Abstract:
A self-propelled harvesting machine has a chassis that is supported for travel over the ground by a front pair of propulsion wheels and a single steerable rear wheel. The rear wheel is mounted for being selectively shifted along the direction of operation for changing the spacing between the front wheels and rear wheels so as to effect a difference in the weight distribution between the front and rear wheels. This adjustment can be made automatically in accordance with the weight of a front-mounted harvesting attachment and/or the load imposed on a trailer coupling by a towed trailer.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention concerns a self-propelled harvesting machine with a chassis, to which rolling support devices in contact with the ground are attached, which are arranged for the forward propulsion and the steering of the harvesting machine and of which the front set of rolling support devices are arranged ahead of the rear rolling support devices in the direction of operation.  
         BACKGROUND OF THE INVENTION  
         [0002]    In self-propelled harvesting machines, the load on the wheels and thereby the compaction of the ground are, to a considerable degree, a function of the weight distribution of a front harvesting attachment mounted on the machine and a possible trailer load. In the state of the art, the rear of the machine is ballasted as a function of the type of the front harvesting attachment. Therefore, with relatively heavy front harvesting attachments, a relatively heavy rear ballast must be mounted in order to assure a safe operating performance of the harvesting machine by providing an adequate load on the steerable rear wheels. These measures considerably increase the weight of the harvesting machine, which contributes to the disadvantage of the compaction of the ground. Furthermore, upon a change in the front harvesting attachment, the rear ballast must be changed to conform which results in a not inconsiderable cost in time.  
           [0003]    DE 100 04 622 A and AT 285 439 A describe ground level conveyor vehicles with an adjustable wheel base that is used to provide greater stability to the vehicle particularly with higher lifting heights.  
           [0004]    The problem underlying the invention is seen in the need to further develop a self-propelled harvesting machine in such a way that the aforementioned disadvantages do not occur or do so only to a lesser degree.  
         SUMMARY OF THE INVENTION  
         [0005]    According to the present invention, there is provided an improved ground support arrangement for a self-propelled harvesting machine.  
           [0006]    It is an object of the invention to provide a harvesting machine including front and rear sets of rolling support devices arranged for the propulsion and steering of the vehicle and wherein at least one of the sets of rolling support devices is mounted for adjustment along the operating direction of the vehicle in order to attain an appropriate distribution of the weight of the machine on the front and rear sets of rolling support devices.  
           [0007]    It is proposed that the spacing between the front and the rear sets of rolling support devices in contact with the ground, which may be wheels or crawler track assemblies, be configured as variable by an appropriate arrangement at the chassis of the self-propelled harvesting machine. When wheels are used, the wheel base can thereby be adjusted. As a rule, the front set of rolling support devices are driven and are rigidly connected to the chassis, while the position of the rear rolling support devices, as seen in the forward direction of operation, which are or is, as a rule, steerable, is changed relative to the chassis.  
           [0008]    In this way, an accommodation to the weight of the front harvesting attachment used at that time can be attained in each case by a variation of the wheelbase of the harvesting machine. The weight of the harvesting machine can be distributed over the front and the rear sets of rolling support devices in an appropriate manner, so as to achieve a sufficiently heavy loading on the rear rolling support devices, that leads to a good steering ability. Simultaneously, the load on the front rolling support device is reduced, so that the compaction of the ground is lessened. The ballasting of the rear of the harvesting machine may possibly be omitted completely, resulting in a reduction of the total weight of the harvesting machine. Moreover, the set-up time of the harvesting machine is shortened considerably, so that its flexibility is increased.  
           [0009]    Basically, it would be conceivable that the aforementioned spacing be provided as input by an operator. The disadvantage here is that inexperienced operators, in particular, could bring about unfavorable operating characteristics of the harvesting machine by erroneous inputs. In a preferred embodiment, an automatic adjustment of the spacing between the front and the rear rolling support devices in contact with the ground is therefore preferred.  
