Improved work machine

Abstract

A grader (1) comprising a body (2), at least one implement (10, 12, 14, 16) movably carried by the body (2), at least one hydraulic actuator (20, 22, 24, 26, 28, 30), adapted to control the movement of the implement (10, 12, 14, 16), a hydraulic arrangement (32) configured to provide pressurized hydraulic fluid towards the hydraulic actuator (20, 22, 24, 26, 28, 30), and comprising a variable-displacement load-sensing pump (36), a main control valve (40), a supply line (39) fluidly connecting the outlet of the pump (36) with the main control valve (40), a control lever (42) connected to the main control valve (40), a load sensing line (46) fluidly connecting the outlet of main control valve (40) with the load-sensing port of the pump (36), and a solenoid-controlled valve (50) fluidly interposed between the load sensing line (46) and the load-sensing port of the hydraulic pump (36), and configured to modify, on command, the pressure signal provided to the load sensing port of the pump (36).

Description

TECHNICAL FIELD

[0001] The present invention relates to a work machine, in particular to an earth-moving machine such as a grader, also referred to as motor grader or road grader.

[0002] More in detail, the present invention relates to a hydraulic arrangement configured to control the operation of a hydraulic arrangement of a grader. Reference will be made to this application by way of the example below, without however losing in generality.BACKGROUND OF THE INVENTION

[0003] As is known, motor graders are construction machines used in many road construction and earth-moving operations. Motor graders may be used for example in road construction operation to shape the final surface of roadbeds, ditches and trenches or in maintenance operation to clean and reform ditches, to reshape and contour worn roadbeds, to spread added material on a roadbed, to remove snow or to loosen and brake up compact soil.

[0004] Motor graders generally comprise an articulated frame provided with a rear portion carrying the engine and the driver's cab and an elongated saddle-shaped front portion pivotally connected to the rear portion, so as to be able to rotate about a vertical steering axis with respect to the rear portion.

[0005] In addition, motor graders comprise a plurality of ground engaging wheels to allow motion of the articulated frame on the ground.

[0006] More in detail, motor graders generally comprise a front pair of steering wheels, which are pivotally carried by the front portion of the articulated frame, are able to steer about a vertical steering axis and are also able to lean about a horizontal camber axis.

[0007] In addition, motor graders usually comprise two pairs of rear driving wheels, which are pivotally carried by the rear portion of the articulated frame and are connected to the engine to be driven in rotation.

[0008] Motor graders further comprise at least one elongated earth scraping blade, also known as moldboard, which is movably carried by front portion of the articulated frame and is adapted to be arranged in contact with the ground.

[0009] More in detail, the moldboard is generally carried in a rotatable manner about a vertical rotation axis and about two mutually orthogonal and horizontal axis, respectively parallel and orthogonal to the advancing direction of the motor grader.

[0010] In addition, the moldboard is generally carried in a sliding manner, so as to be able to move along a vertical direction and along a horizontal direction orthogonal to the advancing direction of the motor grader.

[0011] In addition, motor grader may further comprise a rear ripper carried in a vertical movable manner by the rear portion of the articulated frame and a front dozer blade carried in a vertical movable manner by the front portion of the articulated frame, in front of the front wheels.

[0012] In addition, motor graders are provided with a plurality of hydraulic actuators, such as double-effect hydraulic cylinders or hydraulic motors, configured to control the position of the moldboard, the rear ripper and the front dozer blade with respect to the ground.

[0013] Moreover, such hydraulic actuators may comprise a pair of hydraulic actuators configured to control the steering of the front steering wheels and a pair of hydraulic actuators configured to control the rotation of the articulated frame.

[0014] The aforementioned motor graders usually comprise a hydraulic system, which is fluidly connected to said hydraulic actuators and is configured to control the supply of pressurized hydraulic fluid fed towards the same hydraulic actuators, in order to control their operation.

[0015] More in detail, such hydraulic system generally comprises at least one hydraulic pump driven by the internal combustion engine of the motor grader, and a plurality of mechanically controlled hydraulic valves, fluidly interposed between the outlet of the hydraulic pump and a corresponding hydraulic actuator, to control the flow of pressurized hydraulic fed towards the respective actuator.

[0016] Traditional hydro-mechanical versions of motor graders comprise a plurality of control levers, each of which is carried within the driver's cab, is mechanically connected to the movable spool of a corresponding mechanically controlled hydraulic valve via a linkage and is adapted to be manually actuated by the driver in order to control accordingly the operation of the corresponding hydraulic actuator.

[0017] The aforementioned motor graders are construction machines quite complex to operate and their use requires highly skilled operators. Since most of the operators are used to the traditional hydro-mechanical versions of the motor graders, their demand on the marked is still very high.

[0018] Unfortunately, in the traditional hydro-mechanical versions of motor graders, the ratio between the opening of the hydraulic valves and the movement of the corresponding control levers is fixed, and therefore it is not possible to modify during operation the response and the aggressiveness of the hydraulic actuators to the movement of the control levers.

[0019] In view of the above, the need is felt to provide a hydraulic arrangement suited to be provided in the traditional hydro-mechanical versions of motor graders that allows to modify, during use, the response and the aggressiveness of the hydraulic actuators to the movements of the control levers while maintaining the traditional levers to operate the same motor grader.

[0020] Aim of the present invention is to satisfy the above-mentioned need in an optimized and cost-effective manner.SUMMARY OF THE INVENTION

[0021] The aforementioned aims are reached by a work machine and by a method as claimed in the appended set of claims.BRIEF DESCRIPTION OF DRAWINGS

[0022] 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 an illustration of an exemplarily work vehicle according to the present invention, Figure 2 is a schematic representation of a hydraulic arrangement of the work vehicle illustrated in Figure 1, Figure 3 is a schematic representation of a component of the hydraulic arrangement illustrated in Figure 2, and Figure 4 schematically represent the operation of the hydraulic arrangement illustrated in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0023] With reference to Figure 1, number 1 denotes, as a whole, a work machine, in particular an earth-moving machine such as a grader, also referred to as motor grader or road grader.

[0024] Work machine 1 comprises a body 2, which extends along a reference axis A and is movable on the ground by means of ground resting means 4, in particular wheels.

[0025] As per se known, body 2 preferably comprises an articulated frame 5 provided with a front portion 5a and a rear portion 5b, which are pivotally connected to each other so as to be able to rotate one with respect to the other about a vertical rotation axis R 1 . Preferably, the rear portion 5b carries the driver's cab 7 and the powertrain 8 of the same work machine 1, as per se known and therefore not further described.

[0026] The front portion 5a, on the other hand, has preferably an elongated shape and extends along reference axis A.

[0027] In addition, the front portion 5a is preferably arc-shaped or saddle-shaped with respect to a direction orthogonal to reference axis A.

[0028] Ground resting means 4 preferably comprises one or two pairs of driving rear wheels 4b carried by rear portion of the articulated frame 5b and mechanically connected to the powertrain 8 to be driven in rotation.

[0029] In addition, ground resting means 4 preferably comprises a pair of front steering wheels 4a, which are carried advantageously in a free rotatable manner by front portion 5a of the articulated frame 5 and are rotatable about a vertical steering axis. Optionally, front steering wheels 4a are further carried in a rotatable manner about a horizontal camber axis.

