Bearing selection
1.Allowable PV value and speed
Allowable PV values is calculated and studied by the contact pressure P(MPa) and circumferential speed V(m/min) before using the oil-impregnated sintered bearing.
Calculation method
- Calculation method of the contact pressure P
P(Mpa)=Radial load (N)/{Bore diameter(mm)×Length(mm)} - Calculation method of the circumferential speed V
V(m/min)=Shaft diameter(mm)×π(circular constant)×Number of revolutions(min-1)×10-3 - Calculation method of the PV value
PV value(Mpa･m/min)=P(Mpa)×V(m/min)
| Generally recommended allowable PV values(Mpa･m/min) | |
|---|---|
| Item | Allowable PV values |
| General-purpose machinery | 100 |
| Household appliances | 50 |
| Office electric appliances | 50 |
| Low noise and low wear applications | 25 |
| Especially low noise applications | 20 |
| Axial loaded applications | 20 |
Fig. Relationship between contact pressure and circumferential speed
2.Bearing life
The life of the oil-impregnated sintered bearing is determined by the rate of consumption of the lubricating oil impregnated into the bearing.
Once 40% of the impregnated oil has been consumed, bearing performance deteriorates accordinaly.
In the case of a precisery small moter, severe noise and properties are required. So, the life is aimed by 30% of oil content.
Fig.Basic bearings’ lifetime