Vibration actuator

Abstract

A stator 12 of this vibration actuator 10 comprises: a cylindrical yoke 22; and a cylindrical coil 26 disposed on the inner side of the yoke 22. A movable element 14 includes a magnetic circuit 31 disposed on the inner side of the coil 26. The vibration actuator 10 does not include a spring member for elastically supporting the movable element 14. One among the stator 12 and the movable element 14 includes a shaft 28 extending in a vibration direction, and the other among the stator 12 and the movable element 14 is provided with a hole 14k through which the shaft passes, thereby holding the center of the movable element 14 in the radial direction. Magnetic force between the yoke 22 and the movable element 14 acts as force for returning the movable element 14 to the center position in the vibration direction.

Description

Vibration actuator

[0001] The present disclosure relates to a vibration actuator.

[0002] Patent Document 1 discloses a vibration actuator in which a mover is elastically supported by a spring member (leaf spring).

[0003] Japanese Patent Application Laid-Open No. 2023-126927

[0004] An object of the present disclosure is to miniaturize and reduce the weight of a vibration actuator.

[0005] The vibration actuator according to the first aspect is a vibration actuator, and the vibration actuator includes a stator and a mover. The stator includes a cylindrical yoke and a cylindrical coil disposed inside the yoke. The mover includes a magnetic circuit disposed inside the coil. The magnetic circuit includes a magnet and a magnetic member. The vibration actuator does not include a spring member that elastically supports the mover. One of the stator and the mover includes a shaft extending in the vibration direction, and a hole through which the shaft passes is provided in the other of the stator and the mover, so that the center of the mover in the radial direction is held, and the magnetic force between the yoke and the mover acts as a force for the mover to return to the center position in the vibration direction.

[0006] In this aspect, the vibration actuator includes a stator and a mover. The stator includes a cylindrical yoke and a cylindrical coil disposed inside the yoke. The mover includes a magnetic circuit disposed inside the coil. The magnetic circuit includes a magnet and a magnetic member.

[0007] Furthermore, in this embodiment, the vibration actuator does not include a spring member that elastically supports the movable element. One of the stator and the movable element is provided with a shaft that extends in the direction of vibration, and a hole is provided in the other stator and movable element through which the shaft passes, thereby maintaining the radial center of the movable element. In addition, the magnetic force between the yoke and the movable element acts as a force that returns the movable element to its center position in the direction of vibration. Therefore, compared to embodiments in which the vibration actuator includes a spring member that elastically supports the movable element, the vibration actuator can be made smaller and lighter.

[0008] The vibration actuator according to the second embodiment, in the first embodiment, comprises a stator comprising the shaft, a movable element having the hole, a magnet constituting the vibration center portion of the movable element and being magnetized in the vibration direction, a magnetic member comprising a one-side pole piece fixed to one side of the magnet in the vibration direction and a other-side pole piece fixed to the other side of the magnet in the vibration direction, a coil comprising a one-side coil provided on one side with respect to the vibration direction center and a other-side coil provided on the other side with respect to the vibration direction center, and the one-side coil and the other-side coil are configured such that the directions of the magnetic flux they generate are opposite.

[0009] In this embodiment, the stator has a shaft and the movable element has holes. This makes it possible to suppress the increase in size of the vibration actuator in the direction of vibration. In this embodiment, the magnet constitutes the central part of the movable element in the direction of vibration and is magnetized in the direction of vibration, and the magnetic member comprises a one-side pole piece fixed to one side of the magnet in the direction of vibration and a other-side pole piece fixed to the other side of the magnet in the direction of vibration. Therefore, compared to an embodiment in which the magnetic material constitutes the axial central part of the movable element and two magnets are provided to form a repulsive magnetic field so as to sandwich the magnetic material in the direction of vibration, assembly and magnetization become easier.

[0010] In the third embodiment of the vibration actuator, the yoke does not have a portion positioned between the one coil and the other coil, as in the second embodiment.

[0011] In this embodiment, the yoke does not have a portion positioned between one coil and the other coil. Therefore, the structure of the yoke can be simplified.

[0012] In the fourth embodiment of the vibration actuator, in the second or third embodiment, the vibration direction dimension of the yoke is larger than the vibration direction dimension of the coil.

[0013] In this embodiment, the vibration direction dimension of the yoke is larger than the vibration direction dimension of the coil. Therefore, the structure can be designed so that the coil does not protrude outward from the yoke in the vibration direction, thereby suppressing damage to the coil during manufacturing.

