Internal-combustion engines – Starting device – Condition responsive control of starting device
Reexamination Certificate
2002-01-30
2004-02-24
Kwon, John (Department: 2837)
Internal-combustion engines
Starting device
Condition responsive control of starting device
C123S179250, C290S03800C
Reexamination Certificate
active
06694938
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of controlling a starter system for a heat engine, of the type comprising two starters so arranged that their pinions act in parallel on the starter crown of the engine after the ignition key has been actuated, each starter comprising an electric motor for driving its pinion and a power interrupter connected in the power circuit of the electric motor and controlled by a power supply to a coil.
The invention further relates to apparatus for performing the above methods.
STATE OF THE ART
Methods and apparatus of the above types are known at this time. In this connection, in some installations it is preferable to make use of two small starters in parallel rather than one single large starter. Thus, for very high capacity engines, the use of a pair of small mass produced starters instead of one single large starter made in smaller quantities may be more inexpensive.
Reference is here made to
FIG. 1
of the accompanying drawings, described later herein under the heading “Brief Description of the Drawings”.
The starter system shown diagrammatically in
FIG. 1
includes two small starters
1
and
2
, having respective pinions
3
,
3
′ which actuate in parallel the starter crown
4
of the heat engine (not shown). The electric motors of the starters
1
and
2
are indicated at
5
and
5
′ respectively, and their power interrupters, or “contacts”, at
6
and
6
′ respectively. Each of these interrupters is controlled by the moving core of an electromagnet which includes a starting coil, denoted
7
for the starter
1
and
7
′ for the starter
2
, and a running coil, denoted
8
for the starter
1
and
8
′ for the starter
2
. For more details about the construction of a starter of this type, reference may for example be made to French published patent specification FR 2 749 451A, given that such a starter may include only one coil in the manner described in French published patent specification FR 2 795 884A, in which the starter is again described.
Both starters are supplied with electrical energy from a battery
9
producing a voltage U, once the ignition has been switched on by the key
10
. In such a starter system, each starter contributes its own power.
It has been found that starter systems of the kind shown in
FIG. 1
are susceptible to serious variations in operating behaviour, such as to give rise to rapid deterioration of the starters in order to assist understanding of these behavioural eccentricities, the principle of operation of a starter of the twin-starter type, typified by the starters
1
and
2
in
FIG. 1
, will be briefly mentioned with reference to FIG.
2
.
In
FIG. 2
, current is plotted against time T on the abscissa. It shows in the form of a full line the characteristic curve for the current taken by the starter, and, in broken lines, the voltage U available at the battery
9
. On closure of the ignition key
10
at the moment t0, the running coil
8
and the starting coil
7
are simultaneously energised. The current IC
1
absorbed by the coils is then generally between 40 and 60 amps for a system supplied at a nominal 12 volts. The battery voltage U, equal to U
0
before the ignition key is closed, falls slightly because of the provision of the current IC
1
. Because of the magnetic effects of the coils, the current IC
1
displaces the pinion
3
towards the crown
4
through the interposed moving coil of the starter contactor. At the instant t1, the power interrupter
6
closes the power supply circuit of the electric motor and thus causes the current I
1
to flow, which causes a current peak IC
1
+I
1
, taken by the motor, to occur at the instant T2. This current IC
1
+I
1
then reduces as the motor picks up speed. The starting current produces a very deep trough, which may reach 6 to 7 volts, in the voltage U. With effect from the instant t1, the contactor is supplied with power only through its single running coil
8
. Its consumption falls back to a value of 8 to 10 amps. This results in a large fall in the value of the magnetic forces. However, this value does remain large enough to enable the magnetic core to finish its travel and to ensure, even at the instant t2, that the moving core is held magnetically against the fixed part of the contactor.
Reference is now made to
FIG. 3
of the drawings, to explain the various behavioural anomalies which can occur due to starter operation as described above, where two conventional starters are combined in the manner shown in FIG.
1
.
FIG. 3
shows the characteristic curves of the currents IC
1
and IC
2
which are absorbed by the contactors of the two starters, the currents I
1
, I
2
with which the electric motors
5
,
5
′ are supplied, and the battery voltage U, all as a function of time t. When the ignition key
10
is closed at the instant t0, the power interrupter
6
of the starter
1
closes at the instant t1. The interrupter
6
′ of the starter
2
closes after a slight time delay dt of a few milliseconds, because of variations in the characteristics of the different starters. The total current IC
1
+I
1
absorbed by the starter
1
rises sharply from the instant t1, and then slows and reduces at A because of the second starter
2
, which consumes the total current in accordance with the curve I
2
+IC
2
. This gives rise to a very large drop in the battery voltage U. One of the two starters reaches its unengaged voltage threshold, this being generally the second starter because its moving core may not have finished its travel. The residual air gap existing at this instant reduces the magnetic forces. Since the return force is higher than the motive forces of the electromagnet, the moving core of this starter therefore returns to its rest position. The power interrupter
6
′ opens, and the current intensity drops from B to C. The battery, relieved of the consumption of this starter, sees an increase in its voltage which enables the power interrupter
6
of the starter
1
to stay closed. The starting peak of the latter once again rises, from A to D. This starter then begins to turn, and the intensity of the current I
1
+IC
1
increases to the point E. In conjunction with this, the battery voltage U increases.
During this time, the power interrupter of the second starter
2
, which has been open since the point C, once again permits simultaneous supply of power to the starting and holding coils. The magnetic forces are now increasing very sharply, especially since the battery voltage U is once again rising. The power interrupter of the second starter once again closes and causes a second peak to occur in the intensity of the current I
2
+IC
2
, at the point F. This causes the interrupter once again to open, for the same reasons as before. However, in the meantime, the speed of the motor
1
continues to increase, and therefore the intensity of the current it takes continues to diminish. On the third closing event at H, the sum of the currents absorbed by the two starters is low enough for there no longer to be any re-opening. Starting of the heat engine can then take place normally.
It can easily be understood that, when such starting conditions occur, the starters undergo sharp variations in operating mode, whereby severe forces are applied to them both from the mechanical point of view (by virtue of impulses on the shaft line, risk of disengagement of the crown, and so on), and from the electrical point of view (for example by virtue of sparking, and arcs on the commutators and contactor contacts when current peaks occur).
Apart from the undesirable effects described above, other disadvantageous phenomena can occur. These depend on the type of characteristics of the starters used. It can happen that the time difference dt mentioned above is very large if the first starter has the time to gather a high speed before the pinion of the second starter comes into contact with the starter crown. The velocity of the crown is then too high to enable that pinion t
Kwon John
Valeo Equipements Electriques Moteur
LandOfFree
Method of controlling a starter system for a heat engine, of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of controlling a starter system for a heat engine, of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of controlling a starter system for a heat engine, of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3342283