JP2011239510A - Power generator in tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generator in a tire capable of obtaining high power by efficiently generating power from a state of low speed rotation of a tire.SOLUTION: The power generator in the tire is attached to a tread portion in a tire air chamber. The power generator in the tire includes a rotational body that is partially formed by a magnet so that a center of rotation differs from the center of gravity and that is rotated in accordance with a change in force applied to the tread portion during traveling of a vehicle, a coil unit that faces the rotational body and that generates power by generating a voltage by an electromagnetic induction action of magnetic flux emitted from the magnet, a power storage unit that stores the voltage, and a control unit that controls the power generated by the coil unit in response to the change in force applied to the tread portion.

Description

  The present invention relates to an in-tire power generator, and more particularly to an in-tire power generator capable of obtaining high power by controlling power generation.

  Conventionally, power is supplied to the device when the tire monitoring is performed by installing a wireless device such as a TPMS (tire pressure monitoring system) that detects the temperature and pressure inside the tire in the tire chamber. An in-tire power generation device is known, and specifically, a device that generates power with a magnet and a coil by sliding a power generation body in a spiral shape (see Patent Document 1), or a device that generates power by rotating a rotating weight ( Patent Document 2) is known.

  However, in the power generation device according to Patent Document 1, since the direction of the force applied to the power generation body and the spiral sliding direction of the power generation body are not the same direction, the sliding resistance of the power generation body is large and the rotation speed of the tire is low. Sometimes it can hardly generate electricity. Moreover, since the sliding resistance of the power generation body affects the entire rotation speed of the tire, the power generation efficiency is lowered and high power cannot be obtained. Further, in the power generation device according to Patent Document 2, since the rotational force of the rotary weight and the power generation rotor is transmitted through the gear, power generation using the inertia force of the gear is possible when the tire rotation speed is high. When the rotational speed of the tire is low, the rotational resistance of the gears is high, so power cannot be generated, power generation efficiency is low, and high power cannot be obtained.

JP 2000-92784 A JP 2000-278923 A

  In order to solve the above-mentioned problems, the present invention provides an in-tire power generation device that can efficiently generate power and obtain high power even when a tire is rotated at a low speed.

As a first configuration of the present invention, an in-tire power generation device attached to a tread portion in a tire chamber, a part of which is formed of a magnet so that the center of rotation and the center of gravity are different, and the tread portion when the vehicle travels A rotating body that rotates according to a change in applied force, a rotating body that faces the rotating body, generates a voltage by electromagnetic induction action of magnetic flux emitted from the magnet, and includes a coil unit that generates power, and a power storage unit that stores the voltage, It was set as the structure provided with the control part which controls the electric power generation of a coil part according to the change of the force added to a tread part.
According to the present invention, the control unit controls the power generation by the coil unit in accordance with the change in the force applied to the tread portion, so that the energy that the rotating body rotates due to the power generation is lost due to the power generation, and the rotation of the rotating body is braked Since it can suppress acting, rotation of a rotating body is maintained and high electric power can be obtained by generating electricity efficiently.
As a second configuration of the present invention, the control unit is configured to shut off the circuit between the coil unit and the power storage unit while the tread unit is grounded.
According to the present invention, the tread portion to which the in-tire power generator is attached is the time when the tread portion is in contact with the road surface until the tread portion contacts the road surface and the tread portion contacts the road surface and the tire kicks off when the tread portion leaves the road surface. By cutting off the circuit between the power storage unit and the power storage unit, since the brake caused by the power generation does not act on the rotation of the rotating body between the stepping on of the tire and the kicking of the tire, power can be generated efficiently. That is, it is possible to prevent the rotational energy of the rotating body from being lost due to power generation.
As a third configuration of the present invention, the control unit includes a detection unit that detects the grounding of the tread unit.
According to the present invention, since the control unit has the detection means, it can be detected that the tread portion to which the in-tire power generator is attached is grounded on the road surface. It is possible to control the power storage unit and the coil unit so that the power generation in the coil unit does not hinder the rotation of the rotating body.
As a fourth configuration of the present invention, the detection means is configured by an acceleration sensor that detects the centrifugal force of the tread portion.
According to the present invention, when the tire tread where the tread portion to which the in-tire power generator is attached and the road surface come into contact, when the tire kicks off the tread surface and the road surface, and while the tread surface is grounded, The acceleration acting on the in-tire power generator from the time of kicking to the time of stepping on can be directly detected by the acceleration sensor.
As a fifth configuration of the present invention, the detection means is a strain sensor that detects the strain in the circumferential direction of the tread portion.
ADVANTAGE OF THE INVENTION According to this invention, the distortion | strain of the circumferential direction of a tread part when a tread part and a road surface contact can be detected.

