[Name of Document] DESCRTPTION [Title of tlie Invention] ROLLING APPARATUS FOR FLAT-ROLLED METAL MATERIALS [Technical Field] 5 [OOOl] The present invention relates to a rolling apparatus for flat-rolled metal materials. [Backgrou~idA IZ] [0002] 10 In a rolling process of a flat-rolled metal material, it is very important to roll a sheet material in a form free fro111 camber, or in a form not having bend in tlie left-right direction, ill order to avoid not only a plane shape defect and a di~iiensionaal ccuracy defect of the rolled material but also to avoid sheet pass troubles such as a zigzag movement and a tail crash. I5 [OOO3] Further, a warp that occclrs at the time of rolling a sheet inaterial also has a large influence on productivity of products, soch as reduction in rolling efficiency and increase in the number of refining processes. For example, as for tlie refining processes, there are cases where it is necessary to correct camber or a warp using a leveler or by 20 performing pressing or tlie like, and in an extreme case, a defect part liiay liave to be cut. Still fu~.thet; in the case where camber or a warp occc~rred to a large extent, tlie rolli~ig facility tilay be da~ilagedd ue to the collisio~io f the sheet. In this case, it is not only that the sheet itself loses tlie pmduct value, but that it brings about tremendous damages such as productio~li nteutlption atid repairing of tlie rolling facility. 25 [0004] In addition, in order to cotltrol the above camber with higli accuracy, it is also icnportant to perfonii an initial setting called zero point adjustment. The zero point adjustment is performed as follows: kiss-roll tightening is conducted by operating a screw down device in a roll-rotating state; and, a point in which a measltrement valt~eo f a rolling load corresponding to a preset zero point adjustment load (preset to rated load of 15% to 5 85%) is set as a zero point of a reduction position, and the reduction position is set as a starting point (reference) in reduction control. In this case, the difference between left and right reduction positions, that is, the zero point of reduction leveling is often adjusted simultaneously. Also, as for the zero point adjustment of tlie reduction leveling, the measurenient values of the rolling load on the time of kiss-roll tightening on the operator 10 side and the driving side are adjusted such that the measuretiietit values correspond to the preset zero point adjustment load. Note that the kiss-roll tightening nieans that, under tlie state that a rolled material is not present, the upper and lower work rolls are brought into contact with each other and a load is applied bet\veen the rolls. [0005] 15 Incidentally, to simplif>r expressions, the operator side and the driving side of the rolling mill, as the right atid left sides when the rolling niill is seen fro~ntl ie front of the rolling direction, will be referred to as "right and left", respectively. [0006] In view of the probletns attributed to such camber, Patent Docurnent 1 suggests 20 a rolling niethod ant1 a rolling apparatus capable of stably producing a flat-rolled nietal material free frotn camber or having an extremely light camber. Specifically, in the rolling method and the rolling apparatus described in Patent Docunlerit I, a load detection device measures a rolling direction force acting on roll chocks on an operator side and a driving side of a work roll, atid a calculation device calculates a difference of the rolling 25 direction forces between the operator side and tlie driving side. Then, a control device co~~troal sl eft-right swivellirig cotnponent of a roll gap of a rolling mill such that the difference becomes zero. [0007] In view of the problem of a warp, Patent Document 2 suggests a rolling tilethod and a rolling apparatus capable of stably producing a flat-rolled metal tilaterial having an 5 extremely light warp. Specifically, in the rolling method and the rolling apparatus described in Patent Docutnet~t 2, load detection devices provided on both entry side and exit side of upper and lower roll chocks of work rolls measure rolling direction forces acting on tlie upper and lower work roll chocks. Then, a calcnlation device calculates a difference between the rolling direction force on tlie upper side and the rolling direction 10 force on the lo\ver side, tliat is, an upper and lower rollitig direction force difference. After tliat, upper and lolver asyli~~netrcico mponents of tlie rolling apparatcts is controlled sach that the uppel and lower rolling direction force differetice is decreased. [OOOS] In view of the problem of zero point adjost~nent, in Patent Document 3, it is 15 discovered that a rolling direction force occurs even wit11 zero point adjustment by the kiss roll state, pointed out tliat the rolling tlirectio~if orce does not affect a roll thrust force, and accordingly, there is proposed a lnethod enabling more precise initial reduction position adji~stmetit (reduction zero point adjustment) of a rolling mill. [0009] 20 Further, in order to produce a flat-rolled metal material free from camber, in a rolling method and a rolling apparatus described in Patent Document 4, rolling direction forces acting on roll chocks on an operator side and a driving side of a \\cork roll are measured, a difference of the rolling directioti forces betweeti tlie operator side and the driving side is calculated, a left-right swivelli~~cgom ponent of a roll gap of the rolling mill 25 is cotitrolled by using control gain soch tliat the difference become a control target value, and the control gain is changed depending on a co~iditiod~ui ring rolling. [OO lo] Still fi~tther, Patent Doci~tnent 5 suggests a rollitlg inill and a rolling method capable of producing a flat-rolled tlietal material free fiotn canlber or warp, acliievitlg zero point adjusttnent with high accuracy, and easily achieving application of a strong roll 5 bending force. In the rolling inill and the rolling method described in Patent Docu~netl5t , a work roll chock is pressed against a contact surface with a housing window or a project block of the rolling mill in a mllitig direction. Then, a load detection device measures rolling direction forces acting on roll chocks on an operator side and a driving side of a work roll, and a calculation device a calculatiotl device calculates a difference of the 10 rolling direction forces between the operator side and the driving side. A control device calculates left-right s\vivclling component control quantity of a roll gap of the rolling mill such that the difference become a control target value, and controls the roll gap on the basis of the calculated value of the left-right swivelling component control quantity of the roll gal'. 15 [OOll] Here, in any of the rolling methods and the rolling apparatuses described in the above Patent Doc~~tne~1l ttso 5, the rolling direction fosces are measured. Accordingly, with reference to FIG. 1, the nleasuretnent of the rolling direction forces according to Patent Doclcnents 1 to 5 will be described specifically. FIG. 1 is a view sche~naticaliy 20 showing a rolling apparatus. [0012] The rolling apparatus shown in FIG. 1 includes an upper work roll 1 supported by an upper work roll chock 5, an ul~per backup roll 3 supported by an upper backup roll chock 7, a lower work roll 2 supported by a lo\ver \vork roll chock 6, and a lower backup 25 roll 4 suppol-ted by a lower backup roll chock 8. The upper backup roll 3 is disposed on the upper side of the upper ivork roll 1 in contact with the upper work roll 1. 111 the same 5 manner, the lower backup roll 4 is disposed on the lower side of the lower work roll 2 in contact with the lower work roll 2. Further, the rolling apparatus shown in FIG. 1 includes a screw dowti device 9 that applies a rolling load to the upper work roll 1. A flat-rolled tnetal material M to be rolled by the rolling apparatus moves in a rolling 5 directio~Fi between the upper work roll 1 and tlie lower work roll 2. [0013] Though FIG. 1 basically sliows only the apparatus construction on the operator side, similar devices exist on the driving side, too. [0014] 10 The rollit~g direction force acting on the upper nark roll 1 of the rolling apparatus is basically supported by tlie upper work roll chock 5. Behvee~til ie upper work roll chock 5 and a housing or a project block, there are provided an upper work roll chock exit side load detection device 121 on an exit side of the upper work roll chock 5 it1 tlie rolling direction, and an upper work roll chock entry side load detection device 122 on an 15 entry side of tlie upper work roll chock 5 in the rolli~igd irection. The upper work roll chock exit side load detection device 121 can detect the force acting between the member such as the housing or the project block and the upper work roll chock 5 on the exit side of the upper work roll chock 5 in tlie rolling direction. The upper work roll chock entry side load detection device 122 call detect the force acting between the member sucli as tlie 20 project block and the upper work roll chock 5 011 the entry side of tlie upper work roll chock 5 in the rolling direction. To simplify the device construction, those load detection devices 121 and 122 preferably and ordinarily have