Abstract:
A slue position sensing system and method of modifying a machine to include such a slue position sensing system are disclosed. The slue position sensing system may include a swing sensor housing disposed between a swing motor and a swing drive. The swing sensor housing may be coupled to a rotary position sensor that indirectly detects rotation of the target gear or a speed sensor that directly detects rotation of the target gear. For embodiments with no target gear, but with upper and lower frames rotatably coupled together by a ring gear and a swing gear, the sensor may be a rotary position sensor mounted to a slip ring assembly and magnet that are connected to a hydraulic swivel between the upper and lower frames or the sensor may be a speed sensor that detects rotation of the swing gear. The sensors generate a signal that is communicated to a controller or an ECM that accurately reflects the angular movement imparted to the work implement by the swing drive.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to a system and method for determining the slue position or angular position of one component with respect to another component. For example, this disclosure relates generally to a system and method for determining the slue position of a housing of an excavator, crane, foundation drill, material handler, etc., with respect to an undercarriage that supports the housing. 
       BACKGROUND 
       [0002]    Many machines include one or more components that rotate relative to one another. For example, typical excavators, cranes, foundation drills, material handlers, etc. include a housing disposed on top of an undercarriage. The housing is attached to a work implement such as a bucket connected to an arm and/or a boom. The housing rotates about a vertical axis with respect to the undercarriage. These machines may include a positioning system that includes a motor that rotates a gear assembly associated with a swing gear train, which in turn, rotates the housing. A closed loop control system positions the housing to a desired position. An operator rotates the housing to a desired position by accelerating the housing from a start position and decelerating the housing prior to reaching the desired position. However, the inertial forces created by a rotating housing with varying loads make it difficult to rotate the housing to the desired position accurately. Specifically, once the machine begins a rotational motion, inertia caused by the rotation may cause the housing to overshoot the desired position. This problem is prevalent when the excavator is working on a hillside or when the work implement of the machine is carrying a full load. 
         [0003]    Automated controls that regulate the dig and dump cycles of these machines require accurate sensors to monitor the actual position of the housing. Some machines include a position-sensing system with a sensor that generates a signal related to proximity of the sensor element to a component or to a projection of a component, such as a gear tooth. Other position-sensing systems may include a sensor that senses rotational movement of a component, such as a gear. Unfortunately, a number of factors may cause significant variations in the values of the signals generated by such sensors. For example, vibrations, temperature variations, variations in the characteristics of the sensor and/or variations in the characteristics of power supplied to the sensor may increase or decrease the sensor signal value. Because of variations in such parameters, a position-sensing system employing one or more sensors may be inaccurate and therefore more robust position-sensing systems are needed. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    In one example, a disclosed slue position sensing system may include a swing sensor housing that accommodates a target gear. Slue position may be measured using a speed sensor, which essentially counts the number of target gear teeth that pass the speed sensor. Slue position may also be measured using a target shaft that rotates with the target gear. One end of the target shaft may be directed to a rotary position sensor, which essentially counts the rotation of the target shaft and therefore the rotations of the target gear. 
         [0005]    One disclosed slue position sensing system may include a swing sensor housing that accommodates a target gear and a target shaft. The target gear may be coupled to a drive shaft. The drive shaft may pass through a helical gear. The target shaft may include a magnetized sensor end, a coupling end and a driven gear disposed between the coupling and sensor ends. The swing sensor housing may rotatably support the sensor end of the target shaft and the coupling end of the target shaft with the driven gear being enmeshed with the helical gear and the sensor end in proximity to a rotary position sensor. The rotary position sensor may be coupled to a controller. 
         [0006]    In such an embodiment, the target gear may be coupled to a swing drive motor. The drive shaft may couple the target gear to a sun gear. The swing sensor housing may be disposed between a swing motor and a swing drive. The target shaft may extend across the swing sensor housing and the swing sensor housing may include two openings including a coupling opening and a sensor opening. The coupling end of the target shaft may be received in the coupling opening; the sensor end of the target shaft may be received in the sensor opening. Further, the rotary position sensor may be coupled to the sensor opening. In any of the systems disclosed above, the swing sensor housing may be round (cylindrical) or rectangular with two opposing walls. In systems employing a target shaft, coupling opening may accommodate a first bearing through which the coupling end of the target shaft may pass and the sensor opening may accommodate a second bearing through which the sensor end of the target shaft may pass. At least part of the rotary position sensor may be mounted to an exterior surface of the swing sensor housing. Any of the disclosed systems may further include placement of the swing sensor housing between a swing motor and a swing drive. In any of the disclosed systems, the sensor end of the target shaft may include a non-cylindrical shape. 
