JP4632194B2 - Small DC brushless motor - Google Patents

Description

  The present invention relates to an inner rotor type small DC brushless motor mainly used for mechatronics products such as small robots, medical equipment, precision measuring devices, and the like.

  Conventionally, in an inner rotor magnet type DC (direct current) brushless motor, the housing case itself forms part of the magnetic circuit, and from the viewpoint of mechanical strength, cutting or pressing of magnetic materials such as steel It is common to use a single cylindrical ingot formed of a substantially cylindrical part. Further, steel, brass, aluminum, etc., which are advantageous in terms of mechanical strength and workability, are generally used for the flange and end flange.

  Since this housing case is basically a conductor, an eddy current is generated because the magnetic flux of the magnet changes as it passes through the housing case as the inner rotor magnet rotates. Since this eddy current has an effect of hindering the rotational motion of the inner rotor magnet, a loss due to this eddy current occurs, and the rotational efficiency of the inner rotor is reduced.

  In Patent Document 1, a housing case containing an inner rotor has a structure in which an epoxy insulating thin film is interposed at an interface to be electrically insulated from each other, and a thin cylindrical body made of steel is closely laminated in a radial direction. A small DC brushless motor that realizes a reduction in loss due to the eddy current by being configured is disclosed (Patent Document 1: Paragraphs [0016] and [0017]).

Further, in Patent Document 2, a plurality of substantially ring-shaped laminated cores made of a magnetic material are formed in the region width of the entire length of the inner rotor magnet and electrically insulated from each other, and the laminated core and the field coil are made of resin. A small DC brushless motor is disclosed in which a housing case is formed by integrally molding the same to cut off the main path of eddy current passing through the case (Patent Document 2: Paragraphs [0008] and [0019]. ], [0020]).
JP 2002-1119030 A JP 2002-136034 A

  By the way, in recent years, motors have been reduced in size and have a tendency to increase in speed, and in order to improve torque generated per unit volume of the motor, a magnet having a high energy product is used as a magnet used in the inner rotor. It is common. On the other hand, the loss due to the eddy current is proportional to the square of the rotation speed of the inner rotor and the square of the maximum flux linkage density, so that further increase in the loss due to the eddy current has become a problem.

  Further, since the loss is consumed as heat, there is a problem that the surface area is reduced as the diameter is reduced and heat generation is promoted.

  Accordingly, the present invention has been made in view of the above-described circumstances, and an object thereof is to provide a small DC brushless motor capable of reducing loss due to eddy current, suppressing heat generation, and miniaturizing the motor. Yes.

In order to solve the above-described problem, an invention according to claim 1 is directed to an inner rotor having a rotating shaft at the center of a cylindrical magnet, a stator field coil disposed around the inner rotor, the inner rotor, A housing case that encloses and accommodates the stator field coil, is located on the outer periphery of the stator field coil and forms an exterior portion, and a flange that covers an opening at one end of the housing case; And an end flange provided with a lead wire hole through which a lead wire for supplying a current to the stator field coil is provided while covering an opening at the other end of the housing case.
An inner rotor magnet rotates during driving, and an insulating layer or an insulator is disposed at a position where the main path of eddy current generated mainly by the magnetic flux of the magnet interlinking the conductor, and the inner rotor includes the flange and is rotatably supported by said end flanges, the outer diameter of Ri der less 12mm, the insulating layer or insulator, of the flange and the joint of the housing case or the junction of the end flange and the housing casing, It is a small DC brushless motor characterized by being arranged in at least one of them.

  According to the invention described in claim 1, in the inner rotor type DC brushless motor, a current is supplied from the lead wire to the stator field coil, and a magnetic action is generated between the stator field coil and the inner rotor magnet. The inner rotor rotates.

  At this time, as the inner rotor rotates, the magnetic flux of the magnets links the housing, flange, and end flange, which are conductors, and an eddy current is generated. Through the analysis, it was newly discovered that the main path of this eddy current is not only in the housing case but also in the housing case → flange → housing case → end flange → housing case →. In the present invention, the loss due to the eddy current can be reduced by disposing an insulating layer or an insulator at a position where the main path is interrupted.

