[Che Shu Lecture] What are the unique engine skills of major car companies?
As we all know, with the continuous maturity of engine technology in recent years, the country has more stringent requirements for vehicle emissions. It can be said that the development of engine technology is getting closer to the bottleneck. Nowadays, major manufacturers have different technical research directions, different vehicle positioning, and the technology applied to the engine is also very different. Then Uncle Che will take a look at the black technology on the engine air intake this time.
1. Single overhead camshaft (SOHC)
Early engines will use a single overhead camshaft structure, the role of the camshaft is to provide a more accurate start or close time for the engine's intake and exhaust valves. Both Toyota and Volkswagen have used direct drive, parallel valve structures in single overhead camshaft engines. This design may be the most compact and simple. The disadvantage of a single-top camshaft is that it cannot adapt to too many valves and cannot meet the requirements of large-displacement and high-speed engines.
2. Double overhead camshaft (DOHC)
As the name implies, on the basis of single overhead camshaft, In order to improve the charging efficiency of the engine, the number of valves per cylinder was increased, and then the double overhead camshaft was born. Why do this? Imagine if you use a single nostril to breathe smoothly when you are running, or a double nostril to breathe smoothly. The same applies to the engine. Because of the limited position of the single top camshaft, it is impossible to arrange more cams on one camshaft to drive the valves. To meet the power demand of the engine under high load, double overhead camshafts came into being. From the original 2 valves per cylinder to the current 4 valves (2 intake valves, 2 exhaust valves) and 5 valves (3 intake valves, 2 exhaust valves) per cylinder, this is also a higher-speed engine The high inflation efficiency opens up a technical way.
3. Turbocharger (Turbo)
This is what we usually call 'with or without T, all Look at turbochargers. Generally, each model will be marked with 1.4T, 1.6T, 2.0T, etc. at the rear of the car. Superchargers are divided into exhaust gas turbochargers and mechanical turbochargers, and exhaust gas turbochargers are divided into Single turbocharged and twin turbocharged. Now what we are talking about turbocharging is basically exhaust gas turbocharging, that is, the exhaust gas is used to drive the impeller in the process of engine exhaust, and the pump wheel is driven to increase the pressure of the gas at the intake end, thereby increasing the intake air flow, which can increase The power of the engine allows small-displacement engines to also show the power advantages of large-displacement engines. In the current market where small-displacement engines are prevalent, the contribution of turbochargers is indispensable. In the next issue, I will set up a special section to explain turbochargers for everyone. Let's look forward to it!
4. Variable valve timing and lift electronic control system (VTEC)
VTEC technology is Honda 1989 The first to be developed and used, and also the first to simultaneously control valve timing (valve opening time) and valve lift (valve opening degree). Honda's engineers made them be able to be realized on the engine at the same time, and vividly called it 'usually gentle driving' and 'wartime intense driving'.
5. Intelligent variable valve timing system (i-VTEC)
The i-VTEC system is in the VTEC system On the basis of this, a device called Variable Timing Control (VTC) is added, a set of variable timing control mechanisms for the intake valve camshaft. At this time, the overlap time of increasing the timing and opening of the intake and exhaust valves is variable. It is controlled by the VTC. The introduction of the VTC mechanism enables the engine to have a suitable valve phase in a wide range of speeds, which is very important. To a certain extent, the performance of the engine is improved.
6. Variable valve timing (VVT)
By adjusting the phase of the engine camshaft, so that The opening and closing time of the valve changes with the change of the engine speed, thereby improving the charging efficiency and the combustion efficiency, thereby increasing the power of the engine. The advantage is that it saves fuel and can improve the engine power-to-rise ratio; the disadvantage is that the intermediate speed torque is insufficient. VVT technology has been around for a long time. In 1980, Alfa Romeo (Alfa Romeo) used VVT technology for the first time, and other car companies followed suit.
7. Intelligent variable valve timing system (VVT-i)
VVT-i system is Toyota's unique Some engine technologies can continuously adjust the valve timing, but not the valve lift. It can control the intake valve camshaft to adjust the camshaft angle in the range of 50°, so that the valve timing can meet the requirements of optimal control of the engine's working state, thereby improving the engine's performance in the low, low and high speed range. For example, Toyota's Corolla and Vios are now equipped with this technology.
Today's engine technology is becoming more mature, and the market share of new energy vehicles is gradually increasing. In the new round of competition, will major manufacturers incorporate the research and development of internal combustion engine technology into the category of new energy vehicles, or will they directly transform the research and development of pure electric vehicles to meet market demand? We will wait and see.
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