196 1 year, deeply attracted by the potential advantages of rotary engines, Mazda engineers decided to actively carry out the sustainable development of rotary engines. Six years later, after countless hours of hard work, engineers proudly installed the world's first twin-rotor engine on 1967 Cosmo Sports. Of course, the continuous efforts to improve this unique engine have never stopped. So far, Mazda has produced nearly 2 million cars driven by rotary engines.
The 24 Hours of Le Mans in Paris is a car race to test the performance and endurance limits of vehicles. 199 1 year, Mazda 787B driven by rotary engine became the first Japanese car to win the race. This unprecedented victory has written a brilliant page for Mazda in automobile history. More importantly, this victory proves the company's mature technology in rotary engines. Rotary engines are usually described as "fashionable", "innovative" and "full of energy". These three words can also be used to define Mazda's brand image and its unique technology.
Forty years of pursuit
Since Mazda began to develop the rotary engine, the company has successfully utilized the inherent advantages of this engine, such as light weight, compact structure and high power performance, and gradually overcome its shortcomings of high fuel consumption and large exhaust emissions. On the 13BREW turbocharged rotor engine developed for Mazda RX-7, Mazda has reached the technical peak of maximum power in the development of rotor engine.
However, the passion and dream to promote the development of Mazda rotary engine are endless. Engineers began to make this power plant more compact and improve its intake and combustion efficiency. These efforts have been fully reflected in MSP-RE, which was installed in the RX-0 1 concept car launched at Tokyo Motor Show in 1995. Naturally aspirated MSP-RE was then mass-produced as the power system of Mazda RX-8, and renamed RENESIS, which stands for "the origin of RE (rotary engine)" (meaning "the origin of rotary engine").
The RENESIS rotor engine is a naturally aspirated rotor engine, which can generate the maximum power of 184 kW (250 PS) at 8500 rpm (suitable for high-powered vehicles in Japan). The compact and lightweight body enables Mazda RX-8 to adopt advanced front center powertrain configuration. Compared with the previous RX-7S, the engine position is lower and farther back. Because of its smooth performance, compact size and unique driving characteristics, RENESIS was named the international engine of the year in June 2003, shortly after the brand-new Mazda RX-8 went on the market.
As the only rotary engine manufacturer in the world, and as a sports car manufacturer highly praised by drivers all over the world, Mazda constantly strives to turn the company's dream into reality. It is this dream and our passion for sports car development that makes Mazda customers have high expectations for innovative RENESIS engines.
New generation rotary engine
Structure and working principle of Wankel rotary engine.
In the past 400 years, many inventors and engineers have been trying to develop a continuous running internal combustion engine. I hope that one day the reciprocating piston internal combustion engine can be replaced by an elegant prime engine, and its running track should be very close to one of the great inventions of mankind: the wheel.
In fact, at the end of16th century, the term "continuous running internal combustion engine" first appeared in publications. James watt (1736- 18 19), the inventor of connecting rod crank mechanism, also studied rotary internal combustion engines. Especially in the past 150 years, inventors have put forward many suggestions on the structure of rotary engines. 1846, people drew the geometric structure of today's rotary engine studio, and designed the first conceptual engine by using epicycloid. However, these concepts until Felix? 6? Dr felix wankel developed the Wankel rotary engine in 1957.
By studying and analyzing the feasibility of various types of rotary engines, Dr. Wankel found the best shape of cycloidal shell. He has a deep understanding of the airtight sealing mechanism of rotary valves and superchargers used in aircraft engines. Using these mechanisms in its design makes Wankel rotary engine practical.
Modern rotary engines consist of a cocoon-shaped shell with a triangular rotor inside. The space between the rotor and the shell wall serves as an internal combustion chamber, and the pressure of gas expansion drives the rotor to rotate. Rotary engine, like ordinary internal combustion engine, must complete four working processes: air intake, compression, combustion and exhaust. If the triangular rotor is placed in the center of the circular shell, the volume of the working chamber will not change with the rotation of the rotor inside the shell. Even if the mixture of air and fuel is ignited there, the expansion pressure of combustion gas only acts on the middle of the rotor and will not rotate. This is why the inner circumference of the shell is designed as a trochoid shape and assembled with the rotor mounted on the eccentric shaft. Therefore, the volume of the working chamber changes twice every revolution, thus realizing four working processes of the internal combustion engine.
