Direct-acting actuator

Abstract

To stabilize operation of a direct-acting actuator.SOLUTION: A direct-acting actuator for active dampers comprises: a direct-acting section; a motor which is provided at a position eccentric from a centerline of the direct-acting section and generates drive power for causing the direct-acting section to directly act in a direction of the centerline; a transmission section which connects the motor to the direct-acting section and transfers the drive power of the motor to the direct-acting section; an element provided at a position, which is balanced with the motor, in a view in the centerline direction of the direct-acting section; and a connection section which connects the element to the direct-acting section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a linear actuator, and more particularly to a linear actuator mounted on an electromagnetic suspension. [Background technology]

[0002] Electromagnetic suspensions are sometimes used to suppress vehicle vibration. In the case of an electromagnetic suspension equipped with a linear actuator (ball screw), if the motor of the linear actuator is offset from the axis of the electromagnetic suspension, the rotation of the motor output shaft can be reduced and transmitted to the ball screw, allowing the electromagnetic suspension (linear actuator) to output a large thrust and to have a compact structure by reducing the axial length. An example of the above-mentioned electromagnetic suspension is disclosed in Patent Document 1.

[0003] In the electromagnetic suspension of Patent Document 1, a motor is disposed offset with respect to the screw shaft of the ball screw (that is, the axis of the electromagnetic suspension), and the torque of the motor is transmitted to the ball screw by a belt member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6426794 specification Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration of Patent Document 1, when the motor is subjected to vertical vibration or impact, a torsional force is applied to the link that supports the electromagnetic suspension. Furthermore, the torsional force may cause the motor to unintentionally rotate from a predetermined position, which may affect the operation of the linear actuator. For example, when an electromagnetic suspension (linear actuator) is arranged horizontally to lower the floor and center of gravity of transportation equipment such as railway cars, the above-mentioned problems become more pronounced. When the electromagnetic suspension is arranged horizontally, a torsional force acts on the link section with each road vibration (vertical vibration). Road vibrations occur frequently and have large accelerations in response to vehicle acceleration / deceleration and lateral G, so the vibrations are transmitted to the coil spring of the electromagnetic suspension through the link section, reducing the vibration damping effect or even damaging the link section. In addition, the above-mentioned torsional force increases the possibility that the motor will rotate from a specified position, affecting the operation of the linear actuator. SUMMARY OF THE PRESENT EMBODIMENT In order to solve the above problems, an object of the present invention is to stabilize the operation of a linear actuator. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a linear actuator according to one aspect of the present invention is a linear actuator for an active damper, and includes a linear part, a motor provided at a position eccentric to the center line of the linear part and generating a driving force for linearly moving the linear part in the direction of the center line, a transmission part connecting the motor to the linear part and transmitting the driving force of the motor to the linear part, an element provided at a position that balances with the motor when viewed from the direction of the center line of the linear part, and a connecting part connecting the element to the linear part.

[0007] Preferably, the motor and the element are arranged symmetrically with respect to a center line of the linear motion portion. Preferably, the element is a second motor having the same structure as the motor, the coupling portion has the same structure as the transmission portion, and the linear motion portion is driven by the motor and the second motor. The element may be a mass having the same weight as the motor.

[0008] A plurality of the elements may be provided. In this case, the plurality of elements are a plurality of second motors having the same structure as the motor, and the motor and the plurality of second motors are provided around the center line at equal angular intervals as viewed from the center line direction of the linear motion part.

[0009] When the linear actuator is disposed horizontally and the linear motion portion moves linearly in a horizontal direction, the height of the motor and the height of the element are preferably the same. A coil spring may be wound around an outer periphery of the linear motion portion. Effect of the Invention

[0010] According to the present invention, the operation of the linear actuator can be stabilized. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a front cross-sectional view showing an electromagnetic suspension having a linear actuator according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a top view of the electromagnetic suspension with the cover removed. [Diagram 3] FIG. 3 is an enlarged side cross-sectional view showing a portion of the electromagnetic suspension of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described based on the drawings. In order to avoid unnecessary redundancy in the description and to facilitate understanding by those skilled in the art, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or duplicate description of substantially the same configuration may be omitted. In addition, elements described in the previously described figures may be appropriately referenced in the description of the later figures. The scale of the drawings is not necessarily accurate, and some features may be exaggerated or omitted. The scope of the present invention is not limited to the following embodiments, and changes and modifications may be made within the scope of the technical idea of ​​the present invention.

