Hybrid Drive Systems: Description and Operation

IMA System Description

MCM Inputs and Outputs at Connector A (31P)









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)











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 16-valve power plant with a displacement of 91 cu. in (1.5 liters). To reduce fuel use, the engine is equipped with an auto idle stop system and i-VTEC.

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.

The IMA system contains a 100 V DC battery, an IMA motor, an intelligent power unit (IPU), an IMA motor power cable, a control system, and related parts. The IPU contains a battery module, a motor control module (MCM), a DC-DC converter, and a motor power inverter.

The IMA system improves fuel economy by capturing energy with the electric motor during deceleration, and using that energy to charge the IMA battery.






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 mounted directly to the engine crankshaft.
2. Start running (Engine operation and motor assist):
The IMA motor assists the engine.
3. Slow acceleration (Engine-only operation):
Runs only with the engine.
4. Acceleration (Engine operation and motor assist):
The IMA motor assists the engine.
5. High speed cruise (Engine-only operation):
Runs only with the engine. When the state of charge (SOC) drops, the IMA motor begins to charge the battery module.
6. Deceleration (Battery module charging):
The IMA motor converts the deceleration energy and charges the battery module.
7. Stop (Auto idle stop):
When conditions are satisfied, the ECM/PCM stops the engine automatically.





System Diagram





When the battery module state-of-charge (SOC) is at or above the specified value

When the SOC of the battery module is at or above the specified value, the generation amount is restricted to prevent overcharging. Since regenerative braking force is insufficient at this time, the ECM/PCM increases engine braking power.

When the battery module state-of-charge (SOC) is at or below the specified value

When the SOC of the battery module drops, idle speed is increased to charge the battery module.
CVT model: 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 - General Operation. Charge priority control is canceled when the battery module SOC reaches about 40%.

When the engine cannot be started with the IMA motor

Based on signals from the MCM, when the SOC value drops, when temperature is low, or when there is trouble with the IMA system, the ECM/PCM judges that the engine cannot be started by the IMA motor, so it is started by the 12V starter motor.

3-Mode drive system

M/T model: When the SPORT mode is selected, the MCM increases the IMA motor assist amount more than in NORMAL and/or ECON mode to improve acceleration.

Auto Idle Stop System

To reduce fuel use and to minimize tailpipe emissions, the auto idle stop system shuts off the engine by cutting the fuel injection.

Based on inputs from various sensors and control units, the ECM/PCM may or may not allow auto idle stop under similar operating conditions.

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.






Systems and functions affecting auto idle stop





Auto Idle Stop Conditions

1-Vehicle is stopping or is stopped (M/T model)

When the vehicle is stopped after driving at or above the specified speed, the engine stops when you fully press the clutch pedal and shift to neutral.
Shifting to any gear with the clutch pedal fully pressed restarts the engine.





2-Vehicle is stopping or is stopped (M/T model)

When the vehicle is stopped after driving at or above the specified speed in 2nd gear or higher, the engine stops when you fully press the clutch pedal and shift to neutral.
Shifting to any gear with the clutch pedal fully pressed restarts the engine.





1-Vehicle is decelerating (M/T model)

During deceleration, shifting to neutral from 2nd gear or higher enables auto idle stop. Releasing the brake pedal (1) or shifting into any gear (2) disables auto idle stop and restarts the engine.





2-Vehicle is decelerating (M/T model)

During deceleration, pressing the clutch pedal fully in 2nd gear or higher enables auto idle stop. Releasing the brake pedal (1) or releasing the clutch pedal (2) disables auto idle stop and restarts the engine.





Vehicle is stopping or is stopped (CVT model)

When the vehicle is stopped after driving at or above the specified speed, and the transmission is in D or N, the engine stops when you press the brake pedal.
Releasing the brake pedal disables auto idle stop and restarts the engine.






Restart by Climate Control Unit

M/T model

The ECM restarts the engine from auto idle stop if it is requested by the climate control unit. The restart happens after you press the clutch pedal and shift out of neutral.
When a request to restart is received, the auto stop indicator blinks more quickly than normal.





CVT model

The PCM restarts the engine from auto idle stop if it is requested by the climate control unit.

System Indicators

If there is an operation error or a system failure during auto idle stop, the error information is shown on the multi-information display (MID), the indicator in the gauge control module blinks, and the system buzzer sounds.

Opening the driver's door

If the driver's door is opened during auto idle stop, the auto stop indicator blinks and the system buzzer sounds to remind you that auto stop is in operation.

Clutch pedal is not fully pressed (M/T model)

If the clutch pedal is not fully pressed during auto idle stop, the engine does not restart because the system knows the transmission is in gear. If this happens, a message to fully press the clutch pedal appears on the MID.






