Patent Description:
The present invention relates to a motorized module for the transport of goods, according to the preamble of claim <NUM>, which corresponds to the disclosure of <CIT>.

For the transport of heavy loads variable from several tens up to thousands of tons, it is known to use motorized transport vehicles comprising one or more modules having respective loading platforms and a plurality of tyred axles.

In particular, each module may be of the self-propelled type and therefore capable of operating autonomously, for example, within construction sites or work areas, or it may be connected to a towing tractor when the route involves travelling along stretches of highway and therefore at relatively high speeds or along common roads where winding stretches and/or stretches with steep slopes may occur where the speed is much lower but high and variable driving actions are required.

For this purpose, goods transport modules are known to date having a loading platform and a plurality of axles and wherein the wheels of at least some of the same axles are driven by a closed circuit hydraulic system.

An example of a closed circuit hydraulic system of the type mentioned above is illustrated in Figure A1.

The system comprises a variable displacement hydraulic pump P driven by a heat engine or by an electric motor K1 and a plurality of hydraulic motors M1,M2,. Mn constructively equal to each other and also with variable displacement.

The hydraulic motors are connected to a delivery branch A and to a return branch B and have respective output shafts each coupled to one or more respective wheels R.

In order to increase the torque transmitted to the wheels R, a mechanical reducer, for example of an epicyclic type, is provided between each hydraulic motor and the respective wheel.

As is known, mechanical reducers, on the one hand, enable the torque transmitted to the wheels to be increased but, on the other hand, inevitably progressively reduce the rotation speed of the wheels themselves and therefore the advancement speed of the module.

For these reasons, the known modules are valued for the transport of heavy loads at low speeds but are unsatisfactory when moving at higher speeds, enabled by the low load being transported or by the conditions of the route being travelled, resulting in an increase in transfer times and, consequently, the overall transport costs.

In order to solve said problem it is known, to date, to use reducers with discretely variable reduction ratio, for example, by excluding a reduction stage of the epicyclic reducer. This enables the advancement speed of the vehicle to be slightly increased, but still within a very contained range, but entails a higher cost of the reducer compared to the cost of a traditional reducer with a fixed transmission ratio.

Attempts to improve the above solution have been made by using reducers with a variable reduction ratio deriving from reducers used in the automotive field.

Although theoretically said reducers may solve the problem of low towing or transfer speed outlined above, they have not found an actual application due to their significant axial overall dimension which has prevented them from even being mounted on compact axles such as those of the latest generation.

An alternative technical solution is to increase the number of motorized axles, i.e., the number of wheels. Said solution enables, for the same towing force of the unit, to reduce the reduction ratio of the reducers and therefore to consequently increase the transfer speed at no load or low load, but proves impractical as the increase in the number of axles exponentially increases the cost of the unit and, often, also its length for the same transportable load.

Finally, transport units are known, in which the problem of low advancement speed is solved by disconnecting all the mechanical reducers from the respective hydraulic motors. In the disconnected condition, the module behaves in the same way as an ordinary trailer towed by the tractor, which autonomously tows the unit at the allowed speed without receiving any traction contribution from the module itself.

For this reason, the tractor must, from time to time, be selected according to both the maximum pull foreseeable which depends on the mass to be towed but also on the type of route to be taken, since it must autonomously compensate for sudden, unforeseen, and frequent increases in towing force when traveling at a speed comprised between the speed at which the reducers are disconnected and the maximum cruising speed. This often results in the use of large size tractors with corresponding increased costs and only partial use of the towing power.

An object of the present invention is to produce a motorized module for goods transport, which allows the above problems to be solved in a simple and economical manner.

It is a particular object of the present invention to produce a motorized module for goods transport, which is settable as both the load conditions and the conditions of use such as, for example, the state of the ground vary without substantial wheel slippage or reductions in towing force.

A further object of the present invention is to produce a motorized module capable of moving the load even at high speeds by operating both autonomously and by variably integrating the traction action exerted by other independent tractors.

