JP4504949B2

JP4504949B2 - Workpiece pressing device using servo motor

Info

Publication number: JP4504949B2
Application number: JP2006141553A
Authority: JP
Inventors: 博徳山口
Original assignee: 株式会社武田機械
Priority date: 2006-05-22
Filing date: 2006-05-22
Publication date: 2010-07-14
Anticipated expiration: 2026-05-22
Also published as: JP2007307681A

Description

本発明は、サーボモータを利用するワーク押圧装置に関するものである。より詳しくは、ナット部材が螺合されてなる駆動ネジ軸をサーボモータによって回転制御することを基本として、サイズや材質の異なるワークに対し、ワークに無理を掛けることなく所要の押圧力を付与でき、然も作業能率の向上をも期し得るサーボモータ利用のワーク押圧装置に関するものである。 The present invention relates to a workpiece pressing device that uses a servomotor. More specifically, based on the rotational control of the drive screw shaft with the nut member screwed by a servo motor, the required pressing force can be applied to workpieces of different sizes and materials without overloading the workpiece. The present invention also relates to a workpiece pressing device using a servo motor that can improve the work efficiency.

工作機械例えばフライス盤で、テーブルに固定したワークに対して所要の加工を施すに際し、該ワークをテーブルに押圧状態で固定するワーク押圧装置の一例として、特開２００３−６２７２９号公報が開示するワーク押圧装置が提案されている。 As an example of a workpiece pressing device that fixes a workpiece fixed to a table in a pressed state when a workpiece is fixed to the table by a machine tool, for example, a milling machine, a workpiece pressing disclosed in Japanese Patent Application Laid-Open No. 2003-62729 is disclosed. A device has been proposed.

該ワーク押圧装置ａは図２５に示すように、上下方向で伸縮し得る油圧シリンダｂ１としての押圧手段ｂを用いるものであり、該油圧シリンダｂ１は、テーブルｃを跨ぐようにテーブルベース上で立設された門形フレームの上部をなす横架フレームｆに固定されていた。そして、該油圧シリンダｂ１のロッドｇが前記横架フレームｆの下面側で下方向に突出できるように構成され、該ロッドｇの下端部に設けられた押圧具ｈで、ワークｊをテーブルｃに押圧状態に固定するように構成されていた。 As shown in FIG. 25, the workpiece pressing device a uses pressing means b as a hydraulic cylinder b1 that can expand and contract in the vertical direction, and the hydraulic cylinder b1 stands on a table base so as to straddle the table c. It was fixed to a horizontal frame f that forms the upper part of the installed portal frame. The rod g of the hydraulic cylinder b1 is configured to protrude downward on the lower surface side of the horizontal frame f, and the workpiece j is placed on the table c with a pressing tool h provided at the lower end of the rod g. It was comprised so that it might fix to a press state.

しかしながら、油圧シリンダｂ１を用いる押圧手段ｂによるときには次のような問題点があった。即ち、ワークｊをテーブルｃに押圧状態に固定するに際しては、前記油圧シリンダｂ１のロッドｈを該ワークｊに向けて下方向に突出させるのであるが、該ロッドｈの下端の押圧具ｋがワークｊを押圧する際、該押圧具ｋがワークｊに衝撃的に当たることになる。そのため、衝撃力でワークを破損したり、油圧シリンダｂ１の支持部分を衝撃力で損傷する恐れがあった。 However, when the pressing means b using the hydraulic cylinder b1 is used, there are the following problems. That is, when the workpiece j is fixed to the table c in a pressed state, the rod h of the hydraulic cylinder b1 protrudes downward toward the workpiece j. When pressing j, the pressing tool k impacts the workpiece j. For this reason, there is a possibility that the workpiece is damaged by the impact force or the support portion of the hydraulic cylinder b1 is damaged by the impact force.

このような衝撃力がワークや油圧シリンダの支持部分に加わらないようにするためには、油圧シリンダのロッドの下降速度を小さく設定せざるを得ないが、このようにすると、ワークをテーブルに固定するための作業時間が掛かり過ぎてフライス盤の加工能率が低下する問題が生ずることになった。なお、ワークをテーブルに固定する際、ロッドの下端がワークに当たる直前までは該ロッドを早送りすると共に当たる直前で下降速度を落とすようにリミットスイッチ制御を行うことは可能であったが、テーブルに載置するワークの高さは一定していないために、高さの異なるワーク毎にリミットスイッチの配置状態を変更する面倒な調整作業が必要となって、作業能率が悪いという問題を招来した。又、ワークのサイズや材質に応じてワークを低圧で押圧したり、中圧で押圧したり、高圧で押圧することが求められるが、このような押圧力の選択を可能とするためには、圧力スイッチ等の各種の油圧機器を必要とするばかりか、油圧制御が難しい問題もあった。更には、使用する油が配管接続部分等から漏れて周辺を汚す作業環境汚損の問題も発生させた。 In order to prevent such an impact force from being applied to the workpiece and the support part of the hydraulic cylinder, the lowering speed of the rod of the hydraulic cylinder must be set small, but in this case, the work is fixed to the table. Therefore, it took too much work time to do so, resulting in a problem that the machining efficiency of the milling machine was lowered. When fixing the workpiece to the table, limit switch control was possible so that the rod was fast-forwarded immediately before the lower end of the rod hits the workpiece and the lowering speed was reduced just before hitting the rod. Since the height of the workpiece to be placed is not constant, a troublesome adjustment work for changing the arrangement state of the limit switch is required for each workpiece having a different height, resulting in a problem of poor work efficiency. Also, depending on the size and material of the workpiece, it is required to press the workpiece at a low pressure, press at a medium pressure, or press at a high pressure, but in order to enable selection of such a pressing force, In addition to requiring various hydraulic equipment such as pressure switches, there was a problem that hydraulic control was difficult. Furthermore, there was a problem of contamination of the working environment in which the oil used leaked from the pipe connection part and the like and contaminated the periphery.

特開２００３−６２７２９号公報（４頁、図１−３）Japanese Patent Laying-Open No. 2003-62729 (page 4, FIG. 1-3)

本発明は前記従来の問題点に鑑みて開発されたものであり、サイズや材質の異なるワークに対してワークに無理を掛けることなく所要の押圧力を付与できると共に、作業能率の向上を達成でき、しかも、従来の油圧方式に比して全体を簡素に構成できると共に、油による作業環境汚損の問題を生じさせることもないサーボモータ利用のワーク押圧装置の提供を課題とすものである。 The present invention has been developed in view of the above-mentioned conventional problems, and can apply a required pressing force to a workpiece of different size or material without exerting an excessive force on the workpiece, and can achieve an improvement in work efficiency. Moreover, it is an object of the present invention to provide a work pressing device using a servo motor that can be simply configured as a whole as compared with the conventional hydraulic system and does not cause a problem of contamination of the working environment due to oil.

前記課題を解決するため本発明は以下の手段を採用する。
即ち、本発明に係るサーボモータ利用のワーク押圧装置（以下ワーク押圧装置という）は、サーボモータによって正逆回転せしめられる駆動ネジ軸にナット部材が螺合されており、該駆動ネジ軸が正逆回転することによって該ナット部材が回り止めされて前後進できると共に、該ナット部材には、前端でワークを押圧するワーク押圧部に付設されたバネ部材を前記駆動ネジ軸の長さ方向での前進移動に伴って圧縮させる圧縮押部が設けられ、前記バネ部材はセット状態で圧縮されて設けられている。前記ワーク押圧部は、円筒状を呈し且つ前記バネ部材を収容させる収容筒部を有し、該収容筒部には上下方向に長い規制孔が設けられ、該規制孔には、前記ナット部材にネジ止めされた圧縮押部に螺合されている規制ネジの係合頭部が、該規制孔の中で、前記ワーク押圧部がワークに当接するまでは前記規制孔の上端に弾性的に圧接され、ワークに当接後においては下方に移動可能に嵌合されており、且つ、前記圧縮押部には押圧鍔部が設けられ、該押圧鍔部の下面と前記収容筒部の上端面との間には、前記ワーク押圧部がワークに当接するまでは所要の間隙が設けられ、且つ、前記規制ネジの係合頭部が該規制孔の中で下方移動する範囲において該ワーク押圧部と該ワークとが当接可能に構成されている。そして、該ワーク押圧部の前端がワークに当接した状態で前記駆動ネジ軸が回転することによって、前記圧縮押部が前記バネ部材を圧縮させて、前記圧縮押部の押圧鍔部と前記ワーク押圧部の収容筒部とが当接されるように構成され、又、前記サーボモータは、前記ワーク押圧部がワークに当接した後、前記圧縮押部が前記ワーク押圧部を、互いに接触して直接的に押圧するまでの間において、第１の設定トルク値に達するまで、前記駆動ネジ軸を回転させ続けるように位置制御されると共に、その後は、位置制御状態からトルク制御状態に切り換わり、前記ワーク押圧部が前記ワークを所要押圧力で押圧するように設定された、前記第１の設定トルク値よりも大なる第２の設定トルク値に達するまで前記駆動ネジ軸を回転させ続けるようにトルク制御されることを特徴とするものである。 In order to solve the above problems, the present invention employs the following means.
That is, in the workpiece pressing device using a servo motor according to the present invention (hereinafter referred to as workpiece pressing device), a nut member is screwed to a drive screw shaft that is rotated forward and backward by a servo motor, and the drive screw shaft is forward and backward. By rotating, the nut member is prevented from rotating and can move forward and backward, and a spring member attached to a work pressing portion that presses the work at the front end is advanced to the nut member in the length direction of the drive screw shaft. A compression pressing portion is provided for compression along with the movement, and the spring member is provided compressed in a set state. The workpiece pressing portion has a cylindrical shape and a receiving cylinder portion that accommodates the spring member. The receiving cylinder portion is provided with a restriction hole that is long in the vertical direction. The restriction hole is formed on the nut member. The engaging head of the restriction screw screwed into the screwed compression pushing portion is elastically pressed against the upper end of the restriction hole until the work pressing portion comes into contact with the work in the restriction hole. After the contact with the workpiece, it is fitted so as to be movable downward, and the compression pressing portion is provided with a pressing collar, and the lower surface of the pressing collar and the upper end surface of the accommodating cylinder Between the workpiece pressing portion and the workpiece pressing portion within a range in which a required gap is provided until the workpiece pressing portion abuts against the workpiece, and the engagement head of the regulation screw moves downward in the regulation hole. The workpiece is configured to come into contact with the workpiece. Then, when the drive screw shaft rotates with the front end of the workpiece pressing portion in contact with the workpiece, the compression pressing portion compresses the spring member, and the pressing flange portion of the compression pressing portion and the workpiece The servo motor is configured so that the accommodating cylinder portion of the pressing portion comes into contact with the servo motor. After the workpiece pressing portion comes into contact with the workpiece, the compression pressing portion contacts the workpiece pressing portion with each other. Until the first set torque value is reached, the position of the drive screw shaft is continuously rotated until the first set torque value is reached. Thereafter, the position control state is switched to the torque control state. The drive screw shaft continues to rotate until reaching a second set torque value which is set so that the work pressing portion presses the work with a required pressing force and is larger than the first set torque value. In It is characterized in that the torque control.

