Abstract:
A device for measuring structure-borne noise has a measuring sensor ( 10 ) for detecting the structure-borne noise and a coupling element ( 11 ) connected to the measuring sensor ( 10 ) for reducing interference noises which act upon the measuring sensor ( 10 ) at least during measured-value detection. The coupling element ( 11 ) has an adjustable coupling strength in order to enable measured-value detection that is as flexible and reliable as possible.

Description:
[0001]     Priority is claimed to German Application Serial No. DE 10 2004 016 804.0, filed Apr. 6, 2004, the entire disclosure of which is incorporated herein.  
         [0002]     The present invention is directed to a device for measuring structure-borne noise having a measuring sensor for detecting the structure-borne noise and a coupling element connected to the measuring sensor for reducing interference noises which act upon the measuring sensor at least during measured-value detection.  
       BACKGROUND  
       [0003]     It is known to use acoustic test technology for quality monitoring in work pieces and equipment assemblies. Indications of defects may be obtained from a structure-borne noise measurement. However, the signal-to-disturbance ratio is frequently unfavorable in such structure-borne noise measurements due to the normally high noise level.  
         [0004]     For solving this problem, German Patent No. DE 43 16 473 C2 proposes decoupling a measuring sensor, which is in contact with the part to be tested, from interference noises via a plastic tubular clamp, the interference noises being conveyed via a mount of the measuring sensor.  
       SUMMARY OF THE INVENTION  
       [0005]     An object of the present invention is to provide a device for measuring structure-borne noises enabling improved interpretation of measured values and being usable as variably as possible.  
         [0006]     In a device according to the present invention for measuring structure-borne noise using a measuring sensor for sensing the structure-borne noise and a coupling element, connected to the measuring sensor, the coupling element has an adjustable coupling strength, i.e., depending on the requirements, the coupling element may decouple possible interference noises, which are conveyable via a mount of the measuring sensor, to a greater or lesser extent. This enables an adaptation, a continuously variable adaptation in particular, of decoupling characteristics and damping characteristics to an intended variable and to the conditions prevailing during the measurement. The acoustic test quality depends on a plurality of parameters such as shape, wall thickness, material, internal pressure, characteristics of the damping fluid (density, viscosity in particular), hardness of the coupling element, the measuring sensor and/or a pressing path of the measuring sensor with regard to the part to be tested. In the ideal case, the measuring sensor is only in contact with the part to be tested, at the same time, however, it must be mechanically held and, if needed, it must be movable with respect to the part to be tested. The coupling element separates the measuring sensor, which may be pressed onto the part to be tested by a preferably predefinable force, from its mount by keeping interference noises away from the measuring sensor due to its damping characteristics and largely decoupling the measuring sensor from the surroundings. The measuring sensor is preferably designed in the form of a prod and is put in contact with the part to be tested. Of course, other types of measuring sensors are also conceivable. Those skilled in the art shall select a sensible measuring sensor for the appropriate measuring task. The coupling element is preferably designed as a hollow part having an elastic outer skin, in the form of a rubber ball for example.  
         [0007]     Overall, an improved interpretation of test results is possible so that a well-founded evaluation of the quality of the part to be tested is possible in a preferably automated or at least semi-automated acoustic test process. This is particularly favorable during tests in vehicle construction, in particular during tests of equipment assemblies, such as engines, transmissions, and the like, in which a production rate as high as possible with error rates as low as possible is desired.  
         [0008]     For adjusting the coupling strength, the coupling element is favorably able to be pressurized by a damping fluid, the coupling element, in an advantageous embodiment, being able to be pressurized by the damping fluid via a piston rod of a cylinder, in particular a hollow space of the coupling element is able to be filled with damping fluid. Air or compressed air may be provided as the damping fluid, for example.  
         [0009]     A storage unit for the damping fluid may be appropriately provided. A shutoff valve is provided in a favorable refinement in such a way that the storage is able to be decoupled from a media supply during the reception of structure-borne noise. In particular, a control response of a possible pressure controller in a compressed air line, which fills the storage, may be eliminated as an interference variable.  
         [0010]     A cylinder which is preferably designed as a double-action cylinder including a continuous piston rod may be provided in order to adjust a contact pressure of the coupling element for measured-value detection. By pressurizing one or the other of two cylinder chambers, the piston rod may be displaced in the one or the other direction so that a contact pressure of the measuring sensor onto the part to be tested may be decreased or increased. The coupling element is preferably connected to the piston rod of the cylinder. A pressure, which is exerted on the coupling element, also affects the measuring sensor connected to the coupling element. For measured-value detection, a change in the contact pressure of the coupling element at the measuring sensor and thus an indirectly resulting change in the contact pressure between the measuring sensor and the part to be tested may also take place in addition to the pressurization of the coupling element with damping fluid. This makes a specific optimization of the measuring signal with respect to interference variables possible by searching for an optimum, for example, when one or both of the parameters coupling strength and/or contact pressure is/are changed.  
