JP5759935B2 - DC brushless motor and control method thereof - Google Patents

Description

  The present invention relates to a DC brushless motor and a control method thereof, and more particularly to a motor using a dust core as an iron core.

  Motors are used in a wide range of fields such as automobiles, home appliances, and industrial applications as components that convert electric power into power. The motor includes a stator that is a non-rotating part and a rotor that rotates together with the output shaft. The stator and the rotor include an electromagnetic coil, a magnet, and an iron core.

  Motors are classified into several types depending on the principle and structure for generating a driving force. Motors using permanent magnets are called PM (Permanent Magnet) motors and are used in a wide range of fields. In this PM motor, the rotor is provided with the permanent magnet, and a rotational force is obtained by the interaction between the electromagnetic coil provided in the stator and the magnetic flux generated by the permanent magnet.

  By the way, since the motor is a power source, there is a strong need for downsizing, and it is necessary to generate a stronger magnetic force for downsizing. For a motor that obtains a stronger magnetic force, a magnet that emits a strong magnetic flux is required. For example, in Patent Document 1, a magnet using an Nd—Fe—B element is developed. However, these magnets also have a problem that expensive and rare metals such as Dy (Dysprosium) and Nd (Neodymium) are necessary. On the other hand, it is possible to obtain a strong magnetic force (electromagnetic force) by increasing the magnetic field generated by the electromagnetic coil, and it is effective to increase the excitation current or increase the number of turns of the electromagnetic coil as the method. . However, the former has a cross-sectional area of the coil, and the latter has a space limitation of the winding, and thus has a limit.

  Therefore, in recent years, development of a motor using a powder magnetic core in an iron core has progressed. The powder magnetic core is formed by compacting and heat treatment after forming an insulating film on the surface of the soft magnetic powder. Here, conventionally, a laminated magnetic core obtained by punching and laminating electromagnetic steel sheets has been used for a motor. The laminated magnetic core is difficult to pass magnetic flux in the laminated direction and easily passes magnetic flux in the in-plane direction. Therefore, a conventional motor has been designed with a magnetic circuit in a plane. On the other hand, since the above-mentioned powder magnetic core is formed by compacting a soft magnetic powder, the magnetic characteristics are isotropic, and the magnetic core enables the design of a motor having a three-dimensional magnetic circuit. It can be said that it is a material. In addition, the powder magnetic core can be made into any shape by changing the mold shape in compacting or machining after molding, so the motor core shape can be diversified by three-dimensional magnetic design. It can enable the design of flat and small motors.

  For example, Patent Documents 2 to 4 disclose a claw teeth motor using a three-dimensional magnetic circuit as a motor that is miniaturized by utilizing such a dust core. According to these Patent Documents 2 to 4, by improving the winding density, i.e., by applying a circular coil to a claw pole type iron core, which has been conventionally wound around each tooth, the magnetic force is increased. This makes it possible to reduce the size. In addition, by using a dust core, it is possible to drive with an alternating magnetic field, and by using a three-layered stator with an electrical angle shifted by 120 ° from each other, brushless driving with a three-phase alternating magnetic field is possible. It also makes it possible.

JP 2009-43776 A JP 2006-333545 A JP 2007-32573 A JP 2009-142086 A

  Patent Documents 2 to 4 described above disclose a claw pole motor using a powder magnetic core. However, since the claw pole motor cannot be rotated only with a single-phase basic structure, it is necessary to form a unit of three or more phases by stacking a plurality of claw pole motors. However, in the case of three phases, it is a magnetic circuit for two phases at most that contributes to torque generation on average, and one phase is useless from the viewpoint of output per volume. Further, the claw pole motor requires a permanent magnet on the rotor side, so that there is a problem of high cost. Further, the claw pole motor needs to consider demagnetization characteristics due to temperature changes, and there is a problem that there are restrictions in magnet selection, shape design, cooling system design, and the like.

  An object of the present invention is to provide a DC brushless motor that is low in cost, excellent in space efficiency, and less affected by temperature changes, and a control method thereof.

  A DC brushless motor according to the present invention includes a stator having an excitation coil and a rotor provided coaxially with the stator, and the stator and the rotor against the flow of magnetic flux generated around the excitation coil. A DC brushless motor that performs a switched reluctance operation using a change in magnetoresistance as a driving force. The stator is formed in an approximately E shape with a radius in an axial cross section, and the excitation coil is , Formed in an annular shape and accommodated in the two concave portions of the E-shape, and in the three parallel portions of the E-shape, the upper and lower portions are formed with a plurality of protrusions that serve as magnetic poles in the circumferential direction. The iron core member has an iron core member formed in an annular shape close to the rotor, and the rotor has an iron core in which a plurality of protrusions serving as magnetic poles are repeatedly formed in the circumferential direction. Consisting of members The number of magnetic poles in the upper and lower iron core member in the stator is characterized by being arranged offset equal to one another, and with each other the magnetic pole position in the circumferential direction.

