Source: https://patents.google.com/patent/US7119670B2/en
Timestamp: 2020-01-28 19:04:02
Document Index: 172362135

Matched Legal Cases: ['application no. 102', 'art 10', 'art 10', 'art 10', 'art 10', 'art 100']

US7119670B2 - Tire pressure monitoring system - Google Patents
US7119670B2
US7119670B2 US10/947,953 US94795304A US7119670B2 US 7119670 B2 US7119670 B2 US 7119670B2 US 94795304 A US94795304 A US 94795304A US 7119670 B2 US7119670 B2 US 7119670B2
US10/947,953
US20050057348A1 (en
2002-03-25 Priority to DE10213266.6 priority Critical
2002-03-25 Priority to DE10213266A priority patent/DE10213266A1/en
2004-11-23 Assigned to INFINEON TECHNOLOGIES AG reassignment INFINEON TECHNOLOGIES AG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HAMMERSCHIDT, DIRK
2005-03-17 Publication of US20050057348A1 publication Critical patent/US20050057348A1/en
2006-02-24 Assigned to INFINEON TECHNOLOGIES AG reassignment INFINEON TECHNOLOGIES AG CORRECTIVE ASSIGNMENT TO CORRECT THE INVENTOR'S LAST NAME PREVIOUSLY RECORDED ON REEL 016025 FRAME 0726. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT. Assignors: HAMMERSCHMIDT, DIRK
2006-10-10 Publication of US7119670B2 publication Critical patent/US7119670B2/en
230000001419 dependent Effects 0 claims description 70
In the system for monitoring tire pressure in a tire of a vehicle, temporally successive tire pressure measured values are sensed by a transmitting unit, and at least part of the tire pressure measured values is transmitted to a receiving unit with a variable frequency of occurrence, wherein the frequency of occurrence is derived from the sensed tire pressure measured values by means of a control unit.
This application is a continuation of copending International Application No. PCT/EP03/03093 filed Mar. 25, 2003 which designates the United States, and claims priority to German application no. 102 13 266.6 filed Mar. 25, 2002.
The present invention relates to a pressure sensor system, and in particular to a system for monitoring tire pressure in a vehicle tire.
In vehicle technology, greater and greater efforts are made to develop tire pressure sensor systems with which the tire pressure of a motor vehicle, e.g. a truck, car, or motorbike may be sensed. By means of such tire pressure sensor systems, pressure changes are to be passed to a central unit, e.g. the on-board computer of the vehicle, as early as possible in order to thus recognize damage of a tire as early as possible or warn the driver sufficiently early when tire pressure changes are present, because these indicate gas loss or abnormal deformation of the tire. With this, the driver of a motor vehicle may often still be warned sufficiently early of the bursting of a vehicle tire due to damage or also of a so-called “slow flat”.
Starting from this prior art, it is the object of the present invention to provide an improved concept for monitoring tire pressure in a tire of a vehicle, so that over the entire intended life of a tire pressure sensor arrangement the physical state quantities, such as pressure and temperature in a tire, may be monitored reliably.
FIGS. 2 a–c show, in diagram form, the procedure for the ascertainment of the frequency of the transmission of the tire pressure measured values from a transmitting unit to a receiving unit depending on the tire pressure and the magnitude of the measured value change according to the present invention;
FIGS. 4 a–b are a principle illustration of the change of the time distance for the transmission of the tire pressure measured values depending on the driving state of the vehicle and the tire state;
FIGS. 5 a–c show, in diagram form, the procedure for the classification of the pressure dynamics states in a tire of a motor vehicle, with FIG. 5 a illustrating an exemplary ascertained course of pressure measured values in the tire and their short time averages, FIG. 5 b pressure variations, and FIG. 5 c deviation squares of the pressure variations, filtered deviation squares, and the ascertained driving situation;
With reference to FIG. 1, now a preferred embodiment of the present invention for the monitoring of tire pressure in a vehicle tire will be discussed on the basis of a flow chart.
The ascertained physical state quantities are now made available to a control and evaluation unit for further processing, as this is illustrated by box 23 including boxes 24–38 of flow chart 10.
H 11 ⁢ R ⁡ ( z ) = a 1 - b · z - 1
In a second possible embodiment, the IIR digital filter is a 2nd order low-pass filter. Therefrom the following transfer function of the filter results:
H 11 ⁢ R ⁡ ( z ) = ( a 1 - b · z - 1 ) 2
The optional use of a 2nd order low-pass filter causes an even greater differentiation of the time distances of the wakeups calculated by the method. For this, this embodiment, however, requires a more expensive hardware arrangement.
As illustrated in boxes 44 and 46 of flow chart 10, a serial periphery interface is activated or is active, which is switched off after the transmission of the tire pressure measured value from a main unit (power down from master). Next, the counter is reset to its initial value, e.g. to zero “0”, as illustrated in box 48 of flow chart 10. Thereupon the timer is reset, box 50, whereupon the digital circuit area of the tire pressure sensor arrangement is switched off, as this is illustrated in box 52 of flow chart 10.
