Internal-combustion engines – Starting device – Condition responsive control of starting device
Reexamination Certificate
2001-06-22
2003-06-24
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Starting device
Condition responsive control of starting device
C290S03800C
Reexamination Certificate
active
06581559
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pulse starting method for an internal combustion engine in which, during a wind-up phase, a flywheel mass is accelerated in a rotary driven fashion and then during a coupling phase, the rotating flywheel mass is coupled to a rotatably supported shaft of the engine, preferably the crankshaft, in order to transmit torque. It also relates to a pulse starter for performing the pulse starting method, which includes an electrical starter, which drives a rotatably supported flywheel mass, and having a starting control unit, which controls the starter and a pulse starting clutch.
2. Prior Art
A pulse starting method and a pulse starter for an internal combustion engine are known. In the pulse starting method, a flywheel mass is accelerated in a rotary driven fashion during a wind-up phase. This is achieved by means of an electrical starter. A pulse starting clutch disposed between the internal combustion engine and the flywheel mass is disengaged. The driving of the flywheel mass stores mechanical work. During a coupling phase in which the pulse starting clutch is engaged, the engine is cranked by this stored work, together with the driving torque of the starter. In comparison to a conventional start, in which the engine is cranked for a relatively long phase with a quasi-stationary rotational speed, it is advantageous that in the pulse start, a pulse-like rotational speed progression with a steeply rising edge is produced when the pulse starting clutch is engaged so that a reliable start of the engine is achieved.
In the known pulse starting method and the known device, it is disadvantageous that the starting system must be designed for high output. Particularly because a reliable start must be assured for every operating state of the engine. This high starter output is particularly required with increasing cold because the drag power to be exerted by the starter increases and the starter battery power decreases. In comparison to the conventional starter system, this problem is even more pronounced in pulse starting because the drag power to be exerted by the electrical starter also increases with the rotational speed. The drag power also increases when an automatic transmission is provided to transmit torque into the drive train so that additional drag power must also be exerted for the converter input of the transmission. In addition to being designed based on output, known pulse starting methods and pulse starters are also designed so that a reliable start should be produced even with unfavorable rotational positions of the crankshaft of the engine. In the worst case, it can for example be necessary to rotate the crankshaft by 400° in order to achieve a synchronization of the engine required for the start. In particular, positions of the pistons and/or the valves should be determined in the synchronization. The injection of fuel and the ignition must take place in accordance with these positions. In addition, care must be taken in the pulse start that even with unfavorable initial operating positions and/or environmental parameters, the narrow time window for the starting of the engine can be preserved. This time window results in particular from the fact that when the pulse starting clutch is engaged, the rotational speed of the flywheel mass decreases very rapidly and thus the speed of the engine also remains lower, where a starting of the engine must be achieved at the latest by the point at which the speed of the engine falls below the minimal speed for startability. Since the drag moments increase at low temperatures, for example due to lower viscosity of the lubricants, this time window shrinks. Therefore, in order to assure a cold start, this window must be dimensioned based on a very high starting power, in particular also because in a start interruption, the uncertainty regarding the mixture state of the intake tube and individual cylinders, the chances for a successful second starting attempt decrease even further. An estimate of the starting power for a 3 liter, 6 cylinder engine with an automatic transmission, for example at an outside temperature of −25° C., yields a necessary wind-up rotational speed of the flywheel mass of approx. 1500 rpm, requiring the exertion of a drag moment of approximately 35 Nm. This yields the mechanical output of the starter of approx. 5.2 KW and thus a battery power of approx. 6.6 kW.
SUMMARY OF THE INVENTION
It is an object of the Invention to provide a pulse starting method for an internal combustion engine of the abovetype with a flywheel mass, which does not suffer from the above-described disadvantages, especially encountered during starting under cold conditions.
It is another object of the invention to provide a pulse starter for performing the method according to the invention.
According to the invention the pulse starting method for an internal combustion engine includes the following steps:
a) during a wind-up phase, accelerating a flywheel mass in a rotary driven fashion in order to rotate the flywheel mass;
b) then during a coupling phase following the wind-up phase, coupling the rotating flywheel mass to the crankshaft of the engine, in order transmit torque to the crankshaft for starting;
c) during at least one of the wind-up phase (
15
) and the coupling phase (
21
,
22
), evaluating a rotational speed progression (n(t)) of the flywheel mass (
3
) to obtain evaluation results;
d) deducing whether a successful start of the engine is possible from the evaluation results obtained in step c); and
e) if a successful start is not expected, the engine is brought into an operating position favorable for a subsequent starting attempt by means of the crankshaft.
According to the invention the pulse starter for the internal combustion engine, which has a crankshaft and a fly-wheel mass comprises
an electrical starter for rotatably driving the flywheel mass;
a starter control unit for controlling the starter;
a pulse starting clutch for engaging the flywheel mass with the crankshaft to rotate the crankshaft in order to attempt to start the engine:
a rotation speed sensor for measuring a rotation speed of the flywheel mass and
evaluating means for evaluating the rotational speed of the flywheel mass at individual times over time to determine whether or not a successful start of the engine is possible during successive starting attempts;
wherein the evaluating means includes means for evaluating at least one of a measured rotation speed of the flywheel mass and a rotational speed progression of the flywheel mass, during at least one of a wind-up phase in which the flywheel mass is put into rotation, but not coupled to said crankshaft, and a coupling phase in which the flywheel mass is coupled with the crankshaft to start the engine in order to obtain evaluation results.
ADVANTAGES OF THE INVENTION
The pulse starting method according to the invention and the pulse starter according to the invention have the advantage over the prior art that they permit a considerable reduction of the starting power required to assure a start during pulse starting. Particularly due to the fact that a rotational speed monitor evaluates the rotational speed progression of the flywheel mass during the wind-up phase and/or the coupling phase, a determination can be made as to whether the available starting power, which is reduced in comparison to the prior art, is sufficient to start the engine In a first starting attempt. If this is not the case, then the rotary accelerated flywheel mass and/or the electrical starter at least brings the engine into an operating position that is favorable for a subsequent second starting attempt. Particularly in cold starting conditions during a first cranking of the engine, the drag power for a subsequent second starting attempt can be reduced since the first cranking produces a lubrication of the moving parts in the engine and/or the connected transmission. In particular with automatic transmissions, it has turned out that a few revoluti
Ackermann Manfred
Ahner Peter
Grob Ferdinand
Castro Arnold
Robert & Bosch GmbH
Striker Michael J.
Yuen Henry C.
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