Electric actuator

Abstract

To provide an electric actuator capable of reducing costs, while ensuring position detection accuracy of a driven member.SOLUTION: An electric actuator 10 comprises: a driven member 40 reciprocally driven in a first direction; a magnet part 80 fixed to the driven member; and a magnetic sensor 71 for detecting a magnetic flux of the magnet part, the magnetic sensor being arranged to be opposed to the magnet part in a second direction orthogonal to the first direction. The magnet part is made of a permanent magnet and comprises a magnet body 81 and a magnetic material 82, with the first direction being a magnetization direction. A magnetic member that extends in the first direction by being connected to the magnet body is longer in the first direction than the magnet body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric actuator. [Background technology]

[0002] A linear actuator is known in which a magnet is fixed to a support member that moves back and forth, and the position of the support member is controlled based on the magnetic flux of the magnet detected by an IC sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-080131 Summary of the Invention [Problem to be solved by the invention]

[0004] In the linear actuator described above, an IC sensor detects the change in magnetic flux density that accompanies the movement of the magnet. When using such an IC sensor, in order to increase the detection sensitivity, the magnet may be made larger or an expensive material may be selected for the magnet. This leads to the problem of increasing the cost of the linear actuator.

[0005] In view of the above circumstances, an object of the present invention is to provide an electric actuator that can reduce costs while ensuring the accuracy of detecting the position of a driven member. [Means for solving the problem]

[0006] One aspect of the electric actuator of the present invention comprises a driven member that is driven reciprocatingly in a first direction, a magnet portion fixed to the driven member, and a magnetic sensor arranged opposite the magnet portion in a second direction that intersects the first direction and that detects the magnetic flux of the magnet portion, wherein the magnet portion has a magnet body made of a permanent magnet and whose magnetization direction is the first direction, and a magnetic member made of a magnetic material, connected to the magnet body, extending in the first direction, and longer in the first direction than the magnet body. [Effects of the Invention]

[0007] According to one aspect of the present invention, there is provided an electric actuator that can achieve low costs while ensuring the accuracy of detecting the position of a driven member. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing an electric actuator according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a magnet portion and a magnet body of an electric actuator according to one embodiment. [Figure 3] FIG. 3 is a perspective view showing the configuration of the magnet portion of one embodiment. [Figure 4] FIG. 4 is a perspective view showing a magnetic member of the magnet portion of one embodiment. [Figure 5] FIG. 5 is a perspective development view showing the configuration of a magnet section in a modified example of the embodiment. [Figure 6] FIG. 6 is a perspective view showing a magnet portion in a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In each drawing, the first direction D1 is the direction in which the drive unit can move. In the following description, the side toward which the arrow of the first direction D1 points (+D1 side) is referred to as "one side of the first direction D1," and the side opposite to the side toward which the arrow of the first direction D1 points (-D1 side) is referred to as "the other side of the first direction D1." In each drawing, the second direction D2 is a direction that intersects with the first direction D1. In this embodiment, the second direction D2 is perpendicular to the first direction D1. In the following description, the side toward which the arrow of the second direction D2 points (+D2 side) is referred to as "one side of the second direction D2," and the side opposite to the side toward which the arrow of the second direction D2 points (-D2 side) is referred to as "the other side of the second direction D2." In each drawing, the third direction D3 is a direction that is perpendicular to both the first direction D1 and the second direction D2.

[0010] The rotational axis J shown in FIG. 1 is a virtual axis extending in a direction parallel to the first direction D1. The rotational axis J is the central axis of the motor shaft. In the following description, the radial direction centered on the rotational axis J will be simply referred to as the "radial direction." The circumferential direction centered on the rotational axis J will be simply referred to as the "circumferential direction." In FIG. 1, the circumferential direction is indicated by the arrow θ.

[0011] <Embodiment> The electric actuator 10 of this embodiment shown in Fig. 1 is a linear actuator that moves a driven object (not shown) in a first direction D1. The electric actuator 10 extends as a whole in the first direction D1. The electric actuator 10 includes a housing 11, a motor unit 20, a driven member 40, a magnet unit 80, an output unit 50, a circuit board 70, and a magnetic sensor 71.

