CN210350958U - Ring magnet and magnetic sensor - Google Patents

Abstract

The utility model provides a ring magnet and magnetic sensor, when the rotation angle of detection rotation axis, can stably and accurately detect out this rotation angle. The output portion sensor magnet (63) is a ring magnet used together with an output portion sensor (72) as a detection element for detecting a change in magnetic flux density. The sensor magnet (63) for the output section has an N pole and an S pole arranged in the circumferential direction on a plane perpendicular to the direction of the output central axis (J3), and the thickness of the sensor magnet (63) for the output section in the direction of the output central axis (J3) increases from the top (63N) of the N pole and the top (63S) of the S pole toward the boundary (63B) between the N pole and the S pole.

Description

Ring magnet and magnetic sensor

Technical Field

The utility model relates to a ring magnet and magnetic sensor.

Background

Conventionally, as a drive source of a wiper device mounted on an automobile, for example, a motor with a reduction gear described in patent document 1 is known. The motor with a speed reducer includes an electric motor and a speed reducer connected to the electric motor. The speed reducer can reduce the speed of the output of the electric motor at a predetermined reduction ratio and output the output from the output shaft.

Further, the motor with a reduction gear described in patent document 1 is provided with a rotational position detection sensor that detects the rotational position of the output shaft. The rotational position detection sensor includes: a sensor magnet that is annular, is disposed concentrically with the output shaft, is fixed, and rotates together with the output shaft; and a magnetic sensor disposed separately from the sensor magnet and fixed to, for example, a case. The magnetic sensor is configured to: when the magnetic poles of the portions facing the magnetic sensor change due to the rotation of the sensor magnet, a detection signal is output.

Patent document 1: japanese patent laid-open publication No. 2011-244562

In the sensor magnet of the motor with a speed reducer described in patent document 1, since the magnetic flux density By in the circumferential direction of the sensor magnet is smaller than the magnetic flux density Bz in the direction in which the sensor magnet and the magnetic sensor are separated from each other, a difference occurs between the magnetic flux density Bz and the magnetic flux density By. Then, the detection signal is relatively largely distorted according to the degree of the difference, and as a result, the rotational position of the output shaft cannot be accurately detected.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a when detecting the rotation angle of rotation axis, can stably and accurately detect out this rotation angle's ring magnet and magnetic sensor.

The present invention is a ring magnet used with a detection element for detecting a change in magnetic flux density, and is characterized in that the ring magnet has an N pole and an S pole arranged along a circumferential direction on a plane perpendicular to an axis direction, and the thickness of the ring magnet along the axis direction is increased from the top of the N pole and the top of the S pole toward a boundary portion between the N pole and the S pole, respectively.

In addition, the magnetic sensor according to one aspect of the present invention is characterized in that: a ring magnet fixed to the rotating shaft; and a detection element which is arranged opposite to the ring magnet at a position deviated from the rotating shaft to the radial outside and detects the change of the magnetic flux density caused by the rotation of the ring magnet.

According to the utility model discloses an one mode, when detecting the rotation angle of rotation axis, can stably and accurately detect out this rotation angle.

Drawings

Fig. 1 is a sectional view showing an electric actuator having a magnetic sensor (first embodiment) of the present invention.

Fig. 2 is a perspective view of the magnetic sensor in fig. 1.

Fig. 3A is a plan view of the ring magnet in fig. 2.

Fig. 3B is a side view of the ring magnet of fig. 2.

FIG. 3C is a side view of the ring magnet of FIG. 2

Fig. 4 is a graph showing a relationship between a rotation angle and a magnetic flux density of a conventional magnetic sensor.

Fig. 5 is a graph showing a relationship between the rotation angle and the arctan value of the magnetic sensor.

Fig. 6A is a plan view showing a modification of the ring magnet according to the first embodiment.

Fig. 6B is a side view showing a modification of the ring magnet according to the first embodiment.

Fig. 6C is a side view showing a modification of the ring magnet according to the first embodiment.

Fig. 7A is a plan view of a ring magnet of a magnetic sensor (second embodiment) according to the present invention.

Fig. 7B is a side view of a ring magnet of a magnetic sensor (second embodiment) according to the present invention.

Fig. 7C is a side view of a ring magnet of a magnetic sensor (second embodiment) according to the present invention.

Fig. 8A is a plan view showing a modification of the ring magnet according to the second embodiment.

Fig. 8B is a side view showing a modification of the ring magnet according to the second embodiment.

Fig. 8C is a side view showing a modification of the ring magnet according to the second embodiment.

