Patent Description:
Combine harvesters commonly include a threshing and separating system comprising a rotor at least partially enclosed by and rotatable within a corresponding perforated concave. For example, European patent application <CIT> discloses a combine harvester with an engine, a threshing rotor, and a rotor drive system including a planetary gear assembly and a fluid circuit for driving the threshing rotor during a start-up procedure of the threshing rotor. It would be desirable to ramp-up rotation of the rotor while reducing vibrations of the combine.

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:.

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>, there is shown an agricultural harvester in the form of a combine <NUM>, which generally includes a chassis <NUM>, ground engaging wheels <NUM> and <NUM>, a header <NUM>, a feeder housing <NUM>, an operator cab <NUM>, a threshing and separating system <NUM>, a cleaning system <NUM>, a grain tank <NUM>, and an unloading conveyance <NUM>. Motive force is selectively applied to the front wheels <NUM>, and/or the rear wheel <NUM>, through a power plant in the form of an engine <NUM> and a transmission (not shown).

The header <NUM> is mounted to the front of the combine <NUM> and includes a cutter bar <NUM> for severing crops from a field during forward motion of combine <NUM>. A rotatable reel <NUM> feeds the crop into the header <NUM>, and a double auger <NUM> feeds the severed crop laterally inwardly from each side toward the feeder housing <NUM>. The feeder housing <NUM> conveys the cut crop to threshing and the separating system <NUM>.

The threshing and separating system <NUM> generally includes a rotor <NUM> at least partially enclosed by and rotatable within a corresponding perforated concave <NUM>. The cut crops are threshed and separated by the rotation of the rotor <NUM> within the concave <NUM>, and larger elements, such as stalks, leaves and the like are discharged from the rear of the combine <NUM>. Smaller elements of crop material are discharged through perforations of the concave <NUM>. Grain that has been separated by the threshing and separating assembly <NUM> falls onto a grain pan <NUM> and is conveyed toward the cleaning system <NUM>. Further details of the combine <NUM> are disclosed in <CIT>.

<FIG> depicts a combine rotor hydro-mechanical CVT (continuously variable transmission) drive system <NUM> for driving rotor <NUM> of combine <NUM>. It should be understood at the outset that system <NUM> is not limited for use with combine <NUM>, and the features and functions of combine <NUM> can vary greatly.

System <NUM> provides a rotor drive with flexible speed selection and optimization for harvesting and threshing. In operation of engine <NUM>, for purpose of driving rotor <NUM>, power produced by engine <NUM> is split into two branches, namely, a mechanical branch <NUM> and a hydraulic (or hydrostatic) branch <NUM>. Branches <NUM> and <NUM> are operatively connected together by a planetary gear assembly <NUM>. A gear box <NUM> having a plurality of interconnected gears is mechanically connected to and driven by an output shaft of engine <NUM>. One gear 205a of gear box <NUM> is connected to drive mechanical branch <NUM> and another gear 205b of gear box <NUM> is connected to drive hydraulic branch <NUM>. Mechanical connections (e.g., shafts, gears, etc.) are depicted by solid lines in <FIG>. Of course, the arrangement of gear box <NUM> can vary from that which is shown.

As shown in <FIG>, planetary gear assembly <NUM> comprises an outer ring gear <NUM> that is connected to a sun gear <NUM> by a plurality of planet gears <NUM> (one shown). Planet gears <NUM> are each connected to a carrier <NUM>. It should be understood that rotation of ring gear <NUM> and/or sun gear <NUM> causes rotation of carrier <NUM>. The mechanical branch <NUM> is connected to ring gear <NUM> for rotating ring gear <NUM>, as desired. The hydraulic branch <NUM> is connected to sun gear <NUM> for rotating sun gear <NUM>, as desired. In <FIG> it is noted that only the top halves of gears <NUM> and <NUM> are shown, and the other planet gears <NUM> are not shown. Gears <NUM>, <NUM> and <NUM> rotate about their respective axes which are (optionally) parallel to one another. It should be understood that gears <NUM>, <NUM> and <NUM> and carrier <NUM> can rotate simultaneously.

Power transmitted by engine <NUM> onto gears <NUM> and <NUM> is summed up at carrier <NUM>, which drives rotor gearbox <NUM>, which drives rotor <NUM>. 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 <NUM> 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 <NUM>.

