The present application relates to the field of motors, and particularly to a motor rotor and a motor having the same.
An interior permanent magnet synchronous motor (IPM) is a motor having a layer of permanent magnet placed inside a rotor and primarily utilizing permanent magnet torque and utilizing auxiliary reluctance torque.
Resultant formula of the reluctance torque and the permanent magnet torque is as follows: T=mp(Lq−Ld)idiq−mpΨPMiq.
Wherein, T is an output torque of a motor, the performance of the motor can be improved by increasing the value of T; the first item in the equation following T is the reluctance torque, and the second item is the permanent magnet torque; ΨPM is the maximum value of stator-rotor coupling magnetic flux generated by a permanent magnet of the motor, m is a phase number of a conductor of a stator, P is the number of pole pairs of the motor, Ld and Lq are inductances along axis d and axis q respectively, wherein axis d refers to an axis coincided with an axis of the main magnetic pole, and axis q refers to an axis perpendicular to the axis of the main magnetic pole, the perpendicular relationship refers to perpendicularity of electrical angles, and id and iq are components of an armature current in the directions of axis d and axis q respectively. As can be seen from the above resultant formula, the output torque of the motor T can be increased by increasing both the permanent magnet torque as the second item and a difference of the inductances along axis d and axis q of the motor.
In prior art, the performance of the motor is generally improved by improving the performance of the permanent magnet, that is, by increasing the permanent magnet torque to increase the value of the resultant torque so as to improve the efficiency of the motor, and the common method is to use rare-earth permanent magnets. However, since rare earth is a non-renewable resource and is expensive, the widespread use of this kind of motor is restricted. However, an irreversible demagnetization of the permanent magnet may be caused by using the permanent magnet of non-rare-earth material.
In addition, due to the limited volume of the rotor and the utilization of the reluctance torque, the occupation ratio of the permanent magnets in each pole of the rotor has a limit value, which also limits the improvement of the motor efficiency.
The present application provides a motor rotor which can improve an occupation ratio of a permanent magnet by optimizing a shape of the permanent magnet so as to improve the performance of the motor rotor, and the present application further provides a motor having the motor rotor.
According to an aspect of the present application, a motor rotor is provided, which includes an iron core and a permanent magnet arranged inside the iron core, wherein a plurality of groups of mounting grooves are arranged in the iron core along a circumferential direction of the iron core, and each group of mounting grooves includes two or more than two mounting grooves arranged at intervals in a radial direction of the iron core; a plurality of groups of permanent magnets are provided, and permanent magnets in each group of permanent magnets are correspondingly embedded into corresponding mounting grooves in each group of mounting grooves; and on a cross section, in a direction perpendicular to an axis of the rotor, of each permanent magnet, a center portion of the permanent magnet has a thickness greater than two ends of the permanent magnet.
Further, a thickness of the permanent magnet in a direction along its symmetric line is T, and a thickness of the furthest end of the permanent magnet is A, and wherein,
Further, a magnetic shielding bridge is formed between an edge of each mounting groove and a periphery of the rotor, and a width of the magnetic shielding bridge is ranged from 0.5 mm to 1.0 mm.
Further, a cross section, perpendicular to an axial direction of the iron core, of each mounting groove includes an outer arc segment, and a center of the outer arc segment of the mounting groove are distributed in a symmetry axis of the rotor.
Further, the cross section, perpendicular to the axial direction of the iron core, of the mounting groove further includes an inner arc segment, and a center of the inner arc segment of the mounting groove are distributed in the symmetry axis of the rotor.
Further, the cross section, perpendicular to the axial direction of the iron core, of the mounting groove further includes a first outer straight line segment and a second outer straight line segment which are respectively connected to two ends of the outer arc segment, and an angle β is formed between the first outer straight line segment and the second outer straight line segment, and the angle β satisfies a relational expression of
wherein P is a number of rotor poles of the motor rotor.
