JP2004194370A - Rotating electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating electric motor where the maximum efficiency point is spread to the side of low and medium load high in frequency of usage in case that it travels as a motor for a vehicle, and the high frequency range is also taken wide. <P>SOLUTION: This rotating electric motor 11 has such construction that it has two rotors 1 and 2 different in properties, and the output shafts of the two rotors 1 and 2 are led severally into an output synthesizer 5 having two inputs and one output. The motor distributes the output torque of the two rotors 1 and 2 prior to output, according to the output torque of the output synthesizer 5, and decides the distribution ratio so that the output efficiency may be maximum at each action point determined from the output torque of the output synthesizer 5 and the rotational speed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a rotating electric machine used in a drive system and having high output efficiency.
[0002]
[Prior art]
Conventionally, a permanent magnet motor (PM) using a permanent magnet as a field has been used as a high-efficiency rotating electric machine. In a permanent magnet motor (PM), which is a type of synchronous motor, a rotor having permanent magnets attracts and repels a rotating magnetic field on a stator side, and rotates at a synchronous speed. As the permanent magnet motor (PM), a surface magnet motor (SPM) having a permanent magnet disposed on a rotor surface and an embedded magnet motor (IPM) having a permanent magnet embedded inside the rotor are known.
[0003]
[Problems to be solved by the invention]
In the conventional permanent magnet motor described above, the loss of the motor consists of copper loss and iron loss, and the copper loss is proportional to the torque, and the iron loss is proportional to the rotation speed. Then, as shown in FIG. 7 which shows an example of copper loss and iron loss in a conventional permanent magnet motor, the efficiency of the motor becomes maximum near the minimum of the sum of copper loss and iron loss. That is, at the maximum efficiency point, the torque and the rotation speed are determined, and the current for outputting the torque is uniquely determined. Further, as can be seen from FIG. 8, which shows a map of the efficiency at each operating point defined by the rotation speed and the torque in the conventional permanent magnet motor, the maximum efficiency point is distributed on the high output side. There is a problem that the efficiency of the low and medium load areas, which are frequently used when the vehicle travels, deteriorates.
[0004]
[Means for Solving the Problems]
The present invention advantageously solves the above problems, and provides a rotating electric machine that can be extended to low, medium load sides that are frequently used when the maximum efficiency point is run as a motor for a vehicle, and that can have a wide high efficiency range. SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotating electric machine having two rotors having different characteristics, and inputting the output shafts of the two rotors to an output combiner having two inputs and one output. A rotating electric machine having a structure, wherein output torques of the two rotors are distributed and output at an arbitrary distribution ratio according to an output torque of the output combiner, and the distribution ratio is defined as an output torque of the output combiner. It is characterized in that the output efficiency is determined to be maximum at each operating point determined from the rotation speed.
[0005]
【The invention's effect】
In the rotating electric machine of the present invention, the output torques of the two rotors are distributed and output at an arbitrary distribution ratio according to the output torque of the output combiner, and the distribution ratio is determined by the output torque of the output combiner and the rotation. By determining the maximum output efficiency at each operating point determined from the speed, the maximum output efficiency point can be extended toward low and medium loads, and the high efficiency range can be widened.
[0006]
In the rotating electric machine of the present invention, the two rotors having different characteristics are rotors having different torque characteristics from each other, and the rotor diameter of the two rotors, the number of pole pairs, the number of linkage magnetic fluxes created by the permanent magnets, or dq It is preferable that the torque characteristics are different due to the difference (Ld-Lq) in the inductance of the shaft. With this configuration, two rotors having different characteristics can be easily obtained, and the present invention can be more suitably achieved.
[0007]
Further, in the rotating electric machine of the present invention, a motor having a three-layer coaxial structure having inner and outer rotors and having a stator between an outer rotor and an inner rotor is used as the two rotors having the different characteristics, and the outer rotor and the inner rotor are used. Rotate at the same speed, input the output of each rotor to the output synthesizer, respectively, according to the output torque of the output synthesizer, output and distribute the output torque of the outer rotor and the inner rotor at an arbitrary distribution ratio, Preferably, the distribution ratio is determined so that the output efficiency is maximized at each operating point determined by the output torque and the rotation speed of the output synthesizer. With this configuration, it is possible to output the sum of the output torques of the outer rotor and the inner rotor as one output torque, and to efficiently use a three-layer coaxial motor used for traveling as a vehicle electric motor. Can be.
