Tire condition detection system and induction feed method thereof

An external solenoid positioned external to a tire, and an internal solenoid provided inside a valve of the tire, which transmits and receives power by an alternating magnetic field in a predetermined high frequency band that generates an induced alternating current in the internal solenoid, is used as a new source of power for a tire pressure/temperature detection device instead of a battery. If the alternating magnetic field in a predetermined high frequency band is well matched to the physical structure and electrical structure of the tire, then, in the space between the tire and a wheel, an induced alternating magnetic field component is distributed that is substantially parallel to the axis of rotation of the tire. If the internal solenoid is matched to the direction of maximum magnetic field reception, when the tire rotates, and when the position of the wheel is stopped, substantially stable power may be received.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tire condition detection system with various sensors for determining the physical properties inside a tire, such as the air pressure, the temperature and the like, and an induction supply method for externally supplying the power necessary for the operation of the sensors via wires or mesh embedded in the tire rubber to increase the tire strength.

2. Description of the Related Art

Conventionally, the technology relating to tire condition detection systems is as described in, for example, the following documents.

In Publication 1 is disclosed technology of a tire pressure monitoring device including a central reception evaluation device placed in a vehicle, and used for a vehicle having plural wheels.

In Publication 2 and 4 is disclosed technology relating to a wireless tire condition monitoring device in which the tire internal air pressure and the like may be confirmed from within the cabin of a vehicle.

In Publication 3 is disclosed technology of a tire air pressure detection device that detects the condition of a tire, such as the air pressure, temperature and the like, and transmits the condition of the tire by wireless signal.

Generally, any antennas follow a so-called reversal theorem, i.e., transmission characteristics are exactly the same as reception characteristics, therefore in the following explanation, transmission will be explained, and, except for particular instances, since reception is the same, explanation thereof will be omitted.

Recently, with computers becoming ultra-small, and the possibility of the use of single chip computers has become a reality, there has been remarkable progress in the technical development of vehicles such as cars and the like. Various communications devices, engine control devices, driving safety devices for assisting the driving operation of a driver, and the like, that are provided in vehicles rely, in the main, on computers, and evolution in the performance/functionality of vehicles continues to develop. With the above, it seems that, apart from specialists, the general public do not seem to recognize the extremely important roll that the wheels perform in supporting and moving the vehicle body.

In the past, it was normal for vehicle wheels to be constructed of a wheel, a tube, and a tire. However, due to the development of tubeless tires, tubeless tires are used on nearly all vehicles, with the exception of heavy vehicles, and so car wheels are constructed of a wheel and a tubeless tire (referred to below as “tire” for simplicity). Since air tubes have disappeared, punctures are not the slow leaking of air as before, but a sudden splitting (bursting), and it is not rare that this leads to a serious traffic accident.

Also, there is a close relationship between tires and the engine mileage, and there is good fuel consumption efficiency when running with the optimum pressure, and it is well known that the distance that can be traveled using a given amount of fuel can be extended. The fact that someone will check your tires when refilling with gasoline at a gas station is for this reason.

Even if the value of the air pressure is optimal for normal driving, when driven for an extended period of time, at a high speed, the air within a tire moves intensely, and the tire also deforms while rotating, so generating a large amount of heat, that may raise the internal temperature of the tire to about 150° C. The result is that, whilst the air pressure within the tire should be at the optimum temperature, the air pressure is actually raised by such generated heat, and this may sometimes lead to the tire exploding.

Due to this, as described in the Publications 1 to 4, and the like, devices have been developed for detecting the air pressure and temperature of tires, and currently, it is obligatory to fit such devices to all new models of car in the United States.

FIGS. 3A and 3Bare explanatory diagrams of a conventional tire condition detection system.FIG. 3Ais an external view of a vehicle wheel structure and antenna system provided with a conventional tire condition detection system.FIG. 3Bis a diagram showing the wheel cross section and reception antenna provided in a tire pressure/temperature detection device of the tire condition detection system ofFIG. 3A.

As shown inFIG. 3A, the vehicle body is provided with a vehicle wheel rotating axel1for the front wheels, and a vehicle wheel rotating axel2for the rear wheels, and respective tires10are mounted via wheels3on these vehicle wheel rotating axels1,2. Each of the wheels3on which each of the tires10are mounted has a valve20with an air ingress and egress aperture, and accommodated in each of the valves20is a small, tag-shaped tire pressure/temperature detection device. The small tag-shaped tire pressure/temperature detection device is configured with a sensor for detecting the internal pressure and temperature of the tire10, an IC tag of an integrated circuit for overall control of the device, an internal antenna for use in transmitting and receiving electromagnetic waves R, a battery for use in driving the device, and the like.

A reader antenna40, as an external antenna for transmitting and receiving data and commands from internal antennae of each of the valves20, is fitted to the vehicle body. The reader antenna40is connected to a reader-writer (referred to below as R/W)42via a transmission path41of a coaxial cable or the like. The R/W42is driven by high frequency power supplied by the high frequency power source43, is a device for processing all of the data relating to the tire pressure/temperature detection devices inside all of the valves20, and is connected to a display device44. The display device44is installed in the vehicle cabin, and is a device for displaying to the driver incoming information relating to the physical condition of the tire10that is sent from the R/W42.

As shown inFIG. 3B, the valve20accommodating the tire pressure/temperature detection device is fixed to the wheel3, and a ring shaped tire10is mounted to the outer peripheral surface of the wheel3in a removable state. In the tire10is embedded metal wire or metal mesh formed from steel material or the like, as reinforcement material13for increasing the tire strength. Electromagnetic waves R, transmitting data of the internal air pressure and temperature of the tire10, are radiated from the internal antenna of the valve20, and these electromagnetic waves R are received by the reader antenna40, the received signal is processed by the R/W42, and values of the air pressure and temperature within the tire10are displayed on the display device44.

FIGS. 4A and 4Bare block diagrams of the valve20ofFIGS. 3A and 3B.FIG. 4Ais an external view of the front of the valve20.FIG. 4Bis an external view of the back thereof.

The valve20has a case shaped valve body21that opens to the back side thereof, and accommodates the tire pressure/temperature detection device, and at a side face of the valve body21protrudes a cylindrical shaped air egress and ingress aperture22. The air egress/ingress aperture22is made of a strong metal, for example aluminum alloy or steel, and the rest of the valve body is made from a resin or the like. An air passage hole23is formed in the valve body21for communicating to the inside of the tire10from the air egress/ingress aperture22. The opening portion at the back of the valve body21is constructed to be closed off with a back cover24, protecting internal portions of the device, so that the device does not fall out of the valve body21. On the cover24is formed a post25for positional alignment of the valve body and the back cover24.

FIG. 5is an internal block diagram of the valve20ofFIGS. 4A, B as seen when the back cover24has been removed.

Accommodated in the valve body is a button battery26for supplying power, and a tire pressure/temperature detection device30connected to the button battery26, via a transmission path27of conductive wire of the like. The tire pressure/temperature detection device30has a substrate31for mounting circuit elements. On the substrate31are mounted an air pressure sensor32, a temperature sensor33, an electrical circuit34, for processing data and overall control of the device, and the electrical circuit34is connected to the transmitting antenna35that is the internal antenna.

