JP7555273B2 - Vertical Axis Wind Turbine - Google Patents

Description

This invention relates to a vertical axis wind turbine, and more specifically to a vertical axis wind turbine equipped with an overspeed suppression mechanism.

Conventionally, vertical axis wind turbines have a base with a power generating unit, a rotating unit that rotates around a vertical axis relative to the base, and a number of wind turbine blades (main blades) that are connected to the rotating unit via arms and rotate around the vertical axis. Because their performance is not dependent on wind direction, vertical axis wind turbines have a simple structure and are considered to be suitable for reducing costs.
Recently, it has been shown that by closely arranging small vertical axis wind turbines, it is possible to achieve a higher output per unit of installation area than a wind power plant (wind farm) using large horizontal axis wind turbines, and there are high hopes for the realization of wind farms using small vertical axis wind turbines in promoting the introduction of renewable energy.

On the other hand, vertical axis wind turbines have the disadvantage that braking control is difficult because their performance is independent of wind direction. In other words, with horizontal axis wind turbines, over-rotation can be prevented relatively easily by using tail fins (side fins) to deflect the rotor surface (the surface on which the blades rotate) away from the wind direction (furling), but with vertical axis wind turbines, furling is impossible because they are independent of wind direction. For this reason, the braking mechanism for conventional vertical axis wind turbines is to provide flaps (movable partial blades) or spoilers (projecting plates, etc.) on part of the main wing or part of the arm, which are driven and controlled by hydraulic or pneumatic pressure, etc., to be used as an aerodynamic brake. However, this type of method is complicated and expensive, so it is not practical to apply it to small vertical axis wind turbines.

Therefore, for example, Patent Document 1 proposes a relatively simple method in which a weight is attached to a movable blade that can swing around a movable blade axis that is parallel to the rotation axis of the vertical axis wind turbine, and the rotation speed is controlled by changing the pitch angle (swing angle) of the main blade by the centrifugal force acting on the weight.
Furthermore, Patent Documents 2 and 3 propose a passive air brake that depends on the rotation speed by attaching a movable blade or spoiler to a part of the main blade of a vertical axis wind turbine and opening and closing the movable blade or spoiler by the centrifugal force acting on the movable blade or spoiler.

In addition, although the purpose is not to provide an overspeed suppression mechanism but to improve starting performance, Patent Document 4 proposes a mechanism in which a weight attached to the tip of a movable support rod is hung vertically downward from the lower end of the main wing of a vertical axis wind turbine, and the weight and the movable support rod are swung up by the centrifugal force acting on the weight, and the direction (pitch) of the main wing is changed by the effect of the centrifugal force acting even stronger by this action, thereby switching the characteristics of the wind turbine from drag type to lift type. In this case, if the mass of the weight is adjusted well, it is possible to change the pitch angle of the main wing when the rotation speed exceeds a certain number without a limiting mechanism using an elastic body such as a spring. Therefore, if the initial direction of the main wing is changed by about 90 degrees to be arranged as a lift type at low rotation speed, and the main wing is set to be arranged as a drag type when the rotation speed is high and the operating mechanism is activated by centrifugal force, it is also possible to configure an overspeed suppression mechanism using the method proposed in Patent Document 4.

JP 2007-85182 A JP 2010-261415 A JP 2011-27054 A JP 2013-245564 A

However, in the methods described in Patent Documents 1 to 4, in order to prevent the characteristics of the wind turbine from being impaired when the wind turbine is rotating at low speeds, i.e., to prevent the over-rotation suppression mechanism from working, it is necessary to limit the movement of the weight and movable blades up to a certain rotation speed using an elastic body such as a spring.
However, in the method described in Patent Document 4, when returning from a high rotation speed state to a low rotation speed state, gravity acting on the weight acts as a restoring force, and the swung-up weight itself returns to a vertically downward position; however, without an elastic body such as a spring, the changed orientation of the main wing remains in the orientation after the change and does not return to its initial state.

Ultimately, the methods described in Patent Documents 1 to 4 require a mechanism that uses an elastic body such as a spring to return the movable blade or spoiler to its original state. Furthermore, all of these mechanisms are designed for straight blades, which are equivalent to the main blades of wind turbines, and cannot be applied to main blades of any other shape, such as circular blades. Furthermore, the properties of elastic bodies such as springs change over time, and there are problems with durability.

Furthermore, in the case of an over-speed suppression mechanism that operates solely by centrifugal force, even in strong wind conditions of 30 to 40 m/s or extreme wind conditions of nearly 60 m/s, which have a probability of being experienced once every 50 years, the rotation speed will increase up to a specific maximum rotation speed at which the centrifugal force will stop the over-speed of the wind turbine. Even if it were possible for the over-speed suppression mechanism to operate in such a way that the wind turbine would not exceed a certain rotation speed, repeated high rotation speeds in extremely high wind speeds is not desirable in terms of the structural strength of the wind turbine, and generally the need to increase the strength of the wind turbine at the design stage results in increased costs.

