Automatic wave (automatic transmission) cars can shift gears and torque automatically according to road conditions, so drivers can concentrate on road traffic without the interference of shifting gears. Automatic wave is quite mysterious to the layman. It is necessary to analyze automatic wave's professional knowledge in detail. I hope this article can give you a preliminary impression. There are three common types of automobile automatic wave: hydraulic automatic wave (AT), mechanical stepless automatic wave (CVT) and electronically controlled mechanical automatic wave (AMT). AT present, AT is widely used in automobiles, and AT has almost become synonymous with automatic wave. The old Honda used a four-speed AT automatic gearbox, and the new 03 was changed to a five-speed AT gearbox. AT: Compared with manual wave, hydraulic automatic wave (AT) is quite different in structure and use. Manual wave is mainly composed of gears and shafts, which produce speed change and torque through different gear combinations; AT is composed of hydraulic torque converter, planetary gear and hydraulic control system, which realizes speed change and torque change through hydraulic transmission and gear combination. Among them, hydraulic torque converter is the most distinctive part of AT, which is composed of pump wheel, turbine and guide wheel, and directly inputs engine power to transmit torque and clutch action. Principle Pump impeller and turbine are a pair of working combinations, just like two fans placed opposite each other. The wind of one fan will drive the blades of another fan to rotate, and the wind will become the medium to transfer kinetic energy. If liquid is used instead of air as the medium to transfer kinetic energy, the pump wheel drives the turbine to rotate through the liquid, and then a guide wheel is added between the pump wheel and the turbine, so that the speed difference between the pump wheel and the turbine can be realized through the reaction force. Because the range of automatic speed change and torque change of hydraulic torque converter is not large enough, in order to improve efficiency, several rows of planetary gears are connected in series behind the turbine, and the hydraulic control system will automatically control the planetary gears with the change of engine work, thus realizing automatic speed change and torque change. The automatic shift of auxiliary mechanism can't meet various driving needs such as parking and reversing. Therefore, there is also an intervention device, that is, the manual shift lever, which is marked with P (parking), R (rear gear), N (neutral gear) and D (forward gear). In addition, the forward gear has additional gears of 2nd gear and 1 gear for starting or climbing. Because its transmission is divided into several speed ratio sections, it is stepless only in the specified speed section, so AT is actually an automatic transmission between step and stepless. Advantages and Disadvantages AT does not need to shift gears through clutch, and the gear change is small, the connection is stable and the operation is simple, which brings convenience to drivers and comfort to passengers. However, there are also many shortcomings. First, it is slow to respond to speed changes and insensitive to manual gears, so many riders like to drive manual gears; Second, the fuel consumption is uneconomical, the transmission efficiency is low and the torque range is limited. In recent years, the introduction of electronic control technology has improved this problem; Third, the mechanism is complex and it is difficult to repair. The high-speed circulating hydraulic oil in the torque converter will produce high temperature, so the specified high-temperature resistant hydraulic oil should be used. In addition, if the car cannot be started due to insufficient battery power, it cannot be started by a cart or trailer. If the faulty vehicle is towed away, the driving wheel must be off the ground to protect the automatic wave gear from damage. CVT: The transmission belt with variable groove width and ratchet wheel are used for power transmission, that is, when the ratchet wheel changes the groove width, the contact radius between the driving wheel and the driven wheel also changes, and the transmission belt generally adopts rubber belt, metal belt and metal chain. CVT is truly stepless speed change. Its advantages are light weight, small volume and few parts. Compared with AT, CVT has higher working efficiency and lower fuel consumption. However, the disadvantage of CVT is also obvious, that is, the transmission belt is easy to be damaged and cannot bear a large load. It can only be used in low-power and low-torque vehicles with a displacement of about 1 liter, so the automatic gear occupancy rate is below 4%. AMT: Based on the original mechanical transmission (manual wave), it mainly changes the manual shift control part. That is, under the condition that the overall transmission structure is unchanged, the automation of gear shifting is realized by adding an