JP2017520219A - Piezoelectric energy harvester device with frequency offset vibration harvester - Google Patents

Abstract

The present invention relates to an energy harvester device comprising a plurality of elongated resonator beams. The resonator beam includes a piezoelectric material that extends between a first end and a second end. One or more bases are connected to a first end of each of the resonator beams, and a second end of the resonator beams extends freely from the one or more bases as a cantilever beam. A weight is attached to the second end of the resonator beam. Each of the resonator beams is tuned to a resonant frequency that is offset by 0.1 / W to 0.9 / W with respect to each of the other resonator beams, where W excites the motion of the resonator beam. It is a time width between the first impulse and the second impulse. Similarly, a system comprising an apparatus and an energy harvester device and methods for using and designing the system are disclosed.

Description

  The present invention relates to a piezoelectric energy harvester device having a frequency offset vibration harvester, a system comprising the device, and a method of using and designing the system.

  Vibration energy harvester devices provide power generation in environments lacking light, temperature differences, and / or pressure differences. Instead, vibrations and / or movements emanating from a structural support, which may be in the form of, for example, constant frequency vibrations or impulse vibrations containing multiple frequencies, convert motion (eg vibration energy) into electrical energy. May be scavenged (or harvested) to convert to One particular type of vibration energy harvester is a beam of beams caused by ambient vibration (driving force), such as the resonator beam described in US patent application Ser. No. 14 / 173,131 to Vaeth et al. A resonator beam that freely extends from the base is used as a cantilever beam that incorporates a piezoelectric material that generates a charge when distorted during resonance.

  Improvements in the energy harvesting capability of such devices in systems that receive multiple impulses are needed. In particular, a cantilever-based piezoelectric vibration energy harvester includes a resonator beam having a natural resonance frequency. The resonator beam may be excited and vibrate at a natural resonant frequency with a short acceleration impulse. Further impulses applied to the vibration energy harvester may increase or suppress movement of the resonator beam depending on the timing of subsequent impulses relative to the resonance frequency. If further impulses are applied in phase with the resonator beam motion, the amplitude of the motion increases. However, if further impulses are applied out of phase with the resonator beam motion, the amplitude of the motion will decrease. Thus, the performance of the harvester depends on the timing between impulses applied to the system.

  As an example, the timing between impulses is for a vibration energy harvester used in a system such as a tire pressure monitoring system (TPMS) where the harvester receives an impulse when the tire flexes during rolling movement of the tire on the road. Of particular importance. When the portion of the tire's ground contact surface where the harvester is located contacts the road surface, that portion of the tire is forced into a short flat shape, which in turn changes the acceleration profile for the harvester that is attached to the tire periphery. Bring. This change in tire radial acceleration is incorporated by reference in its entirety. B. Singh et al., “Piezoelectric Vibration Energy Harvesting System With An Adaptive Frequency Tuning Mechanism For Intelligent Tires,” Ref.

  For the majority of tire rotation cycles, there is a relatively constant centripetal acceleration for the portion of the tire located at the periphery of the tire. When that portion of the tire first contacts the road surface, there is an initial increase in radial acceleration. The initial increase in acceleration is then accompanied by a sudden drop in radial acceleration to zero. The sudden drop to zero provides a first impulse to the vibration energy harvester and excites the motion of the resonator beam. The radial acceleration then remains zero for the time it takes for the portion of the tire to rotate through contact with the road surface. As the portion of the tire rotates through contact with the road surface, there is a sharp positive increase in radial acceleration followed by settling back to equilibrium radial acceleration. A sudden increase in radial acceleration returning to or near equilibrium provides a second impulse for the vibration energy harvester system. The second impulse increases or suppresses the vibration of the resonator beam excited by the first impulse according to the time width between the first pulse and the second pulse. The rotation speed of the tire and the circumference (or diameter) of the tire determine the time width. The vibration of the resonator beam, and hence the amount of energy harvested, can vary significantly depending on the speed of the vehicle. Therefore, it would be desirable to develop a piezoelectric energy harvester that provides a more consistent electrical energy source in systems that receive multiple impulses, such as in TPMS.

U.S. Patent Application No. 14 / 173,131

K. B. Singh et al., “Piezoelectric Vibration Energy Harvesting System With An Adaptive Frequency Tuning Mechanical For Intelligent Tires,” 88-Mechanical 9

  The present invention is directed to overcoming these and other deficiencies in the art.

  One aspect of the invention relates to a device comprising a plurality of elongated resonator beams. Each of the resonator beams includes a piezoelectric material that extends between a first end and a second end. One or more bases are connected to a first end of each of the resonator beams, and a second end of the resonator beams extends freely from the one or more bases as a cantilever beam. A mass is attached to each of the second ends of the resonator beams. Each of the resonator beams is tuned to a resonance frequency that is offset by 0.1 / W to 0.9 / W with respect to each of the other resonator beams, and W is a first that excites the motion of the resonator beam. Is the time width between the second impulse and the second impulse.

  Another aspect of the invention relates to a system comprising a motorized device and a device of the invention coupled to the device.

  Yet another aspect of the invention relates to a tire comprising the system of the invention.

  A further aspect of the invention relates to a method for supplying power to an electrically powered device. The method includes providing a system according to the present invention and exposing the system to a plurality of impulses that generate electrical energy in the energy harvester device. Electrical energy is transferred from the energy harvester device to the device to provide power to the device.

