This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2018-136735, filed on Jul. 20, 2018, the entire content of which is incorporated herein by reference.
This disclosure generally relates to a rotating electrical machine configured of fractional slot in which the number of slots of a stator per pole per phase is a fraction.
Conventionally, a rotating electrical machine is known which is configured of fractional slot in which a denominator of an irreducible fraction (the number of slots per pole per phase) equals to four or greater than four, the irreducible fraction is obtained by dividing the number of slots of a stator by the number of phases and the number of poles of a rotor (for example, refer to JP2016-5409A which will be hereinafter referred to as Patent reference 1).
Patent reference 1 discloses a three-phase alternating current electric motor including four poles and fifteen slots or including ten poles and thirty-six slots, in which an irreducible fraction is 5/4 and 6/5, respectively. Coil of the three-phase alternating current electric motor is configured by double-layer-winding including a predetermined coil pitch, and a placement or alignment of a second layer is shifted or offset by a predetermined number of slots relative to a first layer. The technique of Patent reference 1 corresponds to reducing torque ripple, by calculating the predetermined number of slots from a relational expression defined on the basis of the number of pairs of poles and the number of slots.
On a rotating electrical machine configured of fractional slot, due to a magnetic configuration of the rotating electrical machine, an exciting force of a space deformation mode including an order which is less than the number of poles of a rotor is generated. A stator includes a natural frequency that corresponds to the space deformation mode, and the lower the order of the space deformation mode is, the smaller the natural frequency is. In a case where a frequency of the exciting force of the low-order space deformation and the natural frequency of the stator that corresponds to the low-order space deformation mode match each other, resonance occurs, and noise and vibration increase. Accordingly, on the rotating electrical machine configured of the fractional slot, the noise and vibration increase in a range of a low number of revolutions.
In a case where the arrangement or alignment of the second layer is shifted relative to the first layer by the predetermined number of slots as in Patent reference 1, ratio of magnitude of the exciting force generated by coil sides which are accommodated in plural slots continuously adjacent to each other in a circumferential direction of the rotor and which include the same phase and the same direction of electric current as each other is uneven or non-uniform along the circumferential direction of the rotor. For example, in an example of four poles and fifteen slots that is exemplified in Patent reference 1, the ratio of magnitude of the exciting force changes as 3:2:2:3, and thus a magnetic attractive force acting between the rotor and the stator becomes uneven along the circumferential direction of the rotor. As a result, the exciting force of the space deformation mode including a lower order than the number of poles (four poles) of the rotor occurs more easily, and thus the noise and vibration increase in a range of low number of revolutions in which a natural frequency of the stator that corresponds to the low-order space deformation mode and a frequency of the exciting force of the low-order space deformation match with each other. That is, in a case where the rotating electrical machine as described above is applied for driving an electric vehicle and a hybrid vehicle, a vehicle speed range in which the noise and vibration increases becomes lower. Therefore, in a case where the rotating electrical machine as described above is operated on the electric vehicle and/or the hybrid vehicle for driving such vehicles, the vehicle speed range in which the noise and vibration increases comes close to a range of low vehicle speed in which the vehicle is often driven. This increases frequency of opportunities in which the noise and vibration increases.
A need thus exists for a rotating electrical machine which is not susceptible to the drawback mentioned above.
According to an aspect of this disclosure, a rotating electrical machine includes a stator including a plurality of slots on which conductive wire is wound, and a rotor facing the stator and including a plurality of magnetic poles, wherein the rotating electrical machine is configured of fractional slot in which a denominator of an irreducible fraction obtained by dividing a number of the slots of the stator by a number of phases and a number of the magnetic poles of the rotor is equal to or greater than four, and ratio of magnitude of magnetomotive force of each phase is even in respective poles of the magnetic poles of the rotor.
According to another aspect of this disclosure, a rotating electrical machine includes a stator including a plurality of slots on which conductive wire is wound, and a rotor facing the stator and including a plurality of magnetic poles, wherein the rotating electrical machine is configured of fractional slot in which a denominator of an irreducible fraction obtained by dividing a number of the slots of the stator by a number of phases and a number of the magnetic poles of the rotor is equal to or greater than four, and ratio of magnitude of magnetomotive force of each pole coil of each phase is even in a circumferential direction of the rotor.
The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein:
An embodiment of a rotating electrical machine disclosed here will be described hereunder with reference to the drawings. In the embodiment, the explanation will be made on a three-phase alternating current synchronous electric motor (which will be referred to as a motor M) serving as an example of the rotating electrical machine. The present disclosure, however, is not limited to the embodiment and may be changed and modified in various ways without departing from the scope of the disclosure.
