JP2006021691A - Pneumatic pressure sensor system of externally mounted tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire pneumatic pressure sensor system having a simple structure and capable of being simply attached to a tire. <P>SOLUTION: This pneumatic pressure sensor system of the externally mounted tire includes a stretch sensor having displacement characteristic in the longitudinal direction of variable resistance. This stretch sensor is connected with a processor taking sample of resistance of the stretch sensor periodically. A sensor main body is attached to an external part side wall of the pneumatic tire so that the main body is displaced by a tire side wall and resistance becomes function of tire internal pressure. When the processor determines that pressure is less than a threshold value, a radio frequency generator is started by the processor and a low tire pneumatic pressure signal is generated by it. This signal is converted into alarm for a driver by a receiver. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automobile tire pressure sensor. More particularly, the present invention relates to a method and system for monitoring automotive tire internal pressure using externally mounted sensors.

  Tire pressure sensor systems are known per se and monitor the internal air pressure of each of the tires in which the car is inflated, when the internal air pressure of one or more car tires is dangerously low or high Is used to give a warning signal to the driver. When the tire internal pressure measured by the sensor exceeds a predetermined normal operating range, a warning signal is generated by a radio frequency signal generator controlled by a microprocessor connected to the tire pressure sensor. This radio frequency signal is sent to a receiver mounted on the car, which uses the warning signal to make it visible (by activating a warning light or warning indicator) or audible Alert the driver (by activating an audible alarm device) or both.

  Known tire pressure systems generally used one of two basic design arrangements. The arrangement of the first type of design employs an internal arrangement in which all components including the signal transmission portion of the tire pressure sensor system are arranged in the tire casing. In a typical installation of this type, these components are placed in a pneumatic tire casing by attaching a pressure sensor, radio frequency generator, microprocessor, and DC battery power source to the inside of the wheel before inflating the tire. Physically installed. There are several drawbacks to this first type of design arrangement. First, it is not easy to mount the system components in the tire casing, requiring sufficient care in positioning and mounting the components, increasing the manufacturing cost of the entire vehicle. In addition, many automobiles use steel belted tires that interact undesirably with radio frequency signals generated inside the tire. In addition, when a battery or one of the other system components fails, replacing a defective component requires removing the affected tire from the wheel before performing the replacement. This is expensive and time consuming.

  The second type of basic design arrangement used in current tire pressure sensor systems is mounted in a cap that is screwably attached to the exposed outer end of the tire valve stem. The component is adopted. While this design arrangement prevents the aforementioned drawbacks associated with the tire pressure monitoring system mounted therein, the following additional disadvantages arise: First, because the pressure monitoring system is supported by a valve stem that protrudes to the outside, the accuracy of the sensor system can be drastically reduced by the acceleration force reaching 200G generated by rotating wheels and tires. There is. Furthermore, this system component can easily be inadvertently lost or stolen.

Efforts to provide a simple, precise and durable tire pressure monitoring system that does not have the above disadvantages have not been successful so far.
US Patent No. 5900808 US Pat. No. 6,175,301 US Pat. No. 6,453,737

  The present invention is relatively easy and inexpensive to manufacture and attach to an automobile, can accurately read the tire internal pressure, can be easily and inexpensively replaced in the event of a failure, and is suitable for known systems. And a method and system for monitoring the internal tire pressure of an automobile using externally mounted components that do not have the aforementioned drawbacks.

  In the most general aspect, the present invention includes an externally mounted tire pressure sensor system having a variable resistance displacement sensor element that provides a resistance value indicative of tire internal pressure when coupled to an outer wall surface of a pneumatic tire. The variable resistance displacement sensor element has a variable resistance characteristic that is substantially linear with respect to longitudinal displacement. The processor is coupled to the displacement sensor element and converts a resistance value corresponding to insufficient tire pressure to a radio frequency generator activation signal. The radio frequency generator activation signal is activated by the processor and coupled to a radio frequency generator circuit that transmits a low tire pressure warning signal. The variable resistance displacement sensor, processor, and radio frequency generator circuit are all preferably mounted on a flexible substrate so that the completed device can be easily attached to the outer sidewall of the tire.

  The invention further includes a direct current power source such as a variable resistance displacement sensor, a processor, a battery for supplying power to the radio frequency generator circuit.

  In a preferred embodiment, the processor determines a maximum resistance value and a minimum resistance value provided by the variable resistance displacement sensor during one revolution of the pneumatic tire, and a value for calculating a difference between the maximum resistance value and the minimum resistance value. A decision circuit is further included. A comparison circuit in the processor compares the difference with a predetermined threshold value. When this difference is greater than a predetermined threshold value, the processor activates the radio frequency generator.