[0012] The housing 11 accommodates the motor unit 20, the driven member 40, the magnet unit 80, the circuit board 70, and the magnetic sensor 71 inside. The housing 11 has a housing main body 12, a cover member 13, a first bearing holder 14, and a drive unit accommodating member 15. The cover member 13 is fixed to the other end of the housing main body 12 in the first direction D1. The first bearing holder 14 is accommodated inside the housing main body 12. The drive unit accommodating member 15 is fixed to one end of the housing main body 12 in the first direction D1.

[0013] The housing body 12 has a generally cylindrical shape and extends in the first direction D1 around the rotation axis J. The housing body 12 is open on the other side in the first direction D1. The housing body 12 accommodates the motor unit 20 therein. The housing body 12 has a peripheral wall 12a and a bottom wall 12d.

[0014] The peripheral wall portion 12a has a generally cylindrical shape and extends in the first direction D1 around the rotation axis J. The peripheral wall portion 12a surrounds the motor portion 20 from the radially outer side. The other end of the peripheral wall portion 12a in the first direction D1 is the other end of the housing main body portion 12 in the first direction D1. The peripheral wall portion 12a has an opening portion 12b that opens to the other side in the first direction D1.

[0015] The bottom wall portion 12d is plate-shaped and extends in a direction perpendicular to the first direction D1. The radial outer edge of the bottom wall portion 12d is connected to one end of the peripheral wall portion 12a in the first direction D1. The bottom wall portion 12d separates the interior of the housing main body 12 from the interior of the drive unit accommodating member 15. The bottom wall portion 12d is provided with a second bearing holder 12e, a through-hole 12f, and an insertion hole 12g.

[0016] The second bearing holder 12e protrudes from the bottom wall portion 12d to the other side in the first direction D1. The second bearing holder 12e has a generally cylindrical shape centered on the rotation axis J. The second bearing holder 12e opens to the other side in the first direction D1. A second bearing 62 having an annular shape when viewed from the first direction D1 is held on the inner circumferential surface of the second bearing holder 12e.

[0017] The through hole 12f and the insertion hole 12g are each a hole that penetrates the bottom wall portion 12d in the first direction D1. When viewed from the first direction D1, the through hole 12f has a substantially circular shape centered on the rotation axis J. The inner diameter of the through hole 12f is smaller than the inner diameter of the second bearing holder 12e. The insertion hole 12g is provided in an edge portion on one side (+D2 side) of the bottom wall portion 12d in the second direction D2.

[0018] The lid member 13 is disk-shaped and centered on the rotation axis J. The plate surface of the lid member 13 faces the first direction D1. The lid member 13 is fixed to the end of the peripheral wall portion 12a on the other side in the first direction D1. The lid member 13 closes the opening 12b from the other side in the first direction D1.

[0019] The first bearing holder 14 has a substantially circular ring shape centered on the rotation axis J. The outer peripheral surface of the first bearing holder 14 is fixed to the inner peripheral surface of the peripheral wall portion 12a. This fixes the first bearing holder 14 to the housing main body 12. The inner peripheral surface of the first bearing holder 14 holds a first bearing 61 that has a circular ring shape when viewed from the first direction D1.

[0020] The driver housing member 15 has a generally cylindrical shape and extends in the first direction D1 around the rotation axis J. The driver housing member 15 houses therein the driven member 40, the magnet unit 80, the output unit 50, the circuit board 70, and the magnetic sensor 71. The driver housing member 15 has an annular wall portion 15a and a bottom portion 15d.

[0021] The annular wall portion 15a has a generally cylindrical shape and extends in the first direction D1 around the rotation axis J. The annular wall portion 15a surrounds the driven member 40, the magnet portion 80, the output portion 50, the circuit board 70, and the magnetic sensor 71 from the radially outer side. The annular wall portion 15a opens to the other side in the first direction D1. The annular wall portion 15a is provided with a plurality of board holders 15b. Each board holder 15b holds a circuit board 70.

[0022] The bottom portion 15d has a plate shape that extends in a direction perpendicular to the first direction D1. The radial outer edge of the bottom portion 15d is connected to one end of the annular wall portion 15a in the first direction D1. The bottom portion 15d is provided with a sealing member holding portion 15e and a bottom through-hole 15f.

