Abstract:
A computer-controlled method of controlling the speed of an agricultural harvester load that is coupled to an agricultural harvester engine by a power transmitting arrangement having various output speeds. The method includes the steps of electronically receiving a desired new load speed from an operator when the engine is operating at an initial engine speed, and electronically driving the power transmitting arrangement through a sequence of the various output speeds until the actual speed of the agricultural harvester load and the actual speed of the agricultural harvester engine are in the same ratio to each other as the desired new load speed and the initial engine speed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This is a non-provisional application based upon U.S. provisional patent application Ser. No. 60/991,200, entitled “AGRICULTURAL HARVESTER SPEED CONTROL”, filed Nov. 29, 2007, which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The invention relates generally to agricultural harvesters. More particularly, it relates to speed control of auxiliary equipment associated with agricultural harvesters. 
   BACKGROUND OF THE INVENTION 
   An agricultural harvester typically includes a self-propelled vehicle on which an engine and various pieces of auxiliary equipment are mounted. The engine, through several drive trains, drives the auxiliary equipment on the agricultural harvester which typically includes a large threshing rotor, cleaning fans, drive wheels, straw choppers, straw walkers, sieves, chaffers, and headers, among other devices. 
   Many of these devices are driven by mechanical devices such as gear boxes, rotating shafts, belts, pulleys, and hydraulic pumps connected to the engine. In one common arrangement, the engine is coupled to the large threshing rotor and to the cleaning fan by a drive train which includes a series of mechanical drive elements such as gear boxes driven by rotating shafts, belts and pulleys. In a common arrangement, one or more pulleys, having a variable pulley diameter, is disposed in the drive train between the engine and the threshing rotor or the cleaning fan, to control the speed of the rotor or the cleaning fan with respect to the engine. 
   One drawback of these variable pulleys is their slow response time. When a signal is sent to the variable pulley to command a change in its diameter, and thus a change in its speed relative to the engine speed, it takes a relatively long amount of time to affect this change. Variable pulleys cannot tolerate rapid changes in pulley diameter under load without suffering undue wear to the belt and pulley. 
   For this reason, adjustments are seldom made to the variable pulley diameter. Changes in the diameter of the variable pulley function to change the speed of the rotor or the cleaning fan with respect to the engine. As a general matter, the operator typically selects a new desired speed of the rotor or the cleaning fan, and the control system that controls the diameter of the pulley then establishes a new pulley diameter that will provide that new desired speed (assuming the engine keeps running at the same speed). The control system then stops adjusting the diameter of the pulley, at least until the operator requests a new desired speed. 
   If the load on the agricultural harvester increases, such as by running into a heavy crop or starting to climb a hill, then the engine speed will drop. When the engine speed drops, the rotor speed and the cleaning fan speed drop proportionally. 
   Similarly, if the load on the agricultural harvester is reduced, for example, by the crop thinning or the harvester starting to go downhill, the engine speed will increase. When the engine speed increases, the rotor and the cleaning fan speed increase proportionately. 
   In one prior art arrangement, the operator is able to select a desired new speed of the rotor or the fan using an operator input device such as a button, a knob, or a lever to select a desired new rotor or fan speed. In response to this, a control system increases or decreases the diameter of the variable pulley over a period of several seconds, until the speed of the rotor or fan reaches the desired new speed. Once the control system determines that the rotor or fan speed is at the desired new speed, it stops adjusting the diameter of the variable pulley. From that time on, as the engine speed changes, the rotor or fan speed changes proportionately, and the control system makes no further adjustment to the diameter of the variable pulley. 
   Unfortunately, this algorithm, while relatively simple, will not always give the results the operator anticipates. For example, since it takes a finite but nontrivial period of time for the control system to change the diameter of the pulley, occasionally the engine speed changes at the same time. 
   To illustrate the problem from the operator&#39;s perspective, imagine the following situation. The cleaning fan is operating at 1150 rpm and the engine is operating at 2300 rpm. The operator desires to reduce the fan speed to 1050 rpm, and operates the operator input device to select this speed. The control system, responding to the operator input device, begins the process of changing the diameter of the pulley to reduce the speed of the fan. 
