Abstract:
The present disclosure is directed towards a hydraulic motor. The hydraulic motor may include a housing having a fluid inlet and a fluid outlet. The hydraulic motor may further include a shaft rotatably disposed within the housing, a rotating element coupled to the shaft configured to rotate with the shaft, and a plurality of pumping elements coupled to the rotating element in fluid communication with the fluid inlet and fluid outlet. The hydraulic motor may also include a brake rotor coupled to the shaft and a braking mechanism selectively coupled to the brake rotor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from U.S. Provisional Application No. 61/193,771 to Nelson filed on Dec. 22, 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to a hydraulic motor and, more particularly, to a hydraulic motor with a braking system. 
       BACKGROUND 
       [0003]    Machines such as excavators, dozers, loaders, motor graders, or any other earth moving machine generally include an engine-driven hydraulic pump fluidly connected to one or more hydraulic drive motors for powering one or more propulsion devices to propel the machine. The hydraulic drive motors include an integrated braking mechanism to exert a braking force when the supply of driving fluid is suspended. The braking mechanism typically includes a piston that selectively engages a plurality of friction disks associated with a barrel plate of the hydraulic drive motor. When engaged, the piston is pressed against the friction disks, thereby exerting a significant frictional force on the barrel plate, which substantially prevents rotation and, therefore, operation of the hydraulic drive motor. 
         [0004]    An alternative configuration is disclosed in U.S. Pat. No. 4,464,979 (“the &#39;979 patent”) issued to Forster on Aug. 14, 1984. The &#39;979 patent discloses an axial piston machine having a drive-flange shaft supported by two radial bearings and a gear wheel located on the drive-flange shaft between the radial bearings. The axial piston machine further includes a first and second brake disk associated with the gear wheel. Pressurized fluid directs an actuator piston against the first disk which in turn presses against the second disk. In this manner, the actuator piston generates friction against both the first and second disks, thereby slowing rotation of the drive-flange shaft of the axial piston machine. 
         [0005]    Although the axial piston machine arrangement of the &#39;979 patent may be adequate for some situations, other problems persist. In order to service, inspect, and/or repair the brake disks of the axial piston machine disclosed in the &#39;979 patent, a portion of the axial piston machine housing needs to be removed to gain sufficient access to the brake disks. Gaining access to the brake disks by moving at least a portion of the axial piston machine&#39;s housing may be labor intensive and time consuming. 
         [0006]    The following structure and system is directed to one or more improvements in the existing technology. 
       SUMMARY 
       [0007]    In one aspect, the present disclosure is directed towards a hydraulic motor. The hydraulic motor may include a housing having a fluid inlet and a fluid outlet. The hydraulic device may further include a shaft rotatably disposed within the housing, a rotating element coupled to the shaft configured to rotate with the shaft, and a plurality of pumping elements coupled to the rotating element in fluid communication with the fluid inlet and fluid outlet. The hydraulic device may also include a brake rotor coupled to the shaft and a braking mechanism selectively coupled to the brake rotor. 
         [0008]    In another aspect, the present disclosure is directed towards a method of operating a hydraulic motor with a braking system. The hydraulic motor may include a housing having a first port and a second port, a shaft rotatably disposed within the housing, and a brake rotor coupled to the shaft. The method may include adjusting a supply of pressurized fluid delivered to one of the first port and the second port; and selectively engaging the brake rotor to restrain rotation of the shaft 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic illustration of an exemplary disclosed machine; 
           [0010]      FIG. 2  is a cross-sectional illustration of an exemplary hydraulic motor of the machine of  FIG. 1  having a braking system. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1  illustrates an exemplary machine  10 . Machine  10  may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, machine  10  may be an earth moving machine, such as an excavator, a wheel loader, a backhoe, or any other suitable earth moving machine known in the art. Machine  10  may include, among other things, one or more traction devices  12 , a power source  14 , and a transmission  16  including a hydraulic motor  20  having a braking system  43  ( FIG. 2 ). 
         [0012]    Referring back to  FIG. 1 , traction devices  12  may include one or more tracks located on each side of machine  10  (only one side shown). Alternatively, traction devices  12  may include belts, wheels, or other traction devices known in the art. Any of traction devices  12  may be driven and/or steerable. 
