JP5931499B2 - Flywheel device and energy storage device including the same - Google Patents

Description

  The present invention relates to a flywheel device having a rotating body that stores kinetic energy by rotating, and an energy storage device including the flywheel device.

  2. Description of the Related Art As a device that converts electrical energy into kinetic energy and stores it, a flywheel device that is rotatably provided with a cylindrical disk-shaped flywheel (FW) is known.

  The flywheel device is provided with a rotating shaft that passes through the center of gravity of the flywheel, and by rotating the flywheel around the rotating shaft with the electric energy supplied to the generator, the electric energy is converted into kinetic energy to be stored energy. (For example, see Non-Patent Documents 1 and 2).

Takeo Saito, Hiroaki Ogasawara, Noboru Yamada, “Study on Flywheel Energy Storage and Application to Electric Vehicles”, Journal of the Japan Society of Mechanical Engineers, B, Vol. 70, No.697 (2004), pp.244-251. Akira Takeuchi and Isao Takahashi, “Prototype of short-time large-capacity power supply using flywheel energy storage device”, Proceedings of the IEEJ Semiconductor Power Conversion and Industrial Power Application Joint Research Group, pp.83-88, (2000).

  By the way, in order to increase the energy density when energy is stored in the conventional flywheel device, 1) the rotational speed of the rotor of the flywheel, 2) the size of the rotor of the flywheel, 3) the rotor of the flywheel Either of the density needs to be increased, but in any case, an increase in stress on the rotor is inevitable. For this reason, a high-strength lightweight material such as a carbon fiber composite material is required as a member constituting the rotor. Further, when a magnetic bearing or a vacuum rotor container is not used, mechanical loss such as bearing loss and windage loss increases, resulting in problems such as a decrease in the life of components, noise, and heat generation. Further, if the rotor is rotated at a high speed, the degree of freedom in selecting a motor is narrowed, and it becomes difficult to use a general-purpose motor. From the above points, there is a limit to the improvement in cost performance of the conventional flywheel.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a flywheel device capable of storing higher kinetic energy without increasing the size of the device, and an energy storage device including the flywheel device. And

  In order to solve the above-described problems, a first invention (flywheel device) of the present invention includes a rotating body that stores kinetic energy by rotating, and a rotation that rotatably holds the rotating body around two rotational axes. A body holding mechanism.

  A second invention (energy storage device) according to the present invention includes the flywheel device according to the first invention and a conversion device that performs mutual conversion between electric energy and kinetic energy of the rotating body.

  ADVANTAGE OF THE INVENTION According to this invention, the flywheel apparatus which can store still higher kinetic energy, without enlarging an apparatus structure, and an energy storage apparatus provided with the same can be provided.

It is a perspective view showing the basic composition of the flywheel device concerning a 1st embodiment. It is a front view of the rotation part of the flywheel device concerning a 1st embodiment. In the analysis example, it is a perspective view showing that a sphere capable of rotating around two axes is provided as a rotator. It is the schematic of the ellipsoid provided instead of the spherical body as a modification of the flywheel apparatus of 1st Embodiment. It is explanatory drawing which shows the analysis conditions in an analysis example. It is a graph which shows the analysis result in an example of analysis. It is a graph which shows the analysis result in an example of analysis. In an analysis example, it is a perspective view which shows the case where a rotary body is made to be rotatable around two axes. In an analysis example, it is a perspective view which shows the case where a rotary body is made to be rotatable around one axis. In an analysis example, it is a perspective view which shows the case where only what rotates is a disk. In an experiment example, it is a perspective view which shows the structure of an experiment apparatus. In an experiment example, it is explanatory drawing which shows the specification of an experiment apparatus. In an experiment example, it is explanatory drawing which shows the comparison with the measured value and analysis value of stored energy. It is a schematic diagram which shows the structure of the flywheel apparatus and energy storage apparatus which concern on 2nd Embodiment. FIGS. 15A and 15B are perspective views for explaining the flywheel device according to the third embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, the same or similar components as those already described are denoted by the same or similar reference numerals, and detailed description thereof is omitted as appropriate.

  In addition, it should be noted that the drawings are schematic and the dimensional ratios and the like are different from actual ones. Therefore, specific dimensional ratios and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments are exemplifications for embodying the technical idea of the present invention, and the embodiments of the present invention are described below in terms of the material, shape, structure, arrangement, etc. of the components. It is not something specific. The embodiments of the present invention can be implemented with various modifications without departing from the scope of the invention.

