JP2020089258A - Brushless motor - Google Patents

Abstract

To provide a brushless motor capable of reducing an over current.SOLUTION: A brushless motor comprises: a rotor 20 having a plurality of magnetic poles on an external peripheral surface; and a stator 30 having a lamination core 31 in which a teeth part 33 having a winding part to which an excitation coil 34 is wound and a non-winding part 331 which is opposite to the external peripheral surface of the rotor 20, and a base part 32 which is opposite to a side surface of the rotor 20 are integrated. In the teeth part 33, a plurality of steel plates 311 and 312 having a different thickness is laminated in a radial direction, and is laminated to a direction orthogonal to a direction of a magnetic flux generated from the rotor 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a brushless motor including a stator having a core formed by laminating a plurality of steel plates and a rotor having a plurality of magnetic poles.

In information equipment, industrial equipment, and the like, an inner rotor type brushless motor having a structure in which a rotor is arranged inside a stator is used. Since the inner rotor type brushless motor has a small inertial force, it has an advantage of excellent controllability.

Various structures have been proposed to reduce the size and increase the output of the brushless motor. For example, Patent Document 1 includes a rotor having a plurality of magnetic poles in the circumferential direction and a stator having a plurality of projecting iron core portions around which a coil winding body is wound, and the projecting iron core portions extend to the rotor side. By doing so, the rotor and the coil winding area of the protruding core portion are arranged vertically in the rotation axis direction, and the magnetic force lines generated from the coil act on the outer peripheral surface of the rotor via the tip end portion of each protruding core portion. Such a radial gap type motor is described. According to this configuration, it is said that there are advantages that the work of assembling the motor is easy, and that the output can be increased as compared with the conventional one without increasing the outer diameter of the motor.

In a brushless motor, in order to reduce iron loss, for example, as described in Patent Document 2, a stator core in which electromagnetic steel sheets, which are materials having high magnetic permeability, are axially laminated is used to achieve high output. Is being done.

JP, 2013-201884, A JP, 2010-178489, A

In a brushless motor, for example, by changing the resistance value by changing the number of turns (however, the space factor of the winding is not changed), it is possible to change the characteristics such as the rotation speed and torque of the motor, and It can be moved in parallel. For example, when the wire diameter is reduced and the number of turns is increased (the resistance value is increased to suppress the current), the rotation speed decreases in inverse proportion to the number of turns, and the torque decreases in proportion to the square of the wire diameter. When the wire diameter is increased and the number of turns is decreased (the resistance value is decreased and the current is increased), the number of revolutions increases in inverse proportion to the number of turns, and the torque increases in proportion to the square of the wire diameter.

However, in the brushless motor described in Patent Document 1, as shown in FIG. 4, a single steel plate is bent to form a ridged iron core (core), so that the eddy current loss on the core surface is large. Therefore, such a normal characteristic change cannot be made.In particular, if the wire diameter is made thicker and the resistance is lowered, the no-load current will increase significantly, the rotation speed will also increase above the design value, and the desired torque will be obtained. There is a problem that it can not be done. As the no-load current increases, the amount of heat generated increases and the efficiency also decreases.

In the motor described in Patent Document 1, it is not possible to reduce the eddy current loss (iron loss), which causes an increase in the no-load current, resulting in a decrease in torque. Moreover, in this structure, it is difficult to form the stator core (the plurality of projecting iron core portions parallel to the rotation axis) from the electromagnetic steel plate. This is because the electromagnetic steel sheet is an extremely hard material, so by bending the ridge core into a shape that stands upright from the outer circumference of the annular portion, cracks and fine cracks occur, and the magnetic path As a result, the original function as is hindered, which causes a decrease in torque.

The structure in which electromagnetic steel plates are laminated in the axial direction as described in Patent Document 2 cannot be applied to a cup-shaped core such as the brushless motor described in Patent Document 1.

Therefore, an object of the present invention is to provide a brushless motor capable of reducing no-load current.

