1、感谢红星的审阅和指导,文章某些部分还是有翻的不对的地方,如有发现请通知我CHAPTER FIVE:Accurate Diagnosis of Antifriction Bearings章节5滚动轴承的精确诊断INTRODUCTION 简介This chapter describes procedures for identifying defects in antifriction bearings by analyzing frequencies generated by the moving parts. Defects on bearing raceways, rolling eleme
2、nts, and the cage generate different frequencies. The spectrum shape, amplitude, frequency, sum and difference frequencies, and the time domain signal are useful in identifying the nature, location, combination, and size of defects.本章节描述了如何通过分析运动部件产生的频率来识别滚动轴承的缺陷。轴承滚道，滚动元件和保持架上的缺陷会产生不同的频率。频谱形状，振幅，频率
3、，和差频率，以及时域信号都有助于辨认缺陷的性质，位置，组合和大小。Methods are presented to calculate the bearing frequencies; identify if the bearing is in a thrust or radial load; calculate the length of inner race defects with the time domain signal; and measure the length of a defect on the outer race in the frequency domain spe
4、ctra. The nature of the defect, such as shallow flaking, deep fatigue spalls, corrosion, acid etching, fluting, and inadequate lubrication can be determined by analyzing the frequency and time domain data. These techniques can also identify bearings with excessive clearance and bearings that are not
5、 properly installed, such as those turning on the shaft or loose in the housing. Techniques used to predict the life span of a defective bearing are discussed.提出计算轴承频率的方法；确定轴承是否承受轴向或径向负荷；通过时域信号计算内圈缺陷长度；通过频域谱估算外圈上某个缺陷的长度。缺陷的性质，如浅层剥落，深层疲劳碎裂，腐蚀，酸蚀，电蚀和润滑不足等都可以通过分析频域和时域数据确定。这些技术也可以用于识别轴承游隙过量以及轴承安装不当，例如跑内
6、圈或跑外圈。对预测有缺陷轴承寿命的技术进行了讨论。DATA COLLECTION 数据采集Data collection is the most important step in evaluation of bearing condition. Data should be collected by placing the transducer in the bearing load zone with due respect to flexibility. If this is not done, the best signal definition may not be obtained
7、. For example, with a radial bearing in a radial load, the best signal is obtained in the radial position. For an angular contact bearing or a radial bearing in a thrust load, the best signal definition is obtained in the axial direction. The machine internal geometry, as well as which problems gene
8、rate radial or thrust loads, must be determined in order to properly place the transducer. Data should be taken where the transfer function is best; for example, put the transducer on a bolt head, not the cover. For pillow-block, tending side dryer, and similar bearings, the transducer should be pla
9、ced near the top of the bearing. For bearings in gear housings, the transducer should be placed on a bolt head in the load zone.数据采集是评估轴承状况最重要的一步。采集数据时应该把传感器布置在轴承的承载区同时兼并灵活性。不这样做就无法获得最好的清晰信号。举例，在一个承受径向载荷的径向轴承，径向承载区可以采集到最好的信号。对于角接触轴承和径向轴承承受轴向载荷时，最佳的信号的采集位置是在轴向。为了合理安装传感器，必须确认设备内部构造，以及哪些故障会产生径向或轴向载荷。数据
10、应当在信号传递路径最好的位置采集；例如，把传感器放在螺栓头上，而不是轴承座端盖上。针对枕式轴承,操作侧吹风机，和类似的轴承，传感器应当被放在接近轴承顶部的位置。齿轮箱里的轴承，传感器应该放在承载区的螺栓头部上。TRANSDUCER SELECTION 传感器的选择Success or failure in diagnosing bearing defects often depends on the selection of the proper transducer. The discussions of transducer selection in other chapters appl
11、y. However, a few words should be added here. Spherical roller bearings rotating at 1200 RPM can generate harmonics of BPFO in the 3,000 Hz range when fluting occurs. An accelerometer must be used in such cases.诊断轴承缺陷成功或失败通常取决于是否选择了适当的传感器。关于传感器的选择其他章节已经讨论过。但是，这里需要做一些简单说明。转速1200RPM的球面滚子轴承，当出现电蚀的时候能在3
12、000HZ范围内产生外圈缺陷频率的谐波。其他类似情况必须使用加速度传感器Low speed machines rotating as low as 2 or 3 RPM, other machines when bearing frequencies are below 10 Hz, and lightweight shafts installed in heavy housings all require either contacting or non-contacting displacement transducers for accurate diagnostics.低速设备的转速可
