JP2008087512A - Tire power generation device, tire sensor using the same, and tire rigidity varying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire power generation device capable of converting the deformation energy of a tire into electric energy, a vehicle with the tire power generation device mounted thereto, a tire sensor using the same, and a tire rigidity varying device capable of adjusting the rigidity of the tire by the electric energy. <P>SOLUTION: The tire power generation device 5 comprises a wheel 4 having a disk 41 and a rim 42 extending outwardly in the radial direction from the disk 41, a rubber-made tubeless tire 3 composed of a side wall 31 and a tread 32 and held by the rim 42, a power generation element 1 fixed to the inner surface 35 of the tire 3, and a cable 2 as a power-transmission means for transmitting power generated in the power generation element 1 to an external circuit. The power generation element 1 has a dielectric elastomer 11 for converting expansive kinetic energy into the electric energy by performing expansion and contraction following the expansion/contraction of the tire 3, and electrodes 12, 12 arranged at both ends of the dielectric elastomer 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tire power generation device mounted on a vehicle, a tire sensor using the tire power generation device, and a tire stiffness varying device.

  In order to improve the fuel efficiency of automobiles, the effective use of energy is regarded as important. For example, in a hybrid vehicle, a generator is used to convert inertial energy into electric energy, which is effectively used as electric drive energy.

  In addition to inertial energy, there are various types of energy emitted from automobiles such as heat, vibration, and sound. Most of these energies are released to the outside, and most of the energies are not effectively utilized. Therefore, a technique for recovering and effectively using the released energy is desired.

As a method of energy recovery, there is a method of converting emitted energy into other energy. For example, conventionally, there is a piezoelectric element that deforms when a voltage is applied as an energy conversion element. Patent Document 1 discloses an element for converting mechanical energy into electrical energy. The inventor has intensively studied to improve the fuel consumption of vehicles such as automobiles by using such energy conversion elements. In addition, we have earnestly studied to adjust the tire stiffness using electric energy.
Special table 2003-505865 gazette

  The present invention focuses on the expansion and contraction motion of a tire in a vehicle, and a tire power generation device capable of converting the expansion and contraction kinetic energy into electric energy, a vehicle equipped with the tire power generation device, a tire sensor using these, and further electric energy It is an object of the present invention to provide a tire stiffness varying device that can adjust the stiffness of a tire.

Means and effects for solving the problems

  The invention for solving the above-mentioned problems is a tire having a wheel having a disk part and a rim part extending radially outward from the disk part, a sidewall part and a tread part, and being held by the rim part. And a power generating element fixed to the inner surface or inside of the tire, and a power transmission means for transmitting the power generated by the power generating element to an external circuit, the power generating element expands and contracts following the deformation of the tire And a dielectric elastomer that converts the expansion and contraction kinetic energy into electric energy, and electrodes disposed at both ends of the dielectric elastomer.

  According to the said structure, the ground contact part of a tire deform | transforms in response to the load by weight, such as a tire, a wheel, and a vehicle which attached this. When the ground contact portion of the tire shifts to a non-contact state due to the rotation of the tire, the tire returns to its original shape due to the internal pressure of the tire. For this reason, when the tire rotates, a certain portion of the tire is repeatedly expanded and contracted by these deformations. As the tire expands and contracts, the dielectric elastomer fixed to the tire also repeats expansion and contraction following the expansion and contraction of the tire. Dielectric elastomers have the property of generating electromotive force by expansion and contraction. For this reason, expansion and contraction of the dielectric elastomer is repeated by rotation of the tire, and electric power can be generated.

  There is also a vehicle characterized by having a tire power generator. Since the tire expands and contracts during traveling, the vehicle can convert the expansion and contraction kinetic energy into electrical energy by the tire power generator. The generated electric power can be used in a timely manner by storing it in a battery. In addition, it can be used for motor driving, in-vehicle lighting devices, etc., and is useful for improving the fuel efficiency of vehicles.

  There is also a tire sensor that detects a deformation state of a tire based on a response of electric power generated by the tire power generation device. According to this sensor, the deformation state of the tire can be detected.

  Further, a wheel having a disk part and a rim part extending radially outward from the disk part, a tire having a sidewall part and a tread part and held by the rim part, and fixed to the tire The actuator is disposed at both ends of the dielectric elastomer, and a dielectric elastomer that converts electrical energy applied from the external circuit through the power transmission means to expansion and contraction kinetic energy. There is a tire stiffness variable device characterized by having an electrode.

