FIELD HACKERS

Abstract

The invention relates to a forage harvester (2) with a chopping unit (6) comprising a chopping drum (7) and associated chopping knives (8) for chopping crops, a knife sharpening device (17) for sharpening the chopping knives (8), and a sensor arrangement (23), wherein an air gap (33) is formed between the sensor arrangement (23) and the chopping drum (7), wherein when the chopping drum (7) rotates, at least part of the chopping knives (8) passes through the air gap (33) and induces a voltage signal (38) in the sensor arrangement (23), wherein the forage harvester (2) comprises an evaluation unit (36) which is connected to the sensor arrangement (23) in a signal-transmitting manner, and wherein the forage harvester (2) comprises at least one sensor device (44) for determining a state that influences the voltage signal (38).

Description

[0001] The invention relates to a forage harvester according to the preamble of claim 1.

[0002] Forage harvesters comprise a chopping device that features a chopping drum with elongated chopping knives mounted on it, as well as a stationary counter-blade. The crop fed to the chopping drum is chopped, or shredded, by the interaction between the chopping knives and the counter-blade.

[0003] During chopping, wear occurs on the chopping device, which is caused by wear on the chopping knives. Specifically, wear-related material is removed in the area of ​​the cutting edges of the chopping knives, which reduces cut quality and crop throughput. For this reason, the chopping device also includes a grinding device for sharpening the chopping knives. The grinding device performs a grinding process with several grinding cycles at regular or irregular intervals. A grinding stone is guided along the chopping knives in the axial direction of the chopping drum. One grinding cycle corresponds to one movement of the grinding stone towards one end of the chopping drum and a subsequent movement back to the other end of the chopping drum.

[0004] A forage harvester of the type described above is known from EP 3 738 429 A1. The forage harvester comprises a sensor arrangement assigned to the chopper drum, wherein an air gap is formed between the sensor arrangement and the chopper drum. As the chopper drum rotates, the chopper blades pass through the air gap, inducing a voltage signal in the sensor arrangement. This voltage signal can be used, for example, to determine the wear status of the chopper blades. The wear status enables improved control and activation of the grinding device. However, various disturbances can influence the induced voltage signal and make it difficult to accurately determine the wear status and / or other properties of the chopper blades.

[0005] It is therefore an object of the invention to avoid the described disadvantages of the prior art and in particular to improve a field chopper with a chopping device and an inductively acting sensor arrangement associated therewith.

[0006] This object is achieved according to the invention by the characterizing features of claim 1. Advantageous further developments are the subject of the dependent claims.

[0007] According to claim 1, a forage harvester is proposed with a chopping device comprising a chopping drum and chopping knives assigned thereto for shredding crops, a knife grinding device for sharpening the chopping knives, and a sensor arrangement, wherein an air gap is formed between the sensor arrangement and the chopping drum, wherein upon rotation of the chopping drum at least some of the chopping knives pass through the air gap and induce a voltage signal in the sensor arrangement, wherein the forage harvester comprises an evaluation unit which is connected to the sensor arrangement in a signal-transmitting manner, wherein the forage harvester comprises at least one sensor device for determining a state influencing the voltage signal.

[0008] The invention has many advantages. By detecting at least one condition influencing the voltage signal, this condition can be taken into account or compensated for when evaluating the voltage signal. Voltage signals that vary due to the conditions, which could lead to an incorrect determination of the drum condition or the condition of the chopping blades, can be avoided.

[0009] An advantageous development provides that the sensor device comprises a speed sensor for determining the speed of the chopper drum, wherein preferably at least one condition influencing the voltage signal is the speed. The voltage signal is influenced by the speed, since the induced voltage of the sensor arrangement depends on the speed of the chopper blades. In order to compensate for this influence, it is particularly advantageous if the speed is determined.

[0010] To determine the speed, the speed sensor can comprise a cam wheel with cams and a sensor unit for detecting the cams.

[0011] An advantageous embodiment provides that the cam wheel comprises a number of cams corresponding to the number of chopping blades in a chopping blade arrangement, preferably 18 cams, wherein preferably only one cam has a different extension than the other cams. According to this embodiment, the pulses generated by the chopping blades in the voltage signal can each be assigned to a cam and thus also to a specific chopping blade on the chopping drum. Furthermore, using a single cam whose extension differs from the other cams, the time for one revolution of the chopping drum can be measured, and the speed can be determined from this.

