The power unit consisting of CV8-550 engine and X-300-4B transmission is supported at three points on the samurai mechanized infantry fighting vehicle, and adopts quick-release coupling. The upper crankcase adopts the cylinder block connected gantry structure, and is cast into a thin-walled structure by high-strength cast iron with fine metallographic structure, and the thinnest part is 5 ~ 6mm. All the untreated surfaces have been dipped in paint. All internal oil passages are machined. The joint surface between the cylinder bore and the dry cylinder liner is machined. Due to the use of parallel connecting rods, there is a dislocation between the left and right cylinder banks. Because the high-position camshaft is arranged at the upper part of the V-shaped 60-degree included angle, the lower cavity of the V-shaped included angle constitutes the camshaft bearing cavity, and the two rows of cylinders are pulled together by the partition above them, thus enhancing the rigidity of the whole crankcase. There is a main oil passage at the bottom of the V-shaped included angle, and the oil injection pipe of the cooling piston is located below it, and the oil is directly supplied by the main oil passage. The power output end of the upper crankcase is attached to the gear transmission box, and there are four supporting holes for directly installing the gear shaft. There is a hole for installing a temperature sensor above the left cylinder bank. On the side of the crankshaft, there are water inlet holes of each cylinder and exhaust holes connected to the oil storage tank. On the top surface of the cylinder bank, each cylinder has two tappet holes and eight cylinder head bolt holes, and there are * * * bolts between cylinders 1-2, 3-4, 4-5 and 5-6. Each cylinder has 1 water holes and 3 air holes flowing from the crankcase into the cylinder head. Each cylinder group has four oil return holes, locating pin holes and process holes. The weight of the upper crankcase is about 494kg.
The lower crankcase is dried and forms 1 L aluminum alloy casting with the lower half of the oil storage tank. Both Sudan tank and oil storage tank are cast with oil passages. The upper part of the oil storage tank is a single aluminum casting, and the total oil quantity of the whole lubrication system is 91L. A filter screen is arranged between the upper and lower halves of the oil storage tank. The upper half of the oil storage tank is equipped with an inclined defoaming plate, and the top is equipped with a filler cap and a dipstick. L-shaped parts and oil radiator are within the basic size range of the engine.
The cylinder liner is dry, the wall is thin, only 2.75mm, and it is centrifugal cast iron. The cylinder liner is pre-treated, the inner wall is honed and polished, and cracks are detected before assembly. After installation, the ellipticity is not more than 0.025 mm Rolls-Royce uses the company's patented double-throw crankshaft on the engine. This crankshaft is different from the cross crankshaft commonly used in 8-cylinder engines, with the length shortened by 6.6% and the weight reduced by 17%. Shortening the length correspondingly shortens the engine length and increases the rigidity; Reducing the weight can reduce the inertia and increase the natural frequency of the crankshaft, thus increasing the safety factor of the crankshaft. An 8-cylinder engine equipped with such a crankshaft has a small torsional vibration even without using a damping device.
CV 12TCA engine adopts chromium-molybdenum steel forged crankshaft with 7 main journals and 6 connecting rod journals. Arrange 1-6, 2-5 and 3-4 connecting rod journal horse pairs, and the included angle between each pair is 120. Each connecting rod journal is equipped with two parallel connecting rods. The main journal diameter is 146mm, the connecting rod journal diameter is 98mm, and the crank cheeks are very narrow and overlap greatly. Crankshaft is statically and dynamically balanced in the machining stage, so it does not need to be corrected in the final assembly. All crankshaft surfaces are nitrided except the front and rear end faces. There are 1 spiral gears at both ends of the crankshaft, with 45 teeth, and the pitch speed is about 1 8m/s. There are 16 evenly distributed screw holes and1positioning pins on the rear end face of the crankshaft, which are used to fix and position the flywheel. Because the included angle of the cylinder group is 60, it is a fully balanced structure, so there is no assembly weight on the crankshaft. The maximum torsional vibration amplitude of crankshaft is 0.2mm, and only 1 viscous damper is installed. There are 12 equidistant screw holes at the front end of the crankshaft for fixing the silicone oil viscous shock absorber. The weight of shock absorber is about 42.75kg.