  Another aspect of the invention relates to a method of designing an energy harvesting device tuned to the impulse encountered by a tire. The method includes determining a tire rotation period P at a given speed. A first impulse generated when a point on the outer circumference of the tire contacts the road surface, and a point generated on the outer circumference of the tire is pulled away from contact with the road surface at the determined rotation period P A time width between the second impulse is determined. The system of the present invention is a first resonator beam of a plurality of resonator beams tuned to a first resonance frequency that is an integral multiple M of the reciprocal of the time width W, wherein M is 3 or more. One resonator beam is provided. The system of the present invention also includes a plurality of resonators tuned to a second resonance frequency that is offset by 0.1 / W to 0.9 / W with respect to the first resonance frequency of the first resonator beam. A second resonator beam of beams is provided. The system is connected to the tire.

  The energy harvester device of the present invention provides a resonator beam that acts as a cantilever with a slightly offset resonant frequency. The resonant frequency offset provides an energy harvester that provides a more consistent energy source when the system is subjected to multiple impulses by limiting the impact of subsequent impulses on the total average energy output from the harvester. In particular, the resonant frequency is such that when one resonator beam undergoes a decrease in motion due to improper phasing with respect to the received impulse, another resonator beam has increased motion due to favorable phasing of the received impulse. Selected to receive. Additional resonator beams may be applied to provide further consistency in the amount of energy generated at different impulse rates. The device receives multiple impulses at varying rates and provides a more predictable and uniform energy source for systems that improve device performance.

1 is a top view of one embodiment of an energy harvester device of the present invention having a plurality of energy harvesters. FIG. Each of the plurality of energy harvesters is an elongated resonator beam including a piezoelectric material extending between a first end and a second end, and a base connected to the resonator beam at a first end. The second end includes a base that freely extends from the base as a cantilever and a weight attached to the second end of the resonator beam. FIG. 6 is a top view of another embodiment of an energy harvester device of the present invention having an energy harvester with two elongated resonator beams comprising a piezoelectric material. The resonator beam extends freely as a cantilever from a common base, and separate weights are attached to the freely extending ends of both resonator beams. FIG. 2 is a perspective view of the exemplary single energy harvester of the present invention shown in FIG. 1. 4A-4C illustrate an embodiment of the system of the present invention in which a tire pressure monitoring system is electrically coupled to the energy harvester device of the present invention to power the tire pressure monitoring system. 4A and 4B show the direct attachment of the system to the tire (eg, under the tire's ground plane). FIG. 4C is a partial side view and partial block diagram of the system shown attached to the tire of FIGS. 4A and 4B. FIG. 5A shows the position of the system shown in FIGS. 4A-4C during rotation of the tire. FIG. 5B shows a radial acceleration profile for the system at various positions shown in FIG. 5A. FIG. 5 is a graph showing the power output of two energy harvester devices with a resonant frequency offset of 0.635 / W, where W is approximately equal to 8.45 ms.

  The present invention relates to a piezoelectric energy harvester device having a frequency offset vibration harvester, a system comprising the device, and a method of using and designing the system. The energy harvester device of the present invention has improved energy harvest uniformity in a system that receives multiple impulses.

  One aspect of the invention relates to a device comprising a plurality of elongated resonator beams. Each of the resonator beams includes a piezoelectric material that extends between a first end and a second end of the resonator beam. One or more bases are connected to a first end of each of the resonator beams, and a second end of the resonator beams extends freely from the one or more bases as a cantilever beam. A weight is attached to each of the second ends of the resonator beams. Each of the resonator beams is tuned to a resonance frequency that is offset by 0.1 / W to 0.9 / W with respect to each of the other resonator beams, and W is a first that excites the motion of the resonator beam. Is the time width between the second impulse and the second impulse.

FIG. 1 is a top view of one embodiment of an energy harvester 10 device of the present invention that includes a plurality of energy harvesters 11 (1) -11 (n). Each of the energy harvesters 11 (1) -11 (n) is shown positioned on a separate individual die, but two or more of the energy harvesters 11 (1) -11 (n) are together on a single die. It is understood that there is a possibility of being co-located. Elements of the energy harvester 11 (1) ~11 (n), except that the energy harvester 11 (1) ~11 (n) is tuned to operate at different resonant frequencies _f 1 ~f _n, energy harvester Each of 11 (1) -11 (n) will be described with respect to exemplary energy harvester 11 (1) because it includes the same elements as will be described with respect to energy harvester 11 (1). The resonance frequency _f 1 ~f _n energy harvester 11 (1) ~11 (n) is further described as offset from each other below.

  The energy harvester 11 (1) includes an elongated resonator beam 12 (1). The resonator beam extends between the first end 14 (1) and the second end 16 (1). The first end 14 (1) is connected to the base 18 (1), while the second end 16 (1) extends freely from the base 18 (1) as a cantilever. A weight 20 (1) is attached to the second end 16 (1) of the resonator beam 12 (1).

  The energy harvester 11 (1) may be formed of an integrated and self-packaging unit. In particular, as shown in FIG. 1, a package 18 (1) that similarly forms a base to which the first end 16 (1) of the resonator beam 12 (1) is attached has a cantilever structure (at least partially). ) Surrounding the cantilever beam structure (ie, resonator beam 12 (1) and weight 20 (1)). In the present invention, the package may completely enclose the energy harvester device or may be formed to allow the energy harvester device to vent to the atmosphere. When the package completely encloses the energy harvester device, the pressure in the enclosed package may be above atmospheric pressure, equal to atmospheric pressure, or below atmospheric pressure. In one embodiment, the atmospheric pressure within the enclosed package is less than atmospheric pressure, for example less than 1 Torr.

