Variable magnetic flux motor

Abstract

To provide a variable magnetic flux motor in which the efficiency of motor drive can be enhanced at the time of low speed high load and high speed low load by suppressing reduction of maximum torque without using an external circuit.SOLUTION: A synchronous or induction motor 100 includes a stator 10 having a stator core 11 and a winding wound around the stator core 11, and a rotor 20. At least a part of the stator 10 is made of a nonlinear soft magnetic material.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to variable flux motors. [Background technology]

[0002] In recent years, there has been a demand for motors that are highly efficient across all torque and speed ranges, but in reality, it is difficult to realize such a motor. Generally, motors with a large amount of field magnetic flux have a high-efficiency region on the low-speed, high-torque side, while motors with a small amount of field magnetic flux have a high-efficiency region on the high-speed, low-torque side. Because the amount of field magnetic flux is a fixed value determined by the permanent magnet embedded in the rotor, it was thought that it would be impossible to realize a motor that has high-efficiency regions on both the low-speed, high-torque side and the high-speed, low-torque side.

[0003] In recent years, variable magnetic flux motors have been proposed that change the amount of field magnetic flux while the motor is running. There are various mechanisms for adjusting the amount of magnetic flux, but those that have a magnetic flux adjustment mechanism, such as a mechanical system or an excitation coil for field adjustment, are called active variable magnetic flux structures. In contrast, those that do not require such an adjustment mechanism and instead change the amount of field magnetic flux in accordance with the torque generated by the motor, thereby achieving a variable magnetic flux effect, are called passive variable magnetic flux structures.

[0004] Patent Document 1 proposes an example of a passively variable magnetic flux structure. In the motor described in Patent Document 1, when current is applied to the coil wound around the armature, under low load conditions where the armature current is low, the magnetic flux of the permanent magnet leaks to the adjacent pole through the leakage bypass path and does not link with the armature. This reduces the amount of magnetic flux, resulting in a high-efficiency region on the high-speed, low-torque side. Under high load conditions where the armature current is high, the magnetomotive force of the armature winding increases, causing the leakage bypass path to saturate with the magnetic flux of the permanent magnet and the magnetic flux of the armature. This increases the amount of magnetic flux, resulting in a high-efficiency region on the low-speed, high-torque side, because the magnetic flux of the permanent magnet does not leak and links with the armature. As described above, the motor described in Patent Document 1 does not have any special mechanism, and the state of the magnetic flux changes only depending on the magnitude of the armature excitation current, so it has the function of passively varying the magnetic flux, and can expand the high-efficiency range of the motor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-17783 [Non-patent literature]

[0006] [Non-Patent Document 1] "Physics of Ferromagnetic Materials (Volume 2) - Magnetic Properties and Applications" by Satoshi Chikazumi, Shokabo Summary of the Invention [Problem to be solved by the invention]

[0007] However, the variable magnetic flux motor disclosed in Patent Document 1 has a problem in that the maximum torque is reduced because the magnetic flux leaking into the bypass path does not contribute to the torque of the motor but results in a loss of magnetic energy.

[0008] The present disclosure aims to provide a variable magnetic flux motor that can suppress a decrease in maximum torque without using an external circuit and improve the efficiency of motor drive at low speed and high load, and at high speed and low load. [Means for solving the problem]

[0009] A variable magnetic flux motor according to one aspect of the present disclosure includes: A synchronous or induction motor, a stator having a stator core and a winding wound around the stator core; A rotor; Equipped with At least a portion of the stator is made of a nonlinear soft magnetic material. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a stator with a variable magnetic flux structure that is highly efficient under both low load and high load conditions, and a variable magnetic flux motor that includes the stator. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 10 is a horizontal cross-sectional view perpendicular to the rotation axis of a motor according to a reference example. [Figure 2] 1 is a horizontal cross-sectional view perpendicular to the rotation axis of a motor according to an embodiment of the present invention. [Figure 3] 1 is a graph showing BH curves of a linear soft magnetic material and a nonlinear soft magnetic material. [Figure 4] 3 is a partially enlarged view of the motors of Reference Examples 1 and 2 and the present embodiment. FIG. [Figure 5] 1 is an efficiency map of a motor according to Reference Example 1. [Figure 6] 4 is an efficiency map of the motor according to the present embodiment. [Figure 7] FIG. 10 is a diagram showing the magnetic flux density distribution of the motor according to Reference Example 1 when the load is low. [Figure 8] FIG. 4 is a diagram showing a magnetic flux density distribution when the motor according to the present embodiment is under low load. [Figure 9] FIG. 10 is a diagram showing the magnetic flux density distribution of the motor according to Reference Example 1 when a high load is applied. [Figure 10] FIG. 4 is a diagram showing a magnetic flux density distribution when the motor according to the present embodiment is under high load. [Figure 11] 1 is a graph showing BH curves of a plurality of nonlinear soft magnetic materials having different magnetic properties. [Figure 12] 10 is an efficiency map of a motor using the nonlinear soft magnetic material S2 according to the present embodiment. [Figure 13] 10 is an efficiency map of a motor using the nonlinear soft magnetic material S3 according to the present embodiment. [Figure 14] 10 is an efficiency map of a motor using the nonlinear soft magnetic material S4 according to the present embodiment. [Figure 15]FIG. 10 is a diagram showing a stator core of a motor according to a modified example of the invention. [Figure 16] 1 is a graph showing BH curves for a nonlinear soft magnetic material S1, a nonlinear soft magnetic material S4, and a non-oriented electrical steel sheet. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For the sake of convenience, descriptions of components having the same reference numerals as those already described in the description of the embodiments will be omitted. Furthermore, for the sake of convenience, the dimensions of each component shown in the drawings may differ from the actual dimensions of each component.

