JP4599860B2 - Brushless motor - Google Patents

Description

  The present invention relates to a brushless motor used as a drive source for equipment.

  Currently, motors are used as drive sources in various devices such as video / audio devices, OA devices, home appliances, transportation devices, and FA devices. These devices tend to increase year by year as the number of motors used increases. As for motor performance, in recent years, small and high output motors are desired due to downsizing and high functionality of devices.

  Conventionally, many proposals have been made on methods for realizing miniaturization and high output of a motor.

FIG. 10 is a diagram showing a conventional magnetic circuit. This conventional motor has a configuration in which the coil resistance is not increased by increasing only the number of magnetic poles without increasing the number of salient poles of the core, thereby improving the torque performance of the motor. (For example, see Patent Document 1)
JP 2003-61326 A

  However, although the motor structure can greatly improve the torque performance as compared with the conventional brushless motor, there is a case where higher performance is desired.

  In the prior art, several proposals have been made on methods for reducing the cogging torque. However, when a motor is configured using a magnet body having a special configuration, the cogging torque can be reduced sufficiently. In some cases, it could not be obtained, and further improvement was desired.

  An object of the present invention is to further improve the prior art and to reduce the cogging torque of the motor even in the case of a magnet body having a special configuration.

In order to solve the above problems, engaging Ru inventions of the brushless motor in the present application, N-pole in the rotational direction, a rotor having a magnet body magnetized alternately S poles, facing the magnet body and the radial direction And a core having a plurality of salient poles around which a coil is wound, and a portion of the salient pole facing the magnet body has small teeth having substantially the same pitch as that of two magnet poles. A plurality of brushless motors that rotate the rotor by energizing the coil according to the position of the rotor, the brushless motor has a three-phase structure, and is provided per salient pole. when three the number of teeth of the teeth, of the plurality of small teeth of each pre-Symbol salient poles, the open angle of small teeth flux density is increased by less than the opening angle of the small teeth flux density is low, Open angle of small teeth at both ends in the rotation direction It is smaller than the opening angle of the small teeth of the rotating direction central portion is a brushless motor according to claim. In this way, the magnetic saturation of the core can be relaxed and the motor output torque can be improved.

Further, even engagement Ru inventions of the brushless motor in this application, the opening angle of the small teeth of the rotating direction end portions is 140 ° in electrical angle, the opening angle of the small teeth of the rotating direction central portion 170 ° in electrical angle It is a brushless motor characterized by being.

  By providing such a motor structure, a larger torque can be output, and a motor with higher output can be provided even with the same size and mass.

  According to the invention of the present application, it is possible to provide a motor having a high maximum torque while reducing the cogging torque of the motor. In addition, by mounting this motor on a device, it is possible to reduce the size and improve the function of the device.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the first to third embodiments, a method for improving torque by improving the shape of the core will be described. In the fourth to fifth embodiments, the configuration of a magnet body (a field portion using a permanent magnet) will be described.

(Embodiment 1)
FIG. 1 is an explanatory diagram showing the magnetic circuit configuration of the motor according to the first embodiment.

  As shown in FIG. 1, the small teeth 6-1 and 6-2 provided at the tip of the salient pole 5 of the core 3 have different opening angles on the left and right, and the small teeth 6-1 on the front side in the salient pole tip rotation direction are different. The opening angle is formed larger than the opening angle of the small teeth 6-2 on the rear side in the rotation direction.

In the figure, all angles are expressed as electrical angles. Specifically, as shown in FIG. 2 (a) and FIG. 2 (b), the hatched portions of the two cores 3-1 and 3-2 having the same shape and the angle shifted by 30 ° in electrical angle are combined. Is formed. As shown in FIG. 1, the specific opening angle of the small teeth is 120 ° on the rear side in the rotational direction and 180 ° on the front side in the rotational direction.

  Thus, by combining the shapes shifted by an electrical angle of 30 °, which is half the basic period of the cogging torque, by canceling the cogging torque, a motor with extremely small cogging torque and high rotational accuracy can be provided.

  Moreover, in the core 3 of this Embodiment 1, the effect as shown below can be acquired by making the opening angle of the small teeth 6-1 and 6-2 at the tip of the salient pole 5 asymmetrical.

  If the opening angles of the small teeth are made uneven or the pitch is changed, the number of magnetic fluxes incident on the small teeth from each magnetic pole will be different. In general, when the opening angle of the small teeth is large, and the position of the small teeth with respect to the magnetic pole is closer to the front (the phase is advanced), more magnetic flux is collected.

