Backup roll device for multi-stage rolling mill

Abstract

A backup roll device for a multi-roll mill, the backup roll device comprising a shaft, a support body that supports the shaft, a backup roll that is supported on the shaft, and a detector that detects the load applied to the backup roll. The backup roll includes an inner ring that is fixed to the shaft, an outer ring that is arranged on the outside of the inner ring in the radial direction, and a plurality of rolling bodies that are arranged between the inner ring and the outer ring in the radial direction. The detector is attached to the inner ring, and a wiring passage through which a cable for the detector is passed is formed in the shaft along the axial direction of the shaft.

Description

[Technical field]

[0001] The present disclosure relates to a backup roll device for use in a multi-stage rolling mill. [Background technology]

[0002] Patent Document 1 below discloses a multi-stage rolling mill called a Sendzimir mill. As shown in Fig. 1, for example, this multi-stage rolling mill includes a pair of upper and lower rolls 11, four first intermediate rolls 12 supporting the rolls 11, six second intermediate rolls 13 supporting the first intermediate rolls 12, and eight backup rolls 14 supporting the second intermediate rolls 13. The backup rolls 14 are supported by shafts 16 passing through their centers, and the shafts 16 are supported by saddles 18 in a state where they are prevented from rotating. The saddles 18 are supported by a housing 17 of the rolling mill. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-195928 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the multi-stage rolling mill of Patent Document 1, it is not possible to know the degree of load applied to the backup rolls. Therefore, even if an abnormality caused by the load occurs, it cannot be detected until some kind of trouble occurs. In addition, even if a trouble occurs due to an abnormality caused by the load, it is difficult to identify the cause.

[0005] An object of the present disclosure is to provide a backup roll device for a multi-stage rolling mill that is capable of detecting a load applied to a backup roll. [Means for solving the problem]

[0006] The backup roll device of the multi-stage rolling mill disclosed herein is A shaft, A support for supporting the shaft; A backup roll supported by the shaft; A detector for detecting a load applied to the backup roll, The backup roll is An inner ring fixed to the shaft; an outer ring disposed radially outward of the inner ring; a plurality of rolling elements disposed radially between the inner ring and the outer ring, The detector is attached to the inner ring; A wiring passage for passing a cable of the detector is formed axially in the shaft. Effect of the Invention

[0007] According to the backup roll device of the multi-stage rolling mill of the present disclosure, the load applied to the backup roll can be detected by a detector, and therefore, abnormalities caused by the load can be prevented or discovered at an early stage, and the occurrence of troubles caused by the abnormalities can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic side view of a multi-stage rolling mill according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic front view showing a backup roll. [Diagram 3] FIG. 3 is a detailed cross-sectional view of part A in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2. [Diagram 5] FIG. [Figure 6] FIG. 3 is a cross-sectional view taken along the line CC in FIG. 2. [Figure 7] FIG. [Figure 8]FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Overview of the embodiment of the present disclosure> Below, an overview of the embodiments of the present disclosure will be listed and described. (1) A backup roll device of a multi-stage rolling mill according to an embodiment of the present disclosure is A shaft, A support for supporting the shaft; A backup roll supported by the shaft; A detector for detecting a load applied to the backup roll, The backup roll is An inner ring fixed to the shaft; an outer ring disposed radially outward of the inner ring; a plurality of rolling elements disposed radially between the inner ring and the outer ring, The detector is attached to the inner ring; A wiring passage for passing a cable of the detector is formed axially in the shaft.

[0010] The detector cable refers to an electric wire for power distribution, communication, etc., connected to a power source that supplies power to the detector and a recording device that records the detected values ​​of the detector. According to the above-mentioned configuration, the load applied to the backup roll from the reduction roll or intermediate roll of the multi-stage rolling mill can be detected by the detector. Since the shaft has a wiring passage formed along the axial direction, the cable of the detector can be easily routed to a position away from the detector in the axial direction.

[0011] (2) In the backup roll device of the present embodiment, the wire passage includes a first groove formed in the outer circumferential surface of the shaft. With this configuration, the detector cable can be routed along the outer circumferential surface of the shaft, making wiring easy.

