JPH01317815A - Tire pressure display unit conducting temperature compensating pressure measurement and pressure measuring circuit thereof - Google Patents

Abstract

PURPOSE: To always accurately carry out the measurement and display of the pressure of a tire by providing an energy transmitting device fitted to the chassis of a vehicle, an energy transfer device fitted to the wheel thereof, and a tire-pressure signal generating device or the like respectively. CONSTITUTION: When an ignition switch 7 of a vehicle is closed, a current is supplied to a power transmitter 8 from a generator 6. Then, a primary coil 9 fitted to the chassis of the vehicle transmits a prescribed frequency to a tuning circuit 10 fitted to the wheel of the vehicle. A transducer 1 supplied with power from the tuning circuit 10 is compressed up to a prescribed pressure, when it is supplied with power from the tuning circuit 10, to close the open end of the chamber. Further, the output of the transducer 1 is supplied to a signal regulating circuit 2 as a voltage. On the other hand, the change in the consumption of the primary power is detected by a detector 3 connected to the primary coil 9. After converted into pressure information by a processor 4, the detected result is output to a display 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for monitoring the pressure in tires of a vehicle and communicating pressure information to a driver inside the vehicle. The device uses a tire pressure sensor that is mounted within the rim of each of the rider's wheels and changes the value of the tire pressure in response to changes in temperature. Circuitry mounted on the chassis near the wheel receives temperature compensated pressure information inductively transmitted from the wheel. The processing and display circuitry consists of 2
One of the two functions is executed. The circuit allows the driver to selectively interrogate the device to actively monitor tire pressure. Instead, the circuit requires no action from the operator and such devices output a warning, such as a warning light or display, when the pressure drops below an acceptable level.

[Conventional technology]

According to the present invention, a circuit is provided in conjunction with a piezoresistive pressure quadrature transducer that provides accurate and fully reliable adjustment of detected pressure values due to changes in temperature during operation of a vehicle. Various tire pressure sensor devices are known that provide automatic indication of tire pressure. US Patent No. 4
．． A device such as that disclosed in No. 040.380 includes a small indicator connected to the tire valve that raises when the tire pressure falls below a predetermined value. U.S. Patent No. 3.71
7.030 and 4.723.445, the type of tire mounting markings mounted on tires are as follows:
Equipped with a visible display on the wheel itself.

The device just described is mounted only to the wheels of the vehicle and does not require associated circuitry mounted externally on the vehicle to provide a visual indication of tire pressure. However, use of such devices requires visual inspection of the tires and requires the driver to stop and exit the vehicle.

Other approaches to tire pressure sensing are known to provide pressure information to a driver within a vehicle. To provide such a remote display, circuitry or other structure mounted on the rim of the tire must communicate with other circuitry within the vehicle to convey information to the operator within the vehicle. Different approaches have been used, one such approach being a radio with a self-contained independent power supply in the rim and a receiver mounted close to the tire on the car's chassis. Use a transmitter. The information received is communicated to the vehicle console with some type of indicator that notifies the operator if the vehicle tire pressure is not accepted. An example of such an approach is U.S. Patent No. 4.
No. 443.785, No. 4.384.482 and No. 4.
No. 048.614. Of course, when a self-contained independent power source, such as a battery, becomes exhausted, the remote device becomes inoperable.

U.S. Patent No. 3.938.077, L911.434
3.723.986, 3.694.808 and 3.092.806 using known techniques of coordinated circuit modification. . In such a method, the primary coil is connected to the vehicle chassis.
It transmits energy in the radio range, for example at a frequency of 175 KHz. A secondary coil mounted on the rim of the wheel is energized by the transmission of the primary coil. In this way, energy is transferred to the secondary coil for actuation of the detection device in the wheel.

A capacitor is placed across the secondary coil to periodically short the coil in response to tire pressure indications. A short circuit in the secondary coil affects the operation of the primary coil, and the effect during operation is transferred to the support of tire pressure within the vehicle. Remote tire pressure sensing, which receives and transfers energy between the vehicle and the wheels, can be done periodically or continuously.

