JP2004061151A - Contact angle measuring method and apparatus for bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus that reduce measurement time and inspect a contact angle on an in-line (manufacturing line) even if the rotational speed of a turning wheel is low. <P>SOLUTION: A contact angle α is obtained by obtaining one fundamental frequency of an inner ring frequency fi, a revolution frequency fc, an outer ring frequency fo, a rolling element frequency fb from harmonic components in a waviness frequency. The fundamental frequency is estimated by extracting an n-order harmonic component, and the measurement time is reduced to 1/nz in that case, thus contributing to a decrease in measurement time in a line. <P>COPYRIGHT: (C)2004,JPO

Description

【数２】

【数３】

【数４】

但し、式中でＺはボール数、Ｄはボール径、ｄｍはピッチ径、αは接触角、ｆｒは回転輪の回転数である。
【００１６】
本発明によれば、上述したウェビネス周波数の高調波成分から、内輪周波数ｆｉ、公転周波数ｆｃ、外輪周波数ｆｏ、転動体周波数ｆｂのいずれかの基本周波数を求めることで、（１）〜（４）式のいずれかに基づいて接触角αを求めることができる。ここで、ｎ次の高調波成分を抽出することで基本周波数を推定できるが、その場合の測定時間は１／ｎｚに短縮され、ラインでの測定時間短縮に寄与する。尚、内輪周波数ｆｉ、公転周波数ｆｃ、外輪周波数ｆｏ、転動体周波数ｆｂのいずれを用いて接触角αを求めるかは任意であるが、実際の測定時には、回転輪と共に回転するスピンドルの振れ成分や、ノイズ等が現れるので、それらの影響が最も少ない周波数を選択すればよい。尚、軸受の回転数が変動する場合は、回転輪の回転数に一致する振動を同時に計測することで、その影響を回避できる。
【００１７】
【発明の実施の形態】
以下、本発明による実施の形態について図面を用いて説明する。図１は本発明の実施の形態による接触角測定装置の半径方向振動を計測する場合の断面図である。
【００１８】
図１に示すように、接触角αを測定すべき、予圧が付与された組み合わせ軸受１は、内周面に複列の外輪軌道２、２を有する外輪３と、外周面に複列の内輪軌道４、４を有する内輪５と、上記外輪軌道２、２と内輪軌道４、４との間に転動自在に設けられた、転動体の一種である複数の玉６ａ、６ａ、６ｂ、６ｂとから構成される。上記接触角αの測定作業時には、この組み合わせ軸受１の内輪５が、後述するエアースピンドル１７、サーボモ−タ１９等と共に駆動装置を構成するアーバ１６に外嵌支持される。
【００１９】
上記アーバ１６は、スピンドル１７の一端面中心部に形成されたテーパ孔４７に嵌合固定される。そしてこのスピンドル１７は、フレーム１８の内側に回転自在に支持される。このスピンドルを支持する軸受として好ましくは、静圧気体軸受、磁気軸受、超電導軸受等、上記スピンドル１７の回転に伴なって振動を発生しない構造のものを使用する。
【００２０】
この様にしてフレーム１８に支持されたスピンドル１７は、サーボモータ１９により回転駆動自在とされる。又、スピンドル１７をエアスピンドルとすることで、サーボモータ１９によるスピンドル１７の回転駆動時に、このスピンドル１７が振動する事を防止する。図示の実施の形態では、スピンドル１７とサーボモータ１９の出力軸とを同心に配置し、マグネットカップリング等を介して、上記スピンドル１７を回転駆動する。上記サーボモータ１９への通電により上記スピンドル１７は、例えば１８００回転毎分程度の一定速度で回転駆動される。