[0012] (3) In the backup roll device of the present embodiment, the detector and the first groove are positioned at different phases in the circumferential direction, The wire passage includes a second groove formed in the inner ring and extending circumferentially between the detector and the first groove. According to this configuration, for example, in order to efficiently detect the load from the reduction roll or intermediate roll, if a detector is placed at a circumferential position of the backup roll that receives the load (in other words, at a position where the load is easily detected), the first groove of the shaft will be placed at a position circumferentially away from the position where the load is received. Since the first groove can be a factor in reducing the strength of the shaft, by placing the first groove at a position circumferentially away from the point where the load is received, the burden that the load imparts to the shaft can be reduced.

[0013] (4) In the backup roll device of this embodiment, the circumferential phase difference between the first groove and the detector is preferably 150° or more and 210° or less. With this configuration, the first groove can be disposed in a position as far away as possible from the circumferential position of the backup roll that receives a load from the reduction roll or the intermediate roll.

[0014] (5) The backup roll device of the present embodiment further includes a key that prevents the shaft from rotating relative to the support, The first groove also serves as a key groove into which the key fits. According to this configuration, the number of grooves formed in the shaft can be reduced, and a decrease in the strength of the shaft can be suppressed.

[0015] (6) In the backup roll device of this embodiment, the key is formed with a groove or hole for passing the cable therethrough. With this configuration, even if the key is fitted in the first groove, interference between the key and the cable can be avoided by the groove or hole formed in the key.

[0016] (7) In the backup roll device of this embodiment, the detector is a strain gauge, and a recess for accommodating the detector is formed on the inner peripheral surface of the inner ring. This configuration makes it possible to secure space for mounting a detector on the inner ring, while also promoting deformation (distortion) of the inner ring due to the load from the reduction rolls or intermediate rolls, thereby increasing the sensitivity of the detector to detecting the load.

[0017] (8) In the backup roll device of the present embodiment, the backup roll includes a first backup roll provided with the detector, and a second backup roll disposed at a different axial position from the first backup roll and provided with the detector, The cable of the detector attached to the first backup roll and the cable of the detector attached to the second backup roll pass through the wiring passage formed in the shaft and are pulled out from a common pull-out position. With this configuration, the cables attached to each backup roll can be pulled out from the same position on the shaft, making it easy to wire the cables.

[0018] <Details of the embodiment of the present disclosure> Hereinafter, the details of the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view of a multi-stage rolling mill according to an embodiment of the present disclosure. The multi-stage rolling mill 10 of this embodiment is a 20-stage cluster rolling mill having a 1-2-3-4 roll arrangement. A material W to be rolled, such as a thin plate material, is passed between a pair of upper and lower rolling rolls 11 in the left-right direction of FIG. 1 and rolled. The pair of upper and lower rolling rolls 11 are supported by four first intermediate rolls 12 (two on each side). The four first intermediate rolls 12 are supported by six second intermediate rolls 13 (three on each side). The second intermediate rolls 13 are supported by eight backup rolls 14 (four on each side). Note that one backup roll 14 means a backup roll 14 attached to one shaft 16, and the number of backup rolls 14 attached to the shaft 16 is not particularly limited.

[0019] FIG. 2 is a schematic front view showing the backup roll. The backup roll 14 is attached concentrically to the shaft 16. In this embodiment, a plurality of backup rolls 14 are attached to the shaft 16. The shaft 16 is supported by a saddle (support) 18 supported by a housing 17 (see FIG. 1) of the multi-stage rolling mill 10. The shaft 16 is formed in a cylindrical (hollow) shape, but may be formed in a solid shape. In this embodiment, six backup rolls 14 are arranged at predetermined intervals in the axial direction, and saddles 18 are arranged between the six backup rolls 14 and on the axial outside of the backup rolls 14 at both axial ends. In the following description, the axial direction refers to a direction parallel to the central axis C of the shaft 16 and the backup rolls 14, and the circumferential direction refers to a direction around the central axis C of the shaft 16 and the backup rolls 14.

[0020] FIG. 3 is a detailed cross-sectional view of part A in FIG. Each backup roll 14 is substantially composed of a rolling bearing. Specifically, each backup roll 14 includes an inner ring 20 fixed to the outer circumferential surface of the shaft 16, an outer ring 21 arranged radially outside the inner ring 20, a plurality of cylindrical rollers (rolling elements) 22 arranged between the inner ring 20 and the outer ring 21, and a cage 23 that holds the plurality of cylindrical rollers 22.

