Delivery device for positioning a structure-borne sound sensor on a test object, test bench for detecting structure-borne sound from a test object, and method for determining the structure-borne sound characteristics of a test object

Abstract

The invention relates to a delivery device (110) for delivering a structure-borne sound sensor (140) to a test specimen (200), wherein the delivery device (110) has a sensor receptacle (130) for receiving the structure-borne sound sensor (140), the sensor receptacle (130) having a vibration decoupling element (133), the vibration decoupling element (133) being configured to absorb vibrations of the delivery device (110) so that these cannot be transmitted to the structure-borne sound sensor (140). The delivery device (110) according to the invention is characterized in that the sensor receptacle (130) further comprises an additional mass element (132), the additional mass element (132) being configured to shift a natural frequency of the sensor receptacle (130) to a frequency range of less than 20 Hz. The invention further relates to a corresponding test rig and a corresponding method.

Description

[0001] The invention relates to a delivery device for delivering a structure-borne sound sensor to a test object according to the preamble of claim 1, a test stand for detecting structure-borne sound from a test object according to the preamble of claim 8 and a corresponding method.

[0002] Transmission test benches or powertrain test benches for testing motor vehicle transmissions or complete motor vehicle powertrains are known from the prior art. Such test benches are typically used for quality control to detect malfunctions in powertrains at an early stage through a series of load tests. Typical malfunctions arise, for example, from components with play, such as gears, synchronizer rings, synchronizer bodies, multi-plate clutch discs, and shafts, which can be deflected and excited into vibrations. During such functional testing, the acoustic behavior and shift quality are also usually checked. Furthermore, such test benches are also used in the development and continuous improvement of motor vehicle powertrains.

[0003] In this context, DE 101 23 545 A1 describes a sensor system for the quality inspection of mass-produced goods using a structure-borne sound sensor. The structure-borne sound sensor is attached to a component of the test rig, to which the structure-borne sound of the test specimen can be reproduced and transmitted with minimal loss of quality.

[0004] DE 10 2015 220 986 A1 discloses a test rig with an output shaft sensor comprising a base structure and a coupling element for connecting the output shaft sensor to an output shaft of a vehicle. The test rig further comprises recording means for capturing sound or structure-borne sound, as well as analysis means for analyzing the captured sound or structure-borne sound.

[0005] From US patent 2008 / 0271538A1, a method and a device for evaluating the NVH (noise, vibration, and harshness) characteristics of a mechanical system are known. The system comprises a torque transmission assembly with drive and driven elements that are engaged with each other. The method includes measuring a parameter that represents the NVH characteristics of the mechanical system during its operation in a predetermined test cycle in order to obtain at least one NVH characteristic.

[0006] German patent DE 10 2020 122 011 A1 describes a method for testing transmissions, in particular vehicle transmissions, which comprises the following steps: arranging a transmission on or at a test bench, operating the transmission via an electric machine, and sensing the drive to analyze transmission characteristics. Further process steps include recording vibrations or noise from the drive and performing a frequency or order analysis to analyze the transmission characteristics.

[0007] DE 203 20 424 U1 discloses a measuring device for detecting structure-borne sound emissions from a test object. The measuring device comprises a movable support section with an elastically mounted structure-borne sound sensor, which is decoupled from the support section when placed on the test object. Decoupling is achieved by an elastic cushion anchored to one side of the support section, in which the structure-borne sound sensor is mounted. The support section is designed as a linear actuator or a rotary actuator.

[0008] From JP 2011 - 13 176 A it is known to choose the weight of a vibration sensor such that the natural frequency lies outside the range to be measured with the sensor.

[0009] DE 196 21 213 C2 describes a delivery device with a sensor receptacle, wherein the sensor receptacle has a spring which is suitable to absorb vibrations of the delivery device.

[0010] However, conventional vehicle test benches have a disadvantage in that the structure-borne sound sensor used is often insufficiently decoupled from frequencies in comparatively low frequency ranges. This can lead to excitations from the test setup being transmitted to the structure-borne sound sensor, particularly when testing electric drives and axles, and thus distorting the measurement result.

[0011] It is an object of the present invention to propose an improved test bench for a powertrain of a motor vehicle.