[0030] With reference to the preferred embodiment of the present invention, work machine 1 further comprises one or more implements 10, which are carried in a movable manner by the body 2 of work vehicle 1 and are adapted to be arranged in contact with the ground.

[0031] More in detail, work implements 10 comprises at least one central blade 12, also referred to as moldboard, which is carried in a movable manner by body 2, in particular by the front portion 5a of the articulated frame 5.

[0032] In even more detail, moldboard 12 is preferably carried by the underside of front portion 5a, so as to be located below the saddle of the same front portion 5a.

[0033] As known, moldboard 12 is preferably carried in a movable manner by body 2 so as to be rotatable about a first rotation axis R 2 vertical and / substantially parallel to rotation axis R 1 , about a second rotation axis R 3 horizontal and parallel to reference axis A and / or about a third rotation axis R 4 horizontal and transversal to reference axis A.

[0034] In addition, as always known, moldboard 12 is preferably carried in a movable manner by body 2, so as to be translatable along a horizontal direction transversal to reference axis A, i.e. parallel to rotation axis R 4 and along a vertical direction, i.e. parallel to rotation axis R 2 .

[0035] In addition, with reference to the exemplary embodiment illustrated in Figure 1, implements 10 preferably comprises a front dozer blade 14, which is carried in a movable manner by body 2 so as to be movable in a vertical direction. More in detail, front dozer blade 14 is movably carried by front portion 5a of body 5 and is preferably arranged on front of front wheels 5a along reference axis A.

[0036] Moreover, implements 10 preferably comprises a rear ripper 16, which is carried in a movable manner by body 2 so as to be movable in a vertical direction. More in detail, rear ripper 16 is movably carried by rear portion 5b of body 5 and is preferably arranged behind rear wheels 5b along reference axis A.

[0037] According to the preferred embodiment illustrated in Figure 1, work machine 1 comprises a hydraulic actuator assembly 20, which is configured to actuate body 2 and / or the hydraulically actuated work implements 10.

[0038] In other words, work machine 1 comprises a plurality of hydraulic actuators which are operatively coupled to work implements 10, to the front steering wheels 4a and / or to the articulated chassis 5 and are adapted to control the movement / position of these latter.

[0039] More in detail, hydraulic actuator assembly 20 preferably comprise at least a pair of hydraulic actuators (not visible in Figure 1) coupled to front steering wheels 4a and adapted to control the steering of these latter and / or a pair of further hydraulic actuators (not visible in Figure 1) coupled to front steering wheels 4a as well and adapted to control the camber of these latter.

[0040] In addition, hydraulic actuator assembly 20 preferably further comprises a pair of hydraulic actuators (not visible in Figure 1) operatively interposed between front portion 5a and rear portion 5b of articulated frame 5 and configured to control the rotation of these latter about rotation axis R 1 with respect to each other, in order to control the steering of work vehicle 1.

[0041] Preferably, hydraulic actuator assembly 20 further comprises at least one hydraulic actuator 22, in particular a double-effect hydraulic cylinder, operatively interposed between body 2 and front dozer blade 14 and configured to control the movement of this latter with respect to body 2.

[0042] Similarly, hydraulic actuator assembly 20 further comprises at least one hydraulic actuator 24, in particular a double-effect hydraulic cylinder, operatively interposed between body 2 and rear ripper 16 and configured to control the movement of this latter with respect to body 2.

[0043] With reference to Figures 1 and 2, in addition, hydraulic actuator assembly 20 preferably comprises a plurality of hydraulic actuators configured to control the movement of moldboard 12.

[0044] More in detail, hydraulic actuator assembly 20 preferably comprises: at least one hydraulic motor 26 configured to control the rotation of moldboard 12 about rotation axis R 2 ; one double-effect hydraulic cylinder (not visible) configured to control the translation of moldboard 12 along rotation axis R 4 (i.e. its lateral displacement), at least one double-effect hydraulic cylinder 28 (visible in Figure 2) configured to control the rotation of moldboard 12 about rotation axis R 4 (i.e. its pitch), and at least two further double-effect hydraulic cylinders 30 configured to control the translation of moldboard 12 along axis R 2 (i.e. its vertical displacement.

[0045] With reference to the preferred embodiment illustrated in Figure 2, work machine 1 further comprises a hydraulic arrangement / system 32, which is configured to provide pressurized hydraulic fluid towards hydraulic actuator assembly 20, in other to operate / actuate the latter.

[0046] Preferably, as explained more in detail in the following, hydraulic arrangement 32 has a flow-sharing post-compensated configuration.

[0047] Hydraulic arrangement 32 preferably comprises a source of pressurized hydraulic fluid 34, which is configured to provide at outlet a flow of pressurized hydraulic fluid.

[0048] The source of pressurized hydraulic fluid 34 preferably comprises pumping means 36, in particular a load-sensing variable displacement hydraulic pump 36, which may be carried by the engine of work machine 1 and is configured to suck hydraulic fluid from a tank 38 and to provide at outlet a pressurized flow of such hydraulic fluid.

[0049] As per se known and therefore not described in detail, load-sensing variable displacement hydraulic pump 36 preferably comprises a load sensing port adapted to receive a load sensing pressure signal indicative of the pressure of the hydraulic fluid at the hydraulic actuator assembly 10 and a pressure compensator fluidly connected to the load sensing port and adapted to modify the displacement of load-sensing variable displacement hydraulic pump 36 on the basis of such load sensing pressure signal.

[0050] More in detail, pumping means 36 preferably comprises a high-pressure hydraulic pump configured to deliver at outlet a pressurized hydraulic fluid with a pressure greater than 100 bar, more preferably up to or greater than 350 bar.

[0051] In addition, hydraulic arrangement 32 preferably comprises a plurality of main control valves 40 or distributors, each fluidly interposed between the source of pressurized hydraulic fluid 34 and a corresponding hydraulic actuator of hydraulic actuator assembly 20.

[0052] More in detail, hydraulic arrangement 32 preferably comprises a supply line 39, which fluidly connects the outlet of hydraulic pump 36 with the hydraulic actuators of hydraulic actuator assembly 20. Each main control valve 40 is preferably fluidly connected to supply line 39, upstream a corresponding hydraulic actuator of hydraulic actuator assembly 20.

[0053] In other words, according to the flow sharing configuration, supply line 39 is preferably configured to feed pressurized hydraulic fluid towards a plurality of valves 40.

[0054] In addition, main control valves 40 are preferably mechanically controlled valves.

[0055] More in detail, work vehicle 1 comprises a plurality of control levers or similar user interface 42, each of which is mechanically connected to the movable spool of a corresponding main control valve 40 via a linkage, and is adapted to be manually operated by the work vehicle driver in order to control the movement of the corresponding spool, i.e. the actuation of the corresponding valve 40.

[0056] According to the example illustrated in Figure 2, valves 40 are preferably three positions valves. In a first neutral position, valves 40 are configured to not actuate the corresponding hydraulic actuator, while in the second and in the third position valves 40 are configured to actuate the related hydraulic actuator in a corresponding direction, by putting a corresponding end of the hydraulic actuators in fluid communication with the outlet of hydraulic pump 36 and supply line 39.

[0057] With reference to the exemplary embodiment illustrated in Figure 2, hydraulic arrangement 32 preferably comprises a plurality of pressure compensators 44 arranged immediately downstream a corresponding valve 40.

