Rotor structure

Abstract

The present invention provides a rotor structure of a synchronous motor in which a rotor rotates synchronously with a rotating magnetic field generated by a stator, the rotor comprising a cylindrical rotor core and a plurality of permanent magnets embedded in the rotor core and constituting a plurality of magnetic poles arranged in the circumferential direction in the rotor, a first protruding portion is formed on the outer peripheral surface of the rotor core, the first protruding portion extends in the circumferential direction across the adjacent magnetic poles when viewed in the axial direction and protrudes outward in the radial direction, and a first gap extending in the circumferential direction when viewed in the axial direction is formed inside the first protruding portion. And a second protruding portion that protrudes radially outward from a portion that defines the radially inner side of the first gap.

Description

Technical Field

[0001] The present invention relates to a rotor structure, and in particular to a rotor structure of a synchronous motor in which a rotor rotates synchronously with a rotating magnetic field generated by a stator. Background Art

[0002] With the popularization of electric vehicles, there are expectations for improvements in the mountability and productivity of the motors that drive them, as well as for easier expansion of vehicle models and lower costs. To achieve these expectations, it is required to miniaturize the motors while maintaining the output level (torque).

[0003] In this regard, synchronous motors have the characteristic of achieving high output by using magnetic torque generated by attraction / repulsion of magnets and reluctance torque using the magnetic saliency of the rotor core. Therefore, they are suitable for miniaturizing the motor while maintaining the output level.

[0004] To miniaturize the synchronous motor, for example, JP2001-25183A discloses a stator of a motor having an annular auxiliary core made of a magnetic material provided at an axial end of an annular back yoke portion located outside a tooth portion wound with a stator coil.

[0005] According to the stator of JP2001-25183A, since the auxiliary iron core can be used to compensate for the cross-sectional area of ​​the back yoke part required for the magnetic flux to pass through to obtain the required torque, the radial thickness of the back yoke part can be thinned, and the outer diameter of the stator iron core can be reduced, so the outer diameter of the motor can be reduced.

[0006] However, it is difficult to achieve significant miniaturization of the motor simply by reducing the radial thickness of the back yoke. Furthermore, the stator of JP2001-25183A is additionally provided with an auxiliary iron core, which also violates the requirement of cost reduction.

[0007] However, miniaturization of motors means that even with the same motor losses, temperature rise also increases. Furthermore, in synchronous motors, if the internal temperature of the motor rises significantly, for example, the permanent magnets embedded in the rotor core will reach high temperatures, potentially causing demagnetization and a reduction in torque. Therefore, to achieve miniaturization of synchronous motors, internal heat generation must be reduced, and to reduce losses, higher motor efficiency is necessary.

[0008] In addition, in order to miniaturize the motor while maintaining the output level, it is indispensable to increase the current density and magnetic flux density. However, if these current density and magnetic flux density are increased, the vibration (torque pulsation) and the resulting noise will increase. Therefore, in order to achieve the miniaturization of the motor, not only high efficiency but also low vibration and low noise are required. Summary of the Invention

[0009] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a rotor structure capable of achieving high efficiency and low vibration and low noise even when the synchronous motor is miniaturized.

[0010] To achieve the above-mentioned object, in the rotor structure according to the present invention, the generation of magnetic flux harmonic components that hinder the improvement of motor efficiency and the reduction of vibration and noise is suppressed.

[0011] Specifically, the present invention is directed to a rotor structure of a synchronous motor in which a rotor rotates synchronously with a rotating magnetic field generated by a stator.

[0012] Moreover, the rotor structure is characterized in that the rotor includes: a cylindrical rotor core; and a plurality of permanent magnets embedded in the rotor core, which constitute a plurality of magnetic poles arranged circumferentially in the rotor; a first protrusion is formed on the outer peripheral surface of the rotor core, and the first protrusion extends circumferentially across adjacent magnetic poles when viewed in the axial direction and protrudes radially outward, a first gap extending circumferentially when viewed in the axial direction is formed inside the first protrusion, and a second protrusion is formed that protrudes radially outward from a radially inner portion that divides the first gap.

[0013] In the present invention, as described above, even when the synchronous motor is miniaturized, its high efficiency and low vibration / low noise can be achieved. Since the "efficiency" of the motor refers to "output / (output + loss)", in order to achieve high efficiency of the motor, it is required to increase the output while suppressing the loss (Requirement 1) .

[0014] Here, the "output" of the motor refers to "torque × speed", so in order to increase the output, it is necessary to increase the torque that can be generated by the same magnitude of stator coil current (requirement 2) and make the rotor rotate smoothly without waste. In addition, in order to increase the torque that can be generated, it is effective to increase the proportion of magnetic flux (fundamental wave component) that helps generate torque. In addition, in order to make the rotor rotate smoothly without waste, it is ideal to make the magnetic flux density in the space (air gap) between the stator and the rotor in each magnetic pole of the rotor change (distribute) in a sinusoidal wave shape (requirement 3). Therefore, if the magnetic flux density in the air gap between the stator and the rotor changes in a sinusoidal wave shape, the torque pulsation (vibration) will also be suppressed, so that low vibration and low noise can be achieved while improving efficiency.

[0015] However, synchronous motors are known to contain high-harmonic components in the magnetic flux. These high-harmonic components not only do not contribute to torque generation but also overlap with the fundamental component, distorting the waveform of the magnetic flux density in the air gap between the stator and rotor. Furthermore, the "loss" of a rotor, which is primarily composed of magnetic material, refers to iron loss, which depends on the frequency of magnetic flux fluctuations. Since high-harmonic components have high-frequency components, this increased iron loss also hinders achieving higher motor efficiency.

[0016] It is known that such high harmonic components are likely to appear in the air gap where the rotor and stator exchange magnetic fields and between magnetic poles where magnetic flux short circuiting is likely to occur, in other words, near the inter-pole area on the outer periphery of the rotor core.

[0017] In this regard, according to the present invention, a circumferentially extending first gap is formed within a first protrusion extending circumferentially across adjacent magnetic poles on the outer circumferential surface of the rotor core. This first gap blocks magnetic flux, suppressing short-circuiting between magnetic poles and other issues. This, in turn, can suppress the generation of high-harmonic components. By suppressing the generation of high-frequency harmonic components, the frequency of magnetic flux fluctuations can be reduced, thereby suppressing the increase in iron loss that depends on the frequency of magnetic flux fluctuations (satisfying requirement 1). Furthermore, by suppressing the increase in iron loss, heat generation within the synchronous motor can be reduced even when the motor is miniaturized.

[0018] Furthermore, by suppressing the generation of harmonic components, the magnetic flux density in the air gap between the stator and rotor can be made close to an ideal sine wave (satisfying requirement 3). This allows the rotor to rotate smoothly without waste and reduces vibration (torque ripple).

[0019] Furthermore, by using the first gap to suppress the generation of higher harmonic components of the magnetic flux that do not contribute to torque generation, the proportion of the magnetic flux fundamental component that contributes to torque generation can be increased. However, forming only the first gap may result in a reduction in torque. In this case, even if the proportion of the magnetic flux fundamental component is increased, the effect of improving total torque is expected to be reduced.

[0020] In this regard, in the present invention, a first protrusion protruding radially outward is formed on the outer circumferential surface of the rotor core, and a second protrusion protruding radially outward from a radially inner portion defining the first gap is formed within the first protrusion. Therefore, the reduction in torque can be compensated for by the reluctance torque generated by the attractive force between the poles and the salient poles (the first and second protrusions) caused by the rotating magnetic field of the stator. Thus, by combining the reluctance torque ensured by utilizing magnetic saliency with an increase in the proportion of the fundamental wave component of the magnetic flux, the torque that can be generated by the same stator coil current can be increased (satisfying requirement 2).

[0021] Furthermore, the presence of a double radially arranged protrusion, i.e., the first and second protrusions, allows the radially outward projection height of the first protrusion itself to be reduced compared to a rotor structure having only the first protrusion, for example, when generating equivalent reluctance torque. This lower radially outward projection height of the first protrusion allows the outer circumference of the cylindrical rotor core to approximate a true circle, thereby also reducing cogging torque. This reduction in cogging torque, combined with the aforementioned reduction in torque ripple, allows for reliable suppression of motor vibration and the resulting noise, even when current density and magnetic flux density are increased during miniaturization of the synchronous motor.

[0022] As described above, according to the present invention, even when the synchronous motor is miniaturized, high efficiency and low vibration and low noise can be achieved, so the motor can be miniaturized while maintaining the output level without demagnetization of the permanent magnets caused by high temperature, vibration, and noise.

[0023] In the above rotor structure, the first protruding portion may be formed so as to protrude relatively radially outward by recessing the outer peripheral surface of the rotor core corresponding to both circumferential ends thereof radially inward when viewed in the axial direction.

[0024] With this configuration, the first protrusions do not project radially outward from the outer circumferential surface of the cylindrical rotor core. Instead, the outer circumferential surface of the rotor core corresponding to both circumferential ends of the first protrusions is recessed radially inward, thereby projecting relatively radially outward. This further reduces cogging torque. Consequently, even with a smaller synchronous motor, vibration and noise can be further reduced.

[0025] Furthermore, in the above rotor structure, the second protrusion may protrude obliquely with respect to the radial direction so that the second protrusion is inclined at a predetermined angle in the circumferential direction as it progresses radially outward.

[0026] According to this structure, the second protrusion that contributes to the magnetic salient polarity is made to protrude at an inclination relative to the radial direction, so that the second protrusion is inclined at a prescribed angle along the circumferential direction as it moves radially outward. Therefore, by setting the prescribed angle, the pulsating component (high harmonic component) of the reluctance torque can be finely controlled.

[0027] Furthermore, in the above rotor structure, the second protruding portion may extend to a radially outer portion that defines the first gap, so as to partition the first gap in the circumferential direction.

[0028] According to this configuration, the protruding length of the second protrusion can be increased compared to a case where the second protrusion is not formed to reach the radially outer portion defining the first gap, thereby further ensuring the reluctance torque generated by the magnetic saliency.

[0029] However, while the presence of high-harmonic components in the magnetic flux in the air gap between the stator and rotor is a primary cause of torque ripple, since this magnetic flux is a function of inductance, and inductance is a function of reluctance, changes in reluctance can be seen as a factor that amplifies the high-harmonic components in the magnetic flux and worsens torque ripple. Consequently, depending on the arrangement of permanent magnets and flux barriers in each magnetic pole, the positional relationship between the stator teeth and permanent magnets changes as the rotor rotates, potentially causing significant changes in reluctance. In these cases, the high-harmonic components in the magnetic flux can be amplified, exacerbating torque ripple.

