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TECHNICAL FIELD

The present invention concerns a hydraulic brake arrangement, in particular a hydraulic brake arrangement for an off-road vehicle, such as an agricultural vehicle.

BACKGROUND OF THE INVENTION

Off-road vehicles such as agricultural vehicles usually comprises a trailer and use a hydraulic brake arrangement for braking the both the tractor and the trailer. However, existing hydraulic brake arrangements for tractor-trailer combinations that usually present in off-road vehicles suffer of a plurality of drawbacks.

In particular it is noticed that a tractor may be coupled to different typologies of trailers that can be provided with different typologies of trailer brake arrangement, such as ones known as "single line", others compliant with the so- called Mother Regulation or further compliant with CUNA regulation .

Accordingly, the need is continuously felt to provide a hydraulic brake arrangement for a tractor-trailer combination that allows a tractor to comply with different typologies of trailer.

According to the above, the need is felt to improve existing hydraulic brake arrangement to address the aforementioned drawbacks.

An aim of the present invention is to satisfy the above mentioned needs, in a cost-effective way.

SUMMARY OF THE INVENTION The aforementioned aim is reached by a hydraulic brake arrangement as claimed in the appended set of claims.

Preferred embodiments of the invention are realized according to the claims dependent or related to the above independent claims.

BRIEF DESCRIPTION OF DRAWINGS

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 drawings wherein:

• Figure 1 is a hydraulic schematic showing a first embodiment of a hydraulic braked arrangement according to the present invention; and

• Figure 2 is a hydraulic schematic showing a second embodiment of a hydraulic braked arrangement according to the present invention

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 2 discloses a hydraulic brake arrangement 1 for a work vehicle, in particular a work vehicle such as a tractor that can be possibly be connected to a trailer, such hydraulic braking arrangement is configured to provide pressurized fluid to rear brakes 2a, 2b of a tractor and to brakes 3, of a trailer.

Hydraulic brake arrangement 1 a tractor brake module 4 configured to control tractor's brakes 2a, 2b and a trailer brake valve module 5 fluidly interposed between tractor's brakes 2a, 2b and trailer's brakes 3.

In particular, the tractor brake module 4 comprises at least a master brake cylinder 6, in particular a master brake cylinder 6 for each of the rear brake 2a, 2b.

In greater particular, each master brake cylinder 6 comprises a housing 6a and a piston 6b configured to slide inside the housing 6a that is further configured to house fluid in pressure. The housing 6a is fluidly connected via a output conduit 7 to a respective brake 2a, 2b. Indeed a motion of the piston 6b inside the housing 6a tends to push away through conduit 8 the fluid in pressure thereby activating the respective brake 2a, 2b.

The piston 6a is actuated by a pedal 8 so that the user, by pushing the pedal 8 can move the piston 6b into the housing 6a. The presence of elastic means 6c allows the countermotion of the piston 6b in its rest position within the housing 6b.

Tractor brake module 4 comprises other valve elements that are per se known and will not be further described in detail, being not essentially linked to the present invention.

Tractor brake module 4 is fluidly connected to trailer brake valve module 5 via a conduit 9 fluidly connecting with output conduits 7 of each master cylinder 6. In particular such connection is achieved by a shuttle valve 11 fluidly interposed between the pair of output conduits 7 and the conduit 9. Such shuttle valve 11 allows the passage of the greater fluid coming from respective conduit 7 linked to the left or the right rear brake 2a, 2b.

Hydraulic brake arrangement 1 comprises a selection valve 12 fluidly interposed on conduit 9 between the tractor brake module 4 and trailer brake valve module 5, such selection valve 12 being configured to allow or deny the fluid passage on conduit 9 towards trailer brake valve module 5 according to a preset signal.

Advantageously, selection valve 12 in an electro-valve, preferably an ON-OFF electro-valve configured to assume a first position into which it allows the fluid communication between the tractor brake module 4 and trailer brake valve module 5 and a second position into which it denies such fluid communication .

Normally, such selection valve 12 is in its first position when de-energized, i.e. it is needed to provide an electrical signal to avoid fluidic communication between tractor brakes 2 and trailer brakes 3.

