Internal-combustion engines – Starting device – Control of spark ignition during starting
Reexamination Certificate
2002-10-25
2004-10-05
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Starting device
Control of spark ignition during starting
Reexamination Certificate
active
06799547
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for starting a multi-cylinder internal combustion engine, in particular of a motor vehicle, in the forward direction, wherein the position of a piston in a cylinder of the engine is ascertained, and fuel is injected into a combustion chamber of the particular cylinder whose piston is in a working phase.
The invention also relates to a multi-cylinder internal combustion engine, in particular of a motor vehicle. The engine includes a detector for ascertaining the position of a piston in a cylinder of the engine and a fuel metering system for injecting fuel into a combustion chamber of the particular cylinder whose piston is in a working phase. Finally, the present invention also relates to a control unit for a multi-cylinder internal combustion engine of this kind, in particular of a motor vehicle.
A method for starting a multi-cylinder internal combustion engine of the type defined at the outset is known for instance from German Patent Disclosure DE 31 17 144 A1. The method described there operates without an electric-motor starter. When the engine is at a stop, a quantity of fuel required for combustion is injected into the combustion chamber of one or more cylinders (starting cylinders), whose pistons are in the working phase, and is ignited. After that, fuel is injected into the combustion chamber of the cylinder or cylinders whose pistons are executing the next working stroke, and is ignited as soon as the applicable pistons have reached the working position. In this way, the engine can be embodied without an electric starter and the associated components required by such a starter. Moreover, a battery of the engine can be made smaller, since it no longer has to furnish energy for the starter and the other electrical components.
In the known method for starting an internal combustion engine, at one piston position of the starting cylinder near top dead center, only a relatively small quantity of air is contained in the combustion chamber of the starting cylinder. The resultant combustion energy from the combustion of the fuel injected into the combustion chamber can under some circumstances, because of the small air mass, may furnish too little starting energy, preventing the machine from being started. Moreover, the spacing between an injection valve, by way of which the fuel is injected into the combustion chamber, and the piston may be too slight, so that the fuel injected, as a consequence of penetration, changes virtually completely into a piston wall film that is hardly capable of evaporating.
German Patent Disclosure DE 197 43 492 A1 can also be referred to as further prior art; once again, it discloses a method for starting an internal combustion engine without an electric starter.
SUMMARY OF THE INVENTION
The present invention has the object of reliably starting a multi-cylinder internal combustion engine without an electric starter, regardless of the position of the pistons in the cylinders before the starting process.
For attaining this object, the invention, based on the method of the type defined at the outset, proposes that the engine is first moved in the reverse direction, by the injection of fuel into a combustion chamber of at least one cylinder whose piston is—viewed in the forward direction—in a compression phase, and the fuel compressed in the combustion chamber of the at least one cylinder is ignited, and the rotary motion in the reverse direction comes to a stop before the bottom dead center of the pistons of the at least one cylinder is reached, and that the engine is then started in the forward direction.
According to the invention, before the starter-free starting, the engine is accordingly first moved in reverse far enough that the pistons in the starting cylinder are in an optimal starting position. Since for starting the engine in the forward direction fuel is injected into the combustion chamber of a cylinder whose piston is in a working phase, the optimal starting position of the pistons—viewed in the forward direction—is immediately after top dead center. Because of this position of the pistons, combustion of the fuel injected into the combustion chamber of the starting cylinder can generate especially high combustion energy and thus also especially high starting energy.
Moreover, according to the invention, during the reverse motion of the engine, a relatively large air mass is aspirated into the combustion chamber of the particular cylinder which—viewed in the forward direction—is in the working phase. It can therefore be assured that the combustion energy, resulting from the combustion of the fuel injected into the combustion chamber of the starting cylinder, furnishes adequately high starting energy to enable reliable starting of the engine.
Finally, as a result of the reverse motion of the engine before the starting in the forward direction, the piston of the starting cylinder is moved away by the injection valve, so that when the fuel is injected into the combustion chamber of the starting cylinder, only very slight penetration, if any, occurs, and the injected fuel changes over virtually completely into an easily ignitable fuel-air mixture in the form of a fuel cloud.
In an advantageous refinement of the present invention, it is proposed that inlet and/or outlet valves of the at least one cylinder, whose piston is located—viewed in the forward direction—before its top dead center is put, before the starting process, into a position corresponding to the compression phase. To enable putting the valves into a predeterminable position, regardless of the engine, a camshaft-free control of the inlet and/or outlet valves is needed. Thus each inlet valve and outlet valve can be triggered separately from the other valves and independently of the position of the camshaft. For camshaft-free control, the inlet and/or outlet valves are equipped either individually or in groups of several jointly with an actuator device. The actuator device may function hydraulically, piezoelectrically, electromagnetically, or in some other way. From the prior art, many camshaft-free controls for inlet and outlet valves are known that can be used in conjunction with the method of the present invention. In accordance with the refinement, the valves can be opened and closed independently and—if the freedom of valve motion allows it—freely. In this way, it is successfully possible before or during the starting process to change from an aspiration phase to a working phase and vice versa. It is correspondingly also possible to change from a compression phase to an expulsion phase and vice versa.
In a preferred embodiment of the present invention, it is proposed that the inlet and/or outlet valves of two cylinders, whose pistons are located—viewed in the forward direction—before their top dead center are brought, before the starting process, into a position corresponding to the compression phase. Hence the engine is first put in a reverse direction, by injecting fuel into the combustion chambers of two cylinders whose pistons are—viewed in the forward direction—in a compression phase. Then, the fuel compressed in the combustion chamber of the two cylinders is ignited. As a result of the double combustion, sufficiently high combustion energy and thus a sufficiently starting energy are generated to overcome any static frictional or frictional and compression resistances of the engine, and initially to put the engine in a reverse motion reliably.
In another preferred embodiment of the present invention, it is proposed that during the rotary motion of the engine in the reverse direction, the inlet and/or outlet valves of a cylinder, whose piston is located—viewed in the forward direction—in an aspiration phase, are actuated in a targeted way such that the rotary motion of the engine in the reverse direction comes to a stop before bottom dead center of the pistons of the at least one cylinder is reached. By closing the inlet valves and outlet valves of a cylinder whose piston is in an aspiration phase, at t
Dolinar Andrew M.
Robert & Bosch GmbH
Striker Michael J.
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