[0012] This problem is solved according to the invention by the test bench for a motor vehicle drive train according to claim 8. Advantageous embodiments are described in the dependent claims.

[0013] The invention relates to a delivery device for delivering a structure-borne sound sensor to a test specimen, wherein the delivery device has a sensor receptacle for receiving the structure-borne sound sensor. The sensor receptacle in turn comprises a vibration decoupling element designed to absorb vibrations of the delivery device so that these cannot be transmitted to the structure-borne sound sensor.

[0014] The invention therefore describes a delivery device, in particular a delivery device for a test bench, for delivering a structure-borne sound sensor to a test object which is clamped in the test bench for the testing process.

[0015] The delivery device includes a sensor receptacle for the structure-borne sound sensor. The sensor receptacle is designed to hold the sensor securely against the test specimen during the testing process, while simultaneously ensuring it is held firmly and with minimal vibration damping. For example, the sensor can be inserted, clamped, or screwed into the sensor receptacle. A positive-locking connection between the sensor and the sensor is also possible.

[0016] Furthermore, the sensor mount preferably also includes electrical contact means, for example a socket or a plug, to electrically contact the structure-borne sound sensor, supply it with the necessary electrical energy, and read out the measured values. The structure-borne sound sensor can, in particular, have a corresponding socket or plug.

[0017] The delivery device can, for example, be designed as a linear drive which moves the structure-borne sound sensor along a defined axis to the test object and places it against it or removes it from it.

[0018] The sensor mount itself features a vibration decoupling element designed to absorb structure-borne sound vibrations occurring in the delivery device, thus preventing or significantly reducing their transmission to the structure-borne sound sensor. This ensures that the sensor primarily detects structure-borne sound vibrations of the test specimen, thereby improving the quality of the measured values.

[0019] For this purpose, the vibration decoupling element is advantageously designed to be comparatively soft and elastic, so that in particular medium and high frequencies cannot be transmitted via the vibration decoupling element.

[0020] Preferably, the sensor mount also includes a base body on which the vibration decoupling element is arranged. The structure-borne sound sensor is also advantageously arranged on the base body. The base body can advantageously form the core element of the sensor mount, on which further components can be arranged.

[0021] Advantageously, the main body is made of steel or a relatively hard plastic.

[0022] According to the invention, the sensor mount further comprises an additional mass element designed to shift the natural frequency of the sensor mount to a frequency range of less than 20 Hz, in particular less than 10 Hz.

[0023] This results in the advantage that low-frequency excitations, which despite the effect of the vibration decoupling element from the delivery device to the sensor mount, are strongly dampened due to the additional mass of the additional mass element.

[0024] The additional mass element is an extra mass, selected according to the specific application, which is arranged on the sensor mount. By appropriately choosing the size of the additional mass, the vibration behavior of the sensor mount can be influenced in such a way that the frequency range of the respective test specimen to be recorded during a test procedure is not superimposed on natural vibrations of the sensor mount or the structure-borne sound sensor.

[0025] In other words, the additional mass element leads to a detuning of the vibration behavior of the sensor mount, so that a natural frequency of the sensor mount is shifted into the frequency range of less than 20 Hz, in particular less than 10 Hz.

[0026] The invention thus offers the advantage that a test procedure for recording the structure-borne sound behavior of a test specimen can be carried out almost free from structure-borne sound vibrations of the test bench or the delivery device that would otherwise interfere with the test procedure. For this purpose, the sensor mount combines the described vibration decoupling element for avoiding or reducing medium and high frequencies with the described additional mass element for damping low frequencies. This allows the interference of a large proportion of the structure-borne sound vibrations occurring in the test bench and the delivery device to be avoided or reduced.

[0027] The additional mass element advantageously has such a high mass that frequencies below 10 Hz in particular are dampened by it.

[0028] As has been shown, the delivery device according to the invention can reduce the maximum amplitude of the structure-borne sound vibrations still occurring at the structure-borne sound sensor to less than 0.5 µm, which enables very accurate structure-borne sound measurements on the test specimen.