1 is an external perspective view of an in-tire power generator according to the present invention. The disassembled perspective view of the electric power generation apparatus in a tire which concerns on this invention. The partial expanded sectional view of the power generator in a tire concerning the present invention. The perspective view which shows the relationship between the coil part which concerns on this invention, and a magnet. The conceptual diagram which shows the mechanism in which the rotary body which concerns on this invention rotates. The graph which shows the change of the acceleration of the tire radial direction in the tire inner surface which concerns on this invention. The graph which shows the change of the acceleration of the tire radial direction which acts on the in-tire electric power generating apparatus which concerns on this invention, and a tire circumferential direction, and the schematic diagram of the behavior of a rotary body.

  Hereinafter, the present invention will be described in detail through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included in the invention. It is not necessarily essential to the solution, but includes a configuration that is selectively adopted.

Embodiment FIG. 1 shows an external perspective view of an in-tire power generator 1. FIG. 2 is an exploded perspective view of the in-tire power generator 1. FIG. 3 shows a partially enlarged cross-sectional view of the in-tire power generator 1. Hereinafter, the in-tire power generator 1 will be described with reference to FIGS. 1 to 3.
The in-tire power generator 1 attached to the tread portion T2 in the tire chamber includes a base 2 attached to the inner liner T1 of the tread portion T2, a pair of rotary shaft support members 3; 3, and a rotary shaft support member 3; 3 The rotating shaft 4 is pivotally supported by the shaft, the coil portion fixing member 5, the coil portion 6, the rotating bodies 7 and 7, and the electric component group 22. The electrical component group 22 includes a control unit 8 that controls power generation of the coil unit 6, a power storage unit 9 connected by the coil unit 6 and the electric wire 23, and various devices 20 that are driven by the power supplied from the power storage unit 9. Is done. The tire chamber is a space that holds air when surrounded by the wheel and the inner liner of the tire when the tire is assembled to the wheel.

The base 2, the pair of rotating shaft support members 3; 3, the rotating shaft 4, and the coil portion fixing member 5 are formed of a nonmagnetic material. The base 2, the rotation shaft support member 3; 3 and the coil portion fixing member 5 are formed of, for example, acrylic resin, and the rotation shaft 4 is formed of, for example, SUS304 of JIS standard.
In addition, the positional relationship of the up-down, front-back, left-right used for description in this embodiment is shown by the arrow in FIG.

The base 2 includes, for example, a base plate 11 formed of a rectangular flat plate and a fixed base 12 provided on the base plate 11. The fixed table 12 includes a lower plate 13, a pair of left and right side walls 14; 14, a roof plate 15, left and right side installation tables 16; 16, and a storage installation space 17. The lower plate 13 is a rectangular flat plate that is slightly smaller than the base plate 11 and is provided on the base plate 11 concentrically with the base plate 11. The pair of left and right side walls 14; 14 are provided on the lower plate 13 with a space therebetween, and extend in the vertical direction and the front-rear direction. The side walls 14; 14 are provided on the lower plate 13 at equal intervals from the left and right side edges, respectively. The roof plate 15 is provided so as to straddle the upper end surfaces of the pair of left and right side walls 14; The left and right side installation bases 16; 16 are provided so as to extend upward from the upper surface of the lower plate 13 and project from the outer surfaces of the left and right side walls 14; 14 along the left and right side edges on the lower plate 13. The storage installation space 17 is a space that is surrounded by the lower plate 13, the left and right side walls 14;
The base 2 may be formed by assembling the above-described members, or may be formed by integral molding.

  The upper surface of the roof plate 15 and the upper surface of the side installation table 16 are formed as surfaces parallel to the upper surface of the base plate 11. The rotary shaft support member 3; 3 is provided on the upper surface of the side installation table 16 so as to extend upward from the upper surface of the side installation table 16, and the coil portion fixing member 5 extends upward from the upper surface of the roof plate 15. It is provided on the upper surface of the roof plate 15.

The coil portion fixing member 5 is formed of a flat plate having opposing surfaces 5a; 5a that extend in the upward and front-rear directions from the center position between the left and right sides of the roof plate 15 and face each other.
The flat facing surfaces 5 a and 5 a of the coil portion fixing member 5 are surfaces perpendicular to the plane which is the upper surface of the roof plate 15. The coil part fixing member 5 includes a coil part accommodation through hole 5b that penetrates the opposing surface 5a; 5a, and a shaft avoiding part 5c formed by cutting out the upper edge surface in an arc shape. The coil part 6 is fixed to the hole inner wall of the coil part accommodation through hole 5b by a fixing means such as an adhesive.
The coil portion fixing member 5 may be formed integrally with the roof plate 15 or may be formed separately from the roof plate 15.