By the mechanism of such a tire pressure/temperature detection device30, it is possible for a driver, seated in the driver's seat or while driving, to know the air pressure and temperature inside of the tire10. Since a critical cause of bursting of the tire10is the internal air pressure and temperature thereof, if the driver undertakes suitable measures when the condition of the tire10becomes dangerous, then a tire explosion and traffic accident may be avoided before they happen.

FIG. 6is an explanatory diagram of the structure of the tire10inFIGS. 3Aand B.

The tire10has a ring shaped rubber portion11, and on the inside of the rubber portion11is formed a levering portion12for levering the tire10onto the wheel3when mounting. Reinforcement material13of metal wire or mesh formed from steel material or the like is embedded in the rubber portion11for increasing the tire strength. The cross-section13aof the reinforcement material13looks like loop shaped wire as shown inFIG. 6. There are various ways of arranging the reinforcement material13, depending on the tire manufacturer, andFIG. 6shows the simplest arrangement.

However, conventional tire condition detection systems provided with the tire pressure/temperature detection device30have the following problems.

The power source of the tire pressure/temperature detection device30is the dry button battery26, and the power of the button battery26continuously depletes from the time of insertion into the device. From the specifications of the tire pressure/temperature detection devices30on the market, the button battery26should be able to continue to supply power to the devices for 10 years or more, but there are hardly any batteries from the button batteries26currently on the market that are able to satisfy such a specification. Therefore, in order to slow down the power depletion of the button batteries26, measures are undertaken, such as, for example, only transmitting data on the air pressure and temperature of the tire10to the reader antenna40once every 3 minutes or so. But even by taking these measures, it is difficult to prolong the life of the button battery26to 10 years.

As another method it is possible to change over to a new battery when the button battery26depletes, but more than the cost of the batteries themselves there is the time and expense of changing them over, and there is a problem of damage occurring when changing over tubeless tires and the like, reducing the life of the tire10. Also, when it is necessary to detect the air pressure and temperature inside the tire10at small intervals, such as, for example, transmitting data once every second, a 10 year life battery lasts about 2 or 3 months, and it is obvious that conventional tire condition detection systems are not able to meet the demands of such a specification.

SUMMARY OF THE INVENTION

The tire condition detection system of the invention is provided with: a tire, internally provided with conductive reinforcement material; an external antenna, fixed in proximity to the outside of the tire, and radiating to the tire electromagnetic waves that generate an induced alternating current in the reinforcement material; an internal antenna, fixed at the tire side, receiving an alternating magnetic field generated in the space inside the tire due to the induced alternating current generated in the reinforcement material, and outputting a received signal; a power source, fixed at the tire side, converting the received signal into alternating current power and outputting source power; and a detector, fixed at the tire side, operated by the source power, detecting predetermined conditions inside the tire and transmitting the detected signal by electromagnetic waves to the external antenna via the internal antenna and the reinforcement material.

The induction supply method of the invention is the induction supply method of a tire condition detection system provided with: a tire, internally provided with conductive reinforcement material; an external antenna, fixed in proximity to the outside of the tire, radiating to the tire electromagnetic waves for power use, and receiving electromagnetic waves for signal use; an internal antenna, fixed at the tire side, receiving the electromagnetic waves for power use radiated from the external antenna via the reinforcement material, and transmitting the electromagnetic waves for signal use via the reinforcement material to the external antenna.

Electromagnetic waves are radiated from the external antenna with an alternating magnetic field component substantially parallel to the axis of rotation of the tire, an induced alternating current is generated in the reinforcement material due to the alternating magnetic field component, and a secondary alternating magnetic field is generated in the space between the tire and a wheel due to the induced alternating current. Further, the internal antenna receives the alternating magnetic field that is power supplied by the external antenna and receives the secondary alternating magnetic field, and outputs a received signal; converting the received signal into the source power.

According to the tire condition detection system and induction supply method of the invention, by using power from the main battery or the engine of a vehicle, source power may be supplied to a detector by electromagnetic waves of a particular frequency. This means that the air pressure and temperature and the like of the tires may be constantly detected with good precision, without having to worry about the life and remaining power of a dedicated battery used as a power source.

DETAILED DESCRIPTION OF THE INVENTION

In the best mode of the invention, a new source of power may be substituted in a tire pressure/temperature detection device that conventionally uses a battery power source. By using an external antenna installed external to a tire, and an internal antenna provided inside a valve of the tire, power may be transmitted and received through electromagnetic waves in a predetermined high frequency band. If the electromagnetic waves in a predetermined high frequency band are well matched to the physical structure and electrical structure of the tire, then, in the space between the tire and a wheel, a magnetic field component is distributed that is substantially perpendicular to the plane that includes the maximum diameter of the tire. If the internal antenna is matched to the direction of maximum magnetic field reception, both when the tire rotates, and when the position of the wheel is stopped, substantially stable power may be received. There are none of the worries about battery life and remaining power of conventional devices, and unlimited numbers of transmissions may be made of tire internal air pressure and temperature data, through an external antenna, to a R/W or the like. That is, a completely battery-less tire condition detection system provided with a tire pressure/temperature detection device may be realized.

First Embodiment

Configuration of the First Embodiment

FIGS. 1A and 1Bare explanatory diagrams of a tire condition detection system of a first embodiment of the invention;FIG. 1Ashows an external view of a structure of the wheels and an antenna system of a vehicle provided with the tire condition detection system of the first embodiment, andFIG. 1Bis a diagram showing, in the tire condition detection system ofFIG. 1A, a cross-section of a wheel provided with a tire pressure/temperature detection device and a solenoid antenna that is an external antenna.

InFIG. 1A, as in conventionalFIG. 3A, the vehicle body has been omitted for clarity. The vehicle body, as in conventionalFIG. 3A, is provided with a vehicle wheel rotating axel51for the front wheels, and a vehicle wheel rotating axel52for the rear wheels, and respective tires60are mounted via wheels53on these vehicle wheel rotating axels51,52. Each of the wheels53on which each of the tires60are mounted has a valve70having an air ingress and egress aperture, and accommodated in each of the valves70is a power source and a detector (for example a small tag-shaped tire pressure/temperature detection device). The small tag-shaped tire pressure/temperature detection device includes a sensor for detecting the internal pressure and temperature of the tire60, an IC tag of an integrated circuit for overall control of the device, an internal antenna for use in transmitting and receiving (for example a solenoid antenna), and the like.

The vehicle body, in contrast to conventionally, has, fixed in the vicinity of a side face of each of the tires60, respective external antennae (for example solenoid antennae, referred to below as “small circular antennae”)90. Each small circular antenna90has a function for generating an alternating magnetic field H1by excitation, and transmitting electrical power to each of the solenoid antennae within the valve70, and also each small circular antenna90has a function for receiving data on the tire internal pressure and temperature from that solenoid antenna. Each small circular antenna90is connected to a transmitter receptor101via a transmission path100of a coaxial cable or the like. The transmitter receptor101has a power transmitter function for transmitting electrical power to each of the small circular antennae90based on high frequency electrical power supplied from a high frequency power source102, and the transmitter receptor101has a receiver function for receiving a transmission signal from the side of each tire, sent via the small circular antenna90, and a display device103is connected to these. The display device103is provided within the vehicle and is a device for displaying to a driver information relating to the physical condition of the tires60that is sent from the transmitter receptor101.

