WO1993008035A1

WO1993008035A1 - Process, device and valve for measuring and displaying tire pressure

Info

Publication number: WO1993008035A1
Application number: PCT/EP1992/002377
Authority: WO
Inventors: Rainer Achterholt
Original assignee: Rainer Achterholt
Priority date: 1991-10-14
Filing date: 1992-10-14
Publication date: 1993-04-29

Abstract

A valve (4) and a remote control element (50) between which signals are transmitted by means of electromagnetic radiation are useful to measure and display tire (3) pressure. An emitter is arranged at the remote control element (50) for emitting an actuating signal. A receiver for the actuating signal, an actuating arrangement, an absolute pressure sensor, an emitter and circuitry for generating and emitting a pressure signal that represents the tire pressure are arranged at or in the valve (4). The absolute pressure sensor is designed as a semiconductor component and supplies an electric output signal that corresponds to the actual tire pressure. An arrangement for receiving the pressure signal, an LCD display and circuitry for evaluating the pressure signal and for controlling the display are arranged at the remote control element (50).

Description

Method, device and valve for measuring and displaying the pressure in a pneumatic tire

Description:

The invention relates to a method and a device for measuring and displaying the pressure in a pneumatic tire. The invention further relates to a valve for such a device. The device is particularly intended for pressure measurement on the tires of cars, trucks, buses and aircraft.

From document DE-A-39 30 479 a valve with a signal generating device for vehicle tires is known which has a valve foot from which a valve stem protrudes. On the side of the valve base facing away from the valve stem, a device for generating a wirelessly transmitted pressure signal (signal generating device) is attached, which has at least one pressure sensor, one or more circuit devices for generating the pressure signal, and a source for electrical energy. For wireless

Signal transmission serves electromagnetic radiation with frequencies in the kHz range. In this known valve, a membrane serves as the pressure sensor, which can be deflected in the event of abnormal tire pressure. The membrane forms or carries the movable switching element of a mechanical switch, the circuit of which is closed when the membrane is deflected, whereupon the transmitting device is activated. The well-known valve generates a signal frequency only if the one to be monitored

Tire pressure is less than a target pressure. However, there is a desire to change the current tire pressure as desired

To be able to query as part of the tire pressure control.

Document DE-C-36 00 830 discloses a tire pressure measuring and display device in which a deflectable membrane is provided as the pressure sensor, which is arranged within a valve cap and on which the tire pressure acts. A permanent magnet is adjusted according to the tire pressure-dependent membrane deflection, and the distance between the permanent magnet and a reference plane serves as a "pressure signal". This distance of the magnet is detected with the aid of a proximity sensor which operates without contact and is located in a handpiece which can be handled independently of the valve cap and which must be brought into abutment against the valve cap in a defined manner. The output signal of the proximity sensor is processed with the aid of an electronic circuit which supplies a signal for driving a pressure display device.

The pressure display device can be designed as an easily readable liquid crystal or light-emitting diode number display with several display fields. Thanks to a memory device, the tire pressure can also be read away from the valve cap. A disadvantage of the known device is that, in order to transmit the “pressure signal”, the handpiece must be brought to bear against the valve cap in a defined arrangement. Furthermore, the pressure detection with the aid of a deflectable membrane limits the accuracy and the reproducibility of the pressure value determination.

The documents US-A-4 250 759 and US-A-4 704 901 disclose hand-held devices which are equipped with a pressure sensor, a power source and the necessary circuitry for generating a digital pressure display. These handheld devices are mechanically coupled to a tire valve, whereby a valve tappet is depressed so that the tire pressure can act on the pressure sensor in the hand-held device. Another disadvantage is the requirement for mechanical coupling of the hand-held device and the tire valve. In addition, experience has shown that the type of coupling of the device to the tire valve influences the pressure display in such handheld devices.

Document DE-A-28 50 787 relates to a tire pressure alarm device which has a pressure sensor, an electromagnetic current generator and a transmitter for a pressure signal on the rotating wheel, which is transmitted telemetrically to a receiver which is housed on the vehicle chassis . The pressure sensor is a pressure switch equipped with a membrane. The membrane adjusts a movably arranged switching element that opens or closes a circuit. The pneumatically operated pressure switch responds to certain threshold values, and accordingly a "warning" or "alarm" display can be generated. The continuous monitoring and display of the tire pressure is not possible with this known device.

In addition, a handheld device can be provided with which the functionality of the known tire pressure alarm device can be checked. The hand-held device is aimed at a tire in order to telemetrically activate its pressure sensor. A pressure signal is then generated, teletrically transmitted to the handheld device and displayed there. The states mentioned above can be displayed.

Furthermore, a number of systems for monitoring the tire pressure are known, which have a pressure switch on the rotating wheel and a signal transmitter on the chassis adjacent to the wheel. The pressure signal is transmitted by inductive coupling, which is induced by a signal from the signal transmitter (cf. DE-A-37 36 803 or DE-A-38 01 278). Finally, are formed as a semiconductor device

Absolute pressure sensors have become known which deliver an electrical output signal which corresponds to the detected pressure. Such absolute pressure sensors have hitherto not been used for tire pressure monitoring on vehicle tires.

