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The first half of the 2020s is destined to be hybrid, especially the new generation of hybrid systems (such as DHT) that focuses on efficiency and takes into account the upper limit of power.
To say that last year, our column was probably the earliest and most frequent anonymous flag bearer to stir up the FLAME trend. From the beginning of the year, a certain Di DM-i sales are not eye-catching behind a car is difficult to find, to the end of the year the Great Wall and Geely two major groups of hybrid new wheel bombardment, and finally in the tail of the ox Chery finally disclosed the technical details of Kunpeng DHT, a table of mahjong together.
There are many mixed rivers and lakes, and there have long been two poles led by the Japanese, and today there is a DHT army. When the hybrid moves towards the mainstream position of the whale swallowing fuel vehicle market, it is inevitable that a wave of new words will pour out, especially the English abbreviations.
ECVT, a useless word
Both the internal combustion engine and the motor are easy to discuss, and the problem always comes from the lump of things used to "mix" between the two. Some hybrid motors are relatively independent of traditional transmissions (generally closer to the fuel version), while others do not have mechanical transmissions in the traditional sense, and the transmission and motor are integrated in the same housing. The latter can often achieve the infinitely continuous adjustment of the transmission ratio, so there is a general term ECVT.
Whether ECVT or eCVT or E-CVT, the elder abbreviation of this hybrid world, Chinese generally points to the so-called "electronically controlled stepless transmission". Old car fans know the CVT stepless automatic transmission, this sudden emergence of ECVT, at first glance seems to be CVT its relatives, added a certain E starting part of the CVT?
We have long known MT manual transmissions, AT automatic transmissions, CVT continuously variable transmissions, DCT dual-clutch transmissions... Because the earliest widely used is MT and AT, most people's classification of transmissions is "manual or automatic shift", corresponding to manual transmission MT and automatic transmission AT.
But this was clearly a misunderstanding. Otherwise, how to explain that CVT and DCT can also "automatically shift"? How to explain that there is also an "automatic shift manual transmission" AMT in addition? How come there has been another iMT popping up outside of AMT recently?
MT and AT are fundamentally different in structural principle, rather than just manually automatic
Today we classify transmissions based on their fundamental principles and infrastructure for changing gear ratios (i.e., "shifting"), rather than simply automatic or manual. The manual transmission/MT corresponds to "changing the gear ratio by switching the input and output shafts with different gear size combinations", and the automatic transmission/AT corresponds to "changing the gear ratio by locking or not each of the multiple sets of planetary gear sets" - not "automatic".
So you may have heard that dual-clutch is actually closer to a manual transmission, because although DCTs can also be "automatic", the fundamental principle is the same as that of manual transmissions, which is to switch gear combinations with different size proportions. The same is true of the fact that "manual transmissions that can automatically shift gears" are called AMT and not AT. Today's iMT, which replaces the clutch pedal with an electronically controlled clutch, is still called "xMT" structure, and it will not be called "semi-automatic" because of the lack of clutch operation.
DCT, graphically you can also see that it is closer to MT blood
Back to ECVT and CVT.
We often say that CVT actually refers to "belt drive CVT". Whether this "belt" is a belt, a steel chain or a steel belt, its working principle is nothing more than to change the ratio of the working radius of the two pulleys to achieve a variable transmission ratio and is continuously variable, that is, the so-called stepless variable speed.
We are most familiar with steel belt CVT
The belt CVT itself is only one of the large categories of CVT. It is not only the belt drive method that can achieve a continuously variable ratio. It's just that in the passenger car world we are familiar with, there is basically only one kind of CVT, such as the belt CVT, so "CVT" is equivalent to the belt drive CVT.
Another type of ring curved CVT, which is rare in passenger cars
What about ECVT? In addition to the final effect is the "CV/continuously variable" continuous variable ratio, ECVT and steel belt CVT can be said to have no drop of blood. It's like saying," "Run 70km/h on wheels," and you can drive a car and a Tour de France bike, but there's no juxtaposition between them.
Steel belt is the soul of today's passenger car CVT
ECVT is also not a transmission structure/type that can be juxtaposed with MT, AT, DCT, CVT, etc., because it only defines "what effect can be achieved can be counted as ECVT", and there is no constraint on the structure and principle at all. "There are used motors/E" and "stepless variable speed/CV" which can be called ECVTs as long as you meet these two points.
In practice, it is true that there is everything to do. Using different ways to achieve "ECVT effect" will also have different advantages and disadvantages. Therefore, a single "ECVT" cannot describe what kind of hybrid system this is. Just saying ECVT is basically equivalent to not saying anything.
