Editor | Chen Yuyang
Picture | Fu Hongyuan
There has always been a saying in the mixed circle, "There are only two kinds of hybrids in the world, one is Toyota's hybrid, and the other is other hybrids." In fact, objectively speaking, Toyota is the first automobile company to deploy a hybrid system. The original Prius, which appeared in 1997, is not only the first hybrid model in the world to achieve mass production, but also helps Toyota to take the lead in obtaining the THS hybrid system patent.
As of 20 17, the cumulative sales volume of Toyota hybrid vehicles has exceeded100000, which clearly shows the recognition of end consumers. Honda's i-MMD system was forced out by "Toyota Brothers" in a sense.
(? The structure diagram of Toyota THS hybrid technology is taken from official video data? )
With the emergence of Toyota THS, the hybrid market began to develop rapidly. However, Toyota applied for a comprehensive patent for its hybrid system from the beginning, so other car companies want to enter the hybrid field and hit a wall everywhere. In a sense, P0-P4 hybrid architecture was born under the influence of Toyota patent.
Among them, one company doesn't want to be controlled by Toyota, and this is Honda, which is called "technical house". As early as 1990s, Honda began to develop its own hybrid system. At the earliest, Honda introduced a hybrid system called IMA. The whole design is similar to the P 1 architecture mentioned in the last issue, and it was installed on the hybrid models of INSIGHT, Civic and Accord at that time.
(? Honda i-MMD hybrid technical structure diagram? Official? )
However, limited by IMA's own technology, its fuel economy obviously lags behind that of THS system in the same period, so the former will eventually be abandoned. It was not until 20 12 that Honda, the home of technology, finally developed the i-MMD hybrid system in the "little black house". At this point, Honda Sharp Hybrid officially began to emerge in the hybrid market.
So, what is the difference between THS and MMD?
"Toyota THS Hybrid System: Efficiency First"
The biggest feature of Toyota THS system is to cancel the traditional gearbox, but use a set of planetary gear sets to connect different power sources, and realize pure electric and hybrid drive through the cooperation between gears. Another feature of THS system is that there are two motors with clear division of labor, one of which is responsible for generating electricity and starting the engine; The other is responsible for power output and kinetic energy recovery.
(? Schematic diagram of Toyota THS hybrid power architecture? )
The three power sources are connected in parallel through planetary gear sets, and their matching forms are reasonably distributed according to real-time working conditions and vehicle load rate.
First of all, let's learn how the three power sources are connected with the planetary gear set. As can be seen from the figure, the motor 1 responsible for power generation and starting is connected with the inner ring sun gear, and the engine output crankshaft is connected with the intermediate planetary carrier. The No.2 motor responsible for power output is directly connected with the outer gear ring, and the outer gear ring is directly connected with the wheels.
(? Schematic diagram of power distribution in start-up and low-speed phase? )
During normal starting and low speed driving, the planet carrier will be locked and the engine will not start. THS system will give priority to the battery to provide power for the No.2 motor, and directly output power to the wheels through the external gear ring. Due to the planetary gear structure, the motor 1 connected with the inner sun gear will rotate reversely. In order to ensure the efficiency of electric drive, the motor 1 will keep idling and will not generate electricity.
(? Schematic diagram of power distribution in rapid acceleration stage? )
In the rapid acceleration stage, the engine will start to work, and the power will be directly output through the crankshaft and drive the planet carrier to rotate. At the same time, it will drive the outer gear ring and the No.2 motor to rotate together, and finally the power will be directly output to the wheels. When the acceleration demand is high, the motor 1 responsible for power generation will also be electrified to reverse, and the three power sources will jointly ensure the acceleration ability of the vehicle.
(? Schematic diagram of power distribution during mid-high speed cruising? )
In the middle and high speed cruise stage, THS system takes the engine as the main power source. At this time, the engine outputs power to drive the planetary carrier to rotate, and the planetary carrier directly links the power to the outer gear ring and transmits it to the wheels. When there is more power demand, the motor 2 will also provide power assistance. At the same time, THS system will actively control the motor 1 on the inner sun gear to generate electricity according to the real-time working conditions, and recover the redundant working force of the engine.
(? Schematic diagram of power distribution during braking and coasting? )
During braking and coasting, both motors in THS system become generators, which realizes the function of kinetic energy recovery.
Generally speaking, Toyota THS is a hybrid power system with engine as the main power source. Through the planetary gear set, the three kinds of power are reasonably matched, and then the comprehensive efficiency is maximized. The planetary gear set can maximize the comprehensive efficiency, but due to its existence, THS system will inevitably lose power in pure electric high-speed mode.
Constrained by the planetary gear structure, in order to ensure the ride comfort of the engine, the motor needs to drive the output shaft connected to the engine on the planetary carrier in addition to outputting power. At this time, the engine will not ignite and inject fuel, but the piston still moves back and forth in the reverse direction of the motor, and always maintains an appropriate intervention speed. It's completely useless at this time.
Generally speaking, the main demand of Toyota THS hybrid power system is HEV model. In terms of design, the theme of overall design is to keep the fuel engine in the most efficient range. So the whole hybrid system still uses the engine as the main power source. Because of this, THS will perform relatively poorly in pure electric efficiency, and its power consumption level will be 15% higher than that of domestic discrete hybrid electric vehicles.
