Electric drive method for electric drive equipment

Abstract

In an electric drive system equipped with a spindle that transmits the driving force of an electric motor to a powered device, damage to the spindle due to overload is prevented with a simple configuration. [Solution] The electric drive method for an electric drive equipment of the present invention is an electric drive method for an electric drive equipment that includes a spindle for transmitting the driving force of an electric motor to a driven device, wherein the method predicts the torque generated in the spindle, measures the actual torque generated in the spindle when transmitting the driving force of the electric motor to the driven device, determines whether there is an abnormality using a threshold value calculated based on the predicted torque value and the actual torque value, and if an abnormality is determined, releases the load of the drive system from the electric motor to the driven device.

Description

Technical Field

[0001] The present invention relates to a technique for preventing damage to a spindle due to overload in an electric drive equipment provided with a spindle for transmitting the driving force of an electric motor to an electric-driven device.

Background Art

[0002] In an electric drive equipment provided with a spindle for transmitting the driving force of an electric motor to an electric-driven device, as a method for preventing damage due to overload, for example, a method using the current value of the main motor can be mentioned. This method is a method of monitoring the motor current value constantly measured by the main motor and rapidly stopping the main motor when the motor current value becomes equal to or greater than a certain threshold value.

[0003] In addition to this, there is a method of disposing a part called a shear pin that protects the drive equipment by breaking itself by a shearing force when an excessive torque exceeding a set torque value acts on a fastening part of the drive system (see Patent Document 1).

[0004] In recent years, a method of providing a protection device called a safety set in the drive system has also been developed (see Patent Document 2). The safety set, for example, smoothly performs the relative rotation of the outer cylinder and the inner cylinder by minimizing the frictional force generated between the outer cylinder and the inner cylinder when an excessive torque occurs. As a result, the torque transmission between the outer cylinder and the inner cylinder is blocked, preventing the excessive torque from being transmitted to the drive system.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, the method of monitoring motor current values ​​is affected by the moment of inertia (GD2) of the main motor and reduction gear, so the calculated value is larger than the actual torque actually generated in the spindle during acceleration. Therefore, when using the method of monitoring motor current values, it is necessary to set a high threshold for detecting abnormalities. Also, the cause of overload is mainly abnormal jamming in the rolling rolls. Since it takes time for such overload to be transmitted to the main motor, there is a problem that abnormality detection is delayed.

[0007] Furthermore, the shear pin disclosed in Patent Document 1 may break even when the torque value is below the set value. Therefore, if a shear pin is installed, periodic inspections and replacement work will be required separately.

[0008] Furthermore, while the SafeSet disclosed in Patent Document 2 is easy to install in newly constructed equipment, it requires securing new space when installing it in existing equipment. Therefore, there is a problem in that installing the SafeSet in existing equipment involves a high investment that requires modification of the drive system.

[0009] The present invention aims to provide an electric drive method for an electric drive system equipped with a spindle that transmits the driving force of an electric motor to a powered device, which can prevent spindle damage due to overload with a simple configuration. [Means for solving the problem]

[0010] One method for driving an electric drive system is a method for driving an electric drive system that includes a spindle for transmitting the driving force of an electric motor to a driven device, characterized in that it predicts and calculates the torque generated in the spindle, measures the actual torque generated in the spindle when transmitting the driving force of the electric motor to the driven device, determines whether there is an abnormality using a threshold value calculated based on the predicted torque value and the actual torque value, and if an abnormality is determined, releases the load of the drive system from the electric motor to the driven device.

[0011] Furthermore, the driven device is a rolling mill having rolling rolls for rolling steel material, and it is preferable to calculate the predicted torque value based on the rolling conditions when the steel material is rolled by the rolling mill.

[0012] Furthermore, it is preferable that the predicted torque is calculated using the following equation (1). Tk = 2 × F × Ld × γ ... (1) Here, the symbol Tk is the predicted torque, the symbol F is the rolling load set in the rolling mill, the symbol Ld is the contact arc length between the rolling roll and the rolled material, and the symbol γ is the torque arm coefficient.

