A vehicle of this kind is disclosed by the Italian patent application no.

PN2000A000034, filed on June 2nd, 2000 by this same Applicant.

While offering a number of undisputable, clear advantages, these vehicles have two major drawbacks, i. e. the need for the driver to put his/her feet down on the ground when the vehicle is brought to a standstill and to use a stand in order to put the vehicle in a resting condition. From this point of view, no substantial difference appears to exist in the behaviour of rolling-wheel vehicles and the far more widespread motor-cycles provided with only two wheels, since all of them practically lack any static balance.

double track vehicle having two rolling wheels on the front axle and possibly also on the rear one. Their spindles are in fact attached to a first end portion of respective springs, whose second end portion is attached to the end portions of a rocker lever having its fulcrum hinged on to the frame along the longitudinal mid-plane of the vehicle. When banking, said springs do extend and contract in the same manner and this enables a moving vehicle to behave in the same way of a traditional two-wheeled motor-cycle, i. e. to be able to take a well-defined configuration of dynamic equilibrium. Suitable devices, which are adapted to be actuated by the driver, are provided to lock the banking of the rocker lever and of the associated wheels so as to maintain the springs at a different elongation.

The behaviour of the vehicle, when at a standstill or moving at a very low speed, is consequently much like a traditional four-wheeled motor-car, i. e. the vehicle is also permitted to have a configuration of static equilibrium.

In this prior-art solution, however, the actuation resp. the exclusion of the said locking devices occur, if not abruptly, in a manner independent from the actual state and configuration conditions of the vehicle, except for the running speed which, as stated above, must be nil or very low when the banking of the wheels is locked. A certain difficulty in driving the vehicle derives from both these characteristics.

It therefore would be desirable, and is actually a main object of the present invention, to provide a locking device that is capable of acting on the rolling wheels of a vehicle of the kind being considered here, which proves to be superior with respect to the solution disclosed in the afore cited De Monge patent, and which is in particular reliable and easy to use.

According to the present invention, these and further objects are reached in an automatic device adapted to lock the banking of the pairs of rolling wheels (regardless of these pairs being one or two) of the vehicle and having the characterizing features as recited in the appended claims.

Features and advantages will be more readily understood from the

following description of an embodiment of the present invention given by way of non-limiting example and shown the accompanying drawing.

- Figure 1 is a three-dimensional front view of a powered vehicle of the type being considered here, confined to the sole parts thereof which are directly relevant to the purposes of the present invention, in which the two front wheels, shown in their rolling state, are associated to a locking device according to the present invention ; - Figure 2 is a three-dimensional side view confined to the linkage mechanism connecting the two rolling front wheels with each other, as well as to the locking device illustrated in Figure 1; - Figure 3 is a functional diagram relating to that part of the same device which refers to one of the two front wheels.

In order to find all those construction and functional parts and details which have no direct relevance with the present invention, reference should be made to former patent publications, in particular the afore mentioned Italian patent application no. PN200 (:) A000034 ? although the present invention is applicable also to vehicles having rear rolling wheels like the one disclosed by WO-A-98 43872.

In Figure 1, only two steel tubes 1A, 1B which are a part of the loop frame and extend downwards in the front portion of the vehicle and the members 3A, 3B, 4 and 5 of a lattice-like structure 30 are shown. The structure 30 is welded to the tubes 1A, 1B and supports a linkage mechanism 20 connecting the front left-side wheel 2A and the front right- side wheel 2B with each other so as to enable them to not only steer, but also bank, i. e. roll, with respect to the longitudinal mid plane PM of the vehicle.

The linkage mechanism 20 comprises:

- a first pair 21A, 21B and a second pair 22A, 22B of rigid rods arranged above each other, which appear to be in a bifurcate shape when seen from above and are provided with central fulcra 31, 32 for being supported by the lattice-like structure 30 according to axes X, Y that are parallel to each other and lie on the above cited plane PM; - two rigid members 23A, 23B that carry the spindles 24A, 24B of the wheels 2A, 2B; - two pairs of ball-and-socket joints 25A, 26A and 25B, 26B between the rods 21A, 21B, 22A, 22B and the rigid members 23A, 23B-see Figures 1 and 2.

