SYSTEM INCLUDING A HYDRAULIC PRESSURE AMPLIFIER

Description

[0001] The present invention relates to the field of hydraulic pressure generating devices.

[0002] More specifically, the present invention relates to the field of hydraulic pressure amplifiers.

[0003] The present invention finds application, for example, in the production of a hydraulic pressure amplifier intended to ensure the supply of a reserve of hydraulic fluid under high pressure allowing the actuation of the brakes of a vehicle, for example but not limited to a trailer.

[0004] There are various known hydraulic pressure amplifier systems.

[0005] Piston-type hydraulic pressure boosters are particularly well known. Such piston boosters are marketed by the company Minibooster.

[0006] Hydraulic piston pressure amplifiers generally comprise a housing comprising two chambers of different sections which house a stepped piston comprising two piston sections whose sections are respectively complementary to said chambers.

[0007] When hydraulic pressure is applied to a low-pressure inlet chamber on the large-section piston section, a higher pressure is collected in an outlet chamber containing the small-section piston section.

[0008] The pressure ratio between the pressure applied in the inlet chamber and the pressure prevailing in the outlet chamber is equal to the ratio between the sections of the two piston sections.

[0009] The piston is moved in translation in the housing, in successive back and forth movements, by control by suitable detection valves mechanically piloted at the end of the piston stroke, in combination with a bistable valve sensitive to the state of the detection valves which cyclically ensures the supply and discharge of the inlet chamber and the emptying of the high pressure outlet chamber.

[0010] The inversion of the piston movement is based on the control of the very precise operating clearances of the pilot slides integrated into the detection valves.

[0011] Piston displacement control requires successive cycles including supplying the inlet chamber to move the piston in a first direction towards the high pressure chamber to obtain high pressure, then discharging the inlet chamber to move the piston in the opposite direction and return it to the original position, before initiating a new cycle.

[0012] Document FR 3 020 841 presents an end-of-stroke regulator for a piston pressure converter. Like all pressure converters known to date, this document recommends using a piston position sensor.

[0013] Document CA 1 015 639 A presents another known example of a hydraulic pressure amplifier device.

[0014] The known pressure amplifier systems have already provided great service.

[0015] However, they are complex, expensive and lead to pressure pulsations due, according to the inventors' analysis, to a sudden reversal of the direction of movement of the piston.

[0016] The aim of the present invention in this context is to propose a pressure amplifier system having superior performance to the systems known from the state of the art.

[0017] This object is achieved according to the present invention by means of a system comprising a hydraulic pressure amplifier device according to claim 1.

[0018] Other advantageous features of the invention are described in the dependent claims.

[0019] The invention also relates to vehicles equipped with a system of the aforementioned type.

[0020] The invention further relates to a method for amplifying hydraulic pressure according to claim 16.

[0021] Other characteristics, aims and advantages of the present invention will appear on reading the detailed description which follows, and with reference to the appended drawings, given as non-limiting examples and in which: there figure 1 represents a schematic view of the hydraulic circuit of a hydraulic pressure amplifier device according to the present invention, the figure 2 represents the general operation of a device in accordance with the present invention within the framework of control by control means formed of an electronic control controlled by a time base; more precisely, the figure 2a represents the opening cycles of a distributor controlling the power supply to the amplifier box, while the figure 2b represents the piston displacement cycles, the figure 3 schematically represents, in a longitudinal sectional view, a valve for controlling the inlet pressure of the device according to the present invention, the figure 4 represents the piston displacement cycles as a function of a pressure measured at the outlet of a nozzle of the installation, the figure 5 represents a flowchart of operation of the device according to the present invention in the case of control by a measured pressure and the figure 6 represents another variant embodiment in accordance with the present invention according to which the converter comprises two chambers working in pressure increase respectively on the two phases of forward and return movement of the piston.

[0022] As indicated previously, according to an essential characteristic of the invention, the means for controlling the movement of the piston integrated into the hydraulic pressure amplifier are formed of an electronic control piloted by means for estimating the end of travel of the piston.

[0023] More specifically, as will be described later, these control means include a distributor controlled electronically and not by mechanical end-of-travel stops.

[0024] We will first describe a first embodiment in accordance with the present invention according to which the movements of the slide of a control distributor and the consequent movements of the piston of a pressure amplifier are controlled on the basis of a time base and not by mechanical end-of-stroke detection, to limit the number of components of the system.

[0025] More precisely in this case the time base cyclically predefines a period of imposed duration of supply of the input chamber of the amplifier box, then a period of discharge of imposed duration of the input chamber of the amplifier box.

[0026] As seen on the figure 1 attached, the hydraulic pressure amplifier device according to the present invention comprises a housing 10 which has two main chambers 12, 14 which house a stepped piston 20.

[0027] The first main chamber 12, which constitutes a low pressure inlet chamber, has a constant section along its entire length.

[0028] The second main chamber 14, which constitutes a high-pressure outlet chamber, also has a constant cross-section along its entire length. However, the cross-section of the second high-pressure main chamber 14 is smaller than the cross-section of the first low-pressure main chamber 12.

[0029] The stepped piston 20 comprises two sections 22, 24 of sections respectively complementary to said chambers 12, 14.

[0030] The stepped piston 20 is thus mounted in translation in the housing 10 along the longitudinal axis OO of the housing 10.

