Permanent magnet synchronous motor and method of manufacturing the same

Abstract

To reduce cogging torque without using skew.SOLUTION: According to an embodiment, a permanent magnet synchronous motor includes a rotor shaft, a rotor core 130 on which a magnet-containing flux barrier 131 is formed, a permanent magnet rotor 100 including a permanent magnet 120, and a stator 200 including a stator core 210 on which a plurality of stator teeth 211 are formed, and a stator winding. The magnet-containing flux barrier 131 has a magnet housing portion 132 and a flux barrier portion extension 133 extending toward the geometric central axis MC. The flux barrier portion extension offset angle Φ has two values, a first and a second flux barrier portion extension offset angle, and the magnet-containing flux barriers 131 in each magnetic pole pair have the same flux barrier portion extension offset angle Φ and take one of two values.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a permanent magnet synchronous motor and a method for manufacturing the same.

Background Art

[0002] As a permanent magnet synchronous motor, a so-called embedded magnet type synchronous motor in which permanent magnets are arranged inside the iron core is known. This embedded magnet type synchronous motor includes a stator in which stator coils are arranged in a substantially cylindrical stator core having a plurality of stator slots, and a rotor provided on the inner side in the radial direction of the stator and rotatably provided with respect to the stator.

[0003] The rotor has a rotor shaft rotatably provided around the rotation center axis and a rotor core externally fitted and fixed to the rotor shaft. The rotor core is formed with a number of magnet insertion holes corresponding to the number of poles. Permanent magnets are inserted into these magnet insertion holes. Under such a configuration, in a permanent magnet synchronous motor, when an electric current is supplied to the stator coil, a rotational torque is applied to the rotor by the interaction between the magnetic flux generated on the primary side (stator side) and the magnetic flux of the permanent magnets in the rotor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, due to the presence of the stator slots, there are magnetic irregularities between the rotor and the stator. Due to these irregularities, torque ripple (cogging torque) occurs in the rotor, where the value of the rotational torque increases and decreases, which becomes a cause of mechanical vibration and noise during rotation at no load.

[0006] As an effective means of reducing cogging torque, when laminating electromagnetic steel sheets of a stator or a rotor in the axial direction, a method of applying so-called skew in which the electromagnetic steel sheets are arranged at equal intervals in the circumferential direction, which is the rotational direction, is known. However, in this case, there is a problem of an increase in man-hours and the number of parts during manufacturing.

[0007] Also, there is a means of canceling the cogging torque generated at each magnetic pole by changing the shape of the permanent magnet or its housing hole for each magnetic pole, but there is a problem that it cannot cope with the case where the magnetic circuit changes, such as differences due to the number of poles and the number of slots per pole per phase.

[0008] The problem to be solved by the present invention is to provide a permanent magnet synchronous motor and a method for manufacturing a permanent magnet synchronous motor capable of reducing cogging torque without using skew.

Means for Solving the Problem

[0009] To achieve the above object, a permanent magnet synchronous motor according to an embodiment of the present invention includes a rotor shaft that extends in the axial direction and rotates around a rotation center axis, a rotor core attached to the outer side in the radial direction of the rotor shaft and having a magnet housing flux barrier that is circumferentially line-symmetric about a geometric center axis that is the circumferential center of each of a plurality of magnetic poles formed at positions corresponding to the magnetic poles, a permanent magnet rotor including permanent magnets housed in the respective magnet housing flux barriers, a stator core formed to surround the rotor core with a gap on the outer side in the circumferential direction of the rotor core, and a stator winding having portions housed in respective ones of a plurality of stator slots formed between a plurality of stator teeth formed in the stator core. The permanent magnet synchronous motor is characterized in that the magnet housing flux barrier has a magnet housing portion for housing the permanent magnet and a flux barrier portion extension extending from the outer portion in the radial direction of the magnet housing portion toward the side of the geometric center axis, and in a cross section perpendicular to the rotation center axis, a flux barrier portion extension offset angle, which is a circumferential angle at an electrical angle formed by a straight line connecting the tip on the side of the geometric center axis of the flux barrier portion extension and the rotation center axis and the geometric center axis, has two types of values, a first flux barrier portion extension offset angle smaller than the circumferential center angle and a second flux barrier portion extension offset angle smaller than the circumferential center angle, sandwiching a target stator tooth having a circumferential center angle larger than the minimum offset angle, and among the plurality of magnetic poles, two adjacent magnetic poles form a magnetic pole pair, and the magnet housing flux barriers in each of the magnetic pole pairs have the same flux barrier portion extension offset angle and take either one of the two types of values.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

[0011] Hereinafter, with reference to the drawings, a permanent magnet synchronous motor and a manufacturing method of the permanent magnet synchronous motor according to an embodiment of the present invention will be described. Here, the same or similar parts are denoted by common reference numerals, and duplicate descriptions are omitted.

[0012] [Embodiment] FIG. 1 is a cross-sectional view showing a permanent magnet synchronous motor 1 according to a first example of the embodiment. The permanent magnet synchronous motor 1 has a permanent magnet rotor 100 and a stator 200.

[0013] The permanent magnet rotor 100 has a rotor shaft 110 that extends in the axial direction and rotates around the rotation center axis CL (FIG. 3), a rotor core 130 attached to the outer side in the radial direction of the rotor shaft 110, and a plurality of permanent magnets 120 housed in the rotor core 130.

[0014] Hereinafter, the direction parallel to the direction in which the rotation center axis CL extends is referred to as the axial direction, the direction from the rotation center axis CL toward the outside (the direction of moving away) is referred to as the radial direction, and the direction in which the permanent magnet rotor 100 rotates is referred to as the circumferential direction, respectively. Also, the radial direction is referred to as the outer side in the radial direction for the side far from the rotation center axis CL and the inner side in the radial direction for the side close to the rotation center axis CL.