It is worth mentioning that THS is driven by an engine, so the requirements for battery capacity are not high. At the same time, as an HEV model, the power battery pack is always in a state of shallow charging and shallow discharging, so the attenuation of the power battery to the HEV model is basically negligible. In addition, Toyota has also introduced PHEV models on the basis of THS before, but due to the above problems, Lei Ling PHEV models can only achieve the 55km pure battery life of 10.5kWh battery.
"Honda Hybrid Vehicle: i-MMD will be transformed."
As a technology company, Honda does make its i-MMD system the ultimate hybrid vehicle. An engine, an electric motor, a clutch and two reducers with fixed transmission ratio constitute a completely different set of hybrid logic. The integration of these "four big pieces" makes the i-MMD system vehicles have three identities: fuel vehicle, electric vehicle and extended-range hybrid vehicle, which correspond to high-speed cruise mode, pure electric mode and hybrid mode respectively.
(? Schematic diagram of Honda i-MMD hybrid power architecture? )
Different from THS, the driving motor of Honda i-MMD is more powerful and is one of the main power sources of vehicles. Except that the wheels are directly driven by the engine in the high-speed endurance mode, the motor is basically the main power source. When the battery power drops to the set threshold, the engine will also start. At this time, the engine will only drive the generator to generate electricity and supply the motor, but will not provide power for the wheels. In short, the i-MMD system at this time is more like an extended-range hybrid vehicle.
(? Schematic diagram of power distribution in pure electric mode? )
It is not difficult to understand the i-MMD system in pure electric mode. The battery directly supplies power to the motor, which is the only power source at this time. When the clutch between the engine and the wheel is disconnected, neither power generation nor driving is started. I-MMD is equivalent to pure electric vehicle in this state.
(? Schematic diagram of power distribution in hybrid mode? )
When the vehicle needs to accelerate quickly, the engine will start to generate electricity, which together with the battery will provide enough power for the motor to ensure that the motor can reach the peak power output. When the vehicle runs smoothly and the power is low, the engine will also start to drive the generator to generate electricity. At this time, the generator will directly transfer electric energy to the motor to provide driving force, and only excess electric energy will be stored in the battery in the form of shallow charging and shallow discharging.
People often misunderstand that i-MMD system generates electricity and stores it in the battery, and then the battery discharges to provide it to the motor. This is obviously wrong. Whether considering the loss of intermediate power conversion or the durability of battery, direct power supply by generator is the best choice. Of course, this undoubtedly puts forward higher requirements for the electronic control system.
(? Schematic diagram of power distribution in engine direct connection mode? )
In the high-speed cruise stage, the clutches in the i-MMD system will be combined, and the engine power will directly drive the wheels through a group of high-speed gear ratio reducers. Its meaning is also very simple. Old drivers must know that fuel vehicles are at the best stage of fuel economy when cruising at high speed.
Generally speaking, i-MMD is a hybrid vehicle that is closer to a pure tram. Especially in the daily car environment, i-MMD system mostly exists in the form of pure electricity or extended program, so the system efficiency will be higher than that of conventional hybrid electric vehicles. At the same time, regardless of the high-speed engine direct drive or the low-speed extended range hybrid logic, the fuel engine will theoretically run in the high-efficiency range.
But at the same time, in order to maximize fuel efficiency, i-MMD system also needs to match Atkinson engine with higher fuel efficiency for power generation, which has become the first hurdle to limit the research and development of other companies. In addition, the driving computer needs to match two power systems at the same time, which also puts forward higher requirements for the development ability of PCU. Therefore, Honda's title of "technical house" is not for nothing.
In addition, i-MMD itself is closer to pure electric vehicles, so it will affect the maximum power output in the case of battery loss.
"So the question is, which system is better? 」
In fact, there are no obvious advantages and disadvantages between the two, and each has its own insistence. However, in the face of China's preferential policies for new energy vehicles, Toyota's THS seems to be unable to do so. At the beginning of design, the system was developed with the concept of fuel vehicle as the main power source, from which it can be seen that all HEV models of THS have quite good fuel economy. But because of this, if THS model is upgraded to PHEV model by increasing battery capacity, its pure electric efficiency will be significantly lower than other hybrid systems, which has been exemplified in Lei Ling/Corolla PHEV.
In contrast, Honda i-MMD is easier to upgrade to PHEV, and the three modes of i-MMD itself represent three independent systems. Especially in pure electric mode, the hardware structure and driving form of Honda i-MMD are the same as those of pure electric vehicles, and it can be directly upgraded to PHEV vehicles only by increasing the capacity of power battery pack and charging function.
If we have to judge the advantages and disadvantages of the two systems, I can only say that with the continuous development of the new energy era, Honda i-MMD system has greater development potential. On the one hand, i-MMD system has more tolerant reorganization space; On the other hand, because the electric drive structure of i-MMD system is closer to pure electric vehicle, it also means that Honda has a richer accumulation in pure electric technology.
Therefore, Honda i-MMD system can better adapt to the development of new energy era. On the other hand, Toyota has indeed occupied the hybrid field for more than 20 years. However, in the face of the new energy era dominated by pure electricity, Toyota may only be able to put down the name of the "hybrid circle" in the past and re-create a world of its own in the field of pure electric.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.