Arrangement for detecting the degree of wear of chopping knives in a chopping drum of a forage harvester

Abstract

Arrangement for detecting the degree of wear of chopping knives (144) of a chopping drum (36) of a forage harvester (10), comprising: an inductive sensor (152) inserted into or connected to a counter blade (102), which emits a signal when a chopping blade (144) passes by, a mechanism for adjusting the counter blade (102) relative to the outer circle of the chopping drum (36), which is configured to adjust the counter blade (102) on a non-radial path relative to the chopping drum (36), wherein the counter blade (102) is rotatable relative to the outer circle of the chopping drum (36) about a pivot point (156) spaced apart from the pivot point (76) of the chopping drum (36) and the orientation of the counter blade (102) relative to the chopping drum (36) changes when the counter blade (102) is moved closer to the pivot point (76) of the chopping drum (36) as the chopping knives (144) gradually wear down, and an evaluation device (70) connected to the sensor (152), which is configured to generate information regarding the orientation of the counter blade (102) relative to the outer circle of the chopping drum (36) based on the signal from the sensor (152) and to generate an indication signal regarding the degree of wear of the chopping knives (144) by calculating the angle of the counter blade (102) about its pivot point (156) based on the temporal progression, namely the steepness of the leading and trailing flanks, of the signal generated by the sensor (152) when a chopping knife (152) passes by, and based on the angle of the counter blade (102) the diameter of the outer circle of the chopping drum (36) and based on this the length of the chopping knives (144) with which they project beyond their knife holders (146).

Description

[0001] The invention relates to an arrangement for detecting the degree of wear of chopping knives of a chopping drum of a forage harvester and a forage harvester equipped therewith. State of the art

[0002] Forage harvesters are used to pick up plants or their seed heads from a field and cut them into small pieces. The plants standing in the field are usually cut from their roots remaining in the ground using a suitable harvesting head and fed into the forage harvester's intake chute. Alternatively, the plants can be cut and windrowed in previous operations and picked up using a pickup, or only the seed heads can be separated from the plants and conveyed into the intake chute. In the intake chute, the crop mat picked up by the harvesting head is pre-compacted by pairs of counter-tensioned pre-compression rollers, which feed the crop mat into a chopping drum. A number of chopping knives are distributed around the circumference (and possibly across the width) of the chopping drum. The chopping knives, in conjunction with a counter blade, cut the crop into small pieces.The shredded crop (and especially the corn kernels it contains) is optionally further shredded using a post-processing unit, conveyed into a discharge chute by means of a post-accelerator, and transferred to a transport vehicle. The chopped crop is used primarily as animal feed or for biogas production.

[0003] When cutting crops, in addition to the sharpness of the chopping blades, the distance between the cutting edge of the chopping blades and the counter blade is crucial for achieving a good cutting result while conserving energy. To this end, the chopping blades undergo a sharpening process after their initial installation and periodically thereafter. During this process, a grinding stone interacts with the rotating chopping drum. This ensures that all cutting edges are sharp and that all chopping blades maintain at least an approximately equal distance from the drum's axis of rotation. The position of the counter blade is typically adjusted automatically.

[0004] German patent DE 10 2011 005 317 A1 describes a measuring system for determining the wear condition of chopping knives in the chopping drum of a forage harvester. The measuring system is based on an inductive sensor integrated into the counter blade, which detects the changing magnetic field as the chopping knife passes by, inducing a voltage in the sensor. The sharpness of the chopping knives and their distance to the counter blade are determined from the time course of the electrical voltage detected by the sensor. This allows a grinding process and / or a counter blade position adjustment process to be triggered automatically if necessary.

[0005] Each sharpening process removes a certain amount of material from the chopping blades. Consequently, the chopping blades become shorter over time. While this can be compensated for by repositioning the counter blade, allowing the actual cutting process to continue smoothly even with partially worn chopping blades, worn chopping blades protrude only slightly beyond the blade holders, impairing their airflow. This gradually reduces the function of the chopping drum, as it can only convey a small amount of air from the intake chute to the discharge spout. Eventually, the chopping blades become so worn that they can no longer be sharpened.

