Liu Kezhi and Wang Yunsheng

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The S60 series diesel engine developed and produced by Detroit Diesel Engine Company in the United States is characterized in that the whole diesel engine is automatically controlled by a computer, the relevant data is input into the electronic control module through various sensors, the data is quickly processed by the computer, and then the start-stop time of the nozzle of the electronic control pump is controlled by the solenoid valve, so that the diesel engine can achieve the best combustion effect under various working conditions. This series of diesel engines have good external characteristics, good economy and less harmful substances in the exhaust gas. Practice has proved that S60 series diesel engines for vehicles should not be overhauled within 6.5438+0.6 million kilometers. S60 series diesel engines for engineering need no overhaul within 20,000 working hours.

Detroit diesel engine; Structural analysis; performance

Detroit Diesel Company (DDC) is one of the three largest diesel engine manufacturing companies in the United States, which was established in 19 15. For more than 80 years, DDC has been famous for producing two-stroke high-speed diesel engines.

As early as 1978, Detroit Diesel Company began to study the application of computer control technology in high-speed diesel engines. After1100,000 hours of laboratory bench test and field industrial test, the computer-controlled diesel engine was officially put into the market in September of 1985, and nearly one million diesel engines have been put into operation all over the world.

In 1990s, Detroit Diesel Engine Company transplanted many years' experience in producing two-stroke diesel engines and computer control technology to the new S60 series four-stroke diesel engines, and put them on the market in the early 1990s. S60 series diesel engine is a six-cylinder, in-line, water-cooled, turbocharged and air-to-air cooled computer-controlled four-stroke diesel engine. This series has three displacements, and its derivative four-cylinder engine is S50 series.

design feature

1. Computer control (DDEC)

The S60 and S50 series diesel engines in Detroit are all controlled by computers. It consists of a computer, a sensor, an electronically controlled pump nozzle and an electronic display module (see figure 1 computer control is completely different from electronic governor. Electronic governor replaces mechanical or hydraulic governor with electronic components, and automatically adjusts the oil supply when the external load changes, so as to keep the diesel engine at a stable speed. Computer control means that the whole diesel engine is automatically controlled by computer, which not only considers the influence of external load changes and has the function of speed regulation, but also comprehensively considers the influence of many factors of the diesel engine itself and external conditions, such as coolant temperature, fuel temperature, supercharger pressure, load rate and operator's intention. Through microcomputer data processing, an appropriate amount of oil is injected into the cylinder with an optimized injection advance angle, so that the fuel can obtain the best combustion process, and the diesel engine can run in the best state, with the least fuel consumption and gas exhaust.

(1) Computer, namely Electronic Control Module (ECM), was jointly developed by Detroit Company and Motorola Company. There are two microprocessors, one is the host and the other is the standby. Once the host computer fails, it will automatically switch to the standby computer and inform the operator through the LCD screen, which can ensure that each computer will not stop due to its own failure within 30,000 working hours.

This miniature advanced microprocessor has many comprehensive functions, can withstand the strong vibration of off-road vehicles, and can also work normally at -54 ~ 105℃.

(2) The sensor inputs the relevant data into the computer, and the computer processes the data quickly according to the operator's intention, and then controls the start and end fuel injection time of the electronically controlled pump nozzle (EUI) through the solenoid valve, so that the diesel engine can achieve the best combustion effect under various working conditions. If a sensor fails, it will be displayed on the LCD screen in the form of code number to inform the operator to deal with it in time. Among them, timing sensor and synchronous sensor are used to transmit the timing information of diesel engine, and the accuracy can reach 0.25 for every 360 rotation of crankshaft. The timing sensor provides the parameters of "once per cylinder" and the synchronous sensor provides the parameters of "once per revolution", so that the computer can accurately determine the top dead center position of the piston, and control the injection quantity and injection time by integrating other parameters to ensure the best combustion process.

(3) Electronically Controlled Pump Nozzle (EUI) The diesel system produced by Detroit Diesel Company has no high-pressure fuel pump or PT fuel pump, but integrates the four functions of generating high pressure, metering, timing and atomization of each cylinder into an integral pump nozzle, which is compact in structure, easy to check and replace, does not need special test equipment, and the cylinders are not involved with each other, thus reducing maintenance time and cost. When the diesel engine is controlled by computer, the characteristics of mechanical fuel injector are skillfully used, and the original rack and gear for adjusting the fuel quantity in the fuel injector are eliminated, as well as a large number of parts and governors for externally controlling the movement of the rack. The original plunger with spiral groove is changed into a simple cylindrical plunger, which is simple in structure, easy to manufacture and not easy to be damaged; The control valve is used to control the injection timing and injection quantity. The control valve is operated by solenoid and armature. Fig. 2 shows an electronically controlled pump nozzle.