  According to the tire stiffness varying device, when electricity is applied to the actuator, a voltage difference is generated between the electrodes, and the electric field is changed. In this case, different electric charges are attracted to each other depending on the electrodes, so that the dielectric elastomer is compressed between the electrodes and stretched in the plane direction between the electrodes. When the application of power is stopped, the voltage difference between the electrodes disappears. The difference in charge is eliminated. In this case, the dielectric elastomer is released from the compressive force between the electrodes, and returns to its original shape even when contracted from the extended state in the planar direction. In this way, the dielectric elastomer expands and contracts by applying and stopping power.

  As a result, the rigidity of a tire with a built-in or integrated dielectric elastomer changes. That is, when the dielectric elastomer is extended, the tire is extended and the rigidity of the tire is increased. When the dielectric elastomer contracts, the tire contracts and the rigidity decreases. Thus, the rigidity of the tire can be adjusted by changing the applied voltage. For this reason, it is possible to adjust the tire rigidity suitable for the traveling state such as the vehicle speed, the road surface, and the curve.

  As described above, according to the present invention, the tire power generation device capable of converting the deformation energy of the tire into electric energy, the vehicle equipped with the tire power generation device, the tire sensor using these, and further the rigidity of the tire can be adjusted by the electric energy. A tire stiffness variable device can be provided.

(Tire power generator)
The power generation element includes a dielectric elastomer that converts expansion and contraction kinetic energy into electric energy, and electrodes disposed at both ends of the dielectric elastomer. As such a power generation element, for example, a generator disclosed in JP-T-2003-505865 can be used.

  When the dielectric elastomer is deformed, an electric field is generated to generate electric energy. That is, the dielectric elastomer has a high electric resistance value. Therefore, when the dielectric elastomer is stretched, static electricity is generated, and different charges in the dielectric elastomer are attracted to the electrode side. When the dielectric elastomer contracts, the electric charge attracted to each electrode has a higher density in the surface direction of the dielectric elastomer, and the electric energy increases. In addition, since the thickness between the electrodes is increased, charges of different potentials are separated from each other, so that the energy of the charges also increases. Thus, when the dielectric elastomer expands and contracts with the expansion and contraction of the tire, electric energy is generated.

  The dielectric elastomer is created by applying strain to the elastomer in advance. Suitable materials for dielectric elastomers include flexible, high electrical resistance polymers or rubbers that change the electric field upon deformation, or combinations thereof. Specific examples include a silicone elastomer, an acrylic elastomer, a polyurethane, a thermoplastic elastomer, a polymer such as EPDM (ethylene propylene copolymer), a pressure sensitive adhesive, a fluoroelastomer, a polymer containing a silicon component and an acrylic component.

The electric resistance value of the dielectric elastomer is preferably 10 ¹⁴ Ω · m or more. If it is less than 10 ¹⁴ Ω · m, the generated voltage may be low.

  The electrode can be made of a conductive material having a lower electrical resistance than a dielectric elastomer, such as graphite, carbon black, thin metals including silver and gold, silver and carbon filled gels and polymers, ionic or electronically Examples thereof include conductive polymers. The electrode can be formed, for example, by printing on the surface of a dielectric elastomer or using a binder.

The electric resistance value of the electrode is preferably 10 ¹ Ω · m or less. If it exceeds 10 ¹ Ω · m, the conductivity may decrease.

  The power generation element is formed by arranging electrodes on both sides of the dielectric elastomer. The power generation element preferably has a multilayer structure in which dielectric elastomers and electrodes are alternately stacked. In this case, the power generation amount can be increased.

  The power generation element is fixed to the inner side surface of the tire or embedded in the tire. From the viewpoint of ease of power extraction, it is better to be fixed to the inner surface of the tire. It is better not to arrange the power generating element on the outer surface of the tire in order to prevent damage.

  The tire may be a tubeless tire or a tube tire. In the case of a tubeless tire, a power generation element is fixed to the tire itself. In the case of a tube tire, the power generating element may be fixed to either the outer tire house or the inner tube.

  In fixing the power generating element to the tire, for example, it is fixed with an adhesive or the like. Further, when the power generation element is made of rubber, the power generation element and the tire may be integrated by co-crosslinking. In addition, a rubber power generation element and a tire may be co-crosslinked using a rubber adhesive. When an adhesive is used, it is preferably a stretchable adhesive that can be expanded and contracted according to the expansion and contraction of the tire and the power generation element.

  For example, the power generation element is intermittently disposed in the circumferential direction of the tire. In this case, the power generation element may be one or a plurality of two or more. When there are a plurality of power generation elements, the power generation elements are preferably arranged at equal intervals in the circumferential direction of the tire. In this case, constant frequency power can be generated.

