Second, the composition and failure reasons of Hall contactless electronic ignition system.
Hall contactless electronic ignition system is mainly composed of Hall signal generator in distributor, electronic igniter for controlling primary winding of ignition coil, ignition coil and spark plug.
According to the composition of the ignition system, the function of the electronic ignition system is to convert the low-voltage electricity (12V) supplied by the power supply into high-voltage electricity (10 ~ 30kV), and timely and accurately send the high-voltage electricity to the spark plugs of each cylinder according to the working sequence of the engine and the requirements of the ignition time, so as to generate electric sparks and ignite the combustible mixture to make the engine work. The causes of engine high-pressure misfire are as follows.
1. Low voltage circuit failure
(1) The battery voltage is low, and the positive and negative electrodes are poorly connected.
(2) The ignition switch contacts or wires are in poor contact.
(3) The primary winding of the ignition coil is broken or has poor contact.
2. Electronic control circuit failure
(1) Hall signal generator failure. Hall signal generator consists of permanent magnet, magnetic conductive plate and Hall integrated circuit. There is a Hall signal generator on the side of the inner and outer signal wheels. There are four blades and four windows on the trigger impeller of Hall signal generator. When the engine rotates, the valve camshaft drives the distributor shaft to rotate through the intermediate shaft, and the distributor shaft drives the trigger impeller to rotate. Whenever the blade enters the air gap between the permanent magnet and the Hall element, the magnetic field in the Hall integrated circuit is bypassed by the trigger blade (that is, magnetic isolation), and Hall voltage is not generated at this time; When the trigger blade leaves the air gap, the magnetic relaxation of the permanent magnet is transmitted to the Hall element through the magnetic conduction plate, and then the Hall voltage (rectangular wave) signal will be generated. Every time the distributor shaft rotates, the crankshaft rotates, and the Hall sensor outputs four rectangular wave signals. After the Hall voltage signal is amplified and shaped by the electronic igniter circuit, it controls the on-off of the current of the primary winding of the ignition coil, causing a sudden drop of magnetic flux, and generating self-induced electromotive force in the primary winding, reaching 200 ~ 300 V. Because the turn ratio of the primary winding and the secondary winding of the ignition coil is about 1: 100, and both of them are sheathed on the same iron core in the form of inner and outer layers, the secondary winding will be generated under the action of mutual inductance. The electromotive force is enough to break through the gap of the spark plug, produce an electric spark, and finally ignite the mixture, so when the Hall signal generator fails, it will also cause the engine to catch fire.
(2) Electronic igniter failure. When the electronic igniter fails or fails, the ignition voltage cannot be sent to the primary winding of the high-voltage coil, so that the high-voltage ignition coil cannot induce high-voltage electricity.
3. High voltage circuit failure
The faults of high voltage circuit mainly include: the secondary winding of ignition coil is broken or the contact is poor; The distributor cover is cracked and slightly leaked; There is dirt in the socket hole next to the high voltage distribution line of the distributor cover; The carbon contact of distributor cover falls off; Central high voltage or cylinder high voltage conductor failure; The distributor has cracks or slight leakage; The cremation plug is ablated or punctured.
Three, the fault detection of ignition system components
1. Detection of low-voltage circuit
(1) When the battery voltage is low or the positive and negative electrodes are in poor contact, first check whether the positive and negative electrodes are well connected, and then check whether the specific gravity of the electrolyte is between1.24 ~1.31g/cm3.
(2) When the ignition switch contacts or wires are in poor contact, use a multimeter to check whether the voltage on the IG line on the ignition switch is consistent with the voltage on the battery. If it is low, it means that the contact or wire is in poor contact; If there is no voltage, there is a virtual connection or an open circuit in the contact or wire.
(3) When the primary winding of the ignition coil is disconnected or has poor contact, the ignition switch should be disconnected, the wires on the ignition coil should be disassembled, and the resistance value of the primary winding of the ignition coil should be measured with a multimeter. The wire diameter of the primary winding of the ignition coil is generally thicker and the number of turns is less, which makes its resistance value very low. The resistance of the primary winding is usually between1~ 4Ω (if it does not meet the requirements, it needs to be replaced).
2. Detection of control circuit
(1) Hall signal generator is an active component, which needs power supply to work. Its power supply is provided by the igniter. The Hall signal generator has three leads, one is the power input line, the other is the Hall signal output line and the other is the ground line.
