Hydraulic circuit equipped with a control system for a hydraulic component

Abstract

Hydraulic circuit (100) comprising a pump (20) connected to a reservoir (21) and supplying pressurized hydraulic fluid to a component (7) via a spool, and a pressure relief valve (6) connected to the inlet of the component (7) and to the reservoir (21), the hydraulic circuit comprising: - a control system having: * a pressure sensor (8) providing the hydraulic fluid pressure information (P) * a setpoint pressure (PC) - an actuator (23) controlling the movement of the spool (2) - a control unit (10) for generating the control signal (SC) of the actuator (23) from the pressure information (P), the setpoint pressure (PC), and the operator's demand (DO) - a leakage orifice (5) in the spool (2) creating a leak to the reservoir (21) in the initial phase of the spool (2) stroke. Figure 1

Description

Title of the invention: Hydraulic circuit equipped with a system for controlling a hydraulic component FIELD OF THE INVENTION

[0001] The present invention relates to a hydraulic circuit comprising a pump connected to a reservoir and supplying hydraulic fluid under adjusted pressure to a component via a distribution slide valve provided with a distribution orifice connected to the inlet of the component and a decompression orifice connected to the outlet of the component as well as a pressure limiter connected to the inlet of the component. STATE OF THE ART

[0002] Multiple systems are already known for controlling hydraulic components equipping a hydraulic machine such as a public works machine.

[0003] Thus [Fig.5] shows a system for controlling a hydraulic component 7 by an operator actuating its lever or control member 1. The hydraulic component (also called “function”) 7 is here a motor integrated into a hydraulic circuit supplied by a pump 20 drawing the liquid from a reservoir 21 receiving the hydraulic liquid returning from the circuit. The circuit passes through a distribution slide 2a having a distribution orifice 3 and a decompression orifice 4. The section of the distribution orifice 3 follows a distribution law C3 and that of the decompression orifice 4 follows a decompression law C4. [Fig.5A], these laws will be presented later

[0004] The hydraulic circuit 100 is protected upstream of the slide valve 2a by a main pressure limiter 9 connected to the reservoir 21 which limits the pressure of the hydraulic liquid supplied by the pump 20, to a safety pressure, for example 200 bar.

[0005] In the circuit itself, the hydraulic component 7 is protected against overpressure by a secondary pressure limiter 6 between the inlet and the outlet of the hydraulic component 7, downstream of the distribution slide 2a. The secondary limiter 6 is connected directly to the reservoir 21.

[0006] In the event of overpressure opening the secondary limiter 6, the flow coming from the supply orifice 3 is discharged directly into the reservoir 21 without the flow being modified as long as the operator does not modify the flow request by his control member 1 acting directly on the distribution slide 2a.

[0007] In normal operation, the operator generally operates the lever 1 to its maximum travel. If, during operation, the tool 7 becomes blocked, the entire feed flow is discharged through the pressure limiter 6 with direct return to the reservoir 21.

[0008] For example, in the case of a pressure of 100 bar and a flow rate of 60 1 / minute, this corresponds to a loss of 10 Kw.

[0009] Indeed, it is often only a few seconds after the blockage that the operator reacts and releases the lever so that it returns to the neutral position, and completely closes the supply orifice 3.

[0010] The case presented above is that of a non-reversible hydraulic motor 7 whose input is always supplied by orifice 3 and the decompression passes through the return via orifice 4.

[0011] In the case of a reversible motor, the input and return of the motor are exchanged for the movement in the opposite direction; the sections of the orifices then evolve according to curves symmetrical to those of [Fig.5A], by symmetry with respect to the Y axis representing the sections of the orifices; the X axis of the slide travel is oriented in the negative direction.

[0012] Figures 6A, 6B show the case of a component consisting of a double-acting cylinder 7A, formed of a cylindrical enclosure subdivided into two chambers for the piston:

[0013] - one 71 of the chambers is delimited between the piston and the bottom of the cylinder,

[0014] - the other chamber 72 is delimited between the piston, the cylinder rod and the other bottom.