  Conversely, if the combination is made so that the opening angle of the small teeth on the side where the magnetic flux is concentrated becomes small, the magnetic saturation can be alleviated.

  In the case of the present embodiment, the opening angle of the small teeth 6-2 on the rear side in the rotational direction in which the magnetic flux tends to concentrate is made smaller than the small teeth 6-1 on the front side in the rotational direction, thereby reducing the magnetic flux imbalance. Even if a large current is passed, the core is less likely to be magnetically saturated, and as a result, the maximum torque resulting from the magnetic saturation of the core can be improved.

Even if configured in this manner the core unequal shape in the direction of rotation, the torque constant of the motor, the cogging torque is almost never changed, if the rotational direction of the rotor is reversed, shown in For the same reason, the magnetic saturation of the core is accelerated, and the maximum torque is reduced.

  Therefore, configuring the core in an uneven shape in the rotation direction in this way is a technique suitable for an application in which the motor mainly rotates in one direction (for example, fan driving).

  In this way, by changing the opening angle of the small teeth, it is possible to provide a motor having a high maximum torque while reducing the cogging torque.

(Embodiment 2)
FIG. 3 is an explanatory diagram showing a magnetic circuit configuration of the motor according to the second embodiment.

  As shown in FIG. 3, the small teeth 6-1, 6-2, 6-3 provided at the tip of the salient pole 5 of the core 3 have a large opening angle of the central small tooth 6-2, 1, 6-2 are formed with small opening angles. Specifically, as shown in FIGS. 4 (a), 4 (b), and 4 (c), the three cores 3-1, 3-2 having the same shape and the angle deviated by 10 degrees in electrical angle, It is formed by combining hatched portions having a shape of 3-3.

In this way, the opening angle of the small teeth is set to 150 ° in electrical angle, and the shape that generates the cogging torque of the half of the basic period of the cogging torque is used as a base. By combining three core shapes shifted by an electrical angle of 10 °, a motor with extremely small cogging torque and high rotational accuracy can be provided. As shown in FIG. 3, the specific opening angle of the small teeth is 140 ° at both ends in the rotational direction and 170 ° at the central portion in the rotational direction.

  Moreover, in the core shape of this Embodiment 2, the effect as shown below can be acquired by making the opening angle of the small teeth at the tip of the salient pole different from the central part.

  Since the root of the small tooth 6-2 at the center portion of the salient pole tip is directly connected to the winding portion, this portion is not magnetically saturated. On the other hand, since the small teeth 6-1 and 6-3 at both left and right end portions are connected by the thin yoke portion 7, the yoke portion 7 is likely to cause magnetic saturation.

  Therefore, if the combination is made so that the opening angle of the small teeth 6-1 and 6-3 becomes small, the number of magnetic fluxes incident from the small teeth 6-1 and 6-3 decreases, and the magnetic saturation of the yoke portion 7 is alleviated. can do.

  In this way, by reducing the opening angle of the small teeth outside the salient pole tip and reducing magnetic saturation, the core is less likely to be magnetically saturated even when a larger current is passed through the coil. Torque can be improved.

  In the first embodiment, since the core is uneven in the rotation direction, the maximum torque is reduced when the rotation direction of the rotor is reversed. However, the shape of the second embodiment is the same for both forward and reverse rotations. An effect can be obtained.

  In the first and second embodiments, one example is shown, but other configurations are possible in the same way.

  Generally, a brushless motor has a three-phase structure, and when the number of small teeth provided per one salient pole is n, the axial cross-sectional shape of the core is a predetermined angle in the rotational direction. The basic shape of the n cores that have been shifted is combined in a timely manner. Among the small teeth, the small tooth opening angle of the portion where the magnetic flux density at the salient pole tip is high is the small tooth opening angle of the other portion. By making it smaller, the maximum torque of the motor can be improved while keeping the cogging torque small.

(Embodiment 3)
In the third embodiment, a method for improving torque with an approach different from the first and second embodiments with respect to the core shape will be described.

  FIG. 5 is an explanatory diagram showing the magnetic circuit configuration of the motor according to the third embodiment.

  The core shape of the third embodiment is a shape in which the tips of the small teeth 6 are all inclined to one side.

  Thus, forming the tip of the small tooth 6 to be rotationally asymmetric also has an effect of improving the maximum torque.

