WO2013021404A2

WO2013021404A2 - Hydraulic circuit for working machines and working machine

Info

Publication number: WO2013021404A2
Application number: PCT/IT2012/000239
Authority: WO
Inventors: Antonio Bertini
Original assignee: Imer International S.P.A.
Priority date: 2011-08-05
Filing date: 2012-07-31
Publication date: 2013-02-14
Also published as: EP2739862A2; WO2013021404A3; ITFI20110164A1

Abstract

Hydraulic circuit for working machines comprising a power unit (P) for pressurizing a hydraulic fluid, a unit of distribution (D) comprising a plurality of proportional valves downstream of the power unit (P), a control unit (C) connected to the proportional distribution unit (C), a plurality of groups of hydraulic actuators (GA, GT, GS) that can be connected to the power unit (P) by the proportional distribution unit (D), and an operations control panel (CO) connected to the control unit(C). The hydraulic circuit comprises a flow diverter (DF) placed between the distribution unit (D) and the groups of hydraulic actuators (GA, GT, GS), so that the latter are selectively connectable to the distribution unit (D) by means of the diverter (DF). The flow diverter (DF) is controlled manually or by a program by means of the control unit (C). The number of proportional valves of the distribution unit (D) is equal to the maximum number of actuators that can be simultaneously activated. A group of hydraulic actuators (GS) is destined to execute of a phase of stabilization of the machine by activating corresponding stabilizers (4).

Description

TITLE

Hydraulic circuit for working machines and working machine .

DESCRIPTION

The present invention relates to a hydraulic circuit for working machines and a working machine.

More particularly, the present invention basically concerns the working machines equipped with a stabilizing system with stabilizers implemented by means of hydraulic cylinders.

These machines, among which there are, for example, mini-excavators, tracked aerial platforms, auto- concrete-pumps etc.. widely used in the building industry or even agricultural machines, usually involve a plurality of active operating steps or phases that exclude each other, that is, operating steps that are not contemporary, performed by corresponding actuators or actuator groups each of which is responsible for the execution of an operating step. For example, these steps can be:

1. Translation step (the machine is moved to reach the working point)

2. Stabilization step (the machine is stabilized in order to ensure its stability in the working conditions )

3. Aerial step (air movement through movable arms or other equipments to move people or loads)

These steps are commonly carried out thanks to actuators usually consisting of cylinders or hydraulic motors. Said actuators are activated and controlled by means of valves that are intended to isolate, dosing or deflect the energy vector produced by the energy generation system that provides pressure and hydraulic flow to the extent required .

Specific valves, commonly called "proportional distributors" have the purpose of finely dosing the power conveyed to the actuators in response to signals provided by a control unit to which to a control panel provided with levers joystick operable by an operator can also be connected.

In particular, the stabilization step is intended to provide a sufficiently broad supporting base to the machine to enable it to operate safely, that is, without risk of overturning. This is achieved by means of stabilizers that are placed on the ground and suitably adjusted to reach a safety attitude. For this purpose, the stabilizers are implemented as long as an inclinometer of the machine does not indicate a verticality error less than a value that is determined on the basis of the local safety regulations (commonly 2 to 5 degrees) and sensors intended to check the contact of the stabilizers with the ground does not detect the stabilization (that is, a firm contact of the stabilizers with the ground) . Equally critical are the other operational phases of the machine that may require movements controlled with precision. For this reason it is usually made use of proportional valves also for managing the phase translation and/or the aerial phases. But the proportional distributors are particularly expensive and require a relatively complex and consequently expensive control system, which results in a corresponding complexity of the control unit and, therefore, a relatively high cost of the latter.

Conventionally, the proportional valves are equal in number to the movements requiring fine adjustment or control. Consequently, the number of such components of the hydraulic circuit is greater than the number of simultaneous movements requiring the proportional control.

Sometimes, especially for the control of the stabilizers, in order to decrease the cost of the control unit use is made of manually controlled proportional distributors.

However, since the machine working phases (translation, stabilization and aerial phases) are separated and exclude each other, normally such distributors are unused for most of the machine working time.

It is therefore strongly felt the need for a hydraulic circuit for operating machines, in particular of the type fitted with stabilizing system, capable of simultaneously satisfy different needs, including:

- providing an adequate safety level

- minimizing costs while offering high performances in terms of: possibility to control remotely the distributors; maximization of the level of automation of repetitive tasks such as the stabilization phase; control the highest number of movements with proportional valves.

- possibility of having a flexible and open circuit architecture to provide the opportunity to mount accessories like automatic stabilization systems on machines that are not provided with such systems at the origin.