[0029] According to an advantageous embodiment of the invention, the delivery device is designed as a robot arm. A robot arm is comparatively flexible and can also perform complex movements, so that the structure-borne sound sensor can also be applied to surfaces of the test specimen that would not be accessible by a purely linear approach.

[0030] However, due to its design with arm segments and joints arranged one behind the other, a robot arm is also relatively easy to induce vibrations. In particular, vibrations from the test stand can be transmitted to the robot arm via its base, which is usually located on the test stand.

[0031] As described, the robot arm typically has several joints and rigid arm segments. The robot arm is fixed to the test stand via a base. The structure-borne sound sensor is attached to its rigid arm segment furthest from the test stand. Even structure-borne sound vibrations with a comparatively low amplitude, which are prevalent in the test stand, can be amplified by the robot arm – at least without further measures – and appear at the structure-borne sound sensor with a significantly increased amplitude.

[0032] The use of the delivery device according to the invention thus leads to particular advantages, especially when designed as a robot arm.

[0033] According to a further advantageous embodiment of the invention, the vibration decoupling element is made of a soft plastic. This soft plastic can be, for example, a foam or a rubber. This ensures that, in particular, structure-borne sound vibrations exceeding a predetermined frequency are not transmitted to the structure-borne sound sensor via the vibration decoupling element. The softer the plastic, the lower the frequency at which structure-borne sound vibrations are only reduced or not transmitted at all.

[0034] According to a further advantageous embodiment of the invention, the additional mass element is made of metal. Metals typically have a comparatively high density, so that only a relatively small volume is required to provide the necessary additional mass. This additional mass allows, in particular, the efficient damping of low frequencies of structure-borne sound vibrations.

[0035] By combining the vibration decoupling element with the additional mass element, it is advantageously possible to efficiently dampen both high-frequency and low-frequency vibrations or to prevent their transmission to the structure-borne sound sensor.

[0036] According to a particularly advantageous embodiment of the invention, the additional mass element is made of tungsten or a tungsten alloy. Tungsten is a metal with a comparatively very high density. Thus, a high mass can be provided in a small volume.

[0037] This facilitates a compact design of the sensor mount or delivery device without adversely affecting its effectiveness.

[0038] According to a further advantageous embodiment of the invention, the sensor mount is connected to the delivery device exclusively via the vibration decoupling element. This has the advantage that only low-frequency structure-borne sound vibrations can be transmitted to the sensor mount. These vibrations, which are nevertheless transmitted, are then effectively dampened by the additional mass element.

[0039] In particular, the sensor mount is not also connected to the delivery device via the additional mass element. This would result in the vibration decoupling element and the additional mass element being connected in series, forming a oscillating arm which, due to its axial length alone, would lead to a comparatively large, undesirable vibration amplitude at the structure-borne sound sensor.

[0040] According to a further advantageous embodiment of the invention, the additional mass element is connected exclusively to the sensor receptacle. Thus, there is no mechanical connection between the additional mass element and the delivery device. This means that structure-borne sound vibrations from the delivery device can only be transmitted to the sensor receptacle via the vibration decoupling element. However, since this element is relatively soft, only low-frequency structure-borne sound vibrations can be transmitted. These vibrations are then damped at the sensor receptacle by the additional mass element.

[0041] Furthermore, the formation of a swing arm from the vibration decoupling element and the additional mass element is avoided. Instead, the vibration decoupling element and the additional mass element are advantageously arranged next to each other with the smallest possible radial distance between them.

[0042] Advantageously, both the vibration decoupling element and the additional mass element are arranged on the base body of the sensor mount.

[0043] It is particularly preferred that the central axis of the vibration decoupling element be radially spaced no more than 50 mm from the central axis of the additional mass element.

[0044] The invention further relates to a test rig for detecting structure-borne sound from a test specimen. The test rig according to the invention is characterized by the fact that it comprises at least one delivery device according to the invention. Thus, the advantages already described also apply to the test rig according to the invention.

[0045] According to a preferred embodiment of the invention, the test bench is designed as a test bench for an electric vehicle powertrain. The electric vehicle powertrain constitutes the test specimen. Compared to conventional vehicle powertrains, electric vehicle powertrains are relatively quiet and run smoothly. Even structure-borne vibrations with only small amplitudes can therefore be clearly perceived by a driver of a vehicle with an electric vehicle powertrain and be considered disturbing.

