JP3598625B2 - Synchronous rotating electric machine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a synchronous rotating electric machine, and more particularly to an improvement in the structure of a synchronous rotating electric machine that achieves a reduction in size and weight by improving its torque generation efficiency.
[0002]
[Prior art]
FIG. 4 shows a cutaway longitudinal sectional view of the synchronous rotating electric machine, and FIG. 5 shows a transverse sectional view thereof. In the figure, a cylindrical housing 1 has both openings closed by end frames 11 and 12, and a rotating shaft 2 is disposed at the center of the closed space. The rotating shaft 2 is rotatably supported at both ends by bearings provided at the centers of the end frames 11 and 12.
[0003]
A cylindrical rotor 3 formed by laminating electromagnetic steel plates is fixed to the center and outer periphery of the rotating shaft 2, and four plate-like permanent magnets 4 </ b> A to 4 </ b> D are provided inside the rotor 3 at equal intervals in the circumferential direction. It is buried. Each of the permanent magnets 4A to 4D is positioned so that the longitudinal direction of the cross section is directed to the circumferential direction of the rotor, and the outer peripheral surfaces are alternately different magnetic poles. At both ends of each of the permanent magnets 4A to 4D, there are formed through holes 41 which extend in a rectangular shape in the outer peripheral direction of the rotor 3 and limit the leakage magnetic flux. The rotor 3 is fixed to end plates 31 and 32 that are driven into the outer periphery of the rotating shaft 2 so as to be in contact with both end surfaces thereof by fastening through bolts.
[0004]
A ring-shaped stator 5 is fixed to the inner circumference of the housing 1 with a small gap from the outer circumference of the rotor 3. Three-phase stator coils 52 are provided in slots formed at equal intervals on the inner circumference of the stator core 51. It is wound by a known structure. When a three-phase alternating current of a predetermined frequency is supplied from the inverter circuit (not shown) to the stator coil 52, a rotating magnetic field is generated, and the rotor 3 (and the rotating shaft 2) rotates in synchronization with the rotating magnetic field.
[0005]
FIG. 6 shows the torque characteristics of the rotating electric machine having such a structure, in which the horizontal axis represents the phase angle (electric angle) δ of the stator current with respect to the main magnetic flux direction dm of the permanent magnet. Here, the total torque Tt of the rotating electric machine is the sum of the torque Tm due to the main magnetic flux and the reluctance torque Tr.
[0006]
[Problems to be solved by the invention]
As is apparent from the figure, the main magnetic flux torque Tm becomes maximum when the phase angle δ is 0 °, while the reluctance torque Tr becomes maximum when the phase angle δ is 45 °. δ becomes maximum around 30 °.
Therefore, in order to extract the maximum torque of the rotating electric machine, a rotation sensor such as a resolver or an encoder for accurately detecting the value of the phase angle δ is required, and relatively complicated control is required. In addition, there is a problem that the maximum value of the total torque Tt is smaller than the sum of the maximum value of the main magnetic flux torque Tm and the maximum value of the reluctance torque Tr.
[0007]
Incidentally, for example, JP-A-7-143694, although the reluctance torque to form a salient pole on the outer periphery of the rotor that has been shown that a possible change the phase angle δ having the maximum, according to this, the main Since the magnetic flux φ is greatly reduced, the generated torque may be reduced. An object of the present invention is to provide a synchronous rotating electric machine that can efficiently generate torque with low cost and simple control without changing the outer peripheral shape of a rotor.
[0008]
[Means for Solving the Problems]
In the invention described in claim 1, the rotor (3) in a part of the air gap (33 as an asymmetrical distribution of the magnetic resistance against the main flux axis (dm) of each pole (4A - 4D) ) Is provided. This gap Therefore, the phase angle of the reluctance torque indicates the maximum (theta) is changed. Therefore , by appropriately selecting the phase angle (δ) of the stator current with respect to the main magnetic flux direction axis, it is possible to obtain a large output torque as compared with the related art.
[0009]
In the invention described in claim 2, the gap (33) is formed with a plurality unevenly the rotor circumferential direction around the main flux direction axis (dm). By changing the uneven distribution of air gap may be reluctance torque to adjust the phase angle showing the maximum (theta). According to the third aspect of the present invention, each of the plurality of gaps (33) is formed to have a slot-like cross section along the direction of the main magnetic flux (φ) of each of the magnetic poles (4A to 4D). Since the long hole-shaped gap is formed along the main magnetic flux direction of the magnetic pole, it does not become a resistance of the main magnetic flux and does not weaken the main magnetic flux.