   Shortly after the operator selects a desired new speed of 1050 rpm, the engine experiences a heavy load and the engine speed drops to 2100 rpm. When the engine speed drops to 2100 rpm, the cleaning fan speed drops automatically and coincidentally to the new target speed of 1050 rpm since the engine and the cleaning fan operate at speeds that are strictly proportional due to the fixed ratio gear train that couples them together. 
   The control system, even if it has made no change in the diameter of the pulley, senses that the fan is now running at the desired new speed of 1050 rpm. At this point, the control system ceases to adjust the diameter of the variable pulley, assuming that the control system adjustments are complete, based on the cleaning fan operating at the desired new speed. The control system stops adjusting the diameter of the pulley, even though it has made no adjustment to the diameter of the variable pulley. 
   The operator will immediately notice this failure to go to the desired new speed when the engine shortly recovers from its increased load and speeds back up to its normal operating speed of 2300 rpm. When this happens, the cleaning fan will again return to its original operating speed of 1150 rpm. The control system in effect mistakes the change in the cleaning fan speed caused by a temporary drop in the engine speed as actually setting a desired new cleaning fan speed. 
   What is needed in the art is a system for accommodating changes in engine speed while an adjustment is made to the cleaning fan (or threshing rotor) speed so that the operator&#39;s natural expectations are preserved. 
   SUMMARY OF THE INVENTION 
   The invention in one form is directed to a computer-controlled method of controlling the speed of an agricultural harvester load coupled to an agricultural harvester engine of an agricultural harvester by a power transmitting arrangement having various output speeds. The method includes the steps of electronically receiving a desired new load speed from an operator when the engine is operating at an initial engine speed and electronically driving the power transmitting arrangement through a sequence of the various output speeds until the actual speed of the agricultural harvester load and the actual speed of the agricultural harvester engine are in the same ratio to each other as the desired new load speed and the initial engine speed. 
   The step of electronically driving a variable pulley may further include the steps of repeatedly and electronically receiving the actual speed of the agricultural harvester engine from a first speed sensor; repeatedly and electronically receiving the actual speed of the agricultural harvester load from a second speed sensor; repeatedly and electronically calculating a ratio of the actual speeds of the harvester engine and the harvester load; repeatedly and electronically comparing the ratio of the actual speeds to a ratio of the new desired speed and the initial engine speed; and repeatedly and electronically changing the diameter of the variable pulley until the two ratios are the same. 
   The invention in another form is directed to an agricultural harvester including an agricultural harvester engine, an agricultural harvester load, a power transmitting arrangement, and a system for controlling the actual speed of the agricultural harvester load. The agricultural harvester engine has an actual speed when operating and the agricultural harvester load has an actual speed when operating. The power transmitting arrangement connects the load to the engine. The agricultural harvester load is coupled to the agricultural harvester engine of the agricultural harvester by the power transmitting arrangement. The system includes a first sensor coupled to the engine for sensing the actual speed of the engine and a second sensor coupled to the load for sensing the actual speed of the load. The system also includes a power transmitting arrangement, an operator input device, and a control unit. The power transmitting arrangement couples the load to the engine and is configured to provide a selectable plurality of speeds of the load for a given speed of the engine. The operator input device receives input from an operator of the agricultural harvester requesting a change in speed of the load to a revised load speed. The control unit receives a signal from the first sensor indicative of the actual speed of the engine, a signal from the second sensor indicative of the actual speed of load and a signal from the operator input device indicative of the desired load speed. The control unit calculates the ratio of the actual engine speed when the input is received from the operator to the desired load speed. The control unit sends a signal to the power transmitting arrangement to change the actual speed of the load to a different one of the selectable plurality of speeds corresponding to a speed having the same ratio to the actual speed of the engine as the desired load speed has to the actual engine speed when the input was received from the operator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The FIGURE shows an embodiment of a drive train of an agricultural harvester in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the FIGURE, a drive train  100  of an agricultural harvester includes an engine  102  that is coupled to and drives a series of first mechanical drive elements  104 , here illustrated in simplified form as a gear train  104 , although it may be any combination of shafts, gears, belts, pulleys, or other mechanical drive elements. Mechanical drive elements  104  are coupled to a power transmitting arrangement  105 . Power transmitting arrangement  105 , as shown, includes a first pulley  106  which, in turn, is coupled to and drives a second pulley  108 . Belt  110  couples the pulleys  106  and  108  together to transmit power therebetween. Pulley  106 , pulley  108  and belt  110  form power transmitting arrangement  105  in the form of a pulley and belt arrangement  111 . Pulley  108  is coupled to and drives a load  112 , which may be, for example, the rotor of an agricultural harvester, or a cleaning fan. In this typical arrangement, all the mechanical elements in the drive train  100  rotate at speeds that are in fixed proportion to each other, unless, for example, the diameter of one of the pulleys is changed, or a gear ratio of a gearbox in drive train  100  is changed. 
