Patent Description:
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 as shown in <CIT>. 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 socalled 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.

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.

<FIG> and <FIG> discloses a hydraulic brake arrangement <NUM> 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 <NUM>, of a trailer.

Hydraulic brake arrangement <NUM> a tractor brake module <NUM> configured to control tractor's brakes 2a, 2b and a trailer brake valve module <NUM> fluidly interposed between tractor's brakes 2a, 2b and trailer's brakes <NUM>.

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

In greater particular, each master brake cylinder <NUM> 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 <NUM> to a respective brake 2a, 2b. Indeed a motion of the piston 6b inside the housing 6a tends to push away through conduit <NUM> the fluid in pressure thereby activating the respective brake 2a, 2b.

The piston 6a is actuated by a pedal <NUM> so that the user, by pushing the pedal <NUM> 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 <NUM> 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 <NUM> is fluidly connected to trailer brake valve module <NUM> via a conduit <NUM> fluidly connecting with output conduits <NUM> of each master cylinder <NUM>. In particular such connection is achieved by a shuttle valve <NUM> fluidly interposed between the pair of output conduits <NUM> and the conduit <NUM>. Such shuttle valve <NUM> allows the passage of the greater fluid coming from respective conduit <NUM> linked to the left or the right rear brake 2a, 2b.

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

Advantageously, selection valve <NUM> 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 <NUM> and trailer brake valve module <NUM> and a second position into which it denies such fluid communication.

Normally, such selection valve <NUM> 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 <NUM> and trailer brakes <NUM>.

Trailer brake valve module <NUM> essentially comprises a dual hydraulic pilot trailer brake valve <NUM> and a control valve <NUM> configured to provide one of the two hydraulic pilot signals to the trailer brake valve <NUM>.

As said the control valve <NUM> is configured to provide a first pilot signal L1 to control the trailer brake valve <NUM> by modulating the fluid in pressure coming from a source <NUM> of fluid in pressure of the work vehicle, such as a pump or an accumulator.

Preferably, the control vale <NUM> is in an electro-valve, preferably a proportional electro-valve configured to modulate the fluid coming from source <NUM> to generate a signal L1 having the a pressure varying between a maximum value equal to the pressure of such fluid coming from source <NUM> and a minimum value by fluidly connecting signal L1 to tank <NUM>.

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

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

In particular, trailer brake valve <NUM> can assume at least three positions wherein:.

On an opposite side of the spool of trailer brake valve <NUM> with respect to the one where act pilot signals L1, L2, a hydraulic signal L3 picked up by conduit <NUM> acts to balance the force imparted by signals L1, L2. Such signal L3 is picked-up thanks to a conduit <NUM> fluidly connecting the spool of trailer brake valve <NUM> to conduit <NUM> and provided with a narrowing <NUM>.

Optionally, the hydraulic brake arrangement <NUM> may comprise further define a load sensing signal LS picked up from conduit <NUM> downstream to narrowing <NUM>.

As said, trailer brake vale <NUM> is fluidly connected to trailer brakes <NUM> via a trailer brake conduit <NUM>. Advantageously, hydraulic brake arrangement <NUM> comprises a coupling module <NUM> for allowing the hydraulic coupling of trailer brake conduit <NUM> 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 <NUM> may comprise a control line brakes 3a and supplementary line brakes 3b for allowing the control of trailer brakes <NUM> in case of emergency.

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

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

Advantageously, selection valve <NUM> 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 <NUM> and supplementary line brakes 3b and a second position into which it allows the fluid communication of supplementary line brakes 3b and tank <NUM>.

In particular, selection valve <NUM> is energized to maintain supplementary line brakes 3b connected to tank <NUM>. If any electrical power problem is present in the work vehicle, than the selection valve <NUM> de-energize and allows the fluid communication of source <NUM> with supplementary line brakes 3b, allowing the braking of the trailer.

According to the embodiment of <FIG>, coupling module <NUM> is further provided with a valve arrangement comprising a pair of detection valves <NUM>, <NUM> fluidly interposed between trailer brake conduit <NUM> and safe line <NUM> to provide a hydraulic load signal LC.

In particular, such detection valves <NUM>, <NUM> are both mechanically actuated valve that are, each, actuated by the coupling of respectively the control line coupler <NUM> or supplementary line coupler <NUM>.

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

The second detection valve <NUM> is fluidly interposed between conduit <NUM> coming from first detection valve <NUM> and is a three ways - two positions valve wherein comprising a first port connectable to conduit <NUM>, a second port connectable to an output conduit <NUM> and a third port connectable to safe line <NUM>.

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

Hydraulic brake arrangement <NUM> further comprises a plurality of pressure sensor means <NUM> configured to detect the pressure in some crucial points of the hydraulic brake arrangement. In particular, such pressure means <NUM> are pressure transducers configured to detect the pressure at least in conduit <NUM>, in trailer brake conduit <NUM> and, according to the embodiment of <FIG>, of output conduit <NUM>.

Furthermore, hydraulic brake arrangement <NUM> further comprises a plurality of switches <NUM> configured to detect the activation of pedals <NUM> or of a parking brake <NUM> of the work vehicle and, according to the embodiment of <FIG>, of the coupling of couplers <NUM>, <NUM>.

