JP2698069B2 - Thermal displacement compensator for pole screw - Google Patents
Thermal displacement compensator for pole screwInfo
- Publication number
- JP2698069B2 JP2698069B2 JP61121066A JP12106686A JP2698069B2 JP 2698069 B2 JP2698069 B2 JP 2698069B2 JP 61121066 A JP61121066 A JP 61121066A JP 12106686 A JP12106686 A JP 12106686A JP 2698069 B2 JP2698069 B2 JP 2698069B2
- Authority
- JP
- Japan
- Prior art keywords
- ball screw
- thermal displacement
- ball
- displacement
- ball nut
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】
〔発明の利用分野〕
本発明は、ボールねじをモータで回転させることによ
りボールねじに螺入されたボールナツトを直線移動させ
る送り機構において、ボールねじの熱変位によるボール
ナツトの位置ずれ防止に好適するボールねじの熱変位補
正装置に関するものである。
〔発明の背景〕
上述送り機構において、その駆動時にはボールねじと
ボールナツトの摩擦によつて熱が発生し、ボールねじが
熱膨張により伸びることになる。このためボールねじの
伸び発生の前後においては、モータを同一回転角度動か
してもボールナツトの移動量は異なることになる。すな
わち、ホールねじの熱変位によるボールナツトの送り位
置の位置決め精度が低下し、ポールナツトの所期の移動
目標位置に対する実際の移動位置に誤差が生ずる。
そこで従来、このようなボールねじの熱変位対策とし
ては、
（１） ボールねじを組み付けるときにあらかじめテン
シヨンを掛けておくことにより、ボールねじの伸びを吸
収する方法。
（２） ボールねじ内方に空洞を設け、その空洞中に冷
却水を通す方法。
などが採られていた。
しかしながら、上述（１），（２）のいずれの方法に
よつてもボールねじの熱変位に充分対処することはでき
ず、ボールねじの熱変位による位置決め精度の低下は避
け得なかつた。特に長時間に亘つて送り機構を駆動させ
る場合にそれが顕著になるもので、従来、これらについ
ての改善が要望されていた。
〔発明の目的〕
本発明は上述したような要望に鑑みてなされたもの
で、ボールねじの熱変位による位置決め精度を長時間に
亘つて保持させることができるボールねじの熱変位補正
装置を提供することを目的とする。
〔発明の概要〕
本発明装置は、ボールねじの熱変位をセンサで検出
し、この検出信号に応じ、ボールねじ熱変位前に指示さ
れたボールナツトの移動目標位置を、ボールねじ熱変位
によるずれ移動後の位置に変換し、その位置とボールナ
ツトの現在位置とを比較して両者が一致するように制御
し、上述目的を達成するようにしたものである。
〔発明の実施例〕
以下、図面を参照して本発明の実施例を説明する。第
１図は本発明によるボールねじの熱変位補正装置の一実
施例を示すブロツク図、第２図は同装置が適用された送
り機構の一例を一部切断して示す図である。まず第２図
において、１はボールねじ、1a,1bはボールねじ１の両
端側に設けられたフランジ、２はボールねじ１に螺入さ
れたホールナツト、３はボールナツト２に一体的に取り
付けられた移動体である。４はボールねじ１を回転自在
に支持する軸受,5A,5Bはギア、６は軸受４及びギア5a,5
bのハウジング、７はモータである。
このような送り機構において、モータ７が回転すると
ギア5a,5bを介してボールねじ１が回転し、ボールナツ
ト２（移動体３）がボールねじ１に沿つて直線移動す
る。この移動時には、ボールねじ１とボールナツト２の
摩擦によつて熱が発生し、ボールねじ１がその熱によつ
て伸びることになる。このためボールねじ１の伸び発生
の前後においては、モータ７を同一回転角度動かしても
ボールナツト２の移動量は異なつてしまう。
8a,8bはこれを補正するための信号S1a,S1bを得る微小
変位センサで、ボールねじ１自体の上述伸びを直接測定
する。このセンサ8a,8bで得られた信号S1a,S1bは第１図
に示すように演算処理用CPU11に与えられる。一方このC
PU11には、あらかじめオペレータが操作盤12により与え
た移動指令値（移動目標位置）S2と、ボールナツト２
（移動体３）の現在位置をモータ７の回転回数ないし回
転角から検出する位置検出器13からの現在位置座標値S3
とが入力されている。
これによりCPU11は、前記移動指令値S2は、ボールね
じ１の熱変位によるずれ移動後の位置に変換する演算を
行い、その演算結果値と前記現在位置座標値S3とを比較
して両者が一致するようにモータ回転制御回路14を作動
させ、モータ７を回転させる。以下、この詳細を第３図
に基づいて説明する。
まずボールねじ１の伸びを、この伸びの影響を受けな
い微小変位センサ8a,8bの組付位置を基準として測定す
るものとし、その微小変位センサ8a,8bの測定基準相互
間の長さをＬとする。また、ボールナツト２（移動体
３）の座標の原点Ｏを微小変位センサ8bの測定基準から
長さｙのところとすると、ボールナツト２の座標値は微
小変位センサ8bの値が絶えず基準となる。いま仮に、ボ
ールナツト２がセンサ8bの基準から（ｙ＋x1）の距離
（実線で示す位置）にあり、オペレータの指令値S2がx2
であつたとすると、この場合の補正量Δｘは下記（１）
式により算出できる。ここで、ボールねじ１の伸び量は
センサ8a,8bの両信号値の差で求められ、これをΔＬと
する。
Δｘ＝ΔＬ×（x2＋x1＋ｙ）÷Ｌ ……（１）
（ただし、x2は指令値S2の値、x1は現在位置座標値S3
の値である。）
この補正量Δｘは、あくまでボールナツト２（移動体
３）の絶対座標値からみた補正量であるから、オペレー
タの移動指令値S2でx2へ位置決めする場合は、x1へ位置
決めしたときのオペレータの移動指令値S2の絶対座標
と、そのときの補正量Δｘとの差をとり、x2への補正量
Δｘを考慮した移動指令値S2として第１図に示すモータ
回転制御回路14へ送ることになる。
なお、もう１つの方法としては、単純に移動指令値S2
（x2）の補正量を、
Δｘ′＝ΔＬ×x2÷Ｌ ……（２）
として算出する方法も考えられるが、この方法では、ボ
ールねじ１の伸び量ΔＬが刻々と変化した場合、絶対座
標からみた位置は累積誤差が発生し、必ずしも精度がよ
いとはいえない。
したがつて、（１）式を用いた方法により絶対座標を
考慮して補正すれば、どのような稼動条件であつても安
定した位置決めができることになる。
〔発明の効果〕
以上述べたように本発明は、ボールねじの変位量（伸
び量）を直接検出し、絶対座標を考慮した補正を行うの
で、ボールねじにあらかじめテンシヨンを掛けたり、冷
却水を通したりせず、またボールねじの片持支持方式を
用いても、長時間に亘つて安定した高い位置決め精度が
