GB2427497A

GB2427497A - Motor vehicle with tyre pressure monitoring system

Info

Publication number: GB2427497A
Application number: GB0512767A
Authority: GB
Inventors: Ian James Thompson; Johan Granholm; Andrew Fryer
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-06-23
Filing date: 2005-06-23
Publication date: 2006-12-27
Anticipated expiration: 2025-06-23
Also published as: GB0512767D0; GB2427497B

Abstract

The tyre pressure monitoring system comprises a vehicle-based unit and a number of wheel-based units 13 each associated with one of the vehicle tyres 11. Each wheel-based unit 13 periodically sends a signal indicating a detected tyre pressure, wheel speed and ID code to the vehicle-based unit. The vehicle-based unit comprises an electronic unit (ECU) 15 for interpreting the signal and sending a warning signal if a faulty tyre pressure is identified. The vehicle-based unit also comprises three initiators 17, each associated with a one of three running vehicle tyres 11 and operable to send a flag signal to its respective wheel-based unit 13. A logic control is implemented in the ECU 15 to determine the location of each wheel-based unit 13 based upon the reception of the flagged signals. Once all the wheel-based units 13 associated with an initiator 17 have been identified, then, by a process of elimination, the ECU 15 assigns the remaining signal of the wheel-based units 11 to the remaining running tyre location.

