JP2023072998A - linear actuator - Google Patents

Abstract

To render a component less sensitive to coaxiality to prevent loss of motor efficiency and performance.SOLUTION: A linear actuator 1 includes a screw shaft 2, a nut portion 3 into which the screw shaft 2 is screwed along the axial direction, a rotor portion 5 disposed on the axial end face 3C of the nut portion 3, a stator portion 6 arranged to face the rotor portion 5 in the axial direction, and a bearing portion 4 having an outer ring 4A surrounding the nut portion 3, an inner groove 4B continuously formed in the outer circumference 3D of the nut portion 3 in the circumferential direction, and a rolling element 4C received in an outer groove 4Aa and an inner groove 4B formed in the outer ring 4A, and supporting the nut portion 3 so as to be rotatable in the circumferential direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a linear actuator.

Conventionally, there is a linear motion actuator that moves a screw shaft in the axial direction by rotating a screw nut. For example, in the actuator disclosed in Patent Document 1, the rotor of the motor and the inner ring of the bearing are integrated with the screw nut.

JP 2010-002019 A

The direct-acting actuator described in Patent Document 1 has a magnet fixed to the outer periphery of a screw nut so as to face a stator. That is, the motor is configured in a so-called radial gap type, in which the stator is radially arranged so as to surround the rotor.

Here, in a linear motion actuator in which the stator is arranged in the radial direction of the rotor, the coaxiality between the screw nut (rotor) and the screw shaft must be ensured while managing the radial gap between the rotor and stator. Not easy to assemble. Specifically, if the gap between the rotor and the stator is widened, the efficiency of the motor will be lowered, so it is desirable to make the gap as small as possible. On the other hand, if the gap is made smaller, the requirement for coaxiality between the nut (rotor) and the screw shaft becomes stricter. In addition, if the gap varies, the rotation becomes uneven, which leads to the generation of noise and the deterioration of performance such as operation. As described above, it is difficult to assemble the linear actuator as shown in Patent Document 1 while ensuring the coaxiality while preventing the efficiency and performance of the motor from being lowered.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a linear actuator that is less susceptible to coaxiality and that can prevent deterioration in motor efficiency and performance.

In order to achieve the above object, a linear motion actuator according to one aspect of the present disclosure includes a screw shaft, a nut portion into which the screw shaft is axially screwed, and arranged on an axial end surface of the nut portion. a stator portion arranged to face the rotor portion in the axial direction; an outer ring surrounding the nut portion; an inner groove continuously formed in the outer circumference of the nut portion in the circumferential direction; and a bearing portion having rolling elements received in the outer groove and the inner groove formed in the outer ring and supporting the nut portion in a circumferentially rotatable manner.

As a desirable aspect of the linear motion actuator, the rotor portion has a plurality of permanent magnets protruding from an axial end face of the nut portion and arranged in the circumferential direction, and gaps are formed between the permanent magnets adjacent in the circumferential direction. be done.

As a desirable aspect of the linear motion actuator, the rotor portion includes a plurality of permanent magnets protruding from an axial end face of the nut portion and arranged in the circumferential direction, and a non-magnetic member is disposed between the permanent magnets adjacent in the circumferential direction. is placed.

As a desirable aspect of the linear motion actuator, the rotor portion is arranged on both axial end surfaces of the nut portion, and the stator portion is arranged to face each rotor portion in the axial direction.

As a desirable aspect of the linear motion actuator, the stator section has a plurality of coils connected to different electric power systems.

A desirable aspect of the linear motion actuator includes detection means disposed coaxially with the axis of the screw shaft and the nut portion for detecting the amount of movement of the screw shaft accompanying rotation of the nut portion.

As a desirable aspect of the linear motion actuator, the detection means detects rotational displacement or rotation amount of the nut portion.

As a desirable aspect of the linear motion actuator, the detection means detects displacement of the screw shaft itself.

