Hydraulic system with adjustable output flow rate for controlling a cylinder

Abstract

TITLE: Hydraulic Installation with Adjustable Output Flow for Controlling a Cylinder. Hydraulic installation (100), connected to a two-chamber (VA, VB) cylinder (V), comprising: a control unit (CU) connected to a lever (Mn), a pump (P), a supply line (LP), a reservoir (T), and a reservoir line (LT). Two electro-hydraulic units (UA, UB) associated with a chamber (VA, VB), each having an adjustable constriction (SeA, SeB). The control unit (CU) connected to the lever (Mn) generates the electrical control signals (ΣEA, ΣEB) for the output section (Ses) of the unit (UA, UB), which receives the output flow (Qout) from the cylinder (V) as a function of the parameters: - setpoint back pressure (Pcp) of the cylinder (V) outlet, - setpoint pressure of the reservoir (PT), - inlet flow (Qin) to the cylinder (V), Figure 1

Description

Title of the invention: Hydraulic installation with adjustment of the outgoing flow for controlling a cylinder FIELD OF THE INVENTION

[0001] The present invention relates to a hydraulic installation of the outgoing flow for the control of a cylinder. STATE OF THE ART

[0002] Currently, hydraulic installations that supply a cylinder, i.e. the cylinder chamber on the bottom side and the cylinder chamber on the rod side, are made by the same slide valve so that the outlet section of the cylinder depends on the stroke of the slide valve and the inlet section. Since the outgoing flow of the cylinder does not only depend on the incoming flow, this means that the outlet section can be oversized or undersized for normal use of the installation.

[0003] In other words, the control of the outgoing flow is currently done by a mechanical connection between the outgoing flow and the incoming flow. Since the output flow also depends on the load applied to the cylinder or the available flow provided by the slope, the back pressure created is not constant so that the speed of the movement under load is not constant for the same driver input signal and different loads (control lever movement). Limiting the section increases the stability of the operation but consequently increases the energy loss. The output section is mainly sized to guarantee the control of the load in the worst case of the movement. This results in a limitation in several applications and thus increases the energy losses.

[0004] PURPOSE OF THE INVENTION

[0005] The present invention aims to develop a hydraulic installation associated with a jack and making it possible to increase operating efficiency by reducing losses in the return of the hydraulic liquid without reducing the possibilities and efficiency of the installation.

[0006] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0007] To this end, the invention relates to a hydraulic installation, this hydraulic installation, connected to a jack with two chambers separated by a piston, the rod of which passing through one of the chambers is connected to equipment receiving a load, this installation comprising: a control unit connected to a lever actuated by the operator to maneuver the equipment with the jack a pump supplying the chambers of the jack by a supply line and a reservoir receiving the hydraulic fluid returning from the jack by a reservoir line, this installation being ca characterized in that it further comprises: two electrohydraulic units associated with a respective chamber by a chamber line and connected to the supply line and to the reservoir line and each comprising: a throttle of adjustable, controlled section, connecting the chamber line to the pump line and to the return line, the control unit being connected to the handle to generate the electrical control signals of: the inlet section of the unit supplying the incoming flow of the cylinder, the outlet section of the unit receiving the outgoing flow of the cylinder, according to the parameters: set counterpressure of the cylinder outlet, set pressure of the reservoir, flow entering the cylinder.

[0008] The hydraulic installation according to the invention with a hydraulic unit associated with each of the chambers of the cylinder makes it possible to make the control of the inlet section and that of the outlet section independent. This makes it possible to limit the loss of energy through restriction. The separate inlet section and outlet section allow direct control of the backpressure and to define the rigidity of the system. The backpressure is controlled by an open-loop control logic. The general idea is based on a setpoint backpressure from which the control unit calculates the outlet opening section as a function of the flow rate leaving the cylinder. This function results in different possibilities:

[0009] - influence the inertia stiffness function by dynamic ramp adjustment of dynamic section,

[0010] - adapt the purpose of the hydraulic circuit according to the driver's intention by the counterpressure managed by the lever,

[0011] - perform a characteristic floating function, i.e. maintaining the fully open outlet section,

[0012] - increase the accuracy of calculating the outgoing flow rate by sensors.

[0013] In summary, the invention makes it possible to define the management of the output section of the cylinder to effectively reduce losses.