[0030] Furthermore, because the teeth are typically arranged evenly, if the multiple circumferentially arranged magnetic poles are identical (the permanent magnets are arranged identically), the relative positional relationship between one permanent magnet and one tooth will be consistent with the relative positional relationship between other permanent magnets and other teeth. Here, high-harmonic components refer to higher-order frequency components that are "integer multiples" of a fundamental frequency component. Therefore, if there are multiple pairs of pairs with identical permanent magnet-tooth positions, frequency components that are integer multiples, i.e., high-harmonic components, may be more likely to be generated.

[0031] Therefore, in the above-mentioned rotor structure, the permanent magnet can be inserted into the magnet hole that passes through the rotor core axially. When observed along the axial direction, the position, shape, size and inclination of the permanent magnet in each magnetic pole, and at least one of the position, shape, size and inclination of the magnet hole can be set to be asymmetric between the circumferentially adjacent magnetic poles.

[0032] According to this structure, at least one of the position, shape, size, and inclination of the permanent magnets and magnet holes (hereinafter referred to as "position, etc.") is asymmetrical between circumferentially adjacent magnetic poles. By adjusting the position, etc., of the permanent magnets and magnet holes, it is possible to cancel out high harmonic components between adjacent magnetic poles, or to suppress significant changes in the positional relationship between, for example, the teeth and permanent magnets, even when the rotor rotates. This suppresses changes in magnetic resistance, and thus, by combining the suppression of amplification of high harmonic components by suppressing these changes in magnetic resistance with the cancellation of these components, torque ripple can be reliably suppressed, further achieving higher efficiency and lower vibration and noise in the motor.

[0033] However, if the positions of the permanent magnets are set asymmetrically between adjacent magnetic poles, the amount of magnetic flux (fundamental wave component) that contributes to torque generation may deviate between magnetic poles composed of relatively large permanent magnets and magnetic poles composed of relatively small permanent magnets.

[0034] Therefore, in the above-mentioned rotor structure, the first protrusion can be formed as follows: when viewed in the axial direction, the outer peripheral surface of the rotor core corresponding to its two circumferential ends is recessed toward the radial inner side, so that it protrudes relatively toward the radial outer side, and the depth of the recess at the two circumferential ends of the first protrusion can be set to be asymmetric.

[0035] In this structure, the depth of the recess at the circumferential ends of the first protrusion is set to be asymmetric. If the depth of the recess at the end of the first protrusion is deeper, the magnetic flux is difficult to pass through, just like when there is a large gap. If the depth of the recess at the end of the first protrusion is shallower, the magnetic flux can pass through easily, just like when there is a small gap. Therefore, by setting the end of the deep side of the first protrusion on the side of the magnetic pole with a large magnetic flux composed of a large permanent magnet, and setting the end of the shallow side of the first protrusion on the side of the magnetic pole with a small magnetic flux composed of a small permanent magnet, the deviation of the amount of magnetic flux (fundamental wave component) based on the asymmetry between adjacent magnetic poles can be reduced. In addition, by changing the depth of the recess at the circumferential ends of the first protrusion, the zero crossing point (the point where the polarity of the magnetic flux changes) is close to the q-axis, thereby further reducing the deviation of the fundamental wave component of the magnetic flux.

[0036] In addition, in the above rotor structure, the permanent magnet can be inserted into a magnet hole that passes through the rotor core axially, and each magnetic pole can include two circumferentially adjacent permanent magnets in the magnet hole, and a second gap can be between the two adjacent permanent magnets.

[0037] This structure creates a second gap between two adjacent permanent magnets. In other words, there is no bridge between the two permanent magnets that would serve as a leakage flux path. This suppresses short-circuit flux (leakage flux) between the two permanent magnets, which does not contribute to torque, thereby effectively utilizing the magnet flux. This allows high torque to be achieved even with low stator coil current, further reliably improving motor efficiency.

[0038] However, in the past, the bridge portion provided between two adjacent permanent magnets was used to ensure mechanical strength. Therefore, if a second gap is provided between two adjacent permanent magnets (bridge-less), the stress (centrifugal force or stress generated by shrinkage) acting on other parts near these permanent magnets will increase relatively.

[0039] Therefore, in the above rotor structure, the end of the magnet hole into which the two permanent magnets are inserted may be close to the outer peripheral surface of the rotor core, and the third gap at the end not filled by the permanent magnets may be separated by a bridge.

[0040] According to this structure, a double bridge portion is provided in the third gap at the end of the magnet hole that is not filled with the magnet, such as a bridge portion consisting of the surface portion of the rotor core and a bridge portion separating the third gap. This can suppress stress concentration caused by centrifugal force or shrinkage, thereby avoiding deformation of the rotor core.

[0041] Furthermore, in the above-mentioned rotor structure, when observed in the axial direction, at least one of the position, shape, size and inclination of the permanent magnet in each of the magnetic poles can be set to be asymmetric between the circumferentially adjacent magnetic poles, and the relative angle between the permanent magnet and the bridge portion can be set to be asymmetric between the circumferentially adjacent magnetic poles.

[0042] When the positions of the two permanent magnets are asymmetric between the magnetic poles, stress concentration is likely to occur near these permanent magnets. According to this structure, since the relative angle between the permanent magnets and the bridge portion is also set to be asymmetric between the magnetic poles, the stress concentration caused by the asymmetry can be suppressed according to the setting of the relative angle between the permanent magnets and the bridge portion, thereby avoiding deformation of the rotor core.

[0043] In addition, in the above-mentioned rotor structure, the permanent magnets can be inserted into magnet holes that axially penetrate the rotor core, and each of the magnetic poles can include: an outer magnet hole, which is formed at the outermost periphery of the rotor core and extends in the circumferential direction; and an inner magnet hole, which is formed radially inward relative to the outer magnet hole and extends in the circumferential direction. The inner magnet hole can be formed as follows: the radially outer surface of the inner permanent magnet inserted into the inner magnet hole contacts the rotor core, and a relatively large fourth gap is provided in the radially inner portion not buried by the inner permanent magnet. A slender squeezing section can be formed on the rotor core. When viewed in the axial direction, the squeezing section partitions the fourth gap in the circumferential direction and extends radially through the d-axis of each magnetic pole, so that the portion of the rotor core located radially inward relative to the inner permanent magnet is connected to the inner permanent magnet.

[0044] According to this structure, since the rotor core is formed with a relatively large fourth gap radially inward relative to the inner permanent magnet, magnetic flux emanating from the radially outer surface of the inner permanent magnet, for example, in contact with the rotor core (magnetic body), is difficult to pass through the fourth gap. Therefore, the magnetic flux is concentrated in the throttle portion, which separates the fourth gap and extends radially through the d-axis to connect the rotor core and the inner permanent magnet. However, because the throttle portion is formed to be slender, it quickly reaches magnetic saturation under light load (for example, when no load is applied), and the magnetic permeability becomes very low, reaching a value close to that of a vacuum (gap). As a result, the radially inner surface of the inner permanent magnet is in a state similar to that when completely covered by the fourth gap. Thus, since the magnetic flux is suppressed by the magnetic saturation of the throttle portion, it is possible to reduce iron loss under light load (when no load is applied), thereby further improving the efficiency of the motor.

[0045] On the other hand, synchronous motors with reverse saliency usually perform current advance angle control to effectively utilize reluctance torque when generating high torque (under high load). Since the magnetic flux of the permanent magnet generated by the advance angle control of the current is suppressed by the magnetic flux component that opposes the magnetic flux of the permanent magnet generated by the stator coil, the magnetic flux of the permanent magnet generated by the current is suppressed by the magnetic flux component that opposes the magnetic flux of the permanent magnet generated by the stator coil. As a result, the magnetic saturation of the throttle portion is eliminated, so the magnetic flux of the permanent magnet that is limited by the magnetic saturation can be effectively used to generate torque. Therefore, even in the advance angle control ( High torque can be obtained even in weak magnetic field control, thus further improving the efficiency of the motor.

[0046] Therefore, by forming a simple structure such as a throttle portion, the efficiency of the motor can be further reliably improved both under light load and high load conditions.

[0047] Furthermore, in the above rotor structure, the skew angle of the rotor core may be 0 degree.

[0048] This structure reliably suppresses the reduction in average torque, generation of axial thrust, and increase in iron loss caused by the skew angle of the rotor core, thereby further reliably achieving higher efficiency and lower vibration and noise in the motor.

[0049] Furthermore, in the above-mentioned rotor structure, the above-mentioned magnet holes can be used as oil passages through which cooling oil flows.

[0050] This structure uses the magnet holes as oil passages for cooling oil, enabling direct cooling of the permanent magnets inserted into the magnet holes. This direct cooling of the permanent magnets with cooling oil, combined with the reduction of internal heat generation due to higher motor efficiency, can more reliably suppress demagnetization of the permanent magnets when miniaturizing the synchronous motor.

[0051] As described above, according to the rotor structure of the present invention, even when the synchronous motor is miniaturized, high efficiency and low vibration and low noise can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a longitudinal sectional view schematically showing an outline of a synchronous motor according to an embodiment of the present invention. Figure 2 It is a perspective view schematically showing a rotor. Figure 3 It is a cross-sectional view schematically showing the rotor core and the permanent magnets. Figure 4 is a diagram schematically illustrating high harmonic components. Figure 5 Schematically illustrates the influence of high harmonic components on magnetic flux density. Figure 6 It is a diagram schematically showing the first gap and the protruding portion. Figure 7 This is a diagram schematically illustrating the advantages of the double protrusion. Figure 8 Schematic diagram of a modified version of the second protruding portion. Figure 9 A diagram schematically illustrating an equivalent magnetic circuit. Figure 10 is a diagram schematically illustrating changes in conventional magnetic resistance. Figure 11 is a diagram schematically illustrating the spatial distribution of ideal magnetic flux density in the air gap between the stator and the rotor. Figure 12 FIG. 1 is a diagram schematically showing asymmetric adjacent magnetic poles. Figure 13 This is a diagram schematically showing an example of a first protruding portion between adjacent asymmetric magnetic poles. Figure 14 is the spatial distribution of magnetic flux density. Figure 15 is the time distribution of magnetic flux density. Figure 16 This is a diagram schematically showing the time change of torque in the high rotation range. Figure 17 This is a diagram schematically showing changes in the line voltage of the three-phase AC applied to the motor with respect to the rotation angle. Figure 18 It is a diagram schematically illustrating a center bridgeless structure. Figure 19It is a diagram schematically illustrating the bridge portion in the rotor core. Figure 20 It is a graph showing magnetic interlinkage flux. Figure 21 It is a diagram schematically showing a throttle portion. Figure 22 This is a diagram schematically illustrating the function of the throttle portion during light load. Figure 23 This is a diagram schematically illustrating the function of the throttle portion at high load. Figure 24 It is a diagram schematically showing efficiency characteristics and iron loss comparison diagrams related to the embodiment of the present invention and a conventional rotor structure. Figure 25 This is a diagram schematically showing the oil path in the rotor. Figure 26 A diagram schematically showing the flow path of oil in the rotor. Figure 27 It is a cross-sectional view schematically showing an arrangement pattern of permanent magnets according to another embodiment. Figure 28 It is a cross-sectional view schematically showing an arrangement pattern of permanent magnets according to another embodiment. Figure 29 It is a cross-sectional view schematically showing a rotor core according to another embodiment. Figure 30 It is a perspective view schematically showing a rotor core according to another embodiment. 1: Synchronous motor, 10: Rotor, 30, 30': Rotor core, 31: Magnet hole (outer magnet hole), 32: Outer circumferential surface, 32a, 32b: Recess, 34, 35: Magnet hole (inner magnet hole), 32c, 37: Bridge portion, 39: Throttle portion, 61, 61', 61": First protruding portion, 62, 62', 62": Second protruding portion, 90: Stator, 101, 102: Permanent magnets (outer permanent magnets), 103, 106: Permanent magnets, 104, 105: Permanent magnets (inner permanent magnets), 104a, 105a: Radially outer surfaces, G1: First gap, G1a: Portion dividing the radially inner side, G1b: Portion dividing the radially outer side, G2: Second gap, G3: Third gap, G4: Fourth gap, MP1 to MP8: Magnetic poles. DETAILED DESCRIPTION

