JP7394570B2 - brushless motor - Google Patents

Description

The present invention relates to a brushless motor, and particularly to a brushless motor having a magnetic sensor that detects rotation of a rotor.

Brushless motors include position sensor driven type brushless motors that detect the position of the rotor using a magnetic sensor and control the current flowing through the stator coil, and position sensorless driven type brushless motors that do not include a sensor. Since a position sensorless drive type brushless motor does not include a sensor, it can be constructed at low cost and can also be used in harsh environments such as high-temperature environments. On the other hand, a drive type brushless motor with a position sensor can reliably detect the position of the rotor, so it has the advantage of being able to smoothly control rotation from low speed to high speed.

Further, since the drive type brushless motor with a position sensor can supply an appropriate drive current depending on the position of the rotor, it can have higher responsiveness than the drive type without a position sensor. For this reason, brushless motors with high responsiveness are placed inside the lens barrel of cameras for video or still image shooting, and are used to drive the focusing lens and zoom lens installed inside the lens barrel. Preferably, a brushless motor of the drive type with a position sensor is used.

On the other hand, Japanese Patent Laid-Open No. 1-190244 (Patent Document 1) describes a brushless motor. This brushless motor is a drive type brushless motor with a position sensor equipped with a magnetic sensing element, and includes a rotor, a magnetic pole piece constituting a stator, and a winding body. The winding of the coil provided in the stator is wound around the winding body, and the magnetically sensitive element is housed in an element housing provided in the winding body. In the state accommodated in the element housing section, the detection section of the magnetically sensitive element is oriented directly to face the rotor.

Japanese Unexamined Patent Publication No. 1-190244

However, the brushless motor described in Patent Document 1 has a problem in that it is not possible to accurately position the detection section (magnetic flux detection surface) of the magnetically sensitive element (magnetic sensor). That is, in order to detect the magnetism of the rotor and accurately control the current flowing through the winding coils of the stator based on the detected magnetism, it is necessary to position the magnetic flux detection surface of the magnetic sensor with high precision. If there is an error in the mounting position or direction of the magnetic flux detection surface of the magnetic sensor, current will not be able to flow through the stator winding coil at the correct timing, which will reduce the output of the brushless motor and cause vibration and noise. Problems that occur may occur.

This problem is particularly noticeable in small motors, such as brushless motors placed inside the lens barrel of a camera for capturing moving images or still images. That is, in a small brushless motor, a slight error in the position or angle of the magnetic flux detection surface of the magnetic sensor has a great influence on the control of the brushless motor. As described above, research and development by the inventors of the present invention has revealed that a small brushless motor requires extremely high mounting position accuracy on the magnetic flux detection surface of the magnetic sensor.

Therefore, an object of the present invention is to provide a brushless motor that can accurately position the magnetic flux detection surface of a magnetic sensor and suppress a decrease in output and generation of vibration and noise.

In order to solve the above-mentioned problems, the present invention provides a brushless motor having a magnetic sensor that detects the rotation of a rotor, which includes a rotor that is equipped with a magnet and is rotatable around a rotating shaft, and a plurality of wire coils. a plurality of magnetic sensors provided on the stator side and provided with a magnetic flux detection surface for detecting the magnetism of the magnet of the rotor; a single sensor holding member having a plurality of sensor mounting surfaces formed on its outer periphery configured to be mounted with the magnetic flux detection surfaces in contact with each other ; It is characterized by being a plane parallel to the tangent line of the circle, and oriented outward in the radial direction of the circle centered on the axis of rotation.

According to the present invention configured in this way, the sensor mounting surface of the sensor holding member is oriented outward in the radial direction of the circle centered on the rotation axis, parallel to the tangent to the circle centered on the rotation axis. There is. Since the magnetic flux detection surface of the magnetic sensor is attached in contact with this sensor mounting surface, the magnetic flux detection surface is directed toward the rotor, and the angle of the magnetic flux detection surface is defined by the sensor mounting surface. Thereby, the magnetic flux detection surface of the magnetic sensor can be accurately positioned, and a decrease in the output of the brushless motor and generation of vibration and noise can be effectively suppressed.

