JP7718896B2 - rotating electrical machines - Google Patents

Description

The present invention relates to a rotating electric machine.

Conventionally, rotating electric machines are known that can obtain output characteristics according to the rotational speed by adjusting the output of the rotating electric machine at low and high speeds. Various structures of such rotating electric machines are known, but one example is a rotating electric machine that has a stator, a rotor that is rotatable coaxially with the stator, and a moving means that changes the axial position of the stator relative to the rotor, with an armature coil and core provided on the stator, and a magnet provided facing the core.

With this type of rotating electric machine, during low-speed rotation, the stator is moved axially by a movement mechanism to increase the opposing area between the stator and rotor, thereby increasing the effective magnetic flux passing through the stator and achieving high torque. During high-speed rotation, the stator is moved to reduce the opposing area between the stator and rotor, thereby reducing the effective magnetic flux passing through the stator, thereby achieving high-speed rotation.

In addition, various configurations are known for further increasing the range of variation in output characteristics as the stator moves along the axial direction. For example, as described in Patent Document 1, the surfaces where the stator and magnet face each other are configured in a stepped pattern to reduce the area where the stator faces the magnet as the stator moves, effectively reducing the magnetic flux acting on the stator as the stator moves along the axial direction, thereby increasing the range of variation in output characteristics.

JP 2008-141900 A

However, with conventional rotating electric machines, when the rotor magnets are formed in a stepped pattern and the stator is moved relative to the rotor using a movement mechanism to insert or remove it, 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.

To prevent 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.

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

The present invention was made to solve the above-mentioned problems, and aims to provide a rotating electric machine that has a movement mechanism that can move either a stator or a rotor, which have facing surfaces in a stepped shape, so as to insert or remove one of them, while suppressing the increase in attractive force caused by the corners of the stepped shapes of the stator and rotor facing each other, reducing the total number of magnets, and improving the assembly of the rotor.

The rotating electric machine of the present invention, which solves the above-mentioned problems, comprises a stator having a stator core wound with an armature coil, and a rotor arranged to be freely rotatable relative to the stator via a predetermined radial gap, and having a magnet and a rotor core facing 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, the magnets are inserted into the rotor core 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 .

The rotating electric machine of the present invention, which solves the above-mentioned problems, includes a stator having a stator core wound with an armature coil, and a rotor rotatably arranged with a predetermined radial gap relative to the stator and having a magnet and a rotor core facing the stator, wherein the opposing surfaces of the rotor and the stator core are formed with a stepped cross section that extends radially along the rotor's rotational axis, and the axial spacing of the stepped cross section of the rotor is formed at unequal intervals that differ from the axial spacing of the stepped cross section of the stator core.

The rotating electric machine of the present invention has a rotor core structure in which plate-shaped magnets with arc-shaped cross sections are inserted into a rotor core with a stepped inner surface. This facilitates magnet manufacturing and reduces the total number of magnets, thereby reducing assembly man-hours.

1 is an axial cross-sectional view of a rotating electric machine according to an embodiment of the present invention; 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; 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; 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; 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; FIG. 3 is an enlarged cross-sectional view of part A in FIG. 2 . 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. 6 is a graph showing torque of an embodiment of the present invention and a conventional rotating electric machine. 6 is a graph showing changes over time in torque of an embodiment of the present invention and a conventional rotating electric machine; FIG. 10 is a perspective view showing a method for attaching a magnet in a conventional embodiment.

Embodiments of a rotating electric machine according to the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

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 perspective 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 perspective 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 perspective 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 perspective 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 embodiment.

As shown in FIG. 1, the rotating electric machine 10 according to this embodiment is suitable for use as a so-called in-wheel motor incorporated into the 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 periphery of the wheel 3.

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, it generates driving force for the automobile to which the rotating electric machine 10 is attached.

The wheel housing 15 is a pair of hollow, disk-shaped members assembled to sandwich the rotor core 13 in the axial direction. The wheel housing 15 also houses the movement mechanism 20 (described below). Furthermore, the wheel housing 15 is rotatably mounted to the axle 4 by hub members 16 assembled to both axial ends.

The stator 11 is also attached to a movement mechanism 20 that can move in the axial direction of the axle 4. The movement mechanism 20 is arranged so that the axle 4 is coaxial with the central axis of rotation of the stator 11, and includes a ball spline nut member 24 non-rotatably attached to the outer peripheral surface of the axle 4, and a ball screw nut member 25 rotatably attached to the outer peripheral surface of the axle 4.

The ball screw nut member 25 is housed within the wheel housing 15 and is configured to receive rotational force from a drive motor (not shown) that serves as a drive source and has 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 surface of the ball screw nut member 25, transmitting the rotational force of the drive motor to the ball screw nut member 25.