[0015] The rotor core 130 has a plurality of first magnetic poles 121 and a plurality of second magnetic poles 122. In a cross-section perpendicular to the rotation center axis C, two permanent magnets 120 are arranged at linearly symmetric positions in the circumferential direction with respect to each of the first magnetic poles 121 and the second magnetic poles 122, sandwiching the geometric center axis MC (FIG. 3). The two permanent magnets 120 are arranged such that the circumferential interval between them increases toward the radially outer side. This arrangement is sometimes referred to as a V-shaped arrangement. Hereinafter, when referring to the geometric center axis MC, the case in a cross-section perpendicular to the rotation center axis C is shown, but the annotation to that effect is omitted.

[0016] The first magnetic pole 121 has magnetic poles 121a, 121b, 121c, and 121d, and the second magnetic pole 122 has magnetic poles 122a, 122b, 122c, and 122d.

[0017] For example, if in the magnetic pole 121a the direction of the magnetic flux is from the permanent magnet toward the radially outer side, then in the magnetic pole 122a the radial direction of the magnetic flux is the opposite direction. Such a combination of the magnetic pole 121a and the magnetic pole 122a is called a magnetic pole pair. In this case, the magnetic flux goes from the magnetic pole 121a toward the radially outer side and then toward the radially inner side and reaches the magnetic pole 122a. Similarly, the magnetic pole 121b and the magnetic pole 122b form a magnetic pole pair, the magnetic pole 121c and the magnetic pole 122c form a magnetic pole pair, and the magnetic pole 121d and the magnetic pole 122d form a magnetic pole pair. Therefore, in the case illustrated in FIG. 1, the number of magnetic pole pairs is 4. Hereinafter, the number of magnetic pole pairs in the permanent magnet rotor 100 is referred to as the number of pole pairs.

[0018] The rotor core 130 has, for example, a cylindrical structure in which a plurality of electromagnetic steel sheets are laminated. The rotor core 130 has a shaft through-hole 130a formed so that the rotor shaft 110 passes through the center, eight rod through-holes 130b formed at intermediate positions in the radial direction with intervals in the circumferential direction, and two magnet housing flux barriers 131 formed linearly symmetrically in the circumferential direction with respect to the geometric center axis MC (FIG. 3) so as to house two permanent magnets 120 for each magnetic pole.

[0019] The magnet storage flux barrier 131 has a magnet storage portion 132 that is a portion for storing the permanent magnet 120, and a flux barrier portion extension (FB portion extension) 133 that extends from the radially outer portion of the magnet storage portion 132 along the outer periphery of the rotor core 130 toward the geometric central axis MC. The magnet storage portions 132 have the same shape and dimensions within each magnetic pole.

[0020] The magnet storage flux barrier 131 at the magnetic pole 121 has an FB portion extension 133 with the same extension length. Also, the magnet storage flux barrier 131 at the magnetic pole 122 has an FB portion extension 133 with the same extension length. The FB portion extension 133 at the magnetic pole 121 and the FB portion extension 133 at the magnetic pole 122 have different extension lengths from each other. That is, in the permanent magnet synchronous motor 1 according to the first example shown in FIG. 1, there are FB portion extensions 133 having two types of extension lengths. Details regarding the different extension lengths will be described later.

[0021] The stator 200 has a stator core 210 and a stator winding 220. A plurality of stator teeth 211 are formed on the outer peripheral portion of the stator core 210 at intervals from each other. Stator slots 212 are formed by the adjacent stator teeth 211. A part of the stator winding 220 is housed in each stator slot 212.

[0022] The central magnetic paths 130ma and 130mb will be described later with reference to FIG. 3.

[0023] FIG. 2 is a cross-sectional view showing a permanent magnet synchronous motor 1a according to a second example of the embodiment. The permanent magnet synchronous motor 1a has a permanent magnet rotor 100a and a stator 200.

[0024] The permanent magnet rotor 100a has a rotor shaft 110 that extends in the axial direction and rotates around the rotation center axis CL (FIG. 3), a rotor core 130 attached to the radially outer side of the rotor shaft 110, and a plurality of permanent magnets 120 housed in the rotor core 130.

[0025] The permanent magnets 120 are arranged in pairs of two at each of the magnetic poles 121a, 121b, 122a, 122b, 123a, and 123b. Each pair of the permanent magnets 120 is arranged symmetrically about the geometric central axis MC in the circumferential direction and with an increasing spacing from each other toward the radially outer side. As a result, the central magnetic paths 130ma, 130mb, and 130mc are formed.

[0026] In the second example of FIG. 2, the magnetic poles 122a and 122b form a magnetic pole pair, and the magnetic poles 123a and 123b form a magnetic pole pair. That is, in the permanent magnet rotor 100 according to the first example shown in FIG. 1, the number of magnetic pole pairs is 4, which is an even number, while in the permanent magnet rotor 100a according to the second example shown in FIG. 2, the number of magnetic pole pairs is 3, which is an odd number.

[0027] FIG. 3 is a partial cross-sectional view showing the magnet housing flux barrier 131 of the permanent magnet rotor 100 of the permanent magnet synchronous motor 1 according to the embodiment. FIG. 3 shows the configuration of one magnetic pole. The boundary between the magnetic pole and the adjacent magnetic pole is indicated by the geometric boundary axis MB. The geometric boundary axis MB is at the circumferential angular position of half of the circumferential angle formed by two adjacent geometric central axes MC. The circumferential range of the magnetic pole is the region sandwiched between two geometric boundary axes MB.

[0028] As shown in FIG. 3, in the cross-section perpendicular to the rotation center CL, as described above, the two permanent magnets 120 are arranged symmetrically about the geometric central axis MC. Each permanent magnet 120 is housed in a magnet housing flux barrier 131 formed symmetrically about the geometric central axis MC. Each magnet housing flux barrier 131 has a magnet housing portion 132 in which the permanent magnet 120 is housed and an FB portion extension 133 extending from the radially outer portion of the magnet housing portion 132 toward the geometric central axis MC side.

[0029] Now, as shown in FIG. 3, assume a state where the geometric central axis MC coincides with the circumferential center plane of any one stator tooth 211 in the circumferential direction (rotation direction) between the permanent magnet rotor 100 and the stator 200. Hereinafter, this stator tooth 211 will be referred to as the reference stator tooth 211a. Also, let the circumferential angle in the clockwise direction from the geometric central axis MC be Θ. Hereinafter, when referring to angles including circumferential angles and rotation angles, the angles shall all mean electrical angles unless otherwise specified.

