Mercedes-Benz OM 67 diesel engine

Daimler Benz AG
OM 67
Production period:	1935 to 1954
Manufacturer:	Daimler Benz AG
How it works:	diesel
Engine Type:	R6
Valve control:	OHV
displacement:	7274-7413 cm 3
Fuel supply:	indirect injection
Power:	70-88 kW
Dimensions:	780 kg
Previous model:	OM 5
Successor:	OM 315

The Mercedes-Benz OM 67 is a diesel engine of Daimler-Benz AG , which was developed for heavy commercial vehicles.

The OM 67 is an uncharged inline six cylinder four-stroke diesel engine with prechamber injection , pressure circulation lubrication and water cooling. It is suitable for use with crude oil. were produced several prototype. The first model OM 67has 110 mm bore and 130 mm stroke, the displacement is 7413 cm ³ . The power is specified with 95 hp (70  kW ) at 2000  min ^-1 . This engine with three cylinder heads was built from 1935 to 1938. The original OM 67 was replaced by the latest 1937 by the OM 67/3 , which makes 74 kW. The most important differences are a modified bore-to-stroke ratio, now a seven times instead of four-bearing crankshaft and other cylinder heads; the OM 67/3 only has two more cylinder heads. With a cylinder bore of 105 mm and a piston stroke of 140 mm, the displacement is 7274 cm ³ . This engine was followed in 1939 by the model OM 67/4 , in which the power was increased to 112 hp (82 kW) at 2250 min ^-1 . The subsequent examination OM 67/8 provides 120 hp (88 kW) at 2250 min^-1 . The model OM 67/8 is described in more detail below.

The crankcase of the OM 67 is divided into two parts, the upper part and the lower part. The lower part begins below the horizontal center of the crankshaft and consists of light metal casting. The oil pan is below the front two cylinders. The upper part of the crankcase is made of cast iron , the cylinders are cast in it. Since the engine has two cylinder heads for every three cylinders, the distance between the third and fourth cylinders is greater than between the other cylinders. In the right side of the upper part is the camshaft . It is from the crankshaft via a spur geardriven, which engages directly in the camshaft spur gear; The spur gears are located in a cast on the crankcase gear box and are behind a light metal lid accessible from the outside. On the flywheel side a flange for the transmission is cast, which engages around the flywheel . Brackets for alternator , injection pump , starter and water pump are also cast on the crankcase upper part.

The pistons of the OM 67 are made of an aluminum - silicon alloy and have a flat, inclined in the direction of the antechamberpiston recess. They have four compression rings and an oil scraper ring. The pistons transmit power to chrome-chromium steel forgings with an I-shaped shank. The connecting rod bearings are filled with lead bronze . The crankshaft, also made of chromium molybdenum steelforged, seven-fold stored in the crankcase, the flywheel side crankshaft bearing and the middle, designed as a ball bearing bearing bearings are wider than the rest. At the front end of the crankshaft, a friction vibration damper is mounted on a cone outside of the crankcase , to which the pulley for the fan and alternator drive is attached .

For every three cylinders of the OM 67 has a cylinder head, which is cast from light metal. The prechambers are inclined by approx. 45 ° to the combustion chamber, into which the fuel is injected. The injectors are located in the antechambers in the cylinder head and are easily accessible from the outside, the same applies to the glow plugs , which are screwed horizontally below the injectors in the cylinder head. The usual in an OHV engine bumpersfor the valve train, the OM 67 on the prechamber side is guided through the cylinder head. The exhaust ports of all cylinders opposite the pre-chamber open into a common exhaust manifold for all six cylinders. The intake combustion air passes through two wet air filters and the two longitudinally divided cylinder head covers in the inlet channels at the top of the cylinder head. The intake ports are on the same side as the exhaust manifold.

The camshaft in the crankcase is driven directly by the crankshaft. To the camshaft gear, a gear is flanged, which drives the injection pump. In the middle of the camshaft is a drive wheel for the oil pump of the engine. The valves suspended in the cylinder head are actuated by bumpers and rocker arms by the camshaft. The rocker arms mounted in bronze bearings on the box are connected to the pressure circulation lubrication . A Bosch B-type in- line injection pump , which is driven via the aforementioned gear from the camshaft, delivers the fuel to the injectors. The injection pump has a centrifugal governorthat limits the final speed. The position of the injection pump is chosen so that a compressed air compressor for the brake system can be mounted next to it.

The oil pump driven by the camshaft is flanged to the crankcase. It sucks the oil out of the oil sump and presses it through a strainer to feed it to the main oil line. The water pump is mounted centrally on the exhaust side of the engine. The drive is via the 12 volt / 300 W alternator. Water pump, alternator and cooling fan are driven by a common V-belt.