Abstract: An apparatus for measuring inflation pressure of a resilient-walled vessel, e.g. of a vehicle tire associated with an inflation valve and with a rim. The apparatus has an external, portable member and a pressure sensing member, which is separate from the portable member and is located within the tire so as to be exposed to the inflation pressure. The portable member is capable of generating and transmitting energy to the pressure sensing member and in response to receive and to process a pressure signal, which depends on the inflation pressure and upon processing of the pressure signal to derive therefrom an inflation pressure value. The pressure sensing member is capable, upon receiving energy from the portable member, to generate the pressure signal and to transmit it to the portable member. The portable member has a probe that creates an electrical contact between the portable member and the pressure sensing member upon establishing physical contact between the probe and the valve.

Abstract: A tire inflation pressure sensing apparatus according to the invention includes a first pressure sensor, a first transmitter, a second pressure sensor, a second transmitter, and a receiver. The first pressure sensor and first transmitter are provided on a running wheel of a vehicle. The first transmitter works to send out a pressure signal generated by the first pressure sensor upon being triggered by a trigger signal. The second pressure sensor and second transmitter are provided on a spare wheel of the vehicle. The second transmitter works to send out a pressure signal generated by the second pressure sensor upon being triggered by the trigger signal. The receiver is provided on the body of the vehicle and works to send out the trigger signal and identify whether a pressure signal received thereby is sent out from the first transmitter or the second transmitter based on a RSSI signal generated therefor.

Abstract: An apparatus for detecting a tire deformation of a vehicle tire includes a tire pressure sensor for sensing a tire pressure, a signal processor configured to provide a signal indicating the tire deformation based on a difference between the tire pressure at a first time and the tire pressure at a second time. What is achieved thereby is that a tire deformation may efficiently be sensed.

Abstract: An apparatus for detecting motion of a wheel comprising tyre. The apparatus comprises a pressure sensor for measuring the tyre pressure and generating a signal corresponding to the measured tyre pressure, and means for detecting a component of said signal that corresponds to, or is generated by, vibrations of the tyre. Upon detection of the signal component, the apparatus determines that the wheel is in motion. The detecting means may arranged to detect an audio signal component or signal components having a frequency in the range 200 Hz to 300 Hz.

Abstract: A multi-functional tire pressure gauge includes a housing, an air-guide seat, a diaphragm, a helical seat, an annular seat, a tread-measuring device, a display panel and an air-guiding device. The multi-functional tire pressure gauge can measure tire pressure and tread's depth simultaneously. Specifically, when the diaphragm moves up and down under the effect of the tire pressure, the helical seat converts the up-and-down motion of the diaphragm into circular motion, so that the index pointer can display tire pressure value. Furthermore, the probe extending in treads of the tire can obtain the depth of the tread.

Abstract: A System of monitoring the air pressure in the tires of a moving vehicle continuously in real time for measuring the pressure in a rotating tire and transmitting the information via magnetic pulses to a sensor pickup located near the tire, but on a non-rotating part of the vehicle, for transmittal via wire to a micro controller for conversion to air pressure units and display. It comprises a sensor module for each wheel, and an electronics module in the passenger compartment. It computes the air pressure by measuring the phase angle between a fixed magnet and a magnet placed on a piston in an air cylinder within the tire.

Abstract: A tire monitoring system providing tire status and notifying or warning the vehicle operator of early detection of imminent tire failure and performance degradation; thus improving safety by preventing blowouts from occurring, lengthening tire life by encouraging preventive maintenance, and improving fuel mileage by encouraging the operator to fill the tire to its proper pressure or repair it. The system monitors temperature of the rim of the wheel to which the tire is attached, such temperature being transmitted to the vehicle operator or other interested parties via means such as radio frequency.

Abstract: A method for detecting decrease in tire air-pressure in which decrease in internal pressure of a tire is detected on the basis of wheel speed information obtained from wheels attached to a vehicle. The method includes the steps of: detecting wheel speed information of the respective tires; storing the wheel speed information of the respective tires; obtaining a vehicle body velocity of the vehicle; obtaining vehicle information of the vehicle during running such as driving force, wheel torque or slip rate; calculating a judged value of decompression; and detecting decrease in air-pressure of a tire upon calculating a multiple correlation coefficient for the judged value between the vehicle body velocity and the vehicle information and comparing the multiple correlation coefficient with a specified threshold. It is possible to accurately detect decompression of a tire.