  According to said structure, SR motor is conventionally used as a motor which does not use a permanent magnet. This SR motor is a motor that uses reluctance torque caused by a change in magnetic resistance with rotation, and a drive circuit sequentially switches energization to a stator coil to which a rotor salient pole approaches. Thus, the rotor is rotated. Therefore, since no magnet is used for the rotor, there is an advantage of low cost, and thermal demagnetization of the magnet does not become a problem, and there is also an advantage that operation at a high temperature is possible compared with the PM motor. .

  However, since this SR motor does not generate a rotating magnetic field in one phase, depending on the rotation angle, torque may not be obtained in a stationary state and may not be able to start up independently. That is, since the SR motor rotates with the change in magnetoresistance as the driving force, torque cannot be obtained at the rotation angle position where there is no change in magnetoresistance, and therefore at a rotation angle without torque during rotation at a constant speed. Even if it exists, it can rotate by inertia, but in the case of a rotational angle without torque in a stationary state, there is a problem that it does not start and does not rotate.

  Therefore, in the present invention, the exciting coil has a two-layer structure, the iron core member of the stator is formed in an approximately E shape with a radius in the axial cross section, and the annular exciting coil is formed by the two E-shaped recesses. Housed in each. In the three parallel parts of the E-shape, the upper and lower parts form a plurality of protrusions that are magnetic poles in the circumferential direction, and the middle part has an annular shape close to the rotor, that is, the rotor. The surface facing the surface is formed to be a smooth surface on which the protrusion is not formed. Therefore, for example, in the case of an inner rotor, the iron core member of the stator on the outer peripheral side has a shape in which three sides (rings) are extended from the cylindrical outer wall to the inner peripheral side. Further, the rotor is composed of an iron core member in which a plurality of protrusions serving as magnetic poles are formed in the circumferential direction. Then, although the number of magnetic poles in the upper and lower stages of the E-shaped iron core member is formed to be equal to each other, the upper and lower pole positions are shifted in the opposite directions in the circumferential direction.

  Further, as a control method, of the two excitation coils, the drive circuit allows a positive sign current to flow in one excitation coil when starting the rotor in the normal rotation direction, and when starting the rotor in the reverse rotation direction. The other exciting coil is activated by passing a negative sign current. Thereafter, when the rotor starts to rotate, the drive circuit controls rotation such as acceleration and steady rotation by causing a rectangular wave current to flow through the two excitation coils.

  Therefore, it is possible to start the SR motor that does not rotate in one phase, and when the rotation starts, the magnetic circuit for two phases always contributes to the generation of torque, so space efficiency (output per size) is increased. Can be increased. Furthermore, as described above, since the SR motor can obtain the torque necessary for the rotation of the rotor without using a magnet by using the magnetoresistance change between the rotor and the stator as a driving force as described above, In a DC brushless motor which is an essential power source for industrial and consumer use, there is an effect of saving rare metals such as rare earth magnets.

  By the way, if the E-shaped iron core member is also provided with a protrusion on the middle stage, and the upper and lower stage protrusions are formed with a phase shift of ± β with respect to the middle stage protrusion, the protruding poles at each stage Since the opposing phases are different, in the magnetic circuit constituted by the upper stage-middle stage and the lower stage-middle stage, the peak of the maximum value of the inductance and the valley of the minimum value are not sharp (blunted). Here, in the SR motor, the inclination of the ridge line contributes to the torque generation. Therefore, when the protrusion is provided also in the middle stage of the E-shaped iron core member, the torque is lost. On the other hand, if the middle stage unevenness is eliminated as in the present invention, the inductance of the magnetic circuit on both the upper stage side and the lower stage side depends only on the area facing the rotor of the convex pole, The maximum value peak and the minimum value valley become sharp, and as a result, a large torque is obtained.

  In the DC brushless motor of the present invention, the excitation coil is formed by winding a strip-shaped conductor member so that the width direction thereof is along the rotation axis direction of the excitation coil.

  According to the above configuration, the surface perpendicular to the conductor member causing eddy current with respect to the magnetic flux flowing in the magnetic core of the stator is only the width corresponding to the thickness of the band, and suppresses the eddy current. And heat generation can be suppressed. Moreover, since the strip-shaped conductor member can be wound without a gap, the current density can be increased and heat radiation from the inside of the conductor member is good as compared with the case of winding a cylindrical strand.

  Furthermore, in the DC brushless motor of the present invention, the iron core members of the stator and the rotor are made by dispersing a powder magnetic core, a ferrite magnetic core, or a soft magnetic alloy powder made of iron-based soft magnetic powder in a resin. It is characterized by comprising a soft magnetic material.

  According to said structure, a stator and a rotor can be shape | molded in the optimal and complicated arbitrary shape.

  As described above, the DC brushless motor according to the present invention includes a stator having an exciting coil and a rotor provided coaxially with the stator, and in the DC brushless motor performing SR operation, the stator The iron core member is formed into a two-layer structure by forming an approximately E shape with a radius in the axial cross section, and a plurality of poles in the circumferential direction in the upper stage and the lower stage in the three parallel parts of the E shape. The middle stage is formed in an annular shape close to the rotor, the number of magnetic poles in the upper and lower iron core members in the stator is equal to each other, and the magnetic pole positions are shifted in opposite directions. It is possible to start by arranging.

