附 錄 Sensors Performance of any control system is， first of all， related to the accuracy with which information about the operating variables or parameters is relayed to the controlling process. The sensors used to monitor the variables do so by converting the variables physical quantities into related electrical signals. Common measures in automobiles are flow， temperature， position， position/speed， knock and oxygen concentration. Air Flow Sensor Mass Air Flow sensors convert the amount of air drawn into the engine into a voltage signal. The ECM needs to know intake air volume to calculate engine load. This is necessary to determine how much fuel to inject， when to ignite the cylinder， and when to shift the transmission. The air flow sensor is located directly in the intake air stream， between the air cleaner and body where it can measure incoming air. Mass Air Flow Sensor: Hot Wire Type The primary components of the MAF sensor are a thermistor， a platinum hot wire， and an electronic control circuit. The thermistor measures the temperature of incoming air. The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit. An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire. The electronic control circuit simultaneously measures the current flow and puts out a voltage signal (VG) in proportion to current flow. Vane Air Flow Meter The vane air flow meter provides the ECM with an accurate measure of the load placed on the engine. The ECM uses it to calculate basic injection duration and basic ignition advance angle. Temperature sensor The ECM needs to adjust a variety of system based on temperature. It is critical for proper operation of these systems that the engine reaching operating temperature and temperature is accurately signed to the ECM. Temperature sensor measure Engine Coolant Temperature (ECT)， Intake Air Temperature (IAT)， and Exhaust Recirculation Gases (EGR)， etc. Engine Coolant Temperature (ECT) Sensor The ECT responds to change in Engine Coolant Temperature. By measuring engine coolant temperature， the ECT knows the average temperature of the engine. The ECT is usually located in a coolant passage just before the thermostat. Intake Air Temperature (IAT) Sensor The IAT detects the temperature of the incoming air stream. On vehicles equipped with a MAP sensor， the IAT is part of the MAP sensor. The IAT is used for detecting ambient temperature on a cold start and intake air temperature as the engine heats up the incoming air. Exhaust Gas Recirculation Temperature (EGR) Sensor The EGR Temperature Sensor is located in the EGR passage and measures the temperature of the exhaust gases. When the EGR vavle opens， temperature increases. Form the increase in temperature， the ECM knows the EGR vavle is open and that exhaust gases are flowing. ECT， IAT， &EGR Temperature Sensor Operation Though these sensors are measuring different things， they all operate in the same way. From the voltage signal of the temperature sensor， the ECM knows the temperature. As the temperature of the sensor heats up， the voltage signal decreases. The decrease in the voltage signal is caused by the decrease in resistance. The change in resistant causes the voltage signal to drop. From the voltage signal， the ECM can determine the temperature of the coolant， intake air， or