As seen inFIG. 1B, the small circular antennae90placed in the vicinity of the tires60, have resistance and inductance, and, in order to receive high frequency power from the high frequency power source102with good efficiency, they need a matching circuit configured of condensers. InFIG. 1Bis shown an outline diagram of the small circular antenna90combined with a matching circuit. In the small circular antenna90two matching condensers91,92are connected, and by these matching condensers91,92a matching circuit is formed between the small circular antenna90and the high frequency power source102.

For simplicity, in the description below, matching for use with a reader antenna like the small circular antenna90is not mentioned, but is generally necessary. Further, structurally in the reader antenna there are parallel portion(s), like the matching condensers91,92, and serial portion(s). It follows that, in the description below, even when a reader antenna matching circuit is not indicated it should be presumed that there is one present.

An alternating current magnetic field is generated around the small circular antenna90, and in the first embodiment, the energy of a magnetic field component is used, and electromotive force is generated in the solenoid antenna provided in the valve70, and this electromotive force is used for the power source of the tire pressure/temperature device.

The valve70accommodated in the tire pressure/temperature detection device, as conventionally, is fixed to the wheel53, and the tire60of a ring shape is detachably mounted on the outer peripheral surface of the wheel53. In the same way as conventionally, the tire60is a tire formed with steel material, electro conductive synthetic resin fibers and the like, electro conductive reinforcement material63of a mesh or the like embedded therein, for increasing the tire strength. This reinforcement material63becomes an impediment at certain frequency region(s), but for certain frequency bands it does not impede the propagation of electromagnetic waves. In the first embodiment, for example, electromagnetic waves of 13.56 MHz are used, but in practice electromagnetic waves of about 5 MHz to about 50 MHz may be used.

InFIG. 1Bthe cross-section of the lower half portion of the wheel is not shown, but it is the same as the cross-section if the upper half portion, but with the valve70removed. Also, by the induction phenomenon of the reinforcement material63provided in the tire60, a substantially uniform alternating magnetic field H2is distributed in the space between the tire60and the wheel53, but the coupling amount (S21in terms of S parameter) of the small circular antenna90and the solenoid antenna provided in the valve70is, depending on the type of the tire60, from about minus twenty dB (decibels) to about minus thirty dB.

The value of the coupling amount S21indicates the magnetic energy transmission reception level between the solenoid antenna provided in the valve70and the small circular antenna90, and therefore, under certain conditions, the higher the value is, the smaller the magnetic energy may be for transmitting/receiving a signal.

Further, by Faraday's Law of electro magnetic inductance, when a magnetic field of magnetic flux Φ passes through an induction loop, if there are variations with time thereof, then an electromotive force E is generated so as to weaken the amount of change of magnetic flux, and an alternating current flows in the induction loop to generate a magnetic field in the opposite direction to the magnetic field. The electromotive force E is shown in the following equation (1).
E=−dΦ/dt(1)

In the equation (1), Φ is equivalent to the product of the magnetic permeability μ inside the solenoid antenna provided in the valve70, the surface area of the loop and the intensity of the alternating magnetic field H, and is the magnetic flux that passes through the antenna. The first embodiment mainly uses this phenomenon.

The direction of the alternating magnetic field H1generated by the small circular antenna90installed in the vicinity of the tire60is substantially parallel to the rotational axis of the tire60, and, maximum induced electromotive force may be obtained if it is well matched to the impedance of the solenoid antenna provided in the valve70.

The tire60has a diameter of, for example, between about 30 cm to about 180 cm. The small circular antenna90structure is a solenoid shape of several turns to ten or so turns of conductive wire with an insulating cover wound into a circular shape, with a diameter of the circular shape being several cm to ten or so cm, or a construction compressed to a thickness of about 1 cm to about 2 cm in the center axial direction of the solenoid. The electromagnetic field radiated by the small circular antenna90has a frequency band, for example, from about 10 KHz to about 100 MHz, and is placed at a distance of several cm to twenty or so cm from the side face of the tire60.

FIGS. 2A and 2Bare diagrams showing the configuration of the valve70inFIGS. 1A and 1B;FIG. 2Ais an internal block diagram of the valve70when a back cover thereof has been removed, andFIG. 2Bis a perspective diagram of the external appearance of the tire pressure/temperature detection device accommodated therein.

The valve70, in the same way as in the conventionalFIG. 5, has a valve body71of a case shape opening to the rear side, and on the side of this valve body71protrudes a cylindrical shape air ingress and egress aperture72. The air ingress and egress aperture72may be made from metal such as aluminum alloy, steel or the like, and apart from this the valve body71may be made from a resin or the like. A tire pressure/temperature detection device80is accommodated in the valve body71, and structured with the open to the rear side of the valve body71closed with an non-illustrated cover.

The tire pressure/temperature detection device80has a substrate81for mounting circuit elements, and a solenoid antenna86as an internal antenna connected to the substrate81through a transmission path85of conductive wire or the like. On the substrate81are mounted, connected to the solenoid antenna86: an air pressure sensor82; a temperature sensor83; an electrical circuit84for processing data and overall control of the device; and non-illustrated power supply means (for example, a power supply unit) and the like. The non-illustrated power supply unit is a circuit that converts the reception signal received from the solenoid antenna86to alternating current, and supplies each of the circuit elements.

The solenoid antenna86is an antenna made from about 10 turns of copper wire and having about the same diameter as a button battery26in conventionalFIG. 5(10 mm, for example), and an alternating magnetic field H3is generated by electromagnetic induction of the alternating magnetic fields H1, H2radiated from the external small circular antenna90. This solenoid antenna86is disposed so that the plane of the loop therein is orthogonal to the alternating magnetic fields H1, H2, in order to obtain the maximum induced electromotive force.

Normally there is a matching circuit provided between the solenoid antenna86and the substrate81for mounting the circuit elements, and efficient transmission of high frequency signals may be made, suppressing the reflectance loss therebetween. The matching circuit is structured with one parallel condenser, and one serial condenser, but is omitted fromFIGS. 2Aand B.

Operation of the First Embodiment

Since a characteristic of the first embodiment is an induction power supply method related to a power supply role undertaken by an electric supply antenna in a tire condition detection system, in a tire pressure/temperature detection device80with the conventional button battery26removed, explanation will focus on the antenna, and explanation of other elements not related to induction supply operation will be omitted.

InFIGS. 1A and 1B, high frequency power, for example several watts in the 13 MHz band, is transmitted from the high frequency power source102to the transmitter receptor101, and distributed here according to requirements for high frequency power, or supplied to each of the small circular antenna90through the transmission path100by switching a switch either mechanically or electrically. Each of the small circular antennae90are provided with a matching circuit configured by matching condensers91,92, and therefore radiate efficiently as electromagnetic waves the high frequency power supplied from the transmitter receptor101, and since each of the small circular antennae90are configured in the shape of a solenoid, a strong magnetic field component radiated in the central axial direction. Also, this central axis is substantially parallel to the rotational axis of the tire60, and so an alternating magnetic field H1is radiated to the rubber portion of the tire.