[0053] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0054] - Motor Overview - Figure 1It is a longitudinal sectional view schematically showing an outline of the synchronous motor 1 according to the present embodiment. Figure 1 In FIG, the symbol AC represents the axis of the synchronous motor 1, the symbol OS represents the output shaft side, and the symbol AOS represents the opposite side of the output shaft. Figure 1 In order to facilitate observation of the figure, for the stator 90, only the outer shape of the stator core 91 and the stator coil 93 assembled on the stator core 91 are shown (see Figure 4 ) of the coil ends 93a, 93b, and the detailed cross section of the stator core 91 is not shown. Figure 1 The outline of the synchronous motor 1 is merely schematically shown, and for ease of understanding, the circumferential positions of the components in the rotor 10 are not necessarily consistent.

[0055] The synchronous motor 1 is mounted in an electric vehicle, for example. Figure 1 As shown, the synchronous motor 1 includes a rotor 10 having a rotor core 30 with a rotor shaft 20 extending through the center thereof, and a stator 90 having a stator core 91 disposed around the outer periphery of the rotor core 30. The rotor 10 rotates synchronously with the rotating magnetic field generated by the stator 90. As will be described in detail later, the synchronous motor 1 has a rotor structure that achieves high efficiency and low vibration and noise even when miniaturized.

[0056] - Rotor Overview - Figure 2 1 is a perspective view schematically showing the rotor 10. Figure 2 As shown, in addition to the above-mentioned rotor shaft 20 and rotor core 30, the rotor 10 also has: permanent magnets 101, 102, 103, 104, 105, 106 embedded in magnet holes 31 formed on the rotor core 30; and first and second end plates 40, 50 respectively installed at the two axial ends (extension direction of the axis AC) of the rotor core 30.

[0057] The rotor shaft 20 has an oil inlet portion 21 and a shaft body portion 27, and an oil inlet passage 20a for cooling oil to flow is formed inside the shaft. Figure 1 As shown, the first end plate 40 is configured to overlap with the coil end 93a on the axial output shaft opposite side AOS (hereinafter also referred to as "output shaft opposite side AOS") when viewed radially, and the second end plate 50 is configured to overlap with the coil end 93b on the axial output shaft side OS (hereinafter also referred to as "output shaft side OS") when viewed radially.

[0058] The rotor core 30 is a laminated body formed by laminating a predetermined number of annular magnetic thin plates formed into a predetermined shape in the axial direction. It is formed into a cylindrical shape having a center hole 38. The rotor shaft 20 is fixed in the center hole 38 by shrink fitting. Figure 2As shown, the rotor core 30 is constructed as a so-called skewless rotor core, which is composed of stacked bodies 30A, 30B, 30C, and 30D formed by stacking individual magnetic thin plates at a skew angle of 0 degrees. Therefore, in this embodiment, it is possible to suppress the reduction of average torque and the generation of axial thrust. In addition, by adopting a skew-free rotor core 30, the magnet hole 31 and the permanent magnets 101, 102, etc. extend from the end of the rotor core 30 on the opposite side AOS of the output shaft in the axial direction to the end of the output shaft side OS. It should be noted that as the material of the magnetic thin plates, electromagnetic steel plates, which are a type of silicon steel plates, can be used.

[0059] Figure 3 It is a cross-sectional view schematically showing the rotor core 30 and the permanent magnets 101 , 102 , . . . Figure 3 (a) is an overall view of the rotor core 30, Figure 3 (b) is an enlarged view of the magnetic pole MP1. Figure 3 In (a), the cross-section lines of the magnetic body are omitted for easy observation. Figure 3 As shown in (a), permanent magnets 101, 102, 103, 104, 105, and 106 are embedded in the rotor core 30 so that the number of magnetic poles arranged in the circumferential direction of the rotor 10 is 8 and the prospect angle of each magnetic pole along the circumferential direction observed from the axis AC is 45 degrees.

[0060] It should be noted that although the positions and shapes of the magnet holes 31, 33, ... and the permanent magnets 101, 102, ... are different, the basic structures of the magnetic poles MP1, MP2, MP3, MP4, MP5, MP6, MP7, and MP8 are the same, so the following references Figure 3 The magnetic pole MP1 shown in the enlarged view of (b) represents the eight magnetic poles MP1, MP2, ..., and the magnet holes 31, 33, ... and the permanent magnets 101, 102, ... in each magnetic pole MP1, MP2, ... will be described.

[0061] like Figure 3 As shown in (b), each magnetic pole MP1, MP2, ... is composed of a double-layer structure of an outer embedded magnet portion 100A and an inner embedded magnet portion 100B, wherein the outer embedded magnet portion 100A includes two permanent magnets 101 and 102 arranged in a V shape on the radial outside, and the inner embedded magnet portion 100B includes four permanent magnets 103, 104, 105, 106 arranged in a U shape on the radial inside.

[0062] The outer embedded magnet portion 100A has a magnet hole 31 formed in a V shape. The two permanent magnets 101 and 102 are inserted into the magnet hole 31 so that the distance between the two permanent magnets 101 and 102 is widened toward the radial outside and narrowed toward the radial inside. In the V-shaped magnet hole 31, the portion not embedded by the two permanent magnets 101 and 102 ( Figure 3 The blank portion of (b)) is retained as a gap (flux barrier).

[0063] The inner embedded magnet portion 100B has four magnet holes 33, 34, 35, and 36. Permanent magnets 103 and 106 are inserted into magnet holes 33 and 36, respectively, so that the distance between permanent magnets 103 and 106 widens radially outward and narrows radially inward. The portions of magnet holes 33 and 36 not filled with permanent magnets 103 and 106 remain as gaps. Furthermore, permanent magnets 104 and 105 are inserted into magnet holes 34 and 35, respectively, so that the portions of magnet holes 34 and 35 not filled with permanent magnets 104 and 105 remain as gaps.

[0064] - Rotor structure - In this embodiment, as described above, a rotor structure is provided that can achieve high efficiency and low vibration / low noise even when the synchronous motor 1 is miniaturized. Since the "efficiency" of the motor refers to "output / (output + loss)", in order to achieve high efficiency of the motor, it is required to increase the output while suppressing the loss (requirement 1) .

[0065] Here, the "output" of a motor refers to "torque x speed." Therefore, to increase the output, it is necessary to increase the torque that can be generated by the same stator coil current (requirement 2) and ensure that the rotor 10 rotates smoothly and without waste. Furthermore, to increase the torque that can be generated, it is effective to increase the proportion of the magnetic flux (fundamental component) that contributes to torque generation. Furthermore, to ensure that the rotor 10 rotates smoothly and without waste, it is ideal to make the magnetic flux density at the air gap G between the stator 90 and the rotor 10 in each of the magnetic poles MP1, MP2, ... of the rotor 10 vary sinusoidally over time (distribute sinusoidally in space) (requirement 3). Therefore, if the magnetic flux density at the air gap G between the stator 90 and the rotor 10 varies sinusoidally, torque ripple (vibration) is also suppressed, thereby achieving both high efficiency and low vibration and noise. However, it is known that in synchronous motors 1, the magnetic flux generally contains high harmonic components that hinder these requirements 1 to 3.

[0066] <Presence of high harmonic components> Figure 4 is a diagram schematically illustrating high harmonic components, Figure 5This is a diagram schematically illustrating the effect of high harmonic components on magnetic flux density. Figure 5 (a) is a diagram showing the decomposition of the fundamental wave and higher harmonics. Figure 5 (b) is a diagram showing the composite wave of the fundamental wave and the harmonics. Figure 4 The double-dashed line is an imaginary line dividing the magnetic pole MP. Figure 5 In (a), the fundamental wave is represented by a solid line, the nth harmonic is represented by a dotted line, and the n'th harmonic (n'>n) is represented by a double-dashed line.

[0067] like Figure 4 As shown by the symbol BW, the magnetic flux that contributes to the generation of torque is the magnetic flux that rotates greatly inside the rotor core 30 and is called the fundamental wave (fundamental wave component). On the other hand, it is known that the high harmonic component is a high-order frequency component that is an "integer multiple" of the fundamental wave component, such as Figure 4 As shown by the mark H, the high harmonic component passes over the outer periphery of the rotor core 30, so it does not contribute to the generation of torque. In addition, it is known that the high harmonic component is Figure 5 As shown in (a), it overlaps with the fundamental wave that changes in a sinusoidal shape under ideal conditions, such as Figure 5 As shown in (b), the waveform of the magnetic flux density in the air gap G between the stator 90 and the rotor 10 is distorted.

[0068] On the other hand, "loss" refers to "iron loss + copper loss + mechanical loss." In rotor 10, which is primarily made of magnetic material, "loss" refers to "iron loss." This "iron loss" includes hysteresis loss, which is the friction loss generated when the magnetic field direction changes, as derived from the Steinmetz empirical formula (see equation (1) below), and eddy current loss, which is energy loss caused by the resistance of rotor core 30 (see equation (2) below).

