Linearaktor

Abstract

Linear actuator comprising a first element (1) that is movable in one direction relative to a second element (2), wherein the first element (1) comprises a first magnet (6a), a second magnet (6b) and a third magnet (6c) arranged in that direction, wherein the first magnet (6a), the second magnet (6b) and the third magnet (6c) each have N-poles and S-poles in a direction perpendicular to that direction, wherein the N poles and the S poles of the second magnet (6b) are displaced relative to the N poles and the S poles of the first magnet (6a) in a direction perpendicular to that direction, wherein the N poles and the S poles of the third magnet (6c) are displaced relative to the N poles and the S poles of the second magnet (6b) in a direction perpendicular to that direction, wherein the second element (2) has at least two projecting poles (8a) arranged in the direction perpendicular to that direction and facing the first element (1), and at least two coils (4a, 4b, 4c, 4d) arranged in the direction perpendicular to that direction and each wound around the projecting poles (8a), and including at least two coils (4a, 4b, 4c, 4d): an A-phase coil (4a) and a B-phase coil (4b) that is phase-shifted by 90 degrees relative to the A-phase coil (4a), the A-phase coil (4a) and a / B-phase coil (4d) which is phase-shifted by 270 degrees to the A-phase coil (4a), an / A-phase coil (4c) and the / B-phase coil (4d) which is shifted by 90 degrees relative to the / A-phase coil (4c), the / A-phase coil (4c) and the B-phase coil (4b), which is phase-shifted by 270 degrees to the / A-phase coil (4c), or a coil (4a, 4c) that is magnetized by the sine oscillation and a coil (4b, 4d) that is magnetized by a cosine oscillation.

Description

Technical field

[0001] The present invention relates to a linear actuator comprising a first element that can move in a direction relative to a second element. State of the art

[0002] A synchronization-type linear actuator that uses magnets as field systems is a type of linear actuator. This linear actuator comprises a stator having several magnets arranged in one direction such that the polarities of the magnets alternate, and a moving element having several coils arranged in one direction such that the coils face an array of the stator's magnets (see patent document 1). The coils are wound around protruding poles of cores facing the array of magnets in the stator. When an alternating current flows in the coils, the interaction between the magnetic fluxes generated at the magnets and the magnetic fluxes generated at the protruding poles causes the moving element to move relative to the stator in that direction.A linear actuator that has movable coils, such as the linear actuator disclosed in patent document 1, is referred to as a linear actuator of the movable coil type. A specific linear actuator has movable magnets that move instead of coils, and this linear actuator is referred to as a linear actuator of the movable magnet type. List of prior art patent document(s)

[0003] Patent document 1: Japanese patent disclosure JP 2011-217591A

[0004] US 2012 / 0187779A1 concerns a linear motor. JP 2014-209832A concerns a hub dynamo. Summary of the invention; Problems to be solved by the invention

[0005] It is understood that a conventional linear actuator causes the moving element to move in the same direction as the coils are arranged. However, a conventional linear actuator cannot cause the moving element to move in a direction perpendicular to the coils. If such movement were possible, it would be possible to make the moving element move in a way that attracts people's attention and expand the range of applications for the linear actuator.

[0006] Therefore, it is an object of the present invention to create a linear actuator that can cause the movable element to move in a direction perpendicular to the arrangement direction of the coils. Solution to the problems

[0007] To overcome the problems mentioned above, a linear actuator according to claim 1 is provided. Advantageous effects of the invention

[0008] The present invention can cause the movable element (the first element or the second element) to move in a direction perpendicular to an arrangement direction of coils. Brief description of the drawings Fig. Figure 1 is a perspective view of a linear actuator according to an embodiment of the present invention. Fig. 2 is a perspective exploded view of Fig. 1. Fig. Figure 3 is a cross-sectional view of the linear actuator according to the embodiment of the present invention in a YZ plane. Fig. Figure 4 is a set of cross-sectional views of the linear actuator according to the embodiment of the present invention along the X-axis. Fig. Figure 4A shows the case where the moving element is located at one end of a stroke. Fig. Figure 4B shows the case where the moving element is located in the middle of the stroke, and Fig. 4C shows the case where the movable element is located at an opposite end.) Fig. Figure 5 is a perspective view of the moving element to show magnetic polarities along the outer circumferences of the first to third magnets. Fig. Figure 6 is a time diagram for the magnetization of the coils. Fig. Figure 7 is a set of views for representing an oscillation principle of the moving element. Fig. Figure 8 is a perspective view showing another example of the moving element. Type of implementation of the invention