The main bearing cover of the crankshaft is a steel forging. The front, middle and rear three main bearing caps are fastened with four bolts, and the other main bearing caps are fastened with two bolts. The middle main bearing has a thrust plate. In order to ensure the lateral rigidity of the crankcase, there are 1 bolt holes on both sides of each bearing cover, and two bolts are screwed into the bolt holes through the side of the crankcase. The lead bronze main bearing with steel back and a layer of lead-indium alloy on the surface is made by pressing strip. There is a 1 machined annular oil groove in the center of the inner surface of the upper half of each 1 bearing shell, in which 1 oil hole corresponds to the main bearing seat. The oil groove in the lower half of the bearing bush is very short, which is located in the corresponding position of the oil groove in the upper half of the bearing bush, and 1 positioning protrusions are punched out at the edge of the bearing bush.
The small end of the parallel connecting rod forged with Cr-Mo steel is made into a wedge shape to reduce the pressure load on the small end and the piston pin seat. The small head is equipped with a lead bronze bushing with steel back, which is lubricated by the oil hole of the connecting rod body. The big end is made of lead bronze bearing bush with steel back, and the inner surface is plated with 1 layer of lead-indium alloy. The connecting rod big head cover is flat cut and toothless, and is fastened by four specially designed special bolts and double hexagon nuts.
Piston is an aluminum alloy integral casting with low expansion coefficient, with integral cooling oil groove. There is an ω-shaped combustion chamber and four valve pits at the top of the piston. All four piston rings are above the piston pin. Its top ring groove is inlaid with wear-resistant cast iron seat ring. The diameter of the ring row between the first ring groove and the second ring groove is slightly increased, and it is processed into a thin groove section to destroy the formation of carbon deposit. Skirt areas near both ends of the piston pin are recessed inward to reduce weight. A notch is cast at the bottom of the piston skirt to avoid interference with the piston cooling oil injection pipe. In order to match the small end of the wedge-shaped connecting rod, the boss in the pin hole seat is correspondingly machined into an inclined plane. All piston surfaces are tinned except piston pin holes. The cooling oil tank of the piston is placed between the first ring and the combustion chamber. The engine oil is sprayed into the oil inlet of the oil tank through the nozzle, enters the annular boss area of the cooling oil cavity to cool the piston, and then returns to the oil pan through the oil drain hole. Adopt fully floating piston pin, which is fixed by two common snap rings. The top ring of piston ring is a parallel ring, and the surface is sprayed with molybdenum. There is no difference between the top ring and the bottom ring. The second ring is a twisted ring with chrome-plated surface, which is divided into upper and lower parts; The third ring is a twisted ring, and the surface is sprayed with an iron oxide layer; The fourth ring is a two-stage chrome-plated oil scraper ring with lining spring. Two chromium alloy cast high-position camshafts are located in the V-shaped included angle of the cylinder bank. In order to adapt to the dislocation of the left and right cylinders, the right camshaft is longer than the left camshaft, and the flange is equipped with camshaft gear and fuel injection pump transmission gear, while the flange of the left camshaft is only equipped with camshaft gear. These gears are located by locating pins and bolted to the flange. The cast iron thrust piece is stuck in the thrust groove of the camshaft in front of the flange to ensure the axial movement of the camshaft within the range of 0. 1 ~ 0.35 mm ... The camshaft bearing is made of steel-backed lead bronze bushing, and the left camshaft middle bearing, rear bearing and middle bearing are made of double bushings, and its main body is made of single bushing. There is a notch in the middle of the double bushing, which is convenient for lubrication
Hangshang is an alloy iron casting with permanent mold casting, the bottom of which is hardened and all machined and phosphatized. The tappet moves in the tappet hole of the crankcase, which is supplied with oil by the auxiliary oil circuit and lubricated by pressure. In order to promote its rotation, the tappets and their corresponding cams are slightly offset.
