1. The evolution of throttle
1. The birth of a carburetor
The earliest meeting with the world was the carburetor, which is a device that creates a combustible mixture of fuel and air in a spark-ignited internal combustion engine. According to the requirements of different working conditions of the internal combustion engine, it provides a corresponding amount of fuel, atomizes the fuel and evenly mixes with the air to obtain a combustible mixture of certain components, so as to burn well, and ensure a smooth transition between various operating conditions of the internal combustion engine. Carburettor to meet the requirements of each working condition, add the main oil system, idle system, enriched system, acceleration system and starting system. The carburetor-type fuel supply device has a simple structure, reliable operation, low price, and easy maintenance. But its biggest drawback is that it can not accurately control the concentration of the mixture, resulting in incomplete combustion, increased harmful components in the exhaust gas, does not meet the stringent requirements of today's environmental protection. In addition, due to the presence of the throat, the intake resistance increases. There is also the phenomenon that the distribution of gasoline in each cylinder is uneven, and gas resistance and ice formation are easily generated. In order to solve these problems, an electronically controlled fuel injection system emerged in the 1980s.
1. The emergence of electronically controlled fuel injection (EFI)
The use of an electronically controlled fuel injection system (EFI) for automotive engines has the following advantages:
Good start-up performance. The start-up time is only about 50% of the traditional carburetor type; the acceleration performance is good. Fully-accelerated acceleration test, the speed of the vehicle from 0km/h to 100km/h is 7% shorter than that of conventional carburetor; Compared with the use of conventional carburetor systems, engine power can be increased by 5% 10%, torque increased by about 7%; fuel consumption is low, and economy is good. The EFI system can achieve high-precision control of the air-fuel ratio (), and the charge distribution of each cylinder is more uniform. Compared with the conventional carburetor, the fuel consumption is 5% 15%; exhaust pollution is reduced. The EFI system is the best available and can be used in conjunction with a three-way catalyst to keep the CO, HC, and NO in the exhaust gas at a minimum.
The EFI system replaces the carburetor with its superiority, retains the throttle part in the intake system, and adds inspection conditions such as electronic control units (ECUs), throttle position sensors, and air flow meters. The ECU adjusts the fuel injection quantity of the injector according to the signal parameters of these sensors (including air flow rate, rotation speed, temperature, etc.) to obtain the best.
In the EFI system, the throttle valve is controlled by mechanical control and an additional device is installed for air fuel compensation. However, when it is under low load, cold start and other special conditions, the desired requirements cannot be achieved. This led to the introduction of electronic throttle ETC.
1.3 Alternatives to Electronic Throttle ET C
ETC is in the throttle body mechanism of EFI system, remove some auxiliary compensation devices, and increase the drive circuit, drive motor and gear transmission, and its throttle opening is directly controlled by the motor drive under any operating conditions. The ECU can formulate an optimal mixture of components as the engine operating conditions change (simultaneously determined by the engine's power, economy, and emission reduction requirements), and it has good idle, acceleration, and deceleration conditions. Transition performance. Now, electronic (
The throttle valve system has become a very important module in the engine electronic control management system.
Advantages of using Electronic Throttle System (ET CS): Accurate control of throttle opening. The optimal throttle opening is calculated by corresponding to the driving conditions, and is controlled by the throttle valve driven by the control motor.
The control system is compact and cost-effective. Integrated acceleration control, idle speed control, cruise control, etc. to achieve information sharing, and use the same actuator to control the throttle, so that the vehicle structure is greatly simplified.
The vehicle's driving reliability is excellent. ET CS offers the ability to dual-control systems or fault-tolerant processing.
Optimal handling and stability. When the driver receives a command to step on the accelerator, it does not directly open the throttle. Instead, according to the engine's current load and the speed at which the speed increases, the throttle first opens a basic angle T P1 and then slowly moves to the second position. The angle TP2 is advanced. This progressive opening method can reduce the vibration caused by the abrupt change of the engine speed and obtain the most efficient intake control, so that the acceleration of the engine is more supple, faster, and more fuel-efficient.
Lower emissions. Due to the precise control in various situations, the combustion is more completely allowed to increase the stable combustion at the time of idling to increase the stable combustion, improve the fuel economy, and the emissions are further controlled.
2. The composition and working principle of Electronic Throttle System (ETCS)
2. Composition of Electronic Throttle System (ETCS)
At present, the electronic throttle control system (ET CS) produced by some major manufacturers is mainly composed of the following parts: the accelerator pedal position sensor. These sensors convert the amount of pedal movement into two types of electronic signal input ECUs with different output characteristics (downstroke magnitude and rate of change).
Throttle position sensor. The two throttle position sensors convert the mutual monitoring throttle opening signal into an electronic signal input ECU with the same output characteristics as the accelerator pedal sensor.
Throttle control motor. The throttle control motor is a stepping motor or a servo DC motor, which has the characteristics of responsiveness and low energy consumption (in the early stage, it was mostly a stepping motor, and now it is mainly a DC motor because of the control precision and the need for convenient servo control). The ECU performs duty cycle control on the current direction and strength of the throttle control motor, and adjusts the throttle opening through two-stage gear deceleration.
