METHOD FOR OPERATING AN AGRICULTURAL ROUND BALE PRESS

Description

[0001] The present application relates to a method for operating an agricultural round baler according to the preamble of claim 1. Furthermore, the present application relates to an agricultural round baler according to the preamble of claim 12.

[0002] The process involves picking up crop material to be baled, which can consist of stalk-like material such as straw or hay, from the ground and feeding it into the baling chamber of the round baler. The baling chamber is located within the housing of the round baler. Within the housing, the baling chamber is spatially confined by a continuously driven, endless belt. Inside the baling chamber, the crop material is successively compressed into a round bale, with the length of the belt changing as the amount of crop material fed in increases. This change in the belt's length corresponds to an increase in the diameter of the baling chamber. Typically, the volume of the baling chamber is minimal at the beginning of each baling process.As crop is fed into the baling chamber, pressure is exerted on the baling belt, causing it to be displaced within the housing. This increases the volume of the baling chamber, thereby changing the running length of the baling belt. The diameter of the baling chamber thus increases to a maximum. Once this maximum is reached, the baling process is complete, and a round bale is formed. It can then be ejected, reducing the volume of the baling chamber back to its initial minimum. During this process, the running length of the baling belt is adjusted accordingly.

[0003] During the baling process, the tension of the baling belt is controlled by a belt tensioning device. This device comprises a lower tensioning arm and an upper tensioning arm. The lower tensioning arm guides the baling belt by means of at least one tensioning roller, which defines the baling chamber. Typically, the lower tensioning arm includes two tensioning rollers which, in combination with a guide roller fixed to the housing of the round baler, guide the baling belt in a loop. The guide rollers run along a section of the belt from the first tensioning roller of the lower tensioning arm to the fixed guide roller and from there back to the second tensioning roller of the lower tensioning arm. Preferably, the two tensioning rollers of the lower tensioning arm are arranged directly next to each other on the lower tensioning arm. The upper tensioning arm interacts with the baling belt by means of at least one tensioning roller.The lower tension arm is particularly suitable for guiding the press belt directly into the press chamber, thus limiting its size. As the crop is fed into the chamber, the lower tension arm is pushed away from the crop against a tension force, thereby increasing the diameter of the press chamber. The lower tension arm ensures that the press belt reliably exerts pressure on the crop. The upper tension arm typically serves to compensate for changes in the free length of the press belt. The total length of the press belt is the sum of its free length and the length of the belt along its contact area. The longer the contact area becomes during a pressing operation, the shorter the free length of the press belt becomes.To maintain tension on the baling belt, it is tensioned using the upper tensioning arm. As the round bale grows, the upper tensioning arm is moved against a tensioning force, reducing the free length of the baling belt while simultaneously maintaining tension. The belt tensioning device is particularly useful for ensuring that the belt's running length can only be changed against a tensioning force, thereby exerting the appropriate pressing pressure on the crop inside the baling chamber. This pressing pressure ultimately compresses the crop into the desired round bale.

[0004] Methods and associated round balers of the type described above are already known in the prior art. In this regard, particular reference is made to European patent application EP 3 298 881 A1. This application describes a generic round baler comprising a control device. This device is capable of controlling the compression pressure of the baling belt in such a way that it changes during the baling process. It is proposed that the compression pressure be changed according to a control function based on the size of the baling chamber and the effective length of the baling belt.

[0005] The established method has the disadvantage that the control function depends on predefined parameters representing "ideal" conditions. For example, the control function is based on a predetermined length of the press belt, which, however, can deviate from a specified value in individual cases due to manufacturing tolerances. Other parameters, such as those relating to the crop itself, also contribute to the fact that the change in pressing pressure during a given pressing process is not carried out in such a way as to achieve an optimal pressing result.

[0006] The present application is therefore based on the task of providing a method for operating a round baler and an associated round baler, by means of which the pressing of round bales is optimized.

