What Is a Position Sensor?

Position sensor A sensor used to measure the position of the robot itself. Position sensors can be divided into two types, linear displacement sensors and angular displacement sensors.

position sensor

Position sensor A sensor used to measure the position of the robot itself. Position sensors can be divided into two types, straight

A position sensor is a sensor that can sense the position of the measured object and convert it into a usable output signal. It can sense the position of the measured object and convert it into a sensor with available output signals. Major domestic manufacturers have the OTRON brand.

Position sensors can be used

Position sensor DC brushless motor

Position sensor is one of the three major parts that make up a 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 steel pole of the rotor into an electrical signal, and 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 is reversed in order with the change of the rotor position, forming a stepping rotating magnetic field in the air gap, which drives the permanent magnet rotor to continuously rotate.

A DC brushless motor requires a position sensor to measure the position of the rotor. The motor controller accepts the position sensor signal to synchronize the inverter commutation with the rotor to drive the motor to continue running. Although the DC brushless motor can also detect the position of the rotor through the counter-inductive electromotive force generated by the stator winding, and eliminate the position sensor, when the motor starts, the speed is too small, and the counter-electromotive force signal is too small to detect.
Hall sensor chips that can be used as position sensors for DC brushless motors 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 the rotor magnet. The performance of the brushless DC motors made with these two Hall sensor chips, including the output power, efficiency, and torque of the motor, is not different, and they are compatible with the same motor controller.
The application of the position sensor reduces the noise of the motor, improves the life and performance of the motor, and achieves the effect of reducing energy consumption. The application of position sensors has undoubtedly provided a strong driving force for the development of the motor market. ^[1]

Position sensor crankshaft and camshaft

A crankshaft position sensor (CPS) is also called an engine speed and crank angle sensor. Its function is to collect crankshaft rotation angle and engine speed signals and input them to an electronic control unit (ECu) to determine the ignition timing and injection timing.

Camshaft Position Sensor (CPS) is also called Cylinder Identification Sensor (CIS). In order to distinguish it from CPS, camshaft position sensor is generally expressed by CIS. The function of the camshaft position sensor is to collect the position signal of the air distribution camshaft and input it to the ECU, so that the ECU recognizes the top dead center of the compression of the cylinder 1, thereby performing sequential injection control, ignition timing control and knock control. 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 characteristics

The photoelectric crankshaft and camshaft position sensors produced by Nissan are improved by distributors, and are mainly composed of signal discs (that is, signal rotors), signal generators, distributors, sensor housings, and harness plugs.

The signal disk is the signal rotor of the sensor, which is press-fitted on the sensor shaft, as shown in Figure 2-22. The inner and outer light-transmitting holes with uniformly spaced arcs are made near the edge of the signal plate. Among them, the outer ring is made with 360 light-transmitting holes (gap), and the interval arc is 1. (Light-transmitting holes account for 0.5. And light-shielding holes account for 0.5.) It is used to generate crankshaft rotation angle and rotation speed signals. The inner ring is made with 6 light-transmitting holes (rectangular L) with an interval of 60. , Used to generate the top dead center signal of each cylinder, which has a rectangular wide side slightly longer, used to generate the top dead center signal of the cylinder 1.

The signal generator is fixed on the sensor housing. It consists of a Ne signal (speed and rotation angle signal) generator, a G signal (top dead center signal) generator, and a signal processing circuit. The Ne signal and G signal generators are composed of a light emitting diode (LED) and a phototransistor (or photodiode), and the two LEDs face the two phototransistors respectively.

(2) Working principle

The working principle of the photoelectric sensor is shown in Figure 2-22. The signal panel is installed between the light emitting diode (LED) and the phototransistor (or photodiode). When the light transmission hole on the signal panel is rotated between the LED and the phototransistor, the light emitted by the LED will be irradiated on the phototransistor. At this time, the phototransistor is turned on and its collector output is low level (0.1 O .3V); When the light-shielding part on the signal panel is rotated between the LED and the phototransistor, the light emitted by the LED cannot be irradiated on the phototransistor, at this time the phototransistor is turned off and its collector output is high level (4.8 ~ 5.2V).

If the signal disc is continuously rotated, the light-transmitting hole and the light-shielding part will alternately pass through the LED to transmit or block light, and the phototransistor collector will output high and low levels alternately. When the sensor shaft rotates with the crankshaft and the gas distribution camshaft, the light-transmitting holes and light-shielding parts on the signal board are turned between the LED and the phototransistor. 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.

