Fluid handling – Inflatable article – With gauge or indicator
Reexamination Certificate
1998-12-28
2001-03-13
Rivell, John (Department: 3753)
Fluid handling
Inflatable article
With gauge or indicator
C073S146500, C340S447000, C137S557000
Reexamination Certificate
active
06199575
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to electronic pressure measurement devices and, more specifically, to a miniature valve system that includes an integral pressure transducer.
2. Description of the Related Art
A pressure transducer is a device that produces an electric signal in response to a pressure of a gas or liquid. Following the general trend toward miniaturization of electronic components, pressure measurement devices have been produced that include the transducer itself plus associated electronic components needed to produce a useful output signal co-fabricated on a monolithic integrated circuit chip. Such a pressure measurement device is a type of microelectromechanical structure (MEMS). MEMS technology involves producing integrated micro devices or systems that combine electronic components formed on the semiconductor substrate and three-dimensional mechanical components fabricated in the substrate. Sensors and actuators are the primary categories of MEMS devices that have been developed and can range in size from micrometers to millimeters. MEMS devices are fabricated using integrated circuit (IC) lithographic processing as well as micromachining. Micromachining processes include mask-based wet and dry etching and maskless processes such as focused ion beam etching (FIB), laser machining, ultrasonic drilling, and electrochemical discharge machining (EDM) that produce high aspect-ratio features in the substrate.
Examples of MEMS pressure measurement devices are disclosed in M. Schuenemann, et al., “A Highly Flexible Design and Production Framework for Modularized Microelectromechanical Systems,” Micromachine Devices, Vol. 3, March 1998. One such device integrates signal processing, a microcontroller, nonvolatile memory and a bus interface, and is packaged in a co-fired ceramic box with top and bottom ball-grid array contacts. MEMS pressure measurement devices of the type disclosed by Schuenemann et al. are not well-suited for installation in small, confined spaces and through apertures because their packages are relatively large.
U.S. Pat. No. 4,695,823, issued to Vernon, suggests incorporating an apparently unpackaged integrated circuit-based pressure transducer in an automotive tire valve. The integrated circuit includes a transmitter that telemeters measured pressure to a remote display unit. The integrated circuit chip is presumably connected to other circuit elements in the conventional manner of an integrated circuit, i.e., by bonding extremely fine wires between microscopic pads on the chip. Such an arrangement would be impractical because fine wires are likely to break under the stresses to which tires and their valves are typically subjected. Moreover, a pressure transducer chip mounted inside a tire valve in any manner similar to that in which an integrated circuit chip is conventionally mounted in a circuit package would similarly subject the chip to stresses to which the chip would respond by producing erroneous output.
It would be desirable to provide an electronic pressure measurement device that can be economically manufactured and included in, for example, an automotive tire valve with minimal likelihood of failure under normal operating conditions and with minimal deviation from industry tire valve standards. These problems and deficiencies are addressed by the present invention in the manner described below.
SUMMARY OF THE INVENTION
In one respect, the present invention relates to an apparatus combining the features of a mechanical structure operable by a user with a movable microelectromechanically structured (MEMS) pressure sensor that not only senses pressure but also functions as a mechanical actuator for that structure. For example, in an illustrated embodiment of the invention, the mechanical structure is included in a valve, and the movable MEMS not only senses pressure but also opens and closes the valve. In another respect, the present invention relates to a similar MEMS pressure sensor that extends through an aperture in a curved wall, such as a curved wall of a valve body, at an oblique angle to allow it be securely mounted within confined spaces.
In an illustrated embodiment of the invention, the mechanical structure is a valve core of an automotive tire inflation valve. The MEMS sensor extends through an aperture in the barrel of the valve core at an oblique angle, thereby allowing the sensor to fit within the confines of the valve core.
In an alternative but similar embodiment, the MEMS sensor is a movable elongated rod-like member that is disposed generally coaxially within the valve core. In using a conventional valve core, a user, by manually or with the aid of an inflation nozzle depressing an enlarged head at the proximal end of a metal rod or pin that extends coaxially within the valve core, causes the valve cup at the distal end of this actuating pin to unseat itself and thereby open the valve. In contrast, using this embodiment of the invention, the user, causes the MEMS pressure sensor itself to similarly move in an axial direction and unseat the valve cup at its distal end. The MEMS should be made of a suitably strong semiconducting substrate, such as silicon, to enable it to perform these dual functions of sensing pressure within the structure and mechanically actuating the structure.
Embodiments of the present invention may include a transmission circuit that transmits a signal responsive to the measured pressure to a remote location. For example, the measured pressure may be received by a handheld receiver or a receiver mounted in the passenger compartment of an automobile to alert the driver or maintenance personnel of pressure conditions in the tires. The transmission circuit may be formed on the MEMS along with the pressure transducer and its associated circuitry. In a valve core embodiment of the invention, the antenna of such a transmitter may be electrically coupled to the distal end of the MEMS and extend axially away from the valve cup.
The present invention provides electronic pressure measurement in extremely confined spaces, such as the interior of an automotive tire valve core, by integrating the pressure transducer with its associated circuitry in a MEMS and integrating the MEMS in a novel manner within the structure. Mounting the MEMS in a manner in which the MEMS is itself a part of the structure that the user uses to mechanically actuate the structure further promotes integration into such confined spaces and enhances manufacturability.
The foregoing, together with other features and advantages of the present invention, will become more apparent when referring to the following specification, claims, and accompanying drawings.
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BiCMOS Integrated Circuit for Capacitive Pressure Sensors in Automotive Applications, Ph. Dondon, Ch. Zardini and J.L. Aucoutuner, Sen
Brown Martin Haller & McClain LLP
Rivell John
Schoenfeld Meredith H.
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