[0007] The underlying problem is solved according to the invention by means of a method with the features of claim 1. Advantageous embodiments are described in the dependent claims.

[0008] The method according to the invention is characterized in that the actual tension of the press belt is continuously determined by means of at least one measuring device during each pressing operation and compared with a target tension. For the purposes of this application, "continuous determination" means determining the actual tension at a multitude of discrete points in time, which are typically equidistantly distributed over the duration of each pressing operation. In particular, determining the actual tension at a frequency of at least 50 Hz, preferably at least 100 Hz, and more preferably at least 200 Hz, is advantageous. According to the invention, the belt tensioning device is operated such that the actual tension of the press belt is changed in the direction of the target tension.

[0009] The measuring device is preferably designed to include at least one measuring instrument and at least one processing unit for the computational processing of information acquired by the measuring instrument. In particular, the measuring instrument can be a force sensor that detects the bearing force of a roller mounted on the housing of the round baler. The processing unit is suitable for computationally processing this information and thereby determining the actual tension of the baling belt. For this purpose, the measuring instrument and the processing unit are connected by means of data transmission, preferably wirelessly or via a cable.

[0010] The target tension can be determined based on a specific set of parameters, whereby, similar to the state of the art, the target tension can be varied over the course of a baling process. It could, for example, start at an initial minimum as the diameter of the baling chamber increases and be adjusted to a maximum reached when each round bale is completed. This change in target tension can be linear or non-linear over the course of a baling process. Furthermore, the target tension can be varied depending on operating parameters of the round baler, such as the diameter of the baling chamber and / or the contact area of ​​the baling belt. The latter describes the distance along which the baling belt is in contact with the crop in the baling chamber at any given time.The target voltage can also be constant throughout.

[0011] The method according to the invention has many advantages. In particular, by determining the actual tension, it is ensured that the actual pressing pressure exerted on the crop or the emerging round bale by the press belt is known at virtually every point during a baling process. The prior art only provides for a change in pressing pressure depending on the operating parameters of the round baler, but lacks knowledge of the actual tension conditions acting on the emerging round bale. While the target tension specified by the prior art for changing the pressing pressure during a baling process is advantageous in itself for producing a high-quality round bale, as described above, the change in the target tension in the prior art is independent of the actual characteristics of the respective round baler and / or external harvesting conditions.The determination of the actual tension according to the invention, on the other hand, provides information about the actual stress conditions acting on the round bale or the harvested crop, so that the target tension, which is ideal for a high-quality round bale, can actually be aimed for and advantageously achieved. The comparison of actual and target tension, as well as the direct or indirect modification of the actual tension towards the target tension, preferably to the target tension, constitutes a control loop with which the tension of the press belt is regulated. In this way, the harvested crop is compressed at least substantially throughout with a pressure that is actually desired. Therefore, high quality in the production of round bales can be achieved using the method according to the invention.

[0012] In an advantageous embodiment of the method according to the invention, the target tension is a function of the diameter of the press chamber and / or a contact section of the press belt. Thus, the following applies: Ttarget = f(DPK, KP), where Ttarget is the target tension of the press belt, DPK is the diameter of the press chamber, and KP is the contact section of the press belt.

[0013] Furthermore, it can be particularly advantageous if the lower tension arm and / or the upper tension arm are each moved relative to the housing during a pressing operation according to a common, predefined movement function or their own predefined movement functions. The movement of the lower and upper tension arms can depend, in particular, on how the target tension of the press belt is to be changed during a pressing operation.

[0014] If the movement of the tensioning arms is carried out according to one or more predefined motion functions as described above, it can be particularly advantageous if the upper tensioning arm is positioned differently from its assigned motion function, such that the actual tension of the press belt is changed in the direction of the target tension. This "positioning" can involve moving the upper tensioning arm or keeping it stationary or fixed. As explained above, the predefined motion function of the upper tensioning arm can generally serve to maintain or guide the press belt at the predefined target tension. However, since the actual tension can develop differently than planned as a result of the movement of the upper tensioning arm according to the predefined motion function, the upper tensioning arm can be moved differently, thereby changing the actual tension.This change is achieved by altering the actual voltage in the direction of the target voltage.