The rotating shaft support member 3 is formed separately from the side installation table 16, and is formed of, for example, a flat wall and is fixed to the upper surface of the side installation table 16 by a fixing means such as an adhesive. The rotating shaft support member 3 includes a bearing 21 that rotatably supports the end portion 41 of the rotating shaft 4 on the upper side surface.
The bearing 21 is formed by a bearing member attached to a hole formed on the upper side surface of the rotating shaft support member 3 or a bearing hole formed on the upper side surface of the rotating shaft support member 3.

The rotating shaft 4 includes both end portions 41; 41, a yoke body positioning portion 42, a magnet corresponding portion 43, and a shaft reinforcing portion 44.
Both end portions 41; 41 of the rotary shaft 4 are rotatably supported by bearings 21; 21 of the rotary shaft support members 3; As shown in FIG. 2, the rotating shaft 4 includes a shaft reinforcing portion 44 at the center, and includes a yoke body positioning portion 42 and a magnet corresponding portion 43 between the shaft reinforcing portion 44 and the end portion 41. The shaft reinforcing portion 44, the magnet corresponding portion 43, and the end portion 41 are formed in a circular cross section, and the yoke body positioning portion 42 is formed in a square cross section.
The yoke body positioning portion 42 is formed, for example, in a regular hexagonal cross section.
The shaft reinforcing portion 44 and the left and right magnet corresponding portions 43; 43 are provided adjacent to each other, the magnet corresponding portion 43 and the yoke body positioning portion 42 are provided adjacent to each other, and the yoke body positioning portion 42 and the end portion 41 are provided. Are provided next to each other.

  The cross-sectional diameter of the end 41 of the rotating shaft 4 is formed to be equal to or smaller than the diameter of the inscribed circle having a regular hexagonal cross section of the yoke body positioning portion 42. The cross-sectional diameter of the magnet corresponding portion 43 is formed to be equal to or larger than the diameter of the circumscribed circle having a regular hexagonal cross section of the yoke body positioning portion 42. The cross-sectional diameter of the shaft reinforcing portion 44 is formed to be larger than the diameter of the magnet corresponding portion 43.

  The rotating body 7 is constituted by a fan-shaped yoke body 71 and a magnet 72, and a fan-shaped eccentric weight is formed by combining the yoke body 71 and the magnet 72. The yoke body 71 includes a fan-shaped yoke face plate 73, a positioning hole 74, and magnet positioning plates 75; The yoke face plate 73 includes a fan part 73a and a main part 73b of the fan. The fan face of the yoke face plate 73 is formed such that the angle formed by the two radial lines of the fan is 120 °, for example. The positioning hole 74 is a hole formed in the main part 73 b of the fan of the yoke face plate 73, and is formed in a regular hexagonal hole corresponding to the regular hexagonal cross section of the yoke body positioning part 42 of the rotating shaft 4. The magnet positioning plates 75; 75 are provided along two radial line edges of the yoke face plate 73. The magnet positioning plate 76 is provided along the arc edge of the yoke face plate 73. The magnet positioning plates 75; 75; 76 protrude in one direction from one surface of the yoke face plate 73 and are formed perpendicular to the yoke face plate 73.

The magnet 72 is formed of a fan-shaped magnet obtained by dividing a circular plate having a predetermined thickness with a circular hole at the center of the circle into a fan shape that requires the center of the circle.
The main part of the fan of the magnet 72 includes a curved notch 80 corresponding to the outer peripheral surface of the rotating shaft 4. Two unit fan-shaped magnets 77 having an angle formed by two radii of 60 ° are combined to use a fan-shaped magnet 72 formed into a fan shape having an angle formed by two radii of 120 °. A stable magnetic force can be obtained by using the unit fan-shaped magnet 77 having an angle formed by the two radii of 60 °, and the magnetic flux when passing through the space 60 (see FIG. 4) in the cylinder of the coil winding body 61. Since the speed of changing the direction of φ can be increased, the power generation efficiency can be increased.
Although the angle formed by the two radii of the unit fan-shaped magnet 77 is set to 60 °, the magnet 72 may be configured to be set to 30 ° so that different magnetic poles are alternately arranged in the circumferential direction. What is necessary is just to set suitably according to the shape of the coil winding body 61. FIG.