Because the crankshaft rotates for two revolutions, the sensor shaft drives the signal disc to rotate once, so the G signal sensor will generate 6 pulse signals. The Ne signal sensor will generate 360 pulse signals. Because the G signal transmission hole interval arc is 60. Each time the crankshaft rotates 120. A pulse signal is generated, so the G signal is usually called 120. signal. Design and installation guarantee 120. The signal is 70 before TDC. (BTDC70.), And the signal generated by the light transmission hole with the rectangular wide side slightly longer corresponds to 70 before the top dead center of engine cylinder 1. So that the ECU controls the injection advance angle and the ignition advance angle. Because the Ne signal transmission hole interval is 1. (Light-transmitting holes occupy 0.5. And light-shielding holes occupy 0.5.) Therefore, in each pulse period, the high and low levels each occupy 1. Crankshaft rotation angle, 360 signals indicate 720 crankshaft rotation. . Each time the crankshaft rotates 120. The G signal sensor generates one signal, and the Ne signal sensor generates 60 signals.

Magnetic induction crankshaft and camshaft position sensor

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

When the signal rotor rotates clockwise, the air gap between the rotor's convex teeth and the magnetic head decreases, the magnetic resistance of the magnetic circuit decreases, the magnetic flux increases, and the magnetic flux change rate increases (d / dt> 0). The induced electromotive force E Is positive (E> 0), as shown by curve abc in Figure 2-24. When the rotor teeth approach the edge of the magnetic head, the magnetic flux increases sharply, the magnetic flux change rate is the largest [d / dt = (d / dt) max], and the induced electromotive force E is the highest (E = Emax), as shown in the curve b in Figure 2-24. As shown. After the rotor has passed the position of point b, although the magnetic flux is still increasing, the rate of change of the magnetic flux is reduced, so the induced electromotive force E is reduced.

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

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

It can be seen that each time the signal rotor rotates through a convex tooth, a periodic alternating electromotive force is generated in the sensing coil, that is, the maximum and minimum values of the electromotive force appear once, and the sensing coil outputs an alternating voltage signal accordingly. . The outstanding advantage of the magnetic induction sensor is that it does not require an external power supply. The permanent magnet plays the role of converting mechanical energy into electrical energy, and its magnetic energy is not lost. When the engine speed changes, the speed at which the rotor teeth rotate will change, and the change rate of the magnetic flux in the core will also change accordingly. The higher the speed, the greater the magnetic flux change rate, and the higher the induced electromotive force in the sensing coil. Figure 2-24 shows the changes in magnetic flux and induced electromotive force at different speeds.

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

Magnetic induction crankshaft position sensor for Jetta and Santana cars

1) Structural characteristics of the crankshaft position sensor: The magnetic induction crankshaft position sensor of Jetta AT and GTX and Santana 2000GSi cars is installed on the cylinder side near the clutch in the crankcase, which is mainly composed of a signal generator and a signal rotor, as shown in Figure 2 -25 shown.

The signal generator is fixed on the engine block with screws and consists of a permanent magnet, a sensing coil and a harness plug. The sensing coil is also called a signal coil. The permanent magnet is provided with a magnetic head. The magnetic head is directly opposite the toothed disc signal rotor installed on the crankshaft. The magnetic head is connected with the yoke (magnetically permeable plate) to form a magnetically permeable circuit.

The signal rotor is a toothed disc type, with 58 convex teeth, 57 small tooth defects and one large tooth defect evenly spaced on its circumference. The large tooth lacks a reference signal corresponding to a certain angle before the top dead center of engine cylinder 1 or cylinder 4 is compressed. Therefore, the crankshaft angle occupied by the convex teeth and tooth gaps on the circumference of the signal rotor is 360.

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

Each time the signal rotor rotates one revolution with the engine crankshaft, the sensor coil inputs 58 pulse signals to the electronic control unit (ECU). Therefore, each time the ECU receives 58 signals from the crankshaft position sensor, it can know that the crankshaft of the engine has made one revolution. If the ECU receives 116,000 signals from the crankshaft position sensor within 1 minute, the ECU can calculate the crankshaft speed n as 2000 (n = 116000/58 = 2000) r / rain; if the ECU receives 290,000 signals from the crankshaft position sensor every minute, The ECU can calculate the crankshaft speed as 5000 (n = 290000/58 = 5000) r / min. By analogy, the ECU can calculate the rotation speed of the crankshaft of the engine according to the number of pulse signals received by the crankshaft position sensor 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. (Primary coil current on time) Three basic control parameters.