According to the brushless motor of the present invention, the magnetic flux detection surface of the magnetic sensor can be accurately positioned, and a decrease in output and generation of vibration and noise can be suppressed.

FIG. 1 is a perspective view showing a brushless motor according to an embodiment of the present invention. FIG. 1 is a side view showing a brushless motor according to an embodiment of the present invention. 3 is a cross-sectional view of the brushless motor according to the embodiment of the present invention, taken along line III-III in FIG. 2. FIG. FIG. 1 is a side view showing a brushless motor according to an embodiment of the present invention with a flexible substrate removed. FIG. 1 is a perspective view showing a brushless motor according to an embodiment of the present invention with a flexible substrate and a Hall element removed. 1 is a plan view of a Hall element used in a brushless motor according to an embodiment of the present invention. FIG. 2 is a partially enlarged view showing how a Hall element used in a brushless motor according to an embodiment of the present invention is attached to a flexible substrate.

Next, a brushless motor according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view showing a brushless motor according to an embodiment of the invention. FIG. 2 is a side view showing a brushless motor according to an embodiment of the invention. FIG. 3 is a cross-sectional view of the brushless motor according to the embodiment of the present invention taken along line III-III in FIG. 2. FIG. 4 is a side view showing the brushless motor according to the embodiment of the present invention with the flexible substrate removed. FIG. 5 is a perspective view showing a brushless motor according to an embodiment of the present invention with the flexible substrate and Hall element removed. FIG. 6 is a plan view of a Hall element used in a brushless motor according to an embodiment of the present invention. FIG. 7 is a partially enlarged view showing how the Hall element used in the brushless motor according to the embodiment of the present invention is attached to the flexible substrate.

As shown in FIGS. 1 to 3, a brushless motor 1 according to an embodiment of the present invention includes a rotor 2 rotatable around a rotating shaft 2a, a stator 4 provided so as to surround the rotor 2, It has a Hall element 6 which is a magnetic sensor provided on the stator 4 side, and a flexible substrate 8 wound around the stator 4. The brushless motor 1 of this embodiment applies a current to the coil of the stator 4 at a predetermined timing to apply magnetic force between the stator 4 and the rotor 2, thereby rotating the rotor 2 around the rotating shaft 2a. It is configured. Further, the magnetism of the rotor 2 is detected by a Hall element 6, and based on the detection signal of the Hall element 6, a control device (not shown) is configured to control the timing at which current flows through the coil of the stator 4. There is.

The rotor 2 includes a rotating shaft 2a rotatably supported by the stator 4, and a cylindrical magnet 2b provided concentrically with the rotating shaft 2a.
The rotating shaft 2a is a metal shaft with a circular cross section, and its middle portion is rotatably supported by a bearing 2c (FIG. 2), and the lower portion of the shaft 2a protrudes downward in FIG. 2 from the bearing 2c. In this embodiment, a sintered oil-impregnated bearing is used as the bearing 2c.

The magnet 2b is formed in a cylindrical shape, and the rotating shaft 2a extends through the magnet 2b along its central axis. Further, the outer periphery of the magnet 2b is magnetized so that north poles and south poles alternate along the circumferential direction. The magnet 2b is attached to the rotating shaft 2a above the bearing 2c so as to be rotated together with the rotating shaft 2a, and is surrounded by the stator 4. Note that in this embodiment, a rare earth magnet is used as the magnet 2b.

The flexible substrate 8 is a thin, flexible substrate, and is wound around the upper part of the stator 4 so as to go around the circumference. Further, on the flexible substrate 8, there are a wiring pattern for supplying current to each coil of the stator 4, a wiring pattern for supplying current to each Hall element 6, and a wiring pattern for extracting a detection signal of each Hall element 6. A wiring pattern (not shown in FIG. 1) is formed.