[0014] The backpressure control module ensures system rigidity without excessively limiting the output, thereby reducing energy losses without negatively impacting controllability.

[0015] The rigidity of the system depends on the back pressure.

[0016] The higher the back pressure, the more rigid the system is, i.e. responds quickly to the back pressure.

[0017] Particularly advantageously, the adjustable section of the outgoing flow restriction is given by the simplified Bernoulli formula:

[0018] Its =kQout / ^AP,

[0019] In this formula Ses is the outlet section, Qout is the outgoing flow rate and AP is the difference between the set pressure and the reservoir pressure. The coefficient C is a coefficient which depends on the section coefficient Cd of the pipe (length, internal roughness, pressure loss, etc.) and the density. This “section coefficient Cd” is a common concept in hydraulics.

[0020] According to another characteristic, the set pressure is chosen from a predefined fixed value or a variable value depending on the operation of the lever.

[0021] In a particularly advantageous manner, the function giving the set pressure is a strongly increasing function from the pressure of the rest position of the lever then decreasing towards a stabilized value as a function of the operation of the lever and, in the opposite direction, a strongly decreasing function from the pressure of the rest position, decreasing towards a stabilized value, as a function of the operation of the lever from the rest position.

[0022] According to another advantageous characteristic, the two electrohydraulic units each comprise a throttle of adjustable section each produced by: a proportional hydraulic main slide connecting the chamber line to the pump line and to the return line, a pilot valve actuating the main slide and, a proportional electrohydraulic control slide connecting the pump line to the pilot valve and receiving the control signal from the control unit. Brief description of the drawings

[0023] The present invention will be described below in more detail with the aid of embodiments of a hydraulic installation shown in the accompanying drawings in which:

[0024] [Fig. 1] diagram of a hydraulic installation applied to the control of a jack,

[0025] [Fig.2] diagram of a hydraulic unit of the installation according to the invention,

[0026] [Fig.3] variation curve of the setpoint backpressure as a function of the movement of the lever,

[0027] [Fig.4] graph schematizing the response to the control signal emitted by the controller.

[0028] DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0029] According to [Fig.l], the invention relates to an electrohydraulic installation 100, associated with a jack V connected to equipment O maneuvering a load CH. The jack V has two chambers VA, VB separated by a piston VP secured to a jack rod VP connected to the equipment O.

[0030] The piston VP subdivides the cylinder into two chambers VA, VB whose volume varies as a function of the movement of the piston according to the ratio of the free sections SA, SB of the two chambers; the section of the chamber VA at the bottom of the cylinder is the section of its bore; the section SB of the chamber VB crossed by the rod VT is the section of the bore reduced by the section of the rod VT.

[0031] According to the maneuver commanded to the cylinder V, one of the chambers VA, VB receives the incoming flow Qin and the other chamber VB, VA provides the outgoing flow Qout. The ratio of the flow rates, that is to say the variation in volume of a chamber for the stroke AL ​​of the piston is:

[0032] QA=AL.SA

[0033] QB= AL.SB

[0034] so QA / QB= SA / SB.

[0035] The algebraic flow rate (outgoing or incoming) of one chamber as a function of the algebraic flow rate (incoming-outgoing) of the other chamber is therefore

[0036] QB=QA.SB / SA and QA=QB SA / SB

[0037] For example, the movement of the piston VP in the direction of lifting the load CH by the hydraulic liquid supplied by the pump P to the chamber VA or VB must not be slowed down by the reaction of the hydraulic liquid in the other chamber VB or VA by the excessive throttling of the flow of hydraulic liquid leaving the cylinder.

[0038] Conversely, the reverse movement of the piston drive by the load CH creating a pressure in one of the chambers must be braked for various reasons and in particular to avoid cavitation by creating a vacuum in the other chamber. This hydraulic balance of the two chambers VA, VB according to the direction of the action imposed on the cylinder V is adjusted according to the invention by the electrohydraulic control of the flow rates entering / exiting the two chambers VA, VB by the electrohydraulic installation 100.

[0039] The electrohydraulic installation 100 consists of two separate electrohydraulic units UA, UB controlled independently by a control unit UC; these units are associated with the chambers VA, VB of the cylinder and respectively connect one and the other chamber to a pump line LP connected to the pump P and a return line LT to the reservoir T.

