How to design an adjustable clearance rolling ball bearings?

Adjustable clearance rolling ball bearings design methods:

Rolling friction ball bearings for its small, start-sensitive, high-efficiency, high precision rotation, lubrication is simple, easy to replace and many other advantages and is widely used in the production and life. However, because the manufacture of high precision, complex process, the current standard of rolling bearings are used in jet production, by professional factory manufacturing. Since the original design between the spindle bearing inner ring, outer ring, rolling, etc. These rigid parts with little regard adjustable links, so important bearing precision index - the radial clearance depends mainly on machining tolerances to be guaranteed. Thus, even with a high precision machine to machine the bearing parts, due to the method of the inevitable accumulation of influence of the error, it is difficult to use directly by the assembly to achieve the required precision. Generally required by measuring the selection method with a packet assembler to assemble, but still finite precision, high prices make high-precision bearings. While bearing in the use of wear caused by the ultra-poor clearance can not be compensated, lowering real life, resulting in waste. With the development of production, the urgent need to address the technical issues. To this end, the author through analysis and research, to find the main factors bearing radial clearance precision. Then the structure bearing a reasonable design from the start, to design a new structure, the agricultural bearings radial clearance can easily be adjusted to solve the above technical problems. After trial, the better, are made with a brief introduction.

design ideas, works and concrete structures

As we all know, to adjust the bearing radial clearance, you must change the relative positional relationship between the outer ring, inner ring, rolling elements of these three, intuitive approach is to make the inner ring of the outside or inside of the outer ring can be varied as desired. In terms of ball bearings, a method in which prior machining of the bearing inner ring bore into a certain taper, while cooperating therewith are machined journal corresponding taper. Changing the position of the inner ring after assembly on the shaft of the attachment shaft, so that the outer diameter of the inner ring deforms to cause changes to adjust the bearing clearance. In all fairness, this is a better way, can solve this problem to a certain extent, it followed so far. But there are a few obvious shortcomings, namely limited adjustment amount (even very small), clearance on large powerless. Second, the journal to be processed at a higher precision taper, and the need to set up additional adjustment device, so that the axis of the complex manufacturing process. Third, the inner ring under a lot of prestressing, and for the circumferential tensile stress is extremely detrimental to the bearing strength, and sometimes even when adjusting inner "no war since the break." Thus, the traditional approach is not reasonable, a great need for improvement.

Bearing structure analysis shows that the inner part has already been done in this article, it seems no potential to be tapped. The rolling body is "monolithic" obviously "unprofitable." Naturally, we have to look to the outer ring up. But this part of it is simply another Jane, conventional thinking can not start them, must be another way. After wrestling, multi advice, repeated scrutiny, finally enlightened. Realized that: change the bearing radial clearance, like war, like, not only forced the onslaught from the front (radial), or you can take from the side roundabout clever (axial). Prerequisite is to break the traditional stereotype thinking imprison shackles and force of habit, to dare to innovate. It is a bold vision of the bearing outer ring along the cross-section cut, split into two (reverse thinking, reduced to complicated). About two and a half can make relative axial movement, and then by means of the interaction of specific surface and rolling fairways of the inner body, the relative axial displacement of the outer ring into a radial displacement of the rolling elements and thus receives indirect change within the effect of the radial position between rings, the outer ring, rolling three, to adjust the clearance purposes. Based on this, we can have the following technical solutions: the outer ring of the rolling bearing by-piece to the axial split modular, with double rows of rolling elements, combined with the adjustment shim set. Increase or decrease in the assembly by adjusting the thickness of the gasket to easily adjust the bearing radial clearance to the desired value, and finally coat with a threaded coupling assembly as a whole. Similarly, when working for some time after the bearing wear, but also just appropriate to reduce the thickness of the shims can easily eliminate bad clearance, to restore the original accuracy. To achieve the purpose of repairing.

The advantages of linear motion ball bearings

For linear motion ball bearing structure in the interior of the outer ring has a retainer (Click on linear ball bearing describes the installation configuration), the holder is equipped with more than one ball, and make infinite circular motion. Within two ends of the retainer spring retaining ring in each square ball straight track work force has a gap window. This section is subject to the load so that the ball rolling to make contact with the shaft. Relative movement with a very low coefficient of friction, and therefore linear motion ball bearings for machinery and equipment, automation equipment, energy-saving equipment such as the choice of the most suitable bearings.