[0023] The sealing member holding portion 15e protrudes from the bottom portion 15d to one side in the first direction D1. The sealing member holding portion 15e has a substantially annular shape centered on the rotation axis J. The sealing member holding portion 15e opens to one side in the first direction D1. A sealing member 63 having an annular shape when viewed from the first direction D1 is held on the inner surface of the sealing member holding portion 15e.

[0024] The bottom through-hole 15f is a hole that penetrates the bottom 15d in the first direction D1. When viewed from the first direction D1, the bottom through-hole 15f has a substantially circular shape centered on the rotation axis J. The inner diameter of the bottom through-hole 15f is smaller than the inner diameter of the sealing member holding portion 15e.

[0025] The motor unit 20 is accommodated inside the housing main body 12. The motor unit 20 has a rotor 21 and a stator 30. In this embodiment, the motor unit 20 drives the rotor 21 to rotate about the rotation axis J by current supplied from the circuit board 70, and transmits the power of the rotor 21 to the driven member 40.

[0026] The rotor 21 is rotatable about the rotation axis J. The rotor 21 has a rotor core 22, a plurality of rotor magnets 23, and a shaft 24. In other words, the motor section 20 has the shaft 24. The rotor core 22 is annular and has a center on the rotation axis J. Each of the plurality of rotor magnets 23 is fixed to the rotor core 22. The rotor magnets 23 are arranged at intervals from one another along the circumferential direction.

[0027] The shaft 24 has a generally cylindrical shape extending in the first direction D1 around the rotation axis J. The shaft 24 extends in the first direction D1 across the interior of the housing main body 12 and the interior of the drive unit accommodating member 15. The shaft 24 passes through the interior of the rotor core 22 in the first direction D1. The rotor core 22 is fixed to the outer circumferential surface of the shaft 24. The shaft 24 is supported by a first bearing 61 and a second bearing 62 so as to be rotatable around the rotation axis J. One end of the shaft 24 in the first direction D1 passes through a through hole 12f in the first direction D1 and protrudes into the interior of the drive unit accommodating member 15. The shaft 24 is provided with a second threaded portion 24a. The second threaded portion 24a is a male screw provided on a portion of the outer circumferential surface of the shaft 24 that is located inside the drive unit accommodating member 15.

[0028] The stator 30 is disposed radially outward of the rotor 21. The stator 30 is disposed radially opposite the rotor 21 with a gap therebetween. The stator 30 includes a stator core 31, an insulator 32, and a coil portion 33.

[0029] The stator core 31 is annular and surrounds the rotor core 22 from the radial outside. The stator core 31 faces the rotor 21 with a gap in the radial direction. The stator core 31 is fixed to the inner circumferential surface of the peripheral wall portion 12a. This fixes the stator 30 to the housing 11. The insulator 32 is attached to the stator core 31. The insulator 32 insulates the stator core 31 from the coil portion 33.

[0030] The coil portion 33 has multiple coil main bodies 33a and coil lead wires 33b. Each coil main body 33a is attached to the stator core 31 via an insulator 32. The coil main bodies 33a are spaced apart in the circumferential direction. The coil lead wires 33b are drawn from the coil main body 33a to one side in the first direction D1 and connected to the circuit board 70. This electrically connects the coil portion 33 to the circuit board 70. When a current is supplied from the circuit board 70 to the coil portion 33, the rotor 21 rotates around the rotation axis J. The circuit board 70 can control the rotation speed, rotation direction, etc. of the rotor 21 by controlling the current supplied to the coil portions 33. The circuit board 70 can control the movement speed and movement direction of the driven member 40 in the first direction D1 by controlling the rotation speed, rotation direction, etc. of the rotor 21.

[0031] The driven member 40 is accommodated inside the drive unit accommodating member 15. The driven member 40 is connected to a portion of the shaft 24 located inside the drive unit accommodating member 15. The driven member 40 is driven to reciprocate in the first direction D1 by the motor unit 20. The driven member 40 and the driven member 40 convert the rotational motion of the motor unit 20 into linear motion and transmit it to the output unit 50. The driven member 40 has a cylindrical shape extending in the first direction D1. Here, the driven member 40 is made of a non-magnetic material or a material that is weaker magnetic than the magnetic member 82 described below. The driven member 40 in this embodiment is made of, for example, a non-magnetic resin. The driven member 40 surrounds the rotation axis J. The driven member 40 has a cylindrical portion 41 and a protruding portion 42.

