Patent Description:
Agricultural vehicles are known comprising a main body and plurality of wheels adapted to rotate about respective rotational axes so as move the main body with respect to the ground. The agricultural vehicles further comprise a braking system adapted to slow down, stop or prevent the rotation of the wheels about their respective rotational axes.

As is well known, various braking technologies have been developed over time and, in particular, the agricultural vehicles usually employ one or more disc brakes.

In general terms, a disc brake comprises a brake disc, which is integral with one or more wheels, and brake pads, which are adapted to be pressed against the brake disc in order to generate friction and, consequently, a braking action. However, the energy dissipated by friction transforms into waste heat, which must be adequately dispersed. In fact, if the waste heat is not sufficiently dispersed, the brake disc could overheat and lose its friction properties. In addition, the service life of the disc brake could be severely affected.

In detail, when the brake disc is subjected to critical temperatures, the coefficient of friction of the disc decreases and thermal deformation may occur. Moreover, the friction material of the brake disc starts to degrade and some of its particles are teared away.

Further to the above, the thermal load conditions of the disc brakes are worsened during harsh breaking maneuvers, because the brake disc is affected by thermal cycles that are closely spaced in time.

In the light of the foregoing, disc brakes are generally cooled by means of oil lubrication as shown in <CIT>, <CIT>, <CIT>, <CIT>. In detail, the brake disc is partially immersed in a sump, which contains a lubricant oil and is arranged below the brake disc. The brake disc is therefore cooled as a consequence of its rotational movement. More specifically, such rotational movement and the corresponding centrifugal forces cause oil to be splashed over the disc.

However, this cooling arrangement causes an asymmetrical cooling of the disc. In fact, the portion of the disc immersed in oil during rotation is subjected to significantly different thermal conditions than the non-immersed portion of the disc. As a result, the cooling of the disc and, in particular, of the surface comprising the friction material is not optimized.

In addition, the higher the level of oil contained in the sump, the greater the cooling of the brake disc. On the other hand, the greater the amount of oil, the greater the power losses during the rotation of the brake disc.

Other examples of lubrication systems are disclosed in <CIT>, <CIT> and <CIT>.

Therefore, the need is felt to obtain a braking assembly capable of efficiently dispersing waste heat.

An aim of the present invention is to satisfy the above mentioned needs in a cost effective and optimized manner.

The aforementioned aim is reached by a braking assembly and by a work vehicle, as claimed in the appended independent claims.

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

With reference to <FIG>, numeral <NUM> indicates a work vehicle, in particular an agricultural vehicle such as a tractor. Vehicle <NUM> comprises a main body <NUM> and a plurality of wheels <NUM>, which are rotatable about respective rotational axes A so as to move main body <NUM> with respect to the ground. Vehicle <NUM> further comprises at least one braking assembly <NUM>, which is adapted to slow down, stop or prevent the rotation of one or more respective wheels <NUM> about their respective rotational axes A.

In the embodiment shown, vehicle <NUM> comprises two front wheels (not shown) and two rear wheels <NUM>, <NUM> according to an advancement direction X of vehicle <NUM>. In detail, <FIG> shows the two rear wheels <NUM>, <NUM> of vehicle <NUM>, which are mounted on a same axle <NUM> of vehicle <NUM>, are rotatable about coincident rotational axes A and are spaced from each other along a direction Y transversal to advancement direction X. In further detail, vehicle <NUM> comprises two braking assemblies <NUM>, which are adapted to brake rear wheel <NUM> and rear wheel <NUM>, respectively.

For the sake of simplicity, in the following of the present description reference will be made to a single braking assembly <NUM> adapted to brake rear wheel <NUM>, the description of a braking assembly <NUM> adapted to brake rear wheel <NUM> being identical.

As illustrated in <FIG>, braking assembly <NUM> comprises a brake disc <NUM>, which is rotatable integrally with rear wheel <NUM> about rotational axis A and defines a first side 6a and a second side 6b, which are axially opposite to each other. In other words, first side 6a and second side 6b are opposite to each other with respect to a median plane of brake disc <NUM>. More specifically, brake disc <NUM> is mounted on axle <NUM> coaxially to rotational axis A and rear wheel <NUM> is on first side 6a with respect to brake disc <NUM>.

Braking assembly <NUM> further comprises two counter discs <NUM>, <NUM>, which are arranged in close proximity to brake disc <NUM> on first side 6a and second side 6b, respectively, and are rotationally fixed. Preferably, counter discs <NUM> and <NUM> are identical to each other.

