Patent Publication Number: US-2023148477-A1

Title: Control system and method for increasing rotor speed during combine rotor start-up

Description:
FIELD OF THE INVENTION 
     The invention relates to a combine harvester, and more particularly, to a rotor of a combine, and a method for increasing the speed of the rotor at a constant rate during a start-up procedure for the rotor. 
     BACKGROUND OF THE INVENTION 
     Combine harvesters commonly include a threshing and separating system comprising a rotor at least partially enclosed by and rotatable within a corresponding perforated concave. It would be desirable to ramp-up rotation of the rotor while reducing vibrations of the combine. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, in an agricultural vehicle having an engine; a threshing rotor; a planetary gear assembly including (i) a first gear (e.g., a ring gear) that is mechanically connected to an output shaft of the engine, (ii) a second gear (e.g., a sun gear), and (iii) a carrier that is mechanically connected to both the first gear and the second gear, the carrier also being connected to the rotor for driving the rotor; and a fluid circuit including (i) a reversible pump that receives power from the engine and (ii) a motor that is fluidly connected to the pump and has an output shaft that is connected to the second gear for driving the second gear, a method of rotating the rotor during a start-up procedure for the rotor, said method comprising the following steps:
     (a) operating the pump to drive the motor in a forward direction, which rotates the second gear in a forward direction, which rotates the carrier in a forward direction, which rotates the rotor in a forward direction, all while the first gear remains stationary;   (b) rotating the first gear, which rotates the carrier in concert with the second gear of step (a) while the rotor continues to rotate the rotor in the forward direction; and   (c) operating the pump to drive the motor in a reverse direction, which rotates the second gear in a reverse direction while the carrier and the rotor continue to rotate in their forward directions, which step yields a substantially constant acceleration of the rotor over steps (a) through (c).   

     According to another aspect of the invention, in an agricultural vehicle having an engine; a threshing rotor; a planetary gear assembly including (i) a first gear that is mechanically connected to an output shaft of the engine, (ii) a second gear, and (iii) a carrier that is mechanically connected to both the first gear and the second gear, the carrier also being connected to the rotor for driving the rotor; a clutch having an input member that is either directly or indirectly connected to the output shaft of the engine and an output member that is connected to the first gear; and a fluid circuit including (i) a reversible pump that receives power from the engine and (ii) a motor that is fluidly connected to the pump and has an output shaft that is connected to the second gear for driving the second gear, a method of rotating the rotor during a start-up procedure for the rotor, said method comprising the following steps:
     (a) operating the pump to drive the motor in a forward direction, which rotates the second gear in a forward direction, which rotates the carrier in a forward direction, which rotates the rotor in a forward direction, all while the first gear remains stationary;   (b) partially engaging the clutch to rotate the output member of the clutch, which rotates the first gear, which rotates the carrier in concert with the second gear of step (a) while the rotor continues to rotate in the forward direction; and   (c) operating the pump to drive the motor in a reverse direction, which rotates the second gear in a reverse direction while the carrier and the rotor continue to rotate in their respective forward directions, which step yields a substantially constant acceleration of the rotor over steps (a) through (c).   

     According to yet another aspect of the invention, in an agricultural vehicle having an engine; a threshing rotor; and a rotor drive system comprising a hydraulic branch and a separate mechanical branch that each receive power from the engine, a method of starting the rotor comprises: activating the rotor using the hydraulic branch and the mechanical branch while maintaining a constant acceleration of the rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is a side view of an embodiment of an agricultural harvester in the form of a combine, wherein the combine is shown schematically. 
         FIG.  2    is a schematic showing a rotor drive system for driving a rotor of the combine. 
         FIG.  3    is a block diagram depicting a process for setting a rotor speed of the combine. 
         FIG.  4 A  is a graph depicting over time the speed of various components of the rotor drive system of the combine. 
         FIG.  4 B  is a graph depicting over time the pressure of various components of the rotor drive system of the combine. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Aspects of the disclosure provide an agricultural vehicle having an engine, a threshing rotor, and a rotor drive system including a planetary gear assembly and a fluid circuit for driving the rotor at a constant acceleration during a start-up procedure of the rotor. 
