JP6480770B2 - Electric motor rotor - Google Patents

Description

  The present invention relates to a rotor of a multilayer flux barrier type reluctance motor.

  There are various types of rotor structures for electric motors. For example, a rotor of a multilayer flux barrier type reluctance motor in which a plurality of magnetic paths are formed by disposing a plurality of slits inside is known. Hereinafter, the structure of the rotor will be described with reference to FIGS.

  FIG. 4 is a diagram showing an example of a cross section of a rotor structure in a conventional multilayer flux barrier type reluctance motor. As shown in FIG. 4, a plurality of slits 2 are formed in the rotor 1. Of the slits 2, some of the slits 2 have a structure in which permanent magnets 3 that are hatched in the drawing are present.

  FIG. 5 is an enlarged view of a part of the rotor 1 of FIG. In FIG. 5, a plurality of magnetic paths 4 exist between the slits 2. In addition, when a current is applied to a winding at a position indicated by Wd among windings wound in a stator (not shown) that is radially outward of the rotor 1, the inside of the magnetic path 4 A magnetic flux is generated in the direction indicated by ΦL 1, thereby forming a magnetic pole in the rotor 1. This magnetic flux is necessary to make the magnetic pole of the rotor 1. However, in this case, only a magnetic pole is formed on the rotor 1. In order to generate torque in the electric motor, it is necessary that a current is supplied to the winding at the position indicated by Wq. It is known that when a current is also applied to the winding at the position indicated by Wq, a rotational force is generated in the electric motor according to Fleming's left-hand rule, resulting in the electric motor torque. When a current is passed through the winding at the position indicated by Wq, a magnetic flux ΦL2 in a direction orthogonal to the magnetic path 4 is about to be generated. Since this magnetic flux has a function of hindering the torque generation of the electric motor and lowering the efficiency of the electric motor, the magnetic flux ΦL2 is preferably as small as possible.

  When the permanent magnet 3 is disposed in the slit 2, the permanent magnet 3 is disposed for the purpose of canceling the magnetic flux ΦL2, and therefore the magnetic flux of the permanent magnet 3 is disposed in the direction indicated by ΦM. As a result, the magnetic flux ΦL2 that causes a reduction in the efficiency of the electric motor is made as small as possible to improve the characteristics of the electric motor. As described above, the permanent magnet 3 is arranged so that the magnetic flux ΦM is orthogonal to the magnetic path, and thus can be generated when the torque is also orthogonal to the magnetic path and the motor is generated. Cancel the magnetic flux ΦL2.

JP2013-93925A

  As described above, when the motor generates torque, in addition to the magnetic flux indicated by ΦL1 along the magnetic path 4 for creating the magnetic pole in the rotor 1, the magnetic flux indicated by ΦL2 orthogonal to the magnetic path 4 is also simultaneously generated. It has occurred. Since the strength of the magnetic field of the magnetic flux ΦL2 is proportional to the magnitude of the current passed through the winding indicated by Wq, the magnetic flux ΦL2 is directed in the opposite direction when the value of the supplied current is small. Is smaller than the magnetic field strength of the magnetic flux ΦM, and is canceled by the magnetic flux ΦM. However, when the current passed through the stator winding is large, the magnetic field strength of the magnetic flux ΦL2 is larger than the magnetic field strength of the magnetic flux ΦM by the permanent magnet 3, and both magnetic fields are not canceled. The magnetic flux remains in the same direction as ΦL2 by the difference in strength. The magnetic flux generated in this way is defined as ΦL3. Since the magnetic flux ΦL3 is oriented in the same direction as the magnetic flux ΦL2, the magnetic flux is applied in the direction opposite to the magnetic flux originally possessed by the permanent magnet 3 in the permanent magnet 3. This is called reverse field.

