Procedure for checking the tire pressure of a vehicle

Abstract

Method for checking the tire pressure of a vehicle (1) which has at least one vehicle wheel (3) and a vehicle body (2) which is resiliently supported on the vehicle wheel (3), which comprises a tire (7) filled with gas and rests with the tire on a ground (8), characterized in that - the vehicle body (2) is loaded with an additional mass and is thereby excited to a mechanical vibration (16) relative to the ground (8) and - a response signal (A) characterising the mechanical vibration (16) is measured and analysed, whereby at least one response value (ω_max, F_max) characterising the current gas pressure in the tyre (7) is determined, - wherein the loading of the vehicle body (2) with the additional mass occurs when a person (13) gets into the vehicle (1) before the start of the journey and / or when the vehicle is stationary.

Description

[0001] The invention relates to a method for checking the tire pressure of a vehicle having at least one vehicle wheel and a vehicle body that is resiliently supported on the vehicle wheel, which comprises a tire filled with gas and rests with the tire on a ground.

[0002] Such a method is known from DE 100 44 128 A1. According to this method, the vehicle wheel is considered a separate spring-damper system characterized by a natural frequency. This spring-damper system is excited to oscillate after a single excitation.

[0003] If a motor vehicle is parked and stands still, it simply wears out due to aging. If the vehicle is to be used again, it is generally assumed that it will be in the same condition as it was when it was parked. However, if a foreign object has been driven into a tire, the tire may lose pressure. Although it should be clear before setting off whether the vehicle is drivable, drivers do not generally walk around the vehicle to check its condition. Even in the case of autonomous driving, it must be clear before setting off whether the vehicle is drivable or not, for example because tires have been punctured, tire valves are defective, foreign objects have penetrated the tires, or other tampering has occurred with the tires.

[0004] Based on this, the invention is based on the object of being able to check the tire pressure, preferably before starting a journey, in particular automatically.

[0005] This object is achieved by a method according to claim 1. Preferred developments of the method are given in the subclaims and in the following description.

[0006] The method mentioned at the outset for checking the tire pressure of a vehicle, which has at least one vehicle wheel and a vehicle body which is resiliently supported on the vehicle wheel, which comprises a tire filled with gas and rests with it on a surface, is further developed in particular in that - the vehicle body is loaded, preferably abruptly, with an additional mass and is thereby excited to a mechanical vibration, particularly vertical, relative to the ground and - a response signal characterising the mechanical vibration is measured and analysed, preferably automatically, whereby at least one response value characterising the current gas pressure in the tyre is determined.

[0007] The gas-filled tire forms an elastic element whose spring stiffness depends on the gas pressure in the tire. If the gas pressure in the tire is too low, the vehicle body oscillates, preferably in the vertical direction, at a different, for example lower, frequency than if the gas pressure in the tire were sufficient. In particular, the natural frequency of the vehicle body changes to a higher mode. Loading the vehicle body with the additional mass is preferably used to stimulate the vehicle body to oscillate and to detect its vibration behavior. It is advantageous to analyze before starting the journey whether there is too little or no gas pressure in the tire, especially without having to start the engine and / or move the vehicle.

[0008] The gas pressure in the tire corresponds in particular to the pressure of the gas in the tire. For example, the gas pressure is also referred to as tire pressure. Preferably, a preferably predefined reference pressure is assigned to the tire. The reference pressure corresponds to a gas pressure at which, in particular, roadworthiness exists. The gas is preferably air. In particular, the vehicle is a motor vehicle.

[0009] The loading of the vehicle body with the additional mass and the measuring and analysis of the response signal takes place before, preferably each start of a journey and / or when the vehicle is stationary. The method is advantageously carried out when the vehicle is stationary. The method is preferably carried out multiple times. The loading of the vehicle body with the additional mass takes place by a person getting into and / or sitting into the vehicle. The person is in particular a vehicle occupant and / or the driver. The additional mass is advantageously determined by the mass and / or weight of the person. The vehicle body is preferably resiliently supported on the vehicle wheel by means of one or at least one vehicle spring.