The push rod is formed by upsetting both ends of medium carbon steel. High-frequency quenching at both ends, and finally polishing the contact part. Both ends of the push rod are lubricated by the oil return hole near the rocker arm adjusting screw. The length of the push rod is 236 mm.
The rocker arm is a steel forging, and the end contacting with the push rod is a short arm with a threaded hole for installing the adjusting screw. The lower surface of the long arm is in contact with the pressure bridge of the air valve, and the contact part is quenched and polished into an arc shape. The steel-backed lead bronze bushing is installed in the bearing hole of the rocker arm. The rocker shaft is made of steel and quenched only at the rocker bushing. The rocker arm and rocker shaft are placed in the aluminum rocker box above the cylinder head. 1 rocker shaft is used for cylinder 3 * *. The two rocker arms of each cylinder are separated by springs on the rocker shaft. The rocker shaft is hollow and has a single oil inlet hole and an oil hole for supplying oil to each rocker. The rocker shaft positioning screw is located at the upper part of a single oil inlet hole.
The valve pressure bridge is a steel forging with a nitriding thrust button and an adjusting screw at one end. The guide sleeve at the lower part of the pressure bridge moves along the guide rod on the cylinder head with a movement gap of 0.0 16 ~ 0.052 mm, and the guide rod is made of steel. After high-frequency quenching, it is press-fitted with the cylinder head hole, and the guide rod extends out of the top surface of the cylinder head by 26.67 mm ..
The cone angle of intake valve is 45, the seat surface is inlaid with tungsten-cobalt alloy, and the rod is chrome plated. The guide tube of the intake valve is made of cast iron, and the outer side of the lower end has a chamfer with a length of 20. The guide tube hole is machined after being installed in the cylinder head. The top surface of the conduit is 5.0 ~ 5. 1 mm lower than the top surface of the cylinder head. The guide tube and the cylinder head are press-fitted. The running clearance of the intake valve stem in the conduit is 0.043 ~ 0.0 1 mm, and the cone angle of the exhaust valve seat surface is also 45, and the seat surface is inlaid with stellite, and the valve stem is chrome plated. The exhaust valve is cooled by sodium filling. The exhaust valve guide pipe is cast iron, and the lower end has a 20 chamfer. After it is installed in the cylinder head, the conduit hole is machined, the aperture is10.998 ~11.023 mm, and the top surface of the conduit is flush with the top surface of the cylinder head. The conduit is press-fitted to the cylinder head, and the movement gap between the exhaust valve rod and the conduit is 0.127 ~ 0.165 mm cv12 tca. The fuel supply system of the engine consists of a low-pressure system, a high-pressure system, an electronic governor and an intake pipe heating system. The low-pressure system refers to the fuel tank to the filter, and the Plese electric pump installed on the fuel tank delivers the fuel to the filter with a calibrated pressure of 207kPa. Three disposable paper filters are installed on the oil collection bracket in front of the left cylinder bank. The filtered fuel enters the jet pump through the electromagnetic fuel cut-off valve. The maximum lift 1.95mm and the minimum lift 1.65mm of the electromagnetic fuel cut-off valve, the circuit voltage is 26.5V, and the oil delivery capacity of the low-pressure system is about 364l/h. The high-pressure system adopts the Maximec in-line fuel injection pump of CAV company, which is placed in the V-shaped included angle of the engine and driven by the main gear train. When the oil pump speed is 1 150r/min, the oil supply per cycle is adjusted to 300mL and 3 10ml at 850r/min. Using 0.35× 150 6-hole injector, the opening pressure of injection needle is 24.3MPa, and the service life of injector is 500 hours.
