Performance Requirements for Automotive Hydraulic Brake Master Cylinders
Issued by the National Development and Reform Commission of China
Release Date: 2006-06-04
Effective Date: 2008-11-01

①This standard specifies the performance requirements and bench test methods for automotive hydraulic brake master cylinders.

②This standard applies to tandem dual-chamber hydraulic brake master cylinder assemblies (hereinafter referred to as "master cylinders"). Other types of hydraulic brake master cylinders may reference this standard for implementation.

Normative References

The following referenced documents are indispensable for the application of this standard. For dated references, only the editions cited apply. For undated references, the latest edition (including any amendments) applies.

GB/T 10125: Corrosion Tests in Artificial Atmospheres – Salt Spray Tests (equivalent to ISO 9227:1990)

QC/T 572: Guidelines for Automotive Cleanliness – Measurement Methods

The following terms and definitions apply to this standard.

3.1 Fluid Supply Cavity

A cavity connected to the reservoir via a fluid supply port (see Figures 1 and 2). It replenishes brake fluid to the brake cavity during brake release.

3.2 Brake Service Cavity

A cavity connected to the brake circuit through a discharge port or residual valve (see Figures 1 and 2). The hydraulic pressure generated in this cavity during braking matches the pressure in the connected brake circuit.

3.3 Compensating Port

A port in the cylinder body (or piston) that connects the brake cavity to the reservoir (or fluid supply cavity) (see Figures 1 and 2). It compensates brake fluid to the brake cavity or returns excess fluid to the reservoir during brake release.

3.4 Center Valve

A valve located on the piston between the brake cavity and fluid supply cavity (see Figure 1). During braking, it isolates the brake cavity from the fluid supply cavity; during brake release, it allows fluid compensation to the brake cavity.

Fig.1 Typical Hydraulic Master Cylinder (Single Check Valve Type)

1-Dust Boot;2-Primary Piston;3一Piston Guide;4-Backup Washer;5,8-Inlet Port;6,19一Bypass Port;

7一Reservoir Mounting Bolt;9-Locating Pin; 10-Secondary Piston;11-Master Cylinder Body;12-Fluid Reservoir;

13-Secondary Cup Seal;14-Primary Supply Chamber;15-Primary Cup Seal;16-Primary Pressure Chamber;

17,21-Outlet Port;18-Secondary Supply Chamber;20-Check Valve Assembly;22-Secondary Pressure Chamber

3.5 Residual Valve

A valve between the brake cavity and brake circuit (see Figure 2). It maintains residual pressure in the brake circuit after brake release.

3.6 Maximum Service Pressure

The maximum hydraulic pressure specified in the design.

3.7 Maximum Stroke

The total displacement of the primary piston from its initial position to its terminal position.

3.8 Initial Pressure-Building Travel

The displacement of the primary piston when the brake cavity pressure reaches 0.1 MPa (under a total effective test circuit volume of 135–150 mL, including the brake cavity).

Fig.2 Tandem Master Cylinder with Dual Check Valves

1-Master Cylinder Body;2-Secondary Piston Seal;3-Primary Piston;4&9-Supply Ports (Primary/Secondary);

5-Primary Piston Seal;6&10-Compensating Ports ;7一Primary Pressure Chamber (Front Circuit);

8-Secondary Supply Chamber (Rear Circuit);11-Secondary Pressure Chamber (Diagonal Circuit);

12-Primary Supply Chamber ;13-Residual Pressure Valve;14&16-Output Ports;15-Secondary Piston

Products are classified into three categories as A\B\C based on operating temperature ranges (Table 1).

Table 1: Classification by Operating Temperature

5.1 Basic Requirements

The master cylinder's exterior shall be free of rust, burrs, cracks, or defects.

5.2 Performance Requirements

5.2.1 Residual Valve Performance

- Opening pressure: ≤ 0.05 MPa.

- Residual pressure: 0.05 ± 0.03 MPa (see Table 2).

Table 2: Residual Pressure Specifications

5.2.2 Sealing Performance

- 5.2.2.1 Vacuum Sealing

Pressure rise ≤ 0.3 kPa within 5 seconds under specified vacuum.

*Note: Excludes units without vacuum filling requirements.

- 5.2.2.2 Air Pressure Sealing:

- Pressure drop ≤ 3 kPa within 10 seconds at 50 kPa.

- No air leakage or functional deformation at 0.5 MPa.

- 5.2.2.3 Hydraulic Sealing:

- Threaded connectors must withstand specified torque without stripping.

- Pressure drop limits under maximum working pressure and 130% of maximum pressure are defined in Table 3.

Table 3: Permissible Hydraulic Pressure Drop

5.2.3 Initial Pressure-Building Travel

Primary piston displacement ≤ 4 mm when brake cavity pressure reaches 0.1 MPa.

5.2.4 Redundancy Function

The functional brake cavity shall maintain the maximum working pressure if the other cavity fails.

5.2.5 Displacement Tolerance

Brake cavity displacement error: ±10% of design value.

5.2.6 Return Time (Unloaded)

Primary piston return time: ≤ 0.5 seconds.

5.2.7 Pressure Differential

- Slow pressurization: Inter-cavity pressure difference ≤ 0.3 MPa.

- Rapid pressurization: Inter-cavity pressure difference ≤ 0.5 MPa.

5.2.8 Pressure Impact Resistance

- No functional deformation or damage after testing.

- Post-test hydraulic sealing must comply with Table 3.

- No fluid leakage from reservoirs (if equipped).

5.2.9 Durability

- No leakage or abnormalities during 335,000 cycles.

- Post-test hydraulic sealing must meet Table 3.

- Reservoir connections must remain secure.

5.2.10 Vibration Resistance

- No fluid leakage during vibration testing.

- No deformation or loosening post-test.

*Note: Excludes units without reservoirs.

5.2.11 Cleanliness

Total internal contaminants: ≤ 10 mg.

5.2.12 Salt Spray Corrosion Resistance

- No corrosion spots > 2 mm in diameter per 100 cm² surface area.

- Total corroded area ≤ 5 cm².