[0013] An electromagnetic suspension 100 including a linear actuator 1 according to an embodiment of the present invention will be described with reference to Figs. 1 to 3. The electromagnetic suspension 100 can be used, for example, as a vibration damping device for transport equipment (transportation vehicles and railway cars) and structures. The electromagnetic suspension 100 is an electromechanical full active suspension. In the following description, expressions indicating directions and positions such as up, down, left, and right are used, but these expressions do not limit the present invention. Expressions indicating directions and positions such as up, upper part, upper end, down, lower part, lower end, left side, and right side are only used to facilitate the description and understanding of the embodiment. For example, the parts expressed as up and down when the electromagnetic suspension 100 is arranged vertically become left and right when the electromagnetic suspension 100 is arranged horizontally.

[0014] FIG. 1 is a schematic diagram of an electromagnetic suspension 100 according to an embodiment of the present invention. FIG. 2 is a top view of the electromagnetic suspension 100 with a cover 15 of the electromagnetic suspension 100 removed. The electromagnetic suspension 100 is disposed vertically (perpendicular to the road surface or railroad tracks). The electromagnetic suspension 100 includes a linear actuator 1 and a coil spring 50. The electromagnetic suspension 100 is an active damper. The linear actuator 1 is a device for causing the electromagnetic suspension 100 to function as an active damper. The coil spring 50 is wound around the outer periphery of the linear actuator 1. The dashed line A is the center line (axis) of the electromagnetic suspension 1. The electromagnetic suspension 1 of this embodiment has a structure that is symmetrical with respect to the center line A. The dashed line A may also be referred to as the axis A of a feed screw 6, which will be described later.

[0015] The linear actuator 1 has a left motor 2, a right motor 3, a motor driver 4, a gear transmission mechanism (gear train) 5, a feed screw 6, a nut member 7, a linear cylindrical member 8, and a housing 9. The feed screw 6, the nut member 7, and the linear cylindrical member 8 may be collectively referred to as a linear motion unit. The left motor 2 and the right motor 3 are provided at eccentric positions (offset) from the center line A of the linear motion unit. The left motor 2 and the right motor 3 are controlled by one motor driver 4. Note that the arrow extending from the motor driver 4 to the left motor 2 is omitted in Fig. 1. In this embodiment, the left motor 2 and the right motor 3 are disposed symmetrically (line-symmetrically) with respect to the center line A of the electromagnetic suspension 100. In other words, the distance from the center line A of the electromagnetic suspension 100 to the center line B of the left motor 2 is equal to the distance from the center line A of the electromagnetic suspension 100 to the center line C of the right motor 3. It can be said that the right motor 3 is provided at a position that balances with the left motor 2. Note that when the left motor 2 is simply referred to as a motor, the right motor may be referred to as a second motor.

[0016] The left motor 2 and the right motor 3 are, for example, servo motors or stepping motors. The left motor 2 has a rotating shaft (motor output shaft) 2a. The right motor 3 has a rotating shaft 3a. A motor driver 4 controls the rotation of the rotating shafts 2a, 3a. A signal is supplied to the motor driver 4 from an acceleration sensor (not shown) that measures the acceleration applied to the electromagnetic suspension 100. The motor driver 4 controls the rotation of the rotating shafts 2a, 3a based on the signal from the acceleration sensor, so that the linear actuator 1 exerts a vibration damping function. The left motor 2 and the right motor 3 are driving parts that generate a driving force for linearly moving the linear part of the electromagnetic suspension 100 in the direction of the center line A.

[0017] The left motor 2 is fixed to the left underside of the upper flange 9a of the housing 9, and the rotating shaft 2a passes through a hole formed in the left side of the upper flange 9a of the housing 9. The right motor 3 is fixed to the lower right surface of the upper flange 9a of the housing 9, and the rotating shaft 3a passes through a hole formed in the right side of the upper flange 9a of the housing 9. Since the left motor 2 and the right motor 3 have the same structure, they may be referred to as motors 2 and 3 in the following description. The housing 9 is made of a rigid material (for example, a metal or a resin having a predetermined strength).

