JP6925304B2 - Rotating machine - Google Patents

Description

The present invention relates to a rotary electric machine including a rotor and a stator.

In a rotary electric machine, when a voltage is generated on the rotating shaft due to fluctuations in the neutral point potential of the winding, the voltage generated on the rotating shaft is applied to the bearing supporting the rotor. When the voltage applied to the bearing exceeds the dielectric breakdown voltage of the bearing lubricating oil, the bearing surface generates heat locally due to the electric discharge, and an electrolytic corrosion phenomenon occurs in which melting marks are generated.

In recent years, rotary electric machines have come to be driven by a high-frequency inverter, and fluctuations in the neutral point fundamental wave voltage due to the modulation method of the inverter are increasing. Further, the rectangular wavy voltage due to the switching of the inverter is superimposed in a short cycle, and the crest value becomes high. In the inverter-controlled rotary electric machine, the number of discharges is increasing due to the increase in the fluctuation of the neutral point fundamental wave voltage and the increase in the peak value, and electrolytic corrosion progresses in a short period of time to generate abnormal vibration noise. In some cases.

Patent Document 1 provides a cancel coil in which a coil is wound together with an annular yoke of a stator and a magnetic core attached to the annular yoke to form a closed circuit, and an unbalanced magnetic flux flowing in the annular yoke in the circumferential direction. A method has been proposed in which a current that hinders an unbalanced magnetic flux is passed through the cancel coil by inducing a third-order voltage through the cancel coil to reduce the axial voltage and suppress electrolytic corrosion of the bearing.

JP-A-2018-26894

However, the invention disclosed in Patent Document 1 is complicated in structure and processing because it is necessary to connect three element coils in series in one closed circuit in order to minimize the influence on the rotational torque. Become. On the other hand, if the circuit is closed with only one element coil, the effective magnetic flux that generates rotational torque is reduced.

The present invention has been made in view of the above, and it is desired to obtain a rotary electric machine which does not complicate the structure and processing, reduces the shaft voltage without affecting the effective magnetic flux, and suppresses bearing electrolytic corrosion. The purpose.

In order to solve the above-mentioned problems and achieve the object, the present invention comprises a cylindrically formed stator, a rotor arranged inside the stator, and a rotation shaft fixed to the rotor. The first and second bearings that rotatably support the rotating shaft, the outer shell that supports the stator, the first bearing, and the second bearing, one end is connected to the first bearing, and the other end is connected to the second bearing. It has a canceled line. The stator includes a stator core having an annular yoke and a plurality of teeth protruding in the radial direction from the inner peripheral surface of the yoke, and an armature winding wound around the stator core via an insulator. Has. The cancel line penetrates the inner circumference of the yoke.

According to the present invention, it is possible to obtain a rotary electric machine in which the shaft voltage is reduced without affecting the effective magnetic flux and the bearing electrolytic corrosion is suppressed without complicating the structure and processing.

Longitudinal sectional view of the rotary electric machine according to the first embodiment of the present invention. Cross-sectional view of the rotary electric machine according to the first embodiment Perspective view of the stator of the rotary electric machine according to the first embodiment. Wiring diagram of the inverter of the rotary electric machine and the armature winding according to the first embodiment The figure which shows the phase voltage which superposed the voltage of 3 times the frequency of the rotary electric machine which concerns on Embodiment 1, the interphase voltage, and the fundamental wave waveform of a neutral point voltage. The figure which shows the example of the neutral point voltage waveform and the bearing voltage waveform of the rotary electric machine which concerns on Embodiment 1. Cross-sectional view of the rotary electric machine according to the second embodiment of the present invention. Cross-sectional view of the rotary electric machine according to the third embodiment of the present invention. Cross-sectional view of the rotary electric machine according to the fourth embodiment of the present invention. Perspective view of the stator of the rotary electric machine according to the fourth embodiment.