[0046] According to a further preferred embodiment of the invention, the test bench is provided with a drive for powering the test specimen. This makes it possible to test even an electric vehicle powertrain that is not yet fully assembled, since it does not need its own electric motor drive for the test procedure. Rather, the electric vehicle powertrain can initially be tested without its own electric motor drive. For this purpose, the drive of the test bench is preferably coupled to a transmission input shaft of the test specimen. This enables controlled drive of the test specimen, for example at specific speeds or with specific torques. Provided that the test specimen meets the given requirements regarding its structure-borne noise behavior, the electric motor drive intended for the electric vehicle powertrain can then be installed.

[0047] Finally, the invention also relates to a method for determining the structure-borne sound characteristics of a test specimen on a test rig according to the invention. The method according to the invention is characterized in that a first structure-borne sound measurement is carried out while the drive of the test rig is at a standstill and with the structure-borne sound sensor spaced away from the test specimen, a second structure-borne sound measurement is carried out while the drive of the test rig is in operation and with the structure-borne sound sensor spaced away from the test specimen, and a third structure-borne sound measurement is carried out while the drive of the test rig is in operation and with the structure-borne sound sensor in contact with the test specimen.

[0048] Since the first and second structure-borne sound measurements are performed with a structure-borne sound sensor spaced away from the test specimen, only characteristic properties of the test rig and its environment are measured. In particular, properties of the mechanical coupling between the test rig, the feed device, and the sensor mount with the structure-borne sound sensor are also recorded.

[0049] Preferably, the first structure-borne sound measurement with the drive at standstill primarily reveals environmental influences, such as structure-borne sound vibrations of the building in which the test rig is located.

[0050] The second structure-borne sound measurement shows additional resonances compared to the first structure-borne sound measurement, which are generated in particular by an imbalance in the drive of the test bench, for example by an unequal winding of a rotor of an electric motor drive.

[0051] Only the third structure-borne sound measurement then captures the actual structure-borne sound vibrations occurring on the test object.

[0052] By comparing the third structure-borne sound measurement with the second and the first structure-borne sound measurement, the influences or resonances in the third structure-borne sound measurement that do not originate from the test object can then be identified and eliminated from the measured values.

[0053] The first and second structure-borne sound measurements thus represent reference measurements for the third structure-borne sound measurement.

[0054] The test object is preferably an electric vehicle powertrain.

[0055] In the context of the invention, the structure-borne sound characteristic of the test specimen is understood to be the characteristic vibration behavior of the test specimen, in particular the frequency positions of its natural resonances and their amplitudes during testing.

[0056] The invention is explained below by way of example with reference to embodiments shown in the figures.

[0057] They show: Fig. 1. An exemplary and schematic test rig according to the invention for detecting structure-borne sound from a test specimen, Fig. 2. An exemplary and schematic embodiment of a test rig according to the invention for detecting structure-borne sound from a test specimen and Fig. 3. An exemplary embodiment of the inventive method for determining a structure-borne sound characteristic of a test specimen on a test rig according to the invention is shown in the form of a flowchart.

[0058] Identical objects, functional units, and comparable components are designated across all figures using the same reference symbols. These objects, functional units, and comparable components are identical in their technical characteristics unless explicitly or implicitly stated otherwise in the description.

[0059] Fig. Figure 1 shows, by way of example and schematically, a test rig 100 according to the invention for detecting structure-borne sound of a test object 200. The test object 200 is, by way of example, an electric vehicle powertrain, namely an electrically driven axle.

[0060] The test rig 100 includes, for example, a delivery device designed as a robot arm 110 for delivering a structure-borne sound sensor 140, which is divided into three arm segments 111, 112, 113 connected in series.

[0061] The robot arm 110 is mechanically connected to a base 120 of the test stand 100 via arm segment 111. A sensor receptacle 130 according to the invention for receiving the structure-borne sound sensor 140 is arranged on arm segment 113, which is furthest from the base 120 of the test stand 100.