Jetta AT and GTx, Santana 2000GSi sedan magnetic induction crankshaft position sensor signal, the signal generated by the large tooth missing on the rotor is the reference signal, and the ECU controls the injection time and ignition time based on the signal generated by the large tooth missing. After the ECu receives the signal generated by the large tooth missing, it then controls the ignition time, fuel injection time, and the ignition coil primary current on time (ie, conduction angle) according to the small tooth missing signal.

3) Toyota TCCS magnetic induction crankshaft and camshaft position sensor

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

a) Structural features of the Ne signal generator: The Ne signal generator is installed below the G signal generator, and is mainly composed of No. It consists of 2 signal rotor, Ne sensing 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 distribution cam shaft. The upper end of the shaft is equipped with a fire head. The rotor has 24 convex teeth. The sensing coil and the magnetic head are fixed in the sensor housing, and the magnetic head is fixed in the sensing coil.

b) Principle and control process of speed and rotation angle signals: When the engine crankshaft rotates, the distribution camshaft drives the sensor signal rotor to rotate, the air gap between the rotor teeth and the magnetic head changes alternately, and the magnetic flux of the sensor coil varies with The alternating changes occur. From the working principle of the magnetic induction sensor, it can be known that an alternating electromotive force will be 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, one revolution of the rotor will produce 24 alternating signals. Each revolution of the sensor shaft (360 °) is equivalent to two revolutions of the engine crankshaft (720 °), so one alternating signal (ie, one signal period) is equivalent to 30 crankshaft rotations. (720. ÷ 24 = 30.), Which is equivalent to rotating the fire head by 15. (30. ÷ 2 = 15.). Each time the ECU receives 24 signals from the Ne signal generator, it can know that the crankshaft has rotated twice and the sub-fire head has rotated once. The internal program of the ECU can calculate and determine the engine crankshaft speed and ignition head speed based on the time occupied by each Ne signal cycle. In order to accurately control the ignition advance angle and the fuel injection advance angle, the crankshaft rotation angle (30 °) occupied by each signal cycle needs to be further divided. The microcomputer is very convenient to complete this work. Each Ne signal (the crank angle of the crankshaft 30) is equally divided into 30 pulse signals by the frequency divider, and each pulse signal is equivalent to the crank angle of 1. (30. ÷ 30 = 1.). If each Ne signal is equally divided into 60 pulse signals, each pulse signal is equivalent to a crankshaft rotation angle of 0.5. (30. ÷ 60 = 0.5.). The specific setting is determined by the corner accuracy requirements and program design.

c) Structural characteristics of the G signal generator: The G signal generator is used to detect the reference signal of the top dead center position of the piston and determine which cylinder is about to reach the top dead center position. Therefore, the G signal generator is also called a cylinder identification and top dead center signal generator or a reference signal generator. The G signal generator consists of 1 signal rotor, sensor coil G1, G2 and magnetic head. The signal rotor has two flanges and is fixed on the sensor shaft. The sensing coils G1 and G2 are 180 apart. Installed, the signal generated by the G1 coil corresponds to the top tenth dead center of the sixth cylinder compression of the engine. The signal generated by the G2 coil corresponds to 10 before the top dead center of the first cylinder compression of the engine. .

d) 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 Ne signal generator. When the engine camshaft drives the sensor shaft to rotate, the flanges of the G-signal rotor (No. 1 signal rotor) alternately pass through the magnetic head of the sensor coil, and the air gap between the rotor flange and the magnetic head changes alternately. Gl, G2 will induce the alternating electromotive force signal. When the flange portion of the G-signal rotor approaches the magnetic 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 magnetic head decreases, the magnetic flux increases, and the magnetic flux change rate is positive. The pulse signal is called G1 signal; when the flange portion of the G signal rotor approaches the sensing coil G2, the sensor is sensitive to the decrease in the air gap between the flange and the magnetic head, an increase in the magnetic flux, and a positive change in magnetic flux. A positive pulse signal is also generated in the coil G2, which is called a G2 signal. When the flange portion of the G signal rotor passes through the magnetic heads of G1 and G2, the air gap between the flange and the magnetic head does not change, the magnetic flux does not change, and the magnetic flux change rate is zero. The emf is all zero. When the flange portion of the G-signal rotor leaves the magnetic heads of G1 and G2, because the air gap between the flange and the magnetic head increases, the magnetic flux decreases, and the magnetic flux change rate is negative, the sensing coils G1 and G2 will induce Generate a negative alternating electromotive force signal. Each revolution of the sensor (360 °) is equivalent to two revolutions of the crankshaft (720 °), because the sensing coils G1 and G2 are separated by 180. Installation, so G1, G2 each generate a forward 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 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 is close to and aligned with the magnetic heads of the sensor coils G1 and G2 (at this time, the maximum magnetic flux and the signal voltage are zero). This position corresponds to the piston compression. 10 before the stop. (BT-DCl0.) Position.

