air spring

Abstract

The present invention relates to an air spring (1) with a first, lower connection element (10), preferably a piston (10), with a second, upper connection element (2), preferably a cover (2) or flange plate (2), and with a bellows (11) which is airtightly connected along the vertical axis (Z) at one end to the first connection element (10) and at the other opposite end to the second connection element (2), wherein the first connection element (10), the second connection element (2) and the bellows (11) together enclose an internal volume (A) of the air spring (1) at least substantially.The air spring (1) is characterized by at least, preferably exactly, one radar sensor (6) which is arranged within the internal volume (A) of the air spring (1) on the second connection element (2) and is oriented downwards along the vertical axis (Z) towards the first connection element (10), at least, preferably exactly, three reflectors (12a, 12b, 12c) which are arranged in an equilateral triangle with a defined side length in a plane parallel to the surface of the first connection element (10) on the first connection element (10) in a manner that moves together with it, wherein the distance along the vertical axis (Z) between the radar sensor (6) and the first connection element (10) corresponds to the air spring height (h), or vice versa.

Description

[0001] The present invention relates to an air spring.

[0002] Depending on the application, various types of suspension systems can be used to dampen vibrations. These include air suspensions, which utilize the compressibility of gases, and especially air.

[0003] A common type of air suspension is the constant-volume air spring in its normal position. In this case, the air is typically enclosed in a rolling diaphragm, which is airtightly connected to other fittings, such as a cap or flanged plate and a rolling piston in road vehicles. The piston is connected to the lower end of the rolling diaphragm and, usually, to an axle in road vehicles or to the chassis in rail vehicles. The upper end of the rolling diaphragm is connected to a cap or flanged plate, which is attached to the vehicle body or chassis. In rail vehicles, the diaphragm is positioned between a sliding plate at the top and the piston at the bottom. Rolling diaphragm air springs are used in vehicles, while bellows air springs are used in stationary applications.

[0004] The rolling diaphragm is fitted over the piston and rolls along it under pressure. The air spring can be supplied with compressed air by a compressor, allowing air to be pumped in or out depending on the load, thus maintaining a constant air volume and therefore the vehicle's ride height. Such air springs are used in various types of vehicles, particularly road vehicles such as trucks, trailers, and buses, as well as rail vehicles.

[0005] During the operation of air-sprung systems, an electronic controller maintains the spring height—that is, the height of the air spring or the distance between the cap or flange plate and the piston—at its setpoint. For this, the electronic controller requires the actual value of the spring height as an input. In some applications, the angle between the connection elements or contact surfaces of the air spring is also an important input for control and monitoring.

[0006] Numerous methods are known for measuring spring height.

[0007] The angular offset can be determined using acceleration sensors mounted on the connection elements or surfaces. The equal components of the measured vertical accelerations correspond to the magnitudes of the respective surface normals, from which the angular offset can be calculated.

[0008] One disadvantage of this method is that two acceleration sensors are generally required. If a connection element or surface of the air spring is structurally located horizontally, one sensor suffices.

[0009] Alternatively, the angular misalignment between the connection elements or surfaces of an air spring can be measured directly. However, this requires at least three distance sensors to obtain a reliable result. While suitable sensors are available on the market, the cost and effort involved in integrating them into the air springs make this solution economically unattractive.

[0010] One object of the present invention is to provide an improved method for measuring height and angular offset in air springs of the type described above. This should be achieved in a way that is as simple, cost-effective, accurate, and / or compact as possible. At the very least, an alternative to known methods should be provided.

[0011] The problem is solved according to the invention by an air spring and by a vehicle with the features according to the independent claims. Advantageous embodiments are described in the dependent claims.

[0012] Thus, the present invention relates to an air spring with a first, lower connection element, preferably a piston, with a second, upper connection element, preferably a cover or flange plate, and with a bellows which is airtightly connected at one end along the vertical axis to the first connection element and at the other opposite end to the second connection element, wherein the first connection element, the second connection element and the bellows together enclose an internal volume of the air spring at least substantially.