The difference depends primarily on the structure of the antenna or transmitter circuit attached to the rim. U.S. Patent No. 3.
The method disclosed in No. 788.413 only works when the vehicle is in motion. When the circuitry is positioned in a single location on the rim, the circuitry is such that the chassis-mount contacts the circuitry only once per rotation of the wheel. However, when the oscillator's antenna forms a closed circuit around the rim, the chassis-mounted primary coil is in continuous contact with the secondary coil on the rim. Most US patents provide examples of this.

Other examples are found in the following US patents: US Patent No. 4
．． No. 60.9095, No. 4.567.480, No. 4.
582°874, No. 4,554.528, No. 4.5
No. 29.981, No. 4゜510.484, No. 4.45
No. 0.431, No. 4.409.586, No. 4,389
．． No. 884, No. 4. +163.020, No. 4.348
．． No. 854, No. 4.130.817, No. 4,084.
No. 482, No. 4.057.783, No. 4.020,4
No. 58, No. 4,017,828, No. 4゜006.44
No. 9, No. 3.990. (No. 141, No. L950, 728
No. 3,930.224, No. 3,992,839, No. 3,913.065, No. 3.858.174, and No. 3.808.905.

One problem that occurs during the operation of all types of tire pressure sensors is that the tires heat up as they are driven over long periods of time. When a tire is heated, air expands within the closed volume of the tire, creating an increase in pressure within the tire even though the overall amount of air within the tire remains the same. Since the pressure is nominally different, the tire pressure sensor is
Shows different pressure values when the tire is cold and hot.

This is why tire manufacturers and car manufacturers recommend that vehicle owners check tire pressure when the tires are cold. Of course, having a remote tire pressure sensor would provide a continuous indication of tire pressure within the vehicle, but that indication would be inaccurate due to temperature changes. Thus, it is necessary to compensate for changes in temperature.

There are known methods of compensating for temperature changes within a tire. One example of providing temperature compensated pressure support is in U.S. Pat. No. 4,703,650, International Application No. WO87100129, published in PCT Application. In this device, a piezoresistive transducer has a continuous voltage applied to it, compensating for some degree of temperature change, while still incorporating a certain temperature movement inherent within the transducer. I will provide a. To compensate for this movement, a thermistor is provided to modify the instruction given by the transducer. A modified signal indication is provided in digital form for each pulse output. It is possible to derive both temperature and pressure indications from the coded signal output.

The referenced US patent provides separate indications of temperature and pressure per single coded signal. British Published Patent Application No. 2,112.757 provides similar instructions,
Allows readout of temperature and pressure indications for each tire. British Published Patent Application No. 1.301.359 provides further such instructions.

GB Published Patent Application No. 1.301,359 also provides such separate instructions. U.S. Patent Section 4.567
It is known to compensate for ambient temperature outside a tire, as exemplified by US Pat. This additional compensation affects the resulting pressure, since changes in temperature on the outside of the tire will affect the amount of "bend" in the tire and on the volume inside the tire, as will changes in temperature on the inside of the tire. influence

Herein, the PC equivalent of U.S. Patent Section 4.737.781
There is an application No. WO 37100129 published in U.S. Pat. The means are disclosed.

Other known devices also provide temperature compensation. An example of such a device is U.S. Patent Section 4. llO, No. 220 and No. 4,
No. 052,696. U.S. Patent Section 4.8
No. 10.220 shows an on-chip pressure quadrature transducer that uses a thermistor to compensate for temperature changes. The above-mentioned US Pat. No. 4,723,445 also mentions the need for temperature compensation.

The first-mentioned PCT application, as well as other temperature compensations, disclose effective methods of temperature-compensated pressure display, and these devices suffer from some inherent inaccuracies in measurement and inefficiencies in transmission. , which have been modified by the present invention.

In view of the foregoing, one object of the invention is to provide a device that allows reliable, accurate and sufficient transmission to the driver in a vehicle.

Another object of the invention is to provide such a device having all of the circuitry associated with a vehicle wheel housed in a small integrated circuit chip attached to the tire valve.

It is an object of the present invention to store a time sequence of temperature compensated pressure instructions according to the shape of the pressure change, and to provide information to the vehicle driver based on changes in the condition of the vehicle's tires over time. This information is useful, for example, to mechanics or other components convenient to the tires.Another object of the invention is to provide reliable temperature compensation for all of the wheels of a vehicle, including the spare tire, at a central location within the vehicle. Its purpose is to provide pressure indications.