[0015] If the actual tension is lower than the target tension, it is particularly advantageous to hold the upper tension arm in its current position for at least a certain tensioning period. During this tensioning period, which could, for example, occur between two measurement points at which the actual tension of the press belt is determined by the measuring device, additional crop is fed into the press chamber, increasing the diameter of the press chamber and the contact area of ​​the press belt. The free length of the press belt decreases accordingly, which would normally require the upper tension arm to be adjusted to release some of the free length. This would essentially maintain the current actual tension. However, since the latter is lower than the target tension in this scenario, the upper tension arm is held in its position and therefore does not release the press belt.This causes the actual tension of the press belt to increase and change towards the target tension.

[0016] If the actual tension is equal to or greater than the target tension, the upper tension arm is released, at least for a release period, or held in its current position for a time increment. "Releasing" the upper tension arm means that it can move according to a specified parameter. Specifically, if the actual tension is greater than the target tension, the upper tension arm can be moved further than the predefined movement function allows, thus relieving tension on the press belt and consequently reducing its actual tension. Holding the upper tension arm in position is particularly relevant when its swivel angle relative to the housing is smaller than a predefined theoretical swivel angle.The theoretical swivel angle can be part of the predefined motion function of the upper clamping arm and describes the angle by which the upper clamping arm is pivoted about its pivot axis relative to a reference point and the housing. If it is determined that the actual stress is equal to or greater than the target stress, but the actual swivel angle of the upper clamping arm is nevertheless smaller than the predefined theoretical swivel angle, the upper clamping arm is held in place for a time increment, specifically until the next lift. This allows the actual swivel angle to effectively approach the theoretical swivel angle, as the theoretical swivel angle decreases progressively during a pressing operation. In this scenario, the swivel angle of the upper clamping arm is at its maximum at the beginning of a pressing operation and decreases progressively towards the end.If the actual swivel angle is equal to or greater than the theoretical swivel angle, the upper tension arm is released.

[0017] In a particularly advantageous embodiment of the method according to the invention, the actual tension of the press belt is determined with the aid of a guide roller mounted on the housing, which interacts with the press belt. This guide roller can, in particular, be the same roller that, together with two guide rollers of the lower tensioning arm, guides the press belt in a loop. To determine the actual tension, a bearing force on the guide roller, resulting from the mounting of the press belt on the guide roller, is preferably measured using the measuring device. Based on the bearing force acting on the guide roller, a belt force acting in the press belt can be determined using the measuring device. From this, and given a cross-sectional area of ​​the press belt, the currently acting actual tension can be determined. For this purpose, it is particularly advantageous to determine a resultant bearing force with which the guide roller is effectively mounted on the housing.This can be achieved, in particular, by converting a bearing force measured on the roller in a predetermined direction by means of a measuring device, as a function of the deflection of the lower tensioning arm and the resulting engagement angle by which the press belt engages the roller, into the resulting bearing force using the measuring device, especially a processing unit thereof. The latter corresponds at least substantially to the belt force, from which the actual tension is ultimately obtained by dividing by a cross-sectional area of ​​the press belt. These calculations can be performed, in particular, using the measuring device, preferably using a processing unit of the measuring device.

[0018] The underlying problem is further solved by means of an agricultural round baler with the features of claim 12. Advantageous embodiments are described in the dependent claims.

[0019] The round baler according to the invention is characterized by a measuring device and a control device. The measuring device is configured to continuously determine the actual tension of the baling belt during each baling operation. The control device is configured to actuate the belt tensioning device based on the determined actual tension, such that this actual tension is changed in the direction of a predetermined target tension of the baling belt.

