Variable flux motor

Abstract

The invention provides a variable flux motor. The variable flux motor is a synchronous or inductive motor and includes a stator and a rotor, the stator includes a stator core and a winding wound around the stator core, and at least a portion of the stator is composed of a non-linear soft magnetic material.

Description

[0001] Cross-reference of related applications This application is based on Japanese Patent Application No. 2024-118458, filed with the Japan Patent Office on July 24, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to variable flux motors. Background Technology

[0003] In recent years, there has been a demand for motors with high efficiency across all torque and speed ranges. However, achieving such a motor in reality is difficult. Generally, motors with high excitation flux exhibit a high-efficiency region on the low-speed, high-torque side. Conversely, motors with low excitation flux exhibit a high-efficiency region on the high-speed, low-torque side. This excitation flux is a fixed value determined by the permanent magnets embedded in the rotor. Therefore, it is considered impossible to achieve a motor with high-efficiency regions on both the low-speed, high-torque and high-speed, low-torque sides.

[0004] Therefore, in recent years, variable flux motors that change the excitation flux during motor operation have been proposed. Various flux adjustment mechanisms have been proposed. Among them, structures with a mechanical system or an excitation coil for excitation adjustment are called active variable flux structures. In contrast, structures that do not require such an adjustment mechanism and achieve the variable flux effect by changing the excitation flux in accordance with the torque generated by the motor are called passive variable flux structures.

[0005] Japanese Patent Application Publication No. 2017-17783 discloses an example of a passive variable flux structure. In the motor described in this publication, when the coil wound around the armature is energized, under low load conditions with low armature current, the flux of the permanent magnet leaks to the adjacent pole through a leakage bypass. Therefore, the flux does not link with the armature. Consequently, the flux quantity decreases. As a result, a high-efficiency region exists on the high-speed, low-torque side. Under high load conditions with high armature current, the magnetomotive force of the armature winding increases. As a result, the leakage bypass saturates due to the flux of both the permanent magnet and the armature. Therefore, the flux of the permanent magnet does not leak but links with the armature. Consequently, the flux quantity increases. As a result, a high-efficiency region exists on the low-speed, high-torque side. Thus, the motor described in Japanese Patent Application Publication No. 2017-17783 does not have a special mechanism; the state of the flux is changed solely by the magnitude of the armature's excitation current. Therefore, this motor has the function of passively changing the magnetic flux. As a result, it is possible to expand the high-efficiency range of the motor. Summary of the Invention

[0006] However, in the variable flux motor disclosed in Japanese Patent Application Publication No. 2017-17783, the flux leaking into the bypass path does not contribute to the motor's torque. Therefore, a loss of magnetic energy occurs. As a result, a reduction in maximum torque occurs.

[0007] The purpose of this embodiment is to provide a variable flux motor that does not use external circuitry, can suppress the reduction of maximum torque, and can improve the efficiency of motor drive at low speed and high load as well as at high speed and low load.

[0008] One side-mounted variable flux motor disclosed herein is a synchronous or induction type motor, comprising a stator and a rotor, the stator comprising a stator core and windings wound around the stator core, and at least a portion of the stator being made of a nonlinear soft magnetic material.

[0009] According to this embodiment, a stator and a variable flux motor having the stator can be provided, the stator having a variable flux structure that has high efficiency under low load and high load.

[0010] The variable flux motor of this embodiment is a synchronous or induction type motor, including a stator and a rotor. The stator includes a stator core and a winding wound around the stator core, and at least a portion of the stator is made of a nonlinear soft magnetic material. Attached Figure Description

[0011] Figure 1 This is a horizontal sectional view of the motor used for reference, orthogonal to its axis of rotation. Figure 2 This is a horizontal cross-sectional view of the motor of this embodiment, orthogonal to its axis of rotation. Figure 3 It is a graph representing the BH curves of linear soft magnetic materials and nonlinear soft magnetic materials. Figure 4A , Figure 4B and Figure 4C This is a partial enlarged view of the motor in Examples 1 and 2 and this embodiment. Figure 5 This is the efficiency mapping used for the motor in Reference Example 1. Figure 6 This is the efficiency mapping of the motor in this embodiment. Figure 7 This is a graph showing the magnetic flux density distribution of the motor used in Reference Example 1 under low load. Figure 8 This is a graph showing the magnetic flux density distribution of the motor under low load in this embodiment. Figure 9 This is a graph showing the magnetic flux density distribution of the motor used in Reference Example 1 under high load. Figure 10 This is a graph showing the magnetic flux density distribution of the motor under high load in this embodiment. Figure 11 It is a graph representing the BH curves of several nonlinear soft magnetic materials with different magnetic properties. Figure 12 This is the efficiency mapping of the motor using the nonlinear soft magnetic material S2 in this embodiment. Figure 13 This is the efficiency mapping of the motor using the nonlinear soft magnetic material S3 in this embodiment. Figure 14 This is the efficiency mapping of the motor using the nonlinear soft magnetic material S4 in this embodiment. Figure 15 This is a diagram showing the stator core of a motor in a modified example of this embodiment. Figure 16 This is a graph representing the BH curves of nonlinear soft magnetic material S1, nonlinear soft magnetic material S4, and non-oriented electromagnetic steel plate. Detailed Implementation In the following detailed description, numerous specific details are presented for illustrative purposes and to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments can be implemented without these specific details. In other instances, well-known structures and apparatuses are shown schematically for the purpose of simplifying the drawings.

