The present invention concerns a hydraulic arrangement, in particular a hydraulic arrangement for controlling a fan drive system for a work vehicle.

Off-road and on-road machines such as construction and agricultural equipment are provided with cooling fans for cooling a radiator such as the oil or the engine radiator, driven by a dedicated hydraulic motor.

Usually, such hydraulic motor fan drive requires a pump controlled to adapt the fan speed, i.e. to provide a corresponding oil flow for managing the hydraulic motor; usually such pump is a variable displacement pump. However, variable displacement pump with a low maximum displacement as needed in work vehicles are very expensive.

Furthermore, such variable displacement pump and related hydraulic motor are provided with a dedicated hydraulic arrangement that it is distinct to the common pressurized oil source of the vehicle, e.g. the pressurized oil coming from a pump and configured to feed different operational elements of the work vehicle such as steering, brakes or other auxiliary hydraulic work devices.

Therefore, the need is felt to provide a hydraulic arrangement that can control in a cost-effective way the hydraulic motor driving the fan for a work vehicle in wide speed range, in particular at low speed values.

It is furthermore felt to provide a hydraulic arrangement that can use the same hydraulic power source of the work vehicle.

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

The aforementioned aim is reached by a hydraulic arrangement as claimed in the appended set of claims.

For a better understanding of the present invention, a preferred embodiment is described in the following, by way of a non-limiting example, with reference to the attached drawing, which, is a scheme disclosing a hydraulic arrangement according to the present invention.

In figure 1, reference 1 discloses globally a hydraulic arrangement for managing the oil flow provided to a hydraulic motor 2 for driving ventilation means 3 configured to generate an air flow for cooling a heat exchanger (not shown) of a work vehicle (not shown).

Hydraulic arrangement 1 comprises a control valve 4 for controlling the direction of the air flow provided by ventilation means 3. i.e. the oil flow into hydraulic motor 2; such valve 4 is interposed between a hydraulic power source 5, a discharge 6 and the hydraulic motor 2.

According to the exemplarily embodiment disclosed in figure 1, a first circulation line 7 is provided between a first opening 2a of motor 2 and control valve 4 and a second circulation line 8 is provided between a second opening 2b of motor 2 and control valve 4. A feeding line 9 is provided upstream to control valve 4 and fluidly connected the latter with the hydraulic power source 5 and a return line 10 fluidly connects control valve 4 and discharge 6.

According to a preferred embodiment, such control valve 4 may be an electrically controlled valve configured to swap the oil flow direction according to a signal S₁ provided to control valve 4.

More preferably, such control valve 4 is a four ways two positions valve configured to provide a first flow circulation into hydraulic motor 2, e.g. coming from feeding line 9, passing in a counter clockwise way into hydraulic motor 2 and then to discharge 6 via return line 10, or a second flow circulation into hydraulic motor 2, , e.g. coming from feeding line 9, passing in a clockwise way into hydraulic motor 2 and then to discharge 6 via return line 10.

Preferably, hydraulic arrangement 1 comprises a check valve 11 fluidly interposed between return line 10 and feeding line 9 to avoid cavitation during certain fan drive dynamics, e.g. motor stopping or motor speed reversing.

According to an aspect of the invention, hydraulic arrangement 1 comprises a flow regulation valve 16 fluidly interposed on feeding line 9 between hydraulic motor 2 and hydraulic power source 5 and configured to regulate the flow that can be provided from said hydraulic power source 5to hydraulic motor 2, in function of a control signal S₅ representative of a needed speed of ventilation means 3.

Preferably, such flow regulation valve 16 is a proportional valve configured to control the flow provided through feeding circuit 9 from zero to a preset maximum value.

According to a further aspect of the invention, hydraulic arrangement 1 comprises a post- pressure compensator module 12 fluidly interposed on feeding line 9 downstream flow regulation valve 16 and configured to generate a load sensing signal S₄.

Such post- pressure compensator module 12 comprises a hydraulic mechanically controlled proportional valve 13 configured to regulate the flow coming from flow regulation valve 16 toward hydraulic motor 2. Such valve 13 is controlled by a pair of hydraulic signals S₂, S₃ acting from opposite sides of proportional valve 13 and respectively picked from upstream to valve 13 and downstream to this latter.

