METHOD FOR MONITORING TIRE PRESSURE

Description

[0001] The invention is based on a method having the features specified in the preamble of claim 1, as known, for example, from US 2002 / 044050 A1. Similar methods are known, for example, from EP 1 108 568 A2, CN 108 327 A, WO 2005 / 069993 A2, US 2011 / 054728 A1, WO 92 / 14620 A2, and EP 1 826 029 A1.

[0002] Modern tire pressure monitoring units are mounted on vehicle wheels and typically contain a pressure sensor for measuring tire pressure and a transmitter for wirelessly transmitting tire pressure data. Pressure data is transmitted via data transmissions, each containing several data telegrams with identical pressure data. Such data transmissions are also referred to as blocks or blocks and the data telegrams as frames Under unfavorable transmission conditions, it can happen again and again that a data telegram is not received or is received incompletely. By containing multiple data telegrams with identical print data in a data transmission, redundancy is created and the probability is increased that, even under unfavorable conditions, at least one of the data telegrams in a data transmission will be received by a central unit in the vehicle.

[0003] A significant portion of a tire pressure monitoring unit's energy consumption is due to its transmission activity. A constant challenge in the development of tire pressure monitoring systems is therefore optimizing the transmission activity of tire pressure monitoring units so that relevant pressure data can be made available to a vehicle's central unit in a timely manner with minimal energy consumption. This is especially true for tire pressure monitoring units that use a (non-rechargeable) battery as their power source.

[0004] The object of the present invention is to show a way in which the energy consumption of a tire pressure monitoring unit can be reduced without impairing the supply of pressure data to a central unit of the vehicle.

[0005] This object is achieved by a method having the features specified in claim 1. Advantageous developments of the invention are the subject of subclaims.

[0006] In a method according to the invention, the tire pressure monitoring unit transmits pressure data in a first operating mode in the form of data transmissions containing multiple data telegrams with identical pressure data. In a second operating mode, at least some of the data transmissions contain only a single data telegram. In this way, in the first operating mode, redundant transmission of tire pressure data can reliably ensure that the pressure data is received by the vehicle's central unit even under unfavorable transmission or reception conditions. In the second operating mode, it is accepted that a data transmission may not be received and the central unit may therefore not receive current pressure data. However, due to the reduced transmission activity, significantly less energy is consumed in the second operating mode than in the first operating mode.

[0007] The second operating mode is advantageous in situations where it's not a problem if a data transmission is occasionally missed, for example, some time after starting a journey when tire pressure doesn't change significantly or only slightly between data transmissions. The first operating mode, on the other hand, is advantageous in situations where the reception of each data transmission is important, such as at the start of a journey or when tire pressure changes significantly.

[0008] An advantageous development of the invention therefore provides that the tire pressure monitoring unit is operated in the first operating mode at the start of a journey. For example, the tire pressure monitoring unit can contain an acceleration sensor that detects the start of a journey. If this is the case, the tire pressure monitoring unit switches to the first operating state.

[0009] A number of necessary and / or sufficient conditions may be provided for the transition from the first operating mode to the second operating mode, for example: a predetermined minimum period of time that must have elapsed since the start of driving before the tyre pressure monitoring unit switches to the second operating mode, for example 15 minutes or more; a change in tyre pressure compared to the last data transmission by less than a predetermined threshold value, for example less than 5% or by no more than 2%; in the case of a tyre pressure monitoring unit that also contains a temperature sensor, it can also be provided as a necessary condition that the temperature lies within a predetermined temperature range, for example between 0°C and 100°C.

[0010] If a condition is selected as a necessary condition, this means that a transition to the second operating state only occurs if this condition is met. If a condition is selected as a sufficient condition, this means that a transition to the second operating state always occurs as soon as this condition is met. For example, several conditions can be selected as necessary conditions, and a sufficient condition can then be seen in the fact that a predetermined number or all of these necessary conditions, for example, all of the conditions mentioned above, must be met for the tire pressure monitoring unit to transition to the second operating state.

[0011] A number of necessary and / or sufficient conditions may be provided for the transition from the second operating mode to the first operating mode, for example: a change in tire pressure compared to the last data transmission by more than a predetermined threshold, for example, more than 2% or at least 5%; and / or a temperature of more than 100°C.