Further, the cross section, perpendicular to the axial direction of the iron core, of the mounting groove further includes a first outer straight line segment connected to an end of the outer arc segment, and a first inner straight line segment connected to an end of the inner arc segment and positioned at the same side as the first outer straight line segment, and an angle α is formed between the first outer straight line segment and the first inner straight line segment, wherein a is an acute angle.
Further, a cross section, perpendicular to the axial direction of the iron core, of each of the mounting grooves includes an arc segment, and centers of arc segments, distributed sequentially in a direction from an axes to a periphery of the iron core, of each group of mounting grooves are also distributed sequentially in this direction.
Further, clearances are provided between two ends of the permanent magnet and two ends of the mounting groove in which the permanent magnet is embedded.
Further, the clearances between the two ends of the permanent magnet and the two ends of the mounting groove are filled with non-magnetically permeable media.
According to an aspect of the present application, a motor is further provided, which includes the motor rotor described above.
In the motor rotor and the motor having the same provided by the present application, the shape of the permanent magnet is optimized. On a cross section, in a direction perpendicular to an axis of the rotor, of the permanent magnet, a center portion of the permanent magnet has a thickness greater than two ends of the permanent magnet, thus more permanent magnets can be arranged in the rotor with a constant area, thereby increasing an occupation ratio of the permanent magnets in each pole of the rotor, and improving the efficiency of the motor.
The accompanying drawings constituting a part of the present application are provided to help further understanding the present application, and the illustrative embodiments and the description thereof are used to interpret the present application and do not constitute inappropriate limitations to the present application.
The present application is described in detail hereinafter in conjunction with drawings and embodiments.
A motor rotor according to the present application includes an iron core 10 and a permanent magnet 20 arranged inside the iron core 10. Multiple groups of mounting grooves 30 are arranged in the iron core 10 along the circumferential direction of the iron core 10, and each group of mounting grooves 30 includes two or more than two mounting grooves 30 arranged at intervals in the radial direction of the iron core 10. There are multiple groups of permanent magnets 20, and permanent magnets 20 in each group of permanent magnets 20 are correspondingly embedded into corresponding mounting grooves 30 in each group of mounting grooves 30. On a cross section, in a direction perpendicular to an axis of the rotor, of the permanent magnet 20, a center portion of the permanent magnet 20 has a thickness greater than two ends of the permanent magnet 20.
The quadrupole motor rotor with each pole having three layers of permanent magnets in
Since multiple layers of permanent magnets 20 are placed in the direction of axis d, and the permanent magnet 20 has a relatively high magnetic reluctance and has a magnetic permeability approximately equal to air, an inductance Ld in the direction of axis d is relatively low, however, in the direction of axis q, the iron core 10 has a relatively high magnetic permeability, thus an inductance Lq in the direction of axis q is relatively high, thereby increasing the magnetic reluctance torque of the motor rotor, and in turn increasing the output torque of the motor and improving the efficiency of the motor.
In addition, the full utilization of the magnetic reluctance torque requires that both of the magnetic flux path 12 and the connecting rib 11 have a certain width, thus the permanent magnets 20 can be arranged in one pole of the rotor as many as possible when the middle portion of the arc-shaped permanent magnet has a thickness greater than two end thereof the permanent magnet, thereby increasing the occupation ratio of the permanent magnets 20 in each pole of the rotor. The increase of the permanent magnets 20 may greatly increase the permanent magnet torque, thereby improving the efficiency of the motor.
As shown in
Each group of permanent magnets 20 includes a permanent magnet 20 having an arc-shaped cross section in a direction perpendicular to the axis of the rotor, and a surface, close to the center of the rotor in the radial direction of the rotor, of each permanent magnet 20 in each group of permanent magnets 20 is of an arc shape. Since demagnetization tends to happen at two ends of the permanent magnet 20 having a thinner thickness, the permanent magnet 20 does not fill the entire mounting groove 30, and a certain space is provided at two ends of the permanent magnet 20 so as to prevent demagnetization at the ends of the permanent magnets 20. In this embodiment, since the arc-shaped permanent magnet 20 is slightly shorter than the mounting groove 30, there are clearances at both ends of the permanent magnet 20 after the permanent magnet 20 is inserted into the mounting groove 30, and air or other non-magnetically permeable media may be filled in the clearances.