[0014] In the fifth embodiment of the vibration actuator, in any of the second to fourth embodiments, the vibration direction dimension of the yoke is greater than the vibration direction dimension of the magnetic circuit.

[0015] In this embodiment, the vibration direction dimension of the yoke is larger than the vibration direction dimension of the magnetic circuit. Therefore, a vibration actuator with good linearity can be realized.

[0016] In the sixth embodiment of the vibration actuator, in any of the second to fifth embodiments, when the movable element is in its maximum displacement state, the dimension of the magnet of the movable element that extends beyond the range where the yoke is provided in the direction of vibration is less than 50% of the dimension of the magnet in the direction of vibration.

[0017] In this embodiment, when the movable element is at its maximum displacement, the dimension of the magnet of the movable element that extends beyond the range where the yoke is provided in the direction of vibration is less than 50% of the dimension of the magnet in the direction of vibration. Therefore, linearity can be improved.

[0018] In the seventh embodiment, the vibration actuator, in the second embodiment, comprises a sliding member which constitutes the inner circumferential surface of the hole and has better sliding properties with respect to the shaft than the magnetic member.

[0019] In this embodiment, the movable element includes a sliding member that has better sliding properties against the shaft than the magnetic member. The sliding member forms the inner circumferential surface of the hole. Therefore, friction between the movable element and the shaft can be reduced.

[0020] In the eighth embodiment, the vibration actuator, in the seventh embodiment, has a cylindrical shape in which the sliding member is positioned radially inward at the joint between the magnet and the one-sided pole piece and the joint between the magnet and the other-sided pole piece.

[0021] In this embodiment, the sliding member has a cylindrical shape and is positioned radially inward at the joint between the magnet and one pole piece and the joint between the magnet and the other pole piece. Therefore, it is possible to prevent malfunctions caused by leakage of adhesive from the joint between the magnet and one pole piece and the joint between the magnet and the other pole piece.

[0022] In the ninth embodiment, the vibration actuator comprises, in the seventh embodiment, a sliding member which is fixed to one side of the one-side pole piece in the direction of vibration and a other-side fixing member which is fixed to the other side of the other-side pole piece in the direction of vibration.

[0023] In this embodiment, the sliding member comprises a one-side fixing member fixed to one side of the one-side pole piece in the direction of vibration, and a other-side fixing member fixed to the other side of the other-side pole piece in the direction of vibration. Therefore, the mass of the movable element can be easily adjusted by the sliding member.

[0024] In the vibration actuator according to the tenth embodiment, in the eighth embodiment, the outer diameters of the one-side fixing member and the other-side fixing member are 70% or more of the outer diameters of the one-side pole piece and the other-side pole piece.

[0025] In this embodiment, the outer diameter of the fixing member on one side and the fixing member on the other side is 70% or more (98% or more) of the outer diameter of the pole piece on one side and the pole piece on the other side. Therefore, the mass of the movable element can be increased, and the excitation force can be increased.

[0026] According to this disclosure, the vibration actuator can be made smaller and lighter.

[0027] This is a schematic cross-sectional view of a vibration actuator according to the first embodiment. This is an enlarged cross-sectional view showing the right side of the vibration actuator according to the first embodiment. This is an enlarged cross-sectional view showing the state in which the movable element is displaced to its maximum extent. This is a schematic cross-sectional view of a vibration actuator according to a first modification of the first embodiment. This is a schematic cross-sectional view of a vibration actuator according to a second modification of the first modification. This is an enlarged cross-sectional view showing the right side of the vibration actuator according to the second embodiment. This is an enlarged cross-sectional view showing the right side of a vibration actuator according to the third embodiment. This is a graph showing that stiffness can be adjusted by changing the ratio of the lengths of the magnetic circuit components.

[0028] (First Embodiment) The vibration actuator 10 according to the first embodiment of the present disclosure will be described.

[0029] As shown in Figure 1, the vibration actuator 10 comprises a stator 12 and a movable element 14.

[0030] The stator 12 comprises a cylindrical yoke 22, a cylindrical coil 26 positioned inside the yoke 22, covers 27a and 27b, and a shaft 28 extending in the direction of vibration.

[0031] The yoke 22 is made of a magnetic material (for example, iron). The yoke 22 has a cylindrical shape. As shown in Figure 2, the vibration direction dimension L1 of the yoke 22 is larger than the vibration direction dimension L2 of the coil 26. The vibration direction dimension L1 of the yoke 22 is larger than the vibration direction dimension L3 of the magnetic circuit 31, which will be described later.

