The following explains the mechanism by which the IC regulator keeps the generated voltage constant and how it operates to achieve this function using a battery sensing type IC regulator as an example.
1.Normal operation
(1)When ignition switch is ON and engine stops
When the ignition switch is turned on, battery voltage is applied to the IG terminal. As a result, M•IC circuit is activated and Tr1 becomes on, causing the rotor coil to allow the field current to flow. In this condition, electricity is not generated, so the regulator decreases the battery discharge as much as possible by turning Tr1 on and off intermittently. At this time, voltage at terminal P is 0 V and M•IC detects this condition and then transmit the signal to Tr2 to turn the charge warning light on.
(2)When alternator is generating electricity (when below the regulated voltage)
The engine starts and the alternator speed increases, M•IC turns Tr1 on to allow sufficient field current to flow, and the generated voltage is suddenly built up. At this time, if the voltage at terminal B exceeds the battery voltage, electricity flows into the battery to charge and is supplied to the electric devices. As a result, battery voltage at terminal P increases. Therefore, M•IC determines that generation is performed and transmits the off signal to Tr2 to turn the charge warning light off.
(3)When alternator is generating electricity (when above the regulated voltage)
If Tr1 continues on, the voltage at terminal B increases. Then, the voltage at terminal S exceeds the regulated voltage, M•IC detects it and turns Tr1 off. As a result, field current of the rotor coil attenuates via the reverse electromotive power absorption diode D1 and the voltage at terminal B (generated voltage) decreases. Then, if the voltage at terminal S decreases below the regulated voltage, M•IC detects this and turns Tr1 on. Therefore, field current of the rotor coil increases and the voltage at terminal B (generated voltage) also increases. IC regulator regulates the voltage at terminal S (battery terminal voltage) constant (regulated voltage) by repeating the above operations.
2.Abnormal operation
(1)When rotor coil is open
While alternator revolves, if the rotor coil becomes open, alternator stops generating electricity and the output voltage at the terminal P becomes 0 V.
When M•IC detects this condition, it turns Tr2 on to turn on the charge warning light in order to indicate the abnormality.
(2)When rotor coil is short
While alternator revolves, if the rotor coil becomes short, the voltage at terminal B is directly applied to terminal F and a large amount of current will flow. When M•IC detects this condition, it turns off Tr1 to protect and turns Tr2 on at the same time to turn on the charge warning light in order to indicate the abnormality.
(3)When terminal S is disconnected
While the alternator revolves, if terminal S becomes open condition, M•IC detects “no input signal from the terminal S” to turn Tr2 on to turn on the charge warning light. At the same time, in the M•IC, terminal B works as a substitute for terminal S to regulate Tr1 so that the voltage at terminal B becomes the regulated voltage (approx. 14 V) in order to prevent the abnormal increase of the voltage at terminal B.
(4)When the terminal B is disconnected
While the alternator revolves, if the terminal B becomes open condition, charging to the battery is not performed and the battery voltage (voltage at the terminal S) gradually decreases. When the voltage at the terminal S decreases, IC regulator increases the field current to further generate electricity. As a result, the voltage at the terminal B increases more and more. However, M•IC regulates the field current so that the voltage at the terminal B does not exceed 20V to protect the alternator and IC regulator.
When the voltage at the terminal S becomes low (approx. between 11V and 13V), M•IC judges that the battery is not charged. Then it turns Tr2 on to turn on the charge warning light and regulates the field current so that the voltage at the terminal B decreases at the same time to protect the alternator and IC regulator.
(5)When between terminal F and terminal E is short
While alternator revolves, if between the terminal F and terminal E is short, the voltage at the terminal B is grounded from the terminal E via the rotor coil without passing through Tr1. As a result, [the output voltage of alternator] becomes over voltage because the field current cannot be regulated by Tr1 even if the voltage at the terminal S exceeds the regulated voltage. If M•IC detects this condition, it turns Tr2 on to turn on the charge warning light and indicates the abnormality.
1.Operation of alternator sensing type IC regulator
The basic operation of this type is equal to that of battery sensing type, but the alternator sensing type IC regulator has no terminal S that detects the battery voltage. So, M•IC directly detects the generated voltage from the alternator at the terminal B and regulates the generated voltage of the alternator and controls the charge warning light.
2.IC regulator with terminal M
(1)Role of terminal M
For the vehicle with PTC power heater*, if PTC power heater is used at the engine idling, the amount of electricity consumed is larger than that generated at the alternator.
Terminal M is installed. Terminal M transmits the generating condition of the alternator to the engine ECU via Tr3 that synchronizes with Tr1 that regulate the field current.
The engine ECU controls the engine idle up and the PTC power heater according to the signal from the terminal M.
* PTC power heater: This heats the engine coolant when the heater effect is insufficient (built in the heater core).
(2)Operation
Since Tr3 is connected so that it synchronizes with Tr1, when the Tr1 becomes on, Tr3 also becomes on. The terminal M outputs this change by the pulse signal.
When PTC power heater ON
When PTC power heater OFF