At present, in order to reduce the cost of the control unit use is made of manually controlled proportional valves, especially for the control of the stabilizers, but this implies that the control unit is unable to directly control the actuators of the stabilization unit, for which the stabilization is managed by the operator who intervenes manually. Or, in order to reduce the cost of the control unit by minimizing the number of proportional distributors, ON-OFF valves are used for the control of the stabilizers, but in this case, it is necessary to have an electronic inclinometer and the stabilization phase of the machine can be automatic only.

DE102005048280A1 discloses a hydraulic circuit that can equip^' a working machine. DE19633191A1 discloses a valve for hydraulic circuits.

The main purpose of the present invention is to propose a hydraulic circuit for working machines that meets all the requirements listed above.

This result is achieved, according to the present invention, by adopting the idea of realizing a hydraulic circuit and a working machine having the features indicated in the independent claims. Other features of the present invention are the subject of the dependent claims.

Thanks to the present invention, it is possible to reduce the number of proportional valves and consequently to simplify the control unit, while it is possible to remotely control all the actuators by means of the control unit, and at the same time it is possible ensure an adequate safety level.

These and other advantages and features of the present invention will be best understood by anyone skilled in the art thanks to the following description and the accompanying drawings, given by way of example but not to be considered in a limitative sense, wherein:

Fig.l is a simplified block diagram of a hydraulic circuit in accordance with a possible embodiment of the present invention;

- Fig.2 schematically shows a hydraulic circuit in accordance with the present invention corresponding to the block diagram of fig.l;

- Fig.3A is a schematic side view of a crawler crane base provided with the circuit of fig.2;

- Fig.3b is a schematic plan view of the base and the stabilizers of the crawler crane shown Fig.3A;

- Fig.4 is a simplified block diagram of a circuit in accordance with a further possible embodiment of the invention. A hydraulic circuit in accordance with the present invention is particularly intended to equip working machines comprising a stabilizing system which operates in a phase which excludes the execution of other phases.

By way of example, the machine may be a crawler crane (1) of the type shown in Fig. 3A and 3B, comprising a self-propelled base having tracks (2) actuated by a hydraulic motor, an arm (3) operated by hydraulic actuators, and a plurality of stabilizers (4) also operated by hydraulic actuators. With a machine of this type the following tasks are normally performed: a translation step, in which the tracks are driven to move the machine to the selected working point and then spaced to increase the base width; a stabilization phase, in which the actuators connected with the tracks ( 2) are disabled and the stabilizers (4) are extracted in order to have the machine stabilized in the desired safety configuration once reached the working point; and an aerial phase, in which operate only the actuators for moving the arm (3) are enabled, and all the other actuators are disabled. In a working machine of this type, when the actuators used for performing a task are enabled, the actuators used for performing all the other tasks are disabled. For example, when the hydraulic motor driving the tracks (2) is enabled, the actuators controlling the stabilizers (4) and the arm (3) are disabled; when , the actuators controlling the stabilizers (4) are enabled, the hydraulic motor driving the tracks (2) and actuators driving the arm (3) are disabled; and, when the actuators driving the arm (3) are enabled, the hydraulic motor driving the tracks (2) and the actuators controlling the stabilizers (4) are disabled.

Reduced to its essential structure and with reference to the example shown i fig.l, a hydraulic circuit in accordance with the present invention comprises:

- a power unit (P) for the pressurization of a hydraulic fluid;

- a proportional distribution unit (D) downstream of the power unit (P);

- an electro-actuated flow diverter (DF) downstream of the distribution unit (D) ;

- a control unit (C) connected to the power unit (P), to the proportional distribution unit (D) and to the flow diverter (DF) ;

- three groups of hydraulic actuators (GA, GT, GS) each of which can be selectively connected to the proportional distribution unit (D) by means of the flow diverter (DF) ;

- sensors (ST) for detecting the support on the ground of the stabilizers actuated by the actuators of the respective group of hydraulic actuators (GS) ;

- an electronic inclinometer (E) ;

- a control panel (CO) connected to the control unit (C) .

The flow diverter (DF) can also be of the manually operated type.

In the diagram of fig.2, the actuators of the group (GA) are marked by references (Al, A2, A3, A4 ) ; the actuators of the group (GT) are marked by references (Tl, T2, T3, T4), and the actuators of the group (GS) are marked by references (SI, S2, S3, S 4 ) .