[0013] Furthermore, it is preferable that the contact arc length between the rolling roll and the rolled material be calculated using the following equation (2).

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[0014] According to this disclosure, in an electric drive system equipped with a spindle that transmits the driving force of an electric motor to a powered device, damage to the spindle due to overload can be prevented with a simple configuration. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic conceptual diagram showing the configuration of a hot rolling mill as an electrically driven equipment according to one embodiment of the present invention. [Figure 2] (a) is a graph showing an example of the relationship between predicted torque and actual torque, and (b) is a graph showing an example of the relationship between a threshold value obtained from the predicted torque and the actual torque value. [Figure 3] (a) is a graph showing an example of the temporal change in transport speed, (b) is a graph showing an example of the temporal change in motor current value, and (c) is a graph showing an example of the temporal change in actual torque. [Figure 4](a) is a distribution diagram showing an example of the result of measuring the actual torque value in the lead spindle when performing rolling treatment on each of a plurality of rolled materials S, and (b) is a distribution diagram showing an example of the result of measuring the motor current of the actual machine motor when performing rolling treatment on each of the plurality of rolled materials S. [Figure 5] A graph showing the transition of the motor current and the actual torque value measured when the universal joint spindle is damaged, and the output timing of the drive stop signal when applying a certain threshold value to the actual torque value or the threshold value TH in the present embodiment. [Figure 6] (a) is a graph showing an example of the time change of the actual torque at the time of biting, and (b) is a graph showing an example of the time change of the actual torque at the time of noise generation.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The following embodiments illustrate devices and methods for embodying the technical idea of the present invention, and do not specify the configuration to be the following. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

[0017] FIG. 1 is a schematic conceptual diagram showing the configuration of a hot rolling facility as an electric drive facility according to an embodiment of the present invention. The hot rolling facility 10 is a facility for manufacturing a hot rolled steel sheet by hot rolling a steel slab heated to a predetermined temperature in a heating furnace in sequence with a rough rolling mill and a finishing rolling mill.

[0018] As shown in Figure 1, the hot rolling mill 10 includes a main motor 11, a reduction gear 12, a lead spindle 13, a pinion stand 14, universal joint (UJ) spindles 15 and 16, and a rolling mill 20. In the hot rolling mill 10, the driving force of the main motor 11 is distributed vertically from the reduction gear 12 through the lead spindle 13 to the pinion stand 14, and transmitted to the rolling rolls 21a and 21b of the rolling mill 20 via the UJ spindles 15 and 16. Here, the main motor 11 and the rolling mill 20 correspond to the electric motor and driven equipment described in the claims, respectively.

[0019] The drive system, consisting of the reduction gear 12, lead spindle 13, pinion stand 14, and universal joint (UJ) spindles 15 and 16, is installed between the main motor 11 and the rolling mill 20.

[0020] In the hot rolling mill 10, a strain gauge 22, a torque meter 23, a measuring instrument 24, and an anomaly detection device 30 are provided as components to prevent damage to the UJ spindles 15 and 16 due to overload. The strain gauge 22 is provided on the surface of the cylindrical body that constitutes the lead spindle 13. The strain gauge 22 functions as a torque sensor and transmits data non-contact to the torque meter 23. The measuring instrument 24 collects the torque value measured by the torque meter 23 and transmits it to the anomaly detection device 30.

[0021] Here, the torque value acting on the lead spindle 13 is the sum of the torque value acting on the UJ spindle 15 and the torque value acting on the UJ spindle 16. Therefore, by determining whether or not there is an abnormality from the torque measurement result acting on the lead spindle 13 using the strain gauge 22, it is possible to determine whether or not there is an abnormality acting on the UJ spindles 15 and 16.

[0022] In this embodiment, the strain gauge 22 is provided on the lead spindle 13 as an example, but the strain gauge 22 may also be provided on the UJ spindles 15 and 16, for example, to directly measure the load on the UJ spindles 15 and 16.