As shown in FIG. 4, the unit fan-shaped magnet 77 is a two-pole magnet formed by magnetizing one fan face side to the N pole and magnetizing the other fan face side to the S pole. The fan-shaped magnet 72 is formed by adhering the end faces 78; 78 of the two unit fan-shaped magnets 77; 77 so that the different poles are adjacent to each other.
Therefore, since the rotating body 7 includes a plurality of unit magnetic poles 77, 77 of different magnetic poles arranged along the rotation direction of the rotating body 7, the change points of the magnetic poles increase and the rotating body 7 rotates. As a result, the speed of changing the direction of the magnetic flux φ passing through the space 60 in the cylinder of the coil winding body 61 can be increased, so that the power generation efficiency can be increased and high power can be obtained.

The magnet 72 is formed in a size that can be inserted into a magnet installation portion 79 surrounded by magnet positioning plates 75; For example, a fan-shaped magnet 72 having a fan surface having the same area as the one fan surface 73u of the fan portion 73a surrounded by the magnet positioning plates 75; 75; 76 is formed, and the one fan surface 73u of the fan portion 73a The rotating body 7 is formed by fixing one fan surface of the magnet 72 to each other by a fixing means such as an adhesive.
That is, the magnet 72 of the rotating body 7 includes the yoke face plate 73 on the surface opposite to the face facing the coil portion 6, and the magnet positioning plate 75; 75 that functions as a yoke on the outer peripheral surface of the fan of the magnet 72. , 76, the self-complete magnetic field generation state in the magnet 72 can be suppressed, and the magnetic flux density of the magnetic flux φ passing through the space 60 in the cylinder of the coil winding body 61 can be increased, thereby obtaining high power. be able to.
Further, since the yoke body 71 includes the magnet installation portion 79, the magnet 72 can be easily installed on the magnet installation portion 79, which is a fixed position of the yoke body 71, and the rotating body 7: 7 can be easily manufactured. Moreover, since the position shift of the magnet 72 can be prevented, a stable magnetic field can be supplied to the coil unit 6.

In the rotating body 7, the main part 73 b of the fan part of the yoke body 71 includes a positioning hole 74 as an attachment hole to the rotating shaft 4, and the magnet 72 is surrounded by the yoke face plate 73 and the magnet positioning plates 75; The fan 72 is formed in a fan shape corresponding to the fan-shaped magnet installation portion 79, and the main portion of the fan of the magnet 72 is provided with a curved cutout portion 80 corresponding to the outer peripheral surface of the rotating shaft 4. It was.
That is, since the magnet 72 is not provided with the attachment portion to the rotating shaft 4, the rotating body 7 becomes easier to rotate, and the direction of the magnetic flux φ passing through the space 60 in the cylinder of the coil winding body 61 changes. The speed becomes higher, high power can be obtained, and continuous power generation can be efficiently performed, so that the amount of power generation can be increased.
Further, since the magnet 72 is used as an eccentric weight, the number of parts can be reduced, and the magnet 72 can be easily rotated, so that high power can be obtained and the amount of power generation can be increased.

A yoke body positioning portion 42 having a hexagonal cross section from the end 41 side of the rotating shaft 4 is placed in the positioning hole 74 of the yoke body 71 so that the magnet 72 of the rotating body 7 is positioned on the shaft reinforcing portion 44 side of the rotating shaft 4. As shown in FIG. 3, the hole edge surface 46 of the positioning hole 74 in the main portion 73 b of the fan of the yoke face plate 73 and the end surface 45 of the magnet corresponding portion 43 of the rotating shaft 4 are brought into contact with each other. At this time, if the yoke body 71 and the rotating shaft 4 are fixed by a fixing means such as an adhesive, the yoke body 71 and the rotating shaft 4 can be more reliably integrated.
The rotary shaft support member 3 is fixed to the upper surface of the roof plate 15 with a fixing means such as an adhesive in a state where the end portions 41; 41 of the rotary shaft 4 are rotatably inserted into the bearing 21 of the rotary shaft support member 3. To do.
The yoke body positioning portions 42; 42 of the rotary shaft 4 are attached so that the fan surfaces of the magnets 72; 72 of the rotary bodies 7; 7 face each other.

A rotating component 25 is formed by the rotating shaft 4 rotatably supported by the bearing 21 and the rotating body 7 formed so as to rotate together with the rotating shaft 4 about the center line of the rotating shaft 4 as a rotation center. The
The rotating body 7 only needs to have a rotation center and a center of gravity different from each other. For example, a rotating body formed in a fan shape in which an angle between two radii of a fan is 180 ° or less may be used.