     Referring now to the drawings, and more particularly to  FIG.  1   , there is shown an agricultural harvester in the form of a combine  10 , which generally includes a chassis  12 , ground engaging wheels  14  and  16 , a header  18 , a feeder housing  20 , an operator cab  22 , a threshing and separating system  24 , a cleaning system  26 , a grain tank  28 , and an unloading conveyance  30 . Motive force is selectively applied to the front wheels  14 , and/or the rear wheel  16 , through a power plant in the form of an engine  32  and a transmission (not shown). 
     The header  18  is mounted to the front of the combine  10  and includes a cutter bar  34  for severing crops from a field during forward motion of combine  10 . A rotatable reel  36  feeds the crop into the header  18 , and a double auger  38  feeds the severed crop laterally inwardly from each side toward the feeder housing  20 . The feeder housing  20  conveys the cut crop to threshing and the separating system  24 . 
     The threshing and separating system  24  generally includes a rotor  40  at least partially enclosed by and rotatable within a corresponding perforated concave  42 . The cut crops are threshed and separated by the rotation of the rotor  40  within the concave  42 , and larger elements, such as stalks, leaves and the like are discharged from the rear of the combine  10 . Smaller elements of crop material are discharged through perforations of the concave  42 . Grain that has been separated by the threshing and separating assembly  24  falls onto a grain pan  44  and is conveyed toward the cleaning system  26 . Further details of the combine  10  are disclosed in U.S. Pat. No. 9,907,228, which is incorporated by reference herein in its entirety and for all purposes. 
       FIG.  2    depicts a combine rotor hydro-mechanical CVT (continuously variable transmission) drive system  200  for driving rotor  40  of combine  10 . It should be understood at the outset that system  200  is not limited for use with combine  10 , and the features and functions of combine  10  can vary greatly. 
     System  200  provides a rotor drive with flexible speed selection and optimization for harvesting and threshing. In operation of engine  32 , for purpose of driving rotor  40 , power produced by engine  32  is split into two branches, namely, a mechanical branch  202  and a hydraulic (or hydrostatic) branch  204 . Branches  202  and  204  are operatively connected together by a planetary gear assembly  206 . A gear box  205  having a plurality of interconnected gears is mechanically connected to and driven by an output shaft of engine  32 . One gear  205   a  of gear box  205  is connected to drive mechanical branch  202  and another gear  205   b  of gear box  205  is connected to drive hydraulic branch  204 . Mechanical connections (e.g., shafts, gears, etc.) are depicted by solid lines in  FIG.  2   . Of course, the arrangement of gear box  205  can vary from that which is shown. 
     As shown in  FIG.  2   , planetary gear assembly  206  comprises an outer ring gear  208  that is connected to a sun gear  210  by a plurality of planet gears  212  (one shown). Planet gears  212  are each connected to a carrier  214 . It should be understood that rotation of ring gear  208  and/or sun gear  210  causes rotation of carrier  214 . The mechanical branch  202  is connected to ring gear  208  for rotating ring gear  208 , as desired. The hydraulic branch  204  is connected to sun gear  210  for rotating sun gear  210 , as desired. In  FIG.  2    it is noted that only the top halves of gears  208  and  210  are shown, and the other planet gears  212  are not shown. Gears  208 ,  210  and  212  rotate about their respective axes which are (optionally) parallel to one another. It should be understood that gears  208 ,  210  and  212  and carrier  214  can rotate simultaneously. 
     Power transmitted by engine  32  onto gears  208  and  210  is summed up at carrier  214 , which drives rotor gearbox  216 , which drives rotor  40 . As background, the rotational speed of the carrier (Nc) is given by the equation: Nc=(Ns ∗ Zs + Nr ∗ Zr)/(Zs+Zr); where c = carrier, s = sun gear, r = ring gear, Z = number of gear teeth, and N = speed (rpm). It should be understood that, during operation in hydro-mechanical mode, a reduction in the speed of sun gear (for example) will result in a reduction of the carrier speed (Nc), and, conversely, an increase in the speed of sun gear will result in an increase of the carrier speed (Nc). According to the embodiment of planetary gear assembly  206  shown herein, Zr is significantly greater than Zs, and, for at least that reason, the rotational speed of the carrier (Nc) will have a positive value (i.e., indicating forward rotation) during start-up of rotor  40 . 