[0012] A further advantageous embodiment provides that the sensor device comprises at least one temperature sensor, wherein the temperature sensor is provided and configured to determine a temperature of the sensor arrangement. Preferably, the temperature sensor is assigned to a magnetic excitation arrangement of the sensor arrangement, and at least one condition influencing the voltage signal is temperature. The temperature influences the remanent flux density or the strength of the magnets used to determine the induced voltage signal. Therefore, it is particularly advantageous if the temperature of the sensor device is determined so that temperature-related influences on the voltage signal can be compensated.

[0013] A further advantageous embodiment provides that the forage harvester comprises a counter-blade that interacts with the chopper drum. A position sensor is assigned to the counter-blade, and the evaluation unit is configured to determine a radius of the chopper drum using the position sensor. Preferably, the radius of the chopper drum is at least one condition influencing the voltage signal. This embodiment is particularly advantageous because the distance between the sensor arrangement and the chopper drum can vary due to installation tolerances. Measurement errors caused by this can be avoided by using the radius of the chopper drum to calibrate the sensor arrangement.

[0014] The present invention is explained in more detail below with reference to an embodiment shown in the drawings. Figure 1a schematic representation of a self-propelled forage harvester in side view; Figure 2a detailed view of the forage harvester according to Figure 1 ; Figure 3 a detailed view of an inductive sensor arrangement; Figure 4 a cam wheel arranged on the chopper drum with a sensor unit designed as a speed sensor; Figure 5 a sensor arrangement according to Figure 3 voltage signal and a signal generated by the sensor unit and the cam wheel according to Figure 4 Determined speed signal; Figure 6 shows a schematic side view of a chopping drum with a counter-blade and a knife grinding device.

[0015] Figure 1shows a schematic of an agricultural machine 1 designed as a forage harvester 2, which accommodates a harvesting attachment 3 in its front area. In the rear area of ​​the harvesting attachment 3, so-called intake and pre-compression rollers 4 are assigned to it, which receive the crop flow 5 coming from the harvesting attachment 3, compact it, and transfer it in their rear area to a chopping device 6. The chopping device 6 comprises a chopping drum 7, which is equipped with chopping knives 8 of a chopping knife arrangement 9. The rotating chopping knives 8 are moved in the intake area 10 of the chopping drum 7 past a so-called counter-blade 11, via which the crop flow 5 to be shredded is conveyed. In the rear area of ​​the chopping drum 7, the shredded crop 5 is then transferred either to a post-shredding device 13 designed as a so-called cracker 12 or directly to a post-acceleration device 14.While the secondary shredding device 13 further shreds the granular components of the crop stream 5, such as corn kernels, the secondary accelerator 14 accelerates the crop stream 5 in such a way that it is moved through a discharge chute 15 and exits the forage harvester 2 at the end in the area of ​​a discharge flap 16 and can be transferred to a transport vehicle (not shown). Furthermore, a knife grinding device 17, known per se and therefore not described in detail here, is assigned to the circumference of the chopper drum 7. The grinding stone 18 of the knife grinding device is movable horizontally across the width of the chopper drum 7, so that each chopper knife 8 positioned on the circumference of the chopper drum 7 can be sharpened. For the purpose of activating or deactivating the knife grinding process, the knife grinding device 17 is connected to a control device 19 in a signal-transmitting manner.

[0016] According to Figure 2The chopping knife arrangement 9 comprises right- and left-hand chopping knife arrangements 9a, 9b, wherein each chopping knife arrangement 9a, 9b comprises a plurality of chopping knives 8 positioned on the circumference of the chopping drum 7 obliquely to the rotational axis 20 of the chopping drum 7. The chopping drum 7 is enclosed at the bottom by a drum base 21, preferably made of stainless steel. At the top, the chopping drum 7 is enclosed by a drum rear wall 22, preferably also made of stainless steel. A sensor arrangement 23 can be arranged according to the Figure 2In the exemplary embodiment shown, the sensor arrangement 23 can be positioned either on the drum rear wall 22 or on the drum base 21. It is also conceivable for a sensor arrangement 23 to be arranged simultaneously on both the drum base 21 and the drum rear wall 22. Regardless of the specific positioning, at least two sensor arrangements 23a, 23b are assigned to each chopping drum 7 in such a way that one of the sensor arrangements 23a, 23b is assigned to the respective associated chopping knife arrangement 9a, 9b, wherein each sensor arrangement 23a, 23b completely covers the cutting edge 24 of the respective chopping knife 7, so that each cutting edge 24 can be detected over its entire length by the respective sensor arrangement 23a, 23b. Furthermore, it is within the scope of the invention that the respective sensor arrangement 23a, 23b is positioned either parallel to the axis of rotation 20 of the chopping drum 7 or parallel to the cutting edge 24 of the chopping knives 8 on the drum base 21 and / or the drum rear wall 22.The lower right image in . Figure 2 shows only by way of example the possible orientations of the sensor assemblies 23a, 23b in a single representation. Preferably, all sensor assemblies 23a, 23b are positioned either parallel to the rotational axis 20 of the chopping drum 7 or parallel to the cutting edge 24 of the chopping blades 8. In the illustrated embodiment, the sensor assemblies 23a, 23b are designed as induction sensors 25, with each sensor assembly 23 comprising one or more magnetic excitation assemblies 26 and a respective pole assembly 27 cooperating with these.