[0013] [Reference example] In order to explain the details of the motor 100 according to this embodiment, a motor 100' according to a reference example will be explained as a comparison example with reference to FIG.

[0014] Fig. 1 is a horizontal cross-sectional view perpendicular to the rotation axis of a motor 100' according to a reference example. The motor 100' shown in Fig. 1 has a three-phase, six-pole, 45-slot, distributed winding, IPMSM (interior permanent magnet synchronous motor) structure with a per-pole, per-phase slot number q = 2.5. The motor 100' is also a rotating field type and includes a stator 10' and a rotor 20 that can rotate relative to the stator 10'.

[0015] The stator 10' includes a ring-shaped stator core (stator core) 11 formed by laminating multiple electromagnetic steel sheets in the direction of the rotation axis (perpendicular to the plane of the paper in FIG. 1). The stator core 11 is made of electromagnetic steel sheets that are soft magnetic, and has a ring-shaped back yoke (yoke portion) 11b and 45 teeth (magnetic pole portions) 11a arranged on the inner periphery of the back yoke 11b. The teeth 11a protrude radially inward from the inner periphery of the back yoke 11b. The 45 teeth 11a have approximately the same shape and are supported by the back yoke 11b. Slots are provided between two adjacent teeth 11a. A winding is wound around each tooth 11a using the space provided by the slot, and the winding forms a stator coil 12.

[0016] Each stator coil 12 is wound around the teeth 11a by distributed winding and is excited by an external AC current.

[0017] The rotor 20 includes a rotor core 21 formed by laminating multiple electromagnetic steel plates in the direction of the rotation axis. The rotor core 21 is formed in a cylindrical shape. The inner peripheral surface of the rotor core 21 defines a shaft mounting hole 22. A drive shaft (not shown) is fixed to the shaft mounting hole 22, and the drive shaft is supported by a bearing and a housing (not shown) so as to be rotatable about the rotation axis.

[0018] The rotor 20 has a plurality of rotor magnets 23 in the rotor core 21. The rotor magnets 23 are embedded inside slots provided in the rotor core 21. The rotor magnets 23 are made of flat permanent magnets and are approximately the same in size, material, and composition. The plurality of rotor magnets 23 are arranged at equal intervals along a circumference centered on the center of rotation O so as to form six poles that are 60° apart from one another. Therefore, the magnetomotive force exerted on the stator coil 12 by each rotor magnet 23 is approximately the same. Furthermore, rotor gaps 24 extending radially outward are provided at both ends of each rotor magnet 23. There are no components inside the rotor gaps 24, and air is present. The rotor magnet 23 may be a permanent magnet or an electromagnet.

[0019] [Present embodiment] 2 is a horizontal cross-sectional view perpendicular to the rotation axis of the motor 100 according to this embodiment. Only the differences in the configuration from the motor 100' according to the reference example shown in FIG. 1 will be described below.

[0020] The stator 10 includes a ring-shaped stator core 11. The stator core 11 has a ring-shaped back yoke 11b made of non-oriented electromagnetic steel sheet, which is a type of soft magnetic material, and 45 teeth 11a made of a non-linear soft magnetic material. In this specification, a non-linear soft magnetic material is defined as a material that is not magnetized (magnetic flux density remains low) until a certain value of magnetic field strength H is applied, but when the magnetic field strength H exceeds a certain value, the relative permeability μr increases and the magnetic flux density rises sharply. Here, the non-linear soft magnetic material will be described in detail using FIG. 3.

[0021] Figure 3 is a graph showing the BH curves of a typical soft magnetic material and a nonlinear soft magnetic material. The horizontal axis of Figure 3 represents the magnetic field strength H, and the vertical axis represents the magnetic flux density B. As shown in Figure 3, for typical soft magnetic materials, such as non-oriented electrical steel sheets, the magnetic flux density B rises sharply when a magnetic field is applied near zero (H). As the magnetic field strength H increases, the magnetic flux density B converges to the saturation magnetic flux density Bs. In other words, for typical soft magnetic materials, the magnetic flux density B increases immediately when a magnetic field is applied, but as the magnetic field strength H increases, the rate of increase in magnetic flux density B slows down and converges to the saturation magnetic flux density Bs. Generally, soft magnetic materials are developed with a high relative permeability μr (the slope of the graph in Figure 3) and a high saturation magnetic flux density Bs. Furthermore, for electrical steel sheets, which are a type of soft magnetic material, a material that rapidly increases magnetic flux density B when a magnetic field is applied is generally required. In the following explanation, to contrast with nonlinear soft magnetic materials, typical soft magnetic materials that exhibit a rapid increase in magnetic flux density B even in weak magnetic fields are also referred to as linear soft magnetic materials.

