Internal-combustion engines – Starting device – Condition responsive control of starting device
Reexamination Certificate
2001-02-27
2003-02-11
Hirsch, Paul J. (Department: 3747)
Internal-combustion engines
Starting device
Condition responsive control of starting device
C290S03800C, C318S431000
Reexamination Certificate
active
06516767
ABSTRACT:
The present invention relates to methods and apparatus for controlling starters of motor vehicles, and more precisely to methods and apparatus for driving the core of the contactor of the said starters.
As is shown in
FIG. 1
, a motor vehicle starter conventionally comprises a contactor
2
and an electric motor M, the output shaft of which carries a pinion
1
. The pinion
1
is adapted to come into meshing cooperation with the starter crown C of the heat engine. It slides on the motor shaft M between a position in which it is disengaged from the said starter crown and a position in which it meshes with the latter.
The contactor
2
extends parallel to the electric motor M, above the latter, and includes a coil
2
a
and a plunger core
2
b.
It controls the power supply of the electric motor M by displacement of a moving contact
3
between an open position and a closed position, the said contact
3
being pushed by the said plunger crown
2
b,
which is movable axially with respect to the electric motor M when the coil
2
a
is energised.
The contactor
2
also controls displacement of the pinion
1
. Its plunger core
2
b
is, for that purpose, connected to the pinion
1
by mechanical means indicated as a whole by the reference numeral
4
.
These mechanical means include a fork which is attached at its upper end to the plunger core
2
b
and at its lower end to a starter head of which the pinion
1
is a part.
The starter head includes a free wheel which is interposed axially between a hub and the pinion
1
. The hub has internal helical splines which engage with complementary external helical teeth carried locally by the output shaft of the electric motor M.
The fork is mounted for pivoting movement between its two ends on a casing which contains the mechanical means
4
inside it, and which carries the motor M and the contactor
2
. The starter head with its pinion
1
is set in helical motion when it is displaced by the fork so as to engage with the starter crown.
This is achieved by energising the coil
2
a
following action by the ignition key which sets the plunger core
2
b
in motion, so that it is drawn towards a fixed core. mounted at the end of a support of the coil
2
a.
This support has a U-shaped cross section in order to contain the coil
2
a
, and accordingly has a base which constitutes a bearing
2
c.
The core
2
b
is therefore arranged to be displaced between a rest position and a contact position, in which it is in engagement on the fixed core, this closed position of the magnetic circuit being reached after the moving contact
3
, and therefore the electrical circuit, are closed.
The mechanical means also include a return spring mounted around the core
2
b
so as to return the latter to its rest position, a cut-off spring associated with the moving contact
3
to return the latter to its open position, and a spring
5
, called a clamping spring, which is mounted within the core
2
b
and is in engagement with a first rod coupled by a pivot pin to the upper end of the fork, for attaching the latter to the core
2
b.
This spring
5
has a higher stiffness than the return spring.
The fork is therefore interposed at its upper end between the core
2
b
and the pivot pin. The first rod, which is mounted within a blind hole in the core
2
b,
is arranged so that, after a predetermined course of travel, it comes into engagement with a second. rod fixed to the moving contact
3
and mounted for sliding movement within the fixed core. In the position where the contact
3
is closed, it cooperates with a fixed contact in the form of pads which are connected, respectively, to the positive terminal of the battery and to the electric motor M, thereby providing the power supply for the electric motor.
The pads are fixed to the closure cap of the contact, which is of insulating material.
All of these elements are shown in
FIG. 1 and
, in the interests of simplicity, have not been given reference numerals.
The pinion
1
is therefore able to come into engagement with the crown C, that is to say it can come into meshing engagement with the crown C before the moving contact has been closed.
Usually, the pinion
1
comes into axial abutting contact with teeth of the crown C before penetrating into the latter.
Thus, the mechanical means
4
include, in particular, a spring
5
which is interposed mechanically between the plunger core
2
b
and the pinion
1
, and which enables the plunger core
2
b
to continue its course of travel whereby to ensure, before it makes contact with the fixed core, that the moving contact is put into its closed position even if the pinion
1
is prevented from moving by abutment against the teeth of the crown of the heat engine, in a position in which it is not meshing with the said crown.
Nevertheless, having regard to the rapidity of the movement of the moving core
2
b
and the elasticity of the mechanical coupling means
4
, due in particular to the presence of the spring
5
, substantial dephasing may occur between the closing of the contact
3
and the axial displacement of the pinion
1
. Particularly at low temperatures, rotation of the electric motor, and therefore of the pinion
1
, can be found to occur before the latter has had time to penetrate into the crown. Because the electric motor M is supplied at full voltage, the speed of the pinion
1
increases very fast, thereby preventing the pinion from meshing in the crown. The result is rapid destruction of crown and pinion.
In the document FR-A-2 679 717, it has been proposed to mitigate this disadvantage by supplying the contactor with a variable pulsed current.
With reference to
FIG. 2
, in this type of arrangement, a coil B controls both a contactor K and the forward displacement of a pinion, not shown. The coil B is supplied through a transistor T in pulse mode, of the pulse width modulation (PWM) type, the transistor being governed by a micro-controller
10
. A cyclic ratio of the pulses is increased progressively so as to obtain an effective current in the coil which increases progressively. The purpose of this is to enable the moving core to begin its displacement with a minimum of magnetic attraction force and therefore with minimum acceleration, in order to avoid dephasing between the movement of the core and that of the pinion as described above.
This method also aims to reduce the velocity of impact of the pinion against the crown, whereby to reduce frontal wear in the latter.
However, it does not prevent violent displacement of the core from its rest position towards its working position.
In order to obtain a further reduction in this impact velocity, a method was proposed in the document U.S. Pat. No. 4,418,289, which conforms with the preamble to Claim 1, for supplying power to a coil for actuating a moving core of a contactor for an electric starter for a motor vehicle, wherein the effective current is varied in the coil during displacement of the core towards its contact position, and wherein, during this displacement, there take place:
a first driving phase at a high enough effective current to set the core in motion, and then,
a second driving phase with a weaker effective current.
The said document also proposes apparatus for control of the power supply to a coil for driving a moving contact of a motor vehicle starter, arranged to vary the effective current in the coil during displacement of the core towards its contact position, wherein it is arranged to perform, in the course of this displacement:
a first driving phase at an effective current sufficient to set the core in motion, then:
a second driving phase at a lower effective current.
In practice, it is arranged that, during the second phase, the electric motor is energised so that it rotates at reduced speed due to a supplementary disc having supplementary contacts and a supplementary resistor which are incorporated in the contactor. This second phase terminates on closing of the moving contact, which then cooperates with the fixed contact to energise the electric motor at full power.
This soluti
Maillet Régis
Vilou Gerard
Castro Arnold
Hirsch Paul J.
Liniak Berenato & White
Valeo Equipements Electriques Moteur
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