Abstract:
The present disclosure is directed to a method for power management in a machine. The method for power management may include sensing a parameter indicative of a torque applied to a torque consuming device rotatably driven by a power source. The method may further include modifying a quantity of fuel supplied to the power source as a function of the sensed parameter.

Description:
TECHNICAL FIELD  
       [0001]    The present disclosure generally relates to power management and, more particularly, modifying power output of a power source as a function of a sensed torque load on the power source. 
       BACKGROUND  
       [0002]    Machines, such as, for example, wheel loaders, off-highway trucks, and other heavy construction and mining machines are used to perform many tasks. To effectively perform these tasks, the machines require a power source such as a diesel engine, a gasoline engine, a natural gas engine, a turbine engine, or any other type of power source. Such machines may also include a hydraulic power unit such as a pump, motor, and/or transmission configured to transmit an input from the power source into an output to complete these tasks. For example, a hydraulic pump may be configured to convert at least a portion of the power from the engine into a flow of pressurized fluid for driving one or more fluid actuators associated with a ground engaging device or for use in an implement circuit associated with an implement. 
         [0003]    Current power management systems do not effectively measure the amount of torque applied to a hydraulic pump and, therefore, do not recognize how much power a hydraulic pump may be consuming. Instead, current power management systems monitor and adjust based on, among other things, engine speed. As a hydraulic load of a hydraulic pump changes, the hydraulic pump requires a greater amount of power from the power source. This contributes to reduce the engine speed. When the engine speed falls below a desired engine speed, the power management system senses the speed change and reacts by increasing the supply of fuel to the engine to counter the decrease in engine speed and maintain the desired engine speed. 
         [0004]    Such a power management system may result in detrimental engine emissions. For example, the power management system may overcompensate for a speed decrease due to an increased hydraulic load. In such instances, the over fueling of the engine may produced detrimental emissions that may exceed governmental regulations. 
         [0005]    U.S. Pat. No. 6,817,253 (“the &#39;253 patent”) issued to Michael D. Gandrud on Nov. 16, 2004, discloses a hydraulic power unit having torque transducers integrated into the hydraulic power unit. A system controller is communicatively coupled to the torque transducers to use the information provided by the torque transducer to monitor the performance of the hydraulic power unit and control the hydraulic power unit to limit the torque or power required by a power source. Specifically, the controller of the &#39;253 patent is configured to control the hydraulic power unit by reducing the pressure or displacement of the hydraulic power unit in order to prevent over powering the power source such as stalling an internal combustion engine. 
         [0006]    While the &#39;253 patent may disclose a method of controlling a load of a hydraulic power unit to limit the power required of a power source, the &#39;253 patent does not compensate for the over fueling of the power source based on load fluctuations of the hydraulic power unit. Specifically, the &#39;253 patent does not disclose a method of modifying a fueling quantity supplied to the power source as a function of the sensed torque on the hydraulic power unit. Therefore, as the pressure or displacement of the hydraulic power unit of the &#39;253 patent is adjusted, the power source may continue to produce undesirable emissions. 
         [0007]    The disclosed methods and systems are directed to overcoming one or more of the problems set forth above and/or other problems in the art. 
       SUMMARY  
       [0008]    In one aspect, the present disclosure is directed to a method for power management in a machine. The method for power management may include sensing a parameter indicative of a torque applied to a torque consuming device rotatably driven by a power source. The method may further include modifying a quantity of fuel supplied to the power source as a function of the sensed parameter. 
         [0009]    In another aspect, the present disclosure is directed towards a machine. The machine may include a frame, an engine mounted to the frame, and one or more load devices operatively connected to the engine. The machine may further include a controller in communication with the engine and the one or more load device. The controller may be configured to regulate a quantity of fuel supplied to the engine based on a sensed change in load on the one or more load devices. 
         [0010]    In still another aspect, the present disclosure is directed to a method of generating a torque curve associated with a torque consuming device for use in a machine. The method may include measuring a twist angle of a shaft of the torque consuming device upon the application of a load on the torque consuming device, and measuring an actual torque applied to the shaft of the torque consuming device based on the applied load. The method may further include generating the torque curve based on a twist angle versus torque relationship and storing the torque curve on a medium associated with the torque consuming device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an illustration of an exemplary machine according to the present disclosure; 
           [0012]      FIG. 2  is a cross-sectional illustration of the exemplary hydraulic pump of the exemplary machine of  FIG. 1 ; 
           [0013]      FIG. 3  is a flowchart according to an exemplary disclosed embodiment; and 
           [0014]      FIG. 4  is a flowchart according to another exemplary disclosed embodiment. 