[0022] In contrast, the nonlinear soft magnetic material that the inventors focused on exhibits only a gradual change in magnetic flux density when the magnetic field strength H is near 0. However, when the magnetic field strength H reaches a certain value Hk, the magnetic flux density B increases rapidly. As the magnetic field strength H increases, the magnetic flux density B then converges to the saturation magnetic flux density Bs. In other words, the magnetic flux density B of a nonlinear soft magnetic material does not increase significantly when a weak magnetic field below a certain value is applied, but when a strong magnetic field strength H above a certain value is applied, the magnetic flux density B increases rapidly. In other words, a nonlinear soft magnetic material exhibits the characteristic that magnetic flux does not pass easily even when a weak magnetic field strength H is applied, but when a strong magnetic field strength H is applied, magnetic flux passes easily. In Figure 3, the magnetic field strength at which magnetic flux becomes easy to pass is shown as the rising magnetic field Hk. In the B-H curve, the rising magnetic field Hk refers to the magnetic field strength at which the magnetic flux density is 25% of the saturation magnetic flux density of the nonlinear soft magnetic material.

[0023] FIG. 4(a) shows a motor 100′ according to a general reference example 1 in which the magnetic resistance does not change, FIG. 4(b) shows a passive variable magnetic resistance variable magnetic flux motor 100″ according to reference example 2 of Patent Document 1, and FIG. 4(c) is an enlarged view of a portion of the motor 100 according to this embodiment.

[0024] In the motor 100′ of Reference Example 1 shown in FIG. 4(a), in which the magnetic reluctance does not change, both the back yoke 11b and the teeth 11a are made of the same linear soft magnetic material, such as non-oriented electromagnetic steel sheet. In this motor 100′, the rotor magnet 23 used for the field is a permanent magnet with a fixed magnetic flux. Therefore, the faster the rotor 20 operates, the higher the induced voltage becomes, causing a voltage drop. This prevents current from flowing from the power supply, resulting in a decrease in torque. For this reason, the motor 100′ of Reference Example 1 employs a control method generally known as vector control, which advances the phase of the current during high-speed operation and uses the magnetomotive force of the stator coil 12 to generate a magnetic field in the opposite direction to the rotor magnet 23 embedded in the rotor 20, thereby weakening the magnetic force of the rotor magnet 23. This suppresses the induced voltage and allows current to flow, but since the current flowing through the stator coil 12 is the sum of the current for the flux weakening and the current that contributes to torque, this means that extra current is flowing, which leads to increased losses in the high-speed range.

[0025] FIG. 4(b) is a partially enlarged view of a motor 100'' according to Reference Example 2. In this motor 100'' according to Reference Example 2, a leakage bypass path 25 is provided between poles formed by the rotor magnets 23. When the amount of current flowing through the stator coil 12 is small, the magnetic flux of the rotor magnet 23 leaks through the leakage bypass path 25 to the adjacent pole and does not interlink with the stator coil 12, thereby suppressing voltage drop due to induced voltage. In other words, when it is desired to drive the rotor 20 at high speed, the current for weakening the magnetic flux of the rotor magnet 23 (hereinafter referred to as "flux-weakening current") can be suppressed, thereby reducing the amount of current flowing through the stator coil 12 and improving efficiency in the high-speed range.

[0026] On the other hand, when the amount of current flowing through the stator coil 12 is increased, the leakage bypass path 25 is saturated by the magnetic flux of the rotor magnet 23 and the magnetic flux of the stator coil 12. As a result, the magnetic flux of the rotor magnet 23 does not leak into the leakage bypass path 25 but links to the stator coil 12. Therefore, when driving the rotor 20 at high torque and low speed, most of the magnetic flux of the rotor magnet 23 links directly to the stator coil 12, allowing high torque to be maintained. In this way, the variable magnetic flux motor improves efficiency by reducing the amount of magnetic flux in the rotor 20 under low loads, and obtains high torque under high loads by making maximum use of the magnetic flux from the rotor magnet 23 of the rotor 20 and the magnetic flux from the stator coil 12. Because the state of the magnetic flux changes solely depending on the magnitude of the excitation current in the stator coil 12 without requiring any special mechanism, it has a passive variable magnetic flux function and expands the high-efficiency range of the motor.

[0027] In this way, the motor 100'' of Reference Example 2 shown in Figure 4(b) can create high-efficiency regions on both the high-speed, low-torque side and the low-speed, high-torque side. However, a certain amount of magnetic flux from the rotor magnet 23 always leaks into the leakage bypass path 25, resulting in a relatively lower maximum torque than the motor of Reference Example 1 shown in Figure 4(a). The maximum torque required for a motor is often determined by the specifications of the device into which it is incorporated, such as a robot or machine tool. Furthermore, the limiting current value is often limited by the specifications of the inverter module. If the motor's maximum torque decreases under these circumstances, it may not meet the specifications of the device or inverter into which it is incorporated, making it unsuitable for the device into which it is incorporated. Therefore, there is a need for a variable-flux motor that does not reduce maximum torque, can drive efficiently in the medium- to high-speed range, and does not require an active variable-flux mechanism. However, the need for a special mechanism for variable flux remains a problem.