[0023] The anomaly detection device 30 is a computer composed of, for example, a CPU, ROM, and RAM. The anomaly detection device 30 has functions such as a main control unit 31, a predictive calculation unit 32, and an anomaly determination unit 33, by having the CPU execute a control program stored in the ROM.

[0024] The main control unit 31 controls each part of the abnormality detection device 30. The main control unit 31 outputs the measured value (actual torque value) received from the measuring instrument 24 to the abnormality determination unit 33. The main control unit 31 also performs drive control of the main motor 11 based on the determination result input from the abnormality determination unit 33. Specifically, when the abnormality determination unit 33 determines that an abnormality has occurred, the main control unit 31 sends a drive stop signal to the main motor 11. As a result, the drive of the main motor 11 is stopped, and the load on the drive system (each spindle 13, 15, 16 and pinion stand 14) arranged between the main motor 11 and the rolling rolls 21a and 21b of the rolling mill 20 is released.

[0025] The prediction calculation unit 32 predicts the torque value generated in the lead spindle 13 when the rolling mill 20 performs the rolling process on the rolled material S, based on the rolling conditions of the rolled material S. Hereinafter, the predicted torque value may be referred to as the predicted torque value. The calculation of the predicted torque value will be described later.

[0026] The abnormality determination unit 33 determines whether or not there is an abnormality using the predicted torque value calculated by the prediction calculation unit 32 and the measured value (actual torque value) received from the measuring instrument 24.

[0027] Next, the method for calculating the predicted torque value in the prediction calculation unit 32 will be described. Hereinafter, the symbols T, Tk, and TH will be used to describe the actual torque value, predicted torque value, and threshold value, respectively.

[0028] As described above, the predicted torque value is calculated based on the rolling conditions of the rolled material S in the rolling mill 20. The predicted torque value Tk is calculated, for example, using equation (1) below.

[0029] Tk = 2 × F × Ld × γ ... (1) Here, the symbol F represents the load (set rolling load) applied by the rolling roll 21a to the rolled material S during the rolling process. The symbol Ld represents the contact arc length of the rolling roll 21b that contacts the rolled material S. The symbol γ represents the torque arm coefficient.

[0030] The contact arc length Ld of the rolling roll 21b used in equation (1) above is calculated using the following equation (2).

[0031]

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[0032] The reduction amount ΔH is expressed by the following equation (3).

[0033] ΔH = Hin - Hout ···(3)

[0034] The torque arm coefficient mentioned above is calculated using the following equation (4).

[0035]

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[0036] In equation (4) above, the symbol Hin represents the thickness of the rolled material S before rolling by the rolling rolls 21a and 21b, and the symbol Hout represents the thickness of the rolled material S after rolling by the rolling rolls 21a and 21b.

[0037] As described above, the abnormality determination unit 33 uses the predicted torque value Tk calculated by the prediction calculation unit 32 and the actual torque value T received from the measuring instrument 24 to determine whether or not there is an abnormality.

[0038] As shown in Figure 2(a), the actual torque value T and the predicted torque value Tk converge to a predetermined approximation equation, for example, a linear equation. In Figure 2(a), an example is shown where the approximation equation showing the relationship between the actual torque value T and the predicted torque value Tk is, for example, T = 1.0181Tk.

[0039] Therefore, as shown in Figure 2(b), if the actual torque value T deviates by a predetermined value α or more from the approximate formula showing the relationship between the predicted torque value Tk and the predicted torque value T, it can be determined that an abnormality has occurred. The predetermined value α can be, for example, four times the standard deviation σ of the actual torque value T. By setting it to four times the standard deviation σ, it becomes possible to distinguish whether or not the change in the actual torque value T is due to an overload of the lead spindle 13. Hereinafter, the predetermined value α may be referred to as the margin α.

[0040] The threshold TH mentioned above is calculated by equation (5) below. Here, the margin α is the fracture torque T of the UJ spindles 15 and 16. UJ The value is less than the initial value of the margin α, which is set to, for example, 60 ton·m.

