Abstract:
A sensor assembly for determining rotational angular displacement of a first moving component in a machine relative to a second component in the machine includes a base, a magnet housing, and a flexible member. The base is configured to be rigidly secured to the first moving component for movement therewith. The base defines a first axis of rotation. The magnet housing supports a sensor magnet and is rotatably received in the second component. The magnet housing defines a second axis of rotation. The flexible member has a first end rigidly secured to the magnet housing coaxially with the first axis of rotation. A second end of the flexible member is rigidly secured to the magnet housing coaxially with the second axis of rotation. A flexible body portion of the flexible member is capable of accommodating misalignment between the first and second axes of rotation.

Description:
BACKGROUND  
       [0001]     The present invention relates to a device for measuring oscillatory or rotational angular displacement of one component in a machine relative to another component, the second component being stationary, oscillating, or rotating at a different rate and/or direction with respect to the first component.  
         [0002]     In a machine with moving parts, oftentimes a component in the machine moves, rotates, or oscillates at a different rate than another component in the same machine. It is often desirable to measure the oscillatory or rotational angular displacement between the two components. A device can be installed between two parts of a machine to measure this displacement. The device has two ends; a first end coupled to a moving component of a machine and a second end coupled to a moving or stationary component of a machine that includes a portion of a measurement system to measure oscillation or rotational angular displacement of the first moving component. The two ends are connected to one another by a rigid member. In many cases, the measurement device is installed after the machine has been assembled and can be coupled to pre-existing attachment fixtures on the machine. Because the measurement device is typically installed after assembly of the machine, the attachment fixtures should be aligned such that the measurement device fits correctly within the machine. However, if tolerances of the machine parts or the attachment fixtures are such that proper alignment does not exist, the measurement device either cannot be installed, or if installation is possible, accurate and reliable measurement of the movement of a moving component with respect to another component is compromised, or the assembly is bent or fractured.  
       SUMMARY  
       [0003]     The device of the present invention achieves accurate and reliable determination of the oscillatory or rotational angular displacement of a first component in a machine with respect to another component in the machine. The device is able to be installed between two components of a machine even if the pre-existing attachment fixtures or locations are misaligned.  
         [0004]     In one embodiment, the invention provides a sensor assembly for determining rotational angular displacement of a first moving component in a machine relative to a second component in the machine. The sensor assembly includes a base, a magnet housing, and a flexible member. The base is configured to be rigidly secured to the first moving component for movement therewith. The base defines a first axis of rotation. The magnet housing supports a sensor magnet and is rotatably received in the second component. The magnet housing defines a second axis of rotation. The flexible member has a first end rigidly secured to the magnet housing coaxially with the first axis of rotation. A second end of the flexible member is rigidly secured to the magnet housing coaxially with the second axis of rotation. A flexible body portion of the flexible member is capable of accommodating misalignment between the first and second axes of rotation.  
         [0005]     In another embodiment the invention provides an assembly including a stationary housing, a swashplate movable relative to the stationary housing, and a sensor assembly for determining rotational angular displacement of the swashplate relative to the stationary housing. The sensor assembly includes a base rigidly secured to the swashplate for movement therewith. The base defines a first axis of rotation. A magnet housing supporting a sensor magnet and being rotatably received in the stationary housing. The magnet housing defines a second axis of rotation. A flexible member has a first end rigidly secured to the base coaxially with the first axis of rotation, a second end rigidly secured to the magnet housing coaxially with the second axis of rotation, and a flexible body portion capable of accommodating misalignment between the first and second axes of rotation.  
         [0006]     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a perspective view of a measurement device of the present invention located in a portion of a machine whose components are to be measured.  
         [0008]      FIG. 2  is a perspective view of the measurement device shown in  FIG. 1 .  
         [0009]      FIG. 3  is a partial cross-section view of the measurement device of  FIG. 2 .  
         [0010]      FIG. 4  is an exploded view of the machine and measurement device shown in  FIG. 1 .  
     
    
     DETAILED DESCRIPTION  
       [0011]     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
         [0012]      FIG. 1  illustrates a portion of a pump, compressor, or other machine  10  having a first movable component  14  and a second stationary or movable component  18 . In the illustrated embodiment, the machine is a variable displacement pump having a swashplate assembly  22 . The swashplate assembly  22  includes a swashplate  26  coupled to at least one inner race member  30 . Each inner race member  30  is positioned adjacent a respective outer race member  34 . Rolling elements (not shown) are located between each inner race member  30  and outer race member  34  to allow the inner race member  30  to move with respect to the outer race member  34 . The outer race member  34  is coupled to a bearing saddle, or cradle,  38  that is stationary. The swashplate assembly  22  also has a radially centered opening  42  for passage of a rotatable shaft (not shown). In operation, the swashplate  26  oscillates back and forth in the cradle  38  about an axis  46 . The illustrated swashplate  26  can oscillate in the cradle  38  to each side of the axis  46  by about 20 to 25 degrees, however, the oscillation angle can vary as desired. The swashplate  26  is driving or being driven by pistons (not shown) reciprocating in a rotating cylinder block (not shown) of a fluid machine, as is understood to those skilled in the art.  