Abstract: An apparatus for and a method of sensing fluid pressure of a tire and the fluid supply of a tire pressure management system maintaining same, with a central sensor and which requires the control of only two valves. The apparatus for sensing fluid pressure of a tire and the fluid supply of a tire pressure management system maintaining same, includes a sensor disposed so as to be selectably in fluid communication with one or both of: a first valve, operable from an open position through a closed position, for respectively promoting and prohibiting fluid flow from the fluid supply, and a second valve, operable from an open position through a closed position, for respectively promoting and prohibiting fluid flow to or from the tire.

Abstract: A motion sensor system for a tire pressure monitoring system (TPMS) that uses a piezoelectric sensor to sense vibration as an indication of wheel motion. The TPMS uses the detected vibration to transition between operation modes. In one embodiment, the TPMS has a motion mode and a park mode, wherein the TPMS has increased activity (e.g. sampling tire pressure at a higher rate and transmitting tire pressure at a higher rate) during the motion mode than in the park mode.

Abstract: A multifunctional tire pressure gauge for a car functions to measure the inner temperature of the car, the voltage of the car battery and the tire pressure of the tire. Thus, when the plug is inserted into the cigarette lighter of the car, the tire pressure gauge can be used to measure the temperature of the inside of the car and the voltage of the car battery simultaneously. In addition, after the plug is removed from the cigarette lighter, the tire pressure gauge functions as a portable tire pressure gauge.

Abstract: A valve stem pressure poppet incorporated into a tire valve cap for monitoring tire air pressure. The indicator assembly is screw attached by a connector onto an existing valve stem. The assembly includes a hollow outer tube for housing a slideably disposed indicator, a sealed space above the indicator, a compression spring and a connector end fitting. An air passage runs throughout the length the indicator. Once the assembly is engaged, pressurized air feeds directly through the indicator into the sealed space, forcing the indicator down against the force of the compression spring. If the tire remains above a predetermined critical low pressure point, the indicator will remain in the down “equilibrium” position. However, if the air pressure in the tire drops below the critical pressure point the compression force of the spring will overcome the downward pressure on the indicator, and the indicator disengages or “pops” up.

Abstract: Methods and apparatus are provided for relearning associations between tire pressure detectors and tire locations on an automobile. An apparatus comprises tire pressure detectors installed on each wheel having a tire, each configured to transmit a unique identification code in response to a tire pressure change greater than a predetermined magnitude in a predetermined time. The apparatus also includes a monitor having a receiver for receiving and a memory for storing the transmitted identification codes and a processor for associating the identification codes with predetermined locations. A method comprises exciting the tire pressure detectors in a predetermined sequence while monitoring transmitted identification codes. The method may further include storing the received unique identification codes in a predetermined order corresponding to the predetermined sequence.

Abstract: The invention relates to a system for regulating the pressure in a tire comprising an outer casting (3) which is mounted on a rim (2). The tire comprises an inner casting (5) which is disposed at the bottom of the rim (2) and which can constitute a high-pressure air reserve, a first actuator (6) which is integrated in the inner casting (5) and which authorizes the flow of air to the outer casting (3) for inflation purposes, a second actuator (8) which is integrated in the outer casting (3) and which authorize the release of air to the outside for deflation purposes; an electronic assembly which can send information to one or other of the actuators (6, 8) and/or receive the information delivered by the detector(s) (7, 9) in order to control the pressure and the temperature in the outer casting (3) and/or in the inner casting (5), a mean for controlling said electronic assembly and a keyboard. The inventive system is suitable for vehicles.

Abstract: A tire pressure monitor and a method of measuring a pressure in a tire include a decision whether the tire pressure should be measured. The decision is made in dependence on a magnitude of a change in a signal which is output by a sensor which senses the pressure prevailing in the tire or the temperature prevailing in the tire. As a result it is possible to reduce the size and the weight of the components of a tire pressure monitor to be accommodated in the tire or in the rim to a minimum.

Abstract: A tire sensor system for the continuous measurement of the transferred force and of the adhesive friction potential ?, made up of a plurality of sensors situated on the outer circumferential surface of the tire, via which measured variables are picked off and may be supplied as signals to an analyzing unit via an antenna system, in the area of the outer circumferential surface of the tire, a plurality of individually identifiable sensors is situated in each sector that corresponds to the tire contact area, the sensors making it possible to measure mechanical stresses locally in each position of the tire even when it is standing still, thus making it possible to determine the instantaneous force distribution in the tire.