     Turning now to  FIG.  2   , carrier  214  is fixedly connected to the input of a rotor gear box  216 . While one gear set of rotor gear box  216  is shown, rotor gear box  216  includes a plurality of gear sets for varying the output torque and speed of the output shaft of gear box  216 . The output shaft of gear box  216  is fixedly connected to rotor  40  for rotating rotor  40 . A clutch  220  is connected between gear  205   a  and ring gear  208  for engaging and disengaging the power applied to ring gear  208  by engine  32 . Clutch  220  includes an input member (e.g., shaft)  220   a  connected to gear  205   a  and an output member (e.g., shaft)  220   b  connected to ring gear  208 . Output member  220   b  includes a gear  221  that is connected to (i.e., meshed with) ring gear  208 . Gear  221  is non-rotatably connected to member  220   b . A brake  222  is also connected to output member  220   b  for either stopping or slowing output member  220   b , thereby either stopping or slowing ring gear  208 . 
     Hydraulic branch  204  comprises a fluid circuit, a fluid pump  230 , which is powered by engine  32 , and a motor  232 . Fluid pump  230  drives motor  232 , and motor  232  rotates sun gear  210 . 
     A controller  238  is connected to engine  32 , pump  230 , clutch  220 , and brake  222  (among other components) for controlling operation of those components. For example, controller  238  controls the swash rate and flow direction of pump  230 , as well as the engagement of clutch  220 , and the activation of brake  222 . 
     As background to the invention, in the course of ramping-up rotor  40 , if one were to initially rotate rotor  40  using hydraulic branch  204 , and, thereafter, activate mechanical branch  202  to rotate rotor  40  (i.e., by fully engaging clutch  220 ), then the rotor  40 , with huge inertia, would generate vibrations due to the rapid acceleration from the speed produced by hydraulic branch  204  (e.g., 200 rpm) to the significantly higher speed produced by mechanical branch  202  (e.g., 1000 rpm). 
     Described hereinafter is a control strategy for ramping up the rotor speed, in the form of a method for ramping-up rotor  40  to its target speed at constant acceleration. Constant acceleration of rotor  40  yields a smooth and continuous startup process, which reduces vibrations, improves operator comfort, shortens the rotor engagement time and increases productivity. 
       FIG.  3    will be described hereinafter with reference to the graphs shown in  FIGS.  4 A and  4 B .  FIG.  4 A  is a graph depicting over time the speed of various components of rotor drive system  200 . Depicted in the graph are the rotational speeds of ring gear  208  (labeled “RingSpeed”, line  402 ), sun gear  210  (Sun-Motor Speed, line  404 ), rotor  40  (Rotor Speed, line  406 ), and the input speed of clutch  220  (Input Speed, line  408 ), which is also the speed of gear  205   a .  FIG.  4 B  is a graph depicting over time the input control parameters of various components of rotor drive system  200 . Depicted in that graph are the operating pressures of clutch  220  (labeled “Normalized_clutch_P”, line  412 ), brake  222  (“Normalized_Brake_P”, line  414 ), and pump  230  (Pump Displacement, line  416 ). 
     Turning now to  FIG.  3   -4B, the process begins at  302  by activating combine  10 . At steps  304  and  306 , an operator sets the speed of engine  32 , for example at 1000 rpm. See also straight line  408  at time T0 in  FIG.  4 A . Engine speed (optionally) remains constant through the rotor start-up process. Once engine  32  begins operation, rotor  40  begins rotating in a hydrostatic drive mode (i.e., powered by hydraulic branch  204 ) while, at step  308 , brake  222  holds ring gear  208  stationary. During this time, at step  310 , pump  230  is swashed in the forward direction to accelerate rotor  40  to the maximum pure hydrostatic drive speed (i.e., full swash). See also lines  404  and  416  at time T1-T4 in  FIGS.  4 A and  4 B , which depict a decrease in the pump displacement and an increase in the speed of sun gear  210 . At steps  312  and  314 , for each gear available in rotor gear box  216 , a swash rate for pump  230  is defined that will limit the hydrostatic system pressure to a value below a relief setting. 
