Actuator

Abstract

An actuator (10) comprises a stator (12) which is formed in an annular shape and which generates a rotating magnetic field. The actuator (10) comprises a shaft (36) that is formed using a soft magnetic material, is disposed radially inward with respect to the stator (12), is provided with a magnet (38), and rotates as a result of the stator (12) generating the rotating magnetic field. Furthermore, the actuator (10) comprises a linear motion unit (18) which is provided at the center of rotation of the shaft (36) and which is displaced in the axial direction by the rotation of the shaft (36).

Description

Actuator CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-150589, filed on September 15, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to actuators.

[0003] Patent Document 1 below discloses a disconnector device that is provided in a vehicle and switches between a two-wheel drive state and a four-wheel drive state. This disconnector device can switch between a two-wheel drive state and a four-wheel drive state by disconnecting or connecting a differential shaft and a hub depending on the driving conditions. More specifically, the disconnector device includes a ball screw shaft that rotates when a motor is operated, a nut connected to the ball screw shaft, a sleeve that moves together with the nut, and a fork engaged with the sleeve. When the motor is operated, the ball screw shaft rotates, and the nut moves the fork via the sleeve, thereby connecting or disconnecting the differential shaft and the hub.

[0004] Patent No. 7225353

[0005] From the viewpoint of mountability on a vehicle, it is desirable to be able to shorten the shaft from the rotating part such as the motor to the axial displacement part such as the nut, but the configuration described in Patent Document 1 above leaves room for improvement in this regard.

[0006] An object of the present disclosure is to provide an actuator that can shorten the axis from the rotating portion to the axial displacement portion.

[0007] In a first aspect of the present disclosure, the actuator includes a stator formed in an annular shape that generates a rotating magnetic field, a shaft formed using a soft magnetic material, positioned radially inward of the stator, and equipped with a magnet, the shaft rotating when the stator generates a rotating magnetic field, and an axial displacement portion provided at the rotation center of the shaft that displaces axially when the shaft rotates.

[0008] By configuring in this way, it is possible to shorten the shaft from the rotating part to the axially displaceable part.

[0009] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a cross-sectional view showing a cross section of an actuator according to a first embodiment taken along the axial direction, Fig. 2 is a front view showing an engagement portion between a fork and a main shaft, Fig. 3 is a cross-sectional view showing a cross section of an actuator according to a second embodiment taken along the axial direction, Fig. 4 is a cross-sectional view showing a cross section of an actuator according to a third embodiment taken along the axial direction, and Fig. 5 is a cross-sectional view showing a cross section of an actuator according to a fourth embodiment taken along the axial direction.

[0010] 1 and 2, an actuator 10 according to a first embodiment of the present disclosure will be described. Note that the arrow Z direction, arrow R direction, and arrow C direction appropriately shown in the figures respectively indicate one side in the rotational axis direction, the outer side in the rotational radial direction, and one side in the rotational circumferential direction of a rotor 16, which will be described later. Furthermore, hereinafter, when simply referring to an axial direction, a radial direction, or a circumferential direction, this refers to the rotational axis direction, the rotational radial direction, or the rotational circumferential direction of the rotor 16, unless otherwise specified.

[0011] 1, an actuator 10 of this embodiment includes a stator 12 that generates a rotating magnetic field, and a housing 14 that accommodates the stator 12 and other components. The actuator 10 also includes a rotor 16 that rotates when the stator 12 generates a rotating magnetic field, and a linear motion unit 18 that serves as an axial displacement unit that is displaced in the axial direction when the rotor 16 rotates. The actuator 10 also includes a fork 20 that serves as a transmission unit connected to the linear motion unit 18.

[0012] The stator 12 includes a stator core 22 formed in an annular shape and a plurality of coils 24 formed around the stator core 22. A rotating magnetic field is generated around the stator 12 by switching the energization of the plurality of coils 24. The stator 12 is supported by the housing 14 (described later) by, for example, press-fitting the stator core 22 into the housing 14.