[0069] [Number 1] P H =K H ·f·B M 1.6 ·······(1) K H : proportional constant f: frequency (fluctuation frequency of magnetic flux) B M : Maximum magnetic flux density

[0070] [Number 2] K e : proportional constant t: Iron plate thickness f: frequency (fluctuation frequency of magnetic flux) B M: Maximum magnetic flux density ρ: Resistivity of magnetic material

[0071] From the above equations (1) and (2), it can be seen that the hysteresis loss and eddy current loss, i.e., the iron loss, depends on the fluctuation frequency f of the magnetic flux and increases with the increase of the fluctuation frequency f of the magnetic flux. Figure 4 As shown in FIG. 1 , the harmonic components have a higher frequency component than the fundamental wave component. Therefore, the presence of the harmonic components increases the iron loss, which also hinders the improvement of the efficiency of the synchronous motor 1 .

[0072] It is known that such high harmonic components are likely to appear in the air gap G where the rotor 10 and the stator 90 exchange magnetic fields, and between the magnetic poles MP where magnetic flux short circuits are likely to occur. Figure 4 The vicinity of the magnetic poles MP on the outer periphery of the rotor core 30 surrounded by the elliptical frame.

[0073] Therefore, in this embodiment, the generation of magnetic flux harmonic components that would hinder the improvement of efficiency and the reduction of vibration and noise in the synchronous motor 1 is suppressed. The following describes in detail the structures for suppressing the generation of magnetic flux harmonic components and achieving high efficiency and low vibration and noise ((1) the first gap and the protruding portion, and (2) the asymmetric structure), and the structures for mainly achieving further improvement of the efficiency of the synchronous motor 1 ((3) the center bridgeless structure, (4) the throttle portion, and (5) the oil passage).

[0074] <(1) First Gap and Protrusion> Figure 6 Schematically shows the first gap G1 and the protruding portions 61 and 62. More specifically, Figure 6 (a) is a cross-sectional view and an enlarged view showing the magnetic pole MP1 and the magnetic pole MP8, Figure 6 (b) is a diagram showing the effect of the first gap G1. Figure 6 As shown in FIG. 1 , a first protruding portion 61 is formed on the outer peripheral surface 32 of the rotor core 30, and a first gap G1 is formed inside the first protruding portion 61. When viewed in the axial direction, the first protruding portion 61 extends circumferentially across the adjacent magnetic poles MP1 and MP8 and protrudes radially outward. When viewed in the axial direction, the first gap G1 extends circumferentially. It should be noted that the protruding portions 61, 62 and the first gap G1 are formed not only between the magnetic poles MP1 and MP8, but also between the magnetic poles MP1 and MP8, for example. Figure 3 As shown, it is also formed between all circumferentially adjacent magnetic poles MP.

[0075] The first protruding portion 61 is formed such that, when viewed in the axial direction, Figure 6In the enlarged view of (a), comparing the imaginary lines (two-dot chain lines) and the solid lines, both indicated by the markers 32a and 32b, shows that the outer circumferential surfaces 32a and 32b (imaginary lines) of the rotor core 30 corresponding to the respective circumferential ends of the first protrusion 61 are recessed radially inward (recesses 32a and 32b (solid lines)), thereby projecting relatively radially outward. That is, the first protrusion 61 does not absolutely project radially outward from the outer circumferential surface 32 of the cylindrical rotor core 30. Instead, the first protrusion 61 is recessed radially inward at both ends, causing it to project relatively radially outward relative to the recesses 32a and 32b. Furthermore, although the first gap G1 is formed to have a rectangular cross-section, the second protrusion 62, described later, is formed to have a gate-shaped shape that opens radially inward.

[0076] Thus, a first gap G1 extending in the circumferential direction is formed inside the first protruding portion 61 formed across the adjacent magnetic poles MP1 and MP8. Figure 6 As shown in (b), the first gap G1, which serves as a flux barrier, can block the magnetic flux, suppressing magnetic flux short-circuiting between the magnetic poles MP1 and MP8, thereby suppressing the generation of high-harmonic components. Moreover, by suppressing the generation of high-frequency high-harmonic components, the fluctuation frequency of the magnetic flux can be reduced, thereby suppressing the increase in iron loss that depends on the fluctuation frequency of the magnetic flux (satisfying requirement 1). Moreover, by suppressing the increase in iron loss by suppressing such high-harmonic components and combining this with suppressing the increase in iron loss by using a non-skewed rotor core 30, the increase in loss can be reliably suppressed. In addition, by suppressing the increase in loss, even when the synchronous motor 1 is miniaturized, the heat generated inside the motor can be reduced.

[0077] Furthermore, by suppressing the generation of high harmonic components, it is possible to suppress Figure 5 By generating the synthetic wave shown in (b), the magnetic flux density at the air gap G between the stator 90 and the rotor 10 can be made close to an ideal sine wave (satisfying requirement 3). This allows the rotor 10 to rotate smoothly without waste and reduces vibration (torque ripple). Furthermore, by suppressing the generation of magnetic flux harmonic components that do not contribute to torque generation using the first gap G1, the proportion of the magnetic flux fundamental wave component that contributes to torque generation can be increased.

[0078] However, if only the first gap G1 is formed, the torque may be reduced. In this case, even if the ratio of the fundamental wave component of the magnetic flux is increased, the effect of improving the total torque may be reduced.

[0079] Therefore, in the rotor structure of this embodiment, if Figure 6As shown in (a), a second protrusion 62 with a rectangular cross-section is formed within the first protrusion 61. When viewed axially, this second protrusion 62 protrudes radially outward from a radially inner portion G1a that defines the first gap G1. Salient polarity refers to the property whereby magnetic reluctance (reluctance) varies depending on the position on the circumference of the rotor core 30. Since the second protrusion 62, which protrudes radially outward, is formed within the first protrusion 61 formed on the outer circumferential surface 32 of the rotor core 30, the reduced torque can be compensated for by the reluctance torque generated by the attractive force between the poles and the salient poles (the first and second protrusions 61 and 62) caused by the rotating magnetic field of the stator 90. Thus, by combining magnetic saliency to ensure reluctance torque with an increase in the proportion of the fundamental component of the magnetic flux, the torque that can be generated by the same stator coil current can be increased (satisfying requirement 2).

[0080] Figure 7 61 and 62 are diagrams schematically illustrating the advantages of the double protrusions 61 and 62. Figure 7 (a) shows the rotor core 130 having only the first protruding portion 161, Figure 7 (b) shows the rotor core 30 of this embodiment having the first and second protruding portions 61 and 62. Figure 7 (c) shows the rotor core 230 having only the second protrusion 262. In the rotor structure of this embodiment, since the double protrusions 61 and 62 arranged in the radial direction are formed, for example, when generating the same reluctance torque, the rotor core 230 is the same as the rotor core 230 shown in FIG. Figure 7 Compared with the rotor core 130 in which only the first protruding portion 161 is formed as shown in (a), the protruding height of the first protruding portion 61 itself toward the radially outer side can be reduced (see Figure 7 (a)- Figure 7 In other words, if the protrusion height of the first protrusion 161 from the outer peripheral surface 132 is the same as the protrusion height of the first protrusion 61 from the outer peripheral surface 32, the rotor core 30 of this embodiment can ensure a greater reluctance torque than the rotor core 130 in which only the first protrusion 161 is formed.

[0081] As a result, the radially outward projection height of the first protrusion 61 can be set relatively low, making the outer circumferential surface 32 of the cylindrical rotor core 30 closer to a true circle. This reduces cogging torque even when a non-skewed rotor core 30 is used. Furthermore, as described above, by making the first protrusion 61 relatively, rather than absolutely, radially outward project, cogging torque can be further reduced. This reduction in cogging torque, combined with the aforementioned reduction in torque ripple, allows for reliable suppression of motor vibration and the resulting noise, even when the current density and magnetic flux density are increased during miniaturization of the synchronous motor 1.

[0082] In addition, in the rotor structure of this embodiment, since the double protrusions 61 and 62 are arranged in the radial direction, the rotor structure of this embodiment is similar to the rotor structure of the embodiment. Figure 7 Compared to the rotor core 230 shown in (c) in which the outer peripheral surface 232 has no irregularities and only the second protrusion 262 is formed, a larger reluctance torque can be ensured.

[0083] Figure 8 Schematically shows a modified version of the second protruding portion 62. Figure 8 In (a) and (b), for the sake of convenience, the second protrusion 62' is extremely inclined. As long as the second protrusion 62 protrudes from the radially inner portion G1a that divides the first gap G1 toward the radially outer side, it is not necessary to extend straightly toward the radially outer side. For example, Figure 8 As shown in FIG. 2( a ), the second protruding portion 62 ′ may be made to protrude obliquely relative to the radial direction so that the second protruding portion 62 ′ extends in the circumferential direction ( Figure 8 (a) is tilted at a predetermined angle, and Figure 8 As shown in FIG. 2( b ), the second protruding portion 62 ′ may be made to protrude obliquely relative to the radial direction so that the second protruding portion 62 ′ extends in the circumferential direction ( Figure 8 Thus, as long as the second protrusion 62', which contributes to the magnetic salient polarity, is tilted relative to the radial direction, so that the second protrusion 62' is tilted at a predetermined angle along the circumferential direction as it moves radially outward, the pulsating component (high harmonic component) of the reluctance torque can be finely controlled by setting the predetermined angle.

[0084] Furthermore, as long as the second protruding portion 62 protrudes radially outward from the radially inner portion G1a that defines the first gap G1, the first gap G1 does not need to be a gap that is continuous in the circumferential direction. Figure 8 As shown in (c), the second protrusion 62" can also be made to protrude to divide the first gap G1 in the circumferential direction and extend to the radially outer portion G1b that divides the first gap G1. Thus, even if the first gap G1 is divided in the circumferential direction, the generation of high harmonic components can be suppressed, and the protruding length of the second protrusion 62" can be increased compared to the case where the second protrusion 62 is not formed to reach the portion G1b. Thus, the reluctance torque generated by the magnetic salient polarity can be further ensured.

[0085] As described above, according to the rotor structure involved in this embodiment, even when the synchronous motor 1 is miniaturized, high efficiency and low vibration / low noise can be achieved. Therefore, the miniaturization of the synchronous motor 1 while maintaining the output level can be achieved without demagnetization of the permanent magnets 101, 102, etc. caused by high temperature, or vibration / noise.

[0086] <(2) Asymmetric structure> As described above, the high-harmonic components contained in the rotating magnetic field of stator 90 and the magnetomotive force of rotor 10 are the primary cause of torque ripple. As described below, changes in magnetic resistance are known to amplify these high-harmonic components. Torque ripple originally refers to the loss of consistency in torque generated by a motor, resulting in periodic fluctuations in torque output. Furthermore, the motor's torque T is defined by the following equation (3) (the basic equation for torque).