The tire60(10), as shown inFIG. 6, has a reinforcement material13(63), of a loop shape, solenoid shape or mesh shape of metal wire or the like embedded in the rubber portion11, and a macroscopic ring shaped conductor is formed of about the diameter of the tire60(10), and the alternating magnetic field H1passes orthogonally therethrough. Therefore, according to Faraday's Law of induction, a ring shaped alternating current flows in the ring shaped conductor, and, by induction, even the portion of the tire60far distanced from the small circular antenna90radiates a alternating magnetic field H2of substantially the same intensity as the alternating magnetic field H1radiated in the vicinity of the small circular antenna90. As a result, although the relative position of the small circular antenna90and the valve70changes with rotation of the wheel53, the amount of alternating magnetic flux passing through the valve70is substantially constant.

On the other hand, as shown inFIGS. 2A and 2B, the small circular solenoid antenna86accommodated in the valve body71is disposed in a position substantially orthogonal to the alternating magnetic fields H1, H2generated by electromagnetic induction, and receives substantially the maximum amount of alternating magnetic flux, and substantially the maximum electromotive force is generated at the two terminals of the solenoid antenna86. This electromotive force serves the role of an electrical power source, but it is an alternating current, and so it may be first rectified by a non-illustrated power unit and converted into direct current to give the same functionality as the button battery26conventionally mounted as the power source.

The alternating current power obtained in the power unit through the solenoid antenna86, for example, operates: the air pressure sensor82; temperature sensor83; the electrical circuit84for controlling data processing and the device overall; acquisition of physical properties inside the tire60(for example, pressure, temperature and the like); responding to the small circular antenna90after converting signals in the same solenoid antenna86; transmitting to the transmitter receptor101via the transmission path100; processing; and displaying on the display device103. A driver may know the internal pressure and temperature and the like of the tire60by data displayed on the display device103.

A characteristic of the first embodiment is that it does not use the button battery26that depletes and reduces the supply of electrical power to the sensors and the like, as in the conventional tire pressure/temperature detection device30, so when responding with the pressure and temperature data acquired in the tire60there is no need to make a separate oscillator oscillate, for example to respond with the acquired data on oscillations in the 400 MHz frequency band. By a frequency dividing technique a portion of the high frequency energy may be retained of the frequency of the power supplied from the small circular antenna90that is the reader antenna, and therefore the acquired data may be placed on this divided frequency and responded to the small circular antenna90, and so a separate oscillator is not required.

Effect of the First Embodiment

According to the first embodiment, because of the configuration in which power is supplied from outside to a tire pressure/temperature detection device that would conventionally have been operated by a battery, there are the following effects (1) to (4).

(1) Conventionally, in order to make the life of batteries last for 10 years, data of the internal pressure and temperature of the tire could only be supplied to a driver at a rate of about once every 3 minutes, and when nearing the end of the life of the battery the power from the battery decreases and so data errors increase. In contrast, according to the first embodiment, there is an electromagnetic power supply and there is no worry that the power will drain, therefore fine grained data may be supplied to a driver at a rate of about twice every second, for example.

(2) The fine grained data of (1) above is not only for supply of information relating to the pressure and temperature of the tire60to a driver, but it may well be the case that in the near future it will be essential for realizing automated driving of vehicles.

(3) Since it is not necessary to change batteries, not only is the cost of the batteries eliminated but also the time and expense of changing over batteries, and damage to the tire60during the operation of changing over batteries, may be completely eliminated. Further, since the disposal of consumed batteries is eliminated, the first embodiment may provide a tire pressure, temperature, and the like detection device that is environmentally friendly.

(4) By insertion of the vehicle key it is possible to instantaneously know the condition of the tire60, whatever the condition when parked, therefore, accidents due to tire problems may be averted before they occur.

Therefore, the first embodiment can greatly improve the functionality of a tire pressure, temperature and the like detection device conventionally operated by battery, and can greatly contribute to vehicle driving safety and preventing damage due to traffic accidents. Further, batteries having a lifetime of 10 years are highly specific, and incur a cost of disposal afterwards and a large impact on the environment, but these are problems that do not exist at all in the first embodiment.

Mode of Use of the First Embodiment

At the current stage, in the same way as a conventional battery operated tire pressure/temperature detection device, information relating to the pressure and temperature inside tires is provided to a driver, but the fineness of the grain of the data and the reliability of the data is much higher than for a conventional system, and so in the future there is the possibility of application to automatic driving of vehicles.

Second Embodiment

The first embodiment is a tire condition detection system that uses one small circular antenna90for one of the tires60. In contrast, in the second embodiment, there is the same concept as in the first embodiment, but in order to reduce variation in the distribution of the alternating magnetic field H2generated in the space between the tire60and the wheel53, plural small circular antennae are used. In order to simplify explanation, explanation is given of when two small circular antennae90-1and90-2are used.

The two small circular antennae90-1,90-2are the same as each other and are connected in parallel to the high frequency power source102supplying high frequency power, and therefore should radiate the same alternating magnetic field H1to the tire60. Further, in order that the two small circular antennae90-1,90-2do not affect each other, it is necessary to place them in positions that are distanced from each other, for example they may be disposed in positions that are on substantially opposite sides of the center of the tire60.

Details of a second embodiment will now be explained, with reference to the drawings.

Configuration of the Second Embodiment

FIG. 7is an explanatory diagram showing main portions of a tire condition detection system according to the second embodiment of the invention, and common elements to those of the elements inFIG. 1of the first embodiment are indicated by the same numerals.

In the second embodiment, the two small circular antennae90-1,90-2are disposed in the vicinity of the side faces of the tire60, for example in positions that are substantially at opposite sides of the center of the tire60. The respective small circular antennae90-1,90-2are connected to matching circuits configured by condensers91-1,92-1and by condensers92-1,92-2, and are connected to a high frequency power source102via each of respective transmission paths100-1,100-2of coaxial cables and the like. Due to respective alternating magnetic fields H1radiated to the tire60from each of the small circular antennae90-1,90-2, an alternating magnetic field H2are generated in the space between the tire60and the wheel53.

The two small circular antennae90-1,90-2are, for example, disposed in positions that are at substantially 90° or more to each other on the circumference of a circle with the rotational axis of the tire60at the center, or disposed in positions that are at substantially opposite sides on the circumference of a circle with the rotational axis of the tire60at the center. The rest of the configuration is as per the first embodiment.

Operation of the Second Embodiment

The operation of the second embodiment is the same as the operation of the first embodiment, and a brief explanation will be given.

High frequency electrical power is supplied in parallel to each of the small circular antennae90-1,90-2, via each of the transmission paths100-1,100-2, from the high frequency power source102, and respective alternating magnetic fields H1, H1are radiated to a rubber portion of the tire60, substantially parallel to the rotational axis of the tire60, from each of the small circular antennae90-1,90-2. In the rubber portion of the tire60is embedded a reinforcement material63of a loop shape, solenoid shape or mesh shape of metal wire or the like, an induced current flows in the reinforcement material63, and due to this the alternating magnetic fields H2, H2are generated in the space between the tire60and the wheel53.

