Reduce emissions and electrification talk about Toyota TNGA architecture power system

1. Product and engine modularity under the new architecture

GAC Toyota's new Camry will be launched in November this year, and it is also the first domestic Toyota TNGA (Toyota New Global Architecture). In addition to the renewed exterior interior, another big attraction is the new powertrain from the TNGA architecture, which includes the new 2.5L naturally aspirated engine with the highest fuel efficiency in the current production car, and 8AT automatic transmission. Box, new structure E-CVT automatic transmission. Ok, let's sit down and see what Toyota is doing for this "core".

● Toyota TNGA architecture has a number of production models

The first model of the Toyota TNGA architecture was the fourth-generation Prius that was first launched in Japan in December 2015. The C-HR listed overseas last year and the new Camry listed overseas this year are also derived from the TNGA architecture. Toyota expects that more than 60% of Toyota's branded models will be derived from the TNGA structure by 2021.

According to the current news, the first domestic TNGA architecture models are the new Camry and C-HR. The two models will be located at GAC Toyota, which will be produced by GAC Toyota's new third plant in Nansha, Guangzhou, with a designed capacity of 220,000 units/year. The C-HR "sister model" (like the relationship between Ralink and Corolla) will be produced by FAW Toyota's new plant in Tianjin, which has a designed capacity of 200,000 units/year. For some time to come, Toyota's TNGA-based models launched in China will be produced by these two plants.

The concept of Toyota TNGA architecture is slightly different from the modular platform adopted by other manufacturers. In addition to modular production, it forms a more unified whole in project planning, product design and R&D. Compared to the single-single platform of a single model in the early years, the vehicle parts have a higher general rate. Therefore, the use of the TNGA architecture will undoubtedly benefit Toyota's efforts to reduce the cycle and cost of product development and manufacturing.

The application of the Toyota TNGA architecture is optimized for powertrain, body structure, manufacturing process, suspension system, aerodynamics, NVH performance and ergonomics to further improve vehicle performance. The improvement of the power system is the most obvious, and this is what will be explained below.

● Further energy saving, emission reduction and electrification are the goals of the TNGA architecture power system

EU emissions regulations have forced manufacturers to make technological improvements to reduce carbon dioxide and harmful emissions. In 2008, the EU set a target of reducing CO2 emissions from new cars sold in the EU to 95g/km in 2020. As a global car company, Toyota must raise the emission index of its products to EU standards before the arrival of the “big limit” to maintain its product competitiveness. According to Toyota's plan, by 2021, the carbon dioxide emissions of Toyota's models will be reduced by more than 15% (compared to the 2015 product).

Toyota's energy-saving and emission reduction ideas are consistent with major manufacturers in the general direction, by improving engine thermal efficiency, reducing engine running losses, and enhancing the degree of electrification of the power system. The difficulty in upgrading the technology is that it can not reduce the power output performance while saving energy and reducing emissions. It is better to make achievements in terms of weight reduction and miniaturization.

In the past, Toyota has insisted on independent research and development and lean production. The focus on technology has given birth to the world's first mass-produced hybrid Prius and the world's first mass-produced hydrogen fuel cell car Mirai. However, in the auto industry's iterative speed-up, in order to realize the development of new models and keep up with the development of technology, Toyota has to keep up with the times through joint development and technology sharing. The change in Toyota's operating methods is precisely to cope with the conflicts of the above mentioned technology upgrades and the short development cycle. To some extent, the shortened development cycle of the TNGA architecture is also a product of the product iteration speed.

Electrification is an important development trend in the automotive industry in the future, and the “three-electric system” of batteries, motors and electronic controls is a key factor in the achievement of electric/hybrid vehicles. In view of this, Toyota will increase the number of electrification technology developers by 30% by 2021 to meet the needs of personnel in the development of electrification technology. From the major changes in the structure of the hybrid system of the TNGA architecture (the specific changes we will explain in detail below), we can see that Toyota's achievements in the field of electrification have begun to show.

● Engine modular design and flexible production

In the past, Toyota's different series of engine products will adopt different designs, and the versatility of parts is not high. By the time of the TNGA architecture, Toyota will adopt a more unified design to increase the generalization rate of components. The cylinder volume and number of cylinders of the TNGA-engined engine are modularized, and the number of specifications is reduced compared to the past. Engineers design new engine products by selecting specific cylinder volume specifications and number of cylinders.

The modular design of the engine enables uniform processing equipment and tooling to achieve engine parts processing and assembly, and increase production line efficiency and flexibility (the same line can produce more types of engines in parallel). ).

2, the new powertrain

● New 2.5L naturally aspirated engine with long stroke and high compression ratio

The 2.5-liter naturally aspirated engine on the new Camry is the first engine to be born from the TNGA architecture, code-named "A25A-FXS". The engine is tuned to the traditional fuel and hybrid models.