  In one embodiment, as shown in FIG. 2, the energy harvester 110 includes a package 118, which may include two separate cantilever structures that extend freely from the package 118 in opposite directions. The cantilevered resonator beams 112 (1) and 112 (2) may be tuned to a resonant frequency that is slightly offset from each other as described further below. One or more of the energy harvesters 11 (1) to 11 (n) shown in FIG. 1 may be replaced by the energy harvester 110 shown in FIG.

  Referring again to FIG. 1, in one embodiment, the package 18 (1) may further comprise a compliant stopper connected to the package (eg, on the inner wall of the package), the stopper being damaged. Is configured to stabilize the movement of the cantilever. A suitable corresponding stop according to this embodiment of the energy harvester device is shown and described in US patent application Ser. No. 14 / 173,131 to Vaeth et al., Which is incorporated in its entirety by reference. The corresponding stopper of the energy harvester device may be composed of various materials. The stopper may be accommodated through material selection, design, or both material selection and design. According to one embodiment, the stopper is made from a material that is integral with the package. Suitable materials according to this embodiment may include, without limitation, glass, metal, silicon, oxide, or nitride from plasma enhanced chemical vapor deposition (PECVD), or combinations thereof. According to another embodiment, the stopper is not integral with the package. Suitable materials for the stopper according to this embodiment may include, without limitation, glass, metal, rubber, and other polymers, ceramics, foams, and combinations thereof. Other suitable materials for the corresponding stopper include, but are not limited to, polymers with low water permeability such as cycloolefin polymers and liquid crystal polymers. The liquid crystal polymer may be injection molded.

  In an alternative embodiment, the resonator beam 12 (1) may be configured with a stopper feature configured to stabilize the cantilever motion. Suitable stopper features according to this embodiment are shown in US patent application Ser. No. 14 / 145,560 to Andosca et al., Which is incorporated by reference in its entirety. According to this embodiment, the stopper is formed on the weight and / or second end of the resonator beam and is configured to prevent contact between the second end of the resonator beam and the package.

  FIG. 3 is a cross-sectional side view of an exemplary energy harvester 11 (1) showing the energy harvesters 11 (1) -11 (n) shown in FIG. According to one embodiment, the resonator beam 12 (1) comprises a laminate formed of a plurality of layers. The resonator beam 12 (1) includes at least a piezoelectric stack layer 22 (1) that covers the cantilever layer 24 (1) on the oxide layer 26 (1), while the resonator beam 12 (1) In the configuration, other layers may be included. Non-limiting examples of other layers include those described in US patent application Ser. No. 14 / 173,131 to Vaeth et al., Which is incorporated by reference in its entirety. In one particular embodiment, the plurality of layers includes at least two different materials.

  The cantilever layer 24 (1) can be any suitable material such as silicon, poly-Si, metal (eg, Cu or Ni), or other metal oxide semiconductor (CMOS) compatible material, or a high temperature polymer such as polyimide. It may be a material. In one embodiment, the cantilever layer 24 (1) has a thickness range of about 10 μm to about 200 μm, about 10 μm to about 75 μm, or about 10 μm to about 50 μm. In one embodiment, the cantilever layer 24 (1) is a high Q resonator having a natural resonant frequency. The oxide layer 26 (1) is a silicon layer having a thickness of about 1 μm, according to one embodiment.

The piezoelectric stack layer 22 (1) of the resonator beam 12 (1) includes a piezoelectric material. Suitable piezoelectric materials include, without limitation, aluminum nitride, zinc oxide, polyvinylidene fluoride (PVDF), and lead zirconate titanate based compounds. Piezoelectric materials are materials that are electrically polarized when subjected to mechanical strain. The degree of polarization is proportional to the applied strain. Piezoelectric materials are widely known and are available in many forms. Many forms include screen-printable pressure films based on single crystals (eg, quartz), piezoelectric ceramics (eg, lead zirconate titanate or PZT), thin films (eg, sputtered zinc oxide), piezoelectric ceramic powders (eg, Baudry, “Screen-printing Piezoelectric Devices,” Proc. 6 ^th European Microelectronics Conference (London, UK) pp. 456-63 (1987) and ur, sir, T , Present and Future, "Meas. Sci. Technol. 8: 1-20 (1997)), and polyvinylidene fluoride. Emissions ( "PVDF"), and polymeric materials (e.g., entirely incorporated by reference, Lovinger, "Ferroelectric Polymers," Science 220: 1115-21 (1983) refer) a.

として規定できる。
（参照によりその全体が組込まれる、Ｂｅｅｂｙ等,"Ｅｎｅｒｇｙ Ｈａｒｖｅｓｔｉｎｇ Ｖｉｂｒａｔｉｏｎ Ｓｏｕｒｃｅｓ ｆｏｒ Ｍｉｃｒｏｓｙｓｔｅｍｓ Ａｐｐｌｉｃａｔｉｏｎｓ，"Ｍｅａｓ．Ｓｃｉ．Ｔｅｃｈｎｏｌ．１７：Ｒ１７５−Ｒ１９５（２００６）） Polymer materials usually exhibit anisotropic characteristics. Therefore, the material properties differ depending on the direction of force and the orientation of the polarization and the electrode. The level of piezoelectric activity of a material is defined by a series of constants used in conjunction with the axis notation. The piezoelectric strain constant d is

Can be defined as
(Beeby et al., “Energy Harvesting Sources for Microsystems Applications,“ Meas. Sci. Technol. 17: R175-R195 (2006)), which is incorporated by reference in its entirety.)