Description of the reference symbols

10: an electric actuator; 11: a housing; 11 a: a housing main body; 20: a circuit board housing; 21: a circuit board housing body; 21 a: a bottom wall; 21 b: a side wall; 21 c: a recess; 21 d: a central through hole; 22: a metal member; 23 a: a circular plate portion; 23 b: an outer tubular portion; 23 c: an inner tube section; 23 d: a top plate portion; 24: an output shaft support portion; 24 a: a through hole; 25: an arm portion; 26: a circuit board housing cover; 30: a motor housing; 31: a motor housing main body; 32: a motor storage section; 32 a: an annular projection; 33: an output part holding part; 33 a: a base; 33 b: an output shaft holding section; 37: a stator fixing member; 40: a motor section; 41: a motor shaft; 41 a: an eccentric shaft portion; 42: a rotor body; 42 a: a rotor core; 42 b: a rotor magnet; 43: a stator; 43 a: a stator core; 43 b: an insulating member; 43 c: a coil; 44 a: a first bearing; 44 b: a second bearing; 44 c: a third bearing; 44 d: a fourth bearing; 45: a sensor magnet for the motor unit; 46: a magnet holder; 47: a pre-pressing component; 50: a speed reduction mechanism; 51: an outer gear; 51 a: an aperture; 52: an internal gear; 53: an output gear; 53 a: an output gear body; 53 b: a pin; 60: an output section; 61: an output shaft; 61 a: an output shaft main body; 61 b: a flange portion; 61 c: a fitting portion; 61 d: an opening part; 62: a drive gear; 63: a sensor magnet for the output section; 631: a peripheral portion; 632: an inner peripheral portion; 633: a lower surface; 634: an upper surface; 63B: a boundary portion; 63N: a top portion; 63 NE: a flat portion; 63S: a top portion; 63 SE: a flat portion; 64: a magnet holder; 65: a bushing; 70: a circuit board; 70 a: a through hole; 71: a motor portion sensor; 72: an output section sensor; 80: a magnetic sensor; 90: a bus bar holder; by: a magnetic flux density; bz: a magnetic flux density; and (2) DS: a driven shaft; j1: a central axis; j2: an eccentric axis; j3: an output central axis; TL: thickness; TM: thickness; TS: and (4) thickness.

Detailed Description

Hereinafter, the ring magnet and the magnetic sensor according to the present invention will be described in detail with reference to preferred embodiments shown in the drawings.

< first embodiment >

A ring magnet and a magnetic sensor according to a first embodiment of the present invention will be described with reference to fig. 1 to 6A, 6B, and 6C. For convenience of explanation, three axes perpendicular to each other are hereinafter referred to as an X axis, a Y axis, and a Z axis. The XY plane containing the X and Y axes is horizontal and the Z axis is vertical. In addition, the Z-axis direction in fig. 1 and the Z-axis direction in fig. 2 are opposite to each other, but there is no problem in the structure.

The electric actuator 10 of the present embodiment shown in fig. 1 is mounted on a vehicle. More specifically, the electric actuator 10 of the present embodiment is mounted on a vehicle as a Shift-By-Wire (Shift-By-Wire) type actuator that is driven in accordance with a Shift operation By a driver. As shown in fig. 1, the electric actuator 10 includes a motor unit 40, a speed reduction mechanism 50, an output unit 60, a circuit board 70, a motor unit sensor 71, an output unit sensor 72, a housing 11, a bus bar holder 90, and a bus bar not shown.

The motor unit 40 includes a motor shaft 41, a first bearing 44a, a second bearing 44b, a third bearing 44c, a fourth bearing 44d, a rotor body 42, a stator 43, a sensor magnet 45 for the motor unit, and a magnet holder 46.

The motor shaft 41 extends in the Z-axis direction. The first bearing 44a, the second bearing 44b, the third bearing 44c, and the fourth bearing 44d support the motor shaft 41 rotatably about the center axis J1. In the present embodiment, the first bearing 44a, the second bearing 44b, the third bearing 44c, and the fourth bearing 44d are, for example, ball bearings.

The eccentric shaft portion 41a, which is a portion of the motor shaft 41 supported by the third bearing 44c, has a cylindrical shape extending about an eccentric axis J2, and the eccentric axis J2 is parallel to the central axis J1 and is eccentric with respect to the central axis J1. The portion of the motor shaft 41 other than the eccentric shaft portion 41a has a cylindrical shape extending around the central axis J1.

The rotor body 42 is fixed to the motor shaft 41. More specifically, the rotor body 42 is fixed to a lower portion of the motor shaft 41. The rotor body 42 has a rotor core 42a and a rotor magnet 42 b. The rotor core 42a is fixed to the outer peripheral surface of a portion of the motor shaft 41 below the eccentric shaft portion 41 a. The rotor magnet 42b is fixed to the outer peripheral surface of the rotor core 42 a.

The stator 43 is disposed radially outward of the rotor body 42 with a gap. The stator 43 is annular surrounding the radially outer side of the rotor main body 42. The stator 43 has a stator core 43a, an insulator 43b, and a plurality of coils 43 c. The coil 43c is attached to the stator core 43a via an insulator 43 b.

The magnet holder 46 has an annular shape centered on the central axis J1. The magnet holder 46 is made of, for example, metal. In the present embodiment, the magnet holder 46 is a single member manufactured by pressing a metal plate member. The magnet holder 46 is attached to the motor shaft 41. More specifically, the magnet holder 46 is fixed to the outer peripheral surface of the upper end of the motor shaft 41. The magnet holder 46 is disposed above the circuit board 70.

The sensor magnet 45 for the motor unit has an annular plate shape centered on the central axis J1. The plate surface of the sensor magnet 45 for the motor unit is perpendicular to the Z-axis direction. The sensor magnet 45 for the motor portion is fixed to the magnet holder 46.

As described above, the magnet holder 46 is disposed above the circuit board 70. Thus, in the present embodiment, the sensor magnet 45 for the motor unit is attached to the portion of the motor shaft 41 that protrudes upward from the circuit board 70. The motor-section sensor magnet 45 faces the upper surface of the circuit board 70 with a gap therebetween in the Z-axis direction.

The speed reduction mechanism 50 is coupled to an upper side of the motor shaft 41. The speed reduction mechanism 50 is disposed above the rotor body 42 and the stator 43. The reduction mechanism 50 has an external gear 51, an internal gear 52, and an output gear 53.