         [0007]    Another disclosed slue position sensing system may be employed for upper and lower frames that rotate with respect to each other, such as an upper frame and an undercarriage of a wheel excavator that are rotatably coupled together by a ring gear and a swing gear. The upper frame is coupled to at least one of a rotary position sensor or speed sensor. When a rotary position sensor is employed, the rotary position sensor is part of an assembly that includes a slip ring assembly and a magnetized element disposed between the slip ring assembly and the rotary position sensor. The slip ring assembly is mounted to a swivel, one end of which is coupled to the upper frame and the other end of which is coupled to the lower frame. When a speed sensor is employed, the speed sensor is mounted to the upper frame in close proximity to the swing gear so the speed sensor can detect rotation of the swing gear. 
         [0008]    Methods for retrofitting a swing motor and swing drive assembly with a slue position sensing system are also disclosed. One disclosed method may include: disassembling the swing motor from the swing drive; providing a swing sensor housing that may include at least one opening; installing a target gear in the swing sensor housing; installing a speed sensor over the opening so the speed sensor can detect target gear teeth passing the speed sensor. Another method includes installing a target shaft in the swing sensor housing. The target shaft includes a sensor end that is magnetized. The target shaft passes through a driven gear and the drive shaft passes through a helical gear. The driven and helical gears are enmeshed. The method further includes placing the rotary position sensor in the sensor opening in proximity to the sensor end of the target shaft. 
         [0009]    The rotary position sensor or speed sensor may be coupled to a controller. Any of the disclosed methods may further include sealing the rotary position sensor or speed sensor in a sensor opening in the swing sensor housing. Any of the disclosed methods may also include having the swing sensor housing accommodate two speed sensors for redundancy. 
         [0010]    Another method for retrofitting a swing drive assembly with a slue position sensing system includes providing an upper frame and a lower frame. The lower frame is coupled to a ring gear and the upper frame is coupled to a swing gear. The swing gear and ring gear are enmeshed so the upper frame may rotate about the ring gear. The method includes coupling at least one of a rotary position sensor or a speed sensor to the upper frame. 
         [0011]    If a rotary position sensor is used, the rotary position sensor may be supported above a slip ring assembly with a magnetic element disposed between the slip ring assembly and the rotary position sensor. The slip ring assembly is disposed between the magnetic element and a swivel. The swivel includes an upper end coupled to the upper frame and a lower end coupled to the lower frame. The upper and lower ends of the swivel are rotatable with respect to each other. The swivel may be a hydraulic swivel that provides fluid communication between the upper and lower frames. 
         [0012]    If a speed sensor is used, the speed sensor may be coupled to the upper frame in close proximity to the swing gear. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a swing motor, swing drive and a swing sensor housing disposed between the swing motor and swing drive; 
           [0014]      FIG. 2  is a top perspective view of the swing drive illustrated in  FIG. 1  with the swing sensor housing and swing motor removed; 
           [0015]      FIG. 3  is a top perspective view of the swing drive and swing sensor housing illustrated in  FIG. 1  with the swing motor removed; 
           [0016]      FIG. 4  is a perspective view of a disclosed target shaft, particularly illustrating the driven gear that is carried by the target shaft; 
           [0017]      FIG. 5  is a perspective view of the swing drive, target shaft and swing sensor housing, shown in phantom; 
           [0018]      FIG. 6  is a partial perspective view of the splined drive shaft, target gear, target shaft and particularly illustrating the coupling of the driven gear disposed on the target shaft with the helical gear disposed on the splined drive shaft; 
           [0019]      FIG. 7  is a perspective view of the splined drive shaft, helical gear and target gear; 
           [0020]      FIG. 8  is a top perspective view of the swing drive and swing sensor housing with the swing motor removed to reveal the target gear and top female end of the splined drive shaft; 
           [0021]      FIG. 9  is a front perspective view of the swing sensor housing and assembly and planetary gear system, particularly illustrating the lower male end of the splined drive shaft coupled to a sun gear; 
