Generally speaking, increasing or decreasing the accelerator refers to changing the throttle opening of the engine through the accelerator pedal, so as to control the flow of combustible mixture and change the engine speed and power to meet the needs of car driving. The traditional engine throttle control mechanism works by connecting a cable or a lever with one end connected to the accelerator pedal and the other end connected to the throttle linkage plate. However, the scope of this traditional throttle application is limited and lacks accuracy.
With the development of automotive electronics technology, an electronic accelerator (EGAS) came into being. In the current electronic fuel injection engine, in addition to the above-mentioned functions, the electronic throttle can further improve the fuel-saving and emission performance of the engine, because it controls the gate of engine power adjustment. The main function of the electronic accelerator is to convert the angle at which the driver steps on the accelerator pedal into a voltage signal proportional to it. At the same time, various special positions of the accelerator pedal are made into contact switches to control the engine operating conditions such as idling, high load, acceleration and deceleration. The electric pulse signal is sent to the controller ECU of the electronic control engine to achieve optimized automatic control of fuel supply, fuel injection and speed change.
The electronic accelerator control system is mainly composed of accelerator pedal, pedal displacement sensor, ECU (electronic control unit), data bus, servo motor and throttle actuator. The displacement sensor is installed inside the accelerator pedal to monitor the position of the accelerator pedal at any time. When a change in the height position of the accelerator pedal is detected, it will instantly send this information to the ECU, and the ECU will perform arithmetic processing on this information and the data information from other systems, calculate a control signal, and send it to the servo motor relay through the line. The electric motor drives the throttle actuator, and the data bus is responsible for the communication between the system ECU and other ECUs.
Compared with the traditional cable throttle, the electronic throttle is not just replacing the cable with a cable. In the traditional mechanical cable throttle, the opening of the throttle is directly controlled by the driver. However, due to the driver’s experience and limited ability to judge vehicle conditions, it is often difficult to achieve the optimal throttle opening, and the car cannot be kept in a constant position. Economical, environmentally friendly and comfortable; and in a car equipped with an electronic accelerator control system, the throttle opening is not only related to the driver’s pedal opening, but the ECU senses the pedal position sensor signal After analyzing and comparing various other sensors, the best position of the throttle valve under the current working conditions is obtained, so as to achieve a theoretical air-fuel ratio state close to 14.7:1 under different loads and working conditions, which makes fuel economy. Performance and driving comfort are at their best.
In our daily driving, we will encounter some novices or unskilled drivers who will suddenly step on the accelerator pedal due to improper operation or some overly aggressive drivers. We know that this kind of operation is unscientific and not only unfavorable. Fuel economy, and it will cause damage to the engine. The throttle valve is suddenly opened. At this time, it is the maximum load state of the engine. Full load will cause insufficient combustion of the engine. At the same time, the fuel injector will increase the fuel injection, causing fuel waste. The load on the engine increases and the use of the engine is shortened. Life span is not conducive to environmental protection. The ECU cannot control the throttle valve in a vehicle with a cable throttle. It can only default to this misoperation. At most, it will slightly adjust the fuel injection, but it still cannot solve the fundamental problem. For electronic throttle, this is a breeze. At this time, the ECU will think that this is an unscientific driving practice of the driver, so it will issue a command to open the throttle at a certain speed instead of synchronizing with the speed at which the driver steps on the pedal. In addition to protecting the engine and improving fuel economy, it also makes the driver feel very smooth and has no impact, and improves the comfort of the occupants.
The working principle of electronic throttleWhen the sensor detects a change in the height position of the accelerator pedal, it will instantly send this information to the ECU, and the ECU will perform arithmetic processing on this information and the data information from other systems, calculate a control signal, and send it to the servo motor relay through the line. The servo motor drives the throttle actuator, and the data bus is responsible for the communication between the system ECU and other ECUs. Since the electronic throttle system adjusts the throttle through the ECU, the electronic throttle system can be set with various functions to improve driving safety and comfort, the most common of which are ASR (traction control system) and speed control system (cruise control) ).
When the ASR system senses the rotation speed of the wheels, the ECU calculates the slip rate based on the position of the accelerator pedal, wheel speed and steering angle of the steering wheel, and adjusts the air-fuel mixture flow by reducing the throttle opening to reduce the engine Power to achieve control purposes. In the ASR system, the electronic throttle plays a very critical role. It involves functions such as vehicle speed control and idle speed control in the entire ASR system, so that the system can execute instructions quickly and accurately. That is, when the electronic throttle system receives the ASR system command, its throttle control command only comes from the ASR, so that the driver's misoperation can be avoided.
