JP2021052455A - Brushless motor - Google Patents

Abstract

To provide a brushless motor capable of suppressing reduction of output, generation of vibration and noise, etc., by accurately positioning a magnetic flux detection plane of a magnetic sensor.SOLUTION: The present invention relates to a brushless motor (1) comprising a magnetic sensor which detects rotation of a rotor. The brushless motor comprises: a rotor (2) including a magnet (2b) and rotatable around a rotation axis (2a); a stator (4) including a plurality of winding coils; a magnetic sensor (6) provided at the stator side and including a magnetic flux detection plane (6c) for detecting magnetism of the magnet of the rotor; and a sensor holding member (14) provided at the stator side and including a sensor mounting surface (18) configured to mount the magnetic sensor thereon by abutting the magnetic flux detection plane. The sensor mounting surface is a flat surface in parallel with a tangent of a circle with the rotation axis defined as a center, and oriented outward in a radial direction of the circle with the rotation axis defined as the center.SELECTED DRAWING: Figure 1

Description

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

Brushless motors include a drive type brushless motor with a position sensor that detects the position of the rotor with a magnetic sensor and controls the current flowing through the coil of the stator, and a position sensorless drive type brushless motor without a sensor. Since the position sensorless drive type brushless motor does not have a sensor, it can be constructed at low cost and can be used in a bad environment such as a high temperature environment. On the other hand, the drive type brushless motor with a position sensor has an advantage that the rotation can be smoothly controlled from low speed to high speed because the position of the rotor can be reliably detected.

Further, since the drive type brushless motor with a position sensor can supply an appropriate drive current according to the position of the rotor, the responsiveness can be improved as compared with the position sensorless drive type. For this reason, it is highly responsive to a focus lens provided in the lens barrel of a camera for shooting moving images or still images and a brushless motor for driving a zoom lens. It is preferable to use a drive type brushless motor with a position sensor.

On the other hand, Japanese Patent Application Laid-Open No. 1-1090244 (Patent Document 1) describes a brushless motor. This brushless motor is a drive type brushless motor with a position sensor equipped with a magnetically sensitive element, and includes a rotor, a magnetic pole 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 the element accommodating portion provided in the winding body. In the state of being housed in the element accommodating unit, the detection unit of the magnetically sensitive element is directed so as to directly face the rotor.

Japanese Unexamined Patent Publication No. 1-1902244

However, the brushless motor described in Patent Document 1 has a problem that the position of the detection unit (magnetic flux detection surface) of the magnetic sensitive element (magnetic sensor) cannot be accurately positioned. That is, in order to detect the magnetism of the rotor and accurately control the current flowing through the winding coil of the stator based on this, it is necessary to position the magnetic flux detection surface of the magnetic sensor with high accuracy. If there is an error in the mounting position or direction of the magnetic flux detection surface of the magnetic sensor, it will not be possible to pass current through the winding coil of the stator at the correct timing, which will reduce the output of the brushless motor, and cause vibration and noise. There is a problem that it occurs.

This problem becomes particularly remarkable in a small motor such as a brushless motor arranged in the lens barrel of a camera for photographing a moving image or a still image. 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, it has been clarified by the research and development of the present inventor that an extremely high mounting position accuracy is required for the magnetic flux detection surface of the magnetic sensor in a small brushless motor.

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

In order to solve the above-mentioned problems, the present invention is a brushless motor having a magnetic sensor for detecting the rotation of the rotor, the rotor is provided with a magnet and can rotate about a rotation axis, and a plurality of winding coils are provided. A stator provided, a magnetic sensor provided on the stator side and provided with a magnetic flux detection surface for detecting the magnetism of the rotor magnet, and a magnetic sensor provided on the stator side and having a magnetic flux detection surface of the magnetic sensor in contact with each other are attached. It has a sensor holding member having a sensor mounting surface configured as described above, and the sensor mounting surface is a plane parallel to the tangent line of a circle centered on the rotation axis and is a circle centered on the rotation axis. It is characterized by being oriented outward in the radial direction of.