又本発明に係るワーク押圧装置の他の態様は、サーボモータによって正逆回転せしめられる駆動ネジ軸にナット部材が螺合されており、該駆動ネジ軸が正逆回転することによって該ナット部材が回り止めされて前後進できると共に、該ナット部材には、前端でワークを押圧するワーク押圧部に付設されたバネ部材を前記駆動ネジ軸の長さ方向での前進移動に伴って圧縮させる圧縮押部が設けられ、前記バネ部材はセット状態で圧縮されて設けられている。前記ワーク押圧部は、円筒状を呈し且つ前記バネ部材を収容させる収容筒部を有し、該収容筒部には上下方向に長い規制孔が設けられ、該規制孔には前記ナット部材にネジ止めされた圧縮押部に螺合されている規制ネジの係合頭部が、該規制孔の中で、前記ワーク押圧部がワークに当接するまでは前記規制孔の上端に弾性的に圧接され、ワークに当接後においては下方に移動可能に嵌合されており、且つ、前記圧縮押部には押圧鍔部が設けられ、該押圧鍔部の下面と前記収容筒部の上端面との間には、前記ワーク押圧部がワークに当接するまでは所要の間隙が設けられ、且つ、前記規制ネジの係合頭部が該規制孔の中で下方移動する範囲において該ワーク押圧部と該ワークとが当接可能に構成されている。そして、該ワーク押圧部の前端がワークに当接した状態で前記駆動ネジ軸が回転することによって前記圧縮押部が前記バネ部材を圧縮させて前記圧縮押部の押圧鍔部と前記ワーク押圧部の収容筒部とが当接されるように構成され、前記駆動ネジ軸は、少なくとも、前記圧縮押部が前記ワーク押圧部を押圧する状態となるまで回転でき、又、前記サーボモータは、前記ワーク押圧部がワークに当接した後、前記圧縮押部が前記ワーク押圧部を、互いに接触して直接的に押圧するまでの間において、第１の設定トルク値に達するまで、前記駆動ネジ軸を回転させ続けるように位置制御されると共に、その後は、位置制御状態からトルク制御状態に切り換わり、前記ワーク押圧部が前記ワークを所要押圧力で押圧するように設定された、前記第１の設定トルク値よりも大なる第２の設定トルク値に達するまで前記駆動ネジ軸を回転させ続けるようにトルク制御されることを特徴とするものである。 In another aspect of the workpiece pressing device according to the present invention, a nut member is screwed to a drive screw shaft that is rotated forward and backward by a servomotor, and the nut member is rotated by rotating the drive screw shaft forward and backward. The nut member can be moved forward and backward, and the nut member includes a compression member that compresses a spring member attached to a workpiece pressing portion that presses the workpiece at the front end in accordance with a forward movement in the length direction of the drive screw shaft. The spring member is compressed and provided in a set state. The work pressing portion has a cylindrical shape and a receiving cylinder portion that receives the spring member. The receiving cylinder portion is provided with a restriction hole that is long in the vertical direction, and the restriction hole is screwed to the nut member. The engaging head of the restriction screw screwed into the stopped compression pushing portion is elastically pressed against the upper end of the restriction hole until the work pressing portion contacts the work in the restriction hole. After the contact with the work, it is fitted so as to be movable downward, and the compression pressing part is provided with a pressing collar part, and the lower surface of the pressing collar part and the upper end surface of the accommodating cylinder part A necessary gap is provided between the workpiece pressing portion and the workpiece so that the engagement head of the regulating screw moves downward in the regulating hole. It is comprised so that a workpiece | work can contact | abut. Then, when the drive screw shaft rotates with the front end of the workpiece pressing portion in contact with the workpiece, the compression pressing portion compresses the spring member, and the pressing flange portion of the compression pressing portion and the workpiece pressing portion The drive screw shaft can rotate at least until the compression pressing portion is in a state of pressing the work pressing portion, and the servo motor The drive screw shaft until the first set torque value is reached after the workpiece pressing portion abuts against the workpiece until the compression pressing portion contacts the workpiece pressing portion and directly presses the workpiece pressing portion. The position is controlled so as to continue to rotate, and thereafter, the position control state is switched to the torque control state, and the work pressing portion is set to press the work with a required pressing force. It is characterized in that the torque control to continue rotating the drive screw shaft until it reaches the second set torque value composed larger than the constant torque value.

本発明は以下の如き優れた効果を奏する。
(1) 本発明に係るワーク押圧装置はサーボモータを用いて構成されているため、油圧制御によってワークを押圧する従来のワーク押圧装置に比し、ワークの材質や大きさに適合した所要の押圧力の設定が容易である。 The present invention has the following excellent effects.
(1) Since the workpiece pressing device according to the present invention is configured using a servo motor, the required pressing device suitable for the material and size of the workpiece is compared with a conventional workpiece pressing device that presses the workpiece by hydraulic control. Easy to set pressure.

(2) 前記サーボモータは、前記ワーク押圧部がワークに当接した後、第１の設定トルク値に達するまで、前記駆動ネジ軸を回転させ続けるように位置制御されると共に、その後は、位置制御状態からトルク制御状態に切り換わり、前記ワーク押圧部が前記ワークを所要押圧力で押圧するように設定された、前記第１の設定トルク値よりも大なる第２の設定トルク値に達するまで前記駆動ネジ軸を回転させ続けるようにトルク制御されるため、ワーク押圧部がワークに当接した際の衝撃は、前記バネ部材が圧縮されることによって緩衝される。 (2) The position of the servo motor is controlled so as to continue to rotate the drive screw shaft until the first set torque value is reached after the workpiece pressing portion abuts against the workpiece. From the control state to the torque control state, until the workpiece pressing portion reaches the second set torque value that is set to press the workpiece with the required pressing force and is larger than the first set torque value. Since the torque is controlled so that the drive screw shaft continues to rotate, the impact when the workpiece pressing portion comes into contact with the workpiece is buffered by the compression of the spring member.

かかることから、ワークの押圧面の位置（ワークの押圧面の高さ等）によらず、位置制御が行われる間においてはワーク押圧部を早送りすることが可能である。従って本発明に係るワーク押圧装置によるときは、ワーク加工能率の向上を図ることができる。 Therefore, regardless of the position of the workpiece pressing surface (the height of the workpiece pressing surface, etc.), it is possible to fast-forward the workpiece pressing portion during the position control. Therefore, when the workpiece pressing device according to the present invention is used, the workpiece machining efficiency can be improved.

図１〜４において本発明に係るワーク押圧装置１は、工作機械、例えば両頭フライス盤２に付設のテーブル３上に載置されたワーク５を該テーブル３に押圧状態に固定するために応用されており、サーボモータ６によって正逆回転せしめられる駆動ネジ軸７にナット部材９が螺合されており、該駆動ネジ軸７が正逆回転することによって該ナット部材９が回り止めされて前後進（本実施例においては上下動）できるようになされている。そして該ナット部材９には、前端（本実施例においては下端）１０（図１〜２）でワーク５を押圧するワーク押圧部１１に付設されたバネ部材１２を前記駆動ネジ軸７の長さ方向での前進移動（本実施例においては下降）に伴って圧縮させる圧縮押部１３が設けられている。又、該ワーク押圧部１１の下端１０がワーク５の上面１４に当接した状態で前記駆動ネジ軸７が回転することによって前記圧縮押部１３が前記バネ部材１２を圧縮させ、該圧縮押部１３が最大に下降した状態まで前記駆動ネジ軸７が回転することによって該圧縮押部１３が前記ワーク押圧部１１を押圧する如くなされている。 1-4, the workpiece pressing device 1 according to the present invention is applied to fix a workpiece 5 placed on a table 3 attached to a machine tool, for example, a double-headed milling machine 2, to the table 3 in a pressed state. The nut member 9 is screwed to the drive screw shaft 7 that is rotated forward and backward by the servo motor 6, and the nut member 9 is prevented from rotating by forward and reverse rotation of the drive screw shaft 7 to move forward and backward ( In this embodiment, it can be moved up and down). The nut member 9 has a spring member 12 attached to a workpiece pressing portion 11 that presses the workpiece 5 at the front end (lower end in the present embodiment) 10 (FIGS. 1 and 2). There is provided a compression pusher 13 that compresses with forward movement in the direction (down in this embodiment). Further, when the drive screw shaft 7 rotates in a state where the lower end 10 of the workpiece pressing portion 11 is in contact with the upper surface 14 of the workpiece 5, the compression pressing portion 13 compresses the spring member 12, and the compression pressing portion When the drive screw shaft 7 rotates until the position 13 is lowered to the maximum, the compression pressing portion 13 presses the work pressing portion 11.