[0030] Here, for the convenience of the following description, several circumferential angles are defined. The angle between the circumferential center planes of adjacent stator teeth 211 in the circumferential direction, that is, the circumferential angle in the electrical angle between the center lines of adjacent stator teeth 211 in the circumferential direction in the cross section, is defined as the stator-stator tooth pitch angle Θp. The circumferential angle in the electrical angle formed by the geometric central axis MC and the geometric boundary axis MB of the magnetic pole is defined as the magnetic pole region angle Θt. Also, the central angle between the straight line connecting the portion ME farthest from the geometric central axis MC of the permanent magnet 120 and the rotation center CL and the geometric central axis MC is defined as the magnetic pole opening angle Θe. Therefore, the magnetic pole opening angle Θe is smaller than the magnetic pole region angle Θt. Also, the angular width of the stator tooth 211 is defined as the stator tooth angular width Θw.

[0031] For example, in the case shown in FIG. 3, since it is a 6-pole 36-slot, the geometric circumferential angle of one pole is 60 degrees, but since the electrical circumferential angle is 180 degrees, the electrical magnetic pole region angle Θt is 90 degrees, which is half of that.

[0032] In the cross section shown in FIG. 3, the angle in the electrical angle formed by the straight line connecting the tip 133a of the FB portion extension 133 and the rotation center CL and the geometric central axis MC is defined as the FB portion extension offset angle Φ. The longer the extension length of the FB portion extension 133, the closer the tip 133a of the FB portion extension 133 approaches the geometric central axis MC, and the smaller the FB portion extension offset angle Φ becomes. Thus, it can be said that the FB portion extension offset angle Φ is an index in place of the extension length of the FB portion extension 133. In one magnetic pole, the circumferential angle in the electrical angle formed by the two straight lines connecting the respective tips 133a of the magnet housing flux barriers 131 adjacent to each other and the rotation center CL is twice the FB portion extension offset angle Φ.

[0033] Here, the region between the tips 133a facing each other across the geometric central axis MC serves as a path for the magnetic flux of the permanent magnet 120, and this portion is referred to as the central magnetic path 130m. The central magnetic paths 130ma and 130mb shown in FIG. 1 represent the central magnetic path 130m when the width is large and when the width is small. Also, the central magnetic paths 130ma, 130mb, and 130mc shown in FIG. 2 represent the central magnetic path 130m when the width is large, when the width is small, and when the width is intermediate between these.

[0034] The FB portion extension offset angle Φ has a value equal to or greater than a predetermined minimum offset angle Φmin. The predetermined minimum offset angle Φmin will be described later.

[0035] As described above, the FB portion extension 133 of the magnet housing flux barrier 131 in the magnetic pole 121 and the FB portion extension 133 of the magnet housing flux barrier 131 in the magnetic pole 122 each have the same extension length, and the extension length is different between the magnetic pole 121 and the magnetic pole 122. Therefore, the FB portion extension offset angle Φ in the magnetic pole 121 and the FB portion extension offset angle Φ in the magnetic pole 122 each have the same value, and the value is different between the magnetic pole 121 and the magnetic pole 122. In the case shown in FIG. 1, the FB portion extension offset angle Φ in the magnetic pole 121 is smaller than the FB portion extension offset angle Φ in the magnetic pole 122.

[0036] Figure 4 is a flowchart showing the procedure of the manufacturing method of the permanent magnet synchronous motor 1 according to the embodiment. That is, the manufacturing method for obtaining the permanent magnet synchronous motor 1 shown in FIGS. 1 and 3 will be described.

[0037] The manufacturing method of the permanent magnet synchronous motor 1 includes a main target determination step S10 of the permanent magnet synchronous motor 1, a rotor core 130 design step S20, and a manufacturing step S30 of the permanent magnet synchronous motor 1. Regarding the rotor core 130 design step S20, details will be described later while referring to FIGS. 5 and 6.

[0038] The main target determination step S10 of the permanent magnet synchronous motor 1 includes a step S11 of determining the basic dimensions of the rotor shaft 110, the diameter of the rotor core 130, and the number of poles p, a step S12 of determining the main targets of the stator 200, such as the dimensions of the stator core 210, the dimensions and number of the stator teeth 211, etc., and a step S13 of determining the basic dimensions of the rotor core 130 and the dimensions of the permanent magnets 120.

[0039] In the manufacturing step S30 of the permanent magnet synchronous motor 1, each step for manufacturing is included based on the results at each stage of step S10 and step S20. Specifically, it is as follows.

[0040] Based on the results of the step S11 of determining the basic dimensions of the rotor shaft, the diameter of the rotor core, and the number of poles, the material arrangement and processing of the rotor shaft 110 are carried out (step S31). Also, the arrangement of bearings, the arrangement and manufacturing of the housing structure of the stator 200 such as the casing and bearing brackets are carried out (step S32).

[0041] Next, based on the results of the step S12 of setting the main targets of the stator 200, the manufacturing and assembly of the electromagnetic steel sheets of the stator core 210 are carried out (step S33).

[0042] Next, based on the results of step S13 of determining the basic dimensions of the rotor core 130 and determining the dimensions of the permanent magnet 120, the permanent magnet 120 is arranged (step S34).

[0043] Next, based on the results of the design step S20 of the rotor core 130, electromagnetic steel sheets of the rotor core 130 are manufactured and assembled (step S35).

[0044] Next, the rotor shaft 110, the rotor core 130, and the permanent magnet 120 are assembled to assemble the permanent magnet rotor 100. Also, the stator 200 is attached to the storage structure, the storage structure is assembled, the bearings are attached, the permanent magnet rotor 100 is inserted and supported, etc., and the entire permanent magnet synchronous motor 1 is assembled (step S36). Next, the assembled permanent magnet synchronous motor 1 is inspected and commercialized (step S37).

