Rotary electric machine

Abstract

Provided is a rotary electric machine that can improve performance as a generator and performance as a motor in a well-balanced manner. A starter generator 1 according to an embodiment comprises a stator 4 and a rotor 3. Each tooth 14 of the stator 4 comprises: a tooth body 15 around which a coil 12 is wound; and an umbrella portion 16 extending in the circumferential direction from an end in the radial direction of the tooth body 15. The rotor 3 has a plurality of magnetic poles. When m and n are two or more positive integers where m ≠ n, the quantity of teeth 14 is denoted by T, the number of magnetic poles is denoted by P, the angle between circumferential-direction centers of the teeth bodies 15 is denoted by θt, the angle between circumferential-direction centers of the magnetic poles is denoted by θp, and the angle between circumferential-direction centers of the umbrella portions 16 of the same phase is denoted by θk, the quantity T of the teeth 14, the number P of magnetic poles, and the angles θt, θp, and θk satisfy P = 2m, T = 3n, θt < θk < θp, and P < T, and at least two of the teeth 14 of the same phase are adjacent to each other in the circumferential direction.

Description

Rotating electric machines

[0001] The present invention relates to a rotating electric machine.

[0002] A rotating electric machine is known that is used as a motor for starting a vehicle engine and as a generator after the engine has started. This type of rotating electric machine includes a stator fixed to the vehicle body and wound with a coil, and a rotor (flywheel) fixed to the crankshaft and rotatable relative to the stator.

[0003] The stator includes a plurality of teeth arranged in a circumferential direction. The teeth have a tooth body extending radially and an umbrella portion extending circumferentially from the radially outer end of the tooth body. A coil is wound around the tooth body. The rotor includes a rotor yoke formed in a cylindrical shape with a bottom so as to cover the stator from the radial outside. A permanent magnet is provided on the inner peripheral surface of the rotor yoke. The permanent magnet has a plurality of magnetic poles arranged in order circumferentially.

[0004] With this configuration, when the rotating electric machine is used as a motor for starting an engine, current is selectively supplied to a specific coil. This generates magnetic flux in the teeth, and the rotor rotates due to magnetic attraction and repulsion forces generated between this magnetic flux and the permanent magnet of the rotor. When the rotating electric machine is used as a generator after starting the engine, the amount of magnetic flux in the permanent magnet changes as the rotor rotates. This change in magnetic flux becomes an electromotive force, generating current in the coil. The current generated in the coil can be stored in a battery or supplied to an attached electrical device, for example.

[0005] Various technologies have been proposed to improve the performance of rotating electrical machines. For example, a modified tooth shape has been proposed to increase the power output and efficiency of power generation (see, for example, Patent Document 1). In this design, the tooth bodies are arranged at equal intervals, and the angle between the circumferential centers of the umbrella portions (arrangement angle) is aligned with the angle between the circumferential centers of the magnetic poles (magnetic pole pitch angle). This configuration reduces the phase difference within the same phase, improving power generation efficiency.

[0006] Patent No. 6154637

[0007] However, in the above-mentioned conventional technology, the angle between the hoods of different phases differs from the angle between the hoods of the same phase, which causes a problem of reduced motor performance. Thus, there is a trade-off between improving the performance as a generator and improving the performance as a motor.

[0008] Therefore, the present invention provides a rotating electric machine that can improve the performance as a generator and the performance as a motor in a well-balanced manner.

[0009] In order to solve the above problems, in a first aspect of the present invention, a rotating electric machine includes a stator having a plurality of teeth, around which coils are wound, arranged side by side in the circumferential direction, and a rotor rotatably provided relative to the stator, wherein the teeth extend radially and have tooth bodies around which the coils are wound and umbrella portions extending circumferentially from radial ends of the tooth bodies, the rotor has a plurality of magnetic poles radially facing the umbrella portions and arranged side by side at equal intervals in the circumferential direction, and m and n are each a number equal to or greater than 2. When m is a positive integer and m≠n, the number of teeth is T, the number of magnetic poles of the magnetic poles is P, the angle between the circumferential centers of the tooth main body is θt, the angle between the circumferential centers of the magnetic poles is θp, and the angle between the circumferential centers of the umbrella portions of the same phase is θk, the number of teeth T, the number of magnetic poles P, the angle θt, the angle θp, and the angle θk satisfy P=2m, T=3n, θt<θk<θp, P<T, and at least two of the teeth of the same phase are adjacent to each other in the circumferential direction.