Moreover , since the eddy current is interrupted at the joint between the housing case and the flange and at the joint between the housing case and the end flange, the loss due to the eddy current can be reduced.

According to a second aspect of the invention, an inner rotor having a rotating shaft at the center of a cylindrical magnet, a stator field coil disposed around the inner rotor, the inner rotor and the stator field coil are included. A housing case made of a single material and positioned on the outer periphery of the stator field coil, covering the opening at one end of the housing case, and the other end of the housing case And an end flange provided with a lead wire hole through which a lead wire for supplying current to the stator field coil is passed. The inner rotor magnet rotates during driving, and the magnetic flux of the magnet is mainly conducted. An insulating layer or insulator is placed at a position where the main path of eddy current generated by linking the bodies is interrupted, Serial inner rotor is rotatably supported by said flanges and said end flanges, an outer diameter of not more than 12mm, as wherein the insulating layer or insulator, disposed in the cross section perpendicular to the axis of the housing case Yes.

According to the second aspect of the present invention, similarly to the first aspect, it is possible to reduce the loss due to the eddy current by disposing the insulating layer or the insulator at the position where the main path of the eddy current is cut off. In addition, since the eddy current is interrupted while flowing in the housing case in the axial direction, the loss due to the eddy current can be reduced.

Furthermore, the invention according to claim 3 is characterized in that the housing case is formed of a magnetic alloy made of nickel and iron.

According to the third aspect of the present invention, the Fe—Ni alloy, so-called permalloy, is a soft magnetic material and has a high electric resistance with respect to cast iron. Can hardly flow in the housing case, and as a result, loss due to eddy current can be reduced. Therefore, the eddy current shielding effect by the insulating layer or the insulator is further increased.

  According to the first aspect of the present invention, the loss due to the eddy current can be reduced by disposing the insulating layer or the insulator at the position where the main path of the eddy current generated along with the rotation of the inner rotor is interrupted. It becomes possible.

Moreover , since the eddy current is interrupted at the joint between the housing case and the flange and at the joint between the housing case and the end flange, the loss due to the eddy current can be reduced.

According to the second aspect of the present invention, similarly to the first aspect, it is possible to reduce the loss due to the eddy current by disposing the insulating layer or the insulator at the position where the main path of the eddy current is cut off. In addition, since the eddy current is interrupted while flowing in the housing case in the axial direction, the loss due to the eddy current can be reduced.

According to the invention described in claim 3 , the Fe—Ni alloy, so-called permalloy is a soft magnetic material and has a high electric resistance with respect to cast iron. Can hardly flow in the housing case, and as a result, loss due to eddy current can be reduced. Therefore, the eddy current shielding effect by the insulating layer or the insulator is further increased.

In addition, according to the first to third aspects of the present invention, the effect of the present invention can be obtained in an ultra-compact DC brushless motor having an outer diameter of φ12 mm or less.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a first embodiment of a small DC brushless motor. The motor 1 includes a stator field coil 4 that generates a rotating magnetic field by a current supplied through a lead wire 13 from the outside, and a rotating magnetic field. The inner rotor 20 that rotates based on the above, and a housing case 6 in which these members are housed, and the like.

  The inner rotor 20 is composed of a cylindrical magnet 2 made of a rare earth permanent magnet and a rotating shaft 3 and is rotatably supported between two points by bearings 9 and 10 arranged at the center positions of the flange 7 and the end flange 8. Yes. In addition, a rotating shaft 3 is fixed through the center of the magnet 2 along the longitudinal direction.

The housing case 6 has a cylindrical shape with both ends open, preferably Fe.
It is preferable to be made of permalloy which is a Ni-based magnetic alloy.
Further, a flange 7 is provided at the left end of the housing case 6 so as to cover the opening of the housing case 6, and a recess provided in the center position of the flange 7 on the inner side of the motor 1 has an inner rotor 20. A bearing 9 for supporting the rotating shaft 3 is fitted, and the rotating shaft 3 passes through the center of the flange 7 through the bearing 9. The flange 7 is preferably made of a material having high mechanical strength, and is made of, for example, a stainless material.

  Between the bearing 9 and the magnet 2, two flat plate-like liners 15 and 16 made of, for example, polyethylene terephthalate are inserted. The liners 15 and 16 are configured to slide the inner rotor 20 smoothly by sliding between the liners, and the rotation shaft 3 passes through a hole provided in the center.