[First Embodiment]
First, the first embodiment will be described. FIG. 1 is a perspective view showing a basic configuration of an energy storage device 12 including a flywheel device 10 according to the present embodiment. FIG. 2 is a front view of the rotating unit of the flywheel device according to the present embodiment.

  The flywheel device 10 according to the present embodiment includes a rotating body 14 that stores kinetic energy by rotating, and a rotating body holding that rotatably holds the rotating body 14 about the x-axis and y-axis that are two-direction rotating shafts. And a mechanism 16. In the following description, such a rotating body that rotates about two axes is also referred to as a biaxial spin body as appropriate, and rotation around two axes is also referred to as a biaxial spin as appropriate. A rotating body that rotates around one axis is also referred to as a uniaxial spin body as appropriate, and rotation around one axis is also referred to as a uniaxial spin as appropriate.

  In the present embodiment, both the x axis and the y axis pass through the center of gravity G of the rotating body 14 and are orthogonal to each other. In the present embodiment, a spherical body 14 s is provided as the rotating body 14. The energy storage device 12 according to the present embodiment includes the flywheel device 10 and a conversion device 18 that performs mutual conversion between electrical energy and kinetic energy of the rotating body 14.

  In the flywheel device 10 of the present embodiment, the storage energy amount is made to be the sum of the vertical rotation and the horizontal rotation by simultaneously performing the vertical rotation and the horizontal rotation (see also FIG. 8A described later). ing. The axis rotating on the inside (x axis) is rotated by the axis rotating on the outside (y axis), but the axis rotating on the outside always rotates in one direction. In this specification, the former (x axis) is defined as a dependent axis, and the latter (y axis) is defined as an independent axis.

  Hereinafter, specific configurations of the rotating body holding mechanism 16 and the conversion device 18 will be described. The conversion device 18 includes a rod-shaped rotation support shaft 20 that extends toward the flywheel device 10. The rotation support shaft 20 faces the same direction as the y axis.

  The rotating body holding mechanism 16 includes a rotational force transmission shaft 22 that transmits rotational force from the rotational support shaft 20. The rotational force transmission shaft 22 is rotatably attached to a disk (disk) 28 so as to form an angle of 135 ° (45 °) with the y-axis.

  Further, the rotating body holding mechanism 16 includes a second rotation support shaft 24 fixed to the rotating body 14. The second rotation support shaft 24 faces the same direction as the rotation axis x-axis, and the second rotation support shaft 24 rotates by the rotational force from the rotational force transmission shaft 22.

  Gears 30 are attached to the tip of the rotation support shaft 20, both ends of the torque transmission shaft 22, and the torque transmission shaft 22 side of the second rotation support shaft 24, respectively. It is configured to transmit rotational force.

  In the present embodiment, the conversion device 18 can perform mutual conversion between electrical energy and kinetic energy of the rotating body 14. That is, when a power unit (such as a motor) of the converter 18 receives electric energy and rotates the rotation support shaft 20, the rotating body 14 rotates about two axes (x axis and y axis), and the electric energy moves. Converted to energy and stored. When the stored kinetic energy is taken out as electric energy, the kinetic energy of the rotating body 14 is converted into electric energy by the converter 18. Therefore, it is possible to realize the flywheel device 10 and the energy storage device 12 including the flywheel device 10 that can store higher kinetic energy than the conventional one with a simple configuration without increasing the size of the device.

  In the present embodiment, the example in which the x-axis and the y-axis are orthogonal to each other has been described, but a configuration in which they are not orthogonal is also possible. Moreover, although both the x-axis and the y-axis have been described as an example of passing through the center of gravity G of the rotating body 14, it is not always necessary to pass through the center of gravity G.

  Further, although the spherical body 14s has been described as an example of the rotating body 14, the shape may be other than a sphere such as an ellipsoid (see the ellipsoid 34 in FIG. 4).

  Moreover, the hollow part 32 (refer FIG. 2) may be formed in the rotary body 14. FIG. The larger the mass of the portion far from the rotating body center point C (center of gravity G, see FIG. 2) is, the larger the stored energy is stored by the rotation of the rotating body 14. Therefore, by forming the hollow portion 32 in this way, it is not necessary to reduce the stored energy much even if the weight of the rotating body 14 is reduced. Further, by reducing the mass of the rotating body 14 that rotates at a high speed, the fracture resistance required for the second rotating support shaft 24 and the rotating support shaft 20 that support the rotating body 14 is significantly reduced. This is extremely effective in reducing the weight of 10 and simplifying the configuration.