[0062] Inevitably, every mechanical transition – from the base 120 to the arm segment 111, from the arm segment 111 to the arm segment 112, from the arm segment 112 to the arm segment 113, and from the arm segment 113 to the sensor mount 130 – exhibits both damping 150, 151, 152, 153 and stiffness 160, 161, 162, 163 (each shown schematically in Fig. 1).

[0063] These damping values ​​150, 151, 152, 153 and stiffness values ​​160, 161, 162, 163 determine the transferability of structure-borne sound vibrations from the base 120 to the structure-borne sound sensor 140 and thus influence the quality of the measurement data recorded by the structure-borne sound sensor 140 during a test procedure.

[0064] Depending on the amplitude and frequency of the transmitted structure-borne sound vibrations, these can significantly impair the quality of the measurement data recorded by the structure-borne sound sensor 140 during a test procedure and may render it unusable.

[0065] To ensure sufficient decoupling of the structure-borne sound sensor 140 from the base 120 and the robot arm 110, the sensor mount 130 has a vibration decoupling element 133 designed to absorb vibrations of the feed device 110 so that these cannot be transmitted to the structure-borne sound sensor 140. The vibration decoupling element 133 is, for example, made of a soft plastic and exhibits both damping 153 and stiffness 163. The use of soft plastic ensures a very gentle connection between the structure-borne sound sensor 140 and the feed device 110. In particular, high structure-borne sound frequencies can thus only be transmitted to the structure-borne sound sensor 140 to a limited extent from the test stand 100 via the feed device 110 and the sensor mount 130.

[0066] To further improve the vibration characteristics, the sensor receptacle 130 of the delivery device 110 according to the invention additionally has an additional mass element 132, which provides the sensor receptacle 130 with additional mass.

[0067] For example, the additional mass element 132 is made of metal, namely tungsten. Tungsten has a comparatively high density, so that even with small dimensions of the additional mass element 132, a high additional mass can be provided.

[0068] Both the vibration decoupling element 133 and the additional mass element 132 are arranged on a base body 131 of the sensor receptacle 130.

[0069] According to the exemplary embodiment of the Fig. 1 The additional mass element 132 is designed to shift a natural frequency of the sensor mount 130 into a frequency range of about 15 Hz.

[0070] By connecting the sensor mount 130 to the feed device 110 exclusively via the vibration decoupling element 133, structure-borne sound vibrations with a comparatively high frequency are transmitted to the sensor mount 130 only to a very limited extent. The vibrations that are nevertheless transmitted are subsequently damped by the additional mass element 132. For this purpose, the additional mass element 132 is connected exclusively to the sensor mount 130, but not to the feed device 110.

[0071] Fig. Figure 2 shows, by way of example and schematically, another possible embodiment of a test rig 100 according to the invention for detecting structure-borne sound from a test specimen 200 (not shown in Figure 2). Fig. 2).

[0072] For example, the test rig 100 comprises two positioning devices 110 according to the invention, so that two structure-borne sound sensors 140 can be positioned on the test specimen 200 during a test operation. This enables, for example, the detection of structure-borne sound vibrations at different positions of the test specimen 200.

[0073] Furthermore, the test stand 100 includes two electromechanical drives 170, which are designed to apply different torques and speeds to the test specimen 200 during the test operation.

[0074] The test bench 100 of the Fig. 2 is trained to test 200 electric vehicle powertrains.

[0075] Fig. Figure 3 shows an exemplary embodiment of the inventive method for determining a structure-borne sound characteristic of a test specimen on a test rig 100 according to the invention in the form of a flowchart.

[0076] In a first process step 300, an initial structure-borne sound measurement is carried out while a drive 170 of the test rig 100 is stationary and with a structure-borne sound sensor 140 spaced away from the test specimen 200. In this process, only structure-borne sound vibrations that act on the test rig 100 and in particular on the structure-borne sound sensor 140 from the environment are recorded.

[0077] In a second process step 310, a second structure-borne sound measurement is then carried out during the operation of the drive 170 of the test stand 100 and with a structure-borne sound sensor 140 spaced apart from the test specimen 200. Here, structure-borne sound vibrations resulting from the operation of the drive 170 are primarily recorded, for example due to imbalances of the rotor of the electric motor drive 170.