[0012] Hereinafter, this embodiment will be described with reference to the accompanying drawings. Furthermore, in the description of this embodiment, for convenience, descriptions of components having the same reference numerals as those already described are omitted. Also, for ease of explanation, the dimensions of the components shown in these drawings may sometimes differ from the actual dimensions of the components.

[0013] Reference Example To illustrate the details of the motor 100 in this embodiment, a comparison is made using... Figure 1 The motor 100' used in the reference example will be described.

[0014] Figure 1 This is a horizontal sectional view of the motor 100' used for reference example, orthogonal to its axis of rotation. Figure 1 The illustrated motor 100' has a 3-phase, 6-pole, 45-slot configuration with distributed windings and an IPMSM (Internal Permanent Magnet Synchronous Motor) structure with q=2.5 slots per pole per phase. Furthermore, the motor 100' is a rotating excitation type. Moreover, the motor 100' includes a stator 10' and a rotor 20 capable of rotating relative to the stator 10'.

[0015] The stator 10' has a ring-shaped stator core (stator core) 11. The stator core 11 is composed of components in the direction of the rotation axis ( Figure 1 Multiple electromagnetic steel plates are stacked on the paper (vertically). Furthermore, the stator core 11 is constructed from electromagnetic steel plates that are soft magnetic materials. Specifically, the stator core 11 has an annular back yoke (yoke portion) 11b and 45 teeth (pole portions) arranged on the inner circumferential side of the back yoke 11b. The teeth 11a are portions that protrude radially inward from the inner circumferential end of the back yoke 11b. The 45 teeth 11a have approximately the same shape. The teeth 11a are supported by the back yoke 11b. Slots are provided between adjacent teeth 11a. Using the space ensured by the slots, windings are wound around each tooth 11a. The windings form stator coils 12.

[0016] Each stator coil 12 is wound on the tooth 11a by distributed winding. The stator coil 12 is energized by an external alternating current.

[0017] The rotor 20 includes a rotor core 21. The rotor core 21 is formed of multiple electromagnetic steel plates stacked in the direction of the rotation axis. Furthermore, the rotor core 21 is formed into a cylindrical shape. The inner circumferential surface of the rotor core 21 forms a shaft mounting hole 22. A drive shaft (not shown) is fixed in the shaft mounting hole 22. The drive shaft is supported by a bearing (not shown) and a housing, enabling it to rotate about the rotation axis.

[0018] The rotor 20 has multiple rotor magnets 23 in the rotor core 21. The rotor magnets 23 are embedded in slots provided in the rotor core 21. The rotor magnets 23 are composed of flat, permanent magnets. These rotor magnets 23 have approximately the same size, material, and composition. Furthermore, the multiple rotor magnets 23 are arranged to form six poles at positions 60° apart on a circumference centered on the rotation center O. That is, these rotor magnets 23 are arranged at equal intervals along the circumference. Therefore, the magnetomotive force generated by these rotor magnets 23 on the stator coil 12 is approximately the same for each other. In addition, 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. Air is present inside the rotor gaps 24. Alternatively, permanent magnets can be used as rotor magnets 23. Electromagnets can also be used as rotor magnets 23.

[0019] This implementation method Figure 2 This is a horizontal cross-sectional view of the motor 100 of this embodiment, orthogonal to its axis of rotation. Hereinafter, only views with respect to... Figure 1 The differences in the structure of the motor 100' shown for the reference example will be explained.

[0020] The stator 10 has a ring-shaped stator core 11. The stator core 11 includes a ring-shaped back yoke 11b and 45 teeth 11a. The back yoke 11b is made of a non-oriented electromagnetic steel plate, which is a soft magnetic material. The teeth 11a are made of a nonlinear soft magnetic material. In this embodiment, the nonlinear soft magnetic material is defined as a material having the following characteristics: that is, the nonlinear soft magnetic material is not magnetized (maintaining its low magnetic flux density) before a magnetic field with a magnetic field strength H of a certain value is applied. On the other hand, if the magnetic field strength H exceeds a certain value, the relative permeability μ of the material increases. r Increase. Therefore, its magnetic flux density increases sharply. Here, using Figure 3 A detailed explanation of nonlinear soft magnetic materials is provided.

[0021] Figure 3 It is a graph representing the BH curves of general soft magnetic materials and nonlinear soft magnetic materials. Figure 3 The horizontal axis represents the magnetic field strength H. The vertical axis represents the magnetic flux density B. For example... Figure 3 As shown, in general soft magnetic materials such as non-oriented electromagnetic steel sheets, as observed near the strength H0 of the magnetic field, the magnetic flux density B increases sharply when a magnetic field is applied. As the strength H of the magnetic field increases, the magnetic flux density B converges to the saturation magnetic flux density Bs. That is, in general soft magnetic materials, the magnetic flux density B increases immediately when a magnetic field is applied. On the other hand, as the strength H of the magnetic field increases, the rate of increase in the magnetic flux density B becomes slower. Furthermore, the magnetic flux density B converges to the saturation magnetic flux density Bs. In addition, generally, materials with large relative permeability μ have been developed. r Materials with high saturation magnetic flux density Bs are used as soft magnetic materials. Here, the relative permeability μ r yes Figure 3 The slope of the curve. Furthermore, electromagnetic steel sheets, as a type of soft magnetic material, generally require a magnetic flux density B that increases immediately when a magnetic field is applied. In the following description, for the purpose of contrasting with nonlinear soft magnetic materials, general soft magnetic materials will also be referred to as linear soft magnetic materials. As mentioned above, linear soft magnetic materials have the characteristic that the magnetic flux density B increases immediately even when a weak magnetic field is applied.