[0017] Figure 3explains some properties of the sensor assemblies 23a, 23b, with further details on the sensor assemblies being derived from DE 10 2017 103 537 A1, the disclosure of which is hereby incorporated by reference in its entirety. A detection assembly 28 for detecting a condition, in particular a wear condition, of a chopping blade assembly 9a, 9b comprises a plurality of sensor assemblies 23a, 23b, preferably one for each chopping blade assembly 9a, 9b. Each sensor assembly 23a, 23b is formed by a plurality of magnetic excitation assemblies 26, which are coupled to a flux guide device 29. The respective sensor assembly 23a, 23b each provides a pole assembly 27, which forms at least one magnetic pole 30, preferably five magnetic poles 30, each with a pole face 31 for discharging magnetic flux.When the chopping drum 7 rotates, a chopping blade 8 passes the respective pole arrangement 27, wherein the chopping blade 8 passing the pole arrangement 27 forms an air gap arrangement 32 with at least one air gap 33 towards the pole arrangement 27, and thereby at least one magnetic circuit 34 excited by the excitation arrangement 26 is closed via the respective chopping blade 8. The detection arrangement 28 also has a measuring arrangement 35 and an evaluation unit 36. The measuring arrangement 35 detects at least one magnetic measured variable 37 relating to the magnetic flux, preferably an induced voltage 38, in at least one magnetic circuit 34 excited by the excitation arrangement 26, and the evaluation unit 36 ​​determines the wear condition 39 of the respective chopping blade 8 from the at least one detected measured variable 37.

[0018] During operation of the chopping drum 7, the chopping knives 8 are guided past the respective sensor arrangement 23a, 23b in accordance with the direction of rotation of the chopping drum 7. Due to the almost non-magnetic properties of the drum rear wall 22, preferably made of stainless steel, or of the drum base 21, the magnetic circuits 34 formed by adjacent magnetic poles 30 penetrate the chopping knife 8, which each sweeps over the sensor arrangement 23a, 23b. In the illustrated embodiment, four magnetic circuits 34 are formed between the five poles 30, which penetrate the respective chopping knife in four sections. For each of these sections, a voltage 38, the magnetic measurement variable 37, is induced in the measuring arrangement 35 assigned to it. The evaluation unit 36 ​​assigned to the detection arrangement 28 determines the section-by-section induced voltage 38 and records it.In this context, it is within the scope of the invention that the respective sensor arrangement 23 has more or fewer than the disclosed five magnetic poles 30, so that more or fewer than the five induced voltages 38 can result. It is also within the scope of the invention that the voltage signals 38 can be combined into one or more voltage signals 38 for each detected chopping blade 8. Further details regarding the detection of the voltage signals 38 are known from DE 10 2019 112 965 A1, the disclosure of which is hereby incorporated by reference in its entirety.

[0019] The voltage signal 38 can be influenced by various conditions in a manner to be explained in more detail below. These conditions can be the rotational speed of the chopper drum 7 and / or the temperature of the sensor arrangement 23 and / or the radius 43 of the chopper drum 7. To enable better evaluation of the voltage signal 38, the forage harvester 2 comprises at least one sensor device 44 for determining one of these conditions.

[0020] Fig. 4shows a sensor device 44 assigned to the chopper drum 7, wherein the sensor device 44 is designed as a speed sensor 45 for determining the speed of the chopper drum 7. The speed sensor 45 comprises a cam wheel 46 with a plurality of cams 47 arranged one behind the other in the circumferential direction of the cam wheel 46 and a sensor unit 48 for detecting the cams 47. The number of cams 47 corresponds to the number of chopping knives 8 of a chopping knife arrangement 9a, 9b arranged one behind the other in the circumferential direction of the chopper drum 7. In this case, only one cam 51 has an extension that differs from the other cams 47. Here and preferably, the one cam 51 can be smaller than the other cams 47. In order to set the chopper drum 7 in a rotational movement, it is connected to a pulley 49. Here and preferably, the cam wheel 46 can be arranged on the pulley 49.In an alternative embodiment, the cam wheel 46 can also be arranged directly on the chopping drum 7.