  An end flange 8 is provided at the right end of the housing case 6 so as to cover the opening of the housing case 6. The end flange 8 is preferably made of a material having high mechanical strength, and is made of, for example, a stainless material.

  FIG. 2 is an enlarged view of the right end portion of the housing case 6, and a bearing 10 for supporting the rotating shaft 3 of the inner rotor 20 is provided in a recess provided in the center of the end flange 8 on the motor 1 inner side. The rotating shaft 3 is located at the center of the end flange 8 through the bearing 10. A spacer 19 is provided between the bearing 10 and the magnet 2 to secure a space for installing a substrate 5 described later. Further, runners 17 and 18 similar to the above-described runners 15 and 16 are inserted between the spacer 19 and the bearing 10.

A cylindrical field coil 4 for generating a rotating magnetic field is fixed to the inner peripheral surface 6a of the housing case 6, and the above-described inner rotor is provided on the inner side of the field coil 4 via a gap. 20 is housed in a rotatable manner. Further, the inner diameter portion of the opening portion on the end flange 8 side of the housing case 6 is provided with a step in the cylindrical radial direction, and the inner diameter R2 of the portion into which the end flange 8 is fitted rather than the inner diameter R1 of the portion in which the field coil 4 is accommodated. Is designed to be large.

The substrate 5 is disposed so as to be pressed against the fixing portion 25 (regulating portion) formed of the step. The substrate 5 is provided with a wiring pattern for supplying an output current from an external driver (not shown) to the field coil 4 via the lead wire 13. Further, as shown in FIG. 3, the end flange 8 is provided with an oval through-hole 13a through which lead wires 13, 13,... For supplying current to the field coil 4 are passed. The ends of the lines 13, 13,... Are connected to an external driving driver. The lead wire 13 is connected to the field coil 4 via the substrate 5 inside the motor 1.

  At this time, when the field coil 4 is connected in a star connection, the lead wires 13, 13,... Are U, V, W, and COM, and COM is a neutral point. On the other hand, when the field coils 4 are connected by delta connection, there are three U, V, and W. As the motor 1 has a smaller diameter, sensorless brushless driving is generally applied. However, in the case of the sensorless brushless driving system, the neutral point is basically required.

Returning to FIG. 1, insulating layers or insulators 11 and 12 are respectively provided at the interface between the flange 7 and the housing case 6 and at the interface between the end flange 8 and the housing case 6. The insulating layers or insulators 11 and 12 may be made of any material as long as it is an electrically insulating material. For example, the insulating layer or the surface of the housing case 6 may be insulated. For example, an insulating layer formed by electrodeposition coating, an alumite treatment on the aluminum surface, specifically, an insulating layer formed by an alumite treatment at the joint with the housing case in the case of a flange made of aluminum, or the flange 7 (Or end flange 8) and an insulating layer using a resin material as an adhesive layer for bonding the housing case 6 or an insulating material disposed between the flange 7 (or the end flange 8) and the housing case 6, for example, polyphenylene Any insulator made of a resin material such as sulfide (PPS) may be used.
The operation of this embodiment will be described below.

  When a current is supplied to the stator side field coil 4 via the lead wire 13 and the substrate 5, a magnetic action is generated between the stator side field coil 4 and the inner rotor side magnet 2, and the inner rotor is rotationally driven. To do.

At this time, a so-called eddy current is generated because the magnetic flux of the magnet 2 mainly links the conductors as the inner rotor 20 rotates. In the past, it was thought that eddy currents that travel around the housing case as the main path affect the loss of the motor, but a new main path of eddy currents was discovered by analysis by the present inventors.
Below, the main path | route of this eddy current is demonstrated.

  4 and 5 show the results of electromagnetic field analysis using the finite element method for eddy currents generated when a conventional small DC brushless motor and the small DC brushless motor of this embodiment are driven, respectively. Is shown. For the motor of this embodiment, analysis was performed under the same conditions except that boundary conditions of not conducting between the flange and the housing case (R) and between the end flange and the housing case (S) were introduced. It was. 4 and 5, the direction and magnitude of the eddy current are indicated by the direction and magnitude of the quadrangular pyramid shown in the figure. Note that the size of the quadrangular pyramid is shown on the same scale in FIGS. 4 and 5 for comparison.