           [0010]    The spacing that is to be provided as input is primarily a function of the weight of a front harvesting attachment and a trailer load if a trailer is used. These loads are therefore considered by the arrangement for the readjustment of the spacing. The weight of the front harvesting attachment can be manually input by an operator, or detected by a sensor. The use of an electronic memory unit associated with the front harvesting attachment can also be used for the input of the weight of the front harvesting attachment. The memory unit may be located in a fixed position on the front harvesting attachment and transmit the data over a bus line to the arrangement for the readjustment of the spacing. Alternatively, a memory card or the like can be used that is inserted into an appropriate reading implement. The weight of a trailer load is detected analogously.  
           [0011]    If the weight of the front harvesting attachment is to be detected by a sensor, such a sensor can be arranged to measure the hydraulic pressure in the hydraulic circuit of the lifting device of the front harvesting attachment. But measurement with a load cell at the suspension of the front harvesting attachment on the harvesting machine would also be conceivable. Analogously, the support force of a trailer load is preferably detected by a sensor at the trailer coupling.  
           [0012]    It should be noted that it would also be conceivable to adjust the position of the rolling ground support devices automatically or manually on the basis of signals from sensors, which detect the weight borne by the rolling support device on the ground.  
           [0013]    A change in the spacing between the front and the rear sets of rolling support devices in contact with the ground during the operation poses the danger that the operating and steering performance can change suddenly. An obvious solution therefore is to provide the arrangement for the readjustment of the spacing with information as to the immediate speed of the harvesting machine, that can be detected, for example, by a speed sensor, in order to permit a change in the spacing only when the harvesting machine is stopped.  
           [0014]    During operation on public roads, a number of requirements of the law must be fulfilled, that can be met in many cases only when the spacing between the front and the rear sets of rolling support devices in contact with the ground is maintained at a certain value or in a certain range. On the other hand, on the field the spacing can be chosen at will. In a preferred embodiment, the arrangement for the change in the spacing between the front and the rear sets of support devices in contact with the ground can therefore be operated so as to bring the spacing to a certain value, for example, the maximum value, in case the machine is in a public road operating mode.  
           [0015]    The public road operating mode can be detected on the basis of the position of a field/public road operating mode switch. Alternatively, or in addition, the position of an electronic selector switch or a mechanical selector lever for the gear ratio of a shifted gearbox of the operating drive of the harvesting machine can be interrogated. On the other hand, if the harvesting machine is on a field, the automatic adjustment of the spacing. is performed as described above. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The drawings show an embodiment of the invention that shall be described in greater detail in the following.  
         [0017]    [0017]FIG. 1 is a left side elevational view of a self-propelled harvesting machine.  
         [0018]    [0018]FIG. 2 shows a schematic of a arrangement for changing the spacing between the front and the rear rolling support devices in contact with the ground of the harvesting machine.  
         [0019]    [0019]FIG. 3 shows a flow chart that illustrates the method of operation of the arrangement. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    The self-propelled harvesting machine  10  is depicted in the form of a self-propelled forage harvester in FIG. 1 and is supported on a chassis  12  that is carried by a front rolling support device  14  in contact with the ground, in the form of a pair of wheels, and a rear rolling support device  16  in contact with the ground, in the form of a single wheel. The operation of the harvesting machine  10  is controlled by an operator from an operator&#39;s cab  18  from which a front harvesting attachment  20  can be controlled within the view of the operator. Besides its application to forage harvesters, the invention can be applied to any desired harvesting machine such as, for example, combines, grape harvesters, cotton harvesters or self-propelled balers.  