[0028] Therefore, in the motor 100 of this embodiment shown in Figure 4(c), as described above, the back yoke 11b is made of a general linear soft magnetic material such as non-oriented electromagnetic steel sheet, and the teeth 11a are made of a non-linear soft magnetic material. Also, here, as shown in Figure 3, the magnetic field strength Ha of the rotor magnet 23 of the rotor 20 is set to be less than the rising magnetic field Hk. Furthermore, the sum of the magnetic field strength of the rotor magnet 23 of the rotor 20 and the maximum magnetic field strength of the stator coil 12 is set to be equal to or greater than the magnetic field strength Hs that results in the saturation magnetic flux density Bs.

[0029] When this motor is operated at high speed and low torque, the amount of magnetic flux generated in the stator coil 12 is small, as in motors 100' and 100'', and the magnetic flux from the rotor magnet 23 of the rotor 20 is dominant. In this state, the magnetic field strength Ha1 is smaller than the rising magnetic field Hk of the nonlinear soft magnetic material used in the teeth 11a, and the magnetic flux density Ba1 in the teeth 11a is small. Therefore, even when the rotor 20 is operated at high speed, the induced voltage in the stator coil 12 is small, and the flux-weakening current can be reduced. This reduces copper loss in the stator coil 12. Furthermore, the magnetic flux density in the teeth 11a does not increase unless a certain level of magnetic field strength is applied. Therefore, the magnetic flux density in some areas of the teeth 11a that contribute to torque is increased, and the magnetic flux density in other areas that do not contribute to torque can be kept low. This reduces iron loss due to the teeth 11a that do not contribute to torque, thereby improving overall efficiency. In other words, efficiency is improved in the low-torque, high-speed range.

[0030] Furthermore, during high-torque driving, the amount of current flowing through the stator coil 12 increases, so the magnetic field strength Ha2 acting on the teeth 11a is the sum of the magnetic flux from the rotor magnet 23 and the magnetic flux from the stator coil 12, and is therefore greater than the rising magnetic field Hk of the nonlinear soft magnetic material, increasing the magnetic flux density of the teeth 11a. This makes it possible to output high torque. Moreover, the motor 100 of this embodiment does not have the leakage bypass path 25 as in motor 100'' of Reference Example 2, so torque can be generated without leakage of part of the magnetic flux from the stator coil 12 and rotor magnet 23, and therefore maximum torque does not decrease.

[0031] Let Ba be the magnetic flux density when a magnetic field strength Ha of the rotor magnet 23 used in the rotor 20 is applied to a certain material, Bb be the magnetic flux density when a magnetic field strength Hb that is 1 / 2 of Ha is applied, and Bc be the magnetic flux density when a magnetic field strength Hc that is twice Ha is applied. In this case, it is preferable for the nonlinear soft magnetic material to have a characteristic in which the ratio X = (Bc / Ba) / (Ba / Bb) is 5 or greater. It is more preferable for the ratio X to be 10 or greater.

[0032] 3, the motor 100' of the reference example described above will be compared with the motor 100 of this embodiment. When the magnetic field strength Ha from the rotor magnet 23 of the rotor 20 acts on the stator coil 12, the magnetic flux density of the stator coil 12 becomes Ba' if the stator coil 12 is made of a linear soft magnetic material, and becomes Ba if the stator coil 12 is made of a non-linear soft magnetic material. Because the magnetic flux density Ba is lower than the magnetic flux density Ba', the back electromotive force is less likely to increase in the motor 100 of this embodiment, which reduces loss as described above and provides high efficiency at low torque and high speed.

[0033] Furthermore, when a magnetic field strength Hs is applied to the stator coil 12 while it is energized to output high torque, the magnetic flux density of the stator coil 12 will be the saturation magnetic flux density Bs whether the stator coil 12 is made of a linear soft magnetic material or a non-linear soft magnetic material. As a result, the maximum torque of the motor 100 of this embodiment is the same as that of the motor 100 of the reference example.

[0034] In the motor 100 of this embodiment, the nonlinear soft magnetic material used in the stator core 11 preferably has the following characteristics: (1) when a permanent magnet is used as the rotor magnet 23 incorporated in the rotor core 21, the magnetic flux density of the permanent magnet, or when an electromagnet is used as the rotor magnet 23 incorporated in the rotor core 21, the magnetic flux density of the nonlinear soft magnetic material when the magnetomotive force of the electromagnet is applied is 30% or less of the saturation magnetic flux density Bs; and (2) when the maximum magnetomotive force is applied from the stator coil 12, the magnetic flux density of the nonlinear soft magnetic material is 80% or more of the saturation magnetic flux density Bs.

