轴承论文中英文资料外文翻译文献

中英文资料外文翻译文献
EXTENDING BEARING LIFE
Abstract：
Nature works hard to destroy bearings, but their chances of survival can be improved by following a few simple guidelines. Extreme neglect in a bearing leads to overheating and possibly seizure or, at worst, an explosion. But even a failed bearing leaves clues as to what went wrong. After a little detective work, action can be taken to avoid a repeat performance.
Keywords: bearings failures life
Bearings fail for a number of reasons，but the most common are misapplication，contamination，improper lubricant，shipping or handling damage，and misalignment. The problem is often not difficult to diagnose because a failed bearing usually leaves telltale signs about what went wrong．
However，while a postmortem yields good information，it is better to avoid the process altogether by specifying the bearing correctly in The first place．To do this，it is useful to review the manufacturers sizing guidelines and operating characteristics for the selected bearing.
Equally critical is a study of requirements for noise, torque, and runout, as well as possible exposure to contaminants, hostile liquids, and temperature extremes. This can provide further clues as to whether a bearing is right for a job.
1 Why bearings fail
About 40% of ball bearing failures are caused by contamination from dust, dirt, shavings, and corrosion. Contamination also causes torque and noise problems, and is often the result of improper handling or the application environment．Fortunately, a bearing failure caused by environment or handling contamination is preventable，and a simple visual examination can easily identify the cause．
Conducting a postmortem il1ustrates what to look for on a failed or failing bearing．Then，understanding the mechanism behind the failure, such as brinelling or fatigue, helps eliminate the source of the problem.
Brinelling is one type of bearing failure easily avoided by proper handing and
assembly. It is characterized by indentations in the bearing raceway caused by shock loading－such as when a bearing is dropped-or incorrect assembly. Brinelling usually occurs when loads exceed the material yield point(350,000 psi in SAE 52100 chrome steel)．It may also be caused by improper assembly, Which places a load across the races．Raceway dents also produce noise，vibration，and increased torque.
A similar defect is a pattern of elliptical dents caused by balls vibrating between raceways while the bearing is not turning．This problem is called false brinelling. It occurs on equipment in transit or that vibrates when not in operation. In addition, debris created by false brinelling acts like an abrasive, further contaminating the bearing. Unlike brinelling, false binelling is often indicated by a reddish color from fretting corrosion in the lubricant.
False brinelling is prevented by eliminating vibration sources and keeping the bearing well lubricated. Isolation pads on the equipment or a separate foundation may be required to reduce environmental vibration. Also a light preload on the bearing helps keep the balls and raceway in tight contact. Preloading also helps prevent false brinelling during transit.
Seizures can be caused by a lack of internal clearance, improper lubrication, or excessive loading. Before seizing, excessive, friction and heat softens the bearing steel. Overheated bearings often change color，usually to blue-black or straw colored．Friction also causes stress in the retainer，which can break and hasten bearing failure．Premature material fatigue is caused by a high load or excessive preload．When these conditions are unavoidable，bearing life should be carefully calculated so that a maintenance scheme can be worked out．
Another solution for fighting premature fatigue is changing material．When standard bearing materials，such as 440C or SAE 52100，do not guarantee sufficient life，specialty materials can be recommended. In addition，when the problem is traced back to excessive loading，a higher capacity bearing or different configuration may be used．Creep is less common than premature fatigue．In bearings．it is caused by excessive clearance between bore and shaft that allows the bore to rotate on the shaft．Creep can be expensive because it causes damage to other components in addition to the bearing．0ther more likely creep indicators are scratches，scuff marks，or discoloration to shaft and bore．To prevent creep damage，the bearing housing and shaft fittings should be visually checked．
Misalignment is related to creep in that it is mounting related．If races are misaligned or cocked．The balls track in a noncircumferencial path．The problem is incorrect mounting or tolerancing，or insufficient squareness of the bearing mounting site．Misalignment of more than 1/4·can cause an early failure．
Contaminated lubricant is often more difficult to detect than misalignment or creep．Contamination shows as premature wear．Solid contaminants become an abrasive in the lubricant．In addition。