Hall-type crankshaft and camshaft position sensors

(1) Structure and working principle of Hall sensor

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

1) Hall effect: The Hall effect was first discovered in 1879 by Dr. E. Hall, a physicist at Johns Hopkins University. He found that when a rectangular platinum conductor with a current I is passed perpendicular to the magnetic field lines into a magnetic field with a magnetic induction intensity of B (see Figure 2-27), a perpendicular to the current will be generated on the two lateral sides of the platinum conductor. The voltage UH in the direction and direction of the magnetic field disappears immediately when the magnetic field is cancelled. This voltage was later called the Hall voltage, and UH was proportional to the current I and the magnetic induction B through the platinum conductor, ie (see next page)

Elements made using the Hall effect are called Hall elements, and sensors made using the Hall element are called Hall sensors. The Hall effect can be used not only to detect the voltage by turning on and off the magnetic field, but also to 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 number of Hall sensors used in automobiles has increased dramatically. The main reason is that Hall sensors have two outstanding advantages: one is that the output voltage signal is similar to a square wave signal; the other is that the output voltage is high or low. The speed of the measured object is irrelevant. The difference between a Hall sensor and a magnetic sensor is that it requires an external power supply.

2) Basic structure of Hall sensor: Hall sensor is mainly composed of trigger impeller, Hall integrated circuit, magnetic steel sheet (yoke) and permanent magnet. The trigger impeller is installed on the rotor shaft, and the impeller is made 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 blade rotates between the Hall IC and the permanent magnet. Hall integrated circuit is composed of Hall element, amplifier circuit, voltage stabilization circuit, temperature compensation circuit, signal conversion circuit and output circuit.

3) The working principle of the Hall sensor: When the sensor shaft rotates, the blade that triggers the impeller passes through 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 passes The Hall integrated circuit and the magnetically conductive steel sheet form a loop. At this time, the Hall element generates a voltage (UH = 1.9 to 2.0V), the transistor of the Hall integrated circuit output stage is turned on, and the signal voltage U0 output by the sensor is low. Level (actual measurement shows that when the power supply voltage Ucc = 14.4V or 5V, the signal voltage U0 = 0.1 to 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 output stage of the integrated circuit is turned off, and the signal voltage U0 output by the sensor is high (measurement shows that: When the voltage Ucc = 14.4V, the signal voltage U0 = 9.8 V; when the power supply voltage Ucc = 5V, the signal voltage U0 = 4.8 V).

(2) Hall-type camshaft position sensors for Jetta and Santana cars

1) Structural characteristics: The Hall-type camshaft position sensor used by Jetta AT and GTx and Santana 2000GSi cars is installed at one end of the intake camshaft of the engine. The structure is shown in Figure 2-28. It is mainly composed of a Hall signal generator and a signal rotor. The signal rotor is also called the trigger impeller and is installed on the intake camshaft. Position and fix with positioning bolt and seat ring. The partition of the signal rotor is also called a blade. A window is made on the partition. The signal generated by the window is a low-level signal, and the signal generated by the partition (blade) is a high-level signal. Hall signal generator is mainly composed of Hall integrated circuit, permanent magnet and magnetically conductive steel sheet. The Hall element is made of silicon semiconductor material, and a gap of 0.2 to 0.4 mm is left between the permanent magnet. When the signal rotor rotates with the intake camshaft, the partition and the window are separated from the Hall IC and the The air gap between the permanent magnets turns around.

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

2) Working condition: According to the working principle of the Hall sensor, when the partition (blade) enters the air gap (that is, in the air gap), the Hall element does not generate voltage, and the sensor outputs a high-level (5V) signal; when When the partition (blade) leaves the air gap (that is, the window enters the air gap), the Hall element generates a voltage. The sensor outputs a low-level signal (0.1V). The relationship between the signal voltage output by the camshaft position sensor and the signal voltage output by the crankshaft position sensor is shown in Figure 2-29. Every two revolutions of the engine crankshaft (720 °), the Hall-type sensor signal rotor rotates once (360 °), correspondingly generating a low-level signal and a high-level signal, where the low-level signal corresponds to the cylinder 1 Compress a certain angle before top dead center.