         [0011]     A comfortable and reliable measurement is possible if a control element is provided for adjusting a distance between the measuring sensor and a part to be tested. The distance may preferably be continuously adjustable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The present invention is subsequently explained in greater detail based on an exemplary embodiment described in the drawing. The drawing, the description, and the claims contain a plurality of features in combination which those skilled in the art shall also consider individually and form into further sensible combinations.  
         [0013]     The sole FIGURE schematically shows a device for measuring structure-borne noise according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]     The FIGURE shows a measuring sensor  10  designed as a prod which radially protrudes from an outer skin  17  of a coupling element  11  designed as a hollow sphere. Measuring sensor  10  may be put in contact with a part to be tested  40 , shown schematically here. Via a signal path  14 , measuring sensor  10  is connected to an electronic unit  13  which processes a measured value recorded by measuring sensor  10  and/or relays it to a possible analyzer unit and which possibly electrically supplies the measuring sensor  10 . Signal path  14  may be formed by a cable or may also be a wireless signal transmission. A transmitter is provided on measuring sensor  10  in the latter case.  
         [0015]     Coupling element  11  has a hollow space  12  which is filled with a damping fluid. Outer skin  17  is preferably elastic, made of an elastomer for example. Hollow space  12  is in fluid-connection with a storage unit  30  which is designed as an accumulator and in which the damping fluid is stored. The fluid connection is formed via a hollow piston rod  15  of a cylinder  20 , a pneumatic or hydraulic cylinder in particular, coupling element  11  being connected to the piston rod  15 . Via a connecting line  33 , the damping fluid arrives in a bore  16 , which is continuous along its longitudinal extension, of piston rod  15  which meets hollow space  12  of coupling element  11 .  
         [0016]     A coupling strength of coupling element  11  is adjustable by filling hollow space  12  of coupling element  11  with more or less damping fluid, i.e., the hollow space is more or less pressurized. This changes the coupling characteristics between measuring sensor  10  and the other components of the device according to the present invention connected to coupling element  11 . Depending on the amount and the pressure of the damping fluid, damping of coupling element  11  vis-à-vis noise waves from the outside is higher or lower.  
         [0017]     A separator  21 , which is fixedly connected to piston rod  15 , separates cylinder  20  inside into a first cylinder chamber  22  and second cylinder chamber  23 . First cylinder chamber  22  is supplied with a fluid from a media supply  24  and second cylinder chamber  23  is supplied with a fluid from a media supply  25 . Air is preferably used as the fluid. Hydraulic oil may optionally also be used. Cylinder chambers  22 ,  23  may be decoupled with respect to media supplies  24 ,  25  with the aid of two valves  26 ,  27 , thereby suppressing interferences which are caused by the control response of the pressure regulators for the cylinder movement.  
         [0018]     Cylinder  20  is provided in order to adjust a contact pressure of coupling element  11  for measured-value detection. For measured-value detection, a change in the contact pressure of coupling element  11  onto measuring sensor  10  and thus an indirectly resulting change in the contact pressure between measuring sensor  10  and the part to be tested  40  may also take place in addition to the pressurization of coupling element  11  with damping fluid. This makes a specific optimization of the measuring signal with respect to interference variables possible.  
         [0019]     A shutoff valve  31  is able to be shut at least during a measurement of structure-borne noise at an object to be tested in order to decouple storage  30  from a media supply  32  when structure-borne noise is recorded. The media supply is preferably a compressed air supply source.  
         [0020]     Measuring sensor  10 , cylinder  20  and its piston rod  15  are situated along an axis  18 . A control element  35 , via which a distance between measuring sensor  10  and a part to be tested is adjustable, adjoins to the side of cylinder  20  facing away from coupling element  11 . A continuous adjustment is possible by twisting a first part  36 , designed as a nut, vis-à-vis a second part  37 , designed as a tube having a male thread. This may be carried out manually, or an electrical drive or another type of drive considered to be sensible by those skilled in the art may be provided. A pressing path of measuring sensor  10  is preferably continuously adjustable when the device is positioned at the part to be tested and measuring sensor  10  is to be put in contact with the part in a defined manner. The pressing path represents another parameter which, for optimizing the measuring result, is adjustable and possibly alignable with the coupling strength of coupling element  11  and/or the contact pressure of measuring sensor  10 .