  The processor further includes a control circuit for controlling the operation of the value determination circuit and the comparison circuit according to the magnitude of the difference. The control circuit delays the operations of the value determination circuit and the comparison circuit for a first time, for example, 1 minute when the magnitude of the difference does not exceed the threshold, and when the magnitude of the difference exceeds the threshold, The operation of the value determination circuit and the comparison circuit is delayed for a shorter time, for example, 10 seconds.

  The present invention further includes a receiver circuit for converting a low tire pressure warning signal into a warning indication signal to operate a visible or audible driver warning device.

  The present invention provides a convenient solution to the problem of monitoring the tire internal pressure of an automobile equipped with a pneumatic tire. This system can be installed during the manufacture of a new car or as an aftermarket product. According to the present invention, it is not necessary to remove the tire from the wheel in order to replace an installed or worn component. This is particularly effective when replacing the DC battery power supply. In addition, existing vehicles that do not have a tire pressure sensor system can be retrofitted with a modern system at a relatively low cost. This is particularly beneficial in regions that require low tire pressure warning devices for all road vehicles.

  For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken together with the accompanying figures.

  Turning now to the drawings, FIG. 1 is a schematic diagram of the pressure sensor portion of a tire pressure monitoring system according to the present invention. As shown in this figure, a pressure sensor, generally indicated by reference numeral 10, includes a stretch sensor 12, an integrated circuit 14, an antenna 15, and a DC battery power supply 16, which includes a pressure calculation circuit, a signal generation circuit, Incorporates a radio frequency transmission circuit. All four major sensor components are provided on a flexible base or substrate member 17 that is mounted on the exterior surface 18 of the automobile tire sidewall 19.

  The stretch sensor 12 is a known component having an ohmic resistance characteristic that changes by a predictable amount due to a linear displacement in the longitudinal direction of the sensor body. Since the main body of the stretch sensor 12 is fixed to the outer surface 18 of the tire side wall 19, the length of the main body changes when the tire side wall 19 expands or contracts. The amount of tire sidewall 19 expansion or contraction, which is a function of tire pressure and tire angle position, correlates with a resistance value for the stretch sensor 12 that is measured periodically. Therefore, by periodically measuring the resistance value of the stretch sensor 12 over time, the tire internal pressure can be similarly monitored over time. In actual use of the present invention, the resistance change of the stretch sensor 12 over the expected range of longitudinal displacement values is selected to be substantially linear. This simplifies the calibration of the pressure sensor 10. The stretch sensor 12 is preferably a Marlin stretch sensor available from Marlin Systems, Inc. of Plymouth, UK. Other equivalent variable resistance sensors can be used as desired.

  2 and 3, the pressure sensor 10 is securely attached to the tire sidewall 19 in any suitable manner. For example, a strong and durable epoxy-based or silicone-based adhesive can be applied to the facing surfaces of the pressure sensor substrate 17 and the tire sidewall 19 and cured by pressing. Thermal bonding using a substrate 17 material for thermal bonding that is thermally compatible with the tire sidewall material can also be utilized.

  FIG. 4 is a block diagram of the present invention. As shown in this figure, the stretch sensor 12 is electrically coupled to a conventional resistive bridge circuit 31. The output of the bridge circuit 31 is coupled to the microcontroller 32. Direct current power is directly supplied from the battery 16 to the microcontroller 32. The microcontroller 32 controls application of DC power to the bridge 31 and the radio frequency transmitter 34. The output of the radio frequency transmitter 34 is coupled to the antenna 15. The bridge circuit 31, microcontroller 32, and radio frequency transmitter 34 are preferably all incorporated in the integrated circuit 14. Alternatively, the bridge circuit 31 and the radio frequency transmitter can be incorporated in another enclosure as required. As noted above, all components of the present invention are preferably mounted on a flexible substrate 17 (shown in FIG. 1) for ease of attachment to the tire sidewall 19.

  FIGS. 5A and 5B show the resistance measurement process for two different tire pressure conditions: tire pressure within an acceptable range of pressure (FIG. 5A) and tire pressure below an acceptable minimum (FIG. 5B). In the acceptable tire pressure condition shown in FIG. 5A, the measured resistance value of the stretch sensor 12 is located at a minimum distance from the surface on which the pressure sensor 10 is paved and undergoes maximum displacement (paved). Between the maximum Rmax when the pressure sensor 10 is adjacent to the surface and the minimum Rmin when the pressure sensor 10 is at the maximum distance from the paved surface and undergoes the minimum displacement. The parameter used to calculate the tire pressure is the difference R = (Rmax) − (Rmin). This parameter is calculated by the microcontroller 32. When this value is within a predetermined range as shown in FIG. 5A, the tire internal pressure is within the allowable range, and thus no signal is transmitted from the antenna 15. When the value of R is greater than the predetermined value, the microcontroller 32 activates the radio frequency transmitter 34, and a low pressure signal is transmitted from the antenna 15 by the radio frequency transmitter 34. This low pressure signal is received by a receiver circuit (not shown) on a conventional board, which converts the low pressure signal into a sensitive warning signal, such as a visual indication, an audible alarm, or both. In general, the receiver circuit comprises a decoder for decoding the low pressure signal in a form that can be used to operate the warning indicator. Representative examples of such receivers are shown and described in US Pat. No. 5,900,808, US Pat. No. 6,175,301, US Pat. No. 6,453,737. Since the receiver circuit is conventional and well known to those skilled in the art, further explanation is considered unnecessary.

