Vibration power generator

Abstract

A vibration power generator (91) comprises: a frame (1); a damper part (D) that has a hole (2a) in the center thereof, has a peripheral edge section which is fixed to the frame (1), and has a central section which is elastically movable in an axis (CL1) direction; a vibration unit (7) that includes a bobbin (72) which has a cylindrical shape and is fixed to the hole (2a) of the damper part (D) and around which a coil (73) is wound, and a weight holder (71) which is fixed to the bobbin (72) to close an opening on one end side of the bobbin (72) and to which a weight body (74) can be removably attached; and a magnetic circuit (5) that is fixed to the frame (1) and generates a magnetic flux interlinking with the coil (73). The vibration unit (7) moves in the axis (CL1) direction due to external vibration, whereby power is generated.

Description

Vibration generator

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

[0002] Patent Document 1 describes a vibration generator used for environmental power generation called energy harvesting. The vibration generator described in Patent Document 1 is an electromagnetic induction type generator, and includes a housing, an elastic member fixed to the housing, a vibrator supported by the elastic member and having a coil inside, and a group of magnets arranged so as to sandwich the coil. An electromagnetic induction type generator generates an electromotive force in the coil due to a time change in the magnetic flux linked to the coil by the vibration of the vibrator, thereby generating electricity.

[0003] Japanese Patent No. 6715101

[0004] Vibration in environmental power generation is usually weak. Therefore, it is desired that a vibration generator can obtain larger electrical energy from weak vibration. On the other hand, the applications of vibration generators are expanding. For example, it is also expected to be applied to a technology for detecting a specific frequency in the vibration generated in civil engineering structures or building structures and grasping the state (degree of deterioration) of the structures. In this case, in order to obtain an electrical signal of sufficient magnitude for analysis, it is desired to mount a vibrator that resonates at a specific vibration frequency previously grasped in the target structure to generate electricity. However, since the specific vibration frequencies are different for each structure, it is necessary to create a vibration generator dedicated to each structure, which is not easily achievable from the viewpoints of cost and man-hours.

[0005] In addition to grasping the state of the structure, if a vibration generator having a vibrator that resonates at a specific frequency is installed at a place or structure where the vibration of a specific frequency is large, power can be generated with high efficiency.

[0006] As is clear from the above, it is desired that the resonance frequency of the vibrator of the vibration generator can be easily changed.

[0007] An object of the present disclosure is to provide a vibration generator capable of easily changing the resonance frequency of a vibrator.

[0008] The vibration generator according to this embodiment comprises a frame, a damper section, a vibration unit, and a magnetic circuit. The damper section has a hole in the center, its peripheral edge is fixed to the frame, and its central part is elastically movable in the axial direction. The vibration unit includes a bobbin having a cylindrical shape around which a coil is wound and which is fixed to the hole in the damper section, and a weight holder fixed to the bobbin so as to close the opening at one end of the bobbin and on which a weight can be attached and detached. The magnetic circuit is fixed to the frame and generates a magnetic flux that links with the coil. Electricity is generated when the vibration unit moves in the axial direction due to external vibration.

[0009] With the above configuration, the resonant frequency of the oscillator can be easily changed.

[0010] Figure 1 is a longitudinal cross-sectional view showing the configuration of a vibration generator according to an embodiment. Figure 2 is a partially disassembled cross-sectional view illustrating the vibration unit of the vibration generator according to an embodiment. Figure 3 is a top view of the weight holder in the vibration unit according to an embodiment. Figure 4 is a longitudinal cross-sectional view showing a modified vibration generator.

[0011] Hereinafter, the vibration generator 91 according to the embodiment will be described with reference to Figures 1 to 3. A modified vibration generator 91A of the vibration generator 91 will be described with reference to Figure 4. Figure 1 is a longitudinal cross-sectional view showing the configuration of the vibration generator 91 according to the embodiment. Figure 2 is a disassembled cross-sectional view showing a part of the vibration unit 7 of the vibration generator 91 for illustrative purposes. Figure 3 is a top view of the weight holder 71 in the vibration unit 7. Figure 4 is a longitudinal cross-sectional view showing the modified vibration generator 91A. The vertical direction in this description is defined by the direction of the arrows shown in Figures 1, 2, and 4. In Figures 1, 2, and 4, UP indicates the upward direction and DN indicates the downward direction. This vertical direction is the vertical direction and corresponds to the operating orientation of the vibration generator 91 and the vibration generator 91A.