[0009] A linear actuator according to one embodiment of the present invention will now be described with reference to the accompanying drawings. It should be noted that the linear actuator of the present invention can be implemented in various forms and types and is not limited to one embodiment described in this description. This embodiment is intended to enable those skilled in the art to understand the scope of the invention sufficiently as a result of adequate disclosure in this description.

[0010] Fig. Figure 1 shows a perspective view of a linear actuator according to an embodiment of the present invention and Fig. Figure 2 shows a perspective exploded view of Fig. 1. The same reference numerals are assigned to the same configurations in the accompanying drawings and the following description of the patent specification.

[0011] As in Fig. As shown in Figure 1, the linear actuator comprises a movable element 1, which is a first element, and a stator 2, which is a second element. The movable element 1 has a cylindrical shape. The stator 2 has a ring shape that surrounds the movable element 1. The linear actuator is designed such that the movable element 1 is caused to move in one direction (i.e., in an axial direction) when coils 4a-4d of the stator 2 are magnetized. In the following description, the axial direction of the movable element 1 is referred to as the "X-direction," a plane normal to the X-direction is referred to as the "YZ-plane," and a circumferential direction in the YZ-plane is referred to as the "θ-direction."

[0012] Several coils 4a-4d are arranged in the θ-direction on the annular stator 2. In a conventional rotary motor, the movable element 1 rotates in the θ-direction when the coils are arranged in the θ-direction. The linear actuator of the present invention is characterized in that the movable element 1 moves in the X-direction, even though the coils 4a-4d are arranged in the θ-direction. The configurations of the movable element 1 and the stator 2 are described successively in the following description.

[0013] As in Fig. As shown in Figure 2, the movable element 1 comprises a cylindrical yoke 5, a first magnet 6a, a second magnet 6b, and a third magnet 6c. The first, second, and third magnets 6a, 6b, and 6c are arranged along the outer circumference of the yoke 5, and each magnet is ring-shaped. The first magnet 6a, the second magnet 6b, and the third magnet 6c are connected to the outer circumference of the yoke 5 by coupling means such as an adhesive. The first magnet 6a, the second magnet 6b, and the third magnet 6c are of the same size and are arranged side by side in the X direction. The yoke 5 is made of a magnetic material that allows the penetration of magnetic fluxes.

[0014] The first magnet 6a has several arc-shaped segment magnets 7, which alternately have N poles and S poles in the θ direction, and the segment magnets 7 are arranged such that they alternately exhibit different polarities in the θ direction. The number of magnetic poles (the number of segment magnets 7) is not limited to a specific number. For example, the number of magnetic poles can be six. The outer circumference of each segment magnet 7 is magnetized either to the N pole or the S pole, and the inner circumference of each segment magnet 7 is magnetized to the opposite N pole and S pole, respectively. The first magnet 6a can also be designed such that it is not divided into segment magnets 7, but rather has a ring shape and is magnetized alternately to the N poles and S poles in the θ direction.

[0015] Similar to the first magnet 6a, the second magnet 6b and the third magnet 6c each have several arc-shaped segment magnets 7, which alternately have N-poles and S-poles in the θ-direction, and the segment magnets 7 are arranged such that they alternately have different polarities in the θ-direction. The first magnet 6a, the second magnet 6b, and the third magnet 6c have the same number of magnetic poles, for example, six.