[0008]
Further, in the rotating electric machine according to the present invention, it is preferable that the maximum output torque of the outer rotor is larger than that of the inner rotor. In the case of a motor having a three-layer coaxial structure, the outer rotor usually has a larger rotor diameter than the inner rotor. Therefore, the torque characteristics of the outer rotor can be larger than that of the inner rotor. Therefore, with such a configuration, the present invention can be more suitably achieved using a motor having a three-layer coaxial structure.
[0009]
Still further, in the rotating electric machine according to the present invention, the method of maximizing the output efficiency of the output combiner is preferably a method in which the maximum output efficiency is obtained in advance at each operating point of the output torque and the rotation speed of the output combiner. Is prepared, and based on the distribution ratio of the two rotors read from the map, the output torques of the two rotors are determined, and the two rotors are controlled to have the determined output torque. Is preferred. With this configuration, the output efficiency of the output synthesizer can be easily maximized, and the present invention can be more suitably achieved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram for explaining a configuration of an example of the rotating electric machine of the present invention. In the example shown in FIG. 1, a rotating electric machine 11 of the present invention has a first rotor 1 and a second rotor 2 as two rotors having different characteristics, and outputs of the first rotor 1 and the second rotor 2. The axes 3 and 4 are configured to be input to an output synthesizer 5 having two inputs and one output. A feature of the present invention is that, in the rotating electric machine 11 having the above-described structure, the output torque of the output shaft 3 of the first rotor 1 and the output torque of the second rotor 2 are changed in accordance with the output torque of the output shaft 6 of the output synthesizer 5. The point is that the output torque at the output shaft 4 is distributed and output at an arbitrary distribution ratio. At this time, the distribution ratio of the distribution is determined so that the output efficiency is maximized at each operating point determined by the output torque and the rotation speed of the output shaft 6 of the output synthesizing machine 5. As the output synthesizer, for example, using a planetary gear set, one rotor is connected to a ring gear, the other rotor is connected to a sun gear, and the output shaft is connected to a carrier.
[0011]
In the rotating electric machine 11 of the present invention described above, it is conceivable that the first rotor 1 and the second rotor 2 as the two rotors having different characteristics have different torque characteristics. To make the torque characteristics of the first rotor 1 and the second rotor 2 different, the rotor diameters of the first rotor 1 and the second rotor 2 are made different, and the first rotor 1 and the second rotor 2 are made different. The number of pole pairs of the first rotor 1 and the second rotor 2 are different from each other, for example, one is a six-pole pair and the other is a three-pole pair. For example, the two permanent magnets have different surface areas, and the first rotor 1 and the second rotor 2 have different dq-axis inductance differences (Ld-Lq). It is conceivable to use a motor (IPM) and the other a surface magnet motor (SPM). Further, as the output synthesizing device 5, any device having two inputs and one output can be used. For example, a device having a structure such as a planetary gear or a belt CVT can be suitably used. it can.
[0012]
In the rotating electrical machine 11 of the present invention having the above-described configuration, the output torque of the output shaft 6 of the output synthesizer 5 is Tall, the output torque of the output shaft 3 of the first rotor 1 is T1, and the output shaft of the second rotor 2 is T1. Assuming that the output torque at 4 is T2,
Tall = T1 + T2
It becomes. now,
T1 = aTall (0 <= a <= 1)
given that,
T2 = (1-a) Tall
And the degree of freedom of a increases. That is, since the torque of the output shaft 6 of the output synthesizer 5 is constant and the distribution of a is changed, the torque output from each of the first rotor 1 and the second rotor 2 is changed. The motor loss will vary. Therefore, by selecting a that maximizes the efficiency, it is possible to improve the efficiency as compared with the case where a is 1 or 0.
[0013]
Generally, the equation for the output torque of a motor is expressed as follows.
Te = P (φIq + (Ld−Lq) IdIq)
Here, P is the number of pole pairs, φ is the magnetic flux generated by the magnet, Ld and Lq are the d-axis and q-axis inductances, respectively, and Id and Iq are the d-axis and q-axis currents, respectively. For example, a motor having a large φ can output torque with a small current, but the induced voltage shown below increases at a high speed.
V = dφ / dt = ωφ
[0014]
Therefore, for example, in the case of a magnetic flux φ1 of a rotor having a large φ and a magnetic flux φ2 of a rotor having a small φ, for simplicity,
Te = φIq
given that,
T1 = φ1Iq1 = aTall, T2 = φ2Iq2 = (1-a) Tall,
Iq1 = aTall / φ1 and Iq2 = (1-a) Tall / φ2.