  Moreover, the power generation element may be continuously arranged in the circumferential direction of the tire.

  It is preferable that the power generation element is disposed on a sidewall portion of the tire. The side wall portion contracts by receiving a load such as a tire or a wheel in a planar direction when the ground is touched, and is released from the load and stretches when not in contact. The sidewall portion is a portion having a large expansion / contraction difference between when the tire is grounded and when it is not grounded. For this reason, relatively large electric power can be generated.

  Further, the power generation element may be disposed in the trad portion of the tire. In this case, the area in contact with the road surface at the time of grounding is large, and electric power reflecting the state of the road surface at the time of grounding can be generated. For this reason, for example, it is suitable for generating an electric signal for detecting a road surface state. The trad portion expands by receiving a load such as a tire or a wheel in the thickness direction at the time of grounding, and is contracted by being released from the load when not grounded.

  The power transmission means is, for example, a cable disposed in a pressure chamber formed between the tire and the rim portion. The cables are respectively connected to the anode side and cathode side electrodes disposed at both ends of the dielectric elastomer. The cable connected to the cathode side is grounded.

  The rim portion preferably has a conduction hole communicating with the atmospheric pressure chamber, and the conduction hole is preferably sealed with a hermetic seal in a state where the cable is inserted. Since the conduction hole communicates with the pressure chamber in the tire, air can leak out of the pressure chamber through the conduction hole just by inserting a cable into the conduction hole. Therefore, air leakage from the pressure chamber can be suppressed by hermetically sealing with a hermetic seal with the cable inserted through the conduction hole. Here, the hermetic seal refers to a seal structure in which a gap between a conduction hole and a cable inserted therein is baked and hardened with a sealing material such as glass. According to the hermetic seal, the gap between the conduction hole and the cable can be hermetically sealed, so that air can be prevented from leaking out from the pressure chamber in the tire.

(vehicle)
The tire power generation device is mounted on a vehicle, for example. Examples of the vehicle include an automobile, a motorcycle, and a bicycle, but are not particularly limited as long as the vehicle has a tire.
The vehicle has a rotating member that fixes a wheel of a tire and rotates as the wheel rotates, and a fixing member that is fixed to a vehicle body of the vehicle. The power generated by the tire power generation device needs to be transmitted to a device that uses the power. Such power utilization devices are often fixed to the vehicle body. For this reason, a means for deriving from the rotating tire power generation device to the fixing member of the non-rotating vehicle body is required.

  As a means for deriving from the tire power generation device to the fixing member of the vehicle body in this way, for example, there is a method of electrically connecting the external circuits formed on the rotating member and the fixing member with a slip ring.

  One of the electrodes disposed on both sides of the dielectric elastomer is an anode and the other is a cathode. In order to derive to the external circuit from the tire power generation device, it is necessary to separately derive the anode side current and the cathode side current having different potentials to the vehicle. As such a configuration, for example, a rotating member of a vehicle has an inner layer and an outer layer, and an insulating layer that insulates between the inner layer and the outer layer, and the inner layer and the outer layer are respectively connected to the power transmission means of the tire power generation device. And the outer layer is connected to a first external circuit formed on the fixing member by the first slip ring, and the inner layer has an exposed portion exposed from the insulating layer and the outer layer. It is preferable to connect with the 2nd external circuit formed in the fixing member with the slip ring. In this case, the anode-side current and the cathode-side current transmitted separately from the tire power generation device pass through separate conductive paths of the inner layer and the outer layer in the rotating member, and are separately fixed by separate slip rings. To be derived.

  Moreover, it is preferable that a plurality of power generating elements are overlapped and wired in series. In this case, the amount of generated power can be increased.

(Tire sensor)
As a sensor using a tire power generation device, there is a tire sensor that detects a deformation state of a tire based on a response of electric power generated by the tire power generation device.

  For example, the tire sensor is a tire rotation speed sensor that includes a measurement unit that measures a temporal change in electric power generated from a power generation element and a speed calculation unit that calculates a rotation speed of the tire based on the temporal change in electric power.

  The tire rotation speed sensor can be used in a travel control system such as an antilock brake system (ABS) or a traction control system. Further, tire lock and slip can be detected for each tire.

  For example, a tire sensor is an abnormality detection sensor that detects an abnormality of a tire. The abnormality detection sensor includes a storage unit that stores a normal pattern of electromotive force generated per one rotation of the tire, a measurement unit that measures an actual pattern of electromotive force generated along with the rotation of the tire, a normal pattern, and an actual measurement pattern. Are determined to be normal when the measured pattern is the same as the normal pattern, and to determine that the tire is abnormal when the measured pattern is different from the normal pattern. By attaching this abnormality detection sensor to each tire, the tire state such as standing wave phenomenon and slip can be detected for each tire.