Trailer brake valve module 5 essentially comprises a dual hydraulic pilot trailer brake valve 13 and a control valve 14 configured to provide one of the two hydraulic pilot signals to the trailer brake valve 13.

As said the control valve 14 is configured to provide a first pilot signal LI to control the trailer brake valve 13 by modulating the fluid in pressure coming from a source 15 of fluid in pressure of the work vehicle, such as a pump or an accumulator.

Preferably, the control vale 14 is in an electro-valve, preferably a proportional electro-valve configured to modulate the fluid coming from source 15 to generate a signal LI having the a pressure varying between a maximum value equal to the pressure of such fluid coming from source 15 and a minimum value by fluidly connecting signal LI to tank 16.

A second signal L2 is imparted to trailer brake valve 13 by the fluid coming from conduit 9 that is, as described above, modulated by selection valve 12.

The trailer brake valve 13 is a preferably a four ways proportional valve configured to regulate the fluid passage between source 15, tank 16, an excess flow line 17 and a trailer brake conduit 18 fluidly directed to trailer brakes 3. Such proportional valve is configured to modulate the fluid coming from source 15 to flow towards trailer brake conduit 18 with a pressure varying between a maximum value equal to the pressure of such fluid coming from source 15 and a minimum value by fluidly connecting trailer brake conduit 18 to tank 16.

In particular, trailer brake valve 13 can assume at least three positions wherein:

• In a first position fluidly connects the source 15 of fluid in pressure to trailer brake conduit 18 and at the same time fluidly connects excess flow line 17 to tank 16;

• In a second position fluidly connects the source 15 of fluid in pressure to both the trailer brake conduit 18 and at the excess flow line 17; and

• In a third position fluidly connects the source 15 of fluid in pressure to excess flow line 17 and trailer brake conduit 18 to tank 16.

On an opposite side of the spool of trailer brake valve 13 with respect to the one where act pilot signals LI, L2, a hydraulic signal L3 picked up by conduit 18 acts to balance the force imparted by signals LI, L2. Such signal L3 is picked- up thanks to a conduit 19 fluidly connecting the spool of trailer brake valve 13 to conduit 18 and provided with a narrowing 21.

Optionally, the hydraulic brake arrangement 1 may comprise further define a load sensing signal LS picked up from conduit 19 downstream to narrowing 21.

As said, trailer brake vale 12 is fluidly connected to trailer brakes 3 via a trailer brake conduit 18. Advantageously, hydraulic brake arrangement 1 comprises a coupling module 22 for allowing the hydraulic coupling of trailer brake conduit 18 with trailer brake arrangement s provided with different typology of brakes, e.g.

Indeed, it is known that according to mother regulation the trailer brakes 3 may comprise a control line brakes 3a and supplementary line brakes 3b for allowing the control of trailer brakes 3 in case of emergency.

Coupling module 22 may comprise a control line coupler 23 and a supplementary line coupler 24. The control line coupler 23 is configured to fluid connect trailer brake conduit 18 with the control line brakes 3a while the supplementary line coupler 24 is configured to allow the connection of supplementary line brakes 3b, if any, to a safe line 25.

Safe line 25 is fluidly connected to a source of fluid 27 and comprises a safety valve 26 fluidly interposed on the safe line 25 between such source 27 and the coupling module 22. The safety valve 26 is configured to allow or deny the fluid passage on safe line 25 towards supplementary control line brakes 3b according to a preset signal.

Advantageously, selection valve 27 in an electro-valve, preferably a two ways - two positions electro-valve configured to assume a first position into which it allows the fluid communication between the source 27 and supplementary line brakes 3b and a second position into which it allows the fluid communication of supplementary line brakes 3b and tank 16.

In particular, selection valve 27 is energized to maintain supplementary line brakes 3b connected to tank 16. If any electrical power problem is present in the work vehicle, than the selection valve 27 de-energize and allows the fluid communication of source 27 with supplementary line brakes 3b, allowing the braking of the trailer. According to the embodiment of figure 2, coupling module

22 is further provided with a valve arrangement comprising a pair of detection valves 28, 29 fluidly interposed between trailer brake conduit 18 and safe line 25 to provide a hydraulic load signal LC. In particular, such detection valves 28, 29 are both mechanically actuated valve that are, each, actuated by the coupling of respectively the control line coupler 23 or supplementary line coupler 24.