[0040] Each module UA, UB comprises an adjustable throttle section SeA, SeB controlled separately by an electrical signal SeA, SeB generated by the control unit UC receiving the signal Sm from the lever Mm operated by the driver as well as the following parameters:

[0041] - PCP setpoint backpressure in the outlet chamber,

[0042] - PT tank pressure

[0043] - incoming flow Qin.

[0044] As already indicated, the algebraic flow rates (inflow rates or outflow rates) of a chamber are in the inverse ratio of the free surfaces SA, SB of the chambers to the flow rate of the other chamber.

[0045] QA=QB* SA / SB or QB=QA*SBxSA

[0046] Depending on the maneuver performed by the cylinder V, one of the chambers is the chamber inlet chamber receiving the incoming flow Qin and the other chamber is the outlet chamber providing the outgoing flow Qout. This operation alternates depending on whether the piston pulls or pushes the equipment O.

[0047] The parameters allow the control unit UC to calculate the output section Ses of the throttle SEA, SEB for the outgoing flow Qout which provides the throttle signal LEA or LEB for the outgoing flow Qout of the unit UA or UB for the action in progress in the cylinder V.

[0048] The central unit UC applies a simplified Bernoulli equation to obtain the setpoint output section Ses of the throttle for the outgoing flow Qout.

[0049] Ses=k

[0050] AP=PCP-PT

[0051] In this formula:

[0052] K=Cd^p

[0053] Cd= section coefficient

[0054] P= density of the fluid

[0055] PCP = set pressure

[0056] PT= reservoir pressure

[0057] The output setpoint section Ses of the outgoing flow unit Qout is emitted by the central unit UC in the form of an electrical control signal LEA, LEB.

[0058] The output section Ses (A or B) is a value depending on fixed or variable parameters; it is set at the start of a jack operation. The parameters Pcp and PT are set according to the hydraulic installation and its equipment.

[0059] For example:

[0060] The Pcp backpressure at the outlet is in the order of 20 to 250 bars

[0061] The pressure of the PT tank is of the order of 5 bars.

[0062] In summary, the hydraulic installation 100, connected to a cylinder V with two chambers VA, VB separated by a piston VP, the rod VT of which passes through one VB of the chambers VA, VB and is connected to equipment O receiving a load CH, installation comprising: a control unit UC connected to a lever Mn actuated by the operator to maneuver the equipment O with the cylinder V a pump P supplying the chambers VA, VB of the cylinder by a supply line LP and a reservoir T receiving the hydraulic liquid returning from the cylinder by a reservoir line LT, installation characterized in that it further comprises: two electrohydraulic units UA, UB associated with a respective chamber VA, VB by a chamber line LEA, LEB and connected to the supply line LP and to the reservoir line LT) and each comprising: a throttle SeA, SeB of adjustable section, controlled independently, connecting the chamber line LEA, LEB to the LP pump line and to the LT return line,

[0063] - the control unit UC being connected to the controller Mn to generate the signals SEA and SEB control electrics of the Ses inlet section of the UA unit, UB receiving the flow Qin from the cylinder V and the Ses outlet section of the UA unit, UB receiving the outgoing flow Qout from the cylinder (V), depending on the parameters: set backpressure Pcp of the cylinder V outlet, set pressure of the PT tank, incoming flow Qin in the cylinder V.

[0064] The installation 100 is supplied with hydraulic liquid under regulated pressure by a controlled pump P taking the hydraulic liquid from a reservoir T supplied by the hydraulic liquid return. The output of the pump is connected to a line LP to which the modules MA, MB are connected, the outputs of which are connected to the reservoir line LT.

[0065] According to [Fig.2], the UX unit which represents the UA unit or the UB unit comprises a main distribution spool 1, proportional, controlled by a pilot chamber 11 moving the spool 1 from its rest position shown in [Fig.2]; the UX unit has a line LeA, LeB connected to a chamber VA or VB of the cylinder and to the reservoir line LT. The spool 1 is shown in its rest position SI 1 connected to the reservoir line LT, because when the spool control 1 is cut, the spring 12 returns the spool 1 to its rest position (shown by drawing convention) in which the section S11 is connected to the LT line of the reservoir T.

[0066] The pilot chamber 11 controlled by the hydraulic fluid supplied by the control spool 2 moves the main spool 1 to place its supply section S13 between the lines LP and (Lex, LeA, LeB) to supply the hydraulic fluid to the chamber VA or VB.