In the vicinity of their top portion, on to the pipes 1A, 1B there is welded the support 7 to the frame of a locking device according to the present invention, which is generally indicated at 10 in the drawing and is substantially constituted by following mechanical components: - a first double-acting cylinder 11A, whose piston is linked to the rod 21A which is associated to the front left-side wheel 2A; - a second double-effect cylinder 11B, whose piston is linked to the rod 21B which is associated to the front right-side wheel 2B; - a first pair of oil pipes 12A, 13A which belong to a circuit comprising also the first cylinder 11A, a proportional (modulating) two-way valve 17A, for instance of the solenoid-type, and two one-way valves 18A provided to limit the pressure of the oil in the oil pipes 12A resp. 12B, which are arranged in parallel to the proportional valve 17A. All the said valve means, solely shown in the hydraulic diagram of Figure 3, are enclosed in a valve-holding block 14A, which can advantageously be attached to the frame of the vehicle under the vehicle saddle and also encloses a reservoir

19A pre-filled with oil. An electric line 15 ensure a connection between the valve means enclosed in the block 14A with a control unit 50, which shall be described in greater detail further on and is in turn enclosed in a box 16 that is also attached to the frame of the vehicle ; - a second pair of oil pipes 12B, 13B belonging to another circuit, identical to the preceding one, which also comprises the second cylinder 11B. The valve means and the oil reservoir (not shown) of this circuit are enclosed in a second valve-holding block 14B, situated behind the first block 14A and in turn connected through a second electric line 15B to the control unit 50.

To said control unit 50, which among other things comprises a microprocessor, there is further connected, via a corresponding number of conductor leads 52, a number n zu 2 of sensors 51 adapted to detect an equal number of signals referred to state and configuration parameters of the vehicle. Examples of parameters that are suitable to an implementation of the present invention are : speed, acceleration, pressure in the braking-circuit, opening state of the butterfly valve of the carburettor (or the fuel injection valve). The invention calls for the possibility for at least a part of the signals detected by sensors 51 to be displayed on the dashboard of the vehicle and to equip the vehicle with a manual control accessible by the driver for actuating resp. releasing the locking device 10 which can also provided with a corresponding signal display on the dashboard and/or acoustical indication facility.

According to a basic feature of the present invention, the control unit 50 processes, according to an operational programme properly defined when the vehicle itself is being designed, input data consisting of the signals detected by at least two of the said n sensors 51 to obtain an appropriate control of the two double-acting cylinders I 1A, 11 B. more precisely, the said input data form an n-dimension matrix having as result a well defined percentage value of opening (i. e. of the free cross-section) of

the proportional valves such, as the one indicated at 17A, in the circuits also comprising the double acting cylinders 11A, 11B. Variations in one or more of said input signal (namely of the state and configuration conditions of the vehicle) have as a result corresponding different values of the percentage of opening of said proportional valves. The direction of the oil flow in the above mentioned circuits is determined by the banking of the two wheels 2A, 2B, i. e. by the inclination of the rods 21A, 21B (to which the lower end portions of the cylinders 11A, 11B are attached, as explained here above) in their relative movement about the axes X, Y of the fulcra 31, 32 with respect to the longitudinal mid plane PM of the vehicle. The oil arriving from the reservoirs, such as the one indicated at 19A, to the double-acting cylinders 11A and 11B results in a locking effect of the banking of the front wheels 2A, 2B with a progression that depends on the above cited percentage of opening of the proportional valves such as the one indicated at 17A, which in turn depends on the actual conditions of the vehicle.