[0021] Fig. 5shows in the upper graph 41 a voltage signal 38 which was induced in the sensor arrangement 23 during one rotation of a chopper drum 7 by means of the chopper blades 8 and in the lower graph 42 a signal 50 determined by the speed sensor 45 or the sensor unit 48 for determining the speed of the chopper drum 7. The voltage signal 38 comprises a plurality of pulses 40, each of which describes an increase in the induced voltage 38 and a subsequent decrease in the induced voltage 38. As the voltage signal 38 of a pulse 40 increases, a chopper blade 8 approaches the air gap 33 between the sensor arrangement 23 and the chopper drum 7 until it is located centrally within the air gap 33. The drop in pulse 40 describes the subsequent removal of the chopping blade 8 from the air gap 33. The maximum amplitude of a pulse 40 depends on the distance of the respective chopping blade 8 from the sensor arrangement 23.The signal 50 of the speed sensor 45, shown in the lower graph 42, is pulsed, with the cams 47 each generating a pulse 52. The pulse duration of the smaller cam 51 is shorter than that of the other cams 47. Due to the shorter pulse duration of the cam 51, the time for one revolution of the chopper drum 7 can be measured and thus the speed of the chopper drum 7 can be determined. The control device 19 and / or the evaluation unit 36 ​​are provided and configured to determine the speed using the signal 50. Since the number of chopping knives 8 corresponds to the number of cams 47, each pulse 40 of the induced voltage signal 38 induced by the chopper knives 8 is assigned a pulse 52 of the signal 50 generated by a cam 47.Thus, each pulse 40 of the voltage signal 38 is directly and unambiguously assigned to a chopping blade 8, so that a wear condition that can be determined from the voltage signal 38 is assigned to a specific chopping blade 8 in the control device 19 and / or the evaluation unit 36. In an alternative embodiment, the evaluation unit 36 ​​can also be designed as a control device 19.

[0022] Furthermore, the rotational speed of the chopper drum 7 influences the voltage signal 38 induced in the sensor arrangement 23, since the voltage induced in the sensor arrangement 23 changes depending on the rotational speed of the chopper drum 7 or the chopper blades 8. For this reason, to improve the usability of the voltage signal, the control device 19 and / or the evaluation unit 36 ​​are configured such that they assign a rotational speed of the chopper drum 7 to the voltage signal 38. Based on this assignment, the influence of the rotational speed of the chopper drum 7 on the voltage signal 38 can be compensated.

[0023] As the Figure 3As shown, a sensor device 44 designed as a temperature sensor 53 is assigned to the sensor arrangement 23. The temperature sensor 53 is provided and configured to determine the temperature of the magnetic excitation arrangement 26. In the exemplary embodiment shown here, a temperature sensor 53 is assigned to each magnetic excitation arrangement 26. The temperature sensors 53 determine the temperature of the flux-conducting device 29 in order to compensate for the influence of the temperature on the magnetic conductivity of the flux-conducting device 29 when determining or evaluating the voltage signal 38.

[0024] Fig. 6shows a schematic side view of a chopping drum 7. In its upper area, the chopping drum 7 is assigned the knife grinding device 17, wherein the knife grinding device 17 comprises at least the grindstone 18, a carriage 81 receiving the grindstone and an actuating cylinder 82 moving the carriage 81 parallel to the axis of rotation 20 of the chopping drum 7. The grindstone 18 is guided in a conventional manner by means of the carriage 81 such that in a non-working position it is positioned to the side of the chopping drum 7 and in the working position 83 it is guided along the envelope curve 84 spanned by the chopping knives 8 when the chopping drum 7 rotates, so that the grindstone 18 sweeps over at least the grinding surface length 54 of the knife back 56 of the chopping knives 8.