When the two small circular antennae90-1,90-2are, for example, disposed in positions that are at substantially opposite sides of the center of the tire60, then the strengths and weaknesses of each of the generated alternating magnetic fields H1, H1are symmetrical. Also, since each of the alternating magnetic fields H1, H1are topologically in phase with each other, the intensities are additive, and variation in the intensity thereof is suppressed by mutual complementation.

The stable intensity alternating magnetic fields H1, H2generate electromotive force at the two terminals of the solenoid antenna86accommodated in the valve70by induction, with the effect that power necessary for the operation of the tire pressure/temperature detection device80is supplied. Further, the detection signal from an air pressure sensor82and a temperature sensor83is sent to a display device103by the same route and method as in the first embodiment and displayed, presented to a driver.

Effect of the Second Embodiment

The second embodiment is the same in principle as the first embodiment, but to further improve the characteristics the number of small circular antennae90-1, . . . , is increased, and the generation sources of the in phase alternating magnetic field H2generated in the space between the tire60and the wheel53are increased, and by this the intensity of the alternating magnetic field H2is stabilized and there is the effect of suppressing variation thereof. Therefore, in the second embodiment, by increasing the number of the small circular antennae90-1, . . . , the cost is slightly increased, but it could be said that the second embodiment is superior to the first embodiment in terms of performance.

Mode of Use of the Second Embodiment

The mode of use of the second embodiment is the same as the mode of use of the first embodiment.

Third Embodiment

The third embodiment is also based on the concept of the first embodiment, but is different in principle to the second embodiment. The third embodiment also has two small circular antennae90-1,90-2used as reader antenna, but the arrangement thereof is different to that in the second embodiment, and is characterized by arrangement sandwiching the tire60therebetween.

Configuration of the Third Embodiment

FIG. 8is an explanatory diagram showing the main portions of a tire condition detection system according to the third embodiment of the invention, and common elements to those inFIG. 1A, B andFIG. 7of the first embodiment and second embodiment are indicated by the same numerals.

In the third embodiment there are two small circular antennae90-1,90-2with the same structure disposed in the vicinity of both faces of the tire60, for example in a pattern of sandwiching the rubber portion of the tire60, disposed so that they have the same central axis. Respective small circular antennae90-1,90-2are connected to matching circuits configured by condensers91-1,92-1and by condensers92-1,92-2, and the small circular antennae90-1,90-2are connected to a high frequency power source102, via each of respective transmission paths100-1,100-2of coaxial cables and the like. Due to respective alternating magnetic fields H1, H1radiated to the tire60from each of the small circular antennae90-1,90-2, an alternating magnetic field H2is generated in the space between the tire60and the wheel53. Other parts of the configuration are the same as in the first embodiment and the second embodiment.

Operation of the Third Embodiment

The basic operation of the third embodiment is the same as that of the first embodiment, but is different in that two small circular antennae90-1,90-2are used, disposed in a pattern sandwiching the rubber portion of the tire60.

High frequency electrical power is supplied in parallel to each of the small circular antennae90-1,90-2via each of the transmission paths100-1,100-2from the high frequency power source102, and alternating magnetic fields H1, H1are each radiated to a rubber portion of the tire60, substantially parallel to the rotational axis of the tire60, from each of the small circular antennae90-1,90-2. Each of the small circular antennae90-1,90-2are connected in parallel to the high frequency power source102, and the generated alternating magnetic fields H1, H1have the same intensity and direction, and generate alternating magnetic fields H2, H2in the space between the tire60and the wheel53. These alternating magnetic fields H2, H2generate an electromotive force in the solenoid antenna86accommodated in the valve70, and operating power is supplied to the air pressure sensor82, temperature sensor83and electrical circuit84provided in the valve70.

The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the reader antennae of the two small circular antennae90-1,90-2via the solenoid antenna86, and sent to a display device103by the same route and method as those of the first embodiment and displayed, presented to a driver.

Effect of the Third Embodiment

The third embodiment is in principle the same as the first embodiment, but to further improve the characteristics the number of small circular antennae90-1, . . . , is increased to two, and the intensity of the induced alternating magnetic field H2is stronger than the alternating magnetic field H2of the first embodiment and stronger than the alternating magnetic field H2of the second embodiment, therefore, the degree of coupling (S21) between the solenoid antenna86accommodated in the valve70and the two small circular antennae90-1,90-2is, in theory, raised by about 3 dB. In the third embodiment, because the number of small circular antennae90-1,90. . . is raised to 2, the cost is slightly increased, but the third embodiment is superior to the first embodiment in terms of performance. Therefore, the third embodiment contributes to raising the performance of the tire condition detection system80.

Mode of Use of the Third Embodiment

The mode of use of the third embodiment is the same as that of the first embodiment.

Fourth Embodiment

The fourth embodiment is characterized in that the two small circular antennae90-1,90-2of the third embodiment are connected in series to the high frequency power source102.

Configuration of the Fourth Embodiment

FIG. 9is an explanatory diagram showing main portions of a tire condition detection system according to the fourth embodiment of the invention, and common elements to those ofFIG. 8are indicated by the same numerals.

In the fourth embodiment, as in the third embodiment, there are two small circular antennae90-1,90-2with the same structure as each other are disposed in the vicinity of both faces of the tire60and, for example, they are disposed in a pattern of sandwiching the rubber portion of the tire60, having the same central axis. This is to reduce the divergence of the magnetic field. The small circular antennae90-1,90-2are, as opposed to in the third embodiment, connected in series to a high frequency power source102via each of respective transmission paths100. A matching circuit of condensers91,92is only required in the small circular antenna90-2.

By such a configuration, since it may be considered to be a single solenoid, the center of which having been opened out, a matching circuit is only required in practice at the small circular antenna90-2that is directly connected to the high frequency power source102. Each of the small circular antennae90-1,90-2are of the same number of turns and dimensions, and the same alternating current flows, therefore they radiate alternating magnetic fields H1, H1of the same intensity and direction. Therefore, due to the alternating magnetic fields H1, H1, the alternating magnetic field H2is generated in the space between the tire60and the wheel53. The other parts of the configuration are the same as in the first embodiment and the second embodiment.

Operation of the Fourth Embodiment

The basic operation of the fourth embodiment is the same as that of the third embodiment, but the small circular antennae90-1and90-2are not connected in parallel, as they are in the third embodiment, but are connected together in series, and also only the small circular antenna90-2is connected to the high frequency power source102through a matching circuit.

First, high frequency power is supplied from the high frequency power source102through the matching circuit to the small circular antenna90-2, and also the same alternating current flows from the distal end of the small circular antenna90-2to the small circular antenna90-1. Both of the small circular antennae90-1,90-2have the same number of turns and dimensions, therefore radiate the alternating magnetic fields H1, H1of the same intensity and direction. Since the alternating magnetic fields H1, H1are of the same intensity and direction, just as in the third embodiment, the alternating magnetic fields H1, H2are generated distributed in the space between the tire60and the wheel53. Due to the alternating magnetic fields H1, H2electromotive force is generated in the solenoid antenna86accommodated in the valve70, and operating power is supplied to the air pressure sensor82, the temperature sensor83and the electrical circuit84that are provided in the valve70.

The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the two small circular antennae90-1,90-2via the solenoid antenna86, and transmitted to the driver via the same means as in the first embodiment.