Another object of the invention, particularly at the upper end of the price range, is that the wheel mounting utilizes already existing microcomputers to process the information extracted from the circuit.

The foregoing objects of the present invention are achieved with a tire pressure measurement device disclosed and mounted, which includes a wheel-mounted circuit and a chassis-mounted circuit. The wheel-mounted circuit includes a piezoresistive transducer and a constant voltage applied directly to the transducer, according to one embodiment of the invention, and sequentially applied to the transducer according to another embodiment. a constant current source replaced by a low voltage.

Currently, the best contemplated implementation of wheel mounting circuitry is a monolithic integrated circuit.

The chassis-mounted circuit has a primary coil as the energy source and the wheel-mounted circuit has a circuit, preferably in the form of a suitably programmed microprocessor, for processing pressure information from the circuit to the chassis-mounted circuit. including.

The figures shown below include various circuit means of the present invention including several different ways of communicating temperature compensated pressure information from the wheels to the chassis.

〔Example〕

Referring to FIG. 1A, the artificial "interface" is shown in dashed lines and the mounting portion of the present invention on a vehicle is shown to the right of the drawing. It should be noted that all the drawings in this application, as well as the description thereof, apply to each tire, including the spare tire of a vehicle.

Starting counterclockwise from the lower left-hand corner of FIG. 1A, the circuit of the present invention will not operate when the vehicle's engine is stopped. However, when the vehicle is activated, the ignition switch 7 is closed and current flows from the battery or generator 6 to the power transmitter which generates the alternating magnetic field. In the preferred embodiment, the magnetic field is 1
It is 75KHz.

The primary coil 9 transmits a frequency of 175 KHz to a tuned circuit 10 mounted on the rim of the tire. Tuned circuit 1
0 has a secondary coil and a capacitor coupled across the secondary coil. The primary and secondary coils are generally coupled as shown in Figure 1B. The secondary coil is wrapped in a U-shaped groove within the wheel. The U-shaped groove is glued to the inside of the wheel rim. 1
The next coil is attached to a bracket on the associated brake assembly on the vehicle frame.

When power is applied to the primary coil from the vehicle's battery, the primary and secondary coils inductively couple together.

Circuit 10 receives energy from tuning circuit 10 and supplies power to transducer 1 and signal tuning circuit 2, which will be described in detail below.

Transducer 1 includes a piezoresistive sensor as discussed below. The transducer is compressed to a predetermined pressure, closing off the remaining open end of the chamber that exerts a force in one direction. The other end of the transducer faces the air within the tire and is subjected to a second, opposite force whose magnitude is dependent on the air pressure within the tire. The output of the transducer is a function of the differential pressure acting on both sides of the transducer. One example of such a transducer is manufactured by IC Sensors of Milpitas, California.

The output of the transducer 1 is supplied as a voltage to a signal conditioning circuit 2 which loads a frequency of several kilohertz which is tuned by a tuning circuit 10. Detector 3 coupled to first coil 9
detects the change in primary power consumption induced by this several KHz frequency. The output of the detector is amplified and filtered to separate it from a frequency of 175 KHz (power transfer frequency). Processor 4 receives the separated detector output and provides a quantity that is converted within processor 4 to a pressure indication. Pressure information is output on a display 5 mounted inside the vehicle.

As shown in Figure 1A, there are five possible lights shown on display 5, one for each wheel including the spare tire.

As previously mentioned, an example was provided in which one primary coil and one secondary coil were used. However, more than one of each may be used. For example, one primary/
A pair of secondary coils is used to transfer energy to the wheel-mounted circuit, and another pair is used to transfer pressure information to the chassis-mounted circuit.

In FIGS. 2A and 28 a detailed view is provided showing the detector 3 and processor 4 coupled to the primary coil 9. Capacitor 9a and PNP transistor 9b act as an induced oscillator.

PNP) transistor 9b is normally in an inductive state and allows voltage to flow from power supply 6 to primary coil 9.

However, capacitor 9a discharges and transistor 9
When power is applied to the base of b, flow is blocked.

