Electric drive equipment, electric drive method, and method for manufacturing hot-rolled steel sheets

Abstract

To provide an electric drive technology having a protection function which can be applied to an existing facility and is excellent in introduction cost and maintainability.SOLUTION: An electric drive facility that includes a spindle having one end connected to an electric motor side and the other end connected to a driven device side, comprises: a torque sensor mounted on a surface of a cylindrical body constituting the spindle; a torque measurement device main body for supplying electric power to the torque sensor and collecting data from the torque sensor; abnormality determination means for determining the presence or absence of abnormality on the basis of the torque value of the spindle transmitted from the torque measurement device main body; and control means for performing predetermined abnormality avoidance measures to a drive system from the electric motor to the driven device when the torque value is determined to be abnormal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for preventing damage to a spindle due to overload in equipment that transmits the driving force of an electric motor via the spindle.

Background Art

[0002] As a method for overload protection of driving equipment by a conventional electric motor, there is an abnormality detection method using the current value of the electric motor. For the following formula (1), known values are substituted for the output W of the electric motor, the reference rotational speed N, and the rated current value I0, and the feedback of the actual current value I of the electric motor that is constantly measured is applied to calculate the generated torque T. And it is a method of rapidly stopping the electric motor when an abnormal torque occurs based on the calculated torque. Also, there is a method of providing a component called a shear pin that protects other drive devices including the spindle by breaking itself by a shearing force when an excessive torque acts on the fastening portion between the spindle and the drive equipment. (Formula 1) T=(974·W / N)·(I / I0) Here, T: torque [kgf·m] (×9.8 Nm), W: output of the electric motor [kW], N: reference rotational speed [rpm] (1 / min), I: actual current value [A], I0: rated current value of the electric motor [A].

[0003] And in recent years, there is also a case where a safety set is introduced between the spindle and the drive equipment or the electric motor as a protection device as described in Patent Document 1. This safety set encloses hydraulic pressure in one of the double cylinders, and transmits torque to one cylinder by the frictional force generated by the stress generated on the inner surface by the hydraulic pressure. And when an excessive load occurs, the enclosed hydraulic pressure is released, and the frictional force generated between the inner cylinder and the outer cylinder is released, so that the inner cylinder and the outer cylinder behave like a sliding bearing. By doing so, torque transmission is stopped and an excessive load can be prevented from being transmitted to the spindle and other drive equipment. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-257382 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the above-mentioned conventional technology had the following problems. In other words, in torque calculations based on the current value of an electric motor, the external disturbances in the current value used in the calculation are large, making the factors causing torque fluctuations unclear. Therefore, torque values ​​can fluctuate not only due to physical overload but also due to electrical noise, and it is difficult to capture fine behaviors such as torque fluctuations associated with torsional vibrations that occur when the drive shaft is subjected to a load. In addition, the moment of inertia of the electric motor and other drive equipment affects the motor's drive. As a result, there is a problem in that the calculated torque is larger than the actual torque being generated. Moreover, the electric motor is located at the input end of the drive system, and in many cases, malfunctions due to overload occur on the output end equipment side, where the torque is transmitted. For example, if there is a rotating roll at the output end, and the rotation of the roll is constrained for some reason, the overload is transmitted from the roll to the spindle and finally to the electric motor. Therefore, with control based on the electric motor's current value, load detection is delayed, and there are cases where the allowable torque that would destroy the spindle is exceeded by the time the motor detects the overload.

[0006] Shear pins, as protective devices, must not break under steady-state torque, but under excessive torque, they must break under a load lower than the damaging load on the spindle or other drive equipment. Therefore, setting the breaking torque of the shear pin is extremely difficult, and if the shear pin breaks, there is a problem that the connection between the spindle and the motor or surrounding drive equipment is severed. If the connection is severed in the middle of the drive system, the spindle may swing around due to inertia, potentially damaging surrounding equipment, and repairing the shear pin is extremely difficult.

[0007] Furthermore, while the technology described in Patent Document 1 is easy to incorporate into newly installed equipment, there are many problems with its introduction into existing equipment. For example, introducing new components between drive units necessitates changing their respective layouts. As a result, the introduction cost, including modifications to the existing equipment, becomes a considerably high investment.

