Can the sensor signal only correspond to one actuator?

The electronic control unit (ECU) of modern vehicle engine, also known as electronic controller or electronic control component, commonly known as computer, is the core component of engine control system. The electronic control unit is mainly composed of three parts: input circuit, single chip microcomputer and output circuit. The main function of the engine ECU is to receive the engine working condition signals input by various sensors and control switches, determine the parameters suitable for the engine working condition, such as fuel injection time and ignition advance angle, through mathematical calculation and logical judgment according to the pre-programmed control program and test data stored in the ECU, and convert these parameters into electrical signals to control various actuators to perform actions, so as to keep the engine in the best running state. The ECU of modern automobile engine not only has the above control function, but also has the function of fault self-diagnosis and test. The ECU should monitor and identify the signals transmitted by the sensors when implementing the optimal control of the engine running state. When it is found that the signal parameters transmitted by a sensor are beyond the specified range, ECU will determine that the sensor or related lines are out of order; And the fault information is encoded and stored in the memory so as to be called during maintenance. For example, in the engine control system of Santana 2000GSi (see figure), when the circuit of the coolant temperature sensor is broken, the ECU will control the engine with the signal parameter of coolant temperature 19.5℃, so that the engine will run in a fault emergency state, and the car will be driven to a repair shop for repair. The executive mechanism of the electronic control system of modern automobile engine, also known as the executive element, is the executive mechanism of the control system, and its function is to receive the control instructions sent by the electronic control unit ECU and complete the specific execution actions. There are two kinds of actuators commonly used in engine electronic control system: ① electric fuel pump, which is used to supply fuel with specified pressure in engine electronic control system. ② Electromagnetic injector, which is used to receive the fuel injection pulse signal sent by ECU and measure the fuel injection quantity. ③ Idle speed control valve ISC or ISCV is used to adjust the idle speed of the engine. The control content includes two aspects. On the one hand, it is to stabilize the idle speed when the engine is running at normal idle speed to prevent the engine from stalling and reduce fuel consumption. On the other hand, when the engine is idling, when the engine load increases (such as turning on the air conditioner, power steering gear or hydraulic torque converter, etc. ), the idle speed will automatically increase to prevent the engine from stalling. ④ The solenoid valve of activated carbon tank is used to receive the control instruction from the electronic control unit, recover the fuel vapor inside the engine, and reduce the emission of hydrocarbons, thus reducing the exhaust pollution. ⑤ The ignition controller and the ignition coil are used to receive the control instructions sent by the electronic control unit, turn on or off the primary current of the ignition coil in time, and generate high voltage to ignite the combustible mixture. The switch signals commonly used in the electronic control system of modern automobile engines are: (1) The ignition switch signal ign is a signal indicating that the ignition switch is turned on. In the control circuit, when the ignition switch is turned to the "IG" position, a high-level signal is input to the ECU. The ignition switch turns on the power of the electronic control unit ECU (12V). At this time, ECU will control and execute the following actions: ① Idle control the stepping motor to enter the preset position; ② Determine the basic fuel injection time according to air flow or manifold pressure, atmospheric pressure and air temperature sensor signals; ③ According to the signal of the coolant temperature sensor, correct the fuel injection time and ignition time; ④ Monitor the throttle position sensor signal; ⑤ Open the fuel pump circuit. If the engine does not start (that is, the ECU does not receive the start signal STA), the ECU will cut off the fuel pump circuit after the fuel pump works about 1s; ⑥ Turn on the circuit of the oxygen sensor heating element to heat the sensor element; ⑦ In a car equipped with an automatic transmission, the upshift indicator lights up to show the position of the shift switch. (2) The starting switch signal STA is the signal that the ECU turns on the starter circuit, which comes from the starting relay or the ignition starting switch (the electrical system without the starting relay). When the ignition switch is turned to the "ST" position, a high level signal is input to the ECU. The starting signal is input to ECU from the starting relay contact. After receiving the start signal STA, the ECU performs the following control actions: ① In addition to monitoring the input signal when the ignition switch is turned on, it also starts to monitor the input signals of the crankshaft position sensor CPS and the camshaft position sensor CIS, and determines the ignition time and fuel injection time according to these signals. Firstly, which cylinder is about to reach the top dead center is judged, and then the fuel injection and ignition control signals are output. If the signal of crankshaft position sensor is not received within 3 seconds of engine rotation, ECU will cut off the circuit of fuel injection system and store the fault code of crankshaft position sensor in memory for calling during maintenance inspection. ② Control the fuel pump relay to connect the fuel pump circuit to make the fuel pump run. ③ If the throttle valve is fully opened, the ECU will stop fuel