EP4403708A1

EP4403708A1 - Improved system and method for controlling a rotatable upper frame of a work machine

Info

Publication number: EP4403708A1
Application number: EP24152253.1A
Authority: EP
Inventors: Francesco CHIOCCOLA
Original assignee: CNH Industrial Italia SpA
Current assignee: CNH Industrial Italia SpA
Priority date: 2023-01-17
Filing date: 2024-01-16
Publication date: 2024-07-24

Abstract

A method for controlling the rotation of an upper frame (2) of a work machine (1) comprising a lower frame carrying the ground-engaging wheels or tracks that allow motion of the work machine (1) with respect to the ground, the upper frame (2), which is carried by the lower frame in a rotatable manner; and a control system (3) configured to control the rotation of the upper frame (2) the respect to said lower frame;
the control system (3) comprises a hydrostatic transmission (4) driving the upper frame (2) in rotation and provided with a hydraulic pump (6) and a hydraulic motor (10), a control stage (14) interposed between the hydraulic pump (6) and the hydraulic motor (10) and controlling the flow of the fluid fed towards the hydraulic motor (10); a pilot stage (16) connected to the control stage (14) to control its operation; and sensor means (50) to measure the pressure of the hydraulic fluid fed towards the hydraulic motor (10);
the method allows to keep the rotation speed of the upper frame (2) within the limits set out by EN 474-5 regulation.

Description

TECHNICAL FIELD

The present invention relates to a system and to a method for controlling a rotatable upper frame of a work machine.
More in detail, the present invention relates to a system and to a method for controlling the rotation of a pivotable upper frame of a work machine, in particular an earth-moving machine such as an excavator, a digger or the like. Use to which the description below will make explicit reference without however losing in generality.

BACKGROUND OF THE INVENTION

As is known, work machines such as excavators, diggers, cranes and the like are usually provided with: a lower frame, which carries the wheels or tracks that allow motion of the work machine with respect to the ground; a pivotable upper frame, which is carried by the lower frame in a rotatable manner about a vertical rotation axis, and in turn carries an operator's cab and a hydraulically actuated arm; and a hydrostatic transmission, which is operatively interposed between the lower frame and the upper frame, and is configured to drive the upper frame in rotation with respect to the lower frame.
In addition, such work machines are usually provided with a brake assembly adapted to prevent the rotation of this latter.
Work machines field has been recently invested by the new European EN 474-5 regulation, in particular the new EN 474-5:2022 regulation, which requires to regulate/control the maximum pivoting speed of the upper frame of the aforementioned work machine in order to ensure that it does not exceeds a maximum safety threshold.
Such safety threshold is determined according to the aforementioned EN 474-5 regulation and depends, among other things, on the brake assembly configuration and on the moment of inertia of the work machine.
Unfortunately, the moment of inertia of the work machine may vary depending on the bucket and/or equipment temporarily attached on the arm of the work machine.
Therefore, it may happen that, during work machine operation, the maximum pivoting speed of the upper frame may exceeds the safety threshold set out by EN 474-5 regulation, in particular when very heavy buckets and/or equipment are attached to the hydraulically actuated arm.
In view of the above, the need is felt to provide a method and a system adapted to control the rotation of the upper frame of the aforementioned work machines in order to meet the requirements of new EN 474-5 regulation, without increasing the burdens for the work machine operator and at the same time increasing its safety.
An aim of the present invention is to satisfy the above-mentioned needs in an optimized and cost effective manner.

SUMMARY OF THE INVENTION

The aforementioned aims are reached by a method and by a work machine as claimed in the appended set of claims.

BRIEF DESCRIPTION OF DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described in the following, by way of a non-limiting example, with reference to the attached drawings, wherein:

Figure 1 is a schematic representation of a work machine according to the present invention; and
Figures 2, 3, 4 and 5 are schematic representations of the work machine illustrated in Figure 1 according to as many alternative embodiments.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1, number 1 denotes as a whole a work machine or vehicle or machinery, such as an earth-moving machine like an excavator, a digger or the like.
More in detail, work machine 1 comprises: a lower frame (not illustrated) or undercarriage, which carries the ground-engaging wheels or tracks that allow motion of work machine 1 with respect to the ground; and an upper frame 2 or superstructure, which is carried in a rotatable manner by lower frame preferably about a rotation axis orthogonal to the advancing plane of work machine 1 and, in turn, carries a hydraulically actuated arm and preferably also an operator's cab.
In addition, work machine 1 comprises also a control system 3, which is configured to control the rotation of upper frame 2 with respect to the lower frame about said rotation axis.
More in detail, control system 3 preferably comprises a hydrostatic transmission 4, which is preferably carried by the upper frame, and is adapted to drive upper frame 2 in rotation about said rotation axis with respect to the lower frame.
In particular, hydrostatic transmission 4 is preferably an open-circuit hydrostatic transmission.
In addition, as known, work machine 1 is provided with a brake assembly, which is adapted to prevent the rotation of upper frame 2. In particular, brake assembly is preferably configured to be operated when upper frame 2 is still, so as to hold this latter in a stationary condition.
With reference to the exemplary embodiment illustrated in Figure 1, hydraulic transmission 4 preferably comprises a hydraulic pump 6, which is adapted to suck fluid from a tank 7 carried by work machine 1 and to provide at outlet a pressurized flow of hydraulic fluid.
Preferably, hydraulic pump 6 is carried by an engine 8 of work machine 1, such as an internal combustion engine, in order to be driven into rotation.
In addition, hydraulic pump 6 is preferably a variable displacement pump, in particular a high-pressure variable displacement pump.
With reference to the exemplary embodiment illustrated in Figure 1, hydrostatic transmission 4 comprises also a hydraulic motor 10, which is fluidly connected to hydraulic pump 6 and is adapted to be driven in rotation by the pressurized hydraulic fluid provided at outlet by hydraulic pump 6, in order to drive upper frame 2 in rotation about said rotation axis.
In particular, hydraulic motor 10 is preferably mechanically connected to a slewing ring 11 carried by upper frame 2 by means of a gearbox assembly 12, in a manner per se known and therefore not further described.
Preferably, hydraulic motor 10 is a bidirectional or reversible hydraulic motor, in particular a fixed-displacement bidirectional hydraulic motor.
With reference to the exemplary embodiment illustrated in Figure 1, in addition, control system 3 comprises: a control stage 14, which is operatively interposed between the hydraulic pump 6 and hydraulic motor 10 and is configured to control/regulate the flow of pressurized fluid fed from hydraulic pump 6 towards hydraulic motor 10, in order to control the rotation direction and/or the angular velocity of the same hydraulic motor 10; and a pilot stage 16, which is operatively connected to control stage 14 and is configured to control the operation of control stage 14 according to control signals imparted by an operator of work machine 1.
More in detail, control stage 14 is preferably fluidly connected to hydraulic motor 10 by means of a pair of hydraulic feed lines 15 and 17, each of which is connected to a correspondent inlet of hydraulic motor 10.
Accordingly, by controlling control stage 14 to feed the pressurized hydraulic fluid along hydraulic line 15 or along hydraulic line 17, it is possible to control the rotation direction of hydraulic motor 10.
Control stage 14 is preferably hydraulically operated and preferably comprises valve means 18, in particular hydraulically actuated valve means 18, which are operatively interposed between hydraulic pump 6 and hydraulic motor 10, and are configured to control/regulate the flow of pressurized fluid fed towards hydraulic motor 10 from hydraulic pump 6.
For example, valve means 18 may comprise a four-way three-position hydraulically actuated proportional valve 20.
In a first neutral position, schematically represented in Figure 1, valve 20 is configured to prevent the pressurized fluid provided at outlet by hydraulic pump 6 to flow towards hydraulic motor 10 and to put the outlet of hydraulic pump 6 in fluid communication with tank 7.
In a second and in a third operative position, on the other hand, valve 20 is configured to put the outlet of hydraulic pump 6 in fluid communication with a first or with a second inlet of hydraulic motor 10 respectively via hydraulic line 15 or 17, in order to drive the same hydraulic motor 10 in rotation alternatively in a first direction or in a second direction, opposite to the first one.
More in detail, in said second operative position, valve 20 is configured to put the outlet of hydraulic pump 6 in fluid communication with hydraulic line 15 and with said first inlet of hydraulic motor 10.
In said third operative position, on the other hand, valve 20 is configured to put the outlet of hydraulic pump 6 in fluid communication with hydraulic line 17 and with said second inlet of hydraulic motor 10.
Preferably, valve 20 is configured to be biased towards the first neutral position at rest. In addition, valve 20 may be actuated/displaced in said second or third operative position by pilot stage 16, in particular, by the hydraulic pressure applied by pilot stage 16 on valve 20.
With reference to the example shown in Figure 1, in addition, control system 3 preferably comprises a source of fluid 22, which is adapted to feed a flow of pressurized hydraulic fluid towards pilot stage 16.
More in detail, source of fluid 22 preferably comprises a second hydraulic pump 24 carried by engine 8, in particular a fixed displacement low-pressure hydraulic pump.
Pilot stage 16 is preferably interposed between source of fluid 22 and control stage 14.
More in detail, pilot stage 16 is preferably fluidly connected to control stage 14 by means of a first pilot line 26 and a second pilot line 27 and is preferably configured to provide at output a hydraulic pilot signal to control the actuation of control stage 14.
In particular, hydraulic pilot lines 26 and 27 are preferably connected to valve means 18 and are adapted to exert/apply a hydraulic pressure on the same valve means 18 in order to actuate it.
More precisely, hydraulic pilot lines 26 and 27 are preferably connected to valve 20 and are adapted to exert a hydraulic pressure on the same valve 20 in order to arrange/ displace the same valve 20 towards said first operative position or towards said second operative position respectively.