Braking assembly <NUM> comprises not-shown actuation means, which are adapted to press counter disc <NUM> and/or counter disc <NUM> against brake disc <NUM>, in order to obtain a braking action of rear wheel <NUM>.

The actuation means may be actuated by a driver of vehicle <NUM>. In detail, the actuation means are actuated by a brake command oil pressure, which is generated with a master cylinder pump inside the tractor cabin.

Furthermore, braking assembly <NUM> comprises a fluid inlet <NUM> for the inlet of a fluid. In detail, this fluid is a coolant fluid or a cooling lubricant fluid.

Counter disc <NUM> and brake disc <NUM> define first interstices <NUM> with each other; counter disc <NUM> and brake disc <NUM> define second interstices <NUM> with each other. In addition, counter disc <NUM> is formed with one or more holes <NUM>, which are adapted to put in fluidic communication fluid inlet <NUM> with first interstices <NUM>. Similarly, counter disc <NUM> is formed with one or more holes <NUM>, which are adapted to put in fluidic communication fluid inlet <NUM> with second interstices <NUM>.

As illustrated in <FIG>, counter discs <NUM> and <NUM> are arranged coaxially to each other and to rotational axis A. In addition, preferably but not necessarily, each hole <NUM> of counter disc <NUM> is arranged coaxially to a respective hole <NUM> of counter disc <NUM>.

As illustrated in <FIG>, each counter disc <NUM>, <NUM> is shaped like an annulus radially extending between an inner radius and an outer radius with respect to rotational axis A. In addition, counter discs <NUM>, <NUM> comprise respective first faces 7a, 8a, which are substantially flat and are adapted to face brake disc <NUM> and respective second faces 7b, 8b opposite to the first faces 7a, 8a with respect to respective median planes of counter discs <NUM> and <NUM>. In detail, first interstices <NUM> are defined by a surface of brake disc on first side 6a and first face 7a; second interstices <NUM> are defined by a surface of brake disc <NUM> on second side 6b and first face 8a.

Each second face 7b, 8b comprises a surface <NUM>, which is flat or substantially flat and a plurality of regions <NUM> protruding from surface <NUM> parallel to rotational axis A (<FIG>).

Regions <NUM> are shaped like quadrilaterals and extend for at least part of the radial extension of surface <NUM>. In detail, each region <NUM> extends radially between a radius that is greater than the inner radius and the outer radius of the respective counter disc <NUM>, <NUM>. In further detail, each region <NUM> is shaped like an annulus sector.

Regions <NUM> of each counter disc <NUM>, <NUM> are angularly spaced from one another. In addition, preferably, regions <NUM> are angularly equidistant from one another and are identical.

More specifically, since regions <NUM> of each counter disc <NUM>, <NUM> are angularly spaced from one another by respective portions of surface <NUM>, surface <NUM> defines a plurality of grooves <NUM> with respect to regions <NUM>.

Preferably, surface <NUM> and regions <NUM> are formed in one piece.

As illustrated in <FIG>, grooves <NUM> extend in a radial pattern about rotational axis A. In addition, two angularly consecutive grooves <NUM> of each counter disc <NUM>, <NUM> are interposed by a respective region <NUM>.

In the preferred embodiment shown, each counter disc <NUM>, <NUM> comprises twelve regions <NUM>, which are angularly spaced from one another by as many grooves <NUM>. Moreover, since regions <NUM> are shaped like annulus sectors, the circumferential extension of each groove <NUM> decreases from the inner radius toward the outer radius of the relative counter disc <NUM>, <NUM>.

Furthermore, holes <NUM> and <NUM> are through holes and have respective axes that are parallel to one another and to rotational axes A.

Holes <NUM> are radially interposed between the inner radius and regions <NUM> of counter disc <NUM>. Similarly, holes <NUM> are radially interposed between the inner radius and regions <NUM> of counter disc <NUM>. In addition, preferably, counter discs <NUM> and <NUM> comprise as many respective holes <NUM>, <NUM> as the number of respective regions <NUM>. More specifically, each hole <NUM>, <NUM> is arranged circumferentially at the midpoint of a respective region <NUM>.

Furthermore, each counter disc <NUM>, <NUM> comprises a plurality of anti-rotational pin holes <NUM>, which are engaged by respective anti-rotational pins <NUM> (<FIG> and <FIG>). In detail, anti-rotational pin holes <NUM> and anti-rotational pins <NUM> prevent counter discs <NUM>, <NUM> from rotating as a consequence of the rotation of brake disc <NUM> about rotational axis A.