Although not shown, the external gear 51 has an annular plate shape that is centered on the eccentric axis J2 of the eccentric shaft portion 41a and expands in the radial direction of the eccentric axis J2. A gear portion is provided on the radially outer surface of the outer gear 51. The external gear 51 is connected to the motor shaft 41 via a third bearing 44 c. Thereby, the speed reduction mechanism 50 is coupled to the motor shaft 41. The external gear 51 is fitted to the outer ring of the third bearing 44c from the radially outer side. Thereby, the third bearing 44c couples the motor shaft 41 and the external gear 51 to be relatively rotatable about the eccentric axis J2.

The external gear 51 has a plurality of holes 51a penetrating the external gear 51 in the Z-axis direction. Although not shown, the plurality of holes 51a are arranged at equal intervals in a circumferential direction around the eccentric axis J2. The hole 51a has a circular shape as viewed in the Z-axis direction.

The internal gear 52 surrounds the radially outer side of the external gear 51, is fixed to the circuit board housing 20, and meshes with the external gear 51. The internal gear 52 is held by the metal member 22 of the housing 11. The ring gear 52 has an annular shape centered on the central axis J1. A gear portion is provided on an inner peripheral surface of the inner gear 52. The gear portion of the internal gear 52 meshes with the gear portion of the external gear 51.

The output gear 53 has an output gear main body 53a and a plurality of pins 53 b. The output gear main body 53a is disposed below the external gear 51 and the internal gear 52. The output gear main body 53a has an annular plate shape extending in the radial direction with the center axis J1 as the center. A gear portion is provided on the radially outer surface of the output gear body 53 a. The output gear main body 53a is connected to the motor shaft 41 via a fourth bearing 44 d.

The plurality of pins 53b are cylindrical and protrude upward from the upper surface of the output gear main body 53 a. Although not shown, the plurality of pins 53b are arranged at equal intervals in the circumferential direction within one circumferential range. The pin 53b has an outer diameter smaller than the inner diameter of the hole 51 a. The plurality of pins 53b pass through the respective holes 51a of the plurality of holes 51a from the lower side. The outer peripheral surface of the pin 53b is inscribed in the inner peripheral surface of the hole 51 a. The inner peripheral surface of the hole 51a supports the external gear 51 via the pin 53b so as to be swingable around the central axis J1.

The output portion 60 is a portion that outputs the driving force of the electric actuator 10. The output portion 60 is disposed radially outward of the motor portion 40. The output unit 60 includes an output shaft 61, a drive gear 62, an output unit sensor magnet 63, and a magnet holder 64.

The output shaft 61 has a cylindrical shape extending in the Z-axis direction of the motor shaft 41. In this way, the output shaft 61 extends in the same direction as the motor shaft 41, and therefore the structure of the reduction mechanism 50 that transmits the rotation of the motor shaft 41 to the output shaft 61 can be simplified. In the present embodiment, the output shaft 61 is cylindrical with an output center axis J3 as a virtual axis as a center. The output central axis J3 is parallel to the central axis J1 and is disposed radially away from the central axis J1. That is, the motor shaft 41 and the output shaft 61 are arranged apart from each other in the radial direction of the motor shaft 41.

The output shaft 61 has an opening 61d that opens downward. In the present embodiment, the output shaft 61 is open to both axial sides. The output shaft 61 has a spline groove in a lower portion of an inner peripheral surface. The output shaft 61 includes a cylindrical output shaft main body 61a and a flange portion 61b protruding radially outward from the output shaft main body 61a toward the output center axis J3. The output shaft 61 is disposed at a position overlapping the rotor body 42 in the radial direction of the motor shaft 41. The lower end of the output shaft 61, i.e., the opening 61d, is disposed above the lower end of the motor 40. In the present embodiment, the lower end of the motor 40 is the lower end of the motor shaft 41.

The driven shaft DS is inserted into the output shaft 61 from below through the opening 61d and is coupled to the output shaft 61. More specifically, the output shaft 61 is coupled to the driven shaft DS by fitting a spline portion provided on the outer peripheral surface of the driven shaft DS into a spline groove provided on the inner peripheral surface of the output shaft 61. The driving force of the electric actuator 10 is transmitted to the driven shaft DS via the output shaft 61. Thereby, the electric actuator 10 rotates the driven shaft DS about the output central axis J3.

The drive gear 62 is fixed to the output shaft 61 and meshes with the output gear 53. In the present embodiment, the drive gear 62 is fixed to a portion of the outer peripheral surface of the output shaft main body 61a that is above the flange portion 61 b. The drive gear 62 is in contact with the upper surface of the flange portion 61 b. Although not shown, the drive gear 62 is a sector gear that extends from the output shaft 61 toward the output gear 53 and has a larger width as it approaches the output gear 53. A gear portion is provided at an end portion of the drive gear 62 on the output gear 53 side. The gear portion of the drive gear 62 meshes with the gear portion of the output gear 53.

The magnet holder 64 is a substantially cylindrical member extending in the Z-axis direction about the output center axis J3. The magnet holder 64 is open to both axial sides. The magnet holder 64 is disposed above the output shaft 61 and radially outward of the reduction mechanism 50. The magnet holder 64 penetrates the circuit board 70 in the Z-axis direction. The inside of the magnet holder 64 is connected to the inside of the output shaft 61. The upper end portion of the driven shaft DS inserted into the output shaft 61 is press-fitted into the magnet holder 64. Thereby, the magnet holder 64 is fixed to the driven shaft DS.

