Patent Publication Number: US-2023155467-A1

Title: Single-phase brushless dc motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/JP2021/009385, filed on Mar. 9, 2021, and with priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) being claimed from Japanese Patent Application No. 2020-069747, filed on Apr. 8, 2020, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to a single-phase brushless DC motor. 
     BACKGROUND 
     Conventionally, it is known that excitation of a stator is switched by switching energization to a coil wound around the stator on the basis of a rotational position, that is, a circumferential position, of a rotor detected by a Hall element, by which a motor is driven. 
     For the purpose of obtaining the excitation switching timing of the stator, it is conceivable to use a driver that is an IC having incorporated therein a Hall element and capable of outputting the excitation switching timing. When the driver described above is used, a reduction in size and a reduction in cost of the motor can be achieved. 
     On the other hand, recently, there has been a demand for acquiring the rotational position of the rotor for a purpose other than the purpose of obtaining the excitation switching timing of the stator. In this case, it is also conceivable to use an output signal of the driver, but since the driver outputs a signal optimized for switching the excitation of the stator, the output signal may deviate from the actual rotational position of the rotor. Therefore, there is a problem that an accurate rotational position of the rotor cannot be obtained. 
     SUMMARY 
     A single-phase brushless DC motor according to a first example embodiment of the present disclosure includes a rotor rotatable about a central axis, a stator including salient pole portions, a stator core including a slot between the salient pole portions, and a winding wound around the salient pole portions, the stator opposing the rotor with an air gap interposed therebetween, and a substrate fixed to the stator and including a driver to perform energization control of the winding. The driver includes a Hall element to acquire a timing of the energization control, and the substrate includes a Hall IC to detect a circumferential position of the rotor separately from the driver. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating a motor according to a first example embodiment of the present disclosure. 
         FIG.  2    is a side sectional view describing a structure of a motor  10  in  FIG.  1   . 
         FIG.  3    is a cross-sectional plan view illustrating the motor  10  in  FIG.  1    taken along a plane orthogonal to a Y axis and located on a second side in an axial direction with respect to a salient pole portion  220  of a stator  200  and on a first side in the axial direction with respect to an end of a driver  330  on the first side in the axial direction. 
         FIG.  4    is a plan view illustrating the motor  10  in  FIG.  1    without a rotor  100 . 
     
    
    
     DETAILED DESCRIPTION 
     Motors according to example embodiments of the present disclosure will be described below with reference to the drawings. In the following drawings, each structure may be different in contraction scale, number, or the like from an actual structure for easy understanding. 
     In the drawings, an XYZ coordinate system is shown appropriately as a three-dimensional orthogonal coordinate system. In the XYZ coordinate system, a Y-axis direction is defined as a direction parallel to an axial direction of a central axis J illustrated in  FIG.  1   . An X-axis direction is defined as a horizontal direction in  FIG.  3    in a radial direction with respect to the central axis J. A Z-axis direction is defined as a direction orthogonal to both the X-axis direction and the Y-axis direction. In any of the X-axis direction, the Y-axis direction, and the Z-axis direction, an arrow in each drawing indicates a positive side and the side opposite to the positive side is a negative side. 
     In the description below, the positive side of the Y-axis direction (+Y side) is referred to as the “front side” or “first side”, and the negative side of the Y-axis direction (−Y side) is referred to as the “rear side” or “second side”. It is to be understood that the terms “rear side (second side)” and “front side (first side)” are used for description only, and they do not limit the actual positional relation or direction. Unless otherwise particularly stated, a direction parallel to the central axis J (Y-axis direction) is simply referred to as the “axial direction”, a radial direction about the central axis J is simply referred to as the “radial direction”, and a circumferential direction around the central axis J, that is, a direction around the central axis J is simply referred to as the “circumferential direction”. In the radial direction, a direction toward the central axis J is referred to by the term “radially inner” or “radially inward”, and a direction away from the central axis J is referred to by the term “radially outer” or “radially outward”. 
     Herein, the wording “extending in the axial direction” refers to not only a case of strictly extending in the axial direction (Z-axis direction), but also a case of extending in a direction at an angle of less than 45° from the axial direction. 