  When a reverse field is applied to the permanent magnet 3 in the rotor 1, the magnetic flux density in the permanent magnet 3 decreases accordingly, and the operating point on the demagnetization curve of the permanent magnet 3 moves. This will be described with reference to FIG. FIG. 6 is a demagnetization curve at the upper limit of the use temperature of the permanent magnet 3. The vertical axis B indicates the magnetic flux density, and the magnetic flux density increases upward. On the other hand, the horizontal axis H indicates the strength of the magnetic field, and the strength of the magnetic field decreases toward the left. Normally, when no reverse field is applied to the permanent magnet 3, the permanent magnet 3 is at an operating point indicated by Pr on the demagnetization curve, and has a magnetic flux density of Br (Br = 1.22T in FIG. 6). Then, when a reverse field is applied to the permanent magnet 3, the operating point of the permanent magnet 3 moves to the lower left on the demagnetization curve as indicated by a broken arrow according to the strength of the magnetic field of the reverse field indicated by H. Move. Here, the right side of the point indicated by P1 in which the demagnetization curve is a straight line, that is, between Pr and P1, is referred to as a reversible region. When the operating point moves to a point indicated by P2 due to the reverse field, the magnetic field indicated by H2 (H2 = −350 kA / m in FIG. 6) is applied to the permanent magnet 3, and the permanent magnet 3 The magnetic flux density is changed to B2 (B2 = 0.75T in FIG. 6). As shown in the figure, when P2 is on the right side of P1, it is a reversible region, so when the reverse field applied to the permanent magnet 3 disappears, the operating point of the permanent magnet 3 is on the upper right side on the demagnetization curve. The process returns to the point indicated by the original Pr. This state is a state where the permanent magnet 3 is not demagnetized.

  On the other hand, when the strength of the magnetic field due to the reverse field is large, the situation is different. This will be described with reference to FIG. FIG. 7 is a demagnetization curve at the upper limit of the use temperature of the permanent magnet 3 as in FIG. When the strength of the magnetic field due to the reverse field is large and the value is indicated by H3 (H3 = −650 kA / m in FIG. 7), the operating point moves along the demagnetization curve as in FIG. However, the operating point moves out of the reversible region to a point indicated by P3. In this case, when the reverse field disappears, the operating point does not return on the demagnetization curve, but is parallel to the straight line portion of the demagnetization curve and on the straight line indicated by the alternate long and short dash line passing through the point indicated by P3. And proceed to the point indicated by Ps. The magnetic flux density Bs at the point indicated by Ps (Bs = 1.12T in FIG. 7) is smaller than Br (Br = 1.22T in FIG. 7). Thereafter, the permanent magnet 3 has an operating point. Can move only on the dashed line. This is a phenomenon of demagnetization of the permanent magnet 3.

  The demagnetization of the permanent magnet 3 occurs when a large reverse field magnetic flux is applied to the permanent magnet 3 as described above. When the permanent magnet 3 is demagnetized, the magnetic flux indicated by ΦL2 that can be canceled up to now cannot be canceled, and the generated torque of the motor decreases. Therefore, when the motor is designed, the permanent magnet 3 is designed not to demagnetize even if the current supplied to the position of Wq that contributes to torque generation is at least the current supplied when generating the maximum torque. . One of the conditions on the above-mentioned demagnetization curve is that it can be shifted in the reversible region even if a reverse field is applied, but for this purpose, the reversible region is widened. A permanent magnet 3 must be selected.

  The material of the permanent magnet 3 includes various materials such as a material having a high magnetic flux density generated by the permanent magnet 3 and a material having a high demagnetization resistance, which is one standard indicating the difficulty of demagnetization. It is determined by the ratio of chemical substances constituting the magnet 3. Specifically, in the case of rare earth magnets, if the ratio of heavy rare earth materials typified by dysprosium and terbium is increased, the demagnetization resistance is reduced and the demagnetization resistance is decreased. The permanent magnet 3 is easily magnetized. When the permanent magnet 3 is selected when designing the motor as described above, the material of the permanent magnet 3 is high in magnetic flux density so that the magnetic flux ΦL2 can be canceled as much as possible, and is difficult to demagnetize even when a reverse field is applied. Is required. In general, however, the magnetic flux density tends to decrease as the demagnetization tolerance increases. Therefore, when designing the motor, the permanent magnet 3 having a magnetic flux density as high as possible is selected within a range not demagnetized.

  On the other hand, it is known that heavy rare earths are extremely unevenly distributed in the world, and it is known that procurement risks are high in the future. Therefore, when the permanent magnet 3 is selected, it is desired to select the permanent magnet 3 that does not contain heavy rare earth or has as little content as possible. However, as described above, if the content of heavy rare earth is reduced, the demagnetization resistance of the permanent magnet 3 is lowered and the demagnetization is likely to occur.

  In view of the above, an object of the present invention is to form a rotor structure that is difficult to demagnetize even if a permanent magnet with a low demagnetization resistance and a high magnetic flux density is incorporated in the rotor of a multilayer flux barrier reluctance motor. There is.