       
    
    
     DETAILED DESCRIPTION  
       [0015]      FIG. 1  illustrates an exemplary embodiment of a machine  10 . Machine  10  may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, or any other industry known in the art. For example, machine  10  may be an earth moving machine such as a wheel loader, an excavator, a dump truck, a backhoe, a motor grader, or any other suitable machine. Machine  10  may include a frame  12 , a power source  14 , a hydraulic pump  16 , an implement  20 , a ground engaging device  22 , and a controller  18 . 
         [0016]    Power source  14  may include an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel powered engine such as a natural gas engine, or any other engine apparent to one skilled in the art. The power of power source  14  may be expressed as the product of the torque delivered to an output shaft  24  of power source  14  multiplied by the angular speed of output shaft  24 . The angular speed of output shaft  24  may be related to engine speed. As engine speed increases, the angular speed of output shaft  24  may also increase. A decrease in engine speed may produce a corresponding decrease in the angular speed of output shaft  24 . 
         [0017]    Machine  10  may also include one or more load devices rotatably driven by power source  14 . The load device may be a device that applies a load onto power source  14  such as, for example, a torque consuming device. The torque consuming device may be defined as a device that applies a torque load onto power source  14  by consuming torque produced by output shaft  24 . The torque consuming device may be a pump, generator, fan, and/or any other device rotatably driven by power source  14 . Specifically, a rotating pump shaft  28  of hydraulic pump  16  may be coupled to the output shaft  24  of power source  14  by way of, for example, a gear train  30 . Hydraulic pump  16  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 known in the art. 
         [0018]    Hydraulic pump  16  may be configured to transform an input from power source  14  into an output, such as movement of implement  20 , ground engaging device  22 , and/or any other change in state of machine  10 . Specifically, hydraulic pump  16  may be configured to convert at least a portion of the power from power source  14  into a flow of pressurized fluid for an implement circuit associated with an implement  20  and/or for driving one or more drive motors associated with a ground engaging device  22 . Implement  20 , may include a blade, scraper, bucket, gripping device, and/or any other suitable implement. Ground engaging device  22  may include a wheel assembly, track type device, and/or any other suitable ground engaging device. 
         [0019]    Referring now to  FIG. 2 , hydraulic pump  16  may include a stationary pump housing  26  and pump shaft  28 . As described above, pump shaft  28  may be may be coupled to the output shaft  24  of power source  14  in a manner such that the rotation speed of pump shaft  28  is directly proportional to the rotation speed of the output shaft  24  of power source  14 . A barrel  32  may be fixedly attached to pump shaft  28  via a spline engagement so that pump shaft  28  and barrel  32  rotate together. Pump shaft  28  may extend through an opening in proximal end of stationary pump housing  26  and may be rotationally supported by pump housing  26  via a conventional arrangement such as a bearing pair. 
         [0020]    Barrel  32  may further include a plurality of piston openings  34  for receiving portions of a plurality of pump pistons  36 . Piston openings  34  may be equally angularly spaced about a pump shaft  28  longitudinal axis  29 . Piston openings  34  may be sized and oriented to allow for reciprocating movement of pump pistons  36  parallel to longitudinal axis  29  of pump shaft  28 . Ends of pump pistons  36  may be seated in a plurality of piston slippers  37  slidably engaging an adjustable, non-rotating swashplate  33  to control the displacement of pump pistons  36  within the piston openings  34 . In operation, pump pistons  36  rotate with pump shaft  28  and reciprocate in piston openings  34  as a function of the tilt angle of swashplate  33 . 
         [0021]    Pump shaft  28  of hydraulic pump  16  may include a first element  38  attached adjacent to a first end  40  of pump shaft  28  located proximate to the input from gear train  30  and power source  14  and on one side of swashplate  33 . Pump shaft  28  of hydraulic pump  16  may include a second element  42  fixed to a second end  44  of pump shaft  28  located on the side of swashplate  33  that is opposite the input from gear train  30  and power source  14 . In one embodiment, first element  38  may be a first magnet and second element  42  may be a second magnet. In an alternative embodiment, first element  38  may be a first projection and second element  42  may be a second projection. It is to be understood that first element  38  and second element  42  may be any physical configuration or feature on pump shaft  28  that may be detected by a sensor. It is also to be understood that first element  38  and second element  42  may be integral with pump shaft  28  or may be separate components that are attached to pump shaft  28 , and that reference herein to the element being “attached” or “coupled” to the pump shaft  28  includes both integral and separately attached elements. 
