embodiment than in the measured values of the conventional rotating electric machine, and it can be seen that a more stable attractive force is generated that changes little depending on the withdrawal amount.

[0051] This confirmed that the feature of the present invention, in which the timing at which each corner of the step-shaped difference in the rotor 12 faces each corner of the step-shaped difference in the stator 11 differs from each other, has the effect of dispersing the timing at which the attractive force increases and reducing the maximum value of the attractive force.

[0052] FIG. 8 is a graph showing the relationship between the torque and the withdrawal amount of the stator 11, and FIG. 9 is a graph showing the change in torque over time when the stator 11 is at a position where the withdrawal amount is 0 mm.

[0053] 8 and 9, it can be seen that the torque of the rotating electric machine 10 according to this embodiment is equivalent to the torque of a conventional rotating electric machine. This confirms that the configuration of the rotor 12 according to this embodiment, in which the magnets 14 are inserted inside the rotor core 13 formed in a stepped shape and the magnets 14 are partially exposed, does not affect torque performance and can maintain performance equivalent to that of a conventional rotor configuration in which the magnets are attached in a stepped shape and the surface facing the stator is entirely magnetized.

[0054] In the above-described embodiment, the axle 4, the ball spline nut member 24, and the ball screw nut member 25 are assembled via rolling elements, but these members may be assembled so that they slide relative to each other without the rolling elements. Also, in the above-described rotating electric machine 10 according to the present embodiment, the rotating electric machine 10 according to the present embodiment is described as being applied to an automobile wheel 1, but its use is not limited to automobiles, and it may also be applied to, for example, a wind power generator, a press machine, etc.

[0055] Furthermore, although the rotating electric machine 10 according to this embodiment has been described as having a moving mechanism and allowing the stator to be inserted and removed from the rotor in the direction of the rotation axis, the present invention can also be applied to rotating electric machines that do not have such a moving mechanism. It is clear from the claims that such modified or improved embodiments are also included within the technical scope of the present invention. [Explanation of symbols]

[0056] 4 axle, 10 rotating electric machine, 11 stator, 11a stator core, 11b armature coil, 12 rotor, 13 rotor core, 13f slit, 14 magnet, 20 moving mechanism.

Claims

1. A rotating electric machine including a stator having a stator core wound with an armature coil, and a rotor rotatably disposed with respect to the stator via a predetermined radial gap, the rotor having a magnet and a rotor core facing the stator, the rotor and the stator core have opposing surfaces each having a stepped cross section that extends radially along the rotational axis of the rotor; the magnet is inserted into the rotor core along the rotation axis direction of the rotor, a rotating electric machine, characterized in that the axial intervals of the stepped cross section of the rotor are formed at unequal intervals different from the axial intervals of the stepped cross section of the stator core;

2. 2. The rotating electric machine according to claim 1, a step-shaped cross section of the rotor facing the stator core, the magnets being exposed in part of the step-shaped cross section of the rotor;

3. 3. The rotating electric machine according to claim 1, The rotating electric machine is characterized in that the stator is attached to a moving mechanism that is movable in the direction of the rotation axis.

4. A rotating electric machine including a stator having a stator core wound with an armature coil, and a rotor rotatably disposed with respect to the stator via a predetermined radial gap, the rotor having a magnet and a rotor core facing the stator, the rotor and the stator core have opposing surfaces each having a stepped cross section that extends radially along the rotational axis of the rotor; a rotating electric machine, characterized in that the axial intervals of the stepped cross section of the rotor are formed at unequal intervals different from the axial intervals of the stepped cross section of the stator core;

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