As shown in FIG. 4, the coil portion 6 is a space through which the magnetic flux φ generated between the different magnetic poles of the magnets 72; 72 in the two rotating bodies 7; 7 that rotate together with the rotating shaft 4 and face each other. It is formed by two coil winding bodies 61; 61 in which a coil 62 is wound in a cylindrical shape surrounding 60. For example, the coil wound body 61 is configured such that the coil 62 is wound so as to form a fan-shaped cylindrical shape through which the magnetic flux φ generated between the two rotating bodies 7; Preferably, by using a rectangular wire having a rectangular cross section as the coil 62, the winding resistance can be reduced and the number of turns can be increased, and the winding density can be improved, so that the power generation efficiency can be increased.
Moreover, as shown in FIG. 4, the coil winding body 61 is provided in the projection part of the rotation locus which faces the magnets 72:72 of the rotating body 7: 7, thereby passing through the space 60 in the cylinder of the coil winding body 61. The magnetic flux density of the magnetic flux φ can be increased and high power can be obtained.

  When the outer periphery of the coil portion 6 is made larger than the outer periphery of the magnet 72, the coil winding body 61 has a longer winding length, thereby increasing the resistance of the coil winding body 61 and reducing the power generation efficiency. The outer peripheral shape of the cross section of the cylinder and the outer peripheral shape of the cross section of the magnet 72 are formed in the same shape, and further, the rotating body 7 rotates, and the center line of the cross section of the magnet 72 and the center of the cross section of the cylinder of the coil winding body 61 By forming the outer circumference of the cross section of the coil winding body 61 to be smaller than the outer perimeter length of the cross section of the magnet 72 when the line matches, while reducing the resistance of the coil winding body 61, Power generation efficiency can be increased.

The coil unit 6 outputs a current generated by a change in the magnetic flux of the magnet 72 to the electrical component group 22 via the electric wire 23. The electrical component group 22 includes the control unit 8, the power storage unit 9, and the device 20.
The control unit 8 includes an acceleration sensor 24 as a detection unit and a switching circuit 26. The acceleration sensor 24 is attached to the upper surface of the base 2 in the storage installation space 17 (see FIG. 2), and the acceleration of centrifugal force (acceleration in the tire radial direction) acting on the in-tire power generator 1 as the tire rotates. Detect.
The switching circuit 26 includes a plurality of electronic components and includes a conversion circuit that converts a signal output from the acceleration sensor 24 into acceleration. The switching circuit 26 compares a threshold value set in advance in the control circuit with acceleration in the tire radial direction. In addition, a switch is provided that disconnects the connection between the coil unit 6 and the power storage unit 9 when the acceleration is equal to or greater than a threshold value. For example, 10G that is 10 times the gravitational acceleration (10 times the gravitational acceleration) is electrically set as the threshold. For example, the switch is constituted by a comparator and a MOSFET (field effect transistor), and when the difference between the reference voltage of the comparator and the voltage output from the acceleration sensor 24 is equal to or lower than a threshold voltage, the signal voltage from the comparator to the MOSFET Is output, the circuit connecting the coil unit 6 and the power storage unit 9 is cut off, and the circuit between the coil unit 6 and the power storage unit 9 is connected when the voltage is equal to or higher than the threshold value.
The configuration of the control unit 8 is not limited to the above, and may be selected as appropriate so that the weight of the in-tire power generation device 1 does not increase.
The power storage unit 9 includes a rectifier circuit 18 and a charging circuit 19.
The rectifier circuit 18 uses, for example, a rectifier element in which a circuit that rectifies an alternating current output by a voltage generated in the coil unit 6 is configured in one chip. The charging circuit 19 is a capacitance type capacitor that accumulates the electric charge of the generated current.
The device 20 includes a TPMS that measures tire air pressure, a wireless device that wirelessly transmits air pressure and air temperature output from the TPMS, and the like.