[0015] The variation in the volume of the two chambers 71, 72 is different since the section of the chamber crossed by the piston rod is reduced by the section of this rod.

[0016] The operation of the cylinder is represented by the two figures 6A, 6B corresponding respectively to the cylinder supplied on the bottom side and to the cylinder supplied on the rod side; the evolution curves of the orifices (3a, 4a), (3b, 4b) are represented in the graphs of [Fig.7].

[0017] The supply curve C3a for the circuit according to [Fig.6A] is above the return curve C4a, which results in the pressure curve CPa.

[0018] The supply curve C3b of the circuit according to [Fig.6B] is below the return curve C4b, which results in a stable and low pressure curve CPb for the pressure at the inlet of the cylinder in this position. The transition from the operating mode of the cylinder from its supply to operation in the opposite direction with the cylinder supplied according to [Fig.6B] is done by the passage of the slide through the position O to then have orifices 3b, 4b which evolve according to the curves C3b, C4b.

[0019] In the feed according to [Fig.6A], the pressure at the inlet varies according to the curve CPa and in the case of the feed of [Fig.6B], the pressure CPb is established at a low, practically constant level.

[0020] The orifices (3a, 4a) and (3b and 4b) are pairs of separate orifices on the slide 2a; these orifices are connected respectively to the chambers 71, 72 by the orifices 3a, 4a and to the chambers 72, 71 in the reverse order by the orifices 3b, 4b.

[0021] In both operating modes, in the event of the cylinder 7 (7a, 7b) being blocked, the secondary limiter 6 intervenes with consequences similar to those of the circuit in [Fig.5].

[0022] In more detail:

[0023] the orifices 3 and 4 have a section S3, S4 variable according to the translation position of the slide 2a, so as to adjust the flow rate Q through each orifice 3 or 4 according to the Bernoulli formula:

[0024] Qi = kiÆP*Si(x)

[0025] In this formula:

[0026] Qi: flow through orifice (i)

[0027] AP: pressure difference between the pressure supplied by the pump 20 and that of the load represented by the component 7,

[0028] Si(x): section of the orifice (i) as a function of the translation position (x) of the distribution drawer 2a.

[0029] ki: coefficient depending on the machining characteristics of the drawer 2a.

[0030] (i) = 3 or 4

[0031] The section Si(x) of the orifice (i) follows a curve representing the imposed evolution of the section Si as a function of hydraulic imperatives linked to the function (i.e. the operating characteristics of the hydraulic component) as represented in [Fig.3] for the curves C3 and C4 established for the orifices 3 and 4 of the hydraulic circuit of [Fig.4].

[0032] The curves are plotted in a coordinate system with origin O, abscissas (x) and ordinates (y).

[0033] The ordinate (y) represents the section Si (x) of the orifice (i) for the position at (x) of the distribution slide 2a. The origin O of this X axis is the position of the distribution slide 2a in which the section Si(x) is zero, that is to say the orifice is closed:

[0034] As an example:

[0035] * Curve C3 representing the section S3 of the feed orifice 3 comes from the origin O; it increases slowly at first then with a steep slope in an elongated S shape, up to its maximum section S3max for the end of travel xM of the distribution spool 2.

[0036] * Curve C4 representing the section S4 of the return orifice 4, evolves possibly around an undrawn straight line, from the origin O to its maximum section S4max for the end of travel xm of the distribution spool 2a.

[0037] Curves C3 and C4 intersect. In the initial phase, the supply section S3 is below the return section S4; this relationship changes during operating mode to reach the full speed zone until the end of travel xM.

[0038] This known hydraulic system uses the pressure limiter 6 which is a hy- dromechanique installed in the line connected to the tank. The pressure limiter 6 is adjusted by the calibration of its spring, by an adjustment screw or an electroproportional coil to adjust the maximum admissible pressure at the inlet of the component 7.

[0039] An overpressure occurs in the event of blockage of the hydraulic component 7 for an external cause.

[0040] The pressure limiter 6 makes it possible to protect various hydraulic tools with motor or cylinder such as hydraulic hammers, sweepers, augers or other, equipping a public works machine. But this diversity of tools creates more or less annoying disadvantages.

