Introductions of semi-trailers ABS system (Part 4)

Introduction of semi-trailers ABS system (Part 4)

- Installation of ABS system components

1. Installation of exciter ring

As shown in Figure 1 below, the exciter ring is installed with interference fit on the hub. The recommended fit tolerance is H8/s7. When the exciter ring is installed, the axial tolerance should be <0.2mm, and the lateral run-out tolerance of the exciter ring should be <0.04mm.

(Figure 1. Installation diagram of ABS exciter ring)

There are two installation methods for ABS exciter ring:

1) Heating assembly method: heat the exciter ring to about 180℃ ~200℃ for 10 minutes, and then install it.

2) Pressure assembly method: use a special press to apply pressure evenly around the exciter ring.

Note: It is strictly forbidden to use hard objects to hit the exciter ring during installation (maintenance, repair), and the gear surface or shape of the exciter ring cannot be damaged, so as not to affect the accurate reading of the wheel speed signal by the sensor!

2. Installation of wheel speed sensor

Sensor working environment temperature: -40℃～+150℃

Wire working environment temperature: -40℃～+180℃

Connection plug working environment temperature: -40℃～+80℃

Type of protection: IP68

The installed position of the sensor: the installation hole of the clamping sleeve of the front axle sensor is located on the brake bracket or the steering knuckle; the installation of the rear axle sensor requires a clamping body bracket of the sensor, which is installed in the static part of the axle and has sufficient rigidity.

(Figure 2. Installation of sensor and exciter ring)

Installation requirements of the sensor: the axial direction of the sensor is perpendicular to the radial direction of the exciter ring and centered. During installation, first put the bushing into the clamping hole, then apply grease to the sensor, press it into the bushing and push it to the end face of the exciter ring without clearance. Due to the influence of the lateral run-out of the exciter ring and the axle bearing clearance when the wheel is rotating, the sensor is pushed away and a clearance＜0.7mm is formed.

The installation of the sensor is shown in Figure 3 below.

(Figure 3. Installation diagram of sensor)

Test of the sensor: 

After the exciter ring and sensor are installed, the induced voltage of the sensor shall be tested:

① Manually rotate the wheel at a constant speed to 30 rpm;

② Use a multimeter or diagnostic instrument to measure the voltage between the two poles of the sensor;

③ When the wheel speed is faster than 30 rpm, the sensor voltage must be＞0.2V, and the ratio of the maximum induced voltage to the minimum induced voltage should be＜2.0.

The resistance value of the sensor is between 1100Ω and 1250Ω, and the resistance value is greatly affected by temperature.

The installation of exciter ring and sensor and the sensor voltage test are usually done in the axle factory.

3. Installation of solenoid regulating valve

Rated voltage: 24V DC

Working condition: ED 20%/5min

Rated current: 1.65A

Rated working pressure: 1MPa

Working environment temperature: -40℃~+80℃

Installation deviation: ±30°

Installation requirements for solenoid regulating valve: 

The solenoid regulating valve is installed on the frame, with its exhaust port facing down and an exhaust gap ＞30mm. The connecting air hose between the solenoid regulating valve and the brake air chamber shall be as short as possible, and the length of the air hose shall not exceed 1.5m. Interface 1 is connected to the brake air source, interface 2 is connected to the brake air chamber, and the inner diameter of the air hose shall be ＞9mm

The installation diagram of the solenoid regulating valve is shown in Figure 4 below.

(Figure 4. Installation diagram of solenoid regulating valve)

Test of solenoid regulating valve:

Install the ABS system and confirm that the connection is correct. Turn on the ignition switch and listen to the cycling sound of the solenoid regulating valve. If there is no sound cycling, recheck the circuit connection.

4. Installation of circuit harness

Installation requirements for circuit harnesses: the fuse shall be as specified in the circuit diagram, and can only be used for ABS alone, not shared with other electrical loads; cables with appropriate cross-sections are selected; cable arrangement should be firm, insulated, and not be stretched; the cables of sensors and solenoid regulating valves shall not be too long, and they are not allowed to be cut off and reconnected or to add connectors; ECU(Electronic Control Unit) and solenoid regulating valves adopt the same grounding point, which is not shared with other electrical equipment; to avoid confusion of cable connection, check it according to the circuit diagram after installation.

5. Installation of ECU(Electronic Control Unit)

Service voltage: 24V±6V DC;

Protection form: IP 30

Working environment temperature: -40 ℃~+75 ℃

Installation requirements for ECU:

ECU(Electronic Control Unit) shall be connected in strict accordance with the technical requirements of ABS electrical wiring diagram. The connecting plug of the wire shall be connected reliably, and the wire shall be firmly fixed with wire ties.

There are two power supplies connected to ECU(Electronic Control Unit). One is the power supply from the battery, DC24V15A, which is the power supply of the solenoid regulating valve; the other is the power supply from the ignition switch, DC24V5A, which is the power supply of ECU(Electronic Control Unit).

ECU(Electronic Control Unit) shall be installed in a clean and sealed chamber which is away from heat source to prevent muddy water, dust and collision with other objects.

6. Installation of ABS warning lamps

The maximum power of ABS warning lamp is 24V 5W, and LED cannot be used for it.

The terminals of ABS warning lamp and ground wire(including COM terminal of solenoid regulating valve) must be gold-plated terminals to avoid ABS system failure due to corrosion after long-term use.

The ABS warning lamp operates as follows:

Turn on the ignition switch;

ABS warning lamp is on;

About 3 seconds later, the warning lamp extinguishes, and then the solenoid regulating valve operates for 10 times;

If the warning lamp is not on at this moment, it means that the ABS system has passed the static inspection and is working normally;

If the warning lamp flashes at this moment, it indicates that there is a fault in the system. Refer to the flashing code table to determine the fault type and fault location.

The function of the ABS warning lamp is to let the driver understand the condition of the ABS system. In addition, it is also used to display diagnostic flash codes.

Compiled by  WONDEE Autoparts

2022-6-23