In the embodiment shown, each counter disc <NUM>, <NUM> comprises three anti-rotational pin holes <NUM>, which are equally angularly spaced from one another. In addition, anti-rotational pin holes <NUM> are blind holes and have respective axes that are parallel to rotational axis A.

The radial extension of counter discs <NUM> and <NUM> with respect to rotational axis A is substantially equal to the radial extension of brake disc <NUM>. Preferably, the radial extension of counter discs <NUM> and <NUM> is slightly greater than the radial extension of brake disc <NUM>.

As shown in <FIG>, brake disc <NUM> is shaped like a circular disc and comprises a central portion <NUM> and a radially external portion <NUM> surrounding central portion <NUM>.

The external surface of radially external portion <NUM> comprises a friction material and is shaped like an annulus. Central portion <NUM> comprises, in turn, a hole <NUM>, which allows brake disc <NUM> to be mounted to axle <NUM> and a plurality of lightening holes <NUM>. In detail, hole <NUM> is formed at the center of central portion <NUM> and lightening holes <NUM> are angularly equidistant from one another about hole <NUM>.

Furthermore, the axial extension of radially external portion <NUM> is greater than the axial extension of central portion <NUM>. On the contrary, the extension of radially external portion <NUM> radially with respect to rotational axis A is preferably lower than the radial extension of central portion <NUM>.

Furthermore, braking assembly <NUM> comprises a piston plate <NUM>, which is arranged opposite to brake disc <NUM> with respect to counter disc <NUM>. Piston plate <NUM> is operatively connected to the not-shown actuation means and is adapted to press counter disc <NUM> and/or counter disc <NUM> against brake disc <NUM>, in order to obtain the braking action of rear wheel <NUM>. Piston plate <NUM> is slidable parallel to rotational axis A with respect to main body <NUM> as a consequence of the activation of the actuation means.

In addition, piston plate <NUM> is shaped like an annulus and comprises a surface <NUM>, which is arranged so as to face surface <NUM> of counter disc <NUM>. In detail, surface <NUM> and surface <NUM> of counter disc <NUM> (and, in particular, grooves <NUM> of counter disc <NUM>) define at least part of third interstices <NUM>.

Moreover, anti-rotational pins <NUM> of counter disc <NUM> are adapted to engage both anti-rotational pin holes <NUM> of counter disc <NUM> and respective holes formed in piston plate <NUM> (<FIG>).

Braking assembly <NUM> further comprises a limiting device <NUM>, which is adapted to limit the movement of piston plate <NUM> within a specific stroke parallel to rotational axis A. In detail, limiting device <NUM> is adapted to limit the movement of piston plate <NUM> in the direction oriented from counter disc <NUM> to counter disc <NUM>. This allows to control the stroke of piston plate <NUM> parallel to axis A in case of wear of brake disc <NUM>. Braking assembly <NUM> further comprises a cover <NUM>, which is arranged coaxially to rotational axis A and opposite to brake disc <NUM> with respect to counter disc <NUM>.

Cover <NUM> comprises a central portion <NUM> and a radially external portion <NUM> surrounding central portion <NUM> and having an axial extension parallel to rotational axis A. Cover <NUM> is shaped like an annulus having a radial extension greater than the radial extension of brake disc <NUM> and counter discs <NUM>, <NUM> and is adapted to be crossed by axle <NUM>.

In particular, central portion <NUM> and external portion <NUM> form a single piece.

Furthermore, cover <NUM> is adapted to be fixed to frame <NUM> at radially external portion <NUM> by connecting means <NUM>, such as threaded connecting means (<FIG>). As illustrated in <FIG>, when cover <NUM> is fixed to frame <NUM>, cover <NUM> and frame <NUM> define a cavity <NUM>, which is adapted to house at least brake disc <NUM>, counter discs <NUM> and <NUM> and piston plate <NUM>.

Counter disc <NUM> is fixed to cover <NUM>. More specifically, cover <NUM> is at least partially in contact with counter disc <NUM> and, in particular, with regions <NUM>. In addition, cover <NUM> and surface <NUM> of counter disc <NUM> (and, in particular, grooves <NUM>) define at least part of fourth interstices <NUM>.

Moreover, anti-rotational pins <NUM> of counter disc <NUM> are adapted to engage both anti-rotational pin holes <NUM> of counter disc <NUM> and respective holes formed in cover <NUM> (<FIG>).