[0041] Generally, when purchased, a hydraulic machine has basic equipment like that of an excavator. This equipment is then supplemented by certain tools for which the adjustment of the hydraulic circuit is not suitable, so that the hydraulic circuit must then be transformed, which leads to inconveniences and costs.

[0042] The pressure adjustment range is limited and to install the equipment as indicated above, it is necessary to mechanically modify the installation, for example the value of the pressure limiter spring 6.

[0043] In the case of a pressure to be set lower than the system pressure, this reduces the performance of the other functions which will have to work at a temporarily reduced pressure.

[0044] For tools that require a lot of speed, i.e. a high flow rate, the hydromechanical limiter 6 must be able to evacuate the high flow rates to the reservoir 21 and this under high pressure which is the setting pressure of the limiter 6. It is therefore necessary to adapt the dimensioning of the pressure limiter to the power to be evacuated. This hydraulic power lost for a few seconds can represent a significant loss.

[0045] In addition, to evacuate a large flow, the fittings and hoses must be of large diameter, which makes them bulky and difficult to install in an existing hydraulic installation.

[0046] Depending on the rotation speed of the drive system of the motor pump unit supplying the hydraulic installation, there may be parasitic frequencies caused by pressure variations which must be limited to the terminals of the motor or the hydraulic cylinder. This also requires modification of the distribution slide.

[0047] PURPOSE OF THE INVENTION

[0048] The present invention aims to overcome the drawbacks of known control systems for hydraulic circuit components and to provide a hydraulic circuit enabling the hydraulic component to operate more efficiently while simplifying the installation of different hydraulic components on the same hydraulic machine, by adjusting the working pressure.

[0049] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0050] For this purpose, the invention relates to a system for controlling a hydraulic component, this circuit being characterized in that a system for controlling the supply of the hydraulic component having a pressure sensor installed upstream of the hydraulic component downstream of the supply orifice and providing the pressure information of the hydraulic liquid a set pressure an actuator controlling the movement of the distribution spool a control unit for generating the control signal of the actuator from the pressure information measured at the supply orifice, the set pressure and the operator's request a leak orifice in the spool creating a leak towards the reservoir between the supply orifice and the component in the initial phase of the spool stroke.

[0051] The hydraulic circuit according to the invention is produced or installed very simply by combining with the known hydraulic circuit, a supply pressure sensor to monitor this pressure, a leakage orifice in the distributor slide and a control unit making it possible to manage the operation of the slide distributor according to the operator's request by adapting this request to the specific operating characteristics of the different components likely to be installed in the hydraulic circuit, by configuring the management and by protecting the circuit against pressure shocks or excessive pressures and by allowing operation without loss of energy.

[0052] The control system according to the invention is very easily installed on an existing machine by a compact system. The system generally makes it possible to limit energy loss, to recover the available flow rate and to work at a pressure that is lower if necessary and to maintain a high pressure for the other functions. More generally, the control system according to the invention makes it possible to adjust the working pressure by the configurable control unit.

[0053] According to another advantageous characteristic, the control unit forms the difference Ec between the control unit forms the difference between the pressure information from the sensor and the set pressure to convert this pressure difference into a basic signal varying according to stages in operating zones according to the position of the distribution slide, and a scale receiving the operator request signal and the basic signal to emit a control signal equal to the smallest of the two signals, the operator request and the basic signal.

[0054] The invention also makes it possible to have a more complete range of pressure limitation settings and, in general, to ensure the stability of the system at all operating speeds.

[0055] In summary, in this hydraulic circuit according to the invention, in the event of overpressure, before that it reaches the pressure level triggering the secondary limiter, the control unit receives the pressure signal and generates the control signal for the distribution spool to recall it into the decompression zone in which the section and therefore the supply flow rate are reduced and the pressure can be evacuated through the leak orifice whose section is slightly greater than or equal to the supply section in this operating range.