As shown in fig. 2, 3A, 3B, and 3C, the output portion sensor magnet 63 is an annular magnet having an annular shape centered on the output center axis J3 and having a constant width in the circumferential direction. The output portion sensor magnet 63 is fixed to the outer peripheral surface of the upper end portion of the magnet holder 64. The magnet holder 64 is fixed to the driven shaft DS, and thereby the sensor magnet 63 for the output portion is fixed to the driven shaft DS via the magnet holder 64. The output-section sensor magnet 63 faces the upper surface of the circuit board 70 with a gap therebetween. The sensor magnet 63 for the output portion is obtained by injection molding a resin material containing magnetic powder, for example. Examples of the resin material include polyamide, polyphenylene sulfide, and polypropylene. Examples of the constituent material of the magnetic powder include ferrite-based, aluminum nickel cobalt-based, samarium cobalt-based, and neodymium-iron-boron-based magnetic materials.

When the motor shaft 41 rotates about the center axis J1, the eccentric shaft 41a revolves in the circumferential direction around the center axis J1. The revolution of the eccentric shaft portion 41a is transmitted to the external gear 51 via the third bearing 44c, and the external gear 51 oscillates while the position at which the inner circumferential surface of the hole 51a inscribes the outer circumferential surface of the pin 53b changes in the external gear 51. Thereby, the meshing position of the gear portion of the external gear 51 and the gear portion of the internal gear 52 varies in the circumferential direction. Therefore, the rotational force of the motor shaft 41 is transmitted to the internal gear 52 via the external gear 51.

Here, in the present embodiment, the internal gear 52 is fixed and therefore does not rotate. Therefore, the external gear 51 is rotated about the eccentric axis J2 by the reaction force of the rotational force transmitted to the internal gear 52. At this time, the rotation direction of the external gear 51 is opposite to the rotation direction of the motor shaft 41. The rotation of the external gear 51 about the eccentric axis J2 is transmitted to the output gear 53 via the hole 51a and the pin 53 b. Thereby, the output gear 53 rotates about the center axis J1. The rotation of the motor shaft 41 is decelerated and transmitted to the output gear 53.

When the output gear 53 rotates, the drive gear 62 meshed with the output gear 53 rotates about the output center axis J3. Thereby, the output shaft 61 fixed to the drive gear 62 rotates about the output central axis J3. In this way, the rotation of the motor shaft 41 is transmitted to the output shaft 61 via the reduction mechanism 50.

The circuit board 70 is disposed above the rotor body 42. The circuit board 70 is disposed above the reduction mechanism 50. The circuit board 70 has a plate-like shape whose plate surface is perpendicular to the Z-axis direction. The circuit board 70 has a through hole 70a penetrating the circuit board 70 in the Z-axis direction. The motor shaft 41 passes through the through hole 70 a. Thereby, the motor shaft 41 penetrates the circuit board 70 in the Z-axis direction. The circuit board 70 is electrically connected to the stator 43 via a bus bar not shown. That is, the circuit board 70 is electrically connected to the motor portion 40.

The motor portion sensor 71 is fixed to the upper surface of the circuit board 70. More specifically, the motor sensor 71 is fixed to a portion of the upper surface of the circuit board 70, which faces the motor sensor magnet 45 with a gap therebetween in the Z-axis direction. The motor sensor 71 is a magnetic sensor that detects the magnetic field of the motor sensor magnet 45. The motor sensor 71 is, for example, a hall element. Although not shown, for example, three motor portion sensors 71 are provided in the circumferential direction. The motor portion sensor 71 detects the rotation position of the motor portion sensor magnet 45 by detecting the magnetic field of the motor portion sensor magnet 45, thereby detecting the rotation of the motor shaft 41.

In the present embodiment, the speed reduction mechanism 50 is coupled to the upper side of the motor shaft 41, and the circuit board 70 is disposed above the rotor body 42 and above the speed reduction mechanism 50. Therefore, the speed reduction mechanism 50 is disposed between the circuit board 70 and the rotor body 42 in the Z-axis direction. Thereby, the motor section sensor 71 fixed to the circuit board 70 can be disposed away from the rotor body 42 and the stator 43. Therefore, the motor section sensor 71 can be less susceptible to the influence of the magnetic field generated from the rotor body 42 and the stator 43, and the detection accuracy of the motor section sensor 71 can be improved.

The output sensor 72 is fixed to the upper surface of the circuit board 70. More specifically, the output sensor 72 is fixed to a portion of the upper surface of the circuit board 70, which faces the output sensor magnet 63 with a gap therebetween in the Z-axis direction. The output portion sensor 72 is disposed at a position radially outward of the magnet holder 64 (rotation shaft) that fixes the output portion sensor magnet 63. In this way, as an arrangement, the output section sensor 72 adopts a so-called "side shift (side shift) system". The output portion sensor 72 is a detection element that detects a change in magnetic flux density caused by rotation of the output portion sensor magnet 63 (ring magnet). The output sensor 72 is, for example, a hall element. As shown in fig. 2, the output sensor 72 is fixed to the magnet holder 64, and constitutes the magnetic sensor 80 together with the output sensor magnet 63 that rotates about the output center axis J3. The output portion sensor 72 detects a change in magnetic flux density due to rotation of the output portion sensor magnet 63, thereby detecting a rotational position of the output portion sensor magnet 63 and detecting a rotational angle of the driven shaft DS.

According to the present embodiment, the drive gear 62 that transmits the rotational driving force to the output gear 53 can be disposed close to the output portion sensor magnet 63 by the configuration in which the speed reduction mechanism 50 is disposed on the circuit board 70 side of the motor portion 40. Therefore, the distance in the Z-axis direction from the portion of the output gear 53 to which the rotational driving force is transmitted to the portion to which the output unit sensor magnet 63 is fixed can be shortened, and the shaft wobble of the driven shaft DS in the portion to which the output unit sensor magnet 63 is fixed can be suppressed. This can improve the accuracy of the rotation detection of the driven shaft DS by the output section sensor 72.