[0010] According to a further development, the vehicle comprises a passenger compartment. Preferably, at least one vehicle seat is provided in the passenger compartment. Entering and / or seating a person in the vehicle means, in particular, that the person enters the passenger compartment and / or sits down on the vehicle seat.

[0011] Preferably, a first-order resonance is determined by the mass of the vehicle body and the preferably vertical spring stiffness of the vehicle spring, which is, for example, a coil spring, in the preferably vertical mechanical vibration. The resonance frequency is generally in the low single-digit range, depending on the vehicle type, e.g., between 1 and 3 Hz. The preferably vertical spring stiffness of the tire is preferably one to two orders of magnitude higher than the preferably vertical spring stiffness of the vehicle spring. Thus, a higher order of resonance shift results, particularly at low gas pressure in the tire.

[0012] According to one embodiment, the at least one response value is compared with at least one, preferably predetermined, reference value, which is in particular assigned to the or a preferably predetermined reference pressure of the gas. By comparing the at least one response value with the at least one reference value, it can be determined, for example, whether or not the tire pressure is sufficient for roadworthiness. Preferably, the at least one reference value characterizes the or a reference pressure of the gas. In particular, the tire is roadworthy if the gas pressure corresponds to the reference pressure or does not deviate from the reference pressure beyond predetermined tolerance limits.

[0013] Preferably, the tire pressure and / or the roadworthiness of the tire is determined by comparing the at least one response value with the at least one reference value. Preferably, a difference and / or a difference between the at least one response value and the at least one reference value characterizes a deviation of the current gas pressure from the reference pressure and thus, in particular, the roadworthiness of the tire. Advantageously, the at least one response value characterizes the vibration behavior of the vehicle body and / or the tire, which is particularly dependent on the gas pressure. Preferably, the at least one reference value characterizes the vibration behavior of the vehicle body and / or the tire when the gas pressure corresponds to the reference pressure.

[0014] According to a further development, at reference pressure of the gas - the vehicle body is loaded, preferably abruptly, with an additional reference mass and thereby excited relative to the ground to a, in particular vertical, mechanical reference vibration and - a reference response signal characterizing the mechanical reference vibration is measured and analyzed, preferably automatically, thereby determining the at least one reference value. Preferably, the reference additional mass coincides with or approximately coincides with the additional mass.

[0015] Preferably, the at least one response value forms or comprises one or at least one frequency value, in particular characteristic of the vibration behavior of the vehicle body and / or the tire. Preferably, the at least one response value and / or the at least one frequency value characterizes one or at least one frequency characteristic of the vibration behavior of the vehicle body and / or the tire. Advantageously, the at least one response value and / or the at least one frequency value characterizes one or at least one natural frequency of the vehicle body and / or the tire. In this case, the or at least one frequency value forms, for example, one or at least one frequency eigenvalue.

[0016] The at least one reference value preferably forms or comprises one or at least one reference frequency value, in particular one characteristic of the vibration behavior of the vehicle body and / or the tire at a reference gas pressure. The at least one reference value and / or the at least one reference frequency value preferably characterizes one or at least one frequency characteristic of the vibration behavior of the vehicle body and / or the tire at a reference gas pressure. Advantageously, the at least one reference value and / or the at least one reference frequency value characterizes one or at least one natural frequency of the vehicle body and / or the tire at a reference gas pressure. In this case, the or at least one reference frequency value forms, for example, one or at least one reference frequency value.In particular, the vehicle body and / or the tire vibrates at a different frequency at reference gas pressure than when there is no gas pressure, too low gas pressure, or a different gas pressure.

[0017] According to one embodiment, during the analysis of the response signal, the response signal or a signal derived therefrom is transformed into the frequency domain. Preferably, during the analysis of the response signal, the response signal or the signal or a signal derived therefrom is transformed into the frequency domain by Fourier transformation or by discrete Fourier transformation (DFT). The discrete Fourier transformation is, in particular, a fast Fourier transformation (FFT).

[0018] The at least one response value preferably forms or comprises one or at least one value from the spectrum of the response signal. The at least one response value is preferably assigned to one or at least one, in particular relative or absolute, maximum in the spectrum of the response signal. Advantageously, the at least one response value forms or comprises one or at least one amplitude value in the spectrum of the response signal, which is preferably assigned to the or at least one maximum. Additionally or alternatively, the at least one response value forms or comprises, for example, one or at least one frequency value in the spectrum of the response signal, which is preferably assigned to the or at least one maximum.