exhaust gas temperature. Position Sensor In many applications， the ECM needs to know the position of mechanical components. The throttle position sensor (TPS) indicates position of the throttle vavle. Accelerator pedal position sensor indicates position of the accelerator pedal. Exhaust gas (EGR) vavle position sensor indicate position of the EGR vavle， these sensors operate the same way. Throttle position sensor The TPS is mounted on the throttle body and converts the throttle vavle angle into an electronic signal. As the throttle opens， the signal voltage increases. The ECM uses throttle vavle position information to know: Engine mode: idle， part throttle， wide open throttle. Switch off AC and emission controls at Wide Open Throttle (WOT). Air-fuel ratio correction. Fuel cut control. EGR Vavle Position Sensor The EGR vavle position sensor is mounted on the EGR vavle and detects the height of the EGR vavle. The ECM uses this signal to control EGR vavle height. The EGR vavle position sensor converts the movement and position of the EGR vavle into an electrical signal. Operation is identical to the TPS except that the signal arm is moved by the EGR vavle. Position /Speed Sensor Position/Speed sensors provide information to the ECM about the position of a component， the speed of a component， and the change in speed of a component. The following sensors provide this data: Camshaft position sensor (also called G sensor). Crankshaft position sensor (also called NE sensor). Vehicle speed sensor. The camshaft position sensor， crankshaft position sensor and one type of vehicle speed sensor are of the pick-up coil type sensor. Pick-up coil (variable reluctance) type sensor This type of sensor consists of a permanent magnet， yoke， and coil. This sensor is mounted close to toothed gear. As each tooth moves by the sensor， an AC voltage pulses is induced in the coil. Each tooth produces a pulse. As the gear rotates faster there more pulses are produced. The ECM determines the speed the component is revolving based on the number of pulse. Sensors of other types are magnetic resistance element (MRG) type and reed switch type. Camshaft position sensor (G sensor) This sensor is located near one of the camshafts. An AC signal is generated that is directly proportional to camshaft speed. That is， as the camshaft revolves faster the frequency increases. By knowing the position of the camshaft， the ECM determines when cylinder NO.1 is on the compression strike. Crankshaft position sensor (NE sensor) The ECM uses crankshaft position signal to determine engine RPM， crankshaft position， and engine misfire. This signal is referred to as the NE signal. The NE signal combined with the G signal indicates the cylinder that is on compression and ECM can determine from its programming the engine firing order. Vehicle speed sensor (VSS) The ECM uses the vehicle speed sensor (VSS) signal to modify engine function and initiate diagnostic routines. The VSS signal originates from a sensor measuring transmission/transaxle output speed or wheel speed. Different types of sensors have been used depending on models and applications. Knock sensors The knock sensor detects engine knock and sends a voltage signal to the ECM. The ECM uses the knock sensor signal to control timing. Engine knock occurs