In the following, on the basis of the diagrams illustrated in FIGS. 2 a–c, it is explained how the inventive method of monitoring tire pressure in a vehicle tire is performed.
In FIG. 2 a the tire pressure, i.e. the course of the sensed tire pressure measured values, in the vehicle tire is illustrated as course I versus time. The course II now shows the change of the course of the tire pressure in the vehicle tire, i.e. the gradient. The course III shows the count of a counter, which is decremented by a fixed value each, beginning with a starting value “S”, so that the threshold for the triggering of a transmission of a tire pressure measured value decreases depending on the count.
It is to be noted that in FIGS. 2 a–c the magnitude of the measured value change of the tire pressure has only exemplarily been chosen as the tire pressure change dependent parameter, wherein an arbitrary tire pressure change dependent parameter may be used, which is determined from the sensed tire pressure measured values in order to be compared with the count to trigger the transmission of the tire pressure measured value, when the count reaches or falls short of this tire pressure change dependent parameter.
The inventive method of monitoring tire pressure in a vehicle tire illustrated in FIGS. 2 a–c on basis of diagrams may thus be summarized as follows.
Corresponding to a further possible embodiment of the inventive method of monitoring tire pressure in a vehicle tire, it is of course also possible that the derived tire pressure change dependent parameter is added to the count, wherein the counter is reset to an initial value S, e.g. to zero “0”, after each triggering of a transmission and incremented (increased) after each detection of a tire pressure measured value. The transmission of a current tire pressure measured value is then triggered in this embodiment, when the sum of the tire pressure change dependent parameter and the count of the counter exceeds a default fixed threshold.
In the following, it is now discussed on the basis of the diagrams illustrated in FIGS. 3 a–b how the frequency of the transmission of current tire pressure measured values to a receiving unit is determined in a further embodiment of the inventive method of monitoring tire pressure in a vehicle tire.
The course I in FIG. 3 a shows the course of the sensed tire pressure measured values in various vehicle states A–C, wherein the course II illustrates the averaged or low-pass filtered course of the sensed tire pressure measured values. The area A in the diagram of FIG. 3 a describes the course of the tire pressure in a vehicle for example parking in the sun, wherein the tire pressure of the vehicle tire only changes slowly contingent on the small change of the ambient temperature. The area B represents the course of the tire pressure measured values in the vehicle tire during the drive, wherein a pressure change by the deformation of the tire when driving in bends or by driving over uneven ground is also superimposed on the temperature-induced pressure change. The area C represents a continuous pressure loss in the vehicle tire for example due to damage of the tire.
In the diagram illustrated in FIG. 3 b, the course III represents the standard deviation of the temporally successive, sensed tire pressure measured values, wherein by standard deviation of measured values the average deviation of the sensed measured values from the average of the measured values is understood. The course III, i.e. the standard deviation of the sensed tire pressure measured values, thus represents the tire pressure change dependent parameter derived from the sensed tire pressure measured values in the case illustrated in FIG. 3 b.
The course IV in FIG. 3 b represents the count of a counter, which is decremented beginning with a starting value, wherein in the present case the counter does not count in a linear manner, but the decrement changes depending on the count. This is achieved by weighting the counter by the application of a nonlinear function. A nonlinear function may for example be generated by the step response or the pulse response of a digital filter, e.g. a IIR (infinite impulse response) filter.
In the following, the flow of the inventive method for monitoring the tire pressure in the vehicle tire will be explained on the basis of FIGS. 3 a–b.
With each measurement of a tire pressure value that has taken place, the counter is decremented beginning with a starting value S, wherein the counter does count in a nonlinear manner in the present case. Therefrom results the exponentially falling course IV in FIG. 3 b. If the value of the counter reaches the tire pressure change dependent parameter, i.e. the standard deviation of the course of the tire pressure, the transmitting unit is activated to communicate the current tire pressure measured value to the receiving unit. As can be seen from the diagram in FIG. 3 b, in the area A simulating a vehicle parking in the sun, transmission of the tire pressure measured values is triggered with minimum frequency.
On the basis of FIGS. 4 a–c, the change in principle of the time distance and thus the frequency of the transmission of temporally successive tire pressure measured values is now again illustrated in summarized form.
With the present invention it is also possible to process temperature values of the gas volume in the vehicle tire. For example, the quotient from a sensed tire pressure measured value and a temperature measured value may be processed. This is advantageous in so far as, assuming that the volume of the tire does not change significantly, in all pressure changes contingent on temperature changes this quotient should not change, wherein taking the “ideal gas law” into account, p*V/T=const. applies, wherein p is the tire pressure, V the tire volume, and T the temperature.