[0020] The advantages resulting from the use of a round baler according to the invention have already been described above in connection with the method according to the invention. In particular, it is possible to influence the tension of the baling belt in such a way that it corresponds as closely as possible to the target tension of the baling belt. This results in a control loop with which the actual tension of the baling belt can be regulated.

[0021] The belt tensioning device comprises a lower tensioning arm and an upper tensioning arm. The lower tensioning arm preferably includes two tensioning rollers, and the upper tensioning arm includes one tensioning roller. With this design of the belt tensioning device, the running section of the press belt can be shifted particularly easily during a baling process, while simultaneously maintaining tension on the press belt. This design therefore allows the round baler to be operated in a particularly demand-oriented manner.

[0022] Advantageously, the measuring device interacts with a roller that is fixed to the housing of the round baler, with the roller interacting with the baling belt. In other words, the baling belt is guided and deflected by the roller, causing a bearing force to occur at the roller due to the tension acting in the baling belt. This bearing force is then transferred from the roller to the housing. Advantageously, this force can be detected by the measuring device, particularly by means of a measuring instrument within the device. Such a measuring instrument could, for example, be a load cell.

[0023] Furthermore, a round baler can be advantageous in which the lower arm interacts with a tensioning element by means of which the at least one tensioning roller of the lower arm can be tensioned against the baling belt. This tensioning element is preferably formed by a hydraulic cylinder. This has the particular advantage that the tensioning element can act both passively and actively. In particular, a force exerted on the lower arm by means of the tensioning element is preferably freely variable, thereby allowing the target tension of the baling belt to be changed. Thus, as explained above, it is particularly conceivable that the target tension of the baling belt can be changed during a baling process. This is especially easy to achieve with the described tensioning element.

[0024] It can also be particularly advantageous if the upper tensioning arm interacts with a tensioning element by means of which the tensioning roller of the upper tensioning arm can be tensioned directly or indirectly against the press belt. Preferably, the tensioning element is formed by a hydraulic cylinder. The advantages resulting from this have already been described above in connection with the lower tensioning arm.

[0025] In a particularly advantageous embodiment, the clamping element, which interacts with the upper clamping arm, is coupled at one end to the upper clamping arm in a force-transmitting manner and at the other end to the lower clamping arm in a force-transmitting manner. This has the particular advantage that a movement of the lower clamping arm due to an increase in the diameter of the press chamber during the production of a round bale can automatically cause a movement of the upper clamping arm. In other words, the upper clamping arm and the lower clamping arm are kinematically coupled by means of the clamping element, so that the movements of the upper clamping arm and the lower clamping arm are interdependent.Given that a change in the diameter of the press chamber is equivalent to a change in the contact area of ​​the press belt and, conversely, a change in the free length of the press belt, such a kinematic coupling can be particularly advantageous in order to influence the tension of the press belt.

[0026] The invention is explained in more detail below with reference to an exemplary embodiment shown in the figures. These show: Fig. 1: A cross-section through a round baler according to the invention, Fig. 2: A schematic representation of a running section of a press belt of the round baler according to Figure 1 Fig. 3: A detail of a roller mounted on a housing of the round baler, which interacts with the press belt, and Fig. 4: A flow diagram of a control system for the round baler according to Figure 1 .

[0027] One embodiment that Figures 1 to 4The image shows a round baler. 1, using round bales 2 can be manufactured. The round baler 1 includes a housing 3, that one interior 4 the round baler 1 spatially limited. The round baler 1 includes a feeding device 5, by means of the harvested crop lying on a surface, a press chamber 12 can be supplied. In front of the press chamber 12 The round baler indicates 1 furthermore, a cutting device 20 a device that allows the harvested crop to be cut. In this way, the crop stalks, which make up the majority of the harvested crop, are cut, resulting in a reduced length. Inside the press chamber 12 Each round bale will be 2 pressed.