Hereinafter, the rotary electric machine according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a vertical sectional view of a rotary electric machine according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the rotary electric machine according to the first embodiment. FIG. 2 shows a cross section along the line II-II in FIG. FIG. 3 is a perspective view of the stator of the rotary electric machine according to the first embodiment. The rotary electric machine 10 rotates with a stator 11 formed in a cylindrical shape, a cylindrical rotor 12 arranged inside the stator 11 via a gap, and a rotating shaft 13 fixed to the rotor 12. It includes a first bearing 14 and a second bearing 15 that rotatably support the shaft 13. Further, the rotary electric machine 10 includes an outer shell 16 that supports the stator 11, the first bearing 14, and the second bearing 15.

In the first bearing 14, the inner ring 14n is rotatably supported inside the outer ring 14g via a rolling element 14t, and the outer ring 14g is held by the bearing box 16f. In the second bearing 15, the inner ring 15n is rotatably supported inside the outer ring 15g via a rolling element 15t, and the outer ring 15g is held by the bearing box 16r. The rolling elements 14t are held at regular intervals by a cage (not shown). Smooth rotation is possible by rolling the rolling element 14t through the grooves provided in the outer ring 14g and the inner ring 14n. The rolling elements 15t are held at regular intervals by a cage (not shown). Smooth rotation is possible by rolling the rolling element 15t through the grooves provided in the outer ring 15g and the inner ring 15n. Lubricating oil such as grease is contained between the outer ring 14g, the rolling element 14t, the cage, and the inner ring 14n to form a thin oil film on the rolling surface to prevent the metal from coming into direct contact with the metal and wearing. ing. Lubricating oil such as grease is contained between the outer ring 15g, the rolling element 15t, the cage, and the inner ring 15n to form a thin oil film on the rolling surface to prevent the metal from coming into direct contact with the metal and wearing. ing.

The stator 11 includes a stator core 19 composed of an annular yoke 17 and a plurality of teeth 181, 182, 183, 184, 185, 186 protruding in the radial direction from the inner peripheral surface of the yoke 17, and an armature winding 20. And have. Hereinafter, the entire teeth 181, 182, 183, 184, 185, 186 are referred to as teeth 18. The stator core 19 is made of a magnetic material having high magnetic permeability. The yoke 17 includes yoke portions 171, 172, 173, 174, 175, and 176. The teeth 18 project from the yoke 17 toward the rotor 12. The teeth 181 and the teeth 182 are connected by a yoke portion 171. The teeth 182 and the teeth 183 are connected by a yoke portion 172. The teeth 183 and the teeth 184 are connected by a yoke portion 173. The teeth 184 and the teeth 185 are connected by a yoke portion 174. The teeth 185 and the teeth 186 are connected by a yoke portion 175. The teeth 186 and the teeth 181 are connected by a yoke portion 176. The armature winding 20 is wound around the teeth 18 via an insulator (not shown).

The stator core 19 is provided with a slot 21 surrounded by a yoke 17 and a teeth 18 for passing the armature winding 20.

An armature winding 20 composed of six coils of U1, V1, W1, U2, V2, and W2 is wound around the teeth 18, and a canceling wire penetrates through the same slot 21 as the armature winding 20. 22 is provided. The cancel wire 22 has one end 22a electrically connected to the outer ring 14g of the first bearing 14 and the other end 22b electrically connected to the outer ring 15g of the second bearing 15.

FIG. 4 is a wiring diagram of the inverter of the rotary electric machine and the armature winding according to the first embodiment. In the U phase, two coils U1 and U2 are connected in series. In the V phase, two coils V1 and V2 are connected in series. In the W phase, two coils W1 and W2 are connected in series. The U1 side of the U phase, the V1 side of the V phase, and the W1 side of the W phase are connected to the inverter 30. The U2 side of the U phase, the V2 side of the V phase, and the W2 side of the W phase are joined to each other to form a neutral point N, and the U phase, the V phase, and the W phase are Y-connected.