[0018] The gear transmission mechanism 5 has two small gears (pinion gears) 10A and 10B and one large gear (final gear) 11. The small gears 10A and 10B and the large gear 11 are simply referred to as gears 10A, 10B, and 11 in the following description. The gears 10A and 10B have the same structure and are also the same in size. The gears 10A and 10B are smaller than the gear 11. In this embodiment, the gear 11 is rotated and driven by the two gears 10A and 10B. The gear transmission mechanism 5 is a link portion (connecting portion) that connects the motors 2 and 3 to the ball screw 6. The gear transmission mechanism 5 in this embodiment is a two-stage reduction gear mechanism. The gear transmission mechanism 5 may be referred to as a transmission portion that connects the motors 2 and 3 to the linear motion portion (the feed screw 6, the nut member 7, and the linear motion cylindrical member 8) of the electromagnetic suspension 100 and transmits the driving force of the motors 2 and 3 to the linear motion portion. The gears 10A, 10B, and 11 are, for example, spur gears. Incidentally, the gears 10A, 10B, and 11 may be helical gears.

[0019] Gear 10A is a drive gear, and is fixed to the rotating shaft 2a to rotate together with the rotating shaft 2a. Gear 10A is fixed to the rotating shaft 2a with a key 2b and a nut 2c. Gear 10B is also a drive gear, and is fixed to the rotating shaft 3a to rotate together with the rotating shaft 3a. Gear 10B is fixed to the rotating shaft 3a with a key 3b and a nut 3c.

[0020] Gear 11 is a driven gear that meshes with gears 10A and 10B and is driven to rotate by gears 10A and 10B. Gear 11 has a rotating shaft (output shaft of gear transmission mechanism 5) 11a. Gear 11 is fixed to rotating shaft 11a with key 11b and nut 11c. Rotating shaft 11a rotates together with gear 11.

[0021] The rotating shaft 11a is rotatably supported by rolling bearings 12 and 13. The rolling bearings 12 and 13 are supported by a bearing housing 14, which is fixed to an upper flange 9a of the housing 9.

[0022] A cover 15 is fixed to an upper flange 9a of the housing 9. The cover 15 is made of a rigid material (for example, metal or resin having a predetermined strength). The cover 15, together with the housing 9, defines a space for accommodating the gear transmission mechanism 5 and protects the gear transmission mechanism 5. The housing 9 has a guide sleeve 9b extending downward from an upper flange 9a. The guide sleeve 9b is a cylindrical member that guides the linear motion of the linear cylindrical member 8 (sliding in the direction of the center line A of the electromagnetic suspension 100). The linear cylindrical member 8 is inserted into the guide sleeve 9b. The guide sleeve 9b is integrally connected to the upper flange 9a. Since the guide sleeve 9b guides the sliding of the linear cylindrical member 8, it may also be called a sliding sleeve. In addition, since the guide sleeve 9b guides the linear cylindrical member 8, it may also be called a linear guide portion.

[0023] In this embodiment, the rotating shaft 11a of the gear 11 is an output shaft of the gear transmission mechanism 5, and the feed screw 6 of the linear actuator 1 is formed on an extension of the rotating shaft 11a. Therefore, the feed screw 6 is rotated about the axis A of the feed screw 6 as the rotating shaft 2a of the motor 2 and the rotating shaft 3a of the motor 3 rotate.

[0024] The feed screw 6 is arranged coaxially with the guide sleeve 9b. The feed screw 6 may be a trapezoidal screw, a ball screw (e.g., a circulating ball screw), or any of various roller screws. The roller screw may be, for example, a planetary roller screw, a circulating roller screw, or any other roller screw.

[0025] The nut member 7 engages with the feed screw 6, and is moved straight along the axis A of the feed screw 6 as the feed screw 6 rotates. The nut member 7 is made of a rigid material (e.g., metal or resin having a predetermined strength). The nut member 7 has a cylindrical contour. The nut member 7 has an outer circumferential surface 7a, a lower end surface 7b, and an upper end surface 7c. The nut member 7 is provided in the hollow portion of the linear motion cylindrical member 8, and the outer circumferential surface 7a of the nut member 7 is fixed to the inner circumferential wall of the linear motion cylindrical member 8.

[0026] The linear motion cylindrical member 8 is caused to move linearly together with the nut member 7 in the direction of the axis A of the feed screw 6 as the feed screw 6 rotates. The linear motion cylindrical member 8 may be referred to as a linear motion rod.

[0027] The linear motion cylindrical member 8 is a cylindrical member formed from a rigid material (e.g., metal or a resin having a predetermined strength), and the length of the linear motion cylindrical member 8 in the direction of the axis A of the feed screw 6 is greater than the axial length of the feed screw 6. The linear motion cylindrical member 8 is arranged coaxially with the feed screw 6 and the guide sleeve 9b. The linear motion cylindrical member 8 is arranged in the internal space of the guide sleeve 9b so as to be able to reciprocate in the direction of the axis A. The feed screw 6 extends in the center of the internal space of the linear motion cylindrical member 8. The linear motion cylindrical member 8 is a rod-shaped member that slides in the direction of the axis A of the feed screw 6, and may therefore be referred to as a sliding rod.