Next, the configuration of the stator 4 will be explained with reference to FIGS. 4 and 5. FIG. 4 shows a state in which the flexible substrate 8 is removed from the brushless motor 1, and FIG. 5 shows a state in which the flexible substrate 8 and the Hall element 6 are removed.
As shown in FIGS. 4 and 5, the stator 4 includes a stator core 10 that is a magnetic member, a plurality of winding coils 12 attached to the stator core 10, and a sensor holding member for attaching the Hall element 6. 14, and a base member 16 to which the stator core 10 is attached.

The stator core 10 is a member made of a magnetic material, and is configured to guide the magnetism generated by each winding coil 12 to the magnet 2b of the rotor 2. The stator core 10 is attached to a base member 16, and the base member 16 is provided with a bearing 2c for the rotating shaft 2a. The stator core 10 includes six straight portions 10a, and these straight portions 10a extend so as to surround the rotor 2 in parallel to the rotating shaft 2a. Further, the straight portions 10a have a rectangular cross section, and extend at equal intervals around the rotor 2 at a center angle of 60 degrees. Therefore, the six straight portions 10a are arranged in three pairs such that the long sides of their rectangular cross sections face each other.

Further, the base end portion of each straight portion 10a is curved 90 degrees radially inward and continues to the base portion 10b extending in the horizontal direction. The tip of each base 10b is integrated around the rotating shaft 2a. In other words, the base portions 10b of the stator core 10 extend radially horizontally around the rotating shaft 2a, are curved upward by 90 degrees, and are connected to straight portions 10a extending vertically.

The winding coils 12 are coils provided below each linear portion 10a of the stator core 10, and are wound around each linear portion 10a. By passing current through these winding coils 12, the straight portion 10a of the stator core 10 passing through the inside thereof is magnetized, and this magnetism acts on the magnet 2b of the rotor 2, and the driving force that rotates the rotor 2 is generated. generated.

As shown in FIGS. 4 and 5, the sensor holding member 14 is a generally cylindrical member made of a non-magnetic material, and is arranged to surround the rotor 2. As shown in FIGS. In this embodiment, the sensor holding member 14 is made of polycarbonate resin reinforced with glass fibers. The sensor holding member 14 has a generally cylindrical cylindrical portion 14a and three fitting portions 14b (only one shown in FIG. 5) extending downward from the cylindrical portion 14a.

As shown in FIG. 5, the cylindrical portion 14a is a generally cylindrical portion, and rotatably receives the magnet 2b of the rotor 2 inside. The outer circumferential surface of the cylindrical portion 14a is cut out in a planar manner at three locations, and a sensor mounting surface 18 for mounting the Hall element 6 is formed at the center of each of the cutout planes. Three sensor mounting surfaces 18 are formed on the outer peripheral surface of the cylindrical portion 14a at equal intervals of 120 degrees. Each sensor mounting surface 18 is directed outward in the radial direction of a circle centered on the rotating shaft 2a, and extends along a tangent to the circle centered on the rotating shaft 2a. In other words, each sensor mounting surface 18 is oriented in a direction perpendicular to a straight line extending radially from the rotating shaft 2a.

Further, position regulating walls 18a are provided on both sides of each sensor mounting surface 18 so as to face each other. These position regulating walls 18a are provided so as to rise at right angles from the sensor mounting surface 18, and extend in a direction parallel to the rotating shaft 2a. As will be described later, each Hall element 6 is attached to each sensor mounting surface 18 between opposing position regulating walls 18a. Note that since the sensor holding member 14 is made of a non-magnetic material, the magnetic flux from the magnet 2b of the rotor 2 easily passes through the sensor holding member 14, and the transmitted magnetic flux can be detected by each Hall element 6. .

