JP2022131649A - Electric drive device - Google Patents

Abstract

To provide an electric drive device capable of outputting high output torque with small rotational inertia that becomes a load in reverse driving.SOLUTION: A electric drive device 100 includes an eccentric motion input reduction gear (planetary gear 14 and ring gear 16), a rotor 12 having a magnetomotive force source, and a stator 10 having a magnetomotive force source, and the rotor 12 is constrained to rotate on its axis and is only capable of revolving motion with respect to the stator 10. The stator 10 generates a rotating magnetic field with a frequency different from the rotation frequency of the rotor 12, the orbital motion of the rotor 12 is driven by the rotating magnetic field generated by the stator 10, and the orbital motion of the rotor 12 is converted into rotary motion of the output shaft by the reduction gear.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electric drive device.

Nursing care robots and power-assisted suits require compact electric drive devices that can output high torque from the viewpoint of mountability and wearability.

An outer rotor type motor, a wave gear device that decelerates and outputs the input rotation input from the motor, and a device hollow that extends through the wave generator and the output shaft of the wave gear device in the direction of their central axes an end cover that is fixed to the output shaft so as to rotate integrally with the output shaft and closes an output-side opening that opens to the end face of the output shaft in the hollow portion of the device; and a detection portion that detects the rotation of the output shaft. A rotary actuator is disclosed (Patent Document 1).

In addition, the mover is formed by stacking a plurality of mover elements, and each mover element is provided with an internal tooth region in which internal teeth are formed only in a predetermined angular range different from each other. The combination of the provided internal tooth regions constitutes the internal teeth covering the entire circumference of the inner peripheral surface of the mover, and each mover element is fixed for the field so that it can swing only in the direction toward the corresponding internal tooth region. A variable gap motor is disclosed in US Pat.

Japanese Patent No. 6234592 JP 2018-191468 A

By the way, in order to output high torque, generally a speed reducer with a high reduction ratio is used in combination with a motor. However, since the rotor of the motor greatly reduced in speed by the speed reducer rotates at high speed during reverse driving, its rotational inertia becomes a reverse driving load, which may damage the gears or apply a large force to the reverse driving factor. In order to avoid this, a sensor for detecting reverse driving is required, and the response speed of drive control becomes a problem.

Moreover, although the variable gap motor can reduce the rotational inertia, there is a problem that the torque becomes small with respect to the reduction ratio.

One aspect of the present invention includes an eccentric motion input reducer, a rotor having a magnetomotive force source, and a stator having a magnetomotive force source, wherein the rotor is restrained in rotational motion, and the stator The stator generates a rotating magnetic field with a frequency different from the rotation frequency of the rotor, and the rotating magnetic field generated by the stator drives the orbital motion of the rotor. The electric drive device is characterized in that the orbital motion of the rotor is converted into the rotational motion of the output shaft by the speed reducer.

Here, it is preferable that the number of teeth provided on the stator is different from the number of magnetic poles provided on the rotor.

Further, it is preferable that the rotating magnetic field including higher harmonics is generated from the stator by interference of magnetic permeability distribution of the teeth.

Also, it is preferable that the rotor is of an outer rotor type located outside the stator. At this time, the speed reducer preferably includes a planetary gear provided on the outer circumference of the rotor and a ring gear meshing with the planetary gear.

Also, it is preferable that the rotor is of an inner rotor type located inside the stator. At this time, the speed reducer preferably includes a ring gear provided on the inner periphery of the rotor and a sun gear meshing with the ring gear.

Further, it is preferable that the speed reducer has a K-HV type planetary gear mechanism.

Moreover, it is preferable that the speed reducer is a cycloid speed reducer.

Moreover, it is preferable that the speed reducer has a cycloidal magnetic gear.

According to the present invention, it is possible to provide an electric drive device that has a small rotational inertia that acts as a load during reverse driving and that is capable of outputting high output torque.