そして前記サーボモータ６は、図示しない制御部により、前記ワーク押圧部１１の下端１０がワーク５に当接した後、第１の設定トルク値に達するまで、前記駆動ネジ軸７を回転させ続けるように位置制御されると共に、その後は、前記ワーク押圧部１１が前記ワーク５を所要押圧力（ワーク５をテーブル３に固定できる押圧力）で押圧するように設定された、前記第１の設定トルク値よりも大なる第２の設定トルク値に達するまで前記駆動ネジ軸７を回転させ続けるようにトルク制御されるようになされている。 Then, the servo motor 6 continues to rotate the drive screw shaft 7 until the first set torque value is reached after the lower end 10 of the workpiece pressing portion 11 contacts the workpiece 5 by a control unit (not shown). After that, the first set torque is set so that the workpiece pressing portion 11 presses the workpiece 5 with a required pressing force (a pressing force capable of fixing the workpiece 5 to the table 3). Torque control is performed so that the drive screw shaft 7 continues to rotate until a second set torque value larger than the value is reached.

本実施例において前記両頭フライス盤２は、ワークの複数の面に所要の加工を施すことができるように前記テーブル３がその軸線回りに回転可能となされている。そこで、該テーブル３の回転軸線と前記ワーク押圧部１１の軸線とが一致しない場合であっても、該不一致を補正して、ワーク５をテーブル３の回転に伴って正しく円滑に回転させることができるように、該ワーク押圧部１１には芯ずれ補正機構部１５が設けられている。 In the present embodiment, the double-headed milling machine 2 is configured such that the table 3 is rotatable about its axis so that a plurality of surfaces of a workpiece can be processed. Therefore, even when the rotation axis of the table 3 and the axis of the workpiece pressing portion 11 do not match, the mismatch can be corrected and the workpiece 5 can be rotated correctly and smoothly with the rotation of the table 3. The work pressing portion 11 is provided with a misalignment correction mechanism portion 15 so as to be able to do so.

前記ワーク５は、図１に示す第１の位置決め当接部材１６と第２の位置決め当接部材１７とを具えるワーク位置決め装置１８によって、図５に示すようにテーブル３上で所要に位置決めされて後、図２、図５に示すように、前記ワーク押圧装置１によって該テーブル３に所要の押圧力で押圧状態に固定される。 The workpiece 5 is properly positioned on the table 3 as shown in FIG. 5 by a workpiece positioning device 18 including the first positioning contact member 16 and the second positioning contact member 17 shown in FIG. Then, as shown in FIGS. 2 and 5, the work pressing device 1 is fixed to the table 3 in a pressing state with a required pressing force.

このようにしてワーク５がテーブル３に固定された状態で、該テーブル３は、図５に矢印で示す方向に前進する。これにより図６に示すように、該ワーク５が左右のフライス１９，１９間に所要に配置され、該左右のフライス１９，１９によって左右の被加工面２０，２１にフライス加工が施されるようになされている。そしてフライス加工が完了した後、前記テーブル３が図７に示すように当初の状態に戻り、その後、前後の被加工面２２，２３を加工するために、テーブル３は、図７に矢印で示すように９０度回転せしめられる。この回転の円滑化の為に、該回転時のワーク押圧力は、ワークの固定を不安定化させない範囲で低圧に、例えば８００ｋｇｆに設定される。 With the workpiece 5 fixed to the table 3 in this way, the table 3 moves forward in the direction indicated by the arrow in FIG. As a result, as shown in FIG. 6, the workpiece 5 is arranged between the left and right milling cutters 19 and 19 so that the left and right milling surfaces 19 and 19 can mill the left and right workpiece surfaces 20 and 21. Has been made. Then, after the milling is completed, the table 3 returns to the initial state as shown in FIG. 7, and then the table 3 is indicated by arrows in FIG. 7 in order to machine the front and back work surfaces 22 and 23. It can be rotated 90 degrees. For smooth rotation, the workpiece pressing force during the rotation is set to a low pressure, for example, 800 kgf within a range that does not destabilize the workpiece.

前記ワーク押圧装置１の構成をより具体的に説明すれば、図１、図３〜４、図８に示すように、前記駆動ネジ軸７はボールネジ２５として構成されると共に前記ナット部材９はボールネジナット２６として構成されている。該ボールネジ２５は、その上側の部分２７が、前記テーブル３の上方に位置する支持部２９に固定された例えば角筒状を呈するカバー部３０内に収容されると共に、その下側の部分３１が、前記ワーク押圧部１１の円筒状を呈する収容筒部３２内に収容されており、該ボールネジ２５の上端側の部分３３は、前記カバー部３０の上端側の部分３５に内蔵された複数段のアンギュラボールベアリング３６に支持され、軸線回りに回転可能である。そして図１、図３に示すように、該ボールネジ２５の上端３７にはプーリ３９が固定され、該プーリ３９と、前記サーボモータ６の回転軸４０に装着されたプーリ４１とにベルト４２が巻装されており、該サーボモータ６の正逆回転によって前記ボールネジ２５が正逆回転するようになされている。 More specifically, the structure of the work pressing device 1 will be described. As shown in FIGS. 1, 3-4, and 8, the drive screw shaft 7 is configured as a ball screw 25 and the nut member 9 is a ball. The screw nut 26 is configured. The ball screw 25 has an upper portion 27 accommodated in a cover portion 30 having, for example, a rectangular tube shape fixed to a support portion 29 located above the table 3, and a lower portion 31 of the ball screw 25. The upper end portion 33 of the ball screw 25 is housed in a plurality of steps built in the upper end portion 35 of the cover portion 30. It is supported by the angular ball bearing 36 and can rotate around the axis. As shown in FIGS. 1 and 3, a pulley 39 is fixed to the upper end 37 of the ball screw 25, and a belt 42 is wound around the pulley 39 and a pulley 41 attached to the rotating shaft 40 of the servo motor 6. The ball screw 25 is rotated forward and backward by forward and reverse rotation of the servo motor 6.

前記ワーク押圧部１１には図３に示すように、上端開放で有底の前記収容筒部３２の底部４３の下側に位置させて、下端に押圧具４５が設けられた前記芯ずれ補正機構部１５が設けられている。該押圧具４５の下端が前記ワーク押圧部１１の下端１０である。 As shown in FIG. 3, the workpiece pressing portion 11 is positioned below the bottom portion 43 of the bottomed housing cylinder portion 32 with the upper end open, and the misalignment correcting mechanism provided with a pressing tool 45 at the lower end. A portion 15 is provided. The lower end of the pressing tool 45 is the lower end 10 of the work pressing portion 11.

前記収容筒部３２は図３〜４、図８に示すように、その上端部分の対向側に、上下方向に長い規制孔４６，４６が設けられている。該規制孔４６，４６の上下長さは例えば３８ｍｍ程度に設定されると共に、その上下端４７，４９は円弧面に形成されている。そして該収容筒部３２内には、その軸線に沿って前記ボールネジ２５が収容されており、該ボールネジ２５の下端５０が、図３に示すように、前記底部４３の上面５１から稍浮き上がっている。そして該収容筒部３２内には、中心孔部５２が設けられた円錐状の皿バネ５３の多数枚が上下を逆にしながら順次積重されることによって前記バネ部材１２が設けられており、その中心部分に連通状態に設けられた上下方向の連通孔５５に前記ボールネジ２５が挿通せしめられている。 As shown in FIGS. 3 to 4 and FIG. 8, the accommodating cylinder portion 32 is provided with restriction holes 46, 46 that are long in the vertical direction on the opposite side of the upper end portion. The upper and lower lengths of the restriction holes 46, 46 are set to, for example, about 38 mm, and the upper and lower ends 47, 49 are formed in arcuate surfaces. Then, the ball screw 25 is accommodated along the axis in the accommodating cylinder portion 32, and the lower end 50 of the ball screw 25 is raised from the upper surface 51 of the bottom portion 43 as shown in FIG. . And in the accommodation cylinder part 32, the said spring member 12 is provided by laminating | stacking many sheets of the conical disc spring 53 provided with the center hole part 52 upside down, The ball screw 25 is inserted through a vertical communication hole 55 provided in a communication state at the central portion.

前記圧縮押部１３は、図３〜４、図８に示すように、前記収容筒部３２の上端側の部分に内接状態に挿入される押圧筒部５６の上端外周に押圧鍔部５７が周設されてなり、その軸線に沿って、前記ボールネジ２５を挿通させる挿通孔５９が設けられている。そして、該押圧筒部５６の外周面の対向側には、前記規制孔４６，４６と位置合わせしてネジ孔６０，６０が設けられている。 As shown in FIGS. 3 to 4 and FIG. 8, the compression pressing portion 13 has a pressing collar portion 57 on the outer periphery of the upper end of the pressing cylinder portion 56 that is inserted in an inscribed state into the upper end side portion of the receiving cylinder portion 32. An insertion hole 59 is provided along the axis of the ball screw 25. Then, on the opposite side of the outer peripheral surface of the pressing cylinder portion 56, screw holes 60, 60 are provided in alignment with the restriction holes 46, 46.