[0028] A key 16 is fixed to the nut member 7, and a key groove 17 into which the key 16 is fitted is formed in the linear motion cylindrical member 8 (the key groove 17 is shown by an imaginary line in FIG. 1). The nut member 7 is connected to the linear motion cylindrical member 8 via the key 16, and a lower end portion 8a of the linear motion cylindrical member 8 is fixed to a transport device (such as a vehicle) or a building as described below, so that the nut member 7 does not rotate around the axis A of the feed screw 6. In this way, the key 16 functions as a rotation prevention member.

[0029] The linear motion cylindrical member 8 has a lower end portion (lower end wall) 8a and a peripheral wall.

[0030] The guide sleeve 9 b that guides the linear motion of the linear cylindrical member 8 is disposed outside the linear cylindrical member 8 and extends along the axis A of the feed screw 6 . A lower end attachment portion 20 is connected to a lower end portion (end wall) 8a of the linear motion cylindrical member 8 of the linear motion actuator 1. On the other hand, an upper end mounting portion 21 is connected to the cover 15 attached to the guide sleeve 9b.

[0031] When the feed screw 6 rotates in a predetermined direction, the nut member 7 and the linear motion cylindrical member 8 are caused to move linearly (in the retracting direction) in conjunction with the rotation of the feed screw 6. When the feed screw 6 rotates in the reverse direction, the linear motion cylindrical member 8 moves linearly in the reverse direction (extending direction). In this manner, the linear motion cylindrical member 8 is caused to reciprocate.

[0032] In order to facilitate the linear motion (sliding) of the linear motion cylindrical member 8, a first plain bearing 28 is provided on the outer peripheral surface of the linear motion cylindrical member 8, and a second plain bearing 29 is provided on the inner peripheral surface of the guide sleeve 9b. The plain bearings 28, 29 are, for example, cylindrical bushings. The plain bearings 28, 29 may be completely cylindrical (annular) or approximately cylindrical.

[0033] The plain bearing 28 is disposed in a circumferential groove formed on the outer circumferential surface of the linear motion cylindrical member 8. The outer circumferential surface of the plain bearing 28 is in slidable contact with the inner circumferential surface of the guide sleeve 9b. The plain bearing 29 is disposed in a circumferential groove formed on the inner circumferential surface of the guide sleeve 9b. The inner circumferential surface of the plain bearing 29 is in slidable contact with the outer circumferential surface of the linear motion cylindrical member 8. The plain bearings 28, 29 may be referred to as sliding members.

[0034] In order to transmit the linear motion of the nut member 7 to the linear motion cylindrical member 8, a circular ring member 31 is provided which engages with the nut member 7 and the linear motion cylindrical member 8. The circular ring member 31 engages with (is held and fixed in) a groove formed on the inner circumferential surface of the linear motion cylindrical member 8. The circular ring member 31 also abuts (engages) with an upper end surface 7c of the nut member 7 to regulate the movement of the nut member 7 in the vertical direction (axis A direction). The circular ring member 31 is formed of a rigid material (for example, metal or resin having a predetermined strength). The lower end surface 7b of the nut member 7 is engaged with a step portion (reduced diameter portion) 8c formed on the inner circumferential surface of the linear motion cylindrical member 8. The circular ring member 31 is, for example, C-shaped. The circular ring member 31 fixes the nut member 7 to the linear motion cylindrical member 8, and may be called a retaining ring.

[0035] The lower end surface 7b of the nut member 7 abuts against the step portion 8c of the linear motion cylindrical member 8, and the annular member 31 fixed to the linear motion cylindrical member 8 abuts against the upper end surface 7c of the nut member 7, so that the linear motion cylindrical member 8 can move linearly together with the nut member 7 along the axial direction A of the feed screw 6 as the feed screw 6 rotates. Therefore, the linear motion of the nut member 7 can be transmitted to the linear motion cylindrical member 8.

[0036] Fig. 3 is an enlarged cross-sectional view showing the nut member 7 and its surrounding structure. Fig. 3 is a view of Fig. 1 rotated 90 degrees around the axis A of the feed screw 6. As shown in Fig. 3, the length of the key 16 in the direction of the axis A of the feed screw 6 is smaller than the length of the key groove 17. In other words, the key 16 is loosely fitted in the key groove 17.

