Abstract:
An agricultural working machine has intake conveyor mechanisms, a hydraulic circuit via which the intake conveyor mechanisms are hydraulically driven and including at least one hydraulic motor which drives the intake conveyor mechanisms, at least one switching valve system for interrupting or releasing a flow of hydraulic oil being assigned to the at least one hydraulic motor, the switching valve system being configured for interrupting or releasing the flow of hydraulic oil to the hydraulic motor as a function of a signal from a foreign-object position detection device, the switching valve system including at least one braking function for the at least one hydraulic motor, and a section of the hydraulic circuit which realizes the at least one braking function is essentially free of elasticities.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2005 023 047.4 filed on May 13, 2005. This German patent application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an agricultural working machine with intake conveyor mechanisms which are hydraulically driven via a hydraulic circuit. 
     A system of this type was made known in DE 100 36 612 A1, for example. According to that publication, the hydraulically-driven intake conveyor mechanisms—which are designed as intake rollers provided in pairs—convey a flow of crop material between them, the crop-material flow being transferred in the rear region to a crop-material chopping device, such as a chopper drum. Since the crop-material flow often contains foreign objects, such as metallic pieces or stones, which can cause serious damage to the chopper drum as it rotates at a high rate of speed, a “quick stop” function is assigned to the intake conveyor mechanisms. With the “quick stop” function, the foreign objects located in the crop-material flow are detected using a detection device, and, as a function of their detection, a shut-off signal for the intake conveyor mechanisms is generated in a control unit. To reliably prevent the detected foreign objects from reaching the chopper drum anyway after the intake conveyor mechanisms are shut off but continue to move, it is provided according to DE 100 36 612 A1 that a valve combination be assigned to the hydraulic drive of the intake conveyor mechanisms, the valve combination being composed of a main control valve and a pilot directional control valve, the foreign object detection device immediately triggering—when foreign objects are detected—a switching procedure at the pilot directional control valve that induces the quick stop. In addition to the large number of components required to realize the quick-stop function, a design of this type has the disadvantage that the various switching procedures and the distances that must be covered by the switching medium can delay the quick stop procedure such that the detected foreign object reaches the rotating chopper drum anyway, where it causes considerable damage. 
     The problem of inadequate reaction time is alleviated in the related art as disclosed, e.g., in DE 100 21 663 A1, by increasing the number of pairs of intake conveyor mechanisms, so that the length of the path traveled by the crop material through the intake conveyor mechanisms increases, thereby increasing the amount of time the crop material spends in the intake conveyor mechanisms. The interval of time that passes before the intake conveyor mechanisms come to a stop is therefore increased, thereby ensuring, with a greater level of reliability, that the foreign objects will be prevented from reaching the effective region of the rotating chopper drum. A design of this type has the disadvantage, however, that it would require a further, high-cost stage of intake rollers, which would also increase the amount of installation space required. 
     SUMMARY OF THE INVENTION 
     The object of the present invention, therefore, is to avoid the disadvantages of the related art described above, and to provide, in particular, a quick stop of the intake conveyor mechanisms when foreign objects are drawn in, with a minimum amount of components and installation space. 
     In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an agricultural working machine, comprising intake conveyor mechanisms; a hydraulic circuit via which said intake conveyor mechanisms are hydraulically driven and including at least one hydraulic motor which drives said intake conveyor mechanisms; at least one switching valve system for interrupting or releasing a flow of hydraulic oil being assigned to said at least one hydraulic motor, said switching valve system being configured for interrupting or releasing the flow of hydraulic oil to said hydraulic motor as a function of a signal from a foreign-object position detection device, said switching valve system including at least one braking function for said at least one hydraulic motor, and a section of said hydraulic circuit which realizes said at least one braking function is essentially free of elasticities. 