According to the present invention, a motorized module for goods transport is obtained comprising a loading platform; at least a first and at least a second axle each provided with at least one respective rolling body on the ground; and actuation means for actuating said rolling bodies; said actuation means comprising a closed circuit hydraulic system, in turn comprising a closed hydraulic circuit, at least one motorized pump arranged along the closed circuit to send a pressurized operating fluid to a delivery branch and receive the pressurized fluid from a return branch of the closed circuit, at least a first and at least a second variable displacement hydraulic motor both hydraulically connected to the delivery branch and to the return branch to operate the rolling body of the first axle and the rolling body of said second axle, respectively; said actuation means further comprising a first mechanical reducer interposed between the first hydraulic motor and the respective rolling body, a second mechanical reducer interposed between said second hydraulic motor and the respective rolling body, first and second releasable angular connection means interposed between said first hydraulic motor and the respective said rolling body and, between the second hydraulic motor and the respective rolling body, respectively, and an electronic command and control unit comprising means for acquiring the advancement speed of the module, means for controlling said hydraulic motors and means for activating/deactivating said first and second releasable angular connection means; said command and control unit being configured to vary the displacement of said first and second hydraulic motors and to control said first and second releasable angular connection means as a function of the advancement speed of the unit; characterized in that said first mechanical reducer has a reduction ratio less than the reduction ratio of said second mechanical reducer and in that said command and control unit is configured to activate said first angular connection means and subsequently said second angular connection means as said advancement speed of said module decreases.

Lastly, the present invention relates to a method for controlling a motorized module for goods transport.

According to the present invention, a method is provided for controlling a motorized module for goods transport, as claimed in claim <NUM>.

The invention will now be described with reference to the attached figures, which illustrate a non-limiting embodiment thereof, wherein:.

In <FIG> denotes, as a whole, a vehicle for the transport of goods.

The vehicle <NUM> comprises a front towing tractor <NUM>, an intermediate trailer <NUM> having tyred axles with idle wheels coupled to the tractor <NUM> in a per se known manner and a rear motorized module <NUM>.

The module <NUM> is in fact an autonomous self-propelled unit, which, in the example described is firmly connected to the trailer <NUM>.

Alternatively, the module <NUM> is coupled to the trailer <NUM> in a detachable manner or isolated from the trailer <NUM> and from the tractor <NUM> in order to define a vehicle that operates autonomously to transport a respective load.

The module <NUM> cooperates synergistically with the tractor <NUM>, during movement of the load, when firmly connected to trailer <NUM>.

Regardless of whether the module <NUM> operates autonomously or synergistically with the tractor <NUM>, the module <NUM> comprises a frame <NUM> defining a loading platform <NUM> and, four motorized axles designated by <NUM>,<NUM>,<NUM> and <NUM> (<FIG>) each comprising, in the example described, a respective pair of wheels <NUM>.

With reference to <FIG>, the module <NUM> comprises a drive unit <NUM> for the wheels <NUM> and, in turn, comprising, for each axle <NUM>,<NUM>,<NUM> and <NUM>, a respective pair of variable displacement hydraulic motors, designated by 8A,9A,10A and 11A each driving a respective wheel <NUM>.

According to the invention, the hydraulic motors 8A,9A,10A and 11A are equal to each other, meaning that, they have the same maximum displacement C.

Alternatively, according to a different embodiment, the hydraulic motor 11A has a maximum displacement C1 greater than the displacement C.

The hydraulic motors 8A,9A,10A and 11A form part of a closed hydraulic circuit <NUM> which further comprises a variable displacement pump <NUM> driven by its electric motor or an internal combustion engine, designated by <NUM>.

According to a variant not illustrated, the hydraulic system <NUM> comprises two or more pumps <NUM> driven by respective motors <NUM>.

The pump <NUM> and the hydraulic motors 8A,9A,10A and 11A are connected, in a per se known manner, to a delivery branch M and to a return branch R of the circuit <NUM>, as can be seen in <FIG>, and are controlled by an electronic command and control unit <NUM> of the module <NUM>, known per se and illustrated schematically.