  Thus, according to FIG. 4, which is a conventional small DC brushless motor, it is shown that eddy current is generated in the path of housing case → flange → housing case → end flange → housing case →. . Further, according to FIG. 5 which is a small DC brushless motor of the present embodiment, eddy current is generated in the same path as the eddy current generated in FIG. 4, but the magnitude of the eddy current is larger than that in FIG. Very small. That is, due to the difference in boundary conditions in the analysis, an insulating layer or an insulator is disposed between the housing case and the flange (R) and between the housing case and the end flange (S) to cut off the eddy current. It is thought that it was suppressed.

  Therefore, according to the electromagnetic field analysis using this finite element method, the eddy current main path housing case 6 → flange 7 → housing case 6 → end flange 8 → housing case 6 →... If this main path can be interrupted at any position on the same path, not only between (R) and between the housing case and the end flange (S), the eddy current can be effectively suppressed. It is suggested that it can be done.

  Therefore, as shown in FIG. 1, in this embodiment, the insulating layers or insulators 11 and 12 are arranged at the joint between the flange 7 and the housing case 6 and at the joint between the end flange 8 and the housing case 6. Since the main path is cut off at the joint between the housing case 6 and the flange 7 or at the joint between the housing case 6 and the end flange 8, loss due to eddy current can be reduced.

Moreover, in this embodiment, it is preferable to comprise the housing case 6 with the permalloy which is a Fe-Ni type alloy with a high electrical resistance with respect to cast iron. Permalloy has high electrical resistance (for example, permalloy PB resistivity (Fe-45% Ni); 45 μΩ · cm, SUM resistivity: 11 μΩ · cm), so eddy currents generated by rotation of the magnet 2 cause housing case 6 As a result, loss due to eddy current can be reduced. Therefore, the eddy current shielding effect by the insulating layer or the insulators 11 and 12 can be further enhanced. Moreover, in this embodiment, an outer diameter can be made into 12 mm or less, and the further size reduction of a DC brushless motor is attained.

  As described above, according to the present embodiment, loss due to eddy current during motor operation can be reduced more effectively, heat generation can be suppressed, and the motor can be miniaturized. Note that, as in the present embodiment, the insulating layer does not need to be disposed at both the joint between the flange 7 and the housing case 6 and the joint between the end flange 8 and the housing case 6. If there is, it is possible to obtain the effects of the present invention.

FIG. 6 is a view showing a second embodiment of the small DC brushless motor of the present invention. Instead of the insulating layer or the insulators 11 and 12 of the motor 1 shown in FIG. 1, the end flange itself is an insulator. The main path of eddy current is cut off. The motor 21 in FIG. 6 is configured in the same manner as the motor 1 in FIG. 1 except for the end flange 22 portion. The end flange 22 has the same shape as the end flange 8 of the motor 1 shown in FIG. 1, but is made of an insulating material such as polyphenylene sulfide (PPS).
The operation of the second embodiment will be described below.

  Similarly to the first embodiment, when a current is supplied to the stator field coil 4 via the lead wire 13 and the substrate 5, magnetism is generated between the stator side field coil 4 and the inner rotor side magnet 2. As a result, the entire inner rotor 20 rotates. At this time, an eddy current is generated because the magnetic flux of the magnet 2 mainly links the conductors as the inner rotor 20 rotates.

  The main path of this eddy current is: housing case 6 → flange 7 → housing case 6 → end flange 22 → housing case 6 →... In this embodiment, the end flange 22 is formed of an insulator, Cut off at the end flange 22 side in the main current path. Thereby, the loss resulting from eddy current can be reduced. Further, a new space for arranging the insulating layer or the insulators 11 and 12 shown in FIG. 1 is not required, and the motor can be further reduced in size.

  Moreover, in this embodiment, it is preferable to comprise the housing case 6 with the permalloy which is a Fe-Ni type alloy with high electrical resistance with respect to cast iron. Thereby, the eddy current generated with the rotation of the magnet 2 is less likely to flow through the housing case 6, and as a result, the loss due to the eddy current can be reduced. Therefore, the eddy current shielding effect by the end flange 22 as an insulator can be further enhanced.