insufficient lubrication between ball and retainer wears and weakens the retainer．In this situation，lubrication is critical if the retainer is a fully machined type．Ribbon or crown retainers，in contrast，allow lubricants to more easily reach all surfaces．
Rust is a form of moisture contamination and often indicates the wrong material for the application．If the material checks out for the job，the easiest way to prevent rust is to keep bearings in their packaging，until just before installation．
2 Avoiding failures
The best way to handle bearing failures is to avoid them．This can be done in the selection process by recognizing critical performance characteristics．These include noise，starting and running torque，stiffness，nonrepetitive runout，and radial and axial play．In some applications, these items are so critical that specifying an ABEC level alone is not sufficient．
Torque requirements are determined by the lubricant，retainer，raceway quality(roundness cross curvature and surface finish)，and whether seals or shields are used．Lubricant viscosity must be selected carefully because inappropriate lubricant，especially in miniature bearings，causes excessive torque．Also，different lubricants have varying noise characteristics that should be matched to the application. For example，greases produce more noise than oil．
Nonrepetitive runout(NRR)occurs during rotation as a random eccentricity between the inner and outer races，much like a cam action．NRR can be caused by retainer tolerance or eccentricities of the raceways and balls．Unlike repetitive runout, no compensation can be made for NRR.
NRR is reflected in the cost of the bearing．It is common in the industry to provide different bearing types and grades for specific applications．For example，a bearing with an NRR of less than 0.3um is used when minimal runout is needed，such as in disk—drive spindle motors．Similarly，machine—tool spindles tolerate only minimal deflections to maintain precision cuts．Consequently, bearings are manufactured with low NRR just for machine-tool applications．
Contamination is unavoidable in many industrial products，and shields and seals are commonly used to protect bearings from dust and dirt．However，a perfect bearing seal is not possible because of the movement between inner and outer races．Consequently，lubrication migration and contamination are always problems．
Once a bearing is contaminated, its lubricant deteriorates and operation becomes
noisier．If it overheats，the bearing can seize．At the very least，contamination causes wear as it works between balls and the raceway，becoming imbedded in the races and acting as an abrasive between metal surfaces．Fending off dirt with seals and shields illustrates some methods for controlling contamination．
Noise is as an indicator of bearing quality．Various noise grades have been developed to classify bearing performance capabilities．
Noise analysis is done with an Anderonmeter, which is used for quality control in bearing production and also when failed bearings are returned for analysis. A transducer is attached to the outer ring and the inner race is turned at 1,800rpm on an air spindle. Noise is measured in andirons, which represent ball displacement in μm/rad.
With experience, inspectors can identify the smallest flaw from their sound. Dust, for example, makes an irregular crackling. Ball scratches make a consistent popping and are the most difficult to identify. Inner-race damage is normally a constant high-pitched noise, while a damaged outer race makes an intermittent sound as it rotates.
Bearing defects are further identified by their frequencies. Generally, defects are separated into low, medium, and high wavelengths. Defects are also referenced to the number of irregularities per revolution.
Low-band noise is the effect of long-wavelength irregularities that occur about 1.6 to 10 times per revolution. These are caused by a variety of inconsistencies, such as pockets in the race. Detectable pockets are manufacturing flaws and result when the race is mounted too tightly in multiplejaw chucks.
Medium-hand noise is characterized by irregularities that occur 10 to 60 times per revolution. It is caused by vibration in the grinding operation that produces balls and raceways. High-hand irregularities occur at 60 to 300 times per revolution and indicate closely spaced chatter marks or widely spaced, rough irregularities.