The command and control unit <NUM> comprises a detector <NUM> for detecting the advancement speed of the module <NUM> and commands and controls the pump <NUM>, the hydraulic motors 8A,9A,10A and 11A and the motor <NUM> for actuating the pump <NUM> itself as a function of a speed signal received from the detector <NUM>.

Again with reference to <FIG>, the drive unit <NUM> further comprises for each wheel <NUM> of the axles <NUM>-<NUM>, a respective mechanical speed reducer designated respectively by 8R,9R,10R and 11R, conveniently, but not necessarily, with a fixed reduction ratio arranged between the respective hydraulic motor 8A,9A,10A and 11A and the respective wheel <NUM>.

Conveniently, the reducers 8R,9R and 10R all have the same reduction ratio R whereas the reducer 11A has a reduction ratio R1 that is less than the reduction ratio R of the reducers 8R,9R,10R.

In the example described, the reduction ratio R is equal to <NUM>/<NUM>, whereas the reduction ratio R1 is equal to <NUM>/<NUM>. Obviously, the reduction ratios may vary according to the specific application.

According to a variation, at least one of the reducers 8R,9R,10R has its own reduction ratio which is different from the reduction ratios of the other reducers 8R,9R,10R.

Lastly, the drive unit <NUM> comprises, for each wheel <NUM>, a respective releasable angular connection joint, designated by <NUM>,<NUM>,<NUM> and <NUM>, respectively. The angular joints <NUM>,<NUM>,<NUM> and <NUM> are each interposed between the respective mechanical reducer 8R,9R,10R and 11R and the respective wheel <NUM> and are all controlled by the unit <NUM>.

The unit <NUM> is configured to control the angular joints <NUM>,<NUM>,<NUM> and <NUM> independently of each other and to move each of them between a motion transmission condition and a release condition, in which the joints make the respective wheels <NUM> idle according to the advancement speed of the module <NUM>.

Control of the variation of the displacement of the hydraulic motors 8A,9A,10A and 11A and the angular joints <NUM>,<NUM>,<NUM> and <NUM>, as the advancement speed of the module <NUM> varies, is represented by the graphs of <FIG>, where the line E illustrates the variation of the displacements of the hydraulic motors 11A, while the line F illustrates the variation of the displacements of the hydraulic motors 8A,9a, 10A.

The graphs of <FIG> can be divided into four areas, in particular:.

Here and in the following, with the term "operating limit speed" we mean the maximum speed rate allowed by the reducer, which results from the type of construction, the cooling device, the surface treatment of the teeth, type of bearing used, etc. In other words, the operating limit speed is the maximum rotation rate, beyond which an unexpected breakdown of the reducer could occur.

The graph of <FIG> illustrates, in the same four areas "a"-"d" mentioned above and, therefore, again as the advancement speed of the module <NUM> varies, the variation of the traction action F. In particular, the continuous line A represents the trend of the tractive force of the module <NUM>, whereas the line B represents the variation of the tractive force of each axle <NUM>,<NUM> and <NUM>, and the line C represents the tractive force of the axle <NUM> again as the advancement speeds of the module <NUM> vary.

In particular it should be noted that the traction action of the axles <NUM>,<NUM> and <NUM> annuls at the speed V1 and that, for speeds greater than V1 after the speed V1, the traction action is the only action transmitted by the axle <NUM>.

The control logic graphically illustrated in <FIG>, i.e., with simultaneous engagement of the reducers 8R,9R and 10R, is to be preferred and finds advantageous application in case of low-grip conditions in order to reduce the probability of slippage of the wheels <NUM>. In fact, as the advancement speeds of the module <NUM> decrease, when the angular joints <NUM>,<NUM> and <NUM> are activated, with the same overall tractive force, the lowest torque transmitted to wheels <NUM> is guaranteed, with obvious advantages from the point of view of possible slippage of the wheels <NUM>.