  For example, a tire sensor is an air pressure sensor that detects tire air pressure. The air pressure sensor includes storage means for storing correlation data between the tire air pressure during travel and the electromotive force generated from the dielectric elastomer, measurement means for measuring an actual value of the electromotive force generated from the dielectric elastomer during travel, And a collating means for collating the measured value of the electric power with the correlation data to obtain the tire air pressure. The air pressure sensor can be used as a sensor that detects a tire burst.

  For example, a tire sensor is a road surface state detection sensor that detects a state of a road surface on which a tire is traveling. Since the amount of expansion / contraction of the tire changes depending on the road surface state, the expansion / contraction amount of the dielectric elastomer also changes. For this reason, according to the road surface state detection sensor, road surface states such as gravel roads and frozen roads can be detected. The road surface detection sensor is a storage means for storing an electromotive force pattern generated when a tire travels on a reference road surface as a reference pattern, and a measurement for measuring an electromotive force pattern generated during traveling as an actual measurement pattern. Means, and detecting means for comparing the actually measured pattern with the reference pattern and detecting the road surface state based on the difference. For example, when the measured pattern is smoother than the reference pattern, it is determined that the road surface has a small unevenness such as a frozen road. When the measured pattern has a larger pattern unevenness than the reference pattern, it is determined that the road surface has a large unevenness such as a gravel road. It is preferable that the road surface state sensor is disposed in the tread portion of the tire. Since the tread portion is a portion in contact with the ground, the tread portion expands and contracts following the road surface state. For this reason, road surface information can be acquired in detail.

  For example, a tire sensor is a tire wear sensor that detects a wear state of a tire. Since the response of the dielectric elastomer varies depending on the degree of wear of the tire, the tire sensor can be used as a tire wear sensor. The tire wear sensor includes, for example, storage means for storing correlation data between the degree of tire wear and the amount of power generated by the dielectric elastomer, measurement means for measuring an actual value of electric power generated from the dielectric elastomer during travel, and an actual value. And detecting means for detecting the degree of tire wear by checking the correlation data. The tire wear sensor can be used as a tire change notification device for notifying that a tire change is necessary when the tire is in a worn state that requires a tire change. The tire wear sensor is preferably disposed in the tread portion of the tire. Since the tread portion has a large amount of wear, the tire wear amount can be easily detected by disposing a tire wear sensor on the tread portion.

  For example, a tire sensor is a theft sensor that detects theft of a vehicle. When the vehicle is stopped, the dielectric elastomer does not expand and contract and no power is generated. When the vehicle is stolen, the vehicle is lifted or travels and the tire rotates. In either case, the tire expands and contracts and power is generated from the dielectric elastomer. By detecting this power, it can be seen that the vehicle has been stolen by moving from the stop position. It is preferable that the theft sensor is continuously arranged in the entire circumferential direction of the tire. In this case, an electromotive force can be generated when the tire is lifted due to theft or the like, regardless of which surface in the circumferential direction of the tire is grounded and stopped.

  For example, a tire sensor is a braking sensor that detects a braking state. When the braking device is operated, a larger load is applied to the tire than when the braking device is not operated. For this reason, the deformation amount of the tire increases, the expansion and contraction of the dielectric elastomer increases, and the electromotive force also increases. For this reason, when the electromotive force becomes larger than when the brake device is not operated, it can be determined that the brake device is operated.

  The braking sensor includes a storage unit that stores an electromotive force value when the braking device is not operated as a reference value, a measuring unit that measures an electromotive force during traveling as an actual measurement value, and the actual measurement value is compared with the reference value. If it is the same as the reference value, it is determined that the braking device is not operating, and if the measured value is larger than the reference value, it is determined that the braking device is operating. It is also possible to grasp the operating state of the braking device (for example, the degree of brake application) based on the difference between the actually measured value and the reference value. The braking sensor is preferably mounted on all tires of the vehicle. In this case, the braking state can be detected more accurately.

  For example, a tire sensor is an angle sensor that detects a steering angle of a wheel. When the vehicle is turned, a larger load is applied to the inner tire than the outer tire, and the inner tire contracts greatly. Therefore, a tire power generation device is mounted on the inner tire and the outer tire. The balance of the expansion and contraction of the tires on both sides can be detected, and the turning direction and turning angle can be measured based on the degree.