The housing 11 houses the motor unit 40, the speed reduction mechanism 50, the output unit 60, the circuit board 70, the motor unit sensor 71, the output unit sensor 72, the bus bar holder 90, and the bus bar not shown. The housing 11 has a motor case 30 and a circuit board case 20. The motor case 30 is open to the upper side. The motor case 30 has a motor case main body 31 and a stator fixing member 37. The circuit board case 20 has a substantially rectangular parallelepiped box shape. The circuit board housing 20 is mounted on the upper side of the motor housing 30 to close the opening of the motor housing 30. The circuit board case 20 houses the circuit board 70. The circuit board housing 20 has a circuit board housing main body 21, a metal member 22, and a circuit board housing cover 26.

The circuit board housing main body 21 and the motor housing main body 31 are made of resin. In the present embodiment, the circuit board case body 21 and the motor case body 31 constitute a housing body 11 a. That is, the housing 11 has a housing main body 11a made of resin.

The circuit board case body 21 has a box shape with an upward opening. The circuit board housing main body 21 has a bottom wall 21a and a side wall 21 b. The bottom wall 21a expands along a plane perpendicular to the Z-axis direction. The bottom wall 21a expands radially outward from the motor case main body 31 when viewed in the Z-axis direction. The bottom wall 21a closes the opening of the upper side of the motor case 30. The bottom wall 21a covers the upper side of the stator 43.

The bottom wall 21a has a recess 21c recessed from the lower surface of the bottom wall 21a toward the upper side. The bottom wall 21a has a central through hole 21d penetrating the bottom wall 21a in the Z-axis direction. The central through hole 21d penetrates the bottom wall 21a from the bottom surface of the recess 21c to the upper surface of the bottom wall 21 a. The central through hole 21d has a circular shape centered on the central axis J1 when viewed in the Z-axis direction. The motor shaft 41 passes through the central through hole 21 d.

The side wall 21b has a cylindrical shape protruding upward from the outer edge of the bottom wall 21 a. The circuit board 70 is housed inside the side wall 21 b. That is, the circuit board case 20 houses the circuit board 70 at a position above the bottom wall 21 a. The side wall 21b opens to the upper side. The upper opening of the side wall 21b, i.e., the upper opening of the circuit board case 20 is closed by the circuit board case cover 26. The circuit board housing cover 26 is made of, for example, metal.

The metal member 22 is made of metal. The metal member 22 is held by the circuit board case body 21. That is, the metal member 22 is held by the housing main body 11 a. The metal member 22 is housed and held in the recess 21 c. In the present embodiment, a part of the metal member 22 is embedded in the case main body 11 a. Therefore, a part or the whole of the housing main body 11a can be manufactured by insert molding in which the metal member 22 is inserted into a mold and resin is poured. Therefore, the housing 11 is easily manufactured. In the present embodiment, the circuit board case body 21 in the housing body 11a is manufactured by insert molding in which a metal member 22 is inserted into a mold and resin is poured.

The metal member 22 has: a bearing holding portion having an annular plate portion 23a, an outer tube portion 23b, an inner tube portion 23c, and a top plate portion 23 d; an arm portion 25; and an output shaft support portion. The annular plate portion 23a has an annular plate shape centered on the central axis J1. The plate surface of the annular plate 23a is perpendicular to the Z-axis direction.

The outer tube portion 23b is cylindrical and protrudes downward from the outer peripheral edge of the annular plate portion 23 a. The internal gear 52 is held radially inside the outer tube portion 23 b. Thereby, the speed reduction mechanism 50 is held on the lower surface of the bottom wall 21a via the metal member 22. The outer tube portion 23b is embedded and held radially inward of the central through hole 21 d.

The inner tube portion 23c has a cylindrical shape protruding upward from the inner peripheral edge portion of the annular plate portion 23 a. A first bearing 44a is held radially inward of the inner tubular portion 23 c. Thereby, the bearing holding portion holds the first bearing 44 a. The inner tube portion 23c protrudes upward from the bottom wall 21 a. The inner tube portion 23c is disposed radially inward of the side wall 21 b. The inner tube portion 23c penetrates the circuit board 70 in the Z-axis direction through the through hole 70a, and protrudes upward from the circuit board 70.

Thereby, at least a part of the first bearing 44a held by the inner tube portion 23c is inserted into the through hole 70 a. Therefore, the first bearing 44a can support the motor shaft 41 at a position close to the portion of the motor shaft 41 where the sensor magnet 45 for the motor portion is attached. This can suppress the shaft vibration of the portion of the motor shaft 41 to which the sensor magnet 45 for the motor unit is attached, and can suppress the position vibration of the sensor magnet 45 for the motor unit. Therefore, the decrease in the accuracy of detecting the rotation of the motor shaft 41 by the motor sensor 71 can be suppressed. Further, since the first bearing 44a and the circuit board 70 can be arranged to overlap each other when viewed in the radial direction, the electric actuator 10 can be easily downsized in the Z-axis direction.

The top plate portion 23d protrudes radially inward from the upper end of the inner tube portion 23 c. The top plate portion 23d is annular about the center axis J1, and has a plate surface perpendicular to the Z-axis direction. The upper end of the motor shaft 41 passes through the inside of the top plate 23 d. The inner peripheral edge portion of the top plate portion 23d is curved downward. The top plate portion 23d covers the upper side of the first bearing 44 a.

The preload member 47 is disposed between the top plate portion 23d and the first bearing 44a in the Z-axis direction. That is, the electric actuator 10 has the preload member 47. The preload member 47 is an annular wave washer extending in the circumferential direction. The preload member 47 contacts the lower surface of the top plate 23d and the upper end of the outer ring of the first bearing 44 a. The preload member 47 applies a downward preload to the outer race of the first bearing 44 a. Thereby, the preload member 47 applies a preload toward the lower side to the first bearing 44a, and applies a preload toward the lower side to the motor shaft 41 via the first bearing 44 a.

