Motor vehicles – Steering gear – With fluid power assist
Patent
1996-11-15
1998-12-01
Hurley, Kevin
Motor vehicles
Steering gear
With fluid power assist
180439, B62D 312
Patent
active
058425373
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention pertains to a steering gear having a cylinder/piston arrangement to which a hydraulic pressure can be applied, a toothed quadrant which can be brought into engagement with the pinion gear of a steering mechanism and a steering tie rod connection.
Steering gears of the same generic class are known in practical use from the state of the art and comprise a steering gear housing in which a cylinder is arranged in a rigidly connected manner, and a movable piston to which hydraulic pressure can be applied is arranged in said piston.
BACKGROUND OF THE INVENTION
On each side of the piston, a piston rod is arranged which projects laterally out from the cylinder and from the steering gear housing. A steering tie rod connection, e.g., in the form of a mounting flange is formed at the ends of the two piston rods. On one side, one of the piston rods is developed such that, when it projects out from the cylinder, it still moves across a certain length of the inside of the housing. This region of the piston rod features a toothing with which it is engaged with the pinion gear of a steering mechanism. The pinion gear is conventionally a component of a power-assisted steering unit, such that the steering gear transfers the rotary motion of a steering mechanism mechanically, by means of the pinion gear, and, at the same time, with hydraulic assistance by means of the cylinder/piston arrangement. The aforementioned arrangement can be executed in such a way that a piston is pressed onto an asymmetrically designed piston rod element. In order for a full steering swing toward both sides to be possible, conventional steering gears require a minimum overall length of six times the length of travel. It is practically impossible to reduce this overall length. A steering gear is conventionally mounted stationary in the vehicle with the housing. The two steering tie rod connections at the end of the two piston rods are connected to the steering tie rods and steering is brought about by means of the movement of the piston rods.
The development of a toothed quadrant on one of the piston rods necessitates the use of asymmetrical parts, i.e., different components are used on the two sides of the piston. The piston is fixed with respect to its construction, as is the production of the toothing on the piston rod. The piston and piston rod subassembly must be precisely coordinated with each other.
A construction as portrayed makes a hydraulic pressure connection costly. Conventionally, lines are led to the housing and connected through the same to the two cylinder chambers.
EP 0,144,259 B1 discloses a steering gear of this generic class. A cylinder, which moves with respect to a stationary piston on the basis of the application of hydraulic pressure, is arranged within a steering gear housing. A thrust transmitting piece holds this cylinder in the direction of a housing wall, on which a pinion gear housing is formed. A toothing is arranged within the housing to be in engagement with the pinion gear, which toothing is positioned in a resilient manner with respect to the cylinder. That is why a different location of the cylinder must feature a pedestal block for the steering tie rod connection.
A steering gear for a motor vehicles is known from DE-OS 1,933,403, with a steering rack connected directly to steerable wheels and connected to the pinion gear of a steering mechanism, such that, by means of an oblong member located parallel to the latter and connected to the steering rack, the oblong member moves together with the steering rack. DE-OS 1,933,403 discloses a scheme in which hydraulic assistance can also be carried out in a parallel housing segment in such a way that the housing element moves back and forth with respect to a piston that is held stationary by means of rods, and, as a consequence, moves the steering rack with the housing element.
SUMMARY OF THE INVENTION
The aforementioned steering gear, which belongs to the state of the art, is costly with respect to manufacture and assembly, n
REFERENCES:
patent: 1872714 (1932-08-01), Farley
patent: 4599911 (1986-07-01), Rosell
patent: 4608876 (1986-09-01), Rosell
patent: 4629026 (1986-12-01), Rosell
Hurley Kevin
TRW Fahrwerksysteme GmbH & Co. KG
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