[0006] In the prior art, the operator must therefore check from time to time whether the chopping blades are so worn that they need readjusting. In this case, the chopping blades are unscrewed, pulled forward, and then screwed back on to restore the airflow. If the chopping blades are completely worn, they must be replaced. This manual check is prone to errors and can be omitted by inexperienced operators, which can lead to poor performance of the forage harvester. Although it has been proposed to use a sensor capable of detecting the physical properties of the hard coating of the chopping blades (DE 10 2009 047 584 A1) to determine the wear condition of the chopping blades, such sensors are not currently commercially available.As the chopping knives wear down, the position of the counter blade does gradually shift inwards towards the axis of rotation of the chopping drum. However, while the sensors used in the prior art to detect the position of the counter blade are highly precise, they are only designed to detect relative positions (DE 10 2004 016 089 A1). Therefore, knock sensors, which detect contact between the counter blade and the chopping knives, are typically used for counter blade adjustment. These sensors are thus unsuitable for detecting the circumference diameter of the chopping drum and therefore the wear condition of the chopping knives. Object of the invention

[0007] The object underlying the invention is seen as being to provide a self-operating arrangement for detecting the degree of wear of chopping knives of a chopping drum of a forage harvester, which does not have the aforementioned disadvantages or has them to a reduced extent and is able to detect the degree of wear of the chopping knives. Solution

[0008] This problem is solved according to the invention by the teaching of claims 1 and 3, wherein further claims list features which advantageously develop the solution further.

[0009] An arrangement for detecting the degree of wear of chopping knives in a chopping drum of a forage harvester comprises an inductive sensor inserted in or connected to a counter blade, which emits a signal when a chopping knife passes by; a mechanism for adjusting the counter blade relative to the outer circle of the chopping drum, which is configured to adjust the counter blade on a non-radial path relative to the chopping drum; and an evaluation device connected to the sensor, which is configured to generate information regarding the orientation of the counter blade relative to the outer circle of the chopping drum based on the sensor signal and to generate an indication signal regarding the degree of wear of the chopping knives.

[0010] In other words, the counter blade is not moved radially relative to the chopping drum by the counter blade adjustment mechanism, but rather along a non-circular path around a pivot point. This causes the orientation of the counter blade relative to the chopping drum to change as it is moved closer to the drum's pivot point due to the gradually wearing chopping blades. This change in orientation is detected by the inductive sensor integrated into the counter blade, which senses the passing chopping blade. The steepness of the leading and trailing edges of the signal generated by the sensor as the chopping blade passes by changes with the orientation of the counter blade. An evaluation unit analyzes the signal and generates an indicator signal regarding the degree of wear of the chopping blades, which can be displayed to an operator. The operator can then adjust the counter blade's position as needed.If the shredding blades are sufficiently worn and their air-blading effect is no longer adequate, either replace the shredding blades or loosen them, pull them further outwards and tighten them again.

[0011] The evaluation device is capable of calculating the angle of the counter blade around the pivot point based on the temporal progression of the signal generated by the sensor when a chopping blade passes by, and of calculating the diameter of the circumcircle of the chopping drum and the length of the chopping blades with which they protrude beyond their blade holders based on the angle of the counter blade.

[0012] The evaluation unit can be operated to send a warning signal to an operator via an operator interface if the length of the shredding knives is below a threshold value. Example of implementation

[0013] The drawings illustrate an embodiment of the invention, which is described in more detail below. It shows: Fig. 1 a side view of a self-propelled forage harvester, Fig. 2 a schematic representation of the counter blade of the forage harvester of the Fig. 2 with its adjustment device and an evaluation device used to determine the degree of wear of the chopping blades, and Fig. 3a and Fig. 3b Examples of sensor signals depending on the wear level of the shredding blades.

[0014] In the Fig. Figure 1 shows a self-propelled forage harvester 10 in a schematic side view. The forage harvester 10 is built on a frame 12, which is supported by front driven wheels 14 and steerable rear wheels 16. The forage harvester 10 is operated from a driver's cab 18, from which a harvesting head 20 in the form of a pickup is visible. Crop material, e.g., grass or the like, picked up from the ground by the harvesting head 20 is fed via a feed conveyor 22 with pre-compression rollers, which are arranged within a feed housing 24 at the front of the forage harvester 10, to a chopping drum 26 located below the driver's cab 18. The chopping drum, in conjunction with a counter blade 102, chops the material into small pieces and delivers it to a conveying device 28. A grinding device 100 is used to sharpen the shredding knives 144 if required.The crop leaves the harvesting machine 10 and is directed to a transport vehicle traveling alongside it via a discharge spout 30 that is rotatable about an approximately vertical axis and adjustable in inclination. In the following, directional terms such as lateral, below, and above refer to the forward direction V of the harvesting machine 10, which is in the . Fig. 1 runs to the right.