[0058] In particular, according to the post-compensated configuration, hydraulic arrangement 32 preferably comprises a plurality of pressure compensators 44, each arranged immediately downstream a corresponding valve 40 and configured, in use, to maintain downstream the corresponding valve 40 a constant pressure margin independently from the load of the same hydraulic actuator.

[0059] More in detail, with reference to the example illustrated in Figure 1, hydraulic arrangement 32 preferably comprises at least one load-sensing line 46, which fluidly connects the outlet of the main control valves 40 with the load-sensing port of the load sensing variable displacement hydraulic pump 36.

[0060] Pressure compensators 44 are preferably arranged along load sensing line 46, each downstream a corresponding a main control valve 40.

[0061] As per se known and therefore not described in detail, each pressure compensator is configured to set a predetermined and advantageously constant pressure margin or pressure delta downstream the corresponding main control valve 40, so that the flowrate of hydraulic fluid provided at the corresponding hydraulic actuator of hydraulic actuator assembly 20 depends only on the opening of the corresponding main control valve 40, independently from the actual load of the same hydraulic actuator.

[0062] In particular, each pressure compensator 44 is preferably provided with biasing means, such as a spring, configured to set said predetermined pressure margin.

[0063] Load sensing line 46 preferably fluidly connects the pressure compensators 44 to the load-sensing port of the hydraulic pump 36 and is adapted to carry a pressure signal to the same hydraulic pump 36 indicative of the load of the hydraulic actuators of hydraulic actuator assembly 20, in order to adapt its displacement and therefore the flowrate of hydraulic fluid provided at outlet accordingly.

[0064] With reference to the preferred embodiment of the present invention illustrated in Figure 2 and 3, hydraulic arrangement 32 further comprises at least one solenoid-controlled valve or electro-valve 50 arranged along load sensing line 46, upstream the load sensing port of hydraulic pump 36.

[0065] More in detail, valve 50 is preferably interposed between load sensing line 46 and the load sending port of hydraulic pump 36, and is configured to modify, on command, the pressure signal provided to the load sensing port of hydraulic pump 36.

[0066] In use, valve 50 is configured be controllable to modify the load sensing signal provided to hydraulic pump 36.

[0067] In particular, valve 50 is preferably operatively interposed between supply line 39, load sensing line 46 and the load sensing port of hydraulic pump 36, and is configured to spill hydraulic fluid from supply line 39 and to provide a pressure signal to the load-sensing port of hydraulic pump 36 which depends on the actuation of the same valve 50.

[0068] In addition, valve 50 is preferably configured to provide a pressure signal towards the load-sensing port of the variable-displacement load-sensing hydraulic pump 36, which depends on the pressure within the load sending line 46.

[0069] With reference to the preferred embodiment illustrated in Figure 2 and 3, valve 50 is preferably a three-way two-positions valve. In addition, valve 50 is preferably a proportional valve.

[0070] The three ports of solenoid-controlled valve 50 are preferably fluidly connected to supply line 36 via a line 51, to tank 38 via a line 52 and to the load-sensing port of hydraulic pump 36 via a line 53.

[0071] Preferably, line 51 is further provided with a flow restrictor 55 to fluidly decouple supply line 39 with valve 50.

[0072] In the first position 50a, valve 50 is preferably configured to fluidly connect tank 38 and line 52 with line 53 and the load-sensing port of hydraulic pump 36, and to fluidly isolate supply line 39 and line 51.

[0073] In the second position 50b, valve 50 is preferably configured to fluidly supply line 39 and line 51 with line 53 and the load-sensing port of hydraulic pump 36, and to fluidly isolate tank 38 and line 52.

[0074] With reference to the exemplary embodiment illustrated in Figure 2 and 3, valve 50 preferably comprises at least one biasing means 57, for instance a spring, which is operatively connected to a first end of valve 50 and is configured to bias the same valve 50 in its first position 50a.

[0075] Preferably, valve 50 comprises at least one solenoid configured to control the opening of the same solenoid-controlled valve 50, and the pressure signal provided to the load-sensing port of the variable-displacement load-sensing hydraulic pump 36 depends on the actuation of the at least one solenoid.

[0076] More in detail, valve 50 further comprises a first solenoid 58 operatively connected to the first end of valve 50 and configured to bias the same valve 50 in its first position 50a.

[0077] In addition, valve 50 preferably further comprises a second solenoid 59 operatively connected to a second end of valve 50, opposite to the first end, and configured to bias the same valve 50 in its second position 50b.

[0078] With reference to the exemplary embodiment illustrated in Figures 2 and 3, valve 50 may be further hydraulically piloted.

[0079] More in detail, load sensing line 46 may be operatively connected to the second end of valve 50 and may be configured to exert a force on the spool of valve 50 configured to arrange this latter in its second position 50b.

[0080] In other words, the force exerted by load sensing line 46 on the spool of valve 50 may be concordant with the force exerted by solenoid 59 on the same spool.

[0081] In addition, valve 50 may further comprises a second pilot line 60, which branches off from line 53 downstream valve 50, is operatively connected to the first end of valve 50 and may be configured to exert a force on the spool of valve 50 configured to arrange this latter in its first position 50a.

[0082] In other words, the force exerted by pilot line 60 on the spool of valve 50 may be concordant with the force exerted by solenoid 58 on the same spool.

[0083] Preferably, pilot line 60 may be further provided with a flow restrictor 61.

[0084] With reference to the exemplary embodiment illustrated in Figure 2, work vehicle 1 preferably further comprises a user interface 65, such as a knob, a button, a slider, or portions of a touch-sensitive display, which are adapted to be manually actuated / handled by the work machine user to impart commands for controlling the operation of solenoid-controlled valve 50.

[0085] In addition, work vehicle 1 preferably comprises an electronic control unit 70, which is preferably connected to user interface 65 and to solenoid-controlled valve 50, and is provided with elaboration means configured to control the operation of the same valve 50 as function of the signals provided by user interface 65, as explained more in detail in the following.

[0086] Electronic control unit 70, on the basis of the commands imparted by the user by means of user interface 65, is configured to vary the pilot signal provided to the load sensing port of hydraulic pump 36, in order to vary accordingly the response of the same hydraulic pump 36.

[0087] This allows to adapt, for example dynamically, the response of hydraulic system 32 to the actuation of control levers 42.

[0088] In addition, the control of valve 50 may be further carried out in real time, during operation of work vehicle 1.

[0089] In particular, it is possible to control valve 50 to increase the pressure within line 53 to increase the flowrate provided at outlet by hydraulic pump 36. This increases the flowrate provided to the hydraulic actuators for a certain actuation of the control levers 42, thereby increasing the aggressiveness and the response of the same hydraulic actuators and increasing the velocity of movement of the related implement 10.

[0090] This in particular allows to increase the performances of work vehicle 1, since in response to the actuation of control levers 42 the speed of movements of the implements 10 themselves is increased.

[0091] For example, to increase the flowrate provided at outlet by hydraulic pump 36, electronic control unit 70 may be configured to energise solenoid 59 to move valve 50 towards its second position. Accordingly, the pressure within line 53 may be increase, for instance it may be raised to a value higher than the pressure actually present within load sensing line 46.