[0045] FIG. 5 is a flowchart showing the detailed procedure of the design step of the rotor core 130 in the manufacturing method of the permanent magnet synchronous motor 1 according to the embodiment. Hereinafter, the detailed procedure of the design step S20 of the rotor core 130 will be described.

[0046] As the design step S20 of the rotor core 130, first, the magnetic flux conditions of the magnet, such as the magnetic strength of the magnet and the shape and size of the magnet housing flux barrier 131, are confirmed (step S21). That is, the magnetic flux conditions including the magnetic strength of the magnet and the shape and size of the magnet housing flux barrier 131, which are the conditions for evaluating and calculating the magnetic flux (magnet magnetic flux) by the permanent magnet 120, are clarified and confirmed.

[0047] Next, the minimum condition of the FB portion extension offset angle Φ is set (step S22). That is, the minimum offset angle Φmin is set. Details will be described later with reference to FIG. 6.

[0048] Next, the rotational angle dependence characteristics of the cogging torque at each FB portion extension offset angle are obtained (step S23). Details will be described later with reference to FIG. 7.

[0049] Next, the FB portion extension offset angle dependence characteristics of the primary torque maximum amplitude value and the secondary torque maximum amplitude value are derived (step S24). Details will be described later with reference to FIGS. 8 and 9.

[0050] Next, selection of the target stator teeth (step S25) and setting of two FB portion extension offset angles (step S26) are performed. Details of these will be described later with reference to FIGS. 9 and 10, respectively, but two types of FB portion extension offset angles, namely, the first FB portion extension offset angle Φ1 and the second FB portion extension offset angle Φ2, are obtained. That is, a magnet housing flux barrier 131 having two types of extension lengths of the FB portion 133 is obtained.

[0051] Next, it is determined whether the number of pole pairs is odd (step S27). If it is determined in step S27 that the number of pole pairs is not odd (step S27 NO), step S20 is terminated. As a result, when the number of pole pairs is even as in the permanent magnet synchronous motor 1 according to the first example shown in FIG. 1, two types of FB portion extension offset angles, that is, a magnet housing flux barrier 131 having two types of extension lengths of the FB portion 133 is obtained.

[0052] These two types of magnet housing flux barriers 131 are assigned to each magnetic pole pair. That is, the FB portion extension 133 of the magnet housing flux barrier 131 corresponding to the first magnetic pole 121 of the permanent magnet rotor 100 shown in FIG. 1 has the first FB portion extension offset angle Φ1, and the FB portion extension 133 of the magnet housing flux barrier 131 corresponding to the second magnetic pole 122 has the second FB portion extension offset angle Φ2. Thus, the components of the cogging torque in the primary mode and the secondary mode cancel each other out, and the cogging torque can be reduced.

[0053] In step S27, when it is determined that the number of pole pairs is odd (step S27 YES), next, the third FB offset angle is selected (step S28). Although details will be described later, as a result, in the case where the number of pole pairs is odd as in the permanent magnet synchronous motor 1a according to the second example shown in FIG. 2, three types of FB partial extension offset angles, that is, magnet housing flux barriers 131 having the extension lengths of the three types of FB partial extensions 133 are obtained.

[0054] These three types of magnet housing flux barriers 131 are assigned to each pole pair. That is, the FB partial extension 133 of the magnet housing flux barrier 131 corresponding to the first pole 121 of the permanent magnet rotor 100a shown in FIG. 2 has the first FB partial extension offset angle Φ1, and the FB partial extension 133 of the magnet housing flux barrier 131 corresponding to the second pole 122 has the second FB partial extension offset angle Φ2, and the FB partial extension 133 of the magnet housing flux barrier 131 corresponding to the third pole 123 has the third FB partial extension offset angle Φ3. By this, the components of the first mode and the second mode of the cogging torque cancel each other out, and the cogging torque can be reduced.

[0055] FIG. 6 is a flowchart showing the detailed procedure of the setting step S22 of the minimum condition of the FB partial extension offset angle in the design step of the rotor core 100 in the manufacturing method of the permanent magnet synchronous motor 1 according to the embodiment. The detailed procedure in step S22 is as follows.

[0056] First, an initial value and an increment dΦ of the FB partial extension offset angle Φ are set (step S22a). Here, the initial value of the FB partial extension offset angle Φ is set to a sufficiently small value at which magnetic flux saturation does not occur.

[0057] Next, the magnet flux is calculated to obtain the magnetic flux density in the central magnetic path 130m (FIG. 3) (step S22b).

[0058] Next, it is determined whether or not the magnetic flux is saturated based on the magnetic flux density in the central magnetic path 130m obtained in step S22b (step S22c). If it is determined in step S22c that the magnetic flux is not saturated (step S22c NO), a value obtained by adding an increment dΦ to the FB portion extension offset angle Φ is set as the new FB portion extension offset angle Φ (step S22d), and steps S22b and S22c are repeated.

[0059] If it is determined in step S22c that the magnetic flux is saturated (step S22c YES), the minimum offset angle Φmin is calculated (step S22e). Specifically, a value obtained by adding a margin α to the FB portion extension offset angle Φ at that time is set as the minimum offset angle Φmin.

[0060] Note that in step S22c, it is determined whether or not magnetic flux saturation has occurred based on the calculated magnetic flux in the central magnetic path, but it is not limited to this. For example, it may be determined whether or not (100 - x)% has been reached with an x% margin for the saturation condition.

[0061] Through the procedure of step S22 for setting the minimum condition of the FB portion extension offset angle as described above, the minimum offset angle Φmin is obtained. The minimum offset angle Φmin is, for example, in the range of 20 degrees to 30 degrees, and in the following description, the case where the minimum offset angle Φmin is 25 degrees will be taken as an example for explanation.

[0062] Hereinafter, the details of steps S23 and S24 will be described with reference to FIGS. 7 to 9.

[0063] FIG. 7 is a conceptual graph showing an example of the rotational angle dependence characteristic of the cogging torque T obtained in the method for manufacturing a permanent magnet synchronous motor according to the embodiment. The horizontal axis is the rotational angle Θ (electrical angle (degrees)), and the vertical axis is the cogging torque [N·m].