[0028] The round baler 1 has a press chamber 12with variable diameter, where the diameter of the press chamber 12 significantly depends on the running distance of a press belt 8 is determined to be in the interior 4 the round baler 1 around the press belt 8 It is an endless belt equipped with a plurality of rollers. 7 works together and by means of a belt tensioning device 9 is kept under tension so that it exerts pressing forces on the material in the press chamber. 12 promoted crop can exercise. The press belt 8 is continuously driven in a rotating motion at least during each pressing process, whereby the round baler 1 in the example shown via a drive roller 23 features which drive the press belt 8 accomplished. The volume of the press chamber 12 increases during the production of a round bale 2The more crop is placed in the press chamber, the higher the rate increases. 12 is promoted. Consequently, the running distance of the press belt changes. 8 inside 4, which is accompanied by a corresponding increase in the volume of the press chamber 12 or is accompanied by an increase in their diameter.

[0029] The press belt 8 is continuously in contact with a contact area during a pressing process 13 in direct contact with the harvested crop. This contact area 13 is from a partial extent of the press chamber 12 formed, as can be seen in particular from the Figure 1 and 2 The larger the diameter of the press chamber, the greater the result. 12 The longer the contact distance, the longer the contact distance. 13, across the press belt 8 is in direct contact with the harvested crop. Along this contact path 13 is the press belt 8suitable for exerting pressing forces on the harvested crop and thus compacting it. To use the press belt 8 To maintain tension, the round baler has 1 via the described belt tensioning device 9. In the example shown, this includes a lowering arm. 14 as well as an upper tension arm 15. The under-tensioning arm 14 is directly responsible for guiding the press belt 8 in the area of ​​the press chamber 12 responsible. The undertensioning arm is responsible for this. 14 via two tension rollers 10, 11, which together with a fixed part attached to the housing 3 mounted roller 7 the press belt 8 in a loop 29 lead. The underlever arm 14 is about a pivot axis 27 swiveling on the housing 3 supported, with the under-tension arm 14 with increasing volume of the press chamber12 It is successively pivoted upwards. This pivoting of the lower clamping arm 14 This occurs against the clamping force of a clamping element. 21, the thing with the under-tensioning arm 14 interacts. This is particularly evident from the following: Figure 2 . The clamping element 21 This therefore leads to the fact that the underlever arm 14 only then around its pivot axis 27 relative to the case 3 It is twisted when attached to the press belt 8 via the contact path 13 applied tension exerted by the harvested crop on the press belt 8 exerted, in total over the area of ​​the press belt 8 the specified clamping force of the clamping element 21 exceeds. Conversely, this ensures that the pressure belt is used to... 8 Conversely, the pressing force applied to the harvested crop assumes a certain value that results in the desired compression of the harvested crop.2 causes.

[0030] By comparing the states of a pressing process, which are described in the Figure 1 and 2 As illustrated, it is understood that the loop 29, in the press belt 8 between the two tension rollers 10, 11 of the lower tension arm 14 and the one attached to the case 3 fixed roller 7 is guided, with increasing diameter of the press chamber 12 gets smaller. In other words, the tension rollers become smaller. 10, 11 of the lower tension arm 14 with increasing volume of the press chamber 12 progressively closer to the roller 7 led. Meanwhile, the size of the press chamber is increasing. 12 as well as the length of the contact area 13 of the press belt 8 This results in a total length of the press belt being... 8 an increasingly large proportion in the area of ​​the press chamber 12This results in a length reserve for the press belt. 8 is consumed gradually. This length reserve is achieved by means of the upper tension arm. 15 held and tensioned, with the upper tensioning arm 15 via a tension pulley 16 features the press belt 8 together with two fixed rollers 7 in a loop 30 leads. Said loop 30 becomes more with increasing diameter of the press chamber 12 progressively smaller. The upper tension arm 15 works equally with a clamping element 22 together, by means of which the upper tensioning arm 15 with its tensioning roller 16 against the press belt 8 is tense. A tracking of the upper tension arm. 15 The process is similar to that of the under-tensioning arm. 14 by means of a pivoting of the upper tension arm 15 around a pivot axis 28.