In greater detail, a first detection valve 28 is fluidly interposed between trailer brake conduit 18 and is an ON-OFF valve configured to allow or deny the fluid communication between the trailer brake conduit 18 and the second detection valve 29 via a conduit 31. In particular, such fluid communication is allowed only when control line coupler 23 couples a control line trailer brake 3a with trailer brake conduit 18.

The second detection valve 29 is fluidly interposed between conduit 31 coming from first detection valve 28 and is a three ways - two positions valve wherein comprising a first port connectable to conduit 31, a second port connectable to an output conduit 32 and a third port connectable to safe line 25.

In a first position, wherein no supplementary line brakes 3b are coupled to supplementary line coupler 24, second selection valve allows the fluidic communication between first port and second port while third port is closed, while, if supplementary line brakes 3b are coupled to supplementary line coupler 24, second selection valve allows the fluidic communication between third port and second port while first port is closed.

Hydraulic brake arrangement 1 further comprises a plurality of pressure sensor means 33 configured to detect the pressure in some crucial points of the hydraulic brake arrangement. In particular, such pressure means 33 are pressure transducers configured to detect the pressure at least in conduit 9, in trailer brake conduit 18 and, according to the embodiment of figure 2, of output conduit 32.

Furthermore, hydraulic brake arrangement 1 further comprises a plurality of switches 34 configured to detect the activation of pedals 8 or of a parking brake 35 of the work vehicle and, according to the embodiment of figure 1, of the coupling of couplers 23, 24.

Moreover, hydraulic brake arrangement 1 further comprises force sensors 36 configured to detect the angular range of movement of the parking brake 35.

All the above detected values are sent to an electronic control unit (not shown) electrically connected to each sensor means 33, 36 or switch 34. Such electronic control unit comprises elaboration means to elaborate such detected values to actuate consequently selection valve 12 and control valve 14 via output electronic control signals.

The operation of the above-described hydraulic arrangement 1 is the following. The user of the vehicle will impart a force on at least one of pedals 8, thereby pushing the related piston 6b into the housing 6a of the master brake cylinder 6 generating a pressure in conduit 7 directed towards the related tractor brake 2a, 2b. Such pressure signal is furthermore sent via conduit 9, passing through shuttle valve 11, and selection valve 12 to trailer brake valve module 5. Here, it generates pilot signal L2 for actuating trailer brake valve 13 that regulates the amount of fluid coming from source 15 that needs to be directed to trailer brake conduit 18 and then to trailer control brakes 3a. During the above operation, pressure is detected in the related conduits thanks to pressure means 33 and activation of pedals 8 or of couplers 23, 24 by switches 34. Similarly, a possible activation of parking brake 35 is detected by the related switch 34 and force sensor 36.

Then, according to the embodiment of figure 1, the activation of the couplers 23, 24 is detected by a related switch 34 configured to assume value ON if both couplers 23, 24 are detected and value OFF if only coupler 23 is detected.

Accordingly, control unit may select a related control map for controlling valves 12 and 14:

• If value of switch 34 of couplers 23, 24 is ON, then a mother regulation trailer is coupled to the tractor and the control unit select a control curve for trailer brakes 3 conform to mother regulation pressure values;

• If value of switch 34 of couplers 23, 24 is OFF, then a single line trailer is coupled to the tractor and the control unit select a control curve for trailer brakes 3 conform to such single line trailer and/or conform to CUNA regulation or any other country regulation.

Instead, according to the embodiment of figure 2, the activation of the couplers 23, 24 is detected by the pressure sensor 33 configured to detect the pressure LC in output conduit 32.

Accordingly, control unit may select a related control map for controlling valves 12 and 14:

• If value of LC is equal to a first memorized pressure value, then the control line coupler 23 is solely coupled;

• If value of LC is equal to a first memorized pressure value, then both couplers 23, 24 are coupled and a mother regulation trailer is coupled to the tractor.

In the following, some use cases will be described according to the embodiment of figure 2.