[0022] In contrast, in the nonlinear soft magnetic material studied by this developer, as observed near the strength H0 of the magnetic field, its magnetic flux density changes only slowly even when a magnetic field is applied. However, when the strength H of the magnetic field reaches a certain value Hk, the magnetic flux density B increases sharply. Afterward, as the strength H of the magnetic field increases, the magnetic flux density B converges to the saturation magnetic flux density Bs. That is, the magnetic flux density B of the nonlinear soft magnetic material is difficult to increase during the application of a weak magnetic field below a certain value. On the other hand, when a strong magnetic field H above a certain value is applied, the magnetic flux density B increases sharply. In other words, the nonlinear soft magnetic material has the following characteristic: In the nonlinear soft magnetic material, magnetic flux is difficult to pass through when a weak magnetic field of strength H is applied. On the other hand, magnetic flux easily and rapidly passes through when a strong magnetic field of strength H is applied. Figure 3 In the BH curve, the strength of the magnetic field through which magnetic flux easily passes is represented as the rising magnetic field Hk. In the BH curve, the rising magnetic field Hk refers to the strength of the magnetic field corresponding to 25% of the saturation magnetic flux density of the nonlinear soft magnetic material.

[0023] Figure 4A This is a partial enlarged view of a typical motor 100' with constant magnetic reluctance, used in Reference Example 1. Figure 4B This is a partial enlarged view of the passive variable reluctance variable flux motor 100 used in Reference Example 2 as described in Japanese Patent Application Publication No. 2017-17783. Figure 4C This is a partial enlarged view of the motor 100 in this embodiment.

[0024] exist Figure 4A In the motor 100' of Reference Example 1, which has constant magnetic reluctance, the back yoke 11b and teeth 11a are both made of the same linear soft magnetic material, such as non-oriented electromagnetic steel plates. In this motor 100', the rotor magnet 23 used for excitation is a permanent magnet. Furthermore, its magnetic flux is fixed. Therefore, the higher the rotor 20 operates, the higher the induced voltage. As a result, the voltage drops. Consequently, current cannot flow from the power supply side. Therefore, the torque decreases. Therefore, in the motor 100' of Reference Example 1, a control method called vector control is generally used. In this control method, during high-speed driving, the current phase leads. Furthermore, the magnetomotive force of the stator coil 12 generates a magnetic field in the opposite direction to the magnetic field of the rotor magnet 23 embedded in the rotor 20. As a result, weak flux control is applied to weaken the magnetic force of the rotor magnet 23. This suppresses the induced voltage, thus allowing current to flow. However, the current flowing in the stator coil 12 is the sum of the current used for weak flux and the current that contributes to torque. As a result, excess current flows. This leads to increased losses in the high-speed region.

[0025] Figure 4BThis is a partially enlarged view of the motor 100” used in Reference Example 2. In this motor 100” of Reference Example 2, a leakage bypass passage 25 is provided between the poles formed by the rotor magnet 23. When the current carrying capacity of the stator coil 12 is low, the magnetic flux of the rotor magnet 23 leaks to the adjacent pole through the leakage bypass passage 25 and does not link with the stator coil 12. Therefore, the voltage drop caused by the induced voltage can be suppressed. That is, when the rotor 20 is not driven at high speed, the current used to weaken the magnetic flux of the rotor magnet 23 (hereinafter referred to as "weakening flux current") can be suppressed. Therefore, the current carrying capacity to the stator coil 12 is reduced. As a result, the efficiency in the high-speed region is improved.

[0026] On the other hand, if the current flowing through the stator coil 12 is increased, the leakage bypass passage 25 becomes saturated due to the magnetic flux of the rotor magnet 23 and the stator coil 12. Therefore, the magnetic flux of the rotor magnet 23 does not leak into the leakage bypass passage 25, but links with the stator coil 12. Thus, when driving the rotor 20 with high torque and low speed, most of the magnetic flux of the rotor magnet 23 directly links with the stator coil 12. Therefore, high torque can be maintained. Thus, in the variable flux motor, efficiency is improved at low loads due to the reduced magnetic flux of the rotor 20. At high loads, the magnetic flux generated by the rotor magnet 23 of the rotor 20 and the magnetic flux generated by the stator coil 12 are utilized to the maximum extent. Thus, high torque is obtained. Without a special mechanism, the state of the magnetic flux changes only by the magnitude of the excitation current of the stator coil 12. Therefore, the motor 100” has a passive variable flux function. Therefore, the high-efficiency range of the motor is expanded.

[0027] Thus, in Figure 4B In the motor 100 of Reference Example 2 shown, high-efficiency regions can be formed on both the high-speed, low-torque side and the low-speed, high-torque side. However, the magnetic flux of the rotor magnet 23 always leaks into the leakage bypass passage 25. Therefore, the maximum torque is always higher than expected. Figure 4A The motor 100' in Reference Example 1 shown is relatively reduced. In most cases, the specifications of the motor assembly device, such as a robot or machine tool, determine the maximum torque required by the motor. Furthermore, in most cases, the limiting current value is also limited according to the specifications of the inverter module. In such situations, if the maximum torque of the motor is reduced, it may not meet the specifications of the motor assembly device or the inverter. Furthermore, there are concerns that the motor cannot be used in the motor assembly device. Therefore, a variable flux motor is required that does not reduce the maximum torque, enables high-efficiency drive in the medium and high speed ranges, and does not require an active variable flux mechanism. However, this leaves the following challenge: a special mechanism for variable flux is needed.

