PLURALITY OF HYDRAULIC IMPLEMENTS OF A WORK OR AGRICULTURAL MACHINE"

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Field of the invention

The present invention relates to hydraulic systems of the work and agricultural machine.

State of the art

Work or agricultural motor vehicles are well known for handling materials and for carrying out specific heavy tasks. They are often equipped with a hydraulically operated lifting arm to move a shovel or bucket.

A mechanical shovel or "wheel loader" is a heavy machine used in construction to move earth or materials such as asphalt, demolition debris, snow, feed, gravel, logs, raw minerals, recycled material, rock, sand, wood chips, etc. inside or on top of another type of machinery (such as a dump truck, a conveyor belt, a feed hopper or a railroad car). There are many types of loaders (mechanical shovels), which, depending on the design and application, are called by various names, including bucket loader, front loader, front loader, loader, shovel, shovel, skip loader, wheel loader or compact shovel (skid-steer).

Usually, the movement of the arm and bucket is controlled by the user through a joystick located inside the operator's cab of the working vehicle. The progress and steering of the vehicle can also be controlled using a joystick.

Figure 1 shows a motor grader (Grader) which comprises several hydraulically operated members for carrying out 1. Moldboard extender: extension of the share

2. Moldboard pitch: orientation of the share

3. Articulated steering: articulated steering

4. Dozer blade lift: buldozer blade lifter

5. Moldboard lift left: left lift of the share

6. Rotate moldboard: rotation of the share

7. Rear ripper: rear tracker

8. Wheel lean: track adjustment

9. Swing moldboard: swing of the share

10. Moldboard lift right: right lift of the share

A processing unit controls the different hydraulic actuators (not shown) through respective solenoid valves in relation to the commands given by the user through one or more joysticks, levers and buttons.

Each hydraulic actuator includes a hydraulic cylinder operatively connected respectively to the arm, tool or shovel or steering system, which uses the hydraulic power of a working fluid to allow mechanical operation.

In hydraulic circuits called "closed center with flow sharing" that is "closed center with shared flow", the flow of hydraulic fluid generated by the pump does not cross the sliders of the distributor at rest, so that this flow is zeroed, in the case of a variable displacement pump or it is sent to the discharge through a slider, in the case of a fixed displacement pump.

When the distributor is operated, the flow of hydraulic fluid addressed to the user is proportional to the opening of the cursor and the opening of the cursor where the flow starts to flow to the user is constant and if there are multiple users activated simultaneously, the flow generated by the pump is proportionally distributed only when the cursors of each individual user are opened.

In particular, each valve in the circuit is able to guarantee a predetermined pressure to the relative actuator or user, while the flow generated by the hydraulic pump is shared by the various users. This ensures efficient combined operation of multiple actuators or users. The actuation speed of the hydraulic actuator depends on the proportional electric control, integrated with the flow sharing system. These elements combined together allow the simultaneous activation of different actuators by distributing the flow rate proportionally to the actuation speeds defined by the operator, regardless of the different operating pressures.

The hydraulic flow of the working fluid required to operate the arm and the tool is produced by a hydraulic pump which draws from a fluid tank and is driven by an internal combustion engine or an electric motor M, hereinafter simply called " engine "of the vehicle, e.g. from a mechanical link. The same engine is also used to drive the wheels as a means of propulsion of the working vehicle. Therefore, the speed of movement of the arm and the tool in a predetermined position depends on the speed of rotation of the motor. For example, when the engine is running at a high rotation speed, a minimum movement of the joystick by the user is required to perform a movement of the arm and / or the tool. Conversely, when the engine is running at low rotational speed or at idle speed, a large movement of the joystick by the user is required.

Obviously, the problem is increased when multiple electro- hydraulic functions need to be performed simultaneously.

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 improve the response of the hydraulic functions of a work vehicle to the requests of a user.

The basic idea of the present invention is to group the electro-hydraulic functions in two or more groups, to calculate the available flow of hydraulic fluid in relation to the current operating conditions and to limit the flow of hydraulic fluid towards the set of functions having lower priority, when it appears that the available flow is insufficient to supply all the functions. In other words, the flow of hydraulic fluid is divided between the sets of hydraulic functions proportionally to the priority attributed to the group itself.