However, it could be experimentally observed that for values lower than <NUM>-<NUM>% of the maximum available displacement of the hydraulic motors 11A, adjustment of the displacement of the hydraulic motors 11A themselves is, however, disadvantageous in terms of efficiency. Therefore, adjustment of the displacement of the hydraulic motors 11A is carried out by keeping <NUM>% of the maximum available displacement as the lower limit.

The graphs of <FIG> illustrate a control mode of the module <NUM> different from the one represented by the graphs of <FIG>.

In particular, the graphs of <FIG> illustrate a control condition of the module <NUM>, in which the angular joints <NUM>,<NUM> and <NUM> are engaged in succession as the advancement speed decreases. In this manner, it is possible to increase the percentage for adjusting the displacement of the hydraulic motors, due to the fact that the number of the hydraulic motors themselves connected to the wheels is lower. In other words, said control mode allows to initially distribute the maximum overall towing force over a smaller number of axles with respect to the condition of simultaneous engagement of all the angular joints <NUM>,<NUM> and <NUM>.

In said control mode, the area "b" of simultaneous adjustment of the displacement of hydraulic motors is reduced, leaving space for an area "e" where the displacement of the hydraulic motors 11A is the maximum and the displacements of the hydraulic motors 8A,9A and 10A are adjusted, and an area "f" where all the hydraulic motors 8A,9A,10A and 11A operate at their maximum displacement.

As for the control mode that provides for the simultaneous insertion of all the angular joints <NUM>,<NUM> and <NUM>, also in the insertion mode in succession, in the area "a" the advancement of the module is managed only with the adjustment of the hydraulic motor 11A.

In both adjustment modes described above, at the moment in which the advancement speed of the module <NUM> exceeds an operating limit speed of the reducers <NUM>, designated by V2, the angular joint <NUM> is also released making the respective pair of wheels <NUM> idle and the hydraulic motors 11A are brought to their minimum displacement, as can be seen from the graph of <FIG>, area "t".

In this condition, the module <NUM> behaves in the same way as an ordinary trailer with idle wheels so that it remains stationary if operating autonomously, or is dragged when connected to the tractor <NUM>.

In use, starting from the condition illustrated in the graph of <FIG>, in which all the angular joints <NUM>,<NUM>,<NUM> and <NUM> are released and the module <NUM> is dragged only by the tractor <NUM> at a cruising speed, for example <NUM>/h, at the moment in which, for various reasons, the advancement speed begins to decrease, the tractor <NUM> alone increases the pulling action until the speed V2 is reached. At said speed, the unit <NUM> activates the angular joint <NUM> and adjusts the hydraulic motors 11A thereby integrating the traction action. If, despite the action of the hydraulic motors 11A, the speed continues to reduce, at the moment the speed V1 is reached, depending on the transport conditions, one or the other of the control modes described above may be selected. In particular, the control mode can be carried out with simultaneous insertion of the angular joints <NUM>,<NUM> and <NUM> illustrated in <FIG> in a low-grip condition so as to guarantee the lowest torque transmitted to the corresponding wheels <NUM>.

Alternatively, the angular joints <NUM>,<NUM> and <NUM> can be activated in succession, as illustrated in <FIG>. Said mode allows to increase the percentage for adjusting the displacement of the motors 8A,9A and 10A, as the number of hydraulic motors involved progressively increases. In other words, said mode allows the maximum overall towing force to be initially distributed over a smaller number of axles compared to the condition of simultaneous insertion.

From the above it is clear that, compared to the known solutions, the module <NUM> and its various adjustment or setting possibilities allow for use both on special transport vehicles, which require very different speed performances between travelling conditions with no load and with a load, and on modular on-road vehicles, which in traditional conditions of use can be used as simple trailers or semitrailers.

In addition to this, the module <NUM> can be used as an autonomous self-propelled unit, but is capable of allowing movements in a much higher speed range than a traditional self-propelled unit, precisely due to the fact of having mechanical reducers with a different reduction ratio present on a same module <NUM> and in combination, or not, with hydraulic motors with a different displacement.