[0056] According to another advantageous characteristic, the circuits of the supply, decompression and leakage orifices of the slide are divided into zones according to the position of movement of the slide: a closing zone being the zone of closing of the supply from the end of travel position of the slide to a start of opening position, a decompression zone following the closing zone and in which the supply section opens slowly while being lower than the leakage section, the supply sections (S3 and leakage S5) being very lower than the decompression section, a pressure maintenance zone in which the leakage section descends and passes below the supply section, a distribution zone in which the section of the leakage orifice intervenes only very slightly a full flow zone in which the leakage section practically no longer intervenes.

[0057] According to another advantageous characteristic, the control unit comprises a temperature compensation table receiving the basic signal SCo to compensate it as a function of the temperature of the hydraulic liquid, provided by the temperature sensor detecting the temperature of the hydraulic liquid of the circuit, the temperature-compensated signal SCC being applied to the scale receiving the demand signal DO from the operator and this temperature-compensated signal SCC to form the control signal from the smaller of these two signals. Brief description of the drawings

[0058] The present invention will be described below in more detail with the aid of an embodiment of a hydraulic circuit according to the invention, represented in the appended drawings in which:

[0059] [Fig-1] control system of a hydraulic component according to the invention

[0060] [Fig.2] diagram of the system control function.

[0061] [Fig.3] graph of the curves of the sections of the orifices of the distribution drawer,

[0062] [Fig.3A] detail on an enlarged scale of [Fig.3]

[0063] [Fig.4] graph of the curves of the section of the orifices of the drawer as a function of a stroke of the drawer for a reversible hydraulic component such as a hydraulic motor,

[0064] [Fig.5] diagram of a control system of a hydraulic component according to the state of the art,

[0065] [Fig.5A] graph of the curves of the section of the orifices of the distribution drawer of the circuit of [Fig.5],

[0066] [Fig.6A] control diagram of a double-acting hydraulic cylinder for its first supply position,

[0067] [Fig.6B] control diagram of the double-acting cylinder of [Fig.6A] according to its second supply position,

[0068] [Fig.7] graph of the curves of the section of the orifices of the distribution drawer for the supply of a double-acting cylinder.

[0069] DESCRIPTION OF AN EMBODIMENT

[0070] According to [Fig.l] the invention relates to a hydraulic circuit 100 supplied with hydraulic liquid by a pump 20 (motor pump) which supplies the hydraulic liquid at a variable pressure, limited by a main pressure limiter 9. The hydraulic circuit 100 comprises a distribution slide 2 managing the supply of a hydraulic component 7 according to the demand DO of the operator actuating a control member 1 such as a lever and taking into account imposed parameters.

[0071] The hydraulic circuit 100 comprises:

[0072] - a branch connecting the pump 20 to the inlet of the hydraulic component 7 through a feed port 3 of drawer 2

[0073] - a return branch connecting the outlet of the hydraulic component 7 to the reservoir 21 to through the decompression (or return) port 4 of the drawer 2 and

[0074] - a bypass from the inlet of the hydraulic component 7 to the reservoir 21 by a leak hole 5 of drawer 2.

[0075] The hydraulic circuit 100 is completed by a direct connection between the inlet of the hydraulic component 7 and the reservoir 21 by a secondary pressure limiter 6 not passing through the return orifice 4.

[0076] The secondary limiter 6 is an important high safety device for limiting the maximum pressure in the event of failure of the electronic part or by cutting off the electrical power supply. For example, the adjustment range is from 50 bar to 350 bar. The secondary pressure limiter will be set at 360 bar to avoid overpressures which could damage the pipes, hoses or any other component of the hydraulic system if the distribution slide remains closed following a control error or due to a lack of electrical power.

[0077] According to the invention, the almost instantaneous control of the drawer 2 by the actuator 23 controlled by the unit 10, is independent of the operator request DO, that is to say of the position of the actuating member 1.