According to the in-tire power generation device 1 configured as described above, power generation is performed as follows.
In a rotating tire, a centrifugal force due to rotation always acts on the in-tire power generator 1 in the tire radial direction. In the in-tire power generation device 1 under centrifugal force, the rotating body 7: 7 does not receive the centrifugal force of the tire when the tire is stepped on, which is the moment when the tread portion T2 to which the in-tire power generation device 1 is attached contacts the road surface. 0G state (gravity-free state) occurs, and acceleration occurs in the tire circumferential direction. Therefore, the rotating body 7: 7 generates a circumferential acceleration due to the inertial force, and starts rotating with respect to the rotating shaft support member 3. The rotating body 7: 7 that has started rotating continues in a state where no centrifugal force is applied during the ground contact, and rotates to the upper side of the in-tire power generator 1 while maintaining the inertial force generated when the tire is depressed. The rotation of the rotating body 7: 7 is further accelerated by the acceleration at the time of kicking out the tire when the tread portion T2 leaves the road surface. The acceleration due to the kicking out of the tire is that the rotating shaft support member 3 supporting the rotating body 7: 7 is accelerated in the rotating direction by kicking out, and the centrifugal force due to the rotation of the tire acts on the rotating body 7: 7. It is caused by relative movement.
Thereafter, the rotating body 7: 7 starts rotating motion with respect to the rotation support member 3 under the action of the centrifugal force of the tire, and every time the magnetic flux emitted by the magnets 72:72 of the rotating body 7: 7 crosses the coil portion 6. A voltage is generated in the coil portion 6 by the electromagnetic induction action. That is, as the rotating body 7: 7 rotates, a voltage is generated in the coil unit 6 and power generation is started.
Power generation by the coil unit 6 is controlled by the control unit 8.
When the acceleration detected by the acceleration sensor 24 is 10 G or less, the control unit 8 turns off the switching circuit 26 when the rotating body 7: 7 passes through the coil unit 6 and connects the coil unit 6 and the power storage unit 9. Is temporarily cut off, and when the acceleration detected by the acceleration sensor 24 is 10 G or more, the switching circuit 26 is turned on and the coil unit 6 and the power storage unit 9 are connected (see FIG. 5).
Therefore, the current generated by the voltage generated in the coil unit 6 is rectified by the rectifier circuit 18 of the power storage unit 9 via the control unit 8, stored as a charge in the capacitor of the charging circuit 19, and supplied to the device 20.

  As described above, the in-tire power generation device 1 detects the radial acceleration acting on the in-tire power generation device 1 due to the rotation of the tire by the acceleration sensor 24 of the control unit 8 by detecting the radial acceleration acting on the tire rotation. It is detected whether it is located on the back side of the tire in contact with the road surface, and when the acceleration detected by the acceleration sensor 24 is 10 G or less, the connection between the coil unit 6 and the power storage unit 9 is cut off by the switching circuit 26. This is just when the rotator 7: 7 passes through the coil unit 6, and since the connection between the coil unit 6 and the power storage unit 9 is interrupted, no current is generated in the coil unit 6, so the rotator The rotational energy of 7: 7 is not converted into electrical energy, and the rotation of the rotating body 7: 7 is not braked. And after the rotary body 7: 7 passes the coil part 6, the switching circuit 26 connects the coil part 6 and the electrical storage part 9, and can maintain the rotational energy of the rotary body 7: 7. Therefore, the control unit 8 controls the power generation of the rotating body 7: 7 and the coil unit 6 based on the acceleration in the tire radial direction so that the rotational energy of the rotating body 7: 7 can be reduced even when the tire rotates at a low speed. Stable power generation with little loss can be achieved.

Hereinafter, the effect of the in-tire power generator 1 of the present invention will be described.
In order to investigate the effect of the in-tire power generation device 1 of the present invention, the difference in power generation between the case where the tire power generation device 1 is provided with the control unit 8 and the case where the control unit 8 is not provided was examined.
The implementation conditions are shown below.
Tire size: 225 / 55R17 was used.
The in-tire power generator 1 is attached to the back surface 11a of the base 2 by being attached to the center in the width direction of the tread portion T2 in the tire chamber. The rotating shaft 4 was attached in parallel with the rotating shaft of the tire. The distance from the back surface 11a of the base 2 to the rotating shaft 4 was 20 mm.
The charging circuit 19 of the power storage unit 9 uses a circuit in which electric charges are stored in a capacitor, and the wireless device and the capacitor are connected.
-The control part 8 detects the centrifugal force which acts on the in-tire electric power generating apparatus 1 with the acceleration sensor 24, comprises the switching circuit 26 with a comparator and MOSFET, the reference voltage of a comparator, and the voltage which an acceleration sensor outputs In comparison, the threshold setting switching circuit 26 is configured so that the comparator outputs a signal to the MOSFET when the acceleration is 10 G.
The rotary shaft 4 has a total length of 22.5 mm, a length of the shaft reinforcing portion 44 of 3 mm, a length of the magnet corresponding portion 43 of 4 mm, a length of the yoke body positioning portion 42 of 3.25 mm, The length of the end 41 is 2.5 mm, the diameter of the shaft reinforcing portion 44 is 3.5 mm, the diameter of the magnet corresponding portion 43 is 2.5 mm, the maximum diameter of the yoke body positioning portion 42 is 2.5 mm, the end The part 41 having a diameter of 2 mm was used.
The yoke body 71 has a fan inner dimension of 9 mm, which is the distance from the rotation center of the rotating body 7 to the inner surface 76a of the magnet positioning plate 76 provided along the arc line edge of the yoke face plate 73. The outer dimension of the fan, which is the distance to the outer surface 76b of the positioning plate 76, is 9.5 mm, and two magnet positioning plates 75 provided along two radial edges of the yoke surface plate 73; the inner surface 75a and the inner surface 75a of the two magnet positioning plates 75; An angle of 120 ° was used. Further, as shown in FIG. 3, the width dimension a of the magnet positioning plates 75; 75; 76 is 3 mm, and the width dimension b of the yoke face plate 73 is 1 mm.
As the unit fan-shaped magnet 77, a neodymium magnet having an inner diameter of a main arc of 4 mm, an outer diameter of 18 mm, a thickness of 4 mm, and a weight of 2.35 g was used.
The coil wound body 61 used had an inner diameter of the main arc of the fan of 5 mm, an outer diameter of the fan of 18 mm, a total length of the cylinder of 2 mm, a coil wire diameter of 0.08 mm, and 500 turns.
-The in-tire power generation device 1 including a total of 13 g including the electric circuit group 22 was used.
-The vehicle traveled constantly at a vehicle speed of 30 km / h until the battery voltage stabilized from 0V.
The amount of power generation (W = V ² / R) was calculated from the stable voltage and the device load (R = 200Ω).

