Detection device and detection system

Abstract

A detection device according to an embodiment of the present application detects the presence or absence of a workpiece adhered to the inner wall of a drum of a mill for crushing minerals. This detection device stores an initial torque detected at a preset initial rotation angle, calculates a maximum torque on the basis of the initial torque, the initial rotation angle, and a rotation angle greater than the initial rotation angle, calculates the ratio of the torque at the rotation angle divided by the maximum torque, compares the ratio to a preset threshold, and determines that there is a workpiece adhered to the inner wall of the drum if the ratio is equal to or greater than the threshold.

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE An embodiment of the present invention relates to a detection device and system for detecting the presence or absence of mineral-based workpieces adhering to the inner wall of a mill drum for crushing minerals. [Background technology]

[0002] Mineral resources such as ores are extracted from mines and the like, and then sized to a predetermined size and shape, and then pulverized by a grinding machine such as a ball mill, a semi-autogeneous (SAG) mill, or an autogeneous (AG) mill. Mineral resources fed into the drum of a mill may adhere to the inner wall of the drum during the pulverization process. For example, if the workpieces being pulverized remain in the grinding machine and the operation is interrupted and the drum is stopped for a long period of time, there is a high possibility that the workpieces being pulverized will adhere to the inner wall of the drum. In such a case, when the drum starts to rotate when the operation is resumed, the workpieces may peel off from the inner wall at the top of the drum due to their own weight and fall to the bottom of the drum, damaging the inner wall of the drum.

[0003] The operation of the mill is stopped periodically or irregularly to inspect or maintain the inside of the drum. If the workpiece is found to be stuck to the inner wall of the drum during such an inspection, the stuck workpiece is peeled off from the inner wall of the drum.

[0004] The adhesion of the workpieces, such as ores, to the inner wall of the drum cannot be determined unless the mill is stopped and the inside of the drum is observed. Frequent shutdowns of the mill reduce the productivity of the mineral resource collection and processing process.

[0005] A technology has been developed to detect whether or not a workpiece is stuck to the inner wall of a drum while the mill is in operation. For example, a system is known that measures the drive torque when the workpiece is not stuck to the inner wall of the drum, and detects whether or not the workpiece is stuck from the characteristics of the rotation angle of the electric motor and the drive torque after the mill is restarted (see Patent Document 1). However, the drive system of a mill is often designed and optimized depending on the installation location. Therefore, in a system such as that of Patent Document 1, the torque characteristics must be obtained for each installed mill, and it is difficult to easily detect whether or not the workpiece is stuck to the inner wall of the drum.

[0006] What is needed is a detection device and system that can easily detect the presence or absence of a workpiece adhered to the inner wall of a drum without observing the inside of the drum. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 9,522,400 Summary of the Invention [Problem to be solved by the invention]

[0008] The embodiments of the present invention have been made to solve the above problems, and aim to provide a detection device and detection system that can easily detect the presence or absence of a workpiece adhered to the inner wall of a drum. [Means for solving the problem]

[0009] A detection device according to an embodiment of the present invention detects the presence or absence of a workpiece stuck to the inner wall of a mill drum for crushing minerals, the detection device is configured to: store an initial torque detected at a preset initial rotation angle when a workpiece stuck to the inner wall of the drum is present; calculate a maximum torque at the rotation angle when a workpiece stuck to the inner wall of the drum is present based on the initial torque, the initial rotation angle, and a rotation angle greater than the initial rotation angle; calculate a ratio obtained by dividing the torque at the rotation angle by the maximum torque; compare the ratio with a preset threshold value; determine that no workpiece stuck to the inner wall of the drum is present if the ratio is smaller than the threshold value; and determine that a workpiece stuck to the inner wall of the drum is present if the ratio is equal to or greater than the threshold value after the rotation angle of the drum reaches a first rotation angle greater than the initial rotation angle at which the workpiece can fall off the inner wall of the drum. Effect of the Invention