         [0022]    Stationary pump housing  26  may include a first sensor  46  and a second sensor  48  associated with first element  38  and second element  42 , respectively, of pump shaft  28 . First sensor  46  and second sensor  48  may include, for example, electrical and/or mechanical sensors or any combination thereof. First sensor  46  and second sensor  48  may be configured to detect first element  38  and second element  42 , respectively, as they pass during rotation of pump shaft  28 . First sensor  46  and second sensor  48  may be configured to generate a signal responsive to first element  38  and second element  42 . It is contemplated that signals established by first sensor  46  and second sensor  48  may embody any signal, such as, for example, a pulse, a voltage level, a digital signal, a magnetic field, a sound or light waves, and/or other signal formats known in the art. 
         [0023]    First sensor  46  and second sensor  48  may be configured to sense the amount of twist in pump shaft  28  as torque is applied to pump shaft  28 . First sensor  46  and second sensor  48  associated with first element  38  and second element  42 , respectively, may be positioned to sense the twist in pump shaft  28  between barrel  32  and the portion of pump shaft  28  coupled to the output shaft  24 . It will be understood that the position of first sensor  46  and second sensor  48 , as shown in  FIG. 2 , is exemplary, and that first sensor  46  and second sensor  48  may assume any position along pump shaft  28  that may allow first sensor  46  and second sensor  48  to sense a twist in pump shaft  28  between barrel  32  and the portion of pump shaft  28  coupled to the output shaft  24 . It is contemplated that multiple sensors may be used to sense the amount of twist in pump shaft  28  to provide a greater resolution of the amount of twist in pump shaft  28 . First sensor  46  and second sensor  48  may be additionally configured to sense the rotational speed of pump shaft  28 . 
         [0024]    Referring back to  FIG. 1 , controller  18  may be part of the control system for machine  10 , and may be configured to receive operating parameters associated with power source  14 , hydraulic pump  16 , and other machine components. For example, controller  18  may be communicatively coupled, by way of communication links  19 , to first sensor  46  and second sensor  48  associated with hydraulic pump  16 . Controller  18  may be configured to, among other things, determine a twist angle of the pump shaft  28  based upon a rotational time lag between first element  38  passing first sensor  46  and second element  42  passing second sensor  48 . 
         [0025]    Controller  18  may be further configured to store data and algorithms related to twists angles, torques, and/or fueling quantities. Such data may be stored in one or more look up tables within controller  18 . Alternatively or additionally, portions of the data may be derived from calculations using algorithms stored within controller  18  and based on various machine parameters. In one example, data may be stored in a torque curve for reference. The torque curve may provide torque data as a function of twist angle. In another example, data may be stored in a fuel supply adjustment curve for reference. The fuel supply adjustment curve may provide fueling adjustment data as a function of torque data. It will be apparent to one skilled in the art that a single map may be generated to provide fueling adjustment data as a function of twist angle and other inputs. 
         [0026]      FIG. 3  diagrammatically illustrates, in flowchart form, a method for generating a torque curve associated with a hydraulic pump  16 . Torque curves of various hydraulic pumps  16  may differ based on physical properties of, for example, pump shaft  28  of hydraulic pump  16 . Therefore, a torque curve may be generated for each hydraulic pump  16  during a performance test after pump production, i.e., end-of-line testing. While certain actions of the process are indicated in  FIG. 3 , as well as indicated in a particular sequence for purposes of explanation, it should be understood that this is exemplary, and that the sequence of actions may be other than that illustrated in  FIG. 3 . In addition, the actions that occur also may vary from the exemplary embodiment of  FIG. 3 . 
         [0027]    Referring to  FIG. 3 , at step  50 , pump shaft  28  may be set to rotate at a specified rotational speed (step  50 ). At step  55 , a twist may be induced on pump shaft  28  of hydraulic pump  16  by, for example, a load to hydraulic pump  16 . First sensor  46  and second sensor  48  may be used, at step  60 , to determine an amount of twist in pump shaft  28  by determining a rotational time lag between first element  38  passing first sensor  46  and second element  42  passing second sensor  48 . At step  70 , the rotational time lag may be multiplied by the rotational speed of pump shaft  28  to calculate a twist angle. A torque meter such as, for example, a strain gauge may be coupled to pump shaft  28  of hydraulic pump  16 . The torque meter may be configured to directly measure the applied torque to hydraulic pump  16 , as indicated at step  90 . The measured torque may then be recorded, at step  97 , as corresponding to the calculated twist angle. As indicated by arrow  95 , the method may be repeated by varying the load on hydraulic pump  28  to update the torque applied to hydraulic pump  16 , either continuously or at intervals. At step  100 , a torque curve may be generated based on the twist angle versus measured torque relationship. As shown in step  110  of  FIG. 3 , the torque curve may be stored on a medium such as a barcode type tag associated with hydraulic pump  28 . The barcode type tag or other medium may be optically or electronically scanned or manually stored into controller  18  of the control system of machine  10  after hydraulic pump  16  has been associated with machine  10 . Alternatively, the torque curve may be stored on another medium and provided to controller  18 . 