[0013] The air spring according to the invention is characterized by at least, preferably exactly, one radar sensor, which is arranged within the inner volume of the air spring on the second connection element and is oriented downwards along the vertical axis towards the first connection element, and at least, preferably exactly, three reflectors, which are arranged in an equilateral triangle with a defined side length in a plane parallel to the surface of the first connection element and are movable together with the first connection element, wherein the distance along the vertical axis between the radar sensor and the first connection element corresponds to the air spring height, or vice versa.

[0014] This could be a way to determine, by means of a radar signal and its reflections on three geometrically defined reflectors on the opposite side of the inner volume of the air spring, its height and / or orientation relative to the side of the inner volume of the air spring where the radar sensor is located.

[0015] According to one aspect of the invention, the radar sensor is configured and set up to emit electromagnetic waves towards the reflectors, and the radar sensor is further configured and set up to continuously vary the frequency of the electromagnetic waves between a minimum and a maximum transmission frequency. Such a variation is also referred to as chirp modulation.

[0016] This could represent a concrete possibility for implementation.

[0017] According to another aspect of the invention, the radar sensor is further designed and configured to detect a portion of the emitted electromagnetic waves reflected back to the radar sensor by the reflectors.

[0018] This could represent a concrete possibility for implementation.

[0019] According to a further aspect of the invention, the air spring also has an evaluation and calculation unit which is designed and equipped, • to cause the radar sensor to emit electromagnetic waves, • to obtain a reflected portion of the emitted electromagnetic waves from the reflectors and • to determine the relative position between the first terminal element and the second terminal element based on the frequency shifts of the emitted electromagnetic waves and the received reflected parts of the emitted electromagnetic waves.

[0020] This could represent a concrete possibility for implementation.

[0021] According to a further aspect of the invention, a control unit of the air spring and / or an external control unit is designed and configured to regulate the spring height of the air spring based on the relative position between the first connecting element and the second connecting element.

[0022] This could represent a concrete possibility for implementation.

[0023] According to a further aspect of the invention, the evaluation and computing unit is designed and configured to determine the distance between the radar sensor and the reflectors from the frequency shifts by: • Backmixing of the received reflected portions of the emitted electromagnetic waves with the emitted electromagnetic waves, • Fourier transform of the mixed signal, • Calculation of signal propagation times and • Calculation of distances.

[0024] This could represent a concrete possibility for implementation.

[0025] According to another aspect of the invention, the radar sensor has an FMCW radar chip, preferably the radar sensor is an FMCW radar chip.

[0026] This could represent a concrete possibility for implementation.

[0027] According to another aspect of the invention, the radar sensor has a beam-shaped body, preferably a prism, facing the reflectors, which is designed to adapt the characteristics of the emitted electromagnetic waves to the geometry of the air spring, preferably the bellows.

[0028] This could represent a concrete possibility for implementation.

[0029] According to another aspect of the invention, the radar sensor is designed and configured to emit electromagnetic waves with a transmission frequency between 24 GHz and 130 GHz.

[0030] This could represent a concrete possibility for implementation.

[0031] The present invention also relates to a vehicle, preferably a road vehicle or a rail vehicle, with at least one air spring as described above. This can enable the implementation and use of air springs according to the invention in vehicles, particularly road vehicles and / or rail vehicles.

[0032] An exemplary embodiment and further advantages of the invention are explained below in connection with the following figures. These show: Fig. 1 a perspective schematic representation of an air spring according to the invention from an oblique front top view, partly as a section; Fig. 2 a perspective schematic representation of the arrangement of radar sensor and reflectors of the air spring according to the invention from an oblique front top view; Fig. 3 the representation of the Fig. 2 supplemented by an evaluation and processing unit as well as an external processing unit; and Fig. 4 an excerpt of the Fig. 1.

[0033] The above figures are described in Cartesian coordinates with a longitudinal axis X, a transverse axis Y perpendicular to the longitudinal axis X, and a vertical axis Z perpendicular to both the longitudinal axis X and the transverse axis Y, which corresponds to the direction of gravity. The longitudinal axis X can also be referred to as depth X, the transverse axis Y as width Y, and the vertical axis Z as height Z. The longitudinal axis X and the transverse axis Y together form the horizontal X, Y, which can also be referred to as the horizontal plane X, Y. The longitudinal axis X, the transverse axis Y, and the vertical axis Z together can also be referred to as the spatial directions X, Y, Z, or as the Cartesian spatial directions X, Y, Z.