  Therefore, since no magnet is used for the rotor, the cost is low and there is no problem of thermal demagnetization of the magnet. Further, since the magnetic circuit for two phases always contributes to the generation of torque, the space efficiency (output per size) can be improved. In addition, the maximum peak value and the minimum value valley of the inductance of the magnetic circuit are sharper than those in the case where the protrusions are also provided in the middle stage of the E-shaped iron core member, and a large torque can be obtained.

1 is an axial sectional view of a DC brushless motor according to an embodiment of the present invention. It is a perspective view which cuts and shows a part of said DC brushless motor. It is a perspective view which cuts and shows a part of stator of the said DC brushless motor. FIG. 3 is a cross-sectional view perpendicular to the axis of the DC brushless motor. It is a disassembled perspective view of the stator of the DC brushless motor. It is a figure of the magnetic field analysis result which shows the flow of magnetic flux when it supplies with electricity to the exciting coil of the said DC brushless motor. It is a perspective view of the rotor of the DC brushless motor. It is a figure which shows an example of the drive circuit of the said DC brushless motor. It is a wave form diagram for demonstrating an example of the drive method by the said drive circuit. It is a figure which shows the calculation result of the inductance accompanying rotation when the number of magnetic poles of a rotor and a stator is set to 4 and it is set as the predetermined magnetic pole width. It is a wave form diagram for demonstrating the other example of the drive method by the said drive circuit. FIG. 5 is a cross-sectional view perpendicular to the axis corresponding to FIG. 4 in a DC brushless motor of a comparative example of the present invention. It is a figure which shows the calculation result of the inductance accompanying the rotation corresponding to FIG. 10 in the comparative example of FIG. It is a perspective view which removes the casing of the DC brushless motor which concerns on the other form of implementation of this invention, and shows an internal structure. It is a disassembled perspective view of the DC brushless motor shown in FIG. FIG. 6 is a cross-sectional view perpendicular to the axis of a DC brushless motor according to still another embodiment of the present invention. FIG. 6 is a cross-sectional view perpendicular to the axis of a DC brushless motor according to still another embodiment of the present invention.

(Embodiment 1)
Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably.

  FIG. 1 is an axial sectional view of a DC brushless motor 1 according to an embodiment of the present invention, FIG. 2 is a perspective view showing a part of the DC brushless motor 1, and FIG. 3 is a stator. 4 is a perspective view of the DC brushless motor 1 cut along a part of AA, BB, and CC along the axis perpendicular to each other. FIG. 5 is an exploded perspective view of the stator 2.

  The DC brushless motor 1 is generally configured to include a stator 2 having two exciting coils 31 and 32, and an inner rotor rotor 4 provided coaxially inside the stator 2, It is a DC brushless motor that performs an SR operation using a change in magnetoresistance between the stator 2 and the rotor 4 as a driving force with respect to the flow of magnetic flux generated around the exciting coils 31 and 32. And this DC brushless motor 1 implement | achieves the said exciting coils 31 and 32 by 2 layer structure, and has employ | adopted the following structures.

  First, as shown in FIG. 1 to FIG. 3 and FIG. 5, the iron core member 20 of the stator 2 includes members 21, 22, and 23 that are divided into three in the axis Z direction. The iron core member 20 is formed in an approximately E shape with a radius in a cross section in the axis Z direction. That is, in the case of such an inner rotor, the iron core member 20 of the stator 2 on the outer peripheral side has a shape in which three sides (rings) are extended from the cylindrical outer wall to the inner peripheral side.

  It should be noted that, in the E-shaped three-stage parallel portions 211, 221, 231, as shown in FIG. 4, the upper and lower portions 211, 231 have a plurality of protrusions 212, 232 serving as magnetic poles. Each of them is repeatedly formed in the circumferential direction, whereas the middle portion 221 is formed in an annular shape having a minute gap with the rotor 4. The protrusions (magnetic poles) 212 of the upper part 211 and the protrusions (magnetic poles) 232 of the lower part are equal in number to each other and reverse to each other with respect to a predetermined center line Y as shown in FIG. They are offset by an angle β equal to the direction. Therefore, the entire middle portion 221 is a magnetic pole.

  The annular exciting coils 31 and 32 are accommodated in the two E-shaped recesses 24 and 25, respectively. Therefore, for the upper and lower members 21 and 23, the cross section in the axis Z direction when deployed in the circumferential direction is substantially L-shaped, and the L-shaped peripheral walls 213 and 233 are closed by the middle member 22. Thus, the recesses 24 and 25 are formed. In actual assembly, the exciting coils 31 and 32 are accommodated in the L-shaped portions of the upper and lower members 21 and 23, and an adhesive is applied to the peripheral walls 213 and 233, and then the members 21, 22, and 23 are assembled. It is done by raising. Or each member 21, 22, 23 may be bolted instead of adhesion. The excitation coils 31 and 32 are formed by winding a strip-shaped conductor member so that the width direction thereof is along the rotation axis Z direction of the excitation coils 31 and 32.