Classifying bearings by their noise characteristics allows users to specify a noise grade in addition to the ABEC standards used by most manufacturers. ABEC defines physical tolerances such as bore, outer diameter, and runout. As the ABEC class number increase (from 3 to 9), tolerances are tightened. ABEC class, however, does not specify other bearing characteristics such as raceway quality, finish, or noise. Hence, a noise classification helps improve on the industry standard.
GEAR AND SHAFT INTRODUCTION
Abstract:
The important position of the wheel gear and shaft can't falter in traditional machine and modern machines. The wheel gear and shafts mainly install the direction that delivers
the dint at the principal axis box. The passing to process to make them can is divided into many model numbers, useding for many situations respectively. So we must be the multilayers to the understanding of the wheel gear and shaft in many ways .
Key words:Wheel gear Shaft
In the force analysis of spur gears, the forces are assumed to act in a single plane. We shall study gears in which the forces have three dimensions. The reason for this, in the case of helical gears, is that the teeth are not parallel to the axis of rotation. And in the case of bevel gears, the rotational axes are not parallel to each other. There are also other reasons, as we shall learn.
Helical gears are used to transmit motion between parallel shafts. The helix angle is the same on each gear, but one gear must have a right-hand helix and the other a left-hand helix. The shape of the tooth is an involute helicoid. If a piece of paper cut in the shape of a parallelogram is wrapped around a cylinder, the angular edge of the paper becomes a helix. If we unwind this paper, each point on the angular edge generates an involute curve. The surface obtained when every point on the edge generates an involute is called an involute helicoid.
The initial contact of spur-gear teeth is a line extending all the way across the face of the tooth. The initial contact of helical gear teeth is a point, which changes into a line as the teeth come into more engagement. In spur gears the line of contact is parallel to the axis of the rotation; in helical gears, the line is diagonal across the face of the tooth. It is this gradual of the teeth and the smooth transfer of load from one tooth to another, which give helical gears the ability to transmit heavy loads at high speeds. Helical gears subject the shaft bearings to both radial and thrust loads. When the thrust loads become high or are objectionable for other reasons, it may be desirable to use double helical gears. A double helical gear (herringbone) is equivalent to two helical gears of opposite hand, mounted side by side on the same shaft. They develop opposite thrust reactions and thus cancel out the thrust load. When two or more single helical gears are mounted on the same shaft, the hand of the gears should be selected so as to produce the minimum thrust load.
Crossed-helical, or spiral, gears are those in which the shaft centerlines are neither parallel nor intersecting. The teeth of crossed-helical fears have point contact with each other, which changes to line contact as the gears wear in. For this reason they will carry out very small loads and are mainly for instrumental applications, and are definitely not recommended for use in the transmission of power. There is on difference between a crossed helical gear and a helical gear until they are mounted in mesh with each other. They are manufactured in the same way. A pair of meshed crossed helical gears usually have the same hand; that is ,a right-hand driver goes with a right-hand driven. In the design
of crossed-helical gears, the minimum sliding velocity is obtained when the helix angle are equal. However, when the helix angle are not equal, the gear with the larger helix angle should be used as the driver if both gears have the same hand.
Worm gears are similar to crossed helical gears. The pinion or worm has a small number of teeth, usually one to four, and since they completely wrap around the pitch cylinder they are called threads. Its mating gear is called a worm gear, which is not a true helical gear. A worm and worm gear are used to provide a high angular-velocity reduction between nonintersecting shafts which are usually at right angle. The worm gear is not a helical gear because its face is made concave to fit the curvature of the worm in order to provide line contact instead of point contact. However, a disadvantage of worm gearing is the high sliding velocities across the teeth, the same as with crossed helical gears.