Linear motion bearings, is being more and more widely applied to electronics, machinery, equipment, robotics, tools, machinery, food machinery, packaging machinery, medical machinery, printing machinery, textile machinery, machine tools, automobiles and other general or special machinery industry in.

Linear motion ball bearing advantages:

1. Because the flow of contact friction resistance and can start moving friction resistance is small, so you can save energy, easy to get a higher velocity.

2. Load increases, but not sensitive to changes in the friction coefficient, and therefore under heavy load, the friction coefficient is extremely small, and long-term accuracy of the same, we can get long-term mechanical life.

3. Linear motion bearings interchangeability, when the province to install and easy to use, and new mechanical structure, small size, the amount of light of the characteristics.

4. Out to save oil, simplify lubrication and maintenance purposes.

5. The two sides also applies additional bearing seal and dusty places or objects easily penetrated.

How to express the inner diameter of the bearing?

The face of the bearing inner ring on the periphery or the number seen right from the first and second digit is the inner diameter of the bearing, i.e. with the diameter of the shaft. Press the bearing bore size divided into the following methods:
1, codenamed digital since 04 till 99 only, each pair of numbers from right to come ride with five figures represent the two high precision bearings bore size. For example, two digits after the 204 bearing 04, an inner diameter of 04 × 5 = 20 (mm). This section numbers bearing is the most common, it represents the bearing diameter from 20 mm to 495 mm.
2, the inner diameter of 10 to 20 mm in all the bearings (except magneto bearing), which diameter is constant, expressed as follows:
3,1-9 mm (including 9 mm) of small bearings, has its special representation:
Right from the first digit indicates the actual size of the bearing bore,
Right from the second digit indicates the bearing diameter series;
Right from the third digit is O.
For example: There is a small 25 bearings - right from the first digit "5" indicates the bearing inner diameter of 5 mm, the second digit "2" indicates that the bearing is light series single row radial ball bearings, the third digit is " 0 "did not write. Another example: 1006 self aligning roller bearings, represents an inner diameter of 6 mm light series double row spherical ball bearings.
Magneto ball bearings from the right two digits represent the actual size of the inner diameter. As 6015 bearing, represents an inner diameter of 15 mm of magneto ball bearings.
4, bearing diameter is not an integer, is part of a non-standard bearings. In this case, said in an approximation bearing code, and the third from the right in the figures marked with the number 9. Such as the Beijing brand BJ212-road automobile clutch release bearings 688,911, the actual size of the bearing inner diameter = 52.388 mm, diameter = 84.5 mm, width = 20.7 mm. 688911 bearing from the right of the first, two numbers are 11, according to the provisions of its diameter size should be 11 × 5 = 55 mm, but the actual size of the spherical ball bearings

 inner diameter of 52.388 mm. So it takes approximately 55 mm for digital proud bearing diameter code.
5, bearing code figures represented by the following three points:
(1) Bearing in 500 mm diameter size to LIi, the denominator figure represents the actual size of the inner diameter of the molecule digital representation of its series, the type and structure of the method according to the general bearing and regulations. For example 71/900 bearing denominator digital representation of the bearing inner diameter of 900 mm, molecular digital representation for the special lightweight single row tapered roller bearings.
(2) Needle roller bearings do with fractional code, the denominator figure represents the inner diameter of the bearing. For example 943/25 bearing denominator represents the inner diameter of the bearing 25 is of 25 mm.
(3) When the miniature bearings do with fractional code, its denominator figures represent the actual size of the inner diameter of the bearing. Such as 1009 / 2.5) bearing the denominator 2.5, is the diameter of the bearing is 2.5 mm.