Turning now to <FIG>, carrier <NUM> is fixedly connected to the input of a rotor gear box <NUM>. While one gear set of rotor gear box <NUM> is shown, rotor gear box <NUM> includes a plurality of gear sets for varying the output torque and speed of the output shaft of gear box <NUM>. The output shaft of gear box <NUM> is fixedly connected to rotor <NUM> for rotating rotor <NUM>. A clutch <NUM> is connected between gear 205a and ring gear <NUM> for engaging and disengaging the power applied to ring gear <NUM> by engine <NUM>. Clutch <NUM> includes an input member (e.g., shaft) 220a connected to gear 205a and an output member (e.g., shaft) 220b connected to ring gear <NUM>. Output member 220b includes a gear <NUM> that is connected to (i.e., meshed with) ring gear <NUM>. Gear <NUM> is non-rotatably connected to member 220b. A brake <NUM> is also connected to output member 220b for either stopping or slowing output member 220b, thereby either stopping or slowing ring gear <NUM>.

Hydraulic branch <NUM> comprises a fluid circuit, a fluid pump <NUM>, which is powered by engine <NUM>, and a motor <NUM>. Fluid pump <NUM> drives motor <NUM>, and motor <NUM> rotates sun gear <NUM>.

A controller <NUM> is connected to engine <NUM>, pump <NUM>, clutch <NUM>, and brake <NUM> (among other components) for controlling operation of those components. For example, controller <NUM> controls the swash rate and flow direction of pump <NUM>, as well as the engagement of clutch <NUM>, and the activation of brake <NUM>.

As background to the invention, in the course of ramping-up rotor <NUM>, if one were to initially rotate rotor <NUM> using hydraulic branch <NUM>, and, thereafter, activate mechanical branch <NUM> to rotate rotor <NUM> (i.e., by fully engaging clutch <NUM>), then the rotor <NUM>, with huge inertia, would generate vibrations due to the rapid acceleration from the speed produced by hydraulic branch <NUM> (e.g., <NUM> rpm) to the significantly higher speed produced by mechanical branch <NUM> (e.g., <NUM> rpm).

Described hereinafter is a control strategy for ramping up the rotor speed, in the form of a method for ramping-up rotor <NUM> to its target speed at constant acceleration. Constant acceleration of rotor <NUM> yields a smooth and continuous startup process, which reduces vibrations, improves operator comfort, shortens the rotor engagement time and increases productivity.

<FIG> will be described hereinafter with reference to the graphs shown in <FIG> is a graph depicting over time the speed of various components of rotor drive system <NUM>. Depicted in the graph are the rotational speeds of ring gear <NUM> (labeled "RingSpeed", line <NUM>), sun gear <NUM> (Sun-Motor Speed, line <NUM>), rotor <NUM> (Rotor Speed, line <NUM>), and the input speed of clutch <NUM> (Input Speed, line <NUM>), which is also the speed of gear 205a. <FIG> is a graph depicting over time the input control parameters of various components of rotor drive system <NUM>. Depicted in that graph are the operating pressures of clutch <NUM> (labeled "Normalized_clutch_P", line <NUM>), brake <NUM> ("Normalized_Brake_P", line <NUM>), and pump <NUM> (Pump Displacement, line <NUM>).

Turning now to <FIG>, the process begins at <NUM> by activating combine <NUM>. At steps <NUM> and <NUM>, an operator sets the speed of engine <NUM>, for example at 1000rpm. See also straight line <NUM> at time T0 in <FIG>. Engine speed (optionally) remains constant through the rotor start-up process. Once engine <NUM> begins operation, rotor <NUM> begins rotating in a hydrostatic drive mode (i.e., powered by hydraulic branch <NUM>) while, at step <NUM>, brake <NUM> holds ring gear <NUM> stationary. During this time, at step <NUM>, pump <NUM> is swashed in the forward direction to accelerate rotor <NUM> to the maximum pure hydrostatic drive speed (i.e., full swash). See also lines <NUM> and <NUM> at time T1-T4 in <FIG>, which depict a decrease in the pump displacement and an increase in the speed of sun gear <NUM>. At steps <NUM> and <NUM>, for each gear available in rotor gear box <NUM>, a swash rate for pump <NUM> is defined that will limit the hydrostatic system pressure to a value below a relief setting.

Following step <NUM>, the "hydrostatic" stage ends and the "transition" stage begins at about time T4.

