JPH04295260A - Squirrel-cage rotor - Google Patents

Abstract

PURPOSE:To provide a squirrel-cage rotor whereby an effect of suppressing abnormal torque, vibration and noise equivalent to a skew effect can be obtained without applying a skew to a laminated iron core further a temperature rise thereof can be suppressed as low as possible. CONSTITUTION:A punch part 30 of a steel plate is formed in an asymmetrical shape so as be placed in a position where a bridge part 30b in the peripheral side or an opening part is displaced by a distance (d), satisfied by a formula (A), to one side relating to a center line for storing a conductor, and a laminated iron core 24 is laminated in each two or more sheets so that the punch part 30 agrees to obtain an equal effect to applying a skew. Further, a duct part 40 is interposed between each unit block to improve cooling performance by smoothly performing convection of a radial duct. {piD/4(Z+P)}=d={piD /4(Z-P)}...(A) where: D, the rotor diameter; Z, the number of slots of corresponding stator; P, the number of pairs of electrodes.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a squirrel cage rotor having a laminated core made of laminated steel plates each having a plurality of slots for accommodating conductors formed on the outer periphery thereof.

0002

[Prior Art] In general, this type of squirrel cage rotor has a laminated core formed by laminating a large number of magnetic steel plates each having a plurality of slots formed in advance by punching or the like on the outer periphery. A squirrel cage conductor is formed by casting an aluminum secondary conductor into the slot, and connecting the ends of the secondary conductor with an end ring.

In this case, when the rotor is driven, the magnetic flux that enters the laminated core from the stator through the gap contains harmonic components, and the harmonic components of this magnetic flux cause This will generate harmonic electromotive force in the secondary conductor. However, such harmonic electromotive force acts as abnormal torque on the rotor, resulting in pulsating torque and causing vibration or noise.

[0004] Conventionally, in order to suppress the adverse effects of such harmonic components, a laminated iron core in which the rotor is so-called skewed has been used. This is when laminating steel plates.
The position of the slot is shifted slightly in the circumferential direction, for example, there is one that shifts the position of the stator slot as a whole by one pitch. As a result, the phase of the electromotive force generated in the secondary conductor due to the harmonic component of the magnetic flux is slightly shifted, so the harmonic component of the electromotive force as a whole is canceled out, and the amount that contributes to abnormal torque is suppressed. be.

[0005]

However, the above-mentioned conventional configuration has the following problems. That is, first of all, when laminating steel plates while skewing them, a special jig is required to adjust the pitch, and it takes a lot of time to adjust the pitch (especially when the slot is completely closed). In this case, the positions of the slots cannot be seen from the outer circumferential direction in the stacked state, which takes time and effort), which inevitably increases costs.

Second, when a secondary conductor is housed in a laminated core having such skewed slots, it is necessary to form the secondary conductor by casting a metal such as aluminum. At this time, cavities that become defects may occur in the stepped portion of the laminated portion of the steel plates within the slot. and,
Such defective portions cause the rotor to become unbalanced, resulting in a problem of lowering the stability of the rotational state, especially when rotating at high speeds.

Thirdly, in order to solve the problems that occur in the rotor, for example, as shown in Japanese Patent Application Laid-Open No. 64-81647, the secondary conductor is not formed by casting but is made into a bar-shaped secondary conductor. There is one that is press-fitted directly into the slot. In other words, in this case, by skewing the iron core on the stator side, slots are formed on the rotor side without skewing, and the secondary conductor is housed by press-fitting, thereby increasing the strength. By increasing the number of rotors, the rotor has a structure that can sufficiently withstand high-speed rotation. However, in this case, since the iron core on the stator side is skewed, it takes time and effort to store the windings and insulators in the stator slots, reducing assembly work efficiency, especially when it comes to automatic mounting. There are problems that require a large amount of cost, such as being unable to do so. Furthermore, in order to solve the above-mentioned problems, a method was disclosed in Japanese Utility Model Publication No. 17045/1983 in which only the skew effect was obtained without performing skew when laminating steel plates, and the part corresponding to the opening or bridge of the slot was It is formed offset from the slot centerline. however,
In this case, no logical value for the amount of deviation is indicated;
If the dimensions are deviated, the skew effect will almost disappear, and when actually applied, it is necessary to find the optimum value through experiments, etc., which increases the design cost.