[0021] The inner ring 20 is formed in a cylindrical shape, and has a raceway on its outer circumferential surface along which cylindrical rollers 22 roll. The inner ring 20 is fitted to the outer circumferential surface of the shaft 16 by a clearance fit (loose fit). However, the inner ring 20 may also be fitted to the outer circumferential surface of the shaft 16 by an interference fit or intermediate fit. The inner ring 20 is also provided with a detector 46 that detects the load applied to the backup roll 14.

[0022] Two inner rings 20 are provided side by side in the axial direction. The cylindrical rollers 22 are arranged in two rows corresponding to the two inner rings 20.

[0023] The outer ring 21 is formed in a cylindrical shape, and has a raceway on its inner peripheral surface along which the cylindrical rollers 22 roll. The outer ring 21 is disposed concentrically with the inner ring 20. The outer ring 21 is configured to be rotatable in the circumferential direction via the cylindrical rollers 22. The outer peripheral surface of the outer ring 21 constitutes the outer peripheral surface of the backup roll 14.

[0024] FIG. 4 is a cross-sectional view taken along the line BB in FIG. As shown in Figs. 3 and 4, the saddle 18 includes a shoe member 25, an outer ring (saddle ring) 26, an intermediate ring (eccentric ring) 27, and an inner ring 28. The shoe member 25 is made of a plate material having an arc-shaped cross section, and is supported by the housing 17. The outer ring 26 is fixed to the shoe member 25. The shoe member 25 is made of a plate material having an arc-shaped cross section, and is supported by the housing 17. The intermediate ring 27 is rotatably fitted to the inner periphery of the outer ring 26 via a plurality of needle rollers 30 (see Fig. 3). Furthermore, the inner ring 28 is rotatably fitted to the inner periphery of the intermediate ring 27 via needle rollers 31 (see Fig. 3). The shaft 16 is fitted to the inner circumferential surface of the inner ring 28.

[0025] The saddle 18 is equipped with a crown control mechanism for controlling the plate shape of the material W to be rolled. Specifically, as shown in Fig. 4, the inner and outer peripheries of the inner ring 28 are concentric, whereas the inner and outer peripheries of the intermediate ring 27 are eccentric. Therefore, when only the intermediate ring 27 is rotated within the outer ring 26, the inner ring 28 and the central axis C of the shaft 16 move, and the backup roll 14 also moves accordingly. This movement of the backup roll 14 makes it possible to control the crown of the material to be rolled.

[0026] FIG. 5 is a perspective view of the shaft. As shown in Figures 3 to 5, a key groove 32 is formed on the outer circumferential surface of the shaft 16. A key groove 33 is formed in the inner ring 28 of the saddle 18. A key 34 is fitted into both key grooves 32, 33. The key 34 prevents relative rotation between the inner ring 28 and the shaft 16. This key groove (first groove) 32 forms a "wiring passage" for passing a cable 47 of a detector 46, as described below.

[0027] The key groove 32 of the shaft 16 extends continuously in the axial direction of the shaft 16 so as to correspond to the multiple saddles 18 spaced apart in the axial direction. In this embodiment, the key groove 32 is formed over the entire axial direction of the shaft 16.

[0028] As shown in Figs. 3 and 4, a stopper ring 36 is fitted to the outer peripheral surface of one axial end (right end) of the shaft 16 to prevent the shaft 16 from rotating relative to the outer ring 26 of the saddle 18. A key groove 37 is formed on the inner peripheral surface of the stopper ring 36, and a key 34 is fitted into the key groove 37 and the key groove 32 of the shaft 16. A part of the circumferential direction of the stopper ring 36 bulges radially, and a pin 41 protruding laterally is provided on the bulging part. As shown in Fig. 3, the pin 41 is inserted into a recess 42 formed in the outer ring 26 of the saddle 18 at the axial end (right end), thereby preventing the stopper ring 36 from rotating around the central axis C of the shaft 16. With the above structure, the shaft 16 is prevented from rotating relative to the outer ring 26 of the saddle 18 via the stopper ring 36.

[0029] 2, an end cover 19 is provided on the other axial end (left end) of the shaft 16. The end cover 19 regulates relative axial movement between the shaft 16 and the saddle 18 and the backup roll 14.