   A first speed sensor  114  is coupled to one of the first mechanical drive elements  104  in the drive train  100  that is on the engine side of pulley and belt arrangement  111 . In this embodiment, first speed sensor  114  is shown connected to engine  102 . In alternative embodiments, first speed sensor  114  is connected to any of the first mechanical drive elements  104  between engine  102  and pulley  106 . Wherever first speed sensor  114  is located, it provides a speed signal  115  proportional to the speed of one of the first mechanical drive elements  104  on the drive (i.e. the engine) side of pulley and belt arrangement  111 . 
   A second speed sensor  116  is coupled to one of second mechanical drive elements  117  in the drive train  100  that is on the load side of pulley and belt arrangement  111 . In this embodiment, speed sensor  116  is coupled directly to load  112 . Alternatively, it could be connected to second pulley  108  or to any of the second mechanical drive elements  117  coupling second pulley  108  to load  112 . Wherever second speed sensor  116  is located, it provides a speed signal  119  proportional to the speed of one of the second mechanical drive elements  117  on the load (i.e. the cleaning fan or threshing rotor) side of the pulley and belt arrangement  111 . 
   Pulley  106  and/or  108  is a variable diameter pulley. By “variable diameter” we mean that the diameter of belt  110  as it travels over the pulley can be adjusted, typically by moving one side of the pulley closer to or further apart from the other side of the pulley, to close or, alternatively, to open the gap therebetween. Typically, the inner face of the sides of the pulley taper away from each other in the direction of the outer diameter of the pulley, so that belt  110  contacts the inner faces closer to the outside diameter when the sides that are closer together. As the belt moves closer to the outside diameter of the second pulley  108 , the shaft supporting belt  110  rotates more slowly. 
   This adjustment can be affected by a mechanical device, such as a mechanical linkage that forces the pulley sides together, or it may be hydraulic, such as by a piston that is moved by hydraulic fluid under pressure to force the pulley sides together. 
   In the embodiment shown here, second pulley  108  is a variable diameter pulley, and is coupled to actuator  118  that is configured to change the diameter of second pulley  108  when so commanded by a control system  120 . 
   Control system  120  is coupled to drive train  100  to vary the speed of agricultural harvester load  112  relative to agricultural harvester engine  102 . Control system  120  includes an electronic control unit (ECU)  122 , an operator input device  124  (here shown as a keyboard), and an operator signaling device  126  (here illustrated as a visual display). Input device  124  and signaling device  126  are communicatively coupled to ECU  122 . 
   ECU  122  includes a digital microprocessor having random access memory (RAM), read only memory (ROM), and signal conditioning circuits that permit ECU  122  to drive operator signaling device  126  and to receive and process signals  123  from operator input device  124 , to receive and process signals from speed sensors  114  and  116 , and to transmit signals sufficient to drive actuator  118 . ECU  122  is configured to indicate a speed of load  112  with signaling device  126 , preferably by displaying the speed as numeric values on visual display device  126 . ECU  122  is configured to receive speed command signals that the operator enters using operator input device  124 . 
