Method for testing a damper and test arrangement for testing a damper

Abstract

The invention relates to a testing arrangement (2) for testing a damper (4), in particular a vibration damper, of a motor vehicle, which has a housing arrangement (6) with a vibration generator (16), in which the damper (4) is mounted and wherein the vibration generator (16) acts on a vibration element (24) of the damper (4) in such a way that a vibration process with vibrations in the damper (4) can be generated, wherein at least one force sensor (36) is provided which measures the force F acting on the vibration element (24) during the vibration process. K detected, wherein a detection device (32) connected to the force sensor (36) for control purposes is used to detect the detected forces F Ki is provided. Furthermore, the invention relates to a method for testing a damper (4).

Description

[0001] The invention relates to a method for testing a damper on a test assembly. In a first step, the damper is mounted in the housing assembly. In a second step, the vibration element of the damper is excited by the vibration generator. In a third step, the force acting on the vibration element during the vibration process is detected by the force sensor. In a fourth step, the detected forces are recorded in the detection device. Furthermore, the invention relates to a test assembly for testing a damper.

[0002] Dampers, and in particular vibration dampers, are fundamentally designed to absorb and compensate for shocks from the road surface on the wheels. They are supported by the vehicle body, generating vibrations that must be dissipated as quickly as possible. A vibration damper is known to be constructed from a multitude of components, and even the smallest unevenness or inaccuracies, such as scoring on the cut edge of a sleeve, can lead to resonances that are perceived as unpleasant by vehicle users. In order to identify such sources of interference during development as well as during testing in series production, the prior art, as described in German Offenlegungsschrift DE 10 2014 115 612 A1, discloses a test setup and method for testing a damper of a motor vehicle. A resonance body is provided on the damper to capture transmitted sound waves.DE 41 20 169 A1 also discloses a test setup and method for testing a damper, in which a force sensor is used to measure a static extension force in the center position of the piston. However, such test setups have proven to be very inaccurate, so that the sources of interference can ultimately only be identified with considerable effort.

[0003] The object of the invention is therefore to avoid the above-mentioned disadvantage in a simple and cost-effective manner.

[0004] The object is achieved according to the invention by evaluating the recorded forces in an evaluation device in a fifth step to determine force discontinuities. This makes it easy to detect force discontinuities in the force curve. These force discontinuities are directly related to the undesirable resonances.

[0005] A particularly advantageous method is characterized by the fact that, in the fifth step, the evaluation device creates a force curve over the oscillation process time. From this, a force gradient dFdt is calculated and multiplied by the stroke of the oscillation generator. This allows various force discontinuities to be easily qualified. The effort can be easily limited by filtering the evaluation of the force gradient times the stroke over the oscillation process time.

[0006] In order to be able to investigate the resonance behavior in detail, the evaluation device can assign the determined force discontinuities to different excitation frequencies.

[0007] The object of the invention is also achieved by a test arrangement for testing a damper, in particular a vibration damper, of a motor vehicle for carrying out such a method, wherein a housing arrangement with a vibration generator is provided, in which the damper is mounted and wherein the vibration generator acts on a vibration element of the damper in such a way that a vibration process with vibrations can be generated in the damper, wherein at least one force sensor is provided which detects the force acting on the vibration element during the vibration process, wherein a detection device is provided which is control-linked to the force sensor for detecting the detected forces, wherein an evaluation device is provided which is control-linked to the detection device in such a way that the evaluation device creates at least one force curve over the time of the vibration process,to detect force discontinuities. This allows the force discontinuities to be clearly identified with a suitable resolution. A control device for controlling the vibration generator can advantageously be provided, with the detection device and the evaluation device being integrated into a single control device.

[0008] The invention is explained in more detail with reference to a drawing, which shows: Fig. 1 a schematic view of a test arrangement according to the invention, Fig. 2 a schematic representation of a force curve over time, Fig. 3 a schematic representation of an enlargement of a time period from Fig. 2, Fig. 4 a schematic representation of a product of the respective force gradients of the forces F K1 to F K3 out of Fig. 3 multiplied by a stroke of a vibration generator of the test setup from Fig. 1, and Fig. 5 a schematic representation of the forces F K1 to F K3 over a frequency range.

