What is a dual clutch transmission?
Dual Clutch Transmission As name implies, technical key of dual clutch transmission is double clutch, that is, there are two clutches, one of which is responsible for odd gears (1, 3, 5). , 7 gears), and other clutch is responsible for even gears (2, 4, 6 gears). It can be imagined as combining functions of two manual transmissions into one and integrated into a single system that does not have a torque converter and a planetary gear. At first glance, geared part is similar to a manual transmission because it has a synchronizer, but difference is that it uses a "dual" clutch to control on-off power of engine. These two automatically controlled clutches are electronically controlled and hydraulically controlled by Push , can control operation of two sets of clutches at the same time.
Dual Clutch Transmission DCT is different from conventional automatic transmission. It is based on a manual transmission rather than an automatic transmission. Besides flexibility of a manual transmission and comfort of an automatic transmission, it can also provide unlimited intermittent power output. The traditional manual transmission uses a clutch. When shifting gears, driver must press clutch pedal to engage gears of different gears, and power is interrupted during shift period, which makes power output intermittent.
At present, more and more models mainly use dual clutch gearboxes. Dual clutch gearboxes have their own advantages and disadvantages. But despite criticism, many car companies still insist on using it. So why are domestic car companies so fond of using dual-clutch gearboxes? Let's take a look at pros and cons of dual clutch transmissions with help of a car editor.
It is precisely because of inherent advantages of dual clutch transmissions that major manufacturers must find ways to overcome the technical difficulties and develop their own dual clutch transmissions, including under their own brand names, even if they face many difficulties.
What are advantages and disadvantages of a dual clutch transmission
Whether you are accelerating or decelerating, clutch is basically ready to move up and down for you, so when you apply brake you need to immediately accelerate, press accelerator pedal and find that engine is accelerating but there is no power . Similarly, these two conditions will seriously affect life of dual clutch. It is good practice to release brakes and coast for some distance before accelerating.
Especially on busy roads, you can shift to S gear (engine speed is higher in S gear than upshift) or shift to 1st gear in manual mode to prevent shifting between 1st and 2nd too often stop-and-go gears, The gearbox overheats. Do your best to walk around a bit and stop for a while, no semi-connected detour, if there are too many queues then there is no way.
There is another type of gearbox, for example Fiat, when you press brake all way, clutch will not turn off power, but will always be on, it's like a manual transmission without a clutch and gear is still on. The gearbox is "strangled" and broken, so when waiting for a traffic light or traffic jam for more than 5 seconds, it is recommended to put this type of gearbox in neutral. There is such a friend around me. It turned out that he did not know situation with dual clutch, and then he sent box straight to scrap. Fortunately, manufacturer replaced it for free during warranty period.
Dual Clutch Transmission Advantages
The advantages of a dual clutch transmission are as follows:
1. Shift gears quickly. The shift time of dual clutch transmission is very short, faster than manual transmission, only less than 0.2 seconds.
2. Save fuel. A dual-clutch transmission can save a lot of fuel because it eliminates torque interruption, meaning engine's power is always used and it always works at its best. Compared with traditional planetary automatic transmission, it is more conducive to fuel economy, and fuel consumption can be reduced by about 15%.
3. Comfort. Due to high switching speed, each DCT switch is very smooth, and upset is so small that it is difficult for human body to detect it.
4. There is virtually no loss of torque during shifting process.
5. When top gear is already in ready state, upshift speed is very fast, reaching an astonishing 8 milliseconds.
6. Regardless of throttle state or operating mode, shift times can be as short as 600 milliseconds (odd to odd or even to even gears take about 900 milliseconds, e.g. 5th to 3rd gear).
Disadvantages of Dual Clutch Transmission
1. The question of cost. The dual clutch transmission structure is complex, and production process requirements are relatively high, so cost is relatively high. So, we see that some mid-range and high-end models are equipped with dual-clutch gearboxes.
2. Torque problem. While a dual clutch transmission can certainly meet requirements of general purpose vehicles in terms of acceptable torque, it is still not enough for intensive use. Because if it's a dry clutch it will generate too much heat, and if it's a wet clutch there won't be enough friction.
3. Due to presence of an electronic control system and a hydraulic system, efficiency of dual clutch transmission is still not as high as that of traditional manual transmission, especially wet double clutch transmission for large torque transmission.
4. When gear to be shifted is not in ready state, shift time is relatively long, even exceeding 1 second in some cases.
5. Dual clutch transmissions are heavier than traditional manual transmissions. 6. Early dual clutch transmissions were unreliable.
With development of automobiles, shortcomings of dual-clutch transmissions will inevitably become smaller and smaller, and become more and more perfect.