         [0013]    Power source  14  may provide power for the operation of machine  10 . Power source  14  may embody a combustion engine, such as a diesel engine, a gasoline engine, a gaseous fuel powered engine (e.g., a natural gas engine), or any other type of combustion engine known in the art. Power source  14  may alternatively embody a non-combustion source of power such as a power storage device or any other suitable source of power. 
         [0014]    Transmission  16  may include components that cooperate to efficiently transmit energy from power source  14  to traction devices  12 . Transmission  16  may include a torque converter (not shown) for adjusting output torque from power source  14 , a transmission controller (not shown) for controlling the operation of transmission  16 , or any other such device for transmitting energy to traction devices  12 . Although transmission  16  is illustrated as a hydrostatic transmission, it is contemplated that transmission  16  may include a hydro-mechanical transmission or any other means for transmitting power from power source  14 . 
         [0015]    Hydraulic pump  18  of transmission  16  may be operatively coupled to power source  14  and may be configured to convert at least a portion of a power output of power source  14  into a flow of pressurized fluid for driving hydraulic motor  20  associated with machine  10 . Hydraulic pump  18  may be drivably connected to power source  14  via, for example, an input shaft  19 . Alternatively, hydraulic pump  18  may be operably coupled to power source  14  via a torque converter (not shown), a clutch (not shown), a gear box (not shown), or in any other manner known in the art. Hydraulic pump  18  may be variable displacement, variable delivery, fixed displacement, or any other configuration known in the art. Hydraulic pump  18  may include an axial piston pump, a gear pump, a radial piston pump, or any other rotary driven device for pressurizing a flow of fluid. 
         [0016]    Hydraulic motor  20  of transmission  16  may be fluidly connected to hydraulic pump  18  and may be configured to receive a flow of pressurized fluid from hydraulic pump  18 . The flow of pressurized fluid through hydraulic motor  20  may cause an output shaft  22  of hydraulic motor  20  connected to traction devices  12  to rotate, thereby propelling and/or steering machine  10 . Output shaft  22  of hydraulic motor  20  may be connected to traction devices  12  by, for example, a final drive  23 . Final drive  23  may include a reduction gear arrangement, such as, for example, a bevel gear assembly, spur gear assembly, planetary gear assembly, and/or any other assembly known to those having skill in the art that provides a speed reduction. Although hydraulic motor  20  is illustrated as a drive for traction devices  12  it is contemplated that hydraulic motor  20  may be used in any application of machine  10  that may require mechanical energy to operate. 
         [0017]    As illustrated in the embodiment of  FIG. 2 , hydraulic motor  20  may be an assembly of multiple components that interact to produce an output torque. In particular, hydraulic motor  20  may include a housing  28 , a rotor  32 , and output shaft  22 . As described above, output shaft  22  may be coupled to traction devices  12  in a manner such that the rotational speed of output shaft  22  is directly proportional to the rotational speed of traction devices  12 . Rotor  32  may be integral with output shaft  22  or, alternatively, joined to output shaft  22  through welding, sintering, or other known metal joining processes so that rotor  32  and output shaft  22  may rotate together. Output shaft  22  may extend through an opening in one end of housing and may be rotationally supported by housing  28  via bearings  31 . 
         [0018]    A plurality of piston members  34  may be fixedly connected to rotor  32 . Each piston member  34  may be received in a respective piston sleeve  36 . Specifically, each piston sleeve  36  may be coupled in a sealing manner around a spherical seal (not shown) of piston member  34 . The plurality of piston sleeves  36  may be connected to barrel plate components  38  disposed in, for example, a first end  24  and a second end  26  of a central bore  27  of housing  28 . Barrel plate components  38  disposed in first end  24  and second end  26  of central bore  27  may be connected to rotate with output shaft  22 . Specifically, barrel plate components  38  may be fitted around output shaft  22  by a ball hinge and coupled to the output shaft  22  by, for example, a key connection. The ball hinge allows the barrel plate components  38  to wobble or tilt during rotation of output shaft  22  as barrel plate components  38  ride against an axial cam formed by face plates  40  disposed at first end  24  and second end  26  of housing  28 . As output shaft  22 , rotor  32 , and barrel plate components  38  rotate, each piston sleeve  36  may move toward and away from a respective piston member  34  as barrel plate components  38  wobble or tilt. This reciprocation of piston sleeves  36  with respect to the piston members  34  causes an expansion and contraction of a chamber located in piston sleeves  36 . While hydraulic motor  20  illustrated in the exemplary embodiment of  FIG. 2  is described as a motor, it is understood that hydraulic motor  20  may function as both a pump and a motor depending on the tilt angle of the barrel components  38 . 
