METHOD OF TRANSMITTING TIRE PRESSURE INFORMATION AND WIRELESS TIRE PRESSURE MONITOR SYSTEM

Abstract

A wireless tire pressure monitor system configured for transmitting tire pressure information of a tire of a vehicle is described. The wireless tire pressure monitor system comprises a vehicle-based receiver, at least one tire pressure sensor configured to be mounted inside the tire and configured to measure the air pressure within the tire, and a transmitter electronically connected to the tire pressure sensor and configured to transmit a signal comprising the tire pressure information to the vehicle-based receiver. The wireless tire pressure monitor system is configured to transmit the signal in a first transmission mode from the transmitter to the vehicle-based receiver when the tire is rotating, and transmit the signal in a second transmission mode from the transmitter to the vehicle-based receiver when the tire is stationary. Moreover a method of transmitting tire pressure information employing a wireless tire pressure monitor system is described.

Claims

1. A method of transmitting tire pressure information employing a wireless tire pressure monitor system comprising a vehicle-based receiver, at least one tire pressure sensor mounted inside a tire and a transmitter, comprising the following steps: Using a first transmission mode to transmit a first signal from the transmitter to the receiver when the tire is rotating, wherein the first signal comprises the tire pressure information, and Using a second transmission mode to transmit a second signal from the transmitter to the receiver when the tire is stationary, wherein the second signal comprises the tire pressure information.

2. The method of claim 1, wherein the data rate in the second transmission mode is lower than the data rate in the first transmission mode.

3. The method of claim 1, wherein the data rate in the second transmission mode is lower than 5 kbits/s.

4. The method of claim 1, wherein the data rate in the second transmission mode is in the range of 0.5 kbits/s and 2.5 kbits/s.

5. The method of claim 1, wherein the first signal and the second signal are modulated differently.

6. The method of claim 1, wherein the second signal comprises at least one of an amplitude modulation (AM) and an amplitude-shift keying (ASK) modulation.

7. The method of claim 1, wherein the signal is a radio frequency signal.

8. A wireless tire pressure monitor system configured for transmitting tire pressure information of a tire of a vehicle, wherein the wireless tire pressure monitor system comprises a vehicle-based receiver, at least one tire pressure sensor configured to be mounted inside the tire and configured to measure the air pressure within the tire, and a transmitter electronically connected to the tire pressure sensor and configured to transmit a signal comprising the tire pressure information to the vehicle-based receiver, wherein the wireless tire pressure monitor system is configured to transmit the signal in a first transmission mode from the transmitter to the vehicle-based receiver when the tire is rotating, and transmit the signal in a second transmission mode from the transmitter to the vehicle-based receiver when the tire is stationary.

9. The wireless tire pressure monitor system of claim 8, wherein the data rate in the second transmission mode is lower than the data rate in the first transmission mode.

10. The wireless tire pressure monitor system of claim 8, wherein the data rate of the second transmission mode is lower than 5 kbits/s.

11. The wireless tire pressure monitor system of claim 8, wherein the data rate of the second transmission mode is in the range of 0.5 kbits/s and 2.5 kbits/s.

12. The wireless tire pressure monitor system of claim 8, wherein the signal in the second transmission mode is modulated according to at least one of amplitude modulation (AM) and amplitude-shift keying (ASK) modulation.

13. The wireless tire pressure monitor system of claim 8, wherein the vehicle-based receiver is a radio frequency receiver and the transmitter is a radio frequency transmitter.

Description

DESCRIPTION OF THE DRAWINGS

[0034] The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0035] FIG. 1 schematically shows a stationary vehicle with an embodiment of a wireless tire pressure monitor system according to the present disclosure in a side view; and

[0036] FIG. 2 schematically shows the vehicle of FIG. 1 in motion.

DETAILED DESCRIPTION

[0037] The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed.

[0038] FIG. 1 schematically shows a vehicle 10 established by a large truck. In the shown embodiment, the vehicle 10 has six wheels 12 of which only three are visible in FIG. 1 since the vehicle 10 is shown in a side view.

[0039] In an alternative embodiment, the vehicle 10 may be any kind of vehicle with any number of wheels 12, for instance four or rather eight.

[0040] Each wheel 12 has a pneumatic tire 14, 15, 16 that is typically inflated by pressurized air. Of course, the pneumatic tires 14, 15, 16 can be inflated by any kind of gaseous fluid alternatively.

[0041] Further, each wheel 12 is rotatably suspended around an axis 18, in particular in pairs so that each axis 18 is assigned to two wheels 12.

[0042] Moreover, the vehicle 10 has a wireless tire pressure monitor system 20 that comprises a vehicle-based receiver 22 as well as at least one sensor unit 24, 25, 26 for each tire 14, 15, 16.

[0043] The vehicle-based receiver 22 is an RF receiver.

[0044] The vehicle-based receiver 22 may be powered by an automobile battery of the vehicle 10 and is electronically connected to an on-board computer of the vehicle 10, namely a processing device.

