QC/T 1167-2022Service brake dynamometer squeal noise test methods for passenger cars (English PDF)

3.1 Unladen condition

The state of vehicle at which its curb weight is loaded with 110 kg.

3.10 Invariable output mode

During a braking process, the control method where the braking torque output by the tested brake is always kept constant.

3.11 Pressure profile mode

In the drag test, the input control method where the brake pressure is changed with time as specified.

4.1 General requirements

The test bench shall have the test capabilities of invariable input mode, invariable output mode, deceleration brake, parking brake, as well as the drag test capacity of invariable input mode and pressure profile mode; meanwhile the drive motor shall have the ability of forward and reverse rotation.

4.2 Control system

The control system shall be able to realize invariable input mode, pressure profile mode or invariable output mode, etc. Its control shall meet the following requirements:

- The rate of increase and decrease of brake pressure shall not be less than 10 MPa/s; the maximum brake pressure shall not be less than 16 MPa;

- When controlled by pressure profile mode, the deviation -- between the average brake pressure control value and the target value (set value) -- shall not exceed ±0.025 MPa;

- Except for control by pressure profile mode, the brake pressure overshoot of other tests is less than 0.1 MPa;

- When controlled by invariable output mode, the deviation -- between the braking deceleration and the target value (set value) -- shall not exceed 0.5 m/s;

- During the drag test, the speed of the vehicle shall not be lower than 90% of the specified speed.

4.3 Brake cooling system

The inner diameter of the cooling air pipe shall be Phi 200 mm ~ 320 mm; the outlet shall be 300 mm ~ 400 mm away from the outer diameter of the brake disc (or brake drum); the cooling air flow rate at the outlet shall be 10 m/s. If necessary, the cooling air speed shall be adjusted, to meet the background noise requirements, which are specified in 4.7. When the above requirements cannot be met, it can be implemented, according to the negotiation between the supplier and the buyer; meanwhile the background noise measurement value shall be recorded in the test report.

4.4 Environmental control system

4.4.1 During the standard test and fading test, the cooling air temperature shall be controlled at 25 °C ± 5 °C. During the cold state test, the cooling air temperature shall be controlled below 10 °C below the initial braking temperature.

4.4.2 When the cooling air temperature is above 0 °C, the relative humidity of the cooling air shall be controlled within the range of 50% ± 10%. When the cooling air temperature is 0 °C or below, only the cooling air temperature shall be controlled.

4.5 Data acquisition system

4.5.1 The data acquisition system shall have the functions of continuous recording and real-time display.

4.5.2 The sampling frequency of the following parameters shall not be lower than 50 Hz:

- The spindle speed of the test bench;

- The brake pressure;

- The brake output torque.

4.5.3 The sampling frequency of the following parameters shall not be lower than 10 Hz:

- The temperature of the brake disc (or drum);

- Cooling air temperature, relative humidity (or absolute humidity), wind speed (or flow rate).

4.6 Brake noise measurement system

4.6.1 The microphone, which is used for noise measurement, shall comply with the requirements of level 2 and above, as specified in GB/T 3785.1-2010.

a) Drive through the flange;

b) Drive by wheel hub;

c) Drive directly by the main shaft.

6.1 Brake initial temperature control

6.1.1 Brake temperature rise

6.1.1.1 Except for the fading test, when the brake temperature is lower than the required initial braking temperature before the next braking, the temperature shall be raised by dragging, according to the following conditions, until the brake temperature is more than 5 °C higher than that of the next braking:

- When the difference -- between the actual temperature of the brake and the required initial temperature of the brake -- is greater than 30 °C, the drag speed is the speed corresponding to the vehicle speed of 50 km/h; the braking pressure is 2 MPa (disc brake) or 3 MPa (drum brake);

- When the actual temperature of the brake is below 30 °C less than or equal to the required initial brake temperature, the drag speed is the speed corresponding to the vehicle speed of 25 km/h; the brake pressure is 1 MPa (disc brake) or 1.5 MPa (drum brake).

6.1.1.2 For the fading test, when the brake temperature does not meet the requirements of the initial brake temperature, it shall increase the temperature, by dragging at a speed of 80 km/h and a brake pressure equivalent to a brake deceleration of 1.96 m/s2; the drag time shall not exceed 20 s each time.

6.1.2 Brake cooling

When the brake temperature is 5 °C or higher than the initial braking temperature required for the next braking, rotate the brake disc/brake drum, at a speed of 20 km/h, until the difference -- between the brake temperature and the initial braking temperature is less than 5 °C.

6.2 Fading test temperature

See Table 2 for the initial braking temperature of the fading test. Special circumstances shall be determined, through negotiation between the supplier and the buyer.

6.4 Efficiency factor of drum brake

The efficiency factor of the drum brake is calculated according to formula (3):

Where:

C* - Efficiency factor of drum brake; p0 - The braking pressure required when the braking torque reaches 5 N · m, in megapascal (MPa), which usually takes 0.5 MPa unless otherwise specified;

Ag - Piston area of brake wheel cylinder, in square millimeter (mm2); d - Inner diameter of the brake drum, in meters (m).

7.1 Determination of test inertia

The test inertia is calculated according to formula (4) OR stipulated through negotiation between the supplier and the buyer:

Where:

I - Brake test inertia, in grams square meters (kg · m2); k - Mass distribution coefficient;