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

It is a perspective view which shows the brushless motor by embodiment of this invention. It is a side view which shows the brushless motor by embodiment of this invention. FIG. 5 is a cross-sectional view taken along the line III-III of FIG. 2 of the brushless motor according to the embodiment of the present invention. It is a side view which shows the brushless motor by embodiment of this invention in the state which removed the flexible substrate. It is a perspective view which shows the brushless motor according to the embodiment of this invention in the state which removed the flexible substrate and the Hall element. It is a top view of the Hall element used in the brushless motor according to the embodiment of this invention. It is a partially enlarged view which shows the attachment to the flexible substrate of the Hall element used for the brushless motor by embodiment of this invention.

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 present invention. FIG. 2 is a side view showing a brushless motor according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the brushless motor according to the embodiment of the present invention along the line III-III of FIG. FIG. 4 is a side view showing the brushless motor according to the embodiment of the present invention in a state where the flexible substrate is removed. FIG. 5 is a perspective view showing the brushless motor according to the embodiment of the present invention in a state where the flexible substrate and the Hall element are removed. FIG. 6 is a plan view of the Hall element used in the brushless motor according to the embodiment of the present invention. FIG. 7 is a partially enlarged view showing the attachment of the Hall element used in the brushless motor according to the embodiment of the present invention to the flexible substrate.

As shown in FIGS. 1 to 3, the brushless motor 1 according to the embodiment of the present invention includes a rotor 2 that can rotate around a rotating shaft 2a, a stator 4 that is provided so as to surround the rotor 2, and a stator 4. 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. In the brushless motor 1 of the present embodiment, a magnetic force is applied between the stator 4 and the rotor 2 by passing an electric current through the coil of the stator 4 at a predetermined timing, so that the rotor 2 is rotated about the rotation shaft 2a. It is configured. Further, the magnetism of the rotor 2 is detected by the Hall element 6, and the timing of passing a current through the coil of the stator 4 is controlled by a control device (not shown) based on the detection signal of the Hall element 6. There is.

The rotor 2 has 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 having a circular cross section, an intermediate portion thereof is rotatably supported by a bearing 2c (FIG. 2), and a portion below the bearing 2c projects downward in FIG. 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 rotation shaft 2a extends along the central axis thereof. Further, the outer circumference of the magnet 2b is magnetized so that the north 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. In this embodiment, a rare earth magnet is used as the magnet 2b.

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

Next, the configuration of the stator 4 will be described 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 which is a magnetic member, a plurality of winding coils 12 attached to the stator core 10, and a sensor holding member for attaching a Hall element 6. It has 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 the base member 16, and the base member 16 is provided with a bearing 2c of the rotating shaft 2a. The stator core 10 includes six straight lines 10a, and these straight lines 10a extend in parallel with the rotation shaft 2a so as to surround the rotor 2. Further, the straight portion 10a has a rectangular cross section, and extends at equal intervals around the rotor 2 at a central angle of 60 degrees. Therefore, the six straight line portions 10a are arranged so as to form three pairs so that the long sides of the rectangular cross sections face each other.

Further, the base end portion of each straight line portion 10a is curved 90 degrees inward in the radial direction and continues to the base portion 10b extending in the horizontal direction. The tips of the bases 10b are integrated around the rotating shaft 2a. In other words, the base portion 10b of the stator core 10 extends in the horizontal direction radially around the rotation shaft 2a, is curved 90 degrees upward, and is connected to the straight line portion 10a extending in the vertical direction, respectively.

The winding coil 12 is a coil provided below each straight line portion 10a of the stator core 10, and is wound around each straight line portion 10a. By passing an electric current through these winding coils 12, the linear portion 10a of the stator core 10 penetrating the inside thereof is magnetized, and this magnetism acts on the magnet 2b of the rotor 2 to generate a driving force for rotating the rotor 2. Will be generated.

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

As shown in FIG. 5, the cylindrical portion 14a is a substantially cylindrical portion, and the magnet 2b of the rotor 2 is rotatably received inside. The outer peripheral surface of the cylindrical portion 14a is cut out in a plane shape at three points, and a sensor mounting surface 18 for mounting the Hall element 6 is configured in the central portion of the cut-out plane. 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 the circle centered on the rotating shaft 2a, and extends along the tangent line of the circle centered on the rotating shaft 2a. In other words, each sensor mounting surface 18 is oriented in a direction orthogonal to a straight line extending in the radial direction from the rotation axis 2a.