injection (i.e. enter the overflow gap state). Some engine electronic control systems cancel the special starting signal line, and ECU determines the starting state according to the engine speed signal. (3) Air conditioning switch signal A/C, including air conditioning selection and request signal. The air conditioner selection signal is a signal that informs ECU that air conditioner has been selected and predicts the increase of engine load. When the air conditioner switch is turned on, a signal is provided to the electronic control unit. Turn on the air-conditioning switch when the engine is idling. If the low-voltage switch of the air-conditioning system is closed, the power supply voltage l2V is applied to the air-conditioning selection terminal of ECU through the air-conditioning switch and the low-voltage switch. After receiving this "air conditioning selection signal" (high level signal), ECU will control the idle speed control valve or stepping motor to increase the engine speed and prevent the engine from stalling due to increased load. The air conditioning request signal indicates that the evaporator temperature is within the allowable range when the air conditioner is turned on. When the air conditioner is turned on, such as the evaporator switch, the power supply voltage l2V is applied to the "air conditioning request" terminal of the ECU through the air conditioner switch, the low-voltage switch and the evaporator switch. After receiving this "air conditioning request signal" (high level signal), ECU will turn on the coil circuit of air conditioning relay, turn on the electromagnetic clutch coil circuit, and put the air conditioning compressor into operation. When the refrigerant in the air conditioning system is insufficient, the low-voltage switch will be turned off, and the voltage input to the air conditioning request terminal of ECU will be OV. At this point, the ECU will cut off the coil circuit of the air-conditioning relay, so that the air-conditioning compressor will stop working. When the evaporator temperature is too high, the evaporator switch will be turned off, and the input voltage of ECU's "air conditioning request" terminal is 0 V. At this time, ECU will cut off the compressor to prevent the evaporator from being damaged due to too high temperature. (4) The battery voltage signal (UBAT) is a signal indicating the power supply voltage level. In all kinds of cars, the positive electrode of the battery is directly connected to the ECU, which is not controlled by any switch. Battery is not only the power supply of automobile electrical equipment, but also the power supply of various control systems ECU. The main purposes of battery voltage signal input into ECU are: ① When the battery voltage changes, ECU will correct the fuel injection duration. When the voltage increases, the injection time decreases; When the voltage decreases, the injection time increases. ② When the battery voltage changes, ECU will correct the turn-on time of the primary circuit of the ignition coil. When the voltage rises, the conduction time is reduced; When the voltage decreases, the on time is increased. ③ Save the fault code in the memory. In automobiles, fault codes of various electronic control systems are stored in random access memory (RAM), because once the power supply of RAM is cut off, the information stored in RAM will disappear, so it is necessary to keep the battery powered. When the engine stops working, the current consumed by the memory is very small, about 5 ~ 2 OMA. (5) The neutral safety switch signal NSW is a signal indicating the position of the automatic transmission gear selector switch, which is also called a parking/neutral switch signal or a neutral start switch signal. The neutral start switch is installed on the transmission housing, which is a multi-position multifunctional switch controlled by the handle of the automatic transmission selector lever. Used to detect whether the automatic transmission gear selection switch is in the neutral position. NSW signal is used to distinguish whether the selector lever of automatic transmission is in the position of "P" or "N" or in the position of "2", "L", "D" and "R". When the selector lever of the automatic transmission is in the P or N position, the park/neutral switch is turned on, and then the relay coil circuit can be turned on, and the OV signal is input to the ECU. At this point, the engine can be started. When the selector lever is in D, 2, L and R, the park/neutral switch is turned off. Even if the ignition switch is turned to the starting position, the starting relay coil circuit cannot be connected. The ECU will receive a high level (l2V) signal, and the engine cannot be started at this time. (6) The power steering switch signal (PSW) is a signal indicating that the power steering switch is turned on, which increases the engine load. In an automobile with power steering system, the power steering switch is a pressure switch, which is installed in the high-voltage circuit of the power steering system. When the power steering pump is overloaded or the engine speed is low, the pressure of the power steering system is higher than a certain value, the power steering switch is turned on, and the ECU will receive a low-level signal. If the engine is idling at this time, ECU will control the idling control valve or stepping motor to increase the engine speed and prevent the engine from stalling due to the increase of load. Sensor is a kind of signal conversion device, whose function is to detect various parameters such as electric quantity, physical quantity and chemical quantity of engine in different states, and convert these parameters into electrical signals that can be recognized by computer and input to ECU. There are several sensors commonly used in the engine electronic control system: ① Air flow sensor AFS or intake manifold absolute pressure sensor MAP, which are used to detect the intake air sucked into the engine cylinder. The air flow sensor can directly detect the air