[0035] Furthermore, when the magnetic field strength at which the magnetic flux density is 25% of the saturation magnetic flux density on the BH curve is expressed as the rising magnetic field Hk, and the magnetic field strength at which the maximum relative permeability is reached is expressed as Hm, it is preferable that the nonlinear soft magnetic material used for the stator core 11 satisfy all of the following formulas (1) to (3). Hk≧100[A / m] Formula (1) Hm≧100[A / m] Formula (2) Hm>Hk Equation (3)

[0036] Figure 16 shows the BH curves for the nonlinear soft magnetic material S1, the nonlinear soft magnetic material S4, and the non-oriented electrical steel sheet, which were explained in Figure 11. Table 1 shows the saturation magnetic flux density, maximum relative permeability, Hk, and Hm for the nonlinear soft magnetic material S1, the nonlinear soft magnetic material S4, and the non-oriented electrical steel sheet. When calculating Table 1, B=μ r The relational expression μ0H is used. Here, B, μ r , μ0, and H respectively indicate the following. B: Magnetic flux density [T] μ r :Relative permeability μ0: Magnetic permeability of vacuum [H / m] H: Magnetic field strength [A / m]

[0037] [Table 1]

[0038] As shown in Figure 16 and Table 1, the nonlinear soft magnetic material S1 and the nonlinear soft magnetic material S4 satisfy all of the above formulas (1) to (3). Specifically, the rising magnetic field Hkx of the nonlinear soft magnetic material S1 is 9000 [A / m], and the magnetic field strength Hmx at which the maximum relative permeability is reached is 15000 [A / m]. The rising magnetic field Hky of the nonlinear soft magnetic material S4 is 35000 [A / m], and the magnetic field strength Hmy at which the maximum relative permeability is reached is 60000 [A / m]. However, for non-oriented electrical steel sheets, neither Hk nor Hm reaches 100 [A / m], and they do not satisfy formulas (1) and (2). Specifically, the rising magnetic field Hk0 of non-oriented electrical steel sheets is 60 [A / m], and the magnetic field strength at which the maximum relative permeability is reached, Hm0, is 80 [A / m].

[0039] Both the nonlinear soft magnetic material S1 and the nonlinear soft magnetic material S4 satisfy formulas (1) and (2), and have sufficiently large Hk and Hm, so that magnetic flux does not pass easily unless a strong external magnetic field is applied, and the maximum relative permeability is not reached unless a strong external magnetic field is applied. For this reason, a motor using the nonlinear soft magnetic material S1 or the nonlinear soft magnetic material S4 for the stator core 11 achieves high efficiency at low torque and high speed, and does not result in a decrease in maximum torque.

[0040] In contrast, non-oriented electrical steel sheets do not have sufficiently large Hk and Hm, and the application of even a weak magnetic field makes it easier for magnetic flux to pass through, and the application of a weak magnetic field quickly reaches the maximum relative permeability. For this reason, a motor using non-oriented electrical steel sheets for the stator core 11 cannot simultaneously achieve high efficiency at low torque and high speed while suppressing a decrease in maximum torque.

[0041] Note that, in the case of a material whose relative permeability reaches a maximum before the rising magnetic field Hk when the magnetic field is increased, the operating principle of the motor of the present disclosure described above is difficult to achieve. In other words, to avoid a situation in which magnetic flux passes through stator core 11 before the magnetomotive force of stator coil 12 is applied, it is preferable that the nonlinear soft magnetic material used for stator core 11 satisfy formula (3).

[0042] <Efficiency map> Using Figures 5 and 6, the efficiency map of the motor 100 according to this embodiment will be described in comparison with the motor 100' according to Reference Example 1. Figure 5 is the efficiency map of the motor 100' according to Reference Example 1. Figure 6 is the efficiency map of the motor 100 according to this embodiment. In both Figures 5 and 6, the horizontal axis represents the motor rotation speed Nr, the vertical axis represents the torque T, and the density of each region of the efficiency map represents the efficiency μ of the motor. The efficiency map is divided into regions in 6% increments: a high-efficiency region A where the efficiency μ is 94% or higher, and a region B where the efficiency μ is 88% or higher but less than 94%.

[0043] In the motor 100' according to the reference example, the back yoke 11b and the teeth 11a are made of non-oriented electromagnetic steel sheets. In the motor 100 according to this embodiment, the back yoke 11b is made of non-oriented electromagnetic steel sheets, and the teeth 11a are made of a non-linear soft magnetic material. Here, non-oriented refers to the property that the magnetic direction is random and not oriented in a specific direction. Details of non-oriented electromagnetic steel sheets will be described later.

[0044] As shown in FIG. 5, in the motor 100′ according to the reference example, a high efficiency region A′ is formed when the rotation speed Nr is 12200 min -1 The rotation speed Nr is 10,000 min -1 During the above high speed and low load conditions (the area to the right of the dashed line H2' in Figure 5), the efficiency μ remains below 94%.

[0045] In addition, the rotation speed Nr is 5000 min -1At the low speed and high load conditions shown below (the area to the left of dashed line L in Fig. 5), the maximum torque Tmax is 150 Nm and the rotation speed Nr is 3000 min -1 From point P5', the rotation speed Nr is 5000 min -1 The efficiency μ drops sharply around point P6′.

[0046] In contrast, as shown in FIG. 6, in the motor 100 according to this embodiment, the high efficiency region A is at a rotation speed Nr of 13,500 min -1 The area extends to the range below (the area to the left of the dashed line H1 passing through point P4 in Figure 6). -1 At the high speed and low load conditions described above (the area to the right of dashed line H2 in Figure 4), efficiency μ is 95% or less, indicating high efficiency.