[0078] In a third process step 320, the measured values ​​recorded in the first process step 300 and the measured values ​​recorded in the second process step 310 are processed into a reference data set which describes the structure-borne sound behavior of the test bench and its environment.

[0079] In a fourth process step 330, a third structure-borne sound measurement is finally carried out during the operation of the drive 170 of the test stand 100 and with the structure-borne sound sensor 140 in contact with the test specimen 200. Here, the structure-borne sound that occurs on the test specimen 200 is recorded.

[0080] In a fifth process step 340, the reference data set generated in the third process step 320 is subtracted from the measured values ​​recorded in the fourth process step 330.

[0081] Thus, the structure-borne sound behavior of the test specimen 200 can be determined free from structure-borne sound vibrations caused by the test rig 100. Reference sign 100 test bench 110 Delivery device, robot arm 111 Arm segment 112 Arm segment 113 Arm segment 120 Base of the test bench 130 sensor recording 131 Basic body 132 Additional mass element 133 Vibration decoupling element 140 structure-borne sound sensor 150 damping (transition from base to arm segment) 151 Damping (transition arm segment to arm segment) 152 Damping (transition arm segment to arm segment) 153 Damping (transition arm segment to sensor mount) 160 Stiffness (transition base to arm segment) 161 Stiffness (transition between arm segments) 162 Stiffness (transition arm segment to arm segment) 163 Stiffness (transition arm segment to sensor mount) 170 Electromotive drive of the test bench 200 test specimen, electric vehicle powertrain, electrically driven axle 300 Structure-borne sound measurement with the drive at standstill 310 Structure-borne sound measurement during operation of the drive 320 Creating a reference data set 330 Structure-borne sound measurement on the test object 340 Isolation of the structure-borne sound behavior of the test specimen

Claims

Delivery device (110) for delivering a structure-borne sound sensor (140) to a test object (200), wherein the delivery device (110) has a sensor receptacle (130) for receiving the structure-borne sound sensor (140), wherein the sensor receptacle (130) has a vibration decoupling element (133), wherein the vibration decoupling element (133) is configured to absorb vibrations of the delivery device (110) so that these cannot be transmitted to the structure-borne sound sensor (140), characterized in that the sensor receptacle (130) further has an additional mass element (132), wherein the additional mass element (132) is configured to shift a natural frequency of the sensor receptacle (130) into a frequency range of less than 20 Hz. Delivery device (110) according to claim 1, characterized in that the delivery device (110) is designed as a robot arm (110). Delivery device (110) according to one of claims 1 and 2, characterized in that the vibration decoupling element (133) is made of a soft plastic. Delivery device (110) according to one of claims 1 to 3, characterized in that the additional mass element (132) is made of metal. Delivery device (110) according to claim 4, characterized in that the additional mass element (132) consists of tungsten or a tungsten alloy. Delivery device (110) according to one of claims 1 to 5, characterized in that the sensor receptacle (130) is connected to the delivery device (110) exclusively via the vibration decoupling element (133). Delivery device (110) according to one of claims 1 to 6, characterized in that the additional mass element (132) is exclusively connected to the sensor receptacle (130). Test stand (100) for detecting structure-borne sound of a test object (200), characterized in that the test stand (100) comprises at least one delivery device (110) according to one of claims 1 to 7. Test bench (100) according to claim 8, characterized in that the test bench (100) is designed as a test bench (100) for an electric vehicle powertrain (200). Test stand (100) according to one of claims 8 and 9, characterized in that the test stand (100) has a drive (170) for driving the test specimen (200). Method for determining a structure-borne sound characteristic of a test specimen (200) on a test rig (100) according to one of claims 8 to 10, characterized in that a first structure-borne sound measurement is carried out during a standstill of a drive (170) of the test rig (100) and with a structure-borne sound sensor (140) spaced away from the test specimen (200), that a second structure-borne sound measurement is carried out during operation of the drive (170) of the test rig (100) and with a structure-borne sound sensor (140) spaced away from the test specimen (200), and that a third structure-borne sound measurement is carried out during operation of the drive (170) of the test rig (100) and with a structure-borne sound sensor (140) in contact with the test specimen (200).

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