[0031] More precisely, the housing 10 defines an intermediate chamber 13 between the low pressure inlet chamber 12 and the high pressure outlet chamber 14. The intermediate chamber 13 has the same section as the low pressure inlet chamber 12.

[0032] The first section 22 of the piston 20, with a straight section complementary to the low pressure inlet chamber 12 and the intermediate chamber 13, is thus mounted to slide in translation in the inlet 12 and intermediate 13 chambers.

[0033] The small section section 24 of the piston 20 is mounted in translation in the outlet chamber 14. It is also located partly in the intermediate chamber 13.

[0034] The volumes of the main chambers 12, 14 and of the intermediate chamber 13 are variable. The volumes of the intermediate chamber 13 and of the main outlet chamber 14 reduce when the volume of the main inlet chamber 12 increases and vice versa.

[0035] Each of the chambers 12, 13, 14 has communication ports which alternately allow the supply or evacuation of the corresponding chamber.

[0036] The low pressure inlet chamber 12 has a port 11 which serves alternately as an inlet port for its supply and an outlet port for its discharge.

[0037] The high pressure outlet chamber 14 has an outlet port 15 for its discharge and an inlet port 17 for its supply.

[0038] The intermediate chamber 13 has a port 16 which serves alternately as an inlet port for its supply and an outlet port for its discharge.

[0039] The device illustrated on the figure 1 further comprises a control distributor 30.

[0040] The distributor 30 has the function of controlling the supply and discharge of the low pressure inlet chamber 12 and consequently the supply and discharge of the high pressure outlet chamber 14.

[0041] The distributor 30 may typically be formed of a three-port, two-position valve.

[0042] On the figure 1 , these three ports are referenced 32, 34 and 36. Port 32 is an inlet port. Port 34 is an outlet port. Port 36 serves alternately as an outlet port when supplying the low pressure inlet chamber 12 and as an inlet when discharging the low pressure inlet chamber 12.

[0043] The inlet 32 ​​is connected to a fluid supply inlet 40, via a flow restriction 50, typically formed by a nozzle.

[0044] The inlet 40 can typically be supplied by a hydraulic pump itself driven by a main motor, for example a heat engine.

[0045] Port 34 is connected to intermediate chamber 13 via port 16 and to a reservoir via an outlet port 52.

[0046] Port 36 is connected to the low pressure inlet chamber 12 via port 11.

[0047] In a first position, port 36 is connected to input 32.

[0048] In a second position, port 36 is connected to output 34.

[0049] A second flow restriction 56, typically a nozzle, is placed between the outlet of the restriction 50 (i.e. the point common to this restriction 50 and the inlet 32 ​​of the distributor 30) and a pressure measurement point 80.

[0050] A third flow restriction 58, typically a nozzle, is placed between the outlet of the second restriction 56 (i.e. the point common to this restriction 56 and the pressure measurement point 80) and the outlet 52 connected to the tank.

[0051] The nozzle 58 is sized to impose a very limited flow rate. It serves to create a permanent leak so that a pressure drop, resulting for example from a coupling break between a tractor carrying the supply means on the inlet port 40 and the trailer equipped with a braking device, is properly detected.

[0052] A non-return valve 60 is placed between the outlet 15 of the high pressure outlet chamber 14 and an outlet 54 on which the high hydraulic pressure supplied by the device is available.

[0053] The non-return valve 60 passes in the direction from the outlet 15 of the housing to the outlet port 54 and therefore opens when the pressure on the outlet 15 of the housing is greater than the pressure prevailing on the outlet port 54.

[0054] Another non-return valve 70 is placed between the inlet 17 of the high pressure outlet chamber 14 and the point common to the nozzles 56 and 58 and to the measuring point 80.

[0055] The non-return valve 70 passes in the direction leading towards the outlet chamber 14.

[0056] The non-return valve 70 therefore opens when the pressure in the chamber 14 becomes lower than the pressure prevailing at the inlet of the valve 70.

[0057] In the original position, the low pressure inlet chamber 12 is empty and the intermediate chamber 13 occupies its maximum volume.

[0058] When a fluid from the inlet port 40 is injected through the port 11 into the low pressure inlet chamber 12, via the restriction 50 and the distributor 30 placed in the first position, the piston 20 is moved towards the outlet chamber 14. The low pressure inlet chamber 12 expands and conversely the intermediate chamber 13 contracts.

[0059] Originally, the exit chamber 14 occupies its maximum volume.

[0060] Once the piston 20 has been moved by supplying the inlet chamber 12, the outlet chamber 14 occupies a minimal volume but at high pressure, the fluid previously contained in the high-pressure outlet chamber 14 being discharged to the outlet 54 via the non-return valve 60. The outlet chamber 14 can thus deliver a high-pressure fluid to the outlet port 15, and therefore to the outlet 54 via the non-return valve 60.

[0061] During this exit phase of the piston 20, the intermediate chamber 13 is gradually emptied towards the reservoir via the port 16.

[0062] The inlet chamber 12 is thus defined between one end of a large section of the housing 10 and the large section 22 of the piston 20.

[0063] The intermediate chamber 13 is defined between the same large section section 22 of the piston 20 and the opposite end of the large section section of the housing 10.