[0015] The chopping drum 26 is driven by a pulley 48, which is connected via a bevel gear to an internal combustion engine (not shown), via a drive belt 50, which drives a pulley 54 for driving the chopping drum 26 and a pulley 52 for driving the conveyor 28. A grinding device 100 is used to sharpen the chopping knives of the chopping drum 26. In addition, a metal detector 108 is provided in the lower, front pre-compression roller, which can be used to quickly stop the feed conveyor 22 if necessary, and an operator input device 98 coupled to a control unit 70 is located in the driver's cab 18.

[0016] The Fig. Figure 2 shows an enlarged view of the chopping drum 36 and the counter blade 102. The chopping drum 36 comprises a drum shell 72, which is connected to rotary bearings 76 via support discs 74 and stub axles. An open chopping drum 36 could also be used instead of the closed drum shell 72 shown. Knife holders 146 are distributed around the circumference of the chopping drum 36 (and preferably across its width), to which the individual chopping knives 144 are each attached by several screws 150. Pressure plates 148 are arranged between the heads of the screws 150 and the chopping knives 144. The threads of the screws 150 engage with threads in the knife holders or with threaded strips inserted transversely therein.

[0017] The counter blade 102 is rotatably mounted about a pivot axis 156, which is located below the rotary bearing 76 of the chopping drum 36. A lever arm 154 is attached to each of the two lateral ends of the counter blade 102, with one end connected to the pivot axis 156 and the other end to the counter blade 102. An adjusting drive 158, associated with each lever arm 154 or with each end of the counter blade 102, serves to adjust the counter blade 102. The counter blade 102 can additionally be supported on the frame 12 by a bendable plate (not shown), as described in DE 196 33 290 C2, the disclosure of which is incorporated into these documents by reference.

[0018] An inductive sensor 152 is integrated into or connected to the counter blade 102 and is connected to an evaluation unit 70, which in turn is coupled to an operator interface 98. The inductive sensor can be designed in accordance with DE 10 2011 005 317 A1, the disclosure of which is incorporated into these documents by reference.

[0019] The sensor 152 can, for example, be designed as a coil that is driven by an oscillator with a high-frequency alternating current, for example in the kHz or MHz range. When a (usually ferromagnetic) shredding blade 144 passes the counter blade 102 and thus the sensor 152, the inductance of the coil changes, which in turn changes the amplitude of the alternating voltage applied to the coil. This amplitude is detected and evaluated by a detector (e.g., a rectifier), which can be evaluated by an evaluation circuit integrated in the housing of the sensor 152 or in the evaluation unit 70, or by a separate evaluation circuit. The sensor 152 therefore provides a continuous idle or background signal (when no shredding blade 144 is passing by), which is interrupted by negative or positive pulses when a shredding blade 144 passes by, as described in the Fig. 3a and Fig. 3b will be shown.

[0020] The signal from the inductive sensor 152 changes depending on the temperature, even if other boundary conditions remain constant. These temperature changes can cause relevant points in the sensor 152 signal to show a change, even though the actual measured objects (the sharpness of the chopping blades 144 and their distance from the counter blade 102) have not changed, or not to the extent indicated by the signal change. A practical example is that the calculated cutting gap values ​​show a significantly faster (than the actual) increase when the forage harvester 10 and the counter blade 102 warm up after harvesting begins in the morning. Similarly, these values ​​can decrease again when the forage harvester 10 and the counter blade 102 cool down. In principle, this behavior can also occur in reverse – decreasing values ​​when warming up and increasing values ​​when cooling down.

[0021] To compensate for this temperature drift, the evaluation circuit can take into account that the temperature-related signal changes affect both the signal drop when the chopping blade 144 passes by and the idle signal between two chopping blade-induced pulses. The idle voltage of the sensor 152 is influenced only by temperature and by its installation location in the counter blade 102. This location does not change during a harvest day. It should also be noted that wear on the counter blade 102 also alters the pre-damping of the sensor 152. However, this process can be assumed to be significantly slower than the change in sensor temperature and can therefore be disregarded.Temperature compensation is achieved by using the following procedure: as soon as changes in the open-circuit voltage are detected during the operating period (after an initial calibration of the sensor 152, in which the open-circuit voltage is recorded and a value representing it is stored by the evaluation circuit), these changes are used to correct the pulses generated when the shredding blades 144 pass by.