  The brake sensor and the angle sensor can also be used for a drive recorder that records a running state.

  Each sensor may be provided with an amplifier that amplifies a signal emitted from the tire power generation device. In this case, even a weak electric signal can be amplified to a detectable level.

(Tire stiffness variable device)
The actuator includes a dielectric elastomer that converts electrical energy applied from an external circuit into stretching kinetic energy, and electrodes disposed at both ends of the dielectric elastomer.

  An actuator similar to the power generation element can be used. A dielectric elastomer converts expansion and contraction kinetic energy into electrical energy, but when an electrical energy is applied, the dielectric elastomer undergoes a stretching motion. As such an actuator, for example, an actuator shown in Japanese translations of PCT publication No. 2003-505865 can be used.

  Moreover, the power transmission means for transmitting power to the actuator can be the same as the power transmission means of the tire power generator.

  The tire stiffness varying device can be mounted on a vehicle such as an automobile, a motorcycle, or a bicycle.

  The tire stiffness varying device can be used in combination with a tire sensor. For example, by combining a tire stiffness varying device with a tire rotation speed sensor, the tire can be set to a stiffness corresponding to the speed. By combining the tire stiffness varying device with a road surface state detection sensor, the tire can be set to a stiffness corresponding to the road surface. Further, by combining with an angle sensor, the tire can be set to a rigidity corresponding to the turning angle. Furthermore, it is possible to calculate the optimum tire stiffness by using a tire rotation speed sensor, a road surface state detection sensor, and an angle sensor in combination, and to control the tire stiffness based on the optimum stiffness value. Moreover, feedback control is also possible by using a tire stiffness detection sensor that detects the stiffness of the tire.

(Example 1)
Hereinafter, a tire power generator according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the tire power generation device 5 includes a wheel 4 having a disk portion 41 and a rim portion 42 extending radially outward from the disk portion 41, a sidewall portion 31, and a tread portion 32. As a power transmission means for transmitting the power generated by the power generation element 1 to an external circuit, the rubber-made tubeless tire 3 held by the rim portion 42, the power generation element 1 fixed to the inner side surface 35 of the tire 3 With cable 2. The power generation element 1 includes a dielectric elastomer 11 that converts the expansion and contraction kinetic energy into electrical energy by expanding and contracting following the expansion and contraction of the tire 3, and electrodes 12 and 13 disposed at both ends of the dielectric elastomer 11.

The dielectric elastomer 11 of the power generating element 1 is a flexible thin film produced by applying a predetermined strain to EPDM. The electrodes 12 and 13 are conductive polymers formed by adding carbon to EPDM. The dielectric elastomer 11 has an electric resistance value of 10 ¹⁴ Ω · m, and the electrodes 12 and 13 have an electric resistance value of 10 ¹ Ω · m. One electrode 12 is an anode, and the other electrode 13 is a cathode. The cathode-side electrode 13 is grounded by bringing a part of the cable 2 into contact with a conductive member such as a wheel. The power generating element 1 is fixed to the tire 3 with an EPDM rubber adhesive that is a stretchable adhesive.

  As shown in FIGS. 1 and 2, the power generating elements 1 are arranged one by one near the outer periphery of the sidewall portions 31 on both sides of the tire 3, and these are connected in series through the cable 2. The cable 2 has one end connected to the electrodes 12 and 13 of the power generation element 1 and the other end connected to a hub 92 on the vehicle body side. The cable 2 passes through the pressure chamber 30 of the tire 3 and is inserted into a conduction hole 420 that penetrates the wheel 4. The opening 421 on the pressure chamber 30 side in the conduction hole 420 is hermetically sealed by a hermetic seal 422 made of sealing glass.

  The tire power generation device 5 is fixed to a vehicle body 91 of the automobile. The vehicle body 91 includes a hub 92 that fixes the wheel 4 of the tire power generation device 1 and rotates as the wheel 4 rotates, and a case 95 that is fixed to the vehicle body 91 and disposed in a cylindrical shape on the outer periphery of the hub 92. The wheel 4 is fixed to the hub 92 by bolts (not shown). A bearing 94 is rotatably interposed between a hub 92 that is a rotating member and a case 95 that is a non-rotating member. The cable 2 is inserted into the hub 92 and is connected to a rotating shaft 93 that fixes the hub 92.