  In FIG. 5, both the magnetic field generated by the coil 4 and the magnetic field generated by the permanent magnet 1 are applied to the tip of the small teeth 6 during driving, and in particular, a magnet having a large residual magnetic flux density such as an Nd—Fe—B sintered magnet. May be used, the magnetic flux exceeding the magnetic saturation of the core material may flow in the edge portion 8 on the front side in the rotation direction of the tip of the small tooth 6.

  Therefore, by setting the tip portion of the small tooth 6 to be inclined asymmetrically and making the angle of the front edge 8 that is likely to be magnetically saturated more than 90 °, the magnetic saturation of this portion can be relaxed and the maximum torque can be improved. it can.

On the other hand, if the tip portion of the small teeth 6 is formed rotationally asymmetric in this way, the reactive magnetic flux that does not contribute to the generation of torque incident from the side of the small teeth 6 also increases, so the performance in the intermediate region tends to deteriorate. This method is suitable for applications in which the motor always generates a large torque in one direction because the reverse effect occurs when the motor rotates in the reverse direction.

(Embodiment 4)
In the first to third embodiments, the method of reducing the magnetic saturation of the core and increasing the torque by flowing a large current through the coil has been described. However, in the following fourth and fifth embodiments, the configuration of the magnet body is described. A method for increasing the torque by taking out more magnetic flux from the magnet body by changing the above will be described.

  FIG. 6 is an explanatory diagram showing the magnetic circuit configuration of the motor according to the fourth embodiment.

  In FIG. 6, the magnet body has a structure in which a plurality of permanent magnets 1 are inserted into a back yoke 2 configured by stacking a plurality of silicon steel plates in the axial direction, and has a so-called magnet-embedded structure. It has a configuration in which two flat permanent magnets 1 are arranged side by side in a square shape and embedded so that the same poles face each other per magnet body.

  In this way, the projected area in the magnetization direction of the permanent magnet 1 per pole of the magnet body is larger than the rotor surface area per pole of the magnet body, and the magnetic flux is concentrated in the gap portion. Since the magnetic flux density in the gap portion can be made higher than the magnetic flux density of the permanent magnet 1 being used, and more magnetic flux can be extracted from the rotor of the same size, the torque of the motor can be increased.

  Further, by utilizing the difference in permeability between the permanent magnet 1 and the back yoke 2, by providing a difference between the magnetic resistance of the magnetic flux in the direction from the center of the magnetic pole to the other magnetic pole and the magnetic resistance of the magnetic flux passing between the magnetic poles, Not only the magnet torque generated by the permanent magnet 1 but also the reluctance torque accompanying the change in magnetic resistance can be used, and higher torque can be achieved.

  In the fourth embodiment, two permanent magnets are used per magnetic pole. However, as shown in FIG. 7A, a configuration using three or more magnets, or as shown in FIG. A method using one arc magnet is also possible.

  However, there is a limit to the saturation magnetic flux density of the back yoke 2 into which the permanent magnet 1 is inserted, and the two permanent magnets 1 shown in FIG. A configuration in which the permanent magnets on the flat plate are embedded in a square shape so that the same poles face each other is the most suitable configuration.

(Embodiment 5)
FIG. 8 is an explanatory diagram showing the magnetic circuit configuration of the motor according to the fourth embodiment.

  In FIG. 8, the magnet body is configured by alternately laminating the permanent magnets 1 magnetized in the radial direction and the rotational direction on the inner peripheral portion of the back yoke 2 on an annular ring in which silicon steel plates are laminated.

  Such an arrangement of magnets is known as a Halbach magnet arrangement and is known to be able to extract more magnetic flux than a permanent magnet simply magnetized in the radial direction along with polar anisotropic magnets. Yes.

  These Halbach magnet arrays and permanent magnets with polar orientation are the same as increasing the thickness of the magnet because the distance of the magnetic flux passing through the magnet is longer than when the magnet is simply oriented in the radial direction. An effect is obtained, and a larger magnetic flux can be extracted even with a permanent magnet of the same volume.

  Such an effect is prominent when the ratio of the magnetic pole pitch to the radial thickness of the permanent magnet is relatively small.

  Since the structure of the motor of the present invention has a configuration in which the number of magnetic poles is increased without increasing the number of salient poles 5 of the core 3, the magnetic pole pitch is inevitably small, and a Halbach magnet arrangement or polar anisotropic orientation is obtained. The torque increase by the magnet can be more effective than the conventional motor.

  FIG. 9 is an example in which the characteristics of a conventional magnetically oriented magnet and the motor of the Halbach magnet arrangement of the present invention are calculated and compared by magnetic field analysis using a computer.