[0064] The outlet chamber 14 is defined between the end of the small section section 24 of the piston 20 and the opposite end of the small section section of the housing 10.

[0065] In the second position of the distributor 30, the port 36 is connected to the outlet 34. Thus, the inlet chamber 12 is connected to the reservoir via the distributor 30 and the port 52, which allows the discharge of the inlet chamber 12 towards the reservoir and the movement in the opposite direction of the piston 20 towards the inlet chamber 12.

[0066] The outlet chamber 14 is then supplied via the non-return valve 70 connected to the inlet port 40, via the aforementioned nozzles 50 and 56.

[0067] During this re-entry phase of the piston 20, the intermediate chamber 13 is progressively filled with the fluid present in the inlet chamber 12 by means of the distributor 30, via the port 16.

[0068] In the context of the first embodiment in accordance with the present invention, the movements of the distributor slide 30, and thereby the movements of the piston 20, are controlled by a time base and not by mechanical end-of-stroke information as was the case in the known solutions of the state of the art.

[0069] This arrangement in accordance with the present invention makes it possible to limit the number of components compared to known solutions.

[0070] We can see on the figure 2a , the signals defining the opening slots of the distributor 30, that is to say the slots imposed by a time base during which the port 36 is connected to the inlet 32 ​​to allow the supply of the inlet chamber 12 by the fluid coming from the supply inlet port 40.

[0071] On the figure 2a , the control cycles corresponding to an opening of the distributor 30 (connection of the port 36 with the input 32) between the times t0 and t1 and conversely to a closing of the distributor 30 (connection of the port 36 with the output 34) during the time phases between t1 and t2 are represented.

[0072] Once a cycle from t0 to t2 has been completed, a following cycle covering the periods t0 to t1 of opening, then from t1 to t2 of closing, is repeated and so on.

[0073] It was also represented on the figure 2b , the piston displacement cycles 20.

[0074] The piston 20 is moved in the direction of expansion of the chamber 12 between the times t0 and t01, during the opening of the distributor 30. Then, the piston 20 having reached its end of expansion stroke, remains stationary between the times t01 and t1 which corresponds to the end of opening of the distributor 30.

[0075] The piston 20 is then moved in the direction of retraction of the inlet chamber 12 between the times t1 and t12, the time t12 coinciding with the end of the stroke of the piston 20 in retraction.

[0076] The piston 20 having reached its end of travel in retraction then remains stationary between times t12 and t2, time t2 with the resumption of an opening cycle of the distributor 30 at time t0.

[0077] The cycle from t0 to t2 of the movement of the piston 20 is then repeated in synchronism with the opening and closing of the distributor 30 as illustrated in the figure 2b .

[0078] The extension phases of the piston 20 between the times t0 and t01 and the retraction phases of the piston 20 between the times t1 and t12 are preferably operated at a constant speed of movement of the piston 40 by control of the distributor 30.

[0079] It will be noted on examination of the figures 2a et 2b that the opening time of the distributor 30 allowing the supply of the inlet chamber 12 between t0 and t1 and the closing time of the port 32 of the distributor 30 between t1 and t2 are greater than the times from t0 to t01 and from t1 to t12 required to ensure complete strokes of the piston 20 respectively forward and backward.

[0080] More specifically, we will note in the examination of the figures 2 , that the opening time between t0 and t1 of the distributor 30 is greater than the time between t0 and t01 required to ensure the full expansion of the piston 20 while the period from t1 to t2 of closing of the port 32 of the distributor 30 is greater than the period from t1 to t12 required to ensure the retraction of the piston 20.

[0081] As a non-limiting example, a complete cycle from t0 to t2 can last, for example, 6 seconds.

[0082] Those skilled in the art will understand that in the context of this first embodiment, the distributor 30 is therefore controlled by the time base defined by the imposed opening cycles from t0 to t1 and the imposed closing cycles from t1 to t2.

[0083] In this case, the end-of-stroke estimates controlling the distributor 30 are defined by the sequence imposed by the time base, i.e. the instants t0, t1 and t2. More precisely, the end-of-stroke estimates controlling the distributor 30 are defined by the duration period imposed by the time base, of supplying the input chamber of the amplifier box which ends at the instant t1, then the duration period imposed by the time base, of discharging the input chamber of the amplifier box which ends at the instant t2.

[0084] According to the first embodiment in accordance with the present invention, the end-of-stroke estimates of the piston 20 therefore correspond to the predefined instants t1 and t2 imposed by the time base.

[0085] A second embodiment in accordance with the present invention will now be described, according to which the distributor 30, associated with the restriction 50, controls the supply of the low pressure inlet chamber 12 by a proportional control so that the piston 20 does not generate pulsation on the inlet 11 and outlet 15 orifices and consequently on the inlet 40 and outlet 54 orifices. In this embodiment the distributor 30 is controlled on the basis of a pressure measured on the port 80.

[0086] The purpose of this pressure measurement is to provide a signal representing the pressure level on a port of the pressure amplifier box making it possible to detect when the piston 20 is immobilized and therefore has reached the end of its stroke.

[0087] The proportional control makes it possible to avoid excessive acceleration of the piston 20 which would lead to rapidly consuming all the flow available at the inlet 40 and would cause the pressure to drop during the movement of the piston 20, which could consequently generate vibrations.

