Internal-combustion engines – Starting device – Condition responsive control of starting device
Reexamination Certificate
1999-05-01
2001-03-20
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Starting device
Condition responsive control of starting device
C290S035000
Reexamination Certificate
active
06202614
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a drive assembly of a motor vehicle having an internal combustion engine.
It is known to drive motor vehicles via internal combustion engines (hereinafter simply engines). These engines must be rotated up to speed for starting, until the engine begins to run on its own as a consequence of incipient combustion moments. To crank the engine, i.e., to turn it over, it is known to run the engine up to speed with an electric starter, whose pinion meshes with a toothed ring disposed on an engine crankshaft in a manner fixed against relative rotation and starts to turn it. This cranking device has stood the test of time but has the disadvantage of being noisy; also, because of parts subject to mechanical wear, the engine can be started with it only a limited number of times.
By realizing novel vehicle concepts which seek in particular to reduce fuel consumption, engines must be subjected to a high number of starting cycles. To save fuel, engines are turned off when the vehicle is stopped, for instance at a traffic light, in the so-called start-stop engine operating mode, and then automatically cranked again and started when the vehicle is to be driven onward again.
It is known to use electrical machines that are operated in the motor mode and the generator mode and are connected in force-locking fashion to a crankshaft of the engine. In the motor mode, direct starting of the engine can be done; after the engine runs up to speed, the electrical machine is switched over to a generator mode and serves to furnish a supply voltage for the motor vehicle. A disadvantage here is that particularly in cold starting, the electrical machine must be excessively oversized if it is to bring the requisite starting power to bear.
A so-called internal direct start is also known, in which the crankshaft, via a positioning device, is brought into a defined position so that the piston of a starting cylinder—a particular defined piston from among the total number of pistons of the engine—is brought into a starting position, stays there, and then by injection and ignition of fuel, a first combustion moment is generated, which is utilized to crank the engine. A disadvantage here is that because of the prepositioning time, only relatively poor starting dynamics are attainable, so that the engine does not begin to run on its own until after a relatively long time.
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate the disadvantages of the prior art.
In keeping with these objects, one feature of present invention resides, briefly stated, in that in the drive assembly of a motor vehicle the cylinder is the starting cylinder, whose piston can be brought into the starting position over the shortest path (angular rotation of the crankshaft), and a torque can be exerted on the crankshaft during the entire starting operation.
The drive assembly of a motor vehicle according to the invention offers the advantage over the prior art that an internal combustion engine can be made to run on its own quickly, in a simple way. Because when the engine is started the crankshaft can be brought into a predeterminable starting position via an electrical machine connected in the motor mode and coupled in force-locking fashion to a crankshaft of the engine, the direct injection and ignition of the fuel are effected when the crankshaft starting position is reached, and via the electrical machine, a torque can be exerted on the crankshaft during the entire starting operation, it is advantageously possible via a coordinated control of the rotational angle, rotary speed and injection of the engine and the superposition of the torque generated electrically via the electrical machine with combustion moment generated as a consequence of a first ignition of the engine, to attain a continuously accelerated runup of the engine to operating speed, so that the engine changes over seamlessly and automatically to running on its own. In particular because of the imposition of the torque via the electrical machine, the rpm of the crankshaft of the engine, during the first direct injection of fuel and its ensuing ignition, is other than zero, so that via the combustion moment brought to bear, by the first ignition of the engine, a markedly higher torque is developed at the start, compared with a start with a crankshaft at a standstill. This combustion moment is supported by the electrical machine that is still in the motor mode, so that the crankshaft is quickly accelerated, and the engine begins to run on its own no later than from the second injection and ignition on. As a result, a highly dynamic start and highly dynamic runup of the engine to speed are attained. Within a short time, the shortness of which is needed especially in a start-stop engine operating mode, the engine can be brought up to speed or to running on its own for a high number of starting cycles, which can be on the order of several hundred thousand starting cycles, for instance.
In a preferred embodiment of the invention, to initiate the starting operation, the current position of the crankshaft can be ascertained, and independently of the direction of rotation the crankshaft is brought into the starting position over the shortest path from the current crankshaft position and then—from the instant of ignition on—is rotated onward in the correct rotational direction. As a result, it becomes advantageously possible, optionally by reverse rotation of the crankshaft as well, for the starting position of the crankshaft to be attained over the shortest path and thus within the shortest possible time. The advantage is also obtained that particularly upon reverse rotation of the crankshaft, a compression occurs in the starting cylinder that leads to an increase in the combustion moment of the first combustion, without the need to pass through top dead center in the usual way, so that the starting dynamics or runup dynamics of the engine are further improved.
Further advantageous features of the invention will become apparent from the other characteristics recited in the dependent claims.
REFERENCES:
patent: 5323743 (1994-06-01), Kristiansson
patent: 5687682 (1997-11-01), Rembold et al.
Ackermann Manfred
Ahner Peter
Grob Ferdinand
Harms Klaus
Koelle Gerhard
Dolinar Andrew M.
Robert & Bosch GmbH
Striker Michael J.
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