In particular, valve 13 can regulate oil flow between a first opened position where no flow passes through the latter and a second closed position where a maximum amount of fluid passes through the latter.

Furthermore, from the side of downstream picked signal S3 an elastic element acts in favor of this latter signal to maintain the valve 13 into the aforementioned first position. Accordingly, the valve 13 is controlled to provide a constant pressure drop between this latter.

Post- pressure compensator module 12 further comprises an orifice fluidly connected to the line for picking the signal S₃ and configured to pick a load sensing signal S₄ configured to be fluidically sent to a load sensing pump of the work vehicle configured to generate the fluid of hydraulic power source 5.

A load sensing signal S₃ is picked up on feeding conduit 9 downstream to the pressure compensator 12 and coming thorough the load sense shuttle valve 15. The shuttle valve 15 allows load sense signals comparison between all load sense signals from other hydraulic functions in order to resolve the higher load sense signal to the load sense pump on the vehicle.

Advantageously, valve 16 and post- pressure compensator module 12 may be realized in a same physical cartridge.

More in particular, such control signal S₅ is an electric signal and therefore valve 16 is an electric actuated proportional valve, i.e. the oil flow is greater the more the signal S₅ is greater.

In such a case, arrangement 1 further comprises a electronic control unit 17 configured to receive a first input signal I₁ representative of a current speed of the ventilation means 3, a second input signal I₂ representative of a quantity of the heat exchanger to be ventilated by the ventilation means 2, the electronic control unit 17 is configured to elaborated such two input signals I₁, I₂ to provide the control signal S5 to control hydraulic motor 2.

Merely for sake of example, I₂ can represent a temperature of the liquid to be cooled in the heat exchanger, therefore the control unit 17 will implement known thermodynamic laws to control the ventilation means speed in function of the value of I₂.

For sake of example The control unit 17 is configured to regulate the signal S₅ to the flow control valve 16 in order to get a closed loop control of signals I₁ and I₂ or only of I₂.

The operation of the hydraulic arrangement 1 as described above is the following.

Thanks to signal S₅, valve 16 is controlled to increase or decrease the oil flow into hydraulic motor 2. The generation of signal S₅ may be realized in different manner, as described above thanks to a control loop control based on the velocity of ventilation means 3 or can be selected between a plurality of ventilation modes, e.g. "low" or "high" speed, by pushing a specific button/symbol on a display. In such a case, only signal 12 would be sufficient to control ventilation means speed 3.

The flow of oil admitted by valve 16 will then pass to valve 4, which can be controlled to define the rotation direction of ventilation means 4, and then to hydraulic motor 2 which carried the ventilation means 3.

During the passage into compensation module 12, the load signal S₄ is generated and sent to a load sensing pump shared with other hydraulic devices of the work vehicle. Therefore, the oil flow provided by hydraulic power source 5 is regulated in function of the value of load sensing signal S₅.

In view of the foregoing, the advantages of a hydraulic arrangement 1 for managing the oil flow provided to a hydraulic motor 2 for controlling the speed of ventilation means 3 according to the invention are apparent.

Thanks to the use of a post- pressure compensator module 12 ventilation means can be controlled without a dedicated pump but with picking oil form a common pressure source of the work vehicle, thanks to the load sensing signal generated by such post- pressure compensator module 12.

According to the above, the hydraulic arrangement 1 can share its operation with multiple operative hydraulic devices of the work vehicle.

The use of a control valve 16 controlled to regulate the speed of ventilation means 3 allows a wide range, quick and simple regulation of such speed. Furthermore, the control valve can be physically integrated into the post- pressure compensator module 12.

Furthermore, the fact that control valve 16 is electrically controlled by an electronic control unit 17 allows a quick and continuous control of the ventilation means 3 in function of the operative conditions of the heat exchanger/ vehicle's conditions.

It is clear that modifications can be made to the described hydraulic arrangement 1 which do not extend beyond the scope of protection defined by the claims.

For example, it is clear that the proposed valves 4, 12 and 16 and the proposed line topology is merely an example between all the possible covered by the appended claims.

Similarly, it's clear that signal S₅ can be a hydraulic signal and that the control of ventilation means 2 can be achieved in different equivalent ways according to the limit defined by the below claims.