[0032] The cylindrical portion 41 has a substantially cylindrical shape extending in the first direction D1 around the rotation axis J. The cylindrical portion 41 is open on both sides in the first direction D1. A portion of the shaft 24 located inside the drive unit accommodating member 15 is inserted into the cylindrical portion 41. One end of the cylindrical portion 41 on the first direction D1 protrudes to the outside of the electric actuator 10 through the bottom through-hole 15f. The cylindrical portion 41 is provided with a first screw portion 41a that meshes with the second screw portion 24a. The first screw portion 41a is a female screw provided on the inner circumferential surface of the cylindrical portion 41.

[0033] The protruding portion 42 protrudes from the cylindrical portion 41 to one side in the second direction D2 (+D2 side). The protruding portion 42 faces the circuit board 70 with a gap in between in the second direction D2. A magnet portion 80 is fixed to the end of the protruding portion 42 on one side in the second direction D2.

[0034] The output portion 50 is fixed to one end of the cylindrical portion 41 in the first direction D1. The output portion 50 is located outside the housing 11. The output portion 50 has an output main body portion 51 and an output protrusion portion 52. The output main body portion 51 is plate-shaped and protrudes in the first direction D1. In this embodiment, the output main body portion 51 is a substantially rectangular plate-shaped portion extending in a direction perpendicular to the third direction D3. The output main body portion 51 is provided with a mounting hole 53. The mounting hole 53 is a hole that penetrates the output main body portion 51 in the third direction D3. The output protrusion portion 52 protrudes from the other end of the output main body portion 51 in the first direction D1 to the other side in the first direction D1. The output protrusion portion 52 is substantially disk-shaped and centered on the rotation axis J. The output protrusion portion 52 is located inside the cylindrical portion 41. The output protrusion portion 52 is fixed to the inner circumferential surface of the cylindrical portion 41. As a result, the output portion 50 is fixed to the driven member 40.

[0035] A driven object (not shown) that is moved in the first direction D1 by the electric actuator 10 is attached to the attachment hole 53. By attaching the driven object to the attachment hole 53, the output part 50 is prevented from rotating around the rotation axis J. As a result, the driven member 40 fixed to the output part 50 is also prevented from rotating around the rotation axis J.

[0036] When current is supplied from the circuit board 70 to the stator 30 and the shaft 24 rotates about the rotation axis J, the second threaded portion 24a of the shaft 24 rotates relative to the first threaded portion 41a of the driven member 40 about the rotation axis J. As described above, rotation of the driven member 40 about the rotation axis J is restricted. Therefore, when the shaft 24 rotates about the rotation axis J, the first threaded portion 41a is fed in the first direction D1 relative to the second threaded portion 24a. This allows the driven member 40 to move in the first direction D1. When the driven member 40 moves in the first direction D1, the output unit 50 fixed to the driven member 40 moves in the first direction D1. This allows the electric actuator 10 to move a driven object (not shown) in the first direction D1.

[0037] In the present embodiment, the driven member 40 has a cylindrical shape extending in the first direction D1 and a first threaded portion 41a provided on its inner peripheral surface, and the shaft 24 has a second threaded portion 24a provided on its outer peripheral surface that meshes with the first threaded portion 41a. With this configuration, the rotational motion of the shaft 24 about the rotation axis J can be converted into linear motion of the driven member 40 in the first direction D1 by only the first threaded portion 41a provided on the driven member 40 and the second threaded portion 24a provided on the shaft 24. Therefore, an additional member for converting the rotational motion of the shaft 24 into linear motion of the driven member 40 is not required, which prevents an increase in the number of parts and manufacturing costs of the electric actuator 10.

[0038] The sealing member 63 is held on the inner circumferential surface of the sealing member holding portion 15e. In this embodiment, the sealing member 63 is a lip seal having a lip portion on the radially inner side. The lip portion of the sealing member 63 contacts the outer circumferential surface of the cylindrical portion 41 of the driven member 40. In this way, the sealing member 63 seals the gap between the driven member 40 and the housing 11.