[0008] The present invention has been made in view of the above, and aims to provide an electric drive system and an electric drive method that are applicable to existing equipment and have excellent protection functions with low installation costs and ease of maintenance. In addition, the present invention provides a method for manufacturing hot-rolled steel sheets using the same equipment. [Means for solving the problem]

[0009] In order to achieve the above-mentioned objectives, the inventors conducted extensive research and obtained the following findings: They discovered that it is possible to protect electric drive equipment by directly measuring actual torque and using that data to determine overload.

[0010] The electric drive equipment according to the present invention, which advantageously solves the above problems, is an electric drive equipment comprising a spindle with one end connected to an electric motor and the other end connected to a driven device, characterized in that it comprises a torque sensor installed on the surface of a cylindrical body constituting the spindle, a torque measuring device body that supplies power to the torque sensor and collects data from the torque sensor, an abnormality determination means that determines whether or not there is an abnormality based on the torque value of the spindle transmitted from the torque measuring device body, and a control means that performs predetermined abnormality avoidance measures on the drive system from the electric motor to the driven device when the torque value is determined to be abnormal.

[0011] Furthermore, a more preferable solution for the electric drive equipment according to the present invention is that the electric drive equipment is a rolling mill, the driven equipment is a rolling mill, and the torque sensor is a non-contact strain gauge.

[0012] The spindle according to the present invention, which advantageously solves the above problems, is a spindle provided in the above-mentioned electric drive equipment, characterized in that one end is connected to the electric motor side, the other end is connected to the driven equipment side, and a torque sensor is installed on the surface of the cylindrical body. The hot rolling mill according to the present invention, which advantageously solves the above problems, is characterized in that it has the above-mentioned spindle.

[0013] The electric drive method according to the present invention, which advantageously solves the above problems, is characterized in that, when transmitting the driving force of an electric motor to a driven device via a spindle, the torque of the spindle is directly measured, and when the obtained torque value exceeds a predetermined value (a torque threshold for determining torque abnormality), a torque abnormality is determined, and predetermined abnormality avoidance measures are taken.

[0014] Furthermore, in the electric drive method according to the present invention, a more preferable solution is that the driven equipment is a rolling mill, and the abnormality avoidance measure is the release of the load on the drive system from the electric motor to the driven equipment.

[0015] The method for manufacturing a hot-rolled steel sheet according to the present invention that advantageously solves the above problems involves, when hot-rolling a steel slab heated to a predetermined temperature in a heating furnace using the above rolling equipment with a rolling mill, constantly monitoring the torque value of the spindle during rolling, determining an abnormality when the torque value becomes equal to or greater than a predetermined value, and taking predetermined abnormality avoidance measures.

Advantages of the Invention

[0016] According to the electric drive equipment, the electric drive method, and the method for manufacturing a hot-rolled steel sheet according to the present invention, a torque measuring device capable of measuring the actual torque is used. Therefore, excessive equipment modification is unnecessary, and even when the torque sensor fails, only the torque sensor needs to be replaced, and there is no need to remove the drive system. It is excellent in terms of introduction cost and maintainability, and thus is industrially useful.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic conceptual diagram showing the configuration of a rolling equipment as an electric drive equipment according to an embodiment of the present invention. [Figure 2] It is a flowchart showing the configuration of abnormality avoidance measures implemented by the equipment according to the above embodiment. [Figure 3] It is a graph showing an example of the transition between the torque value calculated from the current value of the electric motor and the actual torque value of the lead spindle connected to the rolling roll for the fifth rolling mill of the finishing rolling mill. [Figure 4] It is a graph showing an example of the transition between the torque value calculated from the current value of the electric motor and the actual torque value of the lead spindle connected to the rolling roll for the second rolling mill of the finishing rolling mill. [Figure 5] It is a graph showing the distribution between the actual torque and the torque value calculated from the current value of the electric motor for the second roll of the finishing rolling mill.