Three fitting parts 14b are provided at equal intervals so as to protrude downward from the lower end of the cylindrical part 14a. That is, the side wall surface of the cylindrical portion 14a is partially extended so as to protrude downward, and this portion constitutes the fitting portion 14b. Further, three sensor mounting surfaces 18 are provided at equal intervals on the circumference of the cylindrical portion 14a, and one fitting portion 14b is provided between each sensor mounting surface 18. As shown in FIG. 5, the cylindrical portion 14a of the sensor holding member 14 is arranged on the upper end of the stator core 10, and three sensor mounting surfaces 18 are provided on the side surface of the cylindrical portion 14a. Further, the fitting portion 14b is provided between two adjacent sensor mounting surfaces 18 so as to hang downward from the lower end of the cylindrical portion 14a. Each fitting portion 14b is provided so as to fit between two adjacently arranged linear portions 10a of the stator core 10. That is, the side surfaces on both sides of the fitting portion 14b are configured to match the side surfaces of the straight portion 10a of the stator core 10, respectively, and to fit between the two straight portions 10a.

In this manner, the lower surface of the cylindrical portion 14a of the sensor holding member 14 contacts the upper end surface of the straight portion 10a of the stator core 10, while each of the fitting portions 14b hanging down from the lower surface of the cylindrical portion 14a contacts the straight portion 10a. 10a. As a result, the sensor holding member 14 is accurately positioned with respect to the stator core 10 that constitutes a part of the stator 4, and the position of each sensor mounting surface 18 provided on the sensor holding member 14 is adjusted relative to the stator core 10. position.

Next, with new reference to FIGS. 6 and 7, the configuration of the Hall element 6 and its mounting structure will be described.
As shown in FIG. 6, the Hall element 6 has a rectangular parallelepiped main body 6a and four electrodes 6b protruding from both side surfaces of the main body 6a. Furthermore, in this embodiment, the Hall element 6 is a surface-mounted element with leads. That is, the Hall element 6 is not a type of element that is electrically connected with an electrode extending from the main body passed through a hole in a printed circuit board, etc., but a type in which the electrode is placed on the surface of a printed circuit board, etc. This is the type of element to be implemented.

In this embodiment, in the Hall element 6, an input current is passed through two of the four electrodes 6b, and a voltage proportional to the detected magnetic flux density is output between the remaining two electrodes 6b. It is configured to Further, the upper surface of the rectangular parallelepiped main body portion 6a is a magnetic flux detection surface 6c, and the structure is such that the density of magnetic flux passing through this magnetic flux detection surface 6c is outputted from the Hall element 6 as a detection signal. Further, two of the four electrodes 6b are provided on each side surface 6d on both sides of the main body portion 6a.

Further, as shown in FIG. 3, the Hall element 6 is attached to the sensor holding member 14 so that its magnetic flux detection surface 6c comes into contact with the sensor mounting surface 18 of the sensor holding member 14. Further, side surfaces 6d of the main body portion 6a provided on both sides of the magnetic flux detection surface 6c are arranged so as to match two position regulating walls 18a (FIG. 5) provided on the sensor mounting surface 18 of the sensor holding member 14, respectively. It is configured. Further, as shown in FIG. 4, the position regulating wall 18a fits between the two electrodes 6b provided on each side surface 6d of the Hall element 6, and contacts each side surface 6d between the electrodes 6b. It is configured as follows. In other words, each position regulating wall 18a abuts each side surface 6d of the Hall element 6 at a portion where the electrode 6b of the Hall element 6 does not protrude.

In this way, the direction of the magnetic flux detection surface 6c of the Hall element 6 is defined by the sensor mounting surface 18 of the sensor holding member 14, and the axial and circumferential positions of the magnetic flux detection surface 6c are It is defined by the position regulating wall 18a. Furthermore, by placing the magnetic flux detection surface 6c of the Hall element 6 in direct contact with the sensor mounting surface 18 formed on the sensor holding member 14 so as to face outward in the radial direction, the direction of the magnetic flux detection surface 6c can be adjusted. It can be precisely defined radially inward. That is, since the magnetic flux detection surface 6c is in direct contact with the sensor mounting surface 18, even if there is a dimensional error or a shape error in the main body 6a of the Hall element 6, the direction of the magnetic flux detection surface 6c can be accurately defined. can.