得られるという効果がある。Description: FIELD OF THE INVENTION The present invention relates to a feed mechanism for linearly moving a ball nut screwed into a ball screw by rotating the ball screw with a motor. The present invention relates to a ball screw thermal displacement correction device suitable for preventing displacement. BACKGROUND OF THE INVENTION In the above-described feed mechanism, when driven, heat is generated by friction between a ball screw and a ball nut, and the ball screw is expanded by thermal expansion. Therefore, before and after the elongation of the ball screw occurs, the amount of movement of the ball nut differs even if the motor is moved by the same rotation angle. That is, the positioning accuracy of the ball nut feeding position is reduced due to the thermal displacement of the hole screw, and an error occurs in the actual moving position of the pole nut with respect to the intended moving target position. Therefore, conventionally, as a countermeasure against such thermal displacement of the ball screw, (1) a method of absorbing elongation of the ball screw by previously applying a tension when assembling the ball screw. (2) A method in which a cavity is provided inside the ball screw, and cooling water is passed through the cavity. And so on. However, none of the above-mentioned methods (1) and (2) can sufficiently cope with the thermal displacement of the ball screw, and it is unavoidable to lower the positioning accuracy due to the thermal displacement of the ball screw. This is particularly noticeable when the feed mechanism is driven for a long time, and there has been a demand for improvements in these. [Object of the Invention] The present invention has been made in view of the above-mentioned demands, and provides a ball screw thermal displacement correction device capable of maintaining positioning accuracy due to thermal displacement of a ball screw over a long period of time. The purpose is to: [Summary of the Invention] The device of the present invention detects the thermal displacement of a ball screw with a sensor, and in accordance with this detection signal, shifts the target ball nut movement position designated before the thermal displacement of the ball screw due to the thermal displacement of the ball screw. The position is converted to a later position, the position is compared with the current position of the ball nut, and control is performed so that the two positions coincide with each other, thereby achieving the above object. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a device for correcting thermal displacement of a ball screw according to the present invention, and FIG. 2 is a diagram partially cut away showing an example of a feed mechanism to which the device is applied. First, in FIG. 2, 1 is a ball screw, 1a and 1b are flanges provided at both ends of the ball screw 1, 2 is a hole nut screwed into the ball screw 1, and 3 is integrally attached to the ball nut 2. It is a moving body. 4 is a bearing for rotatably supporting the ball screw 1, 5A and 5B are gears, 6 is a bearing 4 and gears 5a and 5
The housing b and 7 are motors. In such a feed mechanism, when the motor 7 rotates, the ball screw 1 rotates via the gears 5a and 5b, and the ball nut 2 (moving body 3) moves linearly along the ball screw 1. During this movement, heat is generated by the friction between the ball screw 1 and the ball nut 2, and the ball screw 1 is extended by the heat. Therefore, before and after the elongation of the ball screw 1, even if the motor 7 is moved by the same rotation angle, the movement amount of the ball nut 2 will be different. Reference numerals 8a and 8b denote minute displacement sensors for obtaining signals S1a and S1b for compensating for these, and directly measure the elongation of the ball screw 1 itself. The signals S1a and S1b obtained by the sensors 8a and 8b are given to the arithmetic processing CPU 11 as shown in FIG. Meanwhile this C