<Example of analysis>
(1) Analysis Model FIG. 3 is a perspective view showing that a sphere 14s that can rotate around two axes is provided as the rotator 14 in this analysis example. In FIG. 3, the rotation locus K of the intersection A between the surface of the sphere 14s and the z-axis orthogonal to the dependent axis x and the independent axis y (the intersection A when the sphere 14s is rotated). (Movement trajectory) is also shown. When the sphere 14s rotates around two axes, the rotation locus K varies depending on the point on the sphere.

  FIG. 4 is a schematic view of an ellipsoid 34 provided in place of the sphere 14s as a modification of the flywheel device 10 of the first embodiment.

The kinetic energy E stored in a rotating body (single-axis spin body) that can rotate around one axis can be obtained from the inertia moment I and the rotational angular velocity ω of the rotating body by the following equation.

  However, in the case of a rotating body (biaxial spin body) that can rotate around two axes, it is not known whether Formula (1) can be simply applied. Therefore, the present inventor divides the biaxial spin body into minute volume elements using the finite element method (FEM), calculates the kinetic energy from the weight of each element and the tangential translation speed, and the energy of each element The accumulated energy of the biaxial spin body was obtained by analytical calculation. This analysis method can also be applied when the biaxial spin body has a shape other than a sphere.

FIG. 3 shows an FEM model of a biaxial spin sphere. The biaxial spin body is a sphere 14s having a radius R having an independent axis on the y axis and a dependent axis on the x axis. The coordinates here are absolute coordinates fixed in space. Now, when this sphere 14s rotates at an angular velocity ωi around the independent axis (y-axis) and at an angular velocity ωd around the dependent axis (x-axis) (where ω _i = ω _d ), the absolute coordinates P in the sphere at a certain time. Consider the rotation trajectory and speed change of a microelement with the center of gravity G located at (x, y, z). Translation speed v _d and v _i around subordinate axis and independent axes of the microelements, represented by respectively formula (2) and (3).

The translational movement speed v of the minute element is the combined speed of the expressions (2) and (3), and is expressed by the expression (4).

From equation (4), the kinetic energy e stored in the microelement located at the point P is expressed by the following equation.

By using equation (5), the kinetic energy stored in the sphere 14s can be obtained by adding the kinetic energy of all the microelements constituting the sphere 14s. In addition, the time change (trajectory) of the coordinates of a certain minute element depends on the initial coordinates of each element. For example, as shown in FIG. 3, the element having the center of gravity at P ₀ (x = 0, y = 0, z≈R) at the start of rotation is an independent axis and a velocity component around the dependent axis (x axis) at the start of rotation. Although the velocity components around are equal and move at the highest speed, the velocity component around the independent axis (y-axis) decreases as the rotation proceeds (see, for example, coordinate P ₁ ), and coordinate P ₂ (x = 0, At y = 0, z ≠ R), the velocity component around the independent axis disappears, and the velocity component exists only around the dependent axis.

(2) Analysis results FIG. 5 shows the analysis conditions. In this analysis example, analytical calculation was performed for both the sphere 14s and the ellipsoid 34 to calculate the stored energy. The analysis results are shown in FIGS. 6 and 7 also show the stored energy when the sphere 14s and the ellipsoid 34 are rotated only about one axis, respectively, for comparison. In the case of the ellipsoid 34, since the moment of inertia due to the rotation axis is different from that of the sphere 14s, the result when the axis is rotated about each axis of the independent axis (y axis) and the dependent axis (x axis) is obtained. showed that.