a construction for iiieast~ring a compressive force. [0015] 25 The upper work roll chock exit side load detection device 121 and the upper work roll chock etitry side load detection device 122 are co~illectedt o an upper \vork roll rolling direction force calculation device 141. The upper work roll rolling direction force calculation device 141 calctllates a difference between a load detected by the upper work roll chock exit side load detection device 121 and a load detected by the upper work roll chock entry side load detection device 122, and, on the basis of tlie calculation result, 5 calculates the rolling direction force acting on the upper work roll chock 5. [OO 161 In the same tnanner, as for tlie lower work roll 2, between the lower work roll chock 6 atid tlie housing or tlie project block, there are provided an lower work roll chock exit side load detectiotl device 123 on an exit side of the lower work roll cliock 6 in tlie 10 t,olling direction, and a lo\ver work roll chock ently side load detection device 124 on an entry side of the lower work roll chock 6 in tlie rolling direction. The lower work roll chock exit side load detection device 123 and the lower work roll chock entry side load detection device 124 are connected to a lower \\,ark roll rolling direction force calculation device 142. The lower work roll rolling direction force calculation device 142 calculates, 15 on the basis of measuretnent values obtained by those load detection devices 123 atid 124, tlie rolling direction force acting on the lonrer work roll chock 6 in the same manner as in the npper work roll 1. [Prior Art Doc~unent(s)] [Patent Document(s)] 20 [0017] [Patetit Docutnent 11 W020041082860 [Patent Docutnent 21 JP2007-260775 A [Patent Document 31 W020 111129453 [Patent Document 41 JP2006-82118 A 25 [Patent Document 51 JP2012-148339 A [Sutnnlary of the ltivention] [Problem(s) to Be Solved by the Invetition] [OO 181 Here, takitig itito consideration tlie drawings on the figures in Patent Docl~tnetlts 1 to 5 and technical cotiimon knowledge in tlie field of rolling, a load detection 5 device is normally a load cell. It is difficult to attach the load cell on a work roll chock due to size constraint. Accordingly, the load cell is getierally attached to a tileinher that faces the work roll cliock in a rolling direction, such as a project block or a Iiousing. [OO 191 FIG. 2 is an enlarged side view of the work roll chocks of the rolling apparatus 10 sliown in FIG. 1 and a periphery thereof, atid shows an esaliiple in which load detection devices are attached to project blocks. In the esatiiple slio\\~n in FIG. 2, a housing 10 is provided with at1 esit side project block I1 and an entry side project block 12. The esit side project block 11 and the entry side project block 12 are fortiled so as to protrude frotii the hoosiiig 10 towards the inner side of the rolling apparatus. 15 [0020] In the esatnple sliown in FIG. 2, the upper \\.ark roll chock esit side load detection device 121 atid tlie lo\\.er work roll chock esit side load detection device 123 are provided on the exit side project block 11. On tlie other hand, the upper work roll cliock etltry side load detection device 122 acid the Lo\ver work roll chock entry side load 20 detection device 124 are provided on the entty side project block 12. Note that, although a protection cover or \\caterproofing for preventing water or the like entering inside tlie device is generally provided on the surface of the load detection device, they are tiot sliown in the figure. [002 I] 25 FIG. 2 also shows an esa~npleo f a kiss-roll tightening state. As shown in FIG. 2, each of the load detection devices 121, 122, 123, atid 124 has a small size in an openinglclosing direction, that is, a draft direction (also referred to as height direction) of the rolls. Accordingly, tlie distances that the load detection devices 121 and 122 are in contact with side surfaces of the work roll cl~ock5 and the distances that the load detection devices 123 and 124 are in contact with side surfaces of the work roll chock 6 are small. 5 [0022] Here, in the example shown it1 FIG. 2, the positions (heights) of the respective load detection devices 121 and 122 in the draft direction are the satne as the position (height) of a roll axis A1 of the work roll 1 held by the work roll chock 5 in the draft direction, and the positions (heights) of the respective load detection devices123 and 124 in 10 the draft direction are the same as the position (height) of a roll axis A2 of the work roll 2 held by the work roll chock 6 in tlie draft direction. In this case, rolling direction forces applied to the work roll chocks 5 and 6 is appropriately detected by the load detection devices 121, 122, 123, and 124. [0023] 15 However, as sllown in FIG. 3, for example, \vhen the upper work roll 1 rises and a gap between the ivork rolls 1 and 2 increases, the height of the position of the roll axis A1 of the upper work roll 1 in the draft direction is larger than the heights of the positions of the upper work roll chock exit side load detection device 121 and the upper work roll cl~ocke ntry side load detection device 122 in the draft direction. Accordingly, 20 the lnonlent acts on the upper work roll cliock 5, and thus, the upper work roll chock 5 rotates in a direction indicated by an arrow sl~ownin FIG. 3. As a result, the upper work roll chock 5 tilts, and parts on the side surfaces of the upper work roll cliock 5 colile into contact ~vitltil ie project blocks 11, 12, and the like. [0024] 25 In this waj: when parts on the side surfaces of the upper work roll chock 5 come into contact with tl~ep roject blocks 11, 12, and the like, sotile of the rolling direction force applied to the upper work roll chock 5 from tl~eo pper work roll 1 is applied to the parts at which the upper work roll chock 5 comes into contact with the project blocks 11 and 12. Accordingly, it may not be possible for the load detection devices 121 and 122 to accurately detect the rolling direction force. 5 [0025] Further, for example, as shown in FIG. 4, when the \vork rolls 1 and 2 and the backup rolls 3 and 4 are worn away, and thus decrease in the roll diameters, the upper work roll chock 5 and the lower work roll chock 6 tuove downward in the draft direction. When the opper work roll chock 5 and the lower \\cork roll chock 6 move downward, the 10 height of the position of the axis A1 of the work roll 1 in the draft direction is smaller than the heights of the positions of the work roll chock exit side load detection device 121 and the work roll chock entry side load detection device 122, and the height of the position of the axis A2 of the work roll 2 in the draft direction is smaller than the heights of the positions of the work roll chock exit side load detection device 123 and the work roll chock 15 entry side load detection device 124. Also in this case, in the same manner as the case shown in FIG. 3, the nrork roll cliocks 5-and 6 tilt, and parts on the side surfaces of the \vork roll chocks 5 and 6 come into contact wit11 the project blocks 1 I and 12. As a result, it may not possible for the load detection devices 121, 122, 123, and 124 to accurately detect the rolling direction force. 20 [0026] Further, FIG. 5 is a cross-sectional plan view taken along the line V-V of FIG. 2, showing the work roll chocks and a periphery thereof. As call be seen fro111 FIG. 5, the load detection devices 121 and 122 have sizes whose widths in the roll axis direction are small. Accordingl): the load detection devices 121 and 122 come into contact only with 25 palls on the side surfaces ofthe work roll chocks 5 and 6 also in the roll axis direction. That is, for example, as shown in FIG. 5, when the lower work roll 2 moves owing to roll shifting for a shift quantity D in the roll axis direction, it tileans that the center of a bearing (hereinaftel; also referred to as "radial bearing") 5a to which force in a radial direction of the upper work roll chock 5 is applied shifts in the roll axis direction 5 with respect to the positions of the load detection devices 121 and 122. Note that, in FIG. 5, a line C shows a line the center of the radial bearing 5a of the upper work roll chock 5. Accordingly, the moment acts on the upper work roll chock 5, and thus, the upper work roll chock 5 rotates in a direction indicated by an arrow shown in FIG. 5. As a result, the upper work roll chock 5 tilts, and pasts on the side surfaces of the upper work roll cliock 5 10 come into contact \\,it11 the project blocks 11 and 12. [0028] In this way, when parts on the side surfaces of the upper work roll chock 5 conie into contact with the project blocks 11, 12, and the like, some of the rolling direction force applied to the upper work roll chock 5 fsom the upper work roll I is applied to the 15 parts at \\thicIi the upper work roll chock 5 comes into contact with the project blocks 11 and 12. Accordingly, it may not be possible for the load detection devices 121 and 122 to accl~ratelyd etect the rolling direction force. [0029] The present inve~ltiotlh as been nlade in view of the circumstances described 20 above, and an object of the present invention is to provide a rolling apparatus capable of accurately detecting a rolling direction force