With reference to the exemplary embodiment illustrated in Figure 1, pilot stage 16 preferably comprises valve means 30, which are adapted to divert/route the flow of pressurized hydraulic fluid provided at outlet by source 22 towards first pilot line 26 or towards second pilot line 27, in order to provide a hydraulic pilot signal adapted to actuate valve means 18.
Valve means 30 preferably comprises a pair of hydraulic valves 31 and 32, which are adapted to be operated to put hydraulic pilot 26 or hydraulic pilot line 27 in fluid communication with source 22, in order to arrange/displace valve 20 toward said first or second operative position.
For example, valves 31 and 32 may comprise proportional three-way two-position hydraulic valves.
In addition, control system 3 preferably comprises an input device 34, such as a lever or a joystick, which may be carried within the operator's cab and is configured to be handled by a work machine 1 operator in order to impart control signals for controlling the operation of pilot stage 16.
More in detail, input device 34 is operatively connected to valve means 30 and is adapted to be operated by work machine operator to actuate the same valve means 30 in order to pressurize hydraulic pilot line 26 or hydraulic pilot line 27 and actuate control stage 14 accordingly.
With reference to the exemplary embodiment illustrated in Figure 1, control system 3 may further comprise a limiting-pressure or relief valve 38, which is operatively interposed between hydraulic pump 6 and control stage 14, and is configured to limit the maximum pressure of the hydraulic fluid provided at outlet by hydraulic pump 6 and fed towards control stage 14.
Similarly, control system 3 may further comprise a further limiting-pressure or relief valve 40, which is operatively interposed between source of fluid 22 and pilot stage 16, and is configured to limit the maximum pressure of the hydraulic fluid provided at outlet by source of fluid 22 and fed towards pilot stage 16.
With reference to the exemplary embodiment shown in Figure 1, in addition, hydrostatic transmission 4 may be also configured in order to be able to reduce, during operation, the rotation speed of upper frame 2, i.e. to brake upper frame 2. Preferably, the braking operation of upper frame 2 provided by hydrostatic transmission is a passive braking operation.
More in detail, during braking operation of upper frame 2, valve means 18 are preferably closed, meaning that valve 20 is in the first neutral position, and the pressurized hydraulic fluid fed towards hydraulic motor 10 is trapped between the same hydraulic motor 10 and valve means 18, within hydraulic feed line 15 and hydraulic feed line 17.
Accordingly, during rotation of upper frame 2, the rotation of hydraulic motor 10 due to inertial forces causes an increase in the pressure of the hydraulic fluid trapped within the hydraulic feed line 15 or 17 opposite to the rotation direction of hydraulic motor 10 and an increase in the braking torque provided by hydraulic motor 10.
Indeed, the higher is the backpressure of the hydraulic fluid trapped within the hydraulic feed line 15 or 17 opposite to the rotation direction of hydraulic motor 10, the higher will be the braking torque provided by hydraulic motor 10.
In addition, hydrostatic transmission 4 may be provided with a pair of limiting pressure or relief valves 13, which are operatively interposed between hydraulic pump 6 and hydraulic motor 10, along hydraulic feed line 15 and hydraulic feed line 17 respectively, and are configured to discharge/route to tank 7 the pressurized hydraulic fluid trapped within hydraulic feed lines 15 and 17 when the pressure of this latter exceeds a predetermined pressure threshold.
Relief valves 13, in particular, are preferably configured to be normally closed and are adapted to be opened during braking operation of upper frame 2, so that the pressurized hydraulic fluid trapped within hydraulic feed lines 15 and 17 may be routed to tank 7.
More in detail, relief valve 13 are preferably configured to be normally closed, and to open when the pressure of the hydraulic fluid within hydraulic feed line 15 or hydraulic feed line 17 exceeds said predetermined threshold.
Accordingly, during upper frame 2 braking operation, relief valves 13 may limit the maximum pressure of the hydraulic fluid reached within hydraulic feed line 15 or hydraulic feed line 17 opposite to the rotation direction of hydraulic motor 10.
With reference to the exemplary embodiment shown in Figure 1, in addition, control system 3 preferably comprises also electrically actuated valve means 42, which are operatively interposed between pilot stage 16 and control stage 14 and are configured to control/regulate/limit the pressure of the hydraulic fluid fed from pilot stage 16 towards control stage 14, in order to control the actuation of control stage 14 accordingly.
More in detail, electrically actuated valve means 42 preferably comprises a pair of solenoid-controlled proportional hydraulic valves 43 and 44, which are arranged respectively on hydraulic pilot line 26 and hydraulic pilot line 27 and are configured to regulate/limit the hydraulic pressure exerted by the same hydraulic pilot lines 26 and 27 on valve means 18.
In even more detail, solenoid-controlled proportional valves 43 and 44 preferably are two-way two-position solenoid -controlled proportional valves.
With reference to the exemplary embodiment illustrated in Figure 1, in particular, valves 43 and 44 are preferably arranged immediately upstream valve 20 on hydraulic pilot lines 26 and 27 respectively, and they are adapted to limit/regulate the pilot pressure exerted by the same hydraulic pilot lines 26 and 27 on valve 20, in order to control the actuation of control stage 14 accordingly.
Preferably, valves 43 and 44 are configured to be operated between an open position and a closed position.
In said open position, valves 43 and 44 put pilot stage 16 in fluid communication with control stage 14 respectively.
In said closed position, on the other hand, valves 43 and 44 prevent fluid communication between pilot stage 16 and control stage 14 and route the hydraulic fluid fed by source 22 and pilot stage 16 to tank 7.
In addition, valves 43 and 44 are preferably configured to be biased towards said open position at rest, and they may be actuated in said closed positions by their respective solenoid.
With reference to the exemplary embodiment illustrated in Figure 1, in addition, control system 3 further comprises sensor means 50, which are configured to detect/measure the pressure of the hydraulic fluid fed from control stage 14 to hydraulic motor 10.
More in detail, sensor means 50 preferably comprises a pair of pressure sensors 51 and 52, which are configured to detect/measure the pressure of the hydraulic fluid within hydraulic feed lines 15 and 17 respectively.
In other words, pressure sensors 51 and 52 are configured to detect the pressure of the pressurized hydraulic fluid fed towards hydraulic motor 10.
With reference to the exemplary embodiment illustrated in Figure 1, in addition, sensor means may further comprise a pair of pressure sensors 54 and 55, which are respectively connected to hydraulic pilot line 26 and to hydraulic pilot line 27, downstream pilot stage 16, and are adapted to measure/determine the pressure of the hydraulic fluid within these latter.