[0067] The two sections S11 and S13 are separated by the intermediate section S12 which cuts the communication through drawer 1.

[0068] The pilot chamber 11 combined with the main slide 1 is controlled by the control slide 2. This is a proportional slide, actuated by an electrical control 21 receiving the control signal SS from the control unit UC. The control slide 2 is returned by the spring 22 to its rest position in which the line connected to the pilot chamber 11 is connected to the reservoir line LT.

[0069] To adjust the incoming flow rate Qin, the control spool 2 receives the signal SS from the control unit UC and connects its input already connected to the line LP of the pump to its output towards the pilot chamber 11. The control spool 2 thus applies a proportional signal of hydraulic liquid to the pilot chamber 11 which proportionally actuates the main spool 1 by adjusting its section of its throttle according to the signal SEA, SEB.

[0070] The active chamber of the cylinder V, has the section of its main drawer open and for the flow controlled by the lever operated by the driver.

[0071] The UX unit described above as an input unit in its function of adjusting the input section of the cylinder, operates in a similar manner if it is the output unit function but then calculating the output section by applying the simplified Bernoulli equation as indicated above.

[0072] The setpoint backpressure Pcp can be a fixed or variable backpressure according to a predefined curve C or the setpoint pressure is chosen from: a predefined fixed value, a variable value depending on the operation of the lever, a value obtained from a measurement of a pressure sensor. The tank pressure is a pressure chosen from: a predefined fixed value, a value obtained from a pressure provided by a pressure sensor.

[0073] [Fig.3] shows a curve C of the variation of the setpoint backpressure or target reaction pressure, imposed on the hydraulic installation 100 as a function of the operation of the lever Mn from its neutral position Mno to the maximum amplitude of its excursion in one direction or the other from its rest position Mno.

[0074] Curve C is composed in its right part starting from the backpressure PO at rest of the lever of four segments C1, C2, C3, C4. The curve begins with a segment of steep slope C1 continuing with a segment of attenuated slope C2 towards the maximum pressure Pmax and then a decreasing slope C3 until a minimum pressure Pmin continuing with a segment C4 of constant level. This curve is only a representative example.

[0075] The movement of the lever Mn in the opposite direction decreases by the segment C5 extending the segment Cl then joining the slightly decreasing segment C6.

[0076] Curve C results in a variation of the outlet throttling section Se since the back pressure is involved in the calculation of the section Se by ^Ap=^Pcp- PT in the denominator, PT being assumed to be constant so that the denominator increases up to the pressure Pcpmax then decreases and becomes constant so that the section Se decreases up to the back pressure Pcmax then increases and then remains constant. On the negative side of the curve, the section increases sharply at first then practically stabilizes.

[0077] [Fig.4] is a very schematic graph of the response signal to the joystick control signal as a function of time t, applied by the control unit UC.

[0078] The final level PA of the control signal requested for the setpoint section by actuation of the lever from the instant is reached at the instant RI by a proportional rise in the signal level (curve SI) up to the value PA (solid curve).

[0079] According to the invention, this rise is attenuated by imposing an attenuated rise curve according to the form S11 in broken lines modifying the slope of the curve in solid lines between a minimum level min S and a maximum level max S imposed by the equipment and the requirements of the hydraulic system.

[0080] The final level PA is reached at time t2. After stopping controlled by the lever at time t3, the signal level decreases according to the curve in solid lines reaching the zero value at time t4. In the case of damping according to curve 221, the descent is less rapid to reach level 0 at time t5.

[0081] In summary, the control unit UC generates the electrical control signal of the section 2EA, 2EB in the form of a trapezoidal curve according to which the high level value PA is reached according to an inclined rise SI or an attenuated rise 211, the return to the zero value by a proportional inclined descent 22 or an attenuated descent 221, the attenuated rise and descent respectively lengthening the rise time and the fall time.