(Basic configuration) As illustrated in
The stator 3 includes a stator core 31 including a cylindrical shape. The stator core 31 is formed of plural magnetic steel sheets laminated or stacked each other. The stator core 31 is configured of a yoke portion 31a formed in an annular shape at the radially outward direction Y2 side, plural teeth portions 31b protruding from the yoke portion 31 in the radially inward direction Y1, and a flange portion 31c provided at a protruding end of each of the plural teeth portions 31b to be arranged along the circumferential direction X. The slot 32 on which the winding is wound is formed between the teeth portions 31b which are adjacent to each other, that is, which are arranged side by side. The number of the plural slots 32 is the same as the number of the plural teeth portions 31b.
The rotor 2 includes a rotor core 21 including a cylindrical shape and formed of plural magnetic steel sheets laminated or stacked each other. The rotor 2 includes the plural permanent magnets 22 buried in the rotor core 21. The rotor core 21 is supported by a shaft member and is configured in such a manner that the rotor 2 is rotatable in the circumferential direction X relative to the stator 3. The permanent magnets 22 are formed of, for example, rare-earth magnet, and a north pole (N pole) and a south pole (S pole) are arranged alternately with each other in the circumferential direction X. An outer circumferential surface of the plural permanent magnets 22 may be exposed from the rotor core 21.
The motor M of the embodiment is configured of fractional slot in which the denominator of an irreducible fraction (which will be hereinafter referred to also as the number of slots per pole per phase) obtained by dividing the number of slots 32 of the stator 3 by the number of phases (three phases in the embodiment) and by the number of the magnetic poles of the rotor 2 is equal to or greater than four. The motor M is configured by distributed winding in which the number of slots per pole per phase is greater than one. In other words, when the number of slots per pole per phase is expressed in a mixed fraction, the integer portion of the mixed fraction is equal to or greater than one. For example, the number of slots per pole per phase is 5/4 on the motor M including eight poles and thirty slots, and the number of slots per pole per phase is 7/4 on the motor M including eight poles and forty-two slots.
For example, the winding to be wound on the plural slots 32 is configured of the conductive wire which corresponds to copper wire coated with insulation layer. For the winding, round wire including a round cross section and/or various conducting wire including a polygonal cross section are used. A winding method of the winding onto the slots 32 is the distributed winding, and double-layer winding is generally applied.
As an example of the method of winding the wire onto the slots 32, a unit coil 11 of the double-layer winding of the distributed winding is illustrated in
As illustrated in
The coil pitch is an integer which is close to the number of slots per pole obtained by dividing the number of the slots 32 of the stator 3 by the number of the magnetic poles of the rotor 2. For example, in a case where the motor M includes eight poles and thirty slots (the number of slots per pole is 3.75), the coil pitch is three slots (fractional pitch winding or short-pitch winding) or four slots (long-pitch winding). In a case where the motor M includes eight poles and forty-two slots (the number of slots per pole is 5.25), the coil pitch is five slots (fractional pitch winding) or six slots (long-pitch winding).
As described above, according to the embodiment, the coil of each phase includes the coil sides 11a of the two layers of the unit coil 11, which serve as one set of two-layer units 12, accommodated in the slot 32 in a manner that the coil sides 11a are stacked for plural sets in the radial direction Y. The coils of the three phases are electrically connected to one another with Y connection. The connection of the coils is not limited, and the coils of the three phases may be electrically connected with delta connection.
(Phase arrangement in a case where the denominator of the irreducible fraction is an even number) (In a case where the number of the layers of the two-layer units stacked in the radial direction corresponds to a value obtained by dividing the denominator of the irreducible fraction by two) Illustrated in
In the embodiment, in the two-layer unit 12, in each pole (that is, in one of the N pole or one of the S poles), a group of the coil sides 11a which are accommodated in one of the slots 32 or in the plural slots 32 adjacent to each other and which include the same phase and the same direction of electric current is defined as a phase belt 13. “A group of the coil sides 11a which are accommodated in one of the slots 32 or in the plural slots 32 adjacent to each other and which include the same phase and the same direction of electric current in each pole” is synonymous with a group of the coil sides 11a of which the phase is the same as each other, of which the direction of electric current is the same as each other, and which are accommodated in one of the slots 32 or in the plural slots 32 continuously adjacent to each other in the circumferential direction X.