In addition, with reference to the exemplary embodiment illustrated in Figure 1, control system 3 further comprises an electronic control unit 56, which is operatively connected at least to sensor means 50, and comprises elaboration means configured to retrieve data from sensor means 50 related to the pressure of hydraulic fluid fed towards hydraulic motor 10 and to elaborate these latter to provide control signals adapted to control the rotational velocity of upper frame 2 according to the control logic that is described more in detail in the following.
In particular, with reference to the disclosed embodiment, electronic control unit 56 is configured to determine/estimate the inertia of the upper frame 2 based on the data retrieved from sensor means 50.
Indeed, the pressure of the hydraulic fluid fed towards hydraulic motor 10 is associate to the inertia of upper frame 2.
More in detail, during upper frame 2 rotation, and in particular during upper frame 2 acceleration, the higher is the inertia of upper frame 2 the higher will be the pressure of hydraulic fluid fed towards hydraulic motor 10, as it will be required a higher torque to rotate upper frame 2. Furthermore, the higher inertia of upper frame 2 will increase the time needed to get the requested speed, thereby varying the acceleration of the latter.
Accordingly, electronic control unit 56 is configured to determine/estimate the inertia of the upper frame 2 as function of the pressure of hydraulic fluid within hydraulic motor 10.
In addition, electronic control unit 56 is preferably configured to determine/calculate the maximum allowable rotational velocity of upper frame 2 according to the EN 474-5 regulation, in particular the EN 474-5:2022 regulation.
Indeed, EN 474-5 regulation sets out a maximum allowable rotational velocity of upper frame 2, which depends at least on the configuration of the aforementioned brake assembly and on the inertia of upper frame 2 of work machine 1.
More in detail, electronic control unit 56 is preferably configured to determine/calculate, based on the estimated inertia of upper frame 2 and preferably also on said brake assembly configuration, the maximum allowable rotational velocity of upper frame 2 that meets the requirements of EN 474-5 regulation, in particular of EN 474-5:2022 regulation.
In even more detail, electronic control unit 56 is preferably configured to determine/calculate, based on the estimated inertia of upper frame 2 and preferably also on said brake assembly configuration, the maximum allowable rotational velocity of upper frame 2 that allows to not exceed the maximum deceleration swing angle set out by EN 474-5 regulation during upper frame 2 deceleration.
In other words, the maximum allowable rotational velocity set out by EN 474-5 regulation depends on the brake assembly 3 configuration and on the inertia of upper frame 2.
In addition, electronic control unit 56 is preferably configured in order to limit/control the flowrate of the hydraulic fluid fed towards hydraulic motor 10, such that the rotational velocity of upper frame 2 about its rotation axis does not exceed said maximum allowable rotational velocity.
More in detail, according to the disclosed embodiment, electronic control unit 56 is preferably operatively connected to valve means 42 and is preferably configured to provide control signals to the same valve means 42 adapted to limit/regulate the hydraulic pilot pressure applied on control stage 14, in order to limit/control the flowrate of hydraulic fluid fed towards hydraulic motor 10 such that the rotational velocity of hydraulic motor 10 and accordingly of upper frame 2 does not exceed said maximum allowable rotational velocity.
In other words, electronic control unit 56 is preferably configured to provide control signals to valve means 42 adapted to limit/regulate the hydraulic pilot pressure applied valve means 18, in order to limit/regulate the actuation of the same valve means 18 and control the rotational velocity of upper frame 2 accordingly.
In addition or alternative, electronic control unit 56 may be operatively connected to hydraulic pump and may be configured to provide control signals to the same hydraulic pump 6 adapted to control its displacement, in order to limit/control the flowrate of hydraulic fluid fed towards hydraulic motor 10 such that the rotational velocity of hydraulic motor 10 and accordingly of upper frame 2 does not exceed said maximum allowable rotational velocity.
Moreover, electronic control unit 56 may be further configured to determine/calculate the rotational velocity of hydraulic motor 10 and of upper frame 2 based on the flowrate of hydraulic fluid fed towards the same hydraulic motor 10, in a manner per se known and therefore not further described.
Electronic control unit 56 may be further connected to pressure sensors 54 and 55, and may be configured to retrieve data related to the pressure of hydraulic fluid within hydraulic pilot line 26 and within hydraulic pilot line 27, in order to determine the direction of actuation of input device 34.
The operation of the above-described control system 3 is the following.
At first, to rotate upper frame 2, work machine 1 operator handles input device 34 to actuate pilot stage 16, meaning to actuate valve assembly 30.
Then, according to the actuation of pilot stage 16, hydraulic pilot pressure within hydraulic pilot line 26 or within hydraulic pilot line 27 increases and control stage 14 is actuated accordingly.
Based on the actuation of control stage 14, a flow of pressurized hydraulic fluid is fed towards hydraulic motor 10 via hydraulic feed line 15 or via hydraulic feed line 17, in order to drive the same hydraulic engine 10 in rotation.
Clearly, the rotational velocity of hydraulic motor 10 is directly proportional to the flowrate of hydraulic fluid fed towards the same hydraulic motor 10.
Then, electronic control 56 unit retrieves from sensor means 50 data related to the pressure of the hydraulic fluid fed towards hydraulic motor 10.
Based on the said data, electronic control unit 56 calculates the inertia of upper frame 2 and the maximum allowable rotational velocity of upper frame 2 to meet the requirements of EN 474-5 regulations.
Lastly, electronic control unit 56 limits/regulates the flowrate of the hydraulic fluid fed towards hydraulic motor 10 such that the rotational velocity of upper frame does not exceed said maximum allowable rotational velocity.
More in detail, according to the disclosed embodiment, electronic control unit 56 preferably actuates valve means 42 to limit/regulate the hydraulic pilot pressure applied on control stage 14 and limit/control the flowrate of hydraulic fluid fed towards hydraulic motor 10 accordingly.
Alternatively or in addition, electronic control unit 56 controls the displacement of hydraulic pump 6 to limit/control the flowrate of hydraulic fluid it provides at outlet accordingly.
In view of the above, the invention is furthermore directed to a method for controlling the pivotable upper frame 2 of the described work machine 1, which comprises at least the following steps:

i) operating pilot stage 16 according to the control signals imparted by the operator of work machine 1 on input device 34, in order to actuate control stage 14 and feed a flow of pressurized hydraulic fluid towards hydraulic motor 10;
ii) detecting/measuring the pressure of hydraulic fluid fed towards hydraulic motor 10;
iii) calculating/estimating a value associated to upper frame 2 inertia on the basis of the pressure of hydraulic fluid fed towards hydraulic motor 10;
iv) calculating/determining a maximum allowable rotational velocity of upper frame 2, according to the value of the inertia of upper frame 2 calculated at step iii); and
v) controlling/operating control system 3 so that it that the rotational velocity of upper frame 2 does not exceed said maximum allowable rotational velocity.

In particular, said step iii) preferably comprises the step of controlling/regulating the flowrate of the hydraulic fluid fed towards hydraulic motor 10 such that the rotational velocity of upper frame 2 does not exceed said maximum allowable rotational velocity.
More in detail, said step iii) preferably comprises the step of calculating/determining the maximum allowable rotational velocity of upper frame 2 that meets the requirement of EN 474-5 regulation, in particular 474-5:2022 regulation.
In even more detail, said step iii) preferably comprises the step of calculating/determining, based on the estimated inertia of upper frame 2 and preferably also on said brake assembly configuration, the maximum allowable rotational velocity of upper frame 2 that allows to not exceed the maximum deceleration swing angle set out by EN 474-5 regulation during upper frame 2 deceleration.
In addition, according to the disclosed embodiment, said step iv) preferably comprises the step of controlling valve means 42 in order to limit/regulate the hydraulic pilot pressure applied on control stage 14, and limit/control the flowrate of hydraulic fluid fed towards hydraulic motor 10 accordingly, such that the rotational velocity of hydraulic motor 10 and accordingly of upper frame 2 does not exceed said maximum allowable rotational velocity.
In other words, said step iv) preferably comprises the step of controlling valve means 42 in order to limit/regulate the hydraulic pilot pressure applied valve means 18, to control the rotational velocity of upper frame 2 accordingly.
In addition or alternative, said step iv) preferably comprises the step of controlling the displacement of hydraulic pump 6 in order to limit/control the flowrate of hydraulic fluid fed towards hydraulic motor 10, such that the rotational velocity of hydraulic motor 10 and accordingly of upper frame 2 does not exceed said maximum allowable rotational velocity.
In view of the foregoing, the advantages of a control system 3 and a control method for a work machine 1 according to the present invention are apparent.
In fact, thanks to the proposed control system and method, it is possible to control automatically the rotational velocity of upper frame 2 so that it always meets the requirement of new EN 474-5 regulation.
More in detail, according to the proposed control system and method, it is possible to evaluate/estimate automatically the inertia of the upper frame 2 during work 1 machine operation and at the same time determine the maximum allowable rotational velocity of upper frame 2 that meets the requirement of new EN 474-5 regulation.
Therefore, thanks to the proposed invention, it is possible to adapt automatically the work machine 1 operative parameters, such as maximum hydraulic pump 6 displacement, maximum pilot pressure of control stage 14 and/or maximum rotational velocity of upper frame 2, to the bucket or equipment temporarily attached to the hydraulically operated arm, in order to meet the requirement of new EN 474-5 regulation and at the same time exploit the maximum performances of work machine 1, i.e. allow the upper frame 2 to rotate up to the maximum rotational velocity of upper frame 2 allowed by new EN 474-5 regulation.
In addition, work machine 1 operator is not required to set manually the operative parameters of work machine 1 according to the bucket or equipment temporarily attached to the hydraulically operated arm, with all the benefits that this entail.
Indeed, this increase the comfort, the safety and the user-friendliness of work machine 1, as there is no need to set manually the operative parameters of work machine 1 and it is ruled out the possibility of human errors when setting the operative parameters of work machine 1.
It is clear that modifications can be made to the described apparatus and method, which do not extend beyond the scope of protection defined by the claims.
For instance, with reference to Figure 2, according to a different embodiment, control system 3 may be further provided with an angular velocity sensor 100, which is operatively coupled to upper frame 2 and is configured to detect/measure the angular velocity of this latter.
Electronic control unit 56 may be operatively connected to angular velocity sensor 100 in order to be able to retrieve data related to the rotational velocity of upper frame 2 from this latter.
More in detail, electronic control unit 56 may be configured to determined, on the basis of the data provided by angular velocity sensor 100, the angular acceleration of upper frame 2.
In addition, with reference to the Figure 3, according to a different embodiment, hydraulic motor 10 may be a variable displacement hydraulic motor, in particular a reversible or bidirectional variable displacement hydraulic motor.