As can be seen from FIG. 6, in the case of the sphere 14s, the storage energy is larger in the biaxial rotation (biaxial spin) than in the uniaxial rotation (uniaxial spin) at all rotational speeds, and the ratio is always twice. Become. Further, as can be seen from FIG. 7, in the case of the ellipsoid 34 as well, the amount of stored energy is always larger in the case of biaxial spin, and the ratio is calculated by adding the moments of inertia around each rotation axis. It matches the ratio of stored energy calculated by In other words, this analysis example shows that the principle of superposition can be applied to the amount of stored energy when an object is rotated biaxially (biaxial spin) around two axes orthogonal to each other.
<Experimental example>
(1) Experimental device Since it was possible to predict the double of the stored energy by the biaxial spin body according to the analysis example, an example of the flywheel device 10 described in the first embodiment was actually designed, and the principle confirmation and mechanical loss of the experiment were confirmed. Evaluation and performed. FIGS. 8 to 10 show the analysis example in the case where the rotating body 14 can be rotated about two axes, the rotating body 14 can be rotated about one axis, and the rotating disk 14. FIG. FIG. 11 is a perspective view showing the configuration of the experimental apparatus, and FIG. 12 is an explanatory diagram showing the specifications of the experimental apparatus.

  As shown in FIG. 11, the experimental device 40 includes a rotating unit 42, a motor (DC motor) 44, an electromagnetic clutch 46, and a torque meter 48. As shown in FIG. 2, the rotating unit 42 includes a sphere 14 s (Sphere) and a disk-shaped disk 28 with a gear box installed outside the sphere 14 s, and the sphere 14 s and the disk 28 are driven by a motor. Performs a vertical rotation (around an independent axis) and at the same time performs a biaxial spin by rotating the sphere 14s laterally (around the dependent axis) by the action of a gear built in the disk 28. Since the gear ratio is 1: 1, the angular speeds of vertical rotation and horizontal rotation are equal. Moreover, it is the structure which can also perform 1 axis | shaft rotation of the rotation part 42 by removing a gear. Furthermore, free rotation (free run) is possible by disconnecting the electromagnetic clutch 46 attached between the motor 44 and the torque meter 48.

(2) Experimental principle and experimental conditions When a rotational force is applied to the biaxial spin body by driving the motor, the electromagnetic clutch is disengaged when the set rotational speed is reached, and the biaxial spin body is free run. The rotation speed gradually decreases due to the loss, and then stops. At this time, all energy stored in the biaxial spin body is lost due to mechanical loss. Therefore, by measuring the rotational speed dependence of the mechanical loss in advance, the loss energy can be integrated from the relationship between the time of free run and the rotational speed, and can be calculated as the stored energy at the set rotational speed. The mechanical loss referred to here includes windage loss.

  First, the mechanical loss Q (ω) at a certain rotational speed ω is obtained from the following equation by measuring the torque T (ω) necessary to maintain steady rotation at this rotational speed.

本実験例では、図８〜図１０に示すように、回転部４２を(i)２軸スピン（2-axis）、(ii)１軸スピン（1-axis）、および(iii)円盤（Disc）のみで１軸スピン、とした3つのケースにおいて、回転速度ω＝ 600r/minから1000 r/minの間における定常回転試験を行い、機械損と回転速度との関係を明らかにした。

In this experimental example, as shown in FIGS. 8 to 10, the rotating unit 42 is moved to (i) biaxial spin (2-axis), (ii) uniaxial spin (1-axis), and (iii) disc (Disc ) Only three-axis spins, a steady rotation test was performed at a rotation speed ω = 600 r / min to 1000 r / min, and the relationship between mechanical loss and rotation speed was clarified.

Next, a free-run test was performed in which the rotating part 42 during steady rotation at ω = ω _max was separated from the motor 44 and naturally decelerated. Since only the mechanical loss is the factor that slows down the rotation during free run, all the energy stored in the rotating unit 42 is consumed by the mechanical loss. From the relationship between the mechanical loss and rotational speed during steady rotation and the relationship between rotational speed and elapsed time during free run, the measurement lower limit rotational speed ω = of the energy stored in the rotating unit 42 at ω = ω _max The energy E consumed until ω _min is obtained by the following equation.

In this experimental example, the free run start rotational speed ω _max = 900 min ^-1 and the measurement lower limit rotational speed ω _min = 600 due to the motor output limit, the torque tachometer measurement accuracy limit, and the electromagnetic clutch disengagement transmission speed limit. The storage energy E in three cases was calculated in the same manner as in the steady rotation test with min ⁻¹ . Thus, the energy stored in the sphere 14s can be extracted by subtracting the stored energy of case (iii) from case (i) or case (ii). In the above analysis example, it has been shown that the storage energy doubles due to the biaxial rotation in a complete sphere, but the sphere 14s used in this experimental example is not a complete sphere due to the influence of mounting parts, As shown in FIG. 12, since the moment of inertia has anisotropy, the moment of inertia is not doubled but is 1.78 times in the analysis.