     Due to the fact that the switching valve system according to the present invention includes at least one braking function for the at least one hydromotor, and the section of the hydraulic circuit which realizes the braking function is essentially free of elasticities, it is ensured that, when foreign objects are detected in the crop-material flow, it is possible to abruptly stop the intake and pre-compression rollers, since it is not necessary to overcome elasticity-related inertias. 
     A compact embodiment of the hydraulic circuit, according to the present invention, that has few components is attained when the switching valve system is capable of being operated in a “normal operation” operating state, and at least one “quick stop” operating state. 
     In an embodiment with a simple design, the switching valve system makes it possible, when in the “normal operation” operating state, for pressure to be applied to the motor and for the hydraulic medium to be purged. 
     A particularly advantageous embodiment of the present invention is attained when the switching valve system, when in the “quick stop” operating state, runs through a working cycle in which, in an initial step, the delivery of hydraulic medium to the hydromotor is at least partially interrupted, the purging of hydraulic medium is halted in a further step, and, in at least one third step, the hydromotor is braked. In this manner, the entire “quick stop” operating state is carried out using a single valve system. 
     The “quick stop” operating state is realized in a compact, effective manner having a simple design when the switching valve system is designed as a proportionally servo valve, the movement of the valve piston of which can be controlled via the control of at least two control cylinders. 
     To obtain a high degree of flexibility of control of the quick-stop function, it is advantageous—in an embodiment of the present invention—when the control cylinders can be controlled independently of each other. 
     In an advantageous refinement of the present invention, the valve piston that realizes the steps of the working cycle in the “quick stop” operating state includes a piston surface that is contacted on diametrically opposed sides by the cylinder surfaces of the at least two control cylinders. In this manner, the valve piston can be guided by the control cylinders in a reliable manner, using a simple design. 
     An efficient and rapid switching between the operating states is attained when one control cylinder is designed as a closing cylinder and is acted upon continually with a control pressure, the further control cylinder is designed as an opening cylinder, and the control pressure that can be applied to the further control cylinder can be switched on or off. 
     In an advantageous refinement of the present invention, the switching valve system is switched from the “normal operation” operating state to the “quick stop” operating state by switching off the control pressure of the further control cylinder. 
     To ensure that, once the main drive has been switched off, the after-running time of rotating working units, such as the chopper drum, can be reduced, a brake valve is assigned—in an advantageous embodiment of the present invention—to the hydraulic circuit in such a manner that the rotational motion of the hydropump and the working units operatively connected with it are braked. 
     Due to the extremely short reaction times required between the instant when a foreign object is detected and the triggering of the quick-stop function, an evaluation and control unit is assigned to the foreign-object detection device in a manner known per se, the evaluation and control unit generating, as a function of a position-detection signal X from foreign-object detection device, a quick-stop signal Y to switch the switching valve system to the “quick stop” operating state. 
     To ensure that the hydraulic circuit according to the present invention functions reliably in the “normal operation” operating state, and that the drive can be braked extremely quickly during the braking procedure in the “quick stop” operating state, in an advantageous embodiment of the present invention, the at least two control cylinders in the switching valve system are in a state of equilibrium in the “normal operation” operating state, and they are in a state of equilibrium for at least part of the time during execution of the third step in the working cycle of the switching valve system in the “quick stop” operating state. 
     In a manner having a simple design, the state of equilibrium between the control cylinders in the “normal operation” operating state can be achieved by using matched cylinder-surface designs of the control cylinders and/or by applying controlled pressures of the hydraulic medium to the control cylinders. 
     In an advantageous embodiment of the present invention, the state of equilibrium in the “quick stop” operating state is reliably maintained when, essentially at the end of the third step in the working cycle, the resultant pressure force of the pressurized control cylinder is in equilibrium with the reaction force, which is a function of the differential surface of the valve piston and a banking-up pressure which acts on the valve piston. 