The engine adopts two-stage electronic governor with high sensitivity, but it is fully adjustable in the low speed range below 1200r/min. The electronic governor is mainly composed of two parts, namely, pump installation equipment (P.M.E) and host control unit (M.E.C.U). P.M.E transmits the signal received from the host control device and parameters such as exhaust temperature, crankcase temperature and intake pressure to the actuator, thus changing the position of the oil supply rack and changing the oil supply. The exhaust temperature signal is transmitted by thermocouples installed in the exhaust pipes of two rows of cylinders. When the exhaust temperature exceeds the preset value of 800℃, the oil supply gradually decreases. The temperature signal from the axle housing is transmitted by a temperature sensor installed on the crankcase behind the left cylinder bank. When the temperature there exceeds 160℃, the oil supply will be reduced. Intake pressure signal is transmitted to M.E.C.U through 1 pipe leading out from the center of intake pipe of left exhaust cylinder. If the intake pressure decreases, M.E.C.U will send a signal to P.M.E to reduce the fuel supply, so as to obtain the best air-fuel ratio, purify emissions and ensure the normal operation of the engine.
The driver controls the output power of the engine through M.E.C.U in the general traveling state, so that the engine works according to the characteristic curve of 588kW(800 HP) (see curve A in the figure); In combat, the fuel supply of the fuel injection pump can be changed to make the engine work according to the characteristic curve of 882kW( 1200 HP) (see curve B in the figure). In addition, when the exhaust temperature reaches 800℃ or the crankcase metal temperature reaches 160℃ and the boost pressure is low, the control device of the main engine will automatically reduce the fuel supply of the fuel injection pump, so that the engine can work along the C-curve section and reduce the output power. Under normal circumstances, the position of the refueling rack is determined by the position of the accelerator pedal, while under traveling conditions, M.E.C.U will keep the refueling rack in the calibration position. In addition, there is a preset speed signal in M.E.C.U to prevent the engine from overspeed. The intake pipe is placed in the V-shaped included angle of the engine.
The exhaust pipe of the machine is placed outside the second row of cylinders, and the pulse exhaust pipe with the first three cylinders and the last three cylinders separated is adopted. The engine adopts two TV8 1 turbochargers from AiResearch, and the left and right cylinder banks are equipped with 1 turbochargers respectively. The supercharger is a centripetal turbine and a centrifugal compressor, with a pressure increasing ratio of 3. 1 and a rotating speed of 85,000 r/min. The air flow rate of the compressor is 90.7 kg/min. The supercharger is lubricated by oil. The rotational speed of the supercharger is very high, and its lubricating oil also plays a cooling role. Under normal working conditions, the oil pressure should not be lower than 210 kpa; ; At idle speed, the minimum oil pressure is 70 kPa. The minimum oil flow through each supercharger is 4.5 liters/minute.
Two fin-type air-cooled intercoolers are located above the transmission device, installed in parallel between the two coolant radiators, and cooled by the air sucked by the fan. There is a protective grille on the top surface of the intercooler. Under the calibration condition, the ambient temperature is 20℃, and the pressurized air can be reduced from 2 15℃ to 60℃. The cooling system of the machine is closed cycle, with thermostat and expansion/water collecting tank. The refrigeration capacity of the whole system is 206L, and the engine part is 81L. In order to prevent corrosion and icing, a mixed solution of ethylene glycol and water with appropriate concentration must be used. Water should be demineralized drinking water to prevent sediment from forming in the cooling system. Coolant is injected from the expansion/collection tank located above the exhaust pipe of the right cylinder bank. The expansion/water collecting tank is made of cast aluminum, with a volume of 14.5L and a partition plate of 1 in the middle to form a water collecting cavity and an expansion cavity, which are connected by pipes.
A centrifugal cooling water pump with a diameter of 203 mm (8 inches) was used and installed on the transmission gearbox behind the right cylinder bank. The shell of the water pump consists of two aluminum alloy castings with two water outlets. The cooling water from 1 outlet first enters the oil radiator, and then flows into the right exhaust pipe through the water collecting pipe. In addition, the cooling water at the outlet of 1 first enters the transmission oil heat exchanger through the rectangular water pipe of the engine, and then enters the left exhaust pipe. The calibrated flow rate of the water pump is 683 ~ 700 L/min, and the working pressure is 74kPa.