[0030] Fig. 6 is a cross-sectional view taken along the line CC in Fig. 2. Fig. 7 is a perspective view of the inner ring. Fig. 8 is a perspective view of the key 34. As shown in Figures 3, 6, and 7, a recess 45 is formed on the inner peripheral surface of the inner ring 20. This recess 45 is formed across the axial width of the inner ring 20. A detector 46 that detects the load applied to the backup roll 14 is housed in the recess 45. In this embodiment, the detector 46 is a strain gauge. In this embodiment, two detectors 46 are provided for one backup roll 14 (two inner rings 20).

[0031] The recesses 45 and the detector 46 are disposed at positions circumferentially shifted in phase by approximately 180° with respect to the key grooves 32 formed in the shaft 16. The backup roll 14 contacts the outer circumferential surface of the second intermediate roll 13 at a position shifted in phase by approximately 180° with respect to the key grooves 32, in other words, at the same or overlapping phase with the recesses 45 and the detector 46. The key grooves 32 are located between the shoe member 25 of the saddle 18 supported by the housing 17 and the central axis C of the shaft 16.

[0032] A load is applied to the backup roll 14 from the second intermediate roll 13, and the load causes distortion in the inner ring 20. There is a correlation between the magnitude of this distortion and the load applied to the backup roll 14. Therefore, the detector 46 can detect the distortion caused in the inner ring 20 as a value corresponding to the load applied to the backup roll 14.

[0033] A circumferential groove (second groove) 48 extending in the circumferential direction is formed in one axial end face of the inner ring 20, specifically, in one axial end face of the inner ring 20 constituting the axially outer end face of the backup roll 14. This circumferential groove 48 is open not only in the one axial end face of the inner ring 20 but also in the inner peripheral surface of the inner ring 20. The circumferential groove 48 is formed in a circumferential range of about 180° in the inner ring 20. One end of the circumferential groove 48 communicates with an axial end of the recess 45 that houses the detector 46. The other end of the circumferential groove 48 communicates with a key groove 32 formed in the shaft 16.

[0034] A cable 47 is connected to the detector 46. As shown in FIG. 2, the cable 47 is connected to an external device 50, such as a recording device and a power source, disposed outside the backup roll device. The recording device receives a signal of a detected value from the detector 46 and records the detected value. The power source supplies power to the detector 46. The cable 47 passes from the detector 46 in the recess 45 through the circumferential groove 48 to the key groove 32 of the shaft 16. As shown in FIG. 2, the cable 47 passes through the key groove 32 and is drawn out from one end of the shaft 16 to the outside. Note that in FIG. 2, the detector 46 and the cable 47 are drawn with solid lines to clearly show the arrangement of the detector 46 and the cable 47, but in reality, they are disposed in a position hidden inside the backup roll 14, the shaft 16, and the saddle 18.

[0035] As shown in Fig. 8, the key 34 is formed with a groove 34a for passing the cable 47. Specifically, the key 34 is formed in a substantially rectangular parallelepiped shape, with the lower side in Fig. 8 being fitted into the key groove 32 of the shaft 16 and the upper side in Fig. 8 being fitted into the key groove 33 of the saddle 18. The groove 34a extending along the longitudinal direction of the key 34 and avoiding interference with the cable 47 is formed on the lower surface of the key 34 in Fig. 8. By forming such groove 34a in the key 34, the cable 47 can pass through the key groove 32 without being blocked by the key 34. Note that the key 34 may be formed with a hole penetrating in the longitudinal direction instead of the groove 34a.

[0036] As shown in FIG. 8, a protrusion 34b is formed on both longitudinal end faces of the key 34. Meanwhile, as shown in FIG. 7, a recess 20a is formed on one axial end face of the inner ring 20. The protrusion 34b of the key 34 is fitted into the recess 20a of the inner ring 20 arranged adjacent to the key 34. Therefore, the rotation of the inner ring 20 around the central axis C is restricted by the key 34. Since the inner ring 20 is fitted to the outer circumferential surface of the shaft 16 by a clearance fit, it may rotate relative to the shaft 16 due to a creep phenomenon. This relative rotation may cause the cable 47 to be pinched between the shaft 16 and the inner ring 20 at the boundary between the circumferential groove 48 and the key groove 32, resulting in a risk of breakage. By restricting the rotation of the inner ring 20 by the key 34 as in this embodiment, breakage of the cable 47 can be prevented. In addition, the method of restricting the relative rotation of the inner ring 20 with respect to the shaft 16 is not limited to the configuration in which the protrusion 34b of the key 34 is fitted into the recess 20a of the inner ring 20. For example, it is also possible to provide a pin that fits into both the key 34 and the inner ring 20, or to increase the clamping margin between the inner ring 20 and the shaft 16.