[0031] The special feature of the round baler according to the invention 1 The purpose is to ensure that the actual tension of the press belt is maintained throughout the pressing process. 8 The actual voltage is continuously determined so that it is comparable to a predetermined target voltage. If a deviation of the actual voltage from the target voltage is detected, an intervention occurs, causing the actual voltage to change towards the target voltage. In this way, the round baler 1 a control loop by means of which the actual tension of the press belt is determined 8 It is adjustable.

[0032] The target tension is typically not constant during a pressing process, but rather variable, usually non-linearly. The actual tension is determined using the round baler shown. 1 using a measuring device 6, the one with the roller 7works together, in conjunction with the tension rollers 10, 11 of the lower tension arm 14 the press belt 8 in the loop 29 is guided. On the roller 7 deflection forces of the press belt 8 into the case 3 the round baler 1 worn away. Depending on a belt force. 25 of the press belt 8 as well as a gripping angle 17, around the press belt 8 overall the roller 7 encompasses (see Figure 3 ) A bearing force changes, with which the roller 7 in the case 3 is mounted. By measuring this bearing force, which is measured here using a measuring device (not shown) of the measuring system. 6 This can be done with knowledge of the other parameters of the press belt. 8, in particular its cross-sectional area, on the actual tension of the press belt 8The processing of the bearing force measured by the measuring instrument into the actual stress is carried out by means of a processing unit of the measuring device, which is not shown. 6, which is set up accordingly. It should be noted that a resulting 24, the roller 7 its effect depends on the angle of grip. 17 dependent and the gripping angle 17 are not constant throughout a pressing process. Therefore, a change in the bearing force of the roller is possible. 7 not only a change in the actual tension of the press belt 8, but also on a change in the angle of grip 17 This can be taken into account mathematically, particularly depending on the swivel angle of the lower clamping arm. 14, which is directly related to the angle of grip 17 stands.

[0033] The control loop for regulating the actual tension of the press belt 8 This is particularly evident from the flowchart according to Figure 4 . Thus, after determining the actual voltage Tactual, it is checked whether this voltage is lower than the specified target voltage Ttarget. If so, the actual voltage is increased. In the illustrated embodiment, this is achieved by adjusting the upper clamping arm during the ongoing pressing process. 15 not, as is otherwise intended during a pressing process according to the above description, moved around its pivot axis 28 not only is it gradually tilted further upwards, but it is also held in its current position for at least a period of tension. This occurs with the round bale growing simultaneously. 2 This leads to the press belt 8 is tensioned, as the tracking of the upper tension arm 15fails to occur. Holding the upper tension arm 15 This can be done, for example, for the duration of the tensioning period, after which the actual tension of the press belt is measured again. 8 The actual voltage is determined and compared to the target voltage. If the actual voltage remains lower than the target voltage, the upper tension arm can be adjusted. 15 will once again be held in his current position for a period of tension.

[0034] In the example shown, if the actual voltage is equal to or greater than the target voltage, a further check is performed. This check compares a swivel angle. 26 of the upper tension arm 15 (α OSA ) with a theoretical swivel angle of the upper tension arm 15. The latter originates from a control function, which in the example shown is located on a control device. 18The specified tension is stored. It is intended that the target tension will be maintained during the pressing process of a round bale. 2 is changed successively. The control function can, in particular, regulate the pressure with which the press belt is applied. 8 on the one in the press chamber 12 the harvested material acts upon, with a volume and / or a diameter of the press chamber 12 and / or an effective length of the press belt 8 to relate to. However, since manufacturing tolerances exist, for example in the overall length of the press belt, 8 While it may be possible to control the pressing pressure solely based on the respective specification, this does not necessarily mean that the desired pressing pressure is actually exerted on the harvested crop.