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The following embodiments illustrate apparatuses and methods for embodying the technical idea of the present invention, and do not specify the configuration to the following. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

[0019] FIG. 1 is a schematic conceptual diagram showing the configuration of a rolling facility as an electric drive facility according to an embodiment of the present invention. FIG. 2 is a flowchart showing the configuration of an abnormality avoidance measure implemented by the facility according to the above embodiment.

[0020] The rolling facility 100 shown in FIG. 1 passes the rolled material 1 through the rolling mill 2 for rolling. In the rolling facility 100, the driving force of the main machine 7, which is an electric motor, is distributed vertically by the pinion stand 4 from the main reducer 6 via the lead spindle 5. Each driving force is transmitted to the rolling mill 2 via the universal joint spindle 3.

[0021] In this embodiment, a strain gauge 8A as a torque sensor is installed on the surface of the cylinder body constituting the universal joint spindle 3 or the lead spindle 5. Then, data is transmitted non-contact from the strain gauge 8A to the torque measurement device main body 8.

[0022] In this embodiment, the torque value measured by the torque measurement device main body is collected by the data logger 9, which is a measuring instrument, and transmitted to the abnormality detection system 10.

[0023] The abnormality detection system 10 selectively evaluates the abnormality of the torque value from other abnormalities according to the flow of FIG. 2 and is incorporated into the rapid stop procedure of the rolling mill. In the example of FIG. 2, any one of the following eight is determined (S09) as an abnormal phenomenon to be the target of automatic trouble detection (S12). S01: In the plate break determination, it is determined whether the rolled material 1 has broken during rolling. S02: In the bite delay determination, it is determined whether there is a failure in the biting of the rolled material 1 into the rolling mill 2. S03: Guide derailment detection determines abnormalities caused by meandering of the rolled material 1. S04: In the case of a main engine speed abnormality, determine whether the motor 7 is within the range of its rated output. S05: In roll breakage, it is determined whether the rolling rolls constituting the rolling mill 2 have cracked or chipped. S06: In the case of a main unit digital thyristor malfunction (main unit semiconductor element malfunction), it is determined whether there is a malfunction in the main unit's digital thyristor panel (electronic components around the main unit). S07: If the actual values ​​are abnormal, it is determined whether the thickness, width, shape, etc. of the rolled material 1 after rolling are within the specified range. S08: In this embodiment, as an example of an abnormal actual torque, it is determined whether the torque values ​​of spindles 3 and 5 are abnormal.

[0024] If any of the following is detected (S13): automatic trouble detection S12, pressing the emergency stop button on the rolling mill S10, or pressing the emergency stop button on the coiler S11, and the rolling material 1 is being rolled in the rolling mill 2 (S14), then the emergency stop process S16 is performed.

[0025] In this embodiment, the predetermined abnormality avoidance measures refer to, for example, the following processes. The emergency stop process S16 includes the following steps: Forcibly remove the rolled material 1 during rolling (S17). Stop the rolling rolls of the rolling mill 1 while controlling the deceleration (S18). Release the roll reduction of the rolling mill 1 (S19). Emergency stop of hydraulic rolling (S20). Emergency stop of the cooling water for the backup rolls (S21). Emergency stop of the descaling device using high-pressure water (S22).

[0026] In this embodiment, the actual torque of the drive shafts (spindles 3 and 5) constituting the drive system is measured, allowing for more accurate measurement of torque fluctuation behavior compared to the current value of the electric motor 7. In torque calculations based on Equation 1 using the current value of the electric motor 7, the current value generated during acceleration and deceleration becomes large due to the influence of the moment of inertia of the drive system and the main motor 7 itself. Therefore, it was necessary to set the torque setting value for abnormality detection somewhat higher to avoid false detections and unnecessary stops. In this embodiment, by measuring the actual torque, the influence of the moment of inertia required for the rotation of the main motor 7 and the drive system can be ignored. Therefore, it becomes possible to set an appropriate setting value for torque abnormality detection. In addition, there is no longer a need to set the setting value for torque abnormality detection higher as in the past. Therefore, the setting range can be made larger relative to the allowable torque. Consequently, it becomes possible to set appropriate management values ​​for drive equipment that generates a wide variety of loads.