かかる構成を有する圧縮押部１３は、前記押圧鍔部５７が前記ボールネジナット２６の下端で周設された固定鍔部６１にボルト６２で固定されることによって、該ボールネジナット２６に一体的に設けられている。従って、前記ボールネジ２５の正逆回転に伴い該ボールネジナット２６が上下動でき、これに伴い前記圧縮押部１３がナット部材９と一体となって上下動できる。そして該圧縮押部１３は、その押圧筒部５６が前記収容筒部３２の上端側の部分６３に挿入され且つその下端６５で前記バネ部材１２を下方向に若干圧縮した状態とされる。 The compression pressing portion 13 having such a configuration is provided integrally with the ball screw nut 26 by fixing the pressing flange portion 57 to a fixing flange portion 61 provided around the lower end of the ball screw nut 26 with a bolt 62. It has been. Accordingly, the ball screw nut 26 can move up and down as the ball screw 25 rotates forward and backward, and accordingly, the compression pressing portion 13 can move up and down integrally with the nut member 9. The compression pressing portion 13 is in a state in which the pressing cylinder portion 56 is inserted into the upper end portion 63 of the accommodating cylinder portion 32 and the spring member 12 is slightly compressed downward at the lower end 65.

そしてこの状態で、図３〜４に示すように、前記規制孔４６を挿通した規制ネジ（規制軸の一種）６６のネジ軸部６７が前記押圧筒部５６の外周面の対向側に設けられた前記ネジ孔６０，６０に螺合されており、前記バネ部材１２の付勢作用によって、該規制ネジ６６，６６の係合頭部６９の周面部７０が、図４に示すように、前記規制孔４６，４６の円弧状の上端４７，４７に弾性的に圧接された状態にある。本実施例においては、該バネ部材１２のセット状態で、該バネ部材１２が全体として１．７０ｍｍ圧縮された状態としている。 In this state, as shown in FIGS. 3 to 4, a screw shaft portion 67 of a restriction screw (a kind of restriction shaft) 66 inserted through the restriction hole 46 is provided on the opposite side of the outer peripheral surface of the pressing cylinder portion 56. Further, as shown in FIG. 4, the peripheral surface portion 70 of the engaging head 69 of the restriction screw 66, 66 is screwed into the screw holes 60, 60 by the biasing action of the spring member 12. It is in a state of being elastically pressed against the arcuate upper ends 47, 47 of the restriction holes 46, 46. In this embodiment, the spring member 12 is compressed by 1.70 mm as a whole in the set state of the spring member 12.

このように周面部７０と円弧状の上端４７とが当接した状態で、前記収容筒部３２の上端面７２と前記押圧鍔部５７の下面７３との間に１０ｍｍ程度の間隙Ｇが設けられるようになされている。そして前記ボールネジ２５の正回転によって前記ボールネジナット２６が下降するに伴い（例えば、１回転で１０ｍｍ程度下降するようになされている）、前記圧縮押部１３の押圧筒部５６が、前記バネ部材１２を下方向に更に圧縮させ、前記収容筒部３２の上端面７２と前記押圧鍔部５７の下面７３とが当接した状態で、図９に示すように、前記係合頭部６９が前記規制孔４６，４６の下端４９から稍浮き上がった状態となり得る。 A gap G of about 10 mm is provided between the upper end surface 72 of the accommodating cylinder portion 32 and the lower surface 73 of the pressing flange portion 57 in a state where the peripheral surface portion 70 and the arcuate upper end 47 are in contact with each other. It is made like that. As the ball screw nut 26 is lowered by the normal rotation of the ball screw 25 (for example, about 10 mm is lowered by one rotation), the pressing cylinder portion 56 of the compression pressing portion 13 is moved to the spring member 12. 9 is further compressed in the downward direction, and the engagement head 69 is in the state of restriction as shown in FIG. 9 in a state where the upper end surface 72 of the accommodating cylinder portion 32 and the lower surface 73 of the pressing flange portion 57 are in contact with each other. It can be in a state where the ridges are lifted from the lower end 49 of the holes 46, 46.

そして、前記バネ部材１２が全体として８．５０ｍｍ弾性圧縮された状態（前記セット状態から更に６．８ｍｍ弾性圧縮された状態）におけるトルク値（第１の設定トルク値）を検知するまでは、前記位置制御が行なわれる。本実施例においては、毎分２０００ｍｍ〜４０００ｍｍ、例えば毎分２０００ｍｍで、前記ボールネジナット２６を下方向に早送りで移動させ、該第１の設定トルク値に達した後は、前記サーボモータ６を前記位置制御状態からトルク制御状態に切り換える。 Until the spring member 12 detects a torque value (first set torque value) in a state in which the spring member 12 is elastically compressed by 8.50 mm as a whole (a state in which the spring member 12 is further elastically compressed by 6.8 mm), Position control is performed. In this embodiment, the ball screw nut 26 is rapidly moved downward at 2000 mm to 4000 mm per minute, for example, 2000 mm per minute, and after reaching the first set torque value, the servo motor 6 is Switch from the position control state to the torque control state.

前記芯ずれ補正機構部１５は、図１０に拡大して示すように、前記収容筒部３２の下端で下方に延長するように設けられた保持筒部７５を具えている。該保持筒部７５は、下端開放で且つ円形の内部空間７６の上面が押圧部分７７とされた円筒状をなす外筒部７８と、該外筒部７８内に挿入される内筒部７９とを具えている。 The center misalignment correction mechanism portion 15 includes a holding cylinder portion 75 provided so as to extend downward at the lower end of the accommodating cylinder portion 32 as shown in an enlarged view in FIG. The holding cylinder part 75 has a cylindrical outer cylinder part 78 whose lower end is open and whose upper surface of the circular inner space 76 is a pressing part 77, and an inner cylinder part 79 inserted into the outer cylinder part 78. It has.

該内筒部７９は、下端が開放し且つ頂板部８０の中央部に、段付き円柱状を呈する支持軸部８１の小径の軸部８２を挿通させることができ且つ前記ボールネジ２５の軸線と共通の軸線を有した挿通孔８３が設けられてなる円筒状部８４を有し、前記頂板部８０の上面には、該円筒状部８４の軸線と同心に下の円錐面８５が設けられており、又前記軸部８２の上部には、前記下の円錐面８５と面接触し得る上の円錐面８７を具えたナット状の当接部材８９が螺合されており、該上下の円錐面８７，８５が当接した状態で、前記支持軸部８１の軸線と前記下の円錐面８５の軸線とが合致し得るように構成されている。 The inner cylinder portion 79 is open at the lower end and can be inserted into the center portion of the top plate portion 80 with a small-diameter shaft portion 82 of the support shaft portion 81 having a stepped columnar shape, and is common with the axis of the ball screw 25. A cylindrical portion 84 provided with an insertion hole 83 having the same axis line, and a lower conical surface 85 concentric with the axis line of the cylindrical portion 84 is provided on the upper surface of the top plate portion 80. A nut-shaped contact member 89 having an upper conical surface 87 that can come into surface contact with the lower conical surface 85 is screwed onto the upper portion of the shaft portion 82. , 85 are in contact with each other, the axis of the support shaft 81 and the axis of the lower conical surface 85 can be matched.

又前記支持軸部８１の下部には、前記円筒状部８４の内部の下端側に挿入状態となる環状受部９０が設けられ、該環状受部９０の上面と前記頂板部８０の下面との間に円環状の空間部９１が形成されている。そして該円環状の空間部９１には、上から順に、前記頂板部８０の下面側に設けられる第１の支持板９２と、その下方において、外周面９３が前記円筒状部８４の円形の内周面９５に当接した状態で上下方向でスライド可能に設けられた円環状をなす第２の支持板９６と、前記環状受部９０の上面に設けられる円環状をなす第３の支持板９７とを具える。該第１、第２の支持板９２，９６間にはバネ片９９が介装されると共に、前記第２、第３の支持板９６，９７間にはスラストボールベアリング１００が前記軸部８２を取り囲むように介装され、該スラストボールベアリング１００を構成するボール１０１が前記第２、第３の支持板９６，９７を点接触状態で転動する如くなされている。そして、該ボール１０１の転動に伴って、該スラストボールベアリング１００のリテーナ１０２が前記第２、第３の支持板９６，９７間を前記支持軸部８１の半径方向で移動可能となされている。 In addition, an annular receiving portion 90 that is inserted is provided at the lower end side of the cylindrical portion 84 at the lower portion of the support shaft portion 81, and the upper surface of the annular receiving portion 90 and the lower surface of the top plate portion 80 are arranged. An annular space 91 is formed between them. The annular space portion 91 includes, in order from the top, a first support plate 92 provided on the lower surface side of the top plate portion 80, and an outer peripheral surface 93 below the circular inner portion of the cylindrical portion 84. An annular second support plate 96 provided so as to be slidable in the vertical direction in contact with the peripheral surface 95, and an annular third support plate 97 provided on the upper surface of the annular receiving portion 90. With. A spring piece 99 is interposed between the first and second support plates 92 and 96, and a thrust ball bearing 100 connects the shaft portion 82 between the second and third support plates 96 and 97. A ball 101 which is interposed so as to surround and constitutes the thrust ball bearing 100 rolls on the second and third support plates 96 and 97 in a point contact state. As the ball 101 rolls, the retainer 102 of the thrust ball bearing 100 can move between the second and third support plates 96 and 97 in the radial direction of the support shaft 81. .