[0047] In addition, the rotation speed Nr is 5000 min -1 At the low speed and high load conditions shown below (the area to the left of dashed line L in Fig. 6), the maximum torque Tmax is 150 Nm and the rotation speed Nr is 3000 min -1 From point P5, the rotation speed Nr is 5000 min -1 The efficiency μ gradually decreases from point P6.

[0048] Therefore, compared to the motor 100' according to the reference example, the high efficiency region A of the motor 100 according to this embodiment is wider.

[0049] <Magnetic flux density distribution> 7 to 11, the magnetic flux density distribution of the motor 100 according to this embodiment will be described in comparison with the motor 100' according to Reference Example 1. FIG. 7 shows the magnetic flux density distribution of the motor 100' according to Reference Example 1 under low load. FIG. 8 shows the magnetic flux density distribution of the motor 100 according to this embodiment under low load. Note that FIGS. 7 and 8 show the magnetic flux density distribution under low load when the torque T is equal to or less than half the maximum torque Tmax.

[0050] As shown in Fig. 7, when the motor 100' according to Reference Example 1 is under low load, for example, magnetic flux passes through the teeth 11a in the region Ar at a constant magnetic flux density. This is because the teeth 11a are made of non-oriented electrical steel sheets, and as can be seen from Fig. 3, the magnetic flux density B is large even when the magnetic field strength H is small. However, when the motor 100' rotates counterclockwise, the magnetic flux flowing through the teeth 11a in the region Ar', which is located to the left of the region Ar in Fig. 7 with respect to the direction of rotation, contributes to the torque T, while the magnetic flux flowing through the teeth 11a in the region Ar does not contribute to the torque T and may cause iron loss and back electromotive force.

[0051] In contrast, as shown in Figure 8, when the motor 100 according to this embodiment is under low load, the magnetic flux density is limited, for example, in the teeth 11a in the region Ar. This is because the teeth 11a are made of a nonlinear soft magnetic material, and as can be seen from Figure 3, the magnetic flux density B is very small at a small magnetic field strength H of the rising magnetic field Hk. In this way, by using a nonlinear soft magnetic material, the magnetic flux that does not contribute to the torque T of the motor 100' can be limited, thereby improving the efficiency μ.

[0052] Fig. 9 shows the magnetic flux density distribution of the motor 100' according to Reference Example 1 under high load. Fig. 10 shows the magnetic flux density distribution of the motor 100 according to this embodiment under high load. Figs. 7 to 10 show the distribution of magnetic flux density B in terms of density. Figs. 9 and 10 show the magnetic flux density distribution under high load when the torque T is greater than half the maximum torque Tmax.

[0053] 9 and 10, the magnetic flux density distributions under high load for motor 100' according to Reference Example 1 and motor 100 according to this embodiment are nearly identical. This is because, at a magnetic field strength H greater than the rising magnetic field Hk, magnetic flux density B is sufficiently large and reaches saturation magnetic flux density Bs, which is the magnetic flux density required for maximum torque Tmax of motor 100' and motor 100. This makes it possible to suppress a decrease in maximum torque Tmax.

[0054] In this way, the motor 100 according to this embodiment can exert a variable magnetic flux effect, improving efficiency μ by limiting magnetic flux at low loads and maintaining maximum torque Tmax at high loads, without adding any external circuitry.

[0055] <Relationship between the magnetic properties of nonlinear soft magnetic materials and motor efficiency> Fig. 11 is a graph showing the BH curves of multiple nonlinear soft magnetic materials with different magnetic properties. Fig. 11 shows the BH curves of four types of nonlinear soft magnetic materials S1 to S4 with different magnetic properties. The rising magnetic fields Hk1, Hk2, Hk3, and Hk4 increase in the order of nonlinear soft magnetic materials S1, S2, S3, and S4. Figs. 12 to 14 show efficiency maps of the motor according to this embodiment using nonlinear soft magnetic materials S2, S3, and S4, respectively.

[0056] 12 to 14, it can be seen that the range of the high-efficiency region A of the motor 100 using the nonlinear soft magnetic material for the teeth 11a is wider than that of the motor 100 shown in FIG. 6, which is the efficiency map of the motor 100' of Reference Example 1 described above. As the rising magnetic field Hk increases, the range of the high-efficiency region A expands. It can also be seen that as the rising magnetic field Hk increases, the high-efficiency region A expands toward the high-speed range.

[0057] <Nonlinear soft magnetic materials> The nonlinear soft magnetic material used in the motor will be described. There are two types of electromagnetic steel sheets: "grain-oriented electromagnetic steel sheets" with a uniform magnetic direction, and "non-oriented electromagnetic steel sheets" with a random magnetic direction. The magnetic direction is determined by whether the easy axis of magnetization of the crystalline structure of the iron atoms that make up the steel sheet is oriented in a uniform direction. Here, the easy axis of magnetization refers to the direction in which magnetization is easy. The back yoke 11b and teeth 11a of the motor 100' according to the reference example shown in Figure 1, and the back yoke 11b of the motor 100 according to this embodiment shown in Figure 2 are made of non-oriented electromagnetic steel sheets.