     Following step  316 , the “hydrostatic” stage ends and the “transition” stage begins at about time T4. 
     At step  318 , when pump  230  has reached the maximum swash in the forward direction (as checked at step  316 ), the pressure of clutch  220  is then increased to the kiss-point pressure. See also line  412  near time T4 in  FIG.  4 B . The term “kiss point” of a clutch is defined herein as the position of a clutch when the two halves of the clutch make initial frictional contact without transmitting any torque therebetween. 
     Following step  318 , brake  222  is released at step  320 . See also line  414  at time T4 on  FIG.  4 B , which depicts a reduction in braking pressure. At step  322 , clutch  220  is partially engaged (i.e., modulated so that clutch  220  slips) and, consequently, transmits torque between gear  205   a  of gear box  205  (input torque) and ring gear  208  such that ring gear  208  is powered by engine  32 . See also lines  402  and  412  at time T4-T7 in  FIGS.  4 A and  4 B , which depicts an increased in the speed of ring gear  208  and an increase in the pressure of clutch  220 . At this transition stage, ring gear  208  transfers torque to carrier  214 , which rotates rotor  40 . It should be understood that carrier  214  always rotates in the same direction during the start-up process; and, likewise, rotor  40  always rotates in the same direction during the start-up process. 
     At or near the same time that the pressure of clutch  220  is increasing and transferring torque to ring gear  208 , at step  324 , pump  230  is swashed in the reverse direction, which switches the rotational direction of sun gear  210  from a forward direction to a reverse direction. See also lines  404  and  416  at time T4-T7 in  FIGS.  4 A and  4 B , which depict an increase in the pump displacement and a sharp decrease in the speed of sun gear  210 . Swashing pump  230  in the reverse direction at step  324  to switch the rotational direction of sun gear  210  reduces the gear ratio (i.e., applied torque) to carrier  214 . In other words, driving sun gear  210  in the reverse direction counteracts the high torque/speed applied to carrier  214  by ring gear  208  (via engine  32 ). Again, as noted above, gear  205   a  of mechanical branch  202  drives ring gear  208  at a much higher speed than motor  232  of hydraulic branch  204  drives sun gear  210 . Driving sun gear  210  in the reverse direction at step  324  to counteract the higher torque/speed applied to carrier  214  by ring gear  208  yields a constant acceleration of rotor  40 . It should be understood that in the absence of the damping action provided by sun gear  210  at step  324 , rotor  40  would be immediately subjected to the full speed of ring gear  208 , which would cause undesirable vibrations. 
     It is noted that, during the transition stage, the pressure overlap between clutch  220  and brake  222  during reversal of the pump swash (at step  324 ) prevents rotor  40  from inadvertently slowing down or “drooping” and promotes a straight-line constant acceleration of rotor  40 . Stated differently, during the transition stage, the combination of the (i) release of brake  222  by controller  238 , (ii) modulation (i.e., partial engagement) of clutch  220  through closed loop pressure control by controller  238 , and (iii) reversal of the pump swash by controller  238 , holds the rotor acceleration rate constant through the full engagement of clutch  220 , thereby avoiding the aforementioned undesirable vibrations of rotor  40  during the start-up phase. The rotor speed ramp rate is made constant using a combination of input control signals. 
     At step  326 , the acceleration rate of rotor  40  is monitored by a sensor (not shown) to ensure that the acceleration rate is constant. See the constant slope of line  406  in  FIG.  4 A . If the acceleration rate is not constant, then the pressure of clutch  220  is adjusted accordingly at step  322 . A PID loop, for example, may be utilized at steps  322 / 326  to maintain a constant acceleration rate. 
     A large amount of heat is generated due to the partial engagement of clutch  220 . The temperature, or amount of energy, of clutch  220  may be monitored at step  328  to ensure that clutch  220  does not overheat. 