[0037] As shown in FIG. 3, a small annular gap 35 is provided between the outer peripheral surface 7a of the nut member 7 and the inner peripheral surface of the linear motion cylindrical member 8. That is, a gap 35 is formed between the nut member 7 and the linear motion cylindrical member 8 in the radial direction of the linear motion cylindrical member 8. Therefore, the linear motion cylindrical member 8 can move to a certain extent relative to the nut member 7 in the radial direction. In addition, the key groove 17 penetrates the wall of the linear motion cylindrical member 8 in the radial direction, and the key 16 can move to a certain extent in the radial direction of the feed screw 6. Therefore, in this embodiment, when the linear motion cylindrical member 8 moves in the radial direction relative to the nut member 7 (or the nut member 7 moves in the radial direction relative to the linear motion cylindrical member 8), the key 16 can also move in the radial direction together, and the movement of the key 16 is not hindered. As a result, in this embodiment, it is possible to prevent or suppress the twisting of the ball screw 6 caused by the misalignment between the ball screw 6 and the linear motion cylindrical member 8 and the twisting of the ball screw 6 when a bending moment acts on the electromagnetic suspension 100.

[0038] More specifically, an annular gap 35 is provided between the outer peripheral surface 7a of the nut member 7 and the inner peripheral surface of the linear cylindrical member 8, and the key 16 does not contact the linear cylindrical member 8 in the radial direction. Therefore, even if the linear cylindrical member 8 is eccentric with respect to the feed screw 6, the eccentricity of the linear cylindrical member 8 is not transmitted from the key 16 to the nut member 7. Furthermore, even if the linear cylindrical member 8 is bent, the radial displacement of the linear cylindrical member 8 is not transmitted from the key 16 to the nut member 7. Therefore, twisting or bending of the feed screw 6 can be suppressed.

[0039] Since the key groove 17 penetrates the wall of the linear motion cylindrical member 8 in the radial direction, the operation of inserting the key 16 into the key groove 17 from the outside of the linear motion cylindrical member 8 and fixing it to the nut member 7 becomes easy.

[0040] Moreover, in this embodiment, the linear actuator 1 includes two annular radial buffer members 38. In Fig. 3, two radial buffer members 38 are provided, but the number of radial buffer members 38 is not limited to two.

[0041] The radial buffer member 38 is formed from an elastomer material, is disposed radially outside the nut member 7 and radially inside the linear motion cylindrical member 8, and is in contact with the nut member 7 and the linear motion cylindrical member 8. The radial buffer member 38 is an O-ring.

[0042] 3, two circumferential grooves 40 are formed on the inner circumferential surface of the linear motion cylindrical member 8, and each radial buffer member 38 is disposed inside the circumferential groove 40. Each radial buffer member 38 contacts the wall surface of the circumferential groove 40 and also contacts the outer circumferential surface 7a of the nut member 7.

[0043] The radial buffer member 38 prevents the inner circumferential surface of the linear motion cylindrical member 8 from contacting the outer circumferential surface of the nut member 7. Therefore, even if the linear motion cylindrical member 8 moves relative to the nut member 7, neither the linear motion cylindrical member 8 nor the nut member 7 will be damaged, and the operation of the linear motion actuator 1 will not be affected.

[0044] Furthermore, since the radial buffer member 38 surrounds the nut member 7 and is disposed radially inside the linear motion cylindrical member 8, even if the linear motion cylindrical member 8 is eccentric with respect to the feed screw 6, the influence of the radial position of the linear motion cylindrical member 8 on the nut member 7 is reduced. Even if the linear motion cylindrical member 8 is bent, the radial displacement of the linear motion cylindrical member 8 is absorbed by the radial buffer member 38 and is not easily transmitted to the nut member 7. Therefore, twisting or bending of the feed screw 6 can be suppressed.

[0045] The radial buffer member 38 is not limited to an O-ring, and may be, for example, an X-ring or a D-ring.

[0046] The electromagnetic suspension 100 further includes a coil spring 50 for absorbing shocks applied from one member of a structure to another member. The coil spring 50 expands and contracts in the direction of the center line A to absorb vibrations.