applied to a work roll chock. [Means for Solvi~lgth e Problem(s)] [0030] Tlie inventors of the present invention have conducted studies on rollitlg 25 apparatuses having various stroctures, with regard to detection of the rolling direction force applied to the work roll chock. [003 11 As a result, the inventors have found that the rotation of the work roll chock can be suppressed by providing ~nultiple load detection devices on a housing on an entry side or an exit side of the work roll chock in the rolling direction and disposing the 5 tnultiple load detection devices in a manner that the multiple load detection devices are shifted in the rolling direction or in the roll axis direction, and as a result, that the rolling direction force applied to the work roll chock can be accurately detected. Note that a load detection device according to the present invention mainly represents a load cell, and inay also be a device of a strain gauge, a niagnetostriction type, a capacitance type, a gyro type, 10 a hydraalic type, a piezoelectric type, or the like. [0032] The present invention has been achieved on the basis of the above findings, and the sunlmary is as follows. (1) 15 A rolling apparatus for a flat-rolled i~>ctailn aterial, the rolling apparatus including at least a pair of upper and lower xvork rolls, and a pair of upper and lower backup rolls st~pportingth e respective \\.ark rolls, tlie rolling apparatus including: a pair of work roll chocks configured to hold the respective work rolls; housings or project blocks configured to hold the work roll chocks; and 20 one or more rolling direction force meastlrenient devices configured to measure rolling direction forces acting on tlie xvork roll chocks, wherein at least one of the rolling direction force ineasurernent devices includes a plurality of load detection devices on an entry side or an exit side of the work roll chocks in a rolling direction, and tlie plurality of load detection devices are provided to 25 one of the housings or one of the project blocks, and wherein the load detection devices are disposed in a manner that, on all occasiotis, a line extending in the rolling direction and i~icluditig a point of effort of a rolling direction force of one of tlie work rolls is interposed behveen at least two of the load detection devices it1 a draft direction, and the at least two of the load detection devices face a side surface of a corresponding one of the work roll cliocks. 5 (2) The rolling apparatus according to (I), wherein, in at least one of the rolling direction force tneasuretiietit devices, the load detection devices are disposed in a tiianner that, on all occasions, a line extending in tile rolling direction and including a point of effort of a rolling direction force of one of tlie 10 work rolls is interposed between at least tn7o of tlie load detection devices in a roll axis direction of the work rolls, and tlie at least two of the load detection devices face a side surface of a corresj)onding one of the work roll chocks. (3) The rolling apparatus according to (1) or (2), 15 wherein at least one of the rolling direction force measurenient devices includes at least three load detection devices on the entry side or the esit side of tlie work roll chocks it1 a rolli~~dgir ection, and the at least three load detection devices are provided to one of the housitigs or one of the project blocks, and wherein the load detection devices are disposed so as to be shifted in one of the 20 draft direction and the roll axis direction of the work rolls, in a manner that the point of effort of tlie rolling direction force of each of tlie work rolls is located within an area defined by connecting the load detection devices. (4) Tfie rolling apparatus according to ariy one of (I) to (3), filrther including: 25 a rolling direction force calculation device configured to calculate a rolling direction force by adding up loads of the otie or more rolling direction force tneasuretiient devices each iticluding the plurality of load detection devices, the loads being detected by the respective load detection devices. (5) The rolling apparatus according to any otle oE(1) to (4), 5 wherein the rolling apparatus is provided with the rollitig direction force measorement devices on an exit side of an upper work roll chock, an entry side of the tipper work roll chock, an exit side of tlie lower work roll chock, and an entry side of the lower \vork roll chock, respectively. (6) The rollitig apparatus according to (9, wherein, out of the rolli~igd irection force measure~nentd evices, the plurality of load detection devices are provided only to the otie or more rolling directioti force oleasurement tlevices co~ifigttredt o measure any one of a rolling direction force acting in a rolling direction toward tlie exit side and a rolling direction force acting in a rolling 15 direction to\\rard tlie entry side. (7) ~ ~ . . The rolling apparatus according to (5), wherein all of the rolling direction force measurement devices each have the plurality of load d&ection devices. 20 (8) The rolli~iga pparatus accorditlg to (5), wherein, out of the rolling directioti force measuren~entd evices, the plurality of load detection devices are provided otily to the one or more rolling direction force measurement devices for any one of tlie upper work roll chock and tlie lo\ver work roll 25 chock. (9) The rolling apparatlls according to (7) or (8), wherein the plurality of load detection devices are disposed in a tnanner that positions in a drafi direction and positions in a roll axis direction of the plurality of load detection devices provided on tlie entry side in the rolling direction are identical to 5 positions in a dwfi direction and positions in a roll axis direction of the plurality of load detection devices provided on the exit side in the rolling direction. (10) The rolling apparatus according to any one of (7) to (9), wherein the rolling directiot~ force calculation device calculates a rolling 10 direction force on the basis of an ently side load calculated by addiiig up loads detected by the plurality of load detection devices provided on the entry side in the rolling direction and an exit side load calc~ilated by adding up loads detected by tlie plurality of load detection devices provided oil the exit side in tlie rolling direction. (11) 15 The rolling apparatus according to any one of (I) to (lo), wherein the load detection devices are eacli a load cell. (12) The rolling apparatus according to any one of (1) to (ll), further including: a cover configured to cover each of the load detection devices, the cover being 20 provided behveen one of the housings or one of the project blocks and each of tlie load detection devices (13) The rollit~ga pparatus according to any one of (1) to (It), fu~tberin cluding: a cover configured to collectively cover the load detection devices for eacli of 25 the rolling direction force measurement devices, tlie cover being provided between one of tlie housings or one of the project blocks and each of the load detection devices. [Effect(s) of the Invention] [0033] According to the present i~wention, there is provided a rolling apparatus 5 capable of accurately detecting a rolling direction force applied to a work roll chock. [Brief Description of the Drawing(s)] [0034] [FIG. 11 FIG. 1 is a view sche~naticallysh owing a rolling apparatus having load detection devices of prior art. 10 [FIG. 21 FIG. 2 is a side view schematically showing work roll chocks having load detection devices of prior art and a periphery thereof. [FIG. 31 FIG. 3 is a side view illostrating a problem to be solved in ~neast~rilig rolling direction forces by rolling load detection devices of prior art, and shows a state in which a roll axis of an upper work roll shifts with respect to positions of the rolling load 15 detection devices in a draft direction and in \rrllich ao upper ~vorkro ll chock tilts, [FIG. 41 FIG. 4 is a side vie\\, illustrating a problelll to be solved in measuring rolliiig direction forces by rolling load detection devices of prior art, and shows a state in which a roll axis of an upper work roll and a roll axis of a lower work roll shift with respect to positions of the rolling load detection devices in a draft direction arid in which an 20 upper work roll chock and a lower \vork roll chock tilt. [FIG. 51 FIG. 5 is a cross-sectional plan view illustrating a proble~u to be solved in measuring a rollilig direction force by rolli~ig load detection devices of prior art, and slio\vs a state in which a center of a radial bearing shifts with respect to positions of the rolling load detection devices in a roll axis directioi~a nd in which a work roll chock tilts. 25 [FIG. 61 FIG 6 is a view scliematically slio\ving a rolling apparatus according to a first construction example of the present invention. [FIG. 71 FIG. 7 is a side view schelnaticallp showing a main body of the rolling apparatus according to tlie first construction example. [FIG. 81 FIG. 8 is an enlarged side view of an upper work roll chock of the rolling apparatus shown in FIG. 6 and FIG. 7 and a periphely thereof. 