[0010]
According to the fourth aspect of the present invention, the phase angle (θ) formed by the axis (dr) in the direction in which the magnetic resistance is maximum with respect to the main magnetic flux direction axis (dm) is 45 ° in electrical angle. Distribute the voids (33). When the phase angle (θ) is set to 45 °, the reluctance torque (Tr) shows the maximum when the phase angle δ of the stator current is 0 ° as in the case of the main magnetic flux torque Tm, and the total torque Tt affects the magnitude of the stator current. Not done. Therefore, the maximum output torque can be obtained with simple and inexpensive control without requiring a highly accurate rotor position detection or a map of the stator current and the phase angle δ. According to a fifth aspect of the present invention, in the first aspect, the air gap (33) is provided only in the rotation direction of the rotor (3) from the main magnetic flux direction axis (dm).
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
FIG. 1 shows a cross-sectional view of the synchronous rotating electric machine. The structures of a rotor 3 and a stator located around the rotor 3 are the same as those of the conventional one described above, and the same parts are denoted by the same reference numerals. Hereinafter, only the differences from the related art will be described.
[0012]
In the figure, each of the plate-shaped permanent magnets 4A to 4D is buried at four positions in the circumferential direction at regular intervals with the longitudinal direction of the cross section facing the circumferential direction. Of these, the path of the main magnetic flux φ of the permanent magnets 4A to 4D is indicated by arrows. In the figure, dm is an axis passing through the center of the permanent magnet 4A and perpendicular thereto, and the direction along this dm axis is the main magnetic flux direction (direction with the highest magnetic flux density).
[0013]
In the illustrated rotor 3, an elongated hole-shaped opening to both end surfaces (a surface in a vertical direction of the paper) of the rotor 3 is provided in an outer peripheral region from the dm axis to the through hole 41 in the rotor rotation direction. A plurality of through gaps 33 are formed at intervals, and the longitudinal direction of these through gaps 33 is along the path of the main magnetic flux φ. These through gaps 33 are formed by punching long holes in each electromagnetic steel sheet constituting the rotor 3 with a press and stacking them. The width of the through gap 33 is preferably small so as not to weaken the main magnetic flux φ, and such a through gap 33 is similarly formed for the other permanent magnets 4B to 4D.
[0014]
The qm axis in the figure is the axis in the direction in which the magnetic flux density is minimum, and is the axis in the direction in which the electrical angle is 90 ° with respect to the dm axis. Since the rotating electric machine shown has four poles, the mechanical angle of the qm axis is 45 °. The dr axis is the axis in the direction in which the magnetic resistance is maximum, and qr is the axis in the direction in which the magnetic resistance is minimum.
Here, assuming that the phase angle of the stator current with respect to the dm axis, which has already been described in the related art, is δ, the main magnetic flux torque Tm is expressed by Expression 1.
[0015]
(Equation 1)
Tm = Pn (φa × Ia × cosδ)
Here, Pn is the number of pole pairs, φa = √3 / 2φ (φ is the amount of magnetic flux per pole), and Ia is the stator line current.
Further, the reluctance torque Tr is represented by Expression 2.
[0016]
(Equation 2)
Tr = Pn {1/2 (Lqr-Ldr) × Ia ² × sin2 (δ + θ)}
Here, Ldr is the inductance in the dr direction, and Lqr is the inductance in the qr direction.
The phase angle θ changes according to the change of the distribution of the through gaps 33. For example, if the through gap 33 is formed only in a region close to the through hole 41 away from the dm axis, the phase angle θ becomes small. Conversely, if the through gap 33 is formed in a wide region beyond the dm axis, the phase angle θ becomes large. Become. Therefore, if the formation area of the through gap 33 is changed so that the phase angle θ approaches 45 ° and the phase angle δ at each phase angle θ is appropriately selected, the same stator line current Ia will be larger than in the conventional case. The total torque Tt can be obtained.
[0017]
In particular, when the phase angle θ is 45 °, the reluctance torque Tr changes as shown in FIG. 2 with respect to the phase angle δ. In this case, like the main magnetic flux torque φ, when the phase angle δ is Indicates a value. Since the total torque Tt is the sum of the main magnetic flux torque Tm and the reluctance torque Tr, at δ = 0 (°), the total torque Tt becomes the sum of the maximum values of the two torques Tm and Tr. , The largest torque can be obtained.