Coil 9 and capacitor C are selected appropriately, 175K
Provides a frequency of Hz.

Another embodiment of an inductive oscillator circuit is shown in FIG. 2B with a primary coil 9 transferring energy as follows. When power is applied, resistance R is NPN transistor 9b
Flow the base current through '.

In response, a large emitter current flows through the tap on the tuned circuit consisting of coil 9 and capacitor C, increases by the automatic transformer, is applied to the voltage on the base via capacitor 9a, and begins a voltage oscillation that drops to 0. . At this point, the collector-base junction becomes reverse biased and current flow stops. The lower terminal of the tuned circuit oscillates to about 24V and transistor 9b' becomes non-conducting since the base is turned off via capacitor 9a/. During the negative inversion amplitude of the tuned circuit, the resistor R is connected to the capacitor C
is sufficiently charged to make the base conductive and the cycle continues. This circuit is referred to as a Hurley oscillator.

Referring again to FIG. 2A, secondary coil 10b and tuning capacitor 10a form a tuning circuit 1o. The resistor and capacitor associated with diode lla provide the known function of power rectifier 11 of FIG. 1A. The energization of the secondary coil 10b' by the primary coil 9 transfers energy to the transducer 1, which provides an output acting on the tire pressure as described above.

The transducer output is provided to a pressure-to-frequency converter 1a. One example of a pressure-to-frequency converter is the IEEE Journal of Solid State Circuits, published June 1987 by Filling et al., Volume 3 of 5C-22, 343.
It is shown in the article on page 349. This pressure-frequency converter changes the output of the transducer 1 into a frequency value, which is reversely output across the secondary coil 10b and acts on the output of the primary coil 9.

The detector circuit 3a detects the alternating output of the primary coil 9,
A low output is provided by processor 4.

Referring now to FIG. 3, a preferred embodiment of the invention will be described. Transducer 1 is connected to the output and inverting input of operational amplifier A1, respectively. The non-inverting input of operational amplifier A1 is effectively coupled to a fixed amplitude voltage via resistor R1;
Its polarity changes periodically as described below. A substantially constant current flows through resistor R1, and operational amplifier A1 can be thought of as an infinite impedance constant current source.

The non-inverting output of operational amplifier A1 is connected to a fixed voltage and will be explained below.

The output of the transducer 1 is fed to the inverting and non-inverting input of another operational amplifier A2 configured as an integrator, a capacitor C1 being coupled between the output of the operational amplifier and its inverting input. As in the above-mentioned coupling, the transducer bridge 1 is effectively coupled to the feedback circuit of the operational amplifier A1, and the operational amplifier A1 effectively acts as a constant current source.

There are two reasons for coupling the transducer in this way, the first is according to technical note TN-002 provided by IC Sensors for providing instructions for implementing piezoresistive transducers: It is proposed that a constant current be supplied to the transducer 1. In this manner, the positive temperature coefficient of resistance of the transducer substantially cancels the negative temperature coefficient of pressure sensitivity.

A second reason for coupling the bridge in this manner is to reverse the polarity of the current which eliminates the effects of the offset voltage of A2 and its variations with temperature, as disclosed in the article in Rising et al.

A resistor RBB connected between terminals T2 and T3 of transducer 1 makes the bridge unbalanced. Thus, since operational amplifier A2 is configured as an integrator, the voltage at terminal T2 of transducer 1 is somewhat more negative than the voltage at the output of terminal T4, and R
The integrator rises and falls at a rate roughly set by BB and modified by the transducer output. In particular, the output will rise if the voltage at T2 is more negative than the voltage at T4;
If it is not more negative than the voltage of T4, it falls.

Amplifier A3 has a non-inverting input coupled to the output of amplifier A2 via resistor R2. The output of amplifier A3 is coupled in a positive feedback manner via resistor R3 and supplied to resistor R1. Amplifier A3 acts as a Schmitt trigger. When the output of integrator A2 exceeds the trigger threshold, either positively or negatively, the output of amplifier A3 reverses, reversing all voltages applied to A1 and transducer 1. This reversal changes the sweep of T4 and A2 of transducer 1 compared to the immediately advanced polarity, shortening the up sweep and advancing the down sweep, but the overall duration of the sweep is offset is independent of the amount of

In FIG. 3, operational amplifier A4 acts as a bias source and is intended to supply power at 1/2 of the power supply voltage. Two equal resistance voltage dividers provide a supply voltage that is stored by amplifier A4, which acts as a voltage follower.