         [0013]     In the illustrated embodiment, the second stationary or movable component  18  is a stationary wall  50 . The stationary wall  50  includes a bore  54  extending partially or entirely through the stationary wall  50 . The bore defines an axis  48  (see  FIG. 4 ). A sensor (not shown) is attached to the stationary wall  50  to communicate with the bore  54 , and is operable to send signals to a processor, as will be described in more detail below.  
         [0014]      FIG. 1  also illustrates a measurement device, or flexible sensor input assembly  58  of the present invention. The flexible sensor input assembly  58  includes a base  60 , a sensor magnet housing  64 , and a flexible axial connecting member, or flexible member  68  interconnecting the base  60  and the sensor magnet housing  64 . As illustrated in  FIGS. 2 and 3 , the base  60  of the flexible sensor input assembly  58  includes a body portion  72 , that in the illustrated embodiment has a generally plate-like configuration, and a projecting portion  76 , that in the illustrated embodiment has a generally cylindrical configuration. The body portion  72  includes an aperture  80  extending therethrough to facilitate mounting the body portion  72  to the swashplate  26  with a fastener  84  (e.g., a screw—see  FIGS. 1 and 2 ), as will be described below. A protrusion  88  extends from the body portion  72  adjacent the aperture  80  for aligning the body portion  72  with respect to the swashplate assembly  22  during installation.  
         [0015]     The projecting portion  76  is sized and configured to be received in a receiving aperture  92  (see  FIG. 4 ) in the swashplate assembly  22 . The receiving aperture  92  is substantially coaxial with the axis  46  about which the swashplate  26  oscillates so that oscillation of the swashplate  26  causes rotation of the projecting portion  76  of the base  60  about the axis  46  when the projecting portion  76  is received in the aperture  92 . As shown in  FIG. 3 , the projecting portion  76  also defines a receiving aperture  96  for receiving one end  100  of the flexible member  68 . The receiving aperture  96  has a beveled end  104  that aids in locating the end  100  of the flexible member  68  axially. In other embodiments, the aperture  96  can have an alternative end geometry such as rounded, ovoid, cylindrical, conical, or the like.  
         [0016]     The base  60  is made of a suitable polymer or a metallic material. In the illustrated embodiment, the base  60  is a polymer that is molded about the flexible member  68 . In other embodiments, the base  60  can be mechanically fixed to the flexible member  68  by any suitable means.  
         [0017]     With continued reference to  FIG. 3 , the sensor magnet housing  64  includes an aperture  108  for receiving the second end  112  of the flexible member  68 . The sensor magnet housing  64  can be crimped or otherwise mechanically deformed to retain the second end  112  of the flexible member  68 . Other mechanical securing means can also be employed.  
         [0018]     The sensor magnet housing  64  also includes a bore  116  that receives and supports a sensor magnet  120 . In the illustrated embodiment, the sensor magnet  120  is molded into the bore  116  in the sensor magnet housing  64 . The sensor magnet  120  is magnetized after final and complete assembly of the flexible sensor input assembly  58 . Magnetization after final and complete assembly of the flexible sensor input assembly  58  establishes a closed polar magnetic field in a fixed angular relation to the base  60 , and eliminates angular inaccuracies due to a tolerance stack-ups. The tolerance stack-ups can occur if the sensor magnet  120  was magnetized prior to assembly into the sensor magnet housing  64 , or if the magnetization occurred prior to final and complete assembly of the flexible sensor input assembly  58 . The sensor magnet housing  64  can be ferrous, or of any other composition such that the sensor magnet housing  64  aids in the formation of a closed polar magnetic field of sufficient strength to allow accurate measurement of minute angular displacements. An O-ring  124  around the outer circumference of the sensor magnet housing  64  helps to create a seal between the sensor magnet housing  64  and the bore  54  of the stationary wall  50  into which the sensor magnet housing  64  is inserted.  
         [0019]     The sensor magnet housing  64  incorporates axial and radial features to provide permanent axial retention and rotational registration of the sensor magnet  120  relative to the sensor magnet housing  64  and the base  60 . For example, as shown in  FIG. 3 , a circumferential groove  128  in the bore  116  of the magnet housing  64  helps to retain and register the sensor magnet  120  with respect to the sensor magnet housing  64 . The crimped connection between the sensor magnet housing  64  and the flexible member  68  maintains the relative position of the flexible member  68  in relation to the sensor magnet housing  64  and the sensor magnet  120 .  
         [0020]     The flexible member  68  can be made of any strong flexible material such as a polymer, a woven metallic material, or a braided metallic material. As mentioned above, the material of the flexible member  68  can be chosen to facilitate molding the base  60  around the flexible member  68 . Due to the fixed mechanical connection with each of the base  60  and the sensor magnet housing  64 , the flexible member  68  transmits the rotation of the projecting portion  76  caused by oscillation of the swashplate assembly  22  to the sensor magnet housing  64 . Rotation of the sensor magnet housing  64  is sensed by the sensor attached to the stationary wall  50 , and a signal indicative of the angular position of the swashplate assembly  22  can be relayed to the processor.  