The present invention has been made in view of the above-mentioned circumstances, and its object is to be able to obtain abnormal torque, vibration and noise suppression effects equivalent to the skew effect without skewing the laminated core, and to To provide a squirrel cage rotor capable of suppressing temperature rise of a laminated iron core as much as possible. [Structure of the invention]

[0009]

[Means for Solving the Problems] The squirrel cage rotor of the present invention has a laminated iron core formed by laminating a predetermined number of steel plates each having a punched part for forming a slot for accommodating a conductor on the outer periphery. The punched part of the steel plate has a bridge part or an opening on the outer circumferential side thereof on one side with respect to the center line of the main part in which the conductor is housed, and the distance d satisfied by formula (A) is
The laminated core is formed by combining a plurality of unit blocks in the axial direction in which a plurality of unit blocks are laminated with each other so that the punched portions of the steel plates coincide with each other, and the adjacent units The blocks are arranged so that one of the blocks is upside down with respect to the other and the main portions match each other, and further, a gap between the conductor and the inner periphery of the slot in the slot is provided between each unit block. It is characterized by the interposition of a communicating radial duct portion and an axial duct that supplies cooling air to the radial duct portion. {πD/4(z+p)}≦d≦{πD/4
(z-p)} ...(A) However, D: Rotor diameter z: Number of slots in the corresponding stator p: Number of pole pairs

0010

[Operation] According to the squirrel cage rotor of the present invention, as shown in FIG. 1, the laminated core 24 is formed by laminating a plurality of steel plates 29 having punched portions 30 at the same position to form unit blocks 31 and 32. ing. The unit blocks 31 and 32 are combined via a radial duct portion 34 (see FIG. 4). and,
This radial duct part 34 is connected to each unit block 31, 3.
It has a cross-sectional area including the bridge portions 35 and 36 of the slot 25 at 2. Further, the slot 25 is formed parallel to the axis of the rotating shaft, and bridges 35, 36 (in the figure, the slot 25 is a fully closed type, and the outer peripheral side becomes the bridge parts 35, 36) with respect to the main part 30a. ) is formed at a position shifted by a predetermined distance d from the center line l of the main portion 30a, and the unit block 31
, 32, the direction of shift is reversed. As a result, the main part 3 of the slot 25 is
0a has a shape that is not inclined with respect to the axis of the rotating shaft, and there is no step difference in the laminated state of the steel plates 29 when forming the secondary conductor 26 by casting, thereby reducing the occurrence of cavities that become defects. Further, an axial duct 40 is provided on the inner peripheral side of the slot 25, and cooling air is sent to the radial duct portion 34 of each unit block 31, 32.

[0011] In terms of electrical characteristics, the following principle provides the same effect as in the case of skew, and it is possible to suppress as much as possible the generation of abnormal torque, vibration, and noise associated with the drive of the rotor.

That is, as shown in FIG. 2, the magnetic fluxes φA and φB entering the unit blocks 31, 32 from the stator side through the gap have different inflow paths, resulting in a phase difference α (electrical angle). Secondary conductor 2 due to magnetic flux φA and φB
If the voltages induced in 6 are eA and eB, respectively,
This also produces a phase difference α. This phase difference α is the magnetic flux φ
A distance 2d corresponding to the circumferential deviation of the magnetic paths of A and φB
Specifically, it is given by the number of pole pairs p and the pole pitch τ expressed by the outer diameter D of the laminated core 24 as shown in the following equation. α=2dπ/τ

...(1) However, τ=πD/2p

On the other hand, the induced voltages eA and eB are quantities expressed as vector quantities, respectively, as shown in FIG.
The voltage e actually generated in the rotor conductor 26 is a value expressed as the sum of these values e=eA+eB. Magnetic flux φA
and φB include harmonic components, and as a result, harmonic components are also generated in the induced voltages eA and eB. However, since there is a phase difference α between the two, the degree of the harmonic component included in the induced voltage e, which is the combined value of these, becomes a different value depending on each order. A skew coefficient Ksn indicating the degree of harmonic components included in such induced voltage E is given by the following equation. Ksn=|eA +eB |/|eA |
+｜eB｜…(2)