[0010] Advantageous Effects of Invention According to the embodiments of the present invention, a detection device and detection system are provided that can easily detect the presence or absence of a workpiece adhered to the inner wall of a drum. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic block diagram illustrating a mill according to an embodiment. [Diagram 2] 1A and 1B are schematic diagrams for explaining the operation principle of a detection device according to an embodiment. [Diagram 3] 1A and 1B are schematic diagrams for explaining the operation principle of a detection device according to an embodiment. [Figure 4] 1A and 1B are schematic diagrams for explaining the operation principle of a detection device according to an embodiment. [Diagram 5] 4 is an example of a flowchart for explaining an operation of the detection device according to the embodiment. [Figure 6] 1 is a schematic block diagram illustrating a detection device according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

[0013] FIG. 1 is a schematic block diagram illustrating a mill according to an embodiment. 1, the detection system 1 includes an electric motor 5, a driving device 6, a rotation angle detector 7, a torque detector 8, and a detection device 10. The detection system 1 is provided together with the mill body 4.

[0014] The mill body 4 is connected to the electric motor 5 via a speed changer or the like. The mill body 4 has a rotating drum as described below. The drum is a cylindrical member into which minerals of a predetermined size are fed. The drum of the mill body 4 is rotated by the electric motor 5. The electric motor 5 is a DC motor or an AC motor, and in the case of an AC motor, it is, for example, an induction motor or a synchronous motor. The drive unit 6 is connected to the electric motor 5. The drive unit 6 applies a predetermined voltage to the electric motor 5, causes a predetermined current to flow, and drives the electric motor 5 by a magnetic field generated according to the current.

[0015] The drive device 6 drives the electric motor 5 according to a control program and parameters for the control program that are installed in a main control device (not shown). The drive device 6 drives the electric motor 5 so that the rotation speed follows a speed reference, which is a preset parameter, for example.

[0016] The rotation angle detector 7 is connected to the electric motor 5. The rotation angle detector 7 detects, for example, the number of rotations per unit time of the electric motor 5, and calculates and outputs the rotation angle of the drum of the mill body 4 based on the reduction ratio between the electric motor 5 and the mill body 4. The rotation angle detector 7 is, for example, a measuring device including a rotary encoder or the like. An appropriate rotary encoder such as an optical type or a magnetic type is selected. The rotation angle detector 7 may be integrated with the electric motor 5, or may be installed separately from the electric motor 5. The rotation angle detector 7 detects and outputs the number of rotations per unit time of the electric motor 5, and the detection device 10 may convert the number of rotations of the electric motor 5 into the rotation angle of the drum.

[0017] The torque detector 8 is connected to the drive device 6. The torque detector 8 receives a signal related to the output current from the drive device 6, and calculates and outputs the value of the torque output by the electric motor 5 based on the output current. The torque detector 8 may be integrated with the drive device 6, or may be installed separately from the drive device 6. Alternatively, the torque detector 8 may include an individual torque detection mechanism independent of the drive device 6.

[0018] A detection device 10, which detects whether or not a workpiece is stuck to the inner wall of the drum, is connected to the output of the rotation angle detector 7 and to the output of the torque detector 8. The detection device 10 sequentially inputs data on the rotation angle of the electric motor 5 and data on the torque of the electric motor 5, and detects whether or not a workpiece is stuck to the inner wall of the drum of the mill body 4.

[0019] The detector 10 calculates the torque when the workpiece is stuck to the inner wall of the drum as the maximum torque, and when the measured torque is sufficiently smaller than the calculated maximum torque, it determines that the workpiece is not stuck to the inner wall of the drum.When the measured torque is close to the calculated maximum torque, the detector 10 determines that an object is stuck to the inner wall of the drum.