[0087] [Number 3] P n : Pole pairs Magnetic crosslink flux i d : d-axis current i q :q-axis current L d : d-axis inductance L q :q-axis inductance

[0088] In formula (3), L·i (product of inductance and current) represents the linkage flux generated by the stator coil current. If formula (3) is transformed, the torque T can be organized into the linkage flux as shown in the following formula (4). The relationship between the current i.

[0089] [Number 4]

[0090] From formula (4), we can see that the state with torque pulsation refers to the cross-linked magnetic flux Or the current i contains pulsating components (high harmonic components). Also, assuming that the current (i d or i q ) is constant, the main reason for the torque ripple is the magnetic flux ( or ), due to the magnetic flux ( or ) is the inductance (L d or L q ), and inductance is a function of magnetic resistance. Therefore, the change of magnetic resistance can be regarded as a factor that amplifies the high harmonic components in the magnetic flux and worsens the torque ripple.

[0091] Figure 9 is a diagram schematically illustrating the equivalent magnetic circuit, Figure 9 (a) represents the equivalent magnetic circuit, Figure 9 (b) shows the image of the equivalent magnetic circuit network. In addition, Figure 1 θ is a diagram schematically illustrating the change in conventional magnetic resistance. Figure 11 1 is a diagram schematically illustrating the spatial distribution of ideal magnetic flux density in the air gap G between the stator 90 and the rotor 10 .

[0092] like Figure 9 As shown in (a), the equivalent magnetic circuit is used to convert the relationship between magnetic flux, magnetomotive force and magnetic resistance into the relationship between current, voltage and resistance for explanation. Here, "magnetomotive force" is the force that causes the magnetic circuit to generate magnetic flux, and the permanent magnets 101, 102, ... or the stator coil 93 are equivalent to the magnetomotive force. In addition, "magnetic resistance" depends on the shape of the rotor core 30, the shape / configuration of the magnetic flux barrier or the permanent magnets 101, 102, ..., and changes according to the rotation angle of the rotor 10, or changes according to the operating state of the synchronous motor 1 (change in magnetic permeability due to magnetic saturation). Therefore, in the synchronous motor 1, as Figure 9 As shown by the thick arrows in (b), the flow of magnetic flux is determined by the distribution of the magnitude and direction of the magnetomotive force (the magnitude and direction of the permanent magnets 101, 102, ..., etc.) and the magnetic resistance (the shape and configuration of the flux barrier, etc.).

[0093] However, even if Figure 10 (a) shows the flow of magnetic flux MF, as shown in Figure 10 As shown by the bold arrow in (b), when the rotor 10 rotates, the positional relationship between the teeth 95 of the stator 90 and the permanent magnets 100 etc. will also change. Figure 10 (a) and Figure 10 As can be seen from (b), the flow of magnetic flux MF changes. Furthermore, depending on the arrangement of permanent magnets 101, 102, ..., and flux barriers in the magnetic poles MP1, MP2, ..., of the rotor 10, the positional relationship between the teeth 95 of the stator 90 and the permanent magnets 101, 102, ..., etc. changes as the rotor 10 rotates. This can cause a significant change in magnetic resistance. In this case, there is a possibility that higher harmonic components may be amplified, exacerbating torque ripple.

[0094] Therefore, the ideal magnetic flux density state at the air gap G between the stator 90 and the rotor 10 refers to the following state: not only does the magnetic flux density change in a sinusoidal manner so that the magnetic flux density is maximum at the N pole and minimum at the S pole, but also Figure 11 As shown by the bold arrows, even if the rotation angle of rotor 10 changes (rotor 10 rotates), the magnetic flux density at air gap G always maintains a sinusoidal distribution at any rotation angle. Focusing on torque ripple, in other words, even if the rotation angle of rotor 10 changes, suppressing changes in magnetic resistance can suppress amplification of higher harmonic components, effectively suppressing torque ripple.

[0095] Therefore, in the rotor structure involved in this embodiment, when viewed along the axial direction, the position, shape, size and inclination of the permanent magnets 101, 102, 103, 104, 105, 106 in each magnetic pole MP1, MP2,..., and at least one of the position, shape, size and inclination of the magnet holes 31, 33, 34, 35, 36 are set to be asymmetric between circumferentially adjacent magnetic poles.

[0096] Figure 12 1 and 2 are diagrams schematically showing asymmetric adjacent magnetic poles MP1 and MP8. Figure 12 (a) is a cross-sectional view schematically showing an example of adjacent magnetic poles MP1 and MP8. Figure 12 (b) shows a hypothetical state where the magnetic poles MP1 and MP8 overlap. Figure 12 In (a), the cross-hatching of the magnetic body is omitted for the sake of convenience. Figure 12 This is an example, and it is not only the magnetic poles MP1 and MP8 that are asymmetric. Figure 3 As shown in (a), all the magnetic poles MP1, MP2, ... adjacent to each other in the circumferential direction are asymmetrical to each other.

[0097] like Figure 12 As shown in (b), if the magnetic pole MP1 and the magnetic pole MP8 overlap, then Figure 12 In the circumferentially adjacent magnetic poles MP1 and MP8 shown in (a), the following elements are asymmetric: Specifically, the size and inclination of the permanent magnets 101 and 102, the inclination of the permanent magnets 103 and 106, the position of the permanent magnets 104 and 105, the size and shape of the magnet hole 31, the size, shape, and inclination of the magnet holes 33 and 36, and the size and shape of the magnet holes 34 and 35 differ significantly between the magnetic poles MP1 and MP8.

[0098] It should be noted that, between circumferentially adjacent magnetic poles, it is not sufficient to simply have at least one of the position, shape, size, and inclination of the permanent magnets 101, 102, ..., and the magnet holes 31, 33, ... (hereinafter referred to as "position, etc.") be asymmetric. As described above, even when the rotation angle of the rotor 10 changes, it is necessary to asymmetric the position, etc., of the permanent magnets 101, 102, ..., and the magnet holes 31, 33, ... to suppress changes in magnetic resistance. However, the asymmetry required to suppress changes in magnetic resistance cannot be simply determined by, for example, simply increasing the size of the permanent magnets 101 or changing the shape of the magnet holes 31. Rather, it is determined through CAE (computer-aided engineering) simulation analysis or experiments, taking into account the relationship between the teeth 95 and other factors.

[0099] Thus, by making the positions of permanent magnets 101, 102, ..., and magnet holes 31, 33, ..., etc. asymmetrical between circumferentially adjacent magnetic poles, it is possible to suppress significant changes in the positional relationship between teeth 95 and permanent magnets 101, 102, ..., etc., even when rotor 10 rotates. This suppresses changes in magnetic resistance, thereby preventing amplification of higher harmonic components and deterioration of torque ripple.

[0100] Furthermore, since the teeth 95 are typically arranged evenly, if the plurality of circumferentially arranged magnetic poles MP1, MP2, ... are configured identically, the relative positional relationship between one permanent magnet 101, 102, ... and one tooth 95 will be consistent with the relative positional relationship between the other permanent magnets 101, 102, ... and other teeth 95. If there are multiple sets of such sets with consistent positional relationships between the permanent magnets 101, 102, ... and teeth 95, integer multiple frequency components, i.e., higher harmonic components, may be easily generated. However, in this embodiment, by making adjacent magnetic poles asymmetrical, higher harmonic components can be canceled out between adjacent magnetic poles.

[0101] Therefore, by asymmetricizing the permanent magnets 101, 102, ..., and the magnet holes 31, 33, ... between the circumferentially adjacent magnetic poles MP1 and MP8, and combining the suppression of the amplification of high harmonic components by suppressing the change in magnetic resistance with the mutual cancellation of high harmonic components, torque pulsation can be reliably suppressed, further achieving higher efficiency and lower vibration / low noise of the synchronous motor 1.

[0102] However, if the positions of the permanent magnets 101, 102, ..., and the magnet holes 31, 33, ..., are asymmetrical between adjacent magnetic poles MP1 and MP8, there is a possibility that the amount of magnetic flux (fundamental component) contributing to torque generation will differ between the magnetic pole MP1 formed by the relatively large permanent magnets 101 and 102 and the magnetic pole MP8 formed by the relatively small permanent magnets 101 and 102. Furthermore, if the positions of the permanent magnets 101, 102, ..., and the magnet holes 31, 33, ..., are asymmetrical between adjacent magnetic poles MP1 and MP8, there is a possibility that the zero-crossing point of the fundamental component of the magnetic flux will shift from the q-axis.

[0103] Therefore, if the adjacent magnetic poles MP1 and MP8 are to be made asymmetrical, it is preferable to set the depths of the recesses 32 a and 32 b at both circumferential end portions of the first protruding portion 61 to be asymmetrical.

[0104] Figure 13 : is a diagram schematically showing an example of a first protruding portion 61' between adjacent asymmetric magnetic poles MP1 and MP8. Figure 13 (a) is a cross-sectional view showing the magnetic pole MP1 and the magnetic pole MP8, Figure 13 (b) is an enlarged representation Figure 13Figure 1 shows the portion enclosed by circle B in (a).

[0105] like Figure 13 As shown in (a) and (b), if the depth of the recess 32a' at the circumferential end of the first protrusion 61' is deep, the magnetic flux will have difficulty passing through, just as in the case where there is a large gap. In contrast, if the depth of the recess 32b' at the circumferential end of the first protrusion 61' is shallow, the magnetic flux will easily pass through, just as in the case where there is a small gap. Therefore, by setting the deep-side end (recess 32a') of the first protrusion 61' on the side of the magnetic pole MP1 with a large magnetic flux formed by the relatively large permanent magnets 101 and 102, and setting the shallow-side end (recess 32b') of the first protrusion 61' on the side of the magnetic pole MP8 with a small magnetic flux formed by the relatively small permanent magnets 101 and 102, the deviation of the fundamental wave component of the magnetic flux based on the asymmetry between the adjacent magnetic poles MP1 and MP8 can be reduced. Furthermore, by changing the depths of the recesses 32 a and 32 b at both circumferential end portions of the first protruding portion 61 , the zero-crossing point is brought closer to the q-axis, thereby further reducing the deviation of the fundamental wave component of the magnetic flux.

[0106] <<Effects of the structures (1) and (2)>> As described above, in the rotor structure according to this embodiment, harmonic components are suppressed by adopting the first gap G1 , the protruding portions 61 , 62 , and the asymmetric structure between the magnetic poles. These effects will be described below based on the results of simulations and experiments.