[0018]
This means that if the same torque is obtained, the rotating electric machine can be reduced in size and weight. In addition, since the maximum torque is obtained at δ = 0 regardless of the value of the stator line current Ia, it is not necessary to create a map of the line currents Ia and δ for high-efficiency driving, so that the control is simple and Since an expensive rotation sensor such as an encoder or a resolver for accurately detecting the value of δ is not required, the cost can be reduced.
[0019]
Further, since the drive can be performed at δ = 0, the influence on the distribution of the main magnetic flux is minimized, and the distortion of the voltage waveform is small, so that the rotor position can be accurately detected in the sensorless drive. Also, no demagnetization due to the field weakening occurs.
In addition, the through gap 33 contributes to obtaining the maximum torque as described above, and also contributes to the reduction of the leakage magnetic flux φ1 (FIG. 1) because it passes across the through gap 33.
(2nd Embodiment)
In FIG. 3, permanent magnets 4 </ b> A to 4 </ b> D embedded at four locations at equal intervals in the circumferential direction in the rotor 2 have their cross-sectional longitudinal directions oriented in the radial direction of the rotor 2. The side surfaces of the permanent magnets 4A to 4D that are circumferentially opposed are magnetized to have the same polarity, and the main magnetic flux direction in this case is along the symmetry axis dm of the adjacent permanent magnets 4A to 4D. . In the present embodiment, a plurality of elongated through-holes 33 are formed in the rotor from the dm axis to the permanent magnet 4B in the rotor rotation direction, and the longitudinal direction of these through-holes 33 is indicated by an arrow. It is along the path of the main magnetic flux shown. Such a through gap is similarly formed in the other permanent magnets 4B to 4D.
[0020]
With such a structure, the same effect as in the first embodiment can be obtained.
(Other embodiments)
In the second embodiment, the gap 42 is provided around the rotary shaft 2 and the longitudinal ends of the permanent magnets 4A to 4D in order to reduce the leakage magnetic flux. An aluminum die-cast material is preferably poured into these gaps 42.
[0021]
At this time, if an aluminum die-cast material is poured into the through gap 33, the rotor strength is further improved. This is the same in the first embodiment.
In each of the above embodiments, the magnetic pole is formed by a permanent magnet, but may be formed by an electromagnetic coil.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a synchronous rotating electric machine according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating torque characteristics of the synchronous rotating electric machine according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view of a synchronous rotating electric machine according to a second embodiment of the present invention.
FIG. 4 is a cutaway longitudinal sectional view of a conventional synchronous rotating electric machine.
FIG. 5 is a cross-sectional view of the conventional synchronous rotating electric machine taken along line VV of FIG. 4;
FIG. 6 is a diagram illustrating torque characteristics of a conventional synchronous rotating electric machine.
[Explanation of symbols]
3 ... rotor, 33 ... through gap, 4A, 4B, 4C, 4D ... permanent magnet,
5 ... stator, dm ... main magnetic flux direction axis, dr ... axis in the direction in which the magnetic resistance shows the maximum,
θ: phase angle.

Claims (5)

A plurality of magnetic poles (4A to 4D) are buried and formed at intervals in the circumferential direction inside a rotor (3) formed of a steel plate, and follow the rotating magnetic field formed by the stator (5). in synchronous rotating electric machine for rotating a part of the rotor, wherein the distribution of the magnetoresistive main flux axis of the magnetic poles (4A - 4D) (dm) in pairs and such that the asymmetrical air gap (33) Wherein the phase angle (θ) at which the reluctance torque shows a maximum is changed . The gap (33) is synchronous rotary electric machine according to claim 1, characterized in that the central front Symbol main magnetic flux axis of the (dm) unevenly distributed to the rotor circumferential direction formed with a plurality. 3. The device according to claim 2, wherein each of the plurality of gaps is formed to have a slot-shaped cross section along a direction of a main magnetic flux of the magnetic poles. The synchronous rotating electric machine as described. The air gap (33) is distributed so that the phase angle (θ) formed by the axis (dr) in the direction in which the magnetic resistance is maximum with respect to the main magnetic flux direction axis (dm) is 45 ° in electrical angle. The synchronous rotating electric machine according to any one of claims 1 to 3, wherein the synchronous rotating electric machine (10) is driven. 2. The synchronous rotating electric machine according to claim 1, wherein the air gap is provided only in a rotation direction of the rotor with respect to the main magnetic flux direction axis. 3.

Images