Three mixed-flow cooling fans with a diameter of 380mm are placed at the rear end of the transmission, which are driven by the power shunt device at the top of the transmission through the 1 torque limiting clutch and toothed belt, and the rotating speed is 5520r/min. The power consumption of the fan accounts for 8% of the engine power, and the maximum power consumption is 74kW( 100 HP). The air supply of the three fans is 16m3/s, and 1 auxiliary fan is also installed below the left cooling water radiator. This fan only works when the main engine stops and the auxiliary engine works.
The new mixed-flow fan used in this engine has the advantages of large air volume of axial fan and high pressure head of centrifugal fan. Moreover, the noise is low and the fan consumes less power. From the power consumption comparison data of the cooling fan, it can be seen that the power consumption percentage of the fan is the smallest.
Power consumption of cooling fan for military vehicle engine
Engine model? Vehicle model? Nominal power (kW)? Fan power consumption (kW)? Fan power consumption as a percentage of rated power (%)
AV- 1790-7？ M47？ 59689.7 15
AVDS- 1790-2M690？ 55 180? 14.5
6V-53？ m 1 13a 1 158 17.6 1 1. 1
12V-7 1TM55 1？ 22 133.8 15.3
AVCR- 1360-2？ 1 103 1 18 10.8
MB873？ Leopard 2 1 103? 147~ 162 13.3~ 1 4
L60 Chevron 529 103 19.4
Modified CV 12TCA chevotan? 88273.58
The machine adopts two cooling water radiators composed of corrugated sheets and pipes, which are placed above the transmission device and on both sides of the intercooler. The area of each radiator is 0.37m2, the dry weight is about 55kg, and the weight after being filled with cooling water is 68kg. The capacity of cooling water is 13L. The front ends of the two radiators are respectively equipped with 1 thermostats. When the cooling water temperature reaches 68 ~ 73℃, the main circulation valve of the thermostat starts to open and the bypass valve on it closes accordingly. When the temperature reaches 79 ~ 84℃, the main circulation valve is fully opened and the bypass valves are all closed. The lift of the main circulation valve is12.7 mm. When the cooling water temperature is high, the main flow valve will be opened to the maximum working lift of 23.8mm, and the additional lift is realized by compressing the overload spring of the bypass valve. The main flow valve and the bypass valve are located on the same spindle. Thermostats on two radiators cannot be used interchangeably. This machine adopts dry oil pan. The total capacity of the lubrication system is 9 1L, which can ensure the normal operation of the engine under the conditions of 40 forward and backward inclination and 35 lateral inclination. When the engine speed is 2300 rpm, the working pressure of the lubrication system is 4 15 kPa, and the flow rate is 18000 liters/hour ... The normal working temperature is 70 ~ 100℃, and the highest temperature is 120℃.
The oil pump consists of 3 sets of gears, 1 set of oil pressing gears and 2 sets of oil return gears. The oil pump is driven by the crankshaft front gear through the idler.
Two tubular oil radiators with baffles and fins in the middle are adopted and placed outside the right cylinder bank. The deflector guides the oil to flow up and down in waves to enhance the cooling effect, and the cooling water flows through the pipeline.
This machine adopts four disposable full-flow fuel tank oil filters, which are inverted on the oil collecting bracket at the front upper part of the left cylinder bank. The bypass valve is installed on the paper filter element, and the opening pressure is 152 ~ 200 kPa. Check valves are installed at the oil inlet and overflow pipe of each filter to prevent oil from flowing back. A sealing ring with a square section is installed in the oil groove of the base of the wave cleaner. The oil pressure converter is installed at the lower oil outlet end of the oil support seat. This machine adopts two WS6 starters with the same power, which can work simultaneously or independently, and the working voltage is 24V. The starting motor can be started at the ambient temperature of -20℃ without changing the oil. When the ambient temperature is below -20℃, SAE 10 oil needs to be replaced before starting. The starting power supply is 600Ah nickel-iron battery, which needs heating in winter. When the ambient temperature is -37℃, it can be started by heating for 2 minutes.