At step <NUM>, when pump <NUM> has reached the maximum swash in the forward direction (as checked at step <NUM>), the pressure of clutch <NUM> is then increased to the kiss-point pressure. See also line <NUM> near time T4 in <FIG>. 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 <NUM>, brake <NUM> is released at step <NUM>. See also line <NUM> at time T4 on <FIG>, which depicts a reduction in braking pressure. At step <NUM>, clutch <NUM> is partially engaged (i.e., modulated so that clutch <NUM> slips) and, consequently, transmits torque between gear 205a of gear box <NUM> (input torque) and ring gear <NUM> such that ring gear <NUM> is powered by engine <NUM>. See also lines <NUM> and <NUM> at time T4-T7 in <FIG>, which depicts an increased in the speed of ring gear <NUM> and an increase in the pressure of clutch <NUM>. At this transition stage, ring gear <NUM> transfers torque to carrier <NUM>, which rotates rotor <NUM>. It should be understood that carrier <NUM> always rotates in the same direction during the start-up process; and, likewise, rotor <NUM> always rotates in the same direction during the start-up process.

At or near the same time that the pressure of clutch <NUM> is increasing and transferring torque to ring gear <NUM>, at step <NUM>, pump <NUM> is swashed in the reverse direction, which switches the rotational direction of sun gear <NUM> from a forward direction to a reverse direction. See also lines <NUM> and <NUM> at time T4-T7 in <FIG>, which depict an increase in the pump displacement and a sharp decrease in the speed of sun gear <NUM>. Swashing pump <NUM> in the reverse direction at step <NUM> to switch the rotational direction of sun gear <NUM> reduces the gear ratio (i.e., applied torque) to carrier <NUM>. In other words, driving sun gear <NUM> in the reverse direction counteracts the high torque/speed applied to carrier <NUM> by ring gear <NUM> (via engine <NUM>). Again, as noted above, gear 205a of mechanical branch <NUM> drives ring gear <NUM> at a much higher speed than motor <NUM> of hydraulic branch <NUM> drives sun gear <NUM>. Driving sun gear <NUM> in the reverse direction at step <NUM> to counteract the higher torque/speed applied to carrier <NUM> by ring gear <NUM> yields a constant acceleration of rotor <NUM>. It should be understood that in the absence of the damping action provided by sun gear <NUM> at step <NUM>, rotor <NUM> would be immediately subjected to the full speed of ring gear <NUM>, which would cause undesirable vibrations.

It is noted that, during the transition stage, the pressure overlap between clutch <NUM> and brake <NUM> during reversal of the pump swash (at step <NUM>) prevents rotor <NUM> from inadvertently slowing down or "drooping" and promotes a straight-line constant acceleration of rotor <NUM>. Stated differently, during the transition stage, the combination of the (i) release of brake <NUM> by controller <NUM>, (ii) modulation (i.e., partial engagement) of clutch <NUM> through closed loop pressure control by controller <NUM>, and (iii) reversal of the pump swash by controller <NUM>, holds the rotor acceleration rate constant through the full engagement of clutch <NUM>, thereby avoiding the aforementioned undesirable vibrations of rotor <NUM> during the start-up phase. The rotor speed ramp rate is made constant using a combination of input control signals.

At step <NUM>, the acceleration rate of rotor <NUM> is monitored by a sensor (not shown) to ensure that the acceleration rate is constant. See the constant slope of line <NUM> in <FIG>. If the acceleration rate is not constant, then the pressure of clutch <NUM> is adjusted accordingly at step <NUM>. A PID loop, for example, may be utilized at steps <NUM>/<NUM> to maintain a constant acceleration rate.

A large amount of heat is generated due to the partial engagement of clutch <NUM>. The temperature, or amount of energy, of clutch <NUM> may be monitored at step <NUM> to ensure that clutch <NUM> does not overheat.