In the example illustrated in
The numbers of the coil side 11a of the first layer are different between the phase belt 13 in the first and second slots 32 and the phase belt 13 in the twelfth and thirteenth slots 32. Also, the numbers of the coil side 11a of the second layer are different between the phase belt 13 in the first and second slots 32 and the phase belt 13 in the twelfth and thirteenth slots 32. Here, even though the phase belts 13 include the same number of the coil sides 11a to each other, in a case where the arrangements of the coil sides 11a in the first layer and the second layer are different from each other, the difference is indicated by the presence or absence of an asterisk character provided at the numeric character indicating the number of the coil sides 11a, as in 3 and 3*. That is, in the two-layer unit 12 formed of the first layer and the second layer, the numbers of the coil sides 11a of the phase belts 13 are 3, 2, 2, 3* in the mentioned order which correspond to one cycle (four poles), and the two cycles (eight poles) are repeated.
Because the number of the slots per pole per phase is 5/4 in a case of the eight poles and thirty slots, the one cycle is configured by the same number of poles (four poles) as the value of the denominator (four) and the number of the coil sides 11a of the coil of each phase in one layer in one cycle is the value of the numerator (five). That is, the number of the coil sides 11a of each phase forming one cycle in the two-layer unit 12 corresponds to a value (ten) obtained by doubling the numerator. The number of the ten coil sides 11a is divided into four and the ten coil sides 11a are arranged at the four poles, and thus the one cycle is configured by 3, 2, 2, 3* of the coil sides 11a.
As described above, at the motor M of the double-layer winding that is formed of eight poles and thirty slots, the numbers of the coil sides 11a of the phase belts 13 are 3, 2, 2, 3* in the stated order and correspond to one cycle (four poles), and two of the cycles are repeated (eight poles).
In a case where the motor M includes the fractional slot configuration such as eight poles and thirty slots, ratio of magnitude of magnetomotive force of the two-layer unit 12 changes or varies in 3:2:2:3, and thus a magnetic attractive force acting between the rotor 2 and the stator 3 becomes uneven or non-uniform in the circumferential direction X of the rotor 2. As a result, in a case where an electric vehicle and/or a hybrid vehicle are driven by the motor M, an excitation force of a space deformation mode including a low-order which is lower compared to the number of poles (eight poles) of the rotor 2 occurs more easily, and thus the noise and vibration increase in a range of low number of revolutions where a natural frequency of the stator 3 that corresponds to the space deformation mode including a low-order and a frequency of the exciting force of the space deformation mode including the low-order match with each other. That is, a vehicle speed range in which the noise and vibration increase becomes lower. The vehicle speed range in which the noise and vibration increases comes close to a range of low vehicle speed in which the vehicle is often driven. This increases frequency of opportunities in which the noise and vibration become large.
In the embodiment, therefore, as illustrated in
That is, the plural phase belts 13 are formed in a mixed manner such that the ratio of size or magnitude of the magnetomotive force generated by the plural coil sides 11a forming the plural mixed phase belts 13A is even or substantially even in the respective poles. As a consequence, the magnetomotive force occurring upon electrification of the coil is more evenly generated, and it is less likely that the exciting force of the spatial deformation mode including the low-order which is lower compared to the number of poles of the rotor 2 occurs. Accordingly, the noise and vibration in the low-rotation range due to the low-order space deformation mode of the stator 3 that is attributed to the phase arrangement of the stator winding can be reduced. As a result, the vehicle speed range where the noise and vibration increase can be shifted from the range of low vehicle speed at which the vehicle is frequently driven to a range of high vehicle speed or to a range equal to or higher than the maximum vehicle speed, in each of which the vehicle is driven less frequently. Consequently, the frequency of the opportunities in which the noise and vibration increase can be reduced.
As described above, in the embodiment, the denominator of the irreducible fraction (5/4) is an even number. The number of layers of one two-layer unit 12 formed of the phase belt 13 (a first phase belt 13) in the first and second layers and other two-layer unit 12 formed of the phase belt 13 (a second phase belt 13) in the third and fourth layers corresponds to the value (two layers) obtained by dividing the denominator by two. That is, the number of layers of the plural phase belts 13 stacked in the radial direction Y is the value obtained by dividing the denominator of the irreducible fraction by two. Accordingly, the number of layers that are accommodated in each of the slots 32 in the mixed manner can be reduced as much as possible. As a result, the noise and vibration can be reduced without complicating the distributed winding configuration of the winding to each slot 32.