PU11 has a movement command value (movement target position) S2 previously given by the operator through the operation panel 12, and a ball nut 2
The current position coordinate value S3 from the position detector 13 which detects the current position of the (moving body 3) from the number of rotations or the rotation angle of the motor 7
Is entered. Accordingly, the CPU 11 performs an operation of converting the movement command value S2 into a position after the shift movement due to the thermal displacement of the ball screw 1, compares the operation result value with the current position coordinate value S3, and the two match. Then, the motor rotation control circuit 14 is operated to rotate the motor 7. Hereinafter, the details will be described with reference to FIG. First, it is assumed that the elongation of the ball screw 1 is measured with reference to the mounting position of the minute displacement sensors 8a and 8b which are not affected by the elongation, and the length between the measurement references of the minute displacement sensors 8a and 8b is L And When the origin O of the coordinates of the ball nut 2 (moving body 3) is set at a length y from the measurement reference of the minute displacement sensor 8b, the coordinate value of the ball nut 2 is constantly based on the value of the minute displacement sensor 8b. Now, suppose that the ball nut 2 is at a distance (y + x 1 ) from the reference of the sensor 8b (the position indicated by the solid line), and the command value S2 of the operator is x 2
Then, the correction amount Δx in this case is given by the following (1)
It can be calculated by the formula. Here, the amount of elongation of the ball screw 1 is obtained from the difference between the two signal values of the sensors 8a and 8b, and this is defined as ΔL. Δx = ΔL × (x 2 + x 1 + y) ÷ L (1) (where x 2 is the command value S 2, x 1 is the current position coordinate value S 3
Is the value of ) The correction amount Δx is because merely Borunatsuto 2 (correction amount viewed from the absolute coordinate value of the moving body 3), when positioned in the movement command value S2 of the operator to x 2, the operator at the time of positioning the x 1 and absolute coordinates of the movement command value S2, the sending thereof takes the difference between the correction amount Δx of time, the motor control circuit 14 shown in FIG. 1 as a movement command value S2 in consideration of the correction amount Δx in the x 2 become. In addition, as another method, the movement command value S2
A method of calculating the correction amount of (x 2 ) as Δx ′ = ΔL × x 2 ÷ L (2) can be considered. In this method, when the elongation amount ΔL of the ball screw 1 changes every moment, Accumulated errors occur in the position viewed from the absolute coordinates, and the position is not always accurate. Therefore, if the correction is performed in consideration of the absolute coordinates by the method using the equation (1), stable positioning can be performed under any operating conditions. [Effects of the Invention] As described above, the present invention directly detects the amount of displacement (elongation) of the ball screw and performs correction in consideration of the absolute coordinates. Even if the ball screw is not passed through and the cantilever support method of the ball screw is used, there is an effect that stable high positioning accuracy can be obtained for a long time.