(3) Experimental results Mechanical loss was greatest when biaxial spin was used. This is presumably because the gear loss increased because the number of gears and bearings operated in the biaxial spin is three more than in the case of single-axis rotation or a disk alone. In addition, it can be seen that there is no significant difference between the uniaxial rotation and the disk alone, and the influence of the disk windage is dominant.

  FIG. 13 shows a comparison between the measured value and the analytical value of the stored energy calculated by Expression (7). Although the measured value of stored energy was about 10% smaller than the analytical value for both uniaxial spin and biaxial spin, the ratio of the stored energy was in agreement with the analytical value (1.78 times). From this, it was confirmed that the storage energy can be improved in principle by the biaxial rotation of the sphere 14s.

[Second Embodiment]
Next, a second embodiment will be described. FIG. 14 is a schematic diagram showing configurations of the flywheel device 50 and the energy storage device 52 according to the present embodiment. In addition, in order to make an explanation easy to understand, in FIG. 14, the outer sphere 60 and the low-viscosity fluid M are drawn in a cross-sectional view.

  The flywheel device 50 according to the present embodiment includes a rotating body 54 that stores kinetic energy by rotating, and a rotating body holding that rotatably holds the rotating body 54 about the x-axis and y-axis that are two-direction rotating shafts. And a mechanism 56. The energy storage device 52 according to the present embodiment includes a flywheel device 50 and a conversion device (power converter) 58 that performs mutual conversion between electric energy and kinetic energy of the rotating body 54.

  Similar to the first embodiment, in this embodiment, the x-axis and the y-axis both pass through the center of gravity G of the rotating body 54 and are orthogonal to each other. Note that, similarly to the first embodiment, the x-axis and the y-axis do not necessarily pass through the center of gravity G. In the present embodiment, a sphere is provided as the rotating body 54.

  In the present embodiment, the rotating body holding mechanism 56 includes an outer shell sphere 60 that covers the rotating body 54 so as to form a fixed interval with the outer surface of the rotating body 54. A space between the outer sphere 60 and the rotating body 54 is filled with a low-viscosity fluid M (high-pressure carbon dioxide or the like) to be in a supercritical state.

  In the rotating body holding mechanism 56, a pair of induction coils 62a and 62b are arranged on the vertical axis (z axis) passing through the center of the outer shell sphere 60. The induction coils 62a and 62b are disposed on the upper side and the lower side of the outer shell sphere 60, respectively. Further, in the rotating body holding mechanism 56, a pair of induction coils 64 a and 64 b are arranged on a horizontal axis (x axis) passing through the center of the outer shell sphere 60. The induction coils 64 a and 64 b are disposed on both sides of the outer sphere 60.

  In the present embodiment, due to the electric power from the conversion device 58, the rotating body 54 floats by magnetic force and rotates about two axes, the x axis and the z axis, and electric energy is stored as kinetic energy. When the stored kinetic energy is taken out as electric energy, the kinetic energy of the rotating body 14 is converted into electric energy by the converter 58.

  Therefore, energy can be stored by rotating the rotating body 54 around two axes without causing mechanical energy loss.

  As long as the magnetic levitation of the rotating body 54 is not hindered, a configuration in which the low-viscosity fluid M is not provided, and a configuration in which the outer sphere 60 is not provided may be employed.

  Moreover, the hollow part 72 (refer FIG. 2) may be formed in the rotary body 54 similarly to 1st Embodiment.

[Third Embodiment]
Next, a third embodiment will be described. FIGS. 15A and 15B are perspective views for explaining the flywheel device 80 according to the present embodiment. In FIG. 15B, the outer sphere 90 is drawn, and in FIG. 15A, the outer sphere is not drawn.

  The flywheel device 80 according to the present embodiment includes a rotating body 84 that stores kinetic energy by rotating, and a rotating body holding mechanism 86 that rotatably holds the rotating body 84 around two rotational axes. The energy storage device according to the present embodiment includes a flywheel device 80 and a conversion device (not shown) that performs mutual conversion between electrical energy and kinetic energy of the rotating body 84.

