BE1022370B1 - ARRANGEMENT FOR DETECTING THE SHARP OF HACKSELMESSERN - Google Patents

Abstract

A system for detecting the sharpness of a variety of knives (48) that are The circumference of a chopping drum (22) are distributed, comprises: a distance sensor which is set up to detect the width (d) of a gap between a bedknife (38) and the cutting edges of the knives (48); a magnetic sensor (54) with a magnet (58) which generates a magnetic flux in the gap between the counter blade (38) and the cutting edges of the knives (48), and a flux sensor (60) which provides an electrical signal v that represents an influence of the cutting edges passing by on the magnetic flux in the gap; and an evaluation unit which is connected to the gap sensor and the magnetic sensor (54) and is set up to calculate a radius (r) representing the sharpness of the cutting edges (48) according to the following equation: r = exp ((v + c1 * d + c2) * c3), where C1, c2 and c3 are constants and exp is the exponential function.

Description

Arrangement for detecting the sharpness of chopping knives

description

The invention relates to an arrangement for detecting the sharpness of chopping knives.

State of the art

Forage harvesters are used in agriculture to cut or pick up crops, shred the crop into small pieces and overload the shredded crop onto a trailer. The chopped Emtegut is used as cattle feed or biogas production. The Sehneidoperation is carried out by means of a knife drum in the form of a rotating drum around the circumference of a number of knives is distributed, which cooperate with a counter-blade.

The distance (i.e., the distance) between the enveloping circle described by the rotary chopping knives and the counterknife, on the one hand, and the sharpness (i.e., the radius of the cutting edge) of the knives, on the other hand, are the most important parameters for the cut quality and power required for chopping. It is therefore desirable to provide a suitable sensor for detecting the distance between the bedknife and the knives to allow for automatic or manual adjustment of the distance. This or another sensor should also be capable of detecting the sharpness of the knives so as to be able to detect them, i. if they are dull or worn, sharpen or replace.

The distance between the enveloping circle described by the rotating blades and the counter-blade is usually adjustable by electric motors which move the counter-blade relative to the cutterhead. For measuring the distance between the bedknife and the chopping knives, inductive sensors have been described which include a permanent magnet connected to the bedknife and an induction coil in which an electromotive force (EMF) is induced when the chopping knife passes by. This electromotive force is amplified and then detected. In such an arrangement, which is described in EP 0 943 888 A2, the induced voltages are subjected to a frequency analysis. The ratio of the high-frequency components of the signal spectrum to the low-frequency components is derived. The quotient determined in this way provides information about the distance between the counterknife and the chopping knives. This information can be used to automatically place the bedknife in an appropriate position with a sufficiently small gap between the bedknife and the knives.

On the other hand, sharpness sensors have been proposed which also use inductive sensors and are based on the assumption that the shorter the momentum induced by the passing knife in the sensor coil, the sharper the knife. Reference is made to the disclosures of DD 286 735 A5, DD 286 737 A5 and DE 10 2011 005 317 A1. It has been found in experiments, however, that the amplitude and length of the induced pulses also depends on the distance between the enveloping circle described by the rotating knives and the counterknife, since this distance affects the location at which the knives enter the sensitive area of the sensor leave again. Thus, it was not possible to define a reliable relationship between the momentum of the sensor and the sharpness of the chopper blade, which would allow a sharpness value to be deduced with sufficient accuracy.

task

The present invention intends to solve the problem of providing a prior art arrangement for determining the sharpness of chopping knives.

Description of the invention

According to the present invention as defined in the claims, an improved arrangement for detecting the sharpness of knives of a chopper drum is provided.

The system for detecting the sharpness of a plurality of knives distributed around the circumference of a cutterhead rotatable to displace the knives on a web adjacent a bedknife comprises: a distance sensor arranged to set the width of a gap between the bedknife and one of To detect the circumference described the cutting edges of the rotating blades; , a magnetic sensor having a magnet arranged to generate a magnetic flux in the gap between the counterknife and the cutting edges of the knives, and a flow sensor arranged to provide an electrical signal v which influences the passing cutting edges on the magnetic Flow in the gap represents; and an evaluation unit connected to the gap sensor and the magnetic sensor and configured to calculate a radius r representing the sharpness of the cutting edges according to the following equation: r = exp ((v + c1 * d + c2) * c3) where Ci, c2andc3 are constants and exp is the exponential function.

The electrical signal v, which represents an influence of the passing cutting edges on the magnetic flux in the gap, may be the peak voltage or the length of a pulse induced in the flow sensor by a passing cutting edge.

The flow sensor is preferably a coil. The magnetic sensor may be mounted in a bore of the counter-blade or on the counter-blade. The gap sensor may be a magnetoresistive sensor, the flow sensor or an optical sensor.

The evaluation unit is preferably connected to a display unit to indicate the detected radius and / or to give an operator a grinding signal as soon as the detected radius exceeds a predetermined value. The evaluation unit may also be connected to a grinding device to start a grinding process as soon as the detected radius exceeds a predetermined value.