Abstract: A device for monitoring air pressure in the tires of a vehicle includes devices for determining the wheel speed or other characteristic variables for the speed of the tires of the vehicle, a device for calculating differential variables on the basis of the wheel speed variables, a device for evaluating the differential variables with respect to a setpoint value deviation and for generating a warning signal if the setpoint value deviation exceeds a threshold value, and a device for directly measuring the air pressure in the tire of a wheel and for transferring an air pressure characteristic variable to the evaluation device. A warning signal is generated if the deviation of the air pressure characteristic variable with respect to a setpoint value exceeds a corresponding threshold value. A method of monitoring tire pressures is also provided.

Abstract: A transmitter for a tire condition monitoring apparatus, which is powered by a battery. The transmitter includes a sensor for periodically detecting the condition of the tire, a transmission circuit for wirelessly transmitting data representing the detected tire condition, and a controller for controlling the sensor and the transmission circuit. When the detected tire condition is abnormal, the controller shortens the detection interval of the sensor. As a result, the transmitter immediately informs a driver of abnormality in the condition of the tire.

Abstract: A tire monitoring system for a vehicle. The tire monitoring system includes a sensor assembly mountable on a wheel and has a first sensor for detecting a tire parameter and a second sensor for detecting proximity of the sensor assembly to the wheel. The sensor assembly is detached from the wheel when the second sensor is not proximate to the wheel.

Abstract: A detector is mounted on a wheel rim of an automotive vehicle. The provided device comprises a housing receiving the detector, a traction member having an axis, the traction member being adapted to be mounted on the rim, to pull the housing toward this rim along its axis, the housing being articulated relative to this traction member, elements for blocking the traction member relative to the rim, once the housing has been drawn toward the rim, and a sealing joint surrounding the traction member in the region in which it passes through the rim. The housing has a convex bearing surface to bear toward the joint substantially along the axis of the traction member.

Abstract: A method and system for monitoring and reporting vehicle tire pressure information. The system includes tire pressure monitors mounted to the tires of a vehicle. The tire pressure monitors detect tire pressure information from their respective tires and transmit that information to transponders that are fixedly-mounted to the vehicle. Each tire pressure monitor corresponds to a single transponder. When a tire pressure monitor transmits tire pressure information, the corresponding transponder receives the signal and transmits the tire pressure signal along with a unique transponder identification code to a vehicle central system controller. Based upon the transponder identification code, the central controller associates the tire pressure information with a particular tire location. However, under certain conditions, a transmitted tire pressure signal is received by one or more of the non-corresponding transponders as well as the corresponding transponder.

Abstract: An external mount tire pressure sensor system which substantially reduces the effect of centrifugal force on tire pressure measurements. A sensor has a main guide body portion with two parallel leg portions each having a central bore. A slider element is slidably mounted in each leg portion, and the two slider elements are mechanically connected for translatory movement in unison. A spring urges the slider elements to a neutral position. The sensor attaches to a tire valve stem. Gas from a tire encounters one of the slider elements and urges it in opposition to the spring force. The differential interconnection between the two slider elements cancels out the effect of the centrifugal force when the wheel rotates. A stiff flexible wall section enables the axis of the sensor to be aligned with the wheel radius to optimize performance.

Abstract: This pressure sensor (8) is intended to be placed in a tire mounted on a rim (2) equipped with a valve (6) allowing air to be let into and removed from the tire. It comprises a support (22) fixed at the level of the valve (6) by a screw or the like. The support (22) comprises a wall (30) for bearing on the valve (6), this wall (30) being elastically articulated to the rest of the support (22).

Abstract: A method for determining the wheel position (FL, FR, RL, RR) of wheels (R1, R2, R3, R4) of a motor vehicle (10) which, for monitoring purposes, in particular for monitoring the tire pressures, are each assigned a wheel unit (E1, E2, E3, E4) which transmits data (D1, D2, D3, D4) to a central evaluation device (ECU) of the vehicle (10), at least in response to a trigger signal (TR1, TR2, TR3, TR4, TR5, TR6). The wheel positions (FL, FR, RL, RR) of the monitored wheels (R1, R2, R3, R4) can be determined by activating a portable transmitter (12) whose position with respect to the vehicle (10) is sensed.