  Similar to the first embodiment, in this embodiment, the two rotational axes pass through the center of gravity of the rotating body 84 and are orthogonal to each other. As in the first and second embodiments, the x-axis and y-axis do not necessarily have to pass through the center of gravity G. In the present embodiment, a sphere is provided as the rotating body 84.

  In the present embodiment, a plurality of rotating body holding mechanisms 86 are arranged on the outer shell ball 90 located outside the rotating body 84 and on the inner wall side (inner surface side) of the outer shell ball 90, and support the rotating body 84 while supporting the outer surface. And a plurality of rotating body support portions 92 that form a constant interval between the inner surface of the shell sphere 90 and the outer surface of the rotating body 84. The rotating body support portion 92 includes a spherical abutting body 94 that abuts against the rotating body 84 and an abutting body holding portion 96 that is disposed on the inner wall side of the outer shell sphere 90 and rotatably holds the abutting body 94. Have.

  In this embodiment, a plurality of induction coils 98 extending from a predetermined position on the inner wall side of the outer sphere 90 are arranged. The arrangement position of the induction coil is set in advance so that the rotating body 84 can be rotated by magnetic force around two axes orthogonal to each other.

  In the present embodiment, the rotating body 84 rotates around two rotation axes and stores energy by electric power from a conversion device (not shown). Moreover, when taking out this stored kinetic energy as an electrical energy, the kinetic energy of the rotary body 14 is converted into an electrical energy with a converter. Therefore, energy can be stored without causing mechanical energy loss. Further, it is not necessary to set the supercritical state as in the second embodiment, and the apparatus configuration is greatly simplified.

  In addition, the hollow part may be formed in the rotary body 84 similarly to 1st Embodiment or 2nd Embodiment.

  As described above, the flywheel device according to the present invention, and the energy storage device including the flywheel device, can rotate the rotating body that rotates to rotate around the rotational axis in two directions, and the rotating body that stores kinetic energy by rotating. And a rotary body holding mechanism for holding the flywheel device, the flywheel device capable of storing higher kinetic energy without increasing the size of the device configuration, and the energy storage device including the flywheel device.

DESCRIPTION OF SYMBOLS 10 Flywheel apparatus 12 Energy storage apparatus 14 Rotating body 16 Rotating body holding mechanism 18 Conversion apparatus 32 Hollow part 34 Ellipsoidal body 50 Flywheel apparatus 52 Energy storage apparatus 54 Rotating body 56 Rotating body holding mechanism 58 Conversion apparatus 80 Flywheel apparatus 84 Rotation Body 86 Rotating body holding mechanism x Rotating axis y Rotating axis

Claims (7)

A rotating body that stores kinetic energy by rotating;
A rotating body holding mechanism that rotatably holds the rotating body around two rotation axes;
I have a,
The rotating body is spherical,
The said rotary body holding | maintenance mechanism hold | maintains the said rotary body rotatably with the liquid which made the supercritical state, The flywheel apparatus characterized by the above-mentioned.   The flywheel device according to claim 1, wherein the rotating shafts pass through the center of gravity of the rotating body and are orthogonal to each other. The flywheel device according to claim 1, wherein a hollow portion is formed in the rotating body. The flywheel device according to any one of claims 1 to 3 ,
A conversion device that performs mutual conversion between electrical energy and kinetic energy of the rotating body;
An energy storage device comprising:   A rotating body that accumulates kinetic energy by rotating around two rotational axes;
  By converting electrical energy into kinetic energy that rotates the rotating body in two directions, the rotating body accumulates kinetic energy in two directions, and the rotational energy accumulated in the two directions of the rotating body becomes electrical energy. A conversion device that extracts electrical energy by converting; and
  An energy storage device comprising:   A rotation support shaft extending toward the rotating body;
  A second rotation support shaft extending in a direction intersecting the rotation support shaft;
  A rotational force transmission shaft that meshes with the rotation support shaft and the second rotation support shaft with a gear;
With
  The energy storage device according to claim 5, wherein the rotating support shaft rotates, so that the rotating body rotates around the rotation supporting shaft and rotates around the second rotating support shaft. The rotating body is spherical,
The rotating body holding mechanism is
An outer sphere located outside the rotating body;
A plurality of rotating body support portions that are arranged on the inner surface side of the outer shell sphere and that form a fixed interval between the inner surface of the outer shell sphere and the outer surface of the rotating body while supporting the rotating body; ,
The energy storage device according to claim 5, comprising:

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