  The piezoelectric stack layer 22 (1) of the resonator beam 12 (1) similarly includes one or more electrodes 28 (1) in electrical contact with the piezoelectric stack layer 22 (1). According to one embodiment, electrode 28 (1) comprises a material selected from the group consisting of molybdenum and platinum, although other materials suitable for forming the electrode structure may be used as well. In addition, the energy harvester 11 (1) further includes an electrical harvesting circuit in electrical connection with the one or more electrodes 28 (1) to harvest electrical energy from the piezoelectric material of the resonator beam 12 (1). May be. As described in more detail below, the energy harvester circuit may be electrically coupled to the motorized device to provide power generated from the piezoelectric material and supplied to the device.

  In the energy harvester 11 (1), the resonator beam 12 (1) has a second end 16 (1) that freely extends from the base 18 (1) as a cantilever beam. A cantilever structure containing a piezoelectric material is designed to operate in a bending mode, thereby distorting the piezoelectric material and generating charge from the d effect (incorporated in its entirety by reference, Beeby et al., “ Energy Harvesting Vibrations Sources for Microsystems Applications, “Meas. Sci. Technol. 17: R175-R195 (2006)). The cantilever beam provides a low resonant frequency that is further reduced by the presence of a weight 20 (1) attached to the second end 16 (1) of the resonator beam 12 (1).

  The resonator beam 12 (1) may have sidewalls that take various shapes and configurations to help tune the resonator beam 12 (1) and provide structural support. According to one embodiment, the resonator beam 12 (1) is a resonator beam 12 (1) as described in US patent application Ser. No. 14 / 145,534 to Vaeth et al., Which is incorporated by reference in its entirety. ) Having side walls that continuously curve in the plane.

  The energy harvester 11 (1) includes a weight 20 (1) at the second end 16 (1) of the resonator beam 12 (1). A weight 20 (1) is provided to lower the frequency of the resonator beam 12 (1) and also increase the power output (eg, generated by piezoelectric material) of the resonator beam 12 (1). . The weight 20 (1) may be composed of a single material or multiple materials (eg, multiple layers of multiple materials). According to one embodiment, the weight 20 (1) is formed of a silicon wafer material. Other suitable materials include, without limitation, copper, gold, and nickel deposited by electroplating or thermal evaporation.

  In one embodiment, a single weight 20 (1) is provided for one resonator beam 12 (1). However, two or more weights may be attached to the resonator beam 12 (1) as well. In other embodiments, the weights 20 (1) are provided at different locations along the resonator beam 12, for example.

  When the resonator beam 12 (1) is subjected to a motion, such as an impulse motion, applied to the energy harvester device 10 (1), the one or more electrodes 28 (1) are made of the piezoelectric material of the resonator beam 12 (1). Outputs an electrical signal. Thus, electrode 28 (1) is in electrical communication with the piezoelectric material of resonator beam 12 (1). The electrical energy collected from the piezoelectric material of the resonator beam 12 (1) is then transferred to a further circuit. In one embodiment, additional circuitry is formed on the device 10 at or near the electrode 28 (1). In another embodiment, the circuit may be a separate chip or board, or reside on a separate chip or board.

Referring again to FIG. 1, the resonance in the energy harvester devices of the present invention, each of the energy harvester 11 of the energy harvester device within 10 (1) ~11 (n) , which is tuned to the respective resonant frequencies _f 1 ~f _n It includes instrument beams 12 (1) -12 (n). As those skilled in the art will readily recognize, resonator beams 12 (1) -12 (n) are cross-sectional shapes of resonator beams 12 (1) -12 (n), resonator beams 12 (1) -12 ( n) cross-sectional dimensions, length of resonator beams 12 (1) -12 (n), weights of weights 20 (1) -20 (n), weights on resonator beams 12 (1) -12 (n) Vary any one or more of several parameters such as the location of 20 (1) -20 (n) and the material used to make the resonator beams 12 (1) -12 (n) May be tuned by.

The resonant frequency of the energy harvester 11 (1) -11 (n) of the present invention is about 50 Hz to about 4,000 Hz, about 100 Hz to about 3,000 Hz, about 100 Hz to about 2,000 Hz, or about 100 Hz to about 1, A frequency of 000 Hz may be included. The resonance frequencies f _{1 to} f _n of the energy harvesters 11 (1) to 11 (n) are offset by 0.1 / W to 0.9 / W with respect to the other energy harvester resonance frequencies, where W is , The time width between the first and second impulses that excite the motion of the resonator beams 12 (1) -12 (n), but the offset is 0.2 / W to 0.8 / It may be W, 0.3 / W to 0.7 / W, 0.4 / W to 0.6 / W, or 0.45 / W to 0.55 / W. The resonator beams 12 (1) -12 (n) are tuned to the resonance frequency offset so that one or more of the energy harvesters 11 (1) -11 (n) are as described further below. Appropriate phase matching is received with respect to the timing of the received impulse. The offset of the resonant frequencies f ₁ -f _n is one for impulses received at various different time widths W between the impulses that excite the motion of the resonator beams 12 (1) -12 (n) of the energy harvester device 10. Alternatively, a consistent electrical signal output source is provided from the plurality of electrodes 28 (1).