The motor shaft 41, which is subjected to the preload directed downward by the preload member 47, is supported from the lower side by a second bearing 44b shown in fig. 1. More specifically, the outer ring of the second bearing 44b is supported from below by the annular projection 32a of the motor housing 32, and the motor shaft 41 is supported from below by the inner ring fixed to the outer peripheral surface of the motor shaft 41.

By providing the second bearing 44b, even if the motor shaft 41 is preloaded downward by the preload member 47, the downward movement of the motor shaft 41 can be suppressed. The preload member 47 applies a preload directed downward to the motor shaft 41, and presses the motor shaft 41 against the second bearing 44b serving as a support portion. Thus, the position of the motor shaft 41 in the Z-axis direction can be maintained at the lowermost position in a state where no vibration is applied to the electric actuator 10. Therefore, even when vibration is applied to the electric actuator 10 to move the motor shaft 41 in the Z-axis direction, the movement of the motor shaft 41 in the lower direction can be suppressed, and the direction in which the motor shaft 41 moves can be directed to the upper side.

The motor-section sensor magnet 45 faces the upper surface of the circuit board 70 with a gap therebetween in the Z-axis direction, and the motor-section sensor 71 is fixed to a portion of the upper surface of the circuit board 70 that faces the motor-section sensor magnet 45 with a gap therebetween in the Z-axis direction. That is, the sensor magnet 45 for the motor unit attached to the motor shaft 41 is disposed above the motor unit sensor 71. Accordingly, the direction in which the motor shaft 41 moves when vibration is applied to the electric actuator 10 can be directed upward, and thus the sensor magnet 45 for the motor section moves in a direction away from the motor section sensor 71 even when the motor shaft 41 moves. Therefore, the contact between the motor sensor magnet 45 and the motor sensor 71 can be suppressed. When the motor shaft 41 moves upward, the preload member 47 is elastically deformed in the axial direction Z by compression.

As described above, according to the present embodiment, the preload member 47 applies the preload to the motor shaft 41 in the direction from the motor portion sensor magnet 45 toward the motor portion sensor 71, thereby preventing the motor portion sensor magnet 45 from coming into contact with the motor portion sensor 71. Thereby, the electric actuator 10 having the following configuration can be obtained: damage to the motor sensor magnet 45 and the motor sensor 71 can be suppressed.

The output shaft support portion 24 has a through hole 24a penetrating the output shaft support portion 24 in the Z-axis direction. A fitting portion 61c as an upper end portion of the output shaft main body 61a is fitted in the through hole 24 a. That is, the output shaft 61 has a fitting portion 61c that fits into the through hole 24 a. Thereby, the output shaft support portion 24 supports the output shaft 61.

The motor case main body 31 has a motor housing portion 32 and an output portion holding portion 33. The motor housing 32 has a cylindrical shape having a bottom and an upward opening. The motor housing portion 32 is cylindrical with a center axis J1 as a center. The motor housing 32 houses the motor 40. That is, the motor case main body 31 houses the motor section 40.

The motor housing 32 has an annular protrusion 32a protruding upward from the bottom surface of the motor housing 32. Although not shown, the annular projection 32a has an annular shape centered on the central axis J1. The annular projection 32a supports the outer race of the second bearing 44b from below. The radially inner portion of the annular projection 32a overlaps the inner ring of the second bearing 44b and the lower end of the motor shaft 41 as viewed in the Z-axis direction. Therefore, even when the motor shaft 41 is preloaded downward and the inner ring of the second bearing 44b and the lower end portion of the motor shaft 41 are arranged to protrude downward from the outer ring of the second bearing 44b, the inner ring of the second bearing 44b and the lower end portion of the motor shaft 41 can be prevented from contacting the bottom surface of the motor housing portion 32.

The output portion holding portion 33 protrudes radially outward from the motor housing portion 32. The output portion holding portion 33 has a base portion 33a and an output shaft holding portion 33 b. The base portion 33a protrudes radially outward from the motor housing portion 32. The output shaft holding portion 33b protrudes from the radially outer end of the base portion 33a to both axial sides. The output shaft holding portion 33b is cylindrical with the output central axis J3 as the center. The output shaft holding portion 33b is open to both axial sides. The inside of the output shaft holding portion 33b penetrates the base portion 33a in the Z-axis direction.

A cylindrical bush 65 is fitted inside the output shaft holding portion 33 b. A flange portion that protrudes radially outward about the output center axis J3 is provided at an upper end of the bushing 65. The flange portion of the bushing 65 is supported from below by the upper end portion of the output shaft holding portion 33 b. A portion of the output shaft main body 61a below the flange portion 61b is fitted inside the bush 65. The bush 65 supports the output shaft 61 rotatably about the output center axis J3. The flange portion 61b is supported from below by the upper end of the output shaft holding portion 33b via the flange portion of the bushing 65. The lower opening 61d of the output shaft 61 is disposed below the bushing 65.

The stator fixing member 37 has a cylindrical shape having a bottom and an opening toward the upper side. The stator fixing member 37 is cylindrical with a center axis J1 as the center. The stator fixing member 37 is fitted inside the motor housing 32. A plurality of through holes arranged in the circumferential direction are provided in the bottom of the stator fixing member 37. The plurality of projections provided at the bottom of the motor housing portion 32 are fitted into the through holes of the stator fixing member 37.