In a first use case, a single line trailer is connected via coupler 23. Accordingly, valve 12 is in its first position (i.e. de-energized) and depending on the country a CUNA or universal trailer brake curve is selected by software and applied via valve 14 that provides a pilot signal LI. Since LI and L2 signals acts in parallel and normally signal L2 is smaller than signal LI, signal L2 can be used as safety fallback position in case of electronic faults.

Moreover, by detecting the pressure signal in output conduit 32 it is possible to understand the activation of parking brake 35.

Furthermore, valve 14 can be modulated independently to the pressing condition of pedals in order to avoid possible jack-knife phenomenon in certain conditions wherein the pressure at pedal is insufficient (e.g. in a descendent slope).

Another possible control via valve 14 is to provide a hill holder effect on the trailer. In this use case, for instance, if a CUNA tractor is connected, the trailer is braked when pressure is 0 at brake 3a and unbraked when a fixed pressure of around 15 bar is provided to same brake. So, in case of CUNA tractor, the unbraking pressure level can be provided by piloting valve 14, and, at same time, when valve 14 is open to tank, the pressure at 3a is 0 and the trailer is braked. This condition is equivalent to apply parking brake to trailer and it is selected (via electronic control) when vehicle park brake is actuated. In this case, the sensor on line to brake 3a allow to read the status of trailer and confirm that park brake is applied (according to CUNA requirements) . Basically, it is possible to detect trailer park brake.

In a second use case, no trailer is connected to the tractor. Accordingly, to avoid waste of hydraulic energy, valve 12 can be energized, avoiding the fluid communication between tractor brakes 2a, 2b and trailer brakes 3.

In a third use case, a mother regulation trailer is connected via couplers 23, 24. Accordingly, valve 12 is in its first position (i.e. de-energized) and depending a mother regulation trailer brake curve is selected by software and applied via valve 14 that provides a pilot signal LI, as described above to control pressure to trailer brake.

Furthermore, in such case it is possible to obtain a simple fail-safe function thanks to safety valve 26 by detecting the pressure on conduits 9 and 18 and having also a feedback on park brake activation via sensor means 33 coupled to couplers 23, 24. Indeed, by comparing pressure on conduits 9 and 18 it is compared the input from vehicle brake and the output to trailer. If anything is is in fault (hose burst, valve stuck, etc) the output would not be subsequent with the input, and in particular in the worst case of a very important fault, the output would be significantly lower than its expected value. In this case electronic control can operate valve 26 to discharge supply line and suddenly brake the trailer. In view of the foregoing, the advantages of a hydraulic brake arrangement 1 according to the invention are apparent.

Thanks to the proposed hydraulic brake arrangement it is possible to easily control the brakes of a tractor or tractor- trailer combination of different typologies simply by implementing a single software covering a lot of possible typology of trailer combination with the tractor. This is true for the embodiment of figure 1 that defines a "basic configuration" but is furthermore effective with the improved embodiment of figure 2.

The proposed hydraulic brake arrangement 1 is much simpler and comprises a limited number of components, thereby reducing manufacturing costs and its encumbrance on the tractor.

Furthermore, as known, mother regulation requires two different control logic according to a preset vehicle velocity, namely 12 km/h. Thanks to hydraulic brake arrangement 1 of the present invention, the switch between the two different control logic can be controlled simply via valves 12 and 14.

In particular, if the vehicle is under the preset velocity and the brake pedal is pressed, the electronic control unit retrieve this data and closes valve 12 to avoid that the signal from brake reach the trailer brake valve and at the same time it does not operate valve 14 therefore avoiding the braking of the trailer.

The two proposed embodiments allows, by simply changing the coupling module 22, to allow the connection of very different typology of trailers on the same tractor provided with a hydraulic brake arrangement 1 according to the invention.

It is clear that modifications can be made to the described hydraulic brake arrangement 1 which do not extend beyond the scope of protection defined by the claims. For example, the proposed valves 12, 14 or 13 may be varied maintaining their claimed function by equivalent devices.

Moreover, tractor brake module 4 may comprise a single master brake cylinder 6 or a different typology of brake cylinder and related activation.