Abstract:
A palm-held acoustical sensing device provides improved accessibility within an engine compartment for sensing engine noise in order to perform diagnostics. Miniaturized electronics are provided within a compact housing that permits free use of the sensing device within an engine compartment, enabling access to engine components that have previously been accessible only with great difficulty. Clamping sensors having wider bandwidth than existing clamping sensors provide improved sensing capability and an electronics and battery housing having one or more sensor input jacks provides for attachment of multiple sensors, improved storage and a lower cost unit providing the advantages of both a flexible shaft sensing unit and a clamping unit.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to acoustical sensing devices, and more specifically, to a small palm-held acoustical sensing device for engine diagnostic applications.  
           [0003]    2. Background of the Invention  
           [0004]    Acoustical sensing devices have been in use for some time for diagnosing engine problems in automotive and other engines. Mechanical failure is generally preceded by operating conditions that generate various noises (e.g., bearing squeal or knocking from loose parts) that can be detected if a sensing device is acoustically coupled to the noise source.  
           [0005]    U.S. Pat. No. 5,445,026 “ELECTRONIC INSTRUMENT FOR LOCATING AND DIAGNOSING ENGINE SOUNDS”, issued to the inventor of the present invention, describes a first acoustical sensing device having a flexible arm that may be directed toward a noise source within an engine compartment. U.S. Pat. No. 5,435,185 “ELECTRONIC INSTRUMENT FOR LOCATING AND DIAGNOSING AUTOMOTIVE CHASSIS SOUNDS”, also issued to the inventor of the present invention, describes a second acoustical sensing device mounted on a clamp and connected via a flexible cable. The first device is useful for quickly scanning reachable engine components and the second device is useful for more permanently attaching a sensor where the first device cannot reach, or where it is desirable to leave the sensor in place for a longer period of time while adjustments are made, for consultation or in order to maintain precise placement of the sensor.  
           [0006]    The first (flexible arm) device uses a sensing element that has wide bandwidth for the best sensitivity to the spectrum of noises available. The second (clamping) device uses a sensing element that is durable and easily coupled to the clamping device but has a narrow bandwidth. Both devices are useful for different purposes, as the second device can access locations in an engine compartment that the first cannot, and the first device is sensitive to noises that the second device cannot detect. In particular, it has been noticed that a lower bandwidth can exclude normal engine noise, leaving the operator no level of reference to determine the relative level (and hence importance) of a noise detected by the sensing device.  
           [0007]    Therefore, it would be desirable to provide a single low-cost device incorporating the advantages of a clamping device and a device with a flexible shaft. It would be further desirable to provide a clamping device with a wider bandwidth. It would also be desirable to provide a flexible shaft device that improves access to engine compartment locations.  
         SUMMARY OF THE INVENTION  
         [0008]    The above objectives of providing a single low cost device having clamping and flexible shaft device advantages, a clamping device with wider bandwidth and a flexible shaft device with improved access are accomplished in various apparatus in accordance with embodiments of the present invention. A palm-held housing incorporates an amplifier, batteries and volume control, along with an audio jack for connection of headphones and may include one or more input jacks for detachably coupling flexible shaft or clamping sensors. The housing is adapted to fit within the palm of a hand, so that the effective reach of the device with a flexible shaft is greater than the reach of the user&#39;s fingers. The clamping device incorporates a condenser microphone coupled to the clamp with an air-tight seal to provide enhanced bandwidth and sensitivity.  
           [0009]    The foregoing and other objectives, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a pictorial diagram containing depictions of a palm-held acoustical sensing device in accordance with a first embodiment of the present invention.  
         [0011]    [0011]FIG. 2 is a pictorial diagram containing depictions of a palm-held acoustical sensing device in accordance with a second embodiment of the present invention.  
         [0012]    FIGS.  3 A- 3 C are pictorial diagrams containing depictions of components of palm-held acoustical sensing devices for configuration in accordance with other embodiments of the present invention.  
