DE19924830A1 - Electronic tire pressure, temperature and wear monitoring system has a transponder component group and radial coil molded into the tire wall and transmits signals to a vehicle mounted transceiver - Google Patents

Abstract

A microelectronic transponder(3) integrated in the tire wall(2) facing the vehicle comprises receivers for pressure and temperature, a microprocessor, current supply module and connects with a bidirectional inductive coil(4) inside the tire wall radial to the tire axis(5). A transceiver(24) on the vehicle receives and sends signals to the transponder and includes components for filtering, coding and decoding signals, a microprocessor for controlling and processing data and an electronic unit(10) linking with a vehicle data bus system(11).

Description

The invention relates to arrangements for determining the tire pressure and Serve tire temperature of motor vehicles. Both measurements are important for the Vehicle safety and driving comfort and must be within specified limits lie.

It is known that in most motor vehicles in use today, tire pressure is still high is checked by hand by connecting a manometer to the tire valve. The Temperature is at best determined by laying on of hands and rough estimates. Because of the When the wheels are dirty during operation, the tire pressure is only rarely checked, which at Pressure loss causes the tires to heat up excessively, and if the pressure drops completely, the tires are destroyed Tire and hazard to the vehicle. For trucks that have Having twin tires can cause a drop in pressure in a single tire to become so severe Warming lead to the fact that the tire starts to burn and thereby also a severe Accident can be triggered.

Devices are also known which continuously measure the tire pressure on the vehicle in by taking the pressure off the valve and the measured values electrically to the vehicle broadcast where they are then displayed. The transmission can typically inductively with coil arrangements which are arranged in the vicinity of the axis of rotation.

Devices are also known which are integrated into the vehicle rim or from the outside Measure the deformation of the tires without contact and draw conclusions about the pressure.

Devices are also known which measure the temperature in addition to the pressure use this to compensate for pressure measurement and then use the improved signal to Transfer vehicle. The difficulty here is always the temperature sensor to arrange that the measured value is not falsified by the temperature of the metallic axis becomes what expensive constructions became known for.

A particular difficulty in measuring tire pressure is the rapid rotation of the Wheel compared to the vehicle as well as the considerable shock and shaking load that the Measurement arrangement is exposed while driving, also the extreme requirements Reliability and lifespan of the arrangement. They pose further problems Power supply to the measuring device and the accuracy and reliability of the Data transmission.

The invention has for its object the detection of tire temperature and To make tire pressure more accurate, easier, cheaper and more reliable, and thus for the to develop normal motor vehicle traffic. Furthermore, the arrangement should be simple monitor tire wear and take action when a critical level of wear is reached Generate warning signal

Subject of the invention

The object is achieved in that the arrangement for measuring the Tire temperature and and the tire pressure is relocated in the tire itself by the Production of the tire in the tire cover is a very small, highly integrated transponder  is vulcanized in via a flat coil that is also vulcanized into the tire cover communicates with a transceiver permanently mounted on the vehicle.

According to the invention, the transponder has a micromechanically constructed absolute measuring pressure sensor and a microelectronic temperature sensor, both with associated measurement processing electronics, a microprocessor with program and Data storage and the associated transmission and reception electronics for digital Data transmission, as well as the electronics required for voltage conditioning and Stabilization and for clock generation. All of these function blocks are based on the invention integrated in a / a few silicon chips, only individual discrete components are added Small size, so that the plastic can be easily vulcanized into the rubber encapsulated transponder is so small that it does not have the structural strength of the tire cover impaired.

It is also an object of the invention that in addition to the tire pressure and temperature an identification number of the tire, tire type and other data are transmitted (e.g. Date of manufacture, manufacturer).

It is also an object of the invention that a conductive in the profile of the tire Sensor loop, e.g. B. a thin electrically conductive wire, at such a depth of the profile is embedded that when the tire wears down to a predetermined tread depth electrical line interrupted and thus the service life of the tire can be detected can. The conductivity of the sensor loop is queried by the transponder. The Sensor loop can be placed at one or more locations on the circumference of the tire his.

It is also an object of the invention that the transponder programs and Contains evaluation algorithms that process / compensate the sensor values carry out that the transponder is calibratable with regard to pressure and temperature and this Sizes determined independently of each other.

It is also an object of the invention that the program memory of the integrated processor can be partially described when commissioning the transponder, e.g. B. the Filing the tire identification number, the date of manufacture and other data there.

The data transmission from the vehicle transceiver to the measuring module (transponder) takes place According to the invention bidirectionally via the flat coil vulcanized into the tire cheek in inductive form, where the coil consists of a number of turns in constant radial distance from the axis close to each other in the direction of the vehicle Tire cheek are arranged, with a carrier frequency method for data transmission is used with digital modulation. The invention is limited here to Arrangement of the coil in connection with the selected method, the design of the inductive data transmission method is possible and known in many ways.

The data transmission is protected against transmission errors by appropriate coding, Malfunctions can be identified. An interruption in communication is also due Absence of a response to a request can be seen. These arrangements correspond to that State of the art.