The control valve is a normally open reciprocating valve. When it is fully open, the distance between the valve and the valve seat is only 0.4mm, so when it is closed, the impact force is very small and it is not easy to wear. Under the action of the electromagnetic coil and armature, the control valve is closed, and the fuel in the oil chamber generates high pressure under the pressure of the plunger, and the high-pressure fuel is ejected from a plurality of small holes of the fuel injection head until the control valve is opened, the fuel injection is terminated, and the fuel returns to the fuel tank.

(4) Electronic display module (EDM) Electronic display module, or liquid crystal display screen (Figure 3), which can be installed on or near the diesel engine, or installed with the throttle handle at a distance of tens of meters from the diesel engine and connected by special cables.

Fig. 3 LCD screen

During the whole operation time, the electronic display module can display the following data:

① Diesel engine speed;

② Diesel engine coolant or lubricating oil temperature (the lubricating oil temperature is displayed only when the coolant temperature cannot be obtained from the computer);

③ Diesel engine lubricating oil pressure;

④ Computer battery voltage or auxiliary current;

⑤ Vehicle speed or auxiliary pump pressure or diesel engine load;

⑥ Temperature or pressure of main equipment;

⑦ Temperature or pressure of main equipment or pressure of diesel turbocharger;

⑧ Fuel level;

Pet-name ruby inspection and parking instructions.

The number unit in the display can be metric or English. If there is a general abnormality in the diesel engine, the display screen will flash to show the inspection signal, and at the same time, the fault code will be displayed below the display screen, requiring the operator to check as soon as possible and eliminate the fault in time. If there is a serious abnormal situation, the display screen will flash the stop signal, and the fault code will be displayed below the display screen, requiring the operator to stop as soon as possible. There are six keys on the right side of the display screen. Their functions are:

Menu keys are used to display menu items in the information window. At this point, the name of each item in the menu scrolls from right to left in turn.

Scroll keys are used to speed up the display of menu items or submenu items. Each press can go directly to the next item, and it can also be used to modify some menu items during programming.

The selection key is used to select the main item or sub-item required by the menu;

The clear key can be used to return to the previous item. When the menu item is displayed, press this button to clear the screen. If there is a diagnostic code, you can also clear the screen by this button;

The light key is used to turn on the light. If the light button is pressed continuously, the light will gradually dim from strong to weak and finally go out. When setting the warning value, you can also use this key to select a lower value.

The alarm close key is used to clear the warning code and warning sound. When setting the warning value, you can also use this key to select a higher value. According to the operation manual of the electronic display module, the required items can be put forward from the menu.

In addition, Detroit Diesel Engine Company can provide micro readers and micro printers according to users' requirements. Connect the reader to the computer or electronic module with a special wire. The LCD screen of the reader can display four lines of text and data at the same time, and then display all the data when the diesel engine is running in turn, and print it out by the printer. You can also display one or two or three items on the display screen of the reader to observe the changes of other parameters in this case. Another function of the reader is that the operator can stay away from the diesel engine, and the working conditions of each cylinder can be detected one by one only through the reader.

2. Combined piston

The combined piston has been successfully used in Detroit 7 1, 92, 149 series for more than 20 years, which is superior to the traditional integral piston. It has been successfully applied to S60 and S50 diesel engines.

The piston top and the piston skirt are separated, and there is a heat insulation ring in the middle. The skirt is slightly heated and the thermal deformation is small, so it is not necessary to make it oval, which reduces the manufacturing difficulty. The clearance between the piston and the cylinder liner can be reduced accordingly, and the operation is more stable; The piston pin only bears vertical pressure and no longer bears bending moment, so the reliability is greatly improved. It solves the contradiction that the strengthening coefficient of modern high-speed diesel engine increases, the average effective pressure increases, the bending strength of the piston pin can not meet the requirements, and the diameter of the piston pin is limited by the cylinder diameter. Because the piston head and the piston skirt are not a whole, when the piston moves up and down, the slight swing of the skirt will not affect the head, and the piston rings are installed on the piston head, which can achieve a good sealing effect; It is allowed to replace the piston head or piston skirt separately to reduce the maintenance cost.

