Machine element or mechanism – Gearing – Follow-up mechanism
Reexamination Certificate
2001-09-21
2003-05-20
Parekh, Ankur (Department: 3681)
Machine element or mechanism
Gearing
Follow-up mechanism
C074S42100R, C074S397000, C180S444000
Reexamination Certificate
active
06564664
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a steering boost arrangement for motor vehicles with a steering shaft with coaxially disposed electric rotor disc motor and a reducing gear acting onto the steering shaft.
EP 0 124 790 discloses a steering boost with electric drive which is coaxially installed in the steering shaft. The servo force coupling-in takes place with the aid of a servo motor which acts onto the steering shaft via a planetary gear. The gear and the motor are disposed coaxially relative to the steering shaft, with the steering shaft being guided centrally through the arrangement. Since the motor and the gear are developed as a separate assembled unit, the arrangement becomes voluminous and comprises a large number of parts, which is disadvantageous with respect to economy and reliability. A special disadvantage comprises that the sun wheel of the planetary gear is fastened on the rotor of the motor drive with the rotor and the sun wheel being rotatably disposed and supported coaxially with the shaft axis. This makes clear that in this embodiment the sun wheel always has a relatively large diameter, but at least can never have a smaller diameter than the steering shaft itself. Since the reduction ratio of a planetary gear is determined in the first step by the ratio of the diameters of the sun wheel and the planet wheels, it can readily be seen that in this embodiment large diameter ratios of the wheels cannot be attained since the sun wheel itself in this construction always has a relatively large diameter. In the description of the previously described application, a reduction ratio of 1:1 to 1:10 is specified. Larger reduction ratios would only be possible in the present embodiment if the entire gearing diameter were drastically increased, which would lead to impermissible dimensions of the steering boost arrangement.
In addition, small gear reduction ratios have the disadvantage that the motor power must be correspondingly large, and furthermore only slowly rotating motors, which require corresponding expenditures, can be employed. A further disadvantage herein is the less rapid response behavior which leads to reaction inertias in the system.
A further known embodiment comprises employing worm gearing configurations as the reduction gear. But due to the poor overall efficiency, high driving power is required, which, in turn, lead to large overall constructional forms of the servo unit and limit an economic implementation. The rotational axes offset by 90° in the worm gearing impede a compact arrangement.
Due to the voluminous construction also less structural space is available primarily in the direction of the shaft axis, which is of disadvantage primarily with respect to the safety functions. In the event of an impact of the driver onto the steering wheel, the energy must be absorbed as advantageously as possible in order for the motor vehicle driver not to be injured. This is attained thereby that in such case the steering spindle is to yield such that it absorbs the energy by telescopingly sliding one into the other. This forms the basis for the requirement of being able to provide sliding paths of maximum length for the energy absorption device, which is not readily possible with the known servo drives according to prior art. The required large installation space in the axial direction thus is at the expense of the desired energy absorption sliding path in the event of impact.
A further disadvantage in known devices comprises that, due to the complicated structuring, apart from mechanical play, also due to the large masses to be moved, these have a certain reaction inertia, which has a negative effect onto the steering behavior and the economy. The reaction inertia leads, for example, to greater response times of the steering, which, for example during rapid evasion maneuvers, is of disadvantage. Complex constructions, corresponding to the known arrangements, disadvantageously consume much energy during operation. Apart from the expenditures for the energy provision of the necessary energy, additional expenditures are necessary in order to dissipate the corresponding heat losses.
A further disadvantage of known arrangements comprises that the compensation of plays in driving parts is complicated and expensive and is only conditionally possible. This leads to less precise steering behavior and to increased reaction times, connected with a less favorably perceived steering sensation of the motor vehicle driver.
SUMMARY OF THE INVENTION
The task of the present invention lies in eliminating the disadvantages of the previously described prior art. The task lies in particular in realizing an electric steering boost for a steering arrangement which is built highly compactly and which permits attaining rapid response behavior with good dynamics with responsive steering behavior for the driver, and which operates at high efficiency and can be produced economically.
The task is solved according to the invention by the arrangement according to the features of claim 1. The dependent claims define further advantageous embodiments.
The task is solved according to the invention thereby that a disc-shaped electric motor is combined with a spur gearing with the motor being installed coaxially in the shaft of a steering spindle, a steering shaft or a steering gear pin, and the spur gearing is disposed eccentrically with respect to the shaft and coupled to it.
The rotor, which is disposed rotatably and supported about the shaft, drives a tubular fitting-shaped toothed wheel, also coaxially rotating about the shaft, which is developed as a pinion. This pinion, together with an eccentrically disposed spur wheel of greater diameter, which engages it, forms a first stage of a spur reduction gearing. This spur wheel is provided equirotatingly with a further toothed wheel, which acts onto a toothed ring of a further toothed wheel, which is connected with the steering shaft and thus transmits the motor force or acts onto the steering shaft reduced in terms of the rotational number. The sheering shaft is not interrupted and leads with its axis through the arrangement. The gear arrangement can be developed to be single-stage or multi-stage. The necessary gear reduction is defined in known manner through the ratios of the engaged numbers of teeth of the toothed wheel pairs or through its diameter ratios and through the stage number of the gear arrangement.
The stator of the rotor disc motor as well as the gear arrangement are fixed on a carrier plate, or the toothed wheels are rotationally movably supported. The carrier plate is disposed substantially transversely to the steering shaft axis and parallel to the rotor disc plane, and the carrier plate incorporates also housing parts which cover and protect the motor and the gear arrangement. The carrier plate or the housing covers disposed on it comprise fastening means, for example a fastening flange in order to hold the carrier plate with the motor stator and gear elements stationarily on the motor vehicle chassis, preferably with interspaced rubber bearings. The steering shaft itself, which is guided through the arrangement, is preferably supported bilaterially in the proximity of the entrance and exit with respect to housing parts or the carrier plate. As bearings serve for this purpose preferably friction-free rolling bearings such as ball bearings.
As the motor driving are preferably employed electronically commutating rotor disc motors, which comprise a stator winding disposed stationarily, wherein between the stator windings a rotating disc is provided as the rotor, which comprises flat permanent magnets. In order to be able to generate high moments, strong permanent magnets are preferably employed, which have magnetic energy capacity of more than 6000 Gauss, such as, for example, magnetic materials comprising rare earths, such as for example cobalt samarium material and, in particular, neodymium magnetic materials. The motor is controlled via power electronics with regulation, which measures via a torq
Notaro & Michalos P.C.
Parekh Ankur
ThyssenKrupp Presta AG
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