On the Wankel type rotary engine, the vertex of the rotor moves with the elliptical shell on the inner circumference of the engine shell, while maintaining contact with the output shaft gear on the eccentric track around the center of the engine shell. The orbit of the triangular rotor is determined by the phase gear mechanism. The phase gear includes an internal gear ring installed inside the rotor and an external gear installed on the eccentric shaft. If there are 30 teeth on the inner side of the rotor gear, there are 20 teeth on the outer circumference of the shaft gear, so the tooth ratio is 3:2. Because of this transmission ratio, the rotational speed ratio between the rotor and the shaft is limited to 1:3. Compared with the eccentric shaft, the rotation period of the rotor is longer. The rotor rotates once and the eccentric shaft rotates three times. When the engine speed is 3000 rpm, the rotor speed is only 1000 rpm.
Compared with the traditional reciprocating engine
Both reciprocating engines and rotary engines rely on the expansion pressure generated by the combustion of air-fuel mixture to obtain the rotating force. The mechanism difference between the two engines lies in the way of using expansion pressure. In the reciprocating engine, the expansion pressure generated by the piston top surface pushes the piston downward, and the mechanical force is transferred to the connecting rod to drive the crankshaft to rotate.
For a rotary engine, the expansion pressure acts on the rotor side. So as to push one of the three faces of the triangular rotor toward the center of the eccentric shaft. (see PG in the picture). This movement is caused by two different forces. One is the centripetal force pointing to the center of the output shaft (see Pb in the figure), and the other is the tangential force (ft) that makes the output shaft rotate.
The inner space (or spinning room) of the shell is always divided into three workshops. During the movement of the rotor, the volumes of these three working chambers are constantly changing, and four processes of air intake, compression, combustion and exhaust are successively completed in the swing cylinder. Each process is carried out in different positions of the swing cylinder, which is obviously different from the reciprocating engine. The four processes of reciprocating engine are all carried out in one cylinder.
New generation rotary engine
The displacement of rotary engine is usually expressed by the unit working room volume and the number of rotors. For example, a twin-rotor engine with model 13B has a displacement of "654cc × 2".
Unit studio volume refers to the difference between the maximum volume and the minimum volume of the studio; Compression ratio is the ratio of maximum volume to minimum volume. The same definition also applies to reciprocating engines.
As shown in the figure on the previous page, the change of working volume of rotary engine and its comparison with four-stroke reciprocating engine. Although in these two engines, the working chamber volume changes smoothly in a wave shape, there are obvious differences between them. The first is the rotation angle of each process: the reciprocating engine rotates 180 degrees, while the rotary engine rotates 270 degrees, which is 1.5 times that of the reciprocating engine. In other words, in a reciprocating engine, the crankshaft (output shaft) rotates twice (720 degrees) in four working processes; However, in a rotary engine, the eccentric shaft rotates three times (1080 degrees) and the rotor rotates one time. In this way, the rotary engine can obtain a longer processing time and form a smaller torque fluctuation, thus making the operation smooth and smooth.
In addition, even at high speed, the rotation speed of the rotor is quite slow, which makes the intake and exhaust time more relaxed, which provides convenience for the operation of the system with higher dynamic performance.
Characteristics of Wankel rotary engine
Small size and light weight
Rotary engine has several advantages, the most important of which is to reduce volume and weight. In terms of running quietness and stability, the dual-rotor RE is equivalent to an inline six-cylinder reciprocating engine. On the premise of ensuring the same output power level, the design weight of rotary engine is two-thirds of that of reciprocating engine, which is very attractive to automobile engineers. Especially in recent years, the requirements for crashworthiness (collision safety), aerodynamics, weight distribution and space utilization have become more and more strict.
● Streamline the structure
Because the rotary engine directly converts the expansion pressure generated by the combustion of air-fuel mixture into the rotating force of triangular rotor and eccentric shaft, there is no need to set a connecting rod, and the air inlet and air outlet are opened and closed by the movement of the rotor itself; There is no need for valve train, including timing belt, camshaft, rocker arm, valve and valve spring, which are essential components in reciprocating engine. To sum up, the components required for the composition of the rotary engine are greatly reduced.
● Consistent torque characteristics
According to the research results, the rotary engine has a fairly uniform torque curve in the whole speed range. Even with the design of two rotors, the torque fluctuation in operation is the same as that of an in-line six-cylinder reciprocating engine, and the arrangement of three rotors is smaller than that of a V-type eight-cylinder reciprocating engine.
● The operation is quieter and the noise is less.
For reciprocating engines, the piston movement itself is the vibration source, and the valve mechanism will also produce annoying mechanical noise. The vibration caused by the smooth rotation of the rotary engine is quite small, and there is no valve mechanism, so it runs more smoothly and quietly.
● Reliability and durability
As mentioned earlier, the speed of the rotor is one third of the speed of the engine. Therefore, when the rotary engine runs at 9000 rpm, the rotational speed of the rotor is about one third of this rotational speed. In addition, because the rotary engine does not have those high-speed moving parts, such as rocker arms and connecting rods, it is more reliable and durable in high-load movement. The victory of Le Mans 199 1 fully proves this point.