[0027] Furthermore, in this embodiment, excessive load can be detected at an earlier stage than abnormality detection by current value measurement, and commands for abnormality avoidance processing can be issued early. Therefore, it becomes possible to release the load before the allowable torque of the drive equipment is exceeded. Normally, excessive load problems that can occur in the drive system often occur, for example, in the rolling mill 100, not on the main motor 7 side, but when foreign objects get caught in the drive roll 2. In other words, excessive load often occurs at the end of the output of the drive system, so if the main current of the electric motor 7 is measured, it will be at the position furthest from the equipment where the excessive load occurred. Therefore, by the time the excessive load reaches the main motor, the components such as the drive shaft have already been subjected to an excessive load. On the other hand, as in this embodiment, measuring the actual torque in the middle of the drive system makes it possible to detect the occurrence of torque abnormalities closer to the source of the excessive load. Therefore, it becomes possible to issue commands for abnormality processing, such as emergency stop, to the electric drive equipment earlier than if detection were done by the current of the electric motor 7.

[0028] Furthermore, this embodiment has the advantage of requiring almost no modification to existing equipment and not worsening the maintainability of the drive equipment. Safety devices such as the device described in Patent Document 1 require modification of the arrangement and dimensions of the existing drive system, resulting in very high installation costs. While shear pins have lower installation costs than the above safety devices, they have the following problems: Setting the release torque is extremely difficult, resulting in high design and study costs. There is a high risk of accidental release during operation. Even if it operates normally and shears properly, the raised spindle may swing around and damage the surrounding area. Removing and repairing the shear pin is extremely difficult. Therefore, shear pins have very poor maintainability. In comparison to these, the actual torque monitoring technology according to this embodiment does not require any modification to existing equipment, especially by introducing a torque measuring device. If the strain gauge, which is the torque sensor, is damaged, it is only necessary to replace the strain gauge on the cylindrical surface of spindles 3 and 5. Therefore, there is no need to modify or change other devices in the drive system, and it exhibits excellent effects in terms of installation costs and maintainability.

[0029] The above description illustrates a rolling mill, but the embodiment is not limited thereto. This embodiment can be applied to an electric drive system equipped with a spindle having one end connected to an electric motor and the other end connected to a driven device. In this embodiment, a torque sensor 8A is installed on the surface of a cylindrical body that constitutes a drive shaft (spindle) that transmits the input torque of the electric motor, positioned at an intermediate position in the drive system which consists of the driven device, which is the recipient of power, and the electric motor 7, which is the drive source. A torque measuring device body 8, which supplies power to the torque sensor 8A and collects data from the torque sensor 8A, is installed in a position that does not obstruct the operation of the spindle. An abnormality determination means is incorporated into the equipment's abnormality detection system and is constantly monitored as an abnormality determination means that determines whether or not there is an abnormality based on the torque value of the spindle transmitted from the torque measuring device body 8. If the torque value is determined to be abnormal, a control means is provided to perform predetermined abnormality avoidance measures on the drive system from the electric motor 7 to the driven device. This control means is introduced as an excessive torque determination item in the automatic protection function activation items of the drive system by the equipment's abnormality detection system, and is configured so that the drive equipment protection function is activated by the appropriate system if it deviates from a defined control value.

[0030] When introducing measured actual torque data into an operational anomaly detection system for continuous monitoring, it is preferable to set the torque threshold value for determining an anomaly (the torque threshold for determining a torque anomaly) to be greater than or equal to the normal operating torque and less than or equal to the allowable torque of the weakest part of the protected object, for example, the fracture stress. More preferably, it should be set to 180% or less of the maximum normal operating torque. There is no particular lower limit for the maximum normal operating torque, but it should be set within a range that does not misidentify the normal torque as an anomaly, for example, 50% or more of the maximum normal operating torque is preferable. However, this does not apply if 180% of the normal operating torque exceeds the fracture stress of the weakest part of the drive system.