Examples of the rotor structure that is difficult to demagnetize include the following. Before showing a conventional rotor structure that is difficult to demagnetize, the method of applying the reverse field in FIG. 5 will be described with reference to FIG. FIG. 9 is an enlarged view of the vicinity of the permanent magnet 3 in FIG. As described above, when the reverse field magnetic flux ΦL3 due to the difference between the magnetic flux ΦM caused by the permanent magnet 3 and the magnetic flux ΦL2 caused by the reverse field enters the magnetic path 4 that goes straight before the permanent magnet 3, two magnetic fluxes are formed along the magnetic path. Divided into ΦL4. However, since the magnetic flux density of the magnetic flux that can pass through the magnetic path 4 is determined by the width MP0 of the magnetic path 4,
ΦL3> ΦL4 × 2
In this case, the surplus magnetic flux ΦL5 is applied to the permanent magnet 3. Therefore, a rotor structure that is difficult to demagnetize as shown in FIG. 8 can be considered. In FIG. 5, the magnetic flux ΦL2 has reached the magnetic path 4 through the connecting portion Ba, but in the rotor structure shown in FIG. 8, the connecting portion Bb does not face the direction of the permanent magnet 3. Since these are in a straight line, the flow of magnetic flux differs. The connecting portion Bb is a portion that divides the slit 2 extending in a substantially arc shape that opens outward in the radial direction. The manner in which the magnetic flux flows in this case will be described with reference to FIG. In FIG. 10, the magnetic flux ΦL2 tends to go to the permanent magnet 3, but since there is a connecting portion indicated by Bb on the outside thereof, it is divided into the magnetic flux indicated by ΦL6 and further straight above the connecting portion Bb. Since it advances, the magnetic flux of the reverse field applied to the permanent magnet 3 becomes considerably smaller than in the case of the rotor structure shown in FIG.

However, since the magnetic flux ΦL6 traveling on the joint Bb is determined by the thickness of the joint Bb as described above,
ΦL2> ΦL6 × 2
In this case, the surplus magnetic flux ΦL7 moves toward the permanent magnet 3. Although the magnetic flux ΦL7 tries to flow along the magnetic path, the magnetic flux ΦL7 is saturated because the magnetic flux ΦL7 is saturated by the magnetic flux ΦL6 at the connecting portion Bb and the magnetic flux by the permanent magnet 3 at the connecting portion Bc beside the magnet. The destination is lost and eventually the permanent magnet 3 is applied as a reverse field.

  In view of the above, an object of the present invention is to form a rotor structure that is difficult to demagnetize even if a permanent magnet with a low demagnetization resistance and a high magnetic flux density is incorporated in the rotor of a multilayer flux barrier reluctance motor. There is.

  In order to solve the above-mentioned problems, the rotor of the multilayer flux barrier type reluctance motor of the present invention is such that a slit, which is a gap portion, is spaced in the radial direction in a rotor made of a silicon steel plate or a soft magnetic material. By forming a plurality of magnetic paths arranged between the slits, connecting the magnetic paths to form the rotor, and connecting portions for dividing the slits, the plurality of the paths Among the slits, a permanent magnet that is disposed in one or more slits on the inner side and whose magnetic pole direction is orthogonal to the magnetic path, and the slit in which the permanent magnet is disposed, It is divided by a connecting part Bc located just beside both sides, and a connecting part Bd located at a position farther from the permanent magnet than the connecting part Bc, and the permanent magnet is not arranged. The link is divided by one or more connecting portions Bb, and the connecting portions Bb and Bd are located on the same straight line that does not intersect the permanent magnets and face the direction of the magnetic flux of the permanent magnets. In addition, the width of the connecting portion Bd is larger than the width of the connecting portion Bb.

  By using the present invention, it is possible to provide an electric motor having a structure in which a permanent magnet is difficult to demagnetize and has a large generated torque even if a permanent magnet having a low demagnetization resistance and easy to demagnetize is incorporated in the rotor. In other words, it becomes possible to use a permanent magnet with a low or no heavy rare earth content as described above, and can cope with the procurement risk of heavy rare earth in the future.

It is a figure which shows an example of the rotor of the multilayer flux barrier type | mold reluctance motor in this invention. It is a figure for demonstrating an example of the flow of the magnetic flux in the rotor in this invention. It is a figure for demonstrating an example of the flow of the magnetic flux in the rotor in this invention. It is a figure which shows an example of the cross section of the rotor structure in the conventional multilayer flux barrier type | mold reluctance motor. It is the figure which expanded a part of rotor of FIG. It is an example of the demagnetization curve for demonstrating the demagnetization of a magnet. It is an example of the demagnetization curve for demonstrating the demagnetization of a magnet. It is a figure which shows an example of the cross section of the rotor structure in the conventional multilayer flux barrier type | mold reluctance motor. It is a figure for demonstrating an example of the flow of the magnetic flux in the rotor in the conventional multilayer flux barrier type reluctance motor. It is a figure for demonstrating an example of the flow of the magnetic flux in the rotor in the conventional multilayer flux barrier type reluctance motor.

