Patent Description:
The present invention concerns a rocker/lever arm, in particular to a rocker/lever arm assembly for a steering system of a vehicle.

All vehicles are provided with steering system systems configured to allow steering of vehicle wheels.

Such steering system systems are realized in many different ways and may comprise rocker/lever arms configured to torsionally connect together two elements of a steering system. In particular, such a rocker/lever arm comprises a first and a second arms connected to an hub which is carried by vehicle's chassis. Such hub is carried by the chassis in a rotatably free manner around an axis defined by such rotatable connection.

Both arms of the rocker/lever arm comprises a connecting portion for connecting steering system's elements and they are placed on opposite sides with respect to a plane passing from the center of the carrying hub and parallel to ground. Accordingly, steering system's elements are linked in a torsionally way around the axis of the hub, as requested.

An example of such a steering system is described in <CIT> and it is clear that the rotatable free connection of the hub to the chassis is crucial due to the loads which are imparted from this latter to chassis.

Another example of a steering system is described in <CIT>.

Usually, even if not described in <CIT>, hub of rocker/lever arm is carried on a supporting kingpin, realized integral to the chassis, thanks to a pair of rolling bearing mounted in known way thanks between kingpin and rocker/lever arm.

However, such construction is complex and expensive. Indeed, it is necessary to perfectly mount coaxially the two bearings on the kingpin so that loads are symmetrically imparted on support arm. If this condition is not correctly achieved, fatigue life of roller bearings is drastically reduced because of the higher loads acting on one of the bearings.

Furthermore, the necessity of providing axial support to bearings needs to provide shoulders and axial thrusts system, thereby making the mounting of the rocker/lever arm on the kingpin realized on the chassis long and complex.

According to the above, the need is felt to provide simplified and economic rocker/lever arm assembly while maintain at the same time their operational performances.

An aim of the present invention is to satisfy the above mentioned needs.

The aforementioned aim is reached by a rocker arm assembly as claimed in the appended set of claims.

<FIG> discloses an exemplarily steering system <NUM> for a vehicle, (not shown in its entirety) e.g. a light commercial vehicle or a heavy vehicle such as a truck, carried by a chassis <NUM> of the vehicle and configured to control the steering of at least a wheel assembly <NUM> of this latter.

In particular, steering system <NUM> comprises a plurality of known elements, not here described in full for sake of brevity, among which at least an upper element <NUM> and at least a lower element <NUM> connected in a torsional way to a rocker/lever arm assembly <NUM> according to the invention.

According to the described configuration, steering system comprises a pair of rocker/lever arms assembly <NUM>, in particular a first, front, rocker/lever arm assembly <NUM> connecting an upper element <NUM> and a front lower element <NUM> and a second, rear, rocker/lever arm assembly <NUM> connecting such upper element <NUM> together with two rear lower elements <NUM>.

Rocker/lever arm assembly <NUM> is carried by chassis <NUM> and comprises, as better shown in <FIG>, a fixing element <NUM> configured to be fixedly mounted of rocker/lever arm assembly <NUM> on chassis <NUM>. Preferably fixing element <NUM> comprises a plate <NUM> provided with a plurality of holes <NUM> configured to allow the insertion of threaded elements (not shown) to selectively fix plate <NUM> on chassis <NUM>.

Rocker/lever arm assembly <NUM> comprises a rocker/lever arm <NUM> configured to torsionally connect the above mentioned upper and lower elements <NUM>,<NUM> and comprising and hub <NUM> carried in a rotatable free manner by fixing element <NUM> around an axis A of rotation and a pair of arms <NUM>, <NUM> fixedly carried by hub <NUM>.

In particular, axis A is an axis perpendicular to a vertical axis and to longitudinal axis of the vehicle and arms <NUM>, <NUM> are an upper arm <NUM> extending from hub <NUM> getting far from ground above a transversal plane passing from axis A and parallel to ground and a lower arm <NUM> extending from hub <NUM> getting closer to ground. Preferably, hub <NUM> and arms <NUM>, <NUM> are realized in metal and made as one piece.

