We have witnessed too many cases of "the gearbox destroys everything". For most users, the slow gear shift of the gearbox is tolerable, but it must not be frustrated! But if I tell you that the gearbox itself will not frustrate, will you doubt your life after listening? Trust me, the gearbox won't be frustrated! As for the frustration and shock you feel, where does it come from? Look down, I'll explain it to you in 5 minutes!
When the vehicle is coasting at a speed of less than 15km/h per hour, if the vehicle has a very strong drag at this time, it is generally called "gearbox low speed Frustrated". But in fact, the real culprit of the drag is not the gearbox, but the engine!
Because when the vehicle is running at a low speed, the low gear with a larger gear ratio is usually used. So when we let go of the throttle and coast, the braking force generated by the engine will naturally be amplified like the driving force at low speed, which will produce a strong drag. It’s just that under such ultra-low speed conditions, as long as the driver releases the accelerator, most gearboxes will immediately slip through the clutch or torque converter to disconnect the engine and the wheels, thereby avoiding The engine "forcibly" brakes the vehicle.
However, for some gearboxes, due to the insufficient calibration of the program, when the driver releases the throttle, the torque converter or the clutch cannot be controlled for the first time to disconnect the wheel and the engine. connection. Eventually, the vehicle will be "brake" by the engine for one second before it becomes "neutral" coasting. During this period, there will naturally be a sense of frustration as if someone stepped on the brake. At this time, we know that the frustration at low speeds is not caused by the gearbox itself, but because the gearbox and the engine are not matched!
We all know that, except for the CVT gearbox which can continuously and steplessly change the torque on the wheels, whether it is a traditional AT gearbox or a DCT gearbox, it can only be done by interrupting power. Perform a torque change operation. As a result, every time the gearbox changes gears, the engine speed will fluctuate greatly in a short period of time.
For example, during an upshift, because the target speed is lower than the current speed, after the upshift, due to inertia, the speed of the flywheel end of the engine is naturally higher than the speed of the gearbox. In other words, a large amount of useless torque is stored at the flywheel end of the engine. When downshifting, since the target speed is higher than the current speed, the engine speed will naturally rise after the downshift, and the effect of natural engine braking will also increase. Therefore, at this time, the gearbox needs to consider how to release a large amount of useless torque or reduce the effect of engine braking, which is to offset the difference in engine speed.
"Veteran drivers" who are proficient in driving manual gears know that in order to avoid the frustration caused by the difference in engine speed when upshifting in low gears, they usually adopt the method of slowly lifting the clutch to make the friction plate Friction with the flywheel end of the engine for a short period of time to release useless torque, and at the same time allow time for the engine to drop in speed, let the engine drop to a low speed suitable for a higher gear, and then engage with the flywheel to avoid occurrence Needless frustration.
In fact, the automatic gearbox actually uses this method when eliminating the speed difference between the various gears of the engine. The traditional AT gearbox releases the useless torque at the flywheel end of the engine by disconnecting the coupling between the two sides of the torque converter, and then using the oil in the torque converter to mix with each other. The dual-clutch gearbox uses the clutch friction plate to "level out" the speed difference between the flywheel and the gearbox gear like a manual gearbox. In short, whether it is a torque converter or a friction plate, the purpose of their work is to improve the ride comfort of the vehicle.
But it is not the smoother the better. If the time to eliminate the speed difference is too long, it will not only cause a long-term power interruption when the vehicle is accelerating, and affect the continuous acceleration performance of the vehicle. It can also cause the friction plate or gearbox to overheat, resulting in a reduction in life. Then at this moment, Car companies need to find a relatively balanced point between ride comfort and shift speed.
For example, when upshifting, because the shift speed of the dual clutch gearbox is too fast, it may happen that the engine speed has not fallen back to the right place, and the next gear has been engaged , This is also one of the reasons for many dual-clutch setbacks. In the face of this problem, manufacturers can reduce the rotational inertia of the engine to alleviate it, such as reducing the weight of the flywheel or the weight of the piston, which can reduce the weight of the engine's rotational inertia parts, so that the engine has a faster speed of rotation when the power is interrupted. , Thereby improving the smoothness of the vehicle upshift.
At this time, some students may have raised questions: If the speed drops too fast, will the speed difference still occur? In fact, in the face of this kind of low speed problem, the engine only needs to be controlled by the computer to increase and match the speed. But if the speed is too high, there is no other way, and you have to wait for the speed to drop.
In other words, whether it is AT or DCT, when downshifting, as long as the ECU (engine control unit) and TCU (transmission computer) are calibrated well, the speed difference between the two can be calculated , It can be smoothed by automatic oil replenishment. But if it is an upshift, you can only pray for the engine speed to drop back quickly.
For automatic transmissions, because the shift speed is slower than that of dual clutches, you don’t have to worry too much about the speed difference caused by upshifts. There is a torque converter to buffer the impact of the speed difference. This is why, usually AT gearboxes have a smoother relationship when shifting gears.
Seeing this, everyone should understand the reason why the gearbox itself will not frustrate as I said at the beginning of this article. Because a qualified automatic gearbox will basically not produce frustration when it moves up and down. If you are not talking about the gear shifting frustration of the gearbox itself, in fact, only when you shift from P to D gear, or from R to D gear, the intrusion caused by the sudden force of the gearbox can be classified as "gearbox frustration. "Because the source of vibration at this time comes from the gearbox itself, not the engine end as we just mentioned.
Seeing this, everyone should understand. In fact, the so-called gearbox frustration is not the intrusion caused by the gearbox itself when shifting gears, but because the engine produces a speed difference. Caused by nowhere to release the torque. Therefore, the "gearbox frustration" often mentioned in the car critics actually comes from the engine speed difference, not the gearbox. Only because the gearbox fails to break down this force through various technical means will it be called the gearbox frustration.
If you want to understand this way of thinking, if you switch to a manual transmission model, should it be called " driver frustrated"?