The inverter 30 includes six switching elements 31, 32, 33, 34, 35, 36 forming an arm. The switching element 31 forming the upper arm and the switching element 34 forming the lower arm are connected in series to form the first leg. The switching element 32 forming the upper arm and the switching element 35 forming the lower arm are connected in series to form the second leg. The switching element 33 forming the upper arm and the switching element 36 forming the lower arm are connected in series to form a third leg. The first leg, the second leg, and the third leg are connected in parallel to the DC power supply 40. The output terminal R comes out from the first leg and is connected to the U phase of the rotary electric machine 10. The output terminal S comes out from the second leg and is connected to the V phase of the rotary electric machine 10. The output terminal T comes out from the third leg and is connected to the W phase of the rotary electric machine 10.

The DC power supply 40 can be obtained by rectifying an AC power supply with a rectifying element and then smoothing it with a capacitor if it is an AC power supply such as a commercial power supply. The DC power supply 40 can be obtained directly from the storage battery as long as it is DC-powered by an electric vehicle or the like, but the voltage may be adjusted by a DC voltage converter.

Next, the principle of bearing electrolytic corrosion and the mechanism for suppressing electrolytic corrosion in the rotary electric machine 10 according to the first embodiment will be described.

_{The DC voltage VDC} of the DC power supply 40 is applied to the inverter 30. The inverter 30 turns on or off the switching elements 31, 32, 33, 34, 35, 36 based on the pulse width modulation signal, and sets the potentials of the output terminals R, S, and T to the potential VS on the positive side of the DC power supply 40 and the potential VS. Connect to either of the negative potential PSCs, or do not connect to either. The inverter 30 operates so that the phase difference between the average values of the armature windings 20 of the rotary electric machine 10 is a three-phase sinusoidal voltage shifted by 120 degrees. There are various drive methods for pulse width modulation, such as sine wave drive with the average value of the fundamental waves of the interphase voltage as a sine wave, trapezoidal wave drive with a trapezoidal wave shape, and square wave drive with a square wave shape. Looking at the voltage waveforms of the output terminals R, S, and T with reference to the potential PSC, even in the drive method of, it becomes a square wave.

In principle, sine wave-driven pulse width modulation turns on the upper arm of each leg or lowers it by comparing the magnitude of the desired sine wave fundamental wave applied to the armature winding 20 and the triangular wave carrier wave. Decide whether to turn on the arm. However, in _{the range of DC voltage VDC} , in order to make the interphase voltage as large as possible, a sine wave with a frequency three times the sine wave voltage applied to the armature winding 20 is superimposed on the phase voltage of each phase. May be compared with a triangular wave carrier.

When a sine wave with a frequency three times the frequency of the sine wave voltage applied to the armature winding 20 is superimposed on the phase voltage of each phase, the average value of the phase voltage becomes a horseshoe-shaped waveform, but the superimposed frequency is tripled between the phases. Since the sine wave of is subtracted, the interphase voltage becomes the sine wave voltage.

FIG. 5 is a diagram showing a phase voltage, an interphase voltage, and a fundamental wave waveform of a neutral point voltage on which a voltage having a frequency three times that of the rotary electric machine according to the first embodiment is superimposed. The voltages at the output terminals R, S, and T indicate the phase voltages of the U phase, the V phase, and the W phase. The voltage between the output terminal R and the output terminal S indicates the interphase voltage between the U phase and the V phase. The voltage between the output terminal S and the output terminal T indicates the interphase voltage between the V phase and the W phase. The voltage between the output terminal T and the output terminal R indicates the interphase voltage between the W phase and the U phase. When a sine wave voltage having a frequency three times the sine wave voltage is applied to the armature winding 20, the voltage of the entire armature winding 20 called a zero-phase voltage becomes a sine wave having a frequency three times the superimposed frequency described above. It swings with a wave and appears as a neutral point voltage of neutral point N. Due to the zero-phase voltage, a magnetic flux circulating in the circumferential direction is generated in the yoke 17. Then, an axial voltage is generated by the electromagnetic induction electromotive force on the rotating shaft 13 penetrating the yoke 17, and the voltage is applied to the oil films of the first bearing 14 and the second bearing 15.