It is an object of the invention to provide a method for measuring and displaying the pressure in a pneumatic tire of a vehicle grade, with which the current tire pressure can be queried at any time and the tire pressure recorded with an accuracy of at least 1/10 bar and can be displayed.

This object is solved by the features in claim 1.

Another object of the invention is to provide a device for carrying out this method, with which — when the vehicle is stationary — the current tire pressure can be queried simply and conveniently and displayed in a clearly visible manner.

This object is solved by the features in claim 7.

Furthermore, a valve is to be provided for this device.

This task is solved with the entirety of the features in claim 17.

With the present invention, a simple and convenient check of the tire pressure is possible because a direct mechanical or physical coupling between the vehicle wheel and the reading / display instrument is not required. Rather, the remote control element is directed towards the tire to be tested from a comfortable distance, and the activation signal is triggered by actuation of a button or a switch. Immediately afterwards, the large-format LCD display of the remote control element shows the numerical pressure of the tire being shown.

The reading / display instrument is designed as a remote control element, as is known, for example, from the operation of TV sets. The source for the activation signal is located on an end face of the elongated cuboid remote control element. This source is aimed at the tire whose pressure is to be checked.

A distance of approximately 50 to 200 cm between the remote control element and the tire to be tested is typically to be maintained. The remote control element is provided with a button or switch, its actuation triggers the activation signal and the receiving device and the evaluation devices are set to a standby state. Since the power-consuming components of the remote control element are only in operation for a short time, the battery provided for the power supply in the remote control element has a long service life. This battery can be replaced once it has been used up.

The valve is housed:

an absolute pressure sensor which is designed as a semiconductor component and which delivers an electrical output signal,

a circuit device which evaluates this electrical output signal and uses it to generate a pressure signal which represents the tire pressure,

a transmission device for this pressure signal,

- a source of electrical energy,

a receiving device for the activation signal supplied by the remote control element, and

an activation device which controls the absolute pressure sensor, the switching device (s) and the transmission unit. direction then activated after an activation signal has been received.

At the valve, only the receiving device and the activation device have to be kept in a standby condition. All that is required is a minimal current consumption, for example in the order of magnitude of a few microamperes. After the receiver device of the valve has received an activation signal, the activation device activates the components on the valve required to generate and transmit the signal frequency; For example, the absolute pressure sensor is supplied with voltage and the circuit device (s) and the transmitting device are put into operation. A sequence control ensures a short-term transmission of the pressure signal; for example, the duration of the transmission or the number of pressure signal pulses transmitted can be limited. Then the power supply to the absolute pressure sensor, the switching device (s) and the transmitting devices is interrupted again. Thanks to the minimal power consumption, a long service life of the power source is obtained on the valve. For example, with a lithium battery with the dimensions of a button cell, which has a nominal voltage of approximately 3 V and a capacity of approximately 50 rnAh, more than 200 transmissions of the current tire pressure can be carried out. Obviously, even with regular tire pressure monitoring - for example once a week - the valve will function for several years. In addition, a larger battery with a larger capacity could easily be attached to the valve base within the tire cavity.

For the wireless signal transmission between the valve and the remote control element, a signal transmission path with a path length of approximately 50 to is expediently used

200 cm provided. With a shorter path length, the controlling person must bend over unnecessarily. At a A longer path requires an unnecessarily high energy requirement for the transmission devices and increases the risk that not only the tire to be checked is detected, but also other tires on the same or on an adjacent vehicle. A path length of the signal transmission path of approximately 100 to 150 cm has proven particularly useful.

The wireless signal transmission takes place with the aid of electromagnetic radiation, the frequency of which is not particularly limited. For example, comparatively long-wave frequencies in the kilo- and mega-Hertz range can be provided for signal transmission. May further include the signal transmission by means of electromagnetic Strah¬ carried lung, the ER imaging with opto-electronic devices _{and it} can be _Asst f. A suitable frequency range comprises the red part of the visible light and the near infrared radiation, that is to say radiation with wavelengths of approximately 650 to 1400 nm. Radiation in this wavelength range is referred to below as "IR radiation" for short. Radiation with wavelengths between approximately 800 and 1000 nm, which can be generated with the aid of GaAs LEDs, is particularly suitable. Such radiation is sufficiently reflected in the environment in question here to ensure reliable signal transmission between the valve and the remote control element even when the valve is in an unfavorable position. In most countries there are no official requirements for the signal transmission with IR radiation of the radiation power under consideration here. The optoelectronic components (LEDs, photodiodes) required for generation and detection are small, powerful and are available at low cost and are customary in the trade. The known remote control elements for TV sets provide experience with regard to the selection of suitable optoelectronic components and the design of suitable circuits for signal transmission with IR radiation. The known IR LEDs, such as luminescent diodes or laser diodes, can be used as transmitting devices for the IR radiation. Luminescent diodes also provide largely monochromatic radiation. GaAs LEDs are used in particular. They have good efficiency and are suitable for low-frequency modulation in the kHz range. Discrete LED components are small and only have dimensions in the millimeter range. Such LED components can also be integrated in hybrid circuits. The emission and reception characteristics can be influenced with the aid of optically conductive components and / or the housing shape.