Thereby, pressure change caused by gas loss or deformation of the tire may be discriminated from a superimposed temperature-induced change. Therefrom especially the standstill of the car may be derived, wherein in this state the transmission frequency may be reduced in an especially drastic manner. Also considering the average of this quotient over a period of time, it should be almost constant, unless gas escapes from the tire. This again represents the most important state to be sensed for a tire pressure sensor. It is to be noted that temperature measurement, however, does not have to be performed each time, so that the time interval for temperature measurement may be extended against tire pressure measurement (e.g. at ΔTmin ˜1s), e.g. 8s. The battery voltage measurement takes place in even longer time intervals, e.g. 64 seconds.
In the following, on the basis of FIGS. 5 a–c and FIG. 6, the inventive procedure will be explained, in which an instantaneous pressure dynamics state in a tire of a motor vehicle may be ascertained and classified from a number of preceding tire pressure measured values, wherein the temporal distance ΔTsend between successive transmission time instants of the tire pressure measured values and/or also the temporal distance ΔTmeas between successive detection time instants of the tire pressure measured values is adjusted depending on the ascertained instantaneous pressure dynamics state or the classification of the ascertained pressure dynamics state.
In the inventive procedure explained in detail following it is taken advantage of the fact that in the driving operation of a vehicle so-called “dynamic load redistributions” result, which lead to a change of the tire pressure in the vehicle tires, wherein high or low changes of the pressure course in a vehicle tire give rise to an increased or lower pressure dynamics state, respectively. When the vehicle is driven in a bend, for example, the outer vehicle wheels are loaded more strongly, so that consequently also the tire pressure in these vehicle tires increases, whereas the tire pressure in the vehicle tires of the relieved vehicle tires on the inside of the bend decreases. Comparable dynamic load redistributions in a vehicle also occur when breaking or accelerating the vehicle between the vehicle tires of the rear axle and the front axle. When breaking a vehicle, the vehicle tires of the front axle are usually more highly loaded, whereas when accelerating the vehicle, the driven axle(s) of the vehicle are more strongly loaded, and thus the tire pressure increases in these vehicle tires. Further tire pressure changes during the vehicle operation of a motor vehicle occur for example when driving over uneven ground.
H 11 ⁢ R1 ⁡ ( z ) = ( 1 - a 1 - a · z - 1 ) 2 ;
with the parameter a representing the constant determining the cut-off frequency of the 2nd order IIR filter.
H 11 ⁢ R2 ⁡ ( z ) = ( 1 - b 1 - b · z - 1 ) 2
wherein the constant b determines the cut-off frequency of this filter. In FIG. 5 c, the filtered deviation squares of the squared difference values of the pressure measured values are illustrated as course V in FIG. 5 c.
In the procedural step illustrated by the reference numeral 104 in flow chart 100, now the tire pressure dependent function parameter P1 is compared with a comparison threshold or a comparison value PV1 to decide whether high or low pressure dynamics states are present in the vehicle tire, i.e. in which driving situation the vehicle is. This comparison parameter PV1 is ascertained for example via a plurality of past sensed tire pressure measured values.
As illustrated in FIG. 5 c, the vehicle drives for about two hours (cf. course VI in FIG. 5 c), wherein the vehicle is again parked shortly before the time instant tb. This again leads to a classification change after the difference squares have fallen short of their average 256 times in a row. This again purely exemplarily chosen criterion leads to a classification change to the classification for low pressure dynamics states (non-operated state), so that the temporal distance between successive transmission time instants of the tire pressure measured values is again adjusted to the time interval ΔTsend1. A lower limit for the minimum value of the short-time average, which is still taken into account in the criterion, was adjusted to a value of 32 in the embodiment illustrated in FIG. 5 c.
It should be noted that with the change to the classification for low pressure dynamics states the average filter (IIR filter) for the difference squares is preferably again reset to a starting value representing the noise of the tire pressure sensor and electronics used for the measurement. This is required to avoid that with renewed driving away of the vehicle the tire pressure monitoring system remains in a classification for low pressure dynamics states unnecessarily long due to the still high short-time average of the difference squares.
US10/947,953 2002-03-25 2004-09-23 Tire pressure monitoring system Expired - Fee Related US7119670B2 (en)
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PCT/EP2003/003093 Continuation WO2003080371A2 (en) 2002-03-25 2003-03-25 Tyre pressure monitoring system
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US20050057348A1 US20050057348A1 (en) 2005-03-17
US7119670B2 true US7119670B2 (en) 2006-10-10
US10/947,953 Expired - Fee Related US7119670B2 (en) 2002-03-25 2004-09-23 Tire pressure monitoring system
US11/467,743 Expired - Fee Related US7511609B2 (en) 2002-03-25 2006-08-28 Tire pressure monitoring system
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Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE INVENTOR'S LAST NAME PREVIOUSLY RECORDED ON REEL 016025 FRAME 0726;ASSIGNOR:HAMMERSCHMIDT, DIRK;REEL/FRAME:017211/0286