  Hereinafter, an embodiment of a rotor of a multilayer flux barrier type reluctance motor according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an example of a rotor of a multilayer flux barrier type reluctance motor according to the present invention. Among the parts constituting the rotor in FIG. 1, the same elements as those in FIGS. 4, 5, and 8 shown in the background art are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 1, in the rotor of the present embodiment, a plurality of (four in the illustrated example) slits 2 extending in a substantially arc shape are arranged at intervals in the radial direction. A magnetic path 4 is formed between the slit 2 and the slit 2. Among the plurality of slits 2, a permanent magnet 3 is disposed at the approximate center of the two slits 2 b counting from the inside in the radial direction. The permanent magnet is arranged such that the magnetic pole direction is perpendicular to the magnetic path 4. Below, let L1 be the straight line that passes through the center of the permanent magnet 3 and extends in the radial direction. Further, the intersection point of the straight line L1 and the outer periphery of the rotor is C1.

  In addition, the rotor has connecting portions Bb, Bc, and Bd that divide each slit into a plurality (3 or 5 in the illustrated example) and connect two adjacent magnetic paths 4 across the slit 2. Is formed. Below, the connection part provided in the slit 2a in which the permanent magnet 3 is not arranged is referred to as a “connection part Bb”. In addition, among the slits 2b in which the permanent magnets 3 are arranged, a connecting part located just beside the permanent magnets 3 is referred to as a "connecting part Bc". Of the slits 2b in which the permanent magnets 3 are arranged, the permanent magnets 3 A connecting portion that is not located directly beside (a connecting portion located at a position farther from the permanent magnet 3 than the connecting portion Bc) is referred to as a “connecting portion Bd”.

  In the present invention, on the straight line L2 that does not intersect with the permanent magnet 3, the connecting portion Bb of the slit 2a where the permanent magnet 3 is not disposed, and the slit 2b where the permanent magnet 3 is disposed are located directly beside the permanent magnet 3. The connection part Bc which is not provided is provided. The straight line L2 intersects the straight line L1 at the outer periphery (intersection C1) of the rotor. The connecting portion Bb and the connecting portion Bd are set to have a relationship of W2> W1, where W1 is the width of the connecting portion Bb and W2 is the width of the connecting portion Bd. Further, no connecting portion is provided on the center line L1 of the permanent magnet 3 which is the direction of the magnetic flux of the permanent magnet 3.

  As described above, how the magnetic flux of the reverse field changes when the connecting portion Bb and the connecting portion Bd are arranged will be described below.

  FIG. 2 is a diagram for explaining the flow of magnetic flux when a reverse field is applied in the rotor 1 according to the present invention. When the magnetic field φL2 due to the reverse field is applied, the magnetic flux ΦL2 tries to go to the permanent magnet 3 as described above, but since there is a connecting portion indicated by Bb on the outside, the magnetic flux ΦL2 is equal to the magnetic flux indicated by ΦL6. When the connecting portion Bb is further saturated, the remaining magnetic flux ΦL7 goes over the slit and goes straight to the permanent magnet 3. In the prior art, this magnetic flux ΦL7 has lost its place and has been applied to the permanent magnet 3 as an inverted field, but in the present invention, since W2> W1, the magnetic flux is not saturated in the connecting portion Bd. Accordingly, ΦL8 obtained by dividing ΦL7 into two is combined with ΦL6 and passes through the connecting portion Bd as ΦL9. For this reason, a reverse field magnetic flux is not applied to the permanent magnet 3.

  Since the connecting portion existing in the rotor 1 causes a leakage of magnetic flux when torque is generated and causes the characteristics of the motor to deteriorate, it is desired to make the connecting portion as small as possible. When the connecting portion is thickened as in the present invention, it is conceivable that the leakage of magnetic flux increases and the characteristics of the motor deteriorate, but in reality there is almost no deterioration in the characteristics of the motor. This will be described with reference to FIG. In FIG. 3, a current for generating torque is applied to the winding at the position indicated by Wq. However, when this current flows, a magnetic flux tends to be generated in a direction not desired to be generated. That is, when a current is applied to the winding at the position of Wq from the front side to the back side, a magnetic flux is generated around Wq in accordance with the right-handed screw law. This magnetic flux passes through the connecting portion Bb and the connecting portion Bd as the magnetic flux ΦLq in the direction shown in FIG.