With regard to the signal transmission with the aid of IR radiation, a photodiode is preferably used as the receiving device. In particular, an Si photodiode is provided, which has a high sensitivity in the spectral range between about 800 and 1000 nm. The maximum sensitivity of the Si photodiode almost coincides with the emission of the GaAs diode. Compared to other radiation detectors, photodiodes have a high response time in the range of nanoseconds, so that low-frequency modulation of the IR radiation in the kHz range can also be detected. Photodiodes also have small dimensions in the millimeter range and can also be integrated in hybrid circuits. The photodiode on the valve must be kept constantly ready to receive. In order to keep the current consumption as low as possible, a transistor is preferably assigned to the photodiode. In this case, the photo diode is operated in element mode, i.e. operated without preload. When the IR radiation strikes, the photodiode generates a voltage which is applied to the base of the transistor. Stand-by operation with minimal power consumption is obtained.

The tire pressure is detected with an absolute pressure sensor, which is designed as a semiconductor component and the one delivers current tire pressure corresponding electrical output signal. Suitable semiconductor pressure sensors are available with small dimensions, for example as cuboid bodies with dimensions of approximately 6 x 6 x 3 mm. The chip contains a hermetically sealed vacuum reference space and a piezo-resistive transducer to which the tire pressure to be monitored can be applied, the resistance elements of which are typically switched in the manner of a wheat tone bridge. Additional elements for compensating the temperature influences are located on the chip

Sensitivity and zero point adjustment. In addition, a further sensor for temperature measurement can be integrated on the same chip. The chip is located on a ceramic substrate which is designed for the assembly of a circuit board using SMD technology (surface mounted device).

Alternatively, such a semiconductor absolute pressure sensor can be integrated into a hybrid circuit.

Typically, such an absolute pressure sensor generates analog signals in the form of electrical voltages as an electrical output signal. These signals are fed to an amplifier which, if necessary, can be integrated on the same component. Such piezo-resistive solid-body absolute pressure sensors are available, for example, for pressure measurements in the range from 0 to 3.5 bar or 0 to 7.0 bar or 0 to 14 bar overpressure and are in a temperature range from -40 ° C to + + 125 ° C applicable. A temperature measurement can also be carried out in the same temperature range. In the pressure range of about 1 to 14 bar gauge pressure, which is of particular interest here, at least a measuring accuracy of 0.1 bar is achieved.

Another aspect of the invention relates to the components of the device for measuring and displaying the tire pressure, that is the valve and the remote control element. Although the valve is primarily for use in connection with the preferably provided remote control element, other devices for generating the activation signal and for pressure display could also be provided, for example transmitter and receiver devices adjacent to the wheel on the chassis of the vehicle, and display devices on the dashboard.

The valve according to the invention includes:

a conventional valve having the necessary valve devices for a pneumatic tire, in particular for motor vehicle pneumatic tires, with a valve stem on which a valve foot is integrally formed;

an absolute pressure sensor designed as a semiconductor component, which is acted upon by the tire pressure and which supplies an electrical output signal corresponding to the tire pressure;

one or more circuit devices for evaluating the electrical output signals of the absolute pressure sensor and for generating a pressure signal reflecting the tire pressure;

a transmitting device which emits the pressure signal into the environment;

- A receiving device for an activation signal;

an activation device which then activates the pressure sensor, the circuit device (s) and the transmission device after an activation signal has been received; and - a source of electrical energy.

The electrical output signal typically occurs as an analog signal in the form of an electrical voltage. The circuit devices expediently include an amplifier for the electrical output signal, an analog / digital converter, and control logic for generating a certain coded pressure signal which corresponds to the electrical signal Output signal corresponds and an amplifier for this pressure signal. The control logic can, for example, generate a digital signal in the form of rectangular pulses, the width of the pulses carrying the code. Frequencies in the kHz range are provided for this rectangular pulse, for example 100 kHz and more. A carrier frequency is modulated with this digital signal, for example the IR radiation generated by a GaAs diode. Alternatively, a customary frequency modulation of the carrier frequency could also be provided for signal transmission. Periodic sequences of the pressure signal with different frequencies can also be provided in order to rule out any interference with or from ambient radiation.

As already said, the data transmission can be carried out with the help of IR radiation. In this case, an IR transmitter diode is provided as the transmitting device and an IR receiving diode is provided as the receiving device, as has been explained above.

The circuit devices and the transmitting device are preferably subjected to a sequence control which interrupts the generation and transmission of the pressure signals after a short period of time of the signal transmission; For this purpose, the transmitted signal frequencies can be counted and the signal transmission can be interrupted after a predetermined count has been reached; alternatively, a specific duration of the signal transmission can be provided in accordance with a predetermined number of cycles. In any case, such a duration of the signal transmission is necessary and sufficient that guarantees the reception of an evaluable pressure signal at the remote control element. Limiting the duration of the signal transmission reduces the current requirement and increases the useful life of a given current source on the valve. An electronic switch is preferably used as the activation device, which switches the absolute pressure sensor

Circuit devices and the transmitting device either connect to the current / voltage source or interrupt this connection. Such an electronic switch can be implemented with the aid of transistors, for example as a MOS circuit.

