As people's living standards continue to improve, cars are entering more and more families. When people travel, they only need to start the vehicle motor with a key. Even with a single button start, they can drive the car to where we want to go and enjoy the convenience that technology brings to us. However, many people who own a car don't understand how the motor changed from static to normal during the start-up of the vehicle. Today, the Eaton Char-lynn Motor takes everyone to discuss how the motor is started.
The motor start can be divided into three stages: the injection pressure stage is established; the motor control unit determines the cylinder ignition stage; the ignition is successfully converted to the idle stage.
The motor must first establish the injection pressure before starting the ignition. The fuel of the direct injection motor is injected into the cylinder at a certain pressure, so that it can be atomized and fully and evenly mixed with the air. The pressure value is based on the calibration condition. Change with the conditions. Both the gasoline pump and the diesel pump are directly driven by the gears at the crankshaft end of the motor. After the oil pump rotates, the fuel is sucked from the fuel tank and sent to the closed rail to establish the pressure. Usually, the fuel pump can build hundreds of bars in less than one second. The pressure value to meet the needs of fuel injection and atomization. When the oil pressure reaches the injection pressure, the motor will start to inject fuel, and the fuel injection into the cylinder will start to burn after ignition through the spark plug to provide power for starting.
When the motor is ignited, it is necessary to determine the firing order of each cylinder and determine the ignition advance angle. For example, an in-line 4-cylinder motor is usually used as the first cylinder near the fan end, and the ignition sequence is one, three, four, two, so the motor is in the first After the ignition of one cylinder is completed, the three, four, and two just fires are sequentially performed, and the time interval is the rotation time of the crank angle of 180 degrees. Then how does the motor judge the specific identity of the four cylinders? There are two sensors that cannot be separated: the crankshaft speed sensor and the cam speed sensor. Crankshaft and cam speed sensors are typically Hall-type, using the principle that a particular area of the magnetic field changes will induce an induced current in the corresponding loop. Usually, the gear of the crankshaft sensor end has 60 evenly distributed convex teeth, and two adjacent convex teeth are removed, and the cam is usually Z+1 convex teeth, and Z is the number of cylinders. When the crankshaft drives the cam to rotate, the convex teeth of the two shaft ends pass through the respective Hall sensors, and an induced current is generated. The motor has one working cycle. The crankshaft rotates two 720-degree sensors and there are 116 induced current signals. When the cam rotates 360 degrees, there will be five induced current signals. The position of the top dead center of the four cylinders can be determined according to the angular value of the crankshaft missing tooth signal and the cam tooth signal from the top dead center. At a certain moment, when the motor control unit detects the signals sent by the two sensors, It can be arbitrarily determined according to the calibrated angle value whether a certain cylinder is about to reach the top dead center position, and the fuel injection and ignition are performed. After the cylinder is judged, the motor needs to determine the ignition advance angle according to the specific ambient temperature, atmospheric pressure, etc., that is, the motor ignition is not when the piston is at the cylinder top dead center position, but is advanced or delayed by a certain angle as needed. These values will be calibrated for specific angle values based on different conditions, so the true ignition angle at motor start-up should be within a certain range near top dead center.
During start-up, the initial state of the motor is stationary and the motor needs to be driven by the starter motor. When the key is rotated to the ignition position and held, the main relay of the motor control circuit is started to be engaged, and the motor starts to rotate after being energized, so that the cam shaft and the crankshaft rotate together under the driving of the motor, and the sensor signal also generates a corresponding sensing signal. The starting motor speed has a set value. During the continuous acceleration of the motor, the state of the motor can be divided into three stages according to the speed value. The first stage is the motor injection stage. Most of the current motors are direct injection in the cylinder. The motor needs to accelerate to the constant speed to drive the oil pump to establish sufficient pressure. This pressure value can atomize the fuel well and spray it into the cylinder. In order to mix well with the air and burn well. Before the motor speed reaches the injection speed, the motor itself has no power generation and output, and can only be driven by the motor. The second stage is the successful start-up phase. Once the motor reaches the injection speed, the motor can use the energy generated by the combustion to power the start, so the final speed will exceed the set speed of the motor. However, at this stage, the motor's overall speed is low, the combustion is unstable, and even if the motor speed is exceeded, there is a possibility of flameout. Therefore, the motor control unit sets a speed value, and it is considered that the motor start speed exceeds this value and has been successfully started. The third stage is the idle phase. After the motor reaches the successful start speed value, if the driver does not step on the accelerator pedal, the motor will change from the start state to the idle state. During the conversion of these two states, the motor speed will be further increased, and the closed-loop control by the control unit will enable it to reach the idle speed quickly, accurately and stably. Usually, the motor will be stable after a short period of speed fluctuation. Run at idle speed.