[0010] This configuration allows for a balanced improvement in both the performance as a generator and the performance as a motor. Furthermore, when the number of magnetic poles P and the number of teeth T satisfy the relationship P<T, the gap between adjacent umbrella portions of different phases can be minimized. As a result, it becomes possible to use the interlinkage magnetic flux of the coils and the magnetic flux of the magnetic poles as effectively as possible. This ensures an improvement in both the performance as a generator and the performance as a motor.

[0011] Incidentally, when used as a motor, it is particularly important to control energization at appropriate timing according to the rotor rotation speed, etc. In this case, if the number of magnetic poles P and the number of teeth T are set to satisfy P>T, even if the number of teeth T is the same as when P<T, the electrical cycle will change at a cycle of P / 2. If the control cycle becomes shorter in this way, it becomes difficult to maintain the desired energization timing. Therefore, by satisfying P<T as described above, it becomes possible to drive the motor with high precision.

[0012] In a second aspect of the present invention, in the rotating electric machine of the first aspect, n may be an even number.

[0013] This configuration allows for a balanced distribution of adjacent teeth of the same phase in the circumferential direction, thereby increasing the variety of combinations of the number of teeth and the number of magnetic poles.

[0014] In a third aspect of the present invention, in the rotating electric machine of the first or second aspect, the number of magnetic poles P may be 16 poles, the number of teeth T may be 18, and the angle θk may satisfy 20°<θk<22.5°.

[0015] By configuring it in this way, it is possible to provide a rotating electric machine that is optimal for improving the performance as a generator and the performance as a motor in a balanced manner.

[0016] According to the present invention, the performance of a rotating electrical machine as a generator and the performance of a motor can be improved in a well-balanced manner.

[0017] Fig. 2 is a cross-sectional view of a starter-generator according to an embodiment of the present invention; Fig. 3 is a schematic configuration diagram of a starter-generator according to an embodiment of the present invention as seen from the axial direction; Fig. 4 is an enlarged view of part III of Fig. 2; Fig. 5 is a graph showing a change in induced voltage according to an embodiment of the present invention, where the pitch angle of the head portion is changed and each pitch angle is compared; Fig. 6 is a graph showing a change in torque according to an embodiment of the present invention, where the pitch angle of the head portion is changed and each pitch angle is compared.

[0018] Next, an embodiment of the present invention will be described with reference to the drawings.

[0019] <Starter-generator> Figure 1 is a cross-sectional view of a starter-generator 1. As shown in Figure 1, the starter-generator 1 is an outer rotor type rotating electric machine used in, for example, a motorcycle 100. The starter-generator 1 integrates a generator function with a starter motor function (engine starting function). The starter-generator 1 includes a rotor 3 fixed to a crankshaft 2 of an engine (not shown), and a stator 4 arranged coaxially with the rotor 3 and aligned in the direction of a rotation axis A of the rotor 3. In the following description, the direction parallel to the rotation axis A will be referred to as the axial direction.

[0020] <Rotor> The rotor 3 includes a rotor yoke 5 fixed to the crankshaft 2 via an attachment 10. The rotor yoke 5 is formed into a cylindrical shape with a bottom by, for example, pressing a metal plate made of a magnetic material. That is, the rotor yoke 5 includes a disk-shaped bottom wall 6 and a cylindrical peripheral wall 7 that rises from the periphery of the bottom wall 6 toward the stator 4. A permanent magnet 8 having a plurality of magnetic poles is provided on the inner circumferential surface 7a of the peripheral wall 7 over the entire circumference.