The receiving device and the activation device are kept in a standby state with the aid of an energy-saving stand-by circuit. An exemplary stand-by circuit has only a current consumption in the micro-ampere range, so that with a single commercially available button cell a sufficient life span of a valve is given.

A battery is typically used as the source of electrical energy; for example, conventional button cells can be provided. The battery is preferably integrated as a further component with the electronic components of the circuit devices in order to avoid connections susceptible to corrosion.

As already mentioned, the signal generating device with an absolute pressure sensor and energy source is attached to the valve base on the side facing away from the valve stem; ie when the valve is used as intended, the signal generating device is attached behind the tire rim and behind the valve foot inside the tire. An arrangement must be selected for the transmitting and receiving device which ensures the propagation of the activation signal from the outside environment to the receiving device and the propagation of the pressure signal from the sending device into the outside environment. The following alternatives in particular can be provided for this. The transmitting device and the receiving device are integrated in the signal generating device. All of the optoelectronic components and circuit devices, including the absolute pressure sensor, can be combined in one module, which simplifies the manufacture and the

Assembly simplified. In this case, at least one optical component is provided such that the transmitter and the receiver connect "optically" conductively to the outer periphery of the valve stem, in order to ensure such propagation of the signals. This optical component can preferably include at least one optical waveguide, which is inserted into a bore which leads through the valve base and at least a section of the valve stem and opens to the outer circumference of the valve stem. In addition, an annular body can be provided, which is fixed on the outer circumference of the valve stem and which is optically connected to the optical waveguide. The annular body can be assigned a reflector which bears against the outer circumference of the valve stem and which ensures collection / radiation around the valve stem. With these devices for the propagation of the signal radiation, an adequate reception of the activation signal and a sufficient propagation of the pressure signal can be ensured with any valve position.

In this alternative, it is preferred that the components mentioned, that is, the absolute pressure sensor, the electronic components of the circuit devices, the transmitter device, the receiver device, the activation device and the energy source, are combined in a module at the valve base is appropriate. Such a module can, for example, be implemented in hybrid technology and, in addition to the various circuit devices, also include the absolute pressure sensor, the IR LED and the IR photodiode. Alternatively, the module can be designed as a printed circuit board equipped on both sides, on which the different ones Components and components in SMD technology (ε_urface mounted device) are designed and / or attached. The combination of these components in one module facilitates series production and promotes miniaturization. An exemplary module (SMD technology) is designed as a round, disk-shaped body and has a diameter of approximately 15 mm and a structural height of approximately 4 mm. The weight is about 3 to 4 g. If the module is implemented in hybrid technology, all components / functions can be implemented on a chip measuring a few square millimeters.

In an alternative embodiment, the transmitting device and / or the receiving device are attached to the outer circumference of the valve stem. The sending device and the

Receiving devices are provided with housings, reflectors and / or optionally light guide elements in order to ensure a wide-angle collection / radiation of the radiation used for signal transmission, for example IR radiation, preferably around the entire circumference of the valve stem. Furthermore, there is an effective, electrically conductive connection from the receiving device and from the transmitting device to the signal generating device. The activation signal picked up by the receiving device is forwarded in the form of electrical signals to the signal generating device. Furthermore, the electrical pulses generated by the circuit devices of the signal generating device are fed to the transmitting device and emitted by the latter in the form of the pressure signals.

The device according to the invention also includes a remote control element with which the pressure of a particular tire can be queried and displayed without having to make direct physical contact between the tire valve and the remote control element. Such a remote control element has at least: a flat, essentially cuboid housing on which a display for the pressure display and at least one button or switch for activation is formed; - At least one transmission device for an activation signal;

- A receiving device for a pressure signal reflecting the tire pressure; one or more circuit device (s) for providing the activation signal, for evaluating the pressure signal and for controlling the display; and

- a source of electrical energy.

The housing of the remote control element typically consists of plastic, is comparatively elongated in the sense of a "handpiece" and has an end face which is directed at the tire to be tested. There is a transparent insert on this front, on which elements for bundling the transmitted radiation and for collecting the received radiation are formed.

The transmitting device (s) and the receiving device are accommodated behind this insert. On the top of the housing there is a display for a large-area numerical display, preferably in LCD technology. Further buttons or switches can be attached to the housing in order to enter data and / or to carry out certain functions, for example to identify the tire whose pressure is currently being determined in order to store the time of the tire pressure check or to read out data.

As already mentioned, an IR signal transmission path can be provided for the signal transmission between the valve and the remote control element. Consequently, the transmitter (s) on the remote control element are also preferably designed as an IR transmitter diode and the receiver device as an IR receiver diode. The circuit device for evaluating the pressure signals is preferably equipped with a filter in order to eliminate any interference and external signals.

Furthermore, a device for providing, displaying and storing the time of the tire pressure measurement is preferably present on the remote control element. Typical watch crystals with an appropriate module can be used for this setup. Furthermore, the circuit devices preferably include a memory device for data storage, for example in order to store the tire tested, the tire pressure determined and the time of the tire pressure test. The storage of this data is particularly useful for the commercial sector, for example in the case of trucks and buses.

