EP4204631A1

EP4204631A1 - Method and system for releasing the residual pressure of a hydraulic circuit of a work machine and work machine including the system

Info

Publication number: EP4204631A1
Application number: EP21742424.1A
Authority: EP
Inventors: Adriano GARRAMONE; Andrea Gravili; Stefano Liberti; Antonio Venezia
Original assignee: CNH Industrial Italia SpA
Current assignee: CNH Industrial Italia SpA
Priority date: 2020-07-17
Filing date: 2021-07-15
Publication date: 2023-07-05
Also published as: WO2022013327A1

Abstract

Method and system for releasing the residual pressure of a hydraulic circuit of a work machine and work machine including the system Method for releasing the residual pressure of a hydraulic circuit of a work machine, the hydraulic circuit comprising a source (P) of pressurized hydraulic liquid and a discharge tank (T) of the pressurized hydraulic liquid and at least a double-action hydraulic actuator (Al, A2,...) controlled by means of a corresponding actuation hydraulic valve (VI, V2, V3,...), wherein the actuation hydraulic valve has a stand position in which it directs pressurized hydraulic liquid from the source to the discharge tank and, at the same time, compartments opposite chambers (CII, C12; C21, C22; of the corresponding actuator (Al, A2,..) and two opposite actuation positions in which the valve connects the first chamber (CII, C21) with the source and a corresponding second chamber (C12, C22) with the discharge tank, and vice versa, the method comprising a first preliminary step of checking or forcing a deactivation of the source (P) and a subsequent second step of activating alternately the two opposite actuation positions.

Description

"Method and system for releasing the residual pressure of a hydraulic circuit of a work machine and work machine including the system" * * *

Field of the invention

The present invention relates the field of hydraulic circuits of work machines.

State of the art

The work machines are equipped with a hydraulic circuit for the actuation of work organs, such as arms, buckets, etc.

A prime mover, generally an internal combustion engine and/or an electric motor drives a hydraulic pump in rotation which defines a source of hydraulic liquid for the hydraulic circuit .

When it is necessary to replace an implement, it can happen that this includes at least one relative actuator member. In order to operate this actuator it is necessary to connect it to the vehicle's hydraulic circuit in order to be able to supply it. Some quick couplings of the vehicle's hydraulic circuit may not allow the actuator to be connected as long as there is residual pressure in the vehicle's hydraulic circuit. This involves a significant waste of time for the operator who must turn off the vehicle and perform a series of operations to make sure that the hydraulic circuit of the vehicle is vented, i.e. not pressurized.

It is important to ensure that the circuit is vented even when it is necessary to carry out maintenance actions on the circuit itself in order to avoid risks for the operator.

Even when the vehicle has been inactive for some time, residual pressure can be retained in some branches of the hydraulic circuit.

In loaders (mechanical shovels), for example wheel loaders, there are generally two hydraulic lines assigned to control the main organ, namely tool and arm. The tool can be a bucket or shovel or a fork.

These vehicles can be equipped with a third and other additional lines to supply one or more auxiliaries.

In order to be able to selectively feed and control two auxiliaries with the same line, a diverter valve is used. The diverter valve further complicates the draining procedures of the hydraulic circuit, as it compartments it preventing its complete draining.

Each of the hydraulic circuit lines can be connected to the source of pressurized hydraulic liquid and a tank for collecting/venting the hydraulic liquid.

For convenience, in the following, the hydraulic pump is appealed in the following simply as a "source" and the collection/venting tank is appealed as a "tank".

On each line there is generally a hydraulic valve which in rest position discharges the pressurized liquid from the source into the tank and keeps the chambers of the relative actuator compartmented and in two operating positions feeds one of the two opposite chambers of the hydraulic actuator by connecting the other with the tank. Therefore, these hydraulic valves are three-position and in the rest position the actuator is blocked.

The hydraulic actuators, as known, are of the double chamber type, i.e. double action, since the mobile piston separates two opposing chambers which allow, by pressurizing one at a time, to make opposite movements, for example the lifting and lowering of the arm. Therefore, when one chamber is connected to the source, the other is connected to the tank and vice versa, so that the non-powered chamber does not oppose the expansion of the powered chamber and at the same time ejects the excess hydraulic liquid to the tank, from which the source sucks and pressurize the hydraulic fluid.