Further, on both sides of each sensor mounting surface 18, position regulating walls 18a are provided so as to face each other. These position limiting 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 rotation shaft 2a. As will be described later, each Hall element 6 is attached to each sensor mounting surface 18 between the facing position limiting walls 18a. 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 portions 14b are provided at equal intervals so as to project downward from the lower end of the cylindrical portion 14a. That is, the side wall surface of the cylindrical portion 14a is extended so as to partially project 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 the sensor mounting surfaces 18. As shown in FIG. 5, the cylindrical portion 14a of the sensor holding member 14 is arranged on the upper end portion 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 be fitted between two linear portions 10a of the stator core 10 arranged adjacent to each other. 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 and to be fitted between the two straight portions 10a.

As described above, in the sensor holding member 14, the lower surface of the cylindrical portion 14a abuts on the upper end surface of the straight portion 10a of the stator core 10, while each fitting portion 14b hanging from the lower surface of the cylindrical portion 14a is a straight portion. It is configured to fit between 10a. As a result, the sensor holding member 14 is accurately positioned with respect to the stator core 10 forming a part of the stator 4, and the positions of the sensor mounting surfaces 18 provided on the sensor holding member 14 are positioned with respect to the stator core 10. Is positioned.

Next, the configuration of the Hall element 6 and its mounting structure will be described with reference to FIGS. 6 and 7.
As shown in FIG. 6, the Hall element 6 has a rectangular parallelepiped main body portion 6a and four electrodes 6b protruding from both side surfaces of the main body portion 6a. Further, in the present embodiment, the Hall element 6 is a surface mount type element with a lead. That is, the Hall element 6 is not a type of element that is electrically connected with the electrode extending from the main body penetrating the hole of the printed circuit board or the like, but the electrode is placed on the surface of the printed circuit board or the like. It is a type of element to be mounted.

In the present 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 6a is a magnetic flux detection surface 6c, and the density of the magnetic flux passing through the magnetic flux detection surface 6c is configured to be output as a detection signal from the Hall element 6. Further, two electrodes 6b are provided on the side surfaces 6d on both sides of the main body 6a.

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

As described above, the orientation 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 position and the circumferential position of the magnetic flux detection surface 6c are set respectively. It is defined by the position control wall 18a. Further, the direction of the magnetic flux detection surface 6c is oriented by arranging 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. It can be defined accurately inward in the radial direction. That is, since the magnetic flux detection surface 6c is in direct contact with the sensor mounting surface 18, even if the main body 6a of the Hall element 6 has a dimensional error or a shape error, the direction of the magnetic flux detection surface 6c can be accurately defined. it can.

Next, the 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, the three Hall elements 6 are attached to the three sensor attachment 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, the side surfaces 6d on both sides of the magnetic flux detection surface 6c are brought into contact with the position regulating wall 18a provided on the sensor mounting surface 18, respectively. The layer of the adhesive that adheres the magnetic flux detection surface 6c to the sensor mounting surface 18 is preferably extremely thin and uniformly formed. As a result, 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 wound around the straight portion 10a of the stator core 10 and the sensor holding member 14. The flexible substrate 8 is provided with a rectangular notch 8a that receives the magnetic flux detection surface 6c of each Hall element 6, and the electrode 6b of the Hall element 6 is electrically connected to the edge of these notches 8a. A substrate land 8b, which is a connecting portion for the device, is formed. Further, wiring patterns 8c are provided on the flexible substrate 8 so as to extend from each substrate land 8b, and these wiring patterns 8c supply a current to the Hall element 6 and a detection signal of the Hall element 6. It is used for the transmission of. Further, a wiring pattern (not shown) for supplying a current to each winding coil 12 is also provided on the flexible substrate 8.

In a state where 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, as shown in FIG. 7, the flexible substrate 8 detects the magnetic flux of the Hall element 6. It is arranged between the surface 6c and the tip of the electrode 6b of the Hall element 6. In this state, the substrate land 8b of the flexible substrate 8 is 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 on 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 substrate land 8b on the outer peripheral surface of the wound flexible substrate 8, and the electrode 6b can be electrically connected to the substrate land 8b.

