Page 16 - NSK_CAT_E1102m_A7-141

SELECTION OF BEARING SIZE

6. LIMITING SPEED

Fae + 0.6 Fr2 = 2 000 + 0.6 × 3 931 In this application, heavy loads, shocks, and shaft The speed of rolling bearings is subject to certain 6.2 Limiting Speed for Rubber Contact Seals
Y2 1.6 deflection are expected; therefore, spherical roller limits. When bearings are operating, the higher the for Ball Bearings
bearings are appropriate. speed, the higher the bearing temperature due to
= 3 474N, {354kgf} The following spherical roller bearings satisfy the friction. The limiting speed is the empirically obtained The maximum permissible speed for contact rubber
above size limitation (refer to Page B196) value for the maximum speed at which bearings can be sealed bearings (DDU type) is determined mainly by
0.6 Fr1 = 0.6 × 1 569 = 1 290N, {132kgf} continuously operated without failing from seizure or the sliding surface speed of the inner circumference of
Y1 0.73 generation of excessive heat. Consequently, the limiting the seal. Values for the limiting speed are listed in the
speed of bearings varies depending on such factors bearing tables.
Therefore, with this bearing arrangement, the axial Basic dynamic Constant Factor as bearing type and size, cage form and material,
load, lubricating method, and heat dissipating method
load Fae + 0.6 Fr2 is applied on bearing1but not on d D B Bearing No. load rating e Y3 including the design of the bearing's surroundings.
Y2 The limiting speeds for bearings lubricated by grease
Cr and oil are listed in the bearing tables. The limiting
(N) {kgf} speeds in the tables are applicable to bearings of
standard design and subjected to normal loads, i. e.
bearing 2. 300 420 90 23960 CAE4 1 230 000 125 000 0.19 3.5 C/P≥12 and Fa /Fr ≤0.2 approximately. The limiting 1.0
460 118 23060 CAE4 1 920 000 196 000 0.24 2.8 speeds for oil lubrication listed in the bearing tables 0.9
For bearing1 460 160 24060 CAE4 2 310 000 235 000 0.32 2.1 are for conventional oil bath lubrication. 0.8
Some types of lubricants are not suitable for high 0.7
Fr1 = 1 569N, {160kgf} 500 160 23160 CAE4 2 670 000 273 000 0.31 2.2 speed, even though they may be markedly superior Correction Factor 0.6
Fa1 = 3 474N, {354kgf} 500 200 24160 CAE4 3 100 000 315 000 0.38 1.8 in other respects. When speeds are more than 70
percent of the listed limiting speed, it is necessary
since Fa1 / Fr1 = 2.2>e = 0.83 since Fa / Fr = 0.20<e to select an oil or grease which has good high speed
characteristics.
the dynamic equivalent load P1 = XFr1 + Y1Fa1 the dynamic equivalent load P is
(Refer to)
= 0.4 × 1 569 + 0.73 × 3 474 Table 12.2 Grease Properties (Pages A110 and 111)
Table 12.5 Example of Selection of Lubricant for Bearing
= 3 164N, {323kgf} Cr P = Fr + Y3 Fa 4 5 6 7 8 9 10 11 12
P1 Operating Conditions (Page A113)
The fatigue life factor fh = fn Judging from the fatigue life factor fh in Table 5.1 and Table 15.8 Brands and Properties of Lubricating Grease C/P
Fig. 6.1 Limiting Speed Correction Factor Variation with
= 0.42 × 38 000 = 5.04 examples of applications (refer to Page A25), a value (Pages A138 to A141)
Load Ratio
3 164 of fh, between 3 and 5 seems appropriate. 6.1 Correction of Limiting Speed

10 0.444 Cr When the bearing load P exceeds 8 % of the basic load
rating C, or when the axial load Fa exceeds 20 % of
and the rating fatigue life Lh = 500 × 5.04 3 = 109 fh = fn Cr = Fr + Y3 Fa = 3 to 5 the radial load Fr, the limiting speed must be corrected Angular Contact Ball Brgs.
750h P by multiplying the limiting speed found in the bearing 1.0
tables by the correction factor shown in Figs. 6.1 and
For bearing2 Assuming that Y3 = 2.1, then the necessary basic load 6.2. Deep Groove Ball Brgs
rating Cr can be obtained When the required speed exceeds the limiting speed of 0.9
the desired bearing; then the accuracy grade, internal
since Fr2 = 3 931N, {401kgf}, Fa2 = 0 clearance, cage type and material, lubrication, etc., Correction Factor 0.8
the dynamic equivalent load must be carefully studied in order to select a bearing
Cr = (Fr + Y3 Fa) × (3 to 5) capable of the required speed. In such a case, forced- Spherical Roller Brgs.
P2 = Fr2 = 3 931N, {401kgf} circulation oil lubrication, jet lubrication, oil mist 0.7 Tapered Roller Brgs.
the fatigue life factor 0.444 lubrication, or oil-air lubrication must be used.
If all these conditions are considered. The maximum
= (245 000 + 2.1 × 49 000) × (3 to 5) permissible speed may be corrected by multiplying 0.6
the limiting speed found in the bearing tables
fh = fn Cr = 0.42 × 43 000 = 4.59 0.444 by the correction factor shown in Table 6.1. It is 0.5
P2 recommended that NSK be consulted regarding high 0
3 931 speed applications. 0.5 1.0 1.5 2.0

10 = 2 350 000 to 3 900 000 N, Fa /Fr

and the rating fatigue life Lh = 500 × 4.59 3 = 80 400h {240 000 to 400 000 kgf} Fig. 6.2 Limiting Speed Correction Factor for Combined Radial
and Axial Loads
are obtained. The bearings which satisfy this range are 23160CAE4,
and 24160CAE4.
Remarks For face-to-face arrangements (DF type), Table 6.1 Limiting Speed Correction Factor for
please contact NSK. High-Speed Applications

(Example 6) Bearing Types Correction
Select a bearing for a speed reducer under the Factor
following conditions:
Operating conditions Cylindrical Roller Brgs.(single row) 2
Needle Roller Brgs.(except broad width) 2
Radial load Fr = 245 000N, {25 000kgf} Tapered Roller Brgs. 2
Spherical Roller Brgs. 1.5
Axial load Fa = 49 000N, {5 000kgf} Deep Grooove Ball Brgs. 2.5
Angular Contact Ball Brgs.(except matched bearings) 1.5
Speed n = 500min–1

Size limitation

Shaft diameter: 300mm
Bore of housing: Less than 500mm

A 36 A 37