Furthermore, additional sensors for detecting the ambient pressure and / or the ambient temperature can be present on the remote control element. If the ambient pressure deviates considerably from normal pressure, the displayed tire pressure can be corrected automatically. Furthermore, the temperature of the pressure sensor can also be transmitted with the transmission of the pressure signal. If necessary, this temperature can also be taken into account in the formation of the tire pressure display and, if necessary, displayed.

Furthermore, devices for inputting and storing the desired tire pressure for certain tires can be present on the remote control element. A display is expediently coupled to this device, which indicates whether the current tire pressure recorded in each case corresponds to the predetermined tire pressure setpoint or whether a correction of the current tire pressure is necessary, for example by refilling compressed air. With this evaluation, the Boundary conditions such as tire temperature, ambient pressure and ambient temperature are taken into account.

The invention is explained in more detail below on the basis of a preferred embodiment with reference to the drawings; the latter show:

FIG. 1 schematically the measurement and display of the tire pressure of a pneumatic vehicle tire with the aid of a tire valve and a remote control element spatially distant therefrom;

FIG. 2a shows a sectional illustration of a first embodiment of the valve according to FIG. 1;

FIG. 2b shows a sectional illustration of a second embodiment of the valve according to FIG. 1;

FIG. 3 shows a sectional illustration of a remote control element according to FIG. 1;

FIG. 4a shows the components and circuit devices of the valve and their linking on the basis of a block diagram;

FIG. 4b shows a subunit of the circuit devices according to FIG. 4a; and

FIG. 5 uses a block diagram to show the components and circuit devices of the remote control element and their combination.

FIG. 1 shows a conventional, tubeless pneumatic tire 3, which is mounted on the rim 2 of a motor vehicle wheel 1. This pneumatic tire 3 is equipped with a tire valve 4 according to the invention, in addition to the usual and conventional components of a tire valve, a signal generating device and the above-described refined active components. The device also includes a remote control element 50 held by an operator, with which the air pressure of the tire 3 can be queried and displayed at a convenient distance from the motor vehicle wheel 1.

The embodiment of a valve 4 according to the invention shown in FIG. 2a essentially consists of a conventional valve arrangement and a signal generating device. The valve 4 has a valve stem 5 which delimits a valve bore 6. A inner circumference of the valve bore 6 is a valve seat 7, against which a valve body 8 can rest, which is pressed against the valve seat 7 by a spring 9 and closes the valve 1. A valve tappet 10 is integrally connected to the valve body 8, by means of which the valve body 8 can be removed from the valve seat 7, so that pressure medium can pass through the valve bore 6. The outer circumference of the valve stem 5 is provided with a stepped external thread 11 and 12. A valve foot 15 is integrally formed on the valve stem 5.

In a typical application, this valve 4 is guided through a valve hole in a rim 2, so that - with the interposition of one not shown. Seal - the Ventil¬ foot 15 comes to rest on the inner wall of the rim. Then a union nut is screwed onto the external thread 12 and the valve 4 is fixed on the rim 2.

In this case, valve 4 is intended for a tubeless vehicle tire. The entire valve 4 is typically made of metal, such as a zinc / copper alloy or an aluminum alloy.

On the side of the valve base 15 facing away from the valve stem 5, a signal generating device is attached in such a way that a flow connection remains between the valve bore 6 and the interior of the tire. In the present case this signal generating device is designed as a module 40 which contains all the active components required for signal generation and transmission.

As shown, the module 40 has a circuit board 41 on which all active components are attached. These - only schematically indicated - active components include an absolute pressure sensor 42, a microprocessor 43 and other electronic components and components 44, 44 ', 44 "with which the circuit devices are formed, an IR transmitter diode 45 and an IR Photo diode 47. There is also a button cell 48 which supplies the active components with current / voltage, alternatively the button cell 48 could be fastened to the circuit board 41 or integrated in a hybrid module which comprises all active components. Furthermore, the necessary, only schematically indicated, electrically conductive connections are formed between the circuit board 41 and the individual active components and the button cell 48. These active components are preferably included

With the help of SMD technology attached to the circuit board 41 and / or formed. All components of the module 40 can be embedded in synthetic resin, a fluid connection between the absolute pressure sensor 42 and the tire interior being kept open.

As shown, the entire module 49 can be accommodated in a plastic housing 49, which is attached to the side of the valve base 15 facing away from the valve stem 5. The housing 49 has bores (not shown) through which the absolute pressure sensor 42 is constantly subjected to the current tire pressure.

On the outer circumference of the valve stem 5, preferably in the transition area between the narrower thread section 11 and the further thread section 12, an annular body 20 made of transparent plastic material is arranged. The body 20 is around the entire outer circumference of the valve stem 5

/) led around. Between valve stem 5 and annular

Body 20, a reflector 21 can be arranged. At least one optical waveguide 22 provides an optically conductive connection between the ring-shaped body 20 and the IR transmitter diode 45 and the IR photodiode 47. Each optical waveguide 22 can be inserted into a continuous bore 16 which is in the material of the valve stem 5 and of the valve base 15 is recessed. Alternatively, the optical waveguide (s) 22 could be guided over the longer distance within the valve bore 6 and additionally inserted into a short through bore 16 which is recessed in the valve stem material and leads to the annular body 20. After the optical waveguide 22 has been received, the bore 16 is sealed in a pressure-tight manner, for example with the aid of elastic synthetic resin.