[0039] Fig. 2 is a cross-sectional view showing the magnet section 80 and the magnetic sensor 71 of the electric actuator 10 according to one embodiment. Fig. 3 is a perspective view showing the configuration of the magnet section 80 according to one embodiment. Fig. 4 is a perspective view showing the magnetic member 82 of the magnet section 80 according to one embodiment.

[0040] As shown in FIGS. 1 and 2, the magnet part 80 is fixed to the driven member 40. The magnet part 80 is movable in the first direction D1 together with the driven member 40. The magnet part 80 faces the magnetic sensor 71 in the second direction D2 with a gap therebetween. The magnet part 80 has a magnet main body 81 and a magnetic member 82.

[0041] The magnet body 81 is fixed to an end portion on one side (+D2 side) in the second direction D2 of the protruding portion 42. More specifically, a portion of the magnet body 81 on the other side in the second direction D2 is embedded in the protruding portion 42. A portion of the magnet body 81 on one side in the second direction D2 protrudes radially outward relative to the protruding portion 42. The magnet body 81 has, for example, a rectangular parallelepiped shape.

[0042] As shown in FIGS. 2 and 3, the magnet body 81 is a permanent magnet whose magnetization direction is the first direction D1. That is, the magnet body 81 is made of a permanent magnet. The magnet body 81 is, for example, a rare earth magnet such as a neodymium magnet. In this embodiment, the south pole portion 81S of the magnet body 81 is a portion of the magnet body 81 on one side in the first direction D1. The north pole portion 81N of the magnet body 81 is a portion of the magnet body 81 on the other side in the first direction D1. The south pole portion 81S may be a portion of the magnet body 81 on the other side in the first direction D1, and the north pole portion 81N may be a portion of the magnet body 81 on one side in the first direction D1.

[0043] The magnetic member 82 extends in the first direction D1. The magnetic member 82 has a cylindrical shape extending in the first direction D1. The magnetic member 82 is longer in the first direction D1 than the magnet main body 81. The magnetic member 82 protrudes from the magnet main body 81 on both sides in the first direction D1. The magnet main body 81 is disposed in the center of the magnetic member 82 in the first direction D1. The magnetic member 82 is made of a magnetic material such as iron. The magnetic member 82 is connected to the magnet main body 81. As a result, the magnetic member 82 is magnetized by the magnetic field of the magnet main body 81. In this embodiment, a portion of the magnetic member 82 on one side in the first direction D1 becomes an S-pole portion 82S. Furthermore, a portion of the magnetic member 82 on the other side in the first direction D1 becomes an N-pole portion 81N.

[0044] As shown in FIGS. 2 and 4, the magnetic member 82 has a first recess 83 on a side facing the magnet main body 81 in the second direction D2. The first recess 83 is recessed toward the side away from the magnet main body 81 in the second direction D2. The first recess 83 has a contact surface 83f and a pair of end surfaces 83s. The contact surface 83f faces the other side in the second direction D2. As shown in FIG. 2, the contact surface 83f is in surface contact with a top surface 81t of the magnet main body 81 facing one side in the second direction D2. The pair of end surfaces 83s rise from both sides of the contact surface 83f in the first direction D1 toward the other side in the second direction D2. Each of the pair of end surfaces 83s extends along a plane intersecting the first direction D1. Each of the pair of end surfaces 83s is in surface contact with a magnet side surface 81p of the magnet main body 81 facing one side and the other side in the first direction D1. In this way, the magnetic member 82 comes into surface contact with the magnet main body 81, and the magnetic field of the magnet main body 81 is efficiently transmitted to the magnetic member 82. As a result, the magnetic member 82 spreads the magnetic flux from the magnet main body 81 to one side and the other side in the first direction D1. The magnetic member 82 is connected to the magnet main body 81 by, for example, an adhesive or the like.

