Abstract:
A self-propelled forage harvester is provided with a throughput measurement device comprising a computer which makes use of respective signals representative of the displacement of a movable upper pre-compression roll relative to a fixed lower pre-compression roll, of the speed of the lower roll, and of the force exerted by the mat of crop passing between the rolls on the upper roll once the upper roll reaches its upper limit position in the calculation of the crop throughput value. An additional input signal that may be used in the calculation of the crop throughput is generated by a light barrier which determines whether or not any crop is exiting the discharge chute of the forage harvester, this signal causing the throughput calculation to indicate zero throughput when no crop is exiting and causing the calculation to indicate a minimum amount when the upper pre-compression roll is in its lower limit position with crop being sensed exiting the discharge chute.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a throughput measurement device for the determination of the crop throughput in an agricultural harvesting machine, in particular a forage harvester, where the harvesting machine is provided with at least one pair of pre-compression rolls that guide the crop and whose spacing varies on the basis of the current crop throughput between a minimum limit position and a maximum limit position. The throughput measurement device contains a spacing measurement arrangement that makes available signals corresponding to the spacing between the pre-compression rolls, a speed sensor, that makes available signals corresponding to the speed of the crop and a control unit that utilizes the spacing signals and the speed signals for the determination of actual mass throughput values. Furthermore the invention concerns a harvesting machine with a throughput measurement device and process for the measurement of throughput. 
     In the treatise by G. Ihle and W. Dornitz, “Investigations into the Mechanical Measurement of the Throughput on Self-propelled Forage Harvesters”, Agrartechinik, 27.Jg. issue 6, 5. 265 (1977) describes a continuous throughput measurement process for a forage harvester. In the forage harvester, the crop is conducted from a take-up arrangement over a transfer roll and a forward belt to compression rolls and smooth rolls (that are characterized in the following also as pre-compression rolls), which compress the crop to a mat and provide a speed corresponding to the currently effective chopper length for the mat. In a chopper drum, the crop mat is cut into individual lengths which are ejected through a discharge pipe to a transport vehicle. The height of the crop mat is detected by device and is used for the calculation of the throughput, in which the pre-set intake speed is considered a constant. On the basis of the process shown, the variation of the throughput with time can be recorded. However, it does not deliver any throughput signals that could be stored electrically and would be available for further control processes. 
     DE-A-195 24 752 discloses an arrangement and a process for the measurement of the throughput on a forage harvester with a throughput measurement device. Here the vertical movement of a pre-compression roll is transmitted over a lever linkage to the axis of rotation of a potentiometer which delivers lift signals corresponding to the lift path. An inductive sensor generates a signal value derived from the rotational speed of a pre-compression roll, which represents the throughput speed of the flow of the crop flowing through the machine. The signal values are continuously calculated in a microprocessor into an absolute mass flow measurement value. In addition, signals of a torque measurement at the chopper drum and a slip measurement of the drive belt can be detected and used as correction values in regions of defined limit values in which a pre-compression roll approaches the upper or lower stops. It has, however, been found that these corrections in the regions of the upper and lower stops are highly prone to errors and require a large calibration effort. Furthermore the linkage realignment of the vertical movement of a pre-compression roll over a lever linkage to the axis of rotation of a potentiometer described in DE-A-195 24 752 delivers a relatively low resolution of the measured values since the potentiometer disclosed covers a relatively small range of angles of rotation. 
     The problem underlying the invention is seen as that of defining a throughput measurement device, a harvesting machine with a throughput measurement device and a process for determining the crop throughput of the aforementioned type, through which at least some of the aforementioned problems are overcome. In particular, the throughput measurement device should permit a reliable and precise determination of the mass flow of crop with the employment of relatively few sensors. In the application of the measurement process a consideration of dynamic machine data should not be required. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a throughput measurement device for the determination of the mass flow of the crop through an agricultural harvesting machine, in particular a forage harvester, that is provided with a pair of pre-compression rolls that guide and compress the crop, whose spacing varies on the basis of the current crop throughput between a minimum limit position and a maximum limit position. 
     A broad object of the invention is to provide a very reliable crop throughput measuring arrangement that uses few, cost effective sensors and components in an unobtrusive design, with the capability of high resolution even in the region of maximum deflection of the movable pre-compression roll without necessitating any dynamic machine data to be incorporated into the evaluation. 
     A more specific object of the invention is to provide a throughput measurement device containing a spacing measurement arrangement, which detects the spacing between the pre-compression rolls and makes available corresponding spacing signals and a speed sensor that detects the speed of flow of the crop in particular in the region of a pre-compression roll, and makes available corresponding speed signals, the measurement device further including a control unit which calculates, from the distance signals and the speed signals, actual mass throughput values. 