[0009] Fig. 1 shows a test arrangement 2 for testing a schematically illustrated vibration damper 4. The vibration damper 4 is installed in a known manner in a motor vehicle (not shown in detail). The test arrangement 2 has a housing arrangement 6, which in the present embodiment is constructed from a base 8, vertical supports 10, 12, and a cross member 14. Reference numeral 16 designates a vibration generator arranged on the base 8. The vibration generator 16 here has a receptacle 18, into which the vibration damper 4 is inserted. At the opposite end of the receptacle 18, a contact member 20 with an attachment element 22 for a piston rod 24 of the vibration damper 4 is provided. The piston rod 24 is connected in a known manner to a working piston 26, which is provided in a base body 28 of the vibration damper 4.In the present embodiment, a control device 30 is provided in the vibration generator 16, which also integrates a detection device 32 and an evaluation device 34. The detection device 32 is also connected for control purposes to a force sensor 36, which is provided in the contact member 20 and measures a force F acting on the piston rod 24. K detected. The piston rod 24 is designed as a vibration element of the vibration damper 4. For the sake of completeness, it should be noted that the reference numeral 38 schematically indicates vibrations of a respective vibration process.

[0010] Fig. 2 shows a schematic representation of a force curve F Ki 40 with an ideal force curve 42 (see Fig. 3) over a period of one second of an oscillation process. Here, damper 4 was excited at different frequencies f1, f2, and f3. The corresponding forces F K1 44, F K2 46 and F K3 48 largely overlap. Only in the range of 0.25 to 0.27 seconds are there different force discontinuities of the forces F K1 to F K3 (44 - 48). This is in Fig. 3 in an enlarged form. Here, the curve section 42 shows the ideal state of the force curve 40 in this area. The curve F K1 44 shows a very short-term discontinuity and the curve F K3 a force discontinuity that occurs over a longer period of time. In particular, a very short-term discontinuity F K1 44 is perceived as disturbing by the vehicle user.

[0011] Fig. 4 now describes the product of the respective force gradients of the forces FK1 to F K3 multiplied by a stroke of the vibration generator 16 over time. The force gradient DFdt * stroke of the force F K1 shows the highest deflection here.

[0012] Fig. 5 then shows the respective forces F K1 to F K3 over the respective frequencies, which allows disturbing resonances to be derived in detail.

[0013] The method according to the invention for testing a damper 4 on the test assembly 2 is now carried out as follows. In a first step, the damper 4 is mounted in the housing assembly 6, and in particular in the connection 18 and the attachment member 22. In a second step, the vibration member 24, here the piston rod 24 of the damper 4, is excited by the vibration generator 16 at a frequency f. In a third step, the force F acting on the vibration member is Kidetected by the force sensor during the vibration process. In a fourth step, the detected forces F Ki in the detection device 32. In the fifth step, the detected forces F Ki evaluated in the evaluation device 34, whereby a force curve is created over an oscillation process time, from which a force gradient dFdt is calculated and multiplied by a stroke of the oscillation generator 16. The evaluation of force gradient dFdt * stroke is filtered in order to avoid examining insignificant force discontinuities. The force discontinuities determined by the evaluation device 34 are then assigned to the different excitation frequencies in order to draw conclusions about resulting resonances.

Claims

[1] Method for testing a damper (4) on a test arrangement (2), wherein in a first step the damper is mounted in the housing arrangement (6), in a second step the vibration element (24) of the damper (4) is excited by the vibration generator (16), in a third step the force acting on the vibration element (24) during the vibration process is detected by the force sensor (36), in a fourth step the detected forces are recorded in the detection device (32), characterized by that in a fifth step the recorded forces are evaluated in an evaluation device (34) in order to determine force discontinuities. [2] Method for testing a damper according to claim 1, characterized bythat in the fifth step, the evaluation device (34) creates a force curve over an oscillation process time and from this a force gradient dFdt is calculated and this is multiplied by a stroke of the oscillation generator (16). [3] Method for testing a damper according to claim 2, characterized by that the evaluation of force gradient times stroke is filtered over the oscillation process time. [4] Method for testing a damper according to claim 2 or 3, characterized by that the determined force discontinuities are assigned to different excitation frequencies by the evaluation device (34). [5] Test arrangement (2) for testing a damper (4), in particular a vibration damper, of a motor vehicle, which is suitable for carrying out a method according to one of claims 1-4, characterized bythat a housing arrangement (6) with a vibration generator (16) is provided, in which the damper (4) is mounted and wherein the vibration generator (16) acts on a vibration element (24) of the damper (4) in such a way that a vibration process with vibrations in the damper (4) can be generated, wherein at least one force sensor (36) is provided which measures the force F acting on the vibration element (24) during the vibration process K detected, wherein a detection device (32) connected to the force sensor (36) for control purposes is used to detect the detected forces F Ki is provided, wherein an evaluation device (34) is provided which is connected to the detection device (32) in terms of control technology, such that the evaluation device (34) creates at least one force curve over the time of the oscillation process in order to determine force discontinuities. [6] Test arrangement according to claim 5, characterized bythat a control device is provided for controlling the vibration generator (16), wherein the detection device (32) and the evaluation device (34) are integrated in a control device (30).

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