For example, as shown in Figure 18, in terms of power generation performance, it seems desirable to maintain high power generation performance even in strong wind conditions, but in reality, the ideal operation of the over-speed suppression mechanism is to suppress the rotation speed of the wind turbine in strong wind conditions to a state sufficiently lower than the rated rotation speed (maximum rotation speed). Note that Figure 18 shows the power curves of two wind turbines, R with over-speed control and S without it. For ease of calculation, in the case of over-speed control R, it is assumed that the generated power P is a constant value (980.8 W) at a wind speed of 18 m/s. In addition, since the occurrence rate of wind speeds of 31 m/s or more can be considered to be essentially 0, it is assumed that power generation at speeds of 31 m/s or more is not performed.

In the methods described in Patent Documents 1 to 4, the weight is basically driven only by centrifugal force, so the wind speed dependency of the wind turbine equipped with them is expected to have characteristics similar to those shown in Figure 18, and it is expected to rotate at high speeds in strong wind conditions.

This invention was made in consideration of the above circumstances, and aims to provide a vertical axis wind turbine that can be applied to vertical axis wind turbines with main blades of any shape, is highly durable, has a simple structure, and is equipped with an over-speed suppression mechanism that suppresses the wind turbine rotation speed in strong wind conditions to a level sufficiently lower than the rated rotation speed (maximum rotation speed).

In order to achieve the above object, the present invention provides a vertical axis wind turbine comprising a base having a power generating unit, a rotating unit which rotates about a vertical axis relative to the base, and a plurality of wind turbine blades which are connected to the rotating unit via an arm and rotate about the vertical axis, wherein the arm has a movable unit for suppressing over-rotation which is rotatable about a rotation axis which connects the rotating unit and the wind turbine blades, and an over-rotation suppression guide is provided at a lower part of the movable unit which tilts the movable unit about the rotation axis by the action of centrifugal force generated when the vertical axis wind turbine rotates, thereby increasing the projected area of the movable unit as seen from the direction of rotation of the wind turbine , and which returns the movable unit to its initial state when the vertical axis wind turbine stops rotating (claim 1).

By configuring it in this way, the movable part provided on the arm tilts around the rotation axis as the angle (hereinafter referred to as the inclination angle) between the over-rotation suppression inducer and the vertical direction changes due to the rotational component of the centrifugal force acting on the over-rotation suppression inducer when the wind turbine rotates, and a braking force due to aerodynamic force acts on the movable part. In addition, when the wind turbine stops rotating, the movable part automatically returns to its original initial state. Furthermore, it is possible to eliminate the need for elastic bodies such as springs, whose characteristics may change over time.

In the present invention, it is preferable that the mounting positions of the arm and the wind turbine blade and the mounting position of the rotation shaft of the movable part are provided on the same line (claim 2).
Such a configuration improves the structural strength of the arm against tension and compression acting on the arm.

In the present invention, it is preferable that the over-rotation suppressing inductor is provided at a position offset toward the leading edge or trailing edge in the rotation direction with respect to the rotation shaft at the lower part of the movable portion (claim 3).
With this configuration, the inclination angle between the over-rotation suppression inductor and the vertical direction increases, and a large aerodynamic braking force acts on the movable portion.

In the present invention, it is preferable that at least the movable part of the arm including the wind turbine blade and the movable part is formed into an airfoil cross section having a hollow part of the same shape (claim 4).
With this configuration, the wind turbine blade and the movable part can be made of the same material, and the arm having the movable part and the wind turbine blade can be made lighter in weight.

In addition, in this invention, the over-rotation suppression guide is preferably composed of a support rod connected to the lower part of the movable part and a weight attached to the tip of the support rod (claim 5), or is formed into an airfoil cross-sectional shape with a hollow part of the same shape as the wind turbine blade (claim 6).

In this case, by forming the over-rotation suppression inducer into an airfoil-shaped cross section with a hollow portion of the same shape as the wind turbine blade, a rotational component is generated by aerodynamic force, i.e., horizontal lift, and the propulsive force of the wind turbine can be increased. Also, when the moving part is formed into the same shape as the wind turbine blade, the over-rotation suppression inducer is formed into the same shape as the moving part, making it possible to use an over-rotation suppression inducer of the same shape as the moving part.

In addition, in this invention, the arm comprises a first fixed part connected to the rotating part, a second fixed part connected to the wind turbine blade, and the movable part disposed between the first fixed part and the second fixed part, and it is preferable that the movable part and at least the first fixed part are rotatably connected by a rotating shaft protruding from one of them and a bearing provided on the other (claim 7).

This configuration allows the moving part to rotate smoothly, and the over-rotation suppression guide, which has been tilted around the axis by the centrifugal force caused by the rotation of the wind turbine, can be smoothly returned to its original position as the centrifugal force decreases.

In addition, in this invention, it is preferable to provide a stopper on the movable part or on the movable part side of the arm, and to support the movable part in a horizontal position or with the leading edge side in the direction of rotation of the wind turbine facing upward in the initial state by the stopper (claim 8).

This configuration makes it possible to prevent the movable part from tilting forward in the initial state when the over-rotation suppression guide is provided on the leading edge side of the rotational direction relative to the rotating shaft, and also to prevent the movable part from tilting backward in the initial state when the over-rotation suppression guide is provided on the trailing edge side of the rotational direction relative to the rotating shaft.