Effect of the Fourth Embodiment

The fourth embodiment is the same in principle as the third embodiment, but since the small circular antennae90-1,90-2are connected to the high frequency power source102in series to each other, two matching circuits are not necessary and a single matching circuit is sufficient.

Also, other effects are the same as those of the third embodiment, by increasing the number of the small circular antennae90-1, . . . reader antennae so as to improve the characteristics, the induced alternating magnetic field H2is stronger in intensity than the alternating magnetic field H2of the first embodiment and then the alternating magnetic field H2of the second embodiment, and therefore the degree of coupling (S21) of the solenoid antenna86accommodated in the valve70with the small circular antennae90-1,90-2is raised in theory by about 3 dB. In the fourth embodiment, because the number of the small circular antennae90-1, . . . has been increased to 2, there is a slight increase in cost, but the fourth embodiment is significantly superior in performance to that of the first embodiment. Therefore, the fourth embodiment contributes to raising the performance of the tire condition detection system80.

Mode of Use of the Fourth Embodiment

The mode of use of the fourth embodiment is the same as that of the first embodiment.

Fifth Embodiment

The fifth embodiment is characterized by the use of a solenoid antenna90A, or a solenoid antenna90B, instead of the small circular antennae90,90-1,90-2reader antennae of the first to fourth embodiments.

Configuration of the Fifth Embodiment

FIGS. 10A,10B and11are explanatory diagrams showing the main portions of the tire condition detection system of the fifth embodiment of the invention.FIG. 10Ais a cross-sectional diagram of a circular cross-section solenoid antenna,FIG. 10Bis a external view of a rectangular cross-section solenoid antenna, andFIG. 11is an external view of an arc shaped solenoid antenna. InFIGS. 10A,10B and11, common elements to those of the first embodiment are indicated by the same numerals.

In the fifth embodiment, a circular cross-section solenoid antenna90A as shown inFIG. 10A, or a substantially rectangular cross-section solenoid antenna90B as shown in FIG10B, is used instead of the small circular antenna90reader antenna of the first embodiment.

As shown inFIG. 10A, the circular cross-section solenoid antenna90A is disposed in the vicinity of the outer peripheral face of the tire60. The circular cross-section solenoid antenna90A has a solenoid body provided with terminals at both ends of a coil shaped conductor, and the two terminals of the solenoid body are connected to the high frequency power source102through transmission paths100of electrical wires or the like. The solenoid antenna90A, when supplied with high frequency power from the high frequency power source102, radiates alternating magnetic force lines generating an alternating magnetic field H1. Therefore, due to this, an alternating magnetic field H2is generated in the space between the tire60and the wheel53. While not illustrated, it is sometimes necessary to have a matching circuit between the high frequency power source102and the solenoid antenna90A.

As shown inFIG. 10B, the rectangular cross-section solenoid antenna90B may be used in place of the circular cross-section solenoid antenna90A. The rectangular cross-section solenoid antenna90B has a solenoid body provided with terminals at both ends of a coil shaped conductor of substantially square or rectangular shaped turns, and the two terminals of the solenoid body are connected to the high frequency power source102through the transmission paths100.

The solenoid antennae90A,90B are, for example, solenoid shapes of several turns, to ten or so turns, of wound conducting wire that has a diameter of about 0.5 mm to about 3 mm, the solenoid shapes having maximum dimensions in cross-section of several cm to ten or so cm. Or, the small circular antennae90A,90B may be formed of solenoid shapes of conductive foil of thickness from about ten or so microns to about several hundreds of microns, and widths of about several mm to twenty or so mm.

Further, as shown inFIG. 11, the cross-sectional shapes of solenoid antennae90A,90B may be extended in an arc shape around the outer peripheral face of the tire, such that the alternating magnetic field H1may be radiated onto a wide region of the side face of the tire60. These arc shaped solenoid antennae90A or90B extend in an arc shape over a segment of about 30° to about 60° with respect to the center of the tire60, and are disposed at a distance of about 10 cm from the outer peripheral face of the tire. The dimensions of the arc shape are, for example, when used on a car wheel, have a maximum dimension of from about 30 cm to about 50 cm.

Other parts of the configurations ofFIGS. 10A,10B and11are the same as in the first embodiment.

Operation of the Fifth Embodiment

Since the operation of the fifth embodiment is substantially the same as that of the first embodiment, a brief explanation will be given.

High frequency power is supplied from the high frequency power source102, through the transmission path100, to the solenoid antenna90A (or90B), and the alternating magnetic field H1is radiated from both ends of the solenoid antenna90A (or90B), substantially parallel to the rotational axis of the tire60, to a rubber portion of the tire60. Since a reinforcement material63is embedded in the rubber portion of the tire60, an induced current flows in the reinforcement material63. Due to this the alternating magnetic field H2is generated in the space between the tire60and the wheel53.

The alternating magnetic field H2generates by induction an electromotive force at the two terminals of the solenoid antenna86accommodated in the valve70, with the effect that the necessary power for operating the tire pressure/temperature detection device80is supplied. The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the driver by the same route and method as those in the first embodiment.

Effect of the Fifth Embodiment

In the fifth embodiment, the solenoid antenna90A or90B is disposed so that the central axis thereof is substantially parallel to the rotational axis of the tire60, and, it appears inFIGS. 10A and 11that the solenoid antenna90A or90B is disposed directly above the tire60, but it need not necessarily be directly above and may be fixed in a place that is easy to fix depending on the shape of the tire housing.

Since there is effectively left-right symmetry in the alternating magnetic field H1radiated from the solenoid antenna90A or90B, the alternating magnetic field H2generated by induction in the space between the wheel53and the tire60also has left-right symmetry of intensity, and in one way the intensity of the electromotive force generated by induction in the two terminals of the solenoid antenna86accommodated in the valve70is greater compared to that of the first embodiment. Therefore, the fifth embodiment contributes to improving the performance of the tire pressure/temperature detection device80.

Mode of Use of the Fifth Embodiment

The mode of use of the fifth embodiment is the same as that of the first to fourth embodiments, but when, depending on the type of vehicle, the shape of the tire housing and the electrical characteristics of the tire, it is not possible to fix a small circular antenna90at the side face of the tire60, the fifth embodiment provides a method of fixing above, or at a chosen location at, the outer peripheral face of the tire.

Sixth Embodiment

Configuration of the Sixth Embodiment

FIG. 12is a cross-sectional diagram showing a solenoid antenna and a tire in a tire condition detection system according to the sixth embodiment of the invention, and common elements to those of the fifth embodiment shown inFIGS. 10A and 10Bare indicated by the same numerals.

The sixth embodiment has basically the same structure as that of the fifth embodiment, but the circular cross-sectional solenoid antenna90A shown inFIG. 10A, or the rectangular cross-sectional solenoid antenna90B shown inFIG. 10Bis disposed orthogonal to the outer periphery of the tire (disposed in the width direction of the outer peripheral face of the tire), and also the central axis of the solenoid antenna90A or90B is extended in an arc shape around the width directional face of the outer peripheral face of the tire, so that large amounts of magnetic flux may be made to flow into the space between the tire60and the wheel53. Other parts of the structure are the same as those of the fifth embodiment.

Operation of the Sixth Embodiment

The operation of the sixth embodiment is substantially the same as that of the fifth embodiment, and a brief explanation will be given.