It is a figure showing the basic composition of the electric drive in an embodiment of the invention. It is a figure which shows the basic structure of the gear part of the electric drive device in embodiment of this invention. It is a figure which shows the basic composition of the motor part of the electric drive device in embodiment of this invention. It is a figure which shows a common planetary gear mechanism and its collinear chart. It is a figure which shows the example of the fixing method of the planetary gear in embodiment of this invention. It is a figure which shows the planetary gear mechanism with which the planetary gear was fixed, and its collinear chart. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the electric drive device in embodiment of this invention, and its collinear chart. It is a figure for demonstrating the effect|action of the motor part of the electric drive device in embodiment of this invention. It is a figure for demonstrating the effect|action of the motor part of the electric drive device in embodiment of this invention. FIG. 3 is a diagram for explaining a collinear chart of the electric drive device according to the embodiment of the present invention; FIG. It is a figure explaining restrictions of the motor magnetic pole width in the electric drive device in an embodiment of the invention. It is a figure explaining the spatial order modulation|alteration of magnetism in the electric drive device in embodiment of this invention. FIG. 10 is a collinear chart when a mechanical gear, a motor (magnetic gear), and magnetic modulation are applied; FIG. 4 is a diagram showing an example of dimensional characteristics in the electric drive device according to the embodiment of the invention; FIG. 4 is a diagram showing torque characteristics of a normal surface permanent magnet type motor (SPMSM); FIG. 5 is a diagram showing torque characteristics of a conventional eccentric output motor; FIG. 4 is a diagram showing torque characteristics in the electric drive device according to the embodiment of the invention; It is a figure which shows another example of the basic composition of the electric drive device in embodiment of this invention.

[Basic configuration]
An electric drive device 100 according to the present embodiment includes a stator 10, a rotor 12, a planetary gear 14 and a ring gear 16, as shown in the basic configuration diagrams of FIGS. 1 to 3. FIG. The electric drive device 100 is composed of a gear section and a motor section. 2 shows the configuration of the gear portion of the electric drive device 100, and FIG. 3 shows the configuration of the motor portion of the electric drive device 100. As shown in FIG. 1 to 3 schematically show the gears provided in the planetary gear 14 and the ring gear 16, and in practice the number of teeth, tooth shape, etc. are appropriately set.

In the electric drive device 100, for example, the gear portion is composed of an internal planetary gear, and the motor portion is composed of an outer rotor type vernier motor.

The stator 10 is a component for generating a rotating magnetic field with respect to the rotor 12 . In the electric drive device 100, the stator 10 is a cylindrical member and fixed coaxially with the drive shaft. Slots and teeth are provided on the outer peripheral side of the stator 10, coils 10a are wound around the respective slots, and a rotating magnetic field can be generated by passing a current through the coils 10a. 1 to 3 show an example in which 24 slots are provided.

The rotor 12 is a component that rotates by receiving a rotating magnetic field generated by the stator 10 . In electric drive device 100 , rotor 12 is a hollow cylindrical member having an inner circumference larger than the outer circumference of stator 10 . A stator 10 is arranged inside the rotor 12 .

Rotation of the rotor 12 is restrained by the fixing portion 18, and the rotor 12 is fixed so that it can only revolve around the stator 10. As shown in FIG. For example, the rotor 12 integrally formed with the planetary gear 14 is provided with pins 18a along the circumferential direction. The rotation of the gear 14 is restrained, and it is constructed so that it can revolve by the difference in diameter between the fixing hole 12b and the pin 18a. The radius of revolution is set so as to match the amount of revolution in the motor section and at the same time maintain the gap between the stator 10 and the rotor 12 . In addition, fixing holes 12b are provided in the rotor 12 along the circumferential direction, and pins 18a provided in the fixing portion 18 are passed through to constrain the rotation of the rotor 12 and the planetary gear 14. It may be configured so that it can revolve only by the difference in diameter.

Magnets 12a are arranged along the inner circumference of the rotor 12 along the circumferential direction. As a result, the rotor 12 revolves around the stator 10 due to the magnetic interaction between the magnet 12 a of the rotor 12 and the rotating magnetic field of the stator 10 . 1 to 3 show an example in which 42-pole magnets 12a are arranged.