As configured as described above, this invention can be applied to vertical axis wind turbines with main blades of any shape, does not require elastic bodies such as springs, is highly durable, has a simple structure, and can suppress the wind turbine rotation speed in strong wind conditions to a level sufficiently lower than the rated rotation speed (maximum rotation speed).

1A is a schematic side view showing a state in which the vertical axis wind turbine according to the first embodiment of the present invention is used, and FIG. 1B is an enlarged sectional view of a portion I in FIG. FIG. 2 is a perspective view showing a fixed state of the wind turbine blade and the rotating part in the present invention. FIG. 2B is a cross-sectional view taken along line II-II in FIG. 2A. FIG. 2 is a cross-sectional view of the wind turbine blade, the arm, and the movable part in the present invention. FIG. 2 is a schematic plan view showing the arm, the movable portion, the weight constituting the over-rotation suppression guide, and the wind turbine blade in the present invention. 5A is an enlarged cross-sectional view of part III in FIG. 4, and FIG. 5B is an enlarged cross-sectional view taken along line IV-IV in FIG. FIG. 2 is a perspective view showing the movable part and the weight in a low rotation speed state of the wind turbine. FIG. 1 is a perspective view showing the movable part and the weight in a high rotation speed state of the wind turbine. FIG. 4 is a cross-sectional view showing the mounting state of the movable part and the weight. 13 is a cross-sectional view showing another mounting state of the movable part and the weight. FIG. 5A and 5B are a schematic plan view and a schematic side view showing the relationship of forces acting on an over-rotation suppression mechanism using a weight; FIG. 11 is a perspective view showing a movable part in a low rotation speed state of a wind turbine and an aileron constituting an over-rotation suppression guide in a second embodiment of the vertical axis wind turbine according to the present invention. FIG. 2 is a perspective view showing the movable parts and the ailerons of the wind turbine in a high rotation speed state. FIG. 11 is a cross-sectional view showing an example of a mounting state of a movable portion and an aileron in the second embodiment. FIG. 1 is a schematic side view showing another embodiment of the vertical axis wind turbine according to the present invention. FIG. 2 is a schematic plan view showing a specific example of a wind turbine according to a first embodiment using the weight according to the first embodiment. 4 is a graph showing torque characteristics of the wind turbine of Example 1. 1 is a graph showing the wind speed dependence of the rotation speed and the inclination angle of a movable part of the wind turbine of Example 1. 13 is a graph showing torque characteristics of a wind turbine according to Example 2, which uses the aileron of the second embodiment. 13 is a graph showing the wind speed dependence of the rotation speed and the inclination angle of the movable part of the wind turbine of Example 2. 4 is a graph showing power curves with and without conventional overspeed control.

The following describes in detail the embodiment of the present invention with reference to the attached drawings.

First Embodiment
As shown in FIG. 1 , the vertical axis wind turbine 1 (hereinafter simply referred to as wind turbine 1) according to the present invention comprises a base 2 having a power generating unit, a rotating unit 3 which rotates around a vertical axis Z relative to the base 2, and a plurality of (e.g., three) wind turbine blades 10 which are connected to the rotating unit 3 via arms 20 and rotate around the vertical axis Z.

The base 2 is the foundation of the wind turbine 1. The base 2 has legs 2a formed at a predetermined height to position the wind turbine blades 10 of the wind turbine 1 at a predetermined height from the installation surface 4, and a housing section 2b that houses the power generation section (not shown).

When the wind turbine blade 10 receives wind, the rotating part 3 rotates around a vertical axis Z relative to the base 2. As shown in Figures 2A and 2B, the rotating part 3 includes a rotating hub 3a to which the wind turbine blade 10 is attached and rotates, and a shaft part 3b that serves as the rotation axis of the rotating hub 3a and is rotatably supported within the housing part 2b of the base 2.

The wind turbine blades 10 are attached via an arm 20 that is connected to an arm base 5 that is supported by the rotating hub 3a of the rotating part 3 and extends horizontally, and rotate together with the rotating part 3. In this embodiment, multiple wind turbine blades 10 (e.g., three) are provided at equal intervals around the vertical axis Z. Note that the number of wind turbine blades 10 is not limited to this.

In this case, as shown in Figures 2A and 2B, the arm base 5 is fixed by screwing together the upper and lower flanges 3a1, 3a2 of the rotating hub 3a and the fixing bolt 6 that passes through the arm base 5 and a nut (not shown).
On the other hand, the arm 20 is formed of an aluminum extruded material having hollow portions 10a-10g with the same cross-sectional shape as the extension portion 11, main wing 12, and curved portion 13 that form the wind turbine blade 10 described later, and has a streamlined cross section with a curved leading edge and a pointed trailing edge, and the hollow portions 10a-10g are defined by a plurality of ribs 10h as shown in Fig. 3. Also, as shown in Fig. 2B, the rib 10h on the opening side of one end is notched, and the other end of the arm base 5 is inserted into this notch 10i, and a nut (not shown) is screwed onto a connecting bolt 6a that passes through a through hole 5a provided in the arm 20 and the arm base 5, thereby connecting the arm base 5 and the arm 20.