High frequency power is supplied from the high frequency power source102, through the transmission paths100, to the arc shaped solenoid antenna90A or90B, and the alternating magnetic field H1is radiated from both ends of the solenoid antenna90A or90B, substantially parallel to the rotational axis of the tire60, to the rubber portion of the tire60. An induced current flows in the reinforcement material63embedded in the rubber portion of the tire60, and due to this the alternating magnetic field H2is generated in the space between the tire60and the wheel53.

The alternating magnetic field H2generates by induction an electromotive force at the two terminals of the solenoid antenna86accommodated in the valve70, with the effect that the power required for the operation of the tire pressure/temperature detection device80is supplied. The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the driver by the same route and method as those in the first embodiment.

Effect of the Sixth Embodiment

In the sixth embodiment, the arc shaped solenoid antenna90A or90B is, as shown inFIG. 12, curved and extended along the width direction surface of the outer peripheral face of the tire60, and, appears to be disposed directly above the tire60, but it need not necessarily be directly above and may be fixed in a place that is easy to fix depending on the shape of the tire housing.

Since there is effectively left-right symmetry in the alternating magnetic field H1radiated from the arc shaped solenoid antenna90A or90B, the alternating magnetic field H2generated by induction in the space between the wheel53and the tire60also has left-right symmetry of intensity, and, much the same as in the fifth embodiment, in one way the intensity of the electromotive force generated by induction in the two terminals of the solenoid antenna86accommodated in the valve70is greater compared to that of the first embodiment. Therefore, the sixth embodiment contributes to improving the performance of the tire pressure/temperature detection device80.

Mode of Use of the Sixth Embodiment

The mode of use of the sixth embodiment is the same as that of the fifth embodiment, but since the shape of the arc shaped solenoid antenna90A or90B substantially matches that of the tire housing, the sixth embodiment is easier to fix than the fifth embodiment, and provides a method of fixing above, or at a chosen location at, the outer peripheral face of the tire.

Seventh Embodiment

The seventh embodiment is a configuration inserting a bar shaped core93, which is mainly of material such as soft iron, ferrite or the like, into the central axial region of the small circular antennae90,90-1,90-2and the solenoid antenna90A and90B used in the first to the sixth embodiments, suppressing divergence of the alternating magnetic field H1radiated from the respective antennae90, . . . raising the induction efficiency and concentrating the alternating magnetic field H2induced in the space between the wheel53and the tire60.

Since the philosophy is the same, application of the seventh embodiment to the easily explained fifth embodiment will be used as a representative example, and the seventh embodiment will be explained below.

Configuration of the Seventh Embodiment

FIG. 13is a cross-sectional diagram showing a solenoid antenna and tire of a tire condition detection system of the seventh embodiment, and common elements to those of the fifth embodiment shown inFIGS. 10A and 10Bare indicated by the same numerals.

In the seventh embodiment, the structure is basically the same as that of the fifth embodiment, but it differs in that a bar shaped core93, which is mainly of material such as soft iron, ferrite or the like, is inserted into the central axial region of the circular cross-section solenoid antenna90A or the rectangular cross-section solenoid antenna90B used in the fifth embodiment, with other parts of the configuration being the same as those of the fifth embodiment.

Operation of the Seventh Embodiment

The operation of the seventh embodiment is substantially the same as that of the fifth embodiment, and a brief explanation will be given.

High frequency power is supplied from the high frequency power source102, through the transmission path100, to the solenoid antenna90A or90B, and the alternating magnetic field H1is radiated, substantially parallel to the rotational axis of the tire60, from both ends of the solenoid antenna90A or90B. Because of the presence of the bar shaped core93in the seventh embodiment, the alternating magnetic field H1radiated from both ends of the solenoid antenna90A or90B does not immediately diverge, and is concentrated in a narrow region of the rubber portion of the tire60. Since there is the reinforcement material63embedded in the rubber portion of the tire60, an induced current that is stronger than if there was no bar shaped core93present flows in the reinforcement material63, and due to this the alternating magnetic field H2, which is stronger than would have been the case if there was no bar shaped core93, is generated in the space between the tire60and the wheel53.

The alternating magnetic field H2generates by induction an electromotive force, which is stronger than would have been the case if there was no bar shaped core93, at the two terminals of the solenoid antenna86accommodated in the valve70, with the effect that the power required for the operation of the tire pressure/temperature detection device80is supplied. The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the driver by the same route and method as those in the first embodiment.

Effect of the Seventh Embodiment

According to the seventh embodiment, due to the effect of concentrating the magnetic force of the inserted bar shaped core93in the antennae90,90-1,90-2,90A,90B, a stronger electromotive force is generated at the two terminals of the solenoid antenna86accommodated in the valve70than those of the first to sixth embodiments, and more sensors may be operated, and more information relating to the inside of the tire may be provided to the driver. Therefore, that the seventh embodiment contributes to improving the performance of the tire pressure/temperature detection device80.

Mode of Operation of the Seventh Embodiment

The mode of operation of the seventh embodiment is the same as the modes of operation of respective first to sixth embodiments.

Eighth Embodiment

In the seventh embodiment, by insertion of a core into the respective antennae90,90-1,90-2,90A,90B of the first to sixth embodiments, the magnetic force concentrating effect of the respective antennae90, . . . is raised.

In the eighth embodiment the philosophy is the same, but instead of the bar shaped core93, a C-shaped core94is used, raising the magnetic force concentrating effect even further.

Configuration of the Eighth Embodiment

FIG. 14is a cross-sectional diagram showing a solenoid antenna and tire of a tire condition detection system of the eighth embodiment and common elements to those of the fifth embodiment shown inFIGS. 10A and 10Bare indicated by the same numerals.

The reader antenna applied to the eighth embodiment, are the same as the circular cross-sectional solenoid antenna90A or the rectangular cross-sectional solenoid antenna90B of the fifth embodiment, and the C-shaped core94, which is mainly of material such as soft iron, ferrite or the like, is inserted into the central axial region of the solenoid antenna90A or solenoid antenna90B. The C-shaped core94has left and right end faces94aand94bthat face each other, both the end faces94a,94bare vertical, and from whichever face lines of magnetic force are radiated, these lines are largely focused on the opposite face. Due to these lines of magnetic force on alternating magnetic field H2is generated in the space between the wheel53and the tire60.

The separation of the end faces94a,94bis adjustable, and as a rough guide, if the separation is slightly greater than the separation of the two side faces of the tire60then the intensity of the alternating magnetic field H2distributed in the space between the tire60and the wheel53is thought to be the strongest of the above embodiments. However, if the end faces94a,94bare too close to the two side walls of the tire60then, depending on the condition of the tire, it is possible that driving could be impeded, so it is better to provide the end faces94a,94bat about 5 cm or more from the side faces of the tire60.

Operation of the Eighth Embodiment

The operation of the eighth embodiment is substantially the same as that of the fifth embodiment, and a brief explanation will be given.

High frequency power is supplied from the high frequency power source102, through the transmission path100, to the solenoid antenna90A or90B, and the alternating magnetic field H1is radiated, substantially parallel to the rotational axis of the tire60, from both end faces94a,94bof the solenoid antenna90A or90B. Because of the presence of the C-shaped core94in the eighth embodiment, the magnetic force lines of the alternating magnetic field H1radiated from both ends of the solenoid antenna90A or90B nearly all pass through the C-shaped core94and are radiated from the end faces94a,94b.