[0064] The rotational angle dependence characteristic of the cogging torque T obtained in step S23 is the change characteristic of the value of the torque T with respect to the circumferential angle, that is, the circumferential angle (rotation angle) Θ from the stationary state, when the permanent magnet rotor 100 is rotated or pivoted in the rotational direction in a no-load state, that is, a state where no current is passed through the stator winding 220. Here, the rotational angle dependence characteristic of the cogging torque T in FIG. 7 is assumed to be the case where the offset angle of the FB portion extension is Φ degrees. That is, with the offset angle Φ of the FB portion extension as a parameter, the rotational angle dependence characteristic of the cogging torque T for each case can be obtained.

[0065] When the permanent magnet rotor 100 makes one revolution, that is, geometrically rotates 360 degrees, the measured value of the cogging torque T changes with a certain angular period determined by the number of pole pairs and the number of stator teeth 211. FIG. 7 shows the change when the rotation angle Θ is one period.

[0066] As shown in FIG. 7, it can be seen that the aspect of the change of the cogging torque T with respect to one period of the rotation angle Θ includes a fundamental wave and higher-order waves.

[0067] FIG. 8 is a conceptual graph showing an example of the rotational angle dependence characteristics of the primary torque and the secondary torque of the cogging torque obtained in the manufacturing method of the permanent magnet synchronous motor according to the embodiment. The horizontal axis is the rotation angle Θ (electrical angle (degrees)), and the vertical axis is the cogging torque of each order [N·m].

[0068] In order to obtain the primary torque maximum amplitude value and the secondary torque maximum amplitude value in step S24, first, by performing a Fourier transform on the change of the cogging torque T shown in FIG. 7, a primary torque (torque in the fundamental mode) and torques in further higher-order modes of the secondary torque and above can be obtained. FIG. 8 shows the changes of the primary torque and the secondary torque with respect to one period of the rotation angle Θ when the offset angle of the FB portion extension is Φ degrees. Specifically, the solid line A shows the primary torque characteristic and the secondary torque characteristic as the change with respect to the change of the rotation angle Θ of the primary torque, and the broken line B shows the same for the secondary torque.

[0069] In FIG. 8, the value of the absolute value when it becomes maximum in the change of the primary torque for one cycle is defined as the primary torque maximum amplitude value T1. Also, the value of the absolute value when it becomes maximum in the change of the secondary torque for one cycle is defined as the secondary torque maximum amplitude value T2. These are the values when the offset angle of the FB portion extension is Φ degrees. Therefore, as values depending on Φ, they are expressed as functions of the primary torque maximum amplitude value T1(Φ) and the secondary torque maximum amplitude value T2(Φ) and Φ, respectively.

[0070] FIG. 9 is a conceptual graph showing an example of the dependence characteristics (the “dependence characteristics of the cogging torque maximum amplitude value on the offset angle”) of the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 on the flux barrier portion extension offset angle Φ obtained in the manufacturing method of the permanent magnet synchronous motor according to the embodiment, and an explanatory diagram showing the relationship between this characteristic graph and the stator teeth 211. The portion of the stator 200 in FIG. 9 shows the circumferential direction of the cross section perpendicular to the rotation center axis direction linearly. The horizontal axis is the FB portion extension offset angle Φ [electrical angle (degrees)], and the vertical axis is the normalized torque maximum amplitude value T [P.U.].

[0071] In FIG. 9, the state is shown when the center in the circumferential direction of a certain stator tooth 211 (reference stator tooth 211a) denoted as the reference stator slot and the d-axis, which is the geometric center axis of the permanent magnet rotor 100, are in the same position in the circumferential direction. In this case, the scale of the circumferential angle Θ [degrees] from the circumferential center of the reference stator tooth 211a as the origin of the horizontal axis in FIG. 9 is made equal to the scale of the FB portion extension offset angle Φ [degrees] of the lower graph. As described above, all the angles indicate electrical angles.

[0072] In the lower graph in FIG. 9, the solid line indicates the first-order torque maximum amplitude value T1(Φ), and the dashed line indicates the second-order torque maximum amplitude value T2(Φ). The vertical axis of the graph indicates the ratio of the value of the first-order torque maximum amplitude value T1(Φ) and the second-order torque maximum amplitude value T2(Φ) to the maximum value |Φmax| among the absolute values of the first-order torque maximum amplitude value T1(Φ) and the second-order torque maximum amplitude value T2(Φ), that is, the normalized maximum amplitude value T(Φ).

[0073] In FIG. 9, on the right side of the reference stator tooth 211a, there is a stator tooth 211 denoted as the target stator tooth 211b. Here, the circumferential angle at the electrical angle formed by the circumferential center of the reference stator tooth 211a and the circumferential center of the target stator tooth 211b is larger than the minimum offset angle Φmin. Here, Φmin is set to 25 degrees as described above.

[0074] When the circumferential angle at the electrical angle formed by the circumferential center of the reference stator tooth 211a and the circumferential center of the adjacent stator slot 212 is equal to or greater than the minimum offset angle Φmin, the adjacent stator slot 212 becomes the target stator tooth 211b. When the circumferential angle at the electrical angle formed by the circumferential center of the reference stator tooth 211a and the circumferential center of the adjacent stator slot 212 is less than the minimum offset angle Φmin, the stator slot 212 that is more than the minimum offset angle Φmin away from the reference stator tooth 211a is taken as the target stator tooth 211b. As a result, in any case, the circumferential angle Φ at the electrical angle formed by the circumferential center of the reference stator tooth 211a and the circumferential center of the target stator tooth 211b will be equal to or greater than the minimum offset angle Φmin.

[0075] In the example shown in FIG. 9, the case where the circumferential direction angle Θ of the circumferential center of the target stator tooth 211b is 30 degrees is shown. That is, this stator tooth 211 is the first stator tooth 211 whose circumferential direction angle Θ of the circumferential center is larger than 25 degrees.