Description

Motor vehicle equipped with a tyre pressure monitoring system The present invention relates to a motor vehicle equipped with a tyre pressure monitoring system and in particular to a method of determining a tyre location within a motor vehicle fitted with a tyre pressure monitoring system. Tyre pressure monitoring systems are known. See, for example, EP 1486357 which shows a tyre pressure monitoring system comprising sensors that are individually implanted in tyres of the vehicle, each sensor having a transceiver which relays the pressure measurements to a central controller which can trigger a warning should that tyre pressure vary from a datum. In order to identify the tyre that is experiencing a pressure other than that of the datum, each sensor is associated with an initiator that transmits low frequency signals for triggering transmission of the corresponding transceiver and hence locating the position of the emitting transceiver. Each initiator is located in a portion of the vehicle that is close to the tyre and must be oriented according to criteria which enable it to transmit its signal to the corresponding transceiver.Such criteria can lead to some difficulty in installing the initiators in the vehicle due to a lack of available space. To overcome this, it may be possible to rearrange the components which otherwise prevent proper installation of the initiator. However this can increase the cost and complexity of manufacture and is not always practicable. It is an object of the present invention to provide a method of determining a tyre location within tyre pressure monitoring system equipping a motor vehicle which overcomes or alleviates the above problems. According to a first aspect of the invention there is provided a motor vehicle equipped with a tyre pressure monitoring system and a number of tyres of which there are N running tyres, the tyre pressure monitoring system comprising a vehicle-based unit and a number of wheel-based units, each wheel-based unit being associated with a respective one of the tyres, each wheel-based unit being operable to send a signal indicating at least a detected tyre pressure, wheel speed and an Identification Data code to the vehicle-based unit, the vehicle-based unit comprises an electronic control unit (ECU) for interpreting the signal and sending an alarm signal if a faulty tyre pressure is identified,wherein the vehicle-based unit also comprises N-1 initiators each associated with a respective one of N-1 running tyres and operable to send an initiation signal to its respective wheel-based unit and a logic control implemented in the ECU so as to determine the location of each wheel-based unit on the vehicle based upon the reception of a flagged signal and a process of elimination to identify the running tyre which is not associated with an initiator. Preferably, each initiator sequentially sends a flag signal to its corresponding wheelbased unit when the speed of the vehicle is determined to be greater than a threshold value. In a preferably embodiment the threshold value is approximately 20 mph (32.18 kmh). In a preferred arrangement the vehicle also comprises a spare wheel provided with a wheel-based unit in which the logic control is able to identify this wheel among the running wheels based upon the reception of a flagged signal and the wheel speed. According to a second aspect of the invention there is provided a method of determining tyre location within tyre pressure monitoring system equipping a motor vehicle in accordance with said first aspect, when the vehicle is determined to run at a vehicle speed which is greater that the determined threshold value, in which each initiator is commanded in turn by the ECU so as to learn the location of each of the wheel-based units associated with an initiator based upon the reception of a flagged signal and, once all the wheel-based units associated with an initiator have been identified, then assigns the remaining signal of the wheel-based units periodically received by the ECU which has not be flagged to the remaining running tyre location. Preferably, when the vehicle comprises a spare wheel provided with a wheel-based unit, the ECU assigns the remaining signals of the wheel-based units periodically received by the vehicle-based unit which has not been flagged to either the remaining running tyre location or the spare wheel according to whether the remaining signals indicate a wheel speed matching the vehicle or not. The invention will now be described by way of example with reference to the accompanying drawings of which: Fig.1 is a schematic representation of the principal subsystems of a tyre pressure monitoring system mounted to a vehicle in accordance with the present invention; and Fig.2 is a flow chart showing a method for determining tyre location within the tyre pressure monitoring system shown in Fig.1. A vehicle 10 equipped with a tyre pressure monitoring system has a vehicle-based unit and a wheel-based unit associated with each of the tyres. In this example, as the vehicle 10 includes four tyres 11 and a spare tyre 12, there are five wheel-based units 13. It will be appreciated, however, that the vehicle could include more or fewer than four tyres and therefore more or fewer than five wheel-based units 13. Each wheel-based unit 13 has, in a conventional manner, a sensor and a transceiver which are fixed to a wheel of the tyre. The vehicle-based unit includes a receiver 14, an electronic control unit (ECU) 15 and a display unit 16. The display unit 16 and the receiver 14 respectively are connected to the ECU 15. The vehicle-based unit also includes initiators 17, in this example, three initiators 17 which are also connected to the ECU 15. These three initiators 17 are respectively associated with three of the four tyres 11 leaving one tyre 11 and the spare wheel 12 without an initiator. Each initiator 17 is located in a portion of the vehicle 10 that is close to its corresponding wheel-based unit 13. The transmission of the wheel-based units 13 to the receiver 14 is conventional. Thus each of the sensors is capable of sending a radio frequency signal to the receiver 14 in order to periodically report data that indicates detected tyre pressure, an Identification Data (ID) code registered in the transceiver, wheel speed and possibly temperature. The data received by the receiver 14 is stored in a memory of the ECU and compared to a threshold value to determine whether an alarm needs to be triggered and sent to the display 16 to warn the driver. The ECU 15 needs to associate the ID code of the transceiver with a particular location on the vehicle, i.e. front-left (FL), front-right (FR), rear-left (RL), rear-right (RR) or spare wheel (SP), so as to report the faulty tyre pressure to the driver.To do this, the ECU 15 commands, in a well known manner, each initiator 13 to sequentially send an initiation or flag signal to its respective tyre thereby causing the creation of a flagged signal back to the ECU. The location of the wheel-based unit 13 is deduced from the location of each initiator 17 which is known by the ECU 15. However, because the tyre pressure system is provided with three initiators and the vehicle has four "running" tyres there is a problem to send a flag signal to the running wheel-based unit associated with the fourth tyre. To overcome this problem the ECU is provided with a control logic to enable it to determine the location of all the tyres. The term "running tyres" is used for convenience to indicate that the tyres are mounted to the hubs of the vehicle. Fig.2 is a flow diagram of the control logic of the ECU when starting the initiation process to locate the wheel-based units on the vehicle. The control logic starts at 110 where the ECU checks whether vehicle speed is greater than a threshold vehicle speed approximately 20 mph (32.18 kmh). If Yes, the ECU commands one initiator to send a LF signal in order to flag one of the wheel-based signals periodically received through the receiver, at 120. Each initiator is thereby commanded in turn, so as to learn where each wheel-based unit is located on the vehicle. An inquiry is made at 130 to determine whether the ID forming part of the data received is already stored in the memory of the ECU.If No, an inquiry is made at 140 as to whether the wheel-based unit belongs to the vehicle, for instance by checking whether the wheel speed indicated by the signal matched with the speed of the vehicle. If Yes, the ID code of the wheel-based unit is registered in the memory of the ECU, at step 150, then the routine shifts to step 160. If No, the routine initiates the next tyre at step 120. If the ID code is already stored within the memory of the ECU, a check is made at step 160 to determine whether the data is associated with a flagged signal. If Yes, the location of the wheel-based unit is checked or updated within a table, at step 170. A negative answer to this inquiry will store data at step 180.Then inquiries are made at step 190 and 200 to determine whether all running tyres associated with an initiator have been identified with a location and whether the stored data includes a speed signal. A positive answer to these inquiries will assign the stored data of the wheelbased unit to the tyre which remains unassigned position, at step 210. A negative answer to the inquiry concerning the speed will assign the stored data of the wheel-based unit 13 to the spare wheel 12, at step 220. If all the running tyres associated with an initiator have not been identified then the routine is shifted back to step 120 where the ECU initiates the next tyre on its table. Although the vehicle has been described as including a spare wheel provided with a wheelbased unit, it will be appreciated that this is optional. However the determination by the control logic of the running wheel which is not associated with an initiator remains identical to the routine described above. This method of determining tyre location within a tyre pressure monitoring system with control logic can give several advantages. Firstly, it makes it possible to identify N running tyres with only N-1 initiators, reducing the overall cost of a conventional tyre pressure monitoring system. Secondly, the design constraints of a modern motor vehicle make it more and more difficult to find space to install components such as initiators. Furthermore this method also allows a static wheel to be easily identified.

