Hydraulic device with function of adjustment of output flow for controlling cylinder

Abstract

To develop a hydraulic device coupled with a cylinder, the hydraulic device allowing enhancement of operational efficiency by reducing the loss when the pressure medium fluid returns, without deteriorating the capability and efficiency of the device.SOLUTION: Two electrohydraulic units (UA, UB) are coupled with chambers (VA, VB), and each equipped with a throttle (SeA, SeB) with an adjustable cross-section. A control unit (UC) connected to a lever (Mn) generates the electrical signals (ΣEA, ΣEB) for an outlet cross-section of the units receiving an output flow from the cylinder (V) in accordance with the following parameters: a preset backpressure (Pcp) at an outlet of the cylinder (V); a preset pressure (PT) of a tank; and an input flow (Qin) into the cylinder (V).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydraulic device having an adjustment function for the outflow rate for controlling a cylinder. [Background technology]

[0002] 2. Background of the Invention At present, hydraulic devices supplying the cylinders, i.e. the back cylinder chamber and the rod cylinder chamber, are made with identical slide valves, so the outlet cross section of the cylinder changes depending on the stroke and inlet cross section of the slide valve. Since the outflow rate of the cylinder does not depend only on the inflow rate, the outlet cross section can be larger or smaller in size when the device is used normally.

[0003] In other words, the control of the outflow is currently done at the mechanical connection between the outflow and the inflow. Since the outflow also depends on the available volume caused by the load or tilt on the cylinder, the resulting back pressure is not constant and therefore the travel speed under load is not constant for the same input signal from the driver and different loads (control lever movements). Restricting the cross section increases the stability of the operation but results in increased energy losses. The outflow cross section is in principle dimensioned in such a way that the load can be controlled in the worst case of the movement. This leads to restrictions in some applications and therefore increased energy losses. Summary of the Invention [Problem to be solved by the invention]

[0004] Object of the invention The present invention aims to develop a hydraulic device connected to a cylinder, which makes it possible to increase the operating efficiency by suppressing losses caused by the return of hydraulic fluid without reducing the capacity and efficiency of the device. [Means for solving the problem]

[0005] Disclosure and Advantages of the Invention To this end, the invention aims to provide a hydraulic device connected to a cylinder having two chambers separated by a piston, with a rod passing through one of the chambers being connected to the equipment to be loaded, the device comprising a control unit connected to a lever operated by an operator to operate the equipment with the cylinder, a pump supplying the chamber of the cylinder via a supply line and a tank receiving the hydraulic fluid returning from the cylinder via a tank line, characterized in that the device further comprises two electrohydraulic units, linked to the corresponding chamber via the chamber line and connected to the supply line and to the tank line, each electrohydraulic unit having a controlled adjustable cross-sectional throttle connecting the chamber line to the pump line and the return line, and a control unit connected to the lever, which generates an electric signal controlling the inlet cross-section of the unit supplying the inflow flow to the cylinder and the outlet cross-section of the unit receiving the outflow flow from the cylinder depending on the parameters: the set back pressure at the outlet of the cylinder, the set pressure of the tank and the inflow flow to the cylinder.

[0006] The hydraulic system according to the invention, with a hydraulic unit connected to each chamber of the cylinder, allows the control of the inlet cross section and the outlet cross section to be independent, thereby making it possible to reduce the energy losses due to shrinkage. The different inlet and outlet cross sections allow the back pressure to be directly controlled and the stiffness of the system to be defined. The back pressure is controlled by an open-loop control logic. The overall concept is based on a set back pressure, from which the control unit calculates the outlet opening cross section depending on the outflow rate from the cylinder. This functionality allows various possibilities: - Influence the function of inertial stiffness by dynamically adjusting the gradient of the dynamic cross section. -Through the back pressure managed by the lever, the hydraulic circuit objective is adjusted according to the driver's intentions. -Performs a characteristic floating function, i.e. keeps the outlet cross section fully open. -The sensor improves the accuracy of the calculation of the outflow rate.

[0007] In summary, the invention makes it possible to prescribe the management of the exit cross section of the cylinder in order to effectively reduce losses.