  As shown in FIG. 9, the volume of the permanent magnet is exactly the same, the intermediate torque is improved by about 2%, and the maximum torque is improved by about 8%.

  As described above, according to the first to fifth embodiments, the maximum torque of the brushless motor can be improved, and a smaller motor can be provided even with the same torque. Alternatively, the output can be increased with the same size as the conventional one, and the function of the device using the motor can be improved.

  For example, by using the brushless motor of the present invention for a portable information terminal, a portable MD player, etc., it is possible to provide a small and lightweight motor with the same characteristics, and to achieve a reduction in size and weight of the device.

  In addition, by using the brushless motor of the present invention as a drive source for OA equipment, home appliances, etc., it is possible to provide a motor with high output even with the same size, and increase the speed and functionality of the equipment without increasing the size of the equipment. Can be achieved.

  In addition, by using the brushless motor of the present invention as an actuator for joint drive of a robot, a high output motor can be provided even with the same size and weight, and the response performance of an industrial robot or the like can be improved.

  Furthermore, by using the brushless motor of the present invention for driving wheels of transportation equipment represented by fuel cell vehicles and electric vehicles, a small and light motor with the same characteristics can be provided. It is possible to improve driving performance or improve fuel efficiency by reducing the weight.

  The brushless motor of the present invention can provide a motor having a high maximum torque while reducing the cogging torque of the motor. In addition, by mounting this motor on a device, it is possible to reduce the size and improve the function of the device. For example, it is useful as a motor for driving sources of various devices such as video / audio devices and OA devices.

Explanatory drawing which shows the magnetic circuit structure of the brushless motor by Embodiment 1 of this invention. Explanatory drawing which shows the design method of the core of the brushless motor by Embodiment 1 of this invention, (a) is explanatory drawing of core 3-1, (b) is explanatory drawing of core 3-2. Explanatory drawing which shows the magnetic circuit structure of the brushless motor by Embodiment 2 of this invention. Explanatory drawing which shows the design method of the core of the brushless motor by Embodiment 2 of this invention, (a) is explanatory drawing of the core 3-1, (b) is explanatory drawing of the core 3-2, (c) is the core 3 -2 explanatory diagram Explanatory drawing which shows the magnetic circuit structure of the brushless motor by Embodiment 3 of this invention. Explanatory drawing which shows the magnetic circuit structure of the brushless motor by Embodiment 4 of this invention. Explanatory drawing which shows the other structure of Embodiment 4 of this invention, (a) is explanatory drawing of a structure of the magnet body of another example by Embodiment 4 of this invention, (b) is Embodiment 4 of this invention. Explanatory drawing of the structure of another example magnet body by Explanatory drawing which shows the magnetic circuit structure of the brushless motor by Embodiment 5 of this invention. Explanatory drawing which compares the characteristic of the brushless motor by Embodiment 5 of this invention, and a prior art example Illustration of conventional example

DESCRIPTION OF SYMBOLS 1 Permanent magnet 2 Back yoke 3, 3-1, 3-2, 3-3 Core 4 Coil 5, 5-1, 5-2, 5-3, 5-4, 5-5, 5-6 Salient pole 6 , 6-1 6-2, 6-3 Small tooth 7 yoke part 8 small tooth front side edge part

Claims (2)

A rotor having a magnet body in which N poles and S poles are alternately magnetized in the rotation direction;
A core provided with a plurality of salient poles around which the magnet body and the magnetic circuit are opposed to each other in the radial direction and the coil is wound;
The portion of the salient pole facing the magnet body is provided with a plurality of small teeth having substantially the same pitch as that of the two magnet poles,
In a brushless motor that rotationally drives the rotor by energizing the coil according to the position of the rotor,
Brushless motor is a three-phase structure, wherein when the number of salient poles of teeth of small teeth provided per one pole was set to 3, among the plurality of small teeth of each pre-Symbol salient poles, small magnetic flux density is high Make the opening angle of the teeth smaller than the opening angle of the small teeth where the magnetic flux density is low ,
A brushless motor characterized in that the opening angle of the small teeth at both ends in the rotational direction is smaller than the opening angle of the small teeth at the central portion in the rotational direction . 2. The brushless motor according to claim 1, wherein the opening angle of the small teeth at both ends in the rotational direction is 140 ° in electrical angle, and the opening angle of the small teeth in the central portion in the rotational direction is 170 ° in electrical angle .

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