Abstract:
An agricultural combine for supporting an agricultural header and carrying that agricultural header to a field to harvest a crop. The combine includes a chassis, front and rear drive wheels, a hydraulic motor, a device for sensing and a controller. The front and rear drive wheels support the chassis. The hydraulic motor is drivingly coupled to the front wheels. The device for sensing senses a presence of a header mounted to the combine. The controller is configured to monitor the device for sensing and to change the specific displacement of the hydraulic motor dependent upon the presence of the agricultural header.

Description:
FIELD OF THE INVENTION 
   This invention relates to agricultural vehicles, and, more particularly to systems and methods for balancing the torque on combine drive wheels. 
   BACKGROUND OF THE INVENTION 
   A typical agricultural combine weighs 15,000-20,000 kg. Combines are designed to support headers mounted to the front of the combine, which extend forward as a cantilevered load. Agricultural headers for such combines typically weigh 2000-5000 kg. The header weight, therefore, can be as much as ⅓ the weight of the combine itself. Unlike work vehicles, such as front loaders, headers for combines extend substantially beyond the left and right sides of the combine, having a total width of 10-15 m. 
   To compensate for the extremely large cantilevered loads applied by the header to the combine, the combine itself is usually provided with two large front drive wheels disposed on either side of the front of the combine, and two much smaller drive wheels disposed on either side of the rear of the combine. 
   Agricultural combines are typically configured to permit the use of different headers depending upon the type of crop to be harvested. Agricultural combines are equipped with fasteners that permit the different headers to be quickly connected and disconnected from the front of the combine. Headers are not required, however, to operate an agricultural combine. They&#39;re only necessary for harvesting crops. 
   Due to the great weight of the header, the machine dynamics change radically depending on whether the header is installed or removed, and even when a very heavy header is replaced with a very light header (or vice versa). The radical change in total weight and weight distribution will, depending on the configuration, cause the combine to be more prone wheel slippage. 
   Traction may be controlled in construction vehicles with front loading cantilevered buckets according to one system described in US patent application publication No. US2006/0211535 A1, by using a payload sensor to measure the weight of the payload in the bucket. 
   In EP 1 488 676 B1, traction may be controlled in a forage combine by changing the spacing between the front and rear wheels based upon the weight of the harvesting header. 
   In U.S. Pat. No. 7,044,257, it is disclosed that traction may be controlled in an agricultural combine by using wheel speed sensors to measure wheel slippage while the vehicle is being driven through the field, and to change the displacement of hydraulic motors driving those wheels to reduce the relative speed of the slipping wheel. 
   In US patent application publication US 2005/0217261 A1, traction may be controlled in a working vehicle by monitoring the rotational speeds of the front and rear wheels using speed sensors, calculating the diameter of the wheels, and varying the specific displacement of the hydraulic motors driving those wheels in accordance with rotational speeds. 
   None of the above examples balances the torque applied by each of the wheels based on the presence or absence of an implement on the vehicle, are on the type of implement on the vehicle. It is an object of this invention to provide such a system. 
   SUMMARY OF THE INVENTION 
   The present invention provides a traction control system for an agricultural vehicle, and more particularly to an agricultural harvester. 
   The invention in one form is directed to an agricultural combine for supporting an agricultural header and carrying that agricultural header to a field to harvest a crop. The combine includes a chassis, front and rear drive wheels, a hydraulic motor, a device for sensing and a controller. The front and rear drive wheels support the chassis. The hydraulic motor is drivingly coupled to the front wheels. The device for sensing senses a presence of a header mounted to the combine. The controller is configured to monitor the device for sensing and to change the specific displacement of the hydraulic motor dependent upon the presence of the agricultural header. 
   The invention in another form is directed to a control system for an agricultural combine that carries an agricultural header. The combine includes a chassis with front drive wheels and rear wheels coupled to the chassis. The combine has a hydraulic motor drivingly coupled to the front wheels. The control system includes a device for sensing and a controller. The device for sensing senses a presence of the agricultural header mounted to the combine. The controller is configured to monitor the device for sensing and to change the specific displacement of the hydraulic motor dependent upon the presence of the agricultural header. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a ground-engaging vehicle, in the form of a combine that utilizes an embodiment of the control system of the present invention. 
       FIG. 2  is a schematicized diagram illustrating the interconnection of portions of the control system used in the combine of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings, and more particularly to  FIGS. 1 and 2  there is shown a harvester  10  including a chassis  12 , front wheels  14  and  16 , rear wheels  18  and  20 , a header  22  and a control system  24 . 