00
14] Now, if the unit blocks 31 and 32 have the same thickness, |eA |=|eB |, and as shown by the vector in the conceptual diagram in FIG.
It is equal to twice the length of A, 2r. Further, the magnitude of the vector sum in the numerator of the equation is equal to the length q of the line segment OB in the figure. When these values are expressed in accordance with equation (2), they are calculated as follows. q/2r=2Rsinα/4Rsin(α
/2) =cos(α/2
)
...(3) Also, in the n-th harmonic, the phase angle α becomes n times, so if α is replaced by nα, the skew coefficient Ksn in equation (2) can be expressed as follows. Ksn=cos(nα/2)
…(4
)

Now, it is generally well known that harmonics that tend to generate abnormal torque, vibration, or noise are caused by groove harmonics due to stator slots, but the order μs of the harmonics is , is expressed as follows. μs=(z/p)±1

...(5) (However, z is the number of stator slots)

00
[16] Therefore, the value of the skew coefficient Ksn in the case of the present invention at the order shown in the above equation (5) is calculated as follows based on the equation (4). That is, first, with respect to the range (A) of the set distance d, the range of the phase difference α is expressed by the formula (
1), πp/(z+p) ≦α≦ πp/(
z-p)...(6) Based on this result, first find the first-order (n=1) case of the skew coefficient Ksn shown in equation (4), (a)
At the lower limit of α, Ks1 = cos(α/2)
= cos {πp/2(z+p)}
...(7a) (b) At the upper limit of α, Ks1 = cos {πp/2(z-p)}
...(7b) Here,
In general, since the number z of stator slots is larger than the number p of pole pairs (for example, z = 48, p = 2), the (7th
The values of equations a) and (7b) are approximately 1. On the other hand, the skew coefficient Ksn due to the μs-order harmonic shown in equation (5) is
Corresponding to the upper and lower limits of distance d, Ksn=cos{π(z±p)/2(z±
p)} ...(8) Here, considering the general case where the number of stator slots z is larger than the number of pole pairs p, Ksn ~ cos (π/2) = 0
…(9)
Therefore, the μth
The s-th skew coefficient Ksn can be set to approximately zero. Therefore, in any case, the skew coefficient can be set to approximately 1 for the first-order component of the voltage induced in the conductor, which effectively acts as the rotational force of the rotor.
The induced voltage of the μs-order harmonic component, which causes abnormal torque, vibration, or noise, can be reduced as much as possible, and the same effect as when skewing is performed can be obtained.

Table 1 shows the results of calculating the skew coefficients derived in this way according to various conditions.

[0018]

[Table 1] In this case, the coefficient values when conventional skewing is performed are also shown, and the skew coefficient Kns' at that time is given by the following equation. Kns'=sin {(nα/2)/(nα
/2)} …(10)

As can be seen from this result, when conventional skewing is performed, the value of distance d is almost a large value of 0.6 or more even in the range of formula (A), whereas in the present invention The value is less than or near 0.1, and a sufficiently large skew effect is obtained.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a motor will be described below with reference to FIGS. 5 to 7.

First, in FIG. 5 showing the overall configuration in cross section, the stator 19 consists of a stator core 20 and a stator winding 21 housed in a slot (not shown). It is formed by laminating stamped steel plates without skewing them.

On the other hand, the squirrel cage rotor 22 consists of a rotating shaft 23 supported by a bearing (not shown) and a laminated core 24 fitted to the rotating shaft 23. The laminated core 24 has slots 25 along its outer periphery. A large number of them are formed. A secondary conductor 26 is die-cast (cast-molded) in the slot 25 of the laminated core 24, and an end ring 27 is die-cast integrally with the secondary conductor 26 so as to connect their ends. A squirrel cage conductor 28 is formed.