[0107] Figure 14 is the spatial distribution of magnetic flux density, Figure 15 is the time distribution of magnetic flux density. More specifically, Figure 14 The spatial distribution of the magnetic flux density at the air gap G between the stator 90 and the rotor 10 is shown with the magnetic flux density as the vertical axis and the angle on the outer periphery of the rotor core 30 as the horizontal axis. Figure 15 The vertical axis is the magnetic flux density, and the horizontal axis is the time axis, showing the time change of the magnetic flux density at the air gap G between the stator 90 and the rotor 10. Figure 14 (a) and Figure 15 (a) both relate to the synchronous motor 1 according to this embodiment, Figure 14 (b) and Figure 15 (b) Both relate to a conventional synchronous motor (not shown) that does not employ the first gap G1 , the protruding portions 61 , 62 , or the asymmetric structure.

[0108] contrast Figure 14 (a) and Figure 14(b) It can be seen that in the synchronous motor 1 according to this embodiment, since the generation of high harmonic components is suppressed, it does not form a composite wave like the conventional synchronous motor, and the magnetic flux density is distributed in a sinusoidal shape in the air gap G between the stator 90 and the rotor 10. It should be noted that Figure 14 Mark D shown in (a) is a sharp drop in magnetic flux density that is inevitably generated at the slot position (between teeth 95 and 95) of the stator 90 where magnetic flux does not appear, and does not negate the sinusoidal distribution. Figure 15 (a) and Figure 15 (b) It can be seen that in the synchronous motor 1 according to the present embodiment, the magnetic flux density also changes sinusoidally with time in the air gap G between the stator 90 and the rotor 10 .

[0109] Figure 16 It is a diagram schematically showing the time change of torque in the high rotation range. Figure 16 (a) Concerning the synchronous motor 1 according to this embodiment, Figure 16 (b) This relates to a conventional synchronous motor that does not employ the first gap G1, the protruding portions 61, 62, or the asymmetric structure. The high rotation range herein refers to a range where the motor rotation speed is 14,000 to 16,000 rpm.

[0110] As described above, if the magnetic resistance changes significantly with the rotation of the rotor 10, the high harmonic components are amplified, and thus it should be disadvantageous to the torque ripple in the high rotation area. Figure 16 (a) and Figure 16 (b) shows that in the synchronous motor 1 involved in this embodiment, not only the generation of high harmonic components is suppressed, but also, by adopting an asymmetric structure between adjacent magnetic poles, the periodic fluctuation of torque, that is, the generation of torque pulsation, can be significantly reduced compared with the existing synchronous motor even in the high rotation range that should be unfavorable to torque pulsation.

[0111] Figure 17 This is a diagram schematically showing changes in the line voltage of the three-phase AC applied to the motor with respect to the rotation angle. Figure 17 (a) shows the line voltage at the highest rotation point in the synchronous motor 1 according to the present embodiment. Figure 17 (b) shows the line voltage at the highest rotational operating point in a conventional synchronous motor that does not employ the first gap G1, the protrusions 61 and 62, or the asymmetric structure. The voltage ripple of the motor's generated voltage, i.e., the back electromotive force voltage, which opposes the voltage applied to the rotating motor, is derived from the high harmonic components of the magnetic flux, similar to torque ripple. However, in the synchronous motor 1 according to this embodiment, voltage ripple is also reduced as a side effect of reducing torque ripple.

[0112] Specifically, if Figure 17As shown in (b), unlike the conventional synchronous motor in which the line voltage of the three-phase AC is disturbed and reaches the voltage limit according to the rotation angle, the synchronous motor 1 of this embodiment is Figure 17 As shown in (a), the waveform of the three-phase AC line voltage is close to an ideal sine wave within the voltage limit range. This allows the waveform of the three-phase AC line voltage at the highest rotational operating point to be close to a sine wave, thereby improving the controllability of the synchronous motor 1 at high rotational speeds.

[0113] <(3)Center bridgeless structure> Figure 18 is a diagram schematically illustrating a center bridgeless structure. Specifically, Figure 18 (a) shows the outer embedded magnet portion 100A of the rotor core 30 according to this embodiment. Figure 18 (b) shows the conventional rotor core 330 Figure 18 (a) The corresponding parts, Figure 18 (c) Enlarged view Figure 18 (a) The portion surrounded by the circular frame C. In the rotor structure of this embodiment, as described above, the outer embedded magnet portion 100A has a single V-shaped magnet hole 31, and the two permanent magnets 101 and 102 are inserted into the magnet hole 31 in the V shape. In this V-shaped magnet hole 31, the portion not embedded by the two permanent magnets 101 and 102 remains as a gap.

[0114] On the other hand, in the conventional rotor core 330, as shown in FIG. Figure 18 As shown in FIG. 1( b ), a so-called center bridge 337 is provided in the portion of the magnet hole 331 between the two permanent magnets 101 and 102 that is not buried by the two permanent magnets 101 and 102 to ensure mechanical strength. However, this center bridge 337 acts as a leakage flux path, making it easy for short-circuit flux to occur between the two permanent magnets 101 and 102.

[0115] Therefore, in the rotor structure involved in this embodiment, if Figure 18 As shown in (a), a second gap G2 is retained between two adjacent permanent magnets 101 and 102. Thus, since the second gap G2 exists between the two adjacent permanent magnets 101 and 102, in other words, there is no center bridge 337 between the two permanent magnets 101 and 102, which serves as a leakage flux path. This suppresses short-circuit flux (leakage flux) generated between the two permanent magnets 101 and 102 that does not contribute to torque, thereby effectively utilizing the magnet flux. This allows high torque to be achieved even when the stator coil current is low, for example, thereby further reliably achieving higher efficiency for the synchronous motor 1.

[0116] However, the center bridge 337 previously provided between two adjacent permanent magnets 101 and 102 is used to ensure mechanical strength. Therefore, if a second gap G2 (bridgeless) is provided between the two adjacent permanent magnets 101 and 102, the stress (centrifugal force or stress generated by heat-shrink fitting) acting on other parts near these permanent magnets 101 and 102 will be relatively increased.

[0117] Therefore, in the rotor structure of this embodiment, if Figure 18 As shown in (c), the radially outer end of the V-shaped magnet hole 31 is brought close to the outer peripheral surface 32 of the rotor core 30, and the third gap G3 at the end that is not filled with the permanent magnets 101 and 102 is divided into a third gap G3' and a third gap G3" by using the bridge portion 37. Thus, the third gap G3' is divided by a portion of the hole wall of the magnet hole 31, the surface portion (bridge portion 32c) of the rotor core 30, and the bridge portion 37. In addition, the third gap G3" is divided by a portion of the hole wall of the magnet hole 31, the radially outer end surfaces of the permanent magnets 101 and 102, and the bridge portion 37.

[0118] Therefore, in the third gap G3 at the radially outer end of the V-shaped magnet hole 31 that is not filled with the permanent magnets 101 and 102, there are provided double bridge portions 37 and 32c such as a bridge portion 32c formed by the surface portion of the rotor core 30 and a bridge portion 37 that separates the third gap G3, thereby suppressing stress concentration caused by centrifugal force or shrinkage, thereby avoiding deformation of the rotor core 30.

[0119] Figure 19 37 ′ and 37 ″ in the rotor core 30 . Figure 19 (a) shows the stress state of the rotor core 30 during shrinkage. Figure 19 (b) shows the stress state of the rotor core 30 at the highest rotation. Figure 19 (c) shows the relationship between the bridge portions 37, 37', 37" and the permanent magnets 101, 102, ... As described above, in the rotor structure of this embodiment, since the adjacent magnetic poles MP1, MP2, ... are made asymmetric with each other, stress concentration is more likely to occur compared to conventional rotor structures that are not asymmetric.

[0120] For example, when the rotor shaft 20 is fixed in the center hole 38 of the rotor core 30 and is shrink-fitted, stress is easily concentrated in the rotor core 30. Figure 19 (a) is the black part. In addition, when a relatively large centrifugal force acts on the rotor core 30 to perform the highest rotation, stress is likely to be concentrated in the rotor core 30. Figure 19 (b) The blackened part shown.

[0121] Therefore, in the rotor structure of this embodiment, when at least one of the position, shape, size, and inclination of the V-shaped permanent magnets 101 and 102 is set to be asymmetric between circumferentially adjacent magnetic poles (for example, between the magnetic poles MP7 and MP8), as viewed in the axial direction, Figure 19 As shown in (c), the relative angles θ1 and θ2 between the permanent magnets 101 and 102 and the bridge portion 37 are also set to be asymmetric between the magnetic poles MP7 and MP8.

[0122] When the positions of the two V-shaped permanent magnets 101 and 102 are asymmetric between the magnetic poles MP7 and MP8, stress concentration is likely to occur near these permanent magnets 101 and 102. According to this structure, since the relative angle θ1 between the permanent magnet 101 and the bridge portion 37 in the magnetic pole MP7 and the relative angle θ2 between the permanent magnet 102 and the bridge portion 37 in the magnetic pole MP8 are set to be asymmetric, the stress concentration caused by the asymmetry can be suppressed according to the setting of the relative angles θ1 and θ2, thereby avoiding deformation of the rotor core 30 during shrink-fit or maximum rotation.

[0123] Likewise, when the positions of the two permanent magnets 103, 106 are asymmetric between the magnetic poles MP7, MP8, as shown in FIG. Figure 19 As shown in (c), the relative angle θ1' between the permanent magnet 103 and the bridge portion 37' in the magnetic pole MP7 and the relative angle θ2' between the permanent magnet 106 and the bridge portion 37' in the magnetic pole MP8 can be set to be asymmetric. In addition, when the positions of the two permanent magnets 104 and 105 are asymmetric between the magnetic poles MP7 and MP8, the relative angle θ1" between the permanent magnet 104 and the bridge portion 37" in the magnetic pole MP7 and the relative angle θ2" between the permanent magnet 105 and the bridge portion 37" in the magnetic pole MP8 can be set to be asymmetric.

[0124] <(4) Throttle section> Figure 20 This is a graph showing magnetic flux linkage. In this embodiment, the goal is to increase the efficiency of the synchronous motor 1. As mentioned above, since the "efficiency" of a motor refers to "output / (output + loss)", in order to achieve high motor efficiency, it is required to increase the output while suppressing the loss (iron loss).

[0125] For example, since the magnetic flux of the permanent magnet does not contribute to the generation of torque when there is no load, it is preferable to suppress the magnetic flux of the magnet when there is no load from the perspective of reducing iron loss. On the other hand, in order to effectively utilize the reluctance torque, synchronous motors that generally have reverse salient polarity (d-axis reactance is smaller than q-axis reactance) usually use maximum current to advance the current phase to about 50 (deg) when they are highly loaded (advance angle control) to enable the motor to exert maximum torque. However, in this advance angle control, the magnetic flux component generated by the stator coil current that opposes the permanent magnet flux may be used to suppress the magnetic flux of the permanent magnet and weaken the magnetic flux of the motor as a whole. Therefore, in order to achieve high efficiency of the motor, it is preferable to suppress the magnetic flux of the magnet when there is a light load (for example, when there is no load) and ensure the magnetic flux of the magnet when there is a high load (for example, when there is maximum torque).

