Machine element or mechanism – Engine starters – Automatic
Patent
1992-04-27
1994-06-21
Braun, Leslie A.
Machine element or mechanism
Engine starters
Automatic
74 7E, 192 45, F02N 1506
Patent
active
053219872
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a cranking arrangement with an output shaft driven by a rotor and carrying a pinion for driving a toothed ring of an internal combustion engine, the output shaft being supported so that it can be displaced axially for the engagement and disengagement of the pinion.
In motor vehicle technology, such cranking arrangements are used for starting the vehicle internal combustion engines. For the starting procedure of the vehicle internal combustion engines, a driven pinion must engage in a toothed ring of the internal combustion engine. An output shaft carrying the pinion is supported so that it can be displaced axially in order to provide the axial movement necessary for this purpose. When the starting procedure has been ended, the pinion disengages from the toothed ring, the output shaft returning to its initial position (disengaged position). After disengagement, it is disadvantageous for the pinion to continue to rotate for a relatively long time because then, in the event of a possible restart procedure, the engagement is not clean and damage may result due to a large relative motion between the pinion and the toothed ring. The run-down time is particularly long in the case of geared cranking arrangements--compared with direct cranking arrangements (without gear stage) - because the moments of inertia increase with the square of the transmission ratio.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a cranking arrangement which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a cranking arrangement of this type in which the output shaft acts upon the rotor in the disengaged position axially in such a way that the rotor meets a brake surface.
When the cranking arrangement is designed in accordance with the present invention as specified hereinabove, it has, in contrast, the advantage that long pinion run-down times at the end of the starting procedure are prevented. In accordance with the invention, a braking effect is automatically initiated by the output shaft returning into the disengaged position and this-braking effect retards the drive rotor and therefore the pinion also. The teaching in accordance with the invention proposes, for this purpose, that the return motion of the output shaft should be transmitted to the rotor in such a way that the latter is similarly axially displaced and therefore comes against the brake surface. Such braking is particularly effective in the case of geared cranking arrangements because the rotor represents an element which is associated with a relatively small torque. In consequence, even relatively small brake forces lead to a large effect.
An extension of the invention provides for the output shaft meeting a sprung contact element of the rotor. This sprung support between the output shaft and the rotor on the one hand compensates for tolerances but still causes transmission of axial forces to the rotor.
It is advantageous for the contact element to be located coaxially with the rotor. This avoids unbalance and also achieves smaller moments of inertia.
In order to maintain the sprung effect of the contact element, a compression spring is preferably located between the contact element and the rotor.
A construction which is particularly economical in space, but is nevertheless simple, is obtained when the contact element is guided so that it can be displaced axially in an axial hole of a rotor shaft. The contact element can, in particular, be designed as the starting pin. The latter preferably has a circular cross-section, its central axis extending coaxially with the rotor axis.
A good braking effect can be achieved when the brake surface is formed on a brake disc. The latter is preferably located between the end of a commutator associated with the rotor and a casing region of the cranking arrangement.
Provision is made, in particular
REFERENCES:
patent: 2759363 (1956-08-01), Lewis
patent: 2777328 (1957-01-01), Wagner
patent: 4304140 (1981-12-01), Ebihara
patent: 4412457 (1983-01-01), Colvin
patent: 4635489 (1987-01-01), Imamura et al.
Braun Leslie A.
Laub David W.
Robert & Bosch GmbH
Striker Michael J.
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