within a specific frequency range. The knock sensor， located in the engine block， cylinder head， or intake manifold is tuned to detect that frequency. Inside the block sensor is a piezoelectric element. Piezoelectric elements generate a voltage when pressure or a vibration is applied to them. The piezoelectric element in the knock sensor is tuned to the engine knock frequency. The vibrations from engine knocking vibrate piezoelectric element generating a voltage. The voltage output from the knock sensor is highest at this time. Oxygen/Air Fuel Sensors The ECM uses an oxygen sensor to ensure the air/fuel ratio is correct for the catalytic converter. Based on the oxygen sensor signal， the ECM will adjust the amount of fuel injected into the intake air stream. There are different types of oxygen sensors， but two of the more common types are: The narrow range oxygen， the oldest style， simply called the oxygen sensor. Wide range oxygen sensor， the newest style， called the air/fuel ratio (A/F) sensor. Oxygen Sensor This style of oxygen sensor has been in service the longest time. The oxygen sensor generates a voltage signal based on the amount of oxygen in the exhaust compared to the atmospheric oxygen. Air/Fuel Ratio Sensor The air/fuel ratio (A/F) sensor is similar to the narrow range oxygen sensor. It is also referred to as a wide range or wide ratio sensor because of its ability to detect air/fuel ratios over a wide range. The advantage of using the A/F sensor is that the ECM can more accurately meter the fuel reducing emissions. To accomplish this， the A/F sensor: Operates at approximately 650 ， much hotter than oxygen sensor 400 . Changes its current (amperage) output in relation to the amount of oxygen in the exhaust stream. 傳感器 控制系統的性能，首先是控制精度。工作時，關于控制系統中的操作變量或參數的信息要被反饋到控制系統過程中。傳感器的主要功用是監測發動機運行過程中的變量，并將監測到的發物理量轉換成相應的電信號。一般地，汽車測量參數包括氣體流量、溫度、位置、位置 /速度、爆震和氧濃度。 進氣流量傳感器 進氣流傳感器將進入發動機的空氣質量轉換電壓信號輸入 ECM。 ECM根據 空氣的容量來計算發動機的負荷。這是決定噴油量、點火時刻、換檔點的必要參數。進氣流量傳感器直接安裝在進氣道內，在空氣濾清器和節氣門體之間，以便監測進氣量。 進氣流量傳感器：熱線式 熱線式空氣力量計的主要組成部件包括：熱敏電阻、白金導線， 和以電子控制電路。 熱敏電阻測量連續的進氣溫度。以電子控制電路熱敏電阻為基準，白金導線處于恒溫狀態。在空氣流量的增加，導致熱線快速失熱，并且電子控制電路通過導線，補償電流。電子控制電路同步測量目前工況的電流，并按照一定比例輸出電壓信號 (VG)。 翼板式空氣流量計 翼板式空氣流 量計準確地測量發動機的負荷，并以某種形式傳遞給 ECM。ECM 根據這個信號，計算基本噴油時間和基本點火提前角。 溫度傳感器 ECM（發動機電控單元）需要根據溫度的變化調整各系統的工作。發動機達到正常的運行溫度，并將此輸入 ECM；這對于一臺發動機各個系統的完好工作是相當必要的。溫度傳感器主要監測的是發動機冷卻液溫度 (ECT)，進氣溫度 (IAT)和廢氣再循環 (EGR)等。 發動機冷卻液溫度 (ECT)傳感器 ECT 的主要工作就是根據冷卻液溫度的變化而改變輸出信號。冷卻液溫度傳感器通過測量發動機冷卻液的溫度， ECM輸入發動機的平均溫度。 ECT 通常安裝在冷卻液通道的恒溫箱之前。 進氣溫度 (IAT)傳感器 IAT 監測吸入氣缸的空氣的溫度。對于安裝 MAP 傳感器的車輛來說， IAT是 MAP傳感器的一部分。 IAT 的主要功用是監測發動機冷起動溫度和進氣溫度，以便發動機加熱空氣。 廢氣再循環溫度 (EGR)傳感器 EGR 溫度傳感器安裝在 EGR 通道，并測量廢氣的溫度。 EGR 閥打開， 溫度上升。隨著溫度的上升， ECM檢測到 EGR閥處于開啟狀態，且廢氣均處于流動狀態。 ECT， IAT， &EGR 溫度傳感器 盡管這些傳感器檢測的是不 同的參數，但他們的工作原理幾乎相似。根據溫度傳感器的電壓信號， ECM了解到溫度狀況。隨著溫度傳感器監測的溫度升高， 電壓信號減小。電壓信號的減小是由于熱敏電阻的阻值減小。根據電壓信號， ECM 能夠確定冷卻液、進氣以及廢氣的溫度。 位置傳感器 在發動機的運轉過程中， ECM要知道某些機械部件的位置。節氣門位置傳感器 (TPS) 監測節氣門的位置。加速踏板位置傳感器檢測加速踏板的位置。廢氣再循環 (EGR)位置傳感器檢測 EGR閥的位置。這些傳感器均具有同樣的工作原理。 節氣門位置傳感器 TPS 安裝在節氣門體上，并 將節氣門的開度角轉換成電信號。當節氣門打開，電壓信號增大。 ECM 通過節氣門位置了解：發動機工況： 怠速，節氣門部分開啟，節氣門全開。 空調是否開啟，節氣門全開時的尾氣控制。 空燃比。 燃料控制。 EGR 閥位置傳感器 EGR閥位置傳感器安裝在 EGR閥上，用于檢測 EGR閥開啟的高度。 ECM通過該信號控制 EGR 閥的開啟高度。 EGR 閥位置傳感器將 EGR 閥的運動和位置轉換成一個電信號。除了信號臂連同 EGR閥移動外，其工作原理與 TPS相同的。 位置 /速度傳感器 位置 /速度傳感器主要功用就是向 ECM 提供，某些部件的 位置、速度和速度的變化率。主要提供以下數據： 凸輪軸位置傳感器 (也稱為 G 傳感器 )。 曲軸