[0034] The air spring 1 has a piston 10 as its first, lower connection element 10, which is mounted on a chassis (not shown) of a vehicle, such as a rail vehicle. At the upper end of the piston 10, a bellows 4 is radially and airtightly connected to the piston 10 on its outer side. In this embodiment, the bellows 4 is held airtight at its upper end by a cover 2 or a flanged plate 2 as the second, upper connection element 2, which is connected to a body (not shown) of the vehicle.

[0035] A volume of the air spring 1 is hermetically sealed by the bellows 4, the piston 10 and the cover 2, the volume of the air spring 1 being filled with compressed air, the compressed air being able to be released or filled or increased by means of a valve (not shown) in the cover 2 in order to change the height h of the air spring 1, i.e. the distance h between the cover 2 and the piston 10.

[0036] In the arrangement according to the invention, a commercially available, highly integrated FMCW radar chip 6 (Frequency Modulated Continuous Wave), as used in industry and automotive engineering, is located in the cover 2 of the air spring 1 as a radar sensor 6. A transmit / receive unit (not shown) of the FMCW radar chip 6 is oriented directly downwards along the vertical axis Z towards the inside of the piston 10, cf. Fig. 1 and Fig. 4. The distance along the vertical axis Z between the FMCW radar chip 6 and the piston 10 or its inner side corresponds to the distance h between the cover 2 and the piston 10 and thus to the height h of the air spring 1, the spring height h or the air spring height h.

[0037] An evaluation and calculation unit 7, see. Fig.3, determines the relative position between the cover 2 and the piston 10 of the air spring 1 from the data of the FMCW radar chip 6 and transmits the results via a standardized interface (not shown) to an external control unit 16 for controlling the position of the air spring 1.

[0038] The FMCW radar chip 6, or its transmit / receive unit, has integrated transmit and receive antennas (not shown) whose characteristics are adapted to the geometry of the air spring 4 by a suitable beamforming element 8, such as a prism. Depending on the desired spatial resolution, the FMCW radar chip 6 preferably operates at a transmit frequency between 24 GHz and 130 GHz.

[0039] Three reflectors 12a, 12b, 12c or resonators 12a, 12b, 12c are arranged on the piston 10 within the volume of the air spring 1 in an equilateral triangle with a defined side length (2*a). This triangle lies in a cross-sectional plane of the piston 10 in the horizontal X, Y parallel to one of the two connection elements 2, 10 or their connection surfaces of the air spring 1.

[0040] The FMCW radar chip 6 emits electromagnetic waves E during operation, the frequency of which the FMCW radar chip 6 continuously varies between a minimum and a maximum transmission frequency (chirp modulation). When the radar signal, in the form of one of the electromagnetic waves E, encounters the reflectors 12a, 12b, 12c, the radar signal is scattered by the reflectors 12a, 12b, 12c, and a portion of the radar signal returns to the transmit / receive unit of the FMCW radar chip 6.

[0041] Due to propagation delays, the frequencies of the received signals deviate from the time-varying transmitted frequency. From these frequency shifts, the FMCW radar chip 6 determines the spatial distance to the reflectors 12a, 12b, 12c by backmixing with the radar signal, Fourier transforming the mixed signal, and calculating the signal propagation delays and distances. Reference symbol list (part of the description) A Internal volume of the air spring 1 E electromagnetic waves h Air spring height, spring height or distance between the cover 2 and the piston 10 X Longitudinal axis; Depth Y transverse axis; width Z vertical axis; height X, Y Horizontal; horizontal plane 1 air spring 2. Second, upper connection element; cover or crimp plate 4 bellows 6 radar sensor; FMCW radar chip 7 Evaluation and calculation unit 8 beam-shaped bodies 10 First, lower connection element; piston or rolling piston 12a-12c Reflectors; Resonators 16 external control units

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