In this way, after each Hall element 6 is adhered to the sensor holding member 14, the flexible substrate 8 is wound 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 joined. ing. Therefore, when the flexible substrate 8 is wound, it is possible to prevent solder cracks from occurring at the joint between the electrode 6b and the substrate land 8b. The electrode 6b and the substrate land 8b can also be joined with 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 parallel to the tangent of the circle centered on the rotating shaft 2a and outside the radial direction of the circle centered on the rotating shaft 2a. It is directed towards you. Since the magnetic flux detection surface 6c of the Hall element 6 is abutted against the sensor mounting surface 18 and mounted, the magnetic flux detection surface 6c is directed to the rotor 2 and the angle of the magnetic flux detection surface 6c is defined by the sensor mounting surface 18. To. As a result, the magnetic flux detection surface 6c of the Hall element 6 can be accurately positioned, and the decrease in the output of the brushless motor 1 and the generation of vibration and noise can be effectively suppressed.

Further, according to the brushless motor 1 of the present embodiment, since the sensor holding member 14 is positioned with respect to the stator core 10, the sensor holding member 14 can be reliably positioned, and the sensor mounting formed on the sensor holding member 14 can be reliably positioned. The surface 18 can be accurately positioned.

Further, according to the brushless motor 1 of the present embodiment, since the sensor holding member 14 includes a fitting portion 14b that fits with the stator core 10, the position of the sensor holding member 14 with respect to the stator core 10 can be easily positioned. 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 a position regulating wall 18a that matches the side surface 6d of the Hall element 6, respectively. In addition to the angle of the magnetic flux detection surface 6c, the position of the magnetic flux detection surface 6c in the circumferential direction can be accurately positioned.

Further, according to the brushless motor 1 of the present embodiment, the position regulating wall 18a abuts on the portion of the side surface 6d of the Hall element 6 where the electrode 6b does not protrude, so that the position of the Hall element 6 in the axial direction is also the position. It can be positioned by the regulation wall 18a.

Although the preferred embodiment of the present invention has been described above, various modifications can be made to the above-described embodiment. In particular, in the above-described embodiment, the winding coil 12 is wound around the linear portion 10a of the stator core 10 extending parallel to the rotating shaft 2a, but is wound around the stator core extending radially from the rotating shaft. The present invention can also be applied to a 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 body 6b Electrode 6c Magnetic flux detection surface 6d Side surface 8 Flexible substrate 8a Notch 8b Substrate land (connection part)
8c Wiring pattern 10 Stator iron core (magnetic material member)
10a Straight part 10b Base part 12 Winding coil 14 Sensor holding member 14a Cylindrical part 14b Fitting part 16 Base member 18 Sensor mounting surface 18a Position regulation wall

Claims (6)

A brushless motor that has a magnetic sensor that detects the rotation of the rotor.
A rotor equipped with a magnet that can rotate around the axis of rotation,
A stator with multiple winding coils and
A magnetic sensor provided on the stator side and provided with a magnetic flux detecting surface for detecting the magnetism of the magnet of the rotor, and
A sensor holding member having a sensor mounting surface provided on the stator side and configured to abut the magnetic flux detection surface of the magnetic sensor for mounting.
Have,
The sensor mounting surface is a plane parallel to the tangent of the circle centered on the rotation axis, and is directed outward in the radial direction of the circle centered on the rotation axis. .. The brushless motor according to claim 1, wherein the stator includes a magnetic material member for guiding the magnetic flux generated by each winding coil, and the sensor holding member is positioned with respect to the magnetic material member. The magnetic member is configured to extend around the rotating shaft substantially parallel to the rotating shaft, and the sensor holding member is configured with the magnetic member so that the position with respect to the magnetic member is positioned. The brushless motor according to claim 2, further comprising a fitting portion to be fitted. 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 a position regulating wall that matches the side surfaces of the magnetic sensor. The brushless motor according to any one of claims 1 to 3. The fourth aspect of the magnetic sensor, wherein the magnetic sensor has electrodes projecting from the side surfaces on both sides of the magnetic sensor, and the position restricting wall abuts on a portion of the side surface of the magnetic sensor where the electrodes do not project. Brushless motor. Further, the flexible substrate has a notch for receiving the magnetic flux detection surface of the magnetic sensor, a connection portion to be connected to the electrode of the magnetic sensor provided at the edge of the notch, and the connection portion. The sensor holding member is formed in a substantially 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, which is electrically connected to the connection portion on the outer peripheral surface of the flexible substrate.

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