Charging System: Description and Operation
NOTE: The Insight is a hybrid vehicle, for information on the charging system refer to Hybrid Drive Systems.IMA System
The IMA (Integrated Motor Assist) system is a high efficiency hybrid system that consists of a gasoline-powered engine and an electric motor.
The IMA system uses the engine as its main source of power and the motor as a supplemental source of power. By using the two units, overall weight is lower than a powertrain which uses only an electric motor as its source of power.
High voltage DC circuits such as the battery module, junction board, PCU (Power Control Unit), etc. are stored in the IPU (Intelligent Power Unit), which is located at the rear of the car for efficient packaging and for safety.
The engine is an inline 3-cylinder, SOHC, 12-valve engine that displaces 0.995 liter. It is a sequential multipoint fuel injected engine specially developed for the IMA system.
The motor is a DC brushless type located between the engine and the transmission. In addition to providing assist to the engine, it starts the engine and it acts as a generator to recharges the battery.
The MCM (Motor Control Module) controls the motor through the MPI (Motor Power Inverter) module and the voltage control unit. The MCM determines the amount of assist and regenerative power needed by communicating with the BCM (Battery Condition Monitor) module to prevent excessive battery drain and to prevent battery overcharging.
The 144 V Ni-MH (nickel-metal hydride) battery is used as the source of energy for the motor. Power to the car's conventional 12 V circuits is supplied by the battery module with voltage reduction done though the DC-DC converter.
Motor Assist (acceleration)
During acceleration, the motor assists the engine by generating up to 49 Nm (5 kg.m, 36 lb.ft) of torque. The motor assists the engine until the BCM determines the battery state of charge is at or below a predetermined limit. At that point, motor assist will stop to prevent battery discharge.
Regenerative Control (deceleration)
During deceleration, the motor functions as an electrical generator to charge the battery. Kinetic energy that is normally wasted during braking is transformed into electrical energy. The motor will charge the battery until the BCM sees that the battery state of charge reaches a predetermined limit. At that point, the motor stops regeneration to prevent battery overcharge.
Starter Function (at start-up)
The motor starts the engine under normal conditions. Because the motor is directly connected to the engine's crankshaft, it is much quieter and smoother than conventional starter. When outside temperature is extremely low, when the battery state of charge is low, or if there is a problem with the IMA system, the conventional starter is used to start the engine.
Auto-Stop System
Under certain conditions, the ECM automatically stops the engine to conserve fuel and minimize tailpipe emissions when the car comes to a stop. The Auto-Stop indicator will come on, either as a steady light or as a blinking light, to warn the driver that the Auto-Stop system is on.
The engine will not stop and enter Auto-Stop mode under the following conditions:
- When the transmission is in 1st gear or reverse gear.
- When the AUTO or DEF button of the climate control unit is pushed, or when the passenger compartment temperature has not stabilized at the set temperature.
- When the engine coolant temperature is approximately 122 °F (50 °C) or below.
- For approximately 2 minutes after starting the engine.
- When the battery state of charge is low.
- When the electric load on the 12 V system is high.
- When the accelerator pedal is pressed.
- When an Auto-Stop related component is faulty.
When the engine is stopped by the Auto-Stop function, it will restart under the following conditions:
- When the transmission is moved into any position other than neutral with the clutch pedal pressed
- When the accelerator pedal is pressed while the transmission in neutral and the clutch pedal is pressed.
Idle Vibration Reduction
The IMA system is equipped with an Idle Vibration Reduction control function that minimizes fluctuations in the engine's crankshaft. The motor applies opposite phase torque to the engine when the crankshaft is rotating.
IMA Motor
The motor is a synchronous AC type that serves three functions: it converts kinetic energy into electrical energy, it assists the engine during acceleration, and it starts the engine.
The motor is located between the engine and the transmission. It consists of a three-phase coil stator and a permanent magnet rotor that is directly connected to the engine crankshaft. Three commutation sensors are mounted inside the housing to detect the position of the rotor.
MCM (Motor Control Module)
The MCM controls the amount of assist that the motor produces and the amount of regenerative power that the motor absorbs based on input from the ECM and the BCM. The MCM convents 144 V DC power into three-phase AC power required during assist, and converts AC power into DC power during regeneration.
The MCM also communicates with the PGM tester via the 16P data link connector for better serviceability. If any sensors or circuits in the IMA system are abnormal, the MCM turns on the IMA system indicator to warn the driver that there is a problem.
Battery Module
A light-weight and compact Ni-MH (nickel-metal hydride) battery is used to supply energy to the IMA system.
The battery is made up of 20 modules that are connected in series. Within each module are six 1.2 V cells. Total battery voltage is 144 V and maximum capacity is 6.5 Ah.
The battery module has four built-in thermistor-type temperature sensors, and a PTC (positive temperature coefficient) -type temperature sensor for each cell.
BCM (Battery Condition Monitor) Module
The BCM module determines the battery state of charge, and it controls the battery fan speed by looking at battery voltage, battery input/output current, and battery temperature. The BCM module then sends this information to the MCM to indicate the battery's state of charge and to keep the battery within predetermined limits.
Because battery charging and discharging generates heat in the battery module, the BCM module also controls a fan that keeps the battery module from overheating. The fan operates in one of three modes: off, low, or high.
If the BCM module detects an abnormality, it sends a signal to the MCM, which then turns on the IMA system indicator on the gauge assembly.
Junction board
The junction board, mounted on the battery module, houses high voltage components of the IMA system. The battery module switch, contacts, fuses, and the current sensors are all located on the junction board.
Battery Module Switch
The battery module switch is connected in series to the battery module fuse. Always turn the battery module switch to the OFF position whenever service or checks are required on or around the high voltage circuits. Follow these steps exactly:
1. Remove the switch cover from the IPU lid, then turn the switch OFF.
2. Wait at least 5 minutes.
3. Remove the IPU lid.
4. Measure voltage at the output terminals. Make sure the voltage is low enough for safe operation before any service is done to the car.
Contactors
The high voltage contactor and bypass contactor are connected at the positive (+) output side of battery module. These contactors are controlled by the MCM, connecting the battery to the high voltage circuits. The current flows through the bypass contactor and bypass resistor first, protecting the system from current spikes.
PCU (Power Control Unit)
The PCU consists of the MDM, the DC-DC converter, and a heat sink that cools these units. These components are integrated into one, compact unit. The fan circulates air over the heat sink, and cools the MDM and the DC-DC converter.
MDM (Motor Driver Module)
The MDM consists of the MPI module, voltage converter module, capacitor, and the U/V/W phase motor current sensors. The voltage converter acts as a preamplifier for the IGBTs. The IGBTs are used to transfer electrical energy to the motor from the 144 V battery and vice versa. The IGBTs are activated by the MCM based on the amount of assist/regeneration is needed. The voltage converter module monitors voltage and temperature of the MDM, and sends this information to the MCM.
DC-DC Converter
Instead of using an alternator to maintain the 12 V battery, the electrical system uses a DC-DC converter. The converter converts high voltage direct current into low voltage direct current with little energy loss.
The DC-DC converter will illuminate the charging system indicator in the gauge assembly if a problem is detected in the 12 V charging system.
The DC-DC converter has a temperature monitoring system that will signal the MCM if its temperature is abnormally high. If needed, the MCM can signal the DC-DC converter to shut down.