   Control system  24  interacts with elements of a drive system  26  that incorporates hydraulic motors  28 ,  30  and  32 , as well as a transmission  34  and a differential  36 . Power is transferred from differential  36  through final drives  48  and  50 , respectively to wheels  14  and  16 . Hydraulic motors  28 ,  30  and  32  are driven by an engine  38  by way of a hydraulic pump  46 . A controller  40  interacts with a sensor  42  and with tire data  44  in order to coordinate actions of drive system  26 . Harvester  10  is a self-propelled vehicle  10  including chassis  12  to which is connected to the elements of drive system  26 . 
   Hydraulic motors  28 ,  30  and  32  each are a variable displacement hydraulic motor. Hydraulic motor  32  is coupled to left rear wheel  18  and hydraulic motor  30  is coupled to right rear wheel  20 . Engine  28  is coupled to and drives a variable displacement main hydraulic pump  46 , which in turn supplies fluid to and drives hydraulic motors  28 ,  30  and  32 . Hydraulic motor  28  drives a multi-speed transmission  34 , which in turn drives a differential gear box  36 , which in turn is coupled to final drives  48  and  50 , which respectively drive wheels  14  and  16 . 
   Controller  40  is illustrated, for ease of understanding, as being a separate controller connected to elements of drive system  26 , but the functions of controller  40  may be implemented in a controller that performs other control functions for combine  10 . The functions discussed herein may be implemented within an electronic control unit associated with control systems contained in agricultural harvester  10 . The implementation of the system and method described herein may be in the form of an algorithm, hardware or a combination of algorithms and hardware utilized by the electronic control unit or a separate controller. 
   Control system  24  is configured to receive signals from sensor  42 , which indicates the presence or absence of an agricultural header  22 . Additionally, sensor  42  will sense the type of header  22  that is connected to chassis  12 . For example, if header  22  is a cornhead having a predetermined number of row units, the weight of that cornhead is known by controller  40  to be utilized by the method described herein. Additionally, if header  22  is a small grain header, the weight thereof is also known, by way of data that has been entered and is stored as a value that is accessed by controller  40 . 
   Tire configuration data stored in memory  44  is available to controller  40  as an additional input for use by the method carried out by control system  24 . Tire configuration data will include the size of the installed tires as well as other duals installed on harvester  10 . This information is input by the operator or maintenance personnel. 
   Controller  40  coacts with drive system  26  which are together configured to vary the specific displacement of hydraulic pump  46  as well as hydraulic motors  28 ,  30  and  32 . The variation of the specific displacements of pump  46  and motors  28 ,  30 , and  32  is in response to signals received from sensor  42  as well as tire configuration data  44 . 
   Sensor  42  may be disposed adjacent to header  22  to sense the presence and the type of agricultural header  22 , by sensing characteristics of the header that indicate its presence or absence and its type, if installed. Sensor  42  may be one, or more switches that make contact with a physical portion of agricultural header  22  and are coupled to harvester  10 . Alternatively, sensor  42  may be a manual or automatic connection that is engaged either manually or automatically when header  22  is coupled to harvester  10 . Alternatively, sensor  42  can be a proximity sensor, such as a Hall Effect device or an RFID tag reader with an RFID tag connected to header  22 . Sensor  42  may have an electrical or magnetic field sensing device or even a light sensor configured to sense the presence or absence of light when header  22  is connected or disconnected from harvester  10 . 
   Sensor  42  may be disposed on the feeder house of harvester  10  and make physical contact with structures in header  22  when header  22  is physically engaged to the feeder house. The structures may include electrical connections, switches, light sources, hydraulic or electrical couplings, or integrated circuits that indicate the presence, absence or type of header when they interact with sensor  42 . Different types of header  22  may have different structures that interact differently with sensor  42  in order to convey information to sensor  42  relative to the header type as well as the presence or the absence thereof. 
   Alternatively, sensor  42  may be configured to be manipulated by the operator of the vehicle when the operator attaches agricultural header  22  to combine  10 . This manipulation may include making a mechanical, an electrical, a pneumatic or hydraulic connection or connections between combine  10  and agricultural header  22 . These manipulations may be required for the coupling of header  22  to combine  10  in order for it to properly function and the sensing of these couplings is undertaken by sensor  42 . 
   Control system  24  is configured to periodically monitor the status of sensor  42  to determine whether or not agricultural header  22  is supported on the feeder house of combine  10  and to query the type of header that is attached. This polling is preferably done at least when the self-propelled vehicle  10  is started up and control system  24  is energized. This ensures that any changes made while combine  10  was shut down are immediately sensed before the vehicle is driven away. It may also be undertaken at intervals while combine  10  is being operated. 
   Control system  24 , and more particularly controller  40 , stores internally at least two different values, one value representing the specific displacement requirements of hydraulic motor  28  when header  22  is attached to combine  10 , and one value representing the specific displacement requirements of hydraulic motor  28  when header  22  is removed from combine  10 . Additionally, control system  24  internally stores one or more additional values that represent specific displacement requirements of hydraulic motor  28  when an agricultural header  22  of a different type is attached. Agricultural headers  22  of different types may incorporate different switches, different electrical contacts, different integrated circuits, different jumpers, different generators of electromagnetic signals or lights or other similar information conveying devices, any of which can be configured to signal sensor  42  when a header of a different type has been attached to combine  10 . 