     Another object of the invention is to provide a throughput measurement device, as set forth in the immediately preceding object, but which further includes at least one force transducer that is arranged and is effective only in the region of the maximum limit position of the movable pre-compression roll, to produce signals corresponding to the pressures on the stop, with the control unit making use of these force transducer signals into the determination of the actual mass throughput values. 
     These and other objects will become apparent from a reading of the ensuing description together with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side view of a self-propelled forage harvester with a throughput measurement device according to the invention. 
     FIG. 2 shows the intake housing of a forage harvester with a throughput measurement device according to the invention. 
     FIG. 3 shows a flow diagram for the calculation of the mass flow rate. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 reveals an agricultural machine for the collection and processing of crop, in particular, a self-propelled forage harvester  10  with a front harvesting attachment  12  and a crop supply arrangement  14 , that is formed by several pre-compression rolls a forward pair of upper and lower compression rolls  16  and  18  and a rear pair of upper and lower compression rolls  20  and  22 . It is desirable to operate with the most homogeneous crop throughput possible and it has been found that this may be accomplished if the harvesting attachment  12  is a corn picker operating independent of rows. In any event, from the front harvesting attachment  12 , the crop is forced in a direction A through a compression channel formed by the pre-compression rolls  16 ,  18 ,  20  and  22  to a knife or chopper drum  24 . Here the crop is cut and conducted further in a direction B toward a discharge chute or spout  26 . Located between the knife drum  24  and the discharge chute  26  is a blower  28  which accelerates the cut crop at the point where it enters the discharge chute or spout  26 . A light barrier  29  is arranged in the discharge chute  26  for detecting whether or not crop flow exists. 
     FIG. 2 shows details of the crop supply arrangement  14  and the chopper drum  24  that are arranged in an intake housing  30 . The front set of pre-compression rolls  16  and  18  begin compressing the crop as it passes therebetween, with further compression and conveying of the crop being performed by the two rear pre-compression rolls  20  and  22  that are spaced from one another by a variable spacing d. Preferably, the pre-compression roll  20  is arranged generally vertically above the pre-compression roll  22 . Here the lower pre-compression roll  22  is supported in stationary bearings while the upper pre-compression roll  20  is mounted to a pair of vertically swingable arms  31  extending between opposite ends of the roll axle and a pivot pin located on the frame at the opposite sides of the housing  30 . Located at each of the opposite ends the roll axle is a flange  32  having upper ends joined by a transverse strut or leveling rod  33 . Opposite ends of the axle of the roll  20  and of the. leveling rod  33  are located in a pair of clearance slots  34  respectively provided in the opposite side walls of the housing  30  and disposed arcuately about the pivot axis of the arms  31 . Coupled between the frame and the opposite ends of the leveling rod  33  are a pair of helical extension springs  35 , which are not absolutely necessary. Thus, the upper pre-compression roll  20  can deflect increasingly upward against the force of the helical springs  35  and/or gravity with increasing throughput. Upon deflection of the pre-compression roll  22 , the width of the gap carrying the crop varies as well as the spacing d between the pre-compression rolls  20  and  22 . Here the spring characteristic of the spring arrangement is preferably designed in such a way that the spring force and thereby also the force acting upon the throughput material, increases with increasing deflection of the pre-compression roll  22  and with increasing spacing d between the pre-compression rolls. This produces a greater compression of the crop flow and may be incorporated into the determination of the mass flow in which the spacing value is provided with a corresponding correction, as explained below. 
     In order to make possible a reliable determination of the variation between the pre-compression rolls, even with a non-uniform material flow along the length of the pre-compression rolls and hence non-uniform gap between the pre-compression rolls, a preferred embodiment of the invention provides that the spacing measurement arrangement be configured in such a way that it measures the spacing between pre-compression rolls in the central region. The structure provided for accomplishing this measurement includes the pair of flanges  32 , which are respectively mounted at the opposite ends of the upper rear pre-compression roll  20  in such a way that they do not rotate, and the transverse strut or leveling rod  33 . The pre-compression roll  20  can deflect generally in the vertical direction between a lower stop, defined by the bottoms of the slots  34 , and an upper stop  36 , defined by the upper ends of the slots  34 . When the lower stop is reached, the ends of the pre-compression roll axle make contact with the lower ends of the slots  34 , while upon reaching the upper stop  36 , the ends of the transverse strut  33  make contact with the upper ends of the slots  34 . With regard to its longitudinal extent, a rope  37  is attached in the central region of the transverse strut  33  and leads over a deflection pulley  38  to a rope potentiometer  40 . Thereby the vertical deflection of the transverse strut  33  and with it also the upper rear pre-compression roll  20  is detected without any further transmission losses, and converted into a measurement value that is a function of the dimension of the gap or space d between the two rear pre-compression rolls  20  and  22 . The change in resistance generated in the rope potentiometer  40  is converted by an integrated amplifier into a voltage signal and transmitted over a data line  42  to a processor  46 . Preferably the rope potentiometer  40  is designed such that it can cover a lift deflection up to approximately 300 mm. 