FIG. 4 shows another method that does not require amplifier A4.

Transistor TRI and diode DI.

D2. By adding D3 and capacitors C2 and C3, the supply voltage is doubled. Diode D1 takes the positive peak value of the AC on the secondary coil, and diode D3
takes the same negative peak value of AC. Dl cathode and D
The voltage between the anodes of 3 is 2 of the peak voltage of the AC.
The common terminal of the secondary coil is
is the midpoint between the two diode terminals.

As shown in the circuit of FIG. 3, the voltages applied to amplifier A1 and transducer bridge 1 are reversed, and inverter II, 12 acts as a Schmitt trigger, providing the opposite effect. The output of the inverter I2 is the transistor T
Turns RI on and off and provides reverse functionality. The output of inverter I2 turns transistor TRI on and off and provides a switch signal that is transmitted from secondary coil 10b to primary coil 9. Transistor TRI in series with diode lla can short-circuit the secondary coil when the top terminal is positive. Transistor TR2 in series with diode D3 serves the same purpose when the top terminal of the coil is negative.

FIG. 5 shows a possible form of integrated circuit. An integrator is shown including an amplifier A2 and a capacitor C1, a secondary coil 10b and a synchronous capacitor 10a. Capacitors CI, C2 and C3 are positioned away from the chip. Inverters 13, 14 connect P-channel and N-channel enhancement MOSFETs 5, PI, Nl, and P2. Control the gates of each pair of N2. The transducer bridge 1 is provided on a separate chip and has a bridge associated with it that unbalances the resistor RBB.

The circuit shown in FIGS. 3-5 includes a short circuit of the secondary coil 10b via the discharge of the capacitor 10a. Another embodiment is shown in FIG. 6, in which the secondary coil is a transistor T
It is turned on and off according to the operation of Rs. In this implementation, the adjustment of power absorption is simplified by simply opening the resonant circuit. A similar type of information is transmitted from the secondary coil 10b to the primary coil 9, but with lower power consumption. It is usually considered difficult to start an electronic device that is not connected to a power source for disclosure. However, by connecting a diode Ds across the transistor TRs, the diode allows the transfer process to be substantially continuous without the need for a tuned circuit 10 to receive power continuously from the primary coil 9. and hold enough power.

The difference in the circuit of FIG. 6 is that in this embodiment two P
NP) using a current mirror consisting of transistors TR, TR4. Similar p-channel and N-channel enhancement MO8FETs are shown in FIG. 6 as in FIG. One suitable chip that provides suitable MO8FETS is the RCA CMOS chip model CD40070B. A typical Buri-Wub transducer 1 is an IC sensor model IOA. For example, in the RCACMOS chip CD4093B, which combines internal hysteresis, the R
In CACMOS chip CD40109B, gate G1 performs the Schmitt trigger function of amplifier A3 in FIG.

Comparing to FIG. 4, gate G1 has an output that controls the operation of switching transistor TRs. Symmetrically, the output of the second inverter 2 in Figure 4 opens and closes the switching transistor TRI, which is shunted and parallel to the secondary coil, and therefore It must absorb all the power sent to it. The difference between the structure of FIG. 6 and the structure of FIGS. 5 to 4 lies in the action of the current mirror consisting of transistors TR and TR4 as a constant current source.

In each of the diagram bluffs of FIGS. 4-6, it is desirable that the bridge transducer output be substantially independent of temperature. Amplifier A2 operates to zero this voltage by feeding it back through capacitor C1 and is the bridge drain detected.

The current is the ratio of the temperature-insensitive bridge output voltage to the temperature-sensitive bridge resistance, which is temperature dependent.

However, by adding a suitable resistance between the bridge output and the inverting input of amplifier A2, the bridge resistance temperature coefficient is compensated with sufficient accuracy.