[0019] According to one embodiment, the at least one response value comprises a plurality of response values. Furthermore, the at least one, in particular predefined, reference value preferably comprises a plurality of, in particular predefined, reference values. In this case, the comparison of the at least one response value with the at least one reference value takes place in particular by comparing the response values ​​with the at least one reference value or with the reference values. The tire pressure and / or the roadworthiness of the tire is preferably determined by comparing at least one of the response values ​​with the at least one reference value or with at least one of the reference values.In particular, the or a difference and / or the or a difference between at least one of the response values ​​and the at least one reference value or at least one of the reference values ​​characterizes a deviation of the current gas pressure from the reference pressure and thus in particular the roadworthiness of the tire.

[0020] According to a further development, the at least one response value and / or the response values ​​form or comprise one or more response value tuples, each of which comprises a frequency value and an amplitude value associated therewith from the spectrum of the response signal. Preferably, the or each response value tuple and / or its values ​​represent a, in particular relative or absolute, maximum in the spectrum of the response signal. Advantageously, the frequency value of the or each response value tuple represents one or at least one natural frequency of the vehicle body and / or the tire. The or each response value tuple is preferably a 2-tuple and is also referred to, for example, as a response value pair.

[0021] According to one embodiment, the at least one reference value and / or the reference values ​​form or comprise one or at least one reference value tuple. The at least one reference value and / or the or the at least one reference value tuple comprises in particular a frequency value and an amplitude value assigned thereto. The frequency value of the at least one reference value and / or of the or the at least one reference value tuple is also referred to, for example, as a reference frequency value. Furthermore, the amplitude value of the at least one reference value and / or of the or the at least one reference value tuple is also referred to, for example, as a reference amplitude value. The frequency value and the amplitude value of the at least one reference value and / or of the or the at least one reference value tuple form, in particular, values ​​from the or a spectrum of the reference response signal.

[0022] Preferably, the or at least one reference value tuple and / or its values ​​represent one or at least one, in particular relative or absolute, maximum in the spectrum of the reference response signal. Advantageously, the frequency value of the or at least one reference value tuple represents one or at least one natural frequency of the vehicle body and / or the tire at the reference gas pressure. The or at least one reference value tuple is preferably a 2-tuple and is also referred to, for example, as a reference value pair.

[0023] According to a further development, in order to compare the at least one response value with the at least one reference value and / or to compare the response values ​​with the reference values, the amplitude value of the reference value tuple is compared with the amplitude value of the or one of the response value tuples. In particular, in order to compare the at least one response value with the at least one reference value and / or to compare the response values ​​with the reference values, the amplitude value of the reference value tuple is compared with the amplitude value of the or one of the response value tuples whose frequency value matches or approximately matches the frequency value of the reference value tuple and / or, for example, has a deviation from its frequency value that lies within predetermined tolerance limits. The tolerance limits take into account, for example, a frequency deviation due to measurement errors or measurement inaccuracies and / or due to disturbances and / or due to wear.Within the tolerance limits, the frequency value of the response value tuple particularly matches or approximately matches the frequency value of the reference value tuple. Preferably, the difference and / or the difference between the two compared amplitude values ​​characterizes a deviation of the current gas pressure from the reference pressure and thus, in particular, the roadworthiness of the tire.

[0024] According to one embodiment, to compare the at least one response value with the at least one reference value and / or to compare the response values ​​with the reference values, the frequency value of the reference value tuple is compared with the frequency value of the or one of the response value tuples. The difference and / or the difference between the two compared frequency values ​​preferably characterizes a deviation of the current gas pressure from the reference pressure and thus, in particular, the roadworthiness of the tire.