Vehicle stopped for 5 minutes while in gear (M/T model)

During auto idle stop, if the transmission is in gear with the vehicle stopped for 5 minutes, a message to shift into neutral appears on the MID.
Shifting into neutral and then back into a gear resets the timer another 5 minutes. To restart the engine when this message appears, press the clutch pedal while the transmission is in gear.






Engine restart (M/T model)

If the system cannot restart the engine because of a battery module problem (low SOC, battery failure), a message on the MID tells you to restart with the ignition switch.
Even if the RESTART ENGINE message appears, you may still be able to start the engine with the IMA system by pressing the clutch pedal.






Disable Conditions for Auto Idle Stop (M/T model)

When any of the following conditions are met, auto idle stop is disabled.

















Disable Conditions for Auto Idle Stop (CVT model)

When any of the following conditions are met, auto idle stop is disabled.

















Engine Restart Conditions After Auto Idle Stop (M/T model)

When any of the following conditions are met, the engine restarts after idle stop.






Engine Restart Conditions After Auto Idle Stop (CVT model)

When any of the following conditions are met, the engine restarts after idle stop.






Auto Idle Stop Conditions

Battery module SOC

When the MCM determines that the remaining battery module state-of-charge (SOC) is within the idle stop enable area, it allows auto idle stop. When the battery module SOC goes below the idle stop enable area during idle stop, the MCM requests an engine restart from the ECM/PCM. To confirm the battery module SOC, use the HDS data list. An approximate SOC can also be determined by counting the segments in the battery module SOC indicator.










Battery module output

The MCM monitors the temperature of the battery module with the battery module temperature sensors. If the output of the battery module is within the idle stop enable area, the MCM allows auto idle stop. If the battery module enters the idle stop disable area, the MCM disables auto idle stop.






Outside air temperature and engine coolant temperature

The outside air and engine coolant temperatures affecting auto idle stop vary, depending on the A/C system mode and if ECON mode is on or off. When both the outside air and the engine coolant temperatures are within the idle stop enable area, the ECM/PCM allows auto idle stop. When the temperatures are within the idle stop disable area, the ECM/PCM prevents auto idle stop.










Auto Idle Stop Control by the Climate Control System

When you operate the climate control unit (except the OFF and RECIRCULATION functions), auto idle stop is managed by the climate control system. The climate control unit calculates the enabling/disabling and the allowable time for auto idle stop. This is based on the ECON mode, the battery module temperature, and signals transmitted from several sensors.





When idle stop is enabled, the ECM/PCM sets the allowable time in the idle stop cancellation counter. When the counter reaches zero, the engine restarts.
Turning on the defogger switch or selecting DEF on the mode switch causes the climate control unit to request an engine restart from the ECM/PCM.

Climate control unit decision criteria for auto idle stop

The decision criteria is based on which driving mode is selected, NORMAL, SPORT, or ECON. In ECON mode, the enabling of auto idle stop has a higher priority than in NORMAL or SPORT mode.
If the climate control unit calculates any time less than 10 seconds, auto idle stop is not enabled.

Request by the MCM to increase air volume of blower motor

When the temperature of battery module is high, the MCM signals the climate control unit for an increase in air volume from the blower motor. The climate control unit then increases the blower motor speed.

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 area 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 from the battery module.

The MCM controls the DC/AC conversion between the battery module 100 V 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 into 3-phase AC 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 volt 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 volt 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 and temperature information is sent to the MCM. When 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 assists the engine during acceleration, runs the vehicle during low speed cruise, starts the engine, and charges the battery module.

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. Each block generates 14.4 V. The total battery voltage is a nominal 100 V.

The battery module has three built-in thermistor temperature sensors to monitor battery temperature.






Battery module output control

The battery module output control maintains the battery module SOC and temperature. It also prolongs battery life by setting the correct limits for battery output to the IMA motor and battery input from charging. Without this control, the battery module would quickly deteriorate.
















Temperature control










Consecutive output control
To prevent battery module overheating and deterioration, the battery module output control manages the consecutive outputs of battery assist and sets an allowable amount.






Junction board

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. The junction board is mounted on the battery module, and distributes high voltage.






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.

Contactors

The high voltage contactor and bypass contactor are connected at the positive (+) output side of the battery module. These contactors are controlled by the MCM, connecting the battery module to the high voltage circuits. The current flows through the bypass contactor and the bypass resistor at start-up.
The bypass contactor and the bypass resistor are used during start up to charge the capacitors in the PDU, limiting the initial current.

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 module SOC.

IPU Module Fan

The battery module, the MPI module, and the DC-DC converter generate heat during charge/discharge. 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 a rotation sensor that are controlled by the MCM. When the temperature of the battery module, the MPI module, or the DC-DC converter exceeds a 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 cable connects the IMA motor and the MPI module. The cable feeds through an aluminum tube for damage protection and to prevent electrical noise. The 12 volt power cable from the DC-DC converter goes through the same aluminum tube. This tube is attached to the underside of the vehicle by orange-colored tube clamps.