[0028] Therefore, in Figure 4CIn the motor 100 of this embodiment shown, as described above, the back yoke 11b is made of a general linear soft magnetic material such as a non-oriented electromagnetic steel plate. On the other hand, the teeth 11a are made of a non-linear soft magnetic material. Furthermore, here, as... Figure 3 As shown, the strength Ha of the magnetic field of the rotor magnet 23 of the rotor 20 is set to be less than the rising magnetic field Hk. In addition, the sum of the strength of the magnetic field generated by the rotor magnet 23 of the rotor 20 and the strength of the maximum magnetic field of the stator coil 12 is set to be greater than or equal to the strength Hs of the magnetic field when the magnetic flux density B reaches the saturation magnetic flux density Bs.

[0029] When this motor is driven at high speed and low torque, similar to motors 100' and 100"', the magnetic flux generated by the stator coil 12 is low. Therefore, the magnetic flux generated by the rotor magnet 23 of the rotor 20 is dominant. In this state, the strength Ha1 of the magnetic field is less than the rising magnetic field Hk of the nonlinear soft magnetic material used for the tooth 11a. That is, the magnetic flux density Ba1 of the tooth 11a is small. Therefore, when the rotor 20 operates at high speed, the induced voltage of the stator coil 12 is small. Therefore, the weak magnetic flux current can be reduced. As a result, the copper loss of the stator coil 12 can be suppressed. Furthermore, if the tooth 11a is not subjected to a magnetic field strength of a certain or greater, the magnetic flux density does not increase. Therefore, the magnetic flux density of the tooth 11a in the region that contributes to the torque is increased. On the other hand, the magnetic flux density in other parts that do not contribute to the torque can be suppressed to a low level. As a result, the iron loss caused by the tooth 11a that does not contribute to the torque can be suppressed. Therefore, the overall efficiency is improved. That is, the efficiency is improved in the low torque and high speed region.

[0030] Furthermore, during high-torque driving, the current carrying capacity of the stator coil 12 increases. Therefore, the strength Ha2 of the magnetic field acting on the tooth 11a is the sum of the magnetic flux of the rotor magnet 23 and the magnetic flux of the stator coil 12. This sum is greater than the rising magnetic field Hk of the nonlinear soft magnetic material. As a result, the magnetic flux density of the tooth 11a increases. Thus, high torque can be output. Moreover, unlike the motor 100 in Reference Example 2, the motor 100 of this embodiment does not have a leakage bypass path 25. Therefore, the motor 100 does not leak a portion of the magnetic flux of the stator coil 12 and the rotor magnet 23, and can generate torque. Therefore, the maximum torque does not decrease.

[0031] Furthermore, the magnetic flux density when a magnetic field strength Ha is applied to a certain material for the rotor magnet 23 of the rotor 20 is defined as Ba. Additionally, the magnetic flux density when a magnetic field strength Hb, which is half the strength of Ha, is applied is defined as Bb. Furthermore, the magnetic flux density when a magnetic field strength Hc, which is twice the strength of Ha, is applied is defined as Bc. In this case, it is preferable that the nonlinear soft magnetic material has a ratio X = (Bc / Ba) / (Ba / Bb) of 5 or more. More preferably, the nonlinear soft magnetic material has a ratio X of 10 or more.

[0032] use Figure 3 A comparison is made between the motor 100' of the aforementioned reference example and the motor 100 of this embodiment. Through the rotor magnet 23 of the rotor 20, the magnetic field strength Ha acts on the stator coil 12. Therefore, when the stator coil 12 is made of a linear soft magnetic material, the magnetic flux density of the stator coil 12 is Ba'. When the stator coil 12 is made of a nonlinear soft magnetic material, the magnetic flux density of the stator coil 12 is Ba. The magnetic flux density Ba is lower than the magnetic flux density Ba'. Therefore, in the motor 100 of this embodiment, the back electromotive force is less likely to increase. Therefore, as described above, the losses are small. That is, high efficiency is achieved with low torque and high speed.

[0033] Furthermore, in order to output high torque, a magnetic field of intensity Hs is applied to the stator coil 12 while it is energized. Therefore, regardless of whether the stator coil 12 is made of a linear soft magnetic material or a nonlinear soft magnetic material, the magnetic flux density of the stator coil 12 is the same as the saturation magnetic flux density Bs. Thus, the maximum torque of the motor 100 in this embodiment is the same as that of the motor 100 in the reference example.