[0045] As shown in FIGS. 1 and 2, the circuit board 70 is plate-shaped and extends in a direction perpendicular to the second direction D2. The plate surface of the circuit board 70 faces the second direction D2. The circuit board 70 is disposed on one side (+D2 side) of the magnet portion 80 in the second direction D2. The circuit board 70 faces the magnet portion 80 with a gap in between in the second direction D2. As shown in FIG. 1, although not shown, the circuit board 70 has a plurality of board holes penetrating the circuit board 70 in the second direction D2. A different board holder 15b is inserted into each board hole. The board holder 15b is fixed to the inner circumferential surface of each board hole. In this way, the circuit board 70 is fixed to the housing 11. A magnetic sensor 71 is mounted on the surface of the circuit board 70 facing the other side (-D2 side) in the second direction D2.

[0046] The magnetic sensor 71 is a sensor capable of detecting the magnetic flux of the magnet unit 80 fixed to the protrusion 42 of the driven member 40. The magnetic sensor 71 is disposed at an interval from the magnet unit 80 in the second direction D2. The magnetic sensor 71 is disposed facing the magnet unit 80 in the second direction D2. In this embodiment, the magnetic sensor 71 is a magnetic sensor equipped with a Hall element such as a Hall IC. The magnetic sensor 71 may also be a magnetic sensor equipped with an MR (Magnetic Resistance) sensor element. The circuit board 70 can detect the position of the magnet unit 80 in the first direction D1 based on the magnetic flux of the magnet unit 80 detected by the magnetic sensor 71. This allows the circuit board 70 to detect the positions of the driven member 40 and the output unit 50 in the first direction D1. The circuit board 70 controls the motor unit 20 based on the magnetic flux of the magnet unit 80 detected by the magnetic sensor 71. More specifically, the circuit board 70 controls the current supplied to the stator 30 based on the magnetic flux of the magnet part 80 detected by the magnetic sensor 71. In this way, the circuit board 70 controls the rotation speed, rotation direction, etc. of the rotor 21, and determines the position of the driven member 40 in the first direction D1.

[0047] The electric actuator 10 of this embodiment includes a driven member 40 that is driven to reciprocate in a first direction D1, a magnet section 80 fixed to the driven member 40, and a magnetic sensor 71 that is disposed opposite the magnet section 80 in a second direction D2 that intersects with the first direction D1 and detects the magnetic flux of the magnet section 80. The magnet section 80 includes a magnet body 81 made of a permanent magnet and having a magnetization direction in the first direction D1, and a magnetic member 82 made of a magnetic material, connected to the magnet body 81, extending in the first direction D1, and being longer in the first direction D1 than the magnet body 81.

[0048] According to this configuration, the magnetic field of the magnet main body 81 extends over a longer range in the first direction D1 than the magnet main body 81 via the magnetic member 82. As a result, the magnetic sensor 71 can detect the magnetic flux of the magnetic field that extends from the magnet main body 81 to the surrounding area via the magnetic member 82, thereby detecting the position and displacement of the driven member 40 in the first direction D1. In this way, the magnet main body 81 can be shortened in the first direction D1 to achieve miniaturization, while ensuring the accuracy of detecting the position and displacement of the driven member 40. Therefore, it is possible to reduce costs while ensuring the accuracy of detecting the position of the driven member 40.

[0049] In this embodiment, the magnetic member 82 has a first recess 83 recessed on a side facing the magnet main body 81 in the second direction D2 and on a side away from the magnet main body 81 in the second direction D2, and the magnet main body 81 is in contact with the first recess 83. According to this configuration, the magnet main body 81 contacts the first recess 83 of the magnetic member 82, so that the magnetic flux of the magnet main body 81 is efficiently transmitted to the magnetic member 82. This increases the magnetic flux density transmitted from the magnet section 80 to the magnetic sensor 71, and improves the detection accuracy of the magnetic sensor 71.

[0050] In this embodiment, the contact surface 83f between the magnetic member 82 and the magnet main body 81 is flat. This configuration ensures a large contact area between the magnetic member 82 and the magnet main body 81, allowing the magnetic field of the magnet main body 81 to be efficiently propagated to the magnetic member 82.

[0051] In this embodiment, the magnetic member 82 is disposed on the side of the magnet main body 81 that is closer to the magnetic sensor 71 in the second direction D2. With this configuration, the magnetic field propagating from the magnet main body 81 to the magnetic member 82 in the magnetic sensor 71 extends over a wider range in the first direction D1, ensuring high detection accuracy for the position and displacement of the driven member 40.