[0015]
Here, considering Iq1 + Iq2,
Iq1 + Iq2 = a Tall / φ1 + (1-a) Tall / φ2
= ATall (aφ2 + (1-a) φ1) / φ1φ2
Since it suffices that this value be smaller than Iq1 when a = 1, aTall (aφ2 + (1-a) φ1) / φ1φ2 <Tall / φ1
And solving this gives φ1 <φ2
It becomes. That is, by combining rotors having different magnetic fluxes, the current necessarily decreases. This reduces the losses, especially when the copper losses are reduced, so that the efficiency range extends to low, medium load.
[0016]
Next, a method for maximizing the output efficiency of the output synthesizer in the rotating electric machine of the present invention will be specifically described. First, the rotating electric machine 11 is actually created from the first rotor 1, the second rotor 2, and the output synthesizer 5. Then, in the created rotating electric machine 11, the sum of the output torque of the first rotor 1 and the output torque of the second rotor 2 is always the operating point for each operating point determined by the output torque and the rotation speed of the output synthesizer 5. The output torque of the first rotor 1 and the output torque of the second rotor 2 are changed under the condition that the output torque of the output synthesizing machine 5 is satisfied, and the distribution ratio a that maximizes the output efficiency is obtained. By obtaining the distribution ratio a for all operating points determined by the output torque and the rotation speed of the output synthesizer 5, it is possible to obtain a map showing the relationship between the output torque and the rotation speed of the output synthesizer 5 for the distribution ratio a. it can.
[0017]
Here, the output efficiency of the motor is obtained by defining the speed of the output synthesizer × torque / inverter output power. In addition, since the rotating electric machine 11 of the present invention is premised on treating two motors as one motor, the rotation speed of both the first rotor 1 and the second rotor 2 is usually the operating point of the output synthesizing machine 5. It is considered that the rotation speed is the same, but if the ratio is not the same, but has a fixed ratio (for example, a gear ratio), it can be treated as the same even in that case, and the present invention can be applied.
[0018]
FIG. 2 is a diagram illustrating an example of a map in which the distribution ratio a is obtained for all operating points. When actually controlling the rotating electric machine 11 of the present invention at the time of rotation, first, an operating point determined from the rotation speed and the output torque of the output synthesizer 5 to be controlled is defined. When the operating point is determined, the distribution ratio a of the output torque of the first rotor 1 and the second rotor 2 at that operating point is determined from the map shown in FIG. Then, the output torque of the first rotor 1 and the output torque of the second rotor 2 are obtained based on the obtained distribution ratio a, and the output of the first rotor 1 and the second output torque are set so as to have the obtained torque values. The output of the rotor 2 is controlled. This output control is based on a map showing the relationship between the number of rotations and the output torque obtained in advance for the current at each rotor operating point for each of the first rotor 1 and the second rotor 2. And applying the current.
[0019]
FIG. 3 is a map showing the output efficiency obtained by the rotating electric machine 11 of the present invention in relation to the output torque and the rotation speed. As can be seen from FIG. 3, the output efficiency of the rotating electric machine 11 of the present invention in which the rotating shaft is controlled by the above-described method is within the range of the maximum efficiency as compared with the case of the single motor shown in FIG. Is spread to low and medium load regions.
[0020]
An example of the actual control will be described with reference to FIGS. 4A is a map of a current command for obtaining the maximum efficiency at each operating point determined by the torque and the rotation speed of the first rotor 1, and FIG. 4B is a map of the torque and the rotation of the second rotor 2. FIG. 4C is a map of a current command for obtaining the maximum efficiency at each operating point determined by the speed, and a current value is described for each operating point. FIG. 5 is a map showing a distribution ratio a in FIG. The map shown in FIG. 4C corresponds to the map shown in FIG.
[0021]
First, each map shown in FIGS. 4A to 4C is prepared in advance. If the operating point to be controlled is, for example, a point where the output of the output synthesizing machine 5 has a rotation speed of 3000 rpm and an output torque of 150 Nm, the distribution ratio a at the point C (here, 1/3 in FIG. The output torque of the first rotor 1 is controlled to 100 Nm and the output torque of the second rotor 2 is controlled to 50 Nm based on the obtained distribution ratio a (= 1/3). In this control, the first rotor 1 obtains the maximum efficiency at the operating point A where the operation of the first rotor 1 to be controlled, that is, the rotation speed is 3000 rpm and the output torque is 100 Nm, from the map shown in FIG. This can be performed by obtaining a current command and flowing the current to the first rotor 1. Similarly, in the second rotor 2, the maximum efficiency is obtained from the map shown in FIG. 4B at the operating point of the second rotor 2 to be controlled, that is, at the operating point B where the rotation speed is 3000 rpm and the output torque is 50 Nm. This can be performed by obtaining a current command and flowing the current to the second rotor 2.
