IMPACT 3.0
Saturday, 22 September 2012
2/Description, Design and function/FM12, D12C420/Engine
FM12
112118781
Tuesday, 18 September 2007
Engine The D12C is a 12-litre engine that differs from earlier versions of Volvo's 12-litre engines. The engine has been designed to comply with requirements for low fuel consumption and high performance in combination with low exhaust emission. It has an air cooling system between the turbocharger and the charge air cooler (air intake), overhead camshaft and unit injectors. The unit injectors are centred vertically in relation to the pistons and are controlled by the camshaft and an electronic control unit. The control unit is located on the left-hand side of the engine block.
Cylinder head The cylinder head covers all the cylinders in the engine and has the camshaft on the top.
COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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It is secured to the block with 38 bolts evenly distributed around the cylinders. Cylinders in the cylinder head have separate intake and exhaust passages. The unit injectors in the D12C are centrally located with four valves per cylinder, providing uniform combustion chamber geometry. The intake valves are made of a new material and the exhaust valves are fitted with hard metal seat surfaces. The exhaust valve seats are made of harder material than on the D12A engine. The bushing in the unit injector rocker arm has been replaced with a surface treated steel bushing. The cylinder head has undergone the following main modifications: The cylinder head has been reinforced and is made of a new type of material. The intake and exhaust ports are new. Only one fuel port for the unit injectors. The coolant thermostat is integrated in the cylinder head. The flame edge grooves have been discontinued. This entails a completely new method and new special tools for installing the cylinder head. The figure shows three new stop blocks (marked with black arrows) screwed into the cylinder head and timing gear plate to hold the cylinder head in places after installation.
COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Cylinder block/cylinder liner COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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The D12C has a cylinder block with wet cylinder liners (exchangeable) . The water circulation chamber around the cylinder liner is sealed to the bottom part of the cylinder liner with three sealing rings in each liner. The upper part of the water circulation chamber has a sealing ring under the edge of the liner. The cylinder block is reinforced and its front edge has been adapted to the new transmission. To further increase the stiffness of the cylinder block, its bottom section has been reinforced with a stiffening frame. This means that the vibration and noise levels have been reduced and the outer, laminated steel plates are no longer required. New coolant cap for the oil cooler. The cap is designed to suit both the larger and the smaller oil cooler.
COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Piston There are two versions of piston: an articulated or two-piece piston (A) and a one-piece piston (B). The upper part (crown) of the articulated piston (A) is made of steel, while the bottom part (skirt) is made of COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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aluminium. This piston type is oil-cooled. A jet of oil is supplied from a nozzle towards the lower part of the piston skirt. The connecting rods are reinforced and the gudgeon pins are the same for both types of piston. Compression ratio is 18.5:1. The one-piece piston (B) is made of an aluminium alloy and has three top grooves for the compression rings. This piston type is also oil-cooled. A jet of oil is supplied from a nozzle towards the lower part of the piston skirt.
A
B
Crankshaft The press-forged crankshaft has 7 main bearings and induction hardened bearing surfaces with bearing fillets on the transition to the crank throws. COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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The the rear end of the crankshaft only has one retainer. The front end of the crankshaft is located inside the timing gear cover.
Camshaft The D12C has an overhead camshaft resting on seven support bearing bolted into the cylinder head. There are two types of support bearing; one is used in production and the other available as a spare part. Different types of support bearing should not be fitted in the same engine during repair. It should be remembered that irrespective of the type, each support bearing has been matched in production with its bearing cap. The camshaft has three grooves (offset) per cylinder; one for the intake valves, one for the exhaust valves and one for the unit injector. Engines equipped with VEB (Volvo Engine Brake) has another two small grooves (offset) in the eccentric profile of the exhaust valves.
Timing gears The camshaft gear in the D12C differs from other Volvo engines in that the camshaft is located in the cylinder head. There is an adjustable gear between the cylinder block and cylinder head. This gear must be adjusted each time a repair is carried out that affects the camshaft gear. Thermostat valve there must be the same play between the adjustable idler gear and the lower and upper gears which are both fixed. The upper idler gear (6) is adjustable. There is a hydraulic vibration damper mounted outside the camshaft gear (5). COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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New injection nozzle for lubricating the timing gear wheels. Revised drive outputs for fan, alternator and AC compressor. New, stronger bearing housing for engine power take-off. Power take-off torque: 500 Nm for stationary vehicle. 400 Nm for vehicle in operation.
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Crankshaft gear Idler gear Coolant pump gear Air compressor gear Camshaft gear Idler gear Gear for control hydraulics Driving device (pulley and fuel pump) Idler gear Hydraulic pump gear (power take-off) Oil pump gear Idler gear
COPYRIGHT © Copyright Volvo Parts C orporation The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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