[0058] Furthermore, according to Non-Patent Document 1, in a single crystal model of iron with a body-centered cubic lattice structure, the magnetization direction is constrained by the spin directionality of the iron atom Fe located at the center. The position of the iron atom Fe located at the center is taken as the origin O' of the XYZ coordinate system, the

[0001] direction is taken as the direction of the easy axis of magnetization of the single crystal model, and the

[0110] direction is taken as the direction of the hard axis of magnetization of the single crystal model. Also, the magnetization direction, which is the angle between the easy axis of magnetization and the external magnetic field, is taken as θ. The hard axis of magnetization means the direction in which magnetization is difficult. When an excitation magnetic field H is applied to the single crystal model, ex When applied in the

[0110] direction, the magnetization vector M constrained to the magnetization easy axis

[0001] direction s rotates in the

[0110] direction. In this case, the anisotropy energy of the inner surface consisting of the origin O' and the

[0001] and

[0110] directions can be expressed using the first magnetic anisotropy energy constant K1 and the second magnetic anisotropy energy constant K2. The first magnetic anisotropy energy constant K1 and the second magnetic anisotropy energy constant K2 are constants determined for each material. For example, the first magnetic anisotropy energy constant K1 and the second magnetic anisotropy energy constant K2 of pure iron are K1=47200 J / m 3 , K2=-750J / m 3 When this value is used to calculate the magnetic properties in the hard axis direction, the rising magnetic field Hk is 6000 A / m. Note that the rising magnetic field Hk is defined as the magnetic field strength H when the magnetic flux density B becomes 25% of the saturation magnetic flux density Bs.

[0059] In this way, by selecting an appropriate material as the nonlinear soft magnetic material and controlling the direction of the magnetocrystalline anisotropy by utilizing the characteristics of the hard axis of magnetization, desired magnetic characteristics can be obtained. For example, in the stator core 11 of the motor 100 according to this embodiment shown in FIG. 2, the teeth 11a are made of a nonlinear soft magnetic material, and the back yoke 11b is made of a nondirectional electromagnetic steel sheet. Alternatively, the teeth 11a and the back yoke 11b may be made of directional electromagnetic steel sheets, and the teeth 11a and the back yoke 11b may be arranged so that the radial direction of the teeth 11a corresponds to the hard axis of magnetization and the circumferential direction corresponds to the easy axis of magnetization. Alternatively, the back yoke 11b may be made of a nondirectional electromagnetic steel sheet, and the teeth 11a may be made of a single-crystal metal with a body-centered cubic lattice structure, and the single-crystal metal may be arranged so that the radial direction of the teeth 11a corresponds to the hard axis of magnetization and the circumferential direction corresponds to the easy axis of magnetization. This allows the magnetic characteristics of the teeth 11a to be nonlinear, resulting in a variable reluctance variable-flux motor with high maximum torque. By selecting an appropriate material and controlling the direction of the magnetocrystalline anisotropy, the desired characteristics of the nonlinear soft magnetic material can be obtained. In this way, the nonlinear soft magnetic material may be a material having anisotropic magnetic properties. In addition, when the rising magnetic field of a nonlinear soft magnetic material is defined as the magnetic field strength at which the magnetic flux density is 25% of the saturation magnetic flux density in a BH curve, the rising magnetic field is preferably 100 A / m or more. If the nonlinear soft magnetic material has a hard magnetization direction and an easy magnetization direction, the rising magnetic field in the hard magnetization direction is preferably 100 A / m or more.

[0060] <Stator core division structure> In the above-described embodiment, an example has been described in which each tooth 11a is made of a nonlinear soft magnetic material and the back yoke 11b is made of a non-oriented electromagnetic steel sheet. However, the present invention is not limited to this example. The stator core 11 may be made of a plurality of stator core pieces divided at equal intervals in the circumferential direction. Figure 15 is a horizontal partial cross-sectional view perpendicular to the rotation axis of a stator core piece of a motor according to a modified example of the present invention.

[0061] As shown in FIG. 15, a stator may be configured with multiple stator core segments, each integrally including multiple teeth 11a1, 11a2, and 11a3 and a back yoke 11b. In the illustrated stator core segments, the segments are made of grain-oriented electromagnetic steel sheets. The hard-magnetization axis direction DM of the grain-oriented electromagnetic steel sheets is set to be substantially parallel to the radial direction of the teeth 11a1, 11a2, and 11a3. Even with this configuration, when a magnetic field in the hard-magnetization axis direction DM acts on the teeth 11a1, 11a2, and 11a3, the magnetic flux density does not become large unless a certain magnetic field strength is applied, thereby making the magnetic characteristics of the teeth 11a1, 11a2, and 11a3 nonlinear. This configuration also allows for a variable reluctance variable-flux motor with high maximum torque.