[0012] The vibration generator 91 comprises a frame 1, a damper section D, a magnetic circuit 5, and a vibration unit 7 which is an oscillator. The frame 1 is formed in a substantially circular pot shape with an annular side wall 11 and a bottom wall 12 centered on an axis CL1 extending vertically. Two stepped sections 11a and 11b are formed on the side wall 11 at positions separated in the axial direction, and a circular opening 12a is formed on the bottom wall 12 that is concentric with the axis CL1.

[0013] A damper section D is attached to the stepped portion 11a on the opening side (upward side) of the frame 1. The damper section D has one or more dampers. In this embodiment, the damper section D has two dampers: a first damper 2 and a second damper 3.

[0014] The first damper 2 is formed in a disc shape with a circular hole 2a in the center. The peripheral edge of the first damper 2 is connected and fixed to the upper end of the spacer 4 which is fixed to the stepped portion 11a. The first damper 2 has a circular pleated portion in top view, which is undulating in the vertical direction in cross-sectional shape. This pleated portion allows the central portion of the first damper 2, which is near the hole 2a, to move elastically in the vertical direction.

[0015] In this embodiment, the second damper 3 is formed to have the same shape as the first damper 2. The peripheral edge of the second damper 3 is fixed to the base of the spacer 4. The central circular hole 3a of the second damper 3 and the central hole 2a of the first damper 2 are identical in shape and position when viewed from above. The spacer 4 determines and maintains the distance between the first damper 2 and the second damper 3 in the direction of the axis CL1.

[0016] As shown in Figures 1 and 2, a vibration unit 7, which serves as an oscillator, is fixed to the hole 2a of the first damper 2 and the hole 3a of the second damper 3 by adhesive or the like. The vibration unit 7 comprises a weight holder 71, a bobbin 72, a coil 73, and a weight 74. The bobbin 72 is a cylindrical member, for example, made of polyimide resin. The hole 2a of the first damper 2 and the hole 3a of the second damper 3 are adhesively fixed to the outer circumferential surface of the upper part of the bobbin 72. The bobbin 72 is supported so as to be able to move up and down by only the first damper 2 and the second damper 3. The coil 73 is wound around the outer circumferential surface of the lower part of the bobbin 72. Both ends of the coil 73 are pulled out and connected to a pair of connection terminals (not shown).

[0017] The weight holder 71 is adhesively fixed to the bobbin 72 so as to close the opening at the upper end, which is one end of the bobbin 72. The weight holder 71 is made of a non-magnetic material. The weight holder 71 has a flange 711, a peripheral wall portion 712, and a bottom wall portion 713. In Figure 2, the weight holder 71 is formed in the shape of a deep pot, which is circular when viewed from above, with the axis CL7 extending vertically as the center. The peripheral wall portion 712 is formed as an inclined peripheral surface whose vertical cross-sectional shape decreases in diameter from the opening side (upper side) toward the bottom wall portion 713. The flange 711 is the portion that protrudes outward around the entire circumference from the opening edge at the upper end of the peripheral wall portion 712. In the center of the bottom wall portion 713, there is a female thread portion 714 having a female thread concentric with the axis CL7.

[0018] The weight holder 71 has radial slits 712a in a top view that connect the lower part of the peripheral wall portion 712 and the edge of the bottom wall portion 713. In this embodiment, as shown in Figure 3, four slits 712a are formed at 90° intervals in a top view. The number of slits 712a to be formed and their angular spacing are not limited thereto. There may be only one slit 712a, or the slits 712a may not be provided depending on the specifications. When slits 712a are formed, they may be formed in a position and shape that is point-symmetric with respect to the vibration balance of the vibration unit 7 with respect to the axis CL7.

[0019] As shown in Figures 1 and 2, a non-magnetic weight 74 is detachably mounted and fixed inside the weight holder 71. The weight 74 may be a single block, or it may be an assembly of multiple weights 741, as in this embodiment. The weight 741 can be, for example, a non-magnetic flat washer or a flat washer-like member. Any number of weights 741 are stacked and fixed to the weight holder 71 by inserting a small screw, which is a fastener 742, through the central hole of the weight 741 and screwing it into the female thread of the female thread portion 714.