The distribution is progressively variable until the balance between the available hydraulic flow and the power supply of all the active hydraulic functions is obtained. More specifically, this progression of flow limitation is gradually increasing, involving sets of higher priority functions. Therefore, a flow reduction is applied to the hydraulic functions having higher priority only when it is not possible to do otherwise.

According to a preferred variant of the present invention, limit reduction coefficients are defined for each limitation cycle that goes from the lowest priority set to the highest priority set.

"Lower" or "lowest" and "higher" or "highest" are to be considered in the economy of the ordered classification of the priority levels and therefore implicitly have relative meaning in relation to the other levels of predefined or set priorities .

According to a preferred variant of the invention, limit reduction coefficients are defined, beyond which it is not possible to limit the flow within the same cycle. Therefore, when the limit reduction coefficient is reached, the flow of a set with higher priority is reduced. When, however, the limit reduction coefficient is applied to all the sets, it starts again from the lower priority set, in other words another Round is performed, setting a more restrictive limit reduction coefficient.

Preferably, at each subsequent Round the limit reduction coefficient is calculated on the basis of the last reduction coefficient multiplied by the value of the basic limit coefficient, i.e. of the first Round.

According to a first preferred implementation of the invention, when a new Round is performed, for example R2, the calculation of the limitation coefficient for the set L is carried out keeping the limitation coefficients of the sets M and H unchanged calculated at the last Step of the previous Round, for example Step 3.

According to a second preferred implementation of the invention, when performing a new Round, for example R2, the calculation of the limitation coefficient for the set L is performed by resetting any limitation on the sets M and H, in other words, the flow for them is temporarily reset to 1, that is, without any limitation.

While the first implementation turns out to converge more quickly, the second implementation turns out to favour the M and H sets, especially when the number of lower priority organs is greater than the remaining organs that define the M and H sets.

Preferably, the algorithm described above is run on a computer comprising means for processing and storing information, interfaced to control the electro-hydraulic valves of the hydraulic circuit.

According to a first preferred variant of the invention, the regulation is implemented only after the equilibrium condition between the first available flow and the second required flow has been identified.

Since the processing unit can perform calculation cycles in the order of milliseconds, then the implementation of the valves can be performed only after the convergence of the algorithm.

Preferably, the number of cycles is deliberately limited to avoid stall conditions.

According to a second preferred variant of the invention, the algorithm is performed much more slower in the order of seconds and the implementation of the adjustment is performed parallel to the execution of the algorithm and more preferably at the end of each Round.

The present invention can be realized thanks to the implementation of electro-hydraulic directional valves with flow sharing, in which the degree of opening is a function of an electrical signal representative of a position of a joystick or a lever.

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 work machine of the known art;

Figure 2 shows a flowchart for checking the hydraulic functions of the machine of Figure 1;

Figure 3 shows an iteration table of the control of

Figure 2. 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, having no ordinal meaning unless it is clear from the text that there is a precise order to be respected.

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 embodiments The present invention refers to a system for managing the flows of hydraulic liquid in a work machine or an agricultural machine.

The different hydraulic functions are grouped for example into three sets indicated as: High Priority, Medium Priority, Low Priority, i.e. sets having high, medium and low operating priority.

With reference to Figure 2, a flow diagram relating to the control object of the present invention is shown. This flowchart is performed in a closed loop continuously. After the START block, the flow of hydraulic fluid generated A_F and the total flow required R_F necessary for the operation of the various hydraulic functions are acquired simultaneously or in succession, calculated on the basis of the commands given by the user via Joystick, buttons and/or levers.

If the generated flow A_F is greater than or equal to (Yes) the total requested flow R_F, then control resumes from the beginning (START). If, on the other hand, the flow generated A_F is less (No) than the total flow required, then a distribution RED of the available flow of hydraulic fluid is carried out by applying progressively limiting coefficients. Obviously, when the coefficient is equal to 1, this means that no flow limitation is made, while when the coefficient is lower than 1, evidently the flow is limited, step RED, proportionally to the coefficient.