At this time, as described above, the fundamental wave of the output voltage of the inverter 30 is sinusoidal, but since it is a pulse width-modulated rectangular wave-shaped voltage, the voltage of the entire armature winding 20 actually fluctuates in a rectangular wave shape. doing. Therefore, a high-frequency rectangular wavy voltage having a higher crest value than the case of only the fundamental wave is applied to the oil film of the first bearing 14 and the second bearing 15, and discharge due to dielectric breakdown occurs frequently, so that the bearing surface Deterioration progresses rapidly.

FIG. 6 is a diagram showing an actual example of the neutral point voltage waveform and the bearing voltage waveform of the rotary electric machine according to the first embodiment. Although it is slower than the neutral point voltage, the shaft voltage induced by the fluctuation of the neutral point voltage is generated in a period of about 60 microseconds.

When the output of the inverter 30 is applied to the armature winding 20, the voltage of the entire armature winding 20 called the zero-phase voltage fluctuates with a sine wave having a frequency three times superimposed as described above, and the neutral point voltage. Appears as. The neutral point voltage generates a magnetic flux circulating in the circumferential direction in the yoke 17. The magnetic flux circulating in the circumferential direction of the yoke 17 generates a voltage due to the induced electromotive force on the cancel line 22 penetrating the yoke 17 as well as the rotating shaft 13. The induced electromotive force to the rotating shaft 13 due to the magnetic flux circulating in the circumferential direction of the yoke 17 is equal to the induced electromotive force to the cancel line 22 due to the magnetic flux circulating in the circumferential direction of the yoke 17. Therefore, the potential difference between the inner ring 14n of the first bearing 14 electrically connected to the rotating shaft 13 and the inner ring 15n of the second bearing 15 and the outer ring 14g of the first bearing 14 electrically connected to the cancel line 22 And the potential difference between the outer ring 15g of the second bearing 15 becomes equal. Therefore, the potential difference between the inner ring 14n of the first bearing 14 and the outer ring 14g of the first bearing 14 and the potential difference between the inner ring 15n of the second bearing 15 and the outer ring 15g of the second bearing 15 are substantially zero. No discharge is generated inside the first bearing 14 and the second bearing 15, and electrolytic corrosion of the first bearing 14 and the second bearing 15 is suppressed.

The rotary electric machine 10 according to the first embodiment does not complicate the structure and processing, reduces the shaft voltage without affecting the effective magnetic flux, and can suppress the electrolytic corrosion of the first bearing 14 and the second bearing 15.

Embodiment 2.
FIG. 7 is a cross-sectional view of the rotary electric machine according to the second embodiment of the present invention. FIG. 7 shows a cross section corresponding to a cross section along the line II-II in FIG. The rotary electric machine 10 according to the first embodiment has a structure in which the cancel wire 22 is passed through one slot 21, but the rotary electric machine 10 according to the second embodiment has a bearing 181, 182, 183, 184, 185, 186. A cancel wire 22 is wound around each of the teeth, and all of them are connected in series to connect the winding start and winding end to the outer ring 14 g of the first bearing 14 and the outer ring 15 g of the second bearing 15.

Also in the rotary electric machine 10 according to the second embodiment, a voltage due to an induced electromotive force equivalent to that of the rotary shaft 13 is generated on the cancel wire 22 between the inner ring 14n of the first bearing 14 and the outer ring 14g of the first bearing 14. And the potential difference between the inner ring 15n of the second bearing 15 and the outer ring 15g of the second bearing 15 are substantially zero. Therefore, in the rotary electric machine 10 according to the second embodiment, electric discharge is not generated inside the first bearing 14 and the second bearing 15, and electrolytic corrosion of the first bearing 14 and the second bearing 15 is suppressed.

In the rotary electric machine 10 according to the second embodiment, the cancel wire 22 can be stably fixed by winding the cancel wire 22 around the teeth 181, 182, 183, 184, 185, 186, and the rotary electric machine 10 is produced. In addition to improving the productivity, it is possible to suppress problems such as disconnection of the cancel line 22 due to vibration.