  FIG. 6 is a magnetic field analysis result showing the flow of magnetic flux when the exciting coils 31 and 32 of the DC brushless motor 1 are energized. When the thicknesses of the protrusions (magnetic poles) 212 and 232 in the upper and lower members 21 and 23 are 1, the thickness of the middle member 22 is (a) 0.6 times, and (b) 1.5 times, and (c) is 1.9 times. As shown in these drawings, in the middle member 22, the magnetic flux lines from both the upper and lower members 21 and 23 pass, so the magnetic flux lines become overcrowded and the thickness of the middle member 22 is reduced. The more magnetic flux leaks to the surface of the rotor 4 from other than the protrusions (magnetic poles) 212 and 232 and the tip of the middle member 22. Therefore, the thickness of the middle member 22 is preferably 1.5 times or more the thickness of the protrusions (magnetic poles) 212 and 232 in the upper and lower members 21 and 23.

  On the other hand, as shown in FIG. 7, the rotor 4 includes an iron core member 40 in which a plurality of protrusions 41 serving as magnetic poles are repeatedly formed in the circumferential direction. The output shaft 42 of the rotor 4 may be a separate body that is press-fitted into the iron core member 40 or may be molded integrally with the iron core member 40.

  FIG. 8 is a diagram illustrating an example of the drive circuit 5 of the DC brushless motor 1 configured as described above. In the present embodiment, the excitation coils 31 and 32 having the two-layer structure as described above need to generate magnetic fields in opposite directions as shown in FIG. As will be described later, these exciting coils 31 and 32 are connected in series to each other and driven by a rectangular wave pulse during acceleration and steady rotation. For this reason, when the exciting coils 31 and 32 are formed equally as shown in FIG. 5 (in FIG. 5, both are wound clockwise when viewed from above), the directions of the currents are reversed to each other. The inner peripheral end (311) of one exciting coil (31) and the outer peripheral end (321) of the other exciting coil (32) are connected, and the outer peripheral end of one exciting coil (31) is required. (312) and the inner peripheral end (322) of the other exciting coil (32) are connected to lines 52 and 53 from the DC power supply 51, respectively. A switch Tr0 for controlling energization is interposed in one of the lines 52 and 53 (52 on the high side in FIG. 8). Further, between the lines 52 and 53, forward / reverse selection switches Tr1 and Tr2 to be described later are interposed in series, and an inner peripheral end (311) of the one exciting coil (31) is connected to a connection point 54 thereof. And the outer peripheral end (321) of the other exciting coil (32).

  On the other hand, when the winding directions of the two exciting coils 31 and 32 are opposite to each other, the inner peripheral ends (311 and 322) are connected to one of the lines 52 and 53 or the connection point 54 to The end (312 and 321) may be connected to the other of the lines 52 and 53 or the connection point 54.

  FIG. 9 is a waveform diagram for explaining a driving method by the driving circuit 5 configured as described above. FIG. 9A shows the case of forward drive, and FIG. 9B shows the case of reverse drive. FIG. 9 shows drive waveforms when the exciting coils 31 and 32 are equal to each other as described above. And the inductance characteristic of the motor 1 shown in FIG. 4 becomes like FIG. 10, for example. FIG. 10 is a diagram illustrating a calculation result of the inductance L (θ) accompanying the rotation for a half circumference. However, in FIG. 10, the number of magnetic poles in the upper and lower members 21 and 23 of the rotor 4 and the stator 2 is 4, and the magnetic pole width α with respect to the period of the magnetic poles of the rotor 4 is 50%. Similarly, the magnetic pole width γ of the upper and lower protrusions (magnetic poles) 212 and 232 is 50%, and the deviation angle β of the upper and lower protrusions (magnetic poles) 212 and 232 with respect to the center line Y is 22.5 °. The graph of # 1 shows the inductance of one exciting coil 31, and the graph of # 2 shows the inductance of the other exciting coil 32.

  From FIG. 10, when the rotor 4 is activated in the forward rotation direction out of the two excitation coils 31, 32, first, as shown in FIG. 9A, one excitation coil (31 (# 1 graph) )), A positive wave is passed through and the rotor 4 begins to rotate. After that, the rectangular waves whose polarities are reversed are applied to both excitation coils (31 and 32 (graphs of # 1 and # 2)). It is understood that acceleration and steady rotation can be performed by passing a current. On the other hand, in the case of reverse rotation, as shown in FIG. 9B, a negative sign current is supplied to the other exciting coil (32 (graph of # 2)) at the time of startup, and the rotor 4 starts to rotate. It is understood that acceleration and steady rotation can be performed by flowing rectangular wave currents having opposite polarities to both excitation coils (31, 32 (graphs of # 1, # 2)). Therefore, as shown in FIG. 9, the exciting coils 31 and 32 are driven by currents having opposite phases, and are driven in a pseudo two-phase manner. When the winding directions of the exciting coils 31 and 32 are opposite to each other, the exciting coils 31 and 32 are driven with an in-phase current. However, as will be described later, switching control is individually performed in relation to activation.

