position sensor

1 Introduction

Position sensor: A sensor that senses the position of a measured object and converts it into a usable output signal. It can sense the position of the measured object and convert it into a sensor that can use the output signal. The main domestic manufacturers have OTRON brand.

Category 2

The position sensor can be used to detect the position and reflect the switch of a certain state. Different from the displacement sensor, the position sensor has two kinds of contact type and proximity type.

Contact sensor

Contact of the contact sensor is actuated by two objects in contact with each other. There are trip switches, two-dimensional matrix position sensors and the like. The trip switch has a simple structure, reliable operation and low price. When an object touches the limit switch during movement, its internal contacts will act to complete the control. For example, if the travel switch is installed at both ends of the machining center in the X, Y, and Z directions, the movement can be controlled. range. The two-dimensional matrix position sensor is installed on the inside of the palm of the hand to detect the position of its own contact with an object.

The proximity switch is a switch that can send an "action" signal when the object is close to a set distance, and it does not need to be in direct contact with the object. There are many kinds of proximity switches, mainly electromagnetic, photoelectric, differential transformer type, eddy current type, capacitance type, reed switch, Hall type and so on. The application of proximity switches on CNC machine tools is mainly the tool holder selection control, the worktable stroke control, and the cylinder and piston stroke control.

Hall sensor

Hall sensors are sensors made using the Hall phenomenon. When semiconductors such as germanium are placed in a magnetic field and a current is applied in one direction, a potential difference occurs in the vertical direction. This is the Hall phenomenon. The small magnet is fixed on the moving part. When the part is close to the Hall element, a Hall phenomenon is generated, so as to judge whether the object is in place.

3 applications

Brushless DC motor

The position sensor is one of the three major components of the brushless DC motor system, and it is also the main sign that distinguishes it from a brushed DC motor. Its role is to detect the position of the main rotor during the movement, convert the position signal of the magnetic pole of the rotor magnet into an electrical signal, provide the correct commutation information for the logic switch circuit, to control their on and off, and make the motor armature. The current in the winding commutates in sequence with the change of the rotor position, forming a stepped rotating magnetic field in the air gap, driving the permanent magnet rotor to continuously rotate.

The brushless DC motor needs a position sensor to measure the position of the rotor. The motor controller receives the position sensor signal to synchronize the inverter with the rotor to drive the motor to run continuously. Although the brushless DC motor can also detect the position of the rotor through the induced electromotive force generated by the stator windings, and the position sensor is omitted, when the motor is started, the rotation speed is too small and the counter electromotive force signal is too small to be detected.
Hall sensor chips that can be used as DC brushless motor position sensors are classified into two types: switch type and lock type. For electric bicycle motors, both Hall sensor chips can be used to accurately measure the position of rotor magnets. The performance of brushless DC motors manufactured using these two Hall sensor chips does not include any difference in motor output power, efficiency, and torque, and can be compatible with the same motor controller.
The application of the position sensor reduces the noise of the motor operation, improves the life and performance of the motor, and simultaneously achieves the effect of reducing energy consumption. The application of position sensors undoubtedly provides a powerful driving force for the development of the motor market. [1]

Crankshaft and camshaft

Crankshaft Position Sensor (CPS) is also known as the engine speed and crank angle sensor. Its function is to acquire the crankshaft rotation angle and engine speed signal, and input the electronic control unit (ECu) to determine the ignition timing and injection timing.

The Camshaft Position Sensor (CPS) is also referred to as a Cylinder Identification Sensor (CIS). In order to distinguish it from a Crankshaft Position Sensor (CPS), a camshaft position sensor is generally indicated by CIS. The function of the camshaft position sensor is to acquire the position signal of the valve camshaft and input the ECU so that the ECU recognizes the compression top dead center of the cylinder 1 so that sequential injection control, ignition timing control, and deflagration control are performed. In addition, the camshaft position signal is also used to identify the first ignition timing when the engine is started. Because the camshaft position sensor can identify which cylinder piston is about to reach top dead center, it is called a cylinder identification sensor.

Photoelectric crankshaft and camshaft position sensor

(1) Structural features

The photoelectric crankshaft and camshaft position sensor produced by Nissan Co., Ltd. is improved by the distributor. It is mainly composed of a signal plate (ie, a signal rotor), a signal generator, a distributor, a sensor housing, and a harness plug.

