Patent Description:
In the present description, the terms "vehicle" and "motorcycle" are used in an equivalent manner.

As known, a two-wheeled vehicle, when the vehicle is stationary and without the driver, must necessarily have at least one support system normally called "stand" so as not to fall on the ground. The ground support systems are of the central type (which maintain the vehicle in an orthogonal position with respect to the support plane, but need a certain "effort" by the driver to operate) or of the lateral type, (which is simpler to operate, but place the vehicle in an inclined position with respect to the support plane). Both the systems are present in some vehicles. The weight of the vehicle influences said operation and the same becomes "tiring" when it is often repeated for an intensive use of the vehicle, for example for deliveries of various materials with various stops in limited journeys. Documents <CIT>, <CIT> and <CIT>show devices according to the prior art. In particular, <CIT> discloses a three-wheeled motorcycle according to the preamble of claim <NUM>.

In order to overcome all this, a three-wheeled vehicle can be used which, if of the rigid type, remains vertical on its own like the tricycles, such as the toy tricycles for children. However, this simplification does not fit well for a fluid guide, since, during a curve, the centrifugal force which affects the vehicle made in this way tends to move the center of gravity of the same vehicle to the outside, thus risking an overturning, especially at high speed. This is all due to the fact that the driver cannot counteract said force by shifting his weight towards the inside of the curve, as he normally does with a two-wheeled vehicle.

In order to overcome said drawback, three-wheeled vehicles were created which consist of a front portion and a rear portion, which allow, through known mechanisms, to laterally incline the front portion in order to counteract the effects of the above-described centrifugal force. However, these solutions still have the problem of the vertical parking, since, when the front portion is free to rotate, it is necessary to provide mechanisms which are able to keep it in a vertical position when the driver is not performing a curve, otherwise the vehicle would be undriveable. The adoption of mechanisms adapted to connect the front part of a vehicle with the rear portion is known in the art, which mechanisms operate for this purpose under both mechanical and electromechanical and still electromagnetic command, all being however complex mechanisms requiring the installation on the vehicle of auxiliary devices which are necessary for their operation, all this increasing the overall weight and costs of the vehicle.

The purpose of the present invention is to provide a swinging arm suspension which is adapted to mechanically connect a front portion of a three-wheeled motorcycle to the rear portion thereof and allows to maintain the three-wheeled motorcycle in a vertical position only with the aid of elastic elements and mechanical linkages which, if combined with each other, form, as a whole, a swinging mechanical joint, which is adapted to counteract the lateral inclination tendency of the vehicle, so as to vertically support it when stationary.

The attachment points of the elastic elements and the stiffness thereof can modify the force counteracting the lateral inclination tendency of the vehicle due to the force of gravity. Last but not least, this mechanism allows the vehicle to completely emulate a two-wheeled vehicle, in particular in performing the curves, since, together with the geometry of the joint, also said suspension, which takes the form of an articulated quadrilateral, manages to ensure that, when it modifies its vertical inclination, it always rotates with respect to a geometric constant point corresponding to the lateral rotation center of said tire.

A further purpose of the present invention is to provide a joint or a suspension of the above-described type which is combined with a mechanism which allows the front portion of the vehicle to rotate with respect to the rear portion around an axis which is orthogonal to the development direction of the vehicle, allowing to better deal with bumpy routes, thanks to the bending of the vehicle following the stresses due to holes or bumps.

The present invention will now be illustrated and described in detail, with reference to a particular embodiment thereof, given by way of nonlimiting example, with the aid of the attached drawing tables, wherein:.

As known, other solutions with central joints between front part and rear part of the vehicle actually allow the rotation of the front part with respect to the rear part, but with a drift of the same front wheel with respect to the longitudinal plane of symmetry of the vehicle. Essentially, with the joints known in the art, the rotation of the front portion with respect to the rear portion takes place around an axis which does not coincide with the ideal axis of rotation, which would be the axis around which the front tire would be able to rotate if the vehicle has only two wheels. In order to identify this axis, it is necessary to consider the section of the tire which touches the ground, which therefore has the form of a circle arc, indicated in <FIG> with the reference <NUM>; the center of this circle arc is the lateral rotation center <NUM> of the tire and the ideal rotational axis traverses this lateral rotation center and runs parallel to the ground in the longitudinal direction of the vehicle.

