1. Basic requirements
It is necessary to make the journal and the sliding bearing evenly and finely contact, and also have a certain matching clearance.
2, contact angle
It is the central angle of the contact surface between the journal and the sliding bearing.
The contact angle should not be too large or too small. If the contact angle is too small, the pressure of the sliding bearing will increase. In severe cases, the sliding bearing will have a large deformation, accelerate the wear and shorten the service life; if the contact angle is too large, the formation of the oil film will be affected, and good liquid lubrication will not be obtained.
Experimental studies have shown that the limit of the contact angle of the plain bearing is 120°. When the sliding bearing wears to this contact angle, liquid lubrication is destroyed. Therefore, under the premise of not affecting the pressure condition of the sliding bearing, the smaller the contact angle, the better.
From the theoretical analysis of the frictional force distance, when the contact angle is 60°, the friction torque is the smallest. Therefore, it is recommended that for a sliding bearing with a rotational speed higher than 500r/min, the contact angle is 60°, and the sliding bearing with a rotational speed lower than 500r/min is used. The contact angle can be 90° or 60°.
3, the point of contact
The actual contact between the journal and the plain bearing surface can be expressed in terms of the actual number of contact points per unit area. The more the contact points, the finer and more uniform, the better the scratch-off of the sliding bearing, and the worse, the sliding bearing is not good.
Generally speaking, the more fine the contact points, the more difficult it is to scrape. The contact points should be determined in the production according to the performance and working conditions of the sliding bearings. The information listed in the table below is for reference:
Sliding bearing speed
(r/min) contact point
(number of contacts per 25 x 25 mm area)
100 or less 3~5
100~500 10~15
500~1000 15~20
1000~2000 20~25
2000 or more 25 or more
For Class I and Class II precision machines, the above table data can be used. Class III precision machines can be halved according to the above table data.
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