13、能只有2或3RPM，其他设备如当轴承频率低于10HZ时以及重量轻的轴安装在较重的轴承座中时都需要接触式或非接触位移传感器才可以准确诊断The velocity transducer is still the best choice for frequencies between 10 and 2,000 Hz.针对频率处在10-2000Hz内的设备，速度传感器依然是最好的选择。GENERATED FREQUENCIES 产生的频率In order to understand the relationships between the different rotating elements of
14、 a bearing, the equations describing the relative speeds must first be developed. These equations define the frequencies generated by antifriction bearings. A machine with a defective bearing can generate at least five frequencies. These frequencies are:为了理解一个轴承不同旋转部件之间的关系，必须先建立一个描述其相对速度关系的公式。这些公式定义
15、滚动轴承产生的频率。这些频率分别为：1. Rotating unit frequency or speed (S)2. Fundamental train frequency (FTF)3. Ball pass frequency of the outer race (BPFO)4. Ball pass frequency of the inner race (BPFI)5. Two times ball spin frequency (2 X BSF)1 旋转部件的频率或速度(S)2 轴承保持架故障频率 (FTF)3 外圈通过频率(BPFO)4 内圈通过频率(BPFI)5 2倍的滚珠滚动频率
16、 (2 X BSF)Figs. 5-1 and 5-2 show the axial and cross-sectional views of the geometry for a ball bearing, where vo, vc and vi are the linear velocities of the outer race, ball center, and inner race, respectively. Bd is the ball diameter, Pd is the pitch diameter of the bearing and is measured from b
17、all center to ball center, andis the contact angle. If a vertical line is drawn through the bearing and another line is drawn where the ball contacts the inner and outer races, the angle between the two lines is the contact angle. See Fig. 5-2.图5-1和5-2显示了一个普通深沟球轴承的侧面及轴向剖视图，其中v o,vc和v i分别是外圈，滚珠和内圈的线性
18、速度。B d是滚珠直径，P d是轴承的节圆直径（滚动体中心圆直径），即对称位置的滚珠的中心距。是接触角。如果垂直画线垂直通过轴承中心，在画一条线连接滚珠和内外圈的接触点，那么这两条线之间的夹角就是接触角。请参见图 5-2。Fundamental Train Frequency轴承保持架故障频率The train or cage frequency is equivalent to the angular velocity of the individual ball centers. From Fig. 5-1, the linear velocity of each ball center
19、can be described as,轴承保持架故障频率可被描述为单个滚珠中心的角速度。图5-1所示，每个滚珠中心线速度可被描述为，Angular velocity () is defined as the linear velocity (v) about a radius (r) or, 角速度（）可被定义为线速度（v）除以半径（r）,即：Therefore 因此可得到保持架的角速度公式3where c, is the angular velocity of the ball center or cage. Since v =/r from Equation 2, c can be ex
20、pressed as Equation 4, where i and o are the angular velocities of the inner and outer bearing races. The quantity c is also known as the fundamental train frequency.公式3中 c是滚珠中心或保持架的角速度。利用公式2中的v=/r， c可用公式4来表述， i和 o分别为轴承内外圈滚道的角速度。 c的数值也被认为是保持架故障频率。Ball Pass Frequency of Outer Race滚珠外圈通过频率The ball pas
21、s frequency of the outer race is defined as the frequency of the balls passing over a single point on the outer race. The BPFO can be described as the number of balls multiplied by the difference frequency between the cage and the outer race or,滚珠外圈通过频率被定义为滚珠通过外圈滚道面上某一点的频率。BPFO可被说成是滚珠数乘以保持架和外圈的频率差，即
22、：which can be rewritten, using Equation 4, as Equation 6 where Nb is the number of balls.公式5可通过公式4变化，得到公式6，其中N b为滚珠的数量 。Ball Pass Frequency of Inner Race 内圈通过频率The ball pass frequency of the inner race is defined as the frequency of the balls passing over a single point on the inner race. The BPFI c
23、an be described as the number of balls multiplied by the difference frequency between the inner race and the cage or,滚珠内圈通过频率被定义为滚珠通过内圈滚道面上某一点的频率。BPFI可被描述为滚珠数乘以内圈和保持架的频率差，即：which can be rewritten, again using Equation 4, as Equation 8.公式7可通过公式4变换，即公式8.Ball Spin Frequency滚珠自转频率The angular velocity of