[0088] This control ensures both a rapid stroke of the piston 20 and avoids overconsumption on the supply line 40.

[0089] The pressure measurement can be made using any known conventional pressure sensor installed on the measuring port 80.

[0090] The nozzle 50 installed on the inlet line between the inlet port 40 and the port 32 of the distributor 30 allows, thanks to the sensor placed on the port 80, to measure on the one hand the level of pressure available on the inlet 11 of the low pressure inlet chamber 12 when the piston 20 is stationary and the pressure level on the same inlet 11 of the low pressure chamber 12 when the piston 20 is moved in translation in extension.

[0091] The difference between these two pressure measurements represents an image of the flow rate consumed by the box to supply the low pressure inlet chamber 12.

[0092] Thus when the pressure measured at point 80, during the supply phase of the inlet chamber 12, becomes equal to the reference pressure existing when the piston 20 is stationary, the system considers that the piston has reached the end of its supply or extension stroke.

[0093] It will be noted that during the exit of the piston 20, the nozzle 56 does not impact the measurement of the pressure at the level of the inlet nozzle 50 taken from the measuring point 80 because the flow rate through the nozzle 56 is very low.

[0094] This is due in particular to the fact that the outlet nozzle 58 is very small as indicated previously.

[0095] The speed of extension movement of the piston 20, which depends on the flow rate injected into the inlet chamber 12, is controlled by the size of the nozzle 50.

[0096] The output speed of the piston 20 is calculated from the pressure difference measured between the pressure level available without movement of the piston 20 and the pressure measured with the nozzle 50 when the piston 20 is moved in extension.

[0097] The same control principle applies for the retraction of the piston 20, i.e. the movement of the piston 20 in the direction of retraction.

[0098] The nozzle 56 installed on the line comprising the nozzle 50, between the inlet port 40 and the non-return valve 70 makes it possible, thanks to the sensor placed on the port 80, to measure on the one hand the pressure level available on the inlet 17 of the high pressure outlet chamber 14 when the piston 20 is stationary and the pressure level on the same inlet 17 of the high pressure chamber 14 when the piston 20 is moved in translation in retraction.

[0099] The difference between these two pressure measurements represents an image of the flow rate consumed by the housing to supply the high pressure chamber 14 in the retraction phase of the piston 20.

[0100] Thus when the pressure measured at point 80, during the supply phase of the outlet chamber 14, becomes equal to the reference pressure existing when the piston 20 is stationary, the system considers that the piston has reached the end of its retraction stroke.

[0101] The retraction speed of the piston 20 is calculated from the pressure difference measured between the pressure level available without movement of the piston 20 and the pressure measured with the nozzle 56 when the piston 20 is moved in retraction.

[0102] The movements of the piston 20 are therefore monitored by a pressure measurement on the outlet of the nozzle 50 for the extension phase of the piston 20 during which the system applies a pressure setpoint to the low pressure inlet chamber 12, and by a pressure measurement on the outlet of the nozzle 56 for the reentry phase of the piston 20 during which the system applies a pressure setpoint to the high pressure outlet chamber 14.

[0103] A pre-positioning of the pressure setpoint on the low pressure inlet chamber 12 can be carried out by taking into account the desired pressure at the outlet orifice 54 and the surface ratio between the two sections 22 and 24 of the piston 20.

[0104] If we take for example a desired outlet pressure Pout of 120 bars on the outlet port 54, and a surface ratio of 10 between the two sections 22, 24 of the piston 20, the control pressure for the balance on the inlet 11 of the inlet chamber 12 is 12 bars. We can therefore provide a distributor 30 controlling the pressure on the outlet 36 to 12 bars.

[0105] The pre-positioning of the pressure setpoint on the low pressure inlet chamber 12 can be achieved using a suitable valve 30. It is shown in the figure 3 an example of the embodiment of such a valve 30.

[0106] Valve 30 shown on the figure 3 forms a pressure reducer. It comprises a body 31 which houses a slide valve 38. The body 31 comprises the aforementioned ports 32, 34 and 36.

[0107] The movements of the drawer 38 in the body 31 are controlled by an electromagnetic force generated by a coil 37 which cooperates with a plunger 39 secured to the drawer 38.

[0108] A given pilot current on the coil 37 corresponds to an output pressure on the orifice 36 because the valve 30 has a hydraulic counter-reaction which closes the slide 38 when the pressure is reached.

[0109] F is the electromagnetic force which corresponds to a current injected into the coil 37. The pressure available on the outlet 36 is applied to the entire internal surface of the slide 38 and therefore creates a force F', which corresponds to a hydraulic force which opposes F. When F' increases, the slide 38 closes the inlet orifice 32 without the current control F on the coil 37 having changed.

[0110] Valve 30 shown on the figure 3 therefore imposes a pressure of 12 bar on its output 36 to pre-position the setpoint on the low pressure inlet chamber 12.

[0111] If the inlet pressure P available at the outlet of the means applying the pressure to the inlet 40 is however 20 bars, the control pressure applied to the inlet can be increased 11 of the inlet chamber 12 from 12 bars to 20 bars, possibly up to 20 bars, to accelerate the piston 20. To do this, it is sufficient to control the valve 30 accordingly.