[0016] The N poles and the S poles of the second magnet 6b are displaced relative to the N poles and the S poles of the first magnet 6a in one direction (clockwise) of the θ-direction by half a division P1 (a distance in the θ-direction) between the N pole and the S pole. The N poles and the S poles of the third magnet 6c are displaced relative to the N poles and the S poles of the second magnet 6b in one direction (clockwise) of the θ-direction by half a division P1 between the N pole and the S pole. It should be noted that the third magnet 6c is not displaced relative to the second magnet 6b in the opposite direction (counterclockwise) of the θ-direction.The N poles and the S poles of the third magnet 6c are shifted relative to the N poles and the S poles of the first magnet 6a in one direction (clockwise) of the θ-direction by the division P1 between the N pole and the S pole, and the third magnet 6c has the opposite magnetic polarities relative to the first magnet 6a.

[0017] Stator 2 has the following configuration. As shown in Fig. Fig. As shown in Figure 2, the stator 2 has a core 8 and several coils 4a-4d wound around the projecting poles 8a of the core 8. The core 8 has a core body 8b, which is ring-shaped and surrounds the movable element 1, and several projecting poles 8a extending radially inwards from the core body 8b (see also Figure 2). Fig. 3) The number of protruding poles 8a is twice the number of magnetic poles of the first to third magnets 6a-6c of the movable element 1. Since the number of magnetic poles is six, the number of protruding poles 8a is twelve. The free ends of the protruding poles 8a face the movable element 1, leaving a magnetic gap between them. The core 8 is made of a magnetic material such as silicon steel.

[0018] The core 8 is produced, for example, by laminating several steel plates separated by the YZ planes in the X direction. Alternatively, the core 8 can be divided into twelve core segments along division lines running radially along the core 8. The coils 4a-4d can be wound around the protruding poles 8a of the core segments, and the core segments with the coils 4a-4d wound around them can be joined in the θ direction to produce the core 8.

[0019] Fig. Figure 4 shows a set of cross-sectional views of the linear actuator along the X-axis. As in Fig. As shown in Figure 4B, the length t2 of each of the projecting poles 8a of the core 8 in the X-direction is shorter than the length t1 of each of the first to third magnets 6a-6c. Each of the first to third magnets 6a-6c has a length t1 in the X-direction, and the first to third magnets 6a-6c have the same length in the X-direction. The free end of the projecting pole 8a is chamfered at opposite edges in the X-direction, which are labeled 9 (see also Figure 4B). Fig. 2).

[0020] As in Fig. As shown in Figure 2, each of the coils 4a-4d has an inner coil 11, which has a cylindrical shape with a rectangular cross-section, and an outer coil 12, which is arranged outside the inner coil 11 and also has a cylindrical shape with a rectangular cross-section. The inner coil 11 spans the entire length of the associated projecting pole 8a. The outer coil 12 is shorter than the inner coil 11 and is present only around the radially outer portion of the projecting pole 8a. Windings of the inner coil 11 are electrically connected to windings of the outer coil 12.

[0021] As in Fig. Figure 3, which is a cross-sectional view in the YZ plane, shows that the gap between each pair of adjacent protruding poles 8a is larger on the outer circumference and smaller on the inner circumference, i.e., the gap has a fan shape. By dividing the coils 4a-4d into inner coils 11 and outer coils 12, it is possible to efficiently arrange the coils 4a-4d in the fan-shaped gaps. It should be noted that the coils 4a-4d may not be divided into inner coils 11 and outer coils 12, but rather each of the coils may be trapezoidal.

[0022] The in Fig. The movable element 1 shown in Figure 1 is supported by the stator 2 via a support unit such that the movable element 1 can move in the X-direction. The support unit can comprise a known bearing such as a ball-and-socket joint, a ball sleeve, a plain bearing, or the like. Alternatively, a plate spring forming a bridge between the movable element 1 and the stator 2, a cylindrical rubber element arranged between the movable element 1 and the stator 2, or the like can be used instead of the bearing.