[0013] The housing 14 is formed into a cylindrical shape penetrating in the axial direction. The housing 14 includes a stator support portion 14A on the radially inner side where the stator 12 is supported. The housing 14 also includes a bearing support portion 14B on the radially inner side where the bearing 26 is supported. The bearing support portion 14B is disposed adjacent to the stator support portion 14A on one axial side of the stator support portion 14A and has a smaller diameter than the stator support portion 14A. The housing 14 also includes an oil seal support portion 14C on the radially inner side where the oil seal 28 is supported. The oil seal support portion 14C is disposed adjacent to the bearing support portion 14B on one axial side of the bearing support portion 14B and has a smaller diameter than the bearing support portion 14B. A control unit 30 and a housing cover 32 for controlling the supply of current to the stator 12 (plurality of coils 24) are provided on the other axial side of the housing 14. The other axial side of the housing 14 is closed by the control unit 30 and the housing cover 32. Furthermore, a bearing 34 is fixed to the housing cover 32 .

[0014] The rotor 16 includes a shaft 36 made of a soft magnetic material such as steel and a magnet 38 attached to the shaft. The shaft 36 includes a large-diameter portion 36A located radially inward relative to the stator 12. The shaft 36 also includes a medium-diameter portion 36B that protrudes from the large-diameter portion 36A toward one axial side and has an outer diameter smaller than that of the large-diameter portion 36A. The shaft 36 also includes a small-diameter portion 36C that protrudes from the large-diameter portion 36A toward the other axial side and has an outer diameter smaller than that of the medium-diameter portion 36B. The portion of the medium-diameter portion 36B adjacent to the large-diameter portion 36A is supported by the bearing 26, and the other axial end of the small-diameter portion 36C is supported by the bearing 34. This allows the shaft 36 to rotate around the bearings 26 and 34. A magnet 38 is fixed to the radially outer surface of the large-diameter portion 36A. The magnet 38 may be a segment magnet divided in the circumferential direction, or a ring magnet formed in an annular shape. The magnet 38 may also be configured to be provided on the inner periphery of the large diameter portion 36A. A linear motion portion insertion hole 36D is formed in the rotation center of the large diameter portion 36A and the medium diameter portion 36B, into which the linear motion portion 18 (described later) is inserted from one axial side. One axial end of the linear motion portion insertion hole 36D is open to one axial side at one axial end face of the medium diameter portion 36B. The other axial end of the linear motion portion insertion hole 36D is closed inside the large diameter portion 36A. A first thread portion 36E is formed along the axial direction on the inner periphery of the linear motion portion insertion hole 36D.

[0015] The linear motion portion 18 is formed using a rod-shaped steel material. A second screw portion 18A is formed along the axial direction on the outer periphery of the linear motion portion 18. The linear motion portion 18 is inserted into the linear motion portion insertion hole 36D of the shaft 36 with the second screw portion 18A and the first screw portion 36E threadedly engaged with each other.

[0016] As shown in FIGS. 1 and 2 , the fork 20 is disposed on the radially outer periphery of the medium diameter portion 36B of the shaft 36. The fork 20 includes a slide support portion 20A slidably supported on the medium diameter portion 36B of the shaft 36 and a main shaft engagement portion 20B protruding radially outward from the slide support portion 20A. A slide hole 20C into which the medium diameter portion 36B of the shaft 36 is inserted is formed in the slide support portion 20A. The inner circumferential surface of the slide hole 20C slides against the outer circumferential surface of the medium diameter portion 36B, allowing the fork 20 to move (displace) axially along the medium diameter portion 36B of the shaft 36. The main shaft engagement portion 20B of the fork 20 engages with a main shaft 40 that constitutes part of the mechanism controlled by the actuator 10 of this embodiment. This allows power to be transmitted from the fork 20 to the controlled object.

[0017] The fork 20 is also connected to the linear motion unit 18 via a connecting member 42. The connecting member 42 has a first connecting portion 42A that is fixed to one axial end of the linear motion unit 18 via a fastening member 44. The connecting member 42 also has a second connecting portion 42B that extends from the radially outer end of the first connecting portion 42A toward the other axial end. The other axial end of this second connecting portion 42B is fixed to the fork 20 via a fastening member 46. This allows the fork 20 to move axially together with the linear motion unit 18 and the connecting member 42.

[0018] (Operations and Effects of the Present Embodiment) Next, operations and effects of the present embodiment will be described.