[0112] The invention is not limited to the use of a valve 30 of the type illustrated in the figure 3 comprising hydraulic feedback and allowing pressure pre-positioning. The invention may use other types of proportional valves 30 which do not have such hydraulic feedback.

[0113] For example, there are proportional valves that do not have a correspondence between a pilot current and an output pressure, but between a current and an opening section. In this case, pressure prepositioning is not possible and within the framework of the invention, the acceleration of the piston is then managed solely by comparing the pressure of the orifice 80 before the start of the movement, and this same pressure in movement as explained above.

[0114] Without pre-positioning, the opening phase of valve 30 is more delicate. To avoid pressure collapse, the piston must be started slowly. If the pilot current of coil 37 is increased too quickly, the piston or spool 38 moves too quickly.

[0115] In the second embodiment as indicated previously, the end-of-stroke detection simulation is linked to the end of the pressure difference measured on the nozzles 50 or 56, depending on whether the piston 20 extends or retracts, relative to a reference pressure established when the piston 20 is stationary.

[0116] In fact the pressure remains stable and constant, equal to the reference pressure, when the piston 20 remains stationary.

[0117] The retraction displacement speed of the piston 20 is controlled on the one hand by the size of the nozzles 50 and 56 placed in series and which control the flow injected into the outlet chamber 14 from the port 40, and on the other hand by the pressure losses imposed by the distributor 30 through which the flow evacuated from the inlet chamber 12 to the reservoir passes via the port 54.

[0118] It will be noted, however, that if the pilot valve or distributor 30 has a pressure drop level greater than a threshold, the nozzle 56 does not intervene in regulating the speed of the piston 20 in its return stroke. In this case, in fact, the pressure drop necessary to control the retraction phase of the piston 20 is due to the distributor 30 itself and the speed of the piston 50 is limited only because of the pressure drops in the pilot valve 30.

[0119] There figure 4 represents the displacement cycles of the piston 20 as a function of a pressure measured on the nozzle 50.

[0120] As seen on the figure 4 , the pressure measured on the nozzle 50 increases progressively during the progress of the hydraulic pressure amplification process due to the increasing back pressure applied to the outlet 54.

[0121] There figure 5 represents a flowchart of operation of the device within the framework of the second embodiment according to the present invention.

[0122] We can see on this figure 5 a method 100 which comprises the following steps: . Acquisition of an inlet pressure Po when the piston 20 is stationary, preferably by measuring the pressure on the nozzle 50 accessible at the measurement orifice 80 (the nozzle 56 having no impact on this measurement) (step 102), . Acquisition of the pressure P1 prevailing in the accumulator connected to the high pressure outlet 54 (step 104), . Define the ratio between the sections of the two sections 22 and 24 of the piston 20 which corresponds to the pressure amplification ratio (step 106), . Application of an equilibrium pressure P on the low pressure inlet chamber 12 so that P = P1 / R (step 108), . Increase the pressure P in the low pressure inlet chamber 12 to move the piston 20 towards the outlet chamber 14 and cause the oil to exit from the high pressure chamber to the accumulator via the outlet port 54 (step 110), .Acquisition of the pressure Po' on the nozzle 50 when the piston 20 is mobile, by measuring the pressure on the nozzle 50 accessible at the level of the measuring orifice 80 (the nozzle 56 having no impact on this measurement) (step 112), . Calculate the pressure difference ΔP = Po - Po' (step 114), . Define a pressure setpoint ΔPo (step 116), . Increase the pressure P in the low pressure inlet chamber 12 so that ΔP = ΔPo by successive increments and a PID type control (step 118), . Carry out a test to see if ΔP = 0 (step 120); if not, continue the process at step 112, . On the contrary, if the test of step 120 is positive, consider that the simulation of reaching the end of travel of the piston 20 in extension is validated (step 122), . Carry out a test searching if P1 = Pmax (step 124), . If the test of step 124 is positive, consider that the process has reached the end of inflation step (step 126), .On the contrary, if the test of step 124 is negative, the piston 20 having reached its end-of-travel stop in extension without the set pressure in the accumulator being reached, continue the process by a series of steps controlling the retraction sequence of the piston 20 and starting with a step which consists of acquiring the new pressure value P1 prevailing in the accumulator connected to the high-pressure outlet 54 (step 128), . Application of an equilibrium pressure P on the low-pressure inlet chamber 12 so that P = P1 / R (step 130), . Reduce the pressure P in the low-pressure inlet chamber 12 to retract the piston 20, cause the oil to exit the low-pressure chamber 12 and cause the oil to enter the high-pressure chamber 14 via the inlet port 17 (step 132), . Acquisition of the pressure Po' on the nozzle 56 when the piston 20 is mobile, by measuring the pressure accessible at the level of the measuring orifice 80 (step 134),.Calculate the pressure difference ΔP = Po - Po' (step 136), . Reduce the pressure P in the low pressure inlet chamber 12 so that ΔP = ΔPo by successive increments and a PID type control (step 138), . Carry out a test to see if ΔP = 0 (step 140); if not, continue the process at step 134, . On the contrary, if the test of step 140 is positive, consider that the simulation of reaching the end of travel of the piston 20 in retraction is validated (step 142), but the set pressure in the accumulator not being reached (see previous step 124), resume the process by the series of steps intended to control the exit sequence of the piston 20 starting with the aforementioned step 120. .