[0023] Fig. Figure 4 shows a set of cross-sectional views of the linear actuator along the X-axis. Fig. Figure 4B shows the case in which the movable element 1 is located in the middle of the stroke. Fig. Figure 4A shows the case in which the movable element 1 is located at one end of the stroke, and Fig. Figure 4C shows the case in which the movable element 1 is located at the other end of the stroke. The linear actuator of this embodiment is an oscillating actuator comprising the movable element 1, which moves alternately from one end of the stroke to the other end of the stroke and from the other end of the stroke to one end of the stroke. It should be noted that the use of the linear actuator of the present invention is not limited to the oscillating actuator.

[0024] Fig. Figure 5 is a perspective view of the movable element 1, showing the magnetic polarities of the outer circumferences of the first to third magnets 6a-6c. The rectangles in Fig. Figure 5 indicates the coils 4a-4d facing the moving element 1, and the symbols “A”, “B”, “ / A”, and “ / B” in the rectangles indicate the magnetization of coils 4a-4d. Fig. In Figure 5, each of the segment magnets 7 of the first to third magnets 6a-6c is assigned two magnetic polarities NN or SS. This illustrates that the two coils 4d and 4a, or 4b and 4c, or the like, are oriented towards each segment magnet 7, and that the segment magnet 7 exhibits the depicted magnetic polarities when it is oriented towards coils 4d and 4a, or 4b and 4c, or the like. In reality, each segment magnet 7 has one magnetic polarity.

[0025] The magnetic polarities N, N and S are oriented successively towards each of the A-phase coils 4a when viewed from the distal side of Fig. 5. Magnetic polarities S, N, and N are oriented towards each of the B-phase coils 4b. Magnetic polarities S, S, and N are oriented towards each of the / A-phase coils 4c. Magnetic polarities N, S, and S are oriented towards each of the / B-phase coils 4d. The A-phase coils 4a are arranged every four coils in the θ direction. The magnetic polarities of the movable element 1, which are oriented towards the coils 4a, which are arranged every four coils, are the same. This also applies to the coils 4b-4d of other phases.

[0026] Four coils from each of the twelve coils 4a-4d define a set. Each set of four coils 4a-4d is magnetized in a similar manner to form coils of a two-phase stepper motor in phase A, phase B, phase A / A, and phase B. It should be noted that six coils can define a set, and each set of six coils can be magnetized in a similar manner to form coils of a three-phase stepper motor in six phases.

[0027] Fig. Figure 6 is a timing diagram illustrating the magnetization of coils 4a-4d. Phase A is 90 degrees out of phase with phase B. Phase A is 180 degrees out of phase with phase A. Phase A is 270 degrees out of phase with phase B. It should be noted that the magnetization of the coils is not limited to the magnetizations mentioned above. For example, the waveform of a voltage applied to the coils could be a sinusoidal wave instead of a square wave.

[0028] Fig. Figure 7 is a set of schematic views that represent an oscillation principle of the movable element 1. Fig. Figure 7 shows only the A-phase coil 4a and the adjacent B-phase coil 4d, which consists of Fig. 5 are taken from the magnetic polarities of the movable element 1, which face the A-phase coil 4a, are from the distal side of Fig. Figure 5 considers an N-, an N- and an S-pole. The magnetic polarities of the movable element 1, which face the / B-phase coil 4d, are from the distal side of Fig. 5 considers an N-, an S-, and an S-pole. If the A-phase coil 4a is in accordance with the one in Fig. When the magnetization shown in Figure 6 is applied, the polarity of the leading pole 8a of the A-phase coil 4a changes as follows: the N pole at S1, the N pole at S2, the S pole at S3, and the S pole at S4. When the B-phase coil 4d is magnetized in accordance with the magnetization shown in Figure 6, the polarity of the leading pole 8a of the A-phase coil 4a changes as follows: the N pole changes at S1, the N pole changes at S2, the S pole changes at S3, and the S pole changes at S4. Fig. When magnetized as shown in Figure 6, the polarity of the protruding pole 8a of the / B-phase coil 4d changes as follows: the N pole at S1, the S pole at S2, the S pole at S3, and the N pole at S4. As the polarities of the protruding poles 8a of coils 4a and 4d change, the movable element 1 changes its position to the left end position (S1), the center position (S2), the right end position (S3), and the center position (S4). Thus, the movable element 1 oscillates. It should be noted that, although only the combination of the A-phase coil 4a and the / B-phase coil 4d is shown in Figure 6, the polarity of the protruding pole 8a of coils 4a and 4d changes as follows: Fig. As shown in Figure 7, a combination of the A-phase coil 4a and the B-phase coil 4b can similarly cause the movable element 1 to oscillate, a combination of the A-phase coil 4c and the B-phase coil 4b can similarly cause the movable element 1 to oscillate, and a combination of the A-phase coil 4c and the B-phase coil 4d can similarly cause the movable element 1 to oscillate. In short, it is possible to make the movable element 1 oscillate as long as a combination of the coil 4a, 4c, which is magnetized by the sine wave, and the coil 4b, 4d, which is magnetized by a cosine wave, is used.