[0092] In addition, it is possible to control valve 50 to reduce the pressure within line 53 to reduce the flowrate provided at outlet by hydraulic pump 36. This reduces the flowrate provided to the hydraulic actuators for a certain actuation of the control levers 42, thereby reducing the aggressiveness and the response of the same hydraulic actuators and reducing the velocity of movement of the related implement 10.

[0093] This in particular allows to increase the controllability and the accuracy in positioning the implements 10, since in response to the actuation of control levers 42 the speed of movements of the implements 10 themselves is reduced.

[0094] For example, to reduce the flowrate provided at outlet by hydraulic pump 36, electronic control unit 70 may be configured to energise solenoid 58 to move valve 50 towards its first position. Accordingly, the pressure within line 53 may be reduces, for instance it may be reduced to a value lower than the pressure actually present within load sensing line 46.

[0095] The operation of the above-described work machine 1 is the following and is schematically represented in Figure 4.

[0096] In general, during use, hydraulic pump 36 provides at outlet a pressurized flow of hydraulic fluid and main control valves 40 are manually controlled by the user via control levers 42, to control accordingly the operation of the corresponding hydraulic actuator of hydraulic actuator assembly 10.

[0097] Such operation is schematically represented in Figure 4, wherein line P 1 represent the standard / unbiased ratio between the actuation of a control lever 42 and the flowrate provided to the corresponding hydraulic actuator of hydraulic actuator assembly 10. Clearly, the ratio between the actuation of a control lever 42 and the flowrate provided to the corresponding hydraulic actuator of hydraulic actuator assembly 10 depends, among the others, on the structure of the related main control valve 40, in particular on the size of the various orifices or ducts and the structure of the linkage connecting the control lever 42 to the corresponding main control valve 40.

[0098] In addition, supposing that the work vehicle driver desires to increase the controllability and the accuracy in positioning the implements 10, he may operate user interface 65 to power solenoid 58 of valve 50 and therefore reduce the pressure signal provided to the load sensing port hydraulic pump 36, to reduce the flowrate provided to hydraulic actuator in response to actuation of the control lever 42.

[0099] The above is schematically illustrated in curve P 2 depicted in Figure 4.

[0100] Lastly, supposing that the work vehicle driver desires to increase the aggressiveness of hydraulic arrangement 32, to have a faster and more ready response to actuation of control levers 42, he may operate user interface 65 to power solenoid 59 of valve 50 and therefore increase the pressure signal provided to the load sensing port hydraulic pump 36, to increase the flowrate provided to hydraulic actuator in response to actuation of the control lever 42.

[0101] The above is schematically illustrated in curve P3 depicted in Figure 4.

[0102] In view of the foregoing, the advantages of the work machine 1 according to the invention are apparent.

[0103] In particular, the presence of valve 50 allows to adapt dynamically the response of the hydraulic arrangement 32 to the actuation of control levers 42 without requiring further modification to the same hydraulic arrangement 32 and in particular without requiring the substitution of control levers 42.

[0104] This allows to improve the user experience of work machine 1 without requiring the work machine driver to get used to a completely new user interface, with the obvious advantages that this entails.

[0105] In addition, the presence of valve 50 and the associated user interface 65 allows to quickly and simply modify the response of hydraulic arrangement 32. For instance, by operating the user interface 65, it is possible to reduce or to increase the aggressiveness of hydraulic arrangement 32, thus allowing the controllability or speed of hydraulic arrangement 32 to be increased according to the work vehicle driver's momentary needs.

[0106] It is clear that modifications can be made to the work machine 1, which do not extend beyond the scope of protection defined by the claims.

[0107] For instance, hydraulic arrangement 32 may comprise a plurality of load sensing lines 46 and a plurality of valves 50 arranged in parallel to each other.

[0108] In particular, hydraulic arrangement 32 may comprise a first load sensing line 46 and a first valve 50 associated to a first group of hydraulic actuator, for example the actuators configured to control movement of moldboard 12, and a second load sensing line 46 and a second valve 50 associated to a second group of hydraulic actuator, for example the actuators configured the steering of front wheels 4a and the articulation of articulated frame 5.

[0109] In particular, the provision of more valves 50 allows to modify the response of the first group of actuators independently from the response of the second group of actuators, thereby further improving the user experience of work machine 1, as for example it is possible to increase the aggressiveness of the steering of work machine 1 while maintaining a really progressive and controllable actuation of the moldboard 12 or vice-versa.

Examples

Embodiment Construction

[0023]With reference to Figure 1, number 1 denotes, as a whole, a work machine, in particular an earth-moving machine such as a grader, also referred to as motor grader or road grader.

[0024]Work machine 1 comprises a body 2, which extends along a reference axis A and is movable on the ground by means of ground resting means 4, in particular wheels.

[0025]As per se known, body 2 preferably comprises an articulated frame 5 provided with a front portion 5a and a rear portion 5b, which are pivotally connected to each other so as to be able to rotate one with respect to the other about a vertical rotation axis R 1 . Preferably, the rear portion 5b carries the driver's cab 7 and the powertrain 8 of the same work machine 1, as per se known and therefore not further described.

[0026]The front portion 5a, on the other hand, has preferably an elongated shape and extends along reference axis A.

[0027]In addition, the front portion 5a is preferably arc-shaped or saddle-shaped with respect to a dir...

TECHNICAL FIELD

[0001] The present invention relates to a work machine, in particular to an earth-moving machine such as a grader, also referred to as motor grader or road grader.

[0002] More in detail, the present invention relates to a hydraulic arrangement configured to control the operation of a hydraulic arrangement of a grader. Reference will be made to this application by way of the example below, without however losing in generality.BACKGROUND OF THE INVENTION

[0003] As is known, motor graders are construction machines used in many road construction and earth-moving operations. Motor graders may be used for example in road construction operation to shape the final surface of roadbeds, ditches and trenches or in maintenance operation to clean and reform ditches, to reshape and contour worn roadbeds, to spread added material on a roadbed, to remove snow or to loosen and brake up compact soil.

[0004] Motor graders generally comprise an articulated frame provided with a rear portion carrying the engine and the driver's cab and an elongated saddle-shaped front portion pivotally connected to the rear portion, so as to be able to rotate about a vertical steering axis with respect to the rear portion.

[0005] In addition, motor graders comprise a plurality of ground engaging wheels to allow motion of the articulated frame on the ground.

[0006] More in detail, motor graders generally comprise a front pair of steering wheels, which are pivotally carried by the front portion of the articulated frame, are able to steer about a vertical steering axis and are also able to lean about a horizontal camber axis.

[0007] In addition, motor graders usually comprise two pairs of rear driving wheels, which are pivotally carried by the rear portion of the articulated frame and are connected to the engine to be driven in rotation.

[0008] Motor graders further comprise at least one elongated earth scraping blade, also known as moldboard, which is movably carried by front portion of the articulated frame and is adapted to be arranged in contact with the ground.

[0009] More in detail, the moldboard is generally carried in a rotatable manner about a vertical rotation axis and about two mutually orthogonal and horizontal axis, respectively parallel and orthogonal to the advancing direction of the motor grader.

[0010] In addition, the moldboard is generally carried in a sliding manner, so as to be able to move along a vertical direction and along a horizontal direction orthogonal to the advancing direction of the motor grader.

[0011] In addition, motor grader may further comprise a rear ripper carried in a vertical movable manner by the rear portion of the articulated frame and a front dozer blade carried in a vertical movable manner by the front portion of the articulated frame, in front of the front wheels.