Advantageous Effects of Invention According to the present disclosure, it is possible to prevent the efficiency and performance of the motor from deteriorating due to the insensitivity to coaxiality.

FIG. 1 is a cross-sectional view showing a configuration example of a linear motion actuator. FIG. 2 is a perspective view showing a configuration example of a rotor. FIG. 3 is a perspective view showing another configuration example of the rotor. FIG. 4 is a cross-sectional view of a linear actuator showing another configuration example of the rotor. FIG. 5 is a perspective view showing a configuration example of a stator. FIG. 6 is a cross-sectional view showing another configuration example of the linear motion actuator. FIG. 7 is a cross-sectional view showing another configuration example of the linear motion actuator. FIG. 8 is a cross-sectional view showing another configuration example of the linear motion actuator.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the following form. In addition, the components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following forms can be combined as appropriate.

The direct-acting actuator of the embodiment allows a screw shaft to move along a predetermined direction. Applied to steer-by-wire steering systems that give corners.

As shown in FIG. 1, the linear motion actuator 1 includes a screw shaft 2, a nut portion 3, a bearing portion 4, a rotor portion 5, a stator portion 6, a detection means 7, a housing 8, and a control portion 9. and including.

The screw shaft 2 is, as shown in FIG. 1, shaped like a round bar extending in a predetermined direction. In the embodiment, the predetermined direction is the axial direction along the axis C of the screw shaft 2 . The screw shaft 2 is prevented from rotating by a rotation preventing structure (not shown) such as a ball spline, and is provided movably in the axial direction. The screw shaft 2 has a helical external thread groove 2A formed along its outer circumference along the axial direction.

As shown in FIG. 1, the nut portion 3 is formed in a cylindrical shape extending in the axial direction, and a helical internal thread groove 3A is formed along the axial direction on the inner circumference of the cylinder. In the embodiment, the screw shaft 2 and the nut portion 3 are configured as ball screws, and the nut portion 3 is provided with a plurality of spherical balls 3B fitted into the inner thread groove 3A. It also fits into the screw groove 2A. As a result, the screw shaft 2 is screwed into the nut portion 3 via the balls 3B.

The bearing portion 4 supports the nut portion 3 so as to be rotatable in the circumferential direction about the axis C, as shown in FIG. The bearing portion 4 includes an outer ring 4A, an inner groove 4B, and rolling elements 4C. The outer ring 4A is formed in an annular shape arranged around the nut portion 3, and an outer groove 4Aa is formed on the inner periphery thereof. Outer ring 4A is fixed to housing 8 . The inner groove 4B is a groove continuously formed in the outer circumference 3D of the nut portion 3 in the circumferential direction. The rolling elements 4C are received in the outer groove 4Aa and the inner groove 4B of the outer ring 4A. In the embodiment, a plurality of rolling elements 4C are formed in a spherical shape and arranged along the circumferential direction between the outer groove 4Aa and the inner groove 4B. Although not shown in the figure, the rolling elements 4C are held by a retainer. The bearing portion 4 supports the nut portion 3 formed with the inner groove 4B with respect to the outer ring 4A fixed to the housing 8 so as to be rotatable in the circumferential direction via the rolling elements 4C.

In addition, in the bearing portion 4 of the embodiment, the outer groove 4Aa and the inner groove 4B are such that one rolling element 4C contacts each of the outer groove 4Aa and the inner groove 4B at two points, for a total of four points. configured to be in contact. The four-point contact bearing portion 4 can bear not only the radial load but also the axial load in both axial directions by itself, ensuring durability. Therefore, as shown in FIG. 1, the nut portion 3 can be stably supported by the bearing portion 4 alone. Although not shown in the drawings, the bearing portion 4 of the embodiment has two rows of outer grooves 4Aa formed in the outer ring 4A in the axial direction, and two rows of inner grooves 4B formed in the nut portion 3 in the axial direction. Alternatively, the rolling elements 4C may be received in the outer groove 4Aa and the inner groove 4B facing each other in the radial direction (direction perpendicular to the axial direction). Although not shown in the drawings, the bearing 4 of the embodiment may be provided with other bearings to support the nut 3 at a plurality of locations in the axial direction so as to be rotatable in the circumferential direction. In this case, the other bearing portion may not have a configuration in which the inner groove 4B is provided in the nut portion 3 like the bearing portion 4, but a configuration in which an inner groove is formed in an inner ring fixed to the outer circumference 3D of the nut portion 3. may be