The planetary gear 14 is a gear having teeth on its outer periphery. The planetary gear 14 is provided along the outer circumference of the rotor 12 and revolves as the rotor 12 revolves. The planetary gear 14 meshes with the ring gear 16 to transmit the rotational force to the ring gear 16 as the rotor 12 rotates.

Ring gear 16 is a gear that rotates around planetary gear 14 . Ring gear 16 is a hollow cylindrical member having an inner diameter larger than the outer diameter of planetary gear 14 . A planetary gear 14 is arranged inside the ring gear 16 . The inner periphery of the ring gear 16 is provided with teeth that mesh with the teeth of the planetary gear 14 . The deceleration rate of the electric drive device 100 is determined by the ratio of the number of teeth of the planetary gear 14 and the ring gear 16 . For example, if the planetary gear 14 has 120 external teeth and the ring gear 16 has 122 internal teeth, the reduction ratio is 61.

The output of the electric drive device 100 is from an output shaft connected to the outer ring gear 16 . Moreover, the stator 10 and the ring gear 16 are arranged coaxially.

It should be noted that a cycloidal gear having a pin/cam structure as a planetary gear or a configuration in which the cycloidal gear is replaced with a magnetic gear may be employed.

[Structure and characteristics of gear part]
FIG. 4 shows the relationship between the number of teeth and rotational speed of a typical planetary gear mechanism. The numbers of teeth of the sun gear, planetary gear, and ring gear are Zs, Zp, and Zr, respectively, and the rotational angular velocities are ωs, ωp, and ωr, respectively.

The planetary gear of the eccentric shaft used in the electric drive device 100 has no sun gear and is configured so that the planetary gear cannot rotate. Such a configuration is called a KHV type planetary gear mechanism. The method of restraining the rotation of the planetary gears is to use a configuration in which a pin 18a is passed through the fixing hole 12b as in the electric drive device 100, or to use a free joint that allows the eccentricity of the planetary gears as shown in FIG. etc.

FIG. 6 shows a collinear diagram of a KHV type planetary gear mechanism. Since the rotation of the planetary gear is restrained, the ring gear and the carrier shaft rotate in the same direction, and the rotation speed increases in order of the ring gear and the carrier shaft. Here, if the carrier shaft is used as the input and the ring gear is used as the output, the revolutional motion can be converted into the rotational motion. Also, the speed reduction ratio in this case is (Zr-Zp)/Zr. Therefore, a large reduction ratio can be obtained by reducing the difference between the number of teeth Zp of the planetary gear and the number of teeth Zr of the ring gear. It should be noted that the radius of revolution of the carrier shaft must be larger than the height of the teeth of the gear.

The speed reducer functions as a speed increaser during reverse driving, but in the electric drive device 100 there is no rotational motion and only revolving motion. The inertial force during rotation is expressed as the product of rotational inertia and angular acceleration. The rotational inertia is I=∫r ² dm [kgm ² ] (where the gear radius is r and the mass is m). On the other hand, the revolution inertia is I=ε ² m [kgm ² ] (here, eccentricity radius ε, mass m). When the KHV type planetary gear mechanism achieves a large deceleration, the amount of eccentricity is small, so the inertia during reverse driving can be kept small.

[Configuration and characteristics of motor part]
Even if a KHV type planetary gear mechanism is used, the effect of lowering inertia cannot be obtained in the case of rotation input. Therefore, the electric drive device 100 employs a motor mechanism that produces an eccentric output as shown in FIG.

In this case, it is necessary to give the rotor 12 a revolving motion by the rotating magnetic field generated by the stator 10 . Therefore, a means for imparting a revolution motion to the rotor 12 will be examined. For ease of understanding, as shown in FIG. 8, the magnetic field generated by the stator 10 in a system without revolving motion is regarded as the rotor 12 for the time being. That is, the manner in which the rotor 12 rotates due to the interaction with the magnet 12a of the rotor 12 due to the stator 10 generating a rotating magnetic field is replaced by the rotation of another rotor having a magnetic flux distribution within the rotor 12. , in which the rotor 12 rotates due to interaction with the magnet 12a.