【００２１】
尚、図示の実施の形態とは別に、スピンドル１７の他端面中心部に固定した従動プーリとサーボモータ１９の出力軸に固定した駆動プーリとの間に、無端ベルトを掛け渡すことで、上記スピンドル１７を回転駆動する事もできる。
【００２２】
押圧装置２３が、組み合わせ軸受１と並行して設けられ、押圧リング２６がアーバ１６に支持された組み合わせ軸受１の外輪３の端面に対向した状態で設けられる。この押圧装置２３は、支持体２４に対して回転自在に支持されたネジ軸２５と、ネジ軸２５に螺合し、その回転により軸方向に移動するボールスクリューナット２８と、ボールスクリューナット２８に一端を固定し、他端を継手２９に固定したアーム２７と、外輪３の端面を覆う押圧リング２６とを有する。
【００２３】
前記押圧リング２６は、ネジ軸２５上のボールスクリューナット２８が下方向に移動することに伴なってアーム２７及び継手２９が下降するので、前記組み合わせ軸受１の外輪３の端面に押し付けられ、この外輪３をアキシャル方向（図１の下方向）に押圧する。この押圧により、前記内輪５がサーボモータ１９への通電に基づいて回転した場合に於いても、この外輪３が回転するのが防止される。
【００２４】
尚、この押し付け作業時に、前記押圧リング２６を外輪３の端面に、全周に亙って均等な力で押し付ける役目を有する揺動継手（図示せず）を継手２９に替えて取り付けたり、上記押圧装置２３を構成する各部材で生じる振動が外輪３に伝達されるのを防止する役目を有する緩衝材（不図示）を外輪３と押圧リング２６との間に設けてもよい。又、前記押圧リング２６をアキシャル方向に押圧する為の手段は、予圧シリンダ、ソレノイド等、他の機構とする事も出来る。
【００２５】
測定手段すなわち振動測定素子である振動ピックアップ３３が、外輪３の外周面に当接して配置されている。この振動ピックアップ３３は、外輪３のラジアル方向（半径方向）に亙る振動を測定し、測定値を表わす信号Ａをアンプ３５に送る。尚、振動測定素子としては、上記振動ピックアップ３３の他、変位計、速度計、加速度計等、上記ラジアル方向に亙る振動を検出できるものであれば、何れも使用可能である。又、外輪３のアキシアル方向（軸方向）の振動を測定しても良い。
【００２６】
上記アンプ３５は増幅器とローパスフィルタとを含む。従って、このアンプ３５からは、増幅された信号Ｂが、周波数分析器３６に送られる。尚、ローパスフィルタは、次述するフーリエ変換器３８による処理を行なう際の、折り返し防止の為に設けられる。
【００２７】
分析手段である周波数分析器３６は、Ａ／Ｄ変換器３７と、フーリエ変換器３８と、メモリ３９とを含む。上記フーリエ変換器３８は、高速フーリエ変換（ＦＦＴ：ｆａｓｔ　ｆｏｕｒｉｅｒ　ｔｒａｎｓｆｏｒｍ）を利用して、上記アンプ３５から送り込まれ、Ａ／Ｄ変換器３７によりディジタル信号に変換された信号Ｂに基づいて、振動の周波数成分を求めることができる。
【００２８】
尚、メモリ３９は、前記サーボモータ１９による内輪５の回転にむらが生じる恐れのある場合に、これを補正するのに利用される。回転むらを補正する場合には、Ａ／Ｄ変換器３７から送り出された信号は、メモリ３９を介して上記フーリエ変換器３８に送られる。このフーリエ変換器３８は、回転輪の回転数ｆｒと公転周波数のｎ次成分ｎ・ｆｃとを、同じ時間軸データから求めるようになっている。
【００２９】
即ち、上記アンプ３５から周波数分析器３６に送られる信号Ｂには、上記回転数ｆｒに関する信号と、公転周波数のｎ次成分ｎ・ｆｃに関する信号とが、互いに重なり合った状態で含まれる。スペクトルもあるが、本実施形態の場合には、公転周波数のｎ次成分、ｎ・ｆｃの中で重ならないスペクトルを分析している。
【００３０】
上記内輪５の回転にむらがない場合には、上記回転数ｆｒに結び付く信号の処理を第１の計測時間内の信号Ｂで行ない、公転周波数のｎ次成分ｎ・ｆｃに結び付く信号の処理を、この第１の計測時間とは重ならない第２の計測時間内の信号Ｂ′で行なっても良い（メモリ３９は不要）。ところが、内輪５の回転にむらがあると、第１の計測時間の間の回転数ｆｒと第２の計測時間の間の公転周波数のｎ次成分ｎ・ｆｃとが対応しなくなり、この結果求められる接触角αが不正確となる。そこで、この様な場合には、上記メモリ３９を利用する事で、上記回転数ｆｒと公転周波数のｎ次成分ｎ・ｆｃとを何れも同じ時間軸に存在する信号Ｂから求めることができる。
【００３１】