Ausführunasform

The drawings illustrate an embodiment of the invention which will be described in more detail below.

Fig. 1 is a schematic left view of a forage harvester on which the system according to the invention can be used.

Fig. 2 is a schematic representation of a system according to the invention for detecting the sharpness of a plurality of knives.

Fig. 3 is a graph showing a number of voltage curves as detected by the flow sensor at different radii of the cutting edges.

4 is a diagram illustrating a number of voltage curves as detected by the flow sensor at different cutting gaps.

Fig. 5 is a flow chart after which a microprocessor proceeds to determine the radius of the cutting edges.

A harvester shown in FIG. 1 in the form of a self-propelled forage harvester 10 builds on a frame 12 which is supported by front and rear wheels 14 and 16. The operation of the harvesting machine 10 takes place from a cabin 18, from which a pickup 20 can be viewed. Material received by the picker 20 from the ground, such as grass or the like, is fed to a rotary chopper drum 22 which is provided with chopper blades 48 distributed around its circumference and chops the crop into small pieces and feeds it to a conveyor 24. The material exits the harvester 10 through an adjustable spout 26 on a side-by-side trailer. A grain processor 28, through which the crop is fed tangentially to the conveyor 24, extends between the chopper drum 22 and the conveyor 24. However, the grain processor is typically removed from the forage harvester 10 during grass harvesting and used only for maize harvesting.

Between the pickup 20 and the cutterhead 22, the material is under

Prepress rollers 30, 32 and upper pre-press rollers 34, 36 promoted. The knives 48 distributed around the circumference of the chopper drum 22 cooperate with a counter-blade 38 to chop the material. The counter-blade 38 is provided at both ends with adjusting means 40 adapted to move the counter-blade 38 horizontally in the direction of the chopper drum 22 and away therefrom to adjust the width of the cutting gap. A suitable control method for the adjusting devices 40 is described in US Pat. No. 7,222,804 A, the contents of which are incorporated by reference into the available documents. A sharpener grinder 50 is provided to sharpen the knives 48 as needed.

Reference is now made to FIG. 2, which shows the counter-blade 38, the adjusting device 40 and a knife 48 in more detail. The adjusting device 40 comprises an electric motor which is arranged to displace a connecting rod 52 and thus the counter-blade 38 in the direction of the enveloping circle described by the rotating blades 48 of the chopper drum 22 and away therefrom. The cutting edges of the knives 48 have a radius r, which increases by wear with the operating time and can be reduced by grinding with the grinder 50. The cutting edges of the knives 48 pass the counter-blade 38 at a distance (gap width) which is variable by the adjusting device 40.

The present invention relates to the detection of the distance d and the radius r. For this purpose, a magnetic sensor 54 is disposed in a bore 56 in the counter-blade 38. The bore 56 may be located in the surface of the counter-blade 38 facing the blades 48, as shown in FIG. 2, or in its second side surface (shown on the left in FIG. 2) or on the top or bottom of the counter-blade 38 or separate from the counter-blade 38 attached, but are magnetically connected to it. The magnetic sensor 54 includes a permanent magnet 58 and a magnetic flux sensor 60 in the form of a coil wound around the permanent magnet 58. The permanent magnet 58 could be replaced by an electromagnet. The magnetic flux sensor 60 could be spaced from the permanent magnet and attached to, for example, the underside of the bedknife 38. Instead of a coil and a Hall sensor could be used.

The permanent magnet 58 generates a magnetic flux within the counter-blade 38 made of magnetically conductive material, such as steel. The magnetic flux also extends into the gap between the counter blade 38 and the blades 48 and is detected by the magnetic flux sensor 60. The blades 48 are also made of magnetically conductive material, and thus a blade 48 passing through the gap changes the magnetic flux within the gap and also the magnetic flux within the flow sensor 60. This change in magnetic flux induces a voltage in the magnetic flux sensor 60.

FIG. 3 shows the time-dependent voltage v provided by the magnetic sensor 60 when a blade 48 passes by for knives 48 with different radii r of the cutting edges, but at the same gap distance d from the counter-blade 38. The radius r thus uniquely influences the peak voltages vss and the width At of the pulse, with increasing width and peak voltage with increasing radius. The peak voltage vs and the width Ett of the pulse are linked by the following formula:

(1) where a and b are constants.

On the other hand, the voltage v provided by the magnetic flux sensor 60 also depends on the distance d, as shown for a number of different distances but constant radii r in FIG. The peak voltage vs and the width At of the pulse increase with increasing distance d. Equation (1) also applies here.

The magnetic flux sensor 60 is connected to an input of an amplifier 62 whose output is connected to the input of an analog-to-digital converter 64 whose output is in turn connected to a microprocessor 68 on which a program for evaluating the output voltage of the magnetic flux sensor 60th running. The purpose of the microprocessor 68 is to evaluate the digitized signals of the magnetic flux sensor 60 and to determine the radius r of the cutting edges of the knives 48, solving the problem of the dependence of the signals on both the radius r and the distance d, the latter even the has greater influence on the voltage v has. The amplifier 62, the analog-to-digital converter 64 and the microprocessor 60 form an evaluation unit for determining the gap d and the radius r.