In accordance with each of the detailed embodiments, the circuit of the present invention provides reliable temperature compensated pressure indication to chassis-mounted circuits. Many vehicles, especially those at the upper end of the price range, now incorporate a variety of microcomputers that perform various functions, including displaying information. There are many computed computer powers that the present invention can utilize. In various installations, one or more of the processors processes the pressure information and converts it into a pressure value that is displayed for the operator of the vehicle. The value may be displayed on command or automatically as a warning display, for example by flashing a light on the console. Different lights may be provided for each wheel, including the spare.

The present invention takes advantage of the excessive power available in modern vehicles, while continuing improvements in integrated circuits allow processing functions to be performed by microcomputer circuitry housed within the vehicle. However, wheel attachment gradually came to be done by circuits.

One area of application of the technology of the present invention involves storing pressure information in memory. For example, the tire pressure is read at predetermined intervals and the readings are recorded as changes in pressure. This allows monitoring of the rate of change in pressure,
Enables detection of tire leaks with warning to the driver in advance of a potentially dangerous condition. Knowing the rate of decrease in pressure makes it possible to suggest to the driver that the vehicle should be stopped for a period of time to correct the situation. Calculation of the rate of change in pressure is performed by a central computer within the vehicle and, as mentioned above, by more advanced circuitry within the tire.

Maintaining tire pressure trends is useful for tire manufacturers in determining what to do with tires as motorists seek to increase vehicle warranties. The amount of data stored can be minimized by recording only significant changes in pressure. In this way, when the tire pressure is maintained within a predetermined range, it is not entered into memory. However, when changes outside of the expected limits (eg, +5 psi) occurred, data were entered over the time that data was observed.

The vehicle's processor may be linked to an external printer to print out the progress. A flow chart illustrating the operation of this pressure progression method is shown in FIG.

Another embodiment of the invention is shown in FIG. In this embodiment, the ambient temperature outside the tire is compensated by providing a constant voltage to the bridge transducer 1 rather than a constant current.

The output of amplifier A1 is applied to bridge transducer 1 in response to a square wave generated by a Schmitt trigger (amplifier 83 and associated resistors) and an integrator (e.g. amplifier A2 and associated capacitors including capacitor C1). power is provided to a series of inverters 15-17 which invert the voltage applied to the inverter.

If necessary, the scale factor of the bridge is normalized with the selected feedback resistance Rr by reference to the sensor resistance value. If the applied bridge voltage is continuously inverted, the output voltage of amplifier A5 is also square wave and provides an additional input to the integrator via appropriately selected coupling capacitors and resistors. The coupling capacitor blocks offsets in amplifier A5 from the integrator.

The Schmitt trigger A3 is similar to the embodiment shown in FIG.
Shorting the circuit of the secondary coil receiving the power to affect the operation of the primary coil transmitting that power.

The output of the Schmitt trigger is
0°C), it gives an indication of the tire pressure. The output has important meaning to the user for the following reasons. Figures 4 to 6
For the example shown, if we were to fill up to 33 psi at 20°C, the readout from these previous examples would be 0 psi at 20°C but at 20"C if the tire was flat. -7p5i can be +7 psi at 60°C.

If the tire is flat, these should be shown, so the embodiment of Figure 9 shows 0p when the tire is flat.
Provides the output of si. Correspondingly, the readout provided by the example if the tire is filled or substantially filled.

Figure 8 shows how the change in atmospheric temperature is calculated from a predetermined constant value.
If the atmospheric temperature is similar to a predetermined value, the user is informed of the pressure.

FIG. 9 shows the effect of the embodiment of FIG. As best seen in FIG. 9, the output frequency remains substantially constant as a function of ambient temperature. The frequency changes as a function of pressure, and the short circuit frequency of the secondary coil corresponds to the detected pressure.

Although the invention has been described in detail with respect to several specific embodiments, various modifications within the spirit of the invention will be apparent to those of ordinary skill in the art. Accordingly, the invention is to be considered limited only in terms of the claims.

