IMA System Description
IMA System Description
BCM Module Inputs and Outputs at Connector A (40P)
NOTE: Standard battery voltage is about 12 V.
BCM Module Inputs and Outputs at Connector A (40P)
NOTE: Standard battery voltage is about 12 V.
BCM Module Inputs and Outputs at Connector B (14P)
MCM Inputs and Outputs at the MCM Connector (20P)
NOTE: Standard battery voltage is about 12 V.
MCM Inputs and Outputs at the MCM Connector (20P)
NOTE: Standard battery voltage is about 12 V.
IMA System
The IMA (integrated motor assisted) system is a highly-efficient parallel hybrid drive system with a main power unit (gasoline engine) and an assist unit (electric motor).
The engine is an in-line 4-cylinder 8-valve power plant with a displacement of 82 cu. in (1.339 liters). To reduce fuel use, the engine is equipped with i-DSI and a valve pause system that reduces engine pumping loss and increases the regeneration of electric energy during deceleration.
The IMA motor, directly connected to the engine crankshaft, functions as a generator during deceleration, an engine starter, and a motor to assist the engine that drives the wheels.
The IMA system contains a 158 V DC battery and a AC synchronous motor, a control system, and related parts. For safety, the intelligent power unit (IPU) is located behind the rear seat.
The IMA system improves fuel economy by capturing and storing energy during deceleration.
Operating Condition
Vehicle stop mode (Idle stop)
The engine stops idling if the IMA battery has enough electricity left.
Start running mode (Engine and IMA motor)
The engine runs with low lift cam. The IMA motor assists torque.
Slow acceleration mode (Engine only)
The engine runs with low lift cam. The IMA motor does not assist.
Low speed cruise mode (IMA motor only)
The IMA motor runs the vehicle by itself if the IMA battery has enough electricity left. The intake and exhaust valves pause to reduce valve spring compression and pumping loss.
Acceleration from low speed mode (Engine and IMA motor)
The engine runs with low lift cam. The IMA motor assists torque.
High acceleration from low speed mode (Engine and IMA motor)
The engine runs with high lift cam. The IMA motor assists torque.
High speed cruise mode (Engine only)
The engine runs with low lift cam. The IMA motor does not assist.
Deceleration mode (IMA battery charge)
The intake and exhaust valves pause to reduce engine braking force. The IMA motor provides engine braking force by charging the IMA battery.
Engine start
The IMA system drives the IMA motor, starts the engine at normal start, and restarts the engine after auto-stop. The IMA motor is directly connected to the engine crankshaft, so it is quieter than the 12 V starter. If a problem occurs with the IMA system, for example, low battery module state of charge (SOC), low temperature, faulty IMA system, etc, the PCM receives a signal from the MCM and starts the engine with the 12 V starter.
Motor assisting function
During acceleration, energy is supplied from the battery module to the IMA motor, and the motor generates a maximum torque of 103 Nm (10.5 kg-m, 76 lb-ft) to assist the engine. The PCM and MCM communicate to control the assist to maintain the battery module SOC within a specified range. When the battery module SOC is below the specified range, the MCM stops the assist to prevent over-discharge or damage to the battery. Assist is also not available when the IMA battery is very cold or very hot.
Regenerative control (at deceleration)
During deceleration, the IMA motor, driven by the wheels, functions as a generator. It charges the battery module by generating electrical energy. This is done by converting the kinetic energy of the vehicle during braking into electric energy that is stored in the IMA battery. When the battery module is full, regeneration stops to prevent overcharge of the battery.
Auto Idle Stop System
The auto idle stop system stops the engine when the vehicle comes to a stop to reduce overall fuel consumption and minimize tailpipe emissions. Refer to the chart to see the conditions when auto idle stop occurs and when it does not occur.
The PCM restarts the engine by signalling the MCM to drive the IMA motor and by restarting fuel injection. Refer to the chart to see the conditions of engine restart.
Auto Stop Indicator
When auto idle stop is operating, the auto stop indicator blinks. If the driver's door is opened during auto idle stop, the auto stop indicator blinks and the warning buzzer sounds to remind the driver that auto stop is in operation.
Battery Condition Monitor (BCM) Module
The BCM module computes the battery module state of charge (SOC) and controls the IPU module fan. The system's SOC is computed by the BCM module using voltage, temperature, input current, and output current readings from the battery module.
Motor Control Module (MCM)
The MCM converts 158 V DC power into 3-phase AC power to run the electric motor during assist. During regeneration, the MCM converts AC voltage to DC.
The MCM controls the DC/AC conversion (from the IMA battery's 158 V DC to the IMA motor's 3-phase AC, and vice versa).
The MCM is air cooled. The heat fed through the heat sink is exhausted to the trunk compartment and outside the vehicle by the IPU module fan.
The MCM controls the IMA motor to control the assist and regeneration.
IMA Motor
The IMA motor is a synchronous AC type that converts electrical energy into kinetic energy and vice versa. It assists the engine during acceleration and starts the engine.
The IMA motor is located between the engine and the transmission. It consists of a 3-phase coil stator and a permanent magnet rotor that is directly connected to the engine crankshaft. An IMA motor rotor position sensor is mounted on the back of the engine block to detect the position of the rotor.
Battery Module
A light-weight and compact Ni-MH (nickel-metal hydride) battery supplies energy to the IMA system.
The battery module has 11 blocks that are connected in series. Within each block are 121.2 V cells. Total battery voltage is a nominal 158 V, and maximum capacity is 5.5 Ah.
The battery module has three built-in thermistor temperature sensors to monitor the abnormal battery temperatures.
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 the service precautions High Voltage Safety.
Junction board
The junction board is mounted on the battery module, and it distributes high voltage energy to the IMA system. The junction board consists of a high voltage contactor, a bypass contactor, a bypass resistor, a battery current sensor, a fuse and a battery module switch.
'06-08 models
'09-11 models
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.
If a problem is detected in the 12 V charging system, the DC-DC converter turns on the charging system indicator by sending a signal to the gauge control module (tach) via the BCM module.
The DC-DC converter has a temperature monitoring system that will signal the BCM module if its temperature is abnormally high. If needed, the BCM module can signal the DC-DC converter to shut down.
Heat generated by the DC-DC converter is exhausted to the trunk compartment by the IPU module fan.
The DC-DC converter can also generate PGM-FI and/or IMA DTCs.
IPU Module Fan
The battery module, the MCM, the A/C compressor driver, and the DC-DC converter generate heat during assist/regeneration. The IPU is equipped with a fan to cool these parts down, assure proper battery performance, and protect the system. The fan has a control circuit and a rotation sensor that are controlled by the BCM module. The cooling air is drawn into the battery module from the top of the rear tray, then it is exhausted into the trunk compartment and outside the vehicle through the MCM heat sink, the DC-DC converter, and the A/C compressor driver heat sink.
Power Cables
The IMA motor power cable connects the IMA motor and the motor control module (MCM). The cable feeds through an aluminum tube for damage protection and to prevent electrical noise. The A/C compressor power cable also goes through the aluminum tube. Another aluminum tube, parallel to the IMA motor/A/C compressor tube, houses the DC/DC converter cable. These tubes are connected in one piece with a tube clamp (orange), and attached to the underside of the vehicle.