When the Hall signal generator fails, the Hall signal generator can be checked by measuring the voltage at the end of electronic components. The specific methods are: turn off the ignition switch, open the distributor cover, unplug the central high-voltage line to make it grounded, connect the red detection rod of multimeter to the No.6 column, and ground the black detection rod, turn off the ignition switch, and start the engine to make the distributor shaft rotate. At the same time, observe the reading on the voltmeter, which generally varies from 0 to 9 V. When the distributor triggers the impeller blades to be in the air gap, the voltage value is 2 to 9 V. When the blades leave the air gap, the voltage value is between 00.5V V. If the measured voltage value is 10.5V, it means that the Hall signal generator is faulty and needs to be replaced. If the wire is found loose during inspection, tighten the compression nut or insert the connector firmly to make the wire contact well.
(2) Fault detection of electronic igniter. Check the electronic igniter, remove the lead from the "-"terminal of the ignition coil, connect a light bulb in series in the circuit, and connect the anode of the 3V dry battery to the terminal 6 (signal line) of the electronic igniter. Turn on the ignition switch, so that the negative pole of the dry battery is connected to the machine body (grounded), and then manually control its on and off. If the light bulb can't shine normally, it means that the electronic igniter is faulty and needs to be replaced; If the wire is found loose after inspection, tighten the compression nut or insert the connector forcibly to make the wire contact well.
Note: For the electronic igniter equipped with Hall signal generator, dry battery can be used to simulate the trigger signal of turning on and off the signal generator during testing. Because of the high trigger voltage at the input of electronic igniter, it is generally necessary to connect two dry batteries in series.
3. High voltage circuit fault detection
(1) When the secondary winding of the ignition coil is disconnected or in poor contact, turn off the ignition switch, remove the wire on the ignition coil, and measure the resistance value of the primary winding of the ignition coil with a multimeter. The secondary winding of the ignition coil has a smaller wire diameter and more turns, so the resistance value is also higher. The turns ratio of primary and secondary of automobile ignition coil is usually about 1: 100, that is, the turns of primary coil 1 and the turns of secondary coil 100. When measuring, the resistance value of the secondary coil is usually between 8000 ~16000 Ω (if it does not meet the requirements, the ignition coil needs to be replaced).
(2) The channeling and leakage of the distributor cover can be handled in the following ways. (1) If there is electric leakage between the distributor cover sockets or the distributor housing, the dirt at the electric leakage or leakage can be scraped clean. If there is carbon deposit, remove it and bake it with low fire. (2) If the distributor cover cracks and leaks, drill holes in the middle of the cracks and use air insulation to prevent leakage; You can also drill a crack stop hole at both ends of the crack to prevent the crack from extending, and then open a V-shaped groove at the crack, melt the insulating materials such as adhesive, battery sealant, asphalt or lacquer wax and drop them into it, and then use them after solidification. (3) If there is electrical channeling between the central jack and individual branch jacks, the high-voltage line of the cylinder can be unplugged and insulated, so that the engine can work without a cylinder. Pay attention to running in low gear at this time.
(3) When the high-voltage side electrode in the distributor cover is polluted, wipe it clean.
(4) When the carbon contact of the distributor cover is worn to the limit or the spring on it is broken, it can be replaced.
(5) Inspection of high voltage conductor. Check the resistance of high voltage conductor with ohmmeter. The resistance of the central high-voltage line is 0 ~ 2.8kΩ, and that of the branch high-voltage lines is 0.6 ~ 7.4kΩ. It can be checked according to the vehicle type. If the result is not within the specified value range, the high-voltage conductor should be replaced. If the insulation layer on the surface of high-voltage conductor has cracks, it should also be replaced in time.
(6) For the ignition head with slight leakage, sand paper or file can be used to polish the leakage. If there is a crack in the distributor, it can be leached and dissolved and then dripped into the crack, and can be used after reassembly.
(7) Inspection of spark plugs. Check whether the spark plug is severely ablated. If the electrode is severely ablated, replace the electrode. If the spark plug accumulates carbon or oil, it can be cleaned with gasoline and brushed with copper wire if necessary. For clean spark plugs, check and adjust the spark plug electrode gap, and the specified value is 0.7 ~ 0.9 mm (adjusted according to the vehicle type).
Spark plug is a high-voltage component, and its working voltage is about 10000 volts. Therefore, it is not appropriate to use a multimeter when measuring insulation, and a 2500V insulation resistance meter (megger) should be used for measurement. Clamp the two wires of megohmmeter on the middle electrode and thread of the spark plug (the spark plug is placed on the dry ground), shake the megohmmeter at a uniform speed to about 120 rpm, and then read the reading. The insulation resistance of spark plug should be infinite.
(Author: Xinjiang Railway Senior Technical School)