There are really many automatic cars now, and it is undeniable that many auto companies continue to stop production in order to cater to the market. Five years ago, most Class A cars had manual versions, with automatic cars above class B coming standard. However, even for A-Class cars these days, there are very few cars with manual versions. To be sure, there are only a few A0-class cars left on the manual model. However, with the popularity of automatic transmissions, some questions about automatic transmissions are also increasing! When suspected of a car club, will automatic transmissions such as AT, CVT, DCT and other automatic transmissions frequently switch d gear and n gears, which will cause damage to the transmission? Originally, switching between d and n files was a normal operation. Many friends of automatic cars will choose to switch neutrals when they stop and wait for traffic lights, but this operation often occurs several times, dozens of times during driving every day. Because this operation is too frequent, there are claims of damage to the transmission.
How does an automatic transmission shift gear? Friends may suspect that the manual transmission completes the shift under the operation of the driver, and the shift force that changes the transmission comes from the driver; so how does the automatic transmission complete the shift? This is like a solenoid valve, which can be seen as an actuator in an automatic transmission. Under the command of the electronic control unit TCU, the solenoid valve can directly control the multi-plate clutch, brake, fluid drum, etc. of the transmission, realizing the shift of the automatic transmission! Taking an AT transmission as an example, how does it perform gear shifting? In fact, after we start the vehicle, when the transmission is in nth or p gear (p gear = N gear parking lever), the oil pump extracts hydraulic oil from the oil pan, and the actuators ready to be fed into the transmission at this time, because it is kept in n gear, the oil discharge valve will block the hydraulic oil. Press the joystick from nth or p gear to d gear, then the oil discharge valve opens the obstruction of the oil path in the forward mode, and the hydraulic oil directly presses multiple clutches, and the coupling at the 1st gear and the fluid drum end is completed.
At this time into the 1st gear, but then the speed rises, as the hydraulic oil pressure rises, the hydraulic oil pushes open the valve that closes the 2nd gear oil circuit, and the hydraulic oil pushes the 2nd gear clutch piece, at this time entering the 2nd gear. As the speed continues to rise, the pressure of the working oil continues to rise, the valve that closes the 3-stop oil circuit is pushed open, and when the 3-stop oil circuit opens the working oil, one side pushes and presses the multi-sheet clutch of the 3rd gear, the other side pushes and presses the multi-sheet clutch of the 2nd gear, and the multi-sheet clutch of the 2nd gear is lifted, so of course the simple person simply draws the picture, and the multi-segment AT is much more complicated than this in the actual operation!
There are oil ducts densely distributed above, but there are countless solenoid control valves and steel balls (slides) that act as a role in closing the oil ducts. It should be understood that the reason why the AT transmission can complete the shift is to cut off multiple top clutches with hydraulic oil to achieve the coupling of power. Because the gear of the automatic transmission is not 8AT, 9AT, 10AT, etc., so the control of different gears of the oil circuit, valve is also very much solenoid valve stack means to open or close a certain oil circuit, relative to a gear to disconnect the clutch, lift the coupling Car in the car transmission of the solenoid valve is very busy Why explain the automatic transmission speed shift process, mainly the vehicle running in the transmission of the solenoid valve is very slow. We drive around the city every day, so the speed is not necessarily the same. Constantly changing speeds inevitably cause the shift position of the transmission to change constantly. For example, we drove the car from the yard to the road, and the speed of the car completed the transition of 10km-50km. At this point, the transmission ended the process from 1st gear to 3rd gear, just in front of it encountered a red light and began to slow down.
Completing such a process of upshifting and downshifting may only take less than 100 meters to complete. However, the number of times such a solenoid valve works dozens of times, so that the acceleration and deceleration process within a few hundred meters is likely to be repeated dozens to hundreds of times in a day's operation. (So do friends think that the frequent switching of d and n files is terrible?) The number of shift valve actions caused by the d and n gear switching is less than 1% of the number of solenoid valve operations in each gear, and even less than one in a thousand! The d-stop is a pattern that indicates the forward movement, not a specific block
What is D-stop? D gear is actually an abbreviation of the drive, is the meaning of forward or drive, hanging d gear only means that the car begins to move forward or drive, not to represent the gear. On the other hand, when the car is in forward mode, the automatic transmission in the forward mode selects different gears according to the actual situation; the main reason for the problem of "frequent switching d and n gears will not damage the transmission", in the understanding of many friends, in the d gear mistakenly believes that the transmission is static, but in fact, the transmission of the d mode is completely dynamic, as long as the car is non-constant speed can be suspended, d gear braking? As can be seen from the above, frequent d and n gear switching is very simple for automatic transmissions. This is because the number of movements of the shift valve cannot be compared with the number of movements of other solenoid valves. If the shift valve is broken, does the other valves matter? Therefore, when you are driving on a daily basis and waiting for traffic lights, you can switch to nth gear as you like! So, if you don't switch to n gear, will a short stop with the brakes in d gear cause damage to the transmission?
Actual short-term parking, you can completely choose the d gear to step on the brake method, will not cause damage to the transmission; the only drawback is that the fuel consumption is a little higher than the hanging n gear! In the simple diagram of the AT transmission shown in the figure above, d gear, n gear is only the clutch coupling or coupling contact between the fluid drum turbine and the planetary gear group; the coupling state under the d gear is in the braking state at this time, so the planetary gear group is stationary, and the turbine end of the hydraulic torque converter connected to it also remains static; but the hydraulic oil between the pump wheel and the turbine of the hydraulic torque converter is hydraulic oil, so it has not reached the point where the turbine is stationary and the pump does not rotate! As long as the pump wheels are spinning, the engine can continue to run naturally, so this is the secret that the automatic transmission brakes do not turn off. Even with brakes, the engine rotates, but the turbine side of the fluid drum is stationary, thereby increasing the rotational resistance of the engine, and the pump impeller rises very little because the engine is still running and the hydraulic oil is circulating, so the temperature rises very little and does not burn the transmission.
Some of the newer cars are equipped with an automatic neutral function (neutral throttle), which disconnects the coupling of about 90 even if it is braked in d gear, leaving only 10). Of course, such a design is not to protect the transmission, but to increase fuel consumption, retaining 10% to ensure responsiveness at the start; please give it a try. Starting faster next time with the brakes, but starting from nth gear to d gear is a bit slower. Because multi-plate clutch presses also take time. In short, even if the d gear brake is carried out when parking, frequent switching n and d gears will not cause harm to the vehicle, and the naked eye can see that there are many switches between n and d, what is the place that the naked eye cannot see? In fact, as long as the car is driving and changes the speed, the solenoid valve of the transmission will continue to turn on and off. In contrast, the switching of n and d files is of no value. Therefore, the normal use of the transmission can be. You don't have to worry all day. If the operation method is not prohibited in the vehicle manual, it is reasonable.