The axle 4 is a hollow shaft with an axial through-hole 21 formed therein. One axial end of the outer surface is formed with a ball spline groove (not shown) extending axially, and the other end is formed with a spiral ball screw groove 23. 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.

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

The ball spline nut member 24 is a cylindrical member, the inner circumference of which is inserted the axle 4. Second ball spline grooves corresponding to the ball spline grooves of the axle 4 are formed on the inner surface of the ball spline nut member 24, and rolling elements (not shown) are interposed between the ball spline grooves and the second ball spline grooves, allowing the ball spline nut member 24 to be movably mounted in the axial direction of the axle 4. The ball spline nut member 24 is also attached to the stator 11.

The ball screw nut member 25 is an annular member with a second spiral ball screw groove (not shown) formed on its inner periphery that corresponds to the 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 a rolling element (not shown) or the like between the second ball screw groove and the ball screw groove 23, the ball screw nut member 25 is rotatably attached to the axle 4.

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 multiple rolling elements 32 are arranged between the rolling groove 29 and the second rolling groove 33.

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 axially along the ball screw groove 23 formed in the axle 4. Because the ball screw nut member 25 is assembled to the ball spline nut member 24, it moves axially together with the stator 11.

In this way, the rotating electric machine 10 according to this embodiment is capable of moving the stator 11 axially 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, thereby making it possible to vary the output characteristics depending on the relative position of the stator 11 with respect to the rotor 12. Note that in this specification, the direction in which the stator 11 moves from left to right in Figure 1 is defined as the extraction direction, and the direction in which it moves from right to left is defined as the insertion direction.

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

The rotor core 13 has a stepped shape on its surface facing the stator 11, expanding radially along the axial direction of the stator 11. For example, as shown in Figure 3, it has a five-step stepped shape consisting of a first rotating-side step 13a, a second rotating-side step 13b, a third rotating-side step 13c, a fourth rotating-side step 13d, and a fifth rotating-side step 13e. These stepped sections are formed at unequal intervals so that their axial lengths are L1 to L5. Preferably, the stepped shape of the rotor core 13 is formed to expand along the extraction direction.

As shown in FIG. 3, the rotor core 13 is formed with slits 13f that penetrate the first rotation-side step 13a, the second rotation-side step 13b, the third rotation-side step 13c, and the fourth rotation-side step 13d. The slits 13f are arc-shaped slits that correspond to the cross-sectional shape of the magnets 14, and the inner surface of the slit 13f located on the radially outer side is formed to connect with the inner diameter surface of the fifth rotation-side step 13e.

The stepped shape of the rotor core 13 is preferably formed by stacking multiple annular rings with different inner diameters in the direction of the rotation axis, as shown in Figure 3. Furthermore, the method is not limited to stacking multiple annular rings; the stepped shape can also be formed by, for example, casting or cutting.

As shown in Figure 4, the magnets 14 are plate-shaped magnets whose cross section forms an arc coaxially with the rotor 12, and are inserted into the slits 13f of the rotor core 13. By attaching the magnets 14 in this manner, the inner diameter surface of the rotor 12 forms a stepped shape that combines multiple steps formed on the rotor core 13 with the surface where part of the magnet 14 is exposed. The magnets 14 include north-pole magnets 14N and south-pole magnets 14S, and are arranged alternately around the circumferential direction of the rotor core 13.

In this embodiment, an arc-shaped plate-shaped magnet 14 is combined with an arc-shaped slit 13f, but the shapes of the magnet and slit are not limited to this, and a similar effect can be achieved by combining a linear plate-shaped magnet with a linear slit.

In this way, by giving the magnets 14 a plate-like shape, manufacturing the magnets 14 becomes easier. Furthermore, in conventional rotor configurations, as shown in Figure 10, multiple magnets 101 are required per magnetic pole, and positioning adjustments are required when attaching the magnets 101. However, in this embodiment, a single plate-shaped magnet 14 is inserted into the rotor core 13 per magnetic pole, which reduces the total number of magnets and eliminates the need for positioning adjustments during assembly, thereby reducing assembly man-hours.

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

As shown in Figure 2, the stator 11 has armature coils 11b wound around a stator core 11a and arranged circumferentially. The armature coils can be wound using any of a variety of conventionally known winding methods.

As shown in Figure 5, the stator core 11a has multiple stator core bases 41 that extend radially in the radial direction and around which the armature coils 11b are wound, and flanges 42 that extend circumferentially from the ends of each stator core base 41.

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, it has 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. It is preferable that this stepped shape be formed with axial lengths L6 to L8 that are approximately equally spaced. Here, it is preferable that the stepped shape of the flange 42 be formed to expand along the extraction direction, similar to the stepped portion of the rotor core 13.