[0025] In a manner known per se, the counter-blade 11 assigned to the chopping drum 7 is pivotally guided by a pivoting mechanism 85 in a bearing 86 assigned to the underside of the counter-blade 11. The edge 87 of the counter-blade 11 facing the chopping drum 7 is positioned at a specific distance 88, the so-called cutting gap 89, from the envelope curve 84 of the chopping drum 7. Furthermore, at least one servomotor 90 is assigned to the pivoting mechanism 85 in a manner likewise known, which enables a change in the position of the counter-blade 11 and thus a change in the cutting gap 89. In addition, the counter-blade 11 accommodates one or more position sensors 55 designed as so-called knock sensors 91, which are capable of determining the distance 88 of the counter-blade 11 from the envelope curve 84 of the chopping drum 7 using vibration analysis. Based on the distance 88, the control device 19 determines the radius 43 of the chopping drum 7.Tolerances during installation of the sensor arrangement 23 can lead to errors in the evaluation of the voltage signal 38. Here, and preferably, the control device 19 is configured such that it uses the radius 43 to calibrate the sensor arrangement 23. For this purpose, a radius 43 determined by means of the voltage signal 38 can be compared with a radius 43 determined by the position sensor 55. List of reference symbols: 1 Agricultural work machine 34 magnetic circuit 2 forage harvester 35 Measuring arrangement 3 Harvesting header 36 Evaluation unit 4 Feed and pre-press rollers 37 magnetic measurement quantity 5 Crop flow 38 voltage signal 6 Chopping device 39 Wear condition 7 chopping drum 40 pulse 8 chopping knife 41 graph 9 Chopping knife arrangement a... b 42 graph 10 catchment area 43 radius 11 Counter blade 44 Sensor device 12 cracker 45 Speed ​​sensor 13 Post-shredding device 46 cam wheel 14 Post-acceleration device 47 cam 15 discharge spout 48 Sensor unit 16 Discharge spout flap 49 pulley 17 Knife grinding device 50 Speed ​​sensor signal 18 whetstone 51 cam 19 Control device 52 pulse 20 Chopper drum rotation axis 53 Temperature sensor 21 Drum base 54 Grinding surface length 22 Drum back wall 55 Position sensor 23 Sensor arrangement a...b 56 knife back 24 cutting edge 81 Sleds 25 Induction sensor 82 Actuating cylinder 26 magnetic excitation arrangement 83 Working position 27 Pole arrangement 84 Envelope 28 Recording arrangement 85 Swivel mechanism 29 Flow guidance system 86 storage 30 magnetic pole 87 edge 31 Pole face 88 Distance 32 Air gap arrangement 89 Cutting gap 33 air gap 90 actuator 91 Knock sensors

Claims

1. A forage harvester (2) having a chopping device (6) comprising a chopping drum (7) and chopping knives (8) associated therewith for shredding crops, a knife grinding device (17) for sharpening the chopping knives (8), and a sensor arrangement (23), wherein an air gap (33) is formed between the sensor arrangement (23) and the chopping drum (7), wherein upon rotation of the chopping drum (7), at least some of the chopping knives (8) pass through the air gap (33) and induce a voltage signal (38) in the sensor arrangement (23), wherein the forage harvester (2) comprises an evaluation unit (36) which is connected to the sensor arrangement (23) in a signal-transmitting manner, characterized in that the forage harvester (2) comprises at least one sensor device (44) for determining a state influencing the voltage signal (38).

2. Field chopper (2) according to claim 1, characterized in thatthe sensor device (44) comprises a speed sensor (45) for determining a speed of the chopping drum (7), wherein preferably at least one state influencing the voltage signal (38) is the speed.

3. Field chopper (2) according to claim 2, characterized in that the speed sensor (45) comprises a cam wheel (46) with cams (47, 51) and a sensor unit (48) for detecting the cams (47, 51).

4. Field chopper (2) according to claim 3, characterized in that the number of cams (47, 51) of the cam wheel (46) corresponds to a number of chopping knives (8) of a chopping knife arrangement (9a, 9b), wherein preferably only one cam (51) has an extension that differs from the other cams (47).

5. Field chopper (2) according to one of claims 1 to 4, characterized in thatthe sensor device (44) comprises at least one temperature sensor (53), wherein the temperature sensor (53) is provided and configured to determine a temperature of the sensor arrangement (23), wherein preferably the temperature sensor (53) is assigned to a magnetic excitation arrangement (37) of the sensor arrangement (23) and at least one state influencing the voltage signal (38) is the temperature.

6. Field chopper (2) according to one of claims 1 to 5, characterized in that the field chopper (2) comprises a counter-blade (11) cooperating with the chopper drum (7), wherein the counter-blade (11) is assigned a position sensor (55) and the evaluation unit (36) is set up by means of the position sensor (55) to determine a radius (43) of the chopper drum (7), wherein preferably the radius (43) of the chopper drum (7) is at least one state influencing the voltage signal (38).