この為、上記内輪５の回転にむらが生じても、このむらが上記回転数ｆｒと公転周波数のｎ次成分ｎ・ｆｃとの比率ｆｃ／ｎ・ｆｒに影響を与える事はなくなる。最終的に求めるべき接触角αは、前記（１）式から明らかな様に、上記回転数ｆｒと公転周波数ｆｃとの比率により求められる為、この比率が正しければ、正確な接触角αを得られる。
【００３２】
この様に、周波数分析器３６を構成するフーリエ変換器３８により求められた、内輪５の回転数ｆｒと玉６、６の公転周波数のｎ次成分ｎ・ｆｃとを表わす信号Ｃは、玉６、６の外径Ｄａ及び玉６、６のピッチ直径ｄｍを表わす信号と共に、パーソナルコンピュータ等の接触角演算器４０に送り込まれる。それに基づき、演算手段である接触角演算器４０が、前記（１）式に基づいて、前記組み合わせ軸受１の接触角αを求めるようになっている。
【００３３】
以上のように構成された本実施の形態による組み合わせ軸受の接触角測定装置を、いわゆるハブＩＩＩ軸受に適用した例について図１を用いて説明する。
【００３４】
ハブＩＩＩ軸受の場合、加工、組立工程での寸法誤差により接触角αは変化するが、Ｄ／ｄｍに与える影響は無視できるほど小さく、例えばＰＣＤ４４．５ｍｍと比較的サイズの小さい軸受でもＤ／ｄｍの誤差は０．２％程度であり、一定とみなすことができるため、（１）〜（４）の各式における振動成分のみを計測すれば接触角αを推定することができる。また、仮にｎｚ倍のウェビネス成分を計測に用いても誤差の影響度は変わることはない。
【００３５】
図２に示すように、周波数分析器により複列の組み合わせ軸受における接触角αを評価するための、各列の転動体の公転周波数ｎ・Ｚ・ｆｃ１とｎ・Ｚ・ｆｃ２が２本抽出されれば、ｆｃ１、ｆｃ２を推定でき、接触角演算器により（１）〜（４）に示した式に従って、２つの接触角αを求めて評価することができる。
【００３６】
次に、軸受を低速で回転させた場合の接触角を求める例について図３を用いて説明する。図３は、軸受を６００回転毎分で回転させた場合の転動体の公転周波数ｆｃを示すグラフである。図３に示すように、軸受を６００回転毎分と低速で回転させて、転動体の公転周波数ｆｃの１次、２次、３次成分を計測し、１次、２次、３次成分について隣接する２本の周波数の差分を求め、その値を図中△にプロットした。図３より図中の△印はリニアな関係にあることから、２次、３次成分の周波数より１次成分周波数に換算した場合でも、１次成分の周波数を精度良く推定できることを示している。従って、高次成分から基本成分の周波数を推定することができる。
【００３７】
さらに、図中の表は実際に２次、３次成分より換算した１次成分相当の周波数であり、この表より隣接している２本の周波数は共にほぼ１次成分と同じ周波数の値である。このことからも、２次、３次成分の周波数より１次成分の周波数を精度良く推定できる。
【００３８】
図３のデータにより、例えば転動体の公転周波数の３次成分を計測すれば、１次成分の周波数を精度良く推定することができ、１次成分を計測する場合に比べて１／３の計測時間で接触角αを推定することができる。
【００３９】
従って、高次成分から基本成分の周波数を推定することができるだけでなく、基本成分の周波数を計測する場合に比べて、次数分の一の計測時間で接触角αを推定でき、計測時間を短縮することができる。
【００４０】
【発明の効果】
本発明によれば、測定する時間を短縮でき、また、回転輪の回転数が低回転であっても、インライン（製造ライン）上で接触角を検査可能な方法及び装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態による接触角測定装置の半径方向振動を計測する場合の断面図である。
【図２】周波数分析例を示すグラフである。
【図３】軸受を６００回転毎分で回転させた場合の転動体の公転周波数ｆｃを示すグラフである。
【図４】軸受装置の一例であるアンギュラ玉軸受の断面図である。
【符号の説明】
１　組み合わせ軸受
３　外輪
５　内輪
６ａ、６ｂ　玉（転動体）
１７　スピンドル
１８　フレーム
１９　サーボモータ
２３　押圧装置
３３　振動ピックアップ
３５　アンプ
３６　周波数分析器
４０　接触角演算器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for measuring the contact angle of a pre-loaded combination bearing device, for example.