Obviously, the above-mentioned description is intended for explanatory purposes and must not be intended in a limiting sense with respect to the particular geometric configurations of the joint.

A swinging arm suspension <NUM> according to the invention is illustrated in <FIG>. It is adapted to mechanically connect a front portion <NUM> of a three-wheeled motorcycle <NUM> to the rear portion <NUM> thereof and comprises an articulated quadrilateral <NUM>, in turn comprising a pair of first lateral connecting rods <NUM> with the same length, a lower base segment <NUM> and a major base segment <NUM>, wherein the length of the lower base segment <NUM> is shorter than the length of the major base segment <NUM>; at least one elastic element <NUM> acts on said first lateral connecting rods <NUM>, which elastic element is adapted to maintain, when at rest, the articulated quadrilateral <NUM> in a configuration in which said base segments <NUM>, <NUM> are parallel to each other (<FIG>).

In order to ensure that the front tire of the vehicle can rotate around the lateral rotation center described above and accordingly also around the ideal axis of rotation, it is provided that the geometric lengths of said first lateral connecting rods <NUM> and of said major <NUM> and lower <NUM> base segments are proportionate to each other such that the axis of symmetry of the major base segment <NUM>, for any position of said major base segment <NUM> with respect to the lower base segment <NUM>, always traverses the lateral rotation center <NUM>.

Obviously, this means that, operatively, the sizes of the various elements of the articulated quadrilateral <NUM> must be set so as to reach the desired purpose. This also depends on the height from the ground at which the suspension will be installed on the motorcycle (see <FIG>).

In order to obtain this result, the joints of the known type should be placed at few cm from the ground, and this would not allow the use of the motorcycle on the road, due to the closeness of the mechanism to the ground. This is due to the fact that, in the suspension according to the invention, the rotation center is offset to the outside of the articulated quadrilateral <NUM>, while, in the known joints, it is geometrically comprised in the structure of the joint. Suffice it to consider joints which are simply consisting of a rotational coupling, wherein the rotation center coincides with the center of the rotational coupling.

The counteracting force of the first elastic element <NUM> is such as to allow to support the vehicle in a vertical position when it is stationary and to be able to incline it when it moves forward and performs the curves.

The presence of the first elastic element <NUM> ensures that, whenever the two bases <NUM>, <NUM> are not parallel, the elastic force accumulating in said element due to the effect of its deformation pushes the articulated quadrilateral <NUM> so as to bring it back in the configuration in which the two bases <NUM>, <NUM> are parallel.

Advantageously, the first elastic element <NUM> can be placed between the two first connecting rods <NUM>.

In an alternative solution, a pair of elastic elements <NUM> can be used, each being integral with the frame of the vehicle <NUM> by means of a first end thereof and with one of the first two connecting rods <NUM> by means of the further end thereof.

The first elastic element <NUM> can consist, for example, of a wire, air, hydraulic, gas spring or similar.

The major <NUM> and lower <NUM> base segments can also advantageously be part of the frame of the front portion <NUM> and of the rear portion <NUM>, respectively.

The term "articulated quadrilateral" indicates a quadrilateral in which the sides are connected to each other by rotating pairs, for example bearings or bushings, which allow the swinging thereof.

Advantageously, it can provide that both the first connecting rods <NUM> are mounted at an end thereof on a support anchored to the rear portion <NUM> of the vehicle <NUM> through said rotating pairs, on which the same can freely move in a swinging manner, on the other side on a support anchored to the front portion, always through rotating pairs.

In order to increase the comfort of the driver, a suspension according to the invention can be combined with a swinging linkage <NUM>, described below with reference to a first embodiment illustrated in <FIG>, <FIG> and <FIG>.