[0029] Fig. Figure 8 shows another example of the movable element. The movable element 21 in this example comprises a yoke 22 with a round column shape, first magnets 24a, second magnets 24b, and third magnets 24c. The first to third magnets are arranged around the outer circumference of the yoke 22 in the X direction. The first magnet 24a, the second magnet 24b, and the third magnet 24c each have several magnets 25 arranged in the θ direction. The number of magnets 25 is twelve, which is equal to the number of coils 4a-4d. Each of the magnets 25 is a plate-like rectangular magnet magnetized in the vertical (i.e., radial) direction. Alternatively, the magnet 25 can be a round column-shaped magnet.

[0030] Any two magnets 25 adjacent in the θ direction form a pair of magnets 25a or a pair of magnets 25b. The magnetic polarities of the two magnets 25 in each pair 25a, 25b are the same. The magnetic polarities of the magnets 25 in a magnet pair 25a are opposite to the magnetic polarities of the magnets 25 in an adjacent magnet pair 25b. When the magnets 25 are considered in pairs, polarities arise that are those of the Fig.The segment magnets 7 shown in Figure 5 are similar. It should be noted that in this example, the N poles and the S poles of the second magnet 24b are shifted relative to the N poles and the S poles of the first magnet 24a by half the N-pole-S-pole division P1 in one direction (counterclockwise) of the θ-direction. The N poles and the S poles of the third magnet 24c are shifted relative to the N poles and the S poles of the second magnet 24b by half the N-pole-S-pole division P1 in one direction (counterclockwise) of the θ-direction. The N poles and the S poles of the third magnet 24c are shifted relative to the N poles and the S poles of the first magnet 24a by the N-pole-S-pole division P1, which is the distance in the θ direction, in one direction (counterclockwise) of the θ direction and the magnetic polarities of the third magnet 24c are opposite to the magnetic polarities of the first magnet 24a.Similar to the previous example, the movable element 21 of this example can, with the coils 4a, 4c, which are magnetized by the sine oscillation, and the coils 4b, 4d, which are magnetized by the cosine oscillation, cause the movable element 21 to oscillate.

[0031] The linear actuator of this embodiment has the following advantages. Since the first magnet 6a, the second magnet 6b, and the third magnet 6c of the movable element 1 are arranged in the X-direction, and the magnetic polarities of the second magnet 6b and the third magnet 6c are shifted relative to the magnetic polarities of the first magnet 6a in the θ-direction, it is possible to cause the movable element 1 to move in a direction (X-direction) perpendicular to the arrangement direction (θ-direction) of the coils 4a-4d. This makes it possible to reduce the size of the linear actuator in the X-direction and increase the driving force.

[0032] Since the first to third magnets 6a-c are arranged in the X-direction of the movable element 1, it is possible to obtain a linear actuator suitable for the oscillating actuator and to cause the movable element 1 to oscillate in a long stroke.

[0033] Since the magnetic polarities of the second magnet 6b are shifted relative to the magnetic polarities of the first magnet 6a by half of the N-pole-S-pole division in the θ-direction, and the magnetic polarities of the third magnet 6c are shifted relative to the magnetic polarities of the second magnet 6b by half of the N-pole-S-pole division in the θ-direction, it is possible to cause the movable element 1 to oscillate with a strong driving force (high thrust) throughout the entire stroke.