The energy harvester 11 (1) -11 (n) of the energy harvester device of the present invention is described, for example, in US patent application No. 14 / 145,534 to Andosca & Vaeth, US patent application to Vaeth et al., Which is incorporated in its entirety by reference. 14 / 173,131, and US Patent Application No. 14 / 201,293 to Andoca, et al. For example, according to one embodiment, a method for producing an energy harvester device includes providing a silicon wafer having first and second surfaces. A first silicon dioxide (SiO ₂ ) layer is deposited on the first surface of the silicon wafer. A cantilever material is deposited on the first silicon dioxide layer. A second silicon dioxide layer is deposited on the cantilever material. A piezoelectric stack layer is deposited on the second silicon dioxide layer. The piezoelectric stack layer, the second silicon dioxide layer, the cantilever material, and the first silicon dioxide layer are patterned. The second surface of the silicon wafer is etched to produce an energy harvester device.

  Another aspect of the present invention relates to a system comprising the apparatus and device of the present invention. In one embodiment, the device is electrically coupled to the apparatus. Yet another aspect of the invention relates to a tire comprising the system of the invention.

  For example, according to one embodiment, the system of the present invention is a wireless sensor device that includes a sensor that monitors pressure in a tire, but the system of the present invention can be used in any one or more of various environments, for example. The present invention may be applied to a wireless sensor that monitors characteristics (temperature, humidity, light, sound, vibration, wind, movement, pressure, etc.). The energy harvester system of the present invention is coupled to a sensor to provide power to the sensor.

  Referring now to FIGS. 4A-4C, according to one embodiment, the system of the present invention is a tire pressure monitoring system (“TPMS”) 30 that includes a housing 32, but the system of the present invention is based on impulse motion. It may be applied to other systems that are excited. The TPMS 30 is coupled to the tire 36 below the tire 36 (ie, below the tire contact surface 38 and between the contact surface 38 and the wheel rim 40). In this embodiment, the TPMS 30 includes a sensor component 42 that monitors tire pressure, an energy storage 44, and an energy harvester device 10, all of which are in electrical communication and are positioned within the housing 32. According to this embodiment, the energy harvester device 10 provides a stand-alone energy source that powers the sensor 42 of the TPMS 30 for use in place of or in conjunction with another stand-alone energy source. Similarly, the energy harvester device of the present invention may supply power to the electric device by charging an energy storage 44 coupled to the electric device. The energy storage 44 may be a capacitor bank or a super capacitor, but in other applications, the energy storage 44 may be a rechargeable battery. For example, the energy harvester device may provide trickle charging to the energy storage 44 that powers the motorized device.

  The TPMS 30 is mounted directly on the tire 36, so that the movement of the resonator beams 12 (1) -12 (n) of the energy harvester device 10 occurs when the tire 36 enters the rotational footprint region (ie, TPMS 30). Is excited as a result of the impulse generated when the tire 36 touches the road at the point where it is attached to the tire 36. FIG. 5A shows various positions (1-6) of the TPMS 30 during rotation of the tire 36 through a full 360 ° rotation of the tire 36, including the footprint region 46. FIG. FIG. 5B shows the associated radial acceleration profile for the TPMS 30 when attached to the tire 36 throughout the rotation of the tire 36, including radial acceleration at positions 1-6.

  The TPMS 30 travels with a balanced radial acceleration outside the footprint area 46, ie at positions 1, 2 and 6. At position 3, TPMS 30 enters footprint region 46 and undergoes a sudden increase in radial acceleration followed by a sudden decrease in radial acceleration to zero. The sudden decrease provides a first impulse to excite the motion of the resonator beams 12 (1) -12 (n) of the energy harvester device 10. The TPMS 30 remains at zero radial acceleration throughout the footprint area 46 including position 4. At position 5, the TPMS 30 undergoes a sudden increase in radial acceleration before settling out of the footprint region 46 and back to equilibrium radial acceleration. The sudden increase at position 5 provides a second impulse to excite the motion of the resonator beams 12 (1) -12 (n) of the energy harvester device. The time width or duration (W) between the first impulse and the second impulse is determined by the rotation period (P) of the tire 36, and the rotation period (P) is the speed of the vehicle on which the tire 36 is located. Determined by.

In one example, the energy harvester device 10 TPMS30 may comprise two energy harvester 11 having a corresponding resonance frequency _{f 1} and _{f 2} (1) and 11 (2). In this example, the resonance frequency f ₁ of the energy harvester 11 (1) is tuned based on the time width W at a given speed, so that the resonance frequency f ₁ is defined by the equation f ₁ = n / W, Here, n is a positive integer. In one example, n> 4, but larger values of n may be used to provide optimal power generation based on features of the energy harvester 11 (1) such as size, for example. The energy harvester 11 (1) may be tuned to the resonant frequency f ₁ using methods known in the art. As an example, the resonator beam 12 (1) includes a cross-sectional shape of the resonator beam 12 (1), a cross-sectional dimension of the resonator beam 12 (1), a length of the resonator beam 12 (1), and a weight 20 (1). Any one or more of several parameters such as weight, location of weight 20 (1) on resonator beam 12 (1), and material used to make resonator beam 12 (1) May be tuned by varying.