The signal plate is the sensor's signal rotor and is mounted on the sensor shaft. Near the outer edge of the signal plate, two inner and outer light transmission holes with evenly spaced arcs are formed. Among them, there are 360 ​​light-transmitting holes (slits) made in the outer ring, with an interval curvature of 1. (Transmitting holes account for 0.5, and shading holes account for 0.5.) Used to generate crankshaft rotation angle and rotational speed signals; the inner ring is made with 6 light-transmitting holes (rectangular 孑L) with an interval curvature of 60. It is used to generate the top dead center signal of each cylinder. There is a long side of a rectangle which is used to generate the top dead center signal of the cylinder 1.

The signal generator is fixed on the sensor housing and consists of a generator of the Ne signal (rotational and rotational angle signals), a generator of the G signal (top dead center signal) and a signal processing circuit. Both the Ne signal and the G signal generator consist of a light emitting diode (LED) and a phototransistor (or photodiode), with the two LEDs facing the two phototransistors respectively.

(2) Working principle

The photoelectric sensor works as shown in Figure 2-22. The signal plate is mounted between a light emitting diode (LED) and a phototransistor (or photodiode). When the transparent hole on the signal plate rotates between the LED and the phototransistor, the light from the LED will shine on the phototransistor. At this moment, the phototransistor is turned on, and its collector output is low (0.1~0. .3V); When the light-shielding portion of the signal plate rotates between the LED and the phototransistor, the light from the LED cannot be irradiated to the phototransistor. At this time, the phototransistor is turned off, and its collector output is high (4.8. ~ 5.2V).

If the signal plate rotates continuously, the light-transmitting hole and the light-shielding part will alternately turn the LED to transmit light or block light, and the phototransistor collector will alternately output the high level and the low level. When the sensor shaft rotates with the crankshaft and the valve camshaft, the light-transmitting hole and the light-shielding part of the signal plate are turned from between the LED and the phototransistor, and the light emitted by the LED is alternately illuminated by the transmissive and shading effect of the signal plate. To the phototransistor of the signal generator, a pulse signal corresponding to the position of the crankshaft and the position of the camshaft is generated in the signal sensor.

Since the crankshaft rotates two revolutions, the sensor shaft rotates the signal plate one revolution. Therefore, the G signal sensor will generate six pulse signals. The Ne signal sensor will generate 360 ​​pulses. Because the G signal clearance interval arc is 60. The crankshaft rotates 120 per revolution. A pulse signal is generated, so the G signal is usually called 120. signal. Design and installation guarantee 120. The signal is 70 in front of top dead center. (BTDC70.) Signals generated when light-transmitting holes are produced with a longer width and longer sides of the rectangle correspond to the top 70 of the top dead center of the cylinder 1 of the engine. So that the ECU controls the injection advance angle and ignition advance angle. Because the Ne signal transmission hole spacing radian is 1. (Light-transmitting holes account for 0.5, and shading holes account for 0.5.) Therefore, the high and low levels each take one in each pulse cycle. Crank angle, 360 signals for crankshaft rotation 720. . The crankshaft rotates 120 every time. The G signal sensor produces a signal, and the Ne signal sensor produces 60 signals.

Magnetic induction crankshaft and camshaft position sensor

The working principle of the magnetic sensor is shown in Fig. 2-23. The path through which the magnetic flux passes is the air gap between the stator and the rotor of the N pole of a permanent magnet. The rotor is a convex tooth. The air gap between the rotor tooth and the stator head is a magnetic head. Magnetic plate A permanent magnet S pole. When the signal rotor rotates, the air gap in the magnetic circuit will periodically change, and the magnetic resistance of the magnetic circuit and the magnetic flux passing through the head of the signal coil will periodically change. According to the principle of electromagnetic induction, alternating electromotive force is induced in the sensing coil.

When the signal rotor rotates in the clockwise direction, the air gap between the rotor lobe and the magnetic head decreases, the magnetic resistance of the magnetic circuit decreases, the magnetic flux φ increases, the magnetic flux change rate increases (dφ/dt>0), and the induced electromotive force E It is positive (E>0), as shown by the curve abc in Figure 2-24. When the rotor ridges approach the edge of the head, the magnetic flux φ increases sharply, the flux change rate is maximum [dφ/dt=(dφ/dt)max], and the induced electromotive force E is highest (E=Emax), as shown in the curve b of Figure 2-24. Point shown. After the rotor rotates past the point b, although the magnetic flux φ is still increasing, the magnetic flux change rate decreases, and thus the induced electromotive force E decreases.