そして前記支持軸部８１の下端には、前記駆動ネジ軸７と同芯に角柱状の前記押圧具４５が下方向に突設されている。 Further, at the lower end of the support shaft portion 81, the prism-shaped pressing tool 45 concentrically with the drive screw shaft 7 protrudes downward.

又前記押圧具４５が、前記ワーク５を押圧しない自由状態から、前記バネ片９９の圧縮を伴って相対的に稍上昇した、ワーク回転上昇位置においては、図１１に示すように、前記軸部８２の上端１０６が前記押圧部７７と非接触で、且つ上下の円錐面８７，８５が離れた状態となる。又、前記押圧具４５が、前記バネ片９９を更に圧縮させて相対的に上昇した、ワーク押圧上昇位置においては、図１２に示すように、前記軸部８２の上端１０６が前記押圧部分７７で押圧される如くなされている。 Further, in the workpiece rotation ascending position where the pressing tool 45 is relatively lifted with the compression of the spring piece 99 from a free state where the pressing tool 45 is not pressed, as shown in FIG. The upper end 106 of 82 is not in contact with the pressing portion 77, and the upper and lower conical surfaces 87 and 85 are separated. When the pressing tool 45 is relatively lifted by further compressing the spring piece 99, the upper end 106 of the shaft portion 82 is at the pressing portion 77 as shown in FIG. It is supposed to be pressed.

然して、かかる構成の芯ずれ補正機構部１５を具えるワーク押圧装置１によるときは、上下方向の軸線回りに回転せしめられる前記テーブル３上に位置決めセットされたワーク５を押圧するワーク押圧部１１の下端部分、即ち、前記角柱状の押圧具４５が、前記円筒状部８４（図１０）の軸線と平行する軸線を保ったまま、前記テーブル３の軸線を中心として旋回可能であり、且つ、該円筒状部８４に対する前記押圧具４５の上下位置を、前記ワーク回転上昇位置とワーク押圧上昇位置の２段階に設定できる。そして、該ワーク回転上昇位置においては、図１１に示すように、該押圧具４５の上端側をなす軸部８２が前記スラストボールベアリング１００のみによって支持される。従って、テーブル３の回転の軸線Ｌ１と押圧具４５の回転の軸線Ｌ２とが芯ずれしている場合であっても、その芯ずれが補正され、該押圧具４５がテーブル３の回転に追随して旋回できるのであり、しかもその旋回は、前記スラストボールベアリング１００の点接触状態での支持作用によって軽く行なわれることとなる。 However, when the workpiece pressing device 1 having the center misalignment correction mechanism 15 having such a configuration is used, the workpiece pressing unit 11 that presses the workpiece 5 positioned and set on the table 3 that is rotated around the vertical axis. The lower end portion, that is, the prismatic pressing tool 45 can be turned around the axis of the table 3 while maintaining the axis parallel to the axis of the cylindrical portion 84 (FIG. 10), and The vertical position of the pressing tool 45 with respect to the cylindrical portion 84 can be set in two stages: the workpiece rotation rising position and the workpiece pressing lifting position. In the workpiece rotation ascending position, as shown in FIG. 11, the shaft portion 82 forming the upper end side of the pressing tool 45 is supported only by the thrust ball bearing 100. Accordingly, even when the axis of rotation L1 of the table 3 and the axis of rotation L2 of the pressing tool 45 are misaligned, the misalignment is corrected, and the pressing tool 45 follows the rotation of the table 3. Further, the turning is lightly performed by the support action of the thrust ball bearing 100 in the point contact state.

そして前記サーボモータ６は、前記制御部により、前記ワーク押圧部１１の下端１０が、前記テーブル３に載置されたワーク５の上面１４に当接した後、第１の設定トルク値に達するまで、前記ボールネジナット２６を下降させるように前記ボールネジ２５を回転させ続ける如く位置制御される。このように位置制御されている間、前記押圧具４５は例えば毎分２０００ｍｍの速度で早送り状態で下降せしめられる。又、このように位置制御されている間、前記規制ネジ６６は、前記規制孔４６の長さ方向に沿って下降する。 The servo motor 6 is controlled by the control unit until the lower end 10 of the workpiece pressing unit 11 comes into contact with the upper surface 14 of the workpiece 5 placed on the table 3 and then reaches the first set torque value. The position of the ball screw 25 is controlled so as to continue to rotate so that the ball screw nut 26 is lowered. While the position is controlled in this way, the pressing tool 45 is lowered in a fast-feed state at a speed of, for example, 2000 mm per minute. Further, while the position is controlled as described above, the restriction screw 66 descends along the length direction of the restriction hole 46.

そしてかかる位置制御の後は、該サーボモータ６は前記制御部により、ボールネジ２５の回転速度を極端に落とすように回転制御され、前記押圧具４５が前記ワーク５に所要押圧力（ワーク固定の為の所要押圧力）を作用させるように、前記第１の設定トルク値よりも大なる第２の設定トルク値に達するまで前記ボールネジ２５を回転させ続けるようにトルク制御される。 After such position control, the servo motor 6 is rotationally controlled by the control unit so as to extremely reduce the rotational speed of the ball screw 25, and the pressing tool 45 is applied to the work 5 with a required pressing force (for fixing the work). Torque control is performed so that the ball screw 25 continues to rotate until a second set torque value larger than the first set torque value is reached.

本実施例においては、該押圧力が、第２の設定トルク値の大小によって、１２００ｋｇｆの低圧の押圧力と、２０００ｋｇｆの中圧の押圧力と、２８００ｋｇｆの高圧の押圧力の３種類を、ワークの材質や大きさに応じ、切削力を考慮して選択できるようになされている。 In this embodiment, depending on the magnitude of the second set torque value, the pressing force is divided into three types: a low pressure of 1200 kgf, a medium pressure of 2000 kgf, and a high pressure of 2800 kgf. Depending on the material and size, it can be selected in consideration of the cutting force.

なお前記ボールネジナット２６の回り止めは、図１に示すような、上下方向に延長する案内レール１０７と該案内レール１０７に案内されて上下動するするスライダ１０９とからなるリニアガイド装置１１０を用いて行なわれている。なお本実施例においては、図１に示すように、該リニアガイド装置１１０の側方の上下に位置させてリミットスイッチ１１１，１１２を設けているが、これは、サーボモータの暴走を防止する安全装置であって、ワーク押圧部１１の最上昇位置と最下降位置を規制するものである。 The ball screw nut 26 is prevented from rotating by using a linear guide device 110 including a guide rail 107 extending in the vertical direction and a slider 109 moving up and down guided by the guide rail 107 as shown in FIG. It is done. In this embodiment, as shown in FIG. 1, limit switches 111 and 112 are provided on the upper and lower sides of the linear guide device 110. This is a safety for preventing the servomotor from running out of control. It is an apparatus, Comprising: The highest rise position and the lowest fall position of the workpiece | work press part 11 are controlled.

前記ワーク押圧装置１の構成および動作は上記の通りであるが、その動作を、前記低圧の押圧力を選択した場合について前記位置制御状態の動作と前記トルク制御状態の動作に分けてより詳しく説明する。 The configuration and operation of the workpiece pressing device 1 are as described above, and the operation will be described in more detail by dividing the operation in the position control state and the operation in the torque control state when the low pressure is selected. To do.

先ず前記制御部に、前記第１の設定トルク値を第１のトルクリミット値として与えると共に、前記第２の設定トルク値を第２のトルクリミット値として与える。又、前記第１の設定トルク値よりも小さいトルク値を第３のトルクリミット値として与える。 First, the first set torque value is given to the control unit as a first torque limit value, and the second set torque value is given as a second torque limit value. Further, a torque value smaller than the first set torque value is given as a third torque limit value.

前記ワーク押圧部１１の下端１０がワーク５の上面１４に当接するまでは、ワーク押圧部１１が、前記係合頭部６９が前記規制孔４６の上端４７に当接したままの状態で下降する。この状態においては前記バネ部材１２は前記セット状態のままである。 Until the lower end 10 of the workpiece pressing portion 11 comes into contact with the upper surface 14 of the workpiece 5, the workpiece pressing portion 11 descends with the engagement head 69 still in contact with the upper end 47 of the restriction hole 46. . In this state, the spring member 12 remains in the set state.

そして、前記押圧具４５の下端１０が前記ワーク５の上面１４に当接した図１３に示す状態から前記ボールネジ２５が更に正回転することにより、前記圧縮押部１３の下端（前記押圧筒部５６の下端面）６５が前記バネ部材１２を徐々に弾性圧縮させていく。該下端１０がワーク５の上面１４に当接した際の衝撃は、前記バネ部材１２が圧縮することによって緩衝される。該押圧具４５の下端１０がワークの上面１４に当接して後、前記バネ部材１２を圧縮させながら位置制御状態が継続され、この間は、前記圧縮押部１３の早送りが行なわれる。 Then, when the ball screw 25 further rotates forward from the state shown in FIG. 13 in which the lower end 10 of the pressing tool 45 is in contact with the upper surface 14 of the work 5, the lower end of the compression pressing portion 13 (the pressing cylinder portion 56). The lower end surface of the spring member 65 gradually elastically compresses the spring member 12. The impact when the lower end 10 comes into contact with the upper surface 14 of the workpiece 5 is buffered by the compression of the spring member 12. After the lower end 10 of the pressing tool 45 comes into contact with the upper surface 14 of the workpiece, the position control state is continued while the spring member 12 is compressed. During this time, the compression pushing portion 13 is fast-forwarded.