[0012] In addition, motor graders are provided with a plurality of hydraulic actuators, such as double-effect hydraulic cylinders or hydraulic motors, configured to control the position of the moldboard, the rear ripper and the front dozer blade with respect to the ground.

[0013] Moreover, such hydraulic actuators may comprise a pair of hydraulic actuators configured to control the steering of the front steering wheels and a pair of hydraulic actuators configured to control the rotation of the articulated frame.

[0014] The aforementioned motor graders usually comprise a hydraulic system, which is fluidly connected to said hydraulic actuators and is configured to control the supply of pressurized hydraulic fluid fed towards the same hydraulic actuators, in order to control their operation.

[0015] More in detail, such hydraulic system generally comprises at least one hydraulic pump driven by the internal combustion engine of the motor grader, and a plurality of mechanically controlled hydraulic valves, fluidly interposed between the outlet of the hydraulic pump and a corresponding hydraulic actuator, to control the flow of pressurized hydraulic fed towards the respective actuator.

[0016] Traditional hydro-mechanical versions of motor graders comprise a plurality of control levers, each of which is carried within the driver's cab, is mechanically connected to the movable spool of a corresponding mechanically controlled hydraulic valve via a linkage and is adapted to be manually actuated by the driver in order to control accordingly the operation of the corresponding hydraulic actuator.

[0017] The aforementioned motor graders are construction machines quite complex to operate and their use requires highly skilled operators. Since most of the operators are used to the traditional hydro-mechanical versions of the motor graders, their demand on the marked is still very high.

[0018] Unfortunately, in the traditional hydro-mechanical versions of motor graders, the ratio between the opening of the hydraulic valves and the movement of the corresponding control levers is fixed, and therefore it is not possible to modify during operation the response and the aggressiveness of the hydraulic actuators to the movement of the control levers.

[0019] In view of the above, the need is felt to provide a hydraulic arrangement suited to be provided in the traditional hydro-mechanical versions of motor graders that allows to modify, during use, the response and the aggressiveness of the hydraulic actuators to the movements of the control levers while maintaining the traditional levers to operate the same motor grader.

[0020] Aim of the present invention is to satisfy the above-mentioned need in an optimized and cost-effective manner.SUMMARY OF THE INVENTION

[0021] The aforementioned aims are reached by a work machine and by a method as claimed in the appended set of claims.BRIEF DESCRIPTION OF DRAWINGS

[0022] 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 an illustration of an exemplarily work vehicle according to the present invention, Figure 2 is a schematic representation of a hydraulic arrangement of the work vehicle illustrated in Figure 1, Figure 3 is a schematic representation of a component of the hydraulic arrangement illustrated in Figure 2, and Figure 4 schematically represent the operation of the hydraulic arrangement illustrated in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0023] With reference to Figure 1, number 1 denotes, as a whole, a work machine, in particular an earth-moving machine such as a grader, also referred to as motor grader or road grader.

[0024] Work machine 1 comprises a body 2, which extends along a reference axis A and is movable on the ground by means of ground resting means 4, in particular wheels.

[0025] As per se known, body 2 preferably comprises an articulated frame 5 provided with a front portion 5a and a rear portion 5b, which are pivotally connected to each other so as to be able to rotate one with respect to the other about a vertical rotation axis R 1 . Preferably, the rear portion 5b carries the driver's cab 7 and the powertrain 8 of the same work machine 1, as per se known and therefore not further described.

[0026] The front portion 5a, on the other hand, has preferably an elongated shape and extends along reference axis A.

[0027] In addition, the front portion 5a is preferably arc-shaped or saddle-shaped with respect to a direction orthogonal to reference axis A.

[0028] Ground resting means 4 preferably comprises one or two pairs of driving rear wheels 4b carried by rear portion of the articulated frame 5b and mechanically connected to the powertrain 8 to be driven in rotation.

[0029] In addition, ground resting means 4 preferably comprises a pair of front steering wheels 4a, which are carried advantageously in a free rotatable manner by front portion 5a of the articulated frame 5 and are rotatable about a vertical steering axis. Optionally, front steering wheels 4a are further carried in a rotatable manner about a horizontal camber axis.

[0030] With reference to the preferred embodiment of the present invention, work machine 1 further comprises one or more implements 10, which are carried in a movable manner by the body 2 of work vehicle 1 and are adapted to be arranged in contact with the ground.

[0031] More in detail, work implements 10 comprises at least one central blade 12, also referred to as moldboard, which is carried in a movable manner by body 2, in particular by the front portion 5a of the articulated frame 5.

[0032] In even more detail, moldboard 12 is preferably carried by the underside of front portion 5a, so as to be located below the saddle of the same front portion 5a.

[0033] As known, moldboard 12 is preferably carried in a movable manner by body 2 so as to be rotatable about a first rotation axis R 2 vertical and / substantially parallel to rotation axis R 1 , about a second rotation axis R 3 horizontal and parallel to reference axis A and / or about a third rotation axis R 4 horizontal and transversal to reference axis A.

[0034] In addition, as always known, moldboard 12 is preferably carried in a movable manner by body 2, so as to be translatable along a horizontal direction transversal to reference axis A, i.e. parallel to rotation axis R 4 and along a vertical direction, i.e. parallel to rotation axis R 2 .

[0035] In addition, with reference to the exemplary embodiment illustrated in Figure 1, implements 10 preferably comprises a front dozer blade 14, which is carried in a movable manner by body 2 so as to be movable in a vertical direction. More in detail, front dozer blade 14 is movably carried by front portion 5a of body 5 and is preferably arranged on front of front wheels 5a along reference axis A.

[0036] Moreover, implements 10 preferably comprises a rear ripper 16, which is carried in a movable manner by body 2 so as to be movable in a vertical direction. More in detail, rear ripper 16 is movably carried by rear portion 5b of body 5 and is preferably arranged behind rear wheels 5b along reference axis A.

[0037] According to the preferred embodiment illustrated in Figure 1, work machine 1 comprises a hydraulic actuator assembly 20, which is configured to actuate body 2 and / or the hydraulically actuated work implements 10.

[0038] In other words, work machine 1 comprises a plurality of hydraulic actuators which are operatively coupled to work implements 10, to the front steering wheels 4a and / or to the articulated chassis 5 and are adapted to control the movement / position of these latter.

[0039] More in detail, hydraulic actuator assembly 20 preferably comprise at least a pair of hydraulic actuators (not visible in Figure 1) coupled to front steering wheels 4a and adapted to control the steering of these latter and / or a pair of further hydraulic actuators (not visible in Figure 1) coupled to front steering wheels 4a as well and adapted to control the camber of these latter.

[0040] In addition, hydraulic actuator assembly 20 preferably further comprises a pair of hydraulic actuators (not visible in Figure 1) operatively interposed between front portion 5a and rear portion 5b of articulated frame 5 and configured to control the rotation of these latter about rotation axis R 1 with respect to each other, in order to control the steering of work vehicle 1.

[0041] Preferably, hydraulic actuator assembly 20 further comprises at least one hydraulic actuator 22, in particular a double-effect hydraulic cylinder, operatively interposed between body 2 and front dozer blade 14 and configured to control the movement of this latter with respect to body 2.

[0042] Similarly, hydraulic actuator assembly 20 further comprises at least one hydraulic actuator 24, in particular a double-effect hydraulic cylinder, operatively interposed between body 2 and rear ripper 16 and configured to control the movement of this latter with respect to body 2.