When the rotor rotates so that the centerline of the convex tooth aligns with the centerline of the head (see Figure 2-24b), although the air gap between the rotor lobe and the head is the smallest, the reluctance of the magnetic circuit is the smallest and the magnetic flux φ is the largest, but due to the magnetic flux It is impossible to continue to increase and the flux change rate is zero, so the induced electromotive force E is zero, as shown by point c of the curve in Fig. 2-24.

When the rotor rotates clockwise, when the lobes leave the head (see Figure 2-23c), the air gap between the lobe and the head increases, the magnetic resistance of the magnetic circuit increases, and the magnetic flux φ decreases (dφ/dt < 0). Therefore, the induced electromotive force E is negative, as shown by the curve cda in Figure 2-24. When the convex teeth turn to leave the edge of the magnetic head, the magnetic flux φ drastically decreases, the magnetic flux change rate reaches a negative maximum value [dφ/df=−(dφ/dt)max], and the induced electromotive force E also reaches a negative maximum value (E =-Emax), as shown by point d on the curve in Figure 2-24.

It can be seen that each rotation of the signal rotor has a convex tooth, and a periodic alternating electromotive force is generated in the sensing coil, ie, the electromotive force has a maximum and a minimum value, and the sensing coil outputs an alternating voltage signal accordingly. . The outstanding advantage of magnetic sensors is that they do not require an external power supply. The permanent magnets act to convert mechanical energy into electrical energy. Magnetic energy is not lost. When the engine speed changes, the speed of rotation of the rotor lobes will change, and the rate of change of the magnetic flux in the core will also change. The higher the rotational speed, the greater the flux change rate and the higher the induced electromotive force in the sensing coil. The change in magnetic flux and induced electromotive force at different speeds is shown in Figure 2-24.

Since the air gap between the rotor lobe and the magnetic head directly affects the magnetic resistance of the magnetic circuit and the output voltage of the sensing coil, during use, the air gap between the rotor lobe and the magnetic head cannot be arbitrarily changed. If the air gap changes, it must be adjusted according to regulations. The air gap is generally designed to be in the range of 0.2-0.4mm.

Jetta, Santana magnetic induction crankshaft position sensor

1) Crankshaft position sensor structure features: Jetta AT and GTX, Santana 2000GSi car's magnetic induction crankshaft position sensor installed in the crankcase near the clutch side of the cylinder, mainly by the signal generator and the signal rotor, as shown in Figure 2 -25 shows.

The signal generator is screwed to the engine block and consists of permanent magnets, sensing coils, and harness connectors. The sensor coil is also called the signal coil. The permanent magnet has a magnetic head. The magnetic head is facing the toothed disc signal rotor installed on the crankshaft, and the magnetic head is connected with the magnetic yoke (magnetic conductive plate) to form a magnetic conductive loop.

The signal rotor is a toothed disc type, with 58 convex teeth, 57 small teeth missing, and one large tooth missing. The large tooth missing output reference signal corresponds to a certain angle before compression of the top dead center of the engine cylinder 1 or the cylinder 4 . Therefore, the crankshaft angle occupied by the convex teeth and the missing teeth on the signal rotor circumference is 360°.

2) Working status of crankshaft position sensor: When the crankshaft position sensor rotates with the crankshaft, it is known from the working principle of the magnetic induction sensor that each revolution of the signal rotor has a convex tooth, and a periodic alternating electromotive force is generated in the sensing coil (ie, the electromotive force appears. Once maximum and minimum, the coil outputs an alternating voltage signal accordingly. Because the signal rotor is provided with a large missing tooth which generates a reference signal, when the large tooth is turned over the head, the signal voltage takes a longer time, ie the output signal is a wide pulse signal, which corresponds to the cylinder 1 or The cylinder 4 compresses a certain angle before top dead center. When the electronic control unit (ECU) receives a wide pulse signal, it can know that the top dead center position of the cylinder 1 or the cylinder 4 is coming. As for the upcoming cylinder 1 or the cylinder 4, the signal input by the camshaft position sensor is needed. determine. Since there are 58 convex teeth on the signal rotor, each revolution of the signal rotor (the crankshaft of the engine makes one revolution), the sensing coil will generate 58 alternating voltage signals to the electronic control unit.