この圧縮に伴い、前記係合頭部６９が図１４に示すように前記規制孔４６内で下降し、前記押圧鍔部５７の下面７３と前記収容筒部３２の上端面７２との間の前記間隙Ｇが、該下降した分だけ小さくなる。そして前記下面７３と前記上端面７２とが当接するまでの間で、前記圧縮押部１３の下端６５がバネ部材１２を更に圧縮させて１１４２ｋｇｆの押圧力が作用した状態（本実施例においては、バネ部材１２が全体として８．５ｍｍ圧縮された状態）になると、トルク検知指令部の信号によって位置制御状態からトルク制御状態に切り換わる。これによりサーボモータ６は、前記第２のトルクリミット値に達するまでトルク制御され、前記押圧具４５が、図１４に示すように、テーブル３上のワーク５を低圧の押圧力（１２００ｋｇｆ）で押圧し該ワーク５をテーブル３に固定することになる。 With this compression, the engaging head 69 descends in the restriction hole 46 as shown in FIG. 14, and the space between the lower surface 73 of the pressing flange portion 57 and the upper end surface 72 of the accommodating cylinder portion 32 is increased. The gap G becomes smaller by the lowered amount. Then, until the lower surface 73 and the upper end surface 72 come into contact with each other, the lower end 65 of the compression pressing portion 13 further compresses the spring member 12 and a pressing force of 1142 kgf is applied (in this embodiment, When the spring member 12 is compressed by 8.5 mm as a whole, the position control state is switched to the torque control state by a signal from the torque detection command unit. As a result, the torque of the servo motor 6 is controlled until the second torque limit value is reached, and the pressing tool 45 presses the work 5 on the table 3 with a low pressure (1200 kgf) as shown in FIG. Then, the work 5 is fixed to the table 3.

この状態で、ワーク５が固定されてなるテーブル３は、図５に矢印で示す方向に前進し、これにより該ワーク５は、図６に示すように左右のフライス１９，１９間に所要に配置され、該左右のフライス１９，１９によって左右の被加工面２０，２１にフライス加工が施される。フライス加工が完了した後、前記テーブル３は当初の状態に戻り、その後、前後の被加工面２２，２３を加工するために、テーブル３が、図７に矢印で示すように９０度回転せしめられ、図１５に示す回転した状態が得られる。この回転の円滑化の為に、該回転時のワーク押圧力は、ワークの固定を不安定化させない範囲で、前記ワーク固定の押圧力よりも小さく設定するのがよい。例えば８００ｋｇｆの押圧力に設定する。その為、このテーブルの回転時に前記第３のトルクリミット値による制御を行なうのである。即ち図１６、図１１に示すように、前記サーボモータ６を逆回転させて前記押圧具４５を若干上昇させる。サーボモータ６のトルクが前記第３のトルクリミット値に達するとトルクリミット信号によりサーボモータ６は停止し、前記８００ｋｇｆのワーク押圧力が得られることとなる。 In this state, the table 3 to which the workpiece 5 is fixed moves forward in the direction indicated by the arrow in FIG. 5, so that the workpiece 5 is disposed between the left and right milling cutters 19 and 19 as shown in FIG. The left and right milling surfaces 19, 21 are milled by the left and right milling cutters 19, 19. After the milling is completed, the table 3 returns to the original state, and then the table 3 is rotated 90 degrees as shown by the arrows in FIG. 7 in order to process the front and back processed surfaces 22 and 23. The rotated state shown in FIG. 15 is obtained. In order to facilitate this rotation, it is preferable that the workpiece pressing force during the rotation is set to be smaller than the pressing force for fixing the workpiece within a range that does not destabilize the workpiece. For example, the pressing force is set to 800 kgf. Therefore, the control by the third torque limit value is performed when the table is rotated. That is, as shown in FIGS. 16 and 11, the servomotor 6 is rotated in the reverse direction to slightly raise the pressing tool 45. When the torque of the servo motor 6 reaches the third torque limit value, the servo motor 6 is stopped by the torque limit signal, and the workpiece pressing force of 800 kgf is obtained.

このワーク回転上昇位置で、前記テーブル３が前記のように９０度回転せしめられる。その後、サーボモータ６のトルクが前記第２のトルクリミット値に達するまで該サーボモータ６を正回転させる。これによりワーク５は、図１４に示すと同様に、該９０度回転した状態で、低圧の押圧力で押圧されテーブルに固定される。 At the workpiece rotation ascending position, the table 3 is rotated 90 degrees as described above. Thereafter, the servo motor 6 is rotated forward until the torque of the servo motor 6 reaches the second torque limit value. As a result, the workpiece 5 is pressed with a low pressure and fixed to the table in the state rotated 90 degrees as shown in FIG.

その後、テーブル３が前進することによってワーク５が左右のフライス１９，１９間に所要に配置され、該左右のフライス１９，１９によって前後の被加工面２２，２３にフライス加工が施される。 Thereafter, the work 5 is placed between the left and right milling cutters 19 and 19 as the table 3 moves forward, and the front and rear workpiece surfaces 22 and 23 are milled by the left and right milling cutters 19 and 19.

次に、前記ワーク押圧装置１の押圧作用を、中圧の押圧力（２０００ｋｇｆ）を選択した場合について説明すれば、先ず前記第２の設定トルク値を中圧の押圧力を付与できる値に変更し、これを第２のトルクリミット値として前記制御部に与える。図１７、図１２、図９に示すように、前記バネ部材１２が更に圧縮せしめられて前記押圧鍔部５７の下面７３と収容筒部３２の上端面７２とが当接した後は、前記圧縮押部１３が前記収容筒部３２を下方向に押圧することとなる。この状態で前記ボールネジ２５が更に正回転されることにより、サーボモータ６のトルク値が該変更された第２のトルクリミット値に達すると、トルクリミット信号により前記サーボモータ６が停止し、２０００ｋｇｆの中圧の押圧力がワークに作用することになる。 Next, the pressing action of the workpiece pressing device 1 will be described with respect to the case where an intermediate pressure (2000 kgf) is selected. First, the second set torque value is changed to a value capable of applying an intermediate pressure. Then, this is given to the control unit as a second torque limit value. As shown in FIGS. 17, 12, and 9, after the spring member 12 is further compressed and the lower surface 73 of the pressing flange portion 57 and the upper end surface 72 of the housing cylinder portion 32 abut, The pressing portion 13 presses the housing cylinder portion 32 downward. If the torque value of the servo motor 6 reaches the changed second torque limit value by further forward rotation of the ball screw 25 in this state, the servo motor 6 is stopped by the torque limit signal, and 2000 kgf of Medium pressure will act on the workpiece.

更に、前記ワーク押圧装置１が高圧の押圧力（２８００ｋｇｆ）を選択した場合について説明すれば、先ず前記第２の設定トルク値を高圧の押圧力を付与できる値に変更し、これを第２のトルクリミット値として前記制御部に与える。前記ボールネジ２５が更に正回転されることにより、サーボモータのトルク値が該変更された第２のトルクリミット値に達すると、トルクリミット信号により前記サーボモータ６が停止し、２８００ｋｇｆの高圧の押圧力が作用することになる。 Further, in the case where the workpiece pressing device 1 selects a high pressure (2800 kgf), first, the second set torque value is changed to a value that can provide a high pressure, and this is changed to a second value. The torque limit value is given to the control unit. When the torque value of the servo motor reaches the changed second torque limit value by further positively rotating the ball screw 25, the servo motor 6 is stopped by the torque limit signal, and a high pressure of 2800 kgf is pressed. Will act.

前記押圧状態は、前記ボールネジナット２６の上下移動範囲においてワークの高さが異なる場合であっても、前記位置制御と前記トルク制御が所要に行われて達成される。 The pressing state is achieved by performing the position control and the torque control as required even when the workpiece height is different in the vertical movement range of the ball screw nut 26.

前記のようにしてフライス加工が完了した後、次のワークの加工に移るのであるが、その際、前記サーボモータ６を逆回転させることにより前記ボールネジナット２６を上昇させ、これによってワーク押圧部１１を上昇させる。そしてこれにより、図１０に示すような、上の円錐面８７の軸線が前記円筒状部８４の軸線と合致する中立状態に戻る。 After the milling is completed as described above, the next workpiece is processed. At this time, the servo motor 6 is reversely rotated to raise the ball screw nut 26, thereby the workpiece pressing portion 11. To raise. Then, as shown in FIG. 10, the axis of the upper conical surface 87 returns to the neutral state where it matches the axis of the cylindrical portion 84.

図１８〜１９は，本発明に係るワーク押圧装置１の他の実施例を示すものであり、バネ部材１２の付設の構成と、該バネ部材１２を圧縮させる圧縮押部１３の構成と、該圧縮押部１３がワーク押圧部１１を押圧する構成が異なっている。 FIGS. 18 to 19 show another embodiment of the work pressing device 1 according to the present invention. The configuration of the spring member 12 and the configuration of the compression pressing portion 13 for compressing the spring member 12, The configuration in which the compression pressing portion 13 presses the workpiece pressing portion 11 is different.

