Para sa mga cylindrical roller bearings ng NF, NJ, NUP at iba pang mga structural form na may mga ribs sa panloob at panlabas na mga singsing, ang mga ribs ay maaaring magdala ng isang tiyak na axial load. Sa ilalim ng normal na mga pangyayari, ang pagkarga na maaaring dalhin ng tindig ay batay sa buhay ng pagkapagod sa panahon ng pagpapatakbo ng tindig, ngunit ang kapasidad ng pagdadala ng axial load ng cylindrical roller bearing ay hindi nakasalalay sa buhay ng pagkapagod, ngunit sa lakas ng tadyang. at ang mga roller. Ang antas ng pagbuo ng init ng sliding friction sa pagitan ng dulong mukha at rib ng ferrule. Lalo na para sa high-speed o high-vibration na mga kondisyon, kung ang pagpapadulas ay mahina o ang epekto ay masyadong malaki, ito ay mas malamang na maging sanhi ng pagkasira at abrasion ng contact surface sa pagitan ng rib at roller, na nagreresulta sa maagang pagkabigo ng tindig .
1 The maximum allowable axial load of cylindrical roller bearings with ribs Regardless of any working conditions, the axial load that cylindrical roller bearings with ribs can bear depends first on the strength of the ribs. to prevent
The rib is broken, and the axial load it bears cannot exceed CAmax1 [1].
For 2 diameter series bearings
CAmax1 = 0.004 5D1.5(1)
For other diameter series bearings
CAmax1 = 0.002 3D1.7(2)
For bearings in the 2-diameter series that are subjected to brief or shock axial loads
CAmax1 = 0.013D1.5 (3)
Other diameter series bearings
CAmax1 = 0.007D1.7 (4)
In the formula: CAmax1 is the maximum axial load that can withstand to prevent the rib from breaking, kN; D is the outer diameter of the bearing, mm.
At the same time, the axial load that the bearing can bear also depends on the degree of contact friction and heat generation between the rib of the ring and the end face of the roller. Therefore, the following factors need to be considered for the allowable axial load of the bearing: ( 1)
Contact area, machining accuracy and running-in degree between the roller end face and the rib contact surface; (2) Axial load size and action time; (3) Lubricant and lubrication method; (4) Bearing speed or sliding speed; (5) ) cooling and heat dissipation conditions.
The study found that there is a proportional relationship between the heat generation Q in sliding friction and the contact pressure P, the sliding velocity v and the sliding friction factor μ, that is, Q ∝ μPv .
The dynamic axial load capacity refers to the allowable axial load value that can ensure the stable operation of the bearing under the condition that the lubrication is sufficient (viscosity ratio κ ≥2) and the bearing temperature is 60 °C higher than the ambient temperature. The greater the radial load the bearing can bear, the greater the dynamic axial load it can bear.
For low speed conditions, the allowable axial load of cylindrical roller bearings with ribs depends only on the strength of the ribs and does not exceed CAmax1. However, for other working conditions such as high speed or large vibration, the axial load carrying capacity of the bearing must also consider the strength of the rib and the contact lubrication between the rib and the roller, that is, compare CAmax1 and CAmax2 ( C'Amax2 ), take the two The minimum value of is the maximum allowable axial load of the bearing. The exact force of the rib can be calculated by software such as finite element analysis.
In addition to considering factors such as rib shape, contact method and lubrication, the axial load carrying capacity of cylindrical roller bearings should also consider the influence of the size of the overrun groove between the rib and the raceway, the thickness of the rib, etc. Normal failure probability.
2 Improvement of the contact method between the roller and the rib
In the general structural design of cylindrical roller bearings, the end face of the roller and the rib are in plane-to-plane contact, as shown in Figure 1a. This structure can well correct the skew of the roller during the movement, but the sliding of the roller end face and the plane of the rib will cause large friction, which restricts the axial bearing capacity of the bearing.
Cylindrical roller bearings used in railway vehicles, large vibration and other working conditions, in the design of the use of (5) ~ (7) to estimate the axial load capacity. In order to make the rib well bear the axial load when working at high speed, under the premise of ensuring the strength of the rib, the rib and the end face of the roller are respectively designed as a conical surface and a spherical base surface (Fig. 1b), so that the two The contact is changed from surface contact to point contact, thereby improving the force of the rib and the lubrication of the rib and the end face of the roller. At the same time, it avoids the possibility of arc-shaped rib (Fig. 2) during the processing of the flat rib, and eliminates the edge stress of the rib.
It should be noted that the dimension H1 of the contact position between the roller and the rib must satisfy H ＞ H1 ＞ S (preferably the contact point is in the middle of the rib), S is the radial maximum value of the overrun groove, and H is the rib. Side height (Figure 3, Figure 4). In this way, even if the rollers are slightly inclined, the formation of a lubricating oil film can be promoted, the sliding friction can be reduced, and the stress at the root of the rib can be reduced to a minimum. If the load is applied to the edge of the rib or the edge of the overrun groove, there will be a larger joint
contact stress and the optimal lubrication state of the contact is not achieved.
At present, the inclined rib design of cylindrical roller bearings takes into account the axial bearing capacity, speed and stability of the bearing. In the actual design, the radius Re of the base surface of the roller ball can be initially taken as
Re = [( Dw /2) - H1]/sin θf, ( 8)
In the formula: Dw is the diameter of the roller; H1 can be initially taken as half of the effective contact length of the rib, and take the minimum value between the inner and outer rib.
Due to the tolerance of Re and θf, in order to ensure that the contact point is within the required reasonable area, the position of the contact point must be checked.
H1min = ( Dw /2) - Remax sin θfmax > S, ( 9)
H1max = ( Dw /2) - Remin sin θfmin < H. ( 10)
If the requirements are not met, Re can be adjusted until equations (9) to (10) are established.
3 Conclusion
For occasions with high speed and a certain axial load, controlling the temperature rise of the bearing and improving the stress condition of the rib has always been a difficult problem to be solved urgently in the cylindrical roller bearing with rib. On the other hand, the rib and the end face of the roller are designed as cone surfaces and spherical base surfaces with a certain angle respectively, and the surface contact between the roller and the rib is changed to point contact, which not only reduces the contact area but also improves bearing lubrication. , reducing the temperature rise of the bearing and improving the axial bearing capacity of the cylindrical roller bearing.
4 More about VAFEM Single Row Cylindrical Roller Bearings and Double Row Cylindrical Roller Bearings
As a precious high quality cylindrical roller bearings manufacturer and supplier in China, VAFEM can guarantee the quality and precision of the products through complete testing technology and advanced equipment.
Cylindrical Roller Bearings are bearing in which cylinders are used as the rolling elements as opposed to balls in ball bearings. As such, the rollers have a greater (linear) contact area with the outer ring and are distribute loads across a broader surface.
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2022-08-17