[0041] TH = Tk + α ... (5)

[0042] As mentioned above, the threshold TH is the fracture torque T of the UJ spindles 15 and 16. UJ The value is less than TH. Therefore, when the actual torque value T exceeds the threshold TH, the main motor 11 is stopped, which prevents damage to the UJ spindles 15 and 16. In Figure 2(b), an example is shown where the approximate formula showing the relationship between the maximum actual torque value Tmax and the predicted torque value Tk is, for example, Tmax = 1.143·Tk.

[0043] The following describes the transport speed, motor current, and actual torque displacement of the rolled material S during the rolling process in the rolling mill 20, using Figures 3(a) to 3(c). In Figure 3, the dashed line indicates the timing when the rolling process of the rolled material S in the rolling mill 20 begins, that is, when it is caught in the rolling rolls 21a and 21b.

[0044] As shown in Figure 3(a), when the rolling process of the rolled material S is performed by the rolling mill 20, the transport speed of the rolled material S becomes approximately 140 m / min. When the rolled material S is caught in the rolling rolls 21a and 21b of the rolling mill 20, the transport speed of the rolled material S decreases, and at the same time, the motor current increases. As a result, the transport speed of the rolled material S is accelerated by an acceleration a.

[0045] On the other hand, the actual torque value T increases significantly when the rolled material S is caught in the rolling rolls 21a and 21b of the rolling mill 20, but remains at a nearly constant torque value between 10 and 25 seconds. Furthermore, as the transport speed of the rolled material S is accelerated by acceleration a, the actual torque value T also increases, but the amount of increase is small.

[0046] Therefore, by using the measured actual torque value T and the threshold value TH obtained from the predicted torque Tk calculated based on the rolling conditions of the rolled material S, it becomes possible to appropriately determine whether or not there is an abnormality. Furthermore, depending on the rolling conditions of the rolled material S, the rolling process may be high-load or low-load, but regardless of whether the rolling process is high-load or low-load, it becomes possible to appropriately determine whether or not there is an abnormality.

[0047] Figure 4(a) shows an example of the results of measuring the actual torque value in the lead spindle when rolling each of the multiple rolled materials S, and Figure 4(b) shows an example of the results of measuring the motor current of the actual motor when rolling each of the multiple rolled materials S.

[0048] For example, when measuring the maximum actual torque in the lead spindle 13 (hereinafter referred to as the maximum actual torque value), the maximum value of the maximum actual torque value Tmax was 237 ton·m. On the other hand, when measuring the motor current, the maximum value of the motor current was 167%, and when this value was converted to torque, it was 355 ton·m.

[0049] In other words, by measuring the actual torque at the lead spindle 13 instead of the motor current, it becomes possible to set the threshold value TH lower than the threshold value (motor threshold) used when measuring the motor current. As a result, the threshold can be set with a margin of safety against the torque value at which the UJ spindles 15 and 16 are said to break (for example, 489 ton·m).

[0050] For example, consider a case where, as shown in Figure 5, the motor current (thick line in Figure 5) is measured, and an abnormality is determined when the motor current exceeds the motor threshold (180%) for, for example, 2 seconds. Note that it takes approximately 10 seconds from the time the drive stop signal is output until the drive of the drive system between the main motor 11 and the rolling mill 20 is completely stopped, that is, until the load on the drive system is released. In Figure 5, the UJ spindles 15 and 16 are damaged between the time the drive stop signal is output to the main motor 11 and the time the load on the drive system is released. Note that the UJ spindles 15 and 16 are damaged 3.2 seconds after the drive stop signal is output.

[0051] On the other hand, if the actual torque value (medium-thin line in Figure 5) is measured and the threshold for determining abnormality is kept constant, then when the motor current is measured, a drive stop signal is output. In other words, an abnormality can be determined 2.7 seconds earlier than the timing when the motor current exceeds the motor threshold for 2 seconds.