Further, in the present embodiment, the outer diameter of the small DC brushless motor can be reduced to φ12 mm or less while obtaining the eddy current shielding effect, and the small diameter type DC brushless motor can be further downsized.
As described above, according to the present embodiment, loss due to eddy current during motor operation can be reduced more effectively, heat generation can be suppressed, and the DC brushless motor can be miniaturized. Become. As in this embodiment, not only the end flange 22 is made of an insulator, but the flange 7 side may be made of an insulator, and both the flange and the end flange are made of an insulator. Also good.

FIG. 7 is a view showing a third embodiment of the small DC brushless motor of the present invention, and is perpendicular to the axis of the housing case 27 instead of the insulating layer or insulators 11 and 12 of the motor 1 shown in FIG. Insulating layers or insulators 24, 24, 24 having electrical insulating properties are arranged on the cross section in the direction to block the main paths of eddy currents. In the motor 23 of FIG. 7, instead of the insulating layer or the insulators 11 and 12, a substantially cylindrical member 26 constituting a plurality of housing cases and the insulating layers or insulators 24, 24, 24 are sandwiched therebetween. Except for this, the configuration is the same as that of the motor 1 of FIG. Each insulating layer or insulator 24 may be any material as long as it is an electrically insulating material. For example, the insulating treatment of the end surface of the cylindrical member 26, for example, electrodeposition coating, and each member Any of an insulating layer using a resin material for an adhesive layer to which 26 is bonded, and an insulating material disposed between the members 26 and 26, for example, an insulator made of a resin material such as polyphenylene sulfide (PPS) may be used. .
The operation of this embodiment will be described below.

  Similarly to the first embodiment, when a current is supplied to the stator field coil 4 via the lead wire 13 and the substrate 5, magnetism is generated between the stator side field coil 4 and the inner rotor side magnet 2. As a result, the entire inner rotor 20 rotates. At this time, an eddy current is generated because the magnetic flux of the magnet 2 mainly links the conductor as the inner rotor 20 rotates.

  The main path of this eddy current is: housing case 27 → flange 7 → housing case 27 → end flange 8 → housing case 27 →... In this embodiment, a plurality of substantially cylindrical members constituting the housing case 27 By disposing an insulating layer or an insulator 24 between 26 and 26, the main path of eddy current is blocked inside the housing case 27. Thereby, the loss resulting from eddy current can be reduced.

In this embodiment, it is preferable that the substantially cylindrical member 26 of the housing case 27 is made of permalloy, which is an Fe—Ni alloy. Thereby, it becomes difficult for the eddy current generated with the rotation of the magnet 2 to flow, and as a result, the loss due to the eddy current can be further reduced. Therefore, the eddy current shielding effect by the insulating layer or the insulator 24 can be further enhanced. In the present embodiment, the outer diameter can be reduced to φ12 mm or less while obtaining an eddy current shielding effect, and the DC brushless motor can be further reduced in size.
As described above, according to the present embodiment, loss due to eddy current during motor operation can be reduced more effectively, heat generation can be suppressed, and the motor can be miniaturized.

  Below, the concrete structural example of the combination of the material of the housing case of the motor principal part used for the motors A and B as an Example of this invention and the conventional motor C as a comparative example, a flange, and an end flange is shown. . In addition, as the steel in the table below, stainless steel is used this time.

Here, as shown in Table 1, the motor A with alumite treatment on the surface of the end flange, the motor B with alumite treatment on the surfaces of both the flange and the end flange, and as shown in FIG. The loss ratio at the time of driving each motor was measured using a conventional type motor C having the same configuration as described above and having no insulating layer or insulator provided anywhere. This loss ratio was calculated by (no-load current / starting current) × 100 (%). The results are shown in Table 2 below.