Next, the squirrel cage rotor 22 will be described in detail. The steel plate 29 constituting the laminated core 24 is made of a silicon steel plate, and is disk-shaped with an outer diameter of D. As shown in FIG. Form a large number of 30. This punched part 30 is formed by arranging a main part 30a on which the secondary conductor 26 is die-cast, and bridge parts 35 and 36 for generating a skew effect in the following relationship. That is, the positions of the bridge parts 35 and 36 are arranged to be shifted to one side by a predetermined distance d with respect to the center line l of the main part 30a. And the distance d is
The following values are set as values that satisfy the conditions shown in equation (A) above. d=(πD)/(4z)
…(stomach)

A predetermined number of such steel plates 29 are stacked at the same position (that is, without skewing), and the units of the same thickness are stacked so that the thickness is obtained by subtracting a multiple of the width S of the communication portion 33 from the overall thickness L. Blocks 31 and 32 form a pair. Further, a communicating portion 33 is interposed between this unit block 31 and a unit block 32 formed in the same manner and having a punched portion 30 arranged inside out, and this communicating portion 33 includes:
The same number of radial duct parts 34 as slots 25 are formed. As shown in FIG. 6, each of these radial duct parts 34 communicates with the bridge parts 35, 36 of the secondary conductor 26 of the slot 25 in each unit block 31, 32, and the punched part 3
It has a shape that includes 0. The laminated core 24 is constructed by combining both unit blocks 31 and 32 with the radial duct portion 34 in between so that the main portion 30a of the punched portion 30 overlaps. Therefore, when the slot 25 of the laminated core 24 is viewed from the axial direction of the rotating shaft 26,
In each slot 25, the positions of the bridge portions 35, 36 are shifted by a distance of 2d between the unit blocks 31, 32, and the radial duct portion 34 encompasses the bridge portions 35, 36. On the other hand, like the rotor 22, the stator core 20 also has a spacer 37 interposed therebetween so that its axial dimensions are aligned with the rotor 22. Incidentally, the squirrel cage rotor 22 in this embodiment produces the following skew effect in a rotating state. That is, in this embodiment, the above-mentioned distance d
is set as shown in equation (a), so the value of phase difference α corresponding to equation (6) is α=pπ/z

…(b) becomes. Therefore, the skew coefficient Ksn has the following value corresponding to equations (7a), (7b), and equation (8). (a) First-order case (n=1) Ks1 = cos(πp/2z)
...(c) (b) In the case of μs {μ=z/(p±1)}
Ksn=cos[π/2{1±(p/z)}]
(d) Now, for example, if the number of slots z in the stator is 36, the calculation will be as shown in Table 2.

[0025]

[Table 2]

As a result, the value of the skew coefficient Ksn in equation (c) is 0.996, so it can be regarded as approximately 1, and the value of the skew coefficient Ksn in equation (d) is 17th order,
Since both the 19th orders are 0.087, they can be considered to be approximately zero. Therefore, the skew coefficients Ksn and Ks of the conventional and this embodiment are
Comparing n', in the case of the 17th and 19th orders, in the case of this embodiment, it has decreased from 13% in the conventional case to 15%. Therefore, since the harmonic torque is reduced, the generation of abnormal torque is suppressed as much as possible, and the generation of vibration and noise is also reduced.

FIG. 7 shows the relationship between the rotational speed and torque of the motor using the squirrel cage rotor of this embodiment. In the figure, the broken line shows the characteristics of this embodiment, the solid line shows the characteristics when conventional skew is performed, and the dashed line shows the characteristics when no skew is performed. According to this result, when the rotation speed increases in the non-skew engine, the torque decreases and an abnormal torque generation state occurs, whereas in this example, the decrease in torque is improved by reducing the harmonic torque.
It can be seen that the skew effect exhibits characteristics equal to or better than those of the conventional skewed one. Therefore, the engine can be started smoothly and accelerated in a short time.

In this embodiment, since the radial duct portion 34 communicating with the unit blocks 31 and 32 is interposed,
Axial duct 4 provided on the inner peripheral side of the unit block 31
The cooling air flowing in from 0 flows smoothly in the radial direction through the radial duct portion 34 between the unit blocks 31 and 32. That is, in this embodiment, the convection of the cooling air is extremely smooth, so that the laminated core 24 quickly radiates heat.