         [0021]    The front harvesting attachment  20  is attached to the harvesting machine  10  so as to be removable and can be exchanged for any desired front harvesting attachment. Crop taken up from the ground by the front harvesting attachment  20 , for example, corn, grass or the like, is conveyed into the interior of the harvesting machine  10  by rough pressing rolls and conducted to a chopper drum that chops it into small pieces and delivers it to a conveyor arrangement. The crop leaves the harvesting machine  10  to an accompanying trailer over a rotating discharge duct  22 . The front harvesting attachment  20  is connected in joints to the chassis  12  so as to pivot about the axis of rotation of the chopper drum. The pivoting, that is, the input of the height of the front end of the front harvesting attachment  20  is performed by means of a hydraulic cylinder  24  that extends between the front harvesting attachment  20  and the chassis  12 .  
         [0022]    An internal combustion engine  26  is located in the rear region of the harvesting machine  10  and supplies the driven elements of the machine  10  with driving energy.  
         [0023]    The front set of rolling support devices  14  in contact with the ground are connected rigidly with the chassis  12 , that is, they cannot be steered, and can be driven. Optionally, the rear rolling support  16  in contact with the ground is fastened to a suspension  28 , whose position in the forward operating direction V in the harvesting machine  10  is variable. For that purpose, the suspension  28  is supported in bearings, free to slide, on a horizontal guide  30  extending in the forward operating direction V and a hydraulic repositioning cylinder  32  extends between the chassis  12  and the suspension  28 . Thereby, the wheel base of the harvesting machine  10 , that is, the spacing between the rolling support devices  14  and  16  in contact with the ground, can be varied by changing the length of the repositioning cylinder  32 . The rear rolling support device  16  can be steered, that is, it can be rotated about a vertical axis, is fastened to the suspension  28  and provides the input of the direction of operation of the harvesting machine  10 . For this purpose, a steering cylinder (not shown) is provided that is described, for example, by U.S. Pat. No. 4,222,452, whose disclosure is incorporated in the present application by reference.  
         [0024]    An advantage of the use of a single rear wheel lies in the fact that it is offset relative to the front wheels, which contributes to the reduction in the compaction of the ground, and in the smaller steering radius that can be achieved. However, a conventional rear axle with two steerable wheels could also be attached to the harvesting machine  10 . Then, the rear axle would be connected with the guide  30  and the repositioning cylinder  32  over the suspension  28 .  
         [0025]    The complete configuration of the arrangement  34  for the variation of the spacing between the front and the rear sets of rolling support devices  14  and  16  is shown schematically in FIG. 2. An electronic control arrangement  36  operating analogously or digitally is connected electrically with a valve control arrangement  38  that controls a proportional control valve  40  as a function of the current or voltage or a pulse-width modulated valve, or any other desired appropriate valve. The proportional control valve  40  is connected with a hydraulic fluid pressure source  42  and with the repositioning cylinder  32 . A mechanical position detecting arrangement  44 , in the form of a linear potentiometer or any other desired sensor, mounted between the chassis  12  and the suspension  28  provides the control arrangement  36  with information about the immediate position of the suspension  28 . Hence, the control arrangement  36  is arranged to control the spacing between the front and rear sets of rolling support devices  14  and  16  while using a feedback signal.  
         [0026]    Moreover, the control arrangement  36  is connected with a front harvesting attachment weight sensor  46  that is looped into the hydraulic circuit of the hydraulic cylinder  24  used to reposition the height of the front harvesting attachment  20 . The pressure of this hydraulic circuit contains information about the weight of the front harvesting attachment  20  since a higher pressure is required to lift a heavier front harvesting attachment  20  than to lift a lighter front harvesting attachment  20 . The part number call-out  52  identifies an input arrangement that can be used as an alternative, or in addition to, the front harvesting attachment weight sensor  46 , that permits the operator in the operator&#39;s cab  18  to provide as an input the type or the weight or the mass of the front harvesting attachment  20 .  
         [0027]    The control arrangement  36  also receives an input from a sensor  48  that detects the support force of a trailer that is coupled to a coupling  50  at the rear of the harvesting machine  10 . Alternatively, or in addition to the sensor  48 , an input arrangement can be used that permits the operator in the operator&#39;s cab  18  to provide as an input the type, or the weight or the mass of a trailer at the coupling  50 .  