[0020] With the above configuration, the mass and number of each weight 741 can be easily and arbitrarily selected. In other words, by selecting the mass and number of weights 741, the mass of the vibrating unit 7, which is the oscillator, can be set to any mass. Therefore, the resonant frequency, which depends on the mass of the vibrating unit 7 that is supported so as to be able to move up and down by only the first damper 2 and the second damper 3, can be easily set to any frequency.

[0021] As shown in Figure 1, a magnetic circuit 5 is fixed to the stepped portion 11b of the frame 1. The magnetic circuit 5 includes, in order from top to bottom, a sub-magnet 51, a top plate 52, a main magnet 53, and a yoke 54.

[0022] The sub-magnet 51, top plate 52, and main magnet 53 are formed in a ring shape with an opening in the center. The yoke 54 has a cylindrical center pole 541 projecting upward in the center, and its vertical cross-sectional shape is formed in an inverted T shape.

[0023] The center pole 541 enters the central opening of the main magnet 53 and the top plate 52 from below, and is positioned so that its upper surface extends to a position above the top plate 52.

[0024] The gap S, which is the circumferential gap between the center pole 541 and the top plate 52, sub-magnet 51, and main magnet 53, is narrowest when it is between the center pole 541 and the top plate 52. The bobbin 72, around which the coil 73 is wound, enters the gap S from above and is maintained without contact with other components. The vertical winding range of the bobbin 72 includes at least the range facing the top plate 52.

[0025] In the magnetic circuit 5, the highest density of magnetic flux passes between the inner surface of the top plate 52 and the outer surface of the center pole 541, so a high density of magnetic flux links with the coil 73.

[0026] When the vibration generator 91 with the above configuration is fixed to a vibration source or a part through which the vibration propagates, for example, in a position where the axis CL1 is in the vertical direction, the vibration unit 7 moves vertically relative to the frame 1 and magnetic circuit 5 due to the vertical component of the external vibration. As a result, the coil 73, which moves vertically, passes over the magnetic flux of the magnetic circuit 5, generating an electromotive force, and an electrical signal with a waveform and amplitude corresponding to the vibration is obtained from the output terminal.

[0027] If the vibration from the vibration source is of a specific frequency, or if it is desired to detect a specific frequency component in the vibration, the mass and number of weights 741 are selected and fixed with the fixing device 742 so that the vibration unit 7 resonates at that specific frequency. In other words, the resonant frequency can be adjusted by changing the mass of the weights 74. If mass adjustment beyond the range of mass adjustment by the weights 741 is required, this can be addressed, for example, by increasing or decreasing the overall mass of the vibration unit 7.

[0028] A prototype vibration generator 91 with the above configuration was fabricated, and tests were conducted to generate electricity by applying vibration. The results showed that the resonant frequency of the vibration generator 91 could be changed as shown in Table 1 by changing the number of weights 741, that is, by changing the mass of the weight body 74.

[0029]

[0030] Table 1 shows the results for the prototype vibration generator 91. The resonant frequency value and adjustment range can be set to different values ​​depending on the specifications of the vibration generator 91 (magnetic characteristics of the magnetic circuit 5, shape and mass of the vibration unit 7, damping characteristics of the damper section D, etc.).

[0031] Thus, the vibration generator 91, which generates electricity from vibration, allows for the modification of its resonant frequency, and this modification is very simple as it can be done by selecting at least one of the mass and number of weights 741. For example, consider a case where the object of measurement is a bridge, and the natural frequency mainly generated by the passage of vehicles on the bridge is identified as 30 Hz, and power is generated using a vibration generator 91 having the characteristics shown in Table 1. In this case, by attaching two weights 741, each weighing 20 g, to the weight holder 71, the resonant frequency of the vibration generator 91 can be roughly matched to the natural frequency of the bridge. This allows for a large amplitude of vibration unit 7, enabling efficient power generation from the vibration of the bridge.