Worm gearing are either single or double enveloping. A single-enveloping gearing is one in which the gear wraps around or partially encloses the worm.. A gearing in which each element partially encloses the other is, of course, a double-enveloping worm gearing. The important difference between the two is that area contact exists between the teeth of double-enveloping gears while only line contact between those of single-enveloping gears. The worm and worm gear of a set have the same hand of helix as for crossed helical gears, but the helix angles are usually quite different. The helix angle on the worm is generally quite large, and that on the gear very small. Because of this, it is usual to specify the lead angle on the worm, which is the complement of the worm helix angle, and the helix angle on the gear; the two angles are equal for a 90-deg. Shaft angle.
When gears are to be used to transmit motion between intersecting shaft, some of bevel gear is required. Although bevel gear are usually made for a shaft angle of 90 deg. They may be produced for almost any shaft angle. The teeth may be cast, milled, or generated. Only the generated teeth may be classed as accurate. In a typical bevel gear mounting, one of the gear is often mounted outboard of the bearing. This means that shaft deflection can be more pronounced and have a greater effect on the contact of teeth. Another difficulty, which occurs in predicting the stress in bevel-gear teeth, is the fact the teeth are tapered.
Straight bevel gears are easy to design and simple to manufacture and give very good results in service if they are mounted accurately and positively. As in the case of squr gears, however, they become noisy at higher values of the pitch-line velocity. In these cases it is often good design practice to go to the spiral bevel gear, which is the bevel counterpart of the helical gear. As in the case of helical gears, spiral bevel gears give a much smoother tooth action than straight bevel gears, and hence are useful where high speed are encountered.
It is frequently desirable, as in the case of automotive differential applications, to have gearing similar to bevel gears but with the shaft offset. Such gears are called hypoid gears because their pitch surfaces are hyperboloids of revolution. The tooth action between such gears is a combination of rolling and sliding along a straight line and has much in common with that of worm gears.
A shaft is a rotating or stationary member, usually of circular cross section, having mounted upon it such elementsas gears, pulleys, flywheels, cranks, sprockets, and other power-transmission elements. Shaft may be subjected to bending, tension, compression, or torsional loads, acting singly or in combination with one another. When they are combined, one may expect to find both static and fatigue strength to be important design considerations, since a single shaft may be subjected to static stresses, completely reversed, and repeated stresses, all acting at the same time.
The word “shaft” covers numerous variations, such as axles and spindles. Anaxle is a shaft, wither stationary or rotating, nor subjected to torsion load. A shirt rotating shaft is often called a spindle.
When either the lateral or the torsional deflection of a shaft must be held to close limits, the shaft must be sized on the basis of deflection before analyzing the stresses. The reason for this is that, if the shaft is made stiff enough so that the deflection is not too large, it is probable that the resulting stresses will be safe. But by no means should the designer assume that they are safe; it is almost always necessary to calculate them so that he knows they are within acceptable limits. Whenever possible, the power-transmission elements, such as gears or pullets, should be located close to the supporting bearings, This reduces the bending moment, and hence the deflection and bending stress.