[0043] With reference to Figures 1 and 2, in addition, hydraulic actuator assembly 20 preferably comprises a plurality of hydraulic actuators configured to control the movement of moldboard 12.

[0044] More in detail, hydraulic actuator assembly 20 preferably comprises: at least one hydraulic motor 26 configured to control the rotation of moldboard 12 about rotation axis R 2 ; one double-effect hydraulic cylinder (not visible) configured to control the translation of moldboard 12 along rotation axis R 4 (i.e. its lateral displacement), at least one double-effect hydraulic cylinder 28 (visible in Figure 2) configured to control the rotation of moldboard 12 about rotation axis R 4 (i.e. its pitch), and at least two further double-effect hydraulic cylinders 30 configured to control the translation of moldboard 12 along axis R 2 (i.e. its vertical displacement.

[0045] With reference to the preferred embodiment illustrated in Figure 2, work machine 1 further comprises a hydraulic arrangement / system 32, which is configured to provide pressurized hydraulic fluid towards hydraulic actuator assembly 20, in other to operate / actuate the latter.

[0046] Preferably, as explained more in detail in the following, hydraulic arrangement 32 has a flow-sharing post-compensated configuration.

[0047] Hydraulic arrangement 32 preferably comprises a source of pressurized hydraulic fluid 34, which is configured to provide at outlet a flow of pressurized hydraulic fluid.

[0048] The source of pressurized hydraulic fluid 34 preferably comprises pumping means 36, in particular a load-sensing variable displacement hydraulic pump 36, which may be carried by the engine of work machine 1 and is configured to suck hydraulic fluid from a tank 38 and to provide at outlet a pressurized flow of such hydraulic fluid.

[0049] As per se known and therefore not described in detail, load-sensing variable displacement hydraulic pump 36 preferably comprises a load sensing port adapted to receive a load sensing pressure signal indicative of the pressure of the hydraulic fluid at the hydraulic actuator assembly 10 and a pressure compensator fluidly connected to the load sensing port and adapted to modify the displacement of load-sensing variable displacement hydraulic pump 36 on the basis of such load sensing pressure signal.

[0050] More in detail, pumping means 36 preferably comprises a high-pressure hydraulic pump configured to deliver at outlet a pressurized hydraulic fluid with a pressure greater than 100 bar, more preferably up to or greater than 350 bar.

[0051] In addition, hydraulic arrangement 32 preferably comprises a plurality of main control valves 40 or distributors, each fluidly interposed between the source of pressurized hydraulic fluid 34 and a corresponding hydraulic actuator of hydraulic actuator assembly 20.

[0052] More in detail, hydraulic arrangement 32 preferably comprises a supply line 39, which fluidly connects the outlet of hydraulic pump 36 with the hydraulic actuators of hydraulic actuator assembly 20. Each main control valve 40 is preferably fluidly connected to supply line 39, upstream a corresponding hydraulic actuator of hydraulic actuator assembly 20.

[0053] In other words, according to the flow sharing configuration, supply line 39 is preferably configured to feed pressurized hydraulic fluid towards a plurality of valves 40.

[0054] In addition, main control valves 40 are preferably mechanically controlled valves.

[0055] More in detail, work vehicle 1 comprises a plurality of control levers or similar user interface 42, each of which is mechanically connected to the movable spool of a corresponding main control valve 40 via a linkage, and is adapted to be manually operated by the work vehicle driver in order to control the movement of the corresponding spool, i.e. the actuation of the corresponding valve 40.

[0056] According to the example illustrated in Figure 2, valves 40 are preferably three positions valves. In a first neutral position, valves 40 are configured to not actuate the corresponding hydraulic actuator, while in the second and in the third position valves 40 are configured to actuate the related hydraulic actuator in a corresponding direction, by putting a corresponding end of the hydraulic actuators in fluid communication with the outlet of hydraulic pump 36 and supply line 39.

[0057] With reference to the exemplary embodiment illustrated in Figure 2, hydraulic arrangement 32 preferably comprises a plurality of pressure compensators 44 arranged immediately downstream a corresponding valve 40.

[0058] In particular, according to the post-compensated configuration, hydraulic arrangement 32 preferably comprises a plurality of pressure compensators 44, each arranged immediately downstream a corresponding valve 40 and configured, in use, to maintain downstream the corresponding valve 40 a constant pressure margin independently from the load of the same hydraulic actuator.

[0059] More in detail, with reference to the example illustrated in Figure 1, hydraulic arrangement 32 preferably comprises at least one load-sensing line 46, which fluidly connects the outlet of the main control valves 40 with the load-sensing port of the load sensing variable displacement hydraulic pump 36.

[0060] Pressure compensators 44 are preferably arranged along load sensing line 46, each downstream a corresponding a main control valve 40.

[0061] As per se known and therefore not described in detail, each pressure compensator is configured to set a predetermined and advantageously constant pressure margin or pressure delta downstream the corresponding main control valve 40, so that the flowrate of hydraulic fluid provided at the corresponding hydraulic actuator of hydraulic actuator assembly 20 depends only on the opening of the corresponding main control valve 40, independently from the actual load of the same hydraulic actuator.

[0062] In particular, each pressure compensator 44 is preferably provided with biasing means, such as a spring, configured to set said predetermined pressure margin.

[0063] Load sensing line 46 preferably fluidly connects the pressure compensators 44 to the load-sensing port of the hydraulic pump 36 and is adapted to carry a pressure signal to the same hydraulic pump 36 indicative of the load of the hydraulic actuators of hydraulic actuator assembly 20, in order to adapt its displacement and therefore the flowrate of hydraulic fluid provided at outlet accordingly.

[0064] With reference to the preferred embodiment of the present invention illustrated in Figure 2 and 3, hydraulic arrangement 32 further comprises at least one solenoid-controlled valve or electro-valve 50 arranged along load sensing line 46, upstream the load sensing port of hydraulic pump 36.

[0065] More in detail, valve 50 is preferably interposed between load sensing line 46 and the load sending port of hydraulic pump 36, and is configured to modify, on command, the pressure signal provided to the load sensing port of hydraulic pump 36.

[0066] In use, valve 50 is configured be controllable to modify the load sensing signal provided to hydraulic pump 36.

[0067] In particular, valve 50 is preferably operatively interposed between supply line 39, load sensing line 46 and the load sensing port of hydraulic pump 36, and is configured to spill hydraulic fluid from supply line 39 and to provide a pressure signal to the load-sensing port of hydraulic pump 36 which depends on the actuation of the same valve 50.

[0068] In addition, valve 50 is preferably configured to provide a pressure signal towards the load-sensing port of the variable-displacement load-sensing hydraulic pump 36, which depends on the pressure within the load sending line 46.

[0069] With reference to the preferred embodiment illustrated in Figure 2 and 3, valve 50 is preferably a three-way two-positions valve. In addition, valve 50 is preferably a proportional valve.

[0070] The three ports of solenoid-controlled valve 50 are preferably fluidly connected to supply line 36 via a line 51, to tank 38 via a line 52 and to the load-sensing port of hydraulic pump 36 via a line 53.

[0071] Preferably, line 51 is further provided with a flow restrictor 55 to fluidly decouple supply line 39 with valve 50.

