DD145305A1 - VALVE CONTROL FOR STARTING FOUR-STICK THYEL ENGINES - Google Patents

Abstract

The invention relates to a valve control system for starting four-stroke diesel engines, in particular low-number-of-charge, small V-number, highly-charged V-type four-stroke diesel engines. The object of the invention is to allow pneumatic starting from any crank position even for four-stroke diesel engines of this type. As a result, the equipment of engines with starter motors and the required effort is avoided. The features of the invention are that the starting cam and additionally arranged on the control shaft exhaust cam are formed with two cam lobes for a control of the starting and exhaust valves by the two-stroke process and are only in the starting process via actuators in connection with these. The changeover from the operating position to the starting position and vice versa is done by moving the control shaft.

Description

~ ί- 215 5 54

Title of the invention

Valve control for starting four-stroke diesel engines

Field of application of the invention

The invention relates to a valve control system for starting four-stroke diesel engines, in particular low-number-of-charge, small V-number, high-loading V-type four-stroke diesel engines.

Characteristic of the known technical solutions

It is known to provide four-stroke diesel engines with., Pneumatic starting device with cam-controlled starting valves, through which the pistons are acted upon during the starting process according to the firing order with compressed air. The sum of the AnIaßdrehmomente causes a movement of the crankshaft until reaching the required starting speed (DE-PS 868 376). '>

However, in highly supercharged four-stroke V-type diesel engines with a low number of cylinders and a small V-V angle of 45 °, pneumatic starting from any crank position is not possible (DE-OS 2002 982). A V-engine with 8 cylinders and a partially symmetrical cross shaft has at a V-angle of 45 "firing intervals of · 45 ° i 90 ° and 135 ⁰ KW and with the fully symmetrical crankshaft. Ignition intervals of alternately 45 ° and 135 ⁰ IiW. There at

215554 ₂

supercharged diesel engines, the exhaust valve already 50 ° to 60 ⁰ KW before the bottom dead center of the piston opens, remains for the starting process only an angular range of 120 °, so that at ignition intervals of 135 ⁰ KW the engine no longer cranked from any crank position can / can ground. V-engines with 6 cylinders and a V-angle of 45 ° even have firing intervals of alternately 45 ° and 195 ⁰ KW and thus a crank angle range of 75 ° 5 in which no starting torque can be generated.

These motors must therefore be equipped with a pneumatically or electrically operated starter motor in order to be able to start them immediately in the application.

The disadvantage here is the high Luftbö.darf or the dependence on a power source and to be realized for such a drive on the engine great expense

 The pneumatic Anlasseh is therefore particularly preferred for large diesel engines.

Object of the invention

The object of the invention is to reduce the cost of starting particularly high-turbocharged V-type low-V, low-V-ratio four-stroke engines.

Explanation of the essence of the invention

The invention is based on the object, especially for hochatifgeladene-; V-type four-stroke diesel engine with low number of cylinders and small V-angle to allow pneumatic starting from any crank position. Erfinäungsgemäß the object is achieved in that the starting cam and additionally arranged on the control shaft exhaust cams with jeweiiLs two üTockenerhebungen for a control of the starting and exhaust valves after the two-stroke Verfaliren are formed and only during the starting process via actuators

215554

communicate with them. The changeover from the operating position to the starting position and vice versa takes place, for example, by shifting the control shaft.

embodiment

The invention will be explained in more detail below. A V-type four-stroke diesel engine has two camshaft control shafts to control the gas exchange valves. The squats have a cam lobe, so that at half the speed of the Steuerwohl against the crankshaft, the valves are operated after two revolutions of the crankshaft. On the control shafts, two cams for controlling the starting valve and the exhaust valve are additionally arranged for each cylinder portion, which have two cam lobes. The control shafts are displaceable in a known manner. In a control shaft position, the starting of the internal combustion engine takes place. The .Seuerung the starter valves and the exhaust valves is made according to the two-stroke process using the provided with two cam lobes cams, so that at each crankshaft revolution, the valves are operated once. At the top dead center of the piston opens the starter valve and the inlet pressure air flowing into the combustion chamber moves the piston downwards. At bottom dead center or shortly before the exhaust valve opens and the compressed air escapes from the cylinder. The intake valves remain constantly closed during the starting process. But it is also possible, for example, instead of the exhaust valves to use the inlet valves for the outlet of the tempering compressed air.

After reaching the starting speed, the control shaft is moved, the control of the intake and exhaust valves now take over the cams for the operating condition, and it start the 'fuel injections.

Due to the changeover from four-stroke to two-stroke v / grounding when the engine is started, they are grounded

215554

A supercharged Vie rtakt the se! V-type engines with low cylinder numbers and small V-V / inkel occurring large ignition intervals so reduced that a pneumatic starting of the engine can be made from any crank position.

A four-stroke diesel engine in V-type with 6 cylinders and a V-angle of 45 ° has ignition intervals of alternately 45 ° and 195 ⁰ KW. Since only about 120 ⁰ KW are available for the starting process per ZyIindereinheit by the valve overlap, no cranking torque can be generated in a crank angle range of 75 °. If the engine remains in such a position, an immediate pneumatic starting is not possible. When starting after the two-stroke process, the ignition intervals 45 ° and 75 ⁰ KW and the control of the exhaust valves is such that over a range of almost 180 ⁰ ICW an AnI ate torque arises. This' engine can be started after the two-stroke process with only one row, since in this case the firing intervals 120 ⁰ KlY amount. In the other row of cylinders, the injection and ignition can be initiated v / ground after reaching the predetermined starting speed, so that the starter control shaft can be moved back without ignitions in the operating position and then only at this injection begins.

Claims (2)

215 5 54 Brfindungsanspruch , Valve control for starting four-stroke diesel engines, in particular high-V four-stroke V-type low-V, low-V diesel engines, comprising a cam-type control shaft for controlling the intake and exhaust valves and the starting valves for starting the engine by means of compressed air, characterized in that the starting cams and on the control shaft additionally arranged exhaust cams are formed with two cam lobes for a control of the starting and exhaust valves by the two-stroke process and are only in the starting process via actuators with these in combination. 2. Valve control according to item 1, characterized in that the control shaft is displaceable.