3. Overhead camshaft

Detroit S60 and S50 diesel engines draw lessons from the successful experience of 149 series diesel engines and adopt overhead camshafts. The cam of the camshaft is in direct contact with the roller of the intake and exhaust rocker arm and the rocker arm of the fuel injector, and there is no need for a push rod and a tappet, so the structure is simple, the rigidity and sensitivity are high, the fuel injection pressure can be as high as 200 MPa, the combustion is more complete, and there are fewer harmful substances in the exhausted gas. In order to withstand such a large injection pressure, the rocker roller of the pump nozzle is made of silicon nitride ceramic material, which can withstand high pressure and is extremely wear-resistant. S60 and S50 series diesel engines have four valves per cylinder. Detroit Diesel Engine Company has adopted an ingenious design, and a "door" rocker can control two valves at the same time. The two outer valves are exhaust valves, and the two inner valves are intake valves. There is no need for a complicated "cross bridge" between the two valves, so the structure is simple and the friction parts are omitted.

The above measures provide favorable conditions for shortening the intake and exhaust ports in the cylinder head. Short port resistance is small, air flow is smooth, power loss is low, heat loss is low, and working temperature is low.

4. Air to air intercooler

After the turbocharger increases the intake pressure, the intake temperature will also increase. The traditional method is to use diesel engine coolant to cool the charge air. S60 and S50 series diesel engines install the intercooler in front of the water tank or at one side of the water tank, and use the air sucked by the fan for cooling. This air-to-air cooling method has a good effect. The air temperature after pressurization is about 40℃ lower than that of water-to-air cooling method, which increases the intake density, fuel economy and output power. The intercooler is also convenient for inspection and maintenance, which improves the reliability of components.

Basic parameters and performance characteristics

1. Basic parameters

See table 1 for the basic parameters of S60 and S50 series computer-controlled diesel engines in Detroit.

Note: The length, width, height and quality in the table are slightly different for different purposes.

2. Operating characteristics

(1) The torque characteristics and power characteristics of a diesel engine with good external characteristics can be corrected by the electrically erasable programmable memory in the computer. Fig. 4 shows the external characteristic curve of S60 diesel engine when the power is 373kW.

This characteristic curve is beyond the reach of ordinary diesel engines. When the rotating speed is 1800 ~ 2 100r/min, the maximum power is unchanged, while in the range of 1200 ~ 1500r/min, the maximum torque is unchanged, and the maximum torque reserve coefficient is as high as 124%. Constant power in a large speed range is beneficial to adapt to different torque changes; The maximum torque is constant in a large range, which can adapt to the changes of different speeds, expand the matching range between diesel engine and transmission system, and is conducive to improving the efficiency of power and transmission system. Because the electronic display screen can display "instantaneous fuel consumption", it can work at the most economical speed for a long time.

(2) Fuel with good economy is lower than fuel consumption. As can be seen from the fuel consumption characteristics in Figure 4, the output power is 373kW and the rotation speed is 1800.

At r/min, the fuel consumption rate is only 0.1.93g/w.h. Compared with imported advanced diesel engines, it can save about 30000kg of fuel in a year after working for 3,000 h.. Figure 4 S60 Series Diesel Engine External Characteristic Curve

Because S60 and S50 series diesel engines are controlled by computers, they will not emit white smoke when they are cold and black smoke when they are accelerating. Instantaneous fuel consumption can be observed on the electronic display screen. Operators can choose "economic speed", so the accumulated fuel saved in the whole year far exceeds 30000kg.

Detroit computer-controlled diesel engine can give "yellow card warning" or "red card warning" in advance, which can avoid major failures, save maintenance costs and reduce downtime losses.

(3) There are fewer harmful substances in the waste gas. With the emphasis on environmental protection, the control of harmful substances in diesel engine exhaust gas is becoming more and more strict all over the world. Detroit Diesel Engine Company has invested a lot of manpower and material resources in this respect. After years of research and improvement, S60 and S50 series diesel engines can completely meet the requirements of environmental pollution after 200 1 year.

To sum up, the S60 series computer-controlled diesel engine in Detroit is advanced, reliable, economical and has low emission of harmful substances, so it should be the best among many diesel engines today.

Practice has proved that S60 diesel engine for vehicle can be overhauled within 6.5438+0.6 million kilometers, and S60 diesel engine for construction machinery can be overhauled within 20,000 working hours.