[0072] In the first position 50a, valve 50 is preferably configured to fluidly connect tank 38 and line 52 with line 53 and the load-sensing port of hydraulic pump 36, and to fluidly isolate supply line 39 and line 51.

[0073] In the second position 50b, valve 50 is preferably configured to fluidly supply line 39 and line 51 with line 53 and the load-sensing port of hydraulic pump 36, and to fluidly isolate tank 38 and line 52.

[0074] With reference to the exemplary embodiment illustrated in Figure 2 and 3, valve 50 preferably comprises at least one biasing means 57, for instance a spring, which is operatively connected to a first end of valve 50 and is configured to bias the same valve 50 in its first position 50a.

[0075] Preferably, valve 50 comprises at least one solenoid configured to control the opening of the same solenoid-controlled valve 50, and the pressure signal provided to the load-sensing port of the variable-displacement load-sensing hydraulic pump 36 depends on the actuation of the at least one solenoid.

[0076] More in detail, valve 50 further comprises a first solenoid 58 operatively connected to the first end of valve 50 and configured to bias the same valve 50 in its first position 50a.

[0077] In addition, valve 50 preferably further comprises a second solenoid 59 operatively connected to a second end of valve 50, opposite to the first end, and configured to bias the same valve 50 in its second position 50b.

[0078] With reference to the exemplary embodiment illustrated in Figures 2 and 3, valve 50 may be further hydraulically piloted.

[0079] More in detail, load sensing line 46 may be operatively connected to the second end of valve 50 and may be configured to exert a force on the spool of valve 50 configured to arrange this latter in its second position 50b.

[0080] In other words, the force exerted by load sensing line 46 on the spool of valve 50 may be concordant with the force exerted by solenoid 59 on the same spool.

[0081] In addition, valve 50 may further comprises a second pilot line 60, which branches off from line 53 downstream valve 50, is operatively connected to the first end of valve 50 and may be configured to exert a force on the spool of valve 50 configured to arrange this latter in its first position 50a.

[0082] In other words, the force exerted by pilot line 60 on the spool of valve 50 may be concordant with the force exerted by solenoid 58 on the same spool.

[0083] Preferably, pilot line 60 may be further provided with a flow restrictor 61.

[0084] With reference to the exemplary embodiment illustrated in Figure 2, work vehicle 1 preferably further comprises a user interface 65, such as a knob, a button, a slider, or portions of a touch-sensitive display, which are adapted to be manually actuated / handled by the work machine user to impart commands for controlling the operation of solenoid-controlled valve 50.

[0085] In addition, work vehicle 1 preferably comprises an electronic control unit 70, which is preferably connected to user interface 65 and to solenoid-controlled valve 50, and is provided with elaboration means configured to control the operation of the same valve 50 as function of the signals provided by user interface 65, as explained more in detail in the following.

[0086] Electronic control unit 70, on the basis of the commands imparted by the user by means of user interface 65, is configured to vary the pilot signal provided to the load sensing port of hydraulic pump 36, in order to vary accordingly the response of the same hydraulic pump 36.

[0087] This allows to adapt, for example dynamically, the response of hydraulic system 32 to the actuation of control levers 42.

[0088] In addition, the control of valve 50 may be further carried out in real time, during operation of work vehicle 1.

[0089] In particular, it is possible to control valve 50 to increase the pressure within line 53 to increase the flowrate provided at outlet by hydraulic pump 36. This increases the flowrate provided to the hydraulic actuators for a certain actuation of the control levers 42, thereby increasing the aggressiveness and the response of the same hydraulic actuators and increasing the velocity of movement of the related implement 10.

[0090] This in particular allows to increase the performances of work vehicle 1, since in response to the actuation of control levers 42 the speed of movements of the implements 10 themselves is increased.

[0091] For example, to increase the flowrate provided at outlet by hydraulic pump 36, electronic control unit 70 may be configured to energise solenoid 59 to move valve 50 towards its second position. Accordingly, the pressure within line 53 may be increase, for instance it may be raised to a value higher than the pressure actually present within load sensing line 46.

[0092] In addition, it is possible to control valve 50 to reduce the pressure within line 53 to reduce the flowrate provided at outlet by hydraulic pump 36. This reduces the flowrate provided to the hydraulic actuators for a certain actuation of the control levers 42, thereby reducing the aggressiveness and the response of the same hydraulic actuators and reducing the velocity of movement of the related implement 10.

[0093] This in particular allows to increase the controllability and the accuracy in positioning the implements 10, since in response to the actuation of control levers 42 the speed of movements of the implements 10 themselves is reduced.

[0094] For example, to reduce the flowrate provided at outlet by hydraulic pump 36, electronic control unit 70 may be configured to energise solenoid 58 to move valve 50 towards its first position. Accordingly, the pressure within line 53 may be reduces, for instance it may be reduced to a value lower than the pressure actually present within load sensing line 46.

[0095] The operation of the above-described work machine 1 is the following and is schematically represented in Figure 4.

[0096] In general, during use, hydraulic pump 36 provides at outlet a pressurized flow of hydraulic fluid and main control valves 40 are manually controlled by the user via control levers 42, to control accordingly the operation of the corresponding hydraulic actuator of hydraulic actuator assembly 10.

[0097] Such operation is schematically represented in Figure 4, wherein line P 1 represent the standard / unbiased ratio between the actuation of a control lever 42 and the flowrate provided to the corresponding hydraulic actuator of hydraulic actuator assembly 10. Clearly, the ratio between the actuation of a control lever 42 and the flowrate provided to the corresponding hydraulic actuator of hydraulic actuator assembly 10 depends, among the others, on the structure of the related main control valve 40, in particular on the size of the various orifices or ducts and the structure of the linkage connecting the control lever 42 to the corresponding main control valve 40.

[0098] In addition, supposing that the work vehicle driver desires to increase the controllability and the accuracy in positioning the implements 10, he may operate user interface 65 to power solenoid 58 of valve 50 and therefore reduce the pressure signal provided to the load sensing port hydraulic pump 36, to reduce the flowrate provided to hydraulic actuator in response to actuation of the control lever 42.

[0099] The above is schematically illustrated in curve P 2 depicted in Figure 4.

[0100] Lastly, supposing that the work vehicle driver desires to increase the aggressiveness of hydraulic arrangement 32, to have a faster and more ready response to actuation of control levers 42, he may operate user interface 65 to power solenoid 59 of valve 50 and therefore increase the pressure signal provided to the load sensing port hydraulic pump 36, to increase the flowrate provided to hydraulic actuator in response to actuation of the control lever 42.

[0101] The above is schematically illustrated in curve P3 depicted in Figure 4.

[0102] In view of the foregoing, the advantages of the work machine 1 according to the invention are apparent.

[0103] In particular, the presence of valve 50 allows to adapt dynamically the response of the hydraulic arrangement 32 to the actuation of control levers 42 without requiring further modification to the same hydraulic arrangement 32 and in particular without requiring the substitution of control levers 42.

[0104] This allows to improve the user experience of work machine 1 without requiring the work machine driver to get used to a completely new user interface, with the obvious advantages that this entails.

[0105] In addition, the presence of valve 50 and the associated user interface 65 allows to quickly and simply modify the response of hydraulic arrangement 32. For instance, by operating the user interface 65, it is possible to reduce or to increase the aggressiveness of hydraulic arrangement 32, thus allowing the controllability or speed of hydraulic arrangement 32 to be increased according to the work vehicle driver's momentary needs.