The wind turbine blade 10 is fixed to the arm 20 by a fixing member 7 on the side closer to the vertical axis Z of the wind turbine 1. It has a pair of extension parts 11 extending from the rotating part 3 so that the distance between them increases with distance from the vertical axis Z, a main wing 12 extending along a direction approximately parallel to the vertical axis Z of the wind turbine blade 10, and a curved part 13 that connects the extension parts 11 and the main wing 12 in a curved shape by a connecting member (not shown). Specifically, the wind turbine blade 10 is formed in an approximately triangular shape that is approximately symmetrical with respect to the horizontal axis X in a side view. Note that the approximately triangular shape referred to here means that the overall shape of the wind turbine blade 10 is close to a triangle, and includes a triangle with curved corners and one with any of the three sides curved.

The extension 11, main wing 12, and curved portion 13 that form the wind turbine blade 10 are formed from aluminum extrusions with hollows 10a-10g of the same cross-sectional shape. As shown in FIG. 3, the blade has a streamlined cross section with a curved leading edge and a sharp trailing edge, and the hollows 10a-10g are partitioned by multiple ribs 10h. Note that FIG. 3 shows a case in which there are seven hollows 10a, 10b, 10c, 10d, 10e, 10f, and 10g formed by six ribs 10h, but the shape and number of the hollows are arbitrary. In addition, the wind turbine blade 10 (extension 11, main wing 12, curved portion 13) is specifically set to a length from the leading edge to the trailing edge of approximately 380 mm, and a maximum height of the front and back surfaces of approximately 91 mm, but this is not necessarily limited to this.

The fixing member 7 that fixes the wind turbine blade 10 includes a pair of outer brackets 7a bent at an obtuse angle and having abutment pieces that abut against the outer surface of the base end side of the extension portion 11 of the wind turbine blade 10 and the upper or lower surface of the arm 20, a pair of inner brackets 7b bent at an acute angle and having abutment pieces that abut against the inner surface of the base end side of the extension portion 11 and the upper or lower surface of the arm 20, and a fixing bolt 7c and a fixing nut 7d that fix the extension portion 11 to the arm 20 with the pair of outer brackets 7a and inner brackets 7b sandwiching the extension portion 11 and the arm 20, respectively.

In this case, the outer bracket 7a and the inner bracket 7b are formed from aluminum casting, and the contact surfaces of the contact pieces of the outer bracket 7a and the inner bracket 7b are formed in a shape similar to the streamlined outer surfaces of the extension 11 and the arm 20. The contact pieces are provided with a through hole (not shown) through which the fixing bolt 7c passes. In addition, the front and back surfaces of the hollow portions 10b, 10d, and 10f of the arm 20 are provided with a through hole (not shown) through which the fixing bolt 7c passes.

The arm 20 has a movable part 23 for suppressing over-rotation that can rotate around a rotation axis 24 that connects the rotating part 3 and the main blade 12 of the wind turbine blade 10, and an over-rotation suppression guide 30 is provided at the bottom of the movable part 23. The over-rotation suppression guide 30 tilts the movable part 23 around the rotation axis 24 due to the action of centrifugal force generated when the wind turbine 1 rotates, and returns the movable part 23 to its initial state when the wind turbine 1 stops rotating.

The arm 20 is composed of a first fixed part 21 (hereinafter referred to as the first fixed arm 21) connected to the rotating part 3, a second fixed part 22 (hereinafter referred to as the second fixed arm 22) connected to the main wing 12 via a connecting member 25, and a movable part 23 (hereinafter referred to as the movable arm 23) disposed between the first fixed arm 21 and the second fixed arm 22. The horizontally extending rotation shaft 24 provided on the movable arm 23 is fitted into bearings 26 (e.g., rolling bearings) provided on the first fixed arm 21 and the second fixed arm 22, so that the movable arm 23 is rotatably connected. The first fixed arm 21, the second fixed arm 22, and the movable arm 23 constituting the arm 20 are formed into an airfoil cross-sectional shape having a hollow portion of the same shape as the wind turbine blade 10 (see FIG. 3). In order to make the following explanation easier to understand, the hollow portions of the first fixed arm 21, the second fixed arm 22, and the movable arm 23 and the hollow portion of the wind turbine blade 10 are given the same reference numerals.

The connecting member 25 that connects the main wing 12 and the second fixed arm 22 is composed of a pair of right-angle brackets 25a that abut against the inner surface of the main wing 12 and the upper or lower surface of the second fixed arm 22, a connecting bolt 25b that passes through the vertical abutment piece of the right-angle bracket 25a and the main wing 12, the horizontal abutment piece and the second fixed arm 22, and a nut 25c that is screwed onto the connecting bolt 25b, as shown in FIG. 1(b).

In this case, the rotating shaft 24 passes through the hollow portion 10e of the movable arm 23 and is fixed by washers 24a inserted into both ends of the hollow portion 10e, and its protruding portion is rotatably supported by bearings 26 fixed by washers 27 inserted into the hollow portion 10e provided in the first fixed arm 21 and the second fixed arm 22 (see Figures 4A(a) and 4A(b)).