[0047] When the lower end attachment portion 20 of the electromagnetic suspension 100 is connected to, for example, a part (part 22) of a transport device and the upper end attachment portion 21 is connected to another part (part 25) of the transport device, an impact from the road surface acts on the linear motion cylindrical member 8 via the part 22. In this embodiment, as shown in FIG. 1, a first load support plate 51 is engaged with the linear motion cylindrical member 8, and a second load support plate 52 is engaged with a guide sleeve 9b connected to the part 25. The first load support plate 51 is an annular member and has a hole through which the lower end of the linear motion cylindrical member 8 can pass. The second load support plate 52 is also an annular member and has a hole through which the guide sleeve 9b can pass. A small flange 53 that protrudes in the radial direction is formed on the guide sleeve 9b, and the second load support plate 52 is pushed upward by the biasing force of the coil spring 50. Therefore, the upper surface of the second load support plate 52 is brought into contact with the lower surface of the flange 53.

[0048] The coil spring 50 is disposed between the first load support plate 51 and the second load support plate 52, and is compressed between the first load support plate 51 and the second load support plate 52. Therefore, the impact applied from the portion 22 is absorbed by the coil spring 50, and is not easily transmitted to the portion 25.

[0049] The coil spring 50 is disposed coaxially with the guide sleeve 9b, so that an offset load is unlikely to be applied to the guide sleeve 9b, and bending of the guide sleeve 9b is prevented.

[0050] Depending on the device or location in which the electromagnetic suspension 100 is used, the coil spring 50 may not be provided.

[0051] The linear actuator 1 can be used in an electromagnetic suspension 100 for vertical vibration suppression of a transportation device or a building. In this case, for example, the electromagnetic suspension 100 is arranged vertically. In the case of the vertical arrangement, the linear actuator 1 is arranged in a posture in which the upper end mounting part 21 is located at the top and the lower end mounting part 20 is located at the bottom, as shown in FIG. 1. The lower end mounting part 20 is attached to a part 22 of the transportation device or the building, for example, by a bolt 23 and a nut 24. The upper end mounting part 21 is attached to another part 25 of the transportation device or the building, for example, by a bolt 26 and a nut 27. The part 25 is, for example, the vehicle body side, and the part 22 is the wheel side below the vehicle body.

[0052] The linear actuator 1 can also be used in an electromagnetic suspension 100 for vibration suppression in the horizontal direction of transportation equipment (e.g., a railway vehicle) or a building. In this case, the electromagnetic suspension 100 is arranged horizontally, so that the feed screw 6, the nut member 7, the linear cylindrical member 8, and the guide sleeve 9b are arranged in a position in which their longitudinal directions are horizontal (e.g., in a position approximately horizontal to the road surface or the railroad tracks). The lower end mounting part 20 is, for example, the right end mounting part, and the upper end mounting part 21 is the left end mounting part. In other words, the lower end mounting part 20 is attached to a part 22 that is one side of the equipment or the building, and the upper end mounting part 21 is attached to a part 25 that is the other side of the equipment or the building. When the electromagnetic suspension 100 is arranged horizontally, FIG. 1 is a plan view of the electromagnetic suspension 100, and preferably, the two motors 2 and 3 are provided so as to be parallel to the road surface. Furthermore, a plurality of electromagnetic suspensions 100 (vertically arranged electromagnetic suspensions 100 and horizontally arranged electromagnetic suspensions 100) may be provided in a transport device or a building. In this case, the vertically arranged electromagnetic suspensions 100 absorb vibrations in the vertical direction, and the horizontally arranged electromagnetic suspensions 100 absorb vibrations in the horizontal direction.

[0053] In the embodiment described above, the configuration in which the two motors 2 and 3 that drive the linear actuator 1 are arranged symmetrically with respect to the center line A of the electromagnetic suspension 100 is adopted. When the electromagnetic suspension 100 is arranged vertically, the two motors 2 and 3 are positioned so that they are balanced on the left and right sides of the electromagnetic suspension 100. Therefore, even if vibrations from the road surface or railroad tracks are transmitted to the electromagnetic suspension 100, the possibility of a torsional force acting on the parts (gear transmission mechanism 5, housing 9, cover 15) connecting the motors 2 and 3 to the ball screw 6 can be reduced, and the possibility of damage to the parts can be reduced. Even if vibrations from the road surface or railroad tracks are transmitted to the electromagnetic suspension 100, the two motors 2 and 3 are in balanced positions, so the two motors 2 and 3 do not rotate around the center line A of the electromagnetic suspension 100. If only one motor 2 is provided, the motor 2 becomes an unbalanced element (mass body) with respect to the center line A of the electromagnetic suspension 100. If only the motor 2 is provided, the motor 2 may rotate around the center line A of the electromagnetic suspension 100 after vibrating slightly (trembling) due to vibrations from the road surface or the like. In other words, without the motor 3, the motor 2 would generate a rotational moment about the center line A of the electromagnetic suspension 100, causing it to rotate. When the motor 2 rotates about the center line A, the ball screw 6 rotates unintentionally. As a result, the electromagnetic suspension 100 operates unintentionally. In this embodiment, the two motors 2 and 3 are arranged line-symmetrically, so that even if the motors 2 and 3 generate slight vibrations, the ball screw 6 will not operate unintentionally. When the electromagnetic suspension 100 is arranged laterally (horizontally), the axis A of the electromagnetic suspension 100 and the center of gravity of the two motors 2, 3 in the rolling direction (direction of rotation about the axis A) are made to approximately coincide. In other words, the height of the motor 2 and the height of the motor 3 are made to approximately be the same. When the electromagnetic suspension 100 is arranged laterally and attached to a transport device in this manner, it is possible to lower the floor and center of gravity of the transport device while reducing the torsional force on the link section (gear transmission mechanism 5) caused by vertical vibrations and upward thrusts from the road surface or railroad tracks, thereby preventing vibrations generated in the electromagnetic suspension 100 from being transmitted to the coil spring 50 through the link section and preventing damage to the link section.