[0034] Since the coils 4a-4d are arranged in the θ direction and the magnetic polarities of the first to third magnets 6a-6c are arranged in the θ direction, the miniaturization of the linear actuator is achieved.

[0035] Since the protruding poles 8a are connected to the ring-shaped core body 8b, it is possible to facilitate (improve) the flow of magnetic fluxes in the protruding poles 8a.

[0036] Since the first to third magnets 6a-6c are made from the segment magnets 7, it is possible that each segment magnet 7 has a substantially equal magnetic flux density in the radial direction from one end to its opposite end in the θ-direction. The magnitudes of the magnetic flux densities of the first to third magnets 6a-6c in the radial direction correlate with the driving force (the thrust), and therefore it is possible to achieve the strong driving force.

[0037] Since the length t1 of the protruding pole 8a in the X-direction is shorter than the length t2 of the first to third magnets 6a-6c in the X-direction, it is possible to reduce the detent force (detent torque). The detent force is derived from the attractive forces between the protruding poles 8a and the first to third magnets 6a-6c. The detent force acts on the movable element 1 even when no current flows in the coils 4a-4d and affects the thrust. By reducing the detent force, it is possible to increase the thrust. It should be noted that in the case t2 > t1, the detent force becomes large compared to the case t2 < t1.

[0038] Since the edges in the X-direction at the free end of each projecting pole 8a at 9 are chamfered, it is possible to reduce the detent force compared to a case where no chamfer 9 is made. Furthermore, because of the chamfer 9, it is possible for the movable element 1 to have a large stroke.

[0039] It should be noted that the present invention is not limited to the embodiment described above. The present invention can be implemented in various forms, provided that the subject matter of the present invention remains unchanged.

[0040] Although in the embodiment described above the coils of the stator are arranged in the θ-direction and the magnetic polarities of the magnets of the moving element are arranged in the θ-direction i, the stator and the moving element can be unfolded in a single plane to obtain a flat-type linear motor similar to a flat-type linear motor obtained by unfolding one or more rotary motors in a single plane.

[0041] The embodiment described above relates to a linear actuator of the type with movable magnets, but the linear actuator of the invention can be a linear actuator of the type with movable coils.

[0042] Although in the embodiment described above the first to third magnets are arranged inside the coils which are arranged in the θ direction, the first to third magnets can be arranged outside the coils which are arranged in the θ direction.

[0043] Although the movable element in the embodiment described above comprises the first through third magnets, the movable element can also comprise the first through fourth magnets, the first through fifth magnets, or more. In such cases, each magnet is shifted relative to an adjacent magnet by half the N-pole-S-pole division in one direction (e.g., clockwise) of the θ-direction. In other words, the magnetic polarities of the third magnet are opposite to the magnetic polarities of the first magnet, and the magnetic polarities of the fifth magnet are the same as the magnetic polarities of the first magnet.

[0044] Although the stator in the embodiment described above has a single core, the stator can have two or more cores.

[0045] Although the movable element in the embodiment described above is only caused to move in the X direction, the movable element can be caused to move in the X direction and to rotate in the θ direction.

[0046] Although in the embodiment described above the first to third magnets of the movable element have a total of six magnetic polarities, which alternate in the circumferential direction as N-poles and S-poles, the number of protruding poles is twelve, and the number of coils is twelve, the number of protruding poles and the number of coils are not limited to the numbers mentioned above. For example, the first to third magnets can have a total of two or four N- and S-poles. Furthermore, the number of protruding poles can be two, four, or eight, and the number of cores can be two, four, or eight. Reference symbol list

[0047] 1 ... Movable element (first element), 2 ... Stator (second element), 4a-4d ... Coils, 6a ... First magnet, 6b ... Second magnet, 6c ... Third magnet, 5 ... Yoke, 7 ... Segment magnet, 8 ... Core, 8a ... Protruding pole, 8b ... Core body, 11 ... Inner coil, 12 ... Outer coil, P1 ... Division between the N pole and the S pole