[0035] To ensure this, the described control loop is implemented. The control device 18Based on the control function, it sees a theoretical swivel angle of the upper tension arm. 15 depending on at least one other parameter, for example the pressing pressure or the diameter of the pressing chamber 12, before. Should the measured swivel angle 26 of the upper tension arm 15 be smaller than the theoretical swivel angle of the upper tension arm 15, will the upper tension arm 15 at least for a time increment in its current position, while the press chamber 12 continues to be filled with harvested material and increases in diameter. Provided the measured swivel angle 26 of the upper tension arm 15 The tracking of the upper tension arm will be adjusted if the angle of rotation corresponds to or exceeds the theoretical swivel angle. 15 released. In this situation, the upper tension arm is 15 in the manner prescribed by the control unit 18 is planned.

[0036] The actual voltage is checked repeatedly during each pressing operation, for example at a frequency of 100 Hz.

[0037] The clamping elements 21, 22, the one with the under-tensioning arm 14 and the upper tension arm 15 In the example shown, the working units are each formed by a hydraulic cylinder. This is the upper tensioning arm. 15 assigned clamping element 22 with its one end in force-transferring manner with the upper tension arm 15 and with its other end in a force-transferring manner with the under-arm 14 coupled. In this way, movement of the upper tension arm occurs. 15 kinematically coupled to a movement of the lowering arm 14 instead. This is for controlling the movement of the upper tension arm. 14 advantageous. Reference symbol list

[0038] 1 Round baler 2 Round bales 3 Housing 4 Interior 5 Feeding device 6 Measuring device 7 Guide roller 8 Press belt 9 Belt tensioning device 10 Tensioning roller 11 Tensioning roller 12 Pressing chamber 13 Contact section 14 Lower clamping arm 15 Upper clamping arm 16 Tensioning roller 17 Grip angle 18 Control device 19 Feed channel 20 Cutting device 21 Tensioning element 22 Tensioning element 23 Drive roller 24 Resultant 25 Belt force 26 Swivel angle upper clamping arm (α OSA ) 27 Swivel axis 28 Swivel axis 29 Loop 30 Loop

Claims

1. A method for operating an agricultural round baler (1), comprising the following method steps: a) harvested material to be baled is picked up from a substrate and supplied to a bale chamber (12) of the round baler (1) which is disposed in a housing (3) of the round baler (1) and is spatially delimited by a revolvingly driven baler belt (8) configured as a continuous belt; b) within the bale chamber (12), the crop is compacted step by step into a round bale (2), wherein, as the quantity of harvested material supplied increases, a run path of the baler belt (8) is changed and a diameter of the bale chamber (12) is thereby increased step by step; c) during the course of a baling procedure, a tension of the baler belt (8) is influenced by means of a belt tensioning device (9), wherein the belt tensioning device (9) comprises a lower tensioning arm (14) and an upper tensioning arm (15), wherein the lower tensioning arm (14) guides the baler belt (8) in a manner which delimits the bale chamber (12) by means of at least one tensioning roller (10, 11) and the upper tensioning arm (15) cooperates with the baler belt (8) by means of at least one other tensioning roller (16), wherein at least the lower tensioning arm (14) is moved and the run path of the baler belt (8) is changed thereby; characterized in that by means of a measuring device (6), the actual tension of the baler belt (8) is continuously determined during a respective baling procedure and compared with a target tension, wherein the belt tensioning device (9) is operated in a manner such that the actual tension of the baler belt (8) is changed in the direction of the target tension.

2. The method according to claim 1, characterized in that the lower tensioning arm (14) and / or the upper tensioning arm (15) are respectively moved relative to the housing (3) during the course of a baling procedure, in principle in accordance with a shared specified movement function or with their own respective specified movement functions.

3. The method according to claim 2, characterized in that the upper tensioning arm (15) is positioned to deviate from its assigned movement function in a manner such that the actual tension of the baler belt (8) is changed in the direction of the target tension.