[0022]
Next, as a preferred example of the first rotor 1 and the second rotor 2 having different characteristics, a three-layer coaxial motor having a rotor inside and outside and a stator between the outer rotor and the inner rotor will be described. FIG. 5 shows a composite current multi-layer motor as an embodiment of a rotating electric machine, which is combined with a Ravigneaux type planetary gear train to constitute a hybrid transmission for a vehicle. This composite current multilayer motor can be suitably used as a motor having the first rotor 1 and the second rotor 2 having different characteristics according to the present invention. The composite current multi-layer motor having the configuration shown in FIG. 5 includes a single annular stator 21 and inner rotors 22 rotatably arranged on a predetermined rotation axis C coaxial with each other radially inward and outward. The outer rotor 23 has a triple structure, which is housed in a housing 24.
[0023]
Each of the inner rotor 22 and the outer rotor 23 includes laminated cores 44 and 45 that are formed by laminating a plate material formed by pressing an electromagnetic steel plate or the like in the axial direction of the rotor. The permanent magnets penetrating in the direction are arranged at equal intervals in the circumferential direction.
[0024]
In storing the inner rotor 22 and the outer rotor 23 in the housing 24, the outer rotor 23 is provided with a torque transmission shell 25 drivingly connected to the outer periphery of the laminated core 45, and both ends of the torque transmission shell 25 are bearings. The housing 24 is rotatably supported by the housings 27 and 28, and the torque transmission shell 25 is connected to the outer rotor shaft 29 on the bearing 27 side.
[0025]
The inner rotor 22 has a hollow inner rotor shaft 30 which rotatably penetrates the outer rotor shaft 29 therein at the center of the laminated core 44, and between the laminated core 44 and the inner rotor shaft 30 of the inner rotor 22. Drive coupling. The intermediate portion of the inner rotor shaft 30 is rotatably supported in a fixed stator bracket 33 by a bearing 32, and one end (the left end in FIG. 5) is rotatable by a bearing 34 on a corresponding end wall of the torque transmission shell 25. To support.
[0026]
The stator 21 includes a number of stator pieces formed by laminating an I-shaped stator steel plate formed by pressing an electromagnetic steel plate in the axial direction of the stator. As shown in FIG. 5, the individual stator pieces are wound with electromagnetic coils 37 at the teeth between the outer rotor-side yoke and the inner rotor-side yoke, and these coil-wound stator pieces are equally spaced in the same circumferential direction. That is, a stator core is formed by arranging the stator core in a circular shape, and this stator core is sandwiched between brackets 33 and 38 on both sides in the axial direction of the stator with bolts 39 and is entirely molded with a resin 40 to integrally form the stator 21. . A coolant passage 61 is formed in the resin 40 between the adjacent stator pieces 36 in the axial direction, and the bolts 39 are located radially inward and outward of the coolant passage 61, respectively. Here, each bolt 39 is tightened by a nut 39a screwed thereto. Needless to say, the tightening structure using bolts and nuts may be a tightening structure using rivet pins.
[0027]
In driving the motor, the rotation positions of the inner rotor 22 and the outer rotor 23 detected by the rotation sensor 68 and the rotation sensor 67, that is, the two rotors 22, 23 corresponding to the positions of the permanent magnets provided as described above. A composite current obtained by combining the drive currents for the two rotors is supplied to the electromagnetic coil 37 of the stator 1, whereby the rotating magnetic fields for the rotors 22 and 23 are individually generated in the stator, thereby synchronizing with the rotating magnetic field. The rotors 22 and 23 can be individually driven to rotate.
[0028]
In the three-layer coaxial motor having the above-described structure, the hollow inner rotor shaft 30 is used as the first rotor 1, the outer rotor shaft 29 is used as the second rotor 2, the Ravigneaux type planetary gear train is used as the output synthesizer 5, and the hollow inner rotor shaft 30 is used as the output synthesizer 5. By connecting the inner rotor shaft 30 and the outer rotor shaft 29 to the sun gear and the ring gear of the Ravigneaux type planetary gear train, respectively, the rotating electric machine of the present invention can be suitably configured.
[0029]
FIG. 6 shows an example of a composite current to be supplied to the three-layer coaxial motor having the above-described structure. In FIG. 6, a composite current 153 is obtained by superimposing a current 101 for the inner rotor for driving the inner rotor and a current 102 for the outer rotor for driving the outer rotor. , The inner rotor and the outer rotor can be individually rotated. By using the rotating electric machine having this structure as the first rotor 1 and the second rotor 2 having different characteristics to be combined with the output synthesizer in the present invention, the following effects can be obtained. This is a preferred embodiment of the present invention.