In particular, fluid inlet <NUM> comprises an opening formed at cover <NUM> and is fluidly connected to cavity <NUM>. More specifically, fluid inlet <NUM> is arranged at radially external portion <NUM> and is fluidly connected to cavity <NUM> by means of one or more ducts <NUM>.

As illustrated in <FIG>, ducts <NUM> are formed partly inside cover <NUM> and partly inside main body <NUM>. In addition, fluid inlet <NUM> is arranged above brake disc <NUM> and counter discs <NUM>, <NUM> according to a vertical direction Z, which is transversal to both advancement direction X and direction Y and is parallel to the gravitational acceleration vector.

In addition, ducts <NUM> are in fluidic communication with third and fourth interstices <NUM>, <NUM>. Third interstices <NUM>, in turn, are in fluidic communication with second interstices <NUM> through holes <NUM> and fourth interstices <NUM> are in fluidic communication with first interstices <NUM> through holes <NUM> (<FIG>).

Furthermore, braking assembly <NUM> comprises a fluid outlet <NUM> for the outlet of the fluid (<FIG>). Preferably, fluid outlet <NUM> is arranged below brake disc <NUM> and counter discs <NUM>, <NUM> according to vertical direction Z.

The fluid is forced to circulate between fluid inlet <NUM> and fluid outlet <NUM> by means of a pump of vehicle <NUM>, which is known per se and is not described further in detail. The pump may be, by way of example, a reciprocating pump or a turbopump.

Brake disc <NUM> and counter discs <NUM>, <NUM> are partially immersed in the fluid. In particular, the fluid in which brake disc <NUM> and counter discs <NUM>, <NUM> are immersed is the fluid that has passed through first and second interstices <NUM>, <NUM> and has been collected in the lowermost part of cavity <NUM> according to vertical direction Z. In other words, because of gravity, the fluid passing through first and second interstices <NUM>, <NUM> is accumulated in the lowermost part of cavity <NUM>, which acts as a sump. The collected fluid has a fluid level and is adapted to be splashed over brake disc <NUM> because of the rotation thereof about rotational axis A. Therefore, brake disc <NUM> is cooled also by means of passive cooling.

The operation of the braking assembly <NUM> according to the present invention and described as above is the following. In particular, reference will be made to the braking assembly <NUM> adapted to brake rear wheel <NUM>, the operation of braking assembly <NUM> adapted to brake rear wheel <NUM> being identical.

In use, the actuation means are activated so as to press counter disc <NUM> and/or counter disc <NUM> against brake disc <NUM>, and to obtain the braking action of rear wheel <NUM>. During the braking action, the fluid is forced to circulate between fluid inlet <NUM> and fluid outlet <NUM> in order to carry out the forced cooling of brake disc <NUM>. Alternatively, the fluid may be continuously forced to circulate between fluid inlet <NUM> and fluid outlet <NUM> independently of the braking action and, in particular, even after the braking action has stopped.

In detail, the fluid is input into cavity <NUM> through fluid inlet <NUM>, which is arranged above brake disc <NUM> and counter discs <NUM>, <NUM> (<FIG>).

In further detail, the input fluid flows through ducts <NUM> to third and fourth interstices <NUM>, <NUM>. In detail, the fluid flows across grooves <NUM> of counter disc <NUM> from the outer radius toward the inner radius thereof and reaches holes <NUM>. Simultaneously, the fluid flows across grooves <NUM> of counter disc <NUM> from the outer radius toward the inner radius thereof and reaches holes <NUM>.

Subsequently, as illustrated in <FIG>, the fluid flows through holes <NUM> and <NUM> to first and second interstices <NUM>, <NUM>. Therefore, the fluid is put into direct contact with the external surfaces of brake disc <NUM> and, in particular, with radially external portion <NUM>. As a consequence, the waste heat generated during the braking action of braking assembly <NUM> is transmitted to the fluid and the fluid cools the entire brake disc <NUM>.

In conclusion, the fluid entering from fluid inlet <NUM> and passing through first and second interstices <NUM>, <NUM> carries out a forced cooling of brake disc <NUM>.

Subsequently, as a result of the rotation of brake disc <NUM> about rotational axis A and the corresponding centrifugal forces, the fluid is transported radially outwards and tends to accumulate in the lowermost part of cavity <NUM>, because of gravity. The fluid is then output through fluid outlet <NUM> (<FIG>). As a consequence, the flow of waste heat dissipated from braking assembly <NUM> is opposite to the flow of the fluid during the forced cooling. In other words, the flow of the fluid is in counterflow with respect to the flow of waste heat.