Since, as in the fifth embodiment, there is the reinforcement material63embedded in the rubber portion of the tire60, a strong induced current flows in the reinforcement material63, and due to this a strong alternating magnetic field H2is also generated in the space between the tire60and the wheel53. The alternating magnetic field H2generates by induction a strong electromotive force at the two terminals of the solenoid antenna86accommodated in the valve70, with the effect that the power required for the operation of the tire pressure/temperature detection device80is supplied. The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the driver by the same route and method as those in the first embodiment.

Effect of the Eighth Embodiment

According to the eighth embodiment, since the C-shaped core94is provided, a strong alternating magnetic field H2is generated in the space between the tire60and the wheel53. Due to this a strong electromotive force is generated at the terminals of the solenoid antenna86accommodated in the valve70, and more sensors may be operated, and more information relating to the inside of the tire may be provided to the driver. Therefore, the eighth embodiment contributes to improving the performance of the tire pressure/temperature detection device80.

Mode of Use of the Eighth Embodiment

The mode of use of the eighth embodiment is the same as that of the first embodiment, but when, depending on the type of vehicle, the shape of the tire housing and the electrical characteristics of the tire, it is not possible to fix, as in the first embodiment, a small circular antenna90at the side face of the tire60, the eighth embodiment makes it possible to fix the C-shaped core94to a suitable place on the tire housing and bring only the end faces94a,94bof the C-shaped core94into the vicinity of the tire60, generating the strong alternating magnetic field H2in the space between the tire60and the wheel53. Strong operating power may be supplied to the tire pressure/temperature detection device80effectively, and gyros and multiple sensors that will be needed for control of vehicle attitude in the future may be operated, and more information related to the inside of the tire may be provided to the driver.

Ninth Embodiment

In the first to the eighth embodiments the basic structure of the respective reader antennae are solenoid antennae90,90-1,90-2,90A and90B, and proposals are made for raising the magnetic force concentrating effect thereof.

In contrast, in the ninth embodiment, while the philosophy of other portions is the same, the reader antenna is a ring shaped antenna90C, and this is constructed of a single turn loop of one strand of conductive wire. A detailed explanation thereof will be given below.

Configuration of the Ninth Embodiment

FIGS. 15A and 15Bare explanatory diagrams showing the main portions of a tire condition detection system according to the ninth embodiment of the invention.FIG. 15Ais an outline plan view of a ring shaped antenna, andFIG. 15Bis a cross-sectional diagram of a ring shaped antenna and a tire. Common elements to those of the first embodiment shown inFIGS. 1A and 1Bare indicated by the same numerals.

In the ninth embodiment the ring shaped antenna90C is constructed of a single turn of one strand of conductive wire, having resistance and inductance, therefore in order to receive high frequency power with high efficiency, a matching circuit configured with two matching condensers91,92is necessary.

The ring shaped antenna90C is made of conductive wire (for example copper) of about 1 mm to about 5 mm diameter (for example, 3 mm diameter), and, is formed so as to match the diameter of the tire60, being formed into a circular shape with the smallest dimension and the largest dimension of the diameter thereof being several cm or more larger than the smallest diameter of the tire60, and several cm or more smaller than the largest diameter of the tire60(for example having a diameter of about 60 cm). The ring shaped antenna90C is fixed vertically to the car body at a predetermined separation from the side face of the tire60(for example, about 50 mm or less). The structure is such that, due to an alternating magnetic field H1radiated from the ring shaped antenna90C, a strong induced current flows in reinforcement material63embedded in the tire60, and because of this an alternating magnetic field H2is generated in the space between the wheel53and the tire60.

FIG. 15Bis a cross-sectional diagram, and the lower half portion of the wheel, while not illustrated, the same as the top half portion of the wheel because of the symmetry but with the valve70removed. Furthermore, by the induction phenomenon of the reinforcement material63in the tire60, the alternating magnetic field H2has a substantially uniform distribution about the axis in the space between the tire60and the wheel53.

Operation of the Ninth Embodiment

In the same way as in the first embodiment, high frequency power is output from the high frequency power source102, and this is supplied to the ring shaped antenna90C through the matching circuit of the matching condensers91,92. The ring shaped antenna90C receiving the supplied high frequency power radiates the alternating magnetic field H1that is substantially parallel to the rotational axis of the tire60. An induced current flows in the reinforcement material63in the rubber portion of the tire60, and due to this the alternating magnetic field H2is generated by induction in the space between the tire60and the wheel53.

By induction the alternating magnetic field H2generates an electromotive force at the two terminals of the solenoid antenna86in the valve70, with the effect that the power necessary for the operation of the tire pressure/temperature detection device80is supplied. The detection signals from the air pressure sensor82and the temperature sensor83are transmitted to the driver via the same route and method as those of the first embodiment.

Effect of the Ninth Embodiment

The ring shaped antenna90C used in the ninth embodiment is disposed substantially coaxially to the tire60, and the intensity of the alternating magnetic field H2in the space between the tire60and the wheel53is substantially the same for positions with the same distance from the central axis of the tire60. That is to say, the intensity of the alternating magnetic field H2in the space between the tire60and the wheel53is symmetrical about the axis, and extremely stable magnetic energy is supplied to the tire pressure/temperature detection device80in the valve70.

Effectively, when parking, such as with a car, it does not matter which position the valve70is in, and a stable power supply from the ring shaped antenna90C may always be received. This characteristic is one that is not present in the solenoid antennae90, . . . of the first to the eighth embodiments. Furthermore, the ring shaped antenna90C and the tire60are substantially coaxial and so not so much care is required in the up-down, left-right positioning when fixing to the vehicle body. Therefore, the induction supply method using the ring shaped antenna90C of the ninth embodiment is the most superior.

If the ring shaped antenna90C is a substantially circular shaped loop then the same operational effect may be obtained.

Mode of Use of the Ninth Embodiment

The mode of use of the ninth embodiment is the same as that of the first to the eighth embodiments, but since a ring shaped antenna90C that has the same central axis to that of the central axis of the tire in a ring shape or loop shape is used, stable and also strong high frequency power may be supplied without much relation to the position of the valve70moving due to the rotation of the tire60. Because of this, gyros and multiple sensors that will be needed for control of vehicle attitude in the future may be operated, and more information related to the inside of the tire may be provided to the driver.

MODIFIED EXAMPLES

The present invention is not limited to the illustrated first to ninth embodiments and modes of use, and various modifications may be made. These modifications are, for example, such as those of the following (a) to (c).

(a) In the tire pressure/temperature detection device80with antennae90, . . . accommodated in the valve70, apart from the air pressure sensor82and the temperature sensor83, other sensors such as those for detecting the pH of the air inside the tire, acceleration and the like may be provided.

(b) The tire pressure/temperature detection device80with antennae90, . . . may be fixed to other locations in the tire other than the valve70.

(c) In the embodiments tire condition detection systems for fixing to the tire60of vehicles was explained but the present invention may be applied to tires of construction machinery, haulage machinery, agricultural machinery, airplanes and the like.