At step <NUM>, the slip speed of clutch <NUM> is monitored. More particularly, the rotational speed of ring gear <NUM> is monitored and compared with the input drive speed at gear 205a. This comparison is indicative of the engagement condition of clutch <NUM>. If ring gear <NUM> has not reached its drive speed (indicating that clutch <NUM> is not fully engaged), the method returns to step <NUM> to modify the swash setting of pump <NUM>. Once the ring gear speed reaches its drive speed, which indicates that clutch is fully synchronized and not slipping, the pressure of clutch <NUM> is increased at step <NUM> until the clutch pressure reaches the system pressure and clutch <NUM> is fully engaged. See also lines <NUM> and <NUM> at time T6-T7 in <FIG>, which depict increases in the ring gear speed and the clutch pressure. Clutch <NUM> remains fully engaged through the remainder of the rotor start-up process, which is depicted as the "hydromechanical" stage in <FIG>. Also, at the hydromechanical stage, the rotational speed of ring gear <NUM> matches the speed of gear 205a (i.e., the engine speed) and the clutch <NUM> 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 <NUM>, at step <NUM>, the swash of pump <NUM> is reversed again and commanded by controller <NUM> to swash in the forward direction and rotate sun gear <NUM> in the forward direction. At this time, motor <NUM> increases the speed of sun gear <NUM>, which increases the speed of carrier <NUM>. See also lines <NUM> and <NUM> at time T7-T10 in <FIG>. It is noted that combining the speeds (modulation) of the sun gear <NUM> and ring gear <NUM> results in a constant acceleration of carrier <NUM>, and, therefore, constant acceleration of rotor <NUM>. See line <NUM> at time T7-T10 in <FIG>. At step <NUM>, the speed of engine <NUM> may also be adjusted which would, consequently, adjust the speed of rotor <NUM>.

It is noted that the "constant" acceleration of rotor <NUM> may not be perfectly constant. For example, a tolerance of +/- <NUM> % or <NUM>% 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 <NUM> and activating brake <NUM> to slow rotation of ring gear <NUM> at time T4-T7. In such an alternative method, step <NUM> would be replaced by the step of fully engaging clutch <NUM>, and a new step between steps <NUM> and <NUM> would comprise activating brake <NUM> to slow rotation of ring gear <NUM>. And, step <NUM> could be omitted. As another alternative to partially engaging clutch <NUM>, though not as preferable, the speed of engine <NUM> could be adjusted to slow rotation of ring gear <NUM> at time T4-T7.

Claim 1:
A method of rotating a threshing rotor (<NUM>) of an agricultural vehicle during a start-up procedure for the threshing rotor (<NUM>), the agricultural vehicle comprising an engine (<NUM>), the threshing rotor (<NUM>), a planetary gear assembly (<NUM>), and a fluid circuit,
the planetary gear assembly (<NUM>) including
(i) a first gear (<NUM>) that is mechanically connected to an output shaft of the engine,
(ii) a second gear (<NUM>), and
(iii) a carrier (<NUM>) that is mechanically connected to both the first gear (<NUM>) and the second gear (<NUM>), the carrier (<NUM>) also being connected to the threshing rotor (<NUM>) for driving the threshing rotor (<NUM>),
the fluid circuit including
(i) a reversible pump (<NUM>) that receives power from the engine (<NUM>) and
(ii) a motor (<NUM>) that is fluidly connected to the pump (<NUM>) and has an output shaft that is connected to the second gear (<NUM>) for driving the second gear (<NUM>),
wherein said method comprises the following steps:
(a) operating the pump (<NUM>) to drive the motor (<NUM>) in a forward direction, which rotates the second gear (<NUM>) in a forward direction, which rotates the carrier (<NUM>) in a forward direction, which rotates the threshing rotor (<NUM>) in a forward direction, all while the first gear (<NUM>) remains stationary,
(b) rotating the first gear (<NUM>), which rotates the carrier (<NUM>) in concert with the second gear (<NUM>) of step (a) while the carrier (<NUM>) continues to rotate the threshing rotor (<NUM>) in the forward direction, and
(c) operating the pump (<NUM>) on the fluid circuit to drive the motor (<NUM>) in a reverse direction, which rotates the second gear (<NUM>) in a reverse direction while the carrier (<NUM>) and the threshing rotor (<NUM>) continue to rotate in their forward directions,
wherein the vehicle further comprises a clutch (<NUM>) having an input member (220a) that is either directly or indirectly connected to the output shaft of the engine (<NUM>) and an output member (220b/<NUM>) that is connected to the first gear (<NUM>), wherein step (b) further comprises partially engaging and modulating the clutch (<NUM>) to drive rotation of the first gear (<NUM>), and characterized in that
the method further comprises monitoring an acceleration rate of the rotor (<NUM>) by a sensor and adjusting a pressure of the clutch (<NUM>) to ensure that the acceleration rate is constant within a tolerance of +/- <NUM>% or <NUM>%.