  The rotating shaft 93 has an inner layer 931 and an outer layer 932, and the inner layer 931 and the outer layer 932 are insulated by an insulating layer 933. The outer periphery of the rotating shaft 93 is covered with an insulating layer 934 in order to prevent a short circuit with other members. The inner layer 931 and the outer layer 932 are connected to the anode side and the cathode side of the cable 2 via connectors 40 that are detachable from the rotary shaft 93, respectively. The connector 40 is a portion protruding in the axial direction from the disk portion 41 of the wheel 4, and a conduction hole 420 is formed at the center thereof. As shown in FIG. 3A, the connector 40 includes an inner layer connection terminal 902 formed at the end of the conduction hole 420 and an outer layer connection terminal formed in a ring shape on the inner periphery of the conduction hole 420. 901. The inner layer connection terminal 902 and the outer layer connection terminal 901 are electrically connected to the inner layer 931 and the outer layer 932 of the rotary shaft 93 by leads 904 and 903, respectively. When the wheel 4 is removed from the hub 92, the connector 40 is detached from the hub 92 together with the wheel 4. As shown in FIG. 3B, an outer layer exposed portion 935 in which the outer layer 932 is exposed in a ring shape and an inner layer exposed portion 936 in which the inner layer 932 is exposed in a ring shape are partly included in the rotating shaft 93. Is formed. As shown in FIG. 3B, the outer layer exposed portion 935 and the inner layer exposed portion 936 each constitute a rotating current collector of the slip ring 84. The slip ring 84 has a pair of arm portions 840 and 841 fixed to the fixing member 96 and brushes 842 and 843 provided at the tips of the arm portions 840 and 841. Brushes 842 and 843 are in contact with the outer layer exposed portion 935 and the inner layer exposed portion 936. The brushes 842 and 843 are urged in the radial inward direction of the rotary shaft 93 by the spring 849 and always maintain contact with the outer layer exposed portion 935 and the inner layer exposed portion 936.

  The anode-side current and the cathode-side current transmitted from the cable 2 pass through the inner layer 931 and the outer layer 932 of the rotary shaft 93, respectively, and are transmitted to the external circuit 961 of the fixing member 96 by the slip ring 84. The external circuit 961 includes an A / D converter, a capacitor, a motor, and the like. The electric power taken out from the tire generator is stored in an electric storage device and used as an auxiliary for automobile electric power.

  As shown in FIG. 4, when the dielectric elastomer 11 is deformed, an electric field is generated to generate electric energy. That is, as shown in FIG. 4A, the dielectric elastomer 11 has a high electric resistance value. For this reason, when the dielectric elastomer 11 is stretched, static electricity is generated, and different charges in the dielectric elastomer 11 are drawn toward the electrodes 12 and 13. As shown in FIG. 4B, when the dielectric elastomer 11 contracts, the charges drawn to the electrodes 12 and 13 increase in density in the surface direction of the dielectric elastomer 11, and the electrical energy increases. In addition, since the thickness between the electrodes 12 and 13 is increased, charges of different potentials are separated from each other, so that the energy of the charges also increases. Thus, when the dielectric elastomer expands and contracts with the expansion and contraction of the tire, electric energy is generated.

  The electric power generated by the tire power generator of this example is a direct current having the waveform shown in FIG. One power generating element is disposed at each one of the sidewall portions 31 on both sides of the tire 1. A peak P1 in FIG. 5 is a potential when the tire is grounded and compressed in the radial direction, and the dielectric elastomer contracts in the radial direction following the tire. In the dielectric elastomer, static electricity generated during expansion is compressed by contraction, and the voltage increases. This increased voltage value is the peak P1. The maximum voltage was 4000 V, and electricity of several μA was generated with one rotation of the tire.

  In this example, as shown in FIG. 1, the electrical conduction between the hub 92 and the slip ring 84 is performed by a two-layer structure of an inner layer 931 and an outer layer 932, but a hole is formed in the center of the rotating shaft 93. The cable 2 may be passed through it.

(Example 2)
In this example, as shown in FIG. 6, eight power generating elements 1 are arranged at equal intervals in the circumferential direction of the sidewall portion 31 of the tire 3. All the power generating elements 1 are connected in parallel. The voltage waveform is shown in FIG. In this example, since eight power generating elements are arranged in the circumferential direction, eight peaks P2 are generated by one rotation of the tire.

(Example 3)
In this example, as illustrated in FIG. 8, one power generation element 1 is disposed continuously in the circumferential direction of the sidewall portion 31 of the tire 3. The voltage waveform is shown in FIG. During tire rotation, a constant value was always maintained, and when the tire stopped, it decreased to 0V.