Preferably, as shown in
There is a distance between the mounting groove 30 and a periphery of the rotor, thus the magnetic shielding bridge 13 is formed at this position, so as to further reduce the magnetic flux leakage of the permanent magnet 20 at the edge of the permanent magnet 20, and improve the utilization ratio of the permanent magnetic flux. The width of the magnetic shielding bridge 13 should be within a certain range, the magnetic shielding effect may be affected if the magnetic shielding bridge 13 is too wide, and the whole mechanical strength of the rotor may be affected if the magnetic shielding bridge 13 is too narrow, therefore, optimum magnetic shielding effect may be obtained by arranging the width of the magnetic shielding bridge 13 in a range of 0.5 mm to 1.0 mm while ensuring the mechanical strength of the rotor.
As shown in
To avoid an irreversible demagnetization of the permanent magnet 20, and particularly the demagnetization at a central portion of the permanent magnet 20, the ratio of A to T is limited within the aforementioned range. As shown in
As shown in
Reference numerals 90a and 90b in
Preferably, an inner arc of each of the outermost layer of the permanent magnets 20 and the outermost layer of mounting grooves 30 may be in an arc shape, but is generally arranged as a straight line segment 31 perpendicular to the direction of axis d so as to increase the usage of permanent magnets 20 at the outer layer, thereby increasing the magnetic field strength at the surface of the rotor.
As shown in
wherein P is a number of rotor poles of the motor rotor.
The inner layer of grooves closest to the rotor center in
As shown in
The acute angle α is formed between the first outer straight line segment 32a and the first inner straight line segment 32b at the tail end of the mounting groove 30, thus the mounting groove 30 has a convergence effect at the extending portion of the tail ends thereof, and the width of the center, along the axis d, of the mounting groove 30 is greater than the width of two ends of the mounting groove 30. Since the shape of the permanent magnet 20 is designed to closely abut against the mounting groove 30, the purpose of fixing the permanent magnets 20 and preventing the permanent magnets 20 from sliding when the rotor rotates may be realized without using any additional fixing means or adhesive through such convergence effect. This arrangement is also applicable to the configuration of inner and outer edges of grooves in other shapes.
The present application further provides a motor including the above motor rotor.
In the motor provided by the present application, the utilization of the reluctance torque is increased and the efficiency of the motor is improved by defining the relationship between the thickness of the permanent magnets and the distance between the permanent magnets. The motor provided by the present application may be used in air condition compressors, electric vehicles, and fan systems.
As can be seen from the above description, the embodiments of the present application may achieve the following technical effects.
By studying the relationship between the thicknesses at the center and two ends of the permanent magnets placed in the mounting grooves of the motor rotor and the design of the permanent magnets and the mounting grooves, the motor rotor and the motor having the same provided by the present application provide a method for increasing the occupation ratio of the permanent magnets and improving the anti-demagnetization performance of the permanent magnets of the motor rotor without affecting the utilization of the magnetic reluctance torque, which optimizes the shape of the permanent magnet, and improves the efficiency of the motor and achieves the effect that the motor can operate at higher load conditions without a tendency of occurring demagnetization.
The embodiments described hereinabove are only preferred embodiments of the present application, and should not be interpreted as limitation to the present application. For the persons skilled in the art, various variations and modifications may be made to the present application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present application are also deemed to fall into the protection scope of the present application.
Number | Date | Country | Kind |
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201110224882.6 | Aug 2011 | CN | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CN2011/079064 | 8/29/2011 | WO | 00 | 1/28/2014 |