[0021] The permanent magnet 8 has, for example, 16 magnetic poles. The multiple magnetic poles of the permanent magnet 8 are arranged at equal intervals in the circumferential direction. The permanent magnet 8 may be formed in a cylindrical shape, or multiple tile-shaped permanent magnets 8 may be arranged side by side in the circumferential direction. For example, a ferrite magnet is used as the permanent magnet 8. However, this is not limited to this, and various materials can be used. For example, a rare earth magnet can be used instead of the ferrite magnet.

[0022] <Stator> Fig. 2 is a schematic diagram of the starter-generator 1 as viewed from the axial direction. In Fig. 2, the permanent magnets 8 are shown divided into individual poles to make the magnetic poles of the permanent magnets 8 easier to understand. As shown in Figs. 1 and 2, the stator 4 is fixed to a vehicle body 101 such as an engine block. The stator 4 is disposed so as to be housed within the rotor yoke 5. The stator 4 includes a stator core 11 fixed to the vehicle body 101 and a coil 12 wound around the stator core 11.

[0023] The stator core 11 is formed by laminating a plurality of plate materials, such as electromagnetic steel sheets, in the axial direction. The stator core 11 is integrally formed with an annular core body 13 and a plurality of teeth 14 that protrude radially outward from the outer circumferential surface of the core body 13. The number of teeth 14 is, for example, 18.

[0024] In the starter-generator 1 of this embodiment, the number of teeth 14 is T, the number of magnetic poles of the permanent magnet 8 is P, m and n are positive integers of 2 or greater, and m≠n, and the number T of the teeth 14 and the number P of the magnetic poles satisfy the following: P=2m (1) T=3n (2) P<T (3) In this embodiment, the number P of magnetic poles is 16. The number T of the teeth 14 is 18. In other words, since m=8 and n=6, m and n are integers of 2 or greater, and m≠n, and the above formulas (1), (2), and (3) are satisfied.

[0025] Each of the teeth 14 is integrally formed with a tooth body 15 extending in the radial direction and an umbrella portion 16 extending in the circumferential direction from the radially outer end of the tooth body 15. The tooth bodies 15 are arranged at equal intervals in the circumferential direction.

[0026] An insulating insulator 17 is attached to the tooth body 15. The coil 12 is wound around the tooth body 15 from above the insulator 17. The coil 12 and the plurality of teeth 14 are configured in three phases (U phase, V phase, and W phase). In this embodiment, there are 18 teeth 14, so there are six teeth 14 of the same phase. The plurality of teeth 14 are arranged so that three teeth 14 of the same phase are lined up in the circumferential direction.

[0027] 2 shows a state in which the coils 12 (teeth 14) are arranged in the direction of the arrow CCW in the order of U-phase, V-phase, and W-phase. In FIG. 2, the U-phase coils 12 are assigned symbols U1 to U6 in the circumferential direction. The V-phase coils 12 are assigned symbols V1 to V6 in the circumferential direction. The EW-phase coils 12 are assigned symbols W1 to W6 in the circumferential direction.

[0028] Fig. 3 is an enlarged view of part III in Fig. 2. As shown in Fig. 2 and Fig. 3, for teeth 14 of the same phase, the angle between the circumferential centers of the umbrella portions 16 (hereinafter referred to as the pitch angle of the umbrella portions 16) is different from the angle between the circumferential centers of the tooth main bodies 15 (hereinafter referred to as the pitch angle of the tooth main bodies 15). In other words, when the pitch angle of the umbrella portions 16 is θk, the pitch angle of the tooth main bodies 15 is θt, and the angle between the circumferential centers of the magnetic poles (hereinafter referred to as the pitch angle of the magnetic poles) is θp, the angles θk, θt, θp for the teeth 14 of the same phase satisfy the following relationship: θt<θk<θp (4)

[0029] In this embodiment, the number T of teeth 14 is 18, and the tooth bodies 15 are arranged at equal intervals in the circumferential direction. Therefore, the pitch angle θt of the tooth bodies 15 is 20°. Since the number P of magnetic poles is 16, the pitch angle θp of the magnetic poles is 22.5°. Therefore, the above formula (3) becomes: 20°<θk<22.5° (5). The circumferential lengths of the umbrella portions 16 are not the same, but are set to satisfy the above formulas (4) and (5). For example, in this embodiment, for three circumferentially adjacent teeth 14 of the same phase, the circumferential lengths of the umbrella portions 16 of the two teeth 14 on both sides in the circumferential direction are shorter than the circumferential length of the umbrella portion 16 of the circumferentially central tooth 14.