  In order to save battery power, resistance measurements can be made periodically rather than continuously. For example, first, an initial value of R is calculated. If the value of R is below the threshold, the microcontroller 32 waits for 1 minute and continues with the new calculation of the parameter R. When the calculation results in an R value exceeding the threshold, the microcontroller 32 waits for a shorter time (10 seconds) and performs another calculation of the parameter R. If this result is any other value of R that exceeds the threshold, the microcontroller 32 activates the radio frequency transmitter to generate a low tire pressure signal. If this result is a continuous value of R that does not exceed the threshold, the microcontroller 32 waits for one minute and continues with the next calculation.

  So far, the preferred embodiment has been described as a single device for one tire, but in practice, each vehicle tire will be equipped with a tire pressure sensor system. Various encoding methods can be created to uniquely identify individual sensors, and the warning indicator can be configured to identify specific tires that are not currently fully aired.

  As will now be apparent, the present invention provides a simple and low cost tire internal pressure air sensor system that is relatively simple to install in an automobile tire and does not require removal of the tire from the wheel. Furthermore, the tire pressure sensor according to the present invention can be attached to the tire of an automobile during manufacture of the tire, if necessary. In addition, replacement of batteries or other failed system components can be done without the need to remove the tires from the wheels, thereby simplifying the repair or replacement of the entire system, thus reducing maintenance costs. To do. Finally, the present invention provides an accurate and reliable system for monitoring tire safety for all automobiles using pneumatic tires.

  Although the invention has been described with reference to certain preferred embodiments, various modifications, alternative embodiments, and equivalents can be used as desired. For example, the present invention has been described with respect to using adhesives or thermal bonds to attach the sensor to the tire sidewall, but if deemed appropriate, other known techniques may be used to A sensor can be attached to the sidewall. Therefore, the above should not be construed as limiting the invention, but as defined by the appended claims.

1 is a schematic diagram of a single tire pressure monitoring system according to the present invention. FIG. 1 is a perspective view of an automobile tire and wheel showing an air pressure monitoring system mounted on the automobile tire. FIG. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. It is a block diagram of the tire pressure monitoring system by this invention. It is the schematic which showed the change of a sensor resistance value in the position of a wheel angle about each of the tire which did not fully enter the tire which was not fully inflated, and the tire.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Pressure sensor, 12 Stretch sensor, 14 Integrated circuit, 15 Antenna, 16 DC battery power supply, Battery, 17 Board member, Pressure sensor board, Flexible board, 18 External surface, 19 Car tire side wall, 31 Resistance bridge Circuit, 32 microcontroller, 34 radio frequency transmitter

Claims (10)

A variable resistance displacement sensor element for providing a resistance value indicative of tire internal pressure when coupled to an outer wall surface of a pneumatic tire;
A processor coupled to the displacement sensor element for converting a resistance value corresponding to insufficient tire pressure to a radio frequency generator activation signal;
An externally mounted tire pressure sensor system including a radio frequency generator circuit that transmits a low tire pressure warning signal when activated by the processor.   The invention of claim 1, wherein the variable resistance displacement sensor element comprises a substantially linear variable resistance characteristic with respect to longitudinal displacement.   The invention of claim 1, wherein the variable resistance displacement sensor, the processor, and the radio frequency generator circuit are mounted on a flexible substrate.   The invention of claim 1, further comprising a DC power supply for supplying power to the variable resistance displacement sensor, the processor, and the radio frequency generator circuit.   A value determination for determining a maximum resistance value and a minimum resistance value provided by the variable resistance displacement sensor and calculating a difference between the maximum resistance value and the minimum resistance value during one revolution of the pneumatic tire; The invention of claim 1 further comprising a circuit.   6. The invention of claim 5, further comprising a comparator circuit that compares the difference with a predetermined threshold and activates the radio frequency generator when the difference is greater than the predetermined threshold.   The invention according to claim 6, wherein the processor further includes a control circuit that controls the operations of the value determination circuit and the comparison circuit in accordance with the magnitude of the difference.   When the magnitude of the difference does not exceed the threshold, the control circuit delays the operation of the value determination circuit and the comparison circuit for a first time, and when the magnitude of the difference exceeds the threshold, The invention according to claim 7, wherein the operations of the value determination circuit and the comparison circuit are delayed by a second time.   The invention according to claim 8, wherein the first time is longer than the second time.   The invention of claim 1 wherein the pressure sensor system further comprises a receiver circuit that converts the low tire pressure warning signal to a warning indication signal.

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