In this example, referred to the machine schematically shown in Fig. 3, the actuators (Al, A2, A3, A4 ) of the group (GA) are four in number and control the movements of the arm (3); the actuators (Tl , T2, T3, T4) of the group (GT) are four in number and control the movements of the tracks and the distance between the tracks to adjust the base width and / or perform auxiliary functions; and actuators (SI, S2, S3, S4) of the group ( GS) are also four in number and control the movements of the stabilizers (4). In particular, the actuators (Al, A2, A3, A ) of the group (GA) control the various sections of the articulated arm (3) to place and move it as desired, the actuators (Tl, T2, T3, T4) of the group (GT) are hydraulic motors for driving the tracks (2) and actuators which approach or move away the same tracks to vary the width of the base depending on the working condition of the machine (tracks close when the machine translates/tracks spaced when the machine is parked in the selected working point ) , and actuators (SI, S2, S3, S4) of the group (GS) determine the extraction or retraction of the stabilizers (4) which are conventionally constituted by telescopic arms hinged to the frame of the machine and which are retracted when the machine is in motion and are extracted when the machine is parked and it is necessary to stabilize it in order have a safety machine configuration. Moreover, in this example, the proportional valves (Dl, D2, D3, D4) of the unit (D) are four in number.

In fact, in accordance with the present invention, the number of proportional valves of the unit (D) is equal to the maximum number of contemporaneous proportional actuations executable by any of the actuator groups (GA, GT, GS) served by the power unit (P) . In other words, as in the example shown in fig.2, each of the groups (GA, GT, GS) comprises four actuators operable simultaneously for each of which the control is provided by means of a corresponding proportional distributor, and since the use of the actuators of a group excludes the use of the actuators of the other groups, the proportional valves are four in number (which corresponds to the maximum number of f actuators of any group that can be activated simultaneously) . In practice, since the execution of a phase excludes the execution of the other phases, there is a maximization of the use of the proportional distributors by diverting the action of the same proportional distributors on the group of actuators that must be active in the selected working phase.

The control panel (CO) comprises a multi-position selector (S) (for example, the selector can assume three positions corresponding to three groups of actuators served by proportional distributors) and more joystick-type command levers (Jl, J2, J3, J4 ) (for example, four joystick-type command levers, i.e. one joystick-type command levers for each proportional distributor of the unit D) . The position of the selector (S) determines, by means of the diverter (DF) , the hydraulic connection of the proportional distributors of the unit (D) with the chosen group of actuators (GA, GT, GS) . The flow diverter (DF) has inputs corresponding in number to the number of distributors of the unit (D) and a number of outputs corresponding to the number of groups of actuators served by the proportional distributors.

The advantages deriving from the present invention are further highlighted in the following with reference to the description of a possible mode of operation of the machine referred to a semiautomatic stabilization phase, i.e. without the aid of an electronic inclinometer.

In a first step, the operator moves the selector of the control panel (CO) in the position corresponding to the stabilization phase and enables the start of this phase by acting on an appropriate button of the same panel (CO) . In a second step, the control unit (C) activates the individual actuators (SI, S2, S3, S4) of the group (GS) for a predetermined and adjustable time, to obtain the extraction of the stabilizers (4). In a third step, the joysticks are enabled and the operator adjusts the extension of each actuator (SI, S2, S3, S4) to position the machine in the desired attitude (in the absence of an electronic inclinometer, an analog inclinometer can be used and the operator will adjust the attitude of the machine on the basis of the indications provided by the analog inclinometer by acting on each actuator using the joysticks that control the proportional distributors each of which in turn controls a corresponding actuator of the group GS) . This step can be performed with the control panel (CO) at a safety distance from the working machine.

For obtaining the retraction of the stabilizers (4), the control unit (C) can be programmed to perform the following: by means of the control panel (CO) it is started the return phase of the stabilizers (4), phase that can be executed only if the machine is in a rest safety state; then, the control unit (C) simultaneously operates the actuators of all the stabilizers at identical speeds to obtain the return of the latter in their rest position, and stops the actuators when the respective sensors (ST) detect the lack of contact with the ground; when all the stabilizers are raised, the unit (C) commands their return to the respective initial positions. If the machine is provided with an electronic inclinometer, the stabilization phase can be managed completely automatically by the control unit (C) that interacts with the electronic inclinometer and with the sensors (ST) . It is noted that this mode of operation can be implemented via software without intervening on the architecture of the hydraulic circuit .

According to the example schematically shown in Figure 4, that refers to a hypothetical case to further highlight the characteristics of a hydraulic circuit in accordance with the present invention, the group (GA) comprises a single actuator (Al), the group (GT) comprises two actuators (Tl, T2), and the group (GS) comprises three actuators (SI, S2, S3) . In this case, the unit (D) comprises three proportional distributors (Dl, D2, D3) because three is the maximum number of possible simultaneous actuations (i.e., the number of the actuators of the group GS) . In this case, use may be made, for example, of only three j oysticks .