[0078] The leak orifice 5 is connected to the supply orifice 3 upstream of the component 7 which allows it, in the initial phase of the pressure rise in the hydraulic circuit, to attenuate or smooth the pressure rise and also to operate more efficiently. in the event of a strong pressure increase; thus for example in the event of blockage of the hydraulic component 7, the pressure increase upstream of the component is immediately detected by the pressure sensor 8 connected to the inlet of the hydraulic component 7; this pressure is processed by the control unit 10 which immediately returns the distribution slide 2 to the decompression zone B so as to reduce the supply section S3 and therefore the flow rate Q3 arriving at the hydraulic component 7; this low flow rate is discharged through the leak orifice 5 without having to go to full flow at high pressure via the limiter 6. The available flow rate can supply another component.

[0079] As the characteristics of the hydraulic circuit 100 can depend on the temperature T of the hydraulic liquid, according to a variant, to take into account this significant dependence in certain cases, the output of the pump 20, downstream of the connection of the primary limiter 9, is provided with a temperature sensor 22.

[0080] The distribution drawer 2 is controlled by a control unit 10 receiving ([Fig.2]):

[0081] - the DO request from operator 1

[0082] - the set pressure PC

[0083] - the pressure P of the pressure sensor 8

[0084] and alternatively:

[0085] - the temperature T of the hydraulic liquid provided by the sensor 22.

[0086] The set pressure C is a parameter imposed on the operation of the hydraulic circuit 100 to protect the circuit and its SES components and reduce energy losses through liquid returns at high pressure and high flow rate, these losses by not triggering the pressure limiter 6.

[0087] According to [Fig.2], the control unit 10 compares the pressure P supplied by the sensor 8 with the pressure setpoint Pc and forms the difference Ec used to generate a basic control signal SCo which is then compensated, if necessary, in temperature with a compensation table 101. The basic signal SCo is a function of the difference Ec according to a curve Co depending on the control zones A, B, C, D, E of the openings 3, 4, 5 which will be specified later, according to the increasing level steps in the zones A, C, E and the connecting segments in the zones B, D between the steps. The basic signal SCo arrives in a balance 102 which also receives the request from the operator DO to retain as control signal SC, the smaller of these two signals SCo or DO.

[0088] In the case of the circuit variant equipped with a temperature sensor 22 for detecting the temperature of the hydraulic liquid, the basic signal SCo is compensated to give the compensated signal SCC which will be the one compared to the signal DO in the balance 102 to obtain the control signal SC.

[0089] The signal SC controls the distribution drawer 2 which fixes the sections S3, S4, S5 of the orifices 3, 4, 5 by its positioning (x) evolving on the curves C3, C4, C5 of [Fig.3] and of the detail on an enlarged scale, of [Fig.3A].

[0090] Curves C3, C4 of [Fig. 3], already explained in their general principle, represent the evolution of the sections of the orifices 3, 4 as a function of the position of the distribution slide 2 in the distributor body. The same applies to the section S5 of the orifice 5, defined by curve C5.

[0091] In the case of the hydraulic motor 7, the flow of liquid only evolves in one direction so that only the curves of the right part of the graph of figures 3 / 3A intervene whereas in the case of a jack, there is an inversion of the non-symmetrical direction of passage of the liquid in the component (7a, 7b) and it is the curves of the right part and the left part as in the table of [Fig.7] which are used.

[0092] The slide 2 is moved by the actuator 23 controlled by the signal SC and not directly by the request DO from the control member of the operator 1, so that the reaction of the circuit 100 is faster than that of the operator to take into account the sudden increase in pressure detected by the sensor 8 which will act as a priority.

[0093] In addition to the orifices 3, 4 of variable section as indicated below, the slide 2 comprises a leak orifice 5 connecting the inlet of the hydraulic component 7 to the reservoir 21.

[0094] The table of curves C3, C4, C5 is subdivided into several zones along the X axis, i.e. the movement of the drawer 2 by the actuator 23:

[0095] - a sealing zone A, the drawer 2 being closed

[0096] - a decompression zone B

[0097] - a pressurization zone C

[0098] - a distribution zone D

[0099] - a full flow zone E.

[0100] The general shape of the curves C3 and C4 of the supply orifice 3 and the return orifice 4 are those already described.