Although the von Mises-Hencky-Goodman method is difficult to use in design of shaft, it probably comes closest to predicting actual failure. Thus it is a good way of checking a shaft that has already been designed or of discovering why a particular shaft has failed in service. Furthermore, there are a considerable number of shaft-design problems in which the dimension are pretty well limited by other considerations, such as rigidity, and it is only necessary for the designer to discover something about the fillet sizes, heat-treatment, and surface finish and whether or not shot peening is necessary in order to achieve the required life and reliability.
Because of the similarity of their functions, clutches and brakes are treated together. In a simplified dynamic representation of a friction clutch, or brake, two inertias I1 and I2 traveling at the respective angular velocities W1 and W2, one of which may be zero in the case of brake, are to be brought to the same speed by engaging the clutch or brake. Slippage occurs because the two elements are running at different speeds and energy is
dissipated during actuation, resulting in a temperature rise. In analyzing the performance of these devices we shall be interested in the actuating force, the torque transmitted, the energy loss and the temperature rise. The torque transmitted is related to the actuating force, the coefficient of friction, and the geometry of the clutch or brake. This is problem in static, which will have to be studied separately for eath geometric configuration. However, temperature rise is related to energy loss and can be studied without regard to the type of brake or clutch because the geometry of interest is the heat-dissipating surfaces. The various types of clutches and brakes may be classified as follows:
1.Rim type with internally expanding shoes
2.Rim type with externally contracting shoes
3.Band type
4.Disk or axial type
5.Cone type
6.Miscellaneous type
The analysis of all type of friction clutches and brakes use the same general procedure. The following step are necessary:
1.Assume or determine the distribution of pressure on the frictional surfaces.
2.Find a relation between the maximum pressure and the pressure at any point
3.Apply the condition of statical equilibrium to find (a) the actuating force, (b)
the torque, and (c) the support reactions.
Miscellaneous clutches include several types, such as the positive-contact clutches, overload-release clutches, overrunning clutches, magnetic fluid clutches, and others.
A positive-contact clutch consists of a shift lever and two jaws. The greatest differences between the various types of positive clutches are concerned with the design of the jaws. To provide a longer period of time for shift action during engagement, the jaws may be ratchet-shaped, or gear-tooth-shaped. Sometimes a great many teeth or jaws are used, and they may be cut either circumferentially, so that they engage by cylindrical mating, or on the faces of the mating elements.
Although positive clutches are not used to the extent of the frictional-contact type, they do have important applications where synchronous operation is required.
Devices such as linear drives or motor-operated screw drivers must run to definite limit and then come to a stop. An overload-release type of clutch is required for these applications. These clutches are usually spring-loaded so as to release at a predetermined toque. The clicking sound which is heard when the overload point is reached is considered to be a desirable signal.
An overrunning clutch or coupling permits the driven member of a machine to
“freewheel” or “overrun” because the driver is stopped or because another source of power increase the speed of the driven. This type of clutch usually uses rollers or balls mounted between an outer sleeve and an inner member having flats machined around the periphery. Driving action is obtained by wedging the rollers between the sleeve and the flats. The clutch is therefore equivalent to a pawl and ratchet with an infinite number of teeth.
Magnetic fluid clutch or brake is a relatively new development which has two parallel magnetic plates. Between these plates is a lubricated magnetic powder mixture. An electromagnetic coil is inserted somewhere in the magnetic circuit. By varying the excitation to this coil, the shearing strength of the magnetic fluid mixture may be accurately controlled. Thus any condition from a full slip to a frozen lockup may be obtained.
如何延长轴承寿命
摘要：自然界苛刻的工作条件会导致轴承的失效，但是如果遵循一些简单的规则，轴承正常运转的机会是能够被提高的。