[0076] As shown in Fig. 9, the primary torque maximum amplitude value T1(Φ) and the secondary torque maximum amplitude value T2(Φ) cross the line (horizontal axis) where the normalized torque maximum amplitude value T becomes zero at the FB part extension offset angle Φ of about 30 degrees. That is, at the FB part extension offset angle Φ of about 30 degrees, the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 cross the line (horizontal axis) where the value on the vertical axis (normalized torque maximum amplitude value T) becomes zero (zero cross).

[0077] Fig. 10 is a conceptual explanatory diagram for explaining the derivation of the first flux barrier part extension offset angle Φ1 and the second flux barrier part extension offset angle Φ2 in the manufacturing method of the permanent magnet synchronous motor according to the embodiment. The horizontal axis is the FB part extension offset angle Φ [electrical angle (degrees)], and the vertical axis is the normalized torque maximum amplitude value T [P.U.].

[0078] As described above, the zero cross points of the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 are at the angular positions of about 30 degrees, respectively. Here, the value of the horizontal axis (FB part extension offset angle) of the intersection point P0 of the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 is defined as the central flux barrier part extension offset angle Φ0.

[0079] The flux barrier part extension offset angle Φ is shifted to the side smaller than the central flux barrier part extension offset angle Φ0. That is, in Fig. 10, a straight line L1 parallel to the vertical axis is shifted to the side smaller than the central flux barrier part extension offset angle Φ0. Here, the point where the straight line L1 intersects the curve T1 indicating the primary torque maximum amplitude value T1 is P 11 , the point where the straight line L1 intersects the curve T2 indicating the secondary torque maximum amplitude value T2 is P 12 , and the point where the straight line L1 parallel to the vertical axis intersects the horizontal line of zero is O1. The length between the point O1 and the point P 11 is defined as L 11 , and the length between the point O1 and the point P 12 is defined as L 12 . Then, L 11 is the absolute value of the primary torque maximum amplitude value T1 that takes a negative value, and L12 is the absolute value of the maximum amplitude value T2 of the second-order torque that takes a positive value.

[0080] Focusing on the sum value of the maximum amplitude value T1 of the first-order torque and the maximum amplitude value T2 of the second-order torque, its absolute value is the difference between the absolute value of the maximum amplitude value T1 of the first-order torque and the absolute value of the maximum amplitude value T2 of the second-order torque. The smaller this difference is, the more the maximum amplitude value T1 of the first-order torque and the maximum amplitude value T2 of the second-order torque cancel each other out, and the smaller the magnitude of the cogging torque T becomes. From such a perspective, the first flux barrier portion extension offset angle Φ1 is set.

[0081] Similarly, the flux barrier portion extension offset angle Φ is shifted to the side larger than the central flux barrier portion extension offset angle Φ0. That is, in FIG. 10, a straight line L2 parallel to the vertical axis is shifted to the side larger than the central flux barrier portion extension offset angle Φ0. Here, the point where the straight line L2 intersects the curve T1 indicating the maximum amplitude value T1 of the first-order torque is P 21 , and the point where the straight line L2 intersects the curve T2 indicating the maximum amplitude value T2 of the second-order torque is P 22 , and the point where the straight line L2 parallel to the vertical axis intersects the horizontal line of zero is O2. The length between the point O2 and the point P 21 is L 21 , and the length between the point O2 and the point P 22 is L 22 . Then, L 21 is the absolute value of the maximum amplitude value T1 of the first-order torque that takes a positive value, and L 22 is the absolute value of the maximum amplitude value T2 of the second-order torque that takes a negative value. From the perspective of making the difference between the absolute value of the maximum amplitude value T1 of the first-order torque and the absolute value of the maximum amplitude value T2 of the second-order torque smaller, the second flux barrier portion extension offset angle Φ2 is set. Here, the flux barrier portion extension offset angle Φ is, as described above, the angle in the electrical angle formed between the straight line connecting the tip 133a of the FB portion extension 133 and the rotation center CL and the geometric central axis MC in the cross section shown in FIG. 3.

[0082] Next, the flux barrier portion extension offset angle Φ will be described for the case illustrated in FIG. 1. The permanent magnet rotor 100 of the permanent magnet synchronous motor 1 has two types of magnetic poles, the first magnetic pole 121 and the second magnetic pole 122, as described above. The central magnetic path 130ma of the first magnetic pole 121 corresponds to a circumferential angle that is twice the value of the first flux barrier portion extension offset angle Φ1. Also, the central magnetic path 130mb of the second magnetic pole 122 corresponds to a circumferential angle that is twice the value of the second flux barrier portion extension offset angle Φ2.

[0083] Next, the flux barrier portion extension offset angle Φ will be described for the case illustrated in FIG. 2. The permanent magnet rotor 100 of the permanent magnet synchronous motor 1 has three types of magnetic poles, the first magnetic pole 121, the second magnetic pole 122, and the third magnetic pole 123, as described above. The central magnetic path 130ma of the first magnetic pole 121 corresponds to a circumferential angle that is twice the value of the first flux barrier portion extension offset angle Φ1. Also, the central magnetic path 130mb of the second magnetic pole 122 corresponds to a circumferential angle that is twice the value of the second flux barrier portion extension offset angle Φ2. Further, the central magnetic path 130mc of the third magnetic pole 123 corresponds to a circumferential angle that is twice the value of the central flux barrier portion extension offset angle Φ0.

[0084] Next, it will be explained that the relationship with the minimum offset angle Φmin is satisfied for the central flux barrier portion extension offset angle Φ0 whether the permanent magnet synchronous motor 1 has 6 poles and 54 slots or 6 poles and 72 slots.

[0085] FIG. 11 is a partial cross-sectional view showing the case of a 6-pole 54-slot permanent magnet synchronous motor according to an embodiment. FIG. 11 shows a region corresponding to one of the six magnetic poles, and thus a geometric circumferential angle of 60 degrees. In FIG. 11, substantially nine stator teeth 211 and nine stator slots 212 are shown. Therefore, the total number of stator teeth 211 in the stator 200 is 54.