  In the drive circuit 5 of FIG. 8, specifically, when the rotor 4 is started in the forward rotation direction, the drive circuit 5 keeps the selection switch Tr1 OFF and turns on the selection switch Tr2 and the switch Tr0. Then, after the DC power source 51-switch Tr0-excitation coil 31-selection switch Tr2-DC power source 51 is formed and activated, the selection switch Tr2 is turned off, and the DC power source 51-switch Tr0-excitation coil 31 is activated. -Excitation coil 32-Switching to the current path of the DC power supply 51 and turning on / off the switch Tr0 gives a rectangular wave current. On the other hand, when starting the rotor 4 in the reverse rotation direction, the drive circuit 5 keeps the selection switch Tr2 turned off, turns on the selection switch Tr1 and the switch Tr0, and turns on the DC power supply 51-switch Tr0-. After the current path of the selection switch Tr1-excitation coil 32-DC power supply 51 is formed and activated, the selection switch Tr1 is turned OFF, the DC power supply 51-switch Tr0-excitation coil 31-excitation coil 32-current of the DC power supply 51 Switching to the path and turning on / off the switch Tr0 gives a rectangular wave current.

  Preferably, as shown in FIG. 11, the drive circuit 5 applies a current pulse only to the excitation coil on the starting side and then applies a current pulse to both excitation coils for acceleration and steady rotation (afterwards, the current The current pulse to the exciting coil on the tracking side is given with a delay. In FIG. 11, the drive circuit 5 provides a time difference τ for the first current pulse applied to both exciting coils. FIG. 11A and FIG. 11B correspond to FIG. 9A and FIG. 9B, respectively. The time difference τ becomes smaller as the rotational speed becomes higher and becomes larger as the deviation β between the protrusions (magnetic poles) 212 and 232 becomes larger. Such control is performed by a control circuit (not shown) in response to the detection result of the rotation angle position of the rotor 4 by an encoder (not shown). By comprising in this way, it can accelerate more efficiently.

  The starting current is not limited to a single pulse as shown in FIG. 9 or FIG. 11, and may be composed of a plurality of pulses. When an element capable of variable voltage current output is used, a triangular wave is used. May be output. That is, even if the same start pulse or drive pulse is input depending on the position from which to start or the weight of the load, etc., the response to that actually differs, so the examples shown in FIGS. 9 and 11 Is a guide only, and the control circuit sequentially controls the number of start pulses and the peak value of the drive pulse in response to the detection result of the encoder.

  In the following, torque (= attraction force) T · δθ (= N · δθ = F · δx = ΔE) generated in the motor structure of the present embodiment is evaluated. The torque T is proportional to the rate of change ∂L (θ) / ∂θ with respect to the rotation angle θ of the rotor 4 of the inductance L approximately calculated from the model magnetic circuit as follows.

  Since the inductance L is generally defined by an electromotive force, the relationship between the electromotive force V and the geometric dimension is as follows. The electromotive force in the SR motor is a phenomenon in which, when a constant current is passed through the excitation coil and the inductance is changed by turning the rotor to change the inductance, a back electromotive force that does not pass the current is generated. The SR motor can be used as an electromagnetic brake when rotating with no current and passing an (alternating current) current at an appropriate timing.

However, Su and Sm represent the overlapping area of the protrusion 41 of the rotor 4, the upper protrusion (magnetic pole) 212 of the stator 2 and the middle member 22, and gu and gm are the protrusion 41 of the rotor 4. The gap between the upper projection (magnetic pole) 212 and the middle member 22 of the stator 2 is shown. Sc and lc represent the average (effective) cross-sectional area and path length with respect to the magnetic flux lines penetrating through the (yoke) core, and the permeability μ of the (yoke) core is the permeability in vacuum. It is sufficiently larger than the magnetic permeability μ ₀ , and (μ / μ ₀ ) · (lc / Sc) can be regarded as substantially zero. Thus, it is understood that the electromotive force V corresponds to the time change of the magnetic flux density B and the cross-sectional area S with respect to the magnetic flux lines.

  Further, an approximate model is considered in which the gap g between the magnetic poles of the stator 2 and the rotor 4 is sufficiently small, and the magnetic flux lines pass only through the overlap between the magnetic poles. The inductance of the equivalent magnetic circuit of the motor structure at that time is the series magnetism of the magnetic resistance between the protrusions (magnetic poles) 212 and 232 and the rotor 4 and the magnetic resistance between the rotor 4 and the middle member 22. Since it is inversely proportional to the resistance, an approximate estimation expression such as the following expression is obtained. The following equation is the inductance between the upper projection (magnetic pole) 212 of the stator 2 and the middle member 22, and the inductance between the lower projection (magnetic pole) 232 and the middle portion 221 is the same. Can be requested.

  That is, the overlapping area of the magnetic poles becomes the inductance L, and the magnitude of the torque can be evaluated by the difference ΔL between the maximum Lmax and the minimum Lmin of the inductance L (θ).