5 [FIG. 91 FIG. 9 is a side view illustratitig functions and effects in measuring a rolling direction force by a rolling apparatus according to the present invention, atid shows a state in which an upper work roll rises in a draft direction. [FIG. 101 FIG. 10 is a side view illustrating fullctions atid effects in measuring a rolling direction force by a rollitig apparatus according to the present invention, and shows 10 a state in \vIiich an upper work roll and a lower work roll move do\vnward in a draft direction. [FIG. 111 FIG. I1 is a side view showing a modified esample of the first construction example. [FIG. 121 FIG. 12 is an enlarged cross-sectional plan vie\\, of a work roll chock 15 and a periphery thereof taken along the line XII-XI1 of FIG 8, which shows a secot~d construction esaniple of a rolling apparatus accorditig to an embodiment of tlie present invention. [FIG. 131 FIG. 13 is a side view showing a third construction esample of a rolling apparatus according to an embodiment of the present invention. 20 [FIG. 141 FIG. 14 is a side view showing a fifth construction esa~npleo f a rolli~iga pparatus according to at1 eiiibodiment of tlie present invention. [FIG. 151 FIG. 15 is a side view sho\\,ing a sistli construction esa~ilple of a rolling apparatus according to an embodiment of tlie present invention. [FIG. 161 FIG. 16 is an elevational view slio\ving an arrangement esatnple in a 25 case where a rollitig direction force measurement device of a rolling apparatas according to aa embodiment of the present itivelition has three load detection devices. [FIG. 171 FIG. 17 is an elevatiotial view showilig an arrangement exatiiple in a case where a rolling direction force lneasurelnetit device of a rolling apparatus according to an embodiment of tlie presetit invention has four load detection devices. [Mode(s) for Carrying out the Invention] 5 [0035] Hereinaftel; referring to tlie appended drawings, preferred e~iibodicne~iotsf tlie present invention will be described in detail. It should be noted that, in the above description with reference to FIGS. 1 to 5 and the following description, structural elements that have substantially the same functio~ia nd structure are de~~otewdit h the satlie 10 reference ni~merals. [0036] < I . Configuration of rolling apparatus and fitnctions and effects of rolling apparatoY [I-1. First construction example] FIG 6 is a view schematically showing a rolling apparatus according to a first construction example of the present invention. FIG. 7 is a side vie\\' schematically showing a main body of the rolling apparatus. In tlie satiie iiiallner as tlie rolling apparatus showii in FIG. 1, the rolli~iga pparatus shown in FIG. 6 and FIG. 7 includes an upper work roll 1 supported by an upper work roll chock 5, an upper backup roll 3 20 supported by an upper backup roll chock 7, a lower \\cork roll 2 supported by a lower work roll chock 6, and a lower backup roll 4 supported by a lo\ver backup roll chock 8. Ft~ttlier, the rolling apparatus sho\vn in FIG. 6 and FIG. 7 includes a screw down device 9 that controls a gap between the upper and lower work rolls, and an upper drive electric liiotor 35 and a lower drive electric motor 36 that drive the upper and lower work rolls, 25 respectively. A flat-rolled tnetal material M to be rolled by the rolling apparatus moves in a rolling direction F. Though FIG. 6 and FIG. 7 basically show only the apparatus constructioti on the operator side, similar devices exist on the driving side, too. [0037] As shown in FIG. 7, in tlie present embodi~iie~lat ,h ousing 10 is provided with an exit side project block 11 and an entry side project block 12. The exit side project 5 block I I and tlie entry side project block 12 are formed so as to protrude from the housing 10 towards tlie inner side. [0038] Further, in the same manner as tlie rolling apparatuses shown in FIGS. 1 to 5, the rolling apparatus shown in FIG. 6 and FIG. 7 includes rolling direction force 10 ineasuretnent devices measuring rolling direction forces acting on the work roll chocks 5 and 6 at the titile of rolling a flat-rolletl ~uetalm aterial. However, ttie construction of tlie rolling direction force measuretilent devices included in tlie rolling apparatus show11 in FIG. 6 and FIG. 7 is different from the construction of the rolling direction force measurement devices formed of the load detection devices 121, 122, 123, and 124 sho\vn in FIGS. 1 to 5. IS [0039] As shown in FIG. 6 and FIG. 7, tlie rolling apparatus of the present construction exatiiple is provided with four rolling direction force measureinent devices 2 1, 22, 23, and 24 oil the operator side. Note that the measurernetit devices are also provided to tlie driving side, the number of the measclrement devices being the same as the nnmbe~o f the 20 measurement devices on tlie operator side. [0040] An upper work roll chock exit side rolling direction force lneasuretiient device 21 is provided on an exit side of the upper work roll chock 5 in the rolling direction oil an exit side of the housing 10 in the rolling direction. The rolling direction force 25 tiieasure~iient device 21 detects a force acting between tlie housitig 10 and tlie upper work roll chock 5 on the exit side, that is, the rolling direction force measurement device 21 detects a rolling direction force acting 011 the upper work roll chock 5 in tlie rolling direction toward the exit side. An upper work roll cliock entry side rollilig direction force measurement device 22 is provided on an elitly side of the upper work roll chock 5 in the rolling direction on an entry side of the housing 10 in the rolli~igd irection. The rolling 5 direction force measurement device 22 detects a force acting between the housing 10 and the upper work roll chock 5 on the entry side, that is, the rolling direction force measurement device 22 detects a rolling direction force acting on the upper work roll chock 5 in the rolling direction toward the entry side. [0041] 111 the same manner, a lower work roll cliock esit side rolling direction force ~neasurement device 23 is provided on an exit side of tlie lo\ver work roll chock 6 in the rolling direction on the exit side prqject block 11. The rolling direction force measurement device 23 detects a force acting between the esit side project block 11 and the lower work roll chock 6, that is, tlie rolling direction force measurement device 23 15 detects a rolling direction force acting on the lower work roll chock 6 in tlie rolling direction toward the exit side. A lo\ver work roll chock entry side rolling direction force measurement device 24 is provided on ao entry side of tlie lower work roll chock 6 in the rolling direction on the entry side project block 12. The rollilig direction force measurement device 24 detects a force acting between the entry side project block 12 and 20 the lower work roll chock 6, that is, the rolling direction force measarement device 24 detects a rollitig direction force acting on the lower work roll cliock 6 in the rolling directio~tio ward the entry side. 100421 As shown in FIG. 6 atid FIG. 7, in the present embodiment, each of tlie rolling 25 direction force measurement devices 21, 22, 23, and 24 includes multiple load detection devices. For example, the upper \vork roll cliock exit side rolling direction force measurement device 21 includes a first load detection device 21a and a second load detection device 21b. [0043] FIG. 8 is an enlarged schematic side view of an upper work roll cliock 5 of the 5 rolling apparatus shown in FIG. 6 and FIG. 7 and the periphery thereof. The load detection devices 21a and 21b ake both disposed on the hoi~sitlg 10 on the exit side. Further, as showt~ in FIG. 8, the load detection devices 21a and 21b are disposed in a manner that a line extending it1 the rolling direction atid includitig a roll axis Al, which is a point of effort of the rolling direction force of the upper work 1.011 1 in the draft direction of 10 the upper work roll 1 , is interposed between the load detection devices 21a atid 21b. [0044] In particulal; in the present cmbodiinent, during the rolling of the flat-rolled metal material M, the hvo load detection devices 2ia and 21b are always disposed in a tilaliner tliat tlie load detection devices 21a atltl 21b face a side surface of the upper work 15 roll chock 5 even i f tlie position of tlie upper work roll cliock 5 changes in the draft direction witliii~a movable range of the upper work roll cliock 5. It is preferred in the present etnbodiruetlt, even if tile position of the upper work roll cliock 5 cliaiiges in the draft direction within the movable range of the upper work roll chock 5, that one of the load detection devices, tliat is, the load detection device 21a, be always placed above the 20 roll axis of the upper work roll I in the draft direction, and that the other load detection device, that is, the load detection device 21b, be always placed belo\\, the roll axis of the upper \vork roll 1 ill the draft direction. LO0451 The thus constrt~cted t\vo load detection devices 21a and 21b of the rolling 25 direction force measuretilent device 21 are connected to an upper work roll chock exit side load calculation device 31 as slio\\~n in FIG. 6. The load calculation device 3 1 adds up a load detected by the first load detection device 21a and a load detected by tlie second load detection device 21b. The total value of those detected loads