An activation signal impinging on the ring-shaped body 20 is conducted via the optical waveguide 22 to the IR photo diode 47 and generates a photo current there, the voltage of which is recorded and evaluated. The pressure signal generated by the IR transmitter diode 45 is fed into the optical waveguide 22 and emitted into the environment via the annular body 20. If necessary, an annular body could also be provided for reception purposes and another for transmission purposes.

FIG. 2b shows a modified valve 4, which essentially corresponds to the valve 4 according to FIG. 2a. In a different way, the IR transmitter diode 45 and the IR photodiode 47 are arranged on the outer circumference of the valve stem 5 and are connected to the circuit board 41 of the signal generating device via connecting lines 26. Again, the electrically conductive connecting lines 26 can be inserted into bores 16 which are recessed in the valve base 15 and in the valve stem 5. One ring-shaped light-guiding element 25 or 27 is optically coupled to the transmitter diode 45 or to the photodiode 47 and ensures wide-angle reception / radiation of the signals. FIG. 3 schematically shows a remote control element 50, which has a flat, essentially cuboidal housing 51 with the dimensions of a typical handpiece. An insert 53, which consists of transparent plastic material that is transparent to IR radiation, is inserted into the front end 52 of the housing 51. Elements (not shown) for collecting the radiation to be received and for bundling the transmitted radiation are formed on this insert.

The other end face is formed by a removable cover 55, after removal of which batteries 56 can be inserted into a battery compartment. On the top side 57 of the housing 51 there is an LCD display panel 58, a large button 59 and a number of smaller buttons 60, 60 ", 60". The large button 59 serves to activate the components of the remote control element 50. The smaller buttons 60, 60 ', 60 "are used for entering or querying data and for calling up certain functions, for example for characterizing a specific tire , for entering a target tire pressure, for outputting stored data and the like.

In the interior of the housing 51 there is - as only schematically indicated - a circuit board 61 on which a microprocessor 62 and various electronic components 63, 63 'and 63 "are attached, with which the circuit devices for a transmission circuit for A reception circuit and for an evaluation and control circuit are realized. Furthermore, one or more IR transmission diode (s) 66 and an IR photodiode (not shown) are arranged adjacent to the IR-transparent insert 53.

FIG. 4a shows in the form of a block diagram the essential, active components of the valve 4 and their linkage; denote in detail:

VI an IR photodiode for receiving the activation signal; V2 an amplifier for the activation signal;

V3 a testing and evaluation device with filter; V4 an activation device in the form of an electronic switch; V5 an electric battery;

V6 an absolute pressure sensor in the form of a semiconductor component with a Wheatstone bridge circuit, the one. provides an analog output signal in the form of an electrical voltage which reflects the current tire pressure;

V7 an amplifier for the output signal;

V8 an analog / digital converter to the analog

To generate a digital signal; V9 a control logic for generating a digitally encoded print signal;

Vll an amplifier for the pressure signal; and

V12 is an IR transmitter diode which emits the pressure signal.

The components VI, V2, V3 and V4 are combined in a subunit, the design of which is shown in FIG. 4b. An IR square wave signal with a frequency of approximately 100 kHz can serve as the activation signal. The activation signal is received with the aid of the IR photodiode VI. A resistor Rl is located parallel to the receiving diode VI, which converts the photocurrent into a voltage. This voltage is amplified by a transistor TI (field effect transistor). The gain factor is determined by the collector resistance, which is chosen to be as high-resistance as possible. The resulting collector voltage is coupled out by means of a high-pass filter R2 and passed to a capacitor C via a diode D. A discharge resistor R3 is arranged parallel to the capacitor C and discharges the capacitor C after a certain time. When the capacitor C has been charged to a certain voltage, a further transistor T2 becomes conductive, which activates the reset of the circuit (V6 to V12) via the electrical switch V4. Feedback prevents the circuit from being deactivated again before all data is transferred. were wearing. The electronic switch V4 is subjected to such a sequence control that after a short-term signal transmission this electronic switch V4 is opened again and the power supply to the components V6 to V12 is interrupted. For example, these components V6 to V12 are put into operation for a period of about 0.5 seconds.

FIG. 5 shows the essential components of the remote control element 50 and their linking using a block diagram; these components include:

El a battery for power supply to the active components of the remote control element; E2 a button for activating the remote control element; E3 a number of further buttons for entering data; E4 a microprocessor

E5 a signal generator for generating an activation signal;

E6 an amplifier for the activation signal;

E7 an IR transmitter diode with which the activation signal is emitted; E8 an IR photodiode with which the pressure signal generated by the active components of the valve is received; E9 a preamplifier for this pressure signal; Hurry a filter for the pressure signal;

E12 an optional absolute pressure sensor for generating an electrical output signal relating to the ambient pressure; E13 an amplifier for the electrical ambient pressure

Output signal; E14 an analog / digital converter for this electrical output signal; and

E15 an LCD display for the queried tire pressure and possibly other parameters; E16 an optional clock quartz with associated module for continuous formation of the time of day; E17 a storage device.