The swinging linkage <NUM>, according to a first embodiment, comprises a hinge <NUM> which connects the front portion <NUM> of a vehicle <NUM> to a joint element <NUM> with which the major base segment <NUM> of a swinging arm suspension <NUM> according to the invention is integral. The freedom of rotation of the hinge <NUM> is adjusted by at least one second elastic element <NUM>. Advantageously, it can be placed between the joint element <NUM> and the frame of the front portion <NUM>.

In a further alternative embodiment, the second elastic element <NUM> can be coaxial to the hinge <NUM>.

With this solution, the two portion of a vehicle <NUM> are free to rotate with respect to each other around an axis which is substantially orthogonal to the longitudinal development direction of said vehicle, thus allowing to easily deal with rough roads with holes and bumps.

<FIG> shows how, in the presence of a bump, the axis which joins the center of the front wheel to the hinge <NUM> is not aligned with the axis which joins the hinge <NUM> with the center of the rear wheel, while, in <FIG>, in the absence of a bump, said axes are aligned.

The described system therefore allows the front portion <NUM>, as a whole, to move at the same time, both laterally inclining with respect to the rear portion, and introflecting with respect to the same, thus generating, through hinge and elastic means, the longitudinal swinging which is adapted to absorb the roughness of the ground during the travel.

The swinging arm suspension <NUM>, in a second embodiment shown in <FIG> and <FIG>, can comprise a shock absorbing device <NUM>.

Said shock absorbing device <NUM> replaces said second elastic element <NUM> of the previous embodiment and acts as an elastic damper between the front portion <NUM> and the joint element <NUM>, which are constrained by the hinge <NUM>.

It is observed that the further components of the device previously described, particularly the hinge <NUM>, remain substantially unchanged; the same numerical reference previously given is attributed to them in the following description.

Specifically, the shock absorbing device <NUM> takes the form of a deflecting mechanism <NUM>, hinged in two points which are solidly attached respectively to the front portion <NUM> of the vehicle and to the joint element <NUM>, and in a shock absorber cylinder <NUM> which connects the free end of the deflecting mechanism <NUM> to a portion of the vehicle's frame, in particular to the front portion <NUM>.

It is observed that, thanks to the interposition of the deflecting mechanism <NUM>, the shock absorber cylinder <NUM> is oriented in a direction that has a vertical component which is prevalent with respect to the horizontal one, unlike what happens with said second elastic element <NUM>.

The deflecting mechanism <NUM> is connected to the joint element <NUM> by hinging to a support bracket <NUM>. The joint element <NUM> remains solidly attached, as in the previous embodiment, to the major base segment <NUM> of the swinging arm suspension <NUM>, which connects it to the rear portion <NUM> of the vehicle <NUM>.

Said deflecting mechanism comprises a rocker arm <NUM> and a second connecting rod <NUM>, which connects said support bracket <NUM> to the rocker arm <NUM>.

The support bracket <NUM> comprises a base 711a which rises above the joint element <NUM> and an upper portion 711b to which the second connecting rod <NUM> is hinged.

The rocker arm <NUM> comprises a first end 712a hinged, with a first rotating pair, to the second connecting rod <NUM> and a second end 712b hinged, with a second rotating pair, to the shock absorber cylinder <NUM>. The rocker arm <NUM> comprises an intermediate fulcrum 712c hinged to a fixed bar <NUM>, which, as discussed below, is integral with the front portion <NUM> of the frame.

It is further observed that the rocker arm <NUM> comprises, in the depicted embodiment, a minor arm and a major arm inclined one with respect to the other and connected in the intermediate fulcrum 712c. The minor arm supports the first end 712a and the major arm supports the second end 712b. The relative inclination between the two arms is indicatively between <NUM>° and <NUM>°. The concavity defined between the two arms of the rocker arm <NUM> faces upwards.

The mentioned bar <NUM>, that allows to hold in position the intermediate fulcrum 712c, is transversally arranged to connect two lateral spars <NUM> which engage in correspondence of a junction element <NUM>, in particular a metal profile, which supports the hinge <NUM>. The spars can support further structural elements of the vehicle <NUM>, for example the driver's seat.