[0101] The flow rates through the orifices 3, 4, 5 are given by the Bernoulli equation, namely:

[0102] * Flow rate through feed port 3:

[0103] Q3=k3*S3VAP3,

[0104] AP3 is the pressure difference between pump 20 and component 7 (load)

[0105] * Flow rate through decompression port 4:

[0106] Q4=k4*S4*AP4,

[0107] AP4 is the pressure difference between the return of the hydraulic component 7 and the reservoir 21

[0108] * Flow rate through leak orifice 5:

[0109] Q5=k5*S5*VAP5,

[0110] AP5 is the pressure difference between the hydraulic component 7 and the reservoir 21.

[0111] The ratio Q3 / Q4 gives the evolution of the pressure in the supply line.

[0112] - The decompression zone B which follows the closure zone A begins at the position xo at which the sections of the orifices 3, 4, 5 begin to open.

[0113] * Section S4 of the decompression orifice 4 opens frankly while the section S3 of the feed port 3 remains close to closing.

[0114] * the leakage section S5 of the leakage orifice 5 opens more than that of the leakage orifice the supply 3, thus attenuating the supply flow in the supply line of the hydraulic component 7, whether it is a motor or a cylinder.

[0115] - The pressure maintenance zone C:

[0116] the leakage section S5 decreases which makes it possible to carry out a controlled re-pressurization of the supply line of the hydraulic component 7 in order to prepare the conditions for obtaining a movement controlled by the leakage.

[0117] At the end of zone C, the leakage section C5 joins the supply curve C3 which continues to grow.

[0118] A slight leakage section S5 is maintained for the leakage orifice 5 to avoid possible instability, particularly during excitations of the system upon activation of an index response (step response).

[0119] The slide valve 2 distributes the flow proportional to the pressure drop at the edge of the equivalent orifice according to the opening law of curve C3.

[0120] - Distribution zone D:

[0121] The slide 2 distributes the volume flow proportional to the pressure drop at the terminals of the equivalent orifice of the hydraulic component 7 according to the opening law of the curve C4:

[0122] - The full flow zone E:

[0123] In this zone the maximum hydraulic power is reached. Increasing the supply section 3 causes the pressure in the load (component 7) to drop. To ensure a stabilized pressure, the return section C4 is reduced to obtain a pressure ratio close to 1 in the case of a hydraulic motor.

[0124] In full flow stroke, the distribution slide 2 completely closes the leak section 5 to avoid unnecessary loss of flow.

[0125] In the event of blockage of the hydraulic component 7, the increase in the load pressure is immediately detected by the sensor 8 and processed by the control unit 10 which instantly recalls the spool 2 in the zone B to reduce the supply flow rate Q3 by reducing the section S3 and compensating by the section S5 of the leakage orifice 5.

[0126] The measured pressure exceeding the set pressure PC, the difference Ec becomes negative and generates a control signal SC min immediately recalling the drawer into the decompression zone B regardless of the operator's DO request at that time.

[0127] The supply is thus reduced immediately and the return is made via the leakage orifice 05.

[0128] In the case of a hydraulic component 7 consisting of a hydraulic motor, the incoming flow rate is the same as the outgoing flow rate and the curves as shown in [Fig.3] apply.

[0129] In the case of a hydraulic cylinder, the control is carried out in a similar manner to reduce the supply section of the cylinder in the event of blocking of the tool associated with the cylinder.