[0082] NOMENCLATURE OF MAIN ELEMENTS

[0083] 100 Hydraulic installation

[0084] 1 Main drawer

[0085] 11 Pilot room

[0086] 12 Spring

[0087] 2 Control drawer

[0088] 21 Electromechanical pilot

[0089] 22 Return spring

[0090] VA, VB Cylinder chambers

[0091] VP Piston

[0092] VT Piston rod

[0093] O Equipment in its charges

[0094] UC Control Unit

[0095] Mn Manette

[0096] Sm Controller Signal

[0097] P Pump

[0098] LP Pump Line / Feed Line

[0099] T Tank

[0100] LT Return line to tank

[0101] UA Electrohydraulic Unit

[0102] UB Electrohydraulic unit

[0103] UA,UB Electrohydraulic units

[0104] LEA, LEB Room lines

[0105] Its Setpoint Output Section

[0106]

[0107]

[0108] SEA, SEB Electrical control signal Qin incoming flow Qout outgoing flow

Claims

Claims

1. Hydraulic installation (100), connected to a cylinder (V) with two chambers (VA, VB) separated by a piston (VP), the rod (VT) of which passing through one (VB) of the chambers (VA, VB) is connected to equipment (O) receiving a load (CH), installation comprising: - a control unit (UC) connected to a lever (Mn) operated by the operator to maneuver the equipment (O) with the jack (V) - a pump (P) supplying the chambers (VA, VB) of the cylinder via a supply line (LP) and a reservoir (T) receiving the hydraulic fluid returning from the cylinder (V) via a reservoir line (LT), installation characterized in that it further comprises: * two electrohydraulic units (UA, UB) associated with a respective chamber (VA, VB) by a chamber line (LEA, LEB) and connected to the supply line (LP) and to the reservoir line (LT) and each comprising: - a throttle (SeA, SeB) with an adjustable section, independently controlled, connecting the chamber line (LeA, LeB) to the pump line (LP) and to the return line (LT), - the control unit (UC) being connected to the joystick (Mn) to generate the electrical control signals (SEA) and (SEB) of: - the inlet section (SE) of the unit (UA, UB) supplying the incoming flow (Qin) of the cylinder (V), - the output section (Ses) of the unit (UA, UB) receiving the outgoing flow (Qout) from the cylinder (V), depending on the parameters: - set counterpressure (Pcp) of the cylinder outlet (V), - set pressure of the tank (PT), - incoming flow (Qin) in the cylinder (V).

2. Hydraulic installation (100) according to claim 1, characterized in that the adjustable section (Ses) of the constriction (Se) of the outgoing flow (Qout) is given by the Bernoulli formula, simplified: Ses=k formula in which, K=Cd^p Cd being the section coefficient and (p) the density of the fluid. AP= Pcp- PT

3. Hydraulic installation (100) according to claims 1 and 2, characterized in that the set pressure (Pcp) is chosen from: - a predefined fixed value, - a variable value depending (C) on the operation of the lever (Mn), - a value obtained from a measurement of a pressure sensor.

4. Hydraulic installation (100) according to claim 3, characterized in that the function giving the set pressure (Pcp) is - a strongly increasing function (Cl, C2) from the pressure (Po) of the rest position of the lever (Mn) then decreasing towards a stabilized value as a function of the operation of the lever and, in the opposite direction, - a strongly decreasing function from the pressure (Po) of the rest position, decreasing towards a stabilized value, as a function of the operation of the lever (Mn) from the rest position.

5. Hydraulic installation (100) according to claims 1 and 2, characterized in that the reservoir pressure is a pressure chosen from: - a predefined fixed value, - a value obtained from a pressure supplied by a pressure sensor.

6. Hydraulic installation (100) according to any one of claims 1 to 5, characterized in that the two electrohydraulic units (UA, UB) each comprise an adjustable section throttle (SeA, SeB) each produced by: - ​​a proportional hydraulic main slide valve (1) connecting the chamber line (LEA, LEB) to the pump line (LP) and to the return line (LT), * a pilot valve (11) actuating the main slide valve (1) and, * an electrohydraulic, proportional control slide valve (2) connecting the pump line (LP) to the pilot valve (11) and receiving the control signal from the control unit (UC).

7. Hydraulic installation (100) according to claim 1, characterized in that the control unit (UC) generates the electrical control signal of the section (2EA, 2EB) in the form of a trapezoidal curve according to which - the high level value (PA) is reached according to an inclined climb (SI) or an attenuated climb (211), - return to the zero value by a proportional inclined descent (22) or an attenuated descent (221), - the attenuated rise and fall extending the rise time and fall time respectively.

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