Tire pressure sensing system

Details Tire pressure sensing system Tire pressure sensing system

1999-10-29

2002-03-26

Trieu, Van (Department: 2632)

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

C340S444000, C340S448000, C073S146500

Reexamination Certificate

active

06362732

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to condition monitoring systems and, more particularly, to a system that monitors air pressure in the tires of a motor vehicle, and that generates a signal indicative of the tire pressure in each of the tires to improve tire life, minimize tire wear, and increase vehicle performance and safety.
2. Discussion
Correct tire pressure is a critical factor in the safe operation and performance of a motor vehicle. Overinflated tires often result in unnecessary tire wear and less than optimal vehicle performance. Under inflated tires typically result in increased tire wear, decreased vehicle performance, and compromise the ability of the tires to maintain a safe interface with the road.
Conventionally, tire air pressure has been checked with mechanical gauges designed to be inserted over tire inner tube valve stems. Such gauges provide a generally accurate air pressure reading. However, the gauges are incapable of providing continuous monitoring of the air pressure within the tires and are limited in accuracy, and also require a driver concerned about tire air pressure to physically stop and exit the vehicle to check the tire pressure. In addition, such mechanical gauges do not provide any warning indication when the tire pressure reaches a level considered to be dangerous or unsuitable (such as below 14 psi in a typical passenger motor vehicle) for normal driving conditions.
Other systems utilize an active inductor capacitor (LC) circuit affixed within the tire to monitor tire air pressure. However, the active LC circuit requires a power source for operation. Because it is mounted within the tire, the power source, as well as the additional circuit components, are subjected to rotational vibration and other extreme conditions caused by temperature fluctuation. The circuit components are also difficult to install and replace if damaged or depleted due to their location within the tire. In addition, such systems typically provide no warning to the driver when the tire pressure falls below or rises above a certain minimum/maximum acceptable level. Moreover, these active inductor capacitor (LC) type systems generally also utilize battery power when the vehicle is both in operation and also in a parked non-use condition, thereby reducing the overall battery life of the active inductor capacitor (LC) circuit.
Other systems may utilize a sensor system that require the location of the sensor relative to a receiver pickup to be in very close proximity to one another. This provides a great disadvantage in enabling various options for mounting locations of the receiver relative to the sensor which may invariably lead to mounting the receiver in a very harsh environment location. Additionally, such systems may also require very large size inductors (L) which is also very difficult and, in some instances, not practical for mounting within vehicle tires. These types of systems may also increase the overall undamped weight of the overall tire by requiring such a large inductor (L). Other systems also require hard wiring of pickup receivers to indicator devices in the vehicle. This type of hard wiring must be, thereby routed throughout the vehicle wiring system either during production of the vehicle or for after-market use. This makes it very difficult to install such a system for aftermarket use since generally this wiring must be mounted throughout the vehicle. Other systems further do not provide diagnostics to identify whether or not the system is, in fact, working properly.
What is needed then is a tire pressure sensing system which does not suffer from the above-mentioned disadvantages. This, in turn, will provide a sensing system which monitors tire air pressure using a passive sensor, provides improved mounting of the sensor within the tire, provides a system which is less susceptible to interference, provides a sensor system which can accurately monitor the change in tire air pressure, provides improved sensors which operate to identify if the tire air pressure is outside a pre-determined range or identifies the actual tire air pressure based upon variable capacitance or inductive changes, provides a sensor system which enables more versatility in the placement of a pickup receiver, provides a sensor system which conserves sensor battery power when the vehicle is not in use, provides a sensor system which can easily be installed for aftermarket use without requiring hard wiring between a receiver pickup and an indicator device, and provides system diagnostics to confirm proper operation of the overall tire monitoring system. It is, therefore, an object of the present invention to provide such a tire pressure sensing system.
SUMMARY OF THE INVENTION
The present invention provides a tire pressure monitoring system that utilizes either a passive LC circuit or an active LC circuit mounted within the tire for monitoring tire air pressure. The passive circuit requires no power source and therefore is both less expensive to operate and has a longer useful life than conventional tire pressure monitoring systems utilizing active tire pressure sensors. The active circuit conserves battery power by stabling the circuit when the vehicle is not in use. The tire pressure monitoring system of the present invention is configured to provide either an audible or visual indication to the driver when tire pressure in any of the vehicle tires falls below a minimum acceptable level. The tire pressure monitoring system of the present invention may also be configured to provide a continuous digital readout of the actual tire pressure sensed within each of the vehicle tires to the vehicle driver based upon either a variable capacitance sensor or a variable inductance sensor. The tire pressure monitoring system may further be configured to eliminate hard wiring between the pickup receivers and an indicator device.
In one preferred embodiment, a tire pressure monitoring system for monitoring a pressure of at least one tire on a vehicle includes a sensor, a receiver and a tire pressure status indicator. The sensor is mounted relative to the at least one tire of the vehicle and is operable to sense tire pressure within the at least one tire. The receiver is mounted relative to the vehicle at a location external of the tire and within proximity to the sensor. The receiver is operable to generate a signal indicative of the tire pressure sensed by the sensor. The receiver includes a first inductor, a second inductor and an amplifier having a feedback path such that the first inductor and the second inductor are positioned relative to one another to create an electromagnetic coupling between the inductors such that feedback from this coupling is one of either a substantially zero feedback and a negative feedback. The tire pressure status indicator is in communication with the receiver to provide a tire pressure status based on the signal generated by the receiver.
In another preferred embodiment, a monitoring system for monitoring a first parameter includes a sensor, a receiver and an indicator. The sensor is positioned at a first location and is operable to sense a first parameter. The receiver is positioned at a second location remote from the first location and within proximity to the sensor. The receiver is operable to generate a signal indicative of the first parameter. The receiver includes a first inductor, a second inductor and an amplifier having a feedback path. The first inductor and the second inductor are positioned relative to one another to create an electromagnetic coupling between the inductors such that feedback from this coupling is one of either a substantially zero feedback and a negative feedback. The indicator is in communication with the receiver to provide the first parameter to a user.
In another preferred embodiment, a tire pressure monitoring system for monitoring the pressure in at least one tire mounted on a rim of the vehicle includes a sensor, a receiver and a tire pressure status indicator. The sensor i

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