In the above explanation, the movable arm 23 is provided with a rotating shaft 24, and the first fixed arm 21 and the second fixed arm 22 are provided with bearings 26, but this structure is not necessarily required. For example, the first fixed arm 21 and the second fixed arm 22 may have a rotating shaft 24 protruding therefrom, and the movable arm 23 may have a bearing 26. Alternatively, the movable arm 23 and at least the first fixed arm 21 may be rotatably connected to each other by a rotating shaft 24 protruding from one of them and a bearing 26 provided on the other.

By configuring as described above, the mounting positions of the first fixed arm 21, the second fixed arm 22, and the main wing 12 can be aligned with the mounting position of the rotation shaft 24 of the movable arm 23. This increases the structural strength of the arm 20 against tension and compression acting on the arm 20.

The over-rotation suppression inducer 30 is composed of a support rod 31 connected to the lower part of the movable arm 23 at a biased position toward the front edge side in the rotation direction relative to the rotation shaft 24, and a spherical weight 32 attached to the tip of the support rod 31. Note that the weight 32 does not necessarily have to be spherical, and may be any shape other than spherical.

The over-rotation suppression inducer 30 can be attached to the movable arm 23, for example, by providing a male threaded portion 31a at the base end of the support rod 31 and screwing the male threaded portion 31a into a screw hole 28a provided in a washer 28 inserted into the hollow portion 10c of the movable arm 23, as shown in Figure 7A.
Also, as shown in FIG. 7B, the support rod 31 may be inserted through the through holes 23a, 23b provided in the upper and lower parts of the hollow portion 10c of the movable arm 23, and a nut 35 may be screwed to the male threaded portion 31a provided on the protruding portion of the support rod 31 via a spacer 33 and a washer 34, thereby attaching the over-rotation suppression guide 30 to the movable arm 23.

Note that by connecting the over-rotation suppression inducer 30 to the lower part of the movable arm 23 at a position offset toward the front edge in the direction of rotation relative to the rotating shaft 24, the movable arm 23 may be tilted forward in the initial state, which may cause problems with the rotation of the wind turbine 1. To avoid this, for example, a stopper 40 is provided protruding from the end of the first fixed arm 21 on the side of the movable arm 23 to engage the movable arm 23 so that the projected area of the movable arm 23 as seen from the direction of rotation of the wind turbine is almost minimized, and the initial state of the movable arm 23 is supported in a horizontal position, or in an upward position with an angle α (inclination angle α) between the support rod 31 and the vertical direction at a small angle (approximately 1 to 5 degrees).

Next, the operation of the wind turbine 1 having the over-rotation suppression mechanism using the weight 32 configured as above will be described with reference to Figs.
When the wind speed increases and the wind turbine 1 rotates at a high speed, the rotational direction component F1 of the centrifugal force Fc acting on the weight 32 increases. At this time, a net moment acts on the movable arm 23 in a downward direction (a direction in which the leading edge moves downward) due to the sum of (1) the moment due to the aerodynamic force acting on the movable arm 23 around the rotation axis of the movable arm 23 (moment around the mounting position due to drag and lift FL), (2) the moment due to gravity FG1 of the movable arm 23, (3) the moment due to the aerodynamic force acting on the weight 32 and the support rod 31 (drag Fr), and (4) the moment due to gravity FG2 of the weight 32 and the support rod 31 {(1)+(2)+(3)+(4)}. If the head-up moment due to (5) the rotational direction component F1 of the centrifugal force Fc acting on the weight 32 increases compared to this net moment, the inclination angle α increases.

As a result, as shown in Figures 6 and 8(b), the inclination angle α becomes very large, the projected area of the movable arm 23 as seen from the direction of rotation of the wind turbine becomes large, and a large braking force F2 due to aerodynamic forces acts on the movable arm 23, suppressing over-rotation of the wind turbine 1. However, in strong wind conditions, even at low rotation speeds, the moment of aerodynamic forces acting on the movable arm 23 (1) becomes large in the lifting direction (the direction in which the leading edge moves upward), and becomes dominant compared to the rotation moment in the lifting direction due to the centrifugal force Fc acting on the weight 32 (5), generating a large braking force F2. As a result, in strong wind conditions, the wind turbine 1 is suppressed to a low rotation speed.

The rotating shaft 24 of the movable arm 23 is at a right angle (or may be at a slight angle) to the wind turbine rotation axis (vertical axis Z), and the rotating shaft 24 is supported by bearings 26, so that when the weight 32 lifted by centrifugal force decreases and returns to its original position, the movable arm 23 can also naturally return to its original state, eliminating the need for an elastic body such as a spring.