[0032] The coil 26 is joined to the inner circumferential surface of the yoke 22 with an adhesive or the like. The coil 26 comprises a one-side coil 26a provided on one side with respect to the vibration direction center, and a other-side coil 26b provided on the other side with respect to the vibration direction center. The one-side coil 26a and the other-side coil 26b are configured so that the direction of the magnetic flux they generate is opposite. Specifically, the winding direction of the other-side coil 26b is opposite to that of the one-side coil 26a. The one-side coil 26a and the other-side coil 26b are arranged in close proximity in the direction of vibration.

[0033] The covers 27a and 27b are made of, for example, synthetic resin. The covers 27a and 27b comprise one side cover 27a and the other side cover 27b. The one side cover 27a supports the end of the yoke 22 on one side in the direction of vibration and covers the inside of the yoke 22 from that side in the direction of vibration. The other side cover 27b supports the end of the yoke 22 on the other side in the direction of vibration and covers the inside of the yoke 22 from that side in the direction of vibration. The outer circumferential surface 27a1 of the one side cover 27a and the outer circumferential surface 27b1 of the other side cover 27b are flush with the outer circumferential surface of the yoke 22.

[0034] One side cover 27a supports the end of the shaft 28 on one side in the direction of vibration. The other side cover 27b supports the end of the shaft 28 on the other side in the direction of vibration. One side cover 27a has a one side stopper surface 27a2. The one side stopper surface 27a2 is located to one side in the direction of vibration beyond the end of the yoke 22 on one side in the direction of vibration. The other side cover 27b has a other side stopper surface 27b2. The other side stopper surface 27b2 is located to the other side in the direction of vibration beyond the end of the yoke 22 on the other side in the direction of vibration.

[0035] The shaft 28 is a rod-shaped member having a circular cross-sectional shape. The shaft 28 is made of a non-magnetic material (for example, stainless steel). The shaft 28 does not protrude from the vibration-direction outer surfaces 27a3 and 27b3 of one side cover 27a and the other side cover 27b.

[0036] The movable element 14 includes a magnetic circuit 31 located inside the coil 26. The magnetic circuit 31 includes a magnet 32 ​​and a magnetic member 33. The magnet 32 ​​constitutes the central part of the movable element 14 in the direction of vibration and is magnetized in the direction of vibration. The magnetic member 33 includes a one-side pole piece 33a fixed to one side of the magnet 32 ​​in the direction of vibration, and a other-side pole piece 33b fixed to the other side of the magnet 32 ​​in the direction of vibration.

[0037] Each of the pole pieces 33a and 33b is cylindrical. When the movable element 14 is positioned at the center of the vibration direction, the vibration center position of the pole piece 33a is preferably located near the vibration center of the coil 26a, and the vibration center position of the pole piece 33b is preferably located near the vibration center of the coil 26b. Here, "located near the center of the vibration direction" means that, when the vibration direction dimension of each coil 26a and 26b is set to 100%, the pole piece 33b is located within ±10% of the vibration center of each coil 26a and 26b.

[0038] The movable element 14 has a hole 14k through which the shaft 28 passes. Specifically, the magnet 32, one pole piece 33a, and the other pole piece 33b each have a hole through which the shaft 28 passes.

[0039] The vibration actuator 10 does not include a spring member (see Patent Document 1) to elastically support the movable element 14. Instead, the movable element 14 is held radially centered by the shaft 28 of the stator 12 and the hole 14k of the movable element 14. Furthermore, the magnetic force between the yoke 22 and the movable element 14 acts as a force to return the movable element 14 to its center position in the direction of vibration. As a result, the vibration actuator 10 can be made smaller and lighter compared to a configuration in which the vibration actuator 10 includes a spring member to elastically support the movable element 14.

[0040] The vibration actuator 10 may also be equipped with a magnetic fluid (not shown). The magnetic fluid is an oil-like fluid in which magnetic particles such as iron powder are dispersed. The magnetic fluid is held in place by magnetic force. The magnetic fluid is placed between the coil 26 and the pole pieces 33a and 33b, etc.

[0041] <Effects> Next, the effects of this embodiment will be described.