[0019] As shown in FIGS. 1 and 2 , in the actuator 10 of the present embodiment described above, the stator 12 generates a rotating magnetic field, and when the rotor 16 rotates toward one circumferential side, the shaft 36 rotates toward one circumferential side relative to the linear moving part 18. Here, the first threaded portion 36E on the shaft 36 and the second threaded portion 18A on the linear moving part 18 are threadedly engaged. Therefore, when the shaft 36 rotates toward one circumferential side relative to the linear moving part 18, the linear moving part 18 moves (displaces) toward one axial side relative to the shaft 36. In contrast, when the stator 12 generates a rotating magnetic field, and the rotor 16 rotates toward the other circumferential side relative to the linear moving part 18, the shaft 36 rotates toward the other circumferential side relative to the linear moving part 18, and the linear moving part 18 moves toward the other axial side relative to the shaft 36. In the actuator 10 of the present embodiment, the fork 20 can be moved axially along the main shaft 40 by moving the linear moving part 18 axially. This makes it possible to control the controlled object.

[0020] Here, in the actuator 10 of this embodiment, the linear motion part 18 is configured to be inserted into the rotation center of the shaft 36. In this configuration, the axial length of the range from the shaft 36, which is the rotating part, to the linear motion part 18 can be made shorter than in a configuration in which the linear motion part 18 is disposed on an axial extension of the shaft 36.

[0021] In addition, in this embodiment, the fork 20 is slidably supported on the medium diameter portion 36B of the shaft 36. This configuration eliminates the need for a part whose only function is to support the fork 20. As a result, it is possible to prevent the number of parts of the actuator 10 from increasing and the configuration from becoming more complicated.

[0022] Furthermore, in this embodiment, the fork 20 engages with the main shaft 40, thereby preventing the linear motion portion 18 from rotating in the circumferential direction. This configuration eliminates the need to provide a part whose only function is to prevent the linear motion portion 18 from rotating in the circumferential direction. As a result, it is possible to prevent the number of parts of the actuator 10 from increasing and the configuration from becoming complicated.

[0023] In addition, in this embodiment, the magnet 38 is provided on the large diameter portion 36A of the shaft 36. This allows the large diameter portion 36A of the shaft 36 to function as the rotor core of the rotor 16. With this configuration, it is possible to prevent an increase in the number of parts of the rotor 16 compared to a rotor configured such that the rotor core is fixed to the shaft.

[0024] In addition, in this embodiment, the stator support portion 14A, the bearing support portion 14B, and the oil seal support portion 14C of the housing 14 are arranged adjacent to each other in the axial direction, so that the stator 12, the bearing 26, and the oil seal 28 are arranged adjacent to each other in the axial direction. By arranging the stator 12, the bearing 26, and the oil seal 28 closely together in the axial direction in this manner, it is possible to reduce the size of the actuator 10 in the axial direction.

[0025] Second Embodiment Next, an actuator 48 according to a second embodiment will be described with reference to Fig. 3. Note that members and parts of the actuator 48 according to the second embodiment that correspond to those of the actuator 10 described above will be denoted by the same reference numerals as those of the actuator 10 described above, and descriptions thereof may be omitted.

[0026] As shown in FIG. 3 , the shaft 36 of the actuator 48 of this embodiment includes a medium-diameter portion 36B that protrudes from the large-diameter portion 36A toward one axial side and the other axial side. The fork 20 is disposed on the radial outer periphery of the medium-diameter portion 36B of the shaft 36. A linear-moving portion insertion hole 36D, into which the linear-moving portion 18 is inserted, is formed in the rotation center of the large-diameter portion 36A and the medium-diameter portion 36B. One axial end of the linear-moving portion insertion hole 36D opens toward one axial side at the end face of the medium-diameter portion 36B on one axial side. The other axial end of the linear-moving portion insertion hole 36D opens toward the other axial side at the end face of the medium-diameter portion 36B on the other axial side. In other words, the linear-moving portion insertion hole 36D axially penetrates the rotation center of the shaft 36.

[0027] In the actuator 48 of the present embodiment described above, a linear motion portion 18 that is longer than that of the previously described actuator 10 can be provided at the rotation center of the shaft 36. As a result, in the actuator 48 of the present embodiment, the axial movement range of the linear motion portion 18 and the fork 20 can be increased compared to the previously described actuator 10.

[0028] Third Embodiment Next, an actuator 50 according to a third embodiment will be described with reference to Fig. 4. Note that, in the actuator 50 according to the third embodiment, members and parts corresponding to those of the actuator 10 described above will be denoted by the same reference numerals as those corresponding to those of the actuator 10 described above, and descriptions thereof may be omitted.