Abstract: A sensor device mountable on a threaded valve stem of an inflatable tire of a vehicle having an actuating pin adapted to be depressed by a component of an air gauge or a connecting fixture of a compressed air line, generally consisting of a housing defining a closed chamber, having a first threaded opening permitting such housing to be threaded onto the valve stem, and a second opening; an abutment pin disposed in the housing engageable with the actuating pin of the valve stem for depressing the actuating pin of the valve stem and thereby opening the valve stem when the housing is threaded onto the valve stem, providing an intercommunication of the interiors of the tire and the housing; a valve disposed in the second opening of the housing having an actuating pin adapted to be depressed by the component of an air gauge or connecting fixture of a compressed air line; a sensor mounted in the housing for sensing the pressure in the housing chamber; a microcontroller connected to the pressure sensor for receiving

Abstract: An air pressure gauge assembly is mounted to the valve stem of a tire or integrated into a wheel rim for continuous monitoring of the tire inflation pressure. The gauge assembly includes a check valve functionally coupled to the valve stem so that the check valve provides the common function of the valve stem, including allowing for inflation and deflation. The assembly also includes a pressure sensor coupled to a visually perceptible pressure indicator on a dial face.

Abstract: An air pressure detection device for a wheel includes an air pressure sensor provided on the side of a tire for detecting the tire pressure. A detection and transmission unit (transmission unit) is provided for transmitting information detected by the air pressure sensor. An electric cell is provided for driving the detection and transmission unit. The air pressure sensor is located inside the tire and is integrally fitted to an air valve. The electric cell is fitted to a portion of the air valve projecting from a rim. The invention enhances the fitting property of the air pressure sensor, and enhances the convenience in exchange of the electric cell.

Abstract: A system for remote monitoring of vehicle tire pressure includes monitors mounted in the tires, each including a tire pressure sensor, a transmitter for transmitting a tire pressure signal, a battery for the transmitter, and a receiver for receiving an initiation signal. Initiators are mounted on-board the vehicle, each initiator associated with one of the tire monitors. Each initiator is for use in generating a low frequency initiation signal for receipt by a tire receiver to cause the transmitter to transmit a tire pressure signal. A vehicle mounted controller activates the initiators in order to generate the low frequency initiation signals, and processes the tire pressure signals to convey tire pressure information to a user. The controller further activates the initiators in order to generate a low frequency electromagnetic field for use in recharging the batteries in the tire monitors.

Abstract: A tire safety system mounts on a vehicle wheel rim inside a pneumatic tire. A tire air pressure sensor produces a tire air pressure reading mounted inside the tire. An inflatable member forms a toroidal expandable internal safety structure. The inflatable member is mounted against the vehicle wheel rim. The chemicals container inside the inflatable member receives an electrical signal at an activation input. The chemicals container creates pressurized gas inside the inflatable member for inflation when a signal is received at the activation input. A circumferential radially expandable protective belt mounted around the inflatable member expands with inflatable member inflation to accommodate operation the tire when expanded. A computer receiving tire air pressure readings from the tire air pressure sensor sends a signal to the activation input upon a sudden change in tire air pressure.

Abstract: A portable tire pressure gauge measures a value of tire pressure. The gauge can display the measured value digitally and selectively in one of different units of pressure. If the gauge is made for use in a country, the gauge can output the measured value aurally and selectively in one of two languages that a majority of people in the country understand. These languages may be the language of the country and a first foreign language in the country. The gauge includes a display, a switch, a solar battery and an audio output unit. The display digitally displays the measured value. The switch switches the different units of pressure. The solar battery is the power supply for measurement and display. The audio output unit can output the measured value aurally and selectively in one of the two languages.

Abstract: A detecting unit has a housing with a chamber, a cover, an air valve, a circuit board, a detecting assembly and a ground. The cover is attached to the housing to close the chamber. The circuit board is received in the chamber of the housing and has a signal processing unit mounted on the circuit board. The signal processing unit has a reset terminal. The ground is mounted on the circuit board and is electrically connected to the air valve. Accordingly, the signal processing unit will be reset when the reset terminal is electrically connected to the air valve.

Abstract: A transducer includes a substrate and a thin membrane having a shape that can be deflected relative to the substrate to provide an amount of membrane deflection useful for sensing or actuation purposes.