[0012] The first time intervals between the individual data transmissions in the first and second operating modes can be constant. However, with constant time intervals, it can happen that tire pressure monitoring units on different wheels of the vehicle always start transmitting data at the same time, which makes reception more difficult. It can therefore be advantageous to vary the first time intervals, for example by randomly or approximately randomly adding a small time interval to a fixed, predetermined time period. This time interval represents only a small fraction of the first time intervals, for example, between the duration of a data telegram and three times the duration of a data telegram. An advantageous development of the invention provides that the first time intervals are between 20 seconds and 3 minutes.

[0013] The second time intervals between the individual data telegrams of a data transmission in the first and possibly also in the second operating mode can be constant or vary slightly. However, the second time intervals do not exceed 1% of the first time intervals. An advantageous development of the invention provides that the second time intervals are between 50 ms and 200 ms.

[0014] According to the invention, in the second operating mode, several data transmissions containing multiple data telegrams are periodically carried out. For example, every fourth or every fifth data transmission can consist of multiple data telegrams, for example, three data telegrams. Generally speaking, in the second operating mode, every nth data transmission consists of multiple data telegrams, and the remaining data transmissions consist of only a single data telegram, where n is a natural number, for which, for example, 10 ≥ n ≥ 3 applies.

[0015] A further advantageous development of the invention provides that each data telegram contains a section indicating whether this data telegram is the only data telegram in a data transmission. If a data transmission contains multiple data telegrams, this section can also contain information about how many more data telegrams follow in the same data transmission.

[0016] Further details and advantages of the invention are described using an exemplary embodiment with reference to the accompanying drawings. They show: Fig. 1 shows a schematic representation of a tire pressure monitoring system of a vehicle; and Fig. 2 shows a schematic representation of the data transmission from a tire pressure monitoring unit to the central unit in a first operating mode; and Fig. 3 shows a schematic representation of the data transmission from a tire pressure monitoring unit to the central unit in a second operating mode.

[0017] The Fig. 1 The schematically illustrated tire pressure monitoring system comprises a plurality of tire pressure monitoring units 1, each arranged in one of the pneumatic tires of a vehicle and having a pressure sensor 1a, a temperature sensor 1b, an acceleration sensor 1d, a control unit 1c, a power source, e.g., a battery, and a transmitter 1e for wirelessly transmitting pressure data. The system also includes a central unit 2, fixedly mounted on the vehicle, for evaluating data telegrams sent by the tire pressure monitoring units 1, each of which contains pressure information and a characteristic identifier of the transmitting tire pressure monitoring units. A receiver 3 is connected to the central unit 2.

[0018] In a first operating mode, the tire pressure monitoring units 1 transmit pressure data by transmitting data at first time intervals, each data telegram containing a plurality of identical pressure data following one another at second time intervals. Fig. 2 shows schematically the temporal course of the transmission activity in the first operating mode.

[0019] In Fig. 2 Four data transmissions D are shown over time t, each consisting of three data telegrams F. Within a data transmission D, all data telegrams F contain the same print data. The data transmission is thus redundant, and it is sufficient for receiver 3 to receive one data telegram F from each data transmission D.

[0020] The data transmissions D are sent at first time intervals t1, which are, for example, between 20 seconds and 3 minutes. Within a data transmission D, the data telegrams F follow one another at second time intervals t2, which are, for example, between 50 ms and 200 ms. Overall, the second time intervals t2 are less than 1% of the first time intervals t1. The first time intervals t1 and the second time intervals t2 can be constant. To reduce the probability that tire pressure monitoring units 1 of different wheels of the vehicle repeatedly transmit at the same time, it can be advantageous to repeatedly change the first time intervals t1 and / or the second time intervals t2 slightly, for example by sometimes adding, randomly or pseudo-randomly, a small time period to a fixed time period, which is between one and three times the time period of a data telegram F.

[0021] In Fig. 3 The temporal progression of the transmission activity in a second operating mode is shown schematically. In the second operating mode, data transmissions D occur in the same way as in the first operating mode at first time intervals t1. However, some of these data transmissions D consist of only a single data telegram F. For example, in the second operating mode, it can be provided that - as in Fig. 3 shown - only every third data transmission D contains multiple data telegrams F. Alternatively, in the second operating mode, each data transmission D can consist of only a single data telegram F or only every nth data transmission D can consist of a single data telegram F, where n is a natural number, for example 10≥n≥3.