Mechanical direct drive shifting inside the Thor DHT, double planetary gear set in three gears
Like today's popular DHT hybrid, its transmission mechanism also belongs to ECVT: it contains a motor and infinite speed regulation. And such a fully qualified "ECVT", you can even continue to "add" MT, AT, DCT and other different transmission types internally (in theory, ECVT plus CVT is not impossible).
The Great Wall Lemon DHT added a two-speed transmission in the direct drive part of the internal combustion engine, and its paddle-type shift mechanism is similar to the manual transmission; the three-speed transmission added by Geely Leishen DHT is a planetary gear structure, which can be seen as a built-in 3AT; the three-speed direct drive transmission of Chery Kunpeng DHT is a double-clutch replica.
Kunpeng DHT, pay attention to the two clutches of C2-C3 and the three direct drive gears of G1-G3
PSD？DHT？EHS？
The reason why ECVT is an ancient word is that its emergence is almost in sync with Toyota's creation of the hybrid market.
Toyota's hybrid system is called THS (Toyota Hybrid System, Toyota Hybrid System, is just an abbreviation), the basic principle is to use the planetary gear set has three sets of rotating elements, control one of them, you can change the transmission ratio between the remaining two.
Because this change in the planetary gearset is continuous and infinitely adjustable, the core of the Toyota THS system, which contains a planetary gearset and two electric/generators, can be called ECVT, which is probably the earliest and deepest memory of the term ECVT. Because this type of hybrid system is theoretically a power split type (PS, Power Split), the planetary gear set is called PSD, Power Split Device power shunt device.
Toyota THS and the ECVT in it (inside the red circle)
When it comes to THS, it was originally a complete Toyota hybrid system that included an internal combustion engine, a hybrid transmission (including motors), batteries, etc. - but sometimes we are accustomed to using THS to refer to the most core and special hybrid transmission, that is, the (THS) ECVT. So in some loose occasions and statements, there will be THS≈ ECVT, in the final analysis, it is that lump of things.
PSDs are planetary gear sets that act as power shunt devices
The term DHT, which is popular today, was first defined by the CTI Symposium in Berlin in 2015 to refer to the dedicated hybrid transmission for the Dedicated Hybrid Transmission. Dedicated means dedicated, that is, the hybrid system using the dedicated hybrid transmission DHT can be called DHT hybrid. It can be seen that this name is not binding at all, as long as it is "dedicated" and not common with fuel vehicles, it can logically belong to DHT.
According to the definition, in fact, Toyota THS can also be regarded as one of the DHT hybrids. But the actual situation is a little more complicated.
On the one hand, Toyota's DHT route is more unique, born earlier, and has not been a successful follower since then. On the other hand, another type of DHT with honda i-MMD as the basic idea - dual motor series parallel mixing, extended range plus direct drive, has now carried the banner of DHT and attracted universal emulation. Under the two-phase effect, we are accustomed not to count Toyota THS and other types of DHT in the common context of "DHT hybrid".
In today's common context, THS is THS, DHT is DHT, and other types are other types. Without a special explanation for the term DHT, we follow the customary convention that the default refers to the DTT hybrid, which is similar to i-MMD, double motor series parallel hybrid, and is distinguished from other "DEFINITION DHT hybrids".
Both toyota THS and the fledgling DHTs have the same two conditions of "included motor" and "non-pole adjustment", which also belong to the ECVT category - although the two achieve "ECVT effect" in completely different ways. Again, for the efficient hybrid technology that still has the potential to develop today, ECVT has become a useless word, and its ability to define and describe is no longer enough.
WHEN BYD released the DM-i, it also mentioned an EHS electromix system, which is actually the Electric Hybrid System electric hybrid system - basically nothing. In fact, BYD calls the DM-i hybrid dual motors/generators, direct drive clutches, control systems, etc., the so-called ECVT part EHS. Somewhat similar to the relationship between the Toyota THS hybrid system and the ECVT in it.
Hybridization with a mixture of words is itself a relatively complex product. In the embryonic period of hybrid power more than ten or twenty years ago, the biggest challenge in promoting hybridization was to explain how to "mix" to ordinary users who were confused. Today, represented by Liangtian, there have been a number of hybrids that have broken through cognitive barriers, and consumers have been influenced by word of mouth and reputation even if they still do not understand how their hybrid technology is realized.
The current batch of DHT hybrids, which would have been more simplified and easier to understand hybrid systems, should have done a better job of educating users. However, first of all, DHT itself is not a detailed definition, and each DHT often has its own name for certain parts. In addition, the mixing of past accumulated vocabulary such as ECVT is also interfering with everyone's learning path.
In the end, it can only be: learn mathematics, physics and chemistry well and walk all over the world without fear. It doesn't matter what the name is, no matter how many English abbreviations, you can't stop you from figuring out the basic principles at the bottom. Anti-flickering, no shortcuts.