In this example, the energy harvester 11 (2) may be tuned to the resonance frequency f ₂ slightly offset from the resonant frequency f _1. In this example, the offset between f ₁ and f ₂ is 0.1 / W to 0.9 / W, ie, the absolute value of f ₁ −f ₂ is 0.1 / W to 0.9. / W but offset is 0.2 / W to 0.8 / W, 0.3 / W to 0.7 / W, 0.4 / W to 0.6 / W, or 0.45 / It may be W to 0.55 / W. Energy harvester 11 (2) may be tuned to the resonance frequency f ₂ using methods known in the art. As an example, the resonator beam 12 (2) includes a cross-sectional shape of the resonator beam 12 (2), a cross-sectional dimension of the resonator beam 12 (2), a length of the resonator beam 12 (2), and a weight 20 (2). Any one or more of several parameters such as weight, location of weight 20 (2) on resonator beam 12 (2), and material used to make resonator beam 12 (2) May be tuned by varying.

In operation, the resonator beams 12 (1) and 12 (2) of the energy harvesters 11 (1) and 11 (2) are received when the TPMS 30 enters the footprint region 46 at position 3, as shown in FIG. 5A. Excited by the first impulse to be generated. The second impulse is received when TPMS 30 exits footprint area 46 at location 5. The first impulse and the second impulse are separated by a time width W. The resonator beam 12 (1) vibrates with a period of T ₁ = 1 / f ₁ , while the resonator beam 12 (2) vibrates with a period of T ₂ = 1 / f ₂ . If the time width W is approximately an integer multiple of T ₁ or T ₂ , the associated energy harvester motion will be out of phase for the second impulse. This is because the second impulse is a steep increase in acceleration, while the first impulse is a steep decrease in acceleration. Therefore, this harvester will be degraded. However, if the time width W is an integer n +/− 1/2 times the period of T ₁ or T ₂ , the motion of the associated energy harvester will be increased. The offset between f ₁ and f ₂ is that when one energy harvester is slightly out of phase by the time width W, the other energy harvester is in phase and the power output from the energy harvester device 10 is There is a possibility of more equality in various values for the time width W. Although this example utilizes two energy harvesters, it is understood that additional energy harvesters with offset resonant frequencies may be utilized to provide a more uniform power source at various speeds. In one example, the further energy harvester includes a resonator beam having a resonance frequency that is offset by 0.1 / W to 0.9 / W with respect to each of the other resonator beams in the plurality of resonator beams. The offset is 0.2 / W to 0.8 / W, 0.3 / W to 0.7 / W, 0.4 / W to 0.6 / W, or 0.45 / W to 0.55. / W.

  A further aspect of the invention relates to a method for supplying power to an electrically powered device. The method includes providing an energy harvester system of the present invention. The energy harvester receives a plurality of impulses and generates electrical energy from the piezoelectric material. Electrical energy is transferred from the piezoelectric material to the motorized device to provide power to the device. In one example, the method is implemented in connection with a vehicle tire in use, the device being a tire pressure monitoring system or a component of a tire pressure monitoring system as described above.

  Another aspect of the invention relates to a method for designing an energy harvesting device tuned to an impulse encountered by a tire. The method includes determining a rotation period P at a given speed. A first impulse generated when a point on the outer circumference of the tire contacts the road surface, and a point generated on the outer circumference of the tire is pulled away from contact with the road surface at the determined rotation period P A time width between the second impulse is determined. The system of the present invention is a first resonator beam of a plurality of resonator beams tuned to a first resonance frequency that is an integral multiple M of the reciprocal of the time width W, wherein M is 3 or more. One resonator beam is provided. The system of the present invention also includes a plurality of resonators tuned to a second resonance frequency that is offset by 0.1 / W to 0.9 / W with respect to the first resonance frequency of the first resonator beam. A second resonator beam of beams is provided. The system is connected to the tire.

  With reference to FIGS. 1-5B, a method for designing an energy harvesting device 10 that is tuned to an impulse encountered by a tire 36 will be described. A rotation period P of the tire 36 at a given speed is determined. The rotational speed and tire diameter (or circumference) are then utilized to produce a first impulse that is generated when a point on the outer circumference of the tire 36 contacts the road surface, as shown at position 3 in FIG. 5A. As shown at position 5 in FIG. 5A, the time width W between the second impulse generated when the point on the outer periphery of the tire 36 is pulled away from contact with the road surface may be determined. . The time width W depends on the rotation period P, so that the value of P / W remains fairly constant at various vehicle speeds.

  Next, the TPMS 30 of the present invention includes resonator beams 12 (1) to 12 (n) including a piezoelectric material. The resonator beams 12 (1) to 12 (n) freely extend from the bases 18 (1) to 18 (n) as cantilever beams. An exemplary resonator beam 12 (1) is shown in FIG. Resonator beams 12 (1) -12 (n) may be positioned on the same die shown by way of example only in FIG. 2, or, as shown in FIG. 1, individual harvesters 11 (1)- 11 (n) may be positioned separately within the energy harvesting device 10.

The first resonator beam 12 (1) is tuned to a _first resonance frequency f1 that is an integer multiple M of the inverse of the time width W of the tire 36 at a given speed. In one example, M is 3 or greater, but different values of M may be utilized depending on the desired performance characteristics of TPMS 30. The first resonator beam 12 (1) may be tuned to the resonance frequency f ₁ = M / W using methods known in the art. As an example, the first resonator beam 12 (1) includes a cross-sectional shape of the first resonator beam 12 (1), a cross-sectional dimension of the first resonator beam 12 (1), and the first resonator beam 12 The length of (1), the weight 20 (1) weight attached to the end of the first resonator beam 12 (1), and the location of the weight 20 (1) on the first resonator beam 12 (1) And may be tuned by varying any one or more of several parameters, such as the material used to make the first resonator beam 12 (1).