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

[0035] Furthermore, in the BH curve, the strength of the magnetic field when the magnetic flux density B reaches 25% of the saturation magnetic flux density is expressed as the rising magnetic field Hk. In addition, the strength of the magnetic field when the maximum relative permeability is achieved is expressed as Hm. At this time, the nonlinear soft magnetic material used for the stator core 11 preferably satisfies all the following relationships (1) to (3). Hk≥100[A / m] Equation (1) Hm≥100[A / m] Equation (2) Hm>Hk Equation (3)

[0036] Figure 16 Reiterating Figure 11The BH curves for nonlinear soft magnetic materials S1 and S4, and the non-oriented electromagnetic steel plate are described in the text. Table 1 shows the saturation magnetic flux density, maximum relative permeability, Hk, and Hm for each of the nonlinear soft magnetic materials S1 and S4, and the non-oriented electromagnetic steel plate. When calculating the values ​​listed in Table 1, B = μ... r The relationship between μ0H. Here, B and μ r μ0 and H represent the following contents respectively. B: Magnetic flux density [T] μ r Relative permeability μ0: Permeability of vacuum [H / m] H: Strength of the magnetic field [A / m]

[0037] [Table 1]

[0038] like Figure 16 As shown in Table 1, both nonlinear soft magnetic materials S1 and S4 satisfy the relationships in equations (1) to (3) above. Specifically, the rising magnetic field Hkx of nonlinear soft magnetic material S1 is 9000 [A / m]. The magnetic field strength Hmx at which it achieves its maximum relative permeability is 15000 [A / m]. The rising magnetic field Hky of nonlinear soft magnetic material S4 is 35000 [A / m]. The magnetic field strength Hmy at which it achieves its maximum relative permeability is 60000 [A / m]. However, neither Hk nor Hm of the non-oriented electromagnetic steel plate reaches 100 [A / m]. That is, it does not satisfy the relationship in equation (1) nor the relationship in equation (2). Specifically, the rising magnetic field Hk0 of the non-oriented electromagnetic steel plate is 60 [A / m]. The magnetic field strength Hm0 at which it achieves its maximum relative permeability is 80 [A / m].

[0039] Both nonlinear soft magnetic materials S1 and S4 satisfy the relationships in equations (1) and (2). That is, Hk and Hm are sufficiently large. Therefore, magnetic flux is difficult to pass through unless a strong external magnetic field is applied. As a result, the maximum relative permeability cannot be achieved without a strong external magnetic field. Therefore, in motors using nonlinear soft magnetic materials S1 or S4 in the stator core 11, high efficiency can be achieved with low torque and high speed. Moreover, it does not lead to a reduction in the maximum torque.

[0040] In contrast, the Hk and Hm values ​​of non-oriented electromagnetic steel sheets are not sufficiently large. Magnetic flux easily passes through even with a weak magnetic field. Furthermore, the maximum relative permeability is reached immediately under a weak magnetic field. Therefore, in motors using non-oriented electromagnetic steel sheets in the stator core 11, it is difficult to simultaneously achieve high efficiency and suppress the reduction in maximum torque at low torque and high speed.

[0041] Furthermore, when the magnetic field is gradually increased, the operating principle of the motor in this embodiment is difficult to establish in materials where the relative permeability becomes maximum before reaching the rising magnetic field Hk. That is, it is preferable to avoid the situation where the magnetic flux passes through the stator core 11 before the magnetomotive force of the additional stator coil 12. Therefore, it is preferable that the nonlinear soft magnetic material used for the stator core 11 satisfies the relationship of equation (3).

[0042] Efficiency mapping use Figure 5 , Figure 6 The efficiency mapping of the motor 100 in this embodiment will be compared with that of the motor 100' used in Reference Example 1, while the explanation will proceed. Figure 5 This is the efficiency mapping for motor 100' used in Reference Example 1. Figure 6 This is the efficiency mapping of the motor 100 in this embodiment. Figure 5 and Figure 6 In the diagram, the horizontal axis represents the motor's rotational speed Nr. The vertical axis represents the torque T. The concentration of each region in the efficiency map represents the motor's efficiency μ. Furthermore, the efficiency map is divided into regions of 6%, such as high-efficiency region A (efficiency μ ≥ 94%) and region B (efficiency μ ≥ 88% but < 94%).

[0043] Furthermore, in the motor 100' used in the reference example, the back yoke 11b and the teeth 11a are made of non-oriented electromagnetic steel plates. In addition, in the motor 100 of this embodiment, the back yoke 11b is made of a non-oriented electromagnetic steel plate. On the other hand, the teeth 11a are made of a non-linear soft magnetic material. Here, non-oriented refers to the characteristic that the magnetism is random and does not align with a specific direction. Details of the non-oriented electromagnetic steel plate will be described later.

[0044] like Figure 5 As shown, in the motor 100' used for the reference example, the high-efficiency region A' remains at a rotational speed Nr of 12200 min. -1 The following (than passing) Figure 5 The area to the left of the dashed line H1' at point P4'. Furthermore, at a rotational speed Nr of 10000 min... -1 The above high speed and low load (compared to) Figure 5 (The area to the right of the dashed line H2') has an efficiency μ that remains below 94%.

[0045] Furthermore, at a rotational speed Nr of 5000 min -1 The following low-speed, high-load conditions (compared to) Figure 5 (The area to the left of the dashed line L), the maximum torque Tmax is 150 Nm, and the rotational speed Nr is 3000 min. -1 The rotational speed Nr from point P5' is 5000 min -1 At point P6', efficiency μ decreases sharply.

[0046] In contrast, such as Figure 6 As shown, in the motor 100 of this embodiment, the high-efficiency region A is extended to a rotational speed Nr of 13500 min. -1 The following (than passing) Figure 6 The area to the left of the dashed line H1 at point P4. Furthermore, even at a rotational speed Nr of 10000 min... -1 The above high speed and low load (compared to) Figure 6 (In the region to the right of the dashed line H2), the efficiency μ is also below 95%. That is, high efficiency is achieved even in this region.