[0002]
[Prior art]
For example, an angular contact ball bearing 1 having a cross section shown in FIG. 4 has an outer race 3 having an outer raceway 2 on an inner peripheral surface, an inner race 5 having an inner raceway 4 on an outer peripheral surface, and a space between the outer raceway 2 and the inner raceway 4. And a plurality of balls 6, which are rolling elements, provided so as to be able to roll freely. Based on the rolling of the balls 6, 6, relative rotation between a member such as a housing in which the outer ring 3 is internally supported and a member such as a shaft in which the inner ring 5 is externally supported is enabled.
[0003]
Further, the angular contact ball bearing 1 draws a straight line a connecting the contact points of the balls 6, 6 with the outer ring raceway 2 and the inner ring raceway 4 so as to support not only the radial load but also the axial load. 6 and 6 are inclined by an angle α with respect to a straight line b connecting the centers of each other. This angle α, which is called a contact angle, has a great effect on the performance of the ball bearing 1, and therefore it is necessary to regulate the angle α to a predetermined value. In particular, in the case of a high-performance ball bearing, it is necessary to strictly control the contact angle α. Although not shown, the contact angle of the rollers as the rolling elements in the tapered roller bearing also needs to be strictly regulated.
[0004]
Incidentally, a method and apparatus for measuring the contact angle of a bearing device is disclosed in Japanese Patent Application Laid-Open No. 4-364408. Such a method and apparatus are to rotate one of the outer ring and the inner ring of the bearing in a state where rotation is impossible by pressing a part of one of the rings, measure the vibration of the outer ring or the inner ring, and measure the rotation of the rotating ring from the measured value. The contact angle is obtained by obtaining the rotation frequency of the rolling element and the revolution frequency of the rolling element.
[0005]
According to the method for measuring the contact angle of a rolling bearing disclosed in Japanese Patent Application Laid-Open No. 4-364408, before the contact angle was determined from the rotation angle of the outer ring or the inner ring and the rotation angle of the cage holding the rolling elements. As compared with the measurement method and apparatus of the above, the measurementable bearing is not limited, and sufficiently high-precision measurement can be performed, and the measurement operation can be automated. The rolling bearing can be incorporated into the rolling bearing manufacturing line by incorporating the measurement apparatus. It has also become possible to inspect the contact angle on the line.
[0006]
[Problems to be solved by the invention]
By the way, when the revolving frequency of the combined bearing is obtained by forming a double row of tracks on the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and applying a preload to the rolling elements provided between the two tracks, Vibration occurs for each row, and two kinds of revolution frequencies are obtained. In this case, if the contact angles of each row of the combined bearing are adjacent to each other or the contact angles of each row are substantially equal, the difference between the two revolution frequencies is small, so that any of the revolution frequencies is that of any of the rows. Sometimes it was not possible to identify.
[0007]
However, according to the above-described conventional technology, the pressing force that makes one of the outer ring and the inner ring unrotatable is changed to make the contact angles of the rolling elements in each row different so that the two kinds of revolution frequencies have a difference. By doing so, it is possible to identify which orbital frequency belongs to which column.
[0008]
[Problems to be solved by the invention]
However, in the above-described prior art, since either the outer ring or the inner ring is rotated at a practical rotation speed and the contact angle is measured for each row, if the difference between the two types of revolving frequencies of the combined bearing is small, the measurement time is reduced. And the inspection in an in-line (manufacturing line) was sometimes difficult. In particular, when the rotation speed is low, if the difference between the two kinds of revolution frequencies of the combined bearing is small, it is difficult to identify which row of the rolling elements is the revolution frequency, so that sufficient measurement cannot be performed. There was such a problem.