[0031] Pulsating noise may be introduced during torque measurement. On the other hand, pulsed loads due to instantaneous impacts, such as the impact when the rolled material 1 jams in the rolling mill 2, can exceed 1.5 times the normal torque, depending on the equipment structure and operating conditions. To avoid classifying these torque values ​​as abnormal, it is preferable to classify an abnormality only when a high torque value persists for a predetermined period. For example, it is preferable to classify an abnormal torque value when it persists for 0.05 s or longer, which is the period of torsional vibration torque. If the duration for classifying an abnormality is too long, excessive torque will occur for a long time, delaying the activation of protective action and increasing the risk of equipment damage. Therefore, it is preferable to determine an appropriate value based on operating conditions and equipment tolerances. Even more preferable is to calculate the rate of torque increase over a certain period and classify an abnormality by setting a control value for the rate of increase. [Examples]

[0032] Using the hot rolling equipment configuration shown in Figure 1, a torque sensor 8A was installed on the lead spindle 5 to measure the actual torque. In the hot rolling equipment, steel billets heated to a predetermined temperature in a heating furnace are sequentially hot-rolled in a roughing mill and then a finishing mill to produce hot-rolled steel sheets. Figure 3 is a graph showing an example of the transition between the torque value calculated from the electric motor current value and the actual torque value of the lead spindle connected to the rolling rolls for the 5th stage of the finishing mill. Figure 4 is a graph showing an example of the transition between the torque value calculated from the electric motor current value and the actual torque value of the lead spindle connected to the rolling rolls for the 2nd stage of the finishing mill. Figures 3(a) and 4(a) show the transition of the rolling speed (sheet speed). Figures 3(b) and 4(b) show the transition of the torque value calculated from the electric motor current value using Equation 1. Figures 3(c) and 4(c) show the actual torque value measured by the torque measuring device installed on the lead spindle.

[0033] As shown in Figures 3(b) and 4(b), the torque T calculated from the motor current increases with the acceleration a of the rolling speed (plate speed) due to the moment of inertia of the drive system. However, as shown in Figures 3(c) and 4(c), the actual torque T remains constant regardless of the acceleration or deceleration of the rolling speed. Therefore, except for the obvious peak noise Np in Figure 4(c), it can be said that the correct torque is measured in steady state by applying this embodiment. The duration of the peak noise Np was 0.01 s or less.

[0034] Figure 5 shows the distribution of maximum torque measured for the second stage rolling mill of the finishing rolling mill, with the same measurement as in Figure 4 repeated approximately 1500 times. Figure 5(a1) is the distribution of the maximum torque measured when the rolled material is jammed, according to this embodiment. Figure 5(a2) is the distribution of the maximum value of the normal operating torque excluding when the rolled material is jammed, according to this embodiment. Figure 5(b1) is the distribution of the maximum torque when the rolled material is jammed, calculated from the electric motor current value. Figure 5(b2) is the distribution of the maximum value of the normal operating torque excluding when the rolled material is jammed, calculated from the electric motor current value. Figure 5 also shows the fracture stress of the lead spindle 5 as the allowable torque.

[0035] Comparing Figures 5(a1) and (b1) regarding the torque during jamming, the maximum torque calculated from the motor's current value is calculated to be low, about 70% of the actual torque. Therefore, allowing the torque during jamming to reach near the breaking torque of the lead spindle 5 using the torque calculated using the motor's current value is dangerous, as the actual torque will exceed the breaking torque. The reason for this is thought to be as follows: The impact generated in the rolling mill 2 is accurately measured by the actual torque measured at the lead spindle 5. On the other hand, the motor 7 is installed at the downstream end of the drive system to which this impact is transmitted, so the impact is mitigated.

[0036] Comparing the maximum values ​​of the normal operating torque, excluding jamming, it is clear from Figures 5(a2) and 5(b2) that the maximum torque calculated using the motor current value (Figure 5(b2)) is 1.8 times the maximum actual torque (Figure 5(a2)). Despite the same rolling conditions, the difference between the maximum torque calculated using the motor current value and the allowable torque is smaller than that of the actual torque, resulting in a narrower threshold setting range. This demonstrates that the method of this embodiment, which uses actual torque, allows for a very wide range of control values, making it possible to set control values ​​according to operating conditions and equipment characteristics.