A brushless motor according to the present invention includes a rotor having a plurality of magnetic poles on an outer peripheral surface, a winding portion around which an exciting coil is wound, and a tooth portion having a non-winding portion facing the outer peripheral surface of the rotor and the rotor. A stator having a laminated core in which a base portion facing the end face is integrated, and the teeth portion is formed by laminating steel plates in a radial direction and laminating in a direction orthogonal to a direction of magnetic flux generated from the rotor. Is characterized by.

In the brushless motor, the laminated core may have a structure in which a plurality of steel plates are laminated and bent.

In the brushless motor, the laminated core may have a structure in which a plurality of steel plates made of an electromagnetic steel plate or a cold rolled steel plate are laminated.

In the brushless motor, the laminated core may have a two-layer structure, the steel plate on the side facing the outer peripheral surface of the rotor may be an electromagnetic steel plate, and the other steel plate may be a cold rolled steel plate or an electromagnetic steel plate.

In the brushless motor, the laminated core may have a structure in which a plurality of steel plates are laminated, and the steel plate facing the outer peripheral surface of the rotor is thinner than the other steel plate.

In the brushless motor, the rotor may have a multi-pole magnet made of a rare earth sintered magnet.

According to the present invention, since a specific laminated core is used, the eddy current loss can be minimized. Therefore, by reducing the no-load current, the torque loss is suppressed and the torque is close to the theoretical value. You can pull up to the value.

It is an exploded perspective view of the brushless motor of the present invention. It is a top view of the brushless motor shown in FIG. It is the sectional view on the AA line of FIG. It is an exploded perspective view of a stator. It is a top view of a laminated core. It is the BB sectional view taken on the line of FIG. It is sectional drawing which expanded a laminated core and a part of rotor. It is a figure which shows the motor characteristic of Example 1 and a comparative example. It is a figure which shows the motor characteristic of Example 2 and a comparative example. It is a figure which shows the motor characteristic of Example 3 and a comparative example. It is a schematic diagram which shows the flow of the magnetic flux line of a multipolar magnet. It is the arrow line view which looked at FIG. 11 from the C direction.

Modes for carrying out the present invention will be described with reference to FIGS.

As shown in FIGS. 1 to 3, the brushless motor is a 12-pole 9-slot type three-phase DC motor and has a rotor 20 having a multi-pole magnet 23 fixed to the outer peripheral surface of a sleeve 22 fitted to a shaft 21. And a stator 30 surrounding the rotor 20. A rotor 20, a stator 30, and members for supporting these are housed inside a cup-shaped case 10 whose open end side is sealed by an end cover 11. A first core guide 12 is internally provided on the closed end side of the case 10 into which the bearing 14 is press-fitted and fixed, and one end side of the stator 30 is supported therein. A second core guide 13 having a bearing 14 is internally provided on the open end side of the case 10, and the other end side of the stator 30 is supported therein. The rotor 20 is rotatably supported inside the stator 30 via a bearing 14. On the open end side of the case 10, the circuit board 15 on which the Hall element 16 facing the end surface of the multi-pole magnet 23 is mounted is mounted in a state of being sandwiched between the end cover 11 and the second core guide 13. To be done.

As shown in FIG. 3 and FIG. 4, the stator 30 has a laminated core 31 that is a magnetic path forming member and is formed by laminating two steel plates, and an exciting coil 34. The laminated core 31 has an annular base portion 32 that contacts the first core guide 12, and a plurality of teeth portions 33 that extend from the base portion 32 in the axial direction of the rotor 20. The plurality of tooth portions 33 are arranged at equal angular intervals along the circumferential direction so as to surround the rotor 20. The tip of the tooth portion 33 has a non-winding portion 331 that is fitted into the guide groove 131 of the second core guide 13 and faces the magnet, and a winding portion to which the air-core exciting coil 34 is attached. The length of the non-winding portion 331 is set to have substantially the same length as the axial length of the multipolar magnet 23 in order to effectively allow the magnetic flux from the multipolar magnet 23 to flow in.

As shown in FIGS. 5 to 7, the laminated core 31 includes a plurality of steel plates having different thicknesses (steel plates of the same material or steel plates of different materials), for example, a first steel plate 311 having a thickness t1 and a thickness. Since the second steel plate 312 having the thickness t2 (<t1) is laminated, the eddy current can be reduced. The laminated core 31 may be formed of steel plates having the same thickness (t1=t2), or may be formed of three or more steel plates.