intake of the engine, while the manifold pressure sensor can only indirectly detect the air intake of the engine. Because both AFS and MAP are used to detect the intake air, in the same engine electronic control system, if AFS is used, MAP is not needed. Conversely, if MAP is adopted, AFS is not needed. ② Crankshaft position sensor CPS, also known as engine speed and crankshaft position sensor, is used to detect engine crankshaft speed and angle. Its function is to collect crank angle and engine speed signals, and input them into the control unit (ECU) to determine the ignition time and fuel injection time. Crankshaft position sensors commonly used in engine fuel injection system are divided into four types: photoelectric sensor, magnetic induction sensor, Hall sensor and differential Hall sensor. Among them, the differential Hall sensor is also called double Hall sensor. ③ The camshaft position sensor CPS is used to detect the position of the piston at the top dead center, so it is also called cylinder identification sensor CIS. Its function is to collect the position signal of the valve camshaft and input it to the ECU, so that the ECU can identify the position of the piston in the first cylinder at the compression top dead center, so as to carry out sequential fuel injection control, ignition timing control and knock control. In some electronic control systems of automobile engines, the crankshaft position sensor and the camshaft position sensor are integrated together, collectively called the crankshaft position sensor and expressed by CPS. Commonly used camshaft position sensors are divided into three types: photoelectric sensor, magnetic induction sensor and Hall sensor. (4) The throttle position sensor TPS is used to detect the throttle opening, and its function is to convert the throttle opening (that is, engine load) into an electrical signal and input it to the ECU, so that the ECU can distinguish engine working conditions (such as idle working conditions, partial load working conditions and heavy load working conditions). ) and control the injection time according to the requirements of mixed gas concentration under different working conditions. . Such as throttle closed, partially open and fully open. In addition, the electronic control unit can obtain the acceleration or deceleration signal of the automobile by calculating the change rate of the throttle position sensor signal. A throttle position sensor for all types of automobiles is installed at one end of a throttle shaft on a throttle body. In an automobile equipped with an electronically controlled automatic transmission, the TPS signal of the throttle position sensor is input not only to the engine ECU, but also to the transmission electronic control unit (ECTECU) as one of the main signals for determining the transmission shift timing and the locking timing of the torque converter. According to the structure, the throttle position sensor can be divided into three types: contact switch type, variable resistance type and combination type of contact and variable resistance. According to the different types of sensor output signals, it can be divided into linear (quantity) output type and switch (quantity) output type. Santana GLi and 20OOGLi cars adopt contact switch type and variable resistance type, while Li Xia 2000, Jetta AT, GTX, Santana 20OOGSA, Hongqi CA7220E and Cherokee Jeep adopt variable resistance type. Toyota has adopted a comprehensive throttle position sensor. ⑤ Temperature sensor, temperature is an important parameter reflecting the thermal load state of the engine. In order to ensure that the electronic control system can accurately control the working parameters of the engine, it is necessary to monitor the coolant temperature, intake temperature, exhaust temperature sensor and fuel temperature of the engine at any time, so as to correct various control parameters, calculate the mass flow of air sucked into the cylinder and carry out exhaust purification treatment. As we all know, air quality is related to intake temperature and atmospheric (intake) pressure. When the inlet temperature is low, the air density is high and the mass of the same volume of gas increases; On the contrary, when the inlet temperature increases, the mass of the same volume of gas will decrease. In the fuel injection system using manifold pressure type, vane type, Kalman vortex type and core air flow sensor, because the air flow measured by the air flow sensor is volume flow, it is necessary to install air temperature sensor and atmospheric pressure sensor to correct the fuel injection quantity, so that the engine can automatically adapt to the changes of external environment temperature (cold and high temperature) and pressure (plateau and plain). When the intake air temperature is low (air density is high), ECU will control the fuel injector to increase the fuel injection quantity; On the contrary, when the intake air temperature is high (the air density is low), the ECU will control the fuel injector to reduce the fuel injection quantity. There are many kinds of temperature sensors, which can be divided into thermistor, metal film resistor, metal foam resistor, carbon foam resistor, wire wound resistor and semiconductor transistor according to different structures. Thermistor temperature sensor is widely used in automobile electronic control system because of its outstanding advantages such as high sensitivity, good response characteristics, simple structure and low cost. Thermistors can be divided into positive temperature coefficient PTC thermistor, negative temperature coefficient NTC thermistor, critical temperature CTR thermistor and linear thermistor. There are two commonly used thermistors: NTC with negative temperature coefficient and PTC with positive temperature coefficient. NTC thermistor temperature sensor is widely used in automotive electronic control system, such as CTS for coolant temperature, IATS for air temperature sensor, EATS for exhaust temperature, FTS for fuel temperature