         [0013]    [0013]FIG. 4 is an electronic schematic depicting the amplifier, batteries and connectors disposed within the housings of FIGS. 1, 2, and  3 C in accordance with the various disclosed embodiments of the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    Referring now to the figures and in particular to FIG. 1, a palm-held acoustical sensing device  10  in accordance with a first embodiment of the present invention is depicted. A coaxial cable  11  approximately 3 inches long, provides a flexible wiring shaft that couples an acoustical sensor head  12  to an electronics housing  13 . Coaxial cable  11  electrically connects the acoustical sensor head  12  to electronics within electronics housing  13  and mechanically connects acoustical sensor head  12  to electronics housing  13 . Coaxial cable  11  is generally one having a solid center conductor  11 A providing the ability to position acoustical sensor head  12  with respect to electronics housing  13  at different angles, facilitating access to engine compartment components, while also providing a shielded electrical connection to prevent noise from being induced in the interconnecting wiring from external environmental sources. Incorporation of coaxial cable  11 , rather than a metal gooseneck having a separate central wiring cable as previously incorporated in automotive sensing devices, provides a low-cost assembly having improved reliability (due to the larger cable and lack of a separate central cable sliding against an internal gooseneck channel). The woven shield of coaxial cable  11  provides superior shielding and mechanical performance over prior gooseneck approaches, as the shield is less permeable to electrical noise, is electrically grounded and conducts less mechanical noise from housing  13  and any vibration sources that are contacted by the outside of coaxial cable  11 .  
         [0015]    Housing  13  measures approximately 2.0 in×1.0 in by {fraction (1/4)}″ thick and contains a miniaturized amplifier circuit for amplifying signals received from an acoustical sensing element M 1 A within sensor head  12 , which is a condenser microphone element. A volume control knob  16  is disposed on the outside of housing  13  for controlling the volume of sound provided via an external pair of headphones such as EARBUDS or larger headphones that are attached via connector J 3 . A battery cover  15  slides away to provide access to batteries B 1  and B 2 , as depicted in callout  17 . Batteries B 1  and B 2  are hearing aid or watch batteries providing for miniaturization of housing  13 . A belt clip  14  is provided for temporarily attaching sensing device  10  to a belt or shirt pocket, providing a mechanism for freeing the users hands while sensing device  10  is not in use. A case  19  may be provided for storage of sensing device  10  within a pocket or for general use. Case may be made shorter or smaller by designing the case to hold sensing device  10  with coaxial cable  11  bent so that sensor head  12  is near housing  13 . The use of miniaturized electronics, hearing-aid or watch batteries and the reduction of housing  13  and coaxial cable  11  size over existing sensing systems provides for access to components within an engine compartment that were previously inaccessible by such devices. Further, portability and cost are reduced, making sensing device  10  particularly useful to semi-professional mechanics or individuals performing their own automotive diagnosis and repair.  
         [0016]    Referring now to FIG. 2, an acoustical sensing device in accordance with a second embodiment of the present invention is depicted. A clamping acoustical sensor  20  includes a condenser microphone element M 1 B. Clamping sensor  20  is used to coupled the acoustical sensing device to engine components, permitting measurement of sound conducted directly from the engine component.  
         [0017]    Incorporation of condenser microphone element M 1 B provides an enhanced performance over previous clamping sensor devices, which use piezoelectric sensors to detect vibrations from the frame  29  of clamp  20 . A piezoelectric sensor has a comparatively narrow bandwidth centered around 1 to 4 KHz, which does not permit a clamping acoustical sensing device to sense engine background noise. As a result, while previous clamping devices can detect bearing squeal and other noises that indicate impending failure or defects in an engine component, there is no reference providing a measure of the overall severity of the detected noise.  
         [0018]    The sensing device of FIG. 2 overcomes the bandwidth limitations of presently available clamping sensors by incorporating condenser microphone element M 1 B. However, in order to use a condenser microphone element as a detector for vibrations transmitted through clamp  20  frame  29 , is has been determined that an air-tight seal must be employed. Callout  26  depicts one such airtight seal, provided by a bonding agent  28 , which may be epoxy, hot-melt glue or other suitable sealing adhesive. Bonding agent  28  is disposed completely around and over condenser microphone element M 1 B. The active surface of microphone element M 1 B is facing frame  29 , so that the only conducted vibrations sensed by microphone element M 1 B are those from frame  29  and the other surfaces of microphone element M 1 B are likewise sealed off from air-convection transmitted vibration, as in general condenser microphone element M 1 B is sensitive to air pressure changes on all surfaces and therefore must be completely isolated. A second adhesive  27  may be used to attach cable  21  to frame  29  or bonding agent  28  may be disposed over both microphone element M 1 B and one end of cable  21 .  
