Prime-mover dynamo plants – Electric control – Electric-starting motor
Reexamination Certificate
1999-07-21
2001-11-27
Enad, Elvin (Department: 2834)
Prime-mover dynamo plants
Electric control
Electric-starting motor
C290S03800C, C290S03800C, C290S03800C, C290S03600R, C290S03700A
Reexamination Certificate
active
06323562
ABSTRACT:
SUMMARY OF THE INVENTION
The invention is directed to a circuit arrangement for an engagement relay of a starter mechanism of an internal combustion engine, which engagement relay brings two gearwheels in engagement.
A circuit arrangement for an engagement relay is known from DE 195 035 36, wherein the circuit arrangement has a controlling and/or regulating circuit which influences the operating current of an auxiliary relay. The auxiliary relay in the prior art serves to decouple the current flowing across the relay coil of the engagement relay during the starting process of an internal combustion engine from an ignition starter switch or driving switch. This is carried out in that the current needed for the engagement relay, which can amount to about 80 to 100 A, is switched by the auxiliary relay. For this purpose, the auxiliary relay requires an operating current which is smaller compared with the engagement relay current and which can be switched with this construction by the ignition starter switch or driving switch.
Due to the controlled or regulated current, it is possible to reduce the overall dimensions of the auxiliary relay.
A disadvantage in the construction known from the prior art consists in that only the operating current of the auxiliary relay can be controlled or regulated. There is no provision for regulating the current of the engagement relay. Consequently, during the starting process for the internal combustion engine, the engagement relay always operates at a constant current which is so dimensioned that the engagement relay develops a sufficient magnetic force in every instance. A substantial disadvantage of the known construction results from a hyperbolic force-path characteristic of a relay, namely, as the air gap becomes smaller an unnecessarily high acceleration of the engagement relay armature is reached. Since the engagement relay armature moves the driving pinion of the starter mechanism axially by means of a lever mechanism, this also leads to a high acceleration of the driving pinion. During a starting process, if the driving pinion is so positioned relative to the gearwheel to be driven that two teeth of the respective gearwheels are directly opposite one another, the two gearwheels cannot be made to mesh with one another. If the driving pinion which is very highly accelerated by the engagement relay and lever mechanism meets the gearwheel to be driven, very high forces must be compensated when the two gearwheels meet. These high forces can result in complete destruction of the gear teeth.
Further, devices which rotate one gearwheel relative to another when two gearwheel teeth strike against one another are known in the prior art. These devices are known as meshing gear units. It is disadvantageous in this connection that the driving pinion which is moved relative to a gearwheel is accelerated very sharply by an engagement relay via a lever mechanism as was already mentioned. Consequently, there is a further increase in gearwheel wear due to the combination of high forces which are transmitted to the driving pinion via the engagement relay and the rotating movement which is brought about by the meshing gear unit because the two gearwheel elements rub against one another due to the force and rotating movement. This leads to the familiar “grinding” noise.
In another embodiment form known in the prior art, the starter motor of the starter mechanism takes over the task of the meshing gear unit. If the teeth of the driving pinion in this embodiment form strike the gearwheel to be driven, the motor of the starter mechanism is supplied with its nominal current, so that the driving pinion is quickly rotated relative to the gearwheel to be driven and meshes therewith. The force acting on the driving pinion due to the engagement relay combined with the high motor speed leads to extensive wear or even to its destruction as a result of the “grinding” of the gearwheel elements.
In vehicles which are provided for start-stop operation in the interests of reducing gasoline consumption and which consequently have a greater number of starting processes, the life of the starter mechanism would be short.
SUMMARY OF THE INVENTION
The invention is directed to a circuit arrangement for an engagement relay of a starter mechanism of an internal combustion engine, which engagement relay causes the engagement of two toothed gearwheels and comprises a controlling and regulating device that reduces a relay current after a first time period before the meshing of the two gearwheels to a determined current value during a second time period.
The circuit arrangement according to the invention has the advantage that the provided controlling and regulating device reduces the relay current after a first time period before the meshing of the two gearwheels to a predetermined current value during a second time period, resulting in smaller magnetic forces acting on the relay armature. Due to the hyperbolic force-path characteristic of the relay, an unnecessarily high acceleration of the driving pinion is prevented as the air gap between the relay armature and relay coil decreases and while the relay current decreases at the same time.
This results in reduced wear for the starter mechanism due to smaller forces acting when the gearwheel elements strike against one another, so that a longer life is achieved for the starter pinion and the gearwheel ring. The possible number of starts of this starter mechanism can accordingly be increased five-fold to ten-fold.
Further, a reduction in noise during the meshing of the driving pinion in the gearwheel to be driven is achieved by the circuit arrangement according to the invention. The noise reduction is carried out in that the starter motor of the starter mechanism rotates at a sharply reduced speed when the teeth strike against one another, so that the grinding of the two gearwheel elements is prevented.
A further advantage results in that the driving pinion is less highly accelerated during the second time period, wherein no high forces which rebound off the driving pinion take place when the driving pinion stops at a suitable pinion path limiting device, for example, a stop ring arranged on the rotor shaft. This means that the meshing process is reliably carried out in a “tooth-to-gap” position of the two gearwheels, so that the pinion is not thrown back in its engaging movement by large forces occurring when the pinion encounters the stop ring and, in this way, possibly disengaged or de-meshed again from the gearwheel to be driven.
In an advantageous construction of the invention, the controlling and regulating device controls or regulates the current of the engagement relay as well as the current of the starter motor during the engagement process by means of an individual final control stage. For this purpose, the relay winding is designed in such a way that the number of turns is reduced while the conductor cross section is increased at the same time. This can result in the same force-path characteristic of the relay as that in a standard relay; however, for this purpose, the relay current must be increased to a current strength in the order of magnitude of 100 A to 150 A, wherein, of course, the relay current is controlled and regulated by the circuit arrangement according to the invention.
In this embodiment form, for example, in a series-wound motor, the relay is connected in series with the excitation winding or armature winding.
When the relay current during a starting process reaches a level that is needed for spinning the rotor, the relay current flows through the above-mentioned series connection of the relay winding and excitation winding or armature winding and the rotor is set in motion at a low speed. Due to the fact that the driving pinion is fitted to the rotor shaft so as to be fixed with respect to rotation relative to it, the driving pinion rotates relative to the gearwheel to be driven during the engagement process and can mesh in a gap between two teeth of the gearwheel to be driven.
Another advantageous constructi
Daurer Uwe
Kramer Claus
Renner Stefan
Schmidt Karl-Otto
Enad Elvin
Robert & Bosch GmbH
Striker Michael J.
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