If not specifically excluded in the detailed description that follows, what is described in this chapter is to be considered as an integral part of the detailed description.

Summary of the invention

The object of the present invention is to facilitate the pressure relief operations of a hydraulic circuit of a work vehicle, so as to minimize problems and risks associated with the presence of residual pressures in the hydraulic circuit of the work vehicle.

The basic idea of the present invention is to implement a release function of the hydraulic circuit, which permits to actuate automatically the pressure release of the hydraulic circuit.

Fro convenience, in the following, the release function of the hydraulic circuit is called "realise function". In particular, according to the present invention, when the drain functionality is activated, the source is kept deactivated and the hydraulic valves switch alternately in the two actuation positions. Since the source is deactivated, the only effect deriving from switching to the two operating positions is the discharge of the hydraulic circuit. Preferably, the activation of the two actuation positions is repeated a predetermined number of times in order to ensure effective discharge of the hydraulic circuit. If the circuit is equipped with a hydraulic line on which there is a diverter valve, this is activated and the operation described above, with regard to the hydraulic valve, is repeated for all the branches served by the diverter valve.

The present invention relates not only to a method of unloading a hydraulic circuit of a work vehicle, but also to a system implementing the method and a work vehicle comprising the unloading system.

According to a preferred variant of the invention, the source is permanently connected to the prime mover, therefore, the deactivation of the source involves the deactivation of the prime mover, therefore, before activating the aforementioned discharge function, the deactivation state of the prime mover is checked or the deactivation of the prime mover is commanded so that the source is surely deactivated.

According to a preferred variant of the invention which combines with any one of the previous variants, the drain function can only be activated if the key is in the ON position .

The key in ON conventionally indicates that the instrument panel is active, but above all it indicates that the vehicle processing unit which supervises the operation and monitoring of vehicle functions is active.

The dependent claims describe preferred variants of the invention, forming an integral part of this description. Brief description of the figures

Further objects and advantages of the present invention will become clear from the following detailed description of an embodiment thereof (and of its variants) and from the annexed drawings given purely for explanatory and non- limiting purposes, in which:

Figure 1 shows an example of a working vehicle implementing the vehicle object of the present invention;

Figure 2 shows an example hydraulic circuit object of the present invention with means for processing and controlling at least the hydraulic circuit;

Figure 3 shows an exemplary flowchart of the operating method of the present invention. The same numbers and the same reference letters in the figures identify the same elements or components or functions.

In the context of this description, the term "second" component does not imply the presence of a "first" component. These terms are in fact used as labels to improve clarity and should not be understood in a restrictive way.

The elements and characteristics illustrated in the various preferred embodiments, including the drawings, can be combined with each other without however departing from the scope of the present application as described below.

Detailed description of exemplary implementations

Figure 1 shows an example of a CWL work vehicle object of the present invention. This for example consists of a mechanical wheel loader.

The vehicle includes a hydraulic circuit, exemplified in figure 2, comprising the actuator A2 for raising and lowering the arm B and the actuator A1 for adjusting the inclination of the tool TO which can be a shovel or a fork. The hydraulic pump P as well as the prime mover are not shown, even if in the hydraulic circuit of figure 2, the letter "P" identifies the connection of the circuit to the hydraulic pump.

In figure 2, the first actuator A1 is indicated with "BUCKET", while the second actuator A2 is indicated with "ARM" to refer to the operated member. "T" identifies the tank in which the hydraulic liquid is discharged.

The tank T is at atmospheric pressure and from this tank the hydraulic pump P draws the hydraulic liquid to be pressurized.

Valve VI controls the operation of the A1 or Bucket actuator. The VI valve is represented with three drawers, in which the central drawer is at rest.

When no command reaches valve VI, the central drawer is therefore active. In rest conditions, the hydraulic fluid from the source P, i.e. the hydraulic pump, is directed to the tank T.