The laminated core 31 is formed by stamping a steel plate such as an electromagnetic steel plate or a structural steel plate that has been subjected to an insulation treatment into a predetermined shape (the teeth portion 33 is radially formed on the outer circumference of the annular base portion 32) by pressing. It can be formed by swaging the steel plates of No. 3 and integrating them, and then bending the tooth portions 33.

In the stator 30, as shown in FIG. 4, each of the exciting coils 34 wound around the laminated core 31 is formed as an air core coil, and the exciting coil 34 is formed according to the phase of a voltage applied from a controller (not shown). , U-phase, V-phase, and W-phase are three groups of coils, each of which is inserted up to the root of the tooth portion 33.

The hall element 16 is mounted on the annular circuit board 15 connected to the signal line (not shown) of the coil of each phase. The hall element 16 is arranged so as to face the end surface of the magnet 22 in order to detect the rotational position of the rotor 20. The hall element 16 detects the magnetic pole position of the rotor 20 and outputs the detection signal corresponding to the magnetic pole position so that the two poles of the number of the attached magnetic poles are set to one cycle so as to face the end surface of the permanent magnet 22. Of the electrical angle of 360°, the mechanical angle corresponding to the electrical angle of 120° (in the present 12-pole magnetization, since six cycles correspond to the mechanical angle of 360°, the mechanical angle of 120° corresponds to the mechanical angle of 120°). The angles correspond to 20°) and are arranged at predetermined intervals in the circumferential direction. Although not shown, the circuit board 15 includes a comparison circuit that compares the position signal (voltage) output from the Hall element 16, a control circuit that outputs a PWM signal based on the output of the comparison circuit, and an excitation by the PWM signal. An inverter circuit for controlling the energization of the coil 34 is provided to change the drive voltage in a sinusoidal manner according to the rotation angle of the rotor.

The multi-pole magnet 23 can be manufactured by applying multi-pole magnetization to the outer peripheral surface of a ring magnet which is integrally formed as a whole. Not limited to this, the arc segment magnet magnetized in the radial direction can be manufactured by fixing it to the outer peripheral surface of the sleeve 22 so that magnetic poles of different polarities are aligned along the circumferential direction. The multi-pole magnet 23 is preferably formed of a known permanent magnet material, for example, a rare earth bonded magnet, from the viewpoint of reducing the coking torque and the mechanical time constant by reducing the rotor inertia. In order to further increase the torque, it is possible to use an Nd-Fe-B system sintered magnet (neodymium system sintered magnet) having a high energy product.

According to the above brushless motor, the magnetic pole position of the rotor is detected by the three Hall elements 16, the sine wave voltage corresponding to the magnetic pole position is output, the sine wave voltage is compared by the comparison circuit, and the PWM signal is generated by the control circuit. Is output, and then the drive voltages having different phases of 120° are output from the inverter circuit to excite the three-phase coils at appropriate timings, thereby driving the sine wave. In this way, by selectively energizing the coils of each phase and changing the direction of the energizing current, when energizing between the two phases (for example, the U phase and the V phase), one of the coils is generated according to the strength of the generated magnetic flux. An N pole is formed at the tip of the laminated core 31 in one phase, and an S pole is formed at the tip of the laminated core 31 in the other phase. That is, when the U phase is energized to the V phase, the U phase is excited to the N pole and the W phase is excited to the S pole. Subsequently, the U phase is excited to the N pole and the W phase is excited to the S pole. When the W phase is energized to the U phase, the W phase is excited to the N pole and the U phase is excited to the S pole. In this way, the two-phase coils existing in the adjacent slots are sequentially excited, the magnetic flux passes between the two adjacent phases, and the magnetic fluxes are sequentially transferred to the adjacent phases to switch the excitation state. The magnetic pole of the magnet 23 is attracted and repelled, and a rotational torque is generated in the motor. In the present invention, it is needless to say that even if the Hall element is not used (sensorless) without using the Hall element, it can be driven by using a sensorless dedicated drive IC or the like. Furthermore, intermittent or continuous step driving by the step signal input is also possible.