In the above embodiment, the secondary conductor 26
Although the case where the secondary conductor is housed by die-casting has been described, the present invention is not limited to this, and, for example, the secondary conductor may be formed by press-fitting. In this case, both unit blocks 31,
After joining the communicating part 33 between the slots 32, the secondary conductor may be press-fitted into the main part 30 of the slot 25, or a unit block in which the secondary conductor is stored in advance may be joined.

Further, in the above embodiment, the steel plate is a silicon steel plate, but the steel plate is not limited to this, and for example, a cold rolled steel plate or an amorphous magnetic material may be used. In the above embodiment, the slot 25 is a fully closed type, but the slot 25 is not limited to this, but may be a semi-closed type, a double cage type other than a normal cage type, a deep grooved cage type, or a slot 25 of a deep groove type. ,
Although the value of the distance d is set as shown in equation (A), it is not limited thereto, and may be within the range shown in equation (A). Further, in the above embodiment, a case was described in which four unit blocks 31 and 32 were provided, but the present invention is not limited to this, and one or more pairs may be used.

[0031]

As explained above, according to the squirrel cage rotor of the present invention, the punched parts are stacked at the same position and the slots are formed parallel to the axial direction of the rotating shaft. When forming a conductor, the occurrence of cavities that become defects can be suppressed as much as possible. Furthermore, a secondary conductor can also be press-fitted. In this case, since the steel plate is not exposed to high temperatures, materials with high tensile strength such as amorphous magnetic materials can be used as the steel plate without crystallization. Moreover, even in this case, since the bridge part or opening of the slot is set at a distance d within the range shown by formula (A) from the center line of the main part, the same effect as applying skew can be obtained, and the rotation The child can suppress the generation of abnormal torque due to harmonic components as much as possible, and can also suppress the generation of vibration and noise as much as possible.

Furthermore, since an axial duct portion communicating with the radial duct between each unit block is interposed, the cooling air flowing in from the axial direction of the rotor can smoothly convect through the radial duct between the unit blocks. This has the excellent effect of promoting heat dissipation from the laminated cores and conductors of both the stator and rotor, thereby improving cooling performance.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing the appearance of a layered core.

FIG. 2 is an explanatory diagram showing the state of magnetic flux entering the slot.

FIG. 3 is an explanatory diagram showing electromotive force induced in a conductor.

FIG. 4 is a partial cross-sectional view of the laminated core.

FIG. 5 is a vertical side view of the overall configuration.

FIG. 6 is a partial cross-sectional plan view of the laminated core.

FIG. 7 is a characteristic diagram showing the correlation between rotation speed and torque.

[Explanation of symbols]

19...Stator, 20
...Stator core, 22...Squirrel cage rotor, 23...Rotating shaft, 24...Laminated core,
25...Slot, 26...Secondary conductor,
27... End ring, 28... Squirrel cage conductor,
29... Steel plate, 30... Punching part,
30a...main part, 31,
32... Unit block, 33... Communication section, 34... Duct section, 35, 36... Bridge section, 40... Axial duct.

Claims (1)

[Claims] 1. A squirrel-cage rotor comprising a laminated iron core formed by laminating a predetermined number of steel plates in which punched parts for forming slots for accommodating conductors are formed on the outer periphery, the steel plates being punched. The part is formed in an asymmetrical shape such that the bridge part or the opening part on the outer circumferential side thereof is shifted by a distance d that satisfies formula (A) on one side with respect to the center line of the main part in which the conductor is housed; The laminated core is constructed by combining a plurality of unit blocks in the axial direction, each of which is a plurality of laminated steel plates so that the punched portions match each other, and adjacent unit blocks are arranged such that one of the unit blocks is turned upside down relative to the other. The unit blocks are arranged such that the main parts coincide with each other, and further, a duct part is interposed between each unit block to communicate between the conductors in the slot, and a duct part is provided in the axial direction on the inner diameter side of the unit block. A squirrel cage rotor characterized by having a duct. {πD/4(z+p)}≦d≦{πD/4
(z-p)} ...(A) However, D: Rotor diameter z: Number of slots in the corresponding stator p: Number of pole pairs