The two lateral drawers with respect to the central one allow the first one, for example to the right of the central one, to pressurize the chamber Cll of the actuator A1 by connecting the chamber C12 with the tank T. The second drawer performs the exact opposite, i.e. it connects the chamber C12 with source P and chamber Cll with tank T.

The actuators are of the double action type, that is to say with opposite chambers Cll / C12 and C21 / C22 to control opposite movements of the relative organ. For example the raising and lowering of arm B.

The description of valve VI and the relative hydraulic supply line of the first actuator is applicable to valves V2 and V3 and the respective hydraulic lines.

With regard to the V3 valve, this, unlike the others, serves an auxiliary auxiliary actuator and an additional auxiliary actuator, optional, Additional Auxiliary. In order to be able to control the two actuators separately, there is a diverter valve, named "FLOW DIVERTER" which allows the Auxiliary or Additional Auxiliary auxiliary to be connected alternately to the hydraulic valve V3.

A "Control Unit" processing unit oversees at least the operation of the valves VI - V3, FLOW DIVERTER.

According to the present invention, when the function for releasing the residual pressure from the hydraulic circuit is activated, the source P is checked or forced to switch off and immediately thereafter to alternately activate the two opposite actuation positions.

In other words, the first and the second actuation drawer are alternately activated which would lead, if the source were active, to have opposite movements of the relative organ. In this case, on the other hand, since the source deactivates possibly forcibly deactivated, the connection with the source does not lead to the expansion of the chamber connected with the source, but rather the depressurization of the chamber connected with the tank. Preferably, the first drawer is activated, then the second drawer and then again the first and second drawer. As long as there is no absolute certainty that the hydraulic lines are completely discharged.

As far as the third valve V3 is concerned, it is also necessary to keep in mind the presence of the diverter valve, for which the valve V3 must be controlled like the other valves VI and V2 by repeating the same procedure for each of the switching conditions of the diverter valve. In the example, the release cycles must be performed twice since two actuators are connected to the diverter valve: Auxiliary and Additional Auxiliary.

What has been described so far with regard to the V3 valve is applicable to any further ones and can be replicated to supply auxiliary actuators and additional auxiliary actuators .

In other words, the scheme shown can be expanded according to the circumstances.

If the source P of pressurized hydraulic liquid includes a hydraulic pump and this is permanently connected to the prime mover of the vehicle then the first preliminary step includes checking or implementing the deactivation of the prime mover, as this is equivalent to making sure that the source of hydraulic fluid is disabled.

Figure 2 shows the fact that the processing unit is also connected with sensors including the "Engine speed" rpm sensor of the prime mover, the so-called "Key" to switch on the instrument panel, the button for activating the hydraulic functions "Hydraulic Function Switch" and the activation button of the function object of the present invention, called "Activation button". When the processing unit verifies that the key is ON, the prime mover is deactivated, for example because the rotation speed is zero or below the minimum, the hydraulic functions are enabled and the residual pressure release button is pressed, then the activation of the side drawers is activated, that is, the activation of the two opposite actuation positions.

Suitable pressure sensors (not shown) can be present along the circuit which control the residence time in each actuation position or the number of repetitions in the actuation positions until the measured pressure is lower than a predetermined threshold.

Figure 3 shows an example of a flowchart in which in step 1 the source P occurs or forces to deactivate and step 2 to activate the side drawers alternately. Step 2 can be performed multiple times.

The optional step 3 involves switching the diverter valve described above and repeating step 2.

Step 0 is also preliminary with respect to step 1, further verification of other optional conditions, such as, activation of the key, activation of the hydraulic functions and activation of the pressure release function.

The present invention can be advantageously carried out by means of a computer program which comprises coding means for the realization of one or more steps of the method, when this program is executed on a computer. Therefore, it is understood that the scope of protection extends to said computer program and further to computer readable means which comprise a recorded message, said computer readable means comprising program coding means for carrying out one or more steps of the method , when this program is run on a computer.

Possible variations to the non-limiting example described are possible, without however departing from the scope of protection of the present invention, including all the equivalent realizations for a person skilled in the art, to the content of the claims.

From the above description, the person skilled in the art is able to realize the object of the invention without introducing further construction details.