The evaluation unit including the microprocessor 66 operates according to the diagram shown in FIG. After the start in step 100, the distance 102 is evaluated in step 102. This can be done according to the method described in EP 0 943 888 A2, the disclosure of which is incorporated by reference into the present documents, i. by dividing the high-frequency components of the voltage v of the magnetic flux sensor 60 by their low-frequency components (or vice versa) and deriving therefrom the distance d. Alternatively or additionally, the distance d may be detected by another sensor (not shown), e.g. a magnetoresistance sensor attached to the counter-blade 38, which detects the flux generated by the magnet 58, or by an optical sensor (DE 103 46 412 A1, the disclosure of which is incorporated herein by reference).

Another way to determine the distance d is to combine the distance measurement with the time of passing the knife 48 at the magnetic sensor 54. It is typically a lock-in amplifier approach and provides the best option for improving the noise-to-noise ratio of the sensor 54. The timing and thus the distance can be derived only from the signal of the magnetic sensor 54 (as shown in FIG. 4) or in comparison with a signal from a sensor for detecting the respective angle of rotation of the chopper drum 22 to determine the time at which the knife 48 enters the magnetic field and thus determine the distance.

In the following step 104, the peak voltage vSs is derived from the output signal of the converter 64. Alternatively or additionally, the pulse width Δt may be derived from the output signal of the converter 64 and converted to the peak voltage vss based on the equation (1) or vice versa.

Then, in step 106, the radius r is calculated according to the following formula:

(2) where Ci, c2andc3 are constants and exp is the exponential function. The values of the constants c ^ c2 and c3 are determined by test measurements. If Ai is determined instead of vSs in step 104, equation (1) can be substituted into equation (2).

Equation (2) and step 106 thus allow determination of the radius r of the cutting edge of the knives 48 as soon as vSsOderAt on the one hand and the nip width d of the cutting nip on the other hand are known. The influence of the cutting gap d is thus taken into account and can not adversely affect the accuracy of the measurement.

It should be noted that steps 102 and 104 are typically performed for a sufficiently long acquisition time and averages for d and vss are determined and finally used in step 106. During this detection time, the rotational speed of the chopper drum 22 should be constant and correspond to a predetermined value. If the rotational speed should change, this is preferably taken into account in the evaluation.

After step 106, the distance d and the radius r are displayed on a display unit 68 in the cab 18, so that the operator can initiate a grinding operation of the grinder 50 as soon as the radius r exceeds a predetermined threshold, or this is automatically initiated (steps 108 and 112 in FIG. 5).

Having described the preferred embodiment, it will be apparent that various changes are possible. For example, the analog-to-digital converter 64 and the microprocessor 66 could be replaced by a purely analog circuit. The result of step 102 may be used to automatically initiate a column adjustment procedure if the distance d exceeds a predetermined threshold. Finally, it should be noted that two or more magnetic sensors 54 can be distributed over the length of the counter-blade 38, all of which are connected to the evaluation unit.

Drawing texts of Figure 5: 100 Start 102 Distance d 104 Vss 106 Radius r 108 r> Threshold? 110 End '112 Warning on display and / or sharpening

Claims (8)

claims A system for detecting the sharpness of a plurality of knives (48) distributed about the circumference of a chopper drum (22) rotatable to displace the knives (48) on a path adjacent a counterblade (38), comprising: a distance sensor; is arranged to detect the width (d) of a gap between the counter-blade (38) and a circumference described by the cutting edges of the rotating blades (48); a magnetic sensor (54) having a magnet (58) arranged to generate a magnetic flux in the gap between the counter-blade (38) and the cutting edges of the blades (48) and a flow sensor (60) arranged provide an electrical signal v representing an influence of the passing cutting edges on the magnetic flux in the gap; and an evaluation unit connected to the gap sensor and the magnetic sensor (54) and configured to calculate a radius (r) representing the sharpness of the cutting edges (48) according to the following equation: r = exp ((v + ci * d + c2) * c3), where ci, c2andc3 are constants and exp is the exponential function. The system of claim 1, wherein v is the peak voltage v Ss or the length At of a pulse of the flow sensor (60) induced by a passing knife edge. 3. System according to claim 1 or 2, wherein the flow sensor (60) is a coil. A system according to any one of claims 1 to 3, wherein the magnetic sensor (54) is disposed on the counter-blade (38) or in a bore (56) formed therein. A system according to any one of claims 1 to 4, wherein the distance sensor is a magnetoresistive sensor, the flow sensor (60) or an optical sensor. 6. System according to one of claims 1 to 5, wherein the evaluation unit is connected to a grinding device (50). 7. System according to one of claims 1 to 6, wherein the evaluation unit is connected to a display device (68) for displaying the detected radius and / or a grinding signal. A forage harvester (10) comprising a rotatable cutterhead (22) having a plurality of knives (48) distributed about its circumference displaceable into movement on a track adjacent a counterblade (38) and a system according to any one of the preceding claims.