   When control system  24  senses the presence, absence and/or type of agricultural header  22  by monitoring sensor  42 , control system  24  is then configured to use the sensed status to look up the corresponding values indicating appropriate specific displacements by hydraulic motors  28 ,  30  and  32 . Control system  24  then adjusts the displacement to appropriately provide power to wheels  14 ,  16 ,  18  and  20 . The weight that is cantilevered over the front of combine  10  alters the amount of weight that is applied to wheels  14  and  16  considerably. Wheels  14  and  16  bear the main load of combine  10  and the torque applied to wheels  14  and  16  has to be appropriately balanced as is the torque supplied to wheels  18  and  20  to provide balanced traction for combine  10 . 
   Typically control system  24  is configured to increase the specific displacement of hydraulic motor  28  when agricultural header  22  is removed. Removal of header  22  as detected by sensor  42  is passed on to controller  40  and indicates that no header is attached to combine  10 . By increasing the displacement, the torque applied to the ground by front wheels  14  and  16  is reduced. At the same time, the specific displacement of hydraulic motors  30  and  32  that drive rear wheels  18  and  20  is unchanged or reduced by control system  24 . This effectively reduces the front to rear torque ratio applied to the ground by the front and rear wheels. 
   In a similar fashion, control system  24  is configured to decrease the specific displacement of hydraulic motor  28  when agricultural header  22  is attached to vehicle  10 . By decreasing the displacement based on the presence of header  22  and additionally the type of header  22 , this gives controller  40  the information to apply appropriate torque to wheels  14 ,  16 ,  18  and  20 . Control system  24  may adjust displacement of hydraulic motor  28  leaving the displacement of hydraulic motors  30  and  32  unchanged or may adjust the displacements of each to correspond to the weight distribution of combine  10 . 
   Control system  24  is configured to increase and decrease specific displacements of motors  28 ,  30  and  32  as well as the displacement of the pump to effectively control the front to rear torque ratio. The drive torque applied to the front and rear wheels is balanced dependent upon a header of a specific type or when the absence of header  22  becomes the configuration of combine  10 . 
   The present invention includes the capability of shifting gears in transmission  34  as well as changing the displacement of hydraulic motor  28  to control the torque applied to wheels  14  and  16 . This enables the operator to have the capability for traversing obstacles, like levies or hills, at low speed where high torque is required and then to drive faster on level ground while harvesting or transporting without stopping to shift gears and avoiding the slipping of wheels  14 ,  16 ,  18  and  20 . For a given set of tire configurations and weight distribution the present invention changes the torque applied to the wheels to prevent combine  10  from being stuck and reducing wheel spin on combine  10 . 
   The present invention commands the displacement of hydraulic motor  28 , rear motors  30  and  32  and gear ratios of transmission  34  based on parameters sensed by sensor  42  as well as tire data  44 . The information is available on the CAN bus of combine  10 . Combine  10  is configured by factory personnel or by the dealer; a technician can input the tire configuration such as the size and presence or absence of duals installed on the combine. This information about tires also includes the rolling radius and footprint, which is needed to determine the tire/soil interaction capability inherent with that particular set of tires. When a header  22  is connected to combine  10  and when sensor  42  recognizes the type of header  22 , such as a cornhead, chopping cornhead or a cutting platform, etc. This also determines the crop density that can be assumed will be going across header  22  as well as the header weight, both of which affect the weight distribution of combine  10 . The tire and header data utilized by controller  40  is to determine how much torque can be applied to each axle without loss of traction. The front and rear motor displacement values and gear ratio for each axle could additionally be selected automatically to provide the optimal torque level to each axle. 
   The present invention allows for a feathering of the torque output to control and to enhance the traction of vehicle  10 . In the event wheels spin, the hydraulic motors spinning those wheels can be de-stroked to allow the wheels to gain traction. The present invention allows the traction across the ground to take place with matched wheel slippage. Another advantage of the present invention is that it increases the efficiency of transit across a field by reducing fuel consumption. The present invention allows the matching of the displacement of hydraulic motors based on traction and weight distribution of combine  10 . It is additionally contemplated that sensor  42  or other sensors give information to controller  40  to convey the attitude as well as acceleration of vehicle  10 , which can alter the weight distribution on wheels  14 ,  16 ,  18  and  20  thereby allowing controller  40  to adjust the applied torque based upon these other sensed attributes of combine  10 . Controller  40  selects appropriate torque curves based upon these inputs to control the torque supplied to wheels  14 ,  16 ,  18  and  20 . 
   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.