[0008] The back pressure control module ensures system stiffness without unduly restricting the outlet, thereby reducing energy losses without adversely affecting control capabilities.

[0009] The stiffness of the system changes with back pressure.

[0010] The higher the back pressure, the stiffer the system becomes, i.e., the faster it responds to the back pressure.

[0011] Particularly preferably, the adjustable cross section of the outlet flow throttle is determined according to the simplified Bernoulli equation Ses=kQout / √ΔP where Ses is the exit cross section, Qout is the outflow rate, and Δp is the difference between the set pressure and the tank pressure. The coefficient C is a coefficient that varies depending on the section modulus Cd of the conduit (length, internal roughness, load loss, etc.) and density. This "section modulus Cd" is a common concept in hydraulics.

[0012] According to another feature, the set pressure is selected from a predetermined fixed value or a variable value depending on the operation of a lever.

[0013] Particularly advantageously, the function generating the set pressure is a function which increases significantly from the pressure in the rest position of the lever and decreases towards a stable value as the lever is operated, and in the opposite direction, decreases significantly from the pressure in the rest position and decreases from the rest position towards a stable value as the lever is operated.

[0014] According to another advantageous feature, the two electrohydraulic units each have a throttle of adjustable cross section, each throttle being realised by a proportional hydraulic main slide valve connecting the conduits of the chambers to the pump line and to the return line, a pilot valve operating the main slide valve and a proportional electrohydraulic controlled slide valve connecting the pump line to the pilot valve and receiving a control signal from the control unit.

[0015] The invention will be explained in more detail below using an embodiment of a hydraulic device shown in the attached drawings. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram of a hydraulic system applied to the control of a cylinder. [Diagram 2] FIG. 2 is a diagram of a hydraulic unit of the device according to the invention. [Diagram 3] FIG. 11 is a graph showing the curve of change in set back pressure according to the movement of the lever. [Figure 4] FIG. 13 is a schematic diagram of the response of the lever to a control signal issued by the lever. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Description of the Preferred Embodiments of the Invention 1, the object of the invention is an electrohydraulic device 100 associated with a cylinder V connected to an installation O driving a load CH. The cylinder V has two chambers VA, VB separated by a piston VP associated with a cylinder rod VT connected to the installation O.

[0018] The piston VP divides the cylinder into two chambers VA and VB, the volume of the chambers varies with the movement of the piston according to the ratio of the free cross sections SA and SB of the two chambers, the cross section of the chamber VA at the back of the cylinder is the cross section of the bore of the cylinder, and the cross section SB of the chamber VB through which the rod VT passes is the cross section of the bore reduced by the cross section of the rod VT.

[0019] According to the commanded operation of cylinder V, one of the chambers VA, VB receives an inflow flow Qin, while the other chamber VB, VA supplies an outflow flow Qout. The ratio of the flows, i.e. the change in the chamber volume with respect to the piston stroke ΔL, is given by: QA = ΔL SA QB = ΔL SB Therefore, QA / QB=SA / SB.

[0020] Since the algebraic flow rate (in or out) of one chamber varies depending on the algebraic flow rate (in-out) of the other chamber, QB=QA·SB / SA and QA=QB·SA / SB It is.

[0021] For example, the movement of the piston VP in the direction in which the load CH is lifted by the hydraulic fluid supplied by the pump P to the chamber VA or VB must not be slowed down by the reaction of the hydraulic fluid in the other chamber VB or VA by excessively throttling the flow rate of the hydraulic fluid leaving the cylinder.

[0022] Conversely, the reverse movement of the piston driven by the load CH creating a pressure in one of the chambers must be slowed down for various reasons, in particular to prevent a decompression in the other chamber, creating a cavity. This hydraulic balance of the two chambers VA, VB depending on the direction of the action applied to the cylinder V is regulated according to the invention by electrohydraulic control of the flow of fluid into and out of the two chambers VA, VB with the electrohydraulic device 100.

[0023] The electro-hydraulic device 100 consists of two different electro-hydraulic units UA, UB, independently controlled by a control unit UC, which are connected to the chambers VA, VB of the cylinders, each unit connecting one chamber to the pump line LP leading to the pump P and the other to the return line LT to the tank T.