     Additionally, herein, the wording “extending in the radial direction” refers to not only a case of strictly extending in the radial direction, i.e., in a direction perpendicular to the axial direction (Z-axis direction), but also a case of extending in a direction at an angle of less than 45° from the radial direction. The term “parallel” includes not only a case of being strictly parallel but also a case of inclination at an angle of less than 45°. 
       FIG.  1    is a perspective view illustrating a motor according to the first example embodiment of the present disclosure. 
       FIG.  2    is a side sectional view for describing a structure of the motor  10  in  FIG.  1   . 
     In the present example embodiment, the motor  10  is a single-phase brushless DC motor. The motor  10  includes a rotor  100 , a stator  200 , and a substrate  300 . 
     The rotor  100  is rotatable about the central axis J. The rotor  100  includes a shaft  110  disposed along the central axis J. The rotor  100  has an outer peripheral portion  120  that extends radially outward from the shaft  110  and then extends to a second side in the axial direction. The outer peripheral portion  120  has a bottomed cylindrical shape that covers the stator  200  from a first side in the axial direction. The outer peripheral portion  120  has a bottom  120   b  extending radially outward from the shaft  110  and a side wall  120   a  extending to the second side in the axial direction from a radially outer end of the bottom  120   b.  As will be described in detail later, the rotor  100  includes a rotor magnet  130  on the inner peripheral side of the side wall  120   a.  The shaft  110  is integrated with the outer peripheral portion  120 . The shaft  110  may be a member separate from the outer peripheral portion  120 . The shaft  110  is pivotally supported by a bearing, but the bearing is not illustrated. 
     The stator  200  has a cylindrical support column portion  250  through which the shaft  110  passes, and the support column portion  250  passes through a through hole  300   a  of the substrate  300 . The stator  200  has a stator core  210  on the outside of the support column portion  250  in the radial direction. As will be described in detail later, a winding  211  as a motor coil is wound around the stator core  210 . The stator  200  is fixed to the substrate  300 . The stator core  210  of the stator  200  is located on the first side in the axial direction with respect to the substrate  300 . The stator  200  may be directly fixed to the substrate  300  or may be indirectly fixed thereto. 
       FIG.  3    is a cross-sectional plan view illustrating the motor  10  in  FIG.  1    taken along a plane orthogonal to the Y axis and located on the second side in the axial direction with respect to a salient pole portion  220  (see  FIG.  4   ) of the stator  200  and on the first side in the axial direction with respect to the end of a driver  330  on the first side in the axial direction. 
     The rotor magnet  130  is fixed to the inner peripheral surface of the side wall  120   a  on an end of the side wall  120   a  on the second side in the axial direction. The rotor magnet  130  is an annular member in which N poles and S poles are alternately magnetized at equal intervals over the entire circumference in the circumferential direction. 
       FIG.  4    is a plan view illustrating the motor  10  in  FIG.  1    without the rotor  100 . 
     The stator core  210  has a salient pole portion  220  extending radially outward. A plurality of the salient pole portions  220  is disposed in the circumferential direction. In the present example embodiment, four salient pole portions  220  are disposed. The stator core  210  has slots  240  between the adjacent salient pole portions  220 . The stator  200  has the winding  211  that passes through the slot  240  and is wound around the salient pole portion  220 . A radially outer end of the salient pole portion  220  faces the inner peripheral surface of the rotor magnet  130  in the radial direction with an air gap therebetween. That is, the stator  200  faces the rotor  100  in the radial direction with the air gap therebetween. 
     The substrate  300  is equipped with a connector  310 . The connector  310  is mounted on a surface of the substrate  300  on the first side in the axial direction. The connector  310  may be mounted on a surface of the substrate  300  on the second side in the axial direction. The connector  310  electrically connects each component mounted on the substrate  300  to the outside. External wiring is connected to the connector  310 . 