[0106] It is clear that modifications can be made to the work machine 1, which do not extend beyond the scope of protection defined by the claims.

[0107] For instance, hydraulic arrangement 32 may comprise a plurality of load sensing lines 46 and a plurality of valves 50 arranged in parallel to each other.

[0108] In particular, hydraulic arrangement 32 may comprise a first load sensing line 46 and a first valve 50 associated to a first group of hydraulic actuator, for example the actuators configured to control movement of moldboard 12, and a second load sensing line 46 and a second valve 50 associated to a second group of hydraulic actuator, for example the actuators configured the steering of front wheels 4a and the articulation of articulated frame 5.

[0109] In particular, the provision of more valves 50 allows to modify the response of the first group of actuators independently from the response of the second group of actuators, thereby further improving the user experience of work machine 1, as for example it is possible to increase the aggressiveness of the steering of work machine 1 while maintaining a really progressive and controllable actuation of the moldboard 12 or vice-versa.

Examples

Embodiment Construction

[0023]With reference to Figure 1, number 1 denotes, as a whole, a work machine, in particular an earth-moving machine such as a grader, also referred to as motor grader or road grader.

[0024]Work machine 1 comprises a body 2, which extends along a reference axis A and is movable on the ground by means of ground resting means 4, in particular wheels.

[0025]As per se known, body 2 preferably comprises an articulated frame 5 provided with a front portion 5a and a rear portion 5b, which are pivotally connected to each other so as to be able to rotate one with respect to the other about a vertical rotation axis R 1 . Preferably, the rear portion 5b carries the driver's cab 7 and the powertrain 8 of the same work machine 1, as per se known and therefore not further described.

[0026]The front portion 5a, on the other hand, has preferably an elongated shape and extends along reference axis A.

[0027]In addition, the front portion 5a is preferably arc-shaped or saddle-shaped with respect to a dir...

Claims

1. A work machine (1), in particular a grader, comprising: • a body (2) movable on the ground by means of ground resting means (3), • at least one implement (10, 12, 14, 16) movably carried by the body (2), • at least one hydraulic actuator (20, 22, 24, 26, 28, 30), which is operatively coupled to the implement (10, 12, 14, 16) and is adapted to control the movement of the implement (10, 12, 14, 16) with respect to the body (2), • a hydraulic arrangement (32) configured to provide pressurized hydraulic fluid to the hydraulic actuator (20, 22, 24, 26, 28, 30), said hydraulic arrangement (32) comprising: • a variable-displacement load-sensing hydraulic pump (36), which is configured to suck hydraulic fluid from a tank (38) and to provide at outlet a pressurized flow of the hydraulic fluid, • at least one main control valve (40), which is fluidly interposed between the outlet of the variable-displacement load-sensing hydraulic pump (36) and the hydraulic actuator (20, 22, 24, 26, 28, 30), and is configured to control the flow of pressurized hydraulic fluid fed towards the hydraulic actuator (20, 22, 24, 26, 28, 30), • a supply line (39) fluidly connecting the outlet of the variable-displacement load-sensing hydraulic pump (36) with the main control valve (40), • a control lever (42), which is operatively connected to the main control valve (40) and is adapted to be actuated to control the operation of the main control valve (40), • a load sensing line (46) fluidly connecting the outlet of main control valve (40) with the load-sensing port of the variable-displacement load-sensing hydraulic pump (36), and • a solenoid-controlled valve (50), which is fluidly interposed between the load sensing line (46) and the load-sensing port of the variable-displacement load-sensing hydraulic pump (36), and is configured to modify, on command, the pressure signal provided to the load sensing port of the variable-displacement load-sensing hydraulic pump (36).

2. Work machine according to claim 1, wherein said hydraulic arrangement (32) has a post-compensated configuration and comprises a pressure compensator (44) fluidly connected downstream the main control valve (40).

3. Work machine according to claim 1 or 2, wherein said solenoid-controlled valve (50) is fluidly interposed between the supply line (39), the load sensing line (46) and the load-sensing port of the variable-displacement load-sensing hydraulic pump (36), is configured to spill hydraulic fluid from the supply line (39) and is configured to provide a pressure signal towards the load-sensing port of the variable-displacement load-sensing hydraulic pump (36), which depends on the pressure within the load sending line (46).

4. Work machine according to claim 3, wherein the solenoid-controlled valve (50) comprises at least one solenoid (58, 59) configured to control the opening of the solenoid-controlled valve (50), and the pressure signal provided to the load-sensing port of the variable-displacement load-sensing hydraulic pump (36) depends on the actuation of the at least one solenoid (58, 59).

5. Work machine according to any of the preceding claims, wherein the solenoid-controlled valve (50) is a three-way valve, and the three ports of the solenoid-controlled valve (50) are fluidly connected to the supply line (36) via a first line (51), to the tank (38) via a second line (52) and to the load-sensing port of the variable-displacement load-sensing hydraulic pump (36) via a third line (53).

6. Work machine according to claim 5, wherein the solenoid-controlled valve (50) is a two-position valve and comprises a first end and a second end opposite to the first end, in a first position (50a), solenoid-controlled valve (50) is configured to fluidly connect the tank (38) with the load-sensing port of the variable-displacement load-sensing hydraulic pump (36), and to fluidly isolate the supply line (39), in a second position (50b), solenoid-controlled valve (50) is configured to fluidly isolate the tank (38) and to fluidly connect the supply line (39) with the load-sensing port of the variable-displacement load-sensing hydraulic pump (36).

7. Work machine according to claim 6, wherein the solenoid-controlled valve (50) comprises at least one biasing means (57), which is operatively connected to the first end of the solenoid-controlled valve (50) and is configured to bias the solenoid-controlled valve (50) in the first position (50a).

8. Work machine according to claim 6 or 7, wherein the solenoid-controlled valve (50) comprises a first solenoid (58) operatively connected to the first end of the solenoid-controlled valve (50) and configured to bias the solenoid-controlled valve (50) in the first position (50a), and a second solenoid (59) operatively connected to the second end of the solenoid-controlled valve (50) and configured to bias the solenoid-controlled valve (50) in the second position (50b).

9. Work machine according to claim 6, 7 or 8, wherein the load sensing line (46) is connected to the second end of the solenoid-controlled valve (50) and is configured to exert a force configured to arrange the solenoid-controlled valve (50) in the second position 50a.

10. Work machine according to any of claim from 6 to 9, wherein solenoid-controlled valve (50) comprises a pilot line (60), which branches off from the line (53) fluidly connecting the solenoid-controlled valve (50) with the load-sensing port of the variable-displacement load-sensing hydraulic pump (36), downstream the same solenoid-controlled valve (50), is operatively connected to the first end of the solenoid-controlled valve (50), and is configured to exert a force configured to arrange the solenoid-controlled valve (50)in the first position (50a).

11. Work machine according to any of the preceding claim, further comprising: a user interface (65) adapted to be actuated by the work machine user to impart commands for controlling the operation of the solenoid-controlled valve (50), and an electronic control unit (70), which is connected to the user interface (65) and to the solenoid-controlled valve (50) and is provided with elaboration means configured to control the operation of the solenoid-controlled valve (50) as function of the signals provided by the user interface (65).

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