If the button E2 on the remote control element 50 is actuated, the microprocessor E4 and the actual components are supplied with the necessary operating voltage via the battery El. The Mikroprozeεsor E4 starts a signal generator E5 (square wave voltage) _r deεεen signal via an amplifier E6 to an IR transmitting diode E7 passes, which generates an activation εignal. This activation signal reaches the IR photodiode VI in / on the valve 4 and the square-wave voltage is amplified via an amplifier V2 and is evaluated V3. The square-wave voltage must be present at a certain frequency for a certain time (about 1 εec), then the electronic switch V4 is actuated and the actual circuit is started up by the battery V5 for about 0.5 εec. After approximately 1.0 sec, the microprocessor E4 switches the signal generator E5 off again and waits for a received signal. After the electronic switch V4 has been switched on, the tire pressure is measured via the absolute pressure sensor V6. This analog signal is sent via amplifier V7 to an analog / digital converter V8, which converts the analog tire pressure value into a serial digital signal. The analog / digital converter V8 and the amplifier V7 are supplied with the necessary control signals via a control logic V9. The digital signal reaches the IR transmitter diode V12 via amplifier V7, which emits the digital value. The IR photodiode E8 on the remote control element 50 receives the digital tire air pressure value and forwards it to the infrared preamplifier E9. This signal reaches the microprocessor E4 via a filter Eil, which then forms a signal for the corresponding control of the display E15. If necessary, the tire temperature and the ambient conditions (pressure, temperature) can also be taken into account and taken into account. The current tire pressure of the queried tire is shown on the display E15 with an accuracy of 0.1 bar. Optionally, another can be made on the remote control element 50

Absolute pressure sensor E12 can be provided to include the ambient air pressure. The analog value of the absolute pressure sensor E12 goes to the amplifier E13 and from there to the analog / digital converter E14. The difference between the digital value of the ambient air pressure and the digital value of the absolute tire pressure is calculated in the microprocessor E4 and displayed on the display E15.

With the help of a watch crystal E16 and associated module, the time of day can be continuously formed and read into the microprocessor E4. In addition, a memory E17 is assigned to the microprocessor E4. In this memory E17 the time of the measurement, the identity of the tire tested, the measured tire pressure and further data (target pressure of certain tires) can be stored, which are entered with the aid of the further pushbuttons E3. Furthermore, the control signal for the display E15 can be stored for a while with the memory E17.

Claims

1. A method for measuring and displaying the pressure in a pneumatic tire of a vehicle wheel, with the following method steps:

- at a spatial distance from the vehicle wheel

Activation signal generated; . .

- The activation signal becomes a wireless

Receiving device on the vehicle wheel transmits and activates an activation device there;

- The activation device causes the formation of a pressure signal which is based on the current one

Tire condition relates;

- The pressure signal is emitted into the environment with the aid of a transmitting device on the vehicle wheel;

- The pressure signal is recorded at a distance from the vehicle wheel and a display signal is formed therefrom, with which a display of a display device is driven, characterized in that the current tire pressure is detected with the aid of an absolute pressure sensor, which acts as a semiconductor component, to form the pressure signal is trained, and the one The electrical output signal corresponding to the tire pressure is generated, amplified, optionally converted into a digital signal and further processed into the pressure signal.

^

2. The method according to claim 1, characterized in that the activation signal is generated with the aid of a remote control element which also receives the pressure signal and which is provided with the display of the display device 0.

3. The method according to claim 2, characterized in that a wireless signal transmission between the vehicle wheel 5 and remote control element over a signal transmission route with a path length of about 50 to 200 cm follows er¬.

4. The method according to any one of claims 1 to 3, characterized in that the tire pressure is measured and displayed with an accuracy of at least 1/10 bar.

5. The method according to one of claims 1 to 4, characterized in that in addition to the tire pressure, the tire temperature is also determined, transmitted and evaluated.

6. The method according to one of claims 1 to 5, characterized in that the wireless transmission of the activation signal and the pressure signal takes place with the aid of IR radiation.

7. A device for measuring and displaying the pressure in a pneumatic tire, with a valve (4) - - - With a valve foot (15) from which a valve stem (5) protrudes,

- With a device (40) for generating a wirelessly transmitted pressure signal (signal generating device), the least one pressure sensor

(42), one or more circuit device (s) (43, 44, 44 ', 44 "; V7, V8, V9, Vll) for generating the Drucksignaleε and a source (48; V5) for electrical energy, and the the side of the valve base facing away from the valve stem (5)

(15) is attached, and

with a transmitting device for transmitting the printing signals, characterized in that a remote control element (50) is additionally present,

- With a transmitting device (66; E7) for sending an activation signal;

- With a receiving device (E8) for the pressure signal;

- With a display (58; E15) for a pressure display;

- With one or more circuit device (s) (62, 63, 63 ', 63 "; E4, E5, E6, E9, Eil) to provide the active signal, to evaluate the

Pressure signals and for controlling the display (58; E15);

- With a source (56; El) for electrical energy; and the pressure sensor of the signal generating device (40) on the valve (4) is an absolute pressure sensor (42; V6) designed as a semiconductor component which generates an electrical output signal corresponding to the tire pressure; and the valve (4) additionally has a receiving device (47; VI) for the activation signal and an activation device (V2, V3, V4) which has the absolute pressure sensor (42; V6) and the devices (43, 44 , 44 ', - αs -

44 ", 45; V7, V8, V9, Vll, V12) for wireless transmission of the pressure signals is then activated after the activation signal has been received.