corresponds to a rolling direction force applied to the housing 10 on the exit side from the upper work roll chock 5, that is, a rolling direction force of the upper work roll chock 5 toward the exit side. 5 [0046] lo the same manner, the upper work roll cliock entiy side rolling direction force measurement device 22 includes a first load detection device 22a and a second load detection device 22b. The load detection devices 22a and 22b are both disposed on the housing 10 on the entry side. Further, as shown in FIG. S, the load detection devices 22a 10 and 221, are disposed in a lllallner that a line extending in the rolling direction and incloding the roll axis Al, which is a point of effort of tlie rolling direction force of the upper ~vorkro ll I in the draft direction of the upper work roll 1, is interposed behveen the load detection devices 22a and 22b. In particular, in the present embodiinent, the first load detection device 22a is disposed such that tlie position of the first load detection 15 device 22a on the entry side of the upper ~vorkr oll chock in the draft direction is the same as the position of the first load detection device 21a on the exit side of the upper work roll cliock in the draft direction. In the same inanner, the second load detection device 22b is disposed such that the position of the second load detection device 22b on the entry side of the upper work roll chock in the drat? direction is the same as the position of the second 20 load detection device 21b on the exit side of tlie tipper work roll chock in the draft direction. [0047] T11e thus constructed two load detection devices 22a and 22b of the rolling direction force lueasurement device 22 are connected to an upper work roll chock entry 25 side load calculation device 32 as shown in FIG. 6. The load calculation device 32 adds up loads detected by the load detection devices 22a and 22b. 111 this way, a rolling direction force applied to the housing 10 on tlie entty side fro111 the tlpper work roll cliock 5, that is, a rolling direction force of the upper work roll cliock 5 toward tlie entry side is calculated. [0048] 5 In the same tiiannel; the lower work roll chock exit side rolling directioti force tiieasorelnent device 23 includes a first load detection device 23a and a second load detection device 23b. The load detection devices 23a atid 23b are both disposed on tlie exit side project block I I . Furtliel; as slio!w~n in FIG. 8, tlie load detection devices 23a atid 23b are disposed in a manner tliat a line extending it1 the rolling direction and iticluding a 10 roll axis A2, wliich is a poilit of effort of tlie rolling direction force of the lo\ver work mll 2 in the draft direction of the lowver work roll 2, is interposed between the load detection devices 23a and 23b. [0049] Tlie two load detection devices 23a and 23b of the rolling direction force 15 measurement device 23 are connected to a Lower work roll cliock exit side load calculatioti device 33 as sliown in FIG. 6. Tlie load calculatioti device 33 adds up loads detected by the load detectioti devices 23a and 23b. In this way, a rolling direction force applied to the exit side project block 11 from the lower wwrork roll cliock 6, tliat is, a rolling direction force of the lower work roll chock 6 toward the exit side is calculated. 20 [OOSO] In the same inannet; the lower \vork roll cliock entry side rolling direction force measurement device 24 i~icludes a first load detection device 24a and a second load detection device 24b. The load detection devices 24a and 24b are both disposed on the entry side project block 12. Furtliel; as sliown in FIG. 8, tlie load detection devices 24a 25 and 24b are disposed in a manner that a line extending in the rolling direction and including the roll axis A2, wliicl~ is a point of effort of tlie rolling direction force of the lower work roll 2 in tlie draft direction of the lower work roll 2, is interposed between the load detection devices 24a and 24b. [005 11 The two load detection devices 24a and 24b of the rolling direction force 5 meast~renient device 24 are contiected to a lower work roll cliock entry side load calc~~latiodne vice 34 as shown in FIG. 6. The load calculation device 34 adds up loads detected by the load detection devices 24a and 24b. In tliis way, a rolli~igd irection force applied to the entry side project block 12 fiotii tlie lower work roll chock 6, that is, a rolling direction force of the lower work roll chock 6 toward tlie entry side is calculated. 10 [0052] Nest, fc~nctionsa nd effects of the thus constr~~cterdo lling apparatus will be described. [0053] Taking the upper \\cork roll cliock 5 as an example, according to tlie present 15 cmbodiinent as descr.ibctl above, the hvo load detection devices 21a and 21b are always disposed in a tnanlier tliat the load detection devices 21a atid 21b face the side surface of the exit side of the upper work roll chock 5. Accordingly, the side surface of the exit side of the llpper work roll chock 5 is always supported at multiple points in the draft direction. In tliis case, the load detection devices 2121 and 21b are disposed in a manner that a line 20 extending in the rolling direction and including the roll axis Al, which is the poilit of effort of the rolling direction force of the upper work roll 1 in the draft direction of the upper work roll 1, is interposed between the load detection devices 21a and 21b. 111 the satiie manner, accordiiig to the present einbodiine~itt,l ie two load detection devices 22a and 22b are always disposed in a manner tliat the load detection devices 22a and 22b face the side 25 surface of the entry side of the upper work roll cliock 5. Accordingly, the side surface of the entry side of tlie upper work roll cliock 5 is al\vays suppotted at mc~ltiplep oints in the draft direction. In this case, the Ioad detection devices 22a and 22b are also disposed in a manner that a line extending in the rolling direction and including the roll axis Al, which is the point of effort of the rolling direction force of the upper work roll 1 it1 the draft direction of the upper work roll 1, is interposed between the Ioad detection devices 22a and 5 22b. [0054] For example, as shown in FIG. 9, let us assutne that tlie upper work roll 1 rises and a gap behveen tlie work rolls 1 and 2 increases. In this case, tlie position of the roll axis A1 of tlie upper work roll 1 in the draft direction rises, the relative positional relation 10 behveen the roll axis A1 of the upper work roll 1 and the load detection devices 21a, 21b, 22a, and 22b differs fiom tlie state sho\\a in FIG. S. Accordingly, the lnolnetlt acts on the upper work roll chock 5 in the sattie direction as the direction indicated by an arrow shown in FIG. 3. However, even if st1c11 inonlent acts on tlie upper work roll chock 5, the upper work roll cllock 5 does not tilt as sho\vn in FIG. 3, since the upper \vork roll cliock 5 is 15 being supported at multiple points that are shifted it1 the draft direction. Therefore, the upper work roll chock 5 does not come into contact \vith the housing 10. Consequently, even if the gap between the work rolls 1 and 2 increases, the rolling direction force of the upper \vork roll chock 5 toward the exit side can be accurately detected by tlie exit side load detection devices 21a and 2 I b, and the rolling direction force of the upper work roll 20 chock 5 toward the ent~ysi de can be accurately detected by the entry side load detection devices 22a and 22b. [OOSS] Further, for example, let us assume that the work rolls 1 and 2 and the backup rolls 3 and 4 are worn anray and decrease in the roll dianieters. In this case, as shown in 25 FIG. 10, the upper work roll chock 5 and the lower work roll chock 6 nlove down\vard in the draft direction. Accordingly, the relative positional relation between the axis A1 of the upper work roll 1 and the load detection devices 21a, 21b, 22a, and 22b in the draft direction differs from tlie states shown in FIG. 8 and FIG. 9. In the same manner, the relative positiot~al relation between the axis A2 of the lower work roll 2 and the load detection devices 23a, 23b, 24a, and 24b in the draft direction differs from the states shown 5 in FIG. 8 and FIG. 9. Accordingly, the tnotnent acts on the upper work roll chock 5 and the lower work roll chock 6 in the satne directiotl as the direction indicated by an arrow shown in FIG. 4. [0056] Howevei; similarly as the case showti in FIG. 9, even if such tnolnent acts on 10 the work roll chocks 5 and 6, the work roll chocks 5 and 6 do not tilt as shoown in FIG. 4, since tlie work roll chocks 5 and 6 are each being supported at tnaltiple points in the draft direction. Therefore, the work roll chocks 5 and 6 do not conle into contact with the housing 10 and the project blocks 1 I and 12. Consequently, even if the work rolls 1 and 2 and tlie backup rolls 3 ant1 4 are worn away and decrease in the roll diatneters, the rolling 15 direction forces of tlie work roll chocks 5 and 6 call be accurately detected. [0057] Note that, in the etnbodiments described above, the rolli~ig direction force measurement devices 21, 22, 23, and 24 each have two load detection devices which are disposed with predetermined spaces therebetween in the draft direction. Ho\vevel; the 