在轴承的使用过程当中，过分的忽视会导致轴承的过热现象，也可能使轴承不能够再被使用，甚至完全的破坏。

但是一个被损坏的轴承，会留下它为什么被损坏的线索。

通过一些细致的侦察工作，我们可以采取行动来避免轴承的再次失效。

关键词：轴承失效寿命
导致轴承失效的原因很多，但常见的是不正确的使用、污染、润滑剂使用不当、装卸或搬运时的损伤及安装误差等。

诊断失效的原因并不困难，因为根据轴承上留下的痕迹可以确定轴承失效的原因。

然而，当事后的调查分析提供出宝贵的信息时，最好首先通过正确地选定轴承来完全避免失效的发生。

为了做到这一点，再考察一下制造厂商的尺寸定位指南和所选轴承的使用特点是非常重要的。

1 轴承失效的原因
在球轴承的失效中约有40%是由灰尘、脏物、碎屑的污染以及腐蚀造成的。

污染通常是由不正确的使用和不良的使用环境造成的，它还会引起扭矩和噪声的问题。

由环境和污染所产生的轴承失效是可以预防的，而且通过简单的肉眼观察是可以确定产生这类失效的原因。

通过失效后的分析可以得知对已经失效的或将要失效的轴承应该在哪些方面进行查看。

弄清诸如剥蚀和疲劳破坏一类失效的机理，有助于消除问题的根源。

只要使用和安装合理，轴承的剥蚀是容易避免的。

剥蚀的特征是在轴承圈滚道上留有由冲击载荷或不正确的安装产生的压痕。

剥蚀通常是在载荷超过材料屈服极限时发生的。

如果安装不正确从而使某一载荷横穿轴承圈也会产生剥蚀。

轴承圈上的压坑还会产生噪声、振动和附加扭矩。

类似的一种缺陷是当轴承不旋转时由于滚珠在轴承圈间振动而产生的椭圆形压痕。

这种破坏称为低荷振蚀。

这种破坏在运输中的设备和不工作时仍振动的设备中都会产生。

此外，低荷振蚀产生的碎屑的作用就象磨粒一样，会进一步损害轴承。

与剥蚀不同，低荷振蚀的特征通常是由于微振磨损腐蚀在润滑剂中会产生淡红色。

消除振动源并保持良好的轴承润滑可以防止低荷振蚀。

给设备加隔离垫或对底座进行隔离可以减轻环境的振动。

另外在轴承上加一个较小的预载荷不仅有助于滚珠和轴承圈保持紧密的接触，并且对防止在设备运输中产生的低荷振蚀也有帮助。

造成轴承卡住的原因是缺少内隙、润滑不当和载荷过大。

在卡住之前，过大的摩擦和热量使轴承钢软化。

过热的轴承通常会改变颜色，一般会变成蓝黑色或淡黄色。

摩擦还会使保持架受力，这会破坏支承架，并加速轴承的失效。

材料过早出现疲劳破坏是由重载后过大的预载引起的。

如果这些条件不可避免，就应仔细计算轴承寿命，以制定一个维护计划。

另一个解决办法是更换材料。

若标准的轴承材料不能保证足够的轴承寿命，就应当采用特殊的材料。

另外，如果这个问题是由于载荷过大造成的，就应该采用抗载能力更强或其他结构的轴承。

蠕动不象过早疲劳那样普遍。

轴承的蠕动是由于轴和内圈之间的间隙过大造成的。

蠕动的害处很大，它不仅损害轴承，也破坏其他零件。

蠕动的明显特征是划痕、擦痕或轴与内圈的颜色变化。

为了防止蠕动，应该先用肉眼检查一下轴承箱件和轴的配件。

蠕动与安装不正有关。

如果轴承圈不正或翘起，滚珠将沿着一个非圆周轨道运动。

这个问题是由于安装不正确或公差不正确或轴承安装现场的垂直度不够造成的。

如果偏斜超过0.25°，轴承就会过早地失效。

检查润滑剂的污染比检查装配不正或蠕动要困难得多。

污染的特征是使轴承过早的出现磨损。

润滑剂中的固体杂质就象磨粒一样。

如果滚珠和保持架之间润滑不良也
会磨损并削弱保持架。

在这种情况下，润滑对于完全加工形式的保持架来说是至关重要的。