The second resonator beam 12 (2) is then offset by 0.1 / W to 0.9 / W with respect to the first resonance frequency f1 of the _first resonator beam 12 (1). While tuned to a second resonance frequency _{f 2,} offset, 0.2 / W~0.8 / W, 0.3 / W~0.7 / W, 0.4 / W~0.6 / W, or 0.45 / W to 0.55 / W. Second resonator beam 12 (2) may be tuned to the resonance frequency f ₂ using methods known in the art. As an example, the second resonator beam 12 (2) includes the cross-sectional shape of the second resonator beam 12 (2), the cross-sectional dimension of the second resonator beam 12 (2), the second resonator beam 12 The length of (2), the weight 20 (2) weight attached to the end of the second resonator beam 12 (2), and the location of the weight 20 (2) on the second resonator beam 12 (2) , And may be tuned by varying any one or more of several parameters, such as the material used to make the second resonator beam 12 (2).

The TPMS 30 further includes a resonator beam tuned to an offset from another resonator beam with an offset of 0.1 / W to 0.9 / W with respect to the resonator beams 12 (1) -12 (n). A harvester may be included. In one example, the third resonator beam 12 (3), the first resonator beam 12 (1) the resonance frequency _{f 3} which is offset resonant frequency _{f 1} from 0.25 / W~0.75 / W of While the fourth resonator beam 12 (4) may be offset from the resonance frequency f2 of the _second resonator beam 12 (2) by 0.25 / W to 0.75 / W. it may have a resonant frequency f _4. However, an additional number of resonator beams with other offsets may be utilized. Further, the method determines the rotation period of the tire 36 at another given speed, and the frequency interval based on the rotation period P of the tire 36 at another given speed, for two or more resonator beams. Tuning the resonant frequency may be included. Further resonator beams will provide a more uniform power source for the system when subjected to various different speeds of impulse motion.

  The following examples are provided to illustrate embodiments of the invention but are in no way intended to limit its scope.

Example 1-Power output of a device having two energy harvesters with a resonant frequency offset of 0.635 / W (W = 8.45 ms) The system includes a first impulse, similar to that experienced by a rolling tire. It was constructed to provide impulses to one or more harvesters at a delay interval between a second impulse or between impulse pairs. The system was operated at various repetition rates of these impulse pairs and the harvester output power was monitored. Using a time width W of 8.45 ms as a reference point, the system was loaded with a vibration energy harvester having a resonant frequency of 581 Hz. Over an operating frequency of 7 to 10 Hz (equivalent to a rotation period of 143 ms to 100 ms), the generated average power is 4.3 μW, and almost no average power is generated at 7 Hz and 8.5 Hz rotation frequencies.

  The system then vibrates an energy harvester with a resonant frequency of 581 Hz, indicating a difference of 75 Hz in the harvester resonant frequency (or 0.635 / W with W = 8.45 ms as the reference point) offset between the two frequencies. And a second vibration energy harvester with a resonant frequency of 506 Hz. Referring to FIG. 6, the dashed line shows the power output for an energy harvester having a resonant frequency of 581 Hz, while the solid line shows the power output for an energy harvester having a resonant frequency of 506 Hz. The use of two energy harvesters with a frequency offset of 0.635 / W in the system provides a more even power output from the system. The average power generated from this system over an operating frequency of 7 Hz to 10 Hz (equivalent to a rotation period of 143 ms to 100 ms) is 9.9 μW and has no zero average power generation band.

  While the preferred embodiment has been shown and described in detail herein, various modifications, additions, substitutions, etc. may be made without departing from the spirit of the invention, and thus they are described in the appended claims. It will be apparent to those skilled in the art that they are considered to be within the scope of the present invention as defined in

Claims (39)