and so on. Coolant temperature (water temperature) sensor CTS, also known as water temperature sensor. Installed on the engine coolant outlet pipe, its function is to detect the temperature of engine coolant and convert the temperature signal into an electrical signal and transmit it to ECU. ECU corrects the fuel injection time and ignition time according to the engine temperature signal to make the engine work in the best state. The air temperature sensor IATS installed in the intake pipe is used to detect the intake temperature, and convert the temperature signal into an electrical signal and transmit it to ECU. Intake air temperature signal is the correction signal of various control functions. If the signal of the air temperature sensor is interrupted, it will lead to the difficulty of hot start and the increase of exhaust emissions. ⑥ Oxygen sensor or O2 sensor EGO, short for exhaust oxygen sensor EGO, is used to obtain the air-fuel ratio signal of the mixed gas by monitoring the content of oxygen ions in the exhaust gas, and convert the signal into an electrical signal and input it to ECU. It is used to detect the content of oxygen ions in the exhaust gas discharged from the exhaust pipe to reflect the air-fuel ratio of combustible mixture. The ECU corrects the fuel injection timing according to the signal of the oxygen sensor, and realizes the air-fuel ratio feedback control (closed-loop control), so as to control the excess air coefficient within the range of 0.98 ~ 1.02 (the air-fuel ratio A/F is about 14.7), so that the engine can obtain the best mixture concentration, thus achieving the purpose of reducing harmful gas emissions and saving fuel. Since Bosch in Germany took the lead in installing oxygen sensors on Volvo cars in Sweden in 1976, automobile companies such as GM, Ford, Toyota and Nissan have successively completed the development and application of oxygen sensors. Oxygen sensors used in fuel injection system of automobile engines are divided into two types: zirconium oxide (Zr02) and titanium dioxide (TiO2). Zirconia oxygen sensors are divided into two types: heated oxygen sensors and unheated oxygen sensors, and titanium oxide sensors are generally heated oxygen sensors. Because the practical titanium oxide oxygen sensor is cheap and not easy to be corroded by silicon ions, it is widely used in modern cars. ⑦ Knock sensor DS is used to detect whether the engine knocks and its knock intensity. Engine knock is the vibration of engine cylinder caused by the sudden increase of cylinder pressure caused by abnormal combustion of mixed gas. In the electronic control system of the engine, when the closed-loop control is adopted at the ignition time, the engine knock can be effectively suppressed. Knock sensor DS is an important part of closed-loop control of ignition timing. Its function is to convert engine knock signal into electrical signal and transmit it to ECU. ECU corrects the ignition advance angle according to the knock signal to keep the ignition advance angle optimal. There are three methods to detect engine knock: one is to detect the change of engine combustion chamber pressure; The second is to detect the vibration frequency of the engine block; The third is to detect the combustion noise of the mixture. The measurement accuracy of detecting engine vibration by directly detecting the pressure change of combustion chamber is high, but the sensor is difficult to install and has poor durability. Generally used as a measuring instrument, the actual pressure detection sensors are indirect detection. The main advantages of detecting knock by detecting the vibration frequency of engine cylinder block are high measurement accuracy, convenient installation of sensor and high output voltage, so it is widely used in modern cars. The detection of mixed gas combustion noise is non-contact and has good durability, but the measurement accuracy and sensitivity are low and the practical application is less. When detecting the vibration frequency of cylinder block, knock sensor is usually installed on the side of engine cylinder block. According to different detection methods, knock sensors can be divided into * * * mode and non-* * mode. * * * vibration mode knock sensor is characterized by its * * * vibration frequency matching with the natural frequency of engine knock, so it is necessary to set a * * * vibrating body inside the sensor and make the * * * vibration frequency of the * * vibrating body consistent with the engine knock frequency. * * * Vibration knock sensor has the advantages of high output voltage, no need of filter, and more convenient signal processing. Because of the sharp frequency characteristics and narrow frequency band, the mechanical vibrator can not respond to the change of knock frequency caused by the change of engine structure. In other words, the * * * vibration mode knock sensor is only suitable for a specific engine and cannot be used interchangeably with other engines, so the loading freedom is very small, and this sensor is adopted by General Motors of the United States. The outstanding advantage of non-* * mode knock sensor is that it is suitable for all engines and has great loading freedom. However, its output voltage is low, its frequency characteristics are flat and its frequency band is wide, so it is necessary to match a bandpass filter (a filter that only allows signals in a specific frequency band to pass and attenuates signals in other frequencies is called a bandpass filter). Band-pass filters are generally composed of coils and capacitors), and the signal processing is complicated. Most cars in China, Japan and Europe use this sensor. According to the structure, knock sensors commonly used in automobiles can be divided into piezoelectric and magnetostrictive types. Gm and Nissan have adopted magnetostrictive knock sensors. Piezoelectric knock sensor is used in Santana GLi, 20OOGLi, 20OOGSi, Jetta AT, GTX and other domestic cars. References:

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