The rotor portion 5 is arranged integrally with the nut portion 3 as shown in FIGS. 1 to 3 . The rotor portion 5 has a plurality of permanent magnets 5</b>A arranged along the circumferential direction on the axial end surface 3</b>C of the nut portion 3 . Each permanent magnet 5A is formed in an arc shape along the circumferential direction and has the same size. The permanent magnets 5A are provided in an even number in the circumferential direction, and arranged in an even number so that the polarities of the ends in the axial direction are alternately different in the circumferential direction.

The permanent magnet 5A is arranged so as to protrude from the end surface 3C of the nut portion 3 in the axial direction. In the rotor portion 5 shown in FIG. 2, gaps 5B are formed between permanent magnets 5A adjacent in the circumferential direction. In the rotor portion 5 shown in FIGS. 3 and 4, a partition wall 5C made of a non-magnetic member is arranged between the permanent magnets 5A adjacent in the circumferential direction. In the embodiment, the partition wall 5C integrally connects the outer frame 5D made of a non-magnetic material surrounding the outer circumference of each permanent magnet 5A along the circumferential direction and the inner frame 5E made of a non-magnetic material surrounding the inner circumference. It is constructed as a part of a frame member provided as follows. As shown in FIG. 4, the frame member includes an annular bottom plate 5F made of a non-magnetic material and disposed between the end face 3C of the nut portion 3 and the permanent magnets 5A. And the structure integrally provided with the inner frame 5E may be sufficient.

The rotor portion 5 is arranged on both axial end surfaces 3</b>C of the nut portion 3 in the embodiment. The rotor portion 5 may be arranged only on one end surface 3</b>C of the nut portion 3 in the axial direction. When the rotor portion 5 is arranged on both axial end faces 3C of the nut portion 3, it is preferable to displace the permanent magnets 5A in the circumferential direction on the respective end faces 3C, thereby reducing the cogging torque.

The stator portion 6 is arranged to face the rotor portion 5 in the axial direction, as shown in FIG. In the embodiment, since the rotor portions 5 are arranged on both axial end surfaces 3C of the nut portion 3, the stator portion 6 is arranged to face each rotor portion 5 in the axial direction. A stator core 6</b>A of the stator section 6 is fixed to the housing 8 . The stator section 6 includes a stator core 6A and coils 6B, as shown in FIG. The stator core 6A is made of a magnetic material. The stator core 6A has a disk-shaped substrate 6Aa and a plurality of cores 6Ab extending in the axial direction from the plate surface of the substrate 6Aa and provided in the circumferential direction. The substrate 6Aa has a through hole 6Aaa in the center through which the screw shaft 2 is inserted. The core 6Ab extends toward the rotor portion 5 facing it. The cores 6Ab are arranged in multiples of 3 along the circumferential direction, and FIG. 5 shows an example in which nine cores are arranged. Coil 6B is wound around core 6Ab. Therefore, the coils 6B are arranged in multiples of 3 along the circumferential direction. The coil 6B is supplied with AC signals of three phases, U-phase, V-phase, and W-phase, which are phase-shifted every 120°. That is, the stator portion 6 and the rotor portion 5 are configured as a three-phase AC motor or a brassless DC motor. The input of the AC signal to this coil 6B is controlled by the controller 9. FIG. Note that the control unit 9 detects the control current and the amount of rotation for motor control. The amount of rotation can be directly detected, for example, by the method shown in [0030] or [0032] described later, or indirectly detected from the control current.