The power supply of the measuring module takes place by receiving and processing the Carrier signal, wherein the transmitted energy is integrated over a period of time until the power sufficient for a short, impulsive response. Orders of this type are current  of technology and can be carried out in a variety of ways. There are other methods of Power supply to the transponder possible.

The received data are processed in the transceiver electronics so that they are sent to a Vehicle bus system can be reported in digital form. There you will be in one central vehicle computer evaluated and / or displayed. These parts of the Arrangements are also state of the art and can be implemented in a variety of forms.

An important advantage of the invention is the implementation of a continuous automatic Monitoring of the measured variables tire pressure and tire temperature, so that a malfunction Danger to the tire or even the vehicle is avoided and thus road safety is increased.

A disadvantage of the invention initially appears to be the fact that these advantages are only too are achieved if each tire is equipped with the appropriate transponder, which is the Tire price increased. The measuring module (transponder) can be used as a microelectronic product be mass-produced at a very low price and make the tire more expensive only insignificant, in addition there is the possibility of identifying the tire number and the Manufacturer data in the manufacture and handling / storage further advantages, the cost may weigh out for the module. The introduction of the invention is therefore only at high quality tires or with special demands (racing) and start with increasing standardization of the interfaces also apply to general car tires.

Another advantage over existing solutions is the small size. The module is therefore easy to vulcanize, just like the flat coil, an impairment of the The tire does not function. Because of the low mass, the mechanical ones Strains low, so that even with long-term mechanical vibration exposure none Reduction in reliability occurs. The plastic of the housing is invented selected from the same group of materials as the tire, so one can during the vulcanization process intimate connection between the housing and tires are made, which will not be long-term leads to detachment.

Compared to solutions that are connected to the valve of the tire or on one Modification of the rim are based, in addition to the cost advantages more precise Results, since the measurands are obtained where they are relevant and a Adulteration by the rim cannot occur.

Compared to solutions that are implemented by scanning the tire shape or by integrating it into the tire Strain elements work, the advantage is significantly higher accuracy and Reliability, especially when dirty.

Compared to existing solutions, the processing of the sensitive temperature and Pressure values already on the chip are a big advantage not only in terms of cost, but also functional. This is how digital processing makes mutual influence between largely suppressed the measured variables of temperature and pressure and the sensor-specific ones Nonlinearities compensated. Due to the microelectronic manufacturing process good reproducibility and long-term stability, the measuring modules can be adjusted and are calibrated with regard to a required tolerance range. These properties will according to the invention by using a microprocessor with a changeable digital Memory achieved.

Inductive data transmission is proven and very reliable when the data is digital be transmitted. According to the invention, the integrated microprocessor is used for this.  

Compared to solutions in which the measured values are transferred directly in analog form, follows a much higher reliability and accuracy.

Due to the round shape according to the invention of the coil integrated in the tire cheek, the Tranceiver can be placed on the vehicle side at a convenient location above the axle. This place is relatively protected against dirt and damage from the tires absorbed bodies (ice, snow, mud) and easily accessible by cable feed. The Electrical / mechanical design of the inductive transceiver on the vehicle side depends on To design the vehicle type and not the subject of this invention. Here is one Interchangeability of inductive transceivers and tires.

The integrated coil can according to the invention with the sensor loop for tire wear Be connected in series, but it is also a separate arrangement of the sensor loop and Induction coil possible, for which purpose the transponder has 4 connection contacts.

Description of the invention using an example

Figure 1 shows the basic structure of the arrangement for measuring the temperature and pressure of a vehicle tire. In the vehicle tire ( 1 ), the transponder ( 3 ), connected to the flat coil ( 4 ) arranged radially around the axis ( 5 ) and a sensor loop ( 25 ) embedded in the profile, is vulcanized into the cheek ( 2 ) facing the vehicle. Figure 2 shows the arrangement in cross-section, the rim ( 6 ) and the transceiver arranged above the axis ( 5 ) at the level of the tire cheek, consisting of the electromagnetic transducer ( 7 , 8 ), the transceiver electronics ( 9 ) and the bus coupling electronics ( 10 ), which communicates with the vehicle bus system ( 11 ).

The transponder is shown in a typical mechanical design in Figure 3. The plastic housing ( 3 ) with the electrical connections ( 12 ) for the flat coil and the pressure-sensitive area of the housing ( 13 ) can be seen, here as a flat, spherical depression in the otherwise pressure-stable housing.

Figure 4 shows a simplified block diagram of the exemplary transponder electronics. Communication takes place via the flat coil ( 4 ), which is connected to the carrier frequency modem ( 22 ) by an adapter circuit ( 14 ), typically a miniature transformer. The adapter circuit has a filter function so that only signals in the desired transmission band can be received or fed to the coil ( 4 ). The capacitor C1 is used for this purpose in this embodiment. Electrical power is also dissipated from the matching circuit ( 14 ) to the energy storage unit ( 23 ) in the receiving mode, which is collected there. The capacitor C2 is used for this purpose in this embodiment. The microprocessor ( 15 ) with the memories ( 16 ) RAM and ( 17 ) EEPROM is clocked by the clock generation ( 21 ). The sensors for temperature ( 18 ) and absolute pressure ( 19 ) are connected directly to the processor via A / D converters (not shown). Additional auxiliary electronics (e.g. timer, input / output port), which are not to be described in more detail here, are indicated with ( 20 ). All of these modules are largely integrated on one or very few silicon chips. The total size of the transponder in this example is approx. 12 × 8 × 2 mm, smaller versions are possible with an even higher degree of integration.