     With increasing crop throughput, the upper pre-compression roll  20  moves upward until it reaches the upper stop  36 , which limits the maximum gap d of the passage channel. Even when the axle of the upper pre-compression roll  20  is in contact with the upper stop  36 , a higher mass flow can be reached by further compression of the crop. According to a preferred embodiment of the throughput measurement arrangement, a force transducer, here shown as force transducer box  48 , is provided adjacent the upper ends of the guide slots  34  at each of the opposite sides of the housing  31  so as to be in the path of movement of the transverse strut  33 . An appropriate force transducer, for example, is a type C9B, pressure force transducer rated at 20 kN that is available from the Spectris Company, located in Germany. However, with large harvesting machines, force transducers can be successfully applied whose measurement range lies between 0 and 50 kN. The force transducer  48  may be a force measurement box, as shown, or a bending beam. 
     The force transducers  48  may be attached at both sides of the intake roll housing  30  in such a way that the transverse strut  33  of the upper pre-compression roll  20  makes contact with the input point of the force transducer  48  as soon as it reaches a position that corresponds to a certain distance from the upper edge (stop  36 ) of the guide slot  34  of the pre-compression roll  20 . Preferably each force transducer  48  is positioned relative to the mechanical end stop  36  of the pre-compression roll  20  such that it responds approximately 5 mm. before the strut  33  reaches the stop  36 . The signals of the two force transducers  48  are sent to the processor  46  over data lines  50  and can be averaged and processed further in the processor  46  as a common force transducer signal. Even in the case of a non-uniform crop throughput along the pre-compression rolls  20  and  22 , in which the width of the gap between the pre-compression rolls is not uniform, a relatively exact determination of the pressure applied to the crop is obtained. 
     Because the force transducer boxes  48  absorb the force by means of which the upper pre-compression roll  20  is forced upward at very high throughput, protection of each transducer box  48  from overloading is desired and may be provided by locating an elastomeric pad  49  in the region of the contact surface of the transducer box  48 . 
     An impulse sensor  52  measures the rotational speed of the lower pre-compression roll  22 . This measured rotational speed value is proportional to the speed of the material flow in the intake channel between the two rear pre-compression rolls  20  and  22  and is transmitted over a data line  54  to the processor  46 . The rotational speed signals are generally proportional to the speed of the material flow in the intake channel between the two rear pre-compression rolls  20  and  22 . 
     According to an additional particularly preferred further development of the invention, the light barrier  29  is mounted in the discharge spout or chute  26 , as shown in FIG. 1, for the purpose of monitoring the ejected material flow. The signal of the light barrier  29  is used in particular at that time for the determination of the crop throughput when the pre-compression roll  20  and  22  occupy a minimum spacing to each other. At a minimum spacing between pre-compression rolls  20  and  22 , a minimum crop throughput is recorded as long as flow of material is detected in the discharge spout. If no material flow is recorded, the crop throughput is set equal to zero. The signal value of the light barrier  29  is transmitted over a data line  56  to the processor  46 . Furthermore, the processor  46  is connected over a data line  58  with an indicator unit, not shown in any further detail, installed in the operator&#39;s cab, by means of which, for example, inputs regarding the actual crop and calibrations can be provided. The processor  46  evaluates the signals transmitted to it and transmits the results over at least one data line  60  to an indicator arranged in the operator&#39;s cab or to further, in any case not further detailed, control or memory arrangements. 