In the mixed coil 1 in which the number of layers of the phase belts 13 stacked in the radial direction Y corresponds to the value obtained by dividing the denominator of the irreducible fraction by two, an amount of shift or an amount of offset (a predetermined number of slots) between the phase belt 13 (the first phase belt 13) formed of the first and second layers and the phase belt 13 (the second phase belt 13) formed of the third and fourth layers is specified as follows, such that the mixed phase belt 13A includes the same number of the coil sides 11a in each pole.
In the embodiment, the amount of shift of the first phase belt 13 and the second phase belt 13 relative to each other is defined or specified according to any of the following definitions (1) to (3); (1) An integer value obtained by doubling a nearest or closest integer that is nearest or closest to the number of slots per pole, (2) A value obtained by adding one to the integer value obtained by doubling the closest integer that is closest to the number of slots per pole in a case where a value obtained by subtracting the closest integer from the number of slots per pole is positive, and (3) A value obtained by subtracting one from the integer value obtained by doubling the closest integer that is closest to the number of slots per pole in a case where the value obtained by subtracting the closest integer from the number of slots per pole is negative.
Next, verification will be made that an extent or spread of the width of the coil sides 11a, in the circumferential direction X, which form the mixed phase belt 13A can be minimized by following the above-described definition. This is because, by minimizing the extent of the width, in the circumferential direction X, of the coil sides 11a forming the mixed phase belt 13A, an inconvenience that the magnetomotive forces of the respective mixed phase belts 13A arranged adjacent to each other in the circumferential direction X exert influences on each other can be prevented. Thus, decrease in torque can be restricted.
As described above, the motor M with eight poles and thirty slots includes the number of slots per pole per phase of 5/4 (1.25). The value (3.75) obtained by multiplying the number of slots per pole per phase by the number of phases (three phases) corresponds to the number of slots per pole. Accordingly, the closest integer closest to the number of slots per pole is four. Thus, in a case of the definition (1) described above, the amount of shift of the first phase belt 13 and the second phase belt 13 relative to each other is eight slots (refer to
Each of
Each of
In a case of the motor M including eight poles and forty-two slots, the number of slots per pole per phase is 7/4 (1.75). The value (5.25) obtained by multiplying the number of slots per pole per phase by the number of phases (three phases) corresponds to the number of slots per pole. Accordingly, the closest integer closest to the number of slots per pole is five. Thus, in a case of the definition (1) described above, the amount of shift of the of the first phase belt 13 and the second phase belt 13 relative to each other is ten slots. In a case of the definition (2) or (3) described above, the subtracted value (0.25) obtained by subtracting the closest integer that is closest to the number of slots per pole from the number of slots per pole is positive. Thus, the definition (2) is applied, and accordingly the amount of shift of the of the first phase belt 13 and the second phase belt 13 relative to each other is eleven slots.
Each of
Each of
In a case of the motor M including eight poles and twenty-seven slots, the number of slots per pole per phase is 9/8. Accordingly, one cycle includes the same number of poles (eight poles) as the value (8) of the denominator. The number of the coil sides 11a of the winding of each phase in one layer in one cycle corresponds to the value (9) of the numerator. That is, the number of the coil sides 11a of each phase forming one cycle in the two-layer unit 12 corresponds to a value (18) obtained by doubling the numerator. The number of the coil sides 11a of the first phase belt 13 corresponds to 3, 3*, 2, 2*, 2, 2, 2*, 2, that is, eighteen in total.
In a case where the number of layers of the phase belts 13 stacked in the radial direction Y corresponds to a value obtained by dividing the denominator of the irreducible fraction by two, the number of layers of the phase belts 13 is four. Because the number of slots per pole is 3.375 in a case of the eight poles and twenty-seven slots, the amount of shift between the first phase belt 13 and the second phase belt 13 relative to each other corresponds to six slots in a case of the definition (1) where the integer value obtained by doubling the closest integer (3) that is closest to the number of slots per pole. That is, the number of the coils sides 11a of the second phase belt 13 corresponds to 2*, 2, 3, 3*, 2, 2*, 2, 2. On the other hand, the number of layers of the phase belts 13 stacked on each other needs to be four, and therefore another set of a third phase belt 13 and a fourth phase belt 13 is formed to configure the mixed coil 1. When the third phase belt 13 is shifted or offset relative to the second phase belt 13 by six slots, the fourth phase belt 13 is shifted or offset relative to the third phase belt 13 by six slots, the number of the coils sides 11a of the third phase belt 13 corresponds to 2, 2, 2*, 2, 3, 3*, 2, 2* and the number of the coil sides 11a of the fourth phase belt 13 corresponds to 2, 2*, 2, 2, 2*, 2, 3, 3*. The number of the coil sides 11a of the mixed phase belt 13A in which the coil sides 11a are arranged in the radial direction Y of the slots 32 corresponds to 9′, 9′*, 9, 9′, 9′*, 9, 9′, 9′*. As a result, the plural phase belts 13 are configured in the mixed manner so that the ratio of magnitude of magnetomotive force generated by the plural coil sides 11a forming the plural mixed phase belts 13A is equal in the respective poles.