Communication with the transponder takes place via a transceiver that is fixed to the vehicle triggered request, which typically consists of a relatively long preamble and a Command word exists. The preamble where only the carrier is sent without modulation  the transponder is used to collect enough electrical power to be active to recognize the command and, if necessary, carry out measurements and the Report the result. The transponder always responds with an acknowledgment word, which confirms the communication. Other protocols are possible. How often does one Query takes place depends on the higher-level vehicle safety system.

In response to a received request, e.g. B. a measurement of the temperature and Requests tire pressure, the internal processor activates the sensors, initiates the analog digital conversion of the measured values, performs the programmed linearization and Compensation calculations, codes the results and forms together with test words the transmission frame that is transmitted back to the transceiver. Further actions can be the output of the ID number, the date of manufacture, the type of tire, etc., however also storing this data in the internal EEPROM when the request this data together with an electronic keyword. Other commands relate on the transfer of linearization and compensation parameters, it may even be possible be to install the internal program in a new version. Commands of this type are only required for the production of the transponders and are used in Vehicle operation not used. These methods are state of the art today and should not be further detailed.

The vehicle-fixed transceiver ( 24 ), which is typically arranged at a distance of a few centimeters from the tire cheek, sends and receives the data via an electromagnetic coil arrangement. It also has a carrier frequency modem for bidirectional communication and a microprocessor that can handle both the protocol for the transponder and the protocol for the vehicle via the bus interface ( 10 ). Due to the many possible embodiments, details of signal processing and transmission can be dispensed with here. Compared to the transponder in the tire, however, the power generated during transmission is considerably higher, and the sensitivity of the receiver circuit is also improved. This makes sense because, on the one hand, the supply power for the transponder is to be obtained from the transmission power, and on the other hand, the power returned by the transponder is typically quite low. The transponder therefore also has band-limiting filters. The requirements for miniaturization of the transceiver are reduced, the power consumption is not critical because of the cable connection. The transceiver is therefore typically constructed conventionally.

Claims (9)

1. Arrangement for measuring pressure and temperature and for monitoring the wear of vehicle tires, consisting of
a transponder with transducers for absolute pressure and temperature, a microprocessor with read-write memory, means for bidirectional, carrier-frequency inductive data transmission and for power supply to the measuring module
as well as a transceiver attached to the vehicle, consisting of an electrodynamic coil arrangement for receiving carrier-frequency inductive signals and for sending them, means for receiving, filtering, coding and decoding these signals, a microprocessor for controlling and processing this data and a bus coupling electronics for forwarding the data to a vehicle data bus system,
characterized in that
the transponder is integrated in the tire as a microelectronic assembly and the coil (inductive antenna) of the transponder is arranged in the tire cheek radially to the axis. 2. Arrangement like claim 1, characterized in that the sensors for pressure and Temperature as well as the required evaluation compensation and transmission / reception electronics including those required for energy supply and other operations electronic assemblies are integrated on a single silicon chip. 3. Arrangement like claim 1, characterized in that the sensors and the Electronics of the transponder is divided into a few individual silicon chips, which are among themselves are electrically connected via a common substrate (multi-chip module technology) on which they are also mechanically mounted. 4. Arrangement like claim 1, characterized in that the tire wear by a wire loop embedded in the tread of the tire is monitored, which if the Tire is interrupted at the end of the service life, this interruption from Transponder detected and reported as a warning when queried to the vehicle. 5. Arrangement like claims 1 to 4, characterized in that the transponder in one Plastic housing is encapsulated; which is designed so that pressure applied from the outside the pressure sensor is transmitted. 6. Arrangement like claim 5, characterized in that the outer housing material of the transponder comes from the same group of substances as the tire in which it is embedded should be, or consists of a material that during the tire manufacturing process creates an intimate connection with the tire material. 7. Arrangement like claim 1, 2, 3, 4 characterized in that the transponder at the Manufacturing can be configured via the inductive communication link, where the configuration data calibration parameters for the sensors, identification number of the tire, Tire type, manufacturer identification, date of manufacture etc. in digital form in the transponder are saved and this data can be called up at any time during operation on the vehicle. 8. Arrangement as in claims 1 to 7, characterized in that for data transmission a carrier frequency method is used, in which the data in coded form in the half-duplex operation can be transmitted digitally with means for data backup and at the  the transmission protocol is designed so that the failure or disruption of a transmission can be recognized. 9. Arrangement like claims 1 to 8, characterized in that the transponder over Has means to absorb the electrical energy transmitted by the transceiver save and use for the retransmission of the information.