[0025] According to one embodiment, one or at least one sensor is provided on the vehicle body, by means of which the response signal, in particular characterizing the mechanical vibration, can be measured or is measured. The or at least one sensor forms or comprises, for example, one or at least one acceleration sensor and / or one or at least one force sensor and / or one or at least one displacement sensor, which is preferably a height level sensor. The or a signal supplied by the acceleration sensor forms, for example, the response signal. Preferably, the response signal represents and / or characterizes accelerations occurring on the vehicle body, in particular due to the mechanical vibration. Advantageously, the signal supplied by the acceleration sensor is an electrical signal. The or a signal supplied by the force sensor forms, for example, the response signal.The response signal preferably represents and / or characterizes forces occurring on the vehicle body, in particular due to mechanical vibration. The signal supplied by the force sensor is advantageously an electrical signal. The signal or a signal supplied by the displacement sensor is preferably derived twice over time. The signal from the displacement sensor, derived twice over time, forms, for example, the response signal. The response signal preferably represents and / or characterizes accelerations occurring on the vehicle body, in particular due to mechanical vibration. The signal supplied by the displacement sensor is advantageously an electrical signal. In particular, the signal from the displacement sensor, derived twice over time, is an electrical signal.

[0026] The invention is described below using a preferred embodiment with reference to the drawing. In the drawing: Fig. 1 a schematic representation of a vehicle with tires and Fig. 2 is a schematic diagram illustrating a method for checking tire pressure according to an embodiment.

[0027] Out of Fig. Figure 1 shows a schematic representation of a vehicle 1 with a vehicle body (body) 2 and a plurality of vehicle wheels 3, each having a rim 6 mounted on a wheel carrier 4 for rotation about a wheel rotation axis 5, and a tire 7 surrounding the rim 6, resting on a base 8 and filled with a gas, which is preferably air. The vehicle body 2 is resiliently supported on the wheel carriers 4 by means of vehicle springs 9. The vehicle body 2 also has a passenger compartment 10 and a vehicle door 11, by means of which access to the passenger compartment 10 can be released. The vehicle 1 is assigned a vehicle longitudinal direction x, a vehicle transverse direction y, and a vehicle vertical direction z, wherein these directions x, y, and z are schematically represented by a coordinate system. Furthermore, an arrow 12 indicates the usual forward direction of travel of the vehicle 1, which runs in particular in the vehicle longitudinal direction x.

[0028] In Fig. 1, a person 13, also referred to as a vehicle occupant, can be seen in the passenger compartment 10. In particular, person 13 is the driver of vehicle 1. When person 13 enters the passenger compartment 10, the total weight of the vehicle body 2 increases suddenly, since the body weight of person 13 is added to the weight of the vehicle body 2. The vehicle spring 9 is thereby suddenly compressed, causing the vehicle body 2 to undergo a mechanical oscillation in the vehicle's vertical direction z, which, according to the embodiment, corresponds in particular to the vertical direction.A response signal characterizing the vibration of the vehicle body 2 is measured by an acceleration sensor 14, which is provided on the vehicle body 2 and connected to a computing unit 15, by means of which at least one response value characterizing the vibration behavior of the vehicle body 2 is determined from the response signal and compared with at least one reference value that characterizes a corresponding vibration at a reference pressure of the gas in the tire 7. If the at least one response value agrees with the at least one reference value within predetermined tolerance limits, it can be concluded that the gas pressure in the tire corresponds to the reference pressure, so that the tire 7 is roadworthy.If, however, the at least one response value deviates from the at least one reference value beyond these tolerance limits, it can be concluded that the gas pressure in the tire does not correspond to the reference pressure, so that the tire 7 is, in particular, not roadworthy. The at least one response value is preferably determined in the frequency domain. For this purpose, the response signal is transformed into the frequency domain, preferably using a discrete Fourier transformation, and the at least one response value is determined from the spectrum of the response signal. This is described with reference to . Fig. 2 is explained in more detail.