[0126] In this regard, in the rotor structure of this embodiment, by focusing on the shape of the rotor core 30, as shown in FIG. Figure 20 As shown, the state in which the magnetic flux linkage at maximum torque is greater than the magnetic flux linkage at no load (magnetic flux linkage when the current amplitude is zero) is achieved. The "throttling section" that enables this state will be described in detail below.

[0127] Figure 21 It is a diagram schematically showing the throttle portion 39 . Figure 21 (a) shows a portion of the rotor core 30 corresponding to one magnetic pole MP. Figure 21 (b) Enlarged view Figure 21 (a) is the part surrounded by the circle B. As mentioned above, Figure 21 As shown in (a), each magnetic pole MP includes: a magnet hole (outer magnet hole) 31, which is formed on the outermost periphery of the rotor core 30 and extends circumferentially in a V shape; and magnet holes (inner magnet holes) 34, 35, which are formed radially inward relative to the magnet hole 31 and extend circumferentially.

[0128] like Figure 21 As shown in (b), the magnet holes 34, 35 are formed into the following shape: the radially outer surfaces 104a, 105a of the permanent magnets (inner permanent magnets) 104, 105 inserted into these magnet holes 34, 35 are in contact with the rotor core 30, and there is a relatively large fourth gap G4 in the radially inner portion not buried by the permanent magnets 104, 105 (more accurately, the portion located radially inner relative to the fixing portion 30e for fixing the permanent magnets 104, 105).

[0129] Moreover, a slender throttling portion 39 is formed on the rotor core 30. When viewed in the axial direction, the throttling portion 39 divides the fourth gap G4 in the circumferential direction and extends radially through the d-axis of each magnetic pole MP, so that the portion 30f of the rotor core 30 located radially inside the permanent magnets 104 and 105 is connected to the permanent magnets 104 and 105 (more accurately, the fixing portion 30e).

[0130] Figure 22 3 is a diagram schematically illustrating the function of the throttle portion 39 under light load. Since the rotor core 30 is formed to have a relatively large fourth gap G4 on the radially inner side relative to the permanent magnets 104 and 105, the magnetic flux emitted from the radially outer surfaces 104a and 105a of the permanent magnets 104 and 105 in contact with the rotor core 30 is as follows: Figure 22 As shown by the “×” symbol in (a), it is difficult to pass through the fourth gap G4. Figure 22 As shown in (b), the magnet magnetic flux is concentrated on the throttle portion 39 that blocks the fourth gap G4 and connects the rotor core 30 and the permanent magnets 104 and 105.

[0131] However, since the throttle portion 39 is formed to be elongated, for example, under light load, such as Figure 22 As shown by the cross-sectional line in (c), magnetic saturation is reached immediately, and the magnetic permeability becomes very small and reaches a value close to a vacuum (gap). As a result, the radially inner surfaces 104b and 105b of the permanent magnets 104 and 105 are in the same state as when they are completely covered by the fourth gap G4. Therefore, when the load is light (for example, when there is no load), the magnetic saturation of the throttle portion 39 is achieved, as shown in FIG. Figure 20 As shown by the dotted line, the magnet flux (magnetic linkage flux) at the time of maximum torque (Beta=50(deg)) can be suppressed.

[0132] Figure 23 This is a diagram schematically illustrating the function of the throttle unit 39 at high load. As described above, the current advance angle control Field weakening control, so the magnetic flux of the permanent magnets 104, 105 generated by the advance angle control of the current is as follows Figure 23 As shown in (a), the magnetic flux component SF that opposes the magnetic flux of the permanent magnets 104 and 105 generated by the stator coil 93 is suppressed.

[0133] As a result, it can be said that the flux component SF is used to guide the throttle portion 39 in the flux blocking state, such as Figure 23As shown in (b), since the magnetic saturation of the throttle portion 39 is eliminated, the magnetic flux of the permanent magnets 104 and 105, which is limited by magnetic saturation, can be effectively used to generate torque. That is, under high load (for example, under maximum torque), even if the magnetic flux of the entire motor is weakened by the stator coil current through advance angle control, by eliminating the magnetic saturation of the throttle portion 39, as shown in FIG. Figure 20 As shown, the magnet flux (magnetic linkage flux) can also be ensured at the time of maximum torque (Beta=50 (deg)).

[0134] <<Effects of the structures of (1), (2), and (4)>> Figure 24 Schematically shows the efficiency characteristics and iron loss comparison diagram of this embodiment and the conventional rotor structure. Figure 24 (a) is an efficiency characteristic diagram of the synchronous motor 1 according to this embodiment, Figure 24 (b) is an efficiency characteristic diagram of a conventional synchronous motor that does not employ the first gap G1, the protruding portions 61, 62, the asymmetric structure, and the throttle portion 39. Figure 24 (c) is a comparison diagram of the iron losses of the two rotor structures.

[0135] In the synchronous motor 1 of this embodiment, the high harmonic components of the magnetic flux are suppressed, and the magnet magnetic flux is suppressed at light load (for example, no load), while at high load (maximum torque) high torque can be obtained even with advance angle control. Figure 24 As shown in (a), the motor efficiency at the highest rotation point can be increased to 91.6 (%). On the other hand, in the conventional synchronous motor, even under the same control, as shown in Figure 24 As shown in (b), the motor efficiency at the highest rotation point is only 86.9% (%). If this is converted into iron loss, it is as follows Figure 24 As shown in (c), it was confirmed that the synchronous motor 1 of the present embodiment has a reduced iron loss (loss) by 47 (%) compared to the conventional synchronous motor.

[0136] As described above, in the synchronous motor 1 of this embodiment, not only the first gap G1, the protruding portions 61 and 62, and the asymmetric structure are adopted, but also the throttle portion 39 is additionally formed. This simple structure makes it possible to further reliably achieve higher efficiency of the synchronous motor 1 both under light load and high load conditions.

[0137] <(5) Oil circuit> Figure 25 is a diagram schematically showing the oil path in the rotor 10. Figure 261 and 2 are cross-sectional views and perspective views schematically illustrating the oil flow in the rotor 10. In the synchronous motor 1 of this embodiment, as described above, the increase in iron loss (dissipation) is suppressed, thereby reducing the amount of heat generated inside the motor even when the synchronous motor 1 is miniaturized. However, when the current density is increased, the amount of heat generated by the permanent magnets 101, 102, 103, and 106 near the stator 90 may increase, potentially exceeding the reduction in heat generated by suppressing the increase in iron loss.

[0138] Therefore, in the rotor structure of this embodiment, the magnet holes 31, 33, and 36 are used as oil passages for cooling oil to flow. The structure that can realize such oil passages will be described below.

[0139] like Figure 25 As shown, the interior of the first end plate 40 includes: an annular cavity 41 concentric with the axis AC; a connecting flow path 43 connecting the oil inlet path 20a of the rotor shaft 20 to the cavity 41; and radial oil paths 45, whose radially inner ends communicate with the cavity 41 and extend radially outward. The radially outer ends of the radial oil paths 45 communicate with the second gap G2, the portion of the magnet hole 33 not filled with the permanent magnet 103 (gap) 33b, and the portion of the magnet hole 36 not filled with the permanent magnet 106 (gap) 36a.

[0140] By forming the cavity space 41 and the connecting flow path 43 in the first end plate 40, the cooling oil sent from the oil introduction path 20a of the rotor shaft 20 is Figure 26 As shown by the mark OF 1 in (b), the cavity space 41 is filled.

[0141] Furthermore, by forming the radial oil passage 45 inside the first end plate 40, the cooling oil filled in the chamber space 41 is distributed to the second gap G2 and the gaps 33b and 36a through the radial oil passage 45. Figure 26 As shown by OF2 in (b), the cooling oil flows through the second gap G2 and the gaps 33b and 36a (see Figure 26 (a) The blackened portion of the rotor core 30 flows from the opposite-to-output-shaft side AOS to the output-shaft side OS. This allows the cooling oil temporarily filling the cavity space 41 to be transported to the second gap G2 and the gaps 33b and 36a, thereby evenly distributing the oil to the second gap G2 and the gaps 33b and 36a.

[0142] As described above, by using the magnet holes 31, 33, 36 as the oil path for the cooling oil to flow, Figure 26As shown in FIG. 1 , the permanent magnets 101, 102, 103, and 106 inserted into the magnet holes 31, 33, and 36 can be directly cooled. This direct cooling of the permanent magnets 101, 102, 103, and 106 with cooling oil, combined with the reduction in heat generation within the synchronous motor 1 due to the increased efficiency of the synchronous motor 1, can more reliably suppress demagnetization of the permanent magnets 101, 102, and so on when the synchronous motor 1 is miniaturized, and can also increase the current density of the current flowing through the stator coil 93.

[0143] Should be explained, such as Figure 25 As shown, a first oil diffusion passage 47 can be formed inside the first end plate 40. The first oil diffusion passage 47 is connected to the chamber space 41 at its radially inner end, extends radially outward, and opens on the outer peripheral surface of the first end plate 40. By forming such a first oil diffusion passage 47, as shown in FIG. Figure 26 As shown by OF3 in (b), a portion of the cooling oil filling the cavity space 41 can flow through the first diffuser oil passage 47 and, due to the action of centrifugal force, be dispersed radially outward from the outer peripheral surface of the first end plate 40. Furthermore, since the first end plate 40 is arranged so as to overlap with the coil end 93a on the opposite side AOS of the output shaft when viewed in the radial direction, not only the interior of the rotor core 30 but also the coil end 93a can be cooled.

[0144] Furthermore, if Figure 25 As shown, a second diffusion oil passage 51 may be formed inside the second end plate 50. The radially inner end of the second diffusion oil passage 51 is connected to the second gap G2 and the gaps 33b and 36a, extends radially outward in a radial shape, and opens on the outer peripheral surface of the second end plate 50. By forming such a second diffusion oil passage 51, as shown in FIG. Figure 26 As shown by OF4 in (b), cooling oil after cooling the permanent magnets 101, 102, ... can flow through the second oil diffusion passage 51 and, due to the centrifugal force, be dispersed radially outward from the outer peripheral surface of the second end plate 50. Furthermore, since the second end plate 50 is arranged so as to overlap with the coil end 93b on the output shaft side OS when viewed in the radial direction, the coil end 93b can also be cooled.