[0045] Each sensor unit 24, 25, 26 comprises a tire pressure sensor 28 and a transmitter 30, wherein the tire pressure sensor 28 and the transmitter 30 are electronically connected with each other.

[0046] Further, each sensor unit 24, 25, 26 comprises a battery forming the power supply of the sensor unit 24, 25, 26.

[0047] Alternatively, the sensor unit 24, 25, 26 is powered wirelessly via the vehicle-based receiver 22 being a transceiver. Accordingly, the vehicle-based receiver 22 may send out a request signal which activates the sensor unit(s) 24, 25, 26 to sense the pressure and to transmit the pressure information obtained.

[0048] A sensor unit 24, 25, 26 is located within each tire 14, 15, 16 or rather at least assigned thereto enabled to gather pressure information.

[0049] The tire pressure sensor 28 is configured to measure the air pressure within the respective tire 14, 15, 16 the tire pressure sensor 28 is located in or rather assigned to.

[0050] The transmitter 30 is an RF transmitter. Thus, the transmitter 30 is enabled to communicate with the vehicle-based receiver 22 being an RF (trans-)receiver.

[0051] The transmitter 30 is configured to transmit a signal 32 comprising at least the tire pressure information determined by the respective tire pressure sensor 28 to the receiver 22, which in turn is configured to receive the signal transmitted by the transmitter 30.

[0052] Besides the respective tire pressure information, temperature information and/or a sensor ID may be transmitted so that the vehicle-based receiver 22 receiving the signals is enabled to assign the respective information received to the tires 14, 15, 16.

[0053] In FIG. 1 the vehicle 10 is stationary and thus the wheels 12 are stationary, i.e. they do not rotate around their respective axis 18. For instance, the vehicle 10 is shown in a tire inflating mode.

[0054] FIG. 2 schematically shows the vehicle 10 moving in forward direction F with the wheels 12 rotating in circumferential direction C.

[0055] Obviously, the wheels 12 would rotate in opposite direction if the vehicle 10 reverses, i.e. the vehicle 10 moves backwards in opposite direction to forward direction F.

[0056] When the wheels 12 rotate, the tires 14, 15, 16 as well as the sensor units 24, 25, 26 rotate along with the wheels 12 in the respective direction.

[0057] Due to structural conditions as well as due to the design of the vehicle 10 and the wireless tire pressure monitor system 20, there are so-called null positions in which signals 32 between the transmitters 30 and the receiver 22 are significantly attenuated when the respective transmitter 30 is located in such a null position.

[0058] In the embodiment shown, these null positions are located at the 12 o'clock (0 or 360), the 3 o'clock (90), the 6 o'clock (180) and the 9 o'clock (270) positions of the tires 14, 15, 16. These positions are only chosen for illustrative purposes as they may be different in real application. For instance, a null position may also be located at the 7 o'clock position (210).

[0059] In the shown embodiment, the sensor unit 24 located at the 12 o'clock position and the sensor unit 25 located at the 3 o'clock position are in a null position where the signal of their respective transmitter 30 is attenuated to a significant degree.

[0060] The sensor unit 26 located at the 8 o'clock (240) position on the other hand, is not in a null position and thus the signal between the respective transmitter 30 and the receiver 22 is less attenuated.

[0061] Of course, in an alternative embodiment, each wheel 12 may have any number of null positions located in any kind of positions.

[0062] The wireless tire pressure monitor system 20 has a first and a second transmission mode 34, 36.

[0063] Accordingly, the wireless tire pressure monitor system 20 is configured to use the first transmission mode 34 to transmit the tire pressure information in form of a first signal 32 when the vehicle 10 is in motion (see FIG. 2), and the wireless tire pressure monitor system 20 is configured to use the second transmission mode 36 to transmit the tire pressure information in form of a second signal 32 when the vehicle 10 is stationary (see FIG. 1).

[0064] The information of whether or not the vehicle 10 is in motion, can be provided by the on-board computer and/or motion sensors.

[0065] In a further embodiment, the wireless tire pressure monitor system 20 could comprise an individual rotation sensor for each wheel 12 configured to detect the rotation of the respective wheel 12 and/or one or more g-force sensors and/or vibration sensors to determine if the vehicle 10 or the respective wheel 12 is stationary or not.

[0066] Moreover, the wireless tire pressure monitor system 20 may comprise a geolocation system so that a movement can be detected appropriately. Alternatively, the wireless tire pressure monitor system 20 uses the geolocation system of the vehicle 10, for instance the one of a navigation system.

[0067] In the first transmission mode 34 signals 32 are transmitted using a data rate of 9.6 kbits/s. The signals 32 in the first transmission mode 34 are also called first signals.

[0068] Of course, in a different embodiment any suitable data rate could be used in the first transmission mode 34, especially data rates in the range of 8.0 kbits/s and 12.0 kbits/s, preferably in the range of 9.0 kbits/s and 11.0 kbits/s, in particular in the range of 9.5 kbits/s and 10.0 kbits/s.