Toyota 2.5L A25A-FXS engine main parameters

Application model Traditional fuel vehicle Hybrid vehicle displacement (mL) 24872487 Bore diameter (mm) 87.587.5 Stroke (mm) 103.4103.4 Compression ratio 13:114:1 Intake form Naturally aspirated Naturally aspirated Oil supply method Straight spray straight Spray maximum horsepower (Ps) 205177 maximum power speed (rpm) 66005700 maximum torque (N·m) 250220 maximum torque speed (rpm) 48003600-5200

The A25A-FXS engine uses a long stroke design with a piston stroke to cylinder diameter ratio of 1.2. The long-stroke design, combined with the large adjustment range and motor-controlled intake valve timing adjustment mechanism, can achieve the Atkinson duty cycle with a larger expansion ratio than the compression ratio in part of the load range to improve the fuel economy of the engine.

The A25A-FXS engine has a compression ratio of 13:1 for conventional fuel vehicles and the A25A-FXS engine for hybrids with a 14:1 compression ratio. In the current Chinese market, only the Mazda Chuangchi Blue Sky series engines (displacement 1.5L, 2.0L, 2.5L) use a compression ratio of up to 13:1. The use of a higher compression ratio can improve the thermal efficiency of the engine, thereby achieving fuel economy improvement, which is one of the important development directions of the engine in the future.

A valve seat is installed in the general engine cylinder head valve seat position. When the seat ring is installed, the valve will directly contact the seat ring instead of the cylinder head valve seat. Made of alloy cast iron or powder metallurgy or austenitic steel, this valve seat is more resistant to high temperatures and shock loads than ordinary cast iron or aluminum alloys. The presence of the valve seat can extend the life of the cylinder head. The A25A-FXS engine uses a laser cladding process to weld a layer of high-strength alloy to the valve seat at the intake valve seat of the cylinder head to act as a valve seat. After the cladding alloy, subsequent machining is required. The exhaust valve is still traditional. The valve seat is designed to enhance durability).

In terms of the cooling system, the A25A-FXS engine uses an electric water pump, a water jacket gasket, and an EGR exhaust gas recirculation cooling line is integrated on the cylinder head. The electronic water pump does not directly consume engine power and reduces the load of the engine; the water jacket gasket acts as a diversion force for the coolant, which can reduce the temperature near the exhaust valve under high load conditions and reduce the probability of knocking. It provides guarantee for high compression ratio for engine operation; EGR exhaust gas recirculation cooling pipeline integration contributes to engine miniaturization.

The 4-2-1 exhaust system will cause the three-way catalytic converter to heat up more slowly because the exhaust line is longer than the normal 4-1 exhaust system. In order to solve this problem, Toyota shortened the pipeline length of the 4-2-1 exhaust system to avoid the exhaust interference, and made the engine exhaust port closer to the three-way catalytic converter; Catalysts to meet emission targets for warm-up conditions. If we compare Mazda's 4-2-1 exhaust system with the Toyota engine's exhaust system, we can see that Toyota's 4-2-1 exhaust system is shorter and straighter, all for Accelerated design of the temperature of the three-way catalytic converter. (Click to view Mazda 4-2-1 exhaust system analysis)

Comparison of 2.5L A25A-FXS engine and 2.5L 5AR-FE engine parameters

Model A25A-FXS5AR-FE Displacement (mL) 24872494 Bore (mm) 87.590 Stroke (mm) 103.498 Compression ratio 13:110.4 Intake form Naturally aspirated Naturally aspirated Oil supply Direct injection Multi-point EFI Maximum horsepower (Ps) 205184 maximum power speed (rpm) 66006000 maximum torque (N·m) 250235 maximum torque speed (rpm) 48004100

Compared with the 2.5L 5AR-FE engine on the current Camry, the thermal efficiency of the A25A-FXS engine applied to the traditional fuel vehicle is increased from 35% to 40% of the 5AR-FE engine, and the maximum horsepower is increased by 21 hp to 205 hp. The maximum torque has been increased by 15 Nm to 250 Nm. Compared with the old engine, the A25A-FXS engine has a comprehensive improvement in power performance and fuel economy. This engine is currently the world's most thermally efficient 2.5L gasoline engine.

● 8AT gearbox after optimizing the torque converter

The TNGA architecture's 8AT gearbox on the front-wheel drive model is from Aisin (Toyota is one of Aisin's major shareholders), and the new Camry is about to be equipped with this gearbox. The 8AT gearbox (hereinafter referred to as "Toyota's new 8AT gearbox") under the TNGA architecture is greatly optimized in the torque converter assembly.

The torque converter assembly is mainly composed of a lockup clutch, a torsional vibration damper and a torque converter. Toyota's new 8AT transmission uses a multi-plate lock-up clutch and expands the lock-up range of the lock-up clutch (ie, at lower speeds, the lock-up clutch is combined to provide a rigid connection between the engine and the transmission ), giving the vehicle a better direct drive feel, improving the transmission efficiency and fuel economy of the transmission.

Due to the increased lock-up range of the lock-up clutch, the torque converter no longer needs to transmit very large torques, and the drive work between the engine and the gearbox is achieved only at the start, so the size can be designed to be smaller. The same design ideas, we can also see on the Mazda Chuangchi Blue Sky 6AT gearbox (click to view the Chuangchi Blue Sky 6AT gearbox disassembly content). In order to effectively suppress the vibration and impact of the engine from being transmitted to the gearbox after the lock-up clutch is engaged, the inside of the torque converter

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