When the engine is running, the signal voltage generated by the magnetic inductive 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 both the low-level (15.) signal corresponding to the large position of the crankshaft position sensor and the low-level signal corresponding to the camshaft position sensor window, it can recognize that the cylinder 1 is in the compression stroke and the cylinder is at this time. The 4 piston is in the exhaust stroke and controls the ignition advance angle according to the signal output by the small tooth missing of the crankshaft position sensor. After the electronic control unit recognizes that the top dead center position of the cylinder 1 is compressed, it can perform sequential injection control and ignition timing control of each cylinder.

If the engine has deflagration, the electronic control unit can also determine which cylinder has deflagration according to the signal input from the deflagration sensor, thereby reducing the ignition advance angle to eliminate deflagration.

Differential Hall-type crankshaft position sensor

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

(1) Structural characteristics of differential Hall sensors

The differential Hall sensor is also called a dual Hall sensor, and its structure is similar to that of a magnetic induction sensor, as shown in Figure 2-30a. It consists of a signal rotor with convex teeth and a Hall signal generator. The working principle of the differential Hall sensor is the same as the ordinary Hall sensor. According to the working principle of the Hall sensor. When the tooth missing and convex teeth on the engine flywheel pass through the two probes of the differential Hall circuit, the air gap between the tooth missing or convex teeth and the Hall probe changes, and the magnetic flux changes accordingly. An alternating voltage signal is generated in the Hall element, as shown in Figure 2-30b. Its output voltage is made up of two Hall signal voltages. Because the output signal is a superimposed signal, the air gap between the rotor teeth and the signal generator can be increased to (1 ± 0.5) mm (common Hall sensors are only 0.2 to 0.4 mm), so The signal rotor can be made into a disc-like structure like a magnetic induction sensor rotor, and its outstanding advantage is that the signal rotor is easy to install. In automobiles, the convex-toothed 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 characteristics: The Cherokee Jeep 2.5L (four-cylinder) and 4.0L (six-cylinder) electronically controlled fuel injection engines use a Hall-type crankshaft position sensor with a differential Hall circuit. It is mounted on the transmission case. The sensor provides the engine speed and crankshaft position (rotation angle) signals to the ECu as one of the important basis for calculating the injection timing and ignition timing.

The 2.5L four-cylinder electronically controlled engine has eight teeth missing on the flywheel, as shown in Figure 2-31a. The 8 tooth defects are divided into two groups, and each 4 tooth defects is a group, and the angle between the two groups is 180. , The interval angle between two adjacent tooth defects in the same group is 20. . The 4.0L six-cylinder electronically controlled engine has 12 teeth missing on the flywheel, as shown in Figure 2.3lb. The 12 tooth defects are divided into three groups, and each 4 tooth defects is a group, and the interval between adjacent two groups is 120. , The interval angle between two adjacent tooth defects in the same group is also 20.

2) Working condition: When each set of teeth on the flywheel is turned over the Hall probe, the sensor will generate a set of 4 pulse signals. Among them, a four-cylinder engine produces two sets of eight pulse signals per revolution; a six-cylinder engine produces three sets of 12 pulse signals per revolution.

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

The electronic control unit has a certain advance angle when controlling fuel injection and ignition, so it is necessary to know the position of the piston near the top dead center. When the Cherokee Jeep signals each set of signals to the ECU, it can be known that the pistons of the two cylinders are about to reach the top dead center position. For example, in a four-cylinder engine control system, using one set of signals, the ECU can know that the cylinders 1 and 4 are approaching top dead center; using another set of signals, it is known that the cylinders 2 and 3 are approaching top dead center. In a six-cylinder engine control system. Using a set of signals, it can be known that the cylinders 1 and 6, 2 and 5, 3 and 4 pistons are close to the top dead center. The falling edge of the pulse due to the fourth missing tooth corresponds to 4 before the top dead center of compression. (BTDC4.) Therefore, the falling edge of the pulse signal generated by the first tooth gap corresponds to 64 before the top dead center of compression. (BT-DC64.), As shown in Figure 2-32. When the falling edge of the first pulse corresponding to cylinders 1 and 4 comes, the ECU can know that the pistons of cylinders 1 and 4 are now 64 before the top dead center of compression. (BTDC64.), So that the injection advance angle and ignition advance angle can be controlled. However, only with the crank angle signal, the ECU cannot determine which cylinder is located in the compression stroke and which cylinder is located in the exhaust stroke. To this end, a cylinder discrimination signal is required (that is, a camshaft position sensor is required).