即ちワーク押圧部１１は、例えば円板状を呈する基部１１９の上端中央部で例えば円柱状を呈する軸部１２０を立設してなる。そして、前記と同様構成の皿バネ５３の多数枚が、その中心孔部５２に該軸部１２０を挿通させた状態で上下を逆にしながら積重されることによって前記バネ部材１２が構成されている。又、該軸部１２０の上端部分には、上下方向に長い規制孔４６が設けられている。 That is, the workpiece pressing portion 11 is formed by erecting a shaft portion 120 having a columnar shape, for example, at the center of the upper end of a base portion 119 having a disk shape. The spring member 12 is configured by stacking a large number of disc springs 53 having the same configuration as described above while the shaft portion 120 is inserted into the center hole portion 52 while turning upside down. Yes. In addition, a restriction hole 46 that is long in the vertical direction is provided at the upper end portion of the shaft portion 120.

そして前記圧縮押部１３は、下端開放の段付き円筒部１２１を具える。該段付き円筒部１２１は、下側の大径筒部１２２の上端に、稍小径の小径筒部１２３を上方に突設した構成を有しており、該大径筒部１２２の頂部１２５と小径筒部１２３には、前記軸部１２０を密接状態に挿通させ得る挿通孔１２６が設けられている。又、前記大径筒部１２２の上端には固定フランジ１２７が周設されると共に、前記小径筒部１２３の対向側には、規制ネジ軸（規制軸の一種）６７を取り付けるための取付孔１２９，１３０が設けられており、一方の取付孔１２９は該規制ネジ軸６７の係合頭部６９を納める段付きの孔部とされると共に他方の取付孔１３０は該規制ネジ軸６７のネジ軸部１３１を螺合させる雌ネジとされている。 The compression pressing portion 13 includes a stepped cylindrical portion 121 having an open lower end. The stepped cylindrical portion 121 has a configuration in which a small-diameter small-diameter cylindrical portion 123 projects upward from the upper end of the lower large-diameter cylindrical portion 122. The small diameter cylindrical portion 123 is provided with an insertion hole 126 through which the shaft portion 120 can be inserted closely. A fixing flange 127 is provided around the upper end of the large-diameter cylindrical portion 122, and a mounting hole 129 for mounting a restriction screw shaft (a kind of restriction shaft) 67 on the opposite side of the small-diameter cylindrical portion 123. , 130 is provided, and one attachment hole 129 is a stepped hole for receiving the engagement head 69 of the restriction screw shaft 67, and the other attachment hole 130 is a screw shaft of the restriction screw shaft 67. It is a female screw to which the part 131 is screwed.

又、サーボモータ６によって回転制御される駆動ネジ軸７が螺合するネジ孔１３２が設けられたナット部材９の下端部分には、前記小径筒部１２３を密接に挿入させる挿入孔部１３３が該ネジ孔１３２と同心に設けられている。 An insertion hole 133 for closely inserting the small-diameter cylindrical portion 123 is provided at the lower end portion of the nut member 9 provided with the screw hole 132 into which the drive screw shaft 7 whose rotation is controlled by the servo motor 6 is screwed. It is provided concentrically with the screw hole 132.

又該ナット部材９の下端には、前記固定フランジ１２７にボルト１３５で固定される固定フランジ１３６が周設されている。 A fixing flange 136 fixed to the fixing flange 127 with a bolt 135 is provided at the lower end of the nut member 9.

前記圧縮押部１３を前記ワーク押圧部１１に取り付けるに際しては、前記バネ部材１２の上端を前記大径筒部１２２の前記頂部１２５の下面で下方向に押圧して該バネ部材１２を稍圧縮させた状態で、前記規制ネジ（規制軸の一種）６６のネジ軸部１３１を、前記規制孔４６に挿通させ且つ該ネジ軸部１３１を前記取付孔１３０に螺合して締め付けると、該規制ネジ６７が前記小径筒部１２３に固定される。この固定状態で、該ネジ軸部１３１が前記規制孔４６の上端１３８に弾性的に圧接状態となる。そしてこの状態で、図１８に示すように、前記大径筒部１２２の下端１３９が前記基部１１９の上端１４０から例えば１３ｍｍ程度浮き上がっている。 When attaching the compression pressing portion 13 to the workpiece pressing portion 11, the upper end of the spring member 12 is pressed downward by the lower surface of the top portion 125 of the large diameter cylindrical portion 122 to compress the spring member 12. In this state, when the screw shaft 131 of the restriction screw (a kind of restriction shaft) 66 is inserted into the restriction hole 46 and screwed into the mounting hole 130 and tightened, the restriction screw 67 is fixed to the small diameter cylindrical portion 123. In this fixed state, the screw shaft 131 is elastically pressed against the upper end 138 of the restriction hole 46. In this state, as shown in FIG. 18, the lower end 139 of the large-diameter cylindrical portion 122 is lifted from the upper end 140 of the base portion 119 by, for example, about 13 mm.

なお、本実施例においても実施例１におけると同様に、前記ワーク押圧部１１は、前記基部１１９の下端側に、前記と同様構成の芯ずれ補正機構部１５を具えているが、その具体的な構成及び作用は前記と同様であるために説明を省略する。 In this embodiment, as in the first embodiment, the workpiece pressing portion 11 includes a misalignment correcting mechanism portion 15 having the same configuration as that described above on the lower end side of the base portion 119. Since the configuration and operation are the same as described above, the description thereof is omitted.

然して、前記駆動ネジ軸７をサーボモータ６によって正回転させると前記ナット部材９が回り止めされて下降する。それに伴い前記圧縮押部１３が前記バネ部材１２を徐々に弾性圧縮させ、最終的には、図２０に示すように、前記大径筒部１２２の下端１３９が前記基部１１９の上端１４０に当接状態となり得る。このとき前記規制ネジ６６は前記規制孔４６の下端４９から若干浮き上がった状態にある。そして、前記サーボモータ６による位置制御及びトルク制御は前記と同様である。 However, when the drive screw shaft 7 is rotated forward by the servo motor 6, the nut member 9 is prevented from rotating and lowered. Accordingly, the compression pushing portion 13 gradually elastically compresses the spring member 12, and finally, the lower end 139 of the large diameter cylindrical portion 122 abuts on the upper end 140 of the base portion 119 as shown in FIG. It can be a state. At this time, the restriction screw 66 is slightly lifted from the lower end 49 of the restriction hole 46. The position control and torque control by the servo motor 6 are the same as described above.

本発明は、前記実施例で示したものに限定されるものでは決してなく、「特許請求の範囲」の記載内で種々の設計変更が可能であることはいうまでもない。その一例を挙げれば次のようである。 The present invention is by no means limited to those shown in the above-described embodiments, and it goes without saying that various design changes can be made within the scope of the claims. One example is as follows.

(1) 前記トルク制御は、前記圧縮押部１３によるバネ部材１２の圧縮の程度によらず、又、該圧縮押部１３が前記ワーク押圧部１１を押圧した状態にあるかどうかに関わらず行われるものであり、前記実施例においては、前記圧縮押部１３が該ワーク押圧部１１を押圧する前に前記低圧の押圧状態が得られるように構成されている。 (1) The torque control is performed regardless of the degree of compression of the spring member 12 by the compression pressing portion 13 and whether the compression pressing portion 13 is in a state of pressing the work pressing portion 11. In the embodiment, the low pressure pressing state is obtained before the compression pressing portion 13 presses the work pressing portion 11.

(2) 本発明のワーク押圧装置は、前記実施例で示したように、前記駆動ネジ軸７の回転によって前記圧縮押部１３が前記ワーク押圧部１１を押圧するように構成されることの他、駆動ネジ軸７が最大に回転したときにも前記圧縮押部１３が前記ワーク押圧部１１を押圧しないように構成されることもある。 (2) The workpiece pressing device according to the present invention is configured such that the compression pressing portion 13 presses the workpiece pressing portion 11 by the rotation of the drive screw shaft 7 as shown in the embodiment. The compression pressing portion 13 may be configured not to press the workpiece pressing portion 11 even when the drive screw shaft 7 rotates to the maximum.

(3) 実施例１及び実施例２において、前記バネ部材１２は、前記のように皿バネ５３を積重することによって構成されることの他、例えば図２１や図２２に示すようにコイルバネ１４１等を用いて構成することもできる。 (3) In the first and second embodiments, the spring member 12 is configured by stacking the disc springs 53 as described above. In addition, for example, as shown in FIGS. 21 and 22, the coil spring 141 is used. Etc. can also be used.

(4) 前記駆動ネジ軸７と前記ナット部材９は、前記のようにボールネジ２５とボールネジナット２６を以って構成するのが好ましいが、通常のネジ軸とナットとの組み合わせで構成されてもよい。 (4) The drive screw shaft 7 and the nut member 9 are preferably configured with the ball screw 25 and the ball screw nut 26 as described above, but may be configured with a combination of a normal screw shaft and nut. Good.

(5) ナット部材９の前後進は、前記した上下方向の他、横方向等の前後進であることもある。 (5) The forward / backward movement of the nut member 9 may be forward / backward movement in the lateral direction in addition to the above-described vertical direction.

(6) 本発明に係るワーク押圧装置を構成するワーク押圧部１１が前記芯ずれ補正機構部１５を具える場合、図２３に示すように、下端の押圧具４５の下端部分に、平坦な押圧面１０３を有する球形状押圧片１０５を球面接触状態で可動に設けるのが好ましい。 (6) When the workpiece pressing portion 11 constituting the workpiece pressing device according to the present invention includes the misalignment correcting mechanism portion 15, a flat pressing is applied to the lower end portion of the lower end pressing tool 45 as shown in FIG. It is preferable that the spherical pressing piece 105 having the surface 103 is movably provided in a spherical contact state.