(In a case where the number of the layers of the two-layer units stacked in the radial direction corresponds to the denominator of the irreducible fraction) For example, at the motor M including eight poles and thirty slots, four of the two-layer units 12 may be stacked or layered in the radial direction Y of the slots 32 (from the first phase belt 13 to the fourth phase belt 13) so as to form the eight layers. That is, the number of layers (four) of the phase belts 13 stacked in the radial direction Y may be the denominator of the irreducible fraction (5/4). In this case, it is ideal that the amount of shift or offset (the predetermined number of slots) among the phase belts 13 adjacent to one another in the radial direction Y is the integer (four slots) that is closest to the number of slots per pole (3.75). That is, the coil sides 11a of the first phase belt 13 correspond to 3, 2, 2, 3*, the coil sides 11a of the second phase belt 13 correspond to 3*, 3, 2, 2, and the coil sides 11a of the third phase belt 13 correspond to 2, 3*, 3, 2, and the coil sides 11a of the fourth phase belt 13 correspond to 2, 2, 3*, 3. Thus, the mixed phase belts 13A arranged as 10, 10′, 10*, 10″ in the circumferential direction X are formed. As a result, the ratio of magnitude or strength of the magnetomotive forces generated by the coil sides 11a in the same phase is even in the respective poles, and the coil sides 11a are more evenly arranged, and thus the noise and vibration attributed to the phase arrangement of the stator winding are more reduced.
A first mixed phase belt 13A arranged in the circumferential direction X with 5, 5*, 5′, 5′* may be formed in the first to fourth layers and a second mixed phase belt 13A arranged in the circumferential direction X with 5′*, 5, 5*, 5′ may be formed in the fifth to eighth layers. In this case, the mixed phase belt 13A configured of the fifth to eighth layers is formed to be shifted or offset by the predetermined number of slots (fourth slots) relative to the mixed phase belt 13A configured of the first to fourth layers.
(Phase arrangement in a case where the denominator of the irreducible fraction is an odd number) Each of
Similarly to the case in which the number of layers of the phase belts 13 stacked in the radial direction Y corresponds to the denominator of the irreducible fraction, in the present embodiment, it is ideal that the amount of shift (the predetermined number of slots) of the phase belts 13 adjacent to each other in the radial direction Y relative to each other is the closest integer (four) that is closest to the number (3.6) of slots per pole. That is, the amount of shift of the phase belts 13 stacked in the radial direction Y relative to each other is four slots. As a result, as illustrated in
On the other hand,
(Winding configuration) (Winding configuration in the two-layer unit 12) A winding configuration in the two-layer unit 12 formed of the coil sides 11a of the two layers of unit coils 11 stacked in the slot 32 along the radial direction Y will be described with reference to
The sequential numbers indicated at a top portion of the drawings indicate the slot numbers. For example, the slot corresponding to the slot number 1 is the first slot 32. Out of the phase belts 13, the phase belt 13 placed in the first and second slots 32 in the first layer is defined as a layer phase belt 13a in which the plural slots 32 in the same layer are adjacent to each other, and also the phase belt 13 placed in the twelfth and thirteenth slots 32 in the second layer is defined as the layer phase belt 13a in which the plural slots 32 in the same layer are adjacent to each other.
In the example of
As illustrated in
Next, the winding pulled out in the axial front direction Z2 from the twenty-eighth slot 32 in the second layer serves as a pole coil connecting wire 11c and is connected to the first slot 32 in the second layer. Plural unit coils 11 facing a pair of poles (the north pole and the south pole) correspond to pole coils, and the “pole coil connecting wire 11c” is conductive wire connecting the unit coil 11 facing the north pole and the unit coil 11 facing the south pole to each other. Next, the winding is pulled into the first slot 32 in the second layer in the axial rear direction Z1, and the winding is wound between the first slot 32 in the second layer and the fifth slot 32 in the first layer to form the unit coil 11.