[0009]
The present invention provides a method and an apparatus for measuring a contact angle of a combined bearing to which a preload is applied, in which the measuring time can be shortened, and even when the rotation speed of a rotating wheel is low, in-line (production line) An object of the present invention is to provide a method and an apparatus capable of inspecting a contact angle.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a first method for measuring a contact angle of a bearing device according to the present invention comprises:
In a contact angle measuring method for measuring a contact angle of a bearing device (for example, a tapered roller bearing) having an outer ring, an inner ring, and a rolling element rotatably arranged between the two wheels,
When one of the inner ring and the outer ring is rotated, at least one of radial vibration and axial vibration generated in the fixed ring is measured, and a fundamental or harmonic component of a vibration frequency based on the waviness obtained by the measurement result is measured. The contact angle of the rolling element is obtained based on
[0011]
A contact angle measuring device for a bearing device according to a second aspect of the present invention comprises:
In a contact angle measuring device for measuring a contact angle of a bearing device (for example, a tapered roller bearing) having an outer ring, an inner ring, and a rolling element rotatably arranged between the two wheels,
Measuring means for measuring at least one of radial vibration and axial vibration generated in a fixed wheel when one of the inner ring and the outer ring is rotated,
Analyzing means for analyzing the vibration measured by the measuring means to determine a fundamental or harmonic component of the vibration frequency by webininess,
Calculating means for calculating a contact angle of the rolling element based on the fundamental wave or the harmonic component.
[0012]
[Action]
Although each member constituting the rolling bearing is finished very precisely, it is impossible that there is no error in its surface shape and dimensions. For example, it is ideal that the outer diameters of a plurality of rolling elements incorporated in one rolling bearing are the same, but the outer diameters are usually slightly different for each rolling element due to unavoidable manufacturing errors. . As described above, the rotating wheel or the fixed wheel vibrates in the radial direction and the axial direction based on the revolution of the plurality of rolling elements having slightly different outer diameters. By analyzing this vibration, the vibration frequency due to the waviness of the rolling element can be found.
[0013]
In addition, both the outer raceway and the inner raceway have minute undulations. When the rotating wheel rotates, the rotating wheel and the fixed wheel vibrate in the radial and axial directions based on the undulation. By analyzing this vibration, the vibration frequency due to the waviness of the rotating wheel and the waviness frequency of the fixed wheel can be found.
[0014]
In particular, in the case of a combination bearing including double-row rolling elements, since there are two contact angles, the spectrum of each vibration component is measured as two adjacent line spectra. Assuming that the revolution frequencies of the rolling elements at this time are fc1 and fc2, for example, the nth-order component of the radial vibration due to the undulation (webiness) of the fixed wheel is measured. (Nzfc1-nzfc2) / (fc1-fc2), which shows a comparison of the evaluation based on the revolution frequency of the rolling element, is nz times the frequency, and is nz times the evaluation based on the revolution frequencies fc1 and fc2 of the rolling elements. Therefore, when the contact angle is evaluated based on the revolution frequency nzfc of the rolling element of the nth order component, the measurement time required for frequency analysis is reduced to 1 / nz, and the contact angle of the bearing to which the preload is applied in-line is completely reduced It becomes possible to measure. This is because the frequency resolution for obtaining the same detection accuracy may be low by detecting a higher-order component of the revolution frequency of the rolling element.
[0015]
Here, the nth-order component of each webiness frequency can be expressed as follows.
(1) Radial vibration rotating wheel waviness: n · fi ± fr or n · fo ± fr
Fixed wheel webiness: n ・ Z ・ fc
Rolling element webiness: 2 · n · fb ± fc
(2) Axial vibration rotating wheel webiness: n · fi or n · fo
Fixed wheel webiness: n ・ Z ・ fc
Rolling element webiness: 2 ・ n ・ fb
Here, fi is the inner ring frequency, fc is the revolution frequency, fo is the outer ring frequency, and fb is the rolling element frequency. The relationship between these and the contact angle is shown below.