The stator portion 6 and the rotor portion 5 constitute an axial gap type motor. The nut portion 3 integrated with the rotor portion 5 rotates in the circumferential direction around the axis C together with the rotor portion 5 by the stator portion 6 and the rotor portion 5 that constitute the motor. As a result, the screw shaft 2 whose rotation is stopped by the rotation-stopping structure moves relative to the nut portion 3 in the axial direction.

In addition, the stator section 6 is connected to a power system in which the coil 6B is different. For example, the stator unit 6 has two different electric power systems, a first coil group and a second coil group. Only coil groups can be used. The control unit 9 controls the power supply to the first coil group and the second coil group. The control unit 9 is connected to a notification means such as an alarm or a lamp, and if there is an abnormality in one of the coil groups, the notification means can notify the operator of the applicable equipment of the abnormality. . In addition, when there is an abnormality in one of the coil groups, the control unit 9 outputs a signal to the drive control unit and the brake control unit of the applicable device to limit the drive output and perform brake control. can be prepared to safely stop the applicable equipment. When the stator section 6 has the first coil group and the second coil group in this way, the first coil group and the second coil group are alternately arranged in the circumferential direction. As described above, the stator unit 6 of the embodiment receives three-phase AC signals of U-phase, V-phase, and W-phase. V phase of the first coil group, V phase of the second coil group, W phase of the first coil group, and W phase of the second coil group.

The detection means 7 is for detecting the amount of movement of the screw shaft 2 . As shown in FIG. 1, the detection means 7 includes a resolver ring 7A, which is a portion to be detected, which is fixed to the outer circumference 3D of the nut portion 3 along the circumferential direction, and a resolver ring 7A which is spaced apart in the circumferential direction. and a resolver coil 7B, which is a sensing portion arranged along the . The resolver ring 7</b>A is made of a magnetic material, is formed into a shape with a partially different radial dimension from the axis C in the circumferential direction, and rotates together with the nut portion 3 . The resolver coil 7B is configured by winding a coil around a plurality of iron cores extending in the radial direction and provided in the circumferential direction. A resolver coil 7B is fixed to the housing 8 . As the resolver ring 7A rotates together with the nut portion 3, the gap between the resolver coil 7B and the resolver ring 7A changes, and the output signal of the resolver coil 7B changes due to the change in the magnetic flux flowing through the iron core. Thereby, the detection means 7 can detect the rotation angle from the rotational displacement or the amount of rotation of the nut portion 3 . Then, the amount of movement of the screw shaft 2 can be calculated from the rotation angle of the nut portion 3 detected by the detection means 7 . Calculation of the amount of movement of the screw shaft 2 is performed by the control unit 9 . In this way, the detecting means 7 uses the resolver ring 7A arranged coaxially with the axis C of the nut portion 3 and calculates the amount of movement of the screw shaft 2 from the detected rotation angle of the nut portion 3 . This detecting means 7 can be applied when there is a restriction in providing the detected portions 72A and 73A on the screw shaft 2 like the detecting means 72 and 73 described below.

In the linear motion actuator 1, means for detecting the amount of movement of the screw shaft 2 is not limited to the detection means 7 described above. For example, detection means 71 shown in FIG. 6, detection means 72 shown in FIG. 7, and detection means 73 shown in FIG. 8 may be used. The linear actuator 1 shown in FIGS. 6 to 8 has the same configuration as the linear actuator 1 shown in FIG.