           [0022]      FIG. 10  is a top plan view of the swing sensor housing and associated assembly; 
           [0023]      FIG. 11  is a sectional view taken substantially along line  11 - 11  of  FIG. 10 ; 
           [0024]      FIG. 12  is a sectional view taken substantially along line  12 - 12  of  FIG. 10 ; 
           [0025]      FIG. 13  is a perspective view of a swing drive, target gear and drive shaft in an embodiment that features the use of two speed sensors for redundantly detecting rotation of the target gear; 
           [0026]      FIG. 14  is a sectional view of a lower frame, upper frame, rotary position sensor assembly, ring gear and swing gear; 
           [0027]      FIG. 15  is an enlarged sectional view of the lower frame, upper frame, rotary position sensor assembly, ring gear and swing gear illustrated in  FIG. 14 ; 
           [0028]      FIG. 16  is a perspective view of the rotary position sensor assembly illustrated in  FIGS. 14 and 15 ; 
           [0029]      FIG. 17  is a partial sectional view of the rotary position sensor assembly illustrated in  FIGS. 14-16 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Turning to  FIG. 1 , a system  20  for rotating a work implement with respect to a track undercarriage, or, in other words, a slue positioning system  20  is disclosed. The positioning system  20  may include a swing motor assembly  21  disposed on top of a swing sensor housing  22 . The swing sensor housing  22 , in turn, may be disposed on top of a swing drive  23 . The swing drive  23  is illustrated in  FIG. 2  with the swing sensor housing  22  and swing motor assembly  21  removed. Specifically, the swing drive  23  may include a casing  24  and a swing drive cover plate  25 . The swing drive cover plate  25  in combination with the swing casing  24  may house a series of gears, one of which is a sun gear  26  and a plurality of planetary gears, two of which are shown in partial view at  27  in  FIG. 2 . A series of studs  28  may be used to secure the swing sensor housing  22  to the swing drive cover plate  25 . 
         [0031]    Turning to  FIG. 1 , an oil dip stick tube  31  and dip stick  32  are employed to check the oil levels in the swing drive  23 . A speed sensor  33  may be used to measure the speed of the angular motion transmitted from the swing motor assembly  21  to the swing drive  23 . As an alternative or for purposes of redundancy, a rotary position sensor  40  may be mounted to the swing sensor housing  22 . One or both of the sensors  33 ,  40  may be used to determine the slue position and will be described in greater detail below in connection with  FIGS. 10-13 . 
         [0032]    Turning to  FIG. 3 , the swing sensor housing  22  may include a breather assembly  34 , a coupling opening  35 , which is used to accommodate and support a coupling end  36  of the target shaft  38  shown in  FIG. 4 . An additional opening  29  is provided for supporting the speed sensor  33  ( FIG. 1 ), which may be used with the target shaft  38  and rotary position sensor  40  or instead of the target shaft  38  and rotary position sensor  40 . The studs  28  extend through the swing sensor housing  22  and may be used to secure the swing sensor housing  22  to the swing motor assembly  21  ( FIG. 1 ) or, in other words, to sandwich the swing sensor housing  22  between the swing motor assembly  21  and the swing drive  23 . A series of fasteners  37  may be used to secure the swing drive cover plate  25  to the swing casing  24 . 
         [0033]    The target shaft  38 , the function of which will be described in greater detail in below, is illustrated in  FIG. 4  and may be used with a rotary position sensor  40 . Again, as an alternative or as a back-up, a speed sensor  33  may be employed. The target shaft  38  may include a coupling end  36  and a sensor end  39 . Bushings  41  may be used to support the target shaft for rotational movement within the swing sensor housing  22  as discussed below. The target shaft  38  may include a shaft portion  42  that may pass through a driven gear  43 . The shaft portion  42  may extend to the coupling end  36  or, as illustrated in  FIG. 4 , may pass through a separate sleeve  44 . The position and support of the target shaft  38  within the swing sensor housing  22  is illustrated in  FIG. 5 . The swing sensor housing  22  is illustrated in phantom for this purpose. The coupling end  36  of the target shaft  38  may be supported within a coupling opening  35  and the sensor end  39  of the target shaft  38  may be supported within a sensor opening  45 . The sensor housing  22  may include an upper opening  46  through which a splined drive shaft  47  ( FIGS. 6-7 ) may pass as well as through opening  59  through which the studs  28  may pass. 