  Here, as described above, the DC brushless motor 1 of the present embodiment has an upper stage and a lower stage as shown in FIG. 4 among the three parallel parts 211, 221, and 231 in the E-shaped cross section. In the portions 211 and 231, a plurality of protrusions 212 and 232 that are magnetic poles are repeatedly formed in the circumferential direction, whereas the middle portion 221 is in an annular shape having a minute gap between the rotor 4 and the middle portion 221. Is formed. On the other hand, as a comparative example, consider a configuration in which a plurality of protrusions 222 serving as magnetic poles are repeatedly formed in the circumferential direction on the middle portion 221 as shown by a DC brushless motor 1 ′ in FIG. 12. Such a DC brushless motor 1 'is shown, for example, in FIGS. 84 and 85 of International Publication No. 2006/126552 or a microfilm of Japanese Patent Application No. 49-106499, although it is a permanent magnet motor.

  For the DC brushless motor 1 ′ as described above, FIG. 13 is a diagram showing a calculation result of the inductance L (θ) associated with the rotation for half a circle. The DC brushless motor 1 ′ and the DC brushless motor 1 of the present application differ in whether a protrusion (magnetic pole) 222 is formed on the middle portion 221 (FIG. 12) or not (FIG. 4). Only.

  Comparing FIG. 10 with FIG. 13, it is understood that the change in inductance (graphs of # 1 and # 2) is larger in FIG. This is because, in the DC brushless motor 1 of the present application, since the protrusion 222 is not formed in the middle portion 221, the gap gm and the overlapping area Sm of the magnetic poles in the equations 2 and 3 do not change, and especially the overlapping of the magnetic poles This is because the area Sm is always at the maximum value of the DC brushless motor 1 ′ of the comparative example.

  Further, in FIG. 10, the inductances (graphs of # 1 and # 2) change more rapidly near the maximum value Lmax and the minimum value Lmin. In FIG. 12, the increase (decrease) change gradient is particularly small at the rotation angle indicated by a circle, and in particular, in the vicinity of the minimum value Lmin, both inductances (graphs of # 1 and # 2) increase (decrease). The change gradient is small. Accordingly, in the DC brushless motor 1 ′ of the comparative example, there are many phase angles with a small starting torque, and it is expected that starting is particularly difficult in the vicinity of the minimum value Lmin. Good startability can be secured, and rotation at the start can be started in any direction.

  Table 1 shows a comparison result between the DC brushless motor 1 of the present embodiment and each type of motor of the prior art.

  In other words, the DC brushless motor 1 of the present embodiment does not require a permanent magnet, and is an SR motor operation that can be realized with an inexpensive material. Thus, the core and winding structure are simplified as in the case of the crotches motor and the claw pole motor. The cost can be reduced, and thermal demagnetization of the magnet does not become a problem, so that it can be operated at a higher temperature than the PM motor.

  However, since this SR motor does not generate a rotating magnetic field in one phase, depending on the rotation angle, torque may not be obtained in a stationary state and may not be able to start up independently. That is, since the SR motor rotates using the magnetoresistance change as a driving force, torque cannot be obtained at a rotation angle position where there is no magnetoresistance change, and at a rotation angle without torque during rotation at a constant speed. Even if it exists, it can be rotated by inertia, but there is a problem that it cannot start and does not rotate when the rotation angle is stationary and there is no torque.

  Therefore, in the DC brushless motor 1 of the present embodiment, the excitation coil has a two-layer structure of 31 and 32, and the cross section in the axis Z direction when the iron core member 20 of the stator 2 is expanded in the circumferential direction is approximately E-shaped. Furthermore, in the E-shaped three-stage parallel parts 211, 221, 231 thereof, a plurality of protrusions 212, 232 serving as magnetic poles are repeatedly formed in the circumferential direction on the upper and lower parts 211, 231. The middle portion 221 is formed in an annular shape having a minute gap between the rotor 4 and the annular exciting coils 31 and 32 are accommodated in the two E-shaped recesses 24 and 25, respectively. The rotor 4 is composed of an iron core member 40 in which a plurality of protrusions 41 serving as magnetic poles are repeatedly formed in the circumferential direction. Then, although the number of the protrusions (magnetic poles) 212 and 232 is formed to be equal to each other, the positions of the upper and lower protrusions (magnetic poles) 212 and 232 are shifted in opposite directions with respect to a predetermined center line Y. Deploy.

  Therefore, the DC brushless motor 1 according to the present embodiment enables the SR motor that does not rotate in one phase, and the magnetic circuit for two phases always contributes to the generation of torque when the rotation starts. , Space efficiency (output per size) can be increased. Furthermore, as described above, the SR motor uses the change in magnetoresistance between the rotor and the stator as a driving force and does not require a magnet, and can obtain the torque necessary for the rotation of the rotor. The brushless motor 1 has an effect of saving rare metals such as rare earth magnets in a DC brushless motor which is an essential power source for industrial and consumer use.