As shown in FIG. 9, by replacing the state in which both the inner rotor and the outer rotor 12 corresponding to the stator 10 rotate on their own axes with the relative rotation between the inner rotor and the outer rotor 12, the stator 10 can be supported. It can be regarded as an equivalent state in which the internal rotor rotates and revolves, and the external rotor 12 stops. Furthermore, by axially transforming this state, it can be regarded as an equivalent state in which the internal rotor corresponding to the stator 10 rotates and the external rotor 12 revolves. That is, as shown in FIG. 9, when the entire system is relatively rotated so that the rotation of the rotor 12 appears stationary, and the stator 10 is regarded as the center of the system, the rotation of the stator 10 causes the rotor 12 to revolve. A driving state is obtained.

If the stator 10 and the rotor 12 are not coaxial, a collinear diagram similar to that of the KHV planetary gear mechanism is obtained as shown in FIG. This state is used in the electric drive device 100 . At this time, since the rotational force of the facing portion and the attractive/repulsive force of the adjacent magnetic force become the revolving force, a higher torque can be obtained than the existing technology in which the eccentricity is achieved only by the attractive force.

[Restrictions on the motor part]
In order to realize a non-coaxial motor such as the electric drive device 100, the widths of the magnetic poles of the stator 10 and the rotor 12 must match, as shown in FIG. That is, the ratio of the radius Rrt of the rotor 12 to the radius Rst of the stator 10 should be equal to the ratio of the number of magnetic poles Nrt of the rotor 12 to the number of magnetic poles Nst of the stator 10 to satisfy Rrt:Rst=Nrt:Nst. The radii Rrt and Rst can be rational numbers, but the numbers of magnetic poles Nrt and Nst are always even numbers. The ratio of the radii Rrt and Rst must be increased as much as possible. For example, when the number of magnetic poles Nrt of the rotor 12 is 4 and the number of magnetic poles Nst of the stator 10 is 6, and Nrt:Nst=4 poles:6 poles=Nrt:1.5 Nrt, the radius Rrt of the rotor 12 and the stator 10 It is also necessary to satisfy Rrt:Rst=Rrt:1.5Rrt. Further, for example, when the number of magnetic poles Nrt of the rotor 12 is 20 and the number of magnetic poles Nst of the stator 10 is 22, and Nrt:Nst=20:22=Nrt:1.1Nrt, the radius Rrt of the rotor 12 and The ratio of the radius Rst of the stator 10 also needs to satisfy Rrt:Rst=Rrt:1.1Rrt.

Also, if the stator 10 is that of a normal three-phase motor, three slots are required for one magnetic pole pair. Multipolarity relaxes the above geometric restrictions, but increases the number of slots. Although the magnetomotive force of the magnet does not change significantly due to the multipolarization, the coil cross-sectional area per pole of the stator 10 is reduced, so the magnetomotive force is reduced and the power of the motor is lost.

Therefore, it is preferable to use magnetic modulation found in magnetic gears and vernier motors. When magnetic permeability distributions of different spatial orders are given to a certain magnetic flux distribution, the magnetic flux that has passed through the magnetic permeability distributions is the product of them, as shown in FIG. Based on the cosine addition theorem relationship, the product of the magnetic flux distribution and the magnetic permeability distribution can be decomposed into two spatial frequency sum and difference magnetic flux distribution differences. That is, when the permeability distribution is given to the magnetic flux distribution, the magnetic flux distribution having the sum and difference frequencies of both spatial frequencies can be obtained.

In the electric drive device 100, as in the vernier motor, the magnetic permeability distribution is given by the teeth of the stator 10, and harmonics obtained from the magnetic flux distribution obtained by magnetically modulating the magnetic flux generated by the stator 10 are used.