(Equation 2)

[Equation 3]

(Equation 4)

In the equation, Z is the number of balls, D is the ball diameter, dm is the pitch diameter, α is the contact angle, and fr is the number of revolutions of the rotating wheel.
[0016]
According to the present invention, any one of the basic frequencies of the inner ring frequency fi, the revolving frequency fc, the outer ring frequency fo, and the rolling element frequency fb is obtained from the above-described harmonic component of the webininess frequency, thereby obtaining (1) to (4). The contact angle α can be obtained based on any of the equations. Here, the fundamental frequency can be estimated by extracting the n-th harmonic component, but the measurement time in that case is reduced to 1 / nz, which contributes to the reduction of the measurement time in the line. The contact angle α may be determined using any of the inner ring frequency fi, the revolving frequency fc, the outer ring frequency fo, and the rolling element frequency fb. , Noise, etc. appear, so that the frequency having the least influence on them may be selected. When the rotational speed of the bearing fluctuates, the influence can be avoided by simultaneously measuring the vibrations corresponding to the rotational speed of the rotating wheel.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a contact angle measuring device according to an embodiment of the present invention when measuring radial vibration.
[0018]
As shown in FIG. 1, a preloaded bearing 1 for which the contact angle α is to be measured includes an outer ring 3 having multiple rows of outer raceways 2 and 2 on the inner peripheral surface, and a double row inner race on the outer peripheral surface. A plurality of balls 6a, 6a, 6b, 6b, which are a kind of rolling elements, are provided between the outer raceways 2, 2 and the inner raceways 4, 4 so as to roll freely. It is composed of At the time of measuring the contact angle α, the inner ring 5 of the combined bearing 1 is externally supported by an arbor 16 which constitutes a driving device together with an air spindle 17 and a servo motor 19 to be described later.
[0019]
The arbor 16 is fitted and fixed in a tapered hole 47 formed at the center of one end surface of the spindle 17. The spindle 17 is rotatably supported inside the frame 18. As the bearing for supporting the spindle, it is preferable to use a static pressure gas bearing, a magnetic bearing, a superconducting bearing or the like having a structure that does not generate vibration with the rotation of the spindle 17.
[0020]
The spindle 17 supported on the frame 18 in this manner is rotatably driven by a servomotor 19. Also, by using the spindle 17 as an air spindle, the spindle 17 is prevented from vibrating when the spindle 17 is rotationally driven by the servo motor 19. In the illustrated embodiment, the spindle 17 and the output shaft of the servomotor 19 are arranged concentrically, and the spindle 17 is driven to rotate via a magnetic coupling or the like. When the servo motor 19 is energized, the spindle 17 is driven to rotate at a constant speed of, for example, about 1800 revolutions per minute.
[0021]
In addition, separately from the illustrated embodiment, the endless belt is stretched between a driven pulley fixed to the center of the other end surface of the spindle 17 and a drive pulley fixed to the output shaft of the servomotor 19, thereby obtaining the spindle. 17 can also be driven to rotate.
[0022]
A pressing device 23 is provided in parallel with the combination bearing 1, and is provided in a state where the pressing ring 26 faces the end surface of the outer ring 3 of the combination bearing 1 supported by the arbor 16. The pressing device 23 includes a screw shaft 25 rotatably supported by a support 24, a ball screw nut 28 screwed onto the screw shaft 25, and moving in the axial direction by the rotation thereof, and a ball screw nut 28. It has an arm 27 having one end fixed and the other end fixed to a joint 29, and a pressing ring 26 covering the end surface of the outer race 3.
[0023]
The pressing ring 26 is pressed against the end face of the outer ring 3 of the combined bearing 1 because the arm 27 and the joint 29 are lowered as the ball screw nut 28 on the screw shaft 25 moves downward. The outer ring 3 is pressed in the axial direction (downward in FIG. 1). This pressing prevents the outer ring 3 from rotating even when the inner ring 5 rotates based on the energization of the servomotor 19.