         [0019]    Housing  28  may include a plurality of ports in flow communication with the chamber located in piston sleeves  36 . In one embodiment, housing  28  may include a first port  64  and a second port  66 . First port  64  and second port  66  may be configured to provide flow communication between hydraulic pump  18  and the chamber in piston sleeves  36 . More particularly, either one of first port  64  and second port  66  may act as a fluid inlet and deliver pressurized fluid from hydraulic pump  18  to piston sleeves  36  via distribution passageways  60  in housing  28  to drive output shaft  22 . The other of first port  64  and second port  66  may act as a fluid outlet and return low pressure fluid to hydraulic pump  18 . 
         [0020]    Hydraulic motor  20  may include braking system  43  to exert a braking force when the supply of pressurized fluid to hydraulic motor  20  is suspended. Braking system  43  may include a brake rotor  44 , and a braking mechanism  46  including one or more components configured to resist the rotation of brake rotor  44 . Braking mechanism  46  may include brake springs  50 , an actuator piston  52 , and one or more brake disks  48 . 
         [0021]    Brake rotor  44  may be disposed in housing  28  and embody a plate-like member fixedly connected to an end of output shaft  22  such that a rotation of output shaft  22  results in a direct rotation of brake rotor  44 . Brake rotor  44  may be integral to output shaft  22  or, alternatively, joined to output shaft  22  through welding, sintering, or other known metal joining processes. Brake rotor  44  may be held in place by way of a snap ring  54 . It is contemplated that brake rotor  44  may be held in place by a fastener other than a snap ring, if desired, such as, for example a nut, pin, or any other fastener known to one skilled in the art. 
         [0022]    Actuator piston  52  may disposed in housing  28  coaxially with brake rotor  44  on one side of brake rotor  44 . Actuator piston  52  may receive a plurality of brake springs  50  in a plurality of bores formed in actuator piston  52 . In one embodiment, the brake springs  50  may be received in a plurality of bores located on the periphery of actuator piston  52 . The plurality of brake springs  50  may be configured to bias actuator piston  52  against brake disks  48 . An end plate  45  may be provided to seal housing  28  and retain the plurality of brake springs  50  and actuator piston  52  in housing  28 . 
         [0023]    Brake disks  48  may be connected by way of a splined engagement to brake rotor  44  and configured to rotate together with brake rotor  44 . Brake disks  48  may include alternating steel disks and friction disks such that, when actuator piston  52  is acted on by brake springs  50 , brake disks  48  may be sandwiched between actuator piston  52  and housing  28  creating friction that resists the rotation of brake rotor  44 . It will be understood that the number of brake disks  48  may vary, depending, for example, on the machine braking capacity. For example, while two steel disks and one friction disk are illustrated in the exemplary embodiment of  FIG. 2 , three or more steel disks and two or more friction disks may be used. While the exemplary embodiment of  FIG. 2  may depict a gap between actuator piston  52  and brake disks  48 , it is understood that the actuator piston and brake disks may be in frictional contact. 
         [0024]    A pressure modulation chamber  56  may be formed between housing  28  and actuator piston  52 . Pressure modulation chamber  56  may be configured to receive pressurized fluid from one of first port  64  and second port  66 . More particularly, pressure modulation chamber  56  may be fluidly connected to first port  64  and second port  66  via distribution passages  60 . In one embodiment, a resolver  62  may be disposed in a portion of distribution passageway  60 , and may be configured to resolve the pressure of pressurized fluid contained within first and second ports  64 ,  66  and fluidly connect the respective ports thereof having higher pressure with pressure modulation chamber  56 . For example, when the fluid at second port  66  has a pressure less than the pressure of fluid contained within pressure modulation chamber  56 , resolver  62  may fluidly connect pressure modulation chamber  56  with first port  64 . In this manner, pressurized fluid may be communicated to pressure modulation chamber  56  to act on a portion of actuator piston  52  and urge actuator piston  52  in a direction opposite of brake disks  48 . It is contemplated that a valve such as, for example, a hydraulic valve, a pneumatic valve, or an electronic valve may be used in place of resolver  62 . In yet another embodiment, a proportional valve may be placed in distribution passageway  60  to selectively communicate pressurized fluid to pressure modulation chamber  56  and control the braking force applied to brake rotor  44 . 