[0020] The maximum torque Tmax is the maximum value of the torque when the workpiece is stuck to the inner wall of the drum. The detection device 10 calculates the maximum torque Tmax as follows. That is, the detection device 10 inputs an initial torque TL at a preset initial rotation angle θL from the torque detector 8. The initial rotation angle θL is set to a value that is small enough to maintain the workpiece from sticking to the inner wall of the drum.

[0021] The electric motor 5 continues to rotate after the initial rotation angle θL, and the rotation angle θ is detected, for example, periodically by the rotation angle detector 7. Each time the rotation angle θ is detected, the detection device 10 applies the value of the rotation angle θ and the value of the initial torque TL to equation (1) described later to calculate the maximum torque Tmax at the rotation angle θ.

[0022] Each time the detection device 10 calculates the maximum torque Tmax, it calculates the ratio of the maximum torque Tmax to the actually measured torque T. The detection device 10 compares a preset threshold value α with T / Tmax, and when T / Tmax is smaller than the threshold value α, it determines that no material is stuck on the inner wall of the drum. When T / Tmax is equal to or greater than the threshold value α, the detection device 10 determines that material is stuck on the inner wall of the drum.

[0023] In order to facilitate understanding of the detection device 10 of the embodiment, the operation principle of the detection device 10 will be described. 2 to 4 are schematic diagrams for explaining the operation principle of the detection device according to the embodiment. 2 to 4 show the drum 40 constituting the mill body 4 shown in FIG. 1. The drum 40 shown in FIGS. 2 to 4 is drawn so that the inside can be seen. Workpieces P0 to P2 are arranged inside the drum 40. In FIGS. 2 to 4, the drum 40 rotates counterclockwise around C together with the workpieces P0 to P2. The progression of the drawing numbers from FIG. 2 to FIG. 3 to FIG. 4 indicates the passage of time.

[0024] 2 to 4, workpieces P0 to P2 are made of the same material and have the same mass M. G is the center of gravity when mass M is treated as a concentrated mass. r is the shortest distance between center C and center of gravity G. Workpieces P0 to P2 can change shape as drum 40 rotates, but in the following description, unless otherwise specified, center of gravity G is assumed to be constant at a position distance r away from center C.

[0025] FIG. 2 shows the drum 40 before the mill body 4 is started up. As shown in Fig. 2, the workpiece P0 is staying at the bottom of the drum 40. It is assumed that the workpiece P0 is fixed to the inner wall of the drum 40. The workpiece P0 is subjected to a force F = gM in the direction of gravity due to its own mass M. The rotation angle of the drum in the state of Fig. 2 is a reference value, and the rotation angle at this time is, for example, 0°. In the following, it is assumed that the rotation angle is an angle based on 0°.

[0026] FIG. 3 shows a state in which the mill body 4 starts from the state shown in FIG. 2 and the drum 40 rotates counterclockwise by an initial rotation angle θL. As shown in FIG. 3, the workpiece P1 is fixed to the inner wall of the drum 40, and the initial rotation angle θL is the angle between the line segment connecting the center C and the center of gravity G in FIG. 3 and the line segment connecting the center C and the center of gravity G in FIG. 2.

[0027] 3, the force F due to gravity at the center of gravity G is resolved into components tangential and normal to the circumference of the drum 40. The component tangential to the circumference of the drum 40 is calculated as gMsinθL, and the component normal to the circumference of the drum 40 is calculated as gMcosθL.

[0028] A moment is generated in the workpiece P1 based on a force gMsinθL in the tangential direction of the circumference of the drum 40. The moment at this time is calculated as rgMsinθL using the distance r between the center C and the center of gravity G.

[0029] In the state of Fig. 3, the driving device 6 generates a torque to drive the electric motor 5 so as to overcome the moment of rgMsinθL. The torque at the initial rotation angle θL is referred to as an initial torque TL. The detection device 10 performs the following calculations assuming that the initial torque TL is equal to rgMsinθL.