[0123] In the case where a distributor 30 formed by a proportional valve is used and not a piloted flow limiter of the type illustrated in the figure 3 , The aforementioned steps 108 and 130 are omitted.

[0124] The third embodiment according to the present invention will now be described.

[0125] According to this third embodiment, the movement of the piston 20 is controlled by a time reference based on an available flow rate. More precisely, the time reference for the supply phase is defined as being the time required to fill the inlet chamber 12 knowing the flow rate available on the inlet 40, more precisely after passing through the nozzle 50 and the distributor 30 placed in series with the port 11 in the supply phase. The time reference for the retraction phase of the piston 20 is defined as being the most restrictive of the one hand the time required to fill the outlet chamber 14 knowing the flow rate available on the inlet 40, more precisely after passing through the nozzles 50 and 56 placed in series with the port 17 and on the other hand the time required to empty the inlet chamber 12 through the pressure losses of the distributor 30.

[0126] Thus knowing the flow rate available from the source which supplies the inlet port 40 on the one hand and the volume of the inlet chamber 12 of the hydraulic amplifier on the other hand, the distributor 30 is controlled to open for a sufficient duration to ensure the supply of the inlet chamber 12 using the available flow rate, respectively the supply of the outlet chamber and the emptying of the inlet chamber.

[0127] For example, if the available flow rate at the inlet on port 40 is 10 I / min and the volume of the inlet chamber 12 is 38.5cc, we know that the normal time to complete the stroke is approximately 2.3 seconds.

[0128] The reference time for the feeding phase will then be 2.3 seconds.

[0129] If, however, at the end of these 2.3 seconds, the pressure measured on the nozzle 50 has not become equal to the reference pressure when the piston 20 is stationary, which would indicate the end of the stroke of the piston 20, it is possible that the temperature is lower than when measuring the reference time.

[0130] The system then controls the assembly to determine a new reference time allowing the complete stroke of the piston 20 to be completed. The temperature can also be deduced and the pressure difference measured on the nozzles, the flow rate and therefore the control pressure can be adjusted accordingly.

[0131] It has been represented on the figure 6 , an alternative embodiment according to which the piston 120 works to increase pressure both on its outward journey and on its return journey during movement.

[0132] To do this, the converter device has a symmetry with respect to the average plane of the piston section 122, transverse to the displacement axis OO.

[0133] Thus, according to the embodiment shown in the figure 6 , the piston comprises a central section 122 of large section, extended respectively on either side by two sections 124.1 and 124.2 of smaller section.

[0134] The 100 case has a central chamber 111 in which the large section 122 of the piston moves. The large section 122 of the piston 120 thus divides the central chamber 111 en two sub-chambers which respectively and alternately form inlet chamber 112 and intermediate chamber 113 depending on the forward or return piston movement cycle.

[0135] The housing 100 also has, on either side of the central chamber 111, two lateral chambers alternately forming high-pressure outlet chambers 114.1 and 114.2. The two lateral outlet chambers 114.1 and 114.2 respectively accommodate one of the small-section sections 124.1 and 124.2 of the piston.

[0136] We observe on the figure 6 , non-return valves 60.1 and 60.2 connected respectively to the outlet chambers 114.1 and 114.2 and opening onto a pipe connected for example to the inlet of a pressure accumulator. The non-return valves 60.1 and 60.2 pass in the direction of the outlet chambers 114.1 and 114.2 towards the pressure accumulator.

[0137] Finally, we have schematically represented on the figure 6 , a pressure source 160 connected via a distributor 130, four-way, two-position, and via a reducer or nozzle 50, alternately to one of the two sub-chambers of the main chamber 111. The distributor 130 connects the other sub-chamber of the main chamber 111 to a reservoir 172 at atmospheric pressure.

[0138] The forward stroke of the piston 120, arbitrarily chosen from left to right, is obtained when the distributor 130 is placed in a position such that the left sub-chamber of the main chamber 111 is supplied by the pressure source 160. The volume of the left sub-chamber of the main chamber 111 expands and, on the contrary, the volumes of the right sub-chamber of the main chamber 111 and of the right outlet chamber 114.1 reduce. This right outlet chamber 114.1 increases in pressure. The high-pressure fluid available in the right outlet chamber 114.1 is directed towards the outlet, for example towards the pressure accumulator via the non-return valve 60.1. Simultaneously, the left outlet chamber 114.2 expands. It is supplied by the non-return valve 70.2.

[0139] For the embodiment of the figure 6 , restriction 56 is not essential. Measuring point 80 can be taken at the outlet of nozzle 50. Only one nozzle 50 is necessary.

[0140] Symmetrically, the return stroke of the piston 120, arbitrarily chosen from right to left, is obtained when the distributor 130 is placed in a position such that the right sub-chamber of the main chamber 111 is supplied by the pressure source 160. The volume of the right sub-chamber of the main chamber 111 expands and, on the contrary, the volumes of the left sub-chamber of the main chamber 111 and of the left outlet chamber 114.2 are reduced. This left outlet chamber 114.2 increases in pressure. The high-pressure fluid available in the left outlet chamber 114.2 is directed towards the outlet, for example the pressure accumulator, via the non-return valve 60.2. Simultaneously, the right outlet chamber 114.1 expands. It is supplied by the non-return valve 70.1 via the reduction 56.