[0054] In this embodiment, one ball screw 6 (electromagnetic suspension 100) is driven by two motors 2, 3, so the output of each of the motors 2, 3 may be smaller than when only one motor is provided. In other words, in this embodiment, the motors 2, 3 used can be made smaller. If the motors 2, 3 can be made smaller, the space required to provide the motors 2, 3 can also be made smaller.

[0055] Although the preferred embodiment of the present invention has been described above, changes, modifications and alterations can be made to the above-described embodiment without departing from the scope of the invention as defined in the claims. Such changes, modifications and alterations are included within the scope of the present invention.

[0056] For example, in the above embodiment, when viewed in the direction of the center line A of the electromagnetic suspension 100, the two motors 2 and 3 are arranged at 180 degree intervals around the center line A of the electromagnetic suspension 100 to balance the motors 2 and 3, but the balance may be achieved by using three or more motors. When three motors are provided, the three motors are arranged at 120 degree intervals when viewed in the direction of the center line A of the electromagnetic suspension 100 to balance the motors with respect to the center line A of the electromagnetic suspension 100. It is preferable that the three motors have the same structure. In this way, in the present invention, it is sufficient that multiple motors (multiple second motors) are arranged around the center line A at equal angular intervals (on the same circle) when viewed from the center line A of the electromagnetic suspension 100 (the distance from the center line A to each motor is the same).

[0057] The gear transmission mechanism 5 is not limited to a two-stage reduction gear mechanism (gear train), and may be, for example, a three-stage or more reduction gear mechanism. The mechanism for transmitting the rotational motion of the motors 2, 3 to the feed screw 6 is not limited to the gear transmission mechanism 5, and may be, for example, a belt and pulley mechanism, and the belt may be a timing belt or a V-belt. When a timing belt or V-belt is used, the motors 2, 3 are provided so as not to interfere with the timing belt or V-belt, and are arranged so as to be line-symmetrical with respect to the axis A of the electromagnetic suspension 100.

[0058] A rotation prevention mechanism (for example, a key or spline) for the linear motion cylindrical member 8 relative to the guide sleeve 9b may be provided. The gear transmission mechanism 5 may be a bevel gear or a worm gear. In this case, the motors 2 and 3 are disposed at the same opening angle with respect to the axis A of the electromagnetic suspension 100 (the center line B of the motor 2 and the center line C of the motor 3 intersect with the axis A at the same angle).

[0059] 3, the key groove 17 penetrates the wall of the linear motion cylindrical member 8 in the radial direction, but this embodiment is not limited to such a structure. If the nut member 7 (key 16) is structured to be displaceable within a predetermined range in the radial direction relative to the linear motion cylindrical member 8, the key groove 17 does not need to penetrate the wall of the linear motion cylindrical member 8. Depending on the materials of the linear motion cylindrical member 8 and the guide sleeve 9b and the application of the electromagnetic suspension 100, the sliding bearings 28, 29 may not be provided.

[0060] Although it has been stated that a horizontally-placed electromagnetic suspension 100 and a vertically-placed electromagnetic suspension 100 are provided when it is desired to absorb and suppress vibrations in both the horizontal and vertical directions, for example, if the transport equipment is a railway vehicle and a bolster spring (a member that absorbs vibrations in the vertical direction) is already provided, the electromagnetic suspension 100 may be provided only in the horizontally-placed configuration. Also, if a member having the same function as the coil spring 50 is already provided, the coil spring 50 of the electromagnetic suspension 100 may be omitted.