[0052] In this embodiment, the magnet body 81 is disposed in the center in the first direction D1 of the magnetic member 82. With this configuration, the magnetic fluxes of both magnets of the magnet body 81 can be applied in a well-balanced manner to one side and the other side of the magnetic member 82 in the first direction D1.

[0053] In the present embodiment, the magnetic member 82 has a cylindrical shape extending in the first direction D1. With this configuration, the magnetic flux propagated from the magnet main body 81 to the magnetic member 82 can be made to act more uniformly radially from the magnetic member 82 as the center when viewed from the first direction D1.

[0054] In this embodiment, the driven member 40 is made of a non-magnetic material or a material that is weaker magnetic than the magnetic member 82. With this configuration, the magnetic flux from the magnet main body 81 and the magnetic member 82 can be efficiently detected by the magnetic sensor 71 while suppressing the influence of the magnetism of the driven member 40.

[0055] (Variation) Fig. 5 is a perspective development view showing the configuration of a magnet section 80B in a modified example of the embodiment, and Fig. 6 is a perspective view showing a magnet section 80B in a modified example of the embodiment.

[0056] The magnet section 80B of this modified example differs from the magnet section 80 of the above-described electric actuator 10 in the structure of the magnet main body 81B and the magnetic member 82B. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0057] As shown in FIGS. 5 and 6, the magnet section 80B of this modified example has a magnet main body 81B and a magnetic member 82B.

[0058] The magnetic member 82B of this modified example has, for example, a rectangular column shape extending in the first direction D1. The magnetic member 82B has a first recess 84 on the side facing the magnet main body 81B in the second direction D2. The first recess 84 is recessed toward the side away from the magnet main body 81B in the second direction D2. The first recess 84 has a contact surface 84f and a pair of end surfaces 84s. The contact surface 84f faces the other side in the second direction D2. The pair of end surfaces 84s rise from both sides of the contact surface 84f in the first direction D1 toward the other side in the second direction D2. Each of the pair of end surfaces 84s extends along a plane intersecting the first direction D1.

[0059] The magnet main body 81B has a second recess 85 on the side facing the magnetic member 82B in the second direction D2. The second recess 85 is recessed from the top surface 81t of the magnet main body 81B toward the side away from the magnetic member 82B in the second direction D2. The second recess 85 has a bottom surface 85f facing one side in the second direction D2.

[0060] The magnetic member 82B is in contact with the second recess 85. More specifically, the first recess 84 of the magnetic member 82B and the second recess 85 of the magnet main body 81B are engaged with each other. A contact surface 84f of the first recess 84 is in surface contact with a bottom surface 85f of the second recess 85 of the magnet main body 81B, the bottom surface 85f facing one side in the second direction D2. Each of the pair of end surfaces 84s is in surface contact with a magnet side surface 81p of the magnet main body 81B facing one side and the other side in the first direction D1.

[0061] In this modification, the top surface 82t of the magnetic member 82B, which faces one side in the second direction D2, and the top surface 81t of the magnet main body 81B are provided at the same position in the second direction D2. In other words, the top surfaces 82t and 81t are provided along the same plane. This allows the magnetic field propagated from the magnet main body 81B to the magnetic member 82B to be distributed more evenly around the periphery.

[0062] In this modification, the magnet main body 81B has a second recess 85 that is recessed on the side facing the magnetic member 82B in the second direction D2 and away from the magnetic member 82B in the second direction D2, and the magnetic member 82 is in contact with the second recess 85. According to this configuration, the magnetic field of the magnet main body 81B is efficiently propagated to the magnetic member 82 by the magnetic member 82 being in contact with the second recess 85 of the magnet main body 81B.

[0063] Although one embodiment of the present invention and its modifications have been described above, the configurations and combinations thereof in the embodiment and modifications are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiment.