       INDUSTRIAL APPLICABILITY 
       [0025]    The braking system of the present disclosure may find application in any type of machine including a hydraulic motor. For example, the present disclosure may be applicable to any machine including a hydraulic motor for powering one or more propulsion devices to propel the machine. In one embodiment, hydraulic motor may be a floating-cup motor have a plurality of piston members that interact with a plurality of cup-like piston sleeves hydrostatically supported by a barrel plate component. Operation of the disclosed braking system is explained below. 
         [0026]    In operation, according to the exemplary embodiment of  FIG. 1 , power source  14  may drive hydraulic pump, via input shaft  19 , to produced pressurized fluid. The pressurized fluid generated by hydraulic pump  18  may then be supplied to hydraulic motor  20  via one of first and second ports  64 ,  66  ( FIG. 2 ). The flow of pressurized fluid may be distributed to the pumping chambers formed by piston members  34  and piston sleeves  36  via distribution passageways  60  in housing  28 . The other of first port  64  and second port  66  may discharge low pressure fluid from hydraulic motor  20 . 
         [0027]    When pressurized fluid is supplied to one of first port and second ports  64 ,  66 , a portion of the flow of pressurized fluid may be communicated to pressure modulation chamber  56 . More particularly, resolver  62  may be configured to resolve the pressure of pressurized fluid contained within first and second ports  64 ,  66  and fluidly connect the respective ports thereof having higher pressure with pressure modulation chamber  56 . For example, when the fluid at second port  66  has a pressure less than the pressure of fluid contained within pressure modulation chamber  56  (i.e., when first port  64  receives high pressure fluid from hydraulic pump  18 ), resolver  62  may fluidly connect pressure modulation chamber  56  with first port  64 . 
         [0028]    As pressure modulation chamber  56  is filled with pressurized fluid, the fluid may act on a portion of actuator piston  52 . At high fluid pressures, the pressure force may be greater than the spring force of brake springs  50  to drive actuator piston  52  in a direction opposite of brake disks  48  connected to brake rotor  44 . Accordingly, as a portion of the chambers formed by piston member  34  and piston sleeve  36  are filled with pressurized fluid and a second portion of chambers formed by piston members  34  and piston sleeves  36  are drained of fluid, rotor  32  may be urged to rotate. As rotor  32  rotates, output shaft  22  may be free to rotate therewith to propelling machine  10 . 
         [0029]    When the supply of pressurized fluid to hydraulic motor  20  is suspended, a pressure differential may form across the distribution passages  60  between pressure modulation chamber  56  and each of first port  64  and second port  66 . Resolver  62  may fluidly connect pressure modulation chamber  56  with the one of first port  64  and second port  66  discharging fluid from hydraulic motor  20  so that pressurized fluid may drain from pressure modulation chamber  56 . For example, when the fluid at first port  64  has a pressure less than the pressure of fluid contained within pressure modulation chamber  56  (i.e., when first port  64  no longer receives high pressure fluid), resolver  62  may fluidly connect pressure modulation chamber  56  with second port  66 . As fluid drains from pressure modulation chamber  56 , brake springs  50  may return to it&#39;s biased position. In this manner, brake springs  50  may urge actuator piston  52  into frictional contact with brake disks  48  to exert a significant frictional force on brake rotor  44 , which may substantially prevent rotation of output shaft  22 . 
         [0030]    The disclosed braking system  43  may provide an alternative configuration for braking a hydraulic motor  20  in a drive application. Because braking system  43  may be located near at one end of output shaft  22 , closest to end plate  45 , the disclosed braking system  43  may be convenient to inspect/service during the lifetime of the machine. 
         [0031]    It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed braking system and hydraulic motor without departing from the scope of the disclosure. For example, although a single brake rotor  44  is illustrated, multiple brake rotors located on either end of output shaft  22  may be contemplated. In yet another example, brake rotor  44  may be omitted and braking mechanism  46  may alternatively be associated with rotor  32  of hydraulic motor  20 . It is to be understood that hydraulic motor  20  is not be limited to the embodiment illustrated in  FIG. 2 . Hydraulic motor  20  may include an inline motor, a bent-axis motor, or any other rotary driven device configured to receive a flow of pressurized energy and produce an output torque. It is further understood that the application of the disclosed braking system may be readily modified for use with, for example, any electric motor known in the art. 
         [0032]    Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.