         [0034]    Turning to  FIGS. 6-7 , the splined drive shaft  47 , target gear  48 , helical gear  49  and the coupling between the driven gear  43  and the target shaft  38  are illustrated. The splined drive shaft  47  may include a motor end  51  with a female splined opening  50  that may be coupled to the swing motor assembly  21 . The splined drive shaft  47  may pass through the target gear  48  as well as the helical gear  49 . As shown in  FIG. 7 , the splined drive shaft  47  may also include a swing drive end  60 , which may be splined, and which may be received in the sun gear  26  (see  FIGS. 2 and 5 ). The splined drive shaft  47  may pass through the helical gear  49  or the helical gear  49  may be an integral part of the splined drive shaft  47 . The target gear  48  may be held in place on the splined drive shaft  47  by one or more snap rings shown at  53 . A snap ring  54  can also be used to retain the coupling end  36  of the target shaft  38  in the coupling opening  35  ( FIG. 3 ). An additional fastener such as a nut  55  may also be used to secure the bushings  41  in place against the sleeve  44 . The snap ring  56  ( FIG. 7 ) may be used to secure the swing drive end  60  of the splined drive shaft  47  in the sun gear  26  ( FIG. 9 ). 
         [0035]    Turning to  FIGS. 8-10 , and first to  FIG. 8 , the target gear  48  and motor end  51  of the splined drive shaft  47  are accommodated within the swing sensor housing  22 . As shown in  FIG. 9 , the coupling opening  35  may be enclosed by a cover  57  in suitable sealant or sealing members such as silicone or an o-ring. The distal end or swing drive end  60  of the splined drive shaft  47  may be received in the sun gear  26  and secured in place by the snap ring  56 . The sun gear  26  may be enmeshed with a plurality of planetary gears  58  as illustrated in  FIG. 9 . 
         [0036]      FIG. 10  is a top view of the swing sensor housing  22 , particularly illustrating the opening  61  that receives the target gear  48  and splined drive shaft  47 .  FIG. 11  also illustrates the relative position of the target shaft  38 , which is shown in phantom and the rotary position sensor  40 . 
         [0037]      FIGS. 11-12  are sectional views of  FIG. 10 . In  FIGS. 10 and 11 , it can be seen that the target shaft  38  may pass in close proximity to the speed sensor  33 .  FIG. 11  also illustrates the coupling or enmeshment between the helical gear  49  and the driven gear  43  of the target shaft  38 .  FIG. 11  also illustrates the female splined opening  50  for coupling the splined drive shaft  47  to the swing motor assembly  21 . 
         [0038]      FIG. 12  illustrates the relative position between the target shaft  38  and the splined drive shaft  47 . The target shaft  38  may be supported in the sensor opening  45  and the coupling opening  35  by the bushings  41 . The driven gear  43  may be enmeshed with the helical gear  49  which rotates the target shaft  38  and the magnet or magnetized sensor end  39  of the target shaft  38 . Rotation of the sensor end  39  in close proximity to rotary position sensor  40  provides a signal that reflects the number of rotations of the helical gear  49  and therefore the splined drive shaft  47 . This, in turn, can be directly converted to a slue position angle. 
         [0039]    Thus, the slue positioning system  20  illustrated in  FIGS. 1-12  may employ one speed sensor  33 , two speed sensors  33 , a rotary position sensor  40 /target shaft  38  or a combination of a speed sensor  33  and rotary position sensor  40 /target shaft  38 .  FIG. 1  illustrates the use of a speed sensor  33  in combination with a rotary position sensor  40 .  FIG. 13  illustrates the use of two speed sensors  33 . 
         [0040]      FIGS. 14-17  illustrate an embodiment applicable to equipment that does not include a target gear  48 . As shown in  FIGS. 14-15 , and a lower frame  70  (or undercarriage) is rotatably coupled to an upper frame  71  by a ring gear  72  that is enmeshed with the swing gear  73 . The swing gear  73  is accommodated within a bearing  74  that is connected to the upper frame  71 . The lower frame  70  is connected to the ring gear  72  by one or more shafts or posts  75 . Rotation of the upper frame  71  with respect to the lower frame  70  is detected and measured by the rotary position sensor assembly  80 , which is illustrated in greater detail in  FIGS. 15-17 . 