Example 4
In this example, as shown in FIGS. 10 and 11, eight power generating elements 1 are intermittently disposed on the trad portion 32 of the tire 3. In this case, at the time of ground contact, the trad portion of the tire is compressed and extended in the plane direction due to the weight of the vehicle. For this reason, the dielectric elastomer also expands and static electricity is generated. Then, when shifting from grounding to non-grounding, the tire is released from the load and contracts in the plane direction. At this time, the dielectric elastomer also contracts. Then, the number of generated charges per unit area increases, and the voltage increases. Therefore, the dielectric elastomer disposed in the trad portion 32 can also generate electric energy by expansion and contraction.

(Example 5)
This example is a tire rotation speed sensor using the tire power generation device of Example 4. The tire rotation speed sensor includes a measurement unit that measures a temporal change in electric power generated from the power generation element, and a speed calculation unit that calculates a rotation speed of the tire based on the temporal change in the electric power. In addition, when the electrical signal generated by the power generation element is small, the signal may be amplified by an amplifier.

  According to the tire rotation speed sensor, the rotation speed of the tire can be measured.

(Example 6)
This example is a theft detection sensor using the tire power generation device of the third embodiment. The theft detection sensor includes a switching means (such as a switch) for turning on / off the theft detection mode, a monitoring means (such as a voltmeter) for monitoring a change in the electromotive force of the tire in the theft detection mode, and a change in the electromotive force. It has reporting means (wireless reporting system such as a portable terminal) for reporting to an external communication device when it occurs.

  When the theft detection mode is turned on, the presence / absence of a change in tire electromotive force is monitored. When the vehicle is stopped, the dielectric elastomer does not expand and contract and no power is generated. When getting into the vehicle or lifting the vehicle, the dielectric elastomer expands and contracts, causing a change in electromotive force. When the theft sensor detects this change in electromotive force, it reports this to the owner's communication device as theft information.

(Example 7)
This example is an abnormality detection sensor that detects a standing wave phenomenon using the tire power generation device of the second embodiment. The abnormality detection sensor stores in advance the switching means for switching ON / OFF of the abnormality detection mode, the monitoring means for monitoring the change with time of the electromotive force of the power generation element, and the voltage drop timing after the generation of the maximum electromotive force of the power generation element. And determining means for determining that the standing wave phenomenon has occurred when the time is delayed from the normal voltage drop time.

The standing wave phenomenon is a phenomenon in which a waveform remains behind the tire without returning to the original shape because the rotation speed of the tire is faster than the speed at which the deformation on the ground contact surface of the tire returns to the original shape.
As shown in FIG. 12, when the standing wave phenomenon occurs, the voltage drop after the electromotive force reaches the maximum value is delayed for any power generation element from the normal time (dotted line in FIG. 12). To do. When such a waveform is obtained, it can be determined that a standing wave phenomenon has occurred.

  When the standing wave phenomenon occurs, the extension of the sidewall portion is particularly delayed. In this example, as shown in FIG. 6 of Example 2, the power generation element is disposed on the sidewall portion 31 of the tire. The sidewall portion 31 is a portion where the degree of expansion / contraction during tire rotation is large. For this reason, it is possible to generate an electrical signal that sufficiently reflects the state in which the expansion delay occurs, and to easily detect the standing wave phenomenon.

(Example 8)
This example is an example in which the tire power generation device of Example 1 is used for a tire stiffness varying device.

  In the first embodiment, the external circuit is provided with a capacitor that stores electric power transmitted from the tire power generation device, but in this example, the external circuit is provided with power transmission control means for appropriately supplying electricity to the tire stiffness varying device. The power transmission control means includes a generator that generates electric power to be transmitted to the tire stiffness varying device, a measurement means that measures tire rigidity, and a tire expansion / contraction state and a running state such as a tire rotation speed, a road surface state, and a steering angle. Optimum stiffness calculation means for calculating the optimum stiffness of the tire in consideration, transmission amount calculation means for calculating the amount of power transmitted to the actuator so that the measured tire stiffness becomes the optimum stiffness of the tire, and the calculated power Command means for commanding the generator to transmit the quantity to the actuator. The rigidity of the tire is measured based on the degree of expansion / contraction of the tire. When the tire is extended, the rigidity is high, and when the tire is contracted, the rigidity is low.

  When electricity is transmitted from the power transmission control means to the tire stiffness variable device, the dielectric elastomer of the actuator expands. When the dielectric elastomer is stretched, the tire fixing the dielectric elastomer is also stretched to increase the rigidity. When power transmission to the tire stiffness varying device stops, the dielectric elastomer contracts. When the dielectric elastomer shrinks, the tire also shrinks and the rigidity becomes low. Thus, the rigidity of the tire can be adjusted by adjusting the voltage transmitted to the actuator.