For example, if the stator 10 has 8 poles and 24 slots, the magnetic flux distribution is spatially fourth order when no magnetic modulation is applied. The number of teeth of the stator 10 is 24, and the magnetic flux distribution when magnetic modulation is applied has spatial 20th order and spatial 28th order components in addition to the spatial 4th order. At this time, the magnetic flux with the 20th-order distribution advances in the opposite direction to the magnetic flux with the 4th-order distribution (increase/decrease of the phase has an opposite relationship as time progresses). By using this magnetic modulation, it is possible to increase the number of magnetic poles while keeping the number of slots small, thereby alleviating geometric restrictions. Therefore, the electric drive device 100 can be miniaturized.

[Characteristics of electric drive device]
FIG. 13 shows a collinear diagram of the entire system of the electric drive device 100. As shown in FIG. FIG. 13 shows alignment charts when a mechanical gear, a motor (magnetic gear), and a magnetic modulation motor are applied to the electric drive device 100 from the left.

In the electric drive device 100, the three-phase rotating magnetic field generated by the stator 10 is modulated into harmonics by magnetic modulation as described above, and the rotor 12 is driven using the rotating magnetic field. The stator 10 and the rotor 12 are non-coaxial and of a cycloid type with a slightly different number of magnetic poles. By inputting the orbital motion of the rotor 12 to the internal planetary gear mechanism to which the planetary gears 14 are fixed, it is converted into rotational motion. At this time, by setting the difference in the number of teeth between the planetary gear 14 and the ring gear 16 sufficiently smaller than the number of teeth of the ring gear 16, a large reduction ratio can be obtained.

13, only the output shaft and the rotating magnetic field of the stator 10 are rotating in the configuration of the electric drive device 100. As shown in FIG. This achieves low inertia of the electric drive device 100 .

FIG. 14 shows the dimensional characteristics of the electric drive device 100. FIG. In FIG. 14, the unit of each dimension is expressed in mm. As described above, in the electric drive device 100, the magnetic pole widths of the stator 10 and the rotor 12 need to match. Therefore, the size of the electric drive device 100 changes depending on the number of magnetic poles. If the rotating magnetic field of the spatial fourth order generated by the stator 10 is used as it is, the diameter of the rotor 12 is 104 mm (inner diameter 91.3 mm) while the diameter of the stator 10 is 74 mm. This means that the outer diameter of the electric drive device 100 is 15% larger than the outer diameter of the conventional motor. On the other hand, by using harmonics, the outer diameter of the rotor 12 can be suppressed to 90.4 mm, including the back yoke reduction due to the multipolarization.

15, 16, and 17 show changes in torque over time and U using the finite element method for a surface permanent magnet motor (SPMSM), a conventional eccentric output motor, and an eccentric output motor applied to the electric drive device 100, respectively. The results of a simulation of changes in torque with respect to phase current phase are shown. Note that the configuration described in Patent Document 2 was applied to a conventional eccentric output motor.

As shown in FIG. 15, a normal surface permanent magnet motor (SPMSM) provided a maximum torque output of 9.75 Nm at a maximum current of 5 A in the three-phase coils. On the other hand, as shown in FIG. 17, with the eccentric output motor applied to the electric drive device 100, a maximum torque output of 0.3 Nm was obtained at a maximum current of 5A. That is, the eccentric output motor applied to the electric drive device 100 can only obtain a torque output of about 3% of that of a normal surface magnet motor type motor (SPMSM). A high torque output can be achieved by applying a speed reducer that

For example, if the speed reduction ratio of the speed reducer is 1/113 (the number of teeth of the planetary gear 14 is 112:the number of teeth of the ring gear 16 is 113), the eccentric output motor applied to the electric drive device 100 is a normal surface magnet type motor. A torque output of about 339% can be obtained with respect to a type motor (SPMSM).