4. The method according to claim 3, characterized in that, in the case in which the actual tension is smaller than the target tension, the upper tensioning arm (15) is held in its current position for at least a tensioning period.

5. The method according to claim 3 or claim 4, characterized in that, in the case in which the actual tension is equal to or greater than the target tension, the upper tensioning arm (15) is released for at least a release period or is held in its current position for at least a time increment.

6. The method according to claim 5, characterized in that the upper tensioning arm (15) is released when a pivot angle (26) of the upper tensioning arm (15) relative to the housing (3) corresponds to or exceeds a theoretical pivot angle of the upper tensioning arm (15), wherein the theoretical pivot angle is specified.

7. The method according to one of the preceding claims, characterized in that the target tension of the baler belt (8) is changed over a round bale (2) baling procedure.

8. The method according to claim 7, characterized in that the target tension is a function of the diameter of the bale chamber (12) and / or of a contact section (13) of the baler belt (8) over which the baler belt (8) is in contact with the harvested material.

9. The method according to one of the preceding claims, characterized in that a bearing force of a roller (7) mounted on the housing (3), the roller cooperating with the baler belt (8), is detected, wherein the actual tension of the baler belt (8) is determined taking the bearing force into account.

10. The method according to claim 9, characterized in that a resulting bearing force is determined on the basis of the detected bearing force and also as a function of a deflection of the lower tensioning arm (14) and of a resulting encompassing angle (17), by which the baler belt (8) encompasses the roller (7).

11. The method according to claim 10, characterized in that a belt force acting in the baler belt (8) is determined with the aid of the resulting bearing force, and the actual tension of the baler belt (8) is determined using this belt force.

12. An agricultural round baler (1) for compacting stalked harvested material into round bales (2), comprising - a baler belt (8) constructed as a continuous belt, which cooperates with a plurality of guide rollers (7) in a manner such that, in an operating state of the round baler (1), it can revolve continuously along a run path, - a bale chamber (12) delimited by the baler belt (8), - a belt tensioning device (9) comprising a lower tensioning arm (14) and an upper tensioning arm (15), wherein the bale chamber (12) has a variable diameter, wherein the lower tensioning arm (14) comprises two tensioning rollers (10, 11) and the upper tensioning arm (15) comprises one tensioning roller (16), wherein the tensioning rollers (10, 11, 16) respectively cooperate with the baler belt (8), wherein the lower tensioning arm (14) and the upper tensioning arm (15) are constructed to be movable in a manner such that the run path of the baler belt (8) can be changed and the baler belt (8) can be kept under tension during the course of a baling procedure, characterized by a measuring device (6), by means of which an actual tension of the baler belt (8) can be continuously determined during a respective baling procedure, as well as a control device (18), which is configured to control the belt tensioning device (9) as a function of the determined actual tension in a manner such that the actual tension is changed in the direction of a specified target tension of the baler belt (8).

13. The round baler (1) according to claim 12, characterized in that the measuring device (6) cooperates with a roller (7) which is securely disposed on a housing (3) of the round baler (1) and which cooperates with the baler belt (8), wherein preferably, a bearing force with which the roller (7) bears on the housing (3) can be detected by means of the measuring device (6).

14. The round baler (1) according to one of the preceding claims, characterized in that the lower tensioning arm (14) cooperates with a tensioning element (21), by means of which the at least one tensioning roller (10, 11) of the lower tensioning arm (14) can be tightened against the baler belt (8), wherein preferably, the tensioning element (21) is formed by a hydraulic cylinder.

15. The round baler (1) according to one of the preceding claims, characterized in that the upper tensioning arm (15) cooperates with a tensioning element (22), by means of which the tensioning roller (16) of the upper tensioning arm (16) can be tightened against the baler belt (8), wherein preferably, the tensioning element (21) is formed by a hydraulic cylinder.