Embodiment 3.
FIG. 8 is a cross-sectional view of the rotary electric machine according to the third embodiment of the present invention. FIG. 8 shows a cross section corresponding to a cross section along the line II-II in FIG. In the first and second embodiments, the cancel wire 22 is configured to generate an induced electromotive force equivalent to that of the rotating shaft 13, but when the outer shell 16 is made of a conductive material such as metal, both ends of the cancel wire 22 are generated. When a current flows through the outer ring 14g of the first bearing 14, the bearing box 16f, the outer shell 16, the bearing box 16r, and the outer ring 15g of the second bearing 15, the potential difference between both ends of the cancel wire 22 is changed to the inner ring of the first bearing 14. It may be lower than the potential difference between 14n and the inner ring 15n of the second bearing 15.

As shown in FIG. 8, the rotary electric machine 10 according to the third embodiment winds the cancel line 22 around the yoke 17 a plurality of times, and the induced electromotive force generated in the cancel line 22 is generated from the induced electromotive force generated in the rotating shaft 13. By increasing the value, the amount of the current flowing through the outer shell 16 and the decrease in the potential difference at both ends of the cancel line 22 can be compensated.

Embodiment 4.
FIG. 9 is a cross-sectional view of the rotary electric machine according to the fourth embodiment of the present invention. FIG. 9 shows a cross section corresponding to a cross section along the line II-II in FIG. FIG. 10 is a perspective view of the stator of the rotary electric machine according to the fourth embodiment. In the rotary electric machine 10 according to the third embodiment, the induced electromotive force generated in the cancel line 22 is an integral multiple of the number of turns ratio with the induced electromotive force generated in the rotating shaft 13, so that the potential difference between both ends of the cancel line 22 is rotated. In some cases, it may not be exactly matched with the potential difference of the shaft 13. Therefore, as shown in FIG. 9, the rotary electric machine 10 according to the fourth embodiment connects the capacitor 50 in series with the cancel wire 22 to adjust the magnitude of the current via the outer shell 16. By connecting the capacitor 50 in series to the cancel wire 22, the potential difference between both ends of the cancel wire 22 can be made substantially equal to the potential difference between the inner ring 14n of the first bearing 14 and the inner ring 15n of the second bearing 15. The electrolytic corrosion of the 1st bearing 14 and the 2nd bearing 15 can be suppressed.

Further, in the first embodiment and the second embodiment, the fundamental wave of the fluctuation of the neutral point voltage is also generated at both ends of the cancel line 22, but as shown in FIG. 10, in the fourth embodiment, The rotary electric machine 10 can suppress bearing electrolytic corrosion by connecting a capacitor 50 in series to the cancel line 22 and generating only a high-frequency rectangular wave component due to switching of the inverter 30 at both ends of the cancel line 22.

Note that FIGS. 1, 2 and 3 show a structure in which the cancel line 22 is directly connected to the outer ring 14 g of the first bearing 14 and the outer ring 15 g of the second bearing 15, but the bearing boxes 16f and 16r are shown. If it is made of a conductive material, the cancel wire 22 is connected to the bearing boxes 16f and 16r, and the bearing boxes 16f and 16r come into contact with the outer ring 14g of the first bearing 14 and the outer ring 15g of the second bearing 15. The voltage of the canceling wire 22 may be transmitted to the outer ring 14g of the first bearing 14 and the outer ring 15g of the second bearing 15 by conduction.

Further, in the first to fourth embodiments described above, the rolling bearing has been described as an example, but a type in which an insulating film is formed between the rotating portion and the rotating support portion that rotatably supports the rotating portion. By connecting the cancel wire 22 to the rotation support portion, the bearing can be suppressed from electrolytic corrosion. A slide bearing can be exemplified as a bearing in which an insulating film is formed between the rotating portion and the rotating support portion that rotatably supports the rotating portion, but the bearing is not limited thereto.