[0024] Each module UA, UB has an adjustable throttle cross section SeA, SeB which is determined by an electric signal ΣeA, ΣeB generated by a control unit UC which receives a signal Sm of a lever Mm operated by the driver, and by the following parameters: -Set back pressure in the output chamber PCP, -Tank pressure PT -Inflow flow rate Qin are separately controlled by

[0025] As already mentioned, the algebraic flow rate (flow rate in or out) of one chamber is the inverse ratio of the flow rate of the free surface SA, SB of the chamber to the flow rate of the other chamber. QA = QB·SA / SB or QB = QA·SBxSA

[0026] Depending on the operation performed by the cylinder V, one chamber is the inlet chamber receiving the incoming flow Qin and the other chamber is the outlet chamber providing the outgoing flow Qout. This action alternates depending on whether the piston pulls or pushes the fixture O.

[0027] These parameters enable the control unit UC to calculate the exit cross section Se of the throttle ΣEA, ΣEB for the outlet flow rate Qout, related to the actions occurring in the cylinder V, which provides a signal for the throttle ΣEA or ΣEB for the outlet flow rate Qout of the unit UA or UB.

[0028] The central unit UC applies the simplified Bernoulli equation to obtain the setting outlet cross section Ses of the throttle for the outflow rate Qout.

[0029]

number

[0030] The set outlet cross section of the unit for the outflow flow Qout is issued by the central unit UC in the form of control electrical signals ΣEA, ΣEB.

[0031] The outlet cross section Ses (A or B) is a value that varies depending on a fixed or variable parameter, which is adjusted at the start of the operation of the cylinder. The parameters Pcp and PT are set according to the hydraulic system and its installation.

[0032] For example, The outlet back pressure Pcp is about 20 to 250 bar. The pressure in the tank PT is about 5 bar.

[0033] In summary, a hydraulic device 100 is connected to a cylinder V having two chambers VA, VB separated by a piston VP, a rod VT passing through one of the chambers VB is connected to an installation O receiving a load CH, the device comprises a control unit UC connected to a lever Mn operated by an operator to operate the installation O with the cylinder V, a pump P supplying the chambers VA, VB of the cylinder via a supply line LP and a tank T receiving hydraulic fluid returning from the cylinder via a tank line LT, the device comprises two electrohydraulic units UA, UB connected to the corresponding chambers VA, VB via chamber lines LEA, LEB and connected to the supply line LP and the tank line LT, each electrohydraulic unit comprising an independently controlled throttle SeA, SeB of adjustable cross section, which throttles the chamber lines LEA, LEB to the pump line LP and the return line LT, a control unit UC connected to the lever Mn, which generates electric signals ΣEA and ΣEB for controlling the inlet cross section Ses of the units UA, UB receiving the flow Qin of the cylinder V and the outlet cross section Ses of the units UA, UB receiving the flow Qout of the cylinder (V) according to the parameters: the set back pressure Pcp at the outlet of the cylinder V, the set pressure PT of the tank, and the inlet flow Qin to the cylinder V; The hydraulic device 100 further comprises two electro-hydraulic units UA and UB having the above-mentioned components.

[0034] The device 100 is supplied with hydraulic fluid under regulated pressure by a pump P which is controlled by taking hydraulic fluid from a tank T supplied with the hydraulic fluid returning therefrom. The outlet of the pump is connected to a line LP which is connected to modules MA, MB whose outlets are connected to a tank line LT.

[0035] According to Fig. 2, a unit UX, representing a unit UA or a unit UB, has a proportional main distributor slide valve 1, which is controlled by a pilot chamber 11 moving the slide valve 1 from the rest position shown in Fig. 2, the unit UX has lines LEA, LEB connected to the chamber VA or VB of the cylinder and to the tank line LT. The slide valve 1 is shown in the rest position S11 in which it is connected to the tank line LT, because when the control of the slide valve 1 is disconnected, a spring 12 returns the slide valve 1 to the rest position (as shown by the drawing convention) in which the section S11 is connected to the line LT of the tank T.

[0036] The pilot chamber 11, controlled by hydraulic fluid supplied by the control slide valve 2, moves the main slide valve 1 so that the supply section S13 is between the conduits LP and LEX (LEA, LEB) to supply hydraulic fluid to the chamber VA or VB.