         [0019]    Similarly to the embodiment of FIG. 1, the embodiment of FIG. 2 includes a palm-sized housing  22  containing miniaturized electronics. Housing  22  includes a belt clip  23  for holding the housing while clamp  20  is in use or for temporary storage. Volume control knob  25  and battery cover  24  are disposed at the side of housing  22  and headphone connector J 3  is disposed at an end of housing  22 , and providing similar functions to corresponding elements of FIG. 1 as described above.  
         [0020]    Callout  26 B depicts an alternative airtight seal that may be incorporated within an embodiment of the present invention. Rubber (or other flexible material) gasket  28 B isolates air from the active surface of microphone element M 1 B by providing a tight slip-fit connection to microphone element MIB enclosure. The back of microphone element M 1 B is covered by a back cover  28 C substantially sealing microphone element M 1 B from outside air-conducted acoustical vibration. Gasket  28 B may be adhered to frame  29  or may include a shoulder that is press-fit through a hole in frame  29 .  
         [0021]    Referring now to FIGS.  3 A- 3 C, components of an acoustical sensing device that may be combined to form various embodiments of the present invention are depicted. FIG. 3A depicts a detachable sensor assembly  30  including a coaxial cable  32  with a sensor head  31  disposed at a first end of coaxial cable  32  and having an acoustical sensor MIC incorporated therein. A male audio connector  33  provides a means for detachably coupling sensor assembly  30  to a housing  36  as depicted in FIG. 3C. Housing  36  includes two or more female connectors J 1  and J 2  for attaching acoustical sensors to housing  36 . A switch S 1  provides for selection among acoustical sensors inserted in connectors J 1  and J 2  and generally will be used for switching between two clamping type sensors, although combinations of clamping and flexible shaft sensors may be attached. Housing  36  encloses the miniaturized electronics described above (with the addition of switch S 1  and additional input connectors J 1  and J 2 ). Housing similarly includes headphone connector J 3 , volume control knob  39 , battery cover  38  and belt clip  37 .  
         [0022]    A clamping device adapted for use with housing  36  is depicted in FIG. 3B. Clamping device includes condenser microphone element M 1 D attached to a clamp  34  with an air-tight seal, a cable  35  and a male connector  33 B electrically coupled to microphone element M 1 D, so that microphone element M 1 D is selectable by switch S 1  when connector  33 B is inserted into one of connectors J 1  and J 2  on housing  36 .  
         [0023]    Referring now to FIG. 4, miniaturized electronics as incorporated in the various above-described embodiments of the present invention are depicted. Acoustical sensing element M 1  (and optionally second acoustical sensing element M 2 ) are connected to plug P 1  (and optional plug P 2 ). Jack J 1  provides for connection of plug P 1  and optional jack J 2  provides for connection of plug P 2 . Jacks J 1  and J 2  are connected to switch S 1  which selects among sensors connected to jacks J 1  and J 2  and provides the signal from the selected device to amplifier A 1  via resistor R 1 . If only one sensor is used (as depicted in the embodiments of FIGS. 1 and 2), then jacks J 1  and J 2 , P 1  and P 2  and switch S 1  are not needed and the sensor signal is connected directly to resistor R 1 . Resistor R 2  is connected to amplifier A 1  and is a variable resistor for setting the gain of the headphone amplifier A 1 , and is mechanically coupled to the various volume knobs depicted in FIGS.  1 - 3 .  
         [0024]    Amplifier A 1  may be a low-voltage high-current op-amp, or a special low voltage headphone amplifier integrated circuit, or a device fabricated with discrete transistors. While depicted as a differential amplifier configured for a single-ended input, amplifier A 1  may receive a differential signal from acoustical sensors (with appropriate wiring and connector changes) or amplifier A 1  may be a single-ended amplfier. Batteries B 1  and B 2  provide power to amplifier A 1  and headphone jack J 3  is connected to the output of amplifier A 1  to provide a signal to headphones H 1  via connection of headphone plug P 3  to jack J 3 .  
         [0025]    While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form, and details may be made therein without departing from the spirit and scope of the invention.