[0064] For example, in the above-described embodiment (or its modified example), the contact surfaces between the magnet main bodies 81, 81B and the magnetic members 82, 82B are flat, but this is not limiting. For example, a recess may be provided on one of the contact surfaces of the magnet main bodies 81, 81B and the magnetic members 82, 82B, and a protrusion that fits into the recess may be provided on the other of the contact surfaces of the magnet main bodies 81, 81B and the magnetic members 82, 82B. In the above-described embodiment (or its modified example), the magnet parts 80, 80B may be embedded in the driven member 40. In this case, the magnet body 81 and the magnetic member 82 can be reliably fixed to the driven member 40.

[0065] Furthermore, although a linear actuator that moves a driven object in the first direction D1 has been shown as the electric actuator 10, a more specific mechanism for moving the driven member 40 in the first direction D1 may be, for example, a ball screw mechanism, a rack and pinion mechanism, etc. Furthermore, in order to move the driven member 40 in the first direction D1, magnet portions 80, 80B may be provided on an air cylinder, a hydraulic cylinder, etc.

[0066] The present technology can be configured as follows. (1) An electric actuator comprising: a driven member that is driven to reciprocate in a first direction; a magnet portion fixed to the driven member; and a magnetic sensor that is arranged opposite the magnet portion in a second direction that intersects the first direction and detects the magnetic flux of the magnet portion, wherein the magnet portion is made of a permanent magnet and has a magnet body whose magnetization direction is the first direction; and a magnetic member that is made of a magnetic material, connected to the magnet body, extends in the first direction, and is longer in the first direction than the magnet body. (2) An electric actuator as described in (1), wherein the magnetic member has a first recess on the side facing the magnet body in the second direction, the first recess being recessed on the side away from the magnet body in the second direction, and the magnet body is in contact with the first recess. (3) An electric actuator described in (1) or (2), wherein the magnet body has a second recess that is recessed on the side facing the magnetic member in the second direction and away from the magnetic member in the second direction, and the magnetic member is in contact with the second recess. (4) The electric actuator according to any one of (1) to (3), wherein the contact surface between the magnetic member and the magnet body is flat. (5) The electric actuator according to any one of (1) to (4), wherein the magnetic member is disposed on a side of the magnet body closer to the magnetic sensor in the second direction. (6) The electric actuator according to any one of (1) to (5), wherein the magnet body is disposed in a central portion of the magnetic member in the first direction. (7) The electric actuator according to any one of (1) to (6), wherein the magnetic member has a cylindrical shape extending in the first direction. (8) The electric actuator according to any one of (1) to (7), wherein the driven member is made of a non-magnetic material or a material that is weaker in magnetic property than the magnetic member. [Explanation of symbols]

[0067] 10...electric actuator, 40...driven member, 71...magnetic sensor, 80, 80B...magnet portion, 81, 81B...magnet main body, 82, 82B...magnetic member, 83, 84...first recess, 83f, 84f...contact surface, 85...second recess

Claims

1. a driven member that is driven to reciprocate in a first direction; a magnet portion fixed to the driven member; a magnetic sensor disposed opposite the magnet portion in a second direction intersecting the first direction and configured to detect a magnetic flux of the magnet portion; The magnet portion is a magnet body made of a permanent magnet and having a magnetization direction in the first direction; a magnetic member made of a magnetic material, connected to the magnet body, extending in the first direction, and longer than the magnet body in the first direction; Electric actuator.

2. the magnetic member includes a first recess that is recessed on a side facing the magnet body in the second direction and away from the magnet body in the second direction, The magnet body is in contact with the first recess. The electric actuator according to claim 1 .

3. the magnet body includes a second recess that is recessed on a side facing the magnetic member in the second direction and away from the magnetic member in the second direction, The magnetic member is in contact with the second recess. The electric actuator according to claim 1 or 2.

4. The contact surface between the magnetic member and the magnet body is flat. The electric actuator according to claim 1 or 2.

5. the magnetic member is disposed on a side of the magnet body that is closer to the magnetic sensor in the second direction. The electric actuator according to claim 1 or 2.

6. The magnet body is disposed at a center portion of the magnetic member in the first direction. The electric actuator according to claim 1 or 2.

7. The magnetic member has a cylindrical shape extending in the first direction. The electric actuator according to claim 1 or 2.

8. The driven member is made of a non-magnetic material or a material that is weaker magnetic than the magnetic member. The electric actuator according to claim 1 or 2.

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