What is the function of BMW valve motor?
In terms of auto repair, the auto repair master explained that BMW's VALVETRONIC valve consists of a fully variable valve stroke control device and a variable camshaft control device (double VANOS), and the closing time of the intake valve can be selected at will. Electronic valve takes on the function of throttle to a great extent. Therefore, it is necessary to use a fully variable valve stroke control device.
First, the structure of the electronic valve BMW's electronic valve structure as shown in figure 1. When the intake valve is opened, the intake air volume can be completed by adjusting the valve stroke, so that the optimal cylinder air volume can be determined.
1, servo motor The servo motor, also known as the executive motor, is arranged above the camshaft. The worm of the servo motor is embedded in the worm wheel installed on the eccentric shaft. Servo motor is a typical closed-loop feedback system. The reduction gear set is driven by a motor, and its terminal (output) drives a linear proportional potentiometer for position detection. The potentiometer converts the rotating coordinate into proportional voltage and feeds it back to the control circuit board. The control circuit board compares it with the input control pulse signal to generate a correction pulse, which drives the motor to rotate forward or backward, so that the output position of the gear set meets the expected value, thus achieving the purpose of accurate positioning of the servo motor.
2. The contact surface between the roller valve press rod and the middle push rod is an inclined platform, where rolling friction can reduce mechanical loss, and the press rod and the push rod are divided into different grades, and the components of the same grade are always installed on the same cylinder.
3. The eccentric shaft sensor is shown in Figure 2. The eccentric shaft sensor provides actual parameters for the adjustment function by measuring the rotation angle of the eccentric shaft. The eccentric shaft sensor sends the eccentric shaft position to the valve stroke control unit or DME. Its measuring angle range is 180.
The working principle of eccentric axis sensor is magnetoresistance effect: when the nearby magnetic field changes position, ferromagnetic conductor will change its resistance. To this end, the eccentric shaft is equipped with a magnetic wheel with a permanent magnet. When the eccentric shaft rotates, the magnetic lines of these magnets will pass through the magnetic conductive material in the sensor, and the resulting resistance change will be converted into valve stroke by the engine control unit. Therefore, the magnetic wheel must be fixed on the eccentric shaft with non-magnetic fixing bolts, otherwise the sensor will not work normally.
Second, the working principle of electronic valve
1, the working process of the electronic valve, the requirements for the valve stroke of the engine at different speeds are very different. At low speed, due to the small intake air, if the valve stroke is large, it will not generate enough intake negative pressure, and the fuel injector will not be fully mixed with the inhaled air after injecting fuel, resulting in low combustion efficiency, greatly reduced low-speed torque and increased emissions. In this case, a smaller valve stroke should be adopted. Due to the small valve stroke and the increase of intake negative pressure, a large number of eddy currents can fully mix the mixture and meet the normal operation of the engine at low speed. At high speed, the situation is just the opposite. There is a lot of air intake at this time. If the valve stroke is too small, the intake resistance will be too large, and enough air cannot be inhaled, thus affecting the power. Therefore, at high speed, the valve stroke needs to be larger to obtain the best valve distribution demand.
(Photo/Text/Photo: Pacific Auto Network Q&A called Beast)