     At step  330 , the slip speed of clutch  220  is monitored. More particularly, the rotational speed of ring gear  208  is monitored and compared with the input drive speed at gear  205   a  . This comparison is indicative of the engagement condition of clutch  220 . If ring gear  208  has not reached its drive speed (indicating that clutch  220  is not fully engaged), the method returns to step  324  to modify the swash setting of pump  230 . Once the ring gear speed reaches its drive speed, which indicates that clutch is fully synchronized and not slipping, the pressure of clutch  220  is increased at step  332  until the clutch pressure reaches the system pressure and clutch  220  is fully engaged. See also lines  402  and  412  at time T6-T7 in  FIGS.  4 A and  4 B , which depict increases in the ring gear speed and the clutch pressure. Clutch  220  remains fully engaged through the remainder of the rotor start-up process, which is depicted as the “hydromechanical” stage in  FIG.  4 A . Also, at the hydromechanical stage, the rotational speed of ring gear  208  matches the speed of gear  205   a  (i.e., the engine speed) and the clutch  220  remains fully engaged (i.e., locked) through the remainder of the rotor start-up process as well as during operation. 
     At or near the same time as step  332 , at step  334 , the swash of pump  230  is reversed again and commanded by controller  238  to swash in the forward direction and rotate sun gear  210  in the forward direction. At this time, motor  232  increases the speed of sun gear  210 , which increases the speed of carrier  214 . See also lines  404  and  416  at time T7-T10 in  FIGS.  4 A and  4 B . It is noted that combining the speeds (modulation) of the sun gear  210  and ring gear  208  results in a constant acceleration of carrier  214 , and, therefore, constant acceleration of rotor  40 . See line  406  at time T7-T10 in  FIG.  4 A . At step  336 , the speed of engine  32  may also be adjusted which would, consequently, adjust the speed of rotor  40 . 
     It is noted that the “constant” acceleration of rotor  40  may not be perfectly constant. For example, a tolerance of +/- 5 % or 10% may be acceptable. 
     While the method herein describes operating the clutch in a partially engaged state for a limited period of time, it should be understood that the method could also be practiced by fully engaging clutch  220  and activating brake  222  to slow rotation of ring gear  208  at time T4-T7. In such an alternative method, step  322  would be replaced by the step of fully engaging clutch  220 , and a new step between steps  322  and  324  would comprise activating brake  222  to slow rotation of ring gear  208 . And, step  332  could be omitted. As another alternative to partially engaging clutch  220 , though not as preferable, the speed of engine  32  could be adjusted to slow rotation of ring gear  208  at time T4-T7. 
     Various components of system  200  are controlled by controller  238 , as is indicated by the lines in  FIG.  2   . And, various steps of the method shown in  FIG.  3    are performed by controller  238  upon loading and executing software code or instructions which are tangibly stored on a tangible computer readable medium, such as on a magnetic medium, e.g., a computer hard drive, an optical medium, e.g., an optical disc, solid-state memory, e.g., flash memory, or other storage media known in the art. Thus, any of the functionality performed by the controller  238  described herein, such as the steps shown in  FIG.  3   , are implemented in software code or instructions which are tangibly stored on a tangible computer readable medium. Upon loading and executing such software code or instructions by the controller  238 , the controller  238  may perform any of the functionality of the controller  238  described herein, including the steps shown in  FIG.  3    described herein. 
     The term “software code” or “code” used herein refers to any instructions or set of instructions that influence the operation of a computer or controller. They may exist in a computer-executable form, such as machine code, which is the set of instructions and data directly executed by a computer’s central processing unit or by a controller, a human-understandable form, such as source code, which may be compiled in order to be executed by a computer’s central processing unit or by a controller, or an intermediate form, such as object code, which is produced by a compiler. As used herein, the term “software code” or “code” also includes any human-understandable computer instructions or set of instructions, e.g., a script, that may be executed on the fly with the aid of an interpreter executed by a computer’s central processing unit or by a controller. 
     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather various modifications may be made in the details within the scope and range of equivalence of the claims and without departing from the invention.