Injection Molded Energy Harvesting Device

• US 20100236036A1
• Filed: 05/27/2010
• Published: 09/23/2010
• Est. Priority Date: 02/14/2006
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Stark, Brian
• Granted Patent: US 8,225,471 B2
• Time in Patent Office: Days
• US Class Current: 29/25.350
• CPC Class Codes: B60C 23/041 Means for supplying power to the signal- transmitting means on the wheel
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/02 Forming enclosures or casings
• CPC Class Codes: H10N 30/306 Cantilevers
• CPC Class Codes: H10N 30/88 Mounts; Supports; Enclosures; Casings
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49121 Beam lead frame or beam lead device
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

Embodiments of an injection molded energy harvesting device are described. In one embodiment, a piezoelectric cantilever is produced via an injection molding method to harvest vibration energy from an environment being sensed. The cantilever device consists of a piezoelectric material member, a proof mass of high density material coupled to the piezoelectric member, and a leadframe for electrical connection. The piezoelectric member is electrically attached to the leadframe with a standard connecting material. The entire assembly is then injection molded with plastic. The plastic encased piezoelectric member forms a cantilever that generates electricity in response to vibration exerted on the proof mass.

Claims

1. A method comprising:

providing a lead frame comprising paired conductive members connected to rail elements;

attaching adhesive to one or more conductive members of the lead frame;

attaching a piezoelectric element at least one conductive member of the one or more conductive members of the lead frame;

attaching a proof mass to a first portion of piezoelectric element;

forming an injection molded plastic body around a second portion of the piezoelectric element; and

cutting the rail elements of the lead frame from the plastic body to form separate piezoelectric devices.

2. The method of claim 1, wherein the first portion and second portion of the piezoelectric element are coincident such that the injection molded plastic body is formed around the proof mass.

3. The method of claim 1 further comprising the step of forming a piezo bimorph strip by bonding the first portion of the piezoelectric element to a substrate, the substrate comprising a strip material made of one of the following:

plastic, piezoelectric material, and metal.

4. The method of claim 3 further comprising the step of leaving portions of the one or more conductive members of the lead frame exposed from the injection molded plastic body to form electrical contacts.

5. The method of claim 1 further comprising forming the piezoelectric material from Lead Zirconate Titanate (PZT), and forming the proof mass from tungsten.

6. The method of claim 1 wherein the piezoelectric element attached to at least one conductive member form a piezo bimorph element that is configured to deflect in a direction corresponding to a vibration force induced onto the proof mass and generate an electric current in response to the vibration force.

7. The method of claim 6 further comprising:

containing the plastic body in a circuit component attached to an inner surface of a vehicle tire; and

providing the electrical current to a sensor component of a tire pressure sensing system.

8. The method of claim 7 wherein the piezo bimorph element provides operating power to the sensor component, the method further comprising:

providing a transmitter circuit coupled to the sensor circuit; and

providing an antenna coupled to the transmitter circuit for transmission of tire pressure information.

9. The method of claim 2 further comprising orienting the bimorph element and proof mass relative to the injection molded plastic body such that the direction of movement of the proof mass is vertical to, and moves up-and-down relative to the horizontal plane of the plastic body.

10. The method of claim 2 further comprising orienting the bimorph element and proof mass relative to the injection molded plastic body such that the direction of movement of the proof mass is perpendicular to, and moves side-to-side relative to the horizontal plane of the body.

11. A method of manufacturing a power supply circuit for a tire pressure sensing device, comprising:

providing a plurality of die paddle leads comprising a conductive portion of a lead frame;

coupling a substrate strip to a piezoelectric material to form a piezo bimorph element;

mounting the a piezo bimorph element on the plurality of die paddle leads, and coupled to the substrate strip to form;

coupling a proof mass coupled to the bimorph element;

forming an injection molded plastic body around the piezo bimorph element to encase a first portion of the piezo bimorph element to leave at least a second portion of the piezo bimorph element exposed, the second portion containing at least the part of the bimorph element to which the proof mass is coupled; and

cutting away a frame rail portion of the lead frame to allow the plurality die paddle leads to protrude from the injection molded plastic body and comprise conductive leads for connection to the one or more electrical conductors.

12. The method of claim 11, wherein the piezoelectric material is attached to the plurality of electrical leads through a conductive epoxy adhesive material.

13. The method of claim 11, wherein the piezoelectric material comprises Lead Zirconate Titanate (PZT), and wherein the proof mass comprises tungsten.

14. The method of claim 13 wherein the piezo bimorph element is configured to deflect in a direction corresponding to a vibration force induced onto the proof mass and generate an electric current in response to the vibration force.

15. The method of claim 14, further comprising embedding the plastic body at least partially embedded within a portion of an inner surface of the vehicle tire.

16. The method of claim 15 further comprising connecting the conductive leads through the one or more electrical conductors to a pressure sensor module of a tire pressure sensing system that includes a pressure sensor module, an oscillator coupled to the pressure sensor module, and a radio-frequency transmitter coupled to the oscillator;

17. The method of claim 16 wherein the piezo bimorph element is configured to convert vibrational energy from the tire as it rolls into electricity to power the pressure sensor module.

18. The method of claim 11 further comprising orienting the bimorph element and proof mass relative to the injection molded plastic body such that the direction of movement of the proof mass is vertical to, and moves up-and-down relative to the horizontal plane of the plastic body.

19. The method of claim 11 further comprising orienting the bimorph element and proof mass relative to the injection molded plastic body such that the direction of movement of the proof mass is perpendicular to, and moves side-to-side relative to the horizontal plane of the body.