Internal-combustion engines – Starting device – Condition responsive control of starting device
Patent
1992-12-17
1994-06-28
Dolinar, Andrew M.
Internal-combustion engines
Starting device
Condition responsive control of starting device
12317928, F02N 1104
Patent
active
053237439
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for assuring start of an internal combustion engine, comprising an electrical machine drivingly connected to the engine crankshaft, an electrical energy source and means electrically coupled to the electrical machine and to the energy source, whereby the electrical machine can be controlled to operate either as a motor for starting the internal combustion engine or as a generator for supplying energy to the energy source when the engine is driving.
As an internal combustion engine is started, it passes through various phases before it can be considered to be fully started, i.e. when the engine is running so stably that there is no immediate risk of stalling. This state usually occurs within a few seconds after the engine has reached its set idling speed.
In order to start the engine, the starting system, usually consisting of a battery and a starter motor, must overcome both torque due to initial static friction and then torque due to kinetic friction and compression. Torque due to the initial static friction occurs until the crankshaft has begun to turn and the bearings etc become lubricated. Torque due to compression arises and increases as each piston approaches top dead center during its compression stroke. During the starting process, the starting system must be able to rotate the engine crankshaft sufficiently fast for a certain period of time, usually about 100 rpm for 5-10 seconds, in order that a sufficient amount of fuel for ignition will have time to reach the engine cylinders.
Immediately after start, when the idle speed has been reached, the engine will be running unevenly and the risk of stalling will be great. At this phase, a number of different factors can increase the risk of engine stalling, e.g. high load from the generator due to high charging requirement, compressor load by the air-conditioning being turned on during starting, the power steering unit etc.
Various arrangements are known for facilitating starting of an internal combustion engine and minimizing the risk of stalling after start. SE-A-334,778 describes, for example, a mechanical device for positioning the piston system of the engine in a position to facilitate starting. Known devices intended to prevent engine stalling as a result of too high engine load immediately after start comprise for example delay systems which delay engagement of the generator function and/or the air-conditioning compressor.
The purpose of the present invention is, with the aid of a combined starter motor and generator, which is known per se, to achieve a device which facilitates starting of an internal combustion engine and reduces the risk of engine stalling directly after start.
This is achieved according to the invention in a device of the type described by way of introduction by virtue of the fact that said means comprise a current director included in a control unit, which is coupled to a rotational speed and position sensor cooperating with the crankshaft of the engine, and that the control unit and the sensor are disposed, at a certain non-uniformity of engine crankshaft rotation speed, to cooperate to switch the function of the electrical machine between full motor function and full generator function within one rotation of the engine crankshaft.
The control unit can be a microprocessor which is programmed, when there is "uneven running" at low rpm, to control via the current director the electrical machine within the range full starter motor function to full generator function, so that the first function is obtained during the compression stroke and the latter function is obtained during the power stroke. When the engine is turned off, the sensor senses the crankshaft position and the control unit sends a signal to the current director to set, by means of the electrical machine, the crankshaft in a predetermined position so that the piston system is in the most advantageous alignment for the next start.
The invention will be described in more detail below with reference to an embodiment shown in t
REFERENCES:
patent: 3762387 (1973-10-01), Blomberg et al.
patent: 4699097 (1987-10-01), Tanaka et al.
AB Volvo
Dolinar Andrew M.
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