[0042] In this embodiment, as shown in FIG. 1, the vibration actuator 10 includes a stator 12 and a mover 14. The stator 12 includes a cylindrical yoke 22 and a cylindrical coil 26 disposed inside the yoke 22, and the mover 14 includes a magnetic circuit 31 disposed inside the coil. The magnetic circuit 31 includes a magnet 32 and magnetic members 33a and 33b.

[0043] Also, in this embodiment, the vibration actuator 10 does not include a spring member that elastically supports the mover 14. One of the stator 12 and the mover 14 includes a shaft 28 extending in the vibration direction, and a hole 14k through which the shaft 28 passes is provided in the other of the stator 12 and the mover 14, so that the center of the mover 14 is held in the radial direction. Further, the magnetic force between the yoke 22 and the mover 14 acts as a force for the mover 14 to return to the center position in the vibration direction. Therefore, compared with an aspect in which the vibration actuator 10 includes a spring member that elastically supports the mover 14, the vibration actuator 10 can be reduced in size and weight.

[0044] Also, in this embodiment, as shown in FIG. 1, the stator 12 includes a shaft 28, and a hole 14k is provided in the mover 14. Therefore, an increase in size in the vibration direction of the vibration actuator 10 can be suppressed.

[0045] Also, in the present embodiment, as shown in FIG. 1, the coil 26 includes a one-side coil 26a provided on one side with respect to the center in the vibration direction, and a the other-side coil 26b provided on the other side with respect to the center in the vibration direction. The one-side coil 26a and the other-side coil 26b are configured such that the directions of the generated magnetic fluxes are opposite. The magnet 32 constitutes the central portion of the mover 14 in the vibration direction and is magnetized in the vibration direction. The magnetic members 33a and 33b include a one-side pole piece 33a fixed to one side of the magnet 32 in the vibration direction and a the other-side pole piece 33b fixed to the other side of the magnet 32 in the vibration direction. Therefore, compared with the mode (see FIG. 6 showing the second embodiment) in which a magnetic body constitutes the central portion in the axial direction of the mover and two magnets that form a repulsive magnetic field so as to sandwich the magnetic body in the vibration direction are provided, assembly and magnetization are facilitated. Also, since there is one magnet, the component cost is reduced. Also, since there is one magnet, the magnetization process is completed once, and it is easy to manufacture.

[0046] Also, in the present embodiment, as shown in FIG. 1, the yoke 22 does not have a portion disposed between the one-side coil 26a and the other-side coil 26b. Therefore, the structure of the yoke 22 can be simplified.

[0047] Also, in the present embodiment, as shown in FIG. 2, the dimension L1 of the yoke 22 in the vibration direction is larger than the dimension L2 of the coil 26 in the vibration direction. Therefore, a structure can be formed in which the coil 26 does not jump out of the yoke 22 to the outside in the vibration direction, so that damage to the coil 26 during manufacturing can be suppressed. Also, since the yoke 22 can cover the coil 26, it is possible to prevent an operator from touching the coil 26 or bringing the coil 26 into contact with other components during the mounting operation.

[0048] Also, in the present embodiment, as shown in FIG. 2, the dimension L1 of the yoke 22 in the vibration direction is larger than the dimension L3 of the magnetic circuit 31 in the vibration direction. Therefore, a vibration actuator 10 with good linearity can be realized. Also, the yoke 22 can cover the moving range of the magnetic circuit 31 (mover 14) in the vibration direction.

[0049] Furthermore, in this embodiment, as shown in Figure 3, when the movable element 14 is in its maximum displacement state, the dimension of the magnet 32 ​​of the movable element 14 that extends beyond the range where the yoke 22 is provided in the vibration direction (the range indicated by arrow L1) is less than 50% (more preferably less than 10%, specifically 0% in the example shown) of the dimension of the magnet 32 ​​in the vibration direction. Therefore, linearity can be improved.

[0050] Incidentally, recent game consoles and mobile devices incorporate vibration actuators for the purpose of vibration feedback. As the objects in which vibration actuators are built become smaller, vibration actuators are also required to be smaller and lighter. Furthermore, wearable devices and virtual systems are being researched and developed, and miniaturization and weight reduction are essential for them to be built into, for example, gloves, glasses, shoes, and earphones. In this respect, the vibration actuator 10 according to this embodiment can achieve miniaturization and weight reduction, making it easier to meet the above requirements.