  As shown in FIG. 8, the conventional motor C includes an inner rotor 20 composed of a magnet 2 and a rotating shaft 3, a stator field coil 4 disposed around the inner rotor 20, and these inner rotors. 20 and the stator field coil 4 are housed and located on the outer periphery of the stator field coil 4, a housing case 6 that forms an exterior portion, a flange 7 that covers an opening at one end of the housing case 6, An end flange 8 that covers the opening and is provided with a lead wire hole for passing a lead wire 13 that supplies current to the stator field coil 4 and a wiring pattern for supplying this current to the stator field coil 4 are arranged. The same size motor 28 is used, with the same basic parts composed of the substrate 5 and the bearings 9 and 10 that rotatably support the inner rotor 20. Table 2 below shows the loss ratio.

  According to Table 2, it can be seen that the motors A and B are superior to the motor C in the loss ratio. For the motor B shown in Table 1 (for example, equivalent to the motor 1 in FIG. 1) and the conventional motor C (for example, equivalent to the motor 28 in FIG. 8), the rotating shaft 3 when the motor is driven, the housing case 6, the flange 7, Table 3 below shows the results of analysis of eddy current loss and hysteresis loss in the end flange 8 and the bearings 9 and 10 using electromagnetic field analysis.

  For Table 3, FIG. 9 shows a bar graph in which the total loss is broken down by hysteresis loss and eddy current loss. Thus, according to Table 3 and FIG. 9, it can be seen that compared to the motor C, the motor B significantly reduces the eddy current loss and realizes a reduction in the overall loss. In addition, for the motor A in Table 1, the total obtained for the same loss as described above was reduced according to the result of the motor B, and both were effective in reducing eddy current loss.

It is a figure which shows 1st embodiment of the small DC brushless motor which concerns on this invention. It is a figure which expands and shows the principal part of the said embodiment. It is a figure for demonstrating the end flange of the said embodiment. The result of having analyzed by the finite element method about the eddy current when driving the conventional small DC brushless motor is shown. The result of having analyzed the eddy current when driving the small DC brushless motor of the said embodiment by the finite element method is shown. It is a figure which shows 2nd embodiment of the small DC brushless motor which concerns on this invention. It is a figure which shows 3rd embodiment of the small DC brushless motor which concerns on this invention. It is a figure which shows an example of the conventional small DC brushless motor. It is a graph explaining the effect of an Example.

Explanation of symbols

1, 21, 23, 28 Motor 2 Magnet 3 Rotating shaft 4 Field coil 5 Substrate 6, 27 Housing case 7 Flange 8, 22 End flange 9, 10 Bearing
11, 12, 24 Insulating layer (or insulator)
13 Lead wire
20 Inner rotor
26 Cylindrical member

Claims (3)

An inner rotor with a rotating shaft at the center of the cylindrical magnet;
A stator field coil disposed around the inner rotor;
A housing case made of a single material, containing the inner rotor and the stator field coil, being located on the outer periphery of the stator field coil, forming an exterior part,
A flange covering an opening at one end of the housing case;
An end flange provided with a lead wire hole for covering the opening at the other end of the housing case and passing a lead wire for supplying a current to the stator field coil;
An inner rotor magnet rotates at the time of driving, and an insulating layer or an insulator is disposed at a position where the main path of eddy current generated mainly when the magnetic flux of the magnet is linked to the conductor. Rotatably supported by the flange and the end flange,
An outer diameter of Ri der below φ12mm,
The small DC brushless motor, wherein the insulating layer or the insulator is disposed at at least one of a joint portion of the flange and the housing case or a joint portion of the end flange and the housing case . An inner rotor with a rotating shaft at the center of the cylindrical magnet;
A stator field coil disposed around the inner rotor;
A housing case made of a single material, containing the inner rotor and the stator field coil, being located on the outer periphery of the stator field coil, forming an exterior part,
A flange covering an opening at one end of the housing case;
An end flange provided with a lead wire hole for covering the opening at the other end of the housing case and passing a lead wire for supplying a current to the stator field coil;
An inner rotor magnet rotates at the time of driving, and an insulating layer or an insulator is disposed at a position where the main path of eddy current generated mainly when the magnetic flux of the magnet is linked to the conductor. Rotatably supported by the flange and the end flange,
Outer diameter is φ12mm or less,
A small DC brushless motor, wherein the insulating layer or the insulator is disposed in a cross section perpendicular to the axis of the housing case . The small DC brushless motor according to claim 1 , wherein the housing case is formed of an Fe—Ni based magnetic alloy.

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