[0086] FIG. 12 is a conceptual graph showing the dependence characteristics (the dependence characteristics of the cogging torque maximum amplitude value on the offset angle) of the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 on the flux barrier portion extension offset angle Φ in the case of a 6-pole 54-slot obtained in the manufacturing method of the permanent magnet synchronous motor 1 according to the embodiment, and an explanatory diagram showing the relationship with the stator teeth 211. In the graph, the solid line indicates the primary torque maximum amplitude value T1, and the broken line indicates the secondary torque maximum amplitude value T2. Further, in FIG. 12, the case where the minimum offset angle Φmin is 25 degrees is shown as an example. The horizontal axis is the FB portion extension offset angle Φ [electrical angle (degrees)], and the vertical axis is the normalized torque maximum amplitude value T [P.U.].

[0087] The values on the horizontal axis with reference to the reference stator teeth 211a are displayed as the FB portion extension offset angle Φ and the circumferential direction angle Θ. The circumferential direction angle Θ of the circumferential center position of the stator slot 212 is 20 degrees in the case of the stator teeth 211 adjacent to the reference stator teeth 211a, and 40 degrees in the case of the third stator teeth 211 viewed from the reference stator teeth 211a.

[0088] Here, pay attention to the zero-crossing situation of the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 in the vicinity of the FB portion extension offset angle Φ corresponding to 0 degrees, 20 degrees, and 40 degrees, which are the circumferential direction angles Θ of the circumferential centers of the respective stator teeth 211.

[0089] In the vicinity F1 where the FB portion extension offset angle Φ is near 0 degrees, the zero-crossing angle is unclear. In the vicinity F2 where the FB portion extension offset angle Φ is 20 degrees, the zero-crossing angle is around about 21 degrees exceeding 20 degrees, and there is a deviation between the zero-crossing angle and 20 degrees. In the vicinity F3 where the FB portion extension offset angle Φ is 40 degrees, the zero-crossing angle has a small deviation from around about 40 degrees, that is, they are substantially the same. Here, a small deviation or substantially the same means that when the difference from the FB portion extension offset angle Φ is relatively small, for example, less than 1 degree.

[0090] That is, in the case of the third stator tooth 211 as viewed from the reference stator tooth 211a, the FB portion extension offset angle Φ exceeds the minimum offset angle Φmin (25 degrees in FIG. 12), and the zero-cross angle substantially coincides with the FB portion extension offset angle Φ. The stator tooth 211 corresponding to such an FB portion extension offset angle Φ can be selected as the target stator tooth 211b.

[0091] FIG. 13 is a partial cross-sectional view showing the case of a 6-pole 72-slot permanent magnet synchronous motor according to an embodiment. FIG. 13 shows a region corresponding to one of the six poles, and thus a geometric circumferential angle of 60 degrees. In FIG. 13, substantially 12 stator teeth 211 and 12 stator slots 212 are shown. Therefore, the number of stator teeth 211 in the entire stator 200 is 72.

[0092] FIG. 14 is a conceptual graph showing an example of the dependence characteristics of the first torque maximum amplitude value and the second torque maximum amplitude value on the flux barrier portion extension offset angle in the case of a 6-pole 72-slot permanent magnet synchronous motor manufacturing method according to an embodiment, and an explanatory diagram showing the relationship with the stator teeth. In the graph, the solid line indicates the first torque maximum amplitude value T1, and the broken line indicates the second torque maximum amplitude value T2. Also in FIG. 14, the case where the minimum offset angle Φmin is 25 degrees is shown as an example. The horizontal axis is the FB portion extension offset angle Φ [electrical angle (degrees)], and the vertical axis is the normalized torque maximum amplitude value T [P.U.].

[0093] Also in FIG. 14, the values on the horizontal axis with respect to the reference stator tooth 211a are displayed as the FB portion extension offset angle Φ and the circumferential direction angle Θ. The circumferential direction angle Θ of the center position in the circumferential direction of the stator slot 212 is 15 degrees in the case of the stator tooth 211 adjacent to the reference stator tooth 211a, 30 degrees in the case of the third stator tooth 211 as viewed from the reference stator tooth 211a, and 45 degrees in the case of the third stator tooth 211 as viewed from the reference stator tooth 211a.

[0094] Here, attention is paid to the zero-crossing situations of the primary torque maximum amplitude value T1 and the secondary torque maximum amplitude value T2 in the vicinity of the FB portion extension offset angle Φ corresponding to 0 degrees, 15 degrees, 30 degrees, and 45 degrees, which are the circumferential angles Θ at the circumferential centers of the respective stator teeth 211.

[0095] In the vicinity F1 where the FB portion extension offset angle Φ is near 0 degrees, the zero-crossing angle is unclear. In the vicinity F2 where the FB portion extension offset angle Φ is near 20 degrees, the zero-crossing angle is around approximately 16 degrees exceeding 15 degrees, and there is a deviation between the zero-crossing angle and 15 degrees. In the vicinity F3 where the FB portion extension offset angle Φ is near 30 degrees, the zero-crossing angle has a small deviation from around approximately 30 degrees. In the vicinity F4 where the FB portion extension offset angle Φ is near 45 degrees, the zero-crossing angle has an even smaller deviation from around approximately 45 degrees.

[0096] That is, in the case of the third stator tooth 211 and the fourth stator tooth 211 as viewed from the reference stator tooth 211a, the FB portion extension offset angle Φ exceeds the minimum offset angle Φmin (25 degrees in FIG. 12), and the zero-crossing angle substantially coincides with the FB portion extension offset angle Φ. The stator tooth 211 corresponding to such an FB portion extension offset angle Φ can be selected as the target stator tooth 211b.

[0097] FIG. 15 is a graph showing the influence on the dependence characteristic of the offset angle of the cogging torque maximum amplitude value when the stator tooth angle width Θw (FIG. 3) is changed. The horizontal axis is the offset angle Φ [electrical angle (degrees)], and the vertical axis is the cogging torque [N·m].

[0098] As shown in FIG. 15, as the stator tooth angle width Θw of the stator tooth 211 increases, the value of the cogging torque maximum amplitude value increases, but it can be seen that the respective zero-crossing angles in the regions shown as G1 to G4 are not affected by the stator tooth angle width Θw.

[0099] As described above, by deriving a plurality of types of magnet storage flux barriers 131 and assigning them to each magnetic pole pair, cogging torque can be reduced.