20 present invention is not limited such an example, and tlie rolling direction force tneasorement devices niay each have three or tnore load detection devices \\~hich are disposed with a predetenuined space there bet wee^^ in the draft direction. Also in this case, the load detection devices of each the rolliilg direction force tneasureinent device are al\vays disposed in a manner that at least two load detection devices face a side surface of a 25 \\'ark roll chock even if the position of the work roll chock changes in the draft direction. In this case, at least t\vo load detection devices are always disposed in a tnanner that a line extending in the rolling direction and including a roll axis, wliich is a point of effort of the rolling direction force, is interposed between the at least two load detection devices. Note that it is pieferred that the load detection devices of each of the rolling direction force nleasuremeilt devices be disposed such that the load detection devices are spaced apart as 5 much as possible froill each other within the above range. [0058] FIG. 11 shows an exatnple in which the rolling direction force measurement device 21 has three load detection devices 21a, 21b, atid 21c, and the rolling direction force measurement device 22 has three load detection devices 22a, 22b, atid 22c. As seen from 10 FIG. 11, wlien the number of load detection devices increases, it becomes easier to make at least t\vo load detection devices always face a side surface of a work roll chock even if the roll gap increases remarkably compared to the case of FIG. 10. Accordingly, tlie rolling direction force can be accurately determined even in the case where the roll gap is increased re~narkably. 15 [0059] [I -2. Second constroction exatnple] Next, on the basis of FIG. 12, a second construction exatliple of a rolling apparatus according to an einbodilnent of the present i~iventiotlw ill be described. In the ~ o l l i ~ap~pgar atus according to the present entbodiment, multiple load detection devices, 20 which are disposed in the draft direction of a work roll, are disposed in a inatiner that the load detection devices are shifted in tlie roll axis direction of the work roll compared with the first construction example. Note that FIG. 12 is an enlarged cross-sectiotial plan view of a work roll chock and tlie periphery thereoftaken along the line XlI-XlI of FIG. 8. [0060] 25 As shown in FIG. 12, in the rolling apparatus according to the present embodinlent, the load detection devices 21a and 21b of the upper work roll chock exit side rolling direction force ineasureme~~dte vice 21 are disposed in a lllaiiner that the load detection devices 21a and 21b are shifted from each other in the roll axis direction. Furthel; the load detection devices 22a and 22b of the upper work roll chock entry side rolling direction force measurement device 22 are also disposed in a manner that the load 5 detectioil devices 22a and 22b are shifted fiom each other in the roll axis direction. [006 I ] The follo\ving description \\,ill be made using the load detection devices 21a and 21b of the upper \\lark roll chock exit side rolling direction force i~~easuremednet vice 21 as exainples. In a rolling apparatus capable of performing roll shifting, the positiotl of 10 the upper work roll chock 5 in the roll axis direction inay change o\ving to shift roll at the time of rolling the flat-rolled ineta1 material M. In this case, in the rolling apparatus according to the present embodiment, even i f the positio~ls of the load detection devices 21a and 21b oft he upper work roll chock 5 in the roll axis direction cha~lget,h e two load detection devices 21a and 21b are al\vays disposed in a inanner that the load detection 15 devices 21a and 21b face a side surface of the upper work roll chock 5. [0062] It is preferred that the load detection devices 21a and 21b be disposed in a manner that a line extending in the rolling direction and including the center of a radial bearing 5a, \\,liich is a point of effort of the rolling direction force, is interposed between 20 the load detection devices 21a atid 21b. That is, even i f the position of the upper work roll chock 5 in the roll axis direction changes, one of the load detection devices, that is, the load detection device 21a, is always disposed in a manner that the load detection device 21a faces the side surface of the upper work roll chock 5 at an upper work roll 1 side with respect to the center (line C shown in the figore) of the radial bearing 5a provided to the 25 upper \vork roll chock 5 ill the roll axis direction. Further, the other load detection device, that is, the load detection device 21 b, is disposed in a iliatlner that the load detection device 21b faces the side surface of the upper work roll cliock 5 at the side opposite to the upper work roll 1 side with respect to the center C of the radial bearing 5a in the roll axis direction. [0063] 5 Note that, although the rolling direction force measure~nentd evices 21 and 22 of tlie upper work roll chock 5 have been described in the above description based o t F~I G. 12, the rollit~gd irection force measurement devices 23 and 24 of the lower work roll chock 6 can have a similar construction. [0064] 10 Functions and effects of the rolling apparatus constructed as sliomn in FIG. 12 will be described. Taking the upper work roll chock 5 as an example, ill the rolling apparatus according to the present e~nbodillietita s described above, the two load detection devices 21a atid 21b are aln~aysd isposed in a lnatiner that tlie load detection devices 21a and 21b face the side surface of the exit side of the work roll chock 5. Accordingly, the 15 side surface of the exit side of the upper work roll cliock 5 is al\says supported at tnultiple points in the roll axis direction. In the same manner, according to the present embodiment, the hvo load detection devices 22a and 22b are al\vays disposed in a tnanner that the load detection devices 22a and 22b face the side surface of the entry side of the upper work roll cliock 5. Accordingly, the side surface of the entry side of the upper 20 work roll chock 5 is also al\vays supported at ~nultiplep oints in the roll axis direction. [0065] For example, as sho\\rn in FIG. 12, \\ Nest, there \will be described a tliethod of controlling a rolling apparatus on the 25 basis of tlie thus detected rolling direction force. [0087] As shown in FIG. 6, the upper work roll cliock exit side load calculation device 3 1 and the opper work roll chock entry side load calculation device 32 are connected to an upper work roll chock rolling direction force calcnlation device 41. The opper work roll chock rolling direction force calculation device 41 calculates a difference of a calculation 5 result obtained by tlie upper work roll chock exit side load calculation device 31 and a calculation result obtained by the opper work roll chock entry side load calculation device 32, and, on the basis of the calculation result, calculates the rolling direction force acting on the upper work roll chock 5. [OOSS] 10 In the same manner, the lo\ver work roll chock esit side load calculation device 33 and the lower work roll chock entry side load calculation device 34 are connected to a lower work roll chock rolling tlircction force calculation device 42. The lo\ver work roll chock rolling direction force calcc~lation device 42 calculates a difference of a calculation result obtained by the lo\ver work roll chock exit side load calcnlation device 33 and a 15 calculation resolt obtained by the lo\ver work roll chock entry side load calculation device 34, and, on the basis of the calculation result, calculates the rolling direction force on the lowver work roll chock 6. [OOS9] In the case of controlling a zigzag nlovelllent and a catnbel; an operator side 20 work roll chock rolling direction force calculation device 43 calculates the sum of the calculation result of the upper work roll chock rolling direction force calcolation device 41 and the calculation result of the lower work roll chock rolling direction force calculatiotl device 42, to calculate the rolling direction resultant force acting on the upper work roll 1 and tlie lower work roll 2 on the operator side. The calculation processing described 25 above is conducted not only for the operator side but also for the driving side by using entirely the same device construction (not shown), and the rolling direction resultant force acting on tlie upper work roll 1 and the lower work roll 2 on tlie driving side is calculated by a driving side work roll chock rolling direction force calculation device 44. [0090] After that, an operator sideldriving side roiling direction force calculation 5 device 45 calculates the difference between the calculatioti results on tlie operator side and the calculatio~i results on tlie driving side, and in this wa): tlie difference of the rolling direction forces acting on the upper and lower work roll chocks between the operator side and tlie driving side is calculated. [0091] 10 Nest, a control quantity calclllatio~id evice 46 sets the difference of the rolling direction forces acting on tlie work roll chocks 5 and 6 betlvcen the operator side and the driving side to a suitable target value and calculates a left-right swivelling component co~itrolq uantity of the roll gap of the rolling ~iiill0 11 tlie basis of the calculation result of the difference of the rolli~igd irection forces between tlie operator side and tlie driving side 15 for preventing the camber. Here, the co~itt.oql uantity is calculated by PlD calci~latio~thia t takes a proportio~ial (P) gain, an integration (I) gain, and a differential (D) gain into consideratioil, for example, on the basis of the left-right ditTcreilce of the rolli~igd irection force. A co~itrodl evice 47 controls the left-right swivellirig colnpolient of tlie roll gap of tlie rolling mill on tlie basis of this control quantity calculation result. In this way, rolling 20 free froill the occurrence of ca~ilber or having estre~nely slight camber can be accotnplished. 