     In a manner having a simple design, the first step in the working cycle of the proportionally servo valve according to the present invention is realized by assigning a by-pass piston to the closing cylinder, at least one by-pass bore of the by-pass piston opening a by-pass line while the valve piston moves—in the first step of the working cycle—via which at least a portion of the hydraulic medium flowing to the hydromotor is conducted away. 
     To ensure that nearly all of the hydraulic medium available in the hydraulic circuit according to the present invention can be used to realize abrupt braking in the “quick stop” operating state, i.e., to ensure that the hydraulic circuit always has the required accumulated pressure, it is possible, according to an advantageous embodiment of the present invention, to assign a return valve to the by-pass line such that the pressure source can supply the hydraulic circuit with hydraulic medium during the quick-stop procedure, while the return valve is closed during normal operation. 
     In an advantageous embodiment of the present invention, the valve piston has a restrictor which, in the second step of the working cycle, interrupts the connection between the working connection and an exchange portion of oil-channel. This has the advantage, in particular, that it is ensured, before the drive is braked, that all of the hydraulic medium available in the hydraulic circuit is available to realize the braking function. 
     To ensure that all of the hydraulic medium available in the hydraulic circuit is instantaneously available for realizing the braking function, the valve piston has restrictor slits on one end which, in the third step of the working cycle, close the return line from the hydromotor to the hydropump while the valve body is moving, the hydraulic medium being supplied subsequently by the hydropump, which creates a banking-up pressure for braking the hydromotors, the banking-up pressure preferably being within the range of the permissible operating pressure. 
     To ensure that pressure spikes and extreme accelerations are largely avoided in the hydraulic circuit according to the present invention, and, therefore, that stress-related wear is minimized, in an advantageous refinement of the present invention, a large number of restrictor points is assigned to the valve piston such that the passage cross-section exposed to the hydraulic medium changes continually as a function of the path traveled by the valve piston. 
     To ensure that the end regions of the control cylinders do not impact the particular stops unbraked and at a high rate of speed, in a further advantageous embodiment of the present invention, control edges and/or restrictor points are assigned to the at least two control cylinders such that the motion of the valve piston is braked in the end regions. 
     To ensure that the drive according to the present invention has a compact, space-saving shape and is also free of elasticities, such as long hose lines, in an advantageous refinement of the present invention, the hydromotor, hydropump, the switching valve system and switching valves required to control the hydromotor, hydropump and switching valve system in the “normal operation” and “quick stop” operating states are all located in a drive block which forms the drive of the intake conveyor mechanisms. 
     A high degree of flexibility in the design of the drive in the normal, quick stop and reversing operation for the intake and pre-compression rollers, and the cross auger component of the front attachment located in front of the intake and pre-compression rollers is achieved when the intake conveyor mechanisms are coupled with at least one mechanical transfer gearbox, the input shaft of which is coupled with the hydraulic drive ( 13 ), the mechanical transfer gearbox also including a further gearbox outlet, and the further gearbox outlet being coupled with the cross auger component of the front attachment. 