[0037] The two compartments S11 and S13 are separated by an intermediate compartment S12 which blocks communication through the slide valve 1.

[0038] The pilot chamber 11 associated with the main slide valve 1 is controlled by a control slide valve 2. This control slide valve is a proportional slide valve and is operated by an electric control device 21 which receives a control signal ΣS from a control unit UC. The control slide valve 2 is returned by a spring 22 to its rest position, in which the line connected to the pilot chamber 11 is connected to the tank line LT.

[0039] To regulate the inlet flow rate Qin, the control slide valve 2 receives a signal ΣS from the control unit UC and connects the inlet, already connected to the pump line LP, to the outlet leading to the pilot chamber 11. The control slide valve 2 thus applies a proportional signal of hydraulic fluid to the pilot chamber 11, which in turn proportionally operates the main slide valve 1, adjusting the throttle cross section in response to the signals ΣEA, ΣEB.

[0040] The active chamber of cylinder V has a section through which the main slide valve is open and the flow rate is controlled by a lever operated by the operator.

[0041] The unit UX, previously described as an input unit for the function of adjusting the inlet cross section of the cylinder, works in a similar manner to the output unit function, but it calculates the outlet cross section by applying the simplified Bernoulli equation as described above.

[0042] The set back pressure Pcp may be a fixed back pressure or a variable back pressure according to a predetermined curve C.

[0043] FIG. 3 shows a curve C of the change in the set back pressure or target reaction pressure applied to the hydraulic device 100 in response to the operation of the lever Mn from the neutral position Mno in one direction or from the rest position Mno in the other direction to the maximum amplitude of the deflection.

[0044] Curve C is composed of four segments C1, C2, C3, C4 on the right side starting from the back pressure P0 at rest of the lever. The curve starts with a steep segment Cl, followed by a decreasing slope segment C2 towards the maximum pressure Pmax, then a decreasing slope C3 to the minimum pressure Pmin, followed by a constant level segment C4. This curve is merely a representative example.

[0045] The reverse movement of lever Mn decreases at line segment C5, which is an extension of line segment C1, and then continues to line segment C6, which is slightly lower.

[0046] Curve C refers to the change in the outlet throttle cross section Se, due to the intervention of the back pressure in the calculation of the cross section Se by the denominator √Δp=√Pcp-PT, and since PT is assumed to be constant, the denominator increases to the pressure Pcpmax and then decreases and becomes constant, while the cross section Se increases after shrinking to the back pressure Pcmax and then becomes constant. On the negative side of the curve, the cross section actually stabilizes after an initial sharp increase.

[0047] FIG. 4 is a highly schematic representation of a response signal as a function of time t to a control signal from a lever applied by a control unit UC.

[0048] The final level PA of the control signal required for the set cross section by the lever action from a certain moment onwards is reached at the moment R1 by a proportional rise of the signal level (curve Σ1) to the value PA (solid curve).

[0049] According to the invention, this rise is damped by modifying the slope of the solid curve between the minimum level minS and the maximum level maxS imposed by the hardware and needs of the hydraulic system to impose a damped rising curve along the dashed shape Σ11.

[0050] The final level PA is reached at the moment t2. After the lever commands the stop at the moment t3, the signal level drops along the solid curve and reaches the zero value at the moment t4. If it is gentler along the curve Σ21, the drop occurs more slowly and reaches the level 0 at the moment t5.

[0051] In summary, the control unit UC generates electrical signals which control the cross sections ΣEA, ΣEB in the form of a trapezoidal curve, which reaches a high level value PA along a ramp Σ1 or decay ramp Σ11 and returns to the zero value by a proportional ramp Σ2 or decay ramp Σ21, which extend the rise and fall times, respectively. [Explanation of symbols]

[0052] 100 Hydraulic device 1 Main Slide Valve 11 Pilot Chamber 12 Spring 2 Control slide valve 21 Electromechanical control system 22 Return spring VA, VB Cylinder chamber VP Piston VT piston rod O Loaded equipment UC Control Unit Mn Lever Signal from Sm lever P-Pump LP pump line / supply line T Tank LT Return line to tank UA Electric Hydraulic Unit UB Electric Hydraulic Unit UA,UB Electric hydraulic unit LEA, LEB chamber line Ses setting exit cross section ΣEA,ΣEB control electrical signal Qin inflow flow rate Qout Outflow flow rate