Moreover, hydraulic brake arrangement <NUM> further comprises force sensors <NUM> configured to detect the angular range of movement of the parking brake <NUM>.

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

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

Then, according to the embodiment of <FIG>, the activation of the couplers <NUM>, <NUM> is detected by a related switch <NUM> configured to assume value ON if both couplers <NUM>, <NUM> are detected and value OFF if only coupler <NUM> is detected.

Accordingly, control unit may select a related control map for controlling valves <NUM> and <NUM>:.

Instead, according to the embodiment of <FIG>, the activation of the couplers <NUM>, <NUM> is detected by the pressure sensor <NUM> configured to detect the pressure LC in output conduit <NUM>.

In the following, some use cases will be described according to the embodiment of <FIG>.

In a first use case, a single line trailer is connected via coupler <NUM>. Accordingly, valve <NUM> 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 <NUM> that provides a pilot signal L1. Since L1 and L2 signals acts in parallel and normally signal L2 is smaller than signal L1, signal L2 can be used as safety fallback position in case of electronic faults.

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

Furthermore, valve <NUM> 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 <NUM> 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 <NUM> at brake 3a and unbraked when a fixed pressure of around <NUM> bar is provided to same brake. So, in case of CUNA tractor, the unbraking pressure level can be provided by piloting valve <NUM>, and, at same time, when valve <NUM> is open to tank, the pressure at 3a is <NUM> 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 <NUM> can be energized, avoiding the fluid communication between tractor brakes 2a, 2b and trailer brakes <NUM>.

In a third use case, a mother regulation trailer is connected via couplers <NUM>, <NUM>. Accordingly, valve <NUM> 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 <NUM> that provides a pilot signal L1, 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 <NUM> by detecting the pressure on conduits <NUM> and <NUM> and having also a feedback on park brake activation via sensor means <NUM> coupled to couplers <NUM>, <NUM>. Indeed, by comparing pressure on conduits <NUM> and <NUM> 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 <NUM> to discharge supply line and suddenly brake the trailer.

In view of the foregoing, the advantages of a hydraulic brake arrangement <NUM> 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 <FIG> that defines a "basic configuration" but is furthermore effective with the improved embodiment of <FIG>.

The proposed hydraulic brake arrangement <NUM> 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 <NUM>/h. Thanks to hydraulic brake arrangement <NUM> of the present invention, the switch between the two different control logic can be controlled simply via valves <NUM> and <NUM>.

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 <NUM> to avoid that the signal from brake reach the trailer brake valve and at the same time it does not operate valve <NUM> therefore avoiding the braking of the trailer.

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

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

For example, the proposed valves <NUM>, <NUM> or <NUM> may be varied maintaining their claimed function by equivalent devices.

Claim 1:
Hydraulic brake arrangement (<NUM>) for a tractor or a tractor-trailer combination, said hydraulic brake arrangement (<NUM>) comprising:
- a tractor brake module (<NUM>) provided with at least a master brake cylinder (<NUM>) configured to provide pressurized fluid to brakes (2a, 2b) of a tractor,
- a trailer brake valve module (<NUM>) comprising a hydraulically actuated trailer brake valve (<NUM>) and a proportional valve (<NUM>),
- a coupling module (<NUM>) configured to allow the fluidic communication between said trailer brake valve module (<NUM>) and trailer's brakes (<NUM>), said coupling module (<NUM>) comprising a pair of couplers (<NUM>, <NUM>),
wherein said trailer brake valve (<NUM>) is controlled by a pair of hydraulic pilot signals (L1, L2) acting on one side of its spool, a first pilot signal (L1) being generated by said proportional valve (<NUM>) by modulating a flow of fluid coming from a source (<NUM>) of fluid in pressure and a second pilot signal (L2) being picked up via a conduit (<NUM>) by said pressurized fluid directed generated by said master brake cylinder (<NUM>) to control said brakes (2a, 2b) of said tractor,
said trailer brake valve (<NUM>) being configured to modulate the fluid coming from said source (<NUM>) to said trailer brakes (<NUM>) via a trailer brake conduit (<NUM>) between zero to a maximum value, characterised in that
said proportional valve (<NUM>) is electro-actuated,
said hydraulic brake arrangement (<NUM>) further comprises an electro actuated selection valve (<NUM>) configured to allow or deny the fluid passage through said conduit (<NUM>) towards said trailer brake valve (<NUM>),
said hydraulic brake arrangement (<NUM>) further comprises pressure sensor means (<NUM>) configured to detect the pressure in said conduit (<NUM>) and said trailer brake conduit (<NUM>), switches (<NUM>) configured to detect the activation of said at least one master cylinder (<NUM>) and sensors (<NUM>, <NUM>) configured to detect the coupling status of said couplers (<NUM>, <NUM>),
said hydraulic brake arrangement (<NUM>) comprises an electronic unit electrically connected to said pressure sensor means (<NUM>) and to said switches (<NUM>) to retrieve their detected values and comprises elaboration means to elaborate such detected values to control said selection valve (<NUM>) and said proportional valve (<NUM>).