【図面の簡単な説明】
第１図は本発明装置の一実施例を示すブロツク図、第２
図は同装置が適用された送り機構の一例を示す図、第３
図は同装置のCPUの演算内容の一例を説明するための図
である。
１……ボールねじ、２……ボールナツト、７……モー
タ、8a,8b……微小変位センサ、11……CPU（演算装
置）、14……モータ回転制御回路、S1a,S1b……センサ
出力信号、S2……ボールナツト移動指令値（移動目標位
置）、S3……ボールナツト現在位置座標値。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, FIG.
The figure shows an example of a feed mechanism to which the apparatus is applied.
The figure is a diagram for explaining an example of the operation contents of the CPU of the same device. 1 ... ball screw, 2 ... ball nut, 7 ... motor, 8a, 8b ... minute displacement sensor, 11 ... CPU (arithmetic unit), 14 ... motor rotation control circuit, S1a, S1b ... sensor output signal , S2: Ball nut movement command value (movement target position), S3: Ball nut current position coordinate value
Claims (1)
にボールナットを移動させる距離をボールねじの熱変位
を検出するセンサからの信号に応じて演算するように構
成したボールねじの熱変位補正装置において、ボールね
じ上に所定の距離を隔てて２つの測定部位を設け、２個
の変位センサをボールねじの変形の影響を受けない位置
に配置し、それぞれ上記２つの測定部位のうちの一方の
変位を測定するように構成したことを特徴とするボール
ねじの熱変位補正装置。(57) [Claims] For a designated ball nut movement target position, a ball screw thermal displacement correction device configured to calculate the distance to actually move the ball nut according to a signal from a sensor that detects the thermal displacement of the ball screw, Two measurement sites are provided on the ball screw at a predetermined distance from each other, two displacement sensors are arranged at positions not affected by the deformation of the ball screw, and the displacement of one of the two measurement sites is measured. A ball screw thermal displacement compensator configured to measure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61121066A JP2698069B2 (en) | 1986-05-28 | 1986-05-28 | Thermal displacement compensator for pole screw |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61121066A JP2698069B2 (en) | 1986-05-28 | 1986-05-28 | Thermal displacement compensator for pole screw |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62278360A JPS62278360A (en) | 1987-12-03 |
| JP2698069B2 true JP2698069B2 (en) | 1998-01-19 |
Family
ID=14801997
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61121066A Expired - Lifetime JP2698069B2 (en) | 1986-05-28 | 1986-05-28 | Thermal displacement compensator for pole screw |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2698069B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01305403A (en) * | 1988-06-03 | 1989-12-08 | Tokyo Electron Ltd | Error correcting method |
| DE10353029B3 (en) * | 2003-11-13 | 2004-08-19 | Heidelberger Druckmaschinen Ag | Displacement spindle length variation measuring method, for printing plate exposure device, uses measurement of stepping motor clock pulses for displacement of exposure head carrier along reference path |
| JP4957393B2 (en) * | 2007-06-04 | 2012-06-20 | 日本精工株式会社 | Ball screw drive |
| JP4926264B2 (en) * | 2009-07-15 | 2012-05-09 | 智雄 松下 | Pattern forming apparatus and positioning apparatus |
| JP2021085410A (en) * | 2019-11-25 | 2021-06-03 | 日本電子株式会社 | Actuator, specimen positioning device, and charged particle beam apparatus |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5263557A (en) * | 1975-11-20 | 1977-05-26 | Setagaya Seisakusho Kk | Temperature control apparatus for feeding nut |
| JPS53106072A (en) * | 1977-02-28 | 1978-09-14 | Dainippon Screen Mfg | Comparing and concentrating method of error in accumulation pitch in drive screw |
| JPS57124202A (en) * | 1981-01-23 | 1982-08-03 | Fuji Xerox Co Ltd | Position detector for optical system of copying machine |
| JPS6057988B2 (en) * | 1982-09-06 | 1985-12-18 | 日本精工株式会社 | Ball screw thermal expansion control device |
| JPS59157509A (en) * | 1983-02-28 | 1984-09-06 | Niigata Eng Co Ltd | Measuring device of pitch error |
| JP2547395B2 (en) * | 1985-07-29 | 1996-10-23 | 東芝機械株式会社 | Absolute position detection method |
-
1986
- 1986-05-28 JP JP61121066A patent/JP2698069B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62278360A (en) | 1987-12-03 |
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