     The substrate  300  is equipped with the driver  330 . The driver  330  is mounted on the surface of the substrate  300  on the first side in the axial direction. The driver  330  incorporates a Hall element. The driver  330  is mounted at a position facing, in the axial direction, an end of the rotor magnet  130  on the second side in the axial direction. The Hall element incorporated in the driver  330  detects the rotational position of the rotor  100  and acquires a timing of energization control for the winding  211  wound around the salient pole portion  220 . The driver  330  performs energization control on the winding  211  wound around the salient pole portion  220  on the basis of a timing of energization control acquired by the incorporated Hall element. The Hall element incorporated in the driver  330  detects the rotational position of the rotor  100 , that is, the circumferential position of the rotor  100 , by detecting the boundary between the N pole and the S pole of the rotor magnet  130 . The driver  330  is disposed at a circumferential position of the slot  240  of the stator core  210 . Therefore, the driver  330  is less likely to be affected by electromagnetic noise by the stator  200 , and can more accurately detect the circumferential position of the rotor  100 . 
     The substrate  300  is equipped with a Hall IC  320  separately from the driver  330 . That is, the Hall IC  320  is a component different from the Hall element incorporated in the driver  330 . The Hall IC  320  is mounted on the surface of the substrate  300  on the first side in the axial direction. The Hall IC  320  is mounted at a position facing, in the axial direction, the end of the rotor magnet  130  on the second side in the axial direction. The Hall IC  320  detects the rotational position of the rotor  100 , that is, the circumferential position of the rotor  100 , by detecting the boundary between the N pole and the S pole of the rotor magnet  130 . According to the motor  10 , an accurate circumferential position of the rotor  100  can be output by using the circumferential position of the rotor  100  detected by the Hall IC  320 . The feature in which the Hall IC  320  can output the accurate circumferential position of the rotor  100  will be described in detail below. 
     A distance between the Hall IC  320  and the connector  310  is shorter than a distance between the driver  330  and the connector  310 . Therefore, a wire shorter than a wire for connecting the driver  330  and the connector  310  can be used for connecting the Hall IC  320  and the connector  310 , and thus, the Hall IC  320  can detect the circumferential position of the rotor more accurately with little influence of electromagnetic noise. 
     The Hall IC  320  is disposed at a circumferential position of the slot  240  of the stator core  210 . Therefore, the Hall IC  320  is less likely to be affected by electromagnetic noise by the stator  200 , and can more accurately detect the circumferential position of the rotor  100 . For example, the Hall IC  320  faces the end of the rotor magnet  130  on the second side in the axial direction and is disposed in the slot  240  closest to the connector  310 . 
     During rotation of the rotor  100 , a timing at which the driver  330  switches the energization of the winding  211  of the stator  200  is different from a timing at which the boundary between the N pole and the S pole of the rotor magnet  130  comes to the circumferential position of the Hall IC  320 . Due to the arrangement of the driver  330  and the Hall IC  320  as described above, it is possible to shift the timing of switching the energization of the winding of the stator  200  that is likely to have electromagnetic noise from the timing of detecting and outputting the circumferential position of the rotor  100  by the Hall IC  320 . By shifting the timing as described above, electromagnetic noise which may occur at the time of switching energization is not generated during detection by the Hall IC  320 . Thus, the output of the Hall IC  320  is less likely to be affected by the electromagnetic noise, whereby the circumferential position of the rotor  100  can be detected more accurately. 
     In addition, during rotation of the rotor  100 , the timing at which the driver  330  switches the energization of the winding  211  of the stator  200  may be later than the timing at which the boundary between the N pole and the S pole of the rotor magnet  130  comes to the circumferential position of the Hall IC  320 . With this configuration, the Hall IC  320  can detect and output the circumferential position of the rotor  100  at a timing at which little electromagnetic noise is generated, whereby the circumferential position of the rotor  100  can be more accurately detected. 
     In addition, during rotation of the rotor  100 , the timing at which the driver  330  switches the energization of the winding  211  of the stator  200  may be earlier than the timing at which the boundary between the N pole and the S pole of the rotor magnet  130  comes to the circumferential position of the Hall IC  320 . With this configuration, the Hall IC  320  can detect and output the circumferential position of the rotor  100  at a timing at which little electromagnetic noise is generated. Thus, the circumferential position of the rotor  100  can be more accurately detected, and the detection of the circumferential position of the rotor  100  by the Hall element incorporated in the driver  330  can be used as prediction. For example, energizing the Hall IC  320  after receiving prediction can contribute to power saving. 