    
    
     
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
         FIG. 1  shows an agricultural working machine with a drive according to the present invention, in a schematic side view 
         FIG. 2  shows a detailed view of the drive according to the present invention in  FIG. 1   
         FIG. 3  shows a schematic illustration of the hydraulic circuit that is the drive according to the present invention 
         FIG. 4  shows a detailed longitudinal sectional view of the valve system according to the present invention 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an agricultural working machine  1  designed as a self-propelled forage harvester  2 , to the front region of which a front attachment  3  designed as a pick-up  4  is assigned. In the exemplary embodiment shown, front attachment  3  picks up a crop-material strand  6  lying on ground  5  using a pick-up device  7 , compresses it using a hold-down system  8 , and subsequently guides crop-material strand  6  via a cross auger component  9  to intake and pre-compression rollers  10  located downstream of front attachment  3 . Intake and pre-compression rollers  10  are retained, in pairs, in a feeder housing  11 . In a manner known per se, the pairs of intake and pre-compression rollers  10  are driven actively in the direction of arrow  12  using a drive  13  to be described below in greater detail. In the rear region of feeder housing  11  located above a shear bar  14 , compressed crop-material strand  6  enters the working region of cutter blade  15  of an actively driven, rotating chopper drum  16 . Chopped crop-material strand  6  subsequently exits the rear region of chopper drum at a high rate of speed and enters a rising lower discharge chute  17 , in which crop-material strand  6  is conveyed, using a “post-accelerator”  18  in some cases, out of forage harvester  2  to a forage vehicle, which is not shown. To largely prevent foreign objects  19  located in crop-material strand  6  from coming close to chopper drum  16 , a foreign-object detection device  12  known per se is assigned to intake roller pair  20  located on the front. If foreign object  19  located in crop-material strand  6  is conveyed into the vicinity of foreign-object detection device  21 , it generates a position-detection signal X, which is supplied to an evaluation and control unit  22  and, in this, generates a “quick stop” signal Y that switches off drive  13  (to be described below in greater detail) of intake and pre-compression rollers  10 . When the quick-stop procedure has ended, operator  23  of agricultural working machine  1  can trigger, via an input terminal  24 , a reversing signal Z in evaluation and control unit  22 , which triggers a reversing operation of drive  13  and intake and pre-compression rollers  10  coupled with it. Detected foreign object  19  can be conveyed out of the vicinity of intake and pre-compression rollers  10  and can eventually be removed from crop-material strand  6  by operator  23 . An automatic triggering of the reversing procedure described above after intake and pre-compression rollers  10  come to a standstill also lies within the scope of the present invention. 
     Depending on the inertia of drive  13  and the units coupled thereto, a certain amount of time passes until intake and pre-compression rollers  10  come to a standstill after the quick-stop function has been activated. This length of time must not be so great that detected foreign object  19  reaches the vicinity of rotating chopper drum  16  anyway. The present invention, which is described in detail below, takes effect at this point. 
     According to  FIG. 2 , a first drive-belt system  25  transfers the drive energy of motor  26  to chopper drum  16 , among other things, from which a further belt system  27  drives a hydraulic motor-pump unit  28 , which ultimately forms stepless hydraulic drive  13  of intake and pre-compression rollers  10 . For this purpose, a mechanical transfer gearbox  31  is assigned to output shaft  29  of motor-pump unit  28  via a universal drive shaft  30 , mechanical transfer gearbox  31  initially driving each of the intake and pre-compression rollers  10  in a manner known per se. In addition, transfer gearbox  31  includes a further gearbox outlet  32 , which directly drives cross auger component  9  of front attachment  3  located in front of intake and pre-compression rollers  12 . This has the advantage, in particular, that cross auger component  9  of front attachment  3  can now also be integrated in the quick-stop function (which will be described in greater detail, below) and in the reversing procedure of intake and pre-compression rollers  10 . In a manner known per se, the rest of the actively driven units  7 ,  8  of particular front attachment  3  are driven via a further mechanical drive, which is not shown. 
       FIG. 3  shows motor-pump unit  28  in a schematic, detained illustration. Hydromotor  40  and hydropumpe  41  are interconnected via a line system  42  in which switching valve system  44 , according to the present invention, designed as proportionally servo valve  43  is integrated. Motor-pump unit  28  is also integrated in a hydraulic circuit  45  that includes a hydraulic pump  46  designed as a pressure source in a manner known per se, a tank  47  for storing the hydraulic medium, and a pressure reservoir  48 . Due to available external pressure source  46 , hydraulic circuit  45  functions as a constant-pressure circuit in a manner known per se. Further electrohydraulic switching valves  49 - 51  integrated in hydraulic circuit  45  and the mode of operation of hydraulic circuit  45  are described in greater detail with reference to the simplified, longitudinal sectional drawing of switching valve system  44  according to the present invention, in  FIG. 4 . 