[0051] Incidentally, in order to make vibrations from a vibration actuator easily perceived as tactile sensation, vibrations of around 100 Hz are effective, and it is necessary to set the resonant frequency of the vibration actuator low. In this respect, in the vibration actuator 10 according to this embodiment, since only magnetic stiffness (magnetic spring) is used to support the movable element 14 in the direction of vibration, it is easy to reduce stiffness, and as a result, it is easy to set a low resonant frequency. In other words, since the configuration uses only magnetic force to provide spring constant or rigidity to support the movable element in the direction of vibration, it is easy to reduce stiffness, and as a result, it is easy to set a low resonant frequency. The same applies to other embodiments and modifications described later.

[0052] In the vibration actuator 10 according to this embodiment, stiffness and linearity can be adjusted by adjusting the height relationship between the magnetic circuit 31 (magnet 32, pole pieces 33a, 33b) and the yoke 22.

[0053] Incidentally, in order to operate instantaneously as a stimulus vibration, it is advantageous to have a fast rise time. Here, rise time refers to the time it takes for the vibration actuator to reach the target vibration intensity (amplitude and acceleration) after it starts vibrating. In this respect, the vibration actuator 10 according to this embodiment is advantageous in that it can be miniaturized as described above, and therefore has an advantage in terms of having a fast rise time.

[0054] Figure 8 is a graph showing that stiffness can be adjusted by changing the ratio of the lengths of the magnetic circuit components. The slope of the line on the graph represents the stiffness. As shown in Figure 8, the desired stiffness can be obtained by changing the dimensions of each part. As shown in the graph in Figure 8(A), the magnitude of the stiffness can be adjusted by changing the dimensions of each part. As shown in the graph in Figure 8(B), the linear range of the stiffness can be adjusted by changing the dimensions of each part. It is preferable to use the straight-line portion of the graph. In the graph in Figure 8(C), the portion that is close to a straight line also shows high linearity. However, the non-straight-line portion can also be used because the stiffness can be changed by the displacement position of the movable part.

[0055] (First Modified Example) Figure 4 is a schematic cross-sectional view showing the vibration actuator 10A according to the first modified example.

[0056] The movable element 14 of the vibration actuator 10A includes a sliding member 34A that has better sliding properties against the shaft 28 than the magnetic members 33a and 33b, in addition to the magnetic circuit 31. The sliding member 34A is joined to the magnetic circuit 31 and forms the inner circumferential surface of the hole 14k. As a result, the sliding member 34A is configured to slide against the outer circumferential surface of the shaft 28. Specifically, the contact portion between the shaft 28 and the sliding member 34A is linear. Therefore, friction between the movable element 14 and the shaft 28 can be reduced. Examples of materials for the sliding member 34A include polytetrafluoroethylene and polyamide.

[0057] The sliding member 34A has a cylindrical shape and is positioned radially inward at the joint between the magnet 32 ​​and one side pole piece 33a and the joint between the magnet 32 ​​and the other side pole piece 33b. This prevents malfunctions caused by adhesive leakage from the joint between the magnet 32 ​​and one side pole piece 33a and the joint between the magnet 32 ​​and the other side pole piece 33b. Specifically, the sliding member 34A covers the joint, preventing adhesive from leaking into the hole 14k.

[0058] (Second Modification) Figure 5 is a schematic cross-sectional view showing the vibration actuator 10B according to the second modification.

[0059] The movable element 14 of the vibration actuator 10B includes, in addition to the magnetic circuit 31, sliding members 34Ba and 34Bb that have better sliding properties against the shaft 28 than the magnetic members 33a and 33b. The sliding members 34Ba and 34Bb are joined to the magnetic circuit 31 and constitute the inner circumferential surface of the hole 14k. As a result, the sliding members 34Ba and 34Bb are configured to slide against the outer circumferential surface of the shaft 28. This reduces friction between the movable element 14 and the shaft 28. Examples of materials for the sliding members 34Ba and 34Bb include polytetrafluoroethylene and polyamide. Furthermore, the sliding members 34Ba and 34Bb are disc-shaped and have holes smaller than those of the magnet 32 ​​and the magnetic members 33a and 33b. Therefore, only the sliding members 34Ba and 34Bb of the movable element 14 come into contact with and slide against the shaft 28. Furthermore, compared to the first modified example, the contact area between the sliding member and the shaft 28 can be reduced, and the contact points can be distributed to multiple locations.