ECU module. It includes an information processing module and a driver circuit module.
2. 2 working principle
The working principle of the electronic throttle valve system is as follows: the driver operates the accelerator pedal, and the accelerator pedal position sensor generates a corresponding voltage signal to input the throttle control unit. The control unit first filters the input signal to eliminate the influence of environmental noise, and then according to the current The driver's intention is analyzed by the operating mode, pedal movement amount, and rate of change, and the basic demand for the engine torque is calculated, and the basic expected value of the corresponding throttle angle is obtained. Then through the CAN bus and the vehicle control unit to communicate, get other operating conditions and various sensor signals such as engine speed, gear, throttle position, air conditioning energy consumption, etc., from which to calculate the entire vehicle needs The torque is compensated by the desired value of the throttle angle, and the optimal opening degree of the throttle valve is obtained, and the corresponding voltage signal is sent to the drive circuit module to drive the motor so that the throttle valve can reach the optimal opening position. The throttle position sensor feeds back the throttle opening signal to the throttle control unit to form a closed-loop position control.
Throttle drive motors are usually stepper motors or DC motors, and the control methods of the two are different. The stepper motor often uses the H-bridge circuit structure. The control unit controls the stepper motor by controlling the level of the number of pulses, frequency, and direction. The level of the level controls the direction of rotation of the stepper motor. The number of pulses controls the angle at which the motor rotates, ie, it sends a pulse signal. The stepper motor rotates a step angle. The pulse frequency controls the motor rotation speed, which is proportional to the pulse frequency. Therefore, the precise positioning and speed regulation of the motor can be achieved by adjusting the above three parameters.
The control DC motor adopts pulse width modulation (PWM) technology, which is characterized by high frequency, high efficiency, high power density and high reliability. The control unit controls the magnitude of the rotation angle of the DC motor by adjusting the duty cycle of the PWM signal. The motor direction is controlled by the return spring connected to the throttle valve. The output torque of the motor is proportional to the duty cycle of the PWM signal. When the duty cycle is constant, the motor output torque balances with the return spring resistance torque, the throttle opening degree does not change; when the duty cycle increases, the motor drive torque overcomes the return spring resistance torque, and the throttle opening increases. Large; Conversely, when the duty cycle decreases, the motor output torque and throttle opening also decrease.
The ECU monitors the function of the system. If a fault is found, the system fault indicator will light up to indicate that the driver has a fault. At the same time, the electromagnetic clutch is separated and the throttle is no longer controlled by the motor. The throttle returns to a small opening position under the action of the return spring to slow the vehicle to the maintenance location.
3. Status Quo and Prospect Analysis of Electronic Throttle System (ETCS)
Since the 1988 BMW car began to use electronic throttle control systems, the control system has only been applied to a small number of limousines. However, due to its high price and immature technical and market conditions, it was not until 2000 that ETC products were put into the market. Now electronic throttle is not only the equipment of high-end car, it has occupied most of the market, it has been used by many models, such as the home-style Peugeot 206. Now as long as it is required to meet the Euro III and Euro IV standards, then Electronic throttle must be used.
However, the electronic throttle also has deficiencies: In order to ensure that the engine can still run after the system failure, the return spring needs to maintain the throttle valve with a small opening, there is a non-linear spring, coupled with non-linear damping and air intake disturbance resistance moment The instability makes the system difficult to achieve high-precision control; because the air flows through the throttle to the intake manifold into the cylinder for a very short time, even if the ECU processing is very fast, the throttle response to the signal there is also 10 milliseconds Stage delay, which adversely affects the formation of a uniform mixture of the engine; the electronic throttle system is very sensitive. After the dirty carbon deposition of the throttle exceeds the limit, the system control error due to inaccurate signals causes the engine control performance to deteriorate; the control system Complex, not easy to repair.
At present, many foreign companies have made in-depth research and development of electronic throttle systems, such as Germany's Bosch, Pierburg, the United States Delphi, Visteon, Japan Toyota, H itachi, Denso, Italy M arelli has launched series of products used in various Brand of high-end cars. Although some domestic cars, such as POLO, are equipped with electronic throttle systems, there is still much room for excavation of ETC research.
4 Conclusion
Electronic throttle control technology first appeared in the early 1980s. It was only used in high-end cars. With the increasing development of electronic technology, the increasing prominence of energy problems and environmental issues, and the increasing demand for automotive performance, electronic throttles have become The most important control device for electronically controlled engines has been widely applied to various vehicles. The advantage is that the throttle can be quickly and accurately controlled to the optimal opening according to the driver’s wishes, emissions, fuel consumption, and safety requirements. A variety of control functions can be set to improve driving safety and comfort. Currently, BMW, BOSCH, Toyota and other companies are researching this technology, and manufacturers such as BM W, GM, Toyota, AUDI, etc. are already on some of their models. Successfully applied.
In 2002, BMW Corporation produced a throttleless petrol engine. The motor-driven valve directly controls the intake air, eliminating pumping losses and greatly improving engine performance. However, there is still a long way to go before direct drive valve control intake. The ET CS study laid the foundation for the future production of throttleless engines.
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