  Further, in the DC brushless motor 1 of the present embodiment, as shown in FIG. 5 and the like, the excitation coils 31 and 32 are strip-shaped conductor members whose width direction is in the direction of the rotation axis Z of the excitation coils 31 and 32. Along the way, it is wound around flatwise. In general, when a coil is energized, since the coil is composed of a conductor, an eddy current is generated on a plane (orthogonal plane) perpendicular to the magnetic field lines shown in FIG. 1 and FIG. ) Occurs. When the magnetic flux density is the same, the magnitude of the eddy current is proportional to the area intersecting with the magnetic flux lines, that is, the area of a continuous surface perpendicular to the magnetic flux lines. Since the magnetic flux lines are along the axial direction in the coil, the eddy current is proportional to the area of the radial surface perpendicular to the axis Z direction of the conductor constituting the coil. Therefore, in the DC brushless motor 1 of the present embodiment, the strip-shaped conductor members constituting the exciting coils 31 and 32 are formed so that the ratio t / W of the radial thickness t to the width W is 1/10 or less. It is desirable.

  By comprising in this way, the said eddy current can be suppressed and heat_generation | fever can be suppressed. Moreover, since the strip-shaped conductor member can be wound without a gap, the current density can be increased and heat radiation from the inside of the conductor member is good as compared with the case of winding a cylindrical strand. Furthermore, if the thickness t of the conductor member is equal to or smaller than the skin thickness with respect to the frequency in the AC power supplied to the exciting coils 31 and 32, eddy current loss can be further reduced.

  Furthermore, it is preferable that a gap formed between the exciting coils 31 and 32 and the concave portions 24 and 25 of the stator 2 is filled with a heat conducting member. With this configuration, the heat generated in the exciting coils 31 and 32 can be effectively conducted to the iron core member 20 surrounding the exciting coils 31 and 32 through the heat conducting member. , Can improve heat dissipation.

  Furthermore, the inner surfaces of the portions 211 and 231 of the stator 2 facing one end of the exciting coils 31 and 32 in the direction of the rotation axis Z and the inner surfaces of the portion 221 facing the other end are at least those In the area | region which covers each edge part, it forms in parallel. This covers the upper and lower end faces of the exciting coils 31 and 32 even if the conditions relating to the exciting coils 31 and 32 as described above (flat width winding structure and width W is greater than the thickness t) are set. This is because if the portions 211, 211, and 231 are inclined, the magnetic flux lines (magnetic lines) that actually pass through the inside of the exciting coils 31 and 32 do not become substantially parallel to the rotation axis Z direction, particularly near the upper and lower end faces. .

  The present inventor verified the distribution of magnetic flux lines while changing the parallelism of the inner wall surfaces of the portions 211, 211, 231 in various ways. For example, when the parallelism is 1/100, the excitation coils 31, 32 While the magnetic flux lines passing through the inside are parallel to the rotation axis Z direction, when the parallelism is −1/10 or 1/10, the magnetic flux lines passing through the inside of the excitation coils 31 and 32 are aligned in the rotation axis Z direction. It will not be parallel. Under such verification, in order to make the magnetic flux lines passing through the excitation coils 31 and 32 parallel, the absolute value of the parallelism is preferably 1/50 or less.

  Furthermore, in the DC brushless motor 1 of the present invention, the iron core members 20 and 40 of the stator 2 and the rotor 4 are a powder magnetic core, a ferrite magnetic core, or a soft magnetic alloy powder made of iron-based soft magnetic powder. Is formed of a magnetic core made of a soft magnetic material dispersed in a resin. With this configuration, the two magnetic cores of the rotor 4 and the stator 2 can be molded into an optimal and complicated arbitrary shape, so that desired magnetic characteristics can be obtained relatively easily. At the same time, it can be formed in a desired shape relatively easily.

  The soft magnetic powder is a ferromagnetic metal powder, and more specifically, for example, pure iron powder, iron-based alloy powder (Fe-Al alloy, Fe-Si alloy, Sendust, Permalloy, etc.) and amorphous powder, Furthermore, the iron powder etc. with which electric insulation films, such as a phosphoric acid system chemical film, were formed on the surface are mentioned. These soft magnetic powders can be produced, for example, by a method of making fine particles by an atomizing method or the like, or a method of finely pulverizing iron oxide or the like and then reducing it.

  Such soft magnetic powder can be used alone or mixed with non-magnetic powder such as the resin, and the mixing ratio can be adjusted relatively easily, and the mixing ratio can be adjusted appropriately. By doing so, it is possible to easily realize the magnetic characteristics of the magnetic core material to the desired magnetic characteristics. The material of the iron core member 20 of the stator 2 and the material of the iron core member 40 of the rotor 4 are preferably the same raw material from the viewpoint of cost reduction.

(Embodiment 2)
14 is a perspective view showing the internal structure of a DC brushless motor 1a according to another embodiment of the present invention with the casing removed, and FIG. 15 is an exploded perspective view of the DC brushless motor 1a. It should be noted that the DC brushless motor 1a is an outer rotor. Therefore, in this DC brushless motor 1a, the stator 2a on the inner peripheral side is fixed to the fixed shaft 43, and the rotor 4a is provided on the outer peripheral side thereof. FIG. 15A is an exploded perspective view of the stator 2a, and FIG. 15B is an exploded perspective view of the rotor 4a. In this DC brushless motor 1a, portions functionally corresponding to the configuration of the DC brushless motor 1 described above are indicated by the same reference numerals with the suffix a. This facilitates understanding of the function of each part.