[0030] 4 shows the state of the inside of the drum 40 when the drum 40 rotates further counterclockwise from the initial rotation angle θL to reach a rotation angle θ. The rotation angle θ is the angle between the line segment connecting the center C and the center of gravity G in FIG. 4 and the line segment connecting the center C and the center of gravity G in FIG. 2.

[0031] As shown in Figure 4, the force F due to gravity at the center of gravity G is resolved into components tangential and normal to the circumference of the drum 40, as in Figure 3. The component tangential to the circumference of the drum 40 is calculated as gMsinθ, and the component normal to the circumference of the drum 40 is calculated as gMcosθ.

[0032] 4, a moment is generated in the workpiece P2 based on a force gMsinθ in the tangential direction of the circumference of the drum 40. The moment at this time is calculated as rgMsinθ using the distance r between the center C and the center of gravity G.

[0033] When the workpiece P2 is stuck to the inner wall of the drum 40, the drive device 6 generates a torque to drive the electric motor 5 so as to overcome the moment of rgMsinθ. When the workpiece P2 is not stuck to the inner wall of the drum 40, the drive device 6 can drive the electric motor 5 with a torque sufficiently smaller than rgMsinθ. Therefore, rgMsinθ can be set as the maximum torque Tmax generated by the drive device 6 during the operation of the detection device 10.

[0034] The maximum torque Tmax is calculated by applying the initial torque TL, the initial rotation angle θL, and the rotation angle θ to the following equation (1).

[0035] Tmax = rgMsinθ =rgMsinθL×(sinθ / sinθL) =TL × (sinθ / sinθL) (1) Here, θ>θL.

[0036] The initial torque TL is detected by the torque detector 8 and input to the detection device 10. The initial rotation angle θL and the rotation angle θ are detected by the rotation angle detector 7 and input to the detection device 10. The detection device 10 can calculate the maximum torque Tmax by using the formula (1).

[0037] A threshold value α is set in advance in the detection device 10. The detection device 10 calculates the ratio between the maximum torque Tmax and the actual torque T detected by the torque detector 8, calculates T / Tmax every time it detects the rotation angle θ, and compares the calculated result with the threshold value α.

[0038] The initial rotation angle θL is set to a rotation angle small enough to keep the workpiece adhered to the inner wall of the drum. When starting the motor 5, a larger starting torque is required than during steady operation. Therefore, the initial rotation angle θL is preferably set to a rotation angle after the motor 5 has overcome the starting torque, and is set to an appropriate value depending on the mechanical constants of the motor 5 and the mill body 4. The initial rotation angle θL is set to, for example, about 20°.

[0039] The threshold value α is set to an appropriate value through experiments, simulations, or the like depending on the mill body 4. Note that when θ=90°, Tmax is at its maximum value, so that the threshold value α is a value smaller than 1.

[0040] Even if the drum 40 rotates beyond the initial rotation angle θL, T / Tmax is 1 regardless of the presence or absence of a workpiece until the workpiece starts to deform. Therefore, when the drum 40 exceeds the initial rotation angle θL, T / Tmax exceeds the threshold value α, and the detection device 10 judges that the workpiece is stuck even if the workpiece is not stuck. Therefore, in the detection device 10 of this embodiment, a stuck object presence / absence detection angle (first rotation angle) θC is set to detect the presence or absence of a stuck object. Until the rotation angle θ of the drum 40 reaches θC, even if T / Tmax is equal to or greater than the threshold value α, the detection device 10 does not judge that the comparative object is stuck. The stuck object presence / absence detection angle θC is selected to be an angle at which the workpiece starts to deform without any sticking of the workpiece. The stuck object presence / absence detection angle θC is set to be, for example, about 60°.

[0041] The above-mentioned series of operations will be explained using a flowchart. FIG. 5 is an example of a flowchart for explaining the operation of the detection device according to the embodiment. As shown in FIG. 5, in step S1, the detection device 10 inputs the initial rotation angle θL detected by the rotation angle detector 7, inputs the initial torque TL detected by the torque detector 8, and stores the initial rotation angle θL and the initial torque TL.