[0060] The sliding members 34Ba and 34Bb comprise a one-side fixing member 34Ba fixed to one side of the one-side pole piece 33a in the direction of vibration, and a other-side fixing member 34Bb fixed to the other side of the other-side pole piece 33b in the direction of vibration. Therefore, the mass of the movable element 14 can be easily adjusted by the sliding members 34Ba and 34Bb.

[0061] The outer diameters of the fixing member 34Ba on one side and the fixing member 34Bb on the other side are 70% or more (98% or more) of the outer diameters of the pole piece 33a on one side and the pole piece 33b on the other side. Therefore, the mass of the movable element 14 can be increased, and the excitation force can be increased.

[0062] (Second Embodiment) Next, a vibration actuator 210 according to the second embodiment of the present disclosure will be described with reference to Figure 6. Components similar to those in the first embodiment are denoted by the same reference numerals and their description is omitted.

[0063] The stator 12 of the vibration actuator 210 comprises a cylindrical yoke 22, a cylindrical coil 26 positioned inside the yoke 22, covers 27a and 27b, and a shaft 28 extending in the direction of vibration.

[0064] The coil 26 consists of a single coil 26. The shaft 28 is made of a non-magnetic material (e.g., stainless steel).

[0065] The movable element 14 of the vibration actuator 210 includes a magnetic circuit 231 located inside the coil 26. The magnetic circuit 231 comprises magnets 232a, 232b and a magnetic member 233.

[0066] The magnetic member 233 constitutes the central part of the movable element 14 in the direction of vibration. The magnets 232a and 232b consist of a one-side magnet 232a fixed to one side of the magnetic member 33 in the direction of vibration, and a other-side magnet 232b fixed to the other side of the magnetic member 33 in the direction of vibration. The one-side magnet 232a and the other-side magnet 232b are magnetized to form a repulsive magnetic field. The movable element 14 has a hole 14k through which the shaft 28 passes. The inner surface of the hole 14k slides on the shaft 28.

[0067] The vibration actuator 210 does not have a spring member (see Patent Document 1) to elastically support the movable element 14. Instead, the movable element 14 is held centered radially by the shaft 28 of the stator 12 and the hole 14k of the movable element 14. In addition, the magnetic force between the yoke 22 and the movable element 14 acts as a force to return the movable element 14 to the center position in the direction of vibration. As a result, the vibration actuator 210 can be made smaller and lighter compared to a configuration in which the vibration actuator 210 has a spring member to elastically support the movable element 14. Furthermore, since the vibration actuator 210 has only one coil, the electrical connection to the coil 26 is simple, making it easy to manufacture. Also, in the vibration actuator 210, two magnets 232a and 232b are coupled in a repulsive state to an intermediate magnetic member 233 (pole piece), so the magnetic force is strong despite the small size, and the excitation force can be increased.

[0068] (Third Embodiment) Next, a vibration actuator 310 according to the third embodiment of this disclosure will be described with reference to Figure 7.

[0069] The stator 12 of the vibration actuator 310 comprises a cylindrical yoke 22, a cylindrical coil 26 positioned inside the yoke 22, and covers 327a and 327b.

[0070] The coil 26 is composed of a single coil 26. The coil 26 is joined to the inner circumferential surface of the yoke 22 with an adhesive or the like.

[0071] The covers 327a and 327b comprise a one-side cover 327a and a other-side cover 327b. The one-side cover 327a has a one-side hole 12k through which a portion of the shaft 333 on one side in the direction of vibration is inserted. The other-side cover 327b has a other-side hole 12k through which a portion of the shaft 333 on the other side in the direction of vibration is inserted. The inner surfaces of the one-side hole 12k and the other-side hole 12k slide against the outer circumferential surface of the shaft 333.

[0072] The movable element 14 of the vibration actuator 310 includes a magnetic circuit 331 located inside the coil 26. The magnetic circuit 331 includes a magnet 332 and a magnetic member 333.

[0073] The magnetic member 333 is configured to also function as a shaft 333 extending in the direction of vibration. The shaft 333 is a rod-shaped member having a circular cross-sectional shape. The shaft 333 is made of a magnetic material (for example, iron). The shaft 333 has an enlarged diameter portion 333a at its center in the direction of vibration.

[0074] The magnet 332 is provided on the outer circumferential surface of the enlarged diameter portion 333a of the shaft 333. The magnet 332 is cylindrical and radially magnetized. Radial magnetization refers to magnetizing the magnet radially from the center outwards.