[Brief explanation of the drawing]

FIG. 1A is a block diaphragm schematic diagram of the present invention; FIG. 1B is a schematic diagram of the installation of a power receiving circuit around a vehicle wheel; FIG. 2A is a block diaphragm diagram of the present invention; , a diaphragm that provides more detailed information on the flow of operation, FIG. 2B is a circuit diagram explaining the operation of the power transfer circuit, FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG. A circuit diagram of another embodiment of the invention, FIG. 5, is a circuit diagram of one method of the circuit of the invention in integrated circuit form, FIG.
Figure 7 shows a circuit diagram of another possible integrated circuit method of the invention.
FIG. 8 is a flowchart illustrating one aspect of the operation of the invention; FIG. 8 is a circuit diagram of another embodiment of the invention; FIG. 9 is a circuit diagram of another embodiment of the invention; FIG. This is a graph depicting the nature of information. l...transducer, 2...signal conditioning circuit, 3
...Detector, 4...Processor, 5...Display, 6...Battery, 7...Ignition switch, 8...Power transmitter, 9...Primary coil, 1o
... Tuning circuit, 11... Power rectifier circuit.

Claims (1)

Claims: 1. In a vehicle comprising at least one wheel and a chassis to which the at least one wheel is rotatably mounted, an apparatus for communicating temperature compensated tire pressure from the at least one wheel to the chassis. , a first energy transfer device (9) mounted on the chassis to transfer first energy at a first predetermined frequency;
and a first energy transfer device mounted on at least one wheel to receive the first energy.
10); and a tire pressure signal generating device (1, 2) mounted on at least one wheel depending on the tire pressure mounted on at least one wheel for generating a tire pressure signal; It consists of a constant current supply device (A1) for supplying a constant current to the pressure signal generation device, and a voltage polarity reversal device (A2, A3) for reversing the polarity of the voltage supplied to the tire pressure signal generation device, The tire pressure signal generator includes a piezoresistive bridge, and the constant current supply device and voltage polarity reversal device include:
enabling compensation for variations in temperature to produce a temperature compensated tire pressure signal, said temperature compensated tire pressure signal being transmitted by a first energy transfer device to a first energy transfer means to transmit said signal from the at least one wheel to the chassis; altering operation of a first energy transfer device to transmit a temperature-compensated tire pressure signal;
Apparatus consisting of an indicating device for providing an informational indication of temperature compensated tire pressure in a vehicle. 2. The polarity reversing device comprises a first operational amplifier (A2), a capacitor (C1) coupled in a negative loop manner, and a Schmitt trigger device (A3, R2, R3);
2. The constant current source supply device comprises a second operational amplifier (A1) coupled to the Schmitt trigger device, and the piezoresistive bridge is coupled to a feedback circuit comprising the voltage polarity reversal device. equipment. 3. The device of claim 1, wherein the voltage polarity inversion device comprises a plurality of N-channel and P-channel enhancement type MOSFETs. 4. At intervals to provide tire pressure trends,
2. The apparatus of claim 1, comprising a housing device for housing a plurality of temperature compensated tire pressure signals. 5. The voltage polarity inverting device is configured to include a first operational amplifier (A2
), a capacitor (C1) and a Schmitt trigger device (A3, R2, R3) coupled in a negative feedback loop manner, and a constant current source supply device and the piezoresistive bridge to provide a constant voltage to the piezoresistive bridge. an inverting device (15,
16, 17), and the constant current source supply device includes a second operational amplifier (A1) coupled to a Schmitt trigger device.
2. The device of claim 1, wherein the piezoresistive bridge is coupled by a voltage polarity inverter and a feedback circuit. 6. At least one wheel and a rotatably mounted chassis and at least one wheel mounted on the at least one wheel monitor tire pressure and output temperature compensated tire pressure from the at least one wheel to the chassis. a tire pressure sensor for communicating temperature compensated tire pressure from at least one wheel to a chassis in a vehicle, comprising: a first sensor mounted on the chassis for transmitting a first energy at a first predetermined frequency; Energy transfer device (9)
and a first energy transfer device mounted on at least one wheel to receive the first energy (
10); a tire pressure signal generating device (1, 2) mounted on at least one wheel and a tire pressure signal in response to the tire pressure mounted on at least one wheel for generating a tire pressure signal; Voltage polarity reversal device (for reversing the polarity of the voltage supplied to the generator)