Electronic control unit 56 may be operatively connected to hydraulic motor 10 and may be configured to control its displacement in order to control rotation speed of hydraulic motor 10 and of upper frame 2 accordingly, in order to implement the control method above described.
In addition, always with reference to Figure 3, control system 3 may further comprise an acceleration sensor 110, which is operatively connected to upper frame 2 and is configured to detect/measure the angular acceleration of this latter.
Electronic control unit 56 may be operatively connected to acceleration sensor 110 in order to be able to retrieve data related to the angular acceleration of upper frame 2 from this latter.
With reference to Figure 4, according to a further alternative embodiment, control system 3 may be provided with two solenoid-controlled proportional limiting-pressure or relief valves 113, which are operatively interposed between hydraulic pump 6 and hydraulic motor 10, along hydraulic feed line 15 and hydraulic feed line 17, and are adapted to operate during upper frame 2 braking operation, as described with reference to relief valves 13.
Electronic control unit 56 may be operatively connected to relief valves 113 and may be configured to control their operation during upper frame 2 braking operation, in order to control the rotational velocity of upper frame 2 so that it does not exceed said maximum allowable rotational velocity.
More in detail, electronic control unit 56 may be configured to set the threshold pressure of relief valves 113 involved in the braking operation, i.e. the relief valve 113 located on the hydraulic feed line 15 or 17 opposite to the rotation direction of hydraulic motor 10, so as to increase the maximum backpressure allowed within such hydraulic line and increase the braking torque provided by hydraulic motor 10 accordingly.
The method according to the present invention may comprise the step of setting the threshold pressure of relief valves 113 in order to vary the maximum backpressure allowed within hydraulic feed line 15 or hydraulic feed line 17 and vary the braking torque provided by hydraulic motor 10 accordingly.
In addition, with reference to Figure 5, according to a different embodiment, control system 3 may be provided with a brake assembly 200, which is operatively interposed between hydraulic motor 10 and upper frame 2 and is configured to provide a braking torque adapted to reduce the rotational velocity of upper frame 2.
More in detail, brake assembly 200 may be carried by hydraulic motor 10, meaning that it may be arranged immediately upstream gearbox assembly 12.
Electronic control unit 56 may be operatively connected to brake assembly 200 and may be configured to control its operation so that the braking angle does not exceed a maximum allowable value and/or so that the rotational velocity of upper frame 2 does not exceed said maximum allowable rotational velocity.
Accordingly, the method of the present invention may comprise the step of controlling brake assembly 200 so that the rotational velocity of upper frame 2 does not exceed said maximum allowable rotational velocity
The technical effect associated to the presence of solenoid-controlled proportional relief valves 113 and/or brake assembly 200 is related to the possibility of increasing the maximum allowable rotational velocity calculated according to EN 474-5 regulation and therefore to not limit the performances of the work machine 1, meaning without reducing the upper frame 2 maximum allowable rotational velocity, as said maximum allowable rotational velocity set out by EN474-5 regulation increases with the increased braking performances.
In addition, according to a different embodiment, not illustrated, pilot stage 16 may not comprise valve means 30 connected to input device 34.
Input device 34, in turn, may be operatively connected to electronic control unit 56 in order to impart control signals adapted to control the actuation of valve means 42.
In addition, electronic control unit 56 may be configured to control the actuation of valve means 42 according to the control signals provided by input device 34, in order to operate control stage 14 accordingly.
In other words, input device 34 may be configured to provide electronic control signals to electronic control unit 56, and this latter may be configured to control solenoid-controlled proportional hydraulic valves 43 and 44 in order to operate control stage 14 according to the electronic control signals provided by work machine 1 driver via input device 34.
In particular, according to this embodiment, input device 34 may comprise a joystick or a lever electrically connected to electronic control unit 56.
In addition, during braking operation of upper frame 2, electronic control unit 56 may be configured to actuate solenoid-controlled proportional hydraulic valve 43 or 44 in order to arrange valve 20 in said second or third operative position respectively, in order to fluidly connect the outlet of hydraulic pump 6 with the hydraulic feed line 15 or 17 opposite to the rotation direction of hydraulic motor 10.
Accordingly, hydraulic pump 6 may feed a flow of pressurized hydraulic flow towards hydraulic motor 10 along the hydraulic feed line 15 or 17 opposite to the rotation direction of hydraulic motor 10, in order to rapidly increase the backpressure of this latter within the correspondent hydraulic fluid line 15 or 17 and the braking torque provided by hydraulic motor 10.