Furthermore, since brake disc <NUM> is partially immersed in the fluid collected in the lowermost part of cavity, such fluid is splashed over brake disc <NUM> as a result of the rotation thereof about rotational axis A.

In view of the foregoing, the advantages of braking assembly <NUM> and work vehicle <NUM> according to the invention are apparent.

In particular, since braking assembly <NUM> comprises counter discs <NUM> and <NUM> and the fluid is adapted to flow in first and second interstices <NUM>, <NUM>, waste heat can be efficiently dispersed. In fact, the fluid is specifically brought in contact with radially external portion <NUM> on both first and second sides 6a, 6b and a uniform cooling of brake disc <NUM> is obtained. In other words, brake disc <NUM> is cooled at two opposite thermal exchange surfaces. Accordingly, it has been observed that the service life of braking assembly <NUM> is considerably extended and the brake performances are significantly improved.

In addition, since the fluid is adapted to flow across third and fourth interstices and through holes <NUM>, <NUM>, counter discs <NUM>, <NUM> are also cooled down. In detail, counter discs <NUM>, <NUM> are cooled both at external faces 7a, 7b; 8a, 8b and internally. As a result, brake disc <NUM> is in proximity to efficiently cooled down components.

Brake disc <NUM> is partially immersed in the fluid collected in the lowermost portion of cavity <NUM>. Accordingly, the fluid splashed over the surfaces of brake disc <NUM> because of the rotation of brake disc <NUM> contributes to disperse the waste heat by virtue of passive cooling. However, since the waste heat is mainly dispersed by forced cooling, the level of the fluid in which brake disc <NUM> is immersed may be set lower than the fluid level of the known disc brakes discussed in the introductory portion of the present description. As a result, the power losses due to the rotation of brake disc <NUM> immersed in the fluid are very low.

Moreover, since the fluid adapted to contact brake disc <NUM> may be a cooling lubricant fluid, braking assembly <NUM> can be effectively lubricated while being cooled.

Counter disc <NUM> and <NUM> are identical to each other. Accordingly, the manufacturing costs of braking assembly <NUM> can be advantageously kept low.

It is clear that modifications can be made to the described braking assembly <NUM> and work vehicle <NUM> which do not extend beyond the scope of protection defined by the claims. In particular, braking assembly <NUM> might comprise more than one fluid inlet <NUM> and/or more than one fluid outlet <NUM>.

Claim 1:
Braking assembly (<NUM>) for a work vehicle (<NUM>) comprising:
- a brake disc (<NUM>), which is rotatable integrally with at least one wheel (<NUM>, <NUM>, <NUM>) of said work vehicle (<NUM>) about a rotational axis (A);
- a first counter disc (<NUM>), which is arranged on a first side (6a) of said brake disc (<NUM>) along said rotational axis (A) and is rotationally fixed;
- a second counter disc (<NUM>), which is arranged on a second side (6b) of said brake disc (<NUM>) opposite to said first side (6a) along said rotational axis (A) and is rotationally fixed;
- at least one fluid inlet (<NUM>) for the inlet of a fluid;
said fluid being a cooling lubricant fluid; and
- actuation means, which are adapted to press said first and/or second counter discs (<NUM>, <NUM>) against said brake disc (<NUM>);
said first and second counter discs (<NUM>, <NUM>) defining respectively first and second interstices (<NUM>, <NUM>) with said brake disc (<NUM>); said first and second counter discs (<NUM>, <NUM>) being respectively formed with at least one first hole (<NUM>) and at least one second hole (<NUM>), which are respectively adapted to put in fluidic communication said at least one fluid inlet (<NUM>) with said first interstices (<NUM>) and said second interstices (<NUM>);
said braking assembly is characterized in that it further comprises:
- a cover (<NUM>), which is opposite to said brake disc (<NUM>) with respect to said first counter disc (<NUM>) and is rotationally fixed; and
- a piston plate (<NUM>), which is opposite to said brake disc (<NUM>) with respect to said second counter disc (<NUM>) and is operatively connected to said actuation means;
said piston plate (<NUM>) defining third interstices (<NUM>) with said second counter disc (<NUM>); said third interstices (<NUM>) being fluidly connected to said fluid inlet (<NUM>) and to said second interstices (<NUM>) through said at least one second hole (<NUM>) ;
said cover (<NUM>) defining fourth interstices (<NUM>) with said first counter disc (<NUM>); said fourth interstices (<NUM>) being fluidly connected to said fluid inlet (<NUM>) and to said first interstices (<NUM>) through said at least one first hole (<NUM>).