[0141] The dual chamber assembly illustrated in the figure 6 allows the regulation of the pilot flow rates, the leak flow rate and the outgoing flow directed towards the outlet, for example towards the pressure accumulator. It also allows the filling time of this accumulator to be reduced by half.

[0142] The present invention offers, compared to the state of the art, numerous advantages, in particular a smaller footprint, ease of machining and lower cost, a reduced number of parts and an improved noise level.

[0143] It will be noted in particular that the invention makes it possible to avoid the need to integrate into the housing 10 detection valves mechanically controlled at the end of the piston stroke. The absence of such mechanical detection valves and therefore of corresponding hydraulic distribution slides integrated into the amplifier 10 simplifies the machining of the body of the amplifier.

[0144] The electronic control according to the invention makes it possible to reduce the noise of the vibrations generated by the change of direction of the piston.

[0145] The device according to the present invention can be applied in particular to the supply of a hydraulic braking system for a trailer with several axles.

[0146] The invention can be applied for example to the hydraulic braking system proposed by the Applicant and described in document EP 3 103 691.

[0147] The regulations set the volume of oil that must be supplied by a tractor to a trailer when braking at 140cc for 0.6s.

[0148] If the volume of the trailer actuators for braking is greater, which is generally the case with multi-axle trailers, it is necessary to restore a pressurized hydraulic volume on the trailer.

[0149] The only pressure source generally available is a line whose levels are set by regulation at 12 liters per minute and 15 bars minimum.

[0150] Thanks to a pressure amplifier according to the present invention, the pressure can be transformed into a pressure of 150 bars for a volume of approximately 500cc stored in accumulators on the trailer.

[0151] Furthermore, all of the embodiment variants proposed within the framework of the present invention make it possible to limit the number of components of the amplifier system compared to the amplifier devices known from the state of the art.

[0152] All of the embodiment variants proposed within the framework of the present invention also make it possible to avoid pressure pulsations on the different orifices of the system.

[0153] It should be noted that for the embodiment of the figure 1, the nozzle 50 is suitable for passing a large flow rate while the nozzle 56 is suitable for passing a small flow rate.

Claims

1. System comprising: - a hydraulic pressure amplifying device comprising: - a casing (10; 100) including at least one low-pressure inlet chamber (12; 112, 113) and at least one high-pressure outlet chamber (14; 114.1, 114.2) with different cross sections which house a staged piston (20; 120) comprising two piston sections (22, 24; 122, 124.1, 124.2) with cross sections respectively matching the chambers (12, 14; 112, 113, 114.1, 114.2), - a feed inlet (40) - means (30; 130) for controlling the movement of the piston (20; 120), the control means being formed - by a distributor (30; 130) which controls the feeding of the or of each low-pressure inlet chamber (12; 112, 113) and - by an electronic control of the distributor, the control means also comprising: - a flow restriction (50) between the feed inlet (40) and the distributor (30; 130), and / or - a flow restriction (56) between the feed inlet (40) and the or each outlet chamber (14; 114.1, 114.2) characterized in that the system comprises means for estimating the ends-of-stroke of the piston (20; 120), the estimation means being configured to estimate the ends-of-stroke of the piston without an end-of-stroke sensor or a mechanical end-of-stroke stop and to control the electronic control.

2. System according to the preceding claim, wherein the means for estimating the ends-of-stroke of the piston (20) are configured to control the electronic control by a time base, preferably the estimation of the ends-of-stroke being defined by the sequence imposed by the time base which cyclically predefines an imposed duration period for feeding the or one of the inlet chambers (12; 112, 113) of the amplifier casing, then an imposed duration discharge period of the or of one of the inlet chambers of the amplifier casing.

3. System according to one of the preceding claims, wherein the means for estimating the ends-of-stroke of the piston (20; 120) comprise means (80) for measuring the pressure on a port of the casing.

4. System according to the preceding claim wherein the means for estimating the ends-of-stroke of the piston (20; 120) are configured to generate an end-of-stroke signal when the pressure measurement means detect a stable pressure over a predetermined period.

5. System according to one of claims 3 or 4, wherein the means for estimating the end-of-stroke of the piston (20; 120) are configured to generate an end-of-stroke signal when the pressure measurement means detect a stable pressure equal to a reference pressure prevailing in the absence of movement of the piston (20; 120).

6. System according to one of claims 3 to 5, wherein the means for estimating the end-of-stroke of the piston (20; 120) are configured to measure the pressure at the inlet of the or of one of the low-pressure inlet chambers (12; 112, 113) for the extension phase of the piston (20; 120).

7. System according to one of claims 3 to 6, wherein the means for estimating the end-of-stroke of the piston (20; 120) are configured to measure the pressure at the inlet of the or of one of the high-pressure outlet chambers (14; 114.1, 114.2) for the retraction phase of the piston (20; 120).

8. System according to one of the preceding claims, wherein the flow restriction (50) between the feed inlet (40) and the distributor (30; 130) is formed by an atomizer.

9. System according to one of the preceding claims, wherein the flow restriction (56) between the feed inlet (40) and the or one of the outlet chambers (14; 114.1, 114.2) of the casing is formed by an atomizer.