     In addition, in the present example embodiment, the driver  330 , the stator core  210 , the Hall IC  320 , and the connector  310  are arranged on a straight line as illustrated in  FIGS.  3  and  4   . With this arrangement, the wiring can be shortened. Therefore, the circumferential position of the rotor  100  can be detected more accurately with little influence of electromagnetic noise. 
     Next, operations and effects of the motor  10  will be described. 
     The disclosure according to the example embodiment described above provides a single-phase brushless DC motor including: a rotor rotatable about a central axis; a stator including a plurality of salient pole portions, a stator core having a slot between the salient pole portions, and a winding wound around the salient pole portions, the stator facing the rotor with an air gap interposed therebetween; and a substrate fixed to the stator and equipped with a driver that performs energization control of the winding, wherein the driver incorporates a Hall element that acquires a timing of the energization control, and the substrate is equipped with a Hall IC that detects a circumferential position of the rotor separately from the driver. 
     With this configuration, the circumferential position of the rotor is detected by the Hall IC, so that it is not necessary to use the output of the Hall element incorporated in the driver. Thus, the circumferential position of the rotor can be detected more accurately with little influence of electromagnetic noise. 
     In addition, the substrate includes a connector to which external wiring is connected, and a distance between the Hall IC and the connector is shorter than a distance between the driver and the connector. 
     Because of the distance between the Hall IC and the connector being short, the Hall IC is less likely to be affected by electromagnetic noise and can more accurately detect the circumferential position of the rotor. 
     In addition, the Hall element incorporated in the driver and the Hall IC is disposed at a circumferential position of the slot of the stator core. 
     Therefore, the circumferential position of the rotor can be detected more accurately with little influence of electromagnetic noise by the stator. 
     In addition, the rotor includes a rotor magnet that has an N pole and an S pole alternately arranged in the circumferential direction, and during rotation of the rotor, a timing at which the driver switches energization of the winding of the stator is different from a timing at which a boundary between the N pole and the S pole of the rotor magnet reaches a circumferential position of the Hall IC. 
     With this configuration, the timing of switching energization of the winding of the stator that is likely to have electromagnetic noise is shifted from the timing of outputting the position of the rotor by the Hall IC, whereby the output of the Hall IC is less likely to be affected by the electromagnetic noise, and thus, the circumferential position of the rotor can be detected more accurately. 
     In addition, during rotation of the rotor, the timing at which the driver switches the energization of the winding of the stator is later than the timing at which the boundary between the N pole and the S pole of the rotor magnet reaches the circumferential position of the Hall IC. 
     With this configuration, the Hall IC can output the position of the rotor at a timing at which little electromagnetic noise is generated, whereby the circumferential position of the rotor can be more accurately detected. 
     In addition, during rotation of the rotor, the timing at which the driver switches the energization of the winding of the stator is earlier than the timing at which the boundary between the N pole and the S pole of the rotor magnet reaches the circumferential position of the Hall IC. 
     With this configuration, the detection of the position of the rotor by the Hall element incorporated in the driver can be used as prediction. For example, energizing the Hall IC after receiving the prediction can contribute to power saving. 
     In addition, the driver, the stator core, the Hall IC, and the connector are arranged on a straight line. 
     With this configuration, the driver, the stator core, the Hall IC, and the connector are arranged on a straight line, whereby the wiring can be shortened. Therefore, the circumferential position of the rotor can be detected more accurately with little influence of electromagnetic noise. 
     The application of the motor according to the above-described example embodiment is not particularly limited. Also note that features described above may be combined appropriately as long as no conflict arises. 
     While the example embodiment of the present disclosure has been described above, the present disclosure is not limited to such an example embodiment, and various modifications and changes are possible within the scope of the spirit of the present disclosure. The example embodiments described above and modifications thereof are included in not only the scope and gist of the disclosure, but also the disclosure described in the scope of claims and the equivalent thereof. 
     Features of the above-described example embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.