  As a result of the implementation based on the above implementation conditions, a power generation amount of 14.7 mW is obtained in the in-tire power generation device 1 including the control unit 8, and a power generation amount of 13.6 mW is obtained in the in-tire power generation device 1 not including the control unit 8. was gotten. That is, by providing the control unit 8, an output improvement of 8% was obtained.

Hereinafter, the result by the presence or absence of the control part 8 is considered.
FIG. 5 shows a conceptual diagram of a mechanism in which the rotating body 7: 7 of the in-tire power generator 1 rotates in the rotating tire.
FIG. 6 shows the acceleration in the tire radial direction when the acceleration sensor 24 detects the centrifugal force acting on the tread portion T2 during the time when the tread portion T2 to which the in-tire power generator 1 is attached is in contact with the road surface and before and after that time. It is a graph which shows the change of.
FIG. 7A is a graph showing changes in the tire radial acceleration acting on the in-tire power generator 1 and a graph showing changes in the circumferential acceleration. FIG.7 (b) is a figure which shows typically the behavior of the rotary body 7: 7 in the states 1-5 shown in FIG. FIG. 7A is an enlarged view of 8.36 s from 8.32 s in FIG. In the same figure, the tire radial acceleration acting on the in-tire power generator 1 is in the relationship between the acceleration acting on the tire inner surface and the action reaction, so the radial acceleration shown in FIG. Is shown upside down.
As shown in FIG. 6, during the time when the tread portion T2 is in contact with the road surface, the acceleration in the tire radial direction of the tread portion T2 is detected by the acceleration sensor 24 as approximately 0G.
Further, as shown in FIGS. 5 and 7A, the acceleration in the tire circumferential direction of the in-tire power generator 1 changes in acceleration at both ends of the contact time. This corresponds to the time when the tire is stepped on when the tire is in contact with the road surface (state 2) and the time when the tire is kicked away from the road surface (state 4). Further, as shown in FIGS. 5 and 7 (a) and 7 (b), the change in the acceleration in the tire radial direction and the circumferential direction is compared with the schematic diagram of the behavior of the rotating body 7: 7. It can be seen that whether the rotating body 7: 7 rotates or does not rotate is determined depending on the magnitude of the circumferential acceleration.
Therefore, as shown in FIG. 7B, when the control unit 8 is provided, when the coil unit 6 and the power storage unit 9 are shut off, a larger acceleration in the tire circumferential direction is obtained in the state 2, and the state 3 The rotational force of free rotation at is large. In the state 3 in which the rotating body 7 is completely grounded, the acceleration in the tire circumferential direction at the moment of grounding acts on the rotating body 7: 7 and rotates to the upper side of the rotating shaft support member 3. Further, when the tire is kicked out in the state 4, the centrifugal force acts on the rotating body 7: 7, thereby accelerating in the tire radial direction. With this mechanism, the rotating body 7: 7 can stably generate power even at a speed of 30 km / h.
On the other hand, when the control unit 8 is not provided, power generation is performed by the acceleration acting in the circumferential direction in the state 2, so that the rotational energy is insufficient, and further, the power generation is continued even in the state 3, so that the rotational energy is consumed. It will be insufficient, and rotation will be insufficient. And even if acceleration is obtained in the circumferential direction as in state 4, it acts as a rotational force that returns to the original position instead of a rotational force as when the control unit 8 is provided, and the rotating body 7: 7 The case where it cannot rotate will generate | occur | produce. Therefore, it was confirmed that when the control unit 8 is not provided, it is not possible to efficiently generate power at a speed of 30 km / h.

