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【概要描述】Learn four key considerations in disc spring assembly design, including guide clearance, lubrication, stacking arrangements, load distribution, and deflection control.
【概要描述】Learn four key considerations in disc spring assembly design, including guide clearance, lubrication, stacking arrangements, load distribution, and deflection control.
1) Design Calculations for Disc Spring Assemblies
The design calculations for disc spring assemblies are still based on the calculation methods for a single disc spring. Depending on the assembly configuration, the load and deflection of each individual disc spring should be determined before carrying out the design calculations.
2) Guide Components and Their Dimensions
To prevent lateral movement of the disc springs under load, disc spring assemblies should be equipped with a guide mandrel (guide rod) or a guide sleeve. In general, guide sleeves provide better performance.
During deformation, the outer diameter of a disc spring increases while its inner diameter decreases. Therefore, sufficient clearance must be maintained between the disc spring and the guide component. The recommended clearance can be selected according to Table 17-12.
To reduce the effects of friction, lubrication should also be provided between the disc springs and the guide components. For improved wear resistance, the surface hardness of the guide components should be higher than that of the disc springs. Surface carburizing treatment is recommended, with a carburized layer thickness of approximately 0.8 mm and a typical hardness of 55 HRC. The surface roughness should be Ra < 3.2 μm.
Table 17-12 Clearance Between Disc Springs and Guide Components (Unit: mm)
d or D (mm) | Clearance (mm) | d or D (mm) | Clearance (mm) |
|---|---|---|---|
≤16 | 0.2 | >31.5–50 | 0.6 |
>16–20 | 0.3 | >50–80 | 0.8 |
>20–26 | 0.4 | >80–140 | 1.0 |
>26–31.5 | 0.5 | >140–250 | 1.6 |
Note: Extracted from GB/T 1972.
3) Avoid Excessive Numbers of Disc Springs in an Assembly
The number of disc springs in an assembly should not be too large.
When the assembly is under load, the disc springs slide along the surface of the guide component. Part of the load is transferred to the guide component, causing the load carried by each disc spring to decrease progressively from the loaded end toward the opposite end.
As a result, the stress distribution among the disc springs becomes uneven. The disc spring at the loaded end experiences the highest stress and therefore has the shortest service life.
The greater the number of disc springs in an assembly, the more pronounced this uneven load distribution becomes. Therefore, it is generally preferable to use larger-diameter disc springs with fewer pieces to meet the required load and deflection.
When the design requires a larger number of disc springs, the allowable stress used in fatigue strength calculations should be appropriately reduced to ensure that the disc spring at the loaded end has sufficient service life.
Figure 17-19: Structural Design to Prevent Excessive Disc Spring Deflection
4) Disc Spring Assemblies with Different Thicknesses or Different Numbers of Stacked Springs
For disc spring assemblies consisting of disc springs with different thicknesses or different numbers of springs stacked in parallel, structural measures should be taken to prevent thinner disc springs or those with fewer stacked layers from being flattened, which could result in excessive stress.
For example, a spacer ring can be installed between the disc springs (as shown in Figure 17-19) to ensure that the maximum deflection of these disc springs remains within 0.75h₀.
Key Takeaways
The design of disc spring assemblies requires particular attention to four aspects:
Design Calculations: Base the assembly calculations on the load and deflection characteristics of individual disc springs.
Guide Clearance: Select appropriate clearance according to the spring diameter, and ensure proper lubrication and wear resistance.
Number of Springs: Avoid excessive stacking to minimize uneven load distribution and premature fatigue failure.
Structural Protection: For assemblies with different spring thicknesses or stacking configurations, control the maximum deflection to prevent local overloading.