[0022] The following operating principle applies: As a chopping blade 144 passes by, the sensor 152 generates an electrical signal due to the changing magnetic field, which is fed to the evaluation unit 70. If, after a certain operating time of the chopping drum 36, the chopping blades 144 become dull, the operator or an automatic system based on the signals from the sensor 152, which the evaluation unit 70 uses to assess the sharpness of the chopping blades 144, will activate the sharpening device 100. Since the circumscribed circle of the chopping blades 144 inevitably becomes smaller, the grinding process will be followed by a readjustment of the counter blade 102 in order to set the gap between the circumscribed circle of the chopping blades 144 and the counter blade 102 to a desired, relatively small value, for which the evaluation device can use the signals from the sensor 152 to control the adjustment drive 158.

[0023] The adjustment of the counter blade 102, which can also be carried out independently of a grinding process, results in a change in the angle of the counter blade 102 relative to the circumcircle of the shredding knives 144, as shown in the Fig. 2, as can be seen from the dashed lines of the counter blade 102. This also changes the angle between the counter blade 102 and the chopping blade 144, which leads to changing slopes of the signal edges of the sensor 152 as the leading and trailing edges of the chopping blades 144 approach and recede, as shown in the Fig. 3a for the continuous counter-cutting edge 102 of the Fig. 2 and in the Fig. 3b for the opposite edge shown with a dashed line. Fig. 2 is shown schematically. The sloping flank that arises when the chopping blade 144 approaches is in Fig. 3a significantly flatter than in Fig. 3b, while the rising flank created when the chopping blade 144 runs away in Fig. 3a significantly steeper than in Fig. 3b is.

[0024] The evaluation unit 70 is programmed to determine, based on the steepness of one or both flanks, the angle of the counter blade 102 about the axis of rotation 156. This angle is a measure of the degree of wear on the chopping knives 144, i.e., how far they protrude beyond the leading edge of the knife holders 146 in the direction of rotation. If the chopping knives 144 are worn by more than a predefined value or a value that can be entered by the operator into the operator input unit 98, the evaluation unit 70 generates a corresponding message via the operator input unit 98. The degree of wear of the chopping knives 144 can also be continuously displayed there. If necessary, the operator can then replace the chopping knives 144 or loosen the screws 150 and adjust the chopping knives 144 forward by a defined length in the direction of rotation of the chopping drum 36, and then tighten the screws 150 again.

[0025] The automatic monitoring of the wear level of the chopping blades 144 eliminates the need for the operator to monitor this by inspecting the chopping drum 36 himself.

Claims

[1] Arrangement for detecting the degree of wear of chopping knives (144) of a chopping drum (36) of a forage harvester (10), comprising: an inductive sensor (152) inserted into or connected to a counter blade (102), which emits a signal when a chopping blade (144) passes by, a mechanism for adjusting the counter blade (102) relative to the outer circle of the chopping drum (36), which is configured to adjust the counter blade (102) on a non-radial path relative to the chopping drum (36), wherein the counter blade (102) is rotatable relative to the outer circle of the chopping drum (36) about a pivot point (156) spaced apart from the pivot point (76) of the chopping drum (36) and the orientation of the counter blade (102) relative to the chopping drum (36) changes when the counter blade (102) is moved closer to the pivot point (76) of the chopping drum (36) as the chopping knives (144) gradually wear down, and an evaluation device (70) connected to the sensor (152), which is configured to generate information regarding the orientation of the counter blade (102) relative to the outer circle of the chopping drum (36) based on the signal from the sensor (152) and to generate an indication signal regarding the degree of wear of the chopping knives (144) by calculating the angle of the counter blade (102) about its pivot point (156) based on the temporal progression, namely the steepness of the leading and trailing flanks, of the signal generated by the sensor (152) when a chopping knife (152) passes by, and based on the angle of the counter blade (102) the diameter of the outer circle of the chopping drum (36) and based on this the length of the chopping knives (144) with which they project beyond their knife holders (146). [2] Arrangement according to claim 1 wherein the evaluation device (70) is operable to give a warning signal to an operator via an operator interface (98) if the length of the chopping blades (144) is below a threshold value. [3] Forage harvester (10) with an arrangement according to one of the preceding claims.

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