  The tire power generation device, tire sensor, and tire stiffness variable device of the present invention can be applied not only to those mounted on a vehicle but also to those that rotate and expand and contract repeatedly, such as bicycles and wheelchairs.

It is a section explanatory view of the tire power generator of Example 1. FIG. 2 is a front view of a tire for indicating a position where a power generation element is disposed in Example 1. It is explanatory drawing (a) which shows a connector in Example 1, and explanatory drawing (b) of a slip ring. In Example 1, it is sectional explanatory drawing at the time of expansion | extension (a) and contraction (b) of a dielectric elastomer for showing the electric power generation mechanism. In Example 1, it is explanatory drawing which shows the voltage pattern of the electric power generation element. In Example 2, it is a front view of the tire for showing the arrangement position of the power generation element. In Example 2, it is explanatory drawing which shows the voltage pattern of the electric power generation element. In Example 3, it is a front view of the tire for showing the arrangement position of the power generation element. In Example 3, it is explanatory drawing which shows the voltage pattern of the electric power generation element. In Example 4, it is a cross-sectional explanatory drawing of the tire for showing the arrangement position of the power generation element. In Example 4, it is a front view of the tire for showing the arrangement position of the power generation element. FIG. 10 is an explanatory diagram illustrating a voltage pattern when a standing wave phenomenon occurs in Example 7.

Explanation of symbols

1: power generation element, 11: dielectric elastomer, 12, 13: electrode, 2: cable, 3: tire, 31: sidewall portion, 32: tread portion, 4: wheel, 40: connector, 41: disk portion, 42: Rim part, 83, 84: slip ring, 91: vehicle body, 92: hub, 93: rotating shaft

Claims (19)

A wheel having a disk part and a rim part extending radially outward from the disk part, a tire having a sidewall part and a tread part and held by the rim part, and fixed to the tire Having a power generation element and power transmission means for transmitting the power generated by the power generation element to an external circuit;
The power generation element includes a dielectric elastomer that converts expansion and contraction kinetic energy into electrical energy by expanding and contracting following the deformation of the tire, and electrodes disposed at both ends of the dielectric elastomer. Power generation device.   The tire power generation device according to claim 1, wherein the power generation element is intermittently disposed in a circumferential direction of the tire.   The tire power generation device according to claim 2, wherein a plurality of the power generation elements are arranged at equal intervals in the circumferential direction of the tire.   The tire power generation device according to claim 1, wherein the power generation elements are continuously arranged in a circumferential direction of the tire.   The tire power generation device according to any one of claims 1 to 4, wherein the power generation element is disposed in a sidewall portion of the tire.   The tire power generation device according to any one of claims 1 to 4, wherein the power generation element is disposed in the tread portion of the tire.   The said power transmission means is a cable arrange | positioned in the atmospheric | air pressure chamber formed between the said tire and the said rim | limb part, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. Tire power generator. The rim portion has a conduction hole communicating with the atmospheric pressure chamber,
The tire power generation device according to claim 7, wherein the conduction hole is sealed with a hermetic seal in a state where the cable is inserted.   A vehicle comprising the tire power generation device according to any one of claims 1 to 8.   A tire sensor that detects a deformation state of a tire based on a response of electric power generated by the tire power generation device according to any one of claims 1 to 9.   The tire sensor according to claim 10, wherein the tire sensor is a tire rotation speed sensor.   The tire sensor according to claim 10, wherein the tire sensor is an abnormality detection sensor that detects an abnormality of the tire.   The tire sensor according to claim 10, wherein the tire sensor is an air pressure sensor that detects an air pressure of the tire.   The tire sensor according to claim 10, wherein the tire sensor is a road surface state detection sensor that detects a state of a road surface on which the tire contacts the ground.   The tire sensor according to claim 10, wherein the tire sensor is a tire wear sensor that detects a wear state of the tire.   The tire sensor according to claim 10, wherein the tire sensor is a theft sensor that detects theft of a vehicle.   The tire sensor according to claim 10, wherein the tire sensor is a braking sensor that detects a braking state.   The tire sensor according to claim 10, wherein the tire sensor is an angle sensor that detects a steering angle of a wheel. A wheel having a disk part and a rim part extending radially outward from the disk part, a tire having a sidewall part and a tread part and held by the rim part, and fixed to the tire An actuator and a power transmission means for transmitting power from an external circuit to the actuator;
The actuator includes a dielectric elastomer for converting electrical energy applied from the external circuit through the power transmission means into expansion and contraction kinetic energy, and electrodes disposed at both ends of the dielectric elastomer. .

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