More generally, said n_max the maximum number of actuators served by proportional distributors that can activated simultaneously, and said nD the number of proportional distributors, in accordance with the present invention is n_max = nD.

Thanks to the presence of the flow diverter (DF) positioned downstream of the distribution unit (D) and given the possibility to selectively enable the single groups of actuators (GA, G . GS) , it is possible to substantially reduce the number of proportional distributors and, consequently, the cost of t.he circuit.

From the foregoing description are evident the advantages arising from use of a hydraulic circuit in accordance with the present invention, both in terms of costs and in terms of reliability of the system.

In practice, the construction details may vary in any equivalent way as regards the single described and illustrated elements, without nevertheless departing from the scope of the adopted solution and thereby remaining within the limits of the protection granted to the present patent.

Claims

1) Hydraulic circuit for working machines comprising a power unit (P) for pressurizing a hydraulic fluid, a unit of distribution (D) comprising a plurality of proportional valves downstream of the power unit (P), a control unit (C) connected to the proportional distribution unit

(C) , a plurality of groups of hydraulic actuators (GA, GT, GS) that can be connected to the power unit (P) by the proportional distribution unit (D), and an operations control panel (CO) connected to the control unit (C) , characterized in that comprises a flow diverter (DF) placed between the distribution unit (D) and the groups of hydraulic actuators (GA, GT, GS) , so that the latter are selectively connectable to the distribution unit

(D) by means of the diverter (DF) , in that the flow diverter (DF) is controlled manually or by a program by means of the control unit (C) , in that the number of proportional valves of the distribution unit (D) is equal to the maximum number of actuators that can be simultaneously activated, and in that one group (GS) of ^■ said groups (GA, GT, GS) of hydraulic actuators controls a predetermined number of stabilizers (4) of a working machine equipped with the hydraulic circuit .

2) Hydraulic circuit according to claim 1, characterized in that the flow diverter (DF) is controlled manually by means of a selector (S) of the control panel (CO) .

3) Hydraulic circuit according to claim 1, characterized by the fact that said proportional valves (D) are controlled by a program through the control unit (C) .

4) Hydraulic circuit according to claim 1, characterized by the fact that the proportional valves of the distribution unit (D) are four in number .

5) Hydraulic circuit according to claim 1, characterized by the fact that the said flow diverter (DF) is operated electrically.

6) Hydraulic circuit according to one or more of the preceding claims, wherein the control panel (CO) is provided with a predetermined number of joystick-type controls, characterized in that, when an operator switches the selector (S) of the control panel (CO) in a position corresponding to a stabilization phase and enables the start of this phase, the control unit (C) commands the individual actuators (SI, S2, S3, S4) of the stabilization (GS) until all the stabilizers have touched the ground, or related sensors (ST) have switched their state, then the control unit (C) controls, for a preset and adjustable time, the stabilizers lifting the working machine and settling the ground support, and once this phase is completed, the control Unit (C) activates a predetermined number of said joysticks and the operator can adjust the extension of each actuator (SI, S2, S3, S4) to determine the desired attitude of the machine, then the control unit (C) following a command of the operator, manages the automatic return of said stabilizers in the rest position under control of the sensors (ST) that interact with the control unit (C) and detect the contact of the stabilizers with the ground .

7) Working machine comprising a power unit (P) for pressurizing a hydraulic fluid, a unit of distribution (D) comprising a plurality of proportional valves downstream of the power unit (P), a control unit (C) connected to the proportional distribution unit (C) , a plurality of groups of hydraulic actuators. (GA, GT, GS) that can be connected to the power unit (P) by the proportional distribution unit (D) , and an operations control panel (CO) connected to the control unit (C) , characterized in that comprises a flow diverter (DF) placed between the distribution unit (D) and the groups of hydraulic actuators (GA, GT, GS), so that the latter are selectively connectable to the distribution unit (D) by means of the diverter (DF), in that the flow diverter (DF) is controlled manually or by a program by means of the control unit (C) , in that the number of proportional valves of the distribution unit (D) is equal to the maximum number of actuators that can be simultaneously activated, and in that one group (GS) of said groups (GA, GT, GS) of hydraulic actuators controls a predetermined number of stabilizers (4) of a working machine equipped with the hydraulic circuit.

8) Machine according to claim 7, characterized in that the flow diverter (DF) is controlled manually by means of a selector (S) of the control panel (CO) .

9) Machine according to claim 7, characterized by the fact that said proportional valves (D) are controlled by a program through the control unit (C) .

10) Machine according to any of claims 7 to 9 , characterized by the fact that the said flow diverter (DF) is operated electrically.