24、 a ball about its center can be expressed in two different ways. First, considering the linear velocity of a point on the inner race in contact with the ball surface, the linear velocity (Vb) of a point on the ball surface is given as滚珠相对其自身中心的角速度可通过两种不同方式表达。首先，通过到滚珠表面与内圈接触的某一点的线速度来说明，滚珠表面的某一点线速度V b
25、为：where ri, is the radius of the inner race. The ball angular velocity or ball spin frequency is thenri为内圈半径。滚珠角速度或滚珠自转频率为：or, from Fig. 5-2,由图5-2可得到公式11where rb, is the radius of the ball. Equation 11 can also be rewritten, using Equation 4, as Equation 12.rb为滚珠半径。公式11同样可使用公式4变换，其结果为公式12。Second, co
26、nsidering the linear velocity of a point on the outer race in contact with the ball surface, the linear velocity of a point on the ball surface is given as其次，从滚珠表面与外圈接触的某一点的线速度来说明，此时滚珠表面某一点线的速度可表示为：Therefore,因此where ro, is the radius of the outer race. The ball spin frequency can then be expressed a
27、s Equation 15, which is exactly the same as Equation 12.ro为外圈滚道半径。滚珠自转频率可通过公式15表示，其公式变化过程参考公式12。Application of the Bearing Formulas 轴承公式的运用Equations 4, 6, 8, and 12 are general formulas where either bearing race, or both, could be rotating. Also, the bearing can have either balls or rollers and the
28、contact angle may be equal to zero as in deep groove ball bearings.公式4，6，8和公式12是常用公式，可在轴承任一滚道或两个滚道一起旋转的情况下使用。另外，轴承可能是滚珠或滚子并且接触角可能像深沟球轴承那样为0。For the case where the outer race is stationary and the inner race is rotating,针对内圈转动外圈固定的情况，where S is the angular velocity or speed of the rotating system. Eq
29、uations 4,6,8, and 12 can then be reduced to:S为系统角速度或旋转速度。公式4,6,8和公式12可缩写为：For the case where the inner race is stationary and the outer race is rotating针对内圈固定外圈转动的情况，Equations 4,6,8 and 12 can then be reduced, in this case, to在这种情况下，公式4,6,8和12也可缩写为：The formula for BSF calculates the speed of the ba
30、ll or roller. However, the frequency generated by roller speed is seldom measured. This is true because the balls or rollers are incased in the cage and between the inner and outer races. If one of the rolling elements has a defect of any kind, the defect can strike the inner and outer races and/or
31、the front and back side of the cage alternately. This generates two times BSF because the timing for each event is exact and occurs when the roller rotates half a revolution.BSF的公式计算了滚珠或滚子的自转速度。然而，很少测量到由滚子自转产生的频率。的确，这是因为滚珠或滚子都装在保持架中并且处在内外圈滚道之间。如果某一个滚动部件有某种缺陷，则缺陷会击打在内外圈面上或交替击打在保持架的前后两侧上。这产生了2xBSF，因为当
32、滚子旋转每半个周期时该事件都以非常精确的时间发生。All of these ideal bearing frequency formulas are based on the assumption of pure rolling contact between the rollers and races. The small error resulting from any slipping of these surfaces would produce somewhat lower values in the above equations. Also, if the bearing is
33、turning on the shaft or in the housing, the bearing frequencies can be lower. When looseness is involved, the spectral lines at the bearing frequencies can be wide-banded. The outer race frequency may not be generated if the outer race is loose in the housing and the defect is not in the load zone.这
34、些理想的轴承频率公式都基于假定滚子和滚道之间是纯粹的滚动接触。接触面的任何滑动造成的微小误差都会导致上述公式计算得到较低的数值。此外，如果轴承跑内圈或跑外圈，轴承频率也会低一些。当涉及松动时，轴承频率的谱线会呈现宽条带状。如果外圈在轴承座里松动以及缺陷不在承载区时可能不会产生外圈故障频率。Changes in the contact angle cause changes in the bearing frequencies. For example, with the outer race stationary and inner race rotating, if the contact
35、angle increases, FTF, BPFO, and BSF increase and BPFI decreases. If the contact angle decreases, FTF, BPFO, and BSF decrease and BPFI increases. Careful analysis of the measured and calculated bearing frequencies using exact geometry, speed, and measurement accuracy often reveals useful information