A plurality of elongated resonator beams, each of the plurality of resonator beams including a piezoelectric material extending between a first end and a second end;
One or more bases connected to the first end of each of the plurality of resonator beams, wherein each of the second ends of the plurality of resonator beams is a cantilever beam One or more bases freely extending from one or more bases;
A weight attached to each of the second ends
And
Each of the plurality of resonator beams is tuned to a resonance frequency that is offset by 0.1 / W to 0.9 / W with respect to each of the other resonator beams in the plurality of resonator beams, An energy harvester device that is a time width between a first impulse and a second impulse that excite motion of the plurality of resonator beams.   The energy harvester device according to claim 1, wherein the offset is 0.2 / W to 0.8 / W.   The energy harvester device according to claim 1, wherein the offset is 0.3 / W to 0.7 / W.   The energy harvester device according to claim 1, wherein the offset is 0.4 / W to 0.6 / W.   The energy harvester device of claim 1, wherein the offset is 0.45 / W to 0.55 / W.   The energy harvester device according to claim 1, wherein each of the plurality of resonator beams includes a laminate formed of different layers.   The energy harvester device of claim 6, wherein the different layers comprise different materials. Each of the plurality of resonator beams is
The energy harvester device of any one of claims 1 to 7, further comprising one or more electrodes in electrical contact with the piezoelectric material.   The energy harvester device of claim 8, wherein the one or more electrodes comprise a material selected from the group consisting of molybdenum and platinum. Each of the plurality of resonator beams is
10. An energy harvester device according to claim 8 or claim 9, further comprising an electrical harvesting circuit in electrical communication with the one or more electrodes for harvesting electrical energy from the piezoelectric material.   The energy harvester device according to any one of claims 1 to 10, wherein the piezoelectric material is selected from the group consisting of aluminum nitride, zinc oxide, polyvinylidene fluoride, and a lead zirconate titanate compound. An electric device;
12. A system comprising: an energy harvester device according to any one of claims 1-11, electrically coupled to the apparatus.   The system of claim 12, wherein the electric device is a tire pressure monitoring system or a component of a tire pressure monitoring system.   A tire comprising the system according to claim 13.   14. A system according to claim 12 or claim 13, wherein the offset is between 0.2 / W and 0.8 / W.   14. A system according to claim 12 or claim 13, wherein the offset is between 0.3 / W and 0.7 / W.   14. A system according to claim 12 or claim 13, wherein the offset is between 0.4 / W and 0.6 / W.   14. A system according to claim 12 or claim 13, wherein the offset is between 0.45 / W and 0.55 / W.   The system of any one of claims 12, 13, or 15-18, wherein each of the plurality of resonator beams comprises a laminate formed of different layers.   The system of claim 19, wherein the different layers comprise different materials. Each of the plurality of resonator beams is
21. A system according to any one of claims 12, 13, or 15-20, further comprising one or more electrodes in electrical contact with the piezoelectric material.   The system of claim 21, wherein the one or more electrodes comprise a material selected from the group consisting of molybdenum and platinum. Each of the plurality of resonator beams is
23. The system of claim 21 or claim 22, further comprising an electrical harvesting circuit in electrical communication with the one or more electrodes for harvesting electrical energy from the piezoelectric material.   24. The system of claim 12, 13, or 15-23, wherein the piezoelectric material is selected from the group consisting of aluminum nitride, zinc oxide, polyvinylidene fluoride, and lead zirconate titanate compounds. . A method of supplying power to an electric device,
Providing a system according to any one of claims 12, 13, or 15-23,
Exposing the system to a plurality of impulses, whereby the energy harvester device generates electrical energy;
Transferring the electrical energy generated by the energy harvester device to the device to provide power to the device.   26. The method of claim 25, wherein the method is implemented in connection with a vehicle tire in use and the device is a tire pressure monitoring system or a component of a tire pressure monitoring system.   27. A method according to claim 25 or claim 26, wherein each of the plurality of resonator beams further comprises one or more electrodes in electrical contact with the piezoelectric material.   28. The method of claim 27, wherein each of the plurality of resonator beams further comprises an electrical harvesting circuit in electrical communication with the one or more electrodes for harvesting electrical energy from the piezoelectric material. A method of designing an energy harvesting device tuned to an impulse encountered by a tire, comprising:
Determining the rotation period P of the tire at a given speed;
The first impulse generated when a point on the outer periphery of the tire contacts the road surface, and the point on the outer periphery of the tire is separated from contact with the road surface at the determined rotation period P. Determining a time width W between the second impulse generated when
Providing a system according to claim 13 or any one of claims 15 to 24,
Tuning a first resonator beam of the plurality of resonator beams to a first resonance frequency that is an integral multiple M of the reciprocal of the time width W, wherein M is 3 or more;
A second resonance frequency obtained by offsetting the second resonator beam of the plurality of resonator beams by 0.1 / W to 0.9 / W with respect to the first resonance frequency of the first resonator beam. And connecting the system to the tire.   Further comprising tuning a third resonator beam of the plurality of resonator beams to a third resonance frequency that is offset from another resonator beam by a frequency spacing of 0.1 / W to 0.9W. Item 30. The method according to Item 29.   31. A method according to claim 29 or claim 30, wherein the offset in resonance frequency between different resonator beams is between 0.2 / W and 0.8 / W.   31. A method according to claim 29 or claim 30, wherein the offset in resonance frequency between different resonator beams is between 0.3 / W and 0.7 / W.   31. A method according to claim 29 or claim 30, wherein the offset in resonance frequency between different resonator beams is between 0.4 / W and 0.6 / W.   31. A method according to claim 29 or claim 30, wherein the offset in resonance frequency between different resonator beams is between 0.45 / W and 0.55 / W.   35. A method according to any one of claims 29 to 34, wherein each of the plurality of resonator beams further comprises one or more electrodes in electrical communication with the piezoelectric material.   36. The method of claim 35, wherein each of the plurality of resonator beams further comprises an electrical harvesting circuit in electrical communication with the one or more electrodes for harvesting electrical energy from the piezoelectric material. The method further includes tuning a third resonator beam to a third resonance frequency, wherein a frequency interval between the first resonance frequency and the third resonance frequency is 0.25 / W to 0.75. A method that is / W,
37. A method according to any one of claims 29 to 36, wherein the system comprises three resonator beams. The method further includes tuning a fourth resonator beam to a fourth resonance frequency, wherein a frequency interval between the second resonance frequency and the fourth resonance frequency is 0.25 / W to 0.75. A method that is / W,
38. The method of claim 37, wherein the system comprises four resonator beams. Determining the rotation period of the tire at another given speed;
39. Any one of claims 29-38, further comprising tuning the resonant frequencies of two or more resonator beams using a frequency interval based on the rotation period of the tire at the another given speed. The method described in 1.

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