The rocker arm <NUM>, as known, is suitable to continuously swing about the intermediate fulcrum 712c, raising and lowering in opposite directions the first and second ends.

As said, the second connecting rod <NUM> connects the support bracket <NUM> with the rocker arm <NUM> and comprises a first end 713a hinged, with a rotating pair, to the second end 711b of the support bracket <NUM> and a second end 713b hinged, with a rotating pair, to the first end of the rocker arm <NUM>.

The second connecting rod <NUM> and the rocker arm <NUM> define, therefore, two subsequent links of a kinematic chain.

The shock absorber <NUM> comprises a first end 72a coupled through a rotating pair to the second end 712b and a second end 72b coupled through a kinematic pair to a support bracket solidly attached to the front portion <NUM> of the frame, in particular with the junction element <NUM> which also supports the hinge <NUM>.

The shock absorber <NUM>, as known, has an elastic resistance with damping with respect to compression, and therefore opposes the relative skewing of the front and rear portions caused by the roughness of the ground.

During normal operation, when the rear axle raises with respect to the front axle of the vehicle the second connecting rod <NUM>, intermediate between the support bracket <NUM> and the rocker arm <NUM>, rises to a raised position, farther from the ground, causing the lowering of the end 712b of the rocker arm <NUM>, compressing the shock absorber <NUM>. Vice versa, when the rear axle lowers with respect to the front axle of the vehicle, the second connecting rod <NUM> lowers to a position closer to the ground, causing the raising of the end 712b of the rocker arm <NUM>, decompressing the shock absorber <NUM>.

From the above, it can therefore be inferred that the invention described herein solves the problems known in the art by providing a constructively simple solution which allows to improve the drivability of a three-wheeled vehicle.

Specifically, the second embodiment allows, thanks to the vertical arrangement of the shock absorbing device <NUM>, to minimize the axial size of the vehicle. This allows, while respecting the dimensional constraints of the vehicle design, to use a shock absorber cylinder of substantial length and commercially available as an elastic counter element, with consequent improvement in driving comfort and containment of construction costs.

Claim 1:
THREE-WHEELED MOTORCYCLE (<NUM>), comprising a front portion (<NUM>) provided with a tire and a rear portion (<NUM>) provided with two tires, where said front and rear portions (<NUM>, <NUM>) are connected to each other through a swinging arm suspension (<NUM>), said suspension comprising an articulated quadrilateral (<NUM>), in turn comprising a pair of first lateral connecting rods (<NUM>) with the same length, a lower base segment (<NUM>) and a major base segment (<NUM>), wherein the length of the lower base segment (<NUM>) is shorter than the length of the major base segment (<NUM>); at least one first elastic element (<NUM>) acting on said first lateral connecting rods (<NUM>), which elastic element is adapted to maintain, when at rest, the articulated quadrilateral (<NUM>) in a configuration in which said base segments (<NUM>, <NUM>) are parallel to each other; wherein the geometric lengths of said first lateral connecting rods (<NUM>) and of said major (<NUM>) and lower (<NUM>) base segments are proportionate to each other so as to ensure that the axis of symmetry of the major base segment (<NUM>), for any position of said major base segment (<NUM>) with respect to the lower base segment (<NUM>), always traverses a constant geometric point coinciding with the lateral rotation center (<NUM>) of the tire of the front portion (<NUM>) of the motorcycle (<NUM>) with respect to which said tire is adapted to rotate, thus modifying its inclination due to the effect of the action of the driver in the moment in which he has to steer, said three-wheeled motorcycle (<NUM>) being characterized in that it comprises a hinge (<NUM>), which connects the front portion (<NUM>) of said motorcycle (<NUM>) to at least one joint element (<NUM>), with which the major base segment (<NUM>) of the swinging arm suspension (<NUM>) is solidly attached; wherein the freedom of rotation of said hinge (<NUM>) is adjusted by at least a second elastic element (<NUM>,<NUM>).