Application of ceramic ball bearings in high speed spindle unit

   Ultra-high-speed cutting is high quality, efficient and characterized by advanced manufacturing technology, which can bring high-speed cutting mechanism, high-speed spindle unit, high acceleration and deceleration linear feed motor development, high-performance control systems and other related cell technology. Core support high-speed spindle unit is high-speed spindle bearings. Ceramic bearings for its resistance to high speed, light weight, long life, excellent performance, high-speed spindle unit in machine tools are widely used.
   A high-speed spindle unit and the spindle slewing bearing manufacturer High-speed spindle unit is one of the key technology to achieve high-speed processing, but also a key component of high-speed machine tools. The core of the high-speed spindle unit is high-speed precision bearings, its performance directly affects the performance of work spindle unit. With increasing speed, the bearing temperature, vibration and noise increase, decrease in the life. Therefore, increasing the spindle speed on the premise that developed a superior performance, high-speed spindle bearings. Currently, high-speed spindle unit, supporting mainly uses magnetic double direction thrust ball bearing spindle, liquid hybrid bearing, ceramic ball bearings in three forms. Magnetic Bearings and good high-speed performance, high precision, easy to implement diagnostics and online monitoring. But practice shows that the bearing due to electromagnetic measurement and control system is too complex and has not been widely used. Liquid hybrid bearing combines the advantages of hydrostatic bearings and hydrodynamic bearings, but this bearing must be specifically designed according to the specific machine, a separate production,the low degree of standardization, maintenance is also difficult.
   Currently, the most widely used high-speed spindle bearings or hybrid ceramic ball bearings, namely the use of the rolling elements or hot isostatic pressing Si3N4 ceramic ball bearing rings remains rims. Such a high degree of standardization of the bearings, low price, small changes to the machine for easy maintenance, especially for high-speed operation of occasions. It d · n has exceeded the value 2.7 × 106. To increase bearing life, increase the wear resistance of the raceway, the raceway of the coating treatment or other surface treatment.
   2 Experimental Research
   Test conditions
   The ceramic ball bearings used in the test parameters as shown in Table 1. The ceramic ball material HIPSN (hot isostatic pressing Si3N4), the accuracy level is G3 level, balls and rings when assembling the required value of the fine matching. The bearings are "dense beads beads" structure, and use the thin outer cage. In the tests with the ceramic bearing ball flange bearing

 steel having the same structural parameters.
   Spindle tests used are two models, namely A-type and B-type. Structure schematically shown in Figure 1, the bearing installation in the form of DBB. Table 2 is the main performance parameters of the two spindle.
Table 1 Test parameters with ceramic ball bearing Model Dimensions (mm) ball diameter (mm) contact angle of the original number of balls ceramic ball material cage material ferrule material
   B7007CY35 × 62 × 147.1441615HIPSN resin GCr15
   The main performance parameters in Table 2 spindle
Model limit speed (r / min) spindle diameter (mm) output power (kW) Lubrication
A mist type 30000354.5
B-type 24000354.5 fat
    A high-speed spindle unit structure diagram in Fig.

How many of miniature ball bearings paired parts for testing

Since the accuracy of precision miniature ball miniature ball bearings itself within 1μm, thus requiring its matching parts (shafts, housings, end caps, ring, etc.) have a high dimensional accuracy and shape accuracy, especially to control the accuracy of the mating surfaces of the bearing within the same level, which is crucial, but also the most easily overlooked.
You must also pay attention to precision miniature ball bearings to match parts if not meet the above requirements, often makes precision bearings error occurs several times larger than the original bearings after installation, even 10 times higher than the error, completely ceases precision bearings, because Matching mechanical error is often not simply superimposed on the high precision bearings error, but in a different multiples after amplification additions.
Miniature ball bearing dimensions determined in accordance with the requirements are not the same. Parameters are not the same, bearing in determining the size parameters, we start from multiple angles. Here we talk to everyone from all angles:
In many cases, miniature ball bearings bore size has been specifically defined by the structure of a machine or device. Whether working life, static load safety factor and whether the economy will meet the requirements, bearing the rest before the final selection of the size and structure, will be subject to the size of calculus. The calculation includes the actual load with its load miniature linear bearings

 capacity for comparison.
Miniature ball bearing static load refers to the rear bearing load is stationary (no relative movement between the inner and outer rings) or rotational speed is very low. In this case, the calculation and the rolling body raceways and an excess of factor of safety of plastic deformation. Most affected by dynamic load bearing inner and outer rings relative motion, check the size of calculus fatigue damage raceways and rolling elements of early safety factor.
In fact, miniature ball bearings and model parameters are also functional relationship with the intended use. We must pay attention to these issues.