相比之下，带状或冠状保持架能较容易地使润滑剂到达全部表面。

锈是湿气污染的一种形式，它的出现常常表明材料选择不当。

如果某一材料经检验适合工作要求，那么防止生锈的最简单的方法是给轴承包装起来，直到安装使用时才打开包装。

2 避免失效的方法
解决轴承失效问题的最好办法就是避免失效发生。

这可以在选用过程中通过考虑关键性能特征来实现。

这些特征包括噪声、起动和运转扭矩、刚性、非重复性振摆以及径向和轴向间隙。

扭矩要求是由润滑剂、保持架、轴承圈质量（弯曲部分的圆度和表面加工质量）以及是否使用密封或遮护装置来决定。

润滑剂的粘度必须认真加以选择，因为不适宜的润滑剂会产生过大的扭矩，这在小型轴承中尤其如此。

另外，不同的润滑剂的噪声特性也不一样。

举例来说，润滑脂产生的噪声比润滑油大一些。

因此，要根据不同的用途来选用润滑剂。

在轴承转动过程中，如果内圈和外圈之间存在一个随机的偏心距，就会产生与凸轮运动非常相似的非重复性振摆（NRR）。

保持架的尺寸误差和轴承圈与滚珠的偏心都会引起NRR。

和重复性振摆不同的是，NRR是没有办法进行补偿的。

在工业中一般是根据具体的应用来选择不同类型和精度等级的轴承。

例如，当要求振摆最小时，轴承的非重复性振摆不能超过0.3微米。

同样，机床主轴只能容许最小的振摆，以保证切削精度。

因此在机床的应用中应该使用非重复性振摆较小的轴承。

在许多工业产品中，污染是不可避免的，因此常用密封或遮护装置来保护轴承，使其免受灰尘或脏物的侵蚀。

但是，由于轴承内外圈的运动，使轴承的密封不可能达到完美的程度，因此润滑油的泄漏和污染始终是一个未能解决的问题。

一旦轴承受到污染，润滑剂就要变质，运行噪声也随之变大。

如果轴承过热，它将会卡住。

当污染物处于滚珠和轴承圈之间时，其作用和金属表面之间的磨粒一样，会使轴承磨损。

采用密封和遮护装置来挡开脏物是控制污染的一种方法。

噪声是反映轴承质量的一个指标。

轴承的性能可以用不同的噪声等级来表示。

噪声的分析是用安德逊计进行的，该仪器在轴承生产中可用来控制质量，也可对失效的轴承进行分析。

将一传感器连接在轴承外圈上，而内圈在心轴以1800r/min 的转速旋转。

测量噪声的单位为anderon。

即用um/rad表示的轴承位移。

根据经验，观察者可以根据声音辨别出微小的缺陷。

例如，灰尘产生的是不规则的劈啪声；滚珠划痕产生一种连续的爆破声，确定这种划痕最困难；内圈损伤通常产生连续的高频噪声，而外圈损伤则产生一种间歇的声音。

轴承缺陷可以通过其频率特性进一步加以鉴定。

通常轴承缺陷被分为低、中、高三个波段。

缺陷还可以根据轴承每转动一周出现的不规则变化的次数加以鉴定。

低频噪声是长波段不规则变化的结果。

轴承每转一周这种不规则变化可出现1.6~10次，它们是由各种干涉（例如轴承圈滚道上的凹坑）引起的。

可察觉的凹坑是一种制造缺陷，它是在制造过程中由于多爪卡盘夹的太紧而形成的。

中频噪声的特征是轴承每旋转一周不规则变化出现10~60次。

这种缺陷是由在轴承圈和滚珠的磨削加工中出现的振动引起的。

轴承每旋转一周高频不规则变化出现60~300次，它表明轴承上存在着密集的振痕或大面积的粗糙不平。

利用轴承的噪声特性对轴承进行分类，用户除了可以确定大多数厂商所使用的ABEC标准外，还可确定轴承的噪声等级。

ABEC标准只定义了诸如孔、外径、振摆等尺寸公差。

随着ABEC级别的增加（从3增到9），公差逐渐变小。