Claims

[1] Linear actuator comprising a first element (1) that is movable in one direction relative to a second element (2), wherein the first element (1) comprises a first magnet (6a), a second magnet (6b) and a third magnet (6c) arranged in that direction, wherein the first magnet (6a), the second magnet (6b) and the third magnet (6c) each have N-poles and S-poles in a direction perpendicular to that direction, wherein the N poles and the S poles of the second magnet (6b) are displaced relative to the N poles and the S poles of the first magnet (6a) in a direction perpendicular to that direction, wherein the N poles and the S poles of the third magnet (6c) are displaced relative to the N poles and the S poles of the second magnet (6b) in a direction perpendicular to that direction, wherein the second element (2) has at least two projecting poles (8a) arranged in the direction perpendicular to that direction and facing the first element (1), and at least two coils (4a, 4b, 4c, 4d) arranged in the direction perpendicular to that direction and each wound around the projecting poles (8a), and including at least two coils (4a, 4b, 4c, 4d): an A-phase coil (4a) and a B-phase coil (4b) that is phase-shifted by 90 degrees relative to the A-phase coil (4a), the A-phase coil (4a) and a / B-phase coil (4d) which is phase-shifted by 270 degrees to the A-phase coil (4a), an / A-phase coil (4c) and the / B-phase coil (4d) which is shifted by 90 degrees relative to the / A-phase coil (4c), the / A-phase coil (4c) and the B-phase coil (4b), which is phase-shifted by 270 degrees to the / A-phase coil (4c), or a coil (4a, 4c) that is magnetized by the sine oscillation and a coil (4b, 4d) that is magnetized by a cosine oscillation. [2] Linear actuator according to claim 1, wherein the N poles and the S poles of the second magnet (6b) are displaced relative to the N poles and the S poles of the first magnet (6a) by half a division (P1) between the N pole and the S pole in the direction perpendicular to that direction, and the N poles and S poles of the third magnet (6c) are displaced relative to the N poles and the S poles of the second magnet (6b) by half a division (P1) between the N pole and the S pole in the direction perpendicular to that direction. [3] Linear actuator according to claim 1 or 2, wherein that direction is the X-direction and the direction perpendicular to that direction is a circumferential direction (θ) in a YZ-plane perpendicular to the X-direction. [4] Linear actuator according to claim 3, wherein the protruding poles (8a) are connected to a core body (8b) having a ring shape. [5] Linear actuator according to claim 3 or 4, wherein the first magnet (6a), the second magnet (6b) and the third magnet (6c) each consist of several arc-shaped segment magnets (7) which are magnetized in a radial direction. [6] Linear actuator according to one of claims 1 to 4, wherein the first magnet (6a), the second magnet (6b) and the third magnet (6c) each consist of several plate-like magnets (25) which are magnetized in the vertical direction. [7] Linear actuator according to claim 1 or 2, wherein a length (t1) of each of the protruding poles (8a) in that direction is shorter than a respective length (t2) of the first magnet (6a), the second magnet (6b) and the third magnet (6c) in that direction. [8] Linear actuator according to claim 1 or 2, wherein a free end of each of the protruding poles (8a) is chamfered at its edges (9) in that direction. [9] Linear actuator according to any one of claims 1 to 8, comprising at least two coils (4a, 4b, 4c, 4d): the A-phase coil (4a) and the B-phase coil (4b), which is phase-shifted by 90 degrees relative to the A-phase coil (4a), the / A-phase coil (4c), which is shifted by 180 degrees relative to the A-phase coil (4a), and the / B-phase coil (4d), which is phase-shifted by 270 degrees to the A-phase coil (4a). [10] Linear actuator according to any one of claims 1 to 9, wherein the at least two protruding poles (8a) and the at least two coils (4a, 4b, 4c, 4d) are arranged in that direction and only in a row, and the linear actuator causes the first element (1) to oscillate relative to the second element (2) in that direction.

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