[0047] Furthermore, at a rotational speed Nr of 5000 min -1 The following low-speed, high-load conditions (compared to) Figure 6 (The area to the left of the dashed line L), the maximum torque Tmax is 150 Nm. Furthermore, the rotational speed Nr is 3000 min. -1 The rotational speed Nr from point P5 is 5000 min -1 At point P6, efficiency μ decreases slowly.

[0048] Therefore, compared to the motor 100' used in the reference example, the high-efficiency region A is expanded in the motor 100 of this embodiment.

[0049] magnetic flux density distribution use Figures 7-11 The description will proceed while comparing the magnetic flux density distribution of the motor 100 of this embodiment with that of the motor 100' in Reference Example 1. Figure 7 The diagram shows the magnetic flux density distribution of the motor 100' used in Reference Example 1 under low load. Figure 8 The magnetic flux density distribution of the motor 100 of this embodiment under low load is shown. Additionally, Figure 7 and Figure 8 This represents the magnetic flux density distribution under low load when the torque T is less than half of the maximum torque Tmax.

[0050] like Figure 7As shown, under low load conditions in the motor 100' of Reference Example 1, for example, magnetic flux passes through the teeth 11a in region Ar with a certain magnetic flux density. This is because the teeth 11a are made of non-oriented electromagnetic steel plates. That is, from Figure 3 It can also be seen that even when the magnetic field strength H is small, the magnetic flux density B is large. However, when the motor rotates counterclockwise at 100°, the flow is closer to the region Ar relative to the direction of rotation. Figure 7 The magnetic flux through the teeth 11a in region Ar' on the left side of the paper contributes to the torque T. On the other hand, the magnetic flux flowing through the teeth 11a in region Ar does not contribute to the torque T and may be a cause of iron loss or back electromotive force.

[0051] In contrast, such as Figure 8 As shown, under low load conditions, the magnetic flux density of the motor 100 in this embodiment is limited, for example, in the tooth 11a of region Ar. This is because the tooth 11a is made of a nonlinear soft magnetic material. That is, from Figure 3 It is also known that under a relatively small magnetic field strength H, such as the rising magnetic field Hk, the magnetic flux density B is very small. Therefore, by using a nonlinear soft magnetic material, it is possible to limit the magnetic flux that does not contribute to the torque T of the motor 100'. This, in turn, improves the efficiency μ.

[0052] exist Figure 9 The magnetic flux density distribution of the motor 100' used in Reference Example 1 under high load is shown in the figure. Figure 10 The magnetic flux density distribution of the motor 100 under high load in this embodiment is shown in the figure. Figures 7-10 The distribution of magnetic flux density B is expressed as concentration. Figure 9 and Figure 10 This represents the magnetic flux density distribution under high load when the torque T is greater than half of the maximum torque Tmax.

[0053] like Figure 9 and Figure 10 As shown, the magnetic flux density distribution of the motor 100' used in Reference Example 1 is approximately the same as that of the motor 100 in this embodiment under high load. This is because, under a magnetic field strength H greater than the rising magnetic field Hk, the magnetic flux density B is sufficiently large to reach the saturation magnetic flux density Bs. That is, the magnetic flux density B reaches the magnetic flux density required for the maximum torque Tmax of the motor 100' and the motor 100. Therefore, the decrease in the maximum torque Tmax can be suppressed.

[0054] In this way, the motor 100 of this embodiment does not require additional external circuitry, and limits the magnetic flux under low load, thereby improving efficiency μ. On the other hand, it maintains the maximum torque Tmax under high load. In this way, the variable magnetic flux effect can be achieved.

[0055] Relationship between magnetic properties of nonlinear soft magnetic materials and motor efficiency Figure 11It is a graph representing the BH curves of several nonlinear soft magnetic materials with different magnetic properties. Figure 11 The BH curves represent four nonlinear soft magnetic materials S1 to S4 with different magnetic properties. The rising magnetic field Hk1 of nonlinear soft magnetic material S1, Hk2 of nonlinear soft magnetic material S2, Hk3 of nonlinear soft magnetic material S3, and Hk4 of nonlinear soft magnetic material S4 increase sequentially. Figure 12 , Figure 13 and Figure 14 The efficiency mappings of the motors in this embodiment, which use nonlinear soft magnetic materials S2, S3, and S4, are shown respectively.

[0056] By mapping with the efficiency of the motor 100' mentioned above as Reference Example 1 Figure 5 Comparison, from Figures 12-14 The efficiency mapping shown confirms that the range of the high-efficiency region A in the motor 100 using nonlinear soft magnetic materials in tooth 11a expands. As the rising magnetic field Hk increases, the range of the high-efficiency region A expands. Furthermore, it can be confirmed that the larger the rising magnetic field Hk, the more the high-efficiency region A expands towards the high-speed region.

[0057] Nonlinear soft magnetic materials Nonlinear soft magnetic materials used in motors are explained. Electromagnetic steel sheets include "oriented electromagnetic steel sheets" with consistent magnetic orientation and "non-oriented electromagnetic steel sheets" with random magnetic orientation. The magnetic orientation depends on the consistency of the orientation of the easy magnetization axes of the crystal structure of the iron atoms constituting the steel sheet. Here, the easy magnetization axis refers to the direction in which magnetization is easily achieved. Furthermore, Figure 1 The back yoke 11b and teeth 11a of the motor 100' shown for the reference example are as follows: Figure 2 The back yoke 11b of the motor 100 shown in this embodiment is made of a non-oriented electromagnetic steel plate.

