Injection molded energy harvesting device

• US 20070188053A1
• Filed: 02/14/2006
• Published: 08/16/2007
• Est. Priority Date: 02/14/2006
• Status: Abandoned Application

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Stark, Brian
• Application Number:
  US11/354,399
• Publication Number:
  US 20070188053A1
• Time in Patent Office: Days
• US Class Current: 310/339
• 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 device comprising:

a plurality of conductive leads;

a substrate strip coupled to one or more conductive leads of the plurality of conductive leads;

a piezoelectric material coupled to the substrate strip to form a piezo bimorph element;

a proof mass coupled to the bimorph element;

a body coupled to the piezo bimorph element and formed by an injection molding process that encases at least a portion of the piezo bimorph element and at least a portion of the one or more conductive leads.

2. The device of claim 1, wherein the plurality of conductive leads are part of a lead frame comprising one or more rails connected to the plurality of conductive leads, and wherein the body is formed around a portion of the lead frame and electrical leads are formed by removing the one or more rails of the lead frame after forming the body by the injection molding process.

3. The device of claim 1, wherein the piezoelectric material comprises Lead Zirconate Titanate (PZT), and the proof mass comprises tungsten.

4. The device of claim 3, wherein the proof mass is encased in a material formed by the injection molding process.

5. The device of claim 1, wherein the substrate strip comprises one of a plastic substrate, a piezoelectric material substrate, and a strip formed from a portion of the lead frame.

6. The device of claim 1 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.

7. The device of claim 6, wherein the electric current is provided to a sensor device mounted in a system containing the plastic body to provide operating power to the sensor device.

8. A system comprising:

a microsystem sensor including a sensor circuit, a transmitter circuit coupled to the sensor circuit, and an antenna coupled to the transmitter circuit; and

a power circuit coupled to the microsystem sensor, the microsystem sensor including a plastic body, a piezo bimorph strip coupled to the plastic body, and a proof mass coupled to the plastic body, the plastic body formed by an injection molding process configured to encase the plastic body and leave a portion of the piezo bimorph strip exposed.

9. The system of claim 8, wherein the power circuit is coupled to the microsystem sensor through a plurality of leads, and wherein the plastic body is formed around a lead frame and the electrical leads are formed by removing one or more rails of the lead frame after encasing the plastic body by the injection molding process.

10. The system of claim 9, wherein the piezo bimorph strip comprises a piezoelectric material coupled to a substrate.

11. The system of claim 10, wherein the substrate comprises a strip of material made of one of the following:

plastic, piezoelectric material, and metal.

12. The system of claim 10 wherein the piezo bimorph strip 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 to provide operating power to the microsystem sensor.

13. The system of claim 12, wherein the piezoelectric material comprises Lead Zirconate Titanate (PZT), and the proof mass comprises tungsten.

14. The system of claim 9, wherein the proof mass is encased within the plastic body formed by the injection molding process.

15. The system of claim 9, microsystem sensor comprises an air pressure sensor.

16. The system of claim 15, wherein the air pressure sensor and power circuit are mounted inside the tire of a vehicle.

17. 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.

18. The method of claim 17, 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.

19. The method of claim 17 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.

20. The method of claim 19, 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.