automatic control system controlled by a microcomputer. So AMT is actually a robot system to complete the clutch operation and gear selection. Because AMT can be modified on the basis of manual wave in production, it has good production inheritance and low investment responsibility, and is easily accepted by manufacturers. The core technology of AMT is microcomputer control, and the electronic technology and quality will directly determine the performance and operation quality of AMT. It is reported that AMT will focus on the localization of automatic wave automobiles in the future. The automatic transmission shift lever of Accord has seven gears, which are P (parking), R (reverse), N (neutral), 1, 2, D3 and D4. When the gear is in the P position, the transmission is mechanically locked. When the car is blocked here, it is best to step on the brake pedal to avoid increasing the load of the starter. When leaving the P position, you must press the brake pedal and press the release button on the shift lever. When operating in R gear, make sure that the car can't move forward. If it is forward, be sure to stop the car and then enter R gear to avoid damaging the transmission gear. N gear is neutral. You can use N gear when parking for a short time, regardless of whether the car is turned off or not, but it is best to use P gear when driving. When shifting the N gear to other gears, you must press the brake pedal to avoid damaging the transmission gear. D4 gear is a driving gear, which is used during normal driving. The transmission automatically selects the appropriate gear according to the driving speed and acceleration of the vehicle, and changes between 1-4 (or 5) forward gears. Our driving is mainly in D4 gear. D3 gear is also a driving gear, which is basically the same as D4 gear except that only the first three forward gears are changed. But when driving, you must pay attention to the maximum speed allowed in the third gear to avoid damaging the engine. D3 gear should be used for traction in hilly areas, and D3 gear should also be used when descending steep slopes to provide engine braking and reduce the heat generated by brake pad wear and friction. When the transmission is in second gear, it is locked in second gear, even if it stops, it will not automatically shift to first gear. When going up a steep slope, the second gear can provide more power, and when going down a steep slope, the engine braking effect will be improved. When starting the vehicle on wet or snowy roads, the second gear can reduce wheel idling and slipping. When the gear is 1, the transmission is locked in first gear. My experience is that this gear is hardly used. The automatic transmission is controlled by computer during driving, which can automatically increase or decrease the gear according to the engine speed and vehicle speed. During rapid acceleration, the transmission will downshift to increase power. Therefore, when accelerating rapidly, the car will obviously feel that it will accelerate after sitting. My driving experience is that when I accelerate sharply, I will step on the accelerator to 3000 or 4000 rpm, then step on it again and force the transmission to upshift, and repeat this for 3-4 times until I reach the highest gear and drive. Although the automatic transmission is computer controlled, it will automatically remember the shift speed according to your driving habits. Some novices can obviously feel the shift impact when driving, because they dare not refuel when driving, and start the engine to work at low speed for a long time, which leads to the automatic low-speed shift of the transmission. When the engine is at low speed, the torque output is not enough, so it is difficult to drive the high gear, so they will feel the shift impact. Obviously, the reason should be the same as the shift impact when the hand speed is not enough. The key to solve this problem is to increase the working speed of the engine as much as possible, and accelerate it with the big foot throttle as much as possible, so as to improve the shift speed of the gearbox. According to my own experience, taking 2.4 as an example, when the gearbox shifts below 2000 rpm, it will feel the shift impact. The lowest shift impact is 1700 shift, which is very serious. The car accelerated to more than 4000 revolutions at high speed. After a few laps, the transmission automatically shifted to 2500, and the shift was almost imperceptible. Only when the tachometer pointer drops can it be determined that the gear has been engaged by the owner. Pay more attention to automatic transmission gear shifting when driving at ordinary times, change unscientific driving habits and reduce gear shifting impact, which is helpful to reduce transmission gear wear and greatly improve driving comfort and smoothness. Check the transmission oil regularly, so that the transmission can work in a good environment and your car can work better and safer for you. All of the above are my driving experience and perceptual knowledge. Welcome to discuss.