[0058] Furthermore, according to Satoshi Nyanko-sensei's "Physics of Strong Magnetic Materials (Part 2) - Magnetic Properties and Applications -", ​​in the single-crystal model of iron with a body-centered cubic lattice structure, the magnetization direction is constrained by the orientation of the spin of the iron atom Fe located at the center. Here, the position of the iron atom Fe located at the center is defined as the origin O' of the XYZ coordinate system. Furthermore, the

[001] direction of this coordinate system is defined as the easy magnetization axis direction of the single-crystal model. Moreover, its

[110] direction is defined as the difficult magnetization axis direction of the single-crystal model. In addition, the magnetization orientation is represented by θ, which is the angle between the easy magnetization axis and the direction of the external magnetic field. In addition, the difficult magnetization axis refers to the direction that is difficult to magnetize. In the single-crystal model, if the excitation magnetic field Hex acts in the

[110] direction, the magnetization vector Ms, which is constrained in the easy magnetization axis

[001] direction, rotates in the

[110] direction. At this point, the anisotropic energy of the inner surface formed by the origin O', the

[001] direction, and the

[110] direction can be expressed using the first magnetic anisotropic energy constant K1 and the second magnetic anisotropic energy constant K2. The first magnetic anisotropic energy constant K1 and the second magnetic anisotropic energy constant K2 are constants determined for each material. For example, the first magnetic anisotropic energy constant K1 for pure iron is 47200 J / m. 3 Furthermore, the second magnetic anisotropy energy constant K2 of pure iron is -750 J / m. 3 By calculating the magnetism along the difficult-to-magnetize axis, the rising magnetic field Hk was calculated to be 6000 A / m. Furthermore, the rising magnetic field Hk is defined as the strength H of the magnetic field when the magnetic flux density B reaches 25% of the saturation magnetic flux density Bs.

[0059] Thus, by selecting an appropriate material as the nonlinear soft magnetic material, the direction of the crystal magnetic anisotropy can be controlled by utilizing the characteristics of the hard magnetization axis. Therefore, the desired magnetic properties can be obtained. For example, in... Figure 2In the stator core 11 of the motor 100 shown in this embodiment, the teeth 11a are made of a nonlinear soft magnetic material. The back yoke 11b is made of a non-oriented electromagnetic steel plate. Alternatively, the teeth 11a and back yoke 11b can also be made of oriented electromagnetic steel plates. In this case, the teeth 11a and back yoke 11b are arranged such that their radial direction is a difficult-to-magnetize axis and their circumferential direction is an easy-to-magnetize axis. Furthermore, the back yoke 11b can be made of a non-oriented electromagnetic steel plate, and the teeth 11a can be made of a single-crystal metal with a body-centered cubic lattice structure. In this case, the single-crystal metal is arranged such that the radial direction of the teeth 11a is a difficult-to-magnetize axis and its circumferential direction is an easy-to-magnetize axis. This allows the magnetism of the teeth 11a to be nonlinear. Furthermore, a variable reluctance type variable flux motor with a large maximum torque can be realized. By selecting an appropriate material and controlling the direction of the crystal magnetic anisotropy, the desired characteristics as a nonlinear soft magnetic material are obtained. Thus, nonlinear soft magnetic materials can also be materials with anisotropic magnetic properties. Furthermore, the rising magnetic field of the nonlinear soft magnetic material is preferably 100 A / m or more. Here, the rising magnetic field is defined as the strength of the magnetic field when the magnetic flux density B reaches 25% of the saturation magnetic flux density in the BH curve. When the nonlinear soft magnetic material has both a difficult-to-magnetize direction and a easy-to-magnetize direction, the rising magnetic field in the difficult-to-magnetize direction is preferably 100 A / m or more.

[0060] Segmentation of stator core Furthermore, in the example described in the above embodiment, each tooth 11a is made of a nonlinear soft magnetic material. Also, the back yoke 11b is made of a non-oriented electromagnetic steel plate. However, this embodiment is not limited to this example. The stator core 11 may also be composed of multiple stator core chips that are equally spaced in the circumferential direction. Figure 15 This is a partial cross-sectional view in the horizontal direction orthogonal to the rotation axis of the stator iron core of the motor in the modified embodiment of this embodiment.

[0061] like Figure 15 As shown, a stator can also be constructed by integrating multiple stator core segments with multiple teeth 11a1, 11a2, and 11a3 and a back yoke 11b. In the illustrated stator core segment, the segment is made of oriented electromagnetic steel plate. The direction DM of the unmagnetized axis of the oriented electromagnetic steel plate is set in a direction approximately parallel to the radial direction of the teeth 11a1, 11a2, and 11a3. With this structure, when a magnetic field in the direction DM of the unmagnetized axis is applied to the teeth 11a1, 11a2, and 11a3, a large magnetic flux density will not be generated unless a magnetic field of a certain magnitude is applied. That is, nonlinear magnetic characteristics of the teeth 11a1, 11a2, and 11a3 can be achieved. With this structure, a variable reluctance variable flux motor with a large maximum torque can also be realized.