[0075] The vibration actuator 310 does not have a spring member (see Patent Document 1) to elastically support the movable element 14. Instead, the movable element 14 is held radially centered by the hole 12k of the stator 12 and the shaft 333 of the movable element 14. In addition, the magnetic force between the yoke 22 and the movable element 14 acts as a force to return the movable element 14 to the center position in the direction of vibration. As a result, the vibration actuator 310 can be made smaller and lighter compared to an embodiment in which the vibration actuator 310 has a spring member to elastically support the movable element 14. Furthermore, since the vibration actuator 310 has only one coil, the electrical wiring to the coil 26 is simplified, making it easier to manufacture. Also, since the vibration actuator 310 does not require a pole piece, the number of parts can be reduced. Furthermore, since the number of parts in the magnetic circuit 331 of the vibration actuator 310 is small, the parts cost and manufacturing cost can be reduced.

[0076] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above.

[0077] For example, in the vibration actuator 310 according to the third embodiment shown in Figure 7, it is possible to use the movable element 14 and the stator 12 in reverse. That is, by fixing the shaft 333 to another member, the shaft 333, magnet 332, etc. can be used as the stator 14, and the cylindrical yoke 22, the cylindrical coil 26 arranged inside the yoke 22, and the covers 327a and 327b can be used as the movable element 12. In that case, the weight of the movable element 12 can be increased, making it possible to obtain a larger vibration.

[0078] 10 Vibration actuator 10A Vibration actuator 10B Vibration actuator 12 Stator 14 Movable element 14k Hole 22 Yoke 26 Coil 26a One-sided coil 26b Other-sided coil 28 Shaft 31 Magnetic circuit 32 Magnet 33a One-sided pole piece (magnetic member) 33b Other-sided pole piece (magnetic member) 34A Sliding member 34B Sliding member 33Ba One-sided fixing member 33Bb Other-sided fixing member

Claims

1. A vibration actuator comprising: a stator and a movable element; the stator comprising a cylindrical yoke and a cylindrical coil disposed inside the yoke; the movable element comprising a magnetic circuit disposed inside the coil; the magnetic circuit comprising a magnet and a magnetic member; the vibration actuator not comprising a spring member for elastically supporting the movable element; one of the stator and the movable element comprising a shaft extending in the direction of vibration; the other of the stator and the movable element being provided with a hole through which the shaft passes, thereby maintaining the radial center of the movable element; and the magnetic force between the yoke and the movable element acting as a force for the movable element to return to its center position in the direction of vibration.

2. The vibration actuator according to claim 1, wherein the stator comprises the shaft, the movable element is provided with the hole, the magnet constitutes the vibration center portion of the movable element and is magnetized in the vibration direction, the magnetic member comprises a one-side pole piece fixed to one side of the magnet in the vibration direction, and a other-side pole piece fixed to the other side of the magnet in the vibration direction, the coil comprises a one-side coil provided on one side with respect to the vibration center, and a other-side coil provided on the other side with respect to the vibration center, and the one-side coil and the other-side coil are configured such that the directions of the magnetic flux they generate are opposite.

3. The vibration actuator according to claim 2, wherein the yoke does not have a portion disposed between the one coil and the other coil.

4. The vibration direction dimension of the yoke is greater than the vibration direction dimension of the coil, as described in claim 2.

5. The vibration direction dimension of the yoke is greater than the vibration direction dimension of the magnetic circuit, as described in claim 2.

6. The vibration actuator according to claim 2, wherein, when the movable element is in a state of maximum displacement, the dimension of the magnet of the movable element that extends beyond the range in which the yoke is provided in the direction of vibration is less than 50% of the dimension of the magnet in the direction of vibration.

7. The vibration actuator according to claim 2, wherein the movable element comprises a sliding member that constitutes the inner circumferential surface of the hole and has better sliding properties with respect to the shaft than the magnetic member.

8. The vibration actuator according to claim 7, wherein the sliding member has a cylindrical shape and is positioned radially inward at the joint between the magnet and the one-sided pole piece and the joint between the magnet and the other-sided pole piece.

9. The vibration actuator according to claim 7, wherein the sliding member comprises a one-side fixing member fixed to one side of the one-side pole piece in the direction of vibration, and a other-side fixing member fixed to the other side of the other-side pole piece in the direction of vibration.

10. The vibration actuator according to claim 9, wherein the outer diameter of the one-side fixing member and the other-side fixing member is 70% or more of the outer diameter of the one-side pole piece and the other-side pole piece.

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