In a brushless motor, the least common multiple of the number of magnetic poles and the number of slots is the frequency (number of peaks) of the cogging torque, and therefore has a large value in the configuration of 12 poles and 9 slots, so the cogging amplitude is canceled (dispersed). Therefore, the cogging torque is suppressed and smooth rotation is possible. The relationship between the number of magnetic poles and the number of slots is determined in consideration of the motor size, output, and cost. It is appropriately changed depending on the overall shape and the magnetic pole shape. The relationship between the number of magnetic poles and the number of slots may be, for example, 8 poles 9 slots, 10 poles 9 slots, 16 poles 9 slots, or 10 poles 12 slots.

According to the above brushless motor, when the magnetic flux generated in the laminated core 31 due to the energization of the exciting coil 34 flows into the non-winding portion 331, the magnetic flux flows into the multipolar magnet 23. Eddy current can be reduced by using the laminated core 31 in which a plurality of steel plates are laminated as the stator core. In particular, as shown in FIG. 7, in the tooth portion 33, the steel plates 311 and 312 are laminated in the radial direction, and the multipole magnet 23 has a sinusoidal magnetic flux density distribution on the gap side with the tooth portion 33. The stacking direction of the steel plates is orthogonal to the magnetic flux generated from the multipolar magnet (including the case where the angle formed by the stacking direction and the direction of the magnetic flux is not exactly 90°). That is, focusing on one tooth portion 33, the magnetic flux generated from the multi-pole magnet 23 passes through the inside of the tooth portion 33, passes through the annular base portion 32 (see FIG. 11 ), and flows into the adjacent tooth portion 33. Pass through a route like this. Therefore, the direction in which the magnetic flux passes through the inside of the teeth portion 33 is orthogonal to the stacking direction of the steel plates, and the teeth portion 33 is stacked and the cross-sectional area of each is small, so it becomes difficult for eddy currents to flow, and torque loss is reduced. It can be significantly reduced. In FIG. 11, broken lines indicate the flow of magnetic flux lines. Fig. 12 shows the magnetic pole arrangement of a multi-pole magnet (12 poles).

The laminated core 31 is formed by using an electromagnetic steel sheet as the inner steel sheet 312 facing the multi-pole magnet 23, using a general cold-rolled steel sheet as the outer steel sheet 311, and bending these after lamination. Preferably. Since the electromagnetic steel sheet is a steel sheet containing silicon, the iron loss is extremely smaller than that of a normal cold-rolled steel sheet. Therefore, by arranging the electromagnetic steel sheet on the side facing the multipolar magnet 23, the effect of lowering the iron loss is sufficiently achieved. Can be demonstrated to. Electromagnetic steel sheet is a material that is difficult to work, but by bending it together with the cold-rolled steel sheet, the cold-rolled steel sheet fulfills an auxiliary function mechanically and magnetically, greatly reducing the occurrence of folds and cracks. be able to. In the present invention, not limited to this, a plurality of cold rolled steel sheets or a plurality of electromagnetic steel sheets are used, or a cold rolled steel sheet is used as an inner steel sheet 312 and an electromagnetic steel sheet is used as an outer steel sheet 311. It can be formed by stacking and then bending the steel sheets. Even when the cold-rolled steel sheet faces the multi-pole magnet 23, the steel sheets are laminated in the radial direction in the teeth portion 33, and the magnetic flux is orthogonal to the lamination direction of the steel sheets, so that an effect of reducing eddy current loss can be obtained. You can

(Example 1)
A brushless motor having the structure shown in FIG. 1 and having an outer diameter of 12 mm and a length of 17 mm (dimensions of the case 10) was prepared. In this motor, the rotor 20 has 12 arc segment-shaped rare earth bonded magnets (outer diameter 7.5 mm, inner diameter 2.7 mm, thickness 6.0 mm, maximum energy of 96 kJ/m ³ [12 MGOe] as the multi-pole magnet 23. 1.4 mm in width formed by stacking a cold rolled steel plate (SPCC) (steel plate 311) having a thickness of 0.5 mm and an electromagnetic steel sheet (steel plate 312) having a thickness of 0.35 mm. A motor having a tooth portion 33 having a thickness of 0.85 mm and a resistance value of 17Ω was obtained. A DC voltage of 12 V was supplied to the coil to rotate the motor, and the motor characteristics were measured. The result is shown by a broken line in FIG. In FIG. 8, a1 is a TI curve and b1 is a TN curve.

