Control Logic of ME1788 System
1)Control of Oil Injection Amount
In the electric control oil injection system,when the structure and oil injection pressure differential of oil injector are fixed,the control of oil injection amount is realized by controlling the oil injection time of oil injector(injection pulse width).
Oil Injection Time=Basic Injection Time×(Correction Coefficient)+Ineffective Injection Time
（1）Basic injection time.
The original oil injection time is calculated by air flow meter or intake air pressure sensor.
（2）Correction Coefficient.
Mainly include the correction coefficient related with the temperature,acceleration/deceleration running correction coefficient,large-load high rotation speed correction coefficient,theoretical air-fuel ratio feedback coefficient,namely,short-term correction,and study control correction coefficient,namely,long-term correction etc.
（3）Ineffective injection time.
Due to the slow increase of oil injection coil electrifying current,there is a certain period of time between being electrified and complete openness of the oil injector,which is called ineffective injection time.The voltage has some effect on the ineffective injection time,and low voltage and long ineffective injection time will increase the injection pulse width.Fig.4.4 is the wave shape of CX70 oil injector working,and the blue curve is the wave shape of the voltage and the red curve is the wave shape of the current.
Fig.4.4 Oil Injection Wave Shape of CX70 Oil Injector
2)Control of Ignition
（1）Control of Ignition Advance Angle
Ignition Advance Angle=Original Ignition Advance Angle+Basic Ignition Advance Angle+Correction Ignition Advance Angle
①Original ignition advance angle.
When the engine just starts or the rotation speed is below the stipulated one,due to the unsteady signal of intake manifold pressure or intake air amount,the ignition moment is fixed as the original ignition advance angle.This advance angle is controlled by the back-up circuit of ECU and needs no calculation processing.
②Basic ignition advance angle.
Confirm the basic ignition advance angle according to the intake manifold pressure or intake air amount signal,rotation speed signal,throttle position signal and air conditioner switch.The advance angle should increase with the increase of rotation speed and decrease with the increase of the load.(https://www.daowen.com)
③Correction ignition advance angle.
Mainly include the warming up correction,idling stability correction,air-fuel ratio feedback correction and overheat correction etc.
（2）Control of Electrifying Time.
Electrifying time is confirmed by ECU in accordance with the engine’s rotation speed signal and power voltage signal.The best closing angle(ignition conductive time)should,on the premise of not affecting the spark discharge,ensure that the ignition coil has enough time to store the energy without causing overheating loss and damage.When the secondary voltage is fixed,adjust the conductive time of primary circuit according to the battery’s voltage.
（3）Control of Detonation.
When the engine detonation appears,ignition stagnation(Reducing the ignition advance angle)will continue several work loops,and then will gradually recover to the original ignition moment.Do the ignition stagnation adjustment to the cylinders independently(Adjusting the cylinder set selectively)
3)Control of Starting
During the starting process,use the special calculation method to control the intake air amount,oil injection and ignition timing.Before the rotation speed of engine reaches the certain value,fill the rich mixture.Once the engine starts running,the system reduces the filling of rich mixture immediately until the starting operation is over.Under the starting condition,the ignition angle keeps being adjusted and changes with the change of engine temperature,intake air temperature and engine’s rotation speed.
4)Control of Warming Up and Three-way Catalytic Converter Heating
When the engine starts in low temperature,the intake air amount in cylinder,fuel injection and electronic ignition all are adjusted to make up for the engine’s higher torque requirement;the process will continue until the temperature reaches the appropriate value.In that phase,the most important part is the quick heating of three-way catalytic converter,because quick transfer to the work of three-way catalytic converter will greatly reduce the exhaust emission.In this case,use the method of delaying the ignition advance angle appropriately to do“heating of three-way catalytic converter”with the exhaust.
5)Control of Acceleration/Deceleration and Towing Astern Oil Cut-off
When the throttle’s open degree increases,partial injected oil is absorbed by the oil film.Therefore,it is a necessity to inject the corresponding amount of oil to make up for it and prevent the mixture from becoming thinner when accelerating.Once the load coefficient decreases,the additional oil contained in the oil film on the pipe wall of intake manifold will be released again,then,during the deceleration process,it is a necessity to reduce the corresponding injection continuous time.
Towing astern or towing condition means when the power provided by the engine for the flywheel is negative value.In this case,the engine’s friction and pumping gas loss can be used to decelerate the vehicle.Besides,under this condition,oil injection is cut off to reduce the oil consumption and exhaust emission,and more importantly,to protect the three-way catalytic converter.
6)Control of Idling
The control strategy of ME1788 system based on the torque mainly confirms the engine output torque needed to sustain the required idling rotation speed under any condition by controlling the close loop idling.The output torque increases with the decrease of engine’s rotation speed and vice versa.
7)Control of Evaporation Emission
In the system,oil evaporation is collected in the activated carbon canister through the conduit pipe and at appropriate time,will be flushed into the engine to take part in the combustion process.The flow amount control of flush air flow is realized by ECU controlling the carbon canister control valve.