Figure 3 shows an example of a table of the reduction coefficients which are applied progressively to bring the overall flow required at least to equal the available flow of hydraulic liquid.

The labels L, M, H are examples of Low, Medium, High as described above.

At the first step of reduction Step 1, a reduction coefficient is calculated to be applied to the set L.

If this coefficient is greater than the limit reduction coefficient for the set L, at the first step, the limit reduction coefficient is applied, for example equal to 0.65 and the flow is limited to the adjacent set having higher priority .

For the set M and H the basic coefficients are equal to 0.75 and 0.85 and are used as a flow reduction limit in steps Step 2 and Step 3.

The first cycle or Round adopts limit reduction coefficients, called "basic coefficients".

In other words, the basic coefficients are limit coefficients, beyond which, in the first Round it is not possible to reduce the flow for the different sets of users. It is preferred that the basic coefficients are different from each other, with a greater reduction factor for the Low set and so on, progressively to the High set.

When even applying the respective basic coefficient to all the sets L, M, H it is not possible to satisfy the overall flow request, then it starts again with more restrictive coefficients. In other words, it performs a new Round. Rounds are indicated in the figure with Rl, R2, R3....

In particular, at each Round R2, R3, etc .. the limit reduction coefficients are calculated considering the respective limit coefficients of the previous round, multiplied by the base coefficient.

In other words, the current limit reduction coefficient is equal to (base coefficient) ^L i, where i represents the i-th Round. Obviously, in Rl the basic coefficients are used without any modification.

So, first it proceed to apply a flow limitation from the lowest priority set to the highest having power priority set. Once the highest priority set has been reached, if the total flow of hydraulic fluid required is still higher than the available flow, then it starts again from the first set modifying the limit reduction coefficient until the required flow, reduced, is equal to the available flow .

Therefore, the limitation applies by moving from the leftmost column to the rightmost column of the table and starting from the immediately lower row in the leftmost column when the rightmost column of the table is reached.

The arrows indicate the iterative application of the reduction of the flow to the sets and cyclic Rl, R2, R3, until equilibrium is reached.

For example, according to a first operating condition, the actuators relating to the steering system and the roadway management are inserted in set H, while the buldozer blade lifter 4 and the rear tracker 7 are inserted in set L, while all the other actuators are associated with the set M.

Advantageously, when the user operates the joystick that manages the X axis, i.e. the steering of the vehicle, the latter will not notice any delay in the response of the vehicle. The vehicle, on the other hand, will show improved responsiveness and increased reliability while not varying the flow rate of hydraulic fluid generated by the hydraulic pump. According to a preferred variant of the invention, the grouping of the hydraulic functions is preordained in response to the activation of a preordained operating mode.

It is evident that multiple operating modes can be envisaged. For example, if the vehicle is stationary, it can be foreseen to give relatively higher priority to the adjustment of the ploughshare or to the adjustment of the bulldozer blade, therefore, the vehicle can be equipped with appropriate controls to be able to switch between two or more operating modes. According to a preferred variant of the invention, the switching between the different operating modes is automatic .

This automation is based on the acquisition of certain parameters, further to the overall flow of hydraulic fluid generated by the pump, such as, for example, the vehicle's forward speed.

With reference to the table in figure 3, the reduction coefficient applied LI, Ml, HI at each step of a so-called "Round" are less than or at most equal to the respective limit reduction coefficients 0.65; 0.75; 0.85. Therefore, those values represent a saturation limit, beyond which, it is possible to manipulate the flow of the whole with immediately higher priority.

To understand the table in figure 3 more easily, the subscripts of LI, M2, H2, etc .. refer to the Round. Only when, as described above, the coefficient LI, M2, HI, etc .. are saturated with the limit reduction coefficient, it proceeds to manipulate the flow of the set having immediately higher priority. Furthermore, as described above, the "manipulation" may or may not provides for a preventive reset, i.e. unitary value, of the limitation coefficient of the set with immediately higher priority before identifying the value of the coefficient that allows to obtain the balance between the flow generated and flow required .

According to the present description, it is indifferent to speak of sets of organs rather than sets of the relative actuators.

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.