Next, the winding pulled out from the fifth slot 32 in the first layer in the axial front direction Z2 serves as the pole coil connecting wire 11c and is connected to the ninth slot 32 in the first layer. Next, the winding is pulled into the ninth slot 32 in the first layer in the axial rear direction Z1, and winding is wound between the ninth slot 32 in the first layer and the fifth slot 32 in the second layer to form the unit coil 11.
Next, the winding in the axial front direction Z2 that is pulled out from the fifth slot 32 in the second layer is connected to the ninth slot 32 in the second layer as the pole coil connecting wire 11c. Next, the winding is pulled into the ninth slot 32 in the second layer in the axial rear direction Z1, and winding is wound between the ninth slot 32 in the second layer and the thirteenth slot 32 in the first layer to form the unit coil 11. Then, the winding is finished at the thirteenth slot 32 in the first layer towards the axial front direction Z2.
As described above, the phase belt group 13B where the five unit coils 11 are formed of the single winding is configured, and ten of the coil sides 11a exist in the phase belt group 13B. The phase belt group 13B serves as one cycle, and the phase belt groups 13B corresponding to two cycles are formed in each phase (the U phase, the V phase and the W phase). In the example of
In the example of
In the example of
The phase belt 13 includes the layer phase belt 13a in which the plural slots 32 of the same layer (the first and second slots 32 in the first layer in the example of
(Winding configuration in series connection)
In the embodiment, the phase belt 13 is formed of the first phase belt 13 and the second phase belt 13 which are stacked in the radial direction Y. The first phase belt 13 and the second phase belt 13 are arranged to be shifted or offset to each other by eight slots (the integer value obtained by doubling the closest integer that is closest to the number of slots per pole) in the development direction in a manner similar to the example of
Then, a winding end (an end portion of the winding whose winding order is 10) of the first serial phase belt 13B1 and a winding start (an end portion of the winding whose winding order is 6 in
(Winding configuration in parallel connection) In
In the examples of
In the example of
That is, the pattern in which the two-layer unit 12 in the first and second layers and the two-layer unit 12 in the third and fourth layers are connected in series to each other includes four ways in total as follows. Two ways are illustrated in
In the example of
In the examples of
On the other hand, in the examples of
The motor M described in the aforementioned embodiment is not limited to the three-phase alternating current synchronous electric motor, and may be an alternating current electric motor, an induction motor and/or a synchronous electric motor that include two or more phases, for example.
The disclosure is applicable to a rotating electrical machine including fractional slot configuration in which the number of slots of a stator per pole per phase is a fraction.
According to the aforementioned embodiment, the motor M (i.e., the rotating electrical machine) includes the stator 3 including the plural slots 32 on which the winding (i.e., the conductive wire) is wound, and the rotor 2 facing the stator 3 and including the plural permanent magnets (i.e., the magnetic poles) 22, wherein the motor M is configured of the fractional slot in which the denominator of the irreducible fraction obtained by dividing the number of the slots 32 of the stator 3 by the number of phases and the number of the permanent magnets 22 of the rotor 2 is equal to or greater than four, and the ratio of magnitude of magnetomotive force of each phase is even in the respective poles of the permanent magnets 22 of the rotor 2.
According to the above-described configuration, the ratio of magnitude of magnetomotive force of each phase is even in the respective poles of the magnetic poles 22 of the rotor 2. Thus, it is less likely that the exciting force of the spatial deformation mode including the low-order which is lower compared to the number of poles of the rotor 2 occurs in the range of the low number of revolutions. Accordingly, the noise and vibration in the low-rotation range due to the low-order spatial deformation mode of the stator 3 can be reduced.
According to the aforementioned embodiment, the rotating electrical machine M is configured of the distributed winding in which the irreducible fraction is greater than one and which includes the predetermined coil pitch. The two-layer unit 12 includes two layers of the coil sides 11a accommodated in the slots 32 in the radial direction Y of the rotor 2. In the two-layer unit 12, a group of the coil sides 11a which include same phase and same direction of the electric current in each pole and which are accommodated in one of the slots 32 or in the plural slots 32 adjacent to each other corresponds to the phase belt 13. The plural phase belts 13 form the mixed coil 1 formed in a manner that the phase belts 13 are stacked up in the radial direction Y while each of the plural phase belts 13 is shifted in the circumferential direction X of the rotor 2 by the predetermined number of the slots 32. In the mixed coil 1, a group of the coil sides 11a which are accommodated in the plural slots 32 that are continuously adjacent to each other in the circumferential direction X and which include the same phase and same direction of electric current corresponds to the mixed phase belt 13A, and the plural mixed phase belts 13A include the same number of coil sides 11a as each other.