Whenever the signal rotor makes one revolution with the engine crankshaft, the sensing coil will input 58 pulse signals to the electronic control unit (ECU). Therefore, each time the ECU receives 58 signals from the crankshaft position sensor, it knows that the engine crankshaft has rotated one revolution. If the ECU receives 116,000 crankshaft position sensors within 1 min, the ECU can calculate the crankshaft speed n as 2000 (n=116000/58=2000)r/rain; if the ECU receives 290000 crankshaft position sensors per minute, The ECU can calculate the crankshaft speed as 5000 (n=290000/58=5000) r/min. And so on, the ECU can calculate the crankshaft rotation speed according to the number of crankshaft position sensor pulse signals received per minute. The engine speed signal and load signal are the most important and basic control signals of the electronic control system. Based on these two signals, the ECU can calculate the basic injection advance angle (time), basic ignition advance angle (time) and ignition conduction angle. (Ignition coil primary current ON time) Three basic control parameters.

Jetta AT and GTx, Santana 2000GSi car magnetic induction crankshaft position sensor signal signal generated by the large tooth on the rotor as a reference signal, ECU control injection time and ignition time is based on the signal generated by the large tooth is used as the benchmark for control. When Euc receives the signal generated by the large missing tooth, it controls the ignition timing, fuel injection time, and the time for the first current of the ignition coil (ie, the conduction angle) according to the small tooth missing signal.

3) Toyota car TCCS magnetic induction crankshaft and camshaft position sensor

The magnetic induction crankshaft and camshaft position sensors used in the Toyota Computer Control System (1FCCS) are improved by distributors and consist of upper and lower parts. The upper part is the generator that detects the crankshaft position reference signal (that is, cylinder identification and top dead center signal, called G signal); the lower part is crankshaft rotation and rotation angle signal (called Ne signal) generator.

a) Structural features of the Ne signal generator: The Ne signal generator is installed below the G signal generator, mainly by No. 2 signal rotor, Ne sensor coil and magnetic head, as shown in Figure 2-26a. The signal rotor is fixed on the sensor shaft. The sensor shaft is driven by the gas camshaft. The upper end of the shaft is equipped with a sub-firing head, and the rotor has 24 protruding teeth. The sensing coil and head are fixed in the sensor housing, and the head is fixed in the sensing coil.

b) The principle and control process of the rotation speed and angle signal: When the engine crankshaft rotates, the valve camshaft drives the rotation of the sensor signal rotor, the air gap between the rotor lobe and the head changes alternately, the magnetic flux of the sensing coil The alternation changes, and it can be known from the working principle of the magnetic induction sensor that an alternating electromotive force is induced in the sensing coil. The waveform of the signal voltage is shown in Figure 2-26b. Because the signal rotor has 24 convex teeth, the rotor rotates one revolution and the sensing coil generates 24 alternating signals. Each revolution of the sensor shaft (360°) corresponds to two revolutions of the engine crankshaft (720°), so an alternating signal (ie, one signal period) corresponds to 30 crankshaft rotations. (720. ÷ 24 = 30.), which is equivalent to a rotation of 15 minutes. (30. ÷ 2 = 15.). The ECU receives 24 signals from the Ne signal generator and knows that the crankshaft has rotated two revolutions, and the sub-rotor has rotated one revolution. The ECU internal program can calculate and determine the engine crankshaft speed and the sub-head speed according to the time occupied by each Ne signal period. In order to precisely control the ignition advance angle and the injection advance angle, it is also necessary to divide the crank angle (30° angle) occupied by each signal period to be smaller. It is very convenient for the microcomputer to accomplish this task. Each Ne signal (crankshaft rotation angle 30°) is equally divided into 30 pulse signals by the frequency divider. Each pulse signal is equivalent to the crank angle 1. (30. ÷ 30=1.). If each Ne signal is equally divided into 60 pulse signals, each pulse signal corresponds to a crank angle of 0.5. (30. ÷ 60 = 0.5.). The specific setting is determined by the rotation angle accuracy requirements and the program design.