[0042] In step S2, the rotation angle detector 7 detects that the rotation angle θ has reached the stuck object presence detection angle θC, and the torque detector 8 detects the torque at the rotation angle θ. The detection device 10 receives input of the detected data of the rotation angle θ and the data of the torque T.

[0043] In step S3, the detection device 10 calculates the maximum torque Tmax using the stored initial rotation angle θL, the stored initial torque TL, and the input rotation angle θ.

[0044] In step S4, the detection device 10 calculates T / Tmax and compares the calculation result with a preset threshold value α. If T / Tmax is smaller than the threshold value α, the detection device 10 determines in step S6 that no stuck object is present. If the calculated T / Tmax is equal to or larger than the threshold value α, the detection device 10 determines in step S5 that a stuck object has been detected on the inner wall of the drum 40.

[0045] The detection device 10 of the embodiment is a computer device that executes each step of the flowchart shown in Fig. 5, and the computer device stores a program including each step in a storage device or the like, and reads and executes it when necessary. The computer device that realizes the detection device 10 may be a programmable logic controller (PLC). The contents of the flowchart shown in Fig. 5 may be applied to a control program executed on the PLC.

[0046] FIG. 6 is a schematic block diagram illustrating a detection device according to an embodiment. In FIG. 6, the flow chart shown in FIG. 5 has been rewritten to represent the control program implemented in the PLC. The operation of the detection device 10 according to the embodiment will be described below with reference to FIG. As shown in FIG. 6, the detection device 10 includes comparison / determination elements 11, 18, and 19, a storage element 12, calculation elements 13 to 17, numerical limiting elements 21 and 22, and an OR logic element . An initial rotation angle θL is preset in the detection device 10. In this example, a numerical limiting element 21 is provided at an input terminal A for the initial rotation angle. The initial rotation angle θL input to the input terminal A is input to one terminal of a comparison / determination element 11.

[0047] The numerical limiting element 21 is provided to limit the range of the initial rotation angle θL in advance, and for example, a maximum limiting value greater than the rotation angle when the starting torque of the electric motor 5 is generated and a minimum limiting value smaller than 45° are set. The setting of the numerical limiting element 21 is arbitrary, and the numerical limiting element 21 does not necessarily have to be provided.

[0048] The rotation angle θ of the drum 40 obtained from the electric motor 5, or the rotation angle θ of the drum 40 obtained by another method, is detected by the rotation angle detector 7 and input to the input terminal B. The input rotation angle θ is input to the other terminal of the comparison and judgment element 11.

[0049] The comparison and determination element 11 outputs a pulse when the rotation angle θ becomes larger than the initial rotation angle θ L. The output pulse is input to the memory element 12.

[0050] The torque T detected by the torque detector 8 is input to the input terminal C. The input torque T is input to the storage element 12. The storage element stores the torque T when it receives the pulse output by the comparison / determination element 11. Since the pulse output when the rotation angle θ exceeds the initial rotation angle θL is input to the storage element 12, the data stored in the storage element 12 is the initial torque TL at the initial rotation angle θL.

[0051] The storage element 12 outputs the initial torque TL. The rotation angle θ input to the input terminal B is input to the calculation element 13. The calculation element 13 performs a sine calculation and outputs sin θ.

[0052] The calculation element 14 receives the sin θ calculated by the calculation element 13 and the initial torque TL from the storage element 12, and outputs the result TL sin θ obtained by multiplying these.

[0053] The initial rotation angle θL input from the input terminal A is input to the calculation element 15. The calculation element 15 executes a sine calculation and outputs sin θL.