Thrust ball bearing noise judgment for maintenance checks

   In order to determine whether the removed bearing can be reused to wash clean after the thrust ball bearing checking. Carefully check the raceway, rolling surface, with the surface state of cage wear, increasing the bearing clearance and the presence or absence of injury on the dimensional accuracy of the decline, abnormal. Non-isolated type of small ball bearings, the inner ring with one hand support level, rotate the outer ring to confirm whether smooth.
   Tapered roller bearings and other separation-shaped high precision ball bearings, rolling elements can be, respectively, the outer ring raceway surface inspection.Large bearings because they can not rotate by hand, pay attention to check the rolling body raceway, cage, and other exterior wall surface, the importance of bearing the higher the more necessary to be careful inspection.
   Can be used to determine whether, considering the extent of damage thrust ball bearings, mechanical properties, the importance of operating conditions to be determined during the next overhaul. However, if the following defects can no longer use. Must manage new ones bearing.
   Bearing Manufacturing noise caused by factors although essentially due to a
manufacturing error, but in fact still with lubricant selection, installation conditions of the miniature ball bearings, shaft and housing accuracy states. This noise is divided into the cage and the sound of chatter sound categories, as described below:
   (1) cage sound and control with periodic vibration and noise, prone cage refers to violent vibration sound cage and rolling elements emitted shock and friction in the pocket loose big time. This noise occurs mainly in ball bearings and thrust ball bearings and stamping cage and solid cage will occur when using grease or oil lubrication occurs, but in poor lubrication or lubricant dried up, the radial clearance When the large, outer withstand torque loads, and poor cage structure and accuracy is not high, the more prone to severe cage webs or rivet head will suddenly break.
   The method of controlling noise and vibration cage there; use good lubrication performance lubricants; reduce installation errors bearings; compression bearing radial clearance or suitably axial preload, as well as the choice of having a reasonably good accuracy cage structure flanged ball bearing

, or switch to cage firmly and without worn bearings.
   (2) The sound and control chatter chatter sound is directly related to bearing rolling surface waviness related noise, which is a pure tone noise, for a constant speed, its frequency does not change, and for changing speed It also will change the frequency.  

 

Installation and adjustment of the high-speed bearings

   When fit and clearance high speed bearing both due to the high-speed precision bearings according to the requirements, but also by high-temperature bearing requirements, so considering its fit and clearance, to take into account the following points:
  (1) a dimensional change and hardness change from normal temperature was raised at a high temperature;
  (2) due to the centrifugal force at high speed, and change in shape.
In short, high-speed, high-temperature conditions, and clearance from the mating choice should strive to maintain the accuracy and performance of the bearing, which is difficult.
 In order to ensure the bearing raceway deformation after installation, angular contact ball bearings over the amount of interference can not get too much interference fit, while the heat under the centrifugal force and high temperature under high-speed expansion, or offset the mating surfaces of the normal pressure. Or the mating surface relaxation, and therefore the amount of interference must be calculated carefully consider the above two factors in the premise, at room temperature constant speed under effective amount of interference for high-speed bearings may be invalid.
   If the result of this contradiction is too large (usually only in the ultra-high speed only in this case), only to take measures to double the lubrication ring lubrication method and hydrostatic lubrication and use, and this program has the potential to break through the miniature ball bearings dmn value 3 million mark. Thermal expansion at high temperatures, or the mating surfaces to offset the normal pressure. Or the mating surface relaxation, and therefore the amount of interference must be calculated carefully consider the above two factors in the premise, at room temperature constant speed under effective amount of interference for high-speed bearings may be invalid.
   If the result of this contradiction is too large (usually only in the ultra-high speed only in this case), only to take measures to double the lubrication ring lubrication method and hydrostatic lubrication and use, and this program has the potential to break through the bearing dmn value 3 million mark. When considering the high speed bearing clearance only to consider the above factors, but also to consider the impact of thermal elongation axis clearance required bearing in working condition, that have the best clearance at operating temperature, and this species clearance is included,the exact center of the outer ring ball groove to the next state formation. Since the high-speed bearings reduce strive relative sliding and internal friction, angular contact ball bearings best not to use the inner and outer rings relative axial displacement method to adjust ball bearing clearance.
   In considering the amount of interference with the flanged ball bearing and the clearance, to be noted that the material becomes soft and easily deformable features, and many times from room temperature to high temperature changes caused by the possibility of a certain permanent

deformation at high temperatures.