The stepped shape of the stator core 11a is preferably formed by stacking multiple stator core base segments with different flange 42 shapes in the rotational axis direction, as shown in Figure 5. Furthermore, the step shape is not limited to stacking multiple stator core base segments; it may also be formed by, for example, casting or cutting.

With this rotor 12 and stator 11, as shown in FIG. 6, the stepped shape of the rotor 12 and the stepped shape of the stator 11 have different numbers of steps, and the axial lengths L1 to L5 of each step of the stepped shape of the rotor 12 are different. Therefore, even when the stator 11 is moved in the axial direction by the movement mechanism 20, it is possible to prevent multiple corners of the steps of the stepped shape of the 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 the stator 11 and the rotor 12 face each other, it is possible to distribute the timing at which the attractive force increases and lower the maximum value of the attractive force.

In this embodiment, the rotor 12 has a five-step stepped shape made up of the rotor core 13 and magnets 14, and the stator 11 has a three-step stepped shape made up of the stator core 11a. However, the number of steps in each step shape may be increased or decreased as appropriate. The relationship between the number of steps in the rotor 12 and the number of steps in the stator 11 may also 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 shape of the stator 11 are formed at approximately equal intervals. However, they may be formed at unequal intervals, as long as the corners of the stepped shapes of the stator 11 and rotor 12 face each other at different times during axial movement of the stator 11.

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 rotor 12 is the largest and the gap between the stator 11 and rotor 12 is the smallest, resulting in the output characteristics of the rotating electric machine 10 being 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.

In addition, in this state, the back electromotive force increases, so power supply to the armature coil 11b is stopped.When deceleration occurs to brake the wheel 1, the back electromotive force increases, allowing for efficient power generation, allowing the system to function as a highly efficient regenerative brake.

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 and moves axially along the ball screw groove 23 of the axle 4. 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 rotor 12 is smallest, and the gap between the stator 11 and 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.

The rotating electric machine 10 according to this embodiment is held in rotation relative to the axle 4 by hub members 16 located on 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. As a result of this weight reduction, the required rotation speed can be reached more quickly, improving response performance.

In addition, the rotating electric machine 10 according to this embodiment has a coaxial arrangement of the rotating shaft and drive shaft, which allows for a reduction in 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, an increase in the attractive force that counteracts the force in the direction of movement can be suppressed, making it possible to reduce the output of the drive motor. By reducing the size of the drive motor, it is possible to further reduce the size of the rotating electric machine 10.

Furthermore, because 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. Furthermore, because 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.

Next, we will confirm the effects of the present invention by looking at the results of measuring the attractive force and torque for the rotating electric machine 10 according to this embodiment and a conventional rotating electric machine.

Figure 7 is a graph showing the relationship between the amount of axial movement of the stator 11 relative to the rotor 12 (hereinafter referred to as the withdrawal amount). For this measurement, the withdrawal amount was set to 0 mm when the stator 11 was fully inserted into the rotor 12, and the stator 11 was gradually moved axially to withdraw from the rotor 12, and the attractive force was measured.

As is clear from the graph shown in Figure 7, the measured values for the rotating electric machine 10 according to this embodiment show a lower maximum value of attractive force compared to the measured values for the conventional rotating electric machine. Furthermore, the measured values for the rotating electric machine 10 according to this embodiment show a narrower range between the minimum and maximum attractive force values than the measured values for the conventional rotating electric machine, demonstrating that a more stable attractive force is generated with less change depending on the amount of withdrawal.

As a result, it was confirmed that the feature of the present invention, in which the timing at which each corner of the step of the staircase-shaped difference in the rotor 12 faces each corner of the step of the stator 11 is made different, has the effect of dispersing the timing at which the attractive force increases and reducing the maximum value of the attractive force.

Figure 8 is a graph showing the relationship between torque and the amount of withdrawal of the stator 11, and Figure 9 is a graph showing the change in torque over time when the stator 11 is at a withdrawal amount of 0 mm.

As is clear from the graphs shown in Figures 8 and 9, it can be confirmed 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 magnets 14 are inserted inside the rotor core 13 formed in a stepped shape and portions of the magnets 14 are exposed, does not affect torque performance and can maintain performance equivalent to that of a conventional rotor configuration in which magnets are attached in a stepped shape and the entire surface facing the stator is a magnet.

In the above-described embodiment, the axle 4, ball spline nut member 24, and ball screw nut member 25 are assembled via rolling elements, but these members may also be assembled so that they slide relative to each other without rolling elements. Furthermore, 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 applications are not limited to automobiles and may also be applied to, for example, wind turbines, press machines, etc.

Furthermore, while the rotating electric machine 10 according to this embodiment has been described as having a movement 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 movement mechanism. It is clear from the claims that such modified or improved embodiments are also within the technical scope of the present invention.

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 (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;
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. 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. 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. 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;