The detection means 71 shown in FIG. 6 has, for example, a light reflector on the outer circumference 3D of the nut portion 3, and a plurality of non-light reflectors fixed to the outer circumference 3D of the nut portion 3 at predetermined intervals along the circumferential direction. It has a detection unit 71A. That is, non-light reflectors and light reflectors are alternately arranged in the circumferential direction of the detected portion 71A, and the non-light reflectors and the light reflectors rotate in the circumferential direction as the nut portion 3 rotates. Further, the detection means 71 has a detection section 71B having a light source for irradiating a portion of the detection target section 71A with light and a light receiving section for receiving light from the light source reflected by the light reflector. The detection part 71B is fixed to the housing 8 . In the detecting means 71, the detected portion 71A rotates together with the nut portion 3, so that the detecting portion 71B intermittently outputs a light reception signal. Thereby, the detection means 71 can detect the rotation angle of the nut portion 3 from the rotational displacement or the amount of rotation of the nut portion 3 . Then, the amount of movement of the screw shaft 2 can be calculated from the rotation angle of the nut portion 3 detected by the detection means 71 . Calculation of the amount of movement of the screw shaft 2 is performed by the control unit 9 . In this way, the detecting means 71 uses the detected portion 71A arranged coaxially with the axis C with respect to the nut portion 3, and calculates the amount of movement of the screw shaft 2 from the detected rotation angle of the nut portion 3. . In the detecting means 71 of the embodiment, the detected portion 71A and the detecting portion 71B are arranged at two locations in the axial direction. The non-light-reflecting body of one detected portion 71A and the non-light-reflecting body of the other detected portion 71A have different intervals in the circumferential direction. Therefore, the detection means 71 of the embodiment obtains two different light receiving signals. As a result, the linear motion actuator 1 of the embodiment can accurately calculate the amount of movement of the screw shaft 2 from each light receiving signal. This detecting means 71 can be applied when there is a restriction in providing the detected portions 72A and 73A on the screw shaft 2 like the detecting means 72 and 73 described below.

The detection means 72 shown in FIG. 7 is, for example, a portion to be detected in which the outer periphery of the screw shaft 2 is used as a light reflector, and a plurality of non-light reflectors are fixed to the outer periphery of the screw shaft 2 at predetermined intervals along the axial direction. 72A. That is, non-light reflectors and light reflectors are arranged alternately in the axial direction of the detected portion 72A, and the non-light reflectors and the light reflectors move in the axial direction as the screw shaft 2 moves. Further, the detection means 72 has a light source that irradiates light onto a portion of the detection target portion 72A and a detection portion 72B that has a light receiving portion that receives light from the light source that is reflected by the light reflector. The detection part 72B is fixed to the housing 8 . In addition, the detection part 72</b>B may be fixed not only to the housing 8 , but also to a fixing part separate from the housing 8 and not related to the movement of the screw shaft 2 . In the detecting means 72, the detecting portion 72B intermittently outputs a light reception signal by moving the detected portion 72A along with the screw shaft 2 in the axial direction. Thereby, the detection means 72 can detect the displacement of the screw shaft 2 itself. Then, the displacement of the screw shaft 2 detected by the detection means 72 can be calculated as the amount of movement of the screw shaft 2 . Calculation of the amount of movement of the screw shaft 2 is performed by the control unit 9 . This detection means 72 detects the displacement of the screw shaft 2 itself, and can directly calculate this displacement as the amount of movement of the screw shaft 2 . In this way, the detecting means 72 uses the detected portion 72A arranged coaxially with the axis C of the screw shaft 2 and calculates the amount of movement of the screw shaft 2 from the detected displacement of the screw shaft 2 .