According to the above-described configuration, for example, in a case of four poles and fifteen slots, in the two-layer unit 12, the ratio of magnitude of magnetomotive force generated by the coil sides 11a which are accommodated in the plural slots 32 continuously adjacent to each other in the circumferential direction X of the rotor 2 and which include the same phase and the same direction of electric current changes in such a manner of 3:2:2:3 in the phase belt 13, while the above-described ratio of magnitude of magnetomotive force changes in such a manner of 5:5:5:5 in the mixed phase belt 13A.
That is, the plural phase belts 13 are configured in the mixed manner so that the ratio of magnitude of magnetomotive force generated by the plural coil sides 11a forming the mixed phase belt 13A is even at respective poles of the magnetic poles 22 of the rotor 2. As a result, the magnetomotive force generated upon electrification of winding is even, and it is less likely that the exciting force of the spatial deformation mode including the low-order that is lower than the number of poles of the rotor 2 occurs. Accordingly, the noise and vibration in the low-rotation range due to the low-order space deformation mode of the stator 3 can be reduced.
According to the aforementioned embodiment, the denominator of the irreducible fraction corresponds to an even number, and the number of layers of the plurality of phase belts 13 stacked up in the radial direction corresponds to the value obtained by dividing the denominator by two.
According to the above-described configuration, when the denominator of the irreducible fraction is the even number, the number of layers of the plural phase belts 13 stacked in the radial direction Y corresponds to the value obtained by dividing the denominator by two. Therefore, the number, which is in the mixed manner, of the layers accommodated in each slot 32 can be reduced as much as possible. As a result, the noise and vibration can be reduced without making the distributed winding configuration of the winding to each slot 32 complicated. Consequently, it can be prevented that a manufacturing cost of the motor M and a size of the motor M increases.
According to the aforementioned embodiment, the predetermined number of slots 32 corresponds to the integer value obtained by doubling the nearest integer that is nearest to the number of slots 32 per pole, the number of slots 32 per pole is obtained by multiplying the irreducible fraction by the number of phases.
According to the above-described configuration, the plural mixed phase belts 13A including the same number of coil sides 11a as each other can be formed, while the increase of the width, in the circumferential direction X, of the coil sides 11a of the mixed phase belts 13A is minimized. As a result, the inconvenience, in which the mixed phase belts 13A adjacent to each other in the circumferential direction X exert the influence of their exciting forces with each other, can be prevented, thereby restricting decrease in torque.
According to the aforementioned embodiment, the number of slots 32 per pole is obtained by multiplying the irreducible fraction by the number of phase, the subtracted value is obtained by subtracting the nearest integer that is nearest to the number of slots 32 per pole from the number of slots 32 per pole, in a case where the subtracted value is positive, the predetermined number of the slots 32 corresponds to the value obtained by adding one to the integer value obtained by doubling the nearest integer, and in a case where the subtracted value is negative, the predetermined number of the slots 32 corresponds to the value obtained by subtracting one from the integer value.
According to the above-described configuration, the plural mixed phase belts 13A including the same number of coil sides 11a as each other can be formed, while the increase of the width, in the circumferential direction X, of the of the coil sides 11a of the mixed phase belts 13A is minimized. As a result, the inconvenience, in which the mixed phase belts 13A adjacent to each other in the circumferential direction X exert the influence of their exciting forces with each other, can be prevented, thereby restricting the decrease in torque.
According to the aforementioned embodiment, in the layer phase belt 13a which is included in the phase belts 13 and in which the plural slots 32 are arranged to be adjacent to each other in the same layer, the winding start of the winding is provided at the slot 32 which is at the end of the layer phase belt 13a in the direction opposite to the development direction of the unit coil 11 from the winding start of the winding to the winding end of the winding.
According to the above-described configuration, when providing the winding start of the winding (i.e., the conductive wire) at the layer phase belt 13a, the winding start is provided at the slot 32, out of the plural slots 32 in the same layer, which is arranged at the end of the layer phase belt 13a in the direction opposite to the development direction of the unit coil 11. Thus, in one cycle from the winding start to the winding end of the same-phase coil, the arrangement width of the coil sides 11a in the circumferential direction X can be reduced, and thus an assembly jig can be reduced in size. In addition, in one cycle from the winding start to the winding end of the same-phase coil, the connecting wire connecting the slots 32 to each other at the bottom portion side of the slot 32 (that is, a side opposite to a rotor side) can be minimized (to zero or one). And thus, for example, in a case where the phases are assembled in turn from the rotor side, the interference of the connecting wires with each other is eliminated or reduced, thereby enhancing the assembly performance and reducing risk of short circuit.