Claims

1. A motor vehicle equipped with a tyre pressure monitoring system and a number of tyres of which there are N running tyres, the tyre pressure monitoring system comprising a vehicle-based unit and a number of wheel-based units, each wheelbased unit being associated with a respective one of the tyres, each wheel-based unit being operable to send a signal indicating at least a detected tyre pressure, wheel speed and an Identification Data code to the vehicle-based unit, the vehicle-based unit comprises an electronic control unit (ECU) for interpreting the signal and sending an alarm signal if a faulty tyre pressure is identified, wherein the vehicle-based unit also comprises N-1 initiators each associated with a respective one of N-1 running tyres and operable to send an initiation signal to its respective wheel-based unit and a logic control implemented in the ECU so as to determine the location of each wheel-based unit on the vehicle based upon the reception of a flagged signal and a process of elimination to identify the running tyre which is not associated with an initiator.

2. A vehicle as claimed in claim 1 in which each initiator sequentially sends a flag signal to its corresponding wheel-based unit when the speed of the vehicle is determined to be greater than a threshold value.

3. A vehicle as claimed in claim 2 in which the threshold value is approximately 20 mph (32.18 kmh).

4. A vehicle as claimed in any preceding claim wherein the vehicle also comprises a spare wheel provided with a wheel-based unit in which the logic control is able to identify this wheel among the running wheels based upon the reception of a flagged signal and the wheel speed.

5. A method of determining tyre location within tyre pressure monitoring system equipping a motor vehicle as claimed in any of claims 1 to 4 when the vehicle is determined to run at a vehicle speed which is greater that the determined threshold value, in which each initiator is commanded in turn by the ECU so as to learn the location of each of the wheel-based units associated with an initiator based upon the reception of a flagged signal and, once all the wheel-based units associated with an initiator have been identified, then assigns the remaining signal of the wheel-based units periodically received by the ECU which has not be flagged to the remaining running tyre location.

6. A method as claimed in claim 5 when the vehicle is according to claim 4, in which the ECU assigns the remaining signals of the wheel-based units periodically received by the vehicle-based unit which has not been flagged to either the remaining running tyre location or the spare wheel according to whether the remaining signals indicate a wheel speed matching the vehicle or not.

7. A motor vehicle substantially as described herein with reference to the Figure 1 of the accompanying drawings.

8. A method of determining tyre location within tyre pressure monitoring system equipping a motor vehicle substantially as described herein with reference to Figure 2 of the accompanying drawings.