c) The structural characteristics of the G signal generator: The G signal generator is used to detect the reference position of the piston top dead center position and discriminating which cylinder is about to reach the top dead center position. Therefore, the G signal generator is also referred to as the cylinder identification and top dead center signal generator or reference signal generator. G signal generator by No. 1 signal rotor, sensor coils G1, G2 and heads. The signal rotor has two flanges that are fixed to the sensor shaft. The sensing coils G1, G2 are 180 apart. For installation, the signal generated by the G1 coil corresponds to the top ten of the engine's sixth cylinder compression top dead center. The signal generated by the G2 coil corresponds to 10° before the top dead center of the compression of the engine's first cylinder. .

d) The principle and control process of cylinder identification and top dead center signal generation: The working principle of the G signal generator is the same as that of the signal generation by the Ne signal generator. When the engine camshaft drives the sensor shaft to rotate, the flange of the G signal rotor (No. 1 signal rotor) alternately passes through the head of the sensing coil, and the air gap between the rotor flange and the head alternately changes in the sensing coil. The alternating electromotive force signal is induced in Gl and G2. When the flange portion of the G signal rotor approaches the head of the sensing coil G1, a positive direction is generated in the sensing coil G1 because the air gap between the flange and the head is reduced, the magnetic flux is increased, and the magnetic flux change rate is positive. The pulse signal is called the G1 signal; when the flange portion of the G signal rotor approaches the sensing coil G2, sensing occurs because the air gap between the flange and the magnetic head is reduced, the magnetic flux is increased, and the magnetic flux change rate is positive. A positive-going pulse signal is also generated in the coil G2 and is called a G2 signal. When the flange portion of the G signal rotor passes through the heads of G1 and G2, the induction gaps in the sensing coils G1 and G2 are caused because the air gap between the flange and the head does not change, the magnetic flux does not change, and the flux change rate becomes zero. The electromotive force is zero. When the flange portion of the G signal rotor leaves the heads of G1 and G2, since the air gap between the flange and the head increases, the magnetic flux decreases, and the flux change rate is negative, the sensing coils G1 and G2 will sense Generates a negative alternating electromotive force signal. Each revolution of the sensor (360°) corresponds to two revolutions of the crankshaft (720°) because the sensing coils G1 and G2 are 180 apart. Installation, so G1, G2 each produce a positive pulse signal. The G1 signal corresponds to the sixth cylinder of the engine and is used to detect the position of the top dead center of the sixth cylinder. The G2 signal corresponds to the first cylinder and is used to detect the position of the top dead center of the first cylinder. The corresponding position detected by the electronic control unit is actually the position where the front end of the G rotor flange approaches and aligns with the magnetic heads of the sensing coils G1 and G2 (at this time, the magnetic flux is maximum and the signal voltage is zero), and this position corresponds to the compression of the piston. 10 before the stop. (BT-DCl0.) Location.

Hall Crankshaft and Camshaft Position Sensor

(1) Hall sensor structure and working principle

Hall-type crankshaft and camshaft position sensors and other Hall-type sensors are sensors based on the Hall effect.

1) Hall Effect: Hall Effect was first discovered by Dr. E.H. Hall, a physicist at Johns Hopkins University in the United States in 1879. He found that when a rectangular parallelepiped conductor carrying a current I is placed perpendicular to the magnetic field in a magnetic field of magnetic induction B (see Figure 2-27), a perpendicular current is generated on both lateral sides of the platinum conductor. The voltage UH in the direction and direction of the magnetic field, the voltage disappears immediately when the magnetic field is canceled. This voltage is later referred to as the Hall voltage and UH is proportional to the current I through the platinum conductor and the magnetic induction B, ie (see next page)

The Hall effect element is called a Hall element, and the Hall element is called a Hall sensor. Using the Hall effect can not only detect the voltage by turning on and off the magnetic field, but also detect the current flowing in the wire because the strength of the magnetic field around the wire is proportional to the current flowing through the wire. Since the 1980s, the Hall sensor used in automobiles has increased rapidly. The main reason is that the Hall sensor has two outstanding advantages: one is that the output voltage signal is similar to the square wave signal; the other is the output voltage level and being Does not measure the speed of the object. The difference between a Hall sensor and a magnetic sensor is that an external power supply is required.

2) Hall sensor basic structure: The Hall sensor is mainly composed of a trigger impeller, a Hall IC, a magnetic steel sheet (yoke) and a permanent magnet. The triggering impeller is mounted on the rotor shaft and the impeller is equipped with blades (In the Hall ignition system, the number of blades is equal to the number of engine cylinders). When the trigger impeller rotates with the rotor shaft, the blades rotate between the Hall IC and the permanent magnet. The Hall IC consists of a Hall element, an amplifier circuit, a voltage regulator circuit, a temperature compensation circuit, a signal conversion circuit, and an output circuit.