In the first embodiment, the second embodiment, and the third embodiment, the inverter 30 has a pulse width modulation method so that the principle of fluctuation of the neutral point voltage can be easily understood, and a sine wave applied to the armature winding 20 is used. A method of superimposing a sine wave having a frequency three times the voltage on the phase voltage of each phase and comparing it with a triangular carrier wave has been described. However, since the pulse width-modulated rectangular wave-shaped voltage is applied from the inverter 30 to the entire armature winding 20 and the neutral point fluctuates in a rectangular wave shape, a sine wave having a frequency of three times is applied to the phase voltage of each phase. The present invention is effective even when they are not superimposed. The present invention is also effective when the drive method of the inverter 30 is trapezoidal wave drive or square wave drive.

Further, even if the voltage is not supplied from the inverter 30, if the neutral point voltage fluctuates, electrolytic corrosion may occur in the first bearing 14 and the second bearing 15 due to the shaft voltage. According to the present invention, it is possible to suppress electrolytic corrosion of the first bearing 14 and the second bearing 15 even with a power supply other than the inverter 30 in which the neutral point voltage fluctuates. Further, in the present invention, the same effect can be obtained when the armature winding 20 is not a centralized winding but a distributed winding.

In each of the above embodiments, the three-phase, four-pole permanent magnet type synchronous motor has been described, but the number of phases, the number of poles, and the type of the motor are not limited to the illustrated configurations. That is, the present invention is applicable to any AC motor such as an induction motor or a reluctance motor.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

10 Rotor, 11 Stator, 12 Rotor, 13 Rotor shaft, 14 1st bearing, 14g, 15g outer ring, 14n, 15n inner ring, 14t, 15t rolling element, 15 2nd bearing, 16 outer shell, 16f, 16r bearing box , 17 yoke, 18,181,182,183,184,185,186 teeth, 19 stator core, 20 armature winding, 21 slots, 22 cancel wire, 22a one end, 22b other end, 30 inverter, 31, 32 , 33, 34, 35, 36 Switching element, 40 DC power supply, 50 bearing, 171, 172, 173, 174, 175, 176 York part.

Claims (5)

A stator formed in a cylindrical shape, a rotor arranged inside the stator, a rotating shaft fixed to the rotor, and a first bearing and a second bearing that rotatably support the rotating shaft. A rotor, an outer shell supporting the first bearing and the second bearing, and a canceling wire having one end connected to the first bearing and the other end connected to the second bearing.
The stator is
A stator core having an annular yoke and a plurality of teeth protruding in the radial direction from the inner peripheral surface of the yoke.
It has an armature winding wound around the stator core via an insulator, and has an armature winding.
A rotary electric machine characterized in that the canceling wire penetrates the inner circumference of the yoke and is wound around a plurality of the teeth in the same direction as the armature winding. A stator formed in a cylindrical shape, a rotor arranged inside the stator, a rotating shaft fixed to the rotor, and a first bearing and a second bearing that rotatably support the rotating shaft. A rotor, an outer shell supporting the first bearing and the second bearing, and a canceling wire having one end connected to the first bearing and the other end connected to the second bearing.
The stator is
A stator core having an annular yoke and a plurality of teeth protruding in the radial direction from the inner peripheral surface of the yoke.
It has an armature winding wound around the stator core via an insulator, and has an armature winding.
The canceling wire is a rotary electric machine characterized in that it is wound around the yoke. The rotary electric machine according to claim 1 or 2 , further comprising a capacitor connected in series with the canceling wire. The first bearing and the second bearing have a rotating portion that comes into contact with the rotating shaft, a rotating support portion that rotatably supports the rotating portion, and a bearing box that accommodates the rotating support portion.
The rotary electric machine according to any one of claims 1 to 3 , wherein the cancel wire is connected to the rotary support portion of the first bearing and the rotary support portion of the second bearing. .. The first bearing and the second bearing have a rotating portion that comes into contact with the rotating shaft, a rotating support portion that rotatably supports the rotating portion, and a bearing box that accommodates the rotating support portion.
The bearing box has conductivity and
The rotary electric machine according to any one of claims 1 to 3 , wherein the cancel wire is connected to the bearing box of the first bearing and the bearing box of the second bearing.

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