但ABEC等级并不能反映其他轴承特性，如轴承圈质量、粗糙度、噪声等。

因此，噪声等级的划分有助于工业标准的改进。

齿轮和轴的介绍
摘要:在传统机械和现代机械中齿轮和轴的重要地位是不可动摇的。

齿轮和轴主要安装在主轴箱来传递力的方向。

通过加工制造它们可以分为许多的型号，分别用于许多的场合。

所以我们对齿轮和轴的了解和认识必须是多层次多方位的。

关键词:齿轮；轴
在直齿圆柱齿轮的受力分析中，是假定各力作用在单一平面的。

我们将研究作用力具有三维坐标的齿轮。

因此，在斜齿轮的情况下，其齿向是不平行于回转轴线的。

而在锥齿轮的情况中各回转轴线互相不平行。

像我们要讨论的那样，尚有其他道理需要学习，掌握。

斜齿轮用于传递平行轴之间的运动。

倾斜角度每个齿轮都一样，但一个必须右旋斜齿，而另一个必须是左旋斜齿。

齿的形状是一溅开线螺旋面。

如果一张被剪成平行四边形（矩形）的纸张包围在齿轮圆柱体上，纸上印出齿的角刃边就变成斜线。

如果
我展开这张纸，在血角刃边上的每一个点就发生一渐开线曲线。

直齿圆柱齿轮轮齿的初始接触处是跨过整个齿面而伸展开来的线。

斜齿轮轮齿的初始接触是一点，当齿进入更多的啮合时，它就变成线。

在直齿圆柱齿轮中，接触是平行于回转轴线的。

在斜齿轮中，该先是跨过齿面的对角线。

它是齿轮逐渐进行啮合并平稳的从一个齿到另一个齿传递运动，那样就使斜齿轮具有高速重载下平稳传递运动的能力。

斜齿轮使轴的轴承承受径向和轴向力。

当轴向推力变的大了或由于别的原因而产生某些影响时，那就可以使用人字齿轮。

双斜齿轮（人字齿轮）是与反向的并排地装在同一轴上的两个斜齿轮等效。

他们产生相反的轴向推力作用，这样就消除了轴向推力。

当两个或更多个单向齿斜齿轮被在同一轴上时，齿轮的齿向应作选择，以便产生最小的轴向推力。

交错轴斜齿轮或螺旋齿轮，他们是轴中心线既不相交也不平行。

交错轴斜齿轮的齿彼此之间发生点接触，它随着齿轮的磨合而变成线接触。

因此他们只能传递小的载荷和主要用于仪器设备中，而且肯定不能推荐在动力传动中使用。

交错轴斜齿轮与斜齿轮之间在被安装后互相捏合之前是没有任何区别的。

它们是以同样的方法进行制造。

一对相啮合的交错轴斜齿轮通常具有同样的齿向，即左旋主动齿轮跟右旋从动齿轮相啮合。

在交错轴斜齿设计中，当该齿的斜角相等时所产生滑移速度最小。

然而当该齿的斜角不相等时，如果两个齿轮具有相同齿向的话，大斜角齿轮应用作主动齿轮。

蜗轮与交错轴斜齿轮相似。

小齿轮即蜗杆具有较小的齿数，通常是一到四齿，由于它们完全缠绕在节圆柱上，因此它们被称为螺纹齿。

与其相配的齿轮叫做蜗轮，蜗轮不是真正的斜齿轮。

蜗杆和蜗轮通常是用于向垂直相交轴之间的传动提供大的角速度减速比。

蜗轮不是斜齿轮，因为其齿顶面做成中凹形状以适配蜗杆曲率，目的是要形成线接触而不是点接触。

然而蜗杆蜗轮传动机构中存在齿间有较大滑移速度的缺点，正像交错轴斜齿轮那样。

蜗杆蜗轮机构有单包围和双包围机构。

单包围机构就是蜗轮包裹着蜗杆的一种机构。

当然，如果每个构件各自局部地包围着对方的蜗轮机构就是双包围蜗轮蜗杆机构。

着两者之间的重要区别是，在双包围蜗轮组的轮齿间有面接触，而在单包围的蜗轮组的轮齿间有线接触。

一个装置中的蜗杆和蜗轮正像交错轴斜齿轮那样具有相同的齿向，但是其斜齿齿角的角度是极不相同的。

蜗杆上的齿斜角度通常很大，而蜗轮上的则极小，因此习惯常规定蜗杆的导角，那就是蜗杆齿斜角的余角；也规定了蜗轮上的齿斜角，该两角之和就等于90度的轴线交角。