Further, the mass of the rotor 12 is 0.31 kg for a normal surface magnet motor (SPMSM), while the mass for the eccentric output motor applied to the electric drive device 100 is 0.26 kg, which is not much different. However, when converted to rotational inertia, it is 5.38e ⁻⁴ kgm ² in a normal surface magnet motor (SPMSM), whereas in the eccentric output motor applied to the electric drive device 100, the rotor 12 does not rotate. 4.76e ⁻⁷ kgm ² . That is, the rotational inertia of the eccentric output motor applied to the electric drive device 100 can be reduced by 99.91% compared to a normal surface permanent magnet motor (SPMSM). Therefore, it is possible to greatly reduce the decrease in responsiveness due to rotational inertia and the resistance during reverse driving by about two orders of magnitude.

In the conventional eccentric output motor, when a maximum current of 5A is applied, the output becomes 0.105Nm (attraction force is 246N, eccentricity is 0.4mm), and through a rotation conversion mechanism with a reduction ratio of 103, the output becomes 11.1Nm. got the output. In other words, in the electric drive device 100, the output torque is greatly increased even compared to the conventional eccentric output motor.

In addition, the output torque per unit volume of the electric drive device 100 was 216 Nm/L, realizing a large torque density that has never been achieved before.

Further, for example, in the configuration shown in FIGS. 1 to 3, if the speed reduction ratio of the speed reducer is 1/61 (the number of teeth of the planetary gear 14 is 120: the number of teeth of the ring gear 16 is 122), the output torque is 18 .3 (Nm), and the torque density was approximately 116.6 (Nm/L). That is, it was possible to improve the output by about 80% compared to the prior art.

In the present embodiment, the outer rotor type electric drive device 100 has been described as an example, but as shown in the structural conceptual diagram of FIG. It may be device 102 . In the case of the inner rotor type, the gear configuration is reversed from that of the outer rotor type, and the sun gear 20 meshing with the revolving ring gear 16 rotates and becomes the output shaft.

It should be noted that the present invention is not limited to the above-described embodiments and modifications thereof, and it goes without saying that various modifications and improvements are possible within the scope of the matters described in the claims of the present application. .

10 stator, 10a coil, 12 rotor, 12a magnet, 12b fixing hole, 14 planetary gear, 16 ring gear, 18 fixing part, 18a pin, 20 sun gear, 100, 102 electric drive device.

Claims (10)

Equipped with a reducer for eccentric motion input, a rotor having a magnetomotive force source, and a stator having a magnetomotive force source,
The rotor is constrained to rotate on its axis and is only capable of revolving motion with respect to the stator,
The stator generates a rotating magnetic field with a frequency different from the rotation frequency of the rotor,
orbital motion of the rotor is driven by the rotating magnetic field generated by the stator;
An electric drive device, wherein the orbital motion of the rotor is converted into the rotational motion of the output shaft by the speed reducer. The electric drive device according to claim 1,
An electric drive device, wherein the number of teeth provided on the stator is different from the number of magnetic poles provided on the rotor. The electric drive device according to claim 2,
An electric driving device, wherein the rotating magnetic field including harmonics is generated from the stator by interference of the magnetic permeability distribution of the teeth. The electric drive device according to any one of claims 1 to 3,
An electric drive device, wherein the rotor is of the outer rotor type outside the stator. The electric drive device according to claim 4,
An electric drive device, wherein the speed reducer includes a planetary gear provided on the outer periphery of the rotor, and a ring gear meshing with the planetary gear. The electric drive device according to any one of claims 1 to 3,
An electric drive device, wherein the rotor is of an inner rotor type inside the stator. The electric drive device according to claim 6,
An electric drive device, wherein the speed reducer includes a ring gear provided on the inner circumference of the rotor, and a sun gear meshing with the ring gear. The electric drive device according to any one of claims 1 to 7,
The electric drive device, wherein the speed reducer has a K-HV type planetary gear mechanism. The electric drive device according to any one of claims 1 to 7,
The electric drive device, wherein the speed reducer is a cycloidal speed reducer. The electric drive device according to any one of claims 1 to 7,
The electric drive device, wherein the speed reducer has a cycloidal magnetic gear.

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