[0052] Furthermore, when using the threshold TH shown in this embodiment, an abnormality can be detected 6.4 seconds before the motor current is measured and a drive stop signal is output, that is, 2 seconds after the motor current exceeds the motor threshold. In other words, by performing abnormality detection using the threshold TH shown in this embodiment, the presence or absence of an abnormality can be determined earlier than when using motor current. This makes it possible to prevent damage to the UJ spindles 15 and 16.

[0053] In this embodiment, the presence or absence of an abnormality is determined by using the actual torque value T acting on the lead spindle 13 and a threshold value TH obtained by adding a predetermined value α to the predicted torque Tk that is calculated by prediction.

[0054] Incidentally, as shown in Figures 6(a) and 6(b), when the rolling process for the rolled material S is started, that is, when the rolled material S is jammed into the rolling rolls 21a and 21b, or when noise occurs, the actual torque value T may exceed the threshold value TH. In such cases, the UJ spindles 15 and 16 and the lead spindle 13 are temporarily overloaded. However, the overload on each spindle 13, 15, and 16 when the rolled material S is jammed into the rolling rolls 21a and 21b, or when noise occurs, does not damage these spindles. Therefore, it is possible to determine that there is an abnormality if the measured actual torque value T exceeds the threshold value TH for a predetermined period (e.g., 0.5 seconds). This makes it possible to prevent misjudgments when the rolled material S is jammed into the rolling rolls 21a and 21b, or when noise occurs.

[0055] In this embodiment, a hot rolling mill is given as an example of an electric drive system, but the present invention can also be applied to other equipment such as equipment for rolling thick plates or cold rolling equipment.

[0056] <Summary of effects> The electric drive method for the electric drive equipment of this embodiment is a drive method for electric drive equipment equipped with a lead spindle 13 that transmits the driving force of a main motor 11 to a rolling mill 20, and involves predicting the torque generated in the lead spindle 13, measuring the actual torque generated in the lead spindle 13 when the driving force of the main motor 11 is transmitted to the rolling mill 20, determining whether there is an abnormality using a threshold value calculated based on the predicted torque value Tk and the actual torque value T, and if an abnormality is determined, releasing the load of the drive system from the main motor 11 to the rolling mill 20.

[0057] According to this, compared to conventional electric drive equipment, it is only necessary to install strain gauges 22, torque meters 23, measuring instruments 24, etc. on the lead spindle 13, so there is no need to modify existing equipment. Furthermore, since there is no deterioration in the maintainability of existing equipment, it is possible to introduce it with an inexpensive configuration. [Explanation of Symbols]

[0058] 10 Hot rolling equipment 11 Main motor 13 Lead Spindle 20 Rolling mills 21a, 21b Rolling rolls T Actual Torque Value Tk Predicted Torque Value TH threshold

Claims

1. An electric drive method for an electric drive system equipped with a spindle that transmits the driving force of an electric motor to a driven device, The torque generated in the spindle is predicted and calculated, The actual torque generated in the spindle when the driving force of the electric motor is transmitted to the driven device is measured. The presence or absence of an abnormality is determined using a threshold calculated based on the predicted torque value and the actual torque value. An electric drive method for an electric drive system that releases the load of the drive system from the electric motor to the driven device when an abnormality is detected.

2. The driven device is a rolling mill having rolling rolls for rolling steel material, An electric drive method for an electric drive equipment according to claim 1, comprising calculating the predicted torque value based on the rolling conditions when rolling the steel material with the rolling mill.

3. The electric drive method for an electric drive device according to claim 2, wherein the predicted torque value is calculated using the following equation (1). Tk=2×F×Ld×γ...(1) Here, the symbol Tk is the predicted torque value, the symbol F is the rolling load set in the rolling mill, the symbol Ld is the contact arc length of the rolling roll, and the symbol γ is the torque arm coefficient.

4. The electric drive method for an electric drive equipment according to claim 3, wherein the contact arc length of the rolling roll is calculated using the following equation (2). [Math 1] Here, the symbol R represents the radius of the rolling roll, and the symbol ΔH represents the reduction amount.

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