Claims

A method for controlling the rotation of an upper frame (2) of a work machine (1),
said work machine (1) comprising:
• a lower frame, which carries the ground-engaging means that allow motion of said work machine (1) with respect to the ground;

• said upper frame (2), which is carried by said lower frame in a rotatable manner; and

• a control system (3), which is configured to control the rotation of said upper frame (2) with respect to said lower frame;

said control system (3) comprising:
• a hydrostatic transmission (4), which is adapted to drive said upper frame (2) in rotation about said lower frame (2), and comprises a hydraulic pump (6) adapted to provide at outlet a flow of pressurized hydraulic fluid, and a hydraulic motor (10), which is fluidly connected to said hydraulic pump (6) and is adapted to drive said upper frame (2) in rotation with respect to said lower frame;

• a control stage (14), which is operatively interposed between said hydraulic pump (6) and said hydraulic motor (10) and is configured to control the flow of said pressurized hydraulic fluid fed from said hydraulic pump (6) towards said hydraulic motor (10);

• a pilot stage (16), which is operatively connected to said control stage (14) and is configured to control the operation of said control stage (14) according to control signals imparted by an operator of said work machine (1); and

• sensor means (50), which are configured to measure the pressure of the hydraulic fluid fed towards said hydraulic motor (10);

said method comprising the steps of:
i) operating said pilot stage (16) according to control signals imparted by an operator of said work machine (1), in order to actuate said control stage (14) and feed a flow of said pressurized hydraulic fluid towards said hydraulic motor (10);

ii) measuring the pressure of said pressurized hydraulic fluid fed towards said hydraulic motor (10);

iii) determining a value associated to the inertia of said upper frame (2) on the basis of the pressure of said pressurized hydraulic fluid fed towards said hydraulic motor (10);

iv) calculating a maximum allowable rotational velocity for said upper frame (2) according to the value of the inertia of said upper frame (2); and

v) controlling said control system (3) so that the rotational velocity of said upper frame (2) does not exceed said maximum allowable rotational velocity.
Method according to claim 1, wherein said step v) comprises the step of controlling the flowrate of said hydraulic fluid fed towards said hydraulic motor (10) such that the rotational velocity of said upper frame (2) does not exceed said maximum allowable rotational velocity.
Method according to claim 1 or 2, wherein said maximum allowable rotational velocity is calculated according to the EN 474-5 regulation, in particular according to the EN 474-5:2022 regulation.
Method according to claim 1, 2 or 3, wherein said step v) comprises the step of controlling the displacement of said hydraulic pump (6) in order to control the flowrate of said hydraulic fluid fed towards said hydraulic motor (10).
Method according to any of the preceding claims, wherein:
said control stage (14) comprises first hydraulically actuated valve means (18) operatively interposed between said hydraulic pump (6) and said hydraulic motor (10);

said pilot stage (16) comprises second valve means (30) which are operatively interposed between a source of pressurized hydraulic fluid (22) and said first hydraulically actuated valve means (18), are fluidly connected to said first hydraulically actuated valve means (18) by means of a pair of hydraulic pilot lines (26, 27), and are configured to provide at outlet a hydraulic pilot signal adapted to actuate said first hydraulically actuated valve means (18); and

said control system (3) comprises third electrically actuated valve means (42), which are operatively interposed between said pilot stage (16) and said control stage (14), and are adapted to regulate said hydraulic pilot signal;

said step v) comprising the step of controlling said valve means (42) in order to control the hydraulic pilot pressure applied on control stage (14) and to control the flowrate of said hydraulic fluid fed towards said hydraulic motor (10).
Method according to any of the preceding claims, wherein said step v) comprises the step of braking said upper frame (2), so that the rotational velocity of said upper frame (2) does not exceed said maximum allowable rotational velocity.
A work machine (1) comprising:
• a lower frame, which carries the ground-engaging means that allow motion of said work machine (1) with respect to the ground;