8. The device according to claim 7, characterized in that the device for a wireless signal transmission between valve (4) and remote control element (50) via a signal transmission path with a path length of approximately 50 to 200 cm is equipped.

9. The device according to claim 7 or 8, characterized in that the device for wireless signal transmission between the valve (4) and the remote control element (50) is equipped with the aid of IR radiation.

10. The device according to one of claims 7 to 9, characterized in that the absolute pressure sensor is a semiconductor component (42; V6) which has a hermetically sealed reference space and a piezo-resistive transducer.

11. The device according to one of claims 7 to 10, characterized in that the tire pressure can be measured and displayed with an accuracy of at least 1/10 bar.

12. The device according to one of claims 7 to 11, characterized in that, in addition to the tire pressure, the tire temperature can also be determined, transmitted and evaluated.

13. The device according to one of claims 7 to 12, characterized in that the remote control element (50) has a flat, in essence cuboid housing (51) on which at least one front face (52) and one upper face (57) are formed; on the top of the housing (57) a display / 58) for the

Pressure indicator is present; and in the housing (51) at least one push button (59; E2) or

Switch for activating the remote control element

(50) is used.

14. The device according to claim 13, characterized in that further buttons (60, 60 ', 60 "; E3) are provided on the upper side (57) of the housing (51) to transfer data into a microprocessor (E4) and / or to enter a memory device (E17) of the remote control element (50).

15. The device according to claim 14, characterized in that the microprocessor (E4) is additionally a Uhrenguarz (E16) with associated module for forming the time of day is assigned.

16. The device according to claim 14, characterized in that the microprocessor (E4) additionally has a semiconductor component with an absolute pressure sensor (E12, E13, D14) for detecting the ambient pressure as well as optionally a temperature sensor for detecting the ambient temperature ordered iεt.

17. A valve, in particular for a device according to one of claims 7 to 16,

- With a valve base (15) from which a valve stem protrudes,

- With a device (40) for generating a wirelessly transmitted pressure signal (signal generating device), at least one pressure sensor (42; - ~

¹ V6), one or more circuit devices (43)

44, 44 ^« , 44"; v7, V8, V9, Vll) for generating the pressure signal, and has a source (48; V5) for electrical energy, and that on the side of the valve foot 15 facing away from the valve stem (5) ) is attached, and

- With a transmitting device (45; V12) for the pressure signal, 0 characterized in that the pressure sensor is an absolute pressure sensor (42; V6) designed as a semiconductor component, which generates an electrical output signal corresponding to the tire pressure ; and ^ the valve (4) additionally has a receiving device (47; VI) for an externally generated activation signal and an activation device (V2, V3, V4) which comprises the absolute pressure sensor (42; V6) and the devices (43, 44, 44 ', 44 ", 45; V7, V8, V9, Vll, V12) for wireless transmission of the pressure signal is then activated after the activation signal has been received.

18. Daε valve according to claim 17, characterized in that the activation device (V2, V3, V4) has an electronic switch (V4), which switches the downstream active components (V6, V7, V8, V9, Vll, V12 ) of the valve (4) is then supplied with current / voltage after an activation signal has been received.

19. The valve according to claim 18, characterized in that the activation device (V2, V3, V4) is subjected to a sequence control which automatically interrupts the transmission of the pressure signals which represent the tire pressure after this pressure signal has been transmitted for a given duration been.

20. The valve according to one of claims 17 to 19, characterized in that the signal generating device has a circuit board (41) on which, in addition to the absolute pressure sensor (42; V6), the circuitry (43, 44, 44 ') , 44 "; V7, V8, V9, Vll) and the activation device (V2, V3, V4), the transmitting device (45; V12) and the receiving device (47; VI) are attached or designed; and at least one optical component is present , which connects the receiving device (47; VI) and the transmitting device (44; V12) to the outer periphery of the valve stem (5) and the propagation of the activation signals from the outside to the receiving device (47 ; VI) and the propagation of the pressure signal from the transmitting device (45; V12) into the external environment.

21. The valve according to claim 20, characterized in that at least one optical waveguide (22) belongs to the optical component and is inserted into a bore (16) through the valve foot (15) and at least one section of the valve stem ( 5) passes through and opens towards the outer circumference of the valve stem (5).

22. The valve according to one of claims 17 to 21, characterized in that the active components (VI to V12) of the valve (4) are combined in one module (40), that on the valve (4) on the valve stem (5 ) facing away from the valve foot (15) is attached.

23. The valve according to claim 22, characterized in that the module (40) has a circuit board (41) on which the active components (42, 43, 44, 44 ', 44 "; VI, V2, - 73 - V3, V4, V7, V8, V9, Vll, V12) are attached and / or designed using SMD technology.

24. The valve according to claim 22, characterized in that the module (40) iεt forms as an integrated hybrid component.

25. The valve according to one of claims 17 to 19, characterized in that the transmitting device (45; V12) and / or the receiving device (47; VI) is attached to the outer circumference of the valve stem (5); and an effective, electrically conductive connection (26) of this device (s) with the circuit board (41) of the signal generating device is provided.