The detecting means 73 shown in FIG. 8 has, for example, a detected portion 73A having an end face of the screw shaft 2 as a light reflector. That is, the detected portion 73A moves in the axial direction as the screw shaft 2 moves. Further, the detection unit 73 has a detection unit 73B having a light source for irradiating the detected part 73A with laser light and a light receiving part for receiving the laser light from the light source reflected from the detected part 73A. The detection part 73B is fixed to the housing 8 . Note that the detection portion 73B may be fixed to a fixing portion that is separate from the housing 8 and is not involved in the movement of the screw shaft 2, instead of being fixed to the housing 8 . In the detecting means 73, the detected portion 73A moves in the axial direction together with the screw shaft 2, so that the wavelength of the light receiving signal received by the detecting portion 73B is displaced. Thereby, the detection means 73 can detect the displacement of the screw shaft 2 itself. Then, the amount of movement of the screw shaft 2 can be calculated from the displacement of the screw shaft 2 detected by the detection means 73 . Calculation of the amount of movement of the screw shaft 2 is performed by the control unit 9 . In this manner, the detecting means 73 uses the detected portion 73A arranged coaxially with the axis C of the screw shaft 2 and calculates the amount of movement of the screw shaft 2 from the detected displacement of the screw shaft 2 . This detecting means 73 can be effectively applied when the detected portion 72A like the detecting means 72 cannot be provided on the screw shaft 2. FIG.

The housing 8 accommodates the screw shaft 2, the nut portion 3, the bearing portion 4, the rotor portion 5, the stator portion 6, and the detecting means 7, 71, 72, 73, as shown in FIGS. is. As described above, the housing 8 includes the outer ring 4A of the bearing portion 4, the stator core 6A of the stator portion 6, the resolver coil 7B of the detection means 7, the detection portion 71B of the detection means 71, the detection portion 72B of the detection means 72, the detection means 73 is fixed. The housing 8 rotatably supports the nut portion 3, the rotor portion 5, the resolver ring 7A of the detecting means 7, and the detected portion 71A of the detecting means 71 through the bearing portion 4 in the circumferential direction. 72 and the detected portion 73A of the detecting means 73 are allowed to move in the axial direction.

The control unit 9 is electrically connected to the coils 6B of the stator unit 6 as shown in FIGS. 1 and 6 to 8 . The controller 9 is electrically connected to the resolver coil 7B of the detector 7, the detector 71B of the detector 71, the detector 72B of the detector 72, and the light source 73A and detector 73B of the detector 73. FIG. The control unit 9 controls power supply (input of an AC signal) to the coil 6B of the stator unit 6, and controls the circumferential rotation of the nut unit 3 to which the rotor unit 5 is fixed. The controller 9 calculates the movement amount of the screw shaft 2 based on signals from the resolver coil 7B of the detector 7, the detector 71B of the detector 71, the detector 72B of the detector 72, and the detector 73B of the detector 73. At the same time, the power supply (input of AC signal) to the coil 6B of the stator portion 6 is controlled, and the circumferential rotation amount of the nut portion 3 to which the rotor portion 5 is fixed is controlled. Further, when the stator unit 6 has a plurality of coils 6B connected to different electric power systems, the control unit 9 controls single-system operation to operate the other system when one of the systems stops.

As described above, the linear motion actuator 1 of the embodiment includes a screw shaft 2, a nut portion 3 into which the screw shaft 2 is screwed along the axial direction, and a rotor disposed on the end face 3C of the nut portion 3 in the axial direction. a portion 5, a stator portion 6 arranged to face the rotor portion 5 in the axial direction, an outer ring 4A surrounding the nut portion 3, and an inner groove continuously formed in the outer circumference 3D of the nut portion 3 in the circumferential direction. 4B, and a bearing portion 4 having rolling elements 4C received in the outer groove 4Aa and the inner groove 4B formed in the outer ring 4A and supporting the nut portion 3 in a circumferentially rotatable manner.

Since the linear motion actuator 1 constitutes an axial gap type motor by the rotor portion 5 and the stator portion 6, the gap between the rotor portion 5 and the stator portion 6 is adjusted in the axial direction. 3 regardless of coaxiality. For this reason, according to the linear motion actuator 1 of the embodiment, there is no need to precisely match the coaxiality of the screw shaft 2 and the nut portion 3 with the motor, and assembly can be facilitated. It becomes easy to adjust the gap between and, and the rotation unevenness of the motor can be reduced. As a result, according to the linear motion actuator 1 of the embodiment, it is difficult to be affected by the degree of coaxiality, and deterioration in motor efficiency and performance can be prevented. Moreover, according to the linear motion actuator 1 of the embodiment, since the rotor portion 5 is disposed on the axial end face 3C of the nut portion 3, the size in the radial direction can be reduced. Since the axial direction is within the movement range of the screw shaft 2, even if the rotor portion 5 is arranged on the end surface 3C of the nut portion 3 in the axial direction, there is no concern about an increase in size.