[0032] As shown in Figure 1, the space V1 between the center pole 541, bobbin 72, and weight holder 71 is substantially sealed space if there are no other gaps, because the gap S is very small. Therefore, if you do not want to affect the vertical movement of the vibration unit 7, you can eliminate the air resistance in space V1 by providing a slit 712a in the weight holder 71 in a manner that is not blocked by the weight 741, as shown in the above embodiment, to serve as a ventilation passage between space V1 and the outside space. Conversely, if you want the air resistance in space V1 to function as a damper to brake the vertical movement of the vibration unit 7, you do not need to form the slit 712a.

[0033] If the specifications of the vibration generator 91 prevent a large vertical distance between the center pole 541 and the weight holder 71, there is a risk that the weight holder 71 may directly collide with the upper surface of the center pole 541 due to the large vertical movement of the vibration unit 7 caused by resonance. To prevent this direct collision, a buffer member 8, such as a coil spring, may be placed on the upper surface of the center pole 541, as shown in the modified vibration generator 91A in Figure 4. The buffer member 8 is not limited to a coil spring; it may also be a foamed material such as sponge.

[0034] As shown in Figure 1, the vertical position of the center of gravity G of the weight holder 71 to which the weight 74 is fixed changes in the direction of the axis CL1 (vertical direction) depending on the number of weights 741. When the damper section D has two dampers, a first damper 2 and a second damper 3, it is preferable that the range between the position of the center of gravity G when there are no weights 741 in the weight holder 71 and the position of the center of gravity G when the maximum number of weights that can be accommodated is fixed be included between the height position H1 of the first damper 2 and the height position H2 of the second damper 3. As a result, the vertical position of the center of gravity G of the weight holder 71 is determined between the first damper 2 and the second damper 3, regardless of the number of weights 741. Therefore, the vibration unit 7 can be supported more stably by the first damper 2 and the second damper 3, and the vibration unit 7 moves up and down stably without axial wobble.

[0035] Either the first damper 2 or the second damper 3, or both, do not have to be disc-shaped and can be of any shape.

[0036] If the damper section D has one damper, for example, the vertical center of gravity of the weight holder 71 in the direction of the axis CL1 should be set to be within the range centered on the connection position of one damper.

[0037] The vibration generator 91 according to this embodiment has a structure similar to that of an electroacoustic converter that converts electrical signals into sound. Therefore, it can be manufactured using the manufacturing processes, manufacturing technologies, and quality control methods of an electroacoustic converter, and there are many manufacturing advantages, such as being able to maintain high quality well.

[0038] While embodiments and modifications of the present invention have been described above, it is possible to modify or alter these embodiments and modifications based on the above disclosure. All components of the above embodiments and modifications, and all features described in the claims, may be individually selected and combined, provided that they do not contradict each other.

[0039] The entire contents of Japanese Patent Application No. 2024-225967 (Filing Date: December 23, 2024) are incorporated herein by reference.

[0040] This invention is a technology that can be used when generating electricity from the vibration of an object to be installed, or when determining the state of an object to be installed based on its vibration.

Claims

1. A vibration generator comprising: a frame; a damper portion having a hole in the center, with its peripheral edge fixed to the frame and its central portion elastically movable in the axial direction; a vibration unit including a bobbin having a cylindrical shape around which a coil is wound and fixed to the hole in the damper portion; a weight holder fixed to the bobbin so as to close an opening at one end of the bobbin and on which a weight can be attached and detached; and a magnetic circuit fixed to the frame and generating a magnetic flux linked to the coil, wherein the vibration generator generates electricity when the vibration unit moves in the axial direction due to external vibration.

2. The vibration generator according to claim 1, wherein the resonant frequency of the vibration unit is adjustable by changing the mass of the weight attached to the weight holder.

3. The vibration generator according to claim 2, wherein the damper section includes a first damper and a second damper spaced apart in the axial direction.

4. The vibration generator according to claim 3, wherein the center of gravity of the weight in the axial direction is located between the first damper and the second damper.

5. The vibration generator according to claim 4, wherein the weight is a single flat washer-shaped weight, or a plurality of stacked flat washer-shaped weights.

6. The vibration generator according to claim 1, further comprising a buffer member for preventing direct collision between the magnetic circuit and the vibration unit moving in the axial direction.

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