In the above embodiment, the case where the over-rotation suppression inductor 30 is connected to a biased position on the leading edge side in the rotation direction with respect to the rotating shaft 24 at the lower part of the movable arm 23 has been described, but the over-rotation suppression inductor 30 may be connected to a biased position on the trailing edge side in the rotation direction with respect to the rotating shaft 24. In this case, the movable arm 23 may be inclined backward in the initial state, which may cause an impediment to the rotation of the wind turbine 1. In order to avoid this, a stopper (not shown) may be provided as above, and the initial state of the movable arm 23 may be in a horizontal position.
In addition, if the movable arm 23 is tilted in the head-up direction (the direction in which the leading edge moves upward) in the initial state, when the movable arm 23 is tilted, a lift force acts vertically upward, which is desirable because it reduces the gravity of the wind turbine blade 10 and the arm 20 (first fixed arm 21, second fixed arm 22, movable arm 23).

Second Embodiment
The wind turbine 1 of the second embodiment is provided with an auxiliary blade 36 formed in an airfoil cross-sectional shape having a hollow portion of the same shape as the wind turbine blade 10, the first fixed arm 21, the second fixed arm 22, and the movable arm 23, instead of the weight 32 of the over-rotation suppression inducer 30 of the first embodiment.

The aileron 36 in the second embodiment is formed in an airfoil cross-sectional shape having a hollow portion of the same shape as the wind turbine blade 10, so in the following explanation, the hollow portions of the aileron 36 and the wind turbine blade 10 are denoted by the same reference numerals.
The over-rotation suppression inducer 30A in the second embodiment is composed of an aileron 36 connected via a connecting rod 37 attached to a biased position toward the leading edge side in the rotation direction relative to the rotation shaft 24 at the lower part of the movable arm 23.

The over-rotation suppression induction 30A is attached to the movable arm 23, for example, as shown in Fig. 11, by providing male threads 37a at both ends of a connecting rod 37, screwing the male threads 37a at one end into a screw hole 38a of a washer 38 inserted into the upper end side of the hollow portion 10c of the aileron 36 to protrude above the aileron 36, passing the connecting rod 37 through the through holes 23a and 23b provided at the upper and lower parts of the hollow portion 10c of the movable arm 23, and screwing a nut 35 to the male threads 37a provided on the protruding part via a spacer 33 and a washer 34, thereby attaching the over-rotation suppression induction 30A to the movable arm 23. Here, the over-rotation suppression induction 30A is attached to the movable arm 23 using one connecting rod 37, but in order to provide strength, it is better to attach the over-rotation suppression induction 30A to the movable arm 23 in the same manner as above using multiple connecting rods 37.
Incidentally, without using the connecting rod 37, the aileron 36 may be attached directly to the underside of the movable arm 23 via a bracket in the same manner as when the main wing 12 and the second fixed arm 22 are connected.

In the second embodiment, an aileron 36 is used instead of the weight 32. As shown in Figs. 9 and 10, in the case of the weight 32, only drag acts as an aerodynamic force, resulting in some loss of the wind turbine 1. However, in the case of the aileron 36, depending on the rotation azimuth angle (azimuth angle) of the wind turbine blade 10, a rotation direction component F1 is generated by the aerodynamic force Fa (lift force directed in the horizontal direction), which becomes the driving force of the wind turbine 1. Therefore, in a low rotation speed state, it contributes to improving the performance of the wind turbine 1. In addition, it has an advantage of being more designable than the weight 32. The chord length and shape of the aileron 36 do not need to be the same as those of the movable arm 23, but using the same shape as the movable arm 23 for the aileron 36 can reduce the cost required for manufacturing the weight 32.
In the second embodiment, other parts are the same as those in the first embodiment, so the same parts are given the same reference numerals and the description thereof is omitted.

In the wind turbine 1 of the second embodiment configured as described above, when the wind turbine 1 is in a high rotation speed state, the lifting moment due to the rotation direction component F1 of the centrifugal force acting on the aileron 36 becomes large, and the inclination angle α increases. As a result, a large braking force F2 due to aerodynamic forces acts on the movable arm 23, suppressing over-rotation of the wind turbine 1. However, in a strong wind state, even in a low rotation speed state, the moment of the aerodynamic forces acting on the movable arm 23 becomes large in the lifting direction (the direction in which the leading edge moves upward), and becomes dominant compared to the rotation moment in the lifting direction due to the centrifugal force acting on the aileron 36, generating a large braking force F2 . As a result, in a strong wind state, the wind turbine 1 is suppressed to a low rotation speed.

<Other embodiments>
(1) In the above embodiment, the rotation axis 24 of the movable arm 23 is aligned on the same line as the mounting positions of the first fixed arm 21 and the second fixed arm 22 and the main wing 12. However, the rotation axis 24 of the movable arm 23 may be positioned parallel to the mounting positions of the first fixed arm 21 and the second fixed arm 22 and the main wing 12.
In addition, the movable arm 23 may be plate-shaped, but is preferably formed into an airfoil cross-sectional shape having a hollow portion of the same shape as the wind turbine blade 10. The first fixed arm 21 and the second fixed arm 22 may have any shape.

(2) In the above embodiment, the fixed arms are the first fixed arm 21 and the second fixed arm 22. However, the fixed arm may be the first fixed arm 21 only, and the movable arm 23 may be rotatably connected by a rotating shaft 24 fixed (protruding) to the main wing 12 and a bearing 26 provided on the movable arm 23. Also, the fixed arm may be the second fixed arm 22 only, and the movable arm 23 may be rotatably connected by a rotating shaft 24 protruding from either the movable arm 23 or the second fixed arm 22 and a bearing 26 provided on the other.