A2, A3), and the polarity reversing device includes an integrator having a first operational amplifier (A2), a capacitor (C1) coupled with a negative feedback loop, and a Schmitt trigger device (A2).
3, R2, R3), and further includes a constant current source supply device (A1) that supplies a constant current to the tire pressure signal generator, the constant current source supply device being coupled to the Schmitt trigger device. the tire pressure signal generating device has a second actuating amplifier (A1);
a piezoresistive bridge, coupled in a feedback circuit to the voltage polarity reversing device, the constant current supply device and the voltage polarity reversing device allowing compensation for temperature changes to produce a temperature compensated tire pressure signal; The temperature compensated tire pressure signal is transmitted to a first
a device for altering the operation of the first energy transfer device to transmit a signal from the at least one wheel to the chassis; 7. The vehicle includes a plurality of wheels including a spare, and an energy transfer device, the tire pressure signal generator, a constant current application device, and a voltage polarity reversal device are attached to each wheel, and the first energy transfer device 7. A sensor as claimed in claim 1 or claim 6, each of which is in communication with a central portion of the chassis and thereby transmits a respective temperature compensated tire pressure signal to the chassis. 8. The first energy transfer device includes a primary coil;
A tuned circuit comprising a primary coil (10b) and a capacitor (10a) coupled to the secondary coil, the primary coil being excited at a predetermined frequency in response to coupling of an ignition switch. 6 device. 9. The device according to claim 8, further comprising a switching device (TR2) for alternately opening and closing the secondary coil to change the operation of the primary coil. 10. The apparatus of claim 8, further comprising a secondary coil shorting device for shorting the secondary coil to alter operation of the primary coil. 11. Secondary coil open circuit device (TRs, Ds) for opening the secondary coil to change the operation of the primary coil
9. The device according to claim 8. 12. The secondary coil open circuit device consists of a transistor coupled to one end of the secondary coil and a diode coupled between the collector and emitter of the transistor, the base of the transistor being coupled to the output of the Schmitt trigger device. 12. The device according to claim 11. 13. The constant current source device has a current mirror circuit (TR3, TR
4). The device according to claim 1 or claim 6. 14. The voltage polarity reversing device includes an inverting device (15, 16) coupled between the output of the constant current source supply device and the piezoresistive bridge in order to supply a constant voltage to the piezoresistive bridge.
, 17). 15. The device of claim 1 or claim 6, wherein the constant current source supply device, the voltage polarity inverter and the piezoresistive bridge are integrated into a monolithic IC. 16. at least one wheel and a chassis with the at least one wheel rotatably mounted; and a chassis mounted on the at least one wheel for monitoring tire pressure and outputting temperature compensated tire pressure from the at least one wheel to the chassis. a tire pressure sensor for communicating temperature compensated tire pressure from at least one wheel to a chassis, the first tire pressure sensor comprising: a first tire pressure sensor;
a first energy transfer device (9) mounted on the chassis to transmit a first energy of a predetermined frequency; and a first energy transfer device (9) mounted on at least one wheel to receive the first energy. (10
); and a tire pressure signal generator (1, 2) comprising a piezoresistive bridge mounted on at least one wheel in response to tire pressure mounted on at least one wheel for generating a tire pressure signal. , a voltage polarity reversing device (A2, A3) for reversing the polarity of the voltage supplied to the tire pressure signal generating device, and the polarity reversing device is connected to a first actuating amplifier (A2) in a negative feedback loop. It has an integrator consisting of a coupled capacitor (C1), a Schmitt trigger device (A3, R2, R3), and further has a constant current supply device (A1) for supplying a constant current to the tire pressure signal generator. The constant current source supply device has a second actuating amplifier (A1) coupled to the Schmitt trigger device, and the voltage polarity reversal device is configured to supply a constant current source to supply a constant voltage to the piezoresistive bridge. an inverting device (
15, 16, 17), wherein the piezoresistive bridge is connected in a feedback circuit to the voltage polarity reversal device, and the constant current supply device and voltage polarity reversal device are connected to a temperature compensated tire pressure signal to produce a temperature compensated tire pressure signal. the temperature compensated tire pressure signal being transmitted by a first energy transfer means to a first energy transfer device for transmitting the signal from the at least one wheel to the chassis; A device that changes the operation of a device.