[0030]
That is, by using a rotating electric machine having a three-layer coaxial structure, by outputting the sum of the output torques of the two rotors as one output torque, the degree of freedom of the torque output ratio between the inner rotor and the outer rotor is the same as in the above-described example. One more. For example, when the outer rotor is a high-torque (magnet magnetic flux) rotor and the inner rotor is a low-torque high-speed rotor, the torque output of the outer rotor is increased in the torque region where the sum torque is high, and the inner rotor is increased in the high-speed region. By increasing the torque output of the rotor, the current is reduced and the efficiency is increased as compared with the case where one motor covers the entire area. Further, since the inner rotor and the outer rotor rotate at the same speed, only a DC magnetic field is generated in each rotor, and iron loss does not theoretically occur in the rotor. As described above, by varying the torque sharing ratio, the current decreases and the copper loss decreases. In addition, the same rotation reduces iron loss and improves efficiency. Furthermore, in the case of the rotating electric machine having the above-described three-layer coaxial structure, the outer rotor usually has a larger rotor diameter than the inner rotor. Therefore, the torque characteristics of the outer rotor can be made larger than that of the inner rotor, and the torque characteristics can be applied to the present invention without special design. Therefore, it is understood that a rotating electric machine having a three-layer coaxial structure can be suitably used as two rotors having different characteristics of the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an example of a rotating electric machine according to the present invention.
FIG. 2 is a diagram illustrating an example of a map in which distribution ratios a are obtained for all operating points determined by a rotation speed and an output torque in the rotating electric machine of the present invention.
FIG. 3 is a diagram showing a map indicating output efficiency obtained by the rotating electric machine according to the present invention in a relationship between rotation speed and output torque.
FIGS. 4A and 4B are diagrams showing an example of a current command map for obtaining maximum efficiency at each operating point of a first rotor and a second rotor, respectively, and FIG. FIG. 5 is a diagram showing an example of a map indicating a distribution ratio a at each operating point in FIG.
FIG. 5 is a longitudinal sectional side view showing an example of a composite current multi-layer motor that is combined with a Ravigneaux type planetary gear train to constitute a hybrid transmission for a vehicle.
FIG. 6 is a diagram for explaining an example of a composite current to be supplied to a composite current multilayer motor.
FIG. 7 is a graph showing an example of copper loss and iron loss in a conventional permanent magnet motor.
FIG. 8 is a diagram showing a map showing output efficiency obtained by a conventional permanent magnet motor in a relationship between a rotation speed and an output torque.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 first rotor 2 second rotors 3, 4, 6 output shaft 5 output synthesizer 11 rotating electric machine

Claims (5)

A rotating electric machine having two rotors having different characteristics, wherein the output shafts of the two rotors are input to an output combiner having two inputs and one output, respectively, according to an output torque of the output combiner. Distributing and outputting the output torques of the two rotors at an arbitrary distribution ratio, and determining the distribution ratio such that the output efficiency is maximized at each operating point determined from the output torque and the rotation speed of the output synthesizer. A rotating electric machine characterized by the above-mentioned. The two rotors having different characteristics are rotors having different torque characteristics, and the rotor diameter, the number of pole pairs, the number of interlinkage magnetic fluxes created by the permanent magnets, or the difference between the inductances of the dq axes (Ld-Lq). The rotating electric machine according to claim 1, wherein the torque characteristics are different due to the difference in torque characteristics. As the two rotors having different characteristics, a motor having a three-layer coaxial structure having inner and outer rotors and having a stator between the outer rotor and the inner rotor is used. The outer rotor and the inner rotor are rotated at the same speed, and the output of each rotor is Are respectively input to the output synthesizer, and the output torques of the outer rotor and the inner rotor are distributed and output at an arbitrary distribution ratio according to the output torque of the output synthesizer. The rotating electrical machine according to claim 1, wherein the output efficiency is determined to be maximum at each operating point determined from the output torque and the rotation speed. The rotating electric machine according to claim 3, wherein a maximum output torque of the outer rotor is larger than that of the inner rotor. A method for maximizing the output efficiency of the output synthesizer is to prepare a map of the distribution ratio of the two rotors at which the maximum output efficiency is obtained at each operating point of the output torque and the rotation speed of the output synthesizer. The method according to any one of claims 1 to 4, wherein the output torque of the two rotors is determined based on the distribution ratio of the two rotors read from the controller, and the two rotors are controlled to have the determined output torque. The rotating electric machine as described.

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