Motor vehicles – Steering gear – With fluid power assist
Reexamination Certificate
2001-01-30
2003-01-21
Hurley, Kevin (Department: 3611)
Motor vehicles
Steering gear
With fluid power assist
C180S408000, C180S417000, C180S024010, C137S625230
Reexamination Certificate
active
06508330
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device consisting of an oleodynamic distribution system of the rotating type.
More particularly, the present invention relates to an oleodynamic distribution system of the rotating type that can be fit into applications of the oleodynamic type such as for example power steering systems of one or more steering rear axles of vehicles.
The present invention finds a particularly suitable application in the fields of mechanical industry, agriculture and transportation.
BACKGROUND ART
Italian patent application N. EO92A327 discloses a power steering system for power steering systems of the rear steering axle of a vehicle, particularly of a heavy vehicle.
It is the aim of the invention described in the present application that of connecting the front steering system of the vehicle comprising a hydraulic power steering system with the rear steering axle of the vehicle itself, so that a steering manoeuvre carried out by the driver operating on the steering wheel causes a simultaneous and coordinated rotation of the front wheels and of the rear steering axle of the vehicle.
In order to accomplish the above aim, according to present invention, the action is exerted by a double effect actuator whose body is connected to an arm that is rigidly coupled to the pivot that allows the rotation of the wheel about a vertical axis, said arm being connected to a corresponding arm for the rotation of the other wheel of the rear axle by a suitable connecting bar.
The piston encased inside the actuator is fixed to the axle of the vehicle by the end of the stem, and it cuts the inside volume of the body into two distinct chambers, each of which being suitable for being filled with pressurised oil with an oleodynamic control and in so doing for causing the displacement of the body of the actuator which in turn causes the simultaneous rotation of the two wheels of the axle.
According to a form of embodiment of the present invention, the lever of the hydraulic power steering system of the vehicle is connected to the actuator by a flexible cable of the Bowden control type, one end of which is directly connected to the slide valve of the two way and three position axial translation movement distribution system that is fixed onto the body of the actuator; in such a configuration, the steering manoeuvre carried out by the driver on the steering wheel is transmitted to the slide valve of the distribution unit by the hydraulic power steering system and by the Bowden control cable, as a consequence of which the slide valve of the distribution system is displaced, connecting the hydraulic power circuits which are suitable for forwarding the pressurised oil to either of the chambers in the double effect actuator in order to operate the steering of the rear axle.
A system that is similar to that described above was disclosed by European patent application n. EP-A-710601.
In the above case the steering system, that also exploits a double effect actuator, can be controlled by a two way, three position axial distributor, and it is applied to the steering of one or more axles in a vehicle semitrailer or trailer.
In both cases the power chassis front wheel steering angle or, for a semitrailer, the fifth wheel rotation angle, is transferred to said axial distributor by suitable means, for example a Bowden control cable driven by a double effect second actuator.
European patent application number EP-A-786394 discloses an improvement of the system object of the above cited European patent application n. EP-A-710601.
The improvement is therein given by the presence of a double effect actuator which connects between the rotation pivot of the wheel to drive and the axial distribution system; therefore, consequently, the axial distribution system is in this case connected to two double effect actuators, both of which with their bodies rigidly coupled with the rotation pivot of a single wheel.
The distribution of the single pressures among the several hydraulic power circuits therein makes it possible to obtain the steering precision.
Document U.S. Pat. No. 4,955,630 which was filed prior to the above cited European patent applications, discloses a steering system for one couple of semitrailer axles.
Even in this case a sensor for the detection of the angular position of the fifth wheel is provided, with respect to the semitrailer, as well as a Bowden control cable in order to transfer the rotation to an axial type distribution unit.
A double effect actuator is driven by said distribution unit in order to simultaneously set the wheels of one or more axles in rotating motion.
Other steering systems for third axles of power chassis, or for single or multiple axles of semitrailers and trailers provided with at least a two way and three position axial distribution unit are respectively disclosed in European patent n. EP-B1-386370, in U.S. Pat. No. (A) 5,244,226, in international PCT patent N. WO-A-8907065 and in Italian patent N. IT-A-1263504.
The above cited steering systems which are provided with a distribution system of the axial type wherein there is found to be present a slide valve that can be translated along a straight line have some remarkable drawbacks and disadvantages that limit their use, complicate their general mechanics of the system and do not make it possible to envisage the possibility to find additional safety systems provided in case of faults or failures.
In particular and with reference to the systems respectively described by Italian patent application N. BO92A327 and by European patent applications N. EP-A-710601 and N. EP-A-786394, these are provided with an actuating cylinder whose stem is fixed, whereas the movable member is made up by the body of the cylinder itself.
This solution which is made inevitable by the hydraulic control of the steering system of the axle to be rotated requires the employment of a purposefully built actuating cylinder. This results to be expensive, and it does not allow the use of the cylinders normally found in the trade.
Furthermore, in this case the two way and three position distribution system must necessarily be rigidly coupled with the body of the cylinder, that is to the mobile part; for this reason, the Bowden control cable that rigidly connects the hydraulic power steering system lever to the slide valve of the distribution unit must be provided with an expansion member located between the hydraulic power steering system lever and an end of said cable, in order to allow the hydraulic power steering system lever to move even when the body of the cylinder and the wheels of the rear axle are blocked in their most unfavourable position.
The above solution further complicates the general mechanics of the system, raising its costs and introducing possible causes for failures and faults.
Furthermore, conventional systems are not provided with any type of safety device that operates in case of faults or breakdowns of the Bowden control cable or of other connection members during the steering; when such a possibility occurs, there is found to occur an immediate dangerous circumstance because the axle cannot be controlled by the hydraulic power steering system of the power chassis and its wheels tend to remain steered towards where they were directed at the moment the breakdown occurred.
To complete the present section, attention is drawn to the fact that there are found to be known in the art two way and three position distribution systems of the rotating type; said rotating distribution systems are used for hydraulic power steering systems of both light and heavy vehicles, and they fulfil their only function to turn the lights of the distribution system on and off in order to direct the pressurised oil to either of the chambers within a power cylinder.
For this function that they must fulfil, said rotating distribution systems have an extremely limited rotation angle, namely in the 5°-6° range, and the movable members are provided with suitable stops that limit the rotation to the above indicated values.
Document DE-A-26553
Greenberg & Traurig, LLP
Hurley Kevin
LandOfFree
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