100921 Note that, in the calculation processi~ig described above, only additio~i and subtraction are basically done on tlie outputs of 16 load detection devices on both operator 25 side and driving side before the calculation result of the operator sideldriving side rolling direction force calculatio~i device 45 is obtained. Therefore, the sequence of calculation processing described above nlay be arbitrarily changed. For example, it is possible to first add the outputs of the upper and lower exit side load detection devices, then to calculate the difference from the addition result on the entry side and to filially calculate the difference between the operator side and the driving side. Alternatively, it is possible 5 to first calculate the difference of the outputs of the load detection devices at tbe respective positions on the operator side and the driving side, then to calci~latetl ie sutil of the upper and lower detection devices and to finally calculate the difference between the entry side and the exit side. [0093] 10 111 the case of controlling a warp, the operator side \vork roll chock rolling direction force calculation device 43 calculates the difference between the calculation result of the upper work roll chock rolling direction force calculation device 41 and tlie calculatio~ir esult of the lo\\.er work roll chock rolling direction force calculation device 42, to calculate the difference of the rolling direction forces acting on the work roll chocks 011 15 the opclutor side behveen the upper side and the lower side. The calcr~lation processing described above is conducted not only for-the operator side but also for the driving side by using entirely the same device constrllction (not shown), and the difference of tlle rolli~ig direction forces acting on the work roll cl~ockso n the driving side between the upper side aiid the lo\\cer side is calculated by the driving side \\.ark roll chock rolling direction force 20 calculation device 44. The operator sideldriving side rolling direction force calculation device 45 totalizes the calculation results on the operator side and the calculation results of the driving side (difference behveeo the upper side and the lower side), and in this way, the difference of the rolling direction forces acting on the \\,ark roll chocks betjveen the upper side and tlie lower side is calculated. 25 [0094] Nest, tlie control quantity calculation device 46 sets the difference of the rolling direction forces acting on tlie work roll chocks between the upper side and tlie lower side to a suitable target value and calculates an upper side-lower side swivelling coliiponent colitrol quantity of a roll speed of the rolling ~iiil0l1 1 tlie basis of the calculatioti ~.esulot f the difference of tlie rolling direction forces behveeo the upper side and the lower 5 side for preventing the warp. Here, the colitrol quantity is calculated by PID calculation that takes a proportional (P) gain, an integration (I) gain, atid a differential (D) gain into consideration, for exa~npleo, n the basis of the upper side-lower side rolling direction force. [0095] Then, the control device 47 co~itrols tlie upper side-lower side swivelling 10 coliiponent control quantity of the roll speed of the upper drive electric motor 35 and the lonrer drive electric motor 36 of tlie rolling mill on the basis of this control quantity calculation result. In this way, rolling free fro111 tlie occurrence of warp 01. having estretnelp slight warp call be accomplished. [0096] 15 Note that, although the roll speed of the rolling mill is used here as the npper side-lo\ver side swivelling component control quantity,-a fiictio~ial coeficient between a rolling roll and a material to be rolled, a difference it1 temperature of a material to be rolled behveen tlie npper surface and the lower surface, an angle of incidence of a material to be rolled, a position of tlie work roll chock in the horizontal direction, top atid bottolii rolling 20 torqi~es0,1 . the like liiay be also used. [0097] In the case of zero point adjusttilent, after going through tlie satne processes as the calculation processes of the zigzag movement and ca~iiberc ontrol described above, the operator sideldriving side rolling direction force calculation device 45 calculates the 25 difference between the calculation results on the operator side and the calculation resi~lts on the driving side, and in this way, calculates tlie difference of tlie rolling direction forces acting on tlie work roll chocks betweeti the operator side and tlie driving side. [0098] Then, the liydraolic screw down devices 9 are operated sitnultatieously on the operator side and on tlie driving side and are tightened until tlie sutii of right and left 5 counterforces of a backup roll is equal to a preset value (zero point adjustment load), and, under that state, leveling operation for rendering the difference of the rolling directioti forces between the operator side and the driving side zero is executed. [0099] Subsequently, the cotitrol quantity calculatioli device 46 calculates the co~itrol 10 quantity of the hydraulic screw dow~l device 9 such that the difference of the rolling direction forces acting on the work roll chocks 5 and 6 between the operator side and tlie driving side becotiie zero and that the zero point adjustlnent load is maintained, oti tlie basis of the results of the difference of the rolling direction forces between tlie operator side atid tlie driving side (difference between the operator side and the driving side) 15 calct~lated by the operator sideldriving side rolling direction force calculatioti device 45. Then, tlie control device 47 controls tlie reduction positiot~o f a roll of tlie rolling tilill 011 the basis of tlie control quantity calcl~lation result. lo this way, tlie difference of tlie rolling direction forces acting on the work roll chocks betweeti the operator side and tlie driving side is set to zero, and the reduction position at that poitit is set as the zero poitit of 20 the reduction position of the operator side and tlie driving side individually. [O 1001 Note that, as described above, the difference of the rolling direction forces acting on the \\rork roll chocks (upper work roll chock 5 and lo\ver work roll chock 6) behveen tlie operator side atid tlie driving side is not influenced by a roll thrust force. 25 Therefore, eveti if a thrust force occurs between tlie rolls, the zero poitit setting of the reduction leveling call be accomplished with extremely high accurac)r. [OlOl] Heretofore, preferred embodiments of the present invention have been described in detail \vith referencc to the appended drawings, but the presetit invetitio~i is not limited thereto. It should be u~iderstood by those skilled in the art that various 5 changes and alterations tilay be made without departing fiom the spirit and scope of the appended claims. [O 1021 Note that, in the embodiaie~ltsd escribed above, there has been used a four high rolling mill liavi~igo nly the work rolls and the backup rolls for the description, but the 10 presetit itivention is not limited thereto. The technology according to the present invention can be also applied to a six high rolling mill which has interlnediate rolls, for example. [Reference Signs List] [0 1031 15 1 upper work roll 2 lo\ver work roll 3 tipper backup roll 4 lo\\,er backup roll 5 upper work roll chock (operator side) 6 lower work roll chock (operator side) 7 upper backup roll chock (operator side) 8 lower backup roll chock (operator side) 9 screw down device 10 housitig 11 esit side project block (operator side) 12 entry side project block (operator side) 21 upper work roll cliock exit side rolling direction force tneasurement device (operator side) 21a first load detection device on exit side of upper work roll chock 21 b second load detection device on exit side of upper work roll chock 5 22 upper work roll chock entry side rolling direction force measurement device (operator side) 22a first load detection device on entry side of upper work roll chock 22b second load detection device on entry side of upper work roll chock 23 lower work roll chock exit side rolling direction force measureme~~det vice 10 (operator side) 23a first load detection device on exit side of lower work roll chock 23b second load detection device on exit side of lower work roll chock 24 lower work roll chock entry side rolling direction force measurement device (operator side) 15 24a