[0069] In a further embodiment, the first transmission mode 34 employs frequency-shift keying (FSK) modulation and/or phase modulation (PM).

[0070] In the first transmission mode 34 a typical 9.6 kbits/s FSK receiver sensitivity is around 108 dBm. For a large vehicle 10 and high attenuation of the RF transmitter 30 from the large tire 14, the RF link between the transmitter 30 inside the tire 14 and the receiver 22, in particular the receiver 22 inside the cabin, is poor and there are multiple angles of the tire 14 rotation could be classified as nulls. This means the 9.6 kbits/s FSK receiver 22 is not able to reliably receive the signal 32 of the transmitter 30 when the transmitter 30 is in these angle positions.

[0071] When the vehicle 10 is in motion, the wireless tire pressure monitor system 20 works fine, i.e. the tire pressure information is reliably transmitted from the transmitters 30 to the receiver 22 and received by the receiver 22. The reason for this is that since the transmitter 30 transmits many frames, the sensor 28 information will be passed on to the receiver 22 as long as some of the transmission frames occur outside the null angles during the rotation of the tire 14, 15, 16.

[0072] In other words, the information can be transmitted and received in a reliable manner due to the high data rate and the respective short time required for transmitting the respective information.

[0073] However, when the vehicle 10 is stationary, like for tire fill assistant applications, namely inflating operation, no matter how many transmission frames the transmitter 30 sends out, none of the information will be received by the receiver 22 if the transmitter 30 is in a null position.

[0074] To improve the sensitivity of the receiver 22, when the vehicle 10 is stationary, the second transmission mode 36 is used.

[0075] In the second transmission mode 36 signals 32 are transmitted using a data rate of 1.5 kbits/s which is much lower than the data rate of the first transmission mode 34 of 9.6 kbits/s. The signals 32 transmitted in the second transmission mode 36 are also called second signals.

[0076] In a different embodiment, any data rate lower than the data rate of the first transmission mode 34 could be used in the second transmission mode 36, especially data rates in the range of 0.5 kbits/s and 2.5 kbits/s, preferably in the range of 1.0 kbits/s and 2.0 kbits/s, in particular 1.5 kbits/s.

[0077] In a further embodiment, the data rate in the second transmission mode 36 is lower than 5 kbits/s, preferably lower than 3 kbits/s, in particular lower than 2 kbits/s.

[0078] In another embodiment, the second transmission mode 36 employs amplitude modulation (AM) and/or amplitude-shift keying (ASK) modulation and/or other kinds of modulation.

[0079] By using a 1.5 kbits/s ASK transmission in the second transmission mode 36, the receiver sensitivity could be improved by 6 dBm to 114 dBm under test conditions.

[0080] Alternatively or additionally to the data rate change between the stationary and the driving mode, different modulation schemes can be applied for the first and the second transmission mode 34, 36.

[0081] Frequency-shift keying (FSK) modulation and phase modulation (PM) detection are independent of the amplitude. During the high-speed drive, the signal 32 of the transmitter 30 at the input of the receiver 22 can fluctuate, so FSK and PM modulation are good for wireless tire pressure monitor applications while the vehicle 10 is in motion.

[0082] Amplitude-shift keying (ASK) modulation or amplitude modulation (AM) are more sensitive to the amplitude change, so it is not suitable for the high-speed driving wireless tire pressure monitor applications. However, low data rate ASK is a good option for stationary tire 14, 15, 16 fill assistant and pressure loss warning applications as it can have a narrower receiver bandwidth when compared to the FSK which has a wider bandwidth to cover the extra frequency deviation between the bits.

[0083] However, using FSK in stationary mode is not excluded, i.e. FSK can also be applied in stationary mode. In certain applications, for example where other factors like oscillator frequency tolerance dominate the bandwidth requirement, FSK may work as well with its own advantage such as being immune to certain spike noise.

[0084] In this way, by applying a comparably slow data rate in the second transmission mode 36 a high receiver sensitivity of the vehicle-based receiver 22 is achieved which results in a reduced range of null angles or eliminates the nulls entirely.

[0085] Thus, the wireless tire pressure monitor system 20 optimizes the RF system parameters for an optimal RF link at stationary condition, which makes the wireless tire pressure monitor system 20 particularly well suited for tire fill assistant applications and further allows the wireless tire pressure monitor system 20 to reliably detect a pressure loss during parking of the vehicle 10.

[0086] This improvement can occur either at the transmitter 30 side or the receiver 22 side or both.

[0087] In a further embodiment, the wireless tire pressure monitor system 20 is configured to adjust the optimal receiving mode based on the vehicle 10 speed condition to match the optimal transmission mode of the transmitter 30. These vehicle speed dependent communication protocols provide a wireless tire pressure monitor system 20 that is highly reliable and robust.

[0088] A further advantage of this embodiment is, that an improved transmission is achieved through increased sensitivity instead of increased transmission power. Thus, the method described above as well as the wireless tire pressure monitor system 20 employing this method are more energy efficient.