Principle and structure of unidirectional bearing
Keywords:
Unidirectional bearing, ball bearings, one-way bearing, bearing
Unidirectional bearing is a kind of bearing that can rotate freely in one direction and lock in the other direction.
The metal housing of a unidirectional bearing contains a number of rollers, needles, or ball bearings, and the shape of the rolling seat allows it to roll in one direction only, while creating great resistance in the other direction (the so-called "unidirectional").
| 1. Working principle of one-way bearing
In fact, no matter what structure of the unidirectional bearing, its principle is the clamping principle, from the structure can be divided into:
Sloped and roller:
The outer ring of the bearing here is the same as the ordinary bearing, which is a bobbin type outer ring. But it has a special inner ring, which is a circle with a slope.
In addition, it has a roller which is always in contact with the inner and outer ring and a spring which is in contact with the roller. The working face of the roller is a slope, when the bearing along the turn, the roller is in the downhill state, the downhill space is large, the roller will not be affected.
When turning against, the roller is up the slope, the slope is narrow, the roller is stuck, and the bearing is locked.
Another one-way bearing structure is wedge structure:
This type of bearing is arranged between the inner ring and outer ring of the bearing will be a set of CAM wedge. CAM has two different sizes of diameter, wherein the size of the long warp is greater than the distance between the inner ring and the outer ring, and the short warp is less than the distance between the bearing inner ring and the outer ring.
A cylindrical winding spring is connected end to end between the wedges to form a circular spring arranged on the fulcrum of the wedge, and the wedge can be reset by the action of the spring.
| 2. Installation of one-way bearings
Because the one-way bearing has been antirust treatment and packaging, so do not open the packaging before installation. The anti-rust oil coated on the unidirectional bearing has good lubrication performance. For unidirectional bearings for general purposes or unidirectional bearings filled with grease, it can be directly used without cleaning.
The installation method of one-way bearings varies according to the type of bearings and matching conditions.
Since most of them are shaft rotation, interference fit and gap fit can be used for the inner ring and the outer ring respectively, and interference fit is used for the outer ring when the outer ring is rotated.
(1) Press-in installation
Press installation is generally used, bolts and nuts can also be used, if necessary, can be used for installation hammer.
(2) Hot sleeve installation
The hot sleeve method of heating the unidirectional bearing in oil to expand it and then installing it on the shaft can prevent the unidirectional bearing from being subjected to unnecessary external forces and complete installation in a short time.
As an aside, some models on the one-way bearing catalogue do exist, but some non-standard one-way bearings are not in stock in mainland China. Sometimes the futures will be very long, so the time cost and the cost of later replacement should be considered when selecting one-way bearings.
| 3. Repair and maintenance of one-way bearings
General maintenance of one-way bearings requires several steps, including:
- Look at the unidirectional bearing is to observe the external use of the unidirectional bearing, whether the unidirectional bearing is rusty, whether the unidirectional bearing is broken, whether the unidirectional bearing is spalling.
- Listen to whether there is noise in the one-way bearing and whether the noise of the one-way bearing is normal.
- Use instruments to diagnose, such as electronic diagnostics, stethoscopes, etc.
With the maintenance of other bearings, the relative motion of the rolling body and raceway and the invasion of pollutants and dust make the surface of the rolling body and raceway wear. The accuracy of the mainframe is affected.
When regular inspection or replacement of parts, it is necessary to remove one-way bearings. Usually shaft and bearing box almost all need to continue to use, one-way bearings also tend to continue to use. Therefore, the structural design should take into account the disassembly of bearings, without damaging bearings, shafts, bearing boxes and other parts, and at the same time, prepare appropriate disassembly tools. When disassembling the static fitting ferrule, the tension can only be added to the ferrule, and the ferrule can not be pulled through the rolling body.
Unidirectional bearings are widely used in textile machinery; Printing machinery; Automobile industry; Household appliances; Self-checkout counters.
The invention of unidirectional bearings solved many of the institutional problems that needed to prevent inversion. In a lot of household appliances such as washing machines and so on have played a big role. In some transport machinery such as material transport can effectively prevent material back.
Therefore, the standardized structure makes it unnecessary for many machines to design special anti-reversal structures separately, which saves a lot of manpower and material resources. Therefore, the development of one-way bearings has a broad future.
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