• an upper frame (2), which is carried by said lower frame in a rotatable manner; and

• a control system (3), which is configured to control the rotation of said upper frame (2) with respect to said lower frame;
said control system (3) comprising:
• a hydrostatic transmission (4), which is adapted to drive said upper frame (2) in rotation about said lower frame (2), and comprises a hydraulic pump (6) adapted to provide at outlet a flow of pressurized hydraulic fluid, and a hydraulic motor (10), which is fluidly connected to said hydraulic pump (6) and is adapted to drive said upper frame (2) in rotation with respect to said lower frame;

• a control stage (14), which is operatively interposed between said hydraulic pump (6) and said hydraulic motor (10) and is configured to control the flow of said pressurized hydraulic fluid fed from said hydraulic pump (6) towards said hydraulic motor (10);

• a pilot stage (16), which is operatively connected to said control stage (14) and is configured to control the operation of said control stage (14) according to control signals imparted by an operator of said work machine (1);

• sensor means (50), which are configured to measure the pressure of the hydraulic fluid fed towards said hydraulic motor (10); and

• an electronic control unit (56), which is operatively connected at least to said sensor means (50) and comprises elaboration means, which are configured to retrieve data from sensor means (50) related to the pressure of the hydraulic fluid fed towards said hydraulic motor (10) and to carry out the method according to any of the preceding claims.
Work machine according to claim 7, wherein said control stage (14) comprises first hydraulically actuated valve means (18), which are operatively interposed between said hydraulic pump (6) and said hydraulic motor (10).
Work machine according to claim 8, wherein said pilot stage (16) comprises second valve means (30), which are operatively interposed between a source of pressurized hydraulic fluid (22) and said first hydraulically actuated valve means (18), are fluidly connected to said first hydraulically actuated valve means (18) by means of a pair of hydraulic pilot lines (26, 27), and are configured to provide at outlet a hydraulic pilot signal adapted to actuate said first hydraulically actuated valve means (18).
Work machine according to claim 9, wherein said control system (3) comprises third electrically actuated valve means (42), which are operatively interposed between said pilot stage (16) and said control stage (14), and are adapted to regulate said hydraulic pilot signal.
Work machine according to claim 10, wherein said third electrically actuated valve means (42) comprises two solenoid-controlled proportional hydraulic valves (43) and (44), which are arranged respectively on said hydraulic pilot line (26) and said hydraulic pilot line (27), and are configured to regulate the hydraulic pressure exerted by the same hydraulic pilot lines (26, 27) on said first hydraulically actuated valve means (18).
Work machine according to any of claims from 7 to 11, wherein said control system (3) comprises an angular velocity sensor (100), which is configured to measure the angular velocity of said upper frame (2);
said electronic control unit (56) being operatively connected to said sensor (100) in order to retrieve data related to the angular velocity of said upper frame (2) from this latter.
Work machine according to claim 8, wherein said control system (3) comprises second electrically actuated valve means (42), which are operatively interposed between a source of pressurized hydraulic fluid (22) and said first hydraulically actuated valve means (18), and are configured to provide at outlet a hydraulic pilot signal adapted to actuate said first hydraulically actuated valve means (18)
said electronic control unit (56) being operatively connected to a input device (34) configured to be handled by a user to impart electric control signals and being configured to control the operation of said second electrically actuated valve means (42) according to said electric control signals.
Work machine according to any of claims from 7 to 13, wherein said control system comprises a brake assembly (200), which is operatively interposed between said hydraulic motor (10) and said upper frame (2) and is configured to provide a braking torque adapted to reduce the braking angle and/or rotational velocity of said upper frame (2);
said electronic control unit (56) being operatively connected to said brake assembly (200) to control its operation.
Work machine according to any of claims from 7 to 14, wherein said control system (3) comprises two solenoid-controlled proportional relief valves (113), which are operatively interposed between said hydraulic pump (6) and said hydraulic motor (10), and are adapted to discharge to a drain (7) the pressurized hydraulic fluid fed towards said hydraulic motor (10) when its pressure exceeds a predetermined pressure threshold;
said electronic control unit (56) being operatively connected to said solenoid-controlled proportional relief valves (113) and being configured to set their pressure threshold in order to vary the maximum pressure allowed within the hydraulic lines (15, 17) fluidly connecting said hydraulic pump (6) to said hydraulic motor (10).