Next, a connection structure between the Hall element 6 and the flexible substrate 8 will be described with reference to FIGS. 2, 4, and 7.
First, as shown in FIG. 4, three Hall elements 6 are attached to three sensor mounting surfaces 18 provided on the outer peripheral surface of the sensor holding member 14, respectively. That is, the magnetic flux detection surface 6c of the Hall element 6 is adhered to the sensor mounting surface 18 of the sensor holding member 14. At this time, side surfaces 6d on both sides of the magnetic flux detection surface 6c are brought into contact with position regulating walls 18a provided on the sensor mounting surface 18, respectively. Note that it is preferable that the adhesive layer that adheres the magnetic flux detection surface 6c to the sensor mounting surface 18 be extremely thin and uniform. Thereby, each Hall element 6 is accurately positioned with respect to the sensor holding member 14.

Next, as shown in FIG. 2, the flexible substrate 8 is wrapped around the linear portion 10a of the stator core 10 and the sensor holding member 14. Note that the flexible substrate 8 is provided with rectangular notches 8a that receive the magnetic flux detection surfaces 6c of each Hall element 6, and the electrodes 6b of the Hall elements 6 are electrically connected to the edges of these notches 8a. A substrate land 8b is formed as a connection portion for the purpose. Furthermore, wiring patterns 8c are provided on the flexible substrate 8 so as to extend from each substrate land 8b, and these wiring patterns 8c are used to supply current to the Hall element 6 and to receive detection signals from the Hall element 6. It is used for communication. Furthermore, a wiring pattern (not shown) for supplying current to each winding coil 12 is also provided on the flexible substrate 8.

When the magnetic flux detection surface 6c of each Hall element 6 is arranged so as to be received inside the notch 8a of the flexible substrate 8, the flexible substrate 8 can detect the magnetic flux of the Hall element 6, as shown in FIG. It is arranged between the surface 6c and the tip of the electrode 6b of the Hall element 6. In this state, the substrate lands 8b of the flexible substrate 8 are located on the outer peripheral side of the wound flexible substrate 8. On the other hand, each electrode 6b protruding from the side surface of the Hall element 6 passes through the notch 8a of the flexible substrate 8 and extends to the outer peripheral side of the flexible substrate 8. Each substrate land 8b provided at the edge of the notch 8a of the flexible substrate 8 is provided at a position corresponding to each electrode 6b of the Hall element 6. Therefore, the tip of each electrode 6b can be soldered to each board land 8b on the outer peripheral surface of the wound flexible board 8, and the electrode 6b can be electrically connected to the board land 8b.

In this way, after bonding each Hall element 6 to the sensor holding member 14, the flexible substrate 8 is wrapped around the sensor holding member 14, and then the electrode 6b of each Hall element 6 and the substrate land 8b of the flexible substrate 8 are bonded. ing. Therefore, when wrapping the flexible substrate 8, it is possible to prevent solder cracks from occurring at the joint between the electrode 6b and the substrate land 8b. Note that the electrode 6b and the substrate land 8b can also be bonded using a conductive adhesive.

According to the brushless motor 1 of the embodiment of the present invention, the sensor mounting surface 18 of the sensor holding member 14 is arranged radially outward of the circle centered on the rotating shaft 2a, parallel to the tangent of the circle centered on the rotating shaft 2a. is directed towards. Since the magnetic flux detection surface 6c of the Hall element 6 is mounted in contact with this sensor mounting surface 18, the magnetic flux detection surface 6c is directed toward the rotor 2, and the angle of the magnetic flux detection surface 6c is defined by the sensor mounting surface 18. Ru. Thereby, the magnetic flux detection surface 6c of the Hall element 6 can be accurately positioned, and a decrease in the output of the brushless motor 1 and generation of vibration and noise can be effectively suppressed.

Further, according to the brushless motor 1 of the present embodiment, the sensor holding member 14 is positioned with respect to the stator core 10, so that the sensor holding member 14 can be reliably positioned, and the sensor mounting member formed thereon can be reliably positioned. Surface 18 can be accurately positioned.