  That is, also in this DC brushless motor 1a, similarly to the DC brushless motor 1 described above, the exciting coils 31 and 32 have a two-layer structure, and the iron core member 20a of the stator 2a is expanded in the circumferential direction in the Z direction. Is formed in an approximately E shape, and in the three parallel portions 211a, 221a, 231a of the E shape, the upper and lower portions 211a, 231a are provided with a plurality of protrusions 212a, 232a that serve as magnetic poles. The middle portion 221a is formed in an annular shape having a minute gap with the rotor 4a, and the annular exciting coils 31 and 32 are accommodated in the two E-shaped recesses, respectively. . Moreover, the rotor 4a is comprised from the iron core member 40a in which the some protrusion 41a used as a magnetic pole is repeatedly formed in the circumferential direction. And although the number of protrusions (magnetic poles) 212a and 232a in the upper and lower portions 211a and 231a of the E-shape is formed to be equal to each other, the positions are shifted from each other. By configuring in this way, the structure of the outer rotor can also be realized.

(Embodiment 3)
16 and 17 are cross-sectional views perpendicular to the axes of DC brushless motors 1b and 1c according to still another embodiment of the present invention. In the DC brushless motor 1 described above, the protrusions (magnetic poles) 212 and 232 on the stator 2 side and the protrusions (magnetic poles) 41 on the rotor 4 side have arcuate cross sections, but it should be noted that FIG. In the DC brushless motor 1b shown in FIG. 16, the upper and lower protrusions (magnetic poles) 212b and 232b on the stator 2b side and the protrusion (magnetic pole) 41b on the rotor 4b side are formed in a rectangular shape like a stepping motor. It is. The middle part 221b is annular.

  On the other hand, in the DC brushless motor 1c shown in FIG. 17, the protrusions (magnetic poles) 212c and 232c on the stator 2c side and the protrusions (magnetic poles) 41c on the rotor 4c side are formed in five poles. In this case, β ≦ 18 °. FIG. 17 corresponds to FIG. 4 described above, and each cross section of (a), (b), and (c) is the position of each cut plane of AA, BB, and CC in FIG.

  As shown in FIGS. 16 and 17, the number and shape of the magnetic poles can be arbitrarily selected.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

1, 1a, 1b, 1c DC brushless motor 2, 2a, 2b, 2c Stator 20, 20a Iron core member 21, 22, 23 Member 211, 221, 231; 211a, 221a, 221b, 231a Portions 212, 232; 212a , 232a; 212b, 232b Protrusion (magnetic pole)
24, 25 Recesses 213, 233 Peripheral walls 31, 32 Excitation coils 4, 4a, 4b, 4c Rotors 40, 40a Iron core members 41, 41a, 41b, 41c Protrusions 42 Output shaft 43 Fixed shaft 5 Drive circuit 51 DC power supply 52, 53 Line Tr0 switch Tr1, Tr2 selection switch

Claims (5)

A stator having an excitation coil and a rotor provided coaxially with the stator are configured to change a magnetoresistance between the stator and the rotor with respect to a flow of magnetic flux generated around the excitation coil. A DC brushless motor that performs a switched reluctance operation as a driving force,
The stator is formed in an approximately E shape with a radius in an axial cross section,
The exciting coil is formed in an annular shape and accommodated in each of the two E-shaped recesses,
In the three parallel parts of the E shape, the upper and lower parts have iron core members formed with a plurality of protrusions that are magnetic poles in the circumferential direction, and the middle part has an annular shape close to the rotor. Having an iron core member formed,
The rotor is composed of an iron core member in which a plurality of protrusions serving as magnetic poles are repeatedly formed in the circumferential direction,
The DC brushless motor, wherein the number of magnetic poles in the upper and lower iron core members of the stator is equal to each other, and the magnetic pole positions are shifted from each other in the circumferential direction.   The DC brushless motor according to claim 1, wherein the exciting coil is formed by winding a strip-shaped conductor member so that a width direction thereof is along a rotation axis direction of the exciting coil.   The iron core member of the stator and the rotor is made of a soft magnetic material in which a powder magnetic core made of iron-based soft magnetic powder, a ferrite magnetic core, or a soft magnetic alloy powder is dispersed in a resin. The DC brushless motor according to claim 1 or 2. A method for controlling a DC brushless motor according to any one of claims 1 to 3,
Of the two excitation coils, the drive circuit sends a positive sign current to one excitation coil when starting the rotor in the forward direction, and a negative sign to the other excitation coil when starting the rotor in the reverse direction. A method for controlling a DC brushless motor, which is started by flowing a current of   5. The method of controlling a DC brushless motor according to claim 4, wherein after the rotor starts rotating, the drive circuit controls rotation by causing a rectangular wave current to flow through the two exciting coils. 6.