  Therefore, according to the in-tire power generation device 1 of the present invention, the control unit 8 cuts off the connection between the coil unit 6 and the power storage unit 9 in accordance with a change in the acceleration in the tire radial direction that acts due to the centrifugal force of the tire. Thus, even when the tire rotates at a low speed, it can be controlled that the rotational energy of the rotating body 7: 7 is consumed by the power generation, so that the power can be stably generated. Therefore, tire information such as temperature and pressure in the tire can be detected, and power can be stably supplied to the device 20 that requires high power to continuously transmit the dynamic state of the tire.

In the above embodiment, the control unit 8 has been described as having a threshold value of 10G for cutting off the connection between the coil unit 6 and the power storage unit 9, but the threshold acceleration depends on the size of the tire and the rotational speed of the tire to be generated. What is necessary is just to set suitably according to.
Moreover, the attachment position of the in-tire power generation device 1 with respect to the inner surface of the tire is not particularly limited. For example, the in-tire power generator 1 may be attached to the tread portion T2 in the tire chamber so that the rotation shaft 4 is orthogonal to the width direction of the tread portion T2.

Further, although the detection means is configured by the acceleration sensor 24, the strain in the tire circumferential direction of the tread portion T2 in the tire chamber may be detected by a strain gauge.
For example, the strain gauge may be attached to the tread portion T2 in the tire chamber so as to be adjacent to the upstream side in the forward rotation direction of the tire of the in-tire power generation device 1. By arranging the strain gauge in this way, the tread portion T2 to which the in-tire power generator 1 is attached can accurately detect when the tire is in contact with the road surface. Furthermore, by sticking a strain gauge so as to be adjacent to the in-tire power generation device 1 on the downstream side in the forward rotation direction of the tire, it is possible to accurately detect when the tire is kicked out. Moreover, you may make it affix a strain gauge so that the electric power generating apparatus 1 in a tire may be surrounded.

  Further, the in-tire power generation device 1 is not limited to the above-described configuration, and the rotating body and the magnet of the in-tire power generation device may be configured separately, and the tire does not always generate power when the rotation speed of the tire is low. By providing the internal power generation apparatus 1 with the control unit 8, the tire can efficiently and stably generate power from when the tire rotates at a low speed.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above embodiment.

1 In-tire power generator, 2 base, 3 rotating shaft support member, 4 rotating shaft,
5 Coil part fixing member, 5a Opposing surface, 5b Coil part storing through-hole, 5c Shaft avoiding part,
6 coil part, 7 rotating body, 8 control part, 9 power storage part, 11 base plate,
12 fixed base, 13 lower plate, 14 side wall, 15 roof plate, 16 side installation stand,
17 storage installation space, 18 rectifier circuit, 19 charging circuit, 20 devices,
21 bearing, 23 electric wire, 25 acceleration sensor, 26 switching circuit,
41 end portion, 42 yoke body positioning portion, 43 magnet corresponding portion, 44 shaft reinforcing portion,
60 spaces, 61 coil winding bodies, 71 yoke bodies, 72 magnets,
73 yoke face plate, 73a fan part, 73b main part of fan, 73u fan face,
74 positioning hole, 75; 76 magnet positioning plate, 77 magnet, 78 end face,
79 Magnet installation part, 80 curved notch part, a: b width dimension, T2 tread part.

Claims (5)

An in-tire power generator attached to a tread portion in a tire chamber,
A rotating body that is partly formed of a magnet so that the center of rotation and the center of gravity are different, and that rotates according to a change in force applied to the tread portion during vehicle travel,
A coil unit that faces the rotating body, generates a voltage by electromagnetic induction action of magnetic flux emitted from the magnet, and generates power;
A power storage unit that stores the voltage,
An in-tire power generator, comprising: a control unit that controls power generation of the coil unit according to a change in force applied to the tread unit.   The in-tire power generation device according to claim 1, wherein the control unit cuts off a circuit between the coil unit and the power storage unit during a period when the tread unit is grounded.   The in-tire power generation device according to claim 1, wherein the control unit includes a detection unit that detects a ground contact of the tread portion.   The in-tire power generation device according to claim 3, wherein the detection means is an acceleration sensor that detects a centrifugal force of the tread portion.   The in-tire power generator according to claim 3, wherein the detection unit is a strain sensor that detects a strain in a circumferential direction of the tread portion.

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