[0029] In Fig.In Figure 2, the tire 7 is schematically depicted as a spring between the rim 6 and the ground 8. When the person 13 enters the passenger compartment 10, an excitation signal S in the form of a jump is introduced into the vehicle body 2, which excites the vehicle body 2 to a mechanical oscillation, indicated by the double arrow 16. The response signal A, or a response signal characterizing the oscillation, is measured by the acceleration sensor 14 and fed to the computing unit 15, which has a transformation unit 17, by means of which the response signal A is transformed into the frequency domain by a, in particular discrete, Fourier transformation.The transformed response signal F describes a spectrum (frequency spectrum) and is fed to an evaluation unit 18, by means of which at least one maximum of the spectrum is determined and the associated values, which form response values ​​characterizing the oscillation, are determined in the form of at least one frequency value ω_max and at least one amplitude value F_max. The response values ​​thus form or comprise at least one response value tuple, which comprises a frequency value and an amplitude value. In this case, the response value tuple comprises, in particular, the frequency value ω_max and the amplitude value F_max. The computing unit 15 has access to a memory unit 19 in which reference values ​​are stored, which comprise at least one reference frequency value ω_ref and at least one reference amplitude value F_ref and characterize the oscillation at the reference pressure of the gas.The reference values ​​thus form or comprise at least one reference value tuple, which comprises a frequency value and an amplitude value. In this case, the reference value tuple comprises, in particular, the frequency value ω_ref and the amplitude value F_ref. The response values ​​ω_max and F_max as well as the reference values ​​ω_ref and F_ref are fed to a comparison unit 20 and compared with each other, after which the determined comparison result V is output, which characterizes a deviation of the current gas pressure from the reference pressure. Reference symbol 1 vehicle 2 Vehicle body 3 vehicle wheel 4 wheel carriers 5 Wheel rotation axis 6 rim 7 tires 8 Underground 9 Vehicle spring 10 passenger compartment 11 Vehicle door 12 Direction of travel 13 Person / Vehicle Occupant 14 Accelerometer 15 computing unit 16 Vibration 17 Transformation Unit 18 Evaluation unit 19 Storage unit 20 comparison unit x Vehicle longitudinal direction y vehicle transverse direction z Vehicle vertical direction A response signal V Comparison result

Claims

[1] Method for checking the tire pressure of a vehicle (1) which has at least one vehicle wheel (3) and a vehicle body (2) which is resiliently supported on the vehicle wheel (3) which comprises a gas-filled tire (7) and rests with it on a surface (8), characterized by , that - the vehicle body (2) is loaded with an additional mass and is thereby excited to a mechanical vibration (16) relative to the ground (8) and - a response signal (A) characterizing the mechanical vibration (16) is measured and analyzed, whereby at least one response value (ω_max, F_max) characterizing the current gas pressure in the tire (7) is determined, - wherein the loading of the vehicle body (2) with the additional mass is carried out by a person (13) entering the vehicle (1) before the start of the journey and / or when the vehicle is stationary. [2] Method according to claim 1, characterized by, that at least one response value (ω_max, F_max) is compared with at least one predefined reference value (ω_ref, F_ref) which is assigned to a reference pressure of the gas. [3] Method according to claim 2, characterized by , that a difference (V) between the at least one response value (ω_max, F_max) and the at least one reference value (ω_ref, F_ref) characterizes a deviation of the current gas pressure from the reference pressure. [4] Method according to claim 2 or 3, characterized by , that at least one reference value (ω_ref, F_ref) characterizes the vibration behavior of the vehicle body (2) at reference pressure of the gas. [5] Method according to any one of claims 2 to 4, characterized by , that at the reference pressure of the gas - the vehicle body (2) is loaded with a reference additional mass and is thereby excited to a mechanical reference vibration relative to the ground and - a reference response signal characterizing the mechanical reference oscillation is measured and analyzed, thereby determining at least one reference value (ω_ref, F_ref). [6] Method according to any of the preceding claims, characterized by , that in the analysis of the response signal (A) the response signal (A) or a signal derived from it is transformed into the frequency domain and the at least one response value (w_max, F_max) forms at least one value from the spectrum of the response signal (A). [7] Method according to claim 6, characterized by , that at least one response value (ω_max, F_max) is assigned to at least one maximum in the spectrum of the response signal (A). [8] Method according to claim 6 or 7, characterized by , that at least one response value (F_max) includes an amplitude value in the spectrum of the response signal (A) and / or at least one frequency value (F_max) in the spectrum of the response signal (A). [9] Method according to any of the preceding claims, characterized by , that at least one acceleration sensor (17) is provided on the vehicle body, by means of which the response signal (A) is measured, which represents accelerations occurring on the vehicle body (2).

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