(3) In the above embodiment, the movable arm 23 is disposed between the first fixed arm 21 and the second fixed arm 22, but the entire arm may be a movable arm.

(4) In the above embodiment, a butterfly-type wind turbine was described in which the wind turbine blades are formed in a substantially triangular shape with a pair of extensions 11 extending from the rotating part 3, a main wing 12 extending in a direction substantially parallel to the vertical axis Z of the wind turbine blade 10, and a curved part 13 that connects the extensions 11 and the main wing 12 in a curved shape by a connecting member (not shown). The wind turbine according to the present invention is not limited to this, and can also be applied to an H-type Darrieus wind turbine 1A in which a vertical main wing 12 is attached to the tip of a horizontal arm 20 as shown in FIG. 12(a) (in this case, the first fixed arm and the second fixed arm are assumed to be constrained to each other in some way), an H-type Darrieus wind turbine 1B (diagonal arm) in which a vertical main wing 12 is attached to the tip of a diagonal arm 20 as shown in FIG. 12(b), or a Darrieus wind turbine 1C in which an arc-shaped main wing 12 is attached to the tip of a horizontal arm 20 as shown in FIG. 12(c).

Next, we will explain an example (characteristics calculation example) of a wind turbine equipped with an over-rotation suppression mechanism using the weight 32 and an over-rotation suppression mechanism using an aileron 36.

Example 1
Example 1 is an example of calculation of characteristics of a wind turbine equipped with a movable arm type over-rotation suppression mechanism using a weight according to the first embodiment.
An example of calculation of wind turbine characteristics when the movable arm type over-rotation suppression mechanism using a weight of the first embodiment shown in Figs. 5 and 6 is applied to a butterfly type wind turbine having a diameter of 14 m and a height of 14.2 m as shown in Fig. 13 is shown below.

The calculations were based on the Blade Element Momentum method (BEM). The airfoil type was assumed to be the symmetrical NACA0018 type of the National Advisory Committee for Aeronautics, and its aerodynamic data (lift coefficient, drag coefficient, and moment coefficient) were used. The shape of the wind turbine blades is the same as in Figure 1, with a triangular loop as the main wing, and a horizontal arm was assumed to be installed in the center as a reinforcement. However, the cross section of the horizontal arm (fixed arm and movable arm) was also assumed to be the same NACA 0018 airfoil type as the main wing, and the chord length was also assumed to be the same length (375 mm). The number of blades was assumed to be three. The generator was assumed to be a permanent magnet type multi-pole generator rated at 10 kW, and it was also assumed to be equipped with a 7.5x speed-up gearbox.

Figures 14 and 15 are examples of calculation results, and are the results when a large annual power generation amount (21,987 kWh at an annual average wind speed of 3.7 m/s) is obtained under the assumed load torque of the gearbox-equipped generator. In this case, the movable arm 23 is installed as part of the horizontal arm 20 from 5.5 m to 6.8 m in the radial direction from the center of rotation of the wind turbine (i.e., the length of the movable arm 23 is 1.3 m). The weight 32 is located at a position 6.15 m in the radial direction from the center of rotation C of the wind turbine (i.e., the center position of the span of the movable arm 23). It is assumed that the mass of the weight 32 is 5 kg (a stainless steel ball with a diameter of 106 mm), the length of the weight support rod 31 is 0.5 m, and it is suspended at a position 30% of the chord length from the leading edge of the movable arm 23. The main wing 12 and horizontal arm 20 (first and second fixed arms 21, 22 + movable arm 23) are attached to a hub (not shown) at the rotation center C of the wind turbine so that the reference line shown by the dashed line extending in the radial direction in Figure 4 coincides with 58% of the wing chord length. The horizontal arm 20 is set to an initial inclination angle of 2 degrees in advance so that it is slightly raised in the initial state.

As shown in the torque characteristics in Figure 14, regardless of the wind speed (V), the torque curve of the wind turbine is expected to intersect with the load torque curve of the geared generator at a maximum rotation speed of 41.7 rpm or less. Also, as shown in the wind speed dependence of the average rotation speed and average inclination angle at the predicted operating point in Figure 15, as the wind speed increases, the average inclination angle of the movable arm increases and the rotation speed of the wind turbine decreases.

Example 2
Example 2 is an example of calculation of characteristics of a wind turbine equipped with a movable arm type over-rotation suppression mechanism using an aileron according to the second embodiment.
Figures 16 and 17 show examples of calculations of wind turbine characteristics when the movable arm type over-speed suppression mechanism using the aileron 36 shown in Figures 9 and 10 is applied to a butterfly type wind turbine with a diameter of 14 m and a height of 14.2 m. The calculation method and assumed generator and gearbox are the same as those assumed in the calculations of Figures 14 and 15, except that the weight is changed to an aileron.