[0130] NOMENCLATURE OF MAIN ELEMENTS

[0131] 100 Hydraulic circuit

[0132] 1 Control organ / joystick

[0133] 2 Distribution drawer

[0134] 2a Known distribution drawer

[0135] 3 Component feed port 7

[0136] 4 Component return port 7

[0137] 5 Leakage orifice upstream of component 7

[0138] 6 Secondary pressure limiter

[0139] 7 Hydraulic component

[0140] 7 a,b Hydraulic cylinder

[0141] 8 Pressure sensor at the inlet of component 7

[0142] 9 Main pressure limiter

[0143] 10 Control unit

[0144] 101 Temperature compensation table

[0145] 102 B alance

[0146] 20 Hydraulic circuit feed pump

[0147] 21 Hydraulic fluid reservoir

[0148] 22 Hydraulic fluid temperature sensor at the pump outlet 20

[0149] 23 Actuator of the distribution drawer 2

[0150] P Pressure measured by sensor 8

[0151] PC Set Pressure

[0152] DO Operator Request

[0153] SCo Basic Signal

[0154] SCC Compensated Signal

[0155] SC Control Signal

[0156] Ec Difference between the measured pressure and the set pressure

[0157] T Temperature provided by sensor 22

[0158] AE Zones of the opening curves of the orifices 3, 4, 5

[0159] C3 Curve representing the section of the feed orifice

[0160] C4 Curve representing the section of the decompression orifice

[0161] C5 Curve representing the section of the leak orifice

[0162] C6 Pressure curve

[0163] A Closing Zone

[0164] B Decompression zone

[0165] C Pressure maintenance zone

[0166] D Distribution area

[0167] E Full flow zone

[0168] 03 Feed orifice

[0169] S3 Power Supply Section

[0170] 04 Pressure relief or return port

[0171] S4 Decompression or return section

[0172] 05 Leakage orifice

[0173] S5 Leakage section

Claims

Claims

1. Hydraulic circuit (100) comprising a pump (20) connected to a reservoir (21) and supplying the hydraulic fluid under pressure to a component (7) via a distribution slide valve provided with a supply port (3) connected to the inlet of the component (7) and a return port (4) connected to the outlet of the component (7) as well as a pressure limiter (6) connected to the inlet of the component (7) and connected to the reservoir (21),hydraulic circuit characterized in that it comprises - a system for controlling the supply of the hydraulic component (7) having * a pressure sensor (8) installed upstream of the hydraulic component (7) downstream of the supply port (3) and providing the pressure information (P) of the hydraulic liquid * a set pressure (PC) - an actuator (23) controlling the movement of the distribution spool (2) - a control unit (10) for generating the control signal (SC) of the actuator (23) from the pressure information (P) measured at the supply port (3), the set pressure (PC) and a request (DO) from an operator - a leak port (5) in the spool (2) creating a leak towards the reservoir (21) between the supply port (3) and the component (7) in the initial phase of the stroke of the spool (2).,

2. Hydraulic circuit (100) according to claim 1, characterized in that the control unit (10) forms the difference (Ec) between the pressure information (P) of the sensor (8) and the set pressure (PC) to convert this pressure difference into a basic signal (SCo) varying according to stages in operating zones (AE) according to the position of the distribution spool (2), and in that the hydraulic circuit comprises - a scale (102) receiving * the operator's request signal (DO) and * the basic signal (SCo) to emit a control signal equal to the smaller of the two signals, the operator's request (DO) and the basic signal (SCo).

3. Hydraulic circuit according to claim 1, characterized in that the curves of the sections (C3, C4, C5) of the supply, return and leakage orifices (3, 4, 5) of the drawer (2) are cut into zones (AE) according to the position (x) of movement of the drawer (2): - a closing zone (A) being the closing zone of the supply from the end of travel position of the drawer (2) to a start of opening position (xo) - a decompression zone (B) following the closing zone (A) and in which the supply section (S3) opens slowly while being smaller than the leak section (S5), the supply sections (S3) and leak sections (S5) being much smaller than the decompression section (S4), - a pressure maintenance zone (C) in which the leak section (S5) descends and passes below the supply section (S3), - a distribution zone (D) in which the section (S5) of the leak orifice (5) only intervenes very slightly - a full flow zone (E) in which the leakage section (S5) is practically no longer involved.

4. Hydraulic circuit according to claim 2, characterized in that the control unit (10) comprises a temperature compensation table (101) receiving the basic signal SCo to compensate it according to the temperature of the hydraulic fluid, provided by the temperature sensor (22) detecting the temperature of the hydraulic fluid of the circuit (100), the temperature-compensated signal SCC being applied to the scale (102) receiving the operator's request signal DO and this temperature-compensated signal SCC to form the control signal (SC) from the smaller of these two signals (DO, SCC).

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