The upper end of the stator fixing member 37 protrudes upward from the motor housing 32. A second bearing 44b is held at the bottom of the stator fixing member 37. The outer peripheral surface of the stator 43 is fixed to the inner peripheral surface of the stator fixing member 37. The stator fixing member 37 is made of metal. The motor case 30 is manufactured by insert molding in which resin is poured in a state where the stator fixing member 37 is inserted into a mold, for example.

The bus bar holder 90 is disposed in an opening on the upper side of the stator fixing member 37. The bus bar holder 90 is annular about the center axis J1, and has a plate shape with a plate surface perpendicular to the Z-axis direction. The bus bar holder 90 holds a bus bar, not shown. The bus bar holder 90 covers the upper side of the stator 43.

As described above, in the present embodiment, the magnetic sensor 80 is configured by the output unit sensor magnet 63 and the output unit sensor 72. When the driven shaft DS rotates, the output section sensor magnet 63 rotates together with the driven shaft DS. The magnetic sensor 80 can detect the rotational position of the output portion sensor magnet 63 by detecting the change in magnetic flux density caused by the rotation of the output portion sensor magnet 63 by the output portion sensor 72, and can detect the rotation angle of the driven shaft DS.

As shown in fig. 2, the sensor magnet 63 for the output portion has an annular shape. The output unit sensor magnet 63 has N poles and S poles arranged in the circumferential direction on a plane perpendicular to the direction of the output center axis J3 (axis), that is, on an XY plane when the output center axis J3 is parallel to the Z axis. In the present embodiment, the output section sensor magnet 63 is a bipolar ring magnet in which one semicircular arc-shaped N pole and one semicircular arc-shaped S pole are arranged in the circumferential direction. Therefore, the output portion sensor magnet 63 has a direction perpendicular to the output center axis J3 (axial line) direction as the magnetization direction (magnetizing direction).

The magnetic flux density detectable by the output portion sensor 72 includes a magnetic flux density bz (sin) in the output center axis J3(Z axis) direction and a magnetic flux density by (cos) in the circumferential direction of the output portion sensor magnet 63. In the magnetic sensor 80, the output sensor 72 detects two-phase signals of the magnetic flux density Bz and the magnetic flux density By, and calculates an arctangent (Sin/Cos) value, thereby detecting the rotation angle of the driven shaft DS (see fig. 4).

The ideal (theoretical) relationship of the arctan value with the rotation angle is a straight line graph indicated by a dashed line in fig. 5.

As the magnetic field angle of the output portion sensor magnet 63 changes, the amount of change in the magnetic flux density By detected By the output portion sensor 72 is smaller than the amount of change in the magnetic flux density Bz, and there is a difference therebetween.

Therefore, the actual relationship between the arctan (ATAN) value and the rotation angle is a graph indicated by a broken line or a graph indicated by a solid line in fig. 5. In addition, the graph indicated by the broken line is a graph obtained by a conventional product. In contrast, the graph indicated by the solid line is a graph obtained by the utility model product.

Here, as a conventional product, a case is considered in which the outer shape, which is the shape in plan view, of the outer peripheral portion 631 of the sensor magnet 63 for an output portion is circular, and the inner shape, which is the shape in plan view, of the inner peripheral portion 632 is also circular, and the thickness is constant as a whole.

In this case, when the magnetic field angle of the output portion sensor magnet 63 changes, the magnetic flux density Bz fluctuates at an amplitude larger than the magnetic flux density By as shown in fig. 4. Therefore, when the arctan value is calculated from the magnetic flux density Bz and the magnetic flux density By, the detection signal (ATAN signal) from the output section sensor 72 is largely distorted.

Specifically, a graph indicated by a broken line as shown in fig. 5 is obtained, which has a large deviation from a straight line graph (theoretical value) indicated by a chain line, and a large error is generated between them. For example, when looking at a portion where "arctan (deg)" is "120" in fig. 5, the "rotation angle (deg)" should be theoretically detected as "120", but is detected as about "100" in the existing product.

On the other hand, as shown in fig. 2 and fig. 3A, 3B, and 3C, in the utility model, the shape (outer shape) of the outer peripheral portion 631 of the output portion sensor magnet 63 in a plan view is circular, and the shape (inner shape) of the inner peripheral portion 632 in a plan view is also circular, and the thickness changes. In the present embodiment, the thickness of the output unit sensor magnet 63 in the direction of the output central axis J3 (axis) increases continuously from the top 63N of the N-pole toward the boundary 63B between the N-pole and the S-pole, and increases continuously from the top 63S of the S-pole toward the boundary 63B.

That is, in the sensor magnet 63 for an output portion, the thickness TS is smallest at the top 63N and the top 63S, and the thickness TL is largest at the boundary 63B. The thickness TM between the top 63N and the boundary 63B and between the top 63S and the boundary 63B is equal to the thickness TS and the thickness TL. Therefore, the sensor magnet 63 for the output unit has a magnitude relationship of "thickness TS < thickness TM < thickness TL".

The thickness is constant in the radial direction in the boundary portion 63B, and is also constant in the radial direction in the top portion 63N and the top portion 63S.

The lower surface 633, which is the surface on the side of the output unit sensor magnet 63 facing the output central axis J3 and opposite the output unit sensor 72 (detection element), is a plane parallel to a plane (XY plane) perpendicular to the direction of the output central axis J3. In other words, the upper surface 634 of the output section sensor magnet 63 is convex toward the output section sensor 72.

The magnetic flux density Bz of the output portion sensor magnet 63 is maximum at the top portion 63N and the top portion 63S. In the present specification, the top 63N and the top 63S refer to the portion of the N pole and the S pole where the magnetic flux density Bz is the maximum, that is, the central portion in the circumferential direction.