When the driver uses the speed control system, the vehicle speed sensor inputs the vehicle speed signal into the ECU, and then the ECU outputs the command servo motor to control the throttle opening. In such a system, the control system automatically adjusts the throttle opening of the engine according to changes in driving resistance, so that the driving speed remains stable. Therefore, the electronic throttle system can also be compatible with the cruise control function. In the current electronic fuel injection engine, the electronic throttle is not only used to further improve the fuel saving and emission performance of the engine, because it controls the gate of engine power adjustment. Therefore, the electronic throttle can play many roles. In addition to the above-mentioned functions, it can further improve the fuel-saving and emission performance of the engine, because it controls the gate of engine power adjustment. Therefore, the electronic throttle can play many roles.
As an indispensable and important part of a car, the accelerator directly affects the safety performance of the car. Since the 21st century, most cars have used electronic throttles instead of conventional cable throttles. Compared with the old-fashioned cable throttle, the electronic throttle controls the electronic signal to send commands through the depth of the accelerator pedal, so that the engine provides matching power. Its biggest feature is that it can control the throttle opening through the ECU. When the position of the accelerator pedal changes, the signal output by the electronic accelerator can be used as a basis for measuring the accuracy of the automatic control of the electronic accelerator. The electronic accelerator detection system is based on these real-time signals and adopts various schemes to evaluate the quality and reliability of the electronic accelerator. Its performance testing.
Features of ECU-controlled throttle in electronic throttle modelsIn electronic throttle models, when the ECU controls the throttle, it will analyze the depth of the throttle and the vehicle conditions, and finally calculate the current appropriate throttle opening. When the driver suddenly accelerates (depress the pedal to the end) when starting, the ECU analyzes the current vehicle speed, throttle valve size, etc. From the perspective of fuel economy and reasonable emissions, it will appropriately limit the throttle opening range and control the injection rate. The fuel system limits the fuel injectors to maximize fuel injection. This makes the driver feel that there is a delay after the accelerator is stepped on before the car starts to exert force. This is the so-called accelerator lag. Therefore, the throttle lag is actually formed by the ECU by limiting the instantaneous power output of the engine. Of course, doing so also brings benefits-saving fuel and protecting the environment.
However, the electronic accelerator is not used to limit the power output of the engine. After the car is running, if you quickly step on/release the accelerator pedal 1/3 of the depth, you can feel the car's obvious refueling/refueling, and its effect It's almost equivalent to completely depressing/releasing the accelerator. What's going on? This is the case of ECU assisting the driver to speed up/decelerate quickly according to the current vehicle conditions. Therefore, the ECU will help the driver achieve the desired acceleration/deceleration operation according to the vehicle condition during the driving of the electronic accelerator model, making it easier for the driver to operate the accelerator pedal.
Important related parameters of electronic throttleSynchronization: The degree of equalization of the two signal values ​​output by the throttle at a certain stroke angle. Linearity: The difference between the theoretical voltage value and the actual voltage value of the throttle signal at a certain stroke angle. Empty stroke angle: refers to the pedal stroke angle at which the signal continues to change when the pedal starts to change its angle. Pedal force: Including pressure and elasticity, it is the force curve of the pedal from idling to full stroke, and then from full stroke to idling. Throttle signal curve: Including idle speed signal and full stroke signal, the voltage output signal curve of accelerator pedal from idle speed to full stroke. Hysteresis: At a given angle, measure the output pressures in two different rotation directions. The hysteresis effect is the difference between the two output pressures. The maximum acceptable gap is Ua taxi 1%. Repeatability: Under the same conditions, after 10 complete back-and-forth strokes, for a sensor with a given temperature of (23±5)°C and any point in the same direction, the recorded voltage difference cannot exceed 0.5. %.
Advantages and disadvantages of electronic throttleadvantage
1. The electronic throttle control system can make the throttle opening reach a better state. The structure of the traditional mechanical cable throttle is shown in the figure. The figure shows the non-linear relationship between the throttle intake flow and the throttle angle. Therefore, in many working conditions, it is difficult to control the throttle opening directly by the driver. Making precise adjustments, especially under cold start, low load and idling conditions, will result in a decline in the economy, driving performance and ride comfort of the car, and an increase in emissions of harmful substances.
Mechanical throttle structure
Throttle angle and gas flow curve
The electronic accelerator system judges the driver's intention according to the driver's pedal motion range, and comprehensively controls the throttle opening accurately and reasonably according to the vehicle condition, so as to achieve the effect of good comfort and economy.
2,. High stability, not easy to stall and break. In daily driving, misoperations often occur due to the lack of driving experience of the driver or emergencies, while the traditional throttle system directly executes the misoperation of the driver to cause stalls or accidents.