Claims

1. A hydraulic device (100) connected to a cylinder (V) having two chambers (VA, VB) separated by a piston (VP), with a rod (VT) passing through one (VB) of said chambers (VA, VB) being connected to equipment (O) for receiving a load (CH), The hydraulic device (100) comprises: a control unit (UC) connected to a lever (Mn) operated by an operator to operate the equipment (O) using the cylinder (V); a pump (P) supplying the chambers (VA, VB) of the cylinder via a supply line (LP); a tank (T) for receiving hydraulic fluid returning from the cylinder (V) via a tank line (LT); A hydraulic device (100) comprising: The hydraulic device (100) comprises: Two electrohydraulic units (UA, UB) connected to corresponding chambers (VA, VB) via chamber lines (LEA, LEB) and connected to said supply line (LP) and said tank line (LT), each electrohydraulic unit (UA, UB) - independently controlled throttles (SeA, SeB) of adjustable cross section, connecting said chamber lines (LEA, LEB) with said pump line (LP) and with said return line (LT); a control unit (UC) connected to said lever (Mn), which is a parameter - the set back pressure (Pcp) at the outlet of said cylinder (V), - the set pressure of said tank (PT), - the inflow rate (Qin) into said cylinder (V) Depending on - the inlet cross section (SE) of the unit (UA, UB) which supplies the inlet flow rate (Qin) of said cylinder (V), - the outlet cross section (Ses) of the unit (UA, UB) receiving the outflow rate (Qout) from the cylinder (V) a control unit (UC) for generating electrical signals (ΣEA) and (ΣEB) for controlling The hydraulic unit further comprises two electrohydraulic units (UA, UB) having A hydraulic device (100).

2. The adjustable cross section (Ses) of the throttle (Se) of the outlet flow rate (Qout) is calculated by the simplified Bernoulli equation: [0010] is required by During the ceremony, K = Cd√ρ Cd is the section modulus, (ρ) is the density of the fluid, ΔP=Pcp−PT 2. The hydraulic device (100) of claim 1, wherein:

3. The set pressure (Pcp) is - a predetermined fixed value, a variable value (C) depending on the operation of said lever (Mn), - Value obtained from pressure sensor measurement 3. The hydraulic device (100) according to claim 1 or 2, characterized in that it is selected from:

4. The function that produces the set pressure (Pcp) is a function which increases significantly (C1, C2) from the pressure (Po) in the rest position of said lever (Mn) and decreases towards a stable value as said lever is operated, and in the opposite direction: - a function that decreases significantly from the pressure (Po) in the rest position and decreases from the rest position towards a stable value as a function of the lever (Mn) A hydraulic device (100) according to claim 3, characterized in that

5. The pressure of the tank is - a predetermined fixed value, - the value obtained from the pressure provided by the pressure sensor 3. The hydraulic system (100) according to claim 1 or 2, characterized in that the pressure is selected from:

6. The two electrohydraulic units (UA, UB) each have a throttle (SeA, SeB) of adjustable cross section, each throttle (SeA, SeB) having - a proportional hydraulic main slide valve (1) connecting said chamber pipes (LEA, LEB) to said pump line (LP) and to said return line (LT); A pilot valve (11) for operating the main slide valve (1); a proportional electrohydraulic controlled slide valve (2) connecting said pump line (LP) to said pilot valve (11) and receiving said control signal from said control unit (UC); The hydraulic device (100) according to any one of claims 1 to 5, characterized in that it is realized by:

7. The control unit (UC) generates electrical signals for controlling the cross sections (ΣEA, ΣEB) in the form of a trapezoidal curve, in which - reaching a high level value (PA) along a ramp rise (Σ1) or a decaying rise (Σ11), - a proportional ramp down (Σ2) or damping down (Σ21) back to the zero value, The decaying rise and fall extend the rise and fall times, respectively A hydraulic device (100) according to claim 1, characterized in that

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