According to such a configuration, the distance between the top 63N and the top 63S and the output sensor 72 is the largest, and the distance between the boundary 63B and the output sensor 72 is the smallest. The distance from the output section sensor 72 continuously changes between the top section 63N and the boundary section 63B and between the top section 63S and the boundary section 63B.

Therefore, it is possible to reduce the magnetic flux density Bz that can be detected By the output portion sensor 72 when facing the top portion 63N and the top portion 63S, and increase the magnetic flux density By that can be detected when facing the boundary portion 63B. This can reduce the difference between the amount of change in the magnetic flux density Bz detected By the output portion sensor 72 and the amount of change in the magnetic flux density By with a change in the magnetic field angle of the output portion sensor magnet 63.

Therefore, when the arctan value is calculated from the magnetic flux density Bz and the magnetic flux density By, a graph shown By a solid line as shown in fig. 5 is obtained, and a large error generated between them is eliminated By approximating the graph to a straight line shown By a chain line.

For example, when looking at a portion where "arctan (deg)" is "120" in fig. 5, the "rotation angle (deg)" should be theoretically detected as "120", but is detected as about "110" in the utility model product. As described above, it is detected as about "100" in the existing product, and is therefore detected as about "110" closer to "120" in the utility model product, which means that the detection accuracy of the magnetic sensor 80 is improved.

Therefore, according to the magnetic sensor 80, when the rotation angle of the driven shaft DS is detected, the rotation angle can be stably and accurately detected.

As a modification of the sensor magnet 63 for an output unit according to the first embodiment, a configuration as shown in fig. 6A, 6B, and 6C can be adopted. That is, in the structure shown in fig. 6A, 6B, and 6C, the thickness of the boundary portion 63B in the radial direction is larger on the outer side than on the inner side. With this configuration, the same operation and effect as described above can be obtained.

However, as shown in fig. 3A, 3B, and 3C, if the thickness is made constant in the radial direction in the top portion 63N, the top portion 63S, and the boundary portion 63B, the distance between the output portion sensor magnet 63 and the output portion sensor 72 does not change in the radial direction or changes very little, and therefore, the sensor output error in the mounted state can be further reduced.

< second embodiment >

A second embodiment of the ring magnet and the magnetic sensor according to the present invention will be described below with reference to fig. 7A, 7B, and 7C and fig. 8A, 8B, and 8C, but differences from the above-described embodiment will be mainly described, and descriptions of the same items will be omitted.

This embodiment is the same as the first embodiment except that the shape of the sensor magnet for the output unit is different.

As shown in fig. 7A, 7B, and 7C, in the present embodiment, the output section sensor magnet 63 has a flat portion 63NE having a constant thickness at the top portion 63N and the vicinity thereof, and a flat portion 63SE having a constant thickness at the top portion 63S and the vicinity thereof, in addition to the change in thickness in the axial direction shown in fig. 3A, 3B, and 3C. The flat portion 63NE and the flat portion 63SE are preferably the same thickness, but may be different.

By providing the flat portion 63NE and the flat portion 63SE, for example, interference with the sensor magnet 63 for the output portion can be prevented by the configuration around the sensor magnet 63 for the output portion, and the degree of freedom in designing the magnetic sensor 80 can be improved. Further, the influence of the rotational axis wobble of the sensor magnet 63 for the output portion can be reduced.

As a modification of the sensor magnet 63 for an output unit according to the second embodiment, a configuration as shown in fig. 8A, 8B, and 8C can be adopted. That is, in the structure shown in fig. 8A, 8B, and 8C, the thickness of the boundary portion 63B in the radial direction is larger on the outer side than on the inner side. With this configuration, the same operation and effect as described above can be obtained.

The sensor magnet 63 for the output unit in each of the above embodiments has a configuration in which one N pole and one S pole are arranged in the circumferential direction. The magnetic sensor 80 having the output section sensor magnet 63 configured as described above can derive the relationship between the sensor output of the output section sensor 72 and the rotation angle of the driven shaft DS in a one-to-one manner in a range of 360 °.

The ring magnet and the magnetic sensor according to the present invention have been described above with reference to the illustrated embodiments, but the present invention is not limited thereto, and each part constituting the ring magnet and the magnetic sensor may be replaced with any structure capable of performing the same function. In addition, any structure may be added.

The ring magnet and the magnetic sensor according to the present invention may be obtained by combining two or more arbitrary configurations (features) of the above-described embodiments.

Claims (6)

1. A ring magnet for use with a detecting element for detecting a change in magnetic flux density,

the ring magnet has N poles and S poles arranged in the circumferential direction on a plane perpendicular to the axial direction,

the thickness of the ring magnet in the axial direction increases from the top of the N-pole and the top of the S-pole toward the boundary between the N-pole and the S-pole.

2. The ring magnet according to claim 1,

the ring magnet is a bipolar ring magnet in which the N pole and the S pole are circumferentially arranged.

3. The ring magnet according to claim 1,

the thickness increases continuously.

4. The ring magnet according to claim 1,

the ring magnet has the constant thickness portion at and near each of the top portions.

5. The ring magnet according to any one of claims 1 to 4,

the surface on the side of the axial direction opposite to the detection element is along a plane perpendicular to the axial direction.

6. A magnetic sensor characterized in that,

the magnetic sensor includes:

the ring magnet according to any one of claims 1 to 5, which is fixed to a rotating shaft; and

and a detection element which is arranged to face the ring magnet at a position radially outward from the rotation axis and detects a change in magnetic flux density caused by rotation of the ring magnet.

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