[0100] According to the embodiment described above, it is possible to provide a permanent magnet synchronous motor and a method for manufacturing a permanent magnet synchronous motor capable of reducing cogging torque without using skew.

[0101] [Other Embodiments] Although the embodiments of the present invention have been described above, the embodiments are presented as examples and are not intended to limit the scope of the invention. Also, the features of each embodiment may be combined. Furthermore, the embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. Embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and the equivalent scope thereof. [Description of Reference Numerals]

[0102] 1, 1a... Permanent magnet synchronous motor, 100, 100a... Permanent magnet rotor, 110... Rotor shaft, 120... Permanent magnet, 121, 121a, 121b, 121c... First magnetic pole, 122, 122a, 122b, 122c... Second magnetic pole, 123, 123a, 123b... Third magnetic pole, 130... Rotor core, 130a... Shaft through hole, 130b... Rod through hole, 130m, 130ma, 130mb, 130mc... Central magnetic path, 131... Magnet storage flux barrier, 132... Magnet storage portion, 133... Flux barrier portion extension (FB portion extension), 133a... Tip, 200... Stator, 210... Stator core, 211... Stator teeth, 211a... Reference stator teeth, 211b... Target stator teeth, 212... Stator slots, 220... Stator winding

Claims

1. A permanent magnet rotor comprising: a rotor shaft extending in the axial direction and rotating around a rotation center axis; a rotor core attached to the outer side in the radial direction of the rotor shaft and having magnet storage flux barriers formed on both sides of a geometric center axis, which is the circumferential center of the magnetic poles, corresponding to each of the plurality of magnetic poles; and permanent magnets housed in the respective magnet storage flux barriers and arranged symmetrically with respect to the geometric center axis. A stator comprising: a stator core formed to surround the rotor core with a gap on the outer side in the circumferential direction of the rotor core; and a stator winding having portions housed in each of a plurality of stator slots formed between a plurality of stator teeth formed in the stator core. A permanent magnet synchronous motor comprising: The magnet storage flux barrier has a magnet storage portion for storing the permanent magnet and a flux barrier portion extension extending from the radially outer portion of the magnet storage portion toward the geometric center axis side. In a cross section perpendicular to the rotation center axis, the flux barrier portion extension offset angle, which is the circumferential angle formed by the straight line connecting the tip of the flux barrier portion extension on the geometric center axis side and the rotation center axis and the geometric center axis, has two types of values, a first flux barrier portion extension offset angle smaller than the circumferential center angle and a second flux barrier portion extension offset angle smaller than the circumferential center angle, sandwiching a target stator tooth having a circumferential center angle larger than the minimum offset angle. Among the plurality of magnetic poles, two adjacent magnetic poles form a magnetic pole pair, and the magnet storage flux barriers in each magnetic pole pair have the same flux barrier portion extension offset angle and take either of the two types of values. A permanent magnet synchronous motor characterized by the above.

2. When the number of the magnetic pole pairs is odd, the magnet storage flux barriers in each magnetic pole pair take any one of the values of the first flux barrier portion extension offset angle, the second flux barrier portion extension offset angle, or the flux barrier portion extension offset angle equal to the circumferential center angle of the target stator tooth. The permanent magnet synchronous motor according to Claim 1, characterized by the above.

3. The permanent magnet synchronous motor according to claim 1, wherein the offset angle of the first flux barrier portion extension and the offset angle of the second flux barrier portion extension are each equal to or greater than a predetermined first angle and equal to or less than a predetermined second angle from the angular position of the target stator tooth.

4. A rotor shaft extending in the axial direction and rotating around a rotation center axis, and a geometric center axis that is the circumferential center of each of a plurality of magnetic poles, which is attached to the outer side in the radial direction of the rotor shaft and arranged on both sides of the geometric center axis, a magnet housing portion and a flux barrier portion extension extending from the radially outer portion of the magnet housing portion toward the side of the geometric center axis, and a rotor core in which a magnet housing flux barrier is formed, and permanent magnets housed in the magnet housing portion and arranged symmetrically with respect to the geometric center axis. A permanent magnet rotor comprising: A stator core formed to surround the rotor core via a gap on the outer side in the circumferential direction of the rotor core, and a stator winding having a portion housed in each of a plurality of stator slots formed between a plurality of stator teeth formed in the stator core. A stator comprising: A method for manufacturing a permanent magnet synchronous motor comprising: Determining a minimum offset angle that is a minimum value of an offset angle of a flux barrier portion extension, which is a circumferential angle in an electrical angle, based on the magnetic strength of the permanent magnet; Obtaining a cogging torque angle dependence characteristic of the cogging torque with respect to a rotation angle in an electrical angle in the case of the offset angle of the flux barrier portion extension, with the offset angle of the flux barrier portion extension as a parameter; Calculating a first mode and a second mode of the cogging torque angle dependence characteristic, and obtaining a first torque maximum amplitude value and a second torque maximum amplitude value, which are maximum amplitude values of each; Deriving an offset angle dependence characteristic, which is a dependence characteristic of the flux barrier portion extension offset angle based on the first torque maximum amplitude value and the second torque maximum amplitude value, based on the first torque maximum amplitude value and the second torque maximum amplitude value; Selecting a target stator tooth based on the offset angle dependence characteristic; Based on the offset angle dependence characteristics and the selected target stator teeth, a step of deriving a first flux barrier portion extension offset angle and a second flux barrier portion extension offset angle such that the result of the primary torque maximum amplitude value and the secondary torque maximum amplitude value canceling each other out is minimized; having; the first flux barrier portion extension offset angle and the second flux barrier portion extension offset angle are greater than the minimum offset angle; A method for manufacturing a permanent magnet synchronous motor, characterized in that.

5. Determining whether the number of magnetic pole pairs of the permanent magnet rotor is odd; The method for manufacturing a permanent magnet synchronous motor according to claim 4, characterized in that when it is determined to be odd, the first flux barrier portion extension offset angle and the second flux barrier portion extension offset angle are greater than the minimum offset angle.

Images