More in detail, arms <NUM>, <NUM> can be substantially parallel one with respect to the other, e.g. see front rocker/lever arm <NUM> of <FIG>, or inclined one with the other, e.g. see rear rocker/lever arm <NUM> of <FIG>. Both arms <NUM> extends radially from hub <NUM> and comprises, at respective terminal portions, at least one hole <NUM> configured to allow the connection, e. via bolts or by fitting, of the upper and lower steering system elements <NUM>, <NUM>. In the described example of <FIG>, upper arm <NUM> comprises a single hole <NUM>, while the lower arm <NUM> comprises two holes <NUM>.

Making reference to <FIG>,<FIG> and <FIG>, is easily seen that hub <NUM> is carried rotatably around axis A on a kingpin <NUM> extending from fixing element <NUM> parallel to axis A getting away from chassis of the vehicle.

According to a first embodiment of the invention, rotatably free coupling between hub <NUM> and kingpin <NUM> comprises a single bearing <NUM>.

In particular, according to the embodiment of <FIG>, kingpin <NUM> comprises a main cylindrical portion 19a and a shoulder 19b, placed in proximity of plate <NUM> of fixing element <NUM> , the single bearing <NUM> is fitted on cylindrical portion 19a and finds in shoulder 19b a first lower axial endstop.

Hub <NUM> is configured to define, on the same plane of shoulder 19b, a shoulder 13a configured to define a first upper axial endstop for single bearing <NUM>. On the opposite axial side hub <NUM> comprises an annular seat <NUM> configured to house a retaining ring <NUM>, e.g. a Seeger ring, configured to define a second upper axial endstop for single bearing <NUM>.

Preferably, single bearing <NUM> is a single roller bearing, more preferably a double row tapered roller bearing.

In the embodiment of <FIG>, second lower axial endstop is defined by a retaining ring <NUM>, e.g. a snap ring, housed in a relative annular seat realized on cylindrical portion 19a of kingpin <NUM>.

In the alternative embodiment of <FIG>, second lower axial endstop is defined by a washer <NUM> pressed by a self-locking nut <NUM> configured to engage a threaded surface realized on a dedicated portion 19a' extending from cylindrical portion 19a of kingpin <NUM>.

According to a second embodiment of the invention, as shown in <FIG>, rotatably free coupling between hub <NUM> and kingpin <NUM> comprises a sleeve bearing coupling <NUM>.

In particular, according to the embodiment of <FIG>, sleeve bearing coupling <NUM> comprises two sleeve bearings <NUM>', <NUM>'', preferably having a "L-shaped" cross-section. As known, sleeve bearing <NUM> is made of self-lubricating materials, such as plastic material, that do not require the use of grease.

According to the above arrangement, kingpin <NUM> comprises again the main cylindrical portion 19a and the shoulder 19b while hub <NUM> is configured to define the shoulder 13a; according to the L-shape of sleeve bearing <NUM>', shoulder 19b and 13a are not realized on the same plane one with respect to the other, so that sleeve bearing <NUM>' is clamped between this latter.

On the opposite axial side, the other sleeve bearing <NUM>'' is pressed between hub <NUM> and cylindrical portion 19a by a locking nut <NUM> configured to engage the threaded surface realized on the dedicated portion 19a', similarly to <FIG> embodiment.

In order to avoid that dirty elements or dust may damage the rotatably free coupling between hub <NUM> and kingpin <NUM> according to all the above described embodiments of <FIG>, rocker/lever arm assembly <NUM> can comprise a dust cap <NUM> configured to fit inside a hole <NUM> defined by hub <NUM> on the opposite side with respect fixing element <NUM>.