The electronic accelerator system will analyze and judge after receiving the pedal signal, and then send appropriate instructions to the throttle actuator unit to ensure that the vehicle is running stably.
Shortcomings and shortcomings
1. The working principle is relatively complicated and the cost is increased. Compared with the traditional cable throttle, in the hardware, the electronic throttle needs to add the throttle position displacement sensor and the servo motor, its driver and actuator, and increase the ECU wiring; in the software, it is necessary to develop and analyze the position sensor signal and comprehensively give the optimal vehicle condition. The algorithm of the control command is integrated in the on-board ECU, increasing the development cost.
2. There is a delay effect, and the throttle response is not fast. As mentioned earlier, in a car equipped with an electronic throttle system, the driver cannot directly control the throttle opening and can not directly control the engine power. Instead, the ECU analyzes the car with better comfort and saves fuel. Valve control commands, so compared to the direct control type, there will be a slight delay in pulling the throttle.
3. The reliability is not as good as the mechanical throttle.
When a car is driving, it will encounter various vehicle conditions, and there are high-frequency electromagnetic interference inside the car, such as electric motors and ignition coils, which can cause electromagnetic interference. Electronic devices may malfunction or loosen under these conditions; complex analysis and processing algorithms may also be affected. Causes malfunctions such as program runaway, and the driver cannot directly control the power of the engine. Once this happens, it will have unpredictable consequences.
Electronic throttle accelerator
Simply put, the electronic throttle accelerator was born to relieve throttle lag. According to the characteristics of the electronic throttle, the electronic throttle accelerator will have the following characteristics:
1. Amplify the throttle signal to improve static response
The so-called "acceleration" of the electronic throttle accelerator is mainly achieved by improving the sensitivity of the throttle response. Some models will amplify the input throttle signal by 50%. This means that 33% of the accelerator signal at the rear of the pedal is useless at any time, and the accelerator output is already at full throttle when the driver depresses the pedal 66%, which increases the sensitivity of the accelerator response by 50%. %. However, the electronic throttle accelerator does not reduce the grading of the throttle signal as many people say. In fact, the throttle signal is still steplessly adjusted, but the previous 1:1 is adjusted to 1:1.X, and X is the signal. The magnification factor.
2. Amplify the throttle signal growth rate and improve dynamic response
When the accelerator pedal is stepped on, the accelerator will calculate the rate of change of the accelerator signal based on the stepping amplitude and time. The faster the change, the stronger the acceleration requirement, and the accelerator will increase this rate of change. The final result is a dynamic acceleration Correspondingly better.
3. Provide false driving style for ECU to adjust engine parameters
The ECU of modern engines generally has the ability to adapt to driving style. If the driver often presses deeply on the accelerator (commonly known as pulling the speed), the ECU will gradually think that the driver’s style tends to be "fierce", so that the engine will slowly adjust the throttle and fuel injection The system waits to get the best tuning parameters of the engine in this style. After using the electronic accelerator, even if you drive according to the previous "gentle" driving style, the engine will still get a "fierce" driving experience, which is equivalent to cheating the ECU. Over time, the engine will automatically modify its various parameters to suit the style. .
4. The difficulty of oil separation of manual models increases
After the manual gear model is added to the accelerator, the response of the accelerator pedal is too sensitive, and it needs more precise oil-off coordination to achieve the previous effect. This is very similar to the effect of the depth of the clutch on the smooth start. A deep clutch is easy to control, but has a large operating stroke; a shallow clutch has a short operating stroke, but it is difficult to control, and the accelerator pedal has the same effect on starting.
5. Increase fuel consumption
Because the throttle accelerator improves the throttle response, it is equivalent to making the driving style more "intensified". This will undoubtedly increase fuel consumption, but the increase in fuel consumption is not very high. Our measured fuel consumption increase is between 5%-10%. This is acceptable to those who love driving pleasure.
6. Too "foolish"
Once the throttle accelerators currently on the market are installed, regardless of the current road conditions and the driver's wishes, they will faithfully perform the "acceleration" duty, which will cause trouble to the driver in many cases. First of all, for automatic transmission models, rapid increase of the throttle signal will often cause automatic downshifts. When the vehicle is driving at high speed, frequent downshifts will cause excessive engine speed, which increases fuel consumption on the one hand and unnecessary wear on the other. In addition, in many cases, drivers are not necessarily willing to operate the car violently. For example, when driving at night causes poor vision, rain and snow weather causes slippery roads, excessive acceleration increases the risk of driving. However, the current accelerator cannot be turned off at will (unless you remove it), which causes great inconvenience to users.
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