[0037] The cables 47 of the detectors 46 attached to each backup roll 14 are routed through the circumferential grooves 48 of the inner ring 20 and the key grooves 32 of the shaft 16 toward one axial end of the shaft 16, and are pulled out from a predetermined pull-out position D on the shaft 16 as shown in FIG. 2, and connected to an external device 50 such as a storage device and a power source. Specifically, the cables 47 are pulled out from the left end of the shaft 16 in FIG. 2. Since an end cover 19 is provided at the left end of the shaft 16, a hole for pulling out the cables is formed in the end cover 19. In addition, a seal is provided between the inner peripheral surface of the hole and the cable 47 passing through the hole to prevent intrusion of foreign matter and water.

[0038] With the above configuration, when the multi-stage rolling mill 10 is rolling the material W to be rolled, the load applied from the second intermediate roll 13 to the backup roll 14 is detected by the detector 46. Therefore, it is possible to prevent abnormalities caused by the load (for example, damage to the rolling bearings (inner ring 20, outer ring 21, cylindrical rollers 22)) or to discover such abnormalities at an early stage, thereby suppressing the occurrence of problems in the multi-stage rolling mill 10.

[0039] A cable 47 of the detector 46 is pulled out to the outside through a wiring passage formed in the inner ring 20 and the shaft 16, specifically, through a circumferential groove (second groove) 48 formed in the inner ring 20 and a key groove (first groove) 32 formed in the shaft 16, and is connected to an external device 50. By forming a wiring passage in the inner ring 20 and the shaft 16 in this manner, it is possible to easily route the cable 47 and pull out the cable 47 to the outside.

[0040] Moreover, if the cables 47 of the detectors 46 provided on each of the multiple backup rolls 14 were directly and individually pulled out from the position of each backup roll 14 or the position of the saddle 18 adjacent thereto, and the pulled out cables 47 were connected to the external device 50, the wiring work of the cables 47 would be extremely complicated, and problems such as breakage of the cables 47 would easily occur on the way to the external device 50. In this embodiment, the cables 47 of the detectors 46 provided on each backup roll 14 are passed through the key grooves 32 formed in the shaft 16, so that the cables 47 of the detectors 46 can be pulled toward one location (pulling-out position D) on the shaft 16 and pulled out collectively from that location. This makes it possible to easily perform the wiring work of the cables 47, and to prevent the occurrence of breakage of the cables 47.

[0041] In this embodiment, the key groove 32 is used as a wiring passage for the cable 47. Therefore, it is not necessary to form a first groove as a wiring passage in the shaft 16 separately from the key groove 32, so that the number of steps required for processing the shaft 16 can be reduced and a decrease in the strength of the shaft 16 can be suppressed.

[0042] As shown in FIG. 6, the detector 46 is disposed in the same circumferential phase as the contact point P between the backup roll 14 and the second intermediate roll 13. Therefore, the load applied to the backup roll 14 can be efficiently detected by the detector 46. In addition, the key groove 32, which is a wiring passage for the cable 47, is disposed in a position that is approximately 180° out of phase with the detector 46 and the contact point P. Therefore, the key groove 32 can be disposed in a position away from the contact point P to which the load is applied. Since the key groove 32 can be a factor in reducing the strength of the shaft 16, by disposing the key groove 32 in a position away from the contact point P to which the load is applied in the circumferential direction, the burden that the load imparts to the shaft 16 can be reduced.

[0043] The detector 46 may be disposed at a phase overlapping with the contact point P in the circumferential direction, rather than at the same phase as the contact point P. The detector 46 may also be disposed at a position shifted in the circumferential direction from the contact point P within a range indicated by angle θ in FIG. 6. The detector 46 may also be disposed within a range of angle θ from a position shifted 180° in phase with the keyway 32. The angle θ may be, for example, 30°. In this case, the phase difference between the detector 46 and the keyway 32 is 150° or more and 210° or less.