[0030] <Operation and Function of Starter-Generator> Next, the operation and function of the starter-generator 1 will be described. First, a case where the starter-generator 1 is used as a generator will be described. When the engine of the motorcycle 100 is started, the crankshaft 2 rotates. The rotor 3 rotates integrally with the crankshaft 2. This causes a change in the amount of magnetic flux of the permanent magnet 8 with respect to the coil 12 wound around the stator 4. The magnetic flux of the permanent magnet 8 flows to the tooth body 15 via the umbrella portion 16 of the stator core 11. The change in the amount of magnetic flux of the permanent magnet 8 becomes an electromotive force, generating a current in the coil 12. The current generated in the coil 12 may be stored in a battery (not shown) or supplied to an attached electrical device (not shown), for example.

[0031] Next, a case where the starter-generator 1 is used as a starter motor will be described. In this case, current is selectively supplied to predetermined coils 12 from a power source such as a battery via a control unit (neither of which is shown). In this case, a magnetic flux linkage is formed in each tooth 14 of the stator 4. This magnetic flux linkage forms a magnetic field loop via the umbrella portion 16 of the stator core 11. Magnetic attractive and repulsive forces are generated between the magnetic flux linkage and the permanent magnets 8 of the rotor yoke 5, causing the rotor 3 to continuously rotate. The crankshaft 2 rotates integrally with the rotor 3.

[0032] Next, the effect of the position of the umbrella portion 16 will be described. Fig. 4 is a graph showing the change in induced voltage, with the vertical axis representing the induced voltage [V] generated in the coil 12 and the horizontal axis representing the rotation angle [°] of the rotor 3. The pitch angle θk of the umbrella portion 16 is changed and compared for each pitch angle θk. As shown in Fig. 4, it can be seen that the induced voltage increases as the pitch angle θk of the umbrella portion 16 approaches the magnetic pole pitch angle θp (22.5°). It can be seen that when the pitch angle θk of the umbrella portion 16 is greater than the pitch angle θt (20°) of the tooth body 15, the magnitude of the induced voltage falls within a similar range.

[0033] 5 is a graph showing changes in torque when the vertical axis represents the torque [Nm] of the starter-generator 1 and the horizontal axis represents the circumferential width of the umbrella portion 16. The pitch angle θk of the umbrella portion 16 is changed and compared. As shown in FIG. 5, when the pitch angle θk of the umbrella portion 16 is within the range defined by equation (5), torque performance is improved compared to when the pitch angle θk is outside the range defined by equation (5). When the pitch angle θk of the umbrella portion 16 is the same as the pitch angle θp (22.5°) of the magnetic pole or the pitch angle θt (20°) of the tooth body 15, torque performance is reduced.

[0034] Therefore, according to the above-described embodiment, in a starter-generator 1 in which m and n are integers of 2 or greater and m≠n, and which satisfies the above formulas (1), (2), and (3) and has teeth 14 of the same phase that are adjacent in the circumferential direction, by satisfying the above formula (4), it is possible to improve both the performance as a generator and the performance as a motor in a balanced manner.

[0035] By satisfying the above formula (3), the distance between adjacent opposite-phase umbrella portions 16 can be minimized. As a result, it is possible to use the interlinkage magnetic flux of the coils 12 and the magnetic flux of the permanent magnets 8 as effectively as possible. This ensures that the performance of the starter-generator 1 as both a generator and a motor can be improved.