     To ensure that hydraulic circuit  45  according to the present invention can enable an abrupt halt of intake conveyor mechanisms designed as intake and pre-compression rollers  10 , at least hydromotor  40 , hydropump  41  and required switching valves  43 ,  49 - 51  are all located in a drive block  33  which forms drive  13 , individual elements  40 ,  41 ,  43 ,  49 - 51  of hydraulic circuit  45  being interconnected directly using flanges and/or via a piping network. In addition, switching valves  43 ,  49 - 51  of hydraulic circuit  45  are switched in an electrohydraulic manner. A design of this type has the advantage, in particular, that no hose lines or valve controls based on the use of spring force are located, at the least, in the region of hydraulic circuit  45  that realizes the braking of drive  13 , the elastic properties of the hose lines and/or valve controls—e.g., the pressure-dependent expansion of hose lines and the inertia of systems based on the use of spring force—would stand in the way of an abrupt braking of drive  13  of intake and pre-compression rollers  10 . 
     Proportionally servo valve  43  according to the present invention, as shown in  FIG. 4 , has housing sections  52 ,  53  at its ends, which are penetrated by bores  54  in which control cylinders  55 ,  56  are displaceably located, the movement of control cylinders  55 ,  56  being limited by terminal stops  57 . On their end faces, which face each other, control cylinders  55 ,  56  accommodate a piston surface  58  between them, via which a displacement of control cylinders  55 ,  56  also results in a displacement of valve piston  59  inside proportionally servo valve  43 . 
     In this first operating state, i.e., “normal operation”, control cylinders  55 ,  56  are acted upon, independently of each other, in their rear regions via control-pressure lines  60  with a defined control pressure, which holds valve piston  59  state of equilibrium as shown in  FIG. 4 . In this state of equilibrium, the circulation of the hydraulic medium between hydromotor  40  and hydropump  41  is closed. The hydraulic medium is pumped to hydromotor  40  via a pressure line  61 , and is returned via a return line  62 , then it is pumped back to hydromotor  40  by hydropumpe  41 . At the same time, a partial quantity of the hydraulic medium is removed from circulation via an exchange portion of oil-channel  63  to be cooled and/or filtered. It is within the scope of the present invention for the equilibrium between control cylinders  55 ,  56  to be realized using matched cylinder-surface designs or by applying pressure to control cylinders  55 ,  56  using controlled oil pressures. 
     The “normal operation” operating state is maintained until a foreign object  19  is detected at the foreign-object detection device  21 , quick-stop signal Y is generated in evaluation and control unit  22 , and the system switches to the “quick stop” operating state. Quick-stop signal Y causes quick-stop switching valve  49  assigned to proportionally servo valve  43  to be switched to the position shown in  FIG. 3 . In this position, upper control cylinder  56  is depressurized by removing the hydraulic medium via pressure line  60  and quick-stop switching valve  49  assigned thereto and directing it into tank  47 . In the “quick stop” operating state, upper control cylinder  56  functions as an opening cylinder. In the “quick stop” operating state, lower control cylinder  55 , which is also pressurized, functions as a closing cylinder and moves valve piston  59  in the direction of arrow  65  using proportionally servo valve  43  according to the present invention. 
     In its front region assigned to piston surface  58  of valve piston  59 , lower control cylinder  55  accommodates a by-pass piston  66 , which is penetrated by by-pass bores  67 . 