With regard to the first embodiment, single bearing <NUM> is already provided with sealing means, as known, therefore there is no need of sealant engagement between rocker/lever arm assembly <NUM> and fixing plate <NUM>. Conversely, about second embodiment, there is need of sealant means <NUM>, e.g. rotary shaft ring seals, on the opposite side with respect to the one provided with dust cap <NUM>. Accordingly, hub <NUM> and/or kingpin <NUM> are configured to define a seat for such sealant means <NUM>.

The operation of the above defined rocker/lever arm assembly <NUM> is the following.

When a force, e.g. given by an actuator, acts on upper and lower steering system elements <NUM>, <NUM>, this latter is transmitted to rocker/lever arm <NUM> which, thanks to arms <NUM> and <NUM> torsionally couples upper and lower steering system elements <NUM>, <NUM> thereby controlling movement of the connected wheel assembly <NUM> of the vehicle. According to the proposed layout, controlling force is imparted by one of rear lower elements <NUM>, which can be a hydraulic cylinder, and transmitted to wheel assembly <NUM> of the vehicle via remaining steering system elements <NUM>,<NUM>.

Thanks to the proposed embodiment of rotatably free manner coupling between hub <NUM> and kingpin <NUM>, loads are equally distributed on this latter, thereby increasing fatigue life of the rocker/lever arm <NUM>.

In view of the foregoing, the advantages of a rocker/lever arm assembly <NUM> according to the invention are apparent.

Thanks to the use of a single bearing <NUM> or of sleeve bearing <NUM>, it is possible to reduce assembly time of rocker arm assembly <NUM>. Furthermore, the above allows to reduce the number of components needed to guarantee axial stability of the rotatably free coupling between hub <NUM> and kingpin <NUM>, thereby reducing complexity and costs of rocker arm assembly <NUM>.

Moreover, the use of a single bearing <NUM> allows not to use grease or oil since this latter is already contained, and sealed, within bearing <NUM> itself. Furthermore, there is no need of precise coaxiality as in known system with two bearings, since the bearing is single and can be easily fitted on kingpin <NUM> before the mounting of the fixing element <NUM> on the chassis.

The use of sleeve bearing <NUM> is more economic with respect to the use of the single bearing <NUM> and allows a more compact system. Also in the case that sleeve bearing <NUM> comprises more elements, they can be easily centered on kingpin <NUM> and they do not require strict tolerances as known two bearings systems. Moreover, sleeve bearings <NUM> are usually made in self-lubrication materials, accordingly, there is no necessity of grease.

Furthermore, differently with respect to known devices, the rocker/lever arm assembly <NUM> according to the present invention can be realized as a separate element with respect to the chassis of the vehicle and can be assembled separately to the latter and, then, fixed to the chassis. In this way it is reduced and simplified the mounting of steering assemblies <NUM> with respect to the known ones.

It is clear that modifications can be made to the described rocker/lever arm assembly <NUM> which do not extend beyond the scope of protection defined by the claims.

For example, as said, steering system <NUM> may be of any typology and comprising different elements from the one described above.

Clearly, shape of arms <NUM>,<NUM> and number of holes <NUM> may be varied according to the typology of steering system.

Claim 1:
Rocker/lever arm assembly (<NUM>) for a steering system (<NUM>) of a vehicle, said rocker/lever arm assembly (<NUM>) comprising a fixing element (<NUM>) and a kingpin (<NUM>), said kingpin (<NUM>) being fixedly carried by said fixing element (<NUM>) and said fixing element (<NUM>) being configured to be connected to a chassis (<NUM>) of said vehicle and a rocker/lever arm (<NUM>) comprising a first and second arms (<NUM>, <NUM>) configured to be respectively connected to a first and second elements of said steering system (<NUM>), said rocker/lever arm (<NUM>) further comprising an hub (<NUM>) configured to carry said first and second arms (<NUM>, <NUM>), said kingpin (<NUM>) being configured to carry said hub (<NUM>) in a rotatably free manner, wherein said rotatably free connection between said hub (<NUM>) with said kingpin (<NUM>) comprises a single roller bearing (<NUM>).