[0036] In particular, when the starter-generator 1 is used as a motor, it is particularly important to control the energization timing appropriately according to the rotation speed of the rotor 3, etc. In this case, if the number of magnetic poles P and the number of teeth 14 T are set to P>T, even if the number of teeth 14 T is the same as the number of teeth 14 T in this embodiment, the number of teeth 14 will change electrically with a period of P / 2. If the control period becomes shorter in this way, it becomes difficult to maintain the desired energization timing. Therefore, by satisfying the above formula (3), it is possible to drive the motor with high precision.

[0037] In particular, when the number of magnetic poles P is set to 16 and the number of teeth 14 is set to 18 as in the above-described embodiment, a starter generator 1 can be provided that is optimal for improving the performance as a generator and the performance as a motor in a balanced manner.

[0038] Since it is possible to improve both the performance of the starter generator 1 as a generator and as a motor, it will be possible to contribute to Goal 7 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Ensure access to affordable, reliable, sustainable and modern energy for all," and Goal 9, which is to "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0039] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention.

[0040] For example, in the above embodiment, the starter-generator 1 is an outer rotor type rotating electric machine used in the motorcycle 100. However, the invention is not limited to this, and the starter-generator 1 can be used in various devices that require both the functions of a generator and a motor. Even when the starter-generator 1 is an inner rotor type rotating electric machine, the same configuration of teeth 14 as that of the outer rotor type rotating electric machine described above can be employed.

[0041] In the above embodiment, the number of magnetic poles P of the starter-generator 1 is 16. The number of teeth 14 T is 18. However, this is not limited to this, and it is sufficient that m and n are positive integers of 2 or more, m≠n, and the number of magnetic poles P and the number of teeth 14 T satisfy the above formulas (1) and (2). It is sufficient that at least two teeth 14 of the same phase are adjacent to each other in the circumferential direction.

[0042] It is preferable that n is an even number. With this configuration, it is possible to distribute the teeth 14 of the same phase that are adjacent in the circumferential direction in a balanced manner. This increases the variety of combinations of the number of teeth 14 and the number of magnetic poles. This reliably improves the performance of the starter-generator 1 as both a generator and a motor in a balanced manner.

[0043] DESCRIPTION OF SYMBOLS 1...Starter generator (rotating electric machine), 2...Crankshaft, 3...Rotor, 4...Stator, 5...Rotor yoke, 6...Bottom wall, 7...Circumferential wall, 7a...Inner peripheral surface, 8...Permanent magnet, 10...Attachment, 11...Stator core, 12...Coil, 13...Core body, 14...Teeth, 15...Teeth body, 16...Umbrella portion, 17...Insulator, 100...Motorcycle, 101...Vehicle body, A...Axis of rotation, P...Number of magnetic poles, T...Number of teeth, θk...Angle between centers in the circumferential direction of the umbrella portion, θp...Angle between centers in the circumferential direction of the magnetic poles, θt...Angle between centers in the circumferential direction of the tooth body

Claims

1. A rotor comprising a stator having a plurality of teeth arranged in a circumferential direction, around which coils are wound; and a rotor rotatable relative to the stator, wherein the teeth extend radially and have tooth bodies around which the coils are wound; and umbrella portions extending circumferentially from radial ends of the tooth bodies, and the rotor has a plurality of magnetic poles radially facing the umbrella portions and arranged in a circumferentially equally spaced manner, wherein m and n are positive integers of 2 or more, and m≠n, the number of teeth is T, the number of magnetic poles is P, the angle between the circumferential centers of the tooth bodies is θt, the angle between the circumferential centers of the magnetic poles is θp, and the angle between the circumferential centers of the umbrella portions of the same phase is θk, then the number of teeth T, the number of magnetic poles P, the angle θt, the angle θp, and the angle θk satisfy the following conditions: P=2m, T=3n, θt<θk<θp, P<T and at least two of the teeth of the same phase are adjacent to each other in the circumferential direction.

2. The rotating electric machine according to claim 1, wherein n is an even number.

3. A rotating electric machine according to claim 1 or 2, characterized in that the number of magnetic poles P is 16, the number of teeth T is 18, and the angle θk satisfies 20°<θk<22.5°.

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