Diaphragm Spring Introduction

Clutch Plate Spring, Technical Conditions

I. Scope

This standard specifies the structural types, technical requirements, testing methods, and inspection rules for diaphragm springs.

This standard applies to diaphragm springs for mechanical clutches (hereinafter referred to as "diaphragm springs"), and diaphragm springs in dampers are used as references.

II. Normative References

The following documents are essential for the application of this document. For referenced documents with dates, only the version with the noted date applies to this document. For referenced documents without dates, the latest version (including all amendments) applies to this document.

Method for Measuring the Decarburization Depth of Steel according to GB/T 224

GB/T 230.1 Metal Materials Rockwell Hardness Test Part 1: Test Method (Scales A, B, C, D, E, F, G, H, K, N, T)

GB/T 1222 Spring Steel

GB/T 1800.2-2009 Product Geometric Technical Specification (GPS) Limits and Fits Part 2: Standard Tolerance Grades and Tables of Limits of Fit for Holes and Shafts

GB/T 1972 Disc Spring

GB/T 3279 Hot-Rolled Steel Sheets for Springs

YB/T 5058 Cold Rolled Steel Strip for Spring and Tool Steel

3. Parameter Name, Code, and Unit

Parameter names, codes, and units are listed in Table 1.

Table 1 Parameter Name, Code, and Unit

IV. Structural Style

4.1Diaphragm spring structure type

The diaphragm spring structure is as shown in Figure 1.

Figure 1: Diaphragm Spring

Section 6: Technical Requirements

6.1 Materials

6.1.1 Material

The material for diaphragm springs is generally 50CrVA or 60Si2MnA, which should comply with the specifications of GB/T 1222 for chemical composition and physical properties; if other materials are used, they can be agreed upon by both parties.

6.1.2 Requirements

The steel strip used for diaphragm springs should comply with the provisions of YB/T 5058, or meet the requirements of GB/T 3279.

6.1.3 Inspection

Materials should be accompanied by a quality guarantee letter from the material manufacturer and must pass a re-inspection before use.

6.2 Dimensional Tolerance Limit

6.2.1 Thickness

The allowable deviation of the thickness "t" of the diaphragm spring should comply with the specifications in Table 2. In cases of special requirements, the allowable deviation of the thickness "t" shall be agreed upon by both the supplier and the buyer.

Table 2: Limiting Deviation for Thickness tDifference (in millimeters)

6.2.2 Free Height

The allowable deviation of the free height of the diaphragm spring should comply with the specifications in Table 3. The free height can be appropriately adjusted during manufacturing to ensure the characteristic requirements, but the tolerance value remains unchanged.。 

Table 3: Maximum Deviation of Free Height (in millimeters)

6.2.3 Diameter

The inner and outer diameter tolerances of the diaphragm spring are in accordance with the H13 and h13 grades specified in GB/T 1800.2-2009.

6.3 Flatness

The flatness tolerance for the bottom surface of the diaphragm spring's sealing portion should be 0.25mm, and the arc length of the non-contacting surface should not exceed one-third of the circumference.

6.4 Coaxiality

The coaxial tolerance of diaphragm springs should comply with the specifications in Table 4.

Table 4: Axial Tolerance (in millimeters)

6.5 Load Characteristic Limit Deviation

According to customer requirements, the characteristics of the diaphragm spring working area are specified, but the load deviation at the working point is within -10% to 20%.

6.6 Heat Treatment

Blade springs must be quenched and tempered, and the quenching process should not exceed two times.

6.7 Hardness

The hardness value of the sealed part of the spring diaphragm after tempering should be selected within the range of 71.5HRA to 76.8HRA, and the allowable tolerance for the hardness value of a single spring diaphragm is ±2HRA.

Surface hardness values on the separated tip end section (with a maximum ø70mm) must be above 79HRA, with a depth greater than 0.5mm. There is allowance for a hardness transition zone between the separated tip end and the sealed section, but the minimum hardness within the transition zone should not be less than 68.9HRA.

6.8 Decarburization Depth

Heat-treated diaphragm spring, the depth of decarburization on one side should not exceed 1% of its thickness, and the maximum depth should not be more than 0.05mm. 

6.9 High-pressure Treatment

Diaphragm springs should undergo a high-pressure treatment, using a load compression with not less than double the s=0.75h value. The duration of compression should be no less than 12 hours, or the compression should be done in short intervals, with a total of at least 5 compressions.

6.10 Surface Quality

The diaphragm spring surface should be free of burrs, cracks, and any defects harmful to use.

6.11 Surface Corrosion Treatment

Diaphragm springs are typically dipped in anti-rust oil after shot peening, and can also be treated with oxidation, phosphating, electro-phoresis, etc. as per customer requirements. Diaphragm springs are not suitable for electroplating treatment.

6.12 Fatigue Life

When fatigue life requirements are specified, the number of fatigue life cycles may be agreed upon by both the supplier and the buyer.

Section 7: Testing Methods

7.1 Dimensions and Positional Tolerances

7.1.1 Thickness

Measure the thickness of the diaphragm spring with a micrometer at least 3 points along the circumference at both the inner and outer diameters of the diaphragm spring, and take the maximum value.

7.1.2 Diameter

The diameter of the diaphragm spring is measured using a micrometer with a graduation value not exceeding 0.02mm. At least three measurements are taken at different positions along the circumference, with the outer diameter being the largest value and the inner diameter being the smallest value.

7.1.3 Free Height

The free height of the diaphragm spring should be measured using a depth micrometer with a graduation value not exceeding 0.02mm on a grade 2 flatness plate. At least three measurements should be taken at different positions around the circumference, and the maximum value should be taken.

7.1.4 Flatness

Place the diaphragm spring on a secondary precision flat plate, measure the diaphragm spring plane gap under the load of 2% s = 0.75ho using a feeler gauge, and take the largest gap value. The maximum load should not exceed 300N, as shown in Figure 3.

Figure 3: Diagram of Flatness

7.1.5 Coaxiality

Place the diaphragm spring on a secondary precision flat plate and measure its width with a caliper having a least count of 0.02mm or less, as shown in Figure 4. Measure at least three positions, then calculate the difference between the measured maximum value and the theoretical value; this difference is the coaxiality error.

Coaxiality error can also be agreed upon by both parties to be measured using a converted tooling.

Figure 4: Coaxiality Error Measurement

7.2 Load Characteristics

The load of the diaphragm spring is tested on a machine with accuracy not less than 1%, measuring the load when it reaches the required deformation amount by the user. Lubricant must be used during the test. The hardness of the upper and lower plates for measuring the load characteristics of the diaphragm spring must be above 52HRC, and the surface roughness Rz must be less than 1.6μm.

7.3 Hardness

The hardness test of diaphragm springs is conducted according to GB/T 230.1 specifications. The indentation should be made between the outer diameter of the diaphragm spring and the window, with 4 points per piece, the first point being disregarded, and the average value of the last 3 points taken. The separation finger hardness test should be conducted within a range of 2mm to 10mm below the finger tip (refer to Figure 5 of this standard); the method is the same as above.