In particular, the module <NUM> finds advantageous application in so-called "monolithic" vehicles or machines. In this case, high speed movements are possible, for example in the absence of a load, by releasing the reducers 8R, 9R, and 10R so as to make the wheels <NUM> of the axles <NUM>,<NUM>, and <NUM> idle, and by using only the axle <NUM> as the sole towing axle.

Movements in a load condition are, instead, possible by making all four axles <NUM>,<NUM>,<NUM> and <NUM> pulling axles.

The position of each of the angular joints <NUM>,<NUM>,<NUM> and <NUM> between the respective reducer 8R,9R, 10R and 11R and the respective wheels <NUM> allows there to be no moving gears when dragged by the respective wheels <NUM>. In other words, the position of the angular joints allows the module to be towed up to a maximum speed equal to the traditional modules, without encountering resistance generated by the reducers.

In addition to this, the module <NUM> allows the towing tractor <NUM> to be supported during any step of use for the speed range defined in the design stage, generally variable between <NUM> and <NUM>/h to maintain the cruising speed up to the permissible design limit, when the quantity of the load would not allow it, effectively replacing a second towing tractor.

Again, the module <NUM> supports the tractor <NUM> both when tackling uphill climbs, where the necessary towing force exceeds the available performance, and when moving in low-grip conditions.

In absence of the tractor <NUM>, the module <NUM> is able to move the load autonomously, for example in structures, where movement is known to occur at low speed.

The assembly of motorized axles with a different reduction ratio and with hydraulic motors with a different displacement on a same module allows an expansion of the conditions of use of the module <NUM> or of the vehicle <NUM>.

From the foregoing it is firstly clear that several modules <NUM> with the same or different characteristics can be used in the vehicle <NUM> to increase the traction action and, respectively, to increase the range of application or modify the thrust or adjustment action in specific ranges of advancement speed.

Claim 1:
A motorized module (<NUM>) for goods transport comprising a loading platform (<NUM>); at least a first axle (<NUM>) and at least a second axle (<NUM>;<NUM>;<NUM>) each provided with at least one respective rolling body (<NUM>) on the ground; and actuation means for actuating said rolling bodies (<NUM>); said actuation means comprising a closed circuit hydraulic system, in turn comprising a closed hydraulic circuit, at least one motorized pump arranged along the closed circuit to send a pressurized operating fluid to a delivery branch and receive the pressurized fluid from a return branch of the closed circuit, at least a first and at least a second variable displacement hydraulic motor (11A) (8A;9A;10A) both hydraulically connected to the delivery branch and to the return branch to operate the rolling body of the first axle (<NUM>) and the rolling body of said second axle (<NUM>;<NUM>;<NUM>), respectively; said actuation means further comprising a first mechanical reducer (11R) interposed between the first hydraulic motor (11A) and the respective rolling body, a second mechanical reducer (8R;9R;10R) interposed between said second hydraulic motor (8A;9A;10A) and the respective rolling body, first and second releasable angular connection means (<NUM>) (<NUM>;<NUM>;<NUM>) interposed between said first hydraulic motor (11A) and the respective said rolling body and, between the second hydraulic motor (8A;9A;10A) and the respective rolling body, respectively, and an electronic command and control unit (<NUM>) comprising means for acquiring the advancement speed of the module (<NUM>), means for controlling said hydraulic motors (11A) (8A;9A;10A) and means for activating/deactivating said first and second releasable angular connection means (<NUM>)(<NUM>;<NUM>;<NUM>) said command and control unit (<NUM>) being configured to vary the displacement of said first and second hydraulic motors (11A) (8A;9A;10A) and to control said first and second releasable angular connection means (<NUM>) (<NUM>;<NUM>;<NUM>) as a function of said advancement speed of the module (<NUM>); characterized in that said first mechanical reducer (11R) has a reduction ratio less than the reduction ratio of said second mechanical reducer (8R;9R;10R) and in that said command and control unit (<NUM>) is configured to activate said first angular connection means (<NUM>) and subsequently said second angular connection means (<NUM>;<NUM>;<NUM>) as said advancement speed of said module (<NUM>) decreases.