3) Hall-effect sensor working principle: When the sensor shaft rotates, the blade that triggers the impeller rotates from the air gap between the Hall IC and the permanent magnet: when the blade leaves the air gap, the magnetic flux of the permanent magnet will pass through. The Hall IC and the magnetic steel sheet form a loop. At this time, the Hall element generates a voltage (UH=1.9~2.0V), the transistor of the Hall IC output stage is turned on, and the signal voltage U0 of the sensor output is low. Level (actual measurement shows: When the power supply voltage Ucc = 14.4V or 5V, the signal voltage U0 = 0.1 ~ 0.3 V).

When the blade enters the air gap, the magnetic field in the Hall IC is bypassed by the blade, the Hall voltage UH is zero, the transistor of the integrated circuit output stage is turned off, and the signal voltage U0 output by the sensor is high (the actual measurement shows that: when the power When the voltage Ucc=14.4V, the signal voltage U0=9.8V; when the power supply voltage Ucc=5V, the signal voltage U0=4.8V).

(2) Jetta, Santana Hall camshaft position sensor

1) Structure features: Hall-type camshaft position sensors used in Jetta AT and GTx and Santana 2000GSi cars are installed on one end of the engine intake camshaft, as shown in Figure 2-28. It is mainly composed of Hall signal generator and signal rotor. The signal rotor, also called the trigger impeller, is mounted on the intake camshaft. Locating with positioning bolts and seat ring. The partition of the signal rotor is also referred to as a blade. A window is formed on the partition. The signal corresponding to the window is a low-level signal, and the signal generated by the partition (blade) is a high-level signal. Hall signal generators are mainly composed of Hall ICs, permanent magnets, and magnetic steel sheets. The Hall element is made of a silicon semiconductor material with a gap of 0.2-0.4 mm left between the permanent magnet. When the signal rotor rotates together with the intake camshaft, the spacer and the window are separated from the Hall IC. The air gap between permanent magnets turns.

The sensor socket has three lead terminals. The terminal 1 is the positive terminal of the sensor power supply and is connected with the control unit terminal 62. The terminal 2 is the sensor signal output terminal and is connected with the control unit terminal 76: the terminal 3 is the negative terminal of the sensor power supply, and the control The unit terminal 67 is connected.

2) Operating conditions: It is known from the working principle of the Hall sensor that when the spacer (blade) enters the air gap (ie, in the air gap), the Hall element does not generate a voltage and the sensor outputs a high level (5V) signal; The Hall element generates a voltage when the diaphragm (blade) leaves the air gap (ie, the window enters the air gap). The sensor outputs a low signal (0.1V). Figure 2-29 shows the relationship between the signal voltage output by the camshaft position sensor and the signal voltage output by the crankshaft position sensor. For each revolution of the crankshaft of the engine (720°C), the Hall-type sensor signal rotor rotates one revolution (360°), corresponding to a low-level signal and a high-level signal, where the low-level signal corresponds to the cylinder 1 Compression at a certain angle before top dead center.

When the engine is running, the signal voltage generated by the magnetic induction crankshaft position sensor (CPS) and the Hall-type camshaft position sensor (CIS) is continuously input to the electronic control unit (ECU). When the ECU receives the low level (15.) signal corresponding to the large gear missing of the crankshaft position sensor and the low level signal corresponding to the camshaft position sensor window at the same time, it can recognize that the piston of the cylinder 1 is in the compression stroke and the cylinder at this time. 4 The piston is in the exhaust stroke, and the ignition advance angle is controlled according to the signal corresponding to the output of the small position of the crankshaft position sensor. After the electronic control unit recognizes the cylinder 1 compression top dead center position, sequential fuel injection control and cylinder ignition timing control can be performed.

If the engine generates a deflagration, the electronic control unit can also determine which cylinder has produced a knock based on the signal input by the knock sensor, thereby reducing the spark advance angle so as to eliminate the knock.

Differential Hall Crankshaft Position Sensor

Cherokee Jeep and Hongqi CA7220E cars use differential Hall-type crankshaft position sensors, and their camshaft position sensors are common Hall sensors.