[0022] The second operating mode has the advantage of reduced energy consumption, as the redundancy of the data transmission is reduced compared to the first operating mode. The second operating mode can therefore be used advantageously in operating conditions where it is unproblematic if a data transmission cannot be received occasionally, for example, during normal driving. The first operating mode can be used at the start of driving, as well as in the event of critical changes in tire pressure, e.g., a pressure change of 2% or more since the last data transmission D, or a problematic tire temperature, e.g., 100°C or more.

[0023] In addition to the first and second operating modes, the tire pressure monitoring unit 1 can have further operating modes, for example a parking mode with an even further reduced data transmission, which is switched to when the vehicle is parked, and / or a warning mode in which data transmissions are carried out immediately after detection of a critical measured value, such as a dangerous pressure drop, and at shortened time intervals.

[0024] The change to the first operating state or to the second operating state can be regulated by a series of necessary and / or sufficient conditions.

[0025] For example, the tire pressure monitoring unit may enter the first operating state if one of the following conditions is met: an acceleration sensor of the tire pressure monitoring unit detects the start of a journey; a temperature sensor of the tire pressure monitoring unit detects a rise in temperature above a first temperature threshold, for example above 100°C; a change in tire pressure by more than a first threshold is detected since the last data transmission D, for example a change of 2% or more.

[0026] For example, the tire pressure monitoring unit may enter the second operating state while driving if one, several, or all of the following conditions are met: a predetermined period of time has elapsed since the start of the journey, for example 15 minutes, the temperature sensor detects a temperature below a second temperature threshold, for example 95°C, whereby this second temperature threshold may be the same as or different from the first temperature threshold; since the last data transmission, a change in tire pressure of less than a second threshold has been detected, for example less than 2%, whereby this second threshold may be the same as or different from the first threshold.

Claims

1. Method for monitoring tyre pressure of a vehicle tyre by means of a tyre pressure monitoring unit (1) which comprises a pressure sensor (1a) for measuring tyre pressure and a transmitter (1e) for wirelessly transmitting tyre pressure data, wherein pressure data are transmitted in a first operating mode of the tyre pressure monitoring unit (1) in that data transmissions (D) are made at first time intervals (t1), each containing a plurality of data telegrams (F) with identical pressure data which follow one another at second time intervals (t2) which are less than 1% of the first time intervals (t1), and wherein in a second operating mode of the tyre pressure monitoring unit (1) at least some of the data transmissions (D), which follow one another at first time intervals (t1), consist only of a single data telegram (F), characterised in that in the second operating mode, every nth data transmission (D) consists of several data telegrams (F) and the remaining data transmissions (D) consist of only a single data telegram (F), where n is a natural number between 3 and 10.

2. Method according to claim 1, characterised in that pressure data is transmitted in the first operating mode when the tyre temperature exceeds an upper threshold value, preferably more than 100°C.

3. Method according to any one of the preceding claims, characterised in that pressure data is transmitted in the first operating mode if a change in the tyre pressure since the last data transmission (D) exceeds a threshold value.

4. Method according to any one of the preceding claims, characterised in that the tyre pressure monitoring unit (1) switches to the first operating mode when driving starts.

5. Method according to any one of the preceding claims, characterised in that a necessary or a sufficient condition for a transition of the tyre pressure monitoring unit (1) to the second operating state is that a change in the tyre pressure since the last data transmission (D) is below a threshold value.

6. Method according to any one of the preceding claims, characterised in that a necessary or a sufficient condition for a transition of the tyre pressure monitoring unit (1) to the second operating state is that a temperature measured by a temperature sensor (1b) of the tyre pressure monitoring unit (1) is within a predetermined temperature range.

7. Method according to any one of the preceding claims, characterised in that a necessary or a sufficient condition for a transition of the tyre pressure monitoring unit (1) to the second operating state is that a predetermined time has elapsed since the start of the journey.

8. Method according to any one of the preceding claims, characterised in that the first time intervals are between 20 seconds and 3 minutes.

9. Method according to any one of the preceding claims, characterised in that the second time intervals are between 50 ms and 200 ms.

10. Method according to any one of the preceding claims, characterised in that n is a natural number between 4 and 6.

11. Method according to any one of the preceding claims, characterised in that each data telegram (F) contains a section which indicates whether the print data contained in this data telegram (F) deviates by more than a predetermined threshold value from the print data of the last data transmission (D).

12. Tyre pressure monitoring unit with a pressure sensor (1a) for measuring tyre pressure and a transmitter (1e) for wireless transmission of tyre pressure data, characterised in that the tyre pressure monitoring unit (1) performs a method according to any one of the preceding claims during operation.