[0029] 4 , in the actuator 50 of this embodiment, the fork 20 is disposed on the radial outer periphery of the large diameter portion 36A of the shaft 36 and on the radial outer periphery of the stator support portion 14A of the housing 14. The fork 20 is slidably supported by the stator support portion 14A of the housing 14. More specifically, the stator support portion 14A of the housing 14 is inserted into the slide hole 20C of the slide support portion 20A. The inner circumferential surface of the slide hole 20C slides against the outer circumferential surface of the stator support portion 14A, allowing the fork 20 to move axially along the stator support portion 14A of the housing 14.

[0030] In the actuator 50 of this embodiment described above, the axial length of the medium diameter portion 36B of the shaft 36 can be set shorter than in the actuator 10 described above. As a result, the actuator 50 of this embodiment described above can be made smaller in size in the axial direction than in the actuator 10 described above.

[0031] Fourth Embodiment Next, an actuator 52 according to a fourth embodiment will be described with reference to Fig. 5. Note that, in the actuator 52 according to the fourth embodiment, members and parts corresponding to those of the actuator 10 described above will be denoted by the same reference numerals as those corresponding to those of the actuator 10 described above, and descriptions thereof may be omitted.

[0032] 5, in the actuator 52 of this embodiment, the portion of the shaft 36 of the actuator 10 described above that corresponds to the large diameter portion 36A is a small diameter portion 36C. A rotor core 54 is fixed to this small diameter portion 36C by press fitting or the like. A magnet 38 is fixed to the outer circumferential surface of the rotor core 54. The fork 20 is disposed on the radial outer periphery of the medium diameter portion 36B of the shaft 36.

[0033] The actuator 52 of the present embodiment described above has a configuration including a rotor core 54. In this configuration, the actuator 52 can be designed to use the rotor core 54 of another motor.

[0034] In the actuators 10, 48, 50, and 52 of the above-described embodiments, the fork 20 is moved axially by the linear moving unit 18, but the present disclosure is not limited to this. For example, the linear moving unit 18 may be configured to move a member other than the fork 20 in the axial direction. Alternatively, the linear moving unit 18 may be configured to directly engage with the controlled object.

[0035] The above describes one embodiment of the present disclosure, but the present disclosure is not limited to the above, and it goes without saying that it can be implemented in various other modified forms within the scope that does not deviate from the gist of the present disclosure.

[0036] <Notes> (Note 1) An actuator (10, 48, 50, 52) comprising: a stator (12) formed in an annular shape and generating a rotating magnetic field; a shaft (36) formed using a soft magnetic material, disposed radially inward of the stator, and provided with a magnet (38), the shaft rotating when the stator generates a rotating magnetic field; and an axial displacement unit (18) provided at the rotation center of the shaft and displaced axially when the shaft rotates. (Note 2) The actuator according to Note 1, wherein a transmission unit (20) connected to the axial displacement unit is provided radially outward of the shaft, the transmission unit being displaced axially when the axial displacement unit is displaced. (Note 3) The actuator according to Note 2, wherein the transmission unit is provided along the outer circumferential surface of the shaft, and the transmission unit is displaced along the outer circumferential surface of the shaft when the axial displacement unit is displaced axially. (Supplementary Note 4) The actuator according to Supplementary Note 2, wherein the transmission portion is provided radially outward of the stator and along an outer peripheral surface of a housing (14) that supports the stator, and the axial displacement portion displaces the transmission portion along the outer peripheral surface of the housing in an axial direction.

[0037] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. An actuator (10, 48, 50, 52) comprising: a stator (12) formed in an annular shape and generating a rotating magnetic field; a shaft (36) formed of a soft magnetic material, arranged radially inward of the stator, and provided with a magnet (38), the shaft (36) rotating as the stator generates a rotating magnetic field; and an axial displacement portion (18) provided at the rotation center of the shaft and displacing in the axial direction as the shaft rotates.

2. An actuator as described in claim 1, wherein a transmission section (20) connected to the axial displacement section is provided on the radial outside of the shaft, and the transmission section is displaced in the axial direction when the axial displacement section is displaced in the axial direction.

3. An actuator as described in claim 2, wherein the transmission portion is provided along the outer peripheral surface of the shaft, and the transmission portion is displaced along the outer peripheral surface of the shaft as a result of the axial displacement portion being displaced in the axial direction.

4. An actuator as described in claim 2, wherein the transmission portion is provided radially outward from the stator and along the outer circumferential surface of a housing (14) supporting the stator, and the axial displacement portion is displaced in the axial direction, thereby displacing the transmission portion along the outer circumferential surface of the housing.

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