Furthermore, according to the brushless motor 1 of this embodiment, since the sensor holding member 14 includes the fitting portion 14b that fits into the stator core 10, the position of the sensor holding member 14 with respect to the stator core 10 can be easily determined. be able to.

Further, according to the brushless motor 1 of the present embodiment, the sensor mounting surface 18 of the sensor holding member 14 is provided with position regulating walls 18a that match the side surfaces 6d of the Hall element 6. In addition to the angle of the magnetic flux detection surface 6c, the circumferential position of the magnetic flux detection surface 6c can also be accurately positioned.

Furthermore, according to the brushless motor 1 of the present embodiment, the position regulating wall 18a abuts on a portion of the side surface 6d of the Hall element 6 from which the electrode 6b does not protrude, so that the position of the Hall element 6 in the axial direction is also Positioning can be performed using the regulating wall 18a.

Although preferred embodiments of the present invention have been described above, various changes can be made to the embodiments described above. In particular, in the embodiment described above, the winding coil 12 was wound around the straight portion 10a of the stator core 10 extending parallel to the rotating shaft 2a, but it was wound around the stator core extending radially from the rotating shaft. The present invention can also be applied to a type of brushless motor in which a wire coil is wound.

1 Brushless motor 2 Rotor 2a Rotating shaft 2b Magnet 2c Bearing 4 Stator 6 Hall element (magnetic sensor)
6a Main unit 6b Electrode 6c Magnetic flux detection surface 6d Side surface 8 Flexible board 8a Notch 8b Board land (connection part)
8c Wiring pattern 10 Stator core (magnetic material member)
10a Straight portion 10b Base 12 Winding coil 14 Sensor holding member 14a Cylindrical portion 14b Fitting portion 16 Base member 18 Sensor mounting surface 18a Position regulating wall

Claims (6)

A brushless motor having a magnetic sensor that detects rotation of a rotor,
A rotor equipped with a magnet and capable of rotating around a rotating shaft,
a stator with multiple winding coils;
a plurality of magnetic sensors provided on the stator side and including a magnetic flux detection surface for detecting the magnetism of the magnet of the rotor;
A single sensor mounting surface is provided on the stator side so as to surround the rotor , and a plurality of sensor mounting surfaces are formed on the outer periphery and are configured to be mounted with the magnetic flux detection surfaces of the magnetic sensor in contact with each other. A sensor holding member;
has
Each of the sensor mounting surfaces is a plane parallel to a tangent to a circle centered on the rotation axis, and is directed outward in the radial direction of the circle centered on the rotation axis. motor. 2. The brushless motor according to claim 1, wherein the stator includes a magnetic member for guiding the magnetic flux generated by each of the winding coils, and the sensor holding member is positioned with respect to the magnetic member. The magnetic member is configured to extend around the rotating shaft in substantially parallel to the rotating shaft, and the sensor holding member is configured to be positioned with respect to the magnetic member so that the sensor holding member is positioned relative to the magnetic member. The brushless motor according to claim 2, further comprising a fitting portion for fitting. The magnetic sensor has side surfaces provided on both sides of the magnetic flux detection surface, and the sensor mounting surface of the sensor holding member is provided with position regulating walls that match the side surfaces of the magnetic sensor, respectively. A brushless motor according to any one of claims 1 to 3. 5. The magnetic sensor has electrodes protruding from the side surfaces on both sides of the magnetic sensor, and the position regulating wall abuts a portion of the side surface of the magnetic sensor from which the electrodes do not protrude. brushless motor. The flexible substrate further includes a notch for receiving the magnetic flux detection surface of the magnetic sensor, a connecting portion provided at the edge of the notch to be connected to the electrode of the magnetic sensor, and this connecting portion. A wiring pattern is provided extending from the sensor holding member, the sensor holding member is formed in a generally cylindrical shape, the magnetic sensor is a surface-mounted element, and the electrodes of the magnetic sensor are wound around the outer periphery of the sensor holding member. The brushless motor according to any one of claims 1 to 5, wherein the brushless motor is electrically connected to the connecting portion on an outer peripheral surface of the flexible substrate.

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