(1) Differential Hall sensor structure features

Differential Hall sensors, also known as dual-Hall sensors, are similar in structure to magnetic sensors, as shown in Figure 2-30a. It consists of a toothed signal rotor and a Hall signal generator. Differential Hall sensors work in the same way as ordinary Hall sensors. According to the working principle of the Hall sensor. When the missing teeth and convex teeth on the engine flywheel rotate past the two probes of the differential Hall circuit, the air gap between the missing or convex tooth and the Hall probe will change, and the magnetic flux will change accordingly. The alternating voltage signal will be generated in the Hall element, as shown in Figure 2-30b. The output voltage is formed by the superposition of two Hall signal voltages. Because the output signal is a superimposed signal, the air gap between the rotor lobe and the signal generator can be increased to (1 ± 0.5) mm (ordinary Hall sensor is only 0.2 ~ 0.4mm), so The signal rotor can be imaged as a toothed disc structure like a magneto-inductive sensor rotor. Its outstanding advantage is that the signal rotor is easy to install. In automobiles, the convex-tooth rotor is generally mounted on the engine crankshaft or the engine flywheel is used as a sensor.

Signal transfer

(2) Cherokee Jeep differential Hall-type crankshaft position sensor

1) Structural features: The Cherokee Jeep 2.5L (four cylinder), 4.0L (six cylinder) electronically controlled fuel injection engine uses a Hall-type crankshaft position sensor with a differential Hall circuit. It is mounted on the transmission housing. The sensor provides Euc with engine speed and crankshaft position (angle) signals as an important basis for calculating injection timing and ignition timing.

The 2.5L four-cylinder electronically controlled engine has eight missing teeth on the flywheel, as shown in Figure 2-31a. The eight teeth were divided into two groups, each of which lacked a group of teeth. The angle between the two groups was 180. The gap between two adjacent teeth in the same group is 20 degrees. . The 4.0L six-cylinder electronically controlled engine has 12 missing teeth on the flywheel, as shown in Figure 2.3lb. Twelve teeth were divided into three groups, each group lacking four teeth, and the distance between two adjacent groups was 120. The gap between adjacent two missing teeth in the same group is also 20.

2) Working condition: When each set of teeth on the flywheel turns over Hall probe, the sensor will generate a set of 4 pulse signals. Among them, the four-cylinder engine generates two groups of 8 pulse signals for each revolution; the six-cylinder engine generates three groups of 12 pulse signals for each revolution.

For a four-cylinder engine, the ECU knows that the crankshaft has rotated one revolution for every eight signals it receives, and then calculates the crankshaft speed based on the time it takes to receive the eight signals. For a six-cylinder engine, each time the ECU receives 12 signals, it knows that the crankshaft has rotated one revolution, and then based on the time it takes to receive 12 signals, the crankshaft speed can be calculated.

When the electronic control unit controls the injection and ignition, it has a certain advance angle, so it is necessary to know the position of the piston near the top dead center. When the Cherokee jeep enters the ECU with each set of signals, it knows that the piston with two cylinders is about to reach the top dead center position. For example, in a four-cylinder engine control system, using a set of signals, the ECU knows that cylinders 1 and 4 are close to top dead center; using another set of signals, it can be seen that cylinders 2 and 3 are approaching top dead center. In a six-cylinder engine control system. Using a set of signals, it can be seen that cylinders 1 and 6, 2 and 5, 3 and 4 pistons approach top dead center. The falling edge of the pulse due to the 4th tooth deficiency corresponds to 4 before compression TDC. (BTDC4.) Therefore, the falling edge of the pulse signal generated by the first missing tooth corresponds to 64 before compression top dead center. (BT-DC64.) As shown in Figure 2-32. When the falling edge of the first pulse corresponding to the cylinders 1 and 4 arrives, the ECU can know that the cylinders 1, 4 pistons are located 64 before the compression top dead center. (BTDC64.) Thus, the injection advance angle and spark advance angle can be controlled. However, with only the crank angle signal, the ECU cannot determine which cylinder is in the compression stroke and which cylinder is in the exhaust stroke. For this purpose, a cylinder discrimination signal is also required (ie, a camshaft position sensor is required).

(3) Cherokee Jeep Hall Camshaft Position Sensor

1) Structure features: The cylinder discrimination signal of the Cherokee jeep engine control system is provided by a Hall-type camshaft position sensor, also called a synchronous signal sensor, installed in the distributor, mainly by a pulse ring (signal rotor), Hall The signal generator consists of.

