IMA System Description
IMA System Description
MCM Inputs and Outputs at Connector A (31P)
MCM Inputs and Outputs at Connector B (24P)
MCM Inputs and Outputs at Connector B (24P)
MCM Inputs and Outputs at Connector C (22P)
MCM Inputs and Outputs at Connector C (22P)
MCM Inputs and Outputs at Connector E (31P)
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 generation 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 100 V DC battery, a control system, and related parts. For safety, the intelligent power unit (IPU) is located under the cargo compartment.
The IMA system improves fuel economy by capturing and storing energy during deceleration.
Operating Conditions
1. Engine start:
The IMA system drives the IMA motor and starts the engine during normal starts and when re-starting from an idle stop. The IMA motor is linked directly to the engine crankshaft.
2. Start running:
The IMA motor assists the engine.
3. Slow acceleration:
Runs only with the engine.
4. Low speed cruise:
At a constant speed of about 25 mph (40 km/h) with light load, all engine cylinders are deactivated, and the vehicle runs only with the IMA motor. When the state-of-charge (SOC) drops, the engine starts and the IMA motor begins to charge the battery module.
5. Acceleration:
The IMA motor assists the engine.
6. High acceleration:
The IMA motor assists the engine.
7. High speed cruise:
Runs only with the engine. When the state-of-charge drops, the IMA motor begins to charge the battery module.
8. Deceleration:
All engine cylinders are deactivated, and the IMA motor captures the deceleration energy and charges the battery module.
9. Stop:
When conditions are satisfied, the PCM stops the engine automatically (auto stop).
When the battery module charge is at or above a specific value
When the SOC of the battery module is at or above a specific value, the generation amount is restricted to prevent overcharging. Since regenerative braking force is insufficient at this time, the PCM cancels full cylinder deactivation and increases engine braking power.
When the battery module charge is at or below a specific value
When the SOC of the battery module drops, idle speed is increased in each shift position to charge the battery module.
When the battery module SOC value is low, selecting the L range mode gives priority to battery module charging by lowering the IMA motor assist level, increasing the idle speed, and increasing the regeneration amount CVT System Description - Electronic Control System. Charge priority control is canceled when the battery module state-of-charge reaches about 40 percent.
When the engine cannot be started with the IMA motor
Based on signals from the MCM, when the SOC value drops, when the temperature is low, or when there is a problem with the IMA system, the PCM judges that the engine cannot be started by the IMA, so it is started by the starter motor.
Auto Idle Stop System
To reduce fuel use and to minimize tailpipe emissions, auto idle stop system shuts off the engine by stopping fuel injection when the vehicle comes to a stop.
Based on inputs from various sensors and control units, the PCM may or may not allow auto idle stop under different operating conditions.
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 a warning buzzer sounds to remind the driver that auto idle stop is in operation.
Auto Idle Stop Conditions
NOTE:
- Each of the conditions below must be met before the engine goes into auto idle stop.
- The engine may not go into auto idle stop if DTCs in any of these systems are stored: PGM-FI, IMA, CVT, or climate control.
Engine Restart Conditions
NOTE: The engine restarts when one or more of the conditions below are met.
ECT/IAT Auto Idle Stop Conditions
Auto idle stop is disabled by the PCM when the engine coolant and the outside air temperatures are in the range shown below. The thresholds vary, depending on whether ECON ON or ECON OFF is selected.
- ECON ON: The PCM determines a minimum coolant temperature, based on the outside air temperature.
- ECON OFF: The PCM determines a minimum coolant temperature and a minimum/maximum outside air temperature.
- Cooling System Monitoring: Auto idle stop is disabled while the PCM monitors the cooling system for failures. Monitoring occurs during cold engine warm up.
Brake Booster Vacuum Auto Idle Stop Conditions
Auto idle stop is disabled when there is not enough vacuum in the brake booster. The amount of needed vacuum depends on the barometric pressure.
SOC/Battery Temperature Auto Idle Stop Conditions
Auto idle stop is disabled when the IMA battery module state-of-charge (SOC) becomes too low, or the battery temperature becomes too hot or too cold.
In-Vehicle Humidity Auto Idle Stop Conditions
Auto idle stop is disabled when the climate control unit anticipates windshield fogging. The threshold depends on outside air temperature, the in-vehicle temperature, and the in-vehicle humidity. To determine the approximate auto idle stop threshold for the ambient conditions of the vehicle, use the instructions and the graph below:
NOTE: Make a copy of this page to record your results on the graph.