   ECU  122  is also coupled to speed sensors  114  and  116  to receive signals therefrom that indicate the speed of one of the mechanical drive element  104  on the drive side of the pulley and belt arrangement  111  (in this case the engine) and to receive signals that indicate the speed of one of the second mechanical drive elements  117  on the load side of pulley and belt arrangement  111  (in this case, agricultural harvester load  112 ). 
   ECU  122  is also coupled to actuator  118  to drive actuator  118  and, thereby, to change the diameter of second pulley  108 . In this embodiment, actuator  118  is configured to vary the diameter of second pulley  108 . In other embodiments (not shown) first pulley  106  is a variable diameter pulley and actuator  118  is coupled to pulley first  106  to vary the diameter of first pulley  106 . In operation, ECU  122  continuously monitors the speed of load  112 , reading second speed sensor  116  and displaying it on signaling device  126 . Whenever the operator wishes to change the speed of load  112 , he manipulates operator input device  124  to select a desired new speed for load  112 , and this desired new speed is transmitted to ECU  122 . 
   On receipt of this speed, ECU  122  transmits the desired load speed to operator signaling device  126 . ECU  122  also reads the actual engine speed indicated by speed sensor  114  at the same time and calculates a new speed ratio. The speed ratio being the desired new load speed divided by the actual engine speed at the moment the operator selected the desired new load speed and therefore before the engine speed has a chance to change significantly. 
   It is this new speed ratio that the control system  120  uses to vary the diameter of second pulley  108 . Once ECU  122  has established the new speed ratio (which can be thought of generally as the ratio of engine speed to load speed), ECU  122  sends a signal to actuator  118  to change the diameter of second pulley  108 . 
   As the diameter of second pulley  108  changes, load  112  on the engine  102  may change, either due to decreasing or increasing the load on engine  102  because the diameter of second pulley  108  is changing, or because of external conditions, such as changing ground terrain or density of the crop. 
   When ECU  122  changes the diameter of second pulley  108 , it also reads speed signals from first speed sensor  114  and second speed sensor  116  and calculates a ratio of the two. This instantaneous speed ratio changes as the diameter of second pulley  108  changes, the ratio gradually approaching the new speed ratio established at the outset of the speed change process. The diameter of second pulley  108  is typically not changed randomly, but is gradually moved stepwise from a smaller to a larger diameter, or a larger to a smaller diameter, depending on which change will cause the actual speed ratio to approach the new speed ratio. 
   If, for some reason, the actual speed ratio overshoots the new speed ratio during this adjustment process (i.e. the 2 speed ratios pass each other in value and start growing farther and farther apart), ECU  122  is configured to reverse the direction of change of the diameter of the variable pulley in order to make the actual speed ratio again approach the new speed ratio. 
   ECU  122  is configured to keep sequentially repeating these steps of changing the diameter of second pulley  108  and reading the speed signals from speed sensors  114  and  116  until eventually the instantaneous speed ratio equals the new speed ratio (or alternatively comes within a predetermined value from the new speed ratio). When this happens, ECU  122  is configured to stop changing the diameter of second pulley  108  and exit its speed control loop until the operator enters another desired new load speed, at which time the entire process is repeated. 
   By controlling the diameter of the variable pulley based upon the ratio of engine speed to rotor speed instead of controlling the diameter of the variable pulley based upon the rotor speed alone, control system  120  becomes immune to any drift or change in engine speed as ECU  122  changes the diameter of second pulley  108 . 
   Once the speed changing process terminates, and once the load  112  on the engine  102  returns to its typical operating load and the engine speed will return to its original speed, i.e. the engine speed at the time the operator originally requested a desired new load speed, and the actual speed of load  112  will equal the desired new load speed. 
   Using this process, control system  120  is rendered immune to transient changes in engine speed, and the operator achieves what he desires: the load rotating at the desired speed when engine  102  is running at its initial speed. 
   The actual calculations described above need not be performed in the order they are described. The calculations can proceed in any order as long as the result is changing the diameter of second pulley  108  until it permits the engine and the load to rotate with respect to each other at speeds that are proportional to the initial engine speed and the desired load speed selected by the operator. Changing the order of calculations to any arbitrary sequence is well known to programmers skilled in the art. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.