Abstract: An apparatus (10) comprises a controller (82) for receiving a control parameter. At least one tire condition sensor (26-32) senses a tire condition and transmits a tire condition signal (34) indicative of the sensed tire condition. A receiver (78) receives the tire condition signal (34) and compares the received tire condition signal (34) to a changeable threshold to output a digital signal indicative of the received tire condition signal (34). The changeable threshold changes at time intervals determined by a time constant of the receiver (78). The time constant of the receiver (78) is variable. The controller (82) is operatively connected to the receiver (78) and varies the time constant of the receiver (78) in response to the received control parameter.

Abstract: This pressure detector (8) is adapted to be disposed in a tire mounted on a wheel rim (2) provided with a valve (6) permitting the introduction of air into and the withdrawal of air from the tire. This detector (8) is fixed to the valve (6). It comprises, spaced from the point of securement to the valve, a deformable lip (32) creating a substantially continuous bearing zone against the wheel rim (2).

Abstract: A tyre (6) pressure sensor comprises a pressure-sensitive part (8), in particular with a deformable membrane (10), mounted in the centre of the hub (7) of wheel (2), and a transducer part (12) housed in the axle (1) of wheel (2). This arrangement in which the sensor is separated into two mutually rotating parts is nonetheless more practical and simpler than devices in which electric connection is required between a wheel carrying the sensor assembly and the read device.

Abstract: A method for alarming decrease in tire air-pressure. The method includes the steps of: detecting rotational information of respective tires; respectively calculating and storing a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius; accumulating the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels; obtaining a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio; judging whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient; and issuing an alarm of decrease in tire air-pressure.

Abstract: A tire pressure indication system for a single or dual wheel tire assembly includes a pair of analog/digital readout pressure gauges and associated valve stems for individually monitoring and pressurizing the tire or tires of the wheel assembly. The tire pressure indication system may be attached to the outside wheel of the dual wheel assembly by a bracket structure mounted to the outside wheel with an adhesive tape or other suitable fastener. The tire pressure indication system provides for a tire pressure indication system that can be easily mounted to the wheel tire assembly without the use of a hubcap or other similar mounting structure.

Abstract: A tire pressure monitoring system (12) for a spare tire of a vehicle (10) includes an indicator (52) and a timer (44) that generates a first time signal corresponding to the time the spare tire is used as a rolling tire and a second time signal corresponding to a time the spare tire is stowed. The temperature sensor (34) generates a temperature profile and a controller (22) that is coupled to the indicator, the timer, and the temperature sensor generates a spare tire warning signal in response to the temperature profile, the first time signal, and the second time signal.

Abstract: A calibration fixture for calibrating load cells in a tire uniformity machine, the tire uniformity machine having a carriage rotatably supporting a load wheel on a first spindle and a second spindle, a first load cell and second load cell in sensing relation to the load wheel and attached to the carriage, at least one of the load cells having a support portion and a sensing portion rotatable within the support portion the calibration fixture including: a fixture member releasably attached to the cover of the load cell; and an adjustment assembly supported by the tire uniformity machine operable with the fixture member to cause movement of the sensing portion relative to the rim.

Abstract: A method for control of a tire pressure management system (or central tire inflation system) is provided which enables active adaptation of control variables in the system in response to variations in air line volume. The air line volume in a conduit between an air source and a vehicle tire is determined. Subsequently, one or more values for control variables are adjusted in response to the air line volume and various parameters associated with the system are determined in response to the adjusted values of the control variables.

Abstract: A tire pressure monitoring system (12) for a vehicle (10) includes a warning status memory (26) having warning statuses therein and a plurality of tires (14a, b, c and d) in respective rolling locations, each of said plurality of tires having a transmitter (90). When one of the tires has been filled with air, the controller (22) receives a pressure signal from one of the tire transmitters generated in response to a predetermined increase in pressure. The controller (22) clears the warning statuses from the warning status memory (26) when the pressure signal is in a normal range and, thereafter monitors the tires in the rolling locations and generates warning statuses therefor.

Abstract: A signal receiver for tire air pressure monitoring system determines whether the pressure detection signals from all transmitters have been received during an engine stop state. Upon affirmative determination, the receiver sets a timer, and deactivates the entire or partial function of the receiver. The receiver determines whether the second predetermined period has expired after the setting of the timer. Until the period passes, the receiver retains the deactivated state thereby to save electric power consumption during engine stop state.