36、on the integrity of the bearing journal, housing, and thrust loads. This data is then used to determine when the bearing should be replaced, how long it will last, and the additional work required to prevent the new bearing from failing prematurely.接触角的变化也会引起轴承频率的变化。举例说明，当外圈固定内圈转动时，如果接触角增大，FTF，BPFO以
37、及BSF增加，BPFI减小。如果接触角减小，FTF,BPFO和BSF减小，BPFI增大。仔细分析测量到的和使用精确的数据，转速及精度计算得到的轴承频率的差别，往往对发现轴颈轴承，轴承座，和轴向负载的完整性信息非常有用处。然后此数据可用于确定何时应该更换轴承，预测轴承多久后会失效，以及用于防止新轴承过早失效所需要做一些额外工作。Further review of the above formulas indicates:进一步分析上述公式：1. About 40% of the balls pass over a defect on the outer race each revolution,
38、 regardless of which race is rotating.1. 每个周期中约40%的滚珠通过外圈上的一个缺陷，无论哪个滚道转动。2. About 60% of the balls pass over a defect on the inner race each revolution, regardless of which race is rotating.2. 每个周期中约60%的滚珠通过内圈上的一个缺陷，无论哪个滚道转动3. The FTF or cage frequency is about 40% of unit speed if the inner race is
39、 rotating and about 60% of unit speed if the outer race is rotating.3. FTF或者说是保持架频率当内圈转动时约为转速的40%；如果是外圈转动的话约为60%。4. The BSF does not change regardless of which race is rotating. At first, it seems the BSF should increase if the outer race is rotating, because the cage speed increases. However, close
40、r inspection indicates BSF must remain constant if BPFO and BPFI do not change.4. BSF并不会因为哪个滚道转动而改变。首先，如果外圈滚动的话看起来BSF似乎应该增加，因为保持架转速增加了。然而仔细分析表明如果BPFO和BPFI不变的话，BSF必须保持恒定不变。In an effort to visually support the previous formulas, consider a simple eight ball bearing. Fig. 5-3 shows a bearing marked on
41、the inner and outer races, and the cage at one ball. Assuming the inner race is rotating and the outer race is stationary, the inner race is rotated one revolution clockwise, as in Fig. 5-4.为了直观的验证之前的公式，假设有一个简单的有八个滚珠的轴承。如图5-3所示轴承的内外圈上做了记号，在保持架的一个滚珠位置也做了个记号。假设内圈旋转外圈固定，内圈顺时钟方向转动一圈，如图5-4.Note that appr
42、oximately five balls passed over the mark on the inner race. Since five divided by eight equals 0.62, about 60% of the balls passed over the mark on the inner race. Also note that approximately three balls, or about 40%, passed over the mark on the outer race. Finally, notice that the cage turned ab
43、out 40% of one revolution.请注意大约5个滚珠通过了内圈上的记号，58约等于0.62，即大概60%的滚珠通过内圈上的记号。同样注意大概3个滚珠或总滚珠数的40%通过了外圈的记号。最后，注意当内圈转了一圈时，保持架大概转了其自转周期的40%。Assuming the inner race is stationary, the outer race in Fig. 5-3 is now rotated one revolution, as shown in Fig. 5-5.假设内圈固定，外圈转动，在图 5-3所示外圈旋转一周后，如图 5-5 所示。Note that ap
44、proximately three balls passed over the mark on the outer race, and approximately five balls passed over the mark on the inner race. This indicates that it makes no difference whether the inner or outer race is rotating; the ball pass frequencies are the same. Also note that the cage turned about 60
45、% of one revolution while the outer race was rotated one revolution. These results are supported by the bearing frequency equations.请注意大约3个滚珠通过在外圈上的记号并且大约5个滚珠通过了内圈上的记号。这表明无论是内圈还是外圈转动其结果没有什么区别；滚珠通过频率不变。此外注意到当外圈转动一圈后保持架转动约其自转周期的60%。这些结果验证了轴承频率计算公式。Outer Race Analysis 外圈分析If a 6313 bearing containing e
46、ight balls is mounted with the inner race rotating at 1776RPM or 29.6 Hz, the calculated ball pass frequency of the outer race is 90.9 Hz. The time it takes for the inner race to rotate one revolution is:6313轴承有8个球，假设内圈旋转速度为1776RPM即29.6HZ，计算滚珠外圈通过频率为90.9HZ。内圈旋转一周的时间是：The time for one outer race ball pass frequency is:滚珠一次外圈通过频率的时间是Therefore, every 11 milliseconds, a ball passes by a point on the outer race. Divide the time for one revolution by the time for one outer race ball pass frequency:就是说，每11ms，一个滚珠通过外圈上某一点。将每周期需要的时间除以滚珠外圈通过频