[0145] It should be noted that since the rotor core 30 is a laminated body formed by laminating magnetic thin plates, it is also conceivable that the oil flowing in the axial direction inside the rotor core 30 may leak into the gaps between the magnetic thin plates. In this case, although it is conceivable that the leaked oil will be trapped by the first end plate 40 and the second end plate 50 and cannot escape, if Figure 1 As shown, by forming the discharge recesses 49 , 53 in the first and second end plates 40 , 50 , the oil that flows through the discharge recesses 49 , 53 and leaks into the gaps between the magnetic thin plates can be discharged to the outside of the rotor core 30 .

[0146] In addition, these chamber spaces 41, connecting flow paths 43, radial oil paths 45, first diffuser oil paths 47 and second diffuser oil paths 51 can be formed using, for example, a casting sand mold, or can be formed as follows: they are respectively composed of a plurality of plates (not shown) that divide the first and second end plates 40 and 50 in the axial direction, and grooves that become part of the oil paths are provided on the surface and back surface of each plate, and these grooves are combined in the axial direction to form them.

[0147] (Other embodiments) The present invention is not limited to the above-described embodiments, and can be implemented in various other forms without departing from the spirit or main characteristics thereof.

[0148] In the above embodiment, (1) the first gap G1 and the protrusions 61, 62, (2) the asymmetric structure, (3) the center bridgeless structure, (4) the throttling portion 39, and (5) the oil circuit are combined to form a rotor structure. However, as long as it includes at least (1) the first gap G1 and the protrusions 61, 62, it is not limited to this. For example, it can be: a rotor structure having only (1) the first gap G1 and the protrusions 61, 62; a rotor structure formed by combining (1) the first gap G1 and the protrusions 61, 62 with (2) the asymmetric structure; a rotor structure formed by combining (1) the first gap G1 and the protrusions 61, 62 with (4) the throttling portion 39; a rotor structure formed by combining (1) the first gap G1 and the protrusions 61, 62, (2) the asymmetric structure and (5) the oil circuit, etc.

[0149] In addition, in the above embodiment, the eight magnetic poles MP1, MP2,... are composed of a double-layer structure including an outer embedded magnet portion 100A including two permanent magnets 101 and 102 arranged in a V shape, and an inner embedded magnet portion 100B including four permanent magnets 103, 104, 105, and 106 arranged in a U shape, but the structure of the magnetic poles and the number of magnetic poles are not limited to this.

[0150] For example, if (3) the center bridgeless structure or (4) the throttle portion 39 is not used, it can be as follows Figure 27 (a) shows a four-pole rotor 10A, each of which has a magnet portion 110A having a single-layer structure consisting of a permanent magnet substantially parallel to the circumferential direction; Figure 27 (b) shows an eight-pole rotor 10B, each of which has a magnet portion 110B having a single-layer structure consisting of a permanent magnet substantially parallel to the circumferential direction; Figure 27 (c) shows an eight-pole rotor 10C, each of which has a magnet portion 110C having a single-layer structure consisting of two permanent magnets arranged in a V shape. Figure 27 In the eight-pole rotor 10D shown in (d), each magnetic pole MP has a magnet portion 110D having a single-layer structure consisting of a single inverted arc-shaped permanent magnet.

[0151] In addition, for example, if (3) a center bridgeless structure or (4) a throttle portion 39 is adopted, it can be as follows Figure 28 (a) shows an eight-pole rotor 10E, each of which has a double-layer magnet portion 110E consisting of a set of permanent magnets substantially parallel to the circumferential direction and four permanent magnets arranged in a U shape inside the permanent magnets; it can also be as shown in FIG. Figure 28 (b) The eight-pole rotor 10F shown in FIG. 1 has a double-layer magnet portion 110F in which each magnetic pole MP is formed by two permanent magnets arranged in a V shape and two permanent magnets arranged in a V shape inside the two permanent magnets. Figure 28 (c) The eight-pole rotor 10G shown in FIG. 1 has a double-layer magnet portion 110G in which each magnetic pole MP is composed of two permanent magnets arranged in a V shape and four permanent magnets arranged in a U shape inside the V shape. Figure 28 In the eight-pole rotor 10H shown in (d), each magnetic pole MP has a double-layer magnet portion 110H composed of two inverted arc-shaped permanent magnets and four permanent magnets arranged in a U shape inside the two permanent magnets.

[0152] Furthermore, in the above embodiment, the first protruding portion 61 is formed by recessing the outer peripheral surfaces 32a and 32b of the rotor core 30 corresponding to both circumferential ends thereof toward the radial inside and relatively protruding toward the radial outside, but is not limited thereto. For example, Figure 29 As shown, a first protrusion 61" is formed, which absolutely (practically) protrudes radially outward from the outer peripheral surface 32 of the rotor core 30. In this case, although the effect of reducing the cogging torque is weakened, the magnetic salient polarity can be further emphasized.

[0153] In addition, in the above embodiment, the rotor core 30 is so-called non-skewed, but is not limited thereto. For example, Figure 30 As shown, the present invention is applied to a rotor core 30' having a skew angle θ. The rotor core 30' is composed of four stacked bodies 30A', 30B', 30C', and 30D', each of which is stacked axially at a predetermined number of magnetic thin plates, each staggered at a predetermined angle θ. This further reduces cogging torque.

[0154] Furthermore, in the above embodiment, the permanent magnets 101, 102, 103, 106 and the coil ends 93a, 93b are used as the cooling targets, but the present invention is not limited thereto. For example, other cooling means may be used for the coil ends 93a, 93b to cool only the permanent magnets 101, 102, 103, 106.

[0155] In the above embodiment, four permanent magnets 101 , 102 , 103 , 106 of the six permanent magnets 101 , 102 , 103 , 104 , 105 , 106 constituting each magnetic pole are cooled. However, the present invention is not limited thereto. For example, permanent magnets 104 , 105 may also be cooled.

[0156] Therefore, the above embodiments are merely illustrative in all respects and should not be construed as restrictive. Furthermore, all modifications and variations within the scope of the equivalents of the claims are intended to fall within the scope of the present invention.

[0157] The present disclosure is described based on embodiments, but it should be understood that the present disclosure is not limited to the embodiments and structures. The present disclosure also includes various modifications and variations within the scope of equality. In addition, various combinations or forms, further including only one element, more than one element, or less than one element, also fall within the scope and scope of the present disclosure. -Industrial Applicability-

[0158] According to the present invention, even when the synchronous motor is miniaturized, high efficiency and low vibration and low noise can be achieved, and therefore, the present invention is applicable to the rotor structure of the synchronous motor and is extremely beneficial.

Claims

1. A rotor structure of a synchronous motor in which the rotor rotates synchronously with a rotating magnetic field generated by a stator, characterized in that: The rotor includes: a cylindrical rotor core; and a plurality of permanent magnets embedded in the rotor core, constituting a plurality of magnetic poles arranged circumferentially in the rotor; A first protrusion is formed on the outer peripheral surface of the rotor core. When viewed in the axial direction, the first protrusion extends circumferentially across the adjacent magnetic poles and protrudes radially outward. A first gap extending in the circumferential direction when viewed in the axial direction is formed inside the first protruding portion, and a second protruding portion is formed that protrudes radially outward from a radially inner portion defining the first gap.

2. The rotor structure according to claim 1, characterized in that: The first protruding portion is formed so as to protrude relatively radially outward by recessing the outer peripheral surface of the rotor core corresponding to both circumferential ends thereof radially inward when viewed in the axial direction.

3. The rotor structure according to claim 1, characterized in that: The second protrusion protrudes obliquely with respect to the radial direction so as to be inclined at a predetermined angle in the circumferential direction as the second protrusion progresses radially outward.

4. The rotor structure according to claim 1, characterized in that: The second protrusion extends to a radially outer portion that defines the first gap, thereby partitioning the first gap in the circumferential direction.

5. The rotor structure according to claim 1, characterized in that: The permanent magnet is inserted into a magnet hole that penetrates the rotor core in the axial direction. When viewed in the axial direction, at least one of the position, shape, size and inclination of the permanent magnet in each magnetic pole and the position, shape, size and inclination of the magnet hole is set to be asymmetric between the circumferentially adjacent magnetic poles.

6. The rotor structure according to claim 5, characterized in that: The first protruding portion is formed such that, when viewed in the axial direction, the outer peripheral surface of the rotor core corresponding to both circumferential ends thereof is recessed radially inwardly so as to protrude relatively radially outwardly. The depths of the recesses at both circumferential end portions of the first protruding portion are set asymmetrically.

7. The rotor structure according to claim 5, characterized in that: The magnet holes serve as oil passages through which cooling oil flows.

8. The rotor structure according to claim 1, characterized in that: The permanent magnet is inserted into a magnet hole that penetrates the rotor core in the axial direction. Each of the magnetic poles includes two permanent magnets adjacent to each other in the circumferential direction in the magnet hole. A second gap is formed between the two adjacent permanent magnets.

9. The rotor structure according to claim 8, characterized in that: An end portion of the magnet hole into which the two permanent magnets are inserted is close to the outer peripheral surface of the rotor core, and a third gap at the end portion that is not filled by the permanent magnets is separated by a bridge.

10. The rotor structure according to claim 8, characterized in that: The magnet holes serve as oil passages through which cooling oil flows.

11. The rotor structure according to claim 9, characterized in that: When viewed in the axial direction, at least one of the position, shape, size and inclination of the permanent magnets in each magnetic pole is set to be asymmetric between the magnetic poles adjacent in the circumferential direction, The relative angle between the permanent magnet and the bridge portion is set to be asymmetrical between the magnetic poles adjacent to each other in the circumferential direction.

12. The rotor structure according to claim 1, characterized in that The permanent magnet is inserted into a magnet hole that penetrates the rotor core in the axial direction. Each of the magnetic poles includes an outer magnet hole formed at the outermost periphery of the rotor core and extending in the circumferential direction; and an inner magnet hole formed radially inwardly of the outer magnet hole and extending in the circumferential direction; the inner magnet hole is formed in such a shape that a radially outer surface of an inner permanent magnet inserted into the inner magnet hole contacts the rotor core, and a relatively large fourth gap is formed in a radially inner portion not buried by the inner permanent magnet. A slender throttling portion is formed on the rotor core, which, when viewed in the axial direction, separates the fourth gap in the circumferential direction and extends radially through the d-axis of each magnetic pole, so that the portion of the rotor core located radially inward relative to the inner permanent magnet is connected to the inner permanent magnet.

13. The rotor structure according to claim 12, characterized in that: The magnet holes serve as oil passages through which cooling oil flows.

14. The rotor structure according to claim 1, characterized in that The skew angle of the rotor core is 0 degree.

Images