[0024]
During this pressing operation, a rocking joint (not shown) having a function of pressing the pressing ring 26 on the end face of the outer ring 3 with an even force over the entire circumference is attached to the joint 29 instead of the joint 29. A cushioning member (not shown) having a function of preventing the vibration generated by each member constituting the pressing device 23 from being transmitted to the outer ring 3 may be provided between the outer ring 3 and the pressing ring 26. The mechanism for pressing the pressing ring 26 in the axial direction may be another mechanism such as a preload cylinder or a solenoid.
[0025]
A vibration pickup 33, which is a measuring means, that is, a vibration measuring element, is disposed in contact with the outer peripheral surface of the outer race 3. The vibration pickup 33 measures the vibration of the outer ring 3 in the radial direction (radial direction) and sends a signal A representing the measured value to the amplifier 35. In addition, as the vibration measuring element, in addition to the vibration pickup 33, any one that can detect the vibration in the radial direction, such as a displacement meter, a speedometer, and an accelerometer, can be used. Further, the vibration of the outer ring 3 in the axial direction (axial direction) may be measured.
[0026]
The amplifier 35 includes an amplifier and a low-pass filter. Therefore, the amplified signal B is sent from the amplifier 35 to the frequency analyzer 36. The low-pass filter is provided to prevent aliasing when performing processing by the Fourier transformer 38 described below.
[0027]
The frequency analyzer 36, which is an analysis means, includes an A / D converter 37, a Fourier converter 38, and a memory 39. The Fourier transformer 38 uses a fast Fourier transform (FFT) to transmit vibration from the amplifier 35 based on the signal B that is sent from the amplifier 35 and converted into a digital signal by the A / D converter 37. Frequency components can be determined.
[0028]
The memory 39 is used to correct uneven rotation of the inner ring 5 caused by the servo motor 19 when there is a possibility. When correcting rotational unevenness, the signal sent from the A / D converter 37 is sent to the Fourier transformer 38 via the memory 39. The Fourier transformer 38 determines the rotational frequency fr of the rotating wheel and the n-th component n · fc of the revolution frequency from the same time axis data.
[0029]
That is, the signal B sent from the amplifier 35 to the frequency analyzer 36 includes the signal related to the rotation speed fr and the signal related to the n-order component n · fc of the revolution frequency in a state where they overlap each other. Although there is a spectrum, in the case of the present embodiment, a spectrum that does not overlap in the n-order component of the revolution frequency, n · fc, is analyzed.
[0030]
If the rotation of the inner ring 5 is not uneven, the processing of the signal linked to the rotation frequency fr is performed by the signal B within the first measurement time, and the processing of the signal linked to the n-th component n · fc of the revolution frequency is performed. Alternatively, the measurement may be performed with the signal B 'within the second measurement time which does not overlap with the first measurement time (the memory 39 is unnecessary). However, if the rotation of the inner ring 5 is uneven, the number of revolutions fr during the first measurement time and the n-order component n · fc of the revolution frequency during the second measurement time do not correspond to each other. The contact angle α is inaccurate. Therefore, in such a case, by using the memory 39, the rotation speed fr and the n-th component n · fc of the revolution frequency can be obtained from the signal B existing on the same time axis.
[0031]
For this reason, even if the rotation of the inner ring 5 is uneven, the unevenness does not affect the ratio fc / n · fr between the rotation speed fr and the nth-order component n · fc of the revolution frequency. The contact angle α to be finally obtained is determined from the ratio between the rotational speed fr and the revolution frequency fc, as is apparent from the above equation (1). Therefore, if this ratio is correct, an accurate contact angle α can be obtained. Can be
[0032]
As described above, the signal C representing the rotational frequency fr of the inner ring 5 and the n-order component n · fc of the revolving frequency of the balls 6, 6, which is obtained by the Fourier transformer 38 constituting the frequency analyzer 36, is , 6 and a signal representing the pitch diameter dm of the balls 6, 6, are sent to a contact angle calculator 40 such as a personal computer. Based on this, the contact angle calculator 40, which is a calculating means, calculates the contact angle α of the combined bearing 1 based on the equation (1).
[0033]
An example in which the contact angle measuring device for a combined bearing according to the present embodiment configured as described above is applied to a so-called hub III bearing will be described with reference to FIG.