first load detection device on entry side of lower work roll cliock 24b second load detection device on entry side of lower work roll chock 25 cover shared between first and second load detection devices on exit side of upper work roll chock (operator side) 26 cover shared between first and second load detection devices on entry side 20 of upper \vork roll chock (operator side) 27 cover shared between first and second load detection devices on exit side of lower work roll chock (operator side) 28 cover sliared bet\veen first and second load detection devices on entry side of lower work roli chock (operator side) 3 1 upper \vork roll chock exit side load calculation device (operator side) 32 upper mork roll chock entry side load calculation device (operator side) 33 lower work roll chock exit side load calculation device (operator side) 34 lower work roll chock entry side load calculation device (operator side) 35 upper drive electric motor 36 lower drive electric motor 5 41 upper work roll chock rolling direction force calculation device (operator side) 42 lower work roll chock rolling direction force calculation device (operator side) 43 operator side work roll chock rolling direction force calculation device 44 driving side work roll chock rolling direction force calculation device 45 operator side/driving side rolling direction force calculation device 46 control quantity calculation device 47 control device 12 1 upper work roll chock esit side load detection device 122 upper work roll chock entry side load detection device 123 lower work roll chock esit side load detection device 124 lower work roll chock entry side load detection device 141 upper work roll rolling direction force calci~lationd evice 142 lower work roll rolling direction force calculation device pame of Document] CLAlMS [Claim I] A rolling apparatus for a flat-rolled llletal nlaterial, the rolling apparatus including at least a pair of upper and lower work rolls and a pair of upper and lower 5 backup rolls, the rolling apparatus comprising: a pair of work roll chocks collfigl~red to hold the respective work rolls; housings or project blocks configured to llold the work roll chocks; and one or Inore rolling direction force measurement devices configured to measure rolling direction forces acting on the work roll chocks, 10 wherein at least one of the rolling direction force measurement devices includes a plurality of load detection devices on an entry side or an exit side of the work roll chocks in a rolling direction, and the plarality of load detection devices are provided to one of the housings or one of the pro-ject blocks, and \\,herein the load detection devices are disposed in a manner that, on all 15 occasions, a line extending in the rolling direction and including a point of effort of a rollillg direction force of one of the work rolls is interposed between at least two of the ~ ~ . ~ : load detection devices it1 a draft direction, and the at least two ofthe load detection devices face a side surface of a correspoltding one of the work roll chocks. [Claim 21 20 The rolling apparatus according to claitll 1, wherein, in at least one of the rolling direction force measurement devices, the load detection devices are disposed in a manner that, on all occasions, a line extending in the rolling direction atid including a point of effort of a rolling direction force of one of the work rolls is interposed between at least two of the load detection devices in a roll axis 25 direction of the work rolls, and the at least two of the load detection devices face a side surface of a corresponding one of the work roll chocks. [Claim 31 The rolling apparatus according to claim 1 or 2, wherein at least one of the rolling direction force measurement devices includes at least three load detection devices on the ently side or the exit side of the work roll chocks in a rolling direction, and the at least three load detection devices are provided 5 to one of the housings or one of tlie project blocks, and wherein the load detection devices are disposed so as to be shifted in one of the draft direction and the roll axis direction of the work rolls, in a manner that the point of effort of the rolling direction force of each of the work rolls is located within an area defined by connecting tlie load detection devices. 10 [Claim 41 The rolling appaiatus according to aojf one of claims 1 to 3, further comprising: n rolling direction force calculation device configured to calculate a rolling direction force by adding up loads df the one or more rolling direction force measurement devices each including the plurality of load detection devices, the loads being detected by 15 tlie respective load detection devices. [Claim 51 Tlie rolling apparatus according to any one of clailus 1 to 4, wherein the rolling apparatus is provided with the rolling direction force measurement devices on an esit side of an upper work roll chock, an entry side of the 20 upper work roll chock, an exit side of a lower \vork roll chock, and an entry side of the lower \vork roll chock, respectively. [Claim 61 Tlie rolling apparatus according to claim 5, wherein, out of the rolling direction force measorenlent devices, the plurality of 25 load detection devices are provided only to the one or more rolling direction force measurement devices configured to measure any one of a rolling direction force acting in a rolling direction on the exit side and a roilitlg direction force acting in a rolling direction on the entry side. [Claim 71 The roililig apparatus accordir~gto claim 5, 5 wherein all of the rolling direction force measaretnent devices each have the plurality of load detection devices. [Claitm 81 The rolling apparatus according to claim 5, \\herein, out of the rolling direction force measurement devices, the plurality of 10 load detection devices are provided only to the one or inore rolling direction force measurement devices for any one of the upper work roll chock and the lower work roll chock. [Claim 91 The rolling apparatus according to claim 7 or 8, \\therein the plt~rality of load detection devices are disposed in a manner that positiotis in a draft direction and positions in a roll axis direction of the plurality of load detection devices provided on the entry side in the rolling direction are identical to positions in a draft direction and positions in a roll axis direction of the plurality of load detection devices provided on the esit side in the rolling direction. 20 [Claim lo] The rolling apparatus according to any one of claims 7 to 9, wherein the rolling direction force calculation device calcltlates a rolling direction force on the basis of an entry side load calculated by adding up loads detected by the plurality of load detection devices provided on the elltry side in the rolling direction 25 and an exit side load calculated by adding up loads detected by the plurality of load tletectio~l devices provided on the esit side in the rolling direction. [Claim 1 I] The rolling apparatus according to any one of clai~ns1 to 10, wherein the load detection devices are each a load cell. [Claim 121 5 The rolling apparatus according to any one of clainis 1 to 11, fuither comprising: a cover configured to cover each of the load detection devices, the cover being plovided between one of the housings or one of the project blocks and each of the load detection devices. 10 [Claim 131 The rolling apparatus according to any one of clailns 1 to 1 I, further comprising: a cover configured to collectively cover the load detection devices for each of the rolling direction force measurement devices, the cover being provided between one of 15 the housings or one of the project blocks and each of the load detection devices. Dated this 31d day of April, 2014 [RANJNA MEHTA-DUTT] OF REbIFRY & SAGAR ATTORNEY FOR TI-E APPLICANT[S] [Name of Document] ABSTRACT [Abstract] [Object] To provide a rolling apparatus capable of accurately detecting a rolling 5 direction force applied to a work roll chock. [Solution] A rolling apparatus for flat-rolled metal materials including a pair of upper and lower work rolls 1 and 2 includes a pair of work roll chocks 5 and 6 configured to hold the respective work rolls I and 2, housings 10 configured to hold the work roll chocks, and 10 rolling direction force lneasu~elnent devices 21, 22, 23, and 24 configured to measure rolling direction forces. The rolling direction force measurement devices include a plurality of load detection devices on an entry side or at) exit side of the work roll chocks in a rolling direction, and the plt~ralitpo f load detection devices are provided to one of the housings, and the plurality of load detection devices are disposed in a manner that, during 15 rolling of the flat-rolled metal materials, at least hvo of the load detection devices are ar~angeda djacent to each other in a draft direction facing a side surface of a corresponding one of the work roll chocks. In this case, the at least t\vo load detection devices are disposed in a inanner that a line extending in the rolling direction and including a roll axis, which is a point of effort of a rolling direction force, is interposed between the at least two 20 load detection devices in the draft direction. [Representative Drawing] FIG.