         [0041]    Turning to  FIGS. 15-16 , rotary position sensor  40  is mounted to a cover  81  which encloses a slip ring assembly  82  (see  FIG. 17 ). The cover  81  or the slip ring assembly  82  may be mounted to a swivel  83 . The swivel  83  may be a hydraulic swivel with a central passageway  84  and various ports shown at  85  in  FIGS. 15-16  for the purpose of communicating hydraulic fluid between the upper and lower frames  70 ,  71 . 
         [0042]    The swivel  83  includes an upper end  86  that is coupled to the upper frame  71  and a lower end  87  that is coupled to the lower frame  70  as best seen in  FIG. 15 . Turning to  FIG. 16 , the upper end  86  of the swivel  83  includes a tab or fork  88  which is coupled to the upper frame  71  to maintain an alignment between the sensor  40 , cover  81  and the upper frame  71 . Similarly, the lower end  87  of the swivel  83  also includes a tab  89  which is received in the fork  91  that is connected to the lower frame  70  to maintain an alignment between the magnet  92 , slip ring assembly  82  and lower frame  70  (as well as lower end  87  of the swivel  83 ). 
         [0043]    As shown in  FIG. 17 , the rotary position sensor  40  is mounted on top of the cover  81  which encloses the slip ring assembly  82 . The slip ring assembly  82  is coupled to the upper end  86  of the swivel  83 . In operation, as the upper frame  71  rotates with respect to the lower frame  70 , the sensed element or magnet  92  rotates with respect to the rotary position sensor  40 , which has a fixed positional relationship with the upper frame  71 . The rotary position sensor  40  may be coupled to an electronic control module (ECM)  63  as shown. 
         [0044]    If the rotary position sensor assembly  80  of  FIGS. 14-17  is not employed, a speed sensor  33  may be positioned above the swing gear  73  as illustrated in  FIG. 15 . Regardless, the speed sensor  33  could be employed for the sake of redundancy. 
       INDUSTRIAL APPLICABILITY 
       [0045]    Thus, a system for sensing or detecting the slue position of a machine, such as an excavator, crane, foundation drill, material handler, etc. is shown and described. One disclosed system may include a swing sensor housing sandwiched between a swing motor or swing motor assembly and a swing drive. The swing motor may be coupled to the swing drive assembly through the swing sensor housing. A rotary position sensor or a speed sensor may be used to measure the rotation of the target gear. As described above, the rotary position sensor or the speed sensor may be a MEMS based device. 
         [0046]    Another disclosed slue position sensing system may be employed for upper and lower frames that rotate with respect to each other, such as an upper frame and an undercarriage of a wheel excavator that are rotatably coupled together by a ring gear and a swing gear. The upper frame is coupled to at least one of a rotary position sensor or speed sensor. When a rotary position sensor is employed, the rotary position sensor is part of an assembly that includes a slip ring assembly and a magnetized element disposed between the slip ring assembly and the rotary position sensor. The slip ring assembly is mounted to a swivel, one end of which is coupled to the upper frame and the other end of which is coupled to the lower frame. When a speed sensor is employed, the speed sensor is mounted to the upper frame in close proximity to the swing gear so the speed sensor can detect rotation of the swing gear. 
         [0047]    Methods for retrofitting a swing motor and a swing drive assembly with a slue position sensing system are also disclosed. One disclosed method may include disassembling the swing motor from the swing drive and mounting a swing sensor housing between the swing motor and swing drive. A target gear may be installed in the swing sensor housing and may be coupled to a splined drive shaft that may be coupled to the swing motor through the swing sensor housing to the swing drive. A speed sensor or a rotary position sensor may be used to measure the rotation of the target gear for determining slue position. 
         [0048]    Another method for retrofitting a swing drive assembly with a slue position sensing system includes providing an upper frame and a lower frame. The lower frame is coupled to a ring gear and the upper frame is coupled to a swing gear. The swing gear and ring gear are enmeshed so the upper frame may rotate about the ring gear. The method includes coupling at least one of a rotary position sensor or a speed sensor to the upper frame.