Parallel design! Analysis of Honda's IMA hybrid system

Compared with Toyota's hybrid system (CT200h, hybrid Camry and Prius), Honda's hybrid technology may be a little unfamiliar to car enthusiasts. However, as early as 2007, Honda wanted to introduce its IMA hybrid technology to the Chinese market through the Civic Hybrid model, but due to the high price of the hybrid Civic and the limited acceptance of hybrid vehicles by consumers, it failed to promote Honda's hybrid technology to the market.

Times have changed. With the advent of the era of high oil prices and the improvement of people's environmental awareness, hybrid models may not be the first choice for consumers in the short term, but their attention is also increasing. This year, Honda will launch three hybrid models in China, namely the hybrid version of Fit, CR-Z and Insight. Today, I will briefly introduce what Honda's IMA hybrid technology is. Click on the picture below to read the test drive article of Honda CR-Z and Fit hybrid version!

● There are three types of hybrid system structures. Honda uses a parallel design.

The common hybrid power systems on the market can be roughly divided into three categories: Honda's IMA hybrid power system adopts a parallel structure, and its main feature is that the engine is the main power source and the motor is the auxiliary power source; the hybrid power systems on Toyota and Lexus models are mostly parallel-parallel, and the engine and motor can be used as the main power source of the vehicle, and can reliably travel long distances in pure electric mode at low speeds; Chevrolet Volt adopts a series hybrid power system, and its main feature is that the engine does not directly participate in the vehicle drive, but provides power to the motor, and the motor drives the vehicle.

Honda IMA hybrid system features: engine-based, simple structure, light weight, compact layout

The full name of IMA in Honda's IMA hybrid system is Integrated Motor Assist. It was first launched in 1997 and is widely used in models such as Insight, Civic, Accord (seventh generation), Fit and CR-Z. As of now, Honda's IMA hybrid system has developed to the fifth generation of products, but the basic design ideas and concepts are still the same, that is, the engine is the main power source, and the motor is used as an auxiliary power hybrid mechanism. The characteristics are simple structural design, light weight and compact layout.

『Left: CR-Z Right: Hybrid Fit』

『Left: Insight Right: Hybrid Accord (seventh generation)』

Honda's IMA hybrid system is mainly composed of four parts: engine, electric motor, CVT gearbox and IPU intelligent power unit. Among them, the engines of the main hybrid system are mainly 1.3L and 1.5L naturally aspirated four-cylinder engines. There was also a combination of 3.0L V6 engine + 144V motor for the hybrid Accord model. The electric motor is a three-phase ultra-thin DC brushless motor, which is installed between the engine and CVT gearbox as a power auxiliary device.

Both the 1.3L and 1.5L inline four-cylinder naturally aspirated gasoline engines have many Honda signature engine technologies, such as the i-VTEC intelligent variable valve timing system, the I-DSI intelligent dual spark plug sequential ignition system, and the VCM variable cylinder management system. However, the engine power tuning and the working mode of the VCM variable cylinder management system will be different for different models and market positioning.

The engine has an intelligent variable valve timing and lift control system, which can control the valve opening time and lift according to the vehicle's driving conditions, and even completely close the intake and exhaust valves of a certain cylinder, thereby achieving cylinder deactivation. The 1.5L engine equipped on the CR-Z model can shut down the fuel supply and intake and exhaust of one cylinder when the vehicle is cruising at low speed, while the other three cylinders work normally, which relatively reduces energy consumption and emissions. The 1.3L engine on the hybrid version of the Fit and Insight models can automatically stop the fuel supply and air supply of all cylinders when the vehicle is cruising at low speed, achieving true cylinder deactivation and zero emissions.

Honda IMA hybrid system official video explanation:

However, the prerequisite for Honda's IMA system to achieve pure electric driving is cylinder deactivation technology, and the engine crankshaft and motor are connected together. When the vehicle is running in pure electric mode, the engine stops supplying fuel but the cylinder and crankshaft continue to operate, which consumes more or less electricity. When the hybrid systems of brands such as Toyota and Nissan are running in pure electric mode, the connection between the engine and the motor will be "interrupted" through planetary gears or clutches. It consumes less electricity and the technology is more advanced than the cylinder deactivation achieved by Honda through the VCM variable cylinder management system.

As for the gearbox, there is nothing worth introducing too much. Most of the hybrid models currently available on the market use CVT gearboxes. In addition to making the "gear shifting" smoother, the more important thing is that compared to traditional automatic gearboxes, CVT is easier to match with the engine and electric motor, thereby improving transmission efficiency.

The full name of IPU is Intelligent Power Unit, which consists of a power control unit "PCU-PowercontrolUnit", a group of high-performance nickel-hydrogen batteries and a refrigeration unit. The gasoline engine and motor are arranged at the front of the car, and the intelligent power unit is arranged at the rear of the car.

● There are four types of hybrid systems in terms of "mixing ratio", and Honda's IMA system belongs to moderate hybrid system.