[0062] Furthermore, teeth 11a1, 11a2, and 11a3 extend in different directions. Therefore, sometimes the direction in which each tooth 11a1, 11a2, and 11a3 extends is not strictly consistent with the direction of the non-magnetizing axis DM. Here, the force acting on tooth 11a1 comes from the rotor magnet 23 (see reference). Figure 2 The magnetic flux direction of tooth 11a2 is defined as B1. The magnetic flux direction from rotor magnet 23 acting on tooth 11a2 is defined as B2. Furthermore, the magnetic flux direction from rotor magnet 23 acting on tooth 11a3 is defined as B3. Thus, the direction of the difficult-to-magnetize axis DM can be aligned with the magnetic flux direction B1. However, neither magnetic flux directions B2 nor B3 can be aligned with the direction of the difficult-to-magnetize axis DM. That is, if we are concerned with a certain instant, we can imagine that in tooth 11a1, the magnetic flux density B reaches the saturation magnetic flux density Bs, but in teeth 11a2 and 11a3, the magnetic flux density B does not reach the saturation magnetic flux density. Thus, multiple teeth with different magnetic flux densities may become the main cause of the sixth harmonic pulsation component of the torque T. Furthermore, the sixth harmonic pulsation component may become the main cause of motor controllability deterioration, vibration, or noise.

[0063] Therefore, in order to further reduce torque pulsation, when the stator core 11 is composed of multiple stator core chips that are equally spaced in the circumferential direction, the region P corresponding to each pole pair of the motor (refer to...) Figure 2 The stator core 11 is formed by dividing the stator core into segments D and any natural number N in a manner that satisfies the relationship of equation (4). D=6N Equation (4)

[0064] This allows for 6N-order magnetic permeability variations. Furthermore, it enables the suppression of the sixth-order harmonic pulsations of the torque T.

[0065] The present embodiment has been described above. However, the technical scope of the present embodiment should not be interpreted as limited by the above description. The described embodiment is merely an example. Those skilled in the art will understand that various modifications can be made to the described embodiment within the scope disclosed in the claims. The technical scope of the present embodiment should be determined based on the scope disclosed in the claims and its equivalents.

[0066] For example, the motor in the described embodiment has a 3-phase, 6-pole, 45-slot configuration with distributed windings. However, it is not limited to this; the motor in this embodiment may also have a 3-phase, 4-pole, 6-slot configuration with concentrated windings. Furthermore, the motor in the described embodiment has an IPMSM (In-line Permanent Magnet Synchronous Motor) configuration. However, the motor in this embodiment may also have an SPMSM (Surface Mount Permanent Magnet Synchronous Motor) configuration. Moreover, the motor in the described embodiment is a synchronous motor that applies a magnetomotive force from a permanent magnet. However, the motor in this embodiment may also be an induction motor that applies a magnetomotive force generated by an induced current.

[0067] Furthermore, when the teeth are made of a nonlinear soft magnetic material, the back yoke can also be made of a non-oriented electromagnetic steel plate. Alternatively, the back yoke can also be made of an oriented electromagnetic steel plate having a difficult-to-magnetize axis direction set in its circumferential direction. Alternatively, both the teeth and the back yoke can be made of oriented electromagnetic steel plates having a difficult-to-magnetize axis direction set in its circumferential direction. Furthermore, the back yoke 11b can also be made of a non-oriented electromagnetic steel plate. Alternatively, only a portion of the teeth in the stator can be made of a nonlinear soft magnetic material, while the other portion including the teeth can be made of a linear soft magnetic material. The detailed description has been given for illustrative and explanatory purposes. Many variations and modifications are possible in accordance with the teachings above. The detailed description is not without omissions or intended to limit the subject matter described herein. Although the subject matter has been described in words with particular structural features and / or methodological processes, it should be understood that the subject matter defined in the claims is not necessarily limited to the specific features or processes described. Rather, the specific features and processes described are illustrated as examples of implementing the claims.

Claims

1. A variable flux motor, which is a synchronous or induction motor, wherein, The variable flux motor includes a stator and a rotor. The stator includes a stator core and windings wound around the stator core, and, At least a portion of the stator is made of a nonlinear soft magnetic material.

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

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

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

5. The variable flux motor according to claim 1, wherein, The rotor includes permanent magnets or electromagnets, and, The nonlinear soft magnetic material has the following magnetic property 1 and magnetic property 2. Magnetic property 1: The magnetic flux density of the permanent magnet or the magnetic flux density of the electromagnet when a magnetomotive force is applied is less than 30% of the saturation magnetic flux density. Magnetic property 2: The magnetic flux density when the maximum magnetomotive force from the winding is applied is more than 80% of the saturation magnetic flux density.

6. The variable flux motor according to claim 1, wherein, The strength of the magnetic field (Hk) in the BH curve of the difficult magnetization direction of the nonlinear soft magnetic material, when the magnetic flux density reaches 25% of the saturation magnetic flux density, is defined as the rising magnetic field. The rising magnetic field (Hk) is above 100 A / m.

7. The variable flux motor according to claim 1, wherein, The stator core comprises a plurality of stator core plates divided circumferentially. The number of segments D of the multiple stator iron chips corresponding to each pole pair and any natural number N satisfy the relationship D=6N.

8. The variable flux motor according to claim 1, wherein, The strength of the magnetic field (Hk) in the BH curve, which represents the direction of the nonlinear soft magnetic material that is difficult to magnetize, when the magnetic flux density reaches the saturation magnetic flux density, is defined as the rising magnetic field (Hk). The strength of the magnetic field of the permanent magnet of the rotor is set to be less than the rising magnetic field (Hk), and, The sum of the magnetic field strength of the permanent magnet and the maximum magnetic field strength of the winding is set to be greater than or equal to the magnetic field strength when the magnetic flux density reaches the saturation magnetic flux density.

Images