One of the input data of the microprocessor of the control unit 50 is preferably the running speed of the vehicle, in such a manner as to enable, on obvious safety grounds, the device of the present invention to actually be operative only when the vehicle is either stopped or running at a speed that lies below a rather low limit speed.

By mere way of example, the following table shows the percentage of opening of each one of the proportional two-way valves such as the one indicated at 17A (output datum of the microprocessor of the control unit 50) as a function of the speed and the acceleration of the vehicle (input data of the microprocessor), as detected by the respective sensors 51 and received via the respective connection lines 52. % maximum acceleration vehicle speed 20% 40% 60% 80% 100% 0, 5 kmlh 100% 100% 100% 100% 80% I kmlh 100% 100% 100% 75% 70% % 1,5 kmih 80% 80% 75% 65% 40% opening of 2 kmlh 35 % 30 % 30 % 25 % 20 % proportional 5km/h 25% 10% 10% 8% 5% vatves 10km/h O0% 000

The values indicated in the above table (including the intermediate ones, obtained by interpolation, between the various input values) are defined exactly when the vehicle is being designed and, therefore, are usually different for the various models of a given manufacturer, As the vehicle speeds up, e. g. after a stop commanded by traffic lights, depending also on the speed conditions, the proportional two-way valves such as the one indicated at 17A open, thereby enabling the oil to flow from the double-acting cylinders 1IA, 11B with the result that the locking action is gradually terminated. Accordingly, as the vehicle keeps moving on, the two front wheels 2A, 2B with the linkage mechanism 20 will again be free of banking (rolling) with respect to the longitudinal mid plane PM about the axes X, Y of the fulcra 31, 32.

As far as the oil-pressure limiting valves such as the one indicated at 18A are concerned, the microprocessor of the control unit 50 enables them to be energized only when input data are received which indicate an emergency situation in driving the vehicle, such as for instance a situation of overpressure of the oil in the cylinder 11A and/or 11B brought about by at least one of the wheels 2A, 2B having bumped against an obstacle

and the effects of such a bump having therefore been transmitted via the members of the linkage mechanism 20.

From the above description the advantages of the invention can be readily appreciated, namely : - the vehicle is capable of temporarily taking a configuration of stable equilibrium, in a manner that takes into due account its actual conditions of the vehicle, as represented by the different state and configuration parameters which are detected by the sensors connected to the control unit. Therefore, the transition from a configuration of unstable equilibrium to a configuration of stable equilibrium, and vice-versa, takes place smoothly, in a condition of utmost safety, without giving rise to any inconvenience or trouble for the driver.

- the locking device makes use of proven components, which are easily available at a relatively low cost and very reliable.

-for the various models of vehicle made by a manufacturer, the components can be standardized while only the n 2 2 input data in the above referred matrix are selected during the design stage.

It will be further appreciated that, although the above description refers to a preferred embodiment of the present invention, a number of different variants and embodiments, some of which will be shortly mentioned below, may be developed without departing from the scope of the present invention as defined by the appended claims.

A simplified variant of the present invention does not require any use of the afore mentioned one-way oil-pressure limiting valves such as the one indicated at 18A.

Another simplified variant calls for the use of both double-acting cylinders 11A and 11B in a single circuit, so as to be fed in parallel by only one proportional two-way valve 17A and an oil compensating reservoir,

A further variant, which is more sophisticated than the above cited ones, but has the advantage of further improving the convenience in driving the vehicle, calls for the use of a reversible oil pump which, upon the banking of the front wheels 2A and 2B having been locked, reverses the oil flow in the cylinders 11A, 11B, so as to annul the banking.

A different embodiment of the present invention calls for-the use of other operating means than the afore mentioned double-acting cylinders to lock the banking of the wheels. These means may for instance be reversing electric motors which, in response to the output of the control unit 50, either activate or de-activate mechanical joints that are associated to members of the linkage mechanism 20.

It will finally be appreciated that the present invention applies to both vehicles with front rolling wheels and vehicles with rear rolling wheels.