[0037] The spindle provided in the electric drive equipment specified in this invention allows for rapid stopping of the electric motor in the event of abnormal torque. This prevents fracture due to shear force when excessive torque is applied to the fastening portion between the spindle and the drive equipment, resulting in significant economic benefits in terms of equipment maintenance. Furthermore, the hot rolling mill having the aforementioned spindle allows for rapid stopping of the electric motor in the event of abnormal torque. This prevents fracture due to shear force when excessive torque is applied to the fastening portion between the spindle and the drive equipment, resulting in significant economic benefits in terms of equipment maintenance for the hot rolling mill. [Industrial applicability]

[0038] The technology according to the present invention eliminates the need for excessive equipment modifications, requires only replacement of the torque sensor in the event of a torque sensor failure, and does not require removal of the drive system. Therefore, it is industrially useful due to its superior cost-effectiveness and maintainability. Furthermore, the range of control value settings is very wide, allowing for the setting of control values ​​according to operating conditions and equipment characteristics. [Explanation of Symbols]

[0039] 100 Rolling Mill Equipment (Electric Drive Equipment) 1 Rolled material 2. Rolling mill (rolling rolls, drive rolls) 3 (Universal Joint) Spindle 4. Pinion Stand 5 (Lead) Spindle 6 Main reducer 7 Main engine (electric motor) 8 Torque measuring device main unit 8A Strain Gauge (Torque Sensor) 9. Measuring Instruments (Data Loggers) 10 Anomaly detection system a acceleration xa has large fluctuations. Tp Peak Torque Np peak noise t1 (the time the rolled material is jammed) t2 Acceleration start time t3 (Time to remove the rolled material)

Claims

1. An electric drive system comprising a spindle with one end connected to the electric motor and the other end connected to the driven device, A torque sensor is installed on the surface of the cylindrical body constituting the spindle, A torque measuring device main body that supplies power to the torque sensor and collects data from the torque sensor, An abnormality determination means for determining whether or not there is an abnormality based on the torque value of the spindle transmitted from the torque measuring device body, The system includes a control means that performs predetermined abnormality avoidance measures on the drive system from the electric motor to the driven device when the torque value is determined to be abnormal, In the abnormality determination means, the control value of the torque that is determined to be abnormal is set within a range of the smaller of the following: greater than or equal to the normal operating torque, 1.8 times the maximum normal operating torque, and the limit torque corresponding to the breaking stress of the weakest part of the protected object. An electric drive device configured to determine an abnormality when the torque value, which is a predetermined value, continues for 0.05 seconds or longer.

2. The aforementioned electric drive equipment is a rolling mill, The driven device is a rolling mill, The torque sensor is a non-contact strain gauge. The electric drive equipment according to claim 1.

3. When transmitting the driving force of an electric motor to a driven device via the spindle, The torque of the aforementioned spindle is directly measured, When the obtained torque value exceeds a predetermined value, it is determined to be a torque anomaly. When implementing the prescribed abnormality prevention measures, The torque threshold for determining abnormality is set within a range of the smaller of the following: above the normal operating torque, 1.8 times the maximum normal operating torque, and the limit torque corresponding to the breaking stress at the weakest point of the protected object. An electric drive method that determines an abnormality when the torque value, which is a predetermined value, continues for 0.05 seconds or longer.

4. The driven device is a rolling mill, The electric drive method according to claim 3, wherein the abnormality avoidance measure is the release of the load on the drive system from the electric motor to the driven device.

5. Using the rolling equipment described in claim 2, When hot-rolling a steel billet that has been heated to a predetermined temperature in a heating furnace using a rolling mill, The rolling process is carried out while constantly monitoring the torque value of the spindle. An abnormality is detected when the torque value exceeds a predetermined value. When implementing the prescribed abnormality prevention measures, The torque threshold for determining abnormality is set within a range of the smaller of the following: above the normal operating torque, 1.8 times the maximum normal operating torque, and the limit torque corresponding to the breaking stress at the weakest point of the protected object. A method for manufacturing hot-rolled steel sheets, wherein an abnormality is determined when the torque value, which is a predetermined value, continues for 0.05 seconds or longer.

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