Abstract: A tire monitoring method and apparatus is provided to predict tire tread separation for a tire on a wheel of a vehicle. This may involve monitoring a parameter of a tire of a vehicle over time and comparing information regarding the monitored parameter (over time) with a reference threshold value of the parameter (over time). The method may also include providing information to a driver based on the comparison. The parameter may be acceleration (axial, radial or longitudinal) along an axis of the tire. The parameter may also be tire imbalance, temperature inside the tire, speed of the tire, load and/or pressure, for example. Information regarding the comparison may be transmitted to a driver if the monitored parameter exceeds the reference threshold value for a predetermined amount of time.

Abstract: A pressure transducer assembly mountable in an interior of a tire for sensing a pressure of a fluid in the tire comprising: a sensor housing having a first compartment in fluid communication with the fluid; a second compartment separated from the first compartment by a divider slideably engaged with and removable from the sensor housing; the divider having disposed thereon a circuitry; the circuitry including a pressure transducer in fluid communication with the first compartment, and a transmission circuit coupled to the pressure transducer for transmitting a signal responsive to the internal pressure to a remote location; a removable power source coupled to the circuitry contained entirely within the second compartment; and a cover sealingly engaged with the housing and the divider such that the second compartment is not in fluid communication with the first compartment.

Abstract: A rim drop section dented in a shape of a ring is provided on an inner side of a bead seat section of a rim for holding a bead section of a tire. Furthermore, a recessed section is provided on this rim drop section, and a detecting device main body of a tire air pressure detecting device is accommodated in this recessed section. When a tire is assembled on a cast wheel by utilizing a tire changer or the like, or when the tire is removed from the cast wheel, the bead sections of the tire are prevented from interfering with an air pressure sensor, and damaging of the air pressure sensor is prevented.

Abstract: A device for detecting the tire pressure of a motor vehicle tire (6) has an electronic unit (1) with an antenna (2) that is connected therewith. The electronic unit (1) and the antenna (2) are mounted on an elastic, circular support (3), which is fixed coaxially to the wheel axle (8) on the tire sidewall (7) in proximity of the wheel rim (5). The support (3) is fixed to the tire (6) only with its inner circumferential side while the outer circumferential side protrudes freely into the interior of the tire.

Abstract: A pressure monitoring system has a first chamber (11) and a second chamber (12) separated by a diaphragm. The diaphragm carries respective SAW devices on the respective sides thereof, the SAW devices having different resonant frequencies. Variations in pressure within the second chamber (12) relative to the pressure within the first chamber (11) will cause deflection of the diaphragm and the resulting changes in resonant frequency of the SAW devices can be analyzed to indicate the pressure differential between the chambers. The pressure-measuring device is incorporated within a valve assembly for a vehicle tire. When the vehicle tire is inflated, the inflation pressure is trapped within the first chamber (11) as a reference. Any subsequent loss of pressure from the second chamber (12), e.g. as a result of a puncture, will cause deflection of the diaphragm and a corresponding output from the SAW devices.

Abstract: A transmitter device includes a rotational direction sensor that generates a specific pattern signal when a corresponding tire rotates. The pattern signal of the left tires is different from the pattern signal of the right tires. A front reception antenna is near the front tires. A rear reception antenna is near the rear tires. A receiver includes a switch circuit that selectively connects the front reception antenna or the rear reception antenna to a controller. When one transmitter device transmits a radio signal, the controller determines which transmitter device is the source of the radio signal in accordance with the level of the signals from the reception antennas and the pattern signal, which is included in the data transmitted by the transmitter device.

Abstract: A method for alarming decrease in tire air-pressure in which a decrease in internal pressure of a tire is detected on the basis of rotational information obtainable from wheels mounted to a vehicle and a driver is accordingly alarmed. A plurality of thresholds for judging bad road are set. Decrease in air-pressure of a tire can be judged and alarm is issued upon decrease in air-pressure also when running on a bad road so that it is possible to secure safe driving for the driver.

Abstract: Tire air pressure during high speed travel is estimated without a sensor for detecting the tire air pressure directly. An apparatus is constituted by a wheel speed sensor, road surface friction state estimator for estimating a friction state estimation value representing friction between the tire and a road surface from wheel speed detected by the wheel speed sensor, tire air pressure estimator for estimating any reduction in the tire air pressure based on the friction state estimation value, and a display for displaying the estimated reduction in the tire air pressure.