The results shown in Figures 16 and 17 are for an annual power generation of 21,787 kWh at an annual average wind speed of 3.7 m/s. The movable arm 23 is installed from 5.5 m to 6.8 m in the radial direction from the center of rotation of the wind turbine (i.e., the length of the movable arm 23 is 1.3 m). The aileron 36 is located at a position of 6.15 m in the radial direction from the center of rotation of the wind turbine (i.e., the center of the span of the movable arm 23). The aileron 36 is located vertically downward from the center of the movable arm 23 over a length of 50 mm to 700 mm (the aileron length is 650 mm), and its mass is 4.872 kg (assuming an aluminum extrusion). It is assumed that the center of gravity position in the aileron cross section (42.93% from the leading edge) is suspended at a position 30% of the chord length (112.5 mm) from the leading edge of the movable arm 23. The main wing 12 and horizontal arm 20 (first and second fixed arms 21, 22 + movable arm 23) are attached to a hub (not shown) at the rotation center C of the wind turbine so that the reference line shown by the dashed line extending in the radial direction in Figure 4 coincides with 58% of the wing chord length. Note that it is assumed that the horizontal arm 20 is inclined at a 1.2 degree angle in advance so that it is slightly raised in the initial state.

As shown in the torque characteristics of FIG. 16, almost the same as in the case of using the weight in FIG. 14, the torque curve of the wind turbine is expected to intersect with the load torque curve of the gearbox-equipped generator at a maximum rotation speed of 42.3 rpm or less, regardless of the wind speed. Also, as in the case of using the weight in FIG. 15, in the wind speed dependence of the average rotation speed and average inclination angle at the predicted operating point shown in FIG. 17, it is expected that as the wind speed increases, the average inclination angle of the movable arm 23 will increase and the rotation speed of the wind turbine will decrease.

From Figures 15 and 17, it is expected that in either case of weight 32 or aileron 36, even in extreme winds of 40 m/s or more, or even 60 m/s, the wind turbine will rotate at a low rotation speed of less than half the maximum rotation speed (approximately 42 rpm).

Reference Signs List 1, 1A, 1B, 1C Wind turbine 2 Base 3 Rotating portion 10 Wind turbine blade 11 Extension portion 12 Main wing 13 Curved portion 20 Arm 21 First fixed arm (first fixed portion)
22 Second fixed arm (second fixed portion)
23 Movable arm (movable part)
24 Rotating shaft 26 Bearings 30, 30A Over-rotation suppression induction body 31 Support rod 32 Weight 36 Ailerons 37 Connecting rod 40 Stopper α Inclination Fa Aerodynamic force F1 Rotation direction component F2 Braking force C Rotation center X Horizontal axis Z Vertical axis

Claims (8)

A vertical axis wind turbine comprising: a base having a power generating unit; a rotating unit that rotates about a vertical axis relative to the base; and a plurality of wind turbine blades that are connected to the rotating unit via arms and rotate about the vertical axis,
The arm has a movable part for suppressing over-rotation that can rotate around a rotation axis that connects the rotating part and the wind turbine blades, and an over-rotation suppression guide is provided at a lower part of the movable part, which tilts the movable part around the axis of the rotation axis by the action of centrifugal force generated when the vertical axis wind turbine rotates , thereby increasing the projected area of the movable part as seen from the wind turbine rotation direction , and returns the movable part to its initial state when the vertical axis wind turbine stops rotating.
A vertical axis wind turbine. 2. The vertical axis wind turbine according to claim 1,
A vertical axis wind turbine characterized in that the mounting positions of the arm and the wind turbine blades and the mounting position of the rotation shaft of the movable part are provided on the same line. In the vertical axis wind turbine according to claim 1 or 2,
The vertical axis wind turbine, characterized in that the over-rotation suppression inductor is provided at a position offset to a leading edge side or a trailing edge side in a rotation direction with respect to the rotation shaft at a lower part of the movable part. 4. The vertical axis wind turbine according to claim 1,
a vertical axis wind turbine, characterized in that at least the movable part of the arm including the wind turbine blade and the movable part is formed into an airfoil cross-sectional shape having a hollow part of the same shape. 5. The vertical axis wind turbine according to claim 1,
The vertical axis wind turbine, characterized in that the over-rotation suppression inductor is composed of a support rod connected to a lower part of the movable part and a weight attached to a tip of the support rod. 5. The vertical axis wind turbine according to claim 1,
A vertical axis wind turbine, characterized in that the over-rotation suppression guide is formed in an airfoil cross-sectional shape having a hollow portion of the same shape as the wind turbine blade. 7. The vertical axis wind turbine according to claim 1,
the arm comprises a first fixed part connected to the rotating part, a second fixed part connected to the wind turbine blade, and the movable part disposed between the first fixed part and the second fixed part, the movable part and at least the first fixed part being rotatably connected to each other by a rotating shaft protruding from one of them and a bearing provided on the other. In the vertical axis wind turbine according to any one of claims 1 to 7,
a stopper is provided on the movable part or on the movable part side of the arm, and the stopper supports the movable part in an initial state in a horizontal position or in a position in which a front edge side in a rotation direction of the wind turbine faces upward.

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