         [0028]    A speed sensor  54  detects the actual forward propulsion velocity of the harvesting machine  10 . It can interact with one of the sets of rolling support devices  14  and  16  or it may be a radar sensor, that interacts directly with the ground.  
         [0029]    Finally, the control arrangement  36  is connected with a gear ratio sensor  56  or a field/public roads operating mode switch  58 . The gear ratio sensor  56  detects the gear ratio of a gearbox of the operating drive of the harvesting machine  10  selected at a given time. The field/public roads operating mode switch  58  is located in the operator&#39;s cab  18  and is used by the operator to provide an input of the operating mode of the harvesting machine  10 . In the public roads operating mode, all elements of the harvesting machine  10  required only for harvesting cannot be activated. Analogously, during operation on a field, only the elements required for harvesting can be turned on, while the elements required for operation on public roads are deactivated.  
         [0030]    The manner of operating the arrangement is explained in the following on the basis of the flow chart shown in FIG. 3.  
         [0031]    After starting in step  100 , that is performed after starting the harvesting machine  10 , the question is posed initially whether the forward propulsion velocity of the harvesting machine  10  is zero, that is, whether the signal of the speed sensor  54  points to the fact that the machine is stopped. If it is not the case, step  102  again follows. Therefore, a repositioning of the rear rolling support device  16  is not possible during this operation.  
         [0032]    Otherwise, step  104  follows in which the gear ratio sensor  56  and/or the field/public roads operating mode switch  58  is interrogated. If the gear ratio sensor  56  determines that the gearbox of the operating drive of the harvesting machine  10  is in its highest gear ratio, the information is taken from it that the harvesting machine  10  is in the public roads operating mode, since this gear ratio is not used during the harvesting operation. On the basis of the field/public roads operating mode switch  58 , it is also possible to check whether the harvesting machine  10  is in a harvesting mode or not.  
         [0033]    If it is not in a harvesting operation, step  106  follows, in which the question is posed whether the suspension  28  and the rear rolling support device  16  in contact with the ground are in a position for operation on public roads, as permitted by the public roads traffic authorities. If this is the case, step  102  again follows. Otherwise, step  108  follows in which the control arrangement  36  brings the rolling support device  16  into the aforementioned position for the operation on public roads while using the feedback signal of the position detection arrangement  44  and the valve control arrangement  38 .  
         [0034]    If the result in step  104  shows that the harvesting machine  10  is in a harvesting operating mode, then step  110  follows. On the basis of the signals of the front harvesting attachment weight sensor  46  and of the sensor  48  for the support load on the coupling  50  and optionally the input arrangement  52 , the calculation is made into which position the suspension  28  with the rear rolling support device  16  in contact with the ground is to be brought, in order to attain an appropriate weight distribution on the rolling support devices  14  and  16 . This appropriate weight distribution is characterized by the fact that a sufficient proportion of the total weight is absorbed by the rear rolling support device  16 . Thereby, the compaction of the ground by the front set of rolling support devices  14  is reduced and the result is a good steering performance. Corresponding to the result of the calculation, the position of the suspension  28  is varied. In addition, sensors could be used on the axles of the rolling support devices  14  and  16  in order to recheck the weight distribution attained or to fine tune it: Step  110  is again followed by step  102 .  
         [0035]    [0035]FIG. 3 begins with the premise that the gear ratio of the gearbox of the operating drive can be changed only when the machine is stopped, and that the field/public roads operating mode switch  58  can be adjusted only when the machine is stopped. If these conditions do not apply, the chart in FIG. 3 must be subjected to appropriate modifications in order to prevent an undesired position of the suspension  28  and the rear rolling support device  16  from being attained upon a change in mode of operation of the harvesting machine  10  during operation.  
         [0036]    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.