[0034]
In the case of the hub III bearing, the contact angle α changes due to a dimensional error in the machining and assembling processes. However, the influence on D / dm is negligibly small. For example, even a bearing having a relatively small size of PCD 44.5 mm has a D / dm. Is about 0.2% and can be regarded as constant. Therefore, the contact angle α can be estimated by measuring only the vibration components in the equations (1) to (4). Further, even if the webiness component of nz times is used for the measurement, the influence of the error does not change.
[0035]
As shown in FIG. 2, two frequency orbits n · Z · fc1 and n · Z · fc2 of the rolling elements in each row are extracted by the frequency analyzer to evaluate the contact angle α in the double row combination bearing. Then, fc1 and fc2 can be estimated, and two contact angles α can be obtained and evaluated by the contact angle calculator according to the equations shown in (1) to (4).
[0036]
Next, an example of obtaining a contact angle when the bearing is rotated at a low speed will be described with reference to FIG. FIG. 3 is a graph showing the revolution frequency fc of the rolling element when the bearing is rotated at 600 revolutions per minute. As shown in FIG. 3, the bearing is rotated at a low speed of 600 revolutions per minute, and the primary, secondary, and tertiary components of the revolution frequency fc of the rolling element are measured. The difference between two adjacent frequencies was determined, and the value was plotted as 図 in the figure. 3 indicates that the frequency of the primary component can be accurately estimated even when the frequency of the secondary and tertiary components is converted to the frequency of the primary component since the symbol Δ in the diagram has a linear relationship. . Therefore, the frequency of the fundamental component can be estimated from the higher-order component.
[0037]
Further, the table in the figure is the frequency corresponding to the primary component actually converted from the secondary and tertiary components, and the two adjacent frequencies from this table are almost the same frequency value as the primary component. is there. From this, the frequency of the primary component can be accurately estimated from the frequency of the secondary and tertiary components.
[0038]
For example, if the tertiary component of the revolution frequency of the rolling element is measured from the data of FIG. 3, the frequency of the primary component can be accurately estimated. The contact angle α can be estimated in time.
[0039]
Therefore, not only can the frequency of the basic component be estimated from the higher-order components, but also the contact angle α can be estimated in a measurement time that is a fraction of the order compared to the case where the frequency of the basic component is measured, reducing the measurement time can do.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the method and apparatus which can shorten the measurement time and can inspect a contact angle in-line (production line) even if the rotation speed of a rotating wheel is low can be provided. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view when measuring a radial vibration of a contact angle measuring device according to an embodiment of the present invention.
FIG. 2 is a graph showing an example of frequency analysis.
FIG. 3 is a graph showing a revolution frequency fc of a rolling element when a bearing is rotated at 600 revolutions per minute.
FIG. 4 is a sectional view of an angular contact ball bearing which is an example of a bearing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Combination bearing 3 Outer ring 5 Inner ring 6a, 6b Ball (rolling element)
17 Spindle 18 Frame 19 Servo motor 23 Pressing device 33 Vibration pickup 35 Amplifier 36 Frequency analyzer 40 Contact angle calculator

Claims (2)

An outer ring, an inner ring, and a contact angle measuring method for measuring a contact angle of a bearing device having a rolling element rotatably disposed between the two wheels,
When one of the inner ring and the outer ring is rotated, at least one of a radial vibration and an axial vibration generated in a fixed wheel is measured, and a fundamental frequency or a harmonic component of a vibration frequency based on the waviness obtained by the measurement result is measured. A contact angle measuring method for a bearing device, wherein a contact angle of the rolling element is obtained based on the following. In a contact angle measuring device for measuring a contact angle of a bearing device having an outer ring, an inner ring, and a rolling element arranged to be able to roll between the two wheels,
Measuring means for measuring at least one of radial vibration and axial vibration generated in a fixed wheel when one of the inner ring and the outer ring is rotated,
Analyzing means for analyzing the vibration measured by the measuring means to determine a fundamental or harmonic component of the vibration frequency by webininess,
Calculating means for determining a contact angle of the rolling element based on the fundamental wave or the harmonic component.

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