Further, in the linear motion actuator 1 of the embodiment, the bearing portion 4 is configured by integrating the inner ring with the outer circumference 3D of the nut portion 3 . As a result, the inertia of the nut portion 3 can be reduced, and a high-speed, high-response actuator can be realized. Moreover, according to the linear motion actuator 1 of the embodiment, since the bearing portion 4 is configured by integrating the inner ring with the outer circumference 3D of the nut portion 3, the size in the radial direction can be reduced.

In the linear motion actuator 1 of the embodiment, the rotor portion 5 has a plurality of permanent magnets 5A protruding from the axial end face 3C of the nut portion 3 and arranged in the circumferential direction. A gap 5B is formed in . Therefore, in the linear motion actuator 1 of the embodiment, the mutual magnetic force that attracts the adjacent permanent magnets 5A is softened by the gap 5B between the adjacent permanent magnets 5A, and the influence on the magnetic field directed toward the stator portion 6 is suppressed. As a result, according to the linear motion actuator 1 of the embodiment, it is possible to prevent deterioration of motor efficiency and performance.

In the linear motion actuator 1 of the embodiment, the rotor portion 5 has a plurality of permanent magnets 5A protruding from the axial end face 3C of the nut portion 3 and arranged in the circumferential direction. A non-magnetic member (partition wall 5C) is arranged at . Therefore, in the linear motion actuator 1 of the embodiment, the non-magnetic member (the partition wall 5C) softens the mutual magnetic force between the adjacent permanent magnets 5A and suppresses the influence on the magnetic field directed toward the stator portion 6. FIG. As a result, according to the linear motion actuator 1 of the embodiment, it is possible to prevent deterioration of motor efficiency and performance. In the linear motion actuator 1 of the embodiment, when the nut portion 3 is a magnetic member, a non-magnetic member (bottom plate 5F) is arranged between the axial end surface 3C of the nut portion 3 and the permanent magnet 5A. is preferred. Therefore, in the linear motion actuator 1 of this embodiment, the magnetization of the nut portion 3 by the permanent magnet 5A is suppressed by the non-magnetic member (bottom plate 5F), the influence on the magnetic field directed toward the stator portion 6 is suppressed, and the motor efficiency and It is possible to prevent deterioration of performance.

Further, in the linear motion actuator 1 of the embodiment, the rotor portion 5 is arranged on both axial end surfaces 3C of the nut portion 3, and the stator portion 6 is arranged to face each rotor portion 5 in the axial direction. . Therefore, the linear motion actuator 1 of the embodiment can operate the screw shaft 2 by rotating the nut portion 3 stably with high torque by both the stator portion 6 and the rotor portion 5 . Further, the linear motion actuator 1 of the embodiment has redundancy in which the nut portion 3 is rotated by the other stator portion 6 and rotor portion 5 when one of the stator portion 6 and rotor portion 5 has an abnormality.

Further, in the linear motion actuator 1 of the embodiment, the stator section 6 has a plurality of coils 6B connected to different electric power systems. Therefore, the linear motion actuator 1 of the embodiment has redundancy in which the rotor portion 5 (nut portion 3) is rotated by the other coil 6B when there is an abnormality in the coil 6B of one electric power system.