Claims

1. Method for releasing the residual pressure of a hydraulic circuit of a work machine, the hydraulic circuit comprising a source (P) of pressurized hydraulic liquid and a discharge tank (T) of the pressurized hydraulic liquid and at least a double-action hydraulic actuator (Al, A2,...) controlled by means of a corresponding actuation hydraulic valve (VI, V2, V3,...), wherein the actuation hydraulic valve has a stand position in which it directs pressurized hydraulic liquid from the source to the discharge tank and, at the same time, compartments the opposite chambers (Cll, C12; C21, C22; of the corresponding actuator (Al, A2, ..) and two opposite actuation positions in which it connects the first chamber (Cll, C21) with the source and a corresponding second chamber (C12, C22) with the discharge tank, and vice versa, the method comprising a first preliminary step of checking or forcing a deactivation of the source (P) and a second following step of activating alternately the two opposite actuation positions.

2. Metodo secondo la rivendicazione 1, in cui detto secondo passo e ripetuto un predeterminato numero di volte.

3. Method according to claim 1 or 2, wherein the second step is repeated as long as a pressure measured on at least one point of the hydraulic circuit is lower than a predetermined threshold.

4. Method according to any one of the preceding claims, wherein downstream of said actuation valves (V3, V4, ..) a diverter valve (DV) is connected comprising at least two positions for actuating corresponding at least two distinct actuators (Auxiliary, Additional Auxiliary) hydraulic, and wherein said second step is repeated for each of the positions of the diverting valve, after a third switching step of the diverting valve.

5. Method according to any one of the preceding claims, wherein said source (P) of pressurized hydraulic liquid comprises a hydraulic pump stably connected to a prime mover of the vehicle, and wherein said first preliminary step includes checking or implementing the deactivation of the engine first.

6. Method according to any one of the preceding claims, further comprising a preliminary step, preceding the first preliminary step, of verifying that the key is ON, the hydraulic functions are enabled and that a command button is pressed to execute the first and second step or the first, second, third and second step.

7. System for releasing the residual pressure of a hydraulic circuit of a work machine, the hydraulic circuit comprising a source (P) of pressurized hydraulic liquid and a discharge tank (T) of the pressurized hydraulic liquid and at least a double-action hydraulic actuator (Al, A2,...) controlled by means of a corresponding actuation hydraulic valve (VI, V2, V3,...), wherein the actuation hydraulic valve has a stand position in which it directs pressurized hydraulic liquid from the source to the discharge tank and, at the same time, compartments the opposite chambers (Cll, <312; C21, C22; of the corresponding actuator (Al, A2, ..) and two opposite actuation positions in which it connects the first chamber (Cll, C21) with the source and a corresponding second chamber (C12, C22) with the discharge tank, and vice versa, the system comprising elaborating means (control unit) configured for preliminary checking or forcing a deactivation of the source (P) and then for activating alternately the two opposite actuation positions.

8. System according to claim 7, further comprising at least one pressure sensor arranged in a point of the hydraulic circuit and in which said processing means are configured to repeat the alternate activation of the two opposite actuation positions as long as the pressure measured at the point of the hydraulic circuit is lower than a predetermined threshold.

9. System according to any one of the preceding claims 7 or 8, wherein downstream of said actuating valves (V3, V4, ..) there is a diverter valve (DV) comprising at least two positions for actuating corresponding at least two distinct actuators ( Auxiliary, Additional Hydraulic), and in which the processing means are configured to force a changeover of the changeover valve and repeat the alternate activation of the two opposite actuation positions for each of the positions of the diverter valve.

10. System according to any one of the preceding claims 7 - 9, wherein said source (P) of pressurized hydraulic liquid comprises a hydraulic pump stably connected to a prime mover of the vehicle, and wherein the processing means are further configured to check or implement the deactivation of the prime mover.

11. Computer program comprising program coding means adapted to perform all steps (0 - 3) of any one of claims 1 to 7, when said program is run on a computer.

12. Computer readable means comprising a recorded program, said computer readable means comprising program coding means adapted to carry out all steps (0 - 3) of any one of claims 1 to 7, when said program is run on a computer.