         [0021]     The body portion  130  of the flexible member  68  is generally straight when at rest, but should be able to bend and flex when a force is applied to the flexible member  68 . The bending flexibility of the flexible member  68  permits the base  60  and the sensor magnet housing  64  to rotate about different axes  46 ,  48  (see  FIG. 4 ) to compensate for misalignment between the bore  54  in the stationary wall  50  and the receiving aperture  92  in the swashplate assembly  22 . In other words, when the bore  54  in the stationary wall  50  and the receiving aperture  92  in the swashplate assembly  22  are not coaxial, the flexibility of the flexible member  68  enables the flexible sensor input assembly  58  to be installed and to accurately measure the angular displacement of the swashplate assembly  22  despite the misalignment of the machine components  14 ,  18 . This arrangement allows for larger tolerances between the components of the machine. In the embodiment illustrated in  FIGS. 1-4 , the flexible member  68  of the flexible sensor input assembly  58  can generally bend to accommodate misalignment of up to about 0.25 inches between the swashplate  26  and the stationary wall  50 .  
         [0022]     Installation of the assembled flexible sensor input assembly  58  to the machine  10  will now be discussed. The sensor magnet housing  64  is inserted into the bore  54  of the stationary wall  50 , which is sized such that a slip-fit is created between the sensor magnet housing  64  and the stationary wall  50 . The slip-fit allows the sensor magnet housing  64  to rotate about the axis  48  within the bore  54 , but will not allow the sensor magnet housing  64  to slip out of the bore  54  or change its axis of rotation within the bore  54 . The sensor attached to the stationary wall  50  cooperates with the sensor magnet  120  located inside of the sensor magnet housing  64  to generate a signal representative of the relative angular displacement of the swashplate assembly  22 . The O-ring  124  around the sensor magnet housing  64  seals the flexible sensor input assembly  58  to the stationary wall  50 , but allows for rotation of the sensor magnet housing  64  within the bore  54 .  
         [0023]     The protruding portion  76  of the base  60  is inserted into the receiving aperture  92  in the swashplate assembly  22  and the protrusion  88  on the body portion  72  of the base  60  is inserted into a locating hole  132  (see  FIG. 4 ) in the swashplate assembly  22 . The aperture  80  through the body portion  72  of the base  60  will be aligned with a threaded aperture  136  (see  FIG. 4 ) in the swashplate assembly  22  such that the fastener  84  can be inserted through the aperture  80  in the body portion  72  and into the threaded aperture  136  in the swashplate assembly  22 , thereby securing the base  60  to the swashplate assembly  22  and preventing relative motion between the swashplate assembly  22  and the base  60 . The combination of the fastener  84 , the protrusion  88 , and the locating hole  132  will aid in establishing and maintaining angular registration between the swashplate  26  and the base  60  to a high degree of accuracy. In other embodiments, other methods (e.g., rivets, pins, posts, clips, clamps, inter-engaging elements, or any combination of such elements) for registering and fixing the flexible sensor input assembly  58  relative to the swashplate assembly  22  can be substituted.  
         [0024]     In the event that the bore  54  of the stationary wall  50  is not properly aligned with the receiving aperture  92  in the swashplate  26  due to tolerance stack-ups or other reasons, the flexible member  68  will bend or deflect to accommodate the misalignment of the axes  46 ,  48 , and to properly position the base  60  and the sensor magnet housing  64  relative to one another. This enables installation to be completed, while maintaining the accuracy of the measuring capabilities of the flexible sensor input assembly  58 .  
         [0025]     In operation, as the swashplate  26  oscillates, the base  60  of the flexible sensor input assembly  58  oscillates with the swashplate  26  due to the fixed connection between the swashplate  26  and the base  60 . The protruding portion  76  rotates about the axis  46 . As the protruding portion rotates, the flexible member  68  transfers rotational motion to the sensor magnet housing  64  to cause the sensor magnet housing  64  to rotate within the bore  54  of the stationary wall  50  about the axis  48 . The sensor located at the stationary wall  50  receives information regarding the oscillation of the swashplate  26  from the sensor magnet  120  inside of the sensor magnet housing  64 . This information is sent to the processor to determine the oscillation angle of the swashplate  26 . In some embodiments, the magnet and the processor may be able to calculate the amount of oscillation using the velocity of the sensor magnet  120  and the length of time of rotation. In other embodiments, the speed or acceleration of the swashplate  26  may also be measured.  
         [0026]     While the above description describes the use of the flexible input sensor assembly  58  in an oscillating machine application, it is to be understood that the flexible input sensor assembly of the invention can also be used in rotary devices as well.  
         [0027]     Various features and advantages of the invention are set forth in the following claims.