According to the aforementioned embodiment, the denominator of the irreducible fraction is four, and the phase belt 13 is formed of the first phase belt 13 and the second phase belt 13 which are stacked up in the radial direction, the first serial phase belt 13B1 includes the plural first phase belts 13 all of which are electrically connected to each other in series, the second serial phase belt 13B2 includes the plural second phase belts 13 all of which are electrically connected to each other in series. The winding end of the first serial phase belt 13B1 and the winding start of the second serial phase belt 13B2 are electrically connected to each other, the winding start of the second serial phase belt 13B2 is shifted from the winding end of the first serial phase belt 13B1 in the direction opposite to the development direction by the coil pitch.
According to the above-described configuration, at the rotating electrical machine (the motor M) at which each phase includes therein the series connection configuration, the winding end of the first serial phase belt 13B1 and the winding start of the second serial phase belt 13B2 that is shifted from the winding end in the direction opposite to the development direction by the coil pitch are electrically connected to each other. As a result, the connecting wire connecting the winding end of the first serial phase belt 13B1 and the winding start of the second serial phase belt 13B2 can be made shortest or can be minimized, thereby preventing the interference with, for example, the connecting wire connecting between the phase belts 13 within the phase. Consequently, there is no need to stack the connecting wire in the axial direction Z of the motor M, thereby reducing the size of the motor M.
According to the aforementioned embodiment, the phase belts 13 include the outermost phase belt 13, 13B arranged at the outermost side in the radial direction Y and the innermost phase belt 13, 13B arranged at the innermost side in the radial direction Y. The plural outermost phase belts 13, 13B are in the range in which as many the magnetic poles 22 of the rotor 2 as the number obtained by multiplying the denominator of the irreducible fraction by the predetermined number are arranged to be adjacent to each other. The plural outmost phase belts 13, 13B in the range are connected to each other in series to form the first phase belt group 13B, and the plural of the first phase belt groups 13B are electrically connected to each other in parallel. The plural innermost phase belts 13, 13B are in a range in which as many the magnetic poles 22 of the rotor 2 as the number obtained by multiplying the denominator of the irreducible fraction by the predetermined number are arranged to be adjacent to each other. The plural innermost phase belts 13, 13B in the range are connected to each other in series to form the second phase belt group 13B, and the plural of the second phase belt groups 13B are electrically connected to each other in parallel. One of the plural first phase belt groups 13B and one of the plural second phase belt groups 13B are electrically connected to each other in series, and the plural first phase belt groups 13B are electrically connected to each other to configure the phase terminal and the plural second phase belt groups 138 are electrically connected to each other to configure the other phase terminal.
According to the above-described configuration, at the motor M at which each phase includes therein the parallel connection, the plural first phase belt groups 13B are electrically connected to each other to form the phase terminal and the plural second phase belt groups 13B are electrically connected to each other to form the other phase terminal. Thus, there is no need to electrically connect the first phase belt group 13B and the second phase belt group 13B to each other to form the phase terminal or the other phase terminal. Therefore, the phase terminal connecting wire which connects the first phase belt group 13B and the second phase belt group 13B to each other intersects with other connecting wire at less points or less portions, and the intersection can be possibly avoided. As a result, there is no need to stack the phase terminal connecting wire in the axial direction Z of the motor M, thereby allowing the motor M to be compact.
According to the aforementioned embodiment, the motor (i.e., a rotating electrical machine) M includes the stator 3 including the plural slots 32 on which the winding (i.e., the conductive wire) is wound, and the rotor 2 facing the stator 3 and including the plural permanent magnets (i.e., the magnetic poles) 22, wherein the motor M is configured of the fractional slot in which the denominator of the irreducible fraction obtained by dividing the number of the slots 32 of the stator 3 by the number of phases and the number of the permanent magnets 22 of the rotor 2 is equal to or greater than four, and the ratio of magnitude of magnetomotive force of each pole coil of each phase is even in the circumferential direction X of the rotor 2.
The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.
Number | Date | Country | Kind |
---|---|---|---|
2018-136735 | Jul 2018 | JP | national |