(Example 2)
Implemented except that it has a teeth portion 33 having a width of 1.4 mm and a thickness of 0.85 mm formed by laminating an electromagnetic steel plate (steel plate 311) having a thickness of 0.5 mm and an electromagnetic steel plate (steel plate 312) having a thickness of 0.35 mm A brushless motor similar to that of Example 1 was used, and the motor characteristics were measured under the same conditions as in Example 1. The result is shown by a broken line in FIG. In FIG. 8, a2 is a TI curve and b2 is a TN curve.

(Experimental example 3)
Twelve arc segment rare earth sintered magnets are used as the multi-pole magnet 23, and the multi-pole magnet has an outer diameter of 7.5 mm, an inner diameter of 2.7 mm, a thickness of 6.0 mm, and a maximum energy product of 310 kJ/m3 [40 MGOe]. .) 23 was formed, the same brushless motor as in Experimental Example 1 was used, and the motor characteristics were measured under the same conditions as in Example 1. The result is shown by a broken line in FIG. In FIG. 8, a3 is a TI curve and b3 is a TN curve.

(Comparative example)
For comparison, a brushless motor having the same configuration as that of the experimental example was prepared, except that a core formed by bending a cold rolled steel plate (SPCC) having a thickness of 0.8 mm was used instead of the laminated core 31. The motor characteristics were measured under the same conditions as in Example 1. The results are shown by solid lines in FIGS. In FIG. 8, a4 is a TI curve and b4 is a TN curve.

Table 1 shows the torque constant, the no-load current, the no-load rotation speed, and the starting torque of each example and comparative example.

From Table 1, according to the present invention (Examples 1 to 3), a no-load current of about 70% can be reduced by about 70% and a torque constant of about 2 can be compared with a conventional core (comparative example). It can be seen that it can be improved by 8%. Although not shown, the output efficiency for the input can be improved by reducing the no-load current, and it is needless to say that the heat generation of the motor can be reduced by the efficiency improvement.

Reference numeral 10: case, 11: end cover, 12: first core guide, 121: cover portion, 122: neck portion, 13: second core guide, 131: guide groove, 14: bearing, 15: circuit board, 16 : Hall element, 20: Rotor, 21: Shaft, 22: Sleeve, 23: Multipolar magnet 30: Stator, 31: Laminated core, 311: First steel plate, 312: Second steel plate, 32: Base part, 33 : Teeth part, 331: Non-winding part, 34: Excitation coil

Claims (6)

A rotor having a plurality of magnetic poles on the outer peripheral surface, a winding portion around which an exciting coil is wound, a tooth portion having a non-winding portion facing the outer peripheral surface of the rotor, and a base portion facing the end surface of the rotor. A brushless motor comprising a stator having an integrated laminated core, wherein the teeth portion is formed by laminating steel plates in a radial direction and in a direction orthogonal to a direction of magnetic flux generated from the rotor. The brushless motor according to claim 1, wherein the laminated core has a structure in which a plurality of steel plates are laminated and bent. The brushless motor according to claim 2, wherein the laminated core has a structure in which a plurality of steel plates made of an electromagnetic steel plate or a cold rolled steel plate are laminated. The said laminated core laminated|stacks a some steel plate, The steel plate which opposes the outer peripheral surface of the said rotor is an electromagnetic steel plate, and the other steel plate is a cold-rolled steel plate or an electromagnetic steel plate, The claim 1 characterized by the above-mentioned. Brushless motor. The brushless motor according to claim 1, wherein the laminated core has a two-layer structure, and a steel plate facing the outer peripheral surface of the rotor is thinner than the other steel plate. The brushless motor according to claim 1, wherein the rotor has a multi-pole magnet made of a rare earth sintered magnet.