10. Using the climate control sensor input display mode of the HDS, record the outside air temperature (SENSOR 3), the in-vehicle temperature (SENSOR 2), and the in-vehicle humidity (SENSOR A).
11. Draw a vertical line from the outside temperature value to the 80 percent relative humidity curve.
12. Draw a horizontal line from the 80 percent intersection to the right side of the graph.
13. Draw a vertical line from the in-vehicle temperature value to the top to the graph.
- The auto idle stop humidity threshold is where the lines cross. Auto idle stop is disabled when the in-vehicle humidity is above this point, and it is enabled when the humidity is below this point.
- In the example below, auto stop is disabled when the in-vehicle humidity exceeds about 30 percent. This is determined by an outside temperature of 45 °F (7 °C) and an in-vehicle temperature of 72 °F (22 °C).
The auto idle stop enable time depends on how close the in-vehicle humidity is to the calculated humidity threshold. The closer the in-vehicle value is to the threshold, the shorter the auto idle stop enable time will be. Auto idle stop may not occur if the values are too close.
Climate Control Unit Auto Idle Stop Conditions
The climate control unit calculates a maximum time for auto idle stop. This time depends on whether ECON ON or ECON OFF is selected.
- ECON ON: In this mode, the climate control unit prioritizes fuel consumption and calculates the longest time possible before the windshield may fog. The engine restarts when the time expires.
- ECON OFF: In this mode, the climate control unit prioritizes passenger comfort and calculates the time before the in-vehicle temperature would become uncomfortable. The engine restarts when the time expires. This time is typically shorter than when ECON ON is selected.
Intelligent Power Unit (IPU)
The IPU consists of the power control unit (PCU), the battery module, and the junction board. The IPU is located under the cargo compartment to lower the center of gravity of the vehicle and to increase space in the vehicle interior.
Power Control Unit (PCU)
The PCU consists of the motor control module (MCM), the DC-DC converter, the motor power inverter (MPI) module, and the phase motor current sensor.
The MCM controls the IMA motor and monitors the condition of the battery module.
Motor Control Module (MCM)
The MCM calculates the battery module SOC and controls the IPU module fan. The SOC is calculated using voltage, temperature, input current, and output current readings of the battery module.
The MCM controls the DC/AC conversion between the battery module 100 V DC to the 3-phase AC IMA motor.
The MCM also controls the IMA motor assist and regeneration.
Motor Power Inverter (MPI) Module
The MPI module converts 100 V DC power into 3-phase AC power to run the electric motor during assist.
During regeneration, the MPI module converts AC voltage to DC.
The MPI module is air cooled. The heat from the heat sink is exhausted to the cargo area by the IPU module fan.
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 via the MCM.
The DC-DC converter has a built-in temperature sensor that sends temperature information the MCM. When the DC-DC converter temperature rises, the MCM drives the IPU module fan. If the DC-DC converter temperature rises abnormally, DC-DC converter output is limited. If the temperature continues to rise, the DC-DC converter output is stopped.
Heat generated by the DC-DC converter is exhausted to the cargo area by the IPU module fan.
IMA Motor
The IMA motor is a synchronous AC type unit that converts electrical energy into kinetic energy and vice versa. It assists the engine during acceleration, runs the vehicle during low speed cruise, 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 seven blocks that are connected in series. Within each block are 12 1.2 V cells. The total battery voltage is a nominal 100 V.
The battery module has three built-in thermistor temperature sensors to monitor battery temperature.
Junction Board
The junction board is mounted on the battery module, and it distributes high voltage energy within 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.
Battery Module Switch
The battery module switch is connected in series with 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.
Battery Current Sensor
The battery current sensor detects the input and output current of the battery module. The current detected by the sensor is used to compute the battery SOC.
IPU Module Fan
The battery module, the MPI module, and the DC-DC converter generate heat during assist/regeneration. The IPU is equipped with a fan to cool these parts, to assure proper battery performance, and to protect the system. The fan has a control circuit and rotation sensor that are controlled by the MCM. When the temperature of the battery module, the MPI module, or the DC-DC converter exceeds the specified value, the MCM operates the IPU module fan. The cooling air is drawn into the battery module from the left side of the rear seat, then it is exhausted into the cargo area through the MPI module heat sink and the DC-DC converter heat sink.
Power Cables
The IMA motor power cables connect the IMA motor to the MPI module. The cables feed through an aluminum tube for damage protection and to prevent electrical noise. The DC-DC converter cable is also contained inside the aluminum tube. The tube is attached to the underside of the vehicle by orange clamps.