[0044] The recess 45 formed in the inner ring 20 has a first function of ensuring an installation space for the detector 46, and a second function of making the inner ring 20 more easily distorted. In particular, the second function makes it easier for the inner ring 20 to distort due to the load from the second intermediate roll 13, thereby increasing the sensitivity of the detector 46 to detect distortion.

[0045] [Variations] The embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the above-described embodiments, and includes the meaning equivalent to the claims and all modifications within the scope thereof.

[0046] In the above embodiment, two detectors 46 are provided for each backup roll 14, but one or three or more detectors 46 may be provided. Also, in the above embodiment, all backup rolls 14 are provided with a detector 46, but it is sufficient that at least one backup roll 14 is provided with a detector 46. When detectors 46 are provided for at least two backup rolls 14 (first backup roll, second backup roll) 14, the cables 47 of the respective detectors 46 can be pulled out from a common pull-out position D on the shaft 16, making it easy to wire the cables 47.

[0047] The detector 46 is not limited to a strain gauge, and may be of another type capable of detecting the load applied to the backup roll 14 (including a value correlated to the load).

[0048] The first groove, which constitutes the wiring passage for the cable 47 and extends in the axial direction, may be formed separately from the key groove 32 on the shaft 16. The first groove may also be formed in the same or overlapping phase with the detector 46 in the circumferential direction. In this case, the circumferential groove (second groove) 48 of the inner ring 20 can be omitted. The wiring passage may be formed inside the shaft 16 instead of on the outer circumferential surface.

[0049] In the above embodiment, a 20-stage multi-stage rolling mill 10 is exemplified, but the number of stages is not limited, and the present disclosure can be applied to any multi-stage rolling mill 10 having backup rolls 14. The backup rolls 14 may directly back up the reduction rolls 11. [Explanation of symbols]

[0050] 10: Multi-stage rolling mill 14: Backup role 16: Shaft 18: Saddle (support) 20: Insider 21: Outer ring 22: Cylindrical roller (rolling element) 32: Key groove (first groove) 34: Key 34a: Groove 45: Recess 46: Detector 47: Cable 48: Circumferential groove (second groove) 50: External device

Claims

1. A shaft, A support for supporting the shaft; A backup roll supported by the shaft; A detector for detecting a load applied to the backup roll, The backup roll is An inner ring fixed to the shaft; an outer ring disposed radially outward of the inner ring; a plurality of rolling elements disposed radially between the inner ring and the outer ring, The detector is attached to the inner ring; A backup roll device for a multi-stage rolling mill, wherein a wiring passage for passing a cable of the detector is formed in the shaft along the axial direction.

2. 2. The backup roll apparatus of a multi-stage rolling mill according to claim 1, wherein the wire passage includes a first groove formed in an outer circumferential surface of the shaft.

3. the detector and the first groove are positioned at different phases in the circumferential direction, 3. The backup roll device of a multi-stage rolling mill according to claim 2, wherein the wire passage includes a second groove formed in the inner ring and extending in a circumferential direction between the detector and the first groove.

4. 4. The backup roll device for a multi-stage rolling mill according to claim 3, wherein a phase difference between the first groove and the detector in a circumferential direction is equal to or greater than 150° and equal to or less than 210°.

5. a key for preventing the shaft from rotating relative to the support; The backup roll device for a multistage rolling mill according to any one of claims 2 to 4, wherein the first groove also serves as a key groove into which the key fits.

6. 6. The backup roll device for a multi-stage rolling mill according to claim 5, wherein the key is formed with a groove or a hole for passing the cable therethrough.

7. 7. The backup roll device for a multistage rolling mill according to claim 1, wherein the detector is a strain gauge, and a recess for accommodating the detector is formed on an inner peripheral surface of the inner ring.

8. the backup roll includes a first backup roll provided with the detector, and a second backup roll disposed at a different axial position from the first backup roll and provided with the detector, 8. The backup roll device of a multistage rolling mill according to claim 1, wherein a cable of the detector provided on the first backup roll and a cable of the detector provided on the second backup roll pass through the wiring passage formed in the shaft and are pulled out from a common pull-out position.

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