ABS sensor.
Abs sensor is used in the motor vehicle ABS (Anti-lock Braking System). In the ABS system, the speed is monitored by an inductive sensor. The abs sensor outputs a set of quasi-sinusoidal AC electrical signals through the action of the gear ring that rotates synchronously with the wheel, and its frequency and amplitude are related to the wheel speed. The output signal is transmitted to the ABS electronic control unit (ECU) to realize real-time monitoring of wheel speed.
1, linear wheel speed sensor
Linear wheel speed sensor is mainly composed of permanent magnet, pole axis, induction coil and tooth ring. When the gear ring rotates, the tip of the gear and the backlash alternate opposite polar axis. During the rotation of the gear ring, the magnetic flux inside the induction coil changes alternately to generate the induction electromotive force, and this signal is input to the electronic control unit of ABS through the cable at the end of the induction coil. When the speed of the gear ring changes, the frequency of the induced electromotive force also changes.
2, ring wheel speed sensor
Annular wheel speed sensor is mainly composed of permanent magnet, induction coil and tooth ring. The permanent magnet is composed of several pairs of magnetic poles. During the rotation of the gear ring, the magnetic flux inside the induction coil changes alternately to generate the induction electromotive force. This signal is input to the electronic control unit of ABS through the cable at the end of the induction coil. When the speed of the gear ring changes, the frequency of the induced electromotive force also changes.
3, Hall type wheel speed sensor
When the gear is located in the position shown in (a), the magnetic field lines passing through the Hall element are dispersed and the magnetic field is relatively weak; When the gear is located in the position shown in (b), the magnetic field lines passing through the Hall element are concentrated and the magnetic field is relatively strong. When the gear rotates, the density of the magnetic line of force passing through the Hall element changes, which causes the Hall voltage to change, and the Hall element will output a millivolt (mV) level of quasi-sine wave voltage. This signal also needs to be converted by the electronic circuit into a standard pulse voltage.
Install
(1) Stamping gear ring
The tooth ring and the inner ring or mandrel of the hub unit adopt interference fit. In the assembling process of the hub unit, the tooth ring and the inner ring or mandrel are combined together by an oil press.
(2) Install the sensor
The fit between the sensor and the outer ring of the hub unit is interference fit and nut lock. The linear wheel speed sensor is mainly nut lock form, and the ring wheel speed sensor adopts interference fit.
The distance between the inner surface of the permanent magnet and the tooth surface of the ring: 0.5 ± 0.15 mm (mainly through the control of the outer diameter of the ring, the inner diameter of the sensor and the concentricity)
(3) The test voltage uses the self-made professional output voltage and waveform at a certain speed, and the linear sensor should also test whether the short circuit;
Speed: 900rpm
Voltage requirement: 5.3 ~ 7.9 V
Waveform requirements: stable sine wave
Voltage detection
Output voltage detection
Inspection items:
1, output voltage: 650 ~ 850mv(1 20rpm)
2, output waveform: stable sine wave
Second, abs sensor low temperature durability test
Keep the sensor at 40 ° C for 24 hours to test whether the abs sensor can still meet the electrical and sealing performance requirements of normal use
Why is the abs sensor so easy to break
The reasons why ABS sensor is easy to damage mainly include the induction part is covered, the line is loose and the quality of the sensor itself. The details are as follows:
The sensing part is covered: when the sensing part of the ABS sensor is covered by dirt, dust or other foreign bodies, it will interfere with the signal output of the sensor, resulting in the computer being unable to accurately judge the speed, which will affect the normal operation of the brake system.
Loose line: The sensor's line connection is not strong or the connector is loose, which will lead to poor signal transmission, resulting in system faults. A common fault is that the fault light is on.
The quality of the sensor itself: if the quality of the ABS sensor is poor, it may affect the stability of its output signal, and then affect the sensitivity of the ABS system and driving safety.
These factors may cause the ABS sensor to be easily damaged, so during use and maintenance, attention should be paid to keeping the sensor clean and checking the connection status of the line to ensure driving safety.
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