     From the signals transmitted to it, the processor  46  calculates the mass flow M t . It has been shown to be particularly advantageous to determine the mass flow M t  on the basis of the following relationship: 
     
       
           M   t   =k *( d   1   +d   2   +d   3 )*ω 
       
     
     with 
     d 1 =½*d min * f(Boolean) 
     d 2 =f(F)*d max +f Spring 
     d 3 =f(F) 
     Where k is a calibration constant that can be determined by tests; ω is a measured value of the speed sensor, in particular the rotational speed of the pre-compression roll  22 ; d 1 , d 2 , and d 3  are derived roll spacing values; d min  is a minimum spacing between the pre-compression rolls  20  and  22 ; d max  is a maximum spacing between pre-compression rolls  20  and  22 ; f(Boolean) is a logical function on the basis of which a light barrier signal is evaluated; f(R) is a roll spacing value derived from the spacing measurement arrangement and normalized for the maximum roll spacing d max ; f(spring) is a value derived from the spring characteristic of the pre-compression roll spring arrangement as a function of the roll spacing value; and f(F) is an adjustment force value derived from one or more force transducers  48 . The values f(R), f(F) and k may depend upon the particular crop being processed. For example, in various types of crop, different densities can be reached, so that in the processor  46  values specific to different crops are stored, that flow into the constants and functions for the calculation of the mass throughput. A function can also be stored in the processor  46  for the compressibility of the crop. 
     With a calibrated system, the operator uses an input only to specify the type of crop to be harvested and humidity conditions, if required. In the processor  46 , the associated constants and functions are then automatically selected for the calculation of the mass throughput. With the values of the throughput calculated by means of the processor  46  and other data (position, operating speed, scope of the work) the data of the proceeds can be determined and a chart of the proceeds can be filled out. 
     From the signals transmitted to it, the processor  46  calculates the mass flow M t . The calculation may be performed, for example, on the basis of the flow chart shown in FIG.  3 . Upon starting in step  100 , an initialization is performed in which the time t and the mass flow to be determined, M t  are set equal to zero. In step  102 , the value of time is increased by a unit of time. Then the algorithm tests in step  104  whether the light barrier  30  registers a flow of material. If no flow of material is found, then in step  106  values d 1 , d 2 , and d 3  are set equal to zero and the process continued in step  108 . In this case, the result is a mass flow M t =0. 
     If, on the other hand, the light barrier  29  registers a mass flow, then the algorithm continues with step  110  in which it is determined whether the output signal of the rope potentiometer  40  is greater than zero. If this is not the case, then the upper pre-compression roll  20  is in contact with the lower stop. Since in this case, a small gap remains between the pre-compression rolls  20  and  22 , a small mass flow is possible, that is determined by the light barrier  29 . This mass flow is so small in comparison to the mass flows in normal operation, that it can be considered by an average value as an approximation without falsifying the total measurement significantly. If the output signal of the rope potentiometer is zero, than in step  112 , therefore the value of d 1 =d MIN /2 and the values d 2 =d 3  are set to equal zero, and the process is continued with step  108 . This has the result that a constant minimum mass flow M t  is issued. 
     If the flow of material is so great that it lifts the upper pre-compression roll  20  so that it no longer is in contact with its lower stop, then the rope potentiometer transmits a signal greater than zero. In this case, the step  110  takes the algorithm to step  114 . In step  114 , the signals of the force transducer boxes  48  is verified. If these are zero, this means that the upper pre-compression roll  20  had not yet been raised into the region of the upper stop  35  by the flow of material. If this is the case, then in step  116  the values d 1 =d min /2, d 2 =f(R)*d max  and d 3  equal to zero, and the process continues with step  108 . The operating range between the lower and the upper stops is considered by means of the value d 2 , that establishes a linear relationship between the roll spacing and the mass flow. 
     If, however, the upper pre-compression roll  20  is raised by the flow of material to such a degree that it comes into the range of the upper stop  36 , at which point the transverse strut  33  comes into contact with at least one force transducer box  48  and applies a force to this, then a force transducer signal results that is not equal to zero. In this case, in step  118 , the values d 1 =d min /2, d 2 =f(R)*d MAX  and d 3 =f(F), and then the process continues with step  108 . The operating range in which the upper pre-compression roll  20  is located in the region of the upper stop  36 , is covered by the measurement of the contact pressure of the upper roll  20  on the upper stop  36 , which can generally be seen as proportional to the possible further deflection of the roll  20 . 
     In step  108 , the values d 1 , d 2  and d 3  are added to produce a value d total . In step  120 , the mass flow M t  is then calculated in which the value d total  is multiplied by the output signal ω of the impulse sensor  52  as well as by a calibration constant k. Step  122  issues the mass flow M t  thus determined and returns the algorithm to step  102 , in which the time is again increased by a unit of time. The algorithm described can be automatically performed several times a second. 
     Although the invention has been described in terms of one embodiment, anyone skilled in the art will perceive many varied alternatives, modifications and variations in light of the above description as well as the drawings, all of which fall under the present invention.