         [0028]    Fuel supply adjustment curve may be additionally generated as a function of a torque applied to hydraulic pump  16 . Specifically, fuel supply adjustment curve may be generated as a function of machine, power source, and pump parameters to map an adjustment in the quantity of fuel required by power source  14  to maintain engine speed when the load applied to hydraulic pump  16  changes. Fuel supply adjustment curve may be stored on controller  18 . 
         [0029]    Referring to  FIG. 4 , controller  18  of machine  10  may be configured to determine a change in torque applied to hydraulic pump  16 , and consequently a change in power consumed by hydraulic pump  16 . Controller  18  may be further configured to adjust the fueling of power source  14  as a function of the change in torque. In operation, controller  18  may be configured to sense, based on first sensor  46  and a second sensor  48  associated with pump shaft  28  of hydraulic pump  16 , a parameter indicative of a torque applied to hydraulic pump  16 . Specifically, first sensor  46  and a second sensor  48  may provide data associated with the rotational time lag between first element  38  and second element  42 , as shown in step  200 , and as described above. In step  210 , controller  18  may be further configured to receive data corresponding to the rotational speed of pump shaft  28 . In step  230 , controller  18  may determine a twist angle of pump shaft  28 . For example, controller  18  may be configured to determine the twist angle by multiplying the rotational time lag by the rotational speed of pump shaft  28 . In step  240 , controller  18  may be further configured to determine a torque applied to hydraulic pump  16  by correlating the obtained twist angle with a torque curve stored in controller  18 . 
         [0030]    Having the torque applied to hydraulic pump  16 , controller  18  may be further configured to detect whether the torque represents a change in load applied to hydraulic pump  28 , as shown in step  245 . Specifically, controller  18  may be configured to modify a fueling rate for power source  14 , at step  250 , based on the torque applied to hydraulic pump  16 , when a change in load has occurred. Controller  18  may correlate the torque applied to hydraulic pump  16  with the fuel supply adjustment curve to determine a quantity of fuel adjustment to supply to power source  14  in order to maintain the engine speed and meet the power requirements of hydraulic pump  16 . Controller  18  may continuously sense a value indicative of the torque applied to hydraulic pump  16 , based on the method described above. 
         [0031]    In an alternate embodiment, controller  18  may sum the measured torque applied to each of a plurality of hydraulic pumps  16  of machine  10 . Controller  18  may then correlate the sum of the torque applied to each hydraulic pump  16  with the fuel supply adjustment curve to determine a quantity of fuel to supply to power source  14  in order to meet the collective torque consuming demands of hydraulic pumps  16  of machine  10 . Controller  18  may provide a control signal for adjusting the fueling rate of power source  14  accordingly. It is contemplated that in an alternate arrangement, controller  18  may directly correlate the determined rotational time lag or the calculated twist angle with the fuel supply adjustment curve to determine a quantity of fuel to supply to power source  14 . 
       INDUSTRIAL APPLICABILITY  
       [0032]    The disclosed methods may be applicable to any powered system that includes a power source and a load device, such as, for example, a hydraulic pump configured to convert at least a portion of the power from the power source into a flow of pressurized fluid for driving one or more fluid actuators associated with a ground engaging device or an implement circuit associated with an implement. 
         [0033]    The disclosed system and methods may have particular applicability in determining torque applied to hydraulic pump  16  for use by controller  18  in machine  10 . Specifically, controller  18  may continuously monitor the torque applied to hydraulic pump  16  and modify the fueling rate to compensate for load changes and provide a precise supply of fuel to power source  14 . This may allow for accurate control of power source  14  during transient loading conditions of the hydraulic pump  16 , and may result in less gaseous emissions and improved fuel economy. 
         [0034]    Alternatively or additionally, the disclosed system and methods may be used to evaluate the performance of hydraulic pump  16 . In particular, the disclosed system and methods may be used to measure the torque applied to hydraulic pump  16  at a known operating condition, i.e., fixed pressure, speed, or flow rate. If the torque applied to hydraulic pump  16  changes at the known operating condition during the lifetime of hydraulic pump  16 , the deviation may indicate a problem with hydraulic pump  16 . 
         [0035]    It will be apparent to those&#39;skilled in the art that various modifications and variations can be made to the disclosed systems and methods of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being intended by the following claims.