[0054] The calculation element 16 divides TL·sinθ calculated and output by the calculation element 14 by sinθL calculated and output by the calculation element 15, and outputs the result as the maximum torque Tmax. Detailed calculations utilize the derivation process of the above-mentioned formula (1). In this example, the output of the calculation element 16 is provided with a numerical limiting element 22. The numerical limiting element 22 is provided to eliminate inappropriate calculation results due to calculation errors occurring in each calculation element.

[0055] The calculation element 17 divides the torque T detected by the torque detector 8 by the maximum torque Tmax calculated and output by the calculation element 16, and outputs the result.

[0056] A threshold value α is preset at one terminal D of the comparison and judgment element 18 and is input to the comparison and judgment element 18. The other terminal of the comparison and judgment element 18 receives T / Tmax calculated and output by the calculation element 17. The comparison and judgment element 18 compares T / Tmax with the threshold value α, and if T / Tmax is smaller than the threshold value α, it determines that there is no material stuck to the inner wall of the drum, and outputs a signal (Y) indicating that there is no material stuck. If T / Tmax is equal to or larger than the threshold value α, the comparison and judgment element 18 determines that there is material stuck to the inner wall of the drum 40, and outputs a signal (N) indicating that there is material stuck. In this example, the signal (Y) indicating that there is no material stuck corresponds to a logical value "1", and the signal (N) indicating that there is material stuck corresponds to a logical value "0".

[0057] The output of comparison and judgment element 18 is determined based on the magnitude relationship between the rotation angle θ and the stuck-object presence / absence detection angle θC. The comparison and judgment between the rotation angle θ and the stuck-object presence / absence detection angle θC is performed by comparison and judgment element 19. One input of comparison and judgment element 19 is connected to terminal B, and the rotation angle θ is input. The other input of comparison and judgment element 19 is connected to terminal E, and a preset stuck-object presence / absence detection angle θC is input.

[0058] An output of the comparison and judgment element 18 is connected to one input of the OR logic element 23 , and an output of the comparison and judgment element 19 is connected to the other input of the OR logic element 23 .

[0059] When the comparison / determination element 19 determines that the rotation angle θ is smaller than the object presence / absence detection angle θC, it outputs a logical value of “1.” Therefore, the logical value of “1” is input to the OR logical element 23, so that the OR logical element 23 outputs a logical value of “1,” i.e., a signal (Y) indicating that no object is present, regardless of the output of the comparison / determination element 18.

[0060] When the comparison and judgment element 19 judges that the rotation angle θ is equal to or greater than the stuck object presence / absence detection angle θC, it outputs a logical value of "0." Therefore, the OR logic element 23 outputs the logical value of the output of the comparison and judgment element 18. That is, when the comparison and judgment element 18 outputs a signal (N) indicating that a stuck object is present, the OR logic element 23 outputs a signal (N) indicating that a stuck object is present. When the comparison and judgment element 18 outputs a signal (Y) indicating that no stuck object is present, the OR logic element 23 outputs a signal (Y) indicating that no stuck object is present.

[0061] In this manner, the detection device 10 of the embodiment can determine whether or not a mineral-based workpiece is stuck to the inner wall of the drum.

[0062] The above-mentioned detection device 10 operates when the mill body 4 is started up after being stopped for inspection or the like. In other words, when the mill body 4 is started up and the drive device 6 starts driving the electric motor 5, the detection device 10 operates to detect whether the workpiece is stuck to the inner wall of the drum. If the detection device 10 detects that the workpiece is stuck, it generates, for example, a stop command to stop driving the electric motor 5. The main control device (not shown) that receives the stop command uses an interlock to stop the operation of the mill body 4 itself. This allows the stuck-on material to be safely removed.

[0063] When the detector 10 detects that the workpiece is stuck to the inner wall of the drum, the detector 10 may generate a command to the main controller to perform a workpiece removal operation to remove the stuck workpiece, without being limited to the above. For example, when performing a workpiece removal operation, the main controller rotates the workpiece in the opposite direction to the current rotation direction by about -90°, and then rotates it in the original rotation direction, shaking the workpiece and removing the sticking.