[0062] Note that the teeth 11a1, 11a2, and 11a3 extend in different directions. Therefore, the extension direction of each tooth 11a1, 11a2, and 11a3 may not strictly coincide with the hard-axis direction DM. If the magnetic flux directions from the rotor magnet 23 (see FIG. 2) acting on each tooth 11a1, 11a2, and 11a3 are B1, B2, and B3, respectively, the hard-axis direction DM and the magnetic flux direction B1 can be aligned, but the magnetic flux directions B2 and B3 cannot be aligned with the hard-axis direction DM. In other words, at a given moment, it is assumed that the tooth 11a1 has reached the saturation magnetic flux density Bs, but the teeth 11a2 and 11a3 have not. Such different magnetic flux densities in each tooth can cause a sixth-harmonic ripple component in the torque T. The sixth harmonic ripple component can cause deterioration of motor controllability and lead to vibration and noise.

[0063] Therefore, if it is desired to further reduce torque ripple, when the stator core 11 is constructed from multiple stator core pieces divided at equal intervals in the circumferential direction, the number of divisions of the stator core pieces in the region P (see Figure 2) corresponding to each pole pair of the motor is D, and N is an arbitrary natural number, then the number of divisions D should be configured to satisfy equation (4). D=6N formula (4)

[0064] As a result, by applying 6N permeance fluctuations, the sixth harmonic ripple component of the torque T can be suppressed.

[0065] Although the embodiments of the present disclosure have been described above, it goes without saying that the technical scope of the present disclosure should not be interpreted as being limited by the description of the present embodiments. The present embodiments are merely examples, and it will be understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the invention described in the claims. The technical scope of the present disclosure should be determined based on the scope of the invention described in the claims and its equivalents.

[0066] For example, the motor according to this embodiment has a three-phase, six-pole, and 45-slot distributed winding structure, but is not limited to this and may have a three-phase, four-pole, and six-slot concentrated winding structure, etc. Also, the motor according to this embodiment has an IPMSM (interior permanent magnet synchronous motor) structure, but may have an SPMSM (surface permanent magnet synchronous motor) structure. Furthermore, the motor according to this embodiment is a synchronous motor to which a magnetomotive force of a permanent magnet is applied, but may also be an induction motor to which a magnetomotive force is applied due to an induced current.

[0067] Furthermore, when the teeth are made of a nonlinear soft magnetic material, the back yoke may be made of a non-oriented electromagnetic steel sheet, or the back yoke may be made of a directional electromagnetic steel sheet with the hard-to-magnetize axis direction set in the circumferential direction. Alternatively, the teeth may be made of grain-oriented electromagnetic steel sheets with the hard-to-magnetize axis direction set in the circumferential direction, and the back yoke may be made of grain-oriented electromagnetic steel sheets with the hard-to-magnetize axis direction set in the circumferential direction, or the back yoke 11b may be made of non-oriented electromagnetic steel sheets. Alternatively, only a portion of the teeth of the stator may be made of a nonlinear soft magnetic material, and the remaining portion including the teeth may be made of a linear soft magnetic material. [Explanation of symbols]

[0068] 10, 10': Stator 20: Rotor 11: Stator core 11a: Teeth (magnetic pole part) 11b: Back yoke (iron part) 12: Stator coil 100, 100': Motor 21: Rotor core 22: Shaft mounting hole 23: Rotor magnet 24: Rotor gap O: Center of rotation

Claims

1. A synchronous or induction motor, a stator having a stator core and a winding wound around the stator core; A rotor; Equipped with A variable flux motor, wherein at least a portion of the stator is constructed from a nonlinear soft magnetic material.

2. the stator core has teeth and a back yoke, The variable magnetic flux motor according to claim 1 , wherein at least a portion of the teeth is made of the nonlinear soft magnetic material.

3. The variable magnetic flux motor according to claim 1 , wherein the nonlinear soft magnetic material has directional magnetic properties.

4. 2. The variable magnetic flux motor according to claim 1, wherein the nonlinear soft magnetic material is a single crystal of a metal.

5. 2. The variable magnetic flux motor according to claim 1, wherein the nonlinear soft magnetic material has a characteristic that the magnetic flux density when a magnetomotive force of a permanent magnet or an electromagnet is applied is 30% or less of the saturation magnetic flux density, and the magnetic flux density when a maximum magnetomotive force from the winding is applied is 80% or more of the saturation magnetic flux density.

6. In the BH curve in the hard magnetization direction, when the strength of the magnetic field at which the magnetic flux density is 25% of the saturation magnetic flux density is defined as the rising magnetic field Hk, the nonlinear soft magnetic material has the following characteristics:

2. The variable magnetic flux motor according to claim 1, wherein the rising magnetic field is 100 A / m or more.

7. the stator core has a plurality of stator core pieces divided in the circumferential direction, Let D be the number of divisions of the stator core pieces corresponding to each pole pair, and N be an arbitrary natural number. D=6N The variable magnetic flux motor according to claim 1 , wherein

8. When the strength of the magnetic field that gives a magnetic flux density that is 25% of the saturation magnetic flux density of the nonlinear soft magnetic material is defined as a rising magnetic field Hk, The magnetic field strength of the rotor's permanent magnet is set to be less than the rising magnetic field, 2. The variable magnetic flux motor according to claim 1, wherein the sum of the magnetic field strength of the permanent magnet and the maximum magnetic field strength of the winding is set to be equal to or greater than the magnetic field strength that results in the saturation magnetic flux density of the nonlinear soft magnetic material.

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