  At this time, the magnitude of the leakage flux ΦLq is determined by the smaller one of the width W1 of the connecting portion Bb and the width W2 of the connecting portion Bd. Since the connecting portion is very thin, the leakage flux easily saturates in the connecting portion. Therefore, when the leakage magnetic flux is generated as shown in FIG. 3, the magnetic flux can pass through the connecting portion Bb having a small width and cannot pass through the connecting portion Bd. Therefore, the leakage magnetic flux passing through the connecting portion Bb and the connecting portion Bd is equal.

  From the above, it can be said that in the present invention in which the width of the connecting portion Bb is equal to that in FIG. 8 showing the prior art, the magnitude of the leakage magnetic flux is hardly changed, and therefore there is almost no deterioration in the characteristics of the electric motor.

  Next, a method for determining the width W1 of the joint Bb and the width W2 of the joint Bd will be described. First, from the viewpoint of reducing the leakage magnetic flux as much as possible, the width W1 of the connecting portion Bb is desired to be as small as possible. However, since it must be able to withstand the centrifugal force received when the rotor rotates, the smallest value in the range that can withstand the centrifugal force is the size of W1. This can be obtained from intensity analysis or the like.

On the other hand, the width W2 of the connecting portion Bd can be determined as follows. If the maximum value of the current passed through the motor is known, the interlaced magnetic flux induced in the rotor is proportional to the current value and can be obtained. Assuming that this magnetic flux is Φmax, the connecting portion Bd may have a minimum thickness through which the magnetic flux Φmax can pass. That is, assuming that the laminated width of the rotor is L, the cross-sectional area S of the connecting portion Bd is
S = W2 × L
It becomes. Therefore, when the magnetic flux Φmax passes through the joint Bd, the magnetic flux density Bmax in the joint Bd is
Bmax = Φmax / S = Φmax / (W2 × L)
It becomes. Here, the value of Bmax is the saturation magnetic flux density. The saturation magnetic flux density is the value of B when the value of B almost does not increase even if H increases on the BH curve, and varies slightly depending on the material, but is generally 2.0 to 2.3 [ T] grade. The saturation magnetic flux density is obtained from the material characteristics of the rotor to be used, and is set as Bmax. After that, Φmax and L are known. Therefore, the value of W2 can be obtained based on the above formula. As described above, the width of the connecting portion Bd can be obtained.

  As described above, in the present invention, even if a reverse field magnetic flux is applied, most of the magnetic field is released in the slit direction, and the magnetic flux applied to the permanent magnet can be reduced. The fact that the magnetic flux due to the reverse field applied to the permanent magnet 3 becomes smaller means that it is harder to demagnetize. Therefore, it can be said that the rotor according to the present invention is difficult to demagnetize.

  The above is an example of implementation in the present invention. In the description of the embodiment of the present invention, it has been described that the width of the connecting portion is the same with the same symbol, but in order to have a structure that can withstand centrifugal force, even the same symbol goes inside the rotor. It is possible to use a configuration that gradually increases the thickness.

  1 rotor, 2 slits, 3 permanent magnets, 4 magnetic paths.

Claims (3)

In the rotor of a multilayer flux barrier type reluctance motor,
In the rotor composed of a silicon steel plate or a soft magnetic material, a plurality of slits that are gap portions are formed at intervals in the radial direction, and a magnetic path disposed between the slits,
Connecting the magnetic paths to form the rotor, and a connecting part for dividing the slit;
Among the plurality of slits, a permanent magnet that is disposed in one or more slits on the inner side and whose magnetic pole direction is orthogonal to the magnetic path;
With
The slit in which the permanent magnet is arranged is divided by a connecting part Bc located right next to both sides of the permanent magnet and a connecting part Bd located at a position farther from the permanent magnet than the connecting part Bc. ,
The slit in which the permanent magnet is not arranged is divided at one or more connecting portions Bb,
The connecting portion Bb and the connecting portion Bd are located on the same straight line that does not intersect the permanent magnet, and do not face the direction of the magnetic flux of the permanent magnet.
The width of the connecting portion Bd is larger than the width of the connecting portion Bb.
A rotor of a multi-layer flux barrier type reluctance motor. In the rotor shown in claim 1,
A multilayer flux barrier type reluctance motor characterized in that a straight line connecting the connecting part Bb and the connecting part Bd intersects with a straight line passing through the center of the permanent magnet and extending in the radial direction at the outer periphery of the rotor. Rotor. In the rotor shown in claim 1,
When the maximum magnetic flux intermingled with the rotor is Φmax, the saturation magnetic flux density obtained from the material characteristics of the rotor is Bmax, and the laminated width of the rotor is L, the width W2 of the connecting portion Bd is W2 = A rotor of a multilayer flux barrier type reluctance motor, characterized by satisfying an equation of Φmax / (Bmax × L).

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