Further, in the linear motion actuator 1 of the embodiment, detection means 7 is arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3 and detects the amount of movement of the screw shaft 2 accompanying rotation of the nut portion 3. , 71, 72, 73. Therefore, in the linear motion actuator 1 of the embodiment, since the detection means 7, 71, 72, and 73 are arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3, the size of the linear motion actuator 1 as a whole can be increased. suppressed. Further, in the linear motion actuator 1 of the embodiment, since the detection means 7, 71, 72, 73 are arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3, a member such as a gear is provided in the detection portion. Since there is no need to intervene, the rotor portion 5 and the stator portion 6 are not burdened with the output for rotating the gear, and the size of the motor can be suppressed. Further, in the linear motion actuator 1 of the embodiment, since the detection means 7, 71, 72, 73 are arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3, a member such as a gear is provided in the detection portion. Since there is no need to intervene, it is possible to eliminate the influence on the positioning accuracy and response speed of the screw shaft 2 due to the occurrence of backlash and inertia of the gear. Further, in the linear motion actuator 1 of the embodiment, since the detection means 7, 71, 72, 73 are arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3, a member such as a gear is provided in the detection portion. Since there is no need to intervene, it is possible to prevent occurrence of backlash of the gear and deterioration of controllability due to inertia.

Further, in the linear motion actuator 1 of the embodiment, the detection means 7 and 71 detect the rotational displacement or the amount of rotation of the nut portion 3 . Therefore, the linear motion actuator 1 of the embodiment can be arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3 by a configuration for detecting the rotational displacement or amount of rotation of the nut portion 3 .

Further, in the linear motion actuator 1 of the embodiment, the detection means 72 and 73 detect the displacement of the screw shaft 2 itself. Therefore, the direct-acting actuator 1 of the embodiment can be arranged coaxially with the axis C of the screw shaft 2 and the nut portion 3 by a configuration that detects the displacement of the screw shaft 2 itself.

Reference Signs List 1 linear actuator 2 screw shaft 3 nut portion 3C end surface 3D outer periphery 4 bearing portion 4A outer ring 4Aa outer groove 4C rolling element 4B inner groove 5 rotor portion 5A permanent magnet 5B gap 5C partition wall (non-magnetic member)
6 stator section 6B coil 7, 71, 72, 73 detection means

Claims (8)

a screw shaft;
a nut portion into which the screw shaft is axially screwed;
a rotor portion disposed on an axial end face of the nut portion;
a stator portion arranged to face the rotor portion in the axial direction;
An outer ring surrounding the nut portion, an inner groove continuously formed on the outer circumference of the nut portion in the circumferential direction, and rolling elements received in the outer groove formed on the outer ring and the inner groove. a bearing portion that supports the nut portion so as to be rotatable in the circumferential direction;
linear actuator, including In the rotor portion, a plurality of permanent magnets protruding from an axial end surface of the nut portion are arranged in the circumferential direction, and gaps are formed between the permanent magnets adjacent in the circumferential direction.
The linear motion actuator according to claim 1. 2. The rotor part according to claim 1, wherein a plurality of permanent magnets protrude from an axial end face of the nut part and are arranged in the circumferential direction, and a non-magnetic member is arranged between the permanent magnets adjacent in the circumferential direction. Linear Actuator as described. 4. The rotor portion according to claim 1, wherein the rotor portion is arranged on both axial end surfaces of the nut portion, and the stator portion is arranged axially facing each of the rotor portions. Linear Actuator as described. The linear motion actuator according to any one of claims 1 to 4, wherein the stator section has multiple systems of coils connected to different electric power systems. 6. The detecting device according to any one of claims 1 to 5, further comprising detecting means arranged coaxially with the axial centers of said screw shaft and said nut portion for detecting the amount of movement of said screw shaft accompanying rotation of said nut portion. linear actuator described in . 7. The linear motion actuator according to claim 6, wherein said detection means detects rotational displacement or rotation amount of said nut portion. 7. A linear motion actuator according to claim 6, wherein said detection means detects displacement of said screw shaft itself.

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