The pulsating ring is made with raised blades, accounting for 180. Distributor axis angle (equivalent to 360. Crank angle). The part without leaves also accounts for 180. Distributor shaft angle (360. Crankshaft angle). The impulse ring is mounted on the distributor shaft and rotates with the distributor shaft.

2) Working condition: When the blade on the pulse ring enters the signal generator, the sensor outputs a high level (5V); when the leaves on the pulse ring leave the signal generator, the sensor outputs a low level (0V). When the distributor shaft rotates one revolution, the sensor outputs a high level and a low level, and the high and low levels each take 180. Distributor shaft angle (equivalent to 360. Crank angle). The waveform of the synchronization signal is shown in Figure 2-32.

When the leading edge of the pulse ring enters the signal generator and the sensor outputs a high level (5V), for a four-cylinder engine, it means that the cylinders 1 and 4 are about to reach top dead center, with the cylinder 1 piston in the compression stroke and the cylinder 4 piston in the cylinder. Exhaust stroke; For a six-cylinder engine, it means that the cylinders 3 and 4 are about to reach top dead center, in which the cylinder 4 piston is in the compression stroke and the cylinder 3 piston is in the exhaust stroke.

When the trailing edge of the pulse ring enters the signal generator and the sensor output is at a low level (0V), for a four-cylinder engine, it is still the cylinder 1 and 4 pistons that will reach the top dead center, and the cylinder 4 piston is in the compression stroke. The cylinder 1 piston is located at the exhaust stroke; for a six-cylinder engine, the cylinder 3 piston is in the compression stroke and the cylinder 4 piston is in the exhaust stroke.

Using the camshaft position sensor to determine which cylinder is about to reach exhaust top dead center, the ECU can control the injection advance angle and ignition advance angle based on the crankshaft position sensor signal.

Let the injection advance angle at a certain moment be 64 before top dead center. (BTI) C64. When the camshaft position sensor pulse ring blade enters the signal generator and the sensor outputs a high level (5V), the ECU determines that the four-cylinder engine's cylinder 4 piston is located at the exhaust stroke (6 cylinder engine's cylinder 3 piston is located at the exhaust During the stroke, the ECU sends a fuel injection signal to the injector when it receives the falling edge (BTDC64) of the first pulse signal of the crankshaft position sensor (CPS). Fuel injection. When the camshaft position sensor outputs a high level (5V), the ECU also determines that the cylinder 1 piston (6 cylinder engine 4 piston) of the four cylinder engine is located in the compression stroke, at this time the ECU according to the crankshaft position sensor CPS signal and the ignition advance angle The calculated value, when the piston advances to the top dead center, advances the ignition angle, and issues an ignition command to the ignition controller to control the ignition of the spark plug to achieve spark advance.

Using the camshaft position sensor to determine the position of the two cylinders as a reference point, you can follow the working order of the four-cylinder engine 1-3-4-2 (six-cylinder engine l-5-3-6-2-4). Each cylinder performs advanced injection and pre-ignition control.

(4) Red Flag CA7720E Sedan Differential Hall Crank Position Sensor

The differential Hall-type crankshaft position sensor used in the SIMOS4S3 electronically controlled fuel injection system on the Hongqi CA7220E sedan CA488.3 engine is composed of a signal rotor and a signal generator. The signal rotor is a gear disc type and is mounted on the front end of the transmission case. It is similar to the magnetic induction crankshaft position sensor rotor used in Jetta AT and GTX passenger cars. It has 58 convex teeth and 57 small tooth gaps evenly spaced on its circumference. And a big missing tooth. The large tooth missing output reference signal corresponds to a certain angle before compression of the top dead center of the engine cylinder 1 or the cylinder 4 .大齿缺所占的弧度相当于两个凸齿和三个小齿缺所占的弧度。

因为信号转子随曲轴一同旋转，曲轴旋转一圈（360。），信号转子也旋转一圈（360。），所以信号转子圆周上的凸齿和齿缺所占的曲轴转角为360。，每个凸齿和小齿缺所占的曲轴转角均为3。（58×3。+57×3。=345。），大齿缺所占的曲轴转角为15。（2×3。+3×3。= 15。），信号波形如图2-33a所示。