[0064] If the detector 10 does not detect the workpiece sticking to the inner wall of the drum, it may continue to operate as is, or it may stop operating after a preset rotation angle has elapsed.

[0065] The effects of the detection device 10 according to the embodiment will be described. In the detection device 10 of the embodiment, the torque when the workpiece is stuck to the inner wall of the drum can be calculated as the maximum torque Tmax based on the rotation angle detected by the rotation angle detector 7 of the electric motor 5 and the torque detected by the torque detector 8. The maximum torque Tmax can be easily calculated using formula (1). Therefore, by appropriately setting the threshold value α, it is possible to easily determine whether the workpiece is stuck to the inner wall of the drum.

[0066] In the embodiment of the detection device 10, the detection device 10 performs the sticking determination as described above, so there is no need to obtain the torque characteristics of the electric motor, including the mechanical system such as the drum, for each installation state of the mill or each type and state of the workpiece, making installation and adjustment easy.

[0067] In this way, a detection device is realized which can easily detect the presence or absence of a workpiece adhered to the inner wall of the drum.

[0068] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments can be implemented in combination with each other. [Explanation of symbols]

[0069] 1 mill, 4 mill body, 5 electric motor, 6 driving device, 7 rotation speed detector, 8 torque detector, 10 detection device, 11, 18, 19 comparison and judgment element, 12 memory element, 13 to 17 calculation element, 21, 22 numerical limiting element, 23 OR logic element, 40 drum

Claims

1. A detection device for detecting the presence or absence of a workpiece adhered to an inner wall of a drum when a mill for crushing minerals is started, comprising: An initial torque detected at a predetermined initial rotation angle of the drum when a workpiece is stuck to the inner wall of the drum is stored; Calculating a maximum torque at the rotation angle when a workpiece adhered to an inner wall of the drum is present, based on the initial torque, the initial rotation angle, and a rotation angle greater than the initial rotation angle; Calculating a ratio of the torque detected at the rotation angle divided by the maximum torque; Comparing the ratio with a preset threshold value; determining that no workpiece is present on the inner wall of the drum if the ratio is less than the threshold value; A detection device configured to determine that a workpiece is present on the inner wall of the drum when the ratio is equal to or greater than the threshold value after the rotation angle of the drum reaches a first rotation angle that is greater than the initial rotation angle and at which the workpiece may fall off the inner wall of the drum.

2. When the maximum torque is Tmax, the initial torque is TL, the rotation angle is θ, and the initial rotation angle is θL, The detection device of claim 1 , wherein calculating the maximum torque comprises performing a calculation according to equation (1). Tmax=TL×(sinθ / sinθL) (1)

3. 2. The detection system of claim 1, further comprising: a detector for detecting the presence of a workpiece adhered to the inner wall of the drum, the detector generating a command to stop operation of the mill.

4. 2. The detection device according to claim 1, wherein, when it is determined that a workpiece is present on the inner wall of the drum, a command is generated to rotate the drum in a direction opposite to the current direction of rotation, and then rotate the drum in the original direction of rotation, thereby shaking the workpiece to remove the workpiece from the inner wall.

5. an electric motor for driving the drum of the mill; A drive device that drives the electric motor; a rotation angle detector for detecting a rotation angle of the electric motor; a torque detector for detecting a torque output by the driving device; A detection device according to claim 1; Equipped with The mill is any one of a ball mill, a SAG mill, and an AG mill, the rotation angle detector successively detects the rotation angle and transmits it to the detection device; The torque detector detects the initial torque and transmits it to the detection device, and sequentially detects the torque at the rotation angle and transmits it to the detection device; The detection system includes a detection device that calculates the ratio each time the detection device receives the torque at the rotation angle, compares the ratio with the threshold value, and determines whether the ratio is larger or smaller than the threshold value.

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