10. System according to one of the preceding claims, wherein the means for estimating the ends-of-stroke of the piston (20) are configured to control the electronic control by a time reference, preferably the time reference for the feed and piston (20; 120) extension phase, being defined as being the time necessary for filling the or one of the inlet chambers (12; 112, 113) of the casing knowing the available flow rate and the time reference for the piston (20; 120) retraction phase, being for its part defined as being the most constraining, on the one hand, of the time necessary for filling the or one of the outlet chambers (14; 114.1, 114.2) knowing he available flow rate and, on the other hand, of the time necessary for emptying the inlet chamber through the head losses of the distributor (30; 130).

11. System according to one of the preceding claims, wherein the flow restriction (50) between the feed inlet (40) and the distributor being a first flow restriction, and the flow restriction (56) between the feed inlet (40) and the or each exit chamber (14; 114.1, 114.2) being a second flow restriction: - the or one of the inlet chambers and the or one of the outlet chambers form main chambers (12, 14; 112, 113, 114.1, 114.2), - the casing (10; 100) also includes an intermediate chamber (13; 113), - the piston (20; 120) is mounted in translation in the casing (10), - the inlet chamber has a port (11) which serves alternately as an inlet port for its feeding and as an outlet port for its discharge and the outlet chamber has an outlet port (15) for its discharge and in inlet port (17) for its feeding, the intermediate chamber (13; 113) having a port (16) which serves alternately as an inlet port for its feeding and as an outlet port for its discharge - the distributor (30; 130) is formed from three-port valve and two positions for controlling the feed and the discharge of the inlet chamber and consequently of the feed and discharge of the outlet chamber, - the distributor has: -- a first port (32 connected to the feed inlet (40) by means of the first flow restriction (50), formed typically by an atomizer, -- a second port (34) connected to the intermediate chamber (13; 113) and to a reservoir, and -- a third port (36) connected to the inlet chamber, in a first position of the distributor (30), the first port (32) being connected to the third port (36) and in a second position, the third port (36) being connected to the second port (34), - the second flow restriction (56), typically an atomizer, being placed between the outlet of the first restriction (50) and a pressure measurement point (80), - a third flow restriction (58), typically an atomizer, being placed between the outlet of the second restriction (56) and an outlet (52) connected to the reservoir, - a first check valve (60; 60.1, 60.2) being placed between the outlet (15) of the outlet chamber and an outlet (54) at which the high hydraulic pressure supplied by the device is available and - a second check valve (70; 70.1, 70.2) being placed between the inlet (17) of the outlet chamber and the measurement point (80).

12. System according to one of the preceding claims, wherein the distributor (30; 130) is formed of a valve comprising a hydraulic counter-reaction, suited for prepositioning the pressure value applied to the or to each inlet chamber (12; 112, 113) of the casing (10; 100).

13. System according to one of claims 1 to 10, which comprises two chamber (114.1, 114.2) working in pressure augmentation respectively on the extension and return strokes of the piston (120), the device preferably being symmetrical relative to the median plane of the section (122) of the piston with the large cross-section.

14. System according to the preceding claim, wherein: - the piston (120) comprises a central section (122) with a large cross section, continued respectively on either side by two sections (124.1, 124.2) with a smaller cross section, - the casing (100) has a central chamber (111) wherein the section (122) of the piston with the large cross section moves, the section (122) of the piston (120) with the large cross section dividing the central chamber (111) into two sub-chambers which form respectively and alternately the inlet chamber (112) and the intermediate chamber (113) depending on whether the movement cycle of the piston is extending or returning, the casing (100) having moreover on either side of the central chamber (111) two lateral chambers forming alternately high-pressure outlet chambers (114.1, 114.2) respectively accommodating one of the sections (124.1, 124.2) of the piston with a small cross section, - the device comprises check valves (70.1, 70.2) connected to the two outlet chambers (114.1, 114.2), - the device comprises additional check valves (60.1, 60.2) connected respectively to the outlet chambers (114.1, 114.2) and leading to a pipe (54) connected to the inlet of a pressure accumulator, passing in the direction from the outlet chambers (114.1, 114.2) to the pressure accumulator, - the device comprises a pressure source (160) and - the distributor (130) connects alternately one of the two sub-chambers of the main chamber (111) to the pressure source (160) and respectively to a reservoir (172) at atmospheric pressure.

15. Vehicle that comprises a system conforming to one of the preceding claims.

16. Method for amplifying hydraulic pressure by means of a casing (10; 100) comprising at least one low-pressure inlet chamber (12; 112, 113) and at least one high-pressure outlet chamber (14; 114.1, 114.2) with different cross sections, which house a staged piston (20; 120) comprising two piston sections (22, 24; 122 124) with cross sections that respectively match the chambers, the method comprising the step consisting of controlling the movements of the piston (20; 120) by means of an electronic control of a distributor (30; 130), the distributor controlling the feeding of the or each low-pressure inlet chamber (12; 112, 113), and by means of: - a flow restriction (50) between a feed inlet (40) and the distributor (30; 130) and / or - a flow restriction (56) between the feed inlet (40) and the or each outlet chamber, the method being characterized in that the control step takes place by controlling the electronic control by means of estimating the ends-of-stroke of the piston without using an end-of-stroke sensors or a mechanical end-of-stroke stop.