[0061] In the above embodiment, when viewed in the direction of the center line A of the electromagnetic suspension 100, the two motors 2 and 3 are arranged at 180 degree intervals around the center line A of the electromagnetic suspension 100 to balance the motors 2 and 3, but the balance may be achieved by one motor and one counterweight (mass body). For example, a counterweight may be provided instead of the motor 3 in FIG. 1. The weight of the counterweight is the same as that of the motor 2 (motor 3). If the shape of the counterweight is the same as that of the motor 3 and has a rotating shaft 3a, the gear 10B and the gear 11 become a connecting part that connects the counterweight to the linear part of the electromagnetic suspension 100. Since the counterweight is a mass body with the same weight as the motor 2, even if vibration is transmitted to the motor 2 and the counterweight from the road surface or the railroad tracks, the motor 2 (and the counterweight) will not rotate around the center line A of the electromagnetic suspension 100 due to the balance between the motor 2 and the counterweight. The configuration of replacing the motor 3 with a counterweight can be adopted whether the electromagnetic suspension 100 is arranged vertically or horizontally. When the electromagnetic suspension 100 is arranged horizontally, the axis A of the electromagnetic suspension 100 and the center of gravity of the motor 2 and the counterweight in the rolling direction (the direction of rotation about the axis A) are made to approximately coincide. In other words, the height of the motor 2 and the height of the counterweight 3 are made to be approximately the same. Although an example in which three motors are provided has been described above, one of the three motors (or two of the motors) may be a mass body. The left motor 2 and the right motor 3 are controlled by one motor driver 4, but a motor driver dedicated to the left motor 2 and a motor driver dedicated to the right motor 3 may be provided, or the left motor 2 and the right motor 3 may be controlled separately.

[0062] In the above embodiment, the linear actuator 1 is used for vibration suppression of a structure (transportation equipment or a building), but the application of the linear actuator 1 is not limited to vibration suppression of a structure. The linear actuator according to the present invention may be used in other structures or devices in which it is desirable to suppress impact or high-frequency vibration. [Explanation of symbols]

[0063] 1...Linear actuator 2...Left motor 3...Right motor (second motor) 5...Gear transmission mechanism 6...Feed screw (linear motion part) 7...Nut member (linear part) 8...Linear cylindrical member (linear part) 9. Housing 9b…Guide sleeve 16…Key 17...Key groove 20…Lower end mounting part 21…Upper end mounting part 31...Circular member (retaining ring) 35…Gap 38... Radial buffer member 50…Coil spring 51...First load-supporting plate 52...Second load-supporting plate 100...Electromagnetic suspension (active damper) A…Center line of the electromagnetic suspension (center line of the linear motion part)

Claims

1. A linear actuator for an active damper, comprising: A linear motion portion; a motor that is provided at a position eccentric to a center line of the linear motion portion and generates a driving force that linearly moves the linear motion portion in a direction along the center line; a transmission section that connects the motor to the linear motion section and transmits a driving force of the motor to the linear motion section; An element provided at a position for balancing with the motor when viewed from a center line direction of the linear motion portion; A connecting portion connecting the element to the linear motion portion; A linear actuator comprising:

2. The linear actuator according to claim 1 , wherein the motor and the element are disposed symmetrically with respect to a center line of the linear motion portion.

3. 3. The linear actuator according to claim 2, wherein the element is a second motor having the same structure as the motor, the connecting portion has the same structure as the transmission portion, and the linear motion portion is driven by the motor and the second motor.

4. The linear actuator according to claim 2 , wherein the element is a mass body having the same weight as the motor.

5. 2. The linear actuator according to claim 1, wherein a plurality of the elements are provided, the plurality of elements being a plurality of second motors having the same structure as the motor, and the motor and the plurality of second motors are provided around the center line at equal angular intervals as viewed from the center line direction of the linear motion part.

6. The linear actuator according to claim 1 , wherein when the linear actuator is disposed horizontally and the linear motion portion moves linearly in a horizontal direction, the height of the motor and the height of the element are the same.

7. 2. The linear actuator according to claim 1, wherein a coil spring is wound around an outer periphery of the linear motion portion.

8. An electromagnetic suspension comprising the linear actuator according to any one of claims 1 to 7.

9. The electromagnetic suspension according to claim 8 , wherein the electromagnetic suspension is provided in a transport device or structure.

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