     In a first step, the motion of lower control cylinder  55  displaces by-pass piston  66  into the region of pressure line  61  leading to hydromotor  40 . The hydraulic medium by-passes hydromotor  40  via a by-pass line  64  and returns to hydropump  41 , causing the supply of pressurized hydraulic medium to hydromotor  40  to be interrupted, which also causes hydromotor  40  to be shut off. In a further step, the continued motion of valve piston  59  in the direction of arrow  65  closes exchange portion of oil-channel  63  via a restrictor  68  integrally moulded on valve piston  59 , thereby preventing additional hydraulic medium from being conducted away via exchange portion of oil-channel  63 . Once exchange portion of oil-channel  63  has been closed completely, the continued motion of valve piston  59  in the direction of arrow  65  brings about an abrupt braking of hydromotor  40 , therefore bringing intake and pre-compression rollers  10  to a standstill by the fact that valve piston  59  closes return line  62  from hydromotor  40  to hydropump  41 . Since hydropump  41  continues to pump hydraulic medium to hydromotor  40 , but hydraulic medium can no longer flow out, a banking-up pressure abruptly forms in pressure line  61  to hydromotor  40 , which abruptly halts hydromotor  40  and intake and pre-compression rollers  10  coupled therewith. 
     To ensure that the rising banking-up pressure does not overload the units it acts upon, the end of valve piston  59  assigned to control cylinder  56  functioning as an opening cylinder is penetrated by restrictor slits  69 , via which the excess hydraulic medium can flow out of motor return line  62 . 
     Optimally, restrictor slits  69 , control cylinders  55 ,  56  and valve piston  59  are sized such that a banking-up pressure is created which is in the range of the operating pressure of hydraulic circulation and is preferably 350 bar. The motion of closing cylinder  55  in the direction of arrow  65  also results in a continual shrinking of the passage cross-section of restrictor slit  69 . The differential surface of valve piston  59  is sized such that valve piston  59  with the pressurized closing cylinder  55  is in a state of equilibrium when the banking-up pressure has reached a defined value, e.g., 350 bar in the exemplary embodiment shown. It is thereby ensured, in a simple manner, that the braking function will be reliably maintained. 
     In an advantageous refinement of the present invention, a return valve  70  is assigned to valve piston  59  of proportionally servo valve  43  according to the present invention in the form of a sealing disk  73 , which is capable of being moved by the hydraulic medium. Sealing disk  73  is located, in a freely movable manner, between the piston surface of valve piston  59  contacted by control cylinders  55 ,  56  and a set collar  74  fit into valve piston  59 , and is pressed against set collar  74  or valve piston  59 , depending on the direction of flow of the hydraulic medium. Return valve  70  is closed in the “normal operation” operating state, since the hydraulic medium flowing back from hydromotor  40  to hydropump  41  via return line  62  applies pressure to sealing disk  73  in the direction of the piston surface of valve piston  59  and, therefore, in the closing direction. In the “quick stop” operating mode, hydropump  46 , which functions as a pressure source, pumps a pressure-oil flow in the opening direction of return valve  70 —sealing disk  73  bearing against set collar  74  in the opening direction—thereby ensuring that the control-oil flow produced by hydropump  46  during the “quick stop” operating mode reaches hydraulic circuit  45  according to the present invention, thereby ensuring that the accumulated pressure is also maintained in hydraulic circuit  45  during the braking procedure. 
     In a further advantageous embodiment of the present invention, a brake valve  51  designed as an electrohydraulic switching valve can also be assigned to hydropump  41 , which brakes a chopper drum  16  coupled with hydropump  41  via an external drive  71  after the drive of chopper drum  16  is shut off. The main effect of this is that long after-running times of shut-off chopper drum  16  are prevented. The braking function can be triggered, e.g., by the fact that pressure-source switching valve  50  switches brake valve  51  via a control pressure into the locked position, thereby blocking the rotational motion of hydropump  41  and abruptly braking chopper drum  16  until it comes to a standstill. 
     In a further advantageous embodiment, a restrictor cross section  72  is assigned, on the top side, to control cylinder  56  designed as an opening cylinder, via which the hydraulic medium displaced by control cylinder  56  is conducted away. As a result, control cylinder  56  is braked before it reaches stop  57  assigned to it and allows it to come to rest against stop  57  in a non-abrupt manner. 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in an intake conveyor mechanism control for an agricultural working machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.