(3) Hall-type camshaft position sensor for Cherokee Jeep

1) Structural characteristics: The cylinder discrimination signal of the Cherokee Jeep engine control system is provided by a Hall-type camshaft position sensor, which is also called a synchronous signal sensor. It is installed in the distributor and is mainly composed of a pulse ring (signal rotor) and Signal generator.

There are raised leaves on the pulse ring, occupying 180. Distributor shaft rotation angle (equivalent to 360. Crankshaft rotation angle). The part without leaves also accounts for 180. Distributor shaft rotation angle (360. Crankshaft rotation angle). The pulse ring is installed 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 blade on the pulse ring leaves the signal generator, the sensor outputs a low level (0V). The distributor shaft rotates once, and the sensor outputs a high level and a low level, each of which is 180 high and low. Distributor shaft rotation angles (each equivalent to 360. Crankshaft rotation angle). The waveform of the synchronization signal is shown in Figure 2-32.

When the leading edge of the blade 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 pistons are about to reach the top dead center, where the cylinder 1 piston is located in the compression stroke and the cylinder 4 piston is located Exhaust stroke; for a six-cylinder engine, it means that the cylinders 3 and 4 pistons are about to reach the top dead center, where the cylinder 4 pistons are in the compression stroke and the cylinder 3 pistons are in the exhaust stroke.

When the trailing edge of the blade of the pulse ring enters the signal generator and the sensor outputs a low level (0V), for a four-cylinder engine, it is still the cylinders 1 and 4 that indicate that they are about to reach the top dead center, and the cylinder 4 is in the compression stroke. The cylinder 1 piston is in the exhaust stroke; for a six-cylinder engine, it means that the cylinder 3 piston is in the compression stroke and the cylinder 4 piston is in the exhaust stroke.

After using the camshaft position sensor to determine which cylinder is about to reach the 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 time be 64 before the top dead center. (BTI) C64. ), When the blade of the camshaft position sensor pulse ring enters the signal generator and the sensor outputs a high level (5V), the ECU determines that the cylinder 4 piston of the four-cylinder engine is located in the exhaust stroke (the cylinder 3 piston of the six-cylinder engine is located in the exhaust Stroke), when the ECU receives the falling edge (BTDC64.) Of the first pulse signal of the crankshaft position sensor (CPS), it sends an injection signal to the injector, thereby achieving 64 in advance. Fuel injection. When the camshaft position sensor outputs a high level (5V), the ECU also determines that the cylinder 1 piston of the four-cylinder engine (six-cylinder engine cylinder 4 pistons) is in the compression stroke. At this time, the ECU according to the crankshaft position sensor CPS signal and the ignition advance angle Calculated value: When the ignition advance angle is reached before the piston reaches the top dead center, an ignition command is issued to the ignition controller to control the ignition of the spark plug to achieve ignition 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 1-5-3-6-2-2). Each cylinder performs advanced fuel injection and advanced ignition control.

(4) Hongqi CA7720E car differential Hall type crankshaft position sensor

The Hongqi CA7220E sedan CA488.3. Engine equipped with the SIMOS4S3 electronically controlled fuel injection system uses a differential Hall type crankshaft position sensor composed of a signal rotor and a signal generator. The signal rotor is a toothed disc type, which is installed at the front end of the transmission case. It is similar to the magnetic induction crank position sensor rotor for Jetta AT and GTX cars. It has 58 convex teeth and 57 small tooth gaps evenly spaced on its circumference. And a big tooth missing. The large tooth lacks a reference signal, which corresponds to a certain angle before the top dead center of engine cylinder 1 or cylinder 4 is compressed. The arc of the large tooth defect is equivalent to the arc of the two convex teeth and three small tooth defects.

Because the signal rotor rotates with the crankshaft, the crankshaft rotates one revolution (360 °), and the signal rotor also rotates one revolution (360 °), so the crankshaft rotation angle occupied by the convex teeth and tooth missing on the circumference of the signal rotor is 360. , The crankshaft angle occupied by each convex tooth and small tooth missing is 3. (58 × 3. + 57 × 3. = 345.), The crank angle occupied by the large tooth missing is 15. (2 × 3. + 3 × 3. = 15.), the signal waveform is shown in Figure 2-33a.