The hybrid power currently on the market can be divided into four categories based on the "mixing ratio", namely: mild hybrid (abbreviated as mild hybrid, and so on), mild hybrid (abbreviated as: mild hybrid), moderate hybrid (abbreviated as moderate hybrid) and heavy hybrid (heavy hybrid). Among them, mild hybrid mainly has engine start-stop technology, while mild hybrid adds a braking force recovery function on the basis of mild hybrid. Generally speaking, in this mode, the power provided by the motor accounts for a relatively low proportion of the total vehicle power. Currently, models such as the hybrid version of Roewe 750, Mercedes-Benz S400L Hybrid and other models that can be seen in China are all mild hybrids.

As for medium hybrid, the basic technology is similar to mild hybrid, but the electric energy can cooperate with the engine to drive the vehicle, and under certain conditions, pure electric driving can be achieved. Currently, Honda's IMA hybrid system belongs to this category. In addition to Honda, the new Buick LaCrosse hybrid model also belongs to the ranks of medium hybrid. As for heavy hybrid, the representative models are Toyota Prius, Lexus CT200h, RX450h, etc. The biggest feature of this type of model is that it can achieve pure electric driving for a long distance (about 3-5 kilometers), and the motor accounts for a high proportion of the vehicle's power output.

Honda's IMA system belongs to the category of mild hybrid systems. Although from a technical perspective it may not be as advanced as Toyota's series of models that use a heavy hybrid system, and cannot achieve relatively long-distance pure electric driving, the advantage is that Honda's IMA system has a simple and compact structure, relatively low manufacturing cost, takes up less space in the car and has little effect on the weight of the vehicle.

Five power modes: full electric drive at low speeds

Honda's IMA hybrid system has a total of five operating modes, in which the engine and the electric motor work together during the vehicle's starting acceleration phase, rapid acceleration, and high-speed driving phase, which can improve the vehicle's power performance. When the vehicle is driving at a low speed, the engine cylinder is shut down and the vehicle can be driven entirely by electricity, but the speed cannot exceed about 40 kilometers per hour. When the vehicle is in the normal acceleration phase, it is completely driven by the engine, the electric motor stops working, and uses the engine's kinetic energy for charging.

When the vehicle decelerates and brakes, the engine stops working and the vehicle recovers energy to charge the battery pack. When the vehicle is idling, the engine will also automatically stop working to reduce fuel consumption. Of course, at this time, the vehicle's air conditioning system will not provide cold air, but only air.

Editor's comment: Whether Honda's IMA hybrid system can be accepted in China depends on the price

Although oil prices have been rising in recent years and the call for the development of new energy vehicles has been growing, Toyota is the only one in the domestic hybrid vehicle market. Honda's purpose for introducing three hybrid models to China this year is also very clear, that is, to occupy a favorable position and become familiar with Chinese consumers before this market has fully developed and grown. Although from a technical perspective, Honda's IMA hybrid system is a medium-hybrid, not as advanced as Toyota's, and its product diversity is not as rich as Toyota (including the Lexus brand), it also has its own advantages in terms of practicality and popularity. After all, the characteristics of Honda's IMA hybrid system are simple structure, small space occupation and low manufacturing cost. I think as long as there is market demand, it should not be difficult for Honda to extend the breadth of its hybrid model product line.

Let's take the Honda Fit hybrid model as an example. Its price in Japan is about 1.59 million yen, which is about 120,000-130,000 yuan in RMB. The price of the Fit with the same configuration using a regular gasoline engine is about 1.3 million yen, which is 300,000 yen cheaper than the hybrid Fit (about 2.4 yuan in RMB). Judging from the price difference between the two models, it seems that the hybrid model has a good price-performance ratio.

However, the situation in the Chinese mainland market is not optimistic. According to the information we got from the dealers, the Honda hybrid Fit is an imported model with a pre-sale price of about 200,000 yuan, which is nearly twice as expensive as the traditional power Fit produced by GAC Honda, about 100,000 yuan. If this is true, it would be a tragedy!

Another model, the Honda CR-Z, which is about to enter China and is known as the world's first hybrid coupe, has a pre-sale price of around 300,000 yuan given by dealers. Although it is roughly in line with expectations, it is unrealistic to rely on it to sell well due to its special positioning. Therefore, if Honda hybrid cars want to really sell well, more expectations should be placed on the relatively "cheap and large" Insight. There are reports that Dongfeng Honda will introduce the car to the Chinese mainland market within this year, and even produce it domestically. As for the key to success or failure, it still depends on the price.

Looking at the domestic hybrid vehicle market, from being unpopular in the early years to being gradually accepted by people in recent years, Toyota has contributed greatly to the launch of models such as Lexus CT200h, Toyota New Prius and Toyota New Camry ZURI at relatively reasonable prices. If Honda still wants to get a share of the Chinese hybrid vehicle market in its early stages of development, pricing is particularly critical.