(7) 本発明に係るワーク押圧装置は、図２４に示すように、実施例１に示したような芯ずれ補正機構部１５を具えないものとして構成されることもある。 (7) As shown in FIG. 24, the work pressing device according to the present invention may be configured not to include the misalignment correcting mechanism 15 as shown in the first embodiment.

本発明に係るワーク押圧装置をその使用状態で示す斜視図である。It is a perspective view which shows the workpiece | work press apparatus which concerns on this invention in the use condition. ワーク押圧装置によってワークを押圧した状態を示す斜視図である。It is a perspective view which shows the state which pressed the workpiece | work with the workpiece | work press apparatus. ワーク押圧装置を説明する断面図である。It is sectional drawing explaining a workpiece | work press apparatus. その部分拡大図である。FIG. ワーク位置決め装置によって位置決めされたワークをワーク押圧装置によってテーブルに固定した状態を示す平面図である。It is a top view which shows the state which fixed the workpiece | work positioned by the workpiece | work positioning device to the table with the workpiece | work press apparatus. ワークの左右の被加工面にフライス加工を施している状態を示す平面図である。It is a top view which shows the state which is giving the milling process to the to-be-processed surface of the right and left of a workpiece | work. 前後の被加工面を加工するためにテーブルを９０度回転した状態を示す平面図である。It is a top view which shows the state which rotated the table 90 degree | times in order to process the front and back to-be-processed surface. ワーク押圧装置を説明する分解斜視図である。It is a disassembled perspective view explaining a workpiece | work press apparatus. ワーク押圧装置によるワーク押圧状態を示す部分断面図である。It is a fragmentary sectional view showing a work pressing state by a work pressing device. 芯ずれ補正機構部の構成を説明する断面図である。It is sectional drawing explaining the structure of a misalignment correction mechanism part. 芯ずれ補正機構部のワーク回転上昇位置を示す断面図である。It is sectional drawing which shows the workpiece | work rotation raise position of a misalignment correction mechanism part. 芯ずれ補正機構部のワーク押圧上昇位置を示す断面図である。It is sectional drawing which shows the workpiece | work press raising position of a misalignment correction mechanism part. ワーク押圧部の下端がワークの上面に当接した瞬間の状態を示す一部断面正面図である。It is a partial cross section front view which shows the state of the moment when the lower end of the workpiece | work press part contact | abutted to the upper surface of the workpiece | work. テーブル上のワークを低圧の押圧力で押圧した状態を示す一部断面正面図である。It is a partial cross section front view which shows the state which pressed the workpiece | work on a table with the low pressure. ワーク押圧部がワークを軽く押圧した状態で該ワークを９０度回転させた状態を示す斜視図である。It is a perspective view which shows the state which rotated the work 90 degree | times in the state which the work press part pressed the work lightly. ワーク回転上昇位置を示す一部断面正面図である。It is a partial cross section front view which shows a workpiece | work rotation raise position. テーブル上のワークを中圧の押圧力で押圧した状態を示す一部断面正面図である。It is a partial cross section front view which shows the state which pressed the workpiece | work on a table with the pressing force of medium pressure. ワーク押圧装置の他の実施例を示す一部断面正面図である。It is a partial cross section front view which shows the other Example of a workpiece | work press apparatus. その分解斜視図である。FIG. そのワーク押圧装置によってワークを押圧した状態を示す部分断面図である。It is a fragmentary sectional view which shows the state which pressed the workpiece | work with the workpiece | work press apparatus. バネ部材としてコイルバネを用いた場合のワーク押圧装置の一例を示す一部断面正面図である。It is a partial cross section front view which shows an example of the workpiece | work press apparatus at the time of using a coil spring as a spring member. バネ部材としてコイルバネを用いたワーク押圧装置の他の態様を示す一部断面正面図である。It is a partial cross section front view which shows the other aspect of the workpiece | work press apparatus which used the coil spring as a spring member. 平坦な押圧面を有する球形状押圧片を具えるワーク押圧部を示す一部断面正面図である。It is a partial cross section front view which shows the workpiece | work press part which provides the spherical-shaped press piece which has a flat press surface. 芯ずれ補正機構部を具えないワーク押圧装置を示す一部断面正面図である。It is a partial cross section front view which shows the workpiece | work press apparatus which does not provide the misalignment correction mechanism part. 油圧シリンダを用いた従来のワーク押圧装置を説明する正面図である。It is a front view explaining the conventional workpiece | work press apparatus using a hydraulic cylinder.

Explanation of symbols

１ワーク押圧装置
３テーブル
５ワーク
６サーボモータ
７駆動ネジ軸
９ナット部材
１１押圧部
１２バネ部材
１３圧縮押部
１５芯ずれ補正機構部
１８ワーク位置決め装置
１９フライス
２５ボールネジ
２６ボールネジナット
３２収容筒部
４５押圧具
４６規制孔
５３皿バネ
５６押圧筒部
５７押圧鍔部
６１固定鍔部
６６規制ネジ
DESCRIPTION OF SYMBOLS 1 Work pressing apparatus 3 Table 5 Work 6 Servo motor 7 Drive screw shaft 9 Nut member 11 Pressing part 12 Spring member 13 Compression pressing part 15 Center misalignment correction mechanism part 18 Work positioning device 19 Milling machine 25 Ball screw 26 Ball screw nut 32 Housing cylinder part 45 Pressing tool 46 Restriction hole 53 Belleville spring 56 Pressing cylinder part 57 Pressing hook part 61 Fixing hook part 66 Restriction screw

Claims

A nut member is screwed to a drive screw shaft that is rotated forward and backward by a servo motor, and the nut member is prevented from rotating by forward and reverse rotation of the drive screw shaft, and can move forward and backward.
The said nut member, the front end compression pressing portion for compressing with a spring member which is attached to the work pressing portion for pressing the forward movement in the longitudinal direction of the drive screw shaft is provided with a workpiece, said spring member Compressed and provided in the set state,
The workpiece pressing portion has a cylindrical shape and a receiving cylinder portion that accommodates the spring member. The receiving cylinder portion is provided with a restriction hole that is long in the vertical direction. The restriction hole is formed on the nut member. The engaging head of the restriction screw screwed into the screwed compression pushing portion is elastically pressed against the upper end of the restriction hole until the work pressing portion comes into contact with the work in the restriction hole. It is fitted so that it can move downward after contacting the workpiece,
Further, the compression pressing portion is provided with a pressing flange portion, and a required gap is provided between the lower surface of the pressing flange portion and the upper end surface of the accommodating cylinder portion until the workpiece pressing portion contacts the workpiece. Provided, and the work pressing portion and the work are configured to contact each other in a range in which the engaging head of the restriction screw moves downward in the restriction hole,
When the drive screw shaft rotates with the front end of the workpiece pressing portion in contact with the workpiece, the compression pressing portion compresses the spring member, and the pressing flange portion of the compression pressing portion and the workpiece pressing portion Configured to be in contact with the receiving cylinder portion,
In addition, the servo motor has a first set torque value after the workpiece pressing portion comes into contact with the workpiece and until the compression pressing portion contacts and presses the workpiece pressing portion directly. The position of the drive screw shaft is controlled so as to continue to rotate until reaching the position, and thereafter the position control state is switched to the torque control state so that the workpiece pressing portion presses the workpiece with the required pressing force. Torque control is performed so as to continue to rotate the drive screw shaft until a set second set torque value that is larger than the first set torque value is set. .

A nut member is screwed to a drive screw shaft that is rotated forward and backward by a servo motor, and the nut member is prevented from rotating by forward and reverse rotation of the drive screw shaft, and can move forward and backward.
The said nut member, the front end compression pressing portion for compressing with a spring member which is attached to the work pressing portion for pressing the forward movement in the longitudinal direction of the drive screw shaft is provided with a workpiece, said spring member Compressed and provided in the set state,
The work pressing portion has a cylindrical shape and a receiving cylinder portion that receives the spring member. The receiving cylinder portion is provided with a restriction hole that is long in the vertical direction, and the restriction hole is screwed to the nut member. The engaging head of the restriction screw screwed into the stopped compression pushing portion is elastically pressed against the upper end of the restriction hole until the work pressing portion contacts the work in the restriction hole. After contact with the workpiece, it is fitted so that it can move downward,
Further, the compression pressing portion is provided with a pressing flange portion, and a required gap is provided between the lower surface of the pressing flange portion and the upper end surface of the accommodating cylinder portion until the workpiece pressing portion contacts the workpiece. Provided, and the work pressing portion and the work are configured to contact each other in a range in which the engaging head of the restriction screw moves downward in the restriction hole,
When the drive screw shaft rotates with the front end of the workpiece pressing portion in contact with the workpiece, the compression pressing portion compresses the spring member, and the pressing flange portion of the compression pressing portion and the workpiece pressing portion are accommodated. The drive screw shaft is configured to rotate at least until the compression pressing portion presses the workpiece pressing portion.
In addition, the servo motor has a first set torque value after the workpiece pressing portion comes into contact with the workpiece and until the compression pressing portion contacts and presses the workpiece pressing portion directly. The position of the drive screw shaft is controlled so as to continue to rotate until reaching the position, and thereafter the position control state is switched to the torque control state so that the workpiece pressing portion presses the workpiece with the required pressing force. Torque control is performed so as to continue to rotate the drive screw shaft until a set second set torque value that is larger than the first set torque value is set. .